Magnetic recording medium and cartridge

Abstract

Provided is a magnetic recording medium that can suppress shifting of a magnetic tape during actual travel, in both a drive that has a parallel head unit and a drive that has an oblique head unit.　This magnetic recording medium is tape-shaped, and comprises a substrate and a magnetic layer that includes magnetic particles. The average thickness of the magnetic recording medium is 5.30 μm or less. As measured by hanging a 30 g weight on one end of the magnetic recording medium, pressing a round rod that has a diameter of 3 mm and is made of stainless steel against the magnetic layer-side surface, and rotating the round rod at 125 rpm while moving the magnetic recording medium in the longitudinal direction at a speed of 2 mm / s, the average tension T acting in the longitudinal direction of the magnetic recording medium is 55.0 gf or less. The average dynamic friction coefficient μ of the magnetic layer-side surface as measured by moving the magnetic recording medium in the longitudinal direction at a speed of 6 mm / s is 0.35 or less.

Description

Magnetic recording media and cartridges

[0001] The present disclosure relates to a magnetic recording medium and a cartridge including the same.

[0002] Due to the Internet of Things (IoT) and big data analysis, the amount of data to be archived is increasing, and there is a demand for increased capacity in the recording media used for archiving. Tape-type magnetic recording media for archiving (hereinafter sometimes referred to as "magnetic tape") have the advantages of low cost and high capacity.

[0003] In magnetic tapes, it is desirable to suppress an increase in the dynamic friction coefficient so that the head can accurately trace the data track. For example, in Patent Document 1, in order to obtain excellent running stability, the dynamic friction coefficient μ Ｃ (5) and the dynamic friction coefficient μ Ｃ Friction coefficient ratio (μ Ｃ (1000) / μ Ｃ (5)) is set to 1.0 or more and 2.0 or less.

[0004] Japanese Patent Application Laid-Open No. 2021-34077

[0005] Conventional magnetic tapes use symmetric servo stripes (servo patterns) as their servo stripes. In a magnetic tape drive with such symmetric servo stripes, the head unit is maintained parallel to an axis parallel to the width of the magnetic tape during data recording or playback. Hereinafter, a head unit maintained parallel to an axis parallel to the width of the magnetic tape may be referred to as a "parallel head unit."

[0006] On the other hand, for next-generation magnetic tapes, the use of asymmetric servo stripes (servo patterns) is being considered. In a drive for a magnetic tape having such asymmetric servo stripes, in order to read the asymmetric servo stripes, the head unit is maintained at an angle with respect to an axis parallel to the width direction of the magnetic tape when recording or reproducing data. Hereinafter, a head unit maintained at an angle with respect to an axis parallel to the width direction of the magnetic tape in this way may be referred to as a "skewed head unit."

[0007] It is desirable to suppress wobble of the magnetic tape even in drives with slanted head units. However, Patent Document 1 does not disclose any technology for suppressing wobble during running in drives with slanted head units. Furthermore, Patent Document 1 only evaluates the increase in the dynamic friction coefficient after multiple runs at a low speed (10 mm / s), but does not evaluate the dynamic friction coefficient during actual running. In this specification, "actual running" refers to the time when the magnetic tape is running while data is being recorded or reproduced by the drive.

[0008] The object of the present disclosure is to provide a magnetic recording medium and a cartridge equipped therewith that can suppress magnetic tape wobble during actual running in both drives with parallel head units and drives with oblique head units.

[0009] In order to solve the above-mentioned problems, the magnetic recording medium according to the present disclosure is a tape-shaped magnetic recording medium comprising a substrate and a magnetic layer containing magnetic particles, wherein the average thickness of the magnetic recording medium is 5.30 μm or less, the average tension T acting in the longitudinal direction of the magnetic recording medium is measured by hanging a 30 g weight from one end of the magnetic recording medium, pressing a 3 mm diameter stainless steel round rod against the surface of the magnetic layer side, and moving the magnetic recording medium in the longitudinal direction at a speed of 2 mm / s while rotating the round rod at 125 rpm, and the average dynamic friction coefficient μ of the surface of the magnetic layer side is measured by moving the magnetic recording medium in the longitudinal direction at a speed of 6 mm / s.

[0010] FIG. 1 is an exploded perspective view showing an example of the configuration of a cartridge according to an embodiment of the present disclosure. FIG. 2 is a block diagram showing an example of the configuration of a cartridge memory. FIG. 3A is a cross-sectional view showing an example of the configuration of a magnetic tape. FIG. 3B is a cross-sectional view showing an example of the configuration of the surface of a magnetic layer. FIG. 4 is a schematic view showing an example of the layout of a data band and a servo band. FIG. 5 is an enlarged view showing an example of the configuration of a servo band corresponding to a diagonal head unit. FIG. 6 is an enlarged view showing an example of the configuration of a servo band corresponding to a parallel head unit. FIG. 7A is an enlarged view showing an example of the configuration of a data band. FIG. 7B is an enlarged view showing an example of a data track of a shingled magnetic recording system. FIG. 8 is a perspective view showing an example of the shape of a magnetic particle. FIG. 9 is a diagram showing a first example of a cross-sectional TEM image of a magnetic layer. FIG. 10 is a diagram showing a second example of a cross-sectional TEM image of a magnetic layer. FIG. 11 is a side view of an apparatus for measuring tension acting on a magnetic tape. FIG. 12 is a plan view of an apparatus for measuring tension acting on a magnetic tape. FIG. 13 is a graph showing an example of tension (load) measurement results. FIG. 14 is a schematic view of an apparatus for measuring tension acting on a magnetic tape. Fig. 15 is an enlarged view of the head block shown in Fig. 14. Fig. 16 is a diagram for explaining a method for measuring PES using a diagonal head unit. Fig. 17 is a graph for explaining correction of movement in the width direction of the magnetic tape. Fig. 18 is a diagram for explaining a method for measuring PES using a parallel head unit. Fig. 19 is an exploded perspective view showing an example of the configuration of a cartridge according to a modified example of an embodiment of the present disclosure.

[0011] The embodiments of the present disclosure will be described in the following order: 1. Background leading to the creation of the embodiments of the present disclosure 2. Cartridge configuration 3. Cartridge memory configuration 4. Magnetic tape configuration 5. Magnetic tape manufacturing method 6. Effects 7. Modifications

[0012] [1 Background to the creation of the embodiments of the present disclosure] The inventors have conducted extensive research into magnetic tapes that can suppress wobble of the magnetic tape during actual running in both drives with parallel head units and drives with oblique head units.

[0013] As mentioned above, Patent Document 1 does not evaluate the dynamic friction coefficient during actual running. Therefore, the present inventors first conducted extensive research into a technique for measuring the dynamic friction coefficient (dynamic friction force) of the magnetic layer side surface (hereinafter referred to as the "magnetic surface") during actual running. As a result, it was found that it is difficult to measure the dynamic friction coefficient (dynamic friction coefficient in the running direction) of the magnetic surface during actual running. Therefore, the present inventors conducted extensive research into physical properties that can substitute for the dynamic friction coefficient of the magnetic surface during actual running. As a result, they discovered that the physical property that can substitute for the dynamic friction coefficient is the average tension T acting in the longitudinal direction of the magnetic tape (hereinafter referred to as the "average tension T when the SUS rod is rotating"), measured when a 30 g weight is hung from one end of the magnetic tape and a 3 mm diameter stainless steel (Steel Special Use Stainless, hereinafter referred to as "SUS") rod is pressed against the magnetic surface and the rod is rotated at 125 rpm. Furthermore, it was discovered that the average tension T during rotation of the SUS rod correlates with both the wobble of the magnetic tape during actual running in a drive with a parallel head unit and the wobble of the magnetic tape during actual running in a drive with a diagonal head unit, with a particularly strong correlation with the former.

[0014] The inventors further conducted extensive research into the average tension T during SUS rod rotation and discovered the following: When the average tension T during SUS rod rotation is 55.0 gf or less, it is possible to suppress wobble of the magnetic tape during actual running in a drive with a parallel head unit. On the other hand, in a drive with a diagonal head unit, simply having the average tension T during SUS rod rotation be 55.0 gf or less is not sufficient to suppress wobble of the magnetic tape during actual running. This is thought to be due to the following reason: If the head unit is diagonal, the magnetic tape is more likely to shift in the width direction (the width direction of the magnetic tape) during actual running, and when the magnetic tape shifts in the width direction, there is a risk of the magnetic tape getting caught on the diagonal head unit, a so-called stick-slip phenomenon. When this stick-slip phenomenon occurs, it becomes difficult for the magnetic tape to return smoothly to its predetermined running position, making it impossible to suppress wobble of the magnetic tape. Linear tape drives have an actuator mounted on the head block, which can follow low-frequency magnetic tape movements, but has difficulty following high-frequency movements such as stick-slip.

[0015] Therefore, the present inventors further conducted extensive research into techniques for suppressing wobble of a magnetic tape during actual running in a drive with a diagonal head unit. As a result, they discovered that the average dynamic friction coefficient μ of the magnetic surface, measured by moving the magnetic tape in the longitudinal direction at a speed of 6 mm / s (hereinafter referred to as the "average dynamic friction coefficient μ during low-speed running"), correlates with the stick-slip phenomenon, and that when the average tension T during SUS rod rotation is 55.0 gf or less and the average dynamic friction coefficient μ during low-speed running is 0.35 or less, wobble of the magnetic tape during actual running can be suppressed in both a drive with a parallel head unit and a drive with a diagonal head unit.

[0016] Examples of drives with parallel head units include drives that comply with the LTO9 standard or earlier standards, and examples of drives with diagonal head units include drives that are being considered for use with the LTO10 standard or later standards.

[0017] [2 Cartridge Configuration] Figure 1 is an exploded perspective view showing an example of the configuration of a cartridge 10. The cartridge 10 is a single-reel cartridge, and includes 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 unlocking the locked state of the reel 13, a slide door 17 for opening and closing a tape outlet 12C provided in the cartridge case 12 across the lower shell 12A and the upper shell 12B, a door spring 18 for biasing the slide door 17 to a 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 generally 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 peripheral end of the magnetic tape MT, and a leader pin 20 is provided at the tip of the leader tape LT.

[0018] The cartridge 10 may be a magnetic tape cartridge conforming to the LTO (Linear Tape-Open) standard, or may be a magnetic tape cartridge conforming to a standard other than the LTO standard.

[0019] The cartridge memory 11 is provided near one corner of the cartridge 10. When the cartridge 10 is loaded into a recording / playback device, the cartridge memory 11 faces a 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 that complies with the LTO standard.

[0020] 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 a reader / writer using a specified communication standard, a rectification / power circuit 32 that generates power by rectifying and generating electricity from radio waves received by the antenna coil 31 using induced electromotive force, a clock circuit 33 that generates a clock from the radio waves received by the antenna coil 31 using induced electromotive force, 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 that is composed of logic circuits and the like for determining commands and data from the digital signal extracted from the detection / modulation circuit 34 and processing them, and a memory (storage unit) 36 that stores information. The cartridge memory 11 also includes a capacitor 37 connected in parallel to the antenna coil 31, and the antenna coil 31 and the capacitor 37 form a resonant circuit.

[0021] The memory 36 stores information relating to the cartridge 10. The memory 36 is a non-volatile memory (NVM). The memory 36 preferably has a storage capacity of approximately 32 KB or more.

[0022] The memory 36 may have a first memory area 36A and a second memory area 36B. The first memory area 36A corresponds to the memory area of ​​a cartridge memory for a magnetic tape standard prior to a specified generation (e.g., an LTO standard prior to LTO8), and is an area for storing information conforming to the magnetic tape standard prior to the specified generation. The information conforming to the magnetic tape standard prior to the 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.

[0023] The second memory area 36B corresponds to an extended memory area for the cartridge memory storage area for magnetic tape standards prior to the specified generation (e.g., LTO standards prior to LTO8). The second memory area 36B is an area for storing additional information. Here, additional information refers to, for example, information related to the cartridge 10 that is not specified in magnetic tape standards prior to the specified generation (e.g., LTO standards prior to LTO8). The additional information includes, but is not limited to, at least one type of information selected from the group consisting of tension adjustment information, management ledger data, index information, and thumbnail information. The tension adjustment information is information for adjusting the tension applied to the magnetic tape MT in the longitudinal direction. The tension adjustment information includes, for example, at least one type of information selected from the group consisting of 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 be managed in conjunction with information regarding the usage status of the cartridge 10. The tension adjustment information is preferably obtained when or before data is recorded on the magnetic tape MT. The tension information of the drive means information about the tension applied to the magnetic tape MT in the longitudinal direction.

[0024] The management ledger data includes at least one type of data selected from the group consisting of the capacity, creation date, edit date, and storage location of the data files recorded on the magnetic tape MT. The index information is metadata for searching the contents of the data files. The thumbnail information is a thumbnail of the moving or still image stored on the magnetic tape MT.

[0025] The memory 36 may have a plurality of banks. In this case, some of the plurality of banks may constitute a first storage area 36A, and the remaining banks may constitute a second storage area 36B.

[0026] The antenna coil 31 induces an induced voltage by electromagnetic induction. The controller 35 communicates with the recording / playback device in accordance with a specified communication standard via the antenna coil 31. Specifically, for example, mutual authentication, sending and receiving of commands, and data exchange are performed.

[0027] The controller 35 stores information received from the recording / playback device via the antenna coil 31 in the memory 36. For example, the controller 35 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. In response to a request from the recording / playback device, the controller 35 reads information from the memory 36 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, the controller 35 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.

[0028] [4. Magnetic Tape Configuration] FIG. 3A is a cross-sectional view showing an example of the configuration of a magnetic tape MT. The magnetic tape MT is an example of a tape-shaped magnetic recording medium, and includes a long substrate 41, an underlayer 42 provided on one main surface (first main surface) of the substrate 41, a magnetic layer 43 provided on the underlayer 42, and a back layer 44 provided on the other main surface (second main surface) of the substrate 41. The underlayer 42 and the back layer 44 are provided as needed and may be omitted. The magnetic tape MT may be a perpendicular recording type magnetic recording medium or a longitudinal recording type magnetic recording medium. From the viewpoint of improving running performance, the magnetic tape MT preferably includes a lubricant. The lubricant may be contained in at least one of the underlayer 42 and the magnetic layer 43. The magnetic tape MT may further include a lubricant layer provided on the surface (magnetic surface) of the magnetic layer 43.

[0029] The magnetic tape MT may conform to the LTO standard, or may conform to a standard other than the LTO standard. The width of the magnetic tape MT may be 1 / 2 inch, or may be wider than 1 / 2 inch. If 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 that allows the width of the magnetic tape MT to be kept constant or approximately constant by adjusting the tension applied to the magnetic tape MT in the longitudinal direction during running using a recording / playback device (drive).

[0030] The magnetic tape MT has a long shape and runs longitudinally during recording and playback. The magnetic tape MT is preferably used in a recording and playback device equipped with a ring-type head as a recording head. The magnetic tape MT is configured to be capable of recording signals at a linear recording density D. From the viewpoint of achieving high recording capacity, the lower limit of the linear recording density D of signals recordable on the magnetic tape MT is preferably 545 kfci or more, more preferably 549 kfci or more, even more preferably 550 kfci or more, 552 kfci or more, 577 kfci or more, 600 kfci or more, or 635 kfci or more. The upper limit of the linear recording density D of data recordable on the magnetic tape MT is preferably 1270 kfci or less, taking into account the magnetic particle size.

[0031] 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 the data band DB (see FIG. 4) or a servo pattern (servo signal) recorded in the servo band SB (see FIG. 4).

[0032] (Substrate 41) 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 １From the viewpoint of improving the recording capacity that can be recorded on one data cartridge, the upper limit of the average thickness t of the substrate 41 is preferably 4.40 μm or less, more preferably 4.20 μm or less, and even more preferably 4.00 μm or less, 3.80 μm or less, or 3.40 μm or less. １ The lower limit of the average thickness t of the substrate 41 is preferably 3.00 μm or more, more preferably 3.20 μm or more, and even more preferably 3.80 μm or more. １ When the lower limit value is 3.00 μm or more, the decrease in strength of the base 41 can be suppressed.

[0033] Average thickness t of the substrate 41 １ is determined as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and a sample is prepared by cutting out a 250 mm length of the magnetic tape MT at a position 30 to 40 m longitudinally from one end of the outer periphery of the magnetic tape MT. In this specification, the "longitudinal direction" when referring to "the longitudinal direction from one end of the outer periphery of the magnetic tape MT" means the direction from one end of the magnetic tape MT on the outer periphery toward the other end on the inner periphery.

[0034] Next, the layers of the sample other than the substrate 41 (i.e., the underlayer 42, the magnetic layer 43, and the back layer 44) are removed with a solvent such as MEK (methyl ethyl ketone) or dilute hydrochloric acid. Next, the thickness of the sample (substrate 41) is measured at five positions using a Mitutoyo Laser Hologram (LGH-110C) as a measuring device, and the measured values ​​are simply averaged (arithmetic mean) to obtain the average thickness t of the substrate 41. １ The five measurement positions are selected at random from the sample so that they are different positions in the longitudinal direction of the magnetic tape MT.

[0035] From the viewpoint of cost reduction, the base 41 preferably contains a polyester-based resin as a main component. Examples of polyester-based resins include at least one selected from the group consisting of PET (polyethylene terephthalate), PEN (polyethylene naphthalate), PBT (polybutylene terephthalate), PBN (polybutylene naphthalate), PCT (polycyclohexylene dimethylene terephthalate), PEB (polyethylene p-oxybenzoate), and polyethylene bisphenoxycarboxylate. When the base 41 contains two or more polyester-based resins, these two or more polyester-based resins may be mixed, copolymerized, or laminated. At least one of the terminals and side chains of the polyester-based resin may be modified. In addition to the polyester-based resin, the base 41 may also contain a resin other than the polyester-based resin described below.

[0036] In this specification, the term "main component" refers to the component that has the highest content ratio among the components that constitute the base 41. For example, when the main component of the base 41 is a polyester-based resin, the content ratio of the polyester-based resin in the base 41 may be, for example, 50% by mass or more, 60% by mass or more, 70% by mass or more, 80% by mass or more, 90% by mass or more, 95% by mass or more, or 98% by mass or more relative to the mass of the base 41, or the base 41 may be composed only of a polyester-based resin.

[0037] The presence of polyester resin in the substrate 41 can be confirmed, for example, as follows. First, the average thickness t １ Similar to the measurement method of (1), a magnetic tape MT is prepared and cut into a length of 250 mm to prepare a sample, and then the layers other than the substrate 41 of the sample are removed. Next, an IR spectrum of the sample (substrate 41) is obtained by infrared absorption spectrometry (IR). Based on this IR spectrum, it can be confirmed that the substrate 41 contains a polyester-based resin.

[0038] The substrate 41 preferably contains a polyester-based resin. By including a polyester-based 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 tension in the longitudinal direction of the magnetic tape MT during running using a recording / reproducing device, the width of the magnetic tape MT can be kept constant or approximately constant. A method for measuring the Young's modulus in the longitudinal direction of the substrate 41 will be described later.

[0039] The base 41 may contain a resin other than a polyester-based resin. In this case, the resin other than a polyester-based resin may be the main component of the base 41's constituent material. When a resin other than a polyester-based resin is the main component of the base 41's constituent material, the content of the resin other than a polyester-based resin in the base 41 may be, for example, 50% by mass or more, 60% by mass or more, 70% by mass or more, 80% by mass or more, 90% by mass or more, 95% by mass or more, or 98% by mass or more relative to the mass of the base 41. Alternatively, the base 41 may be composed solely of a resin other than a polyester-based resin. The resin other than a polyester-based resin may include, for example, at least one selected from the group consisting of polyolefin-based resins, cellulose derivatives, vinyl-based resins, and other polymer resins. When the base 41 contains two or more of these resins, the two or more materials may be mixed, copolymerized, or laminated.

[0040] The polyolefin resin includes, for example, at least one selected from the group consisting of PE (polyethylene) and PP (polypropylene). The cellulose derivative includes, for example, at least one selected from the group consisting of cellulose diacetate, cellulose triacetate, CAB (cellulose acetate butyrate), and CAP (cellulose acetate propionate). The vinyl resin includes, for example, at least one selected from the group consisting of PVC (polyvinyl chloride) and PVDC (polyvinylidene chloride).

[0041] Examples of other polymer resins include at least one selected from the group consisting of PEEK (polyether ether ketone), PA (polyamide, nylon), aromatic PA (aromatic polyamide, aramid), PI (polyimide), aromatic PI (aromatic polyimide), PAI (polyamideimide), aromatic PAI (aromatic polyamideimide), PBO (polybenzoxazole, for example, Zylon (registered trademark)), polyether, PEK (polyether ketone), polyether ester, PES (polyethersulfone), PEI (polyetherimide), PSF (polysulfone), PPS (polyphenylene sulfide), PC (polycarbonate), PAR (polyarylate), and PU (polyurethane). Specifically, for example, the base 41 may contain, as a main component, PEEK (polyether ether ketone), PA (polyamide, nylon), aromatic PA (aromatic polyamide, aramid), PI (polyimide), aromatic PI (aromatic polyimide), PAI (polyamideimide), aromatic PAI (aromatic polyamideimide), PBO (polybenzoxazole, for example, Zylon (registered trademark)), polyether, PEK (polyether ketone), polyether ester, PES (polyethersulfone), PEI (polyetherimide), PSF (polysulfone), PPS (polyphenylene sulfide), PC (polycarbonate), PAR (polyarylate), or PU (polyurethane).

[0042] The substrate 41 may be biaxially stretched in the longitudinal direction and the width direction. The polymer resin contained in the substrate 41 is preferably oriented in a direction oblique to the width direction of the substrate 41.

[0043] (Magnetic Layer 43) The magnetic layer 43 is configured to be capable of recording signals using a magnetization pattern. The magnetic layer 43 may be a recording layer for perpendicular recording or a recording layer for longitudinal recording. The magnetic layer 43 contains, for example, magnetic particles, carbon particles, abrasive particles, and a binder. If necessary, the magnetic layer 43 may further contain at least one additive selected from the group consisting of a lubricant, an antistatic agent, a curing agent, an anticorrosive agent, and non-magnetic reinforcing particles.

[0044] FIG. 3B is a cross-sectional view showing an example of the configuration of the surface (magnetic surface) of the magnetic layer 43. The magnetic layer 43 preferably has a large number of protrusions 430 on its surface. The large number of protrusions 430 form unevenness on the surface. The large number of protrusions 430 includes protrusions 430 formed by carbon particles 431 protruding from the surface and protrusions 430 formed by abrasive particles 432 protruding from the surface. The carbon particles 431 forming the protrusions 430 may or may not be covered with a binder. Similarly, the abrasive particles 432 forming the protrusions 430 may or may not be covered with a binder. Note that FIG. 3B shows an example in which the carbon particles 431 and abrasive particles 432 forming the protrusions 430 are covered with a binder.

[0045] The magnetic layer 43 may have a plurality of holes on its surface. A lubricant may be stored in the plurality of holes. In this case, the supply of the lubricant to the magnetic surface can be improved. From the viewpoint of improving the supply of the lubricant to the magnetic surface, it is preferable that the holes extend in a direction perpendicular to the magnetic surface.

[0046] As shown in FIG. 4, the magnetic layer 43 may have a plurality of servo bands SB and a plurality of data bands DB in advance. In the following description, when the oblique head unit 56A and the parallel head unit 56B are not particularly distinguished and are collectively referred to as the head unit 56, the plurality of servo bands SB are provided at equal intervals in the width direction of the magnetic tape MT. A data band DB is provided between adjacent servo bands SB. The servo bands SB are used to guide the head unit (magnetic head) 56 (specifically, the servo read head 561) when recording or reproducing data. Servo patterns (servo signals) for tracking control of the head unit 56 are written in advance in the servo bands SB. User data is recorded in the data bands DB.

[0047] In order to read asymmetric servo stripes 113 (see FIG. 5 ), which will be described later, the oblique head unit 56A is configured to be able to maintain an oblique position with respect to an axis Ax parallel to the width direction of the magnetic tape MT during data recording and reproduction, as shown in FIG. 4 . The oblique head unit 56A may be configured to follow the meandering or deformation of the magnetic tape MT and become oblique with respect to the axis Ax during data recording and reproduction. The tilt angle of the head unit 56A with respect to the axis Ax parallel to the width direction of the magnetic tape MT is preferably 3° to 18°, more preferably 5° to 15°.

[0048] The parallel head unit 56B is configured to be able to maintain parallelism with an axis Ax parallel to the width direction of the magnetic tape MT during data recording and playback, as shown in FIG. 4, in order to read the symmetrical servo stripes 113 (see FIG. 6) described below.

[0049] (Servo band SB) The total area S of the plurality of servo bands SB relative to the area S of the magnetic surface (surface on the magnetic layer 43 side) ＳＢ Ratio R Ｓ (=(S ＳＢ From the viewpoint of ensuring a high recording capacity, the upper limit of the ratio (S / S) × 100) is preferably 4.0% or less, more preferably 3.5% or less, and even more preferably 3.0% or less. ＳＢ Ratio R Ｓ The lower limit of is preferably 1.0% or more from the viewpoint of ensuring 5 or more servo bands SB.

[0050] The total area S of the plurality of servo bands SB relative to the area S of the entire magnetic surface ＳＢ Ratio R Ｓ The magnetic tape MT is developed using a ferricolloid developer (Sigma Marker Q, manufactured by Sigma High Chemical Co., Ltd.), and the developed magnetic tape MT is then observed under an optical microscope to determine the servo bandwidth W ＳＢ and the number of servo bands SB. Next, the ratio R is calculated from the following formula: Ｓ Calculate the ratio R Ｓ [%] = (((Servo bandwidth WＳＢ ) × (number of servo bands SB)) / (width of magnetic tape MT)) × 100

[0051] The number of servo bands SB is, for example, 5+4n (where n is an integer greater than or equal to 0) or more. The number of servo bands SB is preferably 5 or more, and more preferably 9 or more. If the number of servo bands SB is 5 or more, the effect on the servo signal due to dimensional changes in the width direction of the magnetic tape MT can be suppressed, and stable recording and reproduction characteristics with less off-track can be ensured. The upper limit of the number of servo bands SB is not particularly limited, but is, for example, 33 or less.

[0052] The number of servo bands SB is determined by the above ratio R Ｓ It can be calculated in the same way as

[0053] Servo Bandwidth W ＳＢ From the viewpoint of ensuring a high recording capacity, 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. ＳＢ The lower limit of the servo bandwidth W is preferably 10 μm or more. ＳＢ It is difficult to manufacture a magnetic head that can read such servo signals.

[0054] Servo Bandwidth W ＳＢ The width of the ratio R Ｓ It can be calculated in the same way as

[0055] (Servo Pattern) The servo band pattern differs between the magnetic tape MT for the drive of the diagonal head unit 56A and the magnetic tape MT for the drive of the parallel head unit 56B.

[0056] (Servo patterns written on magnetic tape for oblique head unit drives) The servo patterns are magnetized regions, and are formed by magnetizing specific regions of the magnetic layer 43 in specific directions using a servo write head during magnetic tape manufacturing. The regions of the servo bands SB where no servo patterns are formed (hereinafter referred to as "non-pattern regions") may be magnetized regions where the magnetic layer 43 is magnetized, or may be non-magnetized regions where the magnetic layer 43 is not magnetized. When the non-pattern regions are magnetized regions, the servo pattern forming regions and the non-pattern regions are magnetized in different directions (for example, opposite directions).

[0057] In the LTO standard, a servo pattern is formed on the servo band SB, as shown in FIG. 5, consisting of a plurality of servo stripes (linear magnetized regions) 113 inclined with respect to an axis Ax parallel to the width direction of the magnetic tape MT.

[0058] The servo band SB includes a plurality of servo frames 110. Each servo frame 110 is made up of 18 servo stripes 113. Specifically, each servo frame 110 is made up of a servo subframe 1 (111) and a servo subframe 2 (112).

[0059] Servo subframe 1 (111) is composed of an A burst 111A and a B burst 111B. The B burst 111B is arranged adjacent to the A burst 111A. The A burst 111A is inclined at a predetermined angle θ with respect to an axis Ax parallel to the width direction of the magnetic tape MT. １ 5, these five servo stripes 113 are inclined at a regular interval from the EOT (End Of Tape) to the BOT (Beginning Of Tape) of the magnetic tape MT, and are labeled with the symbol A. １ , A ２ , A ３ , A ４ , A ５ are indicated with .

[0060] The B burst 111B is at a predetermined angle θ with respect to an axis Ax parallel to the width direction of the magnetic tape MT. ２5, these five servo stripes 113 are inclined at regular intervals from the EOT to the BOT of the magnetic tape MT. １ , B ２ , B ３ , B ４ , B ５ are indicated with .

[0061] The servo stripes 113 of the B burst 111B are inclined in the opposite direction to the servo stripes 113 of the A burst 111A. The servo stripes 113 of the A burst 111A and the servo stripes 113 of the B burst 111B are asymmetric with respect to the axis Ax, which is parallel to the width direction of the magnetic tape MT. That is, the servo stripes 113 of the A burst 111A and the servo stripes 113 of the B burst 111B are arranged in a substantially V-shape. Because the servo stripes 113 of the A burst 111A and the servo stripes 113 of the B burst 111B are asymmetric with respect to the axis Ax, when the oblique head unit 56A is obliquely inclined with respect to the axis Ax, there exists a state in which the servo stripes 113 of the A burst 111A and the servo stripes 113 of the B burst 111B are substantially symmetric with respect to the central axis of the sliding surface of the oblique head unit 56A. By changing the inclination of the oblique head unit 56A based on this state, it is possible to adjust the distance between the servo read heads 561, 561 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 read heads 561, 561 can be made to face the specified positions of the servo bands SB. Note that the central axis of the sliding surface of the oblique head unit 56A means the axis passing through the centers of the multiple servo read heads 561, 561 on the sliding surface of the oblique head unit 56A.

[0062] A predetermined angle θ, which is the inclination angle of the servo stripe 113 of the A burst 111A １ and a predetermined angle θ which is the inclination angle of the servo stripe 113 of the B burst 111B. ２ More specifically, the predetermined angle θ of the servo stripe 113 of the A burst 111A is different from１ However, the predetermined angle θ of the servo stripe 113 of the B burst 111B ２ , or the predetermined angle θ of the servo stripe 113 of the B burst 111B. ２ However, the predetermined angle θ of the servo stripe 113 of the A burst 111A １ That is, the inclination of the servo stripes 113 of the A burst 111A may be larger than the inclination of the servo stripes 113 of the B burst 111B, or the inclination of the servo stripes 113 of the B burst 111B may be larger than the inclination of the servo stripes 113 of the A burst 111A. Note that in FIG. 5, the predetermined angle θ of the servo stripes 113 of the A burst 111A １ However, the predetermined angle θ of the servo stripe 113 of the B burst 111B ２ In the following, the predetermined angle θ of the servo stripe 113 of the A burst 111A is shown. １ However, the predetermined angle θ of the servo stripe 113 of the B burst 111B ２ The case where it is larger than

[0063] Servo subframe 2 (112) is composed of a C burst 112C and a D burst 112D. The D burst 112D is arranged adjacent to the C burst 112C. The C burst 112C is inclined at a predetermined angle θ with respect to an axis Ax parallel to the width direction of the magnetic tape MT. １ 5, the four servo stripes 113 are inclined at a predetermined interval from the EOT to the BOT of the magnetic tape MT and are marked with the symbol C １ , C ２ , C ３ , C ４ are indicated with .

[0064] The D burst 112D is at a predetermined angle θ with respect to an axis Ax parallel to the width direction of the magnetic tape MT. ２ 5, the four servo stripes 113 are inclined at a predetermined interval from the EOT to the BOT of the magnetic tape MT and are denoted by the symbol D. １ , D２ , D ３ , D ４ are indicated with .

[0065] The servo stripes 113 of the D burst 112D are tilted in the opposite direction to the servo stripes 113 of the C burst 112C. The servo stripes 113 of the C burst 112C and the servo stripes 113 of the D burst 112D are asymmetric with respect to the axis Ax, which is parallel to the width direction of the magnetic tape MT. That is, the servo stripes 113 of the C burst 112C and the servo stripes 113 of the D burst 112D are arranged in a generally V-shape. Because the servo stripes 113 of the C burst 112C and the servo stripes 113 of the D burst 112D are asymmetric with respect to the axis Ax, when the diagonal head unit 56A is tilted diagonally with respect to the axis Ax, there exists a state in which the servo stripes 113 of the C burst 112C and the servo stripes 113 of the D burst 112D are generally symmetric with respect to the central axis of the diagonal head unit 56A. By changing the tilt of the diagonal head unit 56A based on this state, it is possible to adjust the servo distance.

[0066] The predetermined angle θ is the inclination angle of the servo stripe 113 of the C burst 112C. １ and a predetermined angle θ which is the inclination angle of the servo stripe 113 of the D burst 112D. ２ More specifically, the predetermined angle θ of the servo stripe 113 of the C burst 112C is different from １ However, the predetermined angle θ of the servo stripe 113 of the D burst 112D ２ , or the predetermined angle θ of the servo stripe 113 of the D burst 112D. ２ However, the predetermined angle θ of the servo stripe 113 of the C burst 112C １ That is, the inclination of the servo stripes 113 of the C burst 112C may be larger than the inclination of the servo stripes 113 of the D burst 112D, or the inclination of the servo stripes 113 of the D burst 112D may be larger than the inclination of the servo stripes 113 of the C burst 112C. Note that in FIG. 5, the predetermined angle θ of the servo stripes 113 of the C burst 112C１ However, the predetermined angle θ of the servo stripe 113 of the D burst 112D ２ In the following, the predetermined angle θ of the servo stripe 113 of the C burst 112C is １ However, the predetermined angle θ of the servo stripe 113 of the D burst 112D ２ The case where it is larger than

[0067] The 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, and more preferably 18° or more and 26° or less. ２ is preferably -4° or more and 6° or less, and 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 a first magnetization region. The servo stripes 113 in the B burst 111B and the D burst 112D are an example of a second magnetization region.

[0068] By reading the servo band SB with the diagonal head unit 56A, information is obtained to determine the tape speed and the longitudinal position of the diagonal head unit 56A. 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 the time between another four timing signals (A1-B1, A2-B2, A3-B3, A4-B4). The servo pattern may have a shape including two parallel lines.

[0069] 5, the servo patterns (i.e., the plurality of servo stripes 113) are preferably arranged linearly in the longitudinal direction of the magnetic tape MT. That is, the servo bands SB preferably have a linear shape in the longitudinal direction of the magnetic tape MT.

[0070] 6, the servo stripes 113 of the A burst 111A and the servo stripes 113 of the B burst 111B are symmetrical with respect to an axis Ax parallel to the width direction of the magnetic tape MT. That is, the inclination angle of the servo stripes 113 of the A burst 111A is a predetermined angle θ １ and a predetermined angle θ which is the inclination angle of the servo stripe 113 of the B burst 111B. ２ are identical.

[0071] The servo stripes 113 of the C burst 112C and the servo stripes 113 of the D burst 112D are symmetrical with respect to an axis Ax parallel to the width direction of the magnetic tape MT. That is, the inclination angle of the servo stripes 113 of the C burst 112C is a predetermined angle θ １ and a predetermined angle θ which is the inclination angle of the servo stripe 113 of the D burst 112D. ２ are identical.

[0072] The predetermined angle θ of the servo stripe 113 in the A burst 111A and the C burst 112C １ is preferably 10° or more and 30° or less, and more preferably 12° or more and 25° or less. ２ is preferably 10° or more and 30° or less, and more preferably 12° or more and 25° or less.

[0073] Except for the above points, the servo patterns written on the magnetic tape MT for the drive of the parallel head unit 56B have the same configuration as the servo patterns written on the magnetic tape MT for the drive of the diagonal head unit 56A.

[0074] (Data Band DB) As shown in Fig. 7A, the magnetic layer 43 is configured so that multiple data tracks Tk can be formed in the data band DB. From the viewpoint of improving track recording density and ensuring high recording capacity, the upper limit of the data track width W is preferably 1200 nm or less, more preferably 1000 nm or less, and even more preferably 850 nm or less, 800 nm or less, or 600 nm or less. The lower limit of the data track width W is preferably 20 nm or more, taking into account the magnetic particle size.

[0075] The data track width W is calculated as follows. First, a cartridge 10 is prepared with data recorded on the entire surface of the magnetic tape MT. The magnetic tape MT is unwound from the cartridge 10, and a 250 mm sample is cut from the magnetic tape MT at a position 30 to 40 m longitudinally from one end of the outer periphery of the magnetic tape MT. Next, the data recording pattern in 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. The MFM used is a Digital Instruments Dimension3100 and its analysis software. The measurement area of ​​the MFM image is 10 μm × 10 μm, and this 10 μm × 10 μm measurement area is divided into 512 × 512 (= 262,144) measurement points. Three 10 μm × 10 μm measurement areas in different locations are measured using the MFM, resulting in three MFM images. The track width was measured at 10 locations on each of the three MFM images obtained, for a total of 30 measurement values, and the average value (simple average) of the 30 measurement values ​​was calculated. This average value is the data track width W. The analysis software included with the Dimension3100 was used to measure the track width. The MFM measurement conditions were: sweep speed: 1 Hz, tip used: MFMR-20, lift height: 20 nm, and correction: Flatten order 3.

[0076] 7A shows an example in which adjacent data tracks Tk are recorded so as not to overlap, but the recording method for the data tracks Tk is not limited to this example. For example, as shown in FIG. 7B, adjacent data tracks Tk may be recorded so as to partially overlap each other in the width direction of the magnetic tape MT by using shingled magnetic recording (SMR).

[0077] 7B, head 61 and head 62 represent a recording head and a reproducing head, respectively. In the case of the shingled magnetic recording method, the data track width W is the recording track width W Ｒ Therefore, in the case of shingled magnetic recording, the width of the read head 62 is narrower than the width of the write head 61. As described above, in the shingled magnetic recording, the data track width W is narrower than the recording track width W Ｒ Since the recording track width W is narrower than the recording track width W, it is advantageous in terms of improving the recording density. Ｒ represents the track width when writing data. When shingled magnetic recording is used as the recording method, the recording track width W Ｒ represents the track width before overwriting (the track width when data is written).

[0078] The magnetic layer 43 has a minimum magnetization reversal distance L min The minimum distance between magnetization reversals L min From the viewpoint of achieving high recording capacity, the upper limit of the distance L is preferably 46.6 nm or less, more preferably 46.3 nm or less, and 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. min Considering the size of the magnetic particles, the lower limit is preferably 20.0 nm or more.

[0079] Minimum distance between magnetization reversals L minis calculated as follows. First, a sample is prepared using the same method as for measuring the data track width W. Next, the data recording pattern in 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. The MFM used is a Dimension3100 manufactured by Digital Instruments and its analysis software. The measurement area of ​​the MFM image is 2 μm × 2 μm, and this 2 μm × 2 μm measurement area is divided into 512 × 512 (= 262,144) measurement points. Three 2 μm × 2 μm measurement areas in different locations are measured using the MFM, resulting in three MFM images. Fifty inter-bit distances are measured from a two-dimensional concavo-convex chart of the recording pattern of the obtained MFM image. The inter-bit distances are measured using the analysis software provided with the Dimension3100. The value that is approximately the greatest common divisor of the 50 measured inter-bit distances is set as the minimum value L of the inter-magnetic reversal distance. min The measurement conditions are: sweep rate: 1 Hz, tip used: MFMR-20, lift height: 20 nm, correction: Flatten order 3.

[0080] The magnetic layer 43 is configured to be able 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 recordable in the data band DB is preferably 46.6 nm or less, more preferably 46.3 nm or less, and 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. Taking the magnetic particle size into consideration, the lower limit of the bit length T of the signal recordable in the data band DB is preferably 20.0 nm or more.

[0081] The bit length T of the signal that can be recorded in the data band DB is the minimum value L min It can be determined in the same manner as in the measurement method of

[0082] The bit area of ​​the signal that can be recorded on the data band DB is preferably 53000 nm from the viewpoint of improving the linear recording density D of the magnetic tape MT. ２or less, more preferably 45,000 nm ２ or less, more preferably 37,000 nm ２ Below 30,000 nm, particularly preferably ２ The following is the result.

[0083] The bit area of ​​a signal recordable on the data band DB can be calculated as follows: First, three MFM images are obtained in the same manner as in the method for measuring the data track width W. Next, the data track width W and bit length T are calculated in the same manner as in the method for measuring the data track width W and bit length T. Next, the bit area (W x T) of a signal recordable on the data band DB is calculated using the data track width W and bit length T.

[0084] (The average thickness t of the magnetic layer 43 ２ ) Average thickness t of the magnetic layer 43 ２ The upper limit of the average thickness t of the magnetic layer 43 is preferably 0.080 μm or less, more preferably 0.070 μm or less, even more preferably 0.060 μm or less, and particularly preferably 0.050 μm or less. ２ If the upper limit value is 0.080 μm or less, when a ring-type head is used as the recording head, the influence of the demagnetizing field can be reduced, and therefore, even better electromagnetic conversion characteristics can be obtained.

[0085] The average thickness t of the magnetic layer 43 ２ The lower limit of the average thickness t of the magnetic layer 43 is preferably 0.035 μm or more. ２ If the lower limit of is 0.035 μm or more, when an MR type head is used as the reproducing head, output can be ensured, and therefore even better electromagnetic conversion characteristics can be obtained.

[0086] The average thickness t of the magnetic layer 43 ２is determined as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and three 250 mm samples are cut from the magnetic tape MT at positions 10 m to 20 m, 30 m to 40 m, and 50 m to 60 m from one end of the outer periphery of the magnetic tape MT in the longitudinal direction, respectively. Each sample is then thinned using a method such as FIB (Focused Ion Beam). When using the FIB method, a carbon layer and a tungsten layer are formed as protective films as a pretreatment for observing the cross-sectional TEM image described below. The carbon layer is formed by vapor deposition on the surface of the magnetic tape MT facing the magnetic layer 43 and the surface facing the back layer 44, and the tungsten layer is then further formed by vapor deposition or sputtering on the surface facing the magnetic layer 43. The thinning is performed along the longitudinal direction of the magnetic tape MT. That is, the thinning process forms a cross section parallel to both the longitudinal direction and the thickness direction of the magnetic tape MT.

[0087] The cross section of each obtained thinned sample was observed under the following conditions using a transmission electron microscope (TEM) to obtain a TEM image of each thinned sample. Note that the magnification and acceleration voltage may be adjusted appropriately depending on the type of device. Device: TEM (H9000NAR manufactured by Hitachi, Ltd.) Acceleration voltage: 300 kV Magnification: 100,000 times

[0088] Next, using the TEM image of each obtained thinned sample, the thickness of the magnetic layer 43 is measured at 10 positions on each thinned sample. The 10 measurement positions on each thinned sample are randomly selected from the sample so that they are different positions in the longitudinal direction of the magnetic tape MT. The measured values ​​of each obtained thinned sample (thickness of the magnetic layer 43 at 30 points in total) are simply averaged (arithmetic average) to obtain an average value, which is the average thickness t of the magnetic layer 43. ２ Let [nm].

[0089] (Magnetic Particles) The magnetic particles may include, for example, particles containing hexagonal ferrite (hereinafter referred to as "hexagonal ferrite particles"), particles containing epsilon 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 have a preferential crystal orientation in the perpendicular direction of the magnetic tape MT. In this specification, the perpendicular direction (thickness direction) of the magnetic tape MT means the thickness direction of the magnetic tape MT in a flat state.

[0090] (Hexagonal Ferrite Particles) The hexagonal ferrite particles have, for example, a plate shape such as a hexagonal plate or a columnar shape such as a hexagonal pillar (however, the thickness or height is smaller than the major axis of the plate surface or base). In the present disclosure, the hexagonal plate shape includes a substantially hexagonal plate shape. Furthermore, the hexagonal pillar shape includes a substantially hexagonal pillar shape.

[0091] The hexagonal ferrite particles contain Fe and a metal M1 other than Fe. The metal M1 contains, for example, at least one alkaline earth metal. The at least one alkaline earth metal contains, for example, at least one selected from the group consisting of Ba, Sr, and Ca. Among these alkaline earth metals, it is preferable to contain at least one of Ba and Sr. The metal M1 may contain Pb in addition to the alkaline earth metal.

[0092] The hexagonal ferrite particles may further contain a metal M2 in addition to Fe and metal M1. The metal M2 is preferably capable of substituting a portion of the Fe sites in the crystal structure of the hexagonal ferrite. The metal M2 includes, for example, 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.

[0093] In the present disclosure, rare earth elements are defined as Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. Transition metal elements other than Fe are defined as 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 are defined as Al, Ga, In, and Tl.

[0094] Specifically, the hexagonal ferrite particles may be, for example, barium ferrite particles or strontium ferrite particles. In the present 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 % 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 % or more. For example, if 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 % or more are called strontium ferrite particles.

[0095] In the present 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 % or more. Therefore, hexagonal ferrite particles containing Ba and a 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 % 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 % or more are called barium ferrite particles.

[0096] The average atomic ratio of Sr to Ba (Sr / Ba) is preferably 0.1 or more and 1 or less. When the average atomic ratio (Sr / Ba) is 0.1 or more, it is possible to suppress a decrease in the effect of adding Sr to improve magnetic properties (for example, the effect of improving thermal stability (Ku) derived from strontium ferrite). When the average atomic ratio (Sr / Ba) is 1 or less, it is possible to suppress variations in magnetic properties.

[0097] More specifically, the hexagonal ferrite may have an average composition represented by the following general formula (A): （１－ｘ） α ｘ Fe （１２－ｙ） β ｙ O １９ ...(A) (In formula (A), α represents at least one element selected from the group consisting of Sr, Ca, and Pb. β represents at least one element 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 within the range of 0≦x≦0.9, preferably 0≦x≦0.7, and more preferably 0.3≦x≦0.7. y is within the range of 0≦y≦0.80, preferably 0.22≦y≦0.80, and more preferably 0.26≦y≦0.80.)

[0098] The average atomic ratio of Sr to Ba is calculated from analytical values ​​obtained using STEM-EDX (Transmission Electron Microscope - Energy Dispersive X-ray Spectroscopy) (HD-2700, manufactured by Hitachi High-Technologies Corporation) as follows. First, the magnetic tape MT is unwound from the cartridge 10, and three magnetic tape MT pieces are cut out at positions 30 to 40 m longitudinally from one end of the outer periphery of the magnetic tape MT to prepare three samples. Next, each sample is processed and sliced ​​using an 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 for observing the cross-sectional TEM images described below. The carbon layer is formed by vapor deposition on the surface of the magnetic layer side and the surface of the back layer side of the magnetic tape MT, and the tungsten layer is further formed on the surface of the magnetic layer side by vapor deposition or sputtering. The slices are formed along the longitudinal direction of the magnetic tape MT. That is, this thinning process forms a cross section parallel to both the longitudinal and thickness directions of the magnetic tape MT. The cross section of each obtained thinned sample was observed using a TEM at an acceleration voltage of 200 kV and a total magnification of 500,000 times to obtain a TEM image of each thinned sample. Next, EDX measurement of the magnetic layer portion of each obtained thinned sample was performed to determine the atomic ratio of Sr to Ba (Sr / Ba). The atomic ratios (Sr / Ba) obtained for each of the three thinned samples were simply averaged (arithmetic mean) to obtain the average atomic ratio (Sr / Ba).

[0099] The average atomic ratio of Sr to metal M1 (Sr / M1) is determined as follows. First, TEM images of three sliced ​​samples are obtained in the same manner as for the average atomic ratio of Sr to Ba (Sr / Ba). Next, EDX measurement of the magnetic layer portion is performed from the TEM image of each obtained sliced ​​sample to determine the average atomic ratio of Sr to metal M1 (Sr / M1). The atomic ratios (Sr / M1) determined for each of the three sliced ​​samples are simply averaged (arithmetic mean) to obtain the average atomic ratio (Sr / M1).

[0100] The average atomic ratio of Ba to metal M1 (Ba / M1) is determined as follows. First, TEM images of three sliced ​​samples are obtained in the same manner as for the average atomic ratio of Sr to Ba (Sr / Ba). Next, EDX measurement of the magnetic layer portion is performed from the TEM image of each obtained sliced ​​sample to determine the average atomic ratio of Ba to metal M1 (Ba / M1). The atomic ratios (Ba / M1) determined for each of the three sliced ​​samples are simply averaged (arithmetic mean) to obtain the average atomic ratio (Ba / M1).

[0101] The average composition represented by the general formula (A) can be determined as follows: First, TEM images of three sliced ​​samples are obtained in the same manner as for the average atomic ratio of Sr to Ba (Sr / Ba). Next, EDX measurement is performed on the magnetic layer portion of each obtained TEM image of each sliced ​​sample, and Ba is calculated. 、 α 、 Fe 、 The average composition ratio (average atomic ratio) of each of β is determined.

[0102] 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.

[0103] When the magnetic particles are hexagonal ferrite particles, the lower limit of the average particle size of the magnetic particles is preferably 13.0 nm or more, and more preferably 14.0 nm or more, from the viewpoint of improving the dispersibility of the magnetic particles and improving the electromagnetic conversion characteristics (e.g., SNR (Signal-to-Noise Ratio)).

[0104] When the magnetic particles are hexagonal ferrite particles, the numerical range of the average particle size of the magnetic particles may be defined by any one of the upper limit values ​​and any one of the lower limit values, and is preferably 13.0 nm or more and 19.0 nm or less, more preferably 13.0 nm or more and 18.0 nm or less, even more preferably 13.0 nm or more and 17.0 nm or less, 14.0 nm or more and 17.0 nm or less, or 14.0 nm or more and 16.0 nm or less.

[0105] When the magnetic particles are hexagonal ferrite particles, the average aspect ratio of the magnetic particles is preferably 1.0 or more and 3.0 or less, more preferably 1.5 or more and 2.8 or less, and even more preferably 1.8 or more and 2.7 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. Furthermore, when the magnetic particles are vertically oriented in the process of forming 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.

[0106] When the magnetic particles are hexagonal ferrite particles, the average particle size and average aspect ratio of the magnetic particles can be determined as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and the magnetic tape MT is cut out at a position 30 to 40 meters longitudinally from one end of the outer periphery of the magnetic tape MT. Next, the magnetic tape MT to be measured is processed and thinned using an 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 for observing the cross-sectional TEM image described below. The carbon layer is formed by vapor deposition on the surface of the magnetic tape MT facing the magnetic layer 43 and the surface facing the back layer 44, and the tungsten layer is further formed by vapor deposition or sputtering on the surface facing the magnetic layer 43. The thinning is performed along the length (longitudinal direction) of the magnetic tape MT. In other words, the thinning results in a cross section parallel to both the longitudinal and thickness directions of the magnetic tape MT.

[0107] The cross section of the obtained thin sample is observed using a transmission electron microscope (H-9500 manufactured by Hitachi High-Technologies Corporation) at an acceleration voltage of 200 kV and a total magnification of 500,000 times, so as to include the entire magnetic layer 43 in the thickness direction of the magnetic layer 43, and a TEM image is taken. The number of TEM images prepared is such that 50 particles can be extracted that can measure the plate diameter DB and plate thickness DA (see Figure 8) shown below.

[0108] In this specification, the size of a hexagonal ferrite particle (hereinafter referred to as "particle size") is defined as the plate diameter DB, which is the major axis of the plate surface or bottom surface, when the particle shape 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 bottom surface) as shown in FIG. 8 . The thickness or height of the particle observed in the TEM image is defined as the plate thickness DA. When the thickness or height of a particle observed in the TEM image is not constant, the thickness or height of the largest particle is defined as the plate thickness DA.

[0109] Next, 50 particles are selected from the captured TEM image based on the following criteria: Particles with parts outside the field of view of the TEM image are not measured, and only particles with clear outlines and that exist independently are measured. When particles overlap, particles with clear boundaries and whose overall shape can be determined are measured as individual particles, but particles with unclear boundaries and whose overall shape cannot be determined are not measured as their shape cannot be determined.

[0110] 9 and 10 show a first example and a second example of TEM images, respectively. In FIGS. 9 and 10, for example, the particles indicated by arrows a and d are selected because their plate thickness (thickness or height) DA can be clearly confirmed. The plate thickness DA of each of the selected 50 particles is measured. The plate thicknesses DA thus obtained are simply averaged (arithmetic mean) to obtain the average plate thickness DA. ａｖｅ Calculate the average plate thickness DA ａｖｅ is the average particle plate thickness. Next, the plate diameter DB of each magnetic particle is measured. To measure the plate diameter DB of the particles, 50 particles whose plate diameter DB can be clearly confirmed are selected from the TEM image. For example, in Figures 9 and 10, the particles indicated by arrows b and c are selected because their plate diameter DB can be clearly confirmed. The plate diameter DB of each of the selected 50 particles is measured. The plate diameter DBs thus determined are simply averaged (arithmetic averaged) to obtain the average plate diameter DB. ａｖｅ Average plate diameter DB ａｖｅ is the average grain size. And the average plate thickness DA ａｖｅ and average plate diameter DBａｖｅ The average aspect ratio of the particles (DB ａｖｅ / DA ａｖｅ ) is required.

[0111] When the magnetic particles are hexagonal ferrite particles, the upper limit of the average particle volume of the magnetic particles is preferably 1.50×10 ３ nm ３ or less, more preferably 1.40 × 10 ３ nm ３ More preferably, 1.30×10 ３ nm ３ Below, 1.20 x 10 ３ nm ３ Below, 1.10 x 10 ３ nm ３ or less or 1.00 x 10 ３ nm ３ The following is the result.

[0112] 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 from the viewpoint of improving the dispersibility of the magnetic particles and improving the electromagnetic conversion characteristics (for example, SNR). ３ nm ３ or more, more preferably 0.600 × 10 ３ nm ３ That's all.

[0113] When the magnetic particles are hexagonal ferrite particles, the numerical range of the average particle volume of the magnetic particles may be defined by any one of the upper limit values ​​and any one of the lower limit values, and is preferably 0.500×10 ３ nm ３ Above 1.50 x 10 ３ nm ３ or less, more preferably 0.500 × 10 ３ nm ３ The above is 1.40 x 10 ３ nm ３ or less, more preferably 0.500 × 10 ３ nm ３ The above is 1.30 x 10 ３ nm ３ Below, 0.500 x 10 ３ nm ３ The above is 1.20 x 10 ３ nm３ Below, 0.600 x 10 ３ nm ３ The above is 1.20 x 10 ３ nm ３ Below, 0.600 x 10 ３ nm ３ 1.10 x 10 ３ nm ３ or less or 0.600 x 10 ３ nm ３ Above 1.00 x 10 ３ nm ３ The following is the result.

[0114] The average particle volume of the magnetic particles can be calculated as follows: First, as described above in relation to the method for calculating the average particle size of the magnetic particles, the average plate thickness DA ａｖｅ and average plate diameter DB ａｖｅ Next, the average particle volume V of the magnetic particles is calculated using the following formula:

[0115] (ε-Iron Oxide Particles) ε-Iron oxide particles are hard magnetic particles that can achieve high coercivity even in the form of fine particles. ε-Iron oxide particles have a spherical or cubic shape. In this specification, spherical includes an almost spherical shape. Furthermore, cubic includes an almost cubic shape. Because ε-Iron oxide particles have the above-described shape, 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 even better electromagnetic conversion characteristics (e.g., SNR) can be obtained.

[0116] The ε-iron oxide particles may have a composite particle structure, specifically, an ε-iron oxide particle and a soft magnetic portion or a magnetic portion having a higher saturation magnetization σs and a lower coercive force Hc than ε-iron oxide (hereinafter referred to as "soft magnetic portion, etc.").

[0117] 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 ３The crystal is preferably the main phase, and the single-phase ε-Fe ２ O ３ More preferably, it consists of:

[0118] The saturation magnetization σs of the soft magnetic portion is preferably 40 emu / g or more. This suppresses a decrease in the saturation magnetization σs of the composite particles, thereby improving the output characteristics of the magnetic tape MT. The soft magnetic portion is in contact with at least a portion of the ε-iron oxide portion. Specifically, the soft magnetic portion may partially cover the ε-iron oxide portion, or may completely cover the ε-iron oxide portion.

[0119] The soft magnetic portion (the magnetic portion having a higher saturation magnetization σs and a smaller coercive force Hc than ε-iron oxide) contains a soft magnetic material such as α-Fe, a Ni-Fe alloy, or an Fe-Si-Al alloy. α-Fe may be obtained by reducing ε-iron oxide contained in the ε-iron oxide portion.

[0120] The soft magnetic portion may be made of, for example, Fe. ３ O ４ , γ-Fe ２ O ３ , or spinel ferrite, etc.

[0121] By providing the ε-iron oxide particle with a portion having soft magnetic properties as described above, the coercive force Hc of the ε-iron oxide portion alone can be maintained at a high value to ensure thermal stability, while the coercive force Hc of the ε-iron oxide particle (composite particle) as a whole can be adjusted to a coercive force Hc suitable for recording.

[0122] The ε-iron oxide particles may contain an additive instead of the above-mentioned composite particle structure, or may have the above-mentioned composite particle structure and also contain an additive. In this case, a portion of the Fe in the ε-iron oxide particles is substituted with the additive. By including an additive in the ε-iron oxide particles, the coercivity Hc of the ε-iron oxide particles as a whole can be adjusted to a coercivity Hc suitable for recording, thereby improving ease of recording. The additive is a metal element other than iron, preferably a trivalent metal element, more preferably 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.

[0123] Specifically, the ε-iron oxide containing additives is ε-Fe ２－ｘ M ｘ O ３ crystal (wherein M is a metal element other than iron, preferably a trivalent metal 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; and x is, for example, 0<x<1).

[0124] When the magnetic particles are ε-iron oxide particles, the upper limit of the average particle size of the magnetic particles is preferably 14.5 nm or less, more preferably 13.5 nm or less, and even more preferably 13.0 nm or less, 12.5 nm or less, or 12.0 nm or less, from the viewpoint of improving linear recording density.

[0125] 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 the electromagnetic conversion characteristics (for example, SNR).

[0126] 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 any one of the upper limit values ​​and any one of the lower limit values, and is preferably 10.0 nm or more and 14.5 nm or less, more preferably 10.0 nm or more and 13.5 nm or less, even more preferably 10.0 nm or more and 13.0 nm or less, 10.0 nm or more and 12.5 nm or less, or 10.0 nm or more and 12.0 nm or less.

[0127] When the magnetic particles are ε-iron oxide 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 2.1 or less, or 1.0 or more and 1.8 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. Furthermore, when the magnetic particles are vertically oriented in the process of forming 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.

[0128] When the magnetic particles are ε-iron oxide particles, the average particle size and average aspect ratio of the magnetic particles can be determined as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and the magnetic tape MT is cut out at a position 30 to 40 m longitudinally from one end of the outer periphery of the magnetic tape MT. Next, the magnetic tape MT to be measured is processed and thinned using an 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 for observing the cross-sectional TEM image described below. The carbon layer is formed by vapor deposition on the surface of the magnetic tape MT facing the magnetic layer 43 and the surface facing the back layer 44, and the tungsten layer is further formed by vapor deposition or sputtering on the surface facing the magnetic layer 43. The thinning is performed along the length (longitudinal direction) of the magnetic tape MT. In other words, the thinning results in a cross section parallel to both the longitudinal and thickness directions of the magnetic tape MT.

[0129] The cross section of the obtained thin film sample was observed using a transmission electron microscope (H-9500 manufactured by Hitachi High-Technologies Corporation) at an acceleration voltage of 200 kV and a total magnification of 500,000 times, so as to include the entire magnetic layer 43 in the thickness direction of the magnetic layer 43, and a TEM image was taken. Next, 50 particles whose particle shape can be clearly confirmed were selected from the taken TEM image, and the major axis length DL and minor axis length DS of each particle were measured. Here, the major axis length DL refers to the longest distance between two parallel lines drawn from any angle so as to be tangent to the contour of each particle (the so-called maximum Feret diameter). Meanwhile, the minor axis length DS refers to the longest length of the particle in the direction perpendicular to the major axis (DL) of the particle. Next, the major axis lengths DL of the measured 50 particles were simply averaged (arithmetic mean) to obtain the average major axis length DL ave The average major axis length DL obtained in this way is ave is the average particle size of the magnetic particles. The minor axis lengths DS of the measured 50 particles are simply averaged (arithmetic mean) to obtain the average minor axis length DS ave Then, calculate the average major axis length DL ave and mean minor axis length DS ave From the average aspect ratio of the particles (DL ave / DS ave ) is required.

[0130] When the magnetic particles are ε-iron oxide particles, the upper limit of the average particle volume of the magnetic particles is preferably 1.50×10 ３ nm ３ or less, more preferably 1.40 × 10 ３ nm ３ More preferably, 1.30×10 ３ nm ３ Below, 1.20 x 10 ３ nm ３ Below, 1.10 x 10 ３ nm ３ or less or 1.00 x 10 ３ nm ３ The following is the result.

[0131] 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 from the viewpoint of improving the dispersibility of the magnetic particles and improving the electromagnetic conversion characteristics (e.g., SNR). ３ nm ３ or more, more preferably 0.600 × 10 ３ nm ３ That's all.

[0132] 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 any one of the upper limit values ​​and any one of the lower limit values, and is preferably 0.500×10 ３ nm ３ Above 1.50 x 10 ３ nm ３ or less, more preferably 0.500 × 10 ３ nm ３ The above is 1.40 x 10 ３ nm ３ or less, more preferably 0.500 × 10 ３ nm ３ The above is 1.30 x 10 ３ nm ３ Below, 0.600 x 10 ３ nm ３ The above is 1.20 x 10 ３ nm ３ Below, 0.600 x 10 ３ nm ３1.10 x 10 ３ nm ３ or less or 0.600 x 10 ３ nm ３ Above 1.00 x 10 ３ nm ３ The following is the result.

[0133] When the ε-iron oxide particles are spherical, the average particle volume of the magnetic particles can be calculated as follows: First, the average major axis length DL is calculated in the same manner as in the above-mentioned method for calculating the average particle size of the magnetic particles. ave Next, the average particle volume V of the magnetic particles is calculated using the following formula: V = (π / 6) × DL ave 3

[0134] When the ε-iron oxide particles have a cubic shape, the average volume of the magnetic particles can be calculated as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and the magnetic tape MT is cut out at a position 30 to 40 m longitudinally from one end of the outer periphery of the magnetic tape MT. Next, the cut magnetic tape MT is processed by FIB or the like to be thinned. When the FIB method is used, a carbon film and a tungsten thin film are formed as protective films as a pretreatment for observing the cross-sectional TEM image described below. The carbon film is formed by vapor deposition on the surface of the magnetic tape MT facing the magnetic layer 43 and the surface facing the back layer 44, and the tungsten thin film is further formed by vapor deposition or sputtering on the surface facing the magnetic layer 43. The thinning is performed along the length (longitudinal direction) of the magnetic tape MT. In other words, the thinning results in a cross section parallel to both the longitudinal and thickness directions of the magnetic tape MT.

[0135] The obtained thin section sample is observed using a transmission electron microscope (Hitachi High-Technologies Corporation H-9500) at an acceleration voltage of 200 kV and a total magnification of 500,000 times to observe the cross section of the magnetic layer 43 in the thickness direction so as to include the entire magnetic layer 43, and a TEM image is obtained. Note that the magnification and acceleration voltage may be adjusted appropriately depending on the type of device. Next, 50 particles whose particle shape is clear are selected from the TEM image taken, and the side length DC of each particle is measured. Next, the side lengths DC of the measured 50 particles are simply averaged (arithmetic mean) to obtain the average side length DC ave Next, calculate the average side length DC ave Using the following formula, the average volume V of the magnetic particles is calculated. ave (particle volume) is calculated. ave = DC ave 3

[0136] (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 crystalline oriented in the perpendicular direction of the magnetic tape MT. The cobalt ferrite particles have, for example, a cubic shape. In this specification, cubic shape includes a nearly cubic shape. The Co-containing spinel ferrite may further contain at least one element selected from the group consisting of Ni, Mn, Al, Cu, and Zn in addition to Co.

[0137] The Co-containing spinel ferrite has an average composition represented by the following formula, for example: Co ｘ M ｙ Fe ２ O Ｚ (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 within the range of 0.4≦x≦1.0. y is a value within the range of 0≦y≦0.3. However, x and y satisfy the relationship (x+y)≦1.0. z is a value within the range of 3≦z≦4. A portion of Fe may be substituted with another metal element.)

[0138] 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.

[0139] 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 more, from the viewpoint of improving the dispersibility of the magnetic particles and improving the electromagnetic conversion characteristics (for example, SNR).

[0140] 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 one of the above upper limits and the above lower limit, and is 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 magnetic particles is the same as the method for calculating the average particle size of the magnetic particles when the magnetic particles are ε-iron oxide particles.

[0141] 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. Furthermore, when the magnetic particles are vertically oriented in the process of forming 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. The method for calculating the average aspect ratio of the magnetic particles is the same as the method for calculating the average aspect ratio of the magnetic particles when the magnetic particles are ε-iron oxide particle powder.

[0142] When the magnetic particles are cobalt ferrite particles, the upper limit of the average particle volume of the magnetic particles is preferably 4.00×10 ３ nm ３ or less, more preferably 2.00 x 10 ３ nm ３ or less, and even more preferably 1.50 x 10 ３ nm ３or less or 1.00 x 10 ３ nm ３ The following is the result.

[0143] When the magnetic particles are cobalt ferrite particles, the lower limit of the average particle volume of the magnetic particles is preferably 0.5×10 from the viewpoint of improving the dispersibility of the magnetic particles and improving the electromagnetic conversion characteristics (for example, SNR). ３ nm ３ or more, more preferably 0.6 × 10 ３ nm ３ That's all.

[0144] 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 one of the upper limit values ​​and any one of the lower limit values, and is preferably 0.5×10 ３ nm ３ Above 4.00 x 10 ３ nm ３ Less than or equal to 0.6 × 10, more preferably 0.6 × 10 ３ nm ３ Above 2.00 x 10 ３ nm ３ or less, and even more preferably 0.6 × 10 ３ nm ３ Above 1.50 x 10 ３ nm ３ or less than 0.6 x 10 ３ nm ３ Above 1.00 x 10 ３ nm ３ The method for calculating the average particle volume of the magnetic particles is the same as the method for calculating the average particle volume when the ε iron oxide particles have a cubic shape.

[0145] 3B , some of the carbon particles 431 contained in the magnetic layer 43 may protrude from the magnetic surface, forming multiple protrusions 430. By forming multiple protrusions 430 from the carbon particles 431, the electrical resistance of the magnetic surface can be reduced, and charging of the magnetic surface can be suppressed. Furthermore, the dynamic friction force between the head unit 56 and the magnetic surface when the magnetic tape MT is running can be reduced.

[0146] The carbon particles 431 may function as an antistatic agent and a solid lubricant. The average primary particle size of the carbon particles 431 is preferably 100.0 nm or less. When the average primary particle size of the carbon particles 431 is 100.0 nm or less, even when the carbon particles 431 are particles with a wide 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.

[0147] For example, at least one selected from the group consisting of carbon black, acetylene black, ketjen black, carbon nanotubes, and graphene can be used as the carbon particles 431. It is preferable to use carbon black among these carbon particles 431. For example, Seast TA manufactured by Tokai Carbon Co., Ltd., Asahi #15 and #15HS manufactured by Asahi Carbon Co., Ltd., etc. can be used as the carbon black.

[0148] The magnetic layer 43 may contain hybrid particles instead of the carbon particles 431, or may contain hybrid particles together with the carbon particles 431. 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, they may be hybrid carbon in which carbon is attached to the surface of silica particles.

[0149] 3B , some of the abrasive particles 432 contained in the magnetic layer 43 may protrude from the magnetic surface to form a plurality of protrusions 430. When the head unit 56 slides over the magnetic tape MT, the protrusions 430 formed by the abrasive particles 432 can come into contact with the head unit 56.

[0150] The lower limit of the Mohs hardness of the abrasive particles 432 is preferably 7.0 or more, more preferably 7.5 or more, even more preferably 8.0 or more, and particularly preferably 8.5 or more, from the viewpoint of suppressing deformation due to contact with the head unit 56. The upper limit of the Mohs hardness of the abrasive particles 432 is preferably 9.5 or less, from the viewpoint of suppressing wear of the head unit 56.

[0151] The abrasive particles 432 are preferably inorganic particles such as alumina particles (aluminum oxide particles). Specific examples of inorganic particles include α-alumina with an α-conversion rate of 90% or more, β-alumina, γ-alumina, silicon carbide, chromium oxide, cerium oxide, α-iron oxide, corundum, silicon nitride, titanium carbide, titanium oxide, silicon dioxide, tin oxide, magnesium oxide, tungsten oxide, zirconium oxide, boron nitride, zinc oxide, calcium carbonate, calcium sulfate, barium sulfate, molybdenum disulfide, acicular α-iron oxide obtained by dehydrating and annealing magnetic iron oxide raw materials, optionally surface-treated with aluminum and / or silica, and diamond powder. The inorganic particles preferably include alumina particles such as α-alumina, β-alumina, and γ-alumina, and silicon carbide. The abrasive particles 432 may be acicular, spherical, or cubic, but those with angular shapes are preferred due to their high abrasiveness.

[0152] (Binder) The binder includes, for example, a thermoplastic resin, and may further include a thermosetting resin or a reactive resin.

[0153] 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, the vinyl chloride resin refers to a polymer containing a structural unit derived from vinyl chloride. More specifically, for example, the vinyl chloride resin refers to a homopolymer of vinyl chloride, a polymer of vinyl chloride and a comonomer copolymerizable therewith, and a mixture of these polymers.

[0154] 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.

[0155] The term "urethane-based resin" refers to a resin containing a urethane bond in at least a portion of the molecular chain constituting the resin, and may be a urethane resin or a copolymer containing a urethane bond in a portion of the molecular chain. The urethane-based resin may be, for example, one obtained by reacting a polyisocyanate with a polyol. Alternatively, the urethane-based resin may be, for example, one obtained by reacting a polyester with a polyol. In this specification, the term "urethane-based resin" also includes one obtained by reaction with a curing agent.

[0156] 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 refers to a compound having two or more isocyanate groups in the molecule. The polyisocyanate may be the polyisocyanate contained in the curing agent.

[0157] Any suitable polyol having two or more OH groups can be used as the polyol. The polyol may include, for example, at least one selected from the group consisting of a polyol (diol) having two OH groups, a polyol (triol) having three OH groups, a polyol (tetraol) having four OH groups, a polyol (pentaol) having five OH groups, and a polyol (hexaol) having six OH groups. Specific examples of the polyol include at least one selected from the group consisting of polyester polyols, polyether polyols, polycarbonate polyols, polyesteramide polyols, and acrylate polyols.

[0158] The polyester includes, for example, at least one selected from the group consisting of phthalic acid polyesters and aliphatic polyesters.

[0159] The thermoplastic resin may further include a thermoplastic resin other than a vinyl chloride resin or a urethane resin. Examples of such a thermoplastic resin include at least one selected from the group consisting of vinyl acetate, an acrylic acid ester-acrylonitrile copolymer, an acrylic acid ester-acrylonitrile copolymer, an acrylic acid ester-vinylidene chloride copolymer, a methacrylic acid ester-vinylidene chloride copolymer, a methacrylic acid ester-ethylene copolymer, polyvinyl fluoride, a vinylidene chloride-acrylonitrile copolymer, an acrylonitrile-butadiene copolymer, a polyamide resin, polyvinyl butyral, cellulose derivatives (cellulose acetate butyrate, cellulose diacetate, cellulose triacetate, cellulose propionate, nitrocellulose), a styrene-butadiene copolymer, a polyester resin, an amino resin, and synthetic rubber.

[0160] The thermosetting resin includes at least one selected from the group consisting of, for example, phenolic resin, epoxy resin, polyurethane curing resin, urea resin, melamine resin, alkyd resin, silicone resin, polyamine resin, and urea formaldehyde resin.

[0161] All of the above binders contain -SO ３ M, -OSO ３ M, -COOM, P=O(OM) ２ (wherein M represents a hydrogen atom or an alkali metal such as lithium, potassium, or sodium), or -NR1R2, -NR1R2R3 ＋ X － a side chain amine having a terminal group represented by >NR1R2 ＋ X － (wherein R1, R2, and R3 represent a hydrogen atom or a hydrocarbon group, and X － represents a halogen element ion such as fluorine, chlorine, bromine, or iodine, or an inorganic ion or an organic ion.) Polar functional groups such as -OH, -SH, -CN, and epoxy groups may also be introduced. The amount of these polar functional groups introduced into the binder is 10 －１ 10 above －８ It is preferably 10 mol / g or less.－２ 10 above －６ It is more preferably mol / g or less.

[0162] (Lubricant) The lubricant may be a liquid lubricant. The lubricant may be, for example, at least one selected from a fatty acid and a fatty acid ester, preferably both a fatty acid and a fatty acid ester. The inclusion of a lubricant in the magnetic layer 43, particularly the inclusion of both a fatty acid and a fatty acid ester in the magnetic layer 43, contributes to improving the running stability of the magnetic tape MT. More particularly, the magnetic layer 43 containing a lubricant and having pores achieves good running stability. This improvement in running stability is thought to be due to the lubricant adjusting the dynamic friction coefficient of the magnetic layer 43-side surface of the magnetic tape MT to a value suitable for running the magnetic tape MT.

[0163] The fatty acid may preferably be a compound represented by the following general formula (1) or (2). For example, the fatty acid may contain either or both of the compound represented by the following general formula (1) and the compound represented by the general formula (2).

[0164] The fatty acid ester may preferably be a compound represented by the following general formula (3), (4), or (5). For example, the fatty acid ester may contain one, two, or three of the compounds represented by the following general formula (3), (4), and (5).

[0165] By including in the lubricant one or both of the compound represented by general formula (1) and the compound represented by general formula (2), and one, two or three of the compound represented by general formula (3), the compound represented by general formula (4) and the compound represented by general formula (5), it is possible to suppress an increase in the coefficient of dynamic friction due to repeated recording or reproduction of the magnetic tape MT.

[0166] CH3 (CH2) k COOH (1) (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.)

[0167] CH3 (CH2) n CH=CH(CH2) m COOH (2) (In the 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.)

[0168] CH3 (CH2) p COO(CH2) q CH3 (3) (wherein, in general formula (3), p is an integer selected from the range of 14 or more and 22 or less, more preferably 14 or more and 18 or less, and q is an integer selected from the range of 2 or more and 5 or less, more preferably 2 or more and 4 or less.)

[0169] CH3 (CH2) r COO-(CH2) s CH(CH3)2 (4) (In the 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.)

[0170] CH3 (CH2) ｔ COO-(CH)(CH3)CH2(CH3) ｕ ...(5) (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.)

[0171] (Antistatic Agent) The antistatic agent reduces the electrical resistance of the magnetic surface and can suppress 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.

[0172] (Curing Agent) The curing agent includes, for example, 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, an allophanate structure, or the like.

[0173] Specific examples of polyisocyanates include aromatic polyisocyanates such as an adduct of tolylene diisocyanate (TDI) and an active hydrogen compound, and aliphatic polyisocyanates such as an adduct of hexamethylene diisocyanate (HMDI) and an active hydrogen compound. The weight average molecular weight of these polyisocyanates is preferably in the range of 100 to 3,000.

[0174] (Rust inhibitor) Examples of the rust inhibitor include phenols, naphthols, quinones, heterocyclic compounds containing a nitrogen atom, heterocyclic compounds containing an oxygen atom, and heterocyclic compounds containing a sulfur atom.

[0175] (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 titanium oxide).

[0176] (Underlayer 42) The underlayer 42 is intended to reduce the surface irregularities of the substrate 41 and adjust the irregularities of the magnetic surface. The underlayer 42 is a non-magnetic layer containing non-magnetic particles, a binder, and a lubricant. The underlayer 42 supplies the lubricant to the magnetic surface. If necessary, the underlayer 42 may further contain at least one additive selected from the group consisting of an antistatic agent, a hardener, an anti-rust agent, etc.

[0177] The underlayer 42 may have a plurality of holes. A lubricant may be stored in the holes. In this case, the supply of the lubricant to the magnetic surface can be improved. From the viewpoint of improving the supply of the lubricant to the magnetic surface, it is preferable that the holes extend in a direction perpendicular to the magnetic surface. From the viewpoint of improving the supply of the lubricant to the magnetic surface, it is preferable that the holes in the underlayer 42 and the holes in the magnetic layer 43 are connected to each other.

[0178] Average thickness t of the underlayer 42 ３ The upper limit of the average thickness t of the underlayer 42 is preferably 0.90 μm or less, more preferably 0.80 μm or less, even more preferably 0.70 μm or less, and particularly preferably 0.60 μm or less. ３ When the average thickness t of the underlayer 42 is 0.90 μm or less, the magnetic tape MT can be stretched and contracted by an external force more easily, and therefore the width of the magnetic tape MT can be adjusted more easily by adjusting the tension. ３ The lower limit of the thickness is preferably 0.30 μm or more from the viewpoint of reducing the unevenness on the surface of the substrate 41 .

[0179] Average thickness t of the underlayer 42 ３ is the average thickness t of the magnetic layer 43 ２ However, the magnification of the TEM image is adjusted appropriately depending on the thickness of the underlayer 42.

[0180] Average thickness t of the substrate 41 １ Whereas, the average thickness t ２ and the average thickness t of the underlayer 42 ３ If the total thickness of the substrate 41 is too large, the bending rigidity will increase, and the stability of contact between the magnetic tape MT and the head may decrease. １ Whereas, the average thickness t ２ and the average thickness t of the underlayer 42 ３ If the total thickness of the substrate 41 is too small, the surface properties of the magnetic surface of the magnetic tape MT may be reduced. １ The average thickness t of the magnetic layer 43 ２ and the average thickness t of the underlayer 42 ３ The ratio of the total thickness ((t ２ +t ３ ) / t１ ) is preferably 0.19 or more and 0.28 or less.

[0181] The underlayer 42 preferably has a plurality of holes. By storing lubricant in these holes, it is possible to further suppress a decrease in the amount of lubricant supplied between the magnetic surface and the head unit 56, even after repeated recording or reproduction (i.e., after repeated running with the head unit 56 in contact with the surface of the magnetic tape MT). This further suppresses an increase in the dynamic friction coefficient. In other words, even better running stability can be obtained.

[0182] (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. The shapes of non-magnetic particles include, for example, various shapes such as needles, spheres, cubes, and plates, but are not limited to these shapes.

[0183] (Binder, Lubricant) The binder and lubricant are the same as those in the magnetic layer 43 described above.

[0184] (Additives) The antistatic agent, hardener, and anticorrosive agent are the same as those in the magnetic layer 43 described above.

[0185] (Back Layer 44) The back layer 44 contains a binder and non-magnetic particles. If necessary, the back layer 44 may further contain at least one additive selected from the group consisting of a lubricant, a curing agent, an antistatic agent, etc. The binder and non-magnetic particles are the same as those in the underlayer 42 described above. The curing agent and antistatic agent are the same as those in the magnetic layer 43 described above.

[0186] The average particle size of the non-magnetic particles is preferably 10.0 nm or more and 150.0 nm or less, more preferably 15.0 nm or more and 110.0 nm or less. 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 two or more particle size distributions.

[0187] Average thickness t of the back layer 44 ４ The upper limit of the average thickness t of the back layer 44 is preferably 0.60 μm or less. ４ When the upper limit of t is 0.60 μm or less, the average thickness t Ｔ Even if the average thickness t of the back layer 44 is 5.40 μm or less, the thickness of the underlayer 42 and the substrate 41 can be kept large, so that the running stability of the magnetic tape MT in a recording / reproducing device can be maintained. ４ The lower limit of the thickness is not particularly limited, but is, for example, 0.20 μm or more.

[0188] Average thickness t of the back layer 44 ４ is calculated as follows: First, the average thickness t of the magnetic tape MT Ｔ Measure the average thickness t Ｔ The method for measuring the average thickness of the magnetic tape is as described below in "Average Thickness of Magnetic Tape." Next, the magnetic tape MT housed in the cartridge 10 is unwound, and a sample is prepared by cutting the magnetic tape MT into a length of 250 mm at a position 30 to 40 m longitudinally from one end of the outer periphery of the magnetic tape MT. 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 positions using a laser hologram gauge (LGH-110C) manufactured by Mitutoyo Corporation, and the measured values ​​are simply averaged (arithmetic mean) to obtain the average thickness t Ｂ Then, the average thickness t of the back layer 44 is calculated using the following formula: ４ The five measurement positions are selected at random from the sample so that they are different positions in the longitudinal direction of the magnetic tape MT. ４ [μm] = t Ｔ [μm]-t Ｂ [μm]

[0189] (Lubricant Layer) The lubricant layer contains a lubricant. The lubricant is the same as the lubricant contained in the magnetic layer 43. The lubricant layer may be formed from a lubricant supplied to the magnetic surface from the magnetic layer 43 and the underlayer 42.

[0190] (The average thickness of the magnetic tape MT is t Ｔ ) Average thickness t of magnetic tape MT Ｔ By making the average thickness (average total thickness) t of the magnetic tape MT thinner, the length of tape wound into one cartridge 10 can be increased, thereby increasing the recording capacity per cartridge 10. Ｔ The upper limit of the average thickness t of the magnetic tape MT is 5.40 μm or less, preferably 5.30 μm or less, more preferably 5.10 μm or less, even more preferably 4.90 μm or less, and particularly preferably 4.70 μm or less. Ｔ The lower limit of the thickness is not particularly limited, but is, for example, 3.50 μm or more.

[0191] Average thickness t of magnetic tape MT Ｔ is obtained as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and a sample is cut out of the magnetic tape MT at a length of 250 mm at a position 30 to 40 m longitudinally from one end of the outer periphery of the magnetic tape MT. Next, the thickness of the sample is measured at five positions using a Mitutoyo Laser Hologram (LGH-110C) as a measuring device, and the measured values ​​are simply averaged (arithmetic mean) to obtain the average thickness t Ｔ The five measurement positions are selected at random from the sample so that they are different positions in the longitudinal direction of the magnetic tape MT.

[0192] (Average tension T when SUS rod rotates) The average tension T when SUS rod rotates is a physical quantity that substitutes for the coefficient of dynamic friction of the magnetic surface in the running direction during actual running, and is correlated with both the wobble of the magnetic tape during actual running in a drive with a parallel head unit and the wobble of the magnetic tape during actual running in a drive with a diagonal head unit, with a particularly strong correlation with the former.

[0193] The average tension T during rotation of the SUS rod is 55.0 gf or less, preferably 50.0 gf or less, more preferably 48.6 gf or less, 45.6 gf or less. If the average tension T during rotation of the SUS rod exceeds 55.0 gf, there is a risk that the wobble of the magnetic tape MT cannot be suppressed when recording or reproducing the magnetic tape MT with a drive having a parallel head unit. In other words, there is a risk that the head unit will not be able to accurately trace the data track. Note that if the average tension T during rotation of the SUS rod exceeds 60.0 gf, there is a risk that the wobble of the magnetic tape MT cannot be suppressed even when recording or reproducing the magnetic tape MT with a drive having a diagonal head unit.

[0194] (Configuration of Measuring Device 70) Prior to describing the method for measuring the average tension T during rotation of the SUS rod, the configuration of the measuring device 70 used in the method for measuring the average tension T will be described with reference to Figs. 11 and 12 .

[0195] The measuring device 70 includes a base 71 , a driving device 72 , a load cell 73 , two plate-like members 74 A and 74 B, two guides 75 A and 75 B, and a round bar 76 .

[0196] (Driver 72) The driver 72 is fixed on the base 71. The driver 72 is configured to be able to move the load cell 73 in a direction to move toward the guide 75A and in a direction to move the load cell 73 away from the guide 75A.

[0197] (Load cell 73) The load cell 73 is supported on the drive device 72. One end of the magnetic tape MT is connected to the load cell 73 via a jig 77. The load cell 73 can measure the tension applied to the magnetic tape MT in the longitudinal direction. A ZTS-5N manufactured by Imada Co., Ltd. is used as the load cell 73. The positions of the load cell 73 and the guide 75A are set so that the magnetic tape MT is approximately horizontal between the jig 77 and the guide 75A.

[0198] (Plate-like members 74A, 74B) The plate-like members 74A, 74B are supported on the base 71 at a predetermined distance apart so that their main surfaces face each other and are parallel to each other. The plate-like members 74A, 74B are made of highly rigid metal plates. Note that the plate-like member 74B is not shown in Figure 11.

[0199] (Guides 75A, 75B) The two guides 75A, 75B are arranged parallel to each other and spaced apart from each other. Bearings (not shown) are provided at both ends of the two guides 75A, 75B, respectively, and the ends of the two guides 75A, 75B are fixed to the plate-like members 74A, 74B via these bearings. This allows the two guides 75A, 75B to rotate smoothly in accordance with the reciprocating movement of the magnetic tape MT, and also fixes the relative positions of the two guides 75A, 75B. As described above, the smooth rotation of the two guides 75A, 75B prevents the dynamic friction between the guides 75A, 75B and the magnetic tape MT from affecting the tension measurement of the magnetic tape MT. The guide 75A is made of a round bar 75A. １ and roll member 75A ２ The guide 75B has a round bar 75B １ and roll member 75B ２ It has the following.

[0200] Round bar 75A １ A bearing (not shown) is provided at each end of the round bar 75B. １ Bearings (not shown) are also provided at both ends of the round bar 75A. １ is the roll member 75A ２The roll member 75A is inserted into the hole of the roll member 75A. ２ is round bar 75A １ Similarly, the round bar 75B is fixed to the peripheral surface of the １ is the roll member 75B ２ The roll member 75B is inserted into the hole of the roll member 75B. ２ Round bar 75B １ The roller member 75A is fixed to the peripheral surface of the roller member 75A. ２ , 75B ２ The peripheral surface of the round bar 75A is the surface that comes into contact with the magnetic tape MT when measuring the tension. １ , 75B １ A 3 mm diameter stainless steel round bar (RGOS3-150 Kenma Rod RGOS, manufactured by Misumi Corporation) is used as the roll member 75A. ２ , 75B ２ A cylindrical member made of SUS and having a diameter of 15 mm is used as the casing.

[0201] (Round Bar 76) When measuring tension, the round bar 76 is fixed between the guides 75A and 75B and at a position approximately equidistant from the guides 75A and 75B. One end of the round bar 76 and a portion of the round bar 76 at a predetermined position from the one end are rotatably supported by the plate-shaped members 74A and 74B, respectively. The other end of the round bar 76 is connected to the output shaft of a motor (BLFM230-A, manufactured by Oriental Motor Co., Ltd.) 79 via a connecting member 79A. The round bar 76 is a 3 mm diameter stainless steel round bar (RGOS3-150 Kenma Rod RGOS, manufactured by Misumi Corporation). A VEXTA Brushless DC Motor Driver BLFD30A is used as the motor driver to control the rotation of the motor 79. When measuring the tension applied to the magnetic tape MT, the round bar 76 is rotated clockwise when viewed from the side opposite to the plate-like member 74A (i.e., the plate-like member 74B side), as shown in FIG.

[0202] (Preparation of Samples) The samples used to measure the average tension T during rotation of the SUS rod are prepared as follows. First, a 1 / 2-inch wide magnetic tape MT housed in the cartridge 10 is unwound, and the magnetic tape MT is cut into a length of 1 m at a position 30 m longitudinally from one end of the outer periphery of the magnetic tape MT, and then divided into two equal pieces to prepare two samples (hereinafter referred to as "Sample 1") each 1 / 2 inch wide and 50 cm long. One of the two Sample 1s is used to measure the average tension T during rotation of the SUS rod, and the other is used to measure the average coefficient of dynamic friction μ during low-speed running, as described below.

[0203] Next, the magnetic tape MT is further unwound, and a 1 m length of the magnetic tape MT is cut out at a position 50 m longitudinally from one end of the inner circumferential side of the magnetic tape MT, and this is divided into two equal parts to prepare two samples (hereinafter referred to as "Sample 2") each 1 / 2 inch wide and 50 cm long. One of the two Samples 2 is used to measure the average tension T during rotation of the SUS rod, and the other is used to measure the average coefficient of dynamic friction μ during low-speed running, as described below.

[0204] (Measurement of Average Tension T During Rotation of SUS Rod) Using one of the two samples 1, the average tension T during rotation of the SUS rod is measured as follows. First, the magnetic tape MT of sample 1 is placed on the two guides 75A, 75B so as to straddle the two guides 75A, 75B, and a round rod 76 is brought into contact with the magnetic surface of the magnetic tape MT. Next, one end of the magnetic tape MT is connected to a load cell 73 via a jig 77. One end of the magnetic tape MT is fixed to the jig 77. Next, a weight 78 with a mass of 30 g is connected to the other end of the magnetic tape MT. A tension of 30.0 gf (approximately 0.294 N) is applied to the magnetic tape MT in the longitudinal direction by the weight 78.

[0205] Next, with the magnetic tape MT in a stationary state, the magnetic surface of the magnetic tape MT is brought into contact with the round bar 76 so that the wrap angle θ (°) is 60°. Here, the wrap angle θ is calculated from the curvature R of the round bar 76 and the amount of pressure the round bar 76 exerts on the magnetic tape MT. The round bar 76 is placed between the guides 75A and 75B.

[0206] Next, the rotating round bar 76 is slid against the magnetic surface of the magnetic tape MT while repeatedly moving back and forth five times relative to the magnetic tape MT. The tension T [gf] of the magnetic tape MT during this reciprocating motion is measured by the load cell 73. The rotation of the round bar 76 is controlled to 125 rpm by a motor driver. As described above, the rotation direction of the round bar 76 is clockwise when viewed from the side opposite the plate-like member 74A (i.e., the side opposite the plate-like member 74B). Hereinafter, the period when the magnetic tape MT is pulled in the direction (pulling direction) in which one end of the magnetic tape MT (the end attached to the jig 77) approaches the load cell 73 is referred to as the "forward pass," and the period when one end of the magnetic tape MT is fed in the direction away from the load cell 73 (opposite the pulling direction) is referred to as the "return pass." The reciprocating motion is controlled so that the distance of movement in each of the forward and backward directions is 55 mm, and the moving speed of the magnetic tape MT relative to the round bar 76 (the moving speed in each of the forward and backward directions) is 2 mm / s.

[0207] The contact between the rotating rod 76 and the magnetic tape MT simulates the contact between the head unit 56 and the magnetic tape MT when it is running in a drive. The rotation speed of the rod 76, 125 rpm, and the diameter of the rod 76, 3 mm, were set in consideration of the running speed (sliding speed) of an actual magnetic tape MT. The reciprocating movement speed of 2 mm / s was set in consideration of ensuring sufficient measurement points for each pulling (one forward movement) and each feeding (one return movement).

[0208] The pulling time (time for one outward movement) and the letting-out time (time for one return movement) are both set to 27.5 seconds. The sampling rate of the load cell 73 is set to 0.1 point / sec. Therefore, the number of measurement points during one pulling (one outward movement) is 275 points. The environment during measurement of the tension T [gf] is maintained at 23°C ± 2°C and 45% RH ± 5% RH. Figure 13 is a graph showing an example of the measurement results of tension (load). In Figure 13, the data enclosed in boxes represents data acquired during the fourth and fifth outward movements.

[0209] Next, the tension T [gf] of Sample 2 is measured in the same manner as in the measurement of the tension T [gf] of Sample 1 above, except that Sample 2 is used as the measurement sample.

[0210] Next, using the acquired data, the average tension values ​​during tension on the fourth and fifth outbound passes of Samples 1 and 2 are calculated. Specifically, data from 15 points before and after each of the measurement data (tension) for the fourth outbound pass (275 point) of Sample 1, the fifth outbound pass (275 point) of Sample 1, the fourth outbound pass (275 point) of Sample 2, and the fifth outbound pass (275 point) of Sample 2 are excluded. The average tension T [gf] is then calculated by simply averaging the measurement data for the fourth outbound pass (245 point) of Sample 1, the measurement data for the fifth outbound pass (245 point) of Sample 1, the measurement data for the fourth outbound pass (245 point) of Sample 2, and the measurement data for the fifth outbound pass (245 point) of Sample 2 (a total of 245 x 4 measurement data).

[0211] (Average dynamic friction coefficient μ during low-speed running) The average dynamic friction coefficient μ during low-speed running is a physical quantity that substitutes for the average dynamic friction coefficient of the magnetic surface in the width direction when recording or playing back the magnetic tape MT using a drive with a diagonal head unit, and is correlated with the wobble of the magnetic tape MT caused by the stick-slip phenomenon when recording or playing back the magnetic tape MT using a drive with a diagonal head unit.

[0212] The average dynamic friction coefficient μ during low-speed running is 0.35 or less, preferably 0.34 or less, more preferably 0.32 or less, and even more preferably 0.30 or less. If the average dynamic friction coefficient μ during low-speed running exceeds 0.35, there is a risk that when recording or reproducing the magnetic tape MT using a drive with a diagonal head unit, it will not be possible to suppress wobble of the magnetic tape MT due to the stick-slip phenomenon. In other words, there is a risk that the head unit will not be able to accurately trace the data tracks.

[0213] (Configuration of Measuring Device 70a) Prior to describing the method for measuring the average dynamic friction coefficient μ during low-speed driving, the configuration of the measuring device 70a used in the method for measuring the average dynamic friction coefficient μ will be described with reference to FIGS. 14 and 15.

[0214] The measuring device 70a differs from the measuring device 70 in that it includes a head block 76a instead of the round bar 76. The head block 76a is movably attached to the plate-like members 74A and 74B so that the wrap angle θ can be changed. Once the wrap angle θ (°) reaches the desired angle (25° in this measurement) by moving the head block 76a, the head block 76a can be fixed in that position, thereby fixing the positional relationship between the guides 75A and 75B and the head block 76a. When measuring tension, the head block 76a is fixed between the guides 75A and 75B and at a position approximately equidistant from the guides 75A and 75B. The head block 76a is a recording / reproducing head for an LTO4 drive manufactured by Hewlett-Packard Enterprises (HPE).

[0215] (Measurement of Average Dynamic Friction Coefficient μ During Low-Speed ​​Travel) The average dynamic friction coefficient μ during low-speed travel is measured as follows: Of the two samples 1 prepared when measuring the average tension T during SUS rod rotation, the remaining sample 1 is used to measure the tension T [gf] of sample 1 as follows.

[0216] First, the magnetic tape of sample 1 is set in the measurement device 70a in the same manner as in measuring the average tension T during rotation of the SUS rod, except for the following points. As shown in Figures 14 and 15, the magnetic surface of the magnetic tape MT is brought into contact with the head block (for recording and playback) 76a so that the wrap angle θ (°) is 25°. Here, the wrap angle θ is calculated from the curvature R of the head block 76a and the amount of pressure the head block 76a places on the magnetic tape MT. A weight 78a with a mass of 100 g is attached to the other end of the magnetic tape MT. A tension of 100.0 gf (approximately 0.9807 N) is applied to the magnetic tape MT in the longitudinal direction by the weight 78a.

[0217] Next, the head block 76a is slid over the magnetic surface of the magnetic tape MT while repeatedly reciprocating five times with respect to the magnetic tape MT. The tension T [gf] of the magnetic tape MT during this reciprocating motion is measured by the load cell 73. The reciprocating motion is controlled so that the sliding distance (movement distance) for each of the forward and backward motions is 55 mm, and the sliding speed (movement distance) of the magnetic tape MT relative to the head block 76a is 6 mm / s. The sliding speed (movement speed) of 6 mm / s is set in consideration of the shift speed in the width direction of the magnetic tape MT during actual running.

[0218] The pulling time (time for one forward movement) and the letting-off time (time for one return movement) are both set to 9.2 seconds. The sampling rate of the load cell 73 is set to 0.5 points / second. Therefore, the number of measurement points during one pulling (one forward movement) is 18 points. The environment during measurement of the tension T [gf] is maintained at 23°C ± 2°C and 45% RH ± 5% RH.

[0219] Next, the tension T [gf] of Sample 2 is measured in the same manner as the measurement of the tension T [gf] of the magnetic tape of Sample 1 above, except that the remaining Sample 2 of the two Samples 2 prepared when measuring the average tension T during rotation of the SUS rod is used.

[0220] Next, the average tension values ​​during the fourth and fifth outgoing passes of Samples 1 and 2 are calculated. Specifically, data for one point before and after is removed from the measurement data (tension) for each of the fourth outgoing pass (18 point) of Sample 1, the fifth outgoing pass (18 point) of Sample 1, the fourth outgoing pass (18 point) of Sample 2, and the fifth outgoing pass (18 point) of Sample 2. Then, the average tension T is calculated by simply averaging the measurement data for the fourth outgoing pass (16 point) of Sample 1, the measurement data for the fifth outgoing pass (16 point) of Sample 1, the measurement data for the fourth outgoing pass (16 point) of Sample 2, and the measurement data for the fifth outgoing pass (16 point) of Sample 2 (a total of 16 x 4 measurement data). ave. Calculate [gf].

[0221] The tension of the magnetic tape MT in a stationary state (T０ The tension T [gf] of the sample 1 is calculated as follows. After measuring the tension T [gf] of the sample 1, the device shown in FIG. 14 is rotated 90° so that the jig 77 is positioned directly below the load cell 73. The device is then held so that the longitudinal direction of the magnetic tape MT coincides with the direction of gravity and the magnetic tape MT hangs directly down without passing through the guides 75A and 75B and the head block 76a. In this state, the tension applied to the magnetic tape MT is measured by the load cell 73, and this tension is calculated as the tension T of the magnetic tape MT in the stationary state. ０１ [gf]. The tension T ０１ The measurement environment for the tension T [gf] is maintained at 23°C ± 2°C and 45% RH ± 5% RH. Next, except for using Sample 2 after measuring the tension T [gf], the tension T of the magnetic tape of Sample 1 is measured. ０１ In the same manner as in the measurement of [gf], the tension T ０２ Then, measure the tension T ０１ [gf] and tension T ０２ The tension T ０ Calculate [gf].

[0222] Average tension T ave. [gf] and tension T ０ [gf] is substituted into the following equation to determine the average dynamic friction coefficient μ: (where θ [°] represents the wrap angle of the magnetic tape MT with respect to the head block 76a, and T ０ [gf] represents the tension of the magnetic tape MT in a stationary state, and T ave. [gf] represents the average tension of the magnetic tape MT during sliding.

[0223] (Standard Deviation σPES in a Drive with Oblique Head Unit 56A) When a full-volume test is performed up to 40 times on a magnetic tape MT using a drive with an oblique head unit 56A, the standard deviation σPES of the PES values ​​obtained from the servo signals corresponding to the servo patterns is preferably 35 nm or less, more preferably 30 nm or less, and even more preferably 28 nm or less. A standard deviation σPES of 35 nm or less is desirable from the perspective of suppressing wobble of the magnetic tape MT when recording or reproducing the magnetic tape MT using a drive with an oblique head unit 56A. Here, the servo pattern of the magnetic tape MT on which the full-volume test is performed has asymmetric servo stripes 113 (see FIG. 5).

[0224] The PES (Position Error Signal) indicates the deviation (error) of the read position of the servo pattern in the width direction of the magnetic tape MT when the servo pattern is reproduced (read) by the drive. Therefore, by measuring the standard deviation σPES, it is possible to evaluate the wobble of the magnetic tape MT during actual running. The standard deviation σPES is also related to the dynamic friction force of the magnetic surface, and as the dynamic friction force of the magnetic surface increases, the standard deviation σPES tends to increase.

[0225] The PES value is measured to determine the standard deviation σPES. A PES measurement head unit 300 is used to measure the PES value. The PES measurement head unit 300 used to measure the PES value will be described with reference to FIG. 16 . An LTO2 head (a head conforming to the LTO2 standard) manufactured by HPE (Hewlett Packard Enterprise) is used as the head unit 300. The head unit 300 has two head units 300A and 300B arranged side by side along the longitudinal direction of the magnetic tape MT. Each head unit 300A and 300B includes a plurality of recording heads 340 for recording data signals on the magnetic tape MT, a plurality of reproducing heads 350 for reproducing the data signals recorded on the magnetic tape MT, and a plurality of servo heads 320 for reproducing the servo signals recorded on the magnetic tape MT. Note that if the head unit 300 is used only for measuring the PES value, the recording head 340 and the reproducing head 350 may not be included in the head unit 300. The PES value is measured with the head unit 300 maintained at an angle to the axis Ax parallel to the width direction of the magnetic tape MT.

[0226] The standard deviation σPES of the PES values ​​is calculated using a servo signal that has been corrected for lateral movement of the magnetic tape MT. The servo signal is also subjected to high pass filtering to reflect the tracking ability of the head unit 300. In the present disclosure, the standard deviation σPES is calculated using a signal obtained by performing the above correction and high pass filtering on the servo signal, and is the so-called written in PESσ.

[0227] A method for measuring the standard deviation σPES will be described with reference to Figs. 5 and 16. First, the magnetic tape MT is demagnetized, and then a servo pattern is written on the magnetic tape MT. Asymmetric servo stripes 113 (see Fig. 5) are used as the servo pattern. The angle θ of the servo stripes 113 in the A burst 111A and the C burst 112C is １ The angle θ of the servo stripe 113 in the B burst 111B and the D burst 112D is 22°.２ is 2°.

[0228] Next, while performing a full volume test, the head unit 300 reads the servo signal from the magnetic tape MT. More specifically, the magnetic tape MT is run at a speed of 2 m / s so that the servo head 320 of head unit 300A and the servo head 320 of head unit 300B sequentially face each servo pattern of a predetermined servo band. The two servo heads 320 then read the servo patterns and output them as servo signals. The servo pattern reading is performed in an environment of 25°C ± 2°C and 50% RH ± 5% RH, with the head unit 300 maintained at an angle to the axis Ax parallel to the width direction of the magnetic tape MT, as shown in FIG. 16 . When reading the servo pattern, the tension applied to the magnetic tape MT in the longitudinal direction is set to 0.50 [N] (51 [gf]). The tilt angle θ of the head unit 300 relative to the axis Ax parallel to the width direction of the magnetic tape MT is 10°.

[0229] Next, the signals acquired by the head units 300A and 300B are subtracted as shown in FIG. 17 to obtain a servo signal in which the lateral movement of the magnetic tape MT has been corrected. Then, high-pass filtering is performed on the corrected servo signal. When the magnetic tape MT is actually run in a drive, the recording / reproducing head mounted on the drive is moved by an actuator in the width direction of the magnetic tape MT to follow the servo signal. Since the Written in PESσ is a noise value that takes into account the width-direction tracking ability of the head, the high-pass filtering process is required. Therefore, although the high-pass filter is not particularly limited, it must be a function that can reproduce the width-direction tracking ability of the drive head.

[0230] Next, using the signal obtained by the high pass filter processing, a PES value is calculated for each servo frame 110 shown in Fig. 6. The standard deviation of the PES values ​​(Written in PESσ) calculated over a 1 meter length from a position 20 m longitudinally from the joint 21 between the magnetic tape MT and the leader tape LT is the standard deviation σPES of the PES values ​​in this disclosure. The standard deviation σPES is measured each time a full volume test is performed, as described above.

[0231] The PES value for each servo frame 110 is calculated using the following formula.

[0232] Here, the center line shown in Figure 5 is the center line of the servo band. X [μm] is the distance between servo pattern A1 and servo pattern B1 on the center line shown in Figure 5, and Y [μm] is the distance between servo pattern A1 and servo pattern C1 on the center line shown in Figure 5. X and Y are determined by developing the magnetic tape MT with a ferricolloid developer after 40 full-volume tests and using a universal tool microscope (TOPCON TUM-220ES) and a data processing device (TOPCON CA-1B). Fifty servo frames were selected at a location 20 m longitudinally from the connection 21 between the magnetic tape MT and the leader tape LT, and X and Y were determined for each servo frame. The simple average of the 50 data was used as X and Y to be substituted into the above calculation formula.

[0233] The difference (B ａ１ -A ａ１ ) indicates the time [sec] on the actual path between two corresponding servo patterns B1 and A1. Similarly, other difference terms also indicate the time [sec] on the actual path between two corresponding servo patterns. These times are calculated from the time between timing signals obtained from the waveform of the servo signal and the tape running speed. In this specification, the actual path means the position where the servo head 320 that reads the servo signal actually runs on the servo signal. φ is the azimuth angle θ １ , θ ２(see FIG. 16), specifically (θ １ +θ ２ ) / 2. １ , θ ２ As in the measurement of the distances X and Y, after 40 full volume tests, the magnetic tape MT is developed with a ferricolloid developer, and is measured using a universal tool microscope (TOPCON TUM-220ES) and a data processing device (TOPCON CA-1B). ａ１ -A ａ１ ) and other differential values ​​are measured in each of the 40 full-volume tests, while the distances X and Y and the azimuth angle θ １ , θ ２ is a value measured only once after 40 full volume tests.

[0234] (Standard Deviation σPES in a Drive with Parallel Head Unit 56B) When a full-volume test is performed up to 40 times on a magnetic tape MT using a drive with parallel head unit 56B, the standard deviation σPES of the PES values ​​obtained from the servo signals corresponding to the servo patterns is preferably 35 nm or less, more preferably 30 nm or less, and even more preferably 28 nm or less. A standard deviation σPES of 35 nm or less is desirable from the perspective of suppressing wobble of the magnetic tape MT when recording or reproducing the magnetic tape MT using a drive with parallel head unit 56B. Here, the servo pattern of the magnetic tape MT on which the full-volume test is performed has symmetrical servo stripes 113 (see FIG. 6).

[0235] A method for measuring the standard deviation σPES will be described with reference to Figures 6 and 18. First, the magnetic tape MT is demagnetized, and then a servo pattern is written on the magnetic tape MT. Symmetric servo stripes 113 (see Figure 6) are used as the servo pattern. The angle θ of the servo stripes 113 in the A burst 111A and the C burst 112C is １ The angle θ of the servo stripe 113 in the B burst 111B and the D burst 112D is 12°. ２ is 12°.

[0236] Next, while performing a full volume test, the head unit 300 reads the servo signals from the magnetic tape MT. More specifically, the magnetic tape MT is run at a speed of 2 m / s so that the servo head 320 of head unit 300A and the servo head 320 of head unit 300B sequentially face each servo pattern in a predetermined servo band. The two servo heads 320 then read the servo patterns and output them as servo signals. The servo pattern reading is performed in an environment of 25°C ± 2°C and 50% RH ± 5% RH, with the head unit 300 maintained parallel to the axis Ax parallel to the width direction of the magnetic tape MT, as shown in FIG. 17 . When reading the servo patterns, the tension applied to the magnetic tape MT in the longitudinal direction is set to 0.65 [N] (66 [gf]). The subsequent steps are the same as the method for calculating the standard deviation σPES in a drive using the oblique head unit 56A.

[0237] (Coercive force Hc2) The upper limit of the coercive force Hc2 of the magnetic layer 43 in the longitudinal direction of the magnetic tape MT is preferably 2000 Oe or less, more preferably 1900 Oe or less, and even more preferably 1800 Oe or less. If the coercive force Hc2 of the magnetic layer 43 in the longitudinal direction of the magnetic tape MT is 2000 Oe or less, sufficient electromagnetic conversion characteristics can be obtained even at high recording densities.

[0238] The lower limit of the coercive force Hc2 of the magnetic layer 43 measured in the longitudinal direction of the magnetic tape MT is preferably 1000 Oe or more. When the coercive force Hc2 of the magnetic layer 43 measured in the longitudinal direction of the magnetic tape MT is 1000 Oe or more, demagnetization due to leakage flux from the recording head can be suppressed.

[0239] The coercive force Hc2 is determined as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and six magnetic tape MTs are cut out at positions 30 to 40 meters longitudinally from one end of the outer periphery of the magnetic tape MT. At this time, markings are made with any non-magnetic ink so that the longitudinal direction (running direction) of the magnetic tape MT can be identified. Next, the three cut-out magnetic tape MTs are stacked with double-sided tape so that the longitudinal direction of the three cut-out magnetic tape MTs is the same, and then punched out with a φ6.39 mm punch to prepare a measurement sample. Next, the M-H loop of the measurement sample (the entire magnetic tape MT) corresponding to the longitudinal direction (running direction) of the magnetic tape MT is measured using a vibrating sample magnetometer (VSM). Next, the coatings (underlayer 42, magnetic layer 43, back layer 44, etc.) of the remaining three cut-out magnetic tape MTs are wiped off using acetone, ethanol, or the like, leaving only the substrate 41. Three of the obtained substrates 41 are then stacked together with double-sided tape, and punched out with a φ6.39 mm punch to prepare a sample for background correction (hereinafter simply referred to as a "correction sample"). Thereafter, 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.

[0240] The MH loop of the measurement sample (the entire magnetic tape MT) and the MH loop of the correction sample (substrate 41) are measured using a high-sensitivity vibrating sample magnetometer "VSM-P7-15" manufactured by Toei Kogyo Co., Ltd. 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, number of MH averages: 20.

[0241] 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), thereby obtaining the background-corrected M-H loop. This background correction calculation is performed using the measurement and analysis program included with the VSM-P7-15. The coercive force Hc2 is calculated from the obtained background-corrected M-H loop. Note that this calculation is performed using the measurement and analysis program included with the VSM-P7-15. Note that all of the above M-H loop measurements are performed at 25°C ± 2°C and 50% RH ± 5% RH. Furthermore, "demagnetization field correction" is not performed when measuring the M-H loop in the longitudinal direction of the magnetic tape MT.

[0242] (Squareness Ratio) The squareness ratio S1 of the magnetic layer 43 in the perpendicular direction of the magnetic tape MT is preferably 62% or more, more preferably 65% ​​or more, and even more preferably 68% or more, 72% or more, or 75% or more. When the squareness ratio S1 is 62% or more, the perpendicular orientation of the magnetic particles is sufficiently high, thereby achieving even better electromagnetic conversion characteristics.

[0243] The squareness ratio S1 in the perpendicular direction of the magnetic tape MT is determined as follows. First, a measurement sample is prepared in the same manner as in the above-described method for measuring the coercive force Hc2. Next, an M-H loop of the measurement sample (the entire magnetic tape MT) corresponding to the perpendicular direction of the magnetic tape MT (the perpendicular direction of the magnetic tape MT) is measured using a VSM. Next, a correction sample is prepared in the same manner as in the above-described method for measuring the coercive force Hc2. Thereafter, an M-H loop of the correction sample (substrate 41) corresponding to the perpendicular direction of the substrate 41 (the perpendicular direction of the magnetic tape MT) is measured using a VSM.

[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), thereby obtaining the M-H loop after background correction. This background correction calculation is performed using the measurement and analysis program included with the "VSM-P7-15 Model."

[0245] The saturation magnetization Ms (emu) and residual magnetization Mr (emu) of the M-H loop after background correction are substituted into the following formula to calculate the squareness ratio S1 (%). Note that all of the above M-H loop measurements are performed at 25°C ± 2°C and 50% RH ± 5% RH. Also, no "demagnetizing field correction" is performed when measuring the M-H loop in the perpendicular direction to the magnetic tape MT. Note that this calculation uses the measurement and analysis program included with the "VSM-P7-15 model." Squareness ratio S1 (%) = (Mr / Ms) × 100

[0246] The squareness ratio S2 of the magnetic layer 43 in the longitudinal direction (running 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 squareness ratio S2 is 35% or less, the perpendicular orientation of the magnetic particles is sufficiently high, thereby achieving even better electromagnetic conversion characteristics. Note that one of the squareness ratio S1 of the magnetic layer 43 in the perpendicular direction of the magnetic tape MT and the squareness ratio S2 of the magnetic layer 43 in the longitudinal direction (running direction) of the magnetic tape MT may be within the above-mentioned preferred range, while the other may be outside the above-mentioned preferred range. Alternatively, both the squareness ratio S1 of the magnetic layer 43 in the perpendicular direction of the magnetic tape MT and the squareness ratio S2 of the magnetic layer 43 in the longitudinal direction (running direction) of the magnetic tape MT may be within the above-mentioned preferred range.

[0247] The squareness ratio S2 in the longitudinal direction of the magnetic tape MT is determined in the same manner as the squareness ratio S1, except that the MH loop is measured in the longitudinal direction (running direction) of the magnetic tape MT and the substrate 41.

[0248] (Ratio Hc2 / Hc1) The ratio Hc2 / Hc1 of the coercive force Hc1 of the magnetic layer 43 in the perpendicular direction of the magnetic tape MT to the coercive force 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, and even more preferably Hc2 / Hc1≦0.7, H2 / Hc1≦0.65, or H2 / Hc1≦0.6. When the coercive forces Hc1 and Hc2 satisfy the relationship Hc2 / Hc1≦0.8, the degree of perpendicular orientation of the 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 even better electromagnetic conversion characteristics. As described above, a small Hc2 allows the magnetization to respond more sensitively to the perpendicular magnetic field from the recording head, thereby forming a good recording pattern.

[0249] When the ratio Hc2 / Hc1 is Hc2 / Hc1≦0.8, the average thickness t ２ It is particularly effective that the average thickness t of the magnetic layer 43 is 0.090 μm or less. ２ If the thickness exceeds 0.090 μm, when a ring-type head is used as the recording head, the lower region of the magnetic layer 43 (the region on the underlayer 42 side) may be magnetized in the longitudinal direction of the magnetic tape MT, which may prevent uniform magnetization of the magnetic layer 43 in the thickness direction. Therefore, even if the ratio Hc2 / Hc1 is set to Hc2 / Hc1≦0.8 (i.e., even if the degree of perpendicular orientation of the magnetic particles is increased), there is a risk that further excellent electromagnetic conversion characteristics may not be obtained.

[0250] The lower limit of Hc2 / Hc1 is not particularly limited, but for example, it is 0.5≦Hc2 / Hc1. Note that Hc2 / Hc1 represents the degree of perpendicular orientation of the magnetic grains, and the smaller Hc2 / Hc1, the higher the degree of perpendicular orientation of the magnetic grains.

[0251] The method for calculating the coercive force Hc2 of the magnetic layer 43 in the longitudinal direction of the magnetic tape MT is as described above. The coercive force Hc1 of the magnetic layer 43 in the perpendicular direction of the magnetic tape MT is determined in the same manner as the coercive force 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.

[0252] (Activation volume V ａｃｔ ) Activation volume V ａｃｔ However, preferably 8000 nm ３ Less than 6000 nm, more preferably ３ or less, more preferably 5000 nm ３ Below, 4000nm ３ or below 3000 nm ３ The activation volume V is ａｃｔ is 8000 nm ３ If the magnetic grains are dispersed at or below this value, the bit inversion region can be made steeper, and the magnetic signal recorded on the adjacent track can be prevented from being degraded by the leakage magnetic field from the recording head, thereby achieving even better electromagnetic conversion characteristics.

[0253] The activation volume V ａｃｔ is calculated by the following formula derived by Street & Woolley: ａｃｔ (nm ３ ) = k Ｂ ×T×X ｉｒｒ / (μ ０ × Ms × S) (where k Ｂ : Boltzmann constant (1.38 × 10 －２３ J / K), T: temperature (K), Χ ｉｒｒ : Irreversible magnetic susceptibility, μ ０ : magnetic permeability of vacuum, S: magnetic viscosity coefficient, Ms: saturation magnetization (emu / cm ３ ))

[0254] Irreversible magnetic susceptibility X substituted into the above formula ｉｒｒ The saturation magnetization Ms and magnetic viscosity coefficient S are determined using a VSM as follows. The measurement direction using the VSM is the perpendicular direction (thickness direction) of the magnetic tape MT. Measurement using the VSM is performed on a measurement sample cut out from a long magnetic tape MT at 25°C ± 2°C and 50% RH ± 5% RH. When measuring the M-H loop in the perpendicular direction (thickness direction) of the magnetic tape MT, no "demagnetizing field correction" is performed.

[0255] (irreversible magnetic susceptibility Χ ｉｒｒ ) Irreversible magnetic susceptibility Χｉｒｒ 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, resulting in a remanent magnetization state. Then, a magnetic field of approximately 15.9 kA / m (200 Oe) is applied in the opposite direction, and the magnetic field is returned to zero again, and the amount of remanent magnetization is measured. After that, similar measurements are repeated, applying a magnetic field 15.9 kA / m greater than the previously applied magnetic field and returning it to zero, and the amount of remanent magnetization is plotted against the applied magnetic field to measure the DCD curve. From the obtained DCD curve, the point where the amount of magnetization is zero is taken as the remanent coercivity Hr, and the DCD curve is further differentiated to determine the slope of the DCD curve at each magnetic field. In the slope of this DCD curve, the slope near the remanent coercivity Hr is X. ｉｒｒ This becomes:

[0256] (Saturation magnetization Ms) First, an MH loop after background correction is obtained in the same manner as in the measurement method for the squareness ratio S1 described above. Next, the value of the saturation magnetization Ms (emu) of the obtained MH loop and the volume (cm ３ ) to 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 ２ The average thickness t of the magnetic layer 43 required to calculate the volume of the magnetic layer 43 is ２ The calculation method is as described above.

[0257] (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 create a state of remanent magnetization. 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 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)

[0258] (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 of the surface roughness R of the back surface is preferably 7.5 nm or less, more preferably 7.2 nm or less, and even more preferably 7.0 nm or less, 6.5 nm or less, 6.3 nm or less, or 6.0 nm or less. ｂ When 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 the electromagnetic conversion characteristics can be suppressed. ｂ The lower limit of is preferably 3.0 nm or more, more preferably 3.2 nm or more, and even more preferably 3.4 nm or more.

[0259] Surface roughness R of the back surface ｂ is determined as follows. 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 100 mm at a position 30 to 40 m longitudinally from one end of the outer periphery of the magnetic tape MT. Next, the sample is placed on a slide glass with the surface to be measured (the surface on the magnetic layer 43 side) facing up, and the end of the sample is fixed with mending tape. The surface shape is measured using a VertScan (20x objective lens) as a 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 measurement conditions are as follows: Equipment: Non-contact roughness meter using optical interference (Non-contact surface / layer cross-sectional shape measurement system VertScan R5500GL-M100-AC, manufactured by Ryoka Systems Co., Ltd.) Objective lens: 20x Measurement area: 640 x 480 pixels (field of view: approximately 237 μm x 178 μm field of view) Measurement mode: phase Wavelength filter: 520 nm CCD: 1 / 3 inch Noise reduction filter: smoothing 3 x 3 Surface correction: correction using 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 positions in the longitudinal direction of the magnetic tape MT, the arithmetic mean roughness Sａ (nm) is the surface roughness R ｂ (nm).

[0260] (Young's modulus in the longitudinal direction of the magnetic tape MT) 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 adjusting the tension. Therefore, off-track can be more appropriately suppressed, and data recorded on the magnetic tape MT can be more accurately reproduced. 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, deterioration of running stability can be suppressed.

[0261] The Young's modulus in the longitudinal direction of the magnetic tape MT is a value that indicates the resistance of the magnetic tape MT to expansion and contraction in the longitudinal direction due to external forces; the larger this value, the less the magnetic tape MT is able to expand and contract in the longitudinal direction due to external forces, and the smaller this value, the more easily the magnetic tape MT is able to expand and contract in the longitudinal direction due to external forces.

[0262] 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 to expansion and contraction in the width direction of the magnetic tape MT. 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 the magnetic tape MT is susceptible to expansion and contraction 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, 9.0 GPa or less.

[0263] A tensile tester (AG-100D, manufactured by Shimadzu Corporation) is used to measure Young's modulus in the longitudinal direction of the tape. When measuring Young's modulus in the longitudinal direction of the tape, the magnetic tape MT housed in the cartridge 10 is unwound and cut into a length of 180 mm at a position 30 to 40 m longitudinally from one end of the outer periphery of the magnetic tape MT to prepare a measurement sample. A jig capable of fixing the tape width (1 / 2 inch) is attached to the tensile tester, and the top and bottom of the tape width are fixed. The distance (length of tape between chucks) is set to 100 mm. After chucking the tape sample, stress is gradually applied in the direction of pulling the sample. The pulling speed is set to 0.1 mm / min. Young's modulus is calculated from the change in stress and the amount of elongation at this time using the following formula: E (N / m ２ )=((ΔN / S) / (Δx / L))×10 ６ ΔN: Change in stress (N) S: Cross-sectional area of ​​test piece (mm ２ ) Δx: elongation (mm) L: distance between gripping jigs (mm) The cross-sectional area S of the measurement sample is the cross-sectional area before the pulling operation and is calculated by multiplying the width (½ inch) of the measurement sample by the thickness of the measurement sample. The range of tensile stress during measurement is set to a linear region of tensile stress depending on 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 for calculation. The above Young's modulus measurement is performed at 25°C ± 2°C and 50% RH ± 5% RH.

[0264] (Young's modulus in the longitudinal direction of the substrate 41) 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 forces is further increased, making it easier to adjust the width of the magnetic tape MT by adjusting the tension. Therefore, off-track can be more appropriately suppressed, and data recorded on the magnetic tape MT can be more accurately reproduced. 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, deterioration of running stability can be suppressed.

[0265] The Young's modulus in the longitudinal direction of the substrate 41 is determined as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and the magnetic tape MT is cut into a length of 180 mm at a position 30 to 40 m longitudinally from one end of the outer periphery of the magnetic tape MT. Next, the underlayer 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 Young's modulus in the longitudinal direction of the substrate 41 is determined using the same procedure as for the Young's modulus in the longitudinal direction of the magnetic tape MT.

[0266] The thickness of the substrate 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 substrate 41 correlates with the resistance of the magnetic tape MT to expansion and contraction due to external forces, and the larger this value, the less the magnetic tape MT is able to expand and contract in the width direction due to external forces, and the smaller this value, the more the magnetic tape MT is able to expand and contract in the width direction due to external forces.

[0267] The Young's modulus of the substrate 41 in the longitudinal direction is a value related to the longitudinal direction of the magnetic tape MT, but it also correlates with the resistance to expansion and contraction of the magnetic tape MT 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 the magnetic tape MT is susceptible to expansion and contraction in the width direction due to external forces. Therefore, from the perspective of tension adjustment, it is advantageous for the Young's modulus of the substrate 41 in the longitudinal direction to be small, as described above, at 7.8 GPa or less.

[0268] [5. Method for Manufacturing Magnetic Tape] Next, an example of a method for manufacturing the magnetic tape MT having the above-described configuration will be described.

[0269] (Paint preparation process) First, a paint for forming a base layer is prepared by kneading and dispersing non-magnetic particles, a binder, etc. in a solvent. Next, a paint for forming a magnetic layer is prepared by kneading and dispersing, for example, magnetic particles, carbon particles, abrasive particles, a binder, etc. in a solvent. The following solvents, dispersing devices, and kneading devices can be used to prepare the paint for forming a magnetic layer and the paint for forming a base layer.

[0270] Examples of solvents used in preparing the coating material include ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone, alcohol solvents such as methanol, ethanol, and propanol, ester solvents such as methyl acetate, ethyl acetate, butyl acetate, propyl acetate, ethyl lactate, and ethylene glycol acetate, ether solvents such as diethylene glycol dimethyl ether, 2-ethoxyethanol, tetrahydrofuran, and dioxane, aromatic hydrocarbon solvents such as benzene, toluene, and xylene, and halogenated hydrocarbon solvents such as methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, and chlorobenzene. These may be used alone or in appropriate combinations.

[0271] Examples of the kneading apparatus used in preparing the above coating material include, but are not limited to, a continuous twin-screw kneader, a continuous twin-screw kneader capable of multi-stage dilution, a kneader, a pressure kneader, a roll kneader, etc. Examples of the dispersing apparatus used in preparing the above coating material include, but are not limited to, 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 (e.g., the "DCP Mill" manufactured by Eirich), a homogenizer, an ultrasonic disperser, etc.

[0272] (Coating Process) Next, a base layer forming paint is applied to one main surface of the substrate 41 and dried to form the base layer 42. Subsequently, a magnetic layer forming paint is applied to the base layer 42 and dried to form the magnetic layer 43 on the base layer 42. During drying, the magnetic particles may be magnetically oriented in the thickness direction of the substrate 41, for example, using a permanent magnet. After the magnetic layer 43 is formed, a back layer 44 is formed on the other main surface of the substrate 41. This results in a magnetic tape MT. The order in which the base layer 42, magnetic layer 43, and back layer 44 are formed 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 in that order on one main surface of the substrate 41.

[0273] The squareness ratios S1 and S2 can be set to desired values ​​by, for example, adjusting 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 between two and three times the coercive force of the magnetic particles. To further increase the squareness ratio S1 (i.e., to further reduce the squareness ratio S2), it is preferable to improve the dispersion state of the magnetic particles in the magnetic layer-forming paint. To further increase the squareness ratio S1, it is also effective to magnetize the magnetic particles before the magnetic layer-forming paint enters an orientation device for magnetically orienting the magnetic particles. The above methods for adjusting the squareness ratios S1 and S2 may be used alone or in combination.

[0274] (Hardening Step) Next, after the magnetic tape MT is wound into a roll, the magnetic tape MT is subjected to a heat treatment in this state, thereby hardening the underlayer 42 and the magnetic layer 43 .

[0275] (Calendering Process) Next, the obtained magnetic tape MT is subjected to a calendering process to smooth the magnetic surface.

[0276] (Aging Step) Next, if necessary, the obtained magnetic tape MT is subjected to an aging treatment.

[0277] (Cutting Process and Strain Relief Process) Next, the magnetic tape MT is cut to a predetermined width (for example, 1 / 2 inch width) and wound onto a take-up hub. Next, if necessary, the wound magnetic tape MT may be subjected to a strain relief process by being held in an environment at a predetermined temperature for a predetermined time. In this manner, the magnetic tape MT is obtained.

[0278] (Servo Write Process) Next, if necessary, the magnetic tape MT may be demagnetized and then a servo pattern may be written onto the magnetic tape MT.

[0279] (Method for adjusting the average tension T during rotation of the SUS rod and the average dynamic friction coefficient μ during low-speed travel) The average tension T during rotation of the SUS rod and the average dynamic friction coefficient μ during low-speed travel can be set to desired values ​​by adjusting, for example, the application thickness of the magnetic layer-forming paint, the conditions for the calendaring treatment, the conditions for the aging treatment, the amount of abrasive particles contained in the magnetic layer-forming paint, the particle size of the abrasive particles contained in the magnetic layer-forming paint, the amount of carbon particles contained in the magnetic layer-forming paint, and the particle size of the carbon particles contained in the magnetic layer-forming paint.

[0280] [6. Effects] As described above, in the magnetic tape MT according to one embodiment, the average tension T during rotation of the SUS rod is 55.0 gf or less, and the average dynamic friction coefficient μ during low-speed running is 0.35 or less. This makes it possible to suppress wobble of the magnetic tape MT during actual running in both drives with parallel head units and drives with oblique head units.

[0281] In recent years, expectations for ever higher capacity have been rising for magnetic tapes, and improvements in track density are desired. To improve track density, it is desirable to suppress wobble of the magnetic tape during actual running, allowing the head to accurately trace the data track. Generally, when the track width is 1000 nm or less, the occurrence of wobble of the magnetic tape is particularly likely to become a problem. In contrast, as described above, the magnetic tape MT according to one embodiment can suppress wobble of the magnetic tape MT during actual running. Therefore, the track density of the magnetic tape MT (e.g., when the track width is 1000 nm or less) can be improved, and the capacity of the magnetic tape MT can be increased.

[0282] [7 Modifications] In the above embodiment, the magnetic tape cartridge 10 is a one-reel type cartridge, but it may also be a two-reel type cartridge.

[0283] 19 is an exploded perspective view showing an example of the configuration of a two-reel type cartridge 221. The cartridge 221 comprises an upper half 202 made of synthetic resin, a transparent window member 223 fitted into and fixed to a window 202a opened in the top surface of the upper half 202, a reel holder 222 fixed to the inside of the upper half 202 to prevent the reels 206 and 207 from floating up, a lower half 205 corresponding to the upper half 202, the reels 206 and 207 stored in the space formed when the upper half 202 and lower half 205 are combined, magnetic tape MT wound on the reels 206 and 207, a front lid 209 closing the front opening formed when the upper half 202 and lower half 205 are combined, and a back lid 209A protecting the magnetic tape MT exposed in this front opening.

[0284] The reels 206 and 207 are used to wind the magnetic tape MT. The reel 206 includes a lower flange 206b having a cylindrical hub portion 206a in the center around which the magnetic tape MT is wound, an upper flange 206c having approximately the same size as the lower flange 206b, and a reel plate 211 sandwiched between the hub portion 206a and the upper flange 206c. The reel 207 has the same configuration as the reel 206.

[0285] The window member 223 has mounting holes 223a for assembling reel holders 222, which are reel holding means for preventing the reels from floating up, at positions corresponding to the reels 206 and 207. The magnetic tape MT is the same as the magnetic tape MT in the embodiment.

[0286] The present disclosure will be specifically described below using examples, but the present disclosure is not limited to these examples.

[0287] In the following examples and comparative examples, the average thickness t of the magnetic tape Ｔ , the average thickness t of the PEN film (substrate) １ , the average thickness of the magnetic layer t ２ , the average thickness of the underlayer t ３ , the average thickness of the back layer t ４ The average particle volume V of the magnetic particles and the composition of the magnetic powder are values ​​determined by the measurement method described in the above embodiment.

[0288] Example 1 (Preparation Process of Magnetic Layer-Forming Coating) A magnetic layer-forming coating was prepared as follows. First, a first composition having the following formulation was kneaded using an extruder. Next, a second composition having the following formulation was placed in a polyethylene bottle (a resin container made of polyethylene), attached to a paint shaker (a rocking shaker manufactured by Seiwa Giken), and mixed for 10 hours. Similarly, a third composition having the following formulation was placed in a polyethylene bottle, attached to a paint shaker (a rocking shaker manufactured by Seiwa Giken), and mixed for 10 hours. Next, the kneaded first composition and the mixed second and third compositions were added to a stirring tank equipped with a disperser, and then 350.0 parts by mass of methyl ethyl ketone, 90.0 parts by mass of toluene, and 150.0 parts by mass of cyclohexanone were added, followed by premixing. Subsequently, further mixing was performed using a Dyno Mill and filtering was performed to prepare a magnetic layer-forming coating.

[0289] (First composition) Barium ferrite (Ba ０．５３ Sr ０．４７ Fe １２ O １９ ) Magnetic powder (hexagonal plate shape, average particle volume 1.05 × 10 ３ nm ３Vinyl chloride resin solution (resin solution composition: vinyl chloride resin 30.0% by mass, cyclohexanone solution 70.0% by mass): 25.0 parts by mass (vinyl chloride resin: degree of polymerization 300, number average molecular weight Mn = 10,000, polar group OSO ３ K=0.07 mmol / g, secondary OH=0.3 mmol / g.) Polyurethane resin solution (resin solution: polyurethane resin content 30.0 mass%, cyclohexanone content 70.0 mass%): 25.0 mass parts (polyurethane resin: number average molecular weight Mn=25,000, glass transition temperature Tg=110°C)

[0290] (Preparation process of coating material for forming magnetic layer) (Second composition) Aluminum oxide powder (α-Al ２ O ３ Particles, arithmetic mean particle diameter 130 nm): 5.0 parts by mass Vinyl chloride resin solution (resin solution composition: vinyl chloride resin 30.0% by mass, cyclohexanone solution 70.0% by mass): 5.0 parts by mass (vinyl chloride resin: degree of polymerization 300, number average molecular weight Mn = 10,000, polar group OSO ３ K = 0.07 mmol / g, secondary OH = 0.3 mmol / g.) Cyclohexanone: 15.0 parts by mass

[0291] (Third composition) Carbon black (manufactured by Tokai Carbon Co., Ltd., product name: Seast S, arithmetic average particle size 70 nm): 1.5 parts by mass Polyurethane resin solution (resin solution: polyurethane resin content 30.0 mass%, cyclohexanone content 70.0 mass%): 3.0 parts by mass (polyurethane resin: number average molecular weight Mn = 25,000, glass transition temperature Tg = 110°C) Cyclohexanone: 14 parts by mass

[0292] Finally, 1.8 parts by mass of polyisocyanate (product name: Coronate L, manufactured by Tosoh Corporation) and 2.0 parts by mass of stearic acid were added as curing agents to the magnetic layer-forming coating material prepared as described above.

[0293] (Preparation process of paint for forming base layer) The paint for forming base layer was prepared as follows. First, the fourth composition having the following formulation was kneaded using an extruder. Next, the kneaded fourth composition and the fifth composition having the following formulation were added to a stirring tank equipped with a disperser and premixed. Subsequently, further mixing was performed using a Dynomill and filtering was performed to prepare the paint for forming base layer.

[0294] (Fourth composition) Acicular iron oxide powder (α-Fe ２ O ３ , average major axis length 0.15 μm): 100.0 parts by mass Vinyl chloride resin solution (resin solution composition: vinyl chloride resin 30.0 mass%, cyclohexanone solution 70.0 mass%): 55.0 parts by mass (vinyl chloride resin: degree of polymerization 300, number average molecular weight Mn = 10,000, polar group OSO ３ K = 0.07 mmol / g, secondary OH = 0.3 mmol / g.) Aluminum oxide powder: 3.0 parts by mass (α-Al ２ O ３ Particles, arithmetic mean particle diameter 0.1 μm)

[0295] (Fifth composition) Carbon black (manufactured by Asahi Carbon Co., Ltd., product name: #80): 30.0 parts by mass Polyurethane resin solution (resin solution: polyurethane resin content 30.0% by mass, cyclohexanone content 70.0% by mass): 45.0 parts by mass (polyurethane resin: number average molecular weight Mn = 25,000, glass transition temperature Tg = 70°C) n-butyl stearate: 2.0 parts by mass Methyl ethyl ketone: 220.0 parts by mass Toluene: 50.0 parts by mass Cyclohexanone: 50.0 parts by mass

[0296] Finally, 1.5 parts by mass of polyisocyanate (product name: Coronate L, manufactured by Tosoh Corporation) and 1.5 parts by mass of stearic acid were added as a curing agent to the paint for forming the base layer prepared as described above.

[0297] (Step of preparing paint for forming back layer) The paint for forming back layer was prepared as follows. The following raw materials were mixed in a stirring tank equipped with a disperser and filtered to prepare the paint for forming back layer. Carbon black (manufactured by Asahi Carbon Co., Ltd., trade name: #80): 100.0 parts by mass Polyester polyurethane (manufactured by Nippon Polyurethane Co., Ltd., trade name: N-2304): 100.0 parts by mass Methyl ethyl ketone: 250.0 parts by mass Toluene: 150.0 parts by mass Cyclohexanone: 250.0 parts by mass Polyisocyanate (trade name: Coronate L, manufactured by Tosoh Corporation): 10.0 parts by mass

[0298] (Coating Process) Using the magnetic layer-forming paint and primer layer-forming paint prepared as described above, a primer 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 primer layer-forming paint was applied to one main surface of the PEN film and dried to form a primer layer such that the average thickness of the primer layer upon completion of the magnetic tape (average thickness of the primer layer after the cutting process) would be 0.85 μm. Next, the magnetic layer-forming paint was applied to the primer layer and dried to form a magnetic layer such that the average thickness of the magnetic layer upon completion of the magnetic tape (average thickness of the magnetic layer after the cutting process) would be 0.07 μm. During drying of the magnetic layer-forming paint, the barium ferrite magnetic powder was magnetically oriented in the thickness direction of the PEN film by a permanent magnet. This adjusted the squareness ratio S2 in the longitudinal direction of the magnetic tape.

[0299] After the underlayer and magnetic layer were formed, a coating material for forming a back layer was applied to the other main surface of the PEN film and dried to form a back layer so that the average thickness of the completed magnetic tape (average thickness after cutting) would be 0.30 μm. This gave a magnetic tape.

[0300] (Curing Step) After the magnetic tape was wound into a roll, the magnetic tape was subjected to a heat treatment at 60° C. for 50 hours in this state to cure the underlayer, magnetic layer and back layer.

[0301] (Calendering process) The cured magnetic tape was subjected to a calendering process to smooth the surface of the magnetic layer. The calendering process was carried out at a temperature close to (slightly higher than) the glass transition temperature Tg (=110°C) of the polyurethane resin (binder) contained in the magnetic layer.

[0302] (Aging Step) After the calendering, the magnetic tape was subjected to an aging treatment in an environment of 60° C. for 20 hours.

[0303] (Cutting Step) The magnetic tape obtained as described above was cut into a width of 1 / 2 inch (12.65 mm), thereby obtaining a magnetic tape with an average thickness of 5.22 μm.

[0304] [Example 2] In the preparation process of the coating material for forming the magnetic layer, the magnetic powder was changed to barium ferrite (BaFe １２ O １９ ) Magnetic powder (hexagonal plate shape, average particle volume 1600 nm ３ ) and the aluminum oxide powder was changed to α-Al having an arithmetic mean particle size of 50 nm. ２ O ３ In the calendering step, the calendering temperature was set to be 10° C. higher than that in Example 1, and the aging treatment time was set to 40 hours. A magnetic tape was obtained in the same manner as in Example 1, except for the above points.

[0305] [Example 3] In the preparation process of the coating material for forming the magnetic layer, the magnetic powder was changed to barium ferrite (Ba ０．５５ Sr ０．４５ Fe １２ O １９ ) Magnetic powder (hexagonal plate shape, average particle volume 1200 nm ３ ) In the coating process, the primer layer-forming paint was applied so that the average thickness of the primer layer on the completed magnetic tape would be 0.80 μm, the magnetic layer-forming paint was applied so that the average thickness of the magnetic layer on the completed magnetic tape would be 0.06 μm, and the back layer-forming paint was applied so that the average thickness of the back layer on the completed magnetic tape would be 0.35 μm. In the calendering process, the calendering temperature was 10° C. higher than that of Example 1. A magnetic tape was obtained in the same manner as in Example 1, except for the points mentioned above.

[0306] [Comparative Example 1] In the preparation step of the paint for forming the undercoat layer, the amount of n-butyl stearate added was changed to 2.5 parts by mass. In the calendering step, the calendering temperature was set 15°C higher than the calendering temperature in Example 1. A magnetic tape was obtained in the same manner as in Example 1, except for the above points.

[0307] [Comparative Example 2] In the preparation process of the coating material for forming the magnetic layer, the magnetic powder was changed to barium ferrite (Ba ０．５５ Sr ０．４５ Fe １２ O １９ ) Magnetic powder (hexagonal plate shape, average particle volume 1100 nm ３ ) and aluminum oxide powder was changed to α-Al ２ O ３ In the step of preparing the base layer-forming paint, the amount of stearic acid was changed to 1.0 part by mass. In the calendering step, the calendering temperature was set 15°C higher than that in Example 1. A magnetic tape was obtained in the same manner as in Example 1, except for the above points.

[0308] [Comparative Example 3] In the preparation process of the coating material for forming the magnetic layer, the magnetic powder was changed to barium ferrite (Ba ０．５５ Sr ０．４５ Fe １２ O １９ ) Magnetic powder (hexagonal plate shape, average particle volume 1100 nm ３ ) and aluminum oxide powder was changed to α-Al ２ O ３ In the calendering step, the calendering temperature was set to be 10° C. higher than that in Example 1.

[0309] [Evaluation] The magnetic tapes obtained as described above were evaluated as follows.

[0310] (Average Tension T During Rotation of SUS Rod) The average tension T during rotation of the SUS rod was measured as described in the above embodiment.

[0311] (Average Dynamic Friction Coefficient μ During Low-Speed ​​Travel) The average dynamic friction coefficient μ during low-speed travel was measured as described in the above embodiment.

[0312] (Standard deviation σPES in a drive with a tilted head unit) The standard deviation σPES in a drive with a tilted head unit was measured as described in the above embodiment. Note that the tension applied to the magnetic tape MT in the longitudinal direction when reading the servo patterns was set to 0.50 [N] (51 [gf]).

[0313] (Standard Deviation σPES in a Drive with a Parallel Head Unit) The standard deviation σPES in a drive with a parallel head unit was measured as described in the above embodiment. Note that the tension applied to the magnetic tape MT in the longitudinal direction when reading the servo patterns was set to 0.65 [N] (66 [gf]).

[0314]

[0315] The above evaluation results reveal the following. In Examples 1, 2, and 3, the average tension T during rotation of the SUS rod was 55.0 gf or less, and the average dynamic friction coefficient μ during low-speed running was 0.35 or less. This made it possible to keep the standard deviation σPES at 35 nm or less in both drives with oblique head units and drives with horizontal head units. Therefore, magnetic tape wobble during actual running can be suppressed in both drives with oblique head units and drives with parallel head units. The reason why a standard deviation σPES of 35 nm or less is used as the standard here is because next-generation magnetic tape standards require a standard deviation σPES of 35 nm or less when narrowing the track width to improve recording density.

[0316] In Comparative Example 1, the average tension T during rotation of the SUS rod is 55.0 gf or less, but the average dynamic friction coefficient μ during low-speed running exceeds 0.35. Therefore, in a drive with a parallel head unit, the standard deviation σPES can be made 35 nm or less, but in a drive with a diagonal head unit, the standard deviation σPES cannot be made 35 nm or less. Therefore, in a drive with a parallel head unit, it is possible to suppress wobble of the magnetic tape during actual running, but in a drive with a diagonal head unit, it is not possible to suppress wobble of the magnetic tape during actual running.

[0317] In Comparative Example 2, the average tension T during rotation of the SUS rod exceeds 55.0 gf, and the average dynamic friction coefficient μ during low-speed running exceeds 0.35. Therefore, in a drive with a diagonal head unit, the standard deviation σPES cannot be reduced to 35 nm or less, and in a drive with a parallel head unit, the standard deviation σPES cannot be reduced to 35 nm or less. Therefore, in both a drive with a diagonal head unit and a drive with a parallel head unit, it is not possible to suppress wobble of the magnetic tape during actual running.

[0318] In Comparative Example 3, the average tension T during rotation of the SUS rod exceeds 55.0 gf, but the average dynamic friction coefficient μ during low-speed running is 0.35 or less. Therefore, in a drive with a diagonal head unit, the standard deviation σPES can be made 35 nm or less, but in a drive with a parallel head unit, the standard deviation σPES cannot be made 35 nm or less. Therefore, in a drive with a diagonal head unit, it is possible to suppress wobble of the magnetic tape during actual running, but it is not possible to suppress wobble of the magnetic tape during actual running in a drive with a parallel head unit.

[0319] In Comparative Example 3, the results showed that the wobble of the magnetic tape during actual running could be suppressed in a drive with a diagonal head unit. However, if the average tension T during SUS rod rotation becomes even higher than 55.0 gf, it is thought that the wobble of the magnetic tape during actual running cannot be suppressed even in a drive with a diagonal head unit. In both a drive with a diagonal head unit and a drive with a parallel head unit, it is thought that the average tension T during SUS rod rotation needs to be 55.0 gf or less in order to suppress the wobble of the magnetic tape during actual running.

[0320] In Example 1, carbon black and α-Al ２ O ３ The hardness of the magnetic layer is increased by the aging treatment without excessively crushing the protrusions formed by the particles, which makes it possible to keep the average tension T during rotation of the SUS rod at 55.0 gf or less and the average dynamic friction coefficient μ during low-speed running at 0.35 or less.

[0321] In Example 2, α-Al ２ O ３ The particles used had a smaller arithmetic mean particle size than those in Example 1, and the α-Al contained in the magnetic layer ２ O ３ The number of particles is increased. As a result, even if the calendering temperature is increased by 10°C higher than in Example 1, the protrusions are not excessively crushed. In addition, the aging treatment time is made longer than in Example 1, thereby increasing the hardness of the magnetic layer. Therefore, the average tension T during rotation of the SUS rod can be made 55.0 gf or less, and the average dynamic friction coefficient μ during low-speed running can be made 0.35 or less.

[0322] In Example 3, the average thickness of the magnetic layer was reduced, and the carbon black and α-Al ２ O ３This makes it easier for the particles to protrude from the magnetic surface. As a result, even if the temperature of the calendering treatment is higher than in Example 1, the average tension T during rotation of the SUS rod can be kept to 55.0 gf or less. Furthermore, because the hardness of the magnetic layer is increased by the aging treatment, in addition to being able to keep the average tension T during rotation of the SUS rod low as described above, it is also possible to reduce the average dynamic friction coefficient μ during low-speed running to 0.35 or less.

[0323] In Comparative Example 1, the temperature of the calendering treatment was high, so the carbon black and α-Al ２ O ３ The protrusions formed by the particles are excessively crushed. As a result, the average dynamic friction coefficient μ during low-speed running exceeds 0.35. On the other hand, since the content of n-butyl stearate in the base layer of Comparative Example 1 is higher than the content of n-butyl stearate in the base layer of Example 1, the average tension T during rotation of the SUS rod does not increase significantly and remains below 55.0 gf.

[0324] In Comparative Example 2, α-Al ２ O ３ The particles used had a smaller arithmetic mean particle size than those in Example 1, and the calendering temperature was higher than in Example 1. As a result, the average tension T during rotation of the SUS rod exceeded 55.0 gf. Furthermore, the amount of stearic acid blended in the paint for forming the base layer was less than in Example 1, so the average dynamic friction coefficient μ during low-speed running exceeded 0.35.

[0325] In Comparative Example 3, α-Al ２ O ３ The particles used in Comparative Example 3 have a smaller arithmetic mean particle size than those in Example 1, and the temperature of the calendering treatment is higher than that in Example 1. Therefore, in Comparative Example 3, the average tension T during rotation of the SUS rod exceeds 55.0 gf.

[0326] Although the embodiments and modifications of the present disclosure have been specifically described above, the present disclosure is not limited to the above embodiments and modifications, and various modifications based on the technical concepts of the present disclosure are possible. For example, the configurations, methods, steps, shapes, materials, and numerical values ​​described in the above embodiments and modifications are merely examples, and different configurations, methods, steps, shapes, materials, and numerical values ​​may be used as necessary. The configurations, methods, steps, 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 and modifications are representative, and are not limited to the valences described, etc., as long as they are the general names of the same compounds. In the numerical ranges described in stages in the above embodiments and modifications, the upper or lower limit of a numerical range in one stage may be replaced with the upper or lower limit of a numerical range in another stage. Unless otherwise specified, the materials exemplified in the above embodiments and modifications can be used alone or in combination of two or more.

[0328] The present disclosure can also employ the following configurations: (1) A tape-shaped magnetic recording medium comprising: a substrate; and a magnetic layer containing magnetic particles, wherein the magnetic recording medium has an average thickness of 5.30 μm or less, wherein the average tension T acting in the longitudinal direction of the magnetic recording medium is measured by hanging a 30 g weight from one end of the magnetic recording medium, pressing a 3 mm diameter stainless steel round rod against the surface of the magnetic layer side, and moving the magnetic recording medium in the longitudinal direction at a speed of 2 mm / s while rotating the round rod at 125 rpm, and wherein the average dynamic friction coefficient μ of the surface of the magnetic layer side is measured by moving the magnetic recording medium in the longitudinal direction at a speed of 6 mm / s, and wherein the average dynamic friction coefficient μ of the surface of the magnetic layer side is 0.35 or less. (2) The magnetic recording medium according to (1), wherein the magnetic layer further contains aluminum oxide particles and carbon particles, and wherein the surface of the magnetic layer side has irregularities, the irregularities being formed by the aluminum oxide particles and the carbon particles. (3) The magnetic recording medium according to (1) or (2), wherein the average tension T is 50.0 gf or less. (4) The magnetic recording medium according to any one of (1) to (3), wherein the average dynamic friction coefficient μ is 0.32 or less. (5) The average particle volume of the magnetic particles is 1.50×10 ３ nm ３The magnetic recording medium according to any one of (1) to (4), wherein the magnetic particles comprise hexagonal ferrite particles containing barium (Ba) and strontium (Sr). (7) The magnetic recording medium according to (6), wherein the average atomic ratio (Sr / Ba) of the strontium (Sr) to the barium (Ba) is 0.1 or more and 1 or less. (8) The magnetic recording medium according to any one of (1) to (5), wherein the magnetic particles comprise epsilon-type iron oxide particles. (9) The magnetic recording medium according to any one of (1) to (8), wherein the average thickness of the substrate is 3.80 μm or more. (10) The magnetic recording medium according to any one of (1) to (9), wherein the magnetic layer has a servo pattern, the servo pattern including 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. (11) The magnetic recording medium according to (10), wherein an inclination angle of the first magnetization region with respect to the axis is different from an 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. (12) The magnetic recording medium according to any one of (1) to (9), wherein the magnetic layer has a servo pattern, the servo pattern including 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 symmetric with respect to an axis parallel to the width direction of the magnetic recording medium. (13) A cartridge comprising the magnetic recording medium according to any one of (1) to (12).

[0329] 10 Cartridge 11 Cartridge memory 31 Antenna coil 32 Rectification and power supply circuit 33 Clock circuit 34 Detection and modulation circuit 35 Controller 36 Memory 36A First memory area 36B Second memory area 41 Substrate 42 Underlayer 43 Magnetic layer 430 Protrusion 431 Carbon particles 432 Abrasive particles 44 Back layer 56A, 56B Head unit 561 Servo read head 61, 62 Head 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

1. A tape-shaped magnetic recording medium comprising a substrate and a magnetic layer containing magnetic particles, wherein the average thickness of the magnetic recording medium is 5.30 μm or less, the average tension T acting in the longitudinal direction of the magnetic recording medium is measured by hanging a 30 g weight from one end of the magnetic recording medium, pressing a 3 mm diameter stainless steel round rod against the surface of the magnetic layer side, and moving the magnetic recording medium in the longitudinal direction at a speed of 2 mm / s while rotating the round rod at 125 rpm, and the average dynamic friction coefficient μ of the surface of the magnetic layer side is measured by moving the magnetic recording medium in the longitudinal direction at a speed of 6 mm / s, and the magnetic recording medium has an average thickness of 5.30 μm or less, the average tension T acting in the longitudinal direction of the magnetic recording medium is measured by hanging a 30 g weight from one end of the magnetic recording medium, pressing a 3 mm diameter stainless steel round rod against the surface of the magnetic layer side, and moving the magnetic recording medium in the longitudinal direction at a speed of 2 mm / s, and the average dynamic friction coefficient μ of the surface of the magnetic layer side is measured by moving the magnetic recording medium in the longitudinal direction at a speed of 6 mm / s, and the average dynamic friction coefficient μ of the surface of the magnetic layer side is measured by moving the magnetic recording medium in the longitudinal direction at a speed of 0.35 or less.

2. The magnetic recording medium according to claim 1, wherein the magnetic layer further contains aluminum oxide particles and carbon particles, and the surface facing the magnetic layer has irregularities, the irregularities being formed by the aluminum oxide particles and the carbon particles.

3. The magnetic recording medium according to claim 1, wherein the average tension T is 50.0 gf or less.

4. The magnetic recording medium according to claim 1, wherein the average dynamic friction coefficient μ is 0.32 or less.

5. The average particle volume of the magnetic particles is 1.50 x 10 ３ nm ３ The magnetic recording medium according to claim 1 , wherein:

6. The magnetic recording medium according to claim 1, wherein the magnetic particles include hexagonal ferrite particles containing barium (Ba) and strontium (Sr).

7. The magnetic recording medium according to claim 6, wherein the average atomic ratio (Sr / Ba) of said strontium (Sr) to said barium (Ba) is 0.1 or more and 1 or less.

8. The magnetic recording medium according to claim 1, wherein the magnetic particles include epsilon iron oxide particles.

9. The magnetic recording medium according to claim 1, wherein the average thickness of the substrate is 3.80 μm or more.

10. The magnetic recording medium according to claim 1, wherein the magnetic layer has a servo pattern, the servo pattern including 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.

11. The magnetic recording medium according to claim 10, wherein the tilt angle of the first magnetization region relative to the axis is different from the tilt angle of the second magnetization region relative to the axis, and the larger of the tilt angles of the first magnetization region and the second magnetization region is between 18° and 28°.

12. The magnetic recording medium according to claim 1, wherein the magnetic layer has a servo pattern, the servo pattern including 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 symmetrical with respect to an axis parallel to the width direction of the magnetic recording medium.

13. A cartridge comprising the magnetic recording medium according to claim 1.

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