Magnetic recording medium and cartridge

Abstract

Provided is a magnetic recording medium capable of suppressing narrowing of an effective recording width.　The magnetic recording medium is a tape-like magnetic recording medium, and comprises a substrate and a laminated film in the stated order. The laminated film includes, on the substrate in the following order, a soft magnetic layer containing a soft magnetic powder and a binder, and a hard magnetic layer containing a hard magnetic powder and a binder. The average thickness of the soft magnetic layer is 250 nm or greater, and the squareness proportion of the laminated film in the longitudinal direction of the magnetic recording medium is 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] Tape-type magnetic recording media, which have a magnetic layer containing magnetic powder and a binder, are widely known as magnetic recording media. As with other magnetic recording media, magnetic recording systems for tape-type magnetic recording media are becoming increasingly high-density. Therefore, various technologies for achieving high recording densities in tape-type magnetic recording media are being investigated.

[0003] Patent Document 1 discloses a magnetic recording medium suitable for the demand for higher recording density, which has, on a non-magnetic support, a soft magnetic layer containing soft magnetic powder and a binder, and a ferromagnetic layer containing ferromagnetic powder and a binder, in that order. Patent Document 1 also discloses that the ferromagnetic powder is oriented in the vertical direction, and the soft magnetic powder is oriented in the longitudinal direction.

[0004] JP 2009-223970 A

[0005] As described above, as the recording density of magnetic recording systems continues to increase, the recording track width is becoming increasingly narrower with each generation. As the recording track width narrows, the influence of the spread of magnetic flux from the recording head on the effective recording width becomes more pronounced, and the effective recording width becomes narrower relative to the width of the recording head. For this reason, it is desirable to suppress the narrowing of the effective recording width even when the recording track width narrows. However, Patent Document 1 does not disclose any technology for suppressing the narrowing of the effective recording width.

[0006] An object of the present disclosure is to provide a magnetic recording medium that can prevent the effective recording width from narrowing, and a cartridge that includes the same.

[0007] In order to solve the above-mentioned problems, the magnetic recording medium according to the present disclosure is a tape-shaped magnetic recording medium, and is provided with a substrate and a laminated film in that order, the laminated film including a soft magnetic layer containing soft magnetic powder and a binder, and a hard magnetic layer containing hard magnetic powder and a binder, in that order, on the substrate, the soft magnetic layer having an average thickness of 250 nm or more, and the squareness ratio of the laminated film in the longitudinal direction of the magnetic recording medium being 35% or less.

[0008] A cartridge according to the present disclosure includes the magnetic recording medium according to the present disclosure.

[0009] 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. 3 is a cross-sectional view showing an example of the configuration of a tape-shaped magnetic recording medium. FIG. 4 is a schematic diagram showing an example of the layout of a data band and a servo band. FIG. 5A is an enlarged view showing an example of the configuration of a data band. FIG. 5B is an enlarged view showing an example of a data track in a shingled magnetic recording system. FIG. 6 is an enlarged view showing an example of the configuration of a servo band. FIG. 7 is a perspective view showing an example of the shape of a hard magnetic particle. FIG. 8 is a diagram showing a first example of a cross-sectional TEM image of a magnetic layer. FIG. 9 is a diagram showing a second example of a cross-sectional TEM image of a magnetic layer. FIG. 10 is an exploded perspective view showing an example of the configuration of a cartridge according to a modified embodiment of the present disclosure. FIG. 11 is a diagram showing an example of an MFM image of a magnetic tape. FIG. 12 is a graph showing the amount of magnetization along line A-A in FIG. 11.

[0010] 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 characteristics of magnetic tape 6. Method for manufacturing magnetic tape 7. Functions and effects 8. Modifications

[0011] In this specification, unless a measurement environment is specifically stated in connection with the explanation of the measurement method and evaluation method, the measurement and evaluation are performed in an environment of 25°C ± 2°C and 50% RH ± 5% RH.

[0012] <1 Background to the Creation of the Embodiments of the Present Disclosure> As the recording density of magnetic recording systems continues to increase, the width of the recording head has become increasingly narrower with each successive generation of tape-shaped magnetic recording media (hereinafter referred to as "magnetic tape"). In the latest LTO standard, the recording track width is close to 1 μm, and it is expected that with each successive generation, the recording track width will narrow by about half, with the next generation potentially seeing the recording track width advance to 500 nm and then 250 nm.

[0013] On the other hand, magnetic tape magnetic recording systems employ ring-type heads as recording heads. As the width of a ring-type head becomes narrower, the spread of magnetic flux from the ring-type head may narrow the effective recording width. For this reason, it is desirable to make the magnetic flux emitted from the recording head as sharp as possible to increase the effective recording width for the recording head. In this disclosure, the effective recording width refers to the width of the portion where the magnetic force remains approximately constant when the magnetic force is measured along the longitudinal direction of a long, narrow rectangular recording pattern (see FIGS. 11 and 12 ).

[0014] In magnetic recording systems for hard disks, perpendicular magnetic recording has been adopted when the recording track width falls below 200 nm, and recording heads have transitioned from ring-type heads to single-pole heads. In magnetic tape recording systems, the recording head and magnetic tape run in contact with each other, making it more difficult to control the distance between the recording head and the magnetic surface than in non-contact hard disks. This makes magnetic tape more susceptible to the effects of the magnetic flux spread from the recording head. Therefore, it is considered preferable to use a single-pole head to widen the effective recording width for magnetic tape when the recording track width is around 300 nm. When using a single-pole head, a soft magnetic layer is provided below the hard magnetic layer to draw the magnetic flux from the recording head into the hard magnetic layer.

[0015] However, according to the inventor's findings, it is difficult to prevent the narrowing of the effective recording width of a magnetic tape by simply providing a soft magnetic layer under a hard magnetic layer. Therefore, the inventor conducted extensive research to prevent the narrowing of the effective recording width in a magnetic tape having a laminated film including a soft magnetic layer and a hard magnetic layer. As a result, the inventor discovered a magnetic tape in which the average thickness of the soft magnetic layer is 250 nm or more and the squareness ratio of the laminated film in the longitudinal direction of the magnetic tape is 35% or less.

[0016] [2 Cartridge Configuration] Figure 1 is an exploded perspective view showing an example of the configuration of a cartridge 10 according to one embodiment. 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 sliding 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 sliding 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.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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 of a magnetic tape standard of a predetermined generation or earlier (e.g., an LTO standard of a predetermined generation or earlier) and is an area for storing information conforming to the magnetic tape standard of the predetermined generation or earlier. The information conforming to the magnetic tape standard of the predetermined generation or earlier may be, for example, manufacturing information (e.g., a unique number of the cartridge 10, etc.), usage history (e.g., the number of times the tape has been pulled out (Thread Count)), etc.

[0022] The second memory area 36B corresponds to an extended memory area for the memory area of ​​the cartridge memory for a magnetic tape standard (e.g., an LTO standard) of a predetermined generation or earlier. 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 a magnetic tape standard (e.g., an LTO standard) of a predetermined generation or earlier. 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 during 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.

[0023] The management ledger data includes at least one type of data selected from the group consisting of the capacity, creation date, editing date, and storage location of the data files recorded on the magnetic tape MT. The index information includes 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.

[0024] 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.

[0025] 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, data exchange, etc. are performed.

[0026] 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.

[0027] [4 Structure of Magnetic Tape] Figure 3 is a cross-sectional view showing an example of the structure of a magnetic tape MT. The magnetic tape MT comprises a long substrate 41, a laminated film 42 provided on one main surface (first main surface) of the substrate 41, and a back layer 43 provided on the other main surface (second main surface) of the substrate 41. The back layer 43 is provided as needed and may be omitted. The laminated film 42 includes a soft magnetic layer 42A and a hard magnetic layer 42B, in that order, on one main surface (first main surface) of the substrate 41.

[0028] The magnetic tape MT is a magnetic recording medium of a perpendicular recording system. The magnetic tape MT is long and runs longitudinally during recording and playback. From the viewpoint of improving running performance, the magnetic tape MT preferably contains a lubricant in the laminate film 42. 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 ½ inch or wider. If the magnetic tape MT conforms to the LTO standard, the width of the magnetic tape MT is ½ 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 longitudinally to the magnetic tape MT during running using a recording and playback device (drive).

[0029] The magnetic tape MT is preferably configured so that it can be recorded and reproduced by a recording and reproducing device equipped with a single-pole head as a recording head. From the viewpoint of improving track recording density and ensuring high recording capacity, the magnetic tape MT is configured so that data can be recorded by a single-pole head (recording head) having a width of preferably 300 nm or less, more preferably 250 nm or less, even more preferably 200 nm or less, and particularly preferably 150 nm or less.

[0030] The magnetic tape MT is preferably configured so as to be reproducible by a reproducing head using a TMR element. The signal reproduced by the reproducing head using the TMR 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).

[0031] (Substrate 41) The substrate 41 is a non-magnetic support that supports the laminated film 42. The substrate 41 has the shape of a long film. From the viewpoint of improving the recording capacity of one data cartridge, the upper limit of the average thickness of the substrate 41 is preferably 4.40 μm or less, more preferably 4.20 μm or less, even more preferably 4.00 μm or less, 3.80 μm or less, or 3.40 μm or less. From the viewpoint of suppressing a decrease in the strength of the substrate 41, the lower limit of the average thickness of the substrate 41 is preferably 3.00 μm or more, more preferably 3.20 μm or more.

[0032] The average thickness of the substrate 41 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 into a length of 250 mm at a position 30 to 40 m longitudinally from one end of the magnetic tape MT on the outer periphery. In this specification, the term "longitudinal direction from one end of the magnetic tape MT on the outer periphery" means the direction from one end of the magnetic tape MT on the outer periphery toward the other end on the inner periphery.

[0033] Next, the layers of the sample other than the substrate 41 (i.e., the laminate film 42 and the back layer 43) are removed with a solvent such as MEK (methyl ethyl ketone) or dilute hydrochloric acid. Next, using a Mitutoyo Laser Hologram (LGH-110C) as a measuring device, the thickness of the sample (substrate 41) is measured at five positions, and these measurements are simply averaged (arithmetic mean) to calculate the average thickness of the substrate 41. The five measurement positions are selected randomly from the sample so that they are each different from the others in the longitudinal direction of the magnetic tape MT.

[0034] The base 41 contains, for example, a polyester-based resin as a main component. The polyester-based resin may include, for example, 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.

[0035] 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.

[0036] The inclusion of a polyester-based resin in the substrate 41 can be confirmed, for example, as follows. First, similar to the method for measuring the average thickness of the substrate 41, a magnetic tape MT is prepared and cut into a length of 250 mm to prepare a sample, and then 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.

[0037] 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.

[0038] 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.

[0039] 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).

[0040] 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).

[0041] 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.

[0042] (Hard Magnetic Layer 42B) The hard magnetic layer 42B is configured to record signals using a magnetization pattern. The hard magnetic layer 42B is a recording layer for perpendicular recording. The hard magnetic layer 42B contains, for example, hard magnetic powder and a binder. If necessary, the hard magnetic layer 42B may further contain at least one additive selected from the group consisting of conductive particles, lubricants, abrasive particles, antistatic agents, hardeners, rust inhibitors, and non-magnetic reinforcing particles. The hard magnetic layer 42B may have multiple protrusions on the surface (magnetic surface) facing the hard magnetic layer 42B. The multiple protrusions may be formed, for example, by conductive particles and abrasive particles protruding from the magnetic surface. The hard magnetic layer 42B may have a single-layer structure or a multilayer structure. In this specification, "multilayer" refers to two or more layers.

[0043] As shown in FIG. 4, the hard magnetic layer 42B may have a plurality of servo bands SB and a plurality of data bands DB in advance. The plurality of servo bands SB are arranged at equal intervals in the width direction of the magnetic tape MT. A data band DB is arranged between adjacent servo bands SB. The servo bands SB are used to guide the head unit (magnetic head) 56 (specifically, the servo read heads 56A and 56B) when recording or reproducing data. A servo pattern (servo signal) for tracking control of the head unit 56 is written in advance in the servo bands SB. User data is recorded in the data bands DB.

[0044] In order to read asymmetric servo stripes 113 (see FIG. 6 ), which will be described later, the head unit 56 may be configured to be able to maintain an inclined 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 . Alternatively, the head unit 56 may be configured to follow the meandering or deformation of the magnetic tape MT and become inclined with respect to the axis Ax during data recording and reproduction. The inclination angle of the head unit 56 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°.

[0045] The total area S of the plurality of servo bands SB relative to the area S of the magnetic surface (the surface on the hard magnetic layer 42B 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.

[0046] 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 W ＳＢ ) × (number of servo bands SB)) / (width of magnetic tape MT)) × 100

[0047] 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.

[0048] The number of servo bands SB is determined by the above ratio R Ｓ It can be calculated in the same way as

[0049] Servo Bandwidth W ＳＢFrom 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.

[0050] Servo Bandwidth W ＳＢ The width of the ratio R Ｓ It can be calculated in the same way as

[0051] 5A, the hard magnetic layer 42B is configured to allow a plurality of data tracks Tk to 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 300 nm or less, more preferably 200 nm or less, and even more preferably 150 nm or less. Taking into account the size of the hard magnetic particles, the lower limit of the data track width W is preferably 20 nm or more.

[0052] 5A 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. 5B, 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).

[0053] 5B, 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. Ｒrepresents 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).

[0054] The servo patterns are magnetized regions, and are formed by magnetizing specific regions of the hard magnetic layer 42B 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-patterned regions") may be magnetized regions where the hard magnetic layer 42B is magnetized, or may be non-magnetized regions where the hard magnetic layer 42B is not magnetized. When the non-patterned regions are magnetized regions, the servo pattern-forming regions and the non-patterned regions are magnetized in different directions (e.g., opposite directions).

[0055] In the LTO standard, a servo pattern is formed on the servo band SB, as shown in FIG. 6, 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.

[0056] 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).

[0057] 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 6, 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 , A５ are indicated with .

[0058] 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. ２ 6, 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 .

[0059] 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 head unit 56 is tilted obliquely 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 head unit 56. By changing the tilt of the head unit 56 based on this state, it is possible to adjust the distance between the servo read heads 56A and 56B in the width direction of the magnetic tape MT. Therefore, in both cases where the width of the magnetic tape MT is increased and where the width of the magnetic tape MT is decreased, the servo read heads 56A and 56B can be made to face the specified positions of the servo bands SB. Note that the central axis of the sliding surface of the head unit 56 refers to the axis that passes through the centers of the multiple servo read heads 56A and 56B on the sliding surface of the head unit 56.

[0060] A predetermined angle θ, which is the inclination angle of the servo stripe 113 of the A burst 111A １and 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 from １ 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. 6, 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

[0061] 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 6, 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 .

[0062] 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. ２6, the four servo stripes 113 are inclined at a predetermined interval from the EOT to the BOT of the magnetic tape MT and are indicated by the symbol D. １ , D ２ , D ３ , D ４ are indicated with .

[0063] The servo stripes 113 of the D burst 112D are inclined 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 head unit 56 is tilted obliquely 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 head unit 56. By changing the tilt of the head unit 56 based on this state, it is possible to adjust the servo distance.

[0064] 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 １That 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. 6, the predetermined angle θ of the servo stripes 113 of the C burst 112C １ 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

[0065] 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.

[0066] Reading the servo bands SB with the head unit 56 provides information for determining the tape speed and the longitudinal position of the head unit 56. The tape speed is calculated from the times between four timing signals (A1-C1, A2-C2, A3-C3, A4-C4). The head position is calculated from the times between the aforementioned four timing signals and another four timing signals (A1-B1, A2-B2, A3-B3, A4-B4). The servo pattern may have a shape including two parallel lines.

[0067] 6, 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.

[0068] The servo band SB and data band DB described above are merely examples, and a different system from the servo band SB and data band DB described above may be adopted.

[0069] Average thickness t of the hard magnetic layer 42B Ｂ The upper limit of the average thickness t of the hard magnetic layer 42B is preferably 80 nm or less, more preferably 70 nm or less, even more preferably 60 nm or less, particularly preferably 50 nm or less, and most preferably 40 nm or less. Ｂ When the thickness is 80 nm or less, the distance from the recording head to the surface of the soft magnetic layer 42A can be reduced. Therefore, when magnetic recording is performed on the hard magnetic layer 42B, the magnetic flux generated from the single-pole head (recording head) can be efficiently drawn into the hard magnetic layer 42B, thereby widening the effective recording width.

[0070] Average thickness t of the hard magnetic layer 42B Ｂ The lower limit of the average thickness t of the hard magnetic layer 42B is preferably 20 nm or more. Ｂ When the lower limit value is 20 nm or more, the decrease in saturation magnetization Ms of the hard magnetic layer 42B in the perpendicular direction of the magnetic tape MT can be suppressed, thereby obtaining excellent electromagnetic conversion characteristics (e.g., SNR (Signal-to-Noise Ratio)).

[0071] Average thickness t of the hard magnetic layer 42B Ｂ The numerical range of may be defined by any one of the upper limit values ​​and the lower limit value, and is preferably 20 nm or more and 70 nm or less, more preferably 20 nm or more and 60 nm or less, even more preferably 20 nm or more and 50 nm or less, and particularly preferably 20 nm or more and 40 nm or less.

[0072] Average thickness t of the hard magnetic layer 42B Ｂis 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 by processing using a focused ion beam (FIB) method or the like. When the FIB method is used, a carbon layer and a tungsten layer are formed as protective layers as a pretreatment for cross-sectional TEM image observation, which will be described later. The carbon layer is formed by vapor deposition on the surface of the magnetic tape MT facing the hard magnetic layer 42B and the surface facing the back layer 43, and the tungsten layer is further formed by vapor deposition or sputtering on the surface facing the hard magnetic layer 42B. 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.

[0073] The cross section of each obtained thinned sample was observed using a transmission electron microscope (TEM) under the following conditions to obtain a cross-sectional 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

[0074] Next, using the cross-sectional TEM image of each obtained sliced ​​sample, the thickness of the hard magnetic layer 42B is measured at 10 positions on each sliced ​​sample. The 10 measurement positions on each sliced ​​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 sliced ​​sample (30 thicknesses of the hard magnetic layer 42B in total) are simply averaged (arithmetic mean), and the obtained average value is the average thickness t of the hard magnetic layer 42B. Ｂ It is set to [nm].

[0075] Average thickness t of the hard magnetic layer 42B Ｂ and half the average maximum height Rmax(ave.) of the surface of the hard magnetic layer 42B, D SUM(=t Ｂ The upper limit of +(Rmax(ave.) / 2)) is preferably 105 nm or less, more preferably 100 nm or less, even more preferably 85 nm or less, and particularly preferably 60 nm or less. In this specification, "ave." represents average. SUM When the distance from the recording head to the surface of the soft magnetic layer 42A is 105 nm or less, the distance can be kept at approximately 105 nm or less. As a result, when magnetic recording is performed on the hard magnetic layer 42B, the magnetic flux generated from the single-pole head can be efficiently drawn into the hard magnetic layer 42B, thereby widening the effective recording width.

[0076] The above sum D SUM The lower limit of the thickness is not particularly limited, but is, for example, 20 nm or more.

[0077] The above sum D SUM The numerical range of may be defined by any one of the upper limit values ​​and the lower limit value, and is preferably 20 nm or more and 105 nm or less, more preferably 20 nm or more and 100 nm or less, even more preferably 20 nm or more and 85 nm or less, and particularly preferably 20 nm or more and 60 nm or less.

[0078] The above sum D SUM is calculated as follows: Ｂ The average thickness t of the hard magnetic layer 42B is calculated. Ｂ The measurement method is as described above.

[0079] The maximum height Rmax of the surface (magnetic surface) of the hard magnetic layer 42B is determined as follows: First, the magnetic tape MT housed in the cartridge 10 is unwound, and three samples of 250 mm are cut out from the magnetic tape MT at positions 10 m to 20 m, 30 m to 40 m, and 50 m to 60 m longitudinally from one end of the outer periphery of the magnetic tape MT, to prepare three samples.

[0080] Next, using the obtained samples, the thickness of the hard magnetic layer 42B is measured at five positions on each sample as follows. The five measurement positions on each sample are randomly selected from the sample so that they are different positions in the longitudinal direction of the magnetic tape MT. The sample is placed on a slide glass with the surface to be measured (the surface on the hard magnetic layer 42B side) facing up, and the ends of the sample are fixed with mending tape. The surface shape is measured using a VertScan (20x objective lens) as a measuring device, and the maximum height Rmax is determined based on the description of the maximum height Rz in JIS B 0601:2001. The measurement conditions are as follows. Equipment: Non-contact roughness meter using optical interference (Ryoka Systems Co., Ltd., non-contact surface and layer cross-sectional shape measurement system VertScan R5500GL-M100-AC) 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

[0081] The measured values ​​of each sample measured as described above (a total of 15 maximum heights Rmax) are simply averaged (arithmetic mean), and the obtained average value is taken as the average maximum height Rmax (ave.) [nm] of the surface of the hard magnetic layer 42B.

[0082] The average thickness t of the hard magnetic layer 42B obtained as described above Ｂ and the average maximum height Rmax(ave.) of the surface of the hard magnetic layer 42B are substituted into the following equation, and the sum D SUM is calculated. SUM [nm] = t １ + (Rmax(ave.) / 2)

[0083] (Hard Magnetic Powder) The hard magnetic powder contained in the hard magnetic layer 42B is preferably oriented in the perpendicular direction of the magnetic tape MT. This allows the magnetic tape MT to be a recording medium suitable for perpendicular recording. In this specification, the perpendicular direction (thickness direction) of the magnetic tape MT refers to the thickness direction of the magnetic tape MT in a flat state. The hard magnetic powder includes, for example, hexagonal ferrite particles or epsilon-type iron oxide particles (hereinafter referred to as "ε-iron oxide particles") as hard magnetic particles. However, the hard magnetic particles are not limited to these particles and may also be, for example, Co-containing spinel ferrite particles (cobalt ferrite particles).

[0084] (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.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] 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 atomic ratio of Sr to metal 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 when the atomic ratio of Sr to metal M1 is 50 atomic % or more. For example, when metal M1 contains Sr and Ba, hexagonal ferrite particles in which the atomic ratio of Sr to the total amount of Sr and Ba is 50 atomic % or more are called strontium ferrite particles.

[0089] In the present disclosure, barium ferrite particles refer to hexagonal ferrite particles in which the atomic ratio of Ba to metal 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 atomic ratio of Ba to metal M1 is 50 atomic % or more. For example, when metal M1 contains Sr and Ba, hexagonal ferrite particles in which the atomic ratio of Ba to the total amount of Sr and Ba is 50 atomic % or more are called barium ferrite particles.

[0090] 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.)

[0091] When the hard magnetic powder contains hexagonal ferrite particles, the upper limit of the average particle size of the hard magnetic powder is preferably 20 nm or less, more preferably 19 nm or less, and even more preferably 18 nm or less, 17 nm or less, or 16 nm or less. When the upper limit of the average particle size of the hard magnetic powder is 20 nm or less, excellent electromagnetic conversion characteristics (e.g., SNR) can be obtained in a high-recording-density magnetic tape MT.

[0092] When the hard magnetic powder contains hexagonal ferrite particles, the lower limit of the average particle size of the hard magnetic powder is preferably 13 nm or more, more preferably 14 nm or more. When the lower limit of the average particle size of the hard magnetic powder is 13 nm or more, the dispersibility of the hard magnetic powder is improved, and excellent electromagnetic conversion characteristics (e.g., SNR) can be obtained.

[0093] When the hard magnetic powder contains hexagonal ferrite particles, the numerical range of the average particle size of the hard magnetic powder may be defined by any one of the upper limit values ​​and any one of the lower limit values, and is preferably 13 nm or more and 20 nm or less, more preferably 13 nm or more and 19 nm or less, even more preferably 13 nm or more and 18 nm or less, 14 nm or more and 17 nm or less, or 14 nm or more and 16 nm or less.

[0094] When the hard magnetic powder contains hexagonal ferrite particles, the average aspect ratio of the hard magnetic powder 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 hard magnetic powder is within the range of 1.0 or more and 3.0 or less, aggregation of the hard magnetic powder can be suppressed. Furthermore, when the hard magnetic powder is vertically oriented in the process of forming the hard magnetic layer 42B, the resistance applied to the hard magnetic powder can be suppressed. Therefore, the vertical orientation of the hard magnetic powder can be improved.

[0095] When the hard magnetic powder contains hexagonal ferrite particles, the average particle size and average aspect ratio of the hard magnetic powder 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 a FIB method or the like. When the FIB method is used, 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 hard magnetic layer 42B and the surface facing the back layer 43, and the tungsten layer is further formed by vapor deposition or sputtering on the surface facing the hard magnetic layer 42B. 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.

[0096] Next, a cross-section of the obtained thin film sample is observed using a transmission electron microscope (H-9500 manufactured by Hitachi High-Technologies Corporation) at an acceleration voltage of 200 kV and a total magnification of 500,000 times, so as to include the entire hard magnetic layer 42B in the thickness direction of the hard magnetic layer 42B, and a cross-sectional TEM image is taken. The number of cross-sectional TEM images prepared is sufficient to extract 50 particles from which the plate diameter DB and plate thickness DA (see FIG. 7) shown below can be measured.

[0097] In the present disclosure, when the shape of the particle observed in the cross-sectional 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 Figure 7, the major axis of the plate surface or bottom surface is taken as the plate diameter DB value. The thickness or height of the particle observed in the cross-sectional TEM image is taken as the plate thickness DA value. When the thickness or height of a particle observed in the cross-sectional TEM image is not constant within a single particle, the thickness or height of the largest particle is taken as the plate thickness DA.

[0098] Next, 50 particles are extracted from the cross-sectional TEM image taken and selected based on the following criteria. Particles with parts outside the field of view of the cross-sectional 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.

[0099] Figures 8 and 9 show first and second examples of cross-sectional TEM images, respectively. In Figures 8 and 9, for example, particles indicated by arrows a and d are selected because their plate thickness (thickness or height) DA is clearly visible. The plate thickness DA of each of the selected 50 particles is measured. The plate thicknesses DA thus determined are simply averaged (arithmetic mean) to determine the average plate thickness DAave. The average plate thickness DAave. is the average particle plate thickness. Next, the plate diameter DB of each hard magnetic particle is measured. To measure the particle plate diameter DB, 50 particles whose plate diameter DB is clearly visible are selected from the cross-sectional TEM image taken. For example, in Figures 8 and 9, particles indicated by arrows b and c are selected because their plate diameter DB is clearly visible. The plate diameter DB of each of the selected 50 particles is measured. The plate diameters DB thus determined are simply averaged (arithmetic mean) to determine the average plate diameter DBave. The average plate diameter DBave. is the average particle size. The average aspect ratio of the particles (DBave. / DAave.) can be calculated from the average plate thickness DAave. and the average plate diameter DBave.

[0100] When the hard magnetic powder contains hexagonal ferrite particles, the average particle volume V of the hard magnetic powder Ｂ The upper limit is preferably 2500 nm ３ or less, more preferably 1800 nm ３ or less, more preferably 1500 nm ３ Below, 1400nm ３ Below, 1150nm ３ Below, 1200nm ３ or less than 1000 nm ３ The average particle volume V of the hard magnetic powder is as follows: Ｂ The upper limit is 2500 nm ３ If the average particle size of the hard magnetic powder is 20 nm or less, the same effect as when the average particle size of the hard magnetic powder is 20 nm or less can be obtained.

[0101] When the hard magnetic powder contains hexagonal ferrite particles, the average particle volume V of the hard magnetic powder Ｂ The lower limit is preferably 500 nm ３ More preferably, 600 nm or more ３ The average particle volume V of the hard magnetic powderＢ is 500 nm ３ If the average particle size of the hard magnetic powder is 13 nm or more, the same effect as that obtained when the average particle size of the hard magnetic powder is 13 nm or more can be obtained.

[0102] When the hard magnetic powder contains hexagonal ferrite particles, the average particle volume V of the hard magnetic powder Ｂ The numerical range may be defined by any of the upper limit values ​​and any of the lower limit values, and is preferably 500 nm. ３ 2500nm or more ３ Less than 500 nm, more preferably ３ 1800nm ​​or more ３ Less than 500 nm, more preferably ３ 1500nm or more ３ Below, 500nm ３ More than 1400 nm ３ Below, 600nm ３ 1200nm or more ３ Below, 600nm ３ 1150nm or more ３ or below 600 nm ３ 1000nm or more ３ The following is the result.

[0103] Average particle volume V of hard magnetic powder Ｂ can be calculated as follows: First, as described above in relation to the method for calculating the average particle size of hard magnetic powder, the average plate thickness DAave. and the average plate diameter DBave. are calculated. Next, the average particle volume V of the hard magnetic powder is calculated using the following formula: Ｂ is required.

[0104] (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 the present disclosure, spherical includes substantially spherical. Furthermore, cubic includes substantially cubic. Because ε-Iron oxide particles have the above-described shape, when ε-Iron oxide particles are used as hard 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 hard magnetic particles. Therefore, the dispersibility of the hard magnetic powder can be improved, and excellent electromagnetic conversion characteristics (e.g., SNR) can be obtained.

[0105] The ε-iron oxide particles may have a composite particle structure. More specifically, the ε-iron oxide particles have an ε-iron oxide portion 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 the “soft magnetic portion, etc.”).

[0106] The ε-iron oxide portion contains ε-iron oxide. The ε-iron oxide contained in the ε-iron oxide portion is ε-Fe ２ O ３ The crystal is preferably the main phase, and the single-phase ε-Fe ２ O ３ More preferably, it consists of:

[0107] 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.

[0108] 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.

[0109] The soft magnetic portion may be made of, for example, Fe. ３ O ４ , γ-Fe ２ O ３, or spinel ferrite, etc.

[0110] 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.

[0111] The ε-iron oxide particles may contain an additive instead of the composite particle structure, or may have the composite particle structure and contain an additive. In this case, a portion of the Fe in the ε-iron oxide particles is substituted with the additive. By containing the 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.

[0112] 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).

[0113] When the hard magnetic powder contains ε-iron oxide particles, the upper limit of the average particle size of the hard magnetic powder is preferably 20 nm or less, more preferably 18 nm or less, and even more preferably 16 nm or less, 15 nm or less, or 14 nm or less. In magnetic tape MT, the actual magnetization region is a region half the size of the recording wavelength. Therefore, by setting the average particle size of the hard magnetic powder to half the shortest recording wavelength or less, excellent electromagnetic conversion characteristics (e.g., SNR) can be obtained. Therefore, when the upper limit of the average particle size of the hard magnetic powder is 20 nm or less, excellent electromagnetic conversion characteristics (e.g., SNR) can be obtained in high-recording-density magnetic tape MT (e.g., magnetic tape MT configured to record signals at the shortest recording wavelength of 40 nm or less).

[0114] When the hard magnetic powder contains ε-iron oxide particles, the lower limit of the average particle size of the hard magnetic powder is preferably 10 nm or more. When the lower limit of the average particle size of the hard magnetic powder is 10 nm or more, the dispersibility of the hard magnetic powder is improved, and excellent electromagnetic conversion characteristics (e.g., SNR) can be obtained.

[0115] When the hard magnetic powder contains ε iron oxide particles, the numerical range of the average particle size of the hard magnetic powder may be defined by any one of the upper limits and the lower limit, and is preferably 10 nm or more and 20 nm or less, more preferably 10 nm or more and 18 nm or less, even more preferably 10 nm or more and 16 nm or less, 10 nm or more and 15 nm or less, or 10 nm or more and 14 nm or less.

[0116] When the hard magnetic powder contains ε-iron oxide particles, the average aspect ratio of the hard magnetic powder 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 hard magnetic powder is within the range of 1.0 or more and 3.0 or less, aggregation of the hard magnetic powder can be suppressed. Furthermore, when the hard magnetic powder is vertically oriented in the process of forming the hard magnetic layer 42B, the resistance applied to the hard magnetic powder can be suppressed. Therefore, the vertical orientation of the hard magnetic powder can be improved.

[0117] When the hard magnetic powder contains ε-iron oxide particles, the average particle size and average aspect ratio of the hard magnetic powder are determined as follows: First, a flake sample is prepared in the same manner as in the case where the hard magnetic powder contains hexagonal ferrite particles to measure the average particle size and average aspect ratio of the hard magnetic powder.

[0118] Next, the cross-section of the obtained thin film sample was 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, so as to include the entire hard magnetic layer 42B in the thickness direction of the hard magnetic layer 42B, and a cross-sectional TEM image was taken. Next, 50 particles whose particle shape could be clearly confirmed were selected from the cross-sectional 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 outline 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 determine the average major axis length DLave. The average major axis length DLave. thus determined is the average particle size of the hard magnetic powder. The minor axis lengths DS of the 50 measured particles are simply averaged (arithmetic mean) to determine the average minor axis length DSave. The average aspect ratio of the particles (DLave. / DSave.) is then determined from the average major axis length DLave. and the average minor axis length DSave.

[0119] When the hard magnetic powder contains ε iron oxide particles, the average particle volume V of the hard magnetic powder Ｂ The upper limit is preferably 4000 nm ３ Less than 3000 nm, more preferably ３ or less, more preferably 2000 nm ３ Below, 1800nm ３ Below, 1600nm ３ Below, 1300nm ３ or below 1150 nm ３Generally, noise in a magnetic tape MT is inversely proportional to the square root of the number of particles (i.e., proportional to the square root of the particle volume), so by making the particle volume smaller, it is possible to obtain excellent electromagnetic conversion characteristics (e.g., SNR). Therefore, the average particle volume V of the hard magnetic powder is Ｂ The upper limit is 4000 nm ３ When the average particle size of the hard magnetic powder is 20 nm or less, excellent electromagnetic conversion characteristics (for example, SNR) can be obtained, similar to when the average particle size of the hard magnetic powder is 20 nm or less.

[0120] When the hard magnetic powder contains ε iron oxide particles, the average particle volume V of the hard magnetic powder Ｂ The lower limit is preferably 500 nm ３ More preferably, 600 nm or more ３ The average particle volume V of the hard magnetic powder Ｂ The lower limit is 500 nm ３ If the average particle size of the hard magnetic powder is 10 nm or more, the same effect as that obtained when the average particle size of the hard magnetic powder is 10 nm or more can be obtained.

[0121] When the hard magnetic powder contains ε iron oxide particles, the average particle volume V of the hard magnetic powder Ｂ The numerical range may be defined by any of the upper limit values ​​and any of the lower limit values, and is preferably 500 nm. ３ 4000nm or more ３ Less than 500 nm, more preferably ３ 3000nm or more ３ Less than 500 nm, more preferably ３ 2000nm or more ３ Below, 500nm ３ 1800nm ​​or more ３ Below, 600nm ３ 1600nm or more ３ Below, 600nm ３ 1300nm or more ３ or below 600 nm ３ 1150nm or more ３ The following is the result.

[0122] When the ε iron oxide particles have a spherical shape, the average particle volume V of the hard magnetic powder Ｂis calculated as follows: First, the average major axis length DLave. is calculated in the same manner as the calculation of the average particle size and average aspect ratio of hard magnetic powder when the hard magnetic powder contains ε-iron oxide particles. Next, the average particle volume V of the hard magnetic powder is calculated using the following formula: Ｂ is required. Ｂ = (π / 6) × DLave. 3

[0123] When the ε iron oxide particles have a cubic shape, the average particle volume V of the hard magnetic powder Ｂ is determined as follows: First, a flake sample is prepared in the same manner as in the method for measuring the average particle size and average aspect ratio of hard magnetic powder when the hard magnetic powder contains hexagonal ferrite particles.

[0124] Next, a cross-section of the obtained thin film sample is observed using a transmission electron microscope (H-9500 manufactured by Hitachi High-Technologies Corporation) at an acceleration voltage of 200 kV and a total magnification of 500,000 times, so as to include the entire hard magnetic layer 42B in the thickness direction of the hard magnetic layer 42B, and a cross-sectional TEM image is taken. Note that the magnification and acceleration voltage may be adjusted appropriately depending on the type of device. Next, 50 particles with clear particle shapes are selected from the taken cross-sectional TEM image, 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 determine the average side length DCave. Next, the average particle volume V of the hard magnetic powder is calculated using the average side length DCave. from the following equation: Ｂ is required. Ｂ =DCave. 3

[0125] (Binder) The binder includes, for example, a thermoplastic resin, and may further include a thermosetting resin or a reactive resin.

[0126] 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, for example, 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.

[0127] 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.

[0128] 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.

[0129] 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.

[0130] 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.

[0131] The polyester includes, for example, at least one selected from the group consisting of phthalic acid polyesters and aliphatic polyesters.

[0132] 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.

[0133] 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.

[0134] 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.

[0135] (Conductive Particles) Some of the conductive particles contained in the hard magnetic layer 42B may protrude from the magnetic surface, forming multiple protrusions. The formation of multiple protrusions by the conductive particles reduces the electrical resistance of the magnetic surface, suppressing charging of the magnetic surface. This also reduces dynamic friction between the head unit 56 and the magnetic surface while the magnetic tape MT is running.

[0136] The conductive particles are preferably an antistatic agent and a solid lubricant. The conductive particles are preferably particles containing carbon. As the carbon-containing particles, for example, at least one type selected from the group consisting of carbon particles and hybrid particles can be used, and carbon particles are preferably used. The average primary particle size of the conductive particles is preferably 100 nm or less. When the average primary particle size of the conductive particles is 100 nm or less, even when the conductive particles 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 hard magnetic layer 42B is suppressed.

[0137] The carbon particles may be, for example, at least one selected from the group consisting of carbon black, acetylene black, ketjen black, carbon nanotubes, and graphene, and among these carbon particles, carbon black is preferably used. Examples of carbon black that can be used include Seast TA manufactured by Tokai Carbon Co., Ltd., and Asahi #15 and #15HS manufactured by Asahi Carbon Co., Ltd.

[0138] 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, the hybrid particles may be hybrid carbon in which carbon is attached to the surface of silica particles.

[0139] (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 hard magnetic layer 42B, particularly the inclusion of both a fatty acid and a fatty acid ester in the hard magnetic layer 42B, contributes to improving the running stability of the magnetic tape MT. More particularly, the hard magnetic layer 42B 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 surface of the magnetic tape MT facing the hard magnetic layer 42B to a value suitable for running the magnetic tape MT.

[0140] 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).

[0141] 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).

[0142] 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.

[0143] 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.)

[0144] 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.)

[0145] 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.)

[0146] 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.)

[0147] 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.)

[0148] (Abrasive particles) Some of the abrasive particles contained in the hard magnetic layer 42B may protrude from the magnetic surface to form multiple protrusions. When the head unit 56 slides over the magnetic tape MT, the protrusions formed by the abrasive particles can come into contact with the head unit 56.

[0149] The lower limit of the Mohs hardness of the abrasive particles 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 is preferably 9.5 or less, from the viewpoint of suppressing wear of the head unit 56.

[0150] The abrasive particles are preferably inorganic particles. 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. Examples of inorganic particles that are preferably used include alumina particles such as α-alumina, β-alumina, and γ-alumina, and silicon carbide. The abrasive particles may be acicular, spherical, or cubic, but those with angular shapes are preferred because they have high abrasiveness.

[0151] (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.

[0152] (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.

[0153] 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.

[0154] (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.

[0155] (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).

[0156] (Soft Magnetic Layer 42A) The soft magnetic layer 42A is configured so that when magnetic recording is performed on the hard magnetic layer 42B, the magnetic flux generated from the single-pole head can be drawn into the hard magnetic layer 42B. By providing the soft magnetic layer 42A, the magnetic field strength from the magnetic head can be increased, and a magnetic tape MT suitable for high-density recording can be obtained.

[0157] The soft magnetic layer 42A may reduce the unevenness of the surface of the substrate 41 and adjust the unevenness of the surface (magnetic surface) of the hard magnetic layer 42B. The soft magnetic layer 42A includes, for example, soft magnetic powder and a binder. The soft magnetic layer 42A may also include additives as needed. The additives may include, for example, at least one selected from the group consisting of conductive particles, lubricants, antistatic agents, hardeners, and anticorrosive agents. The soft magnetic layer 42A may have a single-layer structure or a multi-layer structure.

[0158] The soft magnetic layer 42A preferably has a plurality of holes. By storing lubricant in these holes, it is possible to prevent 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 prevents an increase in the dynamic friction coefficient. In other words, excellent running stability can be obtained.

[0159] Average thickness t of the soft magnetic layer 42A Ａ The lower limit of the average thickness t of the soft magnetic layer 42A is 250 nm or more, preferably 500 nm or more, and more preferably 600 nm or more. Ａ If the thickness is less than 250 nm, the function of drawing the magnetic flux from the single-pole head into the hard magnetic layer 42B is reduced, making it difficult to suppress the spread of the magnetic flux from the single-pole head, and therefore the effective recording width for the single-pole head (recording head) becomes narrow.

[0160] Average thickness t of the soft magnetic layer 42A Ａ The upper limit of the average thickness t of the soft magnetic layer 42A is preferably 1000 nm or less, more preferably 900 nm or less, and even more preferably 800 nm or less. Ａ When the average thickness (average total thickness) t Ｔ This makes it possible to increase the recording capacity of one data cartridge.

[0161] Average thickness t of the soft magnetic layer 42A ＡThe numerical range of may be defined by any one of the above upper limit values ​​and any one of the above lower limit values, and is preferably 250 nm or more and 1000 nm or less, more preferably 250 nm or more and 900 nm or less, and even more preferably 500 nm or more and 800 nm or less.

[0162] Average thickness t of the soft magnetic layer 42A Ａ is the average thickness t of the hard magnetic layer 42B Ａ However, the magnification of the cross-sectional TEM image is adjusted appropriately depending on the thickness of the soft magnetic layer 42A.

[0163] (Soft Magnetic Powder) The soft magnetic powder contained in the soft magnetic layer 42A is preferably oriented in the perpendicular direction (thickness direction) or width direction of the magnetic tape MT. Such orientation of the soft magnetic powder reduces the magnetic flux in the longitudinal direction of the magnetic tape MT. The soft magnetic powder includes soft magnetic particles. Examples of soft magnetic particles include iron (Fe), iron alloys, or iron compounds. More specifically, examples of soft magnetic particles include iron (Fe), permalloy, magnetite, sendust, soft ferrite, manganese-zinc ferrite, iron nitride, iron boride, or iron carbide. Examples of the shape of the soft magnetic particles include, but are not limited to, various shapes such as needles, spindles, spheres, polyhedrons, and plates. Examples of polyhedrons include, but are not limited to, hexahedrons such as cubes and octahedrons.

[0164] Average particle volume V of soft magnetic powder Ａ The upper limit is preferably 4000 nm ３ or less, more preferably 3500 nm ３ or less, more preferably 2800 nm ３ The average particle volume V of the soft magnetic powder is as follows: Ａ The upper limit is 4000 nm ３ If the width is less than this, the magnetic flux generated by the magnetic head during recording can be efficiently guided in the perpendicular direction (thickness direction) of the magnetic tape MT, and the magnetic flux can be prevented from spreading to adjacent recording bits, thereby widening the effective recording width of the recording bits to be written.

[0165] Average particle volume V of soft magnetic powderＡ The lower limit is preferably 600 nm ３ More preferably, 700 nm ３ The average particle volume V of the soft magnetic powder Ａ is 600 nm ３ If the content is above this, the function as soft magnetic powder can be maintained.

[0166] Average particle volume V of soft magnetic powder Ａ The numerical range may be defined by any of the above upper limit values ​​and any of the above lower limit values, and is preferably 600 nm ３ 4000nm or more ３ Less than 600 nm, more preferably ３ 3500nm or more ３ More preferably, 600 nm or less ３ 2800nm ​​or more ３ The following is the result.

[0167] Average particle volume V of soft magnetic powder Ａ is calculated as follows. First, a flake sample is prepared in the same manner as the method for measuring the average particle size and average aspect ratio of hard magnetic powder when the hard magnetic powder contains hexagonal ferrite particles. Next, a cross-section of the obtained flake 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 soft magnetic layer 42A in the thickness direction of the soft magnetic layer 42A, and a cross-sectional TEM image is taken. Next, the average major axis length DLave. is calculated from the cross-sectional TEM image taken in the same manner as the method for calculating the average particle size and average aspect ratio of hard magnetic powder when the hard magnetic powder contains ε-iron oxide particles. Next, the average particle volume (average particle volume equivalent to a sphere) V of the soft magnetic powder is calculated using the following formula: Ａ is required. Ａ = (π / 6) × DLave. 3

[0168] Average particle volume V of soft magnetic powder Ａ Average particle volume V of hard magnetic powder Ｂ Particle volume ratio (V Ｂ / V ＡThe upper limit of the particle volume ratio (V) is preferably 2.0 or less, more preferably 1.6 or less, and even more preferably 1.0 or less. Ｂ / V Ａ The lower limit of ) is preferably 0.3 or more, more preferably 0.4 or more, and even more preferably 0.5 or more.

[0169] Particle volume ratio (V Ｂ / V Ａ The numerical range of ) may be defined by any one of the above upper limit values ​​and any one of the above lower limit values, and is preferably 0.3 or more and 2.0 or 0.4 or more and 2.0 or less, more preferably 0.4 or more and 1.6 or less, even more preferably 0.4 or more and 1.0 or less, and particularly preferably 0.5 or more and 1.0 or less.

[0170] Particle volume ratio (V Ｂ / V Ａ ) is the average particle volume V of the soft magnetic powder obtained by the above-mentioned measurement method. Ａ and the average particle volume V of the hard magnetic powder Ｂ It is calculated using

[0171] The lower limit of the mass magnetization σs of the soft magnetic powder is preferably 45 emu / g or more, more preferably 60 emu / g or more, and even more preferably 180 emu / g or more. When the lower limit of the mass magnetization σs of the soft magnetic powder is 45 emu / g or more, the function of the soft magnetic layer 42A in drawing the magnetic flux from the recording head into the hard magnetic layer 42B can be improved, and the effective recording width can be widened.

[0172] The upper limit of the mass magnetization σs of the soft magnetic powder is not particularly limited, but is, for example, 400 emu / g or less, 350 emu / g or less, or 300 emu / g or less. If the lower limit of the mass magnetization σs of the soft magnetic powder is 400 emu / g or less, the magnetic flux from the magnetic head can be sufficiently attracted to the hard magnetic layer 42B.

[0173] The numerical range of the mass magnetization σs of the soft magnetic powder may be defined by any one of the upper limit values ​​and any one of the lower limit values, and is preferably 45 emu / g or more and 400 emu / g or less, more preferably 60 emu / g or more and 400 emu / g or less, and even more preferably 60 emu / g or more and 350 emu / g or less.

[0174] The mass magnetization σs of soft magnetic powder is determined as follows. First, a soft magnetic powder sample is placed in a powder sample folder, and then the M-H loop of the soft magnetic powder sample is measured using a Hayama Vibrating Sample Magnetometer (VSM) VSM OP01. The volume magnetization of the soft magnetic powder is determined from the saturation magnetization Ms (emu) value of the obtained M-H loop and the volume of the sample. The specific gravity of the soft magnetic powder is also measured using a hydrometer. Using the measurement results of this specific gravity, the volume magnetization is converted to mass magnetization, and the mass magnetization σs of the soft magnetic powder is determined. The measurement of saturation magnetization Ms uses the measurement and analysis program included with the VSM-OP01. The measurement conditions are as follows: measurement mode: hysteresis loop (no initial magnetization curve), applied magnetic field: ±5 kOe, number of data: 20, measurement interval: 15 sec, fine mode available, magnetic field range: ±1000 Oe, number of data: 20, measurement interval: 15 sec, number of initial magnetization curve data: 30, measurement interval: 15 sec, number of measurement data averaged: 100, measurement interval: 0.05 sec, locking amp: 3 mV. The above M-H loop measurement is performed at 25°C ±2°C and 50% RH ±5% RH.

[0175] (Binder) The binder is the same as the binder contained in the hard magnetic layer 42B.

[0176] (Additives) The conductive particles, lubricant, antistatic agent, hardener, and anticorrosive agent are the same as those contained in the hard magnetic layer 42B.

[0177] (Back Layer 43) The back layer 43 contains a binder and non-magnetic powder. If necessary, the back layer 43 may further contain at least one additive selected from the group consisting of a lubricant, a curing agent, an antistatic agent, etc. The binder is the same as the binder contained in the hard magnetic layer 42B described above. The curing agent and antistatic agent are the same as the curing agent and antistatic agent contained in the hard magnetic layer 42B described above.

[0178] The non-magnetic powder includes non-magnetic particles. The non-magnetic particles include, for example, at least one of inorganic particles and organic particles. The 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. The inorganic particles include, for example, metals, metal oxides, metal carbonates, metal sulfates, metal nitrides, metal carbides, or metal sulfides. The shapes of the non-magnetic particles include, for example, various shapes such as needles, spheres, cubes, and plates, but are not limited to these shapes.

[0179] The average particle size of the non-magnetic powder is preferably 10 nm or more and 150 nm or less, more preferably 15 nm or more and 110 nm or less. The average particle size of the non-magnetic powder is determined in the same manner as the average particle size of the magnetic powder. The non-magnetic powder may contain non-magnetic powder having two or more particle size distributions.

[0180] The upper limit of the average thickness of the back layer 43 is preferably 0.60 μm or less. If the upper limit of the average thickness of the back layer 43 is 0.60 μm or less, the thickness of the soft magnetic layer 42A and the substrate 41 can be maintained thick even when the average thickness of the magnetic tape MT is 5.40 μm or less, so that the running stability of the magnetic tape MT in a recording / reproducing device can be maintained. The lower limit of the average thickness of the back layer 43 is not particularly limited, but is, for example, 0.20 μm or more.

[0181] Average thickness t of the back layer 43 Ｃ is calculated as follows: First, the average thickness t of the magnetic tape MT Ｔ The average thickness t Ｔ The measurement method is the "average thickness t of the magnetic tape MT" described later. Ｔ". 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 43 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 (LGH-110C) manufactured by Mitutoyo Corporation, and these measurements are simply averaged (arithmetic mean) to obtain an average value t Ｄ Then, the average thickness t of the back layer 43 is calculated using the following formula: Ｃ 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. Ｃ [μm] = t Ｔ [μm]-t Ｄ [μm]

[0182] (Surface roughness R of the back surface ｂ ) Surface roughness of the back surface (surface roughness of the back layer 43) 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 hard magnetic layer 42B 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.

[0183] Surface roughness R of the back surface ｂis 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 hard magnetic layer 42B 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, the surface roughness is measured at five positions in the longitudinal direction of the magnetic tape MT, and then the arithmetic mean roughness S is automatically calculated from the surface profile obtained at each position. ａ The average value of (nm) is the surface roughness R ｂ (nm).

[0184] (The average thickness of the magnetic tape MT is t Ｔ ) Average thickness of magnetic tape MT (average total thickness) t Ｔ The upper limit of the average thickness t of the magnetic tape MT is preferably 5.40 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 When the average thickness t of the magnetic tape MT is 5.40 μm or less, the recording capacity of one data cartridge can be improved. Ｔ The lower limit of the thickness is not particularly limited, but is, for example, 3.50 μm or more.

[0185] Average thickness t of magnetic tape MT Ｔ The numerical range may be defined by any of the above upper limits and the above lower limit, and is preferably 3.50 μm or more and 5.40 μm or less, more preferably 3.50 μm or more and 5.10 μm or less, even more preferably 3.50 μm or more and 4.90 μm or less, and particularly preferably 3.50 μm or more and 4.70 μm or less.

[0186] 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 the magnetic tape MT is cut 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 to prepare a sample. Next, the thickness of the sample is measured at five positions using a Mitutoyo Laser Hologram (LGH-110C) as a measuring device, and these 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.

[0187] (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 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.

[0188] 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.

[0189] 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.

[0190] A tensile tester (AG-100D, manufactured by Shimadzu Corporation) is used to measure Young's modulus. 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 the tape between the chucks) is set to 100 mm. After the tape sample is chucked, stress is gradually applied in the direction of pulling the sample. The pulling speed is set to 0.1 mm / min. From the change in stress and the amount of elongation at this time, Young's modulus is calculated 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 depending on the thickness of the magnetic tape MT, etc. Here, the stress range is from 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.

[0191] (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 magnetic tape MT becomes more flexible due to external forces, making it easier to adjust the width of the magnetic tape MT by adjusting the tension. Therefore, off-track can be 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, a decrease in running stability can be suppressed.

[0192] 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 soft magnetic layer 42A, the hard magnetic layer 42B, and the back layer 43 are removed from the cut magnetic tape MT, thereby obtaining 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 the method for measuring the Young's modulus in the longitudinal direction of the magnetic tape MT described above.

[0193] 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.

[0194] 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.

[0195] [5. Magnetic Characteristics of Magnetic Tape] (Squareness ratio S of the laminated film 42 in the longitudinal direction of the magnetic tape MT) １ ) Squareness ratio S of the laminated film 42 in the longitudinal direction of the magnetic tape MT １ is 35% or less, preferably 30% or less, more preferably 25% or less, further preferably 20% or less, and particularly preferably 15% or less. １ If the squareness ratio S of the laminated film 42 exceeds 35%, the orientation in the perpendicular direction becomes insufficient, making it difficult to sufficiently draw the magnetic flux from the recording head into the hard magnetic layer 42B, resulting in a narrower effective recording width. １ If the ratio exceeds 35%, the orientation of the soft magnetic powder in the longitudinal direction of the magnetic tape MT becomes high, a magnetic field is generated in the soft magnetic layer 42A in the longitudinal direction, and noise occurs during reproduction.

[0196] The squareness ratio S of the laminated film 42 in the longitudinal direction of the magnetic tape MT １is 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 m to 40 m 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 (soft magnetic layer 42A, hard magnetic layer 42B, back layer 43, etc.) of the remaining three cut-out magnetic tape MTs are wiped off using acetone, ethanol, etc., 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.

[0197] 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 Industry 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.

[0198] 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."

[0199] The saturation magnetization Ms (emu) and remanent magnetization Mr (emu) of the obtained MH loop after background correction are substituted into the following equation to obtain the squareness ratio S １ (%) is calculated. For this calculation, the measurement and analysis program attached to the "VSM-P7-15" is used. All of the above M-H loop measurements are performed at 25°C ± 2°C and 50% RH ± 5% RH. Furthermore, when measuring the M-H loop in the longitudinal direction of the magnetic tape MT, "demagnetizing field correction" is not performed. Squareness ratio S １ (%)=(Mr / Ms)×100

[0200] (Squareness ratio S of the laminated film 42 in the perpendicular direction of the magnetic tape MT) ２ , and the squareness ratio S of the laminated film 42 in the width direction of the magnetic tape MT. ３ ) Squareness ratio S of the laminated film 42 in the perpendicular direction of the magnetic tape MT ２ or the squareness ratio S of the laminated film 42 in the width direction of the magnetic tape MT ３ The lower limit of the squareness ratio S of the laminated film 42 in the perpendicular direction of the magnetic tape MT is preferably 60% or more, 63% or more, 65% or more, or 68% or more, more preferably 70% or more, or 75% or more, even more preferably 80% or more, or 85% or more, and particularly preferably 90% or more, or 91% or more. ２ When the axial orientation of the soft magnetic powder is 60% or more, the orientation of the soft magnetic powder in the perpendicular direction is sufficiently high, so that the magnetic flux from the magnetic head can be sufficiently drawn into the hard magnetic layer 42B. This allows the effective recording width to be widened. Furthermore, the orientation of the soft magnetic powder in the longitudinal direction is reduced, so that noise during playback can be suppressed.

[0201] The squareness ratio S of the laminated film 42 in the perpendicular direction of the magnetic tape MT ２ or the squareness ratio S of the laminated film 42 in the width direction of the magnetic tape MT ３ The upper limit of is not particularly limited, but is, for example, 100% or less.

[0202] The squareness ratio S of the laminated film 42 in the perpendicular direction of the magnetic tape MT ２ , or the squareness ratio S of the laminated film 42 in the width direction of the magnetic tape MT ３ The numerical range of may be defined by any of the above lower limits and the above upper limit, and is preferably 60% or more and 100% or less, 63% or more and 100% or less, 65% or more and 100% or less, or 68% or more and 100% or less, more preferably 70% or more and 100% or less, or 75% or more and 100% or less, even more preferably 80% or more and 100% or less, or 85% or more and 100% or less, and particularly preferably 90% or more and 100% or less, or 91% or more and 100% or less.

[0203] The squareness ratio S of the laminated film 42 in the perpendicular direction of the magnetic tape MT ２ The squareness ratio S of the laminated film 42 in the longitudinal direction of the magnetic tape MT is measured except that the MH loop of the measurement sample (the entire magnetic tape MT) and the MH loop of the correction sample (substrate 41) are measured in the directions perpendicular to the magnetic tape MT and the substrate 41, respectively. １ can be obtained in the same way.

[0204] The squareness ratio S of the laminated film 42 in the width direction of the magnetic tape MT ３ The squareness ratio S of the laminated film 42 in the longitudinal direction of the magnetic tape MT is measured, except that the MH loop of the measurement sample (the entire magnetic tape MT) and the MH loop of the correction sample (substrate 41) are measured in the width direction of the magnetic tape MT and the substrate 41, respectively. １ can be obtained in the same way.

[0205] (Saturation Magnetization Ms of Laminated Film 42 in the Perpendicular Direction of Magnetic Tape MT) The lower limit of the saturation magnetization Ms of Laminated Film 42 in the perpendicular direction of Magnetic Tape MT is preferably 95 emu / cc or more, more preferably 101 emu / cc or more, even more preferably 126 emu / cc or more, and particularly preferably 363 emu / cc or more. If the lower limit of the saturation magnetization Ms of Laminated Film 42 is 95 emu / cc or more, the function of Soft Magnetic Layer 42A in drawing the magnetic flux from the recording head into Hard Magnetic Layer 42B can be improved, and the effective recording width can be widened.

[0206] The upper limit of the saturation magnetization Ms of the laminated film 42 in the perpendicular direction of the magnetic tape MT is preferably 800 emu / cc or less, more preferably 600 emu / cc or less, and even more preferably 500 emu / cc or less. When the upper limit of the saturation magnetization Ms of the laminated film 42 is 800 emu / cc or less, the magnetic flux from the magnetic head can be sufficiently attracted to the hard magnetic layer 42B, and sufficient output can be obtained during playback.

[0207] The numerical range of the saturation magnetization Ms of the laminated film 42 in the perpendicular direction of the magnetic tape MT may be defined by any of the above lower limit values ​​and any of the above upper limit values, and is preferably 95 emu / cc or more and 800 emu / cc or less, more preferably 101 emu / cc or more and 600 emu / cc or less, even more preferably 126 emu / cc or more and 600 emu / cc or less, and particularly preferably 363 emu / cc or more and 500 emu / cc or less.

[0208] The saturation magnetization Ms of the laminated film 42 in the perpendicular direction of the magnetic tape MT can be calculated as follows: First, the squareness ratio S of the laminated film 42 in the perpendicular direction of the magnetic tape MT is calculated as follows: ２The background-corrected M-H loop is obtained in the same manner as in the measurement method described above. Next, the saturation magnetization Ms (emu) is measured from the obtained background-corrected M-H loop. The measurement and analysis program included with the VSM-P7-15 is used to measure this saturation magnetization Ms (emu). Note that all of the above M-H loop measurements are performed at 25°C ± 2°C and 50% RH ± 5% RH. Furthermore, "demagnetizing field correction" is not performed when measuring the M-H loop in the perpendicular direction to the magnetic tape MT.

[0209] Next, the value of the saturation magnetization Ms (emu) of the measured MH loop and the volume (cc (cm ３ )), Ms (emu / cc) is calculated. The volume of the laminated film 42 is calculated by multiplying the area of ​​the measurement sample (laminated film 42) by the average thickness t Ｅ The average thickness t of the laminated film 42 is calculated by multiplying Ｅ is the average thickness t of the hard magnetic layer 42B Ａ However, the magnification of the cross-sectional TEM image is adjusted appropriately depending on the thickness of the laminated film 42.

[0210] (The squareness ratio S of the hard magnetic layer 42B in the longitudinal direction of the magnetic tape MT) Ｂ１ ) Squareness ratio S of the hard magnetic layer 42B in the longitudinal direction (running direction) of the magnetic tape MT Ｂ１ is preferably 33% or less, more preferably 30% or less, even more preferably 25% or less, particularly preferably 20% or less, and most preferably 15% or less. Ｂ１ When the ratio is 33% or less, the hard magnetic powder has a sufficiently high perpendicular orientation, thereby making it possible to obtain excellent electromagnetic conversion characteristics.

[0211] The squareness ratio S of the hard magnetic layer 42B in the perpendicular direction of the magnetic tape MT Ｂ１is calculated as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and a measurement sample is prepared by cutting out a piece 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. At this time, the measurement sample is marked with a non-magnetic ink so that the longitudinal direction (running direction) of the magnetic tape MT can be identified. Next, the Kerr hysteresis loop of the measurement sample corresponding to the longitudinal direction (running direction) of the magnetic tape MT is measured. The measurement of the Kerr hysteresis loop of the measurement sample is performed using an ultraviolet spectroscopic magnetic property evaluation device "BH-M800UV-HD-10" manufactured by NeoArc Corporation. The measurement conditions are: wavelength: 300 nm, applied magnetic field: 20 kOe, sweep time: 30 sec, measurement area: Φ3 mm, and measurement direction: perpendicular to the surface (magnetic surface) of the hard magnetic layer 42B.

[0212] Next, the squareness ratio S is calculated from the Kerr rotation angle at saturation and the Kerr rotation angle when the applied magnetic field is 0 kOe from the Kerr hysteresis loop. Ｂ１ is calculated. Note that this squareness ratio S Ｂ１ The measurement and analysis program included with the "BH-M800UV-HD-10" is used to calculate this.

[0213] (Squareness ratio S of the hard magnetic layer 42B in the perpendicular direction of the magnetic tape MT) Ｂ２ ) Squareness ratio S of the hard magnetic layer 42B in the perpendicular direction (thickness direction) of the magnetic tape MT Ｂ２ is preferably 62% or more, more preferably 65% ​​or more, and even more preferably 68% or more, 72% or more, or 75% or more. Ｂ２ When the ratio is 62% or more, the perpendicular orientation of the magnetic particles is sufficiently high, and therefore excellent electromagnetic conversion characteristics can be obtained.

[0214] The squareness ratio S of the hard magnetic layer 42B in the perpendicular direction of the magnetic tape MT Ｂ２ is the squareness ratio S except that the Kerr hysteresis loop of the measurement sample is measured in the perpendicular direction (thickness direction) of the magnetic tape MT. Ｂ１ It can be determined in the same manner as in the measurement method of

[0215] (Coercive force Hc of soft magnetic layer 42A in the width direction of substrate 41) The upper limit of the coercive force Hc of the soft magnetic layer 42A in the width direction of the substrate 41 (magnetic tape MT) is preferably 24.0 kA / m or less, more preferably 5.0 kA / m or less, and even more preferably 1.0 kA / m or less. When the coercive force Hc of the soft magnetic layer 42A is 24.0 kA / m or less, residual magnetization of the soft magnetic powder is suppressed, so that the magnetization of the soft magnetic layer 42A does not interfere with the recording magnetization of the hard magnetic layer 42B, and the effective recording width can be widened while obtaining a stable SNR.

[0216] The lower limit of the coercive force Hc of the soft magnetic layer 42A in the width direction of the substrate 41 is not particularly limited, but is, for example, 0.1 kA / m or more.

[0217] The numerical range of the coercive force Hc of the soft magnetic layer 42A in the width direction of the substrate 41 may be determined by any of the upper limit values ​​and the lower limit value, and is preferably 0.1 kA / m or more and 24.0 kA / m or less, more preferably 0.1 kA / m or more and 5.0 kA / m or less, and even more preferably 0.1 kA / m or more and 1.0 kA / m or less.

[0218] The coercive force Hc of the soft magnetic layer 42A in the width direction of the substrate 41 is determined as follows. First, after the process of forming the soft magnetic layer 42A and before the process of forming the hard magnetic layer 42B, six magnetic tapes MT are cut out at positions 30 m to 40 m in the longitudinal direction from one end of a long laminate consisting of the substrate 41 and the soft magnetic layer 42A. At this time, markings are made with any non-magnetic ink so that the longitudinal direction (running direction) of the laminate can be identified. Here, the one end of the laminate refers to the end on the side where application of the paint for forming the soft magnetic layer begins.

[0219] Next, the three cut-out laminates are stacked with double-sided tape so that their longitudinal directions are the same, and then punched out with a φ6.39 mm punch to prepare a measurement sample. Next, using a VSM, the M-H loop of the measurement sample (the entire laminate consisting of the substrate 41 and the soft magnetic layer 42A) corresponding to the width direction of the substrate 41 (the width direction of the magnetic tape MT) is measured. Next, the coatings (soft magnetic layer 42A, etc.) of the remaining three cut-out laminates are wiped off with acetone, ethanol, or the like, leaving only the substrate 41. The three obtained substrates 41 are then stacked with double-sided tape and then punched out with a φ6.39 mm punch to prepare a sample for background correction (hereinafter simply referred to as the "correction sample"). Then, using a VSM, the M-H loop of the correction sample (substrate 41) corresponding to the width direction of the substrate 41 (the width direction of the magnetic tape MT) is measured.

[0220] The MH loop of the measurement sample (the entire laminate) 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 Industry 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.

[0221] After obtaining the M-H loop of the measurement sample (the entire laminate) 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 laminate), 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."

[0222] The coercive force Hc (kA / m) is measured from the obtained M-H loop after background correction. This coercive force Hc (kA / m) is measured using the measurement and analysis program attached to the "VSM-P7-15 model." Note that all of the above M-H loop measurements are performed at 25°C ± 2°C and 50% RH ± 5% RH. Furthermore, "demagnetizing field correction" is not performed when measuring the M-H loop in the width direction of the magnetic tape MT.

[0223] [6. 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.

[0224] (Preparation process of paint for forming soft magnetic layer and paint for forming hard magnetic layer) First, the paint for forming soft magnetic layer is prepared by kneading and dispersing soft magnetic powder, binder, etc. in a solvent. Next, the paint for forming hard magnetic layer is prepared by kneading and dispersing hard magnetic powder, etc. in a solvent. For example, the following solvents, dispersing devices, and kneading devices can be used to prepare the paint for forming soft magnetic layer and the paint for forming hard magnetic layer.

[0225] 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.

[0226] 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.

[0227] (Process for Forming Soft Magnetic Layer 42A and Hard Magnetic Layer 42B) Next, a soft magnetic layer-forming paint is applied to one main surface of the substrate 41 and dried to form the soft magnetic layer 42A. During drying, the soft magnetic powder is magnetically oriented in the perpendicular (thickness) or width direction of the substrate 41, for example, using a permanent magnet. Next, a hard magnetic layer-forming paint is applied to the soft magnetic layer 42A and dried to form the hard magnetic layer 42B on the soft magnetic layer 42A. During drying, the hard magnetic powder is magnetically oriented in the perpendicular (thickness) direction of the substrate 41, for example, using a solenoid coil. After the hard magnetic layer 42B is formed, a back layer 43 is formed on the other main surface of the substrate 41. This completes the magnetic tape MT. The order in which the soft magnetic layer 42A, hard magnetic layer 42B, and back layer 43 are formed is not limited to the above example. For example, after the back layer 43 is formed on the other main surface of the substrate 41, the soft magnetic layer 42A and the hard magnetic layer 42B may be formed in this order on one main surface of the substrate 41.

[0228] Squareness ratio S of the hard magnetic layer 42B Ｂ１ , S Ｂ２ can be set to a desired value by adjusting, for example, the strength of the magnetic field applied to the coating film of the hard magnetic layer-forming paint, the concentration of the solid content in the hard magnetic layer-forming paint, and the drying conditions (drying temperature and drying time) of the coating film of the hard magnetic layer-forming paint. The strength of the magnetic field applied to the coating film is preferably two to three times the coercive force of the hard magnetic powder. Ｂ２ In order to further increase the squareness ratio S Ｂ１In order to further reduce the squareness ratio S Ｂ２ In order to further increase the squareness ratio S, it is also effective to magnetize the hard magnetic powder before the paint for forming the hard magnetic layer is introduced into an orientation device for magnetically orienting the hard magnetic powder. Ｂ１ , S Ｂ２ The above adjustment methods may be used alone or in combination of two or more.

[0229] Squareness ratio S of the laminated film 42 １ , S ２ , S ３ can be set to a desired value by adjusting, for example, the strength of the magnetic field applied to the coating film of the paint for forming a soft magnetic layer, the strength of the magnetic field applied to the coating film of the paint for forming a hard magnetic layer, the concentration of the solids in the paint for forming a soft magnetic layer, the concentration of the solids in the paint for forming a hard magnetic layer, the drying conditions (drying temperature and drying time) for the coating film of the paint for forming a soft magnetic layer, and the drying conditions (drying temperature and drying time) for the coating film of the paint for forming a hard magnetic layer. １ , S ２ , S ３ The above adjustment methods may be used alone or in combination of two or more.

[0230] (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 to harden the soft magnetic layer 42A and the hard magnetic layer 42B.

[0231] (Calendering Process) Next, the obtained magnetic tape MT is subjected to a calendering process to smooth the magnetic surface.

[0232] (Demagnetization Process and Servo Pattern Writing Process) Next, if necessary, the magnetic tape MT may be demagnetized and then a servo pattern may be written onto the magnetic tape MT.

[0233] (Cutting Step) Next, the magnetic tape MT may be cut to a predetermined width (for example, 1 / 2 inch width) as needed.

[0234] [7. Effects] As described above, in the magnetic tape MT according to one embodiment, the soft magnetic layer 42A is provided under the hard magnetic layer 42B, and the average thickness t Ａ is 250 nm or more, and the squareness ratio S of the laminated film 42 in the longitudinal direction of the magnetic tape MT is １ is 35% or less. This allows the magnetic flux from the single-pole head to be efficiently drawn into the hard magnetic layer 42B, enabling recording in the perpendicular direction. Therefore, it is possible to prevent the effective recording width from narrowing.

[0235] [8. 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.

[0236] 10 is an exploded perspective view showing an example of the configuration of a two-reel type cartridge 321. The cartridge 321 comprises an upper half 302 made of synthetic resin, a transparent window member 323 fitted into and fixed to a window 302a opened in the top surface of the upper half 302, a reel holder 322 fixed to the inside of the upper half 302 to prevent the reels 306 and 307 from floating up, a lower half 305 corresponding to the upper half 302, the reels 306 and 307 stored in the space formed when the upper half 302 and lower half 305 are combined, the magnetic tape MT wound on the reels 306 and 307, a front lid 309 closing the front opening formed when the upper half 302 and lower half 305 are combined, and a back lid 309A protecting the magnetic tape MT exposed in this front opening.

[0237] The reels 306 and 307 are used to wind the magnetic tape MT. The reel 306 includes a lower flange 306b having a cylindrical hub portion 306a in the center around which the magnetic tape MT is wound, an upper flange 306c having approximately the same size as the lower flange 306b, and a reel plate 311 sandwiched between the hub portion 306a and the upper flange 306c. The reel 307 has the same configuration as the reel 306.

[0238] The window member 323 has mounting holes 323a for assembling reel holders 322, which are reel holding means for preventing the reels from floating up, at positions corresponding to the reels 306 and 307. The magnetic tape MT is the same as the magnetic tape MT in the embodiment.

[0239] The present disclosure will be specifically described below using examples, but the present disclosure is not limited to these examples.

[0240] In the following examples and comparative examples, the average thickness t of the soft magnetic layer Ａ , the average thickness t of the hard magnetic layer Ｂ , the average thickness of the PEN film (substrate), the average thickness of the back layer, and the average thickness t of the magnetic tape Ｔ , mass magnetization σs of the soft magnetic powder, average particle volume V of the soft magnetic powder Ａ , the average particle volume V of the hard magnetic powder Ｂ , particle volume ratio V Ｂ / V Ａ The coercive force Hc of the soft magnetic layer in the width direction of the PEN film (substrate) is a value determined by the measurement method described in the above embodiment.

[0241] [Example 1] (Preparation process of paint for forming hard magnetic layer) The paint for forming hard magnetic layer was prepared as follows. First, a first composition having the following formulation was kneaded using an extruder. Next, the kneaded first composition and a second composition having the following formulation were added to a stirring tank equipped with a disperser and premixed. Subsequently, further mixing was performed using a Dyno Mill and filtering was performed to prepare the paint for forming hard magnetic layer.

[0242] (First composition) Barium ferrite (Ba ０．５５ Sr ０．４５ Fe １２ O １９ ) Magnetic powder (hexagonal plate shape, average aspect ratio 2.6, average particle volume V Ｂ = 1150 nm ３ Vinyl chloride resin solution (resin solution composition: vinyl chloride resin 30.0% by mass, cyclohexanone solution 70.0% by mass): 35.0 parts by mass (vinyl chloride resin: degree of polymerization 300, number average molecular weight Mn = 10,000, polar group OSO ３K = 0.07 mmol / g, secondary OH = 0.3 mmol / g.) Polyurethane resin solution (resin solution formulation: polyurethane resin 30.0 mass%, cyclohexanone 70.0 mass%): 10.0 mass parts (polyurethane resin: number average molecular weight Mn = 25000, glass transition temperature Tg = 110°C) Aluminum oxide powder: 5.0 mass parts (α-Al ２ O ３ , average particle size 0.1 μm)

[0243] (Second composition) Carbon black: 1.5 parts by mass (manufactured by Tokai Carbon Co., Ltd., product name: Seest S, arithmetic average particle size 70 nm) Polyurethane resin solution (resin solution formulation: polyurethane resin 30.0% by mass, cyclohexanone 70.0% by mass): 4.0 parts by mass (polyurethane resin: number average molecular weight Mn = 25,000, glass transition temperature Tg = 110°C) n-butyl stearate: 2.0 parts by mass Methyl ethyl ketone: 121.0 parts by mass Toluene: 121.0 parts by mass Cyclohexanone: 116.0 parts by mass

[0244] Finally, 3.3 parts by mass of polyisocyanate (product name: Coronate L, manufactured by Tosoh Corporation) and 1.0 part by mass of stearic acid were added as a curing agent to the coating material for forming the hard magnetic layer prepared as described above.

[0245] (Preparation process of paint for forming soft magnetic layer) The paint for forming soft magnetic layer was prepared as follows. First, the third composition having the following formulation was kneaded using an extruder. Next, the kneaded third composition and the fourth composition having the following formulation were added to a stirring tank equipped with a disperser and premixed. Subsequently, further mixing was performed using a Dyno Mill and filtering was performed to prepare the paint for forming soft magnetic layer.

[0246] (Third composition) Magnetite (soft magnetic powder) (average particle volume V Ａ = 2800 nm ３ , mass magnetization σs = 60 emu / g): 100.0 parts by mass Vinyl chloride resin solution (resin solution composition: vinyl chloride resin 30.0 mass%, cyclohexanone solution 70.0 mass%): 50.0 parts by mass (polymerization degree 300, number average molecular weight Mn = 10,000, polar group OSO ３K = 0.07 mmol / g, secondary OH = 0.3 mmol / g.) Aluminum oxide powder: 3.0 parts by mass (α-Al ２ O ３ , average particle size 0.1 μm)

[0247] (Fourth composition) Carbon black: 20.0 parts by mass (manufactured by Asahi Carbon Co., Ltd., product name: #80) Polyurethane resin solution (resin solution formulation: polyurethane resin 30.0 mass%, cyclohexanone 70.0 mass%): 35.0 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: 150.0 parts by mass Toluene: 77.0 parts by mass Cyclohexanone: 150.0 parts by mass

[0248] 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 soft magnetic layer-forming paint prepared as described above.

[0249] (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: 100.0 parts by mass (manufactured by Nippon Polyurethane Co., Ltd., trade name: N-2304) Methyl ethyl ketone: 500.0 parts by mass Toluene: 400.0 parts by mass Cyclohexanone: 100.0 parts by mass Polyisocyanate (trade name: Coronate L, manufactured by Tosoh Corporation): 10.0 parts by mass

[0250] (Soft Magnetic Layer Formation Process) A soft magnetic layer was formed by applying a soft magnetic layer-forming paint to one main surface of a long PEN film (substrate) having an average thickness of 4.20 μm and drying it, so that the average thickness of the completed magnetic tape (average thickness after calendaring) would be 500 nm. While the soft magnetic layer-forming paint was drying, a permanent magnet was used to magnetically orient the magnetite (soft magnetic powder) in the width direction of the PEN film. The coercive force Hc of the soft magnetic layer 42A in the width direction of the long PEN film (substrate) was measured. The resulting coercive force Hc was 5.0 kA / m.

[0251] (Hard Magnetic Layer Formation Process) A hard magnetic layer was formed by applying a magnetic layer-forming paint onto the soft magnetic layer and drying it so that the average thickness of the completed magnetic tape (average thickness after calendaring) would be 60 nm. During drying of the hard magnetic layer-forming paint, a solenoid coil was used to magnetically orient the barium ferrite magnetic powder (hard magnetic powder) in the direction perpendicular to the PEN film (thickness direction).

[0252] (Back layer forming process) After forming the soft magnetic layer and the magnetic layer, a back layer forming paint 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 calendaring) would be 0.30 μm. This gave a magnetic tape.

[0253] (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 soft magnetic layer and the magnetic layer.

[0254] (Calendering Step) The magnetic tape after curing was subjected to a calendering process to smooth the surface of the magnetic layer, at a calendering temperature of 100° C. and a calendering pressure of 200 kg / cm.

[0255] (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 5.06 μm.

[0256] Example 2 A magnetic tape was obtained in the same manner as in Example 1, except that in the soft magnetic layer forming step, the hard magnetic layer was formed so that the average thickness of the soft magnetic layer on the completed magnetic tape would be 250 nm.

[0257] Example 3 A magnetic tape was obtained in the same manner as in Example 1, except that in the soft magnetic layer process, the orientation of magnetite (soft magnetic powder) in the width direction of the PEN film was reduced compared to Example 1.

[0258] [Example 4] In the preparation process of the coating material for forming the soft magnetic layer, Fe—Co nano-magnetic powder (average particle volume V Ａ = 2800 nm ３ A magnetic tape was obtained in the same manner as in Example 1 except that a magnetic powder having a mass magnetization σs of 180 emu / g was used.

[0259] [Example 5] In the preparation process of the soft magnetic layer-forming paint, magnetite (soft magnetic powder) with a lower coercive force Hc than in Example 1 was used, thereby making the coercive force Hc of the soft magnetic layer 42A in the width direction of the long PEN film (substrate) 1.0 kA / m. In addition, in the hard magnetic layer formation process, the hard magnetic layer was formed so that the average thickness of the hard magnetic layer when the magnetic tape was completed would be 40 nm. Apart from these, the magnetic tape was obtained in the same manner as in Example 1.

[0260] [Example 6] In the preparation process of the coating material for forming the soft magnetic layer, ３ A magnetic tape was obtained in the same manner as in Example 1, except that magnetite (soft magnetic powder) of the above formula was used.

[0261] [Example 7] A magnetic tape was obtained in the same manner as in Example 1, except that in the preparation process of the paint for forming the soft magnetic layer, magnetite (soft magnetic powder) with a higher coercive force than in Example 1 was used, thereby making the coercive force Hc of the soft magnetic layer 42A in the width direction of the long PEN film (substrate) 13.0 kA / m.

[0262] [Example 8] In the preparation process of the paint for forming the soft magnetic layer, magnetite (soft magnetic powder) (average particle volume V Ａ = 2800 nm ３A tape was produced in the same manner as in Example 1, except that a magnetic material having a mass magnetization σs of 46 emu / g was used, and that in the soft magnetic layer formation process, the soft magnetic layer was formed so that the average thickness of the soft magnetic layer upon completion of the magnetic tape would be 250 nm.

[0263] Example 9 A magnetic tape was obtained in the same manner as in Example 1, except that in the soft magnetic layer process, the orientation of magnetite (soft magnetic powder) in the width direction of the PEN film was made higher than in Example 1.

[0264] Example 10 A magnetic tape was obtained in the same manner as in Example 1, except that in the soft magnetic layer formation step, the soft magnetic layer was formed so that the average thickness of the soft magnetic layer upon completion of the magnetic tape would be 900 nm.

[0265] Example 11 A magnetic tape was obtained in the same manner as in Example 1, except that in the soft magnetic layer formation step, magnetite (soft magnetic powder) was magnetically oriented in the direction perpendicular to the PEN film (thickness direction) using a permanent magnet.

[0266] Example 12 A magnetic tape was obtained in the same manner as in Example 1, except that in the hard magnetic layer formation step, the hard magnetic layer was formed so that the average thickness of the hard magnetic layer on the completed magnetic tape would be 80 nm.

[0267] [Example 13] In the process of preparing the coating material for forming the soft magnetic layer, the average particle volume V Ａ = 4300 nm ３ A magnetic tape was obtained in the same manner as in Example 1, except that magnetite (soft magnetic powder) with a mass magnetization σs of 60 emu / g was used.

[0268] Comparative Example 1 A magnetic tape was obtained in the same manner as in Example 1, except that in the soft magnetic layer formation step, the soft magnetic layer was formed so that the average thickness of the soft magnetic layer when the magnetic tape was completed would be 220 nm.

[0269] Comparative Example 2 A magnetic tape was obtained in the same manner as in Example 1, except that in the soft magnetic layer formation step, the orientation of magnetite (soft magnetic powder) in the width direction of the PEN film was further reduced compared to Example 1.

[0270] [Comparative Example 3] In the preparation process of the paint for forming the soft magnetic layer, magnetite (soft magnetic powder) (average particle volume V Ａ = 2800 nm ３ A magnetic tape was obtained in the same manner as in Example 1, except that a soft magnetic layer was formed in the soft magnetic layer formation step using a magnetic material having a mass magnetization σs of 42 emu / g and an average thickness of the soft magnetic layer upon completion of the magnetic tape of 200 nm.

[0271] Comparative Example 4 A magnetic tape was obtained in the same manner as in Example 1, except that in the soft magnetic layer formation step, magnetite (soft magnetic powder) was magnetically oriented in the longitudinal direction of the PEN film by a permanent magnet.

[0272] [Comparative Example 5] A magnetic tape was obtained in the same manner as in Example 1, except that in the preparation process of the paint for forming the soft magnetic layer, hematite (non-magnetic powder) was used instead of magnetite (soft magnetic powder) to form a non-magnetic layer instead of a soft magnetic layer.

[0273] [Evaluation] (Magnetic Properties of Laminated Film) As the magnetic properties of the laminated film of the soft magnetic layer and the high magnetic layer, the squareness ratio S of the laminated film in the longitudinal direction of the magnetic tape was measured. １ , the squareness ratio S of the laminated film in the perpendicular direction of the magnetic tape ２ , the squareness ratio S of the soft magnetic layer in the width direction of the magnetic tape ３ The magnetic properties of the laminated film were measured in the perpendicular direction of the magnetic tape MT, and the saturation magnetization Ms of the laminated film was measured in the perpendicular direction of the magnetic tape MT. The method for measuring these magnetic properties was as described in the above embodiment.

[0274] (Magnetic Characteristics of Hard Magnetic Layer) As the magnetic characteristics of the hard magnetic layer, the squareness ratio S of the hard magnetic layer 42B in the perpendicular direction of the magnetic tape MT is Ｂ２ The squareness ratio S of the hard magnetic layer 42B was measured. Ｂ２ The measurement method is as described in the above embodiment.

[0275] (Average thickness of the hard magnetic layer t Ｔ and half the average maximum height Rmax (ave.) of the surface of the hard magnetic layer, D SUM Evaluation of the average thickness t of the hard magnetic layer Ｔ and half the average maximum height Rmax (ave.) of the surface of the hard magnetic layer, DSUM was measured. SUM The measurement method is as described in the above embodiment.

[0276] (Evaluation of the size of the effective recording width) Width W of the recording head １ and the average effective recording width W ２ The difference ΔW (= W １ -W ２ ) was calculated as follows to evaluate the size of the effective recording width.

[0277] First, a servo writer was used to DC-demagnetize the magnetic tape, and then a servo pattern was written on the magnetic tape to form five servo bands. The servo pattern conformed to the LTO-9 standard. Next, the magnetic tape was loaded onto a Mountain Engineering II MTS Transport 2'x3' deck. The magnetic tape was then run on the deck at a running speed of 3.7 m / s, and signals were recorded at a single recording frequency of 10 MHz (4T half Nyquist frequency) while the recording / reproducing head slid over the surface of the hard magnetic layer. A perpendicular recording recording / reproducing head removed from an HDD (Hard Disk Drive) was used as the recording / reproducing head. The recording head width of the recording / reproducing head was 300 nm.

[0278] Next, the magnetic tape was unwound from the cartridge, and three samples were cut out in a size of 5 mm x 5 mm from a 5 cm long range at a position approximately 10 m longitudinally from one end of the outer periphery of the magnetic tape. Subsequently, the data recording patterns of the data bands of the hard magnetic layers of the three samples were observed using a magnetic force microscope (MFM), and three MFM images were obtained. The effective recording width was measured at 10 points in each of the three obtained MFM images, and measurements were obtained at 30 points in total. The measurements at 30 points were averaged (simple average) to obtain the average effective recording width W ２was calculated. The effective recording width was obtained by measuring the magnetic force along the longitudinal direction of the elongated rectangular recording pattern, and measuring the width of the part where the magnetic force was maintained as the effective recording width. Figure 11 shows an example of an MFM image of the magnetic tape. Figure 12 shows the amount of magnetization along line A-A in Figure 11. The analysis software attached to the MFM is used to measure the effective recording width.

[0279] The MFM and measurement conditions used for the measurements are as follows: (MFM) NanoScopeIV Dimension ICON (Bruker) Cantilever: SSS-MFMR (NANOSENSORS), Probe material: silicon single crystal coated with magnetic film, cantilever length 225 μm, tuning 0-150 Hz (Measurement conditions) Scan size: 10 μm × 10 μm Number of samples: 512 × 512 Phase detection mode Lift height: 20 nm Filtering process Flatten order: 2 Planefit order XY: 3

[0280] The average value W of the effective recording width obtained as above ２ Using this, the width W of the recording head １ and the average effective recording width W ２ The difference ΔW (= W １ -W ２ ) was obtained. When the recording head width is 300 nm, the effective recording width can be made 130 nm or more by setting ΔW to 170 nm or less. If the effective recording width is less than 130 nm, there is a risk that errors will be more likely to occur due to misalignment between the recording track and the reproducing head.

[0281] D listed in Table 1 SUM and ΔW represent the following: D SUM : average thickness t of the hard magnetic layer Ｔ and half of the average maximum height Rmax (ave.) of the surface of the hard magnetic layer (=t Ｂ + (Rmax(ave.) / 2)) ΔW: width W of recording head １ and the average effective recording width W ２ The difference between (W １ -W２ ) In addition, D SUM corresponds to the average distance from the recording head to the surface of the soft magnetic layer.

[0282] A comparison of the evaluation results of Examples 1 to 13 and Comparative Examples 1 to 5 reveals the following: A soft magnetic layer is provided under a hard magnetic layer, and the average thickness t Ａ is 250 nm or more, and the squareness ratio S of the laminated film in the longitudinal direction of the magnetic tape １ In the magnetic tapes (Examples 1 to 13) in which the width W of the recording head is 35% or less, １ and the average effective recording width W ２ The difference ΔW (= W ２ -W １ ) can be suppressed to 170 nm or less. ２ The soft magnetic layer is provided under the hard magnetic layer, and the squareness ratio S １ is 35% or less, but the average thickness t Ａ In the magnetic tapes (Comparative Examples 1 and 3) in which the effective recording width is less than 250 nm, the difference ΔW is 180 nm or more. ２ It is difficult to prevent the narrowing of the thickness t Ａ is 250 nm or more, but the squareness ratio S １ In the magnetic tapes (Comparative Examples 2 and 4) in which the difference ΔW exceeds 35%, the average effective recording width W ２ In the magnetic tape (Comparative Example 5) in which a non-magnetic layer containing hematite (non-magnetic powder) is provided under the hard magnetic layer, the difference ΔW becomes very large, reaching 240 nm. Therefore, the average effective recording width W ２ It is difficult to prevent the narrowing of the

[0283] From a comparison of the evaluation results of Examples 1 and 2, the average value of the effective recording width W ２ In order to increase the average thickness t Ａ It can be seen that it is preferable that the average effective recording width W is 500 nm or more.２ In order to increase the squareness ratio S of the laminated film in the width direction of the magnetic tape, ３ It can be seen that it is preferable that the average value of the effective recording width W ２ It can be seen that in order to increase the effective recording width, it is preferable that the mass magnetization σs of the soft magnetic powder contained in the soft magnetic layer is 180 emu / g or more. ２ In order to increase the coercive force Hc in the width direction of the magnetic tape, the average thickness t Ｂ It can be seen that the average thickness t of the hard magnetic layer is preferably 40 nm or less. Ｂ is 40 nm or less, the sum D SUM It can be seen that the average particle volume V of the soft magnetic powder contained in the soft magnetic layer can be kept at 60 nm or less, and the distance from the recording head to the surface of the soft magnetic layer can be kept at about 60 nm or less. Ａ is 700 nm ３ 2800nm ​​or more ３ In the following range, the average effective recording width W ２ It can be seen that the average effective recording width W ２ It can be seen that in order to increase the effective recording width, it is preferable that the coercive force Hc in the width direction of the magnetic tape is 5.0 / kA / m or less. ２ In order to increase the average thickness t Ａ It can be seen that it is preferable that the effective recording width W is 500 nm or more and the mass magnetization σs of the soft magnetic powder contained in the soft magnetic layer is 60 emu / g or more. ２ It is clear that in order to increase the squareness ratio of the laminated film in the width direction of the magnetic tape, it is preferable that the squareness ratio be 91% or more. Ａ In the range of 500 nm to 9000 nm, the average effective recording width W ２It can be seen that the effective recording width can be increased to the same extent. From the evaluation results of Examples 1 and 11, it can be seen that even when the soft magnetic powder is oriented in the perpendicular direction of the magnetic tape, the effect of suppressing narrowing of the effective recording width can be obtained, similar to when the soft magnetic powder is oriented in the width direction of the magnetic tape. In other words, even when the squareness ratio of the laminated film in the perpendicular direction of the magnetic tape is set to 60% or more, it can be seen that the effect of suppressing narrowing of the effective recording width can be obtained, similar to when the squareness ratio of the laminated film in the width direction of the magnetic tape is set to 60% or more. From the evaluation results of Examples 1 and 12, it can be seen that the average value W of the effective recording width ２ In order to increase the average thickness t Ｂ It can be seen that the average thickness t of the hard magnetic layer is preferably 60 nm or less. Ｂ When the sum D SUM It can be seen that the effective recording width W can be kept at 85 nm or less, and the distance from the recording head to the surface of the soft magnetic layer can be kept at about 85 nm or less. ２ In order to increase the average particle volume V of the soft magnetic powder contained in the soft magnetic layer, Ａ is 2800 nm ３ It is found that it is preferable that:

[0284] 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.

[0285] 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.

[0286] The present disclosure can also employ the following configurations. (1) A tape-shaped magnetic recording medium comprising, in order, a substrate and a laminated film, wherein the laminated film comprises, on the substrate, a soft magnetic layer containing soft magnetic powder and a binder, and a hard magnetic layer containing hard magnetic powder and a binder, in that order, the soft magnetic layer having an average thickness of 250 nm or more, and a squareness ratio of the laminated film in the longitudinal direction of the magnetic recording medium of 35% or less. (2) The magnetic recording medium according to (1), wherein the sum of the average thickness of the hard magnetic layer and half the average maximum height of the surface of the hard magnetic layer is 100 nm or less. (3) The magnetic recording medium according to (1) or (2), wherein the saturation magnetization Ms of the laminated film in the perpendicular direction of the magnetic recording medium is 95 emu / cc or more. (4) The magnetic recording medium according to any one of (1) to (3), wherein the squareness ratio of the laminated film in the perpendicular direction of the magnetic recording medium or the squareness ratio of the laminated film in the width direction of the magnetic recording medium is 60% or more and 100% or less. (5) The hard magnetic layer has an average thickness of 20 nm or more and 70 nm or less. (6) The magnetic recording medium according to any one of (1) to (5), wherein the squareness ratio of the hard magnetic layer in the perpendicular direction of the magnetic recording medium is 62% or more. (7) The magnetic recording medium according to any one of (1) to (6), wherein the coercivity of the soft magnetic layer in the width direction of the magnetic recording medium is 0.1 kA / m or more and 24.0 kA / m or less. (8) The magnetic recording medium according to any one of (1) to (7), wherein the mass magnetization σs of the soft magnetic powder is 45 emu / g or more. (9) The magnetic recording medium according to any one of (1) to (8), wherein the average thickness of the magnetic recording medium is 5.40 μm or less. (10) The average particle volume of the soft magnetic powder is 600 nm ３ 4000nm or more ３ (11) The magnetic recording medium according to any one of (1) to (9), wherein the average particle volume of the hard magnetic powder is 500 nm or less. ３ 1800nm ​​or more ３ (12) The magnetic recording medium according to any one of (1) to (10), wherein the average particle volume V of the soft magnetic powder is:Ａ the average particle volume V of the hard magnetic powder Ｂ Particle volume ratio (V Ｂ / V Ａ (13) A cartridge comprising the magnetic recording medium according to any one of (1) to (12), wherein the ratio of the magnetic recording medium density to the magnetic recording medium density is 0.4 or more and 2.0 or less.

[0287] 10, 321 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 Laminated film 42A Soft magnetic layer 42B Hard magnetic layer 43 Back layer 56 Head unit 56A, 56B Servo read 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, in order, a substrate and a laminated film, the laminated film including, on the substrate, a soft magnetic layer containing soft magnetic powder and a binder, and a hard magnetic layer containing hard magnetic powder and a binder, the soft magnetic layer having an average thickness of 250 nm or more, and a squareness ratio of the laminated film in the longitudinal direction of the magnetic recording medium being 35% or less.

2. The magnetic recording medium according to claim 1, wherein the sum of the average thickness of said hard magnetic layer and half the average maximum height of the surface of said hard magnetic layer is 100 nm or less.

3. The magnetic recording medium according to claim 1, wherein the saturation magnetization Ms of said laminated film in the perpendicular direction of said magnetic recording medium is 95 emu / cc or more.

4. The magnetic recording medium according to claim 1, wherein the squareness ratio of said laminated film in the perpendicular direction of said magnetic recording medium or the squareness ratio of said laminated film in the width direction of said magnetic recording medium is 60% or more and 100% or less.

5. The magnetic recording medium according to claim 1, wherein the hard magnetic layer has an average thickness of 20 nm to 70 nm.

6. The magnetic recording medium according to claim 1, wherein the squareness of said hard magnetic layer in the perpendicular direction of said magnetic recording medium is 62% or more.

7. The magnetic recording medium according to claim 1, wherein the coercive force of said soft magnetic layer in the width direction of said magnetic recording medium is 0.1 kA / m or more and 24.0 kA / m or less.

8. The magnetic recording medium according to claim 1, wherein the mass magnetization σs of the soft magnetic powder is 45 emu / g or more.

9. The magnetic recording medium according to claim 1, wherein the average thickness of the magnetic recording medium is 5.40 μm or less.

10. The average particle volume of the soft magnetic powder is 600 nm ３ 4000nm or more ３ The magnetic recording medium according to claim 1 , wherein:

11. The average particle volume of the hard magnetic powder is 500 nm ３ 1800nm ​​or more ３ The magnetic recording medium according to claim 1 , wherein:

12. Average particle volume V of the soft magnetic powder Ａ The average particle volume V of the hard magnetic powder Ｂ Particle volume ratio (V Ｂ / V Ａ 2. The magnetic recording medium according to claim 1, wherein the ratio of the surface roughness to the surface roughness is 0.4 or more and 2.0 or less.

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

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