Magnetic recording medium and cartridge

Abstract

Provided is a magnetic recording medium capable of suppressing recording speed dependency of electromagnetic conversion characteristics.　The magnetic recording medium is tape-shaped and includes a base body, a base layer, and a magnetic layer in this order. The average thickness of the magnetic recording medium is 4.40-5.40 μm, and the average thickness of the magnetic layer is 0.07 μm or less. The magnetic layer contains hexagonal ferrite particles containing barium (Ba) and strontium (Sr). The average particle volume of the hexagonal ferrite particles is 1.60 x 103 nm3 or less. The magnetic recording medium has an average value of a standardized SFD curve in the vertical direction thereof over a magnetic field range from 11,500-14,000 Oe of 0.013 or less, and demonstrates an average hardness H50, which is obtained by pushing a triangular pyramid diamond indenter having a ridge angle of 142.3° into the surface on the magnetic layer side at a right angle with a load of 50 μN, of 0.72 GPa or more.

Description

Magnetic recording media and cartridges

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

[0002] In recent years, in order to increase the capacity of cartridges, the thickness of tape-shaped magnetic recording media has been reduced to 5.40 μm or less, and hexagonal ferrite particles containing barium (Ba) are used as magnetic particles.

[0003] To improve the linear recording density of a tape-shaped magnetic recording medium, the particle volume of the hexagonal ferrite particles should be 1.60 × 10⁻⁶ ３ nm ３ Further miniaturization is desired. However, miniaturizing the size of magnetic particles reduces the thermal stability of magnetization. Therefore, it is desirable to increase the magnetic anisotropy constant Ku (i.e., coercivity Hc) of hexagonal ferrite particles. To meet this requirement, a technique is being considered in which both barium (Ba) and strontium (Sr) are incorporated as alkaline earth metals into hexagonal ferrite particles (see, for example, Patent Document 1).

[0004] International Publication No. 2024 / 162177

[0005] However, when fine hexagonal ferrite particles contain both barium (Ba) and strontium (Sr), variations in the composition of individual hexagonal ferrite particles are likely to occur, leading to variations in the magnetic properties (magnetic anisotropy constant Ku and coercivity Hc) of individual hexagonal ferrite particles. When a magnetic recording medium is fabricated using hexagonal ferrite particles with such variations in magnetic properties, differences in magnetic properties (magnetic anisotropy constant Ku and coercivity Hc) are likely to occur at the bit level, resulting in differences in electromagnetic conversion characteristics (e.g., SNR) depending on the recording speed. For example, when the bit area is 40,000 nm. ２ As the size decreases below a certain point, differences in magnetic properties at the bit level become particularly noticeable, and differences in electromagnetic conversion characteristics (SNR) due to differences in recording speed become more pronounced.

[0006] The purpose of this disclosure is to provide information on the average particle volume of 1.60 × 10⁻¹⁰ containing barium (Ba) and strontium (Sr).３ nm ３ In a magnetic recording medium including the following hexagonal ferrite particles in a magnetic layer, there is provided a magnetic recording medium capable of suppressing the recording speed dependency of electromagnetic conversion characteristics, and a cartridge including the same.

[0007] In order to solve the above problems, a magnetic recording medium according to a first aspect of the present disclosure is a tape-shaped magnetic recording medium, including a substrate, an underlayer, and a magnetic layer in this order, the average thickness of the magnetic recording medium is 4.40 μm or more and 5.40 μm or less, the average thickness of the magnetic layer is 0.07 μm or less, the magnetic layer includes hexagonal ferrite particles containing barium (Ba) and strontium (Sr), and the average particle volume of the hexagonal ferrite particles is 1.60×10 ３ nm ３ or less, the average value of the normalized SFD curve in the vertical direction of the magnetic recording medium in a magnetic field range of 11500 Oe or more and 14000 Oe or less is 0.013 or less, and the average hardness H obtained by vertically pressing a triangular pyramid diamond indenter with an edge angle of 142.3° against the surface on the magnetic layer side with a load of 50 μN 50 is 0.72 GPa or more.

[0008] A magnetic recording medium according to a second aspect of the present disclosure is a tape-shaped magnetic recording medium, including a substrate, an underlayer, and a magnetic layer in this order, the average thickness of the magnetic recording medium is 4.40 μm or more and 5.40 μm or less, the average thickness of the magnetic layer is 0.07 μm or less, the magnetic layer includes hexagonal ferrite particles containing barium (Ba) and strontium (Sr), and the average particle volume of the hexagonal ferrite particles is 1.60×10 ３ nm ３ or less, and the average value of the normalized SFD curve in the vertical direction of the magnetic recording medium in a magnetic field range of 11500 Oe or more and 14000 Oe or less is 0.013 or less.

[0009] A cartridge according to the present disclosure includes the magnetic recording medium according to the first aspect of the present disclosure or the magnetic recording medium according to the second aspect of the present disclosure.

[0010] Figure 1 is an exploded perspective view showing an example of the configuration of a cartridge according to one embodiment of the present disclosure. Figure 2 is a block diagram showing an example of the configuration of a cartridge memory. Figure 3 is a cross-sectional view showing an example of the configuration of a magnetic tape. Figure 4 is a schematic diagram showing an example of the layout of a data band and a servo band. Figure 5 is a schematic diagram of the magnetic head viewed from below (back layer side). Figure 6A is an enlarged view showing an example of the configuration of a data band. Figure 6B is an enlarged view showing an example of a data track in a magnetic recording system. Figure 7 is an enlarged view showing an example of the configuration of a servo band. Figure 8 is a perspective view showing an example of the shape of magnetic particles. Figure 9 is a diagram showing a first example of a cross-sectional TEM image of a magnetic layer. Figure 10 is a diagram showing a second example of a cross-sectional TEM image of a magnetic layer. Figure 11A is a graph for explaining the measurement method using a nanoindenter. Figure 11B is a schematic cross-sectional view for explaining the measurement method using a nanoindenter. Figure 12A is a graph showing an example of a normalized SFD curve. Figure 12B is an enlarged view of a part of the normalized SFD curve in Figure 12A. Figure 13 is an exploded perspective view showing an example of the configuration of a cartridge according to a modified embodiment of one embodiment of the present disclosure.

[0011] Embodiments of this disclosure will be described in the following order: 1. Cartridge configuration 2. Cartridge memory configuration 3. Magnetic tape configuration 4. Magnetic tape manufacturing method 5. Effects 6. Modified examples

[0012] In this specification, unless otherwise specified regarding the measurement environment in relation to the description of the measurement method and evaluation method, the measurement and evaluation shall be carried out under conditions of 25°C ± 2°C and 50% RH ± 5% RH.

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

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

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

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

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

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

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

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

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

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

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

[0024] [3. 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 is an example of a tape-shaped magnetic recording medium and comprises a long base body 41, a base layer 42 provided on one main surface (first main surface) of the base body 41, a magnetic layer 43 provided on the base layer 42, and a back layer 44 provided on the other main surface (second main surface) of the base body 41. The back layer 44 is provided as needed and may be omitted. The magnetic tape MT may be a vertical recording type magnetic recording medium or a longitudinal recording type magnetic recording medium. In this specification, the surface of the magnetic tape MT on the magnetic layer 43 side is sometimes referred to as the magnetic surface, and the surface of the magnetic tape MT on the back layer 44 side is sometimes referred to as the back surface.

[0025] The magnetic tape MT may conform to the LTO standard or to a standard other than the LTO standard. The width of the magnetic tape MT may be 1 / 2 inch or wider than 1 / 2 inch. If the magnetic tape MT conforms to the LTO standard, the width of the magnetic tape MT is 1 / 2 inch. The magnetic tape MT may have a configuration that allows the width of the magnetic tape MT to be kept constant or nearly constant by adjusting the tension applied to the longitudinal direction of the magnetic tape MT during travel using a recording and playback device (drive).

[0026] The magnetic tape MT has a long length and is run in the longitudinal direction during recording and playback. The magnetic tape MT is preferably used in a recording and playback device equipped with a ring-type head as the recording head. The magnetic tape MT is configured to record signals at a linear recording density D. From the viewpoint of increasing recording capacity, the lower limit of the linear recording density D of signals that can be recorded on the magnetic tape MT is preferably 545 kfci or more, more preferably 549 kfci or more, even more preferably 550 kfci or more, 552 kfci or more, 577 kfci or more, 600 kfci or more, or 635 kfci or more. The upper limit of the linear recording density D of data that can be recorded on the magnetic tape MT is preferably 1270 kfci or less, considering the size of the magnetic particles.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

[0041] As shown in Figure 4, the magnetic layer 43 may have a plurality of servo bands SB and a plurality of data bands DB pre-configured. In this specification, the longitudinal direction (travel direction) of the magnetic tape MT is the X-axis direction, the width direction of the magnetic tape MT is the Y-axis direction, and the thickness direction of the magnetic tape MT is the Z-axis direction. The plurality of servo bands SB are provided at equal intervals in the width direction of the magnetic tape MT. Data bands DB are provided between adjacent servo bands SB. As shown in Figure 5, the servo bands SB are for guiding the head unit 51 (specifically the servo lead section 52) when recording or playing back data. Servo patterns (servo signals) for tracking control of the head unit 51 are pre-written to the servo bands SB. User data is recorded in the data bands DB.

[0042] The magnetic head 50 is a two-bump type head including two bump-shaped heads, a first head unit 51a and a second head unit 51b. However, the configuration of the magnetic head 50 is not limited to a two-bump type head; for example, it may be a three-bump type head including three bump-shaped heads, a first head unit, a second head unit, and a third head unit. The first head unit, the second head unit, and the third head unit are arranged in this order in the direction of travel of the magnetic tape MT (A in Figure 5). １ They are arranged in the direction. In this specification, when the first head unit 51a and the second head unit 51b are not specifically distinguished, they are collectively referred to simply as the head unit 51, and when the first head unit 51a and the second head unit 51b are specifically distinguished, they are referred to as the first head unit 51a and the second head unit 51b.

[0043] The head unit 51 has a sliding surface (opposing surface) 51S that slides against the magnetic surface of the magnetic tape MT during data recording or playback. The sliding surface 51S has an elongated shape, such as a long rectangle, in a plan view. In describing the head unit 51, the longitudinal direction of the head unit 51 is defined as the Y' axis direction, the width direction of the head unit 51 is defined as the X' axis direction, and the vertical direction of the head unit 51 is defined as the Z' axis direction.

[0044] To read an asymmetric servo pattern (specifically, a servo stripe 113), the head unit 51 may be configured to be maintained at an angle to the Y-axis extending in the width direction of the magnetic tape MT during data recording or playback, as shown in Figure 5. More specifically, the head unit 51 may be configured so that the Y'-axis extending in the longitudinal direction of the sliding surface 51S is maintained at an angle to the Y-axis extending in the width direction of the magnetic tape MT. Hereinafter, a head unit 51 maintained at an angle to the X-axis extending in the width direction of the magnetic tape MT in this manner may be referred to as an "angled head unit 51". The inclination angle θ of the angled head unit 51 with respect to the Y-axis (i.e., the inclination angle θ of the Y'-axis with respect to the Y-axis) is preferably 3° to 18°, more preferably 5° to 15°.

[0045] The first head unit 51a and the second head unit 51b are configured symmetrically in the width direction (Y' axis direction) of the head unit 51, but are basically the same in configuration. The first head unit 51a and the second head unit 51b are made movable integrally in the width direction (Y axis direction) of the magnetic tape MT, thereby enabling data to be written to any of the data band DBs among all the data band DBs.

[0046] The first head unit 51a is a head used when the magnetic tape MT is traveling in the forward direction (direction A1 in Figure 5). On the other hand, the second head unit 51b is a head used when the magnetic tape MT is traveling in the reverse direction (direction A2 in Figure 5).

[0047] The sliding surface 51S of the head unit 51 is provided with two servo lead sections 52 and multiple data write / read sections 53. One servo lead section 52 is provided on each end of the head unit 51 in the longitudinal direction (Y' axis direction). The servo lead sections 52 are configured to reproduce servo signals by reading the magnetic field caused by the servo pattern recorded on the servo band SB of the magnetic tape MT using an MR element (MR: Magneto Resistive effect) or the like.

[0048] Examples of MR elements include anisotropic magnetoresistive (AMR) elements, giant magnetoresistive (GMR) elements, and tunnel magnetoresistive (TMR) elements.

[0049] The data write / read units 53 are arranged at equal intervals along the longitudinal direction (Y' axis direction) of the head unit 51. Furthermore, the data write / read units 53 are positioned to be sandwiched between two servo lead units 52. The number of data write / read units 53 is, for example, around 20 to 40, but this number is not particularly limited.

[0050] The data write / read unit 53 includes a data write unit 54 and a data read unit 55. The data write unit 54 is configured to record data onto the data band DB of the magnetic tape MT using a magnetic field generated from the magnetic gap.

[0051] Furthermore, the data read unit 55 is configured to regenerate data signals by reading the magnetic field generated by the data recorded on the data band DB of the magnetic tape MT using an MR element or the like. As the MR element, anisotropic magnetoresistance (AMR), giant magnetoresistance (GMR), tunnel magnetoresistance (TMR), etc., can be used.

[0052] In the first head unit 51a, the data write unit 54 is located to the left of the data read unit 55 (the upstream side when the magnetic tape MT flows in the forward direction (direction A1 in Figure 5)). On the other hand, in the second head unit 51b, the data write unit 54 is located to the right of the data read unit 55 (the upstream side when the magnetic tape MT flows in the reverse direction (direction A2 in Figure 5)).

[0053] The data read unit 55 is configured to be able to reproduce the data signal immediately after the data write unit 54, which is paired with the data read unit 55, has written the data to the magnetic tape MT. Alternatively, the data written by the data write unit 54 of one of the first head unit 51a and the second head unit 51b may be reproduced by the data read unit 55 of the other head unit 51.

[0054] The magnetic tape MT travels back and forth multiple times, with its direction of travel being changed between forward and reverse, while data is recorded onto the data band DB by the first head unit 51a and the second head unit 51b.

[0055] In the case of a three-bump type head, the sliding surfaces of the first head unit and the third head unit are each provided with two servo lead sections 52 and multiple data write sections 54. The sliding surface of the second head unit, which is positioned between the first and third head units, is provided with two servo lead sections 52 and multiple data read sections 55.

[0056] The total area S of multiple servo bands SB relative to the area S of the magnetic surface. ＳＢ Ratio R Ｓ (=(S ＳＢ The upper limit of (S) × 100) is preferably 4.0% or less, more preferably 3.5% or less, and even more preferably 3.0% or less, from the viewpoint of ensuring high recording capacity. On the other hand, the total area S of the multiple servo bands SB relative to the area S of the magnetic surface. ＳＢ Ratio R Ｓ The lower limit is preferably 1.0% or more, from the viewpoint of ensuring a servo band SB of 5 or more.

[0057] The total area S of multiple servo bands SB relative to the total area S of the magnetic surface ＳＢ Ratio R Ｓ The servobandwidth W is determined as follows: A magnetic tape MT is developed using a ferricolloid developer (Sigma Marker Q, manufactured by Sigma Hi-Chemical Co., Ltd.), and then the developed magnetic tape MT is observed with an optical microscope. ＳＢThen, measure the number of servo bands SB. Next, calculate the ratio R from the following formula. Ｓ We find the ratio R. Ｓ [%] = (((Servobandwidth W ＳＢ ) × (Number of servo bands SB) / (Width of magnetic tape MT) × 100

[0058] The number of servo bands SB is, for example, 5 + 4n (where n is a non-negative integer) or more. Preferably, the number of servo bands SB is 5 or more, more preferably 9 or more. When the number of servo bands SB is 5 or more, the influence of changes in the width direction of the magnetic tape MT on the servo signal is suppressed, and more stable recording and playback characteristics with fewer off-tracks can be ensured. There is no particular upper limit to the number of servo bands SB, but for example, it is 33 or less.

[0059] The number of servo bands SB is the ratio R mentioned above. Ｓ It can be calculated in the same way as the calculation method for [another calculation].

[0060] Servo bandwidth W ＳＢ The upper limit of the servo bandwidth W is preferably 95 μm or less, more preferably 65 μm or less, and even more preferably 50 μm or less, from the viewpoint of ensuring high recording capacity. ＳＢ The lower limit is preferably 10 μm or more. Servo bandwidth W less than 10 μm ＳＢ A magnetic head capable of reading servo signals is difficult to manufacture.

[0061] Servo bandwidth W ＳＢ The width is the ratio R mentioned above. Ｓ It can be calculated in the same way as the calculation method for [another calculation].

[0062] As shown in Figure 6A, the magnetic layer 43 is configured to form multiple data tracks Tk in the data band DB. The upper limit of the data track width W is preferably 1000 nm or less, more preferably 700 nm or less, and even more preferably 650 nm or less, 500 nm or less, or 400 nm or less, from the viewpoint of improving track recording density and ensuring high recording capacity. The lower limit of the data track width W is preferably 20 nm or more, considering the size of the magnetic particles.

[0063] The data track width W is determined as follows. First, a cartridge 10 on which data is recorded across the entire surface of a magnetic tape MT is prepared. The magnetic tape MT is unwound from this cartridge 10, and a 250 mm length of the magnetic tape MT is cut from one end of the outer circumference of the magnetic tape MT at a position 30 m to 40 m in the longitudinal direction to prepare a sample. Next, the data recording pattern of the data band DB portion of the magnetic layer 43 of the sample is observed using a magnetic force microscope (MFM) to obtain an MFM image. BRUKER's Dimension Icon and its analysis software are used as the MFM. The measurement area of ​​the MFM image is set to 10 μm × 10 μm, and this 10 μm × 10 μm measurement area is divided into 512 × 512 (= 262,144) measurement points. Measurements are performed using the MFM on three different 10 μm × 10 μm measurement areas, thus obtaining three MFM images. For each of the three obtained MFM images, the track width is measured at 10 locations, resulting in a total of 30 measurements. The average value (simple average) of these 30 measurements is then calculated. This average value is the data track width W. The analysis software included with Dimension Icon is used to measure the track width. The MFM measurement conditions are as follows: sweep speed: 1 Hz, chip used: MFMR-20, lift height: 20 nm, correction: Flatten order 3.

[0064] Note that while Figure 6A shows an example where adjacent data tracks Tk are recorded without overlapping, the recording method for data tracks Tk is not limited to this example. For example, as shown in Figure 6B, data may be recorded using Shingled Magnetic Recording (SMR) so that parts of adjacent data tracks Tk overlap in the width direction of the magnetic tape MT.

[0065] In the case of magnetic recording, the data track width W is the recording track width W. ＲIt becomes narrower compared to the recording track width W. Therefore, in the case of the magnetic recording method, the width of the data read section 55 is narrower than the width of the data write section. As described above, in the magnetic recording method, the data track width W is narrower than the recording track width W. Ｒ Since it is narrower compared to, it is advantageous in terms of improving recording density. Here, the recording track width W Ｒ This represents the track width during data writing. When magnetic recording is used as the recording method, the recording track width W is used. Ｒ This represents the track width before overwriting (the track width when data is written).

[0066] The magnetic layer 43 has a minimum value L for the distance between magnetization reversals. min The system is configured to record signals. Minimum value L of the magnetization reversal distance. min The upper limit of is preferably 46.6 nm or less, more preferably 46.3 nm or less, even more preferably 46.2 nm or less, 46.0 nm or less, 44.0 nm or less, 42.3 nm or less, or 40.0 nm or less, from the viewpoint of increasing recording capacity. Minimum value L of the magnetization reversal distance min The lower limit is preferably 20.0 nm or more, taking into account the size of the magnetic particles.

[0067] Minimum value L of the distance between magnetization reversals minThe minimum value L of the magnetization reversal distance is obtained as follows. First, a sample is prepared in the same manner as the measurement method for the data track width W. Next, the data recording pattern of the data band DB portion of the magnetic layer 43 of the sample is observed using a magnetic force microscope (MFM) to obtain an MFM image. BRUKER's Dimension Icon and its analysis software are used as the MFM. The measurement area of ​​the MFM image is 2 μm × 2 μm, and this 2 μm × 2 μm measurement area is divided into 512 × 512 (= 262,144) measurement points. MFM measurements are performed on three different 2 μm × 2 μm measurement areas, thus obtaining three MFM images. Fifty inter-bit distances are measured from the two-dimensional relief chart of the recording pattern of the obtained MFM image. These inter-bit distance measurements are performed using the analysis software included with Dimension Icon. The value that is approximately the greatest common divisor of the 50 measured inter-bit distances is the minimum value L of the magnetization reversal distance. min The measurement conditions were as follows: sweep speed: 1 Hz, chip used: MFMR-20, lift height: 20 nm, correction: Flatten order 3.

[0068] The magnetic layer 43 is configured to record signals in the data band DB with a bit length (1 bit length) T. From the viewpoint of improving the linear recording density D of the magnetic tape MT, the upper limit of the bit length T of the signal that can be recorded in the data band DB is preferably 47.0 nm or less, more preferably 46.6 nm or less, even more preferably 46.3 nm or less, 46.2 nm or less, 46.0 nm or less, 44.0 nm or less, 42.3 nm or less, or 40.0 nm or less. Considering the size of the magnetic particles, the lower limit of the bit length T of the signal that can be recorded in the data band DB is preferably 20.0 nm or more.

[0069] The bit length T of the signal that can be recorded in the databand DB is the minimum value L of the magnetization reversal distance. min It can be determined in the same way as the measurement method.

[0070] From the viewpoint of improving the linear recording density D of the magnetic tape MT, the bit area of ​​the signal that can be recorded in the data band DB is preferably 40,000 nm. ２More preferably, 35,000 nm ２ More preferably, 30,000 nm ２ Below, 25000nm ２ or less than 20,000 nm ２ The following applies:

[0071] The bit area of ​​a signal that can be recorded in the databand DB is determined as follows: First, three MFM images are obtained in the same manner as the method for measuring the data track width W. Next, the data track width W and bit length T are determined in the same manner as the methods for measuring the data track width W and bit length T. Then, the bit area (W × T) of the signal that can be recorded in the databand DB is determined using the data track width W and bit length T.

[0072] The servo pattern is a magnetized region formed by magnetizing a specific region of the magnetic layer 43 in a specific direction using a servo light head during magnetic tape manufacturing. The region of the servo band SB in which the servo pattern is not formed (hereinafter referred to as the "non-pattern region") may be a magnetized region in which the magnetic layer 43 is magnetized, or it may be a non-magnetized region in which the magnetic layer 43 is not magnetized. If the non-pattern region is a magnetized region, the servo pattern formation region and the non-pattern region are magnetized in different directions (for example, opposite directions).

[0073] In the LTO standard, the servo band SB has a servo pattern formed on it, consisting of multiple servo stripes (linear magnetization regions) 113 that are inclined with respect to the Y-axis extending in the width direction of the magnetic tape MT, as shown in Figure 7.

[0074] The servo band SB includes multiple servo frames 110. Each servo frame 110 consists of 18 servo stripes 113. Specifically, each servo frame 110 consists of a servo subframe 1 (111) and a servo subframe 2 (112).

[0075] The servo subframe 1 (111) consists of an A-burst 111A and a B-burst 111B. The B-burst 111B is positioned adjacent to the A-burst 111A. The A-burst 111A is positioned at a predetermined angle θ with respect to the Y-axis extending in the width direction of the magnetic tape MT. １ It is equipped with five servo stripes 113 that are inclined and formed at predetermined intervals. In Figure 7, these five servo stripes 113 are arranged from the EOT (End Of Tape) to the BOT (Beginning Of Tape) of the magnetic tape MT, indicated by the symbol A １ A ２ A ３ A ４ A ５ It is indicated by the notation.

[0076] The B-burst 111B is at a predetermined angle θ with respect to the Y-axis extending in the width direction of the magnetic tape MT. ２ It is equipped with five servo stripes 113 that are inclined and formed at predetermined intervals. In Figure 7, these five servo stripes 113 are connected to the magnetic tape MT from EOT to BOT, indicated by the letter B １ , B ２ , B ３ , B ４ , B ５ It is indicated by the notation.

[0077] The servo stripe 113 of B-burst 111B is inclined in the opposite direction to the servo stripe 113 of A-burst 111A. The servo stripe 113 of A-burst 111A and the servo stripe 113 of B-burst 111B are asymmetrical with respect to the Y-axis extending in the width direction of the magnetic tape MT. That is, the servo stripe 113 of A-burst 111A and the servo stripe 113 of B-burst 111B are arranged in a roughly V-shape. Because the servo stripe 113 of A-burst 111A and the servo stripe 113 of B-burst 111B are asymmetrical with respect to the Y-axis, when the head unit 51 is tilted diagonally with respect to the Y-axis, there exists a state in which the servo stripe 113 of A-burst 111A and the servo stripe 113 of B-burst 111B are roughly symmetrical with respect to the central axis (Y' axis) extending in the longitudinal direction of the sliding surface 51S of the head unit 51. By changing the tilt of the head unit 56 based on this state, it becomes possible to adjust the distance between the pair of servo lead sections 52, 52 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 pair of servo lead sections 52, 52 can be positioned to face the specified position of the servo band SB.

[0078] The predetermined angle θ is the inclination angle of the servo stripe 113 of the A-burst 111A. １ And, the predetermined angle θ is the inclination angle of the servo stripe 113 of the B-burst 111B. ２ This is different. More specifically, the predetermined angle θ of the servo stripe 113 of the A-burst 111A １ However, the predetermined angle θ of the servo stripe 113 of B burst 111B ２ It may be larger in comparison, and the predetermined angle θ of the servo stripe 113 of B burst 111B ２ However, the predetermined angle θ of the servo stripe 113 of the A-burst 111A １It may be larger than the angle of the servo stripe 113 of the A-burst 111A. That is, the inclination of the servo stripe 113 of the A-burst 111A may be larger than the inclination of the servo stripe 113 of the B-burst 111B, and the inclination of the servo stripe 113 of the B-burst 111B may be larger than the inclination of the servo stripe 113 of the A-burst 111A. Note that in Figure 7, the predetermined angle θ of the servo stripe 113 of the A-burst 111A １ However, the predetermined angle θ of the servo stripe 113 of B burst 111B ２ A larger example is shown below. Below, the predetermined angle θ of the servo stripe 113 of the A-burst 111A １ However, the predetermined angle θ of the servo stripe 113 of B burst 111B ２ Let's explain the case where it is larger than [the specified value].

[0079] The servo subframe 2 (112) consists of a C-burst 112C and a D-burst 112D. The D-burst 112D is positioned adjacent to the C-burst 112C. The C-burst 112C is positioned at a predetermined angle θ with respect to the Y-axis extending in the width direction of the magnetic tape MT. １ It is equipped with four servo stripes 113 that are inclined and formed at predetermined intervals. In Figure 7, these four servo stripes 113 are connected to the magnetic tape MT from EOT to BOT, indicated by the letter C １ , C ２ , C ３ , C ４ It is indicated by the notation.

[0080] The D-burst 112D is at a predetermined angle θ with respect to the Y-axis extending in the width direction of the magnetic tape MT. ２ It is equipped with four servo stripes 113 that are inclined and formed at predetermined intervals. In Figure 7, these four servo stripes 113 are connected to the magnetic tape MT from EOT to BOT by the symbol D １ , D ２ , D ３ , D ４ It is indicated by the notation.

[0081] The servo stripe 113 of the D-burst 112D is inclined in the opposite direction to the servo stripe 113 of the C-burst 112C. The servo stripe 113 of the C-burst 112C and the servo stripe 113 of the D-burst 112D are asymmetrical with respect to the Y-axis, which extends in the width direction of the magnetic tape MT. That is, the servo stripe 113 of the C-burst 112C and the servo stripe 113 of the D-burst 112D are arranged in a roughly V-shape. Because the servo stripe 113 of the C-burst 112C and the servo stripe 113 of the D-burst 112D are asymmetrical with respect to the Y-axis, when the head unit 51 is tilted diagonally with respect to the X-axis, there is a state in which the servo stripe 113 of the C-burst 112C and the servo stripe 113 of the D-burst 112D are roughly symmetrical with respect to the central axis of the head unit 51. By changing the tilt of the head unit 51 based on this state, it becomes possible to adjust the distance between the servos.

[0082] The predetermined angle θ is the inclination angle of the servo stripe 113 of the C-burst 112C. １ And the predetermined angle θ is the inclination angle of the servo stripe 113 of the D-burst 112D. ２ This is different. More specifically, the predetermined angle θ of the servo stripe 113 of the C burst 112C １ However, the predetermined angle θ of the servo stripe 113 of the D-burst 112D ２ It may be larger in comparison, and the predetermined angle θ of the servo stripe 113 of D-burst 112D ２ However, the predetermined angle θ of the servo stripe 113 of the C burst 112C １ It may be larger than the angle of the servo stripe 113 of the C-burst 112C. That is, the inclination of the servo stripe 113 of the C-burst 112C may be larger than the inclination of the servo stripe 113 of the D-burst 112D, and the inclination of the servo stripe 113 of the D-burst 112D may be larger than the inclination of the servo stripe 113 of the C-burst 112C. In Figure 7, the predetermined angle θ of the servo stripe 113 of the C-burst 112C. １ However, the predetermined angle θ of the servo stripe 113 of the D-burst 112D ２Examples larger than are shown. Below, a predetermined angle θ of the servo stripe 113 of the C burst 112C １ is larger than a predetermined angle θ of the servo stripe 113 of the D burst 112D ２ will be described.

[0083] The above-mentioned predetermined angle θ of the servo stripe 113 in the A burst 111A and the C burst 112C １ is preferably 18° or more and 28° or less, more preferably 18° or more and 26° or less. The above-mentioned predetermined angle θ of the servo stripe 113 in the B burst 111B and the D burst 112D <b ２ is preferably -4° or more and 6° or less, more preferably -2° or more and 6° or less. The servo stripe 113 in the A burst 111A and the C burst 112C is an example of the first magnetization region. The servo stripe 113 in the B burst 111B and the D burst 112D is an example of the second magnetization region.

[0084] By reading the servo band SB with the head unit 51, information for obtaining the tape speed and the vertical position of the head unit 51 is obtained. The tape speed is calculated from the time between four timing signals (A1-C1, A2-C2, A3-C3, A4-C4). The head position is calculated from the time between the aforementioned four timing signals and another four timing signals (A １ -B １ 、A ２ -B ２ 、A ３ -B ３ 、A ４ -B ４ ). The servo pattern may be in a shape including two parallel lines.

[0085] As shown in FIG. 7, the servo pattern (that is, a plurality of servo stripes 113) is preferably arranged linearly in the longitudinal direction of the magnetic tape MT. That is, the servo band SB preferably has a linear shape in the longitudinal direction of the magnetic tape MT.

[0086] The average thickness t of the magnetic layer 43 ２ It should be noted that there may be some inaccuracies in the translation due to the complexity of the patent text and the need to ensure the integrity of the tags. It is recommended to double-check with relevant professionals for important patent translations.The upper limit is 0.07 μm or less, preferably 0.06 μm or less, and more preferably 0.05 μm or less. Average thickness t of the magnetic layer 43 ２ If the upper limit is 0.07 μm or less, the effect of the demagnetizing field can be reduced when a ring-type head is used as the recording head, thereby obtaining excellent electromagnetic conversion characteristics.

[0087] Average thickness t of the magnetic layer 43 ２ The lower limit is preferably 0.03 μm or more, more preferably 0.04 μm or more. Average thickness t of the magnetic layer 43 ２ If the lower limit is 0.03 μm or higher, output can be secured when an MR type head is used as the playback head, thus obtaining excellent electromagnetic conversion characteristics.

[0088] Average thickness t of the magnetic layer 43 ２ The numerical range may be defined by either of the above upper limits and either of the above lower limits, preferably 0.03 μm or more and 0.07 μm or less, more preferably 0.03 μm or more and 0.06 μm or less, and even more preferably 0.03 μm or more and 0.05 μm or less.

[0089] Average thickness t of the magnetic layer 43 ２ The following is how it is obtained. First, the magnetic tape MT housed in the cartridge 10 is unwound, and three samples are prepared by cutting the magnetic tape MT to a length of 250 mm from one end of the outer circumference of the magnetic tape MT at positions 10 m to 20 m, 30 m to 40 m, and 50 m to 60 m in the longitudinal direction. Next, each sample is processed by the FIB (Focused Ion Beam) method or the like to create a thin section. When using the FIB method, a carbon layer and a tungsten layer are formed as protective films as a pretreatment before observing the TEM image of the cross section described later. The carbon layer is formed on the magnetic surface and back surface of the magnetic tape MT by vapor deposition, and the tungsten layer is further formed on the magnetic surface by vapor deposition or sputtering. This thinning is performed along the longitudinal direction of the magnetic tape MT. That is, this thinning creates a cross section parallel to both the longitudinal and thickness directions of the magnetic tape MT.

[0090] The cross-sections of each thinned sample obtained were observed using a transmission electron microscope (TEM) under the following conditions to obtain TEM images of each thinned sample. The magnification and acceleration voltage may be adjusted as appropriate depending on the type of instrument. Instrument: TEM (Hitachi H9000NAR) Acceleration voltage: 300kV Magnification: 100,000x

[0091] Next, the TEM images of each thinned sample are used to measure the thickness of the magnetic layer 43 at 10 points on each thinned sample. The 10 measurement points on each thinned sample are randomly selected from the sample so that they are all different locations along the longitudinal direction of the magnetic tape MT. The average value obtained by simply averaging (arithmetic mean) the measured values ​​of each thinned sample (a total of 30 points of magnetic layer 43 thickness) is then used to determine the average thickness t of the magnetic layer 43. ２ Let it be [nm].

[0092] (Magnetic Particles) The magnetic particles are particles containing hexagonal ferrite (hereinafter referred to as "hexagonal ferrite particles"). Preferably, the magnetic particles are oriented in a magnetic field perpendicular to the magnetic tape MT. In this specification, the perpendicular direction of the magnetic tape MT means the thickness direction of the magnetic tape MT.

[0093] (Hexagonal Ferrite Particles) Hexagonal ferrite particles have a plate-like shape, such as a hexagonal plate, or a columnar shape, such as a hexagonal prism (provided that the thickness or height is smaller than the major axis of the plate or base). In this disclosure, hexagonal plate-like and hexagonal prism-like shapes mean not only mathematically or geometrically defined shapes, but also similar shapes that include differences (e.g., errors or distortions) that are permissible in the properties of the magnetic particles and the manufacturing process of the magnetic particles.

[0094] The hexagonal ferrite particles contain Fe and a metal M1 other than Fe. Metal M1 includes Ba and Sr as alkaline earth metals. Metal M1 may further contain Ca as an alkaline earth metal. Metal M1 may also contain Pb in addition to alkaline earth metals.

[0095] The hexagonal ferrite particles may further contain metal M2 in addition to Fe and metal M1. Preferably, metal M2 can substitute for some of the Fe sites in the crystal structure of the hexagonal ferrite. For example, metal M2 includes at least one selected from the group consisting of rare earth elements, transition metal elements other than Fe, metal elements of group 13 of the periodic table, and metal elements of group 14 of the periodic table, and among these, at least one selected from the group consisting of Ti, Al, and Nd is preferred.

[0096] In this disclosure, rare earth elements refer to Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. Transition metal elements other than Fe refer to Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Zr, Nb, Mo, Ru, Hf, Ta, and W. Metal elements of Group 13 of the periodic table refer to Al, Ga, In, and Tl. Metal elements of Group 14 of the periodic table refer to Ge, Sn, and Pb.

[0097] Hexagonal ferrite particles may specifically be, for example, barium ferrite particles or strontium ferrite particles. In this disclosure, strontium ferrite particles refer to hexagonal ferrite particles in which the average atomic ratio of Sr to metal M1 (Sr / M1) is 50 atomic percent or more. Therefore, hexagonal ferrite particles containing Sr and a metal M1 other than Sr are included in strontium ferrite particles if the average atomic ratio of Sr to metal M1 (Sr / M1) is 50 atomic percent or more. For example, when metal M1 contains Sr and Ba, hexagonal ferrite particles in which the average atomic ratio of Sr to the total amount of Sr and Ba (Sr / (Sr+Ba)) is 50 atomic percent or more are called strontium ferrite particles.

[0098] In this disclosure, barium ferrite particles refer to hexagonal ferrite particles in which the average atomic ratio of Ba to metal M1 (Ba / M1) is 50 atomic percent or more. Therefore, hexagonal ferrite particles containing Ba and metal M1 other than Ba ​​are included in barium ferrite particles if the average atomic ratio of Ba to metal M1 (Ba / M1) is 50 atomic percent or more. For example, when metal M1 contains Sr and Ba, hexagonal ferrite particles in which the average atomic ratio of Ba to the total amount of Sr and Ba (Ba / (Sr+Ba)) is 50 atomic percent or more are called barium ferrite particles.

[0099] The average atomic ratio of Sr to Ba (Sr / Ba) is preferably 0.02 to 3.00, more preferably 0.02 to 2.00, and even more preferably 0.02 to 1.00. When the average atomic ratio (Sr / Ba) is 0.02 or higher, the decrease in the effect of improving magnetic properties due to the addition of Sr (for example, the effect of improving thermal stability (magnetic anisotropy constant Ku) and coercivity Hc derived from strontium ferrite) can be suppressed. On the other hand, when the average atomic ratio (Sr / Ba) is 3.00 or lower, large variations in magnetic properties can be suppressed.

[0100] Hexagonal ferrite may more specifically have an average composition represented by the following general formula (A): Ba （１－ｘ） Sr ｘ Fe （１２－ｙ） α ｙ O １９ ... (A) (However, in formula (A), α represents at least one selected from the group consisting of rare earth elements, transition metal elements other than Fe, metal elements of Group 13 of the periodic table, and metal elements of Group 14 of the periodic table. x is preferably in the range of 0.020 ≤ x ≤ 0.750, more preferably 0.020 ≤ x ≤ 0.670, and even more preferably 0.020 ≤ x ≤ 0.500. y is, for example, in the range of 0 ≤ y ≤ 0.200, preferably 0 ≤ y ≤ 0.160, more preferably 0.002 ≤ y ≤ 0.160, and even more preferably 0.002 ≤ y ≤ 0.140.)

[0101] The average atomic ratio of Sr to Ba is calculated from the analysis values ​​obtained using TEM-EDX (Transmission Electron Microscope - Energy Dispersive X-ray Spectroscopy) (Hitachi High-Technologies Corporation HD-2700) as follows. First, the magnetic tape MT is unwound from the cartridge 10, and three pieces of the magnetic tape MT are cut from one end on the outer circumference of the magnetic tape MT at a position of 30m to 40m in the longitudinal direction to prepare three samples. Next, each sample is processed and thinned using the FIB method or the like. When using the FIB method, a carbon layer and a tungsten layer are formed as protective films as a pretreatment before observing the TEM image of the cross-section described later. The carbon layer is formed on the magnetic layer side surface and the back layer side surface of the magnetic tape MT by vapor deposition, and the tungsten layer is further formed on the magnetic layer side surface by vapor deposition or sputtering. This thinning is performed along the longitudinal direction of the magnetic tape MT. In other words, this thinning process creates cross-sections parallel to both the longitudinal and thickness directions of the magnetic tape MT. The above cross-sections of each thinned sample are observed by TEM at an acceleration voltage of 200kV and a total magnification of 500,000x to obtain TEM images of each thinned sample. Next, EDX measurements are performed on the magnetic layer portion from the TEM images of each thinned sample to determine the atomic ratio of Sr to Ba (Sr / Ba). The atomic ratios (Sr / Ba) obtained from each of the three thinned samples are simply averaged (arithmetic mean) to obtain the average atomic ratio (Sr / Ba).

[0102] The average atomic ratio of Sr to metal M1 (Sr / M1) is determined as follows: First, TEM images are obtained from three thinned samples in the same manner as the average atomic ratio of Sr to Ba (Sr / Ba). Next, EDX measurements are performed on the magnetic layer portion from the TEM images obtained from each thinned sample to determine the average atomic ratio of Sr to metal M1 (Sr / M1). The atomic ratios (Sr / M1) obtained from each of the three thinned samples are simply averaged (arithmetic mean) to obtain the average atomic ratio (Sr / M1).

[0103] The average atomic ratio of Ba to metal M1 (Ba / M1) is determined as follows: First, TEM images are obtained from three thinned samples in the same manner as the average atomic ratio of Sr to Ba (Sr / Ba). Next, EDX measurements are performed on the magnetic layer portion from the TEM images obtained from each thinned sample to determine the average atomic ratio of Ba to metal M1 (Ba / M1). The atomic ratios (Ba / M1) obtained from each of the three thinned samples are simply averaged (arithmetic mean) to obtain the average atomic ratio (Ba / M1).

[0104] The average composition represented by general formula (A) is determined as follows. First, TEM images of three thinned samples are obtained in the same manner as the average atomic ratio of Sr to Ba (Sr / Ba). Next, EDX measurements are performed on the magnetic layer portion from the TEM images of each obtained thinned sample to determine the average composition ratios (average atomic ratios) of Ba, Sr, Fe, and M.

[0105] From the viewpoint of improving linear recording density, the upper limit of the average particle size of magnetic particles is preferably 19.0 nm or less, more preferably 18.0 nm or less, and even more preferably 17.0 nm or less, 16.0 nm or less, or 15.0 nm or less.

[0106] The lower limit of the average particle size of magnetic particles is preferably 12.0 nm or larger, and more preferably 13.0 nm or larger, from the viewpoint of improving the dispersibility of magnetic particles and improving electromagnetic conversion characteristics (e.g., SNR (Signal-to-Noise Ratio)).

[0107] The numerical range of the average particle size of the magnetic particles may be defined by either of the above upper and lower limits, preferably 12.0 nm to 19.0 nm, more preferably 12.0 nm to 18.0 nm, and even more preferably 12.0 nm to 17.0 nm, 13.0 nm to 17.0 nm, or 13.0 nm to 16.0 nm.

[0108] The average aspect ratio of the magnetic particles is preferably 1.0 to 3.0, more preferably 1.5 to 2.8, and even more preferably 1.8 to 2.7. When the average aspect ratio of the magnetic particles is within the range of 1.0 to 3.0, aggregation of the magnetic particles can be suppressed. Furthermore, the resistance applied to the magnetic particles when vertically oriented during the formation process of the magnetic layer 43 can be suppressed. Therefore, the vertical orientation of the magnetic particles can be improved.

[0109] The average particle size and average aspect ratio of magnetic particles are determined as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and the magnetic tape MT is cut at a position 30 to 40 m in the longitudinal direction from one end on the outer circumference of the magnetic tape MT. Next, the magnetic tape MT to be measured is processed and thinned using the FIB method or the like. When using the FIB method, a carbon layer and a tungsten layer are formed as protective films as a pretreatment before observing the TEM image of the cross-section described later. The carbon layer is formed on the magnetic surface and back surface of the magnetic tape MT by vapor deposition, and the tungsten layer is further formed on the magnetic surface by vapor deposition or sputtering. This thinning is performed along the length direction (longitudinal direction) of the magnetic tape MT. That is, this thinning creates a cross-section parallel to both the longitudinal and thickness directions of the magnetic tape MT.

[0110] The cross-section of the obtained thin section sample is observed using a transmission electron microscope (Hitachi High-Technologies Corporation H-9500) with an acceleration voltage of 200kV and a total magnification of 500,000x, ensuring that the entire magnetic layer 43 is included in the thickness direction of the magnetic layer 43, and a TEM image is taken. The TEM images are prepared in a number that allows for the extraction of 50 particles capable of measuring the plate diameter DB and plate thickness DA (see Figure 8) shown below.

[0111] In this specification, the particle size of hexagonal ferrite (hereinafter referred to as "particle size") is defined as follows: If the shape of the particle observed in the TEM image is plate-like or columnar (however, the thickness or height is smaller than the major axis of the plate surface or base) as shown in Figure 8, the major axis of the plate surface or base is defined as the plate diameter DB. The thickness or height of the particle observed in the TEM image is defined as the plate thickness DA. If the thickness or height of a particle is not constant within a single particle observed in the TEM image, the thickness or height of the largest particle is defined as the plate thickness DA.

[0112] Next, 50 particles are selected from the captured TEM image based on the following criteria: Particles whose portion extends outside the field of view of the TEM image are not measured; only particles with clear outlines and existing in isolation are measured. If there is overlap between particles, those with clear boundaries and whose overall shape can be determined are measured as individual particles; however, particles with unclear boundaries and whose overall shape cannot be determined are not measured as their shape cannot be determined.

[0113] Figures 9 and 10 show the first and second examples of TEM images, respectively. In Figures 9 and 10, for example, the particles indicated by arrows a and d are selected because their particle thickness (thickness or height) DA can be clearly identified. The particle thickness DA of each of the 50 selected particles is measured. The average particle thickness DA obtained by simply averaging (arithmetic mean) the obtained particle thicknesses DA is calculated. ave We will find the average plate thickness DA. ave This is the average particle thickness. Next, the diameter DB of each magnetic particle is measured. To measure the particle diameter DB, 50 particles whose diameter DB can be clearly identified are selected from the captured TEM images. For example, in Figures 9 and 10, the particles indicated by arrows b and c are selected because their diameter DB can be clearly identified. The diameter DB of each of the 50 selected particles is measured. The average diameter DB obtained in this way is calculated by taking a simple average (arithmetic mean) of the resulting diameter DB. ave We will find the average plate diameter DB. ave However, this is the average particle size. And the average plate thickness DA ave and average plate diameter DBave From the average aspect ratio of the particles (DB) ave / DA ave )

[0114] The upper limit of the average particle volume of magnetic particles is 1.60 × 10⁻⁶, from the viewpoint of improving linear recording density. ３ nm ３ The following is preferably 1.40 × 10 ３ nm ３ More preferably 1.30 × 10 ３ nm ３ Below, 1.20 × 10 ３ nm ３ Below, 1.10 x 10 ３ nm ３ The following or 1.00 x 10 ３ nm ３ The following applies:

[0115] From the viewpoint of improving the dispersibility of magnetic particles and enhancing electromagnetic conversion characteristics (e.g., SNR), the lower limit of the average particle volume of magnetic particles is preferably 0.500 × 10⁻⁶. ３ nm ３ More preferably 0.600 × 10 ３ nm ３ That's all.

[0116] The numerical range of the average particle volume of the magnetic particles may be defined by either of the above upper and lower limits, preferably 0.500 × 10 ３ nm ３ The above 1.60 x 10 ３ nm ３ More preferably, 0.500 × 10 ３ nm ３ The above 1.40 x 10 ３ nm ３ More preferably, 0.500 × 10 ３ nm ３ The above 1.30 x 10 ３ nm ３ Below, 0.600 x 10 ３ nm ３ The above 1.20 x 10 ３ nm ３ Below, 0.600 x 10 ３ nm ３ The above 1.10 x 10３ nm ３ The following or 0.600 x 10 ３ nm ３ The above 1.00 x 10 ３ nm ３ The following applies:

[0117] The average particle volume of magnetic particles can be determined as follows. First, the average plate thickness DA is calculated using the method described above for calculating the average particle size of magnetic particles. ave and average plate diameter DB ave Next, we calculate the average particle volume V of the magnetic particles using the following formula.

[0118] (Binding agent) The binding agent includes, for example, a thermoplastic resin. The binding agent may further include a thermosetting resin or a reactive resin, etc.

[0119] The thermoplastic resin includes, for example, a first thermoplastic resin (first binder) containing chlorine atoms and a second thermoplastic resin (second binder) containing nitrogen atoms. More specifically, the thermoplastic resin includes a vinyl chloride resin and a urethane resin. In this specification, a vinyl chloride resin means a polymer containing structural units derived from vinyl chloride. More specifically, for example, a vinyl chloride resin means a homopolymer of vinyl chloride, a polymer of vinyl chloride and a comonomer copolymerizable therewith, and mixtures of these polymers.

[0120] 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.

[0121] A urethane resin refers to a resin in which at least a portion of the molecular chains constituting the resin contains urethane bonds, and may be a urethane resin or a copolymer in which a portion of the molecular chains contains urethane bonds. A urethane resin may be obtained, for example, by reacting a polyisocyanate with a polyol. Alternatively, a urethane resin may be obtained, for example, by reacting a polyester with a polyol. In this specification, urethane resins also include those obtained by reaction with a curing agent.

[0122] The polyisocyanate includes, for example, at least one selected from the group consisting of diphenylmethane diisocyanate (MDI), tolylene diisocyanate (TDI), xylylene diisocyanate (XDI), 1,5-pentamethylene diisocyanate (PDI), hexamethylene diisocyanate (HDI), and isophorone diisocyanate (IPDI). In this specification, polyisocyanate means a compound having two or more isocyanate groups in its molecule. The polyisocyanate may also be a polyisocyanate contained in the curing agent.

[0123] Any suitable polyol can be used as the polyol, as long as it has two or more OH groups. The polyol includes, for example, at least one selected from the group consisting of polyols having two OH groups (diols), polyols having three OH groups (triols), polyols having four OH groups (tetraols), polyols having five OH groups (pentaols), and polyols having six OH groups (hexaols). Specifically, the polyol includes, for example, at least one selected from the group consisting of polyester polyols, polyether polyols, polycarbonate polyols, polyesteramide polyols, and acrylate polyols.

[0124] The polyester includes, for example, at least one selected from the group consisting of phthalate polyesters and aliphatic polyesters.

[0125] The thermoplastic resin may further include thermoplastic resins other than vinyl chloride resins and urethane resins. Such thermoplastic resins include, for example, at least one selected from the group consisting of vinyl acetate, acrylic acid ester-acrylonitrile copolymer, acrylic acid ester-acrylonitrile copolymer, acrylic acid ester-vinylidene chloride copolymer, methacrylic acid ester-vinylidene chloride copolymer, methacrylic acid ester-ethylene copolymer, polyvinyl fluoride, vinylidene chloride-acrylonitrile copolymer, acrylonitrile-butadiene copolymer, polyamide resin, polyvinyl butyral, cellulose derivatives (cellulose acetate butyrate, cellulose diacetate, cellulose triacetate, cellulose propionate, nitrocellulose), styrene butadiene copolymer, polyester resin, amino resin, and synthetic rubber.

[0126] The thermosetting resin includes, for example, at least one selected from the group consisting of phenolic resins, epoxy resins, polyurethane curing resins, urea resins, melamine resins, alkyd resins, silicone resins, polyamine resins, and urea-formaldehyde resins.

[0127] All of the above binders contain -SO4 for the purpose of improving the dispersibility of magnetic particles. ３ M, -OSO ３ M, -COOM, P=O(OM) ２ (However, in the formula, M represents a hydrogen atom or an alkali metal such as lithium, potassium, or sodium) or -NR1R2, -NR1R2R3 ＋ X － Side-chain amines having terminal groups represented by >NR1R2 ＋ X － Main-chain amines represented by (wherein R1, R2, and R3 represent hydrogen atoms or hydrocarbon groups, X － ) represents halogen element ions such as fluorine, chlorine, bromine, and iodine, inorganic ions, or organic ions. ), Furthermore, polar functional groups such as -OH, -SH, -CN, and epoxy groups may be introduced. The amount of these polar functional groups introduced into the binder is 10 －１ The above 10 －８ It is preferable that the amount is 10 moles / g or less.－２ The above 10 －６ It is more preferable that the concentration is 1 / mole / g or less.

[0128] (Lubricant) The lubricant may be a liquid lubricant. Preferably, the lubricant contains both fatty acids and fatty acid esters. Containing both fatty acids and fatty acid esters in the lubricant can improve driving stability. Preferably, the melting points of the fatty acids and the fatty acid esters are different. The fatty acid may be a solid lubricant at room temperature. The fatty acid ester may be a liquid lubricant at room temperature. Here, room temperature refers to a temperature range of 20°C ± 15°C (5°C to 35°C).

[0129] The fatty acid may preferably be a compound represented by the following general formula (1) or (2). For example, the fatty acid may include either the compound represented by the following general formula (1) and the compound represented by the following general formula (2), or both.

[0130] Furthermore, the fatty acid ester may preferably be a compound represented by the following general formulas (3), (4), or (5). For example, the fatty acid ester may include one, two, or three of the compounds represented by the following general formulas (3), (4), and (5).

[0131] The lubricant can suppress the increase in the coefficient of dynamic friction due to repeated recording or playback of magnetic tape MT by including either one or both of the compounds shown in general formula (1) and general formula (2), and one, two, or three of the compounds shown in general formula (3), general formula (4), and general formula (5).

[0132] CH3 (CH2) k COOH ... (1) (However, in general formula (1), k is an integer selected from the range of 14 to 22, more preferably from the range of 14 to 18.)

[0133] CH3 (CH2) n CH = CH(CH2)m COOH ... (2) (However, in general formula (2), the sum of n and m is an integer selected from the range of 12 to 20, more preferably from the range of 14 to 18.)

[0134] CH3 (CH2) p COO (CH2) q CH3 ... (3) (However, in general formula (3), p is an integer selected from the range of 14 to 22, more preferably from 14 to 18, and q is an integer selected from the range of 2 to 5, more preferably from 2 to 4.)

[0135] CH3 (CH2) r COO-(CH2) s CH(CH3)² ... (4) (wherein in general formula (4), r is an integer selected from the range of 14 to 22, and s is an integer selected from the range of 1 to 3.)

[0136] CH3 (CH2) ｔ COO-(CH)(CH3)CH2(CH3) ｕ ... (5) (However, in general formula (5), t is an integer selected from the range of 14 to 22, and u is an integer selected from the range of 1 to 3.)

[0137] (Dispersant) The dispersant may be a compound that, in the coating for forming the magnetic layer, assists in the dispersion of magnetic particles by interacting with them. The dispersant may be adsorbable onto the surface of the magnetic particles contained in the magnetic layer 43. The dispersant may, for example, have at least one acidic functional group. The acidic functional group may be an acidic adsorbent group that can be adsorbed onto the surface of the magnetic particles by interacting with them. The at least one acidic functional group may include at least one selected from the group consisting of, for example, a phosphate group, a carboxyl group, and a sulfonic acid group.

[0138] The dispersant includes, for example, at least one selected from the group consisting of phosphonic acid compounds, carboxylic acid compounds, and sulfonic acid compounds. More specifically, the dispersant includes, for example, at least one selected from the group consisting of phenylphosphonic acid, benzoic acid, naphthoic acid, hydroxybenzoic acid, isophthalic acid, oleic acid, cyclohexanecarboxylic acid, adipic acid, and citric acid. Naphthoic acid includes, for example, 1-naphthoic acid. Hydroxybenzoic acid includes, for example, 4-hydroxybenzoic acid.

[0139] The phosphonic acid compound includes, for example, at least one selected from the group consisting of aromatic phosphonic acid compounds, chain-type aliphatic phosphonic acid compounds, and cyclic aliphatic phosphonic acid compounds. The phosphonic acid compound may include, for example, one or both of a monovalent phosphonic acid compound and a polyvalent phosphonic acid compound. The aromatic phosphonic acid compound includes, for example, phenylphosphonic acid.

[0140] Carboxylic acid compounds include, for example, at least one selected from the group consisting of aromatic carboxylic acid compounds, chain-type aliphatic carboxylic acid compounds, and cyclic aliphatic carboxylic acid compounds. Carboxylic acid compounds may include, for example, one or both of monovalent carboxylic acid compounds and polyvalent carboxylic acid compounds. Aromatic carboxylic acid compounds include, for example, at least one selected from the group consisting of benzoic acid, naphthoic acid, hydroxybenzoic acid, and isophthalic acid. Chain-type aliphatic carboxylic acid compounds include, for example, at least one selected from the group consisting of adipic acid, citric acid, and oleic acid. Cyclic aliphatic carboxylic acid compounds include, for example, cyclohexanecarboxylic acid.

[0141] Examples of carboxylic acid compounds include fatty acids with 12 to 18 carbon atoms such as caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, oleic acid, elaidic acid, linoleic acid, linolenic acid, and stearolic acid [RCOOH (where R is an alkyl group or alkenyl group with 11 to 17 carbon atoms)]; metal soaps made from alkali metals or alkaline earth metals of the above fatty acids; fluorine-containing compounds of the above fatty acid esters; amides of the above fatty acids; polyalkylene oxide alkyl phosphate esters; lecithin; trialkyl polyolefin oxyquaternary ammonium salts (alkyl has 1 to 5 carbon atoms, olefin is ethylene, propylene, etc.); phenylphosphonic acid; copper phthalocyanine, etc. These may be used individually or in combination of two or more.

[0142] The sulfonic acid compound includes, for example, at least one selected from the group consisting of aromatic sulfonic acid compounds, chain-type aliphatic sulfonic acid compounds, and cyclic aliphatic sulfonic acid compounds. The sulfonic acid compound may also include, for example, one or both of a monovalent sulfonic acid compound and a polyvalent sulfonic acid compound.

[0143] (Carbon particles) Some of the carbon particles contained in the magnetic layer 43 may protrude from the magnetic surface, forming multiple protrusions. The formation of multiple protrusions by carbon particles reduces the electrical resistance of the magnetic surface and suppresses the charging of the magnetic surface. Furthermore, the coefficient of dynamic friction μ during the running of the magnetic tape MT Ｔ This can be reduced.

[0144] The carbon particles may also function as an antistatic agent and a solid lubricant. Preferably, the average primary particle size of the carbon particles is 100.0 nm or less. When the average primary particle size of the carbon particles is 100.0 nm or less, even if the carbon particles are particles with a large particle size distribution (e.g., carbon black), the inclusion of particles that are excessively large relative to the thickness of the magnetic layer 43 is suppressed.

[0145] As carbon particles, at least one selected from the group consisting of carbon black, acetylene black, Ketjen black, carbon nanotubes, and graphene can be used, and among these carbon particles, carbon black is preferred. As carbon black, for example, Seest TA manufactured by Tokai Carbon Co., Ltd., Asahi #15, #15HS manufactured by Asahi Carbon Co., Ltd. can be used.

[0146] The magnetic layer 43 may contain hybrid particles instead of carbon particles, or it may contain hybrid particles together with carbon particles. The hybrid particles include 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 an inorganic particle. Specifically, for example, they may be hybrid carbon in which carbon is attached to the surface of a silica particle.

[0147] (Abrasive particles) Some of the abrasive particles contained in the magnetic layer 43 may protrude from the magnetic surface, forming multiple protrusions. When the head unit 51 and the magnetic tape MT slide against each other, the protrusions formed by the abrasive particles can come into contact with the head unit 51.

[0148] The lower limit of the Mohs hardness of the abrasive particles is preferably 7.0 or higher, more preferably 7.5 or higher, even more preferably 8.0 or higher, and particularly preferably 8.5 or higher, from the viewpoint of suppressing deformation due to contact with the head unit 51. The upper limit of the Mohs hardness of the abrasive particles is preferably 9.5 or lower, from the viewpoint of suppressing wear of the head unit 51.

[0149] The abrasive particles are preferably inorganic particles. Examples of inorganic particles include α-alumina, β-alumina, γ-alumina, silicon carbide, chromium oxide, cerium oxide, α-iron oxide, corundum, silicon nitride, titanium carbide, titanium oxide, silicon dioxide, tin oxide, magnesium oxide, tungsten oxide, zirconium oxide, boron nitride, zinc oxide, calcium carbonate, calcium sulfate, barium sulfate, molybdenum disulfide, needle-shaped α-iron oxide obtained by dehydrating and annealing raw materials of magnetic iron oxide, surface-treated with aluminum and / or silica as needed, and diamond powder. As inorganic particles, it is preferable to use alumina particles such as α-alumina, β-alumina, and γ-alumina, and silicon carbide. The abrasive particles may be needle-shaped, spherical, cube-shaped, etc., but those with corners on part of their shape are preferred because they have high abrasiveness.

[0150] (Antistatic agent) An antistatic agent can reduce the electrical resistance of a magnetic surface and suppress the charging of the magnetic surface. The antistatic agent includes, for example, at least one selected from the group consisting of natural surfactants, nonionic surfactants, and cationic surfactants.

[0151] (Curing agent) The curing agent includes, for example, a polyisocyanate. The polyisocyanate may include, for example, diphenylmethane diisocyanate (MDI), tolylene diisocyanate (TDI), xylylene diisocyanate (XDI), 1,5-pentamethylene diisocyanate (PDI), hexamethylene diisocyanate (HDI), or isophorone diisocyanate (IPDI) as an isocyanate source. The polyisocyanate may have a TMP adduct structure, an isocyanurate structure, a biuret structure, or an allophanate structure.

[0152] Polyisocyanates specifically include, for example, aromatic polyisocyanates such as adducts of tolylene diisocyanate (TDI) and active hydrogen compounds, and aliphatic polyisocyanates such as adducts of hexamethylene diisocyanate (HMDI) and active hydrogen compounds. The weight-average molecular weight of these polyisocyanates is preferably in the range of 100 to 3000.

[0153] (Rust inhibitors) Examples of rust inhibitors include phenols, naphthols, quinones, heterocyclic compounds containing nitrogen atoms, heterocyclic compounds containing oxygen atoms, and heterocyclic compounds containing sulfur atoms.

[0154] (Non-magnetic reinforcing particles) Examples of non-magnetic reinforcing particles include aluminum oxide (α, β, or γ alumina), chromium oxide, silicon oxide, diamond, garnet, emery, boron nitride, titanium carbide, silicon carbide, titanium carbide, and titanium oxide (rutile or anatase type titanium oxide).

[0155] (Underlayment) The underlayment 42 can alleviate the uneven surface shape of the substrate 41 and adjust the uneven surface shape of the magnetic surface. The underlayment 42 is a non-magnetic layer and includes, for example, non-magnetic particles, a binder, and a lubricant. It is preferable that the underlayment 42 can supply lubricant to the magnetic surface. The underlayment 42 may further include, if necessary, at least one additive selected from the group consisting of antistatic agents, hardening agents, and rust inhibitors.

[0156] The base layer 42 may have a plurality of pores. Lubricant may be stored in the pores. In this case, the supply of lubricant to the magnetic surface can be improved. From the viewpoint of improving the supply of lubricant to the magnetic surface, it is preferable that the pores extend perpendicular to the magnetic surface. From the viewpoint of improving the supply of lubricant to the magnetic surface, it is preferable that the pores of the base layer 42 and the pores of the magnetic layer 43 are connected.

[0157] Average thickness t of the base layer 42 ３The upper limit is preferably 0.80 μm or less, more preferably 0.70 μm or less, and even more preferably 0.60 μm or less, from the viewpoint of improving the recording capacity of the cartridge 10. Average thickness t of the base layer 42 ３ The lower limit is preferably 0.30 μm or more, more preferably 0.40 μm or more. Average thickness t of the underlayer 42 ３ If the lower limit is 0.30 μm or more, a second physical property (specifically, average hardness H) is required for a triangular pyramidal diamond indenter with a 142.3° edge angle to be pressed perpendicularly to the magnetic surface with a load of 150 μN. 150 The measurement of the second physical property can be suppressed from being affected by the substrate 41. Therefore, the decrease in the measurement accuracy of the second physical property can be suppressed.

[0158] Average thickness t of the base layer 42 ３ The numerical range may be defined by either of the above upper limits and either of the above lower limits, preferably 0.30 μm or more and 0.90 μm or less, more preferably 0.30 μm or more and 0.80 μm or less, even more preferably 0.30 μm or more and 0.70 μm or less, and particularly preferably 0.30 μm or more and 0.60 μm or less.

[0159] Average thickness t of the base layer 42 ３ The average thickness t of the magnetic layer 43 is ２ It is determined in the same manner as above. However, the magnification of the TEM image is adjusted as appropriate according to the thickness of the underlying layer 42.

[0160] (Non-magnetic particles) Non-magnetic particles include, for example, at least one of inorganic particles and organic particles. Non-magnetic particles may also be carbon particles such as carbon black. One type of non-magnetic particle may be used alone, or two or more types of non-magnetic particles may be used in combination. Inorganic particles include, for example, metals, metal oxides, metal carbonates, metal sulfates, metal nitrides, metal carbides, or metal sulfides. Examples of non-magnetic particles include needle-shaped, spherical, cubic, and plate-shaped shapes, but are not limited to these shapes.

[0161] (Binding agent, lubricant) The binding agent and lubricant are the same as those used in the magnetic layer 43 described above.

[0162] (Additives) The antistatic agent, hardening agent, and rust inhibitor are the same as those used in the magnetic layer 43 described above.

[0163] (Back layer) The back layer 44 contains a binder and non-magnetic particles. The back layer 44 may further contain at least one additive selected from the group consisting of lubricants, hardeners, and antistatic agents, if necessary. The binder and non-magnetic particles are the same as those in the base layer 42 described above. The lubricant, hardener, and antistatic agent are the same as those in the magnetic layer 43 described above.

[0164] The average particle size of the non-magnetic particles is preferably 10.0 nm to 150.0 nm, more preferably 15.0 nm to 110.0 nm. The average particle size of the non-magnetic particles is determined in the same manner as the average particle size of the magnetic particles. The non-magnetic particles may include non-magnetic particles having a particle size distribution of 2 or more.

[0165] Average thickness t of the back layer 44 ４ The upper limit is preferably 0.60 μm or less. When the upper limit of the average thickness of the back layer 44 is 0.60 μm or less, the average thickness of the magnetic tape MT is less than t Ｔ Even if the thickness is 5.50 μm or less, the thickness of the base layer 42 and the substrate 41 can be kept thick, so that the running stability of the magnetic tape MT can be maintained in the recording and playback device. Average thickness t of the back layer 44 ４ The lower limit is not particularly restricted, but for example, it is 0.20 μm or larger.

[0166] Average thickness t of the back layer 44 ４ This can be calculated as follows: First, the average thickness t of the magnetic tape MT. Ｔ Measure the average thickness t. Ｔ The measurement method is as follows: "Average thickness of magnetic tape t" ＴAs described in "[...]", the following steps are taken. Next, the magnetic tape MT housed in the cartridge 10 is unwound, and a 250 mm length of the magnetic tape MT is cut from one end of the outer circumference of the magnetic tape MT, 30 m to 40 m in the longitudinal direction, to prepare a sample. Next, the back layer 44 of the sample is removed with a solvent such as MEK (methyl ethyl ketone) or dilute hydrochloric acid. Next, the thickness of the sample is measured at five points using a Mitutoyo laser hologage (LGH-110C), and these measurements are simply averaged (arithmetic mean) to obtain the average value t Ｂ The [μm] value is calculated. Then, the average thickness t of the back layer 44 is calculated using the following formula. ４ Determine the [μm]. Note that the five measurement points mentioned above will be randomly selected from the sample so that they are all at different positions along the longitudinal direction of the magnetic tape MT. ４ [μm] = t Ｔ [μm] - t Ｂ [μm]

[0167] (Average thickness of magnetic tape t) Ｔ ) Average thickness (average total thickness) of magnetic tape MT t Ｔ By making the tape thinner, the length of tape wound into one cartridge 10 can be increased, thereby increasing the recording capacity per cartridge 10. Therefore, from the viewpoint of improving the recording capacity of cartridge 10, the average thickness t of the magnetic tape MT is Ｔ The upper limit is 5.40 μm or less, preferably 5.30 μm or less, more preferably 5.10 μm or less, and even more preferably 4.90 μm or less or 4.70 μm or less. Average thickness t of magnetic tape MT Ｔ The lower limit is not particularly restricted, but for example, it is 4.40 μm or larger.

[0168] Average thickness t of magnetic tape Ｔ The numerical range may be defined by either of the above upper limits and the above lower limits, preferably 4.40 μm or more and 5.40 μm or less, more preferably 4.40 μm or more and 5.30 μm or less, even more preferably 4.40 μm or more and 5.10 μm or less, 4.40 μm or more and 4.90 μm or less, or 4.40 μm or more and 4.70 μm or less.

[0169] Average thickness t of magnetic tape MT Ｔ The following is how it is determined. First, the magnetic tape MT housed in the cartridge 10 is unwound, and a 250 mm length of the magnetic tape MT is cut from one end of the outer circumference of the magnetic tape MT at a position 30 m to 40 m in the longitudinal direction to prepare a sample. Next, the thickness of the sample is measured at five points using a laser hologage (LGH-110C) manufactured by Mitutoyo as the measuring device, and these measured values ​​are simply averaged (arithmetic mean) to obtain the average thickness t. Ｔ The measurement value in [μm] is calculated. The five measurement points mentioned above are to be randomly selected from the sample so that they are all at different locations along the longitudinal direction of the magnetic tape MT.

[0170] (Average thickness of the magnetic layer t) ２ and the average thickness t of the underlying layer ３ (Total sum) Average thickness t of magnetic layer 43 ２ and the average thickness t of the base layer 42 ３ The sum (t) ２ +t ３ The upper limit of the magnetic layer t is preferably 0.92 μm or less, more preferably 0.80 μm or less, and even more preferably 0.60 μm or less, from the viewpoint of improving the recording capacity of the cartridge 10. ２ and the average thickness t of the base layer 42 ３ The sum (t) ２ +t ３ The lower limit of ) is, for example, 0.30 μm or more. Average thickness t of the magnetic layer 43 ２ and the average thickness t of the underlayer 42 ３ The measurement method is as described above.

[0171] Average thickness t of the magnetic layer 43 ２ and the average thickness t of the base layer 42 ３ The sum (t) ２ +t ３ The numerical range of ) may be defined by either of the above upper limits and the above lower limit, preferably 0.30 μm or more and 0.92 μm or less, more preferably 0.30 μm or more and 0.80 μm or less, and even more preferably 0.30 μm or more and 0.60 μm or less.

[0172] (Average thickness of the magnetic layer t) ２ and the average thickness t of the underlying layer ３ and the average thickness t of the back layer ４ (Total sum) Average thickness t of magnetic layer 43 ２ and the average thickness t of the base layer 42 ３ and the average thickness t of the back layer 45 ４ The sum (t) ２ +t ３ +t ４ The upper limit of the magnetic layer t is preferably 1.20 μm or less, more preferably 1.10 μm or less, and even more preferably 1.00 μm or less, from the viewpoint of improving the recording capacity of the cartridge 10. ２ and the average thickness t of the base layer 42 ３ and the average thickness t of the back layer 44 ４ The sum (t) ２ +t ３ +t ４ The lower limit of ) is, for example, 0.40 μm or more. Average thickness t of the magnetic layer 43 ２ , average thickness t of the base layer 42 ３ and the average thickness t of the back layer 45 ４ The measurement method is as described above.

[0173] Average thickness t of the magnetic layer 43 ２ and the average thickness t of the base layer 42 ３ and the average thickness t of the back layer 44 ４ The sum (t) ２ +t ３ +t ４ The numerical range of ) may be defined by either of the above upper limits and the above lower limit, preferably 0.40 μm or more and 1.25 μm or less, more preferably 0.40 μm or more and 1.15 μm or less, and even more preferably 0.40 μm or more and 1.00 μm or less.

[0174] (Average thickness of the substrate t) １ The average thickness t of the magnetic layer relative to this ２ , average thickness t of the underlying layer ３ and the average thickness t of the back layer ４ (Ratio of the sum of) Average thickness t of the substrate １ The average thickness t of the magnetic layer 43 relative to this. ２ , average thickness t of the base layer 42 ３and the average thickness t of the back layer 45 ４ The sum of ((t) ２ +t ３ +t ４ ) / t １ The upper limit of ) is preferably 0.32 or less, more preferably 0.31 or less, and more preferably 0.30 or less, from the viewpoint of improving the rigidity of the magnetic tape MT. Average thickness t of the substrate １ The average thickness t of the magnetic layer 43 relative to this. ２ , average thickness t of the base layer 42 ３ and the average thickness t of the back layer 45 ４ The sum of ((t) ２ +t ３ +t ４ ) / t １ The lower limit of ) is, for example, 0.29 or higher. The average thickness t of the substrate 41 １ , average thickness t of the magnetic layer 43 ２ , average thickness t of the base layer 42 ３ and the average thickness t of the back layer 45 ４ The measurement method is as described above.

[0175] Average thickness t of the substrate １ The average thickness t of the magnetic layer 43 relative to this. ２ , average thickness t of the base layer 42 ３ and the average thickness t of the back layer 45 ４ The sum of ((t) ２ +t ３ +t ４ ) / t １ The value may be defined by either of the above upper limits and the above lower limit, preferably 0.29 or more and 0.32 or less, more preferably 0.29 or more and 0.31 or less, and more preferably 0.29 or more and 0.30 or less.

[0176] (First physical property and second physical quantity) The first physical property (specifically, average hardness H) was determined by pressing a triangular pyramidal diamond indenter with a 142.3° edge angle perpendicular to the magnetic surface with a load of 50 μN. 50 and the mean modulus of elasticity Er 50 ), and a second physical property (specifically, average hardness H) determined by pressing a triangular pyramidal diamond indenter with a 142.3° edge angle perpendicular to the magnetic surface with a load of 150 μN.150 This explains ).

[0177] The reason why the indenter load is selected to 50 μN in the measurement of the first physical property is as follows: When the indenter load is 50 μN, the indentation depth of the indenter is shallow compared to the thickness of the magnetic layer 43, and the first physical property (specifically the average hardness H) mainly composed of the magnetic layer 43 is 50 and the mean modulus of elasticity Er 50 It is possible to measure the second physical property (specifically, the average hardness H). Furthermore, the reason why the indenter load is selected to be 150 μN in the measurement of the second physical property is as follows: When the indenter load is 150 μN, the indentation depth of the indenter is approximately equal to or greater than the thickness of the magnetic layer 43, and the second physical property (specifically, the average hardness H) includes the physical properties of the base layer 42 in addition to the physical properties of the magnetic layer 43. 150 It is possible to measure this.

[0178] (Average hardness H) 50 The magnetic tape MT has a substrate 41 on which a base layer 42 and a magnetic layer 43 are arranged in order, and the required properties of each of these layers are different. Therefore, the inventors diligently investigated the factors that affect electromagnetic conversion characteristics by measuring the physical properties by changing the indentation load of the indenter using a nanoindenter and investigating the influence of each layer as seen from the surface on the physical properties. As a result, the average hardness H obtained by pressing a triangular pyramidal diamond indenter with a ridge angle of 142.3° perpendicular to the surface on the magnetic layer side with a load of 50 μN was 50 However, it was discovered that there is a correlation with electromagnetic conversion characteristics. Therefore, the inventors have found an average hardness H that can obtain good electromagnetic conversion characteristics. 50 Further intensive investigation was conducted into the numerical range of H. As a result, as explained below, the average hardness H 50 We found that the pressure should be 0.72 GPa or higher.

[0179] The average hardness H was determined by pressing a triangular pyramidal diamond indenter with a 142.3° edge angle perpendicular to the magnetic surface with a load of 50 μN. 50The lower limit is 0.72 GPa or higher, preferably 0.75 GPa or higher, more preferably 0.80 GPa or higher, even more preferably 0.85 GPa or higher, 0.90 GPa or higher, 0.95 GPa or higher, or 0.98 GPa or higher. The above average hardness H 50 If the pressure is less than 0.72 GPa, the magnetic layer 43 may become too soft, potentially leading to unstable contact between the magnetic tape MT and the head unit 51. Consequently, a stable signal output may not be obtained, potentially degrading the electromagnetic conversion characteristics.

[0180] The above average hardness H 50 The upper limit is preferably 1.10 GPa or less, more preferably 1.05 GPa or less, and even more preferably 1.00 GPa or less. The above average hardness H 50 If the pressure is 1.10 GPa or less, it is possible to suppress the rigidity of the magnetic layer 43 from becoming too high. Therefore, it is possible to suppress the deterioration of the contact state between the magnetic tape MT and the head unit 51.

[0181] The above average hardness H 50 The numerical range may be defined by either of the above upper limits and either of the above lower limits, preferably 0.72 GPa or more and 1.10 GPa or less, more preferably 0.75 GPa or more and 1.10 GPa or less, even more preferably 0.80 GPa or more and 1.10 GPa or less, even more preferably 0.85 GPa or more and 1.10 GPa or less, 0.90 GPa or more and 1.10 GPa or less, 0.95 GPa or more and 1.10 GPa or less, or 0.98 GPa or more and 1.10 GPa or less.

[0182] The above average hardness H 50 This is determined using a nanoindenter. The above average hardness H 50 Before explaining the specific method for determining this, we will first describe the overview of measurement using a nanoindenter.

[0183] Figure 11A is a load-removal curve showing the displacement of the indenter 71 when the load is continuously increased and the indenter 71 is pressed perpendicularly to the magnetic surface of the magnetic tape MT, and the load is released when the load reaches 50 μN. States (1) to (3) shown in Figure 11B each represent the state of the indenter 71 at points (1) to (3) shown in Figure 11A.

[0184] When a load is applied, as shown in the load curve (a), the displacement increases as the load increases, and at 50 μN, the maximum indentation depth (maximum displacement) dmax is reached. When the load is removed, as shown in the unloading curve (b), the displacement gradually decreases and elastic recovery occurs, but even when the load becomes zero, the displacement does not become zero, and permanent strain (plastic deformation) d ０ Therefore, the "maximum indentation depth dmax" is equal to the "permanent strain (amount of plastic deformation) d ０ "and "elastic recovery d １ It is equivalent to the sum of ".

[0185] The hardness H (indentation hardness H) can be calculated from this load-unloading curve. Hardness H is expressed by the following formula. Here, A Ｃ is the contact projected area between the indenter 71 and the sample (magnetic tape MT), and Pmax is the maximum load on the load-unloading curve.

[0186] The above average hardness H 50 The following is how it is determined using a nanoindenter. First, the magnetic tape MT housed in cartridge 10 is unwound, and a length of about 10 cm is cut from the magnetic tape MT at a position of approximately 20 m from one end on the outermost circumference to obtain sample 1. Then, a length of about 10 cm is cut from the magnetic tape MT at a position of approximately 50 m from the other end on the innermost circumference to obtain sample 2. Next, sample 1 is cut to a size that fits the sample stage, MEK (methyl ethyl ketone) is applied to the back surface of sample 1, and then sample 1 is placed on the sample stage so that the back surface of sample 1 faces the sample stage, and sample 1 is fixed to the sample stage.

[0187] Next, using a nanoindenter, an indentation test is performed at 10 points on the magnetic surface of Sample 1 under a load range of 0 μN to 50 μN, and load-unloading curves are obtained for the 10 points. In this process, the 10 measurement points are randomly selected from areas free of scratches or other defects at the optical microscope level, ensuring that each point is at a different location on the magnetic surface. Note that in the following explanation, the average hardness H is used. 50The indentation test used to determine this is sometimes called the indentation test (1).

[0188] The measurement conditions for the nanoindenter are as follows: Material of indenter 71: Triangular pyramidal diamond indenter (Berkovich). Calibration is performed as described in the manual. Edge angle of indenter 71: 142.3° Measuring instrument: Hysitron Triboscope / Shimadzu Corporation Scanning Probe Microscope SPM9500J (Measuring instrument incorporating a device (Hysitron Triboscope) capable of controlling minute loads and measuring indenter displacement into a Shimadzu Corporation Scanning Probe Microscope SPM9500J) Measurement environment: 25℃±2℃, 50%RH±5%RH Load range: 0μN to 50μN (during measurement) Set load: 50μN Load resolution: 0.01μN Indentation direction: Perpendicular to the recording surface Indentation speed: 16.7μN / s (Indentation speed that reaches the set load of 50μN in 3 seconds) During measurement, the load is applied to sample 1 after the indenter 71 has come into contact with sample 1, and is removed immediately after the load reaches the set load.

[0189] When measuring with a nanoindenter, the wear condition of the indenter tip should be checked, and appropriate action should be taken according to the wear condition. Specifically, the following applies: When measuring a standard sample (fused silica) at 1000 μN, if the indenter's indentation depth becomes shallower by 2 μm to 3 μm relative to the maximum indentation depth at the start of use, the indenter should be calibrated. Calibration should be performed as described in the manual, as mentioned above. When measuring a standard sample (fused silica) at 1000 μN, if the indenter's indentation depth becomes shallower than 3 μm relative to the maximum indentation depth at the start of use, the indenter should be replaced. Note that as the indenter tip wears down, the indentation depth tends to decrease.

[0190] Next, the hardness H of each of the 10 points obtained from the load-unloading curves was calculated for each of the 10 points for Sample 1. 11 Next, we determine the hardness H of 10 points. The measurement and analysis program included with the nanoindenter is used to calculate this value. 11 The hardness H of the two points that take the maximum and minimum values.11 Excluding the remaining 8 points, the hardness is H. 11 Simply average (arithmetic mean) the hardness H of sample 1. 11 Calculate the average value.

[0191] Next, we obtained the load-unloading curve for Sample 1 to determine the hardness H. 11 By performing the same process for sample 2 to calculate the average value, the hardness H of sample 2 can be determined. 21 Next, calculate the average value of hardness H of sample 1. 11 The average value and hardness H of sample 2 21 The average value is simply averaged (arithmetic mean), and this is used as the average hardness H. 50 Let's assume that.

[0192] (Average hardness H) 50 and average hardness H 150 The ratio (H 50 / H 150 )) The above average hardness H 50 The average hardness H was determined by pressing a triangular pyramidal diamond indenter with a 142.3° edge angle perpendicular to the magnetic surface with a load of 150 μN. 150 The ratio (H 50 / H 150 The lower limit of the above ratio (H) is preferably 1.42 or higher, more preferably 1.45 or higher, even more preferably 1.50 or higher, 1.60 or higher, 1.70 or higher, 1.80 or higher, 1.90 or higher, or 1.93 or higher. 50 / H 150 If the hardness is 1.42 or higher, the hardness of the magnetic surface (the surface on the magnetic layer 43 side) is high, and the overall hardness of the laminated film of the base layer 42 and the magnetic layer 43 is lower than that of the magnetic surface. This suppresses the impact caused by contact between the protrusions on the magnetic surface and the head unit 51 when the magnetic surface slides against the head unit 51, and stabilizes the contact state.

[0193] The above ratio (H 50 / H 150 The upper limit of the above ratio (H) is preferably 2.20 or less, more preferably 2.10 or less, and even more preferably 2.00 or less. 50 / H 150If the hardness of the magnetic layer is 2.20 or less, it is possible to prevent the hardness of the magnetic layer 43 from becoming too high compared to the hardness of the underlying layer 42 below the magnetic layer 43. Therefore, it is possible to prevent cracks from forming in the edge portions of the magnetic layer 43, etc. (the edge portions in the width direction of the magnetic tape MT).

[0194] The above ratio (H 50 / H 150 The numerical range of ) may be defined by either of the above upper limits and either of the above lower limits, preferably 1.42 or more and 2.20 or less, more preferably 1.45 or more and 2.20 or less, even more preferably 1.50 or more and 2.20 or less, 1.60 or more and 2.20 or less, 1.70 or more and 2.20 or less, 1.80 or more and 2.20 or less, 1.90 or more and 2.20 or less, or 1.93 or more and 2.20 or less.

[0195] The above ratio (H 50 / H 150 ) can be determined using a nanoindenter as follows. First, the average hardness H mentioned above 50 Samples 1 and 2 are prepared in the same manner as the method used to determine the above average hardness H. Next, the above average hardness H 50 In the same manner as the method used to determine the hardness, an indentation test (1) with a load range of 0 μN to 50 μN is performed at 10 points on the magnetic surface of sample 1, and load-unloading curves for 10 points are obtained. Next, an indentation test (2) with a load range of 0 μN to 150 μN is performed at 10 points on the magnetic surface of sample 1 using a nanoindenter, and load-unloading curves for 10 points are obtained. The total of 20 measurement points for indentation tests (1) and (2) are randomly selected from areas free of scratches, etc., at the optical microscope level, so that each point is at a different location on the magnetic surface. The measurement conditions for the nanoindenter in indentation test (2) are the same as those for indentation test (1) (i.e., the average hardness H mentioned above), except for the load range: 0 μN to 150 μN (at measurement), set load: 150 μN, and indentation speed: 50 μN / s (indentation speed that reaches the set load of 150 μN in 3 seconds). 50 This is similar to the measurement conditions for the nanoindenter used in determining the value.

[0196] Next, the hardness H of sample 1 was calculated from the 10 load-unload curves obtained in the indentation test (1) of sample 1. 11 Next, we determine the hardness H of 10 points. The measurement and analysis program included with the nanoindenter is used to calculate this value. 11 The hardness H of the two points that take the maximum and minimum values. 11 Excluding the remaining 8 points, the hardness is H. 11 Simply average (arithmetic mean) the hardness H of sample 1. 11 Calculate the average value.

[0197] Next, except for using the 10-point load-unload curve obtained in the indentation test (2) of Sample 1, the hardness H of Sample 1 is used. 11 Using the same procedure as for calculating the average value, the hardness H of sample 1 was calculated. 12 Calculate the average value.

[0198] Next, indentation tests (1) and (2) are performed on sample 2, and 10 load-unloading curves are obtained for each of indentation tests (1) and (2). In this case, indentation tests (1) and (2) are performed using the same procedure and conditions as indentation tests (1) and (2) for sample 1 above. Next, except for using the 10 load-unloading curves obtained from indentation test (1) of sample 2, the hardness H of sample 1 is used. 11 Using the same procedure as for calculating the average value, the hardness H of sample 2 was calculated. 21 The average value is calculated. Next, the hardness H of sample 1 is used, except for the 10-point load-unload curve obtained in the indentation test (2) of sample 2. 11 Using the same procedure as for calculating the average value, the hardness H of sample 2 was calculated. 22 Calculate the average value.

[0199] Next, the hardness H of sample 1 11 The average value and hardness H of sample 2 21 The average value is simply averaged (arithmetic mean), and this is used as the average hardness H. 50 Next, the hardness H of sample 1. 12 The average value and hardness H of sample 2 22 The average value is simply averaged (arithmetic mean), and this is used as the average hardness H. 150Let it be so. Next, the average hardness H obtained as described above 50 and the average hardness H 150 are used to obtain the above ratio (H 50 / H 150 ).

[0200] (Average elastic modulus Er 50 ) The average elastic modulus Er obtained by vertically pressing a triangular pyramid diamond indenter against the surface of the magnetic layer 43 side with a load of 50 μN 50 has a lower limit value of preferably 7.5 GPa or more, more preferably 8.0 GPa or more, and still more preferably 8.5 GPa or more. When the average elastic modulus Er 50 is 7.5 GPa or more, the magnetic head 50 can be held without brittle fracture of the magnetic layer 43 when the magnetic head 50 contacts.

[0201] The upper limit value of the average elastic modulus Er 50 is preferably 10.0 GPa or less, more preferably 9.5 GPa or less, and still more preferably 9.0 GPa or less. When the upper limit value of the average elastic modulus Er 50 exceeds 10.0 GPa, the magnetic layer 43 becomes too hard and is likely to brittlely fracture.

[0202] The numerical range of the average elastic modulus Er 50 may be defined by any of the above upper limit values and any of the above lower limit values, preferably 7.5 GPa or more and 10.0 GPa or less, more preferably 8.0 GPa or more and 10.0 GPa or less, and still more preferably 8.0 GPa or more and 9.5 GPa or less.

[0203] The average elastic modulus Er 50 is calculated from the load unloading curve obtained by vertically pressing a triangular pyramid diamond indenter against the surface of the magnetic layer 43 side with a load of 50 μN. The average elastic modulus Er 50 is expressed by the following formula. Here, S is the contact stiffness, and A Ｃ is the contact projection area of the indenter 71 and the sample (magnetic tape MT). The contact stiffness S is the slope (dP / dh) of the unloading curve.

[0204] The average elastic modulus Er 50Specifically, it is obtained as follows using a nanoindenter. First, samples 1 and 2 are prepared in the same manner as for obtaining the above average hardness H 50 Next, in the same manner as for obtaining the above average hardness H 50 Using a nanoindenter, a push-in test is performed at 10 points on the magnetic surface of sample 1 within a load range of 0 μN or more and 50 μN or less to obtain the load-unloading curves of 10 points on the magnetic surface of sample 1. Next, the elastic modulus Er1 of sample 1 is calculated from each of the obtained 10 load-unloading curves by calculation. For the calculation of this value, the measurement and analysis program attached to the nanoindenter is used. Next, excluding the two Er1 values with the maximum and minimum values from the 10 elastic modulus Er1 values, the remaining 8 elastic modulus Er1 values are simply averaged (arithmetic mean) to calculate the average value of the elastic modulus Er1 of sample 1.

[0205] Next, the average value of the elastic modulus Er2 of sample 2 is calculated by performing the same steps from obtaining the load-unloading curve of sample 1 to calculating the average value of the elastic modulus Er1 for sample 2.

[0206] Next, the average values of the elastic modulus Er1 of sample 1 and the elastic modulus Er2 of sample 2 are simply averaged (arithmetic mean) to obtain an average value, which is defined as the average elastic modulus Er 50 and used as such.

[0207] (Average value of the normalized SFD curve in the vertical direction of the magnetic tape within a magnetic field range of 11,500 Oe or more and 14,000 Oe or less) The average value of the normalized SFD (Switching Field Distribution) curve in the vertical direction of the magnetic tape MT within a magnetic field range of 11,500 Oe or more and 14,000 Oe or less is 0.013 or less, preferably 0.012 or less, more preferably 0.011 or less, and even more preferably 0.010 or less. When the average value of the above magnetic field range is 0.013 or less, it contains barium (Ba) and strontium (Sr), with an average particle volume of 1.60×10 ３ nm ３Even when the magnetic layer 43 contains the following minute hexagonal ferrite particles, the amount of high-coercivity Hc hexagonal ferrite particles (content in the magnetic layer 43) that make recording difficult in the magnetic field of the recording head (e.g., a ring head) can be reduced. Therefore, differences in magnetic properties (magnetic anisotropy constant Ku and coercivity Hc) on a bit-by-bit basis can be suppressed, and differences in electromagnetic conversion characteristics (e.g., SNR) due to differences in recording speed can be suppressed.

[0208] The reason why the magnetic field range for calculating the average value is selected to be between 11500 Oe and 14000 Oe is as follows: Average particle volume 1.60 × 10⁻⁶ ３ nm ３ When both barium (Ba) and strontium (Sr) are incorporated into the following fine hexagonal ferrite particles, variations in the composition of individual hexagonal ferrite particles are likely to occur, leading to variations in the magnetic properties (magnetic anisotropy constant Ku and coercivity Hc) of individual hexagonal ferrite particles. Using a glass crystallization method, the average particle volume of 1.60 × 10⁻¹⁰ particles containing both barium (Ba) and strontium (Sr) is obtained. ３ nm ３ When the following fine hexagonal ferrite particles are fabricated, variations in composition and magnetic properties as described above are particularly likely to occur. Hexagonal ferrite particles (magnetic powders) exhibiting such variations may include those with high coercivity Hc (i.e., large magnetic anisotropy constant Ku), which makes recording difficult in the magnetic field of a recording head (e.g., a ring head).

[0209] The distribution of coercivity Hc can be evaluated using an SFD curve. The SFD curve values ​​in the magnetic field range of 11500 Oe to 14000 Oe correlate with components having high coercivity Hc (i.e., large magnetic anisotropy constant Ku) in hexagonal ferrite particles (magnetic powder) exhibiting the above-mentioned variations, which are likely to be difficult to record in the magnetic field of the recording head.

[0210] If the coercivity Hc becomes too high, recording of long wavelengths becomes possible, but recording of short wavelengths becomes difficult, or recording is possible with the recording head on the outermost surface of the magnetic layer 43, but recording of parts of the magnetic layer 43 away from the outermost surface becomes difficult. Furthermore, if the coercivity Hc becomes even higher, recording of long wavelengths becomes difficult, or recording of the outermost surface of the magnetic layer 43 becomes difficult as well. Considering the above characteristics, in this disclosure, the magnetic field range for calculating the average value is set to 11500 Oe to 14000 Oe. Also, as shown in Figure 12B, the SFD curve has small vertical oscillations, so the width ΔH (14000 Oe - 11500 Oe) of the above magnetic field range is selected from the viewpoint of reducing the variation caused by these vertical oscillations.

[0211] When the average atomic ratio of strontium (Sr) to barium (Ba) (Sr / Ba) is 0.80 or higher, it is preferable that the average value of the above magnetic field range is 0.013 or lower. When the average atomic ratio of strontium (Sr) to barium (Ba) (Sr / Ba) is 0.90 or higher or 0.96 or higher, it is more preferable that the average value of the above magnetic field range is 0.013 or lower. As the average atomic ratio of strontium (Sr) to barium (Ba) (Sr / Ba) increases, there is a tendency for the variability in the magnetic properties (magnetic anisotropy constant Ku) of individual hexagonal ferrite particles to increase. For this reason, when the average atomic ratio (Sr / Ba) is 0.80 or higher, it is particularly effective to set the average value of the above magnetic field range to 0.013 or lower.

[0212] The average value of the above magnetic field range is determined as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and six rectangular samples measuring 2 mm x 8 mm are cut from the magnetic tape MT at a position 30 m to 40 m in the longitudinal direction from one end of the outer circumference of the magnetic tape MT. At this time, the samples are cut so that the 2 mm side is parallel to the width direction of the magnetic tape MT, and the 8 mm side is parallel to the longitudinal direction of the magnetic tape MT. Next, each of the six samples is folded in four in the longitudinal direction to make a 2 mm x 2 mm square, and then these six are stacked to obtain a stacked sample of 2 mm x 2 mm square with 24 layers. Next, the stacked sample is placed in a sample holder, and M-H measurement (measurement of magnetic properties) is performed in the perpendicular direction of the magnetic tape MT using a physical properties measurement system (PPMS9RST Model 6000®, manufactured by Quantum Design Co., Ltd.) to obtain an M-H curve (hysteresis curve) in the range of -55000Oe to 55000Oe. Dedicated software included with the physical properties measurement system (PPMS) is used to obtain the M-H curve. Background correction is not performed. The physical properties measurement system (PPMS) described above is used as the apparatus because it is capable of measuring magnetic properties in high magnetic fields.

[0213] The chamber status during PPMS measurement is as follows: Chamber Status 300.00K, Stable, Purged and sealed

[0214] The selected sequence of measurements performed by PPMS is as follows: (1) Set Magnetic Field 0.0Oe at 100.0Oe / sec, Linear, Persistent (2) Wait For Field, Delay 1 sec, No Action (3) VSM Moment vs Field 5 Quadrants -55000 Oe to 55000 Oe Sweep H^1 / 2 AutoCenter OFF (4) Set Magnetic Field 0.0Oe at 50.0Oe / sec, No O'Sheet, Persistent (5) Wait For Field, Delay 0 sec, No Action (6) End Sequence

[0215] In step (1), the "SET FIELD Dialog Box" is set as follows: Field [Oe]: 0 Rate [Oe / Sec]: 100 Approach: Linear End Mode: Persistent

[0216] In step (2), the "WAIT Dialog Box" is set as follows: Condition(s) Temperature: Not selected Field: Selected Position: Not selected Camber: Not selected Delay[secs]: 1 On Error Execute: No Action

[0217] In step (3), the "Setup" of the "VSM Moment versus Field Dialog Box" is set as follows: Field Sequence Hmax: 55000 H0: 0 Hmin: -55000 Field Control Sweep Rate: 75 Oe / sec Driven at each field: Not selected Persistent at each field: Not selected Sweep: Selected End Mode: Persistent Data Acquisition Uniform Spacing in Field^1 / 2 Averaging Time: 1 sec Number of Fields Min to Max: 800 Field Increment: Not selected Repetitions at each Field: 1 Keep: All measurements

[0218] In step (4), the "SET FIELD Dialog Box" is set as follows: Field [Oe]: 0 Rate [Oe / Sec]: 50 Approach: NO O'shoot End Mode: Persistent

[0219] In step (5), the "WAIT Dialog Box" is set as follows: Condition(s) Temperature: Not selected Field: Selected Position: Not selected Camber: Not selected Delay[secs]: 0 On Error Execute: No Action

[0220] Next, the M-H curve data obtained from the Physical Properties Measurement System (PPMS) is differentiated to obtain the SFD curve. Then, to remove noise, the central moving average (simple moving average) of five consecutive data points is taken. Next, the SFD curve after the central moving average is normalized as follows: If data exists at the peak top of the SFD curve, the data at the peak top is set to 1 and the SFD curve is normalized. If no data exists at the peak top, the data closest to the peak top is set to 1 and the SFD curve is normalized. An example of a normalized SFD curve is shown in Figure 12A. A magnified portion of the normalized SFD curve in Figure 12A is shown in Figure 12B. Next, the average value for the magnetic field range of 11500Oe to 14000Oe in the normalized SFD curve in the vertical direction of the magnetic tape MT is calculated by simply averaging the data from the measurement points of the SFD curve in the magnetic field range of 11500Oe to 14000Oe. The data from the above measurement points corresponds to the data acquired every second while sweeping at a Sweep Rate of 75 Oe / sec during M-H measurement.

[0221] (Coercivity Hc2) The upper limit of the coercivity Hc2 of the magnetic layer 43 in the longitudinal direction of the magnetic tape MT is preferably 2200 Oe or less, more preferably 2000 Oe or less, and even more preferably 1900 Oe or less. When the coercivity Hc2 of the magnetic layer 43 in the longitudinal direction of the magnetic tape MT is 2200 Oe or less, sufficient electromagnetic conversion characteristics can be obtained even at high recording densities.

[0222] The lower limit of the coercivity Hc2 of the magnetic layer 43 measured in the longitudinal direction of the magnetic tape MT is preferably 1000Oe or more. When the coercivity Hc2 of the magnetic layer 43 measured in the longitudinal direction of the magnetic tape MT is 1000Oe or more, demagnetization due to leakage magnetic flux from the recording head can be suppressed.

[0223] The above coercivity Hc2 is determined as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and six pieces of magnetic tape MT are cut out from one end of the outer circumference of the magnetic tape MT at a position 30m to 40m in the longitudinal direction. At this time, the magnetic tape MT is marked with an arbitrary non-magnetic ink so that the longitudinal direction (travel direction) of the magnetic tape MT can be recognized. Next, the three cut pieces of magnetic tape MT are stacked together with double-sided tape so that their longitudinal directions are the same, and then punched out with a φ6.39 mm punch to create a measurement sample. Next, the M-H loop of the measurement sample (the entire magnetic tape MT) corresponding to the longitudinal direction (travel direction) of the magnetic tape MT is measured using a vibrating sample magnetometer (VSM). Next, the coatings (underlayer 42, magnetic layer 43, and back layer 44, etc.) of the remaining three cut pieces of magnetic tape MT are wiped off with acetone or ethanol, leaving only the substrate 41. Then, the obtained substrate 41 is stacked in three layers using double-sided tape, and punched out with a φ6.39 mm punch to create a sample for background correction (hereinafter simply referred to as the "correction sample"). Subsequently, the M-H loop of the correction sample (substrate 41) corresponding to the longitudinal direction of the substrate 41 (the longitudinal direction of the magnetic tape MT) is measured using a VSM.

[0224] For measuring the M-H loop of the measurement sample (the entire magnetic tape MT) and the M-H loop of the correction sample (substrate 41), a high-sensitivity vibrating sample type magnetometer "VSM-P7-15" manufactured by Toei Kogyo Co., Ltd. is used. The measurement conditions are as follows: measurement mode: full loop, maximum magnetic field: 15 kOe, magnetic field step: 40 bits, time constant of locking amp: 0.3 sec, waiting time: 1 sec, MH average number: 20.

[0225] After obtaining the M-H loop of the measurement sample (the entire magnetic tape MT) and the M-H loop of the correction sample (substrate 41), background correction is performed by subtracting the M-H loop of the correction sample (substrate 41) from the M-H loop of the measurement sample (the entire magnetic tape MT), and the background-corrected M-H loop is obtained. The measurement and analysis program included with the "VSM-P7-15" is used to calculate this background correction. The coercivity Hc2 is determined from the obtained background-corrected M-H loop. The measurement and analysis program included with the "VSM-P7-15" is used for this calculation. All of the above M-H loop measurements are performed at 25℃±2℃ and 50%RH±5%RH. In addition, "demagnetization correction" is not performed when measuring the M-H loop in the longitudinal direction of the magnetic tape MT.

[0226] (Square ratio S1 in the vertical direction) When the square ratio S1 of the magnetic tape MT in the vertical direction is large, the vertical orientation of the magnetic particles is increased, and thus superior electromagnetic conversion characteristics can be obtained. Therefore, from the viewpoint of obtaining superior electromagnetic conversion characteristics, the square ratio S1 of the magnetic tape MT in the vertical direction is preferably 62% or more, more preferably 65% ​​or more, even more preferably 68% or more, 72% or more, or 75% or more.

[0227] The angularity ratio S1 of the magnetic tape MT in the vertical direction is determined as follows. First, the process from sample preparation to M-H measurement is carried out in the same manner as the measurement of the average value in the magnetic field range described above to obtain an M-H curve. Next, the angularity ratio S1 (%) is calculated from the obtained M-H curve. Specifically, the saturation magnetization Ms (emu) and remanent magnetization Mr (emu) are calculated from the obtained M-H curve, and the angularity ratio S1 (%) is calculated by substituting these into the following formula: Angularity ratio S1 (%) = (Mr / Ms) × 100 Note that dedicated software attached to the physical property measurement system (PPMS) is used to calculate this angularity ratio S1 (%).

[0228] (Rectangular ratio S2 in the longitudinal direction) When the rectangular ratio S2 of the magnetic tape MT in the longitudinal direction (travel direction) is small, the vertical orientation of the magnetic particles is increased, and thus better electromagnetic conversion characteristics can be obtained. Therefore, from the viewpoint of obtaining better electromagnetic conversion characteristics, the rectangular ratio S2 of the magnetic tape MT in the longitudinal direction (travel direction) is preferably 35% or less, more preferably 30% or less, and even more preferably 25% or less, 20% or less, or 15% or less. Note that one of the rectangular ratio S1 of the magnetic tape MT in the vertical direction and the rectangular ratio S2 of the magnetic tape MT in the longitudinal direction (travel direction) may be within the above preferred range, while the other may be outside the above preferred range. Alternatively, both the rectangular ratio S1 of the magnetic tape MT in the vertical direction and the rectangular ratio S2 of the magnetic tape MT in the longitudinal direction (travel direction) may be within the above preferred range.

[0229] The angular ratio S2 of the magnetic tape MT in the longitudinal direction can be determined in the same manner as the angular ratio S1, except that the orientation of the stacked sample relative to the coil is changed and the M-H measurement is performed in the longitudinal direction (travel direction) of the magnetic tape MT. The calculation of this angular ratio S2 is performed using dedicated software included with the Physical Properties Measurement System (PPMS).

[0230] (Ratio Hc2 / Hc1) The ratio Hc2 / Hc1 of the coercivity Hc1 of the magnetic tape MT in the vertical direction and the coercivity Hc2 of the magnetic layer 43 of the magnetic tape MT in the longitudinal direction preferably satisfies the relationship Hc2 / Hc1 ≤ 0.8, more preferably Hc2 / Hc1 ≤ 0.75, even more preferably Hc2 / Hc1 ≤ 0.7, Hc2 / Hc1 ≤ 0.65, or Hc2 / Hc1 ≤ 0.6. By satisfying the relationship Hc2 / Hc1 ≤ 0.8 for coercivity Hc1 and Hc2, the degree of vertical orientation of magnetic particles can be increased. Therefore, the magnetization transition width can be reduced and a high-output signal can be obtained during signal reproduction, resulting in better electromagnetic conversion characteristics. As described above, when Hc2 is small, magnetization responds sensitively to the magnetic field in the vertical direction from the recording head, so a good recording pattern can be formed.

[0231] There is no particular lower limit to Hc2 / Hc1, but for example, it is 0.5 ≤ Hc2 / Hc1. Note that Hc2 / Hc1 represents the degree of vertical orientation of the magnetic particles, and the smaller Hc2 / Hc1, the higher the degree of vertical orientation of the magnetic particles.

[0232] The numerical range of Hc2 / Hc1 may be defined by either of the above upper limits and the above lower limit, preferably satisfying the relationship 0.5 ≤ Hc2 / Hc1 ≤ 0.8, more preferably 0.5 ≤ Hc2 / Hc1 ≤ 0.75, even more preferably 0.5 ≤ Hc2 / Hc1 ≤ 0.7, 0.5 ≤ Hc2 / Hc1 ≤ 0.65, or 0.5 ≤ Hc2 / Hc1 ≤ 0.6.

[0233] The method for calculating the coercivity Hc2 of the magnetic tape MT in the longitudinal direction is as described above. The coercivity Hc1 of the magnetic layer 43 in the perpendicular direction of the magnetic tape MT is determined in the same manner as the coercivity Hc2 of the magnetic layer 43 in the longitudinal direction of the magnetic tape MT, except that the M-H loop is measured in the perpendicular direction (thickness direction) of the magnetic tape MT and the substrate 41. The measurement and analysis program included with the "VSM-P7-15 type" is used to calculate the coercivity Hc2, similar to the calculation of the coercivity Hc1.

[0234] (Surface roughness R of the back surface) ｂ) Surface roughness of the back surface (surface roughness of the back layer 44) R ｂ The upper limit is preferably 7.5 nm or less, more preferably 7.2 nm or less, even more preferably 7.0 nm or less, 6.5 nm or less, 6.3 nm or less, or 6.0 nm or less. Surface roughness R of the back surface ｂ If the surface roughness R of the back surface is 7.5 nm or less, the influence of the back surface irregularities on the surface of the magnetic layer 43 during winding of the magnetic tape MT can be reduced, and adverse effects on electromagnetic conversion characteristics can be suppressed. ｂ The lower limit is preferably 3.0 nm or more, more preferably 3.2 nm or more, and even more preferably 3.4 nm or more.

[0235] Back surface roughness R ｂ The following method is used to determine the surface roughness R of the back surface. First, the magnetic tape MT housed in the cartridge 10 is unwound, and a 100 mm length of the magnetic tape MT is cut from one end of the outer circumference of the magnetic tape MT, 30 m to 40 m in the longitudinal direction, to prepare a sample. Next, the sample is placed on a microscope slide with the surface to be measured (magnetic surface) facing upwards, and the ends of the sample are secured with mending tape. The surface shape is measured using a VertScan (20x objective lens) as the measuring device, and the surface roughness R of the back surface is calculated from the following formula based on the ISO 25178 standard. ｂ The following measurement conditions are used to determine the roughness. Equipment: Non-contact roughness meter using optical interference (VertScan R5500GL-M100-AC, non-contact surface / layer cross-sectional shape measurement system manufactured by Ryoka Systems Co., Ltd.) Objective lens: 20x Measurement area: 640 x 480 pixels (field of view: approximately 237 μm x 178 μm) Measurement mode: phase Wavelength filter: 520 nm CCD: 1 / 3 inch Noise reduction filter: Smoothing 3 x 3 Surface correction: Corrected using a quadratic polynomial approximation surface Measurement software: VS-Measure Version 5.5.2 Analysis software: VS-viewer Version 5.5.5 As described above, after measuring the surface roughness at five points along the longitudinal direction of the magnetic tape MT, the arithmetic mean roughness S was automatically calculated from the surface profiles obtained at each location. ａThe average value of (nm) is the surface roughness R of the back surface ｂ is set as (nm).

[0236] (Young's modulus in the longitudinal direction of the magnetic tape) The upper limit of the Young's modulus in the longitudinal direction of the magnetic tape MT is preferably 9.0 GPa or less, more preferably 8.0 GPa or less, still 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 stretchability of the magnetic tape MT due to an external force becomes higher, so that it becomes easier to adjust the width of the magnetic tape MT by tension adjustment. Therefore, off-track can be more appropriately suppressed, and the data recorded on the magnetic tape MT can be reproduced more accurately. The lower limit of the Young's modulus in the longitudinal direction of the magnetic tape MT is preferably 3.0 GPa or more, more preferably 4.0 GPa or more. When the lower limit of the Young's modulus in the longitudinal direction of the magnetic tape MT is 3.0 GPa or more, a decrease in the running stability of the magnetic tape MT can be suppressed.

[0237] The Young's modulus in the longitudinal direction of the magnetic tape MT is a value indicating the difficulty of expansion and contraction of the magnetic tape MT in the longitudinal direction due to an external force. The larger this value is, the more difficult it is for the magnetic tape MT to expand and contract in the longitudinal direction due to an external force, and the smaller this value is, the easier it is for the magnetic tape MT to expand and contract in the longitudinal direction due to an external force.

[0238] Note that 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 is also correlated with the difficulty of expansion and contraction in the width direction of the magnetic tape MT. That is, the larger this value is, the more difficult it is for the magnetic tape MT to expand and contract in the width direction due to an external force, and the smaller this value is, the easier it is for the magnetic tape MT to expand and contract in the width direction due to an external force. Therefore, from the viewpoint of tension adjustment, it is advantageous that the Young's modulus in the longitudinal direction of the magnetic tape MT is small as described above and 9.0 GPa or less.

[0239] A tensile testing machine (Shimadzu Corporation, AG-100D) is used to measure Young's modulus. To measure the Young's modulus in the longitudinal direction of the tape, unwind the magnetic tape MT housed in cartridge 10, and cut a 180 mm length of magnetic tape MT from one end of the outer circumference of the magnetic tape MT, 30 m to 40 m in the longitudinal direction, to prepare the measurement sample. Attach a jig that can fix the tape width (1 / 2 inch) to the tensile testing machine and fix the top and bottom of the tape width. The distance (length of the tape between chucks) is set to 100 mm. After chucking the tape sample, gradually apply stress in the direction of tensile strength to the sample. The tensile speed is set to 0.1 mm / min. From the change in stress and the amount of elongation at this time, calculate the Young's modulus using the following formula: E (N / m) ２ )=((ΔN / S) / (Δx / L))×10 ６ ΔN: Change in stress (N) S: Cross-sectional area of ​​the test specimen (mm²) ２ ) Δx: elongation (mm) L: distance between gripping fixtures (mm) The cross-sectional area S of the measurement sample above is the cross-sectional area before the tensile action, and is obtained by product of the width (1 / 2 inch) and the thickness of the measurement sample. The range of tensile stress when performing the measurement is set to the range of tensile stress in the linear region according to the thickness of the magnetic tape MT, etc. Here, the stress range is set to 0.2 N to 0.7 N, and the stress change (ΔN) and elongation (Δx) at this time are used in the calculation. Note that the above Young's modulus measurement is performed at 25℃ ± 2℃ and 50% RH ± 5% RH.

[0240] (Young's modulus in the longitudinal direction of the substrate) The Young's modulus in the longitudinal direction of the substrate 41 is preferably 7.8 GPa or less, more preferably 7.0 GPa or less, even more preferably 6.6 GPa or less, and particularly preferably 6.4 GPa or less. When the Young's modulus in the longitudinal direction of the substrate 41 is 7.8 GPa or less, the elasticity of the magnetic tape MT due to external force is further increased, making it easier to adjust the width of the magnetic tape MT by tension adjustment. Therefore, off-track can be suppressed more effectively, and the data recorded on the magnetic tape MT can be reproduced more accurately. The lower limit of the Young's modulus in the longitudinal direction of the substrate 41 is preferably 2.5 GPa or more, more preferably 3.0 GPa or more. When the lower limit of the Young's modulus in the longitudinal direction of the substrate 41 is 2.5 GPa or more, a decrease in the running stability of the magnetic tape MT can be suppressed.

[0241] The longitudinal Young's modulus of the substrate 41 described above is determined as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and a 180 mm length of the magnetic tape MT is cut from one end on the outer circumference of the magnetic tape MT at a position 30 m to 40 m in the longitudinal direction. Next, the base layer 42, magnetic layer 43, and back layer 44 are removed from the cut magnetic tape MT to obtain the substrate 41. Using this substrate 41, the longitudinal Young's modulus of the substrate 41 is determined using the same procedure as for the longitudinal Young's modulus of the magnetic tape MT described above.

[0242] The thickness of the base body 41 accounts for more than half of the total thickness of the magnetic tape MT. Therefore, the Young's modulus in the longitudinal direction of the base body 41 is correlated with the resistance of the magnetic tape MT to expansion and contraction due to external forces. The larger this value, the less the magnetic tape MT is likely to expand and contract in the width direction due to external forces, and the smaller this value, the more likely the magnetic tape MT is to expand and contract in the width direction due to external forces.

[0243] The Young's modulus in the longitudinal direction of the base body 41 is a value related to the longitudinal direction of the magnetic tape MT, but it also correlates with the resistance of the magnetic tape MT to expansion and contraction in the width direction. In other words, the larger this value, the less the magnetic tape MT is susceptible to expansion and contraction in the width direction due to external forces, and the smaller this value, the more easily the magnetic tape MT is expanded and contracted in the width direction due to external forces. Therefore, from the viewpoint of tension adjustment, it is advantageous for the Young's modulus in the longitudinal direction of the base body 41 to be small, as described above, and 7.8 GPa or less.

[0244] [4 Method for Manufacturing Magnetic Tape] Next, an example of a method for manufacturing a magnetic tape MT having the above configuration will be described.

[0245] (Paint Preparation Process) First, a base coat paint is prepared by mixing and dispersing non-magnetic particles and binders in a solvent. Next, a magnetic layer paint is prepared by mixing and dispersing magnetic particles and binders in a solvent. One example of a method for producing magnetic particles is the glass crystallization method. Next, after the magnetic layer paint is allowed to stand, any stagnation that has formed in the magnetic layer paint is removed. Next, if necessary, carbon particles and hardeners are further added to the magnetic layer paint after stagnation removal, and then mixed and dispersed. For example, the following solvents, mixing equipment, and dispersion equipment can be used to prepare the magnetic layer paint and the base coat paint.

[0246] Examples of solvents used in the preparation of the above-mentioned paints include ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; alcohol solvents such as methanol, ethanol, and propanol; ester solvents such as methyl acetate, ethyl acetate, butyl acetate, propyl acetate, ethyl lactate, and ethylene glycol acetate; ether solvents such as diethylene glycol dimethyl ether, 2-ethoxyethanol, tetrahydrofuran, and dioxane; aromatic hydrocarbon solvents such as benzene, toluene, and xylene; and halogenated hydrocarbon solvents such as methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, and chlorobenzene. These may be used individually or in appropriate mixtures of two or more.

[0247] For the preparation of the paint described above, mixing equipment such as a continuous twin-screw mixer, a continuous twin-screw mixer capable of multi-stage dilution, a kneader, a pressure kneader, and a roll kneader may be used, but the equipment is not limited to these. Furthermore, for the preparation of the paint described above, dispersion equipment such as a roll mill, a ball mill, a horizontal sand mill, a vertical sand mill, a spike mill, a pin mill, a tower mill, a pearl mill (for example, Eich's "DCP mill"), a homogenizer, and an ultrasonic disperser may be used, but the equipment is not limited to these.

[0248] (Coating Process) Next, a base layer 42 is formed by applying a base layer forming paint to one main surface of the substrate 41 and drying it. Subsequently, a magnetic layer forming paint is applied to the base layer 42 and dried it to form a magnetic layer 43 on the base layer 42. During drying, the magnetic particles may be oriented in the thickness direction of the substrate 41 using a magnetic field, for example, a permanent magnet. After the formation of the magnetic layer 43, a back layer 44 is formed on the other main surface of the substrate 41. This gives rise to a magnetic tape MT. The order of formation of the base layer 42, magnetic layer 43, and back layer 44 is not limited to the above example. For example, the back layer 44 may be formed on the other main surface of the substrate 41, and then the base layer 42 and magnetic layer 43 may be formed sequentially on one main surface of the substrate 41.

[0249] The square ratios S1 and S2 can be set to desired values ​​by adjusting, for example, the strength of the magnetic field applied to the coating film of the magnetic layer forming paint, the concentration of solids in the magnetic layer forming paint, and the drying conditions (drying temperature and drying time) of the coating film of the magnetic layer forming paint. The strength of the magnetic field applied to the coating film is preferably two to three times the coercivity of the magnetic particles. To further increase the square ratio S1 (i.e., to further decrease the square ratio S2), it is preferable to improve the dispersion state of the magnetic particles in the magnetic layer forming paint. Furthermore, to further increase the square ratio S1, it is also effective to magnetize the magnetic particles before the magnetic layer forming paint enters the orientation device for magnetic field orientation of the magnetic particles. Note that the above methods for adjusting the square ratios S1 and S2 may be used individually or in combination of two or more.

[0250] (Curing process) Next, after winding the magnetic tape MT into a roll, the base layer 42 and the magnetic layer 43 are cured by applying a heat treatment to the magnetic tape MT in this state.

[0251] (Calculating process) Next, the cured magnetic tape MT is calendered to smooth the magnetic surface.

[0252] (Aging process) Next, if necessary, the magnetic tape MT after calendaring is subjected to an aging process.

[0253] (Cutting process) Next, the magnetic tape MT is cut to a predetermined width (for example, 1 / 2 inch width).

[0254] (Servo writing process) Next, if necessary, the magnetic tape MT may be demagnetized and then the servo pattern may be written to the magnetic tape MT.

[0255] (Average hardness H) 50 and the mean modulus of elasticity Er 50 (Adjustment method) Average hardness H 50 and the mean modulus of elasticity Er 50 For example, this can be adjusted to a predetermined value by adjusting the curing conditions in the curing process (curing temperature and curing time, etc.), the amount of abrasive particles mixed into the magnetic layer forming paint, the amount of curing agent mixed into the magnetic layer forming paint, and the ratio of the amount of magnetic particles P1 to the amount of binder B1 (P1 / B1) in the magnetic layer forming paint.

[0256] (Average hardness H) 150 (Adjustment method) Average hardness H 150 This can be adjusted to a predetermined value by, for example, adjusting the curing conditions in the curing process (curing temperature and curing time, etc.), the amount of curing agent mixed into the primer-forming paint, and the ratio of the amount of non-magnetic particles P2 to the amount of binder B2 in the primer-forming paint (P2 / B2).

[0257] (Ratio (H 50 / H 150 (Adjustment method) Average hardness H 50 and average hardness H 150 The ratio (H 50 / H150 The curing properties can be adjusted to a predetermined value by, for example, adjusting the curing conditions in the curing process (curing temperature and curing time, etc.), the amount of abrasive particles mixed into the magnetic layer forming paint, the amount of curing agent mixed into the magnetic layer forming paint, the amount of curing agent mixed into the base layer forming paint, the ratio of the amount of magnetic particles P1 to the amount of binder B1 in the magnetic layer forming paint (P1 / B1), and the ratio of the amount of non-magnetic particles P2 to the amount of binder B2 in the base layer forming paint (P2 / B2).

[0258] (Method for adjusting the average value of the magnetic field range of the normalized SFD curve in the vertical direction of the magnetic tape, between 11500Oe and 14000Oe) The average value of the magnetic field range of the normalized SFD curve in the vertical direction of the magnetic tape MT, between 11500Oe and 14000Oe, can be adjusted to a predetermined value by removing large magnetic particles, for example, by adjusting the stagnation removal process and filter processing time in the preparation process of the coating for forming the magnetic layer. Large magnetic particles tend to have high coercivity Hc, so by removing large magnetic particles, the content of high coercivity Hc magnetic particles (content in the magnetic layer 43), which are likely to be difficult to record with the magnetic field of the recording head, can be reduced.

[0259] [5 Effects] As described above, in the magnetic tape MT according to one embodiment, the average hardness H obtained by pressing a triangular pyramidal diamond indenter with a 142.3° edge angle perpendicular to the surface of the magnetic layer 43 with a load of 50 μN is 50 However, it is 0.72 GPa or higher. Therefore, the contact state between the magnetic tape MT and the head unit 51 becomes stable. Consequently, a stable signal output can be obtained, and excellent electromagnetic conversion characteristics can be obtained. In addition, the average value of the magnetic field range of the normalized SFD curve in the vertical direction of the magnetic tape MT, from 11500 Oe to 14000 Oe, is 0.013 or less. Therefore, the average particle volume of 1.60 × 10⁻¹⁰ containing barium (Ba) and strontium (Sr) is 0.013 or less. ３ nm ３Even when the magnetic layer 43 contains the following minute hexagonal ferrite particles, the amount of high-coercivity Hc hexagonal ferrite particles (content in the magnetic layer 43) can be reduced, as recording is likely to be difficult in the magnetic field of the recording head (e.g., a ring head). Therefore, differences in magnetic properties (magnetic anisotropy constant Ku and coercivity Hc) on a bit-by-bit basis can be suppressed, and differences in electromagnetic conversion characteristics (e.g., SNR) due to differences in recording speed can be suppressed. Thus, in a magnetic tape MT according to one embodiment, the average particle volume containing barium (Ba) and strontium (Sr) is 1.60 × 10⁻⁶. ３ nm ３ In a magnetic tape MT containing the following hexagonal ferrite particles in the magnetic layer 43, excellent electromagnetic conversion characteristics can be obtained while suppressing the recording speed dependence of the electromagnetic conversion characteristics (e.g., SNR).

[0260] In conventional magnetic tape, the bit area is, for example, 40,000 nm ２ When the bit area becomes smaller than the specified value, differences in magnetic properties (magnetic anisotropy constant Ku and coercivity Hc) at the bit level become particularly noticeable, and differences in electromagnetic conversion characteristics (e.g., SNR) due to differences in recording speed become more pronounced. In contrast, in a magnetic tape MT according to one embodiment, the average value of the magnetic field range of the normalized SFD curve in the vertical direction of the magnetic tape MT, from 11500Oe to 14000Oe, is 0.013 or less, so the bit area is, for example, 40000 nm. ２ Even at the smallest values, differences in magnetic properties (magnetic anisotropy constant Ku and coercivity Hc) at the bit level are suppressed. Therefore, even if the bit area is, for example, 40,000 nm ２ Even at the smallest values, differences in electromagnetic conversion characteristics (e.g., SNR) due to differences in recording speed are suppressed.

[0261] From the perspective of increasing the capacity of cartridge 10, the average thickness t of the magnetic tape MT Ｔ The thickness is preferably 5.40 μm or less, and from the viewpoint of improving electromagnetic conversion characteristics, the average thickness of the magnetic layer 43 is preferably 0.07 μm or less. Also, from the viewpoint of improving the linear recording density D of the magnetic tape MT, the bit area is 40,000 nm. ２The following is preferable. In order to obtain a stable signal output with such a small bit size, it is desirable that the contact state between the magnetic tape MT and the head unit 51 is stable. In one embodiment of the magnetic tape MT, the average hardness H was determined by pressing a triangular pyramidal diamond indenter with a 142.3° edge angle perpendicular to the surface on the magnetic layer side with a load of 50 μN. 50 However, since the pressure is 0.72 GPa or higher, the contact between the magnetic tape MT and the head unit 51 can be stabilized. Therefore, even with such a small bit size, a stable signal output can be obtained. In other words, even with such a small bit size, excellent electromagnetic conversion characteristics can be obtained.

[0262] Contains barium (Ba) and strontium (Sr), with an average particle volume of 1.60 × 10⁻¹⁰ ３ nm ３ The following fine hexagonal ferrite particle magnetic powder tends to contain high-coercivity Hc magnetic particles during the manufacturing process, which makes recording difficult in the magnetic field of a recording head (e.g., a ring head). Therefore, the above-mentioned hexagonal ferrite particle magnetic powder has thermal stability such that the coercivity Hc changes depending on the head magnetic field exposure time (the time the magnetic field of the recording head is applied to the hexagonal ferrite particles), and in conventionally used magnetic heads (e.g., ring heads), the electromagnetic conversion characteristics (e.g., SNR) change depending on the recording speed. In contrast, in the manufacturing method of magnetic tape MT according to one embodiment, the stagnation removal treatment and filter treatment time adjustment are performed in the preparation process of the coating for forming the magnetic layer, so that the content of high-coercivity Hc magnetic particles, which makes recording difficult in the magnetic field of a recording head, can be reduced. Therefore, it is possible to provide a magnetic tape MT that can suppress the recording speed dependence of electromagnetic conversion characteristics (e.g., SNR).

[0263] [6 Modified Examples] In the above embodiment, the case where the magnetic tape cartridge is a single-reel type cartridge 10 was described, but it may also be a two-reel type cartridge.

[0264] Figure 13 is an exploded perspective view showing an example of the configuration of a two-reel type cartridge 321. The cartridge 321 comprises an upper half 302 made of synthetic resin, a transparent window member 323 fitted into and fixed to a window portion 302a opened on the upper surface of the upper half 302, a reel holder 322 fixed to the inside of the upper half 302 to prevent the reels 306 and 307 from lifting up, a lower half 305 corresponding to the upper half 302, reels 306 and 307 housed in the space created by combining the upper half 302 and the lower half 305, magnetic tape MT wound on the reels 306 and 307, a front lid 309 that closes the front opening created by combining the upper half 302 and the lower half 305, and a back lid 309A that protects the magnetic tape MT exposed to this front opening.

[0265] Reels 306 and 307 are for winding magnetic tape MT. Reel 306 comprises a lower flange 306b having a cylindrical hub portion 306a in the center on which the magnetic tape MT is wound, an upper flange 306c that is approximately the same size as the lower flange 306b, and a reel plate 311 sandwiched between the hub portion 306a and the upper flange 306c. Reel 307 has the same configuration as reel 306.

[0266] The window member 323 is provided with mounting holes 323a at positions corresponding to the reels 306 and 307 for assembling reel holders 322, which are reel holding means for preventing the reels from lifting up. The magnetic tape MT is the same as the magnetic tape MT in one embodiment.

[0267] The present disclosure will be specifically described below with reference to examples, but the present disclosure is not limited to these examples.

[0268] In the following examples and comparative examples, the average thickness t of the magnetic tape Ｔ , average thickness t of the substrate (PEN film) １ , average thickness t of the magnetic layer ２ , average thickness t of the underlying layer ３ , average thickness t of the back layer ４The composition of the magnetic powder (magnetic particles), the average atomic ratio (Sr / Br) of the magnetic powder (magnetic particles), the aspect ratio of the magnetic powder (magnetic particles), and the average particle volume of the magnetic powder (magnetic particles) are values ​​obtained by the measurement method described in the above embodiment.

[0269] [Example 1] (Preparation process for magnetic layer forming coating) A magnetic layer forming coating was prepared as follows. First, the first composition with the following formulation was mixed in a Dynomill, then placed in a container and left to stand for 48 hours. The stagnation at the bottom of the container was removed by discarding a portion equivalent to 10 vol% of the total first composition from the bottom of the container. Next, the first composition after stagnation removal and the second composition with the following formulation were placed in a stirring tank equipped with a disperser and pre-mixed. Subsequently, the magnetic layer forming coating was prepared by further Dynomill mixing followed by filtration.

[0270] (First composition) Barium ferrite (Ba ０．５１ Sr ０．４９ Fe １２ O １９ Magnetic powder (hexagonal plate shape, average aspect ratio 2.8, average particle volume 1.10 × 10⁻⁶) with atomic ratio Sr / Ba = 0.96. ３ nm ３ ): 100.0 parts by mass of vinyl chloride resin solution (resin solution composition: amount of vinyl chloride resin 30.0% by mass, amount of cyclohexanone solution 70.0% by mass) (vinyl chloride resin: degree of polymerization 300, number average molecular weight Mn = 10000, polar group OSO ３ Contains K = 0.07 mmol / g and secondary OH = 0.3 mmol / g. ): 50.0 parts by mass Polyurethane resin solution (Formulation of resin solution: Polyurethane resin content 30% by mass, Cyclohexanone content 70% by mass) (Polyurethane resin: Number average molecular weight Mn = 25000, Glass transition temperature Tg = 110°C): 25.0 parts by mass Aluminum oxide powder (α-Al ２ O ３ Barium ferrite magnetic powder was prepared by a glass crystallization method.

[0271] (Second Composition) Carbon black (manufactured by Tokai Carbon Co., Ltd., product name: Seest S, arithmetic mean particle size 70 nm): 1.4 parts by mass Polyurethane resin solution (resin solution composition: polyurethane resin content 30% by mass, cyclohexanone content 70% by mass) (polyurethane resin: number average molecular weight Mn = 25000, glass transition temperature Tg = 110°C): 1.8 parts by mass n-butyl stearate: 2.0 parts by mass

[0272] Finally, to the magnetic layer-forming coating prepared as described above, 3.5 parts by mass of polyisocyanate (equivalent to Coronate L manufactured by Tosoh Corporation) and 2.0 parts by mass of stearic acid were added as curing agents.

[0273] (Preparation process for primer-forming paint) The primer-forming paint was prepared as follows. First, the third composition with the following formulation was kneaded in an extruder. Next, the kneaded third composition and the fourth composition with the following formulation were placed in a stirring tank equipped with a disperser and pre-mixed. Subsequently, after further mixing with Dynomill, the primer-forming paint was prepared by filtration.

[0274] (Third composition) Needle-shaped iron oxide powder (α-Fe ２ O ３ , average major axis length 0.11 μm): 100.0 parts by mass of vinyl chloride resin solution (resin solution composition: amount of vinyl chloride resin 30.0% by mass, amount of cyclohexanone solution 70.0% by mass) (vinyl chloride resin: degree of polymerization 300, number average molecular weight Mn = 10000, polar group OSO ３ Contains K = 0.07 mmol / g and secondary OH = 0.3 mmol / g. ): 74.0 parts by mass Aluminum oxide powder (α-Al ２ O ３ (Average particle size 0.1 μm): 5.0 parts by mass Methyl ethyl ketone: 240.0 parts by mass Toluene: 120.0 parts by mass Cyclohexanone: 10.0 parts by mass

[0275] (Fourth Composition) Carbon black (manufactured by Asahi Carbon Co., Ltd., trade name: #80): 30.0 parts by mass Polyurethane resin solution (resin solution composition: polyurethane resin content 30% by mass, cyclohexanone content 70% by mass) (polyurethane resin: number average molecular weight Mn = 25000, glass transition temperature Tg = 70°C): 45.0 parts by mass n-butyl stearate: 2.0 parts by mass Methyl ethyl ketone: 60.0 parts by mass Cyclohexanone: 70.0 parts by mass

[0276] Finally, to the primer-forming paint prepared as described above, 3.6 parts by mass of polyisocyanate (equivalent to Coronate L manufactured by Tosoh Corporation) and 1.5 parts by mass of stearic acid were added as curing agents.

[0277] (Preparation process for back layer forming coating) The back layer forming coating was prepared as follows. The following raw materials were mixed in a stirring tank equipped with a disperser, and then filtered to prepare the back layer forming coating. Carbon black (manufactured by Asahi Carbon Co., Ltd., product name: #80): 100.0 parts by mass Polyester polyurethane (manufactured by Nippon Polyurethane Industry Co., Ltd., product name: N-2304): 100.0 parts by mass Methyl ethyl ketone: 500.0 parts by mass Toluene: 400.0 parts by mass Cyclohexanone: 100.0 parts by mass Polyisocyanate (equivalent to Coronate L manufactured by Tosoh Corporation): 10.0 parts by mass

[0278] (Coating process) Using the magnetic layer forming paint and the base layer forming paint prepared as described above, an average thickness t １ A base layer and a magnetic layer were sequentially formed on one main surface of a long PEN film (substrate) having a thickness of 4.00 μm, as follows: First, a paint for forming the base layer was applied to one main surface of the PEN film and dried, thereby forming the average thickness t of the base layer when the magnetic tape was completed. ３ (Average thickness t of the base layer after the cutting process) ３ A base layer was formed such that the thickness was 0.80 μm. Next, a paint for forming the magnetic layer was applied to the base layer and dried, thereby determining the average thickness of the magnetic layer at the time the magnetic tape was completed t ２ (Average thickness t of the magnetic layer after the cutting process) ２A magnetic layer was formed such that its thickness was 0.06 μm. During the drying of the coating for forming the magnetic layer, a permanent magnet was used to orient the barium ferrite magnetic powder in the thickness direction of the PEN film. After the formation of the base layer and the magnetic layer, a coating for forming the back layer was applied to the other main surface of the PEN film and dried, thereby achieving the average thickness t of the completed magnetic tape. ４ (Average thickness t after the cutting process) ４ A back layer was formed such that the thickness was 0.35 μm. This resulted in the acquisition of a magnetic tape.

[0279] (Curing process) After winding the magnetic tape into a roll, the base layer, magnetic layer, and backing layer were cured by heat treatment at 65°C for 25 hours in this state.

[0280] (Calcane process) After curing, the magnetic tape was calendered to smooth the surface of the magnetic layer. The calendering process was carried out at a temperature close to the glass transition temperature Tg (=110°C) of the polyurethane resin (binder) contained in the magnetic layer (slightly higher than Tg).

[0281] (Aging process) The magnetic tape, after calendering, was subjected to an aging process for 40 hours in a 60°C environment.

[0282] (Cutting process) By cutting the magnetic tape after aging treatment, the width is 1 / 2 inch (12.65 mm) and the average thickness is t Ｔ A magnetic tape with a diameter of 5.21 μm was obtained.

[0283] [Example 2] A magnetic tape was obtained in the same manner as in Example 1, except that the filtering time of the magnetic layer forming coating was doubled in the preparation step of the magnetic layer forming coating.

[0284] [Comparative Example 1] A magnetic tape was obtained in the same manner as in Example 1, except for the following points. In order to reduce the amount of magnetic particles with excessively high coercivity Hc among the magnetic particles contained in the magnetic powder, in the preparation step of the coating for forming the magnetic layer, barium ferrite (BaFe) １２ O １９ ) Magnetic powder (hexagonal plate shape, average aspect ratio 2.8, average particle volume 1.30 × 10⁻⁶) ３ nm３ ) was used. As a result, the coercivity Hc1 of the magnetic tape in the vertical direction was reduced by 10% compared to Example 1. In order to ensure thermal stability, in the preparation process of the coating for forming the magnetic layer, the magnetic powder size was set to 1.10 × 10 ３ from 1.30 × 10 ３ nm ３ The amount was increased. In the preparation process of the magnetic layer forming coating, the amount of vinyl chloride resin solution blended into the first composition of the magnetic layer forming coating was changed from 50.0 parts by mass to 40.0 parts by mass. In the coating process, the average thickness t of the long PEN film (substrate) was changed. １ = Using a material having a thickness of 4.20 μm, and the average thickness t of the underlying layer at the time the magnetic tape is completed. ３ (Average thickness t of the base layer after the cutting process) ３ The underlayer was formed such that the thickness was 0.60 μm.

[0285] [Comparative Example 2] The same procedure as in Example 1 except for the following points, with an average thickness t Ｔ A magnetic tape with a thickness of 5.22 μm was obtained. In order to reduce the amount of magnetic particles with excessively high coercivity Hc among the magnetic particles contained in the magnetic powder, barium ferrite (BaFe) was used in the preparation process of the coating for forming the magnetic layer. １２ O １９ ) Magnetic powder (hexagonal plate shape, average aspect ratio 2.8, average particle volume 1.60 × 10⁻⁶) ３ nm ３ ) was used. As a result, the coercivity Hc1 of the magnetic tape in the vertical direction was reduced by 10% compared to Example 1. In order to ensure thermal stability, in the preparation process of the coating for forming the magnetic layer, the magnetic powder size was set to 1.10 × 10 ３ from 1.60 x 10 ３ nm ３ The amount was increased. In the preparation process of the magnetic layer forming coating, the amount of vinyl chloride resin solution blended into the first composition of the magnetic layer forming coating was changed from 50.0 parts by mass to 40.0 parts by mass. In the coating process, the average thickness t of the magnetic layer when the magnetic tape is completed. ２ (Average thickness t of the magnetic layer after the cutting process) ２ A magnetic layer was formed such that its thickness was 0.07 μm.

[0286] [Comparative Example 3] A magnetic tape was obtained in the same manner as in Example 1, except that the process of removing sediment from the bottom of the container was not performed in the preparation step of the coating for forming the magnetic layer.

[0287] [Evaluation] The magnetic tapes obtained as described above were evaluated as follows.

[0288] (Average modulus of elasticity Er 50 ) The average modulus of elasticity Er as described in the above embodiment 50 This value was calculated using the method described above. The results are shown in Table 1.

[0289] (Average hardness H) 50 , H 150 and their ratio (H 50 / H 150 )) The average hardness H described in the above embodiment 50 , H 150 and their ratio (H 50 / H 150 These values ​​were obtained using the method described above. The results are shown in Table 1.

[0290] (Average value of the magnetic field range of 11500 Oe to 14000 Oe in the normalized SFD curve in the vertical direction of the magnetic tape) The average value of the magnetic field range of 11500 Oe to 14000 Oe in the normalized SFD curve in the vertical direction of the magnetic tape was determined by the method described in the above embodiment.

[0291] (Difference in SNR between tape speed 2.00 m / s and tape speed 6.00 m / s, ΔSNR) The SNR at tape speed 2.00 m / s was determined as follows. First, a loop tester (Microphysics) was used to acquire the playback signal of the magnetic tape. The conditions for acquiring the playback signal are shown below. head: GMR headspeed: 2.00 m / s signal: single recording frequency 10.70 MHz (as 2T half Nyquist frequency) recording current: optimal recording current

[0292] Next, the playback signal was captured using a spectrum analyzer with a span of 0 to 20 MHz (resolution bandwidth = 100 kHz, VBW = 30 kHz). The peaks of the captured spectrum were defined as the signal intensity S, and the floor noise, excluding the peaks, was integrated from 3 to 20 MHz to determine the noise intensity N. The signal-to-noise ratio (SNR) was then calculated as the ratio S / N of the signal intensity S to the noise intensity N. Next, the calculated SNR was converted to a relative value (dB) with the SNR of Comparative Example 2, used as a reference medium, as the baseline (0 dB). The results are shown in Table 1. Note that an SNR of 1.0 or higher at a tape speed of 2.00 m / s indicates excellent electromagnetic conversion characteristics (SNR) when playing back magnetic tape using a tape storage drive.

[0293] The SNR at a tape speed of 6.00 m / s was determined as follows. First, the playback signal of the magnetic tape was acquired using a loop tester (Microphysics). The conditions for acquiring the playback signal are shown below. Head: GMR Head Speed: 6.00 m / s Signal: Single recording frequency 26.75 MHz (2T half Nyquist frequency) Recording current: Optimal recording current

[0294] Next, the SNR was calculated in the same manner as for a tape speed of 2.00 m / s, except that the playback signal was captured with a span of 0 to 50 MHz (resolution bandwidth = 100 kHz, VBW = 30 kHz), and the floor noise, excluding peaks, was integrated from 3 to 50 MHz to determine the noise level N. Note that the SNR for a tape speed of 6.00 m / s was not converted to a relative value.

[0295] The ΔSNR was calculated by determining the difference between the SNR at a tape speed of 2.00 m / s and the SNR at a tape speed of 6.00 m / s before relative value conversion ((SNR at tape speed of 2.00 m / s before relative value conversion) - (SNR at tape speed of 6.00 m / s)). The results are shown in Table 1. If the ΔSNR is 0.6 dB or less, the dependence of the electromagnetic conversion characteristics (SNR) on the recording speed can be suppressed, and good electromagnetic conversion characteristics (SNR) can be maintained even when the recording speed of the magnetic tape changes in a tape storage drive.

[0296]

[0297] From the above evaluation results, the following was found: In Examples 1 and 2, the average hardness H 50 The average hardness is 0.72 GPa or higher, and the average value of the normalized SFD curve in the vertical direction of the magnetic tape in the magnetic field range of 11500 Oe to 14000 Oe is 0.013 or lower. Therefore, excellent electromagnetic conversion characteristics can be obtained, and the recording speed dependence of the electromagnetic conversion characteristics can be suppressed. In Comparative Examples 1 and 2, the average hardness H 50 The average value of the magnetic field range is less than 0.72 GPa, and the average value of the magnetic field range exceeds 0.013. Therefore, it becomes difficult to obtain excellent electromagnetic conversion characteristics, and it becomes difficult to suppress the recording speed dependence of the electromagnetic conversion characteristics. In Comparative Example 3, the average hardness H 50 Since the magnetic field is 0.72 GPa or higher, excellent electromagnetic conversion characteristics can be obtained. However, because the average value of the above magnetic field range exceeds 0.013, it becomes difficult to suppress the recording speed dependence of the electromagnetic conversion characteristics.

[0298] While embodiments and modifications of the present disclosure have been described in detail above, the present disclosure is not limited to the embodiments and modifications described above, and various modifications are possible based on the technical idea of ​​the present disclosure. For example, the configurations, methods, processes, shapes, materials, and numerical values ​​given in the above embodiments and modifications are merely examples, and different configurations, methods, processes, shapes, materials, and numerical values ​​may be used as needed. The configurations, methods, processes, shapes, materials, and numerical values ​​of the above embodiments and modifications can be combined with each other as long as they do not deviate from the spirit of the present disclosure.

[0299] The chemical formulas of the compounds exemplified in the above embodiments are representative examples, and the general name of the same compound is not limited to the stated valency, etc. In the numerical ranges described in steps in the above embodiments, the upper or lower limit of one step in the numerical range may be replaced with the upper or lower limit of another step in the numerical range. Unless otherwise specified, the materials exemplified in the above embodiments can be used individually or in combination of two or more.

[0300] Furthermore, the present disclosure may also adopt the following configuration: (1) A tape-shaped magnetic recording medium comprising, in order, a substrate, an underlayer, and a magnetic layer, wherein the average thickness of the magnetic recording medium is 4.40 μm or more and 5.40 μm or less, the average thickness of the magnetic layer is 0.07 μm or less, the magnetic layer contains hexagonal ferrite particles containing barium (Ba) and strontium (Sr), and the average particle volume of the hexagonal ferrite particles is 1.60 × 10⁻⁶ ３ nm ３ The following conditions apply: the average value of the normalized SFD curve in the vertical direction of the magnetic recording medium in the magnetic field range of 11500 Oe to 14000 Oe is 0.013 or less; and the average hardness H is determined by pressing a triangular pyramidal diamond indenter with a 142.3° edge angle perpendicular to the surface of the magnetic layer with a load of 50 μN. 50 A magnetic recording medium having a hardness of 0.72 GPa or more. (2) The magnetic recording medium according to (1), wherein the average atomic ratio of strontium (Sr) to barium (Ba) (Sr / Ba) is 0.02 or more and 3.00 or less. (3) The magnetic recording medium according to (1), wherein the average atomic ratio of strontium (Sr) to barium (Ba) (Sr / Ba) is 0.02 or more and 1.00 or less. (4) The magnetic recording medium according to (1), wherein the average atomic ratio of strontium (Sr) to barium (Ba) (Sr / Ba) is 0.80 or more. (5) The average hardness H 50 The average hardness H was determined by pressing the triangular diamond indenter perpendicularly against the surface of the magnetic layer with a load of 150 μN. 150Ratio to (H 50 / H 150 (1) to (4) The magnetic recording medium according to any one of (1) to (4), wherein the value of the magnetic field range of the normalized SFD curve is 1.42 or more. (6) The magnetic recording medium according to any one of (1) to (5), wherein the average value of the magnetic field range of the normalized SFD curve is 0.011 or less. (7) The magnetic recording medium according to any one of (1) to (6), wherein the substrate contains a polyester resin. (8) The magnetic recording medium according to any one of (1) to (7), wherein the sum of the average thickness of the magnetic layer and the average thickness of the underlayment is 0.92 μm or less. (9) Further comprising a back layer, wherein the back layer is provided on the substrate opposite to the magnetic layer side, and the average thickness of the substrate is t １ The average thickness t of the magnetic layer relative to the above ２ , the average thickness t of the aforementioned underlayer ３ and the average thickness t of the back layer ４ The ratio of the sums ((t) ２ +t ３ +t ４ ) / t １A magnetic recording medium according to any one of (1) to (8), wherein the ratio is 0.29 or more and 0.32 or less. (10) A magnetic recording medium according to any one of (1) to (9), wherein the magnetic layer has a servo pattern, the servo pattern includes a plurality of first magnetization regions and a plurality of second magnetization regions, and the plurality of first magnetization regions and the plurality of second magnetization regions are asymmetric with respect to an axis parallel to the width direction of the magnetic recording medium. (11) A magnetic recording medium according to (10), wherein the inclination angle of the first magnetization region with respect to the axis and the inclination angle of the second magnetization region with respect to the axis are different, and the larger of the inclination angle of the first magnetization region and the inclination angle of the second magnetization region is 18° or more and 28° or less. (12) A tape-shaped magnetic recording medium comprising, in order, a substrate, an underlayer, and a magnetic layer, wherein the average thickness of the magnetic recording medium is 4.40 μm or more and 5.40 μm or less, the average thickness of the magnetic layer is 0.07 μm or less, the magnetic layer contains hexagonal ferrite particles containing barium (Ba) and strontium (Sr), and the average particle volume of the hexagonal ferrite particles is 1.60 × 10⁻⁶ ３ nm ３ A magnetic recording medium wherein the average value of the magnetic field range of the normalized SFD curve in the vertical direction of the magnetic recording medium between 11500Oe and 14000Oe is 0.013 or less. (13) A cartridge comprising the magnetic recording medium described in any one of (1) to (12).

[0301] 10, 321 Cartridge 11 Cartridge memory 31 Antenna coil 32 Rectifier / power supply circuit 33 Clock circuit 34 Detection / modulation circuit 35 Controller 36 Memory 36A First memory area 36B Second memory area 41 Substrate 42 Underlayer 43 Magnetic layer 44 Back layer 50 Magnetic head 51S Sliding surface 51a First head unit 51b Second head unit 52 Servo lead section 53 Data write / read section 54 Data write section 55 Data read section 71 Indenter 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 Databand Tk Datatrack

Claims

1. A tape-shaped magnetic recording medium comprising, in order, a substrate, an underlayer, and a magnetic layer, wherein the average thickness of the magnetic recording medium is 4.40 μm or more and 5.40 μm or less, the average thickness of the magnetic layer is 0.07 μm or less, the magnetic layer contains hexagonal ferrite particles containing barium (Ba) and strontium (Sr), and the average particle volume of the hexagonal ferrite particles is 1.60 × 10⁻⁶ ３ nm ３ The following conditions apply: the average value of the normalized SFD curve in the vertical direction of the magnetic recording medium in the magnetic field range of 11500 Oe to 14000 Oe is 0.013 or less; and the average hardness H is determined by pressing a triangular pyramidal diamond indenter with a 142.3° edge angle perpendicular to the surface of the magnetic layer with a load of 50 μN. 50 However, it is a magnetic recording medium with a capacitance of 0.72 GPa or higher.

2. The magnetic recording medium according to claim 1, wherein the average atomic ratio of strontium (Sr) to barium (Ba) (Sr / Ba) is 0.02 or more and 3.00 or less.

3. The magnetic recording medium according to claim 1, wherein the average atomic ratio of strontium (Sr) to barium (Ba) (Sr / Ba) is 0.02 or more and 1.00 or less.

4. The magnetic recording medium according to claim 1, wherein the average atomic ratio of strontium (Sr) to barium (Ba) (Sr / Ba) is 0.80 or more.

5. The average hardness H 50 The average hardness H was determined by pressing the triangular diamond indenter perpendicularly against the surface of the magnetic layer with a load of 150 μN. 150 Ratio to (H 50 / H 150 The magnetic recording medium according to claim 1, wherein the ratio is 1.42 or greater.

6. The magnetic recording medium according to claim 1, wherein the average value of the normalized SFD curve in the magnetic field range of 11500 Oe to 14000 Oe is 0.011 or less.

7. The magnetic recording medium according to claim 1, wherein the substrate comprises a polyester resin.

8. The magnetic recording medium according to claim 1, wherein the sum of the average thickness of the magnetic layer and the average thickness of the underlayer is 0.92 μm or less.

9. Further comprising a back layer, the back layer being provided on the side of the substrate opposite to the magnetic layer side, the average thickness t of the substrate １ with respect to the average thickness t of the magnetic layer ２ , the average thickness t of the underlayer ３ and the average thickness t of the back layer ４ ratio of the sum ((t ２ +t ３ +t ４ ) / t １ ) is 0.29 or more and 0.32 or less, the magnetic recording medium according to claim 1.

10. The magnetic recording medium according to claim 1, wherein the magnetic layer has a servo pattern, the servo pattern includes a plurality of first magnetization regions and a plurality of second magnetization regions, and the plurality of first magnetization regions and the plurality of second magnetization regions are asymmetric with respect to an axis parallel to the width direction of the magnetic recording medium.

11. The magnetic recording medium according to claim 10, wherein the inclination angle of the first magnetization region with respect to the axis is different from the inclination angle of the second magnetization region with respect to the axis, and the larger of the inclination angles of the first magnetization region and the second magnetization region is 18° or more and 28° or less.

12. A tape-shaped magnetic recording medium comprising, in order, a substrate, an underlayer, and a magnetic layer, wherein the average thickness of the magnetic recording medium is 4.40 μm or more and 5.40 μm or less, the average thickness of the magnetic layer is 0.07 μm or less, the magnetic layer contains hexagonal ferrite particles containing barium (Ba) and strontium (Sr), and the average particle volume of the hexagonal ferrite particles is 1.60 × 10⁻¹⁶ ３ nm ３ A magnetic recording medium wherein the average value of the normalized SFD curve in the vertical direction of the magnetic field range of 11500Oe to 14000Oe is 0.013 or less.

13. A cartridge comprising the magnetic recording medium described in claim 1.

Images