Magnetic tape, magnetic tape cartridge, and magnetic tape device

Abstract

Provided is a magnetic tape comprising a non-magnetic support body and a magnetic layer containing ferromagnetic powder, wherein the magnetic layer has three or more servo bands, and the maximum value of the difference between adjacent tape thicknesses measured at 0.6 mm intervals in the width direction of the magnetic tape is 12 nm or less.

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 include tape-type and disk-type media. For data storage applications such as data backup and archiving, tape-type magnetic recording media, i.e., magnetic tapes, are primarily used (see, for example, Patent Documents 1 to 4).

[0003] Japanese Patent Publication No. 2016-524774, US2019 / 0164573A1, Japanese Unexamined Patent Publication No. 2023-017433, Japanese Unexamined Patent Publication No. 2023-156736

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

[0005] To improve the accuracy with which the magnetic head follows the data band of the magnetic tape during recording and / or playback as described above, a system that uses servo signals to perform head tracking (hereinafter referred to as the "servo system") has been put into practical use. Furthermore, it has been proposed to use servo signals to acquire dimensional information (contraction, expansion, etc.) in the width direction of the magnetic tape while it is running, and to change the angle at which the axial direction of the magnetic head module is tilted relative to the width direction of the magnetic tape (hereinafter also referred to as the "head tilt angle") according to the acquired dimensional information (see Patent Documents 1 to 3, for example, paragraphs 0059 to 0067 and paragraph 0084 of Patent Document 1). If, during recording or playback, the magnetic head for recording or playing back data is misaligned from the target track position due to deformation in the width direction of the magnetic tape (called "off-track"), phenomena such as overwriting of recorded data and playback failures may occur. The inventors believe that changing the head tilt angle as described above is one means of suppressing off-track by dynamically controlling the track position.

[0006] In view of the above, one aspect of the present invention aims to provide a magnetic tape that can record and / or reproduce data well when the head tilt angle is changed while the magnetic tape is running.

[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 magnetic layer has three or more servo bands, and the maximum difference between adjacent tape thicknesses measured at 0.6 mm intervals in the width direction of the magnetic tape is 12 nm or less. [2] The magnetic tape according to [1], further comprising a non-magnetic layer containing non-magnetic powder between the non-magnetic support and the magnetic layer. [3] The magnetic tape according to [1] or [2], 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. [4] The magnetic tape according to any one of [1] to [3], wherein the non-magnetic support is a polyethylene naphthalate support. [5] The magnetic tape according to any one of [1] to [3], wherein the non-magnetic support is a polyethylene terephthalate support. [6] The magnetic tape according to any one of [1] to [3], wherein the non-magnetic support is an aromatic polyamide support. [7] The magnetic tape according to any one of [1] to [6], wherein the tape thickness of the magnetic tape is 5.6 μm or less. [8] The magnetic tape according to any one of [1] to [7], wherein the tape thickness of the magnetic tape is 5.3 μm or less. [9] The magnetic tape according to any one of [1] to [8], wherein the vertical angular ratio of the magnetic tape is 0.60 or more.

[10] The magnetic tape according to any one of [1] to [9], further comprising a non-magnetic layer containing non-magnetic powder between the non-magnetic support and the magnetic layer, 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, wherein the non-magnetic support is a polyethylene naphthalate support, a polyethylene terephthalate support, or an aromatic polyamide support, the tape thickness of the magnetic tape is 5.6 μm or less, and the vertical angular ratio of the magnetic tape is 0.60 or more.

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

[10] . A magnetic tape device including a magnetic tape as described in any of [1] to

[10] .

[13] The magnetic tape device according to

[12] , further comprising a magnetic head, wherein the magnetic head has a module including an element array having a plurality of magnetic head elements between a pair of servo signal reading elements, and 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.

[0008] According to one aspect of the present invention, it is possible to provide a magnetic tape that can record and / or reproduce data well when the head tilt angle is changed while the magnetic tape is running, a magnetic tape cartridge including this magnetic tape, and a magnetic tape device.

[0009] This is a schematic diagram showing a part of 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 movement in a magnetic tape device. This is an explanatory diagram regarding the change in angle θ during magnetic tape movement. This shows an example of the arrangement of data bands and servo bands. This shows an example of the arrangement of servo patterns for LTO Ultrium format tape. This is a schematic explanatory diagram of various deformations occurring in the width direction of the magnetic tape. This is a schematic diagram of a data track (before deformation) formed in a certain micro region. This is an explanatory diagram of the position of the magnetic head element in the magnetic head module that reads the data track shown in Figure 7. This shows the position of the data track shown in Figure 7 and the position of the module's magnetic head element shown in Figure 8 together. This is a schematic diagram showing the state in which the position of the data track shown in Figure 7 has changed due to deformation. This shows a schematic diagram of the state in which dynamic track position is controlled by changing the head tilt angle. This shows the position of the data track (after deformation) shown in Figure 10 and the position of the module's magnetic head element (after deformation) shown in Figure 11 together. This is an explanatory diagram of the formula for calculating the linear deformation amount ΔL. This is the nonlinear deformation amount ΔNL ｉThis is an explanatory diagram of the calculation formula. It shows an image of the evaluation data recording. An example of a track profile is shown. An example of a graph relating to the nonlinear component of the servo band spacing before deformation is shown. This is a graph showing an example of the nonlinear component before and after deformation. This is a graph showing NL-TDS. 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. The magnetic layer has three or more servo bands, and the maximum value of the difference in adjacent tape thickness measured at 0.6 mm intervals in the width direction of the magnetic tape (hereinafter also simply referred to as "maximum value of the difference in adjacent thickness") is 12 nm or less.

[0011] <Maximum Difference in Adjacent Thickness> In the present invention and this specification, the maximum difference between the thickness (total thickness) of the magnetic tape and the adjacent thickness is determined by the following method. Before measurement, the magnetic tape or magnetic tape cartridge containing the magnetic tape is left in an environment with a temperature of 20 to 25°C and a relative humidity of 40 to 60% for at least 5 days to allow it to acclimate to the environment. Then, in the same environment, one tape sample (5 cm in length) is cut from three or more locations (randomly selected) that are different in the longitudinal direction of the magnetic tape. Thus, three or more tape samples are cut. At a randomly selected position on each tape sample, one randomly selected end of the tape sample in the width direction is set as the reference position (0 mm), and the tape thickness is measured at measurement points every 0.6 mm toward the other end in the width direction. For example, in the case of a tape sample cut from a 1 / 2-inch (12.7 mm) magnetic tape, the tape thickness is measured at measurement points (21 measurement points in total) at 0.6 mm, 1.2 mm, 1.8 mm, 2.4 mm, 3.0 mm, 3.6 mm, 4.2 mm, 4.8 mm, 5.4 mm, 6.0 mm, 6.6 mm, 7.2 mm, 7.8 mm, 8.4 mm, 9.0 mm, 9.6 mm, 10.2 mm, 10.8 mm, 11.4 mm, 12.0 mm, and 12.6 mm from the reference position. The arithmetic mean of the measurements obtained by performing the above operation for all the tape samples cut above is taken as the tape thickness of the magnetic tape being measured. The difference between the measured tape thickness values ​​at two adjacent measurement points in the width direction is calculated for all measurement points where measurements were taken. The difference is calculated such that it is zero if the measured tape thickness values ​​at two adjacent measurement points are the same, and a positive value if they are different. The maximum value among all the differences obtained in this way is defined as the "maximum difference in adjacent thicknesses" of the magnetic tape being measured. A known measuring instrument capable of measuring thickness on the order of 5 nm can be used to measure the tape thickness. Conventional technologies such as the one described in Patent Document 4 (Japanese Patent Application Publication No. 2023-156736) do not describe controlling the difference in adjacent thicknesses of the tape thickness in the width direction of the magnetic tape.In response to this, the inventors have conducted extensive research and have newly discovered that magnetic tapes with a maximum difference in adjacent thickness of 12 nm or less have small nonlinear components in the change in servo band spacing due to long-term storage, nonlinear components in the change in servo band spacing due to the usage environment and / or storage environment, and nonlinear components in the change in servo band spacing due to running tension during use. Therefore, it is possible to suppress off-track caused by these nonlinear components. Details of the above-mentioned various nonlinear components will be described later.

[0012] From the above viewpoint, the maximum difference in adjacent thickness of the magnetic tape is 12 nm or less, preferably 11 nm or less, and more preferably 10 nm or less, 9 nm or less, and 8 nm or less, in that order. The maximum difference in adjacent thickness of the magnetic tape can be 0 nm or more, 1 nm or more, 2 nm or more, 3 nm or more, 4 nm or more, or 5 nm or more. The smaller the maximum difference in adjacent thickness of the magnetic tape, the more preferable it is from the viewpoint of suppressing the above off-track.

[0013] To further explain the magnetic tape described above, we will first describe the head tilt angle, servo band, and data band.

[0014] <Head tilt angle>

[0015] For example, each module of a magnetic head conforming to the LTO (Linear Tape-Open) standard, such as an LTO8 head or an LTO9 head (hereinafter also referred to as "LTO head"), includes an element array, i.e., an arrangement of elements, having a total of 32 magnetic head elements between a pair of servo signal reading elements. An "LTO8 head" is a magnetic head conforming to the LTO8 standard, and an "LTO9 head" is a magnetic head conforming to the LTO9 standard. 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 an LTO head, the three modules are arranged so that the axes of the element arrays of each module are oriented parallel to each other. Such "parallel" does not necessarily mean parallel in the strict sense, but includes a range of error that is normally permissible 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.

[0016] In each element array, a pair of servo signal reading elements and a plurality of magnetic head elements (i.e., recording elements or playback elements) are arranged 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.

[0017] 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.

[0018] Figure 1 is a schematic diagram showing a part of an example of a magnetic head module. The module shown in Figure 1 has multiple magnetic head elements between a pair of servo signal reading elements (servo signal reading elements 1 and 2). Magnetic head elements are also called "channels". "Ch" in the figure is an abbreviation for Channel. The module shown in Figure 1 has a total of 32 magnetic head elements, Ch0 to Ch31, between a pair (i.e., two) servo signal reading elements.

[0019] In Figure 1, "L" represents the distance between a pair of servo signal reading elements, that is, the distance between one servo signal reading element and the other. In the module shown in Figure 1, "L" represents the distance between servo signal reading element 1 and servo signal reading element 2. More specifically, it is the distance between the center of servo signal reading element 1 and the center of servo signal reading element 2. This distance can be measured, for example, by an optical microscope.

[0020] Figure 2 is an explanatory diagram of the relative positional relationship between the module and the magnetic tape during magnetic tape movement in a magnetic tape device. In Figure 2, dotted line A indicates the width direction of the magnetic tape. Dotted line B indicates the axis of the element array. Angle θ can be said to be the head tilt angle during magnetic tape movement, and is the angle 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".

[0021] As mentioned earlier, during recording or playback, deformation in the width direction of the magnetic tape can cause the magnetic head responsible for recording or playing back data to shift from the intended track position, resulting in phenomena such as overwriting of recorded data or playback failures. For example, if the width of the magnetic tape shrinks or expands, the magnetic head element that should record or play back at the intended track position may end up recording or playing back at a different track position. Also, if the width of the magnetic tape expands, the effective distance between servo signal reading elements 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 can 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 when the magnetic head for recording or playing back data is misaligned from the target track position due to deformation in the width direction of the magnetic tape during recording or playback.

[0022] Figure 3 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 3, the center diagram shows the state of the module at the start of operation. In Figure 3, the right diagram shows the angle θ, θ ｉｎｉｔｉａｌ An angle θ is a larger angle. ｃshows the state of the module when the condition is satisfied. Effective distance between servo signal reading elements Lcosθ ｃ is Lcosθ at the start of magnetic tape running ｉｎｉｔｉａｌ which has a smaller value. It is preferable to perform such angle adjustment when the width of the magnetic tape contracts (contracted) during running of the magnetic tape. On the other hand, in FIG. 3, the left diagram shows angle θ, where θ ｉｎｉｔｉａｌ is an angle smaller than that, which is angle θ ｅ shows the state of the module when the condition is satisfied. Effective distance between servo signal reading elements Lcosθ ｅ is Lcosθ at the start of magnetic tape running ｉｎｉｔｉａｌ which has a larger value. It is preferable to perform such angle adjustment when the width of the magnetic tape expands (expanded) during running of the magnetic tape.

[0023] As explained above, changing the head tilt angle during running of the magnetic tape can contribute to preventing, or contribute to reducing the frequency of, occurrence of phenomena such as overwriting of recorded data and reproduction failure caused by a magnetic head for recording or reproducing data deviating from a target track position due to deformation occurring in the width direction of the magnetic tape during recording or reproduction, thereby performing recording or reproduction of data.

[0024] <Servo Band, Data Band> In the following, the magnetic head that records and / or plays back recorded data will also be called the "recording / playback head." The elements for recording data (recording elements) and the elements for playing back data (playback elements) will be collectively referred to as "magnetic head elements." When recording 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 elements 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 that case, the servo signal reading element can be moved to a predetermined servo band using the UDIM (Unique DataBand Identification Method) information described above, and tracking for that servo band can be started.

[0025] The magnetic layer of the above-mentioned magnetic tape has three or more servo bands. Figure 4 shows an example of the arrangement of data bands and servo bands. In Figure 4, five 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 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 5. More specifically, in Figure 5, 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 5) and a B burst (indicated as B in Figure 5). 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 5) and D-burst (indicated as D in Figure 5). 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 5 shows one servo frame for illustrative purposes. However, in reality, in the magnetic layer of a magnetic tape where timing-based servo head tracking is performed, multiple servo frames are arranged in the direction of travel in each servo band. In Figure 5, 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.

[0026] The inventors, in their efforts to obtain a magnetic tape that can record and / or play back data well by changing the head tilt angle during magnetic tape travel, focused on the fact that the nonlinear component of the dimensional stability of the magnetic tape (NL-TDS), specifically the nonlinear component of the change in servo band spacing, can change depending on the storage environment, measurement environment, and running tension. As a result of further diligent research, they decided to use the NL-TDS measured in terms of long-term storage of the magnetic tape, the environment during use and / or storage, and the running tension during use, specifically the "nonlinear component of TDSage," the "nonlinear component of TDSenv," and the "nonlinear component of TDStens," which are obtained by the method described later, as indicators. The "nonlinear component of TDSage" is the nonlinear component of the change in servo band spacing that occurs after 30 days of storage in an environment of 35°C and 80% relative humidity. The "nonlinear component of TDSenv" is the nonlinear component of the change in servo band spacing caused by differences in the measurement environment, obtained from the servo band spacing measured under the following four measurement environments: temperature 15°C, relative humidity 10%, temperature 15°C, relative humidity 80%, temperature 35°C, relative humidity 80%, and temperature 35°C, relative humidity 10%. The "nonlinear component of TDStens" is the nonlinear component of the change in servo band spacing caused by differences in tension, obtained from the servo band spacing measured under the following four measurement environments: temperature 15°C, relative humidity 10%, temperature 15°C, relative humidity 80%, temperature 35°C, relative humidity 80%, and temperature 35°C, relative humidity 10%. The "nonlinear component of TDStens" is also written as "NL-TDStens". "NL" is an abbreviation for "Nonlinearity", "TDS" is an abbreviation for "Tape Dimensional Stability", and "age" is intended as an abbreviation for long-term storage. In addition, "env" is intended as an abbreviation for "environment", and "tens" is intended as an abbreviation for "tension".Before describing "NL-TDSage," "NL-TDSenv," and "NL-TDStens," we will first explain the various deformations that occur in the width direction of the magnetic tape.

[0027] <Various Deformations Occurring in the Width Direction of Magnetic Tape> Magnetic tape can experience widthwise deformation of the data band due to long-term storage, widthwise deformation of the data band due to the usage environment and / or storage environment, and widthwise deformation of the data band due to running tension during use. When widthwise deformation of the data band occurs, the track position on the magnetic tape changes, and if no control is performed, this can cause off-tracks. On the other hand, 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. If the degree of widthwise deformation of the data band is uniform throughout the entire magnetic tape, that is, if the widthwise deformation component of the data band is only a linear component, it is possible to completely compensate for off-tracks by changing the head tilt angle. In other words, it becomes possible to perfectly align the data track and the magnetic head elements. However, if the degree of widthwise deformation of the data band differs and is non-uniform depending on the position, that is, if the widthwise deformation component of the data band includes a nonlinear component, it is difficult to compensate for off-track caused by the nonlinear component by changing the head tilt angle. This point will be further explained below with reference to the drawings. However, the embodiments shown in the drawings are illustrative, and the present invention is not limited to the embodiments shown in the drawings. Also, the dimensions, arrangement, number of data tracks, and number of magnetic head elements shown in the drawings are merely illustrative for illustrative purposes, and the present invention is not limited by these examples.

[0028] Figure 6 is a schematic diagram illustrating the various deformations that occur in the width direction of a magnetic tape. In Figure 6, "A" is the width of the magnetic tape before deformation, and "a" is the width of a minute region in the width direction of the magnetic tape (referred to as the "micro region") before deformation. "B" is the width of the magnetic tape after deformation, and "b" is the width of the micro region after deformation. Hereafter, the amount of change in the width of the magnetic tape (B-A) will be called the "macro width deformation amount," and the change in the width of the magnetic tape will be called the "macro width deformation." In contrast, the amount of change in the width of the micro region of the magnetic tape (b-a) will be called the "micro width deformation amount." The change in the width of the micro region of the magnetic tape will be called the "micro width deformation."

[0029] Figure 7 is a schematic diagram of a data track (before deformation) formed in a single micro-region. In Figure 7, the track positions of the four data tracks are "t1", "t2", "t3", and "t4". In Figure 7 and the diagrams described below, the y-direction is the width direction of the magnetic tape.

[0030] Figure 8 is an explanatory diagram of the positions of the magnetic head elements in the magnetic head module that reads the data track shown in Figure 7. In Figure 8, "e1", "e2", "e3", and "e4" indicate the positions of the four magnetic head elements shown in the figure.

[0031] Figure 9 shows the data track positions shown in Figure 7 and the magnetic head element positions of the module shown in Figure 8. As shown in Figure 9, before deformation, t1 = e1, t2 = e2, t3 = e3, and t4 = e4.

[0032] When a databand having the data tracks shown in Figure 7 is deformed in the width direction, the position of the data tracks changes. Figure 10 is a schematic diagram showing the state in which the position of the data tracks shown in Figure 7 has changed due to deformation. In Figure 10, the deformed positions of the four data tracks are "T1", "T2", "T3", and "T4".

[0033] Figure 11 shows a schematic diagram of a state in which the track position is dynamically controlled by changing the head tilt angle. In Figure 11, "E1", "E2", "E3", and "E4" indicate the positions of the four magnetic head elements in the figure when the track position is dynamically controlled by changing the head tilt angle relative to the deformed data track shown in Figure 10.

[0034] Figure 12 shows the data track position (after deformation) shown in Figure 10 and the magnetic head element position (after deformation) of the module shown in Figure 11. When dynamic track position control is performed by changing the head tilt angle, for example, the head tilt position is changed so that T4 and E4 coincide and T1 and E1 coincide. This determines the positions E1 to E4 of the magnetic head elements.

[0035] Here, assuming that macro-width deformation occurs because micro-width deformation occurs with the same amount of deformation (i.e., uniformly) in all micro-regions in the width direction of the magnetic tape, and if we define the amount of deformation when the macro-width deformation is evenly distributed to all micro-regions as the "linear deformation amount ΔL", then the linear deformation amount ΔL can be calculated by the following formula. Figure 13 is an explanatory diagram of the formula for calculating the linear deformation amount ΔL. Formula:

[0036] However, if deformation in the width direction does not occur uniformly across multiple micro-regions in the width direction of the magnetic tape, a discrepancy will occur between the linear deformation amount ΔL, which can be calculated assuming linear deformation, and the actual micro-width deformation amount. If this discrepancy is called the "nonlinear deformation amount," then, for example, for the four data tracks described above, the nonlinear deformation amount can be calculated using the following formula. Figure 14 shows the nonlinear deformation amount ΔNL. ｉ This is an explanatory diagram of the calculation formula. Calculation formula: ΔNL ｉ = T ｉ -E ｉ i = 1 to 4

[0037] When nonlinear deformation occurs in the micro-width deformation described above, the amount of deformation becomes uneven across multiple data bands. In such cases, dynamic track position control by changing the head tilt angle of the magnetic head cannot adequately compensate for the discrepancy between the position of the magnetic head element and the position of the data track, resulting in off-track events. In contrast, "NL-TDS," obtained by the method described below, is an index of the nonlinear component of the change in servo band spacing caused by deformation factors (specifically, long-term storage, usage environment and / or storage environment, or running tension during use). Since the data band is the region sandwiched between two servo bands, evaluating the nonlinear component of the change in servo band spacing is substantially equivalent to evaluating the nonlinear component of the data band width deformation. NL-TDS can be considered an index of the nonlinear component of micro-width deformation, and can also be considered an index that shows the degree to which the position of the magnetic head element relative to the data track position of the magnetic tape deviates in the width direction from the position defined by dynamic track position control due to the influence of micro-width deformation. Furthermore, NL-TDS generated due to long-term storage is the "nonlinear component of TDSage (NL-TDSage)," NL-TDS generated due to the usage environment and / or storage environment is the "nonlinear component of TDSenv (NL-TDSenv)," and NL-TDS generated due to running tension during use is the "nonlinear component of TDStens (NL-TDStens)." The measurement methods for "NL-TDS," "NL-TDSage," "NL-TDSenv," and "NL-TDStens" are described below.

[0038] <NL-TDS Measurement Method> The magnetic tape to be measured for NL-TDS has three or more servo bands in its magnetic layer. More specifically, in a magnetic tape with three or more servo bands in its magnetic layer, the three or more servo bands are arranged in the width direction of the magnetic tape, and data bands are formed between adjacent servo bands. In NL-TDS measurement, three or more servo bands are read in parallel by a magnetic head equipped with a module having three or more servo signal reading elements arranged in a straight line. The spacing between the servo bands that sandwich the data bands is used to evaluate the amount of deformation for each data band. NL-TDS measurement is performed according to the following procedure.

[0039] 1. Recording of evaluation data patterns (1) Allow all devices and the magnetic tape to be measured to acclimate to the environment by leaving them undisturbed in the environment for 24 hours. (2) Equilibrium the humidity by running the entire length of the magnetic tape back and forth. Equipment used: Magnetic tape device Running speed: 6.0 m / sec Running tension: 0.4 N Back and forth time: 24 hours or more (3) Record three or more tracks in single (singled) format (tile recording) along the entire length of the magnetic tape. Equipment used: Magnetic tape device Recording length: Entire data recording area Recording speed: 3.0 m / sec Recording tension: 0.4 N to 1.3 N Recording pattern: Three consecutive tracks are all different patterns Recording bit length: Not specified Recording environment: Temperature 23°C Relative humidity 50% (4) Perform the procedure in (3) above for all data bands of the magnetic tape.

[0040] Figure 15 shows an image of the evaluation data recording. In Figure 15, the reel side is the side that was the reel side when the magnetic tape was housed in the magnetic tape cartridge. As shown in Figure 15, the areas from the side closer to the reel side to the side further away are called the inner circumference region of the tape, the central region of the tape, and the outer circumference region of the tape. For one end and the other end of the magnetic tape, the end on the side where winding onto the reel begins is called the inner circumference end of the tape, and the other end is called the outer circumference end of the tape. The area within 100m from the outer circumference end of the tape is the "outer circumference region of the tape". The area within 100m from the inner circumference end of the tape is the "inner circumference region of the tape". The "central region of the tape" is the area within a length of 100m centered on the longitudinal center of the magnetic tape.

[0041] 2. Acquisition of Track Profiles (1) For the center wrap of three consecutive wraps, data is played back over a length of 60m or more in the "outer edge region of the tape," the "center region of the tape," and the "inner edge region of the tape" (see Figure 15). Here, the track position of the playback element is moved every 10m at intervals of 1 / 30 or less of the track pitch relative to the tape width direction. The playback signal waveform and servo signal waveform are acquired and saved using an oscilloscope or an AD (Analog-Digital) board. (2) The track position is calculated from the acquired servo signal waveform, and the relative track position of each element is calculated with the track center position as the zero point. The "ratio of playback signal to noise" is calculated from the playback signal waveform. A track profile is created with the "relative track position with the track center as the zero point" plotted on the horizontal axis and the "ratio of playback signal to noise" plotted on the vertical axis. A track profile is created for all playback elements. Figure 16 shows an example of a track profile. In Figure 16, "SNRa" on the vertical axis is an abbreviation for Signal-to-Noise Ratio. (3) Perform the above steps (1) and (2) for all data bands of the magnetic tape.

[0042] 3. Calculation of the nonlinear component of the servo band spacing before deformation (1) A fourth-order polynomial approximation curve is obtained for the above track profile of all regenerative elements using the least squares method, and the maximum value at the measurement track position is calculated. The distance from the center element position of all regenerative elements is plotted on the horizontal axis, and the maximum value at the above measurement track position is plotted on the vertical axis, and a linear approximation line is obtained by linear fitting using the least squares method. (2) The amount of deviation between the above linear approximation line and the measured value is determined for all regenerative elements.

[0043] Figure 17 shows an example of a graph relating to the nonlinear component of the servo band spacing before deformation. An example of the linear approximation line is the dashed line in Figure 17. An example of the deviation amount is the difference (nonlinear component) between the solid line and the dashed line in Figure 17.

[0044] 4. Calculation of the nonlinear component of the servo band spacing after deformation After the magnetic tape is deformed by the deformation factor, the above "2. Acquisition of track profile" is performed, and then the nonlinear component of the servo band spacing after deformation is calculated using the method described in "3. Calculation of the nonlinear component of the servo band spacing before deformation".

[0045] 5. Calculation of NL-TDS The NL-TDS is calculated using the following formula. The maximum absolute value of NL-TDS across all data bands is taken as the NL-TDS caused by the deformation of the magnetic tape being measured. NL-TDS = (Nonlinear component of servo band spacing after deformation) - (Nonlinear component of servo band spacing before deformation)

[0046] Figure 18 is a graph showing an example of the nonlinear components before and after deformation, and the difference before and after deformation calculated by the above formula is NL-TDS. Figure 19 is a graph showing NL-TDS.

[0047] <Method for measuring NL-TDSage> "NL-TDSage" is determined by the following method: (A) The magnetic tape cartridge containing the magnetic tape to be measured, on which the above "1. Recording of evaluation data patterns" has been performed, is placed in an environment with an ambient temperature of 23°C and a relative humidity of 50% for 5 days in order to allow the magnetic tape to acclimate to the measurement environment. After that, in the same measurement environment, the magnetic tape is run back and forth for 24 hours with a tension of 0.4N applied to the longitudinal direction of the magnetic tape in a magnetic tape device having a tension adjustment mechanism that applies tension in the longitudinal direction of the magnetic tape, allowing the entire length of the tape to acclimate to the temperature and humidity environment. (B) After that, the tension is changed to 0.7N and the tape is run along the entire length again, and the nonlinear component is calculated by the method described in "2. Calculation of nonlinear component of servo band spacing before deformation" above. (C) After that, the magnetic tape cartridge is stored in a storage environment with an ambient temperature of 35°C and a relative humidity of 80% for 30 days. After storage, the magnetic tape cartridge is placed in a measurement environment with an ambient temperature of 23°C and a relative humidity of 50% for 5 days. Then, in the same measurement environment, the magnetic tape is run for 24 hours along its entire length in a magnetic tape device having a tension adjustment mechanism that applies tension in the longitudinal direction of the magnetic tape, with a tension of 0.4 N applied in the longitudinal direction of the magnetic tape. After that, the tension is changed to 0.7 N and the tape is run along its entire length again. For this run, the nonlinear component is calculated using the method described in "4. Calculation of the nonlinear component of the servo band spacing after deformation" above. (D) The nonlinear component obtained in (B) above is taken as the "nonlinear component of the servo band spacing before deformation," and the nonlinear component obtained in (C) above is taken as the "nonlinear component of the servo band spacing after deformation," and NL-TDS is calculated using the formula shown above. The maximum absolute value of NL-TDS in all data bands is taken as the "NL-TDSage" of the magnetic tape being measured.

[0048] <Measurement Method for NL-TDSenv> "NL-TDSenv" is determined by the following method. (E) The measurement environments for determining "NL-TDSenv" are four environments: "temperature 15°C, relative humidity 10%", "temperature 15°C, relative humidity 80%", "temperature 35°C, relative humidity 80%", and "temperature 35°C, relative humidity 10%". For each measurement environment, the magnetic tape cartridge containing the magnetic tape to be measured, on which "1. Recording of Evaluation Data Patterns" above has been performed, is placed in the measurement environment for 24 hours or more to allow it to acclimate. (F) After that, in the same measurement environment, the magnetic tape is run back and forth for 48 hours with a tension of 0.4N applied to the longitudinal direction of the magnetic tape in a magnetic tape device having a tension adjustment mechanism that applies tension in the longitudinal direction of the magnetic tape, allowing the entire length of the tape to acclimate to the temperature and humidity environment. After that, the tension is changed to 0.7N and the tape is run along the entire length again, and the nonlinear component is calculated by the method described in "2. Calculation of Nonlinear Components of Servo Band Spacing Before Deformation" above. The above measurements are performed in each of the four environments described above. (G) For all combinations within the four environments described above, the NL-TDS generated due to the environmental differences is determined. For the two environments for which NL-TDS is to be determined, the nonlinear component under the condition of relatively low temperature, or, if the temperature is the same, the environmental condition of low relative humidity, is defined as the "nonlinear component of the servo band spacing before deformation". The nonlinear component under the condition of relatively high temperature, or, if the temperature is the same, the environmental condition of high relative humidity, is defined as the "nonlinear component of the servo band spacing after deformation". NL-TDS is calculated using the formula shown above. The maximum absolute value of NL-TDS in all data bands is defined as the "NL-TDSenv" of the magnetic tape being measured.

[0049] <Method for measuring NL-TDStens> "NL-TDStens" is determined by the following method. (H) The measurement environments for determining "NL-TDStens" are four environments: "temperature 15°C, relative humidity 10%", "temperature 15°C, relative humidity 80%", "temperature 35°C, relative humidity 80%", and "temperature 35°C, relative humidity 10%". For each measurement environment, the magnetic tape cartridge containing the magnetic tape to be measured, on which the above "1. Recording of evaluation data patterns" has been performed, is placed in the measurement environment for 24 hours or more to allow it to acclimate. After that, in the same measurement environment, the magnetic tape is run back and forth for 48 hours with a tension of 0.4N applied to the longitudinal direction of the magnetic tape in a magnetic tape device having a tension adjustment mechanism that applies tension in the longitudinal direction of the magnetic tape, allowing the entire length of the tape to acclimate to the temperature and humidity environment. (I) Subsequently, the tension is changed in increments of 0.1N from 0.4N to 1.3N, and the tape is run along its entire length again under the above conditions for each tension condition, and the nonlinear component is calculated by the method described in "2. Calculation of the nonlinear component of the servo band spacing before deformation" above. (J) Using 0.7N as a reference, the nonlinear component under the condition with relatively high tension is defined as the "nonlinear component of the servo band spacing after deformation" and the nonlinear component under the condition with relatively low tension is defined as the "nonlinear component of the servo band spacing before deformation" with respect to the other tension for which the NL-TDS generated by the difference in running tension is to be determined. The NL-TDS is calculated using the formula shown above. The maximum absolute value of NL-TDS in all data bands is defined as the "NL-TDStens" of the magnetic tape to be measured.

[0050] <Equation 1> The fact that the maximum difference in adjacent thickness in the above magnetic tape is 12 nm or less may contribute to enabling good recording and / or playback when recording and / or playing back data by changing the head tilt angle while the magnetic tape is running. The inventors believe that this is because having a maximum difference in adjacent thickness of 12 nm or less may contribute to reducing the nonlinear component of the change in servo band spacing due to long-term storage that causes off-tracking, the nonlinear component of the change in servo band spacing due to the usage environment and / or storage environment, and the nonlinear component of the change in servo band spacing due to running tension during use. A magnetic tape with such small nonlinear components can satisfy, for example, Equation 1 for the nonlinear component of TDSage (NL-TDSage), the nonlinear component of TDSenv (NL-TDSenv), and the nonlinear component of TDStens (NL-TDStens): Nonlinear component of TDSage + Nonlinear component of TDSenv + Nonlinear component of TDStens ≤ 50 nm. Equation 1 can also be written as follows. "NL-TDSage" + "NL-TDSenv" + "NL-TDStens" ≤ 50 nm That is, Equation 1 indicates that the sum of "NL-TDSage", "NL-TDSenv", and "NL-TDStens" is 50 nm or less. The left side of Equation 1, i.e., the sum of "NL-TDSage", "NL-TDSenv", and "NL-TDStens", is preferably 50 nm or less, and more preferably in the order of 45 nm or less, 40 nm or less, 35 nm or less, and 30 nm or less, from the viewpoint of enabling better recording and / or playback when the head tilt angle is changed during magnetic tape running to record and / or play back data. The left side of Equation 1 can be, for example, 0 nm or more, 1 nm or more, 5 nm or more, 10 nm or more, 15 nm or more, or 20 nm or more. The smaller the left-hand side of Equation 1, the more preferable it is from the viewpoint of improving recording and / or playback performance when the head tilt angle is changed during magnetic tape travel for recording and / or playback of data.

[0051] "NL-TDSage" and "NL-TDSenv" can be, for example, 30 nm or less, 25 nm or less, 20 nm or less, or 15 nm or less, respectively. Also, "NL-TDSage" and "NL-TDSenv" can be, for example, 0 nm or more, 1 nm or more, 3 nm or more, or 5 nm or more, respectively. "NL-TDStens" can be, for example, 10 nm or less, 8 nm or less, 6 nm or less, or 4 nm or less. Also, "NL-TDStens" can be, for example, 0 nm or more or 1 nm or more. However, the sum of "NL-TDSage", "NL-TDSenv", and "NL-TDStens" only needs to satisfy Equation 1, and their individual values ​​are not particularly limited.

[0052] The magnetic tape described above will be explained in more detail below.

[0053] <Non-magnetic support> Examples of non-magnetic support materials (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 naphthalate, polyethylene terephthalate, and aromatic polyamide are preferred. In the present invention and this specification, "aromatic polyamide" means a resin containing an aromatic skeleton and multiple amide bonds. The aromatic rings contained in the aromatic skeleton of an aromatic polyamide are not particularly limited. Specific examples of aromatic rings include, for example, benzene rings.

[0054] In one embodiment, the non-magnetic support of the magnetic tape described above may be an aromatic polyester support. In the present invention and this specification, "aromatic polyester" means a resin containing an aromatic skeleton and a plurality of ester bonds, and "aromatic polyester support" means a support containing at least one layer of aromatic polyester film. "Aromatic polyester film" means a film in which the component that constitutes the film by mass is aromatic polyester. In the present invention and this specification, "aromatic polyester support" includes both a support in which all the resin films contained are aromatic polyester films and a support containing aromatic polyester films and other resin films. Specific forms of aromatic polyester support include a single layer of aromatic polyester film, a laminated film of two or more layers of aromatic polyester films with the same constituent components, a laminated film of two or more layers of aromatic polyester films with different constituent components, a laminated film containing one or more layers of aromatic polyester film and one or more layers of resin films other than aromatic polyester, etc. In a laminated film, an adhesive layer or the like may be optionally included between two adjacent layers. Furthermore, the aromatic polyester support may optionally include a metal film and / or a metal oxide film formed by vapor deposition or the like on one or both surfaces. The same applies to the "polyethylene terephthalate support," "polyethylene naphthalate support," and "aromatic polyamide support" as described in the present invention and this specification.

[0055] The aromatic rings contained in the aromatic skeleton of an aromatic polyester are not particularly limited. Specific examples of aromatic rings include, for example, benzene rings and naphthalene rings. For example, polyethylene terephthalate (PET) is a polyester containing a benzene ring and is a resin obtained by polycondensation of ethylene glycol with terephthalic acid and / or dimethyl terephthalate. In the present invention and this specification, "polyethylene terephthalate" also includes structures having one or more other components in addition to the above components (e.g., copolymer components, components introduced into the terminals or side chains, etc.). Polyethylene naphthalate (PEN) is a polyester containing a naphthalene ring and is a resin obtained by esterification of dimethyl 2,6-naphthalenedicarboxylate with ethylene glycol, followed by transesterification and polycondensation reactions. In the present invention and this specification, "polyethylene naphthalate" also includes structures having one or more other components in addition to the above components (e.g., copolymer components, components introduced into the terminals or side chains, etc.).

[0056] Furthermore, the non-magnetic support can be a biaxially oriented film, and may be a film that has been subjected to corona discharge, plasma treatment, easy adhesion treatment, heat treatment, etc.

[0057] One indicator of the physical properties of a non-magnetic support is, for example, its moisture content. In the present invention and this specification, the moisture content of a non-magnetic support is a value obtained by the following method. A sample piece (for example, a sample piece with a mass of several grams) cut from the non-magnetic support to be measured for moisture content is dried in a vacuum dryer at a temperature of 180°C and a pressure of 100 Pa (Pascals) or less until a constant weight is reached. The mass of the dried sample piece is denoted as W1. W1 is a value measured within 30 seconds after removal from the vacuum dryer in a measurement environment of 23°C and 50% relative humidity. Next, the mass of this sample piece after being placed in an environment of 25°C and 75% relative humidity for 48 hours is denoted as W2. W2 is a value measured within 30 seconds after removal from the above environment in a measurement environment of 23°C and 50% relative humidity. The moisture content is calculated by the following formula. Moisture content (%) = [(W2 - W1) / W1] × 100 For example, after removing parts other than the non-magnetic support, such as the magnetic layer, from the magnetic tape by a known method (e.g., defilm removal using an organic solvent), the moisture content of the non-magnetic support can also be determined by the above method.

[0058] In one embodiment, the non-magnetic support of the magnetic tape preferably has a water content of 2.5% or less, more preferably 2.0% or less, and even more preferably 1.5% or less, followed by 1.0% or less. The water content of the non-magnetic support of the magnetic tape can also be 0%, 0% or more, greater than 0%, or 0.1% or more.

[0059] One indicator of the physical properties of a non-magnetic support is, for example, Young's modulus. In the present invention and this specification, the Young's modulus of a non-magnetic support is a value measured by the following method in a measurement environment of 23°C and 50% relative humidity. A sample piece cut from the non-magnetic support to be measured is pulled using a universal tensile testing apparatus under the conditions of a chuck distance of 100 mm, a tensile speed of 10 mm / min, and a chart speed of 500 mm / min. As the universal tensile testing apparatus, for example, a commercially available universal tensile testing apparatus such as the Tensilon manufactured by Toyo Baldwin Co., Ltd. or a universal tensile testing apparatus with a known configuration can be used. From the tangent of the rising portion of the load-elongation curve thus obtained, the Young's modulus in the longitudinal and width directions of the sample piece is calculated, respectively. Here, the longitudinal and width directions of the sample piece refer to the longitudinal and width directions when the sample piece was contained in a magnetic tape. For example, after removing parts other than the non-magnetic support, such as the magnetic layer, from the magnetic tape using a known method (e.g., defilm removal using an organic solvent), the Young's modulus in the longitudinal and width directions of the non-magnetic support can be determined using the method described above.

[0060] In one embodiment, the non-magnetic support of the magnetic tape preferably has a Young's modulus in the longitudinal direction of 3000 MPa or more, more preferably 4000 MPa or more, and even more preferably 5000 MPa or more. The Young's modulus in the longitudinal direction of the non-magnetic support of the magnetic tape can be 15000 MPa or less, 13000 MPa or less, 11000 MPa or less, or 9000 MPa or less. In the width direction, the Young's modulus in the width direction of the non-magnetic support of the magnetic tape preferably has a Young's modulus in the width direction of 2000 MPa or more, more preferably 3000 MPa or more, and even more preferably 4000 MPa or more. The Young's modulus in the width direction of the non-magnetic support of the magnetic tape can be 20000 MPa or less, 15000 MPa or less, 10000 MPa or less, 8000 MPa or less, or 6000 MPa or less. During the manufacture of magnetic tape, non-magnetic supports are typically used with the machine direction (MD) of the film as the longitudinal direction and the transverse direction (TD) as the width direction.

[0061] The water content and Young's modulus of a non-magnetic support can be controlled by the type and mixing ratio of the components constituting the support, the manufacturing conditions of the support, etc. For example, by adjusting the stretching ratio in each direction during biaxial stretching, the Young's modulus in the longitudinal direction and the Young's modulus in the width direction can be controlled, respectively.

[0062] The maximum difference in adjacent thicknesses of magnetic tape can vary depending on the non-magnetic support.

[0063] <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.

[0064] 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.

[0065] 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).

[0066] Below, we will describe hexagonal strontium ferrite powder, a form of hexagonal ferrite powder, in more detail.

[0067] 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.

[0068] "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 values ​​obtained from the following relationship between Hc and activation volume V, measured using a vibrating sample type magnetometer at magnetic field sweep speeds of 3 minutes and 30 minutes in the coercivity Hc measurement section (measurement temperature: 23°C ± 1°C). Note that the unit of the anisotropy constant Ku is 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)]

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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 only once, 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.

[0073] When hexagonal strontium ferrite powder contains rare earth atoms, the rare earth atoms included may be one or more of the rare earth atoms. 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.

[0074] 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.

[0075] 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.

[0076] 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].

[0077] 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 the divalent metal atom. 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.

[0078] The known crystal structures of hexagonal ferrites include magnetoplumbite (also called "M-type"), W-type, Y-type, and Z-type. Hexagonal strontium ferrite powder may have any of these crystal structures. The crystal structure can be confirmed by X-ray diffraction analysis. Hexagonal strontium ferrite powder may show a single crystal structure or two or more crystal structures by X-ray diffraction analysis. For example, in one form, hexagonal strontium ferrite powder may show only the M-type crystal structure by X-ray diffraction analysis. For example, M-type hexagonal ferrite is AFe １２ O １９It is represented by the following compositional formula: Here, A represents a divalent metal atom, and if the hexagonal strontium ferrite powder is of type M, A is either only a strontium atom (Sr), or if A contains multiple divalent metal atoms, then as described above, strontium atoms (Sr) make up the largest proportion on an atomic percentage basis. The divalent metal atom content of hexagonal strontium ferrite powder is usually determined by the type of crystal structure of the hexagonal ferrite and is not particularly limited. The same applies to the iron atom content and oxygen atom content. Hexagonal strontium ferrite powder contains at least iron atoms, strontium atoms and oxygen atoms, and may also contain rare earth atoms. Furthermore, hexagonal strontium ferrite powder may or may not contain atoms other than these atoms. As an example, hexagonal strontium ferrite powder may contain aluminum atoms (Al). The aluminum atom content can be, for example, 0.5 to 10.0 atomic percent relative to 100 atomic percent of iron atoms. From the viewpoint of 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).

[0079] 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.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] In the present invention and this specification, unless otherwise specified, the average particle size of various powders such as ferromagnetic powder shall be the value measured using a transmission electron microscope by the following method: The powder is photographed using a transmission electron microscope at a magnification of 100,000x, and the resulting image is printed on photographic paper or displayed on a screen to obtain a photograph of the particles constituting the powder, with a total magnification of 500,000x. The target particles are selected from the obtained photographs of the particles, and their contours are traced with a digitizer to measure the size of the particles (primary particles). Primary particles refer to independent particles that do not aggregate. The above measurement is performed on 500 randomly selected particles. The arithmetic mean of the particle sizes of these 500 particles is taken as the average particle size of the powder. As the 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 shown 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.

[0085] For example, the method described in paragraph 0015 of Japanese Patent Publication No. 2011-048878 can be used to collect a sample powder from a magnetic tape for particle size measurement.

[0086] In the present invention and this specification, unless otherwise specified, the size of the particles constituting the powder (particle size) is expressed as follows: (1) If the shape of the particles observed in the above particle photograph is needle-shaped, spindle-shaped, columnar (however, the height is greater than the longest major axis of the base), it is expressed as the length of the long axis constituting the particle, i.e., the long axis length; (2) If the shape is plate-shaped or columnar (however, the thickness or height is less than the longest major axis of the plate surface or base), it is expressed as the longest major axis of the plate surface or base; (3) If the shape is spherical, polyhedral, irregular, etc., and the long axis constituting the particle cannot be determined from the shape, it is expressed as the equivalent circle diameter. The equivalent circle diameter refers to the diameter determined by the circular projection method.

[0087] Furthermore, the average needle-shape ratio of the powder refers to the arithmetic mean of the values ​​obtained for the 500 particles by measuring the length of the short axis of each particle in the above measurement, i.e., the short axis length, and determining the (long axis length / short axis length) value for each particle. Here, unless otherwise specified, the short axis length refers to the length of the short axis constituting the particle in the definition of particle size above (1), the thickness or height in the definition of (2), and in the case of (3), since there is no distinction between the long axis and the short axis, (long axis length / short axis length) is considered to be 1 for convenience. And unless otherwise specified, when the shape of the particle is specific, for example, in the definition of particle size above (1), the average particle size is the average long axis length, and in the definition of (2), the average particle size is the average plate diameter. In the definition of (3), the average particle size is the average diameter (also called the average particle size or average particle diameter).

[0088] 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.

[0089] (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 recording media 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)

[0090] (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.

[0091] (Additives) The magnetic layer may contain one or more additives as needed. An example of an additive is the curing agent mentioned above. Other additives that can be included in the magnetic layer include non-magnetic powders (e.g., inorganic powders, carbon black, etc.), lubricants, dispersants, dispersion aids, antifungal agents, antistatic agents, antioxidants, etc. For example, for lubricants, see 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, see paragraphs 0030, 0031, and 0034 to 0036 of Japanese Patent Application Publication No. 2016-126817. For dispersants, see paragraphs 0061 and 0071 of Japanese Patent Application Publication No. 2012-133837. A dispersant may be added to the composition for forming the non-magnetic layer. For dispersants that can be added to the composition for forming a non-magnetic layer, refer to paragraph 0061 of Japanese Patent Application Publication No. 2012-133837. Examples of non-magnetic powders that can be included in the magnetic layer include non-magnetic powders that can function as abrasives, and non-magnetic powders that can function as protrusion-forming agents that form appropriately protruding protrusions on the surface of the magnetic layer (e.g., non-magnetic colloidal particles, carbon black, etc.). From the viewpoint of enabling the protrusion-forming agent and abrasive to better exhibit their functions, the content of the protrusion-forming agent in the magnetic layer is preferably 0.1 to 4.0 parts by mass, more preferably 0.3 to 3.5 parts by mass, and even more preferably 0.5 to 2.5 parts by mass, per 100.0 parts by mass of ferromagnetic powder. On the other hand, the content of the abrasive in the magnetic layer is preferably 1.0 to 20.0 parts by mass, more preferably 3.0 to 15.0 parts by mass, and even more preferably 4.0 to 10.0 parts by mass, per 100.0 parts by mass of ferromagnetic powder. The average particle size of the protrusion-forming agent can be, for example, 30 to 300 nm, preferably 30 to 100 nm, and more preferably 30 to 50 nm. The average particle size of the colloidal silica (silica colloid particles) shown in the Examples section below is the value obtained by the method described in paragraph 0015 of Japanese Patent Application Publication No. 2011-048878 as the method for measuring the average particle size.Using a protrusion-forming agent with a small average particle size can contribute to reducing the maximum difference in adjacent thicknesses of magnetic tapes. Additives can be appropriately selected from commercially available products according to the desired properties, or manufactured by known methods, and used in any amount. An example of an additive that can be used to improve the dispersibility of abrasives in a magnetic layer containing abrasives is the dispersant described in paragraphs 0012 to 0022 of Japanese Patent Application Publication No. 2013-131285.

[0092] The magnetic layer described above can be provided directly on the surface of a non-magnetic support, or indirectly via a non-magnetic layer.

[0093] <Non-magnetic layer> Next, the non-magnetic layer will be described. The magnetic tape described above may have a magnetic layer directly on the surface of a non-magnetic support, or it may have a magnetic layer on the surface of a non-magnetic support via a non-magnetic layer containing non-magnetic powder. The non-magnetic powder used in the non-magnetic layer may be an inorganic powder or an organic powder. Carbon black can also be used. Examples of inorganic powders include metals, metal oxides, metal carbonates, metal sulfates, metal nitrides, metal carbides, and metal sulfides. These non-magnetic powders are commercially available and can also be manufactured by known methods. For details, see paragraphs 0146 to 0150 of Japanese Patent Application Publication No. 2011-216149. For carbon black that can be used in the non-magnetic layer, see paragraphs 0040 and 0041 of Japanese Patent Application Publication No. 2010-24113. The content (filling rate) of non-magnetic powder in the non-magnetic layer is preferably in the range of 50 to 90% by mass, and more preferably in the range of 60 to 90% by mass, relative to the total mass of the non-magnetic layer.

[0094] 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.

[0095] In the present invention and this specification, the non-magnetic layer includes a substantially non-magnetic layer containing a small amount of ferromagnetic powder, for example as an impurity or intentionally, along with the non-magnetic powder. A substantially non-magnetic layer is defined as a layer having a remanent magnetic flux density of 10 mT or less, a coercivity of 7.96 kA / m (100 Oe) or less, or a layer having a remanent magnetic flux density of 10 mT or less and a coercivity of 7.96 kA / m (100 Oe) or less. It is preferable that the non-magnetic layer has no remanent magnetic flux density and coercivity.

[0096] <Backcoat Layer> The magnetic 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. With regard to the binder and additives of the backcoat layer, known technology relating to the backcoat layer may be applied, as may known technology relating to the formulation of the magnetic layer and / or nonmagnetic layer. 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 with respect to the backcoat layer.

[0097] <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 tape. Means of increasing capacity include making the magnetic tape thinner (hereinafter also referred to as "thinning") and increasing the length of magnetic tape that can be accommodated in one 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, and even more preferably 5.4 μm or less, 5.3 μm or less, 5.2 μm or less, 5.1 μm or less, and 5.0 μm or less, in that order. Furthermore, from the viewpoint of ease of handling, the thickness of the magnetic tape is preferably 3.0 μm or more, and more preferably 3.5 μm or more.

[0098] The method for measuring the thickness (total thickness) of magnetic tape is as described above.

[0099] The thickness of the non-magnetic support is preferably 3.0 to 5.0 μm. The thickness of the magnetic layer can be optimized depending on the saturation magnetization of the magnetic head used, the head gap length, the bandwidth of the recording signal, etc., and is generally 0.01 μm to 0.15 μm, 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, and preferably 0.1 to 1.0 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.

[0100] <Manufacturing Process> (Preparation of Compositions for Forming Each Layer) The process of preparing compositions for forming magnetic layers, non-magnetic layers, or backcoat layers usually includes at least a kneading step, a dispersion step, and mixing steps provided before and after these steps as needed. Each individual step may be divided into two or more stages. Components used in the preparation of each layer-forming composition may be added at the beginning or in the middle of any of the steps. As a solvent, one or more of the various solvents commonly used in the manufacture of coated magnetic recording media can be used. For solvents, see, for example, paragraph 0153 of Japanese Patent Application Publication No. 2011-216149. Individual components may also be added in two or more separate steps. For example, a binder may be added in separate steps: a kneading step, a dispersion step, and a mixing step for viscosity adjustment after dispersion. Known manufacturing techniques can be used in various steps to manufacture the above magnetic tape. In the kneading step, it is preferable to use an open kneader, continuous kneader, pressure kneader, extruder, or other equipment with strong kneading force. For details of the kneading process, please refer to Japanese Patent Publication No. 1-106338 and Japanese Patent Publication No. 1-79274. Known dispersers can be used. Increasing the dispersion time when preparing the magnetic layer forming composition may contribute to reducing the maximum difference in adjacent thicknesses of the magnetic tape. Filtration may be performed by known methods at any stage in preparing each layer forming composition. Filtration can be performed, for example, by filter filtration. As filters used for filtration, for example, filters with a pore size of 0.01 to 3 μm (e.g., glass fiber filters, polypropylene filters, etc.) can be used.

[0101] (Coating process) The magnetic layer can be formed by directly coating the magnetic layer-forming composition onto the surface of the non-magnetic support, or by sequentially or simultaneously coating it with the non-magnetic layer-forming composition. The back coat layer can be formed by coating the back coat-forming composition onto the surface of the non-magnetic support opposite to the surface having the non-magnetic layer and / or magnetic layer (or where the non-magnetic layer and / or magnetic layer are subsequently provided). For details of the coating process for each layer formation, refer to paragraph 0066 of Japanese Patent Application Publication No. 2010-231843.

[0102] (Other Processes) For other processes for manufacturing magnetic tape, known technologies can be applied. For various processes, see, for example, paragraphs 0067 to 0070 of Japanese Patent Application Publication No. 2010-231843. For example, after the coating process, the magnetic tape is usually calendered to improve its surface smoothness. Strengthening the calendering conditions can contribute to reducing the maximum difference in adjacent thicknesses of the magnetic tape. Strengthening the calendering conditions includes, for example, increasing the calendering pressure, increasing the calendering temperature, decreasing the calendering speed, and increasing the number of calendering cycles. Regarding the calendering conditions, the calendering pressure (linear pressure) can be, for example, 200 to 500 kg / cm, and preferably 250 to 350 kg / cm. The calendering temperature (surface temperature of the calendering roll) is preferably 90 to 120°C, and the calendering speed is, for example, 50 to 300 m / min, preferably 80 to 200 m / min. The number of calendering cycles is, for example, 1 to 4.

[0103] For example, the coated layer of a magnetic layer-forming composition can be subjected to orientation treatment in an orientation zone while the coated layer is still wet. Various known techniques, including those described in paragraph 0052 of Japanese Patent Application Publication No. 2010-24113, can be applied to the orientation treatment. For example, vertical orientation treatment can be performed by known methods such as using opposing magnets of opposite poles. In the orientation zone, the drying rate of the coated layer can be controlled by the temperature and volume of the drying air and / or the transport speed in the orientation zone. Alternatively, the coated layer may be pre-dried before being transported to the orientation zone.

[0104] Through various processes, a long roll of magnetic tape raw material can be obtained. The obtained magnetic tape raw material is cut (slit) using a known cutting machine to the width of magnetic tape to be wound onto a magnetic tape cartridge, for example. The above width is determined according to standards and is usually 1 / 2 inch. 1 inch = 12.7 mm. A servo pattern is formed on the magnetic tape obtained by slitting. Details of the servo pattern will be described later.

[0105] (Heat treatment) In one embodiment, the above magnetic tape may be a magnetic tape manufactured through the following heat treatment.

[0106] For heat treatment, the magnetic tape, which has been slit and cut to a width determined according to the standard, can be wrapped around a core-shaped member, and the heat treatment can be performed while the tape is still wrapped around the member.

[0107] In one embodiment, the above heat treatment is performed with the magnetic tape wound around a core-shaped member for heat treatment (hereinafter referred to as the "heat treatment core"), and the heat-treated magnetic tape is wound onto a reel of a magnetic tape cartridge to produce a magnetic tape cartridge with the magnetic tape wound on a reel. The heat treatment core can be made of metal, resin, paper, etc. From the viewpoint of suppressing the occurrence of winding failures such as spocking, it is preferable that the material of the heat treatment core is a material with high rigidity. From this point of view, it is preferable that the heat treatment core is made of metal or resin. Furthermore, as an indicator of rigidity, the flexural modulus of the material of the heat treatment core is preferably 0.2 GPa or higher, and more preferably 0.3 GPa or higher. On the other hand, since high-rigidity materials are generally expensive, using a heat treatment core made of a material with rigidity exceeding the rigidity that can suppress the occurrence of winding failures will lead to increased costs. Considering the above points, it is preferable that the flexural modulus of the material of the heat treatment core is 250 GPa or lower. The flexural modulus is a value measured in accordance with ISO (International Organization for Standardization) 178, and the flexural modulus of various materials is well known. The core for heat treatment can be a solid or hollow core-shaped member. In the case of a hollow core, the wall thickness is preferably 2 mm or more from the viewpoint of maintaining rigidity. The core for heat treatment may or may not have a flange. It is preferable to prepare a magnetic tape of a length equal to or greater than the length to be finally housed in a magnetic tape cartridge (hereinafter referred to as the "final product length") as the magnetic tape to be wound around the core for heat treatment, and to perform heat treatment by winding this magnetic tape around the core and placing it in a heat treatment environment. The length of the magnetic tape wound around the core for heat treatment is equal to or greater than the final product length, and from the viewpoint of ease of winding onto the core for heat treatment, it is preferable to set it to "final product length + α". From the viewpoint of ease of winding, this α is preferably 5 m or more. The tension applied when winding the material onto the heat-treated core is preferably 0.1 N (Newtons) or higher. Furthermore, from the viewpoint of suppressing excessive deformation, the tension applied when winding the material onto the heat-treated core is preferably 1.5 N or lower, and more preferably 1.0 N or lower.The outer diameter of the heat-treated core is preferably 20 mm or more, and more preferably 40 mm or more, from the viewpoint of ease of winding and suppression of coiling (longitudinal curling). Furthermore, the outer diameter of the heat-treated core is preferably 100 mm or less, and more preferably 90 mm or less. The width of the heat-treated core should be greater than or equal to the width of the magnetic tape wound around it. In addition, when removing the magnetic tape from the heat-treated core after heat treatment, it is preferable to remove the magnetic tape from the heat-treated core only after the magnetic tape and heat-treated core have cooled sufficiently, in order to suppress unintended tape deformation during the removal operation. It is preferable to first wind the removed magnetic tape onto another core (referred to as a "temporary winding core"), and then wind the magnetic tape from the temporary winding core onto a reel of a magnetic tape cartridge (generally with an outer diameter of about 40 to 50 mm). This allows the relationship between the inside and outside of the magnetic tape with respect to the heat treatment core to be maintained during heat treatment, and enables the magnetic tape to be wound onto the reel of the magnetic tape cartridge. For details of the temporary winding core and the tension when winding the magnetic tape onto this core, please refer to the previous description regarding the heat treatment core. In the configuration in which the above heat treatment is applied to a magnetic tape of a length of "final product length + α", the "+ α" length can be cut off at any stage. For example, in one configuration, the magnetic tape of the final product length can be wound from the temporary winding core onto the reel of the magnetic tape cartridge, and the remaining "+ α" length can be cut off. From the viewpoint of minimizing the portion that is cut off and discarded, it is preferable that α is 20 m or less.

[0108] The specific form of the heat treatment performed with the material wrapped around the core member as described above is explained below. The ambient temperature for heat treatment (hereinafter referred to as "heat treatment temperature") is preferably 40°C or higher, and more preferably 50°C or higher. On the other hand, from the viewpoint of suppressing excessive deformation, the heat treatment temperature is preferably 75°C or lower, more preferably 70°C or lower, and even more preferably 65°C or lower. The absolute humidity by weight of the atmosphere for heat treatment is preferably 0.1 g / kg Dry air or higher, and more preferably 1 g / kg Dry air or higher. An atmosphere with an absolute humidity by weight within the above range is preferable because it can be prepared without using special equipment to reduce moisture. On the other hand, from the viewpoint of suppressing condensation and a decrease in workability, the absolute humidity by weight is preferably 70 g / kg Dry air or lower, and more preferably 66 g / kg Dry air or lower. The heat treatment time is preferably 0.3 hours or more, and more preferably 0.5 hours or more. Furthermore, from the viewpoint of production efficiency, the heat treatment time is preferably 48 hours or less.

[0109] (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.

[0110] 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.

[0111] 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.

[0112] 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.

[0113] 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.

[0114] 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 these shifts 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.

[0115] 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.

[0116] 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.

[0117] 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.

[0118] 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.

[0119] 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.

[0120] The magnetic tape described above can be housed, for example, in a magnetic tape cartridge. The magnetic tape cartridge containing the magnetic tape can then be mounted in a magnetic tape device.

[0121] <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.

[0122] 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.

[0123] [Magnetic Tape Cartridge] One aspect of the present invention relates to a magnetic tape cartridge including the magnetic tape described above.

[0124] Details of the magnetic tape included in the above magnetic tape cartridge are as described above.

[0125] In a magnetic tape cartridge, the magnetic tape is generally housed inside the cartridge body, wound onto a reel. The reel is rotatably mounted inside the cartridge body. Two types of magnetic tape cartridges are widely used: single-reel cartridges, which have one reel inside the cartridge body, and double-reel cartridges, which have two reels inside the cartridge body. When a single-reel magnetic tape cartridge is mounted in a magnetic tape device for recording and / or playing back data on magnetic tape, the magnetic tape is pulled out of the cartridge and wound onto the reel on the magnetic tape device. A magnetic head is positioned in the magnetic tape transport path from the magnetic tape cartridge to the take-up reel. The magnetic tape is fed and wound between the reel on the magnetic tape cartridge side (supply reel) and the reel on the magnetic tape device side (take-up reel). During this time, 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.

[0126] The above-described magnetic tape cartridge may, in one embodiment, include a cartridge memory. The cartridge memory may be, for example, a non-volatile memory, and may already contain or contain head tilt angle adjustment information. The head tilt angle adjustment information is information for adjusting the head tilt angle while the magnetic tape is running within the magnetic tape device. For example, the head tilt angle adjustment information may include the values ​​of the servoband interval at each position 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. When recording and / or playing back data with the head tilted, the angle θ described above may be greater than 0° and may be 45° or less, 40° or less, or 35° or less.

[0127] 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 by changing the head tilt angle while the magnetic tape is running. In such a usage configuration, since the period during data recording and / or playback includes a period in which the head is tilted, a magnetic tape with high running stability when recording and / or playing back data with the head tilted is preferred. However, the magnetic tape and magnetic tape cartridge described above are not limited to those used in such a magnetic tape device. For example, there may be a usage configuration in which the head tilt angle during one recording or playback is changed from the head tilt angle during subsequent recordings or playbacks, but the head tilt angle is fixed and not changed during each recording or playback. In such a usage configuration as well, since the period during data recording and / or playback includes a period in which the head is tilted, a magnetic tape with high running stability when recording and / or playing back data with the head tilted is preferred.

[0128] [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, recording data onto the magnetic tape and / or reproducing data recorded on the magnetic tape can be performed, for example, by bringing the magnetic layer surface of the magnetic tape into contact with a magnetic head and sliding it. The magnetic tape device may detachably include a magnetic tape cartridge according to one aspect of the present invention.

[0129] The above-described magnetic tape cartridge can be mounted in a magnetic tape device equipped with a magnetic head and used for recording and / or reproducing data. In the present invention and this specification, “magnetic tape device” means a device capable of recording data onto a magnetic tape and reproducing data recorded on a magnetic tape. Such a device is generally called a drive.

[0130] <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 described with reference to Figures 1 to 3. In one embodiment, the magnetic head included in the above magnetic tape device may be an LTO8 head or an LTO9 head; in another embodiment, it may be an LTO head of another generation; and in yet another embodiment, it may be a magnetic head other than an LTO head. If the magnetic head includes a regeneration element, a magnetoresistive (MR) element that can read information recorded on the magnetic tape with high sensitivity is preferred as the regeneration element. Various known MR elements (for example, GMR (Giant Magnetoresistive) elements, TMR (Tunnel Magnetoresistive) elements, etc.) can be used as the MR element.

[0131] By using a regeneration element with a narrow width as the regeneration element, data recorded at high density can be regenerated with high sensitivity. From this viewpoint, the regeneration element width is preferably 0.8 μm or less. The regeneration element width can be, for example, 0.3 μm or more. However, a value lower than this is also preferable from the above viewpoint. Here, "regeneration element width" refers to the physical dimension of the regeneration element width. Such physical dimensions can be measured using an optical microscope, scanning electron microscope, etc.

[0132] In the above-described magnetic tape device, the head tilt angle can be changed while the magnetic tape is running within the magnetic tape device. The head tilt angle is, for example, the angle θ that the axis of the element array makes with respect to the width direction of the magnetic tape. The angle θ is as previously explained. 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 that rotates the module. Known technologies can be applied to the angle adjustment unit.

[0133] 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 1 to 3. 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. ｉｎｉｔｉａｌThe 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 between the magnetic layer surface and the contact surface of the magnetic head when the magnetic tape is running and contacting 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.

[0134] 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

[0135] 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.

[0136] In the examples shown in Figures 2 and 3, 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.

[0137] 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 20 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 20 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.

[0138] <Configuration of the Magnetic Tape Device> The magnetic tape device 10 shown in Figure 21 controls the recording / 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.

[0139] The control device 11 includes, for example, a control unit, a storage unit, a communication unit, and the like.

[0140] 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.

[0141] 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.

[0142] 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).

[0143] An embodiment of the present invention will be described below based on examples. However, the present invention is not limited to the embodiments shown in the examples. Unless otherwise specified, the "parts" and "%" mentioned below refer to "parts by mass" and "mass%" respectively. "eq" stands for equivalent and is a unit that cannot be converted to SI units. Furthermore, unless otherwise specified, the following processes and operations were carried out in an environment with a temperature of 20 to 25°C and a relative humidity of 40 to 60%.

[0144] In the table below, "PEN" refers to polyethylene naphthalate support, "PET" refers to polyethylene terephthalate support, and "PA" refers to aromatic polyamide support. The water content and Young's modulus in the table are values ​​measured by the method described above.

[0145] In the table below, "CS" indicates colloidal silica and "CB" indicates carbon black.

[0146] [Example 1] (1) Preparation of alumina dispersion: gelatinization rate approximately 65%, BET (Brunauer-Emmett-Teller) specific surface area 20 m² ２ 100.0 parts of alumina powder (HIT-80, manufactured by Sumitomo Chemical Co., Ltd.) at a concentration of 1 / g, plus 3.0 parts of 2,3-dihydroxynaphthalene (manufactured by Tokyo Chemical Industry Co., Ltd.) and SO as a polar group. ３ 31.3 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: a mixed solvent of methyl ethyl ketone and toluene) were mixed with 570.0 parts of a mixed solution of methyl ethyl ketone and cyclohexanone in a 1:1 (mass ratio) solvent. The mixture was dispersed in the presence of zirconia beads using a paint shaker for 5 hours. After dispersion, the dispersion and beads were separated using a mesh to obtain an alumina dispersion.

[0147] (2) Composition formulation for forming a magnetic layer (magnetic liquid) Ferromagnetic powder: 100.0 parts Hexagonal barium ferrite powder with an average particle size (average plate diameter) of 21 nm (in the table, "BaFe") SO ３ Na group-containing polyurethane resin: 14.0 parts; weight-average molecular weight: 70,000, SO ３ Na group: 0.2 meq / g Cyclohexanone: 150.0 parts Methyl ethyl ketone: 150.0 parts (Abrasive solution) Alumina dispersion prepared in (1) above: 6.0 parts (Silica sol (protrusion-forming agent solution)) Colloidal silica (average particle size: see table below): 2.0 parts Methyl ethyl ketone: 1.4 parts (Other components) Stearic acid: 2.0 parts Stearamide: 0.2 parts Butyl stearate: 2.0 parts Polyisocyanate (Tosoh Corporation's Coronate® L): 2.5 parts (Finishing additive solvent) Cyclohexanone: 200.0 parts Methyl ethyl ketone: 200.0 parts

[0148] (3) Composition formulation for forming a non-magnetic layer Non-magnetic inorganic powder: α-iron oxide: 100.0 parts Average particle size (average long axis length): 0.15 μm Average needle-like ratio: 7 BET specific surface area: 52 m² ２ Carbon black / g: 20.0 parts Average particle size: 20 nm SO ３ Na group-containing polyurethane resin: 18.0 parts; weight-average molecular weight: 70,000, SO ３ Na group: 0.2 meq / g Stearic acid: 2.0 parts Stearamide: 0.2 parts Butyl stearate: 2.0 parts Cyclohexanone: 300.0 parts Methyl ethyl ketone: 300.0 parts

[0149] (4) Composition formulation for backcoat layer formation Carbon black: 100.0 parts DBP (Dibutyl phosphate) Oil absorption: 74 cm ３ / 100g Nitrocellulose: 27.0 parts Polyester polyurethane resin containing sulfonic acid groups and / or salts thereof: 62.0 parts Polyester resin: 4.0 parts Alumina powder (BET specific surface area: 17 m²) ２ (per g): 0.6 parts Methyl ethyl ketone: 600.0 parts Toluene: 600.0 parts Polyisocyanate (Coronate® L, manufactured by Tosoh Corporation): 15.0 parts

[0150] (5) Preparation of each layer-forming composition The magnetic layer-forming composition was prepared by the following method. The magnetic liquid was prepared by dispersing the above components for 24 hours using a batch-type vertical sand mill (bead dispersion). Zirconia beads with a bead diameter of 0.5 mm were used as the dispersion beads. Using the above sand mill, the prepared magnetic liquid, the above polishing liquid, and other components (silica sol, other components, and finishing additive solvent) were mixed and dispersed by beads for the dispersion time indicated in the "Magnetic Layer" column of the table below, and then treated for 0.5 minutes using a batch-type ultrasonic device (20 kHz, 300 W) (ultrasonic dispersion). After that, the mixture was filtered using a filter with a pore size of 0.5 μm to prepare the magnetic layer-forming composition. The non-magnetic layer-forming composition was prepared by the following method. The above components, excluding the lubricants (stearic acid, stearic acid amide, and butyl stearate), were kneaded and diluted using an open kneader, and then dispersed using a horizontal bead mill disperser. Subsequently, lubricants (stearic acid, stearic acid amide, and butyl stearate) were added, and the mixture was stirred and mixed using a dissolver stirrer to prepare a composition for forming a non-magnetic layer. The composition for forming a back coat layer was prepared by the following method: The above components, excluding polyisocyanate, were introduced into a dissolver stirrer and stirred at a peripheral speed of 10 m / s for 30 minutes, after which dispersion was carried out using a horizontal bead mill disperser. Then, polyisocyanate was added, and the mixture was stirred and mixed using a dissolver stirrer to prepare a composition for forming a back coat layer.

[0151] (6) Method for manufacturing magnetic tape and magnetic tape cartridge A non-magnetic layer was formed on the surface of a biaxially stretched support of the type and thickness shown in the table below by applying and drying the non-magnetic layer-forming composition prepared in (5) above so that the thickness after drying was the value shown in the table. Next, a coating layer was formed on the non-magnetic layer by applying the magnetic layer-forming composition prepared in (5) above so that the thickness after drying was 0.1 μm. After that, while the coating layer of the magnetic layer-forming composition was still wet, a magnetic field of strength 0.5 T was applied perpendicular to the surface of the coating layer to perform a vertical orientation treatment, and then it was dried to form a magnetic layer. After that, a back coat layer was formed on the surface of the support opposite to the surface on which the non-magnetic layer and magnetic layer were formed by applying and drying the back coat layer-forming composition prepared in (5) above so that the thickness after drying was 0.5 μm. Subsequently, a surface smoothing treatment (calendering treatment) was performed using a calendering roll composed solely of metal rolls at a speed of 100 m / min, a linear pressure of 300 kg / cm, and a calendering temperature of 90°C (surface temperature of the calendering roll) (number of calendering cycles: see the table below). After that, the long magnetic tape raw material was heat-treated by storing it in a heat treatment furnace at an ambient temperature of 70°C (heat treatment time: 36 hours). After heat treatment, the material was slit into 1 / 2-inch widths to obtain magnetic tape. By recording servo signals on the magnetic layer of the obtained magnetic tape using a commercially available servo writer, a magnetic tape was obtained having data bands, servo bands, and guide bands arranged in accordance with the LTO (Linear Tape-Open) Ultrium format, and having a servo pattern (timing-based servo pattern) on the servo bands arranged and shaped in accordance with the LTO Ultrium format. The servo pattern thus formed 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. The magnetic tape (970 m in length) after the servo pattern formation was wound onto a heat treatment core, and heat treatment was performed while the tape was wound onto this core.As the core for heat treatment, a solid core member made of resin with a flexural modulus of 0.8 GPa (outer diameter: 50 mm) was used, and the tension during winding was set to 0.6 N. The heat treatment was carried out at a heat treatment temperature of 60°C for 5 hours. The absolute weight humidity of the atmosphere in which the heat treatment was performed was 10 g / kg Dry air. After the above heat treatment, after the magnetic tape and the heat treatment core are sufficiently cooled, the magnetic tape is removed from the heat treatment core, wound onto a temporary winding core, and then the magnetic tape is transferred from the temporary winding core to a reel of a magnetic tape cartridge (LTO Ultrium 7 data cartridge) (reel outer diameter: 44 mm), where a length of magnetic tape corresponding to the final product length (960 m) is wound, and the remaining 10 m is cut off. A leader tape according to item 9 of Section 3 of Standard ECMA (European Computer Manufacturers Association)-319 (June 2001) is bonded to the cut end using a commercially available splicing tape. As the temporary winding core, a solid core member made of the same material and having the same outer diameter as the heat treatment core was used, and the tension during winding was set to 0.6 N. Through the above steps, a single-reel type magnetic tape cartridge in which a 960 m long magnetic tape is wound around a reel was produced.

[0152] [Examples 2 to 6, Comparative Examples 1 and 2] A magnetic tape cartridge was produced by the method described in Example 1, except that the items in the table shown below were changed as shown in the table.

[0153] The ferromagnetic powder used for preparing the magnetic layer forming composition in Example 4 is hexagonal strontium ferrite powder ("SrFe" in the table) produced by the following method.

[0154] SrCO ３ 1707 g, H ３ BO ３ 687 g, Fe ２ O ３ 1120 g, Al(OH) ３ 45 g, BaCO ３ 24 g, CaCO ３ 13 g, and Nd ２ O ３235 g thereof was weighed and mixed with a mixer to obtain a raw material mixture. The obtained raw material mixture was melted in a platinum crucible at a melting temperature of 1390°C, and while stirring the melt, a tap hole provided at the bottom of the platinum crucible was heated to allow the melt to flow out in a rod shape at a rate of about 6 g / sec. The outflowed molten liquid was rolled and quenched with water-cooled twin rollers to prepare an amorphous body. 280 g of the prepared amorphous body was charged into an electric furnace, heated to 635°C (crystallization temperature) at a temperature rising rate of 3.5°C / min, and held at the same temperature for 5 hours to precipitate (crystallize) hexagonal strontium ferrite particles. Next, the crystallized product obtained above containing hexagonal strontium ferrite particles was coarsely pulverized in a mortar, 1000 g of zirconia beads with a particle diameter of 1 mm and 800 ml of an aqueous acetic acid solution with a concentration of 1% were added to a glass bottle containing the pulverized product, and dispersion treatment was performed for 3 hours using a paint shaker. Thereafter, the obtained dispersion was separated from the beads and placed in a stainless steel beaker. After the dispersion was allowed to stand at a liquid temperature of 100°C for 3 hours to dissolve the glass component, it was precipitated with a centrifuge, washed by repeating decantation, and dried for 6 hours in a heating furnace with a furnace internal temperature of 110°C to obtain hexagonal strontium ferrite powder. The average particle size of the hexagonal strontium ferrite powder obtained above is 18 nm, and the activation volume is 902 nm ３ , the anisotropy constant Ku is 2.2×10 ５ J / m ３ , the mass magnetization σs is 49 A·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.

[0155] The activation volume and anisotropy constant Ku of the hexagonal strontium ferrite powder described above were obtained using a vibrating sample magnetometer (manufactured by Toei Kogyo Co., Ltd.) by 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.

[0156] For each of Examples 1 to 6, Comparative Example 1, and Comparative Example 2, three magnetic tape cartridges were prepared using the method described above. One was used for (1) below, one for (2) below, and the remaining one was used for (3) described later.

[0157] [Evaluation Method] (1) "NL-TDSage", "NL-TDSenv", and "NL-TDStens" were calculated using the method described in the calculation destination of the left side of Equation 1. The calculated values ​​are shown in the "age", "env", and "tens" columns of "NL-TDS" in the table below, and their sum is calculated and shown in the "Total" column of the table below.

[0158] (2) Before measuring the maximum difference between tape thickness and adjacent thickness, the magnetic tape or magnetic tape cartridge containing the magnetic tape was left in an environment with a temperature of 20-25°C and a relative humidity of 40-60% for at least 5 days to allow it to acclimate to the environment. Subsequently, under the same environment, one tape sample (5 cm in length) was cut from three different locations (randomly selected) along the longitudinal direction of the magnetic tape. Thus, three tape samples were cut. At a randomly selected position on each tape sample, one randomly selected end of the tape sample in the width direction was set as the reference position (0 mm), and the tape thickness was measured at measurement points every 0.6 mm toward the other end in the width direction. Therefore, the tape thickness was measured at measurement points (a total of 21 measurement points) at 0.6 mm, 1.2 mm, 1.8 mm, 2.4 mm, 3.0 mm, 3.6 mm, 4.2 mm, 4.8 mm, 5.4 mm, 6.0 mm, 6.6 mm, 7.2 mm, 7.8 mm, 8.4 mm, 9.0 mm, 9.6 mm, 10.2 mm, 10.8 mm, 11.4 mm, 12.0 mm, and 12.6 mm from the reference position. The arithmetic mean of the measurements obtained by performing the above procedure for all tape samples cut out above was taken as the tape thickness of the magnetic tape being measured. The difference in tape thickness measurements between two adjacent measurement points in the width direction was calculated for all measurement points where measurements were taken. The maximum value among all the differences thus obtained was taken as the "maximum difference in adjacent thickness" of the magnetic tape being measured. Tape thickness was measured using a digital thickness meter consisting of a MARM Millimar 1240 compact amplifier and a Millimar 1301 inductive probe. The thickness of each magnetic tape was as shown in the table below.

[0159] (3) Recording and Playback Performance The recording and playback performance was evaluated using a magnetic tape device with the configuration shown in Figure 21. The arrangement of modules included in the recording and playback head mounted on the recording and playback head unit is "recording module - playback module - recording module" (total number of modules: 3). The number of magnetic head elements in each module is 32 (Ch0 to Ch31), and these magnetic head elements are sandwiched between a pair of servo signal reading elements to form an element array. The playback element width of the playback element included in the playback module is 0.8 μm. The magnetic tape cartridge was placed in one of two environments (arbitrarily selected) that yielded the maximum value of NL-TDSenv for more than 5 days. After acclimatizing to the environment in this way, data was recorded in the same environment as follows: The magnetic tape cartridge was set in the magnetic tape device and the magnetic tape was loaded. Next, while performing servo tracking, the recording and playback head unit recorded pseudo-random data with a specific data pattern onto the magnetic tape. The tension applied in the longitudinal direction of the tape at that time was 0.7 N. For the recording / playback head (magnetic head), at the start of recording and playback, the axis of the element array is tilted toward the direction of magnetic tape travel, with an angle θ of 10°. During data recording, recording is performed three or more times back and forth so that the difference in the value of (PES1 + PES2) / 2 between adjacent tracks is 1.16 μm. PES is an abbreviation for "Position Error Signal". At that time, the angle θ is changed by the control device of the magnetic tape device so that the difference between the effective distance between servo signal reading elements of the element array of the playback module of the recording / playback head and the other servo signal reading element, and "PES2-PES1" which corresponds to the distance between two adjacent servo bands on either side of the data band, is small. Simultaneously with data recording, the value of the servo band spacing along the entire length of the tape is measured every 1 m along the longitudinal position and recorded in the cartridge memory. The magnetic tape cartridge on which data was recorded as described above was placed in a storage environment with an ambient temperature of 35°C and a relative humidity of 80% for 24 hours.Subsequently, the magnetic tape cartridge was placed for more than five days in the other environment (of the two environments) that was not selected above, which was the combination that yielded the maximum value of NL-TDSenv. After allowing the cartridge to acclimate to the environment, data playback was performed in the same environment as follows: The magnetic tape cartridge was set in the magnetic tape device and the magnetic tape was loaded. Next, with the NL-TDStens set to the tension obtained above, the recording / playback head unit played back the data recorded on the magnetic tape while performing servo tracking. At that time, the servo band interval value was measured simultaneously with playback, and based on the information recorded in the cartridge memory, the control device of the magnetic tape device changed the angle θ so that the absolute value of the difference between the servo band interval at the same longitudinal position and the servo band interval at the time of recording approached 0. During playback, the measurement of the servo band interval and the adjustment of the angle θ based on it were performed continuously in real time. In the above playback, the number of playback elements (number of channels) is 32 channels. During playback, if all 32 channels of data are read correctly, the recording and playback performance is evaluated as "3". If the data from channels 31 to 28 is read correctly, the recording and playback performance is evaluated as "2". In all other cases, the recording and playback performance is evaluated as "1".

[0160] The results are shown in the table below.

[0161]

[0162]

[0163]

[0164] Except for the fact that vertical orientation processing was not performed during the manufacturing of the magnetic tape, a magnetic tape cartridge was manufactured in the same manner as described above for Example 1. A sample piece was cut from the magnetic tape removed from the above magnetic tape cartridge. The vertical angular ratio of this sample piece was determined using a Tamagawa Seisakusho TM-TRVSM5050-SMSL type vibrating sample magnetometer in the same manner as described above, and was found to be 0.55. A magnetic tape was also removed from the magnetic tape cartridge of Example 1, and the vertical angular ratio of a sample piece cut from this magnetic tape was similarly determined, and was found to be 0.65.

[0165] The magnetic tapes extracted from the two magnetic tape cartridges described above were each mounted on a 1 / 2-inch reel tester, and their electromagnetic conversion characteristics (SNR: Signal-to-Noise Ratio) were evaluated using the following method. As a result, the magnetic tape extracted from the magnetic tape cartridge of Example 1 showed an SNR value 4 dB higher than that of the magnetic tape manufactured without vertical orientation treatment. Recording and playback were performed in 10 passes under a tension of 0.7 N 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. 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.

[0166] 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 magnetic layer has three or more servo bands, and the maximum difference between adjacent tape thicknesses measured at 0.6 mm intervals in the width direction of the magnetic tape is 12 nm or less.

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

3. 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.

4. The magnetic tape according to claim 1, wherein the non-magnetic support is a polyethylene naphthalate support.

5. The magnetic tape according to claim 1, wherein the non-magnetic support is a polyethylene terephthalate support.

6. The magnetic tape according to claim 1, wherein the non-magnetic support is an aromatic polyamide support.

7. The magnetic tape according to claim 1, wherein the tape thickness of the magnetic tape is 5.6 μm or less.

8. The magnetic tape according to claim 1, wherein the tape thickness of the magnetic tape is 5.3 μm or less.

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

10. 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, 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 non-magnetic support being a polyethylene naphthalate support, a polyethylene terephthalate support, or an aromatic polyamide support, the tape thickness of the magnetic tape being 5.6 μm or less, and the vertical angular ratio of the magnetic tape being 0.60 or more.

11. A magnetic tape cartridge comprising the magnetic tape described in any one of claims 1 to 10.

12. A magnetic tape device including the magnetic tape according to any one of claims 1 to 10.

13. The magnetic tape device according to claim 12, 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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