Magnetic tape, magnetic tape cartridge, and magnetic tape device

Abstract

Provided is a magnetic tape comprising a non-magnetic support and a magnetic layer that contains a ferromagnetic powder, wherein the density of peaks Spd as defined by ISO 25178 of protrusions on the surface of the magnetic layer is 3.5(1 / μm2)-5.3(1 / μm2), and the standard deviation σ of the Spd in the width direction of the surface of the magnetic layer is not more than 2.3(1 / μm2).

Description

Magnetic tape, magnetic tape cartridge, and magnetic tape device

[0001] This invention relates to magnetic tape, magnetic tape cartridges, and magnetic tape devices.

[0002] Magnetic recording media come in tape form and disk form. For data storage applications such as data backup and archiving, tape-shaped magnetic recording media, i.e., magnetic tapes, are primarily used (see, for example, Patent Documents 1 to 3).

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

[0004] Data is typically recorded onto magnetic tape by running the tape through a magnetic tape drive (commonly called a "drive") and using a magnetic head to track the data bands of the tape, thereby recording the data on those bands. This creates data tracks on the data bands. When playing back recorded data, the tape is run through the magnetic tape drive, and the magnetic head tracks the data bands of the tape to read the data recorded on those bands. After recording or playback, the magnetic tape is usually stored wound on a reel inside a magnetic tape cartridge or similar device until the next recording and / or playback takes place.

[0005] To improve the accuracy of the magnetic head following the data band of the magnetic tape during recording and / or playback as described above, a system that uses servo signals to perform head tracking (hereinafter referred to as the "servo system") has been put into practical use. However, when recording and / or playback is performed after storage, deformation of the tape width of the magnetic tape caused by storage can cause a phenomenon in which the magnetic head for recording and / or playback of data shifts from the target track position (generally called "off-track"). Off-track can lead to overwriting of recorded data, playback failures, etc., which reduces the operational stability of the drive. In recent years, with the increase in track density due to the increase in magnetic tape capacity, off-track is more likely to occur, and therefore the need for improved operational stability of the drive is increasing. On the other hand, in recent years, the data storage field has seen the long-term storage of data called archiving. However, generally, the longer the storage period, the more likely tape width deformation of the magnetic tape is to occur, and the more frequently off-track tends to occur.

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

[0007] One aspect of the present invention is as follows: [1] A magnetic tape having a non-magnetic support and a magnetic layer containing ferromagnetic powder, wherein the vertex density Spd of the protrusions on the surface of the magnetic layer as defined in ISO (International Organization for Standardization) 25178 (hereinafter also referred to as "Spd of the magnetic layer surface" or simply "Spd") is 3.5 (1 / μm ２ ) or more 5.3 (1 / μm ２ ) or less, and the standard deviation σ of Spd in the width direction of the surface of the magnetic layer (hereinafter also referred to as "Spd in the width direction σ") is 2.3 (1 / μm ２ ) or less magnetic tape. [2] The standard deviation σ of the above Spd is 2.0 (1 / μm ２The magnetic tape according to [1], which is as follows. [3] The magnetic layer further contains non-magnetic powder with an average plate diameter of 50 nm or more and 1000 nm or less and an average plate thickness of 12 nm or less, the magnetic tape according to [1] or [2]. [4] The magnetic tape according to any one of [1] to [3], further having a non-magnetic layer containing non-magnetic powder between the non-magnetic support and the magnetic layer. [5] The non-magnetic powder of the non-magnetic layer contains Fe-based inorganic oxide powder with an average particle volume of 2.0×10 －６ μm ３ The magnetic tape according to [4], containing the following Fe-based inorganic oxide powder. [6] The magnetic tape according to [4] or [5], wherein the non-magnetic powder of the non-magnetic layer contains carbon black with a pH of 9.0 or less. [7] The magnetic tape according to any one of [4] to [6], wherein the thickness of the non-magnetic layer is 0.1 μm or more and 0.7 μm or less. [8] The magnetic tape according to any one of [1] to [7], further having a back coat layer containing non-magnetic powder on the surface side opposite to the surface side having the magnetic layer of the non-magnetic support. [9] The magnetic tape according to any one of [1] to [8], wherein the tape thickness is 5.2 μm or less.

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

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

[10] , wherein the perpendicular squareness ratio of the magnetic tape is 0.60 or more.

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

[11] , wherein the perpendicular squareness ratio of the magnetic tape is 0.65 or more.

[13] The standard deviation σ of the Spd is 2.0 (1 / μm ２ or less, the magnetic layer further contains non-magnetic powder with an average plate diameter of 50 nm or more and 1000 nm or less and an average plate thickness of 12 nm or less, there is further a non-magnetic layer containing non-magnetic powder between the non-magnetic support and the magnetic layer, and the non-magnetic powder of the non-magnetic layer has an average particle volume of 2.0×10 －６ μm ３A magnetic tape according to any one of [1] to

[12] , comprising the following Fe-based inorganic oxide powder and carbon black with a pH of 9.0 or less, wherein the thickness of the non-magnetic layer is 0.1 μm or more and 0.7 μm or less, and further comprising a back coat layer containing non-magnetic powder on the surface side of the non-magnetic support opposite to the surface side having the magnetic layer, the tape thickness is 5.0 μm or less, and the vertical angular ratio of the magnetic tape is 0.65 or more. A magnetic tape cartridge comprising the magnetic tape according to any one of [1] to

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

[13] . A magnetic tape device according to

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

[0008] According to one aspect of the present invention, a magnetic tape can be provided that contributes to improving the operational stability of a drive during recording and / or playback after long-term storage. Furthermore, according to one aspect of the present invention, a magnetic tape cartridge and a magnetic tape device containing such a magnetic tape can be provided.

[0009] This shows an example of a track profile plotted with track position on the horizontal axis and output of the playback signal on the vertical axis. This shows an example of a graph relating to the initial nonlinear component. This shows an example of a graph relating to the nonlinear component after storage. This is an example of a graph showing the absolute value of the difference between the initial nonlinear component and the nonlinear component after storage (difference in nonlinear component before and after storage) for each playback element. This is a schematic diagram showing an example of a magnetic head module. This is an explanatory diagram of the relative positional relationship between the module and the magnetic tape during magnetic tape running in a magnetic tape device. This is an explanatory diagram of the change in angle θ during magnetic tape running. This shows an example of a magnetic tape manufacturing process (process schematic diagram). This shows an example of the arrangement of data bands and servo bands. This shows an example of the servo pattern arrangement for LTO (Linear Tape-Open) Ultrium format tape. This is an explanatory diagram of the method for measuring the angle θ during magnetic tape running. This is a schematic diagram showing an example of a magnetic tape device.

[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. In the magnetic tape, the vertex density Spd of the protrusions on the surface of the magnetic layer as defined in ISO 25178 is 3.5 (1 / μm). ２ ) or more 5.3 (1 / μm ２ ) or less, and the standard deviation σ of Spd in the width direction of the surface of the magnetic layer is 2.3 (1 / μm ２ ) The following:

[0011] As a result of diligent research, the inventors have newly discovered that a magnetic tape in which the Spd of the magnetic layer surface is within the above range and the width direction σ of the Spd is within the above range can contribute to improving the operational stability of the drive. The inventors' inferences regarding this point are described below. However, the present invention is not limited to the inferences described herein. As described above, tape width deformation caused by long-term storage can cause a decrease in the operational stability of the magnetic tape in the drive. In this regard, in recent years, it has been proposed to acquire widthwise dimensional information of a running magnetic tape using a servo signal and to change the angle at which the axial direction of the magnetic head module is tilted with respect to the width direction of the magnetic tape (hereinafter also referred to as the "head tilt angle") according to the acquired dimensional information (see Patent Documents 1 and 2, for example, paragraphs 0059 to 0067 and paragraph 0084 of Patent Document 1). In addition, it is also possible to control the widthwise dimension of the magnetic tape by acquiring widthwise dimensional information of a running magnetic tape using a servo signal and adjusting the tension applied in the longitudinal direction of the magnetic tape according to the acquired dimensional information (see paragraph 0171 of Patent Document 3 as an example). For example, the dynamic track position control means during magnetic tape travel described above can serve as a means to suppress off-tracking. However, in diligent research to further improve the operational stability of the drive during recording and / or playback after long-term storage, the inventors focused on the possibility that there may be off-track factors that are difficult to compensate for with 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 (more specifically, the recording elements and / or playback elements) changes uniformly according to 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 in the longitudinal direction of the magnetic tape, the tension is usually adjusted across the entire width of the tape, so the tape width changes uniformly regardless of the position in the tape width direction due to the tension adjustment. If the degree of tape width deformation is uniform throughout the entire magnetic tape, that is, if the tape width deformation component is only a linear component, it is possible to completely compensate for off-tracking with the above control means.Therefore, it becomes possible to perfectly align the data track and the magnetic head element. In contrast, if the degree of tape width deformation differs and is non-uniform depending on the position, that is, if the tape width deformation component includes a nonlinear component, it is difficult for the above control means to compensate for off-track caused by the nonlinear component. The inventors considered that reducing this nonlinear component could contribute to suppressing the decrease in drive operation stability caused by off-track factors that are difficult to compensate for with dynamic track position control means. In this regard, the inventors believe that in magnetic tape, having the Spd of the magnetic layer surface within the above range, and having the standard deviation σ of Spd within the above range, contributes to stabilizing the contact state between the magnetic head and the magnetic tape, and as a result, it becomes possible to suppress the occurrence of the above nonlinear component of tape width deformation. The inventors speculate that this can contribute to improving the operation stability of the drive during recording and / or playback after long-term storage.

[0012] <Spd and width σ of Spd on the magnetic layer surface> In the present invention and this specification, Spd is the vertex density Spd of the protrusions as defined in ISO 25178. ISO 25178 is an ISO standard relating to three-dimensional surface texture parameters, more specifically, ISO 25178-2:2021 (Geometric product specifications (GPS) - Surface texture: Area - Part 2: Terms, definitions and surface texture parameters). Spd is a physical property value relating to protrusions on the magnetic layer surface, and is a physical property value that includes the influence of the number of protrusions and the tip shape of the protrusions. To determine the Spd of the magnetic layer surface, measurements are taken on the surface of the magnetic layer of the magnetic tape using an atomic force microscope (AFM) as follows. In this invention and specification, "surface of the magnetic layer" is synonymous with the magnetic layer surface of the magnetic tape. The measurement area is a 40 μm square (40 μm × 40 μm) area. Measurements are performed at five locations. The five locations on the magnetic layer surface to be measured are the same in the longitudinal direction but different in the width direction. The longitudinal position is randomly selected on the magnetic layer surface, and at this longitudinal position, the width direction is divided into five parts with respect to the magnetic tape width (therefore, if the magnetic tape width is W, the width of each part is "W / 5"), and the Spd specified in ISO 25178 is determined for a randomly selected 40 μm square (40 μm × 40 μm) area in each part. For Spd, AFM data analysis software is used to determine the Spd at a threshold of 2%, with the F-operation being the total least squares surface. Any known AFM data analysis software can be used. As an example, Digitalsurf's AFM data analysis software (MountainsSPIP) can be used. The arithmetic mean of the five measured values ​​obtained in this way is taken as the Spd of the magnetic layer surface of the magnetic tape being measured. Furthermore, the standard deviation σ (i.e., the positive square root of the variance) of the five measured values ​​obtained in this way is taken as the standard deviation σ of Spd in the width direction of the magnetic layer surface of the magnetic tape being measured (Spd in the width direction σ).An example of AFM measurement conditions is as follows: An AFM (BRUKER Nanoscope 5) is used in peak-force tapping mode to measure a 40 μm x 40 μm area on the surface of the magnetic layer of a magnetic tape. A BRUKER SCANASYST-AIR probe is used, with a resolution of 512 pixels x 512 pixels, and a scan speed of 512 seconds to measure one screen (512 pixels x 512 pixels).

[0013] (Spd of the magnetic layer surface) The Spd of the magnetic layer surface of the above magnetic tape is 3.5 (1 / μm ２ ) or more 5.3 (1 / μm ２ ) or less. From the viewpoint of improving the operational stability of the drive during recording and / or playback after long-term storage, the Spd of the magnetic layer surface is 3.5 (1 / μm). ２ ) or more, and 4.0 (1 / μm ２ It is preferable that the Spd of the magnetic layer surface is 5.3 (1 / μm). Furthermore, from the above viewpoint, the Spd of the magnetic layer surface is 5.3 (1 / μm). ２ ) or less, and 5.0 (1 / μm ２ Preferably, it is 4.5 (1 / μm) or less. ２ ) or less, 4.0 (1 / μm ２ The following order is preferable:

[0014] (Spd in width direction σ) The standard deviation σ of Spd in the width direction of the surface of the magnetic layer of the magnetic tape (Spd in width direction σ) is set to 2.3 (1 / μm) from the viewpoint of improving the operational stability of the drive during recording and / or playback after long-term storage. ２ ) or less, and 2.2 (1 / μm ２ Preferably, it is 2.1 (1 / μm) or less. ２ It is more preferable that it be less than or equal to 2.0 (1 / μm ２ It is even more preferable that the width σ of Spd is less than or equal to 0.0 (1 / μm). ２ ) or more, 0.1 (1 / μm ２ ) or more, 0.5 (1 / μm ２ ) or more, 1.0 (1 / μm ２ ) or more or 1.5 (1 / μm ２) or greater. From the viewpoint of improving the operational stability of the drive during recording and / or playback after long-term storage, it is presumed that a smaller value of σ in the width direction of Spd is preferable.

[0015] The method for controlling the Spd on the magnetic layer surface and the method for controlling the width σ of the Spd will be described later.

[0016] <Nonlinear component of tape width deformation> The inventors believe that the "nonlinear component in the tape width direction resulting from 10 days of storage in an environment of 60°C and 20% relative humidity," which can be obtained by the following method, can serve as an indicator of the nonlinear component of tape width deformation described above. Note that the storage condition of "10 days of storage in an environment of 60°C and 20% relative humidity" was adopted as an example of storage conditions in an accelerated environment equivalent to long-term data storage called 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 performed 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 is a magnetic tape with a length of 200 m or more. The magnetic tape to be measured is wound onto a magnetic tape reel with a hub diameter (outer diameter, the same applies hereinafter) of 44 mm, with a tension of 0.6 N (Newtons) in the longitudinal direction of the magnetic tape, using a device that has a winding mechanism that winds the magnetic tape while applying tension in the longitudinal direction of the magnetic tape. The magnetic tape, wound onto the reel in this manner, is stored for at least 24 hours in an environment with a temperature of 20-25°C and a relative humidity of 40-60% before the following measurements. For each end of the magnetic tape, the end closest to the starting point of winding onto the reel is called the inner circumference end, and the other end is called the outer circumference end. The following measurements are performed in the central wrap of each data band in the area within 100m from the outer circumference end (hereinafter referred to as the "outer circumference area") and the area within 100m from the inner circumference end (hereinafter referred to as the "inner circumference area"). The following measurements are performed using a magnetic head equipped with a regeneration module containing an element array having 10 or more channels of regeneration elements with an element width (specifically, regeneration element width) of 0.2 μm to 1.0 μm between a pair of servo signal reading elements, and a recording module containing an element array having 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 reading elements. "Element width" refers to the physical dimension of the element width, which can be measured using an optical microscope, scanning electron microscope, etc.In the recording module, the distance between two adjacent recording elements in the head width direction is 83.25 μm. In the playback module, the distance between two adjacent playback elements in the head width direction is 83.25 μm. The above distances are the distance between the centers of two adjacent recording elements in the recording module and the distance between the centers of two adjacent playback elements in the playback module, and can be measured using an optical microscope or the like. In the measurements for the embodiments and comparative examples described later, a magnetic head was used that included a recording module with an element array having 32 channels (channels 0 to 31) of recording elements between a pair of servo signal reading elements, and a playback module with an element array having 32 channels (channels 0 to 31) of playback elements between a pair of servo signal reading elements. The reel on which the magnetic tape to be measured is wound and the magnetic head are attached to the tape transport system of a magnetic tape device to record and play back data. The tape transport system is attached to a recording and playback amplifier capable of driving the magnetic head elements (specifically, the recording elements and playback elements) of the magnetic head. The recording and playback amplifier can be controlled from a computer (PC: Personal Computer) via a controller. The magnetic head is mounted on an actuator (piezo motor or VCM (voice coil motor)) that operates in the tape width direction, and can servo-follow so that the magnetic head remains at a constant track position during tape travel based on the servo signal of the magnetic tape. In addition, to compensate for the linear component of tape width deformation, the head tilt angle of the magnetic head can be changed to dynamically control the track position so that the difference in the width direction reading position PES (Position Error Signal) signals (PES1, PES2) based on the servo signal obtained by two upper and lower servo signal reading elements remains constant. The above-described servo-following and dynamic track position control are performed during the following recording and playback.Next, while running the magnetic tape 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 running in the same direction. The unit "kfci" is the unit of linear recording density (cannot be converted to the SI unit system). Single recording is performed on three or more tracks such that the difference between (PES1 + PES2) / 2 is 1200 nm. Single recording is also called tile recording. Next, for the center wrap of the three consecutive wraps, data is reproduced over a length of 90 m in both the area within 100 m from the outer edge of the tape (outer edge area) and the area within 100 m from the inner edge of the tape (inner edge area). The reproduced signal waveform and servo signal waveform are acquired and saved using an oscilloscope. For each measurement as described above, the track position of the playback element is moved in the tape width direction at intervals of 1 / 30 or less of the track pitch. The "output of the playback signal" is calculated for each playback element from the playback signal waveform acquired and saved using the oscilloscope, and the track position is calculated from the servo signal waveform. From these results, a track profile is created with the track position plotted on the horizontal axis and the output of the playback signal plotted on the vertical axis. Figure 1 shows an example of a track profile thus created. The median value between two track positions that are 1 dB or more below the maximum value of the playback signal output is found, and the median value is plotted on the vertical axis for each playback element, and a linear approximation line is obtained by linear fitting using the least squares method. For both the outer and inner regions of the tape, the difference between the above linear approximation line and the measured value is found for each playback element, 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 (number of channels) is 32 channels (playback element number (No.): channel 0 to channel 31). After measuring the initial nonlinear components as described above, the magnetic tape to be measured is wound onto a magnetic tape reel with a hub diameter of 44 mm, using a device that has a winding mechanism that applies tension to the magnetic tape in the longitudinal direction, with a tension of 0.6 N in the longitudinal direction of the magnetic tape.During winding, the end that was the inner circumference end of the tape when winding onto the reel before the initial measurement of the nonlinear components becomes the inner circumference end of the tape. The magnetic tape wound onto the reel in this manner is stored for 10 days in an environment of 60°C and 20% relative humidity. After the above storage, the magnetic tape to be measured is stored on the reel in an environment of 20-25°C and 40-60% relative humidity for 24 hours or more (but up to a maximum of 120 hours). Then, using the magnetic tape device used for the initial measurement of the nonlinear components, the entire length of the magnetic tape to be measured is run back and forth once (forward and reverse). Using the same recording element, playback element, magnetic tape device and playback conditions as when the initial nonlinear components were measured, data playback is performed over a length of 90m in both the region within 100m from the outer circumference end of the tape (outer circumference region) and the region within 100m from the inner circumference end of the tape (inner circumference region). The output of the playback signal and the servo signal waveform are acquired and saved using the same oscilloscope used for measuring the initial nonlinear components. The track position of the playback element is moved relative to the tape width direction with each measurement at the same intervals as when measuring the initial nonlinear components. The "output of the playback signal" is calculated for each playback element from the playback signal waveform acquired and saved using the above oscilloscope, and the track position is calculated from the servo signal waveform. From these results, a track profile is created with the track position plotted on the horizontal axis and the output of the playback signal plotted on the vertical axis. Figure 1 is an example of a track profile created in this way. The median value between two track positions that have decreased by 1 dB or more from the maximum value of the playback signal output is found, and the median value is plotted on the vertical axis for each playback element, and a linear approximation line is obtained by linear fitting using the least squares method. For both the outer and inner regions of the tape, the difference between the above linear approximation line and the measured value is found for each playback element, and this is defined as the "nonlinear component after storage". Figure 3 shows an example of a graph related to the nonlinear component after storage. The absolute value of the difference between the "initial nonlinear component" and the "nonlinear component after storage" (difference of the nonlinear component before and after storage) for each playback element is found. Figure 4 is an example of a graph showing the absolute value of the above difference obtained for each regeneration element.The maximum absolute value in the outer and inner regions of the tape is defined as the "nonlinear component of tape width deformation" of the magnetic tape being measured. The initial nonlinear component is considered to be a nonlinear component caused by factors other than the magnetic tape. Therefore, the inventors believe that by determining 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.

[0017] The nonlinear component of tape width deformation obtained by the method described above for the magnetic tape 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 that order. Having the Spd and Spd width direction σ on the magnetic layer surface within the above range 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, greater 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.

[0018] <Explanation of Head Tilt Angle> As mentioned earlier, one example of a means for controlling the dynamic track position during magnetic tape travel is to change the head tilt angle. In this regard, the configuration of the magnetic head, the head tilt angle, etc. will be explained below. Furthermore, the reason why it is possible to control the dynamic track position during magnetic tape travel by tilting the axial direction of the magnetic head module with respect to the width direction of the magnetic tape will also be explained below.

[0019] The magnetic head may have one or more modules, two or more, or three or more, which include an element array having multiple magnetic head elements between a pair of servo signal reading elements. The total number of such modules may be, for example, five or fewer, four or fewer, or three or fewer, or the magnetic head may contain more modules than the total number exemplified herein. Examples of arrangements of multiple modules include "recording module - playback module" (total number of modules: 2), "recording module - playback module - recording module" (total number of modules: 3), etc. However, the arrangement is not limited to the examples shown herein.

[0020] Each module may include an element array, i.e., an array of elements, having multiple magnetic head elements between a pair of servo signal reading elements. A module having recording elements as magnetic head elements is a recording module for recording data onto magnetic tape. A module having playback elements as magnetic head elements is a playback module for playing back data recorded on magnetic tape. In a magnetic head, multiple modules are arranged, for example, in a recording / playback head unit, with the axes of the element arrays of each module oriented parallel to each other. Such "parallel" does not necessarily mean parallel in the strict sense, but includes a range of error that is normally acceptable in the art to which the present invention belongs. The range of error can mean, for example, a range of less than ±10° of strict parallelism.

[0021] In each element array, a pair of servo signal reading elements and a plurality of magnetic head elements (i.e., recording elements or playback elements) are typically arranged in a straight line and spaced apart. Here, "arranged in a straight line" means that each magnetic head element is arranged on a straight line connecting the center of one servo signal reading element and the center of the other servo signal reading element. Furthermore, in this invention and specification, "axis of the element array" means the straight line connecting the center of one servo signal reading element and the center of the other servo signal reading element.

[0022] Next, the module configuration and other details will be further explained with reference to the drawings. However, the configurations shown in the drawings are illustrative and do not limit the present invention.

[0023] Figure 5 is a schematic diagram showing an example of a magnetic head module. The module shown in Figure 5 has multiple magnetic head elements between a pair of servo signal reading elements (servo signal reading elements 1 and 2). Magnetic head elements are also called "channels." "Ch" in the figure is an abbreviation for Channel. The module shown in Figure 5 has a total of 32 magnetic head elements, from Ch0 to Ch31.

[0024] In Figure 5, "L" represents the distance between a pair of servo signal reading elements, that is, the distance between one servo signal reading element and the other. In the module shown in Figure 5, "L" is the distance between servo signal reading element 1 and servo signal reading element 2. More specifically, it is the distance between the center of servo signal reading element 1 and the center of servo signal reading element 2. This distance can be measured, for example, by an optical microscope.

[0025] Figure 6 is an explanatory diagram of the relative positional relationship between the module and the magnetic tape during magnetic tape movement in a magnetic tape device. In Figure 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 during magnetic tape movement, and is the angle made between dotted line A and dotted line B. When angle θ is 0° during magnetic tape movement, the distance in the magnetic tape width direction between one servo signal reading element and the other servo signal reading element of the element array (hereinafter also referred to as the "effective distance between servo signal reading elements") is "L". In contrast, when angle θ is greater than 0°, the effective distance between servo signal reading elements is "Lcosθ", and Lcosθ is smaller than L. That is, "Lcosθ < L".

[0026] As mentioned earlier, during recording or playback, if the magnetic head used to record or play back data is misaligned from the target track position due to deformation of the magnetic tape's width, phenomena such as overwriting of recorded data or playback failures may occur. For example, if the width of the magnetic tape shrinks or expands, the magnetic head element that should record or play back at the target track position may end up recording or playing back at a different track position. Also, if the width of the magnetic tape expands, the effective distance between servo signal reading elements becomes shorter than the distance between two adjacent servo bands separated by a data band (also referred to as "servo band spacing" or "servo band interval"; more specifically, the distance between the two servo bands in the width direction of the magnetic tape), which may result in data not being recorded or played back in areas close to the edge of the magnetic tape. In contrast, if the element array is tilted at an angle θ greater than 0°, as explained earlier, the effective distance between servo signal reading elements becomes "Lcosθ". The larger the value of θ, the smaller the value of Lcosθ, and the smaller the value of θ, the larger the value of Lcosθ. Therefore, by changing the value of θ according to the degree of dimensional change (i.e., contraction or expansion) in the width direction of the magnetic tape, it becomes possible to bring the effective distance between servo signal reading elements closer to or matching the spacing of the servo bands. This prevents or reduces the frequency of phenomena such as overwriting of recorded data or playback failures that occur during recording or playback due to the magnetic head for recording or playback being misaligned from the target track position due to width deformation of the magnetic tape.

[0027] Figure 7 is an explanatory diagram regarding the change in angle θ during magnetic tape travel. The angle θ at the start of travel is shown. ｉｎｉｔｉａｌ This can be set to, for example, 0° or greater or greater than 0°. In Figure 7, the center diagram shows the state of the module at the start of operation. In Figure 7, the right diagram shows the angle θ, θ ｉｎｉｔｉａｌ An angle θ is a larger angle. ｃ This shows the state of the module at that time. Servo signal reading element effective distance Lcosθ ｃThis is Lcosθ at the start of magnetic tape movement. ｉｎｉｔｉａｌ The value becomes smaller. If the width of the magnetic tape contracts during magnetic tape travel, it is preferable to perform such angle adjustment. On the other hand, in Figure 7, the left figure shows the angle θ as θ ｉｎｉｔｉａｌ The smaller angle is angle θ. ｅ This shows the state of the module at that time. Servo signal reading element effective distance Lcosθ ｅ This is Lcosθ at the start of magnetic tape movement. ｉｎｉｔｉａｌ This results in a larger value. It is preferable to perform this angle adjustment if the width of the magnetic tape expands during magnetic tape operation.

[0028] As explained above, changing the head tilt angle while the magnetic tape is running can help prevent or reduce the frequency of phenomena such as overwriting of recorded data or playback failures that occur when the magnetic head for recording or playing back data is misaligned from the target track position due to width deformation of the magnetic tape during recording or playback. However, with dynamic track position control means such as those described above, off-track caused by the linear component of tape width deformation can usually be compensated for, but off-track caused by the nonlinear component is difficult to suppress. In contrast, it is presumed that the fact that the Spd and the width direction σ of the Spd on the surface of the magnetic layer of the magnetic tape are within the above range contributes to reducing the nonlinear component of tape width deformation. This is thought to improve the operational stability of the drive. Such a magnetic tape is preferable for increasing the track density.

[0029] The following provides a more detailed explanation of the magnetic tape mentioned above.

[0030] <Magnetic Layer> (Ferromagnetic Powder) The ferromagnetic powder included in the magnetic layer can be one 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.

[0031] A preferred specific example of hexagonal ferrite powder ferromagnetic powder is hexagonal ferrite powder. For details on hexagonal ferrite powder, see, for example, paragraphs 0012 to 0030 of Japanese Patent Publication No. 2011-225417, paragraphs 0134 to 0136 of Japanese Patent Publication No. 2011-216149, paragraphs 0013 to 0030 of Japanese Patent Publication No. 2012-204726, and paragraphs 0029 to 0084 of Japanese Patent Publication No. 2015-127985.

[0032] In the present invention and this specification, "hexagonal ferrite powder" refers to a ferromagnetic powder in which a hexagonal ferrite crystal structure is detected as the main phase by X-ray diffraction analysis. The main phase refers to the structure to which the highest intensity diffraction peak in the X-ray diffraction spectrum obtained by X-ray diffraction analysis belongs. For example, if the highest intensity diffraction peak in the X-ray diffraction spectrum obtained by X-ray diffraction analysis is attributed to the hexagonal ferrite crystal structure, it shall be determined that the hexagonal ferrite crystal structure has been detected as the main phase. If only a single structure is detected by X-ray diffraction analysis, this detected structure shall be considered the main phase. The hexagonal ferrite crystal structure contains at least iron atoms, divalent metal atoms, and oxygen atoms as constituent atoms. Divalent metal atoms are metal atoms that can become divalent cations as ions, and examples include strontium atoms, barium atoms, alkaline earth metal atoms such as calcium atoms, and lead atoms. In the present invention and this specification, hexagonal strontium ferrite powder refers to powder in which the main divalent metal atom contained is strontium, and hexagonal barium ferrite powder refers to powder in which the main divalent metal atom contained is barium. The main divalent metal atom refers to the divalent metal atom that accounts for the largest proportion on an atomic percentage basis among the divalent metal atoms contained in the powder. However, rare earth atoms are not included in the above divalent metal atoms. In the present invention and this specification, "rare earth atoms" are selected from the group consisting of scandium atoms (Sc), yttrium atoms (Y), and lanthanide atoms. Lanthanide atoms are selected from the group consisting of lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu).

[0033] Below, we will describe hexagonal strontium ferrite powder, a form of hexagonal ferrite powder, in more detail.

[0034] The activation volume of the hexagonal strontium ferrite powder is preferably 800 to 1600 nm. ３ The activation volume is within the range described above. Finely milled hexagonal strontium ferrite powder exhibiting an activation volume within the above range is suitable for the production of magnetic tapes that exhibit excellent electromagnetic conversion properties. The activation volume of the hexagonal strontium ferrite powder is preferably 800 nm. ３ That's all, for example, 850 nm ３ It can also be the above. Furthermore, from the viewpoint of further improving electromagnetic conversion characteristics, the activation volume of hexagonal strontium ferrite powder is 1500 nm. ３ The following is more preferable: 1400 nm ３ It is even more preferable that the following occur: 1300 nm ３ It is even more preferable that the following conditions are met: 1200 nm ３ It is even more preferable that the following conditions apply: 1100 nm ３ It is even more preferable that the following conditions be met. The same applies to the activation volume of the hexagonal barium ferrite powder.

[0035] "Activation volume" is a unit of magnetization reversal and an indicator of the magnetic size of a particle. The activation volume and the anisotropy constant Ku described herein and below are measured using a vibrating sample type magnetometer at magnetic field sweep speeds of 3 minutes and 30 minutes for the coercivity Hc measurement section (measurement temperature: 23°C ± 1°C), and are values ​​obtained from the following relationship between Hc and activation volume V. Regarding the unit of the anisotropy constant Ku, 1 erg / cc = 1.0 × 10⁻⁶ －１ J / m ３ Therefore, 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)]

[0036] As an indicator of reducing thermal fluctuations, or in other words, improving thermal stability, the anisotropy constant Ku can be cited. The hexagonal strontium ferrite powder is preferably 1.8 × 10⁻⁶ ５ J / m ３ It can have a Ku of the above, and more preferably 2.0 × 10 ５ J / m ３ It can have a Ku of the above. Also, the Ku of hexagonal strontium ferrite powder is, for example, 2.5 × 10 ５ J / m ３ The following values ​​are possible. However, since a higher Ku value is preferable as it indicates higher thermal stability, the values ​​are not limited to those exemplified above.

[0037] Hexagonal strontium ferrite powder may or may not contain rare earth atoms. When hexagonal strontium ferrite powder contains rare earth atoms, it is preferable that the rare earth atoms are present at a concentration of 0.5 to 5.0 atomic percent (bulk concentration) per 100 atomic percent of iron atoms. In one embodiment, hexagonal strontium ferrite powder containing rare earth atoms may have a surface layer segregation of rare earth atoms. In the present invention and this specification, "rare earth atom surface segregation" means that the rare earth atom content relative to 100% of iron atoms in a solution obtained by partially dissolving hexagonal strontium ferrite powder with acid (hereinafter referred to as "rare earth atom surface content" or simply "surface content" with respect to rare earth atoms) satisfies the ratio of rare earth atom surface content / rare earth atom bulk content > 1.0 with respect to rare earth atoms in a solution obtained by completely dissolving hexagonal strontium ferrite powder with acid (hereinafter referred to as "rare earth atom bulk content" or simply "bulk content" with respect to rare earth atoms). The rare earth atom content of hexagonal strontium ferrite powder described later is synonymous with the rare earth atom bulk content. In contrast, partial dissolution using acid dissolves the surface layer of the particles constituting the hexagonal strontium ferrite powder. Therefore, the rare earth atom content in the solution obtained by partial dissolution is the rare earth atom content in the surface layer of the particles constituting the hexagonal strontium ferrite powder. When the rare earth atom surface layer content satisfies the ratio "rare earth atom surface layer content / rare earth atom bulk content > 1.0", it means that in the particles constituting the hexagonal strontium ferrite powder, rare earth atoms are concentrated in the surface layer (i.e., there are more of them in the surface layer than in the interior). In this invention and specification, the surface layer refers to a part of the region extending from the surface to the interior of the particles constituting the hexagonal strontium ferrite powder.

[0038] When hexagonal strontium ferrite powder contains rare earth atoms, the rare earth atom content (bulk content) is preferably in the range of 0.5 to 5.0 atomic percent relative to 100 atomic percent of iron atoms. It is believed that containing rare earth atoms at the bulk content within the above range, and having the rare earth atoms unevenly distributed on the surface of the particles constituting the hexagonal strontium ferrite powder, contributes to suppressing the decrease in regeneration output during repeated regeneration. This is presumed to be because the anisotropy constant Ku can be increased by containing rare earth atoms at the bulk content within the above range, and having the rare earth atoms unevenly distributed on the surface of the particles constituting the hexagonal strontium ferrite powder. The higher the value of the anisotropy constant Ku, the more it is possible to suppress the occurrence of a phenomenon called thermal fluctuation (in other words, to improve thermal stability). By suppressing the occurrence of thermal fluctuation, the decrease in regeneration output during repeated regeneration can be suppressed. It is speculated that the uneven distribution of rare earth atoms on the surface of hexagonal strontium ferrite powder particles contributes to stabilizing the spin of iron (Fe) sites in the crystal lattice of the surface layer, thereby increasing the anisotropy constant Ku. Furthermore, it is speculated that using hexagonal strontium ferrite powder with uneven distribution of rare earth atoms on the surface as the ferromagnetic powder for the magnetic layer contributes to suppressing wear on the magnetic layer surface due to sliding with the magnetic head. In other words, it is speculated that hexagonal strontium ferrite powder with uneven distribution of rare earth atoms on the surface may also contribute to improving the running durability of magnetic tapes. This is because the uneven distribution of rare earth atoms on the surface of the particles constituting the hexagonal strontium ferrite powder contributes to improved interaction between the particle surface and organic substances (e.g., binders and / or additives) contained in the magnetic layer, resulting in improved strength of the magnetic layer. From the viewpoint of further suppressing the decrease in regeneration output during repeated regeneration and / or further improving running durability, the rare earth atom content (bulk content) is more preferably in the range of 0.5 to 4.5 atomic percent, even more preferably in the range of 1.0 to 4.5 atomic percent, and even more preferably in the range of 1.5 to 4.5 atomic percent.

[0039] The bulk content mentioned above is the content obtained by completely dissolving the hexagonal strontium ferrite powder. In this invention and specification, unless otherwise specified, the content of atoms refers to the bulk content obtained by completely dissolving the hexagonal strontium ferrite powder. The hexagonal strontium ferrite powder containing rare earth atoms may contain only one type of rare earth atom, or it may contain two or more types of rare earth atoms. When two or more types of rare earth atoms are included, the bulk content mentioned above is determined for the sum of the two or more types of rare earth atoms. This also applies to other components in this invention and specification. That is, unless otherwise specified, a certain component may be used alone, or two or more types may be used. When two or more types are used, the content or content refers to the sum of the two or more types.

[0040] When hexagonal strontium ferrite powder contains rare earth atoms, the rare earth atoms included may be one or more of any type of rare earth atom. From the viewpoint of further suppressing the decrease in regeneration output during repeated regeneration, preferred rare earth atoms include neodymium atoms, samarium atoms, yttrium atoms, and dysprosium atoms, with neodymium atoms, samarium atoms, and yttrium atoms being more preferred, and neodymium atoms being even more preferred.

[0041] In hexagonal strontium ferrite powder having a rare-earth atom surface segregation, the rare-earth atoms only need to be segregated in the surface layer of the particles constituting the hexagonal strontium ferrite powder, and the degree of segregation is not limited. For example, in hexagonal strontium ferrite powder having a rare-earth atom surface segregation, the ratio of the rare-earth atom surface content obtained by partial dissolution under the dissolution conditions described later to the rare-earth atom bulk content obtained by total dissolution under the dissolution conditions described later, "surface content / bulk content," is greater than 1.0 and can be 1.5 or greater. A "surface content / bulk content" greater than 1.0 means that in the particles constituting the hexagonal strontium ferrite powder, the rare-earth atoms are segregated in the surface layer (i.e., there are more of them in the surface layer than in the interior). Furthermore, the ratio of the surface content of rare earth atoms obtained by partial dissolution under the dissolution conditions described later to the bulk content of rare earth atoms obtained by total dissolution under the dissolution conditions described later, "surface content / bulk content," can be, for example, 10.0 or less, 9.0 or less, 8.0 or less, 7.0 or less, 6.0 or less, 5.0 or less, or 4.0 or less. However, in hexagonal strontium ferrite powder having a rare earth atom surface distribution bias, the rare earth atoms only need to be biased towards the surface of the particles constituting the hexagonal strontium ferrite powder, and the above "surface content / bulk content" is not limited to the upper or lower limits exemplified.

[0042] The partial and total dissolution of hexagonal strontium ferrite powder is described below. For hexagonal strontium ferrite powder existing as a powder, the sample powders to be partially and completely dissolved are taken from the same lot of powder. On the other hand, for hexagonal strontium ferrite powder contained in the magnetic layer of a magnetic tape, a portion of the hexagonal strontium ferrite powder extracted from the magnetic layer is subjected to partial dissolution, and another portion is subjected to total dissolution. The extraction of hexagonal strontium ferrite powder from the magnetic layer can be performed, for example, by the method described in paragraph 0032 of Japanese Patent Application Publication No. 2015-91747. Partial dissolution refers to dissolving to the extent that residual hexagonal strontium ferrite powder can be visually confirmed in the liquid at the end of dissolution. For example, partial dissolution can dissolve a region of 10 to 20% by mass of the particles constituting the hexagonal strontium ferrite powder, with the total particles being 100% by mass. On the other hand, total dissolution refers to dissolution to the point where no residue of hexagonal strontium ferrite powder can be visually confirmed in the liquid at the end of dissolution. The measurement of partial dissolution and surface layer content is performed, for example, by the following method. However, the dissolution conditions such as the amount of sample powder below are examples, and any dissolution conditions that enable partial and total dissolution can be arbitrarily adopted. A container (e.g., a beaker) containing 12 mg of sample powder and 10 mL of 1 mol / L hydrochloric acid is held on a hot plate at a set temperature of 70°C for 1 hour. The resulting solution is filtered through a 0.1 μm membrane filter. Elemental analysis of the resulting filtrate is performed using an inductively coupled plasma (ICP) analyzer. In this way, the surface layer content of rare earth atoms relative to 100 atomic percent of iron atoms can be determined. If multiple types of rare earth atoms are detected by elemental analysis, the total content of all rare earth atoms is taken as the surface layer content. This also applies to the measurement of bulk content. On the other hand, the measurement of total dissolution and bulk content is performed, for example, by the following method: A container (e.g., a beaker) containing 12 mg of sample powder and 10 mL of 4 mol / L hydrochloric acid is held on a hot plate at a set temperature of 80°C for 3 hours.Subsequently, the bulk content relative to 100 atomic percent of iron atoms can be determined by performing the same procedure as described above for partial dissolution and surface layer content measurement.

[0043] From the perspective of increasing the playback output when reproducing data recorded on magnetic tape, it is desirable for the mass magnetization σs of the ferromagnetic powder contained in the magnetic tape to be high. In this regard, hexagonal strontium ferrite powder containing rare earth atoms but lacking surface segregation of rare earth atoms tended to have a significantly lower σs compared to hexagonal strontium ferrite powder that does not contain rare earth atoms. In contrast, hexagonal strontium ferrite powder having surface segregation of rare earth atoms is considered preferable in order to suppress such a large decrease in σs. In one embodiment, the σs of hexagonal strontium ferrite powder is 45 A·m ２ It can be 47 A·m or more per kg. ２ It can also be greater than / kg. On the other hand, σs is 80 A·m from the viewpoint of noise reduction. ２ It is preferable that the value be less than or equal to 60 A·m / kg. ２ It is more preferable that it be less than or equal to / kg. σs can be measured using a known measuring device capable of measuring magnetic properties, such as a vibrating sample magnetometer. In the present invention and this specification, unless otherwise specified, the mass magnetization σs is the value measured at a magnetic field strength of 15 kOe. 1 [kOe] = 10 ６ It is 4π [A / m].

[0044] Regarding the constituent atom content (bulk content) of hexagonal strontium ferrite powder, the strontium atom content can be in the range of, for example, 2.0 to 15.0 atomic percent relative to 100 atomic percent of iron atoms. In one embodiment, the hexagonal strontium ferrite powder may contain only strontium atoms as divalent metal atoms. In another embodiment, the hexagonal strontium ferrite powder may contain one or more other divalent metal atoms in addition to strontium atoms. For example, it may contain barium atoms and / or calcium atoms. When other divalent metal atoms besides strontium atoms are included, the barium atom content and calcium atom content in the hexagonal strontium ferrite powder can be in the range of, for example, 0.05 to 5.0 atomic percent relative to 100 atomic percent of iron atoms.

[0045] The known crystal structures of hexagonal ferrites include magnetoplumbite (also called "M-type"), W-type, Y-type, and Z-type. Hexagonal strontium ferrite powder may have any of these crystal structures. The crystal structure can be confirmed by X-ray diffraction analysis. Hexagonal strontium ferrite powder may show a single crystal structure or two or more crystal structures by X-ray diffraction analysis. For example, in one embodiment, hexagonal strontium ferrite powder may show only the M-type crystal structure by X-ray diffraction analysis. For example, M-type hexagonal ferrite is AFe １２ O １９It is represented by the following compositional formula: Here, A represents a divalent metal atom, and if the hexagonal strontium ferrite powder is of type M, A is either only a strontium atom (Sr), or if A contains multiple divalent metal atoms, then as described above, strontium atoms (Sr) make up the largest proportion on an atomic percentage basis. The divalent metal atom content of hexagonal strontium ferrite powder is usually determined by the type of crystal structure of the hexagonal ferrite and is not particularly limited. The same applies to the iron atom content and oxygen atom content. Hexagonal strontium ferrite powder contains at least iron atoms, strontium atoms and oxygen atoms, and may also contain rare earth atoms. Furthermore, hexagonal strontium ferrite powder may or may not contain atoms other than these atoms. As an example, hexagonal strontium ferrite powder may contain aluminum atoms (Al). The aluminum atom content can be, for example, 0.5 to 10.0 atomic percent relative to 100 atomic percent of iron atoms. From the viewpoint of further suppressing the decrease in regeneration output during repeated regeneration, 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 percent or less, more preferably in the range of 0 to 5.0 atomic percent, and may even be 0 atomic percent, relative to 100 atomic percent of iron atoms. That is, in one embodiment, the hexagonal strontium ferrite powder does not have to contain atoms other than iron atoms, strontium atoms, oxygen atoms, and rare earth atoms. The above content expressed in atomic percent is obtained by converting the content of each atom (unit: mass%) obtained by completely dissolving the hexagonal strontium ferrite powder into an atomic percent value using the atomic weight of each atom. Furthermore, in the present invention and this specification, "does not contain" for a certain atom means that the content measured by an ICP analyzer after complete dissolution is 0 mass%. The detection limit of an ICP analyzer is typically 0.01 ppm (parts per million) or less by mass. The term "does not contain" above is used to include the presence of substances in amounts below the detection limit of the ICP analyzer.Hexagonal strontium ferrite powder can, in one form, be bismuth atom-free (Bi).

[0046] A preferred specific example of a metal powder ferromagnetic powder is a ferromagnetic metal powder. For details on ferromagnetic metal powders, see, for example, paragraphs 0137 to 0141 of Japanese Patent Application Publication No. 2011-216149 and paragraphs 0009 to 0023 of Japanese Patent Application Publication No. 2005-251351.

[0047] A preferred specific example of ε-iron oxide powder ferromagnetic powder is ε-iron oxide powder. In the present invention and this specification, "ε-iron oxide powder" refers to ferromagnetic powder in which the crystal structure of ε-iron oxide is detected as the main phase by X-ray diffraction analysis. For example, if the highest intensity diffraction peak in the X-ray diffraction spectrum obtained by X-ray diffraction analysis is attributed to the crystal structure of ε-iron oxide, it shall be determined that the crystal structure of ε-iron oxide was detected as the main phase. Methods for producing ε-iron oxide powder include methods from goethite and the reverse micelle method. All of the above production methods are publicly known. Furthermore, for a method of producing ε-iron oxide powder in which a portion of Fe is substituted with substitution atoms such as Ga, Co, Ti, Al, and Rh, see, for example, J. Jpn. Soc. Powder Metallurgy Vol. 61 Supply, No. S1, pp. See S280-S284, J. Mater. Chem. C, 2013, 1, pp. 5200-5206, etc. However, the method for producing ε-iron oxide powder that can be used as ferromagnetic powder in the magnetic layer of the magnetic tape is not limited to the method described herein.

[0048] The activation volume of ε-iron oxide powder is preferably 300 to 1500 nm. ３ The activation volume is within the range described above. Finely milled ε-iron oxide powder exhibiting an activation volume within this range is suitable for producing magnetic tapes that exhibit excellent electromagnetic conversion properties. The activation volume of the ε-iron oxide powder is preferably 300 nm. ３ That's all, for example, 500 nm ３It can also be the above. Furthermore, from the viewpoint of further improving electromagnetic conversion characteristics, the activation volume of ε-iron oxide powder is 1400 nm. ３ The following is more preferable: 1300 nm ３ It is even more preferable that the following conditions apply: 1200 nm ３ It is even more preferable that the following conditions be met: 1100 nm ３ The following is even more preferable.

[0049] The anisotropy constant Ku can be cited as an indicator of the reduction of thermal fluctuations, or in other words, the improvement of thermal stability. The ε-iron oxide powder is preferably 3.0 × 10 ４ J / m ３ It can have a Ku of the above, and more preferably 8.0 × 10 ４ J / m ３ It is possible to have the above Ku content. Also, the Ku content of ε-iron oxide powder is, for example, 3.0 × 10 ５ J / m ３ The following values ​​are possible. However, a higher Ku value indicates higher thermal stability, which is preferable, so the values ​​are not limited to those exemplified above.

[0050] From the perspective of increasing the playback output when reproducing data recorded on magnetic tape, it is desirable for the mass magnetization σs of the ferromagnetic powder contained in the magnetic tape to be high. In this regard, in one embodiment, the σs of ε-iron oxide powder is 8 A·m ２ It can be 12 A·m or more per kg. ２ It can also be more than / kg. On the other hand, the σs of ε-iron oxide powder is 40 A·m from the viewpoint of noise reduction. ２ It is preferable that it be less than or equal to 35 A·m / kg. ２ It is more preferable that the amount is less than or equal to / kg.

[0051] In the present invention and this specification, unless otherwise specified, the average particle size of various powders such as ferromagnetic powders shall be the value measured using a transmission electron microscope by the following method. The powder is photographed using a transmission electron microscope at a magnification of 100,000x, and the image is printed on photographic paper or displayed on a screen to obtain a particle photograph of the particles constituting the powder, with a total magnification of 500,000x. The target particle is selected from the obtained particle photograph, and the contour of the particle is traced with a digitizer to measure the size of the particle (primary particle). A primary particle refers to an independent particle that is not aggregated. The above measurement is performed on 500 randomly selected particles. The arithmetic mean of the particle sizes of the 500 particles thus obtained is taken as the average particle size of the powder. As the above-mentioned transmission electron microscope, for example, a Hitachi H-9000 transmission electron microscope can be used. Furthermore, the particle size measurement can be performed using known image analysis software, for example, Carl Zeiss KS-400 image analysis software. The average particle sizes described in the Examples section below were measured using a Hitachi H-9000 transmission electron microscope and Carl Zeiss KS-400 image analysis software, unless otherwise specified. In the present invention and this specification, "powder" means an aggregate of multiple particles. For example, ferromagnetic powder means an aggregate of multiple ferromagnetic particles. Furthermore, an aggregate of multiple particles is not limited to a form in which the particles constituting the aggregate are in direct contact, but also includes forms in which binders, additives, etc., described later, are interposed between the particles. The word "particle" is sometimes used to refer to powder.

[0052] For example, the method described in paragraph 0015 of Japanese Patent Publication No. 2011-048878 can be used to collect sample powder from a magnetic tape for particle size measurement.

[0053] In the present invention and this specification, with respect to particle shape, "plate-shaped" refers to a shape having two opposing plate-like surfaces. "Plate-like surface" refers to the plane observed on the surface of the particle in the above particle photograph and the plane opposite to that plane. On the other hand, among particle shapes that do not have such plate-like surfaces, a shape with a distinction between a major axis and a minor axis is called "elliptical." The major axis is determined as the axis (straight line) along which the particle length can be taken to be the longest. On the other hand, the minor axis is determined as the axis along which the particle length is longest when the particle length is taken along a straight line perpendicular to the major axis. A shape without a distinction between a major axis and a minor axis, that is, a shape where the major axis length = minor axis length, is called "spherical." A shape in which the major axis and minor axis cannot be determined from the shape is called an irregular shape. In the present invention and this specification, unless otherwise specified, the size of the particles constituting the powder (particle size) is the plate diameter when the particle shape observed in the above particle photograph is plate-shaped, the major axis length when it is elliptical, the diameter when it is spherical, and the equivalent circle diameter when it is irregular. The equivalent circle diameter is determined by the circular projection method.

[0054] For plate-shaped particles, "plate thickness" refers to the longest distance between two opposing plate surfaces, and the average plate thickness is the arithmetic mean of the values ​​obtained for the above 500 particles.

[0055] The content (filling rate) of ferromagnetic powder in the magnetic layer is preferably in the range of 50 to 90% by mass, and more preferably in the range of 60 to 90% by mass, relative to the total mass of the magnetic layer. A high filling rate of ferromagnetic powder in the magnetic layer is preferable from the viewpoint of improving recording density.

[0056] (Binding Agent) The above magnetic tape can be a coated magnetic tape, and the magnetic layer may contain a binding agent. The binding agent is one or more resins. Various resins commonly used as binding agents for coated magnetic tapes can be used as binding agents. For example, as binding agents, a resin selected from polyurethane resin, polyester resin, polyamide resin, vinyl chloride resin, acrylic resin copolymerized with styrene, acrylonitrile, methyl methacrylate, etc., cellulose resin such as nitrocellulose, epoxy resin, phenoxy resin, polyvinyl acetal, polyvinyl alkylal resin such as polyvinyl butyral can be used alone or in mixture of multiple resins. Among these, polyurethane resin, acrylic resin, cellulose resin, and vinyl chloride resin are preferred. These resins may be homopolymers or copolymers. These resins can also be used as binding agents in the non-magnetic layer and / or back coat layer described later. For more information on the binding agents, refer to paragraphs 0028 to 0031 of Japanese Patent Application Publication No. 2010-24113. The average molecular weight of the resin used as a binder can be, for example, 10,000 to 200,000 as a weight-average molecular weight. In this invention and specification, the weight-average molecular weight is the value obtained by converting the value measured under the following measurement conditions by gel permeation chromatography (GPC) to polystyrene equivalent. The weight-average molecular weight of the binder shown in the Examples section below is the value obtained by converting the value measured under the following measurement conditions to polystyrene equivalent. The binder can be used in an amount of, for example, 1.0 to 30.0 parts by mass per 100.0 parts by mass of ferromagnetic powder. GPC apparatus: HLC-8120 (Tosoh Corporation) Column: TSK gel Multipore HXL-M (Tosoh Corporation, 7.8 mm ID (Inner Diameter) × 30.0 cm) Eluent: Tetrahydrofuran (THF)

[0057] (Curing agent) A curing agent can also be used together with a resin that can be used as a binder. In one form, the curing agent can be a thermosetting compound, which is a compound that undergoes a curing reaction (crosslinking reaction) by heating, and in another form, it can be a photocurable compound, which undergoes a curing reaction (crosslinking reaction) by light irradiation. As the curing reaction progresses during the magnetic layer formation process, at least a portion of the curing agent may be included in the magnetic layer in a state where it has reacted (crosslinked) with other components such as the binder. This also applies to layers formed using a composition that contains a curing agent when the composition used to form other layers contains a curing agent. Preferred curing agents are thermosetting compounds, and polyisocyanates are preferred. For details on polyisocyanates, refer to paragraphs 0124 to 0125 of Japanese Patent Application Publication No. 2011-216149. The curing agent can be used in the magnetic layer forming composition in an amount of, for example, 0 to 80.0 parts by mass, preferably 50.0 to 80.0 parts by mass, per 100.0 parts by mass of the binder.

[0058] (Additives) The magnetic layer may contain one or more additives as needed. Commercially available additives can be appropriately selected and used according to the desired properties. Alternatively, compounds synthesized by known methods can be used as additives. Additives can be used in any amount. An example of an additive is the curing agent mentioned above. Additives that can be included in the magnetic layer include non-magnetic powders, lubricants, dispersants, dispersion aids, antifungal agents, antistatic agents, antioxidants, etc. For example, for lubricants, refer to paragraphs 0030 to 0033, 0035 and 0036 of Japanese Patent Application Publication No. 2016-126817. A lubricant may be included in the non-magnetic layer described later. For lubricants that can be included in the non-magnetic layer, refer to paragraphs 0030 to 0031, 0034, 0035 and 0036 of Japanese Patent Application Publication No. 2016-126817. For dispersants, see paragraphs 0061 and 0071 of Japanese Patent Publication No. 2012-133837. Dispersants may be added to the composition for forming a non-magnetic layer. For dispersants that can be added to the composition for forming a non-magnetic layer, see also paragraph 0061 of Japanese Patent Publication No. 2012-133837.

[0059] As a result of the inventors' investigations regarding the Spd and width σ of the Spd on the surface of the magnetic layer, it has become clear that including a non-magnetic powder composed of plate-shaped particles in the magnetic layer is preferable from the viewpoint of controlling the Spd and width σ of the Spd on the surface of the magnetic layer to the range described above. Furthermore, as a result of the inventors' investigations, it has become clear that it is even more preferable for the magnetic layer to include a non-magnetic powder with an average plate diameter of 50 nm or more and an average plate thickness of 12 nm or less, from the viewpoint of controlling the Spd and width σ of the Spd on the surface of the magnetic layer to the range described above. The above average plate thickness can be, for example, 3 nm or more, 4 nm or more, or 5 nm or more, and can also be lower than the values ​​exemplified herein. The non-magnetic powder composed of plate-shaped particles (preferably a non-magnetic powder with an average plate diameter of 50 nm or more and an average plate thickness of 12 nm or less) can be, for example, a metal oxide powder. Specific examples of metal oxides include aluminum oxide, zirconium oxide, cerium oxide, etc. Aluminum oxide is also called alumina, zirconium oxide is also called zirconia, and cerium oxide is also called ceria. For example, plate-shaped metal oxide particles can be obtained by heating an aqueous solution of a metal hydroxide to a liquid temperature of 200°C or higher to allow a hydrothermal synthesis reaction to proceed. The plate diameter and thickness of the plate-shaped particles can be controlled by adjusting various conditions for particle preparation (e.g., concentration of the aqueous solution, mixing time during aqueous solution preparation, heating temperature, heating time, etc.). The content of the non-magnetic powder in the magnetic layer can be, for example, 0.02 to 0.80 parts by mass per 100.0 parts by mass of ferromagnetic powder.

[0060] Non-magnetic powders that can be included in the magnetic layer include non-magnetic powders that can function as abrasives. For example, regarding abrasives, refer to paragraphs 0030 to 0032 of Japanese Patent Application Publication No. 2004-273070. As an abrasive, the specific surface area measured by the Brunauer-Emmett-Teller (BET) method (hereinafter referred to as "BET specific surface area") is 14 m². ２ It is preferable to use abrasives of a concentration of 1 / g or more. Furthermore, from the viewpoint of dispersibility, the BET specific surface area should be 40 m². ２ It is preferable to use an abrasive with a concentration of 1 / g or less.

[0061] As an abrasive, a non-magnetic powder with a Mohs hardness greater than 8 is preferred, and a non-magnetic powder with a Mohs hardness of 9 or higher is more preferred. The maximum value of Mohs hardness is 10. The abrasive can be an inorganic powder or an organic powder. The abrasive can be an inorganic or organic oxide powder or a carbide powder. As for carbides, boron carbide (e.g., B ４ Examples of non-magnetic materials include C), titanium carbide (e.g., TiC). Diamond can also be used as an abrasive. In one form, the abrasive is preferably an inorganic oxide powder. Specifically, examples of inorganic oxides include aluminum oxide (alumina), titanium oxide, cerium oxide (ceria), zirconium oxide (zirconia), etc., with alumina being preferred among them. The Mohs hardness of alumina is approximately 9. For alumina powder that can be used as an abrasive, see paragraph 0021 of Japanese Patent Application Publication No. 2013-229090. The abrasive content in the magnetic layer is preferably 0.02 to 0.80 parts by mass per 100.0 parts by mass of ferromagnetic powder. Only one type of non-magnetic powder can be used as the abrasive, or two or more types of non-magnetic powders with different compositions and / or physical properties (e.g., size) can be used. When two or more types of non-magnetic powders are used as abrasives, the abrasive content refers to the total content of those two or more types of non-magnetic powders. The same applies to the content of various components in the present invention and this specification. It is preferable to disperse the abrasive separately from the ferromagnetic powder (separate dispersion), and it is even more preferable to disperse it separately from the non-magnetic powder described above (separate dispersion). When preparing the composition for forming a magnetic layer, two or more dispersions with different components and / or dispersion conditions can be prepared as abrasive dispersions (hereinafter also referred to as "abrasive solution").

[0062] In order to adjust the dispersion state of the abrasive liquid, a dispersant can also be used. Examples of compounds that can function as a dispersant for improving the dispersibility of the abrasive include aromatic hydrocarbon compounds having a phenolic hydroxy group. The "phenolic hydroxy group" refers to a hydroxy group directly bonded to an aromatic ring. The aromatic ring contained in the aromatic hydrocarbon compound may be a monocyclic ring, a polycyclic structure, or a condensed ring. From the viewpoint of improving the dispersibility of the abrasive, aromatic hydrocarbon compounds containing a benzene ring or a naphthalene ring are preferred. Further, the aromatic hydrocarbon compound may have a substituent other than the phenolic hydroxy group. Examples of the substituent other than the phenolic hydroxy group include a halogen atom, an alkyl group, an alkoxy group, an amino group, an acyl group, a nitro group, a nitroso group, a hydroxyalkyl group, etc., and a halogen atom, an alkyl group, an alkoxy group, an amino group, and a hydroxyalkyl group are 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 form of the aromatic hydrocarbon compound having a phenolic hydroxy group includes a compound represented by the following formula 100.

[0064] [In formula 100, two of X １０１ to X １０８ are hydroxy groups, and the other six 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 represented by formula 100 has two of X １０１ to X １０８ as hydroxy groups (phenolic hydroxy groups), and the other six each independently represent a hydrogen atom or a substituent. Also, X １０１ to X １０８Of these, all but the two hydroxyl groups may be hydrogen atoms, and some or all of them may be substituents. Examples of substituents include those described above. In addition to the two hydroxyl groups, one or more phenolic hydroxyl groups may be included. From the viewpoint of improving the dispersibility of the abrasive, X １０１ ~X １０８ It is preferable that, with the exception of two of the hydroxyl groups, the other hydroxyl groups are not phenolic hydroxyl groups. That is, the compound represented by formula 100 is preferably dihydroxynaphthalene or a derivative thereof, and more preferably 2,3-dihydroxynaphthalene or a derivative thereof. １０１ ~X １０８ Preferred substituents represented by include halogen atoms (e.g., chlorine atoms, bromine atoms), amino groups, C1-C6 (preferably C1-C4) alkyl groups, methoxy and ethoxy groups, acyl groups, nitro and nitroso groups, and -CH ２ An example is the OH group.

[0067] Furthermore, for dispersants to improve the dispersibility of abrasives, please also refer to paragraphs 0024 to 0028 of Japanese Patent Publication No. 2014-179149.

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

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

[0070] <Non-magnetic layer> Next, the non-magnetic layer will be described. The magnetic tape may have a magnetic layer directly on a non-magnetic support, or may have a non-magnetic layer containing non-magnetic powder between the non-magnetic support and the magnetic layer. The non-magnetic powder used for the non-magnetic layer may be a powder of an inorganic substance (inorganic powder) or a powder of an organic substance (organic powder). Also, carbon black or the like can be used. Examples of the inorganic substance include metals, metal oxides, metal carbonates, metal sulfates, metal nitrides, metal carbides, metal sulfides, etc. These non-magnetic powders are available as commercial products and can also be manufactured by known methods. For details, reference can be made to paragraphs 0146 to 0150 of JP-A-2011-216149. Regarding the carbon black that can be used for the non-magnetic layer, reference can also be made to paragraphs 0040 to 0041 of JP-A-2010-24113. The content rate (filling rate) of the non-magnetic powder in the non-magnetic layer is preferably in the range of 50 to 90% by mass, more preferably in the range of 60 to 90% by mass, based on the total mass of the non-magnetic layer.

[0071] In one form, the non-magnetic layer can include Fe-based inorganic oxide powder as the non-magnetic powder. In the present invention and this specification, "Fe-based (Fe-based) inorganic oxide powder" refers to an inorganic oxide powder containing iron as a constituent element. Specific examples of the Fe-based inorganic oxide powder include α-iron oxide powder, goethite powder, etc. In the present invention and this specification, "α-iron oxide powder" refers to a non-magnetic powder in which the crystal structure of α-iron oxide is detected as the main phase by X-ray diffraction analysis. α-iron oxide powder is generally also called hematite or the like.

[0072] From the viewpoint of controlling the width direction σ of Spd within the range described above, as the non-magnetic powder of the non-magnetic layer, the average particle volume is 2.0×10 －６ μm ３ As a result of the study by the present inventors, it has been clarified that it is preferable to use the following Fe-based inorganic oxide powder. Therefore, the average particle volume of the Fe-based inorganic oxide powder contained in the non-magnetic layer is preferably 2.0×10 －６ μm ３ or less, and preferably 1.5×10 －６ μm ３It is more preferable that the following conditions apply: 1.0 × 10 －６ μm ３ It is even more preferable that the average particle volume is, for example, 1.0 × 10⁻⁶. －９ μm ３ The above or 1.0 x 10 －８ μm ３ It can be greater than or less than the values ​​exemplified here.

[0073] In the present invention and this specification, the average particle volume is the value obtained by the following method. To observe the Fe-based inorganic oxide powder contained in the non-magnetic layer of the magnetic tape, the sample is first prepared by microtome thinning. Thinning is performed along the longitudinal direction of the magnetic tape so as to obtain a thin section sample that allows observation of the cross-section in the thickness direction of the magnetic tape. For each of the examples and comparative examples described later, a thin section sample was obtained from one of the prepared magnetic tapes using a Leica EM UC6 manufactured by Leica Corporation as the microtome. A cross-sectional TEM image was obtained by observing the obtained thin section sample using a transmission electron microscope (TEM) with an acceleration voltage of 300 kV and a total magnification of 200,000x, so as to include the range from the non-magnetic support to the magnetic layer. As a transmission electron microscope, for example, a JEM-2100Plus manufactured by JEOL Corporation can be used. For the examples and comparative examples described later, a JEM-2100Plus transmission electron microscope manufactured by JEOL Corporation was used. In the obtained cross-sectional TEM image, 50 particles of Fe-based inorganic oxide powder were identified from the particles contained in the non-magnetic layer using micro-electron diffraction. Electron diffraction in micro-electron diffraction was performed using a transmission electron microscope with an acceleration voltage of 200 kV and a camera length of 50 cm. For the examples and comparative examples described later, a JEM-2100Plus transmission electron microscope manufactured by JEOL Corporation was used for electron diffraction in micro-electron diffraction. Subsequently, the average particle volume was determined using the 50 Fe-based inorganic oxide powder particles identified as described above. First, the long axis length (hereinafter also referred to as "DL") and short axis length (hereinafter also referred to as "DS") of each particle were measured. The major axis length DL refers to the maximum distance between two parallel lines drawn from any angle tangent to the particle's contour (the so-called maximum Ferret's diameter). If we call the direction of the major axis length as defined above the major axis direction, then the minor axis length DS refers to the maximum length of the particle in the direction perpendicular to the major axis direction. Next, the average major axis length DLave is calculated as the arithmetic mean of the major axis lengths DL of the 50 measured particles.Ave is an abbreviation for average. The average short-axis length DSave is calculated as the arithmetic mean of the short-axis lengths DS of the 50 particles mentioned above. From the average long-axis length DLave and the average short-axis length DSave, the average particle volume Vave is calculated using the following formula: Vave = π / 6 × DSave. ２ ×DLave

[0074] In one embodiment, the non-magnetic layer may also contain carbon black as a non-magnetic powder. The average particle size of the carbon black can be, for example, 10 nm to 50 nm. From the viewpoint of controlling the width direction σ of Spd to the range described above, the inventors' studies have shown that it is preferable to use carbon black with a pH of 9.0 or less as the non-magnetic powder of the non-magnetic layer. Therefore, the pH of the carbon black contained in the non-magnetic layer is preferably 9.0 or less, more preferably 8.5 or less, even more preferably 8.0 or less, and even more preferably 7.5 or less. The above pH can be, for example, 1.0 or more, 2.0 or more, 3.0 or more, 4.0 or more, 5.0 or more, or 6.0 or more, or it can be lower than the values ​​exemplified herein.

[0075] In the present invention and this specification, the pH of carbon black shall be the value measured according to the standard test method ASTM D1512.

[0076] The non-magnetic layer has an average particle volume of 2.0 × 10⁻⁶ －６ μm ３ Preferably, the mixture contains at least one of the following Fe-based inorganic oxide powder and carbon black with a pH of 9.0 or lower, and more preferably, both. The average particle volume is 2.0 × 10⁻¹⁶ parts by mass of the total amount of non-magnetic powder contained in the non-magnetic layer. －６ μm ３The content of the following Fe-based inorganic oxide powder may be 50.0 parts by mass or more, 60.0 parts by mass or more, or 70.0 parts by mass or more, and may also be, for example, 90.0 parts by mass or less. The content of carbon black with a pH of 9.0 or less per 100.0 parts by mass of the total amount of non-magnetic powder contained in the non-magnetic layer may be 10.0 parts by mass or more, or 20.0 parts by mass or more, and may also be, for example, 50.0 parts by mass or less, 40.0 parts by mass or less, or 30.0 parts by mass or less.

[0077] The non-magnetic layer may contain a binder and may also contain additives. For further details regarding the binder, additives, etc., of the non-magnetic layer, known technology relating to non-magnetic layers can be applied. Furthermore, for example, regarding the type and content of the binder, the type and content of the additives, etc., known technology relating to magnetic layers can also be applied.

[0078] The non-magnetic layer of the magnetic tape described above includes a substantially non-magnetic layer containing a small amount of ferromagnetic powder, for example, as an impurity or intentionally, along with non-magnetic powder. Here, a substantially non-magnetic layer means a layer whose remanent magnetic flux density is 10 mT or less, or whose coercivity is 7.96 kA / m (100 Oe) or less, or a layer whose remanent magnetic flux density is 10 mT or less and whose coercivity is 7.96 kA / m (100 Oe) or less. It is preferable that the non-magnetic layer has no remanent magnetic flux density and coercivity.

[0079] <Non-magnetic support> Next, non-magnetic support will be described. Examples of non-magnetic support (hereinafter also simply referred to as "support") include known materials such as biaxially oriented polyethylene terephthalate, polyethylene naphthalate, polyamide, polyamide-imide, and aromatic polyamide. Among these, polyethylene terephthalate, polyethylene naphthalate, and polyamide are preferred. These support may be subjected to corona discharge, plasma treatment, easy-adhesion treatment, heat treatment, etc. in advance.

[0080] <Backcoat Layer> The tape may or may not have a backcoat layer containing nonmagnetic powder on the surface side opposite to the surface side having the magnetic layer of the nonmagnetic support. Preferably, the backcoat layer contains either or both carbon black and inorganic powder. The backcoat layer may contain a binder and may also contain additives. For details of the nonmagnetic powder, binder, additives, etc. of the backcoat layer, known technology relating to the backcoat layer may be applied, and known technology relating to the magnetic layer and / or nonmagnetic layer may also be applied. For example, paragraphs 0018 to 0020 of Japanese Patent Application Publication No. 2006-331625 and lines 65 to 38 of column 5 of U.S. Patent No. 7,029,774 can be referenced regarding the backcoat layer.

[0081] <Various Thicknesses> Regarding the thickness (total thickness) of magnetic tape, with the enormous increase in the amount of information in recent years, there is a demand for increased recording capacity (high capacity) in magnetic recording media. As a means of increasing the capacity of tape-shaped magnetic recording media (i.e., magnetic tape), one can reduce the thickness of the magnetic tape and increase the length of magnetic tape that can be accommodated in one reel of magnetic tape cartridge. From this point of view, 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, even more preferably 5.2 μm or less, even more preferably 5.0 μm or less, and even more preferably 4.8 μm or less. Furthermore, from the viewpoint of ease of handling, the thickness of the magnetic tape is preferably 3.0 μm or more, more preferably 3.5 μm or more, and even more preferably 4.0 μm or more.

[0082] The thickness (total thickness) of a magnetic tape can be measured by the following method: Ten samples (for example, 5-10 cm in length) are cut from any part of the magnetic tape, and the thickness of these samples is measured by stacking them. The value obtained by dividing the measured thickness by 10 (thickness per sample) is taken as the total thickness. The above thickness measurement can be performed using a known measuring instrument capable of measuring thickness to the order of 0.1 μm.

[0083] The thickness of the non-magnetic support is preferably 3.0 to 5.0 μm. The thickness of the magnetic layer can be optimized according to the saturation magnetization of the magnetic head used, the head gap length, the bandwidth of the recording signal, etc., and is generally 0.01 μm to 0.15 μm, preferably 0.02 μm to 0.12 μm, and more preferably 0.03 μm to 0.1 μm, from the viewpoint of high-density recording. There only needs to be at least one magnetic layer, and the magnetic layer may be separated into two or more layers having different magnetic properties, and known configurations for multilayer magnetic layers can be applied. When separated into two or more layers, the thickness of the magnetic layer is the total thickness of these layers. The thickness of the non-magnetic layer is, for example, 0.1 to 1.5 μm, preferably 0.1 to 1.0 μm, and more preferably 0.1 to 0.7 μm. The thickness of the back coat layer is preferably 0.9 μm or less, and more preferably 0.1 to 0.7 μm. Various thicknesses such as the thickness of the magnetic layer can be determined by the following method. After exposing the cross-section of the magnetic tape in the thickness direction using an ion beam, the exposed cross-section is observed using a scanning electron microscope or a transmission electron microscope. Various thicknesses can be determined as the arithmetic mean of the thicknesses obtained at any two points during the cross-sectional observation. Alternatively, various thicknesses can be determined as design thicknesses calculated from manufacturing conditions, etc.

[0084] <Manufacturing Process> (Preparation of Layer-Forming Compositions) Compositions for forming magnetic layers, non-magnetic layers, or backcoat layers usually contain a solvent along with the various components described above. As the solvent, one or more of the various solvents commonly used in the manufacture of coated magnetic recording media can be used. The solvent content of each layer-forming composition is not particularly limited. For solvents, refer to paragraph 0153 of Japanese Patent Application Publication No. 2011-216149. The solid content concentration and solvent composition of each layer-forming composition may be appropriately adjusted in accordance with the handling suitability of the composition, the coating conditions, and the thickness of each layer to be formed. The process of preparing a composition for forming a magnetic layer, non-magnetic layer, or backcoat layer usually includes at least a kneading step, a dispersion step, and mixing steps provided before or after these steps as needed. Each individual step may be divided into two or more stages. The various components used in the preparation of each layer-forming composition may be added at the beginning or in the middle of any step. Alternatively, individual components may be added in two or more separate steps. For example, the binder may be added in separate steps during the kneading process, the dispersion process, and the mixing process for adjusting the viscosity after dispersion. In the above magnetic tape manufacturing process, conventional known manufacturing techniques can be used as some of the steps. In the kneading process, kneaders with strong kneading force, such as open kneaders, continuous kneaders, pressure kneaders, and extruders, can be used. Details of the kneading process are described in Japanese Patent Publication No. 1-106338 and Japanese Patent Publication No. 1-79274. As the disperser, various known dispersers that utilize shear force, such as bead mills, ball mills, sand mills, or homomixers, can be used. Dispersion beads can preferably be 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 should be set according to the powder to be dispersed. The dispersion time is not particularly limited. From the viewpoint of controlling the Spd and the width σ of the Spd on the magnetic layer surface to the range described above, the inventors surmise that it is preferable to increase the dispersion time in the preparation of the magnetic layer forming composition.Each layer-forming composition may be filtered by a known method before being subjected to the coating process. Filtration can be carried out, for example, by filter filtration. As the filter used for filtration, for example, a filter with a pore size of 0.01 to 3 μm (e.g., a glass fiber filter, a polypropylene filter, etc.) can be used.

[0085] (Coating process, cooling process, heating and drying process) The magnetic layer can be formed by directly coating the magnetic layer-forming composition onto a non-magnetic support, or by sequentially or simultaneously coating it with the non-magnetic layer-forming composition. For details of the coating process for each layer formation, refer to paragraph 0066 of Japanese Patent Application Publication No. 2010-231843.

[0086] As described above, in one embodiment, the magnetic tape may have a non-magnetic layer between a non-magnetic support and a magnetic layer. Such a magnetic tape can preferably be manufactured by sequential layer coating. The manufacturing process for sequential layer coating can preferably be carried out as follows: The non-magnetic layer is formed by a coating step of forming a coated layer by coating a non-magnetic layer-forming composition onto a non-magnetic support, and a heat drying step of drying the formed coated layer by heat treatment. Then, the magnetic layer is formed by a coating step of forming a coated layer by coating a magnetic layer-forming composition onto the formed non-magnetic layer, and a heat drying step of drying the formed coated layer by heat treatment. In one embodiment, in the non-magnetic layer formation step of the manufacturing method for sequential layer coating, a coating step can be performed using a non-magnetic layer-forming composition to form a coated layer, and a cooling step can be performed between the coating step and the heat drying step to cool the coated layer.

[0087] The following describes an example of the manufacturing process for the magnetic tape described above, based on Figure 8. However, the present invention is not limited to the example below.

[0088] Figure 8 is a schematic diagram showing an example of a process for manufacturing a magnetic tape having a non-magnetic layer and a magnetic layer in that order on one side of a non-magnetic support, and a back coat layer on the other side. In the example shown in Figure 8, the non-magnetic support (long film) is continuously wound from a feed-out section to a feed-back section, and various processes such as coating, drying, and orientation are performed in each section or zone shown in Figure 8. This allows for the sequential layering of the non-magnetic and magnetic layers on one side of the moving non-magnetic support, and the formation of a back coat layer on the other side. The example shown in Figure 8 can be carried out in the same way as the manufacturing process normally performed for the manufacture of coated magnetic recording media, except that it includes a cooling zone.

[0089] On the non-magnetic support fed from the dispensing unit, a non-magnetic layer-forming composition is applied in the first coating unit (coating step of non-magnetic layer-forming composition).

[0090] After the above coating step, the coated layer of the non-magnetic 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 non-magnetic support on which the above-mentioned coated layer is formed through a cooling atmosphere. The ambient 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 coated layer is brought into the cooling zone until it is removed (hereinafter also referred to as "dwell time")) is not particularly limited. In the cooling step, cooled gas may be blown onto the surface of the coated layer.

[0091] After the cooling zone, in the first heat treatment zone, the coated layer is dried by heating it after the cooling process (heat drying process). The heat drying process can be carried out by passing the nonmagnetic support having the coated layer after the cooling process through a heated atmosphere. The ambient temperature of the heated atmosphere here, as well as the ambient temperature of the heated atmosphere in the heat drying process in the second heat treatment zone and the heat drying process in the third heat treatment zone described later, are also called the "drying temperature". In one embodiment, the drying temperature in each heat treatment zone is preferably 95°C or higher, and 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 be higher than the temperatures listed here. Additionally, heated gas may be optionally blown onto the surface of the coated layer.

[0092] Next, in the second coating section, a magnetic layer-forming composition is applied to the non-magnetic layer formed by the heat drying process in the first heat treatment zone (application step of magnetic layer-forming composition).

[0093] Subsequently, in the configuration in which orientation processing is performed, the orientation processing of the ferromagnetic powder in the coated layer of the magnetic layer-forming composition is carried out in the orientation zone while the coated layer is still wet. Various known techniques, including those described in paragraph 0067 of Japanese Patent Application Publication No. 2010-231843, can be applied to the orientation processing. For example, vertical orientation processing can be performed by known methods such as using opposite-polarity opposing magnets. In the orientation zone, the drying speed of the coated layer can be controlled by the temperature and airflow of the drying air and / or the transport speed of the magnetic tape in the orientation zone. Alternatively, the coated layer may be pre-dried before being transported to the orientation zone.

[0094] The coated layer, after orientation treatment, is subjected to a heat drying process in a second heat treatment zone.

[0095] Next, in the third coating section, the back coat layer forming composition is applied to the surface of the non-magnetic support opposite to the surface on which the non-magnetic and magnetic layers are formed, thereby forming a coating layer (coating step of back coat layer forming composition). After that, in the third heat treatment zone, the coating layer is heat-treated and dried.

[0096] Through the above process, a magnetic tape can be obtained having a non-magnetic layer and a magnetic layer in that order on one side of a non-magnetic support, and a back coat layer on the other side.

[0097] (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 σ in the width direction of Spd. Specific examples of strengthening the calendering conditions include increasing the calendering pressure, increasing the calendering temperature, and decreasing the calendering speed. Regarding the calendering conditions, the calendering pressure (linear pressure) is preferably 300 to 500 kN / m, more preferably 310 to 350 kN / m, the calendering temperature (surface temperature of the calendering roll) is preferably 95 to 120°C, more preferably 100 to 120°C, and the calendering speed is preferably 50 to 75 m / min. For other various processes for manufacturing magnetic tape, refer to paragraphs 0067 to 0070 of Japanese Patent Application Publication No. 2010-231843. By going through various processes, a long roll of magnetic tape raw material can be obtained. The resulting magnetic tape raw material is cut (slit) using a known cutting machine to the width of the magnetic tape to be housed in, for example, a magnetic tape cartridge. The above 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.

[0098] (Formation of servo patterns) "Formation of servo patterns" can also be described as "recording of servo signals." The formation of servo patterns is explained below.

[0099] Servo patterns are typically formed along the longitudinal direction of the magnetic tape. Examples of control methods that utilize servo signals (servo control) include timing-based servo (TBS), amplitude servo, and frequency servo.

[0100] As stated in ECMA (European Computer Manufacturers Association) - 319 (June 2001), magnetic tapes conforming to the LTO (Linear Tape-Open) standard (commonly called "LTO tapes") employ a timing-based servo system. In this timing-based servo system, the servo pattern is composed of multiple pairs of non-parallel magnetic stripes (also called "servo stripes") arranged continuously in the longitudinal direction of the magnetic tape. In the present invention and this specification, "timing-based servo pattern" refers to a servo pattern that enables head tracking in a timing-based servo system. As described above, the reason why the servo pattern is composed of pairs of non-parallel magnetic stripes is to inform the servo signal reading element passing over the servo pattern of its position. Specifically, the pair of magnetic stripes described above are formed such that their spacing changes continuously along the width of the magnetic tape, and the servo signal reading element reads this spacing to determine the relative position between the servo pattern and the servo signal reading element. This relative position information enables the tracking of data tracks. For this purpose, multiple servo tracks are typically set up on the servo pattern along the width of the magnetic tape.

[0101] A servo band consists of a servo pattern that runs continuously along the longitudinal direction of the magnetic tape. Typically, multiple servo bands are provided on a magnetic tape. For example, in an LTO tape, there are five. The area between two adjacent servo bands is the data band. A data band consists of multiple data tracks, each corresponding to a servo track.

[0102] In one embodiment, as shown in Japanese Patent Publication No. 2004-318983, each servo band has embedded information indicating the servo band number (also called "servo band ID (identification)" or "UDIM (Unique DataBand Identification Method) information"). This servo band ID is recorded by shifting a specific pair of servo stripes within a servo band so that its position is displaced relative to the longitudinal direction of the magnetic tape. Specifically, the method of shifting a specific pair of servo stripes is changed for each servo band. As a result, the recorded servo band ID is unique for each servo band, so that a servo band can be uniquely identified by reading it with a servo signal reading element.

[0103] Furthermore, one method for uniquely identifying a servo band is the staggered method, as described in ECMA-319 (June 2001). In this staggered method, a group of non-parallel magnetic stripes (servo stripes) arranged continuously along the longitudinal direction of the magnetic tape are recorded in a manner that shifts each servo band along the longitudinal direction of the magnetic tape. Since the combination of this shift between adjacent servo bands is unique across the entire magnetic tape, it is possible to uniquely identify a servo band when reading the servo pattern using two servo signal reading elements.

[0104] Furthermore, each servo band typically has embedded information indicating its position along the longitudinal direction of the magnetic tape (also known as "LPOS (Longitudinal Position) information"), as shown in ECMA-319 (June 2001). This LPOS information, like the UDIM information, is recorded by shifting the positions of a pair of servo stripes along the longitudinal direction of the magnetic tape. However, unlike the UDIM information, the same signal is recorded for each servo band in this LPOS information.

[0105] It is also possible to embed information other than the UDIM and LPOS information described above into the servo bands. In this case, the embedded information may be different for each servo band, like the UDIM information, or it may be common to all servo bands, like the LPOS information. Furthermore, methods other than those described above can be used to embed information into the servo bands. For example, a predetermined code may be recorded by thinning out a predetermined pair from a group of servo stripes.

[0106] A servo pattern forming head is called a servo light head. A servo light head typically has a pair of gaps corresponding to the pair of magnetic stripes mentioned above, for each servo band. Typically, a core and a coil are connected to each pair of gaps, and by supplying current pulses to the coils, the magnetic field generated in the core can create a leakage magnetic field in the pair of gaps. When forming a servo pattern, by inputting current pulses while running a magnetic tape over the servo light head, the magnetic patterns corresponding to the pair of gaps are transferred to the magnetic tape, thereby forming the servo pattern. The width of each gap can be appropriately set according to the density of the servo pattern to be formed. For example, the width of each gap can be set to 1 μm or less, 1 to 10 μm, 10 μm or more, etc.

[0107] Before forming a servo pattern on a magnetic tape, it is usually demagnetized (erased). This erasing process can be performed by applying a uniform magnetic field to the magnetic tape using a DC or AC magnet. There are two types of erasing: DC (Direct Current) erasing and AC (Alternating Current) erasing. AC erasing is performed by gradually reducing the strength of the magnetic field while reversing the direction of the magnetic field applied to the magnetic tape. On the other hand, DC erasing is performed by applying a unidirectional magnetic field to the magnetic tape. There are two further methods of DC erasing. The first method is horizontal DC erasing, which applies a unidirectional magnetic field along the longitudinal direction of the magnetic tape. The second method is vertical DC erasing, which applies a unidirectional magnetic field along the thickness direction of the magnetic tape. The erasing process may be performed on the entire magnetic tape or on each servo band of the magnetic tape.

[0108] The direction of the magnetic field of the formed servo pattern is determined according to the direction of the erase. For example, when a magnetic tape is horizontally DC erased, the servo pattern is formed such that the direction of the magnetic field is opposite to the direction of the erase. This makes it possible to increase the output of the servo signal obtained by reading the servo pattern. As shown in Japanese Patent Application Publication No. 2012-53940, when a magnetic pattern using the above gap is transferred to a vertically DC erased magnetic tape, the servo signal obtained by reading the formed servo pattern is in the shape of a single-pole pulse. On the other hand, when a magnetic pattern using the above gap is transferred to a horizontally DC erased magnetic tape, the servo signal obtained by reading the formed servo pattern is in the shape of a double-pole pulse.

[0109] <Vertical Angle Ratio> In one embodiment, the vertical angle ratio of the magnetic tape can be, for example, 0.55 or more, and from the viewpoint of improving electromagnetic conversion characteristics, it is preferable to be 0.60 or more, and more preferable to be 0.65 or more. The upper limit of the angle ratio is, in principle, 1.00 or less. The vertical angle ratio of the magnetic tape can be 1.00 or less, and can be 0.95 or less, 0.90 or less, 0.85 or less, or 0.80 or less. A large value for the vertical angle ratio of the magnetic tape is preferable from the viewpoint of improving electromagnetic conversion characteristics. The vertical angle ratio of the magnetic tape can be controlled by known methods such as performing a vertical orientation process.

[0110] In the present invention and this specification, "vertical angular ratio" refers to the angular ratio measured in the vertical direction of the magnetic tape. "Vertical direction" as used in relation to the angular ratio refers to the direction perpendicular to the magnetic layer surface, and can also be referred to as the thickness direction. In the present invention and this specification, the vertical angular ratio is determined by the following method: A sample piece of a size suitable for introduction into a vibrating sample magnetometer is cut from the magnetic tape to be measured. Using a vibrating sample magnetometer, a magnetic field is applied to this sample piece in the direction perpendicular to the sample piece (perpendicular to the magnetic layer surface) at a maximum applied magnetic field of 3979 kA / m, a measurement temperature of 296 K, and a magnetic field sweep speed of 8.3 kA / m / sec, and the magnetization intensity of the sample piece with respect to the applied magnetic field is measured. The measured magnetization intensity is obtained as a value after demagnetization correction and after subtracting the magnetization of the sample probe of the vibrating sample magnetometer as background noise. When the magnetization intensity at the maximum applied magnetic field is Ms and the magnetization intensity at zero applied magnetic field is Mr, the squareness ratio SQ (Squareness Ratio) is calculated as SQ = Mr / Ms. The measurement temperature refers to the temperature of the sample piece, and by setting the ambient temperature around the sample piece to the measurement temperature, temperature equilibrium is achieved, thereby setting the sample piece temperature to the measurement temperature.

[0111] [Magnetic Tape Cartridge] One aspect of the present invention relates to a magnetic tape cartridge including the magnetic tape described above.

[0112] Details of the magnetic tape included in the above-mentioned magnetic tape cartridge are as previously described. The above-mentioned magnetic tape cartridge can be mounted in a magnetic tape device equipped with a magnetic head and used for recording and / or playing back data.

[0113] In a magnetic tape cartridge, the magnetic tape is generally housed inside the cartridge body, wound onto a reel. The reel is rotatably mounted inside the cartridge body. Two types of magnetic tape cartridges are widely used: single-reel cartridges, which have one reel inside the cartridge body, and double-reel cartridges, which have two reels inside the cartridge body. When a single-reel magnetic tape cartridge is mounted in a magnetic tape device for recording and / or playing back data, the magnetic tape is pulled out of the cartridge and wound onto the reel on the magnetic tape device. A magnetic head is positioned along the magnetic tape transport path from the magnetic tape cartridge to the take-up reel. The magnetic tape is fed and wound between the reel on the magnetic tape cartridge side (supply reel) and the reel on the magnetic tape device side (take-up reel). For example, during this process, the magnetic head and the magnetic layer surface of the magnetic tape come into contact and slide against each other, enabling data recording and / or playback. In contrast, a dual-reel magnetic tape cartridge has both a supply reel and a take-up reel located inside the magnetic tape cartridge.

[0114] The above-described magnetic tape cartridge may, in one embodiment, include a cartridge memory. The cartridge memory may be, for example, a non-volatile memory, and in one embodiment, head tilt angle adjustment information may already be recorded or may be recorded. The head tilt angle adjustment information is information for adjusting the head tilt angle while the magnetic tape is running within the magnetic tape device. For example, the head tilt angle adjustment information may include the values ​​of the servoband interval at each position in the longitudinal direction of the magnetic tape during data recording. For example, when playing back data recorded on the magnetic tape, the value of the servoband interval is measured during playback, and the control device of the magnetic tape device can change the head tilt angle so that the absolute value of the difference between this value and the servoband interval recorded in the cartridge memory at the same longitudinal position during recording approaches zero. The head tilt angle may be, for example, the angle θ described above.

[0115] The magnetic tape and magnetic tape cartridge described above can be suitably used in a magnetic tape device (in other words, a magnetic recording and playback system) that records and / or plays back data at different head tilt angles. In one embodiment, such a magnetic tape device can record and / or play back data by changing the head tilt angle while the magnetic tape is running. For example, the head tilt angle can be changed according to the widthwise dimensional information of the magnetic tape acquired while the magnetic tape is running. Alternatively, for example, the head tilt angle for one recording and / or playback cycle may be changed from the head tilt angle for subsequent recordings and / or playback cycles, and the head tilt angle may be fixed without changing it during the magnetic tape running for each recording and / or playback cycle.

[0116] [Magnetic Tape Device] One aspect of the present invention relates to a magnetic tape device including the magnetic tape described above. In the magnetic tape device described above, recording data onto the magnetic tape and / or reproducing data recorded on the magnetic tape can be performed, for example, by bringing the magnetic layer surface of the magnetic tape into contact with and sliding a magnetic head.

[0117] In one configuration, the magnetic tape is treated as a removable medium (a so-called interchangeable medium), and a magnetic tape cartridge containing the magnetic tape is inserted into and removed from a magnetic tape device. In another configuration, the magnetic tape is not treated as an interchangeable 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 housed within the magnetic tape device.

[0118] In the present invention and in this specification, “magnetic tape device” means a device capable of recording data onto a magnetic tape and playing back data recorded on a magnetic tape. Such a device is generally called a drive.

[0119] <Magnetic Head> The above magnetic tape device may include a magnetic head. The configuration of the magnetic head and the angle θ, which is the head tilt angle, are as previously explained with reference to Figures 5 to 7. If the magnetic head includes a playback element, a magnetoresistive (MR) element that can read information recorded on the magnetic tape with high sensitivity is preferred as the playback element. Various known MR elements (for example, GMR (Giant Magnetoresistive) elements, TMR (Tunnel Magnetoresistive) elements, etc.) can be used as the MR element. Hereinafter, the magnetic head that records data and / or plays back recorded data will also be called the "recording / playback head". The elements for recording data (recording element) and the elements for playing back data (playback element) will be collectively referred to as "magnetic head elements".

[0120] When recording data and / or playing back recorded data, tracking using a servo signal can be performed first. That is, by making the servo signal reading element follow a predetermined servo track, the magnetic head element can be controlled to pass over the target data track. The movement of the data track is performed by changing the servo track read by the servo signal reading element in the tape width direction. The recording / playback head can also record and / or play back data on other data bands. In this case, the servo signal reading element can be moved to a predetermined servo band using the UDIM information described above, and tracking for that servo band can be started.

[0121] Figure 9 shows an example of the arrangement of data bands and servo bands. In Figure 9, multiple servo bands 1 are arranged on the magnetic layer of the magnetic tape MT, sandwiched between guide bands 3. Multiple regions 2 sandwiched between two servo bands are the data bands. A servo pattern is a magnetized region, formed by magnetizing a specific region of the magnetic layer with a servo light head. The region magnetized by the servo light head (the position where the servo pattern is formed) is defined by the standard. For example, in the industry standard LTO Ultrium format tape, multiple servo patterns inclined with respect to the tape width direction are formed on the servo bands during magnetic tape manufacturing, as shown in Figure 10. More specifically, in Figure 10, the servo frame SF on the servo band 1 consists of a servo subframe 1 (SSF1) and a servo subframe 2 (SSF2). The servo subframe 1 consists of an A burst (indicated as A in Figure 10) and a B burst (indicated as B in Figure 10). A-burst consists of servo patterns A1 to A5, and B-burst consists of servo patterns B1 to B5. On the other hand, servo subframe 2 consists of C-burst (indicated as C in Figure 10) and D-burst (indicated as D in Figure 10). C-burst consists of servo patterns C1 to C4, and D-burst consists of servo patterns D1 to D4. These 18 servo patterns are arranged in sets of 5 and 4 in subframes arranged in a 5, 5, 4, 4 sequence, and are used to identify the servo frames. Figure 10 shows one servo frame for illustrative purposes. However, in reality, in the magnetic layer of a magnetic tape where timing-based servo tracking is performed, multiple servo frames are arranged in the direction of travel in each servo band. In Figure 10, the arrows indicate the direction of travel of the magnetic tape. For example, LTO Ultrium format tape typically has more than 5000 servo frames per meter of tape length in each servo band of the magnetic layer.

[0122] In one embodiment, 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 that the axis of the element array makes with respect to the width direction of the magnetic tape. The angle θ is as previously described. For example, by providing an angle adjustment unit in the recording / playback head unit of the magnetic head to adjust the angle of the magnetic head module, the angle θ can be variably adjusted while the magnetic tape is running. Such an angle adjustment unit may include, for example, a rotation mechanism for rotating the module. Known technologies can be applied to the angle adjustment unit.

[0123] Regarding the head tilt angle during magnetic tape travel, if the magnetic head contains multiple modules, the angle θ can be defined for a randomly selected module, as explained with reference to Figures 5 to 7. The angle θ at the start of magnetic tape travel is θ. ｉｎｉｔｉａｌ It can be set to 0° or greater than or equal to 0°. ｉｎｉｔｉａｌ The larger the angle θ, the greater the change in the effective distance between servo signal reading elements in response to the change in angle θ. This is preferable from the standpoint of adjustment capability to adjust the effective distance between servo signal reading elements in response to changes in the width direction of the magnetic tape. ｉｎｉｔｉａｌ The angle is preferably 1° or more, more preferably 5° or more, and even more preferably 10° or more. On the other hand, regarding the angle formed between the magnetic layer surface and the contact surface of the magnetic head when the magnetic tape is running and contacts the magnetic head (generally called the "lap angle"), keeping the deviation in the tape width direction small is effective in improving the uniformity of friction in the tape width direction caused by contact between the magnetic head and the magnetic tape during magnetic tape running. Furthermore, improving the uniformity of the friction in the tape width direction is desirable from the viewpoint of the magnetic head's position tracking ability and running stability. From the viewpoint of reducing the deviation of the lap angle in the tape width direction, θ ｉｎｉｔｉａｌ The angle is preferably 45° or less, more preferably 40° or less, and even more preferably 35° or less.

[0124] Regarding the change in angle θ during magnetic tape movement, for recording data onto magnetic tape and / or for playing back data recorded on magnetic tape, the angle θ of the magnetic head remains constant from the initial angle θ while the magnetic tape is moving in the magnetic tape drive. ｉｎｉｔｉａｌ When it changes from, the maximum change in angle θ during magnetic tape travel, Δθ, is calculated by the following formula: ｍａｘ and Δθ ｍｉｎ Among these, it is the larger value. The maximum value of the angle θ during magnetic tape travel is θ ｍａｘ The minimum value is θ. ｍｉｎ Therefore, "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

[0125] In one embodiment, Δθ can be greater than 0.000°, and from the viewpoint of adjustment capability to adjust the effective distance between servo signal reading elements in response to changes in the width direction of the magnetic tape, it is preferably 0.001° or more, and more preferably 0.010° ​​or more. Furthermore, from the viewpoint of ease of ensuring synchronization of recorded data and / or playback data between multiple magnetic head elements during data recording and / or playback, 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.

[0126] In the examples shown in Figures 6 and 7, the axis of the element array is tilted toward the direction in which the magnetic tape travels. However, the present invention is not limited to such examples. Embodiments in which the axis of the element array is tilted toward the direction opposite to the direction in which the magnetic tape travels are also included in the present invention.

[0127] θ is the head tilt angle at the start of magnetic tape playback. ｉｎｉｔｉａｌThis can be set by the control device of the magnetic tape device, etc. Regarding the head tilt angle during magnetic tape travel, Figure 11 is an explanatory diagram of the method for measuring the angle θ during magnetic tape travel. The angle θ during magnetic tape travel can be determined, for example, by the following method. When determining the angle θ during magnetic tape travel by the following method, the angle θ shall be varied within the range of 0 to 90° during magnetic tape travel. That is, if the axis of the element array is tilted toward the magnetic tape travel direction at the start of magnetic tape travel, the element array shall not be tilted during magnetic tape travel so that the axis of the element array is tilted toward the direction opposite to the magnetic tape travel direction at the start of magnetic tape travel, and if the axis of the element array is tilted toward the direction opposite to the magnetic tape travel direction at the start of magnetic tape travel, the element array shall not be tilted during magnetic tape travel so that the axis of the element array is tilted toward the magnetic tape travel direction at the start of magnetic tape travel. Measure the phase difference (i.e., time difference) ΔT of the playback signals of a pair of servo signal reading elements 1 and 2. ΔT can be measured by a measurement unit provided in the magnetic tape device. The configuration of such a measurement unit is well known. The distance L between the center of servo signal reading element 1 and the center of servo signal reading element 2 can be measured by an optical microscope or the like. When the magnetic tape is traveling at speed v, the distance between the centers of the two servo signal reading elements in the direction of magnetic tape travel is Lsinθ, and the relationship Lsinθ = v × ΔT holds. Therefore, the angle θ during magnetic tape travel can be calculated by the formula "θ = arcsin(vΔT / L)". Note that the right-hand figure of Figure 11 shows an example where the axis of the element array is tilted toward the direction of magnetic tape travel. In this example, the phase difference (i.e., time difference) ΔT between the phase of the playback signal of servo signal reading element 2 and the phase of the playback signal of servo signal reading element 1 is measured. If the axis of the element array is tilted in the direction opposite to the direction in which the magnetic tape travels, θ can be determined by the above method, except that ΔT is measured as the phase difference (i.e., time difference) between the phase of the regenerated signal of servo signal reading element 1 and the phase of the regenerated signal of servo signal reading element 2.Furthermore, the measurement pitch of the angle θ, that is, the measurement interval of the angle θ in the longitudinal direction of the tape, can be selected to be appropriate according to the frequency of tape width deformation in the longitudinal direction of the tape. For example, the measurement pitch can be set to, for example, 250 μm.

[0128] <Configuration of the Magnetic Tape Device> The magnetic tape device 10 shown in Figure 12 controls the recording and playback head unit 12 by command from the control device 11 to record and play back data on the magnetic tape MT. The magnetic tape device 10 has a configuration that allows detection and adjustment of tension applied in the longitudinal direction of the magnetic tape from the spindle motors 17A, 17B and their drive devices 18A, 18B that control the rotation of the magnetic tape cartridge reel and the take-up reel. The magnetic tape device 10 has a configuration that allows loading of a magnetic tape cartridge 13. The magnetic tape device 10 has a cartridge memory read / write device 14 that can read from and write to the cartridge memory 131 in the magnetic tape cartridge 13. From the magnetic tape cartridge 13 mounted in the magnetic tape device 10, the end of the magnetic tape MT or the leader pin is pulled out by an automatic loading mechanism or manually, and the magnetic layer surface of the magnetic tape MT passes over the recording / playback head of the recording / playback head unit 12 through guide rollers 15A and 15B so that it is in contact with the surface of the recording / playback head, and the magnetic tape MT is wound onto the take-up reel 16. The rotation and torque of the spindle motors 17A and 17B are controlled by signals from the control device 11, and the magnetic tape MT runs at an arbitrary speed and tension. A servo pattern pre-formed on the magnetic tape can be used to control the tape speed and the head tilt angle. A tension detection mechanism may be provided between the magnetic tape cartridge 13 and the take-up reel 16 for tension detection. In addition to control by the spindle motors 17A and 17B, tension control may also be performed using the guide rollers 15A and 15B. The cartridge memory read / write device 14 is configured to read and write information to the cartridge memory 131 in response to commands from the control device 11. 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.

[0129] The control device 11 includes, for example, a control unit, a storage unit, a communication unit, and the like.

[0130] The recording / playback head unit 12 consists of, for example, a recording / playback head, a servo tracking actuator for adjusting the position of the recording / playback head in the track width direction, a recording / playback amplifier 19, and a connector cable for connecting to the control device 11. The recording / playback head consists of, for example, a recording element for recording data on magnetic tape, a playback element for reproducing data on magnetic tape, and a servo signal reading element for reading servo signals recorded on magnetic tape. Within a single magnetic head, for example, one or more recording elements, playback elements, and servo signal reading elements are mounted. Alternatively, each element may be separately contained in multiple magnetic heads corresponding to the direction in which the magnetic tape travels.

[0131] The recording / playback head unit 12 is configured to record data onto the magnetic tape MT in response to commands from the control device 11. It is also configured to play back data recorded on the magnetic tape MT in response to commands from the control device 11.

[0132] The control device 11 has a mechanism to determine the running position of the magnetic tape MT from the servo signals read from the servo bands when the magnetic tape MT is running, and to control the servo tracking actuator so that the recording element and / or playback element are positioned at the target running position (track position). This track position control is performed, for example, by feedback control. The control device 11 has a mechanism to determine the servo band spacing from the servo signals read from two adjacent servo bands when the magnetic tape MT is running. The control device 11 can store the determined servo band spacing information in its internal storage unit, cartridge memory 131, or external connected equipment. Furthermore, the control device 11 can change the head tilt angle according to the dimensional information in the width direction of the running magnetic tape. This makes it possible to make the effective distance between servo signal reading elements close to or match the servo band spacing. The above dimensional information can be obtained using a servo pattern pre-formed on the magnetic tape. For example, in this way, while the magnetic tape is running within the magnetic tape device, the angle θ that the axis of the element array makes with respect to the width direction of the magnetic tape can be changed according to the width direction dimensional information of the magnetic tape acquired during the running process. The head tilt angle can be adjusted, for example, by feedback control. Alternatively, the head tilt angle can also be adjusted, for example, by the method described in Japanese Patent Publication No. 2016-524774 (Patent Document 1) or US2019 / 0164573A1 (Patent Document 2).

[0133] The present invention will be described below based on examples. However, the present invention is not limited to the embodiments shown in the examples. In the following, "parts" and "%" refer to "parts by mass" and "mass%", respectively. In addition, the processes and evaluations described below were carried out in an environment of 23°C ± 1°C unless otherwise specified. In the following, "eq" refers to equivalent weight and is a unit that cannot be converted to SI units.

[0134] [Abrasive Solution] 100.0 parts of the abrasive (alumina powder) shown in Table 1, plus the amount of 2,3-dihydroxynaphthalene (manufactured by Tokyo Chemical Industry Co., Ltd.) shown in Table 1, and SO as a polar group. ３31.3 parts of a 32% solution of a polyester polyurethane resin containing sodium groups (UR-4800, manufactured by Toyobo Co., Ltd. (polar group content: 80 meq / kg)) (solvent: mixed solvent of methyl ethyl ketone and toluene) and 570.0 parts of a mixture of methyl ethyl ketone and cyclohexanone in a 1:1 mass ratio were mixed and dispersed in the presence of zirconia beads (bead diameter: 0.1 mm) using a paint shaker for the time shown in Table 1 (bead dispersion time). After dispersion, the dispersion and beads were separated using a mesh and the resulting dispersion was subjected to centrifugation. Centrifugation was performed using a Hitachi Koki CS150GXL centrifuge (rotor: Hitachi Koki S100AT6) at the rotation speed (rpm: rotation per minute) shown in Table 1 for the time shown in Table 1 (centrifugation time). This centrifugation process causes relatively large particles to settle and relatively small particles to disperse in the supernatant. The supernatant was then collected by decantation. In the examples and comparative examples described later, this collected liquid was used as the abrasive solution. Before using it to prepare the magnetic layer forming composition, the abrasive solution was subjected to ultrasonic dispersion treatment for 0.5 minutes using a batch-type ultrasonic device (20 kHz, 300 W).

[0135]

[0136] [Ferromagnetic Powder] In Table 2, "BaFe" refers to hexagonal barium ferrite powder (coercivity Hc: 196 kA / m, average particle size (average plate diameter) 24 nm).

[0137] In Table 2, "SrFe1" is hexagonal strontium ferrite powder prepared by the following method: SrCO ３ 1707g, H ３ BO ３ 687g, Fe ２ O ３ 1120g of Al(OH) ３ 45g of BaCO ３ 24g of CaCO2 ３ 13 g of Nd ２ O ３235 g was weighed and mixed in a mixer to obtain a raw material mixture. The obtained raw material mixture was melted in a platinum crucible at a melting temperature of 1390°C. While stirring the molten material, the outlet at the bottom of the platinum crucible was heated, and the molten material was dispensed in a rod shape at a rate of approximately 6 g / second. The dispensed material was rolled and rapidly cooled with water-cooled twin rollers to produce an amorphous material. 280 g of the prepared amorphous material was placed in an electric furnace and heated to 635°C (crystallization temperature) at a heating rate of 3.5°C / min. It was held at this temperature for 5 hours to precipitate (crystallize) hexagonal strontium ferrite particles. Next, the crystalline material obtained above, containing the hexagonal strontium ferrite particles, was coarsely ground in a mortar. 1000 g of zirconia beads with a particle size of 1 mm and 800 ml of a 1% aqueous acetic acid solution were added to a glass bottle containing this material, and the mixture was dispersed in a paint shaker for 3 hours. After that, the resulting dispersion was separated from the beads and placed in a stainless steel beaker. The dispersion was allowed to stand at a liquid temperature of 100°C for 3 hours to dissolve the glass components. Then, the material was precipitated using a centrifuge, washed by repeated decantation, and dried in a heating furnace at a temperature of 110°C for 6 hours to obtain hexagonal strontium ferrite powder. The average particle size of the hexagonal strontium ferrite powder obtained was 18 nm, and the activation volume was 902 nm. ３ The anisotropy constant Ku is 2.2 × 10⁻⁶. ５ J / m ３ , mass magnetization σs is 49A・m ２The result was / kg. 12 mg of sample powder was taken from the hexagonal strontium ferrite powder obtained above, and elemental analysis of the filtrate obtained by partially dissolving this sample powder under the previously exemplified dissolution conditions was performed using an ICP analyzer to determine the surface layer content of neodymium atoms. Separately, 12 mg of sample powder was taken from the hexagonal strontium ferrite powder obtained above, and elemental analysis of the filtrate obtained by completely dissolving this sample powder under the previously exemplified dissolution conditions was performed using an ICP analyzer to determine the bulk content of neodymium atoms. The neodymium atom content (bulk content) relative to 100 atomic percent of iron atoms in the hexagonal strontium ferrite powder obtained above was 2.9 atomic percent. The surface layer content of neodymium atoms was 8.0 atomic percent. The ratio of surface layer content to bulk content, "surface layer content / bulk content", was 2.8, confirming that neodymium atoms are unevenly distributed on the surface of the particles. The hexagonal ferrite crystal structure of the powder obtained above was confirmed by scanning CuKα rays 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 showed a magnetoplanbite-type (M-type) hexagonal ferrite crystal structure. Furthermore, the crystal phase detected by X-ray diffraction analysis was a single phase of the magnetoplanbite type. PANical X'Pert Pro diffractometer, PIXcel detector. Soller slits for incident and diffracted beams: 0.017 radians. Fixed angle of dispersion slit: 1 / 4 degree. Mask: 10 mm. Anti-scattering slit: 1 / 4 degree. Measurement mode: continuous. Measurement time per step: 3 seconds. Measurement speed: 0.017 degrees per second. Measurement step: 0.05 degrees.

[0138] In Table 2, "SrFe2" is hexagonal strontium ferrite powder prepared by the following method: SrCO ３ 1725g, H ３ BO ３ 666g, Fe ２ O ３ 1332g of Al(OH) ３ 52g of CaCO2 ３ 34g of BaCO ３141 g was weighed and mixed in a mixer to obtain a raw material mixture. The obtained raw material mixture was melted in a platinum crucible at a melting temperature of 1380°C. While stirring the molten material, the outlet at the bottom of the platinum crucible was heated, and the molten material was dispensed in a rod shape at approximately 6 g / second. The dispensed material was rolled and rapidly cooled with water-cooled twin rollers to produce an amorphous material. 280 g of the obtained amorphous material was placed in an electric furnace, heated to 645°C (crystallization temperature), and held at the same temperature for 5 hours to precipitate (crystallize) hexagonal strontium ferrite particles. Next, the crystalline material obtained above, containing the hexagonal strontium ferrite particles, was coarsely ground in a mortar, and 1000 g of 1 mm particle size zirconia beads and 800 ml of 1% acetic acid aqueous solution were added to a glass bottle containing this material and dispersed in a paint shaker for 3 hours. After that, the obtained dispersion was separated from the beads and placed in a stainless steel beaker. The dispersion was allowed to stand at 100°C for 3 hours to dissolve the glass components. The mixture was then precipitated using a centrifuge, washed by repeated decantation, and dried in a heating furnace at 110°C for 6 hours to obtain hexagonal strontium ferrite powder. The average particle size of the obtained hexagonal strontium ferrite powder was 19 nm, and the activation volume was 1102 nm. ３ The anisotropy constant Ku is 2.0 × 10⁻⁶. ５ J / m ３ , mass magnetization σs is 50A・m ２ It was / kg.

[0139] In Table 2, "ε-iron oxide" refers to ε-iron oxide powder prepared by the following method: 8.3 g of iron(III) nitrate nonahydrate, 1.3 g of gallium(III) nitrate octahydrate, 190 mg of cobalt(II) nitrate hexahydrate, 150 mg of titanium(IV) sulfate, and 1.5 g of polyvinylpyrrolidone (PVP) were dissolved in 90 g of pure water. While stirring with a magnetic stirrer, 4.0 g of a 25% aqueous ammonia solution was added in an air atmosphere at an ambient temperature of 25°C, and the mixture was stirred for 2 hours at the same ambient temperature of 25°C. To the resulting solution, a citric acid solution obtained by dissolving 1 g of citric acid in 9 g of pure water was added, and the mixture was stirred for 1 hour. After stirring, the precipitated powder was collected by centrifugation, washed with pure water, and dried in a heating furnace at an ambient temperature of 80°C. 800 g of pure water was added to the dried powder, and the powder was dispersed in water again to obtain a dispersion. The obtained dispersion was heated to 50°C, and 40 g of a 25% ammonia aqueous solution was added dropwise while stirring. After stirring for 1 hour while maintaining the temperature at 50°C, 14 mL of tetraethoxysilane (TEOS) was added dropwise, and the mixture was stirred for 24 hours. 50 g of ammonium sulfate was added to the resulting reaction solution, and the precipitated powder was collected by centrifugation, washed with pure water, and dried in a heating furnace at 80°C for 24 hours to obtain a ferromagnetic powder precursor. The obtained ferromagnetic powder precursor was loaded into a heating furnace at 1000°C under an atmospheric atmosphere and subjected to a heat treatment for 4 hours. The heat-treated ferromagnetic powder precursor was added to a 4 mol / L sodium hydroxide (NaOH) aqueous solution, and stirred for 24 hours while maintaining the temperature at 70°C to remove silicic acid compounds, which are impurities, from the heat-treated ferromagnetic powder precursor. Subsequently, the ferromagnetic powder from which the silicic acid compounds had been removed was collected by centrifugation, washed with pure water, and obtained ferromagnetic powder. The composition of the obtained ferromagnetic powder was confirmed by inductively coupled plasma emission spectroscopy (ICP-OES), and it was found to be Ga, Co, and Ti-substituted ε-iron oxide (ε-Ga ０．２８ Co ０．０５ Ti ０．０５ Fe １．６２ O ３Furthermore, X-ray diffraction analysis was performed under the same conditions as those previously described for SrFe1, and from the peaks of the X-ray diffraction pattern, it was confirmed that the obtained ferromagnetic powder had a single-phase crystalline structure of the ε phase (crystalline structure of ε-iron oxide), without the crystalline structures of the α and γ phases. The average particle size of the obtained ε-iron oxide powder was 12 nm, and the activation volume was 746 nm. ３ The anisotropy constant Ku is 1.2 × 10⁻⁶. ５ J / m ３ , mass magnetization σs is 16A・m ２ It was / kg.

[0140] The activation volume and anisotropy constant Ku of the hexagonal strontium ferrite powder and ε-iron oxide powder described above were obtained for each ferromagnetic powder using a vibrating sample magnetometer (manufactured by Toei Kogyo Co., Ltd.) and the method described above. The mass magnetization σs was measured using a vibrating sample magnetometer (manufactured by Toei Kogyo Co., Ltd.) at a magnetic field strength of 15 kOe.

[0141] [Non-magnetic powder for the magnetic layer] In the examples and comparative examples in Table 2 where the "Average plate diameter of non-magnetic powder" and "Average plate thickness of non-magnetic powder" are listed in the "Magnetic layer" column, the magnetic layer was formed using non-magnetic powder composed of plate-shaped particles with the average plate diameter and average plate thickness values ​​listed in Table 2. These non-magnetic powders were prepared by the following methods: A metal hydroxide and water were mixed in a sealed container (mixing time and molar concentration of the metal hydroxide aqueous solution: see Table 2). The mixed aqueous solution was heated for 10 days in an autoclave set to an internal temperature of 270°C. After heating, the generated particles were recovered by centrifugation. Non-magnetic powder was thus prepared. Alumina powder was prepared by using aluminum hydroxide as the metal hydroxide, zirconia powder was prepared by using zirconium hydroxide, and ceria powder was prepared by using cerium hydroxide.

[0142] In Table 2, "CS" listed under "Type of non-magnetic powder" in the "Magnetic layer" column is an abbreviation for colloidal silica. The particle shape of the colloidal silica was spherical or elliptical.

[0143] In Table 2, the "Average plate diameter of non-magnetic powder," "Average plate thickness of non-magnetic powder," and "Average particle size of non-magnetic powder" listed in the "Magnetic Layer" column were measured using a Hitachi H-9000 transmission electron microscope and Carl Zeiss KS-400 image analysis software, and the values ​​were obtained as described above.

[0144] [Example 1] (1) Formulation of composition for forming a magnetic layer (magnetic liquid) Ferromagnetic powder (see Table 2): 100.0 parts SO ３ Na group-containing polyurethane resin: 14.0 parts; weight-average molecular weight: 70,000, SO ３ Na group: 0.4 meq / g Cyclohexanone: 150 parts Methyl ethyl ketone: 150 parts (Abrasive solution) The abrasive solution prepared by the method described above is used in an amount such that the abrasive content in the abrasive solution is 0.80 parts per 100.0 parts of ferromagnetic powder. (Non-magnetic powder) Non-magnetic powder listed in Table 2: 0.2 parts (Other components) Stearic acid: 2.0 parts Butyl stearate: 10.0 parts Polyisocyanate (Coronate, manufactured by Nippon Polyurethane Co., Ltd.): 2.5 parts Cyclohexanone: 200.0 parts Methyl ethyl ketone: 200.0 parts

[0145] (2) Formulation of composition for forming a non-magnetic layer α-iron oxide powder (average particle volume: see Table 2): 100.0 parts Carbon black (average particle size: 20 nm, pH: see Table 2): 25.0 parts SO ３ Na group-containing polyurethane resin: 18 parts, weight-average molecular weight: 70,000, SO ３ Na group: 0.2 meq / g Stearic acid: 1.0 part Cyclohexanone: 300.0 parts Methyl ethyl ketone: 300.0 parts

[0146] (3) Formulation of composition for backcoat layer formation Carbon black: 100.0 parts Cabot BP-800, average particle size: 17 nm SO ３ Na group-containing polyurethane resin (SO ３ Na group: 70eq / ton): 20.0 parts OSO ３ K-group-containing polyvinyl chloride resin (OSO ３K group: 70 eq / ton): 30.0 parts Cyclohexanone: 140.0 parts Methyl ethyl ketone: 170.0 parts Butyl stearate: 2.0 parts Stearamide: 0.1 parts

[0147] (4) Preparation of each layer-forming composition The above components of the magnetic liquid were dispersed for 24 hours using a batch-type vertical sand mill to prepare the magnetic liquid. Zirconia beads with a bead diameter of 0.5 mm were used as the dispersion beads. The magnetic liquid and abrasive liquid were mixed with the above non-magnetic powder and other components, and then dispersed using a batch-type ultrasonic device (20 kHz, 300 W) (dispersion time: see Table 2). After that, the mixture was filtered using a filter with a pore size of 0.5 μm to prepare the magnetic layer-forming composition. For the non-magnetic layer-forming composition, the above components were dispersed for 24 hours using a batch-type vertical sand mill. Zirconia beads with a bead diameter of 0.1 mm were used as the dispersion beads. The obtained dispersion was filtered using a filter with a pore size of 0.5 μm to prepare the non-magnetic layer-forming composition. For the back coat layer-forming composition, the above components were kneaded in a continuous kneader and then dispersed using a sand mill. To the obtained dispersion, 40.0 parts of polyisocyanate (Coronate L, manufactured by Nippon Polyurethane Industries Co., Ltd.) and 1000.0 parts of methyl ethyl ketone were added, and the mixture was filtered using a filter with a pore size of 1 μm to prepare a composition for forming a backcoat layer.

[0148] (5) Manufacturing of Magnetic Tape A magnetic tape was manufactured according to the manufacturing process shown in Figure 8. The details are as follows: A polyethylene naphthalate support with a thickness of 3.7 μm was fed from the feeding section, and a non-magnetic layer forming composition was applied to one surface in the first coating section so that the thickness after drying would be 0.7 μm to form a coating layer. While the formed coating layer was still wet, it was passed through a cooling zone adjusted to an ambient temperature of 0°C for a cooling process (cooling zone stay time: 1 second), and then passed through a first heat treatment zone with a drying temperature (ambient temperature, the same applies hereafter) of 105°C for a heat drying process to form a non-magnetic layer. After that, the magnetic layer forming composition prepared above was applied to the non-magnetic layer in the second coating section so that the thickness after drying would be 0.1 μm to form a coating layer. While this coating layer was still wet, a magnetic field with a magnetic field strength of 0.5 T was applied perpendicularly to the surface of the coating layer of the magnetic layer forming composition in the orientation zone for a vertical orientation treatment, and then dried in the second heat treatment zone with a drying temperature of 105°C. Subsequently, in the 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 non-magnetic and magnetic layers were formed, so that the thickness after drying was 0.3 μm, to form a coating layer. The formed coating layer was then dried in the third heat treatment zone at a drying temperature of 105°C. After that, calendering (surface smoothing treatment) was performed using a calendering roll consisting only of metal rolls under the calendering conditions shown in Table 2. Then, heat treatment was performed for 36 hours in an environment with an ambient temperature of 70°C. After the heat treatment, magnetic tape was produced by slitting to a width of 1 / 2 inch. By demagnetizing the magnetic layer of the fabricated magnetic tape and recording servo signals on the magnetic layer using a commercially available servo writer, a magnetic tape was obtained having data bands, servo bands, and guide bands arranged in accordance with the LTO (Linear Tape-Open) Ultrium format, and having a servo pattern (timing-based servo pattern) on the servo band in an arrangement and shape 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 is 5, and the total number of data bands is 4. A magnetic tape (960 m in length) on which the servo signals were recorded was then fabricated.

[0149] [Examples 2-16, Comparative Examples 1-11] Magnetic tapes were obtained using the method described for Example 1, except that the items shown in Table 2 were changed as shown in Table 2.

[0150] For each example and comparative example, four magnetic tapes with a length of 960 m were prepared and used for the evaluations described in (1) to (4) below.

[0151] [Evaluation Method] (1) Spd and width σ of Spd on the magnetic layer surface The following conditions were adopted as AFM measurement conditions, and the Spd and width σ of Spd on the magnetic layer surface of the magnetic tape were determined by the method described above. Spd was determined using AFM data analysis software (MountainsSPIP) provided by Digitalsurf, with the F-operation set to the total least squares surface and the Spd at a threshold of 2%. An AFM (BRUKER Nanoscope 5) was used in peak force tapping mode to measure a 40 μm × 40 μm area on the surface of the magnetic layer of the magnetic tape. A BRUKER SCANASYST-AIR probe will be used, with a resolution of 512 pixels x 512 pixels, and a scan speed of 512 seconds to measure one screen (512 pixels x 512 pixels).

[0152] (2) Nonlinear component of tape width deformation For each magnetic tape in the examples and comparative examples, the nonlinear component of tape width deformation that occurs after 10 days of storage in an environment of 60°C and 20% relative humidity was measured using the method described above.

[0153] (3) Total thickness of magnetic tape (tape thickness) Ten tape samples (5 cm in length) were cut from any part of each magnetic tape in the examples and comparative examples, and the thickness was measured by stacking these tape samples. The thickness was measured using a digital thickness meter consisting of a MARM Millimar 1240 compact amplifier and a Millimar 1301 inductive probe. The value obtained by dividing the measured thickness by 10 (thickness per tape sample) was defined as the tape thickness. For all magnetic tapes, the tape thickness was 4.8 μm. The thickness of the magnetic layer, non-magnetic layer, and back coat layer of each magnetic tape in the examples and comparative examples was confirmed by cross-sectional observation as described above, and it was confirmed that the respective thicknesses were as described above.

[0154] (4) Recording and Playback Performance The recording and playback performance of each magnetic tape in the examples and comparative examples was evaluated by the following method. As the magnetic head, a magnetic head was used that included a playback module having an element array with 10 or more channels of playback elements with a playback element width of 0.2 μm or less between a pair of servo signal reading elements, and a recording module having an element array with 10 or more channels of recording elements with a recording element width of 1.5 times or more the playback element width between a pair of servo signal reading elements. In the above element array, the distance between two adjacent elements (i.e., two adjacent playback elements and two adjacent recording elements) in the head width direction is 40 μm or more. The environment in which data was recorded and played back was set to a temperature of 20 to 25°C and a relative humidity of 40 to 60%. After leaving the magnetic tape device, with the magnetic tape and magnetic head attached to a tape transport system (reel tester), in this environment for 24 hours or more, data was recorded and played back. The recording and playback amplifier attached to the tape transport system of the magnetic tape device was the recording and playback amplifier described earlier for the measurement of the nonlinear component of tape width deformation. During data recording and playback, the servo-following and dynamic track position control (changes in head tilt angle) described above were implemented. Data recording and playback were performed in detail as follows: The magnetic tape was run at a constant speed of 5 m / s while the signal was recorded by the recording element. The bit sequence to be recorded was a 255-bit pseudo-random bit sequence (PRBS: Pseudo Random Bit Sequence) generated according to the generating polynomial x^8 + x^6 + x^5 + x^4 + 1. The symbol "^" represents exponentiation. The linear recording density was set to 600 kbpi. The unit "kbpi" is the unit of linear recording density (cannot be converted to the SI unit system). Single recording was performed on three or more tracks such that the difference between adjacent tracks (PES1 + PES2) / 2 was 1.5 times the playback track width. The magnetization pattern recorded on the magnetic tape is reproduced by the next regeneration element (i.e., the regeneration element with the same channel number), and the signal is amplified by the regeneration amplifier.The regenerated signal is processed by 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 regenerated and decoded bit sequences are compared bit by bit, and if the two are different bits, it is counted as a 1-bit error. The data is compared over 10 Mbits, and the cumulative error bit count divided by 10 Mbits is defined as the bit error rate. For the regenerated signal immediately after recording, it was confirmed that the bit error rate was 1 / 1000 or less for all channels. Next, the magnetic tape, wound on the reel tester described above, was stored for 10 days in an environment of 60°C and 20% relative humidity. After the above storage, the magnetic tape was removed from the storage environment and mounted in the same magnetic tape drive used before storage. It was then placed in an environment with a temperature of 20-25°C and a relative humidity of 40-60% for at least 24 hours. Under these conditions, the data tracks recorded before storage were played back (no new recording was performed). Playback was performed only on data tracks with data tracks recorded on both sides. The bit error rate of all channels was calculated, and channels with a bit error rate of 1 / 100 or more were considered defective channels. The recording and playback performance was evaluated according to the following evaluation 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.

[0155] The results are shown in Table 2 (Tables 2-1 to 2-5).

[0156]

[0157]

[0158]

[0159]

[0160]

[0161] As shown in Table 2, the magnetic tape of the example showed superior recording and playback performance compared to the magnetic tape of the comparative example after being stored in an accelerated environment equivalent to long-term storage. From these results, it can be confirmed that the magnetic tape of the example contributed to improving the operational stability of the drive (magnetic tape device).

[0162] A magnetic tape was manufactured using the same method as described in Example 1, except that vertical orientation processing was not performed during the manufacturing of the magnetic tape. A sample piece was cut from the above magnetic tape. The vertical angular ratio of this sample piece was determined using a Tamagawa Seisakusho TM-TRVSM5050-SMSL type vibrating sample magnetometer and the method described above, and was found to be 0.55. The vertical angular ratio was similarly determined for a sample piece cut from the magnetic tape of Example 1, and was found to be 0.65.

[0163] The two magnetic tapes described above were each mounted on a 1 / 2-inch reel tester, and their electromagnetic conversion characteristics (SNR: Signal-to-Noise Ratio) were evaluated using the following method. As a result, the magnetic tape of Example 1 obtained an SNR value 4 dB higher than the magnetic tape manufactured without vertical orientation treatment. Recording and playback were performed in 10 passes under a tension of 0.7 N (Newtons) in the longitudinal direction of the magnetic tape in an environment of 23°C and 50% relative humidity. The relative speed between the magnetic tape and the magnetic head was set to 6 m / s, and recording was performed using a MIG (Metal-in-gap) head (gap length 0.15 μm, track width 1.0 μm) as the recording head, with the recording current set to the optimal recording current for each magnetic tape. Playback was performed using a GMR (Giant-magnetoresistive) head (element thickness 15 nm, shielding gap 0.1 μm, playback element width 0.8 μm) as the playback head. The head tilt angle was set to 0°. A signal with a linear recording density of 300 kfci was recorded, and the playback signal was measured using a spectrum analyzer manufactured by Shibasoku. The unit kfci is the unit of linear recording density (cannot be converted to the SI unit system). The signal used was a portion of the signal that had stabilized sufficiently after the magnetic tape started running.

[0164] One aspect of the present invention is useful in the technical field of various data storage technologies.

Claims

1. A magnetic tape comprising a non-magnetic support and a magnetic layer containing ferromagnetic powder, wherein the vertex density Spd of the protrusions on the surface of the magnetic layer as defined in ISO 25178 is 3.5 (1 / μm). ２ ) or more 5.3 (1 / μm ２ ) or less, and the standard deviation σ of Spd in the width direction of the surface of the magnetic layer is 2.3 (1 / μm ２ ) Magnetic tape as follows.

2. The standard deviation σ of Spd is 2.0 (1 / μm). ２ The magnetic tape according to claim 1, wherein the following conditions apply.

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

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

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

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

7. The magnetic tape according to claim 4, wherein the thickness of the non-magnetic layer is 0.1 μm or more and 0.7 μm or less.

8. The magnetic tape according to claim 1, further comprising a back coat layer containing non-magnetic powder on the surface side of the non-magnetic support opposite to the surface side having the magnetic layer.

9. The magnetic tape according to claim 1, wherein the tape thickness is 5.2 μm or less.

10. The magnetic tape according to claim 1, wherein the tape thickness is 5.0 μm or less.

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

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

13. The standard deviation σ of the Spd is 2.0 (1 / μm ２ ), and the magnetic layer further includes non-magnetic powder having an average plate diameter of 50 nm or more and 1000 nm or less and an average plate thickness of 12 nm or less. Further, between the non-magnetic support and the magnetic layer, there is a non-magnetic layer containing non-magnetic powder. The non-magnetic powder of the non-magnetic layer includes Fe-based inorganic oxide powder having an average particle volume of 2.0×10 －６ μm ３ or less and carbon black having a pH of 9.0 or less. The thickness of the non-magnetic layer is 0.1 μm or more and 0.7 μm or less. On the surface side of the non-magnetic support opposite to the surface side having the magnetic layer, there is a back coat layer containing non-magnetic powder. The tape thickness is 5.0 μm or less, and the perpendicular squareness ratio of the magnetic tape is 0.65 or more. The magnetic tape according to claim 1.

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

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

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

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