magnetic tape device

Abstract

To enable data to be satisfactorily recorded and / or reproduced when recording and / or reproducing data while changing a head tilt angle during magnetic tape running after storing the magnetic tape in a storage environment exposed to change of temperature and humidity.SOLUTION: A magnetic tape device is provided. An angle θ formed by the axis of the element array of a magnetic head with respect to a width direction of the magnetic tape is changed during running of the magnetic tape in the magnetic tape device. When A represents the maximum value of absolute value of difference between a servo band interval obtained before being stored and a servo band interval obtained after being stored for cycles N, and N is 1, 2, 3, 4 or 5, a medium life calculated by a primary function of A and logarithm of T, logeT, having been derived from the value A obtained with a prescribed storage being assumed to be one cycle, and a logarithm of total storage time T of cycles N of storage, is 5 years or longer. The medium life is T when A satisfies formula a: A=1.5-B+C.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] Magnetic recording media are available in tape and disk form, and tape-type magnetic recording media, ie, magnetic tape, are primarily used for various data storage applications (see, for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

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

[0004] Data is typically recorded on a magnetic tape by running the magnetic tape in a magnetic tape device and recording data on the data band by moving a magnetic head along the data band. This forms a data track on the data band. When reproducing the recorded data, the magnetic tape is run in the magnetic tape device and the magnetic head follows the data band of the magnetic tape to read the data recorded on the data band. To improve the accuracy with which the magnetic head follows the data band of the magnetic tape during the above-described recording and / or reproduction, a system (hereinafter referred to as a "servo system") that performs head tracking using a servo signal has been put into practical use. After such recording or reproduction, the magnetic tape is typically stored wound on a reel (hereinafter referred to as a "cartridge reel") in a magnetic tape cartridge until the next recording and / or reproduction is performed.

[0005] In recent years, it has been proposed to use servo signals to acquire dimensional information (such as contraction or expansion) in the width direction of a running magnetic tape, and to change the angle at which the axial direction of the magnetic head module is tilted relative to the width direction of the magnetic tape (hereinafter also referred to as the "head tilt angle") based on the acquired dimensional information (see Patent Documents 1 and 2, for example, paragraphs 0059-0067 and 0084 of Patent Document 1). During recording or playback, if the magnetic head for recording or playing back data deviates from the target track position due to width deformation of the magnetic tape, this can result in problems such as overwriting of recorded data or playback failure. Meanwhile, in the data storage field, there has been a growing need for long-term data storage, known as archiving. However, the longer the storage period, the more likely magnetic tape deformation occurs. Therefore, it is expected that there will be an increasing need to prevent the occurrence of the above-mentioned phenomena after storage. In this regard, the present inventor believes that changing the head tilt angle as described above is one means for preventing such phenomena.

[0006] In recent years, magnetic tape cartridges containing magnetic tapes with recorded data are often stored in temperature- and humidity-controlled data centers. Meanwhile, data centers are seeking to reduce power consumption to reduce costs. To achieve this, it would be desirable to relax the temperature and humidity control requirements in data centers, or even eliminate them altogether. However, if temperature and humidity control requirements are relaxed or not implemented at all, magnetic tapes are likely to be exposed to temperature and humidity changes during long-term storage. Generally, the longer a magnetic tape is stored in such an environment, the more likely it is that it will become deformed. Therefore, it is expected that there will be an even greater need in the future to prevent problems such as overwriting recorded data and playback issues after storage.

[0007] In view of the above, one aspect of the present invention aims to enable good recording and / or playback when recording and / or playing back data by changing the head tilt angle while the magnetic tape is running, after the magnetic tape has been stored in a storage environment where it is exposed to changes in temperature and humidity. [Means for solving the problem]

[0008] One aspect of the present invention is A magnetic tape device including a magnetic tape and a magnetic head, the magnetic head has a module including an element array having a plurality of magnetic head elements between a pair of servo signal read elements, the magnetic tape device changes an angle θ formed by an axis of the element array with respect to a width direction of the magnetic tape while the magnetic tape is running within the magnetic tape device; The magnetic tape has a non-magnetic support and a magnetic layer containing ferromagnetic powder, the magnetic layer has a plurality of servo bands; The maximum absolute value of the difference between the servo band interval obtained before the storage described below and the servo band interval obtained after N storage cycles, where one cycle is 12 hours of storage in an environment with a temperature of 23°C and a relative humidity of 50% and another 12 hours of storage in an environment with a temperature of 32°C and a relative humidity of 55%, is A, and the unit of A is μm. The logarithm of the total storage time T for N storage cycles is logarithm of the value of A obtained for each of N, where N is 1, 2, 3, 4, or 5. e The logarithm of A and T, log, is derived from the value of T. e The media life calculated by a linear function of T (hereinafter also referred to as "media life") is 5 years or more, The above media life is calculated by the following formula: (Formula a) A=1.5-B+C T when The above B is Under the following five environments: Temperature 16℃, relative humidity 20%, Temperature 16℃, relative humidity 80%, Temperature 26℃, relative humidity 80%, Temperature 32℃, relative humidity 20%, Temperature 32℃, relative humidity 55%, The value is calculated by multiplying the difference between the maximum and minimum values ​​of the servo band intervals obtained in each of the above by 1 / 2, and is expressed in μm. The above C is C=L{cos(θ initial -Δθ)-cos(θ initial +Δθ)} The value is calculated by the following equation, and the unit is μm. L is the distance between the pair of servo signal reading elements, and is expressed in μm. The angle θ at the start of the magnetic tape running is θ initial year, The maximum value of the angle θ during the running of the magnetic tape is set to θ max , the minimum value is θ min As, The above Δθ is Δθ max =θ max -θ initial Δθ min =θ initial -θ min The magnetic tape device, which has the larger value among the values ​​calculated by Regarding.

[0009] In one embodiment, the media life can be 5 years or more and 400 years or less.

[0010] In one embodiment, the magnetic tape device can change the angle θ that the axis of the element array makes with respect to the width direction of the magnetic tape while the magnetic tape is running within the magnetic tape device, in accordance with the width direction dimensional information of the magnetic tape obtained during the running.

[0011] In one embodiment, the magnetic tape can further include a non-magnetic layer containing non-magnetic powder between the non-magnetic support and the magnetic layer.

[0012] In one embodiment, the magnetic tape can further have a backcoat layer containing nonmagnetic powder on the surface of the nonmagnetic support opposite to the surface on which the magnetic layer is formed.

[0013] In one embodiment, the non-magnetic support can be an aromatic polyester support.

[0014] In one embodiment, the aromatic polyester support can be a polyethylene terephthalate support.

[0015] In one embodiment, the aromatic polyester support can be a polyethylene naphthalate support.

[0016] In one embodiment, the non-magnetic support can be an aromatic polyamide support.

[0017] In one embodiment, the squareness ratio of the magnetic tape in the perpendicular direction can be 0.60 or more. [Effects of the Invention]

[0018] According to one aspect of the present invention, after storing a magnetic tape in a storage environment where it is exposed to changes in temperature and humidity, it is possible to perform good recording and / or reproduction when recording and / or reproducing data by changing the head tilt angle while the magnetic tape is running. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 2 is a schematic diagram showing an example of a magnetic head module. [Figure 2] 1 is an explanatory diagram of the relative positional relationship between a module and a magnetic tape while the magnetic tape is running in a magnetic tape device. [Figure 3] FIG. 10 is an explanatory diagram regarding changes in angle θ while the magnetic tape is running. [Figure 4] FIG. 10 is an explanatory diagram of a method for measuring an angle θ while a magnetic tape is running. [Figure 5]FIG. 1 is a schematic diagram illustrating an example of a magnetic tape device. [Figure 6] 1 shows an example of the arrangement of data bands and servo bands. [Figure 7] An example of servo pattern layout for an LTO (Linear Tape-Open) Ultrium format tape is shown below. [Figure 8] FIG. 1 is a perspective view of an example of a magnetic tape cartridge. [Figure 9] FIG. 1 is a perspective view showing when the magnetic tape starts to be wound around the reel. [Figure 10] FIG. 2 is a perspective view of the state when the magnetic tape has been completely wound around the reel. DETAILED DESCRIPTION OF THE INVENTION

[0020] One aspect of the present invention relates to a magnetic tape device including a magnetic tape and a magnetic head.

[0021] Magnetic tape is usually housed in a magnetic tape cartridge. In an unused magnetic tape cartridge before it is installed in a magnetic tape device for recording and / or reproducing data, the magnetic tape is usually housed in a state wound on a cartridge reel (hereinafter also simply referred to as a "reel"). In a magnetic tape device, data can be recorded on the magnetic tape and / or recorded data can be reproduced by running the magnetic tape between a cartridge reel (supply reel) and a take-up reel. After recording or reproducing data, the magnetic tape is rewound onto the cartridge reel and stored in the magnetic tape cartridge in a state wound on the cartridge reel until the next recording and / or reproduction is performed. It is believed that during storage, the magnetic tape housed in the magnetic tape cartridge undergoes deformation that varies depending on the position, with the portion closer to the cartridge reel deforming wider than the initial width due to compressive stress in the tape thickness direction, and the portion farther from the cartridge reel deforming narrower than the initial width due to tensile stress in the tape longitudinal direction. If deformation that varies significantly depending on the position occurs, it is thought that this could cause the magnetic head to record and / or reproduce data while shifting from the target track position when recording and / or reproducing data after storage. The present inventors have considered that the above-mentioned deformations are mainly caused by stresses received during storage, and mainly caused by the temperature and humidity of the environment in which data is recorded and / or reproduced (hereinafter referred to as the "usage environment"). Through further investigations, the present inventors have come to believe that comprehensive consideration of deformations caused by the above-mentioned factors will enable successful recording and / or reproduction of data on a magnetic tape after it has been housed in a magnetic tape cartridge and stored. After further intensive investigations, the present inventors have adopted media life as a comprehensive index regarding deformations caused by the above-mentioned factors, and have newly discovered that a magnetic tape device with a media life of five years or more can perform successful recording and / or reproduction of data by changing the head tilt angle while the magnetic tape is running after it has been housed in a magnetic tape cartridge and stored in an environment exposed to changes in temperature and humidity.

[0022] The magnetic tape device will be described in more detail below. Below, one embodiment of the magnetic tape cartridge and magnetic tape device will be described with reference to the drawings. However, the present invention is not limited to the embodiment shown in the drawings. The dimensions of each part in the drawings are merely examples. Furthermore, the present invention is not limited by the inventor's speculations described in this specification.

[0023] [Media Life] The method for measuring the above-mentioned media life will be explained below.

[0024] <Procedure for deriving a linear function> (Servo band interval measurement) In order to derive the formula a for calculating A, various servo band intervals are measured using the following method. The servo band spacing before storage is measured in a measurement environment with an ambient temperature of 23°C and a relative humidity of 50%. The magnetic tape cartridge containing the magnetic tape to be measured wound on a reel is placed in an environment with an ambient temperature of 23°C and a relative humidity of 50% for five days to allow it to acclimate to the measurement environment. Then, in a measurement environment with an ambient temperature of 23°C and a relative humidity of 50%, the magnetic tape is run in a magnetic tape device equipped with a tension adjustment mechanism that applies tension in the longitudinal direction of the magnetic tape, with a tension of 0.70 N applied in the longitudinal direction of the magnetic tape. During this run, the distance between two adjacent servo bands sandwiching a data band is measured at 1-meter intervals along the entire length of the magnetic tape. In measurements to determine various values ​​described in this invention and this specification, the tension applied in the longitudinal direction of the magnetic tape is the set value set in the magnetic tape device. Furthermore, in this invention and this specification, "measured at 1-meter intervals" refers to a measurement area of ​​length L meters (m), where one end of the measurement area is 0 m, and positions toward the other end are 1 m, 2 m, 3 m, and so on, with the other end position being L m. The first measurement position is the 1-meter position, and the last measurement position is the position immediately before L m. Furthermore, if there are multiple servo band intervals, the servo band intervals are measured for all servo band intervals in the same manner. The servo band interval measured in this manner is defined as the "servo band interval before storage" at each measurement position. The storage of the following magnetic tape cartridges is carried out in one cycle, where the magnetic tape cartridge is stored for 12 hours in a storage environment with an ambient temperature of 23°C and a relative humidity of 50% (also referred to as "storage environment A"), and then stored for 12 hours in a storage environment with an ambient temperature of 32°C and a relative humidity of 55% (also referred to as "storage environment B"). Therefore, the total storage time per cycle is 24 hours. After measuring the servo band interval before storage, one cycle of storage is carried out. After this storage, the magnetic tape cartridge was placed in a measurement environment with an ambient temperature of 23°C and a relative humidity of 50% for five days to allow it to acclimate to the measurement environment. Then, in the same measurement environment, the magnetic tape was run in a magnetic tape device equipped with a tension adjustment mechanism that applies tension to the magnetic tape in the longitudinal direction, with a tension of 0.70 N applied to the magnetic tape in the longitudinal direction. During this run, the servo band spacing was measured in the same manner as described above. The servo band spacing measured in this way was designated the "servo band spacing after 24 hours of storage" at each measurement position. For all servo band intervals, the difference between the servo band intervals measured at 1m intervals before storage and the servo band intervals after storage is calculated. In this way, multiple difference values ​​are calculated. The maximum absolute value of the calculated differences is taken as "A after 24 hours of storage." The unit of A is μm. This also applies to the various A values ​​described below. The distance between two adjacent servo bands sandwiching a data band can be calculated using, for example, a PES (Position Error Signal) obtained from a servo signal obtained by reading a servo pattern using a servo signal reading element. For details, see the description of the embodiment below. After 12 hours of storage in storage environment A, the ambient temperature and relative humidity of the environment in which the magnetic tape cartridge is placed are changed within 60 minutes to that of storage environment B, and then the magnetic tape cartridge is stored for 12 hours in storage environment B. When performing storage for two or more cycles, with regard to the change in environment from storage environment B to storage environment A, after 12 hours of storage in storage environment B, the ambient temperature and relative humidity of the environment in which the magnetic tape cartridge is placed are changed within 60 minutes to that of storage environment A, and then the magnetic tape cartridge is stored for 12 hours in storage environment A. After measuring the servo band interval after 24 hours (1 cycle) of storage, the magnetic tape cartridge is subjected to two cycles of storage, with the total storage time for these two cycles being 48 hours. After this storage, the magnetic tape cartridge is placed in a measurement environment with an ambient temperature of 23°C and a relative humidity of 50% for five days, and then, under the same measurement environment, the magnetic tape is run in a magnetic tape device having a tension adjustment mechanism that applies tension to the magnetic tape in the longitudinal direction, with a tension of 0.70 N applied to the magnetic tape in the longitudinal direction. During this run, the servo band spacing is measured in the same manner as described above. The servo band spacing measured in this way is defined as the "servo band spacing after 48 hours of storage" at each measurement position. For all servo band intervals, the difference between the servo band intervals measured at 1m intervals before storage and the servo band intervals after storage is calculated. In this way, multiple difference values ​​are calculated. The maximum absolute value of the calculated difference is taken as "A after 48 hours of storage." After measuring the servo band interval after 48 hours (2 cycles) of storage, the magnetic tape cartridge is subjected to 3 cycles of storage, with the total storage time for these 3 cycles being 72 hours. After this storage, the magnetic tape cartridge is placed in a measurement environment with an ambient temperature of 23°C and a relative humidity of 50% for 5 days, and then, under the same measurement environment, the magnetic tape is run in a magnetic tape device having a tension adjustment mechanism that applies tension to the magnetic tape in the longitudinal direction, with a tension of 0.70 N applied to the magnetic tape in the longitudinal direction. During this run, the servo band spacing is measured in the same manner as described above. The servo band spacing measured in this way is defined as the "servo band spacing after 72 hours of storage" at each measurement position. For all servo band intervals, the difference between the servo band intervals measured at 1m intervals before storage and the servo band intervals after storage is calculated. In this way, multiple difference values ​​are calculated. The maximum absolute value of the calculated difference is taken as "A after 72 hours of storage." After measuring the servo band interval after 72 hours (3 cycles) of storage, the magnetic tape cartridge is subjected to 4 cycles of storage, with the total storage time for these 4 cycles being 96 hours. After this storage, the magnetic tape cartridge was placed in a measurement environment with an ambient temperature of 23°C and a relative humidity of 50% for five days, and then, under the same measurement environment, the magnetic tape was run in a magnetic tape device equipped with a tension adjustment mechanism that applies tension to the magnetic tape in the longitudinal direction, with a tension of 0.70 N applied to the magnetic tape in the longitudinal direction. During this run, the servo band spacing was measured in the same manner as described above. The servo band spacing measured in this way was designated the "servo band spacing after 96 hours of storage" at each measurement position. For all servo band intervals, the difference between the servo band intervals measured at 1m intervals before storage and the servo band intervals after storage is calculated. In this way, multiple difference values ​​are calculated. The maximum absolute value of the calculated difference is taken as "A after 96 hours of storage." After measuring the servo band interval after 96 hours (4 cycles) of storage, the magnetic tape cartridge is subjected to 5 cycles of storage, with the total storage time for these 5 cycles being 120 hours. After this storage, the magnetic tape cartridge was placed in a measurement environment with an ambient temperature of 23°C and a relative humidity of 50% for five days, and then, under the same measurement environment, the magnetic tape was run in a magnetic tape device equipped with a tension adjustment mechanism that applies tension to the magnetic tape in the longitudinal direction, with a tension of 0.70 N applied to the magnetic tape in the longitudinal direction. During this run, the servo band spacing was measured in the same manner as described above. The servo band spacing measured in this way was designated the "servo band spacing after 120 hours of storage" at each measurement position. For all servo band spacings, the difference between the servo band spacing measured at 1m intervals before storage and the servo band spacing after storage is calculated. In this way, multiple difference values ​​are calculated. The maximum absolute value of the calculated difference is taken as "A after 120 hours of storage."

[0025] The inventors believe that the value of A obtained as described above can be an indicator of deformation that occurs primarily due to stresses that the magnetic tape experiences while being stored in a magnetic tape cartridge in an environment exposed to changes in temperature and humidity.

[0026] (Derivation of linear functions) In the above process, values of A are determined for five types of total storage times T. From these values of A and the logarithms log e of the values of T, a linear function of A and log e T is derived by the least squares method. The linear function is expressed as Y = cX + d, where Y is A and X is log e T. c and d are coefficients determined by the least squares method, and usually both c and d are positive values.

[0027] <Procedure for determining B> B, which is used to obtain the media life, is a value determined by the following method. B is a value (unit: μm) calculated by multiplying by 1 / 2 the difference between the maximum value and the minimum value among the servo band intervals respectively obtained under the following five environments: temperature 16°C, relative humidity 20%; temperature 16°C, relative humidity 80%; temperature 26°C, relative humidity 80%; temperature 32°C, relative humidity 20%; temperature 32°C, relative humidity 55%. B is obtained by the following method. For each measurement environment, the magnetic tape cartridge containing the magnetic tape to be measured wound around a reel is placed in the measurement environment for 5 days in order to acclimatize it to the measurement environment. The measurement environments are the five environments described above (i.e., temperature 16°C, relative humidity 20%; temperature 16°C, relative humidity 80%; temperature 26°C, relative humidity 80%; temperature 32°C, relative humidity 20%; temperature 32°C, relative humidity 55%). Then, under the measurement environment, the magnetic tape is run in a magnetic tape device equipped with a tension adjustment mechanism that applies tension in the longitudinal direction of the magnetic tape, with a tension of 0.70 N applied to the magnetic tape in the longitudinal direction. The end of the magnetic tape wound onto the reel of the magnetic tape cartridge is called the inner end, and the opposite end is called the outer end. The outer end is designated as 0 m, and the servo band spacing is measured at 1 m intervals in a region ranging from 0 m to 100 m in length (hereinafter referred to as the "100 m region around the reel") for the above run at data band 0 (zero) at 1 m intervals. "Data band 0" is the data band defined by the standard as the first data band where data is embedded (recorded). The arithmetic mean of the measured servo band spacing is taken as the servo band spacing in the measurement environment. After determining the servo band spacing in each of the five environments as described above, the maximum and minimum values ​​among the determined values ​​are used to calculate "(maximum value - minimum value) x 1 / 2," which is the value "B" of the magnetic tape cartridge being measured. The inventors believe that B determined in this way can be a value that can be used as an index of deformation that occurs mainly due to the temperature and humidity of the usage environment.

[0028] <Calculating media life> The media life is the logarithm of A and T calculated above. eA is a linear function of T, and is calculated as T when A satisfies the formula a: A = 1.5 - B + C. The inventors believe that the media life calculated in this way being 5 years or more, i.e., the time T at which A + B becomes 1.5 + C μm, being 5 years or more, indicates that the total deformation caused primarily by stresses experienced by the magnetic tape during storage in a magnetic tape cartridge in an environment exposed to temperature and humidity changes, plus deformation caused primarily by the temperature and humidity of the operating environment, is unlikely to increase over the long term. Furthermore, the inventors believe that C in formula a can be an indicator of the amount of track position deviation allowable when recording and / or reproducing data by changing the head tilt angle while the magnetic tape is running. Details of C will be discussed later. The reasons for adopting 1.5 μm and 5 years as thresholds are based on consideration of future needs for long-term storage and high-density recording. Regarding media life, one year is defined as 365 days. Therefore, one year is 365 x 24 hours = 8,760 hours. Also, 0.5 years is 6 months, and 1 month is 30 days. Therefore, 0.5 years is 6 x 30 x 24 hours = 4320 hours. Note that the various measurement environments described above are examples, and the magnetic tape is not limited to being stored and / or used in the environments described above.

[0029] From the viewpoint of enabling good recording and / or reproduction when the head tilt angle is changed during magnetic tape running after the magnetic tape is housed and stored in a magnetic tape cartridge, the above-mentioned medium life is 5 years or more, preferably 10 years or more, and more preferably 20 years or more, 30 years or more, 40 years or more, 50 years or more, 60 years or more, 70 years or more, 80 years or more, 90 years or more, and 100 years or more. The above-mentioned medium life can be, for example, 500 years or less, 450 years or less, 400 years or less, 350 years or less, or 300 years or less, and can also exceed the values ​​exemplified here. A method for controlling the medium life will be described later.

[0030] The value of B can be, for example, 0.0 μm or more, more than 0.0 μm, 0.05 μm or more, or 0.1 μm or more, or can be, for example, 2.0 μm or less, 1.5 μm or less, or 0.5 μm or less. However, as long as the medium life of the magnetic tape device is 5 years or more, the value of B is not limited to the above range.

[0031] [Magnetic head] The magnetic head included in the magnetic tape device can have one or more modules, two or more, or three or more, each module including an element array having a plurality of magnetic head elements between a pair of servo signal read elements. The total number of such modules can be, for example, five or less, four or less, or three or less, or the magnetic head may include a number of modules exceeding the total number exemplified here. Examples of arrangements of multiple modules include "recording module-playback module" (total number of modules: 2) and "recording module-playback module-recording module" (total number of modules: 3). However, this is not limited to the examples shown here.

[0032] Each module includes an element array, i.e., an array of elements, having multiple magnetic head elements between a pair of servo signal read elements. A module having a write element as a magnetic head element is a recording module for recording data to magnetic tape. A module having a read element as a magnetic head element is a reproducing module for reproducing data recorded on magnetic tape. In a magnetic head, multiple modules are arranged, for example, in a recording / reproducing head unit, with the axes of the element arrays of each module oriented parallel. This "parallel" does not necessarily mean only parallel in the strict sense, but also includes the range of error normally tolerated in the technical field to which the present invention pertains. The range of error can mean, for example, a range of less than ±10° from strict parallelism.

[0033] If the magnetic head contains one module in total, C is calculated for this module. If the magnetic head contains two or more modules in total, C is calculated for a randomly selected module. The module for which C is calculated may be a recording module or a playback module.

[0034] The reproducing element is preferably a magnetoresistive (MR) element that can read information recorded on a magnetic tape with high sensitivity. Various known MR elements (e.g., a giant magnetoresistive (GMR) element, a tunnel magnetoresistive (TMR) element, etc.) can be used as the MR element. Hereinafter, a magnetic head that records data and / or reproduces recorded data is also referred to as a "recording / reproducing head." The element for recording data (the recording element) and the element for reproducing data (the reproducing element) are collectively referred to as a "magnetic head element."

[0035] By using a read element with a narrow read element width as the read element, data recorded at a high density can be read with high sensitivity. From this perspective, the read element width of the read element is preferably 0.8 μm or less. The read element width of the read element can be, for example, 0.3 μm or more. However, from the above perspective, a width below this value is also preferable. Here, the "reading element width" refers to the physical dimension of the reading element width, which can be measured using an optical microscope, a scanning electron microscope, or the like.

[0036] In each element array, a pair of servo signal read elements and multiple magnetic head elements (i.e., write elements or read elements) are typically arranged linearly and spaced apart. Here, "arranged linearly" means that each magnetic head element is arranged on a straight line connecting the center of one servo signal read element to the center of the other servo signal read element. In this invention and this specification, the "axis of the element array" refers to the straight line connecting the center of one servo signal read element to the center of the other servo signal read element.

[0037] The configuration of the module will be further described below with reference to the drawings. However, the embodiments shown in the drawings are merely examples and do not limit the present invention.

[0038] FIG. 1 is a schematic diagram showing an example of a magnetic head module. The module shown in FIG. 1 has multiple magnetic head elements between a pair of servo signal read elements (servo signal read elements 1 and 2). A magnetic head element is also called a "channel." "Ch" in the diagram is an abbreviation for Channel. The module shown in FIG. 1 has a total of 32 magnetic head elements, Ch0 to Ch31.

[0039] "L" for calculating C is the distance between a pair of servo signal read elements, i.e., the distance between one servo signal read element and the other servo signal read element. In the module shown in FIG. 1, "L" is the distance between servo signal read element 1 and servo signal read element 2. More specifically, it is the distance between the center of servo signal read element 1 and the center of servo signal read element 2. This distance can be measured using, for example, an optical microscope.

[0040] FIG. 2 is an explanatory diagram of the relative positional relationship between a module and a magnetic tape while the magnetic tape is running in a magnetic tape device. In FIG. 2, dotted line A indicates the width direction of the magnetic tape. Dotted line B indicates the axis of the element array. Angle θ can be called the head tilt angle, and is the angle formed by dotted lines A and B. When angle θ is 0° while the magnetic tape is running, the distance in the width direction of the magnetic tape between one servo signal read element and the other servo signal read element of the element array (hereinafter also referred to as "effective distance between servo signal read elements") is "L". On the other hand, when angle θ is greater than 0°, the effective distance between the servo signal read elements is "L cos θ", and L cos θ is smaller than L. That is, "L cos θ" <L」である。

[0041] As described above, if the magnetic head for recording or reproducing data deviates from the target track position due to deformation of the magnetic tape during recording or reproduction, it may result in overwriting of recorded data, poor reproduction, and other problems. For example, if the width of the magnetic tape shrinks or expands, a magnetic head element that should be recording or reproducing data at the target track position may end up recording or reproducing data at a different track position. Furthermore, if the width of the magnetic tape expands, the effective distance between servo signal reading elements may become shorter than the distance between two adjacent servo bands across a data band (also referred to as the "servo band distance" or "servo band distance"; more specifically, the distance between the two servo bands in the width direction of the magnetic tape), which may result in data not being recorded or reproduced near the edge of the magnetic tape. In contrast, when the element array is tilted at an angle θ greater than 0°, the effective distance between the servo signal read elements becomes "Lcosθ," as explained above. The larger the value of θ, the smaller the value of Lcosθ, and the smaller the value of θ, the larger the value of Lcosθ. Therefore, by changing the value of θ according to the degree of dimensional change in the width direction of the magnetic tape (i.e., contraction or expansion), it is possible to make the effective distance between the servo signal read elements approach or match the spacing between the servo bands. This can prevent or reduce the frequency of phenomena such as overwriting of recorded data or playback failures caused by the magnetic head for recording or playing back data shifting from the target track position due to width deformation of the magnetic tape.

[0042] Therefore, 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 is changed while the magnetic tape is running inside the magnetic tape device. For example, by providing an angle adjustment unit that adjusts the angle of the module in the recording / reproducing head unit of the magnetic head, the angle θ can be variably adjusted while the magnetic tape is running. Such an angle adjustment unit can include, for example, a rotation mechanism that rotates the module. Publicly known technology can be applied to the angle adjustment unit.

[0043] FIG. 3 is an explanatory diagram showing the change in angle θ while the magnetic tape is running. θ is the angle θ at the start of travel initial can be set to be greater than or equal to 0°. initial The larger the angle θ, the larger the change in the effective distance between the servo signal read elements becomes, and therefore, it is preferable from the viewpoint of the ability to adjust the effective distance between the servo signal read elements in response to the change in the dimension of the magnetic tape in the width direction. initialis preferably 1.000° or more, more preferably 5.000° or more, and even more preferably 10.000° or more. On the other hand, with regard to the angle formed by the magnetic layer surface and the contact surface of the magnetic head when the magnetic tape runs and comes into contact with the magnetic head (generally called the "wrap angle"), keeping the deviation in the tape width direction small is effective in increasing the uniformity in the tape width direction of the friction generated by contact between the magnetic head and the magnetic tape while the magnetic tape is running. Furthermore, increasing the uniformity of the friction in the tape width direction is desirable from the viewpoint of the position tracking ability and running stability of the magnetic head. From the viewpoint of reducing the deviation in the tape width direction of the wrap angle, θ initial is preferably 45,000° or less, more preferably 40,000° or less, and even more preferably 35,000° or less. θ is the head tilt angle when the magnetic tape starts running initial can be set by the control device of the magnetic tape device, etc.

[0044] In the examples shown in FIGS. 2 and 3, the axis of the element array is inclined toward the magnetic tape running direction. However, the present invention is not limited to such an example. In the above-described magnetic tape device, an embodiment in which the axis of the element array is inclined toward the direction opposite to the magnetic tape running direction is also encompassed within the present invention. In the present invention and this specification, the angle θ is changed within a range of 0 to 90° during magnetic tape running. 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 inclined during magnetic tape running so that the axis of the element array is inclined toward the direction opposite to the magnetic tape running direction at the start of magnetic tape running. Furthermore, if the axis of the element array is inclined toward the direction opposite to the magnetic tape running direction at the start of magnetic tape running, the element array is not inclined during magnetic tape running so that the axis of the element array is inclined toward the magnetic tape running direction at the start of magnetic tape running.

[0045] In Figure 3, the central figure shows the state of the module at the start of driving. In Figure 3, the right figure shows the angle θ as θ initial The larger angle is angle θ c The effective distance between the servo signal reading elements is L cos θ. c is Lcosθ when the magnetic tape starts running initial It is preferable to perform such angle adjustment when the width of the magnetic tape contracts while the magnetic tape is running. On the other hand, in Figure 3, the left figure shows the angle θ as θ initial The smaller angle θ e The effective distance between the servo signal reading elements is L cos θ. e is Lcosθ when the magnetic tape starts running initial If the width of the magnetic tape expands while the magnetic tape is running, it is preferable to perform such angle adjustment.

[0046] 4 is an explanatory diagram of a method for measuring the angle θ while the magnetic tape is running. In the present invention and this specification, the angle θ while the magnetic tape is running is determined by the following method. The phase difference (i.e., time difference) ΔT between the playback signals of a pair of servo signal read elements 1 and 2 is measured. ΔT can be measured using a measurement unit included in the magnetic tape drive. The configuration of such a measurement unit is well known. The distance L between the center of servo signal read element 1 and the center of servo signal read element 2 can be measured using an optical microscope or other device. When the magnetic tape running speed is v, the distance between the centers of the two servo signal read elements in the magnetic tape running direction is L sin θ, and the relationship L sin θ = v × ΔT holds. Therefore, the angle θ during magnetic tape running can be calculated using the formula "θ = arcsin(vΔT / L)." Note that the right diagram in Figure 4 shows an example in which the axis of the element array is tilted toward the magnetic tape running direction. In this example, the phase difference (i.e., time difference) ΔT between the phase of the playback signal of servo signal read element 1 and the phase of the playback signal of servo signal read element 2 is measured. When the axis of the element array is tilted in the opposite direction to the running direction of the magnetic tape, θ is calculated using the above method, except that ΔT is measured as the phase difference (i.e., time difference) between the phase of the playback signal of servo signal read element 2 and the phase of the playback signal of servo signal read element 1. The measurement pitch of the angle θ, i.e., the measurement interval of the angle θ relative to the tape longitudinal direction, can be selected to be appropriate depending on the frequency of the tape width deformation relative to the tape longitudinal direction. As an example, the measurement pitch can be set to 250 μm, and the measurement pitch was set to 250 μm in the examples and comparative examples described below.

[0047] <c> "C" in formula a is "C=L{cos(θ initial -Δθ)-cos(θ initial +Δθ)}" (unit: μm). As mentioned above, the inventors believe that C can be an index of the amount of track position deviation that is permissible when recording and / or reproducing data by changing the head tilt angle (angle θ) while the magnetic tape is running. L in the above formula is as described above. θ initial is the angle θ at the start of travel, as described above. Δθ is the maximum value of the angle θ during magnetic tape running. max , the minimum value is θ min Δθ is calculated by the following formula: max and Δθ min It is the larger value among the two. Δθ max =θ max -θ initial Δθ min =θ initial -θ min

[0048] The above Δθ can be said to be the maximum change in angle θ while the magnetic tape is running. Note that "max" is an abbreviation for maximum, and "min" is an abbreviation for minimum. θ max and θ min are the maximum and minimum values ​​of the angle θ during the running of the magnetic tape determined by the method described above. initial is θ max θ initial is θ min In other words, the angle θ may simply become smaller or larger during running than at the start of running. Δθ may be greater than 0.000°, and from the viewpoint of the ability to adjust the effective distance between servo signal read elements in response to dimensional changes in the magnetic tape width direction, Δθ is preferably 0.001° or greater, and more preferably 0.010° ​​or greater. Furthermore, from the viewpoint of the ease of ensuring synchronization of recorded data and / or reproduced data between multiple magnetic head elements during data recording and / or reproduction, Δθ is preferably 1.000° or less, more preferably 0.900° or less, even more preferably 0.800° or less, even more preferably 0.700° or less, and even more preferably 0.600° or less.

[0049] With regard to C, the magnetic tape device is only required to satisfy formula a, and there are no particular limitations on the value of C. In one embodiment, C can be, for example, more than 0 μm, 0.1 μm or more, 0.3 μm or more, or 0.5 μm or more, or, for example, 3.0 μm or less, 2.5 μm or less, 2.0 μm or less, or 1.5 μm or less.

[0050] [Magnetic tape device configuration] In this invention and this specification, the term "magnetic tape device" refers to a device that can record data on a magnetic tape and / or reproduce data recorded on a magnetic tape. Such a device is generally called a drive.

[0051] FIG. 5 is a schematic diagram showing an example of a magnetic tape device. A magnetic tape device 10 shown in FIG. 5 controls a recording / reproducing head unit 12 in response to commands from a control device 11, and records and reproduces data on a magnetic tape MT. The magnetic tape device 10 has a configuration that allows detection and adjustment of tension applied to the magnetic tape in the longitudinal direction from spindle motors 17A, 17B that control the rotation of cartridge reel 130 and take-up reel 16 and their drive devices 18A, 18B. The magnetic tape device 10 has a configuration in which a magnetic tape cartridge 13 can be installed. The magnetic tape device 10 has a cartridge memory read / write device 14 that can read and write data from and to a cartridge memory 131 in the magnetic tape cartridge 13 . The end or leader pin of the magnetic tape MT is pulled out from the magnetic tape cartridge 13 loaded into the magnetic tape device 10 by an automatic loading mechanism or manually, and the magnetic tape MT passes over the recording / playback head through guide rollers 15A and 15B with the magnetic layer surface in contact with the recording / playback head surface of the recording / playback head unit 12, and the magnetic tape MT is wound onto the take-up reel 16. The rotation and torque of spindle motors 17A and 17B are controlled by signals from control device 11, allowing magnetic tape MT to run at a desired speed and tension. Servo patterns pre-formed on the magnetic tape can be used to control the tape speed and angle θ. A tension detection mechanism may be provided between magnetic tape cartridge 13 and take-up reel 16 to detect tension. In addition to control by spindle motors 17A and 17B, tension adjustment may also be performed using guide rollers 15A and 15B. The cartridge memory read / write device 14 is configured to be able to read and write information from and to the cartridge memory 131 in response to commands from the control device 11. As a communication method between the cartridge memory read / write device 14 and the cartridge memory 131, for example, the ISO (International Organization for Standardization) 14443 method can be adopted.

[0052] The control device 11 includes, for example, a control unit, a storage unit, a communication unit, and the like.

[0053] The recording / reproducing head unit 12 is composed of, for example, a recording / reproducing head, a servo tracking actuator that adjusts the position of the recording / reproducing head in the track width direction, a recording / reproducing amplifier 19, and a connector cable for connecting to the control device 11. The recording / reproducing head is as explained above for the magnetic head.

[0054] The recording / playback head unit 12 is configured to be able to record data onto the magnetic tape MT in response to a command from the control device 11. It is also configured to be able to play back the data recorded on the magnetic tape MT in response to a command from the control device 11.

[0055] The control device 11 has a mechanism for determining the running position of the magnetic tape MT from servo signals read from the servo bands while the magnetic tape MT is running, and for controlling the servo tracking actuator so that the recording element and / or the reproducing element are positioned at the target running position (track position). This track position control is performed, for example, by feedback control. The control device 11 also has a mechanism for determining the servo band spacing from servo signals read from two adjacent servo bands while the magnetic tape MT is running. The control device 11 can store information about the determined servo band spacing in an internal storage unit of the control device 11, a cartridge memory 131, an external connected device, or the like. The control device 11 also changes the angle θ according to dimensional information about the width of the running magnetic tape. This allows the effective distance between the servo signal reading elements to approach or match the spacing between the servo bands. The dimensional information can be obtained using a servo pattern pre-formed on the magnetic tape. The angle θ can be adjusted, for example, by feedback control. For example, the angle θ can be adjusted by the method described in the examples below. Alternatively, the angle θ can be adjusted by the method described in Japanese Patent Laid-Open No. 2016-524774 (Patent Document 1) or US2019 / 0164573A1 (Patent Document 2).

[0056] For example, by using the control device 11 as described above, in the magnetic tape device, the angle θ can be variably adjusted while the magnetic tape is running, for example, when recording data on the magnetic tape and / or when reproducing data recorded on the magnetic tape.

[0057] When recording and / or reproducing data, tracking can be performed using servo signals. That is, by making the servo signal reading element follow a predetermined servo track, the magnetic head element can be controlled to pass over the target data track. The data track is moved by changing the servo track read by the servo signal reading element in the tape width direction. The read / write head can also record and / or read data from other data bands by using the UDIM information described above to move the servo signal read element to a specific servo band and start tracking that servo band.

[0058] FIG. 6 shows an example of the arrangement of data bands and servo bands. In FIG. 6, multiple servo bands 1 are sandwiched between guide bands 3 on the magnetic layer of the magnetic tape MT. Multiple regions 2 sandwiched between two servo bands form data bands. Servo patterns are magnetized regions formed by magnetizing specific regions of the magnetic layer with a servo write head. The regions magnetized by the servo write head (the positions where servo patterns are formed) are determined by standards. For example, in the industry-standard LTO Ultrium format tape, multiple servo patterns inclined with respect to the tape width direction are formed on the servo bands during magnetic tape manufacturing, as shown in FIG. 7. Specifically, in FIG. 7, a servo frame SF on servo band 1 is composed of a servo subframe 1 (SSF1) and a servo subframe 2 (SSF2). Servo subframe 1 is composed of an A burst (labeled A in FIG. 7) and a B burst (labeled B in FIG. 7). The A burst is composed of servo patterns A1 to A5, and the B burst is composed of servo patterns B1 to B5. On the other hand, servo subframe 2 is composed of a C burst (reference symbol C in FIG. 7) and a D burst (reference symbol D in FIG. 7). The C burst is composed of servo patterns C1 to C4, and the D burst is composed of servo patterns D1 to D4. These 18 servo patterns are arranged in subframes, arranged in a 5, 5, 4, 4, 5 ...

[0059] [Magnetic tape cartridge] Before being loaded into a magnetic tape device and after being removed from the magnetic tape device, a magnetic tape cartridge generally contains a magnetic tape wound around a cartridge reel within the cartridge body. The cartridge reel is rotatably provided within the cartridge body. Widely used magnetic tape cartridges include single-reel magnetic tape cartridges with one reel within the cartridge body and twin-reel magnetic tape cartridges with two reels within the cartridge body. The magnetic tape cartridge can be a single-reel magnetic tape cartridge in one form, or a twin-reel magnetic tape cartridge in another form. For twin-reel magnetic tape cartridges, the cartridge reel refers to the reel onto which the magnetic tape is primarily wound when stored after data has been recorded and / or played back, and the other reel is referred to as the take-up reel. When a single-reel magnetic tape cartridge is loaded into a magnetic tape device for recording and / or reproducing data on the magnetic tape, the magnetic tape is pulled out from the magnetic tape cartridge and wound onto the take-up reel of the magnetic tape device, as shown in FIG. 5, for example. A magnetic head is disposed in the magnetic tape transport path from the magnetic tape cartridge to the take-up reel. The magnetic tape runs by being fed out and taken up between the cartridge reel (also called the "supply reel") of the magnetic tape cartridge and the take-up reel of the magnetic tape device. During this time, data is recorded and / or reproduced by, for example, contact and sliding between the magnetic head and the magnetic layer surface of the magnetic tape. In contrast, a dual-reel magnetic tape cartridge is provided with both a supply reel and a take-up reel inside the magnetic tape cartridge. In one embodiment, the magnetic tape cartridge is preferably a single-reel magnetic tape cartridge, which has been mainly adopted in the data storage field in recent years.

[0060] In one embodiment, the magnetic tape cartridge may include a cartridge memory. The cartridge memory may be, for example, a nonvolatile memory, and angle θ adjustment information may already be recorded therein, or angle θ adjustment information may be recorded therein. The angle θ adjustment information is information for adjusting the angle θ while the magnetic tape is running in the magnetic tape device. For example, the angle θ adjustment information may record the value of the servo band spacing at each position in the longitudinal direction of the magnetic tape when data is recorded. For example, when reproducing data recorded on the magnetic tape, the value of the servo band spacing may be measured during reproduction, and the angle θ may be changed by a control device of the magnetic tape device so that the absolute value of the difference between the servo band spacing at the same longitudinal position recorded in the cartridge memory during recording approaches zero.

[0061] Fig. 8 is a perspective view of an example of a magnetic tape cartridge, which shows a single-reel magnetic tape cartridge.

[0062] The magnetic tape cartridge 13 shown in Fig. 8 has a case 112. The case 112 is formed in the shape of a rectangular box. The case 112 is usually made of a resin such as polycarbonate. Only one reel 130 is rotatably housed inside the case 112.

[0063] Fig. 9 is a perspective view when the magnetic tape starts to be wound around the reel, and Fig. 10 is a perspective view when the magnetic tape has been completely wound around the reel.

[0064] The reel 130 has a cylindrical reel hub 122 that forms the axial center portion.

[0065] The reel hub is a cylindrical member that forms the axial center around which the magnetic tape is wound within the magnetic tape cartridge. In the magnetic tape cartridge, the reel hub can be a cylindrical member with a single layer structure, or a cylindrical member with a multi-layer structure of two or more layers. From the viewpoints of manufacturing cost and ease of manufacturing, it is preferable that the reel hub be a cylindrical member with a single layer structure.

[0066] The inventors believe that a high rigidity of the reel hub around which the reel is wound inside the magnetic tape cartridge is desirable for increasing the media life value, for the following reasons. As the magnetic tape is wound around the reel hub, it is believed that it is subjected to a winding force toward the center, tending to deform in a direction that reduces its diameter. It is believed that the lower the rigidity of the reel hub, the more susceptible it is to deformation. It is believed that compressive stress occurs on the cartridge core side of the magnetic tape in a direction that shortens the tape length in response to deformation of the reel hub. This compressive stress then generates tensile stress in a direction that expands the tape width. The greater the stress generated, the more likely the magnetic tape is to deform significantly during storage in the magnetic tape cartridge. On the other hand, a reel hub with high rigidity can suppress the above-mentioned deformation and therefore the generation of the above-mentioned stress, which is believed to contribute to extending the media life. From this perspective, in one embodiment, the flexural modulus of the material constituting at least the outer peripheral surface layer of the reel hub is preferably 5 GPa or more, more preferably 6 GPa or more, even more preferably 7 GPa or more, and even more preferably 8 GPa or more. The flexural modulus can be, for example, 20 GPa or less, 15 GPa or less, or 10 GPa or less. However, since a high flexural modulus is preferable from the viewpoint of suppressing deformation of the reel hub, the flexural modulus may exceed the value exemplified here.

[0067] If the reel hub is a cylindrical member with a single layer, the flexural modulus is that of the material constituting the cylindrical member. On the other hand, if the reel hub is a cylindrical member with two or more layers, the flexural modulus is that of the material constituting at least the outer surface layer of the reel hub. In this specification and the present invention, the "flexural modulus" refers to a value determined in accordance with JIS (Japanese Industrial Standards) K 7171:2016. JIS K 7171:2016 is a Japanese Industrial Standard based on ISO (International Organization for Standardization) 178 and Amendment 1:2013, the fifth edition of which was published in 2010, without any technical changes. The test specimen used to measure the flexural modulus is prepared in accordance with Section 6, "Test Specimen," of JIS K 7171:2016.

[0068] Examples of materials constituting the reel hub include resin and metal. An example of a metal is aluminum. From the standpoints of cost and productivity, resin is preferred. Examples of resin include fiber-reinforced resin. Examples of fiber-reinforced resin include glass fiber-reinforced resin and carbon fiber-reinforced resin. Fiber-reinforced polycarbonate is preferred as such a fiber-reinforced resin. This is because polycarbonate is easily procured and can be molded with high precision and low cost using a general-purpose molding machine such as an injection molding machine. Furthermore, the glass fiber content of the glass fiber-reinforced resin is preferably 15% by mass or more. The higher the glass fiber content, the higher the flexural modulus of the glass fiber-reinforced resin tends to be. For example, the glass fiber content of the glass fiber-reinforced resin can be 50% by mass or less or 40% by mass or less. In one embodiment, glass fiber-reinforced polycarbonate is preferred as the resin constituting the reel hub. Furthermore, examples of resins constituting the reel hub include high-strength resins commonly known as super engineering plastics. An example of a super engineering plastic is polyphenylene sulfide (PPS).

[0069] The thickness of the reel hub is preferably in the range of 2.0 to 3.0 mm from the viewpoint of achieving both the strength of the reel hub and dimensional accuracy during molding. For reel hubs with a multi-layer structure of two or more layers, the thickness of the reel hub refers to the total thickness of the layers. The outer diameter of the reel hub is usually determined by the specifications of the magnetic tape device and can be, for example, in the range of 20 to 60 mm.

[0070] At both ends of the reel hub 122, flanges (lower flange 124 and upper flange 126) are provided that protrude radially outward from the lower and upper ends of the reel hub 122, respectively. Here, with regard to "upper" and "lower," the side positioned at the top when the magnetic tape cartridge is loaded into the magnetic tape device is referred to as "upper," and the side positioned at the bottom is referred to as "lower." It is preferable that one or both of the lower flange 124 and the upper flange 126 be integrally formed with the reel hub 122 in order to reinforce the upper end side and / or the lower end side of the reel hub 122. "Integratedly formed" means that they are formed as a single member, rather than as separate members. In a first embodiment, the reel hub 122 and the upper flange 126 are formed as a single member, and this member is joined to the lower flange 124, which is formed as a separate member, by a known method. In the second embodiment, the reel hub 122 and the lower flange 124 are configured as a single member, and this member is joined to the upper flange 126, which is configured as a separate member, by a known method. The reel of the magnetic tape cartridge may be in either form. Each member can be manufactured by a known molding method such as injection molding.

[0071] The magnetic tape MT is wound around the reel hub 122, starting from the tape inner end Tf (see FIG. 9). Reducing the tension applied in the longitudinal direction of the magnetic tape when winding the magnetic tape around the reel hub of the cartridge reel during manufacturing of the magnetic tape cartridge (hereinafter also referred to as "manufacturing winding tension") can also contribute to extending the media life value. From this perspective, the manufacturing winding tension is preferably 0.40 N or less, and can be, for example, 0.30 N or less. The manufacturing winding tension can be, for example, 0.10 N or more or 0.20 N or more, or can be tension-free. The manufacturing winding tension can be a constant value or can be varied. The manufacturing winding tension is a set value set in the manufacturing device for the magnetic tape cartridge.

[0072] The side wall of the case 112 has an opening 114 for pulling out the magnetic tape MT wound on the reel 130, and a leader pin 116 is fixed to the outer end Te of the magnetic tape MT pulled out from this opening 114, and is engaged and pulled out by a pull-out member (not shown) of a magnetic tape device (not shown).

[0073] The opening 114 is opened and closed by a door 118. The door 118 is formed in the shape of a rectangular plate large enough to close the opening 114, and is biased by a biasing member (not shown) in the direction of closing the opening 114. When the magnetic tape cartridge 13 is loaded into the magnetic tape device, the door 118 is opened against the biasing force of the biasing member.

[0074] Known techniques can be applied to other details of the magnetic tape cartridge. The total length of the magnetic tape housed in the magnetic tape cartridge is not particularly limited and can be, for example, in the range of about 800 m to 2500 m. The longer the total length of the tape housed in one magnetic tape cartridge, the more preferable it is from the viewpoint of increasing the capacity of the magnetic tape cartridge.

[0075] [Magnetic tape] The magnetic tape device includes a magnetic tape. The magnetic tape device may include a detachable magnetic tape cartridge containing the magnetic tape wound around a reel. The magnetic tape will be described in more detail below.

[0076] <Nonmagnetic support> The magnetic tape has a non-magnetic support and a magnetic layer containing ferromagnetic powder. Examples of the non-magnetic support (hereinafter simply referred to as "support") include known biaxially oriented polyethylene terephthalate, polyethylene naphthalate, polyamide, polyamideimide, and aromatic polyamide.

[0077] In one embodiment, the non-magnetic support of the magnetic tape can be an aromatic polyester support. In the present invention and this specification, "aromatic polyester" refers to a resin containing an aromatic backbone and multiple ester bonds, and "aromatic polyester support" refers to a support containing at least one layer of aromatic polyester film. "Aromatic polyester film" refers to a film in which the component that constitutes the film in the largest proportion by mass is an aromatic polyester. In the present invention and this specification, "aromatic polyester support" includes support in which all resin films contained in the support are aromatic polyester films, and support containing an aromatic polyester film and another resin film. Specific forms of aromatic polyester support include a single-layer aromatic polyester film, a laminate film of two or more aromatic polyester film layers with the same constituent components, a laminate film of two or more aromatic polyester film layers with different constituent components, and a laminate film containing one or more aromatic polyester film layers and one or more resin film layers other than aromatic polyester. An adhesive layer or the like may optionally be included between two adjacent layers in the laminate film. Furthermore, the aromatic polyester support may optionally include a metal film and / or metal oxide film formed by vapor deposition or the like on one or both surfaces. The same applies to the "polyethylene terephthalate support" and the "polyethylene naphthalate support" in the present invention and this specification.

[0078] The aromatic ring contained in the aromatic skeleton of the aromatic polyester is not particularly limited, and specific examples of the aromatic ring include a benzene ring and a naphthalene ring. For example, polyethylene terephthalate (PET) is a polyester containing a benzene ring, and is a resin obtained by polycondensation of ethylene glycol with terephthalic acid and / or dimethyl terephthalate. The term "polyethylene terephthalate" used in this specification and the present invention also includes structures having one or more other components (e.g., copolymerized components, components introduced into the terminals or side chains, etc.) in addition to the above components. Polyethylene naphthalate (PEN) is a polyester containing a naphthalene ring, and is a resin obtained by esterifying dimethyl 2,6-naphthalenedicarboxylate with ethylene glycol, followed by transesterification and polycondensation. The term "polyethylene naphthalate" used in this invention and this specification also includes structures having one or more other components (e.g., copolymerized components, components introduced into the terminals or side chains, etc.) in addition to the above components.

[0079] In one embodiment, the non-magnetic support of the magnetic tape can be an aromatic polyamide support. In the present invention and this specification, "aromatic polyamide" refers to a resin containing an aromatic backbone and multiple amide bonds. The aromatic ring contained in the aromatic backbone of the aromatic polyamide is not particularly limited. Specific examples of aromatic rings include a benzene ring. An "aromatic polyamide support" refers to a support containing at least one layer of aromatic polyamide film. An "aromatic polyamide film" refers to a film in which the component that constitutes the film in the largest proportion by mass is an aromatic polyamide. In the present invention and this specification, "aromatic polyamide support" includes support in which all resin films contained in the support are aromatic polyamide films and support containing an aromatic polyamide film and another resin film. Specific forms of aromatic polyamide support include a single-layer aromatic polyamide film, a laminate film of two or more layers of aromatic polyamide film with the same constituent components, a laminate film of two or more layers of aromatic polyamide film with different constituent components, and a laminate film containing one or more layers of aromatic polyamide film and one or more layers of resin film other than aromatic polyamide. The laminated film may optionally contain an adhesive layer between two adjacent layers, and the aromatic polyamide support may optionally contain a metal film and / or a metal oxide film formed by vapor deposition or the like on one or both surfaces.

[0080] The non-magnetic support may be a biaxially stretched film, and may be a film that has been subjected to corona discharge, plasma treatment, easy-adhesion treatment, heat treatment, or the like.

[0081] An example of an index of the physical properties of a non-magnetic support is its moisture content. In the present invention and this specification, the moisture content of a non-magnetic support is a value determined by the following method. The moisture contents shown in the tables below are values ​​determined by the following method. A sample piece (e.g., a sample piece with a mass of several grams) cut from the non-magnetic support for which moisture content is to be measured is dried to a constant weight in a vacuum dryer at a temperature of 180°C and a pressure of 100 Pa (Pascal) or less. The mass of the sample piece dried in this manner is designated as W1. W1 is a value measured in a measurement environment at a temperature of 23°C and a relative humidity of 50% within 30 seconds after removal from the vacuum dryer. Next, W2 is the mass of the sample piece after placing it in an environment at a temperature of 25°C and a relative humidity of 75% for 48 hours. W2 is a value measured in a measurement environment at a temperature of 23°C and a relative humidity of 50% within 30 seconds after removal from the environment. The moisture content is calculated using the following formula. Moisture content (%)=[(W2-W1) / W1]×100 For example, after removing the magnetic layer and other portions of the magnetic tape other than the non-magnetic support by a known method (such as film removal using an organic solvent), the water content of the non-magnetic support can be determined by the above method.

[0082] In one embodiment, the non-magnetic support of the magnetic tape preferably has a moisture content of 2.0% or less, more preferably 1.8% or less, even more preferably 1.6% or less, even more preferably 1.4% or less, even more preferably 1.2% or less, and even more preferably 1.0% or less. The moisture content of the non-magnetic support of the magnetic tape can be 0%, 0% or more, more than 0%, or 0.1% or more. Using a non-magnetic support with a low moisture content can contribute to increasing the media life value. This is primarily because using a non-magnetic support with a low moisture content is thought to contribute to reducing the value of "B" determined by the method described above.

[0083] Young's modulus can also be mentioned as an index of the physical properties of a non-magnetic support. In this invention and this specification, the Young's modulus of a non-magnetic support is a value measured by the following method in a measurement environment at a temperature of 23°C and a relative humidity of 50%. The Young's moduli shown in the table below are values ​​determined by the following method using a Tensilon manufactured by Toyo Baldwin Co., Ltd. as a universal tensile testing device. A sample piece cut from the nonmagnetic support to be measured is pulled using a universal tensile testing machine under conditions of a chuck distance of 100 mm, a pulling speed of 10 mm / min, and a chart speed of 500 mm / min. The universal tensile testing machine can be, for example, a commercially available universal tensile testing machine such as the Toyo Baldwin Tensilon, or a universal tensile testing machine with a known configuration. The Young's modulus of the sample piece in the longitudinal and transverse directions is calculated from the tangent to the rising portion of the load-elongation curve thus obtained. Here, the longitudinal and transverse directions of the sample piece refer to the longitudinal and transverse directions when the sample piece is contained in a magnetic tape. For example, after removing the magnetic layer and other portions of the non-magnetic support from the magnetic tape using a known method (e.g., removal using an organic solvent), the Young's modulus in the longitudinal and transverse directions of the non-magnetic support can be determined using the above method.

[0084] In one embodiment, the Young's modulus of the non-magnetic support of the magnetic tape in the longitudinal direction is preferably 3,000 MPa or more, more preferably 4,000 MPa or more, even more preferably 5,000 MPa or more, and even more preferably 6,000 MPa or more. The Young's modulus of the non-magnetic support of the magnetic tape in the longitudinal direction may be 15,000 MPa or less, 13,000 MPa or less, or 12,000 MPa or less. In the width direction, the Young's modulus of the non-magnetic support of the magnetic tape in the width direction is preferably 2,000 MPa or more, more preferably 3,000 MPa or more, even more preferably 4,000 MPa or more, and even more preferably 5,000 MPa or more. The Young's modulus of the non-magnetic support of the magnetic tape in the width direction may be 12,000 MPa or less, 11,000 MPa or less, or 10,000 MPa or less. During magnetic tape production, the non-magnetic support is typically used with the MD (machine direction) of the film as the longitudinal direction and the TD (transverse direction) as the width direction. In one embodiment, the Young's modulus in the longitudinal direction is preferably greater than the Young's modulus in the width direction, and the difference (Young's modulus in the longitudinal direction - Young's modulus in the width direction) is more preferably in the range of 800 to 3000 MPa. The medium life can also be controlled by the Young's modulus of the non-magnetic support.

[0085] The water content and Young's modulus of the non-magnetic support can be controlled by the types and mixing ratios of the components constituting the support, the manufacturing conditions of the support, etc. For example, by adjusting the stretching ratio in each direction in a biaxial stretching process, the Young's modulus in the longitudinal direction and the Young's modulus in the width direction can be controlled.

[0086] <Magnetic layer> (Ferromagnetic powder) The ferromagnetic powder contained in the magnetic layer of the magnetic tape can be one or a combination of two or more ferromagnetic powders known for use in the magnetic layers of various magnetic recording media. Using a ferromagnetic powder with a small average particle size is preferable from the viewpoint of improving recording density. From this viewpoint, the average particle size of the ferromagnetic powder is preferably 50 nm or less, more preferably 45 nm or less, even more preferably 40 nm or less, even more preferably 35 nm or less, even more preferably 30 nm or less, even more preferably 25 nm or less, and even more preferably 20 nm or less. On the other hand, from the viewpoint of magnetization stability, the average particle size of the ferromagnetic powder is preferably 5 nm or more, more preferably 8 nm or more, even more preferably 10 nm or more, even more preferably 15 nm or more, and even more preferably 20 nm or more.

[0087] Hexagonal ferrite powder A preferred example of the ferromagnetic powder is hexagonal ferrite powder. For details of the hexagonal ferrite powder, see, for example, JP 2011-225417 A, paragraphs 0012 to 0030, JP 2011-216149 A, paragraphs 0134 to 0136, JP 2012-204726 A, paragraphs 0013 to 0030, and JP 2015-127985 A, paragraphs 0029 to 0084.

[0088] In the present invention and this specification, "hexagonal ferrite powder" refers to a ferromagnetic powder in which a hexagonal ferrite crystal structure is detected as the main phase by X-ray diffraction analysis. The main phase refers to the structure to which the highest diffraction peak belongs in the X-ray diffraction spectrum obtained by X-ray diffraction analysis. For example, if the highest diffraction peak in the X-ray diffraction spectrum obtained by X-ray diffraction analysis is assigned to the hexagonal ferrite crystal structure, it is determined that the hexagonal ferrite crystal structure has been detected as the main phase. If only a single structure is detected by X-ray diffraction analysis, this detected structure is considered to be the main phase. The hexagonal ferrite crystal structure contains at least iron atoms, divalent metal atoms, and oxygen atoms as constituent atoms. Divalent metal atoms are metal atoms that can become divalent cations as ions, and examples of such atoms include alkaline earth metal atoms such as strontium atoms, barium atoms, and calcium atoms, and lead atoms. In the present invention and this specification, "hexagonal strontium ferrite powder" refers to a powder in which the main divalent metal atom contained therein is strontium atom, and "hexagonal barium ferrite powder" refers to a powder in which the main divalent metal atom contained therein is barium atom. "Main divalent metal atom" refers to the divalent metal atom that is the most abundant, on an atomic % basis, among the divalent metal atoms contained in the powder. However, rare earth atoms are not included in the above divalent metal atoms. In the present invention and this specification, "rare earth atom" refers to a powder selected from the group consisting of scandium atom (Sc), yttrium atom (Y), and lanthanoid atom. The lanthanoid atom is selected from the group consisting of lanthanum atom (La), cerium atom (Ce), praseodymium atom (Pr), neodymium atom (Nd), promethium atom (Pm), samarium atom (Sm), europium atom (Eu), gadolinium atom (Gd), terbium atom (Tb), dysprosium atom (Dy), holmium atom (Ho), erbium atom (Er), thulium atom (Tm), ytterbium atom (Yb), and lutetium atom (Lu).

[0089] Hereinafter, hexagonal strontium ferrite powder, which is one form of hexagonal ferrite powder, will be described in more detail.

[0090] The activation volume of the hexagonal strontium ferrite powder is preferably 800 to 1600 nm 3 The microparticulated hexagonal strontium ferrite powder exhibiting an activation volume in the above range is suitable for producing a magnetic tape that exhibits excellent electromagnetic conversion characteristics. The activation volume of the hexagonal strontium ferrite powder is preferably 800 nm 3 or more, for example, 850 nm 3 From the viewpoint of further improving the electromagnetic conversion characteristics, the activation volume of the hexagonal strontium ferrite powder can be 1500 nm or more. 3 More preferably, it is 1400 nm or less. 3 More preferably, it is 1300 nm or less. 3 More preferably, it is 1200 nm or less. 3 It is even more preferable that the value is equal to or less than 1100 nm. 3 It is even more preferable that the activation volume of the hexagonal barium ferrite powder is equal to or less than 10 ...

[0091] "Activation volume" is a unit of magnetization reversal and is an index showing the magnetic size of a particle. The activation volume described in this invention and this specification and the anisotropy constant Ku described below are values ​​obtained by measuring the coercive force Hc using a vibrating sample magnetometer at magnetic field sweep speeds of 3 minutes and 30 minutes (measurement temperature: 23°C ± 1°C) in the coercive force Hc measurement section, and by using the following relational expression between Hc and activation volume V. Note that the unit of the anisotropy constant Ku is 1 erg / cc = 1.0 x 10 -1 J / m 3 is. Hc=2Ku / Ms{1-[(kT / KuV)ln(At / 0.693)] 1 / 2 } [In the above formula, Ku: anisotropy constant (unit: J / m 3 ), Ms: saturation magnetization (unit: kA / m), k: Boltzmann constant, T: absolute temperature (unit: K), V: activation volume (unit: cm 3 ), A: spin precession frequency (unit: s -1 ), t: magnetic field reversal time (unit: s)]

[0092] The anisotropy constant Ku can be used as an index for reducing thermal fluctuation, in other words, improving thermal stability. The hexagonal strontium ferrite powder preferably has an anisotropy constant of 1.8×10 5 J / m 3 and more preferably 2.0×10 5 J / m 3 The Ku of the hexagonal strontium ferrite powder can be, for example, 2.5×10 5 J / m 3 However, since a higher Ku value means higher thermal stability and is therefore preferred, the Ku value is not limited to the above-mentioned values.

[0093] The hexagonal strontium ferrite powder may or may not contain rare earth atoms. When the hexagonal strontium ferrite powder contains rare earth atoms, it is preferable that the rare earth atoms are contained at a content (bulk content) of 0.5 to 5.0 atomic % relative to 100 atomic % of iron atoms. In one embodiment, the hexagonal strontium ferrite powder containing rare earth atoms can have rare earth atoms unevenly distributed in the surface layer portion. In the present invention and this specification, the term "surface layer distribution of rare earth atoms" refers to the ratio of the rare earth atom content relative to 100 atomic % of iron atoms in a solution obtained by partially dissolving a hexagonal strontium ferrite powder in an acid (hereinafter referred to as "surface layer content of rare earth atoms" or simply "surface layer content" with respect to rare earth atoms) to the ratio of the rare earth atom content relative to 100 atomic % of iron atoms in a solution obtained by completely dissolving a hexagonal strontium ferrite powder in an acid (hereinafter referred to as "bulk content of rare earth atoms" or simply "bulk content" with respect to rare earth atoms), Rare earth atom surface content / rare earth atom bulk content > 1.0 This means that the ratio of "surface rare earth atom content / bulk rare earth atom content > 1.0" is satisfied. The rare earth atom content of the hexagonal strontium ferrite powder described below is synonymous with the rare earth atom bulk content. In contrast, partial dissolution using an acid dissolves the surface layer of the particles constituting the hexagonal strontium ferrite powder, so the rare earth atom content in the solution obtained by partial dissolution is the rare earth atom content in the surface layer of the particles constituting the hexagonal strontium ferrite powder. When the surface rare earth atom content satisfies the ratio "surface rare earth atom content / bulk rare earth atom content > 1.0", this means that the rare earth atoms are unevenly distributed in the surface layer of the particles constituting the hexagonal strontium ferrite powder (i.e., present in greater amounts in the surface layer than in the interior). In the present invention and this specification, the surface layer refers to a partial region extending from the surface toward the interior of the particles constituting the hexagonal strontium ferrite powder.

[0094] When the hexagonal strontium ferrite powder contains rare earth atoms, the rare earth atom content (bulk content) is preferably in the range of 0.5 to 5.0 atomic percent relative to 100 atomic percent of iron atoms. Having rare earth atoms in the above-mentioned bulk content range and having the rare earth atoms unevenly distributed in the surface layers of the particles constituting the hexagonal strontium ferrite powder is thought to contribute to suppressing a decrease in playback output during repeated playback. This is presumably because the hexagonal strontium ferrite powder contains rare earth atoms in the above-mentioned bulk content range and having the rare earth atoms unevenly distributed in the surface layers of the particles constituting the hexagonal strontium ferrite powder can increase the anisotropy constant Ku. The higher the anisotropy constant Ku, the more the occurrence of a phenomenon known as thermal fluctuation can be suppressed (in other words, thermal stability can be improved). By suppressing the occurrence of thermal fluctuation, the decrease in playback output during repeated playback can be suppressed. It is speculated that the uneven distribution of rare earth atoms in the surface layer of hexagonal strontium ferrite powder particles contributes to stabilizing the spin of the iron (Fe) sites in the crystal lattice in the surface layer, thereby increasing the anisotropy constant Ku. Furthermore, it is believed that using a hexagonal strontium ferrite powder having rare earth atoms unevenly distributed in the surface layer as the ferromagnetic powder for the magnetic layer also contributes to preventing the magnetic layer surface from being worn away by friction with the magnetic head. That is, it is believed that a hexagonal strontium ferrite powder having rare earth atoms unevenly distributed in the surface layer can also contribute to improving the running durability of magnetic tapes. This is believed to be because the uneven distribution of rare earth atoms on the surfaces of the particles that make up the hexagonal strontium ferrite powder contributes to improving the interaction between the particle surfaces and organic substances (e.g., binders and / or additives) contained in the magnetic layer, thereby improving the strength of the magnetic layer. From the viewpoint of further suppressing a decrease in reproduction output during repeated reproduction and / or further improving running durability, the rare earth atom content (bulk content) is more preferably in the range of 0.5 to 4.5 atomic %, even more preferably in the range of 1.0 to 4.5 atomic %, and even more preferably in the range of 1.5 to 4.5 atomic %.

[0095] The bulk content is the content determined by completely dissolving the hexagonal strontium ferrite powder. In the present invention and this specification, unless otherwise specified, the content of an atom refers to the bulk content determined by completely dissolving the hexagonal strontium ferrite powder. The hexagonal strontium ferrite powder containing rare earth atoms may contain only one rare earth atom or two or more rare earth atoms. When two or more rare earth atoms are contained, the bulk content is determined for the total of the two or more rare earth atoms. This also applies to other components in the present invention and this specification. That is, unless otherwise specified, a certain component may be used alone or in combination with two or more. When two or more components are used, the content or content refers to the total of the two or more components.

[0096] When the hexagonal strontium ferrite powder contains rare earth atoms, the rare earth atoms may be any one or more of rare earth atoms. From the viewpoint of further suppressing the decrease in playback output during repeated playback, preferred rare earth atoms include neodymium atoms, samarium atoms, yttrium atoms, and dysprosium atoms, with neodymium atoms, samarium atoms, and yttrium atoms being more preferred, and neodymium atoms being even more preferred.

[0097] In a hexagonal strontium ferrite powder having rare earth atoms unevenly distributed in the surface layer, the rare earth atoms need only be unevenly distributed in the surface layer of the particles constituting the hexagonal strontium ferrite powder, and the degree of uneven distribution is not limited. For example, for a hexagonal strontium ferrite powder having rare earth atoms unevenly distributed in the surface layer, the ratio of the surface content of rare earth atoms determined by partial dissolution under the dissolution conditions described below to the bulk content of rare earth atoms determined by complete dissolution under the dissolution conditions described below, i.e., "surface content / bulk content," is greater than 1.0 and can be 1.5 or greater. A "surface content / bulk content" ratio greater than 1.0 means that the rare earth atoms are unevenly distributed in the surface layer (i.e., present in greater amounts than in the interior) in the particles constituting the hexagonal strontium ferrite powder. Furthermore, the ratio of the surface content of rare earth atoms determined by partial dissolution under the dissolution conditions described below to the bulk content of rare earth atoms determined by complete dissolution under the dissolution conditions described below, i.e., "surface content / bulk content," can be, for example, 10.0 or less, 9.0 or less, 8.0 or less, 7.0 or less, 6.0 or less, 5.0 or less, or 4.0 or less. However, in a hexagonal strontium ferrite powder having rare earth atoms unevenly distributed in the surface layers, it is sufficient that the rare earth atoms are unevenly distributed in the surface layers of the particles constituting the hexagonal strontium ferrite powder, and the above "surface content / bulk content" is not limited to the exemplified upper or lower limits.

[0098] The partial and total dissolution of hexagonal strontium ferrite powder is described below. For hexagonal strontium ferrite powder present as a powder, sample powders to be partially and completely dissolved are collected from the same powder lot. On the other hand, for hexagonal strontium ferrite powder contained in the magnetic layer of a magnetic tape, a portion of the hexagonal strontium ferrite powder removed from the magnetic layer is subjected to partial dissolution, and another portion is subjected to total dissolution. The hexagonal strontium ferrite powder can be removed from the magnetic layer by, for example, the method described in paragraph 0032 of JP 2015-91747 A. The term "partial dissolution" as used herein refers to dissolving the hexagonal strontium ferrite powder to such an extent that the remaining hexagonal strontium ferrite powder can be visually confirmed in the liquid at the end of dissolution. For example, partial dissolution can dissolve 10 to 20 mass% of the particles constituting the hexagonal strontium ferrite powder, with the total particles being 100 mass%. On the other hand, the term "complete dissolution" as used herein refers to dissolving the hexagonal strontium ferrite powder to such an extent that the remaining hexagonal strontium ferrite powder cannot be visually confirmed in the liquid at the end of dissolution. The partial dissolution and measurement of the surface layer content are carried out, for example, by the following method. Note that the dissolution conditions such as the amount of sample powder described below are merely examples, and any dissolution conditions that allow partial or complete dissolution can be adopted. A container (e.g., a beaker) containing 12 mg of sample powder and 10 mL of 1 mol / L hydrochloric acid is placed on a hot plate set at 70°C for 1 hour. The resulting solution is filtered through a 0.1 μm membrane filter. Elemental analysis of the filtrate is performed using an inductively coupled plasma (ICP) analyzer. This allows the surface content of rare earth atoms relative to 100 atomic percent iron atoms to be determined. If multiple types of rare earth atoms are detected by elemental analysis, the total content of all rare earth atoms is taken as the surface content. This also applies to measurements of bulk content. On the other hand, the total dissolved and bulk contents are measured, for example, by the following method. A container (e.g., a beaker) containing 12 mg of sample powder and 10 mL of 4 mol / L hydrochloric acid is placed on a hot plate set at 80°C for 3 hours. After that, the bulk content relative to 100 atomic % of iron atoms can be determined by carrying out the same procedures as for the partial dissolution and surface layer content measurements described above.

[0099] From the viewpoint of increasing the reproduction output when reproducing data recorded on magnetic tape, it is desirable that the mass magnetization σs of the ferromagnetic powder contained in the magnetic tape is high. In this regard, hexagonal strontium ferrite powder that contains rare earth atoms but does not have the rare earth atoms unevenly distributed in the surface layer tends to have a significantly lower σs than hexagonal strontium ferrite powder that does not contain rare earth atoms. On the other hand, hexagonal strontium ferrite powder that has the rare earth atoms unevenly distributed in the surface layer is considered preferable in order to suppress such a large decrease in σs. In one embodiment, the σs of the hexagonal strontium ferrite powder is 45 A·m 2 / kg or more, and 47A·m 2 / kg or more. On the other hand, from the viewpoint of noise reduction, σs is 80A·m 2 / kg or less is preferable, and 60A·m 2 / kg or less is more preferable. σs can be measured using a known measuring device capable of measuring magnetic properties, such as a vibrating sample magnetometer. In the present invention and this specification, unless otherwise specified, the mass magnetization σs is a value measured at a magnetic field strength of 15 kOe. 1 [kOe] = 10 6 / 4π[A / m].

[0100] Regarding the content (bulk content) of constituent atoms of the hexagonal strontium ferrite powder, the strontium atom content can be, for example, in the range of 2.0 to 15.0 atomic % relative to 100 atomic % of iron atoms. In one embodiment, the hexagonal strontium ferrite powder can contain only strontium atoms as divalent metal atoms. In another embodiment, the hexagonal strontium ferrite powder can contain one or more other divalent metal atoms in addition to strontium atoms. For example, barium atoms and / or calcium atoms can be contained. When divalent metal atoms other than strontium atoms are contained, the barium atom content and calcium atom content in the hexagonal strontium ferrite powder can each be, for example, in the range of 0.05 to 5.0 atomic % relative to 100 atomic % of iron atoms.

[0101] Known crystal structures of hexagonal ferrite include magnetoplumbite type (also called "M type"), W type, Y type, and Z type. The hexagonal strontium ferrite powder may have any of these crystal structures. The crystal structure can be confirmed by X-ray diffraction analysis. The hexagonal strontium ferrite powder may be one in which a single crystal structure or two or more types of crystal structures are detected by X-ray diffraction analysis. For example, in one embodiment, the hexagonal strontium ferrite powder may be one in which only the M-type crystal structure is detected by X-ray diffraction analysis. For example, the M-type hexagonal ferrite is AFe 12 O 19 The composition formula is represented by the formula: where A represents a divalent metal atom. When the hexagonal strontium ferrite powder is of M type, A is only strontium atom (Sr). Alternatively, when A contains multiple divalent metal atoms, strontium atom (Sr) accounts for the largest proportion on an atomic % basis, as described above. The divalent metal atom content of the hexagonal strontium ferrite powder is usually determined by the type of crystalline structure of the hexagonal ferrite and is not particularly limited. The same applies to the iron atom content and oxygen atom content. The hexagonal strontium ferrite powder contains at least iron atoms, strontium atoms, and oxygen atoms, and may further contain rare earth atoms. Furthermore, the hexagonal strontium ferrite powder may or may not contain atoms other than these atoms. As an example, the hexagonal strontium ferrite powder may contain aluminum atoms (Al). The content of aluminum atoms can be, for example, 0.5 to 10.0 atomic % relative to 100 atomic % of iron atoms. From the viewpoint of further suppressing a decrease in playback output during repeated playback, the hexagonal strontium ferrite powder contains iron atoms, strontium atoms, oxygen atoms, and rare earth atoms, and the content of atoms other than these atoms is preferably 10.0 atomic % or less, more preferably 0 to 5.0 atomic %, relative to 100 atomic % of iron atoms, and may even be 0 atomic %. That is, in one embodiment, the hexagonal strontium ferrite powder may contain no atoms other than iron atoms, strontium atoms, oxygen atoms, and rare earth atoms. The content expressed in atomic % above is determined by converting the content (unit: mass %) of each atom obtained by completely dissolving the hexagonal strontium ferrite powder into a value expressed in atomic % using the atomic weight of each atom. Furthermore, in the present invention and this specification, "not containing" a certain atom means that the content is 0 mass % when completely dissolved and measured by an ICP analyzer. The detection limit of an ICP analyzer is usually 0.01 ppm (parts per million) or less by mass. The above term "free from" is used to mean that the substance is contained in an amount below the detection limit of the ICP analyzer.In one form, the hexagonal strontium ferrite powder can be one that does not contain bismuth atoms (Bi).

[0102] metal powder A preferred example of the ferromagnetic powder is ferromagnetic metal powder. For details of the ferromagnetic metal powder, see, for example, paragraphs 0137 to 0141 of JP-A No. 2011-216149 and paragraphs 0009 to 0023 of JP-A No. 2005-251351.

[0103] ε-iron oxide powder A preferred example of the ferromagnetic powder is ε-iron oxide powder. In the present invention and this specification, the term "ε-iron oxide powder" refers to a ferromagnetic powder in which an ε-iron oxide crystalline structure is detected as the main phase by X-ray diffraction analysis. For example, if the highest intensity diffraction peak in an X-ray diffraction spectrum obtained by X-ray diffraction analysis is assigned to the ε-iron oxide crystalline structure, it is determined that the ε-iron oxide crystalline structure is detected as the main phase. Known methods for producing ε-iron oxide powder include a method using goethite and a reverse micelle method. All of these production methods are publicly known. For a method for producing ε-iron oxide powder in which part of the Fe atoms are replaced by atoms such as Ga, Co, Ti, Al, or Rh, see, for example, J. Jpn. Soc. Powder Metallurgy, Vol. 61, Supplement, No. S1, pp. S280-S284 and J. Mater. Chem. C, 2013, 1, pp. 5200-5206. However, the method for producing the ε-iron oxide powder that can be used as the ferromagnetic powder in the magnetic layer of the magnetic tape is not limited to the method given here.

[0104] The activation volume of the ε-iron oxide powder is preferably 300 to 1500 nm 3 The finely divided ε-iron oxide powder exhibiting an activation volume in the above range is suitable for producing a magnetic tape that exhibits excellent electromagnetic conversion characteristics. The activation volume of the ε-iron oxide powder is preferably 300 nm 3 For example, 500 nm or more 3 From the viewpoint of further improving the electromagnetic conversion characteristics, the activation volume of the ε-iron oxide powder can be 1400 nm or more. 3 More preferably, it is 1300 nm or less. 3 More preferably, it is 1200 nm or less. 3 More preferably, it is 1100 nm or less. 3 It is even more preferred that:

[0105] The anisotropy constant Ku can be used as an index of the reduction in thermal fluctuation, in other words, the improvement in thermal stability. The ε-iron oxide powder is preferably 3.0×10 4 J / m 3 and more preferably 8.0×10 4 J / m 3 The Ku of the ε-iron oxide powder can be, for example, 3.0×10 5 J / m 3 However, since a higher Ku value means higher thermal stability and is therefore preferred, the Ku value is not limited to the above-mentioned values.

[0106] From the viewpoint of increasing the reproduction output when reproducing data recorded on a magnetic tape, it is desirable that the mass magnetization σs of the ferromagnetic powder contained in the magnetic tape is high. In this regard, in one embodiment, the σs of the ε-iron oxide powder is 8 A m 2 / kg or more, and 12 A m 2 On the other hand, the σs of ε-iron oxide powder can be 40 A m 2 / kg or less, and 35A·m 2 / kg or less is more preferable.

[0107] In the present invention and this specification, unless otherwise specified, the average particle size of various powders such as ferromagnetic powders is a value measured by the following method using a transmission electron microscope. The powder is photographed using a transmission electron microscope at a magnification of 100,000x, and a photograph of the particles that make up the powder is obtained by printing it on photographic paper or displaying it on a display so that the total magnification is 500,000x. From the obtained particle photograph, the target particle is selected and the particle outline is traced with a digitizer to measure the particle (primary particle) size. Primary particles are independent particles that do not aggregate. The above measurements are performed on 500 randomly selected particles. The arithmetic mean of the particle sizes of the 500 particles thus obtained is the average particle size of the powder. The transmission electron microscope may be, for example, a Hitachi H-9000 transmission electron microscope. Furthermore, particle size measurements can be performed using known image analysis software, such as Carl Zeiss KS-400 image analysis software. Unless otherwise specified, the average particle sizes shown in the examples below are values ​​measured using a Hitachi H-9000 transmission electron microscope and Carl Zeiss KS-400 image analysis software. In this invention and this specification, "powder" refers to a collection of multiple particles. For example, "ferromagnetic powder" refers to a collection of multiple ferromagnetic particles. Furthermore, a collection of multiple particles is not limited to a configuration in which the particles constituting the collection are in direct contact with each other, but also includes a configuration in which binders, additives, etc., as described below, are interposed between the particles. The term "particle" is sometimes used to refer to powder.

[0108] As a method for collecting sample powder from the magnetic tape for particle size measurement, for example, the method described in paragraph 0015 of JP-A No. 2011-048878 can be used.

[0109] In the present invention and this specification, unless otherwise specified, the size of particles constituting the powder (particle size) is determined by the shape of the particles observed in the particle photograph. (1) In the case of needle-shaped, spindle-shaped, columnar (where the height is greater than the maximum diameter of the base), etc., the particle size is expressed by the length of the major axis that constitutes the particle, i.e., the major axis length. (2) In the case of a plate or columnar shape (where the thickness or height is smaller than the maximum major axis of the plate surface or base), it is expressed by the maximum major axis of the plate surface or base, (3) When the particle is spherical, polyhedral, irregular, etc., and the long axis of the particle cannot be identified from its shape, it is expressed as the equivalent circle diameter, which is determined by the circle projection method.

[0110] The average acicular ratio of a powder refers to the arithmetic average of the minor axis length of the particles measured in the above measurement, i.e., the minor axis length, the value of (major axis length / minor axis length) for each particle, and the values ​​obtained for the above 500 particles. Here, unless otherwise specified, the minor axis length refers to the length of the minor axis constituting the particle in the above definition of particle size (1), and in the same case (2), the thickness or height, respectively. In the case of (3), since there is no distinction between the major axis and the minor axis, (major axis length / minor axis length) is considered to be 1 for convenience. Unless otherwise specified, when the particle shape is specific, for example, in the case of the above definition of particle size (1), the average particle size is the average major axis length, in the case of definition (2), the average particle size is the average plate diameter, and in the case of definition (3), the average particle size is the average diameter (also called the average particle diameter or average particle size).

[0111] The content (filling rate) of the ferromagnetic powder in the magnetic layer is preferably in the range of 50 to 90 mass % and more preferably in the range of 60 to 90 mass % relative to the total mass of the magnetic layer. A high filling rate of the ferromagnetic powder in the magnetic layer is preferable from the viewpoint of improving recording density.

[0112] (binder) The magnetic tape may be a coated magnetic tape, and the magnetic layer may contain a binder. The binder is one or more resins. Various resins commonly used as binders for coated magnetic tapes can be used. For example, the binder may be selected from polyurethane resin, polyester resin, polyamide resin, vinyl chloride resin, acrylic resin copolymerized with styrene, acrylonitrile, methyl methacrylate, etc., cellulose resin such as nitrocellulose, epoxy resin, phenoxy resin, polyvinyl acetal, polyvinyl butyral, etc., and may be used alone or in combination. Among these, polyurethane resin, acrylic resin, cellulose resin, and vinyl chloride resin are preferred. These resins may be homopolymers or copolymers. These resins may also be used as binders in the nonmagnetic layer and / or backcoat layer, which will be described later. For details of the binders described above, see paragraphs 0028 to 0031 of JP 2010-24113 A. The average molecular weight of the resin used as the binder can be, for example, 10,000 or more and 200,000 or less in weight average molecular weight. The binder can be used in an amount of, for example, 1.0 to 30.0 parts by mass per 100.0 parts by mass of the ferromagnetic powder.

[0113] (hardening agent) A curing agent can also be used together with a resin usable as a binder. In one form, the curing agent can be a thermosetting compound, which undergoes a curing reaction (crosslinking reaction) upon heating. In another form, the curing agent can be a photocurable compound, which undergoes a curing reaction (crosslinking reaction) upon irradiation with light. As the curing reaction progresses during the magnetic layer-forming process, at least a portion of the curing agent can be included in the magnetic layer in a state of reaction (crosslinking) with other components, such as the binder. This also applies to layers formed using compositions containing a curing agent when the composition used to form other layers contains the curing agent. A preferred curing agent is a thermosetting compound, and polyisocyanate is suitable. For details about polyisocyanates, see paragraphs 0124-0125 of JP 2011-216149 A. The curing agent can be used in the magnetic layer-forming composition in an amount of, for example, 0 to 80 parts by weight per 100 parts by weight of the binder. From the perspective of improving the strength of the magnetic layer, 50 to 80 parts by weight is preferred.

[0114] (additives) The magnetic layer may contain one or more additives as needed. Commercially available additives can be selected and used depending on the desired properties. Alternatively, compounds synthesized by known methods can be used as additives. Additives can be used in any amount. Examples of additives include the curing agents mentioned above. Examples of additives contained in the magnetic layer include non-magnetic powders (e.g., inorganic powders, carbon black, etc.), lubricants, dispersants, dispersion aids, antifungal agents, antistatic agents, and antioxidants. For information on lubricants, see paragraphs 0030 to 0033, 0035, and 0036 of JP 2016-126817 A. The non-magnetic layer, described below, may contain a lubricant. For information on lubricants that can be contained in the non-magnetic layer, see paragraphs 0030, 0031, 0034, 0035, and 0036 of JP 2016-126817 A. For details on dispersants, see paragraphs 0061 and 0071 of JP 2012-133837 A. Furthermore, compounds having a polyalkyleneimine chain and a vinyl polymer chain can function as dispersants to improve the dispersibility of ferromagnetic powders. Furthermore, the above compounds can also contribute to improving the strength of the magnetic layer. Increasing the strength of the magnetic layer can lead to suppressing the occurrence of show-through, which will be described later. This can contribute to extending the media life value. For details on compounds having a polyalkyleneimine chain and a vinyl polymer chain, see paragraphs 0024 to 0064 of JP 2019-169225 A and the examples therein. The above compound is preferably contained in the magnetic layer in an amount of at least 0.5 parts by weight per 100.0 parts by weight of ferromagnetic powder, more preferably at least 1.0 part by weight, even more preferably at least 3.0 parts by weight, even more preferably at least 5.0 parts by weight, even more preferably at least 10.0 parts by weight, even more preferably at least 15.0 parts by weight, and even more preferably at least 200 parts by weight. The content of the above compound in the magnetic layer can be 40.0 parts by weight or less or 35.0 parts by weight or less per 100.0 parts by weight of ferromagnetic powder. One or more dispersants such as the above compounds may be added to the composition for forming the nonmagnetic layer.For dispersants that can be added to the nonmagnetic layer-forming composition, see paragraph 0061 of JP 2012-133837 A. Nonmagnetic powders that can be included in the magnetic layer include nonmagnetic powders that can function as abrasives and nonmagnetic powders (e.g., nonmagnetic colloidal particles) that can function as protrusion-forming agents that form moderately protruding protrusions on the surface of the magnetic layer. For abrasives, see paragraphs 0030 to 0032 of JP 2004-273070 A. As protrusion-forming agents, colloidal particles are preferred, and inorganic colloidal particles are preferred from the standpoint of availability, inorganic oxide colloidal particles are more preferred, and silica colloidal particles (colloidal silica) are even more preferred. The average particle size of the abrasive and protrusion-forming agent is preferably in the range of 30 to 200 nm, and more preferably in the range of 50 to 100 nm.

[0115] The magnetic layer described above can be provided directly on the surface of the non-magnetic support, or indirectly via a non-magnetic layer.

[0116] <Nonmagnetic layer> Next, the nonmagnetic layer will be described. The magnetic tape may have a magnetic layer directly on the surface of a nonmagnetic support, or may have a magnetic layer on the surface of a nonmagnetic support via a nonmagnetic layer containing nonmagnetic powder. The nonmagnetic powder used in the nonmagnetic layer may be an inorganic or organic powder. Carbon black, etc., can also be used. Examples of inorganic powders include powders of metals, metal oxides, metal carbonates, metal sulfates, metal nitrides, metal carbides, and metal sulfides. These nonmagnetic powders are commercially available or can be produced by known methods. For details, see paragraphs

[0146] to

[0150] of JP 2011-216149 A. For information on carbon black that can be used in the nonmagnetic layer, see paragraphs

[0040] and

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

[0117] The non-magnetic layer may contain a binder and may also contain additives. For other details of the binder, additives, etc. of the non-magnetic layer, known techniques related to non-magnetic layers can be applied. Furthermore, for example, for the type and content of the binder, the type and content of the additive, known techniques related to magnetic layers can also be applied.

[0118] In the present invention and this specification, the term "nonmagnetic layer" also includes a substantially nonmagnetic layer that contains a small amount of ferromagnetic powder, for example as an impurity or intentionally, along with a nonmagnetic powder. Here, a substantially nonmagnetic layer refers to a layer having a remanence of 10 mT or less, a coercivity of 7.96 kA / m (100 Oe) or less, or a remanence of 10 mT or less and a coercivity of 7.96 kA / m (100 Oe) or less. It is preferable that the nonmagnetic layer have no remanence or coercivity.

[0119] <Backcoat layer> The magnetic tape may or may not have a backcoat layer containing nonmagnetic powder on the surface of the nonmagnetic support opposite to the surface having the magnetic layer. For the nonmagnetic powder in the backcoat layer, see the above description of the nonmagnetic powder in the nonmagnetic layer.

[0120] Indentations on the magnetic layer surface can be formed during the manufacturing process of a magnetic tape, when the magnetic layer is wound into a roll and the surface and backside of the magnetic layer are in contact with each other, resulting in the transfer of the surface shape of the backside to the magnetic layer (so-called "show-through"). The backside refers to the backcoat layer surface if a backcoat layer is present, or the support surface if one is not present. It is believed that the presence of a large number of indentations on the magnetic layer surface and / or the presence of deep indentations is likely to result in differences in temperature and / or moisture content between different parts of the magnetic tape during storage and / or use. This is thought to lead to localized deformation of the magnetic tape, resulting in a shorter media life. Therefore, to extend the media life, it is preferable to suppress the occurrence of indentations on the magnetic layer surface. From this perspective, it is preferable to incorporate a compound having a polyalkyleneimine chain and a vinyl polymer chain into the magnetic layer, as described above. One example of a method for controlling the presence of indentations on the magnetic layer surface is to select the type of components added to the composition used to form the backcoat layer in order to adjust the surface shape of the backside. From this perspective, it is preferable to use a combination of carbon black and a non-magnetic powder other than carbon black, or to use carbon black alone (i.e., the non-magnetic powder in the backcoat layer consists of carbon black). Examples of non-magnetic powders other than carbon black include the non-magnetic powders listed above as examples of powders that can be contained in the non-magnetic layer. The proportion of carbon black in the non-magnetic powder in the backcoat layer, based on 100.0 parts by mass of the total amount of non-magnetic powder, is preferably in the range of 50.0 to 100.0 parts by mass, more preferably 70.0 to 100.0 parts by mass, and even more preferably 90.0 to 100.0 parts by mass. It is also preferable that the total amount of non-magnetic powder in the backcoat layer is carbon black. The content (filling rate) of the non-magnetic powder in the backcoat layer is preferably in the range of 50 to 90% by mass, more preferably 60 to 90% by mass, based on the total mass of the backcoat layer.

[0121] In one embodiment, from the viewpoint of suppressing the occurrence of depressions on the magnetic layer surface, it is preferable to use a non-magnetic powder having an average particle size of 50 nm or less as the non-magnetic powder for the backcoat layer. Only one type of non-magnetic powder may be used as the non-magnetic powder for the backcoat layer, or two or more types can also be used. When two or more types (for example, carbon black and a non-magnetic powder other than carbon black) are used, it is preferable that the average particle size of each type is 50 nm or less. The average particle size of the non-magnetic powder is more preferably in the range of 10 to 50 nm, and even more preferably in the range of 10 to 30 nm. In one embodiment, it is preferable that the entire amount of the non-magnetic powder contained in the backcoat layer is carbon black, and that its average particle size is 50 nm or less.

[0122] To prevent the occurrence of depressions on the magnetic layer surface, the backcoat layer-forming composition preferably contains a component (dispersant) capable of increasing the dispersibility of the nonmagnetic powder contained in the composition. The backcoat layer-forming composition more preferably contains nonmagnetic powder with an average particle size of 50 nm or less and a component capable of increasing the dispersibility of the nonmagnetic powder, and even more preferably contains carbon black with an average particle size of 50 nm or less and a component capable of increasing the dispersibility of the carbon black.

[0123] An example of such a dispersant is a compound having an ammonium salt structure of an alkyl ester anion represented by the following formula 1. Note that the "alkyl ester anion" can also be called an "alkyl carboxylate anion."

[0124] [ka]

[0125] In formula 1, R represents an alkyl group having 7 or more carbon atoms or a fluorinated alkyl group having 7 or more carbon atoms, and Z + represents an ammonium cation.

[0126] In addition, in one embodiment, from the viewpoint of improving the dispersibility of carbon black, two or more components capable of forming the compound having the above-described salt structure can be used when preparing the composition for forming a backcoat layer, so that at least some of the components can form the compound having the above-described salt structure when preparing the composition for forming a backcoat layer.

[0127] Unless otherwise specified, the groups described below may have a substituent or may be unsubstituted. Furthermore, with respect to a group having a substituent, the "number of carbon atoms" refers to the number of carbon atoms excluding the number of carbon atoms of the substituent, unless otherwise specified. In the present invention and this specification, examples of the substituent include an alkyl group (e.g., an alkyl group having 1 to 6 carbon atoms), a hydroxy group, an alkoxy group (e.g., an alkoxy group having 1 to 6 carbon atoms), a halogen atom (e.g., a fluorine atom, a chlorine atom, a bromine atom, etc.), a cyano group, an amino group, a nitro group, an acyl group, a carboxy group, a salt of a carboxy group, a sulfonic acid group, a salt of a sulfonic acid group, etc.

[0128] Formula 1 will be explained in more detail below.

[0129] In formula 1, R represents an alkyl group having 7 or more carbon atoms or a fluorinated alkyl group having 7 or more carbon atoms. The fluorinated alkyl group has a structure in which some or all of the hydrogen atoms constituting the alkyl group are substituted with fluorine atoms. The alkyl group or fluorinated alkyl group represented by R may have a linear structure, a branched structure, or a cyclic alkyl group or fluorinated alkyl group, and preferably has a linear structure. The alkyl group or fluorinated alkyl group represented by R may have a substituent or may be unsubstituted, and is preferably unsubstituted. The alkyl group represented by R is, for example, C n H 2n+1 -, where n is an integer of 7 or more. The fluorinated alkyl group represented by R can be, for example, C n H 2n+1 The alkyl group or fluorinated alkyl group represented by R may have a structure in which some or all of the hydrogen atoms constituting the alkyl group represented by R are substituted with fluorine atoms. The number of carbon atoms in the alkyl group or fluorinated alkyl group represented by R is 7 or more, preferably 8 or more, more preferably 9 or more, even more preferably 10 or more, still more preferably 11 or more, even more preferably 12 or more, and still more preferably 13 or more. The number of carbon atoms in the alkyl group or fluorinated alkyl group represented by R is preferably 20 or less, more preferably 19 or less, and even more preferably 18 or less.

[0130] In equation 1, Z + represents an ammonium cation. Specifically, the ammonium cation has the following structure: In the present invention and this specification, "*" in a formula representing a part of a compound represents the bonding position between the part of the structure and the adjacent atom.

[0131] [ka]

[0132] Nitrogen cation N of ammonium cation + and the oxygen anion O in Eq. - and form a salt bridging group to form an ammonium salt structure of an alkyl ester anion represented by Formula 1. Whether a compound having an ammonium salt structure of an alkyl ester anion represented by Formula 1 is contained in the backcoat layer can be confirmed by analyzing the magnetic tape using X-ray photoelectron spectroscopy (ESCA; Electron Spectroscopy for Chemical Analysis), infrared spectroscopy (IR; infrared spectroscopy), etc.

[0133] In one form, Z + The ammonium cation represented by the formula (I) can be obtained, for example, by converting a nitrogen atom of a nitrogen-containing polymer into a cation. A nitrogen-containing polymer refers to a polymer containing nitrogen atoms. In the present invention and this specification, the terms "polymer" and "polymeric polymer" are used to encompass homopolymers and copolymers. In one form, the nitrogen atom can be included as an atom constituting the main chain of the polymer, or in another form, as an atom constituting the side chain of the polymer.

[0134] One example of the nitrogen-containing polymer is polyalkyleneimine, which is a ring-opening polymer of alkyleneimine and has a plurality of repeating units represented by the following formula 2.

[0135] [ka]

[0136] The nitrogen atom N constituting the main chain in formula 2 is a nitrogen cation N + So Z in Equation 1 + This can result in an ammonium cation represented by the formula: and can form an ammonium salt structure with an alkyl ester anion, for example, as follows:

[0137] [ka]

[0138] Equation 2 will be explained in more detail below.

[0139] In formula 2, R 1 and R 2 each independently represents a hydrogen atom or an alkyl group, and n1 represents an integer of 2 or more.

[0140] R 1 or R 2 Examples of the alkyl group represented by R include alkyl groups having 1 to 6 carbon atoms, preferably alkyl groups having 1 to 3 carbon atoms, more preferably a methyl group or an ethyl group, and even more preferably a methyl group. 1 or R 2 The alkyl group represented by the formula (2) is preferably an unsubstituted alkyl group. 1 and R 2 The combinations include one in which one is a hydrogen atom and the other is an alkyl group, both in which hydrogen atoms are present, and both in which alkyl groups (the same or different alkyl groups) are present, with both in which hydrogen atoms are preferred. The alkyleneimine that yields the polyalkyleneimine has the smallest number of carbon atoms in the ring, which is ethyleneimine, and the alkyleneimine (ethyleneimine) obtained by ring-opening the ethyleneimine has two carbon atoms in its main chain. Therefore, n1 in Formula 2 is 2 or more. n1 in Formula 2 can be, for example, 10 or less, 8 or less, 6 or less, or 4 or less. The polyalkyleneimine may be a homopolymer containing only the same repeating structure represented by Formula 2, or a copolymer containing two or more different repeating structures represented by Formula 2. The number-average molecular weight of the polyalkyleneimine that can be used to form a compound having an ammonium salt structure of an alkyl ester anion represented by Formula 1 can be, for example, 200 or more, preferably 300 or more, and more preferably 400 or more. The number average molecular weight of the polyalkyleneimine can be, for example, 10,000 or less, preferably 5,000 or less, and more preferably 2,000 or less.

[0141] In the present invention and this specification, the average molecular weight (weight average molecular weight and number average molecular weight) refers to a value measured by gel permeation chromatography (GPC) and calculated in terms of standard polystyrene. Unless otherwise specified, the average molecular weight shown in the examples described below is a value (polystyrene-equivalent value) calculated in terms of standard polystyrene from a value measured using GPC under the following measurement conditions. GPC equipment: HLC-8220 (Tosoh Corporation) Guard column: TSKguardcolumn Super HZM-H Columns: TSKgel Super HZ 2000, TSKgel Super HZ 4000, TSKgel Super HZ-M (Tosoh Corporation, 4.6 mm (inner diameter) x 15.0 cm, three columns connected in series) Eluent: tetrahydrofuran (THF), containing stabilizer (2,6-di-t-butyl-4-methylphenol) Eluent flow rate: 0.35mL / min Column temperature: 40℃ Inlet temperature: 40℃ Refractive Index (RI) measurement temperature: 40℃ Sample concentration: 0.3% by mass Sample injection volume: 10 μL

[0142] Another example of the nitrogen-containing polymer is polyallylamine, which is a polymer of allylamine and has a plurality of repeating units represented by the following formula 3:

[0143] [ka]

[0144] The nitrogen atom N constituting the amino group in the side chain in formula 3 is a nitrogen cation N + So Z in Equation 1 + This can result in an ammonium cation represented by the formula: and can form an ammonium salt structure with an alkyl ester anion, for example, as follows:

[0145] [ka]

[0146] The weight-average molecular weight of the polyallylamine that can be used to form the compound having the ammonium salt structure of an alkyl ester anion represented by Formula 1 can be, for example, 200 or more, preferably 1,000 or more, and more preferably 1,500 or more. The weight-average molecular weight of the polyallylamine can be, for example, 15,000 or less, preferably 10,000 or less, and more preferably 8,000 or less.

[0147] The presence of a compound having a structure derived from polyalkyleneimine or polyallylamine in the backcoat layer as a compound having an ammonium salt structure of an alkyl ester anion represented by Formula 1 can be confirmed by analyzing the surface of the backcoat layer using time-of-flight secondary ion mass spectrometry (TOF-SIMS) or the like.

[0148] The compound having the ammonium salt structure of an alkyl ester anion represented by Formula 1 can be a salt of a nitrogen-containing polymer and one or more fatty acids selected from the group consisting of fatty acids having 7 or more carbon atoms and fluorinated fatty acids having 7 or more carbon atoms. The nitrogen-containing polymer that forms the salt can be one or more nitrogen-containing polymers, such as a nitrogen-containing polymer selected from the group consisting of polyalkyleneimines and polyallylamines. The fatty acids that form the salt can be one or more fatty acids selected from the group consisting of fatty acids having 7 or more carbon atoms and fluorinated fatty acids having 7 or more carbon atoms. Fluorinated fatty acids have a structure in which some or all of the hydrogen atoms constituting the alkyl group bonded to the carboxyl group COOH in the fatty acid are substituted with fluorine atoms. For example, the salt-forming reaction can easily proceed by mixing the nitrogen-containing polymer with the above-mentioned fatty acids at room temperature. Room temperature is, for example, about 20 to 25°C. In one embodiment, one or more nitrogen-containing polymers and one or more fatty acids are used as components of the backcoat layer-forming composition, and the salt-forming reaction can be carried out by mixing them in the preparation step of the backcoat layer-forming composition. In another embodiment, prior to the preparation of the backcoat layer-forming composition, one or more nitrogen-containing polymers and one or more fatty acids are mixed to form a salt, and then this salt can be used as a component of the backcoat layer-forming composition to prepare the backcoat layer-forming composition. When the nitrogen-containing polymer and the fatty acids are mixed to form the ammonium salt of the alkyl ester anion represented by Formula 1, the nitrogen atoms constituting the nitrogen-containing polymer may also react with the carboxyl groups of the fatty acids to form the following structure, and forms including such structures are also included in the above-mentioned compounds.

[0149] [ka]

[0150] Examples of the fatty acids include fatty acids having an alkyl group as described above for R in Formula 1 and fluorinated fatty acids having a fluorinated alkyl group as described above for R in Formula 1.

[0151] The mixing ratio of the nitrogen-containing polymer and the fatty acids used to form the compound having an ammonium salt structure of an alkyl ester anion represented by Formula 1 is preferably 10:90 to 90:10, more preferably 20:80 to 85:15, and even more preferably 30:70 to 80:20, in terms of the mass ratio of nitrogen-containing polymer to fatty acids. Furthermore, when preparing a composition for forming a backcoat layer, the compound having an ammonium salt structure of an alkyl ester anion represented by Formula 1 can be used in an amount of, for example, 1.0 to 20.0 parts by mass, preferably 1.0 to 10.0 parts by mass, per 100.0 parts by mass of carbon black. Furthermore, when preparing a composition for forming a backcoat layer, for example, 0.1 to 10.0 parts by mass of the nitrogen-containing polymer can be used, preferably 0.5 to 8.0 parts by mass, per 100.0 parts by mass of carbon black. The fatty acids can be used in an amount of, for example, 0.05 to 10.0 parts by mass, and preferably 0.1 to 5.0 parts by mass, per 100.0 parts by mass of carbon black.

[0152] Regarding components that can be contained in the backcoat layer, the backcoat layer can include a binder and / or additives. Known techniques related to backcoat layers can be applied to the binder and additives of the backcoat layer, and known techniques related to the formulation of magnetic layers and / or nonmagnetic layers can also be applied. For example, see paragraphs

[0018] to

[0020] of JP 2006-331625 A and U.S. Pat. No. 7,029,774, column 4, line 65 to column 5, line 38, for information regarding the backcoat layer.

[0153] <Various thicknesses> With regard to the thickness (total thickness) of magnetic tape, with the enormous increase in the amount of information in recent years, there is a demand for magnetic tape with an increased recording capacity (higher capacity). One way to increase capacity is to reduce the thickness of the magnetic tape (hereinafter also referred to as "thinning") and increase the length of magnetic tape that can be accommodated in one magnetic tape cartridge. From this perspective, the thickness (total thickness) of the magnetic tape is preferably 5.6 μm or less, more preferably 5.5 μm or less, even more preferably 5.4 μm or less, and even more preferably 5.3 μm or less. Furthermore, from the perspective of ease of handling, the thickness of the magnetic tape is preferably 3.0 μm or more, and more preferably 3.5 μm or more.

[0154] The thickness (total thickness) of the magnetic tape can be measured by the following method. Ten tape samples (e.g., 5 to 10 cm long) are cut from any portion of the magnetic tape, and these tape samples are stacked and measured for thickness. The measured thickness is divided by 10 to obtain the value (thickness per tape sample), which is taken as the tape thickness. The thickness measurement can be performed using a known measuring device capable of measuring thickness to the order of 0.1 μm.

[0155] The thickness of the non-magnetic support is preferably 3.0 to 5.0 μm. The thickness of the magnetic layer can be optimized depending on the saturation magnetization of the magnetic head used, the head gap length, the bandwidth of the recording signal, etc., and is generally 0.01 μm to 0.15 μm, and from the viewpoint of high-density recording, it is preferably 0.02 μm to 0.12 μm, and more preferably 0.03 μm to 0.1 μm. At least one magnetic layer is sufficient, and the magnetic layer may be separated into two or more layers with different magnetic properties, and known configurations related to multilayer magnetic layers can be applied. When the magnetic layer is separated into two or more layers, the thickness of the magnetic layer refers to the total thickness of these layers. The thickness of the non-magnetic layer is, for example, 0.1 to 1.5 μm, and preferably 0.1 to 1.0 μm. The thickness of the backcoat layer is preferably 0.9 μm or less, and more preferably 0.1 to 0.7 μm. The thickness of the magnetic layer and other thicknesses can be determined by the following method. After exposing a cross section of the magnetic tape in the thickness direction with an ion beam, the exposed cross section is observed using a scanning electron microscope. The thicknesses can be calculated as the arithmetic mean of the thicknesses measured at any two points during the cross section observation. Alternatively, the thicknesses can be calculated as the design thickness calculated from the manufacturing conditions, etc.

[0156] <Manufacturing process> (Preparation of compositions for forming each layer) Compositions for forming the magnetic layer, nonmagnetic layer, or backcoat layer typically contain a solvent in addition to the various components described above. The solvent can be one or more of the various solvents commonly used in the production of particulate magnetic recording media. The solvent content of each layer-forming composition is not particularly limited. For details about solvents, see paragraph 0153 of JP 2011-216149 A. The solids concentration and solvent composition of each layer-forming composition can be adjusted appropriately depending on the composition's handling suitability, coating conditions, and the thickness of each layer to be formed. The process for preparing a composition for forming the magnetic layer, nonmagnetic layer, or backcoat layer typically includes at least a kneading step, a dispersion step, and optionally, a mixing step before or after these steps. Each individual step may be divided into two or more stages. The various components used in preparing each layer-forming composition may be added at the beginning or during any step. Alternatively, individual components may be added in separate steps in two or more steps. For example, the binder may be added in separate steps in the kneading step, the dispersion step, and the mixing step for adjusting the viscosity after dispersion. The magnetic tape manufacturing process can employ some conventional manufacturing techniques. In the kneading process, devices with strong kneading power, such as an open kneader, continuous kneader, pressure kneader, or extruder, can be used. Details of the kneading process are described in Japanese Patent Application Laid-Open Nos. 1-106338 and 1-79274. Various known dispersers utilizing shear force, such as a bead mill, ball mill, sand mill, or homomixer, can be used. Dispersion beads are preferably used for dispersion. Examples of dispersion beads include ceramic beads and glass beads, with zirconia beads being preferred. Two or more types of beads may be used in combination. The bead diameter (particle size) and bead packing rate of the dispersion beads are not particularly limited and may be set depending on the powder to be dispersed. Each layer-forming composition may be filtered by a known method before being subjected to the coating process. Filtration can be performed, for example, by filter filtration. Filters with a pore size of 0.01 to 3 μm (e.g., glass fiber filters, polypropylene filters, etc.) can be used for filtration.

[0157] (Coating process) The magnetic layer can be formed by applying the magnetic layer-forming composition directly to the surface of the non-magnetic support, or by sequentially or simultaneously applying the magnetic layer-forming composition and the non-magnetic layer-forming composition in a multilayer. The backcoat layer can be formed by applying the backcoat layer-forming composition to the surface of the non-magnetic support opposite to the surface having the non-magnetic layer and / or magnetic layer (or on which the non-magnetic layer and / or magnetic layer will be subsequently formed). For details on the coating for forming each layer, see paragraph 0066 of JP 2010-231843 A.

[0158] (Other processes) Known techniques can be applied to various other steps in the manufacture of magnetic tapes. For details of the various steps, see, for example, paragraphs 0067 to 0070 of JP 2010-231843 A. For example, a coating layer of a magnetic layer-forming composition can be subjected to an orientation treatment in an orientation zone while the coating layer is still wet. Various known techniques, including those described in paragraph 0052 of JP 2010-24113 A, can be applied to the orientation treatment. For example, vertical orientation treatment can be performed by known methods, such as a method using magnets with opposite poles facing each other. In the orientation zone, the drying rate of the coating layer can be controlled by the temperature and volume of the drying air and / or the transport speed in the orientation zone. The coating layer may also be pre-dried before being transported to the orientation zone. For example, the magnetic field strength in the vertical orientation treatment can be 0.1 to 1.5 T.

[0159] A long magnetic tape roll can be obtained by going through various processes. The obtained magnetic tape roll is usually cut (slit) to the width of the magnetic tape to be wound into a magnetic tape cartridge using a known cutting machine. The width is determined according to a standard, for example, 1 / 2 inch. 1 / 2 inch = 12.65 mm. A servo pattern is usually formed on the magnetic tape obtained by slitting. The formation of the servo pattern will be described in detail later.

[0160] (Heat treatment) In one embodiment, the magnetic tape can be a magnetic tape manufactured through the following heat treatment. In another embodiment, the magnetic tape can be a magnetic tape manufactured without the following heat treatment. Performing the following heat treatment can contribute to increasing the media life value. This is mainly because performing the following heat treatment is thought to contribute to suppressing deformation of the magnetic tape that occurs mainly due to stress experienced during storage in a magnetic tape cartridge in an environment exposed to changes in temperature and humidity.

[0161] The heat treatment can be carried out by winding the magnetic tape, which has been slit and cut to a width determined in accordance with a standard, around a core member and carrying out the heat treatment in the wound state.

[0162] In one embodiment, the above-mentioned heat treatment is performed with the magnetic tape wound around a core-shaped member for heat treatment (hereinafter referred to as the "heat treatment core"), and the magnetic tape after the heat treatment is wound onto the cartridge reel of a magnetic tape cartridge, thereby producing a magnetic tape cartridge with the magnetic tape wound around the cartridge reel. The heat treatment core can be made of metal, resin, paper, or the like. The material of the heat treatment core is preferably a highly rigid material from the viewpoint of suppressing winding defects such as spalling. From this viewpoint, the heat treatment core is preferably made of metal or resin. Furthermore, as an index of rigidity, the flexural modulus of the material of the heat treatment core is preferably 0.2 GPa or more, more preferably 0.3 GPa or more. On the other hand, since highly rigid materials are generally expensive, using a heat treatment core made of a material having a rigidity exceeding that required to suppress winding defects leads to increased costs. In consideration of the above, the flexural modulus of the material of the heat treatment core is preferably 250 GPa or less. Furthermore, the heat treatment core can be a solid or hollow core-shaped member. If the core is hollow, the wall thickness is preferably 2 mm or more from the viewpoint of maintaining rigidity. Furthermore, the heat treatment core may or may not have a flange. It is preferable to prepare a magnetic tape having a length equal to or greater than the length to be ultimately accommodated in a magnetic tape cartridge (hereinafter referred to as the "final product length") as the magnetic tape to be wound around the heat treatment core, and to perform heat treatment by placing this magnetic tape wound around the heat treatment core in a heat treatment environment. The length of the magnetic tape to be wound around the heat treatment core is equal to or greater than the final product length, and from the viewpoint of ease of winding onto the heat treatment core, it is preferable that it be "final product length + α". From the viewpoint of ease of winding, this α is preferably 5 m or more. The tension during winding onto the heat treatment core is preferably 0.10 N or more. Furthermore, from the viewpoint of suppressing excessive deformation during manufacturing, the tension during winding onto the heat treatment core is preferably 1.50 N or less, more preferably 1.00 N or less. The outer diameter of the heat treatment core is preferably 20 mm or more, more preferably 40 mm or more, from the viewpoints of ease of winding and suppression of coiling (longitudinal curl). The outer diameter of the heat treatment core is preferably 100 mm or less, more preferably 90 mm or less. The width of the heat treatment core need only be equal to or greater than the width of the magnetic tape wound around the core. After the heat treatment, when removing the magnetic tape from the heat treatment core, it is preferable to remove the magnetic tape from the heat treatment core after the magnetic tape and the heat treatment core have cooled sufficiently to prevent unintended deformation of the tape during the removal operation. The removed magnetic tape is preferably temporarily wound onto another core (referred to as a "temporary winding core"), and then wound from the temporary winding core onto the cartridge reel of the magnetic tape cartridge (typically with an outer diameter of approximately 40 to 50 mm). This allows the magnetic tape to be wound onto the cartridge reel of the magnetic tape cartridge while maintaining the inner and outer relationship of the magnetic tape with respect to the heat treatment core during the heat treatment. For details about the temporary winding core and the tension when winding the magnetic tape onto this core, please refer to the previous description of the heat treatment core. In a form in which the above-mentioned heat treatment is performed on a magnetic tape having a length of "final product length + α", the length of "+ α" can be cut off at any 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 viewpoint of reducing the portion that is cut off and discarded, it is preferable that the above-mentioned α be 20 m or less.

[0163] A specific example of the heat treatment carried out in the state where the core member is wound as described above will be described below. The atmospheric temperature at which the heat treatment is performed (hereinafter referred to as "heat treatment temperature") is preferably 40° C. or higher, and more preferably 50° C. or higher. On the other hand, from the viewpoint of suppressing excessive deformation, the heat treatment temperature is preferably 75° C. or lower, more preferably 70° C. or lower, and even more preferably 65° C. or lower. The absolute humidity by weight of the atmosphere in which the heat treatment is carried out is preferably 0.1 g / kg dry air or more, more preferably 1 g / kg dry air or more. An atmosphere with an absolute humidity by weight in the above range is preferred because it can be prepared without using special equipment for reducing moisture. On the other hand, from the viewpoint of preventing condensation from forming and reducing workability, the absolute humidity by weight is preferably 70 g / kg dry air or less, more preferably 66 g / kg dry air or less. The heat treatment time is preferably 0.3 hours or more, more preferably 0.5 hours or more. Furthermore, from the viewpoint of production efficiency, the heat treatment time is preferably 48 hours or less.

[0164] (Servo pattern formation) The magnetic tape has multiple servo bands in its magnetic layer. The servo bands are composed of servo patterns that run continuously along the length of the magnetic tape. The servo patterns enable tracking control of the magnetic head in a magnetic tape device, control of the running speed of the magnetic tape, and the like. "Forming servo patterns" can also be referred to as "recording servo signals." For example, the width of the magnetic tape can be controlled by using the servo signals to obtain dimensional information about the width of the magnetic tape while it is running, and adjusting and changing the tension applied to the magnetic tape in the lengthwise direction according to the obtained dimensional information.

[0165] The formation of the servo pattern will be described below.

[0166] The servo patterns are formed along the length of the magnetic tape. Control methods that use servo signals (servo control) include timing-based servo (TBS), amplitude servo, and frequency servo.

[0167] As specified in ECMA (European Computer Manufacturers Association)-319 (June 2001), magnetic tapes (commonly referred to as "LTO tapes") conforming to the LTO (Linear Tape-Open) standard employ a timing-based servo system. In this timing-based servo system, a servo pattern is formed by a pair of non-parallel magnetic stripes (also called "servo stripes") arranged continuously along the longitudinal direction of the magnetic tape. A servo system is a system that performs head tracking using servo signals. In this invention and this specification, the term "timing-based servo pattern" refers to a servo pattern that enables head tracking in a timing-based servo system. The reason why the servo pattern is formed by a pair of non-parallel magnetic stripes, as described above, is to inform a servo signal reading element passing over the servo pattern of its passing position. Specifically, the spacing between the pair of magnetic stripes is formed so that it continuously changes along the width direction of the magnetic tape. By reading this spacing, the servo signal reading element can determine the relative position between the servo pattern and the servo signal reading element. This relative position information enables tracking of data tracks. For this reason, a plurality of servo tracks are usually set on the servo pattern along the width direction of the magnetic tape.

[0168] A servo band is made up of a continuous servo pattern in the longitudinal direction of the magnetic tape. The magnetic tape has multiple servo bands in its magnetic layer. For example, an LTO tape has five servo bands. The area between two adjacent servo bands is the data band. The data band is made up of multiple data tracks, and each data track corresponds to one servo track.

[0169] Also, in one embodiment, as disclosed in Japanese Patent Application Laid-Open No. 2004-318983, information indicating the servo band number (also called "servo band ID (identification)" or "UDIM (Unique Data Band Identification Method) information") is embedded in each servo band. This servo band ID is recorded by shifting a specific one of a plurality of pairs of servo stripes in the servo band so that its position is displaced relative to the longitudinal direction of the magnetic tape. Specifically, the way in which a specific one of a plurality of pairs of servo stripes is shifted varies for each servo band. As a result, the recorded servo band ID is unique for each servo band, and therefore, simply by reading one servo band with a servo signal reading element, that servo band can be uniquely identified.

[0170] One method for uniquely identifying servo bands is the staggered method described in ECMA-319 (June 2001). In this staggered method, pairs of non-parallel magnetic stripes (servo stripes) are continuously arranged along the length of the magnetic tape, and are recorded so that each servo band is offset along the length of the magnetic tape. The combination of this offset between adjacent servo bands is unique across the entire magnetic tape, making it possible to uniquely identify servo bands when reading the servo pattern with two servo signal reading elements.

[0171] As specified in ECMA-319 (June 2001), each servo band also typically contains information indicating the longitudinal position of the magnetic tape (also known as "LPOS (Longitudinal Position) information"). Like UDIM information, this LPOS information is recorded by shifting the positions of a pair of servo stripes along the longitudinal direction of the magnetic tape. However, unlike UDIM information, the same signal is recorded in each servo band for this LPOS information.

[0172] It is also possible to embed information other than the UDIM information and LPOS information described above in the servo bands. In this case, the embedded information may be different for each servo band, such as UDIM information, or it may be common to all servo bands, such as LPOS information. Furthermore, methods other than those described above can be used to embed information in the servo bands. For example, a predetermined code may be recorded by thinning out a predetermined pair from a group of pairs of servo stripes.

[0173] The head for forming a servo pattern is called a servo write head. A servo write head typically has a pair of gaps corresponding to the pair of magnetic stripes, the number of which is equal to the number of servo bands. Typically, a core and a coil are connected to each pair of gaps. By supplying a current pulse to the coil, the magnetic field generated in the core can generate a leakage magnetic field in the pair of gaps. To form a servo pattern, a current pulse is input while running a magnetic tape over the servo write head, thereby transferring the magnetic pattern corresponding to the pair of gaps onto the magnetic tape, thereby forming the servo pattern. The width of each gap can be appropriately set depending on the density of the servo pattern to be formed. The width of each gap can be set, for example, to 1 μm or less, 1 to 10 μm, or 10 μm or more.

[0174] Before forming a servo pattern on a magnetic tape, the magnetic tape is usually subjected to a demagnetization (erase) process. This erase process can be performed by applying a uniform magnetic field to the magnetic tape using a direct current magnet or an alternating current magnet. There are two types of erase processes: direct current (DC) erase and alternating current (AC) erase. AC erase is performed by gradually reducing the strength of the magnetic field applied to the magnetic tape while reversing the direction of the magnetic field. DC erase, on the other hand, is performed by applying a unidirectional magnetic field to the magnetic tape. There are two other DC erase methods. The first method is horizontal DC erase, in which a unidirectional magnetic field is applied along the length of the magnetic tape. The second method is vertical DC erase, in which a unidirectional magnetic field is applied along the thickness of the magnetic tape. The erase process can be performed on the entire magnetic tape or on each servo band of the magnetic tape.

[0175] The direction of the magnetic field of the formed servo pattern is determined by the erase direction. For example, when a magnetic tape is subjected to horizontal DC erasure, the servo pattern is formed so that the direction of the magnetic field is opposite to the erase direction. This increases the output of the servo signal obtained by reading the servo pattern. As shown in Japanese Patent Application Laid-Open No. 2012-53940, when a magnetic pattern is transferred to a magnetic tape that has been vertically DC erased using the gap, the servo signal obtained by reading the formed servo pattern has a unipolar pulse shape. On the other hand, when a magnetic pattern is transferred to a magnetic tape that has been horizontally DC erased using the gap, the servo signal obtained by reading the formed servo pattern has a bipolar pulse shape.

[0176] Usually, after the servo patterns are formed, the magnetic tape is wound onto a reel hub of a cartridge reel and housed in a magnetic tape cartridge.

[0177] <Vertical squareness ratio> In one embodiment, the perpendicular squareness of the magnetic tape can be, for example, 0.55 or more, and preferably 0.60 or more. A perpendicular squareness of the magnetic tape of 0.60 or more is preferred from the viewpoint of improving electromagnetic conversion characteristics. The upper limit of the squareness is, in principle, 1.00 or less. The perpendicular squareness of the magnetic tape can be 1.00 or less, and can be 0.95 or less, 0.90 or less, 0.85 or less, or 0.80 or less. A large perpendicular squareness of the magnetic tape is preferred from the viewpoint of improving electromagnetic conversion characteristics. The perpendicular squareness of the magnetic tape can be controlled by a known method, such as performing a perpendicular orientation treatment.

[0178] In the present invention and this specification, the "perpendicular squareness" refers to the squareness measured in the perpendicular direction of the magnetic tape. The "perpendicular direction" in relation to the squareness refers to the direction perpendicular to the surface of the magnetic layer, which can also be referred to as the thickness direction. In the present invention and this specification, the perpendicular squareness is determined by the following method. A sample piece of a size suitable for insertion into a vibrating sample magnetometer is cut from the magnetic tape to be measured. A magnetic field is applied to this sample piece perpendicular to the sample piece (perpendicular to the magnetic layer surface) using a vibrating sample magnetometer at a maximum applied magnetic field of 3979 kA / m, a measurement temperature of 296 K, and a magnetic field sweep rate of 8.3 kA / m / s. The magnetization strength of the sample piece in response to the applied magnetic field is measured. The measured magnetization strength is obtained after demagnetization field correction and after subtracting the magnetization of the sample probe of the vibrating sample magnetometer as background noise. The squareness ratio (SQ) is calculated as SQ = Mr / Ms, where Ms is the magnetization strength at the maximum applied magnetic field and Mr is the magnetization strength at zero applied magnetic field. The measurement temperature refers to the temperature of the sample piece. By setting the ambient temperature surrounding the sample piece to the measurement temperature, the temperature of the sample piece can be adjusted to the measurement temperature through temperature equilibrium. [Example]

[0179] The present invention will be described below based on examples. However, the present invention is not limited to the embodiments shown in the examples. The indications of "parts" and "%" below mean "parts by mass" and "% by mass" unless otherwise specified. "eq" is an equivalent, and is a unit that cannot be converted to SI units. Unless otherwise specified, the following steps and operations were carried out in an environment with a temperature of 20 to 25°C and a relative humidity of 40 to 60%.

[0180] [Nonmagnetic support] In Table 1, "PEN" indicates a polyethylene naphthalate substrate, "PET" indicates a polyethylene terephthalate substrate, and "PA" indicates an aromatic polyamide substrate. The water content and Young's modulus in Table 1 were measured by the method described above.

[0181] [Ferromagnetic powder] In Table 1, "BaFe" in the ferromagnetic powder column indicates hexagonal barium ferrite powder with an average particle size (average plate diameter) of 21 nm.

[0182] In Table 1, "SrFe1" in the ferromagnetic powder column indicates a hexagonal strontium ferrite powder prepared as follows. 1707 g of SrCO3, 687 g of H3BO3, 1120 g of Fe2O3, 45 g of Al(OH)3, 24 g of BaCO3, 13 g of CaCO3, and 235 g of Nd2O3 were weighed and mixed in a mixer to obtain a raw material mixture. The resulting raw material mixture was melted in a platinum crucible at a melting temperature of 1390°C, and the melt was stirred while heating the tapping hole at the bottom of the platinum crucible, causing the melt to be poured into a rod shape at a rate of approximately 6 g / sec. The tapped liquid was rolled and quenched using a water-cooled twin roller to produce an amorphous body. 280 g of the produced amorphous body was placed in an electric furnace, heated to 635°C (crystallization temperature) at a rate of 3.5°C / min, and held at that temperature for 5 hours to precipitate (crystallize) hexagonal strontium ferrite particles. The crystallized material containing hexagonal strontium ferrite particles was then coarsely crushed in a mortar. 1,000 g of 1 mm zirconia beads and 800 mL of 1% acetic acid solution were added to a glass bottle and dispersed for 3 hours using a paint shaker. The resulting dispersion was then separated from the beads and placed in a stainless steel beaker. The dispersion was left to stand at 100°C for 3 hours to dissolve the glass components, then precipitated in a centrifuge and washed by repeated decantation. It was then dried for 6 hours in a heating furnace at 110°C to obtain hexagonal strontium ferrite powder. The average particle size of the hexagonal strontium ferrite powder obtained above was 18 nm, and the activation volume was 902 nm. 3 , the anisotropy constant Ku is 2.2×10 5 J / m 3 , mass magnetization σs is 49A m 2 / kg. A 12 mg sample powder was taken from the hexagonal strontium ferrite powder obtained above, and this sample powder was partially dissolved under the dissolution conditions exemplified above. The filtrate was subjected to elemental analysis using an ICP analyzer to determine the neodymium atom content in the surface layer. Separately, 12 mg of sample powder was collected from the hexagonal strontium ferrite powder obtained above, and this sample powder was completely dissolved under the dissolution conditions exemplified above. The filtrate thus obtained was subjected to elemental analysis using an ICP analyzer to determine the bulk content of neodymium atoms. The neodymium atom content (bulk content) of the hexagonal strontium ferrite powder obtained above relative to 100 atomic percent of iron atoms was 2.9 atomic percent. The neodymium atom content in the surface layer was 8.0 atomic percent. The ratio of the surface layer content to the bulk content, "surface layer content / bulk content," was 2.8, confirming that neodymium atoms were unevenly distributed in the surface layers of the particles.

[0183] The powder obtained above was confirmed to have a hexagonal ferrite crystal structure by scanning with CuKα radiation at a voltage of 45 kV and an intensity of 40 mA and measuring the X-ray diffraction pattern under the following conditions (X-ray diffraction analysis). The powder obtained above exhibited a magnetoplumbite (M-type) hexagonal ferrite crystal structure. Furthermore, the crystalline phase detected by X-ray diffraction analysis was a single magnetoplumbite phase. PANalytical X'Pert Pro diffractometer, PIXcel detector Soller slits for incident and diffracted beams: 0.017 radians Dispersion slit fixed angle: 1 / 4 degree Mask: 10mm Anti-scatter slit: 1 / 4 degree Measurement mode: Continuous Measurement time per step: 3 seconds Measurement speed: 0.017 degrees per second Measurement step: 0.05 degrees

[0184] In Table 1, "SrFe2" in the ferromagnetic powder column indicates hexagonal strontium ferrite powder prepared as follows. 1725 g of SrCO3, 666 g of H3BO3, 1332 g of Fe2O3, 52 g of Al(OH)3, 34 g of CaCO3, and 141 g of BaCO3 were weighed and mixed in a mixer to obtain a raw material mixture. The resulting raw material mixture was melted in a platinum crucible at a melting temperature of 1380°C, and the melt was stirred while heating the tapping hole at the bottom of the platinum crucible, causing the melt to be poured into a rod shape at a rate of approximately 6 g / sec. The tapped liquid was rolled and quenched using a water-cooled twin roll mill to produce an amorphous body. 280 g of the obtained amorphous body was placed in an electric furnace, heated to 645°C (crystallization temperature), and held at this temperature for 5 hours to precipitate (crystallize) hexagonal strontium ferrite particles. The crystallized material containing hexagonal strontium ferrite particles was then coarsely crushed in a mortar. 1,000 g of 1 mm zirconia beads and 800 mL of 1% acetic acid solution were added to a glass bottle and dispersed for 3 hours using a paint shaker. The resulting dispersion was then separated from the beads and placed in a stainless steel beaker. The dispersion was left to stand at 100°C for 3 hours to dissolve the glass components, then precipitated in a centrifuge and washed by repeated decantation. It was then dried for 6 hours in a heating furnace at 110°C to obtain hexagonal strontium ferrite powder. The average particle size of the obtained hexagonal strontium ferrite powder was 19 nm, and the activation volume was 1102 nm. 3 , the anisotropy constant Ku is 2.0×10 5 J / m 3 , mass magnetization σs is 50A m 2 / kg.

[0185] In Table 1, "ε-iron oxide" in the ferromagnetic powder column indicates ε-iron oxide powder prepared as follows. 8.3 g of iron(III) nitrate nonahydrate, 1.3 g of gallium(III) nitrate octahydrate, 190 mg of cobalt(II) nitrate hexahydrate, 150 mg of titanium(IV) sulfate, and 1.5 g of polyvinylpyrrolidone (PVP) were dissolved in 90 g of pure water. While stirring using a magnetic stirrer, 4.0 g of a 25% aqueous ammonia solution was added in air at 25°C. The mixture was stirred for 2 hours at 25°C. A citric acid solution (1 g of citric acid dissolved in 9 g of pure water) was added to the resulting solution and stirred for 1 hour. The precipitated powder was collected by centrifugation, washed with pure water, and dried in a heating oven at 80°C. 800g of pure water was added to the dried powder, and the powder was dispersed in water again to obtain a dispersion. The resulting dispersion was heated to 50°C, and 40g of a 25% aqueous ammonia solution was added dropwise while stirring. After stirring for 1 hour while maintaining the temperature at 50°C, 14mL of tetraethoxysilane (TEOS) was added dropwise and stirred for 24 hours. 50g of ammonium sulfate was added to the resulting reaction solution, and the precipitated powder was collected by centrifugation, washed with pure water, and dried for 24 hours in a heating furnace at 80°C to obtain a precursor of the ferromagnetic powder. The obtained precursor of the ferromagnetic powder was placed in a heating furnace at an internal temperature of 1000° C. in an air atmosphere and subjected to heat treatment for 4 hours. The heat-treated ferromagnetic powder precursor was placed in a 4 mol / L aqueous solution of sodium hydroxide (NaOH), and the liquid temperature was maintained at 70°C while stirring for 24 hours, thereby removing the impurity silicate compound from the heat-treated ferromagnetic powder precursor. Thereafter, the silicate compound was removed by centrifugation, and the ferromagnetic powder was collected and washed with pure water to obtain a ferromagnetic powder. The composition of the obtained ferromagnetic powder was confirmed by inductively coupled plasma optical emission spectrometry (ICP-OES). It was found that the powder consisted of Ga, Co, and Ti substituted ε-iron oxide (ε-Ga 0.28 Co 0.05 Ti 0.05 Fe 1.62 In addition, X-ray diffraction analysis was performed under the same conditions as those described above for the hexagonal strontium ferrite powder SrFe1, and it was confirmed from the peaks in the X-ray diffraction pattern that the obtained ferromagnetic powder had a single-phase ε-phase crystal structure (ε-iron oxide crystal structure) that did not contain α-phase or γ-phase crystal structures. The average particle size of the obtained ε-iron oxide powder was 12 nm, and the activation volume was 746 nm. 3 , the anisotropy constant Ku is 1.2×10 5 J / m 3 , mass magnetization σs is 16A m 2 / kg.

[0186] The activation volume and anisotropy constant Ku of the above hexagonal strontium ferrite powder and ε-iron oxide powder were determined for each ferromagnetic powder using a vibrating sample magnetometer (manufactured by Toei Kogyo Co., Ltd.) by the method described above. The mass magnetization σs is a value measured using a vibrating sample magnetometer (manufactured by Toei Kogyo Co., Ltd.) at a magnetic field strength of 1194 kA / m (15 kOe).

[0187] [Example 1] (1) Formulation of the composition for forming the magnetic layer (Magnetic liquid) Ferromagnetic powder (see Table 1): 100.0 parts Dispersant: See Table 1 SO3Na group-containing polyurethane resin: 14.0 parts Weight average molecular weight: 70,000, SO3Na group: 0.4meq / g Cyclohexanone: 150 parts Methyl ethyl ketone: 150 parts (Abrasive liquid A) Alumina abrasive (average particle size: 100 nm): 3.0 parts Sulfonic acid group-containing polyurethane resin: 0.3 parts Weight average molecular weight: 70,000, SO3Na group: 0.3meq / g Cyclohexanone: 26.7 parts (Abrasive liquid B) Diamond abrasive (average particle size: 100 nm): 1.0 parts Sulfonic acid group-containing polyurethane resin: 0.1 parts Weight average molecular weight: 70,000, SO3Na group: 0.3meq / g Cyclohexanone: 26.7 parts (silica sol) Colloidal silica (average particle size: 100 nm): 0.2 parts Methyl ethyl ketone: 1.4 parts (Other ingredients) Stearic acid: 2.0 parts Butyl stearate: 10.0 parts Polyisocyanate (Coronate manufactured by Nippon Polyurethane Co., Ltd.): 2.5 parts Cyclohexanone: 200.0 parts Methyl ethyl ketone: 200.0 parts

[0188] The dispersant is a compound (a compound having a polyalkyleneimine chain and a vinyl polymer chain) described in JP 2019-169225 A as a component of the magnetic layer-forming composition of Example 1. The reaction solution obtained after synthesizing the compound was used as a component of the magnetic layer-forming composition. The content of the dispersant in the magnetic layer shown in Table 1 below is the amount of the compound in the reaction solution.

[0189] (2) Formulation of the composition for forming the nonmagnetic layer Non-magnetic inorganic powder (α-iron oxide): 100.0 parts Average particle size (average major axis length): 10nm Average acicular ratio: 1.9 BET (Brunauer-Emmett-Teller) specific surface area: 75m 2 / g Carbon black: 25.0 parts Average particle size: 20nm SO3Na group-containing polyurethane resin: 18 parts Weight average molecular weight: 70,000, SO3Na group: 0.2meq / g Stearic acid: 1.0 parts Cyclohexanone: 300.0 parts Methyl ethyl ketone: 300.0 parts

[0190] (3) Formulation of the composition for forming the backcoat layer Carbon black: 100.0 parts Cabot BP-800, average particle size: 17 nm SO3Na group-containing polyurethane resin (SO3Na group: 70 eq / ton): 20.0 parts Vinyl chloride resin containing OSO3K group (OSO3K group: 70 eq / ton): 30.0 parts Polyethyleneimine (manufactured by Nippon Shokubai Co., Ltd., number average molecular weight: 600): See Table 1 Stearic acid: See Table 1 Cyclohexanone: 140.0 parts Methyl ethyl ketone: 170.0 parts Butyl stearate: 2.0 parts Stearic acid amide: 0.1 parts

[0191] (4) Manufacturing of magnetic tapes and magnetic tape cartridges The magnetic liquid was prepared by dispersing the above components for 24 hours using a batch-type vertical sand mill. Zirconia beads with a diameter of 0.5 mm were used as dispersion beads. The above components of the polishing compound liquids A and B were dispersed for 24 hours using a batch-type ultrasonic device (20 kHz, 300 W) to obtain the polishing compound liquids A and B. The magnetic liquid, abrasive liquid A, and abrasive liquid B were mixed with the silica sol and other components, and then dispersed for 30 minutes using a batch-type ultrasonic device (20 kHz, 300 W).The mixture was then filtered using a filter with a pore size of 0.5 μm to prepare a magnetic layer-forming composition. The non-magnetic layer-forming composition was prepared by dispersing the above components for 24 hours using a batch-type vertical sand mill. Zirconia beads with a diameter of 0.1 mm were used as dispersion beads. The resulting dispersion was filtered using a filter with a pore size of 0.5 μm to prepare the non-magnetic layer-forming composition. The backcoat layer-forming composition was prepared by kneading the above components in a continuous kneader and then dispersing them in a sand mill. 40.0 parts of polyisocyanate (Coronate L, manufactured by Nippon Polyurethane Industry Co., Ltd.) and 1000.0 parts of methyl ethyl ketone were added to the resulting dispersion, and the mixture was filtered through a filter with a pore size of 1 μm to prepare a backcoat layer-forming composition. The nonmagnetic layer-forming composition prepared above was applied to the surface of a 4.1 μm thick support shown in Table 1 and dried to a thickness of 0.7 μm, thereby forming a nonmagnetic layer. Next, the magnetic layer-forming composition prepared above was applied onto the non-magnetic layer so as to have a thickness of 0.1 μm after drying, thereby forming a coating layer. Then, while the coating layer of the magnetic layer-forming composition was still wet, a magnetic field with a strength of 0.3 T was applied perpendicular to the surface of the coating layer to perform a vertical alignment treatment, followed by drying to form a magnetic layer. Thereafter, the backcoat layer-forming composition prepared above was applied to the surface of the support opposite to the surface on which the non-magnetic layer and magnetic layer were formed, and dried to form a backcoat layer with a thickness of 0.3 μm after drying. The long magnetic tape was then heat-treated by storing it in a heat treatment furnace at an ambient temperature of 70°C (heat treatment time: 36 hours). After heat treatment, the tape was slit into 1 / 2-inch widths to obtain magnetic tape. Servo signals were recorded on the magnetic layer of the obtained magnetic tape using a commercially available servo writer, resulting in a magnetic tape with data bands, servo bands, and guide bands arranged in accordance with the LTO (Linear Tape-Open) Ultrium format, and with servo patterns (timing-based servo patterns) on the servo bands arranged and shaped in accordance with the LTO Ultrium format. The servo patterns thus formed conform to the specifications of JIS (Japanese Industrial Standards) X6175:2006 and Standard ECMA-319 (June 2001). The total number of servo bands was five, and the total number of data bands was four. The magnetic tape (length 970 m) after the servo pattern formation was taken up on a core for heat treatment, and was heat treated while still wound on this core. A solid core-shaped member (outer diameter: 50 mm) made of resin with a flexural modulus of 0.8 GPa was used as the core for heat treatment, and the tension during winding was 0.60 N. The heat treatment was carried out for 5 hours at the heat treatment temperature shown in Table 1. The weight absolute humidity of the atmosphere in which the heat treatment was carried out was 10 g / kg dry air. After the above heat treatment, once the magnetic tape and heat treatment core had sufficiently cooled, the magnetic tape was removed from the heat treatment core and wound onto a temporary take-up core, and then the magnetic tape, the length of the final product (960 m), was wound longitudinally from the temporary take-up core onto the reel hub of the reel of the magnetic tape cartridge, with tension applied as shown in the "Winding tension during manufacture" column in Table 1. The remaining 10 m was cut off, and a leader tape in accordance with item 9 of Section 3 of Standard ECMA (European Computer Manufacturers Association)-319 (June 2001) was spliced ​​to the end of the cut-off side using commercially available splicing tape. The temporary take-up core was a solid core-shaped member made of the same material and having the same outer diameter as the heat treatment core. The magnetic tape cartridge used to house the magnetic tape described above was a single-reel magnetic tape cartridge with the configuration shown in Figure 8. The reel hub of this magnetic tape cartridge was a single-layer reel hub (thickness: 2.5 mm, outer diameter: 44 mm) injection-molded from glass fiber-reinforced polycarbonate. The glass fiber content of this glass fiber-reinforced polycarbonate is the value shown in Table 1 (unit: mass %). A portion of the glass fiber-reinforced polycarbonate for injection molding was sampled and used to prepare the recommended test specimens described in JIS K 7171:2016, item 6.3.1 (production from molding material), as specified in JIS item 6.1.2. The flexural modulus (arithmetic average of five test specimens) was determined in accordance with JIS, yielding the value shown in Table 1. In the examples and comparative examples described below, the flexural modulus of the reel hub material was determined using the above method. The flexural modulus of the above-mentioned winding core for heat treatment was also determined in the same manner. As a result of the above, a single-reel magnetic tape cartridge was produced in which a 960 m long magnetic tape was wound around a reel.

[0192] The presence of a compound containing an ammonium salt structure of an alkyl ester anion represented by formula 1, which is formed from polyethyleneimine and stearic acid, in the backcoat layer of a magnetic tape can be confirmed by the following method. A sample is cut from the magnetic tape, and the surface of the backcoat layer (measurement area: 300 μm × 700 μm) is subjected to X-ray photoelectron spectroscopy using an ESCA instrument. Specifically, wide scan measurement is performed using the ESCA instrument under the following measurement conditions. The measurement results show peaks at the position of the binding energy of the ester anion and the position of the binding energy of the ammonium cation. Equipment: Shimadzu AXIS-ULTRA Excitation X-ray source: Monochromated Al-Kα radiation Scan range: 0 to 1200 eV Pass energy: 160 eV Energy resolution: 1 eV / step Capture time: 100ms / step Accumulation count: 5 In addition, a sample piece 3 cm long was cut out from the magnetic tape, and the surface of the backcoat layer was measured by ATR-FT-IR (Attenuated Total Reflection-Fourier Transform-Infrared Spectrometer) (reflection method). - The wavenumber corresponding to the absorption of -1 or 1430cm -1 ), and the wavenumber corresponding to the absorption of ammonium cation (2400 cm -1 ) absorption is confirmed.

[0193] Two magnetic tape cartridges were prepared, one of which was used to evaluate the medium life and tape thickness described below, and the other was used to evaluate the recording and reproduction performance described later.

[0194] [Evaluation method] <Media Life> (Servo band interval measurement) The magnetic tape cartridge to be measured was placed in a measurement environment with an ambient temperature of 23°C and a relative humidity of 50% for five days to allow it to acclimate to the measurement environment. Then, under the above measurement environment, the magnetic tape was run in the magnetic tape device shown in Figure 5 with a tension of 0.70 N applied in the longitudinal direction of the magnetic tape. During this run, the spacing between two adjacent servo bands sandwiching a data band was measured at 1 m intervals over the entire length of the magnetic tape. Measurements were performed for all servo band spacings. The servo band spacing measured in this way was designated the "servo band spacing before storage" at each measurement position. The spacing between two adjacent servo bands sandwiching a data band was determined as follows. To determine the distance between two adjacent servo bands sandwiching a data band, the dimensions of the servo pattern are required. The standard dimensions of the servo pattern differ depending on the LTO generation. Therefore, first, using a magnetic force microscope or similar, we measure the average distance AC between the four corresponding stripes of the A burst and C burst, and the azimuth angle α of the servo pattern. Next, the servo patterns formed on the magnetic tape are sequentially read along the tape length using a reel tester and a servo head equipped with two servo signal read elements (hereinafter, one will be referred to as the upper side and the other as the lower side) fixed at a distance perpendicular to the longitudinal direction of the magnetic tape. The average time between five stripes corresponding to the A and B bursts over the length of one LPOS word is defined as a. The average time between four stripes corresponding to the A and C bursts over a length of 1 m is defined as b. The value defined as AC × (1 / 2 - a / b) / (2 × tan(α)) represents the read position PES in the width direction based on the servo signal obtained by the servo signal read element. The servo pattern is read simultaneously by two servo signal read elements, one on the upper side and one on the lower side. The PES value obtained by the upper servo signal read element is defined as PES1, and the PES value obtained by the lower servo signal read element is defined as PES2. The distance between two adjacent servo bands across the data band can be calculated as "PES2 - PES1." This is because the upper and lower servo pattern reading elements are fixed to the servo head and the distance between them does not change. Then, for the magnetic tape cartridge, the "servo band interval after 24 hours of storage" and "A after 24 hours of storage," "servo band interval after 48 hours of storage" and "A after 48 hours of storage," "servo band interval after 72 hours of storage" and "A after 72 hours of storage," "servo band interval after 96 hours of storage" and "A after 96 hours of storage," and "servo band interval after 120 hours of storage" and "A after 120 hours of storage" were determined using the methods described above.

[0195] (Derivation of linear functions) The logarithm of the value of A obtained in the above process and the storage time T e From the value of T, A and log e A linear function with T was derived. The linear function is log e With T as X, Y is expressed as cX+d, where c and d are coefficients determined by the least squares method and are both positive values.

[0196] (Decision of B) Measurements were carried out in five environments (temperature 16°C and relative humidity 20%, temperature 16°C and relative humidity 80%, temperature 26°C and relative humidity 80%, temperature 32°C and relative humidity 20%, and temperature 32°C and relative humidity 55%) using the following methods. For each measurement environment, the magnetic tape cartridge to be measured was placed in the measurement environment for 5 days to allow it to acclimate to the measurement environment. Then, under this measurement environment, the magnetic tape was run in the magnetic tape device shown in Figure 5 with a tension of 0.70 N applied in the longitudinal direction of the magnetic tape. The servo band spacing was measured at 1 m intervals in a 100 m area around the reel's periphery for this run using the above method at data band 0 (zero). As described above, the arithmetic mean of the measured servo band spacing was taken as the servo band spacing in that measurement environment. After determining the servo band spacing in each of the five environments as described above, the maximum and minimum values ​​among the determined values ​​were used to calculate "(maximum value - minimum value) x 1 / 2", which was used as "B" for the magnetic tape cartridge being measured.

[0197] (Calculation of media life) The logarithm of A and T derived above, log e Using a linear function with T, T was calculated when A satisfies the formula a: A = 1.5 - B. The method for calculating C will be described later.

[0198] <Tape thickness> After the above evaluation, the magnetic tape cartridges were placed in an environment with a temperature of 20-25°C and a relative humidity of 40-60% for at least five days to allow them to acclimate to the environment. Subsequently, in the same environment, ten tape samples (5 cm long) were cut from any portion of the magnetic tape removed from the magnetic tape cartridge, and these tape samples were stacked and measured for thickness. The thickness was measured using a digital thickness meter equipped with a Millimar 1240 compact amplifier and a Millimar 1301 inductive probe manufactured by MARH. The measured thickness was divided by 10 to obtain the value (thickness per tape sample), which was used as the tape thickness. The tape thickness for each magnetic tape was 5.2 μm.

[0199] <Evaluation of recording / playback performance> The recording and playback performance was evaluated using a magnetic tape device with the configuration shown in Figure 5. The arrangement of modules included in the recording and playback head mounted in the recording and playback head unit is "recording module - playback module - recording module" (total number of modules: 3). Each module has 32 magnetic head elements (Ch0 to Ch31), and these magnetic head elements are sandwiched between a pair of servo signal reading elements to form an element array. The playback element width of the playback element included in the playback module is 0.8 μm. The environment in which the following recording was performed was the environment in which the servo band spacing obtained in the measurement to determine B was the largest of the five environments above. The environment in which the following playback was performed was the environment in which the servo band spacing obtained in the measurement to determine B was the smallest of the five environments above. The magnetic tape cartridge was left in the recording environment for at least five days. After acclimatizing to the recording environment, data was recorded in the same environment as described below. A magnetic tape cartridge is set in the magnetic tape device and the magnetic tape is loaded. Next, while performing servo tracking, pseudo-random data having a specific data pattern is recorded on the magnetic tape by the recording / playback head unit. At this time, the tension applied in the longitudinal direction of the tape is 0.7 N. For the recording / playback head (magnetic head), at the start of recording and at the start of playback, the axis of the element array is tilted toward the magnetic tape running direction, and the angle θ is as shown in Table 1 as "θ initial " column. When recording data, recording is performed three or more times so that the difference in the value of (PES1 + PES2) / 2 between adjacent tracks is 1.16 μm. During this process, the angle θ is changed by the magnetic tape device's control device so that the difference between the effective distance between one servo signal read element and the other servo signal read element in the element array of the read module of the recording / reading head and "PES2 - PES1," which corresponds to the spacing between two adjacent servo bands sandwiching a data band, becomes small. Simultaneously with data recording, the servo band spacing value along the entire length of the tape is measured every 1 meter along the length and recorded in the cartridge memory. The magnetic tape cartridges on which data had been recorded as described above were stored in a storage environment with an ambient temperature of 23°C and a relative humidity of 50% for 12 hours, followed by a storage cycle of 12 hours in a storage environment with an ambient temperature of 32°C and a relative humidity of 55%. Each cycle consisted of five storage cycles. The magnetic tape cartridge was then placed in the playback environment for at least five days. After acclimatizing to the playback environment, data was played back in the same environment as described below. Set a magnetic tape cartridge in the magnetic tape device and load the magnetic tape. Next, while performing servo tracking, reproduce the data recorded on the magnetic tape by the recording and reproducing head unit. At that time, while reproducing, measure the value of the servo band interval, and based on the information recorded in the cartridge memory, change the angle θ 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 approaches 0. During reproduction, the measurement of the servo band interval and the adjustment of the angle θ based thereon are continuously performed in real time. The number of reproducing elements (number of channels) in the above reproduction is 32 channels. During reproduction, when all the data of 32 channels are correctly read, the recording and reproducing performance is evaluated as "3", when the data of 31 to 28 channels are correctly read, the recording and reproducing performance is evaluated as "2", and in other cases, the recording and reproducing performance is evaluated as "1".

[0200] <Calculation of C> Regarding the above reproduction, the angle θ for the reproducing module was obtained by the method described above. Calculate Δθ from the obtained value, and calculate C by "C = L{cos(θ initial -Δθ)-cos(θ initial +Δθ)}". In the reproducing module included in the above recording and reproducing head, L was 2859 μm.

[0201] [Examples 2 to 32, Comparative Examples 1 to 12] A magnetic tape cartridge was produced by the method described for Example 1 except for the points where the items in Table 1 were changed as shown in Table 1, and various evaluations were performed. In the comparative examples described as "none" in the column of "heat treatment temperature" in Table 1, a magnetic tape with a final product length of 960 m was housed in the magnetic tape cartridge without performing heat treatment in a state wound around a heat treatment core. In Table 1, for the comparative examples described as "none" in the columns of "θ initial " and "Δθ", the angle θ = 0° was set at the start and during the running of the magnetic tape.

[0202] The results are shown in Table 1 (Table 1-1 to Table 1-4).

[0203] [Table 1-1]

[0204] [Table 1-2]

[0205] [Table 1-3]

[0206] [Table 1-4]

[0207] A magnetic tape cartridge was produced in the same manner as described above for Example 1, except that no vertical orientation treatment was performed during the production of the magnetic tape. A sample piece was cut from the magnetic tape removed from the magnetic tape cartridge. The squareness in the vertical direction of this sample piece was measured using a vibrating sample magnetometer, Model TM-TRVSM5050-SMSL, manufactured by Tamagawa Seisakusho, according to the method described above, and was found to be 0.55. The magnetic tape was also removed from the magnetic tape cartridge of Example 1, and a sample piece was cut out from this magnetic tape, and the squareness ratio in the vertical direction was similarly determined to be 0.60.

[0208] The magnetic tapes removed from the two magnetic tape cartridges were each attached to a 1 / 2-inch reel tester, and the electromagnetic conversion characteristics (SNR; Signal-to-Noise Ratio) were evaluated using the following method. As a result, the magnetic tape removed from the magnetic tape cartridge of Example 1 had an SNR value 2 dB higher than that of the magnetic tape produced without vertical orientation treatment. Ten passes of recording and playback were performed in an environment with a temperature of 23°C and a relative humidity of 50%, applying a tension of 0.70 N in the longitudinal direction of the magnetic tape. The relative speed between the magnetic tape and the magnetic head was 6 m / s. Recording was performed using a metal-in-gap (MIG) head (gap length 0.15 μm, track width 1.0 μm) as the recording head, with the recording current set to the optimum recording current for each magnetic tape. Playback was performed using a giant-magnetoresistive (GMR) head (element thickness 15 nm, shield spacing 0.1 μm, playback element width 0.8 μm) as the playback head. A signal with a linear recording density of 300 kfci was recorded, and the playback signal was measured using a Shibasoku spectrum analyzer. The unit kfci is the unit of linear recording density (not convertible to SI units). The signal was recorded from the point where the signal had sufficiently stabilized after the magnetic tape started running. [Industrial Applicability]

[0209] One aspect of the present invention is useful in the technical fields of various data storage such as archives.< / c>

Claims

1. A magnetic tape device including a magnetic tape and a magnetic head, the magnetic head has a module including an element array having a plurality of magnetic head elements between a pair of servo signal read elements, the magnetic tape device changes an angle θ formed by an axis of the element array with respect to a width direction of the magnetic tape while the magnetic tape is running within the magnetic tape device; The magnetic tape has a non-magnetic support and a magnetic layer containing ferromagnetic powder, the magnetic layer has a plurality of servo bands; The maximum absolute value of the difference between the servo band interval determined before the storage described below and the servo band interval determined after storage for N cycles, where one cycle is 12 hours of storage in an environment with a temperature of 23°C and a relative humidity of 50% and another 12 hours of storage in an environment with a temperature of 32°C and a relative humidity of 55%, is defined as A, the unit of A is μm, and the logarithm log of the total storage time T for the storage for N cycles is calculated. ｅ The logarithm of A and T, derived from the value of T ｅ The media life calculated by a linear function of T is 5 years or more, The media life is calculated by a linear function of the logarithm of T, log e T, calculated above, where A is expressed as follows: A = 1.5 - B + C is the value calculated as T when The B is Under the following five conditions: Temperature 16°C, relative humidity 20%, Temperature 16°C, relative humidity 80%, Temperature 26°C, relative humidity 80%, Temperature 32°C, relative humidity 20%, Temperature 32°C, relative humidity 55%, The value is calculated by multiplying the difference between the maximum and minimum values ​​of the servo band intervals obtained in the above by 1 / 2, and the unit is μm. The C is C=L{cos(θ) ｉｎｉｔｉａｌ -Δθ) -cos(θ) ｉｎｉｔｉａｌ +Δθ)} The value is calculated by the following equation, and the unit is μm. L is the distance between the pair of servo signal reading elements, and is expressed in μm. The angle θ at the start of magnetic tape running is θ ｉｎｉｔｉａｌ year, The maximum value of the angle θ during the running of the magnetic tape is set to θ ｍａｘ , the minimum value is θ ｍｉｎ As, The Δθ is Dth ｍａｘ =θ ｍａｘ -θ ｉｎｉｔｉａｌ Dth ｍｉｎ =θ ｉｎｉｔｉａｌ -θ ｍｉｎ The larger value among the values ​​calculated by Magnetic tape device.

2. 2. The magnetic tape device according to claim 1, wherein the medium life is between 5 years and 400 years.

3. 3. The magnetic tape device according to claim 1, wherein, while the magnetic tape is running in the magnetic tape device, an angle θ formed by an axis of the element array with respect to a width direction of the magnetic tape is changed in accordance with dimensional information of the magnetic tape in the width direction obtained during the running.

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

5. 5. The magnetic tape device according to claim 1, wherein the magnetic tape further comprises a backcoat layer containing non-magnetic powder on the surface of the non-magnetic support opposite to the surface having the magnetic layer.

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

7. 7. The magnetic tape device according to claim 6, wherein the aromatic polyester support is a polyethylene terephthalate support.

8. 7. The magnetic tape device according to claim 6, wherein the aromatic polyester support is a polyethylene naphthalate support.

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

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

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