Magnetic tape, magnetic tape cartridge, and magnetic tape device

Abstract

To provide a magnetic tape that offers excellent running stability when recording and / or playing back with the head tilted in a high-temperature, low-humidity environment. [Solution] A magnetic tape having a non-magnetic support and a magnetic layer containing ferromagnetic powder. The average valley depth Rvm measured at one edge of the surface of the magnetic layer and the average valley depth Rvm measured at the other edge are both between -0.55 μm and -0.20 μm. The edge portion is the part between 0 μm and 1 μm in the tape width direction, with the edge position being 0 μm. A magnetic tape cartridge and a magnetic tape device including the above magnetic tape.

Description

Technical Field

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

Background Art

[0002] Magnetic recording media include tape-shaped and disk-shaped ones. For data storage applications such as data backup and archive, tape-shaped magnetic recording media, that is, magnetic tapes, are mainly used (see, for example, Patent Documents 1 to 4).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0004] Recording of data on a magnetic tape is usually performed by running the magnetic tape in a magnetic tape device and causing a magnetic head (also simply referred to as a "head") to follow the data band of the magnetic tape and record data on the data band. Thereby, data tracks are formed on the data band. Also, at the time of reproducing the recorded data, the magnetic tape is run in the magnetic tape device, and the magnetic head is caused to follow the data band of the magnetic tape to read the data recorded on the data band.

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

[0006] For example, if we consider changing the head tilt angle as described above, it is desirable that the magnetic tape has high stability when recording and / or playing back data by tilting the axial direction of the magnetic head module relative to the width direction of the magnetic tape (i.e., tilting the head). This is because high stability in the magnetic tape's movement can, for example, further suppress the occurrence of the above-mentioned phenomenon.

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

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

[0009] One aspect of the present invention is as follows: [1] A magnetic tape having a non-magnetic support and a magnetic layer containing ferromagnetic powder, The average valley depth Rvm measured at one edge of the surface of the magnetic layer described above, and the average valley depth Rvm measured at the other edge, are both between -0.55 μm and -0.20 μm. The edge portion described above is the magnetic tape portion between 0 μm and 1 μm in the tape width direction, where the edge position is defined as 0 μm. [2] The magnetic tape described in [1], wherein the tape thickness of the magnetic tape is 5.0 μm or less. [3] The magnetic tape described in [1] or [2], wherein the vertical aspect ratio of the magnetic tape is 0.65 or greater. [4] The magnetic tape according to any one of the items [1] to [3], wherein the non-magnetic support is an aromatic polyester support. [5] The magnetic tape according to any one of [1] to [3], wherein the non-magnetic support is an aromatic polyamide support. [6] A magnetic tape according to any one of [1] to [5], further comprising a non-magnetic layer containing non-magnetic powder between the non-magnetic support and the magnetic layer. [7] A magnetic tape according to any one of [1] to [6], 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. [8] The tape thickness of the above magnetic tape is 5.0 μm or less. The vertical aspect ratio of the above magnetic tape is 0.65 or greater. The above nonmagnetic support is an aromatic polyester support or an aromatic polyamide support. The non-magnetic support and the magnetic layer further comprise a non-magnetic layer containing non-magnetic powder, A magnetic tape according to any one of [1] to [7], 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. A magnetic tape cartridge containing a magnetic tape as described in any of [9][1] to [8]. A magnetic tape device including a magnetic tape as described in any of

[10] [1] to [8].

[11] Further including a magnetic head, The magnetic head has a module including an element array having a plurality of magnetic head elements between a pair of servo signal reading elements, and The magnetic tape device described in

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

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

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

[0012] [Magnetic tape] One aspect of the present invention relates to a magnetic tape having a non-magnetic support and a magnetic layer containing ferromagnetic powder. The average valley depth Rvm measured at one edge of the surface of the magnetic layer and the average valley depth Rvm measured at the other edge are both between -0.55 μm and -0.20 μm. The edge is the portion from 0 μm to 1 μm in the tape width direction, with the edge position being 0 μm. Hereinafter, the average valley depth Rvm measured at one edge of the surface of the magnetic layer and the average valley depth Rvm measured at the other edge will be collectively referred to as "edge Rvm".

[0013] <Head tilt angle> The magnetic head may have one or more modules, two or more, or three or more, which include an element array having multiple magnetic head elements between a pair of servo signal reading elements. The total number of such modules may be, for example, five or fewer, four or fewer, or three or fewer, or the magnetic head may contain more modules than the total number exemplified herein. Examples of arrangements of multiple modules include "recording module - playback module" (total number of modules: 2), "recording module - playback module - recording module" (total number of modules: 3), etc. However, the arrangement is not limited to the examples shown herein.

[0014] Each module may include an element array, i.e., an array of elements, having multiple magnetic head elements between a pair of servo signal reading elements. A module having recording elements as magnetic head elements is a recording module for recording data onto magnetic tape. A module having playback elements as magnetic head elements is a playback module for playing back data recorded on magnetic tape. In a magnetic head, multiple modules are arranged, for example, in a recording / playback head unit, with the axes of the element arrays of each module oriented parallel to each other. Such "parallel" does not necessarily mean parallel in the strict sense, but includes a range of error that is normally acceptable in the art to which this invention belongs. The range of error can mean, for example, a range of less than ±10° of strict parallelism.

[0015] In each element array, a pair of servo signal reading elements and a plurality of magnetic head elements (i.e., recording elements or playback elements) are typically arranged in a straight line and spaced apart. Here, "arranged in a straight line" means that each magnetic head element is arranged on a straight line connecting the center of one servo signal reading element and the center of the other servo signal reading element. Furthermore, in this invention and specification, "axis of the element array" means the straight line connecting the center of one servo signal reading element and the center of the other servo signal reading element.

[0016] 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.

[0017] Figure 1 is a schematic diagram showing an example of a magnetic head module. The module shown in Figure 1 has multiple magnetic head elements between a pair of servo signal reading elements (servo signal reading elements 1 and 2). Magnetic head elements are also called "channels." "Ch" in the figure is an abbreviation for Channel. The module shown in Figure 1 has a total of 32 magnetic head elements, from Ch0 to Ch31.

[0018] 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.

[0019] Figure 2 is an explanatory diagram of the relative positional relationship between the module and the magnetic tape during magnetic tape movement in a magnetic tape device. In Figure 2, dotted line A indicates the width direction of the magnetic tape. Dotted line B indicates the axis of the element array. Angle θ can be said to be the head tilt angle during magnetic tape movement, and is the angle between dotted line A and dotted line B. When angle θ is 0° during magnetic tape movement, the distance in the magnetic tape width direction between one servo signal reading element and the other servo signal reading element of the element array (hereinafter also referred to as the "effective distance between servo signal reading elements") is "L". In contrast, when angle θ is greater than 0°, the effective distance between servo signal reading elements is "Lcosθ", and Lcosθ is smaller than L. That is, "Lcosθ <L」である。

[0020] As mentioned earlier, during recording or playback, if the magnetic head used to record or play back data is misaligned from the intended track position due to deformation of the magnetic tape's width, phenomena such as overwriting of recorded data or playback failures may occur. For example, if the width of the magnetic tape shrinks or expands, the magnetic head element that should record or play back at the intended track position may end up recording or playing back at a different track position. Also, if the width of the magnetic tape expands, the effective distance between servo signal reading elements may become shorter than the distance between two adjacent servo bands separated by a data band (also referred to as "servo band spacing" or "servo band interval"; more specifically, the distance between the two servo bands in the width direction of the magnetic tape), which may result in data not being recorded or played back in areas close to the edge of the magnetic tape. In contrast, when the element array is tilted at an angle θ greater than 0°, as explained earlier, the effective distance between servo signal reading elements becomes "Lcosθ". The larger the value of θ, the smaller the value of Lcosθ, and the smaller the value of θ, the larger the value of Lcosθ. Therefore, by changing the value of θ according to the degree of dimensional change (i.e., contraction or expansion) in the width direction of the magnetic tape, it becomes possible to bring the effective distance between servo signal reading elements closer to or matching the spacing of the servo bands. This prevents or reduces the frequency of phenomena such as overwriting of recorded data or playback failures that occur when the magnetic head used to record or play back data is misaligned from the target track position due to width deformation of the magnetic tape during recording or playback.

[0021] Figure 3 is an explanatory diagram regarding the change in angle θ during magnetic tape travel. The angle θ at the start of the journey is θ initial This can be set to, for example, 0° or greater than or equal to 0°. In Figure 3, the central diagram shows the state of the module at the start of operation. In Figure 3, the right-hand figure shows the angle θ as θ initial An angle θ is a larger angle. cshows the state of the module when [conditions]. The effective distance Lcosθ between servo signal reading elements c is a value smaller than Lcosθ at the start of magnetic tape running. When the width of the magnetic tape contracts during magnetic tape running, it is preferable to perform such angle adjustment. initial When the width of the magnetic tape contracts during magnetic tape running, it is preferable to perform such angle adjustment. On the other hand, in FIG. 3, the left figure shows the state of the module when the angle θ is set to an angle θ initial smaller than [original angle]. The effective distance Lcosθ between servo signal reading elements e shows the state of the module when [conditions]. The effective distance Lcosθ between servo signal reading elements e is a value larger than Lcosθ at the start of magnetic tape running. When the width of the magnetic tape expands during magnetic tape running, it is preferable to perform such angle adjustment. initial When the width of the magnetic tape expands during magnetic tape running, it is preferable to perform such angle adjustment.

[0022] As described above, changing the head tilt angle during magnetic tape running can contribute to preventing phenomena such as overwriting of recorded data and playback failure that may occur when the magnetic head deviates from the target track position due to width deformation of the magnetic tape during recording or playback and recording or playing back data, or can contribute to reducing the occurrence frequency thereof. On the other hand, recording data on the magnetic tape and playing back the recorded data are usually performed by running the magnetic tape and sliding the magnetic layer surface and the magnetic head. The inventor speculated that when the head is tilted and the magnetic tape is run during such recording and / or playback, the contact state between the magnetic head and the magnetic layer surface becomes unstable, which may be a factor in reducing the running stability. Based on the above inference, the inventors conducted extensive research. As a result, the inventors have newly discovered that magnetic tapes in which the edge portion Rvm (details to be described later) is between -0.55 μm and -0.20 μm at both edges of the magnetic tape can exhibit excellent running stability when recording and / or playing back data with the head tilted in a high-temperature, low-humidity environment. The inventors believe that the edge portion Rvm is a value that can serve as an indicator of the depth of minute cracks occurring at the edges of the magnetic layer surface. The inventors speculate that by suppressing the occurrence of deep minute cracks at the edges and allowing appropriately shallow cracks to exist, it is possible to suppress the partial peeling of the magnetic tape from cracks present at the edges of the magnetic layer surface when the head is tilted and the head slides against the magnetic layer surface, thereby suppressing the generation of detached pieces called debris. Since the adhesion of debris to the head is thought to destabilize the contact state between the head and the magnetic layer surface, the inventors speculate that suppressing the generation of debris contributes to improved running stability. However, the present invention is not limited by the inventors' inferences described herein. In this specification, the stability of data recording and / or playback when the head is tilted during magnetic tape travel in a high-temperature, low-humidity environment is also simply referred to as "travel stability." A high-temperature, low-humidity environment can be, for example, an environment with a temperature of approximately 30°C to 50°C. The humidity of that environment can be, for example, approximately 0% to 30% as relative humidity. In this invention and this specification, the temperature and humidity described for the environment refer to the ambient temperature and relative humidity of that environment.

[0023] <Edge RVM> In the present invention and this specification, the edge portion Rvm is determined by the following method. Measurements are performed under the following conditions, including one edge of the magnetic layer surface of the magnetic tape in the tape width direction in the measurement field of view, and the other edge of the magnetic layer surface in the measurement field of view. An example of a non-contact optical surface roughness meter is the Bruker Contour GT-I. The measurements described in the Examples section below are performed using the Bruker Contour GT-I as the non-contact optical surface roughness meter. In the present invention and this specification, "magnetic layer surface" is synonymous with the magnetic layer side surface of the magnetic tape. (Measurement conditions) Environment: Temperature 23℃, relative humidity 50% Device: Non-contact optical surface roughness meter Measurement mode: VSI (Vertical Scan Interferometry) Objective lens: 50x Intermediate lens: 2.0x Measurement viewing angle: X axis 48.2μm x Y axis 36.2μm Average: 3 times Sample orientation: The magnetic tape should be positioned so that its longitudinal direction is parallel to the X-axis in the measurement field of view before measurement. Sample fixation method: To prevent shifting during measurement and lifting of the magnetic tape, the sample is fixed by adsorption onto the adsorption layer of the adsorption film, ensuring that the edges are not covered. A commercially available adsorption film can be used as the adsorption film.

[0024] Measurements that include one edge of each of the two edges in the tape width direction of the magnetic tape are performed at a total of three measurement points, shifted by 5 mm or more in the longitudinal direction of the tape. The position of the edge in the tape width direction within the measurement field is set to 0 μm, and the arithmetic mean of the average valley depth Rvm obtained for each of the three measurement points in the range of 0 μm to 1 μm is taken as the edge Rvm of one of the edges. Measurements including the other edge of both edges in the tape width direction of the magnetic tape are also performed at a total of three measurement points, shifted by 5 mm or more in the longitudinal direction of the tape. The position of the edge in the tape width direction within the measurement field is set to 0 μm, and the arithmetic mean of the average valley depth Rvm obtained for each of the three measurement points in the range of 0 μm to 1 μm is taken as the edge Rvm of the other edge. In the data obtained from each of the above measurements, a line in the longitudinal direction of the tape (X-axis direction) that does not have any data loss is defined as an "edge". For each measurement point, the software calculates the average valley depth Rvm by processing the data under the following data processing conditions. Examples of data processing software include Bruker Vision64. The edge Rvm values ​​described in the "Examples" section below are obtained by processing the data using Bruker Vision64 software for each measurement point to acquire the Rvm. (Data processing conditions) Distortion / Tilt Correction: Tilt Only (Plane Fit)

[0025] In the magnetic tape described above, the average valley depth Rvm measured at one edge of the magnetic layer surface and the average valley depth Rvm measured at the other edge are both between -0.55 μm and -0.20 μm. The edge Rvm of one edge and the edge Rvm of the other edge may be the same value or different values, as long as they are both within the range of -0.55 μm and -0.20 μm. From the viewpoint of further improving running stability, the edge Rvm of each edge is preferably -0.50 μm or more, and more preferably -0.45 μm or more, -0.40 μm or more, and -0.35 μm or more. Furthermore, from the viewpoint of further improving running stability, the Rvm of each edge portion is preferably -0.25 μm or less, and more preferably -0.30 μm or less. The control means for the edge RVM will be described later.

[0026] The magnetic tape described above will be explained in more detail below.

[0027] <Magnetic layer> (Ferromagnetic powder) As the ferromagnetic powder contained in the magnetic layer, one or more known ferromagnetic powders used in the magnetic layers of various magnetic recording media can be used in combination. Using a ferromagnetic powder with a small average particle size is preferable from the viewpoint of improving recording density. From this viewpoint, the average particle size of the ferromagnetic powder is preferably 50 nm or less, more preferably 45 nm or less, even more preferably 40 nm or less, even more preferably 35 nm or less, even more preferably 30 nm or less, even more preferably 25 nm or less, and even more preferably 20 nm or less. On the other hand, from the viewpoint of magnetization stability, the average particle size of the ferromagnetic powder is preferably 5 nm or more, more preferably 8 nm or more, even more preferably 10 nm or more, even more preferably 15 nm or more, and even more preferably 20 nm or more.

[0028] Hexagonal ferrite powder A preferred example of ferromagnetic powder is hexagonal ferrite powder. For details on hexagonal ferrite powder, see, for example, paragraphs 0012 to 0030 of Japanese Patent Publication No. 2011-225417, paragraphs 0134 to 0136 of Japanese Patent Publication No. 2011-216149, paragraphs 0013 to 0030 of Japanese Patent Publication No. 2012-204726, and paragraphs 0029 to 0084 of Japanese Patent Publication No. 2015-127985.

[0029] 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).

[0030] Below, we will describe hexagonal strontium ferrite powder, a form of hexagonal ferrite powder, in more detail.

[0031] The activation volume of hexagonal strontium ferrite powder is 2500 nm. 3 Preferably, the following: 2300nm 3 The following is more preferable: 2000 nm 3 It is even more preferable that the following conditions are met. On the other hand, from the viewpoint of magnetization stability, the activation volume of the hexagonal strontium ferrite powder is, for example, 800 nm. 3 Preferably, it is 1000 nm or more. 3 It is more preferable that the above is true, and 1200nm 3 It is even more preferable that the above conditions are met. The same applies to the activation volume of the hexagonal barium ferrite powder.

[0032] "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℃±1℃). Note that the unit of the anisotropy constant Ku is 1erg / cc = 1.0 × 10⁻⁶. -1 J / m 3 That is the case. Hc=2Ku / Ms{1-[(kT / KuV)ln(At / 0.693)] 1 / 2} [In the above formula, Ku: anisotropy constant (unit: J / m 3 ), Ms: Saturation magnetization (unit: kA / m), k: Boltzmann constant, T: Absolute temperature (unit: K), V: Activation volume (unit: cm) 3 ), A: Spin precession frequency (unit: s) -1 ), t: magnetic field reversal time (unit: s)]

[0033] 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 × 105 J / m 3 It can have a Ku content of the above. Also, the Ku content of hexagonal strontium ferrite powder is, for example, 2.5 × 10⁻⁶. 5 J / m 3 The following values ​​are possible. However, since a higher Ku value is preferable as it indicates higher thermal stability, the values ​​are not limited to those exemplified above.

[0034] Hexagonal strontium ferrite powder may or may not contain rare earth atoms. When hexagonal strontium ferrite powder contains rare earth atoms, it is preferable that the rare earth atoms are present at a concentration of 0.5 to 5.0 atomic percent (bulk concentration) per 100 atomic percent of iron atoms. In one embodiment, hexagonal strontium ferrite powder containing rare earth atoms may exhibit a segregation of rare earth atoms in the surface layer. In the present invention and this specification, "rare earth atom surface layer segregation" means that the rare earth atom content relative to 100% of iron atoms in a solution obtained by partially dissolving hexagonal strontium ferrite powder with acid (hereinafter referred to as "rare earth atom surface layer content" or simply "surface layer content" with respect to rare earth atoms) is different from the rare earth atom content relative to 100% of iron atoms in a solution obtained by completely dissolving hexagonal strontium ferrite powder with acid (hereinafter referred to as "rare earth atom bulk content" or simply "bulk content" with respect to rare earth atoms), Rare earth atom surface content / Rare earth atom bulk content > 1.0 This means that the ratio is satisfied. The rare earth atom content of hexagonal strontium ferrite powder described later is synonymous with the rare earth atom bulk content. In contrast, partial dissolution using acid dissolves the surface layer of the particles constituting the hexagonal strontium ferrite powder, so the rare earth atom content in the solution obtained by partial dissolution is the rare earth atom content in the surface layer of the particles constituting the hexagonal strontium ferrite powder. When the rare earth atom surface layer content satisfies the ratio "rare earth atom surface layer content / rare earth atom bulk content > 1.0", it means that in the particles constituting the hexagonal strontium ferrite powder, rare earth atoms are concentrated in the surface layer (i.e., there are more of them in the surface layer than in the interior). In this invention and specification, the surface layer means a part of the region extending from the surface to the interior of the particles constituting the hexagonal strontium ferrite powder.

[0035] When hexagonal strontium ferrite powder contains rare earth atoms, the rare earth atom content (bulk content) is preferably in the range of 0.5 to 5.0 atomic percent relative to 100 atomic percent of iron atoms. It is believed that containing rare earth atoms at the bulk content within the above range, and having the rare earth atoms unevenly distributed on the surface of the particles constituting the hexagonal strontium ferrite powder, contributes to suppressing the decrease in regeneration output during repeated regeneration. This is presumed to be because the anisotropy constant Ku can be increased by containing rare earth atoms at the bulk content within the above range, and having the rare earth atoms unevenly distributed on the surface of the particles constituting the hexagonal strontium ferrite powder. The higher the value of the anisotropy constant Ku, the more it is possible to suppress the occurrence of a phenomenon called thermal fluctuation (in other words, to improve thermal stability). By suppressing the occurrence of thermal fluctuation, the decrease in regeneration output during repeated regeneration can be suppressed. It is speculated that the uneven distribution of rare earth atoms on the surface of hexagonal strontium ferrite powder particles contributes to stabilizing the spin of iron (Fe) sites within the crystal lattice of the surface layer, thereby increasing the anisotropy constant Ku. Furthermore, it is presumed that using hexagonal strontium ferrite powder with a rare-earth atom uneven distribution on the surface as the ferromagnetic powder for the magnetic layer contributes to suppressing wear on the magnetic layer surface due to sliding with the magnetic head. In other words, it is presumed that hexagonal strontium ferrite powder with a rare-earth atom uneven distribution on the surface may also contribute to improving the running durability of the magnetic tape. This is presumed to be because the uneven distribution of rare-earth atoms on the surface of the particles constituting the hexagonal strontium ferrite powder contributes to improved interaction between the particle surface and organic substances (e.g., binders and / or additives) contained in the magnetic layer, resulting in improved strength of the magnetic layer. From the viewpoint of 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.

[0036] The bulk content mentioned above is the content obtained by completely dissolving the hexagonal strontium ferrite powder. In this invention and specification, unless otherwise specified, the content of atoms refers to the bulk content obtained by completely dissolving the hexagonal strontium ferrite powder. The hexagonal strontium ferrite powder containing rare earth atoms may contain only one type of rare earth atom, or it may contain two or more types of rare earth atoms. When two or more types of rare earth atoms are included, the bulk content mentioned above is determined for the sum of the two or more types of rare earth atoms. This also applies to other components in this invention and specification. That is, unless otherwise specified, a certain component may be used alone, or two or more types may be used. When two or more types are used, the content or content refers to the sum of the two or more types.

[0037] 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.

[0038] In hexagonal strontium ferrite powder having a rare-earth atom surface segregation, the rare-earth atoms only need to be segregated in the surface layer of the particles constituting the hexagonal strontium ferrite powder, and the degree of segregation is not limited. For example, in hexagonal strontium ferrite powder having a rare-earth atom surface segregation, the ratio of the rare-earth atom surface content obtained by partial dissolution under the dissolution conditions described later to the rare-earth atom bulk content obtained by total dissolution under the dissolution conditions described later, "surface content / bulk content," is greater than 1.0 and can be 1.5 or greater. A "surface content / bulk content" greater than 1.0 means that in the particles constituting the hexagonal strontium ferrite powder, rare-earth atoms are segregated in the surface layer (i.e., there are more of them in the surface layer than in the interior). Furthermore, the ratio of the surface content of rare earth atoms obtained by partial dissolution under the dissolution conditions described later to the bulk content of rare earth atoms obtained by total dissolution under the dissolution conditions described later, "surface content / bulk content," can be, for example, 10.0 or less, 9.0 or less, 8.0 or less, 7.0 or less, 6.0 or less, 5.0 or less, or 4.0 or less. However, in hexagonal strontium ferrite powder having a rare earth atom surface distribution bias, the rare earth atoms only need to be biased towards the surface of the particles constituting the hexagonal strontium ferrite powder, and the above "surface content / bulk content" is not limited to the upper or lower limits exemplified.

[0039] The partial and total dissolution of hexagonal strontium ferrite powder is described below. For hexagonal strontium ferrite powder existing as a powder, the sample powders to be partially and completely dissolved are taken from the same lot of powder. On the other hand, for hexagonal strontium ferrite powder contained in the magnetic layer of a magnetic tape, a portion of the hexagonal strontium ferrite powder extracted from the magnetic layer is subjected to partial dissolution, and another portion is subjected to total dissolution. The extraction of hexagonal strontium ferrite powder from the magnetic layer can be carried out, for example, by the method described in paragraph 0032 of Japanese Patent Application Publication No. 2015-91747. Partial dissolution, as described above, refers to a state where the hexagonal strontium ferrite powder is dissolved to the extent that residual particles can be visually confirmed in the liquid at the end of the dissolution process. For example, partial dissolution can dissolve 10 to 20% by mass of the particles constituting the hexagonal strontium ferrite powder, with the total particles being 100% by mass. On the other hand, total dissolution, as described above, refers to a state where the hexagonal strontium ferrite powder is dissolved to the extent that no residual particles can be visually confirmed in the liquid at the end of the dissolution process. The above-mentioned partial dissolution and surface layer content measurement are performed, for example, by the following method. However, the dissolution conditions such as the amount of sample powder described below are examples only, and any dissolution conditions that enable partial and total dissolution can be arbitrarily adopted. A container (e.g., a beaker) containing 12 mg of sample powder and 10 mL of 1 mol / L hydrochloric acid is held on a hot plate at a set temperature of 70°C for 1 hour. The resulting solution is filtered through a 0.1 μm membrane filter. Elemental analysis of the resulting filtrate is performed using an inductively coupled plasma (ICP) analyzer. In this way, the surface content of rare earth atoms relative to 100% iron atoms can be determined. If multiple types of rare earth atoms are detected by elemental analysis, the total content of all rare earth atoms is taken as the surface content. This is also the case when measuring bulk content. On the other hand, the measurement of total dissolution and bulk content is performed, for example, by the following method. A container (e.g., a beaker) containing 12 mg of sample powder and 10 mL of 4 mol / L hydrochloric acid is held on a hot plate at a set temperature of 80°C for 3 hours. Afterward, the bulk content relative to 100 atomic percent of iron can be determined by performing the same procedure as described above for partial dissolution and surface layer content measurement.

[0040] From the perspective of increasing the playback output when reproducing data recorded on magnetic tape, it is desirable for the mass magnetization σs of the ferromagnetic powder contained in the magnetic tape to be high. In this regard, hexagonal strontium ferrite powder containing rare earth atoms but lacking surface segregation of rare earth atoms tended to have a significantly lower σs compared to hexagonal strontium ferrite powder that does not contain rare earth atoms. In contrast, hexagonal strontium ferrite powder with surface segregation of rare earth atoms is considered preferable in order to suppress such a large decrease in σs. In one embodiment, the σs of hexagonal strontium ferrite powder is 45 A·m 2 It can be 47 A·m or more per kg. 2 It can also be more than / kg. On the other hand, σs is 80 A·m from the viewpoint of noise reduction. 2 Preferably less than / kg, at 60A·m 2 It is more preferable that it be less than or equal to / kg. σs can be measured using a known measuring device capable of measuring magnetic properties, such as a vibrating sample magnetometer. In this invention and specification, unless otherwise specified, the mass magnetization σs is the value measured at a magnetic field strength of 15 kOe. 1 [kOe] = 10 6 It is / 4π[A / m].

[0041] Regarding the constituent atom content (bulk content) of hexagonal strontium ferrite powder, the strontium atom content can be in the range of, for example, 2.0 to 15.0 atomic percent per 100 atomic percent of iron atoms. In one form, hexagonal strontium ferrite powder may contain only strontium atoms as the divalent metal atom. In another form, hexagonal strontium ferrite powder may contain one or more other divalent metal atoms in addition to strontium atoms. For example, it may contain barium atoms and / or calcium atoms. When other divalent metal atoms besides strontium atoms are included, the barium atom content and calcium atom content in the hexagonal strontium ferrite powder can be in the range of, for example, 0.05 to 5.0 atomic percent per 100 atomic percent of iron atoms.

[0042] 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 preferably contains iron atoms, strontium atoms, oxygen atoms, and rare earth atoms, and the content of atoms other than these atoms is preferably 10.0 atomic percent or less, more preferably in the range of 0 to 5.0 atomic percent, and may even be 0 atomic percent, relative to 100 atomic percent of iron atoms. That is, in one embodiment, the hexagonal strontium ferrite powder does not need to contain atoms other than iron atoms, strontium atoms, oxygen atoms, and rare earth atoms. The above content expressed in atomic percent is obtained by converting the content of each atom (unit: mass%) obtained by completely dissolving the hexagonal strontium ferrite powder into an atomic percent value using the atomic weight of each atom. Furthermore, in the present invention and this specification, "does not contain" for a certain atom means that the content measured by an ICP analyzer after complete dissolution is 0 mass%. The detection limit of an ICP analyzer is typically 0.01 ppm (parts per million) or less by mass. The term "does not contain" above is used to include the presence of substances in amounts below the detection limit of the ICP analyzer.Hexagonal strontium ferrite powder can, in one form, be bismuth-free (Bi).

[0043] metal powder A preferred specific example of ferromagnetic powder is ferromagnetic metal powder. For details on ferromagnetic metal powder, see, for example, paragraphs 0137-0141 of Japanese Patent Publication No. 2011-216149 and paragraphs 0009-0023 of Japanese Patent Publication No. 2005-251351.

[0044] ε-Iron oxide powder A preferred specific example of a ferromagnetic powder is ε-iron oxide powder. In the present invention and this specification, "ε-iron oxide powder" refers to a ferromagnetic powder in which the crystalline structure of ε-iron oxide is detected as the main phase by X-ray diffraction analysis. For example, if the highest intensity diffraction peak in the X-ray diffraction spectrum obtained by X-ray diffraction analysis is attributed to the crystalline structure of ε-iron oxide, it shall be determined that the crystalline structure of ε-iron oxide has been detected as the main phase. Methods for producing ε-iron oxide powder include methods from goethite and the reverse micelle method. All of the above production methods are publicly known. Furthermore, for methods for producing ε-iron oxide powder in which some of the Fe is substituted with substitution atoms such as Ga, Co, Ti, Al, and Rh, see, for example, J. Jpn. Soc. Powder Metallurgy Vol. 61 Supplement, No. S1, pp. S280-S284, J. Mater. Chem. C, 2013, 1, pp. 5200-5206, etc. However, the method for producing ε-iron oxide powder that can be used as ferromagnetic powder in the magnetic layer of the magnetic tape described above is not limited to the method described herein.

[0045] The activation volume of ε-iron oxide powder is preferably 300 to 1500 nm. 3 The activation volume is within the range described above. Micronized ε-iron oxide powder exhibiting an activation volume within the above range is suitable for the production of magnetic tapes that exhibit excellent electromagnetic conversion properties. The activation volume of the ε-iron oxide powder is preferably 300 nm. 3 That's all, for example, 500nm3 It can also be the above. Furthermore, from the viewpoint of further improving electromagnetic conversion characteristics, the activation volume of ε-iron oxide powder is 1400 nm. 3 The following is more preferable: 1300nm 3 It is even more preferable that the following occur: 1200 nm 3 It is even more preferable that the following conditions be met: 1100 nm 3 The following is even more preferable.

[0046] 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 can have the above amount of Ku. Also, the amount of Ku in ε-iron oxide powder is, for example, 3.0 × 10⁻⁶. 5 J / m 3 The following values ​​are possible. However, a higher Ku value indicates higher thermal stability and is therefore preferable, so the values ​​are not limited to those exemplified above.

[0047] From the perspective of increasing the playback output when reproducing data recorded on magnetic tape, it is desirable for the mass magnetization σs of the ferromagnetic powder contained in the magnetic tape to be high. In this regard, in one embodiment, the σs of ε-iron oxide powder is 8 A·m 2 It can be 12 A·m or more / kg. 2 It can also be more than / kg. On the other hand, the σs of ε-iron oxide powder is 40 A·m from the viewpoint of noise reduction. 2 Preferably less than / kg, 35A·m 2 It is more preferable that the amount be less than or equal to / kg.

[0048] In the present invention and this specification, unless otherwise specified, the average particle size of various powders such as ferromagnetic powders shall be the value measured using a transmission electron microscope by the following method. The powder is photographed using a transmission electron microscope at a magnification of 100,000x, and the resulting image is printed on photographic paper or displayed on a screen to obtain a total magnification of 500,000x, thereby obtaining a photograph of the particles that make up the powder. From the obtained photographs of the particles, the target particles are selected, and their contours are traced with a digitizer to measure the size of the particles (primary particles). Primary particles are defined as independent particles that do not aggregate. The above measurements are performed on 500 randomly selected particles. The arithmetic mean of the particle sizes of these 500 particles is taken as the average particle size of the powder. As the transmission electron microscope, for example, a Hitachi H-9000 transmission electron microscope can be used. The particle size can be measured using known image analysis software, for example, Carl Zeiss KS-400 image analysis software. Unless otherwise specified, the average particle sizes described in the Examples section below are values ​​measured using a Hitachi H-9000 transmission electron microscope and Carl Zeiss KS-400 image analysis software. In the present invention and this specification, "powder" means a collection of multiple particles. For example, ferromagnetic powder means a collection of multiple ferromagnetic particles. Furthermore, a collection of multiple particles is not limited to a form in which the particles constituting the collection are in direct contact, but also includes forms in which binders, additives, etc., described later, are interposed between the particles. The word "particle" is sometimes used to refer to powder.

[0049] For example, the method described in paragraph 0015 of Japanese Patent Publication No. 2011-048878 can be used to collect sample powder from a magnetic tape for particle size measurement.

[0050] In the present invention and this specification, unless otherwise specified, the size of the particles constituting the powder (particle size) is determined by the shape of the particles observed in the above particle photograph. (1) In the case of needle-shaped, spindle-shaped, columnar (however, the height is greater than the longest diameter of the base), etc., the length of the long axis constituting the particle is expressed as the long axis length, (2) In the case of a plate or column (provided that the thickness or height is less than the longest diameter of the plate or base), it shall be expressed by the longest diameter of the plate or base. (3) If the shape is spherical, polyhedral, irregular, etc., and the major axis constituting the particle cannot be determined from the shape, it shall be represented by the equivalent diameter of a circle. The equivalent diameter of a circle refers to the diameter obtained by the circular projection method.

[0051] Furthermore, the average needle-shape ratio of the powder refers to the arithmetic mean of the values ​​obtained for the 500 particles by measuring the length of the short axis of each particle, i.e., the short axis length, in the above measurement, and determining the (long axis length / short axis length) value for each particle. Here, unless otherwise specified, the short axis length refers to the length of the short axis constituting the particle in the above definition of particle size (1), the thickness or height in the case of (2), and in the case of (3), since there is no distinction between the long axis and the short axis, (long axis length / short axis length) is considered to be 1 for convenience. Unless otherwise specified, when the particle shape is specific, for example, in the case of definition (1) above, the average particle size is the average major axis length, and in the case of definition (2), the average particle size is the average plate diameter. In the case of definition (3), the average particle size is the average diameter (also called the average particle size or average particle diameter).

[0052] 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.

[0053] (Binder) The above magnetic tape can be a coated magnetic tape, and the magnetic layer may contain a binder. The binder is one or more resins. Various resins commonly used as binders for coated magnetic recording media can be used as the binder. For example, as the binder, a resin selected from polyurethane resin, polyester resin, polyamide resin, vinyl chloride resin, acrylic resin copolymerized with styrene, acrylonitrile, methyl methacrylate, etc., cellulose resin such as nitrocellulose, epoxy resin, phenoxy resin, polyvinyl acetal, polyvinyl alkylal resin such as polyvinyl butyral can be used alone or in mixture of multiple resins. Among these, polyurethane resin, acrylic resin, cellulose resin, and vinyl chloride resin are preferred. These resins may be homopolymers or copolymers. These resins can also be used as binders in the non-magnetic layer and / or back coat layer described later. For more information on the binders, refer to paragraphs 0028 to 0031 of Japanese Patent Application Publication No. 2010-24113. The binder may also be a radiation-curable resin such as an electron beam-curable resin. For radiation-curable resins, refer to paragraphs 0044 to 0045 of Japanese Patent Publication No. 2011-048878. The average molecular weight of the resin used as a binder can be, for example, 10,000 to 200,000 as a weight-average molecular weight. The weight-average molecular weight in this invention and specification is the value obtained by converting the value measured by gel permeation chromatography (GPC) under the following measurement conditions to polystyrene equivalent. The weight-average molecular weight described 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, preferably in an amount of 1.0 to 20.0 parts by mass. GPC device: HLC-8120 (manufactured by Tosoh Corporation) Column: TSK gel Multipore HXL-M (manufactured by Tosoh Corporation, 7.8mm ID (Inner Diameter) × 30.0cm) Eluent: Tetrahydrofuran (THF)

[0054] (Hardening 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.

[0055] (Additives) The magnetic layer may contain one or more additives as needed. Commercially available additives can be appropriately selected and used according to the desired properties. Alternatively, compounds synthesized by known methods can be used as additives. Additives can be used in any amount. An example of an additive is the curing agent mentioned above. Additives that can be included in the magnetic layer include non-magnetic powders (e.g., inorganic powders, carbon black, etc.), lubricants, dispersants, dispersion aids, antifungal agents, antistatic agents, antioxidants, etc. For example, for lubricants, refer to paragraphs 0030-0033, 0035, and 0036 of Japanese Patent Application Publication No. 2016-126817. A lubricant may also be included in the non-magnetic layer described later. For lubricants that can be included in the non-magnetic layer, refer to paragraphs 0030-0031, 0034, 0035, and 0036 of Japanese Patent Application Publication No. 2016-126817. For dispersants, see paragraphs 0061 and 0071 of Japanese Patent Publication No. 2012-133837. Dispersants may be added to the composition for forming a non-magnetic layer. For dispersants that can be added to the composition for forming a non-magnetic layer, see paragraph 0061 of Japanese Patent Publication No. 2012-133837. Non-magnetic powders that may be included in the magnetic layer include non-magnetic powders that can function as abrasives, and non-magnetic powders included in the magnetic layer to form appropriate protrusions on the magnetic layer surface for controlling frictional properties (generally also called "fillers"). For example, for abrasives, see paragraphs 0030 to 0032 of Japanese Patent Publication No. 2004-273070. As an abrasive, the specific surface area measured by the BET (Brunauer-Emmett-Teller) method (hereinafter referred to as "BET specific surface area") is 14 m². 2 It is preferable to use abrasives of 1 / g or more. From the viewpoint of dispersibility, a BET specific surface area of ​​40 m² is preferable. 2 It is preferable to use an abrasive with a weight of 1 / g or less. For dispersants to improve the dispersibility of the abrasive, refer to paragraphs 0017 to 0028 of Japanese Patent Application Publication No. 2014-179149.

[0056] One form of filler included in the magnetic layer is carbon black. The BET specific surface area of ​​carbon black is 10 m². 2It is preferable that it be 15m or more / g 2 It is more preferable that the concentration is 50 m² or higher. The BET specific surface area of ​​carbon black is 50 m² from the viewpoint of ease of improving dispersibility. 2 It is preferable that the amount be less than or equal to 40m 2 It is more preferable that the amount is less than or equal to / g. Another form of filler is colloidal particles. From the viewpoint of availability, inorganic colloidal particles are preferred, inorganic oxide colloidal particles are more preferred, and silica colloidal particles (colloidal silica) are even more preferred. In the present invention and this specification, "colloidal particles" means particles that, when 1 g is added per 100 mL of at least one organic solvent, such as methyl ethyl ketone, cyclohexanone, toluene or ethyl acetate, or a mixed solvent containing two or more of the above solvents in any mixing ratio, disperse without settling and yield a colloidal dispersion. The average particle size of the colloidal particles can be, for example, 30 to 300 nm, and is preferably 40 to 200 nm. The filler content in the magnetic layer is preferably 0.1 to 0.8 parts by mass per 100.0 parts by mass of ferromagnetic powder. It is preferable to disperse the filler separately from the ferromagnetic powder, and more preferably separately from the abrasive.

[0057] The magnetic layer described above can be provided directly on the surface of a non-magnetic support, or indirectly via a non-magnetic layer.

[0058] <Nonmagnetic layer> Next, the non-magnetic layer will be described. The magnetic tape described above may have a magnetic layer directly on a non-magnetic support, or it may have a non-magnetic layer containing non-magnetic powder between the non-magnetic support and the magnetic layer. The non-magnetic powder used in the non-magnetic layer may be an inorganic powder or an organic powder. Carbon black can also be used. Examples of inorganic substances include metals, metal oxides, metal carbonates, metal sulfates, metal nitrides, metal carbides, and metal sulfides. These non-magnetic powders are available commercially and can also be manufactured by known methods. For details, see paragraphs 0146 to 0150 of Japanese Patent Publication No. 2011-216149. For carbon black that can be used in the non-magnetic layer, see paragraphs 0040 to 0041 of Japanese Patent Publication No. 2010-24113. The content (filling rate) of non-magnetic powder in the non-magnetic layer is preferably in the range of 50 to 90% by mass, and more preferably in the range of 60 to 90% by mass, relative to the total mass of the non-magnetic layer.

[0059] In one embodiment, the non-magnetic layer may include Fe-based inorganic oxide powder as a non-magnetic powder. In this invention and specification, "Fe-based inorganic oxide powder" refers to an inorganic oxide powder containing iron as a constituent element. Specific examples of Fe-based inorganic oxide powder include α-iron oxide powder and goethite powder. In this invention and specification, "α-iron oxide powder" refers to a non-magnetic powder in which the crystalline structure of α-iron oxide is detected as the main phase by X-ray diffraction analysis. α-iron oxide powder is also commonly called red iron oxide. The average particle volume of the Fe-based inorganic oxide powder contained in the non-magnetic layer is, for example, 2.0 × 10⁻⁶. -6 μm 3 The following is possible: The above average particle volume is, for example, 1.0 × 10⁻⁶. -9 μm 3 The above or 1.0 × 10 -8 μm 3 It may be greater than or less than the values ​​exemplified herein. In the present invention and herein, the above average particle volume is a value obtained by the method described in paragraph 0073 of Japanese Patent Application Publication No. 2024-84954.

[0060] 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.

[0061] The inventors believe that the flexibility of the non-magnetic layer can help suppress the occurrence of deep cracks at the edges of magnetic tape during the cutting (slitting) process in the manufacturing of magnetic tape. If the occurrence of deep cracks at the edges of magnetic tape can be suppressed, the value of the edge Rvm can be reduced. The following are examples of means for forming a flexible non-magnetic layer.

[0062] The proportion of carbon black in the non-magnetic powder of the non-magnetic layer is increased. The proportion of carbon black in the non-magnetic powder of the non-magnetic layer can be, for example, 10.0% by mass or more, 20.0% by mass or more, 30.0% by mass or more, 40.0% by mass or more, 50.0% by mass or more, 60.0% by mass or more, 70.0% by mass or more, 80.0% by mass or more, 90.0% by mass or more, relative to the total amount of non-magnetic powder, and can also be 100.0% by mass (i.e., the non-magnetic powder is carbon black only).

[0063] As a binder for the non-magnetic layer, use a binder with a low glass transition temperature (Tg). In the present invention and this specification, the glass transition temperature (Tg) is determined from the measurement results of heat flow measurement using a differential scanning calorimeter as the baseline shift start temperature of the heat flowchart during heating. As a binder for the non-magnetic layer, for example, resins with a glass transition temperature (Tg) of 150°C or less, 130°C or less, 110°C or less, 90°C or less, 70°C or less, or 50°C or less can be used. The glass transition temperature (Tg) of the resin used as a binder for the non-magnetic layer can be, for example, 30°C or higher or 40°C or higher, and may be lower than the values ​​exemplified herein.

[0064] The non-magnetic layer of the magnetic tape described above includes a substantially non-magnetic layer containing a small amount of ferromagnetic powder, for example as an impurity or intentionally, along with non-magnetic powder. Here, a substantially non-magnetic layer means a layer whose remanent magnetic flux density is 10 mT or less, or whose coercivity is 7.96 kA / m(100 Oe) or less, or a layer whose remanent magnetic flux density is 10 mT or less and whose coercivity is 7.96 kA / m(100 Oe) or less. It is preferable that the non-magnetic layer has no remanent magnetic flux density and coercivity.

[0065] <Nonmagnetic support> Next, non-magnetic supports will be described. Examples of non-magnetic supports (hereinafter also simply referred to as "supports") include known materials such as biaxially oriented polyethylene terephthalate, polyethylene naphthalate, polyamide, polyamide-imide, and aromatic polyamide. Among these, polyethylene terephthalate, polyethylene naphthalate, and polyamide are preferred. These supports may be subjected to pre-treatment such as corona discharge, plasma treatment, easy-adhesion treatment, or heat treatment.

[0066] The non-magnetic support of the magnetic tape described above may, in one embodiment, be an aromatic polyester support. In the present invention and this specification, "aromatic polyester" means a resin containing an aromatic skeleton and multiple 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 most abundant component by mass among the components constituting the film 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 contain 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" and "polyethylene naphthalate support" in the present invention and this specification.

[0067] 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 terminals or side chains, etc.). Polyethylene naphthalate (PEN) is a polyester containing a naphthalene ring, 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 terminals or side chains, etc.).

[0068] In one embodiment, the non-magnetic support of the magnetic tape described above may be an aromatic polyamide support. 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 the aromatic polyamide are not particularly limited. Specific examples of aromatic rings include, for example, benzene rings. "Aromatic polyamide support" means a support containing at least one layer of aromatic polyamide film. "Aromatic polyamide film" means a film in which the component that constitutes the film by mass is aromatic polyamide. In the present invention and this specification, "aromatic polyamide support" includes both a support in which all the resin films contained are aromatic polyamide films and a support containing aromatic polyamide films and other resin films. Specific forms of aromatic polyamide support include a single layer of aromatic polyamide film, a laminated film of two or more layers of aromatic polyamide films with the same constituent components, a laminated film of two or more layers of aromatic polyamide films with different constituent components, and a laminated film containing one or more layers of aromatic polyamide film and one or more layers of resin films other than aromatic polyamide. In the laminated film, an adhesive layer or the like may be optionally included between two adjacent layers. Furthermore, the aromatic polyamide 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.

[0069] Furthermore, as mentioned above, the non-magnetic support can be a biaxially oriented film, and may be a film that has undergone corona discharge, plasma treatment, easy adhesion treatment, heat treatment, etc.

[0070] Examples of indicators of the physical properties of a non-magnetic support include water content. In the present invention and this specification, the water content of a non-magnetic support is a value determined 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 the 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 the 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 using 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 using a known method (e.g., defilm removal using an organic solvent), the water content of the non-magnetic support can be determined using the method described above.

[0071] In one embodiment, the non-magnetic support of the magnetic tape preferably has a water content of 2.0% or less, more preferably 1.8% or less, even more preferably 1.6% or less, even more preferably 1.4% or less, even more preferably 1.2% or less, and even more preferably 1.0% or less. Furthermore, the water content of the non-magnetic support of the magnetic tape can be 0%, 0% or more, greater than 0%, or 0.1% or more.

[0072] Young's modulus can also be cited as an indicator of the physical properties of a non-magnetic support. 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, commercially available universal tensile testing apparatuses such as the Tensilon manufactured by Toyo Baldwin Co., Ltd., or universal tensile testing apparatuses with known configurations can be used. From the tangents 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.

[0073] 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, even more preferably 5000 MPa or more, and even more preferably 6000 MPa or more. Furthermore, 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, or 12000 MPa or less. Regarding 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, even more preferably 4000 MPa or more, and even more preferably 5000 MPa or more. Furthermore, the Young's modulus in the width direction of the non-magnetic support of the magnetic tape can be 12000 MPa or less, 11000 MPa or less, or 10000 MPa or less. During the manufacture of the magnetic tape, the non-magnetic support is usually used with the MD direction (Machine direction) of the film as the longitudinal direction and the TD direction (Transverse direction) as the width direction. Furthermore, in one embodiment, it is preferable that the Young's modulus in the longitudinal direction is greater than the Young's modulus in the width direction, and it is more preferable that the difference (Young's modulus in the longitudinal direction - Young's modulus in the width direction) is in the range of 800 to 3000 MPa.

[0074] 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.

[0075] <Backcoat layer> The above tape may or may not have a back coat layer containing non-magnetic powder on the surface side opposite to the surface side having the magnetic layer of the non-magnetic support. Preferably, the back coat layer contains either or both carbon black and inorganic powder. The back coat layer may contain a binder and may also contain additives. For details regarding the non-magnetic powder, binder, additives, etc. of the back coat layer, known technology relating to back coat layers may be applied, as may known technology relating to magnetic layers and / or non-magnetic layers. For example, paragraphs 0018 to 0020 of Japanese Patent Application Publication No. 2006-331625 and lines 65 to 38 of column 5 of U.S. Patent No. 7,029,774 can be referenced regarding the back coat layer.

[0076] <Various thicknesses> Regarding the tape thickness (total thickness) of magnetic tape, with the enormous increase in the amount of information in recent years, there is a demand for increased recording capacity (higher capacity) in magnetic tape. Means of increasing capacity include reducing the thickness of the magnetic tape and increasing the length of magnetic tape that can be stored in one magnetic tape cartridge. From this point of view, the tape thickness (total thickness) of the magnetic tape is preferably 5.6 μm or less, and more preferably 5.5 μm or less, 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 tape thickness of the magnetic tape is preferably 3.0 μm or more, and more preferably 3.5 μm or more.

[0077] The tape thickness (total thickness) of a magnetic tape can be measured by the following method. Ten pieces of measurement sample (e.g., 5-10 cm in length) are cut from any part of the magnetic tape, and the thickness is measured by stacking these measurement samples. The measured thickness is divided by 10 to obtain the value obtained (thickness per measurement sample), which is taken as the tape thickness. The above thickness measurement can be performed using a known measuring instrument capable of measuring thickness on the order of 0.1 μm.

[0078] The thickness of the non-magnetic support is preferably 3.0 to 5.0 μm. The thickness of the magnetic layer can be optimized according to the saturation magnetization of the magnetic head used, the head gap length, the bandwidth of the recording signal, etc., and is generally 0.01 μm to 0.15 μm, preferably 0.02 μm to 0.12 μm, and more preferably 0.03 μm to 0.1 μm from the viewpoint of high-density recording. At least one magnetic layer is sufficient, and the magnetic layer may be separated into two or more layers having different magnetic properties, and known configurations for multilayer magnetic layers can be applied. When separated into two or more layers, the thickness of the magnetic layer is the total thickness of these layers. The thickness of the non-magnetic layer is, for example, 0.1 to 1.5 μm, preferably 0.1 to 1.0 μm, and more preferably 0.1 to 0.7 μm. The thickness of the backcoat layer is preferably 0.9 μm or less, and more preferably 0.1 to 0.7 μm. Various thicknesses, such as the thickness of the magnetic layer, can be determined by the following method. After exposing the cross-section of the magnetic tape in the thickness direction using an ion beam, the exposed cross-section is observed using a scanning electron microscope or a transmission electron microscope. Various thicknesses can be determined as the arithmetic mean of the thicknesses obtained at any two locations during the cross-sectional observation. Alternatively, various thicknesses can be determined as design thicknesses calculated from manufacturing conditions, etc.

[0079] <Manufacturing method> (Preparation of compositions for each layer) A composition for forming a magnetic layer, a non-magnetic layer, or a backcoat layer typically contains a solvent along with the various components described above. As the solvent, various organic solvents commonly used for manufacturing coated magnetic recording media can be used. In particular, from the viewpoint of solubility of binders commonly used in coated magnetic recording media, it is preferable that each layer-forming composition contains one or more ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, cyclohexanone, isophorone, and tetrahydrofuran. The amount of solvent in each layer-forming composition is not particularly limited and can be the same as that used for the layer-forming compositions of typical coated magnetic recording media. Furthermore, the process for preparing each layer-forming composition typically includes at least a kneading step, a dispersion step, and mixing steps provided before or after these steps as needed. Each individual step may be divided into two or more stages. The components used in the preparation of each layer-forming composition may be added at the beginning or in the middle of any of the steps. Individual components may also be added in two or more separate steps. For example, the binder may be added in stages during the kneading, dispersion, and mixing stages for viscosity adjustment after dispersion. Alternatively, filtration may be performed after the dispersion process. For information on the filters used for filtration, please refer to the following description.

[0080] In the manufacturing process of the magnetic tape described above, some or all of the conventional known manufacturing techniques can be used in some or all of the processes. In the kneading process, it is preferable to use a kneader with strong kneading force, such as an open kneader, continuous kneader, pressure kneader, or extruder. Details of these kneading processes are described in Japanese Patent Publication No. 1-106338 and Japanese Patent Publication No. 1-79274. In addition, glass beads and / or other beads can be used to disperse each layer-forming composition. Suitable dispersion beads include high-density dispersion beads such as zirconia beads, titania beads, and steel beads. It is preferable to optimize the particle size (bead diameter) and packing rate of these dispersion beads. Known dispersers can be used. Each layer-forming composition may be filtered by a known method before being subjected to the coating process. Filtration can be performed, for example, by filter filtration. As filters used for filtration, for example, filters with a pore size of 0.01 to 3 μm (e.g., glass fiber filters, polypropylene filters, etc.) can be used.

[0081] (coating process) The magnetic layer can be formed by, for example, directly coating a magnetic layer-forming composition onto a non-magnetic support, or by sequentially or simultaneously overcoating it with a non-magnetic layer-forming composition. When orientation processing is performed, the orientation processing is carried out on the coated layer in the orientation zone while the coated layer of the magnetic layer-forming composition is wet. Various known techniques, including those described in paragraph 0052 of Japanese Patent Application Publication No. 2010-24113, can be applied to the orientation processing. For example, vertical orientation processing can be performed by known methods such as using opposite-polarity opposing magnets. In the orientation zone, the drying rate of the coated layer can be controlled by the temperature and airflow of the drying air and / or the transport speed in the orientation zone. Alternatively, the coated layer may be pre-dried before being transported to the orientation zone. The backcoat layer can be formed by applying the backcoat layer forming composition to the side of the non-magnetic support opposite to the side that has (or will have) a magnetic layer. For details on the coating process for forming each layer, refer to paragraph 0066 of Japanese Patent Publication No. 2010-231843.

[0082] (Other processes) After the above coating process, the magnetic tape is usually calendered to improve its surface smoothness. Regarding the calendering conditions, the calendering pressure (linear pressure) is, for example, 200 to 500 kN / m, preferably 250 to 350 kN / m, the calendering temperature (surface temperature of the calender roll) is preferably 80 to 95°C, and the calendering speed is, for example, 50 to 300 m / min, preferably 80 to 200 m / min. After calendering, the magnetic tape can be heat-treated before the following cutting (slitting) process. Regarding the heat treatment conditions, for example, the ambient temperature of the heat treatment environment (hereinafter also referred to as "heating temperature") is, for example, 35 to 100°C, preferably 50 to 80°C. The heat treatment time is, for example, 12 to 72 hours, preferably 24 to 48 hours. The inventors believe that the lower the heating temperature, the more flexible the non-magnetic layer becomes after heat treatment, and the smaller the value of Rvm at the edge portion. Furthermore, the inventors believe that the shorter the heat treatment time, the more flexible the non-magnetic layer becomes after heat treatment, and the smaller the value of Rvm at the edge portion. For other processes for manufacturing magnetic tape, refer to paragraphs 0067 to 0070 of Japanese Patent Publication No. 2010-231843. Through various processes, a long roll of magnetic tape raw material can be obtained. The obtained magnetic tape raw material is then cut (slit) using a known cutting machine to the width of a magnetic tape to be housed in a magnetic tape cartridge, for example. The above width can be determined according to standards and is usually 1 / 2 inch. 1 inch = 2.54 cm. A servo pattern is typically formed on the magnetic tape obtained by slitting.

[0083] (Formation of servo patterns) "Forming a servo pattern" can also be described as "recording a servo signal." The formation of a servo pattern is explained below.

[0084] 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.

[0085] As indicated in ECMA (European Computer Manufacturers Association)-319 (June 2001), magnetic tapes conforming to the LTO (Linear Tape-Open) standard (commonly referred to as "LTO tapes") employ a timing-based servo system. In this timing-based servo system, the servo pattern is composed of multiple pairs of non-parallel magnetic stripes (also called "servo stripes") arranged continuously along the longitudinal direction of the magnetic tape. In this invention and specification, "timing-based servo pattern" refers to a servo pattern that enables head tracking in a timing-based servo system. The reason the servo pattern is composed of pairs of non-parallel magnetic stripes, as described above, is to inform the servo signal reading element of its position as it passes over the servo pattern. Specifically, the pair of magnetic stripes are formed such that their spacing continuously changes along the width direction of the magnetic tape, and the servo signal reading element can determine the relative position between the servo pattern and the servo signal reading element by reading this spacing. This relative position information enables tracking of the data track. Therefore, multiple servo tracks are typically set up on the servo pattern, aligned with the width of the magnetic tape.

[0086] 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.

[0087] 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.

[0088] Furthermore, one method for uniquely identifying a servo band is the staggered method, as described in ECMA-319 (June 2001). In this staggered method, a group of non-parallel magnetic stripes (servo stripes) arranged continuously along the longitudinal direction of the magnetic tape are recorded in a manner that shifts each servo band along the longitudinal direction of the magnetic tape. Since the combination of this shift between adjacent servo bands is unique across the entire magnetic tape, it is possible to uniquely identify a servo band when reading the servo pattern with two servo signal reading elements.

[0089] Furthermore, each servo band typically contains embedded information indicating its position along the longitudinal direction of the magnetic tape (also known as "LPOS (Longitudinal Position) information"), as described in ECMA-319 (June 2001). This LPOS information, like the UDIM information, is recorded by shifting the positions of a pair of servo stripes along the longitudinal direction of the magnetic tape. However, unlike the UDIM information, the same signal is recorded for each servo band in this LPOS information.

[0090] It is also possible to embed information other than the UDIM and LPOS information mentioned above into the servo bands. In this case, the embedded information may be different for each servo band, like the UDIM information, or it may be common to all servo bands, like the LPOS information. Furthermore, methods other than those described above can be used to embed information in the servo bands. For example, a predetermined code may be recorded by thinning out a predetermined pair from a group of servo stripes.

[0091] 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.

[0092] 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.

[0093] 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.

[0094] <Vertical squareness ratio> In one embodiment, the vertical aspect ratio of the magnetic tape can be, for example, 0.55 or more, preferably 0.60 or more, and more preferably 0.65 or more, from the viewpoint of improving electromagnetic conversion characteristics. The upper limit of the aspect ratio is, in principle, 1.00 or less. The vertical aspect ratio of the magnetic tape can be 1.00 or less, and can be 0.95 or less, 0.90 or less, 0.85 or less, or 0.80 or less. A large value for the vertical aspect ratio of the magnetic tape is preferable from the viewpoint of improving electromagnetic conversion characteristics. The vertical aspect ratio of the magnetic tape can be controlled by known methods such as performing a vertical orientation process.

[0095] In the present invention and this specification, "vertical angle ratio" refers to the angle ratio measured in the vertical direction of the magnetic tape. In relation to the angle ratio, "vertical direction" refers to the direction perpendicular to the surface of the magnetic layer, and can also be referred to as the thickness direction. In the present invention and this specification, the vertical angle ratio is determined by the following method. A sample of a size suitable for introduction into a vibrating sample magnetometer is cut from the magnetic tape to be measured. Using the vibrating sample magnetometer, a magnetic field is applied to this sample perpendicular to the sample (orthogonal 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 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 is calculated as SQ = Mr / Ms. The measurement temperature refers to the temperature of the sample, and the temperature of the sample can be set to the measurement temperature by setting the ambient temperature around the sample to the measurement temperature, thereby achieving thermal equilibrium.

[0096] [Magnetic tape cartridge] One aspect of the present invention relates to a magnetic tape cartridge including the magnetic tape described above.

[0097] Details of the magnetic tape included in the above magnetic tape cartridge are as described above.

[0098] 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.

[0099] 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 0. 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.

[0100] 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 magnetic tape devices. For example, there may be usage configurations in which the head tilt angle is changed for one recording or playback cycle and for subsequent recording or playback cycles, but the head tilt angle is fixed and does not change during each recording or playback cycle. In such usage configurations, since there is a period during data recording and / or playback in which the head is tilted, magnetic tape with high running stability when recording and / or playing back data with the head tilted is preferred.

[0101] [Magnetic tape drive] One aspect of the present invention relates to a magnetic tape device including the magnetic tape described above. In the magnetic tape device, recording data onto the magnetic tape and / or reproducing data recorded on the magnetic tape can be performed, for example, by bringing the magnetic layer surface of the magnetic tape into contact with a magnetic head and sliding it. The magnetic tape device may detachably include a magnetic tape cartridge according to one aspect of the present invention.

[0102] The above-described magnetic tape cartridge can be mounted in a magnetic tape device equipped with a magnetic head and used for recording and / or reproducing data. In the present invention and herein, “magnetic tape device” means a device capable of recording data onto a magnetic tape and reproducing data recorded on a magnetic tape. Such a device is generally referred to as a drive.

[0103] <Magnetic head> The above magnetic tape device may include a magnetic head. The configuration of the magnetic head and the angle θ, which is the head tilt angle, are as previously explained with reference to Figures 1 to 3. The magnetic head included in the above magnetic tape device may be an LTO8 head in one embodiment, an LTO head of another generation in another embodiment, or a magnetic head other than an LTO head in yet another embodiment. If the magnetic head includes a regeneration element, a magnetoresistive (MR) element that can read information recorded on the magnetic tape with high sensitivity is preferred as the regeneration element. Various known MR elements (e.g., GMR (Giant Magnetoresistive) elements, TMR (Tunnel Magnetoresistive) elements, etc.) can be used as the MR element. Hereinafter, the magnetic head that records data and / or reproduces recorded data will also be called the "recording / reproduction head". The elements for recording data (recording elements) and the elements for reproducing data (reproduction elements) will be collectively referred to as "magnetic head elements".

[0104] When recording data and / or playing back recorded data, tracking using servo signals can be performed first. That is, by making the servo signal reading element follow a predetermined servo track, the magnetic head element can be controlled to pass over the target data track. The movement of the data track is achieved by changing the servo track read by the servo signal reading element in the tape width direction. Furthermore, the recording / playback head can also record and / or play back data for other data bands. In this case, the servo signal reading element can be moved to a predetermined servo band using the UDIM information described earlier, and tracking for that servo band can be started.

[0105] Figure 4 shows an example of the arrangement of data bands and servo bands. In Figure 4, multiple servo bands 1 are arranged on the magnetic layer of the magnetic tape MT, sandwiched between guide bands 3. Multiple regions 2 sandwiched between two servo bands are the data bands. A servo pattern is a magnetized region, formed by magnetizing a specific region of the magnetic layer with a servo light head. The region magnetized by the servo light head (the position where the servo pattern is formed) is defined by the standard. For example, in the industry standard LTO Ultrium format tape, multiple servo patterns inclined with respect to the tape width direction are formed on the servo bands during magnetic tape manufacturing, as shown in Figure 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). The A-burst consists of servo patterns A1 to A5, and the B-burst consists of servo patterns B1 to B5. On the other hand, servo subframe 2 consists of C-bursts (indicated as C in Figure 5) and D-bursts (indicated as D in Figure 5). C-bursts consist of servo patterns C1 to C4, and D-bursts consist of servo patterns D1 to D4. These 18 servo patterns are arranged in sets of 5 and 4 on subframes in a 5, 5, 4, 4 sequence, and are used to identify the servo frames. Figure 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 for 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.

[0106] 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.

[0107] 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. initial The angle is preferably 1° or more, more preferably 5° or more, and even more preferably 10° or more. On the other hand, regarding the angle between the magnetic layer surface and the contact surface of the magnetic head when the magnetic tape is running and in contact with 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.

[0108] 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 That is the case. Note that "max" is an abbreviation for maximum, and "min" is an abbreviation for minimum. Δθ max =θ max -θ initial Δθ min =θ initial -θ min

[0109] 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.

[0110] 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.

[0111] 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 drive, etc. Regarding the head tilt angle during magnetic tape travel, Figure 6 is an explanatory diagram of the method for measuring the angle θ during magnetic tape travel. The angle θ during magnetic tape travel can be determined, for example, by the following method. When determining the angle θ during magnetic tape travel by the following method, the angle θ is to be varied within the range of 0 to 90° during magnetic tape travel. That is, if the axis of the element array is tilted toward the direction of magnetic tape travel at the start of magnetic tape travel, the element array will not be tilted during magnetic tape travel so that the axis of the element array is tilted toward the direction of magnetic tape travel at the start of magnetic tape travel, and if the axis of the element array is tilted toward the direction of magnetic tape travel at the start of magnetic tape travel, the element array will not be tilted during magnetic tape travel so that the axis of the element array is tilted toward the direction of magnetic tape travel at the start of magnetic tape travel. The phase difference (i.e., time difference) ΔT of the regenerated signals from a pair of servo signal reading elements 1 and 2 is measured. ΔT can be measured by a measurement unit provided in the magnetic tape device. The configuration of such a measurement unit is well known. The distance L between the center of servo signal reading element 1 and the center of servo signal reading element 2 can be measured using an optical microscope or the like. When the magnetic tape travels at speed v, the distance between the centers of the two servo signal reading elements in the direction of magnetic tape travel is Lsinθ, and the relationship Lsinθ = v × ΔT holds. Therefore, the angle θ during magnetic tape travel can be calculated using the formula "θ = arcsin(vΔT / L)". Note that Figure 6 (right) shows an example where the axis of the element array is tilted toward the direction of magnetic tape travel. In this example, the phase difference (i.e., time difference) ΔT between the phase of the regenerated signal from servo signal reading element 1 and the phase of the regenerated signal from servo signal reading element 2 is measured. If the axis of the element array is tilted in the direction opposite to the direction 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 for the angle θ, that is, the measurement interval for the angle θ in the longitudinal direction of the tape, can be selected according to the frequency of tape width deformation in the longitudinal direction of the tape. For example, the measurement pitch can be set to, for example, 250 μm.

[0112] <Configuration of a magnetic tape drive> The magnetic tape device 10 shown in Figure 7 controls the recording and playback head unit 12 based on commands from the control device 11, and performs data recording and playback on the magnetic tape MT. The magnetic tape device 10 has a configuration that allows for the detection and adjustment of tension applied in the longitudinal direction of the magnetic tape from spindle motors 17A, 17B and their drive units 18A, 18B that control the rotation of the magnetic tape cartridge reel and the take-up reel. The magnetic tape device 10 has a configuration that allows a magnetic tape cartridge 13 to be loaded. The magnetic tape device 10 has a cartridge memory read / write device 14 that can read from and write to the cartridge memory 131 in the magnetic tape cartridge 13. From the magnetic tape cartridge 13 mounted in the magnetic tape device 10, the end of the magnetic tape MT or the leader pin is pulled out by an automatic loading mechanism or manually, and the magnetic layer surface of the magnetic tape MT passes over the recording / playback head of the recording / playback head unit 12 through guide rollers 15A and 15B with the magnetic layer surface of the magnetic tape MT in contact with the surface of the recording / playback head, and the magnetic tape MT is wound onto the take-up reel 16. The rotation and torque of spindle motors 17A and 17B are controlled by signals from the control device 11, so that the magnetic tape MT runs at a desired speed and tension. A servo pattern pre-formed on the magnetic tape can be used to control the tape speed and head tilt angle. A tension detection mechanism may be provided between the magnetic tape cartridge 13 and the take-up reel 16 for tension detection. In addition to control by spindle motors 17A and 17B, tension may also be controlled using guide rollers 15A and 15B. The cartridge memory read / write device 14 is configured to read and write information to the cartridge memory 131 in response to commands from the control device 11. For example, the ISO (International Organization for Standardization) 14443 standard can be used as the communication method between the cartridge memory read / write device 14 and the cartridge memory 131.

[0113] The control device 11 includes, for example, a control unit, a storage unit, a communication unit, and the like.

[0114] 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.

[0115] 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.

[0116] The control device 11 has a mechanism to determine the running position of the magnetic tape MT from the servo signals read from the servo bands when the magnetic tape MT is running, and to control the servo tracking actuator so that the recording element and / or playback element are positioned at the target running position (track position). This track position control is performed, for example, by feedback control. The control device 11 has a mechanism to determine the servo band spacing from the servo signals read from two adjacent servo bands when the magnetic tape MT is running. The control device 11 can store the determined servo band spacing information in its internal storage unit, cartridge memory 131, or external connected equipment. Furthermore, the control device 11 can change the head tilt angle according to the dimensional information in the width direction of the running magnetic tape. This makes it possible to bring the effective distance between servo signal reading elements close to or match the servo band spacing. The above dimensional information can be obtained using a servo pattern pre-formed on the magnetic tape. For example, while the magnetic tape is running within the magnetic tape device, the angle θ that the axis of the element array makes with respect to the width direction of the magnetic tape can be changed according to the width direction dimensional information of the magnetic tape acquired during the running process. The head tilt angle can be adjusted, for example, by feedback control. Alternatively, the head tilt angle can also be adjusted, for example, by the method described in Japanese Patent Publication No. 2016-524774 (Patent Document 1) or US2019 / 0164573A1 (Patent Document 2). [Examples]

[0117] The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to the embodiments shown in the examples. Unless otherwise specified, "parts" and "%" below refer to "parts by mass" and "mass%". Unless otherwise specified, the following processes and evaluations are carried out in air at room temperature (20-25°C). Unless otherwise specified, "eq" below refers to equivalent and is a unit that cannot be converted to SI units.

[0118] [Non-magnetic support] In Table 1, "PET" refers to polyethylene terephthalate support, and "PA" refers to aromatic polyamide support.

[0119] [Glass transition temperature Tg] The glass transition temperatures (Tg) of polyurethane resins A and B shown in Table 1 were determined by the following method. Resin (pellet or powder sample) was placed in an aluminum sample pan and sealed using a press. Heat flow measurements were performed using a T.A. Instruments Q100 differential scanning calorimeter under the following conditions. From the measurement results, the glass transition temperature Tg of the resin was determined as the baseline shift start temperature of the heat flow chart during heating. (Measurement conditions) Scanning temperature: -80.0℃ to 200.0℃ Heating rate: 10.0℃ / min

[0120] [Example 2] <Preparation of alumina dispersion (abrasive solution)> Alpha-ization rate approximately 65%, BET specific surface area 20m² 2 100.0 parts of alumina powder (HIT-80, manufactured by Sumitomo Chemical Co., Ltd.) at a concentration of 1 / g was mixed with 3.0 parts of 2,3-dihydroxynaphthalene (manufactured by Tokyo Chemical Industry Co., Ltd.), 31.3 parts of a 32% solution of polyester polyurethane resin having SO3Na groups as polar groups (UR-4800, manufactured by Toyobo Co., Ltd. (polar group amount: 80 meq / kg)) (solvent: mixed solvent of methyl ethyl ketone and toluene), and 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.

[0121] <Preparation of carbon black dispersion (filler solution)> 3.3 parts of filler (carbon black) were mixed with 19.3 parts of cyclohexanone as a solvent, and dispersed in the presence of zirconia beads (bead diameter: 0.1 mm) using a paint shaker for 360 minutes. The filler used was Asahi Carbon Co., Ltd.'s Asahi #50 (BET specific surface area: 23 m²). 2 ( / g) was used. After dispersion, the carbon black dispersion obtained by separating the dispersion liquid and beads using a mesh was used to prepare the following magnetic layer forming compositions.

[0122] <Formulation of magnetic layer-forming composition> (Magnetic liquid) Ferromagnetic powder (hexagonal barium ferrite powder, activation volume: 1500 nm) 3 ):100.0 copies Vinyl chloride copolymer (MR-104, manufactured by Nippon Zeon Co., Ltd.): 10.0 parts SO3Na group-containing polyurethane resin: 4.0 parts Weight average molecular weight: 70,000, SO3Na group: 0.07meq / g Cyclohexanone: 150.0 parts Methyl ethyl ketone: 170.0 parts (Abrasive solution) Use the alumina dispersion prepared above in an amount such that the amount of alumina in the alumina dispersion is 4.5 parts. (Filler liquid) The carbon black dispersion prepared above is used such that the amount of carbon black in the dispersion is 0.5 parts by mass. (Other ingredients) Stearic acid: 1.0 part Butyl stearate: 3.3 parts Polyisocyanate (Takenate D-101E, manufactured by Mitsui Chemicals): 2.5 parts (Finishing additive solvent) Cyclohexanone: 300.0 parts Methyl ethyl ketone: 140.0 parts

[0123] <Formulation of a composition for forming a non-magnetic layer> Non-magnetic inorganic powder (α-iron oxide): See Table 1. Average particle volume: 2.0 × 10⁻⁶ -6 μm 3 Carbon black: See Table 1 Average particle size: 20nm SO3Na group-containing vinyl chloride copolymer: 20.0 parts Weight average molecular weight: 70,000, SO3Na group: 0.2meq / g Polyurethane resin B (glass transition temperature Tg: see Table 1): see Table 1 Weight average molecular weight: 70,000, SO3Na group: 0.2meq / g Trioctylamine: 1.0 part Phenylephosphonic acid: 4.0 parts Stearic acid: 1.0 part Stearic acid amide: 0.3 parts Butyl stearate: 3.0 parts Cyclohexanone: 450.0 parts Methyl ethyl ketone: 450.0 parts

[0124] <Formulation for backcoat layer formation composition> Carbon Black: 100.0 parts Average particle size: 40nm, DBP (Dibutyl phthalate) oil absorption: 74cm 3 / 100g Copper phthalocyanine: 3.0 parts Nitrocellulose: 25.0 parts SO3Na group-containing polyester polyurethane resin: 60.0 parts Weight average molecular weight: 70,000, SO3Na group: 0.2meq / g Polyester resin (Toyobo Byron 500): 4.0 parts Alumina powder (BET specific surface area 21 m²) 2 α-alumina per gram: 1.0 part Polyisocyanate (Takenate D-101E, manufactured by Mitsui Chemicals): 15.0 parts Methyl ethyl ketone: 600.0 parts Toluene: 600.0 parts

[0125] <Preparation of compositions for forming each layer> A composition for forming a magnetic layer was prepared by the following method. The various components of the magnetic liquid described above were mixed using a homogenizer, and then the magnetic liquid was prepared by dispersing them in a continuous horizontal bead mill using zirconia beads with a diameter of 0.05 mm for 10 minutes. Using the bead mill described above, the magnetic solution was mixed with an abrasive solution, a filler solution, other components, and a finishing additive solvent, and then treated with a batch-type ultrasonic device (20 kHz, 300 W) for 0.5 minutes (ultrasonic dispersion). Subsequently, the mixture was filtered using a filter with a pore size of 0.5 μm to prepare a composition for forming a magnetic layer. A composition for forming a non-magnetic layer was prepared by the following method. The components, excluding stearic acid, stearamide, and butyl stearate, were dispersed for 12 hours using a batch-type vertical sand mill to obtain a dispersion. Zirconia beads with a diameter of 0.1 mm were used as the dispersion beads. The remaining components were then added to the obtained dispersion and stirred with a disperser. The resulting dispersion was filtered using a filter with a pore size of 0.5 μm to prepare a composition for forming a non-magnetic layer. The backcoat layer forming composition was prepared by the following method. The above components, excluding the polyisocyanate, were introduced into a dissolver stirrer and stirred at a peripheral speed of 10 m / s for 30 minutes. Dispersion was then performed using a horizontal bead mill disperser. Subsequently, the polyisocyanate was added and stirred and mixed using the dissolver stirrer to prepare a composition for forming the backcoat layer.

[0126] <Manufacturing of magnetic tapes and magnetic tape cartridges> A non-magnetic layer was formed by coating the surface of a 3.9 μm thick non-magnetic support (see Table 1) with a non-magnetic layer-forming composition such that the thickness after drying was 0.7 μm, and then drying the mixture. A magnetic layer-forming composition was applied to the surface of the formed non-magnetic layer to create a coated layer with a drying thickness of 50 nm. While this coated layer was still wet, a magnetic field with a strength of 0.4 T was applied perpendicular to the surface of the coated layer to perform a vertical orientation treatment, after which the coated layer was dried. After drying the above-mentioned coating layer, a backcoat layer-forming composition was applied to the surface of the polyethylene terephthalate support opposite to the surface on which the non-magnetic and magnetic layers were formed, so that the thickness after drying was 0.3 μm, and then dried. Subsequently, a calendering treatment (calendering process) was performed using a calender roll composed solely of metal rolls, at a calendering speed of 100 m / min, a calendering pressure (linear pressure) of 294 kN / m, and a calendering temperature (surface temperature of the calender roll) of 90°C. Subsequently, heat treatment was performed in the ambient temperature environment and for the heat treatment time specified in the "Pre-slitting heat treatment conditions" column of Table 1. After that, the material was slit into 1 / 2-inch (1.27 cm) width strips. The surface of the magnetic layer was then cleaned (referred to as "surface treatment") using a tape cleaning device equipped with a feed and winding device for the slit strips, in which the nonwoven fabric and razor blade were mounted so that they pressed against the magnetic layer surface, thereby obtaining a magnetic tape. In Table 1, "h" indicates "hours". The thickness of each layer mentioned above is the design thickness calculated from the manufacturing conditions. By recording servo signals on the magnetic layer of the obtained magnetic tape using a commercially available servo writer, a magnetic tape was obtained having data bands, servo bands, and guide bands arranged in accordance with the LTO (Linear Tape-Open) Ultrium format, and having a servo pattern (timing-based servo pattern) on the servo bands arranged and shaped in accordance with the LTO Ultrium format. The servo pattern thus formed is a servo pattern that conforms to the descriptions in JIS (Japanese Industrial Standards) X6175:2006 and Standard ECMA-319 (June 2001). The total number of servo bands is 5, and the total number of data bands is 4. The magnetic tape on which the servo signals were recorded was then wound onto a reel in a magnetic tape cartridge (LTO Ultrium8 data cartridge). The reel of the magnetic tape cartridge has a cylindrical reel hub that forms the axis. Both ends of the reel hub are provided with flanges (lower flange and upper flange) that extend radially outward from the lower and upper ends of the reel hub, respectively. Here, "upper" and "lower" refer to the side that is located above the magnetic tape cartridge when it is mounted in the magnetic tape device, and the side that is located below it. In this way, a magnetic tape cartridge was created in which magnetic tape was wound onto a reel and housed within it.

[0127] For Example 2, multiple magnetic tape cartridges were manufactured and each was used for the following evaluations.

[0128] [Edge RVM] For the magnetic tape removed from the magnetic tape cartridge of Example 2, the Rvm of the edges on the upper flange side and the lower flange side was determined using the method described above. A Bruker Contour GT-I non-contact optical surface roughness meter was used. Bruker Vision64 software was used for data processing. The obtained results are shown in Table 1.

[0129] [Magnetic tape thickness] Ten measurement samples (5 cm in length) were cut from the magnetic tape removed from the magnetic tape cartridge of Example 2, and the thickness of these measurement samples was measured by stacking them. The thickness was measured using a digital thickness meter consisting of a MAHR Millimar 1240 compact amplifier and a Millimar 1301 inductive probe. The measured thickness was divided by 10 to obtain the value obtained (thickness per measurement sample), which was defined as the tape thickness. The tape thickness of the magnetic tape of Example 2 was 5.0 μm.

[0130] [Vertical squareness ratio] A sample for measurement was cut from the magnetic tape removed from the magnetic tape cartridge of Example 2. The vertical angular ratio of this sample was determined using a Tamagawa Seisakusho TM-TRVSM5050-SMSL vibrating sample magnetometer by the method described above. The vertical angular ratio of the magnetic tape of Example 2 was 0.65.

[0131] [Driving stability] Driving stability was evaluated in an environment with a temperature of 40°C and a relative humidity of 10% using the following method. Using the magnetic tape cartridge of Example 2, data recording and playback were performed using a magnetic tape device configured as shown in Figure 7. The arrangement of modules included in the recording / playback head mounted on the recording / playback head unit is "recording module - playback module - recording module" (total number of modules: 3). Each module has 32 magnetic head elements (Ch0 to Ch31), and these magnetic head elements are sandwiched between a pair of servo signal reading elements to form an element array. The following method was used to record and play back data and evaluate playback stability during playback, with the head tilt angle set to 15°. The head tilt angle is the angle θ that the axis of the element array of the playback module makes with respect to the width direction of the magnetic tape at the start of playback. The angle θ was set by the control device of the magnetic tape device at the start of magnetic tape playback, and the head tilt angle was fixed during magnetic tape playback. A magnetic tape cartridge is set in the magnetic tape drive, and the magnetic tape is loaded. Next, while performing servo tracking, the recording / playback head unit records pseudo-random data with a specific data pattern onto the magnetic tape. The tension applied along the length of the tape is kept constant. Simultaneously with data recording, the servo band spacing along the entire length of the tape is measured every 1 meter along the length and recorded in the cartridge memory. Next, the recording / playback head unit plays back the data recorded on the magnetic tape while performing servo tracking. The tension applied in the longitudinal direction of the tape during this process is kept constant. During the playback described above, the standard deviation of the reading position PES (Position Error Signal) in the width direction, based on the servo signal obtained by the servo signal reading element (hereinafter referred to as "σPES"), was used as an indicator to evaluate driving stability. PES is calculated using the following method. To determine the PES, the dimensions of the servo pattern are necessary. The standard for servo pattern dimensions varies depending on the generation of the LTO. Therefore, first, the average distance AC between the four corresponding stripes of the A-burst and C-burst, and the azimuth angle α of the servo pattern are measured using a magnetic force microscope or similar device. The average time between the 5 stripes corresponding to A-bursts and B-bursts over the length of 1 LPOS word is defined as a. The average time between the 4 stripes corresponding to A-bursts and C-bursts over the length of 1 LPOS word is defined as b. In this case, the value defined as AC × (1 / 2 - a / b) / (2 × tan(α)) is the widthwise reading position PES (Position Error Signal) based on the servo signal obtained by the servo signal reading element over the length of 1 LPOS word. For magnetic tape, the end on the side wound onto the reel of the magnetic tape cartridge is called the inner end, and the end on the opposite side is called the outer end. With the outer end set as 0m, the tape was repeatedly run 3500 times back and forth in a region in the longitudinal direction of the tape from 30m to 200m in an environment of 40℃ and 10% relative humidity, and the standard deviation (σPES) of the PES obtained by the above method was calculated in the final back and forth run. If the σPES obtained in this way is 70nm or less, it can be judged that the running stability is excellent.

[0132] [Examples 5 and 6, Comparative Example 6] Except for the changes shown in Table 1 to the items listed in Table 1, magnetic tapes and magnetic tape cartridges were manufactured and various evaluations were performed using the method described for Example 2. The results obtained are shown in Table 1.

[0133] [Comparative Example 7] A magnetic tape and magnetic tape cartridge were prepared using the method described for Example 2, except that the items shown in Table 1 were changed as shown in Table 1. In Comparative Example 7, instead of polyurethane resin A for the non-magnetic layer, polyurethane resin A with the glass transition temperature Tg shown in Table 1 was used. Various evaluations were performed using the magnetic tape cartridge thus prepared, as described for Example 2, and the results shown in Table 1 were obtained.

[0134] [Example 1, Comparative Example 5] Except for changing the items shown in Table 1 as shown in Table 1, the magnetic tape and magnetic tape cartridge are manufactured using the method described for Comparative Example 7. When various evaluations are performed using the magnetic tape cartridge thus manufactured, as described for Example 2, the results shown in Table 1 are obtained.

[0135] [Examples 3 and 4, Comparative Examples 1 and 3] Except for changing the items shown in Table 1 as shown in Table 1, the magnetic tape and magnetic tape cartridge are manufactured using the method described in Example 2. When various evaluations are performed using the magnetic tape cartridge thus manufactured, as described in Example 2, the results shown in Table 1 are obtained.

[0136] [Comparative Example 2] The items shown in Table 1 are changed as shown in Table 1, and the magnetic tape and magnetic tape cartridge are manufactured using the method described for Example 2, except that the magnetic tape is rewound after slitting and before surface treatment. Comparative Example 2 is the same as Comparative Example 1 except that the rewinding is performed before surface treatment. By performing the rewinding before surface treatment, the magnetic tape is housed in the magnetic tape cartridge such that the edge portion that is on the upper flange side in Comparative Example 1 is located on the lower flange side, and the edge portion that is on the lower flange side in Comparative Example 1 is located on the upper flange side. When various evaluations are performed using the magnetic tape cartridge thus produced, as described in Example 2, the results shown in Table 1 are obtained. In Table 1, if re-wrapping is not performed before surface treatment, write "None" in the "Re-wrapping before surface treatment" column. If re-wrapping is performed before surface treatment, write "Yes" in the "Re-wrapping before surface treatment" column.

[0137] [Comparative Example 4] The items shown in Table 1 are changed as shown in Table 1, and the magnetic tape and magnetic tape cartridge are manufactured using the method described for Example 2, except that the magnetic tape is rewound after slitting and before surface treatment. Comparative Example 4 is the same as Comparative Example 3 except that the rewinding is performed before surface treatment. By rewinding before surface treatment, the magnetic tape is housed in the magnetic tape cartridge such that the edge portion that is on the upper flange side in Comparative Example 3 is located on the lower flange side, and the edge portion that is on the lower flange side in Comparative Example 3 is located on the upper flange side. When various evaluations are performed using the magnetic tape cartridge thus produced, as described in Example 2, the results shown in Table 1 are obtained.

[0138] Details of Examples 1-6 and Comparative Examples 1-7 are shown in Table 1 (Tables 1-1 to 1-7).

[0139] [Table 1-1]

[0140] [Table 1-2]

[0141] [Table 1-3]

[0142] [Table 1-4]

[0143] [Table 1-5]

[0144] [Table 1-6]

[0145] [Table 1-7]

[0146] As shown in Table 1, the magnetic tapes of Examples 1 to 6 are magnetic tapes with excellent running stability. [Industrial applicability]

[0147] One aspect of the present invention is useful in the technical field of various data storage technologies.

Claims

1. A magnetic tape comprising a non-magnetic support and a magnetic layer containing ferromagnetic powder, The average valley depth Rvm measured at one edge of the surface of the magnetic layer and the average valley depth Rvm measured at the other edge are both between -0.55 μm and -0.20 μm. The edge portion is a magnetic tape that, in the tape width direction, is the portion between 0 μm and 1 μm, where the edge position is defined as 0 μm.

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

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

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

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

6. 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.

7. 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.

8. The thickness of the magnetic tape is 5.0 μm or less. The vertical aspect ratio of the magnetic tape is 0.65 or greater. The non-magnetic support is an aromatic polyester support or an aromatic polyamide support. The non-magnetic support and the magnetic layer further comprise a non-magnetic layer containing non-magnetic powder, The magnetic tape according to claim 1, further comprising a back coat layer containing non-magnetic powder on the surface side of the non-magnetic support opposite to the surface side having the magnetic layer.

9. A magnetic tape cartridge comprising the magnetic tape described in any one of claims 1 to 8.

10. A magnetic tape device including a magnetic tape according to any one of claims 1 to 8.

11. Further including a magnetic head, The magnetic head has a module including an element array having a plurality of magnetic head elements between a pair of servo signal reading elements, The magnetic tape device according to claim 10, wherein the magnetic tape device changes the angle θ that the axis of the element array makes with respect to the width direction of the magnetic tape while the magnetic tape is running within the magnetic tape device.

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