Magnetic tape, magnetic tape cartridge, and magnetic tape device

Abstract

Provided is a magnetic tape that is a data tape wherein the arithmetic mean peak curvature Spc as defined in ISO 25178 of the surface of a magnetic layer is 0.30–0.70 (1 / μm), the standard deviation σ of the Spc in the width direction of the surface of the magnetic layer is no more than 0.15 (1 / μm), and a leader pin is directly attached to an end part.

Description

Magnetic tape, magnetic tape cartridge and magnetic tape device

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

[0002] Magnetic recording media include tape-type and disk-type recording media, and tape-type magnetic recording media, i.e., magnetic tape, are mainly used for data storage applications such as data backup and archiving (see, for example, Patent Documents 1 to 3).

[0003] Special Publication No. 2016-524774 US2019 / 0164573A1 Patent No. 6590102

[0004] Data is typically recorded on magnetic tape by running the magnetic tape in a magnetic tape device (commonly called a "drive") and recording data on the data band by moving a magnetic head along the data band of the magnetic tape. This forms a data track on the data band. To play back the recorded data, the magnetic tape is run in the magnetic tape device and the magnetic head is moved along the data band of the magnetic tape to read the data recorded on the data band. After recording or playback, the magnetic tape is typically stored wound on a reel inside a magnetic tape cartridge or the like until the next recording and / or playback is performed.

[0005] To improve the accuracy with which a magnetic head tracks the data band of a magnetic tape during the above-described recording and / or playback, a system (hereinafter referred to as a "servo system") that performs head tracking using a servo signal has been put into practical use. However, when recording and / or playback is performed after the above-described storage, deformation of the magnetic tape width caused by storage can cause a phenomenon (commonly referred to as "off-track") in which the magnetic head for recording and / or playback of data deviates from the target track position. Off-track can cause overwriting of recorded data, playback problems, and other issues, thereby reducing the operational stability of the drive. In recent years, the track density has increased along with the increase in magnetic tape capacity, making off-track more likely to occur, and therefore there is a growing need for improved operational stability of the drive. Meanwhile, in the field of data storage, long-term data storage, known as archiving, has become common. However, generally, the longer the storage period, the more likely the magnetic tape width deformation occurs, and the frequency of off-track tends to increase.

[0006] In view of the above, an object of one aspect of the present invention is to provide a magnetic tape that can contribute to improving the operational stability of a drive during recording and / or playback after long-term storage.

[0007] 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, wherein the arithmetic mean peak curvature Spc (hereinafter also referred to as "Spc of the magnetic layer surface" or simply "Spc") of the surface of the magnetic layer as defined in ISO (International Organization for Standardization) 25178 is 0.30 (1 / μm) or more and 0.70 (1 / μm) or less, the standard deviation σ of the Spc in the width direction of the surface of the magnetic layer (hereinafter also referred to as "Spc width direction σ") is 0.15 (1 / μm) or less, and the magnetic tape is a data tape in which a leader pin is directly attached to an end. [2] The magnetic tape according to [1], wherein the standard deviation σ of the Spc is 0.12 (1 / μm) or less. [3] The magnetic tape according to [1] or [2], wherein the magnetic layer further contains non-magnetic powder having an average plate diameter of 50 nm or more and 1000 nm or less and an average plate thickness of 12 nm or less. [4] The magnetic tape according to any one of [1] to [3], wherein the data tape further has a non-magnetic layer between the non-magnetic support and the magnetic layer, the non-magnetic powder containing non-magnetic powder. [5] The non-magnetic powder in the non-magnetic layer has an average particle volume of 2.0 x 10 －６ μm ３The magnetic tape according to [4], which contains the following Fe-based inorganic oxide powder. [6] The magnetic tape according to [4] or [5], wherein the non-magnetic powder in the non-magnetic layer contains carbon black having a pH of 9.0 or less. [7] The magnetic tape according to any one of [4] to [6], wherein the thickness of the non-magnetic layer is 0.1 μm or more and 0.7 μm or less. [8] The magnetic tape according to any one of [1] to [7], wherein the data tape further has a backcoat layer containing non-magnetic powder on the surface of the non-magnetic support opposite to the surface having the magnetic layer. [9] The magnetic tape according to any one of [1] to [8], wherein the data tape has a tape thickness of 5.2 μm or less.

[10] The magnetic tape according to any one of [1] to [9], wherein the data tape has a tape thickness of 5.0 μm or less.

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

[10] , wherein the data tape has a perpendicular squareness ratio of 0.60 or more.

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

[11] , wherein the data tape has a squareness ratio in the perpendicular direction of 0.65 or more.

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

[12] , wherein the end of the data tape to which the leader pin is directly attached further has a reinforcing layer on at least one of the magnetic layer side and the side opposite to the magnetic layer side.

[14] The magnetic tape according to

[13] , wherein the reinforcing layer has a thickness of 10.0 μm or more.

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

[14] , wherein the non-magnetic support is an aromatic polyamide support.

[16] The standard deviation σ of the Spc is 0.12 (1 / μm) or less, the magnetic layer further contains non-magnetic powder having an average tabular diameter of 50 nm or more and 1000 nm or less and an average tabular thickness of 12 nm or less, the data tape further has a non-magnetic layer between the non-magnetic support and the magnetic layer, the non-magnetic powder containing non-magnetic powder having an average particle volume of 2.0 × 10 －６ μm ３The magnetic tape according to any one of [1] to

[15] , comprising the following Fe-based inorganic oxide powder and carbon black having a pH of 9.0 or less, the thickness of the non-magnetic layer being 0.1 μm or more and 0.7 μm or less, the data tape further having a backcoat layer containing a non-magnetic powder on the surface of the non-magnetic support opposite to the surface having the magnetic layer, the tape thickness of the data tape being 5.0 μm or less, the squareness ratio of the data tape in the perpendicular direction being 0.65 or more, and the end of the data tape to which the leader pin is directly attached further having a reinforcing layer having a thickness of 10.0 μm or more on at least one of the magnetic layer side and the side opposite to the magnetic layer side.

[17] A magnetic tape cartridge comprising the magnetic tape according to any one of [1] to

[16] .

[18] A magnetic tape device comprising the magnetic tape according to any one of [1] to

[16] .

[19] The magnetic tape device described in

[18] , further comprising a magnetic head, wherein the magnetic head has a module including an element array having a plurality of magnetic head elements between a pair of servo signal reading elements, and wherein the magnetic tape device changes the angle θ formed by the axis of the element array with respect to the width direction of the magnetic tape while the magnetic tape is running within the magnetic tape device.

[0008] According to one aspect of the present invention, it is possible to provide a magnetic tape that contributes to improving the operational stability of a drive during recording and / or playback after long-term storage, and a magnetic tape cartridge and a magnetic tape device that include such a magnetic tape.

[0009] 1 shows an example of a track profile plotting track position on the horizontal axis and playback signal output on the vertical axis. 1 shows an example of a graph relating to initial nonlinear components. 1 shows an example of a graph relating to nonlinear components after storage. 1 shows an example of a graph showing the absolute value of the difference between the initial nonlinear component for each playback element and the nonlinear component after storage (the difference in nonlinear components before and after storage), calculated for each playback element. 1 is a schematic diagram showing an example of a magnetic head module. 1 is an explanatory diagram of the relative positional relationship between the module and the magnetic tape while the magnetic tape is running in a magnetic tape device. 1 is an explanatory diagram of the change in angle θ while the magnetic tape is running. 1 shows an example of a magnetic tape manufacturing process (schematic diagram). 1 shows an example of the arrangement of data bands and servo bands. 1 shows an example of the servo pattern arrangement of an LTO (Linear Tape-Open) Ultrium format tape. 1 is an explanatory diagram of a method for measuring angle θ while the magnetic tape is running. 1 is a schematic diagram showing an example of a magnetic tape device. 1 is a perspective view of an example of a state in which a magnetic tape having a leader tape has been pulled out of a magnetic tape cartridge. 1 is a cross-sectional view of an example of a state in which a data tape and a leader tape have been spliced ​​together by a splicing tape. 1 is a cross-sectional view showing a portion of an example of a magnetic tape provided with a reinforcing layer.

[0010] Hereinafter, magnetic tapes, magnetic tape cartridges, and magnetic tape devices will be described with reference to the drawings. However, the embodiments shown in the drawings are merely examples, and the present invention is not limited to the embodiments shown in the drawings.

[0011] [Magnetic Tape] One aspect of the present invention relates to a magnetic tape. The magnetic tape has a non-magnetic support and a magnetic layer containing ferromagnetic powder, and the arithmetic mean peak curvature Spc of the surface of the magnetic layer as defined in ISO 25178 is 0.30 (1 / μm) or more and 0.70 (1 / μm) or less, and the standard deviation σ of the Spc in the width direction of the surface of the magnetic layer is 0.15 (1 / μm) or less. Furthermore, the magnetic tape is a data tape in which a leader pin is directly attached to the end.

[0012] In this invention and this specification, a "data tape" is a magnetic tape on which data is recorded, and typically has a servo pattern formed thereon. In contrast, no data is recorded on a "leader tape." A leader tape is typically a tape on which no servo pattern is formed. A leader pin is typically attached to the end of the leader tape. The leader pin is attached to the outer end of the magnetic tape housed in a magnetic tape cartridge. When the magnetic tape cartridge is loaded into a magnetic tape device, the leader pin is pulled out while being engaged by the pull-out member of the magnetic tape device, and is attached to the take-up reel of the magnetic tape device.

[0013] FIG. 13 is a perspective view of an example of a magnetic tape having a leader tape pulled out from a magnetic tape cartridge. In FIG. 13, the magnetic tape cartridge 13 has a cartridge case 132 in which an upper case 132a and a lower case 132b are fastened together with screws or the like. A leader pin 133 is attached to the outer end of the magnetic tape MT. At the other end of the magnetic tape MT, the end of the data tape is typically wound around a cartridge reel 135. One side wall of the cartridge case 132 has an opening 132c for pulling out the magnetic tape MT, which is opened and closed by a sliding door 136 biased in a closing direction by an elastic means (not shown). When the magnetic tape cartridge 13 is not in use, with the magnetic tape MT completely wound around the cartridge reel 135, the leader pin 133 attached to the tape end is locked in a recessed storage portion 132d formed near the opening 132c.

[0014] Although not shown in Figure 13, a center hole is opened in the center of the lower case 132b for rotating the cartridge reel 135 by the drive shaft of the magnetic tape device, and a rotation restricting mechanism (not shown) is provided in the center of the cartridge reel 135 to restrict rotation of the cartridge reel 135 when not in use. A reel plate is attached to the bottom of the cartridge reel 135 in the center for attracting and holding a magnetic rotation drive means, and a reel gear that meshes with the drive gear of the rotation drive means is engraved on the outer periphery. When the reel gear and drive gear are meshed, the rotation restricting mechanism is released and the cartridge reel 135 is allowed to rotate freely.

[0015] The leader pin 133 is attached to the end of the leader tape LT of the magnetic tape MT using a clamp 138 having a C-shaped cross section.

[0016] Fig. 14 is a cross-sectional view of an example of a state in which a data tape and a leader tape are joined by a splicing tape. In the example shown in Fig. 14, a leader tape LT is joined by a splice tape ST with one end of the leader tape LT butted against one end of a data tape DT.

[0017] In contrast, in the magnetic tape described above, the leader pin is attached directly to the data tape. In other words, the magnetic tape does not have a leader tape. After extensive research, the present inventors have newly discovered that a magnetic tape in which the Spc of the magnetic layer surface is within the above-mentioned range, the width direction σ of the Spc is within the above-mentioned range, and in which the leader pin is attached directly to the data tape without a leader tape can contribute to improving the operational stability of a drive. The present inventors' speculations on this point are described below. However, the present invention is not limited to the speculations described in this specification.

[0018] As described above, tape width deformation caused by long-term storage can cause a decrease in the operational stability of the magnetic tape in the drive. In response to this issue, it has recently been proposed to use servo signals to acquire width-direction dimensional information about 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") based on the acquired dimensional information (see Patent Documents 1 and 2, e.g., paragraphs 0059-0067 and 0084 of Patent Document 1). Another approach is to acquire width-direction dimensional information about the magnetic tape while it is running based on servo signals, and to adjust the tension applied to the magnetic tape in the longitudinal direction based on the acquired dimensional information, thereby controlling the width direction of the magnetic tape (see, for example, paragraph 0171 of Patent Document 3). For example, the above-described dynamic track position control means for controlling the track position during magnetic tape running can be used to suppress off-track. However, the present inventors, in their extensive research into further improving the operational stability of the drive during recording and / or playback after long-term storage, have noticed that there may be off-track factors that are difficult to compensate for using dynamic track position control means. This point will be further explained below. When dynamic track position control is performed by changing the head tilt angle, the pitch of the magnetic head elements (specifically, the recording elements and / or reproducing elements) changes uniformly depending on the head tilt angle, regardless of the position in the tape width direction. When dynamic track position control is performed by adjusting the tension applied to the magnetic tape in the longitudinal direction, the tension is usually adjusted across the entire tape width, so tension adjustment results in a uniform change in tape width regardless of the position in the tape width direction. If the degree of tape width deformation is uniform across the magnetic tape, i.e., if the tape width deformation component is only a linear component, it is possible to completely compensate for off-track using the control means. Therefore, it is possible to completely align the data track and the magnetic head element. On the other hand, if the degree of tape width deformation varies non-uniformly depending on the position, i.e., if the tape width deformation component includes a non-linear component, it is difficult for the control means to compensate for off-track caused by the non-linear component.The inventors believe that reducing this nonlinear component can contribute to suppressing the deterioration of drive operational stability due to off-track factors, which are difficult to compensate for using dynamic track position control means. In this regard, the inventors believe that the Spc of the magnetic layer surface of the data tape within the above-mentioned range and the standard deviation σ of Spc within the above-mentioned range can contribute to suppressing the occurrence of the nonlinear component of the tape width deformation. Furthermore, the inventors believe that the inclusion of a leader pin contributes to the occurrence of the nonlinear component of the tape width deformation. That is, the inventors believe that the magnetic tape having a leader pin directly attached to the data tape without a leader tape can also contribute to suppressing the occurrence of the nonlinear component of the tape width deformation. Thus, the inventors believe that the magnetic tape can contribute to improving drive operational stability during recording and / or playback after long-term storage.

[0019] <<Spc and Width Direction σ of Spc of Magnetic Layer Surface>> In the present invention and this specification, Spc is the arithmetic mean curvature Spc of the peaks defined in ISO 25178. ISO 25178 is an ISO standard related to three-dimensional surface texture parameters, specifically ISO 25178-2:2021 (Geometrical product specifications (GPS) - Surface texture: Areal - Part 2: Terms, definitions and surface texture parameters). To determine the Spc of the magnetic layer surface, measurements are made on the surface of the magnetic layer of a data tape using an atomic force microscope (AFM) as follows. In this specification and the present invention, the "surface of the magnetic layer" of a data tape is synonymous with the surface of the magnetic layer of the data tape. The measurement area is a 40 μm square (40 μm × 40 μm) area. Measurements are performed at five locations. The five locations where the magnetic layer surface is measured are five locations with the same longitudinal position but different widthwise positions. The longitudinal positions are randomly selected on the magnetic layer surface, and the width of this longitudinal position is divided into five sections relative to the data tape width (therefore, if the data tape width is W, the width of each section is "W / 5"). Spc, as defined in ISO 25178, is determined for a randomly selected 40 μm square (40 μm × 40 μm) area in each section. Spc can be calculated using known AFM data analysis software. An example of AFM data analysis software is AFM data analysis software (Nanoscope Analysis) provided by BRUKER. The arithmetic mean of the five measured values ​​thus obtained is taken as the Spc of the magnetic layer surface of the data tape being measured. The standard deviation σ (i.e., the positive square root of the variance) of the five measured values ​​thus obtained is taken as the standard deviation σ of Spc in the width direction of the surface of the magnetic layer of the data tape being measured (Spc width direction σ). The following measurement conditions can be given as an example of AFM measurement conditions: An AFM (Nanoscope 5 manufactured by BRUKER) is used in peak force tapping mode to measure an area of ​​40 μm × 40 μm on the surface of the magnetic layer of the data tape.The probe used is a SCANASYST-AIR manufactured by BRUKER, with a resolution of 512 pixels x 512 pixels and a scan speed of measuring one screen (512 pixels x 512 pixels) in 512 seconds.

[0020] (Spc of magnetic layer surface) The Spc of the magnetic layer surface of the data tape is 0.30 (1 / μm) or more and 0.70 (1 / μm) or less. From the viewpoint of improving the operational stability of the drive during recording and / or playback after long-term storage, the Spc of the magnetic layer surface is 0.30 (1 / μm) or more, preferably 0.40 (1 / μm) or more, and more preferably 0.50 (1 / μm) or more. Furthermore, from the above viewpoint, the Spc of the magnetic layer surface is preferably 0.70 (1 / μm) or less and 0.60 (1 / μm) or less.

[0021] (Spc Width Direction σ) The standard deviation σ of Spc in the width direction of the surface of the magnetic layer of the data tape (Spc Width Direction σ) is 0.15 (1 / μm) or less, preferably 0.14 (1 / μm) or less, more preferably 0.13 (1 / μm) or less, even more preferably 0.12 (1 / μm) or less, even more preferably 0.11 (1 / μm) or less, and even more preferably 0.10 (1 / μm) or less, from the viewpoint of improving the operational stability of the drive during recording and / or playback after long-term storage. The Spc Width Direction σ can be, for example, 0.00 (1 / μm) or more, 0.01 (1 / μm) or more, 0.05 (1 / μm) or more, or 0.08 (1 / μm) or more. From the viewpoint of improving the operational stability of the drive during recording and / or playback after long-term storage, it is presumed that the smaller the value of Spc Width Direction σ, the more preferable.

[0022] The method for controlling the Spc on the surface of the magnetic layer and the method for controlling the Spc in the width direction σ will be described later.

[0023] <<Nonlinear Component of Tape Width Deformation>> The inventors believe that the "nonlinear component in the tape width direction resulting from 20 days of storage in an environment with a temperature of 60°C and a relative humidity of 20%" obtained by the following method can serve as an indicator of the nonlinear component of the tape width deformation described above. Note that the "20 days of storage in an environment with a temperature of 60°C and a relative humidity of 20%" storage condition is an example of storage conditions in an accelerated environment equivalent to long-term data storage known as an archive. The magnetic tape described above is not limited to those stored under such conditions. Unless otherwise specified, the following operations and measurements are performed in an environment with a temperature of 20-25°C and a relative humidity of 40-60%. The magnetic tape to be measured is a magnetic tape with a data tape length (including the length of the portion where the leader pin is attached) of 200 m or more. If the magnetic tape to be measured is housed in a magnetic tape cartridge, the magnetic tape is removed from the magnetic tape cartridge. The magnetic tape to be measured is wound onto a magnetic tape reel with a hub diameter (outer diameter, hereinafter the same) of 44 mm, applying a tension of 0.6 N (Newton) in the longitudinal direction of the magnetic tape using a device with a winding mechanism that applies tension to the magnetic tape in the longitudinal direction. The magnetic tape wound onto the reel in this manner is stored for at least 24 hours in an environment with a temperature of 20-25°C and a relative humidity of 40-60% before the following measurements. Regarding one end and the other end of the magnetic tape, the end closest to the start point of winding onto the reel is referred to as the inner peripheral end of the tape, and the other end is referred to as the outer peripheral end of the tape. Here, the inner peripheral end of the tape is the end of the tape on the side where the leader pin is attached, and the following measurements are performed with the leader pin attached. The outer peripheral end of the tape is the end of the tape opposite the side where the leader pin is attached, and is usually the end of the data tape. The following measurements are performed in an area within 100 m from the outer edge of the data tape (hereinafter referred to as the "outer edge of the tape") and an area within 100 m from the inner edge of the data tape (hereinafter referred to as the "inner edge of the tape"), at the center wrap of each data band.The following measurements were performed using a magnetic head equipped with a reproduction module including an element array having 10 or more channels of reproduction elements with an element width (more specifically, reproduction element width) of 0.2 μm to 1.0 μm between a pair of servo signal read elements, and a recording module including an element array having 10 or more channels of recording elements with an element width (more specifically, recording element width) of 1.2 μm to 2.9 μm between a pair of servo signal read elements. "Element width" refers to the physical dimension of the element width and can be measured using an optical microscope, scanning electron microscope, or the like. In the recording module, the spacing between two adjacent recording elements in the head width direction is 83.25 μm. In the reproduction module, the spacing between two adjacent reproduction elements in the head width direction is 83.25 μm. The spacing is the spacing between the centers of two adjacent recording elements in the recording module, and the spacing is the spacing between the centers of two adjacent reproduction elements in the reproduction module, and can be measured using an optical microscope, or the like. In the measurements for the examples and comparative examples described below, a magnetic head was used, which included a recording module including an element array with 32 channels (0 to 31 channels) of recording elements between a pair of servo signal reading elements, and a playback module including an element array with 32 channels (0 to 31 channels) of playback elements between a pair of servo signal reading elements. The reel on which the magnetic tape to be measured is wound and the magnetic head are attached to the tape transport system of a magnetic tape device to record and play back data. The tape transport system is attached to a recording / playback amplifier capable of driving the magnetic head elements (more specifically, the recording element and playback element) of the magnetic head. The recording / playback amplifier can be controlled from a computer (PC: Personal Computer) via a controller. The magnetic head is attached to an actuator (piezoelectric motor or VCM (voice coil motor)) that operates in the tape width direction, and can perform servo following so that the magnetic head is positioned at a constant track during tape running based on the servo signal from the magnetic tape.Furthermore, to compensate for the linear component of tape width deformation, the head tilt angle of the magnetic head can be changed to maintain a constant difference between the widthwise read position PES (Position Error Signal) signals (PES1, PES2) based on the servo signals obtained by the upper and lower servo signal reading elements, thereby dynamically controlling the track position. The servo following and dynamic track position control are performed during the following recording and playback operations. Next, while the magnetic tape is running at a constant speed of 3.0 m / s, a DC (Direct Current) pattern is recorded on the first wrap, a 255 kfci single-frequency signal is recorded on the second wrap, and a DC pattern is recorded on the third wrap. The unit "kfci" is a unit of linear recording density (not convertible to SI units). Shingle recording is performed on three or more tracks so that the difference between (PES1 + PES2) / 2 is 1200 nm. Shingle recording is also called shingled recording. Next, data is reproduced over a length of 90 m for each of the three consecutive central wraps in an area within 100 m from the outer edge of the tape (the outer tape area) and an area within 100 m from the inner edge of the tape (the inner tape area). The reproduced signal waveform and servo signal waveform are acquired and saved using an oscilloscope. For each measurement, the track position of the reproducing element is moved across the tape width at intervals of 1 / 30 or less of the track pitch. The "reproduced signal output" is calculated for each reproducing element from the reproduced signal waveform acquired and saved using the oscilloscope, and the track position is calculated from the servo signal waveform. From these results, a track profile is created, plotting track position on the horizontal axis and reproduced signal output on the vertical axis. Figure 1 shows an example of a track profile created in this way. The median value between two track positions where the output of the playback signal is 1 dB or more lower than the maximum value is found, and the median value is plotted on the vertical axis for each playback element. A linear approximation line is obtained by linear fitting using the least squares method. For each playback element in the outer and inner tape regions, the difference between the linear approximation line and the actual measured value is found, and this is defined as the "initial nonlinear component." Figure 2 shows an example of a graph related to the initial nonlinear component.In the example shown in Figure 2 and the example shown in Figure 3 described below, the number of reproducing elements (number of channels) is 32 (reproducing element numbers (No.): channel 0 to channel 31). After measuring the initial nonlinear component as described above, the magnetic tape to be measured is wound onto a magnetic tape reel with a hub diameter of 44 mm, with a tension of 0.6 N applied to the magnetic tape in the longitudinal direction using a device having a winding mechanism that applies tension to the magnetic tape in the longitudinal direction and winds the magnetic tape. During this winding, the end that was the inner peripheral end of the tape when wound onto the reel before measuring the initial nonlinear component becomes the inner peripheral end of the tape. The magnetic tape wound onto the reel in this manner is stored in an environment at a temperature of 60°C and a relative humidity of 20% for 20 days. After the above storage, the magnetic tape to be measured is stored in a reeled state in an environment with a temperature of 20-25°C and a relative humidity of 40-60% for 24 hours or more (but up to 120 hours at most). Then, using the magnetic tape device used to measure the initial nonlinear component, the magnetic tape to be measured is run back and forth once (forward and reverse) over the entire length. Using the same recording element, reproducing element, magnetic tape device, and reproduction conditions as used in measuring the initial nonlinear component, data is reproduced over a length of 90 m in an area within 100 m from the outer edge of the tape (outer tape area) and an area within 100 m from the inner edge of the tape (inner tape area). The reproduced signal output and servo signal waveform are acquired and saved using the same oscilloscope as used in measuring the initial nonlinear component. The track position of the reproducing element is moved across the tape width for each measurement at the same intervals as used in measuring the initial nonlinear component. The "reproduction signal output" is calculated for each reproduction element from the reproduction signal waveform acquired and saved using the oscilloscope, and the track position is calculated from the servo signal waveform. From these results, a track profile is created with track position on the horizontal axis and reproduction signal output on the vertical axis. Figure 1 is also an example of a track profile created in this way. The median between two track positions that are 1 dB or more lower than the maximum reproduction signal output is found, and the median value is plotted on the vertical axis for each reproduction element, and a linear approximation line is obtained by linear fitting using the least squares method.For each reproducing element in the outer and inner tape regions, the difference between the linear approximation line and the actual measurement value is calculated, and this is defined as the "nonlinear component after storage." Figure 3 shows an example of a graph related to the nonlinear component after storage. The absolute value of the difference between the "initial nonlinear component" and the "nonlinear component after storage" for each reproducing element (the difference in the nonlinear component before and after storage) is calculated. Figure 4 shows an example of a graph showing the absolute value of the difference calculated for each reproducing element. The maximum value of the absolute value in the outer and inner tape regions is defined as the "nonlinear component of tape width deformation" of the magnetic tape being measured. The initial nonlinear component can be considered to be a nonlinear component caused by factors other than the magnetic tape. Therefore, the inventors believe that by calculating the difference in the nonlinear component before and after storage as described above, it is possible to accurately evaluate the nonlinear component caused by the magnetic tape.

[0024] The nonlinear component of the tape width deformation determined for the magnetic tape by the method described above is preferably 90 nm or less, in order of preference, 85 nm or less, 80 nm or less, 75 nm or less, 70 nm or less, 65 nm or less, 60 nm or less, 55 nm or less, and 50 nm or less, from the viewpoint of improving the operational stability of the drive during recording and / or playback after long-term storage. Having the Spc and width-direction σ of the Spc on the magnetic layer surface of the data tape within the above ranges, and having a leader pin directly attached to the data tape without a leader tape, can contribute to controlling the value of the nonlinear component within the above range. Furthermore, the nonlinear component of the tape width deformation can be, for example, 0 nm or more, more than 0 nm, 1 nm or more, 5 nm or more, 10 nm or more, 15 nm or more, 20 nm or more, 25 nm or more, 30 nm or more, 35 nm or more, or 40 nm or more. From the viewpoint of improving the operational stability of the drive, the smaller the nonlinear component of the tape width deformation, the more preferable.

[0025] <<Explanation of Head Tilt Angle>> As described above, one example of a means for dynamically controlling the track position while the magnetic tape is running is to change the head tilt angle. In this regard, the configuration of the magnetic head, the head tilt angle, etc. will be described below. Furthermore, the reason why it is possible to dynamically control the track position while the magnetic tape is running by tilting the axial direction of the magnetic head module with respect to the width direction of the magnetic tape while the magnetic tape is running will also be described below.

[0026] The magnetic head may have one or more modules, two or more, or three or more, each module including an element array having a plurality of magnetic head elements between a pair of servo signal read elements. The total number of such modules may be, for example, five or less, four or less, or three or less, or the magnetic head may include a number of modules exceeding the total number exemplified here. Examples of the arrangement of multiple modules include "recording module-reproducing module" (total number of modules: 2) and "recording module-reproducing module-recording module" (total number of modules: 3). However, this is not limited to the examples shown here.

[0027] Each module may include an element array, i.e., an array of elements, having multiple magnetic head elements between a pair of servo signal read elements. A module having a recording element as a magnetic head element is a recording module for recording data onto a magnetic tape data tape. A module having a reproducing element as a magnetic head element is a reproducing module for reproducing data recorded on the magnetic tape data tape. In a magnetic head, multiple modules are arranged, for example, in a recording / reproducing head unit, with the axes of the element arrays of each module oriented parallel. This "parallel" does not necessarily mean only parallel in the strict sense, but also includes the range of error normally accepted in the technical field to which the present invention pertains. The range of error may, for example, mean a range of less than ±10° from strict parallelism.

[0028] In each element array, a pair of servo signal read elements and multiple magnetic head elements (i.e., write elements or read elements) are typically arranged linearly and spaced apart. Here, "arranged linearly" means that each magnetic head element is arranged on a straight line connecting the center of one servo signal read element to the center of the other servo signal read element. In this invention and this specification, the "axis of the element array" refers to the straight line connecting the center of one servo signal read element to the center of the other servo signal read element.

[0029] Next, the configuration of the module will be further described with reference to the drawings. However, the embodiments shown in the drawings are merely examples and do not limit the present invention.

[0030] FIG. 5 is a schematic diagram showing an example of a magnetic head module. The module shown in FIG. 5 has multiple magnetic head elements between a pair of servo signal read elements (servo signal read elements 1 and 2). The magnetic head elements are also called "channels." "Ch" in the diagram is an abbreviation for Channel. The module shown in FIG. 5 has a total of 32 magnetic head elements, Ch0 to Ch31.

[0031] In Fig. 5, "L" is the distance between a pair of servo signal read elements, i.e., the distance between one servo signal read element and the other servo signal read element. In the module shown in Fig. 5, "L" is the distance between servo signal read element 1 and servo signal read element 2. More specifically, it is the distance between the center of servo signal read element 1 and the center of servo signal read element 2. This distance can be measured using, for example, an optical microscope.

[0032] FIG. 6 is an explanatory diagram of the relative positional relationship between a module and a magnetic tape while the magnetic tape is running in a magnetic tape device. In FIG. 6, dotted line A indicates the width direction of the magnetic tape. Dotted line B indicates the axis of the element array. Angle θ can be said to be the head tilt angle while the magnetic tape is running, and is the angle formed by dotted lines A and B. When angle θ is 0° while the magnetic tape is running, the distance in the width direction of the magnetic tape between one servo signal 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 the servo signal reading elements is "L cos θ", and L cos θ is smaller than L. In other words, "L cos θ < L".

[0033] As described above, during recording or playback, if the magnetic head for recording or playing back data deviates from the target track position due to width deformation of the magnetic tape (more specifically, data tape), recording or playing back data can result in phenomena such as overwriting of recorded data or playback failure. For example, if the width of the data tape shrinks or expands, a magnetic head element that should be recording or playing back at the target track position can end up recording or playing back at a different track position. Furthermore, if the width of the data tape expands, the effective distance between servo signal reading elements can become shorter than the distance between two adjacent servo bands across a data band (also referred to as the "servo band distance" or "servo band distance"; more specifically, the distance between the two servo bands in the width direction of the data tape), resulting in data not being recorded or played back near the edge of the data tape. In contrast, if the element array is tilted at an angle θ greater than 0°, the effective distance between servo signal reading elements becomes "L cos θ," as described above. The larger the value of θ, the smaller the value of L cos θ, and the smaller the value of θ, the larger the value of L cos θ. 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 (specifically, data tape), it is possible to make the effective distance between the servo signal read elements closer to or equal to the spacing between the servo bands. This makes it possible to prevent or reduce the frequency of phenomena such as overwriting of recorded data or playback failures caused by the magnetic head for recording or playing back data being shifted from the target track position due to width deformation of the magnetic tape (specifically, data tape) during recording or playback.

[0034] 7 is an explanatory diagram showing the change in the angle θ during magnetic tape running. ｉｎｉｔｉａｌ can be set to, for example, 0° or more or more than 0°. In FIG. 7, the central diagram shows the state of the module at the start of running. In FIG. 7, the right diagram shows the angle θ as ｉｎｉｔｉａｌ The larger angle is angle θ ｃThe effective distance between the servo signal reading elements is L cos θ. ｃ is L cos θ when the magnetic tape starts running ｉｎｉｔｉａｌ It is preferable to adjust the angle in this way when the width of the data tape is contracted during magnetic tape running. On the other hand, in the left diagram of FIG. 7, the angle θ is ｉｎｉｔｉａｌ The smaller angle θ ｅ The effective distance between the servo signal reading elements is L cos θ. ｅ is L cos θ when the magnetic tape starts running ｉｎｉｔｉａｌ It is preferable to make such an angle adjustment when the width of the data tape expands during magnetic tape running.

[0035] As explained above, changing the head tilt angle during magnetic tape running can contribute to preventing or reducing the frequency of phenomena such as overwriting of recorded data and playback failures, which occur when the magnetic head for recording or playing back data deviates from the target track position due to width deformation of the magnetic tape (specifically, data tape) during recording or playback. However, while the dynamic track position control means described above can usually compensate for off-track caused by the linear component of tape width deformation, it is difficult to suppress off-track caused by the nonlinear component. In contrast, in the magnetic tape described above, the Spc and width-direction σ of the Spc on the magnetic layer surface of the data tape within the above range, and the fact that a leader pin is attached directly to the data tape without an intervening leader tape, are presumably responsible for reducing the nonlinear component of tape width deformation. This is believed to improve the operational stability of the drive. Such a magnetic tape is preferable for achieving higher track density.

[0036] <<Data Tape>> The magnetic tape may consist solely of a continuous piece of data tape (i.e., no spliced ​​portions where two or more tapes are spliced) that does not include a leader tape and has a leader pin directly attached to one end, or may have a reinforcing layer on at least one of the magnetic layer side and the side opposite to the magnetic layer side of the end of the data tape where the leader pin is directly attached. The data tape of the magnetic tape will be described in more detail below. The reinforcing layer will be described later.

[0037] <Magnetic Layer> (Ferromagnetic Powder) The ferromagnetic powder contained in the magnetic layer can be one or a combination of two or more known ferromagnetic powders used in the magnetic layers of various magnetic recording media. Using a ferromagnetic powder with a small average particle size is preferable from the viewpoint of improving recording density. From this viewpoint, the average particle size of the ferromagnetic powder is preferably 50 nm or less, more preferably 45 nm or less, even more preferably 40 nm or less, even more preferably 35 nm or less, even more preferably 30 nm or less, even more preferably 25 nm or less, and even more preferably 20 nm or less. On the other hand, from the viewpoint of magnetization stability, the average particle size of the ferromagnetic powder is preferably 5 nm or more, more preferably 8 nm or more, even more preferably 10 nm or more, even more preferably 15 nm or more, and even more preferably 20 nm or more.

[0038] Hexagonal Ferrite Powder A preferred specific example of the ferromagnetic powder is hexagonal ferrite powder. For details of the hexagonal ferrite powder, see, for example, JP 2011-225417 A, paragraphs 0012 to 0030, JP 2011-216149 A, paragraphs 0134 to 0136, JP 2012-204726 A, paragraphs 0013 to 0030, and JP 2015-127985 A, paragraphs 0029 to 0084.

[0039] 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 most intense diffraction peak belongs in the X-ray diffraction spectrum obtained by X-ray diffraction analysis. For example, if the most intense diffraction peak in the X-ray diffraction spectrum obtained by X-ray diffraction analysis is assigned to the hexagonal ferrite crystal structure, it is determined that the hexagonal ferrite crystal structure has been detected as the main phase. If only a single structure is detected by X-ray diffraction analysis, this detected structure is considered to be the main phase. The hexagonal ferrite crystal structure contains at least iron atoms, divalent metal atoms, and oxygen atoms as constituent atoms. Divalent metal atoms are metal atoms that can become divalent cations as ions, and examples of such atoms include alkaline earth metal atoms such as strontium atoms, barium atoms, and calcium atoms, and lead atoms. In the present invention and this specification, the term "hexagonal strontium ferrite powder" refers to a powder in which the main divalent metal atom contained therein is strontium, and the term "hexagonal barium ferrite powder" refers to a powder in which the main divalent metal atom contained therein is barium. The term "main divalent metal atom" refers to the divalent metal atom that is the most prevalent among the divalent metal atoms contained in the powder on an atomic percentage basis. However, the above divalent metal atoms do not include rare earth atoms. In the present invention and this specification, the "rare earth atom" is selected from the group consisting of scandium (Sc), yttrium (Y), and lanthanoid atoms. The lanthanoid atom is selected from the group consisting of lanthanum atom (La), cerium atom (Ce), praseodymium atom (Pr), neodymium atom (Nd), promethium atom (Pm), samarium atom (Sm), europium atom (Eu), gadolinium atom (Gd), terbium atom (Tb), dysprosium atom (Dy), holmium atom (Ho), erbium atom (Er), thulium atom (Tm), ytterbium atom (Yb), and lutetium atom (Lu).

[0040] Hereinafter, hexagonal strontium ferrite powder, which is one form of hexagonal ferrite powder, will be described in more detail.

[0041] The activation volume of the hexagonal strontium ferrite powder is preferably 800 to 1600 nm ３ The microparticulated hexagonal strontium ferrite powder exhibiting an activation volume in the above range is suitable for producing a data tape exhibiting excellent electromagnetic conversion characteristics. The activation volume of the hexagonal strontium ferrite powder is preferably 800 nm ３ or more, for example, 850 nm ３ From the viewpoint of further improving the electromagnetic conversion characteristics, the activation volume of the hexagonal strontium ferrite powder can be 1500 nm or more. ３ More preferably, it is 1400 nm or less. ３ More preferably, it is 1300 nm or less. ３ More preferably, it is 1200 nm or less. ３ It is even more preferable that the value is 1100 nm or less. ３ It is even more preferable that the activation volume of the hexagonal barium ferrite powder is equal to or less than 10 ...

[0042] "Activation volume" is a unit of magnetization reversal and is an index showing the magnetic size of a particle. The activation volume described in this invention and this specification and the anisotropy constant Ku described later are values ​​obtained by measuring the coercive force Hc using a vibrating sample magnetometer at magnetic field sweep rates of 3 minutes and 30 minutes (measurement temperature: 23°C ± 1°C) in the coercive force Hc measurement section, and by using the following relational expression between Hc and activation volume V. Note that the unit of the anisotropy constant Ku is 1 erg / cc = 1.0 x 10 －１ J / m ３ Hc = 2Ku / Ms {1 - [(kT / KuV)ln(At / 0.693)] １／２} [In the above formula, Ku: anisotropy constant (unit: J / m ３ ), Ms: saturation magnetization (unit: kA / m), k: Boltzmann constant, T: absolute temperature (unit: K), V: activation volume (unit: cm ３ ), A: spin precession frequency (unit: s －１ ), t: magnetic field reversal time (unit: s)]

[0043] The anisotropy constant Ku can be used as an index of the reduction in thermal fluctuation, in other words, the improvement in thermal stability. The hexagonal strontium ferrite powder preferably has an anisotropy constant of 1.8×10 ５ J / m ３ and more preferably 2.0 × 10 ５ J / m ３ The Ku of the hexagonal strontium ferrite powder can be, for example, 2.5×10 ５ J / m ３ However, since a higher Ku value means higher thermal stability and is therefore preferred, the Ku value is not limited to the above-mentioned values.

[0044] The hexagonal strontium ferrite powder may or may not contain rare earth atoms. When the hexagonal strontium ferrite powder contains rare earth atoms, it is preferable that the rare earth atoms be contained at a content (bulk content) of 0.5 to 5.0 atomic % relative to 100 atomic % of iron atoms. In one embodiment, the hexagonal strontium ferrite powder containing rare earth atoms can have rare earth atoms unevenly distributed in the surface layer portion. In the present invention and this specification, "surface layer distribution of rare earth atoms" means that the rare earth atom content relative to 100 atomic % of iron atoms in a solution obtained by partially dissolving a hexagonal strontium ferrite powder in an acid (hereinafter referred to as "surface layer content of rare earth atoms" or simply "surface layer content" for rare earth atoms) satisfies the ratio of the rare earth atom content relative to 100 atomic % of iron atoms in a solution obtained by completely dissolving a hexagonal strontium ferrite powder in an acid (hereinafter referred to as "bulk content of rare earth atoms" or simply "bulk content" for rare earth atoms) > 1.0. The rare earth atom content of the hexagonal strontium ferrite powder described below is synonymous with the bulk content of rare earth atoms. In contrast, partial dissolution using an acid dissolves the surface layer of the particles constituting the hexagonal strontium ferrite powder, so the rare earth atom content in the solution obtained by partial dissolution is the rare earth atom content in the surface layer of the particles constituting the hexagonal strontium ferrite powder. The rare earth atom surface layer content satisfying the ratio "rare earth atom surface layer content / rare earth atom bulk content > 1.0" means that rare earth atoms are unevenly distributed in the surface layer of the particles constituting the hexagonal strontium ferrite powder (i.e., more present in the surface layer than in the interior). In the present invention and this specification, the surface layer refers to a partial region extending from the surface toward the interior of the particles constituting the hexagonal strontium ferrite powder.

[0045] When the hexagonal strontium ferrite powder contains rare earth atoms, the rare earth atom content (bulk content) is preferably in the range of 0.5 to 5.0 atomic percent relative to 100 atomic percent of iron atoms. The presence of rare earth atoms at a bulk content within the above range and the uneven distribution of rare earth atoms in the surface layer of the particles constituting the hexagonal strontium ferrite powder is believed to contribute to suppressing a decrease in playback output during repeated playback. This is presumably because the hexagonal strontium ferrite powder contains rare earth atoms at a bulk content within the above range and the uneven distribution of rare earth atoms in the surface layer of the particles constituting the hexagonal strontium ferrite powder can increase the anisotropy constant Ku. The higher the anisotropy constant Ku, the more the occurrence of a phenomenon known as thermal fluctuation can be suppressed (in other words, thermal stability can be improved). By suppressing the occurrence of thermal fluctuation, the decrease in playback output during repeated playback can be suppressed. It is speculated that the uneven distribution of rare earth atoms in the particle surface layer of hexagonal strontium ferrite powder contributes to stabilizing the spin of iron (Fe) sites in the crystal lattice of the surface layer, thereby increasing the anisotropy constant Ku. It is also speculated that using hexagonal strontium ferrite powder with uneven distribution of rare earth atoms in the surface layer as the ferromagnetic powder of the magnetic layer also contributes to suppressing the abrasion of the magnetic layer surface due to sliding with the magnetic head. In other words, it is speculated that hexagonal strontium ferrite powder with uneven distribution of rare earth atoms in the surface layer can also contribute to improving the running durability of data tapes. It is speculated that this is because the uneven distribution of rare earth atoms on the surface of the particles constituting the hexagonal strontium ferrite powder contributes to improving the interaction between the particle surface and the organic substances (e.g., binders and / or additives) contained in the magnetic layer, resulting in improved strength of the magnetic layer. From the viewpoint of further suppressing the decrease in reproduction output during repeated reproduction and / or further improving running durability, the rare earth atom content (bulk content) is more preferably in the range of 0.5 to 4.5 atomic %, even more preferably in the range of 1.0 to 4.5 atomic %, and even more preferably in the range of 1.5 to 4.5 atomic %.

[0046] The bulk content is the content determined by completely dissolving the hexagonal strontium ferrite powder. In the present invention and this specification, unless otherwise specified, the content of an atom refers to the bulk content determined by completely dissolving the hexagonal strontium ferrite powder. The hexagonal strontium ferrite powder containing rare earth atoms may contain only one rare earth atom, or may contain two or more rare earth atoms. When two or more rare earth atoms are contained, the bulk content is determined for the total of the two or more rare earth atoms. This also applies to other components in the present invention and this specification. That is, unless otherwise specified, a certain component may be used alone or in combination with two or more. When two or more components are used, the content or content refers to the total of the two or more components.

[0047] When the hexagonal strontium ferrite powder contains a rare earth atom, the rare earth atom may be any one or more of rare earth atoms. From the viewpoint of further suppressing a decrease in the reproduction output during repeated reproduction, preferred rare earth atoms include neodymium, samarium, yttrium, and dysprosium atoms, with neodymium, samarium, and yttrium atoms being more preferred, and neodymium atoms being even more preferred.

[0048] In a hexagonal strontium ferrite powder having rare earth atoms unevenly distributed in the surface layer, the rare earth atoms need only be unevenly distributed in the surface layer of the particles constituting the hexagonal strontium ferrite powder, and the degree of uneven distribution is not limited. For example, for a hexagonal strontium ferrite powder having rare earth atoms unevenly distributed in the surface layer, the ratio of the surface content of rare earth atoms determined by partial dissolution under the dissolution conditions described below to the bulk content of rare earth atoms determined by complete dissolution under the dissolution conditions described below, i.e., "surface content / bulk content," is greater than 1.0 and can be 1.5 or greater. A "surface content / bulk content" greater than 1.0 means that rare earth atoms are unevenly distributed in the surface layer (i.e., present in greater amounts than in the interior) in the particles constituting the hexagonal strontium ferrite powder. Furthermore, the ratio of the surface content of rare earth atoms determined by partial dissolution under the dissolution conditions described below to the bulk content of rare earth atoms determined by complete dissolution under the dissolution conditions described below, i.e., "surface content / bulk content," can be, for example, 10.0 or less, 9.0 or less, 8.0 or less, 7.0 or less, 6.0 or less, 5.0 or less, or 4.0 or less. However, in a hexagonal strontium ferrite powder having rare earth atoms unevenly distributed in the surface layer, it is sufficient that the rare earth atoms are unevenly distributed in the surface layer of the particles constituting the hexagonal strontium ferrite powder, and the above "surface content / bulk content" is not limited to the exemplified upper or lower limits.

[0049] The partial and total dissolution of hexagonal strontium ferrite powder is described below. For hexagonal strontium ferrite powder present as a powder, sample powders to be partially and completely dissolved are collected from the same powder lot. On the other hand, for hexagonal strontium ferrite powder contained in the magnetic layer of a data tape, a portion of the hexagonal strontium ferrite powder removed from the magnetic layer is subjected to partial dissolution, and another portion is subjected to total dissolution. Removal of the hexagonal strontium ferrite powder from the magnetic layer can be performed, for example, by the method described in paragraph 0032 of JP 2015-91747 A. The partial dissolution refers to dissolving the hexagonal strontium ferrite powder to such an extent that residual hexagonal strontium ferrite powder can be visually confirmed in the liquid at the end of dissolution. For example, partial dissolution can dissolve 10 to 20% by mass of the particles constituting the hexagonal strontium ferrite powder, with the total particles being 100% by mass. On the other hand, the term "complete dissolution" refers to dissolution to the point where no residual hexagonal strontium ferrite powder is visually detectable in the solution at the end of dissolution. The 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 merely examples, and any dissolution conditions that allow partial or complete dissolution can be adopted. A container (e.g., a beaker) containing 12 mg of sample powder and 10 mL of 1 mol / L hydrochloric acid is placed on a hot plate set at 70°C for 1 hour. The resulting solution is filtered through a 0.1 μm membrane filter. Elemental analysis of the filtrate obtained in this manner is performed using an inductively coupled plasma (ICP) analyzer. In this way, the surface layer content of rare earth atoms relative to 100 atomic % of iron atoms can be determined. If multiple rare earth atoms are detected by elemental analysis, the total content of all rare earth atoms is taken as the surface layer content. The same applies to the measurement of the bulk content. Meanwhile, the total dissolution and bulk content measurements are carried out, for example, by the following method: A container (e.g., a beaker) containing 12 mg of sample powder and 10 mL of 4 mol / L hydrochloric acid is placed on a hot plate set at 80° C. for 3 hours.Thereafter, the same procedures as in the partial dissolution and measurement of the surface layer content are carried out, and the bulk content relative to 100 atomic % of iron atoms can be determined.

[0050] From the viewpoint of increasing the reproduction output when reproducing data recorded on a data tape, it is desirable that the mass magnetization σs of the ferromagnetic powder contained in the data tape is high. In this regard, hexagonal strontium ferrite powder that contains rare earth atoms but does not have the rare earth atoms unevenly distributed in the surface layer tends to have a significantly lower σs than hexagonal strontium ferrite powder that does not contain rare earth atoms. On the other hand, hexagonal strontium ferrite powder that has the rare earth atoms unevenly distributed in the surface layer is considered preferable in order to suppress such a large decrease in σs. In one embodiment, the σs of the hexagonal strontium ferrite powder is 45 A m ２ / kg or more, and ２ On the other hand, from the viewpoint of noise reduction, σs is 80 A m ２ / kg or less, and ２ / kg or less is more preferable. σs can be measured using a known measuring device capable of measuring magnetic properties, such as a vibrating sample magnetometer. In the present invention and this specification, unless otherwise specified, the mass magnetization σs is a value measured at a magnetic field strength of 15 kOe. 1 [kOe] = 10 ６ / 4π[A / m].

[0051] Regarding the content (bulk content) of the constituent atoms of the hexagonal strontium ferrite powder, the strontium atom content can be, for example, in the range of 2.0 to 15.0 atomic % relative to 100 atomic % of iron atoms. In one embodiment, the hexagonal strontium ferrite powder can contain only strontium atoms as divalent metal atoms. In another embodiment, the hexagonal strontium ferrite powder can contain one or more other divalent metal atoms in addition to strontium atoms. For example, barium atoms and / or calcium atoms can be contained. When divalent metal atoms other than strontium atoms are contained, the barium atom content and calcium atom content in the hexagonal strontium ferrite powder can each be, for example, in the range of 0.05 to 5.0 atomic % relative to 100 atomic % of iron atoms.

[0052] Known crystal structures of hexagonal ferrite include magnetoplumbite type (also called "M type"), W type, Y type, and Z type. The hexagonal strontium ferrite powder may have any of these crystal structures. The crystal structure can be confirmed by X-ray diffraction analysis. The hexagonal strontium ferrite powder may be one in which a single crystal structure or two or more types of crystal structures are detected by X-ray diffraction analysis. For example, in one embodiment, the hexagonal strontium ferrite powder may be one in which only the M-type crystal structure is detected by X-ray diffraction analysis. For example, the M-type hexagonal ferrite is AFe １２ O １９The composition is represented by the formula: where A represents a divalent metal atom. When the hexagonal strontium ferrite powder is of M type, A is only strontium atom (Sr). Alternatively, when A contains multiple divalent metal atoms, strontium atom (Sr) accounts for the majority on an atomic % basis as described above. The divalent metal atom content of the hexagonal strontium ferrite powder is usually determined by the type of crystalline structure of the hexagonal ferrite and is not particularly limited. The same applies to the iron atom content and the oxygen atom content. The hexagonal strontium ferrite powder contains at least iron atoms, strontium atoms, and oxygen atoms, and may further contain rare earth atoms. Furthermore, the hexagonal strontium ferrite powder may or may not contain atoms other than these atoms. As an example, the hexagonal strontium ferrite powder may contain aluminum atoms (Al). The content of aluminum atoms can be, for example, 0.5 to 10.0 atomic % relative to 100 atomic % of iron atoms. From the viewpoint of further suppressing a decrease in playback output during repeated playback, the hexagonal strontium ferrite powder contains iron atoms, strontium atoms, oxygen atoms, and rare earth atoms, and the content of atoms other than these atoms is preferably 10.0 atomic % or less, more preferably in the range of 0 to 5.0 atomic %, relative to 100 atomic % of iron atoms, and may even be 0 atomic %. That is, in one embodiment, the hexagonal strontium ferrite powder does not need to contain atoms other than iron atoms, strontium atoms, oxygen atoms, and rare earth atoms. The content expressed in atomic % above is determined by converting the content (unit: mass %) of each atom obtained by completely dissolving the hexagonal strontium ferrite powder into a value expressed in atomic % using the atomic weight of each atom. Furthermore, in the present invention and this specification, "not containing" a certain atom means that the content measured by completely dissolving the powder and using an ICP analyzer is 0 mass %. The detection limit of an ICP analyzer is usually 0.01 ppm (parts per million) or less by mass. The above term "free from" is used to mean that the amount is below the detection limit of the ICP analyzer.In one form, the hexagonal strontium ferrite powder can be one that does not contain bismuth atoms (Bi).

[0053] Metal Powder A preferred specific example of the ferromagnetic powder is ferromagnetic metal powder. For details of the ferromagnetic metal powder, see, for example, paragraphs

[0137] to

[0141] of JP 2011-216149 A and paragraphs

[0009] to

[0023] of JP 2005-251351 A.

[0054] ε-Iron Oxide Powder A preferred example of the ferromagnetic powder is ε-iron oxide powder. In the present invention and this specification, the term "ε-iron oxide powder" refers to a ferromagnetic powder in which an ε-iron oxide crystal structure is detected as the main phase by X-ray diffraction analysis. For example, if the highest intensity diffraction peak in an X-ray diffraction spectrum obtained by X-ray diffraction analysis is assigned to the ε-iron oxide crystal structure, it is determined that the ε-iron oxide crystal structure has been detected as the main phase. Known methods for producing ε-iron oxide powder include a method of producing it from goethite and a reverse micelle method. All of these production methods are publicly known. Furthermore, a method for producing ε-iron oxide powder in which part of the Fe is substituted with a substitution atom such as Ga, Co, Ti, Al, or Rh is described, for example, in J. Jpn. Soc. Powder Metallurgy, Vol. 61, Supplement, No. S1, pp. 111-115. S280-S284, J. Mater. Chem. C, 2013, 1, pp. 5200-5206, etc. However, the method for producing ε-iron oxide powder that can be used as the ferromagnetic powder in the magnetic layer of the data tape is not limited to the methods mentioned here.

[0055] The activation volume of the ε-iron oxide powder is preferably 300 to 1500 nm ３ The microparticulated ε-iron oxide powder exhibiting an activation volume in the above range is suitable for producing a data tape that exhibits excellent electromagnetic conversion characteristics. The activation volume of the ε-iron oxide powder is preferably 300 nm ３ or more, for example, 500 nm ３From the viewpoint of further improving the electromagnetic conversion characteristics, the activation volume of the ε-iron oxide powder can be 1400 nm or more. ３ More preferably, it is 1300 nm or less. ３ More preferably, it is 1200 nm or less. ３ More preferably, it is 1100 nm or less. ３ It is even more preferred that:

[0056] The anisotropy constant Ku can be used as an index for reducing thermal fluctuation, in other words, improving thermal stability. The ε-iron oxide powder preferably has an anisotropy constant of 3.0×10 ４ J / m ３ and more preferably 8.0 × 10 ４ J / m ３ The Ku of the ε-iron oxide powder can be, for example, 3.0×10 ５ J / m ３ However, since a higher Ku value means higher thermal stability and is therefore preferred, the Ku value is not limited to the above-mentioned values.

[0057] From the viewpoint of increasing the reproduction output when reproducing data recorded on a data tape, it is desirable that the mass magnetization σs of the ferromagnetic powder contained in the data tape is high. In this regard, in one embodiment, the σs of the ε-iron oxide powder is 8 A m ２ / kg or more, and ２ On the other hand, the σs of the ε-iron oxide powder can be 40 A m ２ / kg or less, and 35 A m ２ / kg or less is more preferable.

[0058] Unless otherwise specified, in this invention and this specification, the average particle size of various powders, such as ferromagnetic powders, is a 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 photograph is printed on photographic paper or displayed on a display screen so that the total magnification is 500,000x, thereby obtaining a particle photograph of the particles constituting the powder. From the obtained particle photograph, a target particle is selected, and the particle outline is traced with a digitizer to measure the particle (primary particle) size. Primary particles are independent particles without agglomeration. The above measurement is performed on 500 randomly selected particles. The arithmetic mean of the particle sizes of the 500 particles thus obtained is taken as the average particle size of the powder. As the transmission electron microscope, for example, a Hitachi transmission electron microscope model H-9000 can be used. Furthermore, particle size measurement can be performed using known image analysis software, such as Carl Zeiss image analysis software KS-400. Unless otherwise specified, the average particle size described in the Examples section below is a value measured using a Hitachi H-9000 transmission electron microscope and Carl Zeiss KS-400 image analysis software. In this invention and this specification, powder refers to an aggregate of multiple particles. For example, ferromagnetic powder refers to an aggregate of multiple ferromagnetic particles. Furthermore, an aggregate of multiple particles is not limited to a form in which the particles constituting the aggregate are in direct contact with each other, but also includes forms in which a binder, additive, etc., described below, is interposed between the particles. The term "particle" is sometimes used to refer to powder.

[0059] As a method for collecting sample powder from a data tape for particle size measurement, for example, the method described in paragraph 0015 of JP 2011-048878 A can be used.

[0060] In this invention and this specification, with regard to particle shape, "plate-like" refers to a shape having two opposing plate surfaces. "Plate surface" refers to the plane observed on the surface of a particle in the particle photograph and the plane opposite to that plane. Among particle shapes that do not have such plate-like surfaces, shapes with a distinct major and minor axis are "elliptical." The major axis is determined as the axis (straight line) along which the particle length can be measured. Meanwhile, the minor axis is determined as the axis with the longest length when the particle length is measured along a line perpendicular to the major axis. A shape without a distinct major and minor axis, i.e., a shape where the major axis length = the minor axis length, is "spherical." Shapes whose major and minor axes cannot be identified from the shape are called amorphous. Unless otherwise specified, in this invention and this specification, the size (particle size) of particles constituting a powder refers to the plate diameter if the particle shape observed in the particle photograph is plate-like; the major axis length if elliptical; the diameter if spherical; and the equivalent circle diameter if amorphous. The equivalent circle diameter is determined by the circle projection method.

[0061] For plate-like particles, the "plate thickness" is the longest distance between two opposing plate surfaces, and the average plate thickness is the arithmetic mean of the values ​​obtained for the 500 particles.

[0062] The content (filling rate) of the ferromagnetic powder in the magnetic layer is preferably in the range of 50 to 90 mass %, and more preferably in the range of 60 to 90 mass %, relative to the total mass of the magnetic layer. A high filling rate of the ferromagnetic powder in the magnetic layer is preferable from the viewpoint of improving recording density.

[0063] (Binder) The data tape may be a coated magnetic tape, and the magnetic layer may contain a binder. The binder is one or more resins. Various resins commonly used as binders for coated magnetic tapes can be used. For example, binders may be selected from polyurethane resins, polyester resins, polyamide resins, vinyl chloride resins, acrylic resins copolymerized with styrene, acrylonitrile, methyl methacrylate, etc., cellulose resins such as nitrocellulose, epoxy resins, phenoxy resins, polyvinyl acetal, polyvinyl butyral, etc., and may be used alone or in combination. Among these, polyurethane resins, acrylic resins, cellulose resins, and vinyl chloride resins are preferred. These resins may be homopolymers or copolymers. These resins can also be used as binders in the nonmagnetic layer and / or backcoat layer, as described below. For details on the binders mentioned above, see paragraphs 0028 to 0031 of JP 2010-24113 A. The average molecular weight of the resin used as the binder can be, for example, 10,000 or more and 200,000 or less in weight average molecular weight. The weight average molecular weight in this invention and this specification is a value obtained by converting a value measured by gel permeation chromatography (GPC) under the following measurement conditions into polystyrene equivalent. The weight average molecular weight of the binder shown in the Examples section below is a value obtained by converting a value measured under the following measurement conditions into polystyrene equivalent. The binder can be used in an amount of, for example, 1.0 to 30.0 parts by mass per 100.0 parts by mass of the ferromagnetic powder. GPC apparatus: HLC-8120 (manufactured by Tosoh Corporation) Column: TSK gel Multipore HXL-M (manufactured by Tosoh Corporation, 7.8 mm ID (Inner Diameter) × 30.0 cm) Eluent: tetrahydrofuran (THF)

[0064] (Curing Agent) A curing agent can also be used together with a resin that can be used as a binder. In one form, the curing agent can be a thermosetting compound, which is a compound that undergoes a curing reaction (crosslinking reaction) upon heating. In another form, the curing agent can be a photocurable compound, which undergoes a curing reaction (crosslinking reaction) upon irradiation with light. As the curing reaction progresses during the magnetic layer formation process, at least a portion of the curing agent can be included in the magnetic layer in a state where it has reacted (crosslinked) with other components, such as the binder. This also applies to layers formed using compositions used to form other layers that contain a curing agent. A preferred curing agent is a thermosetting compound, and polyisocyanate is suitable. For details on polyisocyanates, see paragraphs 0124 to 0125 of JP 2011-216149 A. The curing agent can be used in the magnetic layer-forming composition in an amount of, for example, 0 to 80.0 parts by weight per 100.0 parts by weight of binder, preferably 50.0 to 80.0 parts by weight from the perspective of improving the strength of the magnetic layer.

[0065] (Additives) The magnetic layer may contain one or more additives as needed. Commercially available additives can be selected and used depending on the desired properties. Alternatively, compounds synthesized by known methods can be used as additives. Additives can be used in any amount. Examples of additives include the curing agents described above. Examples of additives contained in the magnetic layer include non-magnetic powders, lubricants, dispersants, dispersion aids, antifungal agents, antistatic agents, and antioxidants. For information on lubricants, see paragraphs 0030 to 0033, 0035, and 0036 of JP 2016-126817 A. The non-magnetic layer described below may contain a lubricant. For information on lubricants that can be contained in the non-magnetic layer, see paragraphs 0030 to 0031, 0034, 0035, and 0036 of JP 2016-126817 A. For details about dispersants, see paragraphs 0061 and 0071 of JP-A 2012-133837. A dispersant may be added to the nonmagnetic layer-forming composition. For details about dispersants that can be added to the nonmagnetic layer-forming composition, see paragraph 0061 of JP-A 2012-133837.

[0066] Regarding the Spc and width direction σ of the Spc on the magnetic layer surface, the inventors' investigations have revealed that it is preferable for the magnetic layer to contain non-magnetic powder composed of plate-like particles in order to control the Spc and width direction σ of the Spc on the magnetic layer surface within the ranges described above. Furthermore, the inventors' investigations have also revealed that, from the perspective of controlling the Spc and width direction σ of the Spc on the magnetic layer surface within the ranges described above, it is more preferable for the magnetic layer to contain non-magnetic powder having an average plate diameter of 50 nm to 1000 nm and an average plate thickness of 12 nm or less. The average plate thickness can be, for example, 3 nm or more, 4 nm or more, or 5 nm or more, and can also be less than the values ​​exemplified here. The non-magnetic powder composed of plate-like particles (preferably a non-magnetic powder having an average plate diameter of 50 nm to 1000 nm and an average plate thickness of 12 nm or less) can be, for example, a metal oxide powder. Specific examples of metal oxides include aluminum oxide, zirconium oxide, and cerium oxide. Aluminum oxide is also called alumina, zirconium oxide is also called zirconia, and cerium oxide is also called ceria. For example, plate-shaped metal oxide particles can be obtained by heating an aqueous solution of a metal hydroxide to a liquid temperature of 200°C or higher to cause a hydrothermal synthesis reaction. The plate diameter and plate thickness of the plate-shaped particles can be controlled by adjusting various conditions for particle preparation (e.g., the concentration of the aqueous solution, the mixing time during preparation of the aqueous solution, the heating temperature, the heating time, etc.). The content of the non-magnetic powder in the magnetic layer can be, for example, 0.02 to 0.80 parts by mass per 100.0 parts by mass of the ferromagnetic powder.

[0067] Non-magnetic powders that can be contained in the magnetic layer include non-magnetic powders that can function as abrasives. For example, see paragraphs 0030 to 0032 of Japanese Patent Application Laid-Open No. 2004-273070 for abrasives. Examples of abrasives include non-magnetic powders that have a specific surface area measured by the BET (Brunauer-Emmett-Teller) method (hereinafter referred to as "BET specific surface area") of 14 m. ２ From the viewpoint of dispersibility, it is preferable to use an abrasive having a BET specific surface area of ​​40 m ２ It is preferable to use an abrasive having a surface roughness of 0.1 / g or less.

[0068] As the abrasive, a non-magnetic powder having a Mohs hardness of more than 8 is preferred, and a non-magnetic powder having a Mohs hardness of 9 or more is more preferred. The maximum Mohs hardness is 10. The abrasive can be a powder of an inorganic substance or a powder of an organic substance. The abrasive can be a powder of an inorganic or organic oxide or a powder of a carbide. As the carbide, boron carbide (e.g., B ４ Examples of suitable abrasives include titanium carbide (e.g., TiC), titanium carbide (e.g., TiC), and the like. Diamond can also be used as an abrasive. In one form, the abrasive is preferably an inorganic oxide powder. Specific examples of inorganic oxides include aluminum oxide (alumina), titanium oxide, cerium oxide (ceria), and zirconium oxide (zirconia), with alumina being preferred. Alumina has a Mohs hardness of approximately 9. For alumina powder that can be used as an abrasive, see paragraph 0021 of JP 2013-229090 A. The content of the abrasive in the magnetic layer is preferably 0.02 to 0.80 parts by mass per 100.0 parts by mass of the ferromagnetic powder. Only one type of nonmagnetic powder can be used as the abrasive, or two or more types of nonmagnetic powders with different compositions and / or physical properties (e.g., size) can be used. When two or more types of nonmagnetic powders are used as the abrasive, the content of the abrasive refers to the total content of those two or more types of nonmagnetic powders. The above also applies to the contents of various components in the present invention and this specification. The abrasive is preferably subjected to a dispersion treatment separately from the ferromagnetic powder (separate dispersion), and more preferably to a dispersion treatment separately from the non-magnetic powder described above (separate dispersion). When preparing the magnetic layer-forming composition, two or more dispersions with different components and / or dispersion conditions can also be prepared as a dispersion of the abrasive (hereinafter also referred to as "abrasive liquid").

[0069] A dispersant can also be used to adjust the dispersion state of the abrasive liquid. Compounds that can function as dispersants to improve the dispersibility of abrasives include aromatic hydrocarbon compounds having a phenolic hydroxy group. A "phenolic hydroxy group" refers to a hydroxy group directly bonded to an aromatic ring. The aromatic ring contained in the aromatic hydrocarbon compound may be a monocyclic ring, a polycyclic structure, or a fused ring. From the perspective of improving the dispersibility of abrasives, aromatic hydrocarbon compounds containing a benzene ring or a naphthalene ring are preferred. The aromatic hydrocarbon compound may also have a substituent other than the phenolic hydroxy group. Examples of the substituent other than the phenolic hydroxy group include a halogen atom, an alkyl group, an alkoxy group, an amino group, an acyl group, a nitro group, a nitroso group, and a hydroxyalkyl group. A halogen atom, an alkyl group, an alkoxy group, an amino group, and a hydroxyalkyl group are preferred. The number of phenolic hydroxy groups contained in one molecule of the aromatic hydrocarbon compound may be one, two, three, or more.

[0070] A preferred example of the aromatic hydrocarbon compound having a phenolic hydroxy group is a compound represented by the following formula 100.

[0071] [In formula 100, X １０１ ~X １０８ Two of the groups are hydroxy groups, and the other six groups each independently represent a hydrogen atom or a substituent.

[0072] In the compound represented by formula 100, the substitution positions of the two hydroxy groups (phenolic hydroxy groups) are not particularly limited.

[0073] The compound of formula 100 is X １０１ ~X １０８ Two of the X's are hydroxy groups (phenolic hydroxy groups), and the other six each independently represent a hydrogen atom or a substituent. １０１ ~X １０８In the above, all the moieties other than the two hydroxy groups may be hydrogen atoms, or some or all may be substituents. Examples of the substituents include the substituents described above. One or more phenolic hydroxy groups may be included as the substituents other than the two hydroxy groups. From the viewpoint of improving the dispersibility of the abrasive, X １０１ ~X １０８ It is preferred that the other than the two hydroxy groups among X are not phenolic hydroxy groups. That is, the compound represented by formula 100 is preferably dihydroxynaphthalene or a derivative thereof, and more preferably 2,3-dihydroxynaphthalene or a derivative thereof. １０１ ~X １０８ Preferred examples of the substituent represented by the formula (I) include a halogen atom (e.g., a chlorine atom, a bromine atom), an amino group, an alkyl group having 1 to 6 carbon atoms (preferably 1 to 4 carbon atoms), a methoxy group, an ethoxy group, an acyl group, a nitro group, a nitroso group, and —CH ２ OH groups can be mentioned.

[0074] For details about dispersants for improving the dispersibility of abrasives, see paragraphs 0024 to 0028 of JP 2014-179149 A.

[0075] The dispersant for improving the dispersibility of the abrasive can be used, for example, in the preparation of the abrasive liquid in a proportion of 0.5 to 20.0 parts by mass, preferably 1.0 to 10.0 parts by mass, per 100.0 parts by mass of the abrasive.

[0076] The magnetic layer described above can be provided directly on the surface of the non-magnetic support, or indirectly via a non-magnetic layer.

[0077] <Nonmagnetic Layer> Next, the nonmagnetic layer will be described. The data tape may have a magnetic layer directly on the nonmagnetic support, or may have a nonmagnetic layer containing nonmagnetic powder between the nonmagnetic support and the magnetic layer. The nonmagnetic powder used in the nonmagnetic layer may be an inorganic powder (inorganic powder) or an organic powder (organic powder). Carbon black, etc., can also be used. Examples of inorganic substances include metals, metal oxides, metal carbonates, metal sulfates, metal nitrides, metal carbides, and metal sulfides. These nonmagnetic powders are commercially available or can be produced by known methods. For details, see paragraphs 0146 to 0150 of JP 2011-216149 A. For carbon black usable in the nonmagnetic layer, see paragraphs 0040 to 0041 of JP 2010-24113 A. The content (filling rate) of the non-magnetic powder in the non-magnetic layer is preferably in the range of 50 to 90% by mass, and more preferably in the range of 60 to 90% by mass, relative to the total mass of the non-magnetic layer.

[0078] In one embodiment, the non-magnetic layer can contain Fe-based inorganic oxide powder as the non-magnetic powder. In the present invention and this specification, "Fe-based inorganic oxide powder" refers to an inorganic oxide powder containing iron as a constituent element. Specific examples of Fe-based inorganic oxide powder include α-iron oxide powder and goethite powder. In the present invention and this specification, "α-iron oxide powder" refers to a non-magnetic powder in which an α-iron oxide crystal structure is detected as the main phase by X-ray diffraction analysis. α-iron oxide powder is also commonly called hematite.

[0079] From the viewpoint of controlling the width direction σ of Spc within the range described above, the non-magnetic powder for the non-magnetic layer is preferably a powder having an average particle volume of 2.0×10 －６ μm ３ As a result of investigations by the present inventors, it has become clear that it is preferable to use the following Fe-based inorganic oxide powder. Therefore, the average particle volume of the Fe-based inorganic oxide powder contained in the non-magnetic layer is 2.0×10 －６ μm ３ Preferably, it is 1.5 × 10 or less. －６ μm ３More preferably, it is 1.0 × 10 or less. －６ μm ３ The average particle volume is more preferably 1.0×10 or less. －９ μm ３ or more or 1.0 x 10 －８ μm ３ It can be greater than or less than the values ​​exemplified here.

[0080] In the present invention and this specification, the above-mentioned average particle volume is a value determined by the following method. To observe the Fe-based inorganic oxide powder contained in the nonmagnetic layer of a data tape, the sample is first pretreated by microtoming. The microtoming is performed along the longitudinal direction of the data tape to obtain a thin section sample that allows for observation of the cross section in the thickness direction of the data tape. For each of the examples and comparative examples described below, a thin section sample was obtained from one of the prepared data tapes using a Leica EM UC6 microtome. The obtained thin section sample was then observed using a transmission electron microscope (TEM) at an acceleration voltage of 300 kV and a total magnification of 200,000 times, so as to include the area from the nonmagnetic support to the magnetic layer, and a cross-sectional TEM image was obtained. As the transmission electron microscope, for example, a JEM-2100Plus manufactured by JEOL can be used. For the examples and comparative examples described below, a JEOL JEM-2100Plus transmission electron microscope was used. In the obtained cross-sectional TEM image, 50 particles of the Fe-based inorganic oxide powder were identified using a microelectron diffraction method for the particles contained in the nonmagnetic layer. Electron diffraction by the microelectron diffraction method was performed using a transmission electron microscope at an acceleration voltage of 200 kV and a camera length of 50 cm. For the examples and comparative examples described below, a JEOL JEM-2100Plus transmission electron microscope was used for electron diffraction by the microelectron diffraction method. Then, using 50 particles of the Fe-based inorganic oxide powder identified as described above, the average particle volume was determined as follows. First, the major axis length (hereinafter also referred to as "DL") and minor axis length (hereinafter also referred to as "DS") of each particle were measured. The major axis length DL refers to the maximum distance between two parallel lines drawn from any angle so as to be tangent to the particle contour (the so-called maximum Feret's diameter). If the direction of the major axis length defined above is called the major axis direction, the minor axis length DS refers to the maximum length of the particle in the direction perpendicular to the major axis direction of the particle. Next, the average major axis length DLave is calculated as the arithmetic mean of the major axis lengths DL of the measured 50 particles."ave" is an abbreviation for "average." The average minor axis length DSave is calculated as the arithmetic mean of the minor axis lengths DS of the 50 particles. The average particle volume Vave is calculated from the average major axis length DLave and the average minor axis length Dsave using the following formula: Vave = π / 6 × Dsave. ２ ×DLave

[0081] In one embodiment, the non-magnetic layer may also contain carbon black as the non-magnetic powder. The average particle size of the carbon black may be, for example, 10 nm or more and 50 nm or less. From the viewpoint of controlling the Spc width direction σ within the range described above, the inventors' investigations have revealed that it is preferable to use carbon black with a pH of 9.0 or less as the non-magnetic powder in the non-magnetic layer. Therefore, the pH of the carbon black contained in the non-magnetic layer is preferably 9.0 or less, more preferably 8.5 or less, even more preferably 8.0 or less, and even more preferably 7.5 or less. The pH may be, for example, 1.0 or more, 2.0 or more, 3.0 or more, 4.0 or more, 5.0 or more, or 6.0 or more, or may be lower than the values ​​exemplified herein.

[0082] In the present invention and throughout this specification, the pH of carbon black is the value measured in accordance with standard test method ASTM D1512.

[0083] The non-magnetic layer has an average grain volume of 2.0×10 －６ μm ３ It is preferable to include at least one of the following Fe-based inorganic oxide powder and carbon black having a pH of 9.0 or less, and more preferable to include both: －６ μm ３The content of the Fe-based inorganic oxide powder described below can be 50.0 parts by mass or more, 60.0 parts by mass or more, or 70.0 parts by mass or more, and can be, for example, 90.0 parts by mass or less. The content of carbon black having a pH of 9.0 or less, relative to 100.0 parts by mass of the total amount of non-magnetic powder contained in the non-magnetic layer, can be 10.0 parts by mass or more, or 20.0 parts by mass or more, and can be, for example, 50.0 parts by mass or less, 40.0 parts by mass or less, or 30.0 parts by mass or less.

[0084] The non-magnetic layer may contain a binder and may also contain additives. For other details of the binder, additives, etc. of the non-magnetic layer, known techniques related to non-magnetic layers can be applied. Furthermore, for example, for the type and content of the binder, the type and content of the additive, known techniques related to magnetic layers can also be applied.

[0085] The non-magnetic layer of the data tape also includes a substantially non-magnetic layer that contains a small amount of ferromagnetic powder, either as an impurity or intentionally, along with the non-magnetic powder. Here, a substantially non-magnetic layer refers to a layer having a residual magnetic flux density of 10 mT or less, a coercive force of 7.96 kA / m (100 Oe) or less, or a residual magnetic flux density of 10 mT or less and a coercive force of 7.96 kA / m (100 Oe) or less. It is preferable that the non-magnetic layer have no residual magnetic flux density or coercive force.

[0086] <Non-magnetic Support> Next, the non-magnetic support will be described. Examples of non-magnetic supports (hereinafter also simply referred to as "support") include known biaxially stretched polyethylene terephthalate, polyethylene naphthalate, polyamide, polyamideimide, aromatic polyamide, etc. Among these, polyethylene terephthalate, polyethylene naphthalate, and polyamide are preferred. These supports may be previously subjected to corona discharge, plasma treatment, easy-adhesion treatment, heat treatment, etc.

[0087] In one embodiment, the non-magnetic support of the magnetic tape may be an aromatic polyester support. In the present invention and this specification, "aromatic polyester" refers to a resin containing an aromatic backbone and multiple ester bonds, and "aromatic polyester support" refers to a support containing at least one layer of aromatic polyester film. "Aromatic polyester film" refers to a film in which the component that constitutes the film in the largest proportion by mass is an aromatic polyester. In the present invention and this specification, "aromatic polyester support" includes support in which all the resin films contained in the support are aromatic polyester films, and support containing an aromatic polyester film and another resin film. Specific forms of aromatic polyester support include a single-layer aromatic polyester film, a laminate film of two or more aromatic polyester film layers with the same constituent components, a laminate film of two or more aromatic polyester film layers with different constituent components, and a laminate film containing one or more aromatic polyester film layers and one or more resin films other than aromatic polyester. An adhesive layer or the like may optionally be included between two adjacent layers in the laminate film. Furthermore, the aromatic polyester support may optionally include a metal film and / or metal oxide film formed by vapor deposition or the like on one or both surfaces. The same applies to the "polyethylene terephthalate support" and the "polyethylene naphthalate support" in the present invention and this specification.

[0088] The aromatic ring contained in the aromatic skeleton of the aromatic polyester is not particularly limited. Specific examples of aromatic rings include a benzene ring and a naphthalene ring. For example, polyethylene terephthalate (PET) is a polyester containing a benzene ring and is a resin obtained by polycondensation of ethylene glycol with terephthalic acid and / or dimethyl terephthalate. The term "polyethylene terephthalate" in this invention and this specification also includes structures having one or more other components (e.g., copolymerized components, components introduced into the terminal or side chain) in addition to the above components. Polyethylene naphthalate (PEN) is a polyester containing a naphthalene ring and is a resin obtained by esterification of dimethyl 2,6-naphthalenedicarboxylate with ethylene glycol, followed by transesterification and polycondensation reactions. The term "polyethylene naphthalate" in this invention and this specification also includes structures having one or more other components (e.g., copolymerized components, components introduced into the terminal or side chain) in addition to the above components.

[0089] In one embodiment, the non-magnetic support of the magnetic tape can be an aromatic polyamide support. In the present invention and this specification, "aromatic polyamide" refers to a resin containing an aromatic backbone and multiple amide bonds. The aromatic ring contained in the aromatic backbone of the aromatic polyamide is not particularly limited. Specific examples of aromatic rings include a benzene ring. An "aromatic polyamide support" refers to a support containing at least one layer of aromatic polyamide film. An "aromatic polyamide film" refers to a film in which aromatic polyamide is the predominant component by mass among the components constituting the film. In the present invention and this specification, "aromatic polyamide support" includes support in which all resin films contained in the support are aromatic polyamide films, and support containing an aromatic polyamide film and another resin film. Specific forms of aromatic polyamide support include a single-layer aromatic polyamide film, a laminate film of two or more layers of aromatic polyamide films with the same constituent components, a laminate film of two or more layers of aromatic polyamide films with different constituent components, and a laminate film containing one or more layers of aromatic polyamide film and one or more layers of resin film other than aromatic polyamide. The laminated film may optionally contain an adhesive layer or the like between two adjacent layers. The aromatic polyamide support may also optionally contain a metal film and / or a metal oxide film formed by vapor deposition or the like on one or both surfaces.

[0090] As described above, the non-magnetic support may be a biaxially stretched film, and may be a film that has been subjected to corona discharge, plasma treatment, easy-adhesion treatment, heat treatment, or the like.

[0091] An example of an index of the physical properties of a non-magnetic support is moisture content. In the present invention and this specification, the moisture content of a non-magnetic support is a value determined by the following method. A sample piece (e.g., a sample piece having a mass of several grams) cut out from the non-magnetic support to be measured for moisture content is dried to a constant mass in a vacuum dryer at a temperature of 180°C and a pressure of 100 Pa (Pascal) or less. The mass of the dried sample piece is designated as W1. W1 is a value measured in a measurement environment at a temperature of 23°C and a relative humidity of 50% within 30 seconds after removal from the vacuum dryer. Next, W2 is the mass of the sample piece after placing it in an environment at a temperature of 25°C and a relative humidity of 75% for 48 hours. W2 is a value measured in a measurement environment at a temperature of 23°C and a relative humidity of 50% within 30 seconds after removal from the environment. The moisture content is calculated using the following formula: Water content (%) = [(W2 - W1) / W1] × 100 For example, after removing the magnetic layer and other portions of the magnetic tape other than the non-magnetic support by a known method (for example, film removal using an organic solvent), the water content of the non-magnetic support can be determined by the above method.

[0092] In one embodiment, the moisture content of the non-magnetic support of the magnetic tape is preferably 2.0% or less, more preferably 1.8% or less, even more preferably 1.6% or less, even more preferably 1.4% or less, even more preferably 1.2% or less, and even more preferably 1.0% or less. The moisture content of the non-magnetic support of the magnetic tape can be 0%, 0% or more, more than 0%, or 0.1% or more.

[0093] Young's modulus can also be used as an indicator of the physical properties of a non-magnetic support. In this invention and this specification, the Young's modulus of a non-magnetic support is a value measured by the following method in a measurement environment at a temperature of 23°C and a relative humidity of 50%. A sample piece cut out from the non-magnetic support to be measured is pulled using a universal tensile tester under conditions of a chuck distance of 100 mm, a pulling speed of 10 mm / min, and a chart speed of 500 mm / min. As the universal tensile tester, for example, a commercially available universal tensile tester such as the Tensilon manufactured by Toyo Baldwin Co., Ltd., or a universal tensile tester with a known configuration can be used. The Young's modulus in the longitudinal and width directions of the sample piece is calculated from the tangent to the rising portion of the load-elongation curve thus obtained. Here, the longitudinal and width directions of the sample piece refer to the longitudinal and width directions when the sample piece is included in a magnetic tape. For example, after removing the magnetic layer and other portions of the non-magnetic support from the magnetic tape by a known method (e.g., removal using an organic solvent), the Young's modulus in the longitudinal and transverse directions of the non-magnetic support can be determined by the above-mentioned method.

[0094] In one embodiment, the Young's modulus of the non-magnetic support of the magnetic tape in the longitudinal direction is preferably 3,000 MPa or more, more preferably 4,000 MPa or more, even more preferably 5,000 MPa or more, and even more preferably 6,000 MPa or more. The Young's modulus of the non-magnetic support of the magnetic tape in the longitudinal direction may be 15,000 MPa or less, 13,000 MPa or less, or 12,000 MPa or less. In the width direction, the Young's modulus of the non-magnetic support of the magnetic tape in the width direction is preferably 2,000 MPa or more, more preferably 3,000 MPa or more, even more preferably 4,000 MPa or more, and even more preferably 5,000 MPa or more. The Young's modulus of the non-magnetic support of the magnetic tape in the width direction may be 12,000 MPa or less, 11,000 MPa or less, or 10,000 MPa or less. In the manufacture of magnetic tapes, non-magnetic supports are typically used with the MD (machine direction) of the film as the longitudinal direction and the TD (transverse direction) as the width direction. In one embodiment, the Young's modulus in the longitudinal direction is preferably greater than the Young's modulus in the width direction, and the difference (Young's modulus in the longitudinal direction - Young's modulus in the width direction) is more preferably in the range of 800 to 3000 MPa.

[0095] The water content and Young's modulus of the non-magnetic support can be controlled by the types and mixing ratios of the components constituting the support, the manufacturing conditions of the support, etc. For example, by adjusting the stretching ratio in each direction in a biaxial stretching process, the Young's modulus in the longitudinal direction and the Young's modulus in the width direction can be controlled.

[0096] <Backcoat Layer> The data tape may or may not have a backcoat layer containing nonmagnetic powder on the surface of the nonmagnetic support opposite the surface having the magnetic layer. The backcoat layer preferably contains one or both of carbon black and inorganic powder. The backcoat layer may also contain a binder and additives. For details on the nonmagnetic powder, binder, additives, etc. of the backcoat layer, known techniques related to backcoat layers can be applied, as can known techniques related to magnetic layers and / or nonmagnetic layers. For example, see paragraphs

[0018] to

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

[0097] <Various Thicknesses> Regarding the thickness (total thickness) of data tapes, with the enormous increase in the amount of information in recent years, magnetic recording media are required to have higher recording capacities (higher capacities). For tape-type magnetic recording media (i.e., data tapes), one way to increase the capacity is to reduce the thickness of the data tape and increase the length of magnetic tape accommodated in one magnetic tape cartridge. From this perspective, the thickness (total thickness) of the data tape is preferably 5.6 μm or less, more preferably 5.5 μm or less, even more preferably 5.4 μm or less, even more preferably 5.3 μm or less, even more preferably 5.2 μm or less, even more preferably 5.0 μm or less, and even more preferably 4.8 μm or less. Furthermore, from the perspective of ease of handling, the thickness of the data tape is preferably 3.0 μm or more, more preferably 3.5 μm or more, and even more preferably 4.0 μm or more. The thickness (total thickness) of a data tape can be measured by the following method. Ten tape samples (e.g., 5 to 10 cm long) are cut from any portion of the data tape, and these tape samples are stacked and measured for thickness. The measured thickness is divided by 10 to obtain the value (thickness per tape sample), which is taken as the tape thickness. The thickness measurement can be performed using a known measuring device capable of measuring thickness to the order of 0.1 μm.

[0098] The thickness of the non-magnetic support is preferably 2.0 to 5.0 μm, more preferably 3.0 to 5.0 μm. The thickness of the magnetic layer can be optimized depending on the saturation magnetization of the magnetic head used, the head gap length, the bandwidth of the recording signal, etc., and is generally 0.01 μm to 0.15 μm. From the viewpoint of high-density recording, it is preferably 0.02 μm to 0.12 μm, and more preferably 0.03 μm to 0.1 μm. The magnetic layer must be at least one layer, and may be separated into two or more layers with different magnetic properties, and known multilayer magnetic layer configurations can be applied. When the magnetic layer is separated into two or more layers, the thickness refers to 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 backcoat 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. A cross section of the data tape in the thickness direction is exposed to an ion beam, and then 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 thicknesses determined at any two points during cross-sectional observation. Alternatively, various thicknesses can be determined as design thicknesses calculated from manufacturing conditions, etc.

[0099] <Manufacturing Process> (Preparation of Compositions for Forming Each Layer) The compositions for forming the magnetic layer, non-magnetic layer, or backcoat layer typically contain a solvent in addition to the various components described above. The solvent can be one or more of the various solvents typically used in the production of particulate magnetic recording media. The solvent content of each layer-forming composition is not particularly limited. For details about solvents, see paragraph

[0153] of JP 2011-216149 A. The solids concentration and solvent composition of each layer-forming composition can be adjusted appropriately depending on the handling suitability of the composition, the coating conditions, and the thickness of each layer to be formed. The process for preparing the composition for forming the magnetic layer, non-magnetic layer, or backcoat layer typically includes at least a kneading step, a dispersing step, and a mixing step, optionally provided before or after these steps. Each individual step may be divided into two or more stages. The various components used in the preparation of each layer-forming composition may be added at the beginning or during any step. Alternatively, each component may be added in separate steps over two or more steps. For example, the binder may be added in portions during the kneading process, the dispersion process, and the mixing process for adjusting the viscosity after dispersion. The data tape manufacturing process described above can employ conventional manufacturing techniques as some of the steps. In the kneading process, devices with strong kneading power, such as open kneaders, continuous kneaders, pressure kneaders, and extruders, can be used. Details of the kneading process are described in Japanese Patent Application Laid-Open Nos. 1-106338 and 1-79274. Various known dispersers that utilize shear force, such as bead mills, ball mills, sand mills, and homomixers, can be used. Dispersion beads are preferably used for dispersion. Examples of dispersion beads include ceramic beads and glass beads, with zirconia beads being preferred. Two or more types of beads may be used in combination. The bead diameter (particle size) and bead packing ratio of the dispersion beads are not particularly limited and may be set according to the powder to be dispersed. The dispersion time is not particularly limited. The present inventors surmise that from the viewpoint of controlling the Spc and width direction σ of the Spc on the magnetic layer surface within the ranges described above, it is preferable to extend the dispersion time in preparing the magnetic layer-forming composition.Each layer-forming composition may be filtered by a known method before being subjected to the coating step. Filtration can be performed, for example, by filter filtration. The filter used for filtration may be, for example, a filter with a pore size of 0.01 to 3 μm (e.g., a glass fiber filter, a polypropylene filter, etc.).

[0100] (Coating step, cooling step, heat drying step) The magnetic layer can be formed by coating the magnetic layer-forming composition directly onto the non-magnetic support, or by sequentially or simultaneously coating the magnetic layer-forming composition and the non-magnetic layer-forming composition in multiple layers. For details of the coating steps for forming each layer, see paragraph

[0066] of JP2010-231843A.

[0101] As described above, in one embodiment, the data tape can have a non-magnetic layer between the non-magnetic support and the magnetic layer. Such a data tape can preferably be manufactured by sequential multilayer coating. The manufacturing process using sequential multilayer coating can be preferably carried out as follows: The non-magnetic layer is formed through a coating step in which a non-magnetic layer-forming composition is applied to the non-magnetic support to form a coating layer, and a heat-drying step in which the formed coating layer is dried by heat treatment. The magnetic layer is then formed through a coating step in which a magnetic layer-forming composition is applied to the formed non-magnetic layer to form a coating layer, and a heat-drying step in which the formed coating layer is dried by heat treatment. In one embodiment, in the non-magnetic layer-forming process of the manufacturing method using sequential multilayer coating, a coating layer can be formed by performing a coating step using a non-magnetic layer-forming composition, and a cooling step in which the coating layer is cooled can be performed between the coating step and the heat-drying step.

[0102] An example of the manufacturing process for the data tape will be described below with reference to Figure 8. However, the present invention is not limited to the following example.

[0103] 8 is a process schematic diagram showing an example of a process for producing a magnetic tape having a non-magnetic layer and a magnetic layer in this order on one side of a non-magnetic support, and a backcoat layer on the other side. In the example shown in FIG. 8, the non-magnetic support (long film) is continuously wound from the feeding section to the winding section, and various processes such as coating, drying, and orientation are performed in each section or zone shown in FIG. 8, so that a non-magnetic layer and a magnetic layer are formed by sequential multilayer coating on one side of the running non-magnetic support, and a backcoat layer is formed on the other side. The example shown in FIG. 8 can be similar to the manufacturing process normally performed for producing particulate magnetic recording media, except that it includes a cooling zone.

[0104] The non-magnetic support delivered from the delivery section is coated with a non-magnetic layer forming composition in the first coating section (non-magnetic layer forming composition coating step).

[0105] After the coating step, the coating layer of the nonmagnetic layer-forming composition formed in the coating step is cooled in a cooling zone (cooling step). For example, the cooling step can be performed by passing the nonmagnetic support on which the coating layer has been formed through a cooling atmosphere. The temperature of the cooling atmosphere can preferably be in the range of -10°C to 0°C, and more preferably in the range of -5°C to 0°C. The time for performing the cooling step (for example, the time from when any part of the coating layer is carried into the cooling zone until when it is carried out (hereinafter also referred to as "residence time")) is not particularly limited. In the cooling step, cooled gas may be blown onto the surface of the coating layer.

[0106] After the cooling zone, the coating layer is dried by heating it in the first heat treatment zone (heat drying process). The heat drying process can be carried out by passing the non-magnetic support bearing the coating layer after the cooling process through a heated atmosphere. The ambient temperature of the heated atmosphere here, as well as the ambient temperature of the heated atmosphere in the heat drying process in the second heat treatment zone and the heat drying process in the third heat treatment zone described below, are also referred to as the "drying temperature." In one embodiment, the drying temperature in each heat treatment zone is preferably 95°C or higher, more preferably 100°C or higher. The drying temperature in each heat treatment zone can be, for example, 140°C or lower or 130°C or lower, and can also be higher than the temperatures listed here. Optionally, heated gas may be blown onto the surface of the coating layer.

[0107] Next, in the second coating section, a magnetic layer-forming composition is coated onto the non-magnetic layer formed by the heat drying step in the first heat treatment zone (magnetic layer-forming composition coating step).

[0108] In a subsequent orientation treatment, the ferromagnetic powder in the coating layer is oriented in the orientation zone while the coating layer of the magnetic layer-forming composition is still wet. Various known techniques, including those described in paragraph 0067 of JP 2010-231843 A, can be applied to the orientation treatment. For example, vertical orientation treatment can be performed by known methods, such as a method using magnets with opposite poles facing each other. In the orientation zone, the drying speed of the coating layer can be controlled by the temperature and volume of the drying air and / or the transport speed of the magnetic tape in the orientation zone. The coating layer may also be pre-dried before being transported to the orientation zone.

[0109] After the orientation treatment, the coated layer is subjected to a heat drying step in the second heat treatment zone.

[0110] Next, in the third coating section, a backcoat layer-forming composition is applied to the surface of the non-magnetic support opposite to the surface on which the non-magnetic layer and the magnetic layer are formed, thereby forming a coating layer (backcoat layer-forming composition application step).Then, in the third heat treatment zone, the coating layer is heat-treated and dried.

[0111] Through the above steps, a magnetic tape can be obtained which has a nonmagnetic layer and a magnetic layer in this order on one side of a nonmagnetic support and a backcoat layer on the other side.

[0112] (Other Processes) In the manufacturing process of magnetic tape, calendering is usually performed to improve the surface smoothness of the magnetic tape. Strengthening the calendering conditions can contribute to reducing the Spc width direction σ value. Specific examples of strengthening the calendering conditions include increasing the calendering pressure, increasing the calendering temperature, and decreasing the calendering speed. Regarding the calendering conditions, the calendering pressure (linear pressure) is preferably 300 to 500 kN / m, more preferably 310 to 350 kN / m, the calendering temperature (calender roll surface temperature) is preferably 95 to 120°C, more preferably 100 to 120°C, and the calendering speed is preferably 50 to 75 m / min. For other various processes for manufacturing magnetic tape, see paragraphs 0067 to 0070 of JP 2010-231843 A. A long magnetic tape roll can be obtained by going through various processes. The obtained magnetic tape roll is cut (slit) by a known cutter to the width of the magnetic tape to be housed in a magnetic tape cartridge, for example. The width can be determined according to standards and is usually 1 / 2 inch. 1 inch = 2.54 cm. The width of the reinforcing layer, which will be described later, is also usually 1 / 2 inch. A servo pattern is usually formed on the magnetic tape obtained by slitting.

[0113] (Formation of Servo Pattern) “Formation of servo pattern” can also be called “recording of servo signal.” Formation of servo pattern will be explained below.

[0114] The servo patterns are usually formed along the longitudinal direction of the magnetic tape. Control methods using servo signals (servo control) include timing-based servo (TBS), amplitude servo, and frequency servo.

[0115] As set forth in ECMA (European Computer Manufacturers Association)-319 (June 2001), magnetic tapes conforming to the LTO (Linear Tape-Open) standard (commonly referred to as "LTO tapes") employ a timing-based servo system. In this timing-based servo system, a servo pattern is formed by a pair of non-parallel magnetic stripes (also referred to as "servo stripes") arranged continuously in the longitudinal direction of the magnetic tape. In this invention and this specification, the term "timing-based servo pattern" refers to a servo pattern that enables head tracking in a servo system employing the timing-based servo system. As described above, the reason that the servo pattern is formed by a pair of non-parallel magnetic stripes is to inform a servo signal reading element passing over the servo pattern of its passing position. Specifically, the pair of magnetic stripes is formed so that the spacing between them changes continuously across the width 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 the spacing. This relative position information enables tracking of the data track. For this purpose, multiple servo tracks are usually set on the servo pattern across the width of the magnetic tape.

[0116] A servo band is made up of a continuous servo pattern in the longitudinal direction of the magnetic tape. A magnetic tape usually has multiple servo bands. For example, in an LTO tape, there are five such bands. The area sandwiched between two adjacent servo bands is the data band. A data band is made up of multiple data tracks, and each data track corresponds to one of the servo tracks.

[0117] Also, in one embodiment, as disclosed in Japanese Patent Laid-Open Publication No. 2004-318983, information indicating the servo band number (also referred to as "servo band ID (identification)" or "UDIM (Unique Data Band Identification Method) information") is embedded in each servo band. This servo band ID is recorded by shifting a specific one of a plurality of pairs of servo stripes in the servo band so that its position is displaced relative to the longitudinal direction of the magnetic tape. Specifically, the way in which a specific one of a plurality of pairs of servo stripes is shifted is changed for each servo band. As a result, the recorded servo band ID is unique for each servo band, and therefore, simply by reading one servo band with a servo signal reading element, that servo band can be uniquely identified.

[0118] One method for uniquely identifying servo bands is the staggered method described in ECMA-319 (June 2001). In this staggered method, a group of pairs of non-parallel magnetic stripes (servo stripes) arranged continuously along the longitudinal direction of the magnetic tape are recorded so that each servo band is shifted along the longitudinal direction of the magnetic tape. 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 using two servo signal reading elements.

[0119] Furthermore, as specified in ECMA-319 (June 2001), information indicating the longitudinal position of the magnetic tape (also called "LPOS (Longitudinal Position) information") is usually embedded in each servo band. Like UDIM information, this LPOS information is also recorded by shifting the positions of a pair of servo stripes in the longitudinal direction of the magnetic tape. However, unlike UDIM information, the same signal is recorded in each servo band for this LPOS information.

[0120] It is also possible to embed information other than the above-mentioned UDIM information and LPOS information in the servo bands. In this case, the embedded information may be different for each servo band, such as UDIM information, or may be common to all servo bands, such as LPOS information. Furthermore, methods other than those described above can also be used to embed information in the servo bands. For example, a predetermined code may be recorded by thinning out a predetermined pair from a group of pairs of servo stripes.

[0121] The head for forming a servo pattern is called a servo write head. A servo write head typically has a pair of gaps corresponding to the pair of magnetic stripes, the number of which is equal to the number of servo bands. Typically, a core and a coil are connected to each pair of gaps, and by supplying a current pulse to the coil, the magnetic field generated in the core can generate a leakage magnetic field in the pair of gaps. When forming a servo pattern, a current pulse is input while running a magnetic tape over the servo write head, thereby transferring the magnetic pattern corresponding to the pair of gaps to the magnetic tape, thereby forming the servo pattern. The width of each gap can be appropriately set depending on the density of the servo pattern to be formed. The width of each gap can be set, for example, to 1 μm or less, 1 to 10 μm, or 10 μm or more.

[0122] Before forming a servo pattern on a magnetic tape, the magnetic tape is usually subjected to a demagnetization (erase) process. This erase process can be performed by applying a uniform magnetic field to the magnetic tape using a direct current magnet or an alternating current magnet. Erase processes include DC (direct current) erase and AC (alternating current) erase. AC erase 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 erase is performed by applying a unidirectional magnetic field to the magnetic tape. There are two other DC erase methods. The first method is horizontal DC erase, in which a unidirectional magnetic field is applied along the longitudinal direction of the magnetic tape. The second method is vertical DC erase, in which a unidirectional magnetic field is applied along the thickness direction of the magnetic tape. The erase process can be performed on the entire magnetic tape or on each servo band of the magnetic tape.

[0123] The direction of the magnetic field of the formed servo pattern is determined according to the direction of erasure. For example, when horizontal DC erasure is performed on a magnetic tape, the servo pattern is formed so that the direction of the magnetic field is opposite to the direction of erasure. This makes it possible to increase the output of the servo signal obtained by reading the servo pattern. As shown in Japanese Patent Application Laid-Open No. 2012-53940, when a magnetic pattern is transferred using the above-mentioned gap to a magnetic tape that has been vertically DC erased, the servo signal obtained by reading the formed servo pattern has a unipolar pulse shape. On the other hand, when a magnetic pattern is transferred using the above-mentioned gap to a magnetic tape that has been horizontally DC erased, the servo signal obtained by reading the formed servo pattern has a bipolar pulse shape.

[0124] <Perpendicular Squareness> In one embodiment, the perpendicular squareness of the data tape can be, for example, 0.55 or more. From the viewpoint of improving electromagnetic conversion characteristics, it is preferably 0.60 or more, and more preferably 0.65 or more. In principle, the upper limit of the squareness is 1.00 or less. The perpendicular squareness of the data tape can be 1.00 or less, and can be 0.95 or less, 0.90 or less, 0.85 or less, or 0.80 or less. A large perpendicular squareness of the data tape is preferable from the viewpoint of improving electromagnetic conversion characteristics. The perpendicular squareness of the data tape can be controlled by a known method, such as performing a perpendicular orientation treatment.

[0125] In the present invention and this specification, "perpendicular squareness" refers to the squareness measured in the perpendicular direction of the data tape. The "perpendicular direction" in relation to squareness refers to the direction perpendicular to the magnetic layer surface, which can also be referred to as the thickness direction. In the present invention and this specification, the perpendicular squareness is determined by the following method: A sample piece of a size that can be introduced into a vibrating sample magnetometer is cut from the data tape to be measured. A magnetic field is applied to this sample piece in the perpendicular direction (perpendicular to the magnetic layer surface) using a vibrating sample magnetometer at a maximum applied magnetic field of 3979 kA / m, a measurement temperature of 296 K, and a magnetic field sweep rate of 8.3 kA / m / sec, and the magnetization intensity of the sample piece relative to the applied magnetic field is measured. The measured value of the magnetization intensity is obtained as a value after demagnetization field correction and after subtracting the magnetization of the sample probe of the vibrating sample magnetometer as background noise. When the magnetization strength at the maximum applied magnetic field is Ms and the magnetization strength at zero applied magnetic field is Mr, the squareness ratio SQ is a value calculated as SQ = Mr / Ms. The measurement temperature refers to the temperature of the sample piece, and by setting the ambient temperature around the sample piece to the measurement temperature, temperature equilibrium is established and the temperature of the sample piece can be set to the measurement temperature.

[0126] <<Reinforcing Layer>> In one embodiment, the magnetic tape does not have the reinforcing layer described below, and in another embodiment, it has the reinforcing layer described below. The present inventors believe that having the reinforcing layer can contribute to further suppressing the occurrence of the nonlinear component of the tape width deformation described above. Therefore, the present inventors speculate that having the reinforcing layer described below on the magnetic tape can contribute to further improving the operational stability of the drive during recording and / or playback after long-term storage.

[0127] In this invention and in this specification, the term "reinforcing layer" refers to one or more layers provided on the outermost surface of one or both surfaces of a data tape having a non-magnetic support with a magnetic layer (optionally with a non-magnetic layer as described above) on one surface side and an optional backcoat layer as described above on the other surface side. Such a reinforcing layer can serve to reinforce the data tape.

[0128] Fig. 15 is a cross-sectional view showing a portion of an example of a magnetic tape provided with a reinforcing layer. In the example shown in Fig. 15, splice tape ST, which is typically used to join a leader tape and a data tape in a magnetic tape having a leader tape, is used as the reinforcing layer. However, as described above, the magnetic tape according to one aspect of the present invention does not include a leader tape.

[0129] In the example shown in FIG. 15 , the reinforcing layer (splice tape ST) is provided on one surface of the end of the data tape DT where the leader pin 133 is attached, and is in direct contact with the clamp 138. The reinforcing layer can be provided on either the magnetic layer side of the data tape or the opposite side, or both. For example, the side wound around the leader pin 133 can be the magnetic layer side of the data tape, and the splice tape can be attached to the backcoat layer on the other side. Known techniques for splicing tapes used to join the data tape and leader tape of magnetic tapes can be applied to the splice tape. For example, adhesive tapes having an adhesive layer on the substrate surface can be used as splice tapes. Such adhesive tapes are commercially available or can be prepared by known methods. An example of an adhesive tape is an adhesive tape having an acrylic adhesive layer on a polyester substrate. In this invention and this specification, "adhesion" also encompasses "stickiness." An "acrylic adhesive layer" refers to a layer containing a polymer and / or copolymer of a (meth)acrylic compound as an adhesive component. The term "(meth)acrylic compound" refers to a polymerizable compound having one or more polymerizable groups selected from the group consisting of acryloyl, methacryloyl, acryloyloxy, and methacryloyloxy groups per molecule. In the present invention and this specification, the term "polyester substrate" refers to a substrate containing at least one layer of polyester film. Examples of polyester substrates include a single-layer polyester film, a laminate film of two or more polyester film layers with the same constituent components, a laminate film of two or more polyester film layers with different constituent components, and a laminate film containing one or more polyester film layers and one or more non-polyester resin film layers. An adhesive layer or the like may optionally be included between two adjacent layers in the laminate film. The reinforcing layer may be provided, for example, in a region extending from the end of the end of the data tape.

[0130] The thickness of the reinforcing layer can be, for example, 5.0 μm or more, and preferably 10.0 μm or more from the viewpoint of further improving the operational stability of the drive during recording and / or playback after long-term storage. The thickness of the reinforcing layer can also be, for example, 30.0 μm or less or 25.0 μm or less. The thickness of the reinforcing layer can be determined, for example, by the method described above for measuring various thicknesses, such as the thickness of the magnetic layer. Alternatively, for example, when splice tape is used as the reinforcing layer, the thickness can be determined using the original tape of the splice tape by the method described above for measuring the thickness of a data tape, and this thickness can be used as the thickness of the reinforcing layer (splice tape).

[0131] [Magnetic Tape Cartridge] One aspect of the present invention relates to a magnetic tape cartridge including the magnetic tape described above.

[0132] The magnetic tape contained in the magnetic tape cartridge is as described above in detail. The magnetic tape cartridge can be mounted in a magnetic tape device equipped with a magnetic head and used to record and / or reproduce data.

[0133] A magnetic tape cartridge generally contains a magnetic tape wound on a reel within the cartridge body. The reel is rotatably mounted within the cartridge body. Widely used magnetic tape cartridges include single-reel magnetic tape cartridges with one reel within the cartridge body and dual-reel magnetic tape cartridges with two reels within the cartridge body. When a single-reel magnetic tape cartridge is loaded into a magnetic tape device for recording and / or reproducing data on the magnetic tape, the magnetic tape is pulled out from the magnetic tape cartridge and wound onto a reel on the magnetic tape device. A magnetic head is disposed 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 (supply reel) on the magnetic tape cartridge and the reel (take-up reel) on the magnetic tape device. For example, data is recorded and / or reproduced by contact and sliding between the magnetic head and the magnetic layer surface of the magnetic tape during this process. In contrast, a dual-reel magnetic tape cartridge is provided with both a supply reel and a take-up reel inside the magnetic tape cartridge.

[0134] In one embodiment, the magnetic tape cartridge may include a cartridge memory. The cartridge memory may be, for example, a non-volatile memory. In one embodiment, head tilt angle adjustment information may already be recorded in the cartridge memory, or head tilt angle adjustment information may be recorded in the cartridge memory. The head tilt angle adjustment information is information for adjusting the head tilt angle while the magnetic tape is running in the magnetic tape device. For example, the head tilt angle adjustment information may record the value of the servo band spacing at each position in the longitudinal direction of the magnetic tape when data is recorded. For example, when reproducing data recorded on the magnetic tape, the value of the servo band spacing may be measured during reproduction, and the head tilt angle may be changed by a control device of the magnetic tape device so that the absolute value of the difference between the servo band spacing measured during reproduction and the servo band spacing recorded in the cartridge memory during recording at the same longitudinal position approaches zero. The head tilt angle may be, for example, the angle θ described above.

[0135] The magnetic tape and magnetic tape cartridge described above can be suitably used in a magnetic tape device (i.e., a magnetic recording and / or playback system) that records and / or plays back data at different head tilt angles. In one embodiment of such a magnetic tape device, data can be recorded and / or played back by changing the head tilt angle while the magnetic tape is running. For example, the head tilt angle can be changed in accordance with widthwise dimension information of the magnetic tape acquired while the magnetic tape is running. Another possible use mode is to change the head tilt angle during a given recording and / or playback session from that during subsequent recording and / or playback sessions, and then keep the head tilt angle fixed during each recording and / or playback session.

[0136] [Magnetic Tape Device] One aspect of the present invention relates to a magnetic tape device including the magnetic tape described above. In the magnetic tape device, data can be recorded on the magnetic tape and / or data recorded on the magnetic tape can be reproduced, for example, by contacting and sliding a magnetic head over the surface of the magnetic layer of the magnetic tape.

[0137] For example, magnetic tape is treated as a removable medium (so-called exchangeable medium), and a magnetic tape cartridge containing the magnetic tape is inserted into and removed from a magnetic tape device.

[0138] In this invention and this specification, the term "magnetic tape device" refers to a device that can record data on a magnetic tape and / or reproduce data recorded on a magnetic tape. Such a device is generally called a drive.

[0139] <Magnetic Head> The 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 described above with reference to FIGS. 5 to 7. If the magnetic head includes a reproducing element, the reproducing element is preferably a magnetoresistive (MR) element that can read information recorded on a magnetic tape (specifically, a data tape) with high sensitivity. As the MR element, various known MR elements (e.g., a GMR (Giant Magnetoresistive) element, a TMR (Tunnel Magnetoresistive) element, etc.) can be used. Hereinafter, a magnetic head that records data and / or reproduces recorded data will also be referred to as a "recording / reproducing head." The element for recording data (recording element) and the element for reproducing data (reproducing element) will be collectively referred to as a "magnetic head element."

[0140] When recording data and / or reproducing recorded data, tracking can first be performed using a servo signal. That is, by making the servo signal reading element follow a predetermined servo track, the magnetic head element can be controlled so that it passes over the target data track. The data track is moved by changing the servo track read by the servo signal reading element in the tape width direction. The recording / reproducing head can also record and / or reproduce data on other data bands. In this case, the servo signal reading element is moved to a predetermined servo band using the UDIM information described above, and tracking on that servo band can be started.

[0141] FIG. 9 shows an example of the arrangement of data bands and servo bands. In FIG. 9, multiple servo bands 1 are sandwiched between guide bands 3 on the magnetic layer of the data tape of the magnetic tape MT. Multiple regions 2 sandwiched between two servo bands constitute the data bands. Servo patterns are magnetized regions formed by magnetizing specific regions of the magnetic layer with a servo write head. The regions magnetized by the servo write head (the positions where the servo patterns are formed) are determined by standards. For example, in the industry-standard LTO Ultrium format tape, multiple servo patterns inclined with respect to the tape width direction are formed on the servo bands during magnetic tape manufacturing, as shown in FIG. 10. Specifically, in FIG. 10, the servo frame SF on the servo band 1 is composed of a servo subframe 1 (SSF1) and a servo subframe 2 (SSF2). The servo subframe 1 is composed of an A burst (labeled A in FIG. 10) and a B burst (labeled B in FIG. 10). The A burst is composed of servo patterns A1 to A5, and the B burst is composed of servo patterns B1 to B5. Meanwhile, servo subframe 2 is composed of a C burst (labeled C in FIG. 10) and a D burst (labeled D in FIG. 10). The C burst is composed of servo patterns C1 to C4, and the D burst is composed of servo patterns D1 to D4. These 18 servo patterns are arranged in subframes, arranged in a 5, 5, 4, 4, 5, set of 5, 4, 4, arrangement, and are used to identify servo frames. For illustrative purposes, FIG. 10 shows one servo frame. However, in reality, multiple servo frames are arranged in each servo band in the magnetic layer of a data tape for a magnetic tape that uses timing-based servo head tracking, in the running direction. In FIG. 10, the arrow indicates the running direction of the magnetic tape. For example, an LTO Ultrium format tape typically has 5,000 or more servo frames per meter of tape length in each servo band of the magnetic layer.

[0142] In one embodiment, in the magnetic tape device, the head tilt angle can be changed while the magnetic tape is running 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 that adjusts the angle of the magnetic head module in the recording / reproducing head unit of the magnetic head, the angle θ can be variably adjusted while the magnetic tape is running. Such an angle adjustment unit can include, for example, a rotation mechanism that rotates the module. Publicly known technology can be applied to the angle adjustment unit.

[0143] Regarding the head tilt angle during magnetic tape running, if the magnetic head includes multiple modules, the angle θ described with reference to Figures 5 to 7 can be defined for randomly selected modules. ｉｎｉｔｉａｌ can be set to be equal to or greater than 0°. ｉｎｉｔｉａｌ The larger the angle θ, the larger the change in the effective distance between the servo signal read elements relative to the change in angle θ, which is preferable in terms of the ability to adjust the effective distance between the servo signal read elements in response to changes in the width direction of the magnetic tape. ｉｎｉｔｉａｌ is preferably 1° or more, more preferably 5° or more, and even more preferably 10° or more. On the other hand, with regard to the angle formed by the magnetic layer surface and the contact surface of the magnetic head when the magnetic tape runs and comes into contact with the magnetic head (generally called the "wrap angle"), keeping the deviation in the tape width direction small is effective in increasing the uniformity in the tape width direction of the friction generated by contact between the magnetic head and the magnetic tape while the magnetic tape is running. Furthermore, increasing the uniformity of the friction in the tape width direction is desirable from the viewpoint of the position tracking ability and running stability of the magnetic head. From the viewpoint of reducing the deviation in the tape width direction of the wrap angle, θ ｉｎｉｔｉａｌ is preferably 45° or less, more preferably 40° or less, and even more preferably 35° or less.

[0144] Regarding the change in angle θ during magnetic tape running, while the magnetic tape is running in the magnetic tape device for recording data on the magnetic tape and / or for reproducing data recorded on the magnetic tape, the angle θ of the magnetic head is changed from θ at the start of running. ｉｎｉｔｉａｌ When the angle θ changes from ｍａｘ and Δθ ｍｉｎ The maximum value of the angle θ during magnetic tape running is θ ｍａｘ and the minimum value is θ ｍｉｎ Note that "max" is an abbreviation for maximum, and "min" is an abbreviation for minimum. Δθ ｍａｘ = θ ｍａｘ -θ ｉｎｉｔｉａｌ Δθ ｍｉｎ = θ ｉｎｉｔｉａｌ -θ ｍｉｎ

[0145] In one embodiment, Δθ can be greater than 0.000°, and from the viewpoint of the ability to adjust the effective distance between the servo signal reading elements in response to dimensional changes in the width direction of the magnetic tape, Δθ is preferably 0.001° or greater, and more preferably 0.010° ​​or greater. Furthermore, from the viewpoint of ease of ensuring synchronization of recording data and / or reproduction data between multiple magnetic head elements during data recording and / or reproduction, Δθ is preferably 1.000° or less, more preferably 0.900° or less, even more preferably 0.800° or less, even more preferably 0.700° or less, and even more preferably 0.600° or less.

[0146] 6 and 7, the axis of the element array is inclined toward the magnetic tape running direction. However, the present invention is not limited to such an example. In the above-mentioned magnetic tape device, an embodiment in which the axis of the element array is inclined toward the direction opposite to the magnetic tape running direction is also included in the present invention.

[0147] θ is the head tilt angle when the magnetic tape starts running ｉｎｉｔｉａｌcan be set by a control device of the magnetic tape device, etc. Regarding the head tilt angle during magnetic tape running, FIG. 11 is an explanatory diagram of a method for measuring the angle θ during magnetic tape running. The angle θ during magnetic tape running can be determined, for example, by the following method. When determining the angle θ during magnetic tape running by the following method, the angle θ is changed within the range of 0 to 90° during magnetic tape running. That is, if the axis of the element array is tilted toward the magnetic tape running direction at the start of magnetic tape running, the element array is not tilted during magnetic tape running so that the axis of the element array is tilted toward the direction opposite to the magnetic tape running direction at the start of magnetic tape running. If the axis of the element array is tilted toward the direction opposite to the magnetic tape running direction at the start of magnetic tape running, the element array is not tilted during magnetic tape running so that the axis of the element array is tilted toward the magnetic tape running direction at the start of magnetic tape running. The phase difference (i.e., time difference) ΔT of the reproduction signals of the pair of servo signal reading elements 1 and 2 is measured. Measurement of ΔT can be performed by a measurement unit provided in the magnetic tape device. The configuration of such a measurement unit is known. The distance L between the center of servo signal read element 1 and the center of servo signal read element 2 can be measured using an optical microscope or the like. When the running speed of the magnetic tape is v, the distance in the magnetic tape running direction between the centers of the two servo signal read elements is L sin θ, and the relationship L sin θ = v × ΔT holds. Therefore, the angle θ during magnetic tape running can be calculated using the formula "θ = arcsin(vΔT / L)." Note that the right diagram in Figure 11 shows an example in which the axis of the element array is tilted toward the magnetic tape running direction. In this example, the phase difference (i.e., time difference) ΔT between the phase of the playback signal of servo signal read element 1 and the phase of the playback signal of servo signal read element 2 is measured. When the axis of the element array is tilted in the opposite direction to the running direction of the magnetic tape, θ can be found by the above method, except that ΔT is measured as the phase difference (i.e., time difference) between the phase of the playback signal of servo signal read element 2 and the phase of the playback signal of servo signal read element 1.The measurement pitch of the angle θ, i.e., the measurement interval of the angle θ relative to the tape longitudinal direction, can be selected to be appropriate depending on the frequency of the tape width deformation relative to the tape longitudinal direction. As an example, the measurement pitch can be set to 250 μm.

[0148] <Configuration of Magnetic Tape Device> The magnetic tape device 10 shown in Figure 12 controls a recording / reproducing head unit 12 in response to commands from a control device 11, and records and reproduces data on a magnetic tape MT. The magnetic tape device 10 is configured to detect and adjust the tension applied to the magnetic tape in the longitudinal direction from spindle motors 17A, 17B that control the rotation of the magnetic tape cartridge reel and take-up reel, and their drive devices 18A, 18B. The magnetic tape device 10 is configured to allow a magnetic tape cartridge 13 to be loaded. The magnetic tape device 10 has a cartridge memory read / write device 14 that can read from and write to a cartridge memory 131 in the magnetic tape cartridge 13. A leader pin attached to the magnetic tape MT is pulled out of the magnetic tape cartridge 13 loaded into the magnetic tape device 10 by an automatic loading mechanism or manually. The magnetic tape MT passes over the recording / playback head via guide rollers 15A and 15B with the magnetic layer surface facing the recording / playback head surface of the recording / playback head unit 12, and is then wound onto the take-up reel 16. The rotation and torque of the spindle motors 17A and 17B are controlled by signals from the control device 11, allowing the magnetic tape MT to run at a desired speed and tension. Servo patterns pre-formed on the magnetic tape can be used to control the tape speed and head tilt angle. A tension detection mechanism may be provided between the magnetic tape cartridge 13 and the take-up reel 16 to detect tension. Tension control may be performed using the guide rollers 15A and 15B in addition to control by the spindle motors 17A and 17B. The cartridge memory read / write device 14 is configured to be able to read and write information from the cartridge memory 131 in response to commands from the control device 11. As a communication method between the cartridge memory read / write device 14 and the cartridge memory 131, for example, the ISO (International Organization for Standardization) 14443 method can be adopted.

[0149] The control device 11 includes, for example, a control unit, a storage unit, a communication unit, and the like.

[0150] The recording / playback head unit 12 is composed of, for example, a recording / playback head, a servo tracking actuator that adjusts the position of the recording / playback head in the track width direction, a recording / playback amplifier 19, a connector cable for connecting to the control device 11, etc. The recording / playback head is composed of, for example, a recording element that records data on the magnetic tape, a reproducing element that reproduces the data from the magnetic tape, and a servo signal reading element that reads the servo signals recorded on the magnetic tape. One magnetic head may have, for example, one or more recording elements, one or more reproducing elements, and one or more servo signal reading elements. Alternatively, each element may be provided separately in multiple magnetic heads corresponding to the running direction of the magnetic tape.

[0151] The recording / reproducing head unit 12 is configured to be able to record data onto the magnetic tape MT in response to a command from the control device 11. It is also configured to be able to reproduce data recorded onto the magnetic tape MT in response to a command from the control device 11.

[0152] The control device 11 has a mechanism for determining the running position of the magnetic tape MT from servo signals read from the servo bands and controlling the servo tracking actuator so that the recording element and / or reproducing element is 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 for determining the servo band spacing from servo signals read from two adjacent servo bands as the magnetic tape MT runs. The control device 11 can store the determined servo band spacing information in its internal memory, the cartridge memory 131, an external connected device, etc. The control device 11 can also change the head tilt angle according to dimensional information in the width direction of the running magnetic tape. This allows the effective distance between the servo signal reading elements to approach or match the spacing between the servo bands. The dimensional information can be obtained using servo patterns pre-formed on the magnetic tape. For example, while the magnetic tape is running in the magnetic tape device, the angle θ formed by the axis of the element array with respect to the width direction of the magnetic tape can be changed in accordance with the dimensional information of the magnetic tape in the width direction acquired during running. The head tilt angle can be adjusted, for example, by feedback control. Furthermore, the head tilt angle can also be adjusted, for example, by the method described in JP-A-2016-524774 (Patent Document 1) or US 2019 / 0164573 A1 (Patent Document 2).

[0153] The present invention will be described below based on examples. However, the present invention is not limited to the embodiments shown in the examples. "Parts" and "%" described below represent "parts by mass" and "% by mass", respectively. Furthermore, the steps and evaluations described below were carried out in an environment at a temperature of 23°C ± 1°C unless otherwise specified. "eq" described below is equivalent, and is a unit that cannot be converted to SI units.

[0154] [Abrasive Liquid] Abrasive liquid containing 100.0 parts of an abrasive (alumina powder) shown in Table 1 was mixed with 2,3-dihydroxynaphthalene (manufactured by Tokyo Chemical Industry Co., Ltd.) and SO as a polar group in the amounts shown in Table 1. ３31.3 parts of a 32% solution (solvent: a mixed solvent of methyl ethyl ketone and toluene) of a polyester polyurethane resin having a Na group (UR-4800 (polar group amount: 80 meq / kg) manufactured by Toyobo Co., Ltd.) and 570.0 parts of a 1:1 (mass ratio) mixture of methyl ethyl ketone and cyclohexanone as a solvent were mixed and dispersed using a paint shaker in the presence of zirconia beads (bead diameter: 0.1 mm) for the time shown in Table 1 (bead dispersion time). After dispersion, the dispersion and beads were separated using a mesh, and the resulting dispersion was centrifuged. The centrifugation process was carried out using a Hitachi Koki Co., Ltd. CS150GXL centrifuge (using a rotor manufactured by the same company: S100AT6) at the rotation speed (rpm: rotation per minute) shown in Table 1 for the time shown in Table 1 (centrifugation time). This centrifugation process precipitates particles with relatively large particle sizes, while particles with relatively small particle sizes are dispersed in the supernatant. The supernatant was then recovered by decantation. In the Examples and Comparative Examples described below, this recovered liquid was used as the abrasive liquid. Before being used to prepare the magnetic layer-forming composition, the abrasive liquid was subjected to ultrasonic dispersion treatment for 0.5 minutes using a batch-type ultrasonic device (20 kHz, 300 W).

[0155]

[0156] [Ferromagnetic Powder] In Table 2, "BaFe" is hexagonal barium ferrite powder (coercive force Hc: 196 kA / m, average particle size (average plate diameter): 24 nm).

[0157] In Table 2, "SrFe1" is a hexagonal strontium ferrite powder prepared by the following method: SrCO ３ 1707g, H ３ BO ３ 687g, Fe ２ O ３ 1120 g of Al(OH) ３ 45g, BaCO ３ 24 g, CaCO ３ 13 g, and Nd ２ O ３235 g of the above was weighed and mixed in a mixer to obtain a raw material mixture. The resulting raw material mixture was melted in a platinum crucible at a melting temperature of 1,390 ° C. The melt was stirred while heating the tapping port at the bottom of the platinum crucible, and the melt was tapped into a rod-like shape at approximately 6 g / sec. The tapped liquid was rolled and quenched with a water-cooled twin roller to produce an amorphous material. 280 g of the produced amorphous material was placed in an electric furnace, heated to 635 ° C (crystallization temperature) at a heating rate of 3.5 ° C / min, and held at the same temperature for 5 hours to precipitate (crystallize) hexagonal strontium ferrite particles. Next, the crystallized material obtained above containing hexagonal strontium ferrite particles was coarsely crushed in a mortar, and 1,000 g of zirconia beads with a particle size of 1 mm and 800 ml of a 1% aqueous acetic acid solution were added to the glass bottle containing the material, and the mixture was dispersed for 3 hours using a paint shaker. The resulting dispersion was then separated from the beads and placed in a stainless steel beaker. The dispersion was left to stand at a liquid temperature of 100°C for 3 hours to dissolve the glass component, and then the mixture was precipitated in a centrifuge and washed by repeated decantation, and dried in a heating furnace at a furnace temperature of 110°C for 6 hours to obtain a hexagonal strontium ferrite powder. The hexagonal strontium ferrite powder obtained above had an average particle size of 18 nm and an activation volume of 902 nm. ３ , the anisotropy constant Ku is 2.2 × 10 ５ J / m ３ , mass magnetization σs is 49A・m ２ / kg. 12 mg of sample powder was collected from the hexagonal strontium ferrite powder obtained above, and this sample powder was partially dissolved under the dissolution conditions exemplified above. The obtained filtrate was subjected to elemental analysis using an ICP analyzer to determine the surface content of neodymium atoms. Separately, 12 mg of sample powder was collected from the hexagonal strontium ferrite powder obtained above. This sample powder was completely dissolved under the dissolution conditions exemplified above. The obtained filtrate was subjected to elemental analysis using an ICP analyzer to determine the bulk content of neodymium atoms. The content of neodymium atoms (bulk content) relative to 100 atomic % of iron atoms in the hexagonal strontium ferrite powder obtained above was 2.9 atomic %. The surface content of neodymium atoms was 8.0 atomic %. The ratio of the surface content to the bulk content, "surface content / bulk content," was 2.8, confirming that neodymium atoms were unevenly distributed in the surface layers of the particles. The powder obtained above was confirmed to have a hexagonal ferrite crystal structure by scanning with CuKα radiation at a voltage of 45 kV and an intensity of 40 mA and measuring the X-ray diffraction pattern under the following conditions (X-ray diffraction analysis). The powder obtained above exhibited a magnetoplumbite-type (M-type) hexagonal ferrite crystal structure. The crystalline phase detected by X-ray diffraction analysis was a single magnetoplumbite-type phase. PANalytical X'Pert Pro diffractometer, PIXcel detector. Soller slits for incident beam and diffracted beam: 0.017 radians. Fixed angle of dispersion slit: 1 / 4 degree. Mask: 10 mm. Anti-scatter slit: 1 / 4 degree. Measurement mode: continuous. Measurement time per step: 3 seconds. Measurement speed: 0.017 degrees per second. Measurement step: 0.05 degrees.

[0158] In Table 2, "SrFe2" is a hexagonal strontium ferrite powder prepared by the following method: SrCO ３ 1725g, H ３ BO ３ 666g, Fe ２ O ３ 1332 g of Al(OH) ３ 52 g, CaCO ３ 34 g, BaCO ３141 g of the above was weighed and mixed in a mixer to obtain a raw material mixture. The resulting raw material mixture was melted in a platinum crucible at a melting temperature of 1380 °C. The melt was stirred while heating the tapping port at the bottom of the platinum crucible, and the melt was tapped into a rod-like shape at approximately 6 g / sec. The tapped liquid was rolled and quenched with a water-cooled twin roller to produce an amorphous material. 280 g of the resulting 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 crystallized material obtained above containing hexagonal strontium ferrite particles was coarsely crushed in a mortar, and 1000 g of zirconia beads with a particle size of 1 mm and 800 ml of a 1% acetic acid aqueous solution were added to the glass bottle containing the material, and the mixture was dispersed for 3 hours using a paint shaker. The resulting dispersion was then separated from the beads and placed in a stainless steel beaker. The dispersion was left to stand at a liquid temperature of 100°C for 3 hours to dissolve the glass component, and then the mixture was precipitated in a centrifuge and washed by repeated decantation, and dried in a heating furnace at a furnace temperature of 110°C for 6 hours to obtain a hexagonal strontium ferrite powder. The obtained hexagonal strontium ferrite powder had an average particle size of 19 nm and an activation volume of 1102 nm. ３ , the anisotropy constant Ku is 2.0 × 10 ５ J / m ３ , mass magnetization σs is 50A・m ２ / kg.

[0159] In Table 2, "ε-iron oxide" refers to ε-iron oxide powder prepared by the following method. 8.3 g of iron(III) nitrate nonahydrate, 1.3 g of gallium(III) nitrate octahydrate, 190 mg of cobalt(II) nitrate hexahydrate, 150 mg of titanium(IV) sulfate, and 1.5 g of polyvinylpyrrolidone (PVP) were dissolved in 90 g of pure water. While stirring using a magnetic stirrer, 4.0 g of a 25% aqueous ammonia solution was added in the air at an ambient temperature of 25°C, and the mixture was stirred for 2 hours at an ambient temperature of 25°C. A citric acid solution obtained by dissolving 1 g of citric acid in 9 g of pure water was added to the resulting solution, and the mixture was stirred for 1 hour. The precipitated powder after stirring was collected by centrifugation, washed with pure water, and dried in a heating furnace at an internal temperature of 80°C. 800 g of pure water was added to the dried powder, and the powder was dispersed in water again to obtain a dispersion. The resulting dispersion was heated to 50°C, and 40 g of a 25% aqueous ammonia solution was added dropwise while stirring. After stirring for 1 hour while maintaining the temperature at 50°C, 14 mL of tetraethoxysilane (TEOS) was added dropwise and stirred for 24 hours. 50 g of ammonium sulfate was added to the resulting reaction solution, and the precipitated powder was collected by centrifugation, washed with pure water, and dried for 24 hours in a heating furnace at an internal temperature of 80°C to obtain a ferromagnetic powder precursor. The resulting ferromagnetic powder precursor was loaded into a heating furnace at an internal temperature of 1000°C under atmospheric conditions and subjected to heat treatment for 4 hours. The heat-treated ferromagnetic powder precursor was then added to a 4 mol / L aqueous sodium hydroxide (NaOH) solution, and the liquid temperature was maintained at 70°C while stirring for 24 hours to remove impurities, such as silicate compounds, from the heat-treated ferromagnetic powder precursor. The ferromagnetic powder from which the silicate compounds had been removed was then collected by centrifugation and washed with pure water to obtain a ferromagnetic powder. The composition of the obtained ferromagnetic powder was confirmed by inductively coupled plasma-optical emission spectrometry (ICP-OES), and it was found to be Ga, Co, and Ti substituted ε-iron oxide (ε-Ga ０．２８ Co ０．０５ Ti ０．０５ Fe １．６２ O ３) In addition, X-ray diffraction analysis was performed under the same conditions as those described above for SrFe1, and it was confirmed from the peaks in the X-ray diffraction pattern that the obtained ferromagnetic powder had a single-phase ε-phase crystal structure (ε-iron oxide crystal structure) that did not contain α-phase or γ-phase crystal structures. The average particle size of the obtained ε-iron oxide powder was 12 nm, and the activation volume was 746 nm ３ , the anisotropy constant Ku is 1.2 × 10 ５ J / m ３ , mass magnetization σs is 16A・m ２ / kg.

[0160] The activation volume and anisotropy constant Ku of the hexagonal strontium ferrite powder and ε-iron oxide powder were determined for each ferromagnetic powder by the method described above using a vibrating sample magnetometer (manufactured by Toei Industry Co., Ltd.) The mass magnetization σs was measured at a magnetic field strength of 15 kOe using a vibrating sample magnetometer (manufactured by Toei Industry Co., Ltd.).

[0161] [Non-magnetic Powder for Magnetic Layer] In Table 2, in the examples and comparative examples where the "average plate diameter of non-magnetic powder" and "average plate thickness of non-magnetic powder" are listed in the "Magnetic Layer" column, the magnetic layer was formed using a non-magnetic powder composed of plate-shaped particles with the average plate diameter and average plate thickness values ​​listed in Table 2. These non-magnetic powders were prepared by the method described below. Metal hydroxide and water were mixed in a sealed container (mixing time and molar concentration of the metal hydroxide aqueous solution: see Table 2). The mixed aqueous solution was heated for 10 days in an autoclave with an internal temperature set to 270°C. After heating, the resulting particles were collected by centrifugation. Non-magnetic powders were prepared in this manner. Aluminum hydroxide was used as the metal hydroxide to prepare alumina powder, zirconium hydroxide was used to prepare zirconia powder, and cerium hydroxide was used to prepare ceria powder.

[0162] In Table 2, "CS" listed in the "Type of non-magnetic powder" in the "Magnetic layer" column is an abbreviation for colloidal silica. The colloidal silica particles were spherical or elliptical.

[0163] In Table 2, the "average plate diameter of non-magnetic powder," "average plate thickness of non-magnetic powder," and "average particle size of non-magnetic powder" listed in the "Magnetic layer" column were measured using a Hitachi H-9000 transmission electron microscope and Carl Zeiss KS-400 image analysis software, and were determined as described above.

[0164] [Non-magnetic Support] In Table 2, "PEN" indicates a polyethylene naphthalate support, and "PA" indicates an aromatic polyamide support.

[0165] [Example 1] (1) Formulation of composition for forming magnetic layer (magnetic liquid) Ferromagnetic powder (see Table 2): 100.0 parts SO ３ Na group-containing polyurethane resin: 14.0 parts Weight average molecular weight: 70,000, SO ３ Na group: 0.4 meq / g Cyclohexanone: 150 parts Methyl ethyl ketone: 150 parts (Abrasive liquid) The abrasive liquid prepared by the method described above was used in an amount such that the content of the abrasive contained in the abrasive liquid was 0.8 parts per 100.0 parts of ferromagnetic powder. (Non-magnetic powder) Non-magnetic powder shown in Table 2: 0.2 parts (Other components) Stearic acid: 2.0 parts Butyl stearate: 10.0 parts Polyisocyanate (Coronate, manufactured by Nippon Polyurethane Co., Ltd.): 2.5 parts Cyclohexanone: 200.0 parts Methyl ethyl ketone: 200.0 parts

[0166] (2) Formulation of composition for forming non-magnetic layer α-iron oxide powder (average particle volume: see Table 2): 100.0 parts Carbon black (average particle size: 20 nm, pH: see Table 2): 25.0 parts SO ３ Na group-containing polyurethane resin: 18 parts Weight average molecular weight: 70,000, SO ３ Na group: 0.2 meq / g Stearic acid: 1.0 part Cyclohexanone: 300.0 parts Methyl ethyl ketone: 300.0 parts

[0167] (3) Formulation of composition for forming backcoat layer Carbon black: 100.0 parts Cabot BP-800, average particle size: 17 nm SO ３ Na group-containing polyurethane resin (SO ３Na group: 70eq / ton): 20.0 parts OSO ３ K-group-containing vinyl chloride resin (OSO ３ K group: 70 eq / ton): 30.0 parts Cyclohexanone: 140.0 parts Methyl ethyl ketone: 170.0 parts Butyl stearate: 2.0 parts Stearic acid amide: 0.1 parts

[0168] (4) Preparation of Compositions for Forming Each Layer The above components of the magnetic liquid were dispersed for 24 hours using a batch-type vertical sand mill to prepare a magnetic liquid. Zirconia beads with a bead diameter of 0.5 mm were used as dispersion beads. The magnetic liquid and abrasive liquid were mixed with the above non-magnetic powder and other components, and then dispersed using a batch-type ultrasonic device (20 kHz, 300 W) (dispersion time: see Table 2). The mixture was then filtered using a filter with a pore size of 0.5 μm to prepare a composition for forming a magnetic layer. For the composition for forming a non-magnetic layer, the above components were dispersed for 24 hours using a batch-type vertical sand mill. Zirconia beads with a bead diameter of 0.1 mm were used as dispersion beads. The resulting dispersion was filtered using a filter with a pore size of 0.5 μm to prepare a composition for forming a non-magnetic layer. For the composition for forming a backcoat layer, the above components were kneaded using a continuous kneader and then dispersed using a sand mill. To the resulting dispersion, 40.0 parts of polyisocyanate (Coronate L manufactured by Nippon Polyurethane Industry Co., Ltd.) and 1000.0 parts of methyl ethyl ketone were added, and the mixture was filtered using a filter having a pore size of 1 μm to prepare a composition for forming a backcoat layer.

[0169] (5) Preparation of Magnetic Tape (Data Tape) A magnetic tape was prepared according to the manufacturing process shown in Figure 8. The details are as follows. A non-magnetic support having the thickness and type shown in Table 2 was fed from a feed section, and a coating layer was formed on one surface by applying a non-magnetic layer-forming composition in a first coating section so that the thickness after drying would be 0.7 µm. While the formed coating layer was still wet, it was passed through a cooling zone adjusted to an ambient temperature of 0°C (cooling zone residence time: 1 second) to perform a cooling process, and then passed through a first heat treatment zone with a drying temperature (ambient temperature, the same applies below) of 105°C to perform a heat drying process to form a non-magnetic layer. The magnetic layer-forming composition prepared above was then applied to the non-magnetic layer in a second coating section so that the thickness after drying would be 0.1 µm, forming a coating layer. While this coating layer was still wet, a magnetic field with a strength of 0.5 T was applied perpendicular to the surface of the magnetic layer-forming composition coating layer in an orientation zone, performing a vertical orientation treatment, and then drying in a second heat treatment zone with a drying temperature of 105°C. Thereafter, in a third coating section, the backcoat layer-forming composition prepared above was applied to the surface of the non-magnetic support opposite the surface on which the non-magnetic layer and magnetic layer were formed, to form a coating layer so that the thickness after drying was 0.3 μm, and the formed coating layer was dried in a third heat treatment zone at a drying temperature of 105° C. Thereafter, a calendering treatment (surface smoothing treatment) was carried out using a calendering roll consisting only of a metal roll under the calendering conditions shown in Table 2. Thereafter, a heat treatment was carried out for 36 hours in an environment at an atmospheric temperature of 70° C. After the heat treatment, the tape was slit into ½ inch widths to prepare magnetic tapes. The magnetic layer of the prepared magnetic tape was demagnetized, and then a servo signal was recorded on the magnetic layer using a commercially available servo writer, thereby obtaining a magnetic tape having a data band, a servo band, and a guide band in an arrangement conforming to the LTO (Linear Tape-Open) Ultrium format, and a servo pattern (timing-based servo pattern) on the servo band in an arrangement and shape conforming to the LTO Ultrium format.The servo pattern thus formed conforms to the specifications of JIS (Japanese Industrial Standards) X6175:2006 and Standard ECMA-319 (June 2001). The total number of servo bands is 5, and the total number of data bands is 4. In this way, a magnetic tape (length 960 m) on which servo signals were recorded was produced as a data tape.

[0170] (6) Preparation of magnetic tape with leader pin The magnetic layer side of the data tape prepared above was wound around a leader pin, and the backcoat layer side was held down with a C-shaped clamp, thereby attaching a leader pin directly to one end of the data tape.

[0171] Examples 2 to 26, Comparative Examples 1 to 13 Magnetic tapes with leader pins were obtained by the method described for Example 1, except that the items shown in Table 2 were changed as shown in Table 2. In producing the magnetic tapes of Comparative Examples 1 to 11 and 13, one end of the data tape was joined to the end of the leader tape (width: 1 / 2 inch) using a splice tape (width: 1 / 2 inch) as shown in FIG. 14. The leader tape used was a magnetic tape having a non-magnetic support and a magnetic layer containing ferromagnetic powder, a non-magnetic layer containing non-magnetic powder between the non-magnetic support and the magnetic layer, and a backcoat layer containing non-magnetic powder on the surface of the non-magnetic support opposite the surface with the magnetic layer. The splice tape used was a commercially available adhesive tape having an adhesive layer on the substrate surface. The splice tape was attached to the backcoat layer side of the data tape and leader tape. A leader pin was attached to the end of the leader tape. In the preparation of the magnetic tapes of Examples 17 to 23, for which "Yes" is written in the "Reinforcement with splice tape" column in Table 2, splice tape (width: 1 / 2 inch) was applied to the backcoat layer side of the data tape before attaching the leader pin, as shown in Figure 15. The splice tape used was a commercially available adhesive tape having an acrylic adhesive layer on the surface of a polyester substrate. In Table 2, the thickness of the splice tape used for reinforcement is shown in parentheses in the "Reinforcement with splice tape" column.

[0172] For each example and comparative example, four magnetic tapes were prepared by the above method and used for the following evaluations (1) to (4).

[0173] [Evaluation Method] (1) Spc and Spc Width Direction σ of the Magnetic Layer Surface of a Data Tape The following conditions were used as the AFM measurement conditions, and the Spc and Spc Width Direction σ of the magnetic layer surface of a data tape were determined using the method described above. The AFM data analysis software used was AFM data analysis software (Nanoscope Analysis) provided by BRUKER. An AFM (Bruker's Nanoscope 5) was used in peak force tapping mode to measure an area of ​​40 μm × 40 μm on the surface of the magnetic layer of the data tape. A Bruker's SCANASYST-AIR probe was used, with a resolution of 512 pixels × 512 pixels and a scan speed of 512 seconds per screen (512 pixels × 512 pixels).

[0174] (2) Nonlinear component of tape width deformation For each magnetic tape of the examples and comparative examples, the nonlinear component of tape width deformation caused by storage for 20 days in an environment of a temperature of 60°C and a relative humidity of 20% was measured using the method described above.

[0175] (3) Data Tape Thickness Ten tape samples (5 cm long) were cut from any portion of the data tape of each magnetic tape in the Examples and Comparative Examples, and the thickness of these tape samples was measured by stacking them. The thickness was measured using a digital thickness meter equipped with a MARH Millimar 1240 compact amplifier and a Millimar 1301 inductive probe. The measured thickness was divided by 10 to obtain the value (thickness per tape sample) as the tape thickness. The data tape thickness of each magnetic tape in Examples 1 to 23 and Comparative Examples 1 to 13 was 4.8 μm. The data tape thickness of each magnetic tape in Examples 24 to 26 was as follows: Example 24: 4.7 μm, Example 25: 4.1 μm, Example 26: 3.5 μm. The thickness of the splice tape used as the reinforcing layer shown in Table 2 was determined by the above method using the original splice tape. The thicknesses of the magnetic layer, non-magnetic layer, non-magnetic support, and backcoat layer of each of the magnetic data tapes in the Examples and Comparative Examples were confirmed by cross-sectional observation as described above to be the thicknesses described above or shown in Table 2.

[0176] (4) Recording and Reproduction Performance The recording and reproduction performance of each magnetic tape in the examples and comparative examples was evaluated using the following method. The magnetic head used consisted of a reproduction module including an element array with 10 or more channels of reproduction elements with a reproduction element width of 0.2 μm or less between a pair of servo signal read elements, and a recording module including an element array with 10 or more channels of recording elements with a recording element width of 1.5 times or more the reproduction element width between a pair of servo signal read elements. In the element array, the spacing between two adjacent elements (i.e., two adjacent reproduction elements and two adjacent recording elements) in the head width direction was 40 μm or more. The environment for recording and reproduction of data was a temperature of 20 to 25°C and a relative humidity of 40 to 60%. A magnetic tape device with a magnetic tape and magnetic head attached to a tape transport system (reel tester) was placed in this environment for 24 hours or more, after which data was recorded and reproduced. The recording and reproduction amplifier attached to the tape transport system of the magnetic tape device was the recording and reproduction amplifier described above for measuring the nonlinear component of tape width deformation. During data recording and playback, the previously described servo following and dynamic track position control (change in head tilt angle) were implemented. Data recording and playback were performed in detail as follows. Signals were recorded using the recording element while the magnetic tape was running at a constant speed of 5 m / s. The bit sequence used was a 255-bit pseudo random bit sequence (PRBS) generated according to the generating polynomial x^8 + x^6 + x^5 + x^4 + 1. The symbol "^" indicates exponentiation. The linear recording density was 600 kbpi. The unit "kbpi" is the unit of linear recording density (not convertible to the SI unit system). Shingle recording was performed on three or more tracks so that the difference in (PES1 + PES2) / 2 between adjacent tracks was 1.5 times the playback track width. The magnetization pattern recorded on the magnetic tape is reproduced by the immediately succeeding reproducing element (i.e., the reproducing element with the same channel number), and the signal is amplified by a reproducing amplifier.The playback signal is processed by a phase lock loop (PLL) and an auto gain control (AGC), and then decoded into a bit sequence based on data-dependent noise predictive maximum likelihood (DD-NPML) signal processing. The recorded bit sequence and the playback and decoded bit sequence are compared bit by bit, and if the two are different, a one-bit error is counted as occurring. Data is compared over 10 Mbits, and the cumulative error bit count divided by 10 Mbits is defined as the bit error rate. It was confirmed that the playback signal immediately after recording had a bit error rate of 1 / 1000 or less in all channels. Next, the magnetic tape was stored wound on the reel of the reel tester for 20 days in an environment with a temperature of 60°C and a relative humidity of 20%. After the storage, the magnetic tape was removed from the storage environment and placed in the same magnetic tape device as the one used before storage, where the temperature was 20-25°C and the relative humidity was 40-60% for at least 24 hours. Then, under the same conditions, the data tracks recorded before storage were played back (no recording was performed). Only data tracks with data tracks recorded on both sides were played back. The bit error rate for all channels was calculated, and channels with a bit error rate of 1 / 100 or higher were considered defective. The recording and playback performance was evaluated according to the following criteria: (Evaluation Criteria) A: The ratio of defective channels to the total number of channels was less than 5%. B: The ratio of defective channels to the total number of channels was 5% or more but less than 10%. C: The ratio of defective channels to the total number of channels was 10% or more.

[0177] The results are shown in Table 2 (Table 2-1 to Table 2-11).

[0178]

[0179]

[0180]

[0181]

[0182]

[0183]

[0184]

[0185]

[0186]

[0187]

[0188]

[0189] As shown in Table 2, the magnetic tapes of the Examples exhibited superior recording and playback performance after being stored under an accelerated environment equivalent to long-term storage, compared to the magnetic tapes of the Comparative Examples. These results confirm that the magnetic tapes of the Examples contributed to improving the operational stability of drives (magnetic tape devices).

[0190] A magnetic tape was produced in the same manner as in Example 1, except that no vertical orientation treatment was performed during the production of the data tape. A sample piece was cut out from the data tape portion of the magnetic tape. The vertical squareness ratio of this sample piece was determined using a Tamagawa Seisakusho TM-TRVSM5050-SMSL vibration sample magnetometer by the method described above, and was found to be 0.55. The vertical squareness ratio of the sample piece cut out from the magnetic tape of Example 1 was also determined to be 0.65.

[0191] The two magnetic tapes were each mounted on a 1 / 2-inch reel tester, and the electromagnetic conversion characteristics (SNR: Signal-to-Noise Ratio) were evaluated using the following method. As a result, the magnetic tape of Example 1 achieved an SNR value 4 dB higher than that of the magnetic tape produced without vertical orientation treatment. In an environment with a temperature of 23°C and a relative humidity of 50%, 10 passes of recording and reproduction were performed with a tension of 0.7 N (Newton) applied in the longitudinal direction of the magnetic tape. The relative speed between the magnetic tape and the magnetic head was 6 m / s, and recording was performed using a MIG (Metal-in-gap) head (gap length 0.15 μm, track width 1.0 μm) as the recording head, with the recording current set to the optimum recording current for each magnetic tape. Reproduction was performed using a GMR (Giant-magnetoresistive) head (element thickness 15 nm, shield spacing 0.1 μm, reproduction element width 0.8 μm) as the reproduction head. The head tilt angle was set to 0°. A signal with a linear recording density of 300 kfci was recorded, and the reproduction signal was measured with a spectrum analyzer manufactured by Shibasoku Corporation. The unit kfci is a unit of linear recording density (cannot be converted to SI units). The signal was taken from a portion where the signal had sufficiently stabilized after the magnetic tape started running.

[0192] One aspect of the present invention is useful in various data storage technical fields.

Claims

1. A magnetic tape having a non-magnetic support and a magnetic layer containing ferromagnetic powder, wherein the arithmetic mean peak curvature Spc of the surface of the magnetic layer as defined in ISO 25178 is 0.30 (1 / μm) or more and 0.70 (1 / μm) or less, the standard deviation σ of Spc in the width direction of the surface of the magnetic layer is 0.15 (1 / μm) or less, and a leader pin is attached directly to the end of the data tape.

2. The magnetic tape according to claim 1, wherein the standard deviation σ of Spc is 0.12 (1 / μm) or less.

3. The magnetic tape according to claim 1, wherein said magnetic layer further contains non-magnetic powder having an average tabular diameter of 50 nm or more and 1000 nm or less and an average tabular thickness of 12 nm or less.

4. The magnetic tape of claim 1, wherein said data tape further comprises a non-magnetic layer between said non-magnetic support and said magnetic layer, said non-magnetic layer comprising a non-magnetic powder.

5. The non-magnetic powder of the non-magnetic layer has an average particle volume of 2.0×10 －６ μm ３ 5. The magnetic tape according to claim 4, comprising the following Fe-based inorganic oxide powder:

6. The magnetic tape according to claim 4, wherein the non-magnetic powder in the non-magnetic layer contains carbon black having a pH of 9.0 or less.

7. The magnetic tape according to claim 4, wherein the thickness of said non-magnetic layer is from 0.1 μm to 0.7 μm.

8. The magnetic tape according to claim 1, wherein said data tape further comprises a backcoat layer containing a nonmagnetic powder on the surface of said nonmagnetic support opposite to the surface having said magnetic layer.

9. The magnetic tape of claim 1, wherein said data tape has a tape thickness of 5.2 μm or less.

10. The magnetic tape of claim 1, wherein the data tape has a tape thickness of 5.0 μm or less.

11. The magnetic tape of claim 1, wherein said data tape has a perpendicular squareness ratio of 0.60 or greater.

12. The magnetic tape of claim 1, wherein said data tape has a perpendicular squareness ratio of 0.65 or greater.

13. The magnetic tape according to claim 1, wherein said end of said data tape to which the leader pin is directly attached further comprises a reinforcing layer on at least one of the side facing the magnetic layer and the side opposite to the magnetic layer.

14. The magnetic tape according to claim 13, wherein the reinforcing layer has a thickness of 10.0 μm or more.

15. The magnetic tape of claim 1, wherein said non-magnetic support is an aromatic polyamide support.

16. The standard deviation σ of the Spc is 0.12 (1 / μm) or less, the magnetic layer further contains non-magnetic powder having an average plate diameter of 50 nm or more and 1000 nm or less and an average plate thickness of 12 nm or less, the data tape further has a non-magnetic layer between the non-magnetic support and the magnetic layer, the non-magnetic powder containing non-magnetic powder, and the non-magnetic powder in the non-magnetic layer has an average particle volume of 2.0×10 －６ μm ３ 2. The magnetic tape of claim 1, wherein the data tape comprises an Fe-based inorganic oxide powder as specified below and carbon black having a pH of 9.0 or less, the nonmagnetic layer has a thickness of 0.1 μm or more and 0.7 μm or less, the data tape further has a backcoat layer containing a nonmagnetic powder on a surface side of the nonmagnetic support opposite to the surface side having the magnetic layer, the data tape has a tape thickness of 5.0 μm or less, the data tape has a vertical squareness ratio of 0.65 or more, and the end of the data tape to which a leader pin is directly attached further has a reinforcing layer having a thickness of 10.0 μm or more on at least one of the magnetic layer side and the side opposite to the magnetic layer side.

17. A magnetic tape cartridge comprising a magnetic tape according to any one of claims 1 to 16.

18. A magnetic tape device comprising the magnetic tape according to any one of claims 1 to 16.

19. The magnetic tape device of claim 18, further comprising a magnetic head, the magnetic head having a module including an element array having a plurality of magnetic head elements between a pair of servo signal reading elements, and the magnetic tape device changes an 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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