Magnetic tape, magnetic tape cartridge and magnetic tape device

Abstract

Provided is magnetic tape wherein, in an environment having a temperature of 23°C and a relative humidity of 50%, the AlFeSil wear value45° of a magnetic layer surface that is measured at a 45° AlFeSil square bar tilt angle is 20-50 µm, inclusive, and the standard deviation of the AlFeSil wear value of the magnetic layer surface measured at each of a 0°, 15°, 30°, and 45° AlFeSil square bar tilt angle is at most 30 µm. The AlFeSil square bar tilt angle is the angle formed between the lengthwise direction of the AlFeSil square bar and the width direction of the magnetic tape. Also provided are a magnetic tape cartridge including the magnetic tape, and a magnetic tape device.

Description

[Technical Field]

[0001] The present invention relates to a magnetic tape, a magnetic tape cartridge, and a magnetic tape device. [Background technology]

[0002] Magnetic recording media are available in tape and disk form, and tape-type magnetic recording media, i.e., magnetic tape, are primarily used for data storage applications such as data backup and archiving (see, for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-524774 [Patent Document 2] US2019 / 0164573A1 Summary of the Invention [Problem to be solved by the invention]

[0004] Data is typically recorded on a magnetic tape by running the magnetic tape in a magnetic tape device and recording data on the data band by moving a magnetic head along the data band of the magnetic tape. This forms a data track on the data band. When reproducing the recorded data, the magnetic tape is run in the magnetic tape device and the magnetic head is moved along the data band of the magnetic tape to read the data recorded on the data band.

[0005] In order to improve the accuracy with which the magnetic head follows the data band of the magnetic tape during the above-described recording and / or playback, a system that performs head tracking using a servo signal (hereinafter referred to as a "servo system") has been put into practical use. Furthermore, it has been proposed to use servo signals to acquire dimensional information (such as contraction or expansion) of the magnetic tape in the width direction while it is running, and to change the angle at which the axial direction of the magnetic head module is tilted relative to the width direction of the magnetic tape (hereinafter also referred to as the "head tilt angle") according to the acquired dimensional information (see Patent Documents 1 and 2, for example, paragraphs 0059-0067 and 0084 of Patent Document 1). During recording or playback, if the magnetic head for recording or playing back data deviates from the target track position due to width deformation of the magnetic tape, this can result in phenomena such as overwriting of recorded data or playback failure. The inventor believes that changing the angle as described above is one means for suppressing such phenomena.

[0006] For magnetic recording, excellent electromagnetic conversion characteristics are required. For example, when considering changing the head tilt angle as described above, a magnetic tape that exhibits minimal degradation in electromagnetic conversion characteristics when recording and / or reproducing data at different head tilt angles is desirable.

[0007] An object of one aspect of the present invention is to provide a magnetic tape that suffers little deterioration in electromagnetic conversion characteristics when data is recorded and / or reproduced at different head tilt angles. [Means for solving the problem]

[0008] One aspect of the present invention is as follows. [1] A magnetic tape having a non-magnetic support and a magnetic layer containing ferromagnetic powder, In an environment with a temperature of 23°C and a relative humidity of 50%, AlFeSil wear value of the magnetic layer surface measured with an AlFeSil square pillar tilted at an angle of 45° 45° is 20 μm or more and 50 μm or less, and The standard deviation of the AlFeSil wear values ​​on the magnetic layer surface measured at inclination angles of 0°, 15°, 30°, and 45° of the AlFeSil rectangular pillars (hereinafter also simply referred to as "standard deviation of AlFeSil wear values") is 30 μm or less, The tilt angle of the AlFeSil prism is the angle formed between the longitudinal direction of the AlFeSil prism and the width direction of the magnetic tape. [2] The magnetic tape according to [1], wherein the standard deviation of the AlFeSil wear values ​​is 15 μm or more and 30 μm or less. [3] The magnetic tape according to [1] or [2], wherein the standard deviation of the amount of curvature in the longitudinal direction of the magnetic tape (hereinafter also simply referred to as "standard deviation of the amount of curvature") is 5 mm / m or less. [4] The magnetic tape according to any one of [1] to [3], wherein the magnetic layer contains one or more types of non-magnetic powder. [5] The magnetic tape according to [4], wherein the non-magnetic powder contains alumina powder. [6] The magnetic tape according to any one of [1] to [5], which has a non-magnetic layer containing non-magnetic powder between the non-magnetic support and the magnetic layer. [7] The magnetic tape according to any one of [1] to [6], wherein the non-magnetic support has a backcoat layer containing non-magnetic powder on the surface opposite to the surface having the magnetic layer. [8] The magnetic tape according to any one of [1] to [7], wherein the squareness ratio in the perpendicular direction of the magnetic tape is 0.60 or more. [9] A magnetic tape cartridge comprising the magnetic tape according to any one of [1] to [8].

[10] A magnetic tape device including the magnetic tape according to any one of [1] to [8].

[11] Further comprising a magnetic head; the magnetic head has a module including an element array having a plurality of magnetic head elements between a pair of servo signal read elements, The magnetic tape device according to

[10] , wherein the angle θ formed by the axis of the element array with respect to the width direction of the magnetic tape is changed while the magnetic tape is running within the magnetic tape device. [Effects of the Invention]

[0009] According to one aspect of the present invention, it is possible to provide a magnetic tape that exhibits minimal degradation in electromagnetic conversion characteristics when data is recorded and / or reproduced at different head tilt angles. Also, according to another aspect of the present invention, it is possible to provide a magnetic tape cartridge and a magnetic tape device that include the magnetic tape. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 2 is a schematic diagram showing an example of a magnetic head module. [Figure 2] 1 is an explanatory diagram of the relative positional relationship between a module and a magnetic tape while the magnetic tape is running in a magnetic tape device. [Figure 3] FIG. 10 is an explanatory diagram regarding changes in angle θ while the magnetic tape is running. [Figure 4] 10A and 10B are diagrams illustrating the amount of curvature of a magnetic tape in the longitudinal direction. [Figure 5] 1 shows an example of the arrangement of data bands and servo bands. [Figure 6] An example of servo pattern layout for an LTO (Linear Tape-Open) Ultrium format tape is shown. [Figure 7] FIG. 10 is an explanatory diagram of a method for measuring an angle θ while a magnetic tape is running. [Figure 8] FIG. 1 is a schematic diagram illustrating an example of a magnetic tape device. DETAILED DESCRIPTION OF THE INVENTION

[0011] [Magnetic tape] One aspect of the present invention relates to a magnetic tape having a non-magnetic support and a magnetic layer containing ferromagnetic powder. The AlFeSil abrasion value of the magnetic layer surface measured at an inclination angle of 45° of AlFeSil rectangular pillars of the magnetic tape in an environment of a temperature of 23°C and a relative humidity of 50% is 45°is 20 μm or more and 50 μm or less, and the standard deviation of the AlFeSil wear values ​​of the magnetic layer surface measured at inclination angles of the AlFeSil square pillars of 0°, 15°, 30°, and 45° is 30 μm or less. In this invention and this specification, the term "surface of the magnetic layer" is synonymous with the magnetic layer-side surface of a magnetic tape.

[0012] <Explanation of head tilt angle> Before describing the tilt angle of the AlFeSil rectangular pillars, we will first explain the configuration of the magnetic head, the head tilt angle, etc. Furthermore, we will also explain the reason why it is believed that the phenomenon occurring during recording or reproduction described above can be suppressed by tilting the axial direction of the magnetic head module with respect to the width direction of the magnetic tape while the magnetic tape is running.

[0013] The magnetic head may have one or more modules, two or more, or three or more, each module including an element array having a plurality of magnetic head elements between a pair of servo signal read elements. The total number of such modules may be, for example, five or less, four or less, or three or less, or the magnetic head may include a number of modules exceeding the total number exemplified here. Examples of arrangements of multiple modules include "recording module-playback module" (total number of modules: 2) and "recording module-playback module-recording module" (total number of modules: 3). However, this is not limited to the examples shown here.

[0014] Each module may include an element array, i.e., an array of elements, having multiple magnetic head elements between a pair of servo signal read elements. A module having a write element as a magnetic head element is a recording module for recording data to magnetic tape. A module having a read element as a magnetic head element is a reproducing module for reproducing data recorded on magnetic tape. In a magnetic head, multiple modules are arranged, for example, in a recording / reproducing head unit, with the axes of the element arrays of each module oriented parallel. This "parallel" does not necessarily mean only parallel in the strict sense, but also includes the range of error normally accepted in the technical field to which the present invention pertains. The range of error may, for example, mean a range of less than ±10° from strict parallelism.

[0015] In each element array, a pair of servo signal read elements and multiple magnetic head elements (i.e., write elements or read elements) are typically arranged linearly and spaced apart. Here, "arranged linearly" means that each magnetic head element is arranged on a straight line connecting the center of one servo signal read element to the center of the other servo signal read element. In this invention and this specification, the "axis of the element array" refers to the straight line connecting the center of one servo signal read element to the center of the other servo signal read element.

[0016] Next, the configuration of the module will be further described with reference to the drawings. However, the embodiments shown in the drawings are merely examples and do not limit the present invention.

[0017] FIG. 1 is a schematic diagram showing an example of a magnetic head module. The module shown in FIG. 1 has multiple magnetic head elements between a pair of servo signal read elements (servo signal read elements 1 and 2). A magnetic head element is also called a "channel." "Ch" in the diagram is an abbreviation for Channel. The module shown in FIG. 1 has a total of 32 magnetic head elements, Ch0 to Ch31.

[0018] In FIG. 1, "L" is the distance between a pair of servo signal read elements, i.e., the distance between one servo signal read element and the other servo signal read element. In the module shown in FIG. 1, "L" is the distance between servo signal read element 1 and servo signal read element 2. More specifically, it is the distance between the center of servo signal read element 1 and the center of servo signal read element 2. This distance can be measured, for example, using an optical microscope.

[0019] FIG. 2 is an explanatory diagram of the relative positional relationship between a module and a magnetic tape while the magnetic tape is running in a magnetic tape device. In FIG. 2, dotted line A indicates the width direction of the magnetic tape. Dotted line B indicates the axis of the element array. Angle θ can be said to be the head tilt angle while the magnetic tape is running, and is the angle formed by dotted lines A and B. When angle θ is 0° while the magnetic tape is running, the distance in the width direction of the magnetic tape between one servo signal read element and the other servo signal read element of the element array (hereinafter also referred to as the "effective distance between servo signal read elements") is "L". On the other hand, when angle θ is greater than 0°, the effective distance between the servo signal read elements is "L cos θ", and L cos θ is smaller than L. That is, "L cos θ" <L」である。

[0020] As described above, if the magnetic head for recording or reproducing data deviates from the target track position due to deformation of the magnetic tape during recording or reproduction, it may result in overwriting of recorded data, poor reproduction, and other problems. For example, if the width of the magnetic tape shrinks or expands, a magnetic head element that should be recording or reproducing data at the target track position may end up recording or reproducing data at a different track position. Furthermore, if the width of the magnetic tape expands, the effective distance between servo signal reading elements may become shorter than the distance between two adjacent servo bands across a data band (also referred to as the "servo band distance" or "servo band distance"; more specifically, the distance between the two servo bands in the width direction of the magnetic tape), which may result in data not being recorded or reproduced near the edge of the magnetic tape. In contrast, when the element array is tilted at an angle θ greater than 0°, the effective distance between the servo signal read elements becomes "Lcosθ," as explained above. The larger the value of θ, the smaller the value of Lcosθ, and the smaller the value of θ, the larger the value of Lcosθ. Therefore, by changing the value of θ according to the degree of dimensional change in the width direction of the magnetic tape (i.e., contraction or expansion), it is possible to make the effective distance between the servo signal read elements approach or match the spacing between the servo bands. This can prevent or reduce the frequency of phenomena such as overwriting of recorded data or playback failures caused by the magnetic head for recording or playing back data shifting from the target track position due to width deformation of the magnetic tape.

[0021] FIG. 3 is an explanatory diagram showing the change in angle θ while the magnetic tape is running. θ is the angle θ at the start of travel initial can be set to, for example, greater than or equal to 0°. In Figure 3, the central diagram shows the state of the module at the start of driving. In Figure 3, the right figure shows the angle θ as θ initial The larger angle is angle θ cThe effective distance between the servo signal reading elements is L cos θ. c is Lcosθ when the magnetic tape starts running initial It is preferable to perform such angle adjustment when the width of the magnetic tape contracts while the magnetic tape is running. On the other hand, in Figure 3, the left figure shows the angle θ as θ initial The smaller angle θ e The effective distance between the servo signal reading elements is L cos θ. e is Lcosθ when the magnetic tape starts running initial If the width of the magnetic tape expands while the magnetic tape is running, it is preferable to perform such angle adjustment.

[0022] As explained above, changing the head tilt angle while the magnetic tape is running can contribute to preventing phenomena such as overwriting of recorded data or playback failures that occur when the magnetic head for recording or playing back data deviates from the target track position due to width deformation of the magnetic tape during recording or playback, or can contribute to reducing the frequency of such occurrences. On the other hand, data recording on magnetic tape and reproduction of recorded data are usually performed by contacting and sliding a magnetic head with the magnetic layer surface of the magnetic tape. The inventors have considered that if the head tilt angle during such sliding varies, the contact state between the magnetic head and the magnetic layer surface may change, which may be a factor in the deterioration of electromagnetic conversion characteristics. Specifically, the inventors have inferred that if the head tilt angle varies, the degree of wear of the magnetic head due to contact with the magnetic layer surface will change significantly, which will result in the deterioration of electromagnetic conversion characteristics. Based on the above speculation, the inventors of the present invention have conducted extensive research. As a result, the wear characteristics of magnetic tapes were measured using AlFeSil square pillars with an inclination angle of 45° in an environment with a temperature of 23°C and a relative humidity of 50%. 45°By setting the standard deviation of the AlFeSil wear value on the surface of the magnetic layer measured at the tilt angles of 0°, 15°, 30°, and 45° of the AlFeSil prism to the ranges described above respectively, it has been newly found that it is possible to suppress the degradation of electromagnetic conversion characteristics when recording and / or reproducing data at different head tilt angles. Hereinafter, the degradation of electromagnetic conversion characteristics when recording and / or reproducing data at different head tilt angles will also be simply referred to as "degradation of electromagnetic conversion characteristics". The temperature and humidity of the measurement environment are those adopted as exemplary values of the temperature and humidity of the magnetic tape usage environment. Therefore, the environment in which data is recorded on the magnetic tape and the recorded data is reproduced is not limited to the environment of the above temperature and humidity. The tilt angle of the AlFeSil prism when measuring the AlFeSil wear value is also adopted as an exemplary value of the angle that can be adopted when changing the head tilt angle during magnetic tape running to record and / or reproduce data. Therefore, the head tilt angle when recording data on the magnetic tape and reproducing the recorded data is not limited to the above angle. Also, according to the speculation of the inventors described in this specification, the present invention is not limited.

[0023] <AlFeSil wear value 45° , standard deviation of AlFeSil wear value> (Measurement method) In the present invention and this specification, the AlFeSil wear values at the tilt angles of 0°, 15°, 30°, and 45° of the AlFeSil prism are values measured by the following method in an environment of 23°C temperature and 50% relative humidity. The magnetic tape to be measured is run using a reel tester under the following running conditions, and the wear width of the AlFeSil rectangular pillars is measured. The AlFeSil rectangular pillars are made of AlFeSil, a sendust-based alloy. For evaluation, AlFeSil rectangular pillars specified in ECMA (European Computer Manufacturers Association)-288 / Annex H / H2 are used. The wear width of the AlFeSil rectangular pillars is determined by observing the edge of the AlFeSil rectangular pillar from above using an optical microscope, and is calculated as the wear width described in paragraph 0015 of Japanese Patent Laid-Open Publication No. 2007-026564 based on Figure 1 of the same publication. The tilt angle of the AlFeSil prism (hereinafter simply referred to as "tilt angle") is the angle between the longitudinal direction of the AlFeSil prism and the width direction of the magnetic tape, and is specified in the range of 0° to 90°. When the longitudinal direction of the AlFeSil prism coincides with the width direction of the magnetic tape, the tilt angle of the AlFeSil prism is defined as 0°, and when the longitudinal direction of the AlFeSil prism coincides with the longitudinal direction of the magnetic tape, the tilt angle of the AlFeSil prism is defined as 90°.

[0024] Driving conditions The AlFeSil prism was tilted at an angle of 0°, 15°, 30°, or 45°, and the magnetic layer surface of the magnetic tape was brought into contact with one edge of the AlFeSil prism at a wrap angle of 12°. In this state, the magnetic tape to be measured was run back and forth over a length of 580 m in the longitudinal direction at a speed of 3 m / s.

[0025] When measuring the AlFeSil wear value at each tilt angle, a tension of 1.0 N is applied to the magnetic tape in the longitudinal direction during the run. The tension applied to the magnetic tape in the longitudinal direction during the run is the setting value of the reel tester. The AlFeSil wear width measured after one round trip in this manner is taken as the AlFeSil wear value at each tilt angle. One unused AlFeSil rectangular pillar not used for AlFeSil wear value measurement is prepared. The AlFeSil wear value measurements at the four different tilt angles are performed in any order by contacting the magnetic layer surface with a different edge among the four edges of this AlFeSil wear value. The AlFeSil wear value measurements at each tilt angle are performed on a different part of the magnetic tape being measured. Furthermore, before measurements at each tilt angle, the magnetic tape being measured is left in the measurement environment for at least 24 hours to allow it to acclimate to the measurement environment.

[0026] Among the AlFeSil wear values ​​obtained by the above method, the AlFeSil wear value obtained by measurement at an inclination angle of 45° was the AlFeSil wear value of 45°. ° The standard deviation (i.e., the positive square root of the variance) of the AlFeSil wear values ​​obtained at the above four different tilt angles is taken as the standard deviation of the AlFeSil wear values ​​of the magnetic tape to be measured.

[0027] (AlFeSil wear value 45° ) Regarding the wear characteristics of the magnetic tape, from the viewpoint of suppressing the deterioration of the electromagnetic conversion characteristics when recording and / or reproducing data at different head tilt angles, the AlFeSil wear value 45° In order to further suppress the deterioration of the electromagnetic conversion characteristics, the AlFeSil wear value is 45° is preferably 45 μm or less, more preferably 40 μm or less, and even more preferably 35 μm or less. 45° is preferably 23 μm or more, and more preferably 25 μm or more.

[0028] (Standard deviation of AlFeSil wear values) The standard deviation of the AlFeSil wear value of the magnetic tape is 30 μm or less, preferably 28 μm or less, more preferably 25 μm or less, even more preferably 23 μm or less, and even more preferably 20 μm or less, from the viewpoint of suppressing deterioration of electromagnetic conversion characteristics when recording and / or reproducing data at different head tilt angles. The standard deviation of the AlFeSil wear value can be, for example, 0 μm or more, more than 0 μm, 1 μm or more, 3 μm or more, 5 μm or more, 7 μm or more, 10 μm or more, 12 μm or more, or 15 μm or more. A small standard deviation of the AlFeSil wear value is preferable from the viewpoint of further suppressing deterioration of electromagnetic conversion characteristics.

[0029] The wear characteristics of the magnetic tape can be adjusted, for example, by changing the types of components used to form the magnetic layer, as will be described in detail later.

[0030] <Standard deviation of curvature> Next, the standard deviation of the amount of curvature will be described. In this invention and this specification, the amount of curvature in the longitudinal direction of a magnetic tape is a value determined by the following method in an environment with an ambient temperature of 23°C and a relative humidity of 50%. Magnetic tapes are usually distributed housed in magnetic tape cartridges. The magnetic tape to be measured is a magnetic tape removed from an unused magnetic tape cartridge that is not installed in a magnetic tape device. FIG. 4 is an explanatory diagram of the amount of curvature in the longitudinal direction of the magnetic tape. A tape sample 100 m long is cut from a randomly selected portion of the magnetic tape to be measured. One end of this tape sample is defined as the 0 m position, and the position D m ​​(D meters) away from this end in the longitudinal direction toward the other end is defined as the D m position. Therefore, a position 10 m away in the longitudinal direction is the 10 m position, a position 20 m away is the 20 m position, and so on, at 10 m intervals, to the 30 m position, 40 m position, 50 m position, 60 m position, 70 m position, 80 m position, 90 m position, and 100 m position. A tape sample having a length of 1 m is cut out from the 0 m position to the 1 m position. This tape sample is used to measure the amount of curvature at the 0 m position. A tape sample having a length of 1 m is cut out from the 10 m position to the 11 m position. This tape sample is used to measure the amount of curvature at the 10 m position. A tape sample having a length of 1 m is cut out from the 20 m position to the 21 m position. This tape sample is used to measure the amount of curvature at the 20 m position. A tape sample having a length of 1 m is cut out from the 30 m position to the 31 m position. This tape sample is used to measure the amount of curvature at the 30 m position. A tape sample having a length of 1 m is cut out from the 40 m position to the 41 m position. This tape sample is used to measure the amount of curvature at the 40 m position. A tape sample having a length of 1 m is cut out from the 50 m position to the 51 m position. This tape sample is used to measure the amount of curvature at the 50 m position. A tape sample having a length of 1 m is cut out from the 60 m position to the 61 m position. This tape sample is used to measure the amount of curvature at the 60 m position. A tape sample having a length of 1 m is cut out from the 70 m position to the 71 m position. This tape sample is used to measure the amount of curvature at the 70 m position. A tape sample having a length of 1 m is cut out from the 80 m position to the 81 m position. This tape sample is used to measure the amount of curvature at the 80 m position. A tape sample having a length of 1 m is cut out from the 90 m position to the 91 m position. This tape sample is used to measure the amount of curvature at the 90 m position. A tape sample having a length of 1 m is cut out from the 99 m position to the 100 m position. This tape sample is used to measure the amount of curvature at the 100 m position. The tape sample at each position is held at its upper end with a holding member (clip, etc.) with its lengthwise direction facing vertically, and is hung in a tension-free state for 24 hours ± 4 hours. After that, the following measurements are taken within one hour. As shown in Figure 4, a piece of tape is placed on a flat surface in a tension-free state. The tape piece may be placed on the flat surface with the magnetic layer surface facing upward, or with the other surface facing upward. In Figure 4, S indicates the tape sample, and W indicates the width direction of the tape sample. Using an optical microscope, measure the distance L1 (unit: mm) in the longitudinal direction of the tape sample S, which is the shortest distance between the imaginary line 54 connecting the two end portions 52 and 53 of the tape sample S and the maximum curvature 55. Figure 4 shows an example of a tape curved upward on the paper. The distance L1 (mm) is measured in the same way even if the tape is curved downward. Regardless of the curvature, the distance L1 is displayed as a positive value. If no curvature in the longitudinal direction is confirmed, L1 is set to 0 (zero) mm. In this way, the standard deviation (i.e., the positive square root of the variance) of the curvature amount L1 measured at a total of 11 positions from the 0 m position to the 100 m position is taken as the standard deviation (unit: mm / m) of the curvature amount in the longitudinal direction of the magnetic tape being measured.

[0031] In the magnetic tape, the standard deviation of the amount of curvature determined by the above method can be, for example, 7 mm / m or less, or 6 mm / m or less, and from the viewpoint of further suppressing deterioration of the electromagnetic conversion characteristics, it is preferably 5 mm / m or less, more preferably 4 mm / m or less, and even more preferably 3 mm / m or less. The standard deviation of the amount of curvature of the magnetic tape can be, for example, 0 mm / m or more, more than 0 mm / m, 1 mm / m or more, or 2 mm / m or more. A small value of the standard deviation of the amount of curvature is preferable from the viewpoint of further suppressing deterioration of the electromagnetic conversion characteristics. The standard deviation of the amount of curvature can be controlled by adjusting the manufacturing conditions of the magnetic tape manufacturing process, as will be described in detail later.

[0032] The magnetic tape will now be described in more detail.

[0033] <Magnetic layer> (Ferromagnetic powder) The ferromagnetic powder contained in the magnetic layer can be one or a combination of two or more known ferromagnetic powders used in the magnetic layers of various magnetic recording media. Using a ferromagnetic powder with a small average particle size is preferable from the viewpoint of improving recording density. From this viewpoint, the average particle size of the ferromagnetic powder is preferably 50 nm or less, more preferably 45 nm or less, even more preferably 40 nm or less, even more preferably 35 nm or less, even more preferably 30 nm or less, even more preferably 25 nm or less, and even more preferably 20 nm or less. On the other hand, from the viewpoint of magnetization stability, the average particle size of the ferromagnetic powder is preferably 5 nm or more, more preferably 8 nm or more, even more preferably 10 nm or more, even more preferably 15 nm or more, and even more preferably 20 nm or more.

[0034] Hexagonal ferrite powder A preferred example of the ferromagnetic powder is hexagonal ferrite powder. For details of the hexagonal ferrite powder, see, for example, JP 2011-225417 A, paragraphs 0012 to 0030, JP 2011-216149 A, paragraphs 0134 to 0136, JP 2012-204726 A, paragraphs 0013 to 0030, and JP 2015-127985 A, paragraphs 0029 to 0084.

[0035] In the present invention and this specification, "hexagonal ferrite powder" refers to a ferromagnetic powder in which a hexagonal ferrite crystal structure is detected as the main phase by X-ray diffraction analysis. The main phase refers to the structure to which the highest diffraction peak belongs in the X-ray diffraction spectrum obtained by X-ray diffraction analysis. For example, if the highest diffraction peak in the X-ray diffraction spectrum obtained by X-ray diffraction analysis is assigned to the hexagonal ferrite crystal structure, it is determined that the hexagonal ferrite crystal structure has been detected as the main phase. If only a single structure is detected by X-ray diffraction analysis, this detected structure is considered to be the main phase. The hexagonal ferrite crystal structure contains at least iron atoms, divalent metal atoms, and oxygen atoms as constituent atoms. Divalent metal atoms are metal atoms that can become divalent cations as ions, and examples of such atoms include alkaline earth metal atoms such as strontium atoms, barium atoms, and calcium atoms, and lead atoms. In the present invention and this specification, "hexagonal strontium ferrite powder" refers to a powder in which the main divalent metal atom contained therein is strontium atom, and "hexagonal barium ferrite powder" refers to a powder in which the main divalent metal atom contained therein is barium atom. "Main divalent metal atom" refers to the divalent metal atom that is the most abundant, on an atomic % basis, among the divalent metal atoms contained in the powder. However, rare earth atoms are not included in the above divalent metal atoms. In the present invention and this specification, "rare earth atom" refers to a powder selected from the group consisting of scandium atom (Sc), yttrium atom (Y), and lanthanoid atom. The lanthanoid atom is selected from the group consisting of lanthanum atom (La), cerium atom (Ce), praseodymium atom (Pr), neodymium atom (Nd), promethium atom (Pm), samarium atom (Sm), europium atom (Eu), gadolinium atom (Gd), terbium atom (Tb), dysprosium atom (Dy), holmium atom (Ho), erbium atom (Er), thulium atom (Tm), ytterbium atom (Yb), and lutetium atom (Lu).

[0036] Hereinafter, hexagonal strontium ferrite powder, which is one form of hexagonal ferrite powder, will be described in more detail.

[0037] The activation volume of the hexagonal strontium ferrite powder is preferably 800 to 1600 nm 3 The microparticulated hexagonal strontium ferrite powder exhibiting an activation volume in the above range is suitable for producing a magnetic tape that exhibits excellent electromagnetic conversion characteristics. The activation volume of the hexagonal strontium ferrite powder is preferably 800 nm 3 or more, for example, 850 nm 3 From the viewpoint of further improving the electromagnetic conversion characteristics, the activation volume of the hexagonal strontium ferrite powder can be 1500 nm or more. 3 More preferably, it is 1400 nm or less. 3 More preferably, it is 1300 nm or less. 3 More preferably, it is 1200 nm or less. 3 It is even more preferable that the value is equal to or less than 1100 nm. 3 It is even more preferable that the activation volume of the hexagonal barium ferrite powder is equal to or less than 10 ...

[0038] "Activation volume" is a unit of magnetization reversal and is an index showing the magnetic size of a particle. The activation volume described in this invention and this specification and the anisotropy constant Ku described below are values ​​obtained by measuring the coercive force Hc using a vibrating sample magnetometer at magnetic field sweep rates of 3 minutes and 30 minutes (measurement temperature: 23°C ± 1°C) in the coercive force Hc measurement section, and then calculating from the following relational expression between Hc and activation volume V. The unit of the anisotropy constant Ku is 1 erg / cc = 1.0 x 10 -1 J / m 3 is. Hc=2Ku / Ms{1-[(kT / KuV)ln(At / 0.693)] 1 / 2} [In the above formula, Ku: anisotropy constant (unit: J / m 3 ), Ms: saturation magnetization (unit: kA / m), k: Boltzmann constant, T: absolute temperature (unit: K), V: activation volume (unit: cm 3 ), A: spin precession frequency (unit: s -1 ), t: magnetic field reversal time (unit: s)]

[0039] The anisotropy constant Ku can be used as an index for reducing thermal fluctuation, in other words, improving thermal stability. The hexagonal strontium ferrite powder preferably has an anisotropy constant of 1.8×10 5 J / m 3 and more preferably 2.0×10 5 J / m 3 The Ku of the hexagonal strontium ferrite powder can be, for example, 2.5×10 5 J / m 3 However, since a higher Ku value means higher thermal stability and is therefore preferred, the Ku value is not limited to the above-mentioned values.

[0040] The hexagonal strontium ferrite powder may or may not contain rare earth atoms. When the hexagonal strontium ferrite powder contains rare earth atoms, it is preferable that the rare earth atoms are contained at a content (bulk content) of 0.5 to 5.0 atomic % relative to 100 atomic % of iron atoms. In one embodiment, the hexagonal strontium ferrite powder containing rare earth atoms can have rare earth atoms unevenly distributed in the surface layer portion. In the present invention and this specification, the term "surface layer distribution of rare earth atoms" refers to the ratio of the rare earth atom content relative to 100 atomic % of iron atoms in a solution obtained by partially dissolving a hexagonal strontium ferrite powder in an acid (hereinafter referred to as "surface layer content of rare earth atoms" or simply "surface layer content" with respect to rare earth atoms) to the ratio of the rare earth atom content relative to 100 atomic % of iron atoms in a solution obtained by completely dissolving a hexagonal strontium ferrite powder in an acid (hereinafter referred to as "bulk content of rare earth atoms" or simply "bulk content" with respect to rare earth atoms), Rare earth atom surface content / rare earth atom bulk content > 1.0 This means that the ratio of "surface rare earth atom content / bulk rare earth atom content > 1.0" is satisfied. The rare earth atom content of the hexagonal strontium ferrite powder described below is synonymous with the rare earth atom bulk content. In contrast, partial dissolution using an acid dissolves the surface layer of the particles constituting the hexagonal strontium ferrite powder, so the rare earth atom content in the solution obtained by partial dissolution is the rare earth atom content in the surface layer of the particles constituting the hexagonal strontium ferrite powder. When the surface rare earth atom content satisfies the ratio "surface rare earth atom content / bulk rare earth atom content > 1.0", this means that the rare earth atoms are unevenly distributed in the surface layer of the particles constituting the hexagonal strontium ferrite powder (i.e., present in greater amounts in the surface layer than in the interior). In the present invention and this specification, the surface layer refers to a partial region extending from the surface toward the interior of the particles constituting the hexagonal strontium ferrite powder.

[0041] When the hexagonal strontium ferrite powder contains rare earth atoms, the rare earth atom content (bulk content) is preferably in the range of 0.5 to 5.0 atomic percent relative to 100 atomic percent of iron atoms. Having rare earth atoms in the above-mentioned bulk content range and having the rare earth atoms unevenly distributed in the surface layers of the particles constituting the hexagonal strontium ferrite powder is thought to contribute to suppressing a decrease in playback output during repeated playback. This is presumably because the hexagonal strontium ferrite powder contains rare earth atoms in the above-mentioned bulk content range and having the rare earth atoms unevenly distributed in the surface layers of the particles constituting the hexagonal strontium ferrite powder can increase the anisotropy constant Ku. The higher the anisotropy constant Ku, the more the occurrence of a phenomenon known as thermal fluctuation can be suppressed (in other words, thermal stability can be improved). By suppressing the occurrence of thermal fluctuation, the decrease in playback output during repeated playback can be suppressed. It is speculated that the uneven distribution of rare earth atoms in the surface layer of hexagonal strontium ferrite powder particles contributes to stabilizing the spin of the iron (Fe) sites in the crystal lattice in the surface layer, thereby increasing the anisotropy constant Ku. Furthermore, it is believed that using a hexagonal strontium ferrite powder having rare earth atoms unevenly distributed in the surface layer as the ferromagnetic powder for the magnetic layer also contributes to preventing the magnetic layer surface from being worn away by friction with the magnetic head. That is, it is believed that a hexagonal strontium ferrite powder having rare earth atoms unevenly distributed in the surface layer can also contribute to improving the running durability of magnetic tapes. This is believed to be because the uneven distribution of rare earth atoms on the surfaces of the particles that make up the hexagonal strontium ferrite powder contributes to improving the interaction between the particle surfaces and organic substances (e.g., binders and / or additives) contained in the magnetic layer, thereby improving the strength of the magnetic layer. From the viewpoint of suppressing a decrease in reproduction output during repeated reproduction and / or further improving running durability, the rare earth atom content (bulk content) is more preferably in the range of 0.5 to 4.5 atomic %, even more preferably in the range of 1.0 to 4.5 atomic %, and even more preferably in the range of 1.5 to 4.5 atomic %.

[0042] The bulk content is the content determined by completely dissolving the hexagonal strontium ferrite powder. In the present invention and this specification, unless otherwise specified, the content of an atom refers to the bulk content determined by completely dissolving the hexagonal strontium ferrite powder. The hexagonal strontium ferrite powder containing rare earth atoms may contain only one rare earth atom or two or more rare earth atoms. When two or more rare earth atoms are contained, the bulk content is determined for the total of the two or more rare earth atoms. This also applies to other components in the present invention and this specification. That is, unless otherwise specified, a certain component may be used alone or in combination with two or more. When two or more components are used, the content or content refers to the total of the two or more components.

[0043] When the hexagonal strontium ferrite powder contains rare earth atoms, the rare earth atoms may be any one or more of rare earth atoms. From the viewpoint of suppressing a decrease in playback output during repeated playback, preferred rare earth atoms include neodymium atoms, samarium atoms, yttrium atoms, and dysprosium atoms, with neodymium atoms, samarium atoms, and yttrium atoms being more preferred, and neodymium atoms being even more preferred.

[0044] In a hexagonal strontium ferrite powder having rare earth atoms unevenly distributed in the surface layer, the rare earth atoms need only be unevenly distributed in the surface layer of the particles constituting the hexagonal strontium ferrite powder, and the degree of uneven distribution is not limited. For example, for a hexagonal strontium ferrite powder having rare earth atoms unevenly distributed in the surface layer, the ratio of the surface content of rare earth atoms determined by partial dissolution under the dissolution conditions described below to the bulk content of rare earth atoms determined by complete dissolution under the dissolution conditions described below, i.e., "surface content / bulk content," is greater than 1.0 and can be 1.5 or greater. A "surface content / bulk content" ratio greater than 1.0 means that the rare earth atoms are unevenly distributed in the surface layer (i.e., present in greater amounts than in the interior) in the particles constituting the hexagonal strontium ferrite powder. Furthermore, the ratio of the surface content of rare earth atoms determined by partial dissolution under the dissolution conditions described below to the bulk content of rare earth atoms determined by complete dissolution under the dissolution conditions described below, i.e., "surface content / bulk content," can be, for example, 10.0 or less, 9.0 or less, 8.0 or less, 7.0 or less, 6.0 or less, 5.0 or less, or 4.0 or less. However, in a hexagonal strontium ferrite powder having rare earth atoms unevenly distributed in the surface layers, it is sufficient that the rare earth atoms are unevenly distributed in the surface layers of the particles constituting the hexagonal strontium ferrite powder, and the above "surface content / bulk content" is not limited to the exemplified upper or lower limits.

[0045] The partial and total dissolution of hexagonal strontium ferrite powder is described below. For hexagonal strontium ferrite powder present as a powder, sample powders to be partially and completely dissolved are collected from the same powder lot. On the other hand, for hexagonal strontium ferrite powder contained in the magnetic layer of a magnetic tape, a portion of the hexagonal strontium ferrite powder removed from the magnetic layer is subjected to partial dissolution, and another portion is subjected to total dissolution. The hexagonal strontium ferrite powder can be removed from the magnetic layer by, for example, the method described in paragraph 0032 of JP 2015-91747 A. The term "partial dissolution" as used herein refers to dissolving the hexagonal strontium ferrite powder to such an extent that the remaining hexagonal strontium ferrite powder can be visually confirmed in the liquid at the end of dissolution. For example, partial dissolution can dissolve 10 to 20 mass% of the particles constituting the hexagonal strontium ferrite powder, with the total particles being 100 mass%. On the other hand, the term "complete dissolution" as used herein refers to dissolving the hexagonal strontium ferrite powder to such an extent that the remaining hexagonal strontium ferrite powder cannot be visually confirmed in the liquid at the end of dissolution. The partial dissolution and the surface layer content are measured, for example, by the following method. Note that the dissolution conditions such as the amount of sample powder are merely examples, and any dissolution conditions that allow partial or complete dissolution can be used. A container (e.g., a beaker) containing 12 mg of sample powder and 10 mL of 1 mol / L hydrochloric acid is placed on a hot plate set at 70°C for 1 hour. The resulting solution is filtered through a 0.1 μm membrane filter. Elemental analysis of the filtrate is performed using an inductively coupled plasma (ICP) analyzer. This allows the surface content of rare earth atoms relative to 100 atomic percent iron atoms to be determined. If multiple types of rare earth atoms are detected by elemental analysis, the total content of all rare earth atoms is taken as the surface content. This also applies to measurements of bulk content. On the other hand, the total dissolved and bulk contents are measured, for example, by the following method. A container (e.g., a beaker) containing 12 mg of sample powder and 10 mL of 4 mol / L hydrochloric acid is placed on a hot plate set at 80°C for 3 hours. After that, the bulk content relative to 100 atomic % of iron atoms can be determined by carrying out the same procedures as for the partial dissolution and surface layer content measurements described above.

[0046] From the viewpoint of increasing the reproduction output when reproducing data recorded on magnetic tape, it is desirable that the mass magnetization σs of the ferromagnetic powder contained in the magnetic tape is high. In this regard, hexagonal strontium ferrite powder that contains rare earth atoms but does not have the rare earth atoms unevenly distributed in the surface layer tends to have a significantly lower σs than hexagonal strontium ferrite powder that does not contain rare earth atoms. On the other hand, hexagonal strontium ferrite powder that has the rare earth atoms unevenly distributed in the surface layer is considered preferable in order to suppress such a large decrease in σs. In one embodiment, the σs of the hexagonal strontium ferrite powder is 45 A·m 2 / kg or more, and 47A m 2 / kg or more. On the other hand, from the viewpoint of noise reduction, σs is 80A·m 2 / kg or less is preferable, and 60A·m 2 / kg or less is more preferable. σs can be measured using a known measuring device capable of measuring magnetic properties, such as a vibrating sample magnetometer. In the present invention and this specification, unless otherwise specified, the mass magnetization σs is a value measured at a magnetic field strength of 15 kOe. 1 [kOe] = 10 6 / 4π[A / m].

[0047] Regarding the content (bulk content) of constituent atoms of the hexagonal strontium ferrite powder, the strontium atom content can be, for example, in the range of 2.0 to 15.0 atomic % relative to 100 atomic % of iron atoms. In one embodiment, the hexagonal strontium ferrite powder can contain only strontium atoms as divalent metal atoms. In another embodiment, the hexagonal strontium ferrite powder can contain one or more other divalent metal atoms in addition to strontium atoms. For example, barium atoms and / or calcium atoms can be contained. When divalent metal atoms other than strontium atoms are contained, the barium atom content and calcium atom content in the hexagonal strontium ferrite powder can each be, for example, in the range of 0.05 to 5.0 atomic % relative to 100 atomic % of iron atoms.

[0048] Known crystal structures of hexagonal ferrite include magnetoplumbite type (also called "M type"), W type, Y type, and Z type. The hexagonal strontium ferrite powder may have any of these crystal structures. The crystal structure can be confirmed by X-ray diffraction analysis. The hexagonal strontium ferrite powder may be one in which a single crystal structure or two or more types of crystal structures are detected by X-ray diffraction analysis. For example, in one embodiment, the hexagonal strontium ferrite powder may be one in which only the M-type crystal structure is detected by X-ray diffraction analysis. For example, the M-type hexagonal ferrite is AFe 12 O 19The composition formula is represented by the formula: where A represents a divalent metal atom. When the hexagonal strontium ferrite powder is of M type, A is only strontium atom (Sr). Alternatively, when A contains multiple divalent metal atoms, strontium atom (Sr) accounts for the largest proportion on an atomic % basis, as described above. The divalent metal atom content of the hexagonal strontium ferrite powder is usually determined by the type of crystalline structure of the hexagonal ferrite and is not particularly limited. The same applies to the iron atom content and oxygen atom content. The hexagonal strontium ferrite powder contains at least iron atoms, strontium atoms, and oxygen atoms, and may further contain rare earth atoms. Furthermore, the hexagonal strontium ferrite powder may or may not contain atoms other than these atoms. As an example, the hexagonal strontium ferrite powder may contain aluminum atoms (Al). The content of aluminum atoms can be, for example, 0.5 to 10.0 atomic % relative to 100 atomic % of iron atoms. From the viewpoint of suppressing a decrease in playback output during repeated playback, the hexagonal strontium ferrite powder contains iron atoms, strontium atoms, oxygen atoms, and rare earth atoms, and the content of atoms other than these atoms is preferably 10.0 atomic % or less, more preferably 0 to 5.0 atomic %, relative to 100 atomic % of iron atoms, and may even be 0 atomic %. That is, in one embodiment, the hexagonal strontium ferrite powder may contain no atoms other than iron atoms, strontium atoms, oxygen atoms, and rare earth atoms. The content expressed in atomic % above is determined by converting the content (unit: mass %) of each atom obtained by completely dissolving the hexagonal strontium ferrite powder into a value expressed in atomic % using the atomic weight of each atom. Furthermore, in the present invention and this specification, "not containing" a certain atom means that the content is 0 mass % when completely dissolved and measured by an ICP analyzer. The detection limit of an ICP analyzer is usually 0.01 ppm (parts per million) or less by mass. The above term "free from" is used to mean that the substance is contained in an amount below the detection limit of the ICP analyzer.In one form, the hexagonal strontium ferrite powder can be one that does not contain bismuth atoms (Bi).

[0049] metal powder A preferred example of the ferromagnetic powder is ferromagnetic metal powder. For details of the ferromagnetic metal powder, see, for example, paragraphs 0137 to 0141 of JP-A No. 2011-216149 and paragraphs 0009 to 0023 of JP-A No. 2005-251351.

[0050] ε-iron oxide powder A preferred example of the ferromagnetic powder is ε-iron oxide powder. In the present invention and this specification, the term "ε-iron oxide powder" refers to a ferromagnetic powder in which an ε-iron oxide crystalline structure is detected as the main phase by X-ray diffraction analysis. For example, if the highest intensity diffraction peak in an X-ray diffraction spectrum obtained by X-ray diffraction analysis is assigned to the ε-iron oxide crystalline structure, it is determined that the ε-iron oxide crystalline structure is detected as the main phase. Known methods for producing ε-iron oxide powder include a method using goethite and a reverse micelle method. All of these production methods are publicly known. For a method for producing ε-iron oxide powder in which part of the Fe atoms are replaced by atoms such as Ga, Co, Ti, Al, or Rh, see, for example, J. Jpn. Soc. Powder Metallurgy, Vol. 61, Supplement, No. S1, pp. S280-S284 and J. Mater. Chem. C, 2013, 1, pp. 5200-5206. However, the method for producing the ε-iron oxide powder that can be used as the ferromagnetic powder in the magnetic layer of the magnetic tape is not limited to the method given here.

[0051] The activation volume of the ε-iron oxide powder is preferably 300 to 1500 nm 3 The finely divided ε-iron oxide powder exhibiting an activation volume in the above range is suitable for producing a magnetic tape that exhibits excellent electromagnetic conversion characteristics. The activation volume of the ε-iron oxide powder is preferably 300 nm 3 or more, for example, 500 nm3 From the viewpoint of further improving the electromagnetic conversion characteristics, the activation volume of the ε-iron oxide powder can be 1400 nm or more. 3 More preferably, it is 1300 nm or less. 3 More preferably, it is 1200 nm or less. 3 More preferably, it is 1100 nm or less. 3 It is even more preferred that:

[0052] The anisotropy constant Ku can be used as an index of the reduction in thermal fluctuation, in other words, the improvement in thermal stability. The ε-iron oxide powder is preferably 3.0×10 4 J / m 3 and more preferably 8.0×10 4 J / m 3 The Ku of the ε-iron oxide powder can be, for example, 3.0×10 5 J / m 3 However, since a higher Ku value means higher thermal stability and is therefore preferred, the Ku value is not limited to the above-mentioned values.

[0053] From the viewpoint of increasing the reproduction output when reproducing data recorded on a magnetic tape, it is desirable that the mass magnetization σs of the ferromagnetic powder contained in the magnetic tape is high. In this regard, in one embodiment, the σs of the ε-iron oxide powder is 8 A m 2 / kg or more, and 12 A m 2 On the other hand, the σs of ε-iron oxide powder can be 40 A m 2 / kg or less, and 35A·m 2 / kg or less is more preferable.

[0054] In the present invention and this specification, unless otherwise specified, the average particle size of various powders such as ferromagnetic powders is a value measured by the following method using a transmission electron microscope. The powder is photographed using a transmission electron microscope at a magnification of 100,000x, and a photograph of the particles that make up the powder is obtained by printing it on photographic paper or displaying it on a display so that the total magnification is 500,000x. From the obtained particle photograph, the target particle is selected and the particle outline is traced with a digitizer to measure the particle (primary particle) size. Primary particles are independent particles that do not aggregate. The above measurements are performed on 500 randomly selected particles. The arithmetic mean of the particle sizes of the 500 particles thus obtained is the average particle size of the powder. The transmission electron microscope may be, for example, a Hitachi H-9000 transmission electron microscope. Furthermore, particle size measurements can be performed using known image analysis software, such as Carl Zeiss KS-400 image analysis software. Unless otherwise specified, the average particle sizes shown in the examples below are values ​​measured using a Hitachi H-9000 transmission electron microscope and Carl Zeiss KS-400 image analysis software. In this invention and this specification, "powder" refers to a collection of multiple particles. For example, "ferromagnetic powder" refers to a collection of multiple ferromagnetic particles. Furthermore, a collection of multiple particles is not limited to a configuration in which the particles constituting the collection are in direct contact with each other, but also includes a configuration in which binders, additives, etc., as described below, are interposed between the particles. The term "particle" is sometimes used to refer to powder.

[0055] As a method for collecting sample powder from the magnetic tape for particle size measurement, for example, the method described in paragraph 0015 of JP-A No. 2011-048878 can be used.

[0056] In the present invention and this specification, unless otherwise specified, the size of particles constituting the powder (particle size) is determined by the shape of the particles observed in the particle photograph. (1) In the case of needle-shaped, spindle-shaped, columnar (where the height is greater than the maximum diameter of the base), etc., the particle size is expressed by the length of the major axis that constitutes the particle, i.e., the major axis length. (2) In the case of a plate or columnar shape (where the thickness or height is smaller than the maximum major axis of the plate surface or base), it is expressed by the maximum major axis of the plate surface or base, (3) When the particle is spherical, polyhedral, irregular, etc., and the long axis of the particle cannot be identified from its shape, it is expressed as the equivalent circle diameter, which is determined by the circle projection method.

[0057] The average acicular ratio of a powder refers to the arithmetic average of the minor axis length of the particles measured in the above measurement, i.e., the minor axis length, the value of (major axis length / minor axis length) for each particle, and the values ​​obtained for the above 500 particles. Here, unless otherwise specified, the minor axis length refers to the length of the minor axis constituting the particle in the above definition of particle size (1), and in the same case (2), the thickness or height, respectively. In the case of (3), since there is no distinction between the major axis and the minor axis, (major axis length / minor axis length) is considered to be 1 for convenience. Unless otherwise specified, when the particle shape is specific, for example, in the case of the above definition of particle size (1), the average particle size is the average major axis length, in the case of definition (2), the average particle size is the average plate diameter, and in the case of definition (3), the average particle size is the average diameter (also called the average particle diameter or average particle size).

[0058] The content (filling rate) of the ferromagnetic powder in the magnetic layer is preferably in the range of 50 to 90 mass % and more preferably in the range of 60 to 90 mass % relative to the total mass of the magnetic layer. A high filling rate of the ferromagnetic powder in the magnetic layer is preferable from the viewpoint of improving recording density.

[0059] (binder) The magnetic tape may be a coated magnetic tape, and the magnetic layer may contain a binder. The binder is one or more resins. Various resins commonly used as binders for coated magnetic recording media can be used as binders. For example, the binder may be selected from polyurethane resins, polyester resins, polyamide resins, vinyl chloride resins, acrylic resins copolymerized with styrene, acrylonitrile, methyl methacrylate, etc., cellulose resins such as nitrocellulose, epoxy resins, phenoxy resins, polyvinyl acetal, polyvinyl butyral, etc., and may be used alone or in combination. Among these, polyurethane resins, acrylic resins, cellulose resins, and vinyl chloride resins are preferred. These resins may be homopolymers or copolymers. These resins can also be used as binders in the nonmagnetic layer and / or backcoat layer, which will be described later. For details on the binders, see paragraphs 0028 to 0031 of JP 2010-24113 A. The binder may also be a radiation-curable resin, such as an electron beam-curable resin. For details about radiation curable resins, see paragraphs 0044 to 0045 of JP-A No. 2011-048878. The average molecular weight of the resin used as the binder, as a weight average molecular weight, can be, for example, 10,000 to 200,000. The binder can be used in an amount of, for example, 1.0 to 30.0 parts by mass per 100.0 parts by mass of the ferromagnetic powder.

[0060] (hardening agent) A curing agent can also be used together with the binder. In one form, the curing agent can be a thermosetting compound, which undergoes a curing reaction (crosslinking reaction) upon heating. In another form, the curing agent can be a photocurable compound, which undergoes a curing reaction (crosslinking reaction) upon irradiation with light. As the curing reaction progresses during the magnetic tape manufacturing process, at least a portion of the curing agent can be contained in the magnetic layer in a state of reacting (crosslinking) with other components, such as the binder. A preferred curing agent is a thermosetting compound, and polyisocyanate is suitable. For details about polyisocyanates, see paragraphs 0124 to 0125 of JP 2011-216149 A. The curing agent can be used in the magnetic layer-forming composition in an amount of, for example, 0 to 80 parts by weight per 100 parts by weight of the binder. From the perspective of improving the strength of each layer, such as the magnetic layer, it is preferably 50 to 80 parts by weight.

[0061] (additives) The magnetic layer may contain one or more additives as needed. Examples of additives include the curing agents mentioned above. Examples of additives contained in the magnetic layer include non-magnetic powders, lubricants, dispersants, dispersion aids, antifungal agents, antistatic agents, and antioxidants.

[0062] Dispersants that can be added to the magnetic layer-forming composition include known dispersants for improving the dispersibility of ferromagnetic powders, such as carboxyl group-containing compounds and nitrogen-containing compounds. For example, the nitrogen-containing compound may be a primary amine represented by NHR, a secondary amine represented by NHR, or a tertiary amine represented by NR. In the above, R represents any structure constituting the nitrogen-containing compound, and multiple Rs may be the same or different. The nitrogen-containing compound may be a compound (polymer) having multiple repeating structures in its molecule. The nitrogen-containing portion of the nitrogen-containing compound functions as an adsorbent to the particle surface of the ferromagnetic powder, which is thought to be the reason why the nitrogen-containing compound can function as a dispersant. Examples of carboxyl group-containing compounds include fatty acids such as oleic acid. The carboxyl group of the carboxyl group-containing compound functions as an adsorbent to the particle surface of the ferromagnetic powder, which is thought to be the reason why the carboxyl group-containing compound can function as a dispersant. It is also preferable to use a carboxyl group-containing compound in combination with a nitrogen-containing compound. The amount of these dispersants used can be appropriately determined.

[0063] A dispersant may be added to the nonmagnetic layer-forming composition. For dispersants that can be added to the nonmagnetic layer-forming composition, see paragraph 0061 of JP-A No. 2012-133837.

[0064] Additives that can be added to the magnetic layer include, for example, the polyalkyleneimine polymers described in JP 2016-51493 A. For details of such polyalkyleneimine polymers, see paragraphs 0035 to 0077 of JP 2016-51493 A and the examples therein.

[0065] Non-magnetic powders that can be contained in the magnetic layer include non-magnetic powders that can function as abrasives, and non-magnetic powders that can function as protrusion-forming agents that form moderately protruding protrusions on the magnetic layer surface.

[0066] The abrasive is preferably a non-magnetic powder with a Mohs hardness of greater than 8, more preferably a non-magnetic powder with a Mohs hardness of 9 or greater. The maximum Mohs hardness is 10. The abrasive can be a powder of an inorganic substance or a powder of an organic substance. The abrasive can be a powder of an inorganic or organic oxide or carbide. Examples of carbides include boron carbide (e.g., BC) and titanium carbide (e.g., TiC). Diamond can also be used as the abrasive. In one form, the abrasive is preferably a powder of an inorganic oxide. Specific examples of inorganic oxides include alumina (e.g., AlO), titanium oxide (e.g., TiO), cerium oxide (e.g., CeO), and zirconium oxide (e.g., ZrO), with alumina being preferred. The Mohs hardness of alumina is approximately 9. For details on alumina powder, see paragraph 0021 of JP 2013-229090 A. Furthermore, the specific surface area can be used as an index of the particle size of an abrasive. It can be considered that the larger the specific surface area, the smaller the particle size of the primary particles that make up the abrasive. For the abrasive, a specific surface area measured by the BET (Brunauer-Emmett-Teller) method (hereinafter referred to as "BET specific surface area") of 14 m 2 From the viewpoint of dispersibility, it is preferable to use an abrasive having a BET specific surface area of ​​40 m 2It is preferable to use an abrasive with a concentration of 1.0 to 20.0 parts by mass, and more preferably 1.0 to 15.0 parts by mass, per 100.0 parts by mass of ferromagnetic powder. Only one type of nonmagnetic powder can be used as the abrasive, or two or more types of nonmagnetic powders with different compositions and / or physical properties (e.g., size) can also be used. When two or more types of nonmagnetic powders are used as the abrasive, the abrasive content refers to the total content of those two or more nonmagnetic powders. The same applies to the content of various components in this invention and this specification. The abrasive is preferably dispersed separately from the ferromagnetic powder (separate dispersion), and more preferably dispersed separately from the protrusion-forming agent described below (separate dispersion). When preparing the magnetic layer-forming composition, using two or more dispersions with different components and / or dispersion conditions as the abrasive dispersion (hereinafter also referred to as the "abrasive liquid") is preferable in terms of controlling the wear characteristics of the magnetic tape.

[0067] A dispersant can also be used to adjust the dispersion state of the abrasive dispersion. Compounds that can function as dispersants to improve the dispersibility of abrasives include aromatic hydrocarbon compounds having a phenolic hydroxy group. A "phenolic hydroxy group" refers to a hydroxy group directly bonded to an aromatic ring. The aromatic ring contained in the aromatic hydrocarbon compound may be a monocyclic ring, a polycyclic structure, or a fused ring. From the perspective of improving the dispersibility of abrasives, aromatic hydrocarbon compounds containing a benzene ring or a naphthalene ring are preferred. The aromatic hydrocarbon compound may also have a substituent other than the phenolic hydroxy group. Examples of the substituent other than the phenolic hydroxy group include a halogen atom, an alkyl group, an alkoxy group, an amino group, an acyl group, a nitro group, a nitroso group, and a hydroxyalkyl group. A halogen atom, an alkyl group, an alkoxy group, an amino group, and a hydroxyalkyl group are preferred. The number of phenolic hydroxy groups contained in one molecule of the aromatic hydrocarbon compound may be one, two, three, or more.

[0068] A preferred embodiment of the aromatic hydrocarbon compound having a phenolic hydroxy group is a compound represented by the following formula 100.

[0069] [ka] [In formula 100, X 101 ~X 108 Two of the groups are hydroxy groups, and the other six groups each independently represent a hydrogen atom or a substituent.

[0070] In the compound represented by formula 100, the substitution positions of the two hydroxy groups (phenolic hydroxy groups) are not particularly limited.

[0071] In formula 100, X 101 ~X 108 Two of the X's are hydroxy groups (phenolic hydroxy groups), and the other six each independently represent a hydrogen atom or a substituent. 101 ~X 108 In the above, all the moieties other than the two hydroxyl groups may be hydrogen atoms, or some or all may be substituents. Examples of the substituents include the substituents described above. One or more phenolic hydroxyl groups may be included as the substituents other than the two hydroxyl groups. From the viewpoint of improving the dispersibility of the abrasive, X 101 ~X 108 Preferably, the two hydroxy groups other than the two hydroxy groups are not phenolic hydroxy groups. That is, the compound represented by formula 100 is preferably dihydroxynaphthalene or a derivative thereof, more preferably 2,3-dihydroxynaphthalene or a derivative thereof. 101 ~X 108 Preferred examples of the substituent represented by the formula (I) include a halogen atom (for example, a chlorine atom or a bromine atom), an amino group, an alkyl group having 1 to 6 carbon atoms (preferably 1 to 4 carbon atoms), a methoxy group, an ethoxy group, an acyl group, a nitro group, a nitroso group, and a —CHOH group.

[0072] Furthermore, for dispersants for improving the dispersibility of abrasives, reference can also be made to paragraphs 0024 to 0028 of JP 2014-179149 A.

[0073] A dispersant for improving the dispersibility of an abrasive can be used, for example, when preparing an abrasive liquid (for each abrasive liquid if multiple abrasive liquids are prepared), in a proportion of, for example, 0.5 to 20.0 parts by mass per 100.0 parts by mass of the abrasive, and is preferably used in a proportion of 1.0 to 10.0 parts by mass.

[0074] One example of the protrusion-forming agent is carbon black. The BET specific surface area of ​​carbon black is 10 m 2 / g or more, and 15m 2 From the viewpoint of easiness in improving dispersibility, the BET specific surface area of ​​carbon black is preferably 50 m / g or more. 2 / g or less, and 2 / g or less is more preferable. Another form of the protrusion-forming agent is colloidal particles. Inorganic colloidal particles are preferred as colloidal particles due to their availability, inorganic oxide colloidal particles are more preferable, and silica colloidal particles (colloidal silica) are even more preferable. In the present invention and this specification, "colloidal particles" refers to particles that can disperse without settling and form a colloidal dispersion when added at 1 g per 100 mL of at least one organic solvent, such as methyl ethyl ketone, cyclohexanone, toluene, or ethyl acetate, or a mixed solvent containing two or more of the above solvents in any desired ratio. The average particle size of the colloidal particles can be, for example, 30 to 300 nm, preferably 40 to 200 nm. The content of the protrusion-forming agent in the magnetic layer is preferably 0.5 to 4.0 parts by mass, more preferably 0.5 to 3.5 parts by mass, per 100.0 parts by mass of the ferromagnetic powder. The protrusion-forming agent is preferably subjected to a dispersion treatment separately from the ferromagnetic powder, and more preferably from the abrasive. When preparing the magnetic layer-forming composition, two or more dispersions with different components and / or dispersion conditions can also be prepared as the dispersion of the protrusion-forming agent (hereinafter also referred to as "protrusion-forming agent liquid").

[0075] One type of additive that can be contained in the magnetic layer is a compound having an ammonium salt structure of an alkyl ester anion, as represented by the following formula 1.

[0076] [ka]

[0077] (In formula 1, R represents an alkyl group having 7 or more carbon atoms or a fluorinated alkyl group having 7 or more carbon atoms, and Z + represents an ammonium cation.)

[0078] The inventors believe that the above compounds may function as lubricants, as will be further explained below. Lubricants can be broadly divided into fluid lubricants and boundary lubricants. The inventors believe that compounds having an ammonium salt structure of an alkyl ester anion, as represented by the above formula 1, can function as fluid lubricants. Fluid lubricants are thought to be able to provide lubrication to the magnetic layer by forming a liquid film on the magnetic layer surface. AlFeSil wear value 45° It is presumed that in order to control the standard deviation of the AlFeSil wear value, it is desirable for the fluid lubricant to form a liquid film on the magnetic layer surface. Furthermore, the more stable the sliding between the magnetic layer surface and the AlFeSil rectangular pillars during measurement of the AlFeSil wear value, the smaller the measured value can be. Regarding the liquid film of the fluid lubricant, from the viewpoint of enabling more stable sliding, it is considered desirable to use an appropriate amount of fluid lubricant forming a liquid film on the magnetic layer surface. This is because it is presumed that if the amount of liquid lubricant forming a liquid film on the magnetic layer surface is excessive, the magnetic layer surface and the AlFeSil rectangular pillars will stick together, making the sliding stability more likely to decrease. Furthermore, it is presumed that if the amount of liquid lubricant forming a liquid film on the magnetic layer surface is excessive, the protrusions formed on the magnetic layer surface by, for example, a protrusion-forming agent will be covered with the liquid film. This is also considered to be a factor that makes the sliding stability more likely to decrease. In this regard, the above compound contains an ammonium salt structure of an alkyl ester anion represented by formula 1. It is believed that a compound containing such a structure can play an excellent role as a fluid lubricant even in a relatively small amount. Therefore, the inclusion of the above compound in the magnetic layer leads to an improvement in the sliding stability between the magnetic layer surface of the magnetic tape and the AlFeSil rectangular pillars, and the AlFeSil wear value 45° and may contribute to controlling the standard deviation of AlFeSil wear values.

[0079] The above compounds will be described in more detail below.

[0080] In the present invention and this specification, unless otherwise specified, the groups described may have a substituent or may be unsubstituted. Furthermore, with respect to a group having a substituent, the "number of carbon atoms" refers to the number of carbon atoms excluding the number of carbon atoms of the substituent, unless otherwise specified. In the present invention and this specification, examples of the substituent include an alkyl group (e.g., an alkyl group having 1 to 6 carbon atoms), a hydroxy group, an alkoxy group (e.g., an alkoxy group having 1 to 6 carbon atoms), a halogen atom (e.g., a fluorine atom, a chlorine atom, a bromine atom, etc.), a cyano group, an amino group, a nitro group, an acyl group, a carboxy group, a salt of a carboxy group, a sulfonic acid group, a salt of a sulfonic acid group, etc.

[0081] At least a portion of the compound having the ammonium salt structure of the alkyl ester anion represented by Formula 1 contained in the magnetic layer can form a liquid film on the surface of the magnetic layer, and a portion can be contained within the magnetic layer and migrate to the surface of the magnetic layer during sliding contact with the magnetic head, forming a liquid film. Furthermore, a portion can be contained in the non-magnetic layer described below, and can migrate to the magnetic layer and then to the surface of the magnetic layer to form a liquid film. The "alkyl ester anion" can also be called an "alkyl carboxylate anion."

[0082] In formula 1, R represents an alkyl group having 7 or more carbon atoms or a fluorinated alkyl group having 7 or more carbon atoms. The fluorinated alkyl group has a structure in which some or all of the hydrogen atoms constituting the alkyl group are substituted with fluorine atoms. The alkyl group or fluorinated alkyl group represented by R may have a linear structure, a branched structure, or a cyclic alkyl group or fluorinated alkyl group, and preferably has a linear structure. The alkyl group or fluorinated alkyl group represented by R may have a substituent or may be unsubstituted, and is preferably unsubstituted. The alkyl group represented by R is, for example, C n H 2n+1 -, where n is an integer of 7 or more. The fluorinated alkyl group represented by R can be, for example, C n H 2n+1The alkyl group or fluorinated alkyl group represented by R may have a structure in which some or all of the hydrogen atoms constituting the alkyl group represented by R are substituted with fluorine atoms. The number of carbon atoms in the alkyl group or fluorinated alkyl group represented by R is 7 or more, preferably 8 or more, more preferably 9 or more, even more preferably 10 or more, still more preferably 11 or more, even more preferably 12 or more, and still more preferably 13 or more. The number of carbon atoms in the alkyl group or fluorinated alkyl group represented by R is preferably 20 or less, more preferably 19 or less, and even more preferably 18 or less.

[0083] In equation 1, Z + represents an ammonium cation. Specifically, the ammonium cation has the following structure: In the present invention and this specification, "*" in a formula representing a part of a compound represents the bonding position between the part of the structure and the adjacent atom.

[0084] [ka]

[0085] Nitrogen cation N of ammonium cation + and the oxygen anion O in Eq. - and form a salt bridging group to form an ammonium salt structure of an alkyl ester anion represented by formula 1. The presence of a compound having an ammonium salt structure of an alkyl ester anion represented by formula 1 in the magnetic layer can be confirmed by analyzing the magnetic tape using X-ray photoelectron spectroscopy (ESCA; Electron Spectroscopy for Chemical Analysis), infrared spectroscopy (IR; infrared spectroscopy), etc.

[0086] In one form, Z +The ammonium cation represented by the formula (I) can be obtained, for example, by converting a nitrogen atom of a nitrogen-containing polymer into a cation. A nitrogen-containing polymer refers to a polymer containing nitrogen atoms. In the present invention and this specification, the terms "polymer" and "polymeric polymer" are used to encompass homopolymers and copolymers. In one form, the nitrogen atom can be included as an atom constituting the main chain of the polymer, or in another form, as an atom constituting the side chain of the polymer.

[0087] One example of the nitrogen-containing polymer is polyalkyleneimine, which is a ring-opening polymer of alkyleneimine and has a plurality of repeating units represented by the following formula 2.

[0088] [ka]

[0089] The nitrogen atom N constituting the main chain in formula 2 is a nitrogen cation N + So Z in Equation 1 + This can result in an ammonium cation represented by the formula: and can form an ammonium salt structure with an alkyl ester anion, for example, as follows:

[0090] [ka]

[0091] Equation 2 will be explained in more detail below.

[0092] In formula 2, R 1 and R 2 each independently represents a hydrogen atom or an alkyl group, and n1 represents an integer of 2 or more.

[0093] R 1 or R 2Examples of the alkyl group represented by R include alkyl groups having 1 to 6 carbon atoms, preferably alkyl groups having 1 to 3 carbon atoms, more preferably a methyl group or an ethyl group, and even more preferably a methyl group. 1 or R 2 The alkyl group represented by the formula (2) is preferably an unsubstituted alkyl group. 1 and R 2 The combinations include one in which one is a hydrogen atom and the other is an alkyl group, both in which hydrogen atoms are present, and both in which alkyl groups (the same or different alkyl groups) are present, with both in which hydrogen atoms are preferred. The alkyleneimine that yields the polyalkyleneimine has the smallest number of carbon atoms in the ring, which is ethyleneimine, and the alkyleneimine (ethyleneimine) obtained by ring-opening the ethyleneimine has two carbon atoms in its main chain. Therefore, n1 in Formula 2 is 2 or more. n1 in Formula 2 can be, for example, 10 or less, 8 or less, 6 or less, or 4 or less. The polyalkyleneimine may be a homopolymer containing only the same repeating structure represented by Formula 2, or a copolymer containing two or more different repeating structures represented by Formula 2. The number-average molecular weight of the polyalkyleneimine that can be used to form a compound having an ammonium salt structure of an alkyl ester anion represented by Formula 1 can be, for example, 200 or more, preferably 300 or more, and more preferably 400 or more. The number average molecular weight of the polyalkyleneimine can be, for example, 10,000 or less, preferably 5,000 or less, and more preferably 2,000 or less.

[0094] In the present invention and this specification, the average molecular weight (weight average molecular weight and number average molecular weight) refers to a value measured by gel permeation chromatography (GPC) and calculated in terms of standard polystyrene. Unless otherwise specified, the average molecular weight shown in the examples described below is a value (polystyrene-equivalent value) calculated in terms of standard polystyrene from a value measured using GPC under the following measurement conditions. GPC equipment: HLC-8220 (Tosoh Corporation) Guard column: TSKguardcolumn Super HZM-H Columns: TSKgel Super HZ 2000, TSKgel Super HZ 4000, TSKgel Super HZ-M (Tosoh Corporation, 4.6 mm (inner diameter) x 15.0 cm, three columns connected in series) Eluent: tetrahydrofuran (THF), containing stabilizer (2,6-di-t-butyl-4-methylphenol) Eluent flow rate: 0.35mL / min Column temperature: 40℃ Inlet temperature: 40℃ Refractive Index (RI) measurement temperature: 40℃ Sample concentration: 0.3% by mass Sample injection volume: 10 μL

[0095] Another example of the nitrogen-containing polymer is polyallylamine, which is a polymer of allylamine and has a plurality of repeating units represented by the following formula 3:

[0096] [ka]

[0097] The nitrogen atom N constituting the amino group in the side chain in formula 3 is a nitrogen cation N + So Z in Equation 1 + This can result in an ammonium cation represented by the formula: and can form an ammonium salt structure with an alkyl ester anion, for example, as follows:

[0098] [ka]

[0099] The weight-average molecular weight of the polyallylamine that can be used to form the compound having the ammonium salt structure of an alkyl ester anion represented by Formula 1 can be, for example, 200 or more, preferably 1,000 or more, and more preferably 1,500 or more. The weight-average molecular weight of the polyallylamine can be, for example, 15,000 or less, preferably 10,000 or less, and more preferably 8,000 or less.

[0100] The fact that the compound having an ammonium salt structure of an alkyl ester anion represented by formula 1 includes a compound having a structure derived from polyalkyleneimine or polyallylamine can be confirmed by analyzing the surface of the magnetic layer using time-of-flight secondary ion mass spectrometry (TOF-SIMS) or the like.

[0101] The compound having the ammonium salt structure of an alkyl ester anion represented by Formula 1 can be a salt of a nitrogen-containing polymer and one or more fatty acids selected from the group consisting of fatty acids having 7 or more carbon atoms and fluorinated fatty acids having 7 or more carbon atoms. The nitrogen-containing polymer that forms the salt can be one or more nitrogen-containing polymers, such as a nitrogen-containing polymer selected from the group consisting of polyalkyleneimines and polyallylamines. The fatty acids that form the salt can be one or more fatty acids selected from the group consisting of fatty acids having 7 or more carbon atoms and fluorinated fatty acids having 7 or more carbon atoms. Fluorinated fatty acids have a structure in which some or all of the hydrogen atoms constituting the alkyl group bonded to the carboxyl group COOH in the fatty acid are substituted with fluorine atoms. For example, the salt-forming reaction can easily proceed by mixing the nitrogen-containing polymer and the fatty acid at room temperature. Room temperature is, for example, about 20 to 25°C. In one embodiment, the salt-forming reaction can proceed by using one or more nitrogen-containing polymers and one or more fatty acids as components of the magnetic layer-forming composition and mixing them in the preparation process of the magnetic layer-forming composition. In one embodiment, prior to preparing the magnetic layer-forming composition, one or more nitrogen-containing polymers and one or more fatty acids are mixed to form a salt, and then this salt is used as a component of the magnetic layer-forming composition to prepare the magnetic layer-forming composition. This also applies to forming a non-magnetic layer containing a compound having an ammonium salt structure of an alkyl ester anion represented by Formula 1. For example, for the magnetic layer, 0.1 to 10.0 parts by weight of the nitrogen-containing polymer can be used per 100.0 parts by weight of ferromagnetic powder, with 0.5 to 8.0 parts by weight being preferred. The fatty acids can be used in an amount of, for example, 0.05 to 10.0 parts by weight, with 0.1 to 5.0 parts by weight being preferred, per 100.0 parts by weight of ferromagnetic powder. For the non-magnetic layer, 0.1 to 10.0 parts by weight of the nitrogen-containing polymer can be used per 100.0 parts by weight of non-magnetic powder, with 0.5 to 8.0 parts by weight being preferred.The fatty acids can be used in an amount of, for example, 0.05 to 10.0 parts by mass, and preferably 0.1 to 5.0 parts by mass, per 100.0 parts by mass of the non-magnetic powder. When the nitrogen-containing polymer and the fatty acids are mixed to form the ammonium salt of the alkyl ester anion represented by formula 1, the nitrogen atoms constituting the nitrogen-containing polymer may also react with the carboxy groups of the fatty acids to form the following structure, and forms containing such structures are also encompassed in the above-mentioned compounds.

[0102] [ka]

[0103] Examples of the fatty acids include fatty acids having an alkyl group as described above for R in Formula 1 and fluorinated fatty acids having a fluorinated alkyl group as described above for R in Formula 1.

[0104] The mixing ratio of the nitrogen-containing polymer and the fatty acids used to form the compound having an ammonium salt structure of an alkyl ester anion represented by Formula 1 is preferably 10:90 to 90:10, more preferably 20:80 to 85:15, and even more preferably 30:70 to 80:20, in terms of the mass ratio of nitrogen-containing polymer to fatty acids. Furthermore, the compound having an ammonium salt structure of an alkyl ester anion represented by Formula 1 is preferably contained in the magnetic layer in an amount of 0.01 parts by mass or more, more preferably 0.1 parts by mass or more, and even more preferably 0.5 parts by mass or more, per 100.0 parts by mass of ferromagnetic powder. Here, the content of the compound in the magnetic layer refers to the total amount of the compound forming a liquid film on the surface of the magnetic layer and the amount contained within the magnetic layer. On the other hand, a high content of ferromagnetic powder in the magnetic layer is preferable from the perspective of high-density recording. Therefore, from the perspective of high-density recording, a low content of components other than the ferromagnetic powder is preferable. From this viewpoint, the content of the above compounds in the magnetic layer is preferably 15.0 parts by mass or less, more preferably 10.0 parts by mass or less, and even more preferably 8.0 parts by mass or less, per 100.0 parts by mass of the ferromagnetic powder. The same applies to the preferred range of the content of the above compounds in the magnetic layer-forming composition used to form the magnetic layer.

[0105] The lubricant may be, for example, a fatty acid amide, which can function as a boundary lubricant. Boundary lubricants are considered to be lubricants that can reduce contact friction by adsorbing to the surface of powder (e.g., ferromagnetic powder) and forming a strong lubricating film. Examples of fatty acid amides include amides of various fatty acids such as lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, behenic acid, erucic acid, and elaidic acid, specifically lauric acid amide, myristic acid amide, palmitic acid amide, and stearic acid amide. The fatty acid amide content in the magnetic layer is, for example, 0 to 3.0 parts by weight, preferably 0 to 2.0 parts by weight, and more preferably 0 to 1.0 part by weight per 100.0 parts by weight of the ferromagnetic powder. The fatty acid amide may also be contained in the non-magnetic layer. The fatty acid amide content in the non-magnetic layer is, for example, 0 to 3.0 parts by weight, preferably 0 to 1.0 part by weight per 100.0 parts by weight of the non-magnetic powder. For details about dispersants, see paragraphs 0061 and 0071 of JP 2012-133837 A. A dispersant may be added to the nonmagnetic layer-forming composition. For details about dispersants that can be added to the nonmagnetic layer-forming composition, see paragraph 0061 of JP 2012-133837 A.

[0106] The present inventors have the following idea regarding suppressing the deterioration of electromagnetic conversion characteristics when recording data on a magnetic tape and / or reproducing recorded data at different head tilt angles. As mentioned above, if the head tilt angle differs, it is presumed that the degree of wear on the magnetic tape head caused by contact with the magnetic tape head will differ greatly during recording and / or playback (the degree of wear will vary greatly). This large variation in the degree of wear is thought to be the cause of the deterioration of electromagnetic conversion characteristics. Wear is thought to be affected by factors such as the size and content of the abrasive, the shear stress on the magnetic head (which can affect frictional characteristics), and normal force. As the head tilt angle increases, the normal force tends to increase, which is thought to lead to deeper penetration of the abrasive into the magnetic head, increasing friction and increasing wear. In contrast, using the above-mentioned compounds, which are thought to function as liquid lubricants, as components of the magnetic layer can improve the lubricity (slipperiness) of the magnetic layer surface and contribute to suppressing large variations in the degree of wear of the magnetic head due to differences in head tilt angle. Furthermore, with regard to the abrasive, it is thought that the greater the amount of abrasive contained in the magnetic layer, the more likely the magnetic head will wear when the head tilt angle is large. When the head tilt angle is small, if multiple abrasives of different sizes are used as components of the magnetic layer, it is thought that the larger the size of the abrasive, the more likely it is that the magnetic head will wear. In regard to the above points, the present inventors have found that, for example, the use of the above compounds as components used as lubricants for forming the magnetic layer, the combination of abrasives used, and / or adjustment of the content of the abrasives can improve the AlFeSil wear value. 45° It is believed that this can contribute to controlling the standard deviation of the AlFeSil wear value. 45° and the standard deviation of the AlFeSil wear values ​​within the ranges described above, it is presumed that this will lead to suppression of deterioration in electromagnetic conversion characteristics when recording data to a magnetic tape and / or reproducing recorded data at different head tilt angles.

[0107] <Nonmagnetic layer> Next, the nonmagnetic layer will be described. The magnetic tape may have a magnetic layer directly on the nonmagnetic support, or may have a nonmagnetic layer containing nonmagnetic powder between the nonmagnetic support and the magnetic layer. The nonmagnetic powder used in the nonmagnetic layer may be an inorganic powder (inorganic powder) or an organic powder (organic powder). Carbon black, etc., can also be used. Examples of inorganic substances include metals, metal oxides, metal carbonates, metal sulfates, metal nitrides, metal carbides, and metal sulfides. These nonmagnetic powders are commercially available or can be produced by known methods. For details, see paragraphs

[0146] to

[0150] of JP 2011-216149 A. For carbon black usable in the nonmagnetic layer, see paragraphs

[0040] to

[0041] of JP 2010-24113 A. The content (filling rate) of the non-magnetic powder in the non-magnetic layer is preferably in the range of 50 to 90 mass %, and more preferably in the range of 60 to 90 mass %, relative to the total mass of the non-magnetic layer.

[0108] The non-magnetic layer may contain a binder and may also contain additives. For other details of the binder, additives, etc. of the non-magnetic layer, known techniques related to non-magnetic layers can be applied. Furthermore, for example, for the type and content of the binder, the type and content of the additive, known techniques related to magnetic layers can also be applied.

[0109] The non-magnetic layer of the magnetic tape also includes a substantially non-magnetic layer that contains a small amount of ferromagnetic powder, either as an impurity or intentionally, along with the non-magnetic powder. Here, a substantially non-magnetic layer refers to a layer having a residual magnetic flux density of 10 mT or less, a coercive force of 7.96 kA / m (100 Oe) or less, or a residual magnetic flux density of 10 mT or less and a coercive force of 7.96 kA / m (100 Oe) or less. It is preferable that the non-magnetic layer have no residual magnetic flux density or coercive force.

[0110] <Nonmagnetic support> Next, the non-magnetic support will be described. Examples of the non-magnetic support (hereinafter also simply referred to as "support") include known biaxially stretched polyethylene terephthalate, polyethylene naphthalate, polyamide, polyamideimide, aromatic polyamide, etc. Among these, polyethylene terephthalate, polyethylene naphthalate, and polyamide are preferred. These supports may be previously subjected to corona discharge, plasma treatment, easy-adhesion treatment, heat treatment, etc.

[0111] <Backcoat layer> The tape may or may not have a backcoat layer containing nonmagnetic powder on the surface of the nonmagnetic support opposite the surface having the magnetic layer. The backcoat layer preferably contains one or both of carbon black and inorganic powder. The backcoat layer may also contain a binder and additives. For details of the nonmagnetic powder, binder, additives, etc., of the backcoat layer, known techniques related to backcoat layers can be applied, as can known techniques related to magnetic and / or nonmagnetic layers. For example, see paragraphs

[0018] to

[0020] of Japanese Patent Laid-Open No. 2006-331625 and U.S. Patent No. 7,029,774, column 4, line 65 to column 5, line 38, regarding the backcoat layer.

[0112] <Various thicknesses> With regard to the thickness (total thickness) of magnetic tape, with the enormous increase in the amount of information in recent years, there is a demand for magnetic tape with an increased recording capacity (higher capacity). One way to increase capacity is to reduce the thickness of the magnetic tape and increase the length of magnetic tape that can be accommodated in one magnetic tape cartridge. From this perspective, the thickness (total thickness) of the magnetic tape is preferably 5.6 μm or less, more preferably 5.5 μm or less, more preferably 5.4 μm or less, even more preferably 5.3 μm or less, and even more preferably 5.2 μm or less. Furthermore, from the viewpoint of ease of handling, the thickness of the magnetic tape is preferably 3.0 μm or more, and more preferably 3.5 μm or more.

[0113] The thickness (total thickness) of the magnetic tape can be measured by the following method. Ten tape samples (e.g., 5 to 10 cm long) are cut from any portion of the magnetic tape, and these tape samples are stacked and measured for thickness. The measured thickness is divided by 10 to obtain the value (thickness per tape sample), which is taken as the tape thickness. The thickness measurement can be performed using a known measuring device capable of measuring thickness to the order of 0.1 μm.

[0114] The thickness of the non-magnetic support is preferably 3.0 to 5.0 μm. The thickness of the magnetic layer can be optimized depending on the saturation magnetization of the magnetic head used, the head gap length, the bandwidth of the recording signal, etc., and is generally 0.01 μm to 0.15 μm, and from the viewpoint of high-density recording, it is preferably 0.02 μm to 0.12 μm, and more preferably 0.03 μm to 0.1 μm. At least one magnetic layer is sufficient, and the magnetic layer may be separated into two or more layers with different magnetic properties, and known configurations related to multilayer magnetic layers can be applied. When the magnetic layer is separated into two or more layers, the thickness of the magnetic layer refers to the total thickness of these layers. The thickness of the non-magnetic layer is, for example, 0.1 to 1.5 μm, and preferably 0.1 to 1.0 μm. The thickness of the backcoat layer is preferably 0.9 μm or less, and more preferably 0.1 to 0.7 μm. The thickness of the magnetic layer and other thicknesses can be determined by the following method. After exposing a cross section of the magnetic tape in the thickness direction with an ion beam, the exposed cross section is observed using a scanning electron microscope or a transmission electron microscope. The thicknesses can be calculated as the arithmetic mean of the thicknesses measured at any two points during the cross section observation. Alternatively, the thicknesses can be calculated as the design thickness calculated from the manufacturing conditions, etc.

[0115] <Manufacturing method> (Preparation of compositions for forming each layer) Compositions for forming the magnetic layer, nonmagnetic layer, or backcoat layer typically contain a solvent in addition to the various components described above. Various organic solvents commonly used in the production of particulate magnetic recording media can be used as the solvent. In particular, from the perspective of the solubility of binders commonly used in particulate magnetic recording media, each layer-forming composition preferably contains one or more ketone solvents, such as acetone, methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, cyclohexanone, isophorone, and tetrahydrofuran. The amount of solvent in each layer-forming composition is not particularly limited and can be the same as that used in each layer-forming composition for typical particulate magnetic recording media. Furthermore, the process for preparing each layer-forming composition typically includes at least a kneading step, a dispersion step, and mixing steps, optionally provided before or after these steps. Each individual step may be divided into two or more stages. The components used in the preparation of each layer-forming composition may be added at the beginning or during any step. Furthermore, each component may be added in separate steps over two or more steps. For example, the binder may be added in portions during the kneading process, the dispersion process, and the mixing process for adjusting the viscosity after dispersion. As described above, one or more nitrogen-containing polymers and one or more fatty acids are used as components of the magnetic layer-forming composition, and the salt-forming reaction can be promoted by mixing these components during the preparation process of the magnetic layer-forming composition. In one embodiment, one or more nitrogen-containing polymers and one or more fatty acids are mixed to form a salt before preparing the magnetic layer-forming composition, and then this salt can be used as a component of the magnetic layer-forming composition to prepare the magnetic layer-forming composition. This also applies to the preparation process of the non-magnetic layer-forming composition. The abrasive liquid is preferably prepared by dispersing the ferromagnetic powder and the protrusion-forming agent separately. The abrasive liquid is preferably prepared as one or more abrasive liquids containing an abrasive, a solvent, and preferably a binder, separately from the ferromagnetic powder and the protrusion-forming agent, and can be used in the preparation of the magnetic layer-forming composition. Dispersion and / or classification can be performed to prepare the abrasive liquid. For these treatments, commercially available equipment can be used.

[0116] In the manufacturing process of the magnetic tape, conventional known manufacturing techniques can be used in some or all of the steps. In the kneading process, it is preferable to use a kneader with strong kneading power, such as an open kneader, continuous kneader, pressure kneader, or extruder. Details of these kneading processes are described in JP-A-1-106338 and JP-A-1-79274. Glass beads and / or other beads can be used to disperse the layer-forming compositions. High-specific-gravity dispersion beads such as zirconia beads, titania beads, and steel beads are suitable as such dispersion beads. It is preferable to optimize the particle size (bead diameter) and packing rate of these dispersion beads. Known dispersers can be used. Each layer-forming composition may be filtered by a known method before being subjected to the coating process. Filtration can be performed, for example, by filter filtration. Filters with a pore size of 0.01 to 3 μm (e.g., glass fiber filters, polypropylene filters, etc.) can be used for filtration.

[0117] Regarding the dispersion treatment of the magnetic layer-forming composition, in one embodiment, the dispersion treatment of the ferromagnetic powder can be carried out by a two-stage dispersion treatment, in which the first stage disintegrates coarse agglomerates of the ferromagnetic powder, and then the second stage dispersion treatment is carried out in which the collision energy applied to the ferromagnetic powder particles by collision with the dispersion beads is smaller than that in the first dispersion treatment. It is believed that such a dispersion treatment can achieve both improved dispersibility of the ferromagnetic powder and suppression of chipping (partial chipping of particles).

[0118] An example of the two-stage dispersion treatment is a dispersion treatment including a first stage in which a ferromagnetic powder, a binder, and a solvent are dispersed in the presence of first dispersion beads to obtain a dispersion, and a second stage in which the dispersion obtained in the first stage is dispersed in the presence of second dispersion beads having a smaller diameter and density than the first dispersion beads. The above-mentioned dispersion treatment will be further described below.

[0119] To improve the dispersibility of the ferromagnetic powder, the first and second steps are preferably carried out as dispersion treatments before the ferromagnetic powder is mixed with other powder components. For example, the first and second steps are preferably carried out as dispersion treatments of a liquid (magnetic liquid) containing the ferromagnetic powder, binder, solvent, and optional additives before mixing with the abrasive and protrusion-forming agent.

[0120] The bead diameter of the second dispersion beads is preferably 1 / 100 or less, more preferably 1 / 500 or less, of the bead diameter of the first dispersion beads. The bead diameter of the second dispersion beads can be, for example, 1 / 10,000 or more of the bead diameter of the first dispersion beads. However, the bead diameter is not limited to this range. For example, the bead diameter of the second dispersion beads is preferably in the range of 80 to 1,000 nm. On the other hand, the bead diameter of the first dispersion beads can be, for example, in the range of 0.2 to 1.0 mm. The bead diameter in the present invention and this specification is a value measured by the same method as the method for measuring the average particle size of the powder described above.

[0121] The second step is preferably carried out under conditions in which the second dispersion beads are present in an amount, by mass, of 10 times or more the amount of the ferromagnetic hexagonal ferrite powder, and more preferably in an amount of 10 to 30 times the amount. On the other hand, the amount of the first dispersion beads in the first stage is also preferably within the above range.

[0122] The second dispersed beads are beads having a lower density than the first dispersed beads. "Density" is defined as the mass (unit: g) of the dispersed beads divided by the volume (unit: cm 3 The density of the second dispersion beads is preferably 3.7 g / cm. 3 More preferably, it is 3.5 g / cm or less. 3 The density of the second dispersion beads is, for example, 2.0 g / cm 3 It may be 2.0 g / cm or more. 3Preferred second dispersion beads in terms of density include diamond beads, silicon carbide beads, silicon nitride beads, etc., and preferred second dispersion beads in terms of density and hardness include diamond beads. On the other hand, the first dispersion beads have a density of 3.7 g / cm 3 Highly dispersed beads are preferred, with a density of 3.8 g / cm 3 Dispersion beads of 4.0 g / cm or more are more preferable. 3 The above dispersion beads are more preferred. The density of the first dispersion beads is, for example, 7.0 g / cm 3 It may be less than 7.0 g / cm 3 As the first dispersion beads, zirconia beads, alumina beads, etc. are preferably used, and zirconia beads are more preferably used.

[0123] The dispersion time is not particularly limited and may be set depending on the type of dispersing machine used.

[0124] (coating process) The magnetic layer can be formed by applying the magnetic layer-forming composition directly to the surface of the non-magnetic support, or by sequentially or simultaneously applying the magnetic layer-forming composition and the non-magnetic layer-forming composition in a multilayer. The backcoat layer can be formed by applying the backcoat layer-forming composition to the surface of the non-magnetic support opposite to the surface having the non-magnetic layer and / or magnetic layer (or on which the non-magnetic layer and / or magnetic layer will be subsequently formed). For details on the coating for forming each layer, see paragraph 0066 of JP 2010-231843 A.

[0125] (Other processes) Known techniques can be applied to various other steps in the manufacture of magnetic tapes. For details of the various steps, see, for example, paragraphs 0067 to 0070 of JP 2010-231843 A. For example, a coating layer of a magnetic layer-forming composition can be subjected to an orientation treatment in an orientation zone while the coating layer is still wet. Various known techniques, including those described in paragraph 0052 of JP 2010-24113 A, can be applied to the orientation treatment. For example, vertical orientation treatment can be performed by known methods, such as a method using magnets with opposite poles facing each other. In the orientation zone, the drying rate of the coating layer can be controlled by the temperature and volume of the drying air and / or the transport speed in the orientation zone. The coating layer may also be pre-dried before being transported to the orientation zone. For example, the magnetic field strength in the vertical orientation treatment can be 0.1 to 1.5 T. A long magnetic tape roll can be obtained through various processes. The obtained magnetic tape roll is cut (slit) to the width of the magnetic tape to be housed in a magnetic tape cartridge, for example, using a known cutting machine. The width can be determined according to standards and is usually 1 / 2 inch. 1 inch = 2.54 cm. A servo pattern is usually formed on the magnetic tape obtained by slitting.

[0126] (Heat treatment) In one embodiment, the magnetic tape may be a magnetic tape manufactured through the following heat treatment: In another embodiment, the magnetic tape may be a magnetic tape manufactured without the following heat treatment.

[0127] The heat treatment can be carried out in a state where the magnetic tape has been slit and cut to a width determined in accordance with a standard and is wound around a core member.

[0128] In one embodiment, the above-mentioned heat treatment is performed with the magnetic tape wound around a core-shaped member for heat treatment (hereinafter referred to as the "heat treatment core"), and the magnetic tape after the heat treatment is wound onto the cartridge reel of a magnetic tape cartridge, thereby producing a magnetic tape cartridge in which the magnetic tape is wound onto the cartridge reel. The heat treatment core can be made of metal, resin, paper, or the like. The material of the heat treatment core is preferably a highly rigid material from the viewpoint of suppressing winding defects such as spalling. From this viewpoint, the heat treatment core is preferably made of metal or resin. Furthermore, as an index of rigidity, the flexural modulus of the material of the heat treatment core is preferably 0.2 GPa (gigapascal) or more, more preferably 0.3 GPa or more. On the other hand, since highly rigid materials are generally expensive, using a heat treatment core made of a material with a rigidity exceeding the rigidity required to suppress winding defects leads to increased costs. In consideration of the above, the flexural modulus of the material of the heat treatment core is preferably 250 GPa or less. The flexural modulus is a value measured in accordance with ISO (International Organization for Standardization) 178, and the flexural moduli of various materials are known. Furthermore, the heat treatment core can be a solid or hollow core-shaped member. If the core is hollow, the wall thickness is preferably 2 mm or more from the viewpoint of maintaining rigidity. The core for heat treatment may or may not have a flange. It is preferable to prepare a magnetic tape having a length equal to or greater than the length to be ultimately accommodated in a magnetic tape cartridge (hereinafter referred to as the "final product length") as the magnetic tape to be wound around the heat treatment core, and to perform heat treatment by placing this magnetic tape wound around the heat treatment core in a heat treatment environment. The length of the magnetic tape to be wound around the heat treatment core is equal to or greater than the final product length, and from the viewpoint of ease of winding onto the heat treatment core, it is preferable that it be "final product length + α". From the viewpoint of ease of winding, this α is preferably 5 m or more. The tension when winding onto the heat treatment core is preferably 0.1 N (Newton) or more. Furthermore, from the viewpoint of suppressing excessive deformation during manufacturing, the tension when winding onto the heat treatment core is preferably 1.5 N or less, more preferably 1.0 N or less. The outer diameter of the heat treatment core is preferably 20 mm or more, more preferably 40 mm or more, from the viewpoints of ease of winding and suppression of coiling (longitudinal curl). The outer diameter of the heat treatment core is preferably 100 mm or less, more preferably 90 mm or less. The width of the heat treatment core need only be equal to or greater than the width of the magnetic tape wound around the core. After the heat treatment, when removing the magnetic tape from the heat treatment core, it is preferable to remove the magnetic tape from the heat treatment core after the magnetic tape and the heat treatment core have sufficiently cooled in order to prevent unintended deformation of the tape during the removal operation. The removed magnetic tape is preferably temporarily wound onto another core (referred to as a "temporary take-up core"), and then wound from the temporary take-up core onto the cartridge reel of the magnetic tape cartridge (typically with an outer diameter of approximately 40 to 50 mm). This allows the magnetic tape to be wound onto the cartridge reel of the magnetic tape cartridge while maintaining the inner and outer positions of the magnetic tape relative to the heat treatment core during the heat treatment. For details about the temporary take-up core and the tension when winding the magnetic tape onto this core, please refer to the previous description of the heat treatment core. In a form in which the above-mentioned heat treatment is performed on a magnetic tape having a length of "final product length + α", the length of "+ α" can be cut off at any stage. For example, in one form, the magnetic tape of the final product length can be wound from the temporary winding core onto the reel of the magnetic tape cartridge, and the remaining length of "+ α" can be cut off.From the viewpoint of reducing the portion that is cut off and discarded, it is preferable that the above-mentioned α be 20 m or less.

[0129] A specific example of the heat treatment carried out in the state where the core member is wound as described above will be described below. The atmospheric temperature at which the heat treatment is performed (hereinafter referred to as "heat treatment temperature") is preferably 40° C. or higher, and more preferably 50° C. or higher. On the other hand, from the viewpoint of suppressing excessive deformation, the heat treatment temperature is preferably 75° C. or lower, more preferably 70° C. or lower, and even more preferably 65° C. or lower. The absolute humidity by weight of the atmosphere in which the heat treatment is carried out is preferably 0.1 g / kg dry air or more, more preferably 1 g / kg dry air or more. An atmosphere with an absolute humidity by weight in the above range is preferred because it can be prepared without using special equipment for reducing moisture. On the other hand, from the viewpoint of preventing condensation from forming and reducing workability, the absolute humidity by weight is preferably 70 g / kg dry air or less, more preferably 66 g / kg dry air or less. The heat treatment time is preferably 0.3 hours or more, more preferably 0.5 hours or more. Furthermore, from the viewpoint of production efficiency, the heat treatment time is preferably 48 hours or less.

[0130] Regarding the control of the standard deviation of the curvature described above, the larger the values ​​of the heat treatment temperature, heat treatment time, bending modulus of the core for heat treatment, and tension during winding onto the core for heat treatment, the smaller the value of the standard deviation of the curvature tends to be.

[0131] (Servo pattern formation) "Forming a servo pattern" can also be called "recording a servo signal." Forming a servo pattern will be explained below.

[0132] The servo pattern is usually formed along the length of the magnetic tape. Control methods that use servo signals (servo control) include timing-based servo (TBS), amplitude servo, and frequency servo.

[0133] As specified in ECMA (European Computer Manufacturers Association)-319 (June 2001), magnetic tapes conforming to the LTO (Linear Tape-Open) standard (commonly referred to as "LTO tapes") employ a timing-based servo system. In this timing-based servo system, a servo pattern is formed by a pair of non-parallel magnetic stripes (also called "servo stripes") arranged continuously along the longitudinal direction of the magnetic tape. In this invention and this specification, the term "timing-based servo pattern" refers to a servo pattern that enables head tracking in a timing-based servo system. The reason why the servo pattern is formed by a pair of non-parallel magnetic stripes as described above is to inform a servo signal reading element passing over the servo pattern of its passing position. Specifically, the spacing between the pair of magnetic stripes is formed so that it continuously changes along the width direction of the magnetic tape. By reading this spacing, the servo signal reading element can determine the relative position between the servo pattern and the servo signal reading element. This relative position information enables tracking of data tracks. For this reason, a plurality of servo tracks are usually set on the servo pattern along the width direction of the magnetic tape.

[0134] A servo band is made up of a continuous servo pattern along the length of the magnetic tape. Typically, multiple servo bands are provided on a magnetic tape. For example, there are five servo bands on an LTO tape. The area between two adjacent servo bands is the data band. A data band is made up of multiple data tracks, and each data track corresponds to one of the servo tracks.

[0135] Also, in one embodiment, as disclosed in Japanese Patent Application Laid-Open No. 2004-318983, information indicating the servo band number (also called "servo band ID (identification)" or "UDIM (Unique Data Band Identification Method) information") is embedded in each servo band. This servo band ID is recorded by shifting a specific one of a plurality of pairs of servo stripes in the servo band so that its position is displaced relative to the longitudinal direction of the magnetic tape. Specifically, the way in which a specific one of a plurality of pairs of servo stripes is shifted varies for each servo band. As a result, the recorded servo band ID is unique for each servo band, and therefore, simply by reading one servo band with a servo signal reading element, that servo band can be uniquely identified.

[0136] One method for uniquely identifying servo bands is the staggered method described in ECMA-319 (June 2001). In this staggered method, pairs of non-parallel magnetic stripes (servo stripes) are continuously arranged along the length of the magnetic tape, and are recorded so that each servo band is offset along the length of the magnetic tape. The combination of this offset between adjacent servo bands is unique across the entire magnetic tape, making it possible to uniquely identify servo bands when reading the servo pattern with two servo signal reading elements.

[0137] As specified in ECMA-319 (June 2001), each servo band also typically contains information indicating the longitudinal position of the magnetic tape (also known as "LPOS (Longitudinal Position) information"). Like UDIM information, this LPOS information is recorded by shifting the positions of a pair of servo stripes along the longitudinal direction of the magnetic tape. However, unlike UDIM information, the same signal is recorded in each servo band with this LPOS information.

[0138] It is also possible to embed information other than the UDIM information and LPOS information described above in the servo bands. In this case, the embedded information may be different for each servo band, such as UDIM information, or it may be common to all servo bands, such as LPOS information. Furthermore, methods other than those described above can be used to embed information in the servo bands. For example, a predetermined code may be recorded by thinning out a predetermined pair from a group of pairs of servo stripes.

[0139] The head for forming a servo pattern is called a servo write head. A servo write head typically has a pair of gaps corresponding to the pair of magnetic stripes, the number of which is equal to the number of servo bands. Typically, a core and a coil are connected to each pair of gaps. By supplying a current pulse to the coil, the magnetic field generated in the core can generate a leakage magnetic field in the pair of gaps. To form a servo pattern, a current pulse is input while running a magnetic tape over the servo write head, thereby transferring the magnetic pattern corresponding to the pair of gaps onto the magnetic tape, thereby forming the servo pattern. The width of each gap can be appropriately set depending on the density of the servo pattern to be formed. The width of each gap can be set, for example, to 1 μm or less, 1 to 10 μm, or 10 μm or more.

[0140] Before forming a servo pattern on a magnetic tape, the magnetic tape is usually subjected to a demagnetization (erase) process. This erase process can be performed by applying a uniform magnetic field to the magnetic tape using a direct current magnet or an alternating current magnet. There are two types of erase processes: direct current (DC) erase and alternating current (AC) erase. AC erase is performed by gradually reducing the strength of the magnetic field applied to the magnetic tape while reversing the direction of the magnetic field. DC erase, on the other hand, is performed by applying a unidirectional magnetic field to the magnetic tape. There are two other DC erase methods. The first method is horizontal DC erase, in which a unidirectional magnetic field is applied along the length of the magnetic tape. The second method is vertical DC erase, in which a unidirectional magnetic field is applied along the thickness of the magnetic tape. The erase process can be performed on the entire magnetic tape or on each servo band of the magnetic tape.

[0141] The direction of the magnetic field of the formed servo pattern is determined by the erase direction. For example, when a magnetic tape is subjected to horizontal DC erasure, the servo pattern is formed so that the direction of the magnetic field is opposite to the erase direction. This increases the output of the servo signal obtained by reading the servo pattern. As shown in Japanese Patent Application Laid-Open No. 2012-53940, when a magnetic pattern is transferred to a magnetic tape that has been vertically DC erased using the gap, the servo signal obtained by reading the formed servo pattern has a unipolar pulse shape. On the other hand, when a magnetic pattern is transferred to a magnetic tape that has been horizontally DC erased using the gap, the servo signal obtained by reading the formed servo pattern has a bipolar pulse shape.

[0142] <Vertical squareness ratio> In one embodiment, the perpendicular squareness of the magnetic tape can be, for example, 0.55 or more, and preferably 0.60 or more. A perpendicular squareness of the magnetic tape of 0.60 or more is preferred from the viewpoint of improving electromagnetic conversion characteristics. The upper limit of the squareness is, in principle, 1.00 or less. The perpendicular squareness of the magnetic tape can be 1.00 or less, and can be 0.95 or less, 0.90 or less, 0.85 or less, or 0.80 or less. A large perpendicular squareness of the magnetic tape is preferred from the viewpoint of improving electromagnetic conversion characteristics. The perpendicular squareness of the magnetic tape can be controlled by a known method, such as performing a perpendicular orientation treatment.

[0143] In the present invention and this specification, the "perpendicular squareness" refers to the squareness measured in the perpendicular direction of the magnetic tape. The "perpendicular direction" in relation to the squareness refers to the direction perpendicular to the surface of the magnetic layer, which can also be referred to as the thickness direction. In the present invention and this specification, the perpendicular squareness is determined by the following method. A sample piece of a size suitable for insertion into a vibrating sample magnetometer is cut from the magnetic tape to be measured. A magnetic field is applied to this sample piece perpendicular to the sample piece (perpendicular to the magnetic layer surface) using a vibrating sample magnetometer at a maximum applied magnetic field of 3979 kA / m, a measurement temperature of 296 K, and a magnetic field sweep rate of 8.3 kA / m / s. The magnetization strength of the sample piece in response to the applied magnetic field is measured. The measured magnetization strength is obtained after demagnetization field correction and after subtracting the magnetization of the sample probe of the vibrating sample magnetometer as background noise. The squareness ratio (SQ) is calculated as SQ = Mr / Ms, where Ms is the magnetization strength at the maximum applied magnetic field and Mr is the magnetization strength at zero applied magnetic field. The measurement temperature refers to the temperature of the sample piece. By setting the ambient temperature surrounding the sample piece to the measurement temperature, the temperature of the sample piece can be adjusted to the measurement temperature through temperature equilibrium.

[0144] [Magnetic tape cartridge] One aspect of the present invention relates to a magnetic tape cartridge including the above-mentioned magnetic tape.

[0145] The details of the magnetic tape contained in the magnetic tape cartridge are as described above.

[0146] A magnetic tape cartridge generally contains a magnetic tape wound on a reel within the cartridge body. The reel is rotatably mounted within the cartridge body. Widely used magnetic tape cartridges include single-reel magnetic tape cartridges with one reel within the cartridge body and dual-reel magnetic tape cartridges with two reels within the cartridge body. When a single-reel magnetic tape cartridge is loaded into a magnetic tape device for recording and / or reproducing data on the magnetic tape, the magnetic tape is pulled out from the magnetic tape cartridge and rewound onto a reel on the magnetic tape device. A magnetic head is located in the magnetic tape transport path from the magnetic tape cartridge to the take-up reel. The magnetic tape is fed and rewound between the reel (supply reel) on the magnetic tape cartridge and the reel (take-up reel) on the magnetic tape device. During this process, the magnetic head comes into contact with and slides against the magnetic layer surface of the magnetic tape, thereby recording and / or reproducing data. In contrast, a dual-reel magnetic tape cartridge is provided with both a supply reel and a take-up reel inside the magnetic tape cartridge.

[0147] In one embodiment, the magnetic tape cartridge may include a cartridge memory. The cartridge memory may be, for example, a nonvolatile memory, and may already contain head tilt angle adjustment information or may be recorded with head tilt angle adjustment information. The head tilt angle adjustment information is information for adjusting the head tilt angle while the magnetic tape is running in the magnetic tape device. For example, the head tilt angle adjustment information may record the value of the servo band spacing at each position in the longitudinal direction of the magnetic tape when data is recorded. For example, when reproducing data recorded on the magnetic tape, the value of the servo band spacing may be measured during reproduction, and the head tilt angle may be changed by a control device of the magnetic tape device so that the absolute value of the difference between the servo band spacing measured during reproduction and the servo band spacing recorded in the cartridge memory during recording at the same longitudinal position approaches zero. The head tilt angle may be, for example, the angle θ described above.

[0148] The magnetic tape and magnetic tape cartridge described above can be suitably used in a magnetic tape device (in other words, a magnetic recording and playback system) that records and / or plays back data by changing the head tilt angle while the magnetic tape is running. However, the magnetic tape and magnetic tape cartridge described above are not limited to those used in such magnetic tape devices. For example, there may be a usage pattern in which the head tilt angle during one recording or playback is changed from that during the next recording or playback, and then the head tilt angle is fixed without changing during each recording or playback. Even in such a usage pattern, a magnetic tape that experiences little degradation in electromagnetic conversion characteristics when recording and / or playing back data at different head tilt angles is preferred.

[0149] [Magnetic tape device] One aspect of the present invention relates to a magnetic tape device including the magnetic tape. In the magnetic tape device, data can be recorded on the magnetic tape and / or data recorded on the magnetic tape can be reproduced, for example, by contacting and sliding a magnetic head against the magnetic layer surface of the magnetic tape. The magnetic tape device can detachably include a magnetic tape cartridge according to one aspect of the present invention.

[0150] The magnetic tape cartridge can be mounted in a magnetic tape device equipped with a magnetic head and used to record and / or reproduce data. In this invention and this specification, the term "magnetic tape device" refers to a device that can record data on a magnetic tape and / or reproduce data recorded on a magnetic tape. Such devices are generally called drives.

[0151] <Magnetic head> The magnetic tape device can include a magnetic head. The configuration of the magnetic head and the angle θ, which is the head tilt angle, are as described above with reference to FIGS. 1 to 3. When the magnetic head includes a reproducing element, the reproducing element is preferably a magnetoresistive (MR; Magnetoresistive) element that can read information recorded on a magnetic tape with high sensitivity. As the MR element, various known MR elements (e.g., GMR (Giant Magnetoresistive) element, TMR (Tunnel Magnetoresistive) element, etc.) can be used. Hereinafter, a magnetic head that records data and / or reproduces recorded data is also referred to as a "recording / reproducing head." An element for recording data (recording element) and an element for reproducing data (reproducing element) are collectively referred to as a "magnetic head element."

[0152] By using a read element with a narrow read element width as the read element, data recorded at a high density can be read with high sensitivity. From this perspective, the read element width of the read element is preferably 0.8 μm or less. The read element width of the read element can be, for example, 0.3 μm or more. However, from the above perspective, a width below this value is also preferable. Here, the "reading element width" refers to the physical dimension of the reading element width, which can be measured using an optical microscope, a scanning electron microscope, or the like.

[0153] When recording and / or reproducing data, tracking can be performed using servo signals. That is, by making the servo signal reading element follow a predetermined servo track, the magnetic head element can be controlled to pass over the target data track. The data track is moved by changing the servo track read by the servo signal reading element in the tape width direction. The read / write head can also record and / or read data from other data bands by using the UDIM information described above to move the servo signal read element to a specific servo band and start tracking that servo band.

[0154] FIG. 5 shows an example of the arrangement of data bands and servo bands. In FIG. 5, multiple servo bands 1 are sandwiched between guide bands 3 on the magnetic layer of the magnetic tape MT. Multiple regions 2 sandwiched between two servo bands form data bands. Servo patterns are magnetized regions formed by magnetizing specific regions of the magnetic layer with a servo write head. The regions magnetized by the servo write head (the positions where servo patterns are formed) are determined by standards. For example, in the industry-standard LTO Ultrium format tape, multiple servo patterns inclined with respect to the tape width direction are formed on the servo bands during magnetic tape manufacturing, as shown in FIG. 6. Specifically, in FIG. 6, a servo frame SF on servo band 1 is composed of a servo subframe 1 (SSF1) and a servo subframe 2 (SSF2). Servo subframe 1 is composed of an A burst (labeled A in FIG. 6) and a B burst (labeled B in FIG. 6). The A burst is composed of servo patterns A1 to A5, and the B burst is composed of servo patterns B1 to B5. On the other hand, servo subframe 2 is composed of a C burst (C in FIG. 6) and a D burst (D in FIG. 6). The C burst is composed of servo patterns C1 to C4, and the D burst is composed of servo patterns D1 to D4. These 18 servo patterns are arranged in subframes in a 5, 5, 4, 4 arrangement, in groups of 5 and 4, and are used to identify servo frames. For illustrative purposes, FIG. 6 shows one servo frame. However, in reality, multiple servo frames are arranged in each servo band in the running direction on the magnetic layer of a magnetic tape that performs head tracking using a timing-based servo system. In FIG. 6, the arrow indicates the running direction of the magnetic tape. For example, an LTO Ultrium format tape typically has more than 5,000 servo frames per meter of tape length in each servo band on the magnetic layer.

[0155] In the magnetic tape device, the head tilt angle can be changed while the magnetic tape is running inside the magnetic tape device. The head tilt angle is, for example, the angle θ formed by the axis of the element array with respect to the width direction of the magnetic tape. The angle θ is as described above. For example, by providing an angle adjustment unit that adjusts the angle of the magnetic head module in the recording / reproducing head unit of the magnetic head, the angle θ can be variably adjusted while the magnetic tape is running. Such an angle adjustment unit can include, for example, a rotation mechanism that rotates the module. Publicly known technology can be applied to the angle adjustment unit.

[0156] Regarding the head tilt angle during magnetic tape running, if the magnetic head includes multiple modules, the angle θ described with reference to Figures 1 to 3 can be specified for randomly selected modules. θ, which is the angle θ at the start of magnetic tape running, initial can be set to be greater than or equal to 0°. initial The larger the angle θ, the larger the change in the effective distance between the servo signal read elements relative to the change in angle θ, which is preferable in terms of the ability to adjust the effective distance between the servo signal read elements in response to changes in the width direction of the magnetic tape. initial is preferably 1° or more, more preferably 5° or more, and even more preferably 10° or more. On the other hand, with regard to the angle formed by the magnetic layer surface and the contact surface of the magnetic head when the magnetic tape runs and comes into contact with the magnetic head (generally called the "wrap angle"), keeping the deviation in the tape width direction small is effective in increasing the uniformity in the tape width direction of the friction generated by contact between the magnetic head and the magnetic tape while the magnetic tape is running. Furthermore, increasing the uniformity of the friction in the tape width direction is desirable from the viewpoint of the position tracking ability and running stability of the magnetic head. From the viewpoint of reducing the deviation in the tape width direction of the wrap angle, θ initial is preferably 45° or less, more preferably 40° or less, and even more preferably 35° or less.

[0157] Regarding the change in angle θ during magnetic tape running, while the magnetic tape is running in the magnetic tape device for recording data on the magnetic tape and / or for reproducing data recorded on the magnetic tape, the angle θ of the magnetic head is changed from θ at the start of running. initial When the angle θ changes from max and Δθ min The maximum value of the angle θ during magnetic tape running is θ max and the minimum value is θ min Note that "max" is an abbreviation for maximum, and "min" is an abbreviation for minimum. Δθ max =θ max -θ initial Δθ min =θ initial -θ min

[0158] In one embodiment, Δθ can be greater than 0.000°, and is preferably 0.001° or greater, more preferably 0.010° ​​or greater, from the viewpoint of the ability to adjust the effective distance between servo signal read elements in response to dimensional changes in the magnetic tape width direction. Furthermore, from the viewpoint of ease of ensuring synchronization of recorded data and / or reproduced data between multiple magnetic head elements during data recording and / or reproduction, Δθ is preferably 1.000° or less, more preferably 0.900° or less, even more preferably 0.800° or less, even more preferably 0.700° or less, and even more preferably 0.600° or less.

[0159] 2 and 3, the axis of the element array is inclined toward the magnetic tape running direction. However, the present invention is not limited to such an example. The present invention also includes an embodiment in which the axis of the element array in the above-mentioned magnetic tape device is inclined toward the direction opposite to the magnetic tape running direction.

[0160] θ is the head tilt angle when the magnetic tape starts running initialcan be set by the control device of the magnetic tape device, etc. Regarding the head tilt angle during magnetic tape running, FIG. 7 is an explanatory diagram of a method for measuring the angle θ during magnetic tape running. The angle θ during magnetic tape running can be determined, for example, by the following method. When determining the angle θ during magnetic tape running by the following method, the angle θ is changed within a range of 0 to 90° during magnetic tape running. In other words, if the axis of the element array is tilted toward the magnetic tape running direction at the start of magnetic tape running, the element array is not tilted during magnetic tape running so that the axis of the element array is tilted toward the opposite direction from the magnetic tape running direction at the start of magnetic tape running. Conversely, if the axis of the element array is tilted toward the opposite direction from the magnetic tape running direction at the start of magnetic tape running, the element array is not tilted during magnetic tape running so that the axis of the element array is tilted toward the magnetic tape running direction at the start of magnetic tape running. The phase difference (i.e., time difference) ΔT between the playback signals of a pair of servo signal read elements 1 and 2 is measured. ΔT can be measured using a measurement unit included in the magnetic tape drive. The configuration of such a measurement unit is well known. The distance L between the center of servo signal read element 1 and the center of servo signal read element 2 can be measured using an optical microscope or other device. When the magnetic tape running speed is v, the distance between the centers of the two servo signal read elements in the magnetic tape running direction is L sin θ, and the relationship L sin θ = v × ΔT holds. Therefore, the angle θ during magnetic tape running can be calculated using the formula "θ = arcsin(vΔT / L)." Note that the right diagram in Figure 7 shows an example in which the axis of the element array is tilted toward the magnetic tape running direction. In this example, the phase difference (i.e., time difference) ΔT between the phase of the playback signal of servo signal read element 1 and the phase of the playback signal of servo signal read element 2 is measured. When the axis of the element array is tilted in the opposite direction to the running direction of the magnetic tape, θ can be found by the above method, except that ΔT is measured as the phase difference (i.e., time difference) between the phase of the playback signal of servo signal read element 2 and the phase of the playback signal of servo signal read element 1. The measurement pitch of the angle θ, i.e., the measurement interval of the angle θ relative to the tape longitudinal direction, can be selected to be appropriate depending on the frequency of the tape width deformation relative to the tape longitudinal direction. As an example, the measurement pitch can be set to 250 μm.

[0161] <Configuration of magnetic tape device> A magnetic tape device 10 shown in FIG. 8 controls a recording / reproducing head unit 12 in response to commands from a control device 11, and records and reproduces data on a magnetic tape MT. The magnetic tape device 10 has a configuration that can detect and adjust tension applied to the magnetic tape in the longitudinal direction from spindle motors 17A, 17B that control the rotation of the magnetic tape cartridge reel and take-up reel and their drive devices 18A, 18B. The magnetic tape device 10 has a configuration in which a magnetic tape cartridge 13 can be loaded. The magnetic tape device 10 has a cartridge memory read / write device 14 that can read and write data from and to a cartridge memory 131 in the magnetic tape cartridge 13 . The end or leader pin of the magnetic tape MT is pulled out from the magnetic tape cartridge 13 loaded into the magnetic tape device 10 by an automatic loading mechanism or manually, and the magnetic tape MT passes over the recording / playback head through guide rollers 15A and 15B with the magnetic layer surface in contact with the recording / playback head surface of the recording / playback head unit 12, and the magnetic tape MT is wound onto the take-up reel 16. The rotation and torque of spindle motors 17A and 17B are controlled by signals from control device 11, allowing magnetic tape MT to run at a desired speed and tension. Servo patterns pre-formed on the magnetic tape can be used to control the tape speed and head tilt angle. A tension detection mechanism may be provided between magnetic tape cartridge 13 and take-up reel 16 to detect tension. In addition to control by spindle motors 17A and 17B, tension control may also be performed using guide rollers 15A and 15B. The cartridge memory read / write device 14 is configured to be able to read and write information from and to the cartridge memory 131 in response to commands from the control device 11. As a communication method between the cartridge memory read / write device 14 and the cartridge memory 131, for example, the ISO (International Organization for Standardization) 14443 method can be adopted.

[0162] The control device 11 includes, for example, a control unit, a storage unit, a communication unit, and the like.

[0163] The recording / playback head unit 12 is composed of, for example, a recording / playback head, a servo tracking actuator that adjusts the position of the recording / playback head in the track width direction, a recording / playback amplifier 19, a connector cable for connecting to the control device 11, etc. The recording / playback head is composed of, for example, a recording element that records data on the magnetic tape, a reproducing element that reproduces the data from the magnetic tape, and a servo signal reading element that reads the servo signals recorded on the magnetic tape. One magnetic head may have, for example, one or more recording elements, one or more reproducing elements, and one or more servo signal reading elements. Alternatively, each element may be provided separately in multiple magnetic heads corresponding to the running direction of the magnetic tape.

[0164] The recording / playback head unit 12 is configured to be able to record data onto the magnetic tape MT in response to a command from the control device 11. It is also configured to be able to play back the data recorded on the magnetic tape MT in response to a command from the control device 11.

[0165] The control device 11 has a mechanism for determining the running position of the magnetic tape MT from the servo signals read from the servo bands while the magnetic tape MT is running, and for controlling the servo tracking actuator so that the recording element and / or the reproducing element are positioned at the target running position (track position). This control of the track position is performed, for example, by feedback control. The control device 11 has a mechanism for determining the servo band spacing from servo signals read from two adjacent servo bands while the magnetic tape MT is running. The control device 11 can store the determined servo band spacing information in its internal storage unit, the cartridge memory 131, an external connected device, or the like. The control device 11 can also change the head tilt angle according to dimensional information about the width of the magnetic tape while it is running. This allows the effective distance between the servo signal reading elements to approach or match the spacing between the servo bands. The dimensional information can be obtained using a servo pattern pre-formed on the magnetic tape. For example, in this way, while the magnetic tape is running in the magnetic tape device, the angle θ between the axis of the element array and the width of the magnetic tape can be changed according to dimensional information about the width of the magnetic tape obtained during running. The head tilt angle can be adjusted, for example, by feedback control. Furthermore, for example, the head tilt angle can also be adjusted by the method described in JP 2016-524774 A (Patent Document 1) or US 2019 / 0164573 A1 (Patent Document 2). [Example]

[0166] The present invention will be described below based on examples. However, the present invention is not limited to the embodiments shown in the examples. The "parts" and "%" indicated below refer to "parts by mass" and "% by mass" unless otherwise specified. The steps and evaluations described below were carried out in an environment with a temperature of 23°C ± 1°C unless otherwise specified. Furthermore, the "eq" indicated below refers to equivalent, a unit that cannot be converted into SI units.

[0167] [Ferromagnetic powder] In Table 2, "BaFe" is a hexagonal barium ferrite powder with an average particle size (average plate diameter) of 21 nm.

[0168] In Table 2, "SrFe1" is a hexagonal strontium ferrite powder produced by the following method. 1707 g of SrCO3, 687 g of H3BO3, 1120 g of Fe2O3, 45 g of Al(OH)3, 24 g of BaCO3, 13 g of CaCO3, and 235 g of Nd2O3 were weighed and mixed in a mixer to obtain a raw material mixture. The resulting raw material mixture was melted in a platinum crucible at a melting temperature of 1390°C, and the melt was stirred while heating the tapping hole at the bottom of the platinum crucible, causing the melt to be poured into a rod shape at a rate of approximately 6 g / sec. The tapped liquid was rolled and quenched using a water-cooled twin roller to produce an amorphous body. 280 g of the produced amorphous body was placed in an electric furnace, heated to 635°C (crystallization temperature) at a rate of 3.5°C / min, and held at that temperature for 5 hours to precipitate (crystallize) hexagonal strontium ferrite particles. The resulting crystallized material containing hexagonal strontium ferrite particles was then coarsely crushed in a mortar, and 1,000 g of 1 mm zirconia beads and 800 ml of a 1% aqueous acetic acid solution were added to a glass bottle and dispersed for 3 hours using a paint shaker. The resulting dispersion was then separated from the beads and placed in a stainless steel beaker. The dispersion was left to stand at 100°C for 3 hours to dissolve the glass components, after which it was precipitated in a centrifuge and washed by repeated decantation. It was then dried for 6 hours in a heating furnace at 110°C to obtain hexagonal strontium ferrite powder. The average particle size of the hexagonal strontium ferrite powder obtained above was 18 nm, and the activation volume was 902 nm. 3 , the anisotropy constant Ku is 2.2×10 5 J / m 3 , mass magnetization σs is 49A m 2 / kg. A 12 mg sample powder was taken from the hexagonal strontium ferrite powder obtained above, and this sample powder was partially dissolved under the dissolution conditions exemplified above. The filtrate was subjected to elemental analysis using an ICP analyzer to determine the neodymium atom content in the surface layer. Separately, 12 mg of sample powder was collected from the hexagonal strontium ferrite powder obtained above, and this sample powder was completely dissolved under the dissolution conditions exemplified above. The filtrate thus obtained was subjected to elemental analysis using an ICP analyzer to determine the bulk content of neodymium atoms. The neodymium atom content (bulk content) of the hexagonal strontium ferrite powder obtained above relative to 100 atomic percent of iron atoms was 2.9 atomic percent. The neodymium atom content in the surface layer was 8.0 atomic percent. The ratio of the surface layer content to the bulk content, "surface layer content / bulk content," was 2.8, confirming that neodymium atoms were unevenly distributed in the surface layers of the particles. The powder obtained above was confirmed to have a hexagonal ferrite crystal structure by scanning with CuKα radiation at a voltage of 45 kV and an intensity of 40 mA and measuring the X-ray diffraction pattern under the following conditions (X-ray diffraction analysis). The powder obtained above exhibited a magnetoplumbite (M-type) hexagonal ferrite crystal structure. Furthermore, the crystalline phase detected by X-ray diffraction analysis was a single magnetoplumbite phase. PANalytical X'Pert Pro diffractometer, PIXcel detector Soller slits for incident and diffracted beams: 0.017 radians Dispersion slit fixed angle: 1 / 4 degree Mask: 10mm Anti-scatter slit: 1 / 4 degree Measurement mode: Continuous Measurement time per step: 3 seconds Measurement speed: 0.017 degrees per second Measurement step: 0.05 degrees

[0169] In Table 2, "SrFe2" is a hexagonal strontium ferrite powder produced by the following method. 1725 g of SrCO3, 666 g of H3BO3, 1332 g of Fe2O3, 52 g of Al(OH)3, 34 g of CaCO3, and 141 g of BaCO3 were weighed and mixed in a mixer to obtain a raw material mixture. The resulting raw material mixture was melted in a platinum crucible at a melting temperature of 1380°C, and the melt was stirred while heating the tapping hole at the bottom of the platinum crucible, causing the melt to be poured into a rod shape at a rate of approximately 6 g / sec. The tapped liquid was rolled and quenched using a water-cooled twin roll mill to produce an amorphous body. 280 g of the obtained amorphous body was placed in an electric furnace, heated to 645°C (crystallization temperature), and held at this temperature for 5 hours to precipitate (crystallize) hexagonal strontium ferrite particles. The resulting crystallized material containing hexagonal strontium ferrite particles was then coarsely crushed in a mortar, and 1,000 g of 1 mm zirconia beads and 800 ml of a 1% aqueous acetic acid solution were added to a glass bottle and dispersed for 3 hours using a paint shaker. The resulting dispersion was then separated from the beads and placed in a stainless steel beaker. The dispersion was left to stand at 100°C for 3 hours to dissolve the glass components, after which it was precipitated in a centrifuge and washed by repeated decantation. It was then dried for 6 hours in a heating furnace at 110°C to obtain hexagonal strontium ferrite powder. The average particle size of the obtained hexagonal strontium ferrite powder was 19 nm, and the activation volume was 1102 nm. 3 , the anisotropy constant Ku is 2.0×10 5 J / m 3 , mass magnetization σs is 50A m 2 / kg.

[0170] In Table 2, "ε-iron oxide" is ε-iron oxide powder prepared by the following method. 8.3 g of iron(III) nitrate nonahydrate, 1.3 g of gallium(III) nitrate octahydrate, 190 mg of cobalt(II) nitrate hexahydrate, 150 mg of titanium(IV) sulfate, and 1.5 g of polyvinylpyrrolidone (PVP) were dissolved in 90 g of pure water. While stirring using a magnetic stirrer, 4.0 g of 25% aqueous ammonia was added in air at an ambient temperature of 25°C. The mixture was stirred for 2 hours at 25°C. A citric acid solution prepared by dissolving 1 g of citric acid in 9 g of pure water was added to the resulting solution and stirred for 1 hour. The precipitated powder was collected by centrifugation, washed with pure water, and dried in a heating oven at 80°C. 800g of pure water was added to the dried powder, and the powder was dispersed in water again to obtain a dispersion. The resulting dispersion was heated to 50°C, and 40g of a 25% aqueous ammonia solution was added dropwise while stirring. After stirring for 1 hour while maintaining the temperature at 50°C, 14mL of tetraethoxysilane (TEOS) was added dropwise and stirred for 24 hours. 50g of ammonium sulfate was added to the resulting reaction solution, and the precipitated powder was collected by centrifugation, washed with pure water, and dried for 24 hours in a heating furnace at 80°C to obtain a precursor of the ferromagnetic powder. The obtained precursor of the ferromagnetic powder was placed in a heating furnace at an internal temperature of 1000° C. in an air atmosphere and subjected to a heat treatment for 4 hours. The heat-treated ferromagnetic powder precursor was placed in a 4 mol / L aqueous solution of sodium hydroxide (NaOH), and the liquid temperature was maintained at 70°C while stirring for 24 hours, thereby removing the impurity silicate compound from the heat-treated ferromagnetic powder precursor. Thereafter, the silicate compound was removed by centrifugation, and the ferromagnetic powder was collected and washed with pure water to obtain a ferromagnetic powder. The composition of the obtained ferromagnetic powder was confirmed by inductively coupled plasma optical emission spectrometry (ICP-OES). It was found that the powder consisted of Ga, Co, and Ti substituted ε-iron oxide (ε-Ga 0.28 Co 0.05 Ti 0.05 Fe 1.62 In addition, X-ray diffraction analysis was performed under the same conditions as those described above for SrFe1, and it was confirmed from the peaks in the X-ray diffraction pattern that the obtained ferromagnetic powder had a single-phase ε-phase crystal structure (ε-iron oxide crystal structure) without containing α-phase or γ-phase crystal structures. The average particle size of the obtained ε-iron oxide powder was 12 nm, and the activation volume was 746 nm. 3 , the anisotropy constant Ku is 1.2×10 5 J / m 3 , mass magnetization σs is 16A m 2 / kg.

[0171] The activation volume and anisotropy constant Ku of the above hexagonal strontium ferrite powder and ε-iron oxide powder were determined for each ferromagnetic powder using a vibrating sample magnetometer (manufactured by Toei Kogyo Co., Ltd.) by the method described above. The mass magnetization σs is a value measured at a magnetic field strength of 15 kOe using a vibrating sample magnetometer (manufactured by Toei Kogyo Co., Ltd.).

[0172] [Preparation of abrasive liquid] <Preparation of abrasive liquid A> 100.0 parts of the abrasive (alumina powder) shown in Table 1 was mixed with the amount of 2,3-dihydroxynaphthalene (manufactured by Tokyo Chemical Industry Co., Ltd.) shown in Table 1, 31.3 parts of a 32% solution (solvent: a mixed solvent of methyl ethyl ketone and toluene) of a polyester polyurethane resin having SO3Na groups as polar groups (UR-4800 (polar group amount: 80 meq / kg) manufactured by Toyobo Co., Ltd.), and 570.0 parts of a 1:1 (mass ratio) mixed solution of methyl ethyl ketone and cyclohexanone as the solvent, and dispersed in the presence of zirconia beads (bead diameter: 0.1 mm) using a paint shaker for the time (bead dispersion time) shown in Table 1. After dispersion, the dispersion was separated from the beads using a mesh, and the resulting dispersion was centrifuged. The centrifugation was carried out using a Hitachi Koki CS150GXL centrifuge (using a Hitachi Koki S100AT6 rotor) at the rotation speed (rpm; rotations per minute) shown in Table 1 for the time (centrifugation time) shown in Table 1. This centrifugation caused particles with relatively large particle sizes to settle, while particles with relatively small particle sizes dispersed in the supernatant. The supernatant was then recovered by decantation. This recovered liquid was called "abrasive liquid A."

[0173] <Preparation of Polishing Compounds B and C> Abrasive liquids B and C were prepared in the same manner as for abrasive liquid A, except that various items were changed as shown in Table 1.

[0174] [Table 1]

[0175] [Example 1] <Preparation of Magnetic Layer-Forming Composition> (Magnetic liquid) Ferromagnetic powder (see Table 2): 100.0 parts Oleic acid: 2.0 parts Vinyl chloride copolymer (Zeon MR-104): 10.0 parts SO3Na group-containing polyurethane resin: 4.0 parts (Weight average molecular weight 70000, SO3Na group: 0.07meq / g) Polyalkyleneimine polymer (a synthetic product obtained by the method described in paragraphs 0115 to 0123 of JP 2016-51493 A): 6.0 parts Methyl ethyl ketone: 150.0 parts Cyclohexanone: 150.0 parts (abrasive liquid) The abrasive liquid shown in Table 2 was used so that the amount of abrasive in the abrasive liquid was the amount shown in Table 2. (Other ingredients) Carbon black (average particle size: 20 nm): 0.7 parts Polyethyleneimine (manufactured by Nippon Shokubai Co., Ltd., number average molecular weight 300): 2.0 parts Stearic acid: 0.5 parts Stearic acid amide: 0.3 parts Butyl stearate: 6.0 parts Methyl ethyl ketone: 110.0 parts Cyclohexanone: 110.0 parts Polyisocyanate (Tosoh Coronate (registered trademark) L): 3.0 parts

[0176] (Preparation method) The various components of the magnetic liquid were mixed in a batch-type vertical sand mill with zirconia beads (first dispersion beads, density 6.0 g / cm) with a diameter of 0.5 mm. 3 ) for 24 hours (first step), and then filtered using a filter with a pore size of 0.5 μm to prepare Dispersion A. The amount of zirconia beads used was 10 times the mass of the ferromagnetic powder. Dispersion A was then mixed with diamond beads (second dispersion beads, density 3.5 g / cm) with a bead diameter of 500 nm in a batch-type vertical sand mill. 3 The diamond beads were separated using a centrifuge to prepare a dispersion (Dispersion B). The diamond beads were used in an amount 10 times the mass of the ferromagnetic powder. Dispersion B obtained above, the abrasive liquid, and the other components described above were introduced into a dissolver mixer and stirred for 360 minutes at a peripheral speed of 10 m / s. After that, ultrasonic dispersion treatment was performed for 60 minutes at a flow rate of 7.5 kg / min using a flow ultrasonic disperser, and then the mixture was filtered three times using a filter with a pore size of 0.3 μm to prepare a composition for forming a magnetic layer.

[0177] <Preparation of composition for forming nonmagnetic layer> The various components of the non-magnetic layer-forming composition described below were dispersed for 24 hours using zirconia beads with a bead diameter of 0.1 mm in a batch-type vertical sand mill, and then filtered using a filter with a pore size of 0.5 μm to prepare a non-magnetic layer-forming composition.

[0178] Non-magnetic inorganic powder α-iron oxide: 100.0 parts (Average particle size 10nm, BET specific surface area 75m 2 / g) Carbon black: 25.0 parts (average particle size 20nm) SO3Na group-containing polyurethane resin: 18.0 parts (Weight average molecular weight 70000, SO3Na group content 0.2meq / g) Stearic acid: 1.0 parts Cyclohexanone: 300.0 parts Methyl ethyl ketone: 300.0 parts

[0179] <Preparation of Composition for Forming Backcoat Layer> The components of the following backcoat layer-forming composition, excluding lubricant (stearic acid and butyl stearate), polyisocyanate and 200.0 parts of cyclohexanone, are kneaded and diluted by an open kneader, and then subjected to 12-pass dispersion treatment using a horizontal bead mill disperser, with zirconia beads of 1 mm diameter, a bead filling rate of 80 volume%, a rotor tip peripheral speed of 10 m / s, and a residence time of 2 minutes per pass.Then, the remaining components are added and stirred by a dissolver, and the resulting dispersion is filtered through a filter with a pore size of 1 μm, to prepare a backcoat layer-forming composition.

[0180] Non-magnetic inorganic powder alpha iron oxide: 80.0 parts (Average particle size 0.15 μm, BET specific surface area 52 m 2 / g) Carbon black: 20.0 parts (average particle size 20nm) Vinyl chloride copolymer: 13.0 parts Sulfonate group-containing polyurethane resin: 6.0 parts Phenylphosphonic acid: 3.0 parts Cyclohexanone: 155.0 parts Methyl ethyl ketone: 155.0 parts Stearic acid: 3.0 parts Butyl stearate: 3.0 parts Polyisocyanate: 5.0 parts Cyclohexanone: 200.0 parts

[0181] <Magnetic tape and magnetic tape cartridge production> The non-magnetic layer-forming composition prepared above was applied to the surface of a 4.1 μm thick polyethylene naphthalate support and dried to a thickness of 0.7 μm after drying, thereby forming a non-magnetic layer. Next, the magnetic layer-forming composition prepared above was applied onto the non-magnetic layer so as to have a thickness of 0.1 μm after drying, thereby forming a coating layer. Then, while the coating layer of the magnetic layer-forming composition was still wet, a magnetic field with a strength of 0.3 T was applied perpendicular to the surface of the coating layer to perform a vertical alignment treatment, followed by drying to form a magnetic layer. Thereafter, the backcoat layer-forming composition prepared above was applied to the surface of the support opposite to the surface on which the non-magnetic layer and magnetic layer were formed, and dried to form a backcoat layer with a thickness of 0.3 μm after drying. Thereafter, a surface smoothing treatment (calendering treatment) was carried out using a calender roll consisting only of a metal roll at a speed of 100 m / min, a linear pressure of 300 kg / cm, and a calender temperature (calender roll surface temperature) of 90° C. In this way, a long magnetic tape raw web was obtained. Thereafter, the magnetic tape was subjected to a heat treatment in an atmosphere at 70° C. for 36 hours, and then the long magnetic tape raw material was slit into 1 / 2 inch widths to obtain magnetic tapes. Servo signals were recorded on the magnetic layer of the resulting magnetic tape using a commercially available servo writer, resulting in a magnetic tape with data bands, servo bands, and guide bands arranged in accordance with the LTO (Linear Tape-Open) Ultrium format, and with servo patterns (timing-based servo patterns) on the servo bands arranged and shaped in accordance with the LTO Ultrium format. The servo patterns thus formed conform to the specifications of JIS (Japanese Industrial Standards) X6175:2006 and Standard ECMA-319 (June 2001). The total number of servo bands is five, and the total number of data bands is four. The magnetic tape (960 m long) on ​​which the servo signals were recorded was wound onto a reel of a magnetic tape cartridge (LTO Ultrium 8 data cartridge), and a leader tape conforming to item 9 of Section 3 of Standard ECMA (European Computer Manufacturers Association)-319 (June 2001) was spliced ​​to the end of the tape using commercially available splicing tape. In this way, a magnetic tape cartridge in which the magnetic tape was wound around a reel was produced.

[0182] The presence of a compound containing an ammonium salt structure of an alkyl ester anion represented by formula 1, formed from polyethyleneimine and stearic acid, in the magnetic layer of a magnetic tape can be confirmed by the following method. A sample is cut from the magnetic tape, and the magnetic layer surface (measurement area: 300 μm × 700 μm) is subjected to X-ray photoelectron spectroscopy using an ESCA instrument. Specifically, wide scan measurements are performed using the ESCA instrument under the following measurement conditions. The measurement results show peaks at the position of the binding energy of the ester anion and the position of the binding energy of the ammonium cation. Equipment: Shimadzu AXIS-ULTRA Excitation X-ray source: Monochromated Al-Kα radiation Scan range: 0 to 1200 eV Pass energy: 160 eV Energy resolution: 1 eV / step Capture time: 100ms / step Accumulation count: 5 In addition, a sample piece 3 cm long was cut out from the magnetic tape, and the magnetic layer surface was measured by ATR-FT-IR (Attenuated Total Reflection-Fourier Transform-Infrared Spectrometer) (reflection method). - The wavenumber corresponding to the absorption of -1 or 1430cm -1 ), and the wavenumber corresponding to the absorption of ammonium cation (2400 cm -1 ) absorption is confirmed.

[0183] [Examples 2 to 18, Comparative Examples 1 to 10] A magnetic tape and a magnetic tape cartridge were obtained by the method described in Example 1, except that the items shown in Table 2 were changed as shown in Table 2. For Examples 15 to 18, the process after recording the servo signal was changed as follows: That is, heat treatment was performed after recording the servo signal. In contrast, for Examples 2 to 14 and Comparative Examples 1 to 10, such heat treatment was not performed, and therefore "None" is entered in the "Heat Treatment Conditions" column in Table 2. For Examples 15 to 18, the magnetic tape (length 970 m) after recording servo signals as described for Example 1 was wound around a core for heat treatment, and heat treatment was carried out while the tape was wound around this core. A solid core-shaped member (outer diameter: 50 mm) made of resin with a flexural modulus of elasticity shown in Table 2 was used as the core for heat treatment, and the tension during winding was the value shown in Table 2. The heat treatment temperature and heat treatment time were the values ​​shown in Table 2. The weight absolute humidity of the atmosphere in which the heat treatment was carried out was 10 g / kg dry air. After the above heat treatment, once the magnetic tape and heat treatment core had sufficiently cooled, the magnetic tape was removed from the heat treatment core and wound onto a temporary take-up core. Thereafter, the magnetic tape of the final product length (960 m) was wound from the temporary take-up core onto the reel of a magnetic tape cartridge (LTO Ultrium 8 data cartridge). The remaining 10 m was cut off, and a leader tape in accordance with item 9 of Section 3 of Standard ECMA (European Computer Manufacturers Association)-319 (June 2001) was spliced ​​to the end of the cut-off side using commercially available splicing tape. The temporary take-up core was a solid core-shaped member made of the same material and with the same outer diameter as the heat treatment core, and the tension during winding was 0.6 N. In this way, a magnetic tape cartridge in which the magnetic tape was wound around a reel was produced.

[0184] For each of the above examples and comparative examples, four magnetic tape cartridges were produced, one of which was used to evaluate the deterioration of electromagnetic conversion characteristics described below, and the other three were used to evaluate the magnetic tapes (1) to (3) described below.

[0185] [Evaluation of deterioration of electromagnetic conversion characteristics (decrease in SNR (Signal-to-Noise Ratio))] The SNR reduction amount was determined by the following method to evaluate the deterioration of electromagnetic conversion characteristics. The following recording and playback were performed using a 1 / 2-inch reel tester with a fixed magnetic head, and a total of four runs were performed by sequentially changing the head tilt angle from 0°, 15°, 30°, to 45°. The head tilt angle is the angle θ formed by the axis of the element array of the playback module described below with respect to the width direction of the magnetic tape at the start of each run. The angle θ was set by the control device of the magnetic tape device at the start of each run of the magnetic tape, and the head tilt angle was fixed throughout each run of the magnetic tape. For each magnetic tape (total length: 960 m) in the examples and comparative examples, 1,000 recording and playback passes were performed with a tension of 1.5 N applied in the longitudinal direction of the magnetic tape (hereinafter referred to as "running tension") in an environment with a temperature of 23°C and a relative humidity of 50%, followed by 1,000 recording and playback passes with a tension of 0.2 N applied in the longitudinal direction of the magnetic tape. The relative speed between the magnetic tape and the magnetic head was 8 m / s, and the magnetic head used had the following module arrangement: recording module - playback module - recording module (total number of modules: 3). Each module contained 32 magnetic head elements (Ch0 to Ch31), and these magnetic head elements were sandwiched between a pair of servo signal reading elements to form an element array. The recording elements in the recording module were MIG (metal-in-gap) elements (gap length: 0.15 μm, track width: 1.0 μm), and recording was performed with the recording current set to the optimum recording current for each magnetic tape. The playback element of the playback module is a GMR (Giant-magnetoresistive) element (element thickness 15 nm, shield spacing 0.1 μm, playback element width 0.8 μm). A signal with a linear recording density of 300 kfci was recorded, and the playback signal was measured using a Shibasoku spectrum analyzer. The unit kfci is the unit of linear recording density (cannot be converted to SI units). The signal was taken from the point where the signal had stabilized sufficiently after the magnetic tape started running. For each run, the difference between the SNR on the first pass at a running tension of 1.5 N and the SNR on the 1000th pass at a running tension of 0.2 N (SNR on the 1000th pass at a running tension of 0.2 N - SNR on the first pass at a running tension of 1.5 N) was calculated as the SNR decrease. The arithmetic mean of the SNR decrease calculated for the four different head tilt angles is shown in the "SNR decrease" column in Table 2.

[0186] [Magnetic tape evaluation] (1) AlFeSil wear value 45° , standard deviation of AlFeSil wear values The magnetic tape was removed from each magnetic tape cartridge of the Examples and Comparative Examples, and the AlFeSil abrasion value was measured by the method described above in an environment of a temperature of 23°C and a relative humidity of 50%. 45° The standard deviation of the AlFeSil wear values ​​was also calculated.

[0187] (2) Standard deviation of the amount of curvature in the longitudinal direction of the magnetic tape The magnetic tape was removed from each of the magnetic tape cartridges of the examples and comparative examples, and the standard deviation of the amount of curvature in the longitudinal direction of the magnetic tape was determined by the method described above.

[0188] (3) Tape thickness Ten tape samples (5 cm long) were cut from any portion of the magnetic tape removed from each magnetic tape cartridge in the Examples and Comparative Examples, and these tape samples were stacked and measured for thickness. The thickness was measured using a digital thickness meter equipped with a Millimar 1240 compact amplifier and a Millimar 1301 inductive probe manufactured by MARH. The measured thickness was divided by 10 to obtain the value (thickness per tape sample), which was used as the tape thickness. The tape thickness for each magnetic tape was 5.2 μm.

[0189] The above results are shown in Table 2 (Table 2-1 to Table 2-2).

[0190] [Table 2-1]

[0191] [Table 2-2]

[0192] From the results shown in Table 2, the AlFeSil wear value 45° It can be confirmed that in the magnetic tapes of the examples in which the standard deviations of the AlFeSil wear values ​​and the AlFeSil wear values ​​are both within the ranges described above, the deterioration of the electromagnetic conversion characteristics when the magnetic tape is run at different head tilt angles is suppressed compared to the magnetic tapes of the comparative examples.

[0193] A magnetic tape cartridge was produced in the same manner as in Example 1, except that no vertical orientation treatment was performed during the production of the magnetic tape. A sample piece was cut from the magnetic tape removed from the magnetic tape cartridge. The squareness in the vertical direction of this sample piece was measured using a vibrating sample magnetometer, Model TM-TRVSM5050-SMSL, manufactured by Tamagawa Seisakusho, according to the method described above, and was found to be 0.55. The magnetic tape was also removed from the magnetic tape cartridge of Example 1, and a sample piece was cut out from this magnetic tape, and the squareness ratio in the vertical direction was similarly determined to be 0.60.

[0194] The magnetic tapes removed from the two magnetic tape cartridges were each attached to a 1 / 2-inch reel tester, and the electromagnetic conversion characteristics (SNR; Signal-to-Noise Ratio) were evaluated using the following method. As a result, the magnetic tape removed from the magnetic tape cartridge of Example 1 had an SNR value 2 dB higher than that of the magnetic tape produced without vertical orientation treatment. Ten recording and playback passes were performed in an environment with a temperature of 23°C and a relative humidity of 50% with a longitudinal tension of 0.7 N applied to the magnetic tape. The relative speed between the magnetic tape and the magnetic head was 6 m / s. Recording was performed using a metal-in-gap (MIG) head (gap length 0.15 μm, track width 1.0 μm) as the recording head, with the recording current set to the optimum recording current for each magnetic tape. Playback was performed using a giant-magnetoresistive (GMR) head (element thickness 15 nm, shield spacing 0.1 μm, playback element width 0.8 μm) as the playback head. The head tilt angle was 0°. A signal with a linear recording density of 300 kfci was recorded, and the playback signal was measured using a Shibasoku spectrum analyzer. The unit kfci is the unit of linear recording density (not convertible to SI units). The signal was recorded from the point where the signal had stabilized sufficiently after the magnetic tape started running. [Industrial Applicability]

[0195] One aspect of the present invention is useful in various data storage technical fields.

Claims

1. A magnetic tape having a non-magnetic support and a magnetic layer containing ferromagnetic powder, In an environment with a temperature of 23°C and a relative humidity of 50%, AlFeSil wear value on the magnetic layer surface measured with an AlFeSil rectangular pillar tilted at an angle of 45° ４５° is 20 μm or more and 50 μm or less, and the standard deviation of the AlFeSil abrasion values ​​on the magnetic layer surface measured at inclination angles of the AlFeSil rectangular pillars of 0°, 15°, 30° and 45° is 30 μm or less; A magnetic tape, wherein the tilt angle of the AlFeSil prism is the angle formed between the longitudinal direction of the AlFeSil prism and the width direction of the magnetic tape.

2. 2. The magnetic tape of claim 1, wherein the standard deviation of the AlFeSil wear values ​​is 15 [mu]m or more and 30 [mu]m or less.

3. 2. The magnetic tape according to claim 1, wherein the standard deviation of the amount of curvature of the magnetic tape in the longitudinal direction is 5 mm / m or less.

4. The magnetic tape of claim 1 , wherein the magnetic layer comprises one or more non-magnetic powders.

5. 5. The magnetic tape of claim 4, wherein the non-magnetic powder includes an alumina powder.

6. 2. The magnetic tape according to claim 1, further comprising a non-magnetic layer containing non-magnetic powder between the non-magnetic support and the magnetic layer.

7. 2. The magnetic tape according to claim 1, further comprising a backcoat layer containing nonmagnetic powder on the surface of said nonmagnetic support opposite to the surface on which said magnetic layer is formed.

8. 2. The magnetic tape according to claim 1, wherein the squareness ratio in the perpendicular direction of the magnetic tape is 0.60 or more.

9. The standard deviation of the AlFeSil wear value is 15 μm or more and 30 μm or less, the standard deviation of the amount of curvature in the longitudinal direction of the magnetic tape is 5 mm / m or less; the magnetic layer contains alumina powder, a non-magnetic layer containing non-magnetic powder between the non-magnetic support and the magnetic layer; a backcoat layer containing nonmagnetic powder on the surface of the nonmagnetic support opposite to the surface on which the magnetic layer is formed, and 2. The magnetic tape according to claim 1, wherein the squareness ratio in the perpendicular direction of the magnetic tape is 0.60 or more.

10. A magnetic tape cartridge comprising the magnetic tape according to any one of claims 1 to 9.

11. A magnetic tape device comprising the magnetic tape according to any one of claims 1 to 9.

12. further comprising a magnetic head; the magnetic head has a module including an element array having a plurality of magnetic head elements between a pair of servo signal read elements, 12. The magnetic tape device according to claim 11, wherein the magnetic tape device changes an angle θ formed by an axis of the element array with respect to a width direction of the magnetic tape while the magnetic tape is running inside the magnetic tape device.

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