Magnetic Tape, Magnetic Tape Cartridge, and Magnetic Tape Device

Abstract

To provide a magnetic tape that can exhibit excellent electromagnetic conversion characteristics, and suppresses large reduction in the electromagnetic conversion characteristics in recording and / or playing back data at different head inclination angles.SOLUTION: There is provided a magnetic tape in which a vertical direction switching field distribution SFD of the magnetic tape is 1.5 or less, in an environment of a temperature of 23°C and relative humidity of 50%, an AlFeSil wear value 45° on a surface of a magnetic layer measured at an inclination angle of an AlFeSil rectangular column of 45° is 20 μm or more and 50 μm or less, a standard deviation of the AlFeSil wear values on the surface of the magnetic layer measured at inclination angles of the AlFeSil rectangular column of 0°, 15°, 30°, and 45° is 30 μm or less, and the inclination angle of the AlFeSil rectangular column is an angle formed by a longitudinal direction of the AlFeSil rectangular column and a width direction of the magnetic tape. Also there are provided a magnetic tape cartridge including the magnetic tape, and a magnetic tape device including the magnetic tape.SELECTED DRAWING: None

Description

Technical Field

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

Background Art

[0002] Magnetic recording media include tape-shaped and disk-shaped ones. For data storage applications such as data backup and archive, tape-shaped magnetic recording media, that is, magnetic tapes, are mainly used (see, for example, Patent Documents 1 and 2).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] There is always a demand for further improvement in the electromagnetic conversion characteristics of magnetic recording media. Therefore, a magnetic tape that can exhibit excellent electromagnetic conversion characteristics is desirable.

[0005] On the other hand, data recording on a magnetic tape is usually performed by running the magnetic tape in a magnetic tape device and causing a magnetic head to follow the data band of the magnetic tape to record data on the data band. Thereby, data tracks are formed on the data band. Also, at the time of reproducing the recorded data, the magnetic tape is run in the magnetic tape device, and the magnetic head is caused to follow the data band of the magnetic tape to read the data recorded on the data band.

[0006] In order to improve the accuracy with which the magnetic head follows the data band of the magnetic tape during recording and / or playback as described above, 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 a servo signal to obtain dimensional information (such as shrinkage and elongation) in the width direction of a running magnetic tape, and to change the angle (hereinafter also referred to as the "head tilt angle") at which the axial direction of the magnetic head module is tilted with respect to the width direction of the magnetic tape according to the obtained dimensional information (see Patent Documents 1 and 2, for example, paragraphs 0059 to 0067 and paragraph 0084 of Patent Document 1). During recording or playback, if the magnetic head for recording or playing back data is displaced from the target track position due to the width deformation of the magnetic tape and recording or playback of data is performed, phenomena such as overwriting of recorded data and playback failure will occur. The inventor believes that changing the angle as described above is one of the means for suppressing the occurrence of such phenomena. For example, assuming that the head tilt angle is changed as described above, a magnetic tape with little deterioration in electromagnetic conversion characteristics is desirable when recording and / or playing back data at different head tilt angles.

[0007] One aspect of the present invention aims to provide a magnetic tape that can exhibit excellent electromagnetic conversion characteristics and has little deterioration in electromagnetic conversion characteristics when recording and / or playing back data at different head tilt angles.

Means for Solving the Problems

[0008] One aspect of the present invention is a magnetic tape having a non-magnetic support and a magnetic layer containing ferromagnetic powder, wherein the perpendicular direction reversal magnetic field distribution SFD (Switching field distribution) of the magnetic tape is 1.5 or less, in an environment of a temperature of 23°C and a relative humidity of 50%, the AlFeSil wear value on the surface of the magnetic layer measured at an inclination angle of 45° of the AlFeSil prism 45°is 20 μm or more and 50 μm or less, and a magnetic tape in which the standard deviation of the AlFeSil wear value of the surface of the magnetic layer measured at inclination angles of 0°, 15°, 30°, and 45° of the AlFeSil prism (hereinafter, also simply referred to as "standard deviation of the AlFeSil wear value") is 30 μm or less, relates to the following. Hereinafter, the perpendicular direction reversal magnetic field distribution SFD of the magnetic tape is also referred to as "perpendicular SFD".

[0009] The inclination angle of the AlFeSil prism is an angle formed by the longitudinal direction of the AlFeSil prism and the width direction of the magnetic tape.

[0010] In one form, the standard deviation of the AlFeSil wear value can be 15 μm or more and 30 μm or less.

[0011] In one form, the perpendicular SFD can be 0.5 or more and 1.5 or less.

[0012] In one form, 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") can be 5 mm / m or less.

[0013] In one form, the magnetic layer can contain one or more non-magnetic powders.

[0014] In one form, the non-magnetic powder can contain alumina powder.

[0015] In one form, the magnetic tape can have a non-magnetic layer containing a non-magnetic powder between the non-magnetic support and the magnetic layer.

[0016] In one form, the magnetic tape can have a back coat layer containing a non-magnetic powder on the surface side opposite to the surface side having the magnetic layer of the non-magnetic support.

[0017] In one form, the tape thickness of the magnetic tape can be 5.2 μm or less.

[0018] One aspect of the present invention relates to a magnetic tape cartridge including the above magnetic tape.

[0019] One aspect of the present invention relates to a magnetic tape device including the above magnetic tape.

[0020] In one form, the magnetic tape device can further include a magnetic head, the magnetic head can have a module including an element array having a plurality of magnetic head elements between a pair of servo signal reading elements, the magnetic tape device can change an angle θ formed by an axis of the element array with respect to a width direction of the magnetic tape during running of the magnetic tape in the magnetic tape device.

Advantages of the Invention

[0021] According to one aspect of the present invention, it is possible to provide a magnetic tape that exhibits excellent electromagnetic conversion characteristics and has little degradation in electromagnetic conversion characteristics when recording and / or reproducing data at different head tilt angles. Further, according to one aspect of the present invention, it is possible to provide a magnetic tape cartridge and a magnetic tape device including the above magnetic tape.

Brief Description of the Drawings

[0022]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Embodiments for Carrying Out the Invention

[0023] [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 perpendicular direction reversal magnetic field distribution SFD (perpendicular SFD) of the above magnetic tape is 1.5 or less. Further, in an environment of temperature 23°C and relative humidity 50%, the AlFeSil wear value on the surface of the magnetic layer measured at an inclination angle of 45° of the AlFeSil prism of the above magnetic tape 45° is 20 μm or more and 50 μm or less, and the standard deviation of the AlFeSil wear values on the surface of the magnetic layer measured at inclination angles of 0°, 15°, 30° and 45° of the AlFeSil prism is 30 μm or less. In the present invention and this specification, the "surface (of the) magnetic layer" is synonymous with the side surface of the magnetic layer of the magnetic tape.

[0024] <Perpendicular SFD> In the present invention and this specification, the perpendicular direction reversal magnetic field distribution SFD (perpendicular SFD) of a magnetic tape is the reversal magnetic field distribution measured in the perpendicular direction of the magnetic tape. The "perpendicular direction" described with respect to the reversal magnetic field distribution is the direction orthogonal to the surface of the magnetic layer, and can also be referred to as the thickness direction. In the present invention and this specification, the perpendicular direction reversal magnetic field distribution SFD of a magnetic tape is a value obtained by the following method at a measurement temperature of 25°C using a vibrating sample magnetometer. A measurement sample piece is cut out from the magnetic tape to be measured. The size of the sample piece may be any size that can be introduced into the vibrating sample magnetometer used for measurement. For such a sample piece, using a vibrating sample magnetometer, a magnetic field is applied in the vertical direction of the sample piece (the direction perpendicular to the surface of the magnetic layer) at a maximum applied magnetic field of 3979 kA / m, a measurement temperature of 25°C, and a magnetic field sweep rate of 8.3 kA / m / second, and the magnetization intensity of the sample piece at the maximum applied magnetic field is measured. The measured value shall be obtained as a value obtained by subtracting the magnetization of the sample probe of the vibrating sample magnetometer as background noise. In the magnetic field-magnetization curve (referred to as the "M-H curve") obtained by such measurement, the magnitude H of the magnetic field at which the magnetization intensity M becomes zero is defined as the coercive force Hc (unit: Oe). Also, among the peaks seen in the differential curve when the magnetization is differentiated with respect to the magnetic field, the half-width of the peak at a magnetic field higher than 2000 Oe is defined as HPW (unit: Oe). "HPW" is an abbreviation for Half Peak Width. SFD is obtained by SFD = HPW ÷ Hc. Note that regarding the unit, 1 Oe (1 oersted) = 79.6 A / m. The measurement temperature is the temperature of the sample piece. By setting the ambient temperature around the sample piece to the measurement temperature (25°C), the temperature of the sample piece can be made the measurement temperature (25°C) due to the establishment of temperature equilibrium.

[0025] The vertical SFD of the magnetic tape is 1.5 or less from the viewpoint of improving the electromagnetic conversion characteristics, preferably 1.3 or less, and more preferably 1.0 or less. The vertical SFD of the magnetic tape can be, for example, 0.1 or more, 0.3 or more, or 0.5 or more, or can also be less than the values exemplified herein. A small value of the vertical SFD is preferable from the viewpoint of further improving the electromagnetic conversion characteristics. The vertical SFD of the magnetic tape can be controlled by known methods such as adjusting the vertical alignment treatment conditions.

[0026] <Explanation of the head tilt angle> Next, prior to explaining the tilt angle of the above-described AlFeSil prism, the configuration of the magnetic head, the head tilt angle, etc. will be described. Further, the reason why it is considered that the phenomenon occurring during recording or reproduction described above can be suppressed by tilting the axial direction of the module of the magnetic head with respect to the width direction of the magnetic tape during magnetic tape running will also be described below.

[0027] The magnetic head can have one or more modules including an element array having a plurality of magnetic head elements between a pair of servo signal reading elements, and can have two or more or three or more. The total number of such modules can be, for example, five or less, four or less, or three or less, or a number of modules exceeding the total numbers exemplified herein may be included in the magnetic head. Examples of the arrangement of a plurality of modules include "recording module - reproducing module" (total number of modules: 2), "recording module - reproducing module - recording module" (total number of modules: 3), etc. However, it is not limited to the examples shown here.

[0028] Each module can include an element array having a plurality of magnetic head elements between a pair of servo signal reading elements, that is, an arrangement of elements. A module having a recording element as a magnetic head element is a recording module for recording data on a magnetic tape. A module having a reproducing element as a magnetic head element is a reproducing module for reproducing data recorded on a magnetic tape. In the magnetic head, a plurality of modules are arranged, for example, in a recording and reproducing head unit such that the axes of the element arrays of the respective modules are oriented parallel to each other. Such "parallel" does not necessarily mean only parallel in a strict sense, but includes the range of errors normally allowed in the technical field to which the present invention belongs. The range of errors can mean, for example, a range of strict parallel ± less than 10°.

[0029] In each element array, a pair of servo signal reading elements and a plurality of magnetic head elements (i.e., recording elements or reproducing elements) are usually arranged linearly spaced apart. Here, "arranged linearly" means that each magnetic head element is arranged on a straight line connecting the central portions of one servo signal reading element and the other servo signal reading element. And the "axis of the element array" in the present invention and this specification refers to the straight line connecting the central portions of one servo signal reading element and the other servo signal reading element.

[0030] Next, the configuration of the module and the like will be further described with reference to the drawings. However, the forms shown in the drawings are examples and do not limit the present invention.

[0031] FIG. 1 is a schematic diagram showing an example of a magnetic head module. The module shown in FIG. 1 has a plurality of magnetic head elements between a pair of servo signal reading elements (servo signal reading elements 1 and 2). The magnetic head elements are also called "channels". "Ch" in the figure is an abbreviation of Channnel. The module shown in FIG. 1 has a total of 32 magnetic head elements from Ch0 to Ch31.

[0032] In FIG. 1, "L" is the distance between a pair of servo signal reading elements, that is, the distance between one servo signal reading element and the other servo signal reading element. In the module shown in FIG. 1, "L" is the distance between servo signal reading element 1 and servo signal reading element 2. Specifically, it is the distance between the central portions of servo signal reading element 1 and servo signal reading element 2. Such a distance can be measured by, for example, an optical microscope or the like.

[0033] FIG. 2 is an explanatory diagram of the relative positional relationship between a module and a magnetic tape during magnetic tape running in a magnetic tape device. In FIG. 2, the dotted line A indicates the width direction of the magnetic tape. The dotted line B indicates the axis of the element array. The angle θ can be referred to as the head tilt angle during magnetic tape running and is the angle formed by the dotted line A and the dotted line B. During magnetic tape running, when the angle θ is 0°, the distance in the width direction of the magnetic tape between one servo signal reading element and the other servo signal reading element of the element array (hereinafter, also referred to as the "effective distance between servo signal reading elements") is "L". On the other hand, the effective distance between servo signal reading elements is "Lcosθ" when the angle θ is greater than 0°, and Lcosθ is smaller than L. That is, "Lcosθ < L".

[0034] As described above, during recording or playback, if the magnetic head for recording or playing back data is displaced from the target track position due to the width deformation of the magnetic tape and recording or playback of data is performed, phenomena such as overwriting of recorded data and playback failure may occur. For example, when the width of the magnetic tape contracts or expands, a phenomenon may occur in which the magnetic head element that should perform recording or playback at the target track position performs recording or playback at a different track position. Also, when the width of the magnetic tape expands, the effective distance between servo signal reading elements becomes shorter than the interval between two servo bands adjacent to each other across the data band (also referred to as the "servo band interval" or the "interval between servo bands". Specifically, it is the distance between the two servo bands in the width direction of the magnetic tape), and a phenomenon may occur in which recording or playback of data is not performed at a portion close to the edge of the magnetic tape. On the other hand, when the element array is tilted at an angle θ greater than 0°, as described above, the effective distance between the servo signal reading elements becomes "Lcosθ". 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 (i.e., shrinkage or elongation) in the width direction of the magnetic tape, it becomes possible to bring the effective distance between the servo signal reading elements closer to or match the interval of the servo band. As a result, during recording or playback, it is possible to prevent or reduce the occurrence frequency of phenomena such as overwriting of recorded data and playback failure caused by the magnetic head for recording or playing back data deviating from the target track position due to the width deformation of the magnetic tape during recording or playback.

[0035] Figure 3 is an explanatory diagram regarding the change in the angle θ during the running of the magnetic tape. The angle θ at the start of running initial can be set, for example, to 0° or more or greater than 0°. In Figure 3, the central figure shows the state of the module at the start of running. In Figure 3, the right figure shows the state of the module when the angle θ is an angle θ initial greater than θ c The effective distance Lcosθ between the servo signal reading elements c is a value smaller than Lcosθ at the start of running of the magnetic tape. When the width of the magnetic tape contracts during the running of the magnetic tape, it is preferable to perform such angle adjustment. initial On the other hand, in Figure 3, the left figure shows the state of the module when the angle θ is an angle θ initial smaller than θ e The effective distance Lcosθ between the servo signal reading elements e is a value larger than Lcosθ at the start of running of the magnetic tape. When the width of the magnetic tape expands during the running of the magnetic tape, it is preferable to perform such angle adjustment. initial

[0036] As described above, changing the head tilt angle during magnetic tape running can contribute to preventing phenomena such as overwriting of recorded data and playback failure, which occur when the magnetic head for recording or playing back data is displaced from the target track position due to width deformation of the magnetic tape during recording or playback, or can contribute to reducing the occurrence frequency thereof. On the other hand, recording of data on a magnetic tape and playback of the recorded data are usually performed by bringing the magnetic layer surface of the magnetic tape into contact with the magnetic head and sliding them. The inventor considered that if the head tilt angle during such sliding is different, 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 inventor speculated that if the head tilt angle is different, the degree of wear of the magnetic head due to contact with the magnetic layer surface will change significantly, thereby deteriorating the electromagnetic conversion characteristics. Based on the above speculation, the inventor conducted intensive studies. As a result, regarding the wear characteristics of the magnetic tape, in an environment of a temperature of 23 °C and a relative humidity of 50%, the AlFeSil wear value measured at an inclination angle of 45° of the AlFeSil prism 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 deterioration of the electromagnetic conversion characteristics when recording and / or reproducing data at different head tilt angles. Hereinafter, the deterioration of the electromagnetic conversion characteristics when recording and / or reproducing data at different head tilt angles will also be simply referred to as "deterioration 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 inventor described in this specification, the present invention is not limited.

[0037] <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. Measure the wear width of the AlFeSil prism when the magnetic tape to be measured is run under the following running conditions using a reel tester. The AlFeSil prism is a prism made of AlFeSil, which is a Sendust-based alloy. For the evaluation, use the AlFeSil prism specified in ECMA (European Computer Manufacturers Association)-288 / Annex H / H2. The wear width of the AlFeSil prism is determined as the wear width described based on FIG. 1 of Japanese Patent Application Laid-Open No. 2007-026564 by observing the edge of the AlFeSil prism from above using an optical microscope. The inclination angle of the AlFeSil prism (hereinafter, also simply referred to as "inclination angle") is the angle formed by the longitudinal direction of the AlFeSil prism and the width direction of the magnetic tape, and is defined 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 inclination angle of the AlFeSil prism is 0°, and when the longitudinal direction of the AlFeSil prism coincides with the longitudinal direction of the magnetic tape, the inclination angle of the AlFeSil prism is 90°.

[0038] Running conditions With the inclination angle of the AlFeSil prism being 0°, 15°, 30°, or 45°, bring the surface of the magnetic layer of the magnetic tape into contact with one edge of the AlFeSil prism at a wrap angle of 12°. In this state, run a portion of the magnetic tape to be measured with a length of 580 m in the longitudinal direction back and forth once at a speed of 3 m / s.

[0039] In the measurement of the AlFeSil wear value at each inclination angle, during the above-mentioned running, the tension applied in the longitudinal direction of the magnetic tape is set to 1.0 N. Here, the value of the tension applied in the longitudinal direction of the magnetic tape during running is the set value of the reel tester. In this way, the AlFeSil wear width measured after one round trip is taken as the AlFeSil wear value at each inclination angle. Prepare one unused AlFeSil prism that has not been subjected to the measurement of the AlFeSil wear value. The measurement of the AlFeSil wear value at the above four different inclination angles is carried out in an arbitrary order by bringing the magnetic layer surface into contact with different one of the four edges of this AlFeSil wear value. The measurement of the AlFeSil wear value at each inclination angle is carried out at different parts of the magnetic tape to be measured. Also, before the measurement at each inclination angle, in order to adapt to the measurement environment, the magnetic tape to be measured is left in the measurement environment for 24 hours or more.

[0040] Among the AlFeSil wear values obtained by the above method, the AlFeSil wear value obtained by the measurement at an inclination angle of 45° is the AlFeSil wear value 45 ° That is. The standard deviation (i.e., the positive square root of the variance) of the AlFeSil wear values obtained at the above four different inclination angles is taken as the standard deviation of the AlFeSil wear value of the magnetic tape to be measured.

[0041] (AlFeSil wear value 45° ) Regarding the wear characteristics of the above magnetic tape, from the viewpoint of suppressing the deterioration of the electromagnetic conversion characteristics when recording and / or reproducing data at different head inclination angles, the AlFeSil wear value 45° is 20 μm or more and 50 μm or less. From the viewpoint of further suppressing the deterioration of the electromagnetic conversion characteristics, the AlFeSil wear value 45° is preferably 45 μm or less, more preferably 40 μm or less, and still more preferably 35 μm or less. From the same viewpoint, the AlFeSil wear value 45° is preferably 23 μm or more, and more preferably 25 μm or more.

[0042] (Standard deviation of AlFeSil wear value) 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, still more preferably 23 μm or less, and even more preferably 20 μm or less, from the viewpoint of suppressing deterioration of the 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 smaller value of the standard deviation of the AlFeSil wear value is preferable from the viewpoint of further suppressing deterioration of the electromagnetic conversion characteristics.

[0043] The wear characteristics of the magnetic tape can be adjusted, for example, by the type of components used to form the magnetic layer and the like. Details of this will be described later.

[0044] <Standard deviation of the amount of curvature> Next, the standard deviation of the amount of curvature will be described. In the present invention and this specification, the amount of curvature in the longitudinal direction of the magnetic tape is a value obtained by the following method in an environment of an ambient temperature of 23°C and a relative humidity of 50%. A magnetic tape is usually housed in a magnetic tape cartridge and distributed. As the magnetic tape to be measured, a magnetic tape taken out from an unused magnetic tape cartridge not attached to a magnetic tape device is used. FIG. 4 is an explanatory diagram of the amount of curvature in the longitudinal direction of the magnetic tape. A tape sample having a length of 100 m in the longitudinal direction is cut out 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 a position D m (D meters) away in the longitudinal direction from this one end toward the other end is defined as the D m position. Therefore, the position 10 m away in the longitudinal direction is the 10 m position, the position 20 m away is the 20 m position, and in sequence, at 10 m intervals, 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 are determined. Cut out a tape sample with a length of 1 m from the position of 0 m to the position of 1 m. This tape sample is used as a tape sample for measuring the amount of curvature at the position of 0 m. Cut out a tape sample with a length of 1 m from the position of 10 m to the position of 11 m. This tape sample is used as a tape sample for measuring the amount of curvature at the position of 10 m. Cut out a tape sample with a length of 1 m from the position of 20 m to the position of 21 m. This tape sample is used as a tape sample for measuring the amount of curvature at the position of 20 m. Cut out a tape sample with a length of 1 m from the position of 30 m to the position of 31 m. This tape sample is used as a tape sample for measuring the amount of curvature at the position of 30 m. Cut out a tape sample with a length of 1 m from the position of 40 m to the position of 41 m. This tape sample is used as a tape sample for measuring the amount of curvature at the position of 40 m. Cut out a tape sample with a length of 1 m from the position of 50 m to the position of 51 m. This tape sample is used as a tape sample for measuring the amount of curvature at the position of 50 m. Cut out a tape sample with a length of 1 m from the position of 60 m to the position of 61 m. This tape sample is used as a tape sample for measuring the amount of curvature at the position of 60 m. Cut out a tape sample with a length of 1 m from the position of 70 m to the position of 71 m. This tape sample is used as a tape sample for measuring the amount of curvature at the position of 70 m. Cut out a tape sample with a length of 1 m from the position of 80 m to the position of 81 m. This tape sample is used as a tape sample for measuring the amount of curvature at the position of 80 m. Cut out a tape sample with a length of 1 m from the position of 90 m to the position of 91 m. This tape sample is used as a tape sample for measuring the amount of curvature at the position of 90 m. Cut out a tape sample with a length of 1 m from the position of 99 m to the position of 100 m. This tape sample is used as a tape sample for measuring the amount of curvature at the position of 100 m. Grip the tape sample at each position with the longitudinal direction vertical and the upper end with a gripping member (such as a clip), and hang it for 24 hours ± 4 hours in a tension-free state. Then, within 1 hour, perform the following measurements. As shown in Fig. 4, place the tape piece on a plane in a tension-free state. The tape piece may be placed on the plane with the surface on the magnetic layer side facing upward, or the other surface facing upward. In Fig. 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), which is the shortest distance between the virtual line 54 connecting both end portions 52 and 53 of the tape sample S and the maximum curved portion 55 in the longitudinal direction of the tape sample S. Fig. 4 shows an example of curving upward on the paper surface. When curving downward, measure the distance L1 (mm) in the same manner. Regardless of which side is curved, the distance L1 is displayed as a positive value. When no curving is confirmed in the longitudinal direction, L1 is set to 0 (zero) mm. In this way, the standard deviation (i.e., the positive square root of the variance) of the amount of curvature L1 measured at a total of 11 positions from the 0 m position to the 100 m position is taken as the standard deviation of the amount of curvature in the longitudinal direction of the magnetic tape to be measured (unit: mm / m).

[0045] In the above magnetic tape, the standard deviation of the amount of curvature obtained by the above method can be, for example, 7 mm / m or less, 6 mm / m or less. From the viewpoint of further suppressing the deterioration of the electromagnetic conversion characteristics, it is preferably 5 mm / m or less, more preferably 4 mm / m or less, and still more preferably 3 mm / m or less. The standard deviation of the amount of curvature of the above 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 the deterioration of the electromagnetic conversion characteristics. Also, a small value of the standard deviation of the amount of curvature is preferable from the viewpoint of further improving the electromagnetic conversion characteristics. From such a viewpoint, it is preferable that the standard deviation of the amount of curvature is within the above range. The standard deviation of the amount of curvature can be controlled by adjusting the manufacturing conditions in the manufacturing process of the magnetic tape. Details thereof will be described later.

[0046] Hereinafter, the above magnetic tape will be described in more detail.

[0047] <Magnetic layer> (Ferromagnetic powder) As the ferromagnetic powder contained in the magnetic layer, one or more known ferromagnetic powders used in the magnetic layers of various magnetic recording media can be used in combination. From the viewpoint of improving the recording density, it is preferable to use a ferromagnetic powder having a small average particle size. From this point, the average particle size of the ferromagnetic powder is preferably 50 nm or less, more preferably 45 nm or less, still more preferably 40 nm or less, even more preferably 35 nm or less, even more preferably 30 nm or less, still even more preferably 25 nm or less, and even still 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, still more preferably 10 nm or more, even more preferably 15 nm or more, and even more preferably 20 nm or more.

[0048] Hexagonal ferrite powder Preferable specific examples of the ferromagnetic powder can include hexagonal ferrite powder. For details of the hexagonal ferrite powder, reference can be made to, for example, paragraphs 0012 to 0030 of JP-A No. 2011-225417, paragraphs 0134 to 0136 of JP-A No. 2011-216149, paragraphs 0013 to 0030 of JP-A No. 2012-204726, and paragraphs 0029 to 0084 of JP-A No. 2015-127985.

[0049] In the present invention and in this specification, the "hexagonal ferrite powder" refers to a ferromagnetic powder in which the crystal structure of hexagonal ferrite is detected as the main phase by X-ray diffraction analysis. The main phase refers to the structure to which the diffraction peak with the highest intensity in the X-ray diffraction spectrum obtained by X-ray diffraction analysis is attributed. For example, when the diffraction peak with the highest intensity in the X-ray diffraction spectrum obtained by X-ray diffraction analysis is attributed to the crystal structure of hexagonal ferrite, it is determined that the crystal structure of hexagonal ferrite has been detected as the main phase. When only a single structure is detected by X-ray diffraction analysis, this detected structure is taken as the main phase. The crystal structure of hexagonal ferrite contains, as constituent atoms, at least iron atoms, divalent metal atoms, and oxygen atoms. The divalent metal atoms are metal atoms that can become divalent cations as ions, and examples thereof include alkaline earth metal atoms such as strontium atoms, barium atoms, and calcium atoms, and lead atoms. In the present invention and in this specification, the hexagonal strontium ferrite powder refers to a powder in which the main divalent metal atom contained in this powder is a strontium atom, and the hexagonal barium ferrite powder refers to a powder in which the main divalent metal atom contained in this powder is a barium atom. The main divalent metal atom refers to the divalent metal atom that occupies the largest proportion on an atomic percentage basis among the divalent metal atoms contained in this powder. However, rare earth atoms are not included in the above divalent metal atoms. The "rare earth atoms" in the present invention and in this specification are selected from the group consisting of scandium atoms (Sc), yttrium atoms (Y), and lanthanoid atoms. The lanthanoid atoms are selected from the group consisting of lanthanum atoms (La), cerium atoms (Ce), praseodymium atoms (Pr), neodymium atoms (Nd), promethium atoms (Pm), samarium atoms (Sm), europium atoms (Eu), gadolinium atoms (Gd), terbium atoms (Tb), dysprosium atoms (Dy), holmium atoms (Ho), erbium atoms (Er), thulium atoms (Tm), ytterbium atoms (Yb), and lutetium atoms (Lu).

[0050] Hereinafter, the hexagonal strontium ferrite powder, which is one form of the hexagonal ferrite powder, will be described in more detail.

[0051] The activation volume of the hexagonal strontium ferrite powder is preferably in the range of 800 to 1600 nm 3 . The micronized hexagonal strontium ferrite powder showing the 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 or more. Also, from the viewpoint of further improving the electromagnetic conversion characteristics, the activation volume of the hexagonal strontium ferrite powder is more preferably 1500 nm 3 or less, still more preferably 1400 nm 3 or less, even more preferably 1300 nm 3 or less, still even more preferably 1200 nm 3 or less, yet even more preferably 1100 nm 3 or less, and even yet more preferably. The same applies to the activation volume of the hexagonal barium ferrite powder.

[0052] The "activation volume" is a unit of magnetization reversal and is an index indicating the magnetic size of particles. The activation volume of the present invention and described in this specification and the anisotropy constant Ku described later are measured using a vibrating sample magnetometer at magnetic field sweep rates of 3 minutes and 30 minutes in the coercive force Hc measurement section (measurement temperature: 23°C ± 1°C), and are values obtained from the following relational expression between Hc and the activation volume V. Regarding the unit of the anisotropy constant Ku, 1 erg / cc = 1.0×10 -1 J / m 3 . 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)]

[0053] As an index for reducing thermal fluctuations, in other words, improving thermal stability, the anisotropy constant Ku can be cited. The hexagonal strontium ferrite powder preferably has a Ku of 1.8×10 5 J / m 3 or more, and more preferably 2.0×10 5 J / m 3 or more. Also, the Ku of the hexagonal strontium ferrite powder can be, for example, 2.5×10 5 J / m 3 or less. However, since a higher Ku means higher thermal stability and is preferable, it is not limited to the values exemplified above.

[0054] The hexagonal strontium ferrite powder may or may not contain rare earth atoms. When the hexagonal strontium ferrite powder contains rare earth atoms, it preferably contains rare earth atoms at a content rate (bulk content rate) of 0.5 to 5.0 atomic% with respect to 100 atomic% of iron atoms. The hexagonal strontium ferrite powder containing rare earth atoms can, in one form, have a rare earth atom surface layer partiality. As used in the present invention and this specification, the "rare earth atom surface layer partiality" means the rare earth atom content rate (hereinafter, referred to as "rare earth atom surface layer content rate" or simply "surface layer content rate" with respect to rare earth atoms) with respect to 100 atomic% of iron atoms in the dissolution solution obtained by partially dissolving the hexagonal strontium ferrite powder with an acid, and the rare earth atom content rate (hereinafter, referred to as "rare earth atom bulk content rate" or simply "bulk content rate" with respect to rare earth atoms) with respect to 100 atomic% of iron atoms in the dissolution solution obtained by completely dissolving the hexagonal strontium ferrite powder with an acid, and Rare earth atom surface layer content rate / Rare earth atom bulk content rate > 1.0 It means satisfying the ratio. The rare earth atom content of the hexagonal strontium ferrite powder described below is synonymous with the rare earth atom bulk content. On the other hand, since partial dissolution using an acid dissolves the surface layer part of the particles constituting the hexagonal strontium ferrite powder, the rare earth atom content in the dissolution solution obtained by partial dissolution is the rare earth atom content in the surface layer part of the particles constituting the hexagonal strontium ferrite powder. That the rare earth atom surface layer content satisfies the ratio of "rare earth atom surface layer content / rare earth atom bulk content > 1.0" means that in the particles constituting the hexagonal strontium ferrite powder, the rare earth atoms are unevenly distributed in the surface layer part (that is, there are more than in the interior). The surface layer part in the present invention and this specification means a partial region from the surface of the particles constituting the hexagonal strontium ferrite powder toward the interior.

[0055] 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% with respect to 100 atomic% of iron atoms. It is considered that including rare earth atoms at the bulk content in the above range and the uneven distribution of rare earth atoms in the surface layer part of the particles constituting the hexagonal strontium ferrite powder contributes to suppressing the decrease in the reproduction output in repeated reproduction. This is presumably because the hexagonal strontium ferrite powder contains rare earth atoms at the bulk content in the above range and the uneven distribution of rare earth atoms in the surface layer part of the particles constituting the hexagonal strontium ferrite powder can increase the anisotropy constant Ku. The higher the value of the anisotropy constant Ku, the more the occurrence of a phenomenon called so-called thermal fluctuation can be suppressed (in other words, the thermal stability can be improved). By suppressing the occurrence of thermal fluctuation, the decrease in the reproduction output in repeated reproduction can be suppressed. It is speculated that the uneven distribution of rare earth atoms in the particle surface layer part of the hexagonal strontium ferrite powder contributes to stabilizing the spin of the iron (Fe) sites in the crystal lattice of the surface layer part, thereby increasing the anisotropy constant Ku. Moreover, it is presumed that using hexagonal strontium ferrite powder having a rare earth atom surface layer bias as the ferromagnetic powder of the magnetic layer also contributes to suppressing the wear of the magnetic layer surface due to sliding with the magnetic head. That is, it is presumed that hexagonal strontium ferrite powder having a rare earth atom surface layer bias can contribute to improving the running durability of the magnetic tape. This is presumably because the uneven distribution of rare earth atoms on the surface of the particles constituting the hexagonal strontium ferrite powder contributes to improving the interaction between the particle surface and the organic substances (for example, binders and / or additives) contained in the magnetic layer, and as a result, the strength of the magnetic layer is improved. From the viewpoint of suppressing the decrease in the reproduction output during repeated reproduction and / or from the viewpoint of further improving the running durability, the rare earth atom content (bulk content) is more preferably in the range of 0.5 to 4.5 atomic %, still 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 %.

[0056] The above 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 kind of rare earth atom as the rare earth atom, or may contain two or more kinds of rare earth atoms. The above bulk content in the case of containing two or more kinds of rare earth atoms is determined for the total of two or more kinds of rare earth atoms. This also applies to other components in the present invention and this specification. That is, unless otherwise specified, one kind of a certain component may be used, or two or more kinds may be used. The content or content ratio in the case of using two or more kinds refers to the total of two or more kinds.

[0057] When the hexagonal strontium ferrite powder contains rare earth atoms, the rare earth atoms contained may be any one or more of the rare earth atoms. From the viewpoint of suppressing the decrease in the reproduction output in repeated reproduction, preferable rare earth atoms include neodymium atoms, samarium atoms, yttrium atoms, and dysprosium atoms, more preferably neodymium atoms, samarium atoms, and yttrium atoms, and even more preferably neodymium atoms.

[0058] In the hexagonal strontium ferrite powder having rare earth atom surface layer partiality, the rare earth atoms only need to 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 the hexagonal strontium ferrite powder having rare earth atom surface layer partiality, the ratio of the surface layer content rate of rare earth atoms obtained by partial dissolution under the dissolution conditions described later to the bulk content rate of rare earth atoms obtained by complete dissolution under the dissolution conditions described later, "surface layer content rate / bulk content rate" is more than 1.0 and can be 1.5 or more. That the "surface layer content rate / bulk content rate" is greater than 1.0 means that in the particles constituting the hexagonal strontium ferrite powder, the rare earth atoms are unevenly distributed in the surface layer (that is, there are more than in the interior). Also, the ratio of the surface layer content rate of rare earth atoms obtained by partial dissolution under the dissolution conditions described later to the bulk content rate of rare earth atoms obtained by complete dissolution under the dissolution conditions described later, "surface layer content rate / bulk content rate", 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 the hexagonal strontium ferrite powder having rare earth atom surface layer partiality, the rare earth atoms only need to be unevenly distributed in the surface layer of the particles constituting the hexagonal strontium ferrite powder, and the above "surface layer content rate / bulk content rate" is not limited to the exemplified upper or lower limits.

[0059] The partial dissolution and complete dissolution of hexagonal strontium ferrite powder will be described below. For the hexagonal strontium ferrite powder existing as powder, the sample powders for partial dissolution and complete dissolution are taken from the same lot of powder. On the other hand, for the hexagonal strontium ferrite powder contained in the magnetic layer of the magnetic tape, a part of the hexagonal strontium ferrite powder taken out from the magnetic layer is subjected to partial dissolution, and the other part is subjected to complete dissolution. The extraction of the hexagonal strontium ferrite powder from the magnetic layer can be carried out, for example, by the method described in paragraph 0032 of JP-A-2015-91747. The above partial dissolution means dissolution to such an extent that the residue of the hexagonal strontium ferrite powder can be visually confirmed in the liquid at the end of dissolution. For example, by partial dissolution, for the particles constituting the hexagonal strontium ferrite powder, a region of 10 to 20% by mass can be dissolved with the whole particle being 100% by mass. On the other hand, the above complete dissolution means dissolution until the residue of the hexagonal strontium ferrite powder cannot be visually confirmed in the liquid at the end of dissolution. The above partial dissolution and the measurement of the surface layer portion content are carried out, for example, by the following method. However, the dissolution conditions such as the amount of the sample powder below are illustrative, and any dissolution conditions that enable partial dissolution and complete dissolution can be adopted. A container (for example, a beaker) containing 12 mg of sample powder and 10 mL of 1 mol / L hydrochloric acid is held on a hot plate at a set temperature of 70°C for 1 hour. The obtained dissolution solution is filtered through a 0.1 μm membrane filter. The elemental analysis of the filtrate thus obtained is carried out by an inductively coupled plasma (ICP) analyzer. Thus, the surface layer portion content of the rare earth atoms with respect to 100 atomic% of iron atoms can be determined. When a plurality of types of rare earth atoms are detected by elemental analysis, the total content of all rare earth atoms is taken as the surface layer portion content. This is the same also in the measurement of the bulk content. On the other hand, the above complete dissolution and the measurement of the bulk content are carried out, for example, by the following method. Place a container (e.g., a beaker) containing 12 mg of sample powder and 10 mL of 4 mol / L hydrochloric acid on a hot plate set at a temperature of 80°C and hold for 3 hours. Thereafter, perform the same operations as the above partial dissolution and measurement of the surface layer content rate to obtain the bulk content rate with respect to 100 atomic % of iron atoms.

[0060] From the viewpoint of increasing the playback output when playing back the data recorded on the magnetic tape, it is desirable that the mass magnetization σs of the ferromagnetic powder contained in the magnetic tape is high. In this regard, the hexagonal strontium ferrite powder containing rare earth atoms but having no uneven distribution of rare earth atoms in the surface layer portion has a tendency that σs is significantly reduced compared to the hexagonal strontium ferrite powder not containing rare earth atoms. On the other hand, in order to suppress such a significant reduction in σs, the hexagonal strontium ferrite powder having uneven distribution of rare earth atoms in the surface layer portion is considered preferable. In one form, the σs of the hexagonal strontium ferrite powder can be 45 A·m 2 / kg or more, and can also be 47 A·m 2 / kg or more. On the other hand, from the viewpoint of noise reduction, σs is preferably 80 A·m 2 / kg or less, and more preferably 60 A·m 2 / kg or less. σs can be measured using a known measuring device capable of measuring magnetic properties such as a vibrating sample type magnetometer. In the present invention and this specification, unless otherwise specified, the mass magnetization σs is taken as the value measured at a magnetic field strength of 15 kOe.

[0061] Regarding the content ratio (bulk content ratio) of constituent atoms of the hexagonal strontium ferrite powder, the strontium atom content ratio can be, for example, in the range of 2.0 to 15.0 atomic% with respect to 100 atomic% of iron atoms. In one form, the hexagonal strontium ferrite powder can be such that the divalent metal atoms contained in this powder are only strontium atoms. In another form, the hexagonal strontium ferrite powder can also contain one or more other divalent metal atoms in addition to strontium atoms. For example, it can contain barium atoms and / or calcium atoms. When other divalent metal atoms other than strontium atoms are contained, the barium atom content ratio and calcium atom content ratio in the hexagonal strontium ferrite powder can each be, for example, in the range of 0.05 to 5.0 atomic% with respect to 100 atomic% of iron atoms.

[0062] As the crystal structure of hexagonal ferrite, the magnetoplumbite type (also called "M type"), W type, Y type, and Z type are known. The hexagonal strontium ferrite powder can take any of these crystal structures. The crystal structure can be confirmed by X-ray diffraction analysis. The hexagonal strontium ferrite powder can be such that a single crystal structure or two or more crystal structures are detected by X-ray diffraction analysis. For example, in one form, the hexagonal strontium ferrite powder can be such that only the M-type crystal structure is detected by X-ray diffraction analysis. For example, the M-type hexagonal ferrite is AFe 12 O 19It is represented by the following compositional formula. Here, A represents a divalent metal atom. When the hexagonal strontium ferrite powder is of the M type, A is only a strontium atom (Sr), or when A contains a plurality of divalent metal atoms, the strontium atom (Sr) occupies the most in terms of atomic percentage as described above. The content rate of the divalent metal atom in the hexagonal strontium ferrite powder is usually determined by the type of crystal structure of the hexagonal ferrite and is not particularly limited. The same applies to the iron atom content rate and the oxygen atom content rate. 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 an aluminum atom (Al). The content rate of the aluminum atom can be, for example, 0.5 to 10.0 atomic% with respect to 100 atomic% of iron atoms. From the viewpoint of suppressing the reduction in the reproduction output during repeated reproduction, the hexagonal strontium ferrite powder contains iron atoms, strontium atoms, oxygen atoms, and rare earth atoms, and the content rate of atoms other than these atoms is preferably 10.0 atomic% or less, more preferably in the range of 0 to 5.0 atomic%, and may be 0 atomic% with respect to 100 atomic% of iron atoms. That is, in one form, the hexagonal strontium ferrite powder may not contain atoms other than iron atoms, strontium atoms, oxygen atoms, and rare earth atoms. The content rate expressed in the above atomic percentage is obtained by converting the content rate (unit: mass%) of each atom obtained by completely dissolving the hexagonal strontium ferrite powder into a value expressed in atomic percentage using the atomic weight of each atom. Also, in the present invention and this specification, "not containing" a certain atom means that the content rate measured by an ICP analyzer after complete dissolution is 0 mass%. The detection limit of the ICP analyzer is usually 0.01 ppm (parts per million) or less on a mass basis. The above "not containing" is used in the sense of including being contained in an amount less than the detection limit of the ICP analyzer.The hexagonal strontium ferrite powder can, in one form, be free of bismuth atoms (Bi).

[0063] Metal powder Preferable specific examples of the ferromagnetic powder can also include ferromagnetic metal powders. For details of the ferromagnetic metal powders, reference can be made to, for example, paragraphs 0137 to 0141 of JP-A-2011-216149 and paragraphs 0009 to 0023 of JP-A-2005-251351.

[0064] ε-iron oxide powder Preferable specific examples of the ferromagnetic powder can also include ε-iron oxide powder. In the present invention and this specification, the “ε-iron oxide powder” refers to a ferromagnetic powder in which the crystal structure of ε-iron oxide is detected as the main phase by X-ray diffraction analysis. For example, when the diffraction peak with the highest intensity in the X-ray diffraction spectrum obtained by X-ray diffraction analysis is attributed to the crystal structure of ε-iron oxide, it is determined that the crystal structure of ε-iron oxide has been detected as the main phase. As methods for producing ε-iron oxide powder, a method of producing from goethite, an inverse micelle method, etc. are known. All of the above production methods are well-known. Also, for methods of producing ε-iron oxide powder in which a part of Fe is substituted by substitution atoms such as Ga, Co, Ti, Al, Rh, etc., reference can be made to, for example, J. Jpn. Soc. Powder Metallurgy Vol. 61 Supplement, No. S1, pp. S280-S284, J. Mater. Chem. C, 2013, 1, pp.5200-5206, etc. However, the method for producing ε-iron oxide powder that can be used as the ferromagnetic powder in the magnetic layer of the above magnetic tape is not limited to the methods listed here.

[0065] The activation volume of the ε-iron oxide powder is preferably in the range of 300 to 1500 nm 3 is. The micronized ε-iron oxide powder showing the 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 It can also be as described above. Further, from the viewpoint of further improving the electromagnetic conversion characteristics, the activation volume of the ε-iron oxide powder is 1400 nm 3 It is more preferably below, and 1300 nm 3 It is still more preferably below, and 1200 nm 3 It is even more preferably below, and 1100 nm 3 It is still even more preferably below.

[0066] As an index for reducing thermal fluctuations, in other words, improving thermal stability, the anisotropy constant Ku can be cited. The ε-iron oxide powder preferably has a Ku of 3.0×10 4 J / m 3 or more, and more preferably has a Ku of 8.0×10 4 J / m 3 or more. Further, the Ku of the ε-iron oxide powder can be, for example, 3.0×10 5 J / m 3 or less. However, the higher the Ku, the higher the thermal stability, which is preferable, so it is not limited to the values exemplified above.

[0067] From the viewpoint of increasing the playback output when playing back 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 form, the σs of the ε-iron oxide powder can be 8 A·m 2 / kg or more, and can also be 12 A·m 2 / kg or more. On the other hand, from the viewpoint of noise reduction, the σs of the ε-iron oxide powder is preferably 40 A·m 2 / kg or less, and more preferably 35 A·m 2 / kg or less.

[0068] In the present invention and in this specification, unless otherwise specified, the average particle size of various powders such as ferromagnetic powder is the value measured by the following method using a transmission electron microscope. The powder is photographed at a magnification of 100,000 times using a transmission electron microscope, and printed on a print paper or displayed on a display so that the total magnification becomes 500,000 times, etc., to obtain a photograph of the particles constituting the powder. From the obtained photograph of the particles, the target particles are selected and the contour of the particles is traced with a digitizer to measure the size of the particles (primary particles). The primary particles refer to independent particles without aggregation. The above measurement is performed on 500 particles randomly extracted. The arithmetic mean of the particle sizes of the 500 particles thus obtained is taken as the average particle size of the powder. As the above transmission electron microscope, for example, the Hitachi transmission electron microscope model H-9000 can be used. Also, the measurement of the particle size can be performed using known image analysis software, for example, the Carl Zeiss image analysis software KS-400. Unless otherwise specified, the average particle size shown in the examples described later is a value measured using the Hitachi transmission electron microscope model H-9000 as the transmission electron microscope and the Carl Zeiss image analysis software KS-400 as the image analysis software. In the present invention and this specification, the powder means a collection of a plurality of particles. For example, the ferromagnetic powder means a collection of a plurality of ferromagnetic particles. Also, the collection of a plurality of particles is not limited to the form in which the particles constituting the collection are in direct contact, and forms in which binders, additives, etc. described later are interposed between the particles are also included. The term "particle" may also be used to represent the powder.

[0069] As a method for collecting the sample powder from the magnetic tape for particle size measurement, for example, the method described in paragraph 0015 of JP-A-2011-048878 can be adopted.

[0070] In the present invention and this specification, unless otherwise specified, the size of the particles (particle size) constituting the powder is such that the shape of the particles observed in the above particle photograph is (1) In the case of needle-like, spindle-shaped, columnar (however, the height is larger than the maximum major axis of the bottom surface), etc., it is represented by the length of the major axis constituting the particle, that is, the major axis length, (2) In the case of being plate-shaped or columnar (however, the thickness or height is smaller than the maximum major axis diameter of the plate surface or bottom surface), it is represented by the maximum major axis diameter of the plate surface or bottom surface, (3) In the case of being spherical, polyhedral, amorphous, etc., and when the major axis constituting the particles cannot be specified from the shape, it is represented by the equivalent circle diameter. The equivalent circle diameter refers to that obtained by the circular projection method.

[0071] Also, the average aspect ratio of the powder is measured as the length of the minor axis of the particles, i.e., the minor axis length, in the above measurement, and the value of (major axis length / minor axis length) for each particle is obtained, and it refers to the arithmetic mean of the values obtained for the above 500 particles. Here, unless otherwise specified, the minor axis length means the length of the minor axis constituting the particles in the case of (1) in the above definition of particle size, and also the thickness or height in the case of (2), 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 regarded as 1 for convenience. And, unless otherwise specified, when the shape of the particles is specified, for example, in the case of the above definition of particle size (1), the average particle size is the average major axis length, and in the case of the same definition (2), the average particle size is the average plate diameter. In the case of the same definition (3), the average particle size is the average diameter (also referred to as the average particle diameter, average particle size).

[0072] The content (filling rate) of the ferromagnetic powder in the magnetic layer is preferably in the range of 50 to 90% by mass, more preferably in the range of 60 to 90% by mass, based on 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 the recording density.

[0073] (Binder) The magnetic tape can be a coated magnetic tape and can contain a binder in the magnetic layer. The binder is one or more resins. As the binder, various resins commonly used as binders for coated magnetic recording media can be used. For example, as the binder, polyurethane resin, polyester resin, polyamide resin, vinyl chloride resin, acrylic resin copolymerized with styrene, acrylonitrile, methyl methacrylate, etc., cellulose resin such as nitrocellulose, epoxy resin, phenoxy resin, polyvinyl acetal, polyvinyl butyral, etc. A resin selected from polyvinyl alkylal resins can be used alone or a plurality of resins can be mixed and used. Among these, preferred are polyurethane resin, acrylic resin, cellulose resin, and vinyl chloride resin. These resins may be homopolymers or copolymers. These resins can also be used as binders in the non-magnetic layer and / or backcoat layer described later. For the above binders, reference can be made to paragraphs 0028 to 0031 of JP-A-2010-24113. Further, the binder may be a radiation-curable resin such as an electron beam-curable resin. For radiation-curable resins, reference can be made to paragraphs 0044 to 0045 of JP-A-2011-048878. The average molecular weight of the resin used as the binder can be, for example, 10,000 or more and 200,000 or less as the weight average molecular weight. The binder can be used in an amount of, for example, 1.0 to 30.0 parts by mass with respect to 100.0 parts by mass of the ferromagnetic powder.

[0074] (Hardening agent) In addition, a curing agent can also be used together with the binder. The curing agent can be a thermosetting compound which is a compound in which the curing reaction (crosslinking reaction) proceeds by heating in one form, and can be a photocurable compound in which the curing reaction (crosslinking reaction) proceeds by light irradiation in another form. The curing agent can be contained in the magnetic layer in a state where at least a part thereof reacts (crosslinks) with other components such as the binder when the curing reaction proceeds during the manufacturing process of the magnetic tape. A preferred curing agent is a thermosetting compound, and polyisocyanate is suitable. For details of the polyisocyanate, reference can be made to paragraphs 0124 to 0125 of JP-A-2011-216149. The curing agent can be used in the composition for forming the magnetic layer in an amount of, for example, 0 to 80.0 parts by mass, preferably 50.0 to 80.0 parts by mass, based on 100.0 parts by mass of the binder, from the viewpoint of improving the strength of each layer such as the magnetic layer.

[0075] (Additive) The magnetic layer may contain one or more additives as necessary. As an example of the additive, the above-mentioned curing agent can be mentioned. In addition, examples of the additives contained in the magnetic layer can include non-magnetic powder, lubricant, dispersant, dispersion aid, antifungal agent, antistatic agent, antioxidant, and the like.

[0076] Examples of the dispersant that can be added to the composition for forming the magnetic layer include known dispersants for enhancing the dispersibility of ferromagnetic powders, such as carboxy group-containing compounds and nitrogen-containing compounds. For example, the nitrogen-containing compound may be any of primary amines represented by NH2R, secondary amines represented by NHR2, and tertiary amines represented by NR3. In the above, R represents any structure constituting the nitrogen-containing compound, and a plurality of Rs may be the same or different. The nitrogen-containing compound may be a compound (polymer) having a plurality of repeating structures in the molecule. It is considered that the reason why the nitrogen-containing compound can function as a dispersant is that the nitrogen-containing part of the nitrogen-containing compound functions as an adsorption part on the particle surface of the ferromagnetic powder. Examples of the carboxy group-containing compound include fatty acids such as oleic acid. For the carboxy group-containing compound, it is considered that the reason why the carboxy group-containing compound can function as a dispersant is that the carboxy group functions as an adsorption part on the particle surface of the ferromagnetic powder. It is also preferable to use a carboxy group-containing compound and a nitrogen-containing compound in combination. The amount of these dispersants used can be set appropriately.

[0077] The dispersant may be added to the composition for forming the non-magnetic layer. For the dispersant that can be added to the composition for forming the non-magnetic layer, reference can be made to paragraph 0061 of JP-A-2012-133837.

[0078] Examples of the additive that can be added to the magnetic layer include, for example, polyalkyleneimine-based polymers described in JP-A-2016-51493. For such polyalkyleneimine-based polymers, reference can be made to paragraphs 0035 to 0077 of JP-A-2016-51493 and the descriptions of the examples in the same publication.

[0079] Examples of the non-magnetic powder 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 for forming protrusions that moderately protrude from the surface of the magnetic layer.

[0080] As the abrasive, a non-magnetic powder with a Mohs hardness exceeding 8 is preferred, and a non-magnetic powder with a Mohs hardness of 9 or more is more preferred. The maximum value of the 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 a powder of a carbide. Examples of the carbide include boron carbide (e.g., B4C), titanium carbide (e.g., TiC), etc. Also, diamond can be used as the abrasive. In one form, the abrasive is preferably a powder of an inorganic oxide. Specifically, examples of the inorganic oxide include alumina (e.g., Al2O3), titanium oxide (e.g., TiO2), cerium oxide (e.g., CeO2), zirconium oxide (e.g., ZrO2), etc., and alumina is particularly preferred. The Mohs hardness of alumina is about 9. Regarding alumina powder, reference can also be made to paragraph 0021 of JP-A-2013-229090. Also, the specific surface area can be used as an index of the particle size of the abrasive. It can be considered that the larger the specific surface area, the smaller the particle size of the primary particles constituting the abrasive. As the abrasive, it is preferable to use an abrasive having a specific surface area (hereinafter referred to as "BET specific surface area") measured by the BET (Brunauer-Emmett-Teller) method of 14 m 2 / g or more. Also, from the viewpoint of dispersibility, the BET specific surface area is 40 m 2It is preferable to use an abrasive agent of 1 g or less. The content of the abrasive agent in the magnetic layer is preferably 1.0 to 20.0 parts by mass, more preferably 1.0 to 15.0 parts by mass with respect to 100.0 parts by mass of the ferromagnetic powder. As the abrasive agent, only one kind of non-magnetic powder can be used, or two or more kinds of non-magnetic powders having different compositions and / or physical properties (e.g., size) can be used. When two or more kinds of non-magnetic powders are used as the abrasive agent, the content of the abrasive agent means the total content of these two or more kinds of non-magnetic powders. The above points are the same for the content of various components in the present invention and this specification. The abrasive agent is preferably subjected to a dispersion treatment separately from the ferromagnetic powder (separate dispersion), and more preferably subjected to a dispersion treatment separately from the projection forming agent described later (separate dispersion). When preparing the composition for forming the magnetic layer, it is preferable to use two or more kinds of dispersion liquids having different components and / or dispersion conditions as the dispersion liquid of the abrasive agent (hereinafter also referred to as "abrasive agent liquid") in controlling the wear characteristics of the magnetic tape.

[0081] A dispersant can also be used to adjust the dispersion state of the dispersion liquid of the abrasive agent. Examples of the compound that can function as a dispersant for enhancing the dispersibility of the abrasive agent include aromatic hydrocarbon compounds having a phenolic hydroxy group. The "phenolic hydroxy group" refers to a hydroxy group directly bonded to an aromatic ring. The aromatic ring contained in the above aromatic hydrocarbon compound may be a monocyclic ring, a polycyclic structure, or a condensed ring. From the viewpoint of improving the dispersibility of the abrasive agent, aromatic hydrocarbon compounds containing a benzene ring or a naphthalene ring are preferable. Further, the above aromatic hydrocarbon compound may 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, a hydroxyalkyl group, etc., and a halogen atom, an alkyl group, an alkoxy group, an amino group, and a hydroxyalkyl group are preferable. The number of phenolic hydroxy groups contained in one molecule of the above aromatic hydrocarbon compound may be one, or two, three, or more.

[0082] As a preferred form of the aromatic hydrocarbon compound having a phenolic hydroxy group, a compound represented by the following formula 100 can be mentioned.

[0083]

Chemical formula

[0084] In the compound represented by formula 100, the substitution positions of the two hydroxy groups (phenolic hydroxy groups) are not particularly limited.

[0085] In formula 100, two of X 101 ~X 108 are hydroxy groups (phenolic hydroxy groups), and the other six each independently represent a hydrogen atom or a substituent. Also, among X 101 ~X 108 , the parts other than the two hydroxy groups may all be hydrogen atoms, or some or all of them may be substituents. Examples of the substituent can be the substituents described above. As substituents other than the two hydroxy groups, one or more phenolic hydroxy groups may be included. From the viewpoint of improving the dispersibility of the abrasive, it is preferable that parts other than the two hydroxy groups among X 101 ~X 108 are not phenolic hydroxy groups. That is, the compound represented by formula 100 is preferably dihydroxynaphthalene or its derivative, and more preferably 2,3-dihydroxynaphthalene or its derivative. Preferred substituents as the substituent represented by X 101 ~X 108 include a halogen atom (for example, a chlorine atom, a bromine atom), an amino group, an alkyl group having 1 to 6 carbon atoms (preferably 1 to 4), a methoxy group and an ethoxy group, an acyl group, a nitro group and a nitroso group, and a -CH2OH group.

[0086] Regarding the dispersant for enhancing the dispersibility of the abrasive, reference can also be made to paragraphs 0024 to 0028 of JP-A-2014-179149.

[0087] The dispersant for enhancing the dispersibility of the abrasive can be used, for example, at a ratio of 0.5 to 20.0 parts by mass, preferably 1.0 to 10.0 parts by mass, per 100.0 parts by mass of the abrasive when preparing the abrasive liquid (or for each abrasive liquid when preparing a plurality of abrasive liquids).

[0088] As one form of the projection-forming agent, carbon black can be mentioned. The average particle size of the carbon black is preferably in the range of 5 to 200 nm, more preferably in the range of 10 to 150 nm. Further, the BET specific surface area of the carbon black is preferably 10 m 2 / g or more, more preferably 15 m 2 / g or more. From the viewpoint of ease of improving dispersibility, the BET specific surface area of the carbon black is preferably 50 m 2 / g or less, preferably 40 m 2It is more preferable that it is below / g. As another form of the projection-forming agent, colloidal particles can be mentioned. As the colloidal particles, inorganic colloidal particles are preferable from the viewpoint of easy availability, more preferably inorganic oxide colloidal particles, and even more preferably silica colloidal particles (colloidal silica). In the present invention and this specification, "colloidal particles" means that when 1 g is added per 100 mL of at least one organic solvent of methyl ethyl ketone, cyclohexanone, toluene or ethyl acetate, or a mixed solvent containing two or more of the above solvents in an arbitrary mixing ratio, particles that can be dispersed without sedimentation to give a colloidal dispersion. The average particle size of the colloidal particles can be, for example, 30 to 300 nm, and preferably 40 to 200 nm. The content of the projection-forming agent in the magnetic layer is preferably 0.5 to 4.0 parts by mass, and more preferably 0.5 to 3.5 parts by mass with respect to 100.0 parts by mass of the ferromagnetic powder. The projection-forming agent can be subjected to a dispersion treatment separately from the ferromagnetic powder, and can also be subjected to a dispersion treatment separately from the abrasive. When preparing the composition for forming the magnetic layer, it is also possible to prepare two or more kinds of dispersion liquids having different components and / or dispersion conditions as a dispersion liquid of the projection-forming agent (hereinafter, also referred to as "projection-forming agent liquid").

[0089] Further, as one form of the additive that can be contained in the magnetic layer, a compound having an ammonium salt structure of an alkyl ester anion represented by the following formula 1 can be mentioned.

[0090] [Chemical formula]

[0091] (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.)

[0092] The present inventor believes that the above compound can function as a lubricant. This point will be further explained below. Lubricants can be broadly classified into fluid lubricants and boundary lubricants. The inventor believes that a compound having an ammonium salt structure of an alkyl ester anion represented by the above formula 1 can function as a fluid lubricant. It is considered that a fluid lubricant can play a role of imparting lubricity to the magnetic layer by forming a liquid film on the surface of the magnetic layer by itself. AlFeSil wear value 45° In order to control the 45° and the standard deviation of the AlFeSil wear value, it is presumed that it is desirable that a fluid lubricant forms a liquid film on the surface of the magnetic layer. Also, the more stably the magnetic layer surface and the AlFeSil prism can slide during the 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 have an appropriate amount of the fluid lubricant forming the liquid film on the surface of the magnetic layer. This is because if the amount of the liquid lubricant forming the liquid film on the surface of the magnetic layer is excessive, it is presumed that the magnetic layer surface and the AlFeSil prism will stick together and the sliding stability will tend to decrease. Also, if the amount of the liquid lubricant forming the liquid film on the surface of the magnetic layer is excessive, it is presumed that, for example, the protrusions formed on the surface of the magnetic layer by the protrusion forming agent will be covered by the liquid film. This can also be considered a factor that tends to reduce the sliding stability. Regarding the above points, the above compound contains an ammonium salt structure of an alkyl ester anion represented by formula 1. A compound containing such a structure is considered to be able to play an excellent role as a fluid lubricant even in a relatively small amount. Therefore, incorporating the above compound into the magnetic layer can lead to an improvement in the sliding stability between the surface of the magnetic layer of the magnetic tape and the AlFeSil prism, and is considered to contribute to controlling the 45° 45° and the standard deviation of the AlFeSil wear value.

[0093] Hereinafter, the above compound will be described in more detail.

[0094] In the present invention and in this specification, unless otherwise specified, the groups described may have substituents or may be unsubstituted. Further, for a group having a substituent, "the number of carbon atoms" shall mean the number of carbon atoms excluding the carbon atoms of the substituent, unless otherwise specified. In the present invention and in 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, and the like.

[0095] A compound having an ammonium salt structure of an alkyl ester anion represented by Formula 1 can form a liquid film on the surface of the magnetic layer at least in part, and a part thereof can be contained inside the magnetic layer and move to the surface of the magnetic layer during sliding with a magnetic head or the like to form a liquid film. Further, a part thereof can be contained in a non-magnetic layer described later, move to the magnetic layer, and further move to the surface of the magnetic layer to form a liquid film. Note that "alkyl ester anion" can also be referred to as "alkyl carboxylate anion".

[0096] 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 by 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 substituents or may be unsubstituted, and is preferably unsubstituted. The alkyl group represented by R can be represented by, for example, C n H 2n+1 -. Here, n represents an integer of 7 or more. Further, the fluorinated alkyl group represented by R can be represented by, for example, C n H 2n+1It can have a structure in which some or all of the hydrogen atoms constituting the alkyl group represented by - are substituted by 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, still more preferably 10 or more, even more preferably 11 or more, even more preferably 12 or more, and even more preferably 13 or more. Also, 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 still more preferably 18 or less.

[0097] In Formula 1, Z + represents an ammonium cation. Specifically, the ammonium cation has the following structure. In the present invention and in this specification, "*" in the formula representing a part of the compound represents the bonding position of a part of its structure to an adjacent atom.

[0098] [Chemical formula]

[0099] The nitrogen cation N of the ammonium cation + and the oxygen anion O in Formula 1 - can form a salt crosslinking group to form an ammonium salt structure of the alkyl ester anion represented by Formula 1. That a compound having an ammonium salt structure of the alkyl ester anion represented by Formula 1 is contained in the magnetic layer can be confirmed by analyzing the magnetic tape by X-ray photoelectron spectroscopy (ESCA: Electron Spectroscopy for Chemical Analysis), infrared spectroscopy (IR), etc.

[0100] In one form, Z +The ammonium cation represented by can be brought about, for example, by the nitrogen atom of a nitrogen-containing polymer becoming a cation. A nitrogen-containing polymer means a polymer containing a nitrogen atom. In the present invention and in this specification, the terms "polymer" and "polymerization product" are used in a meaning that includes homopolymers and copolymers. The nitrogen atom can be included as an atom constituting the main chain of the polymer in one form, and can also be included as an atom constituting the side chain of the polymer in one form.

[0101] As one form of the nitrogen-containing polymer, polyalkyleneimine can be mentioned. Polyalkyleneimine is a ring-opening polymer of alkyleneimine and is a polymer having a plurality of repeating units represented by the following formula 2.

[0102]

Chemical formula

[0103] The nitrogen atom N constituting the main chain in formula 2 becomes a nitrogen cation N + and the ammonium cation represented by Z + in formula 1 can be brought about. And an alkyl ester anion can form an ammonium salt structure as follows, for example.

[0104]

Chemical formula

[0105] Hereinafter, formula 2 will be described in more detail.

[0106] In formula 2, R 1 and R 2 each independently represent a hydrogen atom or an alkyl group, and n1 represents an integer of 2 or more.

[0107] R 1 or R 2Examples of the alkyl group represented by [alkyl group] include alkyl groups having 1 to 6 carbon atoms, preferably alkyl groups having 1 to 3 carbon atoms, more preferably methyl or ethyl groups, and even more preferably a methyl group. R 1 Or R 2 The alkyl group represented by [alkyl group] is preferably an unsubstituted alkyl group. R in Formula 2 1 And R 2 As combinations of [alkyl group] and [alkyl group], there are forms in which one is a hydrogen atom and the other is an alkyl group, forms in which both are hydrogen atoms, and forms in which both are alkyl groups (the same or different alkyl groups), and preferably forms in which both are hydrogen atoms. As the alkyleneimine that gives rise to polyalkyleneimine, the structure with the fewest carbon atoms constituting the ring is ethyleneimine, and the number of carbon atoms in the main chain of the alkyleneimine (ethyleneimine) obtained by ring-opening of ethyleneimine is 2. 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 structure as the repeating structure represented by Formula 2, or may be a copolymer containing two or more different structures as the repeating structure 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 the alkyl ester anion represented by Formula 1 can be, for example, 200 or more, preferably 300 or more, and more preferably 400 or more. Further, the number average molecular weight of the above polyalkyleneimine can be, for example, 10,000 or less, preferably 5,000 or less, and more preferably 2,000 or less.

[0108] 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 determined by standard polystyrene conversion. The average molecular weight shown in the examples described later is, unless otherwise specified, a value obtained by converting the value measured under the following measurement conditions using GPC to standard polystyrene conversion (polystyrene conversion value). GPC device: HLC-8220 (manufactured by Tosoh Corporation) Guard column: TSKguardcolumn Super HZM-H Column: TSKgel Super HZ 2000, TSKgel Super HZ 4000, TSKgel Super HZ-M (manufactured by Tosoh Corporation, 4.6 mm (inner diameter) × 15.0 cm, three columns connected in series) Eluent: Tetrahydrofuran (THF) containing a stabilizer (2,6-di-t-butyl-4-methylphenol) Eluent flow rate: 0.35 mL / min Column temperature: 40 °C Inlet temperature: 40 °C Refractive index (RI) measurement temperature: 40 °C Sample concentration: 0.3 mass% Sample injection volume: 10 μL

[0109] Another form of the nitrogen-containing polymer can include polyallylamine. Polyallylamine is a polymer of allylamine and is a polymer having a plurality of repeating units represented by the following formula 3.

[0110]

Chemical formula

[0111] The nitrogen atom N constituting the amino group in the side chain in formula 3 can become a nitrogen cation N + resulting in an ammonium cation represented by Z in formula 1 + and can form an ammonium salt structure with an alkyl ester anion, for example, as follows.

[0112]

Chemical formula

[0113] The weight-average molecular weight of the polyallylamine 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 1,000 or more, and more preferably 1,500 or more. Further, 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.

[0114] That a compound having a structure derived from a polyalkyleneimine or polyallylamine is included as a compound having an ammonium salt structure of an alkyl ester anion represented by Formula 1 can be confirmed by analyzing the surface of the magnetic layer by time-of-flight secondary ion mass spectrometry (TOF-SIMS) or the like.

[0115] The compound having an ammonium salt structure of an alkyl ester anion represented by Formula 1 can be a salt with one or more fatty acids selected from the group consisting of a nitrogen-containing polymer and fatty acids having 7 or more carbon atoms and fluorinated fatty acids having 7 or more carbon atoms. The nitrogen-containing polymer forming the salt can be one or more nitrogen-containing polymers, and can be, for example, a nitrogen-containing polymer selected from the group consisting of polyalkyleneimine and polyallylamine. The fatty acids forming 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. The fluorinated fatty acid has a structure in which some or all of the hydrogen atoms constituting the alkyl group bonded to the carboxy group COOH in the fatty acid are substituted with fluorine atoms. For example, by mixing a nitrogen-containing polymer and the above fatty acids at room temperature, the salt formation reaction can proceed easily. Room temperature is, for example, about 20 to 25 °C. In one form, one or more nitrogen-containing polymers and one or more fatty acids are used as components of the composition for forming a magnetic layer, and the salt formation reaction can be made to proceed by mixing them in the process of preparing the composition for forming a magnetic layer. Also, in one form, before preparing the composition for forming a magnetic layer, 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 composition for forming a magnetic layer to prepare the composition for forming a magnetic layer. This also applies to the case of forming a non-magnetic layer containing a compound having an ammonium salt structure of an alkyl ester anion represented by Formula 1. For example, regarding the magnetic layer, 0.1 to 10.0 parts by mass of a nitrogen-containing polymer can be used per 100.0 parts by mass of ferromagnetic powder, and it is preferable to use 0.5 to 8.0 parts by mass of a nitrogen-containing polymer. The above fatty acids can be used, for example, in an amount of 0.05 to 10.0 parts by mass per 100.0 parts by mass of ferromagnetic powder, and it is preferable to use 0.1 to 5.0 parts by mass. Also, regarding the non-magnetic layer, 0.1 to 10.0 parts by mass of a nitrogen-containing polymer can be used per 100.0 parts by mass of non-magnetic powder, and it is preferable to use 0.5 to 8.0 parts by mass of a nitrogen-containing polymer.The above fatty acids can be used in an amount of, for example, 0.05 to 10.0 parts by mass, 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 above fatty acids are mixed to form an ammonium salt of the alkyl ester anion represented by Formula 1, the nitrogen atom constituting the nitrogen-containing polymer may react with the carboxy group of the above fatty acids to form the following structure, and a form containing such a structure is also included in the above compound.

[0116]

Chemical formula

[0117] Examples of the above fatty acids include fatty acids having an alkyl group described as R in Formula 1 above and fluorinated fatty acids having a fluorinated alkyl group described as R in Formula 1 above.

[0118] The mixing ratio of the nitrogen-containing polymer used to form a compound having an ammonium salt structure of an alkyl ester anion represented by Formula 1 and the above fatty acids is preferably 10:90 to 90:10, more preferably 20:80 to 85:15, and still more preferably 30:70 to 80:20, in terms of the mass ratio of the nitrogen-containing polymer to the above fatty acids. Further, the compound having an ammonium salt structure of an alkyl ester anion represented by Formula 1 is preferably contained in an amount of 0.01 part by mass or more, more preferably 0.1 part by mass or more, and still more preferably 0.5 part by mass or more with respect to 100.0 parts by mass of the ferromagnetic powder in the magnetic layer. Here, the content of the above compound in the magnetic layer means the total amount of the amount forming a liquid film on the surface of the magnetic layer and the amount contained inside the magnetic layer. On the other hand, a large content of the ferromagnetic powder in the magnetic layer is preferable from the viewpoint of high-density recording. Therefore, from the viewpoint of high-density recording, it is preferable that the content of components other than the ferromagnetic powder is small. From this viewpoint, the content of the above compound in the magnetic layer is preferably 15.0 parts by mass or less, more preferably 10.0 parts by mass or less, and still more preferably 8.0 parts by mass or less with respect to 100.0 parts by mass of the ferromagnetic powder. Further, the preferable range of the content of the above compound in the composition for forming a magnetic layer used to form the magnetic layer is the same.

[0119] The magnetic layer can further contain one or more lubricants. As an example of such a lubricant, a fatty acid amide that can function as a boundary lubricant, for example, can be mentioned. A boundary lubricant is considered to be a lubricant that can reduce contact friction by adsorbing on the surface of powder (for example, 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, elaidic acid, etc., specifically, lauric acid amide, myristic acid amide, palmitic acid amide, stearic acid amide, etc. The content of fatty acid amide in the magnetic layer is, for example, 0 to 3.0 parts by mass, preferably 0 to 2.0 parts by mass, and more preferably 0 to 1.0 parts by mass per 100.0 parts by mass of ferromagnetic powder. Also, the non-magnetic layer may contain fatty acid amide. The content of fatty acid amide in the non-magnetic layer is, for example, 0 to 3.0 parts by mass, preferably 0 to 1.0 parts by mass per 100.0 parts by mass of non-magnetic powder. Regarding the dispersant, reference can be made to paragraphs 0061 and 0071 of JP-A-2012-133837. The dispersant may be added to the composition for forming the non-magnetic layer. Regarding the dispersant that can be added to the composition for forming the non-magnetic layer, reference can be made to paragraph 0061 of JP-A-2012-133837.

[0120] Regarding suppressing a decrease in electromagnetic conversion characteristics when recording data on and / or reproducing recorded data on a magnetic tape at different head tilt angles, the present inventor thinks as follows. When the head tilt angle is different, as described above, it is presumed that the degree of wear of the magnetic tape head due to contact with the magnetic tape head varies greatly during recording and / or reproduction (a large variation occurs in the degree of wear). This large variation in the degree of wear is considered to be a factor in the decrease in electromagnetic conversion characteristics. Incidentally, it is considered that abrasion is affected by the size and content of the abrasive, the shear stress on the magnetic head (which can affect the friction characteristics), the vertical resistance, and the like. Since the vertical resistance tends to increase as the value of the head tilt angle increases, it is considered that the penetration of the abrasive into the magnetic head becomes deeper, the friction increases, and the abrasion increases. On the other hand, using the above compound as a component of the magnetic layer, which is considered to be able to function as a liquid lubricant, for example, leads to an improvement in the lubricity (slip property) of the magnetic layer surface, and is considered to contribute to suppressing a large variation in the degree of wear of the magnetic head depending on the difference in the head tilt angle. Also, regarding the abrasive, it is presumed that the more the amount of abrasive contained in the magnetic layer, the more likely the magnetic head is to wear when the head tilt angle is large. When the head tilt angle is small, when using a plurality of abrasives with different sizes as components of the magnetic layer, it is presumed that the larger-sized abrasive is more likely to cause wear of the magnetic head. Regarding the above points, the inventor believes that, for example, using the above compound as a component used as a lubricant for forming the magnetic layer, the combination of abrasives used, and / or adjusting the content of the abrasive can contribute to controlling the 45° AlFeSil wear value 45° and the standard deviation value of the AlFeSil wear value. And controlling both the AlFeSil wear value

[0121] <Non-magnetic layer> Next, the non-magnetic layer will be described. The magnetic tape may have a magnetic layer directly on a non-magnetic support, or may have a non-magnetic layer containing non-magnetic powder between the non-magnetic support and the magnetic layer. The non-magnetic powder used for the non-magnetic layer may be a powder of an inorganic substance (inorganic powder) or a powder of an organic substance (organic powder). Also, carbon black or the like can be used. Examples of the inorganic substance include metals, metal oxides, metal carbonates, metal sulfates, metal nitrides, metal carbides, metal sulfides, and the like. These non-magnetic powders are available as commercial products and can also be manufactured by known methods. For details, reference can be made to paragraphs 0146 to 0150 of JP-A-2011-216149. Regarding the carbon black that can be used for the non-magnetic layer, reference can also be made to paragraphs 0040 to 0041 of JP-A-2010-24113. The content (filling rate) of the non-magnetic powder in the non-magnetic layer is preferably in the range of 50 to 90% by mass, more preferably in the range of 60 to 90% by mass, based on the total mass of the non-magnetic layer.

[0122] The non-magnetic layer can contain a binder and can also contain additives. Regarding other details such as the binder and additives of the non-magnetic layer, known techniques related to the non-magnetic layer can be applied. Also, for example, regarding the type and content of the binder, the type and content of the additives, etc., known techniques related to the magnetic layer can also be applied.

[0123] The non-magnetic layer of the magnetic tape shall also include a substantially non-magnetic layer containing a small amount of ferromagnetic powder, for example, as an impurity or intentionally, together with the non-magnetic powder. Here, the substantially non-magnetic layer means 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 layer having 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 does not have a residual magnetic flux density and a coercive force.

[0124] <Non-magnetic support> Next, the non-magnetic support will be described. Examples of the non-magnetic support (hereinafter also simply referred to as "support") include known ones such as biaxially stretched polyethylene terephthalate, polyethylene naphthalate, polyamide, polyamideimide, and aromatic polyamide. Among these, polyethylene terephthalate, polyethylene naphthalate, and polyamide are preferred. These supports may be subjected to corona discharge, plasma treatment, easy adhesion treatment, heat treatment, etc. in advance.

[0125] <Back coat layer> The above tape may or may not have a back coat layer containing non-magnetic powder on the surface side opposite to the surface side having the magnetic layer of the non-magnetic support. It is preferable that the back coat layer contains one or both of carbon black and inorganic powder. The back coat layer can contain a binder and can also contain additives. Regarding the details of the non-magnetic powder, binder, additives, etc. of the back coat layer, known techniques related to the back coat layer can be applied, and known techniques related to the magnetic layer and / or non-magnetic layer can also be applied. For example, the descriptions in paragraphs 0018 to 0020 of JP-A-2006-331625 and lines 65 to 38 of column 5 of US Patent No. 7,029,774 can be referred to for the back coat layer.

[0126] <Various thicknesses> Regarding the thickness (total thickness) of the magnetic tape, with the huge increase in the amount of information in recent years, there is a demand for increasing the recording capacity (high capacity) of the magnetic tape. As a means for high capacity, reducing the thickness of the magnetic tape and increasing the length of the magnetic tape accommodated per magnetic tape cartridge can be mentioned. From this point of view, the thickness (total thickness) of the above magnetic tape is preferably 5.6 μm or less, more preferably 5.5 μm or less, still more preferably 5.4 μm or less, further more preferably 5.3 μm or less, and even more preferably 5.2 μm or less. Also, 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.

[0127] The thickness (total thickness) of the magnetic tape can be measured by the following method. Cut out 10 tape samples (for example, 5 - 10 cm in length) from an arbitrary part of the magnetic tape, stack these tape samples, and measure the thickness. The value obtained by dividing the measured thickness by 10 (the thickness per tape sample) is taken as the tape thickness. The above thickness measurement can be performed using a known measuring instrument capable of measuring thickness on the order of 0.1 μm.

[0128] The thickness of the non - magnetic support is preferably 3.0 - 5.0 μm. The thickness of the magnetic layer can be optimized according to the saturation magnetization amount of the magnetic head used, the head gap length, the bandwidth of the recording signal, etc. Generally, it is 0.01 μm - 0.15 μm. From the viewpoint of high - density recording, it is preferably 0.02 μm - 0.12 μm, and more preferably 0.03 μm - 0.1 μm. There may be at least one magnetic layer, and the magnetic layer may be separated into two or more layers having different magnetic properties, and a known configuration regarding the multi - layer magnetic layer can be applied. When separating into two or more layers, the thickness of the magnetic layer means the total thickness of these layers. The thickness of the non - magnetic layer is, for example, 0.1 - 1.5 μm, and preferably 0.1 - 1.0 μm. The thickness of the back - coat layer is preferably 0.9 μm or less, and more preferably 0.1 - 0.7 μm. The various thicknesses such as the thickness of the magnetic layer can be obtained by the following method. After exposing the cross - section in the thickness direction of the magnetic tape by an ion beam, perform cross - section observation on the exposed cross - section using a scanning electron microscope or a transmission electron microscope. The various thicknesses can be obtained as the arithmetic mean of the thicknesses obtained at any two locations in the cross - section observation. Alternatively, the various thicknesses can also be obtained as the designed thickness calculated from the manufacturing conditions, etc.

[0129] <Manufacturing method> (Preparation of the composition for forming each layer) Compositions for forming a magnetic layer, a non-magnetic layer, or a backcoat layer generally contain a solvent together with the various components described above. As the solvent, various organic solvents commonly used for manufacturing a coated magnetic recording medium can be used. Among them, from the viewpoint of the solubility of the binder usually used for the coated magnetic recording medium, the composition for forming each layer 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 the solvent in the composition for forming each layer is not particularly limited and can be the same as that of the composition for forming each layer of a normal coated magnetic recording medium. Further, the process of preparing the composition for forming each layer can usually include at least a kneading step, a dispersion step, and a mixing step provided as necessary before and after these steps. Each individual step may be divided into two or more stages. The components used in the preparation of the composition for forming each layer may be added at the beginning or in the middle of any step. Also, the individual components may be added in divided portions in two or more steps. For example, the binder may be added in divided portions in the kneading step, the dispersion step, and the mixing step for adjusting the viscosity after dispersion. Also, as described above, as components of the composition for forming the magnetic layer, one or more nitrogen-containing polymers and one or more of the above fatty acids are used, and by mixing them in the preparation process of the composition for forming the magnetic layer, a salt-forming reaction can be advanced. Also, in one form, before preparing the composition for forming the magnetic layer, 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 composition for forming the magnetic layer to prepare the composition for forming the magnetic layer. This also applies to the preparation process of the composition for forming the non-magnetic layer. The abrasive liquid is preferably prepared separately from the ferromagnetic powder and the projection-forming agent. The abrasive liquid is preferably prepared separately from the ferromagnetic powder and the projection-forming agent as one or more kinds of abrasive liquids containing an abrasive, a solvent, and preferably a binder, and can be used in the preparation of the composition for forming the magnetic layer. For the preparation of the abrasive liquid, dispersion treatment and / or classification treatment can be performed. Commercially available devices can be used for these treatments.

[0130] In the manufacturing process of the magnetic tape, known conventional manufacturing techniques can be used in part or all of the steps. In the kneading step, it is preferable to use a kneader having a strong kneading force such as an open kneader, a continuous kneader, a pressure kneader, an extruder, etc. Details of these kneading processes are described in JP-A-1-106338 and JP-A-1-79274. In addition, glass beads and / or other beads can be used to disperse the composition for forming each layer. As such dispersion beads, zirconia beads, titania beads, and steel beads, which are high-specific gravity dispersion beads, are suitable. These dispersion beads are preferably used with the particle size (bead diameter) and filling rate optimized. Known dispersers can be used. The composition for forming each layer may be filtered by a known method before being subjected to the coating step. Filtration can be performed, for example, by filter filtration. As the filter used for filtration, for example, a filter having a pore size of 0.01 to 3 μm (for example, a glass fiber filter, a polypropylene filter, etc.) can be used.

[0131] Regarding the dispersion treatment of the composition for forming the magnetic layer, in one form, the dispersion treatment of the ferromagnetic powder is performed by a two-stage dispersion treatment. After crushing the coarse aggregates of the ferromagnetic powder by the first-stage dispersion treatment, a second-stage dispersion treatment can be performed in which the collision energy applied to the particles of the ferromagnetic powder by the collision with the dispersion beads is smaller than that of the first dispersion treatment. According to such a dispersion treatment, it is considered that both the improvement of the dispersibility of the ferromagnetic powder and the suppression of the occurrence of chipping (part of the particles being chipped) can be achieved.

[0132] As an example of the above two-stage dispersion treatment, a dispersion treatment including a first stage of obtaining a dispersion liquid by dispersing a ferromagnetic powder, a binder, and a solvent in the presence of first dispersion beads, and a second stage of dispersing the dispersion liquid obtained in the first stage in the presence of second dispersion beads having a smaller bead diameter and density than the first dispersion beads can be mentioned. The above dispersion treatment will be further described below.

[0133] In order to enhance the dispersibility of the ferromagnetic powder, it is preferable that the above-described first and second steps be performed as a dispersion treatment before mixing the ferromagnetic powder with other powder components. For example, it is preferable to perform the above-described first and second steps as a dispersion treatment of a liquid (magnetic liquid) containing a ferromagnetic powder, a binder, a solvent, and optionally added additives before mixing with an abrasive and a projection-forming agent.

[0134] The bead diameter of the second dispersion beads is preferably 1 / 100 or less of the bead diameter of the first dispersion beads, more preferably 1 / 500 or less. Also, the bead diameter of the second dispersion beads can be, for example, 1 / 10000 or more of the bead diameter of the first dispersion beads. However, it is not limited to this range. For example, the bead diameter of the second dispersion beads is preferably in the range of 80 to 1000 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. Note that the bead diameter in the present invention and in this specification is a value measured by the same method as the method for measuring the average particle size of the powder described above.

[0135] The above-described second step is preferably performed under the condition that the second dispersion beads are present in an amount 10 times or more that of the ferromagnetic hexagonal ferrite powder on a mass basis, and more preferably under the condition that they are present in an amount of 10 to 30 times. On the other hand, it is also preferable that the amount of the first dispersion beads in the first step be within the above range.

[0136] The second dispersion beads are beads having a density lower than that of the first dispersion beads. "Density" is obtained by dividing the mass (unit: g) of the dispersion beads by the volume (unit: cm 3 ). The measurement is performed by the Archimedes method. The density of the second dispersion beads is preferably 3.7 g / cm 3 or less, more preferably 3.5 g / cm 3 or less. The density of the second dispersion beads can be, for example, 2.0 g / cm 3 or more, and 2.0 g / cm 3It may also be less than. Preferred second dispersion beads from the density point of view include diamond beads, silicon carbide beads, silicon nitride beads, etc. Preferred second dispersion beads from the density and hardness points of view include diamond beads. On the other hand, as the first dispersion beads, those with a density of 3.7 g / cm 3 are preferably dispersion beads exceeding, and those with a density of 3.8 g / cm 3 or more are more preferred, and those with a density of 4.0 g / cm 3 or more are even more preferred. The density of the first dispersion beads may be, for example, 7.0 g / cm 3 or less, or may be more than 7.0 g / cm 3 Preferably, zirconia beads, alumina beads, etc. are used as the first dispersion beads, and zirconia beads are more preferably used.

[0137] The dispersion time is not particularly limited and may be set according to the type of disperser used, etc.

[0138] (Coating process) The magnetic layer can be formed by directly coating the magnetic layer-forming composition, for example, on a non-magnetic support, or by sequentially or simultaneously applying a multi-layer coating with the non-magnetic layer-forming composition. When performing the alignment treatment, the alignment treatment is performed on the coating layer in the alignment zone while the coating layer of the magnetic layer-forming composition is in a wet state. For the alignment treatment, various known techniques can be applied, including the description in paragraph 0052 of JP-A-2010-24113. For example, the vertical alignment treatment can be performed by a known method such as a method using a magnet with opposite poles facing each other. The magnetic field strength in the vertical alignment treatment can be, for example, 0.40 T (tesla) or more and 1.20 T or less. The higher the magnetic field strength, the more the value of the vertical SFD tends to decrease. In the alignment zone, the drying speed of the coating layer can be controlled by the temperature, air volume of the drying air, and / or the conveyance speed in the alignment zone. Also, the coating layer may be pre-dried before being conveyed to the alignment zone. The backcoat layer can be formed by applying a composition for forming a backcoat layer on the side opposite to the side of the non-magnetic support having a magnetic layer (or on which the magnetic layer will be provided later). For details of the coating for forming each layer, reference can be made to paragraph 0066 of JP-A-2010-231843.

[0139] (Other processes) After the above coating process, usually, calendering is performed to improve the surface smoothness of the magnetic tape. Regarding the calendering conditions, the calendering pressure is, for example, 200 to 500 kN / m, preferably 250 to 350 kN / m, the calendering temperature (the surface temperature of the calender roll) is, for example, 70 to 120°C, preferably 80 to 120°C, and the calendering speed is, for example, 50 to 300 m / min, preferably 80 to 200 m / min. Also, the more a roll with a hard surface is used as the calender roll and the more the number of stages is increased, the more the surface of the magnetic layer tends to be smoothed. For various other processes for manufacturing the magnetic tape, reference can be made to paragraphs 0067 to 0070 of JP-A-2010-231843. By going through various processes, a long magnetic tape web can be obtained. The obtained magnetic tape web is slit (cut) by a known cutting machine to the width of the magnetic tape to be accommodated in, for example, a magnetic tape cartridge. The above width can be determined according to the standard and is usually 1 / 2 inch. 1 inch = 2.54 cm. Usually, a servo pattern is formed on the magnetic tape obtained by slitting.

[0140] (Heat treatment) In one form, the magnetic tape can be a magnetic tape manufactured through the following heat treatment. In another form, it can be a magnetic tape manufactured without going through the following heat treatment.

[0141] The heat treatment can be performed with the magnetic tape slit and cut to the width determined according to the standard wound around a core member.

[0142] In one embodiment, the above heat treatment is performed with a magnetic tape wound around a core member for heat treatment (hereinafter referred to as "heat treatment core"). After the heat treatment, the magnetic tape is wound around a cartridge reel of a magnetic tape cartridge, and a magnetic tape cartridge with the magnetic tape wound around the cartridge reel can be produced. The heat treatment core can be made of metal, resin, paper, etc. From the viewpoint of suppressing the occurrence of winding failures such as spoiling, the material of the heat treatment core is preferably a material with high rigidity. From this point, the heat treatment core is preferably made of metal or resin. Also, as an index of rigidity, the flexural modulus of the material of the heat treatment core is preferably 0.2 GPa (gigapascal) or more, and more preferably 0.3 GPa or more. On the other hand, since high-rigidity materials are generally expensive, using a heat treatment core made of a material having a rigidity exceeding the rigidity that can suppress the occurrence of winding failures leads to an increase in cost. Considering the above points, the flexural modulus of the material of the heat treatment core is preferably 250 GPa or less. The flexural modulus is a value measured according to ISO (International Organization for Standardization) 178, and the flexural moduli of various materials are known. Also, the heat treatment core can be a solid or hollow core member. In the case of a hollow shape, from the viewpoint of maintaining rigidity, the wall thickness is preferably 2 mm or more. Also, the heat treatment core may or may not have a flange. Prepare a magnetic tape that is longer than the length to be finally accommodated in a magnetic tape cartridge (hereinafter referred to as the "final product length") as a magnetic tape to be wound around a core for heat treatment, and it is preferable to perform heat treatment by placing the magnetic tape wound around the core for heat treatment in a heat treatment environment. The length of the magnetic tape wound around the core for heat treatment is equal to or greater than the final product length, and from the viewpoint of ease of winding around the core for heat treatment and the like, it is preferably set to "final product length + α". This α is preferably 5 m or more from the viewpoint of the above-mentioned ease of winding. The tension during winding around the core for heat treatment is preferably 0.1 N (Newton) or more. Also, from the viewpoint of suppressing excessive deformation during manufacturing, the tension during winding around the core for heat treatment is preferably 1.5 N or less, more preferably 1.0 N or less. The outer diameter of the core for heat treatment is preferably 20 mm or more, more preferably 40 mm or more, from the viewpoints of ease of winding and suppression of coiling (curl in the longitudinal direction). Also, the outer diameter of the core for heat treatment is preferably 100 mm or less, more preferably 90 mm or less. The width of the core for heat treatment may be equal to or greater than the width of the magnetic tape wound around this core. Further, when removing the magnetic tape from the core for heat treatment after heat treatment, in order to suppress unintentional tape deformation during the removal operation, it is preferable to remove the magnetic tape from the core for heat treatment after the magnetic tape and the core for heat treatment have been sufficiently cooled. The removed magnetic tape is preferably wound around another core (referred to as a "temporary winding core") once, and then the magnetic tape is wound from the temporary winding core onto the cartridge reel of the magnetic tape cartridge (generally having an outer diameter of about 40 to 50 mm). Thereby, the relationship between the inner side and the outer side of the magnetic tape with respect to the core for heat treatment during heat treatment can be maintained, and the magnetic tape can be wound onto the cartridge reel of the magnetic tape cartridge. For details of the temporary winding core and the tension when winding the magnetic tape around this core, reference can be made to the previous description regarding the core for heat treatment. In the form of performing the above heat treatment on a magnetic tape having a length of "final product length + α", the length of "+α" can be cut off at an arbitrary stage. For example, in one form, the magnetic tape of the final product length is 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 to be cut off and discarded, the above α is preferably 20 m or less.

[0143] The specific form of the heat treatment performed in the state of being wound around the core member as described above will be described below. The ambient temperature at which the heat treatment is performed (hereinafter referred to as "heat treatment temperature") is preferably 40°C or higher, 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 still more preferably 65°C or lower. The absolute humidity by weight of the atmosphere in which the heat treatment is performed 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 preferable because it can be prepared without using a special device for reducing moisture. On the other hand, from the viewpoint of suppressing the occurrence of dew condensation and the deterioration of workability, the absolute humidity by weight is preferably 70 g / kg Dry air or lower, more preferably 66 g / kg Dry air or lower. The heat treatment time is preferably 0.3 hours or more, more preferably 0.5 hours or more. Also, from the viewpoint of production efficiency, the heat treatment time is preferably 48 hours or less.

[0144] Regarding the control of the standard deviation of the bending amount described above, the heat treatment temperature, the heat treatment time, the bending elastic modulus of the core for heat treatment, and the tension at the time of winding around the core for heat treatment all tend to make the value of the standard deviation of the bending amount smaller as the values are larger.

[0145] (Formation of servo pattern) "Formation of servo pattern" can also be referred to as "recording of servo signal". The formation of the servo pattern will be described below.

[0146] The servo pattern is usually formed along the longitudinal direction of the magnetic tape. Examples of the method of control (servo control) using the servo signal include timing-based servo (TBS), amplitude servo, frequency servo, and the like.

[0147] As shown in ECMA (European Computer Manufacturers Association)-319 (June 2001), in a magnetic tape compliant with the LTO (Linear Tape-Open) standard (commonly referred to as an "LTO tape"), a timing-based servo system is adopted. In this timing-based servo system, the servo pattern is composed of a plurality of a pair of magnetic stripes (also called "servo stripes") that are non-parallel to each other and are continuously arranged in the longitudinal direction of the magnetic tape. In the present invention and this specification, the "timing-based servo pattern" refers to a servo pattern that enables head tracking in the servo system of the timing-based servo method. As described above, the reason why the servo pattern is composed of a pair of magnetic stripes that are non-parallel to each other is to inform the servo signal reading element passing over the servo pattern of its passing position. Specifically, the pair of magnetic stripes are formed such that their interval continuously changes along the width direction of the magnetic tape, and by reading the interval by the servo signal reading element, the relative position between the servo pattern and the servo signal reading element can be known. This relative position information enables tracking of the data track. For this purpose, a plurality of servo tracks are usually set on the servo pattern along the width direction of the magnetic tape.

[0148] The servo band is composed of a servo pattern that is continuous in the longitudinal direction of the magnetic tape. Usually, a plurality of such servo bands are provided on the magnetic tape. For example, in an LTO tape, the number is five. The area sandwiched between two adjacent servo bands is the data band. The data band is composed of a plurality of data tracks, and each data track corresponds to each servo track.

[0149] Also, in one form, as shown in Japanese Patent Application Laid-Open No. 2004-318983, information indicating the number of each servo band (also referred to as "servo band ID (identification)" or "UDIM (Unique DataBand 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 relatively in the longitudinal direction of the magnetic tape. Specifically, the shifting method of a specific one of a plurality of pairs of servo stripes is changed for each servo band. As a result, the recorded servo band ID becomes unique for each servo band, so that by simply reading one servo band with a servo signal reading element, the servo band can be uniquely identified.

[0150] Note that there is also a method of uniquely identifying a servo band using a staggered method as shown in ECMA-319 (June 2001). In this staggered method, a group of a pair of magnetic stripes (servo stripes) that are arranged continuously in the longitudinal direction of the magnetic tape and are not parallel to each other is recorded so as to be shifted in the longitudinal direction of the magnetic tape for each servo band. Since the combination of this shifting method between adjacent servo bands is unique throughout the magnetic tape, it is also possible to uniquely identify a servo band when reading a servo pattern with two servo signal reading elements.

[0151] Also, as shown in ECMA-319 (June 2001), information indicating the position in the longitudinal direction of the magnetic tape (also referred to as "LPOS (Longitudinal Position) information") is usually embedded in each servo band. This LPOS information is also recorded by shifting the positions of a pair of servo stripes in the longitudinal direction of the magnetic tape. However, unlike the UDIM information, the same signal is recorded in each servo band for this LPOS information.

[0152] It is also possible to embed other information different from the above UDIM information and LPOS information in the servo band. In this case, the information to be embedded may be different for each servo band like the UDIM information, or may be common to all servo bands like the LPOS information. Also, as a method of embedding information in the servo band, it is possible to adopt a method other than the above. For example, a predetermined code may be recorded by thinning out a predetermined pair from a group of a pair of servo stripes.

[0153] The servo pattern forming head is called a servo write head. The servo write head usually has a pair of gaps corresponding to the above pair of magnetic stripes for the number of servo bands. Usually, a core and a coil are connected to each pair of gaps, and by supplying a current pulse to the coil, the magnetic field generated in the core can cause a leakage magnetic field in the pair of gaps. When forming the servo pattern, by inputting a current pulse while running a magnetic tape on the servo write head, a magnetic pattern corresponding to the pair of gaps can be transferred to the magnetic tape to form a servo pattern. The width of each gap can be appropriately set according to 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, 10 μm or more, etc.

[0154] 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 DC magnet or an AC magnet. There are two types of erase processes: DC (Direct Current) erase and AC (Alternating Current) erase. The AC erase is performed by gradually decreasing the intensity of the magnetic field while reversing the direction of the magnetic field applied to the magnetic tape. On the other hand, the DC erase is performed by applying a magnetic field in one direction to the magnetic tape. There are further two methods for DC erase. The first method is a horizontal DC erase in which a magnetic field in one direction is applied along the longitudinal direction of the magnetic tape. The second method is a vertical DC erase in which a magnetic field in one direction is applied along the thickness direction of the magnetic tape. The erase process may be performed on the entire magnetic tape or on each servo band of the magnetic tape.

[0155] The direction of the magnetic field of the servo pattern to be formed is determined according to the direction of the erase. For example, when a horizontal DC erase is performed on the magnetic tape, the servo pattern is formed such that the direction of the magnetic field is opposite to the direction of the erase. Thereby, the output of the servo signal obtained by reading the servo pattern can be increased. As shown in Japanese Patent Application Laid-Open No. 2012-53940, when a magnetic pattern is transferred using the above gap to a vertically DC-erased magnetic tape, 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 using the above gap to a horizontally DC-erased magnetic tape, the servo signal obtained by reading the formed servo pattern has a bipolar pulse shape.

[0156] [Magnetic Tape Cartridge] One aspect of the present invention relates to a magnetic tape cartridge including the above magnetic tape.

[0157] Details of the magnetic tape included in the above magnetic tape cartridge are as described above.

[0158] In a magnetic tape cartridge, generally, a magnetic tape is accommodated in a state of being wound around a reel inside a cartridge body. The reel is rotatably provided inside the cartridge body. As the magnetic tape cartridge, a single-reel type magnetic tape cartridge having one reel inside the cartridge body and a double-reel type magnetic tape cartridge having two reels inside the cartridge body are widely used. When the single-reel type magnetic tape cartridge is mounted on 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 wound around the reel on the magnetic tape device side. A magnetic head is disposed in the magnetic tape conveyance path from the magnetic tape cartridge to the take-up reel. Feeding and take-up of the magnetic tape are performed between the reel on the magnetic tape cartridge side (supply reel) and the reel on the magnetic tape device side (take-up reel). During this period, data recording and / or reproduction are performed by the contact and sliding between the magnetic head and the surface of the magnetic layer of the magnetic tape. On the other hand, in the double-reel type magnetic tape cartridge, both the supply reel and the take-up reel are provided inside the magnetic tape cartridge.

[0159] In one form, the magnetic tape cartridge can include a cartridge memory. The cartridge memory can be, for example, a non-volatile memory, in which head tilt angle adjustment information has already been recorded or is to be recorded. The head tilt angle adjustment information is information for adjusting the head tilt angle during magnetic tape running in a magnetic tape device. For example, as the head tilt angle adjustment information, values of servo band intervals at each position in the longitudinal direction of the magnetic tape at the time of data recording can be recorded. For example, when reproducing data recorded on the magnetic tape, the value of the servo band interval is measured during reproduction, and the head tilt angle is changed by a control device of the magnetic tape device so that the absolute value of the difference from the servo band interval at the time of recording at the same longitudinal position recorded in the cartridge memory approaches zero. The head tilt angle can be, for example, the angle θ described above.

[0160] The above magnetic tape and magnetic tape cartridge can be suitably used in a magnetic tape device (in other words, a magnetic recording and reproducing system) that records and / or reproduces data at different head tilt angles. In such a magnetic tape device, in one form, the head tilt angle can be changed during magnetic tape running to record and / or reproduce data. For example, the head tilt angle can be changed according to the dimension information in the width direction of the magnetic tape obtained during magnetic tape running. Also, for example, there can be a usage form in which the head tilt angle in a certain recording and / or reproduction is changed from the head tilt angle in the subsequent recording and / or reproduction, and the head tilt angle is fixed without being changed during magnetic tape running for each recording and / or reproduction. In any usage form, a magnetic tape with less degradation in electromagnetic conversion characteristics when recording and / or reproducing data at different head tilt angles is preferable.

[0161] [Magnetic Tape Device] One aspect of the present invention relates to a magnetic tape device including the above magnetic tape. In the above magnetic tape device, recording of data on the magnetic tape and / or reproduction of data recorded on the magnetic tape can be performed, for example, by bringing the surface of the magnetic layer of the magnetic tape into contact with and sliding it against a magnetic head. The above magnetic tape device can detachably include a magnetic tape cartridge according to one aspect of the present invention.

[0162] The above magnetic tape cartridge can be attached to a magnetic tape device equipped with a magnetic head and used for recording and / or reproducing data. In the present invention and this specification, the "magnetic tape device" shall mean a device capable of performing at least one of recording data on a magnetic tape and reproducing data recorded on the magnetic tape. Such a device is generally called a drive.

[0163] <Magnetic head> The above 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, as the reproducing element, a magnetoresistive (MR) element capable of sensitively reading information recorded on the magnetic tape is preferable. As the MR element, various known MR elements (for example, GMR (Giant Magnetoresistive) element, TMR (Tunnel Magnetoresistive) element, etc.) can be used. Hereinafter, a magnetic head that records and / or reproduces recorded data is also referred to as a "recording and reproducing head". An element for data recording (recording element) and an element for data reproduction (reproducing element) are collectively referred to as "magnetic head elements".

[0164] By reproducing data using a reproducing element with a narrow reproducing element width as the reproducing element, it is possible to reproduce highly dense recorded data with high sensitivity. From this perspective, the reproducing element width of the reproducing element is preferably 0.8 μm or less. The reproducing element width of the reproducing element can be, for example, 0.3 μm or more. However, from the above perspective, it is also preferable to be below this value. Here, the "reproducing element width" refers to the physical dimension of the reproducing element width. Such a physical dimension can be measured by an optical microscope, a scanning electron microscope, or the like.

[0165] When recording data and / or reproducing the recorded data, first, tracking using a servo signal can be performed. That is, by causing the servo signal reading element to follow a predetermined servo track, the magnetic head element can be controlled to pass over the target data track. The movement of the data track is performed by changing the servo track read by the servo signal reading element in the tape width direction. In addition, the recording and reproducing head can also perform recording and / or reproducing with respect to other data bands. In that case, the servo signal reading element can be moved to a predetermined servo band using the UDIM information described above, and tracking with respect to that servo band can be started.

[0166] Fig. 5 shows an example of the arrangement of data bands and servo bands. In Fig. 5, on the magnetic layer of the magnetic tape MT, a plurality of servo bands 1 are arranged sandwiched between guide bands 3. A plurality of regions 2 sandwiched between two servo bands are data bands. The servo pattern is a magnetized region, which is formed by magnetizing a specific region of the magnetic layer with a servo write head. The region magnetized by the servo write head (the position where the servo pattern is formed) is defined by a standard. For example, in the LTO Ultrium format tape, which is an industry standard, a plurality of servo patterns inclined with respect to the tape width direction as shown in Fig. 6 are formed on the servo bands during the manufacture of the magnetic tape. Specifically, in Fig. 6, the servo frame SF on the servo band 1 is composed of a servo sub-frame 1 (SSF1) and a servo sub-frame 2 (SSF2). The servo sub-frame 1 is composed of an A burst (reference A in Fig. 6) and a B burst (reference 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, the servo sub-frame 2 is composed of a C burst (reference C in Fig. 6) and a D burst (reference 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. Such 18 servo patterns are arranged in sets of 5 and 4, in an arrangement of 5, 5, 4, 4, and are used to identify the servo frame. Fig. 6 shows one servo frame for explanation purposes. However, actually, on the magnetic layer of the magnetic tape where head tracking of the timing-based servo method is performed, a plurality of servo frames are arranged in the running direction on each servo band. In Fig. 6, the arrow indicates the running direction of the magnetic tape. For example, an LTO Ultrium format tape usually has 5000 or more servo frames per meter of tape length on each servo band of the magnetic layer.

[0167] In the above magnetic tape device, the tilt angle of the head 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 for adjusting the angle of the module of the magnetic head in the recording and 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 for rotating the module. Known techniques can be applied to the angle adjustment unit.

[0168] Regarding the head tilt angle during magnetic tape running, when the magnetic head includes a plurality of modules, for a randomly selected module, the angle θ described with reference to FIGS. 1 to 3 can be defined. θ which is the angle θ at the start of magnetic tape running initial can be set to 0° or more or more than 0°. θ initial The larger θ is, the larger the change amount of the effective distance between the servo signal reading elements with respect to the change amount of the angle θ becomes. Therefore, from the viewpoint of the adjustment ability to adjust the effective distance between the servo signal reading elements in correspondence with the dimensional change in the width direction of the magnetic tape, it is preferable. From this point, θ initial is preferably 1° or more, more preferably 5° or more, and even more preferably 10° or more. On the other hand, regarding the angle formed by the contact surface between the magnetic layer surface and the magnetic head when the magnetic tape runs and contacts the magnetic head (generally referred to as the "wrap angle"), keeping the deviation in the tape width direction small is effective for enhancing the uniformity in the tape width direction of the friction generated when the magnetic head and the magnetic tape come into contact during magnetic tape running. Also, enhancing the uniformity of the above friction in the tape width direction is desirable from the viewpoints of the position tracking performance and running stability of the magnetic head. From the viewpoint of reducing the deviation in the tape width direction of the above wrap angle, θ initial is preferably 45° or less, more preferably 40° or less, and even more preferably 35° or less.

[0169] Regarding the change in the angle θ during the running of the magnetic tape, for recording data on the magnetic tape and / or for reproducing the data recorded on the magnetic tape, while the magnetic tape is running in the magnetic tape device, the angle θ of the magnetic head changes from θ at the start of running initial When changing, the maximum change amount Δθ of the angle θ during the running of the magnetic tape is the Δθ calculated by the following formula max and Δθ min Among them, it is the larger value. The maximum value of the angle θ during the running of the magnetic tape is θ max and the minimum value is θ min Note that "max" is an abbreviation of maximum and "min" is an abbreviation of minimum. Δθ max = θ max - θ initial Δθ min = θ initial - θ min

[0170] In one form, Δθ can be more than 0.000°, and from the viewpoint of the adjustment ability to adjust the effective distance between the servo signal reading elements corresponding to the dimensional change in the width direction of the magnetic tape, it is preferably 0.001° or more, and more preferably 0.010° or more. Also, from the viewpoint of the ease of ensuring synchronization of the recorded data and / or the reproduced data among a plurality of magnetic head elements during data recording and / or reproduction, Δθ is preferably 1.000° or less, more preferably 0.900° or less, still more preferably 0.800° or less, even more preferably 0.700° or less, and even more preferably 0.600° or less.

[0171] In the examples shown in FIGS. 2 and 3, the axis of the element array is inclined in the direction of the magnetic tape running direction. However, the present invention is not limited to such examples. In the above magnetic tape device, embodiments in which the axis of the element array is inclined in the direction opposite to the magnetic tape running direction are also included in the present invention.

[0172] θ which is the head tilt angle at the start of magnetic tape running initialIt can be set by a control device of a magnetic tape device or the like. 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 obtained, for example, by the following method. When obtaining the angle θ during magnetic tape running by the following method, during magnetic tape running, the angle θ is changed in the range of 0 to 90°. That is, if the axis of the element array is inclined toward the magnetic tape running direction at the start of magnetic tape running, the element array is not inclined so that the axis of the element array is inclined in the direction opposite to the magnetic tape running direction at the start of magnetic tape running during magnetic tape running. If the axis of the element array is inclined in the direction opposite to the magnetic tape running direction at the start of magnetic tape running, it is assumed that the element array is not inclined so that the axis of the element array is inclined toward the magnetic tape running direction at the start of magnetic tape running during magnetic tape running. Measure the phase difference (i.e., time difference) ΔT of the reproduction signals of the pair of servo signal reading elements 1 and 2. The measurement of ΔT can be performed by a measurement unit provided in the magnetic tape device. The configuration of such a measurement unit is known. The distance L between the central part of the servo signal reading element 1 and the central part of the servo signal reading element 2 can be measured by an optical microscope or the like. When the running speed of the magnetic tape is v, the distance in the magnetic tape running direction between the central parts of the two servo signal reading elements is Lsinθ, and the relationship Lsinθ = v×ΔT holds. Therefore, the angle θ during magnetic tape running can be calculated by the formula "θ = arcsin(vΔT / L)". In the right figure of FIG. 7, an example in which the axis of the element array is inclined toward the magnetic tape running direction is shown. In this example, the phase difference (i.e., time difference) ΔT of the reproduction signal of the servo signal reading element 2 with respect to the reproduction signal of the servo signal reading element 1 is measured. When the axis of the element array is inclined in the direction opposite to the running direction of the magnetic tape, θ can be obtained by the above method except that ΔT is measured as the phase difference (i.e., time difference) of the reproduction signal of the servo signal reading element 1 with respect to the reproduction signal of the servo signal reading element 2. Note that the measurement pitch of the angle θ, i.e., the measurement interval of the angle θ in the longitudinal direction of the tape, can be selected to be a pitch suitable according to the frequency of the tape width deformation in the longitudinal direction of the tape. As an example, the measurement pitch can be, for example, 250 μm.

[0173] <Configuration of Magnetic Tape Device> The magnetic tape device 10 shown in FIG. 8 controls the recording and reproducing head unit 12 according to commands from the control device 11, and records and reproduces data on the magnetic tape MT. The magnetic tape device 10 has a configuration capable of detecting and adjusting the tension applied in the longitudinal direction of the magnetic tape from the spindle motors 17A and 17B that rotationally control the magnetic tape cartridge reel and the take-up reel, and their driving devices 18A and 18B. The magnetic tape device 10 has a configuration capable of loading the magnetic tape cartridge 13. The magnetic tape device 10 has a cartridge memory read / write device 14 capable of reading and writing to the cartridge memory 131 in the magnetic tape cartridge 13. From the magnetic tape cartridge 13 attached to the magnetic tape device 10, the end of the magnetic tape MT or the leader pin is automatically pulled out by the loading mechanism or manually, and the magnetic tape MT passes over the recording and reproducing head through the guide rollers 15A and 15B in a direction where the magnetic layer surface of the magnetic tape MT is in contact with the recording and reproducing head surface of the recording and reproducing head unit 12, and the magnetic tape MT is wound around the take-up reel 16. The rotation and torque of the spindle motor 17A and the spindle motor 17B are controlled by signals from the control device 11, and the magnetic tape MT travels at an arbitrary speed and tension. For the control of the tape speed and the control of the head tilt angle, a servo pattern pre-formed on the magnetic tape can be used. For the detection of the tension, a tension detection mechanism may be provided between the magnetic tape cartridge 13 and the take-up reel 16. The control of the tension may be performed using the guide rollers 15A and 15B in addition to the control by the spindle motors 17A and 17B. The cartridge memory read / write device 14 is configured to be able to read and write information of the cartridge memory 131 according to an instruction 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.

[0174] The control device 11 includes, for example, a control unit, a storage unit, a communication unit, etc.

[0175] The recording / reproducing head unit 12 is composed of, for example, a recording / reproducing head, a servo tracking actuator for adjusting the position of the recording / reproducing head in the track width direction, a recording / reproducing amplifier 19, a connector cable for connecting to the control device 11, etc. The recording / reproducing head is composed of, for example, a recording element for recording data on a magnetic tape, a reproducing element for reproducing data on the magnetic tape, and a servo signal reading element for reading a servo signal recorded on the magnetic tape. In one magnetic head, one or more recording elements, reproducing elements, and servo signal reading elements are mounted, respectively. Or, each element may be separately provided in a plurality of magnetic heads according to the running direction of the magnetic tape.

[0176] The recording / reproducing head unit 12 is configured to be able to record data on the magnetic tape MT according to an instruction from the control device 11. Also, it is configured to be able to reproduce the data recorded on the magnetic tape MT according to an instruction from the control device 11.

[0177] The control device 11 has a mechanism for obtaining the running position of the magnetic tape from the servo signal read from the servo band during the running of the magnetic tape MT, and controlling the servo tracking actuator so that the recording element and / or the reproducing element is located at the target running position (track position). The control of this track position is performed, for example, by feedback control. The control device 11 has a mechanism for obtaining the servo band interval from the servo signals read from two adjacent servo bands during the running of the magnetic tape MT. The control device 11 can store the obtained servo band interval information in the storage unit inside the control device 11, the cartridge memory 131, an external connected device, etc. Further, the control device 11 can change the head tilt angle according to the dimensional information in the width direction of the magnetic tape during running. Thereby, the effective distance between the servo signal reading elements can be made close to or equal to the interval of the servo bands. The above dimensional information can be obtained by using a servo pattern pre-formed on the magnetic tape. For example, in this way, during the running of the magnetic tape in the magnetic tape device, the angle θ formed by the axis of the element array with respect to the width direction of the magnetic tape can be changed according to the dimensional information in the width direction of the magnetic tape obtained during running. The adjustment of the head tilt angle can be performed, for example, by feedback control. Also, for example, the adjustment of the head tilt angle can also be performed by the method described in Japanese Patent Application Laid-Open No. 2016-524774 (Patent Document 1) or US2019 / 0164573A1 (Patent Document 2).

Example

[0178] Hereinafter, the present invention will be described based on examples. However, the present invention is not limited to the embodiments shown in the examples. The notations of "parts" and "%" described below indicate "parts by mass" and "% by mass" unless otherwise specified. The processes and evaluations described below were carried out in an environment at a temperature of 23°C ± 1°C unless otherwise specified. Also, the "eq" described below indicates an equivalent, which is a unit that cannot be converted into the SI unit system.

[0179] [Ferromagnetic powder] In Table 2, "BaFe" is hexagonal barium ferrite powder with an average particle size (average plate diameter) of 21 nm.

[0180] In Table 2, "SrFe1" is hexagonal strontium ferrite powder produced by the following method. Weighed 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, and mixed them in a mixer to obtain a raw material mixture. The obtained raw material mixture was melted in a platinum crucible at a melting temperature of 1390 °C. While stirring the melt, the outlet provided at the bottom of the platinum crucible was heated, and the melt was discharged in a rod shape at about 6 g / second. The discharged liquid was rolled and rapidly cooled by a water-cooled double roller to produce an amorphous body. Charged 280 g of the produced amorphous body into an electric furnace, heated it to 635 °C (crystallization temperature) at a heating rate of 3.5 °C / min, and held it at the same temperature for 5 hours to precipitate (crystallize) hexagonal strontium ferrite particles. Next, the crystallized product obtained above containing hexagonal strontium ferrite particles was roughly pulverized in a mortar. 1000 g of zirconia beads with a particle size of 1 mm and 800 ml of an acetic acid aqueous solution with a concentration of 1% were added to a glass bottle, and dispersion treatment was performed for 3 hours using a paint shaker. Then, the obtained dispersion was separated from the beads and put into a stainless steel beaker. The dispersion was allowed to stand at a liquid temperature of 100 °C for 3 hours to dissolve the glass component, then precipitated with a centrifuge and decantation was repeated for washing, and dried in a heating furnace with an internal temperature of 110 °C for 6 hours 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 was 2.2×10 5 J / m 3 The mass magnetization σs was 49 A·m 2 / kg. Collected 12 mg of sample powder from the hexagonal strontium ferrite powder obtained above, and performed elemental analysis of the filtrate obtained by partially dissolving this sample powder under the dissolution conditions exemplified above using an ICP analyzer to determine the surface layer content rate of neodymium atoms. Separately, 12 mg of sample powder was collected from the hexagonal strontium ferrite powder obtained above, and elemental analysis of the filtrate obtained by completely dissolving this sample powder under the dissolution conditions exemplified above was performed using an ICP analyzer to determine the bulk content rate of neodymium atoms. The content rate (bulk content rate) of neodymium atoms with respect to 100 atomic % of iron atoms in the hexagonal strontium ferrite powder obtained above was 2.9 atomic %. Further, the surface layer content rate of neodymium atoms was 8.0 atomic %. The ratio of the surface layer content rate to the bulk content rate, "surface layer content rate / bulk content rate", was 2.8, and it was confirmed that neodymium atoms were unevenly distributed on the surface of the particles. That the powder obtained above exhibits the crystal structure of hexagonal ferrite was confirmed by scanning with CuKα rays under the conditions of 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 the crystal structure of hexagonal ferrite of the magnetoplumbite type (M type). Further, the crystal phase detected by X-ray diffraction analysis was a single phase of the magnetoplumbite type. PANalytical X’Pert Pro diffractometer, PIXcel detector Soller slits for incident beam and diffracted beam: 0.017 radians Fixed angle of dispersion slit: 1 / 4 degree Mask: 10 mm Anti-scattering 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

[0181] In Table 2, "SrFe2" is 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 with a mixer to obtain a raw material mixture. The obtained raw material mixture was melted in a platinum crucible at a melting temperature of 1380 °C, and while stirring the melt, the outlet provided at the bottom of the platinum crucible was heated, and the melt was discharged in a rod shape at about 6 g / second. The discharged liquid was rolled and rapidly cooled with a water-cooled twin roll to produce an amorphous body. 280 g of the obtained amorphous substance was charged into an electric furnace, heated to 645 °C (crystallization temperature), and held at the same temperature for 5 hours to precipitate (crystallize) hexagonal strontium ferrite particles. Next, the crystallized product obtained above containing hexagonal strontium ferrite particles was roughly pulverized in a mortar, 1000 g of zirconia beads with a particle size of 1 mm and 800 ml of an acetic acid aqueous solution with a concentration of 1% were added to a glass bottle, and dispersion treatment was carried out for 3 hours with a paint shaker. Then, the obtained dispersion was separated from the beads and put into a stainless steel beaker. The dispersion was allowed to stand at a liquid temperature of 100 °C for 3 hours to dissolve the glass component, then precipitated with a centrifuge and decantation was repeated for washing, and dried in a heating furnace with an internal temperature of 110 °C for 6 hours 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 was 2.0×10 5 J / m 3 , and the mass magnetization σs was 50 A·m 2 / kg.

[0182] In Table 2, "ε-iron oxide" is ε-iron oxide powder prepared by the following method. Dissolve 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) in 90 g of pure water. While stirring using a magnetic stirrer, 4.0 g of an aqueous ammonia solution with a concentration of 25% was added under the conditions of an air atmosphere and an ambient temperature of 25 °C, and stirring was carried out for 2 hours while maintaining the temperature condition of an ambient temperature of 25 °C. To the obtained solution, a citric acid solution obtained by dissolving 1 g of citric acid in 9 g of pure water was added, and stirring was carried out for 1 hour. The powder precipitated after stirring was collected by centrifugation, washed with pure water, and dried in a heating furnace with an internal temperature of 80 °C. 800 g of pure water was added to the dried powder, and the powder was dispersed in water again to obtain a dispersion. The obtained dispersion was heated to a liquid temperature of 50 °C, and 40 g of a 25% aqueous ammonia solution was added dropwise with stirring. After stirring for 1 hour while maintaining the temperature at 50 °C, 14 mL of tetraethoxysilane (TEOS) was added dropwise and stirred for 24 hours. 50 g of ammonium sulfate was added to the obtained reaction solution, and the precipitated powder was collected by centrifugation, washed with pure water, and dried in a heating furnace at a furnace temperature of 80 °C for 24 hours to obtain a precursor of the ferromagnetic powder. The obtained precursor of the ferromagnetic powder was loaded into a heating furnace with a furnace temperature of 1000 °C under an air atmosphere and subjected to a heat treatment for 4 hours. The heat-treated precursor of the ferromagnetic powder was put into a 4 mol / L aqueous sodium hydroxide (NaOH) solution, and the liquid temperature was maintained at 70 °C and stirred for 24 hours to remove the silicate compound, which is an impurity, from the heat-treated precursor of the ferromagnetic powder. Thereafter, the ferromagnetic powder from which the silicate compound had been removed was collected by centrifugation, washed with pure water, and the ferromagnetic powder was obtained. When the composition of the obtained ferromagnetic powder was confirmed by high-frequency inductively coupled plasma optical emission spectrometry (ICP-OES: Inductively Coupled Plasma-Optical Emission Spectrometry), it was Ga, Co and Ti-substituted ε-iron oxide (ε-Ga 0.28 Co 0.05 Ti 0.05 Fe 1.62 O3). Also, X-ray diffraction analysis was performed under the same conditions as those described above for SrFe1, and from the peaks of the X-ray diffraction pattern, it was confirmed that the obtained ferromagnetic powder had a single-phase crystal structure of the ε-phase (crystal structure of ε-iron oxide) that did not include the crystal structures of the α-phase and γ-phase. The average particle size of the obtained ε-iron oxide powder was 12 nm, the activation volume was 746 nm 3 , the anisotropy constant Ku was 1.2×10 5 J / m 3 , and the mass magnetization σs was 16 A·m 2 / kg.

[0183] The activation volume and anisotropy constant Ku of the above hexagonal strontium ferrite powder and ε-iron oxide powder are the values obtained by the method described above using a vibrating sample magnetometer (manufactured by Toei Industry Co., Ltd.) for each ferromagnetic powder. The mass magnetization σs is the value measured at a magnetic field strength of 15 kOe using a vibrating sample magnetometer (manufactured by Toei Industry Co., Ltd.).

[0184] [Preparation of Abrasive Liquid] [Preparation of Abrasive Liquid A] To 100.0 parts of the abrasive (aluminum oxide powder) shown in Table 1, 31.3 parts of 2,3-dihydroxynaphthalene (manufactured by Tokyo Chemical Industry Co., Ltd.) in the amount shown in Table 1, and a 32% solution of a polyester polyurethane resin (UR-4800 manufactured by Toyobo Co., Ltd. (polar group amount: 80 meq / kg)) having an SO3Na group as a polar group (the solvent is a mixed solvent of methyl ethyl ketone and toluene), and 570.0 parts of a mixed liquid of methyl ethyl ketone and cyclohexanone 1:1 (mass ratio) as a solvent were mixed, and in the presence of zirconia beads (bead diameter: 0.1 mm), it was dispersed by a paint shaker for the time (bead dispersion time) shown in Table 1. After dispersion, centrifugation of the dispersion obtained by separating the dispersion liquid and the beads with a mesh was carried out. The centrifugation was carried out using CS150GXL manufactured by Hitachi Koki Co., Ltd. as a centrifuge (the rotor used was S100AT6 manufactured by the same company) at the rotation speed (rpm: rotation per minute) shown in Table 1 for the time (centrifugation time) shown in Table 1. By this centrifugation, particles with a relatively large particle size precipitate, and particles with a relatively small particle size are dispersed in the supernatant liquid. Thereafter, the supernatant liquid was recovered by decantation. This recovered liquid is called "abrasive liquid A".

[0185] [Preparation of Abrasive Liquids B and C] Abrasive liquids B and C were each prepared in the same manner as the preparation method of abrasive liquid A except that various items were changed as shown in Table 1.

[0186]

Table 1

[0187] [Example 1] <Preparation of Composition for Forming Magnetic Layer> (Magnetic liquid) Ferromagnetic powder (see Table 2): 100.0 parts Oleic acid: 2.0 parts Vinyl chloride copolymer (MR-104 manufactured by Nippon Zeon Co., Ltd.): 10.0 parts SO3Na group-containing polyurethane resin: 4.0 parts (Weight average molecular weight 70,000, SO3Na group content 0.07 meq / g) Polyalkyleneimine polymer (synthetic product obtained by the method described in paragraphs 0115 to 0123 of JP-A-2016-51493): 6.0 parts Methyl ethyl ketone: 150.0 parts Cyclohexanone: 150.0 parts (Abrasive liquid) Use the abrasive liquid shown in Table 2 so that the amount of abrasive in the abrasive liquid is the amount shown in Table 2 (Other components) Carbon black (average particle size: 20 nm): 0.7 part Polyethyleneimine (manufactured by Nippon Shokubai Co., Ltd., number average molecular weight 300): 2.0 parts Stearic acid: 0.5 part Stearamide: 0.3 part Butyl stearate: 6.0 parts Methyl ethyl ketone: 110.0 parts Cyclohexanone: 110.0 parts Polyisocyanate (Coronate (registered trademark) L manufactured by Tosoh Corporation): 3.0 parts

[0188] (Preparation method) Disperse the various components of the above magnetic liquid using a batch vertical sand mill with zirconia beads (first dispersion beads, density 6.0 g / cm 3 ) having a bead diameter of 0.5 mm for 24 hours (first stage), and then prepare dispersion liquid A by filtering using a filter having a pore size of 0.5 μm. The zirconia beads were used in an amount 10 times the mass of the ferromagnetic powder on a mass basis. Thereafter, dispersion liquid A was dispersed for 1 hour (second stage) using diamond beads (second dispersion beads, density 3.5 g / cm 3 ) with a bead diameter of 500 nm in a batch vertical sand mill, and a dispersion liquid (dispersion liquid B) from which the diamond beads were separated using a centrifuge was prepared. The diamond beads were used in an amount 10 times the mass of the ferromagnetic powder on a mass basis. Dispersion liquid B obtained above, the abrasive liquid, and the other components described above were introduced into a dissolver stirrer and stirred for 360 minutes at a peripheral speed of 10 m / sec. Thereafter, ultrasonic dispersion treatment was performed for 60 minutes at a flow rate of 7.5 kg / min using a flow-type ultrasonic disperser, and then filtration was performed three times through a filter with a pore diameter of 0.3 μm to prepare a composition for forming a magnetic layer.

[0189] <Preparation of Composition for Forming Non-Magnetic Layer> Various components of the following composition for forming a non-magnetic layer were dispersed for 24 hours using zirconia beads with a bead diameter of 0.1 mm in a batch vertical sand mill, and then filtered using a filter having a pore diameter of 0.5 μm to prepare a composition for forming a non-magnetic layer.

[0190] Non-magnetic inorganic powder α-iron oxide: 100.0 parts (average particle size 10 nm, BET specific surface area 75 m 2 / g) Carbon black: 25.0 parts (average particle size 20 nm) SO3Na group-containing polyurethane resin: 18.0 parts (weight average molecular weight 70000, SO3Na group content 0.2 meq / g) Stearic acid: 1.0 part Cyclohexanone: 300.0 parts Methyl ethyl ketone: 300.0 parts

[0191] <Preparation of Composition for Forming Back Coat Layer> Of the various components of the composition for forming a backcoat layer below, the components excluding the lubricants (stearic acid and butyl stearate), polyisocyanate, and 200.0 parts of cyclohexanone were kneaded and diluted with an open kneader, and then zirconia beads with a bead diameter of 1 mm were used with a horizontal bead mill disperser. The residence time per pass was set to 2 minutes at a bead filling rate of 80% by volume and a rotor tip peripheral speed of 10 m / second, and subjected to 12 passes of dispersion treatment. Then, the remaining components above were added and stirred with a dissolver, and the resulting dispersion was filtered using a filter having a pore size of 1 μm to prepare a composition for forming a backcoat layer.

[0192] Non-magnetic inorganic powder α-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 20 nm) 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

[0193] <Manufacture of magnetic tape and magnetic tape cartridge> On the surface of a polyethylene naphthalate support with a thickness of 4.1 μm, the composition for forming a non-magnetic layer prepared above was applied and dried so that the thickness after drying was 0.7 μm to form a non-magnetic layer. Next, the composition for forming a magnetic layer prepared above was applied onto the non-magnetic layer to form a coating layer with a dried thickness of 0.1 μm. While this coating layer was in a wet state, in the alignment zone, a magnetic field with the magnetic field strength shown in Table 2 was applied in a direction perpendicular to the surface of the coating layer to perform vertical alignment treatment, and then the coating layer was dried to form a magnetic layer. Thereafter, the composition for forming a backcoat layer prepared above was applied and dried onto the surface of the support opposite to the surface on which the non-magnetic layer and the magnetic layer were formed to form a backcoat layer with a dried thickness of 0.3 μm. Thereafter, using a calendar roll composed only of metal rolls, surface smoothing treatment (calendering) was performed at a speed of 100 m / min, a line pressure of 300 kg / cm, and a calendar temperature (surface temperature of the calendar roll) of 90°C. Thus, a long magnetic tape web was obtained. Thereafter, after performing heat treatment for 36 hours in an environment with an ambient temperature of 70°C, the long magnetic tape web was slit into 1 / 2-inch widths to obtain magnetic tapes. By recording servo signals on the magnetic layer of the obtained magnetic tape using a commercially available servo writer, a magnetic tape having a data band, a servo band, and a guide band in an arrangement conforming to the LTO (Linear Tape-Open) Ultrium format, and having a servo pattern (timing-based servo pattern) in an arrangement and shape conforming to the LTO Ultrium format on the servo band was obtained. The servo pattern thus formed is a servo pattern conforming to the descriptions of JIS (Japanese Industrial Standards) X6175:2006 and Standard ECMA-319 (June 2001). The total number of servo bands is 5, and the total number of data bands is 4. The magnetic tape (length 960 m) on which the servo signals were thus recorded was wound around the reel of a magnetic tape cartridge (LTO Ultrium8 data cartridge), and at its end, a leader tape conforming to item 9 of Section 3 of Standard ECMA (European Computer Manufacturers Association)-319 (June 2001) was joined using a commercially available splicing tape. Thus, a magnetic tape cartridge with the magnetic tape wound around the reel was produced.

[0194] That the magnetic layer of the magnetic tape contains a compound including an ammonium salt structure of an alkyl ester anion represented by Formula 1, formed by polyethyleneimine and stearic acid, can be confirmed by the following method. A sample is cut out from the magnetic tape, and X-ray photoelectron spectroscopy is performed using an ESCA apparatus on the surface of the magnetic layer (measurement region: 300 μm × 700 μm). Specifically, wide scan measurement is performed using the ESCA apparatus under the following measurement conditions. In the measurement results, peaks are confirmed at the positions of the binding energy of the ester anion and the binding energy of the ammonium cation. Apparatus: AXIS-ULTRA manufactured by Shimadzu Corporation Excitation X-ray source: Monochromatic Al-Kα ray Scan range: 0 to 1200 eV Pass energy: 160 eV Energy resolution: 1 eV / step Capture time: 100 ms / step Number of integrations: 5 Also, a 3-cm-long sample piece was cut out from the magnetic tape, and ATR-FT-IR (Attenuated total reflection - fourier transform - infrared spectrometer) measurement (reflection method) was performed on the surface of the magnetic layer. In the measurement results, the wave numbers corresponding to the absorption of COO - (1540 cm -1 or 1430 cm -1 ), and the wave number corresponding to the absorption of ammonium cation (2400 cm -1 ) showed absorption.

[0195] [Examples 2 to 22, Comparative Examples 1 to 28] Magnetic tapes and magnetic tape cartridges were obtained by the method described for Example 1, except that the items shown in Table 2 were changed as shown in Table 2. In Comparative Examples 1 to 10, since the vertical alignment treatment was not performed, "none" was described in the column of "vertical alignment treatment conditions" in Table 2. For Examples 19 to 22 and Comparative Examples 25 to 28, the steps after servo signal recording were changed as follows. That is, heat treatment was performed after servo signal recording. On the other hand, for the other examples and comparative examples, since such heat treatment was not performed, "none" was described in the column of "heat treatment conditions" in Table 2. For Examples 19 to 22 and Comparative Examples 25 to 28, the magnetic tape (length: 970 m) after recording the servo signal as described for Example 1 was wound around a heat treatment core, and heat treatment was performed in the state of being wound around this core. As the heat treatment core, a solid resin core member (outer diameter: 50 mm) with a flexural modulus of the value shown in Table 2 was used, and the tension during winding was set to the value shown in Table 2. The heat treatment temperature and heat treatment time in the heat treatment were set to the values shown in Table 2. The absolute humidity by weight of the atmosphere in which the heat treatment was performed was 10 g / kg Dry air. After the above heat treatment, after the magnetic tape and the heat treatment core are sufficiently cooled, the magnetic tape is removed from the heat treatment core, wound around a temporary winding core, and then, from the temporary winding core, a magnetic tape of the final product length (960 m) is wound around a reel of a magnetic tape cartridge (LTO Ultrium8 data cartridge), and the remaining 10 m is cut off. At the end on the cut-off side, a leader tape conforming to item 9 of Standard ECMA (European Computer Manufacturers Association)-319 (June 2001) Section 3 is joined by a commercially available splicing tape. As the temporary winding core, a solid core member made of the same material as the heat treatment core and having the same outer diameter was used, and the tension during winding was set to 0.6 N. In this way, a magnetic tape cartridge in which the magnetic tape is wound around a reel was produced.

[0196] For each of the above Examples and Comparative Examples, six magnetic tape cartridges were produced. One was used for the evaluation of the following electromagnetic conversion characteristics, another was used for the evaluation of the following deterioration of electromagnetic conversion characteristics, and the other four were used for the following evaluations (1) to (4) of the magnetic tape, respectively.

[0197] [Evaluation of Electromagnetic Conversion Characteristics (SNR: Signal-to-Noise Ratio)] The magnetic tapes taken out from each of the magnetic tape cartridges of the Examples and Comparative Examples were respectively attached to a 1 / 2-inch reel tester, and the electromagnetic conversion characteristics (SNR: Signal-to-Noise Ratio) were evaluated by the following method. In the following evaluation, the head tilt angle was set to 0°. In an environment with a temperature of 23°C and a relative humidity of 50%, recording and playback were performed 10 passes with a tension of 0.70 N applied in the longitudinal direction of the magnetic tape. The relative speed between the magnetic tape and the magnetic head was 6 m / s. For recording, a MIG (Metal-in-gap) head (gap length 0.15 μm, track width 1.0 μm) was used as the recording head, and the recording current was set to the optimum recording current for each magnetic tape. For playback, a GMR (Giant-magnetoresistive) head (element thickness 15 nm, shield spacing 0.1 μm, playback element width 0.8 μm) was used. A signal with a linear recording density of 350 kfci was recorded, and the playback signal was measured with a spectrum analyzer manufactured by Shibasoku, and the SNR was obtained from the measurement results. In Table 2, the SNR is shown as a relative value with respect to Comparative Example 11. The unit kfci is a unit of linear recording density (not convertible to the SI unit system). As the signal, a portion where the signal was sufficiently stable after the start of magnetic tape running was used.

[0198] [Evaluation of deterioration of electromagnetic conversion characteristics (amount of SNR (Signal-to-Noise-Ratio) decrease)] By the following method, the amount of SNR decrease was obtained as an evaluation of the deterioration of electromagnetic conversion characteristics. The following recording and playback were performed using a 1 / 2-inch reel tester with the magnetic head fixed, and the head tilt angle was sequentially changed in the order of 0°, 15°, 30°, and 45° for a total of 4 times. The above head tilt angle is the angle θ formed by the axis of the element array of the following playback module 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 magnetic tape run, and the head tilt angle was fixed during each magnetic tape run. For each magnetic tape (total length of magnetic tape: 960 m) in the examples and comparative examples, in an environment of temperature 23°C and relative humidity 50%, a tension of 1.5 N (hereinafter referred to as "running tension") was applied in the longitudinal direction of the magnetic tape, and recording and playback were performed for 1000 passes. Then, a tension of 0.2 N was applied in the longitudinal direction of the magnetic tape, and recording and playback were performed for 1000 passes. The relative speed between the magnetic tape and the magnetic head was 8 m / s. In the magnetic head used, the arrangement order of the modules was "recording module - playback module - recording module" (total number of modules: 3). The number of magnetic head elements in each module was 32 (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 element of the recording module was a MIG (Metal-in-gap) element (gap length 0.15 μm, track width 1.0 μm), and recording was performed by setting the recording current to the optimum recording current of each magnetic tape. The playback element of the playback module was a GMR (Giant-magnetoresistive) element (element thickness 15 nm, shield interval 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 with a spectrum analyzer manufactured by Shibasoku Corporation. As the signal, a portion where the signal was sufficiently stable after the start of magnetic tape running was used. In each run, the difference between the SNR of the first pass at a running tension of 1.5 N and the SNR of the 1000th pass at a running tension of 0.2 N (SNR of the 1000th pass at a running tension of 0.2 N - SNR of the first pass at a running tension of 1.5 N) was calculated and taken as the amount of SNR decrease. The arithmetic mean of the amounts of SNR decrease obtained for the above four different head tilt angles is shown in the column of "Amount of SNR decrease" in Table 2.

[0199] [Evaluation of Magnetic Tape] (1) Vertical SFD For each magnetic tape in the examples and comparative examples, a size of 3.6 cm × 3.2 cm (area: 11.5 cm 2A sample piece of was cut out. For this sample piece, using a TM-VSM6050-SM type manufactured by Tamagawa Seisakusho as a vibrating sample magnetometer, the perpendicular SFD (measurement temperature: 25°C) was determined by the method described above.

[0200] (2) AlFeSil wear value 45° , the standard deviation of the AlFeSil wear value Magnetic tapes were taken out from each magnetic tape cartridge of the examples and comparative examples, and in an environment of a temperature of 23°C and a relative humidity of 50%, the AlFeSil wear value 45° and the standard deviation of the AlFeSil wear value were determined by the method described above.

[0201] (3) Standard deviation of the amount of curvature in the longitudinal direction of the magnetic tape Magnetic tapes were taken out from each magnetic tape cartridge 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.

[0202] (4) Tape thickness Ten tape samples (length: 5 cm) were cut out from arbitrary portions of the magnetic tapes taken out from each magnetic tape cartridge of the examples and comparative examples, and these tape samples were stacked and the thickness was measured. The thickness was measured using a digital thickness gauge of a Millimar 1240 compact amplifier and a Millimar 1301 induction probe manufactured by MARH. The value obtained by dividing the measured thickness by 10 (the thickness per tape sample) was taken as the tape thickness. For each magnetic tape, the tape thickness was 5.2 μm in all cases.

[0203] The above results are shown in Table 2 (Tables 2-1 to 2-2).

[0204]

Table 2-1

[0205]

Table 2-2

[0206] From the results shown in Table 2, it can be confirmed that the magnetic tapes of the examples in which the vertical SFD is 1.5 or less exhibited excellent electromagnetic conversion characteristics (high SNR). Furthermore, from the results shown in Table 2, the AlFeSil wear value 45° and the standard deviation of the AlFeSil wear value are both within the ranges described above. It can also be confirmed that the deterioration of the electromagnetic conversion characteristics when the magnetic tape is run at different head tilt angles is suppressed in the magnetic tapes of the examples.

Industrial Applicability

[0207] One aspect of the present invention is useful in the technical field of various data storage.

Claims

1. A magnetic tape having a non-magnetic support and a magnetic layer containing ferromagnetic powder, wherein the perpendicular direction reversal magnetic field distribution SFD of the magnetic tape is 1.5 or less, in an environment of a temperature of 23 ° C and a relative humidity of 50%, The wear value of AlFeSil on the surface of the magnetic layer measured at an inclination angle of 45° of the AlFeSil prism ４５° is 20 μm or more and 50 μm or less, and 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 is 30 μm or less, wherein the tilt angle of the AlFeSil prism is the angle formed by the longitudinal direction of the AlFeSil prism and the width direction of the magnetic tape.

2. The magnetic tape according to claim 1, wherein the standard deviation of the AlFeSil wear value is 15 μm or more and 30 μm or less.

3. The magnetic tape according to claim 1 or 2, wherein the perpendicular direction reversal magnetic field distribution SFD of the magnetic tape is 0.5 or more and 1.5 or less.

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

5. The magnetic tape according to any one of claims 1 to 4, wherein the magnetic layer contains one or more non-magnetic powders.

6. The magnetic tape according to claim 5, wherein the non-magnetic powder contains alumina powder.

7. The magnetic tape according to any one of claims 1 to 6, having a non-magnetic layer containing non-magnetic powder between the non-magnetic support and the magnetic layer.

8. The magnetic tape according to any one of claims 1 to 7, having a back coat layer containing non-magnetic powder on the surface side opposite to the surface side having the magnetic layer of the non-magnetic support.

9. The magnetic tape according to any one of claims 1 to 8, wherein the tape thickness is 5.2 μm or less.

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

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

12. Further including a magnetic head, wherein the magnetic head has a module including an element array having a plurality of magnetic head elements between a pair of servo signal reading elements, the magnetic tape device according to claim 11, wherein, during the running of the magnetic tape in the magnetic tape device, the angle θ formed by the axis of the element array with respect to the width direction of the magnetic tape is changed.

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