Magnetic tape, magnetic tape cartridge and magnetic tape device

Abstract

To provide a magnet tape which may contribute to operational stability improvement of a drive during recording and / or reproduction after prolonged storage.SOLUTION: A magnetic tape comprising a non-magnetic support body and a magnetic layer containing ferromagnetic powder, a magnetic tape cartridge comprising the magnetic tape, and a magnetic tape device are provided. In a binarized image of a secondary electronic image obtained by imaging a surface of the magnetic layer using a scanning electron microscope at an acceleration voltage of 5 kV, the number of bright regions with circle-equivalent diameters of 60 nm to less than 120 nm, is 8000 to 30000, inclusive. A standard deviation σ of the number of bright regions in a width direction of the surface of the magnetic layer is 2000 or less.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] Magnetic recording media are available in tape and disk form, and tape-type magnetic recording media, that is, magnetic tape, are primarily used for data storage applications such as data backup and archiving (see, for example, Patent Documents 1 to 3). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-524774 [Patent Document 2] US2019 / 0164573A1 [Patent Document 3] Patent No. 6590102 specification Summary of the Invention [Problem to be solved by the invention]

[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. When reproducing the recorded data, the magnetic tape is run in the magnetic tape device and the magnetic head is moved along the data band of the magnetic tape to read the data recorded on the data band. After such recording or reproduction, the magnetic tape is typically stored wound on a reel inside a magnetic tape cartridge or the like until the next recording and / or reproduction 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 due to storage can cause the magnetic head for recording and / or playback of data to deviate from the target track position (commonly referred to as "off-track"). If off-track causes overwriting of recorded data or playback problems, the operational stability of the drive deteriorates. 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 data storage field, 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. [Means for solving the problem]

[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, In a binarized secondary electron image obtained by imaging the surface of the magnetic layer with a scanning electron microscope at an acceleration voltage of 5 kV, the number of bright regions having a circle equivalent diameter of 60 nm or more and less than 120 nm (hereinafter also simply referred to as "bright regions") is 8,000 or more and 30,000 or less, and A magnetic tape in which the standard deviation σ of the number of bright regions in the width direction of the surface of the magnetic layer (hereinafter also referred to as "width direction σ of the number of bright regions") is 2000 or less. [2] The magnetic tape according to [1], wherein the standard deviation σ of the number of bright areas is 100 or more and 2000 or less. [3] The magnetic tape according to [1] or [2], wherein the standard deviation σ of the number of bright areas is 100 or more and 850 or less. [4] The magnetic tape according to any one of [1] to [3], wherein the squareness ratio in the perpendicular direction of the magnetic tape is 0.60 or more. [5] The magnetic tape according to any one of [1] to [4], further comprising a non-magnetic layer containing non-magnetic powder between the non-magnetic support and the magnetic layer. [6] The magnetic tape according to any one of [1] to [5], further comprising a backcoat layer containing nonmagnetic powder on the surface of the nonmagnetic support opposite to the surface having the magnetic layer. [7] The magnetic tape according to any one of [1] to [6], wherein the tape thickness is 5.2 μm or less. [8] A magnetic tape cartridge including the magnetic tape according to any one of [1] to [7]. [9] A magnetic tape device including the magnetic tape according to any one of [1] to [7].

[10] Further comprising a magnetic head, the magnetic head has a module including an element array having a plurality of magnetic head elements between a pair of servo signal read elements; The magnetic tape device according to [9], wherein the angle θ formed by the axis of the element array with respect to the width direction of the magnetic tape is changed while the magnetic tape is running within the magnetic tape device. [Effects of the Invention]

[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. [Brief explanation of the drawings]

[0009] [Figure 1]An example of a track profile is shown, with the horizontal axis representing the track position and the vertical axis representing the output of the reproduced signal. [Figure 2] 1 shows an example of a graph relating to an initial nonlinear component. [Figure 3] 10 shows an example of a graph regarding the nonlinear component after storage. [Figure 4] 10 is an example of a graph showing the absolute value of the difference between the initial nonlinear component and the nonlinear component after storage for each reproducing element (the difference between the nonlinear component before and after storage). [Figure 5] FIG. 2 is a schematic diagram showing an example of a magnetic head module. [Figure 6] 1 is an explanatory diagram of the relative positional relationship between a module and a magnetic tape while the magnetic tape is running in a magnetic tape device. [Figure 7] FIG. 10 is an explanatory diagram regarding changes in angle θ while the magnetic tape is running. [Figure 8] An example of a manufacturing process for a magnetic tape (schematic diagram) is shown. [Figure 9] 1 shows an example of the arrangement of data bands and servo bands. [Figure 10] An example of servo pattern layout for an LTO (Linear Tape-Open) Ultrium format tape is shown below. [Figure 11] FIG. 10 is an explanatory diagram of a method for measuring an angle θ while a magnetic tape is running. [Figure 12] FIG. 1 is a schematic diagram illustrating an example of a magnetic tape device. DETAILED DESCRIPTION OF THE INVENTION

[0010] [Magnetic tape] One aspect of the present invention relates to a magnetic tape having a non-magnetic support and a magnetic layer containing ferromagnetic powder, wherein a binarized secondary electron image of the surface of the magnetic layer obtained by imaging the surface of the magnetic layer with a scanning electron microscope at an accelerating voltage of 5 kV has a number of bright regions with an equivalent circle diameter of 60 nm to 120 nm of 8,000 to 30,000, and the standard deviation σ of the number of bright regions across the width of the surface of the magnetic layer is 2,000 or less.

[0011] As a result of extensive research, the present inventors have newly discovered that a magnetic tape in which the number of bright regions is within the above-mentioned range and the width direction σ of the number of bright regions is within the above-mentioned range 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. As described above, tape width deformation caused by long-term storage can cause a decrease in the operational stability of the magnetic tape in a drive. In response to this issue, a method has been proposed in recent years for acquiring widthwise dimensional information of a running magnetic tape using a servo signal and varying the angle at which the axial direction of the magnetic head module is tilted relative to the widthwise 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 method for controlling the widthwise dimension of a magnetic tape is acquiring widthwise dimensional information of a running magnetic tape using a servo signal and adjusting the tension applied to the magnetic tape in the longitudinal direction based on the acquired dimensional information (see, for example, paragraph 0171 of Patent Document 3). For example, the above-described dynamic track position control method for controlling the track position of a running magnetic tape can be used to suppress off-track motion. However, in the course of extensive research into further improving the operational stability of drives during recording and / or playback after long-term storage, the inventors 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 explained further below. When dynamic track position control is performed by changing the head tilt angle, the pitch of the magnetic head elements (specifically, the recording element and / or the reproducing element) 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 uniform changes in the 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 unevenly depending on the position, i.e., if the tape width deformation component includes a nonlinear component, it is difficult for the control means to compensate for off-track caused by the nonlinear component. The inventors believed that reducing this nonlinear component could contribute to suppressing deterioration in drive operational stability due to off-track factors that are difficult to compensate for using dynamic track position control means. In this regard, the present inventors believe that the magnetic tape having the number of bright regions within the above range and the standard deviation σ of the number of bright regions within the above range can contribute to suppressing the occurrence of nonlinear components in the tape width deformation, and thus the magnetic tape can contribute to improving the operational stability of the drive during recording and / or playback after long-term storage.

[0012] <Number of bright areas, number of bright areas in width direction σ> In the present invention and this specification, the scanning electron microscope used to determine the number of bright regions having a circle-equivalent diameter of 60 nm or more and less than 120 nm is a field emission scanning electron microscope (FE-SEM). As the FE-SEM, for example, an FE-SEM S4800 manufactured by Hitachi, Ltd. can be used, and this FE-SEM was used in the measurements for the examples and comparative examples described below. Furthermore, when determining the number of bright regions, no coating treatment is performed on the surface of the magnetic layer before taking the SEM image. Imaging is carried out by selecting an unimaged area on the surface of the magnetic layer. The captured SEM image is a secondary electron image. The equivalent circle diameter is calculated in 1 nm increments by rounding off to one decimal place and discarding any decimal places after the first decimal place. In counting the number of bright regions, bright regions only partially included in the binarized image and the remaining portion outside the binarized image are excluded from the measurement.

[0013] In the present invention and this specification, the number of bright areas is determined by the following method. A scanning electron microscope (FE-SEM) is used to capture a secondary electron image of the magnetic layer surface of the magnetic tape to be measured. The imaging conditions are an acceleration voltage of 5 kV, a working distance of 5 mm, and a magnification of 10,000 times. When imaging, an unimaged area of ​​the magnetic layer surface is selected, the focus is adjusted under the above imaging conditions, and a secondary electron image is captured. Portions indicating size, etc. (micron bars, cross marks, etc.) are erased from the captured image, and a secondary electron image with 960 x 1280 pixels is obtained. The width direction is divided into five sections relative to the width of the magnetic tape (therefore, if the width of the magnetic tape is W, the width of each section is "W / 5"), and the above operation is performed 100 times at different randomly selected locations in each section of the magnetic layer surface of the magnetic tape being measured. The secondary electron image thus obtained is imported into image processing software and binarized using the following procedure. The image analysis software can be, for example, the free software ImageJ. The binarization process divides the image into bright areas (white areas) and dark areas (black areas). The thresholds for binarizing the secondary electron image acquired above are set at a lower limit of 210 gradations and an upper limit of 255 gradations, and binarization is performed using these two thresholds. After binarization, noise components are removed using image analysis software. Noise component removal can be performed, for example, by the following method. In the image analysis software ImageJ, the noise cut processing "Despeckle" is selected to remove noise components. The number of bright areas (i.e., white areas) and the area of ​​each bright area are determined for the binarized image obtained in this way using image analysis software. The circle-equivalent diameter of each bright area is then determined from the area of ​​the bright area thus determined. Specifically, the circle-equivalent diameter L is calculated from the determined area A using the formula (A / π)^(1 / 2)×2=L. Here, the symbol "^" represents exponentiation. The above steps are carried out for the binarized images obtained above (100 images for each of the five sections, thus a total of 500 images). In this way, for each of the five sections, the number of bright areas with a circular equivalent diameter of 60 nm or more and less than 120 nm is calculated as the sum of the numbers for the 100 images. The arithmetic mean of the values ​​calculated for the five sections is taken as the number of bright areas with a circular equivalent diameter of 60 nm or more and less than 120 nm on the magnetic tape being measured. The standard deviation σ (i.e., the positive square root of the variance) is calculated for the five values ​​calculated for the above five sections, and this is taken as the width-wise σ of the number of bright areas on the magnetic tape being measured.

[0014] The magnetic layer is typically formed using a magnetic layer-forming composition that contains one or more non-magnetic powders in addition to a ferromagnetic powder. The inventors believe that the number of bright regions and the width direction σ of the number of bright regions determined by the method described above can serve as an indicator of the presence, on the surface of the magnetic layer, of the non-magnetic powder (hereinafter also referred to as "abrasive") contained in the magnetic layer to impart abrasiveness to the surface of the magnetic layer.

[0015] In the magnetic tape, the number of bright areas is 8,000 or more and 30,000 or less from the viewpoint of improving the operational stability of the drive during recording and / or playback after long-term storage. From this viewpoint, the number of bright areas is preferably 10,000 or more, more preferably 12,000 or more, and even more preferably 14,000 or more. Also from this viewpoint, the number of bright areas is preferably 28,000 or less, more preferably 26,000 or less, and even more preferably 24,000 or less.

[0016] From the viewpoint of improving the operational stability of the drive during recording and / or playback after long-term storage, the width direction σ of the number of bright regions is 2000 or less, preferably 1800 or less, more preferably 1500 or less, and further preferably 1300 or less, 1100 or less, 900 or less, 950 or less, and 800 or less in that order. Furthermore, the value of the width direction σ of the number of bright regions can be, for example, 0 or more, 1 or more, 10 or more, 100 or more, 200 or more, 300 or more, or 400 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 the width direction σ of the number of bright regions, the more preferable.

[0017] The number of bright regions and a method for controlling the number of bright regions in the width direction σ will be described later.

[0018] <Nonlinear component of tape width deformation> The inventors believe that the "nonlinear component in the tape width direction resulting from storage for 10 days in an environment at a temperature of 60°C and a relative humidity of 20%," which can be determined by the following method, can serve as an indicator of the nonlinear component of the tape width deformation described above. Note that the storage condition of "storage for 10 days in an environment at a temperature of 60°C and a relative humidity of 20%" is adopted as an example of storage conditions in an accelerated environment equivalent to long-term data storage known as archiving, and the magnetic tape described above is not limited to those stored under such storage conditions. Unless otherwise specified, the following operations and measurements are carried out in an environment with a temperature of 20 to 25°C and a relative humidity of 40 to 60%. The magnetic tape to be measured must be 200m or longer. The magnetic tape to be measured is wound onto a magnetic tape reel with a hub diameter (outer diameter, the same applies below) of 44 mm, with a tension of 0.6 N (Newton) applied to the magnetic tape in the longitudinal direction using a device with a winding mechanism that applies tension to the magnetic tape in the longitudinal direction.The magnetic tape thus wound onto the reel is stored for at least 24 hours in an environment with a temperature of 20 to 25°C and a relative humidity of 40 to 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 called the inner end of the tape, and the other end is called the outer end of the tape. The following measurements are performed in an area within 100 m from the outer end of the tape (hereinafter referred to as the "outer tape area") and an area within 100 m from the inner end of the tape (hereinafter referred to as the "inner tape area"), at the center wrap of each data band. The following measurements were performed using a magnetic head equipped with a reproducing module including an element array with 10 or more channels of reproducing elements with an element width (specifically, reproducing 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 with 10 or more channels of recording elements with an element width (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 reproducing module, the spacing between two adjacent reproducing elements in the head width direction is 83.25 μm. The above spacing is the spacing between the centers of two adjacent reproducing elements in the recording module, and the spacing between the centers of two adjacent recording elements in the reproducing 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 that 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 reproducing module including an element array with 32 channels (0 to 31 channels) of reproducing 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 the 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 (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 moves in the tape width direction. Based on the servo signal from the magnetic tape, the magnetic head can perform servo following to maintain a constant track position while the tape is running. 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. 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 for three consecutive wraps in the same running direction. The unit "kfci" is a unit of linear recording density (cannot be converted to SI units). Shingled recording is performed on three or more tracks so that the difference between (PES1 + PES2) / 2 is 1200 nm. Shingled recording is also called shingled recording. Next, data is reproduced over a 90-meter length from the center wrap of three consecutive wraps in an area within 100 meters of the outer edge of the tape (the outer tape area) and an area within 100 meters of the inner edge of the tape (the inner tape area). The reproduced signal waveforms and servo signal waveforms are acquired and saved using an oscilloscope. For each measurement, the track position of the reproducing element is moved across the tape width by an interval of less than 1 / 30 of the track pitch. The "reproduced signal output" is calculated for each reproducing element from the reproduced signal waveforms 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 plotted on the horizontal axis and reproduced signal output plotted on the vertical axis. Figure 1 shows an example of a track profile created in this way. The median value between two track positions that are 1 dB or more lower than the maximum output of the playback signal 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. The difference between the linear approximation line and the actual measured value is found for each playback element in both the outer and inner tape regions, 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 later), the number of playback elements (channels) is 32 (playback 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 with a winding mechanism that applies tension to the magnetic tape in the longitudinal direction. During this winding, the end of the tape that was the inner peripheral end 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 10 days. After the storage described above, the magnetic tape to be measured was stored wound on a reel in an environment with a temperature of 20-25°C and a relative humidity of 40-60% for at least 24 hours (but up to a maximum of 120 hours). Then, using the magnetic tape device used to measure the initial nonlinear components, the magnetic tape was run back and forth once (forward and reverse) over its entire length. Using the same recording element, reproducing element, magnetic tape device, and reproduction conditions as used in the measurement of the initial nonlinear components, data was reproduced over a length of 90 m 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 output and servo signal waveform were acquired and saved using the same oscilloscope used in the measurement of the initial nonlinear components. The track position of the reproducing element was moved across the tape width for each measurement at the same intervals as used in the measurement of the initial nonlinear components. The "reproduced signal output" for each reproducing element was calculated from the reproduced signal waveforms acquired and saved using the oscilloscope, and the track position was calculated from the servo signal waveforms. From these results, a track profile is created by plotting the track position on the horizontal axis and the playback signal output on the vertical axis. Figure 1 is an example of a track profile created in this way. The median value between two track positions where the playback signal output 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. The difference between the linear approximation line and the actual measured value is found for each playback element for both the outer and inner tape regions, and this is defined as the "nonlinear component after storage." Figure 3 shows an example of a graph of 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 in this way. The maximum value of the absolute value in the outer and inner tape regions is taken 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.

[0019] The nonlinear component of tape width deformation determined for the magnetic tape by the method described above is preferably 100 nm or less, more preferably 95 nm or less, and even more preferably 90 nm or less, 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, in this order, from the viewpoint of improving the operational stability of the drive during recording and / or playback after long-term storage. Having the number of bright regions and the width direction σ of the number of bright regions within the above ranges can contribute to controlling the value of the nonlinear component within the above range. Furthermore, the nonlinear component of 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 tape width deformation, the better.

[0020] <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 relative to the width direction of the magnetic tape while the magnetic tape is running will be described below.

[0021] The magnetic head may have one or more modules, two or more, or three or more, each module including an element array having a plurality of magnetic head elements between a pair of servo signal read elements. The total number of such modules may be, for example, five or less, four or less, or three or less, or the magnetic head may include a number of modules exceeding the total number exemplified here. Examples of arrangements of multiple modules include "recording module-playback module" (total number of modules: 2) and "recording module-playback module-recording module" (total number of modules: 3). However, this is not limited to the examples shown here.

[0022] Each module may include an element array, i.e., an array of elements, having multiple magnetic head elements between a pair of servo signal read elements. A module having a write element as a magnetic head element is a recording module for recording data to magnetic tape. A module having a read element as a magnetic head element is a reproducing module for reproducing data recorded on magnetic tape. In a magnetic head, multiple modules are arranged, for example, in a recording / reproducing head unit, with the axes of the element arrays of each module oriented parallel. This "parallel" does not necessarily mean only parallel in the strict sense, but also includes the range of error normally accepted in the technical field to which the present invention pertains. The range of error may, for example, mean a range of less than ±10° from strict parallelism.

[0023] 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.

[0024] 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.

[0025] 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). A magnetic head element is also called a "channel." "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.

[0026] 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, for example, using an optical microscope.

[0027] 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 read element and the other servo signal read element of the element array (hereinafter also referred to as the "effective distance between servo signal read elements") is "L". On the other hand, when angle θ is greater than 0°, the effective distance between the servo signal read elements is "L cos θ", and L cos θ is smaller than L. That is, "L cos θ" <L」である。

[0028] As described above, if the magnetic head for recording or reproducing data deviates from the target track position due to deformation of the magnetic tape during recording or reproduction, it may result in overwriting of recorded data, poor reproduction, and other problems. For example, if the width of the magnetic tape shrinks or expands, a magnetic head element that should be recording or reproducing data at the target track position may end up recording or reproducing data at a different track position. Furthermore, if the width of the magnetic tape expands, the effective distance between servo signal reading elements may become shorter than the distance between two adjacent servo bands across a data band (also referred to as the "servo band distance" or "servo band distance"; more specifically, the distance between the two servo bands in the width direction of the magnetic tape), which may result in data not being recorded or reproduced near the edge of the magnetic tape. In contrast, when the element array is tilted at an angle θ greater than 0°, the effective distance between the servo signal read elements becomes "Lcosθ," as explained above. The larger the value of θ, the smaller the value of Lcosθ, and the smaller the value of θ, the larger the value of Lcosθ. Therefore, by changing the value of θ according to the degree of dimensional change in the width direction of the magnetic tape (i.e., contraction or expansion), it is possible to make the effective distance between the servo signal read elements approach or match the spacing between the servo bands. This can prevent or reduce the frequency of phenomena such as overwriting of recorded data or playback failures caused by the magnetic head for recording or playing back data shifting from the target track position due to width deformation of the magnetic tape.

[0029] FIG. 7 is an explanatory diagram regarding the change in angle θ while the magnetic tape is running. θ is the angle θ at the start of travel initial can be set to, for example, greater than or equal to 0°. The central diagram in Figure 7 shows the state of the module at the start of driving. In Figure 7, the right figure shows the angle θ as θ initial The larger angle is angle θ cThe effective distance between the servo signal reading elements is L cos θ. c is Lcosθ when the magnetic tape starts running initial It is preferable to perform such angle adjustment when the width of the magnetic tape contracts while the magnetic tape is running. On the other hand, in Figure 7, the left figure shows the angle θ as θ initial The smaller angle θ e The effective distance between the servo signal reading elements is L cos θ. e is Lcosθ when the magnetic tape starts running initial If the width of the magnetic tape expands while the magnetic tape is running, it is preferable to perform such angle adjustment.

[0030] As explained above, changing the head tilt angle while the magnetic tape is running can contribute to preventing phenomena such as overwriting of recorded data or playback failures that occur when the magnetic head for recording or playing back data deviates from the target track position due to width deformation of the magnetic tape during recording or playback, or can contribute to reducing the frequency of such occurrences. 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, it is presumed that the number of bright areas and the width direction σ of the number of bright areas within the above range contribute to 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.

[0031] The magnetic tape will now be described in more detail.

[0032] <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.

[0033] Hexagonal ferrite powder A preferred example of the ferromagnetic powder is hexagonal ferrite powder. For details of the hexagonal ferrite powder, see, for example, JP 2011-225417 A, paragraphs 0012 to 0030, JP 2011-216149 A, paragraphs 0134 to 0136, JP 2012-204726 A, paragraphs 0013 to 0030, and JP 2015-127985 A, paragraphs 0029 to 0084.

[0034] In the present invention and this specification, "hexagonal ferrite powder" refers to a ferromagnetic powder in which a hexagonal ferrite crystal structure is detected as the main phase by X-ray diffraction analysis. The main phase refers to the structure to which the highest diffraction peak belongs in the X-ray diffraction spectrum obtained by X-ray diffraction analysis. For example, if the highest diffraction peak in the X-ray diffraction spectrum obtained by X-ray diffraction analysis is assigned to the hexagonal ferrite crystal structure, it is determined that the hexagonal ferrite crystal structure has been detected as the main phase. If only a single structure is detected by X-ray diffraction analysis, this detected structure is considered to be the main phase. The hexagonal ferrite crystal structure contains at least iron atoms, divalent metal atoms, and oxygen atoms as constituent atoms. Divalent metal atoms are metal atoms that can become divalent cations as ions, and examples of such atoms include alkaline earth metal atoms such as strontium atoms, barium atoms, and calcium atoms, and lead atoms. In the present invention and this specification, "hexagonal strontium ferrite powder" refers to a powder in which the main divalent metal atom contained therein is strontium atom, and "hexagonal barium ferrite powder" refers to a powder in which the main divalent metal atom contained therein is barium atom. "Main divalent metal atom" refers to the divalent metal atom that is the most abundant, on an atomic % basis, among the divalent metal atoms contained in the powder. However, rare earth atoms are not included in the above divalent metal atoms. In the present invention and this specification, "rare earth atom" refers to a powder selected from the group consisting of scandium atom (Sc), yttrium atom (Y), and lanthanoid atom. The lanthanoid atom is selected from the group consisting of lanthanum atom (La), cerium atom (Ce), praseodymium atom (Pr), neodymium atom (Nd), promethium atom (Pm), samarium atom (Sm), europium atom (Eu), gadolinium atom (Gd), terbium atom (Tb), dysprosium atom (Dy), holmium atom (Ho), erbium atom (Er), thulium atom (Tm), ytterbium atom (Yb), and lutetium atom (Lu).

[0035] Hereinafter, hexagonal strontium ferrite powder, which is one form of hexagonal ferrite powder, will be described in more detail.

[0036] The activation volume of the hexagonal strontium ferrite powder is preferably 800 to 1600 nm 3 The microparticulated hexagonal strontium ferrite powder exhibiting an activation volume in the above range is suitable for producing a magnetic tape that exhibits excellent electromagnetic conversion characteristics. The activation volume of the hexagonal strontium ferrite powder is preferably 800 nm 3 or more, for example, 850 nm 3 From the viewpoint of further improving the electromagnetic conversion characteristics, the activation volume of the hexagonal strontium ferrite powder can be 1500 nm or more. 3 More preferably, it is 1400 nm or less. 3 More preferably, it is 1300 nm or less. 3 More preferably, it is 1200 nm or less. 3 It is even more preferable that the value is equal to or less than 1100 nm. 3 It is even more preferable that the activation volume of the hexagonal barium ferrite powder is equal to or less than 10 ...

[0037] "Activation volume" is a unit of magnetization reversal and is an index showing the magnetic size of a particle. The activation volume described in this invention and this specification and the anisotropy constant Ku described below are values ​​obtained by measuring the coercive force Hc using a vibrating sample magnetometer at magnetic field sweep speeds 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 is. Hc=2Ku / Ms{1-[(kT / KuV)ln(At / 0.693)] 1 / 2} [In the above formula, Ku: anisotropy constant (unit: J / m 3 ), Ms: saturation magnetization (unit: kA / m), k: Boltzmann constant, T: absolute temperature (unit: K), V: activation volume (unit: cm 3 ), A: spin precession frequency (unit: s -1 ), t: magnetic field reversal time (unit: s)]

[0038] The anisotropy constant Ku can be used as an index for reducing thermal fluctuation, in other words, improving thermal stability. The hexagonal strontium ferrite powder preferably has an anisotropy constant of 1.8×10 5 J / m 3 and more preferably 2.0×10 5 J / m 3 The Ku of the hexagonal strontium ferrite powder can be, for example, 2.5×10 5 J / m 3 However, since a higher Ku value means higher thermal stability and is therefore preferred, the Ku value is not limited to the above-mentioned values.

[0039] The hexagonal strontium ferrite powder may or may not contain rare earth atoms. When the hexagonal strontium ferrite powder contains rare earth atoms, it is preferable that the rare earth atoms are contained at a content (bulk content) of 0.5 to 5.0 atomic % relative to 100 atomic % of iron atoms. In one embodiment, the hexagonal strontium ferrite powder containing rare earth atoms can have rare earth atoms unevenly distributed in the surface layer portion. In the present invention and this specification, the term "surface layer distribution of rare earth atoms" refers to the ratio of the rare earth atom content relative to 100 atomic % of iron atoms in a solution obtained by partially dissolving a hexagonal strontium ferrite powder in an acid (hereinafter referred to as "surface layer content of rare earth atoms" or simply "surface layer content" with respect to rare earth atoms) to the ratio of the rare earth atom content relative to 100 atomic % of iron atoms in a solution obtained by completely dissolving a hexagonal strontium ferrite powder in an acid (hereinafter referred to as "bulk content of rare earth atoms" or simply "bulk content" with respect to rare earth atoms), Rare earth atom surface content / rare earth atom bulk content > 1.0 This means that the ratio of "surface rare earth atom content / bulk rare earth atom content > 1.0" is satisfied. The rare earth atom content of the hexagonal strontium ferrite powder described below is synonymous with the rare earth atom bulk content. In contrast, partial dissolution using an acid dissolves the surface layer of the particles constituting the hexagonal strontium ferrite powder, so the rare earth atom content in the solution obtained by partial dissolution is the rare earth atom content in the surface layer of the particles constituting the hexagonal strontium ferrite powder. When the surface rare earth atom content satisfies the ratio "surface rare earth atom content / bulk rare earth atom content > 1.0", this means that the rare earth atoms are unevenly distributed in the surface layer of the particles constituting the hexagonal strontium ferrite powder (i.e., present in greater amounts in the surface layer than in the interior). In the present invention and this specification, the surface layer refers to a partial region extending from the surface toward the interior of the particles constituting the hexagonal strontium ferrite powder.

[0040] When the hexagonal strontium ferrite powder contains rare earth atoms, the rare earth atom content (bulk content) is preferably in the range of 0.5 to 5.0 atomic percent relative to 100 atomic percent of iron atoms. Having rare earth atoms in the above-mentioned bulk content range and having the rare earth atoms unevenly distributed in the surface layers of the particles constituting the hexagonal strontium ferrite powder is thought to contribute to suppressing a decrease in playback output during repeated playback. This is presumably because the hexagonal strontium ferrite powder contains rare earth atoms in the above-mentioned bulk content range and having the rare earth atoms unevenly distributed in the surface layers of the particles constituting the hexagonal strontium ferrite powder can increase the anisotropy constant Ku. The higher the anisotropy constant Ku, the more the occurrence of a phenomenon known as thermal fluctuation can be suppressed (in other words, thermal stability can be improved). By suppressing the occurrence of thermal fluctuation, the decrease in playback output during repeated playback can be suppressed. It is speculated that the uneven distribution of rare earth atoms in the surface layer of hexagonal strontium ferrite powder particles contributes to stabilizing the spin of the iron (Fe) sites in the crystal lattice in the surface layer, thereby increasing the anisotropy constant Ku. Furthermore, it is believed that using a hexagonal strontium ferrite powder having rare earth atoms unevenly distributed in the surface layer as the ferromagnetic powder for the magnetic layer also contributes to preventing the magnetic layer surface from being worn away by friction with the magnetic head. That is, it is believed that a hexagonal strontium ferrite powder having rare earth atoms unevenly distributed in the surface layer can also contribute to improving the running durability of magnetic tapes. This is believed to be because the uneven distribution of rare earth atoms on the surfaces of the particles that make up the hexagonal strontium ferrite powder contributes to improving the interaction between the particle surfaces and organic substances (e.g., binders and / or additives) contained in the magnetic layer, thereby improving the strength of the magnetic layer. From the viewpoint of further suppressing a decrease in reproduction output during repeated reproduction and / or further improving running durability, the rare earth atom content (bulk content) is more preferably in the range of 0.5 to 4.5 atomic %, even more preferably in the range of 1.0 to 4.5 atomic %, and even more preferably in the range of 1.5 to 4.5 atomic %.

[0041] The bulk content is the content determined by completely dissolving the hexagonal strontium ferrite powder. In the present invention and this specification, unless otherwise specified, the content of an atom refers to the bulk content determined by completely dissolving the hexagonal strontium ferrite powder. The hexagonal strontium ferrite powder containing rare earth atoms may contain only one rare earth atom or two or more rare earth atoms. When two or more rare earth atoms are contained, the bulk content is determined for the total of the two or more rare earth atoms. This also applies to other components in the present invention and this specification. That is, unless otherwise specified, a certain component may be used alone or in combination with two or more. When two or more components are used, the content or content refers to the total of the two or more components.

[0042] When the hexagonal strontium ferrite powder contains rare earth atoms, the rare earth atoms may be any one or more of rare earth atoms. From the viewpoint of further suppressing the decrease in playback output during repeated playback, preferred rare earth atoms include neodymium atoms, samarium atoms, yttrium atoms, and dysprosium atoms, with neodymium atoms, samarium atoms, and yttrium atoms being more preferred, and neodymium atoms being even more preferred.

[0043] In a hexagonal strontium ferrite powder having rare earth atoms unevenly distributed in the surface layer, the rare earth atoms need only be unevenly distributed in the surface layer of the particles constituting the hexagonal strontium ferrite powder, and the degree of uneven distribution is not limited. For example, for a hexagonal strontium ferrite powder having rare earth atoms unevenly distributed in the surface layer, the ratio of the surface content of rare earth atoms determined by partial dissolution under the dissolution conditions described below to the bulk content of rare earth atoms determined by complete dissolution under the dissolution conditions described below, i.e., "surface content / bulk content," is greater than 1.0 and can be 1.5 or greater. A "surface content / bulk content" ratio greater than 1.0 means that the rare earth atoms are unevenly distributed in the surface layer (i.e., present in greater amounts than in the interior) in the particles constituting the hexagonal strontium ferrite powder. Furthermore, the ratio of the surface content of rare earth atoms determined by partial dissolution under the dissolution conditions described below to the bulk content of rare earth atoms determined by complete dissolution under the dissolution conditions described below, i.e., "surface content / bulk content," can be, for example, 10.0 or less, 9.0 or less, 8.0 or less, 7.0 or less, 6.0 or less, 5.0 or less, or 4.0 or less. However, in a hexagonal strontium ferrite powder having rare earth atoms unevenly distributed in the surface layers, it is sufficient that the rare earth atoms are unevenly distributed in the surface layers of the particles constituting the hexagonal strontium ferrite powder, and the above "surface content / bulk content" is not limited to the exemplified upper or lower limits.

[0044] The partial and total dissolution of hexagonal strontium ferrite powder is described below. For hexagonal strontium ferrite powder present as a powder, sample powders to be partially and completely dissolved are collected from the same powder lot. On the other hand, for hexagonal strontium ferrite powder contained in the magnetic layer of a magnetic tape, a portion of the hexagonal strontium ferrite powder removed from the magnetic layer is subjected to partial dissolution, and another portion is subjected to total dissolution. The hexagonal strontium ferrite powder can be removed from the magnetic layer by, for example, the method described in paragraph 0032 of JP 2015-91747 A. The term "partial dissolution" as used herein refers to dissolving the hexagonal strontium ferrite powder to such an extent that the remaining hexagonal strontium ferrite powder can be visually confirmed in the liquid at the end of dissolution. For example, partial dissolution can dissolve 10 to 20 mass% of the particles constituting the hexagonal strontium ferrite powder, with the total particles being 100 mass%. On the other hand, the term "complete dissolution" as used herein refers to dissolving the hexagonal strontium ferrite powder to such an extent that the remaining hexagonal strontium ferrite powder cannot be visually confirmed in the liquid at the end of dissolution. The partial dissolution and measurement of the surface layer content are carried out, for example, by the following method. Note that 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 is performed using an inductively coupled plasma (ICP) analyzer. This allows the surface content of rare earth atoms relative to 100 atomic percent iron atoms to be determined. If multiple types of rare earth atoms are detected by elemental analysis, the total content of all rare earth atoms is taken as the surface content. This also applies to measurements of bulk content. On the other hand, the total dissolved and bulk contents are measured, for example, by the following method. A container (e.g., a beaker) containing 12 mg of sample powder and 10 mL of 4 mol / L hydrochloric acid is placed on a hot plate set at 80°C for 3 hours. After that, the bulk content relative to 100 atomic % of iron atoms can be determined by carrying out the same procedures as for the partial dissolution and surface layer content measurements described above.

[0045] From the viewpoint of increasing the reproduction output when reproducing data recorded on magnetic tape, it is desirable that the mass magnetization σs of the ferromagnetic powder contained in the magnetic tape is high. In this regard, hexagonal strontium ferrite powder that contains rare earth atoms but does not have the rare earth atoms unevenly distributed in the surface layer tends to have a significantly lower σs than hexagonal strontium ferrite powder that does not contain rare earth atoms. On the other hand, hexagonal strontium ferrite powder that has the rare earth atoms unevenly distributed in the surface layer is considered preferable in order to suppress such a large decrease in σs. In one embodiment, the σs of the hexagonal strontium ferrite powder is 45 A·m 2 / kg or more, and 47A m 2 / kg or more. On the other hand, from the viewpoint of noise reduction, σs is 80A·m 2 / kg or less is preferable, and 60A·m 2 / kg or less is more preferable. σs can be measured using a known measuring device capable of measuring magnetic properties, such as a vibrating sample magnetometer. In the present invention and this specification, unless otherwise specified, the mass magnetization σs is a value measured at a magnetic field strength of 15 kOe. 1 [kOe] = 10 6 / 4π[A / m].

[0046] Regarding the content (bulk content) of constituent atoms of the hexagonal strontium ferrite powder, the strontium atom content can be, for example, in the range of 2.0 to 15.0 atomic % relative to 100 atomic % of iron atoms. In one embodiment, the hexagonal strontium ferrite powder can contain only strontium atoms as divalent metal atoms. In another embodiment, the hexagonal strontium ferrite powder can contain one or more other divalent metal atoms in addition to strontium atoms. For example, barium atoms and / or calcium atoms can be contained. When divalent metal atoms other than strontium atoms are contained, the barium atom content and calcium atom content in the hexagonal strontium ferrite powder can each be, for example, in the range of 0.05 to 5.0 atomic % relative to 100 atomic % of iron atoms.

[0047] Known crystal structures of hexagonal ferrite include magnetoplumbite type (also called "M type"), W type, Y type, and Z type. The hexagonal strontium ferrite powder may have any of these crystal structures. The crystal structure can be confirmed by X-ray diffraction analysis. The hexagonal strontium ferrite powder may be one in which a single crystal structure or two or more types of crystal structures are detected by X-ray diffraction analysis. For example, in one embodiment, the hexagonal strontium ferrite powder may be one in which only the M-type crystal structure is detected by X-ray diffraction analysis. For example, the M-type hexagonal ferrite is AFe 12 O 19The composition formula is represented by the formula: where A represents a divalent metal atom. When the hexagonal strontium ferrite powder is of M type, A is only strontium atom (Sr). Alternatively, when A contains multiple divalent metal atoms, strontium atom (Sr) accounts for the largest proportion on an atomic % basis, as described above. The divalent metal atom content of the hexagonal strontium ferrite powder is usually determined by the type of crystalline structure of the hexagonal ferrite and is not particularly limited. The same applies to the iron atom content and oxygen atom content. The hexagonal strontium ferrite powder contains at least iron atoms, strontium atoms, and oxygen atoms, and may further contain rare earth atoms. Furthermore, the hexagonal strontium ferrite powder may or may not contain atoms other than these atoms. As an example, the hexagonal strontium ferrite powder may contain aluminum atoms (Al). The content of aluminum atoms can be, for example, 0.5 to 10.0 atomic % relative to 100 atomic % of iron atoms. From the viewpoint of 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 0 to 5.0 atomic %, relative to 100 atomic % of iron atoms, and may even be 0 atomic %. That is, in one embodiment, the hexagonal strontium ferrite powder may contain no atoms other than iron atoms, strontium atoms, oxygen atoms, and rare earth atoms. The content expressed in atomic % above is determined by converting the content (unit: mass %) of each atom obtained by completely dissolving the hexagonal strontium ferrite powder into a value expressed in atomic % using the atomic weight of each atom. Furthermore, in the present invention and this specification, "not containing" a certain atom means that the content is 0 mass % when completely dissolved and measured by an ICP analyzer. The detection limit of an ICP analyzer is usually 0.01 ppm (parts per million) or less by mass. The above term "free from" is used to mean that the substance is contained in an amount below the detection limit of the ICP analyzer.In one form, the hexagonal strontium ferrite powder can be one that does not contain bismuth atoms (Bi).

[0048] metal powder A preferred example of the ferromagnetic powder is ferromagnetic metal powder. For details of the ferromagnetic metal powder, see, for example, paragraphs 0137 to 0141 of JP-A No. 2011-216149 and paragraphs 0009 to 0023 of JP-A No. 2005-251351.

[0049] ε-iron oxide powder A preferred example of the ferromagnetic powder is ε-iron oxide powder. In the present invention and this specification, the term "ε-iron oxide powder" refers to a ferromagnetic powder in which an ε-iron oxide crystalline structure is detected as the main phase by X-ray diffraction analysis. For example, if the highest intensity diffraction peak in an X-ray diffraction spectrum obtained by X-ray diffraction analysis is assigned to the ε-iron oxide crystalline structure, it is determined that the ε-iron oxide crystalline structure is detected as the main phase. Known methods for producing ε-iron oxide powder include a method using goethite and a reverse micelle method. All of these production methods are publicly known. For a method for producing ε-iron oxide powder in which part of the Fe atoms are replaced by atoms such as Ga, Co, Ti, Al, or Rh, see, for example, J. Jpn. Soc. Powder Metallurgy, Vol. 61, Supplement, No. S1, pp. S280-S284 and J. Mater. Chem. C, 2013, 1, pp. 5200-5206. However, the method for producing the ε-iron oxide powder that can be used as the ferromagnetic powder in the magnetic layer of the magnetic tape is not limited to the method given here.

[0050] The activation volume of the ε-iron oxide powder is preferably 300 to 1500 nm 3 The finely divided ε-iron oxide powder exhibiting an activation volume in the above range is suitable for producing a magnetic tape that exhibits excellent electromagnetic conversion characteristics. The activation volume of the ε-iron oxide powder is preferably 300 nm 3 For example, 500 nm or more3 From the viewpoint of further improving the electromagnetic conversion characteristics, the activation volume of the ε-iron oxide powder can be 1400 nm or more. 3 More preferably, it is 1300 nm or less. 3 More preferably, it is 1200 nm or less. 3 More preferably, it is 1100 nm or less. 3 It is even more preferred that:

[0051] The anisotropy constant Ku can be used as an index of the reduction in thermal fluctuation, in other words, the improvement in thermal stability. The ε-iron oxide powder is preferably 3.0×10 4 J / m 3 and more preferably 8.0×10 4 J / m 3 The Ku of the ε-iron oxide powder can be, for example, 3.0×10 5 J / m 3 However, since a higher Ku value means higher thermal stability and is therefore preferred, the Ku value is not limited to the above-mentioned values.

[0052] From the viewpoint of increasing the reproduction output when reproducing data recorded on a magnetic tape, it is desirable that the mass magnetization σs of the ferromagnetic powder contained in the magnetic tape is high. In this regard, in one embodiment, the σs of the ε-iron oxide powder is 8 A m 2 / kg or more, and 12 A m 2 On the other hand, the σs of ε-iron oxide powder can be 40 A m 2 / kg or less, and 35A·m 2 / kg or less is more preferable.

[0053] In the present invention and this specification, unless otherwise specified, the average particle size of various powders such as ferromagnetic powders is a value measured by the following method using a transmission electron microscope. The powder is photographed using a transmission electron microscope at a magnification of 100,000x, and then printed on photographic paper at a total magnification of 500,000x to obtain a photograph of the particles that make up the powder. From the obtained particle photograph, the target particle is selected, and the particle outline is traced with a digitizer to measure the particle (primary particle) size. Primary particles are independent particles that are not aggregated. The above measurements are performed on 500 randomly selected particles. The arithmetic mean of the particle sizes of the 500 particles thus obtained is the average particle size of the powder. The transmission electron microscope may be, for example, a Hitachi H-9000 transmission electron microscope. Furthermore, particle size measurements can be performed using known image analysis software, such as Carl Zeiss KS-400 image analysis software. Unless otherwise specified, the average particle sizes shown in the examples below are values ​​measured using a Hitachi H-9000 transmission electron microscope and Carl Zeiss KS-400 image analysis software. In this invention and this specification, "powder" refers to a collection of multiple particles. For example, "ferromagnetic powder" refers to a collection of multiple ferromagnetic particles. Furthermore, a collection of multiple particles is not limited to a configuration in which the particles constituting the collection are in direct contact with each other, but also includes a configuration in which binders, additives, etc., as described below, are interposed between the particles. The term "particle" is sometimes used to refer to powder.

[0054] As a method for collecting sample powder from the magnetic tape for particle size measurement, for example, the method described in paragraph 0015 of JP-A No. 2011-048878 can be used.

[0055] In the present invention and this specification, unless otherwise specified, the size of particles constituting the powder (particle size) is determined by the shape of the particles observed in the particle photograph. (1) In the case of needle-shaped, spindle-shaped, columnar (where the height is greater than the maximum diameter of the base), etc., the particle size is expressed by the length of the major axis that constitutes the particle, i.e., the major axis length. (2) In the case of a plate or columnar shape (where the thickness or height is smaller than the maximum major axis of the plate surface or base), it is expressed by the maximum major axis of the plate surface or base, (3) When the particle is spherical, polyhedral, irregular, etc., and the long axis of the particle cannot be identified from its shape, it is expressed as the equivalent circle diameter, which is determined by the circle projection method.

[0056] The average acicular ratio of a powder refers to the arithmetic average of the minor axis length of the particles measured in the above measurement, i.e., the minor axis length, the value of (major axis length / minor axis length) for each particle, and the values ​​obtained for the above 500 particles. Here, unless otherwise specified, the minor axis length refers to the length of the minor axis constituting the particle in the above definition of particle size (1), and in the same case (2), the thickness or height, respectively. In the case of (3), since there is no distinction between the major axis and the minor axis, (major axis length / minor axis length) is considered to be 1 for convenience. Unless otherwise specified, when the particle shape is specific, for example, in the case of the above definition of particle size (1), the average particle size is the average major axis length, in the case of definition (2), the average particle size is the average plate diameter, and in the case of definition (3), the average particle size is the average diameter (also called the average particle diameter or average particle size).

[0057] 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.

[0058] (binder) The magnetic tape may be a coated magnetic tape, and the magnetic layer may contain a binder. The binder is one or more resins. Various resins commonly used as binders for coated magnetic tapes can be used. For example, the binder may be selected from polyurethane resin, polyester resin, polyamide resin, vinyl chloride resin, acrylic resin copolymerized with styrene, acrylonitrile, methyl methacrylate, etc., cellulose resin such as nitrocellulose, epoxy resin, phenoxy resin, polyvinyl acetal, polyvinyl butyral, etc., and may be used alone or in combination. Among these, polyurethane resin, acrylic resin, cellulose resin, and vinyl chloride resin are preferred. These resins may be homopolymers or copolymers. These resins may also be used as binders in the nonmagnetic layer and / or backcoat layer, which will be described later. For details of the binders described 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 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.

[0059] (hardening agent) A curing agent can also be used together with a resin usable as a binder. In one form, the curing agent can be a thermosetting compound, which undergoes a curing reaction (crosslinking reaction) upon heating. In another form, the curing agent can be a photocurable compound, which undergoes a curing reaction (crosslinking reaction) upon irradiation with light. As the curing reaction progresses during the magnetic layer-forming process, at least a portion of the curing agent can be included in the magnetic layer in a state of reaction (crosslinking) with other components, such as the binder. This also applies to layers formed using compositions containing a curing agent when the composition used to form other layers contains the curing agent. A preferred curing agent is a thermosetting compound, and polyisocyanate is suitable. For details about polyisocyanates, see paragraphs 0124-0125 of JP 2011-216149 A. The curing agent can be used in the magnetic layer-forming composition in an amount of, for example, 0 to 80 parts by weight per 100 parts by weight of the binder. From the perspective of improving the strength of the magnetic layer, 50 to 80 parts by weight is preferred.

[0060] (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 mentioned above. Examples of additives contained in the magnetic layer include non-magnetic powders (e.g., inorganic powders, carbon black, etc.), 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 on dispersants, see paragraphs 0061 and 0071 of JP 2012-133837 A. Compounds having polyalkyleneimine chains and vinyl polymer chains can function as dispersants to improve the dispersibility of ferromagnetic powders. Furthermore, the above compounds can also contribute to reducing the widthwise σ value of the number of bright regions. For details on compounds having polyalkyleneimine chains and vinyl polymer chains, see paragraphs 0024 to 0064 of JP 2019-169225 A and the Examples therein. The above compounds are preferably contained in the magnetic layer in an amount of 0.5 parts by weight or more per 100.0 parts by weight of ferromagnetic powder, more preferably 1.0 parts by weight or more, even more preferably 3.0 parts by weight or more, even more preferably 5.0 parts by weight or more, and even more preferably 10.0 parts by weight or more. The content of the above compounds in the magnetic layer is preferably 25.0 parts by weight or less per 100.0 parts by weight of ferromagnetic powder. One or more dispersants such as the above compounds may be added to the nonmagnetic layer-forming composition. See paragraph 0061 of JP2012-133837A for information on dispersants that can be added to the nonmagnetic layer-forming composition.Non-magnetic powders that can be contained in the magnetic layer include non-magnetic powders that can function as abrasives, and non-magnetic powders (e.g., non-magnetic colloidal particles) that can function as protrusion-forming agents that form moderately protruding protrusions on the surface of the magnetic layer. For abrasives, see paragraphs 0030 to 0032 of JP 2004-273070 A. For abrasives, see the description below. Colloidal particles are preferred as protrusion-forming agents, and inorganic colloidal particles are preferred from the standpoint of availability, inorganic oxide colloidal particles are more preferred, and silica colloidal particles (colloidal silica) are even more preferred. The average particle size of the abrasive and protrusion-forming agent is preferably in the range of 30 to 200 nm, and more preferably in the range of 50 to 100 nm.

[0061] The number of bright areas described above is thought to be an indicator of the state of the abrasive on the magnetic layer surface. Therefore, the number of bright areas can be controlled by the type of non-magnetic powder added as the abrasive, the method of preparing the abrasive liquid, and other factors. A non-magnetic powder with a Mohs hardness of greater than 8 is preferred as the abrasive, with a Mohs hardness of 9 or higher being more preferred. The maximum Mohs hardness is 10. The abrasive can be a powder of an inorganic substance or an organic substance. The abrasive can be a powder of an inorganic or organic oxide or carbide. Examples of carbides include boron carbide (e.g., B4C) and titanium carbide (e.g., TiC). Diamond can also be used as the abrasive. In one form, the abrasive is preferably an inorganic oxide powder. Specifically, inorganic oxides include alumina (e.g., Al2O3), titanium oxide (e.g., TiO2), cerium oxide (e.g., CeO2), and zirconium oxide (e.g., ZrO2), with alumina being preferred. Alumina has a Mohs hardness of approximately 9. Regarding alumina powder, see paragraph 0021 of JP 2013-229090 A. The content of the abrasive in the magnetic layer is preferably 1.0 to 20.0 parts by mass, and more preferably 1.0 to 15.0 parts by mass, per 100.0 parts by mass of 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 also 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 powder. The same applies to the content 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 protrusion-forming agent (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").

[0062] 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.

[0063] A preferred embodiment of the aromatic hydrocarbon compound having a phenolic hydroxy group is a compound represented by the following formula 100.

[0064] [ka] [In formula 100, X 101 ~X 108 Two of the groups are hydroxy groups, and the other six groups each independently represent a hydrogen atom or a substituent.

[0065] In the compound represented by formula 100, the substitution positions of the two hydroxy groups (phenolic hydroxy groups) are not particularly limited.

[0066] The compound of formula 100 is X 101 ~X 108Two of the X's are hydroxy groups (phenolic hydroxy groups), and the other six each independently represent a hydrogen atom or a substituent. 101 ~X 108 In the above, all the moieties other than the two hydroxyl groups may be hydrogen atoms, or some or all may be substituents. Examples of the substituents include the substituents described above. One or more phenolic hydroxyl groups may be included as the substituents other than the two hydroxyl groups. From the viewpoint of improving the dispersibility of the abrasive, X 101 ~X 108 Preferably, the two hydroxy groups other than the two hydroxy groups are not phenolic hydroxy groups. That is, the compound represented by formula 100 is preferably dihydroxynaphthalene or a derivative thereof, more preferably 2,3-dihydroxynaphthalene or a derivative thereof. 101 ~X 108 Preferred examples of the substituent represented by the formula (I) include a halogen atom (for example, a chlorine atom or a bromine atom), an amino group, an alkyl group having 1 to 6 carbon atoms (preferably 1 to 4 carbon atoms), a methoxy group, an ethoxy group, an acyl group, a nitro group, a nitroso group, and a —CHOH group.

[0067] Furthermore, for dispersants for improving the dispersibility of abrasives, reference can also be made to paragraphs 0024 to 0028 of JP 2014-179149 A.

[0068] A dispersant for improving the dispersibility of an abrasive can be used, for example, when preparing an abrasive liquid, in a proportion of, for example, 0.5 to 20.0 parts by mass per 100.0 parts by mass of the abrasive, and is preferably used in a proportion of 1.0 to 10.0 parts by mass.

[0069] The magnetic layer described above can be provided directly on the surface of the non-magnetic support, or indirectly via a non-magnetic layer.

[0070] <Nonmagnetic layer> Next, the nonmagnetic layer will be described. The magnetic tape may have a magnetic layer directly on the surface of a nonmagnetic support, or may have a magnetic layer on the surface of a nonmagnetic support via a nonmagnetic layer containing nonmagnetic powder. The nonmagnetic powder used in the nonmagnetic layer may be an inorganic or organic powder. Carbon black, etc., can also be used. Examples of inorganic powders include powders of 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 information on carbon black that can be used in the nonmagnetic layer, see paragraphs

[0040] and

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

[0071] 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.

[0072] In the present invention and this specification, the term "nonmagnetic layer" also includes a substantially nonmagnetic layer that contains a small amount of ferromagnetic powder, for example as an impurity or intentionally, along with a nonmagnetic powder. Here, a substantially nonmagnetic layer refers to a layer having a remanence of 10 mT or less, a coercivity of 7.96 kA / m (100 Oe) or less, or a remanence of 10 mT or less and a coercivity of 7.96 kA / m (100 Oe) or less. It is preferable that the nonmagnetic layer have no remanence or coercivity.

[0073] <Nonmagnetic support> Next, the non-magnetic support will be described. Examples of the non-magnetic support (hereinafter also simply referred to as "support") include known biaxially stretched polyethylene terephthalate, polyethylene naphthalate, polyamide, polyamideimide, aromatic polyamide, etc. Among these, polyethylene terephthalate, polyethylene naphthalate, and polyamide are preferred. These supports may be previously subjected to corona discharge, plasma treatment, easy-adhesion treatment, heat treatment, etc.

[0074] <Backcoat layer> The magnetic recording medium 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. Known techniques related to backcoat layers can be applied to the binder and additives of the backcoat layer, and known techniques related to the formulation of magnetic and / or nonmagnetic layers can also be applied. 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 regarding the backcoat layer.

[0075] <Various thicknesses> With regard to the thickness (total thickness) of magnetic tape, with the enormous increase in the amount of information in recent years, there is a demand for magnetic recording media with increased recording capacity (higher capacity). For tape-type magnetic recording media (i.e., magnetic tape), one way to increase the capacity is to reduce the thickness of the magnetic tape and increase the length of magnetic tape that can be accommodated in one magnetic tape cartridge. From this perspective, the thickness (total thickness) of the magnetic tape is preferably 5.6 μm or less, more preferably 5.5 μm or less, even more preferably 5.4 μm or less, even more preferably 5.3 μm or less, and even more preferably 5.2 μm or less. Furthermore, from the perspective of ease of handling, the thickness of the magnetic tape is preferably 3.0 μm or more, and more preferably 3.5 μm or more.

[0076] The thickness (total thickness) of the magnetic tape can be measured by the following method. Ten samples (e.g., 5 to 10 cm long) are cut from any part of the magnetic tape, and these samples are stacked and measured for thickness. The measured thickness is divided by 10, and the resulting value (thickness per sample) is taken as the total thickness. The thickness measurement can be performed using a known measuring device capable of measuring thickness to the order of 0.1 μm.

[0077] The thickness of the non-magnetic support is preferably 3.0 to 5.0 μm. The thickness of the magnetic layer can be optimized depending on the saturation magnetization of the magnetic head used, the head gap length, the bandwidth of the recording signal, etc., and is generally 0.01 μm to 0.15 μm, and from the viewpoint of high-density recording, it is preferably 0.02 μm to 0.12 μm, and more preferably 0.03 μm to 0.1 μm. At least one magnetic layer is sufficient, and the magnetic layer may be separated into two or more layers with different magnetic properties, and known configurations related to multilayer magnetic layers can be applied. When the magnetic layer is separated into two or more layers, the thickness of the magnetic layer refers to the total thickness of these layers. The thickness of the non-magnetic layer is, for example, 0.1 to 1.5 μm, and preferably 0.1 to 1.0 μm. The thickness of the backcoat layer is preferably 0.9 μm or less, and more preferably 0.1 to 0.7 μm. The thickness of the magnetic layer and other thicknesses can be determined by the following method. After exposing a cross section of the magnetic tape in the thickness direction with an ion beam, the exposed cross section is observed using a scanning electron microscope or a transmission electron microscope. The thicknesses can be calculated as the arithmetic mean of the thicknesses measured at any two points during the cross section observation. Alternatively, the thicknesses can be calculated as the design thickness calculated from the manufacturing conditions, etc.

[0078] <Manufacturing process> (Preparation of compositions for forming each layer) Compositions for forming the magnetic layer, nonmagnetic layer, or backcoat layer typically contain a solvent in addition to the various components described above. The solvent can be one or more of the various solvents commonly 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 composition's handling suitability, coating conditions, and the thickness of each layer to be formed. The process for preparing a composition for forming the magnetic layer, nonmagnetic layer, or backcoat layer typically includes at least a kneading step, a dispersion step, and optionally, a mixing step before or after these steps. Each individual step may be divided into two or more stages. The various components used in preparing each layer-forming composition may be added at the beginning or during any step. Alternatively, individual components may be added in separate steps in two or more steps. For example, the binder may be added in separate steps in the kneading step, the dispersion step, and the mixing step for adjusting the viscosity after dispersion. The magnetic tape manufacturing process can employ some conventional manufacturing techniques. In the kneading process, devices with strong kneading power, such as an open kneader, continuous kneader, pressure kneader, or extruder, 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 utilizing shear force, such as a bead mill, ball mill, sand mill, or homomixer, 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 rate of the dispersion beads are not particularly limited and may be set depending on the powder to be dispersed. Each layer-forming composition may be filtered by a known method before being subjected to the coating process. Filtration can be performed, for example, by filter filtration. Filters with a pore size of 0.01 to 3 μm (e.g., glass fiber filters, polypropylene filters, etc.) can be used for filtration.

[0079] (Coating process, cooling process, heating and drying process) The magnetic layer can be formed by applying the magnetic layer-forming composition directly onto the non-magnetic support, or by sequentially or simultaneously applying the magnetic layer-forming composition and the non-magnetic layer-forming composition in a multilayer manner. For details on the coating for forming each layer, see paragraph 0066 of JP2010-231843A.

[0080] As described above, in one embodiment, the magnetic tape can have a non-magnetic layer between the non-magnetic support and the magnetic layer. Such a magnetic tape can preferably be manufactured by sequential multi-layer coating. The manufacturing process for sequential multi-layer coating can preferably be 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.

[0081] The inventors believe that in the non-magnetic layer formation process of such a manufacturing method involving successive multi-layer coating, it is preferable to carry out a coating process using a non-magnetic layer-forming composition to form a coating layer, and to carry out a cooling process to cool the coating layer between the coating process and the heat drying process, in order to reduce the value of the width direction σ of the number of bright areas.

[0082] An example of the manufacturing process for the magnetic tape will be described below with reference to Fig. 8. However, the present invention is not limited to the following example.

[0083] Fig. 8 is a process schematic diagram showing an example of a process for producing a magnetic tape having a nonmagnetic layer and a magnetic layer, in that order, on one side of a nonmagnetic support, and a backcoat layer on the other side. In the example shown in Fig. 8, the nonmagnetic support (long film) is continuously wound from a feed section to a take-up section, and various processes such as coating, drying, and orientation are performed in each section or zone shown in Fig. 8, so that a nonmagnetic layer and a magnetic layer can be formed by sequential multilayer coating on one side of the running nonmagnetic support, and a backcoat layer can be formed on the other side. The example shown in Fig. 8 can be similar to a manufacturing process typically used for producing particulate magnetic recording media, except that it includes a cooling zone.

[0084] 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).

[0085] 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. The longer the residence time, the smaller the value of the width direction σ of the number of bright areas tends to be. In the cooling step, cooled gas may be blown onto the surface of the coating layer.

[0086] After the cooling zone, the coating layer is dried by heating it in the first heat treatment zone (heat drying step). The heat drying step can be performed by passing the non-magnetic support bearing the coating layer after the cooling step 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 step in the second heat treatment zone and the heat drying step in the third heat treatment zone described below, are also referred to as the "drying temperature." Increasing the drying temperature in each heat treatment zone can contribute to reducing the value of the width direction σ of the number of bright areas. From this perspective, 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 also 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.

[0087] 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).

[0088] In the case of a subsequent orientation treatment, the ferromagnetic powder in the coating layer of the magnetic layer-forming composition is oriented in the orientation zone while the coating layer 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.

[0089] After the orientation treatment, the coated layer is subjected to a heat drying step in the second heat treatment zone.

[0090] 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, to form a coating layer (backcoat layer-forming composition application step).Then, in the third heat treatment zone, the coating layer is heat-treated and dried.

[0091] 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.

[0092] (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 value of the width direction σ of the number of bright areas. Specific examples of strengthening the calendering conditions include increasing the calendering pressure, increasing the calendering temperature, and reducing 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 steps for manufacturing magnetic tape, reference can be made to paragraphs 0067 to 0070 of JP-A-2010-231843. A long magnetic tape roll can be obtained through various processes. The obtained magnetic tape roll is cut (slit) to the width of the magnetic tape to be housed in a magnetic tape cartridge, for example, using a known cutting machine. The width can be determined according to standards and is usually 1 / 2 inch. 1 inch = 2.54 cm. A servo pattern is usually formed on the magnetic tape obtained by slitting.

[0093] (Servo pattern formation) "Forming a servo pattern" can also be called "recording a servo signal." Forming a servo pattern will be explained below.

[0094] The servo pattern is usually formed along the length of the magnetic tape. Control methods that use servo signals (servo control) include timing-based servo (TBS), amplitude servo, and frequency servo.

[0095] As specified in ECMA (European Computer Manufacturers Association)-319 (June 2001), magnetic tapes conforming to the LTO (Linear Tape-Open) standard (commonly referred to as "LTO tapes") employ a timing-based servo system. In this timing-based servo system, a servo pattern is formed by a pair of non-parallel magnetic stripes (also called "servo stripes") arranged continuously along the longitudinal direction of the magnetic tape. In this invention and this specification, the term "timing-based servo pattern" refers to a servo pattern that enables head tracking in a timing-based servo system. The reason why the servo pattern is formed by a pair of non-parallel magnetic stripes as described above is to inform a servo signal reading element passing over the servo pattern of its passing position. Specifically, the spacing between the pair of magnetic stripes is formed so that it continuously changes along the width direction of the magnetic tape. By reading this spacing, the servo signal reading element can determine the relative position between the servo pattern and the servo signal reading element. This relative position information enables tracking of data tracks. For this reason, a plurality of servo tracks are usually set on the servo pattern along the width direction of the magnetic tape.

[0096] A servo band is made up of a continuous servo pattern along the length of the magnetic tape. Typically, multiple servo bands are provided on a magnetic tape. For example, there are five servo bands on an LTO tape. The area between two adjacent servo bands is the data band. A data band is made up of multiple data tracks, and each data track corresponds to one of the servo tracks.

[0097] Also, in one embodiment, as disclosed in Japanese Patent Application Laid-Open No. 2004-318983, information indicating the servo band number (also called "servo band ID (identification)" or "UDIM (Unique Data Band Identification Method) information") is embedded in each servo band. This servo band ID is recorded by shifting a specific one of a plurality of pairs of servo stripes in the servo band so that its position is displaced relative to the longitudinal direction of the magnetic tape. Specifically, the way in which a specific one of a plurality of pairs of servo stripes is shifted varies for each servo band. As a result, the recorded servo band ID is unique for each servo band, and therefore, simply by reading one servo band with a servo signal reading element, that servo band can be uniquely identified.

[0098] One method for uniquely identifying servo bands is the staggered method described in ECMA-319 (June 2001). In this staggered method, pairs of non-parallel magnetic stripes (servo stripes) are continuously arranged along the length of the magnetic tape, and are recorded so that each servo band is offset along the length of the magnetic tape. The combination of this offset between adjacent servo bands is unique across the entire magnetic tape, making it possible to uniquely identify servo bands when reading the servo pattern with two servo signal reading elements.

[0099] As specified in ECMA-319 (June 2001), each servo band also typically contains information indicating the longitudinal position of the magnetic tape (also known as "LPOS (Longitudinal Position) information"). Like UDIM information, this LPOS information is recorded by shifting the positions of a pair of servo stripes along the longitudinal direction of the magnetic tape. However, unlike UDIM information, the same signal is recorded in each servo band with this LPOS information.

[0100] It is also possible to embed information other than the UDIM information and LPOS information described above in the servo bands. In this case, the embedded information may be different for each servo band, such as UDIM information, or it may be common to all servo bands, such as LPOS information. Furthermore, methods other than those described above can be used to embed information in the servo bands. For example, a predetermined code may be recorded by thinning out a predetermined pair from a group of pairs of servo stripes.

[0101] The head for forming a servo pattern is called a servo write head. A servo write head typically has a pair of gaps corresponding to the pair of magnetic stripes, the number of which is equal to the number of servo bands. Typically, a core and a coil are connected to each pair of gaps. By supplying a current pulse to the coil, the magnetic field generated in the core can generate a leakage magnetic field in the pair of gaps. To form a servo pattern, a current pulse is input while running a magnetic tape over the servo write head, thereby transferring the magnetic pattern corresponding to the pair of gaps onto the magnetic tape, thereby forming the servo pattern. The width of each gap can be appropriately set depending on the density of the servo pattern to be formed. The width of each gap can be set, for example, to 1 μm or less, 1 to 10 μm, or 10 μm or more.

[0102] Before forming a servo pattern on a magnetic tape, the magnetic tape is usually subjected to a demagnetization (erase) process. This erase process can be performed by applying a uniform magnetic field to the magnetic tape using a direct current magnet or an alternating current magnet. There are two types of erase processes: direct current (DC) erase and alternating current (AC) erase. AC erase is performed by gradually reducing the strength of the magnetic field applied to the magnetic tape while reversing the direction of the magnetic field. DC erase, on the other hand, is performed by applying a unidirectional magnetic field to the magnetic tape. There are two other DC erase methods. The first method is horizontal DC erase, in which a unidirectional magnetic field is applied along the length of the magnetic tape. The second method is vertical DC erase, in which a unidirectional magnetic field is applied along the thickness of the magnetic tape. The erase process can be performed on the entire magnetic tape or on each servo band of the magnetic tape.

[0103] The direction of the magnetic field of the formed servo pattern is determined by the erase direction. For example, when a magnetic tape is subjected to horizontal DC erasure, the servo pattern is formed so that the direction of the magnetic field is opposite to the erase direction. This increases the output of the servo signal obtained by reading the servo pattern. As shown in Japanese Patent Application Laid-Open No. 2012-53940, when a magnetic pattern is transferred to a magnetic tape that has been vertically DC erased using the gap, the servo signal obtained by reading the formed servo pattern has a unipolar pulse shape. On the other hand, when a magnetic pattern is transferred to a magnetic tape that has been horizontally DC erased using the gap, the servo signal obtained by reading the formed servo pattern has a bipolar pulse shape.

[0104] <Vertical squareness ratio> In one embodiment, the perpendicular squareness of the magnetic tape can be, for example, 0.55 or more, and preferably 0.60 or more. A perpendicular squareness of the magnetic tape of 0.60 or more is preferred from the viewpoint of improving electromagnetic conversion characteristics. The upper limit of the squareness is, in principle, 1.00 or less. The perpendicular squareness of the magnetic tape can be 1.00 or less, and can be 0.95 or less, 0.90 or less, 0.85 or less, or 0.80 or less. A large perpendicular squareness of the magnetic tape is preferred from the viewpoint of improving electromagnetic conversion characteristics. The perpendicular squareness of the magnetic tape can be controlled by a known method, such as performing a perpendicular orientation treatment.

[0105] In the present invention and this specification, the "perpendicular squareness" refers to the squareness measured in the perpendicular direction of the magnetic tape. The "perpendicular direction" in relation to the squareness refers to the direction perpendicular to the surface of the magnetic layer, which can also be referred to as the thickness direction. In the present invention and this specification, the perpendicular squareness is determined by the following method. A sample piece of a size suitable for insertion into a vibrating sample magnetometer is cut from the magnetic tape to be measured. A magnetic field is applied to this sample piece perpendicular to the sample piece (perpendicular to the magnetic layer surface) using a vibrating sample magnetometer at a maximum applied magnetic field of 3979 kA / m, a measurement temperature of 296 K, and a magnetic field sweep rate of 8.3 kA / m / s. The magnetization strength of the sample piece in response to the applied magnetic field is measured. The measured magnetization strength is obtained after demagnetization field correction and after subtracting the magnetization of the sample probe of the vibrating sample magnetometer as background noise. The squareness ratio (SQ) is calculated as SQ = Mr / Ms, where Ms is the magnetization strength at the maximum applied magnetic field and Mr is the magnetization strength at zero applied magnetic field. The measurement temperature refers to the temperature of the sample piece. By setting the ambient temperature surrounding the sample piece to the measurement temperature, the temperature of the sample piece can be adjusted to the measurement temperature through temperature equilibrium.

[0106] [Magnetic tape cartridge] One aspect of the present invention relates to a magnetic tape cartridge including the above-mentioned magnetic tape.

[0107] 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.

[0108] A magnetic tape cartridge generally contains a magnetic tape wound on a reel within the cartridge body. The reel is rotatably mounted within the cartridge body. Widely used magnetic tape cartridges include single-reel magnetic tape cartridges with one reel within the cartridge body and dual-reel magnetic tape cartridges with two reels within the cartridge body. When a single-reel magnetic tape cartridge is loaded into a magnetic tape device for recording and / or reproducing data on the magnetic tape, the magnetic tape is pulled out from the magnetic tape cartridge and rewound onto a reel on the magnetic tape device. A magnetic head is located in the magnetic tape transport path from the magnetic tape cartridge to the take-up reel. The magnetic tape is fed and rewound between the reel (supply reel) on the magnetic tape cartridge and the reel (take-up reel) on the magnetic tape device. 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.

[0109] In one embodiment, the magnetic tape cartridge may include a cartridge memory. The cartridge memory may be, for example, a nonvolatile 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 at the same longitudinal position during recording approaches zero. The head tilt angle may be, for example, the angle θ described above.

[0110] The magnetic tape and magnetic tape cartridge described above can be suitably used in a magnetic tape device (in other words, a magnetic recording and / 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 according to dimensional information in the width direction of the magnetic tape obtained while the magnetic tape is running. Also, for example, there can be a use mode in which the head tilt angle during one recording and / or playback is different from the head tilt angle during subsequent recording and / or playback, and the head tilt angle is fixed and not changed during each recording and / or playback magnetic tape run.

[0111] [Magnetic tape device] One aspect of the present invention relates to a magnetic tape device including the above-mentioned magnetic tape, in which data can be recorded on the magnetic tape and / or data recorded on the magnetic tape can be reproduced, for example, by bringing a magnetic head into contact with the surface of the magnetic layer of the magnetic tape and sliding it over it.

[0112] In one form, 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. In another form, magnetic tape is not treated as an exchangeable medium, and the magnetic tape is wound onto a reel of a magnetic tape device equipped with a magnetic head, and the magnetic tape is stored in the magnetic tape device.

[0113] 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.

[0114] <Magnetic head> The magnetic tape device can include a magnetic head. The configuration of the magnetic head and the angle θ, which is the head tilt angle, are as described above with reference to FIGS. 5 to 7. When 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 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 is also referred to as a "recording / reproducing head." The element for recording data (recording element) and the element for reproducing data (reproducing element) are collectively referred to as a "magnetic head element."

[0115] When recording and / or reproducing data, tracking can be performed using servo signals. That is, by making the servo signal reading element follow a predetermined servo track, the magnetic head element can be controlled to pass over the target data track. The data track is moved by changing the servo track read by the servo signal reading element in the tape width direction. The read / write head can also record and / or read data from other data bands by using the UDIM information described above to move the servo signal read element to a specific servo band and start tracking that servo band.

[0116] 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 magnetic tape MT. Multiple regions 2 sandwiched between two servo bands form data bands. Servo patterns are magnetized regions formed by magnetizing specific regions of the magnetic layer with a servo write head. The regions magnetized by the servo write head (the positions where servo patterns are formed) are determined by standards. For example, in the industry-standard LTO Ultrium format tape, multiple servo patterns inclined with respect to the tape width direction are formed on the servo bands during magnetic tape manufacturing, as shown in FIG. 10. Specifically, in FIG. 10, a servo frame SF on servo band 1 is composed of a servo subframe 1 (SSF1) and a servo subframe 2 (SSF2). Servo subframe 1 is composed of an A burst (labeled A in FIG. 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. On the other hand, 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 through C4, and the D burst is composed of servo patterns D1 through D4. These 18 servo patterns are arranged in subframes, arranged in a 5, 5, 4, 4, 5 ...

[0117] 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.

[0118] 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 specified for randomly selected modules. initial can be set to be greater than or equal to 0°. initial The larger the angle θ, the larger the change in the effective distance between the servo signal read elements relative to the change in angle θ, which is preferable in terms of the ability to adjust the effective distance between the servo signal read elements in response to changes in the width direction of the magnetic tape. initial is preferably 1° or more, more preferably 5° or more, and even more preferably 10° or more. On the other hand, with regard to the angle formed by the magnetic layer surface and the contact surface of the magnetic head when the magnetic tape runs and comes into contact with the magnetic head (generally called the "wrap angle"), keeping the deviation in the tape width direction small is effective in increasing the uniformity in the tape width direction of the friction generated by contact between the magnetic head and the magnetic tape while the magnetic tape is running. Furthermore, increasing the uniformity of the friction in the tape width direction is desirable from the viewpoint of the position tracking ability and running stability of the magnetic head. From the viewpoint of reducing the deviation in the tape width direction of the wrap angle, θ initial is preferably 45° or less, more preferably 40° or less, and even more preferably 35° or less.

[0119] 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

[0120] In one embodiment, Δθ can be greater than 0.000°, and is preferably 0.001° or greater, more preferably 0.010° ​​or greater, from the viewpoint of the ability to adjust the effective distance between servo signal read elements in response to dimensional changes in the magnetic tape width direction. Furthermore, from the viewpoint of ease of ensuring synchronization of recorded data and / or reproduced data between multiple magnetic head elements during data recording and / or reproduction, Δθ is preferably 1.000° or less, more preferably 0.900° or less, even more preferably 0.800° or less, even more preferably 0.700° or less, and even more preferably 0.600° or less.

[0121] 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. The present invention also includes an embodiment in which the axis of the element array in the above-mentioned magnetic tape device is inclined toward the direction opposite to the magnetic tape running direction.

[0122] θ is the head tilt angle when the magnetic tape starts running initialcan be set by the control device of the magnetic tape device, etc. Regarding the head tilt angle during magnetic tape running, FIG. 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 a range of 0 to 90° during magnetic tape running. In other words, if the axis of the element array is tilted toward the magnetic tape running direction at the start of magnetic tape running, the element array is not tilted during magnetic tape running so that the axis of the element array is tilted toward the opposite direction from the magnetic tape running direction at the start of magnetic tape running. Conversely, if the axis of the element array is tilted toward the opposite direction from the magnetic tape running direction at the start of magnetic tape running, the element array is not tilted during magnetic tape running so that the axis of the element array is tilted toward the magnetic tape running direction at the start of magnetic tape running. The phase difference (i.e., time difference) ΔT between the playback signals of a pair of servo signal read elements 1 and 2 is measured. ΔT can be measured using a measurement unit included in the magnetic tape drive. The configuration of such a measurement unit is well known. The distance L between the center of servo signal read element 1 and the center of servo signal read element 2 can be measured using an optical microscope or the like. When the magnetic tape running speed is v, the distance between the centers of the two servo signal read elements in the magnetic tape running direction is L sin θ, and the relationship L sin θ = v × ΔT holds. Therefore, the angle θ during magnetic tape running can be calculated using the formula "θ = arcsin(vΔT / L)." Note that the right diagram in Figure 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.

[0123] <Configuration of magnetic tape device> A magnetic tape device 10 shown in FIG. 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 has a configuration that can detect and adjust tension applied to the magnetic tape in the longitudinal direction from spindle motors 17A, 17B that control the rotation of the magnetic tape cartridge reel and take-up reel and their drive devices 18A, 18B. The magnetic tape device 10 has a configuration in which a magnetic tape cartridge 13 can be loaded. The magnetic tape device 10 has a cartridge memory read / write device 14 that can read and write data from and to a cartridge memory 131 in the magnetic tape cartridge 13 . The end or leader pin of the magnetic tape MT is pulled out from the magnetic tape cartridge 13 loaded into the magnetic tape device 10 by an automatic loading mechanism or manually, and the magnetic tape MT passes over the recording / playback head through guide rollers 15A and 15B with the magnetic layer surface in contact with the recording / playback head surface of the recording / playback head unit 12, and the magnetic tape MT is wound onto the take-up reel 16. The rotation and torque of spindle motors 17A and 17B are controlled by signals from control device 11, allowing magnetic tape MT to run at a desired speed and tension. Servo patterns pre-formed on the magnetic tape can be used to control the tape speed and head tilt angle. A tension detection mechanism may be provided between magnetic tape cartridge 13 and take-up reel 16 to detect tension. In addition to control by spindle motors 17A and 17B, tension control may also be performed using guide rollers 15A and 15B. The cartridge memory read / write device 14 is configured to be able to read and write information from and to the cartridge memory 131 in response to commands from the control device 11. As a communication method between the cartridge memory read / write device 14 and the cartridge memory 131, for example, the ISO (International Organization for Standardization) 14443 method can be adopted.

[0124] The control device 11 includes, for example, a control unit, a storage unit, a communication unit, and the like.

[0125] 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.

[0126] The recording / playback head unit 12 is configured to be able to record data onto the magnetic tape MT in response to a command from the control device 11. It is also configured to be able to play back the data recorded on the magnetic tape MT in response to a command from the control device 11.

[0127] 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 also has a mechanism for determining the servo band spacing from servo signals read from two adjacent servo bands while the magnetic tape MT is running. The control device 11 can store information about the determined servo band spacing in its internal storage unit, cartridge memory 131, an external connected device, or the like. The control device 11 can also change the head tilt angle according to dimensional information about the width of the 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 the 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 2016-524774 A (Patent Document 1) or US 2019 / 0164573 A1 (Patent Document 2). [Example]

[0128] 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 with a temperature of 23°C ± 1°C unless otherwise specified. "eq" described below is equivalent, a unit that cannot be converted to SI units.

[0129] [Ferromagnetic powder] In Table 1, "BaFe" is hexagonal barium ferrite powder (coercive force Hc: 196 kA / m, average particle size (average plate diameter): 24 nm).

[0130] In Table 1, "SrFe1" is a hexagonal strontium ferrite powder produced by the following method. 1707 g of SrCO3, 687 g of H3BO3, 1120 g of Fe2O3, 45 g of Al(OH)3, 24 g of BaCO3, 13 g of CaCO3, and 235 g of Nd2O3 were weighed and mixed in a mixer to obtain a raw material mixture. The resulting raw material mixture was melted in a platinum crucible at a melting temperature of 1390°C, and the melt was stirred while heating the tapping hole at the bottom of the platinum crucible, causing the melt to be poured into a rod shape at a rate of approximately 6 g / sec. The tapped liquid was rolled and quenched using a water-cooled twin roller to produce an amorphous body. 280 g of the produced amorphous body was placed in an electric furnace, heated to 635°C (crystallization temperature) at a rate of 3.5°C / min, and held at that temperature for 5 hours to precipitate (crystallize) hexagonal strontium ferrite particles. The resulting crystallized material containing hexagonal strontium ferrite particles was then coarsely crushed in a mortar, and 1,000 g of 1 mm zirconia beads and 800 ml of a 1% aqueous acetic acid solution were added to a glass bottle and dispersed for 3 hours using a paint shaker. The resulting dispersion was then separated from the beads and placed in a stainless steel beaker. The dispersion was left to stand at 100°C for 3 hours to dissolve the glass components, then precipitated in a centrifuge, washed by repeated decantation, and dried for 6 hours in a heating furnace at 110°C to obtain hexagonal strontium ferrite powder. The average particle size of the hexagonal strontium ferrite powder obtained above was 18 nm, and the activation volume was 902 nm. 3 , the anisotropy constant Ku is 2.2×10 5 J / m 3 , mass magnetization σs is 49A m 2 / kg. A 12 mg sample powder was taken from the hexagonal strontium ferrite powder obtained above, and this sample powder was partially dissolved under the dissolution conditions exemplified above. The filtrate was subjected to elemental analysis using an ICP analyzer to determine the neodymium atom content in the surface layer. Separately, 12 mg of sample powder was collected from the hexagonal strontium ferrite powder obtained above, and this sample powder was completely dissolved under the dissolution conditions exemplified above. The filtrate thus obtained was subjected to elemental analysis using an ICP analyzer to determine the bulk content of neodymium atoms. The neodymium atom content (bulk content) of the hexagonal strontium ferrite powder obtained above relative to 100 atomic percent of iron atoms was 2.9 atomic percent. The neodymium atom content in the surface layer was 8.0 atomic percent. The ratio of the surface layer content to the bulk content, "surface layer content / bulk content," was 2.8, confirming that neodymium atoms were unevenly distributed in the surface layers of the particles. The powder obtained above was confirmed to have a hexagonal ferrite crystal structure by scanning with CuKα radiation at a voltage of 45 kV and an intensity of 40 mA and measuring the X-ray diffraction pattern under the following conditions (X-ray diffraction analysis). The powder obtained above exhibited a magnetoplumbite (M-type) hexagonal ferrite crystal structure. Furthermore, the crystalline phase detected by X-ray diffraction analysis was a single magnetoplumbite phase. PANalytical X'Pert Pro diffractometer, PIXcel detector Soller slits for incident and diffracted beams: 0.017 radians Dispersion slit fixed angle: 1 / 4 degree Mask: 10mm Anti-scatter slit: 1 / 4 degree Measurement mode: Continuous Measurement time per step: 3 seconds Measurement speed: 0.017 degrees per second Measurement step: 0.05 degrees

[0131] In Table 1, "SrFe2" is a hexagonal strontium ferrite powder produced by the following method. 1725 g of SrCO3, 666 g of H3BO3, 1332 g of Fe2O3, 52 g of Al(OH)3, 34 g of CaCO3, and 141 g of BaCO3 were weighed and mixed in a mixer to obtain a raw material mixture. The resulting raw material mixture was melted in a platinum crucible at a melting temperature of 1380°C, and the melt was stirred while heating the tapping hole at the bottom of the platinum crucible, causing the melt to be poured into a rod shape at a rate of approximately 6 g / sec. The tapped liquid was rolled and quenched using a water-cooled twin roller to produce an amorphous body. 280 g of the obtained amorphous body was placed in an electric furnace, heated to 645°C (crystallization temperature), and held at this temperature for 5 hours to precipitate (crystallize) hexagonal strontium ferrite particles. The resulting crystallized material containing hexagonal strontium ferrite particles was then coarsely crushed in a mortar, and 1,000 g of 1 mm zirconia beads and 800 ml of a 1% aqueous acetic acid solution were added to a glass bottle and dispersed for 3 hours using a paint shaker. The resulting dispersion was then separated from the beads and placed in a stainless steel beaker. The dispersion was left to stand at 100°C for 3 hours to dissolve the glass components, then precipitated in a centrifuge, washed by repeated decantation, and dried for 6 hours in a heating furnace at 110°C to obtain hexagonal strontium ferrite powder. The average particle size of the obtained hexagonal strontium ferrite powder was 19 nm, and the activation volume was 1102 nm. 3 , the anisotropy constant Ku is 2.0×10 5 J / m 3 , mass magnetization σs is 50A m 2 / kg.

[0132] In Table 1, "ε-iron oxide" is ε-iron oxide powder prepared by the following method. 8.3 g of iron(III) nitrate nonahydrate, 1.3 g of gallium(III) nitrate octahydrate, 190 mg of cobalt(II) nitrate hexahydrate, 150 mg of titanium(IV) sulfate, and 1.5 g of polyvinylpyrrolidone (PVP) were dissolved in 90 g of pure water. While stirring using a magnetic stirrer, 4.0 g of 25% aqueous ammonia was added in air at an ambient temperature of 25°C. The mixture was stirred for 2 hours at 25°C. A citric acid solution prepared by dissolving 1 g of citric acid in 9 g of pure water was added to the resulting solution and stirred for 1 hour. The precipitated powder was collected by centrifugation, washed with pure water, and dried in a heating oven at 80°C. 800g of pure water was added to the dried powder, and the powder was dispersed in water again to obtain a dispersion. The resulting dispersion was heated to 50°C, and 40g of a 25% aqueous ammonia solution was added dropwise while stirring. After stirring for 1 hour while maintaining the temperature at 50°C, 14mL of tetraethoxysilane (TEOS) was added dropwise and stirred for 24 hours. 50g of ammonium sulfate was added to the resulting reaction solution, and the precipitated powder was collected by centrifugation, washed with pure water, and dried for 24 hours in a heating furnace at 80°C to obtain a precursor of the ferromagnetic powder. The obtained precursor of the ferromagnetic powder was placed in a heating furnace at an internal temperature of 1000° C. in an air atmosphere and subjected to a heat treatment for 4 hours. The heat-treated ferromagnetic powder precursor was placed in a 4 mol / L aqueous solution of sodium hydroxide (NaOH), and the liquid temperature was maintained at 70°C while stirring for 24 hours, thereby removing the impurity silicate compound from the heat-treated ferromagnetic powder precursor. Thereafter, the silicate compound was removed by centrifugation, and the ferromagnetic powder was collected and washed with pure water to obtain a ferromagnetic powder. The composition of the obtained ferromagnetic powder was confirmed by inductively coupled plasma optical emission spectrometry (ICP-OES). It was found that the powder consisted of Ga, Co, and Ti substituted ε-iron oxide (ε-Ga 0.28 Co 0.05 Ti 0.05 Fe 1.62In addition, X-ray diffraction analysis was performed under the same conditions as those described above for SrFe1, and it was confirmed from the peaks in the X-ray diffraction pattern that the obtained ferromagnetic powder had a single-phase ε-phase crystal structure (ε-iron oxide crystal structure) without containing α-phase or γ-phase crystal structures. The average particle size of the obtained ε-iron oxide powder was 12 nm, and the activation volume was 746 nm. 3 , the anisotropy constant Ku is 1.2×10 5 J / m 3 , mass magnetization σs is 16A m 2 / kg.

[0133] The activation volume and anisotropy constant Ku of the above hexagonal strontium ferrite powder and ε-iron oxide powder were determined for each ferromagnetic powder using a vibrating sample magnetometer (manufactured by Toei Kogyo Co., Ltd.) by the method described above. The mass magnetization σs is a value measured at a magnetic field strength of 15 kOe using a vibrating sample magnetometer (manufactured by Toei Kogyo Co., Ltd.).

[0134] [Abrasive liquid] <Abrasive Liquid A> The following components were dispersed for 24 hours using a batch-type ultrasonic device (20 kHz, 300 W) to obtain abrasive liquid A. Alumina abrasive (average particle size: 100 nm): 3.0 parts Sulfonic acid group-containing polyurethane resin: 0.3 parts Weight average molecular weight: 70,000, SO3Na group: 0.3meq / g Cyclohexanone: 26.7 parts

[0135] <Abrasive Liquid B> The following components were dispersed for 24 hours using a batch-type ultrasonic device (20 kHz, 300 W) to obtain abrasive liquid B. Diamond abrasive (average particle size: 100 nm): 1.0 parts Sulfonic acid group-containing polyurethane resin: 0.1 parts Weight average molecular weight: 70,000, SO3Na group: 0.3meq / g Cyclohexanone: 26.7 parts

[0136] <Abrasive Liquid C> 100.0 parts of alumina abrasive (average particle size: 100 nm) was mixed with 3.0 parts of 2,3-dihydroxynaphthalene (Tokyo Chemical Industry Co., Ltd.), 31.3 parts of a 32% solution of polyester polyurethane resin (UR-4800 manufactured by Toyobo Co., Ltd. (polar group amount: 80 meq / kg)) having SO3Na groups as polar groups (solvent: a mixed solvent of methyl ethyl ketone and toluene), and 570.0 parts of a 1:1 (mass ratio) mixed solution of methyl ethyl ketone and cyclohexanone as solvent, and the mixture was dispersed in the presence of zirconia beads (bead diameter: 0.1 mm) using a paint shaker for 180 minutes (bead dispersion time). After dispersion, the dispersion was separated from the beads using a mesh and the resulting dispersion was centrifuged. The centrifugal separation was carried out using a Hitachi Koki CS150GXL centrifuge (using a Hitachi Koki S100AT6 rotor) at a rotation speed of 4000 rpm (rpm; rotations per minute). The supernatant was then recovered by decantation. This recovered liquid is referred to as "abrasive liquid C."

[0137] [Example 1] (1) Formulation of the composition for forming the magnetic layer (Magnetic liquid) Ferromagnetic powder (see Table 1): 100.0 parts Dispersant: See Table 1 SO3Na group-containing polyurethane resin: 14.0 parts Weight average molecular weight: 70,000, SO3Na group: 0.4meq / g Cyclohexanone: 150 parts Methyl ethyl ketone: 150 parts (abrasive liquid) See Table 1 (in Table 1, the content listed in the "abrasive liquid" column is the content of abrasive contained in the abrasive liquid per 100.0 parts of ferromagnetic powder.) (silica sol) Colloidal silica (average particle size: 100 nm): 0.2 parts Methyl ethyl ketone: 1.4 parts (Other ingredients) 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

[0138] The dispersant is a compound (a compound having a polyalkyleneimine chain and a vinyl polymer chain) described in JP 2019-169225 A as a component of the magnetic layer-forming composition of Example 1. The reaction solution obtained after synthesizing the compound was used as a component of the magnetic layer-forming composition. The content of the dispersant in the magnetic layer shown in Table 1 below is the amount of the compound in the reaction solution.

[0139] (2) Formulation of the composition for forming the nonmagnetic layer Non-magnetic inorganic powder (α-iron oxide): 100.0 parts Average particle size (average major axis length): 10nm Average acicular ratio: 1.9 BET (Brunauer-Emmett-Teller) specific surface area: 75m 2 / g Carbon black: 25.0 parts Average particle size: 20nm SO3Na group-containing polyurethane resin: 18 parts Weight average molecular weight: 70,000, SO3Na group: 0.2meq / g Stearic acid: 1.0 parts Cyclohexanone: 300.0 parts Methyl ethyl ketone: 300.0 parts

[0140] (3) Formulation of the composition for forming the backcoat layer Carbon black: 100.0 parts Cabot BP-800, average particle size: 17 nm SO3Na group-containing polyurethane resin (SO3Na group: 70 eq / ton): 20.0 parts Vinyl chloride resin containing OSO3K group (OSO3K 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

[0141] (4) Preparation of compositions for forming each layer The magnetic liquid was prepared by dispersing the above components for 24 hours using a batch-type vertical sand mill. Zirconia beads with a diameter of 0.5 mm were used as dispersion beads. The magnetic liquid and the abrasive listed in Table 1 were mixed with the silica sol and other ingredients, and then dispersed for 30 minutes using a batch-type ultrasonic device (20 kHz, 300 W).The mixture was then filtered using a filter with a pore size of 0.5 μm to prepare a magnetic layer-forming composition. The non-magnetic layer-forming composition was prepared by dispersing the above components for 24 hours using a batch-type vertical sand mill. Zirconia beads with a 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 the non-magnetic layer-forming composition. The backcoat layer-forming composition was prepared by kneading the above components in a continuous kneader and then dispersing them in a sand mill. 40.0 parts of polyisocyanate (Coronate L, manufactured by Nippon Polyurethane Industry Co., Ltd.) and 1000.0 parts of methyl ethyl ketone were added to the resulting dispersion, and the mixture was filtered through a filter with a pore size of 1 μm to prepare a backcoat layer-forming composition.

[0142] (5) Preparation of magnetic tape The magnetic tape was produced according to the manufacturing process shown in Figure 8. The details are as follows. A 4.1 μm thick polyethylene naphthalate support was fed from a feed section, and a coating layer was formed on one surface by applying a nonmagnetic 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 atmospheric temperature of 0°C for the residence time shown in Table 1 to perform a cooling step, and then passed through a first heat treatment zone at a drying temperature (atmospheric temperature, the same applies below) shown in Table 1 to perform a heat drying step, thereby forming a nonmagnetic layer. The magnetic layer-forming composition prepared above was then applied to the non-magnetic layer in the 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 0.3 T was applied in the orientation zone in a direction perpendicular to the surface of the magnetic layer-forming composition coating layer to perform a vertical orientation treatment, and then the coating layer was dried in the second heat treatment zone at the drying temperature shown in Table 1. Thereafter, in a third coating section, the backcoat layer forming composition prepared above was applied to the surface of the polyethylene naphthalate support opposite to the surface on which the nonmagnetic layer and magnetic layer were formed, to form a coating layer having a thickness of 0.3 μm after drying, and the formed coating layer was dried in a third heat treatment zone at the drying temperature shown in Table 1. Thereafter, calendering (surface smoothing) was carried out under the calendering conditions shown in Table 1 using calender rolls consisting of only metal rolls. Thereafter, the film was subjected to a heat treatment for 36 hours in an atmosphere at 70° C. After the heat treatment, the film was slit into a width of 1 / 2 inch to prepare a magnetic tape. The magnetic layer of the prepared magnetic tape was demagnetized and then servo signals were recorded on the magnetic layer using a commercially available servo writer. This resulted in a magnetic tape with data bands, servo bands, and guide bands arranged in accordance with the LTO (Linear Tape-Open) Ultrium format, and with a servo pattern (timing-based servo pattern) on the servo band arranged and shaped in accordance with 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 was five, and the total number of data bands was four. A magnetic tape (960 m long) with recorded servo signals was thus prepared.

[0143] [Examples 2 to 15, Comparative Examples 1 to 10] A magnetic tape was obtained by the method described for Example 1, except that the items shown in Table 1 were changed as shown in Table 1. In the comparative examples in Table 1 where "none" is written in the column for residence time in cooling zone, the magnetic tape was produced by a manufacturing process that did not include a cooling zone in the non-magnetic layer formation process.

[0144] For each example and comparative example, four magnetic tapes each having a length of 960 m were prepared and used for the following evaluations (1) to (4).

[0145] [Evaluation method] (1) The number of bright areas with a circle-equivalent diameter of 60 nm or more and less than 120 nm, and the width direction σ of the number of bright areas Using a Hitachi FE-SEM S4800 scanning electron microscope (FE-SEM), the number of bright areas with a circular equivalent diameter of 60 nm or more and less than 120 nm was determined on the magnetic layer surface of each magnetic tape in the examples and comparative examples using the following method. A scanning electron microscope (FE-SEM) is used to capture a secondary electron image of the magnetic layer surface of the magnetic tape to be measured. The imaging conditions are an acceleration voltage of 5 kV, a working distance of 5 mm, and a magnification of 10,000 times. When imaging, an unimaged area of ​​the magnetic layer surface is selected, the focus is adjusted under the above imaging conditions, and a secondary electron image is captured. Portions indicating size, etc. (micron bars, cross marks, etc.) are erased from the captured image, and a secondary electron image with 960 x 1280 pixels is obtained. The width of the magnetic tape is divided into five sections, and the above operation is carried out 100 times at different randomly selected locations in each section of the magnetic layer surface of the magnetic tape to be measured. The secondary electron image thus obtained is imported into image processing software (freeware ImageJ) and binarized using the following procedure. The thresholds for binarizing the secondary electron image obtained above are set at a lower limit of 210 gradations and an upper limit of 255 gradations, and binarization is performed using these two thresholds. After binarization, noise components are removed by selecting the noise-cutting process "Despeckle" in the image analysis software (freeware ImageJ). The number of bright areas (i.e., white areas) and the area of ​​each bright area are determined for the binarized image obtained in this way using image analysis software (freeware ImageJ). From the area A of each bright area thus determined, the circle-equivalent diameter L of each bright area is calculated using the formula (A / π)^(1 / 2)×2=L. The above steps are carried out for the binarized images obtained above (100 images for each of the five sections, thus a total of 500 images). In this way, for each of the five sections, the number of bright areas with a circular equivalent diameter of 60 nm or more and less than 120 nm is calculated as the sum of the numbers for the 100 images. The arithmetic mean of the values ​​calculated for the five sections is taken as the number of bright areas with a circular equivalent diameter of 60 nm or more and less than 120 nm on the magnetic tape being measured. The standard deviation σ is calculated for the five values ​​calculated for the above five sections, and this is taken as the width-wise σ of the number of bright areas on the magnetic tape being measured.

[0146] (2) Nonlinear component of tape width deformation For each of the magnetic tapes of the examples and comparative examples, the nonlinear component of the tape width deformation caused by storage for 10 days in an environment of a temperature of 60° C. and a relative humidity of 20% was measured by the method described above.

[0147] (3) Total thickness of magnetic tape (tape thickness) Ten tape samples (5 cm long) were cut from any portion of each magnetic tape in the Examples and Comparative Examples, and these tape samples were stacked and measured for thickness. The thickness was measured using a digital thickness meter with a Millimar 1240 compact amplifier and a Millimar 1301 inductive probe manufactured by MARH. The measured thickness was divided by 10 to obtain the value (thickness per tape sample) as the tape thickness. The tape thickness for all magnetic tapes was 5.2 μm.

[0148] (4) Recording and playback performance The recording and reproducing performance of each of the magnetic tapes of the examples and comparative examples was evaluated by the following method. The magnetic head used was equipped with a reproducing module including an element array with 10 or more channels of reproducing elements with a reproducing element width of 0.2 μm or less between a pair of servo signal reading 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 between a pair of servo signal reading elements. In the element array, the spacing between two adjacent elements (i.e., two adjacent reproducing elements and two adjacent recording elements) in the head width direction was 40 μm or more. The environment for recording and reproducing 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 at least 24 hours, after which data was recorded and reproduced. The recording and reproducing amplifier attached to the tape transport system of the magnetic tape device was the same as the recording and reproducing amplifier described above for measuring the nonlinear component of tape width deformation. During data recording and reproduction, the servo following and dynamic track position control (change in head tilt angle) described above were performed. Data recording and reproduction were carried out 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 for recording 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 (cannot be converted to SI units). Shingled recording was performed on three or more tracks so that the difference (PES1+PES2) / 2 between adjacent tracks was 1.5 times the playback track width. The magnetic pattern recorded on the magnetic tape is reproduced by the next reproducing element (i.e., the reproducing element with the same channel number) and the signal is amplified by the reproducing amplifier. The reproduced signal is processed by a PLL (Phase Lock Loop) and AGC (Auto Gain Control), and then decoded into a bit sequence based on DD-NPML (Data Dependent Noise Predictive Maximum Likelihood) signal processing. The recorded bit sequence and the reproduced and decoded bit sequence are compared bit by bit, and if the two bits differ, a single bit error is counted. 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 bit error rate for the reproduced signal immediately after recording was 1 / 1000 or less in all channels. Next, the magnetic tape was stored for 10 days in an environment of a temperature of 60° C. and a relative humidity of 20% while wound on the reel of the reel tester. After the storage described above, the magnetic tape was removed from the storage environment and placed in the same magnetic tape device as before storage, in an environment with a temperature of 20-25°C and a relative humidity of 40-60% for at least 24 hours. Then, under the same environment, 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 was calculated for all channels, 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 is less than 5% B: The ratio of defective channels to the total number of channels is 5% or more and less than 10% C: The ratio of defective channels to the total number of channels is 10% or more.

[0149] The above results are shown in Table 1 (Table 1-1 to Table 1-3).

[0150] [Table 1-1]

[0151] [Table 1-2]

[0152] [Table 1-3]

[0153] As shown in Table 1, the magnetic tape of the example exhibited superior recording and playback performance after being stored under an accelerated environment equivalent to long-term storage, compared to the magnetic tape of the comparative example. This result confirms that the magnetic tape of the example contributed to improving the operational stability of the drive (magnetic tape device).

[0154] 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 magnetic tape. A sample piece was cut out from the magnetic tape, and the squareness in the vertical direction of the sample piece was measured using a vibrating sample magnetometer, Model TM-TRVSM5050-SMSL, manufactured by Tamagawa Seisakusho, in accordance with the method described above, and was found to be 0.55. The squareness ratio in the perpendicular direction of a sample piece cut out from the magnetic tape of Example 1 was similarly determined and was found to be 0.60.

[0155] The two magnetic tapes were each attached to a 1 / 2-inch reel tester, and the electromagnetic conversion characteristics (SNR: Signal-to-Noise Ratio) were evaluated using the following method. As a result, the magnetic tape of Example 1 exhibited an SNR value 2 dB higher than that of the magnetic tape produced without vertical orientation treatment. Ten passes of recording and playback were performed in an environment with a temperature of 23°C and a relative humidity of 50%, applying a tension of 0.7 N (Newton) in the longitudinal direction of the magnetic tape. The relative speed between the magnetic tape and the magnetic head was 6 m / s. Recording was performed using a metal-in-gap (MIG) head (gap length 0.15 μm, track width 1.0 μm) as the recording head, with the recording current set to the optimal recording current for each magnetic tape. Playback was performed using a giant-magnetoresistive (GMR) head (element thickness 15 nm, shield spacing 0.1 μm, playback element width 0.8 μm) as the playback head. The head tilt angle was 0°. A signal with a linear recording density of 300 kfci was recorded, and the playback signal was measured using a Shibasoku spectrum analyzer. The unit kfci is the unit of linear recording density (not convertible to SI units). The signal was recorded from the point where the signal had stabilized sufficiently after the magnetic tape started running. [Industrial Applicability]

[0156] One aspect of the present invention is useful in various data storage technical fields.

Claims

1. A magnetic tape having a non-magnetic support and a magnetic layer containing ferromagnetic powder, In a binarized secondary electron image obtained by imaging the surface of the magnetic layer with a scanning electron microscope at an acceleration voltage of 5 kV, the number of bright regions having a circle equivalent diameter of 60 nm or more and less than 120 nm is 8,000 or more and 30,000 or less, and A magnetic tape in which the standard deviation σ of the number of bright regions in the width direction of the surface of the magnetic layer is 2000 or less.

2. 2. The magnetic tape according to claim 1, wherein the standard deviation σ of the number of bright regions is 100 or more and 2000 or less.

3. 2. The magnetic tape according to claim 1, wherein the standard deviation σ of the number of bright regions is 100 or more and 850 or less.

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

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

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

7. 2. The magnetic tape of claim 1, wherein the tape has a thickness of 5.2 μm or less.

8. 5. The magnetic tape of claim 4, wherein the tape thickness is 5.2 μm or less.

9. A magnetic tape cartridge comprising the magnetic tape of claim 1.

10. A magnetic tape device comprising the magnetic tape of claim 1.

11. further comprising a magnetic head; the magnetic head has a module including an element array having a plurality of magnetic head elements between a pair of servo signal read elements; 11. The magnetic tape device according to claim 10, wherein the angle θ formed by the axis of the element array with respect to the width direction of the magnetic tape is changed while the magnetic tape is running inside the magnetic tape device.

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