Magnetic tape, magnetic tape cartridge, and magnetic tape device

Abstract

To provide a magnetic tape that is excellent in running stability in recording and / or playing back data at different head inclination angles in a high temperature and high humidity environment.SOLUTION: There is provided a magnetic tape in which a tape thickness of the magnetic tape is 5.2 μm or less, in an environment of a temperature of 32°C and relative humidity of 80%, frictional force F45° on a surface of a magnetic layer with respect to an LTO8 head measured at a head inclination angle of 45° is 4 gf or more and 15 gf or less, and a standard deviation of the frictional force F on the surface of the magnetic layer with respect to the LTO8 head measured at head inclination angles of 0°, 15°, 30°, and 45° is 10 gf or less. 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] This invention relates to magnetic tape, magnetic tape cartridges, and magnetic tape devices. [Background technology]

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

[0003] [Patent Document 1] Japanese Patent Publication No. 2016-524774 [Patent Document 2] US2019 / 0164573A1 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] Data is typically recorded onto magnetic tape by running the tape through a magnetic tape drive and using a magnetic head to track the data bands of the tape, thereby recording the data on those bands. This creates data tracks on the data bands. During playback of the recorded data, the tape is run through the magnetic tape drive again, and the magnetic head tracks the data bands of the tape to read the data recorded on those bands.

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

[0006] For example, if we consider changing the head tilt angle as described above, it is desirable for the magnetic tape to have high stability when recording and / or playing back data at different head tilt angles. This is because high stability in the magnetic tape's movement can, for example, further suppress the occurrence of the phenomenon described above.

[0007] Incidentally, in recent years, magnetic tape has sometimes been used in data centers where temperature and humidity are controlled. On the other hand, data centers are required to reduce power consumption in order to lower costs. To achieve power consumption, it is desirable to relax the management conditions for the magnetic tape usage environment in data centers, or to eliminate management altogether. However, if the control conditions for the operating environment are relaxed or not controlled at all, magnetic tape may be used in environments such as high temperature and high humidity. Therefore, magnetic tape that offers excellent running stability when recording and / or playing back data at different head tilt angles in high temperature and high humidity environments is desirable.

[0008] One aspect of the present invention primarily aims to provide a magnetic tape that exhibits excellent running stability when recording and / or playing back data at different head tilt angles in a high-temperature, high-humidity environment. [Means for solving the problem]

[0009] One aspect of the present invention is as follows: [1] A magnetic tape having a non-magnetic support and a magnetic layer containing ferromagnetic powder, The tape thickness of the above magnetic tape is 5.2 μm or less. In an environment with a temperature of 32°C and a relative humidity of 80%, The frictional force F on the magnetic layer surface of an LTO (Linear Tape-Open) 8 head, measured at a head tilt angle of 45°. 45° The gf is between 4 gf and 15 gf, and A magnetic tape in which the standard deviation of the frictional force F on the magnetic layer surface for an LTO8 head, measured at head tilt angles of 0°, 15°, 30°, and 45° (hereinafter also simply referred to as "standard deviation of frictional force F" or "standard deviation of F") is 10gf or less. [2] The magnetic tape described in [1], wherein the standard deviation of F is 2gf or more and 10gf or less. [3] The magnetic tape described in [1] or [2], wherein the tape thickness is 4.0 μm or more and 5.2 μm or less. [4] The magnetic tape described in any of [1] to [3], wherein the tape thickness is 4.0 μm or more and 5.0 μm or less. [5] A magnetic tape as described in any of [1] to [4], wherein the standard deviation of the amount of curvature in the longitudinal direction of the magnetic tape (hereinafter also simply referred to as "standard deviation of curvature") is 5 mm / m or less. [6] The magnetic tape according to any one of [1] to [5], wherein the magnetic layer comprises inorganic oxide particles. [7] The magnetic tape according to [6], wherein the inorganic oxide particles are composite particles of an inorganic oxide and a polymer. [8] The magnetic layer comprises carbon black, as described in any of [1] to [5]. [9] A magnetic tape according to any one of [1] to [8], having a non-magnetic layer containing non-magnetic powder between the non-magnetic support and the magnetic layer.

[10] The magnetic tape according to [9], wherein the thickness of the non-magnetic layer is 0.1 μm or more and 0.7 μm or less.

[11] The magnetic tape according to any one of [1] to

[10] , wherein the non-magnetic support has a back coat layer containing non-magnetic powder on the surface side opposite to the surface side having the magnetic layer.

[12] The magnetic tape described in any of [1] to

[11] , wherein the vertical aspect ratio of the magnetic tape is 0.60 or greater.

[13] The magnetic tape described in any of [1] to

[12] , wherein the vertical aspect ratio of the magnetic tape is 0.65 or greater. A magnetic tape cartridge containing the magnetic tape described in any of

[14] [1] to

[13] . A magnetic tape device including a magnetic tape as described in any of

[15] [1] to

[13] .

[16] Further including a magnetic head, The above 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 described in

[15] , wherein the angle θ made between the axis of the element array and the width direction of the magnetic tape while the magnetic tape is running within the magnetic tape device is changed. [Effects of the Invention]

[0010] According to one aspect of the present invention, a magnetic tape with excellent running stability when recording and / or playing back data at different head tilt angles in a high-temperature, high-humidity environment can be provided. Furthermore, according to one aspect of the present invention, a magnetic tape cartridge and a magnetic tape device including the above-mentioned magnetic tape can be provided. [Brief explanation of the drawing]

[0011] [Figure 1] This is a schematic diagram showing an example of a magnetic head module. [Figure 2] This is an explanatory diagram illustrating the relative positional relationship between the module and the magnetic tape while the magnetic tape is running in a magnetic tape drive. [Figure 3]This is an explanatory diagram regarding the change in angle θ during magnetic tape travel. [Figure 4] This is an explanatory diagram of the amount of curvature in the longitudinal direction of a magnetic tape. [Figure 5] An example of the arrangement of data bands and servo bands is shown. [Figure 6] This shows an example of a servo pattern arrangement for an LTO (Linear Tape-Open) Ultrium format tape. [Figure 7] This is an explanatory diagram of the method for measuring the angle θ while a magnetic tape is running. [Figure 8] This is a schematic diagram showing an example of a magnetic tape drive. [Modes for carrying out the invention]

[0012] [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 tape thickness of the magnetic tape is 5.2 μm or less. Furthermore, in an environment of 32°C and 80% relative humidity, the frictional force on the magnetic layer surface of the magnetic tape with respect to the LTO8 head is measured at a head tilt angle of 45°. 45° The friction force is between 4gf and 15gf, and the standard deviation of the friction force F on the magnetic layer surface relative to the LTO8 head, measured at head tilt angles of 0°, 15°, 30°, and 45°, is 10gf or less. In this invention and specification, "magnetic layer surface" is synonymous with the magnetic layer side surface of the magnetic tape. Regarding units, "gf" represents grams-force, and 1 N (Newton) is approximately 102 gf.

[0013] <Head tilt angle> In explaining the head tilt angle mentioned above, we will first describe the LTO8 head. Furthermore, we will explain below why tilting the axial direction of the magnetic head module relative to the width direction of the magnetic tape during magnetic tape transport is thought to suppress the phenomena that occur during recording or playback as described earlier. In the present invention and this specification, "LTO8 head" refers to a magnetic head conforming to the LTO8 standard. For the measurement of the frictional force described above, a magnetic head mounted on an LTO8 drive may be removed and used, or a commercially available magnetic head for LTO drives may be used. Here, an LTO8 drive refers to a drive (magnetic tape device) conforming to the LTO8 standard. An LTO9 drive refers to a drive conforming to the LTO9 standard, and the same applies to drives of other generations. Furthermore, when measuring the frictional force F on the magnetic layer surface of the LTO8 head at head tilt angles of 0°, 15°, 30°, and 45°, a new (i.e., unused) LTO8 head shall be used for each measurement at each head tilt angle. Note that the LTO8 standard was adopted as the head for frictional force measurement considering that the LTO8 standard is a standard that can accommodate recent high-density recording, and the magnetic tape described above is not limited to that used in an LTO8 drive. Data may be recorded and / or played back on the above magnetic tape using an LTO8 drive, or using an LTO9 drive or a further next-generation drive, or using an earlier generation drive such as an LTO7 drive.

[0014] The LTO8 head has three modules, each containing an element array with multiple magnetic head elements between a pair of servo signal reading elements. The three modules are arranged in the LTO8 head in a "recording module-playback module-recording module" configuration (total number of modules: 3).

[0015] Each module includes an element array, i.e., an array of elements, having a total of 32 magnetic head elements between a pair of servo signal reading elements. Modules having recording elements as magnetic head elements are recording modules for recording data onto magnetic tape. Modules having playback elements as magnetic head elements are playback modules for reproducing data recorded on magnetic tape. In the LTO8 head, the three modules are arranged so that the axes of the element arrays of each module are oriented parallel to each other. Such "parallel" does not necessarily mean parallel in the strict sense, but includes a range of error that is normally acceptable in the art to which this invention belongs. The range of error can mean, for example, a range of less than ±10° of strict parallelism.

[0016] The head tilt angle used in friction force measurement shall be the head tilt angle in the playback module of the LTO8 head.

[0017] In each element array, a pair of servo signal reading elements and a plurality of magnetic head elements (i.e., recording elements or playback elements) are arranged linearly and spaced apart. Here, "arranged linearly" means that each magnetic head element is arranged on a straight line connecting the center of one servo signal reading element and the center of the other servo signal reading element. Furthermore, in this invention and specification, "axis of the element array" means the straight line connecting the center of one servo signal reading element and the center of the other servo signal reading element.

[0018] Next, the module configuration and other details will be further explained with reference to the drawings. However, the configurations shown in the drawings are illustrative and do not limit the present invention.

[0019] Figure 1 is a schematic diagram showing an example of a magnetic head module. The module shown in Figure 1 has multiple magnetic head elements between a pair of servo signal reading elements (servo signal reading elements 1 and 2). Magnetic head elements are also called "channels." "Ch" in the figure is an abbreviation for Channel. The module shown in Figure 1 has a total of 32 magnetic head elements, from Ch0 to Ch31. The regeneration module for an LTO8 head has a total of 32 regeneration elements, from Ch0 to Ch31.

[0020] In Figure 1, "L" represents the distance between a pair of servo signal reading elements, that is, the distance between one servo signal reading element and the other. In the module shown in Figure 1, "L" represents the distance between servo signal reading element 1 and servo signal reading element 2. More specifically, it is the distance between the center of servo signal reading element 1 and the center of servo signal reading element 2. This distance can be measured, for example, by an optical microscope.

[0021] Figure 2 is an explanatory diagram of the relative positional relationship between the module and the magnetic tape during magnetic tape movement in a magnetic tape device. In Figure 2, dotted line A indicates the width direction of the magnetic tape. Dotted line B indicates the axis of the element array. Angle θ can be said to be the head tilt angle during magnetic tape movement, and is the angle between dotted line A and dotted line B. When angle θ is 0° during magnetic tape movement, the distance in the magnetic tape width direction 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". In contrast, when angle θ is greater than 0°, the effective distance between servo signal reading elements is "Lcosθ", and Lcosθ is smaller than L. That is, "Lcosθ <L」である。

[0022] As mentioned earlier, during recording or playback, if the magnetic head used to record or play back data is misaligned from the intended track position due to deformation of the magnetic tape's width, phenomena such as overwriting of recorded data or playback failures may occur. For example, if the width of the magnetic tape shrinks or expands, the magnetic head element that should record or play back at the intended track position may end up recording or playing back at a different track position. Also, if the width of the magnetic tape expands, the effective distance between servo signal reading elements may become shorter than the distance between two adjacent servo bands separated by a data band (also referred to as "servo band spacing" or "servo band interval"; more specifically, the distance between the two servo bands in the width direction of the magnetic tape), which may result in data not being recorded or played back in areas close to the edge of the magnetic tape. In contrast, when the element array is tilted at an angle θ greater than 0°, as explained earlier, the effective distance between 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., contraction or expansion) in the width direction of the magnetic tape, it becomes possible to bring the effective distance between servo signal reading elements closer to or matching the spacing of the servo bands. This prevents or reduces the frequency of phenomena such as overwriting of recorded data or playback failures that occur when the magnetic head used to record or play back data is misaligned from the target track position due to width deformation of the magnetic tape during recording or playback.

[0023] Figure 3 is an explanatory diagram regarding the change in angle θ during magnetic tape travel. The angle θ at the start of the journey is θ initial This can be set to, for example, 0° or greater than or equal to 0°. In Figure 3, the central diagram shows the state of the module at the start of operation. In Figure 3, the right-hand figure shows the angle θ as θ initial An angle θ is a larger angle. cshows the state of the module when [the angle is set as such]. The effective distance Lcosθ between the servo signal reading elements c is a value smaller than Lcosθ at the start of magnetic tape running. When the width of the magnetic tape contracts during magnetic tape running, it is preferable to perform such angle adjustment. initial On the other hand, in FIG. 3, the left figure shows the state of the module when the angle θ is set as an angle θ smaller than [a certain angle]. The effective distance Lcosθ between the servo signal reading elements initial is a value larger than Lcosθ at the start of magnetic tape running. When the width of the magnetic tape expands during magnetic tape running, it is preferable to perform such angle adjustment. e shows the state of the module when [the angle is set as such]. The effective distance Lcosθ between the servo signal reading elements e is a value larger than Lcosθ at the start of magnetic tape running. When the width of the magnetic tape expands during magnetic tape running, it is preferable to perform such angle adjustment. initial As described above, changing the head tilt angle during magnetic tape running can contribute to preventing or reducing the occurrence frequency of phenomena such as overwriting of recorded data and playback failure that may occur when recording or playing back data due to the magnetic head deviating from the target track position due to the width deformation of the magnetic tape during recording or playback.

[0024] On the other hand, recording data on the magnetic tape and playing back 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 when the head tilt angle changes during such sliding, the contact state between the magnetic head and the magnetic layer surface may change, which may be a factor in reducing the running stability. Specifically, if the contact state between the magnetic layer surface of the magnetic tape and the magnetic head (for example, the contact state between the portion near the edge of the module of the magnetic head and the magnetic layer surface) changes significantly due to the difference in the head tilt angle, the running stability will decrease, and the inventor推测 that such a decrease in running stability may become more prominent in a high-temperature and high-humidity environment. ​Based on the above inference, the inventors conducted extensive research. As a result, regarding the frictional characteristics of the magnetic tape, the frictional force F on the magnetic layer surface relative to the LTO8 head, measured at a head tilt angle of 45° in an environment of 32°C and 80% relative humidity, was determined. 45° Furthermore, by setting the standard deviation of the frictional force F on the magnetic layer surface for the LTO8 head, measured at head tilt angles of 0°, 15°, 30°, and 45°, respectively, to the ranges described above, it has been newly discovered that it is possible to improve the running stability when recording and / or playing back data at different head tilt angles in high-temperature and high-humidity environments. The temperature and humidity of the measurement environment are adopted as exemplary values ​​for a high-temperature and high-humidity environment. Therefore, the environment in which data is recorded on the magnetic tape and recorded data is played back is not limited to the above temperature and humidity environment. The head tilt angle used when measuring the frictional force is also adopted as an exemplary value for an angle that can be used when recording and / or playing back data by changing the head tilt angle during magnetic tape running. Therefore, the head tilt angle when data is recorded on the magnetic tape and recorded data is played back is not limited to the above angle. Moreover, the present invention is not limited by the inventors' inferences described herein. In the following, the running stability when recording and / or playing back data by changing the head tilt angle during magnetic tape travel in a high-temperature, high-humidity environment will also be simply referred to as "running stability." A high-temperature, high-humidity environment can be, for example, an environment with a temperature of approximately 30 to 50°C. The humidity in that environment can be, for example, approximately 70 to 100% as relative humidity. In this invention and specification, the temperature and humidity described for the environment refer to the ambient temperature and relative humidity of that environment.

[0025] In the present invention and this specification, the measurement of frictional force at head tilt angles of 0°, 15°, 30°, and 45° shall be performed in an environment with a temperature of 32°C and a relative humidity of 80% by the following method. Furthermore, the head tilt angle for friction force measurement refers to the angle formed by the axis of the element array of the LTO8 head's regeneration module with the direction perpendicular to the sliding direction during the first forward stroke of the following 100 reciprocating slides. This angle is the angle θ formed by A and B in Figure 2, where A is read as the direction perpendicular to the sliding direction. The head tilt angle is fixed during the 100 reciprocating slides. The magnetic tape to be measured is placed on two cylindrical guide rolls, each 1 inch in diameter (1 inch = 2.54 cm), positioned parallel to each other and spaced apart, so that the magnetic layer surface is in contact with them. In a randomly selected portion of the magnetic tape, the magnetic layer surface of the tape is slid against the LTO8 head at head tilt angles of 0°, 15°, 30°, or 45°, and the resistance force generated during sliding is detected using a strain gauge. The back-and-forth sliding motion is performed 100 times. For the measurement conditions, the wrap angle θ is 6°, and the sliding speed is 30 mm / second. The tension applied to the longitudinal direction of the magnetic tape during sliding is 0.55 N. The sliding distance for both the forward and return strokes is 5 cm. The kinetic friction force during the 100th forward stroke is defined as the friction force at each head tilt angle. During the above measurement, one end of the magnetic tape in the longitudinal direction is connected to the strain gauge, and a tension of 0.20 N is applied to the other end. Let T0 (in N) be the tension applied here, and T (in N) be the resistance force detected by the strain gauge. The friction force F is calculated using the following formula. That is, here the friction force F is calculated with T0 = 0.20. The friction force F is measured at the four head tilt angles described above in any order, on different parts of the magnetic tape being measured. In addition, before each measurement, the magnetic tape being measured is left on the guide roll as described above for 24 hours or more to allow it to acclimate to the measurement environment. The standard deviation (i.e., the positive square root of the variance) is calculated from the friction force F values ​​at the four head tilt angles described above.

[0026]

number

[0027] <Frictional force F45° , Standard deviation of frictional force F > Regarding the frictional characteristics of the magnetic tape described above, from the viewpoint of improving running stability when recording and / or playing back data at different head tilt angles in a high-temperature, high-humidity environment, the frictional force F 45° The friction force F is between 4gf and 15gf. From the perspective of further improving driving stability, 45° The frictional force F is preferably 14 gf or less, more preferably 13 gf or less, even more preferably 12 gf or less, and even more preferably 11 gf or less. 45° The pressure is 4gf or higher, and from the viewpoint of further improving driving stability, it is preferably 5gf or higher. The standard deviation of the frictional force F on the magnetic layer surface for the LTO8 head, measured at head tilt angles of 0°, 15°, 30°, and 45°, respectively, is preferably 10gf or less, more preferably 9gf or less, more preferably 8gf or less, even more preferably 7gf or less, even more preferably 6gf or less, even more preferably 5gf or less, and even more preferably 4gf or less, from the viewpoint of improving running stability when recording and / or playing back at different head tilt angles in a high-temperature, high-humidity environment. The above standard deviation can be, for example, 0gf or more, greater than 0gf, 1gf or more, or 2gf or more. A smaller value of the above standard deviation is preferable from the viewpoint of further improving running stability. The frictional properties of the magnetic tape described above can be adjusted, for example, by the type of components used to create the magnetic layer. Further details on this will be discussed later.

[0028] <Tape thickness> Regarding the tape thickness (total thickness) of magnetic tape, with the enormous increase in the amount of information in recent years, there is a demand for increased recording capacity, i.e., higher capacity, in magnetic tape. From the viewpoint of achieving higher capacity, the tape thickness of the above-mentioned magnetic tape is 5.2 μm or less. By reducing the tape thickness of the magnetic tape, for example, the length of magnetic tape that can be accommodated in one magnetic tape cartridge can be increased, thereby achieving higher capacity. From the viewpoint of further increasing capacity, the tape thickness of the above-mentioned magnetic tape is preferably 5.0 μm or less, and more preferably 4.8 μm or less. Furthermore, from the viewpoint of ease of handling, the tape thickness of the magnetic tape is preferably 3.0 μm or more, more preferably 3.5 μm or more, and even more preferably 4.0 μm or more.

[0029] In the present invention and this specification, the tape thickness of a magnetic tape shall be measured by the following method. Ten tape samples (e.g., 5-10 cm in length) are cut from any part of the magnetic tape, and the thickness of these tape samples is measured by stacking them. The measured thickness is divided by 10 to obtain the value obtained (thickness per tape sample), which is defined 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.

[0030] <Standard deviation of curvature> Next, we will explain the standard deviation of the curvature. In the present invention and this specification, the amount of curvature in the longitudinal direction of a magnetic tape is a value determined by the following method in an environment with an ambient temperature of 23°C and a relative humidity of 50%. Magnetic tapes are usually distributed in magnetic tape cartridges. The magnetic tape to be measured is a magnetic tape removed from an unused magnetic tape cartridge that is not installed in a magnetic tape device. Figure 4 is an explanatory diagram of the amount of curvature in the longitudinal direction of the magnetic tape. A tape sample 100m long is cut from a randomly selected section of the magnetic tape to be measured. One end of this tape sample is defined as the 0m position, and the position Dm (D meters) away from this end in the longitudinal direction toward the other end is defined as the Dm position. Therefore, the position 10m away in the longitudinal direction is the 10m position, the position 20m away is the 20m position, and so on, with the positions at 10m intervals being determined sequentially: 30m, 40m, 50m, 60m, 70m, 80m, 90m, and 100m. Cut a tape sample that is 1 meter long, from the 0m position to the 1m position. This tape sample will be used to measure the amount of curvature at the 0m position. Cut a 1-meter length of tape sample from the 10-meter mark to the 11-meter mark. This tape sample will be used to measure the amount of curvature at the 10-meter mark. Cut a 1-meter length of tape sample from the 20-meter mark to the 21-meter mark. This tape sample will be used to measure the amount of curvature at the 20-meter mark. Cut a 1-meter length of tape sample from the 30m mark to the 31m mark. This tape sample will be used to measure the amount of curvature at the 30m mark. Cut a 1-meter length of tape sample from the 40m mark to the 41m mark. This tape sample will be used to measure the amount of curvature at the 40m mark. Cut a 1-meter length of tape sample from the 50m mark to the 51m mark. This tape sample will be used to measure the amount of curvature at the 50m mark. Cut a 1-meter length of tape sample from the 60m mark to the 61m mark. This tape sample will be used to measure the amount of curvature at the 60m mark. Cut a 1-meter length of tape sample from the 70m mark to the 71m mark. This tape sample will be used to measure the amount of curvature at the 70m mark. Cut a 1-meter length of tape sample from the 80m mark to the 81m mark. This tape sample will be used to measure the amount of curvature at the 80m mark. Cut a 1-meter length of tape sample from the 90m mark to the 91m mark. This tape sample will be used to measure the amount of curvature at the 90m mark. A 1-meter length tape sample is cut from the 99m mark to the 100m mark. This tape sample will be used to measure the amount of curvature at the 100m mark. Each tape sample at a given location is positioned with its longitudinal direction vertical, and its upper end is held by a gripping member (such as a clip). It is then suspended for 24 hours ± 4 hours in a tension-free state. After that, the following measurements are taken within 1 hour. As shown in Figure 4, the tape sample is placed on a plane in a tension-free state. The tape sample may be placed on the plane with the magnetic layer side facing upwards, or with the other side facing upwards. In Figure 4, S represents the tape sample, and W represents the width direction of the tape sample. Using an optical microscope, the distance L1 (in mm) is measured in the longitudinal direction of the tape sample S, which is the shortest distance between the imaginary line 54 connecting the two ends 52 and 53 of the tape sample S and the maximum curvature 55. Figure 4 shows an example where the tape is curved upwards on the plane of the paper. The distance L1 (mm) is measured similarly when the tape is curved downwards. Regardless of which side it is curved in, the distance L1 is displayed as a positive value. If no curvature is observed in the longitudinal direction, L1 is set to 0 (zero) mm. Thus, the standard deviation (i.e., the positive square root of the variance) of the curvature L1 measured at a total of 11 positions from 0m to 100m is taken as the standard deviation (unit: mm / m) of the curvature in the longitudinal direction of the magnetic tape being measured.

[0031] In the above-mentioned magnetic tape, the standard deviation of the curvature amount determined by the above-mentioned method can be, for example, 7 mm / m or less, 6 mm / m or less, and from the viewpoint of further improving running stability, it is preferably 5 mm / m or less, more preferably 4 mm / m or less, and even more preferably 3 mm / m or less. The standard deviation of the curvature amount of the above-mentioned magnetic tape can be, for example, 0 mm / m or more, greater than 0 mm / m, 1 mm / m or more, or 2 mm / m or more. A small value for the standard deviation of the curvature amount is preferable from the viewpoint of further improving running stability. The standard deviation of the curvature can be controlled by adjusting the manufacturing conditions in the magnetic tape manufacturing process. Further details on this will be discussed later.

[0032] The magnetic tape described above will be explained in more detail below.

[0033] <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. Using a ferromagnetic powder with a small average particle size is preferable from the viewpoint of improving recording density. From this viewpoint, the average particle size of the ferromagnetic powder is preferably 50 nm or less, more preferably 45 nm or less, even more preferably 40 nm or less, even more preferably 35 nm or less, even more preferably 30 nm or less, even more preferably 25 nm or less, and even more preferably 20 nm or less. On the other hand, from the viewpoint of magnetization stability, the average particle size of the ferromagnetic powder is preferably 5 nm or more, more preferably 8 nm or more, even more preferably 10 nm or more, even more preferably 15 nm or more, and even more preferably 20 nm or more.

[0034] Hexagonal ferrite powder A preferred example of ferromagnetic powder is hexagonal ferrite powder. For details on hexagonal ferrite powder, see, for example, paragraphs 0012 to 0030 of Japanese Patent Publication No. 2011-225417, paragraphs 0134 to 0136 of Japanese Patent Publication No. 2011-216149, paragraphs 0013 to 0030 of Japanese Patent Publication No. 2012-204726, and paragraphs 0029 to 0084 of Japanese Patent Publication No. 2015-127985.

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

[0036] Below, we will describe hexagonal strontium ferrite powder, a form of hexagonal ferrite powder, in more detail.

[0037] The activation volume of the hexagonal strontium ferrite powder is preferably 800 to 1600 nm. 3 The activation volume is within the range described above. Finely milled hexagonal strontium ferrite powder exhibiting an activation volume within this range is suitable for fabricating magnetic tapes that exhibit excellent electromagnetic conversion properties. The activation volume of the hexagonal strontium ferrite powder is preferably 800 nm. 3 That's all, for example, 850nm 3 It can also be the above. Furthermore, from the viewpoint of further improving electromagnetic conversion characteristics, the activation volume of hexagonal strontium ferrite powder is 1500 nm. 3 The following is more preferable: 1400nm 3 It is even more preferable that the following occur: 1300 nm 3 It is even more preferable that the following conditions be met: 1200 nm 3 It is even more preferable that the following conditions be met: 1100 nm 3 It is even more preferable that the following conditions be met. The same applies to the activation volume of the hexagonal barium ferrite powder.

[0038] "Activation volume" is the unit of magnetization reversal and is an indicator of the magnetic size of a particle. The activation volume and the anisotropy constant Ku described herein and below are values ​​obtained from the following relationship between Hc and activation volume V, measured using a vibrating sample type magnetometer at magnetic field sweep speeds of 3 minutes and 30 minutes in the coercivity Hc measurement section (measurement temperature: 23℃±1℃). Regarding the unit of the anisotropy constant Ku, 1erg / cc = 1.0 × 10⁻⁶ -1 J / m 3 That is the case. Hc=2Ku / Ms{1-[(kT / KuV)ln(At / 0.693)] 1 / 2} [In the above formula, Ku: anisotropy constant (unit: J / m 3 ), Ms: Saturation magnetization (unit: kA / m), k: Boltzmann constant, T: Absolute temperature (unit: K), V: Activation volume (unit: cm) 3 ), A: Spin precession frequency (unit: s) -1 ), t: magnetic field reversal time (unit: s)]

[0039] As an indicator of reducing thermal fluctuations, or in other words, improving thermal stability, the anisotropy constant Ku can be cited. The hexagonal strontium ferrite powder is preferably 1.8 × 10⁻⁶ 5 J / m 3 It can have a Ku of the above, and more preferably 2.0 × 10 5 J / m 3 It can have a Ku content of the above. Also, the Ku content of hexagonal strontium ferrite powder is, for example, 2.5 × 10⁻⁶. 5 J / m 3 The following values ​​are possible. However, since a higher Ku value is preferable as it indicates higher thermal stability, the values ​​are not limited to those exemplified above.

[0040] Hexagonal strontium ferrite powder may or may not contain rare earth atoms. When hexagonal strontium ferrite powder contains rare earth atoms, it is preferable that the rare earth atoms are present at a concentration of 0.5 to 5.0 atomic percent (bulk concentration) per 100 atomic percent of iron atoms. In one embodiment, hexagonal strontium ferrite powder containing rare earth atoms may exhibit a segregation of rare earth atoms in the surface layer. In the present invention and this specification, "rare earth atom surface layer segregation" means that the rare earth atom content relative to 100% of iron atoms in a solution obtained by partially dissolving hexagonal strontium ferrite powder with acid (hereinafter referred to as "rare earth atom surface layer content" or simply "surface layer content" with respect to rare earth atoms) is different from the rare earth atom content relative to 100% of iron atoms in a solution obtained by completely dissolving hexagonal strontium ferrite powder with acid (hereinafter referred to as "rare earth atom bulk content" or simply "bulk content" with respect to rare earth atoms), Rare earth atom surface content / Rare earth atom bulk content > 1.0 This means that the ratio is satisfied. The rare earth atom content of hexagonal strontium ferrite powder described later is synonymous with the rare earth atom bulk content. In contrast, partial dissolution using acid dissolves the surface layer of the particles constituting the hexagonal strontium ferrite powder, so the rare earth atom content in the solution obtained by partial dissolution is the rare earth atom content in the surface layer of the particles constituting the hexagonal strontium ferrite powder. When the rare earth atom surface layer content satisfies the ratio "rare earth atom surface layer content / rare earth atom bulk content > 1.0", it means that in the particles constituting the hexagonal strontium ferrite powder, rare earth atoms are concentrated in the surface layer (i.e., there are more of them in the surface layer than in the interior). In this invention and specification, the surface layer means a part of the region extending from the surface to the interior of the particles constituting the hexagonal strontium ferrite powder.

[0041] When hexagonal strontium ferrite powder contains rare earth atoms, the rare earth atom content (bulk content) is preferably in the range of 0.5 to 5.0 atomic percent relative to 100 atomic percent of iron atoms. It is believed that containing rare earth atoms at the bulk content within the above range, and having the rare earth atoms unevenly distributed on the surface of the particles constituting the hexagonal strontium ferrite powder, contributes to suppressing the decrease in regeneration output during repeated regeneration. This is presumed to be because the anisotropy constant Ku can be increased by containing rare earth atoms at the bulk content within the above range, and having the rare earth atoms unevenly distributed on the surface of the particles constituting the hexagonal strontium ferrite powder. The higher the value of the anisotropy constant Ku, the more it is possible to suppress the occurrence of a phenomenon called thermal fluctuation (in other words, to improve thermal stability). By suppressing the occurrence of thermal fluctuation, the decrease in regeneration output during repeated regeneration can be suppressed. It is speculated that the uneven distribution of rare earth atoms on the surface of hexagonal strontium ferrite powder particles contributes to stabilizing the spin of iron (Fe) sites within the crystal lattice of the surface layer, thereby increasing the anisotropy constant Ku. Furthermore, it is presumed that using hexagonal strontium ferrite powder with a rare-earth atom uneven distribution on the surface as the ferromagnetic powder for the magnetic layer contributes to suppressing wear on the magnetic layer surface due to sliding with the magnetic head. In other words, it is presumed that hexagonal strontium ferrite powder with a rare-earth atom uneven distribution on the surface may also contribute to improving the running durability of the magnetic tape. This is presumed to be because the uneven distribution of rare-earth atoms on the surface of the particles constituting the hexagonal strontium ferrite powder contributes to improved interaction between the particle surface and organic substances (e.g., binders and / or additives) contained in the magnetic layer, resulting in improved strength of the magnetic layer. From the viewpoint of suppressing the decrease in regeneration output during repeated regeneration and / or further improving running durability, the rare earth atom content (bulk content) is more preferably in the range of 0.5 to 4.5 atomic percent, even more preferably in the range of 1.0 to 4.5 atomic percent, and even more preferably in the range of 1.5 to 4.5 atomic percent.

[0042] The bulk content mentioned above is the content obtained by completely dissolving the hexagonal strontium ferrite powder. In this invention and specification, unless otherwise specified, the content of atoms refers to the bulk content obtained by completely dissolving the hexagonal strontium ferrite powder. The hexagonal strontium ferrite powder containing rare earth atoms may contain only one type of rare earth atom, or it may contain two or more types of rare earth atoms. When two or more types of rare earth atoms are included, the bulk content mentioned above is determined for the sum of the two or more types of rare earth atoms. This also applies to other components in this invention and specification. That is, unless otherwise specified, one type of component may be used, or two or more types may be used. When two or more types are used, the content or content refers to the sum of the two or more types.

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

[0044] In hexagonal strontium ferrite powder having a rare-earth atom surface segregation, the rare-earth atoms only need to be segregated in the surface layer of the particles constituting the hexagonal strontium ferrite powder, and the degree of segregation is not limited. For example, in hexagonal strontium ferrite powder having a rare-earth atom surface segregation, the ratio of the rare-earth atom surface content obtained by partial dissolution under the dissolution conditions described later to the rare-earth atom bulk content obtained by total dissolution under the dissolution conditions described later, "surface content / bulk content," is greater than 1.0 and can be 1.5 or greater. A "surface content / bulk content" greater than 1.0 means that in the particles constituting the hexagonal strontium ferrite powder, rare-earth atoms are segregated in the surface layer (i.e., there are more of them in the surface layer than in the interior). Furthermore, the ratio of the surface content of rare earth atoms obtained by partial dissolution under the dissolution conditions described later to the bulk content of rare earth atoms obtained by total dissolution under the dissolution conditions described later, "surface content / bulk content," can be, for example, 10.0 or less, 9.0 or less, 8.0 or less, 7.0 or less, 6.0 or less, 5.0 or less, or 4.0 or less. However, in hexagonal strontium ferrite powder having a rare earth atom surface distribution bias, the rare earth atoms only need to be biased towards the surface of the particles constituting the hexagonal strontium ferrite powder, and the above "surface content / bulk content" is not limited to the upper or lower limits exemplified.

[0045] The partial and total dissolution of hexagonal strontium ferrite powder is described below. For hexagonal strontium ferrite powder existing as a powder, the sample powders to be partially and completely dissolved are taken from the same lot of powder. On the other hand, for hexagonal strontium ferrite powder contained in the magnetic layer of a magnetic tape, a portion of the hexagonal strontium ferrite powder extracted from the magnetic layer is subjected to partial dissolution, and another portion is subjected to total dissolution. The extraction of hexagonal strontium ferrite powder from the magnetic layer can be carried out, for example, by the method described in paragraph 0032 of Japanese Patent Application Publication No. 2015-91747. Partial dissolution, as described above, refers to a state where the hexagonal strontium ferrite powder is dissolved to the extent that residual particles can be visually confirmed in the liquid at the end of the dissolution process. For example, partial dissolution can dissolve 10 to 20% by mass of the particles constituting the hexagonal strontium ferrite powder, with the total particles being 100% by mass. On the other hand, total dissolution, as described above, refers to a state where the hexagonal strontium ferrite powder is dissolved to the extent that no residual particles can be visually confirmed in the liquid at the end of the dissolution process. The above-mentioned partial dissolution and surface layer content measurement are performed, for example, by the following method. However, the dissolution conditions such as the amount of sample powder described below are examples only, and any dissolution conditions that enable partial and total dissolution can be arbitrarily adopted. A container (e.g., 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 resulting solution is filtered through a 0.1 μm membrane filter. Elemental analysis of the resulting filtrate is performed using an inductively coupled plasma (ICP) analyzer. In this way, the surface content of rare earth atoms relative to 100% iron atoms can be determined. If multiple types of rare earth atoms are detected by elemental analysis, the total content of all rare earth atoms is taken as the surface content. This is also the case when measuring bulk content. On the other hand, the measurement of total dissolution and bulk content is performed, for example, by the following method. A container (e.g., a beaker) containing 12 mg of sample powder and 10 mL of 4 mol / L hydrochloric acid is held on a hot plate at a set temperature of 80°C for 3 hours. Afterward, the bulk content relative to 100 atomic percent of iron can be determined by performing the same procedure as described above for partial dissolution and surface layer content measurement.

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

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

[0048] The known crystal structures of hexagonal ferrites include magnetoplumbite (also called "M-type"), W-type, Y-type, and Z-type. Hexagonal strontium ferrite powder may have any of these crystal structures. The crystal structure can be confirmed by X-ray diffraction analysis. Hexagonal strontium ferrite powder may show a single crystal structure or two or more crystal structures by X-ray diffraction analysis. For example, in one form, hexagonal strontium ferrite powder may show only the M-type crystal structure by X-ray diffraction analysis. For example, M-type hexagonal ferrite is AFe 12 O 19It is represented by the following compositional formula: Here, A represents a divalent metal atom, and if the hexagonal strontium ferrite powder is of type M, A is either only a strontium atom (Sr), or if A contains multiple divalent metal atoms, then as described above, strontium atoms (Sr) make up the largest proportion on an atomic percentage basis. The divalent metal atom content of 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 and oxygen atom content. Hexagonal strontium ferrite powder contains at least iron atoms, strontium atoms and oxygen atoms, and may also contain rare earth atoms. Furthermore, hexagonal strontium ferrite powder may or may not contain atoms other than these atoms. As an example, hexagonal strontium ferrite powder may contain aluminum atoms (Al). The aluminum atom content can be, for example, 0.5 to 10.0 atomic percent relative to 100 atomic percent of iron atoms. From the viewpoint of suppressing a decrease in regeneration output during repeated regeneration, the hexagonal strontium ferrite powder preferably contains iron atoms, strontium atoms, oxygen atoms, and rare earth atoms, and the content of atoms other than these atoms is preferably 10.0 atomic percent or less, more preferably in the range of 0 to 5.0 atomic percent, and may even be 0 atomic percent, relative to 100 atomic percent of iron atoms. That is, in one embodiment, the hexagonal strontium ferrite powder does not need to contain atoms other than iron atoms, strontium atoms, oxygen atoms, and rare earth atoms. The above content expressed in atomic percent is obtained by converting the content of each atom (unit: mass%) obtained by completely dissolving the hexagonal strontium ferrite powder into an atomic percent value using the atomic weight of each atom. Furthermore, in the present invention and this specification, "does not contain" for a certain atom means that the content measured by an ICP analyzer after complete dissolution is 0 mass%. The detection limit of an ICP analyzer is typically 0.01 ppm (parts per million) or less by mass. The term "does not contain" above is used to include the presence of substances in amounts below the detection limit of the ICP analyzer.Hexagonal strontium ferrite powder can, in one form, be bismuth-free (Bi).

[0049] metal powder A preferred specific example of ferromagnetic powder is ferromagnetic metal powder. For details on ferromagnetic metal powder, see, for example, paragraphs 0137-0141 of Japanese Patent Publication No. 2011-216149 and paragraphs 0009-0023 of Japanese Patent Publication No. 2005-251351.

[0050] ε-Iron oxide powder A preferred specific example of a ferromagnetic powder is ε-iron oxide powder. In the present invention and this specification, "ε-iron oxide powder" refers to a ferromagnetic powder in which the crystalline structure of ε-iron oxide is detected as the main phase by X-ray diffraction analysis. For example, if the highest intensity diffraction peak in the X-ray diffraction spectrum obtained by X-ray diffraction analysis is attributed to the crystalline structure of ε-iron oxide, it is determined that the crystalline structure of ε-iron oxide has been detected as the main phase. Methods for producing ε-iron oxide powder include methods from goethite and the reverse micelle method. All of the above production methods are publicly known. Furthermore, for methods for producing ε-iron oxide powder in which some of the Fe is substituted with substitution atoms such as Ga, Co, Ti, Al, and Rh, see, 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 ferromagnetic powder in the magnetic layer of the magnetic tape described above is not limited to the method described herein.

[0051] The activation volume of ε-iron oxide powder is preferably 300 to 1500 nm. 3 The activation volume is within the range described above. Micronized ε-iron oxide powder exhibiting an activation volume within the above range is suitable for the production of magnetic tapes that exhibit excellent electromagnetic conversion properties. The activation volume of the ε-iron oxide powder is preferably 300 nm. 3 That's all, for example, 500nm3 It can also be the above. Furthermore, from the viewpoint of further improving electromagnetic conversion characteristics, the activation volume of ε-iron oxide powder is 1400 nm. 3 The following is more preferable: 1300nm 3 It is even more preferable that the following occur: 1200 nm 3 It is even more preferable that the following conditions be met: 1100 nm 3 The following is even more preferable.

[0052] The anisotropy constant Ku can be cited as an indicator of the reduction of thermal fluctuations, or in other words, the improvement of thermal stability. The ε-iron oxide powder is preferably 3.0 × 10⁻⁶ 4 J / m 3 It can have a Ku of the above, and more preferably 8.0 × 10 4 J / m 3 It can have the above amount of Ku. Also, the amount of Ku in ε-iron oxide powder is, for example, 3.0 × 10⁻⁶. 5 J / m 3 The following values ​​are possible. However, a higher Ku value indicates higher thermal stability, which is preferable, so the values ​​are not limited to those exemplified above.

[0053] From the perspective of increasing the playback output when reproducing data recorded on magnetic tape, it is desirable for the mass magnetization σs of the ferromagnetic powder contained in the magnetic tape to be high. In this regard, in one embodiment, the σs of ε-iron oxide powder is 8 A·m 2 It can be 12 A·m or more / kg. 2 It can also be more than / kg. On the other hand, the σs of ε-iron oxide powder is 40 A·m from the viewpoint of noise reduction. 2 Preferably less than / kg, 35A·m 2 It is more preferable that the amount be less than or equal to / kg.

[0054] In the present invention and this specification, unless otherwise specified, the average particle size of various powders such as ferromagnetic powders shall be the value measured using a transmission electron microscope by the following method. The powder is photographed using a transmission electron microscope at a magnification of 100,000x, and the resulting image is printed on photographic paper or displayed on a screen to obtain a total magnification of 500,000x, thereby obtaining a photograph of the particles that make up the powder. From the obtained photographs of the particles, the target particles are selected, and their contours are traced with a digitizer to measure the size of the particles (primary particles). Primary particles are defined as independent particles that do not aggregate. The above measurements are performed on 500 randomly selected particles. The arithmetic mean of the particle sizes of these 500 particles is taken as the average particle size of the powder. As the transmission electron microscope, for example, a Hitachi H-9000 transmission electron microscope can be used. The particle size can be measured using known image analysis software, for example, Carl Zeiss KS-400 image analysis software. Unless otherwise specified, the average particle sizes shown in the examples described later are values ​​measured using a Hitachi H-9000 transmission electron microscope and Carl Zeiss KS-400 image analysis software. In the present invention and this specification, "powder" means a collection of multiple particles. For example, ferromagnetic powder means a collection of multiple ferromagnetic particles. Furthermore, a collection of multiple particles is not limited to a form in which the particles constituting the collection are in direct contact, but also includes forms in which binders, additives, etc., described later, are interposed between the particles. The word "particle" is sometimes used to refer to powder.

[0055] For example, the method described in paragraph 0015 of Japanese Patent Publication No. 2011-048878 can be used to collect sample powder from a magnetic tape for particle size measurement.

[0056] In the present invention and this specification, unless otherwise specified, the size of the particles constituting the powder (particle size) is determined by the shape of the particles observed in the above particle photograph. (1) In the case of needle-shaped, spindle-shaped, columnar (however, the height is greater than the longest diameter of the base), etc., the length of the long axis constituting the particle is expressed as the long axis length, (2) In the case of a plate or column (provided that the thickness or height is less than the longest diameter of the plate or base), it shall be expressed by the longest diameter of the plate or base. (3) If the shape is spherical, polyhedral, irregular, etc., and the major axis constituting the particle cannot be determined from the shape, it shall be represented by the equivalent diameter of a circle. The equivalent diameter of a circle refers to the diameter obtained by the circular projection method.

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

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

[0059] (Binder) The above magnetic tape can be a coated magnetic tape, and the magnetic layer may contain a binder. The binder is one or more resins. Various resins commonly used as binders for coated magnetic recording media can be used as the binder. For example, as the binder, a resin selected from 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 alkylal resin such as polyvinyl butyral can be used alone or in mixture of multiple resins. Among these, polyurethane resin, acrylic resin, cellulose resin, and vinyl chloride resin are preferred. These resins may be homopolymers or copolymers. These resins can also be used as binders in the non-magnetic layer and / or back coat layer described later. For more information on the binders, refer to paragraphs 0028 to 0031 of Japanese Patent Application Publication No. 2010-24113. The binder may also be a radiation-curable resin such as an electron beam-curable resin. For radiation-curable resins, refer to paragraphs 0044 to 0045 of Japanese Patent Publication No. 2011-048878. The average molecular weight of the resin used as a binder can be, for example, 10,000 to 200,000 as a weight-average molecular weight. The binder can be used in an amount of, for example, 1.0 to 30.0 parts by mass per 100.0 parts by mass of ferromagnetic powder.

[0060] (Hardening agent) A curing agent can also be used together with the binder. In one form, the curing agent can be a thermosetting compound, which undergoes a curing reaction (crosslinking reaction) upon heating, and in another form, it can be a photocurable compound, which undergoes a curing reaction (crosslinking reaction) upon light irradiation. During the manufacturing process of the magnetic tape, the curing reaction of the curing agent can occur, and at least a portion of it may be included in the magnetic layer in a state where it has reacted (crosslinked) with other components such as the binder. A preferred curing agent is a thermosetting compound, and polyisocyanate is preferred. For details on polyisocyanate, refer to paragraphs 0124 to 0125 of Japanese Patent Application Publication No. 2011-216149. The curing agent can be used in the magnetic layer forming composition in an amount of, for example, 0 to 80.0 parts by mass per 100.0 parts by mass of the binder, and preferably 50.0 to 80.0 parts by mass from the viewpoint of improving the strength of each layer such as the magnetic layer.

[0061] (Other ingredients) The magnetic layer may contain one or more additives as needed. Commercially available additives can be appropriately selected and used according to the desired properties. Alternatively, compounds synthesized by known methods can be used as additives. An example of an additive is the curing agent mentioned above. Other possible additives in the magnetic layer include non-magnetic fillers, lubricants, dispersants, dispersion aids, antifungal agents, antistatic agents, antioxidants, etc. Non-magnetic fillers are synonymous with non-magnetic particles or non-magnetic powders. Examples of non-magnetic fillers include non-magnetic fillers that can function as protrusion-forming agents and non-magnetic fillers that can function as abrasives. Furthermore, known additives such as various polymers described in paragraphs 0030 to 0080 of Japanese Patent Application Publication No. 2016-051493 can also be used.

[0062] As a protrusion-forming agent, which is a form of non-magnetic filler, inorganic particles, organic particles, or composite particles of inorganic and organic substances can be used. Carbon black can also be used. Examples of inorganic substances include inorganic oxides such as metal oxides, metal carbonates, metal sulfates, metal nitrides, metal carbides, and metal sulfides, with inorganic oxides being preferred. In one form, the protrusion-forming agent can be inorganic oxide-based particles. Here, "system" is used to mean "containing". One form of inorganic oxide-based particles is particles made of inorganic oxides. Another form of inorganic oxide-based particles is composite particles of inorganic oxides and organic substances, and a specific example is composite particles of inorganic oxides and polymers. For example, such particles include particles in which a polymer is bonded to the surface of inorganic oxide particles.

[0063] The average particle size of the protrusion-forming agent can be, for example, 30 to 300 nm, and preferably 40 to 200 nm. Furthermore, regarding the shape of the protrusion-forming agent, it is thought that particles closer to a perfect sphere in shape are more susceptible to changes in frictional properties due to differences in head tilt angle. This is for the following reasons: When the head tilt angle differs, the contact state between the LTO8 head and the magnetic layer surface of the magnetic tape when measuring frictional force can change, and therefore the pressure applied to the magnetic layer surface due to contact with the LTO8 head can also change. Particles closer to a perfect sphere have a smaller indentation resistance when pressure is applied, and are therefore more susceptible to changes in pressure. In contrast, particles with a shape far from a perfect sphere, such as a so-called irregular shape, tend to have a larger indentation resistance when pressure is applied, and are therefore less susceptible to changes in pressure. Also, particles with heterogeneous surfaces and low surface smoothness tend to have a larger indentation resistance when pressure is applied, and are therefore less susceptible to changes in pressure. Therefore, using a protrusion-forming agent in which the particle shape is deviated from a perfect sphere, and / or using a protrusion-forming agent in which the particle surface is heterogeneous and has low surface smoothness, results in a frictional force F 45°The inventors believe that this can contribute to keeping the standard deviation of the frictional force F within the ranges described above. In one embodiment, a so-called irregularly shaped protrusion-forming agent can also be used.

[0064] Another form of nonmagnetic filler, the abrasive, is preferably a nonmagnetic powder with a Mohs hardness greater than 8, and more preferably a nonmagnetic powder with a Mohs hardness of 9 or higher. In contrast, the Mohs hardness of the protrusion-forming agent can be, for example, 8 or less, or 7 or less. The maximum Mohs hardness is 10, which is diamond. Specifically, examples of abrasives include powders of alumina (e.g., Al2O3), silicon carbide, boron carbide (e.g., B4C), SiO2, TiC, chromium oxide (Cr2O3), cerium oxide, zirconium oxide (e.g., ZrO2), iron oxide, and diamond, with alumina powder such as α-alumina and silicon carbide powder being preferred. The average particle size of the abrasive can be, for example, in the range of 30 to 300 nm, and is preferably in the range of 50 to 200 nm.

[0065] Furthermore, from the viewpoint of enabling the protrusion-forming agent and abrasive to exhibit their functions more effectively, the content of the protrusion-forming agent in the magnetic layer is preferably 0.1 to 4.0 parts by mass, more preferably 0.3 to 3.5 parts by mass, and even more preferably 0.5 to 2.5 parts by mass, per 100.0 parts by mass of ferromagnetic powder. On the other hand, the content of the abrasive in the magnetic layer is preferably 1.0 to 20.0 parts by mass, more preferably 3.0 to 15.0 parts by mass, and even more preferably 4.0 to 10.0 parts by mass, per 100.0 parts by mass of ferromagnetic powder.

[0066] An example of an additive that can be used in a magnetic layer containing an abrasive is the dispersant described in paragraphs 0012 to 0022 of Japanese Patent Publication No. 2013-131285, which can be used as a dispersant to improve the dispersibility of the abrasive in a magnetic layer forming composition. For more information on dispersants, see paragraphs 0061 and 0071 of Japanese Patent Publication No. 2012-133837. The dispersant may also be included in the non-magnetic layer. For more information on dispersants that can be included in the non-magnetic layer, see paragraph 0061 of Japanese Patent Publication No. 2012-133837.

[0067] Furthermore, one form of additive that may be included in the magnetic layer is a compound having an ammonium salt structure of an alkyl ester anion represented by the following formula 1.

[0068] [ka]

[0069] (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, Z + (This represents an ammonium cation.)

[0070] The inventors believe that the above-mentioned 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 inventors believe that compounds having an ammonium salt structure of an alkyl ester anion represented by the above formula 1 can function as fluid lubricants. Fluid lubricants are thought to be able to impart lubrication to the magnetic layer by forming a liquid film on the surface of the magnetic layer. Friction force F 45° Furthermore, in order to control the standard deviation of the friction force F, it is presumed that it is desirable for a fluid lubricant to form a liquid film on the surface of the magnetic layer. Also, the more stably the magnetic layer surface and the LTO8 head can slide against each other during friction force measurement, the more desirable the friction force F 45°Furthermore, the standard deviation of the friction force F may become smaller. Regarding the liquid film of the fluid lubricant, from the viewpoint of enabling more stable sliding, it is desirable to use an appropriate amount of fluid lubricant forming a liquid film on the magnetic layer surface. This is because if the amount of liquid lubricant forming a liquid film on the magnetic layer surface is excessive, the magnetic layer surface and the LTO8 head will stick together, and sliding stability is likely to decrease. Also, if the amount of liquid lubricant forming a liquid film on the magnetic layer surface is excessive, it is likely that protrusions formed on the magnetic layer surface by non-magnetic fillers, for example, will be covered by the liquid film. This is also considered to be a factor that can easily reduce sliding stability. In relation to the above, the above compound contains an ammonium salt structure of an alkyl ester anion represented by Formula 1. Compounds containing such a structure are thought to be able to play an excellent role as a fluid lubricant even in relatively small amounts. Therefore, incorporating the above compound into the magnetic layer leads to improved sliding stability between the magnetic layer surface of the magnetic tape and the LTO8 head, and the frictional force F 45° It is also thought that this could contribute to controlling the standard deviation of the frictional force F.

[0071] The above compounds will be described in more detail below.

[0072] In the present invention and this specification, unless otherwise specified, the groups described may or may not have substituents. Furthermore, with respect to substituted groups, "number of carbon atoms" means the number of carbon atoms excluding the substituents, unless otherwise specified. In the present invention and this specification, examples of substituents include alkyl groups (e.g., alkyl groups having 1 to 6 carbon atoms), hydroxyl groups, alkoxy groups (e.g., alkoxy groups having 1 to 6 carbon atoms), halogen atoms (e.g., fluorine atoms, chlorine atoms, bromine atoms, etc.), cyano groups, amino groups, nitro groups, acyl groups, carboxyl groups, salts of carboxyl groups, sulfonic acid groups, salts of sulfonic acid groups, and the like.

[0073] Compounds 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, with at least a portion contained within the magnetic layer, and a portion that can move to the surface of the magnetic layer and form a liquid film when sliding with the magnetic head, etc. Furthermore, a portion can be contained in the non-magnetic layer described later, and can move to the magnetic layer and then to the surface of the magnetic layer to form a liquid film. Note that "alkyl ester anion" can also be called "alkyl carboxylate anion".

[0074] 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. A fluorinated alkyl group has a structure in which some or all of the hydrogen atoms constituting the alkyl group are substituted with fluorine atoms. The alkyl group or fluorinated alkyl group represented by R may have a linear structure, a branched structure, or a cyclic alkyl group or fluorinated alkyl group, but a linear structure is preferred. The alkyl group or fluorinated alkyl group represented by R may have substituents or be unsubstituted, but it is preferred to be unsubstituted. The alkyl group represented by R is, for example, C n H 2n+1 It can be represented by -, where n is an integer greater than or equal to 7. Also, the alkyl fluoride represented by R is, for example, C n H 2n+1 The alkyl group represented by - may have a structure in which some or all of the hydrogen atoms constituting the alkyl group are substituted with fluorine atoms. The alkyl group or fluorinated alkyl group represented by R has 7 or more carbon atoms, preferably 8 or more, more preferably 9 or more, even more preferably 10 or more, even more preferably 11 or more, even more preferably 12 or more, and even more preferably 13 or more. Furthermore, the alkyl group or fluorinated alkyl group represented by R has 20 or fewer carbon atoms, more preferably 19 or fewer, and even more preferably 18 or fewer.

[0075] In equation 1, Z +* represents an ammonium cation. The ammonium cation has, in detail, the following structure. In this invention and specification, the asterisk (*) in a formula representing a part of a compound represents the bond position between that part of the structure and adjacent atoms.

[0076] [ka]

[0077] Nitrogen cation of ammonium cation N + and the oxygen anion O in Equation 1 - These can form a salt crosslinking group, creating an ammonium salt structure of an alkyl ester anion represented by formula 1. The presence of a compound having an ammonium salt structure of an alkyl ester anion represented by formula 1 in the magnetic layer can be confirmed by analyzing the magnetic tape using X-ray photoelectron spectroscopy (ESCA: Electron Spectroscopy for Chemical Analysis), infrared spectroscopy (IR: infrared spectroscopy), etc.

[0078] In one form, Z + The ammonium cation represented by can be obtained, for example, by the nitrogen atom of a nitrogen-containing polymer becoming a cation. A nitrogen-containing polymer means a polymer that contains nitrogen atoms. In this invention and specification, the terms "polymer" and "polymer" are used to encompass both homopolymers and copolymers. Nitrogen atoms can be included in one form as atoms constituting the main chain of the polymer, and in another form as atoms constituting the side chain of the polymer.

[0079] One form of nitrogen-containing polymer is polyalkyleneimines. Polyalkyleneimines are ring-opening polymers of alkyleneimines, and are polymers having multiple repeating units represented by the following formula 2.

[0080] [ka]

[0081] In Equation 2, the nitrogen atom N that makes up the main chain is a nitrogen cation N + And so Z in equation 1 + An ammonium cation represented by [formula] can be obtained. Then, with an alkyl ester anion, it can form an ammonium salt structure, for example, as shown below.

[0082] [ka]

[0083] The following provides a more detailed explanation of Equation 2.

[0084] In formula 2, R 1 and R 2 Each of these independently represents a hydrogen atom or an alkyl group, and n1 represents an integer greater than or equal to 2.

[0085] R 1 or R 2 Examples of alkyl groups represented by include alkyl groups having 1 to 6 carbon atoms, preferably alkyl groups having 1 to 3 carbon atoms, more preferably a methyl group or an ethyl group, and even more preferably a methyl group. 1 or R 2 The alkyl group represented by is preferably an unsubstituted alkyl group. 1 and R 2The combinations include a form in which one is a hydrogen atom and the other is an alkyl group, a form in which both are hydrogen atoms, and a form in which both are alkyl groups (identical or different alkyl groups), with the form in which both are hydrogen atoms being preferred. As an alkylene imine that yields a polyalkylene imine, the structure with the fewest number of carbon atoms constituting the ring is ethyleneimine, and the number of carbon atoms in the main chain of the alkylene imine (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 polyalkylene imine may be a homopolymer containing only the same structure as the repeating structure represented by formula 2, or it 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 polyalkylene imine that can be used to form a compound having an ammonium salt structure of an alkyl ester anion represented by formula 1 can be, for example, 200 or more, preferably 300 or more, and more preferably 400 or more. Furthermore, the number-average molecular weight of the polyalkyleneimine can be, for example, 10,000 or less, preferably 5,000 or less, and more preferably 2,000 or less.

[0086] In the present invention and this specification, average molecular weight (weight-average molecular weight and number-average molecular weight) refers to the value obtained by measuring by gel permeation chromatography (GPC) and converting it to standard polystyrene equivalent. Unless otherwise specified, the average molecular weights shown in the examples described below are values ​​obtained by converting the values ​​measured using GPC under the following measurement conditions to standard polystyrene equivalent (polystyrene equivalent value). GPC device: HLC-8220 (manufactured by Tosoh Corporation) Guard Column: TSKguardcolumn Super HZM-H Columns: TSKgel Super HZ 2000, TSKgel Super HZ 4000, TSKgel Super HZ-M (manufactured by Tosoh Corporation, 4.6mm (inner diameter) x 15.0cm, three types of columns connected in series) Eluent: Contains tetrahydrofuran (THF) and stabilizer (2,6-di-t-butyl-4-methylphenol). Eluent flow rate: 0.35mL / min Column temperature: 40℃ Inlet temperature: 40℃ Refractive Index (RI) measurement temperature: 40℃ Sample concentration: 0.3% by mass Sample injection volume: 10 μL

[0087] Another form of nitrogen-containing polymer is polyallylamine. Polyallylamine is a polymer of allylamine, having multiple repeating units represented by the following formula 3.

[0088] [ka]

[0089] In formula 3, the nitrogen atom N constituting the amino group of the side chain is a nitrogen cation N + And so Z in equation 1 + An ammonium cation represented by [formula] can be obtained. Then, with an alkyl ester anion, it can form an ammonium salt structure, for example, as shown below.

[0090] [ka]

[0091] 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. Furthermore, the weight-average molecular weight of the above polyallylamine can be, for example, 15,000 or less, preferably 10,000 or less, and more preferably 8,000 or less.

[0092] The presence of compounds having an ammonium salt structure of an alkyl ester anion represented by Formula 1, including compounds with structures derived from polyalkylene imines or polyallylamines, can be confirmed by analyzing the magnetic layer surface using time-of-flight secondary ion mass spectrometry (TOF-SIMS) or the like.

[0093] Compounds having an ammonium salt structure of an alkyl ester anion represented by Formula 1 can be salts of a nitrogen-containing polymer and one or more fatty acids selected from the group consisting of fatty acids having 7 or more carbon atoms and fluorinated fatty acids having 7 or more carbon atoms. The nitrogen-containing polymer that forms the salt can be one or more nitrogen-containing polymers, for example, a nitrogen-containing polymer selected from the group consisting of polyalkylene imines and polyallylamines. The fatty acids that form the salt can be one or more fatty acids selected from the group consisting of fatty acids having 7 or more carbon atoms and fluorinated fatty acids having 7 or more carbon atoms. Fluorinated fatty acids have a structure in which some or all of the hydrogen atoms constituting the alkyl group bonded to the carboxyl group COOH in the fatty acid are replaced with fluorine atoms. For example, the salt formation reaction can easily proceed by mixing the nitrogen-containing polymer and the above fatty acids at room temperature. Room temperature is, for example, about 20 to 25°C. In one embodiment, one or more nitrogen-containing polymers and one or more fatty acids can be used as components of a magnetic layer forming composition, and the salt formation reaction can be carried out by mixing them in the preparation step of the magnetic layer forming composition. In one embodiment, before preparing the magnetic layer-forming composition, one or more nitrogen-containing polymers and one or more fatty acids can be mixed to form a salt, and this salt can then be used as a component of the magnetic layer-forming composition to prepare the magnetic layer-forming composition. This also applies when forming a non-magnetic layer containing a compound having an ammonium salt structure of an alkyl ester anion represented by Formula 1. For example, with respect to the magnetic layer, 0.1 to 10.0 parts by mass of 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 nitrogen-containing polymer. The above fatty acids can be used, for example, 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. With respect to the non-magnetic layer, 0.1 to 10.0 parts by mass of 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 nitrogen-containing polymer.The above fatty acids can be used in amounts of, for example, 0.05 to 10.0 parts by mass per 100.0 parts by mass of non-magnetic powder, and preferably in amounts of 0.1 to 5.0 parts by mass. When mixing the nitrogen-containing polymer and the above fatty acids to form an ammonium salt of the alkyl ester anion represented by formula 1, the nitrogen atoms constituting the nitrogen-containing polymer may also react with the carboxyl groups of the above fatty acids to form the following structure, and forms including such a structure are also included in the above compound.

[0094] [ka]

[0095] Examples of the above fatty acids include fatty acids having the alkyl group described earlier as R in Formula 1, and fluorinated fatty acids having the fluorinated alkyl group described earlier as R in Formula 1.

[0096] The mixing ratio of the nitrogen-containing polymer used to form the compound having the ammonium salt structure of the alkyl ester anion represented by Formula 1 to the above fatty acids is preferably 10:90 to 90:10, more preferably 20:80 to 85:15, and even more preferably 30:70 to 80:20, as the mass ratio of nitrogen-containing polymer to the above fatty acids. Furthermore, the compound having the ammonium salt structure of the alkyl ester anion represented by Formula 1 is preferably contained in the magnetic layer in an amount of 0.01 parts by mass or more, more preferably 0.1 parts by mass or more, and even more preferably 0.5 parts by mass or more, per 100.0 parts by mass of ferromagnetic powder. Here, the content of the above compound in the magnetic layer refers to 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 high content of ferromagnetic powder in the magnetic layer is preferable from the viewpoint of high-density recording. Therefore, from the viewpoint of high-density recording, a low content of components other than ferromagnetic powder is preferable. 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 even more preferably 8.0 parts by mass or less, per 100.0 parts by mass of ferromagnetic powder. The same applies to the preferred range of the content of the above compound in the magnetic layer forming composition used to form the magnetic layer.

[0097] As a lubricant, for example, a fatty acid amide that can function as a boundary lubricant can be used. Boundary lubricants are considered to be lubricants that can reduce contact friction by adsorbing onto the surface of powder (e.g., ferromagnetic powder) and forming a strong lubricating film. Examples of fatty acid amides include amides of various fatty acids such as lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, behenic acid, erucic acid, and elaidic acid, specifically lauric acid amide, myristic acid amide, palmitic acid amide, and stearic acid amide. The fatty acid amide content in the magnetic layer is, for example, 0 to 3.0 parts by 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. Fatty acid amides may also be contained in the non-magnetic layer. The fatty acid amide content in the non-magnetic layer is, for example, 0 to 3.0 parts by mass, preferably 0 to 1.0 parts by mass, per 100.0 parts by mass of non-magnetic powder. For dispersants, see paragraphs 0061 and 0071 of Japanese Patent Publication No. 2012-133837. Dispersants may be added to the composition for forming a non-magnetic layer. For dispersants that can be added to the composition for forming a non-magnetic layer, see paragraph 0061 of Japanese Patent Publication No. 2012-133837.

[0098] <Nonmagnetic layer> Next, the non-magnetic layer will be described. The magnetic tape described above may have a magnetic layer directly on a non-magnetic support, or it may have a non-magnetic layer containing non-magnetic powder between the non-magnetic support and the magnetic layer. The non-magnetic powder used in the non-magnetic layer may be an inorganic powder or an organic powder. Carbon black can also be used. Examples of inorganic substances include metals, metal oxides, metal carbonates, metal sulfates, metal nitrides, metal carbides, and metal sulfides. These non-magnetic powders are available commercially and can also be manufactured by known methods. For details, see paragraphs 0146 to 0150 of Japanese Patent Publication No. 2011-216149. For carbon black that can be used in the non-magnetic layer, see paragraphs 0040 to 0041 of Japanese Patent Publication No. 2010-24113. The content (filling rate) of non-magnetic powder in the non-magnetic layer is preferably in the range of 50 to 90% by mass, and more preferably in the range of 60 to 90% by mass, relative to the total mass of the non-magnetic layer.

[0099] The non-magnetic layer may contain a binder and may also contain additives. For further details regarding the binder, additives, etc., of the non-magnetic layer, known technology relating to non-magnetic layers can be applied. Furthermore, for example, regarding the type and content of the binder, the type and content of the additives, etc., known technology relating to magnetic layers can also be applied.

[0100] The non-magnetic layer of the magnetic tape described above includes a substantially non-magnetic layer containing a small amount of ferromagnetic powder, for example as an impurity or intentionally, along with non-magnetic powder. Here, a substantially non-magnetic layer means a layer whose remanent magnetic flux density is 10 mT or less, or whose coercivity is 7.96 kA / m(100 Oe) or less, or a layer whose remanent magnetic flux density is 10 mT or less and whose coercivity is 7.96 kA / m(100 Oe) or less. It is preferable that the non-magnetic layer has no remanent magnetic flux density and coercivity.

[0101] <Nonmagnetic support> Next, non-magnetic supports will be described. Examples of non-magnetic supports (hereinafter also simply referred to as "supports") include known materials such as biaxially oriented polyethylene terephthalate, polyethylene naphthalate, polyamide, polyamide-imide, and aromatic polyamide. Among these, polyethylene terephthalate, polyethylene naphthalate, and polyamide are preferred. These supports may be subjected to pre-treatment such as corona discharge, plasma treatment, easy-adhesion treatment, or heat treatment.

[0102] <Backcoat 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. Preferably, the back coat layer contains either or both carbon black and inorganic powder. The back coat layer may contain a binder and may also contain additives. For details regarding the non-magnetic powder, binder, additives, etc. of the back coat layer, known technology relating to back coat layers may be applied, as may known technology relating to magnetic layers and / or non-magnetic layers. For example, paragraphs 0018 to 0020 of Japanese Patent Application Publication No. 2006-331625 and lines 65 to 38 of column 5 of U.S. Patent No. 7,029,774 can be referenced regarding the back coat layer.

[0103] <Various thicknesses> The tape thickness of the magnetic tape mentioned above is as previously stated.

[0104] The thickness of the non-magnetic support is preferably 3.0 to 5.0 μm. The thickness of the magnetic layer can be optimized according to the saturation magnetization of the magnetic head used, the head gap length, the bandwidth of the recording signal, etc., and is generally 0.01 μm to 0.15 μm, preferably 0.02 μm to 0.12 μm, and more preferably 0.03 μm to 0.1 μm from the viewpoint of high-density recording. At least one magnetic layer is sufficient, and the magnetic layer may be separated into two or more layers having different magnetic properties, and known configurations for multilayer magnetic layers can be applied. When separated into two or more layers, the thickness of the magnetic layer is the total thickness of these layers. The thickness of the non-magnetic layer is, for example, 0.1 to 1.5 μm, preferably 0.1 to 1.0 μm, and more preferably 0.1 to 0.7 μm. The thickness of the back coat layer is preferably 0.9 μm or less, and more preferably 0.1 to 0.7 μm. Various thicknesses, such as the thickness of the magnetic layer, can be determined by the following method. After exposing the cross-section of the magnetic tape in the thickness direction using an ion beam, the exposed cross-section is observed using a scanning electron microscope or a transmission electron microscope. Various thicknesses can be determined as the arithmetic mean of the thicknesses obtained at any two locations during the cross-sectional observation. Alternatively, various thicknesses can be determined as design thicknesses calculated from manufacturing conditions, etc.

[0105] <Manufacturing method> (Preparation of compositions for each layer) A composition for forming a magnetic layer, a non-magnetic layer, or a backcoat layer typically contains a solvent along with the various components described above. Various organic solvents commonly used for manufacturing coated magnetic recording media can be used as the solvent. In particular, from the viewpoint of solubility of binders commonly used in coated magnetic recording media, it is preferable that each layer-forming composition contains one or more ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, cyclohexanone, isophorone, and tetrahydrofuran. The amount of solvent in each layer-forming composition is not particularly limited and can be the same as that used for the layer-forming compositions of typical coated magnetic recording media. Furthermore, the process for preparing each layer-forming composition typically includes at least a kneading step, a dispersion step, and mixing steps provided before or after these steps as needed. Each individual step may be divided into two or more stages. The components used in the preparation of each layer-forming composition may be added at the beginning or in the middle of any of the steps. Individual components may also be added in two or more separate steps. For example, the binder may be added in separate steps during the kneading process, the dispersion process, and the mixing process for viscosity adjustment after dispersion. Furthermore, as previously described, one or more nitrogen-containing polymers and one or more of the above-mentioned fatty acids can be used as components of the magnetic layer-forming composition, and the salt formation reaction can be carried out by mixing them during the preparation process of the magnetic layer-forming composition. In one embodiment, before preparing the magnetic layer-forming composition, one or more nitrogen-containing polymers and one or more of the fatty acids can be mixed to form a salt, and this salt can then be used as a component of the magnetic layer-forming composition to prepare it. This also applies to the preparation process of the non-magnetic layer-forming composition. In one embodiment, during the preparation of the magnetic layer-forming composition, a dispersion containing a protrusion-forming agent (hereinafter referred to as "protrusion-forming agent solution") can be prepared, and this protrusion-forming agent solution can then be mixed with one or more of the other components of the magnetic layer-forming composition. For example, the protrusion-forming agent solution can be prepared by known dispersion treatments such as ultrasonic treatment. Ultrasonic treatment is used for, for example, 200cc (1cc = 1cm³). 3This can be performed for 1 to 300 minutes at an ultrasonic output of approximately 10 to 2000 watts per unit. Filtration may also be performed after the dispersion treatment. For information on filters to be used for filtration, please refer to the following description.

[0106] In the manufacturing process of the magnetic tape described above, some or all of the conventional known manufacturing techniques can be used in some or all of the processes. In the kneading process, it is preferable to use a kneader with strong kneading force, such as an open kneader, continuous kneader, pressure kneader, or extruder. Details of these kneading processes are described in Japanese Patent Publication No. 1-106338 and Japanese Patent Publication No. 1-79274. In addition, glass beads and / or other beads can be used to disperse each layer-forming composition. Suitable dispersion beads include high-density dispersion beads such as zirconia beads, titania beads, and steel beads. It is preferable to optimize the particle size (bead diameter) and packing rate of these dispersion beads. Known dispersers can be used. Each layer-forming composition may be filtered by a known method before being subjected to the coating process. Filtration can be performed, for example, by filter filtration. As filters used for filtration, for example, filters with a pore size of 0.01 to 3 μm (e.g., glass fiber filters, polypropylene filters, etc.) can be used.

[0107] (Coating process) The magnetic layer can be formed by, for example, directly coating a magnetic layer-forming composition onto a non-magnetic support, or by sequentially or simultaneously overcoating it with a non-magnetic layer-forming composition. When orientation processing is performed, the orientation processing is carried out on the coated layer in the orientation zone while the coated layer of the magnetic layer-forming composition is wet. Various known techniques, including those described in paragraph 0052 of Japanese Patent Application Publication No. 2010-24113, can be applied to the orientation processing. For example, vertical orientation processing can be performed by known methods such as using opposite-polarity opposing magnets. In the orientation zone, the drying rate of the coated layer can be controlled by the temperature and airflow of the drying air and / or the transport speed in the orientation zone. Alternatively, the coated layer may be pre-dried before being transported to the orientation zone. The backcoat layer can be formed by applying the backcoat layer-forming composition to the side of the non-magnetic support opposite to the side having (or subsequently having) the magnetic layer. For details on the application for each layer formation, refer to paragraph 0066 of Japanese Patent Application Publication No. 2010-231843.

[0108] (Other processes) After the above coating process, the magnetic tape is usually subjected to calendering to improve its surface smoothness. Regarding the calendering conditions, the calendering pressure is, for example, 200 to 500 kN / m, preferably 250 to 350 kN / m; the calendering temperature (surface temperature of the calender roll) is, for example, 70 to 120°C, preferably 80 to 100°C; and the calendering speed is, for example, 50 to 300 m / min, preferably 80 to 200 m / min. Furthermore, the harder the surface of the calender roll used, and the more layers are added, the smoother the surface of the magnetic layer tends to become. For other processes for manufacturing magnetic tape, refer to paragraphs 0067 to 0070 of Japanese Patent Publication No. 2010-231843. Through various processes, a long roll of magnetic tape raw material can be obtained. The obtained magnetic tape raw material is then cut (slit) using a known cutting machine to the width of a magnetic tape to be housed in a magnetic tape cartridge, for example. The above width can be determined according to standards and is usually 1 / 2 inch. A servo pattern is typically formed on the magnetic tape obtained by slitting.

[0109] (Heat treatment) In one embodiment, the magnetic tape described above may be a magnetic tape manufactured through the following heat treatment. In another embodiment, the magnetic tape may be a magnetic tape manufactured without the following heat treatment.

[0110] The heat treatment can be performed with the magnetic tape, which has been slit and cut to a width determined according to the standard, wrapped around the core member.

[0111] In one embodiment, the above heat treatment is performed with the magnetic tape wound around a core-shaped member for heat treatment (hereinafter referred to as the "heat-treated winding core"), and the heat-treated magnetic tape is wound onto the cartridge reel of a magnetic tape cartridge, thereby producing a magnetic tape cartridge with the magnetic tape wound onto the cartridge reel. The core for heat treatment can be made of metal, resin, paper, etc. From the viewpoint of suppressing winding failures such as spocking, the material of the heat treatment core is preferably one with high rigidity. For this reason, the heat treatment core is preferably made of metal or resin. Furthermore, as an indicator of rigidity, the flexural modulus of the material of the heat treatment core is preferably 0.2 GPa (gigapascals) or higher, and more preferably 0.3 GPa or higher. On the other hand, since high-rigidity materials are generally expensive, using a heat treatment core made of a material with rigidity exceeding the rigidity required to suppress winding failures leads to increased costs. Considering these 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 publicly known. The heat treatment core can also be a solid or hollow core-shaped member. In the case of a hollow core, from the viewpoint of maintaining rigidity, the wall thickness is preferably 2 mm or more. Furthermore, the core for heat treatment may or may not have a flange. It is preferable to prepare a magnetic tape of a length equal to or greater than the length to be ultimately housed in a magnetic tape cartridge (hereinafter referred to as the "final product length") to be wound onto a heat treatment core, and to perform heat treatment by winding this magnetic tape onto a heat treatment core and placing it in a heat treatment environment. The length of the magnetic tape wound onto the heat treatment core is equal to or greater than the final product length, and from the viewpoint of ease of winding onto the heat treatment core, it is preferable to set it to "final product length + α". From the viewpoint of ease of winding, this α is preferably 5m or more. The tension when winding onto the heat treatment core is preferably 0.1N (Newtons) or more. Furthermore, from the viewpoint of suppressing excessive deformation during manufacturing, the tension when winding onto the heat treatment core is preferably 1.5N or less, and more preferably 1.0N or less. The outer diameter of the heat treatment core is preferably 20mm or more, and more preferably 40mm or more, from the viewpoint of ease of winding and suppression of coiling (longitudinal curling). Furthermore, the outer diameter of the heat treatment core is preferably 100 mm or less, and more preferably 90 mm or less. The width of the heat treatment core should be greater than or equal to the width of the magnetic tape wound around it. Also, when removing the magnetic tape from the heat treatment core after heat treatment, it is preferable to remove the magnetic tape from the heat treatment core only after the magnetic tape and heat treatment core have cooled sufficiently, in order to prevent unintended tape deformation during the removal operation. It is preferable to first wind the removed magnetic tape onto another core (referred to as a "temporary winding core"), and then wind the magnetic tape from the temporary winding core onto the cartridge reel of the magnetic tape cartridge (generally with an outer diameter of about 40-50 mm). This allows the relationship between the inside and outside of the magnetic tape relative to the heat treatment core during heat treatment to be maintained when winding the magnetic tape onto the cartridge reel of the magnetic tape cartridge. For details of the temporary winding core and the tension when winding the magnetic tape onto this core, please refer to the previous description regarding the heat treatment core. In the configuration in which the above heat treatment is applied to a magnetic tape of a length of "final product length + α", the "+ α" length can be cut off at any stage. For example, in one configuration, the magnetic tape of the final product length can be wound from the temporary winding core onto the reel of the magnetic tape cartridge, and the remaining "+ α" length can be cut off.From the standpoint of minimizing the amount that is cut off and discarded, it is preferable that α is 20m or less.

[0112] The specific form of heat treatment performed while the material is wrapped around the core member, as described above, is explained below. The ambient temperature for heat treatment (hereinafter referred to as the "heat treatment temperature") is preferably 40°C or higher, and more preferably 50°C or higher. On the other hand, from the viewpoint of suppressing excessive deformation, the heat treatment temperature is preferably 75°C or lower, and more preferably 70°C or lower. The absolute humidity by weight of the atmosphere used for heat treatment is preferably 0.1 g / kg Dry air or higher, and more preferably 1 g / kg Dry air or higher. An atmosphere with an absolute humidity by weight within the above range is preferable because it can be prepared without using special equipment to reduce moisture. On the other hand, from the viewpoint of suppressing condensation and the resulting decrease in workability, the absolute humidity by weight is preferably 70 g / kg Dry air or lower, and more preferably 66 g / kg Dry air or lower. The heat treatment time is preferably 0.3 hours or longer, and more preferably 0.5 hours or longer. Furthermore, from the viewpoint of production efficiency, the heat treatment time is preferably 48 hours or less.

[0113] Regarding the control of the standard deviation of the curvature amount described above, the larger the values ​​of the heat treatment temperature, heat treatment time, flexural modulus of the heat treatment core, and tension during winding onto the heat treatment core, the smaller the standard deviation of the curvature amount tends to be.

[0114] (Formation of servo patterns) "Forming a servo pattern" can also be described as "recording a servo signal." The formation of a servo pattern is explained below.

[0115] Servo patterns are typically formed along the longitudinal direction of the magnetic tape. Examples of control methods that utilize servo signals (servo control) include timing-based servo (TBS), amplitude servo, and frequency servo.

[0116] As indicated in ECMA (European Computer Manufacturers Association) - 319 (June 2001), magnetic tapes conforming to the LTO (Linear Tape-Open) standard (commonly referred to as "LTO tapes") employ a timing-based servo system. In this timing-based servo system, the servo pattern is composed of multiple pairs of non-parallel magnetic stripes (also called "servo stripes") arranged continuously along the longitudinal direction of the magnetic tape. In this invention and specification, "timing-based servo pattern" refers to a servo pattern that enables head tracking in a timing-based servo system. The reason the servo pattern is composed of pairs of non-parallel magnetic stripes, as described above, is to inform the servo signal reading element of its position as it passes over the servo pattern. Specifically, the pair of magnetic stripes described above are formed such that their spacing changes continuously along the width direction of the magnetic tape, and the servo signal reading element can determine the relative position between the servo pattern and the servo signal reading element by reading this spacing. This relative position information enables tracking of the data track. Therefore, multiple servo tracks are typically set up on the servo pattern, aligned with the width of the magnetic tape.

[0117] A servo band consists of a servo pattern that runs continuously along the longitudinal direction of the magnetic tape. Typically, multiple servo bands are provided on a magnetic tape. For example, in an LTO tape, there are five. The area between two adjacent servo bands is the data band. A data band consists of multiple data tracks, each corresponding to a servo track.

[0118] In one embodiment, as shown in Japanese Patent Publication No. 2004-318983, each servo band has embedded information indicating the servo band number (also called "servo band ID (identification)" or "UDIM (Unique DataBand Identification Method) information"). This servo band ID is recorded by shifting a specific pair of servo stripes within a servo band so that its position is displaced relative to the longitudinal direction of the magnetic tape. Specifically, the method of shifting a specific pair of servo stripes is changed for each servo band. As a result, the recorded servo band ID is unique for each servo band, so that a servo band can be uniquely identified by reading it with a servo signal reading element.

[0119] Furthermore, one method for uniquely identifying a servo band is the staggered method, as described in ECMA-319 (June 2001). In this staggered method, a group of non-parallel magnetic stripes (servo stripes) arranged continuously along the longitudinal direction of the magnetic tape are recorded in a way that they are shifted along the longitudinal direction of the magnetic tape for each servo band. Since the combination of this shift between adjacent servo bands is unique across the entire magnetic tape, it is possible to uniquely identify a servo band when reading the servo pattern with two servo signal reading elements.

[0120] Furthermore, each servo band typically contains embedded information indicating its position along the longitudinal direction of the magnetic tape (also known as "LPOS (Longitudinal Position) information"), as described in ECMA-319 (June 2001). This LPOS information, like the UDIM information, is recorded by shifting the positions of a pair of servo stripes along the longitudinal direction of the magnetic tape. However, unlike the UDIM information, the same signal is recorded for each servo band in this LPOS information.

[0121] It is also possible to embed information other than the UDIM and LPOS information mentioned above into the servo bands. In this case, the embedded information may be different for each servo band, like the UDIM information, or it may be common to all servo bands, like the LPOS information. Furthermore, methods other than those described above can be used to embed information in the servo band. For example, a predetermined code may be recorded by thinning out a predetermined pair from a group of servo stripes.

[0122] A servo pattern forming head is called a servo light head. A servo light head typically has a pair of gaps corresponding to the pair of magnetic stripes mentioned above, for each servo band. Typically, a core and a coil are connected to each pair of gaps, and by supplying current pulses to the coils, the magnetic field generated in the core can create a leakage magnetic field in the pair of gaps. When forming a servo pattern, by inputting current pulses while running a magnetic tape over the servo light head, the magnetic patterns corresponding to the pair of gaps are transferred to the magnetic tape, thereby forming the servo pattern. The width of each gap can be appropriately set according to the density of the servo pattern to be formed. For example, the width of each gap can be set to 1 μm or less, 1 to 10 μm, 10 μm or more, etc.

[0123] Before forming a servo pattern on a magnetic tape, it is usually demagnetized (erased). This erasing process can be performed by applying a uniform magnetic field to the magnetic tape using a DC or AC magnet. There are two types of erasing: DC (Direct Current) erasing and AC (Alternating Current) erasing. AC erasing is performed by gradually reducing the strength of the magnetic field while reversing the direction of the magnetic field applied to the magnetic tape. On the other hand, DC erasing is performed by applying a unidirectional magnetic field to the magnetic tape. There are two further methods of DC erasing. The first method is horizontal DC erasing, which applies a unidirectional magnetic field along the longitudinal direction of the magnetic tape. The second method is vertical DC erasing, which applies a unidirectional magnetic field along the thickness direction of the magnetic tape. The erasing process may be performed on the entire magnetic tape or on each servo band of the magnetic tape.

[0124] The direction of the magnetic field of the formed servo pattern is determined according to the direction of the erase. For example, when a magnetic tape is horizontally DC erased, the servo pattern is formed such that the direction of the magnetic field is opposite to the direction of the erase. This makes it possible to increase the output of the servo signal obtained by reading the servo pattern. As shown in Japanese Patent Application Publication No. 2012-53940, when a magnetic pattern using the above gap is transferred to a vertically DC erased magnetic tape, the servo signal obtained by reading the formed servo pattern is in the shape of a single-pole pulse. On the other hand, when a magnetic pattern using the above gap is transferred to a horizontally DC erased magnetic tape, the servo signal obtained by reading the formed servo pattern is in the shape of a double-pole pulse.

[0125] <Vertical squareness ratio> In one embodiment, the vertical aspect ratio of the magnetic tape can be, for example, 0.55 or more, preferably 0.60 or more, and more preferably 0.65 or more, from the viewpoint of improving electromagnetic conversion characteristics. The upper limit of the aspect ratio is, in principle, 1.00 or less. The vertical aspect ratio of the magnetic tape can be 1.00 or less, and can be 0.95 or less, 0.90 or less, 0.85 or less, or 0.80 or less. A large value for the vertical aspect ratio of the magnetic tape is preferable from the viewpoint of improving electromagnetic conversion characteristics. The vertical aspect ratio of the magnetic tape can be controlled by known methods such as performing a vertical orientation process.

[0126] In the present invention and this specification, "vertical angle ratio" refers to the angle ratio measured in the vertical direction of the magnetic tape. In relation to the angle ratio, "vertical direction" refers to the direction perpendicular 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 vertical angle ratio is determined by the following method. A sample piece of a size suitable for introduction into a vibrating magnetometer is cut from the magnetic tape to be measured. Using a vibrating magnetometer, a magnetic field is applied to this sample piece perpendicular to the sample piece (in the direction perpendicular to the magnetic layer surface) at a maximum applied magnetic field of 3979 kA / m, a measurement temperature of 296 K, and a magnetic field sweep speed of 8.3 kA / m / sec, and the magnetization intensity of the sample piece against the applied magnetic field is measured. The measured magnetization intensity is obtained as a value after demagnetization correction and after subtracting the magnetization of the sample probe of the vibrating magnetometer as background noise. When the magnetization intensity at the maximum applied magnetic field is Ms and the magnetization intensity at zero applied magnetic field is Mr, the squareness ratio SQ is calculated as SQ = Mr / Ms. The measurement temperature refers to the temperature of the sample piece, and the temperature of the sample piece can be set to the measurement temperature by setting the ambient temperature around the sample piece to the measurement temperature, thereby achieving thermal equilibrium.

[0127] [Magnetic tape cartridge] One aspect of the present invention relates to a magnetic tape cartridge including the magnetic tape described above.

[0128] Details of the magnetic tape included in the above magnetic tape cartridge are as described above.

[0129] In a magnetic tape cartridge, the magnetic tape is generally housed inside the cartridge body, wound onto a reel. The reel is rotatably mounted inside the cartridge body. Two types of magnetic tape cartridges are widely used: single-reel cartridges, which have one reel inside the cartridge body, and double-reel cartridges, which have two reels inside the cartridge body. When a single-reel magnetic tape cartridge is mounted in a magnetic tape device for recording and / or playing back data on magnetic tape, the magnetic tape is pulled out of the cartridge and wound onto the reel on the magnetic tape device. A magnetic head is positioned along the magnetic tape transport path from the magnetic tape cartridge to the take-up reel. The magnetic tape is fed and wound 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 process, the magnetic head and the magnetic layer surface of the magnetic tape come into contact and slide against each other, enabling data recording and / or playback. In contrast, a dual-reel magnetic tape cartridge has both a supply reel and a take-up reel located inside the magnetic tape cartridge.

[0130] The above-described magnetic tape cartridge may, in one embodiment, include a cartridge memory. The cartridge memory may be, for example, a non-volatile memory, and may already contain or contain head tilt angle adjustment information. The head tilt angle adjustment information is information for adjusting the head tilt angle while the magnetic tape is running within the magnetic tape device. For example, the head tilt angle adjustment information may include the values ​​of the servoband interval at each position along the longitudinal direction of the magnetic tape during data recording. For example, when playing back data recorded on the magnetic tape, the value of the servoband interval is measured during playback, and the control device of the magnetic tape device can change the head tilt angle so that the absolute value of the difference between this value and the servoband interval recorded in the cartridge memory at the same longitudinal position during recording approaches 0. The head tilt angle may be, for example, the angle θ described above.

[0131] The magnetic tape and magnetic tape cartridge described above can be suitably used in a magnetic tape device (in other words, a magnetic recording and playback system) that records and / or plays back data at different head tilt angles. In one embodiment, such a magnetic tape device can record and / or play back data by changing the head tilt angle while the magnetic tape is running. For example, the head tilt angle can be changed according to the widthwise dimensional information of the magnetic tape acquired while the magnetic tape is running. Alternatively, for example, the head tilt angle for one recording and / or playback cycle may be changed from the head tilt angle for subsequent recording and / or playback cycles, and the head tilt angle may be fixed without changing it during the magnetic tape running for each recording and / or playback cycle. In any of these embodiments, a magnetic tape with high running stability when recording and / or playing back data at different head tilt angles is preferred.

[0132] [Magnetic tape drive] One aspect of the present invention relates to a magnetic tape device including the magnetic tape described above. In the magnetic tape device, recording data onto the magnetic tape and / or reproducing data recorded on the magnetic tape can be performed, for example, by bringing the magnetic layer surface of the magnetic tape into contact with a magnetic head and sliding it. The magnetic tape device may detachably include a magnetic tape cartridge according to one aspect of the present invention.

[0133] The above-described magnetic tape cartridge can be mounted in a magnetic tape device equipped with a magnetic head and used for recording and / or reproducing data. In the present invention and herein, “magnetic tape device” means a device capable of recording data onto a magnetic tape and reproducing data recorded on a magnetic tape. Such a device is generally referred to as a drive.

[0134] <Magnetic head> The above magnetic tape device may include a magnetic head. The configuration of the magnetic head and the angle θ, which is the head tilt angle, are as previously explained with reference to Figures 1 to 3. The magnetic head included in the above magnetic tape device may be an LTO8 head in one embodiment, an LTO head of another generation in another embodiment, or a magnetic head other than an LTO head in yet another embodiment. If the magnetic head includes a regeneration element, a magnetoresistive (MR) element that can read information recorded on the magnetic tape with high sensitivity is preferred as the regeneration element. Various known MR elements (e.g., GMR (Giant Magnetoresistive) elements, TMR (Tunnel Magnetoresistive) elements, etc.) can be used as the MR element. Hereinafter, the magnetic head that records data and / or reproduces recorded data will also be called the "recording / reproduction head". The elements for recording data (recording elements) and the elements for reproducing data (reproduction elements) will be collectively referred to as "magnetic head elements".

[0135] By using a regeneration element with a narrow width as the regeneration element, high-density recorded data can be regenerated with high sensitivity. From this viewpoint, the regeneration element width is preferably 0.8 μm or less. The regeneration element width can be, for example, 0.3 μm or more. However, a value lower than this is also preferable from the above viewpoint. Here, "regenerative element width" refers to the physical dimension of the regenerative element width. Such physical dimensions can be measured using an optical microscope, a scanning electron microscope, or the like.

[0136] When recording data and / or playing back recorded data, tracking using servo signals can be performed first. That is, by making the servo signal reading element follow a predetermined servo track, the magnetic head element can be controlled to pass over the target data track. The movement of the data track is achieved by changing the servo track read by the servo signal reading element in the tape width direction. Furthermore, the recording / playback head can also record and / or play back data for other data bands. In this case, the servo signal reading element can be moved to a predetermined servo band using the UDIM information described earlier, and tracking for that servo band can be started.

[0137] Figure 5 shows an example of the arrangement of data bands and servo bands. In Figure 5, multiple servo bands 1 are arranged on the magnetic layer of the magnetic tape MT, sandwiched between guide bands 3. Multiple regions 2 sandwiched between two servo bands are the data bands. A servo pattern is a magnetized region, formed by magnetizing a specific region of the magnetic layer with a servo light head. The region magnetized by the servo light head (the position where the servo pattern is formed) is defined by the standard. For example, in the industry standard LTO Ultrium format tape, multiple servo patterns inclined with respect to the tape width direction are formed on the servo bands during magnetic tape manufacturing, as shown in Figure 6. More specifically, in Figure 6, the servo frame SF on the servo band 1 consists of a servo subframe 1 (SSF1) and a servo subframe 2 (SSF2). The servo subframe 1 consists of an A-burst (indicated as A in Figure 6) and a B-burst (indicated as B in Figure 6). The A-burst consists of servo patterns A1 to A5, and the B-burst consists of servo patterns B1 to B5. On the other hand, servo subframe 2 consists of C-bursts (indicated as C in Figure 6) and D-bursts (indicated as D in Figure 6). The C-bursts consist of servo patterns C1 to C4, and the D-bursts consist of servo patterns D1 to D4. These 18 servo patterns are arranged in sets of 5 and 4 on subframes in a 5, 5, 4, 4 sequence, and are used to identify the servo frames. Figure 6 shows one servo frame for illustrative purposes. However, in reality, in the magnetic layer of a magnetic tape where timing-based servo head tracking is performed, multiple servo frames are arranged in the direction of travel for each servo band. In Figure 6, the arrows indicate the direction of travel of the magnetic tape. For example, LTO Ultrium format tape typically has more than 5000 servo frames per meter of tape length in each servo band of the magnetic layer.

[0138] In the above magnetic tape device, the tilt angle of the head can be changed during the running of the magnetic tape within 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 during the running of the magnetic tape. 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.

[0139] Regarding the head tilt angle during the running of the magnetic tape, 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 the running of the magnetic tape 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. 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 still 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 contact during the running of the magnetic tape. Also, enhancing the uniformity in the tape width direction of the above friction 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 still more preferably 35° or less.

[0140] Regarding the change in the angle θ during the running of the magnetic tape, for the recording of data on the magnetic tape and / or for the reproduction of 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 If it changes, 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

[0141] In one form, Δθ can be more than 0.000°, and from the perspective 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 perspective of the ease of ensuring the synchronization of the recorded data and / or the reproduced data between the 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

[0142] 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, an embodiment in which the axis of the element array is inclined in the direction opposite to the magnetic tape running direction is also included in the present invention

[0143] θ which is the head tilt angle at the start of the magnetic tape running initialThis can be set by the control device of the magnetic tape drive, etc. Regarding the head tilt angle during magnetic tape travel, Figure 7 is an explanatory diagram of the method for measuring the angle θ during magnetic tape travel. The angle θ during magnetic tape travel can be determined, for example, by the following method. When determining the angle θ during magnetic tape travel by the following method, the angle θ is to be varied within the range of 0 to 90° during magnetic tape travel. That is, if the axis of the element array is tilted toward the direction of magnetic tape travel at the start of magnetic tape travel, the element array will not be tilted during magnetic tape travel so that the axis of the element array is tilted toward the direction of magnetic tape travel at the start of magnetic tape travel, and if the axis of the element array is tilted toward the direction of magnetic tape travel at the start of magnetic tape travel, the element array will not be tilted during magnetic tape travel so that the axis of the element array is tilted toward the direction of magnetic tape travel at the start of magnetic tape travel. The phase difference (i.e., time difference) ΔT of the regenerated signals from a pair of servo signal reading elements 1 and 2 is measured. ΔT can be measured by a measurement unit provided in the magnetic tape device. The configuration of such a measurement unit is well known. The distance L between the center of servo signal reading element 1 and the center of servo signal reading element 2 can be measured using an optical microscope or the like. When the magnetic tape travels at speed v, the distance between the centers of the two servo signal reading elements in the direction of magnetic tape travel is Lsinθ, and the relationship Lsinθ = v × ΔT holds. Therefore, the angle θ during magnetic tape travel can be calculated using the formula "θ = arcsin(vΔT / L)". Note that Figure 7 (right) shows an example where the axis of the element array is tilted toward the direction of magnetic tape travel. In this example, the phase difference (i.e., time difference) ΔT between the phase of the regenerated signal from servo signal reading element 1 and the phase of the regenerated signal from servo signal reading element 2 is measured. If the axis of the element array is tilted in the direction opposite to the direction of travel of the magnetic tape, θ can be determined by the above method, except that ΔT is measured as the phase difference (i.e., time difference) between the phase of the regenerated signal of servo signal reading element 1 and the phase of the regenerated signal of servo signal reading element 2. Furthermore, the measurement pitch for the angle θ, that is, the measurement interval for the angle θ in the longitudinal direction of the tape, can be selected according to the frequency of tape width deformation in the longitudinal direction of the tape. For example, the measurement pitch can be set to 250 μm.

[0144] <Configuration of a magnetic tape drive> The magnetic tape device 10 shown in Figure 8 controls the recording and playback head unit 12 based on commands from the control device 11, and performs data recording and playback on the magnetic tape MT. The magnetic tape device 10 has a configuration that allows for the detection and adjustment of tension applied in the longitudinal direction of the magnetic tape from spindle motors 17A, 17B and their drive units 18A, 18B that control the rotation of the magnetic tape cartridge reel and the take-up reel. The magnetic tape device 10 has a configuration that allows for the loading of a magnetic tape cartridge 13. The magnetic tape device 10 has a cartridge memory read / write device 14 that can read from and write to the cartridge memory 131 in the magnetic tape cartridge 13. From the magnetic tape cartridge 13 mounted in the magnetic tape device 10, the end of the magnetic tape MT or the leader pin is pulled out by an automatic loading mechanism or manually, and the magnetic layer surface of the magnetic tape MT passes over the recording / playback head of the recording / playback head unit 12 through guide rollers 15A and 15B with the magnetic layer surface of the magnetic tape MT in contact with the surface of the recording / playback head, and the magnetic tape MT is wound onto the take-up reel 16. The rotation and torque of spindle motors 17A and 17B are controlled by signals from the control device 11, so that the magnetic tape MT runs at a desired speed and tension. A servo pattern pre-formed on the magnetic tape can be used to control the tape speed and head tilt angle. A tension detection mechanism may be provided between the magnetic tape cartridge 13 and the take-up reel 16 for tension detection. In addition to control by spindle motors 17A and 17B, tension may also be controlled using guide rollers 15A and 15B. The cartridge memory read / write device 14 is configured to read and write information to the cartridge memory 131 in response to commands from the control device 11. For example, the ISO (International Organization for Standardization) 14443 standard can be used as the communication method between the cartridge memory read / write device 14 and the cartridge memory 131.

[0145] The control device 11 includes, for example, a control unit, a storage unit, a communication unit, and the like.

[0146] The recording / playback head unit 12 consists of, for example, a recording / playback head, a servo tracking actuator for adjusting the position of the recording / playback head in the track width direction, a recording / playback amplifier 19, and a connector cable for connecting to the control device 11. The recording / playback head consists of, for example, a recording element for recording data on magnetic tape, a playback element for reproducing data on magnetic tape, and a servo signal reading element for reading servo signals recorded on magnetic tape. Within a single magnetic head, for example, one or more recording elements, playback elements, and servo signal reading elements are mounted. Alternatively, each element may be separately contained in multiple magnetic heads corresponding to the direction in which the magnetic tape travels.

[0147] The recording / playback head unit 12 is configured to record data onto the magnetic tape MT in response to commands from the control device 11. It is also configured to play back data recorded on the magnetic tape MT in response to commands from the control device 11.

[0148] The control device 11 has a mechanism to determine the running position of the magnetic tape MT from the servo signals read from the servo bands when the magnetic tape MT is running, and to control the servo tracking actuator so that the recording element and / or playback element are positioned at the target running position (track position). This track position control is performed, for example, by feedback control. The control device 11 has a mechanism to determine the servo band spacing from the servo signals read from two adjacent servo bands when the magnetic tape MT is running. The control device 11 can store the determined servo band spacing information in its internal storage unit, cartridge memory 131, or external connected equipment. Furthermore, the control device 11 can change the head tilt angle according to the dimensional information in the width direction of the running magnetic tape. This makes it possible to bring the effective distance between servo signal reading elements close to or match the servo band spacing. The above dimensional information can be obtained using a servo pattern pre-formed on the magnetic tape. For example, while the magnetic tape is running within the magnetic tape device, the angle θ that the axis of the element array makes with respect to the width direction of the magnetic tape can be changed according to the width direction dimensional information of the magnetic tape acquired during the running process. The head tilt angle can be adjusted, for example, by feedback control. Alternatively, the head tilt angle can also be adjusted, for example, by the method described in Japanese Patent Application Publication No. 2016-524774 (Patent Document 1) or US2019 / 0164573A1 (Patent Document 2). [Examples]

[0149] The present invention will be described below based on examples. However, the present invention is not limited to the embodiments shown in the examples. In the following, "parts" refers to "parts by mass". Furthermore, unless otherwise specified, the processes and evaluations described below were carried out in an environment with a temperature of 23°C ± 1°C. In the following, "eq" refers to equivalent, and is a unit that cannot be converted to SI units.

[0150] [Protrusion-forming agent] The protrusion-forming agents used in preparing the magnetic layer-forming composition for the production of the magnetic tape described later are as follows: Protrusion-forming agents A and D are particles with low surface smoothness. The particle shape of protrusion-forming agent B is so-called irregular. The particle shape of protrusion-forming agent C is cocoon-shaped. The particle shape of protrusion-forming agent E is close to a perfect sphere. Protrusion-forming agent A: ATLAS (composite particles of silica and polymer) manufactured by Cabot Corporation, average particle size 100 nm Protrusion-forming agent B: Asahi Carbon Co., Ltd. Asahi #52 (carbon black), average particle size 60 nm Protrusion-forming agent C: Cabot TGC6020N (silica particles), average particle size 140 nm Protrusion-forming agent D: Cataloid (aqueous dispersion sol of silica particles) manufactured by JGC Catalysts & Chemicals Co., Ltd.; the dry product obtained by heating the above aqueous dispersion sol to remove the solvent is used as a protrusion-forming agent for preparing a composition for forming a magnetic layer), average particle size 120 nm Protrusion-forming agent E: Quattron PL-10L manufactured by Fuso Chemical Industries, Ltd. (aqueous dispersion sol of silica particles; the dry product obtained by heating the above aqueous dispersion sol to remove the solvent is used as a protrusion-forming agent for preparing a composition for forming a magnetic layer), average particle size 130 nm

[0151] [Ferromagnetic powder] In Table 1, "BaFe" refers to hexagonal barium ferrite powder (coercivity Hc: 196 kA / m, average particle size (average plate diameter) 24 nm).

[0152] In Table 1, "SrFe1" is hexagonal strontium ferrite powder prepared by the following method. 1707g of SrCO3, 687g of H3BO3, 1120g of Fe2O3, 45g of Al(OH)3, 24g of BaCO3, 13g of CaCO3, and 235g of Nd2O3 were weighed out and mixed 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 molten material, the outlet at the bottom of the platinum crucible was heated, and the molten material was dispensed in a rod shape at approximately 6 g / second. The dispensed material was rolled and rapidly cooled using water-cooled twin rollers to produce an amorphous body. 280g of the prepared amorphous material was placed in an electric furnace and heated to 635°C (crystallization temperature) at a heating rate of 3.5°C / min. The temperature was maintained at this temperature for 5 hours to precipitate (crystallize) hexagonal strontium ferrite particles. Next, the crystalline material obtained above, containing hexagonal strontium ferrite particles, was coarsely ground in a mortar. 1000g of 1mm particle size zirconia beads and 800ml of 1% aqueous acetic acid solution were added to a glass bottle and dispersed in a paint shaker for 3 hours. After that, the resulting dispersion was separated from the beads and placed in a stainless steel beaker. The dispersion was allowed to stand at a liquid temperature of 100°C for 3 hours to dissolve the glass components, then precipitated in a centrifuge and washed by repeated decantation. Finally, it was dried in a heating furnace at a furnace 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 is 2.2 × 10⁻⁶. 5 J / m 3 , mass magnetization σs is 49A m 2 It was / kg. A sample powder of 12 mg was taken from the hexagonal strontium ferrite powder obtained above, and the elemental analysis of the filtrate obtained by partially dissolving this sample powder under the dissolution conditions exemplified earlier was performed using an ICP analyzer to determine the surface layer content of neodymium atoms. Separately, 12 mg of sample powder was taken from the hexagonal strontium ferrite powder obtained above, and the elemental analysis of the filtrate obtained by completely dissolving this sample powder under the dissolution conditions exemplified earlier was performed using an ICP analyzer to determine the bulk content of neodymium atoms. The neodymium atom content (bulk content) relative to 100 atomic percent of iron atoms in the hexagonal strontium ferrite powder obtained above was 2.9 atomic percent. Furthermore, the neodymium atom content in the surface layer was 8.0 atomic percent. The ratio of surface layer content to bulk content, "surface layer content / bulk content," was 2.8, confirming that neodymium atoms were concentrated in the surface layer of the particles. The hexagonal ferrite crystal structure of the powder obtained above was confirmed by scanning with CuKα rays at a voltage of 45kV and intensity of 40mA, and measuring the X-ray diffraction pattern under the following conditions (X-ray diffraction analysis). The powder obtained above showed a magnetoplanbite-type (M-type) hexagonal ferrite crystal structure. Furthermore, the crystalline phase detected by X-ray diffraction analysis was a single phase of the magnetoplanbite type. PANalytical X'Pert Pro diffractometer, PIXcel detector Soller slit for incident and diffracted beams: 0.017 radians Fixed angle of dispersion slit: 1 / 4 degree Mask: 10mm Scatter prevention 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

[0153] In Table 1, "SrFe2" is hexagonal strontium ferrite powder prepared by the following method. 1725g of SrCO3, 666g of H3BO3, 1332g of Fe2O3, 52g of Al(OH)3, 34g of CaCO3, and 141g of BaCO3 were weighed out and mixed 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 1380°C. While stirring the molten material, the outlet at the bottom of the platinum crucible was heated, and the molten material was dispensed in a rod shape at a rate of approximately 6 g / second. The dispensed material was rolled and rapidly cooled using water-cooled twin rolls to produce an amorphous body. 280g of the obtained amorphous material was placed in 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 crystalline material obtained above, containing hexagonal strontium ferrite particles, was coarsely ground in a mortar. 1000g of 1mm particle size zirconia beads and 800ml of 1% aqueous acetic acid solution were added to a glass bottle and dispersed in a paint shaker for 3 hours. After that, the resulting dispersion was separated from the beads and placed in a stainless steel beaker. The dispersion was allowed to stand at a liquid temperature of 100°C for 3 hours to dissolve the glass components, then precipitated in a centrifuge and washed by repeated decantation. Finally, it was dried in a heating furnace at a furnace 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 is 2.0 × 10⁻⁶. 5 J / m 3 , mass magnetization σs is 50A m 2 It was / kg.

[0154] In Table 1, "ε-iron oxide" refers to ε-iron oxide powder prepared by the following method. In 90 g of pure water, 8.3 g of iron(III) nitrate nonahydrate, 1.3 g of gallium(III) nitrate octahydrate, 190 mg of cobalt(II) nitrate hexahydrate, 150 mg of titanium(IV) sulfate, and 1.5 g of polyvinylpyrrolidone (PVP) were dissolved. While stirring with a magnetic stirrer in an air atmosphere at an ambient temperature of 25°C, 4.0 g of a 25% aqueous ammonia solution was added, and the mixture was stirred for 2 hours at the same ambient temperature of 25°C. To the resulting solution, a citric acid solution obtained by dissolving 1 g of citric acid in 9 g of pure water was added, and the mixture was stirred for 1 hour. After stirring, the precipitated powder was collected by centrifugation, washed with pure water, and dried in a heating furnace at an ambient temperature of 80°C. 800g of pure water was added to the dried powder, and the powder was dispersed in the water again to obtain a dispersion. The obtained dispersion was heated to 50°C, and 40g of a 25% aqueous ammonia solution was added dropwise while stirring. After stirring for 1 hour while maintaining the temperature at 50°C, 14mL of tetraethoxysilane (TEOS) was added dropwise, and the mixture was stirred for 24 hours. 50g of ammonium sulfate was added to the resulting reaction solution, and the precipitated powder was collected by centrifugation, washed with pure water, and dried in a heating furnace at a temperature of 80°C for 24 hours to obtain a precursor of ferromagnetic powder. The obtained ferromagnetic powder precursor was loaded into a heating furnace at a temperature of 1000°C under an atmospheric environment and subjected to a heat treatment for 4 hours. A heat-treated ferromagnetic powder precursor was added to a 4 mol / L sodium hydroxide (NaOH) aqueous solution, and the solution was stirred for 24 hours while maintaining the temperature at 70°C to remove silicate compounds, which are impurities, from the heat-treated ferromagnetic powder precursor. Subsequently, the ferromagnetic powder, from which the silicate compounds were removed by centrifugation, was collected and washed with pure water to obtain ferromagnetic powder. The composition of the obtained ferromagnetic powder was confirmed by inductively coupled plasma emission spectroscopy (ICP-OES), revealing that it was a Ga, Co, and Ti-substituted ε-iron oxide (ε-Ga 0.28 Co 0.05 Ti 0.05 Fe 1.62 It was O3). Furthermore, X-ray diffraction analysis was performed under the same conditions as described earlier for SrFe1, and from the peaks of the X-ray diffraction pattern, it was confirmed that the obtained ferromagnetic powder had a single-phase crystalline structure of the ε phase (crystalline structure of ε-iron oxide), which did not contain the crystalline structures of the α phase and γ phase. The average particle size of the obtained ε-iron oxide powder was 12 nm, and the activation volume was 746 nm. 3 The anisotropy constant Ku is 1.2 × 10⁻⁶. 5 J / m 3 , mass magnetization σs is 16A m 2 It was / kg.

[0155] The activation volume and anisotropy constant Ku of the hexagonal strontium ferrite powder and ε-iron oxide powder described above were obtained for each ferromagnetic powder using a vibrating sample magnetometer (manufactured by Toei Kogyo Co., Ltd.) and the method described above. Furthermore, the mass magnetization σs was measured using a vibrating sample type magnetometer (manufactured by Toei Kogyo Co., Ltd.) at a magnetic field strength of 15 kOe.

[0156] [Example A1] <Composition for forming magnetic layer>

[0157] (Magnetic liquid) Ferromagnetic powder (see Table 1): 100.0 parts Oleic acid: 2.0 parts Vinyl chloride copolymer (Kaneka Corporation MR-104): 10.0 parts SO3Na group-containing polyurethane resin: 4.0 parts (Weight average molecular weight 70000, SO3Na group: 0.07meq / g) Additive A: 10.0 parts Methyl ethyl ketone: 150.0 parts Cyclohexanone: 150.0 parts (Abrasive solution) α-Alumina (average particle size: 110 nm): 6.0 parts Vinyl chloride copolymer (Kaneka Corporation MR110): 0.7 parts Cyclohexanone: 20.0 parts (Protrusion-forming agent liquid) Protrusion-forming agent (see Table 1): See Table 1 Methyl ethyl ketone: 9.0 parts Cyclohexanone: 6.0 parts (Other ingredients) Polyethyleneimine (manufactured by Nippon Shokubai Co., Ltd., number average molecular weight 300): 2.0 parts Stearic acid: 0.5 parts Stearic acid amide: 0.3 parts Butyl stearate: 6.0 parts Methyl ethyl ketone: 110.0 parts Cyclohexanone: 110.0 parts Polyisocyanate (Tosoh Corporation's Coronate® L): 3.0 parts

[0158] The above-mentioned additive A is a polymer synthesized by the method described in paragraphs 0115 to 0123 of JP-A-2016-051493.

[0159] <Composition for forming non-magnetic layer> Non-magnetic inorganic powder (α-iron oxide): 80.0 parts (Average particle size: 0.15 μm, average aspect ratio: 7, BET (Brunauer-Emmett-Teller) specific surface area: 52 m 2 / g) Carbon black (average particle size: 20 nm): 20.0 parts Electron beam curable vinyl chloride copolymer: 13.0 parts Electron beam curable polyurethane resin: 6.0 parts Phenylphosphonic acid: 3.0 parts Cyclohexanone: 140.0 parts Methyl ethyl ketone: 170.0 parts Butyl stearate: 2.0 parts Stearic acid: 1.0 part

[0160] <Composition for forming back coat layer> Non-magnetic inorganic powder (α-iron oxide): 80.0 parts (Average particle size: 0.15 μm, average aspect ratio: 7, BET specific surface area: 52 m 2 / g) Carbon black (average particle size: 20 nm): 20.0 parts Carbon black (average particle size: 100 nm): 3.0 parts Vinyl chloride copolymer: 13.0 parts Sulfonic acid group-containing polyurethane resin: 6.0 parts Phenylphosphonic acid: 3.0 parts Cyclohexanone: 140.0 parts Methyl ethyl ketone: 170.0 parts Stearic acid: 3.0 parts Polyisocyanate (Coronate (registered trademark) L manufactured by Tosoh Corporation): 5.0 parts Methyl ethyl ketone: 400.0 parts

[0161] <Preparation of Composition for Forming Each Layer> The composition for forming the magnetic layer was prepared by the following method. After kneading and diluting the components of the above magnetic liquid with an open kneader, using a horizontal bead mill disperser, zirconia (ZrO2) beads with a particle size of 0.5 mm (hereinafter referred to as "Zr beads") were used, with a bead filling rate of 80% by volume and a rotor tip peripheral speed of 10 m / s. The residence time per pass was set to 2 minutes, and a dispersion treatment of 12 passes was performed. After mixing the components of the abrasive liquid, it was put into a vertical sand mill disperser together with Zr beads with a particle size of 1 mm, adjusted so that the bead volume / (abrasive liquid volume + bead volume) was 60%, and subjected to a sand mill dispersion treatment for 180 minutes. After the treatment, the liquid was taken out and subjected to ultrasonic dispersion filtration treatment using a flow-through ultrasonic dispersion filtration device. The projection forming agent liquid was prepared by mixing the components of the projection forming agent liquid and then filtering the dispersion liquid obtained by ultrasonic treatment (dispersion treatment) at an ultrasonic output of 500 watts per 200 cc for 60 minutes using a horn-type ultrasonic disperser with a filter having a pore size of 0.5 μm. The magnetic liquid, abrasive liquid, projection forming agent liquid, and the above other components were introduced into a dissolver stirrer, stirred at a peripheral speed of 10 m / s for 30 minutes, then treated in 3 passes at a flow rate of 7.5 kg / min using a flow-through ultrasonic disperser, and then filtered through a filter with a pore size of 1 μm to prepare the composition for forming the magnetic layer.

[0162] The composition for forming the non-magnetic layer was prepared by the following method. The above components excluding the lubricants (butyl stearate and stearic acid) were kneaded and diluted with an open kneader, and then subjected to a dispersion treatment using a horizontal bead mill disperser. Thereafter, the lubricants (butyl stearate and stearic acid) were added and stirred with a dissolver stirrer to perform a mixing treatment to prepare the composition for forming the non-magnetic layer.

[0163] The composition for forming the back coat layer was prepared by the following method. The above components, excluding the lubricant (stearic acid), polyisocyanate, and methyl ethyl ketone (400.0 parts), were kneaded and diluted using an open kneader, and then dispersed using a horizontal bead mill disperser. Subsequently, the lubricant (stearic acid), polyisocyanate, and methyl ethyl ketone (400.0 parts) were added and mixed using a dissolver stirrer to prepare a composition for forming the back coat layer.

[0164] <Manufacturing of magnetic tapes and magnetic tape cartridges> A non-magnetic layer-forming composition was applied to a biaxially oriented polyethylene naphthalate support of the thickness shown in Table 1, so that the thickness after drying was as shown in Table 1, and then dried. After that, it was irradiated with an electron beam at an accelerating voltage of 125 kV to an energy of 40 kGy. On top of that, a magnetic layer-forming composition was applied and dried so that the thickness after drying was as shown in Table 1, and then a back coat layer-forming composition was applied to the surface of the support opposite to the surface where the non-magnetic layer and magnetic layer were formed, so that the thickness after drying was as shown in Table 1, and then dried. Subsequently, calendering was performed using a 7-stage calendering roll consisting solely of metal rolls, at a calendering speed of 80 m / min, a linear pressure of 294 kN / m, and a calendering temperature (surface temperature of the calendering roll) of 80°C. After that, heat treatment was performed for 36 hours in an ambient temperature of 70°C. After the heat treatment, the material was slit into 1 / 2-inch width strips, and the surface of the magnetic layer was cleaned using a tape cleaning device equipped with a feed and winding mechanism for the slit strips, with the nonwoven fabric and razor blade pressed against the magnetic layer surface to obtain a magnetic tape. By recording servo signals on the magnetic layer of the obtained magnetic tape using a commercially available servo writer, a magnetic tape was obtained having data bands, servo bands, and guide bands arranged in accordance with the LTO (Linear Tape-Open) Ultrium format, and having a servo pattern (timing-based servo pattern) on the servo bands arranged and shaped in accordance with the LTO Ultrium format. The servo pattern thus formed is a servo pattern that conforms to the description in 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 960m) on which the servo signals were recorded was wound onto a reel of a magnetic tape cartridge (LTO Ultrium8 data cartridge), and a leader tape conforming to item 9 of Section 3 of Standard ECMA (European Computer Manufacturers Association)-319 (June 2001) was spliced ​​to the end using commercially available splicing tape. In this way, a magnetic tape cartridge was created in which magnetic tape was wound onto a reel.

[0165] The presence of a compound containing an ammonium salt structure of an alkyl ester anion represented by Formula 1, formed from polyethyleneimine and stearic acid, in the magnetic layer of the magnetic tape can be confirmed by the following method. A sample is cut from the magnetic tape, and X-ray photoelectron spectroscopy analysis is performed on the magnetic layer surface (measurement area: 300 μm × 700 μm) using an ESCA instrument. For details, wide-scan measurements are performed using the ESCA instrument under the measurement conditions described below. In the measurement results, peaks are observed at the bond energy positions of the ester anion and the ammonium cation. Equipment: Shimadzu Corporation AXIS-ULTRA Excitation X-ray source: Monochromatic Al-Kα rays Scan range: 0~1200eV Pass energy: 160 eV Energy resolution: 1 eV / step Data acquisition time: 100ms / step Total number of times: 5 Furthermore, a 3cm long sample piece was cut 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, and the measurement results showed that the COO - Wavefrequency corresponding to absorption (1540 cm) -1 or 1430cm -1 ), and the wavenumber corresponding to the absorption of ammonium cations (2400 cm²). -1 Absorption is confirmed in ).

[0166] [Example A2~Example A27, Example B1~Example B34] A magnetic tape and magnetic tape cartridge were obtained using the method described for Example A1, except that the items shown in Table 1 were changed as shown in Table 1. For Examples A23 to A27 and B30 to B34, the post-serial signal recording process was modified as follows: heat treatment was performed after servo signal recording. In contrast, for Examples A1 to A22 and B1 to B29, no such heat treatment was performed, so "None" is written in the "Heat Treatment Conditions" column in Table 1. For Examples A23 to A27 and B30 to B34, as described for Example A1, the magnetic tape (length 970m) after recording the servo signal was wound onto a heat treatment core, and heat treatment was performed while the tape was wound onto this core. As the heat treatment core, a solid resin core member (outer diameter: 50mm) with a bending modulus of elasticity shown in Table 1 was used, and the tension during winding was set to the value shown in Table 1. The heat treatment temperature and heat treatment time were set to the values ​​shown in Table 1. The absolute humidity by weight of the atmosphere during heat treatment was 10g / kg dry air. After the heat treatment described above, once the magnetic tape and the heat treatment core had cooled sufficiently, the magnetic tape was removed from the heat treatment core and wound onto a temporary winding core. Then, the final product length (960m) of magnetic tape was wound from the temporary winding core onto a reel of a magnetic tape cartridge (LTO Ultrium8 data cartridge). The remaining 10m was cut off, and a leader tape was joined to the cut end using commercially available splicing tape, in accordance with item 9 of Section 3 of Standard ECMA (European Computer Manufacturers Association)-319 (June 2001). As the temporary winding core, a solid core member made of the same material and having the same outer diameter as the heat treatment core was used, and the tension during winding was set to 0.6N. In this way, a magnetic tape cartridge was created in which magnetic tape was wound onto a reel.

[0167] For each of the above examples, four magnetic tape cartridges were prepared. One was used for the evaluation of running stability described below, and the other three were used for the magnetic tape evaluations (1) to (3) described below.

[0168] [Evaluation of magnetic tape] (1)Frictional force Remove the magnetic tape from each of the above examples of magnetic tape cartridges, and in an environment with a temperature of 32°C and a relative humidity of 80%, apply the frictional force F as described above. 45° The standard deviation of the frictional force F was also calculated. A commercially available LTO8 head (manufactured by IBM) was used as the LTO8 head.

[0169] (2) Standard deviation of the curvature of the magnetic tape in the longitudinal direction The magnetic tape was removed from each of the above examples of magnetic tape cartridges, and the standard deviation of the curvature in the longitudinal direction of the magnetic tape was determined using the method described above.

[0170] (3) Tape thickness Ten tape samples (5 cm in length) were cut from arbitrary sections of the magnetic tape cartridges used in each of the above examples. These tape samples were stacked and their thickness was measured. The thickness was measured using a digital thickness meter consisting of a MARH Millimar 1240 compact amplifier and a Millimar 1301 inductive probe. The measured thickness was divided by 10 to obtain the value obtained (thickness per tape sample), which was defined as the tape thickness.

[0171] [Evaluation of driving stability] The driving stability was evaluated using the following method in an environment with a temperature of 32°C and a relative humidity of 80%. Using each of the magnetic tape cartridges in the above examples, data recording and playback were performed using a magnetic tape device configured as shown in Figure 8. The arrangement of modules in the recording / playback head mounted on the recording / playback head unit is "recording module - playback module - recording module" (total number of modules: 3). Each module has 32 magnetic head elements (Ch0~Ch31), and these magnetic head elements are sandwiched between a pair of servo signal reading elements to form an element array. The playback element width of the playback element included in the playback module is 0.8 μm. The following method was used to record and play back data and evaluate the playback stability during playback, performing this process a total of four times by sequentially changing the head tilt angle in the order of 0°, 15°, 30°, and 45°. The head tilt angle is the angle θ that the axis of the element array of the playback module makes with respect to the width direction of the magnetic tape at the start of each playback. The angle θ was set by the control device of the magnetic tape device at the start of each magnetic tape playback, and the head tilt angle was fixed during each magnetic tape playback. A magnetic tape cartridge is set in the magnetic tape drive, and the magnetic tape is loaded. Next, while performing servo tracking, the recording / playback head unit records pseudo-random data with a specific data pattern onto the magnetic tape. The tension applied along the length of the tape is kept constant. Simultaneously with data recording, the servo band spacing along the entire length of the tape is measured every 1 meter along the length and recorded in the cartridge memory. Next, while performing servo tracking, the recording and playback head unit plays back the data recorded on the magnetic tape. The tension in the longitudinal direction of the tape at that time is set to a constant value. During the above playback, the running stability was evaluated using, as an index, the standard deviation (hereinafter referred to as "σPES") of the reading position PES (Position Error Signal) in the width direction based on the servo signal obtained by the servo signal reading element. PES is obtained by the following method. To obtain PES, the dimensions of the servo pattern are required. The standards for the dimensions of the servo pattern vary depending on the generation of LTO. Therefore, first, using a magnetic force microscope or the like, the average distance AC between the corresponding 4 stripes of A burst and C burst, and the azimuth angle α of the servo pattern are measured. The average time between the 5 stripes corresponding to the A burst and the B burst over the length of 1 LPOS word is defined as a. The average time of the 4 stripes corresponding to the A burst and the C burst over the length of 1 LPOS word is defined as b. At this time, the value defined by AC×(1 / 2 - a / b) / (2×tan(α)) is the reading position PES (Position Error Signal) in the width direction based on the servo signal obtained by the servo signal reading element over the length of 1 LPOS word. For the magnetic tape, the end on the side wound around the reel of the magnetic tape cartridge is called the inner end, and the opposite end is called the outer end. With the outer end set to 0 m, the standard deviation (σPES) of PES obtained by the above method was calculated for the region in the longitudinal direction of the tape over a length of 30 m to 200 m. The arithmetic mean of σPES obtained for a total of 4 recordings and playbacks is shown in the column of "σPES" in Table 1. If σPES is less than 70 nm, it can be determined that the running stability is excellent.

[0172] [Recording Capacity] In each of the above examples, magnetic tapes of the same length were housed in the magnetic tape cartridge even when the tape thicknesses of the magnetic tapes were different. On the other hand, magnetic tape cartridges generally house the magnetic tape wound on a reel inside the casing, so they cannot accommodate magnetic tape longer than the volume of the casing. The thicker the magnetic tape, the larger the tape volume per unit length, and therefore the shorter the maximum tape length that can be accommodated inside the casing. Regarding recording capacity, the longer the length of the magnetic tape that can be stored in one magnetic tape cartridge, the higher the recording capacity per cartridge can be. From the above, the longer the maximum tape length that can be accommodated in a certain volume of enclosure, the more desirable the magnetic tape is for achieving high capacity, and this maximum tape length decreases as the thickness of the magnetic tape increases. Therefore, the recording capacity of the magnetic tapes in each of the above examples was evaluated as follows. The magnetic tape B12 with a tape thickness of 5.6 μm will be used as the standard for recording capacity (evaluation index below: 100). For magnetic tapes with a thickness of Tμm, the evaluation index (unitless) for recording capacity is calculated as follows: "Evaluation index = (5.6-T) / 5.6×100+100". A magnetic tape with a larger calculated value is considered more desirable for achieving higher capacity.

[0173] The results are shown in Table 1 (Tables 1-1 to 1-2).

[0174] [Table 1-1]

[0175] [Table 1-2]

[0176] From the results shown in Table 1, the magnetic tapes of Examples A1 to A27 are, It demonstrated excellent running stability when running magnetic tape at different head tilt angles in a high-temperature, high-humidity environment, and, This is desirable from the standpoint of increasing recording capacity. This can be confirmed.

[0177] Magnetic tape cartridge P-1 was manufactured using the same method as described for Example A1, except that during the production of the magnetic tape, a magnetic layer-forming composition was applied to form a coating layer, and then, while the coating layer of the magnetic layer-forming composition was still wet, a magnetic field with a magnetic field strength of 0.3T was applied perpendicularly to the surface of the coating layer to perform a vertical orientation treatment, and then the magnetic layer was formed by drying. Furthermore, magnetic tape cartridge P-2 was manufactured using the same method as described for Example A2, except that during magnetic tape production, after applying the magnetic layer-forming composition to form a coating layer, a magnetic field of strength 0.5T was applied perpendicularly to the surface of the coating layer while the coating layer of the magnetic layer-forming composition was still wet to perform a vertical orientation treatment, and then it was dried to form the magnetic layer. A sample piece was cut from the magnetic tape removed from magnetic tape cartridge P-1. The vertical angular ratio of this sample piece was determined using the method described above with a Tamagawa Seisakusho TM-TRVSM5050-SMSL vibrating sample magnetometer, and it was found to be 0.60. The magnetic tape was also extracted from the magnetic tape cartridge P-2, and the vertical aspect ratio was similarly determined for a sample piece cut from this magnetic tape, which was found to be 0.65. A magnetic tape was also extracted from the magnetic tape cartridge of Example A1, and the vertical aspect ratio was similarly determined for a sample piece cut from this magnetic tape, which was found to be 0.55.

[0178] The magnetic tapes extracted from the three magnetic tape cartridges described above were each mounted on a 1 / 2-inch reel tester, and their electromagnetic conversion characteristics (SNR: Signal-to-Noise Ratio) were evaluated using the following method. As a result, the magnetic tape extracted from magnetic tape cartridge P-1 (with vertical alignment treatment) showed an SNR value 2 dB higher than the magnetic tape extracted from magnetic tape cartridge A1 (without vertical alignment treatment). The magnetic tape extracted from magnetic tape cartridge P-2 (with vertical alignment treatment) showed an SNR value 4 dB higher than the magnetic tape extracted from magnetic tape cartridge A1. Recording and playback were performed in 10 passes under a tension of 0.7N in the longitudinal direction of the magnetic tape in an environment of 23°C and 50% relative humidity. The relative speed between the magnetic tape and the magnetic head was set to 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 optimal recording current for each magnetic tape. For playback, a GMR (Giant-magnetoresistive) head (element thickness 15 nm, shielding gap 0.1 μm, playback element width 0.8 μm) was used as the playback head. The head tilt angle was set to 0°. A signal with a linear recording density of 300 kfci was recorded, and the playback signal was measured using a spectrum analyzer manufactured by Shibasoku. The unit kfci is the unit of linear recording density (not convertible to the SI system). As the signal, the portion where the signal was sufficiently stable after the start of magnetic tape movement was used. [Industrial applicability]

[0179] One aspect of the present invention is useful in the technical field of various data storage technologies.

Claims

1. A magnetic tape comprising a non-magnetic support and a magnetic layer containing ferromagnetic powder, The tape thickness of the magnetic tape is 5.2 μm or less. In an environment with a temperature of 32°C and a relative humidity of 80%, The frictional force F on the magnetic layer surface of an LTO8 head, measured at a head tilt angle of 45°. ４５° is 4 gf or more and 15 gf or less, and A magnetic tape in which the standard deviation of the frictional force F on the magnetic layer surface for an LTO8 head, measured at head tilt angles of 0°, 15°, 30°, and 45°, is 10gf or less.

2. The magnetic tape according to claim 1, wherein the standard deviation of F is 2 gf or more and 10 gf or less.

3. The magnetic tape according to claim 1, wherein the tape thickness is 4.0 μm or more and 5.2 μm or less.

4. The magnetic tape according to claim 1, wherein the tape thickness is 4.0 μm or more and 5.0 μm or less.

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

6. The magnetic tape according to claim 1, wherein the magnetic layer includes inorganic oxide particles.

7. The magnetic tape according to claim 6, wherein the inorganic oxide particles are composite particles of an inorganic oxide and a polymer.

8. The magnetic tape according to claim 1, wherein the magnetic layer comprises carbon black.

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

10. The magnetic tape according to claim 9, wherein the thickness of the non-magnetic layer is 0.1 μm or more and 0.7 μm or less.

11. The magnetic tape according to claim 1, wherein the non-magnetic support has a back coat layer containing non-magnetic powder on the surface side opposite to the surface side having the magnetic layer.

12. The magnetic tape according to claim 1, wherein the vertical aspect ratio of the magnetic tape is 0.60 or greater.

13. The magnetic tape according to claim 1, wherein the vertical aspect ratio of the magnetic tape is 0.65 or more.

14. A magnetic tape cartridge comprising the magnetic tape described in any one of claims 1 to 13.

15. A magnetic tape device including a magnetic tape according to any one of claims 1 to 13.

16. Further including a magnetic head, The magnetic head has a module including an element array having a plurality of magnetic head elements between a pair of servo signal reading elements, The magnetic tape device according to claim 15, wherein the magnetic tape device changes the angle θ that the axis of the element array makes with respect to the width direction of the magnetic tape while the magnetic tape is running within the magnetic tape device.

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