Magnetic tape, magnetic tape cartridge, and magnetic tape device

Abstract

To provide a magnetic tape having excellent running stability upon data recording and / or playback at different head inclination angles in high-temperature and low-humidity environment.SOLUTION: Provided are: a magnetic tape having a non-magnetic support body and a magnetic layer containing a ferromagnetic powder, in which an arithmetic mean roughness Ra (called an edge part Ra) is 1.50 nm as measured at an edge part on the surface of the magnetic layer, an arithmetic mean roughness Ra (called a central part Ra) is equal to or greater than 0.30 nm and equal to or less than 1.30 nm as measured at the central part on the surface of the magnetic layer, and the Ra ratio (between the central part Ra and the edge part Ra) is equal to or greater than 0.75 and equal to or less than 0.95; a magnetic tape cartridge including the magnetic tape; and a magnetic tape device including the magnetic tape.SELECTED DRAWING: None

Description

[Technical field]

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

[0002] Magnetic recording media include tape-type and disk-type recording media, and tape-type magnetic recording media, i.e., magnetic tapes, are primarily used for data storage applications such as data backup and archiving (see, for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-524774 A [Patent Document 2] US2019 / 0164573A1 Summary of the Invention [Problem to be solved by the invention]

[0004] Data is usually recorded on a magnetic tape by running the magnetic tape in a magnetic tape device and recording data on the data band of the magnetic tape by moving a magnetic head along the data band of the magnetic tape. This forms a data track on the data band. When reproducing the recorded data, the magnetic tape is usually run in the magnetic tape device and the magnetic head is moved along the data band of the magnetic tape to read the data recorded on the data band.

[0005] In order to improve the accuracy with which the magnetic head tracks the data band of the magnetic tape during the above-described recording and / or playback, a system that performs head tracking using a servo signal (hereinafter also referred to as a "servo system") has been put into practical use. Furthermore, it has been proposed to use a servo signal to obtain dimensional information (such as shrinkage and elongation) in the width direction of a magnetic tape during travel, and to change the angle (hereinafter also referred to as "head tilt angle") at which the axial direction of the magnetic head module is tilted with respect to the width direction of the magnetic tape according to the obtained dimensional information (see Patent Documents 1 and 2, for example, paragraphs 0059 to 0067 and paragraph 0084 of Patent Document 1). During recording or playback, if the magnetic head for recording or playing back data is displaced from the target track position due to the width deformation of the magnetic tape and recording or playback of data is performed, phenomena such as overwriting of recorded data and playback failure will occur. The present inventor considers that changing the head tilt angle as described above is one of the means for suppressing the occurrence of such phenomena.

[0006] For example, assuming that the head tilt angle is changed as described above, it is desirable that the magnetic tape has high running stability when recording and / or playing back data at different head tilt angles. This is because it is considered that high running stability of the magnetic tape can lead to further suppression of the occurrence of the above phenomena, for example.

[0007] By the way, in recent years, magnetic tapes are sometimes used in data centers where temperature and humidity are controlled. On the other hand, in data centers, power saving is required to reduce costs. For power saving, it is desirable to be able to relax the management conditions of the usage environment of magnetic tapes in data centers compared to the current situation, or to eliminate the need for management. However, if the management conditions of the usage environment are relaxed or not managed, it is also assumed that the magnetic tape will be used in, for example, a high-temperature and low-humidity environment. Therefore, a magnetic tape with excellent running stability when recording and / or playing back data at different head tilt angles in a high-temperature and low-humidity environment is desirable.

[0008] An aspect of the present invention aims to provide a magnetic tape with excellent running stability when recording and / or playing back data at different head tilt angles in a high-temperature and low-humidity environment.

Means for Solving the Problem

[0009] One aspect of the present invention is a magnetic tape having a non-magnetic support and a magnetic layer containing ferromagnetic powder, wherein an edge portion Ra, which is the arithmetic mean roughness Ra measured at the edge portion of the surface of the magnetic layer, is 1.50 nm or less, a central portion Ra, which is the arithmetic mean roughness Ra measured at the central portion of the surface of the magnetic layer, is 0.30 nm or more and 1.30 nm or less, and a magnetic tape in which the Ra ratio (central portion Ra / edge portion Ra) is 0.75 or more and 0.95 or less. It relates to.

[0010] In one form, the magnetic tape may further have a non-magnetic layer containing non-magnetic powder between the non-magnetic support and the magnetic layer.

[0011] In one form, the non-magnetic powder may contain Fe-based inorganic oxide powder having an average particle volume of 2.0×10 -6 μm 3 or less.

[0012] In one form, the non-magnetic powder may contain carbon black having a pH of 5.0 or less.

[0013] In one form, the standard deviation of the amount of curvature in the longitudinal direction of the magnetic tape can be 5 mm / m or less.

[0014] In one form, the magnetic tape may further 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.

[0015] In one form, the tape thickness of the magnetic tape can be 5.2 μm or less.

[0016] In one form, the vertical direction squareness ratio of the magnetic tape can be 0.60 or more.

[0017] One aspect of the present invention relates to a magnetic tape cartridge including the above magnetic tape.

[0018] One aspect of the present invention relates to a magnetic tape device including the above magnetic tape.

[0019] In one form, the magnetic tape device can further include a magnetic head. The magnetic head can have 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 can change an angle θ formed by an axis of the element array with respect to a width direction of the magnetic tape during running of the magnetic tape in the magnetic tape device.

Advantages of the Invention

[0020] According to one aspect of the present invention, it is possible to provide a magnetic tape excellent in running stability when recording and / or reproducing data at different head tilt angles in a high-temperature and low-humidity environment. Further, according to one aspect of the present invention, it is possible to provide a magnetic tape cartridge and a magnetic tape device including the above magnetic tape.

Brief Description of the Drawings

[0021]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Embodiments for Carrying Out the Invention

[0022] [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 arithmetic mean roughness Ra measured at the edge portion of the surface of the magnetic layer is referred to as edge portion Ra, and the arithmetic mean roughness Ra measured at the central portion of the surface of the magnetic layer is referred to as central portion Ra. In the magnetic tape, the edge portion Ra is 1.50 nm or less, the central portion Ra is 0.30 nm or more and 1.30 nm or less, and the Ra ratio (central portion Ra / edge portion Ra) is 0.75 or more and 0.95 or less. In the present invention and this specification, the "surface (of the) magnetic layer" is synonymous with the surface on the magnetic layer side of the magnetic tape.

[0023] <Explanation of Head Tilt Angle> Prior to the description of the magnetic tape below, the configuration of the magnetic head, the head tilt angle, etc. will be described. Further, the reason why it is considered that the phenomenon occurring during recording or playback described above can be suppressed by inclining the axial direction of the module of the magnetic head with respect to the width direction of the magnetic tape during magnetic tape running will also be described below.

[0024] The magnetic head can have one or more modules each including an element array having a plurality of magnetic head elements between a pair of servo signal reading elements, and can have two or more or three or more such modules. The total number of such modules can be, for example, five or less, four or less, or three or less, or a number of modules exceeding the total numbers exemplified herein may be included in the magnetic head. Examples of the arrangement of a plurality of modules include "recording module - playback module" (total number of modules: 2), "recording module - playback module - recording module" (total number of modules: 3), etc. However, it is not limited to the examples shown here.

[0025] Each module can include an element array having a plurality of magnetic head elements between a pair of servo signal reading elements, that is, an arrangement of elements. A module having a recording element as a magnetic head element is a recording module for recording data on a magnetic tape. A module having a reproducing element as a magnetic head element is a playback module for reproducing data recorded on a magnetic tape. In the magnetic head, a plurality of modules are arranged, for example, in a recording and playback head unit such that the axes of the element arrays of the respective modules are oriented parallel to each other. Such "parallel" does not necessarily mean only parallel in a strict sense, but includes the range of errors normally allowed in the technical field to which the present invention pertains. The range of errors can mean, for example, a range of strict parallel ± less than 10°.

[0026] In each element array, a pair of servo signal reading elements and a plurality of magnetic head elements (i.e., recording elements or reproducing elements) are usually arranged linearly spaced apart. Here, "arranged linearly" means that each magnetic head element is arranged on a straight line connecting the central portion of one servo signal reading element and the central portion of the other servo signal reading element. And the "axis of the element array" in the present invention and this specification means a straight line connecting the central portion of one servo signal reading element and the central portion of the other servo signal reading element.

[0027] Next, with reference to the drawings, the configuration of the module and the like will be further described. However, the form shown in the drawings is an example and does not limit the present invention.

[0028] FIG. 1 is a schematic diagram showing an example of a module of a magnetic head. The module shown in FIG. 1 has a plurality of magnetic head elements between a pair of servo signal reading elements (servo signal reading elements 1 and 2). The magnetic head element is also called a "channel". "Ch" in the figure is an abbreviation of Channnel. The module shown in FIG. 1 has a total of 32 magnetic head elements from Ch0 to Ch31.

[0029] In FIG. 1, "L" is the distance between a pair of servo signal reading elements, that is, the distance between one servo signal reading element and the other servo signal reading element. In the module shown in FIG. 1, "L" is the distance between servo signal reading element 1 and servo signal reading element 2. Specifically, it is the distance between the central part of servo signal reading element 1 and the central part of servo signal reading element 2. Such a distance can be measured by, for example, an optical microscope or the like.

[0030] FIG. 2 is an explanatory diagram of the relative positional relationship between the module and the magnetic tape during the running of the magnetic tape in the magnetic tape device. In FIG. 2, the dotted line A indicates the width direction of the magnetic tape. The dotted line B indicates the axis of the element array. The angle θ can be called the head tilt angle during the running of the magnetic tape and is the angle formed by the dotted line A and the dotted line B. When the angle θ is 0° during the running of the magnetic tape, the distance in the width direction of the magnetic tape between one servo signal reading element and the other servo signal reading element of the element array (hereinafter, also referred to as the "effective distance between servo signal reading elements") is "L". On the other hand, when the 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".

[0031] As described above, during recording or playback, if the magnetic head for recording or playing back data is displaced from the target track position due to the width deformation of the magnetic tape and recording or playback of data is performed, phenomena such as overwriting of recorded data and playback failure may occur. For example, when the width of the magnetic tape contracts or expands, a phenomenon may occur in which the magnetic head element that should perform recording or playback at the target track position performs recording or playback at a different track position. Also, when the width of the magnetic tape expands, the effective distance between the servo signal reading elements becomes shorter than the interval between two adjacent servo bands sandwiching the data band (also described as "servo band interval" or "interval between servo bands". Specifically, it is the distance between the two servo bands in the width direction of the magnetic tape.), and a phenomenon may occur in which recording or playback of data is not performed at a portion close to the edge of the magnetic tape. On the other hand, when the element array is tilted at an angle θ greater than 0°, as described above, the effective distance between the 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, if the value of θ is changed 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 the servo signal reading elements closer to or equal to the interval between the servo bands. As a result, during recording or playback, it is possible to prevent or reduce the occurrence frequency of phenomena such as overwriting of recorded data and playback failure caused by the magnetic head for recording or playing back data being displaced from the target track position due to the width deformation of the magnetic tape and performing recording or playback of data.

[0032] Figure 3 is an explanatory diagram regarding the change in the angle θ during the running of the magnetic tape. θ which is the angle θ at the start of running initial can be set, for example, to 0° or more or greater than 0°. In Figure 3, the central figure shows the state of the module at the start of running. In Figure 3, the right figure shows the angle θ being an angle θ initial greater than θ cThe effective distance between the servo signal reading elements Lcosθ is shown. c is Lcosθ when the magnetic tape starts running initial It is preferable to perform such an angle adjustment when the width of the magnetic tape contracts during its running. On the other hand, in the left diagram of Figure 3, the angle θ is initial The smaller angle, θ e The effective distance between the servo signal reading elements Lcosθ is shown. e is Lcosθ when the magnetic tape starts running initial It is preferable to perform such an angle adjustment when the width of the magnetic tape expands during its running.

[0033] As described above, changing the head tilt angle while the magnetic tape is running can help prevent phenomena such as overwriting of recorded data and playback failures that occur when the magnetic head for recording or reproducing data deviates from the target track position due to deformation of the magnetic tape during recording or reproduction, or can help reduce the frequency of such occurrences. On the other hand, recording of data on a magnetic tape and reproduction of the recorded data are usually performed by contacting and sliding the magnetic head against the magnetic layer surface of the magnetic tape. The inventors considered that if the head tilt angle changes during such sliding, the contact state between the magnetic head and the magnetic layer surface may change, which may be a factor in reducing running stability. In detail, the inventors considered that if the contact state between the magnetic layer surface of the magnetic tape and the magnetic head (for example, the contact state between the part near the edge of the module of the magnetic head and the edge part of the magnetic layer surface) changes significantly due to the difference in the head tilt angle, the running stability will decrease, and such a decrease in running stability may become more noticeable in a high temperature and low humidity environment. However, the present invention is not limited by the inventors' speculation described in this specification. Based on the above speculation, the inventor of the present invention has conducted intensive studies. As a result, regarding the surface properties of the surface of the magnetic layer of the magnetic tape, by making the surface roughness of the edge portion coarser than that of the central portion, specifically, by setting the edge portion Ra, the central portion Ra, and the Ra ratio (central portion Ra / edge portion Ra) within the ranges described above, respectively, it has been newly found that it is possible to improve the running stability when recording and / or reproducing data at different head tilt angles in a high-temperature and low-humidity environment. Hereinafter, the running stability when changing the head tilt angle during the running of the magnetic tape to record and / or reproduce data in a high-temperature and low-humidity environment is also simply referred to as "running stability". The high-temperature and low-humidity environment can be, for example, an environment with a temperature of about 30 to 50 °C. The humidity of the environment can be, for example, about 0 to 30% as the relative humidity. The temperature and humidity described for the environment in this specification are the ambient temperature and relative humidity of the environment.

[0034] <Edge portion Ra, Central portion Ra, Ra ratio (Central portion Ra / Edge portion Ra)> In the present invention and this specification, the arithmetic mean roughness Ra is measured by a non-contact optical surface roughness meter. The measurement conditions and data processing conditions are as follows. As the non-contact optical surface roughness meter, for example, the non-contact optical surface roughness meter Contour manufactured by Bruker can be mentioned, and this non-contact optical surface roughness meter was used in the examples described later. (Measurement conditions) Measurement environment: Temperature 23 °C, Relative humidity 50% Measurement mode: PSI (Phase Shift Interferometry) Objective lens: 10 times Intermediate lens: 1.0 times Measurement field of view: 355 μm × 474 μm (Data processing conditions) Strain and tilt correction: Cylinder and Tilt (Zero Level: Zero Mean) Filter: Gaussian -Band Pass: Order = 0 -Type=Regular -High Pass Filter=1.11μm -Low Pass Filter=50μm

[0035] In the present invention and in this specification, the edge Ra, which is the arithmetic mean roughness Ra measured at the edge portion of the magnetic layer surface, shall be a value obtained by the following method. Both ends in the width direction of the magnetic tape are referred to as edges. At an arbitrary position on the magnetic layer surface of the magnetic tape to be measured, while including one edge in the measurement field of view, measurement is performed with a non-contact optical surface roughness meter under the above measurement conditions. After performing data processing on the obtained measurement results under the above data processing conditions, in a region with a width of 200 μm from "a position 50 μm inside from the edge" to "a position 200 μm further inside from a position 50 μm inside from the edge", at an arbitrary position within the measurement field of view, a range of 200 μm in width × 200 μm in length (i.e., the distance in the longitudinal direction of the magnetic tape) is specified, and the Ra of the specified range is acquired. The analysis unit provided in the non-contact optical surface roughness meter can calculate and output the Ra. Thereafter, while including the other edge in the measurement field of view, the Ra is acquired by the above method. For each of one edge side and the other edge side, the measurement position is shifted by 1 mm or more and a total of three measurements are performed. Through the above measurements, a total of six Ras are acquired. The arithmetic mean of the Ras thus acquired shall be the edge Ra.

[0036] In the present invention and in this specification, the center Ra, which is the arithmetic mean roughness Ra measured at the center portion of the magnetic layer surface, shall be a value obtained by the following method. On the surface of the magnetic layer, for one randomly selected edge out of both edges of the magnetic tape, in a region with a width of 6 mm from the position "3 mm inside the edge" to the position "6 mm further inside from the position 3 mm inside the edge", a range with a width of 200 μm × length of 200 μm is specified at an arbitrary position within the measurement field of view, and the Ra of the specified range is obtained. For the selected edge side described above, the measurement position is shifted by 1 mm or more and a total of 6 measurements are performed. Through the above measurements, a total of 6 Ra values are obtained. The arithmetic mean of the Ra values thus obtained is defined as the central part Ra.

[0037] From the edge part Ra and the central part Ra obtained by the above method, the Ra ratio (central part Ra / edge part Ra) is calculated. In the above magnetic tape, the Ra ratio (central part Ra / edge part Ra) is 0.75 or more from the viewpoint of improving the running stability when recording and / or reproducing data at different head tilt angles in a high-temperature and low-humidity environment, preferably 0.77 or more, and more preferably 0.80 or more. Also, from the above viewpoint, the Ra ratio (central part Ra / edge part Ra) is 0.95 or less, preferably 0.93 or less, and more preferably 0.90 or less.

[0038] In the above magnetic tape, from the viewpoint of improving the running stability, the edge part Ra is 1.50 nm or less, preferably 1.30 nm or less, more preferably 1.00 nm or less, still more preferably 0.95 nm or less, and even more preferably 0.90 nm or less. The edge part Ra can be, for example, 0.10 nm or more, 0.20 nm or more, or 0.30 nm or more, or can be less than the values exemplified herein.

[0039] In the above magnetic tape, from the viewpoint of improving running stability, the center Ra is 1.30 nm or less, preferably 1.20 nm or less, more preferably 1.10 nm or less, still more preferably 1.00 nm or less, even more preferably 0.90 nm or less, and yet more preferably 0.80 nm or less. Also, from the above viewpoint, the center Ra is 0.30 nm or more, preferably 0.40 nm or more, and more preferably 0.50 nm or more.

[0040] The method for controlling the Ra ratio, the edge Ra, and the center Ra will be described later.

[0041] <Standard deviation of the amount of curvature> Next, the standard deviation of the amount of curvature will be described. In the present invention and this specification, the amount of curvature in the longitudinal direction of the magnetic tape is a value obtained by the following method in an environment of an ambient temperature of 23°C and a relative humidity of 50%. The magnetic tape is usually housed in a magnetic tape cartridge and circulated. As the magnetic tape to be measured, a magnetic tape taken out from an unused magnetic tape cartridge not attached to a magnetic tape device is used. FIG. 4 is an explanatory diagram of the amount of curvature in the longitudinal direction of the magnetic tape. A tape sample having a length of 100 m in the longitudinal direction is cut out from a randomly selected portion of the magnetic tape to be measured. One end of this tape sample is defined as the 0 m position, and a position D m (D meters) away in the longitudinal direction from this one end toward the other end is defined as the D m position. Therefore, the position 10 m away in the longitudinal direction is the 10 m position, the position 20 m away is the 20 m position, and in sequence, at 10 m intervals, the 30 m position, 40 m position, 50 m position, 60 m position, 70 m position, 80 m position, 90 m position, and 100 m position are determined. A tape sample having a length of 1 m from the 0 m position to the 1 m position is cut out. This tape sample is used as a tape sample for measuring the amount of curvature at the 0 m position. Cut out a tape sample with a length of 1 m from the position of 10 m to the position of 11 m. This tape sample is used as a tape sample for measuring the amount of curvature at the 10 m position. Cut out a tape sample with a length of 1 m from the position of 20 m to the position of 21 m. This tape sample is used as a tape sample for measuring the amount of curvature at the 20 m position. Cut out a tape sample with a length of 1 m from the position of 30 m to the position of 31 m. This tape sample is used as a tape sample for measuring the amount of curvature at the 30 m position. Cut out a tape sample with a length of 1 m from the position of 40 m to the position of 41 m. This tape sample is used as a tape sample for measuring the amount of curvature at the 40 m position. Cut out a tape sample with a length of 1 m from the position of 50 m to the position of 51 m. This tape sample is used as a tape sample for measuring the amount of curvature at the 50 m position. Cut out a tape sample with a length of 1 m from the position of 60 m to the position of 61 m. This tape sample is used as a tape sample for measuring the amount of curvature at the 60 m position. Cut out a tape sample with a length of 1 m from the position of 70 m to the position of 71 m. This tape sample is used as a tape sample for measuring the amount of curvature at the 70 m position. Cut out a tape sample with a length of 1 m from the position of 80 m to the position of 81 m. This tape sample is used as a tape sample for measuring the amount of curvature at the 80 m position. Cut out a tape sample with a length of 1 m from the position of 90 m to the position of 91 m. This tape sample is used as a tape sample for measuring the amount of curvature at the 90 m position. Cut out a tape sample with a length of 1 m from the position of 99 m to the position of 100 m. This tape sample is used as a tape sample for measuring the amount of curvature at the 100 m position. Grip the tape sample at each position with the longitudinal direction vertical and the upper end with a gripping member (such as a clip), and hang it for 24 hours ± 4 hours in a tension-free state. Then, within 1 hour, perform the following measurements. As shown in Fig. 4, place the tape piece on a plane in a tension-free state. The tape piece may be placed on the plane with the surface on the magnetic layer side facing upward, or the other surface facing upward. In Fig. 4, S indicates the tape sample, and W indicates the width direction of the tape sample. Using an optical microscope, measure the distance L1 (unit: mm), which is the shortest distance between the virtual line 54 connecting both end portions 52 and 53 of the tape sample S and the maximum curved portion 55 in the longitudinal direction of the tape sample S. Fig. 4 shows an example of curving upward on the paper surface. When curving downward, measure the distance L1 (mm) in the same manner. Regardless of which side it curves, the distance L1 is displayed as a positive value. When no curving is confirmed in the longitudinal direction, L1 is set to 0 (zero) mm. In this way, the standard deviation (i.e., the positive square root of the variance) of the amount of curvature L1 measured at a total of 11 positions from the 0 m position to the 100 m position is defined as the standard deviation of the amount of curvature (unit: mm / m) in the longitudinal direction of the magnetic tape to be measured.

[0042] In the above magnetic tape, the standard deviation of the amount of curvature obtained by the above method can be, for example, 7 mm / m or less, 6 mm / m or less. From the perspective of further improving the running stability, it is preferably 5 mm / m or less, more preferably 4 mm / m or less, and even more preferably 3 mm / m or less. The standard deviation of the amount of curvature of the above magnetic tape can be, for example, 0 mm / m or more, more than 0 mm / m, 1 mm / m or more, or 2 mm / m or more. A smaller value of the standard deviation of the amount of curvature is preferable from the perspective of further improving the running stability. The standard deviation of the amount of curvature can be controlled by adjusting the manufacturing conditions in the manufacturing process of the magnetic tape. Details in this regard will be described later.

[0043] Hereinafter, the above magnetic tape will be described in more detail.

[0044] <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. From the viewpoint of improving the recording density, it is preferable to use a ferromagnetic powder having a small average particle size. From this point of view, the average particle size of the ferromagnetic powder is preferably 50 nm or less, more preferably 45 nm or less, still more preferably 40 nm or less, even more preferably 35 nm or less, yet more preferably 30 nm or less, still yet more preferably 25 nm or less, and most 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, still more preferably 10 nm or more, even more preferably 15 nm or more, yet more preferably 20 nm or more.

[0045] Hexagonal ferrite powder Preferable specific examples of the ferromagnetic powder include hexagonal ferrite powder. For details of the hexagonal ferrite powder, reference can be made to, for example, paragraphs 0012 to 0030 of JP-A-2011-225417, paragraphs 0134 to 0136 of JP-A-2011-216149, paragraphs 0013 to 0030 of JP-A-2012-204726, and paragraphs 0029 to 0084 of JP-A-2015-127985.

[0046] In the present invention and this specification, the "hexagonal ferrite powder" refers to a ferromagnetic powder in which the crystal structure of hexagonal ferrite is detected as the main phase by X-ray diffraction analysis. The main phase refers to the structure to which the diffraction peak with the highest intensity in the X-ray diffraction spectrum obtained by X-ray diffraction analysis is attributed. For example, when the diffraction peak with the highest intensity in the X-ray diffraction spectrum obtained by X-ray diffraction analysis is attributed to the crystal structure of hexagonal ferrite, it is determined that the crystal structure of hexagonal ferrite has been detected as the main phase. When only a single structure is detected by X-ray diffraction analysis, this detected structure is taken as the main phase. The crystal structure of hexagonal ferrite contains at least iron atoms, divalent metal atoms, and oxygen atoms as constituent atoms. The divalent metal atom is a metal atom that can become a divalent cation as an ion, and examples thereof include alkaline earth metal atoms such as strontium atoms, barium atoms, and calcium atoms, and lead atoms. In the present invention and this specification, the hexagonal strontium ferrite powder refers to a powder in which the main divalent metal atom contained in this powder is a strontium atom, and the hexagonal barium ferrite powder refers to a powder in which the main divalent metal atom contained in this powder is a barium atom. The main divalent metal atom refers to the divalent metal atom that occupies the largest proportion on an atomic percentage basis among the divalent metal atoms contained in this powder. However, rare earth atoms are not included in the above divalent metal atoms. The "rare earth atoms" in the present invention and this specification are selected from the group consisting of scandium atoms (Sc), yttrium atoms (Y), and lanthanoid atoms. The lanthanoid atoms are selected from the group consisting of lanthanum atoms (La), cerium atoms (Ce), praseodymium atoms (Pr), neodymium atoms (Nd), promethium atoms (Pm), samarium atoms (Sm), europium atoms (Eu), gadolinium atoms (Gd), terbium atoms (Tb), dysprosium atoms (Dy), holmium atoms (Ho), erbium atoms (Er), thulium atoms (Tm), ytterbium atoms (Yb), and lutetium atoms (Lu).

[0047] Hereinafter, the hexagonal strontium ferrite powder, which is one form of the hexagonal ferrite powder, will be described in more detail.

[0048] The activation volume of the hexagonal strontium ferrite powder is preferably in the range of 800 to 1600 nm 3 The particulate hexagonal strontium ferrite powder having an activation volume within the above range is suitable for producing a magnetic tape that exhibits excellent electromagnetic conversion characteristics. The activation volume of the hexagonal strontium ferrite powder is preferably 800 nm 3 or more, for example, 850 nm 3 or more. Also, from the viewpoint of further improving the electromagnetic conversion characteristics, the activation volume of the hexagonal strontium ferrite powder is more preferably 1500 nm 3 or less, still more preferably 1400 nm 3 or less, even more preferably 1300 nm 3 or less, still even more preferably 1200 nm 3 or less, yet even more preferably 1100 nm 3 or less is even yet more preferably. The same applies to the activation volume of the hexagonal barium ferrite powder.

[0049] The "activation volume" is a unit of magnetization reversal and is an index indicating the magnetic size of particles. The activation volume described in the present invention and this specification and the anisotropy constant Ku described later are measured using a vibrating sample magnetometer at magnetic field sweep rates of 3 minutes and 30 minutes in the coercive force Hc measurement section (measurement temperature: 23°C ± 1°C), and are values obtained from the following relational expression between Hc and the activation volume V. Regarding the unit of the anisotropy constant Ku, 1 erg / cc = 1.0×10 -1 J / m 3 is. Hc = 2Ku / Ms{1 - [(kT / KuV)ln(At / 0.693)] 1 / 2} [In the above formula, Ku: anisotropy constant (unit: J / m 3 ), Ms: saturation magnetization (unit: kA / m), k: Boltzmann constant, T: absolute temperature (unit: K), V: activation volume (unit: cm 3 ), A: spin precession frequency (unit: s -1 )), t: magnetic field reversal time (unit: s)]

[0050] As an index for reducing thermal fluctuations, in other words, improving thermal stability, the anisotropy constant Ku can be cited. The hexagonal strontium ferrite powder preferably has a Ku of 1.8×10 5 J / m 3 or more, and more preferably 2.0×10 5 J / m 3 or more. Also, the Ku of the hexagonal strontium ferrite powder can be, for example, 2.5×10 5 J / m 3 or less. However, since a higher Ku means higher thermal stability and is preferable, it is not limited to the values exemplified above.

[0051] The hexagonal strontium ferrite powder may or may not contain rare earth atoms. When the hexagonal strontium ferrite powder contains rare earth atoms, it preferably contains rare earth atoms at a content rate (bulk content rate) of 0.5 to 5.0 atomic% with respect to 100 atomic% of iron atoms. The hexagonal strontium ferrite powder containing rare earth atoms can, in one form, have a rare earth atom surface layer partiality. In the present invention and this specification, the "rare earth atom surface layer partiality" means the rare earth atom content rate (hereinafter, referred to as "rare earth atom surface layer content rate" or simply "surface layer content rate" with respect to rare earth atoms) with respect to 100 atomic% of iron atoms in the dissolution liquid obtained by partially dissolving the hexagonal strontium ferrite powder with an acid, and the rare earth atom content rate (hereinafter, referred to as "rare earth atom bulk content rate" or simply "bulk content rate" with respect to rare earth atoms) with respect to 100 atomic% of iron atoms in the dissolution liquid obtained by completely dissolving the hexagonal strontium ferrite powder with an acid, and Rare earth atom surface layer content rate / Rare earth atom bulk content rate > 1.0 It means satisfying the ratio. The rare earth atom content of the hexagonal strontium ferrite powder described below is synonymous with the rare earth atom bulk content. In contrast, partial dissolution using an acid dissolves the surface layer portion of the particles constituting the hexagonal strontium ferrite powder. Therefore, the rare earth atom content in the dissolution solution obtained by partial dissolution is the rare earth atom content in the surface layer portion of the particles constituting the hexagonal strontium ferrite powder. That the rare earth atom surface layer content satisfies the ratio of "rare earth atom surface layer content / rare earth atom bulk content > 1.0" means that in the particles constituting the hexagonal strontium ferrite powder, rare earth atoms are unevenly distributed in the surface layer portion (that is, there are more than in the interior). The surface layer portion in the present invention and this specification means a partial region from the surface to the interior of the particles constituting the hexagonal strontium ferrite powder.

[0052] When the hexagonal strontium ferrite powder contains rare earth atoms, the rare earth atom content (bulk content) is preferably in the range of 0.5 to 5.0 atomic% with respect to 100 atomic% of iron atoms. It is considered that including rare earth atoms with a bulk content in the above range and the uneven distribution of rare earth atoms in the surface layer portion of the particles constituting the hexagonal strontium ferrite powder contribute to suppressing the decrease in the reproduction output in repeated reproduction. This is presumably because the hexagonal strontium ferrite powder contains rare earth atoms with a bulk content in the above range and the uneven distribution of rare earth atoms in the surface layer portion of the particles constituting the hexagonal strontium ferrite powder can increase the anisotropy constant Ku. The higher the value of the anisotropy constant Ku, the more the occurrence of a phenomenon called so-called thermal fluctuation can be suppressed (in other words, the thermal stability can be improved). By suppressing the occurrence of thermal fluctuation, the decrease in the reproduction output in repeated reproduction can be suppressed. It is speculated that the uneven distribution of rare earth atoms in the particle surface layer portion of the hexagonal strontium ferrite powder contributes to stabilizing the spin of the iron (Fe) sites in the crystal lattice of the surface layer portion, thereby increasing the anisotropy constant Ku. In addition, it is presumed that using hexagonal strontium ferrite powder having a rare earth atom surface layer bias as the ferromagnetic powder of the magnetic layer also contributes to suppressing the wear of the magnetic layer surface due to sliding with the magnetic head. That is, it is presumed that hexagonal strontium ferrite powder having a rare earth atom surface layer bias can contribute to improving the running durability of the magnetic tape. This is presumably because the uneven distribution of rare earth atoms on the surface of the particles constituting the hexagonal strontium ferrite powder contributes to improving the interaction between the particle surface and the organic substances (for example, binders and / or additives) contained in the magnetic layer, and as a result, the strength of the magnetic layer is improved. From the viewpoint of suppressing a decrease in the reproduction output during repeated reproduction and / or from the viewpoint of further improving the running durability, the rare earth atom content (bulk content) is more preferably in the range of 0.5 to 4.5 atomic%, still more preferably in the range of 1.0 to 4.5 atomic%, and even more preferably in the range of 1.5 to 4.5 atomic%.

[0053] The above bulk content is the content determined by completely dissolving the hexagonal strontium ferrite powder. In the present invention and this specification, unless otherwise specified, the content of an atom means the bulk content determined by completely dissolving the hexagonal strontium ferrite powder. The hexagonal strontium ferrite powder containing rare earth atoms may contain only one kind of rare earth atom as the rare earth atom, or may contain two or more kinds of rare earth atoms. The above bulk content in the case of containing two or more kinds of rare earth atoms is determined for the total of two or more kinds of rare earth atoms. This also applies to other components in the present invention and this specification. That is, unless otherwise specified, one kind of a certain component may be used, or two or more kinds may be used. The content or content rate in the case of using two or more kinds means the total of two or more kinds.

[0054] When the hexagonal strontium ferrite powder contains rare earth atoms, the rare earth atoms included may be any one or more of the rare earth atoms. From the viewpoint of suppressing the decrease in the reproduction output in repeated reproduction, preferable rare earth atoms include neodymium atoms, samarium atoms, yttrium atoms, and dysprosium atoms, more preferably neodymium atoms, samarium atoms, and yttrium atoms, and even more preferably neodymium atoms.

[0055] In the hexagonal strontium ferrite powder having rare earth atom surface layer partiality, the rare earth atoms only need to be unevenly distributed in the surface layer of the particles constituting the hexagonal strontium ferrite powder, and the degree of uneven distribution is not limited. For example, for the hexagonal strontium ferrite powder having rare earth atom surface layer partiality, the ratio of the surface layer content rate of rare earth atoms obtained by partial dissolution under the dissolution conditions described later to the bulk content rate of rare earth atoms obtained by complete dissolution under the dissolution conditions described later, "surface layer content rate / bulk content rate" is more than 1.0, and can be 1.5 or more. That the "surface layer content rate / bulk content rate" is greater than 1.0 means that in the particles constituting the hexagonal strontium ferrite powder, rare earth atoms are unevenly distributed in the surface layer (that is, there are more than in the interior). Also, the ratio of the surface layer content rate of rare earth atoms obtained by partial dissolution under the dissolution conditions described later to the bulk content rate of rare earth atoms obtained by complete dissolution under the dissolution conditions described later, "surface layer content rate / bulk content rate" 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 the hexagonal strontium ferrite powder having rare earth atom surface layer partiality, the rare earth atoms only need to be unevenly distributed in the surface layer of the particles constituting the hexagonal strontium ferrite powder, and the above "surface layer content rate / bulk content rate" is not limited to the exemplified upper or lower limits.

[0056] The partial dissolution and complete dissolution of hexagonal strontium ferrite powder will be described below. For the hexagonal strontium ferrite powder existing as powder, the sample powders for partial dissolution and complete dissolution are taken from the same lot of powder. On the other hand, for the hexagonal strontium ferrite powder contained in the magnetic layer of the magnetic tape, a part of the hexagonal strontium ferrite powder taken out from the magnetic layer is subjected to partial dissolution, and the other part is subjected to complete dissolution. The extraction of the hexagonal strontium ferrite powder from the magnetic layer can be carried out, for example, by the method described in paragraph 0032 of JP-A-2015-91747. The above-mentioned partial dissolution means dissolution to such an extent that the residue of the hexagonal strontium ferrite powder can be visually confirmed in the liquid at the end of dissolution. For example, by partial dissolution, for the particles constituting the hexagonal strontium ferrite powder, a region of 10 to 20% by mass can be dissolved with the whole particle being 100% by mass. On the other hand, the above-mentioned complete dissolution means dissolution until the residue of the hexagonal strontium ferrite powder cannot be visually confirmed in the liquid at the end of dissolution. The measurement of the above-mentioned partial dissolution and surface layer portion content is carried out, for example, by the following method. However, the dissolution conditions such as the amount of the sample powder below are examples, and dissolution conditions that enable partial dissolution and complete dissolution can be arbitrarily adopted. A container (for example, a beaker) containing 12 mg of the 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 obtained dissolution solution is filtered through a 0.1 μm membrane filter. The elemental analysis of the filtrate thus obtained is carried out by an inductively coupled plasma (ICP) analyzer. Thus, the surface layer portion content of the rare earth atoms with respect to 100 atomic% of iron atoms can be determined. When a plurality of types of rare earth atoms are detected by elemental analysis, the total content of all rare earth atoms is taken as the surface layer portion content. This is the same in the measurement of the bulk content. On the other hand, the measurement of the above-mentioned complete dissolution and bulk content is carried out, for example, by the following method. A container (e.g., a beaker) containing 12 mg of sample powder and 10 mL of 4 mol / L hydrochloric acid is held on a hot plate at a set temperature of 80°C for 3 hours. Thereafter, it is carried out in the same manner as the above partial dissolution and measurement of the surface layer portion content rate, and the bulk content rate with respect to 100 atomic% of iron atoms can be determined.

[0057] From the viewpoint of increasing the playback output when playing back the data recorded on the magnetic tape, it is desirable that the mass magnetization σs of the ferromagnetic powder contained in the magnetic tape is high. In this regard, the hexagonal strontium ferrite powder containing rare earth atoms but having no uneven distribution of rare earth atoms in the surface layer portion has a tendency that σs is significantly reduced compared to the hexagonal strontium ferrite powder not containing rare earth atoms. On the other hand, in order to suppress such a significant decrease in σs, the hexagonal strontium ferrite powder having uneven distribution of rare earth atoms in the surface layer portion is considered preferable. In one form, the σs of the hexagonal strontium ferrite powder can be 45 A·m 2 / kg or more, and can also be 47 A·m 2 / kg or more. On the other hand, from the viewpoint of noise reduction, σs is preferably 80 A·m 2 / kg or less, and more preferably 60 A·m 2 / kg or less. σs can be measured using a known measuring device capable of measuring magnetic properties such as a vibrating sample type magnetometer. In the present invention and this specification, unless otherwise specified, the mass magnetization σs is a value measured at a magnetic field strength of 15 kOe. 1 [kOe] = 10 6 / 4π [A / m].

[0058] Regarding the content ratio (bulk content ratio) of constituent atoms of the hexagonal strontium ferrite powder, the strontium atom content ratio can be, for example, in the range of 2.0 to 15.0 atomic% with respect to 100 atomic% of iron atoms. In one form, the hexagonal strontium ferrite powder can be such that the divalent metal atoms contained in this powder are only strontium atoms. In another form, the hexagonal strontium ferrite powder can also contain one or more other divalent metal atoms in addition to strontium atoms. For example, it can contain barium atoms and / or calcium atoms. When other divalent metal atoms other than strontium atoms are contained, the barium atom content ratio and calcium atom content ratio in the hexagonal strontium ferrite powder can each be, for example, in the range of 0.05 to 5.0 atomic% with respect to 100 atomic% of iron atoms.

[0059] As the crystal structure of hexagonal ferrite, the magnetoplumbite type (also called "M type"), W type, Y type and Z type are known. The hexagonal strontium ferrite powder can take any of these crystal structures. The crystal structure can be confirmed by X-ray diffraction analysis. The hexagonal strontium ferrite powder can be such that a single crystal structure or two or more crystal structures are detected by X-ray diffraction analysis. For example, in one form, the hexagonal strontium ferrite powder can be such that only the M-type crystal structure is detected 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. When the hexagonal strontium ferrite powder is of the M type, A is only a strontium atom (Sr), or when A contains a plurality of divalent metal atoms, the strontium atom (Sr) occupies the most in terms of atomic percentage as described above. The content rate of the divalent metal atom in the 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 rate and the oxygen atom content rate. The hexagonal strontium ferrite powder contains at least iron atoms, strontium atoms, and oxygen atoms, and may further contain rare earth atoms. Furthermore, the hexagonal strontium ferrite powder may or may not contain atoms other than these atoms. As an example, the hexagonal strontium ferrite powder may contain an aluminum atom (Al). The content rate of the aluminum atom can be, for example, 0.5 to 10.0 atomic% with respect to 100 atomic% of the iron atoms. From the viewpoint of suppressing the reduction in the reproduction output in repeated reproduction, the hexagonal strontium ferrite powder contains iron atoms, strontium atoms, oxygen atoms, and rare earth atoms, and the content rate of atoms other than these atoms is preferably 10.0 atomic% or less, more preferably in the range of 0 to 5.0 atomic%, and may be 0 atomic% with respect to 100 atomic% of the iron atoms. That is, in one form, the hexagonal strontium ferrite powder may not contain atoms other than iron atoms, strontium atoms, oxygen atoms, and rare earth atoms. The content rate expressed in the above atomic percentage is obtained by converting the content rate (unit: mass%) of each atom obtained by completely dissolving the hexagonal strontium ferrite powder into a value expressed in atomic percentage using the atomic weight of each atom. Also, in the present invention and this specification, "not containing" a certain atom means that the content rate measured by an ICP analyzer after complete dissolution is 0 mass%. The detection limit of the ICP analyzer is usually 0.01 ppm (parts per million) or less on a mass basis. The above "not containing" is used in the sense of including being contained in an amount less than the detection limit of the ICP analyzer.The hexagonal strontium ferrite powder can, in one form, be free of bismuth atoms (Bi).

[0060] Metal powder Preferred specific examples of the ferromagnetic powder can also include ferromagnetic metal powders. For details of the ferromagnetic metal powders, reference can be made to, for example, paragraphs 0137 to 0141 of JP-A-2011-216149 and paragraphs 0009 to 0023 of JP-A-2005-251351.

[0061] ε-iron oxide powder Preferred specific examples of the ferromagnetic powder can also include ε-iron oxide powder. In the present invention and this specification, the "ε-iron oxide powder" refers to a ferromagnetic powder in which the crystal structure of ε-iron oxide is detected as the main phase by X-ray diffraction analysis. For example, in the X-ray diffraction spectrum obtained by X-ray diffraction analysis, when the diffraction peak with the highest intensity is attributed to the crystal structure of ε-iron oxide, it is determined that the crystal structure of ε-iron oxide is detected as the main phase. As methods for producing ε-iron oxide powder, a method of producing from goethite, an inverse micelle method, etc. are known. All of the above production methods are well-known. Also, for methods of producing ε-iron oxide powder in which a part of Fe is substituted by substitution atoms such as Ga, Co, Ti, Al, Rh, etc., reference can be made to, 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 a ferromagnetic powder in the magnetic layer of the above magnetic tape is not limited to the methods listed here.

[0062] The activation volume of the ε-iron oxide powder is preferably in the range of 300 to 1500 nm 3 is. The micronized ε-iron oxide powder showing the activation volume in the above range is suitable for producing a magnetic tape that exhibits excellent electromagnetic conversion characteristics. The activation volume of the ε-iron oxide powder is preferably 300 nm 3 or more, for example 500 nm3 It can also be the above. Further, from the viewpoint of further improving the electromagnetic conversion characteristics, the activation volume of the ε-iron oxide powder is 1400 nm 3 It is more preferably below, and 1300 nm 3 It is even more preferably below, and 1200 nm 3 It is still more preferably below, and 1100 nm 3 It is even more preferably below.

[0063] As an index for reducing thermal fluctuations, in other words, improving thermal stability, the anisotropy constant Ku can be cited. The ε-iron oxide powder preferably has a Ku of 3.0×10 4 J / m 3 or more, and more preferably has a Ku of 8.0×10 4 J / m 3 or more. Further, the Ku of the ε-iron oxide powder can be, for example, 3.0×10 5 J / m 3 or less. However, the higher the Ku, the higher the thermal stability, which is preferable, so it is not limited to the values exemplified above.

[0064] From the viewpoint of increasing the playback output when playing back data recorded on a magnetic tape, it is desirable that the mass magnetization σs of the ferromagnetic powder contained in the magnetic tape is high. In this regard, in one form, the σs of the ε-iron oxide powder can be 8 A·m 2 / kg or more, and can also be 12 A·m 2 / kg or more. On the other hand, from the viewpoint of noise reduction, the σs of the ε-iron oxide powder is preferably 40 A·m 2 / kg or less, and more preferably 35 A·m 2 / kg or less.

[0065] In the present invention and this specification, unless otherwise specified, the average particle size of various powders such as ferromagnetic powders is the value measured by the following method using a transmission electron microscope. Photograph the powder at a magnification of 100,000 times using a transmission electron microscope, and print it on photographic paper or display it on a display so that the total magnification becomes 500,000 times to obtain a photograph of the particles constituting the powder. Select the target particles from the obtained particle photographs and trace the contours of the particles with a digitizer to measure the size of the particles (primary particles). The primary particles refer to independent particles without aggregation. Perform the above measurements on 500 randomly selected particles. The arithmetic mean of the particle sizes of the 500 particles thus obtained is defined as the average particle size of the powder. As the above transmission electron microscope, for example, a Hitachi transmission electron microscope model H-9000 can be used. Also, the measurement of the particle size can be performed using known image analysis software, for example, Carl Zeiss image analysis software KS-400. Unless otherwise specified, the average particle size shown in the examples described later is a value measured using a Hitachi transmission electron microscope model H-9000 as the transmission electron microscope and Carl Zeiss image analysis software KS-400 as the image analysis software. In the present invention and this specification, the powder means a collection of a plurality of particles. For example, ferromagnetic powder means a collection of a plurality of ferromagnetic particles. Also, the collection of a plurality of particles is not limited to the form in which the particles constituting the collection are in direct contact, and forms in which binders, additives, etc. described later are interposed between the particles are also included. The term "particle" may also be used to represent the powder.

[0066] As a method for collecting the sample powder from the magnetic tape for particle size measurement, for example, the method described in paragraph 0015 of JP-A-2011-048878 can be adopted.

[0067] In the present invention and this specification, unless otherwise specified, the size of the particles (particle size) constituting the powder is such that the shape of the particles observed in the above particle photographs is (1) In the case of acicular, spindle-shaped, columnar (however, the height is greater than the maximum major axis length of the bottom surface), etc., it is represented by the length of the major axis constituting the particle, that is, the major axis length. (2) In the case of being plate-shaped or columnar (however, the thickness or height is smaller than the maximum major axis diameter of the plate surface or bottom surface), it is represented by the maximum major axis diameter of the plate surface or bottom surface, (3) In the case of being spherical, polyhedral, amorphous, etc., and when the major axis constituting the particles cannot be specified from the shape, it is represented by the equivalent circle diameter. The equivalent circle diameter refers to that obtained by the circular projection method.

[0068] Also, the average aspect ratio of the powder is measured as the length of the minor axis of the particles, i.e., the minor axis length, in the above measurement, and the value of (major axis length / minor axis length) for each particle is obtained, and it refers to the arithmetic mean of the values obtained for the above 500 particles. Here, unless otherwise specified, the minor axis length refers to the length of the minor axis constituting the particles in the case of (1) in the above definition of particle size, and also refers to the thickness or height in the case of (2), respectively. In the case of (3), since there is no distinction between the major axis and the minor axis, (major axis length / minor axis length) is regarded as 1 for convenience. And, unless otherwise specified, when the shape of the particles is specified, for example, in the case of the above definition of particle size (1), the average particle size is the average major axis length, and in the case of the same definition (2), the average particle size is the average plate diameter. In the case of the same definition (3), the average particle size is the average diameter (also referred to as the average particle diameter, average particle size).

[0069] The content rate (filling rate) of the ferromagnetic powder in the magnetic layer is preferably in the range of 50 to 90% by mass, more preferably in the range of 60 to 90% by mass, with respect to the total mass of the magnetic layer. A high filling rate of the ferromagnetic powder in the magnetic layer is preferable from the viewpoint of improving the recording density.

[0070] (Binder) The magnetic tape can be a coated magnetic tape and can contain a binder in the magnetic layer. The binder is one or more resins. As the binder, various resins commonly used as binders for coated magnetic recording media can be used. For example, as the binder, polyurethane resin, polyester resin, polyamide resin, vinyl chloride resin, acrylic resin copolymerized with styrene, acrylonitrile, methyl methacrylate, etc., cellulose resin such as nitrocellulose, epoxy resin, phenoxy resin, polyvinyl acetal, polyvinyl butyral, etc. A resin selected from polyvinyl alkylal resins can be used alone or a plurality of resins can be mixed and used. Among these, preferred are polyurethane resin, acrylic resin, cellulose resin, and vinyl chloride resin. These resins may be homopolymers or copolymers (copolymers). These resins can also be used as binders in the non-magnetic layer and / or backcoat layer described later. Regarding the above binders, reference can be made to paragraphs 0028 to 0031 of JP-A-2010-24113. Further, the binder may be a radiation-curable resin such as an electron beam-curable resin. Regarding the radiation-curable resin, reference can be made to paragraphs 0044 to 0045 of JP-A-2011-048878. The average molecular weight of the resin used as the binder can be, for example, 10,000 or more and 200,000 or less as the weight average molecular weight. The weight average molecular weight in the present invention and this specification is a value obtained by converting the value measured under the following measurement conditions by gel permeation chromatography (GPC) into polystyrene. The weight average molecular weight of the binder shown in the examples described later is a value obtained by converting the value measured under the following measurement conditions into polystyrene. The binder can be used in an amount of, for example, 1.0 to 30.0 parts by mass with respect to 100.0 parts by mass of the ferromagnetic powder. GPC apparatus: HLC-8120 (manufactured by Tosoh Corporation) Column: TSK gel Multipore HXL-M (manufactured by Tosoh Corporation, 7.8 mm ID (Inner Diameter) × 30.0 cm) Eluent: Tetrahydrofuran (THF)

[0071] (Hardening agent) A hardening agent can also be used together with the binder. The hardening agent can be a thermosetting compound which is a compound in which the hardening reaction (crosslinking reaction) proceeds by heating in one form, and can be a photocurable compound in which the hardening reaction (crosslinking reaction) proceeds by light irradiation in another form. The hardening agent can be contained in the magnetic layer in a state where at least a part thereof has reacted (crosslinked) with other components such as the binder by the progress of the hardening reaction during the manufacturing process of the magnetic tape. A preferable hardening agent is a thermosetting compound, and polyisocyanate is suitable. For details of the polyisocyanate, reference can be made to paragraphs 0124 to 0125 of JP-A-2011-216149. The hardening agent can be used in the composition for forming the magnetic layer in an amount of, for example, 0 to 80.0 parts by mass, preferably 50.0 to 80.0 parts by mass, based on 100.0 parts by mass of the binder, from the viewpoint of improving the strength of each layer such as the magnetic layer.

[0072] (Additive) The magnetic layer may contain one or more additives as necessary. As an example of the additive, the above-mentioned curing agent can be mentioned. Further, examples of the additives contained in the magnetic layer include non-magnetic powders (for example, inorganic powders, carbon black, etc.), lubricants, dispersants, dispersion aids, fungicides, antistatic agents, antioxidants, and the like. For example, regarding the lubricant, paragraphs 0030 to 0033, 0035, and 0036 of JP-A-2016-126817 can be referred to. The lubricant may be contained in the non-magnetic layer described later. Regarding the lubricant that can be contained in the non-magnetic layer, paragraphs 0030, 0031, 0034 to 0036 of JP-A-2016-126817 can be referred to. Regarding the dispersant, paragraphs 0061 and 0071 of JP-A-2012-133837 can be referred to. The dispersant may be added to the composition for forming the non-magnetic layer. Regarding the dispersant that can be added to the composition for forming the non-magnetic layer, paragraph 0061 of JP-A-2012-133837 can be referred to. Further, examples of the non-magnetic powder that can be contained in the magnetic layer include non-magnetic powders that can function as abrasives, non-magnetic powders that can function as protrusion-forming agents for forming protrusions that moderately protrude from the surface of the magnetic layer (for example, non-magnetic colloidal particles, etc.). The average particle size of the colloidal silica (silica colloidal particles) shown in the examples described later is a value obtained by the method described in paragraph 0015 of JP-A-2011-048878 as a method for measuring the average particle diameter. The additives can be appropriately selected from commercially available products according to the desired properties, or manufactured by known methods, and used in any amount. As an example of the additive that can be used to improve the dispersibility of the abrasive in the magnetic layer containing the abrasive, the dispersants described in paragraphs 0012 to 0022 of JP-A-2013-131285 can be mentioned.

[0073] The magnetic layer described above can be provided directly on the surface of the non-magnetic support or indirectly via the non-magnetic layer.

[0074] <Non-magnetic layer> Next, the non-magnetic layer will be described. The magnetic tape may have a magnetic layer directly on a non-magnetic support, or may have a non-magnetic layer containing non-magnetic powder between the non-magnetic support and the magnetic layer. The non-magnetic powder used for the non-magnetic layer may be a powder of an inorganic substance (inorganic powder) or a powder of an organic substance (organic powder). Also, carbon black or the like can be used. Examples of the inorganic substance include metals, metal oxides, metal carbonates, metal sulfates, metal nitrides, metal carbides, metal sulfides, and the like. These non-magnetic powders are available as commercial products and can also be manufactured by known methods. For details, reference can be made to paragraphs 0146 to 0150 of JP-A-2011-216149. Regarding the carbon black that can be used for the non-magnetic layer, reference can also be made to paragraphs 0040 to 0041 of JP-A-2010-24113. The content rate (filling rate) of the non-magnetic powder in the non-magnetic layer is preferably in the range of 50 to 90% by mass, more preferably in the range of 60 to 90% by mass, based on the total mass of the non-magnetic layer.

[0075] In one form, the non-magnetic layer can contain Fe-based inorganic oxide powder as the non-magnetic powder. In the present invention and this specification, "Fe-based inorganic oxide powder" refers to an inorganic oxide powder containing iron as a constituent element. Specific examples of the Fe-based inorganic oxide powder include α-iron oxide powder, goethite powder, and the like. In the present invention and this specification, "α-iron oxide powder" refers to a non-magnetic powder in which the crystal structure of α-iron oxide is detected as the main phase by X-ray diffraction analysis. α-iron oxide powder is generally also called hematite or the like.

[0076] Regarding the non-magnetic layer, according to the study by the present inventor, the average particle volume is 2.0×10 -6 μm 3The non-magnetic layer containing the following Fe-based inorganic oxide powder tended to have high hardness. In this regard, the inventor of the present invention considers this to be preferable for stably performing the burnishing process described later. When the burnishing process is stably performed, the inventor speculates that it becomes easier to control the Ra at the edge portion and the Ra at the central portion, and as a result, it also becomes easier to control the Ra ratio. From this point, the average particle volume of the Fe-based inorganic oxide powder contained in the non-magnetic layer is 2.0×10 -6 μm 3 or less is preferable, and 1.5×10 -6 μm 3 or less is more preferable, and 1.0×10 -6 μm 3 or less is even more preferable. The above average particle volume can be, for example, 1.0×10 -9 μm 3 or more, or 1.0×10 -8 μm 3 or more, or it can be less than the values exemplified herein.

[0077] In the present invention and this specification, the above average particle volume is defined as the value obtained by the following method. In order to observe the Fe-based inorganic oxide powder contained in the non-magnetic layer of the magnetic tape, first, as a sample pretreatment, sectioning is performed by the microtome method. The sectioning is performed along the longitudinal direction of the magnetic tape so as to obtain a thin sample capable of observing a cross-section in the thickness direction of the magnetic tape. For the examples described later, in order to obtain the average particle volume of the Fe-based inorganic oxide powder, Leica EM UC6 manufactured by Leica was used as the microtome. For the obtained thin sample, cross-sectional observation is performed using a transmission electron microscope (TEM: Transmission Electron Microscope) at an acceleration voltage of 300 kV and a total magnification of 200,000 times so as to include the range from the non-magnetic support to the magnetic layer, and a cross-sectional TEM image is obtained. As the transmission electron microscope, for example, JEM-2100Plus manufactured by JEOL can be used. For the examples described later, in order to obtain the average particle volume of the Fe-based inorganic oxide powder, JEM-2100Plus manufactured by JEOL was used as the transmission electron microscope. In the obtained cross-sectional TEM image, 50 particles of the Fe-based inorganic oxide powder are specified for the particles contained in the non-magnetic layer by using the ultramicro electron beam diffraction method. The electron beam diffraction in the ultramicro electron beam diffraction method is carried out using a transmission electron microscope at an acceleration voltage of 200 kV and a camera length of 50 cm. For the examples described later, JEM-2100Plus manufactured by JEOL was used as the transmission electron microscope for the electron beam diffraction in the ultramicro electron beam diffraction method. Thereafter, using 50 particles of the Fe-based inorganic oxide powder specified as described above, the average particle volume is determined as follows. First, the major axis length (hereinafter referred to as "DL") and the minor axis length (hereinafter referred to as "DS") of each particle are measured. The major axis length DL means the maximum of the distances between two parallel lines drawn from all angles so as to be in contact with the contour of the particle (the so-called maximum Feret's Diameter). When the direction of the major axis length defined as above is called the major axis direction, the minor axis length DS means the maximum of the lengths of the particle in the direction perpendicular to the major axis direction of the particle. Next, the average major axis length DLave is obtained as the arithmetic mean of the major axis lengths DL of the 50 measured particles. Ave is an abbreviation for average. Also, the average minor axis length DSave is obtained as the arithmetic mean of the minor axis lengths DS of the above 50 particles. From the average major axis length DLave and the average minor axis length DSave, the average volume Vave of the particle is obtained by the following formula. Vave = π / 6 × DSave 2 × DLave

[0078] Also, in one embodiment, the non-magnetic layer can include carbon black as a non-magnetic powder. The average particle size of the carbon black can be, for example, 10 nm or more and 50 nm or less. According to the study by the present inventors, the non-magnetic layer containing carbon black with a pH of 5.0 or less tended to have high hardness. The present inventors consider this point to be preferable for stably performing the burnishing process described later. When the burnishing process is stably performed, the present inventors speculate that it becomes easier to control the Ra at the edge portion and the Ra at the center portion, and as a result, it also becomes easier to control the Ra ratio. From this point, the pH of the carbon black contained in the non-magnetic layer is preferably 5.0 or less, and more preferably 4.0 or less. The above pH can be, for example, 1.0 or more, 2.0 or more, or 3.0 or more, or can be less than the values exemplified herein.

[0079] In the present invention and this specification, the pH of carbon black is the value measured according to the standard test method ASTM D1512.

[0080] The non-magnetic layer preferably contains at least one of Fe-based inorganic oxide powder having an average particle volume of 2.0×10 -6 μm 3 or less and carbon black having a pH of 5.0 or less, and more preferably contains both. With respect to 100 parts by mass of the total amount of non-magnetic powder contained in the non-magnetic layer, the content of Fe-based inorganic oxide powder having an average particle volume of 2.0×10 -6 μm 3 or less can be 50 parts by mass or more, 60 parts by mass or more, or 70 parts by mass or more, and can be, for example, 90 parts by mass or less. With respect to 100 parts by mass of the total amount of non-magnetic powder contained in the non-magnetic layer, the content of carbon black having a pH of 5.0 or less can be 10 parts by mass or more or 20 parts by mass or more, and can be, for example, 50 parts by mass or less, 40 parts by mass or less, or 30 parts by mass or less.

[0081] The non-magnetic layer can contain a binder and can also contain additives. Regarding other details such as the binder and additives of the non-magnetic layer, known techniques related to the non-magnetic layer can be applied. Also, for example, regarding the type and content of the binder, the type and content of the additives, etc., known techniques related to the magnetic layer can also be applied.

[0082] The non-magnetic layer of the magnetic tape is assumed to include a substantially non-magnetic layer containing, for example, as impurities or intentionally, a small amount of ferromagnetic powder together with non-magnetic powder. Here, a substantially non-magnetic layer means a layer in which the residual magnetic flux density of this layer is 10 mT or less, the coercive force is 7.96 kA / m (100 Oe) or less, or the residual magnetic flux density is 10 mT or less and the coercive force is 7.96 kA / m (100 Oe) or less. The non-magnetic layer preferably has no residual magnetic flux density and coercive force.

[0083] <Non-magnetic support> Next, the non-magnetic support will be described. Examples of the non-magnetic support (hereinafter also simply referred to as "support") include known ones such as biaxially stretched polyethylene terephthalate, polyethylene naphthalate, polyamide, polyamideimide, and aromatic polyamide. Among these, polyethylene terephthalate, polyethylene naphthalate, and polyamide are preferred. These supports may be subjected to corona discharge, plasma treatment, easy adhesion treatment, heat treatment, etc. in advance.

[0084] <Backcoat layer> The above tape may or may not have a backcoat layer containing non-magnetic powder on the surface side opposite to the surface side having the magnetic layer of the non-magnetic support. It is preferable that the backcoat layer contains one or both of carbon black and inorganic powder. The backcoat layer can contain a binder and can also contain additives. Regarding details such as the non-magnetic powder, binder, additives, etc. of the backcoat layer, known techniques regarding the backcoat layer can be applied, and known techniques regarding the magnetic layer and / or non-magnetic layer can also be applied. For example, the descriptions in paragraphs 0018 to 0020 of JP-A-2006-331625 and lines 65 to 38 in column 4 of US Patent No. 7,029,774 can be referred to for the backcoat layer.

[0085] <Various thicknesses> Regarding the thickness (total thickness) of the magnetic tape, with the huge increase in the amount of information in recent years, there has been a demand for increasing the recording capacity (increasing the capacity) of the magnetic tape. As a means for increasing the capacity, thinning the thickness of the magnetic tape and increasing the length of the magnetic tape accommodated per magnetic tape cartridge can be mentioned. From this point, the thickness (total thickness) of the above magnetic tape is preferably 5.6 μm or less, more preferably 5.5 μm or less, still more preferably 5.4 μm or less, further preferably 5.3 μm or less, and even more preferably 5.2 μm or less. Also, from the viewpoint of ease of handling, the thickness of the magnetic tape is preferably 3.0 μm or more, and more preferably 3.5 μm or more.

[0086] The thickness (total thickness) of the magnetic tape can be measured by the following method. Cut out 10 tape samples (for example, 5 to 10 cm in length) from an arbitrary part of the magnetic tape, stack these tape samples, and measure the thickness. The value obtained by dividing the measured thickness by 10 (the thickness per tape sample) is taken as the tape thickness. The above thickness measurement can be performed using a known measuring instrument capable of measuring the thickness on the order of 0.1 μm.

[0087] 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 band of the recording signal, etc. Generally, it is 0.01 μm to 0.15 μm. From the viewpoint of high-density recording, it is preferably 0.02 μm to 0.12 μm, and more preferably 0.03 μm to 0.1 μm. At least one magnetic layer is sufficient, and the magnetic layer may be separated into two or more layers having different magnetic properties, and the configuration regarding the known multi-layer magnetic layer can be applied. The thickness of the magnetic layer in the case of separating into two or more layers is the total thickness of these layers. The thickness of the non-magnetic layer is, for example, 0.1 to 1.5 μm, and preferably 0.1 to 1.0 μm. The thickness of the back coat layer is preferably 0.9 μm or less, and more preferably 0.1 to 0.7 μm. The various thicknesses such as the thickness of the magnetic layer can be obtained by the following method. After exposing the cross-section in the thickness direction of the magnetic tape with an ion beam, cross-section observation is performed on the exposed cross-section with a scanning electron microscope or a transmission electron microscope. The various thicknesses can be obtained as the arithmetic average of the thicknesses obtained at any two locations in the cross-section observation. Alternatively, the various thicknesses can also be obtained as the designed thickness calculated from the manufacturing conditions, etc.

[0088] <Manufacturing method> (Preparation of the composition for forming each layer) The process of preparing a composition for forming a magnetic layer, a non-magnetic layer, or a backcoat layer can usually include at least a kneading process, a dispersion process, and a mixing process provided as needed before and after these processes. Each individual process may be divided into two or more steps. The components used in the preparation of each layer-forming composition may be added at the beginning or during any of the processes. As the solvent, one or more of various solvents commonly used for manufacturing a coated magnetic recording medium can be used. For the solvent, reference can be made to, for example, paragraph 0153 of JP-A-2011-216149. Also, the individual components may be added in portions divided over two or more processes. For example, the binder may be added in portions divided over the kneading process, the dispersion process, and the mixing process for viscosity adjustment after dispersion. To manufacture the above magnetic tape, known manufacturing techniques can be used in various processes. In the kneading process, it is preferable to use one having a strong kneading force such as an open kneader, a continuous kneader, a pressure kneader, an extruder, etc. For details of the kneading treatment, reference can be made to JP-A-1-106338 and JP-A-1-79274. Known dispersers can be used. Filtration may be performed by a known method at any stage of preparing each layer-forming composition. Filtration can be performed, for example, by filter filtration. As the filter used for filtration, for example, a filter having a pore size of 0.01 to 3 μm (for example, a glass fiber filter, a polypropylene filter, etc.) can be used.

[0089] (Coating process) The magnetic layer can be formed by directly applying a composition for forming a magnetic layer, for example, onto a non-magnetic support, or by applying it in multiple layers sequentially or simultaneously with a composition for forming a non-magnetic layer. When performing an alignment treatment, the alignment treatment is performed on the coating layer in the alignment zone while the coating layer of the composition for forming a magnetic layer is in a wet state. For the alignment treatment, various known techniques can be applied, including the description in paragraph 0052 of JP-A-2010-24113. For example, the vertical alignment treatment can be performed by a known method such as a method using a magnet with opposite poles facing each other. In the alignment zone, the drying rate of the coating layer can be controlled by the temperature, air volume of the drying air, and / or the conveyance speed in the alignment zone. Also, the coating layer may be pre-dried before being conveyed to the alignment zone. The backcoat layer can be formed by applying a composition for forming a backcoat layer on the side of the non-magnetic support opposite to the side having (or to be provided with) the magnetic layer. For details of the coating for forming each layer, reference can be made to paragraph 0066 of JP-A-2010-231843.

[0090] (Other processes) After performing the above coating process, usually, a calendering process can be performed to enhance the surface smoothness of the magnetic tape. Regarding the calendering conditions, the calendering pressure is, for example, 200 to 500 kN / m, preferably 250 to 350 kN / m, the calendering temperature is, for example, 70 to 120 °C, preferably 80 to 100 °C, and the calendering speed is, for example, 50 to 300 m / min, preferably 80 to 200 m / min. Also, the surface of the magnetic layer tends to be smoothed as the roll with a harder surface is used as the calendering roll and as the number of stages increases. For various other processes for manufacturing a magnetic tape, reference can be made to paragraphs 0067 to 0070 of JP-A-2010-231843. By going through various processes, a long magnetic tape web can be obtained. The obtained magnetic tape web is cut (slit) by a known cutting machine to the width of the magnetic tape to be accommodated in, for example, a magnetic tape cartridge. The above width can be determined according to the standard and is usually 1 / 2 inch. 1 inch = 2.54 cm.

[0091] Burnishing process The burnish process is a process of rubbing the surface of an object to be processed with a member (for example, a polishing tape, or a grinding tool such as a grinding blade or a grinding wheel). The burnish process can preferably be carried out by rubbing (polishing) the surface of the coating layer to be processed with a polishing tape, or by rubbing (grinding) the surface of the coating layer to be processed with a grinding tool, or both. As the polishing tape, a commercially available product may be used, or a polishing tape produced by a known method may be used. As the grinding tool, known grinding blades such as fixed blades, diamond wheels, rotary blades, and grinding wheels can be used. Further, a wiping process of wiping the surface of the coating layer rubbed by the polishing tape and / or the grinding tool with a wiping material may be performed. For details of preferred polishing tapes, grinding tools, burnish processes, and wiping processes, reference can be made to paragraphs 0034 to 0048, FIG. 1, and the examples of Japanese Patent Laid-Open No. 6-52544. The roughness of the surface of the object to be processed can be controlled by the burnish process, and the surface of the object to be processed tends to become smoother as the burnish process conditions are strengthened. Examples of the burnish process conditions include the tension applied in the longitudinal direction of the magnetic tape during the burnish process (hereinafter referred to as the "burnish process tension"). The larger the value of the burnish process tension, the more likely the surface of the object to be processed is to become smooth. In order to control the Ra of the edge portion and the central portion of the magnetic layer surface respectively, and further to control the Ra ratio (central portion Ra / edge portion Ra) thereby, when performing the burnish process on the magnetic layer surface of the magnetic tape after slitting, it is preferable to perform the burnish process on the central region of the magnetic layer surface and the region near each edge (hereinafter referred to as the "edge-near region") under different process conditions. The central region refers to, for example, in a magnetic tape slit to a width of 1 / 2 inch, the region between the position 3 mm inside from one edge and the position 3 mm inside from the other edge in the width direction of the magnetic tape, and the region other than such a central region can be referred to as the edge-near region. The central region and the edge-near region described in the examples below are the above regions. For example, by making the value of the burnishing tension during burnishing treatment of the central region larger than the value of the burnishing tension during burnishing treatment of the region near the edge, the central region can be made smoother than the region near the edge, and as a result, the value of the edge Ra can be made larger than the value of the central part Ra. In either the burnishing treatment of the central region or the burnishing treatment of the region near the edge, the burnishing tension can be in the range of, for example, 50 gf or more and 250 gf or less, and the difference (burnishing tension in the central region - burnishing tension in the region near the edge) can be, for example, 3 gf or more and 30 gf or less. However, the above ranges are merely illustrative and do not limit the present invention. Regarding the unit, "gf" indicates gram weight, and 1 N (Newton) is approximately 102 gf.

[0092] Formation of servo pattern A servo pattern is usually formed on the magnetic tape obtained by slitting. The formation of the servo pattern can be performed, for example, after the above-mentioned burnishing treatment (or further after the wiping treatment). "Formation of the servo pattern" can also be referred to as "recording of the servo signal". The formation of the servo pattern will be described below.

[0093] The servo pattern is usually formed along the longitudinal direction of the magnetic tape. Examples of the method of control (servo control) using the servo signal include timing-based servo (TBS), amplitude servo, frequency servo, and the like.

[0094] As shown in ECMA (European Computer Manufacturers Association) - 319 (June 2001), in a magnetic tape compliant with the LTO (Linear Tape - Open) standard (commonly referred to as an "LTO tape"), a timing - based servo system is adopted. In this timing - based servo system, the servo pattern is constituted by arranging a plurality of pairs of magnetic stripes (also called "servo stripes") that are non - parallel to each other continuously in the longitudinal direction of the magnetic tape. In the present invention and this specification, the "timing - based servo pattern" refers to a servo pattern that enables head tracking in the servo system of the timing - based servo method. As described above, the reason why the servo pattern is constituted by a pair of non - parallel magnetic stripes is to inform the servo signal reading element passing over the servo pattern of its passing position. Specifically, the pair of magnetic stripes is formed such that the interval between them changes continuously along the width direction of the magnetic tape. By reading this interval by the servo signal reading element, the relative position between the servo pattern and the servo signal reading element can be known. This relative position information enables tracking of the data track. Therefore, usually, a plurality of servo tracks are set along the width direction of the magnetic tape on the servo pattern.

[0095] The servo band is constituted by a servo pattern continuous in the longitudinal direction of the magnetic tape. Usually, a plurality of such servo bands are provided on the magnetic tape. For example, in an LTO tape, the number is 5. The region sandwiched between two adjacent servo bands is the data band. The data band is composed of a plurality of data tracks, and each data track corresponds to each servo track.

[0096] Also, in one form, as shown in Japanese Patent Application Laid-Open No. 2004-318983, information indicating the number of each servo band (also called "servo band ID (identification)" or "UDIM (Unique DataBand Identification Method) information") is embedded in each servo band. This servo band ID is recorded by shifting a specific one of a plurality of pairs of servo stripes in the servo band so that its position is displaced relatively in the longitudinal direction of the magnetic tape. Specifically, the shifting method of a specific one of the plurality of pairs of servo stripes is changed for each servo band. As a result, the recorded servo band ID becomes unique for each servo band, so that by simply reading one servo band with a servo signal reading element, the servo band can be uniquely identified.

[0097] Note that there is also a method of uniquely identifying a servo band that uses a staggered method as shown in ECMA-319 (June 2001). In this staggered method, a group of a pair of magnetic stripes (servo stripes) that are arranged continuously in the longitudinal direction of the magnetic tape and are not parallel to each other is recorded so as to be shifted in the longitudinal direction of the magnetic tape for each servo band. Since the combination of the shifting methods between adjacent servo bands is unique throughout the magnetic tape, it is also possible to uniquely identify the servo band when reading the servo pattern with two servo signal reading elements.

[0098] Also, as shown in ECMA-319 (June 2001), information indicating the position in the longitudinal direction of the magnetic tape (also called "LPOS (Longitudinal Position) information") is usually embedded in each servo band. This LPOS information is also recorded by shifting the positions of a pair of servo stripes in the longitudinal direction of the magnetic tape. However, unlike the UDIM information, the same signal is recorded in each servo band for this LPOS information.

[0099] It is also possible to embed other information different from the above UDIM information and LPOS information in the servo band. In this case, the information to be embedded may be different for each servo band like the UDIM information, or may be common to all servo bands like the LPOS information. Also, as a method of embedding information in the servo band, it is possible to adopt a method other than the above. For example, a predetermined code may be recorded by thinning out a predetermined pair from a group of a pair of servo stripes.

[0100] The servo pattern forming head is called a servo write head. The servo write head usually has a pair of gaps corresponding to the above pair of magnetic stripes, the number of which is the same as the number of servo bands. Usually, a core and a coil are connected to each pair of gaps, and by supplying a current pulse to the coil, the magnetic field generated in the core can cause a leakage magnetic field in the pair of gaps. When forming the servo pattern, a magnetic pattern corresponding to the pair of gaps can be transferred to the magnetic tape by inputting a current pulse while running the magnetic tape on the servo write head, 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. The width of each gap can be set, for example, to 1 μm or less, 1 to 10 μm, 10 μm or more, etc.

[0101] Before forming a servo pattern on a magnetic tape, the magnetic tape is usually subjected to a demagnetization (erase) process. This erase process can be performed by applying a uniform magnetic field to the magnetic tape using a DC magnet or an AC magnet. There are DC (Direct Current) erase and AC (Alternating Current) erase for the erase process. The AC erase is performed by gradually decreasing the intensity of the magnetic field while reversing the direction of the magnetic field applied to the magnetic tape. On the other hand, the DC erase is performed by applying a magnetic field in one direction to the magnetic tape. There are further two methods for the DC erase. The first method is a horizontal DC erase that applies a magnetic field in one direction along the longitudinal direction of the magnetic tape. The second method is a vertical DC erase that applies a magnetic field in one direction along the thickness direction of the magnetic tape. The erase process may be performed on the entire magnetic tape or for each servo band of the magnetic tape.

[0102] The direction of the magnetic field of the formed servo pattern is determined according to the direction of the erase. For example, when a horizontal DC erase is applied to the magnetic tape, the servo pattern is formed such that the direction of the magnetic field is opposite to the direction of the erase. Thereby, the output of the servo signal obtained by reading the servo pattern can be increased. As shown in Japanese Patent Application Laid-Open No. 2012-53940, when a magnetic pattern is transferred using the above gap to a vertically DC-erased magnetic tape, the servo signal obtained by reading the formed servo pattern has a monopolar pulse shape. On the other hand, when a magnetic pattern is transferred using the above gap to a horizontally DC-erased magnetic tape, the servo signal obtained by reading the formed servo pattern has a bipolar pulse shape.

[0103] Heat treatment In one form, the magnetic tape can be a magnetic tape manufactured through heat treatment as follows. Also, in another form, it can be a magnetic tape manufactured without going through heat treatment as follows.

[0104] The heat treatment can be performed while the magnetic tape slit and cut to a width determined according to the standard is wound around the core member.

[0105] In one form, the above heat treatment is performed while the magnetic tape is wound around a core member for heat treatment (hereinafter referred to as "heat treatment winding core"), and after the heat treatment, the magnetic tape is wound around the cartridge reel of the magnetic tape cartridge, and a magnetic tape cartridge in which the magnetic tape is wound around the cartridge reel can be produced. The heat treatment winding core can be made of metal, resin, paper, etc. From the viewpoint of suppressing the occurrence of winding failures such as spoke winding, the material of the heat treatment winding core is preferably a material with high rigidity. From this point, the heat treatment winding core is preferably made of metal or resin. Also, as an index of rigidity, the flexural modulus of the material of the heat treatment winding core is preferably 0.2 GPa (gigapascal) or more, and more preferably 0.3 GPa or more. On the other hand, since high-rigidity materials are generally expensive, using a heat treatment winding core made of a material having a rigidity exceeding the rigidity that can suppress the occurrence of winding failures will lead to an increase in cost. Considering the above points, the flexural modulus of the material of the heat treatment winding core is preferably 250 GPa or less. The flexural modulus is a value measured according to ISO (International Organization for Standardization) 178, and the flexural moduli of various materials are known. Also, the heat treatment winding core can be a solid or hollow core member. In the case of a hollow shape, from the viewpoint of maintaining rigidity, the wall thickness is preferably 2 mm or more. Also, the heat treatment winding core may or may not have a flange. Prepare a magnetic tape that is longer than the length to be finally accommodated in a magnetic tape cartridge (hereinafter referred to as the "final product length") as a magnetic tape to be wound around a core for heat treatment, and it is preferable to perform heat treatment by placing this magnetic tape wound around the core for heat treatment in a heat treatment environment. The length of the magnetic tape wound around the core for heat treatment is equal to or greater than the final product length, and from the viewpoint of ease of winding around the core for heat treatment and the like, it is preferably set to "final product length + α". This α is preferably 5 m or more from the viewpoint of the above-mentioned ease of winding. The tension during winding around the core for heat treatment is preferably 0.1 N (Newton) or more. Also, from the viewpoint of suppressing excessive deformation during manufacturing, the tension during winding around the core for heat treatment is preferably 1.5 N or less, and more preferably 1.0 N or less. The outer diameter of the core for heat treatment is preferably 20 mm or more, and more preferably 40 mm or more, from the viewpoints of ease of winding and suppression of coiling (curl in the longitudinal direction). Also, the outer diameter of the core for heat treatment is preferably 100 mm or less, and more preferably 90 mm or less. The width of the core for heat treatment may be equal to or greater than the width of the magnetic tape wound around this core. Further, when removing the magnetic tape from the core for heat treatment after heat treatment, in order to suppress the occurrence of unintended tape deformation during the removal operation, it is preferable to remove the magnetic tape from the core for heat treatment after the magnetic tape and the core for heat treatment have been sufficiently cooled. The removed magnetic tape is preferably wound around another core (referred to as a "temporary winding core") once, and then the magnetic tape is wound from the temporary winding core onto the cartridge reel of the magnetic tape cartridge (generally having an outer diameter of about 40 to 50 mm). Thereby, the relationship between the inner side and the outer side of the magnetic tape with respect to the core for heat treatment during heat treatment can be maintained, and the magnetic tape can be wound onto the cartridge reel of the magnetic tape cartridge. For details of the temporary winding core and the tension when winding the magnetic tape around this core, reference can be made to the previous description regarding the core for heat treatment. In the form of performing the above heat treatment on a magnetic tape having a length of "final product length + α", the length of "+α" can be cut off at an arbitrary stage. For example, in one form, the magnetic tape of the final product length can be wound from the temporary winding core onto the reel of the magnetic tape cartridge, and the remaining length of "+α" can be cut off.From the perspective of reducing the portion to be cut off and discarded, it is preferable that the above α is 20 m or less.

[0106] The specific form of the heat treatment performed in the state of being wound around the core member as described above will be described below. The ambient temperature at which the heat treatment is performed (hereinafter referred to as "heat treatment temperature") is preferably 40°C or higher, more preferably 50°C or higher. On the other hand, from the perspective of suppressing excessive deformation, the heat treatment temperature is preferably 75°C or lower, more preferably 70°C or lower. The absolute humidity by weight of the atmosphere in which the heat treatment is performed is preferably 0.1 g / kg Dry air or higher, more preferably 1 g / kg Dry air or higher. An atmosphere with an absolute humidity by weight in the above range is preferable because it can be prepared without using a special device for reducing moisture. On the other hand, from the perspective of suppressing the occurrence of dew condensation and reducing workability, the absolute humidity by weight is preferably 70 g / kg Dry air or lower, more preferably 66 g / kg Dry air or lower. The heat treatment time is preferably 0.3 hours or more, more preferably 0.5 hours or more. Also, from the perspective of production efficiency, the heat treatment time is preferably 48 hours or less.

[0107] Regarding the standard deviation control of the bending amount described above, for the heat treatment temperature, heat treatment time, bending elastic modulus of the heat treatment core, and tension during winding around the heat treatment core, the larger the value of each, the more likely the value of the standard deviation of the bending amount can be made smaller.

[0108] <Vertical direction angular ratio> In one embodiment, the perpendicular squareness ratio of the magnetic tape can be, for example, 0.55 or more, preferably 0.60 or more. That the perpendicular squareness ratio of the magnetic tape is 0.60 or more is preferable from the viewpoint of improving electromagnetic conversion characteristics. The upper limit of the squareness ratio is, in principle, 1.00 or less. The perpendicular squareness 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 larger value of the perpendicular squareness ratio of the magnetic tape is preferable from the viewpoint of improving electromagnetic conversion characteristics. The perpendicular squareness ratio of the magnetic tape can be controlled by a known method such as performing perpendicular orientation treatment.

[0109] In the present invention and this specification, the "perpendicular squareness ratio" is the squareness ratio measured in the perpendicular direction of the magnetic tape. The "perpendicular direction" described with respect to the squareness ratio is 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 perpendicular squareness ratio is obtained by the following method. Cut out a sample piece of a size that can be introduced into a vibrating sample magnetometer from the magnetic tape to be measured. For this sample piece, using a vibrating sample magnetometer, a magnetic field is applied in the perpendicular direction (the direction perpendicular to the surface of the magnetic layer) of the sample piece at a maximum applied magnetic field of 3979 kA / m, a measurement temperature of 296 K, and a magnetic field sweep rate of 8.3 kA / m / second, and the magnetization intensity of the sample piece with respect to the applied magnetic field is measured. The measured value of the magnetization intensity is taken as the value after diamagnetic field 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 an applied magnetic field of zero is Mr, the squareness ratio SQ (Squareness Ratio) is a value calculated as SQ = Mr / Ms. The measurement temperature refers to the temperature of the sample piece, and the temperature of the sample piece can be made the measurement temperature by achieving temperature equilibrium by making the ambient temperature around the sample piece the measurement temperature.

[0110] [Magnetic Tape Cartridge] One aspect of the present invention relates to a magnetic tape cartridge including the above magnetic tape.

[0111] The details of the magnetic tape included in the magnetic tape cartridge are as described above.

[0112] In a magnetic tape cartridge, generally, the magnetic tape is accommodated in a state of being wound around a reel inside the cartridge body. The reel is rotatably provided inside the cartridge body. As the magnetic tape cartridge, a single-reel type magnetic tape cartridge having one reel inside the cartridge body and a double-reel type magnetic tape cartridge having two reels inside the cartridge body are widely used. When the single-reel type magnetic tape cartridge is attached to a magnetic tape device for recording and / or reproducing data on the magnetic tape, the magnetic tape is pulled out from the magnetic tape cartridge and wound around the reel on the magnetic tape device side. A magnetic head is disposed in the magnetic tape conveyance path from the magnetic tape cartridge to the take-up reel. Feeding and take-up of the magnetic tape are performed between the reel on the magnetic tape cartridge side (supply reel) and the reel on the magnetic tape device side (take-up reel). For example, during this period, recording and / or reproduction of data are performed by the magnetic head coming into contact with and sliding on the surface of the magnetic layer of the magnetic tape. On the other hand, in the double-reel type magnetic tape cartridge, both the supply reel and the take-up reel are provided inside the magnetic tape cartridge.

[0113] In one form, the magnetic tape cartridge can include a cartridge memory. The cartridge memory can be, for example, a non-volatile memory. In one form, head tilt angle adjustment information is already recorded or the head tilt angle adjustment information is to be recorded. The head tilt angle adjustment information is information for adjusting the head tilt angle during magnetic tape running in a magnetic tape device. For example, as the head tilt angle adjustment information, the values of the servo band intervals at each position in the longitudinal direction of the magnetic tape at the time of data recording can be recorded. For example, when reproducing data recorded on the magnetic tape, the value of the servo band interval is measured during reproduction, and the head tilt angle is changed by the control device of the magnetic tape device so that the absolute value of the difference from the servo band interval at the time of recording at the same longitudinal position recorded in the cartridge memory approaches 0. The head tilt angle can be, for example, the angle θ described above.

[0114] The above magnetic tape and magnetic tape cartridge can be suitably used in a magnetic tape device (in other words, a magnetic recording and reproducing system) that records and / or reproduces data at different head tilt angles. In such a magnetic tape device, in one form, the head tilt angle can be changed during magnetic tape running to record and / or reproduce data. For example, the head tilt angle can be changed according to the dimension information in the width direction of the magnetic tape acquired during magnetic tape running. Also, for example, there can be a usage form in which the head tilt angle in a certain recording and / or reproduction is changed from the head tilt angle in the subsequent recordings and / or reproductions, and the head tilt angle is fixed without being changed during the magnetic tape running for each recording and / or reproduction. In any usage form, a magnetic tape with high running stability when recording and / or reproducing data at different head tilt angles is preferable.

[0115] [Magnetic Tape Device] One aspect of the present invention relates to a magnetic tape device including the above magnetic tape. In the magnetic tape device, recording of data on the magnetic tape and / or reproduction of data recorded on the magnetic tape can be performed, for example, by bringing the surface of the magnetic layer of the magnetic tape into contact with and sliding it against the magnetic head. The magnetic tape device can detachably include, for example, a magnetic tape cartridge according to one aspect of the present invention.

[0116] The above magnetic tape cartridge can be attached to a magnetic tape device equipped with a magnetic head and used for recording and / or reproducing data. In the present invention and this specification, the "magnetic tape device" shall mean a device capable of performing at least one of recording data on a magnetic tape and reproducing data recorded on the magnetic tape. Such a device is generally called a drive.

[0117] <Magnetic head> The above magnetic tape device can include a magnetic head. The configuration of the magnetic head and the angle θ which is the head tilt angle are as described above with reference to FIGS. 1 to 3. When the magnetic head includes a reproducing element, as the reproducing element, a magnetoresistive (MR) element capable of sensitively reading information recorded on the magnetic tape is preferable. As the MR element, various known MR elements (for example, Giant Magnetoresistive (GMR) element, Tunnel Magnetoresistive (TMR) element, etc.) can be used. Hereinafter, a magnetic head that records and / or reproduces recorded data is also referred to as a "recording / reproducing head". An element for data recording (recording element) and an element for data reproduction (reproducing element) are collectively referred to as "magnetic head elements".

[0118] By performing data reproduction using a reproduction element with a narrow reproduction element width as the reproduction element, it is possible to reproduce highly densely recorded data with high sensitivity. From this perspective, the reproduction element width of the reproduction element is preferably 0.8 μm or less. The reproduction element width of the reproduction element can be, for example, 0.3 μm or more. However, it is also preferable from the above perspective to be below this value. Here, the "reproduction element width" refers to the physical dimension of the reproduction element width. Such a physical dimension can be measured by an optical microscope, a scanning electron microscope, or the like.

[0119] When recording data and / or reproducing the recorded data, first, tracking using a servo signal can be performed. That is, by causing the servo signal reading element to follow a predetermined servo track, the magnetic head element can be controlled to pass over the target data track. The movement of the data track is performed by changing the servo track read by the servo signal reading element in the tape width direction. In addition, the recording and reproducing head can also perform recording and / or reproduction for other data bands. In that case, the servo signal reading element can be moved to a predetermined servo band using the UDIM information described above, and tracking for that servo band can be started.

[0120] Fig. 5 shows an example of the arrangement of data bands and servo bands. In Fig. 5, on the magnetic layer of the magnetic tape MT, a plurality of servo bands 1 are arranged sandwiched between guide bands 3. A plurality of regions 2 sandwiched between two servo bands are data bands. The servo pattern is a magnetized region, which is formed by magnetizing a specific region of the magnetic layer with a servo write head. The region magnetized by the servo write head (the position where the servo pattern is formed) is defined by standards. For example, in the LTO Ultrium format tape, which is an industry standard, a plurality of servo patterns inclined with respect to the tape width direction as shown in Fig. 6 are formed on the servo bands during the manufacture of the magnetic tape. Specifically, in Fig. 6, the servo frame SF on the servo band 1 is composed of a servo sub-frame 1 (SSF1) and a servo sub-frame 2 (SSF2). The servo sub-frame 1 is composed of an A burst (reference sign A in Fig. 6) and a B burst (reference sign B in Fig. 6). The A burst is composed of servo patterns A1 to A5, and the B burst is composed of servo patterns B1 to B5. On the other hand, the servo sub-frame 2 is composed of a C burst (reference sign C in Fig. 6) and a D burst (reference sign D in Fig. 6). The C burst is composed of servo patterns C1 to C4, and the D burst is composed of servo patterns D1 to D4. Such 18 servo patterns are arranged in sets of 5 and 4, and are arranged in a 5, 5, 4, 4 sequence in the sub-frame, and are used to identify the servo frame. Fig. 6 shows one servo frame for the sake of explanation. However, actually, on the magnetic layer of the magnetic tape where head tracking of the timing-based servo method is performed, a plurality of servo frames are arranged in the running direction on each servo band. In Fig. 6, the arrow indicates the running direction of the magnetic tape. For example, an LTO Ultrium format tape usually has 5000 or more servo frames per meter of tape length on each servo band of the magnetic layer.

[0121] In the above magnetic tape device, the head tilt angle can be changed during the running of the magnetic tape within the magnetic tape device. The head tilt angle is, for example, the angle θ formed by the axis of the element array with respect to the width direction of the magnetic tape. The angle θ is as described above. For example, by providing an angle adjustment unit for adjusting the angle of the module of the magnetic head in the recording and reproducing head unit of the magnetic head, the angle θ can be variably adjusted during the running of the magnetic tape. Such an angle adjustment unit can include, for example, a rotation mechanism for rotating the module. Known techniques can be applied to the angle adjustment unit.

[0122] Regarding the head tilt angle during the running of the magnetic tape, when the magnetic head includes a plurality of modules, for a randomly selected module, the angle θ described with reference to FIGS. 1 to 3 can be defined. θ which is the angle θ at the start of the running of the magnetic tape initial can be set to 0° or more or more than 0°. θ initial The larger θ is, the larger the change amount of the effective distance between the servo signal reading elements with respect to the change amount of the angle θ becomes. Therefore, it is preferable from the viewpoint of the adjustment ability to adjust the effective distance between the servo signal reading elements in correspondence with the dimensional change in the width direction of the magnetic tape. From this point, θ initial is preferably 1° or more, more preferably 5° or more, and still more preferably 10° or more. On the other hand, regarding the angle formed by the contact surface between the magnetic layer surface and the magnetic head when the magnetic tape runs and contacts the magnetic head (generally referred to as the "wrap angle"), keeping the deviation in the tape width direction small is effective in enhancing the uniformity in the tape width direction of the friction generated when the magnetic head and the magnetic tape contact during the running of the magnetic tape. Also, enhancing the uniformity of the above friction in the tape width direction is desirable from the viewpoints of the position followability and running stability of the magnetic head. From the viewpoint of reducing the deviation in the tape width direction of the above wrap angle, θ initial is preferably 45° or less, more preferably 40° or less, and still more preferably 35° or less.

[0123] Regarding the change in the angle θ during the running of the magnetic tape, for recording data on the magnetic tape and / or for reproducing the data recorded on the magnetic tape, while the magnetic tape is running in the magnetic tape device, the angle θ of the magnetic head changes from θ at the start of running initial If it changes, the maximum change amount Δθ of the angle θ during the running of the magnetic tape is the Δθ calculated by the following formula max and Δθ min and is the larger value. The maximum value of the angle θ during the running of the magnetic tape is θ max and the minimum value is θ min Here, "max" is an abbreviation of maximum, and "min" is an abbreviation of minimum. Δθ max = θ max - θ initial Δθ min = θ initial - θ min

[0124] In one form, Δθ can be more than 0.000°, and from the viewpoint of the adjustment ability to adjust the effective distance between the servo signal reading elements corresponding to the dimensional change in the width direction of the magnetic tape, it is preferably 0.001° or more, and more preferably 0.010° or more. Also, from the viewpoint of the ease of ensuring synchronization of the recorded data and / or the reproduced data among a plurality of magnetic head elements during data recording and / or reproduction, Δθ is preferably 1.000° or less, more preferably 0.900° or less, still more preferably 0.800° or less, even more preferably 0.700° or less, and even more preferably 0.600° or less.

[0125] In the examples shown in FIGS. 2 and 3, the axis of the element array is inclined toward the running direction of the magnetic tape. However, the present invention is not limited to such examples. In the above magnetic tape device, an embodiment in which the axis of the element array is inclined in the direction opposite to the running direction of the magnetic tape is also included in the present invention.

[0126] θ which is the head tilt angle at the start of running of the magnetic tape initialIt can be set by a control device of a magnetic tape device or the like. Regarding the head tilt angle during magnetic tape running, FIG. 7 is an explanatory diagram of a method for measuring the angle θ during magnetic tape running. The angle θ during magnetic tape running can be obtained, for example, by the following method. When obtaining the angle θ during magnetic tape running by the following method, during magnetic tape running, the angle θ is changed in the range of 0 to 90°. That is, if the axis of the element array is inclined toward the magnetic tape running direction at the start of magnetic tape running, the element array is not tilted so that the axis of the element array is inclined in the direction opposite to the magnetic tape running direction at the start of magnetic tape running during magnetic tape running. If the axis of the element array is inclined in the direction opposite to the magnetic tape running direction at the start of magnetic tape running, it is assumed that the element array is not tilted so that the axis of the element array is inclined toward the magnetic tape running direction at the start of magnetic tape running during magnetic tape running. Measure the phase difference (i.e., time difference) ΔT between the reproduction signals of the pair of servo signal reading elements 1 and 2. The measurement of ΔT can be performed by a measurement unit provided in the magnetic tape device. The configuration of such a measurement unit is known. The distance L between the central part of the servo signal reading element 1 and the central part of the servo signal reading element 2 can be measured by an optical microscope or the like. When the running speed of the magnetic tape is v, the distance in the magnetic tape running direction between the central parts of the two servo signal reading elements is Lsinθ, and the relationship Lsinθ = v×ΔT holds. Therefore, the angle θ during magnetic tape running can be calculated by the formula "θ = arcsin(vΔT / L)". In the right diagram of FIG. 7, an example in which the axis of the element array is inclined toward the magnetic tape running direction is shown. In this example, the phase difference (i.e., time difference) ΔT between the reproduction signal of the servo signal reading element 2 and the reproduction signal of the servo signal reading element 1 is measured. When the axis of the element array is inclined in the direction opposite to the running direction of the magnetic tape, θ can be obtained by the above method except that ΔT is measured as the phase difference (i.e., time difference) between the reproduction signal of the servo signal reading element 1 and the reproduction signal of the servo signal reading element 2. Note that the measurement pitch of the angle θ, that is, the measurement interval of the angle θ with respect to the longitudinal direction of the tape, can be selected to be a pitch suitable according to the frequency of the tape width deformation with respect to the longitudinal direction of the tape. As an example, the measurement pitch can be, for example, 250 μm.

[0127] <Configuration of Magnetic Tape Device> The magnetic tape device 10 shown in FIG. 8 controls the recording and reproducing head unit 12 according to commands from the control device 11, and records and reproduces data on the magnetic tape MT. The magnetic tape device 10 has a configuration capable of detecting and adjusting the tension applied in the longitudinal direction of the magnetic tape from the spindle motors 17A and 17B that rotationally control the magnetic tape cartridge reel and the take-up reel, and their driving devices 18A and 18B. The magnetic tape device 10 has a configuration capable of loading the magnetic tape cartridge 13. The magnetic tape device 10 has a cartridge memory read / write device 14 capable of reading and writing the cartridge memory 131 in the magnetic tape cartridge 13. From the magnetic tape cartridge 13 mounted on the magnetic tape device 10, the end portion or the leader pin of the magnetic tape MT is automatically or manually pulled out, passes over the recording and reproducing head through the guide rollers 15A and 15B in a direction in which the magnetic layer surface of the magnetic tape MT is in contact with the recording and reproducing head surface of the recording and reproducing head unit 12, and the magnetic tape MT is wound around the take-up reel 16. The rotation and torque of the spindle motor 17A and the spindle motor 17B are controlled by signals from the control device 11, and the magnetic tape MT runs at an arbitrary speed and tension. For the control of the tape speed and the control of the head tilt angle, a servo pattern pre-formed on the magnetic tape can be used. For the detection of the tension, a tension detection mechanism may be provided between the magnetic tape cartridge 13 and the take-up reel 16. The control of the tension may be performed using the guide rollers 15A and 15B in addition to the control by the spindle motors 17A and 17B. The cartridge memory read / write device 14 is configured to be able to read and write information of the cartridge memory 131 according to an instruction from the control device 11. As a communication method between the cartridge memory read / write device 14 and the cartridge memory 131, for example, the ISO (International Organization for Standardization) 14443 method can be adopted.

[0128] The control device 11 includes, for example, a control unit, a storage unit, a communication unit, and the like.

[0129] The recording / reproducing head unit 12 is composed of, for example, a recording / reproducing head, a servo tracking actuator for adjusting the position of the recording / reproducing head in the track width direction, a recording / reproducing amplifier 19, a connector cable for connecting to the control device 11, and the like. The recording / reproducing head is composed of, for example, a recording element for recording data on a magnetic tape, a reproducing element for reproducing data on the magnetic tape, and a servo signal reading element for reading a servo signal recorded on the magnetic tape. In one magnetic head, one or more recording elements, reproducing elements, and servo signal reading elements are mounted, respectively. Alternatively, each element may be separately provided in a plurality of magnetic heads according to the running direction of the magnetic tape.

[0130] The recording / reproducing head unit 12 is configured to be able to record data on the magnetic tape MT according to an instruction from the control device 11. Also, it is configured to be able to reproduce data recorded on the magnetic tape MT according to an instruction from the control device 11.

[0131] The control device 11 determines the running position of the magnetic tape from the servo signal read from the servo band during the running of the magnetic tape MT, and has a mechanism for controlling the servo tracking actuator so that the recording element and / or the reproducing element is positioned at the target running position (track position). The control of this track position is performed, for example, by feedback control. The control device 11 has a mechanism for obtaining the servo band interval from the servo signals read from two adjacent servo bands during the running of the magnetic tape MT. The control device 11 can store the obtained servo band interval information in the storage unit inside the control device 11, the cartridge memory 131, an external connected device, etc. Further, the control device 11 can change the head tilt angle according to the dimension information in the width direction of the magnetic tape during running. Thereby, the effective distance between the servo signal reading elements can be made close to or equal to the interval of the servo bands. The above dimension information can be obtained using a servo pattern previously formed on the magnetic tape. For example, in this way, during the running of the magnetic tape in the magnetic tape device, the angle θ formed by the axis of the element array with respect to the width direction of the magnetic tape can be changed according to the dimension information in the width direction of the magnetic tape obtained during running. The adjustment of the head tilt angle can be performed, for example, by feedback control. Further, for example, the adjustment of the head tilt angle can also be performed by the method described in Japanese Patent Application Laid-Open No. 2016-524774 (Patent Document 1) or US2019 / 0164573A1 (Patent Document 2).

Example

[0132] Hereinafter, the present invention will be described based on examples. However, the present invention is not limited to the embodiments shown in the examples. The “parts” and “%” described below indicate “parts by mass” and “mass%”, respectively. Further, the steps and evaluations described below were performed in an environment at a temperature of 23°C ± 1°C unless otherwise specified. The “eq” described below is an equivalent, which is a unit that cannot be converted into SI units. [Ferromagnetic powder] In Table 1, "BaFe" is hexagonal barium ferrite powder (coercive force Hc: 196 kA / m, average particle size (average plate diameter) 24 nm).

[0133] In Table 1, "SrFe1" is hexagonal strontium ferrite powder prepared by the following method. Weighed 1707 g of SrCO3, 687 g of H3BO3, 1120 g of Fe2O3, 45 g of Al(OH)3, 24 g of BaCO3, 13 g of CaCO3, and 235 g of Nd2O3, and mixed them in a mixer to obtain a raw material mixture. The obtained raw material mixture was melted in a platinum crucible at a melting temperature of 1390 °C. While stirring the melt, the outlet provided at the bottom of the platinum crucible was heated, and the melt was discharged in a rod shape at about 6 g / sec. The discharged liquid was rolled and rapidly cooled by a water-cooled double roller to produce an amorphous body. Charged 280 g of the prepared amorphous body into an electric furnace, heated it to 635 °C (crystallization temperature) at a heating rate of 3.5 °C / min, and held it at the same temperature for 5 hours to precipitate (crystallize) hexagonal strontium ferrite particles. Next, the crystallized product obtained above containing hexagonal strontium ferrite particles was roughly pulverized in a mortar. 1000 g of zirconia beads with a particle size of 1 mm and 800 ml of 1% acetic acid aqueous solution were added to a glass bottle, and dispersion treatment was carried out in a paint shaker for 3 hours. Then, the obtained dispersion was separated from the beads and put into a stainless steel beaker. The dispersion was allowed to stand at a liquid temperature of 100 °C for 3 hours for dissolution treatment of the glass component, then precipitated by a centrifuge and washed by repeating decantation, and dried in a heating furnace with a furnace temperature of 110 °C for 6 hours to obtain hexagonal strontium ferrite powder. The average particle size of the hexagonal strontium ferrite powder obtained above is 18 nm, the activation volume is 902 nm 3 , the anisotropy constant Ku is 2.2×10 5 J / m 3 , the mass magnetization σs is 49 A·m 2 / kg. 12 mg of sample powder was collected from the hexagonal strontium ferrite powder obtained above, and elemental analysis of the filtrate obtained by partially dissolving this sample powder under the dissolution conditions exemplified above was performed using an ICP analyzer to determine the surface layer content ratio of neodymium atoms. Separately, 12 mg of sample powder was collected from the hexagonal strontium ferrite powder obtained above, and elemental analysis of the filtrate obtained by completely dissolving this sample powder under the dissolution conditions exemplified above was performed using an ICP analyzer to determine the bulk content ratio of neodymium atoms. The content ratio (bulk content ratio) of neodymium atoms to 100 atomic % of iron atoms in the hexagonal strontium ferrite powder obtained above was 2.9 atomic %. Also, the surface layer content ratio of neodymium atoms was 8.0 atomic %. The ratio of the surface layer content ratio to the bulk content ratio, "surface layer content ratio / bulk content ratio", was 2.8, and it was confirmed that neodymium atoms were unevenly distributed on the surface of the particles. That the powder obtained above exhibits the crystal structure of hexagonal ferrite was confirmed by scanning with CuKα rays under the conditions of a voltage of 45 kV and an intensity of 40 mA and measuring the X-ray diffraction pattern under the following conditions (X-ray diffraction analysis). The powder obtained above exhibited the crystal structure of magnetoplumbite-type (M-type) hexagonal ferrite. Also, the crystal phase detected by X-ray diffraction analysis was a single phase of the magnetoplumbite type. PANalytical X’Pert Pro diffractometer, PIXcel detector Soller slits for incident beam and diffracted beam: 0.017 radians Fixed angle of dispersion slit: 1 / 4 degree Mask: 10 mm Anti-scattering slit: 1 / 4 degree Measurement mode: continuous Measurement time per step: 3 seconds Measurement speed: 0.017 degrees per second Measurement step: 0.05 degrees

[0134] In Table 1, "SrFe2" is hexagonal strontium ferrite powder produced by the following method. Weighed 1725 g of SrCO3, 666 g of H3BO3, 1332 g of Fe2O3, 52 g of Al(OH)3, 34 g of CaCO3, and 141 g of BaCO3, and mixed them in a mixer to obtain a raw material mixture. The obtained raw material mixture was melted in a platinum crucible at a melting temperature of 1380 °C. While stirring the melt, the outlet provided at the bottom of the platinum crucible was heated, and the melt was discharged in a rod shape at about 6 g / second. The discharged liquid was rapidly cooled by rolling with a water-cooled double roll to produce an amorphous body. Charged 280 g of the obtained amorphous body into an electric furnace, heated it to 645 °C (crystallization temperature), and held it at the same temperature for 5 hours to precipitate (crystallize) hexagonal strontium ferrite particles. Next, the crystallized product obtained above containing hexagonal strontium ferrite particles was roughly pulverized in a mortar. 1000 g of zirconia beads with a particle size of 1 mm and 800 ml of an acetic acid aqueous solution with a concentration of 1% were added to a glass bottle, and dispersion treatment was carried out with a paint shaker for 3 hours. Then, the obtained dispersion was separated from the beads and put into a stainless steel beaker. The dispersion was allowed to stand at a liquid temperature of 100 °C for 3 hours for dissolution treatment of the glass component, then precipitated with a centrifuge, and decantation was repeated for washing, and dried in a heating furnace with a furnace temperature of 110 °C for 6 hours to obtain hexagonal strontium ferrite powder. The average particle size of the obtained hexagonal strontium ferrite powder was 19 nm, and the activation volume was 1102 nm 3 The anisotropy constant Ku was 2.0×10 5 J / m 3 The mass magnetization σs was 50 A·m 2 / kg.

[0135] In Table 1, "ε-iron oxide" is ε-iron oxide powder produced by the following method. Dissolve 8.3 g of iron(III) nitrate nonahydrate, 1.3 g of gallium(III) nitrate octahydrate, 190 mg of cobalt(II) nitrate hexahydrate, 150 mg of titanium(IV) sulfate, and 1.5 g of polyvinylpyrrolidone (PVP) in 90 g of pure water. While stirring using a magnetic stirrer, add 4.0 g of an aqueous ammonia solution with a concentration of 25% under an air atmosphere and at an ambient temperature of 25 °C, and stir for 2 hours while maintaining the temperature condition of 25 °C. To the resulting solution, add a citric acid solution obtained by dissolving 1 g of citric acid in 9 g of pure water, and stir for 1 hour. Collect the precipitated powder by centrifugation after stirring, wash it with pure water, and dry it in a heating furnace with an internal temperature of 80 °C. Add 800 g of pure water to the dried powder and disperse the powder in water again to obtain a dispersion. Raise the temperature of the obtained dispersion to 50 °C, and while stirring, dropwise add 40 g of an aqueous ammonia solution with a concentration of 25%. After stirring for 1 hour while maintaining the temperature of 50 °C, dropwise add 14 mL of tetraethoxysilane (TEOS), and stir for 24 hours. Add 50 g of ammonium sulfate to the obtained reaction solution, collect the precipitated powder by centrifugation, wash it with pure water, and dry it in a heating furnace with an internal temperature of 80 °C for 24 hours to obtain a precursor of ferromagnetic powder. Load the obtained precursor of ferromagnetic powder into a heating furnace with an internal temperature of 1000 °C under an air atmosphere, and perform a heat treatment for 4 hours. Put the heat-treated precursor of ferromagnetic powder into an aqueous solution of sodium hydroxide (NaOH) with a concentration of 4 mol / L, maintain the liquid temperature at 70 °C, and stir for 24 hours to remove the silicate compound, which is an impurity, from the heat-treated precursor of ferromagnetic powder. After that, collect the ferromagnetic powder from which the silicate compound has been removed by centrifugation, wash it with pure water, and obtain ferromagnetic powder. When the composition of the obtained ferromagnetic powder was confirmed by high-frequency inductively coupled plasma optical emission spectrometry (ICP-OES: Inductively Coupled Plasma-Optical Emission Spectrometry), it was found that ε-iron oxide substituted with Ga, Co, and Ti (ε-Ga 0.28 Co 0.05 Ti 0.05 Fe 1.62It was O3). Also, X-ray diffraction analysis was performed under the same conditions as those described above for SrFe1, and from the peaks of the X-ray diffraction pattern, it was confirmed that the obtained ferromagnetic powder had a single-phase crystal structure of the ε-phase (crystal structure of ε-iron oxide) that did not contain the crystal structures of the α-phase and γ-phase. The average particle size of the obtained ε-iron oxide powder was 12 nm, and the activation volume was 746 nm 3 , and the anisotropy constant Ku was 1.2×10 5 J / m 3 , and the mass magnetization σs was 16 A·m 2 / kg.

[0136] The activation volume and anisotropy constant Ku of the above hexagonal strontium ferrite powder and ε-iron oxide powder are values obtained by the method described above using a vibrating sample magnetometer (manufactured by Toei Industry Co., Ltd.) for each ferromagnetic powder. Also, the mass magnetization σs is a value measured at a magnetic field strength of 15 kOe using a vibrating sample magnetometer (manufactured by Toei Industry Co., Ltd.).

[0137] [Example 1] [Preparation of Alumina Dispersion] To 100.0 parts of alumina powder (HIT-80 manufactured by Sumitomo Chemical Co., Ltd.) with an α-alumina conversion rate of about 65% and a BET (Brunauer-Emmett-Teller) specific surface area of 20 m 2 / g, 3.0 parts of 2,3-dihydroxynaphthalene (manufactured by Tokyo Chemical Industry Co., Ltd.), 31.3 parts of a 32% solution of a polyester polyurethane resin (UR-4800 manufactured by Toyobo Co., Ltd. (polar group amount: 80 meq / kg)) having a SO3Na group as a polar group (the solvent is a mixed solvent of methyl ethyl ketone and toluene), and 570.0 parts of a mixed solution of methyl ethyl ketone and cyclohexanone 1:1 (mass ratio) as a solvent were mixed, and dispersed for 5 hours by a paint shaker in the presence of zirconia beads. After dispersion, the dispersion liquid and the beads were separated by a mesh to obtain an alumina dispersion.

[0138] [Composition for Forming Magnetic Layer] (Magnetic Liquid) Ferromagnetic powder (see Table 1): 100.0 parts SO3Na group-containing polyurethane resin: 14.0 parts Weight average molecular weight: 70,000, SO3Na group: 0.2 meq / g Cyclohexanone: 150.0 parts Methyl ethyl ketone: 150.0 parts (Abrasive liquid) The alumina dispersion prepared above: 6.0 parts (Silica sol (protrusion-forming agent liquid)) Colloidal silica (average particle size 120 nm): 2.0 parts Methyl ethyl ketone: 1.4 parts (Other components) Stearic acid: 2.0 parts Stearamide: 0.2 parts Butyl stearate: 2.0 parts Polyisocyanate (Coronate (registered trademark) L manufactured by Tosoh Corporation): 2.5 parts (Finishing additive solvent) Cyclohexanone: 200.0 parts Methyl ethyl ketone: 200.0 parts

[0139] <Composition for forming non-magnetic layer> α-Ferric oxide powder (average particle volume: see Table 1): 80.0 parts Carbon black (average particle size: 20 nm, pH: see Table 1): 20.0 parts Electron beam curable vinyl chloride copolymer: 13.0 parts Electron beam curable polyurethane resin: 6.0 parts Phenylphosphonic acid: 3.0 parts Cyclohexanone: 140.0 parts Methyl ethyl ketone: 170.0 parts Butyl stearate: 2.0 parts Stearic acid: 1.0 part

[0140] <Composition for forming backcoat layer> Non-magnetic inorganic powder (α-ferric oxide powder): 80.0 parts (Average particle size: 0.15 μm, average acicular ratio: 7, BET specific surface area: 52 m 2 / g) Carbon black (average particle size: 20 nm): 20.0 parts Carbon black (average particle size: 100 nm): 3.0 parts Vinyl chloride copolymer: 13.0 parts Sulfonic acid group-containing polyurethane resin: 6.0 parts Phenylphosphonic acid: 3.0 parts Cyclohexanone: 140.0 parts Methyl ethyl ketone: 170.0 parts Stearic acid: 3.0 parts Polyisocyanate (Coronate (registered trademark) L manufactured by Tosoh Corporation): 5.0 parts Methyl ethyl ketone: 400.0 parts

[0141] <Preparation of the composition for forming each layer> The composition for forming the magnetic layer was prepared by the following method. The above magnetic liquid was prepared by dispersing (bead dispersion) the above components using a batch vertical sand mill for 24 hours. As the dispersion beads, zirconia beads with a bead diameter of 0.5 mm were used. Using the above sand mill, the prepared magnetic liquid, the above abrasive liquid, and other components (silica sol, other components, and finishing additive solvent) were mixed and bead-dispersed for 5 minutes, and then treated (ultrasonic dispersion) with a batch ultrasonic device (20 kHz, 300 W) for 0.5 minutes. Thereafter, filtration was performed using a filter having a pore diameter of 0.5 μm to prepare the composition for forming the magnetic layer.

[0142] The composition for forming the non-magnetic layer was prepared by the following method. The above components excluding the lubricants (butyl stearate and stearic acid) were kneaded and diluted using an open kneader, and then dispersion treatment was performed using a horizontal bead mill disperser. Thereafter, lubricants (butyl stearate and stearic acid) were added, and stirring and mixing treatment were performed using a dissolver stirrer to prepare the composition for forming the non-magnetic layer.

[0143] The composition for forming the backcoat layer was prepared by the following method. The above components except lubricant (stearic acid), polyisocyanate and methyl ethyl ketone (400.0 parts) were kneaded and diluted by an open kneader, and then dispersed by a horizontal bead mill disperser. Thereafter, lubricant (stearic acid), polyisocyanate and methyl ethyl ketone (400.0 parts) were added and stirred with a dissolver stirrer for mixing to prepare a composition for forming a back coat layer.

[0144] <Manufacture of Magnetic Tape and Magnetic Tape Cartridge> On a biaxially stretched polyethylene naphthalate support with a thickness of 4.1 μm, a composition for forming a non-magnetic layer was applied and dried so that the thickness after drying became 0.7 μm, and then irradiated with an electron beam at an acceleration voltage of 125 kV to have an energy of 40 kGy. A composition for forming a magnetic layer was applied and dried thereon so that the thickness after drying became 0.1 μm, and further, a composition for forming a back coat layer was applied to the surface opposite to the surface on which the non-magnetic layer and the magnetic layer of the support were formed so that the thickness after drying became 0.3 μm and dried. Subsequently, calendering was performed at a calender speed of 80 m / min, a linear pressure of 294 kN / m, and a calender temperature (surface temperature of the calender roll) of 80°C using a seven-stage calender roll composed only of metal rolls. Thereafter, heat treatment was performed for 36 hours in an environment with an ambient temperature of 70°C. After the heat treatment, it was slit into a 1 / 2-inch width. Then, burnishing treatment and wiping treatment were performed on the surface of the magnetic layer of the 1 / 2-inch-wide magnetic tape thus obtained. The burnishing treatment and wiping treatment were carried out using a commercially available polishing tape (product name MA22000 manufactured by Fuji Film Co., abrasives: diamond / Cr2O3 / α-iron oxide) as the polishing tape, a commercially available sapphire blade (manufactured by Kyocera Corporation, width 5 mm, length 35 mm, tip angle 60 degrees) as the grinding blade, and a commercially available wiping material (product name WRP736 manufactured by Kuraray Co., Ltd.) as the wiping material in a processing apparatus having the configuration described in FIG. 1 of JP-A-6-52544. The processing conditions were the same as those in Example 12 of JP-A-6-52544 except that the burnishing treatment tension during the burnishing treatment of the central region and the region near the edge of the magnetic layer surface was set to the values shown in Table 1. Thereafter, a servo signal is recorded on the magnetic layer of the obtained magnetic tape by a commercially available servo writer, thereby obtaining a magnetic tape having a data band, a servo band, and a guide band in an arrangement conforming to the LTO (Linear Tape-Open) Ultrium format, and having a servo pattern (timing-based servo pattern) in an arrangement and shape conforming to the LTO Ultrium format on the servo band. The servo pattern thus formed is a servo pattern conforming to the descriptions of JIS (Japanese Industrial Standards) X6175:2006 and Standard ECMA-319 (June 2001). The total number of servo bands is 5, and the total number of data bands is 4. The magnetic tape (length 960 m) on which the servo signal has been recorded in this way is wound around the reel of a magnetic tape cartridge (LTO Ultrium8 data cartridge), and at its end, a leader tape conforming to item 9 of Section 3 of Standard ECMA (European Computer Manufacturers Association)-319 (June 2001) is joined by a commercially available splicing tape. Thus, a magnetic tape cartridge with the magnetic tape wound around the reel was produced.

[0145] [Examples 2 to 24, Comparative Examples 1 to 10] Magnetic tapes and magnetic tape cartridges were obtained by the method described for Example 1, except for the points where the items shown in Table 1 were changed as shown in Table 1. For Examples 18 to 24, the process after servo signal recording was changed as follows. That is, heat treatment was performed after servo signal recording. In contrast, for Examples 1 to 17 and Comparative Examples 1 to 10, since such heat treatment was not carried out, "none" was described in the column of "heat treatment conditions" in Table 1. For Examples 18 to 24, after recording the servo signal as described in Example 1, the magnetic tape (length 970 m) was wound around a core for heat treatment, and heat treatment was performed in a state of being wound around this core. As the core for heat treatment, a solid core member made of resin with a flexural modulus of the value shown in Table 1 (outer diameter: 50 mm) was used, and the tension during winding was set to the value shown in Table 1. The heat treatment temperature and heat treatment time in the heat treatment were set to the values shown in Table 1. The absolute humidity by weight of the atmosphere in which the heat treatment was performed was 10 g / kg Dry air. After the above heat treatment, after the magnetic tape and the core for heat treatment were sufficiently cooled, the magnetic tape was removed from the core for heat treatment and wound around a core for temporary winding. As the core for temporary winding, a solid core member made of the same material as the core for heat treatment and having the same outer diameter was used, and the tension during winding was set to 0.6 N. Thereafter, a magnetic tape of the final product length (960 m) was wound from the core for temporary winding onto the reel of a magnetic tape cartridge (LTO Ultrium8 data cartridge), and the remaining 10 m was cut off. At the end on the cut-off side, a leader tape conforming to item 9 of Standard ECMA (European Computer Manufacturers Association)-319 (June 2001) Section 3 was joined by a commercially available splicing tape. In this way, a magnetic tape cartridge with the magnetic tape wound around the reel was produced.

[0146] For the above Examples and Comparative Examples, four magnetic tape cartridges were produced respectively. One was used for the evaluation of the following running stability, and the other three were used for the evaluations (1) to (3) of the following magnetic tape respectively.

[0147] [Evaluation of running stability] In an environment with a temperature of 40°C and a relative humidity of 10%, the running stability was evaluated by the following method. Note that the above temperature and humidity are examples of the temperature and humidity in a high-temperature and low-humidity environment. Also, the following head tilt angles were adopted as exemplary values of the angles that can be adopted when recording and / or reproducing data at different head tilt angles. Therefore, the temperature and humidity of the environment and the head tilt angle when recording data on the magnetic tape and reproducing the recorded data according to one aspect of the present invention are not limited to the above values and the following values. Using each magnetic tape cartridge of the examples and comparative examples, data recording and reproduction were performed using a magnetic tape device having the configuration shown in FIG. 8. The arrangement order of the modules included in the recording and reproduction head mounted on the recording and reproduction head unit is "recording module - reproduction module - recording module" (total number of modules: 3). The number of magnetic head elements in each module is 32 (Ch0 to Ch31), and these magnetic head elements are sandwiched between a pair of servo signal reading elements to form an element array. The reproduction element width of the reproduction elements included in the reproduction module is 0.8 μm. By the following method, data recording and reproduction were performed, and the running stability during reproduction was evaluated. The head tilt angle was sequentially changed in the order of 0°, 15°, 30°, and 45° for a total of 4 times. The above head tilt angle is the angle θ formed by the axis of the element array of the reproduction module with respect to the width direction of the magnetic tape at the start of each run. The angle θ was set by the control device of the magnetic tape device at the start of each magnetic tape run, and the head tilt angle was fixed during each magnetic tape run. Set a magnetic tape cartridge in the magnetic tape device and load the magnetic tape. Next, while performing servo tracking, the recording and reproduction head unit records pseudo-random data having a specific data pattern on the magnetic tape. The tension in the longitudinal direction of the tape at that time is set to a constant value. Simultaneously with the data recording, the value of the servo band interval for the entire tape length is measured every 1 m in the longitudinal position and recorded in the cartridge memory. Next, while performing servo tracking, the recording and reproducing head unit reproduces the data recorded on the magnetic tape. The tension in the longitudinal direction of the tape at that time shall be a constant value. During the above reproduction, the running stability was evaluated using, as an index, the standard deviation (hereinafter referred to as "σPES") of the reading position PES (Position Error Signal) in the width direction based on the servo signal obtained by the servo signal reading element. PES is obtained by the following method. To obtain PES, the dimensions of the servo pattern are required. The standards for the dimensions of the servo pattern differ depending on the generation of LTO. Therefore, first, using a magnetic force microscope or the like, the average distance AC between the corresponding 4 stripes of the A burst and the C burst, and the azimuth angle α of the servo pattern are measured. The average time between the 5 stripes corresponding to the A burst and the B burst over the length of 1 LPOS word is defined as a. The average time between the 4 stripes corresponding to the A burst and the C burst over the length of 1 LPOS word is defined as b. At this time, the value defined by AC×(1 / 2 - a / b) / (2×tan(α)) is the reading position PES (Position Error Signal) in the width direction based on the servo signal obtained by the servo signal reading element over the length of 1 LPOS word. Regarding the magnetic tape, the end on the side wound around the reel of the magnetic tape cartridge is called the inner end, and the opposite end is called the outer end. With the outer end as 0 m, the standard deviation (σPES) of PES obtained by the above method was calculated for the region in the longitudinal direction of the tape with a length ranging from 30 m to 200 m. The arithmetic mean of σPES obtained for a total of 4 recordings and reproductions is shown in the column of "σPES" in Table 1. If σPES is less than 70 nm, it can be determined that the running stability is excellent.

[0148] [Evaluation of Magnetic Tape] (1) Edge part Ra, central part Ra, Ra ratio (central part Ra / edge part Ra) The magnetic tape was taken out from each of the magnetic tape cartridges of the examples and comparative examples, and the Ra of the edge part and the central part were obtained by the method described above, and the Ra ratio (central part Ra / edge part Ra) was calculated from the obtained values.

[0149] (2) Standard deviation of the amount of curvature in the longitudinal direction of the magnetic tape The magnetic tape was taken out from the magnetic tape cartridge, and the standard deviation of the amount of curvature in the longitudinal direction of the magnetic tape was obtained by the method described above.

[0150] (3) Tape thickness Ten tape samples (length 5 cm) were cut out from arbitrary parts of the magnetic tapes taken out from each of the magnetic tape cartridges of the examples and comparative examples, and these tape samples were stacked and the thickness was measured. The thickness was measured using a digital thickness gauge of Millimar 1240 compact amplifier and Millimar 1301 induction probe manufactured by MARH. The value obtained by dividing the measured thickness by 10 (thickness per tape sample) was taken as the tape thickness. For each magnetic tape, the tape thickness was 5.2 μm in all cases.

[0151] The above results are shown in Table 1 (Table 1-1 to Table 1-2).

[0152]

Table 1-1

[0153]

Table 1-2

[0154] From the results shown in Table 1, it can be confirmed that the magnetic tapes of the examples showed excellent running stability when the magnetic tapes were run at different head tilt angles in a high temperature and low humidity environment.

[0155] When manufacturing the magnetic tape, after applying a composition for forming a magnetic layer to form a coating layer, while the coating layer of the composition for forming a magnetic layer was in a wet state, a magnetic field with a magnetic field strength of 0.3 T was applied in a direction perpendicular to the surface of the coating layer to perform vertical alignment treatment, and then dried to form a magnetic layer. A magnetic tape cartridge was manufactured by the method described for Example 1, except for this point. A sample piece was cut out from the magnetic tape taken out from the above magnetic tape cartridge. For this sample piece, using a TM-TRVSM5050-SMSL type manufactured by Tamagawa Seiki Co., Ltd. as a vibrating sample magnetometer, the vertical angular ratio was determined by the method described above, and it was 0.60. A magnetic tape was also taken out from the magnetic tape cartridge of Example 1, and the vertical angular ratio was similarly determined for the sample piece cut out from this magnetic tape, and it was 0.55.

[0156] The magnetic tapes taken out from the above two magnetic tape cartridges were respectively attached to a 1 / 2-inch reel tester, and the electromagnetic conversion characteristics (SNR: Signal-to-Noise Ratio) were evaluated by the following method. As a result, for the above magnetic tape manufactured with vertical alignment treatment, a SNR value 2 dB higher than that of the magnetic tape of Example 1 manufactured without vertical alignment treatment was obtained. In an environment with a temperature of 23°C and a relative humidity of 50%, recording and playback were performed 10 passes in the longitudinal direction of the magnetic tape with a tension of 0.7 N. The relative speed between the magnetic tape and the magnetic head was 6 m / s. For recording, a MIG (Metal-in-gap) head (gap length 0.15 μm, track width 1.0 μm) was used as the recording head, and the recording current was set to the optimum recording current for each magnetic tape. For playback, a GMR (Giant-magnetoresistive) head (element thickness 15 nm, shield interval 0.1 μm, playback element width 0.8 μm) was used as the playback head. The head tilt angle was 0°. A signal with a linear recording density of 300 kfci was recorded, and the playback signal was measured with a spectrum analyzer manufactured by Shibasoku Corporation. The unit kfci is a unit of linear recording density (not convertible to the SI unit system). As the signal, a portion where the signal was sufficiently stable after the start of magnetic tape travel was used.

Industrial Applicability

[0157] One aspect of the present invention is useful in the technical field of various data storage.

Claims

1. A magnetic tape having a non-magnetic support and a magnetic layer containing ferromagnetic powder, wherein an edge Ra, which is an arithmetic mean roughness Ra measured at an edge portion of the surface of the magnetic layer, is 1.50 nm or less, a central Ra, which is an arithmetic mean roughness Ra measured at a central portion of the surface of the magnetic layer, is 0.30 nm or more and 1.30 nm or less, and a magnetic tape in which the Ra ratio, central Ra / edge Ra, is 0.75 or more and 0.95 or less.

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

3. The non-magnetic powder has an average particle volume of 2.0×10 －６ μm ３ The magnetic tape according to claim 2, comprising the following Fe-based inorganic oxide powder.

4. The magnetic tape according to claim 2 or 3, wherein the non-magnetic powder contains carbon black having a pH of 5.0 or less.

5. The magnetic tape according to any one of claims 1 to 4, wherein a standard deviation of the amount of curvature in the longitudinal direction of the magnetic tape is 5 mm / m or less.

6. The magnetic tape according to any one of claims 1 to 5, further having a back coat layer containing non-magnetic powder on a surface side of the non-magnetic support opposite to the surface side having the magnetic layer.

7. The magnetic tape according to any one of claims 1 to 6, wherein the tape thickness is 5.2 μm or less.

8. The magnetic tape according to any one of claims 1 to 7, wherein a perpendicular direction squareness ratio of the magnetic tape is 0.60 or more.

9. A magnetic tape cartridge containing the magnetic tape according to any one of claims 1 to 8.

10. A magnetic tape device containing the magnetic tape according to any one of claims 1 to 8.

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

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