Magnetic recording medium and cartridge

Abstract

Provided is a magnetic recording medium that can improve running durability.　A magnetic recording medium according to the present invention is tape-shaped and comprises a substrate and a magnetic layer that includes magnetic particles. The ratio (A / B) of the fatty acid ester content A (mg / m2) at the surface on the magnetic layer side as measured by transferring a lubricant on the surface on the magnetic layer side to a glass fiber sheet and the amount B (mg / m2) of fatty acids extracted from the magnetic recording medium by immersing the magnetic recording medium in n-hexane for 5 minutes is no more than 0.10, the fatty acid ester content A being no more than 0.80 mg / m2, and the amount B of fatty acids extracted being at least 5.0 mg / m2.

Description

Magnetic recording media and cartridges

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

[0002] In recent years, tape-shaped magnetic recording media have been widely used for storing electronic data. In tape-shaped magnetic recording media, a lubricant is contained in the magnetic layer to reduce the coefficient of dynamic friction between the surface of the magnetic layer and the head unit (magnetic head). From the viewpoint of running stability, it has been proposed to use both fatty acids and fatty acid esters as lubricants (see, for example, Patent Document 1).

[0003] Japanese Patent Publication No. 2021-34077

[0004] However, using both fatty acids and fatty acid esters as lubricants may reduce driving durability and driving stability.

[0005] The purpose of this disclosure is to provide a magnetic recording medium and a cartridge equipped therewith that can improve running durability and running stability.

[0006] To solve the above-mentioned problems, the magnetic recording medium according to this disclosure is a tape-shaped magnetic recording medium comprising a substrate and a magnetic layer containing magnetic particles, wherein the fatty acid ester content A [mg / m²] on the surface of the magnetic layer is measured by transferring the lubricant on the surface of the magnetic layer to a glass fiber sheet. ２ ] and the amount of fatty acids extracted from the magnetic recording medium by immersing the magnetic recording medium in n-hexane for 5 minutes is B [mg / m³]. ２ The ratio (A / B) to ] is 0.10 or less, and the fatty acid ester content A is 0.80 mg / m³. ２ The following is the result: the amount of fatty acid extracted, B, is 5.0 mg / m². ２ That's all.

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

[0008] Figure 1 is an exploded perspective view showing an example of the configuration of a cartridge according to one embodiment of the present disclosure. Figure 2 is a block diagram showing an example of the configuration of a cartridge memory. Figure 3 is a cross-sectional view showing an example of the configuration of a magnetic tape. Figure 4 is a schematic diagram showing an example of the layout of a data band and a servo band. Figure 5A is an enlarged view showing an example of the configuration of a data band. Figure 5B is an enlarged view showing an example of a data track in a magnetic recording system. Figure 6 is an enlarged view showing an example of the configuration of a servo band. Figure 7 is a perspective view showing an example of the shape of magnetic particles. Figure 8 is a diagram showing a first example of a cross-sectional TEM image of a magnetic layer. Figure 9 is a diagram showing a second example of a cross-sectional TEM image of a magnetic layer. Figure 10 is a diagram illustrating a method for transferring fatty acid esters from the surface on the magnetic layer side to a glass fiber sheet. Figure 11 is a diagram showing an example of a sample sheet used for measuring the amount of fatty acid extracted. Figure 12 is a side view of a device for measuring the tension acting on a magnetic tape. Figure 13 is a plan view of a device for measuring the tension acting on a magnetic tape. Figure 14 is an enlarged view of the head block shown in Figure 12. Figure 15 is a diagram illustrating a method for measuring PES. Figure 16 is a graph illustrating the correction of the movement of the magnetic tape in the width direction. Figure 17 is an exploded perspective view showing an example of the configuration of a cartridge according to a modified embodiment of one embodiment of the present disclosure.

[0009] Embodiments of this disclosure will be described in the following order: 1. Cartridge configuration 2. Cartridge memory configuration 3. Magnetic tape configuration 4. Magnetic tape manufacturing method 5. Effects and benefits 6. Modified examples

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

[0011] [1. 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.

[0012] 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.

[0013] 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.

[0014] [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.

[0015] 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.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] [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 base layer 42 and the back layer 44 are provided as needed and may be omitted. The magnetic tape MT may be a vertical recording type magnetic recording medium or a longitudinal recording type magnetic recording medium. From the viewpoint of improving runability, the magnetic tape MT contains a lubricant on the surface on the magnetic layer 43 side. In this specification, the surface on the magnetic layer 43 side of the magnetic tape MT is sometimes referred to as the magnetic surface, and the surface on the back layer 44 side of the magnetic tape MT is sometimes referred to as the back surface.

[0023] 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).

[0024] 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.

[0025] 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).

[0026] (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 value is preferably 4.40 μm or less, more preferably 4.20 μm or less, still 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 recordable on one data cartridge. The average thickness t of the substrate 41 １ The lower limit value is preferably 3.00 μm or more, more preferably 3.20 μm or more, still more preferably 3.80 μm or more. The average thickness t of the substrate 41 １ When the lower limit value is 3.00 μm or more, a decrease in the strength of the substrate 41 can be suppressed.

[0027] The average thickness t of the substrate 41 １ is obtained as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and the magnetic tape MT is cut out to a length of 250 mm at a position 30 m to 40 m in the longitudinal direction from one end on the outer peripheral side of the magnetic tape MT to prepare a sample. In this specification, the "longitudinal direction" in the case of "from one end on the outer peripheral side of the magnetic tape MT in the longitudinal direction" means the direction from one end on the outer peripheral side of the magnetic tape MT toward the other end on the inner peripheral side.

[0028] Subsequently, layers other than the substrate 41 of the sample (that is, the underlayer 42, the magnetic layer 43, and the back layer 44) are removed with a solvent such as MEK (methyl ethyl ketone) or dilute hydrochloric acid. Next, using a laser hologauge (LGH-110C) manufactured by Mitutoyo as a measuring device, the thickness of the sample (substrate 41) is measured at 5 positions, and their measured values are simply averaged (arithmetic mean) to calculate the average thickness t of the substrate 41 １ It should be noted that the 5 measurement positions are randomly selected from the sample so as to be different positions in the longitudinal direction of the magnetic tape MT.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] (Magnetic layer) The magnetic layer 43 is configured to record signals by a magnetization pattern. The magnetic layer 43 may be a vertical recording layer or a longitudinal recording layer. The magnetic layer 43 may include, for example, magnetic particles, a binder, and a lubricant. The magnetic layer 43 may further include, if necessary, at least one additive selected from the group consisting of a dispersant, carbon particles, abrasive particles, an antistatic agent, a curing agent, a rust inhibitor, and non-magnetic reinforcing particles. The magnetic layer 43 may have a plurality of protrusions on its magnetic surface. The plurality of protrusions may be formed, for example, by carbon particles and abrasive particles protruding from the magnetic surface.

[0038] 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.

[0039] The magnetic layer 43 may have a plurality of servo bands SB and a plurality of data bands DB, as shown in Figure 4. The plurality of servo bands SB are provided at equal intervals in the width direction of the magnetic tape MT. Data bands DB are provided between adjacent servo bands SB. The servo bands SB are for guiding the head unit (magnetic head) 56 (specifically, servo read heads 56A, 56B) when recording or playing back data. Servo patterns (servo signals) for tracking control of the head unit 56 are prewritten on the servo bands SB. User data is recorded on the data bands DB.

[0040] In order to read the asymmetric servo stripe 113 (see Figure 6) described later, the head unit 56 may be configured to be maintained at an angle with respect to the axis Ax extending in the width direction of the magnetic tape MT during data recording and playback, as shown in Figure 4. Hereinafter, the head unit 56 maintained at an angle with respect to the axis Ax extending in the width direction of the magnetic tape MT in this manner may be referred to as the "angled head unit 56". The inclination angle of the head unit 56 with respect to the axis Ax extending in the width direction of the magnetic tape MT is preferably 3° to 18°, more preferably 5° to 15°.

[0041] 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.

[0042] The total area S of multiple servo bands SB relative to the total area S of the magnetic surface ＳＢ Ratio R Ｓ The servobandwidth W is determined as follows: A magnetic tape MT is developed using a ferricolloid developer (Sigma Marker Q, manufactured by Sigma Hi-Chemical Co., Ltd.), and then the developed magnetic tape MT is observed with an optical microscope. ＳＢ Then, measure the number of servo bands SB. Next, calculate the ratio R from the following formula. Ｓ We find the ratio R. Ｓ [%] = (((Servobandwidth W ＳＢ ) × (Number of servo bands SB) / (Width of magnetic tape MT) × 100

[0043] 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.

[0044] 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].

[0045] Servo bandwidth W ＳＢ The upper limit of the servo bandwidth W is preferably 95 μm or less, more preferably 65 μm or less, and even more preferably 50 μm or less, from the viewpoint of ensuring high recording capacity. ＳＢ The lower limit is preferably 10 μm or more. Servo bandwidth W less than 10 μm ＳＢ A magnetic head capable of reading the servo signal is difficult to manufacture.

[0046] 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].

[0047] As shown in Figure 5A, the magnetic layer 43 is configured to form multiple data tracks Tk in the data band DB. The upper limit of the data track width W is preferably 700 nm or less, more preferably 650 nm or less, even more preferably 500 nm or less, and particularly preferably 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.

[0048] 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.

[0049] Although Figure 5A shows an example where adjacent data tracks Tk are recorded without overlapping, the recording method for data tracks Tk is not limited to this example. For example, as shown in Figure 5B, a Shingled Magnetic Recording (SMR) method may be used to record adjacent data tracks Tk so that parts of them overlap in the width direction of the magnetic tape MT.

[0050] In Figure 5B, heads 61 and 62 represent the recording head and playback head, respectively. In the case of magnetic recording, the data track width W is the recording track width W ＲIt becomes narrower compared to the recording head 61. Therefore, in the case of magnetic recording, the width of the playback head 62 is narrower than the width of the recording head 61. As described above, in the magnetic recording method, the data track width W is narrower than the recording track width W. Ｒ Since it is narrower compared to, it is advantageous in terms of improving recording density. Here, the recording track width W Ｒ This represents the track width during data writing. When magnetic recording is used as the recording method, the recording track width W is used. Ｒ This represents the track width before overwriting (the track width when data is written).

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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:

[0056] 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.

[0057] 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).

[0058] In the LTO standard, the servo band SB has a servo pattern formed on it, consisting of multiple servo stripes (linear magnetized regions) 113 that are inclined with respect to the axis Ax extending in the width direction of the magnetic tape MT, as shown in Figure 6.

[0059] 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).

[0060] The servo subframe 1 (111) consists of an A-burst 111A and a B-burst 111B. The B-burst 111B is positioned adjacent to the A-burst 111A. The A-burst 111A is positioned at a predetermined angle θ with respect to the axis Ax extending in the width direction of the magnetic tape MT. １ It is equipped with five servo stripes 113 that are inclined and formed at predetermined intervals. In Figure 6, these five servo stripes 113 are arranged from the EOT (End Of Tape) to the BOT (Beginning Of Tape) of the magnetic tape MT, indicated by the symbol A １ A ２ A ３ A ４ A ５ It is indicated by the notation.

[0061] The B-burst 111B is at a predetermined angle θ with respect to the axis Ax extending in the width direction of the magnetic tape MT. ２ It is equipped with five servo stripes 113 that are inclined and formed at specified intervals. In Figure 6, these five servo stripes 113 are connected to the magnetic tape MT from EOT to BOT, indicated by the letter B １ , B ２ , B ３ , B ４ , B ５ It is indicated by the notation.

[0062] The servo stripe 113 of the B-burst 111B is inclined in the opposite direction to the servo stripe 113 of the A-burst 111A. The servo stripe 113 of the A-burst 111A and the servo stripe 113 of the B-burst 111B are asymmetrical with respect to the axis Ax that extends in the width direction of the magnetic tape MT. That is, the servo stripe 113 of the A-burst 111A and the servo stripe 113 of the B-burst 111B are arranged in a roughly V-shape. Because the servo stripe 113 of the A-burst 111A and the servo stripe 113 of the B-burst 111B are asymmetrical with respect to the axis Ax, when the head unit 56 is tilted diagonally with respect to the axis Ax, there exists a state in which the servo stripe 113 of the A-burst 111A and the servo stripe 113 of the B-burst 111B are roughly symmetrical with respect to the central axis of the sliding surface of the head unit 56. By changing the tilt of the head unit 56 based on this state, it becomes possible to adjust the distance between the servo lead heads 56A and 56B in the width direction of the magnetic tape MT. Therefore, in both cases where the width of the magnetic tape MT is increased and where the width of the magnetic tape MT is decreased, the servo lead heads 56A and 56B can be positioned to face the specified position of the servo band SB. Note that the central axis of the sliding surface of the head unit 56 refers to the axis that passes through the centers of the multiple servo lead heads 56A and 56B on the sliding surface of the head unit 56.

[0063] The predetermined angle θ is the inclination angle of the servo stripe 113 of the A-burst 111A. １ And, the predetermined angle θ is the inclination angle of the servo stripe 113 of the B-burst 111B. ２ This is different. More specifically, the predetermined angle θ of the servo stripe 113 of the A-burst 111A １ However, the predetermined angle θ of the servo stripe 113 of B burst 111B ２ It may be larger in comparison, and the predetermined angle θ of the servo stripe 113 of B burst 111B ２ However, the predetermined angle θ of the servo stripe 113 of the A-burst 111A １It may be larger than the angle of the servo stripe 113 of the A-burst 111A. That is, the inclination of the servo stripe 113 of the A-burst 111A may be larger than the inclination of the servo stripe 113 of the B-burst 111B, and the inclination of the servo stripe 113 of the B-burst 111B may be larger than the inclination of the servo stripe 113 of the A-burst 111A. Note that in Figure 6, the predetermined angle θ of the servo stripe 113 of the A-burst 111A １ However, the predetermined angle θ of the servo stripe 113 of B burst 111B ２ A larger example is shown below. Below, the predetermined angle θ of the servo stripe 113 of the A-burst 111A １ However, the predetermined angle θ of the servo stripe 113 of B burst 111B ２ Let's explain the case where it is larger than [the specified value].

[0064] The servo subframe 2 (112) consists of a C-burst 112C and a D-burst 112D. The D-burst 112D is positioned adjacent to the C-burst 112C. The C-burst 112C is positioned at a predetermined angle θ with respect to the axis Ax extending in the width direction of the magnetic tape MT. １ It is equipped with four servo stripes 113 that are inclined and formed at predetermined intervals. In Figure 6, these four servo stripes 113 are connected to the magnetic tape MT from EOT to BOT, indicated by the letter C １ , C ２ , C ３ , C ４ It is indicated by the notation.

[0065] The D-burst 112D is at a predetermined angle θ with respect to the axis Ax extending in the width direction of the magnetic tape MT. ２ It is equipped with four servo stripes 113 that are inclined and formed at predetermined intervals. In Figure 6, these four servo stripes 113 are shown with the magnetic tape MT from EOT to BOT indicated by the symbol D １ , D ２ , D ３ , D ４ It is indicated by the notation.

[0066] The servo stripe 113 of the D-burst 112D is inclined in the opposite direction to the servo stripe 113 of the C-burst 112C. The servo stripe 113 of the C-burst 112C and the servo stripe 113 of the D-burst 112D are asymmetrical with respect to the axis Ax that extends in the width direction of the magnetic tape MT. That is, the servo stripe 113 of the C-burst 112C and the servo stripe 113 of the D-burst 112D are arranged in a roughly V-shape. Because the servo stripe 113 of the C-burst 112C and the servo stripe 113 of the D-burst 112D are asymmetrical with respect to the axis Ax, when the head unit 56 is tilted diagonally with respect to the axis Ax, there exists a state in which the servo stripe 113 of the C-burst 112C and the servo stripe 113 of the D-burst 112D are roughly symmetrical with respect to the central axis of the head unit 56. By changing the tilt of the head unit 56 based on this state, it becomes possible to adjust the distance between the servos.

[0067] The predetermined angle θ is the inclination angle of the servo stripe 113 of the C-burst 112C. １ And the predetermined angle θ is the inclination angle of the servo stripe 113 of the D-burst 112D. ２ This is different. More specifically, the predetermined angle θ of the servo stripe 113 of the C burst 112C １ However, the predetermined angle θ of the servo stripe 113 of the D-burst 112D ２ It may be larger in comparison, and the predetermined angle θ of the servo stripe 113 of D-burst 112D ２ However, the predetermined angle θ of the servo stripe 113 of the C burst 112C １ It may be larger than the angle of the servo stripe 113 of the C-burst 112C. That is, the inclination of the servo stripe 113 of the C-burst 112C may be larger than the inclination of the servo stripe 113 of the D-burst 112D, and the inclination of the servo stripe 113 of the D-burst 112D may be larger than the inclination of the servo stripe 113 of the C-burst 112C. In Figure 6, the predetermined angle θ of the servo stripe 113 of the C-burst 112C. １ However, the predetermined angle θ of the servo stripe 113 of the D-burst 112D ２Examples larger than are shown. Below, a predetermined angle θ of the servo stripe 113 of the C burst 112C １ is larger than the predetermined angle θ of the servo stripe 113 of the D burst 112D ２ will be described.

[0068] The above-mentioned predetermined angle θ of the servo stripe 113 in the A burst 111A and the C burst 112C １ is preferably 18° or more and 28° or less, more preferably 18° or more and 26° or less. The above-mentioned predetermined angle θ of the servo stripe 113 in the B burst 111B and the D burst 112D ２ is preferably -4° or more and 6° or less, more preferably -2° or more and 6° or less. The servo stripes 113 in the A burst 111A and the C burst 112C are an example of the first magnetization region. The servo stripes 113 in the B burst 111B and the D burst 112D are an example of the second magnetization region.

[0069] By reading the servo band SB with the head unit 56, information for obtaining the tape speed and the vertical position of the head unit 56 is obtained. The tape speed is calculated from the time between four timing signals (A1 - C1, A2 - C2, A3 - C3, A4 - C4). The head position is calculated from the time between the aforementioned four timing signals and the time between 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.

[0070] As shown in FIG. 6, the servo pattern (that is, a plurality of servo stripes 113) is preferably linearly arranged 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.

[0071] The average thickness t of the magnetic layer 43 ２The upper limit value is preferably 80 nm or less, more preferably 70 nm or less, still more preferably 60 nm or less, and particularly preferably 50 nm or less. The average thickness t of the magnetic layer 43 ２ When the upper limit value of ２ is 80 nm or less, when a ring type head is used as the recording head, the influence of the demagnetizing field can be reduced, and excellent electromagnetic conversion characteristics can be obtained.

[0072] The average thickness t of the magnetic layer 43 ２ The lower limit value is preferably 30 nm or more, more preferably 40 nm or more. The average thickness t of the magnetic layer 43 ２ When the lower limit value of ２ is 30 nm or more, when an MR type head is used as the reproducing head, the output can be ensured, and excellent electromagnetic conversion characteristics can be obtained.

[0073] The average thickness t of the magnetic layer 43 ２ The numerical range of ２ may be defined by any of the above upper limit values and any of the above lower limit values, preferably 30 nm or more and 80 nm or less, more preferably 40 nm or more and 70 nm or less, still more preferably 40 nm or more and 60 nm or less, and particularly preferably 40 nm or more and 50 nm or less.

[0074] The average thickness t of the magnetic layer 43 ２ is obtained as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and the magnetic tape MT is cut out to a length of 250 mm from each of the positions 10 m to 20 m, 30 m to 40 m, and 50 m to 60 m in the longitudinal direction from one end on the outer peripheral side of the magnetic tape MT to produce three samples. Subsequently, each sample is processed by a method such as the FIB (Focused Ion Beam) method to be thinned. When using the FIB method, as a pretreatment for observing the TEM image of the cross section described later, a carbon layer and a tungsten layer are formed as protective films. The carbon layer is formed on the magnetic surface and the 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. The thinning is performed along the longitudinal direction of the magnetic tape MT. That is, by the thinning, a cross section parallel to both the longitudinal direction and the thickness direction of the magnetic tape MT is formed.

[0075] 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

[0076] 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].

[0077] (Magnetic Particles) The magnetic particles are ferrite particles. The ferrite particles may include, for example, particles containing hexagonal ferrite (hereinafter referred to as "hexagonal ferrite particles"), particles containing epsilon-type iron oxide (ε-iron oxide) (hereinafter referred to as "ε-iron oxide particles"), or particles containing Co-containing spinel ferrite (hereinafter referred to as "cobalt ferrite particles"). It is preferable that the magnetic particles are preferentially crystallinely oriented in the direction perpendicular to the magnetic tape MT. In this specification, the direction perpendicular to the magnetic tape MT (thickness direction) means the thickness direction of the magnetic tape MT in a planar state.

[0078] (Hexagonal ferrite particles) Hexagonal ferrite particles have a plate-like shape, such as a hexagonal plate, or a columnar shape, such as a hexagonal prism (provided that the thickness or height is smaller than the major axis of the plate surface or base surface). In this disclosure, hexagonal plate-like shape includes a substantially hexagonal plate-like shape. Also, hexagonal prism-like shape includes a substantially hexagonal prism-like shape.

[0079] The hexagonal ferrite particles contain Fe and a metal M1 other than Fe. The metal M1 includes, for example, at least one alkaline earth metal. The at least one alkaline earth metal includes, for example, at least one selected from the group consisting of Ba, Sr, and Ca. It is preferable that it includes at least one of Ba and Sr among these alkaline earth metals. The metal M1 may also contain Pb in addition to alkaline earth metals.

[0080] The hexagonal ferrite particles may further contain metal M2 in addition to Fe and metal M1. Preferably, metal M2 can substitute for some of the Fe sites in the crystal structure of the hexagonal ferrite. For example, metal M2 includes at least one selected from the group consisting of rare earth elements, transition metal elements other than Fe, and metal elements of Group 13 of the periodic table, and among these, at least one selected from the group consisting of Ti, Al, and Nd is preferred.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] The average atomic ratio of Sr to Ba (Sr / Ba) is preferably 0.02 to 2.00, and more preferably 0.02 to 1.00. When the average atomic ratio (Sr / Ba) is 0.02 or higher, the decrease in the effect of improving magnetic properties due to the addition of Sr (for example, the effect of improving the thermal stability (Ku) derived from strontium ferrite) can be suppressed. When the average atomic ratio (Sr / Ba) is 2.00 or lower, variations in magnetic properties can be suppressed.

[0085] Hexagonal ferrite may more specifically have an average composition represented by the following general formula (A): Ba （１－ｘ） α ｘ Fe （１２－ｙ） β ｙ O １９ ... (A) (However, in formula (A), α represents at least one selected from the group consisting of Sr, Ca, and Pb. β represents at least one selected from the group consisting of rare earth elements, transition metal elements other than Fe, and metal elements of Group 13 of the periodic table. x is in the range of 0 ≤ x ≤ 0.9, preferably 0 ≤ x ≤ 0.7, and more preferably 0.3 ≤ x ≤ 0.7. y represents 0 ≤ y ≤ 0.80, preferably 0.22 ≤ y ≤ 0.80, and more preferably 0.26 ≤ y ≤ 0.80.)

[0086] 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).

[0087] 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).

[0088] 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).

[0089] The average composition represented by general formula (A) is determined as follows. First, TEM images of three thinned samples are obtained in the same manner as the average atomic ratio of Sr to Ba (Sr / Ba). Next, EDX measurements are performed on the magnetic layer portion from the TEM images of each obtained thinned sample, and Ba 、 α 、 Fe 、 Determine the average composition ratio (average atomic ratio) of each component of β.

[0090] When the magnetic particles are hexagonal ferrite particles, the upper limit of the average particle size of the magnetic particles is preferably 19.0 nm or less, more preferably 18.0 nm or less, and even more preferably 17.0 nm or less, 16.0 nm or less, or 15.0 nm or less, from the viewpoint of improving linear recording density.

[0091] When the magnetic particles are hexagonal ferrite particles, the lower limit of the average particle size of the magnetic particles is preferably 12.0 nm or larger, and more preferably 13.0 nm or larger, from the viewpoint of improving the dispersibility of the magnetic particles and improving electromagnetic conversion characteristics (e.g., SNR (Signal-to-Noise Ratio)).

[0092] When the magnetic particles are hexagonal ferrite particles, the numerical range of the average particle size of the magnetic particles may be defined by either of the above upper and lower limits, preferably 12.0 nm to 19.0 nm, more preferably 12.0 nm to 18.0 nm, and even more preferably 12.0 nm to 17.0 nm, 13.0 nm to 17.0 nm, or 13.0 nm to 16.0 nm.

[0093] When the magnetic particles are hexagonal ferrite particles, the average aspect ratio of the magnetic particles is preferably 1.0 to 3.0, more preferably 1.5 to 2.8, and even more preferably 1.8 to 2.7. When the average aspect ratio of the magnetic particles is within the range of 1.0 to 3.0, aggregation of the magnetic particles can be suppressed. Furthermore, when the magnetic particles are vertically oriented during the formation process of the magnetic layer 43, the resistance applied to the magnetic particles can be suppressed. Therefore, the vertical orientation of the magnetic particles can be improved.

[0094] When the magnetic particles are hexagonal ferrite particles, the average particle size and average aspect ratio of the magnetic particles are determined as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and the magnetic tape MT is cut at a position 30 to 40 m in the longitudinal direction from one end on the outer circumference of the magnetic tape MT. Next, the magnetic tape MT to be measured is processed and thinned using the FIB method or the like. When using the FIB method, a carbon layer and a tungsten layer are formed as protective films as a pretreatment before observing the TEM image of the cross-section described later. The carbon layer is formed on the magnetic surface and back surface of the magnetic tape MT by vapor deposition, and the tungsten layer is further formed on the magnetic surface by vapor deposition or sputtering. This thinning is performed along the length direction (longitudinal direction) of the magnetic tape MT. That is, this thinning creates a cross-section parallel to both the longitudinal and thickness directions of the magnetic tape MT.

[0095] The cross-section of the obtained thin section sample is observed using a transmission electron microscope (Hitachi High-Technologies Corporation H-9500) with an acceleration voltage of 200kV and a total magnification of 500,000x, ensuring that the entire magnetic layer 43 is included in the thickness direction of the magnetic layer 43, and a TEM image is taken. The TEM images are prepared in a number that allows for the extraction of 50 particles capable of measuring the plate diameter DB and plate thickness DA (see Figure 7) shown below.

[0096] In this specification, the particle size of hexagonal ferrite (hereinafter referred to as "particle size") is determined as follows: If the shape of the particle observed in the TEM image is plate-like or columnar (however, the thickness or height is smaller than the major axis of the plate surface or base) as shown in Figure 7, the major axis of the plate surface or base is used as the value of plate diameter DB. The thickness or height of the particle observed in the TEM image is used as the value of plate thickness DA. If the thickness or height of a particle is not constant within a single particle observed in the TEM image, the thickness or height of the largest particle is used as plate thickness DA.

[0097] 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.

[0098] Figures 8 and 9 show the first and second examples of TEM images, respectively. In Figures 8 and 9, for example, the particles indicated by arrows a and d are selected because their particle thickness (thickness or height) DA can be clearly identified. The particle thickness DA of each of the 50 selected particles is measured. The particle thicknesses DA obtained in this way are simply averaged (arithmetic mean) to obtain the average particle thickness DA. ave We will find the average plate thickness DA. ave This is the average particle thickness. Next, the diameter DB of each magnetic particle is measured. To measure the particle diameter DB, 50 particles whose diameter DB can be clearly identified are selected from the captured TEM images. For example, in Figures 8 and 9, the particles indicated by arrows b and c are selected because their diameter DB can be clearly identified. The diameter DB of each of the 50 selected particles is measured. The average diameter DB obtained in this way is calculated by taking a simple average (arithmetic mean) of the resulting diameter DB. ave We will find the average plate diameter DB. ave However, this is the average particle size. And the average plate thickness DA ave and average plate diameter DB aveFrom the average aspect ratio of the particles (DB) ave / DA ave )

[0099] When the magnetic particles are hexagonal ferrite particles, the upper limit of the average particle volume of the magnetic particles is preferably 1.50 × 10⁻¹⁰ from the viewpoint of improving linear recording density. ３ nm ３ More preferably 1.40 × 10 ３ nm ３ More preferably, 1.37 × 10 ３ nm ３ Below, 1.30 × 10 ３ nm ３ Below, 1.20 × 10 ３ nm ３ Below, 1.10 x 10 ３ nm ３ The following or 1.00 x 10 ３ nm ３ The following applies:

[0100] When the magnetic particles are hexagonal ferrite particles, the lower limit of the average particle volume of the magnetic particles is preferably 0.500 × 10⁻¹⁰, from the viewpoint of improving the dispersibility of the magnetic particles and improving electromagnetic conversion characteristics (e.g., SNR). ３ nm ３ More preferably 0.600 × 10 ３ nm ３ That's all.

[0101] When the magnetic particles are hexagonal ferrite particles, the numerical range of the average particle volume of the magnetic particles may be defined by either of the above upper and lower limits, preferably 0.500 × 10⁻⁶. ３ nm ３ The above 1.50 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, 0.500 x 10 ３ nm３ The above 1.20 x 10 ３ nm ３ Below, 0.600 x 10 ３ nm ３ The above 1.20 x 10 ３ nm ３ Below, 0.600 x 10 ３ nm ３ The above 1.10 x 10 ３ nm ３ The following or 0.600 x 10 ３ nm ３ The above 1.00 x 10 ３ nm ３ The following applies:

[0102] The average particle volume of magnetic particles can be determined as follows. First, as described above regarding the method for calculating the average particle size of magnetic particles, the average plate thickness DA ave and average plate diameter DB ave Next, we calculate the average particle volume V of the magnetic particles using the following formula.

[0103] (ε-iron oxide particles) ε-iron oxide particles are hard magnetic particles that can obtain high coercivity even in fine particles. ε-iron oxide particles are either spherical or cubic in shape. In this specification, spherical includes substantially spherical particles, and cubic includes substantially cubic particles. Because ε-iron oxide particles have the shapes described above, when ε-iron oxide particles are used as magnetic particles, the contact area between particles in the thickness direction of the magnetic tape MT can be reduced and particle aggregation can be suppressed compared to when hexagonal plate-shaped barium ferrite particles are used as magnetic particles. Therefore, the dispersibility of the magnetic particles can be improved, and excellent electromagnetic conversion characteristics (e.g., SNR) can be obtained.

[0104] The ε-iron oxide particles may have a composite particle structure. More specifically, the ε-iron oxide particles comprise an ε-iron oxide portion and a portion having soft magnetism or a portion having magnetism with a saturation magnetization σs higher than that of ε-iron oxide and a coercivity Hc lower (hereinafter referred to as "the portion having soft magnetism, etc.").

[0105] The ε-iron oxide portion contains ε-iron oxide. The ε-iron oxide contained in the ε-iron oxide portion is ε-Fe２ O ３ A crystalline phase is preferred, and a single-phase ε-Fe ２ O ３ A combination of these is preferable.

[0106] The saturation magnetization σs of the soft magnetic portion is preferably 40 emu / g or more. This suppresses the decrease in the saturation magnetization σs of the composite particles and improves the output characteristics of the magnetic tape MT. The soft magnetic portion is in contact with the ε iron oxide portion in at least a part. Specifically, the soft magnetic portion may partially cover the ε iron oxide portion, or it may cover the entire periphery of the ε iron oxide portion.

[0107] The portion having soft magnetism (a portion having magnetism with a saturation magnetization σs higher than that of ε-iron oxide and a coercivity Hc lower) includes, for example, soft magnetic materials such as α-Fe, Ni-Fe alloy, or Fe-Si-Al alloy. α-Fe may be obtained by reducing the ε-iron oxide contained in the ε-iron oxide portion.

[0108] Furthermore, the part having soft magnetism is, for example, Fe ３ O ４ γ-Fe ２ O ３ , or it may contain spinel ferrite, etc.

[0109] By having soft magnetic portions as described above, the ε-iron oxide particles can maintain a high coercivity Hc of the ε-iron oxide portion alone in order to ensure thermal stability, while adjusting the overall coercivity Hc of the ε-iron oxide particles (composite particles) to a coercivity Hc suitable for recording.

[0110] The ε-iron oxide particles may contain additives in place of the structure of the composite particles described above, or they may have the structure of the composite particles and also contain additives. In this case, a portion of the Fe in the ε-iron oxide particles is replaced by the additives. By including additives in the ε-iron oxide particles, the coercivity Hc of the ε-iron oxide particles as a whole can be adjusted to a coercivity Hc suitable for recording, thereby improving ease of recording. The additives are metal elements other than iron, preferably trivalent metal elements, more preferably at least one selected from the group consisting of Al, Ga, and In, and even more preferably at least one selected from the group consisting of Al and Ga.

[0111] Specifically, ε-iron oxide containing additives is ε-Fe ２－ｘ M ｘ O ３ The material is a crystal (wherein M is a metallic element other than iron, preferably a trivalent metallic element, more preferably at least one selected from the group consisting of Al, Ga, and In, and even more preferably at least one selected from the group consisting of Al and Ga. x is, for example, 0 < x < 1).

[0112] When the magnetic particles are ε-iron oxide particles, the upper limit of the average particle size of the magnetic particles is preferably 14.5 nm or less, more preferably 13.5 nm or less, even more preferably 13.0 nm or less, 12.5 nm or less, or 12.0 nm or less, from the viewpoint of improving linear recording density.

[0113] When the magnetic particles are ε-iron oxide particles, the lower limit of the average particle size of the magnetic particles is preferably 10.0 nm or more, from the viewpoint of improving the dispersibility of the magnetic particles and improving electromagnetic conversion characteristics (e.g., SNR).

[0114] When the magnetic particles are ε-iron oxide particles, the numerical range of the average particle size of the magnetic particles may be defined by either of the above upper limits and the above lower limit, preferably 10.0 nm to 14.5 nm, more preferably 10.0 nm to 13.5 nm, even more preferably 10.0 nm to 13.0 nm, 10.0 nm to 12.5 nm, or 10.0 nm to 12.0 nm.

[0115] When the magnetic particles are ε-iron oxide particles, the average particle size of the magnetic particles is determined as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and the magnetic tape MT is cut at a position 30 to 40 m in the longitudinal direction from one end on the outer circumference of the magnetic tape MT. Next, the magnetic tape MT to be measured is processed and thinned using the FIB method or the like. When using the FIB method, a carbon layer and a tungsten layer are formed as protective layers as a pretreatment before observing the TEM image of the cross-section described later. The carbon layer is formed on the magnetic surface and back surface of the magnetic tape MT by vapor deposition, and the tungsten layer is further formed on the magnetic surface by vapor deposition or sputtering. Thinning is performed along the length direction (longitudinal direction) of the magnetic tape MT. That is, this thinning creates a cross-section parallel to both the longitudinal and thickness directions of the magnetic tape MT.

[0116] The cross-section of the obtained thin section sample is observed using a transmission electron microscope (Hitachi High-Technologies Corporation H-9500) with an acceleration voltage of 200kV and a total magnification of 500,000x, ensuring that the entire magnetic layer 43 is included in the thickness direction of the magnetic layer 43, and a TEM image is taken. Next, 50 particles whose particle shape can be clearly confirmed are selected from the acquired TEM image, and the diameter of each particle is measured. Here, diameter refers to the maximum distance between two parallel lines drawn from any angle tangent to the contour of each particle (the so-called maximum Ferret diameter). Subsequently, the average diameter is obtained by simply averaging (arithmetic mean) the diameters of the 50 measured particles. The average diameter obtained in this way is taken as the average particle size of the magnetic particles.

[0117] When the magnetic particles are ε-iron oxide particles, the upper limit of the average particle volume of the magnetic particles is preferably 1.50 × 10⁻¹⁰ from the viewpoint of improving linear recording density. ３ nm ３ More 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 10３ nm ３ The following or 1.00 x 10 ３ nm ３ The following applies:

[0118] When the magnetic particles are ε-iron oxide particles, the lower limit of the average particle volume of the magnetic particles is preferably 0.500 × 10⁻¹⁰, from the viewpoint of improving the dispersibility of the magnetic particles and improving electromagnetic conversion characteristics (e.g., SNR). ３ nm ３ More preferably 0.600 × 10 ３ nm ３ That's all.

[0119] When the magnetic particles are ε-iron oxide particles, the numerical range of the average particle volume of the magnetic particles may be defined by either of the above upper and lower limits, preferably 0.500 × 10 ３ nm ３ The above 1.50 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 10 ３ nm ３ The following or 0.600 x 10 ３ nm ３ The above 1.00 x 10 ３ nm ３ The following applies:

[0120] The average particle volume of magnetic particles can be determined as follows: First, the average particle size D is determined in the same manner as the method for calculating the average particle size of magnetic particles described above. Next, the average particle volume V of the magnetic particles is determined using the following formula: V = (π / 6) × D 3

[0121] (Cobalt ferrite particles) The cobalt ferrite particles preferably have uniaxial crystal anisotropy. The uniaxial crystal anisotropy of the cobalt ferrite particles allows the magnetic particles to be preferentially crystal-oriented in the direction perpendicular to the magnetic tape MT. The cobalt ferrite particles have, for example, a cubic shape. In this specification, the cubic shape includes a substantially cubic shape. The Co-containing spinel ferrite may further contain at least one selected from the group consisting of Ni, Mn, Al, Cu, and Zn in addition to Co.

[0122] Co-containing spinel ferrite has an average composition represented, for example, by the following formula: Co ｘ M ｙ Fe ２ O Ｚ (However, in the formula, M is at least one metal selected from the group consisting of, for example, Ni, Mn, Al, Cu, and Zn. x is a value in the range 0.4 ≤ x ≤ 1.0. y is a value in the range 0 ≤ y ≤ 0.3, where x and y satisfy the relationship (x + y) ≤ 1.0. z is a value in the range 3 ≤ z ≤ 4. Part of Fe may be substituted with other metallic elements.)

[0123] When the magnetic particles are cobalt ferrite particles, the upper limit of the average particle size of the magnetic particles is preferably 16.0 nm or less, more preferably 13.0 nm or less, and even more preferably 10.0 nm or less, from the viewpoint of improving linear recording density.

[0124] When the magnetic particles are cobalt ferrite particles, the lower limit of the average particle size of the magnetic particles is preferably 8.0 nm or larger, from the viewpoint of improving the dispersibility of the magnetic particles and improving electromagnetic conversion characteristics (e.g., SNR).

[0125] When the magnetic particles are cobalt ferrite particles, the numerical range of the average particle size of the magnetic particles may be defined by either of the above upper limits and the above lower limit, preferably 8.0 nm or more and 16.0 nm or less, more preferably 8.0 nm or more and 13.0 nm or less, and even more preferably 8.0 nm or more and 10.0 nm or less. The method for calculating the average particle size of the magnetic particles is the same as the method for calculating the average particle size of magnetic particles when the magnetic particles are ε iron oxide particles.

[0126] When the magnetic particles are cobalt ferrite particles, the average aspect ratio of the magnetic particles is preferably 1.0 to 3.0, more preferably 1.0 to 2.5, and even more preferably 1.0 to 2.0. When the average aspect ratio of the magnetic particles is within the range of 1.0 to 3.0, aggregation of the magnetic particles can be suppressed. Furthermore, when the magnetic particles are vertically oriented in the process of forming the magnetic layer 43, the resistance applied to the magnetic particles can be suppressed. Therefore, the vertical orientation of the magnetic particles can be improved. The method for calculating the average aspect ratio of the magnetic particles is the same as the method for calculating the average aspect ratio of magnetic particles when the magnetic particles are ε iron oxide particle powder.

[0127] When the magnetic particles are cobalt ferrite particles, the upper limit of the average particle volume of the magnetic particles is preferably 4.00 × 10⁻¹⁰ from the viewpoint of improving linear recording density. ３ nm ３ More preferably, 2.00 × 10 ３ nm ３ More preferably, 1.50 × 10 ３ nm ３ The following or 1.00 x 10 ３ nm ３ The following applies:

[0128] When the magnetic particles are cobalt ferrite particles, the lower limit of the average particle volume of the magnetic particles is preferably 0.5 × 10⁻¹⁰, from the viewpoint of improving the dispersibility of the magnetic particles and improving the electromagnetic conversion characteristics (e.g., SNR). ３ nm ３ More preferably 0.6 × 10 ３ nm ３ That's all.

[0129] When the magnetic particles are cobalt ferrite particles, the numerical range of the average particle volume of the magnetic particles may be defined by either of the above upper and lower limits, preferably 0.5 × 10 ３ nm ３ The above 4.00 x 10 ３ nm ３ More preferably, 0.6 × 10 ３ nm ３ The above 2.00 x 10 ３ nm ３ More preferably, 0.6 × 10 ３ nm ３ The above 1.50 x 10 ３ nm ３ The following or 0.6 × 10 ３ nm ３ The above 1.00 x 10 ３ nm ３ The method for calculating the average particle volume of magnetic particles is the same as the method for calculating the average particle volume when the magnetic particles are ε-iron oxide particle powder.

[0130] (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.

[0131] 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.

[0132] 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.

[0133] 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.

[0134] 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.

[0135] 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.

[0136] The polyester includes, for example, at least one selected from the group consisting of phthalate polyesters and aliphatic polyesters.

[0137] 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.

[0138] 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.

[0139] 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.

[0140] (Lubricant) The lubricant may be a liquid lubricant. The lubricant contains both fatty acids and fatty acid esters. The inclusion of 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).

[0141] (Fatty Acids) Fatty acids have a higher melting point than fatty acid esters and also have a higher oil film strength than fatty acid esters. Fatty acids have a dynamic friction coefficient μ due to the repeated sliding of the head unit 56 against the magnetic tape MT. Ｔ It has the effect of suppressing the increase of the dynamic friction coefficient μ due to repeated recording and playback of magnetic tape MT. Ｔ It has the effect of suppressing the increase of. In this specification, the coefficient of dynamic friction μ Ｔ This refers to the coefficient of dynamic friction μ between the magnetic surface and the head unit 56 during the operation of the magnetic tape MT. Ｔ This shall represent the coefficient of dynamic friction μ of the magnetic tape MT when the running speed of the magnetic tape MT changes, such as when the magnetic tape MT starts running and when it reverses direction (for example, when the running speed of the magnetic tape MT changes from a stopped state to high speed, and when the running speed of the magnetic tape MT changes from high speed to a stopped state). Ｔ It also has the effect of suppressing the rise in [the substance].

[0142] Furthermore, fatty acids have a coefficient of kinetic friction μ at low speeds. ＴIt also has the effect of suppressing the increase of [unclear value]. For this reason, fatty acids also have the effect of suppressing the occurrence of stick-slip phenomena during low-speed driving. The occurrence of stick-slip phenomena during low-speed driving is correlated with the wobble (standard deviation σPES) in the width direction of the magnetic tape MT during high-speed driving, and by suppressing stick-slip phenomena during low-speed driving, it is possible to suppress the wobble (standard deviation σPES) in the width direction of the magnetic tape MT during high-speed driving. Here, low-speed driving refers to driving in a speed range of 3 mm / s to 10 mm / s.

[0143] The fatty acid may be one type of fatty acid or two or more types of fatty acids. The two or more fatty acids may have different melting points. The fatty acid may include, for example, at least one selected from saturated fatty acids and unsaturated fatty acids. The saturated fatty acid may include, for example, at least one selected from straight-chain saturated fatty acids and branched-chain saturated fatty acids. The unsaturated fatty acid may include, for example, at least one selected from straight-chain unsaturated fatty acids and branched-chain unsaturated fatty acids. The unsaturated fatty acid may include at least one selected from monounsaturated fatty acids, which have one carbon-carbon double bond, and polyunsaturated fatty acids, which have two or more carbon-carbon double bonds. The carbon-carbon double bond in the unsaturated fatty acid may be cis (Z-type) or trans (E-type).

[0144] The fatty acids preferably include at least one selected from the above-mentioned fatty acids, specifically from straight-chain saturated fatty acids and straight-chain unsaturated fatty acids. The straight-chain saturated fatty acids are preferably compounds represented by the following general formula (1). The unsaturated fatty acids preferably include straight-chain unsaturated fatty acids. The straight-chain unsaturated fatty acids are preferably compounds represented by the following general formula (2).

[0145] 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.)

[0146] CH3 (CH2) n CH = CH(CH2) mCOOH ... (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.)

[0147] A specific example of a compound (linear saturated fatty acid) represented by the above general formula (1) is palmitic acid (k=14:CH3(CH2) １４ COOH), stearic acid (k=16:CH3(CH2) １６ COOH), nonadecanoic acid (k=17:CH3(CH2) １７ COOH), arachidic acid (k=18:CH3(CH2) １８ COOH), behenic acid (k=20:CH3(CH2) ２０ COOH), lignoceric acid (k=22:CH3(CH2) ２２ Examples include COOH. These may be used individually or in combination of two or more.

[0148] A specific example of a compound (linear unsaturated fatty acid) represented by the general formula (2) above is palmitoleic acid (n=5, m=7: CH3(CH2) ５ CH = CH(CH2) ７ COOH), vaccenic acid (n=5, m=9: CH3(CH2) ５ CH = CH(CH2) ９ COOH), oleic acid (n=7, m=7 (cis type): CH3(CH2) ７ CH = CH(CH2) ７ COOH), elaidic acid (n=7, m=7 (trans form): CH3(CH2) ７ CH = CH(CH2) ７ COOH), eicosenoic acid (n=7, m=9: CH3(CH2) ７ CH = CH(CH2) ９ COOH), gadleic acid (n=9, m=7: CH3(CH2) ９ CH = CH(CH2) ７ COOH), erucic acid (n=7, m=11 (cis type): CH3(CH2) ７ CH = CH(CH2) １１ COOH), brassic acid (n=7, m=11 (trans form): CH3(CH2) ７CH = CH(CH2) １１ COOH), cetoleic acid (n=9, m=9: CH3(CH2) ９ CH = CH(CH2) ９ COOH), nervonic acid (n=7, m=13: CH3(CH2) ７ CH = CH(CH2) １３ Examples include COOH. These may be used individually or in combination of two or more.

[0149] (Fatty acid esters) Fatty acid esters have a lower melting point than fatty acids. Fatty acid esters are mainly used to improve the coefficient of dynamic friction μ during high-speed operation of magnetic tape MT. Ｔ It has the effect of suppressing the increase of [unclear value]. In other words, fatty acid esters have the effect of suppressing the instability of the running performance of magnetic tape MT during high-speed running. Here, high-speed running refers to, for example, running in a speed range of 2 m / s to 7 m / s.

[0150] A fatty acid ester may be one type of fatty acid ester or two or more types of fatty acid esters. The two or more fatty acid esters may have different melting points. A fatty acid ester may include, for example, at least one selected from saturated fatty acid esters and unsaturated fatty acid esters. A saturated fatty acid ester may include, for example, at least one selected from straight-chain saturated fatty acid esters and branched-chain saturated fatty acid esters. An unsaturated fatty acid ester may include, for example, at least one selected from straight-chain unsaturated fatty acid esters and branched-chain unsaturated fatty acid esters. An unsaturated fatty acid ester may include at least one selected from monounsaturated fatty acid esters having one carbon-carbon double bond and polyunsaturated fatty acid esters having two or more carbon-carbon double bonds. The carbon-carbon double bond in an unsaturated fatty acid ester may be in the cis (Z) or trans (E) configuration.

[0151] The fatty acid ester preferably contains at least one selected from the above-mentioned fatty acid esters, specifically from straight-chain saturated fatty acid esters and branched-chain saturated fatty acid esters. The straight-chain saturated fatty acid ester is preferably a compound represented by the following general formula (3). The branched-chain saturated fatty acid ester is preferably a compound represented by the following general formula (4).

[0152] 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.)

[0153] 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.)

[0154] A specific example of a compound (linear saturated fatty acid ester) represented by the above general formula (3) is butyl stearate (p=16, q=3:CH3(CH2) １６ COO (CH2) ３ CH3), butyl palmitate (p=3, q=14: CH3(CH2) ３ COO (CH2) １４ Examples include CH3). These may be used individually or in combination of two types.

[0155] A specific example of the compound represented by the above general formula (4) (branched-chain saturated fatty acid ester) is isobutyl stearate (r=16, s=1:CH3(CH2) １６ COO-(CH2) １ Examples include CH(CH3)2).

[0156] (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.

[0157] 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.

[0158] 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.

[0159] 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.

[0160] 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.

[0161] 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.

[0162] (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.

[0163] 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.

[0164] 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.

[0165] 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.

[0166] (Abrasive particles) Some of the abrasive particles contained in the magnetic layer 43 may protrude from the magnetic surface and form multiple protrusions. When the head unit 56 and the magnetic tape MT slide against each other, the protrusions formed by the abrasive particles can come into contact with the head unit 56.

[0167] 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 56. 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 56.

[0168] 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.

[0169] (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.

[0170] (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.

[0171] 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.

[0172] (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.

[0173] (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).

[0174] (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.

[0175] 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.

[0176] Average thickness t of the base layer 42 ３The upper limit of the magnetic surface is preferably 0.95 μm or less, more preferably 0.90 μm or less, even more preferably 0.80 μm or less, 0.70 μm or less, or 0.60 μm or less, from the viewpoint of improving the elasticity of the magnetic surface. Since the elasticity of the substrate 41 is higher than that of the base layer 42, the elasticity of the magnetic surface is improved when the base layer 42 is made thinner. Average thickness t of the base layer 42 ３ The lower limit is preferably 0.30 μm or more, from the viewpoint of mitigating the uneven shape on the surface of the substrate 41.

[0177] Average thickness t of the base layer 42 ３ The numerical range may be defined by either of the above upper limits and the above lower limit, preferably 0.30 μm or more and 0.90 μm or less, more preferably 0.30 μm or more and 0.80 μm or less, even more preferably 0.30 μm or more and 0.70 μm or less, and particularly preferably 0.30 μm or more and 0.60 μm or less.

[0178] 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.

[0179] Average thickness t of the substrate 41 １ In contrast, the average thickness t of the magnetic layer 43 ２ and the average thickness t of the base layer 42 ３ If the total thickness is too large, the bending rigidity will increase, which may reduce the stability of the contact between the magnetic tape MT and the head. On the other hand, the average thickness t of the base body 41 １ In contrast, the average thickness t of the magnetic layer 43 ２ and the average thickness t of the base layer 42 ３ If the total thickness is too small, there is a risk that the surface quality of the magnetic surface of the magnetic tape MT will deteriorate. Therefore, the average thickness t of the substrate 41 １ The average thickness t of the magnetic layer 43 relative to this. ２ and the average thickness t of the base layer 42 ３ The ratio of the total thickness ((t) ２ +t ３ ) / t １ ) is preferably 0.19 or more and 0.28 or less.

[0180] (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.

[0181] (Binding agent, lubricant) The binding agent and lubricant are the same as those used in the magnetic layer 43 described above.

[0182] (Additives) The antistatic agent, hardening agent, and rust inhibitor are the same as those used in the magnetic layer 43 described above.

[0183] (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 hardener and antistatic agent are the same as those in the magnetic layer 43 described above.

[0184] 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.

[0185] 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 t Ｔ Even if the thickness is 5.40 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.

[0186] Average thickness t of the back layer 44 ４ This can be calculated as follows: First, the average thickness t of the magnetic tape MT. Ｔ Measure the average thickness t. Ｔ The measurement method is as described in "Average Thickness of Magnetic Tape" below. Next, the magnetic tape MT housed in the cartridge 10 is unwound, and a 250 mm length of the magnetic tape MT is cut from one end of the outer circumference of the magnetic tape MT at a position 30 m to 40 m in the longitudinal direction to prepare a sample. Next, the back layer 44 of the sample is removed with a solvent such as MEK (methyl ethyl ketone) or dilute hydrochloric acid. Next, the thickness of the sample is measured at five points using a Mitutoyo laser hologage (LGH-110C), and these measurements are simply averaged (arithmetic mean) to obtain the average value t Ｂ The [μm] value is calculated. Then, the average thickness t of the back layer 44 is calculated using the following formula. ４ Determine the [μm]. Note that the five measurement points mentioned above will be randomly selected from the sample so that they are all at different positions along the longitudinal direction of the magnetic tape MT. ４ [μm] = t Ｔ [μm] - t Ｂ [μm]

[0187] (Average thickness of magnetic tape) By reducing the average thickness of the magnetic tape MT, the length of tape wound into one cartridge 10 can be increased, thereby increasing the recording capacity per cartridge 10. Therefore, from the viewpoint of improving the recording capacity of cartridge 10, the average thickness (average total thickness) of the magnetic tape MT t Ｔ The upper limit is preferably 5.40 μm or less, more preferably 5.30 μm or less, even more preferably 5.10 μm or less, 4.90 μm or less, or 4.70 μm or less. Average thickness t of magnetic tape MT Ｔ The lower limit is not particularly restricted, but for example, it is 3.50 μm or larger.

[0188] Average thickness t of magnetic tape MT ＴThe 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.

[0189] (Ratio of fatty acid ester content A on the surface of magnetic layer 43 to the amount of fatty acids extracted B from magnetic tape MT (A / B)) Fatty acid ester content A [mg / m²] on the magnetic surface was measured by transferring the lubricant on the magnetic surface to a glass fiber sheet. ２ By immersing the magnetic tape MT in n-hexane for 5 minutes, the amount of fatty acid extracted from the magnetic tape MT is B [mg / m ２ The upper limit of the ratio (A / B) to ] is 0.10 or less, preferably 0.09 or less. If the ratio (A / B) exceeds 0.10, the amount of fatty acid ester on the magnetic surface becomes excessively large compared to the amount of fatty acid on the magnetic surface, causing the fatty acid to be buried in the fatty acid ester on the magnetic surface, and the effect of the fatty acid to not be fully exerted. Therefore, the dynamic friction coefficient μ due to repeated recording and playback of magnetic tape MT Ｔ It becomes difficult to suppress the increase in the coefficient of friction. In other words, the running durability of the magnetic tape MT decreases. Also, when the ratio (A / B) exceeds 0.10, the dynamic friction coefficient μ occurs when the speed of the magnetic tape MT changes, such as when the magnetic tape MT starts running and when it reverses direction. Ｔ It may also become difficult to suppress the increase in speed. In other words, the running stability of the magnetic tape MT will also decrease when the speed changes.

[0190] The lower limit of the above ratio (A / B) is preferably 0.02 or higher, more preferably 0.04 or higher. If the ratio (A / B) is less than 0.02, it is possible to suppress the amount of fatty acid ester on the magnetic surface from becoming excessively low compared to the amount of fatty acid on the magnetic surface. Therefore, it is possible to suppress the decrease in the effect of fatty acid ester on the magnetic surface. Therefore, the dynamic friction coefficient μ during high-speed running of the magnetic tape MT Ｔ This can suppress the increase in [the specified value]. In other words, it can suppress the decrease in running stability during high-speed operation of the magnetic tape MT.

[0191] The numerical range of the above ratio (A / B) may be defined by either of the above upper limit values ​​and either of the above lower limit values, preferably 0.02 or more and 0.10 or less, and more preferably 0.04 or more and 0.09 or less.

[0192] (Fatty acid ester content A on the surface of magnetic layer 43) The upper limit of the fatty acid ester content A on the surface of magnetic layer 43, measured by transferring the lubricant of the magnetic surface to a glass fiber sheet, is 0.80 mg / m². ２ Preferably, 0.50 mg / m² ２ The following is the result: The fatty acid ester content A is 0.80 mg / m³. ２ The following conditions can suppress the amount of fatty acid esters on the magnetic surface from becoming excessively large. Therefore, it is possible to suppress the magnetic tape MT from sticking to the head unit 56 when the magnetic tape MT is running.

[0193] The lower limit of the fatty acid ester content A on the surface of the magnetic layer 43 is preferably 0.05 mg / m². ２ More preferably, 0.10 mg / m² ２ That concludes the report. The fatty acid ester content A is 0.05 mg / m³. ２ As described above, the decrease in the effect of fatty acid esters on the magnetic surface can be suppressed. In other words, the decrease in running stability of the magnetic tape MT during high-speed running can be suppressed. Here, the effect of fatty acid esters on the magnetic surface refers to the decrease in the dynamic friction coefficient μ during high-speed running of the magnetic tape MT, as described above. Ｔ This has the effect of suppressing the rise in [the substance].

[0194] The numerical range of the fatty acid ester content A may be defined by either of the upper and lower limits, preferably 0.05 mg / m². ２ 0.80mg / m or more ２ More preferably, 0.10 mg / m² ２ 0.50mg / m or more ２ The following applies:

[0195] (Amount of fatty acids extracted from magnetic tape MT B) By immersing magnetic tape MT in n-hexane for 5 minutes, the lower limit of the amount of fatty acids extracted from magnetic tape MT B is 5.0 mg / m ２ Preferably, the above is 5.2 mg / m². ２ The following applies: If the amount of fatty acid extracted (B) is 5.0 mg or more, the decrease in the effect of fatty acids on the magnetic surface can be suppressed. The effect of fatty acids on the magnetic surface refers to the reduction in the coefficient of dynamic friction μ due to repeated recording and playback of magnetic tape MT, as described above. Ｔ The effect of suppressing the rise of the dynamic friction coefficient μ during changes in the speed of the magnetic tape MT, such as when the magnetic tape MT starts moving and when it reverses direction. Ｔ The effect of suppressing the increase, and the coefficient of dynamic friction μ during low-speed driving. Ｔ This has the effect of suppressing the rise in [the substance].

[0196] By immersing the magnetic tape MT in n-hexane for 5 minutes, the upper limit of the amount B of fatty acids extracted from the magnetic tape MT is preferably 13.0 mg / m². ２ More preferably, 10.0 mg / m² ２ The following is the result: The amount of fatty acid extracted (B) is 13.0 mg / m². ２ The following conditions can suppress the amount of fatty acids on the magnetic surface from becoming excessively large. Therefore, it is possible to suppress the magnetic tape MT from sticking to the head unit 56 when the magnetic tape MT is running.

[0197] The numerical range of the extracted fatty acid amount B may be defined by either of the upper and lower limits, preferably 5.0 mg / m². ２ 13.0mg / m or more ２More preferably, 5.0 mg / m² ２ 10.0mg / m or more ２ More preferably, 5.2 mg / m² ２ 10.0mg / m or more ２ The following applies:

[0198] (Method for measuring the fatty acid ester content A on the surface of the magnetic layer 43) The fatty acid ester content A on the surface of the magnetic layer 43, which is measured by transferring the lubricant of the magnetic surface to a glass fiber sheet, 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 a position of approximately 20 m from one end of the outermost edge of the magnetic tape MT, with a length of 76 mm or more, to obtain six tape samples TS.

[0199] Next, using six tape samples TS, six transferable samples 80, as shown in Figure 10, are prepared as follows: A 1 / 2-inch wide tape sample TS is wrapped around a slide glass 81 (manufactured by Toshin Riko Co., Ltd., whole slide glass, dimensions 76 mm x 26 mm) so that the longitudinal direction of the tape sample TS coincides with the longitudinal direction of the slide glass 81 and the magnetic surface of the tape sample TS faces outwards. Then, both ends of the tape sample TS in the longitudinal direction are fixed to the first surface of the slide glass 81 with mending tape 82. This gives rise to the transferable samples 80.

[0200] Next, using two of the six transfer samples 80, the content of fatty acid esters on the surface of the magnetic layer 43 was determined. １The following is how it is measured: A glass fiber sheet 83 (manufactured by ADVANTEC, GA-100) is cut to the same size as the slide glass 81, and the two transfer samples 80 are placed between the two transfer samples 80 and the glass fiber sheet 83. A 50g cylindrical weight 84 is placed in the center of the top surface of this laminate, and the laminate is held for 20 hours in an environment with a temperature of 22-25°C and a humidity of 37-38% RH, thereby transferring the lubricant from the magnetic surfaces of the two transfer samples 80 to the glass fiber sheet 83. The amount of lubricant transferred to the glass fiber sheet 83 can be considered as the amount of lubricant on the magnetic surface of the tape sample TS. In this specification, numerical ranges are indicated using the symbol "~" as "X １ ~X ２ If it is written as "X １ ~X ２ " is X １ and X ２ These are included as the lower and upper limits, respectively. In the above lubricant transfer process, the lubricant from the magnetic surfaces of the two transfer samples 80 is transferred to both sides of the glass fiber sheet 83 in order to increase the amount detected during analysis and minimize measurement variability.

[0201] The above holding time (transfer time) of 20 hours and the above ambient temperature of 22-25°C are selected so that the amount of lubricant transferred to the glass fiber sheet 83 can be considered as the amount of lubricant on the magnetic surface of the tape sample TS. Specifically, this is as follows: If the holding time (transfer time) is too short, there is a risk that the amount of lubricant transferred to the glass fiber sheet 83 will be less than the amount of lubricant on the magnetic surface of the tape sample TS. On the other hand, if the holding time (transfer time) is too long, there is a risk that the lubricant will seep out from inside the magnetic layer 43 of the tape sample TS and be transferred to the glass fiber sheet 83. In other words, there is a risk that lubricant other than that on the magnetic surface of the tape sample TS will be transferred to the glass fiber sheet 83. Taking these points into consideration, the holding time (transfer time) is selected to be 20 hours. If the temperature of the holding environment is lower than the melting point of the fatty acid ester, the fatty acid ester will become solid, and there is a risk that the amount of fatty acid ester transferred to the glass fiber sheet 83 will be small. Taking this into consideration, the ambient temperature has been set to 22-25°C.

[0202] The glass fiber sheet 83 to which the lubricant has been transferred is punched out in two pieces with a φ5 mm punch, inserted into a sample cup, and subjected to GCMS (Gas Chromatography-Mass Spectrometry) analysis. At this time, hexane solutions of fatty acid esters with different concentrations are prepared, and GCMS analysis is performed in the same manner to create a calibration curve from the peak intensities. Based on this calibration curve, the amount of fatty acid ester transferred to the glass fiber sheet 83 is determined, and this is defined as the content a of the fatty acid ester on the surface of the magnetic layer 43 １ and is denoted as such.

[0203] The GCMS analysis conditions are as follows. ・Pyrolyzer (manufactured by Frontier Lab, PY-3030) Temperature: 250 °C Interface temperature: 280 °C ・GCMS (manufactured by Agilent, 7890B / 6977B) Column: Agilent DB-5 50 °C (2 min hold) ⇒ 150 °C (heating rate 20 °C / min) ⇒ 250 °C (10 °C / min) ⇒ 300 °C (20 °C / min)

[0204] Next, except for using the remaining four transfer samples 80 out of the six transfer samples 80, the content a of the above fatty acid ester on the surface of the magnetic layer 43 １ is measured in the same manner as the measurement method described above, and the content a of the fatty acid ester on the surface of the magnetic layer 43 ２ and a ３ are determined. Next, the contents a of the fatty acid ester １ and a ２ and a ３ are simply averaged (arithmetic mean) to obtain the content A of the fatty acid ester on the surface of the magnetic layer 43. That is, in the present disclosure, the content A of the fatty acid ester on the surface of the magnetic layer 43 refers to the average value obtained from the contents a of the fatty acid ester on the surface of the magnetic layer 43 １ and a ２ and a ３ and represents the average value obtained therefrom.

[0205] ​(Method for Measuring Extraction Amount B of Fatty Acids Extracted from Magnetic Tape MT) By immersing the magnetic tape MT in n-hexane for 5 minutes, the extraction amount B of fatty acids extracted from the magnetic tape MT is determined as follows.

[0206] First, unwind the magnetic tape MT housed in the cartridge 10, cut out five 1 m lengths of the magnetic tape MT with a width of 1 / 2 inch from a position approximately 20 m from one end on the outermost peripheral side of the magnetic tape MT, and place them in a conical beaker. Next, completely immerse the magnetic tape MT in 60 ml of n-hexane and stir for 5 minutes to extract the lubricant. After drying this extract with an evaporator, add 5 ml of a solution obtained by mixing acetonitrile and pure water at a ratio of 100:3 to dissolve the extract and obtain a lubricant solution. Next, put this solution into a vial through a 0.5 μm filter. Measure the thus obtained extraction sample by high performance liquid chromatography (Dionex Ultimate3000 manufactured by Thermo Fisher Scientific). At this time, prepare solutions of fatty acids with different concentrations, create a calibration curve from the peak intensities, determine the amount of fatty acids in the extraction sample, and define it as the extraction amount B of fatty acids.

[0207] The content A of fatty acid esters on the surface of the magnetic layer 43 is determined from the average value of three measurements, whereas the extraction amount B of fatty acids is a value determined by one measurement. This is because in the method for measuring the extraction amount B of fatty acids, the amount of sample measured is larger than that in the method for measuring the content A of fatty acid esters, so the variation in the measured values is small.

[0208] Hereinafter, the details of the method for measuring the extraction amount B of fatty acids will be described.

[0209] <Preliminary Preparation> A. Cut out four sheets of graph paper for setting the sample mount, and draw a 1 m mark line at a position inside 6 squares at both ends so that the center is 1 m in size. FIG. 11 is a diagram showing an example of a sample mount used for measuring the extraction rate. As shown in FIG. 11, mark an inverted triangle mark at the center 50 cm of the graph paper. Place the graph paper parallel to the desk and fix both ends of the graph paper with double-sided tape. Set the sample mount by attaching double-sided tape so as to cover the two 1 m mark lines.

[0210] B. Preparation of a mixed solvent of acetonitrile and ultrapure water (acetonitrile:ultrapure water = 100:3) Add 30 ml of ultrapure water to 1000 ml of acetonitrile. Close the lid, shake gently up and down, then loosen the lid and degas in an ultrasonic cleaner for 15 minutes.

[0211] C. Preparing the aluminum lid: Set the black lid, white rubber, and aluminum sheet.

[0212] D. Preparing the syringe: Set the filter on the outer shaft of the syringe. Also extend the inner shaft.

[0213] E. Preparation of Standard Reagents The type of standard reagent varies depending on the fatty acid used. The concentration is arbitrary. As an example, the preparation when stearic acid is used as the fatty acid is shown below. The standard reagent for stearic acid is prepared as follows: Weigh out 4.0 mg, 10.0 mg, and 30.0 mg of stearic acid, weigh out acetonitrile / water = 100 / 3 solvent, and make up each to 200 mL. Prepare the standard reagent for stearic acid (manufactured by Junsei Chemical, purity 95.0%).

[0214] <Starting up reversed-phase liquid chromatography> For reversed-phase liquid chromatography (HPLC), we will use the Ultimate 3000 (manufactured by Thermo) (column: ODS-2 5um 4.6×150mm (GL Sciences)). Turn on the power to the pump, autosampler, differential refractometer (Shodex RI-101, manufactured by Showa Denko, set temperature: 30℃), and PC. Purge the pump for 5 minutes. Wash the autosampler. Start the software. When the flow rate / pressure is increased to 2 ml, the liquid will start to flow, so wait for more than 1 hour until it stabilizes. The measurement conditions are set as follows: mobile phase acetonitrile / water = 100 / 3 (volume ratio), solvent acetonitrile / water = 100 / 3, column temperature 40℃, measurement time 10 minutes, flow rate 2 ml / min, injection volume 200 μl.

[0215] <Preparation of Standard Reagents> Place the prepared standard reagents in an ultrasonic cleaner for 15 minutes. Once the ultrasonic cleaning is complete, insert a syringe with a filter into the vial and pour the standard reagents directly into the syringe. Fill the vial with the standard reagents. Push the central shaft to push the liquid into the vial. Once the liquid reaches about the shoulder of the vial, close the aluminum cap. Return any remaining standard reagents in the syringe to the screw-cap vial through the filter.

[0216] <Sample Collection> Unwind the magnetic tape MT contained in cartridge 10, and cut a length of approximately 5m from the magnetic tape MT at a point 20m longitudinally from the connection point between the magnetic tape MT and the leader tape LT. Using the lines on the graph paper, attach the magnetic tape to the double-sided tape of the sample sheet, overlapping the Mag / Back lines alternately in parallel. Be careful not to apply too much tension when attaching the magnetic tape. Discard the P / C surface layer and collect five 1m lengths of magnetic tape. Place a ruler along the 1m mark on the sample sheet and cut 1m of magnetic tape with a cutter. Gather the five magnetic tapes together, pick them up in half at the center indicated by the inverted triangle mark using tweezers, and crumple the curled ends. Separate the magnetic tapes one by one and place them in a 120ml round-bottom flask, then cover with aluminum foil.

[0217] A. 5-minute extraction Measure 60 ml of hexane into a 100 ml graduated cylinder. Set the stopwatch to 5 minutes. Place the 120 ml screw tube containing the sample into an automatic shaker placed at 25°C, and leave the aluminum lid open. Pour the 60 ml of hexane measured into a 120 ml round-bottom flask, close the aluminum lid, and turn on the stopwatch and the automatic shaker simultaneously to start shaking (set the automatic shaker speed to 300 rpm). Five minutes after starting shaking, measure 50 ml of the sample into a 100 ml graduated cylinder. Transfer the sample from the graduated cylinder to a round-bottom flask. Insert the round-bottom flask containing the sample into the round-bottom flask mounting port of the evaporator and secure it. Start the evaporator, set the rotation speed of the round-bottom flask to 50 rpm, and rotate the round-bottom flask. Begin vacuuming to 160 hPa. Submerge the round-bottom flask in a water bath. In about 4 minutes, the hexane will have evaporated, leaving only fatty acids and fatty acid esters in the round-bottom flask. Once all the hexane has been used up, remove the round-bottom flask from the water bath. Release the reduced pressure and allow atmospheric pressure to be released (around 1013 hPa). Stop the evaporator from rotating. Remove the round-bottom flask and allow it to dry.

[0218] B. After the hexane has been removed by the solvent-purging evaporator, pipette 5 ml of the mixed solvent of acetonitrile and ultrapure water into the dried round-bottom flask and pour it in through the neck. Cover with an aluminum cap and shake while holding the neck of the round-bottom flask. Sonicate for 15 minutes. After sonication, shake the round-bottom flask again and pour all the liquid into a vial with a syringe fitted with a 0.5 μm filter. Push in the central shaft and fill the vial with liquid up to the shoulder, then cover and discard any liquid remaining in the syringe.

[0219] C. HPLC Measurement: After the reversed-phase liquid chromatography (HPLC) setup is complete, start the measurement.

[0220] <Data Analysis> Data analysis will be performed according to the following procedure: (1) Determine the area value of the standard reagent and create a calibration curve (in the form y = ax). (2) Determine the area value of the measurement sample and calculate the concentration from the calibration curve (the method of subtracting the peak area will be the same as that of the standard reagent). Then, determine the amount of fatty acid (mg) in 5 ml (or 10 ml) of acenitide solution. (3) Determine the amount of fatty acid extracted B (mg / m) based on the following formula. ２ Convert to: Fatty acid extraction amount B = (fatty acid amount × (60 / 50)) / tape area Fatty acid amount = value obtained in (2) above Tape area (5m × (1 / 2 inch)) = 0.06325m ２ (1 / 2 inch x length [m]) *Correction made because the amount of fatty acids measured was from 50 ml of the 60 ml of hexane extracted.

[0221] (Method for measuring the ratio (A / B)) The above ratio (A / B) is calculated using the fatty acid ester content A [mg / m³] determined as described above. ２ ] and the amount of fatty acid extracted B [mg / m] obtained as described above. ２ It can be found using ].

[0222] (Average Dynamic Friction Coefficient μ) The average dynamic friction coefficient μ, measured by running the magnetic tape MT at a speed of 5 mm / s (low speed), is a physical quantity that replaces the average dynamic friction coefficient of the magnetic surface in the width direction when the magnetic tape MT is recorded or played back by the drive of the oblique head unit 56, and is correlated with the vibration of the magnetic tape MT caused by the stick-slip phenomenon when the magnetic tape MT is recorded or played back by the drive of the oblique head unit 56. Here, the average dynamic friction coefficient μ is the average dynamic friction coefficient between the recording / playback head of the LTO4 drive manufactured by Hewlett Packard Enterprise (HPE) and the magnetic surface of the magnetic tape MT, and the details of its measurement method will be described later.

[0223] After 250 round trips, the average kinetic friction coefficient μ (hereinafter referred to as "average kinetic friction coefficient μ(250) at low speed") measured by running the magnetic tape MT at a speed of 5 mm / s (low speed) is preferably 0.45 or less, more preferably 0.40 or less, even more preferably 0.39 or less, 0.35 or less, or 0.33 or less. When the average kinetic friction coefficient μ(250) at low speed is 0.45 or less, the vibration of the magnetic tape MT caused by the stick-slip phenomenon described above can be suppressed even after 250 round trips. In other words, even after 250 round trips, the amount of deviation (error) in the reading position of the servo pattern in the width direction of the magnetic tape MT by the oblique head unit 56 can be suppressed, and the data track Tk can be accurately traced by the oblique head unit 56. Therefore, even after 250 round trips, the running stability of the magnetic tape MT can be maintained in the drive of the oblique head unit 56.

[0224] (Configuration of measuring device 70) Before explaining the method for measuring the average kinetic friction coefficient μ(250) during low-speed driving, the configuration of the measuring device 70 used in the method for measuring the average kinetic friction coefficient μ(250) will be described with reference to Figures 12, 13, and 14.

[0225] The measuring device 70 comprises a base 71, a drive unit 72, a load cell 73, two plate-shaped members 74A and 74B, two guides 75A and 75B, and a head block 76.

[0226] (Drive unit 72) The drive unit 72 is fixed on the base 71. The drive unit 72 is configured to move in a direction that moves the load cell 73 closer to and further away from the guide 75A.

[0227] (Load cell 73) The load cell 73 is supported on the drive unit 72. One end of the magnetic tape MT is connected to the load cell 73 via a jig 77. The load cell 73 can measure the tension applied to the magnetic tape MT in the longitudinal direction. The load cell 73 used is a ZTS-5N manufactured by Imada Corporation. The positions of the load cell 73 and the guide 75A are set so that the magnetic tape MT is approximately horizontal between the jig 77 and the guide 75A.

[0228] (Plate-shaped members 74A, 74B) The plate-shaped members 74A and 74B are supported on the base 71 at a predetermined distance apart, with their main surfaces facing each other and parallel to each other. The plate-shaped members 74A and 74B are made of metal plates with high rigidity. Note that the plate-shaped member 74B is not shown in Figure 12.

[0229] (Guides 75A, 75B) The two guides 75A and 75B are spaced apart from each other and arranged parallel to each other. Bearings (not shown) are provided at both ends of the two guides 75A and 75B, and these bearings are used to fix both ends of the two guides 75A and 75B to the plate-shaped members 74A and 74B. As a result, the two guides 75A and 75B can rotate smoothly in conjunction with the reciprocating movement of the magnetic tape MT, and the relative positions of the two guides 75A and 75B are fixed. Because the two guides 75A and 75B can rotate smoothly as described above, the dynamic friction force between the guides 75A and 75B and the magnetic tape MT does not affect the tension measurement of the magnetic tape MT. Guide 75A has a round bar 75A1 and a roll member 75A2. Guide 75B has a round bar 75B1 and a roll member 75B2.

[0230] Bearings (not shown) are provided at both ends of the round bar 75A1. Similarly, bearings (not shown) are provided at both ends of the round bar 75B1. The round bar 75A1 is inserted into the hole of the roll member 75A2, and the roll member 75A2 is fixed to the circumferential surface of the round bar 75A1. Similarly, the round bar 75B1 is inserted into the hole of the roll member 75B2, and the roll member 75B2 is fixed to the circumferential surface of the round bar 75B1. The circumferential surfaces of the roll members 75A2 and 75B2 are the surfaces that the magnetic tape MT contacts when measuring tension. Round bars 75A1 and 75B1 are 3mm diameter SUS round bars (manufactured by Misumi Corporation, RGOS3-150 Kenma Rod RGOS). Roll members 75A2 and 75B2 are 15mm diameter SUS cylindrical members.

[0231] (Head Block 76) The head block 76 is movably mounted on plate-shaped members 74A and 74B so that the gripping angle θ can be adjusted. When the gripping angle θ (°) reaches a desired angle (20° in this measurement) by moving the head block 76, the head block 76 is configured to be fixed in that position, thereby fixing the positional relationship between the guides 75A and 75B and the head block 76. When measuring tension, the head block 76 is fixed between the guides 75A and 75B, and at approximately equidistant distances from each of the guides 75A and 75B. As the head block 76, a recording and playback head from an LTO4 drive manufactured by Hewlett Packard Enterprise (HPE) is used.

[0232] (Sample Preparation) Samples used to measure the mean kinetic friction coefficient μ(250) during low-speed driving are prepared as follows. First, a 50 cm length of magnetic tape MT is cut from one end of the outer circumference of the magnetic tape MT at a position 30 m in the longitudinal direction, and a sample with a width of 1 / 2 inch and a length of 50 cm (hereinafter referred to as "Sample 1") is prepared.

[0233] Next, the magnetic tape MT is unwound further, and a 50 cm length is cut from one end of the inner circumference of the magnetic tape MT at a point 50 m in the longitudinal direction, creating a sample (hereinafter referred to as "Sample 2") with a width of 1 / 2 inch and a length of 50 cm.

[0234] (Measurement of average kinetic friction coefficient μ(250) during low-speed driving) The average kinetic friction coefficient μ(250) during low-speed driving is measured using the above measuring device 70 as follows.

[0235] The sample 1 produced as described above is attached to the measuring device 70, and the tension T [N] of the sample 1 during sliding is measured by the measuring device 70 as follows. First, the magnetic tape MT of the sample 1 is placed on the two guides 75A and 75B so as to straddle the two guides 75A and 75B, and the head block 76 is brought into contact with the magnetic surface of the magnetic tape MT. At this time, as shown in FIG. 14, the magnetic surface of the magnetic tape MT is brought into contact with the head block (for recording and playback) 76 so that the holding angle θ (°) = 20°. Here, the holding angle θ is calculated from the curvature R of the head block 76 and the amount of pushing-in of the head block 76 with respect to the magnetic tape MT. Next, one end of the magnetic tape MT is connected to the load cell 73 via the jig 77. One end of the magnetic tape MT is fixed to the jig 77. Next, a weight 78 of 80 g is connected to the other end of the magnetic tape MT. By the weight 78, a tension of 80 gf (about 0.79 N) is applied in the longitudinal direction of the magnetic tape MT.

[0236] Next, while repeating 251 reciprocating operations on the magnetic tape MT, the head block 76 is slid on the magnetic surface of the magnetic tape MT. Then, the tension T [N] of the magnetic tape MT during this reciprocating operation is measured by the load cell 73. The above reciprocating operation is controlled such that the sliding distance (travel distance) of each of the forward and return paths is 55 mm, and the sliding speed (travel distance) of the magnetic tape MT with respect to the head block 76 is 5 mm / s. The sliding speed (travel speed) of 5 mm / s is a value set in consideration of the shift speed in the width direction of the magnetic tape MT during actual running.

[0237] Both the one-way pulling time (travel time of the forward path) and the one-way feeding time (travel time of the return path) are set to 11 sec. Also, the sampling rate of the load cell 73 is set to 0.5 points / sec. Therefore, the number of measurement points during one pull (during the travel of one forward path) is 22 points excluding the measurement point at 0 sec. The environment during the measurement of the tension T [N] is maintained at 23°C ± 2°C and 45% RH ± 5% RH.

[0238] Next, the tension T [N] of sample 2 is measured in the same manner as the measurement of the magnetic tape tension T [N] of sample 1, except that sample 2 prepared as described above is used.

[0239] Next, the average tension values ​​during tensile stress are calculated for the 250th and 251st forward passes of samples 1 and 2. Specifically, the data for the preceding and succeeding 1 point (data at 0 seconds and 11 seconds) are removed from the measurement data (tension) for each of the 250th forward pass (22 points) of sample 1, the 251st forward pass (22 points) of sample 1, the 250th forward pass (22 points) of sample 2, and the 251st forward pass (22 points) of sample 2. Then, the measurement data for the 250th forward pass (20 points) of sample 1, the measurement data for the 251st forward pass (20 points) of sample 1, the measurement data for the 250th forward pass (20 points) of sample 2, and the measurement data for the 251st forward pass (20 points) of sample 2 (totaling 20 × 4 measurement data) are simply averaged to obtain the average tension T during sliding. ave Find [N].

[0240] Tension of magnetic tape MT in a stationary state (T ０ [N]) is determined as follows. After measuring the tension T [N] of sample 1 above, the apparatus shown in Figure 12 is rotated 90° so that the jig 77 is positioned directly below the load cell 73. The apparatus is then held so that the longitudinal direction of the magnetic tape MT coincides with the direction of gravity, and the magnetic tape MT hangs down directly without going through the guides 75A and 75B and the head block 76. In this state, the tension applied to the magnetic tape MT is measured by the load cell 73, and this tension is determined to be the tension T of the magnetic tape MT in a stationary state. ０１ Let [N] be the value. Note that the tension T is also present. ０１ The measurement environment for [N] is maintained at 23°C ± 2°C and 45% RH ± 5% RH. Subsequently, except for using sample 2 after the measurement of tension T [N], the tension T of the magnetic tape of sample 1 described above is used. ０１ The tension T of the magnetic tape of sample 2 was measured in the same manner as for [N]. ０２ Measure [N]. Then, measure the tension T. ０１[N] and tension T ０２ The average tension T is obtained by simply averaging [N]. ０ Find [N].

[0241] Average tension T ave [N] and average tension T ０ [N] is substituted into the following equation to find the mean kinetic friction coefficient μ(250) at low speeds. (However, in the formula, θ [°] represents the angle of the magnetic tape MT with respect to the head block 76, T ０ [N] represents the average tension of the magnetic tape MT in a stationary state, and T ave [N] represents the average tension of the magnetic tape MT during sliding.

[0242] (Standard deviation of PES value σPES) Hereinafter, as shown in Figure 15, a head unit 200 maintained parallel to the axis Ax extending in the width direction of the magnetic tape MT may be referred to as a "parallel head unit 200". When a full volume test is performed on the magnetic tape MT using the drive of the parallel head unit 200, the standard deviation σPES of the PES (Position Error Signal) value obtained from the servo signal corresponding to the servo pattern is preferably 15.5 nm or less, more preferably 15.0 nm or less, and even more preferably 14.6 nm or less, 14.5 nm or less, 14.2 nm or less, or 14.1 nm or less. A full volume test is a test in which data is recorded and played back over the entire length of the magnetic tape MT.

[0243] In this embodiment, the standard deviation σPES when using the drive of the parallel head unit 200 will be described, but the standard deviation σPES when using the drive of the oblique head unit 56 may also be within the above numerical range.

[0244] PES (Performance Error) indicates the amount of deviation (error) in the reading position of the servo pattern in the width direction of the magnetic tape MT when the servo pattern is reproduced (read) by the drive (recording / playback device). The standard deviation σPES is related to the kinetic friction force of the magnetic surface, and as the kinetic friction force of the magnetic surface increases, the standard deviation σPES tends to increase. Therefore, by measuring the standard deviation σPES, an increase in the kinetic friction force of the magnetic surface can be determined.

[0245] When the standard deviation σPES is kept below 15.5 nm, the increase in kinetic friction force on the magnetic surface associated with the movement of the magnetic tape MT is suppressed, and the occurrence of track misalignment is suppressed. Therefore, the decrease in the running stability of the magnetic tape MT can be suppressed.

[0246] Referring to Figure 15, a parallel head unit 200 for measuring PES values ​​will be described. As the parallel head unit 200, an LTO8 head (a head conforming to the LTO8 standard) manufactured by HPE (Hewlett Packard Enterprise) is used. The parallel head unit 200 has two head sections 200A and 200B arranged side by side along the longitudinal direction of the magnetic tape MT. Each head section 200A and 200B includes a plurality of recording heads 240 for recording data signals on the magnetic tape MT, a plurality of playback heads 250 for reproducing the data signals recorded on the magnetic tape MT, and a plurality of servo heads 220 for reproducing the servo signals recorded on the magnetic tape MT. Note that if the parallel head unit 200 is used only for measuring PES values, the recording heads 240 and playback heads 250 do not need to be provided in the parallel head unit 200.

[0247] The method for measuring the standard deviation σPES will be explained with reference to Figures 6 and 15. The PES value is measured in order to determine the standard deviation σPES. The parallel head unit 200 for PES measurement described above is used to measure the PES value. The measurement of the standard deviation σPES is performed with the parallel head unit 200 maintained parallel to the axis Ax that extends in the width direction of the magnetic tape MT.

[0248] The standard deviation σPES of the PES value is calculated using a servo signal that corrects for the lateral movement of the magnetic tape MT. Furthermore, the servo signal is subjected to a High Pass Filter to reflect the tracking performance of the parallel head unit 200. In this disclosure, the standard deviation σPES is obtained using the signal obtained by performing the above correction and High Pass Filter processing on the servo signal, and is so-called Written in PESσ.

[0249] First, while performing a full-volume test, the parallel head unit 200 reads the servo signals of the magnetic tape MT. More specifically, the magnetic tape MT is run at a speed of 2 m / s so that the servo head 220 of head unit 200A and the servo head 220 of head unit 200B sequentially face each servo pattern of a predetermined servo band. Then, the two servo heads 220 read the servo patterns and output them as servo signals. The reading of these servo signals is performed in an environment of 25°C ± 2°C and 50% RH ± 5% RH.

[0250] Next, the signals acquired by head units 200A and 200B are subtracted as shown in Figure 16 to obtain a servo signal corrected for the lateral movement of the magnetic tape MT. Then, a High Pass Filter is applied to this corrected servo signal. When the magnetic tape MT is actually driven, the recording / playback head mounted on the drive moves in the width direction of the magnetic tape MT by an actuator to follow the servo signal. Written in PESσ is a noise value after taking into account the width direction tracking ability of this head, so the above High Pass Filter processing is necessary. Therefore, although the High Pass Filter is not particularly limited, it needs to be a function that can reproduce the width direction tracking ability of the drive head.

[0251] Next, the PES value is calculated for each servo frame 110 shown in Figure 6 using the signal obtained by the High Pass Filter processing described above. The standard deviation of the PES value calculated over a 1m distance from a position 20m longitudinally from the connection point 21 between the magnetic tape MT and the leader tape LT (Written in PESσ) is the standard deviation of the PES value σPES in this disclosure.

[0252] The PES value for each servo frame 110 is calculated using the following formula.

[0253] Here, the center line shown in Figure 6 is the center line of the servo band. X [μm] is the distance between servo pattern A1 and servo pattern B1 on the center line shown in Figure 6, and Y [μm] is the distance between servo pattern A1 and servo pattern C1 on the center line shown in Figure 6. X and Y are determined after one full-volume test by developing the magnetic tape MT with ferricolloid developer and using a universal tool microscope (TOPCON TUM-220ES) and data processing device (TOPCON CA-1B). Fifty servo frames are selected at a point 20 m longitudinally from the connection point 21 between the magnetic tape MT and the leader tape LT, and X and Y are determined for each servo frame. The simple average of the 50 data points is used as the X and Y to be substituted into the above calculation formula.

[0254] The above difference (B ａ１ -A ａ１ ) represents the time [sec] on the actual path between the two corresponding servo patterns B1 and A1. Similarly, the other difference terms also represent the time [sec] on the actual path between the two corresponding servo patterns. These times are obtained from the time between timing signals obtained from the servo signal waveforms and the tape running speed. In this specification, the actual path means the position where the servo head 220 that reads the servo signal actually travels along the servo signal. φ is the azimuth angle θ １ , θ ２ (See Figure 15) This is the average value, specifically (θ １ +θ２ θ can be calculated from ) / 2. １ , θ ２ Similar to the measurement of distances X and Y described above, the magnetic tape MT is developed with ferric colloid developer after a single full-volume test, and then determined using a universal tool microscope (TOPCON TUM-220ES) and data processing device (TOPCON CA-1B).

[0255] (Arithmetic mean roughness Ra of the magnetic surface) The upper limit of the arithmetic mean roughness Ra of the magnetic surface is preferably 2.00 nm or less, more preferably 1.60 nm or less, even more preferably 1.53 nm or less, 1.52 nm or less, 1.50 nm or less, 1.46 nm or less, or 1.45 nm or less, in order to suppress the decrease in drivability due to the increase in kinetic friction force. The lower limit of the arithmetic mean roughness Ra of the magnetic surface is preferably 1.00 nm or more, more preferably 1.20 nm or more, in order to suppress the decrease in drivability due to the increase in kinetic friction force.

[0256] The arithmetic mean roughness Ra is determined as follows. 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, 30 m to 40 m in the longitudinal direction, to prepare a sample. Next, the magnetic surface of the sample is observed using an AFM (Atomic Force Microscope) to obtain a 40 μm × 40 μm AFM image. A Dimension Icon manufactured by BRUKER is used as the AFM, and a silicon single crystal cantilever is used (Note 1). The measurement is performed with a lift height of 20 nm and a tapping frequency tuning of 200 to 400 Hz.

[0257] Next, the AFM image is divided into 256 × 256 (= 65,536) measurement points, and the height Z(i) (i: measurement point number, i = 1 to 65,536) is measured at each measurement point. The heights Z(i) measured at each measurement point are simply averaged (arithmetic mean) to obtain the average height (average plane) Z ave We calculate (= (Z(1) + Z(2) + ... + Z(65,536)) / 65,536). Next, we calculate the deviation Z''(i) (= Z(i) - Z) from the average center line at each measurement point.ave The arithmetic mean roughness Ra [nm] (= (Z''(1) + Z''(2) + ... + Z''(65,536)) / 65,536) is calculated. In this process, the data used is filtered using Flatten order 2 and planefit order 3 XY as image processing. (Note 1) Nano World SPM probe NCH-10T normal type PointProbe L (cantilever length) = 125 μm

[0258] (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 2000Oe or less, more preferably 1900Oe or less, and even more preferably 1800Oe or less. When the coercivity Hc2 of the magnetic layer 43 in the longitudinal direction of the magnetic tape MT is 2000Oe or less, sufficient electromagnetic conversion characteristics can be obtained even at high recording density.

[0259] 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.

[0260] 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.

[0261] 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.

[0262] After obtaining the M-H loop of the measurement sample (the entire magnetic tape MT) and the M-H loop of the correction sample (substrate 41), background correction is performed by subtracting the M-H loop of the correction sample (substrate 41) from the M-H loop of the measurement sample (the entire magnetic tape MT), and the background-corrected M-H loop is obtained. The measurement and analysis program included with the "VSM-P7-15" is used to calculate this background correction. The coercivity Hc2 is determined from the obtained background-corrected M-H loop. The measurement and analysis program included with the "VSM-P7-15" is used for this calculation as well. All of the above M-H loop measurements are performed at 25℃±2℃ and 50%RH±5%RH. Furthermore, "demagnetization correction" is not performed when measuring the M-H loop in the longitudinal direction of the magnetic tape MT.

[0263] (Square Ratio) The square ratio S1 of the magnetic layer 43 in the vertical direction of the magnetic tape MT is preferably 62% or more, more preferably 65% ​​or more, even more preferably 68% or more, 72% or more, or 75% or more. When the square ratio S1 is 62% or more, the vertical orientation of the magnetic particles becomes sufficiently high, so that excellent electromagnetic conversion characteristics can be obtained.

[0264] The aspect ratio S1 of the magnetic tape MT in the vertical direction is determined as follows. First, a measurement sample is prepared in the same manner as the method for measuring the coercivity Hc2 described above. Next, the M-H loop of the measurement sample (the entire magnetic tape MT) corresponding to the vertical direction of the magnetic tape MT is measured using a VSM. Next, a correction sample is prepared in the same manner as the method for measuring the coercivity Hc2 described above. After that, the M-H loop of the correction sample (substrate 41) corresponding to the vertical direction of the substrate 41 (the vertical direction of the magnetic tape MT) is measured using a VSM.

[0265] After obtaining the M-H loops of the measurement sample (the entire magnetic tape MT) and the correction sample (substrate 41), background correction is performed by subtracting the M-H loop of the correction sample (substrate 41) from the M-H loop of the measurement sample (the entire magnetic tape MT), and the M-H loop after background correction is obtained. The measurement and analysis program included with the "VSM-P7-15" is used to calculate this background correction.

[0266] The saturation magnetization Ms(emu) and remanent magnetization Mr(emu) of the M-H loop obtained after background correction are substituted into the following formula to calculate the square aspect ratio S1 (%). Note that all M-H loop measurements above are performed at 25°C ± 2°C and 50% RH ± 5% RH. Furthermore, "demagnetization correction" is not performed when measuring the M-H loop perpendicular to the magnetic tape MT. Note that the measurement and analysis program included with the "VSM-P7-15" is used for this calculation. Square aspect ratio S1 (%) = (Mr / Ms) × 100

[0267] The angularity ratio S2 of the magnetic layer 43 in the longitudinal direction (travel direction) of the magnetic tape MT is preferably 35% or less, more preferably 30% or less, and even more preferably 25% or less, 20% or less, or 15% or less. When the angularity ratio S2 is 35% or less, the vertical orientation of the magnetic particles becomes sufficiently high, so excellent electromagnetic conversion characteristics can be obtained. Note that one of the angularity ratio S1 of the magnetic layer 43 in the vertical direction of the magnetic tape MT and the angularity ratio S2 of the magnetic layer 43 in the longitudinal direction (travel direction) of the magnetic tape MT may be within the above preferred range, while the other may be outside the above preferred range. Alternatively, both the angularity ratio S1 of the magnetic layer 43 in the vertical direction of the magnetic tape MT and the angularity ratio S2 of the magnetic layer 43 in the longitudinal direction (travel direction) of the magnetic tape MT may be within the above preferred range.

[0268] The angular ratio S2 of the magnetic tape MT in the longitudinal direction is determined in the same manner as the angular ratio S1, except that the M-H loop is measured in the longitudinal direction (travel direction) of the magnetic tape MT and the base 41.

[0269] (Ratio Hc2 / Hc1) The ratio Hc2 / Hc1 of the coercivity Hc1 of the magnetic layer 43 in the vertical direction of the magnetic tape MT to the coercivity Hc2 of the magnetic layer 43 in the longitudinal direction of the magnetic tape MT preferably satisfies the relationship Hc2 / Hc1 ≤ 0.8, more preferably Hc2 / Hc1 ≤ 0.75, even more preferably Hc2 / Hc1 ≤ 0.7, Hc2 / Hc1 ≤ 0.65, or Hc2 / Hc1 ≤ 0.6. By satisfying the relationship Hc2 / Hc1 ≤ 0.8 for coercivity Hc1 and Hc2, the degree of vertical orientation of magnetic particles can be increased. Therefore, the magnetization transition width can be reduced and a high-output signal can be obtained during signal reproduction, resulting in excellent electromagnetic conversion characteristics. As described above, when Hc2 is small, magnetization responds sensitively to the magnetic field in the vertical direction from the recording head, so a good recording pattern can be formed.

[0270] When the ratio Hc2 / Hc1 is Hc2 / Hc1 ≤ 0.8, the average thickness t of the magnetic layer 43 ２ It is particularly effective if the thickness is 0.090 μm or less. Average thickness t of the magnetic layer 43 ２ If the thickness exceeds 0.090 μm, when a ring-type head is used as the recording head, the lower region of the magnetic layer 43 (the region on the base layer 42 side) may be magnetized in the longitudinal direction of the magnetic tape MT, making it impossible to uniformly magnetize the magnetic layer 43 in the thickness direction. Therefore, even if the ratio Hc2 / Hc1 is set to Hc2 / Hc1 ≤ 0.8 (i.e., even if the degree of vertical orientation of the magnetic particles is increased), there is a risk that excellent electromagnetic conversion characteristics cannot be obtained.

[0271] 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.

[0272] The method for calculating the coercivity Hc2 of the magnetic layer 43 in the longitudinal direction of the magnetic tape MT is as described above. The coercivity Hc1 of the magnetic layer 43 in the perpendicular direction of the magnetic tape MT is determined in the same manner as the coercivity Hc2 of the magnetic layer 43 in the longitudinal direction of the magnetic tape MT, except that the M-H loop is measured perpendicular to the magnetic tape MT and the substrate 41 (thickness direction).

[0273] (Activation volume V) ａｃｔ ) Activation volume V ａｃｔ However, preferably 8000 nm ３ More preferably, 6000 nm ３ More preferably, 5000 nm ３ Below, 4000nm ３ or less than 3000 nm ３ The following is the activation volume V. ａｃｔ 8000nm ３ Under the following conditions, the dispersion state of magnetic particles is improved, allowing for a steeper bit inversion region and suppressing degradation of magnetization signals recorded on adjacent tracks due to leakage magnetic fields from the recording head. Therefore, excellent electromagnetic conversion characteristics can be obtained.

[0274] The above activation volume V ａｃｔ V can be obtained by the following formula derived by Street & Wolley. ａｃｔ (nm ３ ) = k Ｂ ×T×X ｉｒｒ / (μ ０ ×Ms×S) (However, k Ｂ : Boltzmann constant (1.38 × 10⁻⁶) －２３ J / K), T: temperature (K), Χ ｉｒｒ : Irreversible magnetic susceptibility, μ ０ : Permeability of vacuum, S: Magnetoviscosity, Ms: Saturation magnetization (emu / cm²) ３ ))

[0275] The irreversible magnetic susceptibility X is substituted into the above formula. ｉｒｒ The saturation magnetization Ms and magnetoviscosity coefficient S are determined using VSM as follows. The measurement direction using VSM is perpendicular to the magnetic tape MT (thickness direction). The VSM measurement is performed on a measurement sample cut from a long magnetic tape MT at 25°C ± 2°C and 50% RH ± 5% RH. No "demagnetization correction" is performed when measuring the M-H loop perpendicular to the magnetic tape MT (thickness direction).

[0276] (irreversible magnetic susceptibility Χ ｉｒｒ ) Irreversible magnetic susceptibility Χ ｉｒｒX is defined as the slope of the remanent magnetization curve (DCD curve) near the remanent coercivity Hr. First, a magnetic field of -1193 kA / m (15 kOe) is applied to the entire magnetic tape MT, and the magnetic field is returned to zero to enter a remanent magnetization state. Then, a magnetic field of approximately 15.9 kA / m (200 Oe) is applied in the opposite direction, and the remanent magnetization amount is measured again by returning to zero. Similarly, the measurement is repeated by applying a magnetic field 15.9 kA / m larger than the previously applied magnetic field and returning to zero, and the remanent magnetization amount is plotted against the applied magnetic field to measure the DCD curve. From the obtained DCD curve, the point where the magnetization amount is zero is defined as the remanent coercivity Hr, and the DCD curve is further differentiated to find the slope of the DCD curve at each magnetic field. In this slope of the DCD curve, the slope near the remanent coercivity Hr is X. ｉｒｒ This is the result.

[0277] (Saturation magnetization Ms) First, the M-H loop after background correction is obtained in the same manner as the measurement method for the square ratio S1 described above. Next, the value of the saturation magnetization Ms (emu) of the obtained M-H loop and the volume (cm³) of the magnetic layer 43 in the measurement sample are calculated. ３ ) from Ms(emu / cm ３ The volume of the magnetic layer 43 is calculated by multiplying the area of ​​the measurement sample by the average thickness t of the magnetic layer 43. ２ The average thickness t of the magnetic layer 43 is required to calculate the volume of the magnetic layer 43. ２ The calculation method is as described above.

[0278] (Magnetic viscosity coefficient S) First, a magnetic field of -1193 kA / m (15 kOe) is applied to the entire magnetic tape MT (measurement sample), and the magnetic field is returned to zero to return to a remanent magnetized state. Then, a magnetic field equivalent to the value of the remanent coercivity Hr obtained from the DCD curve is applied in the opposite direction. With the magnetic field applied, the amount of magnetization is continuously measured at regular time intervals for 1000 seconds. The relationship between time t and the amount of magnetization M(t) obtained in this way is compared with the following formula to calculate the magnetic viscosity coefficient S: M(t) = M0 + S × ln(t) (where M(t): amount of magnetization at time t, M0: initial amount of magnetization, S: magnetic viscosity coefficient, ln(t): natural logarithm of time)

[0279] (Surface roughness R of the back surface) ｂ) Surface roughness of the back surface (surface roughness of the back layer 44) R ｂ The upper limit is preferably 7.5 nm or less, more preferably 7.2 nm or less, even more preferably 7.0 nm or less, 6.5 nm or less, 6.3 nm or less, or 6.0 nm or less. Surface roughness R of the back surface ｂ If the surface roughness R of the back surface is 7.5 nm or less, the influence of the unevenness of the back surface on the surface of the magnetic layer 43 during winding of the magnetic tape MT can be reduced, and adverse effects on electromagnetic conversion characteristics can be suppressed. ｂ The lower limit is preferably 3.0 nm or more, more preferably 3.2 nm or more, and even more preferably 3.4 nm or more.

[0280] Back surface roughness R ｂ The following method is used to determine the surface roughness R of the back surface. First, the magnetic tape MT housed in the cartridge 10 is unwound, and a 100 mm length of the magnetic tape MT is cut from one end of the outer circumference of the magnetic tape MT, 30 m to 40 m in the longitudinal direction, to prepare a sample. Next, the sample is placed on a microscope slide with the surface to be measured (magnetic surface) facing upwards, and the ends of the sample are secured with mending tape. The surface shape is measured using a VertScan (20x objective lens) as the measuring device, and the surface roughness R of the back surface is calculated from the following formula based on the ISO 25178 standard. ｂ The following measurement conditions are used to determine the roughness. Equipment: Non-contact roughness meter using optical interference (VertScan R5500GL-M100-AC, non-contact surface / layer cross-sectional shape measurement system manufactured by Ryoka Systems Co., Ltd.) Objective lens: 20x Measurement area: 640 x 480 pixels (field of view: approximately 237 μm x 178 μm) Measurement mode: phase Wavelength filter: 520 nm CCD: 1 / 3 inch Noise reduction filter: Smoothing 3 x 3 Surface correction: Corrected using a quadratic polynomial approximation surface Measurement software: VS-Measure Version 5.5.2 Analysis software: VS-viewer Version 5.5.5 As described above, after measuring the surface roughness at five points along the longitudinal direction of the magnetic tape MT, the arithmetic mean roughness S was automatically calculated from the surface profiles obtained at each location. ａThe average value in nm represents the surface roughness R of the back surface. ｂ (nm)

[0281] (Young's modulus in the longitudinal direction of magnetic tape) The upper limit of the Young's modulus in the longitudinal direction of the magnetic tape MT is preferably 9.0 GPa or less, more preferably 8.0 GPa or less, even more preferably 7.5 GPa or less, and particularly preferably 7.1 GPa or less. When the Young's modulus in the longitudinal direction of the magnetic tape MT is 9.0 GPa or less, the elasticity of the magnetic tape MT due to external forces is further increased, making it easier to adjust the width of the magnetic tape MT by tension adjustment. Therefore, off-tracking can be suppressed more effectively, and the data recorded on the magnetic tape MT can be reproduced more accurately. The lower limit of the Young's modulus in the longitudinal direction of the magnetic tape MT is preferably 3.0 GPa or more, more preferably 4.0 GPa or more. When the lower limit of the Young's modulus in the longitudinal direction of the magnetic tape MT is 3.0 GPa or more, a decrease in the running stability of the magnetic tape MT can be suppressed.

[0282] The Young's modulus in the longitudinal direction of a magnetic tape MT is a value that indicates how difficult it is for the magnetic tape MT to expand or contract in the longitudinal direction due to external forces. The larger this value, the more difficult it is for the magnetic tape MT to expand or contract in the longitudinal direction due to external forces, and the smaller this value, the more easily the magnetic tape MT expands or contracts in the longitudinal direction due to external forces.

[0283] The Young's modulus in the longitudinal direction of the magnetic tape MT is a value related to the longitudinal direction of the magnetic tape MT, but it also correlates with the resistance of the magnetic tape MT to stretching and contracting in the width direction. In other words, the larger this value, the less the magnetic tape MT is susceptible to stretching and contracting in the width direction due to external forces, and the smaller this value, the more easily the magnetic tape MT is stretched and contracted in the width direction due to external forces. Therefore, from the viewpoint of tension adjustment, it is advantageous for the Young's modulus in the longitudinal direction of the magnetic tape MT to be small, as described above, and 9.0 GPa or less.

[0284] 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.

[0285] (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-tracking can be suppressed more effectively, and the data recorded on the magnetic tape MT can be reproduced more accurately. The lower limit of the Young's modulus in the longitudinal direction of the 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.

[0286] 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.

[0287] 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.

[0288] 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.

[0289] [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.

[0290] (Paint preparation process) First, a primer-forming paint is prepared by mixing and dispersing non-magnetic particles, binders, lubricants, etc., in a solvent. Next, a magnetic layer-forming paint is prepared by mixing and dispersing magnetic particles, binders, lubricants, etc., in a solvent. For the preparation of the magnetic layer-forming paint and the primer-forming paint, for example, the following solvents, dispersion equipment, and mixing equipment can be used.

[0291] 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.

[0292] 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.

[0293] (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.

[0294] 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.

[0295] (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.

[0296] (Calculating process) Next, the cured magnetic tape MT is calendered to smooth the magnetic surface.

[0297] (Aging process) Next, if necessary, the magnetic tape MT after calendaring is subjected to an aging process.

[0298] (Cutting process) Next, the magnetic tape MT is cut to a predetermined width (for example, 1 / 2 inch width). This completes the process of obtaining the magnetic tape MT.

[0299] (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.

[0300] (Method for adjusting the fatty acid ester content A and ratio (A / B) on the surface of the magnetic layer 43) The fatty acid ester content A and ratio (A / B) on the surface of the magnetic layer 43 can be adjusted to predetermined values ​​by, for example, adjusting the amount of fatty acids and fatty acid esters blended into the base coat and magnetic layer forming paint, and the conditions of the calendering treatment.

[0301] [5 Effects] As described above, in the magnetic tape MT according to one embodiment, the fatty acid ester content A [mg / m²] on the magnetic surface was measured by transferring the lubricant of the magnetic surface of the magnetic tape MT to a glass fiber sheet. ２ By immersing the magnetic tape MT in n-hexane for 5 minutes, the amount of fatty acid extracted from the magnetic tape MT is B [mg / m ２ The ratio (A / B) to ] is 0.10 or less. This prevents the amount of fatty acid ester present on the magnetic surface from being excessively large compared to the amount of fatty acid present on the magnetic surface, thus suppressing the embedding of fatty acids in fatty acid ester. Therefore, the effect of fatty acids present on the magnetic surface (dynamic friction coefficient μ due to repeated recording and playback of magnetic tape MT) ＴThis allows for the effective suppression of the increase in [unclear value], etc., and thus improves the running durability of the magnetic tape MT. Furthermore, the fatty acid ester content A on the magnetic surface is 0.80 mg / m². ２ The following conditions apply, and the amount of fatty acid extracted from magnetic tape MT (B) is 5.0 mg / m². ２ This concludes the explanation. As a result, the amount of fatty acid ester on the magnetic surface becomes excessively large, which can suppress the magnetic tape MT from sticking to the head unit 56 when the magnetic tape MT is running, and can also suppress the decrease in the effect of fatty acids on the magnetic surface. Therefore, running stability can be improved.

[0302] [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.

[0303] Figure 17 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.

[0304] 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.

[0305] 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.

[0306] The present disclosure will be specifically described below with reference to examples, but the present disclosure is not limited to these examples.

[0307] In the following examples and comparative examples, the average thickness of the magnetic tape, the average thickness of the substrate (PEN film), the average thickness of the magnetic layer, the average thickness of the underlayer, the average thickness of the backing layer, the composition of the magnetic particles (magnetic powder), and the average particle volume of the magnetic particles (magnetic powder) are values ​​obtained by the measurement method described in the above embodiment.

[0308] [Example 1] (Preparation process for magnetic layer forming paint) A magnetic layer forming paint was prepared as follows. First, the first composition with the following formulation was kneaded in an extruder. Next, the second composition with the following formulation was placed in a poly bottle (polyethylene resin container), attached to a paint shaker (manufactured by Seiwa Giken Co., Ltd., rocking shaker), and mixed for 10 hours. Similarly, the third composition with the following formulation was placed in a poly bottle, attached to a paint shaker (manufactured by Seiwa Giken Co., Ltd., rocking shaker), and mixed for 10 hours. Next, the kneaded first composition, the mixed second and third compositions were added to a stirring tank equipped with a disperser, and then methyl ethyl ketone: 520.00 parts by mass, toluene: 210.00 parts by mass, cyclohexanone: 240.00 parts by mass, and fatty acid ester (mixture of butyl stearate and butyl palmitate): 1.00 part by mass were added, followed by pre-mixing. Next, the mixture was further mixed using Dynomill and filtered to prepare a coating for forming a magnetic layer.

[0309] (First composition) Barium ferrite (Ba ０．６ Sr ０．４ Fe １２ O １９ ) Magnetic powder (hexagonal plate shape, average particle volume 1.27 × 10⁻⁶) ３ nm ３): 100.00 parts by mass of vinyl chloride resin solution (composition of resin solution: vinyl chloride resin 30.00% by mass, cyclohexanone solution 70.00% 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 = 0.30 mmol / g. : 32.00 parts by mass Polyurethane resin solution (Formulation of resin solution: Polyurethane resin content 30.00% by mass, Cyclohexanone content 70.00% by mass) (Polyurethane resin: Number average molecular weight Mn = 25000, Glass transition temperature Tg = 110°C): 32.00 parts by mass Phenylphosphonic acid: 5.00 parts by mass

[0310] (Second composition) Alumina (aluminum oxide) powder (α-Al ２ O ３ (Arithmetic mean particle size 0.10 μm): 5.00 parts by mass of vinyl chloride resin solution (resin solution composition: vinyl chloride resin 30.00% by mass, cyclohexanone solution 70.00% by mass) (vinyl chloride resin: degree of polymerization 300, number average molecular weight Mn = 10000, polar group OSO ３ It contains K = 0.07 mmol / g and secondary OH = 0.30 mmol / g. (5.00 parts by mass) Cyclohexanone: 10.00 parts by mass

[0311] (Third Composition) Carbon black (manufactured by Tokai Carbon Co., Ltd., product name: Seest S, arithmetic mean particle size 70 nm): 1.00 part by mass Polyurethane resin solution (resin solution composition: polyurethane resin content 30.00% by mass, cyclohexanone content 70.00% by mass) (polyurethane resin: number average molecular weight Mn = 25000, glass transition temperature Tg = 110°C): 2.00 parts by mass Cyclohexanone: 18.50 parts by mass

[0312] Finally, to the magnetic layer-forming coating prepared as described above, 3.20 parts by mass of polyisocyanate (equivalent to Coronate L manufactured by Tosoh Corporation) was added as a curing agent, and 0.50 parts by mass of fatty acid (stearic acid) was added as a lubricant.

[0313] (Preparation process for primer-forming paint) The primer-forming paint was prepared as follows. First, the fourth composition with the following formulation was kneaded in an extruder. Next, the kneaded fourth composition and the fifth composition with the following formulation were added to a stirring tank equipped with a disperser and pre-mixed. Subsequently, dynomill mixing was performed, followed by filtration to prepare the primer-forming paint.

[0314] (Fourth composition) Needle-shaped iron oxide powder (α-Fe ２ O ３ , average major axis length 0.15 μm): 100.00 parts by mass of vinyl chloride resin solution (resin solution composition: vinyl chloride resin 30.00% by mass, cyclohexanone solution 70.00% by mass) (vinyl chloride resin: degree of polymerization 300, Mn = 10000, polar group OSO ３ Contains K = 0.07 mmol / g and secondary OH = 0.30 mmol / g. ): 65.00 parts by mass Aluminum oxide powder (α-Al ２ O ３ (Arithmetic mean particle size 0.1 μm): 3.00 parts by mass Cyclohexanone: 140.00 parts by mass Citric acid: 1.00 parts by mass

[0315] (Fifth Composition) Carbon black (manufactured by Asahi Carbon Co., Ltd., product name: #80): 30.00 parts by mass Polyurethane resin solution (resin solution composition: amount of polyurethane resin 30.00% by mass, amount of cyclohexanone 70.00% by mass) (polyurethane resin: number average molecular weight Mn = 25000, glass transition temperature Tg = 70°C): 45.00 parts by mass Fatty acid ester (mixture of butyl stearate and butyl palmitate): 0.50 parts by mass Methyl ethyl ketone: 380.00 parts by mass Toluene: 150.00 parts by mass

[0316] Finally, to the primer-forming paint prepared as described above, 1.50 parts by mass of polyisocyanate (equivalent to Coronate L manufactured by Tosoh Corporation) was added as a curing agent, and 1.30 parts by mass of fatty acid (stearic acid) was added as a lubricant.

[0317] (Preparation process for back layer forming paint) The back layer forming paint was prepared as follows: The following raw materials were mixed in a stirring tank equipped with a disperser and filtered to prepare the back layer forming paint.

[0318] Carbon black (manufactured by Asahi Carbon Co., Ltd., product name: #80): 100.00 parts by mass Polyester polyurethane (manufactured by Nippon Polyurethane Industry Co., Ltd., product name: N-2304): 50.00 parts by mass Methyl ethyl ketone: 500.00 parts by mass Toluene: 400.00 parts by mass Cyclohexanone: 100.00 parts by mass Polyisocyanate (equivalent to Coronate L manufactured by Tosoh Corporation): 10.00 parts by mass

[0319] (Coating Process) Using the primer-forming paint and magnetic layer-forming paint prepared as described above, a primer layer and a magnetic layer were formed on one main surface of a long PEN film (substrate) having an average thickness of 4.00 μm as follows. First, the primer-forming paint was applied to one main surface of the PEN film and dried to form a primer layer such that the average thickness of the primer layer at the time of completion of the magnetic tape (average thickness of the primer layer after the cutting process) was 0.95 μm. Next, the magnetic layer-forming paint was applied to the primer layer and dried to form a magnetic layer such that the average thickness of the magnetic layer at the time of completion of the magnetic tape (average thickness of the magnetic layer after the cutting process) was 52 nm. During the drying of the magnetic layer-forming paint, a permanent magnet was used to orient the barium ferrite magnetic powder in the thickness direction of the PEN film using a magnetic field.

[0320] After forming the underlayer and magnetic layer, a back layer-forming coating was applied to the other main surface of the PEN film and dried to form a back layer such that the average thickness of the completed magnetic tape (average thickness after the cutting process) was 0.35 μm. This resulted in the acquisition of a magnetic tape.

[0321] (Curing process) After winding the magnetic tape into a roll, the base layer, magnetic layer, and backing layer were cured by heating the magnetic tape at 60°C for 24 hours in this state.

[0322] (Calendering 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 (100-120°C) close to the glass transition temperature Tg (=110°C) of the polyurethane resin (binder) contained in the magnetic layer.

[0323] (Aging process) The magnetic tape, after calendering, was subjected to an aging process for 24 hours in a 60°C environment.

[0324] (Cutting process) The magnetic tape obtained as described above was cut into strips with a width of 1 / 2 inch (12.65 mm) to obtain magnetic tape with an average thickness of 5.35 μm.

[0325] (Servo writing process and assembly process) After demagnetizing the obtained magnetic tape, a servo pattern was written to the magnetic tape using a servo writer to form five servo bands. The magnetic tape with the servo bands formed was assembled into a cartridge case to obtain a cartridge (LTO cartridge). An LTO9 standard cartridge case was used.

[0326] [Example 2] A cartridge was obtained in the same manner as in Example 1, except for the following points. In the preparation step of the base coat forming paint, the amount of fatty acid ester (a mixture of butyl stearate and butyl palmitate) was changed from 0.50 parts by mass to 0.90 parts by mass. In the coating step, the coating conditions of the magnetic layer forming paint were adjusted to change the average thickness of the magnetic layer at the time of completion of the magnetic tape from 52 nm to 50 nm.

[0327] [Example 3] A cartridge was obtained in the same manner as in Example 1, except for the following points. In the preparation step of the base layer forming coating, 0.50 parts by mass of isobutyl stearate was added as the fatty acid ester instead of 0.50 parts by mass of a mixture of butyl stearate and butyl palmitate. In the coating step, the coating conditions of the magnetic layer forming coating were adjusted to change the average thickness of the magnetic layer at the time of completion of the magnetic tape from 52 nm to 49 nm.

[0328] [Example 4] A cartridge was obtained in the same manner as in Example 1, except for the following points. In the preparation step of the base layer forming coating, 0.90 parts by mass of isobutyl stearate was added as the fatty acid ester instead of 0.50 parts by mass of a mixture of butyl stearate and butyl palmitate. In the coating step, the coating conditions of the magnetic layer forming coating were adjusted to change the average thickness of the magnetic layer at the time of completion of the magnetic tape from 52 nm to 49 nm.

[0329] [Comparative Example 1] A cartridge was obtained in the same manner as in Example 1, except for the following points. In the preparation step of the base layer forming coating, the amount of fatty acid ester (a mixture of butyl stearate and butyl palmitate) was changed from 0.50 parts by mass to 1.25 parts by mass. In the coating step, the coating conditions of the magnetic layer forming coating were adjusted to change the average thickness of the magnetic layer at the time of completion of the magnetic tape from 52 nm to 50 nm.

[0330] [Comparative Example 2] A cartridge was obtained in the same manner as in Example 1, except for the following points. In the preparation step of the coating for forming the magnetic layer, the Dynomil mixing time was made longer than the Dynomil mixing time in Example 1, to 1.5 times the Dynomil mixing time in Example 1. In the preparation step of the coating for forming the base layer, the amount of fatty acid (stearic acid) was changed from 1.30 parts by mass to 1.00 parts by mass, the amount of fatty acid ester (mixture of butyl stearate and butyl palmitate) was changed from 0.50 parts by mass to 2.00 parts by mass, and the amount of citric acid was changed from 1.00 parts by mass to 2.00 parts by mass. In the coating step, the coating conditions for the coating for forming the magnetic layer were adjusted to change the average thickness of the magnetic layer at the time of completion of the magnetic tape from 52 nm to 49 nm.

[0331] [Comparative Example 3] First, a magnetic tape with an average thickness of 4.96 μm was obtained in the same manner as in Example 1, except for the following points. In the preparation step of the coating for forming the magnetic layer, 1.00 part by mass of isobutyl stearate was added as the fatty acid ester instead of 1.00 part by mass of a mixture of butyl stearate and butyl palmitate. In the preparation step of the coating for forming the base layer, the amount of fatty acid (stearic acid) was changed from 1.30 parts by mass to 0.50 parts by mass, and 1.50 parts by mass of isobutyl stearate was added as the fatty acid ester instead of 0.50 parts by mass of a mixture of butyl stearate and butyl palmitate. In the coating step, the coating conditions for the coating for forming the magnetic layer were adjusted to change the average thickness of the magnetic layer at the time of completion of the magnetic tape from 52 nm to 60 nm. In addition, the coating conditions for the coating for forming the base layer were adjusted to change the average thickness of the base layer at the time of completion of the magnetic tape from 0.95 μm to 0.60 μm. Furthermore, by adjusting the application conditions of the coating for forming the back layer, the average thickness of the back layer at the time of completion of the magnetic tape was changed from 0.35 μm to 0.30 μm.

[0332] Next, a cartridge was obtained in the same manner as in Example 1, except that a magnetic tape with an average thickness of 4.96 μm was used.

[0333] [Comparative Example 4] A cartridge was obtained in the same manner as in Example 1, except for the following points. In the preparation step of the coating for forming the magnetic layer, the Dynomil mixing time was made longer than the Dynomil mixing time in Example 1, to 1.5 times the Dynomil mixing time in Example 1. In the preparation step of the coating for forming the base layer, the amount of fatty acid (stearic acid) was changed from 1.30 parts by mass to 1.00 parts by mass, the amount of fatty acid ester (mixture of butyl stearate and butyl palmitate) was changed from 0.50 parts by mass to 1.25 parts by mass, and the amount of citric acid was changed from 1.00 parts by mass to 2.00 parts by mass. In the coating step, the coating conditions for the coating for forming the magnetic layer were adjusted to change the average thickness of the magnetic layer at the time of completion of the magnetic tape from 52 nm to 47 nm.

[0334] [Evaluation] The cartridges obtained as described above were evaluated as follows.

[0335] (Arithmetic mean roughness Ra of the magnetic surface) The arithmetic mean roughness Ra of the magnetic surface was measured using the method for measuring the arithmetic mean roughness Ra of the magnetic surface described in the above embodiment.

[0336] (Fatty acid ester content A, fatty acid extraction amount B, and their ratio A / B) The values ​​were measured using the method for measuring the fatty acid ester content A on the surface of the magnetic layer, the fatty acid extraction amount B extracted from the magnetic tape, and their ratio A / B, as described in the above embodiment.

[0337] (Average dynamic friction coefficient μ(250) during low-speed driving) The average dynamic friction coefficient μ(250) during low-speed driving was measured using the method for measuring the average dynamic friction coefficient μ(250) during low-speed driving described in the above embodiment. When the average dynamic friction coefficient μ(250) during low-speed driving is 0.45 or less, the driving stability of the magnetic tape can be maintained even after the magnetic tape has been run back and forth 250 times in a tape storage drive having an oblique head unit 56. Therefore, the driving durability of the magnetic tape can be improved.

[0338] (Standard Deviation σPES) The standard deviation σPES was measured using the standard deviation σPES measurement method described in the above embodiment. Note that the standard deviation σPES is the value measured in one full-volume test. When the standard deviation σPES is 15.5 or less, excellent magnetic tape running performance can be obtained when the magnetic tape is run by a tape storage drive.

[0339]

[0340]

[0341] The symbols in Tables 1 and 2 are as follows: SA: Stearic acid BS: Butyl stearate BP: Butyl palmitate iso-BS: Isobutyl stearate Ra: Arithmetic mean roughness of the magnetic surface A: Fatty acid ester content on the magnetic surface, measured by transferring the lubricant on the magnetic surface to a glass fiber sheet B: Amount of fatty acid extracted from magnetic tape MT by immersing the magnetic tape in n-hexane for 5 minutes μ(250): Average kinetic friction coefficient measured by running the magnetic tape at a speed of 5 mm / s (low speed) after 250 back-and-forth runs

[0342] From the above evaluation results, the following was found: In the magnetic tapes of Examples 1 to 4, the fatty acid ester content A [mg / m²] on the surface of the magnetic layer was ２ ] and the amount of fatty acids extracted from magnetic tape B [mg / m ２ The ratio (A / B) to [ ] is 0.10 or less, and the fatty acid ester content A on the magnetic surface is 0.80 mg / m². ２ The following is the result, and the amount of fatty acid extracted from the magnetic tape, B, was 5.0 mg / m². ２ The above results were obtained. As a result, the average kinetic friction coefficient μ(250) at low speeds was suppressed to 0.45 or less, and the standard deviation σPES was suppressed to 15.5 nm. Therefore, the running durability and running stability of the magnetic tape were improved. In the magnetic tape of Comparative Example 1, the fatty acid ester content A on the magnetic surface was 0.80 mg / m ２ It exceeded and the ratio A / B exceeded 0.10. Therefore, in the evaluation test of the average kinetic friction coefficient μ (250) during low-speed driving, the magnetic tape tended to stick slightly to the head unit, and the kinetic friction coefficient μ Ｔ The coefficient of friction increased, and the average coefficient of kinetic friction μ(250) exceeded 0.45. In the magnetic tape of Comparative Example 2, the amount of fatty acid extracted from the magnetic tape B was 5.0 mg / m ２ It was less than , and the ratio A / B exceeded 0.10. Therefore, in the evaluation test of the average kinetic friction coefficient μ (250) during low-speed driving, stick-slip was likely to occur, and the kinetic friction coefficient μ ＴThe coefficient of friction increased, the mean kinetic friction coefficient μ(250) exceeded 0.45, and in the evaluation test of the standard deviation σPES, σPES worsened and exceeded 15.5 nm. In the magnetic tape of Comparative Example 3, the amount of fatty acid extracted from the magnetic tape B was 5.0 mg / m ２ This is significantly less, and the fatty acid ester content A on the magnetic surface is also 0.80 mg / m². ２ Because it exceeded this, the ratio A / B significantly exceeded 0.10. Therefore, in the evaluation test of the average kinetic friction coefficient μ (250) during low-speed driving, the kinetic friction coefficient μ was affected by stick-slip. Ｔ The coefficient of friction increased significantly, the mean kinetic friction coefficient μ(250) exceeded 0.45 by a large margin, and in the evaluation test of the standard deviation σPES, the standard deviation σPES worsened and exceeded 15.5 nm. In the magnetic tape of Comparative Example 4, the amount of fatty acid extracted from the magnetic tape B was 5.0 mg / m². ２ It was less than 15.5 nm. As a result, stick-slip became slightly more likely, and in the evaluation test of the standard deviation σPES, the standard deviation σPES worsened and exceeded 15.5 nm.

[0343] 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.

[0344] The chemical formulas of the compounds exemplified in the above embodiments and modifications are representative examples, and are not limited to the valencies, etc., described, as long as they are the same compound's common name. In the numerical ranges described stepwise in the above embodiments and modifications, 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 and modifications can be used individually or in combination of two or more.

[0345] Furthermore, the present disclosure may also adopt the following configuration: (1) A tape-shaped magnetic recording medium comprising a substrate and a magnetic layer containing magnetic particles, wherein the content A [mg / m²] of fatty acid esters on the surface of the magnetic layer is measured by transferring the lubricant on the surface of the magnetic layer to a glass fiber sheet. ２ ] and, by immersing the magnetic recording medium in n-hexane for 5 minutes, the amount of fatty acid extracted from the magnetic recording medium is B [mg / m³ ２ The ratio (A / B) to ] is 0.10 or less, and the content A of the fatty acid ester is 0.80 mg / m³. ２ The following applies, and the amount of fatty acid extracted B is 5.0 mg / m². ２ The above is a magnetic recording medium. (2) The content A of the fatty acid ester is 0.05 mg / m ２ 0.80mg / m or more ２ The following applies, and the amount of fatty acid extracted B is 5.0 mg / m². ２ 13.0mg / m or more ２The magnetic recording medium according to (1) below. (3) The magnetic recording medium according to (1) or (2), wherein the ratio (A / B) is 0.02 or more and 0.10 or less. (4) The magnetic recording medium according to any one of (1) to (3), wherein the fatty acid ester comprises at least one selected from linear saturated fatty acid esters and branched saturated fatty acid esters, and the fatty acid comprises a linear saturated fatty acid. (5) The magnetic recording medium according to (4), wherein the linear saturated fatty acid ester comprises at least one selected from butyl stearate and butyl palmitate, the branched saturated fatty acid ester comprises isobutyl stearate, and the linear saturated fatty acid comprises stearic acid. (6) The magnetic recording medium according to any one of (1) to (5), wherein the average thickness of the magnetic layer is 60 nm or less. (7) The magnetic recording medium according to any one of (1) to (6), wherein the substrate comprises an aromatic polyamide resin or a polyester resin. (8) The magnetic recording medium according to any one of (1) to (7), wherein the magnetic particles include hexagonal ferrite or epsilon-type iron oxide. (9) The magnetic recording medium according to any one of (1) to (7), wherein the magnetic particles include hexagonal ferrite containing barium (Ba) and strontium (Sr). (10) The magnetic recording medium according to any one of (1) to (9), wherein the average dynamic friction coefficient μ of the surface on the magnetic layer side, measured by running the magnetic recording medium at a speed of 5 mm / s after 250 back-and-forth runs, is 0.45 or less. (11) The magnetic recording medium according to any one of (1) to (10), wherein the magnetic layer has a servo pattern, and the standard deviation σPES of the PES (Position Error Signal) value obtained from the servo signal corresponding to the servo pattern is 15.5 nm or less. (12) The magnetic recording medium according to any one of (1) to (11), 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 extending in the width direction of the magnetic recording medium.(13) The magnetic recording medium according to (12), 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. (14) A cartridge comprising the magnetic recording medium according to any one of (1) to (13).

[0346] 10,321 Cartridge 11 Cartridge memory 31 Antenna coil 32 Rectifier / power supply circuit 33 Clock circuit 34 Detection / modulation circuit 35 Controller 36 Memory 36A First memory area 36B Second memory area 41 Substrate 42 Underlayer 43 Magnetic layer 44 Back layer 56,200 Head unit 56A,56B Servo read head 61,62 Head 70 Measuring device 80 Transfer sample 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 TS Tape sample SB Servo band DB Data band Tk Data track

Claims

A tape-shaped magnetic recording medium, Substrate and, A magnetic layer containing magnetic particles, Equipped with, The fatty acid ester content A [mg / m²] on the surface of the magnetic layer was measured by transferring the lubricant from the magnetic layer side to the glass fiber sheet. ２ ] and, by immersing the magnetic recording medium in n-hexane for 5 minutes, the amount of fatty acid extracted from the magnetic recording medium is B [mg / m³]. ２ The ratio (A / B) to ] is 0.10 or less, The content A of the aforementioned fatty acid ester is 0.80 mg / m². ２ The following: The amount of fatty acid extracted, B, is 5.0 mg / m². ２ That's all. Magnetic recording medium. 　 The content A of the aforementioned fatty acid ester is 0.05 mg / m². ２ 0.80mg / m or more ２ The following: The amount of fatty acid extracted, B, is 5.0 mg / m². ２ 13.0mg / m or more ２ The following is: The magnetic recording medium according to claim 1. 　 The ratio (A / B) is 0.02 or more and 0.10 or less. The magnetic recording medium according to claim 1. 　 The fatty acid ester comprises at least one selected from straight-chain saturated fatty acid esters and branched-chain saturated fatty acid esters. The aforementioned fatty acids include straight-chain saturated fatty acids. The magnetic recording medium according to claim 1. 　 The linear saturated fatty acid ester comprises at least one selected from butyl stearate and butyl palmitate. The branched-chain saturated fatty acid ester includes isobutyl stearate, The aforementioned straight-chain saturated fatty acid includes stearic acid. The magnetic recording medium according to claim 4. 　 The average thickness of the magnetic layer is 60 nm or less. The magnetic recording medium according to claim 1. 　 The substrate includes an aromatic polyamide resin or a polyester resin. The magnetic recording medium according to claim 1. 　 The magnetic particles include hexagonal ferrite or epsilon-type iron oxide. The magnetic recording medium according to claim 1. 　 The magnetic particles include hexagonal ferrite containing barium (Ba) and strontium (Sr). The magnetic recording medium according to claim 1. 　 After 250 round trips, the average kinetic friction coefficient μ of the magnetic layer side surface, measured by running the magnetic recording medium at a speed of 5 mm / s, is 0.45 or less. The magnetic recording medium according to claim 1. 　 The magnetic layer has a servo pattern, The standard deviation σPES of the PES (Position Error Signal) value obtained from the servo signal corresponding to the aforementioned servo pattern is 15.5 nm or less. The magnetic recording medium according to claim 1. 　 The magnetic layer has a servo pattern, The servo pattern includes a plurality of first magnetization regions and a plurality of second magnetization regions. The plurality of first magnetization regions and the plurality of second magnetization regions are asymmetrical with respect to an axis extending in the width direction of the magnetic recording medium. The magnetic recording medium according to claim 1. 　 The inclination angle of the first magnetization region with respect to the axis and the inclination angle of the second magnetization region with respect to the axis are different. The larger of the inclination angles of the first magnetization region and the second magnetization region is 18° or more and 28° or less. The magnetic recording medium according to claim 12. 　 A magnetic recording medium as described in claim 1, cartridge.

Images