Magnetic recording medium and cartridge

Abstract

Provided is a magnetic recording medium that makes it possible to obtain satisfactory electromagnetic conversion characteristics and to suppress wear of a head.　The magnetic recording medium is a tape-shaped magnetic recording medium, and includes a base, an underlayer, and a magnetic layer in this order. The average thickness of the magnetic recording medium is 5.50 μm or less, and the average thickness of the magnetic layer is 0.07 μm or less. The average hardness H50 obtained by vertically pushing a triangular pyramid diamond indenter having a ridge angle of 142.3° against the surface on the magnetic layer side with a load of 50 μN is 0.72 GPa or more. The average plastic deformation amount D50 obtained by vertically pushing the triangular pyramid diamond indenter against the surface on the magnetic layer side with a load of 50 μN is 16.50 nm or less.

Description

Magnetic recording media and cartridges

[0001] This disclosure relates to a magnetic recording medium and a cartridge equipped therewith.

[0002] In recent years, in order to realize tape storage with a high total capacity, the capacity of cartridges has been increased, and the thickness of tape-shaped magnetic recording media has been reduced to 5.50 μm or less. Furthermore, the thickness of the magnetic layer has also been reduced to 0.07 μm or less (70 nm or less) (see, for example, Patent Document 1).

[0003] International Publication No. 2021 / 199453

[0004] The high-capacity cartridges mentioned above are increasingly being used in archival tape libraries. In archival tape libraries, dozens to nearly a hundred cartridges are swapped out for a single drive, which leads to wear and tear on the heads and makes them prone to damage. Furthermore, improvements in the electromagnetic conversion characteristics are desired for these high-capacity cartridges.

[0005] The object of this disclosure is to provide a magnetic recording medium and a cartridge equipped therewith that can obtain good electromagnetic conversion characteristics and suppress head wear.

[0006] To solve the above-mentioned problems, the magnetic recording medium according to this disclosure is a tape-shaped magnetic recording medium comprising a substrate, a base layer, and a magnetic layer in that order, wherein the average thickness of the magnetic recording medium is 5.50 μm or less, the average thickness of the magnetic layer is 0.07 μm or less, and the average hardness H is determined by pressing a triangular pyramidal diamond indenter with a 142.3° edge angle perpendicular to the surface of the magnetic layer with a load of 50 μN. 50 However, the average plastic deformation amount D was determined by pressing a triangular diamond indenter perpendicularly to the surface of the magnetic layer with a load of 50 μN. 50 However, it is below 16.50 nm.

[0007] The cartridge relating to this disclosure comprises a magnetic recording medium relating to this disclosure.

[0008] Figure 1 is an exploded perspective view showing an example of the configuration of a cartridge according to one embodiment of the present disclosure. Figure 2 is a block diagram showing an example of the configuration of a cartridge memory. Figure 3 is a cross-sectional view showing an example of the configuration of a magnetic tape. Figure 4 is a schematic diagram showing an example of the layout of a data band and a servo band. Figure 5A is an enlarged view showing an example of the configuration of a data band. Figure 5B is an enlarged view showing an example of a data track in a magnetic recording system. Figure 6 is an enlarged view showing an example of the configuration of a servo band. Figure 7 is a perspective view showing an example of the shape of magnetic particles. Figure 8 is a diagram showing a first example of a cross-sectional TEM image of a magnetic layer. Figure 9 is a diagram showing a second example of a cross-sectional TEM image of a magnetic layer. Figure 10A is a graph illustrating a measurement method using a nanoindenter. Figure 10B is a schematic cross-sectional view illustrating a measurement method using a nanoindenter. Figure 11A is a diagram showing the prism face and bottom face of an Alfesil prism. Figure 11B is a diagram showing a fixing jig to which an Alfesil prism is attached. Figure 11C is a diagram illustrating a method for measuring the wear width of an Alfesil prism. Figure 12 is an exploded perspective view showing an example of the configuration of a cartridge according to a modified embodiment of one embodiment of the present disclosure.

[0009] Embodiments of this disclosure will be described in the following order: 1. Background leading to the creation of embodiments of this disclosure 2. Cartridge configuration 3. Cartridge memory configuration 4. Magnetic tape configuration 5. Method for manufacturing magnetic tape 6. Effects and benefits 7. Modifications

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

[0011] [1. Background to the Creation of the Embodiments of the Present Disclosure] Tape-shaped magnetic recording media have a substrate with a base layer and a magnetic layer in sequence, and the properties required for each of these layers are different. Therefore, the inventors diligently investigated the factors affecting electromagnetic conversion characteristics and head wear by measuring the physical properties by changing the indentation load of the indenter using a nanoindenter and examining the influence of each layer as seen from the surface on the physical properties. As a result, (1) the average hardness H obtained by pressing a triangular pyramidal diamond indenter with a ridge angle of 142.3° perpendicular to the surface on the magnetic layer side with a load of 50 μN was found. 50 However, it correlates with the electromagnetic conversion characteristics, and (2) the average plastic deformation amount D obtained by pressing a triangular pyramidal diamond indenter perpendicular to the surface on the magnetic layer side with a load of 50 μN 50 However, it was found to be correlated with head wear.

[0012] Therefore, the present inventors have found an average hardness H that can obtain good electromagnetic conversion characteristics. 50 The numerical range and the average plastic deformation amount D can suppress head wear. 50 Further intensive investigation was conducted into the numerical range of H. As a result, the average hardness H 50 The pressure is set to 0.72 GPa or higher, and the average plastic deformation amount D 50 We found that the wavelength should be 16.50 nm or less.

[0013] [2. Cartridge Configuration] Figure 1 is an exploded perspective view showing an example of the configuration of the cartridge 10. The cartridge 10 is a single-reel type cartridge and comprises a cartridge case 12 composed of a lower shell 12A and an upper shell 12B, a reel 13 on which magnetic tape MT is wound, a reel lock 14 and a reel spring 15 for locking the rotation of the reel 13, a spider 16 for releasing the locked state of the reel 13, a sliding door 17 that opens and closes the tape outlet 12C provided in the cartridge case 12 spanning the lower shell 12A and the upper shell 12B, a door spring 18 that biases the sliding door 17 to the closed position of the tape outlet 12C, a write protect 19 for preventing accidental erasure, and a cartridge memory 11. The reel 13 for winding the magnetic tape MT is substantially disc-shaped with an opening in the center and is composed of a reel hub 13A and a flange 13B made of a hard material such as plastic. A leader tape LT is connected to the outer edge of the magnetic tape MT. A leader pin 20 is provided at the tip of the leader tape LT.

[0014] Cartridge 10 may be a magnetic tape cartridge conforming to the LTO (Linear Tape-Open) standard, or it may be a magnetic tape cartridge conforming to a standard other than the LTO standard.

[0015] The cartridge memory 11 is located near one corner of the cartridge 10. When the cartridge 10 is loaded into the recording / playback device, the cartridge memory 11 faces the reader / writer of the recording / playback device. The cartridge memory 11 communicates with the recording / playback device, specifically the reader / writer, using a wireless communication standard compliant with the LTO standard.

[0016] [3. Configuration of Cartridge Memory] Figure 2 is a block diagram showing an example of the configuration of the cartridge memory 11. The cartridge memory 11 includes an antenna coil (communication unit) 31 that communicates with the reader / writer according to a specified communication standard, a rectifier / power supply circuit 32 that generates power by generating and rectifying electricity using induced electromotive force from radio waves received by the antenna coil 31, a clock circuit 33 that generates a clock using induced electromotive force from radio waves received by the antenna coil 31, a detection / modulation circuit 34 that detects the radio waves received by the antenna coil 31 and modulates the signal to be transmitted by the antenna coil 31, a controller (control unit) 35 composed of logic circuits, etc., that distinguishes commands and data from the digital signals extracted from the detection / modulation circuit 34 and processes them, and a memory (storage unit) 36 that stores information. The cartridge memory 11 also includes a capacitor 37 connected in parallel with the antenna coil 31, and a resonant circuit is formed by the antenna coil 31 and the capacitor 37.

[0017] The memory 36 stores information related to the cartridge 10. The memory 36 is a non-volatile memory (NVM). The storage capacity of the memory 36 is preferably about 32 KB or more.

[0018] The memory 36 may have a first storage area 36A and a second storage area 36B. The first storage area 36A corresponds to, for example, the storage area of ​​a cartridge memory of a magnetic tape standard prior to a specified generation (e.g., an LTO standard prior to LTO8), and is an area for storing information compliant with the magnetic tape standard prior to a specified generation. Information compliant with the magnetic tape standard prior to a specified generation may include, for example, manufacturing information (e.g., a unique number for the cartridge 10), usage history (e.g., the number of times the tape has been pulled out (Thread Count)), etc.

[0019] The second storage area 36B corresponds to an extended storage area for the cartridge memory of a magnetic tape standard prior to the specified generation (e.g., LTO standard prior to LTO8). The second storage area 36B is an area for storing additional information. Here, additional information means, for example, information related to the cartridge 10 that is not specified in a magnetic tape standard prior to the specified generation (e.g., LTO standard prior to LTO8). The additional information includes, but is not limited to, at least one type of information selected from the group consisting of, for example, tension adjustment information, management ledger data, index information, and thumbnail information. The tension adjustment information is information for adjusting the tension applied in the longitudinal direction of the magnetic tape MT. The tension adjustment information includes, for example, at least one type of information selected from the group consisting of, for example, information obtained by intermittently measuring the width between servo bands in the longitudinal direction of the magnetic tape MT, drive tension information, and drive temperature and humidity information. This information may also be managed in conjunction with information regarding the usage status of the cartridge 10. It is preferable that the tension adjustment information is acquired when recording data to the magnetic tape MT, or before recording data. Drive tension information refers to information about the tension applied to the magnetic tape (MT) in the longitudinal direction.

[0020] Management ledger data is data that includes at least one type of information selected from a group consisting of the capacity, creation date, editing date, and storage location of data files recorded on magnetic tape MT. Index information is metadata used to search the contents of data files. Thumbnail information is a thumbnail of a video or still image stored on magnetic tape MT.

[0021] The memory 36 may have multiple banks. In this case, a first storage area 36A may be formed by some of the multiple banks, and a second storage area 36B may be formed by the remaining banks.

[0022] The antenna coil 31 induces an induced voltage through electromagnetic induction. The controller 35 communicates with the recording and playback device via the antenna coil 31 using a specified communication standard. Specifically, it performs mutual authentication, sending and receiving commands, or exchanging data.

[0023] The controller 35 stores information received from the recording / playback device via the antenna coil 31 in the memory 36. For example, it stores tension adjustment information received from the recording / playback device via the antenna coil 31 in the second storage area 36B of the memory 36. The controller 35 reads information from the memory 36 in response to a request from the recording / playback device and transmits it to the recording / playback device via the antenna coil 31. For example, in response to a request from the recording / playback device, it reads tension adjustment information from the second storage area 36B of the memory 36 and transmits it to the recording / playback device via the antenna coil 31.

[0024] [4. Structure of Magnetic Tape] Figure 3 is a cross-sectional view showing an example of the structure of a magnetic tape MT. A magnetic tape MT is an example of a tape-shaped magnetic recording medium and comprises a long base body 41, a base layer 42 provided on one main surface (first main surface) of the base body 41, a magnetic layer 43 provided on the base layer 42, and a back layer 44 provided on the other main surface (second main surface) of the base body 41. The base layer 42 and the back layer 44 are provided as needed and may be omitted. The magnetic tape MT may be a vertical recording type magnetic recording medium or a longitudinal recording type magnetic recording medium. From the viewpoint of improving runability, the magnetic tape MT contains a lubricant on the surface on the magnetic layer 43 side. In this specification, the surface on the magnetic layer 43 side of the magnetic tape MT is sometimes referred to as the magnetic surface, and the surface on the back layer 44 side of the magnetic tape MT is sometimes referred to as the back surface.

[0025] The magnetic tape MT may conform to the LTO standard or may conform to a standard different from the LTO standard. The width of the magnetic tape MT may be 1 / 2 inch, or may be wider than 1 / 2 inch. When the magnetic tape MT conforms to the LTO standard, the width of the magnetic tape MT is 1 / 2 inch. The magnetic tape MT may have a configuration capable of keeping the width of the magnetic tape MT constant or substantially constant by adjusting the tension applied in the longitudinal direction of the magnetic tape MT during running by a recording and reproducing device (drive).

[0026] The magnetic tape MT has a long shape and runs in the longitudinal direction during recording and reproduction. The magnetic tape MT is preferably used in a recording and reproducing device provided with a ring head as a recording head. The magnetic tape MT is configured to be able to record a signal at a linear recording density D. The lower limit value of the linear recording density D of the signal that can be recorded on the magnetic tape MT is preferably 545 kfci or more, more preferably 549 kfci or more, still more preferably 550 kfci or more, 552 kfci or more, 577 kfci or more, 600 kfci or more, or 635 kfci or more from the viewpoint of increasing the recording capacity. The upper limit value of the linear recording density D of the data that can be recorded on the magnetic tape MT is preferably 1270 kfci or less in consideration of the magnetic particle size.

[0027] The magnetic tape MT is preferably reproduced by a reproducing head using a tunnel magnetoresistance (TMR) element. The signal reproduced by the reproducing head using the TMR element may be data recorded in a data band DB (see FIG. 4) or a servo pattern (servo signal) recorded in a servo band SB (see FIG. 4).

[0028] (Substrate) The substrate 41 is a non-magnetic support that supports the underlayer 42 and the magnetic layer 43. The substrate 41 has a long film shape. The average thickness t of the substrate 41 １The upper limit of the substrate 41 is preferably 4.40 μm or less, more preferably 4.20 μm or less, even more preferably 4.00 μm or less, 3.80 μm or less, or 3.40 μm or less, from the viewpoint of improving the recording capacity that can be recorded on one data cartridge. １ The lower limit is preferably 3.00 μm or more, more preferably 3.20 μm or more, and even more preferably 3.80 μm or more. Average thickness t of the substrate 41 １ If the lower limit is 3.00 μm or more, the decrease in strength of the substrate 41 can be suppressed.

[0029] Average thickness t of the substrate 41 １ The following is how it is obtained. First, the magnetic tape MT housed in the cartridge 10 is unwound, and a sample is prepared by cutting the magnetic tape MT to a length of 250 mm at a position 30 m to 40 m in the longitudinal direction from one end on the outer circumference of the magnetic tape MT. In this specification, "longitudinal direction" when referring to "from one end on the outer circumference of the magnetic tape MT" means the direction from one end on the outer circumference of the magnetic tape MT toward the other end on the inner circumference.

[0030] Next, the layers of the sample other than the substrate 41 (i.e., the underlayer 42, magnetic layer 43, and backing layer 44) are removed with a solvent such as MEK (methyl ethyl ketone) or dilute hydrochloric acid. Then, using a Mitutoyo laser hologage (LGH-110C) as a measuring device, the thickness of the sample (substrate 41) is measured at five points, and these measurements are simply averaged (arithmetic mean) to obtain the average thickness t of the substrate 41. １ The following is calculated. The five measurement points mentioned above will be randomly selected from the sample so that they are all at different positions along the longitudinal direction of the magnetic tape MT.

[0031] From the viewpoint of cost reduction, the base material 41 preferably contains a polyester resin as its main component. The polyester resin includes, for example, at least one selected from the group consisting of PET (polyethylene terephthalate) resin, PEN (polyethylene naphthalate) resin, PBT (polybutylene terephthalate) resin, PBN (polybutylene naphthalate) resin, PCT (polycyclohexylene dimethylene terephthalate) resin, PEB (polyethylene-p-oxybenzoate) resin, and polyethylene bisphenoxycarboxylate resin. If the base material 41 contains two or more polyester resins, these two or more polyester resins may be mixed, copolymerized, or laminated. At least one of the terminals and side chains of the polyester resin may be modified. In addition to the polyester resin, the base material 41 may also contain resins other than the polyester resins described later.

[0032] In this specification, "main component" means the component that has the highest content among the components constituting the substrate 41. For example, if the main component of the substrate 41 is a polyester resin, the content of the polyester resin in the substrate 41 may be, for example, 50% or more by mass, 60% or more by mass, 70% or more by mass, 80% or more by mass, 90% or more by mass, 95% or more by mass, or 98% or more by mass relative to the mass of the substrate 41, or the substrate 41 may be composed solely of a polyester resin.

[0033] The presence of a polyester resin in the substrate 41 can be confirmed, for example, as follows: First, the average thickness t of the substrate 41. １ Similar to the measurement method, a magnetic tape MT is prepared, cut to a length of 250 mm, and a sample is prepared. After that, layers other than the substrate 41 of the sample are removed. Next, the IR spectrum of the sample (substrate 41) is obtained by infrared absorption spectroscopy (IR). Based on this IR spectrum, it can be confirmed that the substrate 41 contains a polyester resin.

[0034] The substrate 41 preferably contains a polyester resin. By including a polyester resin in the substrate 41, the Young's modulus in the longitudinal direction of the substrate 41 can be reduced, preferably to 2.5 GPa or more and 7.8 GPa or less, more preferably to 3.0 GPa or more and 7.0 GPa or less. Therefore, by adjusting the longitudinal tension of the magnetic tape MT during operation using the recording and playback device, the width of the magnetic tape MT can be kept constant or nearly constant. The method for measuring the Young's modulus in the longitudinal direction of the substrate 41 will be described later.

[0035] The substrate 41 may contain resins other than polyester resins. In this case, the resins other than polyester resins may be the main components of the constituent materials of the substrate 41. When the resins other than polyester resins are the main components of the constituent materials of the substrate 41, the content of the resins other than polyester resins in the substrate 41 may be, for example, 50% or more by mass, 60% or more by mass, 70% or more by mass, 80% or more by mass, 90% or more by mass, 95% or more by mass, or 98% or more by mass relative to the mass of the substrate 41, or the substrate 41 may be composed solely of resins other than polyester resins. The resins other than polyester resins include, for example, at least one selected from the group consisting of polyolefin resins, cellulose derivative resins, vinyl resins, and other polymer resins. When the substrate 41 contains two or more of these resins, the two or more materials may be mixed, copolymerized, or laminated.

[0036] Polyolefin resins include, for example, at least one selected from the group consisting of PE (polyethylene) resins and PP (polypropylene) resins. Cellulose derivative resins include, for example, at least one selected from the group consisting of cellulose diacetate resins, cellulose triacetate resins, CAB (cellulose acetate butyrate) resins, and CAP (cellulose acetate propionate) resins. Vinyl resins include, for example, at least one selected from the group consisting of PVC (polyvinyl chloride) resins and PVDC (polyvinylidene chloride) resins.

[0037] Other polymer resins include, for example, at least one selected from the group consisting of PEEK (polyether ether ketone) resins, PA (polyamide, nylon) resins, aromatic PA (aromatic polyamide, aramid) resins, PI (polyimide) resins, aromatic PI (aromatic polyimide) resins, PAI (polyamide imide) resins, aromatic PAI (aromatic polyamide imide) resins, PBO (polybenzoxazole, e.g., Zylon®) resins, polyether resins, PEK (polyether ketone) resins, polyether ester resins, PES (polyethersulfone) resins, PEI (polyetherimide) resins, PSF (polysulfone) resins, PPS (polyphenylene sulfide) resins, PC (polycarbonate) resins, PAR (polyarylate) resins, and PU (polyurethane) resins. Specifically, for example, the base material 41 may mainly contain PEEK (polyether ether ketone) resin, PA (polyamide, nylon) resin, aromatic PA (aromatic polyamide, aramid) resin, PI (polyimide) resin, aromatic PI (aromatic polyimide) resin, PAI (polyamide imide) resin, aromatic PAI (aromatic polyamide imide) resin, PBO (polybenzoxazole, e.g., Zylon®) resin, polyether resin, PEK (polyether ketone) resin, polyether ester resin, PES (polyether sulfone) resin, PEI (polyetherimide) resin, PSF (polysulfone) resin, PPS (polyphenylene sulfide) resin, PC (polycarbonate) resin, PAR (polyarylate) resin, or PU (polyurethane) resin.

[0038] The substrate 41 may be biaxially stretched in the longitudinal and width directions. Preferably, the polymer resin contained in the substrate 41 is oriented obliquely to the width direction of the substrate 41.

[0039] (Magnetic layer) The magnetic layer 43 is configured to record signals by a magnetization pattern. The magnetic layer 43 may be a vertical recording type recording layer or a longitudinal recording type recording layer. The magnetic layer 43 includes, for example, magnetic particles and a binder. The magnetic layer 43 may further include, if necessary, at least one additive selected from the group consisting of lubricants, dispersants, carbon particles, abrasive particles, antistatic agents, hardening agents, rust inhibitors, and non-magnetic reinforcing particles. The magnetic layer 43 may have a plurality of protrusions on its magnetic surface. The plurality of protrusions are formed, for example, by carbon particles and abrasive particles protruding from the magnetic surface.

[0040] The magnetic layer 43 may have a plurality of pores on its surface. Lubricant may be stored in the pores. In this case, the supply of lubricant to the magnetic surface can be improved. From the viewpoint of improving the supply of lubricant to the magnetic surface, it is preferable that the pores extend perpendicular to the magnetic surface.

[0041] The magnetic layer 43 may have a plurality of servo bands SB and a plurality of data bands DB, as shown in Figure 4. The plurality of servo bands SB are provided at equal intervals in the width direction of the magnetic tape MT. Data bands DB are provided between adjacent servo bands SB. The servo bands SB are for guiding the head unit (magnetic head) 56 (specifically, servo read heads 56A, 56B) when recording or playing back data. Servo patterns (servo signals) for tracking control of the head unit 56 are prewritten on the servo bands SB. User data is recorded on the data bands DB.

[0042] In order to read the asymmetric servo stripe 113 (see Figure 6) described later, the head unit 56 may be configured to be maintained at an angle with respect to the axis Ax extending in the width direction of the magnetic tape MT during data recording and playback, as shown in Figure 4. Hereinafter, the head unit 56 maintained at an angle with respect to the axis Ax extending in the width direction of the magnetic tape MT in this manner may be referred to as the "angled head unit 56". The inclination angle of the head unit 56 with respect to the axis Ax extending in the width direction of the magnetic tape MT is preferably 3° to 18°, more preferably 5° to 15°.

[0043] The total area S of multiple servo bands SB relative to the area S of the magnetic surface. ＳＢ Ratio R Ｓ (=(S ＳＢ The upper limit of (S) × 100) is preferably 4.0% or less, more preferably 3.5% or less, and even more preferably 3.0% or less, from the viewpoint of ensuring high recording capacity. On the other hand, the total area S of the multiple servo bands SB relative to the area S of the magnetic surface. ＳＢ Ratio R Ｓ The lower limit is preferably 1.0% or more, from the viewpoint of ensuring a servo band SB of 5 or more.

[0044] The total area S of multiple servo bands SB relative to the total area S of the magnetic surface ＳＢ Ratio R Ｓ The servobandwidth W is determined as follows: A magnetic tape MT is developed using a ferricolloid developer (Sigma Marker Q, manufactured by Sigma Hi-Chemical Co., Ltd.), and then the developed magnetic tape MT is observed with an optical microscope. ＳＢ Then, measure the number of servo bands SB. Next, calculate the ratio R from the following formula. Ｓ We find the ratio R. Ｓ [%] = (((Servobandwidth W ＳＢ ) × (Number of servo bands SB) / (Width of magnetic tape MT) × 100

[0045] The number of servo bands SB is, for example, 5 + 4n (where n is a non-negative integer) or more. Preferably, the number of servo bands SB is 5 or more, more preferably 9 or more. When the number of servo bands SB is 5 or more, the influence of changes in the width direction of the magnetic tape MT on the servo signal is suppressed, and more stable recording and playback characteristics with fewer off-tracks can be ensured. There is no particular upper limit to the number of servo bands SB, but for example, it is 33 or less.

[0046] The number of servo bands SB is the ratio R mentioned above. Ｓ It can be calculated in the same way as the calculation method for [another calculation].

[0047] Servo bandwidth W ＳＢ The upper limit of the servo bandwidth W is preferably 95 μm or less, more preferably 65 μm or less, and even more preferably 50 μm or less, from the viewpoint of ensuring high recording capacity. ＳＢ The lower limit is preferably 10 μm or more. Servo bandwidth W less than 10 μm ＳＢ A magnetic head capable of reading the servo signal is difficult to manufacture.

[0048] Servo bandwidth W ＳＢ The width is the ratio R mentioned above. Ｓ It can be calculated in the same way as the calculation method for [another calculation].

[0049] As shown in Figure 5A, the magnetic layer 43 is configured to form multiple data tracks Tk in the data band DB. The upper limit of the data track width W is preferably 1000 nm or less, more preferably 700 nm or less, and even more preferably 650 nm or less, 500 nm or less, or 400 nm or less, from the viewpoint of improving track recording density and ensuring high recording capacity. The lower limit of the data track width W is preferably 20 nm or more, considering the size of the magnetic particles.

[0050] The data track width W is determined as follows. First, a cartridge 10 on which data is recorded across the entire surface of a magnetic tape MT is prepared. The magnetic tape MT is unwound from this cartridge 10, and a 250 mm length of the magnetic tape MT is cut from one end of the outer circumference of the magnetic tape MT at a position 30 m to 40 m in the longitudinal direction to prepare a sample. Next, the data recording pattern of the data band DB portion of the magnetic layer 43 of the sample is observed using a magnetic force microscope (MFM) to obtain an MFM image. BRUKER's Dimension Icon and its analysis software are used as the MFM. The measurement area of ​​the MFM image is set to 10 μm × 10 μm, and this 10 μm × 10 μm measurement area is divided into 512 × 512 (= 262,144) measurement points. Measurements are performed using the MFM on three different 10 μm × 10 μm measurement areas, thus obtaining three MFM images. For each of the three obtained MFM images, the track width is measured at 10 locations, resulting in a total of 30 measurements. The average value (simple average) of these 30 measurements is then calculated. This average value is the data track width W. The analysis software included with Dimension Icon is used to measure the track width. The MFM measurement conditions are as follows: sweep speed: 1 Hz, chip used: MFMR-20, lift height: 20 nm, correction: Flatten order 3.

[0051] Although Figure 5A shows an example where adjacent data tracks Tk are recorded without overlapping, the recording method for data tracks Tk is not limited to this example. For example, as shown in Figure 5B, a Shingled Magnetic Recording (SMR) method may be used to record adjacent data tracks Tk so that parts of them overlap in the width direction of the magnetic tape MT.

[0052] In Figure 5B, heads 61 and 62 represent the recording head and playback head, respectively. In the case of magnetic recording, the data track width W is the recording track width W ＲIt becomes narrower compared to the recording head 61. Therefore, in the case of magnetic recording, the width of the playback head 62 is narrower than the width of the recording head 61. As described above, in the magnetic recording method, the data track width W is narrower than the recording track width W. Ｒ Since it is narrower compared to, it is advantageous in terms of improving recording density. Here, the recording track width W Ｒ This represents the track width during data writing. When magnetic recording is used as the recording method, the recording track width W is used. Ｒ This represents the track width before overwriting (the track width when data is written).

[0053] The magnetic layer 43 has a minimum value L for the distance between magnetization reversals. min The system is configured to record signals. Minimum value L of the magnetization reversal distance. min The upper limit of is preferably 46.6 nm or less, more preferably 46.3 nm or less, even more preferably 46.2 nm or less, 46.0 nm or less, 44.0 nm or less, 42.3 nm or less, or 40.0 nm or less, from the viewpoint of increasing recording capacity. Minimum value L of the magnetization reversal distance min The lower limit is preferably 20.0 nm or more, taking into account the size of the magnetic particles.

[0054] Minimum value L of the distance between magnetization reversals minThe minimum value L of the magnetization reversal distance is obtained as follows. First, a sample is prepared in the same manner as the measurement method for the data track width W. Next, the data recording pattern of the data band DB portion of the magnetic layer 43 of the sample is observed using a magnetic force microscope (MFM) to obtain an MFM image. BRUKER's Dimension Icon and its analysis software are used as the MFM. The measurement area of ​​the MFM image is 2 μm × 2 μm, and this 2 μm × 2 μm measurement area is divided into 512 × 512 (= 262,144) measurement points. MFM measurements are performed on three different 2 μm × 2 μm measurement areas, thus obtaining three MFM images. Fifty inter-bit distances are measured from the two-dimensional relief chart of the recording pattern of the obtained MFM image. These inter-bit distance measurements are performed using the analysis software included with Dimension Icon. The value that is approximately the greatest common divisor of the 50 measured inter-bit distances is the minimum value L of the magnetization reversal distance. min The measurement conditions were as follows: sweep speed: 1 Hz, chip used: MFMR-20, lift height: 20 nm, correction: Flatten order 3.

[0055] The magnetic layer 43 is configured to record signals in the data band DB with a bit length (1 bit length) T. From the viewpoint of improving the linear recording density D of the magnetic tape MT, the upper limit of the bit length T of the signal that can be recorded in the data band DB is preferably 47.0 nm or less, more preferably 46.6 nm or less, even more preferably 46.3 nm or less, 46.2 nm or less, 46.0 nm or less, 44.0 nm or less, 42.3 nm or less, or 40.0 nm or less. Considering the size of the magnetic particles, the lower limit of the bit length T of the signal that can be recorded in the data band DB is preferably 20.0 nm or more.

[0056] The bit length T of the signal that can be recorded in the databand DB is the minimum value L of the magnetization reversal distance. min It can be determined in the same way as the measurement method.

[0057] From the viewpoint of improving the linear recording density D of the magnetic tape MT, the bit area of ​​the signal that can be recorded in the data band DB is preferably 40,000 nm. ２More preferably, 35,000 nm ２ More preferably, 30,000 nm ２ Below, 25000nm ２ or less than 20,000 nm ２ The following applies:

[0058] The bit area of ​​a signal that can be recorded in the databand DB is determined as follows: First, three MFM images are obtained in the same manner as the method for measuring the data track width W. Next, the data track width W and bit length T are determined in the same manner as the methods for measuring the data track width W and bit length T. Then, the bit area (W × T) of the signal that can be recorded in the databand DB is determined using the data track width W and bit length T.

[0059] The servo pattern is a magnetized region formed by magnetizing a specific region of the magnetic layer 43 in a specific direction using a servo light head during magnetic tape manufacturing. The region of the servo band SB in which the servo pattern is not formed (hereinafter referred to as the "non-pattern region") may be a magnetized region in which the magnetic layer 43 is magnetized, or it may be a non-magnetized region in which the magnetic layer 43 is not magnetized. If the non-pattern region is a magnetized region, the servo pattern formation region and the non-pattern region are magnetized in different directions (for example, opposite directions).

[0060] In the LTO standard, the servo band SB has a servo pattern formed on it, consisting of multiple servo stripes (linear magnetized regions) 113 that are inclined with respect to the axis Ax extending in the width direction of the magnetic tape MT, as shown in Figure 6.

[0061] The servo band SB includes multiple servo frames 110. Each servo frame 110 consists of 18 servo stripes 113. Specifically, each servo frame 110 consists of a servo subframe 1 (111) and a servo subframe 2 (112).

[0062] The servo subframe 1 (111) consists of an A-burst 111A and a B-burst 111B. The B-burst 111B is positioned adjacent to the A-burst 111A. The A-burst 111A is positioned at a predetermined angle θ with respect to the axis Ax extending in the width direction of the magnetic tape MT. １ It is equipped with five servo stripes 113 that are inclined and formed at predetermined intervals. In Figure 6, these five servo stripes 113 are arranged from the EOT (End Of Tape) to the BOT (Beginning Of Tape) of the magnetic tape MT, indicated by the symbol A １ A ２ A ３ A ４ A ５ It is indicated by the notation.

[0063] The B-burst 111B is at a predetermined angle θ with respect to the axis Ax extending in the width direction of the magnetic tape MT. ２ It is equipped with five servo stripes 113 that are inclined and formed at specified intervals. In Figure 6, these five servo stripes 113 are connected to the magnetic tape MT from EOT to BOT, indicated by the letter B １ , B ２ , B ３ , B ４ , B ５ It is indicated by the notation.

[0064] The servo stripe 113 of the B-burst 111B is inclined in the opposite direction to the servo stripe 113 of the A-burst 111A. The servo stripe 113 of the A-burst 111A and the servo stripe 113 of the B-burst 111B are asymmetrical with respect to the axis Ax that extends in the width direction of the magnetic tape MT. That is, the servo stripe 113 of the A-burst 111A and the servo stripe 113 of the B-burst 111B are arranged in a roughly V-shape. Because the servo stripe 113 of the A-burst 111A and the servo stripe 113 of the B-burst 111B are asymmetrical with respect to the axis Ax, when the head unit 56 is tilted diagonally with respect to the axis Ax, there exists a state in which the servo stripe 113 of the A-burst 111A and the servo stripe 113 of the B-burst 111B are roughly symmetrical with respect to the central axis of the sliding surface of the head unit 56. By changing the tilt of the head unit 56 based on this state, it becomes possible to adjust the distance between the servo lead heads 56A and 56B in the width direction of the magnetic tape MT. Therefore, in both cases where the width of the magnetic tape MT is increased and where the width of the magnetic tape MT is decreased, the servo lead heads 56A and 56B can be positioned to face the specified position of the servo band SB. Note that the central axis of the sliding surface of the head unit 56 refers to the axis that passes through the centers of the multiple servo lead heads 56A and 56B on the sliding surface of the head unit 56.

[0065] The predetermined angle θ is the inclination angle of the servo stripe 113 of the A-burst 111A. １ And, the predetermined angle θ is the inclination angle of the servo stripe 113 of the B-burst 111B. ２ This is different. More specifically, the predetermined angle θ of the servo stripe 113 of the A-burst 111A １ However, the predetermined angle θ of the servo stripe 113 of B burst 111B ２ It may be larger in comparison, and the predetermined angle θ of the servo stripe 113 of B burst 111B ２ However, the predetermined angle θ of the servo stripe 113 of the A-burst 111A １It may be larger than the angle of the servo stripe 113 of the A-burst 111A. That is, the inclination of the servo stripe 113 of the A-burst 111A may be larger than the inclination of the servo stripe 113 of the B-burst 111B, and the inclination of the servo stripe 113 of the B-burst 111B may be larger than the inclination of the servo stripe 113 of the A-burst 111A. Note that in Figure 6, the predetermined angle θ of the servo stripe 113 of the A-burst 111A １ However, the predetermined angle θ of the servo stripe 113 of B burst 111B ２ A larger example is shown below. Below, the predetermined angle θ of the servo stripe 113 of the A-burst 111A １ However, the predetermined angle θ of the servo stripe 113 of B burst 111B ２ Let's explain the case where it is larger than [the specified value].

[0066] The servo subframe 2 (112) consists of a C-burst 112C and a D-burst 112D. The D-burst 112D is positioned adjacent to the C-burst 112C. The C-burst 112C is positioned at a predetermined angle θ with respect to the axis Ax extending in the width direction of the magnetic tape MT. １ It is equipped with four servo stripes 113 that are inclined and formed at predetermined intervals. In Figure 6, these four servo stripes 113 are connected to the magnetic tape MT from EOT to BOT, indicated by the letter C １ , C ２ , C ３ , C ４ It is indicated by the notation.

[0067] The D-burst 112D is at a predetermined angle θ with respect to the axis Ax extending in the width direction of the magnetic tape MT. ２ It is equipped with four servo stripes 113 that are inclined and formed at predetermined intervals. In Figure 6, these four servo stripes 113 are shown with the magnetic tape MT from EOT to BOT indicated by the symbol D １ , D ２ , D ３ , D ４ It is indicated by the notation.

[0068] The servo stripe 113 of the D-burst 112D is inclined in the opposite direction to the servo stripe 113 of the C-burst 112C. The servo stripe 113 of the C-burst 112C and the servo stripe 113 of the D-burst 112D are asymmetrical with respect to the axis Ax that extends in the width direction of the magnetic tape MT. That is, the servo stripe 113 of the C-burst 112C and the servo stripe 113 of the D-burst 112D are arranged in a roughly V-shape. Because the servo stripe 113 of the C-burst 112C and the servo stripe 113 of the D-burst 112D are asymmetrical with respect to the axis Ax, when the head unit 56 is tilted diagonally with respect to the axis Ax, there exists a state in which the servo stripe 113 of the C-burst 112C and the servo stripe 113 of the D-burst 112D are roughly symmetrical with respect to the central axis of the head unit 56. By changing the tilt of the head unit 56 based on this state, it becomes possible to adjust the distance between the servos.

[0069] The predetermined angle θ is the inclination angle of the servo stripe 113 of the C-burst 112C. １ And the predetermined angle θ is the inclination angle of the servo stripe 113 of the D-burst 112D. ２ This is different. More specifically, the predetermined angle θ of the servo stripe 113 of the C burst 112C １ However, the predetermined angle θ of the servo stripe 113 of the D-burst 112D ２ It may be larger in comparison, and the predetermined angle θ of the servo stripe 113 of D-burst 112D ２ However, the predetermined angle θ of the servo stripe 113 of the C burst 112C １ It may be larger than the angle of the servo stripe 113 of the C-burst 112C. That is, the inclination of the servo stripe 113 of the C-burst 112C may be larger than the inclination of the servo stripe 113 of the D-burst 112D, and the inclination of the servo stripe 113 of the D-burst 112D may be larger than the inclination of the servo stripe 113 of the C-burst 112C. In Figure 6, the predetermined angle θ of the servo stripe 113 of the C-burst 112C. １ However, the predetermined angle θ of the servo stripe 113 of the D-burst 112D ２Examples larger than [comparison target] are shown. Below, a predetermined angle θ of the servo stripe 113 of the C burst 112C １ is larger than a predetermined angle θ of the servo stripe 113 of the D burst 112D ２ will be described.

[0070] The above-mentioned predetermined angle θ of the servo stripe 113 in the A burst 111A and the C burst 112C １ is preferably 18° or more and 28° or less, more preferably 18° or more and 26° or less. The above-mentioned predetermined angle θ of the servo stripe 113 in the B burst 111B and the D burst 112D ２ is preferably -4° or more and 6° or less, more preferably -2° or more and 6° or less. The servo stripes 113 in the A burst 111A and the C burst 112C are an example of the first magnetization region. The servo stripes 113 in the B burst 111B and the D burst 112D are an example of the second magnetization region.

[0071] By reading the servo band SB with the head unit 56, information for obtaining the tape speed and the vertical position of the head unit 56 is obtained. The tape speed is calculated from the time between four timing signals (A1 - C1, A2 - C2, A3 - C3, A4 - C4). The head position is calculated from the time between the aforementioned four timing signals and another four timing signals (A １ -B １ , A ２ -B ２ , A ３ -B ３ , A ４ -B ４ ). The servo pattern may be in a shape including two parallel lines.

[0072] As shown in FIG. 6, the servo pattern (that is, a plurality of servo stripes 113) is preferably arranged linearly in the longitudinal direction of the magnetic tape MT. That is, the servo band SB preferably has a linear shape in the longitudinal direction of the magnetic tape MT.

[0073] The average thickness t of the magnetic layer 43 ２The upper limit is 0.07 μm or less, preferably 0.06 μm or less, and more preferably 0.05 μm or less. Average thickness t of the magnetic layer 43 ２ If the upper limit is 0.07 μm or less, the effect of the demagnetizing field can be reduced when a ring-type head is used as the recording head, thereby obtaining excellent electromagnetic conversion characteristics.

[0074] Average thickness t of the magnetic layer 43 ２ The lower limit is preferably 0.03 μm or more, more preferably 0.04 μm or more. Average thickness t of the magnetic layer 43 ２ If the lower limit is 0.03 μm or higher, output can be secured when an MR type head is used as the playback head, thus obtaining excellent electromagnetic conversion characteristics.

[0075] Average thickness t of the magnetic layer 43 ２ The numerical range may be defined by either of the above upper limits and either of the above lower limits, preferably 0.03 μm or more and 0.07 μm or less, more preferably 0.03 μm or more and 0.06 μm or less, and even more preferably 0.03 μm or more and 0.05 μm or less.

[0076] Average thickness t of the magnetic layer 43 ２ The following is how it is obtained. First, the magnetic tape MT housed in the cartridge 10 is unwound, and three samples are prepared by cutting the magnetic tape MT to a length of 250 mm from one end of the outer circumference of the magnetic tape MT at positions 10 m to 20 m, 30 m to 40 m, and 50 m to 60 m in the longitudinal direction. Next, each sample is processed by the FIB (Focused Ion Beam) method or the like to create a thin section. 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 magnetic surface and back surface of the magnetic tape MT by vapor deposition, and the tungsten layer is further formed on the magnetic surface by vapor deposition or sputtering. This thinning is performed along the longitudinal direction of the magnetic tape MT. That is, this thinning creates a cross section parallel to both the longitudinal and thickness directions of the magnetic tape MT.

[0077] The cross-sections of each thinned sample obtained were observed using a transmission electron microscope (TEM) under the following conditions to obtain TEM images of each thinned sample. The magnification and acceleration voltage may be adjusted as appropriate depending on the type of instrument. Instrument: TEM (Hitachi H9000NAR) Acceleration voltage: 300kV Magnification: 100,000x

[0078] Next, the TEM images of each thinned sample are used to measure the thickness of the magnetic layer 43 at 10 points on each thinned 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 MT. The average value obtained by simply averaging (arithmetic mean) the measured values ​​of each thinned sample (a total of 30 points of magnetic layer 43 thickness) is then used to determine the average thickness t of the magnetic layer 43. ２ Let it be [nm].

[0079] (Magnetic Particles) The magnetic particles are ferrite particles. The ferrite particles may include, for example, particles containing hexagonal ferrite (hereinafter referred to as "hexagonal ferrite particles"), particles containing epsilon-type iron oxide (ε-iron oxide) (hereinafter referred to as "ε-iron oxide particles"), or particles containing Co-containing spinel ferrite (hereinafter referred to as "cobalt ferrite particles"). It is preferable that the magnetic particles are preferentially crystallinely oriented in the direction perpendicular to the magnetic tape MT. In this specification, the direction perpendicular to the magnetic tape MT (thickness direction) means the thickness direction of the magnetic tape MT in a planar state.

[0080] (Hexagonal ferrite particles) Hexagonal ferrite particles have a plate-like shape, such as a hexagonal plate, or a columnar shape, such as a hexagonal prism (provided that the thickness or height is smaller than the major axis of the plate surface or base surface). In this disclosure, hexagonal plate-like shape includes a substantially hexagonal plate-like shape. Also, hexagonal prism-like shape includes a substantially hexagonal prism-like shape.

[0081] The hexagonal ferrite particles contain Fe and a metal M1 other than Fe. The metal M1 includes, for example, at least one alkaline earth metal. The at least one alkaline earth metal includes, for example, at least one selected from the group consisting of Ba, Sr, and Ca. It is preferable that it includes at least one of Ba and Sr among these alkaline earth metals. The metal M1 may also contain Pb in addition to alkaline earth metals.

[0082] The hexagonal ferrite particles may further contain metal M2 in addition to Fe and metal M1. Preferably, metal M2 can substitute for some of the Fe sites in the crystal structure of the hexagonal ferrite. For example, metal M2 includes at least one selected from the group consisting of rare earth elements, transition metal elements other than Fe, and metal elements of Group 13 of the periodic table, and among these, at least one selected from the group consisting of Ti, Al, and Nd is preferred.

[0083] In this disclosure, rare earth elements refer to Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. Transition metal elements other than Fe refer to Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Zr, Nb, Mo, Ru, Hf, Ta, and W. Metal elements of Group 13 of the periodic table refer to Al, Ga, In, and Tl.

[0084] Hexagonal ferrite particles may specifically be, for example, barium ferrite particles or strontium ferrite particles. In this disclosure, strontium ferrite particles refer to hexagonal ferrite particles in which the average atomic ratio of Sr to metal M1 (Sr / M1) is 50 atomic percent or more. Therefore, hexagonal ferrite particles containing Sr and a metal M1 other than Sr are included in strontium ferrite particles if the average atomic ratio of Sr to metal M1 (Sr / M1) is 50 atomic percent or more. For example, when metal M1 contains Sr and Ba, hexagonal ferrite particles in which the average atomic ratio of Sr to the total amount of Sr and Ba (Sr / (Sr+Ba)) is 50 atomic percent or more are called strontium ferrite particles.

[0085] In this disclosure, barium ferrite particles refer to hexagonal ferrite particles in which the average atomic ratio of Ba to metal M1 (Ba / M1) is 50 atomic percent or more. Therefore, hexagonal ferrite particles containing Ba and metal M1 other than Ba ​​are included in barium ferrite particles if the average atomic ratio of Ba to metal M1 (Ba / M1) is 50 atomic percent or more. For example, when metal M1 contains Sr and Ba, hexagonal ferrite particles in which the average atomic ratio of Ba to the total amount of Sr and Ba (Ba / (Sr+Ba)) is 50 atomic percent or more are called barium ferrite particles.

[0086] The average atomic ratio of Sr to Ba (Sr / Ba) is preferably 0.02 to 2.00, and more preferably 0.02 to 1.00. When the average atomic ratio (Sr / Ba) is 0.02 or higher, the decrease in the effect of improving magnetic properties due to the addition of Sr (for example, the effect of improving the thermal stability (Ku) derived from strontium ferrite) can be suppressed. When the average atomic ratio (Sr / Ba) is 2.00 or lower, variations in magnetic properties can be suppressed.

[0087] Hexagonal ferrite may more specifically have an average composition represented by the following general formula (A): Ba （１－ｘ） α ｘ Fe （１２－ｙ） β ｙ O １９ ... (A) (However, in formula (A), α represents at least one selected from the group consisting of Sr, Ca, and Pb. β represents at least one selected from the group consisting of rare earth elements, transition metal elements other than Fe, and metal elements of Group 13 of the periodic table. x is in the range of 0 ≤ x ≤ 0.9, preferably 0 ≤ x ≤ 0.7, and more preferably 0.3 ≤ x ≤ 0.7. y represents 0 ≤ y ≤ 0.80, preferably 0.22 ≤ y ≤ 0.80, and more preferably 0.26 ≤ y ≤ 0.80.)

[0088] The average atomic ratio of Sr to Ba is calculated from the analysis values ​​obtained using TEM-EDX (Transmission Electron Microscope - Energy Dispersive X-ray Spectroscopy) (Hitachi High-Technologies Corporation HD-2700) as follows. First, the magnetic tape MT is unwound from the cartridge 10, and three pieces of the magnetic tape MT are cut from one end on the outer circumference of the magnetic tape MT at a position of 30m to 40m in the longitudinal direction to prepare three samples. Next, each sample 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 described later. The carbon layer is formed on the magnetic layer side surface and the back layer side surface of the magnetic tape MT 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 longitudinal direction of the magnetic tape MT. In other words, this thinning process creates cross-sections parallel to both the longitudinal and thickness directions of the magnetic tape MT. The above cross-sections of each thinned sample are observed by TEM at an acceleration voltage of 200kV and a total magnification of 500,000x to obtain TEM images of each thinned sample. Next, EDX measurements are performed on the magnetic layer portion from the TEM images of each thinned sample to determine the atomic ratio of Sr to Ba (Sr / Ba). The atomic ratios (Sr / Ba) obtained from each of the three thinned samples are simply averaged (arithmetic mean) to obtain the average atomic ratio (Sr / Ba).

[0089] The average atomic ratio of Sr to metal M1 (Sr / M1) is determined as follows: First, TEM images are obtained from three thinned samples in the same manner as the average atomic ratio of Sr to Ba (Sr / Ba). Next, EDX measurements are performed on the magnetic layer portion from the TEM images obtained from each thinned sample to determine the average atomic ratio of Sr to metal M1 (Sr / M1). The atomic ratios (Sr / M1) obtained from each of the three thinned samples are simply averaged (arithmetic mean) to obtain the average atomic ratio (Sr / M1).

[0090] The average atomic ratio of Ba to metal M1 (Ba / M1) is determined as follows: First, TEM images are obtained from three thinned samples in the same manner as the average atomic ratio of Sr to Ba (Sr / Ba). Next, EDX measurements are performed on the magnetic layer portion from the TEM images obtained from each thinned sample to determine the average atomic ratio of Ba to metal M1 (Ba / M1). The atomic ratios (Ba / M1) obtained from each of the three thinned samples are simply averaged (arithmetic mean) to obtain the average atomic ratio (Ba / M1).

[0091] The average composition represented by general formula (A) is determined as follows. First, TEM images of three thinned samples are obtained in the same manner as the average atomic ratio of Sr to Ba (Sr / Ba). Next, EDX measurements are performed on the magnetic layer portion from the TEM images of each obtained thinned sample, and Ba 、 α 、 Fe 、 Determine the average composition ratio (average atomic ratio) of each component of β.

[0092] When the magnetic particles are hexagonal ferrite particles, the upper limit of the average particle size of the magnetic particles is preferably 19.0 nm or less, more preferably 18.0 nm or less, and even more preferably 17.0 nm or less, 16.0 nm or less, or 15.0 nm or less, from the viewpoint of improving linear recording density.

[0093] When the magnetic particles are hexagonal ferrite particles, the lower limit of the average particle size of the magnetic particles is preferably 12.0 nm or larger, and more preferably 13.0 nm or larger, from the viewpoint of improving the dispersibility of the magnetic particles and improving electromagnetic conversion characteristics (e.g., SNR (Signal-to-Noise Ratio)).

[0094] When the magnetic particles are hexagonal ferrite particles, the numerical range of the average particle size of the magnetic particles may be defined by either of the above upper and lower limits, preferably 12.0 nm to 19.0 nm, more preferably 12.0 nm to 18.0 nm, and even more preferably 12.0 nm to 17.0 nm, 13.0 nm to 17.0 nm, or 13.0 nm to 16.0 nm.

[0095] When the magnetic particles are hexagonal ferrite particles, the average aspect ratio of the magnetic particles is preferably 1.0 to 3.0, more preferably 1.5 to 2.8, and even more preferably 1.8 to 2.7. When the average aspect ratio of the magnetic particles is within the range of 1.0 to 3.0, aggregation of the magnetic particles can be suppressed. Furthermore, when the magnetic particles are vertically oriented during the formation process of the magnetic layer 43, the resistance applied to the magnetic particles can be suppressed. Therefore, the vertical orientation of the magnetic particles can be improved.

[0096] When the magnetic particles are hexagonal ferrite particles, the average particle size and average aspect ratio of the magnetic particles are determined as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and the magnetic tape MT is cut at a position 30 to 40 m in the longitudinal direction from one end on the outer circumference of the magnetic tape MT. Next, the magnetic tape MT 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 described later. The carbon layer is formed on the magnetic surface and back surface of the magnetic tape MT by vapor deposition, and the tungsten layer is further formed on the magnetic surface by vapor deposition or sputtering. This thinning is performed along the length direction (longitudinal direction) of the magnetic tape MT. That is, this thinning creates a cross-section parallel to both the longitudinal and thickness directions of the magnetic tape MT.

[0097] 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 43 is included in the thickness direction of the magnetic layer 43, and a TEM image is taken. The TEM images are prepared in a number that allows for the extraction of 50 particles capable of measuring the plate diameter DB and plate thickness DA (see Figure 7) shown below.

[0098] In this specification, the particle size of hexagonal ferrite (hereinafter referred to as "particle size") is determined as follows: If the shape of the particle observed in the TEM image 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 7, the major axis of the plate surface or base is used as the value of plate diameter DB. The thickness or height of the particle observed in the TEM image is used as the value of plate thickness DA. If the thickness or height of a particle is not constant within a single particle observed in the TEM image, the thickness or height of the largest particle is used as plate thickness DA.

[0099] Next, 50 particles are selected from the captured TEM image 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.

[0100] Figures 8 and 9 show the first and second examples of TEM images, respectively. In Figures 8 and 9, for example, the particles indicated by arrows a and d are selected because their particle thickness (thickness or height) DA can be clearly identified. The particle thickness DA of each of the 50 selected particles is measured. The particle thicknesses DA obtained in this way are simply averaged (arithmetic mean) to obtain the average particle thickness DA. ave We will find the average plate thickness DA. ave This is the average particle thickness. Next, the diameter DB of each magnetic particle is measured. To measure the particle diameter DB, 50 particles whose diameter DB can be clearly identified are selected from the captured TEM images. For example, in Figures 8 and 9, 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 DB. ave We will find the average plate diameter DB. ave However, this is the average particle size. And the average plate thickness DA ave and average plate diameter DB aveFrom the average aspect ratio of the particles (DB) ave / DA ave )

[0101] When the magnetic particles are hexagonal ferrite particles, the upper limit of the average particle volume of the magnetic particles is preferably 1.80 × 10⁻¹⁰ from the viewpoint of improving linear recording density. ３ nm ３ More preferably, 1.60 × 10 ３ nm ３ More preferably, 1.40 × 10 ３ nm ３ Below, 1.30 × 10 ３ nm ３ Below, 1.20 × 10 ３ nm ３ Below, 1.10 x 10 ３ nm ３ The following or 1.00 x 10 ３ nm ３ The following applies:

[0102] When the magnetic particles are hexagonal ferrite particles, the lower limit of the average particle volume of the magnetic particles is preferably 0.500 × 10⁻¹⁰, from the viewpoint of improving the dispersibility of the magnetic particles and improving electromagnetic conversion characteristics (e.g., SNR). ３ nm ３ More preferably 0.600 × 10 ３ nm ３ That's all.

[0103] When the magnetic particles are hexagonal ferrite particles, the numerical range of the average particle volume of the magnetic particles may be defined by either of the above upper and lower limits, preferably 0.500 × 10⁻⁶. ３ nm ３ The above 1.80 x 10 ３ nm ３ More preferably, 0.500 × 10 ３ nm ３ The above 1.60 x 10 ３ nm ３ More preferably, 0.500 × 10 ３ nm ３ The above 1.40 x 10 ３ nm ３ Below, 0.500 x 10 ３ nm３ The above 1.30 x 10 ３ nm ３ Below, 0.600 x 10 ３ nm ３ The above 1.20 x 10 ３ nm ３ Below, 0.600 x 10 ３ nm ３ The above 1.10 x 10 ３ nm ３ The following or 0.600 x 10 ３ nm ３ The above 1.00 x 10 ３ nm ３ The following applies:

[0104] The average particle volume of magnetic particles can be determined as follows. First, as described above regarding the method for calculating the average particle size of magnetic particles, the average plate thickness DA ave and average plate diameter DB ave Next, we calculate the average particle volume V of the magnetic particles using the following formula.

[0105] (ε-iron oxide particles) ε-iron oxide particles are hard magnetic particles that can obtain high coercivity even in fine particles. ε-iron oxide particles are either spherical or cubic in shape. In this specification, spherical includes substantially spherical, and cubic includes substantially cubic. Here, substantially cubic includes a shape in which the corners of a cube are rounded. Because ε-iron oxide particles have the shapes described above, when ε-iron oxide particles are used as magnetic particles, the contact area between particles in the thickness direction of the magnetic tape MT can be reduced and particle aggregation can be suppressed compared to when hexagonal plate-shaped barium ferrite particles are used as magnetic particles. Therefore, the dispersibility of the magnetic particles can be improved, and excellent electromagnetic conversion characteristics (e.g., SNR) can be obtained.

[0106] 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 "the portion having soft magnetism, etc.").

[0107] The ε-iron oxide portion contains ε-iron oxide. The ε-iron oxide contained in the ε-iron oxide portion is ε-Fe ２ O ３ A crystalline phase is preferred, and a single-phase ε-Fe ２ O ３ A combination of these is preferable.

[0108] The saturation magnetization σs of the soft magnetic portion is preferably 40 emu / g or more. This suppresses the decrease in the saturation magnetization σs of the composite particles and improves the output characteristics of the magnetic tape MT. The soft magnetic portion is in contact with the ε iron oxide portion in at least a part. 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.

[0109] 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.

[0110] Furthermore, the part having soft magnetism is, for example, Fe ３ O ４ γ-Fe ２ O ３ , or it may contain spinel ferrite, etc.

[0111] 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.

[0112] 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 metal elements other than iron, preferably trivalent metal elements, 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.

[0113] Specifically, ε-iron oxide containing additives is ε-Fe ２－ｘ M ｘ O ３ The material is a 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).

[0114] When the magnetic particles are ε-iron oxide particles, the upper limit of the average particle size of the magnetic particles is preferably 15.0 nm or less, more preferably 14.5 nm or less, and even more preferably 13.5 nm or less, 12.5 nm or less, or 12.0 nm or less, from the viewpoint of improving linear recording density.

[0115] When the magnetic particles are ε-iron oxide particles, the lower limit of the average particle size of the magnetic particles is preferably 10.0 nm or more, from the viewpoint of improving the dispersibility of the magnetic particles and improving electromagnetic conversion characteristics (e.g., SNR).

[0116] When the magnetic particles are ε-iron oxide particles, the numerical range of the average particle size of the magnetic particles may be defined by either of the above upper limits and either of the above lower limits, preferably 10.0 nm to 15.0 nm, more preferably 10.0 nm to 14.5 nm, even more preferably 10.0 nm to 13.5 nm, 10.0 nm to 12.5 nm, or 10.0 nm to 12.0 nm.

[0117] When the magnetic particles are ε-iron oxide particles, the average particle size of the magnetic particles is determined as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and the magnetic tape MT is cut at a position 30 to 40 m in the longitudinal direction from one end on the outer circumference of the magnetic tape MT. Next, the magnetic tape MT 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 layers as a pretreatment before observing the TEM image of the cross-section described later. The carbon layer is formed on the magnetic surface and back surface of the magnetic tape MT by vapor deposition, and the tungsten layer is further formed on the magnetic surface by vapor deposition or sputtering. Thinning is performed along the length direction (longitudinal direction) of the magnetic tape MT. That is, this thinning creates a cross-section parallel to both the longitudinal and thickness directions of the magnetic tape MT.

[0118] 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 43 is included in the thickness direction of the magnetic layer 43, and a TEM image is taken. Next, 50 particles whose particle shape can be clearly confirmed are selected from the acquired TEM image, and the diameter of each particle is measured. Here, diameter 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). Subsequently, the average diameter is obtained by simply averaging (arithmetic mean) the diameters of the 50 measured particles. The average diameter obtained in this way is taken as the average particle size of the magnetic particles.

[0119] When the magnetic particles are ε-iron oxide particles, the upper limit of the average particle volume of the magnetic particles is preferably 1.80 × 10⁻¹⁰ from the viewpoint of improving linear recording density. ３ nm ３ More preferably, 1.60 × 10 ３ nm ３ More preferably, 1.30 × 10 ３ nm ３ Below, 1.20 × 10 ３ nm ３ Below, 1.00 x 10３ nm ３ The following or 0.90 x 10 ３ nm ３ The following applies:

[0120] When the magnetic particles are ε-iron oxide particles, the lower limit of the average particle volume of the magnetic particles is preferably 0.500 × 10⁻¹⁰, from the viewpoint of improving the dispersibility of the magnetic particles and improving electromagnetic conversion characteristics (e.g., SNR). ３ nm ３ More preferably 0.600 × 10 ３ nm ３ That's all.

[0121] When the magnetic particles are ε-iron oxide particles, the numerical range of the average particle volume of the magnetic particles may be defined by either of the above upper and lower limits, preferably 0.500 × 10 ３ nm ３ The above 1.80 x 10 ３ nm ３ More preferably, 0.500 × 10 ３ nm ３ The above 1.60 x 10 ３ nm ３ More preferably, 0.500 × 10 ３ nm ３ The above 1.30 x 10 ３ nm ３ Below, 0.600 x 10 ３ nm ３ The above 1.20 x 10 ３ nm ３ Below, 0.600 x 10 ３ nm ３ The above 1.00 x 10 ３ nm ３ The following or 0.600 x 10 ３ nm ３ The above is 0.90 x 10 ３ nm ３ The following applies:

[0122] The average particle volume of magnetic particles can be determined as follows: First, the average particle size D is determined in the same manner as the method for calculating the average particle size of magnetic particles described above. Next, the average particle volume V of the magnetic particles is determined using the following formula: V = (π / 6) × D 3

[0123] (Cobalt ferrite particles) The cobalt ferrite particles preferably have uniaxial crystal anisotropy. The uniaxial crystal anisotropy of the cobalt ferrite particles allows the magnetic particles to be preferentially crystal-oriented in the direction perpendicular to the magnetic tape MT. The cobalt ferrite particles have, for example, a cubic shape. In this specification, the cubic shape includes a substantially cubic shape. The Co-containing spinel ferrite may further contain at least one selected from the group consisting of Ni, Mn, Al, Cu, and Zn in addition to Co.

[0124] Co-containing spinel ferrite has an average composition represented, for example, by the following formula: Co ｘ M ｙ Fe ２ O Ｚ (However, in the formula, M is at least one metal selected from the group consisting of, for example, Ni, Mn, Al, Cu, and Zn. x is a value in the range 0.4 ≤ x ≤ 1.0. y is a value in the range 0 ≤ y ≤ 0.3, where x and y satisfy the relationship (x + y) ≤ 1.0. z is a value in the range 3 ≤ z ≤ 4. Part of Fe may be substituted with other metallic elements.)

[0125] When the magnetic particles are cobalt ferrite particles, the upper limit of the average particle size of the magnetic particles is preferably 16.0 nm or less, more preferably 13.0 nm or less, and even more preferably 10.0 nm or less, from the viewpoint of improving linear recording density.

[0126] When the magnetic particles are cobalt ferrite particles, the lower limit of the average particle size of the magnetic particles is preferably 8.0 nm or larger, from the viewpoint of improving the dispersibility of the magnetic particles and improving electromagnetic conversion characteristics (e.g., SNR).

[0127] When the magnetic particles are cobalt ferrite particles, the numerical range of the average particle size of the magnetic particles may be defined by any of the above upper limit values and the above lower limit value, preferably 8.0 nm or more and 16.0 nm or less, more preferably 8.0 nm or more and 13.0 nm or less, and even more preferably 8.0 nm or more and 10.0 nm or less. The method for calculating the average particle size of the cobalt ferrite particles is the same as the method for calculating the average particle size of the ε magnetic particles.

[0128] When the magnetic particles are cobalt ferrite particles, the average aspect ratio of the magnetic particles is preferably 1.0 or more and 3.0 or less, more preferably 1.0 or more and 2.5 or less, and even more preferably 1.0 or more and 2.0 or less. When the average aspect ratio of the magnetic particles is within the range of 1.0 or more and 3.0 or less, aggregation of the magnetic particles can be suppressed. Further, when the magnetic particles are vertically oriented in the formation step of the magnetic layer 43, the resistance applied to the magnetic particles can be suppressed. Therefore, the vertical orientation of the magnetic particles can be improved.

[0129] The average aspect ratio of the magnetic particles is obtained as follows. First, a TEM image is obtained by performing each step from the step of taking out a measurement sample from the magnetic tape MT to the step of taking a cross-sectional TEM image in the same manner as the method for calculating the average particle size of the ε iron oxide particles. Next, 50 particles whose particle shapes can be clearly confirmed are selected from the taken TEM image, and the major axis length DL and the minor axis length DS of each particle are measured. Here, the major axis length DL means the maximum of the distances between two parallel lines drawn from all angles so as to contact the contour of each particle (so-called maximum Feret diameter). On the other hand, the minor axis length DS means the maximum of the lengths of the particle in the direction orthogonal to the major axis (DL) of the particle. Subsequently, the major axis lengths DL of the 50 measured particles are simply averaged (arithmetic mean) to obtain an average major axis length DL ave and the minor axis lengths DS of the 50 measured particles are simply averaged (arithmetic mean) to obtain an average minor axis length DS ave and then the average aspect ratio of the particles (DL ave / DS ave is obtained from the average major axis length DL ave and the average minor axis length DS aveFind

[0130] When the magnetic particles are cobalt ferrite particles, the upper limit value of the average particle volume of the magnetic particles is preferably 4.00×10 ３ nm ３ or less, more preferably 2.00×10 ３ nm ３ or less, even more preferably 1.50×10 ３ nm ３ or less or 1.00×10 ３ nm ３ or less.

[0131] When the magnetic particles are cobalt ferrite particles, the lower limit value of the average particle volume of the magnetic particles is preferably 0.5×10 ３ nm ３ or more, more preferably 0.6×10 ３ nm ３ or more.

[0132] When the magnetic particles are cobalt ferrite particles, the numerical range of the average particle volume of the magnetic particles may be defined by any of the above upper limit values and any of the above lower limit values, preferably 0.5×10 ３ nm ３ or more and 4.00×10 ３ nm ３ or less, more preferably 0.6×10 ３ nm ３ or more and 2.00×10 ３ nm ３ or less, even more preferably 0.6×10 ３ nm ３ or more and 1.50×10 ３ nm ３ or less or 0.6×10 ３ nm ３ or more and 1.00×10 ３ nm ３ or less.

[0133] The average particle volume of magnetic particles is determined as follows. First, a TEM image is obtained by performing each step from the extraction of the measurement sample from the magnetic tape MT to the acquisition of a cross-sectional TEM image in the same manner as the method for calculating the average particle size of ε iron oxide particles. Next, 50 particles whose shape is clear are selected from the acquired TEM image, and the side length DC of each particle is measured. Subsequently, the average side length DC is obtained by simply averaging (arithmetic mean) the side lengths DC of the 50 measured particles. ave Next, we calculate the mean side length DC. ave Using the following formula, the average volume V of magnetic particles can be derived. ave Determine the (particle volume). V ave = DC ave 3

[0134] (Binding agent) The binding agent includes, for example, a thermoplastic resin. The binding agent may further include a thermosetting resin or a reactive resin, etc.

[0135] The thermoplastic resin includes, for example, a first thermoplastic resin (first binder) containing chlorine atoms and a second thermoplastic resin (second binder) containing nitrogen atoms. More specifically, the thermoplastic resin includes a vinyl chloride resin and a urethane resin. In this specification, a vinyl chloride resin means a polymer containing structural units derived from vinyl chloride. More specifically, for example, a vinyl chloride resin means a homopolymer of vinyl chloride, a polymer of vinyl chloride and a comonomer copolymerizable therewith, and mixtures of these polymers.

[0136] The vinyl chloride resin includes, for example, at least one selected from the group consisting of vinyl chloride, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, acrylic acid ester-vinyl chloride-vinylidene chloride copolymer, and methacrylic acid ester-vinyl chloride copolymer.

[0137] A urethane resin refers to a resin in which at least a portion of the molecular chains constituting the resin contains urethane bonds, and may be a urethane resin or a copolymer in which a portion of the molecular chains contains urethane bonds. A urethane resin may be obtained, for example, by reacting a polyisocyanate with a polyol. Alternatively, a urethane resin may be obtained, for example, by reacting a polyester with a polyol. In this specification, urethane resins also include those obtained by reaction with a curing agent.

[0138] The polyisocyanate includes, for example, at least one selected from the group consisting of diphenylmethane diisocyanate (MDI), tolylene diisocyanate (TDI), xylylene diisocyanate (XDI), 1,5-pentamethylene diisocyanate (PDI), hexamethylene diisocyanate (HDI), and isophorone diisocyanate (IPDI). In this specification, polyisocyanate means a compound having two or more isocyanate groups in its molecule. The polyisocyanate may also be a polyisocyanate contained in the curing agent.

[0139] Any suitable polyol can be used as the polyol, as long as it has two or more OH groups. The polyol includes, for example, at least one selected from the group consisting of polyols having two OH groups (diols), polyols having three OH groups (triols), polyols having four OH groups (tetraols), polyols having five OH groups (pentaols), and polyols having six OH groups (hexaols). Specifically, the polyol includes, for example, at least one selected from the group consisting of polyester polyols, polyether polyols, polycarbonate polyols, polyesteramide polyols, and acrylate polyols.

[0140] The polyester includes, for example, at least one selected from the group consisting of phthalate polyesters and aliphatic polyesters.

[0141] The thermoplastic resin may further include thermoplastic resins other than vinyl chloride resins and urethane resins. Such thermoplastic resins include, for example, at least one selected from the group consisting of vinyl acetate, acrylic acid ester-acrylonitrile copolymer, acrylic acid ester-acrylonitrile copolymer, acrylic acid ester-vinylidene chloride copolymer, methacrylic acid ester-vinylidene chloride copolymer, methacrylic acid ester-ethylene copolymer, polyvinyl fluoride, vinylidene chloride-acrylonitrile copolymer, acrylonitrile-butadiene copolymer, polyamide resin, polyvinyl butyral, cellulose derivatives (cellulose acetate butyrate, cellulose diacetate, cellulose triacetate, cellulose propionate, nitrocellulose), styrene butadiene copolymer, polyester resin, amino resin, and synthetic rubber.

[0142] The thermosetting resin includes, for example, at least one selected from the group consisting of phenolic resins, epoxy resins, polyurethane curing resins, urea resins, melamine resins, alkyd resins, silicone resins, polyamine resins, and urea-formaldehyde resins.

[0143] All of the above binders contain -SO4 for the purpose of improving the dispersibility of magnetic particles. ３ M, -OSO ３ M, -COOM, P=O(OM) ２ (However, in the formula, M represents a hydrogen atom or an alkali metal such as lithium, potassium, or sodium) or -NR1R2, -NR1R2R3 ＋ X － Side-chain amines having terminal groups represented by >NR1R2 ＋ X － Main-chain amines represented by (wherein R1, R2, and R3 represent hydrogen atoms or hydrocarbon groups, X － ) represents halogen element ions such as fluorine, chlorine, bromine, and iodine, inorganic ions, or organic ions. ), Furthermore, polar functional groups such as -OH, -SH, -CN, and epoxy groups may be introduced. The amount of these polar functional groups introduced into the binder is 10 －１ The above 10 －８ It is preferable that the amount is 10 moles / g or less.－２ The above 10 －６ It is more preferable that the concentration is 1 / mole / g or less.

[0144] (Lubricant) The lubricant may be a liquid lubricant. Preferably, the lubricant contains both fatty acids and fatty acid esters. Containing both fatty acids and fatty acid esters in the lubricant can improve driving stability. Preferably, the melting points of the fatty acids and the fatty acid esters are different. The fatty acid may be a solid lubricant at room temperature. The fatty acid ester may be a liquid lubricant at room temperature. Here, room temperature refers to a temperature range of 20°C ± 15°C (5°C to 35°C).

[0145] The fatty acid may preferably be a compound represented by the following general formula (1) or (2). For example, the fatty acid may include either the compound represented by the following general formula (1) and the compound represented by the following general formula (2), or both.

[0146] Furthermore, the fatty acid ester may preferably be a compound represented by the following general formulas (3), (4), or (5). For example, the fatty acid ester may include one, two, or three of the compounds represented by the following general formulas (3), (4), and (5).

[0147] The lubricant can suppress the increase in the coefficient of dynamic friction due to repeated recording or playback of magnetic tape MT by including either one or both of the compounds shown in general formula (1) and general formula (2), and one, two, or three of the compounds shown in general formula (3), general formula (4), and general formula (5).

[0148] CH3 (CH2) k COOH ... (1) (However, in general formula (1), k is an integer selected from the range of 14 to 22, more preferably from the range of 14 to 18.)

[0149] CH3 (CH2) n CH = CH(CH2)m COOH ... (2) (However, in general formula (2), the sum of n and m is an integer selected from the range of 12 to 20, more preferably from the range of 14 to 18.)

[0150] CH3 (CH2) p COO (CH2) q CH3 ... (3) (However, in general formula (3), p is an integer selected from the range of 14 to 22, more preferably from 14 to 18, and q is an integer selected from the range of 2 to 5, more preferably from 2 to 4.)

[0151] CH3 (CH2) r COO-(CH2) s CH(CH3)² ... (4) (wherein in general formula (4), r is an integer selected from the range of 14 to 22, and s is an integer selected from the range of 1 to 3.)

[0152] CH3 (CH2) ｔ COO-(CH)(CH3)CH2(CH3) ｕ ... (5) (However, in general formula (5), t is an integer selected from the range of 14 to 22, and u is an integer selected from the range of 1 to 3.)

[0153] (Dispersant) The dispersant may be a compound that, in the coating for forming the magnetic layer, assists in the dispersion of magnetic particles by interacting with them. The dispersant may be adsorbable onto the surface of the magnetic particles contained in the magnetic layer 43. The dispersant may, for example, have at least one acidic functional group. The acidic functional group may be an acidic adsorbent group that can be adsorbed onto the surface of the magnetic particles by interacting with them. The at least one acidic functional group may include at least one selected from the group consisting of, for example, a phosphate group, a carboxyl group, and a sulfonic acid group.

[0154] The dispersant includes, for example, at least one selected from the group consisting of phosphonic acid compounds, carboxylic acid compounds, and sulfonic acid compounds. More specifically, the dispersant includes, for example, at least one selected from the group consisting of phenylphosphonic acid, benzoic acid, naphthoic acid, hydroxybenzoic acid, isophthalic acid, oleic acid, cyclohexanecarboxylic acid, adipic acid, and citric acid. Naphthoic acid includes, for example, 1-naphthoic acid. Hydroxybenzoic acid includes, for example, 4-hydroxybenzoic acid.

[0155] The phosphonic acid compound includes, for example, at least one selected from the group consisting of aromatic phosphonic acid compounds, chain-type aliphatic phosphonic acid compounds, and cyclic aliphatic phosphonic acid compounds. The phosphonic acid compound may include, for example, one or both of a monovalent phosphonic acid compound and a polyvalent phosphonic acid compound. The aromatic phosphonic acid compound includes, for example, phenylphosphonic acid.

[0156] Carboxylic acid compounds include, for example, at least one selected from the group consisting of aromatic carboxylic acid compounds, chain-type aliphatic carboxylic acid compounds, and cyclic aliphatic carboxylic acid compounds. Carboxylic acid compounds may include, for example, one or both of monovalent carboxylic acid compounds and polyvalent carboxylic acid compounds. Aromatic carboxylic acid compounds include, for example, at least one selected from the group consisting of benzoic acid, naphthoic acid, hydroxybenzoic acid, and isophthalic acid. Chain-type aliphatic carboxylic acid compounds include, for example, at least one selected from the group consisting of adipic acid, citric acid, and oleic acid. Cyclic aliphatic carboxylic acid compounds include, for example, cyclohexanecarboxylic acid.

[0157] Examples of carboxylic acid compounds include fatty acids with 12 to 18 carbon atoms such as caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, oleic acid, elaidic acid, linoleic acid, linolenic acid, and stearolic acid [RCOOH (where R is an alkyl group or alkenyl group with 11 to 17 carbon atoms)]; metal soaps made from alkali metals or alkaline earth metals of the above fatty acids; fluorine-containing compounds of the above fatty acid esters; amides of the above fatty acids; polyalkylene oxide alkyl phosphate esters; lecithin; trialkyl polyolefin oxyquaternary ammonium salts (alkyl has 1 to 5 carbon atoms, olefin is ethylene, propylene, etc.); phenylphosphonic acid; copper phthalocyanine, etc. These may be used individually or in combination of two or more.

[0158] The sulfonic acid compound includes, for example, at least one selected from the group consisting of aromatic sulfonic acid compounds, chain-type aliphatic sulfonic acid compounds, and cyclic aliphatic sulfonic acid compounds. The sulfonic acid compound may also include, for example, one or both of a monovalent sulfonic acid compound and a polyvalent sulfonic acid compound.

[0159] (Carbon particles) Some of the carbon particles contained in the magnetic layer 43 may protrude from the magnetic surface, forming multiple protrusions. The formation of multiple protrusions by carbon particles reduces the electrical resistance of the magnetic surface and suppresses the charging of the magnetic surface. Furthermore, the coefficient of dynamic friction μ during the running of the magnetic tape MT Ｔ This can be reduced.

[0160] The carbon particles may also function as an antistatic agent and a solid lubricant. Preferably, the average primary particle size of the carbon particles is 100.0 nm or less. When the average primary particle size of the carbon particles is 100.0 nm or less, even if the carbon particles are particles with a large particle size distribution (e.g., carbon black), the inclusion of particles that are excessively large relative to the thickness of the magnetic layer 43 is suppressed.

[0161] As the carbon particles, for example, at least one selected from the group consisting of carbon black, acetylene black, ketjen black, carbon nanotubes, and graphene can be used, and among these carbon particles, it is preferable to use carbon black. As the carbon black, for example, Seast TA manufactured by Tokai Carbon Co., Ltd., Asahi #15, #15HS of Asahi Carbon Co., Ltd., etc. can be used.

[0162] The magnetic layer 43 may contain hybrid particles instead of carbon particles, or may contain hybrid particles together with carbon particles. The hybrid particles contain carbon and a material other than carbon. The material other than carbon is, for example, an organic material or an inorganic material. The hybrid particles may be hybrid particles in which carbon is attached to the surface of inorganic particles. Specifically, for example, it may be hybrid carbon in which carbon is attached to the surface of silica particles.

[0163] (Abrasive particles) Some of the abrasive particles contained in the magnetic layer 43 may protrude from the magnetic surface and form a plurality of protrusions. When the head unit 56 slides on the magnetic tape MT, the protrusions formed by the abrasive particles can contact the head unit 56.

[0164] From the viewpoint of suppressing deformation due to contact with the head unit 56, the lower limit value of the Mohs hardness of the abrasive particles is preferably 7.0 or more, more preferably 7.5 or more, still more preferably 8.0 or more, and particularly preferably 8.5 or more. From the viewpoint of suppressing wear of the head unit 56, the upper limit value of the Mohs hardness of the abrasive particles is preferably 9.5 or less.

[0165] The abrasive particles are preferably inorganic particles. Examples of inorganic particles include α-alumina, 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 raw materials of magnetic iron oxide, surface-treated with aluminum and / or silica as needed, and diamond powder. As inorganic particles, it is preferable to use alumina particles such as α-alumina, β-alumina, and γ-alumina, and silicon carbide. The abrasive particles may be needle-shaped, spherical, cube-shaped, etc., but those with corners on part of their shape are preferred because they have high abrasiveness.

[0166] (Antistatic agent) An antistatic agent can reduce the electrical resistance of a magnetic surface and suppress the charging of the magnetic surface. The antistatic agent includes, for example, at least one selected from the group consisting of natural surfactants, nonionic surfactants, and cationic surfactants.

[0167] (Curing agent) The curing agent includes, for example, a polyisocyanate. The polyisocyanate may include, for example, diphenylmethane diisocyanate (MDI), tolylene diisocyanate (TDI), xylylene diisocyanate (XDI), 1,5-pentamethylene diisocyanate (PDI), hexamethylene diisocyanate (HDI), or isophorone diisocyanate (IPDI) as an isocyanate source. The polyisocyanate may have a TMP adduct structure, an isocyanurate structure, a biuret structure, or an allophanate structure.

[0168] Polyisocyanates specifically include, for example, aromatic polyisocyanates such as adducts of tolylene diisocyanate (TDI) and active hydrogen compounds, and aliphatic polyisocyanates such as adducts of hexamethylene diisocyanate (HMDI) and active hydrogen compounds. The weight-average molecular weight of these polyisocyanates is preferably in the range of 100 to 3000.

[0169] (Rust inhibitors) Examples of rust inhibitors include phenols, naphthols, quinones, heterocyclic compounds containing nitrogen atoms, heterocyclic compounds containing oxygen atoms, and heterocyclic compounds containing sulfur atoms.

[0170] (Non-magnetic reinforcing particles) Examples of non-magnetic reinforcing particles include aluminum oxide (α, β, or γ alumina), chromium oxide, silicon oxide, diamond, garnet, emery, boron nitride, titanium carbide, silicon carbide, titanium carbide, and titanium oxide (rutile or anatase type titanium oxide).

[0171] (Underlayment) The underlayment 42 can alleviate the uneven surface shape of the substrate 41 and adjust the uneven surface shape of the magnetic surface. The underlayment 42 is a non-magnetic layer and includes, for example, non-magnetic particles, a binder, and a lubricant. It is preferable that the underlayment 42 can supply lubricant to the magnetic surface. The underlayment 42 may further include, if necessary, at least one additive selected from the group consisting of antistatic agents, hardening agents, and rust inhibitors.

[0172] The base layer 42 may have a plurality of pores. Lubricant may be stored in the pores. In this case, the supply of lubricant to the magnetic surface can be improved. From the viewpoint of improving the supply of lubricant to the magnetic surface, it is preferable that the pores extend perpendicular to the magnetic surface. From the viewpoint of improving the supply of lubricant to the magnetic surface, it is preferable that the pores of the base layer 42 and the pores of the magnetic layer 43 are connected.

[0173] Average thickness t of the base layer 42 ３The upper limit is preferably 0.80 μm or less, more preferably 0.70 μm or less, and even more preferably 0.60 μm or less, from the viewpoint of improving the recording capacity of the cartridge 10. Average thickness t of the base layer 42 ３ The lower limit is preferably 0.30 μm or more, more preferably 0.40 μm or more. Average thickness t of the underlayer 42 ３ If the lower limit is 0.30 μm or more, a second physical property (specifically, average hardness H) is required for a triangular pyramidal diamond indenter with a 142.3° edge angle to be pressed perpendicularly to the magnetic surface with a load of 150 μN. 150 , average plastic deformation amount D 150 and the mean modulus of elasticity Er 150 The measurement of the second physical property can be suppressed from being affected by the substrate 41. Therefore, the decrease in the measurement accuracy of the second physical property can be suppressed.

[0174] Average thickness t of the base layer 42 ３ The numerical range may be defined by either of the above upper limits and the above lower limit, preferably 0.30 μm or more and 0.90 μm or less, more preferably 0.30 μm or more and 0.80 μm or less, even more preferably 0.30 μm or more and 0.70 μm or less, and particularly preferably 0.30 μm or more and 0.60 μm or less.

[0175] Average thickness t of the base layer 42 ３ The average thickness t of the magnetic layer 43 is ２ It is determined in the same manner as above. However, the magnification of the TEM image is adjusted as appropriate according to the thickness of the underlying layer 42.

[0176] Average thickness t of the substrate 41 １ In contrast, the average thickness t of the magnetic layer 43 ２ and the average thickness t of the base layer 42 ３ If the total thickness is too large, the bending rigidity will increase, which may reduce the stability of the contact between the magnetic tape MT and the head unit 56. On the other hand, the average thickness t of the base body 41 １ In contrast, the average thickness t of the magnetic layer 43 ２ and the average thickness t of the base layer 42 ３ If the total thickness is too small, there is a risk that the surface quality of the magnetic surface of the magnetic tape MT will deteriorate. Therefore, the average thickness t of the substrate 41 １ The average thickness t of the magnetic layer 43 relative to this.２ and the average thickness t of the base layer 42 ３ The ratio of the total thickness ((t) ２ +t ３ ) / t １ ) is preferably 0.19 or more and 0.28 or less.

[0177] (Non-magnetic particles) Non-magnetic particles include, for example, at least one of inorganic particles and organic particles. Non-magnetic particles may also be carbon particles such as carbon black. One type of non-magnetic particle may be used alone, or two or more types of non-magnetic particles may be used in combination. Inorganic particles include, for example, metals, metal oxides, metal carbonates, metal sulfates, metal nitrides, metal carbides, or metal sulfides. Examples of non-magnetic particles include needle-shaped, spherical, cubic, and plate-shaped shapes, but are not limited to these shapes.

[0178] (Binding agent, lubricant) The binding agent and lubricant are the same as those used in the magnetic layer 43 described above.

[0179] (Additives) The antistatic agent, hardening agent, and rust inhibitor are the same as those used in the magnetic layer 43 described above.

[0180] (Back layer) The back layer 44 contains a binder and non-magnetic particles. The back layer 44 may further contain at least one additive selected from the group consisting of lubricants, hardeners, and antistatic agents, if necessary. The binder and non-magnetic particles are the same as those in the base layer 42 described above. The lubricant, hardener, and antistatic agent are the same as those in the magnetic layer 43 described above.

[0181] The average particle size of the non-magnetic particles is preferably 10.0 nm to 150.0 nm, more preferably 15.0 nm to 110.0 nm. The average particle size of the non-magnetic particles is determined in the same manner as the average particle size of the magnetic particles. The non-magnetic particles may include non-magnetic particles having a particle size distribution of 2 or more.

[0182] Average thickness t of the back layer 44 ４ The upper limit of is preferably 0.60 μm or less. When the upper limit of the average thickness of the back layer 44 is 0.60 μm or less, the average thickness of the magnetic tape MT is t ＴEven if the thickness is 5.50 μm or less, the thickness of the base layer 42 and the substrate 41 can be kept thick, so that the running stability of the magnetic tape MT can be maintained in the recording and playback device. Average thickness t of the back layer 44 ４ The lower limit is not particularly restricted, but for example, it is 0.20 μm or larger.

[0183] Average thickness t of the back layer 44 ４ This can be calculated as follows: First, the average thickness t of the magnetic tape MT. Ｔ Measure the average thickness t. Ｔ The measurement method is as described in "Average Thickness of Magnetic Tape" below. Next, the magnetic tape MT housed in the cartridge 10 is unwound, and a 250 mm length of the magnetic tape MT is cut from one end of the outer circumference of the magnetic tape MT at a position 30 m to 40 m in the longitudinal direction to prepare a sample. Next, the back layer 44 of the sample is removed with a solvent such as MEK (methyl ethyl ketone) or dilute hydrochloric acid. Next, the thickness of the sample is measured at five points using a Mitutoyo laser hologage (LGH-110C), and these measurements are simply averaged (arithmetic mean) to obtain the average value t Ｂ The [μm] value is calculated. Then, the average thickness t of the back layer 44 is calculated using the following formula. ４ Determine the [μm]. Note that the five measurement points mentioned above will be randomly selected from the sample so that they are all at different positions along the longitudinal direction of the magnetic tape MT. ４ [μm] = t Ｔ [μm] - t Ｂ [μm]

[0184] (Average thickness of magnetic tape) By reducing the average thickness of the magnetic tape MT, the length of tape wound into one cartridge 10 can be increased, thereby increasing the recording capacity per cartridge 10. Therefore, from the viewpoint of improving the recording capacity of cartridge 10, the average thickness (average total thickness) of the magnetic tape MT t ＴThe upper limit is preferably 5.50 μm or less, more preferably 5.40 μm or less, even more preferably 5.30 μm or less, 5.10 μm or less, 4.90 μm or less, or 4.70 μm or less. Average thickness t of magnetic tape MT Ｔ The lower limit is not particularly restricted, but for example, it is 3.50 μm or larger.

[0185] Average thickness t of magnetic tape MT Ｔ The following is how it is determined. First, the magnetic tape MT housed in the cartridge 10 is unwound, and a 250 mm length of the magnetic tape MT is cut from one end of the outer circumference of the magnetic tape MT at a position 30 m to 40 m in the longitudinal direction to prepare a sample. Next, the thickness of the sample is measured at five points using a laser hologage (LGH-110C) manufactured by Mitutoyo as the measuring device, and these measured values ​​are simply averaged (arithmetic mean) to obtain the average thickness t. Ｔ The measurement value in [μm] is calculated. The five measurement points mentioned above are to be randomly selected from the sample so that they are all at different locations along the longitudinal direction of the magnetic tape MT.

[0186] (Sum of the average thickness of the magnetic layer and the average thickness of the underlying layer) Average thickness t of magnetic layer 43 ２ and the average thickness t of the base layer 42 ３ The upper limit of the sum is preferably 0.95 μm or less, more preferably 0.80 μm or less, and even more preferably 0.60 μm or less, from the viewpoint of improving the recording capacity of the cartridge 10. Average thickness t of the magnetic layer 43 ２ and the average thickness t of the base layer 42 ３ The lower limit of the sum is, for example, 0.30 μm or more. Average thickness t of the magnetic layer 43 ２ and the average thickness t of the underlayer 42 ３ The measurement method is as described above.

[0187] Average thickness t of the magnetic layer 43 ２ and the average thickness t of the base layer 42 ３The numerical range of the sum may be defined by either of the above upper and lower limits, preferably 0.30 μm or more and 0.95 μm or less, more preferably 0.30 μm or more and 0.80 μm or less, and even more preferably 0.30 μm or more and 0.60 μm or less.

[0188] (Sum of the average thickness of the magnetic layer, the average thickness of the underlayer, and the average thickness of the backing layer) Average thickness t of magnetic layer 43 ２ and the average thickness t of the base layer 42 ３ and the average thickness t of the back layer 45 ４ The upper limit of the sum is preferably 1.20 μm or less, more preferably 1.10 μm or less, and even more preferably 1.00 μm or less, from the viewpoint of improving the recording capacity of the cartridge 10. Average thickness t of the magnetic layer 43 ２ and the average thickness t of the base layer 42 ３ and the average thickness t of the back layer 44 ４ The lower limit of the sum is, for example, 0.40 μm or more. Average thickness t of the magnetic layer 43 ２ , average thickness t of the base layer 42 ３ and the average thickness t of the back layer 45 ４ The measurement method is as described above.

[0189] Average thickness t of the magnetic layer 43 ２ and the average thickness t of the base layer 42 ３ and the average thickness t of the back layer 44 ４ The numerical range of the sum may be defined by either of the above upper limits and the above lower limit, preferably 0.40 μm or more and 1.20 μm or less, more preferably 0.40 μm or more and 1.10 μm or less, and even more preferably 0.40 μm or more and 1.00 μm or less.

[0190] (Indenter load) The following is the first physical property (specifically, average hardness H) obtained by pressing a triangular pyramidal diamond indenter with a 142.3° edge angle perpendicular to the magnetic surface with a load of 50 μN. 50 , average plastic deformation amount D 50 and the mean modulus of elasticity Er 50 ), and a second physical property (specifically, average hardness H) determined by pressing a triangular pyramidal diamond indenter with a 142.3° edge angle perpendicular to the magnetic surface with a load of 150 μN.150 , average plastic deformation amount D 150 and the mean modulus of elasticity Er 150 This explains ).

[0191] The reason why the indenter load is selected to 50 μN in the measurement of the first physical property is as follows: When the indenter load is 50 μN, the indentation depth of the indenter is shallow compared to the thickness of the magnetic layer 43, and the first physical property (specifically the average hardness H) mainly composed of the magnetic layer 43 is 50 , average plastic deformation amount D 50 and the mean modulus of elasticity Er 50 It is possible to measure the second physical property (specifically, the average hardness H). Furthermore, the reason why the indenter load is selected to be 150 μN in the measurement of the second physical property is as follows: When the indenter load is 150 μN, the indentation depth of the indenter is approximately equal to or greater than the thickness of the magnetic layer 43, and the second physical property (specifically, the average hardness H) includes the physical properties of the base layer 42 in addition to the physical properties of the magnetic layer 43. 150 , average plastic deformation amount D 150 and the mean modulus of elasticity Er 150 It is possible to measure this.

[0192] (Average hardness H) 50 The average hardness H was determined by pressing a triangular pyramidal diamond indenter with a 142.3° edge angle perpendicular to the magnetic surface with a load of 50 μN. 50 The lower limit is 0.72 GPa or higher, preferably 0.75 GPa or higher, more preferably 0.80 GPa or higher, even more preferably 0.85 GPa or higher, 0.90 GPa or higher, or 0.93 GPa or higher. The above average hardness H 50 If the pressure is less than 0.72 GPa, the magnetic layer 43 may become too soft, potentially leading to unstable contact between the magnetic tape MT and the head unit 56. Consequently, a stable signal output may not be obtained, potentially degrading the electromagnetic conversion characteristics.

[0193] The above average hardness H 50 The upper limit is preferably 1.10 GPa or less, more preferably 1.05 GPa or less, and even more preferably 1.00 GPa or less. The above average hardness H 50If the pressure is 1.10 GPa or less, it is possible to suppress the rigidity of the magnetic layer 43 from becoming too high. Therefore, it is possible to suppress the deterioration of the contact state between the magnetic tape MT and the head unit 56.

[0194] The above average hardness H 50 The numerical range may be defined by either of the above upper limits and either of the above lower limits, preferably 0.72 GPa or more and 1.10 GPa or less, more preferably 0.75 GPa or more and 1.10 GPa or less, even more preferably 0.80 GPa or more and 1.10 GPa or less, even more preferably 0.85 GPa or more and 1.10 GPa or less, 0.90 GPa or more and 1.10 GPa or less, or 0.93 GPa or more and 1.10 GPa or less.

[0195] The above average hardness H 50 This is determined using a nanoindenter. The above average hardness H 50 Before explaining the specific method for determining this, we will first describe the overview of measurement using a nanoindenter.

[0196] Figure 10A is a load-removal curve showing the displacement of the indenter 71 when the load is continuously increased and the indenter 71 is pressed perpendicularly to the magnetic surface of the magnetic tape MT, and the load is released when the load reaches 50 μN. States (1) to (3) shown in Figure 10B each represent the state of the indenter 71 at points (1) to (3) shown in Figure 10A.

[0197] When a load is applied, as shown in the load curve (a), the displacement increases as the load increases, and at 50 μN, the maximum indentation depth (maximum displacement) dmax is reached. When the load is removed, as shown in the unloading curve (b), the displacement gradually decreases and elastic recovery occurs, but even when the load becomes zero, the displacement does not become zero, and permanent strain (plastic deformation) d ０ Therefore, the "maximum indentation depth dmax" is equal to the "permanent strain (amount of plastic deformation) d ０ "and "elastic recovery d １ It is equivalent to the sum of ".

[0198] The hardness H (indentation hardness H) can be calculated from this load-unloading curve. Hardness H is expressed by the following formula. Here, A Ｃ is the contact projected area between the indenter 71 and the sample (magnetic tape MT), and Pmax is the maximum load on the load-unloading curve.

[0199] The above average hardness H 50 The following is how it is determined using a nanoindenter. First, the magnetic tape MT housed in cartridge 10 is unwound, and a length of about 10 cm is cut from the magnetic tape MT at a position of approximately 20 m from one end on the outermost circumference to obtain sample 1. Then, a length of about 10 cm is cut from the magnetic tape MT at a position of approximately 50 m from the other end on the innermost circumference to obtain sample 2. Next, sample 1 is cut to a size that fits the sample stage, MEK (methyl ethyl ketone) is applied to the back surface of sample 1, and then sample 1 is placed on the sample stage so that the back surface of sample 1 faces the sample stage, and sample 1 is fixed to the sample stage.

[0200] Next, using a nanoindenter, an indentation test is performed at 10 points on the magnetic surface of Sample 1 under a load range of 0 μN to 50 μN, and load-unloading curves are obtained for the 10 points. In this process, the 10 measurement points are randomly selected from areas free of scratches or other defects at the optical microscope level, so that each of the 10 measurement points is at a different location on the magnetic surface.

[0201] The following are the measurement conditions for the nanoindenter. Material of indenter 71: Triangular pyramidal diamond indenter (Berkovich) Calibration is performed as described in the manual. Edge angle of indenter 71: 142.3° Measuring instrument: Hysitron Triboscope / Shimadzu Corporation Scanning Probe Microscope SPM9500J (A measuring instrument that incorporates a device (Hysitron Triboscope) capable of controlling minute loads and measuring indenter displacement into a Shimadzu Corporation Scanning Probe Microscope SPM9500J) Measurement environment: 25℃±2℃, 50%RH±5%RH Load range: 0μN to 50μN (during measurement) Set load: 50μN Load resolution: 0.01μN Indentation direction: Perpendicular to the recording surface Indentation speed: 66.67μN / s During measurement, the load is applied to sample 1 after the indenter 71 has come into contact with the sample 1, and the load is removed immediately after the load reaches the set load.

[0202] When measuring with a nanoindenter, the wear condition of the indenter tip should be checked, and appropriate action should be taken according to the wear condition. Specifically, the following applies: When measuring a standard sample (fused silica) at 1000 μN, if the indenter's indentation depth becomes shallower by 2 μm to 3 μm relative to the maximum indentation depth at the start of use, the indenter should be calibrated. Calibration should be performed as described in the manual, as mentioned above. When measuring a standard sample (fused silica) at 1000 μN, if the indenter's indentation depth becomes shallower than 3 μm relative to the maximum indentation depth at the start of use, the indenter should be replaced. Note that as the indenter tip wears down, the indentation depth tends to decrease.

[0203] Next, the hardness H of each of the 10 points obtained from the load-unloading curves was calculated for each of the 10 points for Sample 1. 11 Next, we determine the hardness H of 10 points. The measurement and analysis program included with the nanoindenter is used to calculate this value. 11 The hardness H of the two points that take the maximum and minimum values. 11 Excluding the remaining 8 points, the hardness is H. 11 Simply average (arithmetic mean) the hardness H of sample 1. 11 Calculate the average value.

[0204] Next, we obtained the load-unloading curve for Sample 1 to determine the hardness H. 11 By performing the same process for sample 2 to calculate the average value, the hardness H of sample 2 can be determined. 21 Next, calculate the average value of hardness H of sample 1. 11 The average value and hardness H of sample 2 21 The average value is simply averaged (arithmetic mean), and this is used as the average hardness H. 50 Let's assume that.

[0205] (Average hardness H) 50 and average hardness H 150 The ratio (H 50 / H 150 )) The above average hardness H 50The average hardness H was determined by pressing a triangular pyramidal diamond indenter with a 142.3° edge angle perpendicular to the magnetic surface with a load of 150 μN. 150 The ratio (H 50 / H 150 The lower limit of the above ratio (H) is preferably 1.42 or higher, more preferably 1.44 or higher, even more preferably 1.50 or higher, 1.60 or higher, 1.70 or higher, 1.80 or higher, or 1.86 or higher. 50 / H 150 If the hardness is 1.42 or higher, the hardness of the magnetic surface (the surface on the magnetic layer 43 side) is high, and the overall hardness of the laminated film of the base layer 42 and the magnetic layer 43 is lower than that of the magnetic surface. This suppresses the impact caused by contact between the protrusions on the magnetic surface and the head unit 56 when the magnetic surface slides against the head unit 56, and stabilizes the contact state.

[0206] The above ratio (H 50 / H 150 The upper limit of the above ratio (H) is preferably 2.20 or less, more preferably 2.10 or less, and even more preferably 2.00 or less. 50 / H 150 If the hardness of the magnetic layer is 2.20 or less, it is possible to prevent the hardness of the magnetic layer 43 from becoming too high compared to the hardness of the underlying layer 42 below the magnetic layer 43. Therefore, it is possible to prevent cracks from forming in the edge portions of the magnetic layer 43, etc. (the edge portions in the width direction of the magnetic tape MT).

[0207] The above ratio (H 50 / H 150 The numerical range of ) may be defined by either of the above upper limits and either of the above lower limits, preferably 1.42 or more and 2.20 or less, more preferably 1.44 or more and 2.20 or less, even more preferably 1.50 or more and 2.20 or less, 1.60 or more and 2.20 or less, 1.70 or more and 2.20 or less, 1.80 or more and 2.20 or less, or 1.86 or more and 2.20 or less.

[0208] The above ratio (H 50 / H 150 ) can be determined using a nanoindenter as follows. First, the average hardness H mentioned above 50 Samples 1 and 2 are prepared in the same manner as the method used to determine the above average hardness H. Next, the above average hardness H 50In the same manner as the method used for determining the load range, an indentation test (1) with a load range of 0 μN to 50 μN is performed at 10 points on the magnetic surface of sample 1, and load-unloading curves for 10 points are obtained. Next, an indentation test (2) with a load range of 0 μN to 150 μN is performed at 10 points on the magnetic surface of sample 1 using a nanoindenter, and load-unloading curves for 10 points are obtained. The total of 20 measurement points for indentation tests (1) and (2) are randomly selected from areas free of scratches, etc., at the optical microscope level, so that each point is at a different location on the magnetic surface. The measurement conditions for the nanoindenter in indentation test (2) are the same as those for indentation test (1), except for the load range: 0 μN to 150 μN (at measurement) and set load: 150 μN. 50 This is similar to the measurement conditions for the nanoindenter used in determining the value.

[0209] Next, the hardness H of sample 1 was calculated from the 10 load-unload curves obtained in the indentation test (1) of sample 1. 11 Next, we determine the hardness H of 10 points. The measurement and analysis program included with the nanoindenter is used to calculate this value. 11 The hardness H of the two points that take the maximum and minimum values. 11 Excluding the remaining 8 points, the hardness is H. 11 Simply average (arithmetic mean) the hardness H of sample 1. 11 Calculate the average value.

[0210] Next, except for using the 10-point load-unload curve obtained in the indentation test (2) of Sample 1, the hardness H of Sample 1 is used. 11 Using the same procedure as for calculating the average value, the hardness H of sample 1 is calculated. 12 Calculate the average value.

[0211] Next, indentation tests (1) and (2) are performed on sample 2, and 10 load-unloading curves are obtained for each of indentation tests (1) and (2). In this case, indentation tests (1) and (2) are performed using the same procedure and conditions as indentation tests (1) and (2) for sample 1 above. Next, except for using the 10 load-unloading curves obtained from indentation test (1) of sample 2, the hardness H of sample 1 is used. 11Using the same procedure as for calculating the average value, the hardness H of sample 2 was calculated. 21 The average value is calculated. Next, the hardness H of sample 1 is used, except for the 10-point load-unload curve obtained in the indentation test (2) of sample 2. 11 Using the same procedure as for calculating the average value, the hardness H of sample 2 was calculated. 22 Calculate the average value.

[0212] Next, the hardness H of sample 1 11 The average value and hardness H of sample 2 21 The average value is simply averaged (arithmetic mean), and this is used as the average hardness H. 50 Next, the hardness H of sample 1. 12 The average value and hardness H of sample 2 22 The average value is simply averaged (arithmetic mean), and this is used as the average hardness H. 150 Next, the average hardness H obtained as described above. 50 and average hardness H 150 Using the above ratio (H 50 / H 150 )

[0213] (Average plastic deformation amount D) 50 ) The above average plastic deformation amount D 50 The upper limit is 16.50 nm or less, preferably 16.00 nm or less, more preferably 15.00 nm or less, even more preferably 14.47 nm or less, 14.00 nm or less, or 13.60 nm or less. The above average plastic deformation amount D 50 If the value exceeds 16.50 nm, the polishing force of the magnetic tape MT against the head unit 56 becomes excessively high, which may cause the head unit 56 to wear down easily. Consequently, the head unit 56 may be more susceptible to damage due to wear.

[0214] The above average plastic deformation amount D 50 The lower limit of the average plastic deformation amount D is preferably 12.00 nm or more, and more preferably 13.00 nm or more. 50 If the wavelength is 12.00 nm or higher, the decrease in the cleaning effect on the head unit 56 can be suppressed.

[0215] The above average plastic deformation amount D 50The numerical range may be defined by either of the above upper limits and either of the above lower limits, preferably 12.00 nm to 16.50 nm, more preferably 12.00 nm to 16.00 nm, even more preferably 12.00 nm to 15.00 nm, 12.00 nm to 14.47 nm, 12.00 nm to 14.00 nm, or 12.00 nm to 13.60 nm.

[0216] The above average plastic deformation amount D 50 This can be determined using a nanoindenter as follows. First, the average hardness H mentioned above. 50 Samples 1 and 2 are prepared in the same manner as the method used to determine the above average hardness H. Next, the above average hardness H 50 Using the same method as before, load-unloading curves are obtained at 10 points on the magnetic surface of sample 1. Next, the amount of plastic deformation D of sample 1 is calculated from each of the obtained 10 load-unloading curves. 11 The value of D is calculated using the measurement and analysis program included with the nanoindenter. 11 This is the permanent strain d shown in Figure 10A. ０ It is equal to. Next, the plastic deformation amount D at 10 points. 11 The amount of plastic deformation D at two points where the maximum and minimum values ​​are obtained. 11 Excluding this, the remaining 8 points of plastic deformation amount D 11 Simply average (arithmetic mean) the plastic deformation amount D of sample 1. 11 Calculate the average value.

[0217] Next, from obtaining the load-unloading curve in Sample 1, we obtain the amount of plastic deformation D 11 By performing the same process for sample 2 to calculate the average value, the amount of plastic deformation D of sample 2 can be calculated. 21 Calculate the average value.

[0218] Next, the amount of plastic deformation D of Sample 1 above. 11 The average value and the amount of plastic deformation D of sample 2 above. 21 The average value is simply averaged (arithmetic mean), and this is used to determine the average plastic deformation D. 50 Let's assume that.

[0219] (Average plastic deformation amount D) 50and average plastic deformation amount D 150 The ratio (D 50 / D 150 )) The above average plastic deformation amount D 50 The average plastic deformation amount D was determined by pressing a triangular pyramidal diamond indenter perpendicularly against the surface of the magnetic layer 43 with a load of 150 μN. 150 The ratio (D 50 / D 150 The upper limit of the ratio (D) is preferably 0.36 or less, more preferably 0.35 or less, and even more preferably 0.34 or less or 0.33 or less. 50 / D 150 If the ratio is 0.36 or less, it is possible to suppress the brittleness of the base layer 42 from becoming excessively high compared to the brittleness of the magnetic layer 43, and to suppress the excessive influence of the transfer of protrusions on the surface of the back layer 44 to the magnetic surface. Therefore, it is possible to suppress the amount of lubricant supplied to the magnetic surface through the pores from becoming excessive. However, if the amount of lubricant supplied to the magnetic surface becomes excessive, it may lead to deterioration of running performance (for example, the magnetic tape MT sticking to the head).

[0220] The above ratio (D 50 / D 150 The lower limit of the above ratio (D) is preferably 0.25 or higher. 50 / D 150 If the value is 0.25 or higher, it is possible to suppress the brittleness of the magnetic layer 43 from becoming excessively high compared to the brittleness of the underlying layer 42, thereby suppressing the occurrence of powder shedding from the magnetic surface during recording or playback of the magnetic tape MT.

[0221] The above ratio (D 50 / D 150 The numerical range of ) may be defined by either of the above upper limits and either of the above lower limits, preferably 0.25 or more and 0.36 or less, more preferably 0.25 or more and 0.35 or less, and even more preferably 0.25 or more and 0.34 or 0.25 or more and 0.33 or less.

[0222] The above ratio (D 50 / D 150 ) can be determined using a nanoindenter as follows. First, the average hardness H mentioned above 50Samples 1 and 2 are prepared in the same manner as the method used to determine the above average hardness H. Next, the above average hardness H 50 In the same manner as the method used to determine the above, an indentation test (1) with a load range of 0 μN to 50 μN is performed at 10 points on the magnetic surface of sample 1, and the load-unload curves for the 10 points are obtained. Next, the above average hardness H 150 In the same manner as the method used for determining the load, an indentation test (2) with a load range of 0 μN to 150 μN is performed at 10 points on the magnetic surface of sample 1 using a nanoindenter, and load-unloading curves for the 10 points are obtained. The total of 20 measurement points for indentation tests (1) and (2) are randomly selected from areas free of scratches or other defects at the optical microscope level, so that each point is at a different location on the magnetic surface.

[0223] Next, the amount of plastic deformation D of Sample 1 was calculated from the 10 load-unloading curves obtained in the indentation test (1) of Sample 1. 11 Next, the plastic deformation amount D at 10 points is calculated. The measurement and analysis program included with the nanoindenter is used to calculate this value. 11 The plastic deformation D at two points that take the maximum and minimum values. 11 Excluding this, the remaining 8 points of plastic deformation amount D 11 Simply average (arithmetic mean) the plastic deformation amount D of sample 1. 11 Calculate the average value.

[0224] Next, except for using the 10-point load-unloading curve obtained in the indentation test (2) of Sample 1, the amount of plastic deformation D of Sample 1 is used. 11 The plastic deformation amount D of sample 1 is calculated using the same procedure as for calculating the average value. 12 Calculate the average value.

[0225] Next, indentation tests (1) and (2) are performed on sample 2, and 10 load-unloading curves are obtained for each of indentation tests (1) and (2). In this case, indentation tests (1) and (2) are performed using the same procedure and conditions as indentation tests (1) and (2) for sample 1 above. Next, the amount of plastic deformation D of sample 1 is used, except for the 10 load-unloading curves obtained from indentation test (1) of sample 2. 11 The plastic deformation amount D of sample 2 is calculated using the same procedure as for calculating the average value. 21The average value is calculated. Next, the amount of plastic deformation D of Sample 1 is used, except that the 10-point load-unloading curve obtained in the indentation test (2) of Sample 2 is used. 11 The plastic deformation amount D of sample 2 is calculated using the same procedure as for calculating the average value. 22 Calculate the average value.

[0226] Next, the amount of plastic deformation D of Sample 1 11 The average value and the amount of plastic deformation D of sample 2 21 The average value is simply averaged (arithmetic mean), and this is used to determine the average plastic deformation D. 50 Next, let's consider the amount of plastic deformation D of sample 1. 12 The average value and the amount of plastic deformation D of sample 2 22 The average value is simply averaged (arithmetic mean), and this is used to determine the average plastic deformation D. 150 Next, the average plastic deformation amount D obtained as described above. 50 and average plastic deformation amount D 150 Using the above ratio (D 50 / D 150 )

[0227] (Average modulus of elasticity Er 150 The average modulus of elasticity Er was determined by pressing a triangular diamond indenter perpendicularly against the surface of the magnetic layer 43 with a load of 150 μN. 150 The upper limit of is 9.00 GPa or less, preferably 8.00 GPa or less, more preferably 7.00 GPa or less or 6.60 GPa or less. The above average modulus of elasticity Er 150 If the pressure is 9.00 GPa or less, it is possible to suppress the magnetic surface of the magnetic tape MT from coming into excessive contact with the head unit 56, and to suppress the excessive polishing force of the magnetic tape MT on the head unit 56. Therefore, it is possible to suppress damage to the head unit 56 caused by wear.

[0228] The above average modulus of elasticity Er 150 The lower limit of the average modulus Er is preferably 5.50 GPa or higher. 150 If the lower limit is 5.50 GPa or higher, the occurrence of powder shedding from the magnetic surface during recording or playback of magnetic tape MT can be suppressed.

[0229] The above average modulus of elasticity Er 150 The numerical range may be defined by either of the above upper limits and the above lower limit, preferably 5.50 GPa or more and 9.00 GPa or less, more preferably 5.50 GPa or more and 8.00 GPa or less, and even more preferably 5.50 GPa or more and 7.00 GPa or less or 5.50 GPa or more and 6.60 GPa or less.

[0230] The above average modulus of elasticity Er 150 This is calculated from the load-unloading curve obtained by pressing a triangular pyramidal diamond indenter perpendicularly to the surface of the magnetic layer 43 with a load of 150 μN. Average modulus of elasticity Er 150 It can be expressed by the following formula. Here, S is the contact stiffness, and A Ｃ is the contact projected area between the indenter 71 and the sample (magnetic tape MT). The contact stiffness S is the slope of the unloading curve (dP / dh).

[0231] The above average modulus of elasticity Er 150 Specifically, it can be determined using a nanoindenter as follows. First, the average hardness H 50 Samples 1 and 2 are prepared in the same manner as the method used to determine the above average hardness H. Next, the above average hardness H 150 Similarly to the method used to determine the value, an indentation test is performed at 10 points on the magnetic surface of Sample 1 using a nanoindenter within a load range of 0 μN to 150 μN, and load-unload curves are obtained for the 10 points on the magnetic surface of Sample 1. Next, the elastic modulus Er1 of Sample 1 is calculated from the obtained 10 load-unload curves. The measurement and analysis program attached to the nanoindenter is used to calculate this value. Next, the two points with the maximum and minimum values ​​are excluded from the 10 points of elastic modulus Er1, and the remaining 8 points of elastic modulus Er1 are simply averaged (arithmetic mean) to calculate the average value of the elastic modulus Er1 of Sample 1.

[0232] Next, the process from obtaining the load-unloading curve for sample 1 to calculating the average value of the elastic modulus Er1 is performed similarly for sample 2 to calculate the average value of the elastic modulus Er2 for sample 2.

[0233] Next, the average value of the elastic modulus Er1 of sample 1 and the average value of the elastic modulus Er2 of sample 2 are simply averaged (arithmetic mean) to obtain the average value, and this is the average elastic modulus Er. 150 Let's assume that.

[0234] (Wear width of Alfesil prism) The longitudinal direction of the magnetic tape MT and the longitudinal direction of the Alfesil prism are perpendicular, and the overlap angle θ of both the magnetic tape MT and the Alfesil prism is perpendicular. １ , θ ２ The magnetic surface (the surface on the magnetic layer 43 side) is brought into contact with one edge of the Alfesil prism so that the angle is 12 degrees (see Figure 11B). In this state, after 100 passes (50 round trips) of a 580m length of magnetic tape MT at a speed of 3.0m / s under a tension of 1.0N ± 0.1N, the wear width of the Alfesil prism is preferably 17μm or less, more preferably 16μm or less, and even more preferably 15μm or less. Here, the above wear width measurement is performed in an environment of 23°C ± 2°C and 45%RH ± 5%RH. The wear width of the Alfesil prism represents the tendency of the magnetic layer 43 to wear down the magnetic recording head. If the wear width of the Alfesil prism is 17μm or less, damage to the magnetic recording head due to wear can be suppressed when data is repeatedly recorded on the magnetic tape MT with a tape storage drive equipped with a new (unused) magnetic recording head.

[0235] The wear width of Alfesil prisms is measured according to the measurement method described in ECMA-319 (9.12 Abrasivity (P.43), and Annex C - Tape Abrasivity Measurement Procedure (P.91-93)). Specifically, it is measured as follows:

[0236] First, as shown in Figure 11A, an Alfesil prism 81 is prepared having a minimum height of 18 mm and a square base of (4.5 mm ± 0.3 mm) × (4.5 mm ± 0.3 mm). The material and manufacturing conditions of the Alfesil prism 81 are as follows: Material: Sendust-based alloy of Al 5.4 wt%, Si 9.6 wt%, Fe 85.0% Heat treatment: 1000°C Rockwell C hardness: 46 ± 1 Manufacturing process: Vacuum melting and casting The surface finish of the four prism faces of the Alfesil prism 81 is 0.05 μm of nitrogen (N ２ This is the process. The Alfesil prism 81 must be a square with a difference in base length within 0.05 mm.

[0237] Next, as shown in Figure 11B, the Alfesil prism 81 is attached to the fixing jig 82 so that its edges face upward. At this time, the Alfesil prism 81 is fixed to the fixing jig 82 by two support plates 83, and each of the two support plates 83 is fixed to the inclined surface of the fixing jig 82 by multiple screws 84. The Alfesil prism 81 used is one in which the edges that come into contact with the magnetic tape MT are free from wear and have no chips or chips larger than 1 μm.

[0238] Next, viewed from above the magnetic tape MT, the longitudinal direction of the magnetic tape MT and the longitudinal direction of the Alfesil prism 81 are perpendicular, and the overlap angle θ of both the magnetic tape MT and the Alfesil prism 81 is perpendicular. １ , θ ２The edge of the Alfesil prism is brought into contact with the magnetic surface (the surface of the magnetic layer side 43) so that the angle is 12 degrees. In this state, a 580m section of the magnetic tape MT is passed through 100 passes (50 back and forth) at a speed of 3.0m / s under a tension of 1.0N ± 0.1N. Next, the edge angle after wear is observed from above (perpendicular to the wear pattern) using an optical microscope, and the wear pattern width is measured at a total of three points in the tape width direction, 1 / 4, 1 / 2, and 3 / 4, as shown in Figure 11C. Next, the average value is calculated by simply averaging (arithmetic mean) the wear pattern widths of the three points, and this average value is taken as the wear width of the Alfesil prism 81. Note that both the above wear test and the measurement of wear width are performed in an environment of 23°C ± 2°C and 45% RH ± 5% RH.

[0239] Here, both wrap angles θ １ , θ ２ As shown in Figure 11B, the incident angle θ of the magnetic tape MT on the upstream side in the direction of travel of the magnetic tape MT. １ And the exit angle θ of the magnetic tape MT on the downstream side in the direction of travel of the magnetic tape MT. ２ This represents the incident angle θ of the magnetic tape MT. １ and the exit angle θ ２ This is an angle with the horizontal as the reference (0 degrees). Furthermore, upstream and downstream refer to the upstream and downstream of the moving magnetic tape MT as viewed from the point of contact between the magnetic tape MT and one edge of the Alfesil prism 81.

[0240] (Coercivity Hc2) The upper limit of the coercivity Hc2 of the magnetic layer 43 in the longitudinal direction of the magnetic tape MT is preferably 2200 Oe or less, more preferably 2000 Oe or less, and even more preferably 1900 Oe or less. When the coercivity Hc2 of the magnetic layer 43 in the longitudinal direction of the magnetic tape MT is 2200 Oe or less, sufficient electromagnetic conversion characteristics can be obtained even at high recording densities.

[0241] The lower limit of the coercivity Hc2 of the magnetic layer 43 measured in the longitudinal direction of the magnetic tape MT is preferably 1000Oe or more. When the coercivity Hc2 of the magnetic layer 43 measured in the longitudinal direction of the magnetic tape MT is 1000Oe or more, demagnetization due to leakage magnetic flux from the recording head can be suppressed.

[0242] The above coercivity Hc2 is determined as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and six pieces of magnetic tape MT are cut out from one end of the outer circumference of the magnetic tape MT at a position 30m to 40m in the longitudinal direction. At this time, the magnetic tape MT is marked with an arbitrary non-magnetic ink so that the longitudinal direction (travel direction) of the magnetic tape MT can be recognized. Next, the three cut pieces of magnetic tape MT are stacked together with double-sided tape so that their longitudinal directions are the same, and then punched out with a φ6.39 mm punch to create a measurement sample. Next, the M-H loop of the measurement sample (the entire magnetic tape MT) corresponding to the longitudinal direction (travel direction) of the magnetic tape MT is measured using a vibrating sample magnetometer (VSM). Next, the coatings (underlayer 42, magnetic layer 43, and back layer 44, etc.) of the remaining three cut pieces of magnetic tape MT are wiped off with acetone or ethanol, leaving only the substrate 41. Then, the obtained substrate 41 is stacked in three layers using double-sided tape, and punched out with a φ6.39 mm punch to create a sample for background correction (hereinafter simply referred to as the "correction sample"). Subsequently, the M-H loop of the correction sample (substrate 41) corresponding to the longitudinal direction of the substrate 41 (the longitudinal direction of the magnetic tape MT) is measured using a VSM.

[0243] For measuring the M-H loop of the measurement sample (the entire magnetic tape MT) and the M-H loop of the correction sample (substrate 41), 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.

[0244] After obtaining the M-H loop of the measurement sample (the entire magnetic tape MT) and the M-H loop of the correction sample (substrate 41), background correction is performed by subtracting the M-H loop of the correction sample (substrate 41) from the M-H loop of the measurement sample (the entire magnetic tape MT), and the background-corrected M-H loop is obtained. The measurement and analysis program included with the "VSM-P7-15" is used to calculate this background correction. The coercivity Hc2 is determined from the obtained background-corrected M-H loop. The measurement and analysis program included with the "VSM-P7-15" is used for this calculation as well. All of the above M-H loop measurements are performed at 25℃±2℃ and 50%RH±5%RH. Furthermore, "demagnetization correction" is not performed when measuring the M-H loop in the longitudinal direction of the magnetic tape MT.

[0245] (Square Ratio) The square ratio S1 of the magnetic layer 43 in the vertical direction of the magnetic tape MT is preferably 62% or more, more preferably 65% ​​or more, even more preferably 68% or more, 72% or more, or 75% or more. When the square ratio S1 is 62% or more, the vertical orientation of the magnetic particles becomes sufficiently high, so that excellent electromagnetic conversion characteristics can be obtained.

[0246] The aspect ratio S1 of the magnetic tape MT in the vertical direction is determined as follows. First, a measurement sample is prepared in the same manner as the method for measuring the coercivity Hc2 described above. Next, the M-H loop of the measurement sample (the entire magnetic tape MT) corresponding to the vertical direction of the magnetic tape MT is measured using a VSM. Next, a correction sample is prepared in the same manner as the method for measuring the coercivity Hc2 described above. After that, the M-H loop of the correction sample (substrate 41) corresponding to the vertical direction of the substrate 41 (the vertical direction of the magnetic tape MT) is measured using a VSM.

[0247] After obtaining the M-H loops of the measurement sample (the entire magnetic tape MT) and the correction sample (substrate 41), background correction is performed by subtracting the M-H loop of the correction sample (substrate 41) from the M-H loop of the measurement sample (the entire magnetic tape MT), and the M-H loop after background correction is obtained. The measurement and analysis program included with the "VSM-P7-15" is used to calculate this background correction.

[0248] The saturation magnetization Ms(emu) and remanent magnetization Mr(emu) of the M-H loop obtained after background correction are substituted into the following formula to calculate the square aspect ratio S1 (%). Note that all M-H loop measurements above are performed at 25°C ± 2°C and 50% RH ± 5% RH. Furthermore, "demagnetization correction" is not performed when measuring the M-H loop perpendicular to the magnetic tape MT. Note that the measurement and analysis program included with the "VSM-P7-15" is used for this calculation. Square aspect ratio S1 (%) = (Mr / Ms) × 100

[0249] The angularity ratio S2 of the magnetic layer 43 in the longitudinal direction (travel direction) of the magnetic tape MT is preferably 35% or less, more preferably 30% or less, and even more preferably 25% or less, 20% or less, or 15% or less. When the angularity ratio S2 is 35% or less, the vertical orientation of the magnetic particles becomes sufficiently high, so excellent electromagnetic conversion characteristics can be obtained. Note that one of the angularity ratio S1 of the magnetic layer 43 in the vertical direction of the magnetic tape MT and the angularity ratio S2 of the magnetic layer 43 in the longitudinal direction (travel direction) of the magnetic tape MT may be within the above preferred range, while the other may be outside the above preferred range. Alternatively, both the angularity ratio S1 of the magnetic layer 43 in the vertical direction of the magnetic tape MT and the angularity ratio S2 of the magnetic layer 43 in the longitudinal direction (travel direction) of the magnetic tape MT may be within the above preferred range.

[0250] The angular ratio S2 of the magnetic tape MT in the longitudinal direction is determined in the same manner as the angular ratio S1, except that the M-H loop is measured in the longitudinal direction (travel direction) of the magnetic tape MT and the base 41.

[0251] (Ratio Hc2 / Hc1) The ratio Hc2 / Hc1 of the coercivity Hc1 of the magnetic layer 43 in the vertical direction of the magnetic tape MT to the coercivity Hc2 of the magnetic layer 43 in the longitudinal direction of the magnetic tape MT preferably satisfies the relationship Hc2 / Hc1 ≤ 0.8, more preferably Hc2 / Hc1 ≤ 0.75, even more preferably Hc2 / Hc1 ≤ 0.7, Hc2 / Hc1 ≤ 0.65, or Hc2 / Hc1 ≤ 0.6. By satisfying the relationship Hc2 / Hc1 ≤ 0.8 for coercivity Hc1 and Hc2, the degree of vertical orientation of magnetic particles can be increased. Therefore, the magnetization transition width can be reduced and a high-output signal can be obtained during signal reproduction, resulting in excellent electromagnetic conversion characteristics. As described above, when Hc2 is small, magnetization responds sensitively to the magnetic field in the vertical direction from the recording head, so a good recording pattern can be formed.

[0252] There is no particular lower limit to Hc2 / Hc1, but for example, it is 0.5 ≤ Hc2 / Hc1. Note that Hc2 / Hc1 represents the degree of vertical orientation of the magnetic particles, and the smaller Hc2 / Hc1, the higher the degree of vertical orientation of the magnetic particles.

[0253] The method for calculating the coercivity Hc2 of the magnetic layer 43 in the longitudinal direction of the magnetic tape MT is as described above. The coercivity Hc1 of the magnetic layer 43 in the perpendicular direction of the magnetic tape MT is determined in the same manner as the coercivity Hc2 of the magnetic layer 43 in the longitudinal direction of the magnetic tape MT, except that the M-H loop is measured in the perpendicular direction (thickness direction) of the magnetic tape MT and the substrate 41.

[0254] (Activation volume V) ａｃｔ ) Activation volume V ａｃｔ However, preferably 8000 nm ３ More preferably, 6000 nm ３ More preferably, 4000 nm ３ Below, 3000nm ３ or less than 2000 nm ３ The following is the activation volume V. ａｃｔ 8000nm ３Under the following conditions, the dispersion state of magnetic particles is improved, allowing for a steeper bit inversion region and suppressing degradation of magnetization signals recorded on adjacent tracks due to leakage magnetic fields from the recording head. Therefore, excellent electromagnetic conversion characteristics can be obtained.

[0255] The above activation volume V ａｃｔ V can be obtained by the following formula derived by Street & Wolley. ａｃｔ (nm ３ ) = k Ｂ ×T×X ｉｒｒ / (μ ０ ×Ms×S) (However, k Ｂ : Boltzmann constant (1.38 × 10⁻⁶) －２３ J / K), T: temperature (K), Χ ｉｒｒ : Irreversible magnetic susceptibility, μ ０ : Permeability of vacuum, S: Magnetoviscosity, Ms: Saturation magnetization (emu / cm²) ３ ))

[0256] The irreversible magnetic susceptibility X is substituted into the above formula. ｉｒｒ The saturation magnetization Ms and magnetoviscosity coefficient S are determined using VSM as follows. The measurement direction using VSM is perpendicular to the magnetic tape MT (thickness direction). The VSM measurement is performed on a measurement sample cut from a long magnetic tape MT at 25°C ± 2°C and 50% RH ± 5% RH. No "demagnetization correction" is performed when measuring the M-H loop perpendicular to the magnetic tape MT (thickness direction).

[0257] (irreversible magnetic susceptibility Χ ｉｒｒ ) Irreversible magnetic susceptibility Χ ｉｒｒX is defined as the slope of the remanent magnetization curve (DCD curve) near the remanent coercivity Hr. First, a magnetic field of -1193 kA / m (15 kOe) is applied to the entire magnetic tape MT, and the magnetic field is returned to zero to enter a remanent magnetization state. Then, a magnetic field of approximately 15.9 kA / m (200 Oe) is applied in the opposite direction, and the remanent magnetization amount is measured again by returning to zero. Similarly, the measurement is repeated by applying a magnetic field 15.9 kA / m larger than the previously applied magnetic field and returning to zero, and the remanent magnetization amount is plotted against the applied magnetic field to measure the DCD curve. From the obtained DCD curve, the point where the magnetization amount is zero is defined as the remanent coercivity Hr, and the DCD curve is further differentiated to find the slope of the DCD curve at each magnetic field. In this slope of the DCD curve, the slope near the remanent coercivity Hr is X. ｉｒｒ This is the result.

[0258] (Saturation magnetization Ms) First, the M-H loop after background correction is obtained in the same manner as the measurement method for the square ratio S1 described above. Next, the value of the saturation magnetization Ms (emu) of the obtained M-H loop and the volume (cm³) of the magnetic layer 43 in the measurement sample are calculated. ３ ) from Ms(emu / cm ３ The volume of the magnetic layer 43 is calculated by multiplying the area of ​​the measurement sample by the average thickness t of the magnetic layer 43. ２ The average thickness t of the magnetic layer 43 is required to calculate the volume of the magnetic layer 43. ２ The calculation method is as described above.

[0259] (Magnetic viscosity coefficient S) First, a magnetic field of -1193 kA / m (15 kOe) is applied to the entire magnetic tape MT (measurement sample), and the magnetic field is returned to zero to return to a remanent magnetized state. Then, a magnetic field equivalent to the value of the remanent coercivity Hr obtained from the DCD curve is applied in the opposite direction. With the magnetic field applied, the amount of magnetization is continuously measured at regular time intervals for 1000 seconds. The relationship between time t and the amount of magnetization M(t) obtained in this way is compared with the following formula to calculate the magnetic viscosity coefficient S: M(t) = M0 + S × ln(t) (where M(t): amount of magnetization at time t, M0: initial amount of magnetization, S: magnetic viscosity coefficient, ln(t): natural logarithm of time)

[0260] (Surface roughness R of the back surface) ｂ) Surface roughness of the back surface (surface roughness of the back layer 44) R ｂ The upper limit is preferably 7.5 nm or less, more preferably 7.2 nm or less, even more preferably 7.0 nm or less, 6.5 nm or less, 6.3 nm or less, or 6.0 nm or less. Surface roughness R of the back surface ｂ If the surface roughness R of the back surface is 7.5 nm or less, the influence of the unevenness of the back surface on the surface of the magnetic layer 43 during winding of the magnetic tape MT can be reduced, and adverse effects on electromagnetic conversion characteristics can be suppressed. ｂ The lower limit is preferably 3.0 nm or more, more preferably 3.2 nm or more, and even more preferably 3.4 nm or more.

[0261] Back surface roughness R ｂ The following method is used to determine the surface roughness R of the back surface. First, the magnetic tape MT housed in the cartridge 10 is unwound, and a 100 mm length of the magnetic tape MT is cut from one end of the outer circumference of the magnetic tape MT, 30 m to 40 m in the longitudinal direction, to prepare a sample. Next, the sample is placed on a microscope slide with the surface to be measured (magnetic surface) facing upwards, and the ends of the sample are secured with mending tape. The surface shape is measured using a VertScan (20x objective lens) as the measuring device, and the surface roughness R of the back surface is calculated from the following formula based on the ISO 25178 standard. ｂ The following measurement conditions are used to determine the roughness. Equipment: Non-contact roughness meter using optical interference (VertScan R5500GL-M100-AC, non-contact surface / layer cross-sectional shape measurement system manufactured by Ryoka Systems Co., Ltd.) Objective lens: 20x Measurement area: 640 x 480 pixels (field of view: approximately 237 μm x 178 μm) Measurement mode: phase Wavelength filter: 520 nm CCD: 1 / 3 inch Noise reduction filter: Smoothing 3 x 3 Surface correction: Corrected using a quadratic polynomial approximation surface Measurement software: VS-Measure Version 5.5.2 Analysis software: VS-viewer Version 5.5.5 As described above, after measuring the surface roughness at five points along the longitudinal direction of the magnetic tape MT, the arithmetic mean roughness S was automatically calculated from the surface profiles obtained at each location. ａThe average value in nm represents the surface roughness R of the back surface. ｂ (nm)

[0262] (Young's modulus in the longitudinal direction of magnetic tape) The upper limit of the Young's modulus in the longitudinal direction of the magnetic tape MT is preferably 9.0 GPa or less, more preferably 8.0 GPa or less, even more preferably 7.5 GPa or less, and particularly preferably 7.1 GPa or less. When the Young's modulus in the longitudinal direction of the magnetic tape MT is 9.0 GPa or less, the elasticity of the magnetic tape MT due to external forces is further increased, making it easier to adjust the width of the magnetic tape MT by tension adjustment. Therefore, off-tracking can be suppressed more effectively, and the data recorded on the magnetic tape MT can be reproduced more accurately. The lower limit of the Young's modulus in the longitudinal direction of the magnetic tape MT is preferably 3.0 GPa or more, more preferably 4.0 GPa or more. When the lower limit of the Young's modulus in the longitudinal direction of the magnetic tape MT is 3.0 GPa or more, a decrease in the running stability of the magnetic tape MT can be suppressed.

[0263] The Young's modulus in the longitudinal direction of a magnetic tape MT is a value that indicates how difficult it is for the magnetic tape MT to expand or contract in the longitudinal direction due to external forces. The larger this value, the more difficult it is for the magnetic tape MT to expand or contract in the longitudinal direction due to external forces, and the smaller this value, the more easily the magnetic tape MT expands or contracts in the longitudinal direction due to external forces.

[0264] The Young's modulus in the longitudinal direction of the magnetic tape MT is a value related to the longitudinal direction of the magnetic tape MT, but it also correlates with the resistance of the magnetic tape MT to stretching and contracting in the width direction. In other words, the larger this value, the less the magnetic tape MT is susceptible to stretching and contracting in the width direction due to external forces, and the smaller this value, the more easily the magnetic tape MT is stretched and contracted in the width direction due to external forces. Therefore, from the viewpoint of tension adjustment, it is advantageous for the Young's modulus in the longitudinal direction of the magnetic tape MT to be small, as described above, and 9.0 GPa or less.

[0265] A tensile testing machine (Shimadzu Corporation, AG-100D) is used to measure Young's modulus. To measure the Young's modulus in the longitudinal direction of the tape, unwind the magnetic tape MT housed in cartridge 10, and cut a 180 mm length of magnetic tape MT from one end of the outer circumference of the magnetic tape MT, 30 m to 40 m in the longitudinal direction, to prepare the measurement sample. Attach a jig that can fix the tape width (1 / 2 inch) to the tensile testing machine and fix the top and bottom of the tape width. The distance (length of the tape between chucks) is set to 100 mm. After chucking the tape sample, gradually apply stress in the direction of tensile strength to the sample. The tensile speed is set to 0.1 mm / min. From the change in stress and the amount of elongation at this time, calculate the Young's modulus using the following formula: E (N / m) ２ )=((ΔN / S) / (Δx / L))×10 ６ ΔN: Change in stress (N) S: Cross-sectional area of ​​the test specimen (mm²) ２ ) Δx: elongation (mm) L: distance between gripping fixtures (mm) The cross-sectional area S of the measurement sample above is the cross-sectional area before the tensile action, and is obtained by product of the width (1 / 2 inch) and the thickness of the measurement sample. The range of tensile stress when performing the measurement is set to the range of tensile stress in the linear region according to the thickness of the magnetic tape MT, etc. Here, the stress range is set to 0.2 N to 0.7 N, and the stress change (ΔN) and elongation (Δx) at this time are used in the calculation. Note that the above Young's modulus measurement is performed at 25℃ ± 2℃ and 50% RH ± 5% RH.

[0266] (Young's modulus in the longitudinal direction of the substrate) The Young's modulus in the longitudinal direction of the substrate 41 is preferably 7.8 GPa or less, more preferably 7.0 GPa or less, even more preferably 6.6 GPa or less, and particularly preferably 6.4 GPa or less. When the Young's modulus in the longitudinal direction of the substrate 41 is 7.8 GPa or less, the elasticity of the magnetic tape MT due to external force is further increased, making it easier to adjust the width of the magnetic tape MT by tension adjustment. Therefore, off-track can be suppressed more effectively, and the data recorded on the magnetic tape MT can be reproduced more accurately. The lower limit of the Young's modulus in the longitudinal direction of the substrate 41 is preferably 2.5 GPa or more, more preferably 3.0 GPa or more. When the lower limit of the Young's modulus in the longitudinal direction of the substrate 41 is 2.5 GPa or more, a decrease in the running stability of the magnetic tape MT can be suppressed.

[0267] The longitudinal Young's modulus of the substrate 41 described above is determined as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and a 180 mm length of the magnetic tape MT is cut from one end on the outer circumference of the magnetic tape MT at a position 30 m to 40 m in the longitudinal direction. Next, the base layer 42, magnetic layer 43, and back layer 44 are removed from the cut magnetic tape MT to obtain the substrate 41. Using this substrate 41, the longitudinal Young's modulus of the substrate 41 is determined using the same procedure as for the longitudinal Young's modulus of the magnetic tape MT described above.

[0268] The thickness of the base body 41 accounts for more than half of the total thickness of the magnetic tape MT. Therefore, the Young's modulus in the longitudinal direction of the base body 41 is correlated with the resistance of the magnetic tape MT to expansion and contraction due to external forces. The larger this value, the less the magnetic tape MT is likely to expand and contract in the width direction due to external forces, and the smaller this value, the more likely the magnetic tape MT is to expand and contract in the width direction due to external forces.

[0269] The Young's modulus in the longitudinal direction of the base body 41 is a value related to the longitudinal direction of the magnetic tape MT, but it also correlates with the resistance of the magnetic tape MT to expansion and contraction in the width direction. In other words, the larger this value, the less the magnetic tape MT is susceptible to expansion and contraction in the width direction due to external forces, and the smaller this value, the more easily the magnetic tape MT is expanded and contracted in the width direction due to external forces. Therefore, from the viewpoint of tension adjustment, it is advantageous for the Young's modulus in the longitudinal direction of the base body 41 to be small, as described above, and 7.8 GPa or less.

[0270] [5 Method for Manufacturing Magnetic Tape] Next, an example of a method for manufacturing a magnetic tape MT having the above configuration will be described.

[0271] (Paint preparation process) First, a primer-forming paint is prepared by mixing and dispersing non-magnetic particles and binders in a solvent. Next, a magnetic layer-forming paint is prepared by mixing and dispersing magnetic particles and binders in a solvent. For the preparation of the magnetic layer-forming paint and the primer-forming paint, for example, the following solvents, mixing equipment and dispersion equipment can be used.

[0272] Examples of solvents used in the preparation of the above-mentioned paints include ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; alcohol solvents such as methanol, ethanol, and propanol; ester solvents such as methyl acetate, ethyl acetate, butyl acetate, propyl acetate, ethyl lactate, and ethylene glycol acetate; ether solvents such as diethylene glycol dimethyl ether, 2-ethoxyethanol, tetrahydrofuran, and dioxane; aromatic hydrocarbon solvents such as benzene, toluene, and xylene; and halogenated hydrocarbon solvents such as methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, and chlorobenzene. These may be used individually or in appropriate mixtures of two or more.

[0273] For the preparation of the paint described above, mixing equipment such as a continuous twin-screw mixer, a continuous twin-screw mixer capable of multi-stage dilution, a kneader, a pressure kneader, and a roll kneader may be used, but the equipment is not limited to these. Furthermore, for the preparation of the paint described above, dispersion equipment such as a roll mill, a ball mill, a horizontal sand mill, a vertical sand mill, a spike mill, a pin mill, a tower mill, a pearl mill (for example, Eich's "DCP mill"), a homogenizer, and an ultrasonic disperser may be used, but the equipment is not limited to these.

[0274] (Coating Process) Next, a base layer 42 is formed by applying a base layer forming paint to one main surface of the substrate 41 and drying it. Subsequently, a magnetic layer forming paint is applied to the base layer 42 and dried it to form a magnetic layer 43 on the base layer 42. During drying, the magnetic particles may be oriented in the thickness direction of the substrate 41 using a magnetic field, for example, a permanent magnet. After the formation of the magnetic layer 43, a back layer 44 is formed on the other main surface of the substrate 41. This gives rise to a magnetic tape MT. The order of formation of the base layer 42, magnetic layer 43, and back layer 44 is not limited to the above example. For example, the back layer 44 may be formed on the other main surface of the substrate 41, and then the base layer 42 and magnetic layer 43 may be formed sequentially on one main surface of the substrate 41.

[0275] The square ratios S1 and S2 can be set to desired values ​​by adjusting, for example, the strength of the magnetic field applied to the coating film 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 film of the magnetic layer forming paint. The strength of the magnetic field applied to the coating film is preferably two to three times the coercivity of the magnetic particles. To further increase the square ratio S1 (i.e., to further decrease the square ratio S2), it is preferable to improve the dispersion state of the magnetic particles in the magnetic layer forming paint. Furthermore, to further increase the square ratio S1, it is also effective to magnetize the magnetic particles before the magnetic layer forming paint enters the orientation device for magnetic field orientation of the magnetic particles. Note that the above methods for adjusting the square ratios S1 and S2 may be used individually or in combination of two or more.

[0276] (Curing process) Next, after winding the magnetic tape MT into a roll, the base layer 42 and the magnetic layer 43 are cured by applying a heat treatment to the magnetic tape MT in this state.

[0277] (Calculating process) Next, the cured magnetic tape MT is calendered to smooth the magnetic surface.

[0278] (Aging process) Next, if necessary, the magnetic tape MT after calendaring is subjected to an aging process.

[0279] (Cutting process) Next, the magnetic tape MT is cut to a predetermined width (for example, 1 / 2 inch width).

[0280] (Servo writing process) Next, if necessary, the magnetic tape MT may be demagnetized and then the servo pattern may be written to the magnetic tape MT.

[0281] (Average hardness H) 50 , average plastic deformation amount D 50 and the mean modulus of elasticity Er 50 (Adjustment method) Average hardness H 50 , average plastic deformation amount D 50 and the mean modulus of elasticity Er 50 For example, this can be adjusted to a predetermined value by adjusting the curing conditions in the curing process (curing temperature and curing time, etc.), the amount of abrasive particles mixed into the magnetic layer forming paint, the amount of curing agent mixed into the magnetic layer forming paint, and the ratio of the amount of magnetic particles P1 to the amount of binder B1 (P1 / B1) in the magnetic layer forming paint.

[0282] (Average hardness H) 150 , average plastic deformation amount D 150 and the mean modulus of elasticity Er 150 (Adjustment method) Average hardness H 150 , average plastic deformation amount D 150 and the mean modulus of elasticity Er 150This can be adjusted to a predetermined value by, for example, adjusting the curing conditions in the curing process (curing temperature and curing time, etc.), the amount of curing agent mixed into the primer-forming paint, and the ratio of the amount of non-magnetic particles P2 to the amount of binder B2 in the primer-forming paint (P2 / B2).

[0283] (Ratio (H 50 / H 150 ) and ratio (D 50 / D 150 (Adjustment method) Average hardness H 50 and average hardness H 150 The ratio (H 50 / H 150 ) and average plastic deformation amount D 50 and average plastic deformation amount D 150 The ratio (D 50 / D 150 The curing properties can be adjusted to a predetermined value by, for example, adjusting the curing conditions in the curing process (curing temperature and curing time, etc.), the amount of abrasive particles mixed into the magnetic layer forming paint, the amount of curing agent mixed into the magnetic layer forming paint, the amount of curing agent mixed into the base layer forming paint, the ratio of the amount of magnetic particles P1 to the amount of binder B1 in the magnetic layer forming paint (P1 / B1), and the ratio of the amount of non-magnetic particles P2 to the amount of binder B2 in the base layer forming paint (P2 / B2).

[0284] [6. Effects] As described above, in the magnetic tape MT according to one embodiment, the average hardness H obtained by pressing a triangular pyramidal diamond indenter with a 142.3° edge angle perpendicular to the surface of the magnetic layer 43 with a load of 50 μN is 50 However, since it is 0.72 GPa or higher, the contact state between the magnetic tape MT and the head unit 56 becomes stable. Therefore, a stable signal output can be obtained, and good electromagnetic conversion characteristics can be obtained. In addition, the average plastic deformation amount D, which is determined by pressing a triangular pyramidal diamond indenter perpendicularly to the surface of the magnetic layer 43 with a load of 50 μN, is obtained. 50However, since it is 16.50 nm or less, it is possible to suppress the excessive polishing force of the magnetic tape MT on the head unit 56. Therefore, wear of the head unit 56 can be suppressed. Thus, in the magnetic tape MT according to one embodiment, good electromagnetic conversion characteristics can be obtained and wear of the head unit 56 can be suppressed.

[0285] As described above, the magnetic tape MT according to one embodiment can suppress wear of the head unit 56, and therefore can suppress damage to the drive's head unit 56 in the tape library. Consequently, the reliability of the tape library can be improved.

[0286] From the viewpoint of increasing the capacity of the cartridge 10, the average thickness of the magnetic tape MT is preferably 5.50 μm or less, and from the viewpoint of improving electromagnetic conversion characteristics, the average thickness of the magnetic layer 43 is preferably 0.07 μm or less. Furthermore, from the viewpoint of improving the linear recording density D of the magnetic tape MT, the bit area is 40,000 nm. ２ The following conditions are met, and it is preferable that the bit length T of the signal that can be recorded in the data band DB is 47.0 nm or less, and the data track width W is 1000 nm or less. In order to obtain a stable signal output with such a small bit size, it is desirable that the contact state between the magnetic tape MT and the head unit 56 is stable. In one embodiment of the magnetic tape MT, the average hardness H was determined by pressing a triangular pyramidal diamond indenter with a 142.3° edge angle perpendicular to the surface on the magnetic layer side with a load of 50 μN. 50 However, since the pressure is 0.72 GPa or higher, the contact between the magnetic tape MT and the head unit 56 can be stabilized. Therefore, even with such a small bit size, a stable signal output can be obtained. In other words, even with such a small bit size, good electromagnetic conversion characteristics can be obtained.

[0287] [7 Modified Examples] In the above embodiment, the case where the magnetic tape cartridge is a single-reel type cartridge 10 was described, but it may also be a two-reel type cartridge.

[0288] Figure 12 is an exploded perspective view showing an example of the configuration of a two-reel type cartridge 321. The cartridge 321 comprises an upper half 302 made of synthetic resin, a transparent window member 323 fitted into and fixed to a window portion 302a opened on the upper surface of the upper half 302, a reel holder 322 fixed to the inside of the upper half 302 to prevent the reels 306 and 307 from floating up, a lower half 305 corresponding to the upper half 302, reels 306 and 307 housed in the space created by combining the upper half 302 and the lower half 305, magnetic tape MT wound on the reels 306 and 307, a front lid 309 that closes the front opening created by combining the upper half 302 and the lower half 305, and a back lid 309A that protects the magnetic tape MT exposed to this front opening.

[0289] Reels 306 and 307 are for winding magnetic tape MT. Reel 306 comprises a lower flange 306b having a cylindrical hub portion 306a in the center on which the magnetic tape MT is wound, an upper flange 306c that is approximately the same size as the lower flange 306b, and a reel plate 311 sandwiched between the hub portion 306a and the upper flange 306c. Reel 307 has the same configuration as reel 306.

[0290] The window member 323 is provided with mounting holes 323a at positions corresponding to the reels 306 and 307 for assembling reel holders 322, which are reel holding means for preventing the reels from lifting up. The magnetic tape MT is the same as the magnetic tape MT in one embodiment.

[0291] The present disclosure will be specifically described below with reference to examples, but the present disclosure is not limited to these examples.

[0292] In the following examples and comparative examples, the average thickness of the magnetic tape, the average thickness of the substrate (PEN film, aramid film), the average thickness of the magnetic layer, the average thickness of the underlayer, the average thickness of the backing layer, the composition of the magnetic particles (magnetic powder), and the average particle volume of the magnetic powder (magnetic particles) are values ​​obtained by the measurement method described in the above embodiment.

[0293] [Example 1] (Preparation process for magnetic layer forming coating) A magnetic layer forming coating was prepared as follows. First, the first composition with the following formulation was kneaded in an extruder. Next, the kneaded first composition and the 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 magnetic layer forming coating.

[0294] (First composition) Barium ferrite (Ba ０．５４ Sr ０．４６ Fe １２ O １９ ) Magnetic powder (hexagonal plate shape, average aspect ratio 2.8, average particle volume 1.10 × 10⁻⁶) ３ nm ３ ): 100.0 parts by mass of vinyl chloride resin solution (composition of resin solution: vinyl chloride resin 30.0% by mass, cyclohexanone solution 70.0% by mass) (vinyl chloride resin: degree of polymerization 300, number average molecular weight Mn = 10000, polar group OSO ３ Contains K = 0.07 mmol / g and secondary OH = 0.3 mmol / g. ): 50.0 parts by mass Polyurethane resin solution (Formulation of resin solution: Polyurethane resin content 30.0% by mass, Cyclohexanone content 70.0% by mass) (Polyurethane resin: Number average molecular weight Mn = 25000, Glass transition temperature Tg = 110°C): 25.0 parts by mass Aluminum oxide powder (α-Al ２ O ３ (Average particle size 0.1 μm): 7.0 parts by mass Methyl ethyl ketone: 540 parts by mass Toluene: 210 parts by mass Cyclohexanone: 245 parts by mass

[0295] (Second Composition) Carbon black (manufactured by Tokai Carbon Co., Ltd., product name: Seest S, arithmetic mean particle size 70 nm): 1.5 parts by mass Polyurethane resin solution (resin solution composition: polyurethane resin content 30.0% by mass, cyclohexanone content 70.0% by mass) (polyurethane resin: number average molecular weight Mn = 25000, glass transition temperature Tg = 110°C): 2.0 parts by mass n-butyl stearate: 2.0 parts by mass

[0296] Finally, to the magnetic layer-forming coating prepared as described above, 3.5 parts by mass of polyisocyanate (equivalent to Coronate L manufactured by Tosoh Corporation) and 2.0 parts by mass of stearic acid were added as curing agents.

[0297] (Preparation process for primer-forming paint) The primer-forming paint 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 paint.

[0298] (Third composition) Needle-shaped iron oxide powder (α-Fe ２ O ３ , average major axis length 0.11 μm): 100.0 parts by mass of vinyl chloride resin solution (resin solution composition: vinyl chloride resin 30.0% by mass, cyclohexanone solution 70.0% by mass) (vinyl chloride resin: degree of polymerization 300, number average molecular weight Mn = 10000, polar group OSO ３ Contains K = 0.07 mmol / g and secondary OH = 0.3 mmol / g. ): 74.0 parts by mass Aluminum oxide powder (α-Al ２ O ３ (Average particle size 0.1 μm): 5.0 parts by mass Methyl ethyl ketone: 240.0 parts by mass Toluene: 120.0 parts by mass Cyclohexanone: 10.0 parts by mass

[0299] (Fourth Composition) Carbon black (manufactured by Asahi Carbon Co., Ltd., product name: #80): 30.0 parts by mass Polyurethane resin solution (resin solution composition: amount of polyurethane resin 30.0% by mass, amount of cyclohexanone 70.0% by mass) (polyurethane resin: number average molecular weight Mn = 25000, glass transition temperature Tg = 70°C): 45.0 parts by mass n-butyl stearate: 2.0 parts by mass Methyl ethyl ketone: 60.0 parts by mass Cyclohexanone: 70.0 parts by mass

[0300] Finally, to the primer-forming paint prepared as described above, 3.6 parts by mass of polyisocyanate (equivalent to Coronate L manufactured by Tosoh Corporation) and 1.5 parts by mass of stearic acid were added as curing agents.

[0301] (Preparation process for back layer forming coating) The back layer forming coating was prepared as follows. The following raw materials were mixed in a stirring tank equipped with a disperser and filtered to prepare the back layer forming coating. Carbon black (manufactured by Asahi Carbon Co., Ltd., product name: #80): 100.0 parts by mass Polyester polyurethane (manufactured by Nippon Polyurethane Industry Co., Ltd., product name: N-2304): 100.0 parts by mass Methyl ethyl ketone: 500.0 parts by mass Toluene: 400.0 parts by mass Cyclohexanone: 100.0 parts by mass Polyisocyanate (equivalent to Coronate L manufactured by Tosoh Corporation): 10.0 parts by mass

[0302] (Coating Process) Using the magnetic layer forming paint and the base layer forming paint prepared as described above, a base layer and a magnetic layer were formed on one main surface of a long PEN film (substrate) having an average thickness of 4.00 μm as follows. First, the base layer forming paint was applied to one main surface of the PEN film and dried to form a base layer such that the average thickness of the base layer at the time of completion of the magnetic tape (average thickness of the base layer after the cutting process) was 0.80 μm. Next, the magnetic layer forming paint was applied on the base layer and dried to form a magnetic layer such that the average thickness of the magnetic layer at the time of completion of the magnetic tape (average thickness of the magnetic layer after the cutting process) was 0.06 μm. During the drying of the magnetic layer forming paint, a permanent magnet was used to orient the barium ferrite magnetic powder in the thickness direction of the PEN film using a magnetic field. After forming the underlayer and magnetic layer, a back layer-forming coating was applied to the other main surface of the PEN film and dried to form a back layer such that the average thickness of the completed magnetic tape (average thickness after the cutting process) was 0.33 μm. This resulted in the acquisition of a magnetic tape.

[0303] (Curing process) After winding the magnetic tape into a roll, the base layer, magnetic layer, and backing layer were cured by heat treatment at 65°C for 25 hours in this state.

[0304] (Calcane process) After curing, the magnetic tape was calendered to smooth the surface of the magnetic layer. The calendering process was carried out at a temperature close to the glass transition temperature Tg (=110°C) of the polyurethane resin (binder) contained in the magnetic layer (slightly higher than Tg).

[0305] (Aging process) The magnetic tape after calendering was subjected to an aging process for 20 hours in a 60°C environment.

[0306] (Cutting process) By cutting the magnetic tape after aging treatment, a magnetic tape with a width of 1 / 2 inch (12.65 mm) and an average thickness of 5.19 μm was obtained.

[0307] [Example 2] A magnetic tape was obtained in the same manner as in Example 1, except that the amount of aluminum oxide powder added to the first composition was changed from 7.0 parts by mass to 5.0 parts by mass in the preparation step of the coating for forming the magnetic layer.

[0308] [Comparative Example 1] A magnetic tape was obtained in the same manner as in Example 1, except that in the preparation step of the coating for forming the magnetic layer, the amount of vinyl chloride resin solution added to the first composition was changed from 50.0 parts by mass to 35.0 parts by mass, and in the preparation step of the coating for forming the base layer, the amount of vinyl chloride resin solution added to the third composition was changed from 74.0 parts by mass to 54.0 parts by mass.

[0309] [Comparative Example 2] A magnetic tape was obtained in the same manner as in Example 1, except that the amount of vinyl chloride resin solution added to the first composition was changed from 50.0 parts by mass to 35.0 parts by mass in the preparation step of the coating for forming the magnetic layer.

[0310] [Comparative Example 3] A magnetic tape was obtained in the same manner as in Example 1, except that the amount of polyisocyanate added to the base layer forming paint in the preparation step of the base layer forming paint was changed from 3.6 parts by mass to 7.1 parts by mass.

[0311] [Comparative Example 4] A magnetic tape was obtained in the same manner as in Example 1, except for the following points. In the preparation step of the coating for forming the magnetic layer, the amount of vinyl chloride resin solution added to the first composition was changed from 50.0 parts by mass to 35.0 parts by mass. In the preparation step of the coating for forming the base layer, the amount of vinyl chloride resin solution added to the third composition was changed from 74.0 parts by mass to 54.0 parts by mass. In the coating step, the substrate was changed from a PEN film to an aramid film. In the curing step, the heat treatment temperature was lowered by 5°C.

[0312] [Evaluation] The magnetic tapes obtained as described above were evaluated as follows.

[0313] (Average modulus of elasticity Er 50 Er 150 ) The average modulus of elasticity Er as described in the above embodiment 150 This value was determined by the method described above. The average modulus of elasticity Er is the same as described in the above embodiment, except that the indentation test is performed within a load range of 0 μN to 50 μN. 150 Similarly to the method for calculating the mean modulus of elasticity, 50 The average modulus of elasticity Er was calculated. 50 and the mean modulus of elasticity Er 150 The average modulus of elasticity Er was determined using the same samples 1 and 2. 50 and the mean modulus of elasticity Er 150 This is shown in Table 1.

[0314] (Average hardness H) 50 H 150 and their ratio (H 50 / H 150 )) The average hardness H described in the above embodiment 50 H 150 and their ratio (H 50 / H 150 These values ​​were obtained using the method described above. The results are shown in Table 1.

[0315] (Average plastic deformation amount D) 50 , D 150 and their ratio (D 50 / D 150)) The average plastic deformation amount D described in the above embodiment 50 , D 150 and their ratio (D 50 / D 150 These values ​​were obtained using the method described above. The results are shown in Table 1.

[0316] (Wear width of Alfesil prism) This value was determined using the method for determining the wear width of the Alfesil prism described in the above embodiment. The results are shown in Table 1. Note that if the wear width of the Alfesil prism exceeds 17 μm, there is a high possibility that the magnetic recording head will be damaged due to wear when data is repeatedly recorded on magnetic tape using a tape storage drive equipped with a new (unused) magnetic recording head. Therefore, the quality of the wear width was judged based on a wear width of 17 μm.

[0317] (Electromagnetic Conversion Characteristics) The electromagnetic conversion characteristics were evaluated by SNR. The SNR was measured as follows. First, a loop tester (Microphysics) was used to acquire the playback signal of the magnetic tape. The conditions for acquiring the playback signal are shown below. head: GMR headspeed: 1.85 m / s signal: single recording frequency 10 MHz (as 2T half Nyquist frequency) recording current: optimal recording current

[0318] Next, the playback signal was captured using a spectrum analyzer with a span of 0 to 20 MHz (resolution bandwidth = 100 kHz, VBW = 30 kHz). The peaks of the captured spectrum were defined as the signal intensity S, and the floor noise, excluding the peaks, was integrated from 3 MHz to 20 MHz to determine the noise intensity N. The signal-to-noise ratio (SNR) was then calculated as the ratio S / N of the signal intensity S to the noise intensity N. Next, the calculated SNR was converted to a relative value (dB) with the SNR of Comparative Example 2, used as a reference medium, as the reference (0 dB). The results are shown in Table 1. Note that if the SNR value is below that of Comparative Example 2, there is a risk that good electromagnetic conversion characteristics (SNR) will not be obtained when playing the magnetic tape using a tape storage drive; therefore, the SNR of Comparative Example 2 was used as the reference as described above.

[0319]

[0320] The following was found from the above evaluation results. In the following explanation of the evaluation results, the P1 / B1 ratio of the magnetic layer refers to the ratio (P1 / B1) of the amount of magnetic powder P1 and the amount of binder B1 contained in the magnetic layer, and the P2 / B2 ratio of the base layer refers to the ratio (P2 / B2) of the amount of non-magnetic powder (acupuncture iron oxide powder) P2 and the amount of binder B2 contained in the base layer.

[0321] In Examples 1 and 2, the average hardness H 50 The pressure is 0.72 GPa or higher, and the average plastic deformation amount D 50 The hardness is 16.50 nm or less. Therefore, good electromagnetic conversion characteristics can be obtained, and wear of the magnetic recording head can be suppressed. Average hardness H of Example 2 50 The average hardness H of Example 1 50 Because it is higher, the electromagnetic conversion characteristics of Example 2 are improved compared to the electromagnetic conversion characteristics of Example 1. Also, the average plastic deformation amount D of Example 2 50 The average plastic deformation amount D in Example 1 is 50 Because it is smaller than the wear width of the Alfesil prism in Example 2, the wear width of the Alfesil prism in Example 1 is narrower than the wear width of the Alfesil prism in Example 1.

[0322] The P1 / B1 ratio of the magnetic layer in Comparative Example 1 is larger than that of the magnetic layer in Example 1, and the P2 / B2 ratio of the underlayer in Comparative Example 1 is larger than that of the underlayer in Example 1. Therefore, in Comparative Example 1, the average hardness H 50 The pressure decreased to 0.64 GPa, resulting in a deterioration of the electromagnetic conversion characteristics. In Comparative Example 1, the average plastic deformation amount D 50 The size increased to 17.03 nm, and as a result, the wear width of the Alfesil prism increased to 20 nm.

[0323] The P1 / B1 ratio of the magnetic layer in Comparative Example 2 is larger than that of the magnetic layer in Example 1. Therefore, in Comparative Example 2, the average hardness H 50 The pressure has decreased to 0.71 GPa, resulting in a deterioration of the electromagnetic conversion characteristics.

[0324] The amount of polyisocyanate (hardener) in the substrate layer of Comparative Example 3 is greater than the amount of polyisocyanate (hardener) in the substrate layer of Example 1. Therefore, the average hardness H of Comparative Example 3 is lower. 50 This is the average hardness H of Example 1. 50 It is higher than the average plastic deformation D of Comparative Example 3. 50 This is the average plastic deformation amount D of Example 1. 50 It has become larger than that, reaching 18.00 nm, and as a result, the wear width of the Alfesil prism has increased to 18 nm.

[0325] In Comparative Example 4, the P1 / B1 ratio of the magnetic layer is larger than that of the magnetic layer in Example 1, and the P2 / B2 ratio of the underlayer in Comparative Example 4 is larger than that of the magnetic layer in Example 1. Therefore, in Comparative Example 4, the average plastic deformation amount D 50 The average hardness H increased to 16.60 nm, and as a result, the wear width of the Alfesil prism increased to 19 nm. However, in Comparative Example 4, the average hardness H 50 The pressure is maintained at 0.72 GPa or higher. Therefore, in Comparative Example 4, good electromagnetic conversion characteristics were obtained. As described above, the average hardness H 50The reason why the hardness is maintained above 0.72 GPa is thought to be as follows: The curing temperature in the curing process of Comparative Example 4 is lower than the curing temperature in the curing process of Example 1, so the calendering efficiency is improved, that is, the curing of the magnetic layer and the substrate layer progresses slowly in the curing process, and because the magnetic layer and the substrate layer are soft, they are more easily crushed in the calendering process. As a result, the average hardness H 50 The pressure will be maintained above 0.72 GPa.

[0326] While embodiments and modifications of the present disclosure have been described in detail above, the present disclosure is not limited to the embodiments and modifications described above, and various modifications are possible based on the technical idea of ​​the present disclosure. For example, the configurations, methods, processes, shapes, materials, and numerical values ​​given in the above embodiments and modifications are merely examples, and different configurations, methods, processes, shapes, materials, and numerical values ​​may be used as needed. The configurations, methods, processes, shapes, materials, and numerical values ​​of the above embodiments and modifications can be combined with each other as long as they do not deviate from the spirit of the present disclosure.

[0327] The chemical formulas of the compounds exemplified in the above embodiments are representative examples, and the general name of the same compound is not limited to the stated valency, etc. In the numerical ranges described in steps in the above embodiments, 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 the above embodiments can be used individually or in combination of two or more.

[0328] Furthermore, the present disclosure may also adopt the following configuration: (1) A tape-shaped magnetic recording medium comprising, in order, a substrate, a base layer, and a magnetic layer, wherein the average thickness of the magnetic recording medium is 5.50 μm or less, the average thickness of the magnetic layer is 0.07 μm or less, and the average hardness H is determined by pressing a triangular pyramidal diamond indenter with a 142.3° edge angle perpendicular to the surface of the magnetic layer with a load of 50 μN. 50However, the average plastic deformation amount D is 0.72 GPa or higher, and is determined by pressing the triangular pyramidal diamond indenter perpendicularly to the surface on the magnetic layer side with the load of 50 μN. 50 However, the magnetic recording medium is 16.50 nm or less. (2) The average plastic deformation amount D 50 The average plastic deformation amount D is determined by pressing the triangular pyramidal diamond indenter perpendicularly against the surface of the magnetic layer with a load of 150 μN. 150 The ratio (D 50 / D 150 (1) The magnetic recording medium described in (1), wherein the average hardness H 50 The average hardness H was determined by pressing the triangular diamond indenter perpendicularly against the surface of the magnetic layer with a load of 150 μN. 150 Ratio to (H 50 / H 150 (1) or (2), wherein the average modulus Er obtained by pressing the triangular diamond indenter perpendicular to the surface on the magnetic layer side with a load of 150 μN is 9.00 GPa or less, according to any one of (1) to (3). (5) The average hardness H 50 However, the average plastic deformation amount D is 0.75 GPa or higher. 50A magnetic recording medium according to any one of (1) to (4), wherein the thickness is 14.47 nm or less. (6) A magnetic recording medium according to any one of (1) to (5), wherein the longitudinal direction of the magnetic recording medium and the longitudinal direction of the Alfesil prism are perpendicular, and the overlap angle of both the magnetic recording medium and the Alfesil prism is 12 degrees, and the surface on the magnetic layer side is brought into contact with one edge of the Alfesil prism, and in this state, the wear width of the Alfesil prism after 100 passes (50 round trips) of a 580 m length portion of the magnetic recording medium at a speed of 3.0 m / s under a tension of 1.0 N ± 0.1 N is 17 μm or less. (7) A magnetic recording medium according to any one of (1) to (6), wherein the sum of the average thickness of the magnetic layer and the average thickness of the underlayer is 0.95 μm or less. (8) The magnetic recording medium according to any one of (1) to (7), wherein the average thickness of the underlayment is 0.80 μm or less. (9) The magnetic recording medium according to any one of (1) to (8), wherein the average thickness of the magnetic layer is 0.03 μm or more. (10) The magnetic recording medium according to any one of (1) to (9), further comprising a back layer, wherein the sum of the average thickness of the magnetic layer, the average thickness of the underlayment, and the average thickness of the back layer is 1.20 μm or less. (11) The magnetic recording medium according to any one of (1) to (10), wherein the magnetic layer has a servo pattern, the servo pattern includes a plurality of first magnetization regions and a plurality of second magnetization regions, and the plurality of first magnetization regions and the plurality of second magnetization regions are asymmetric with respect to an axis parallel to the width direction of the magnetic recording medium. (12) The magnetic recording medium according to (11), wherein the inclination angle of the first magnetization region with respect to the axis is different from the inclination angle of the second magnetization region with respect to the axis, and the larger of the inclination angles of the first magnetization region and the second magnetization region is 18° or more and 28° or less. (13) A cartridge comprising the magnetic recording medium according to any one of (1) to (12).

[0329] 10, 321 Cartridge 11 Cartridge memory 31 Antenna coil 32 Rectifier / power supply circuit 33 Clock circuit 34 Detection / modulation circuit 35 Controller 36 Memory 36A First memory area 36B Second memory area 41 Substrate 42 Underlayer 43 Magnetic layer 44 Back layer 56 Head unit 56A, 56B Servo lead head 61, 62 Head 71 Indenter 81 Alfesil prism 82 Fixing jig 83 Support plate 84 Screw 110 Servo frame 111 Servo subframe 1 112 Servo subframe 2 113 Servo stripe 111A A burst 111B B burst 112C C burst 112D D burst MT Magnetic tape SB Servo band DB Data band Tk Data Track

Claims

A tape-shaped magnetic recording medium, It comprises a substrate, a base layer, and a magnetic layer in that order. The average thickness of the magnetic recording medium is 5.50 μm or less. The average thickness of the magnetic layer is 0.07 μm or less. The average hardness H was determined by pressing a triangular pyramidal diamond indenter with a 142.3° edge angle perpendicular to the surface of the magnetic layer with a load of 50 μN. 50 However, it is 0.72 GPa or higher. The average plastic deformation amount D was determined by pressing the aforementioned triangular diamond indenter perpendicularly against the surface of the magnetic layer with a load of 50 μN. 50 However, it is less than 16.50 nm. Magnetic recording medium. The average plastic deformation amount D 50 The average plastic deformation amount D is determined by pressing the triangular pyramidal diamond indenter perpendicularly against the surface of the magnetic layer with a load of 150 μN. 150 The ratio (D 50 / D 150 ) is 0.36 or less. The magnetic recording medium according to claim 1. The average hardness H 50 and the average hardness H obtained by pushing the triangular pyramid diamond indenter vertically against the surface on the magnetic layer side with a load of 150 μN 150 The ratio (H 50 / H 150 ) is 1.42 or more The magnetic recording medium according to claim 1. 　 The average modulus Er, determined by pressing the aforementioned triangular diamond indenter perpendicularly against the surface of the magnetic layer with a load of 150 μN, is 9.00 GPa or less. The magnetic recording medium according to claim 1. The aforementioned average hardness H 50 However, it is 0.75 GPa or higher, The average plastic deformation amount D 50 However, it is less than 14.47 nm. The magnetic recording medium according to claim 1. 　 The longitudinal direction of the magnetic recording medium and the longitudinal direction of the Alfesil prism are perpendicular to each other, and the overlap angle of both the magnetic recording medium and the Alfesil prism is 12 degrees. The surface on the magnetic layer side is brought into contact with one edge of the Alfesil prism, and in this state, after 100 passes (50 reciprocals) of a 580 m length portion of the magnetic recording medium at a speed of 3.0 m / s under a tension of 1.0 N ± 0.1 N, the wear width of the Alfesil prism is 17 μm or less. The magnetic recording medium according to claim 1. 　 The sum of the average thickness of the magnetic layer and the average thickness of the underlayer is 0.95 μm or less. The magnetic recording medium according to claim 1. 　 The average thickness of the aforementioned subsoil is 0.80 μm or less. The magnetic recording medium according to claim 1. 　 The average thickness of the magnetic layer is 0.03 μm or more. The magnetic recording medium according to claim 1. 　 With an additional back layer, The sum of the average thickness of the magnetic layer, the average thickness of the underlayment layer, and the average thickness of the backing layer is 1.20 μm or less. The magnetic recording medium according to claim 1. 　 The magnetic layer has a servo pattern, The servo pattern includes a plurality of first magnetization regions and a plurality of second magnetization regions. The plurality of first magnetization regions and the plurality of second magnetization regions are asymmetrical with respect to an axis parallel to the width direction of the magnetic recording medium. The magnetic recording medium according to claim 1. 　 The inclination angle of the first magnetization region with respect to the axis and the inclination angle of the second magnetization region with respect to the axis are different. The larger of the inclination angles of the first magnetization region and the second magnetization region is 18° or more and 28° or less. The magnetic recording medium according to claim 11. 　 A magnetic recording medium as described in claim 1, cartridge.

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