Magnetic tape cartridges and magnetic recording / recovery devices

Abstract

Provided are a magnetic tape cartridge in which a magnetic tape is accommodated, and a magnetic recording playback device including the magnetic tape cartridge. The magnetic tape includes a polyethylene naphthalate support having a Young's modulus of 10000 MPa or greater in the width direction. The media life calculated according to a linear function derived from the value of A and the value of the logarithm logeT of total storage time T for storage for N cycles is 3 years or more, where A is the maximum absolute value of the difference between a servo band interval before storage of the magnetic tape and a servo band interval determined after storage for N cycles, with prescribed storage being one cycle.

Description

Technical Field

[0001] The present invention relates to a magnetic tape cartridge and a magnetic recording and reproducing apparatus.

Background Art

[0002] Magnetic recording media include tape-shaped and disk-shaped ones. For various data storage applications, a tape-shaped magnetic recording media, i.e., a magnetic tape, is mainly used (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Recording of data on a magnetic tape is usually performed by running the magnetic tape in a magnetic recording and reproducing apparatus (generally called a "drive"), causing a magnetic head to follow a data band of the magnetic tape, and recording the data on the data band. Thereby, data tracks are formed on the data band. Also, at the time of reproducing the recorded data, the magnetic tape is run in the magnetic recording and reproducing apparatus, the magnetic head is caused to follow the data band of the magnetic tape, and the data recorded on the data band is read. And after such recording or reproduction, the magnetic tape is stored in a state of being wound around a reel (hereinafter referred to as a "cartridge reel") in a magnetic tape cartridge until the next recording and / or reproduction is performed. ​​After storage as described above, when recording and / or playback is performed, deformation of the magnetic tape can cause the magnetic head used to record and / or play back data to shift from the intended track position, resulting in overwriting of recorded data, playback failures, and other problems. On the other hand, in recent years, there has been a growing need in the data storage field for long-term data storage, known as archiving.

[0006] Magnetic tape cartridges containing data-recorded magnetic tapes are sometimes stored in data centers where temperature and humidity are controlled. Meanwhile, data centers are required to reduce power consumption to lower costs. To achieve this, it is desirable to relax or eliminate temperature and humidity control conditions in data centers. However, if temperature and humidity control conditions are relaxed or eliminated, magnetic tapes are expected to be exposed to temperature and humidity fluctuations during long-term storage. Generally, the longer the storage period in such an environment, the more likely the magnetic tape is to deform. Therefore, it is expected that there will be an increasing need to suppress phenomena such as overwriting of recorded data and playback failures after such storage.

[0007] In view of the foregoing, one aspect of the present invention aims to enable good recording and / or playback of data on a magnetic tape after the magnetic tape cartridge containing the magnetic tape has been stored in a storage environment exposed to changes in temperature and humidity. [Means for solving the problem]

[0008] One aspect of the present invention is as follows: [1] A magnetic tape cartridge in which magnetic tape is wound and housed on a cartridge reel (hereinafter also simply referred to as "reel"), The above magnetic tape comprises a non-magnetic support and a magnetic layer containing ferromagnetic powder. The above non-magnetic support is a polyethylene naphthalate support with a Young's modulus in the width direction of 10,000 MPa or more. The above magnetic layer has multiple servo bands, Let A be 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 N cycles of storage, where one cycle consists of 12 hours of storage at 23°C and 50% relative humidity, followed by 12 hours of storage at 32°C and 80% relative humidity. The unit of A is μm, and the logarithm of the total storage time T for N cycles is calculated by taking the value of A as N = 1, 2, 3, 4, or 5. e The logarithm of A and T, derived from the value of T. e The media life calculated by a linear function with respect to T (hereinafter also referred to as "media life (life)") is 3 years or more. The above media life is A as shown in the following formula a: (Formula a) A = 1.5 - B T is when the conditions are met, 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%. This value is calculated by multiplying the difference between the maximum and minimum values ​​within the servo band intervals obtained by 1 / 2, and its unit is μm, for a magnetic tape cartridge. [2] The magnetic tape cartridge described in [1], wherein the media life is between 3 and 120 years. [3] The magnetic tape cartridge according to [1] or [2], wherein the Young's modulus in the width direction of the polyethylene naphthalate support is 10,000 MPa or more and 20,000 MPa or less. [4] The magnetic tape cartridge according to any one of [1] to [3], wherein the magnetic tape further comprises a non-magnetic layer containing non-magnetic powder between the non-magnetic support and the magnetic layer. [5] The magnetic tape cartridge according to any one of [1] to [4], wherein the magnetic tape further comprises a back coat layer containing non-magnetic powder on the surface side of the non-magnetic support opposite to the surface side having the magnetic layer. [6] The magnetic tape cartridge described in any of [1] to [5], wherein the tape thickness of the magnetic tape is 5.2 μm or less. [7] A magnetic tape cartridge as described in any of [1] to [6], wherein the vertical aspect ratio of the magnetic tape is 0.60 or greater. A magnetic recording and playback device including a magnetic tape cartridge as described in any one of items [8][1] to [7]. [9] The magnetic recording and reproducing apparatus according to [8], further comprising a magnetic head having a reproducing element width of 0.8 μm or less.

[10] The magnetic tape cartridge mentioned above, A reel and Includes, Between the above-mentioned take-up reel and the cartridge reel of the above-mentioned magnetic tape cartridge, the magnetic tape is run with tension applied in the longitudinal direction of the magnetic tape, and the maximum value of this tension is 0.50 N (Newtons) or more, and A magnetic recording and playback device according to [8] or [9], wherein the magnetic tape, after being run under the above tension, is wound onto the cartridge reel of the magnetic tape cartridge under a tension of 0.40 N or less in the longitudinal direction of the magnetic tape. [Effects of the Invention]

[0009] According to one aspect of the present invention, it is possible to enable good recording and / or playback of data on a magnetic tape after the magnetic tape cartridge containing the magnetic tape has been stored in a storage environment exposed to changes in temperature and humidity. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic diagram showing an example of a magnetic recording and playback device. [Figure 2]This is a perspective view of an example of a magnetic tape cartridge. [Figure 3] This is a perspective view of the moment when magnetic tape is being wound onto a reel. [Figure 4] This is a perspective view of the reel after the magnetic tape has been wound onto it. [Figure 5] An example of the arrangement of data bands and servo bands is shown. [Figure 6] This shows an example of a servo pattern arrangement for an LTO (Linear Tape-Open) Ultrium format tape. [Modes for carrying out the invention]

[0011] One aspect of the present invention relates to the magnetic tape cartridge described above.

[0012] Furthermore, one aspect of the present invention relates to a magnetic recording and playback device including the magnetic tape cartridge described above.

[0013] The magnetic tape cartridge described above includes a magnetic tape and a cartridge reel. In an unused magnetic tape cartridge before being installed in a magnetic recording and / or playback device for recording and / or playback of data, the magnetic tape is usually housed wound on the cartridge reel. In a magnetic recording and / or playback device, the magnetic tape is run between the cartridge reel (supply reel) and the take-up reel to record data onto the magnetic tape and / or play back recorded data. After recording or playback, the magnetic tape is rewound onto the cartridge reel and stored wound on the cartridge reel within the magnetic tape cartridge until the next recording and / or playback takes place. It is presumed that during storage, magnetic tape housed in a magnetic tape cartridge undergoes different deformations depending on its location. The portion near the cartridge reel deforms wider than its initial width due to compressive stress in the tape thickness direction, while the portion farther from the cartridge reel deforms narrower than its initial width due to tensile stress in the tape longitudinal direction. Such significant differences in deformation depending on location could cause the magnetic head to shift from the intended track position during recording and / or playback after storage. The inventors considered that the above deformations mainly consist of deformations caused by stress during storage and deformations mainly caused by the temperature and humidity of the environment in which data is recorded and / or played back (hereinafter referred to as the "usage environment"). Through further investigation, the inventors came to believe that comprehensively considering the deformations caused by the above factors would enable good recording and / or playback of data on magnetic tape after it has been stored in a magnetic tape cartridge. As a result of further diligent investigation, the inventors adopted media life as a comprehensive indicator regarding the deformations caused by the above factors, and newly discovered that magnetic tape cartridges with a media life of 3 years or more enable good recording and / or playback of data on magnetic tape after it has been stored in a magnetic tape cartridge in an environment exposed to changes in temperature and humidity.

[0014] The magnetic tape cartridge and magnetic recording / recovery device described above will be explained in more detail below. In the following, one form of the magnetic tape cartridge and magnetic recording / recovery device may be described with reference to the drawings. However, the magnetic tape cartridge and magnetic recording / recovery device are not limited to the forms shown in the drawings. Furthermore, the present invention is not limited by the inventors' inferences described herein.

[0015] [Media Life] The method for measuring media life, as described above, is explained below.

[0016] <Steps for deriving a linear function> (Measurement of servo band spacing) To derive the formula a for calculating A, the following servo band intervals are measured. The servo band spacing before storage is measured in a measurement environment of 23°C and 50% relative humidity. The magnetic tape cartridge to be measured is placed in an environment of 23°C and 50% relative humidity for 5 days to allow it to acclimate to the measurement environment. Subsequently, 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 recording and playback device having 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, with the data band in between, is measured at 1 m intervals along the entire length of the magnetic tape. In the measurements for determining the various values ​​described in this invention and specification, the value of the tension applied in the longitudinal direction of the magnetic tape is the set value set in the magnetic recording and playback device. Furthermore, in this invention and specification, "measurement at 1 m intervals" means that for a measurement target area of ​​length L meters (m), the position of one end of the measurement target area is 0 m, and each position in the direction toward the other end is 1 m, 2 m, 3 m, ..., and the position of the other end is L m. Then, the first measurement position is at 1 m, and the last measurement position is one position before L m. Furthermore, if there are multiple servo band intervals, all servo band intervals are measured in the same manner. The servo band spacing measured in this way is defined as the "servo band spacing before storage" at each measurement position. The following storage procedure for magnetic tape cartridges involves storing the cartridges in a storage environment with an ambient temperature of 23°C and a relative humidity of 50% (also referred to as "Storage Environment A") for 12 hours, followed by storage in a storage environment with an ambient temperature of 32°C and a relative humidity of 80% (also referred to as "Storage Environment B") for 12 hours. This constitutes one cycle. Therefore, the total storage time per cycle is 24 hours. After measuring the servo band spacing before storage as described above, perform one storage cycle. After storage, the magnetic tape cartridge is placed in a measurement environment with an ambient temperature of 23°C and a relative humidity of 50% for 5 days to allow it to acclimate to the measurement environment. Then, under the same measurement environment, the magnetic tape is run in a magnetic recording and playback 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. The servo band interval is measured during this run in the same manner as described above. The servo band interval measured in this way is defined as the "servo band interval after 24 hours of storage" at each measurement position. For all servo band spacings, the difference between the servo band spacing before storage and the servo band spacing after storage, measured at 1m intervals, is calculated. Multiple difference values ​​are obtained in this way. The maximum absolute value of the calculated difference is defined as "A after 24 hours of storage". The unit of A is μm. This is also true for the various A values ​​described below. The interval between two adjacent servo bands separated by a data band can be determined, for example, using the PES (Position Error Signal) obtained from the servo signal acquired by reading the servo pattern with a servo signal reading element. For details, please refer to the description of the embodiment below. After 12 hours of storage in storage environment A, the ambient temperature and relative humidity of the environment where the magnetic tape cartridge is located are changed to the ambient temperature and relative humidity of storage environment B within 60 minutes, and then storage is carried out in storage environment B for 12 hours. For environmental changes from storage environment B to storage environment A when two or more storage cycles are performed, after 12 hours of storage in storage environment B, the ambient temperature and relative humidity of the environment where the magnetic tape cartridge is located are changed to the ambient temperature and relative humidity of storage environment A within 60 minutes, and then storage is carried out in storage environment A for 12 hours. After measuring the servo band interval following 24 hours (1 cycle) of storage, the magnetic tape cartridge is subjected to 2 cycles of storage. The total storage time for these 2 cycles is 48 hours. After storage, the magnetic tape cartridge is placed in a measurement environment with an ambient temperature of 23°C and a relative humidity of 50% for 5 days. Then, under the same measurement environment, the magnetic tape is run in a magnetic recording and playback 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. The servo band interval is measured during this run in the same manner as described above. The servo band interval measured in this manner is defined as the "servo band interval after 48 hours of storage" at each measurement position. For all servo band spacings, the difference between the servo band spacing before storage and the servo band spacing after storage, measured at 1m intervals, is calculated. Multiple difference values ​​are obtained in this way. The maximum absolute value of the calculated difference is defined as "A after 48 hours of storage". After measuring the servo band interval following 48 hours (2 cycles) of storage, the magnetic tape cartridge is subjected to 3 cycles of storage. The total storage time for these 3 cycles is 72 hours. After storage, the magnetic tape cartridge is placed in a measurement environment with an ambient temperature of 23°C and a relative humidity of 50% for 5 days. Then, under the same measurement environment, the magnetic tape is run in a magnetic recording and playback 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. The servo band interval is measured during this run in the same manner as described above. The servo band interval measured in this manner is defined as the "servo band interval after 72 hours of storage" at each measurement position. For all servo band spacings, the difference between the servo band spacing before storage and the servo band spacing after storage, measured at 1m intervals, is calculated. Multiple difference values ​​are obtained in this way. The maximum of the calculated absolute values ​​of the differences is defined as "A after 72 hours of storage". After measuring the servo band interval following 72 hours (3 cycles) of storage, the magnetic tape cartridge is subjected to 4 cycles of storage. The total storage time for these 4 cycles is 96 hours. After storage, the magnetic tape cartridge is placed in a measurement environment with an ambient temperature of 23°C and a relative humidity of 50% for 5 days. Then, under the same measurement environment, the magnetic tape is run in a magnetic recording and playback 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. The servo band interval is measured during this run in the same manner as described above. The servo band interval measured in this manner is defined as the "servo band interval after 96 hours of storage" at each measurement position. For all servo band spacings, the difference between the servo band spacing before storage and the servo band spacing after storage, measured at 1m intervals, is calculated. Multiple difference values ​​are obtained in this way. The maximum of the calculated absolute values ​​of the differences is defined as "A after 96 hours of storage". After measuring the servo band interval following 96 hours (4 cycles) of storage, the magnetic tape cartridge is subjected to 5 cycles of storage. The total storage time for these 5 cycles is 120 hours. After storage, the magnetic tape cartridge is placed in a measurement environment with an ambient temperature of 23°C and a relative humidity of 50% for 5 days. Then, under the same measurement environment, the magnetic tape is run in a magnetic recording and playback 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. The servo band interval is measured during this run in the same manner as described above. The servo band interval measured in this manner is defined as the "servo band interval after 120 hours of storage" at each measurement position. For all servo band spacings, the difference between the servo band spacing before storage and the servo band spacing after storage, measured at 1m intervals, is calculated. Multiple difference values ​​are obtained in this way. The maximum absolute value of the calculated difference is defined as "A after 120 hours of storage".

[0017] The inventors believe that the value of A obtained as described above can serve as an indicator of deformation mainly caused by stress on the magnetic tape during storage in a magnetic tape cartridge in an environment exposed to changes in temperature and humidity.

[0018] (Derivation of a linear function) In the above process, the values of A are obtained for five types of storage times T. From these values of A and the logarithms log e of the values of T, a linear function between 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.

[0019] <Procedure for determining B>[[]]END]] 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 half of 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 to be measured 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%). Subsequently, under the measurement environment, the magnetic tape is run in a magnetic recording and playback device equipped with a tension adjustment mechanism that applies tension in the longitudinal direction of the magnetic tape, with a tension of 0.70N applied in the longitudinal direction of the magnetic tape. For the magnetic tape, the end on the side wound on the reel of the magnetic tape cartridge is called the inner end, and the end on the opposite side is called the outer end. The outer end is set to 0m, and the servoband interval is measured at 1m intervals in the region from 0m to 100m in length (hereinafter referred to as the "100m outer circumference region of the reel") during the above run at databand 0 (zero). "Databand 0" is the databand defined by the standard as the databand in which data is first embedded (recorded). The arithmetic mean of the measured servoband intervals is taken as the servoband interval in that measurement environment. After determining the servo band interval in each of the five environments as described above, the maximum and minimum values ​​among the obtained values ​​are used to calculate the value "B" of the magnetic tape cartridge being measured as "(maximum value - minimum value) × 1 / 2". The inventors believe that the B thus obtained can serve as an indicator of deformation mainly caused by the temperature and humidity of the operating environment.

[0020] <Calculation of media life> The media life is the logarithm of A and T derived above. eThe value of T is calculated as the value of T when A satisfies the equation "Equation a: A = 1.5 - B" using a linear function with T. The inventors believe that the media life thus calculated being 3 years or more, that is, the time T at which A + B becomes 1.5 μm being 3 years or more, indicates that the total amount of deformation, mainly caused by stress on the magnetic tape during storage in a magnetic tape cartridge in an environment exposed to changes in temperature and humidity, and mainly caused by temperature and humidity in the usage environment, is unlikely to increase significantly over a long period of time. The reason for adopting 1.5 μm and 3 years as thresholds is to take into account the needs for long-term storage and high-density recording that are expected to be desired in the future. Regarding media life, 1 year is defined as 365 days. Therefore, 1 year is 365 × 24 hours = 8760 hours. Also, 0.5 years is defined as 6 months, and 1 month is defined as 30 days. Therefore, 0.5 years is 6 × 30 × 24 hours = 4320 hours. The above-mentioned measurement environments are examples only, and the magnetic tape cartridges are not limited to those stored and / or used in the environments described above.

[0021] The media life of the above magnetic tape cartridge is preferably 3 years or more, and more preferably 10 years or more, in order of preference, to enable good recording and / or playback of data on the magnetic tape after it has been stored in the magnetic tape cartridge. The media life of the above magnetic tape cartridge can be, for example, 250 years or less, 240 years or less, 230 years or less, 220 years or less, 210 years or less, 200 years or less, 190 years or less, 180 years or less, 170 years or less, 160 years or less, 150 years or less, 140 years or less, 130 years or less, or 120 years or less, and can exceed the values ​​exemplified herein. The method for controlling the media life will be described later.

[0022] The value of B for the above magnetic tape cartridge can be, for example, 0.0 μm or more, greater than 0.0 μm, 0.05 μm or more, or 0.1 μm or more, or it can be, for example, 2.0 μm or less, 1.5 μm or less, or 0.5 μm or less. However, the above magnetic tape cartridge only needs to have a media life of 3 years or more, and the value of B is not limited to the above range.

[0023] [Configuration of a magnetic recording and playback device] Figure 1 is a schematic diagram showing an example of a magnetic recording and playback device. The magnetic recording and playback device 10 shown in Figure 1 controls the recording and playback head unit 12 by command from the control device 11 to record and play back data on the magnetic tape MT. The magnetic recording and playback device 10 has a configuration that allows for the detection and adjustment of tension applied in the longitudinal direction of the magnetic tape from the spindle motors 17A, 17B and their drive units 18A, 18B that control the rotation of the cartridge reel 130 and the take-up reel 16. The magnetic recording and playback device 10 has a configuration that allows a magnetic tape cartridge 13 to be installed. The magnetic recording and playback device 10 has a cartridge memory read / write device 14 that can read from and write to the cartridge memory 131 in the magnetic tape cartridge 13. From the magnetic tape cartridge 13 mounted in the magnetic recording and playback device 10, the end of the magnetic tape MT or the leader pin is pulled out by an automatic loading mechanism or manually, and the magnetic layer surface of the magnetic tape MT passes over the recording and playback head through guide rollers 15A and 15B with the magnetic layer surface of the recording and playback head unit 12 in contact with the surface of the recording and playback head, and the magnetic tape MT is wound onto the take-up reel 16. The rotation and torque of spindle motors 17A and 17B are controlled by signals from the control device 11, so that the magnetic tape MT runs at a desired speed and tension. A servo pattern pre-formed on the magnetic tape can be used to control the tape speed. A tension detection mechanism may be provided between the magnetic tape cartridge 13 and the take-up reel 16 for tension detection. In addition to control by spindle motors 17A and 17B, tension adjustment may also be performed using guide rollers 15A and 15B. The cartridge memory read / write device 14 is configured to read and write information to the cartridge memory 131 in response to commands from the control device 11. For example, the ISO (International Organization for Standardization) 14443 standard can be used as the communication method between the cartridge memory read / write device 14 and the cartridge memory 131.

[0024] The control device 11 includes, for example, a control unit, a storage unit, a communication unit, and the like.

[0025] The recording / playback head unit 12 consists of, for example, a recording / playback head, a servo tracking actuator for adjusting the position of the recording / playback head in the track width direction, a recording / playback amplifier 19, and a connector cable for connecting to the control device 11. The recording / playback head consists of, for example, a recording element for recording data on magnetic tape, a playback element for reproducing data on magnetic tape, and a servo signal reading element for reading servo signals recorded on magnetic tape. Within a single magnetic head, for example, one or more recording elements, playback elements, and servo signal reading elements are mounted. Alternatively, each element may be separately contained in multiple magnetic heads corresponding to the direction in which the magnetic tape travels.

[0026] The recording / playback head unit 12 is configured to record data onto the magnetic tape MT in response to commands from the control device 11. It is also configured to play back data recorded on the magnetic tape MT in response to commands from the control device 11.

[0027] The control device 11 has a mechanism to determine the running position of the magnetic tape MT from the servo signals read from the servo bands when the magnetic tape MT is running, and to control the servo tracking actuator so that the recording element and / or playback element are positioned at the target running position (track position). This track position control is performed, for example, by feedback control. The control device 11 has a mechanism to determine the servo band interval from the servo signals read from two adjacent servo bands when the magnetic tape MT is running. It also has a mechanism to adjust and change the tension applied to the longitudinal direction of the magnetic tape by controlling the torque of the spindle motor 17A and spindle motor 17B and / or the guide rollers 15A and 15B so that the servo band interval becomes a target value. This tension adjustment is performed, for example, by feedback control. Furthermore, the control device 11 can store the determined servo band interval information in an internal memory unit of the control device 11, a cartridge memory 131, or external connected equipment.

[0028] In the magnetic recording and playback device described above, tension can be applied to the magnetic tape in the longitudinal direction during recording and / or playback. In one embodiment, the tension applied to the magnetic tape in the longitudinal direction during recording and / or playback is a constant value, and in another embodiment, it changes. With respect to tension in the present invention and this specification, the value of the tension applied to the magnetic tape in the longitudinal direction in the magnetic recording and playback device is the value of tension that the control device of the magnetic recording and playback device uses to control the mechanism for adjusting the above tension, as the tension that should be applied to the magnetic tape in the longitudinal direction. Furthermore, the tension actually applied to the magnetic tape in the longitudinal direction in the magnetic recording and playback device can be detected, for example, by providing a tension detection mechanism between the magnetic tape cartridge 13 and the take-up reel 16 in Figure 1, as described above. In addition, the control device of the magnetic recording and playback device can also control the tension so that, for example, the minimum tension does not fall below a value specified or recommended by standards, and / or the maximum tension does not exceed a value specified or recommended by standards.

[0029] In one embodiment, a magnetic recording and playback device may have a tension adjustment mechanism that can adjust the tension applied to the magnetic tape running in the longitudinal direction within the magnetic recording and playback device. Such a tension adjustment mechanism can variably control the tension applied to the magnetic tape in the longitudinal direction, and preferably, by adjusting the tension applied to the magnetic tape in the longitudinal direction, the width dimension of the magnetic tape can be controlled. In the above tension adjustment, the tension applied to the magnetic tape in the longitudinal direction can change. An example of a magnetic recording and playback device having a tension adjustment mechanism has been described above with reference to Figure 1. However, the present invention is not limited to the example shown in Figure 1.

[0030] [Magnetic tape cartridge] Before being installed in a magnetic tape recorder and after being removed from the magnetic tape recorder, a magnetic tape cartridge generally contains the magnetic tape wound on a cartridge reel inside the cartridge body. The cartridge reel is rotatably mounted inside the cartridge body. Commonly used magnetic tape cartridges include single-reel cartridges, which have one reel inside the cartridge body, and dual-reel cartridges, which have two reels inside the cartridge body. In one form, the magnetic tape cartridge can be a single-reel cartridge, and in another form, a dual-reel cartridge. In the case of a dual-reel magnetic tape cartridge, the cartridge reel refers to the reel that is primarily used to wind the magnetic tape when it is stored after data recording and / or playback, while the other reel is called the take-up reel. When a single-reel magnetic tape cartridge is mounted in a magnetic recording and playback device for recording and / or playing back data onto magnetic tape, the magnetic tape is pulled out of the cartridge and wound onto the take-up reel of the magnetic recording and playback device, for example, as shown in Figure 1. A magnetic head is positioned along the magnetic tape transport path from the magnetic tape cartridge to the take-up reel. The magnetic tape moves by being fed out and wound back between the cartridge reel of the magnetic tape cartridge (also called the "supply reel") and the take-up reel of the magnetic recording and playback device. During this time, data is recorded and / or played back by contact and sliding between, for example, the magnetic head and the magnetic layer surface of the magnetic tape. In contrast, a dual-reel magnetic tape cartridge has 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.

[0031] The above-mentioned magnetic tape cartridge may, in one form, include cartridge memory. The cartridge memory may be, for example, non-volatile memory, and may already contain or contain tension adjustment information. Tension adjustment information is information for adjusting the tension applied to the magnetic tape in the longitudinal direction. See also the previous description for more information on cartridge memory.

[0032] Figure 2 is a perspective view of an example of a magnetic tape cartridge. Figure 2 shows a single-reel magnetic tape cartridge.

[0033] The magnetic tape cartridge 13 shown in Figure 2 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. Inside the case 112, a single reel 130 is rotatably housed.

[0034] Figure 3 is a perspective view of the moment when the magnetic tape is first wound onto the reel. Figure 4 is a perspective view of the moment when the magnetic tape has been completely wound onto the reel.

[0035] The reel 130 has a cylindrical reel hub 122 that forms the axial center.

[0036] The reel hub is a cylindrical member that constitutes the central axis around which the magnetic tape is wound within the magnetic tape cartridge. In the magnetic tape cartridge described above, the reel hub can be a single-layer cylindrical member or a multi-layer cylindrical member with two or more layers. From the viewpoint of manufacturing cost and ease of manufacturing, the reel hub is preferably a single-layer cylindrical member.

[0037] The inventors believe that high rigidity of the reel hub around which the reel is wound within the magnetic tape cartridge is desirable for increasing the media lifespan. This is for the following reasons: It is thought that the reel hub is subjected to a winding force towards the center as the magnetic tape is wound around it, and tends to deform in the direction of decreasing diameter. The lower the rigidity of the reel hub, the more easily it is thought to deform. On the cartridge core side of the magnetic tape, compressive stress is generated in the direction of shortening the tape length in response to the deformation of the reel hub, and then, due to the compression caused by this compressive stress, tensile stress is generated in the direction of widening the tape width. It is thought that the greater the stress generated in this way, the more likely the magnetic tape is to undergo significant deformation during storage in the magnetic tape cartridge. In contrast, if the rigidity of the reel hub is high, it is possible to suppress the above deformation, and thus it is possible to suppress the generation of the above stress, which is thought to contribute to increasing the media life value. From this point of view, in one embodiment, the flexural modulus of the material constituting at least the outer 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 above 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 desirable from the viewpoint of suppressing deformation of the reel hub, the flexural modulus may exceed the value exemplified here.

[0038] The above flexural modulus is the flexural modulus of the material constituting the cylindrical member when the reel hub is a single-layer cylindrical member. On the other hand, when the reel hub is a multilayer cylindrical member with two or more layers, the above flexural modulus is the flexural modulus of the material constituting at least the outer surface layer of the reel hub. In the present invention and this specification, "flexural modulus" is a value obtained in accordance with JIS (Japanese Industrial Standards) K 7171:2016. JIS K 7171:2016 is a Japanese Industrial Standard created without changing the technical content, based on ISO (International Organization for Standardization) 178 and Amendment 1:2013, which were published as the 5th edition in 2010. The test specimen used to measure the flexural modulus is prepared in accordance with item 6 "Test specimen" of JIS K 7171:2016.

[0039] Materials that can constitute a reel hub include resins and metals. An example of a metal is aluminum. From the viewpoint of cost and productivity, resins are preferred. An example of a resin is fiber-reinforced resin. Examples of fiber-reinforced resins include glass fiber reinforced resins and carbon fiber reinforced resins. Fiber-reinforced polycarbonate is preferred as such a fiber-reinforced resin. This is because polycarbonate is readily available and can be molded with high precision and at low cost using general-purpose molding machines such as injection molding machines. Furthermore, in glass fiber reinforced resins, the glass fiber content 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. As an example, the glass fiber content of a 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. Other resins that can constitute the reel hub include high-strength resins generally known as super engineering plastics. One example of a super engineering plastic is polyphenylene sulfide (PPS).

[0040] The thickness of the reel hub is preferably in the range of 2.0 to 3.0 mm, from the viewpoint of achieving both strength and dimensional accuracy during molding. For reel hubs with a multilayer structure of two or more layers, the thickness of the reel hub refers to the total thickness of such multilayers. The outer diameter of the reel hub is usually determined by the specifications of the magnetic recording and playback device, and can be in the range of, for example, 20 to 60 mm.

[0041] The reel hub 122 is provided with flanges (lower flange 124 and upper flange 126) that extend radially outward from the lower and upper ends of the reel hub 122, respectively. Here, "upper" refers to the side located above when the magnetic tape cartridge is mounted on a magnetic recording and playback device, and "lower" refers to the side located below. It is preferable that one or both of the lower flange 124 and the upper flange 126 are integrally configured with the reel hub 122 from the viewpoint of reinforcing the upper and / or lower end sides of the reel hub 122. Integral configuration means that they are configured as a single component rather than as separate components. In the first embodiment, the reel hub 122 and the upper flange 126 are configured as a single component, and this component is joined to the lower flange 124, which is configured as a separate component, in a known manner. In the second embodiment, the reel hub 122 and the lower flange 124 are configured as a single component, and this component is joined to the upper flange 126, which is configured as a separate component, in a known manner. The reel of the magnetic tape cartridge may take any of the above forms. Each component can be manufactured by a known molding method such as injection molding.

[0042] The magnetic tape MT is wound around the outer circumference of the reel hub 122, starting from the inner end Tf of the tape (see Figure 3). Reducing the tension applied in the longitudinal direction of the magnetic tape when winding it onto the reel hub of the cartridge reel during the manufacturing of the magnetic tape cartridge (hereinafter also referred to as "manufacturing winding tension") can also contribute to increasing the media life. From this point of view, the manufacturing winding tension is preferably 0.40 N or less, and can also 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 it can be tension-free. The manufacturing winding tension can be a constant value or it can be varied. The manufacturing winding tension is set to a set value in the magnetic tape cartridge manufacturing apparatus.

[0043] 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, which is pulled out while being locked in place by a pull-out member (not shown) of a magnetic recording and playback device (not shown).

[0044] Furthermore, 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 in the direction of closing the opening 114 by a biasing member (not shown). The door 118 is then opened against the biasing force of the biasing member when the magnetic tape cartridge 13 is installed in the magnetic recording and playback device.

[0045] For other details of the magnetic tape cartridge, known technology can be applied. The total length of the magnetic tape housed in the magnetic tape cartridge is not particularly limited and can be in the range of, for example, 800m to 2500m. A longer total length of tape housed in one magnetic tape cartridge is preferable from the viewpoint of increasing the capacity of the magnetic tape cartridge.

[0046] [Tension during operation, tension when winding onto the cartridge reel] In a magnetic recording and playback device, data can be recorded on the magnetic tape and / or recorded data can be played back by running the magnetic tape between a cartridge reel (supply reel) and a take-up reel. In the above magnetic recording and playback device, tension can be applied to the magnetic tape in the longitudinal direction during this running. The greater the tension applied to the magnetic tape in the longitudinal direction, the greater the reduction in the width dimension of the magnetic tape (i.e., the narrower it can be made), and the smaller the tension, the smaller the degree of reduction. Therefore, the width dimension of the magnetic tape can be controlled by the value of the tension applied to the magnetic tape running in the longitudinal direction within the magnetic recording and playback device. In one embodiment of the above magnetic recording and playback device, the magnetic tape can be run with a tension of up to 0.50 N or more applied to the longitudinal direction. If the magnetic tape is stored in the magnetic tape cartridge immediately after running under such high tension, it is thought that deformation of the magnetic tape is likely to occur during storage. As mentioned earlier, it is presumed that during storage, magnetic tapes housed in magnetic tape cartridges undergo different deformations depending on their location. For example, the portion of the tape closest to the cartridge reel deforms wider than its initial width due to compressive stress in the tape thickness direction, while the portion further from the cartridge reel deforms narrower than its initial width due to tensile stress in the tape longitudinal direction. In such cases, magnetic tapes stored under high tension are likely to exhibit even greater differences in deformation depending on their location. Therefore, in one embodiment, when winding a magnetic tape onto a cartridge reel after it has been run with a tension of 0.50 N or more applied to its longitudinal direction, it is preferable to set the tension applied to the magnetic tape in its longitudinal direction to 0.40 N or less. This makes it possible to wind the magnetic tape onto the cartridge reel with a tension smaller than the tension applied in the longitudinal direction during run and store it in the magnetic tape cartridge, which the inventors believe can further suppress the occurrence of the phenomena that may occur due to the deformation described above. Furthermore, the inventors surmise that setting the tension applied to the magnetic tape in its longitudinal direction to 0.40 N or less when winding the magnetic tape onto a cartridge reel after run, regardless of whether tension was applied during run or the value of the tension, is preferable in further suppressing the occurrence of the phenomena that may occur due to the deformation described above.

[0047] In the above-described magnetic recording and playback device, when tension is applied to the longitudinal direction of the magnetic tape while it is running, the maximum value of such tension can be 0.50 N or more, and can also be 0.60 N or more, 0.70 N or more, or 0.80 N or more. Furthermore, such a maximum value can be, for example, 1.50 N or less, 1.40 N or less, 1.30 N or less, 1.20 N or less, 1.10 N or less, or 1.00 N or less. The tension applied to the longitudinal direction of the magnetic tape while it is running can be a constant value or can be changed. In the case of a constant value, the tension applied to the longitudinal direction of the magnetic tape can be controlled, for example, by the control device of the magnetic recording and playback device, so that a constant value of tension is applied to the longitudinal direction of the magnetic tape. On the other hand, when the tension applied to the longitudinal direction of the magnetic tape is changed while it is running, for example, dimensional information in the width direction of the magnetic tape while it is running can be obtained using a servo signal, and the tension applied to the longitudinal direction of the magnetic tape can be adjusted and changed according to the obtained dimensional information. This makes it possible to control the width direction dimension of the magnetic tape. One form of such tension adjustment has been explained earlier with reference to Figure 1. However, the magnetic recording and playback device described above is not limited to the exemplary form. In the magnetic recording and playback device described above, when the tension applied to the longitudinal direction of the magnetic tape while it is running is changed, the minimum value can be, for example, 0.10 N or more, 0.20 N or more, 0.30 N or more, or 0.40 N or more. In one embodiment, such a minimum value can be, for example, 0.40 N or less or less than 0.40 N, and in another embodiment, it can be 0.60 N or less or 0.50 N or less.

[0048] In a magnetic recording and playback device, when running a magnetic tape for recording and / or playback of data, the following are examples of specific forms of how the magnetic tape is run. Form 1: At the end of the run for data recording and / or playback, the entire length of the magnetic tape is wound onto the take-up reel. Form 2: At the end of the run for data recording and / or playback, the entire length of the magnetic tape is wound onto the cartridge reel. Configuration 3: At the end of the run for data recording and / or playback, part of the magnetic tape is wound onto a cartridge reel and part of it is wound onto a take-up reel.

[0049] The tension applied when winding the magnetic tape onto the cartridge reel after it has been run, in the longitudinal direction of the magnetic tape (hereinafter also referred to as "rewinding tension") refers to the following tension: In Embodiment 1, the rewinding tension is the tension applied in the longitudinal direction of the magnetic tape when winding the entire length of the magnetic tape onto the cartridge reel in order to house it in the magnetic tape cartridge. In Form 2, the magnetic tape is first wound from the cartridge reel onto the take-up reel. The tension applied to the magnetic tape in the longitudinal direction at this time is not particularly limited. It may be a constant value, may be varied, and may or may not follow the previously described value of tension during operation. The tension applied to the magnetic tape in the longitudinal direction when it is subsequently wound onto the cartridge reel is the rewinding tension. This tension is the tension applied to the magnetic tape in the longitudinal direction when the entire length of the magnetic tape is wound from the take-up reel onto the cartridge reel. Form 3 can be one of the following two forms. The first form (Form 3-1) is a form in which, at the end of running for data recording and / or playback, the portion of the magnetic tape wound on the cartridge reel is wound with tension applied in the longitudinal direction when being wound onto the cartridge reel. This tension during winding is the rewinding tension. The second form (Form 3-2) is a form of Form 3 other than Form 3-1. In Form 3-1, in order to wind the entire length of the magnetic tape onto the cartridge reel and house it in the cartridge, the tension applied in the longitudinal direction of the magnetic tape when winding the magnetic tape that is not wound on the cartridge reel onto the cartridge reel is the rewinding tension. Form 3-2 is the same as Form 2. That is, first the magnetic tape is wound from the cartridge reel to the take-up reel. Then the tension applied in the longitudinal direction of the magnetic tape when winding the entire length of the magnetic tape from the take-up reel to the cartridge reel is the rewinding tension. In any of the above embodiments 1, 2, and 3, the tension applied to the longitudinal direction of the magnetic tape when winding it onto the cartridge reel (rewinding tension) is preferably 0.40 N or less. The rewinding tension may be a constant value or may be varied. In one embodiment, the rewinding tension may be a constant value of 0.40 N or less, or may be varied within a range of 0.40 N or less. When varied, the maximum value of the tension applied to the longitudinal direction of the magnetic tape when winding it onto the cartridge reel is preferably 0.40 N or less, and can also be, for example, 0.30 N or less. The minimum value of the tension applied to the longitudinal direction of the magnetic tape when winding it onto the cartridge reel can be, for example, 0.10 N or more or 0.20 N or more, or may be lower than the values ​​exemplified here. The tension applied when winding onto the cartridge reel (rewinding tension) can be controlled, for example, by the control device of the magnetic recording and playback device. Alternatively, an operation program may be recorded in the cartridge memory so that after recording and / or playing back data on the magnetic tape, the set rewind tension is applied in the longitudinal direction of the magnetic tape and it is wound onto the cartridge reel. The control device may then read this program and execute the winding operation.

[0050] [Magnetic tape] In the magnetic tape cartridge described above, the magnetic tape is wound onto a cartridge reel and housed within it. The following provides a more detailed explanation of such magnetic tape.

[0051] <Nonmagnetic support> The above magnetic tape includes a polyethylene naphthalate support as a non-magnetic support (hereinafter also simply referred to as "support"), with a Young's modulus in the width direction of 10,000 MPa (megapascals) or more.

[0052] Polyethylene naphthalate (PEN) is a resin containing a naphthalene ring and multiple ester bonds (i.e., a polyester containing a naphthalene ring), which can be obtained by esterification of 2,6-naphthalenedicarboxylate dimethyl with ethylene glycol, followed by transesterification and polycondensation reactions. In this invention and specification, "polyethylene naphthalate" also includes structures having one or more other components in addition to the above components (e.g., copolymer components, components introduced into terminals or side chains, etc.). In this invention and specification, "polyethylene naphthalate support" means a support containing at least one layer of polyethylene naphthalate film. "Polyethylene naphthalate film" means a film in which polyethylene naphthalate is the most abundant component by mass among the components constituting the film. In this invention and specification, "polyethylene naphthalate support" includes supports in which all resin films contained in the support are polyethylene naphthalate films, and supports containing polyethylene naphthalate films and other resin films. Specific embodiments of the polyethylene naphthalate support include a single-layer polyethylene naphthalate film, a laminated film of two or more polyethylene naphthalate films with the same constituent components, a laminated film of two or more polyethylene naphthalate films with different constituent components, and a laminated film containing one or more polyethylene naphthalate films and one or more layers of resin films other than polyethylene naphthalate. In the laminated film, an adhesive layer or the like may be optionally included between two adjacent layers. Furthermore, the polyethylene naphthalate support may optionally include a metal film and / or a metal oxide film formed by vapor deposition or the like on one or both surfaces.

[0053] Furthermore, the non-magnetic support can be a biaxially oriented film, and may be a film that has been subjected to corona discharge, plasma treatment, easy adhesion treatment, heat treatment, etc.

[0054] In the present invention and this specification, the Young's modulus of a non-magnetic support is a value measured by the following method in a measurement environment of 23°C and 50% relative humidity. The Young's moduli shown in the table below are values ​​obtained by the following method using a Tensilon universal tensile testing device manufactured by Toyo Baldwin Co., Ltd. A sample piece cut from the non-magnetic support to be measured is pulled using a universal tensile testing apparatus under the conditions of a chuck distance of 100 mm, a tensile speed of 10 mm / min, and a chart speed of 500 mm / min. As the universal tensile testing apparatus, commercially available universal tensile testing apparatuses such as the Tensilon manufactured by Toyo Baldwin Co., Ltd., or universal tensile testing apparatuses with known configurations can be used. From the tangents of the rising portion of the load-elongation curve thus obtained, the Young's modulus in the longitudinal and width directions of the sample piece is calculated, respectively. Here, the longitudinal and width directions of the sample piece refer to the longitudinal and width directions when the sample piece was contained in a magnetic tape. For example, after removing parts other than the non-magnetic support, such as the magnetic layer, from the magnetic tape using a known method (e.g., defilm removal using an organic solvent), the Young's modulus in the longitudinal and width directions of the non-magnetic support can be determined using the method described above.

[0055] The Young's modulus in the width direction of the polyethylene naphthalate support is 10,000 MPa or more. The inventors believe that including such a non-magnetic support in the magnetic tape can contribute to increasing the media life. The Young's modulus in the width direction of the polyethylene naphthalate support can also be, for example, 11,000 MPa or more. Furthermore, the Young's modulus in the width direction of the polyethylene naphthalate support may be, for example, 20,000 MPa or less, 18,000 MPa or less, 16,000 MPa or less, or 14,000 MPa or less, and may exceed the values ​​exemplified herein.

[0056] The polyethylene naphthalate support described above only needs to have a Young's modulus of 10,000 MPa or more in the width direction, and the Young's modulus in the longitudinal direction is not particularly limited. In one embodiment, the Young's modulus in the longitudinal direction of the polyethylene naphthalate support is preferably 2,500 MPa or more, and more preferably 3,000 MPa or more. Furthermore, the Young's modulus in the longitudinal direction of the polyethylene naphthalate support can be, for example, 10,000 MPa or less, 9,000 MPa or less, 8,000 MPa or less, 7,000 MPa or less, or 6,000 MPa or less. When manufacturing magnetic tape, non-magnetic supports are usually used with the MD direction (Machine direction) of the film as the longitudinal direction and the TD direction (Transverse direction) as the width direction. In one embodiment, the Young's modulus in the longitudinal direction and the Young's modulus in the width direction of the non-magnetic support can be the same value, and in another embodiment, they can be different values. In one embodiment, the Young's modulus in the width direction of the polyethylene naphthalate support can be a larger value than the Young's modulus in the longitudinal direction.

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

[0058] In one embodiment, the polyethylene naphthalate support preferably has a water content of 2.0% or less, more preferably 1.8% or less, even more preferably 1.6% or less, even more preferably 1.4% or less, even more preferably 1.2% or less, and even more preferably 1.0% or less. The water content of the polyethylene naphthalate support can also be 0%, 0% or more, greater than 0%, or 0.1% or more. Using a non-magnetic support with a low water content may contribute to increasing the media life value. This is mainly because using a non-magnetic support with a low water content is thought to contribute to reducing the value of "B" obtained by the method described above.

[0059] The water content and Young's modulus of a non-magnetic support can be controlled by the type and mixing ratio of the components constituting the support, the manufacturing conditions of the support, etc. For example, by adjusting the stretching ratio in each direction during biaxial stretching, the Young's modulus in the longitudinal direction and the Young's modulus in the width direction can be controlled, respectively.

[0060] <Magnetic layer> (Ferromagnetic powder) As the ferromagnetic powder contained in the magnetic layer of the above-mentioned magnetic tape, one or more ferromagnetic powders known as ferromagnetic powders used in the magnetic layers of various magnetic recording media can be used. 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 still 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.

[0061] Hexagonal ferrite powder A preferred example of ferromagnetic powder is hexagonal ferrite powder. For details on hexagonal ferrite powder, see, for example, paragraphs 0012 to 0030 of Japanese Patent Publication No. 2011-225417, paragraphs 0134 to 0136 of Japanese Patent Publication No. 2011-216149, paragraphs 0013 to 0030 of Japanese Patent Publication No. 2012-204726, and paragraphs 0029 to 0084 of Japanese Patent Publication No. 2015-127985.

[0062] In the present invention and this specification, "hexagonal ferrite powder" refers to a ferromagnetic powder in which a hexagonal ferrite crystal structure is detected as the main phase by X-ray diffraction analysis. The main phase refers to the structure to which the highest intensity diffraction peak in the X-ray diffraction spectrum obtained by X-ray diffraction analysis belongs. For example, if the highest intensity diffraction peak in the X-ray diffraction spectrum obtained by X-ray diffraction analysis is attributed to the hexagonal ferrite crystal structure, it shall be determined that the hexagonal ferrite crystal structure has been detected as the main phase. If only a single structure is detected by X-ray diffraction analysis, this detected structure shall be considered the main phase. The hexagonal ferrite crystal structure contains at least iron atoms, divalent metal atoms, and oxygen atoms as constituent atoms. Divalent metal atoms are metal atoms that can become divalent cations as ions, and examples include strontium atoms, barium atoms, alkaline earth metal atoms such as calcium atoms, and lead atoms. In the present invention and this specification, hexagonal strontium ferrite powder refers to powder in which the main divalent metal atom contained is strontium, and hexagonal barium ferrite powder refers to powder in which the main divalent metal atom contained is barium. The main divalent metal atom refers to the divalent metal atom that accounts for the largest proportion on an atomic percentage basis among the divalent metal atoms contained in the powder. However, rare earth atoms are not included in the above divalent metal atoms. In the present invention and this specification, "rare earth atoms" are selected from the group consisting of scandium atoms (Sc), yttrium atoms (Y), and lanthanide atoms. Lanthanide atoms are selected from the group consisting of lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu).

[0063] Below, we will describe hexagonal strontium ferrite powder, a form of hexagonal ferrite powder, in more detail.

[0064] The activation volume of the hexagonal strontium ferrite powder is preferably in the range of 800 to 1600 nm 3 The particulate hexagonal strontium ferrite powder having an activation volume within the above range is suitable for producing a magnetic tape that exhibits excellent electromagnetic conversion characteristics. The activation volume of the hexagonal strontium ferrite powder is preferably 800 nm 3 or more, for example, 850 nm 3 or more. Further, from the viewpoint of further improving the electromagnetic conversion characteristics, the activation volume of the hexagonal strontium ferrite powder is more preferably 1500 nm 3 or less, still more preferably 1400 nm 3 or less, even more preferably 1300 nm 3 or less, still even more preferably 1200 nm 3 or less, yet still even more preferably 1100 nm 3 or less, and yet still even more preferably. The same applies to the activation volume of the hexagonal barium ferrite powder.

[0065] The "activation volume" is a unit of magnetization reversal and is an index indicating the magnetic size of particles. The activation volume described in the present invention and this specification and the anisotropy constant Ku described later are measured using a vibrating sample magnetometer at magnetic field sweep rates of 3 minutes and 30 minutes in the coercive force Hc measurement section (measurement temperature: 23°C ± 1°C), and are values obtained from the following relational expression between Hc and the activation volume V. Regarding the unit of the anisotropy constant Ku, 1 erg / cc = 1.0×10 -1 J / m 3 . 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)]

[0066] As an indicator of reducing thermal fluctuations, or in other words, improving thermal stability, the anisotropy constant Ku can be cited. The hexagonal strontium ferrite powder is preferably 1.8 × 10⁻⁶ 5 J / m 3 It can have a Ku of the above, and more preferably 2.0 × 10 5 J / m 3 It can have a Ku content of the above. Also, the Ku content of hexagonal strontium ferrite powder is, for example, 2.5 × 10⁻⁶. 5 J / m 3 The following values ​​are possible. However, since a higher Ku value is preferable as it indicates higher thermal stability, the values ​​are not limited to those exemplified above.

[0067] Hexagonal strontium ferrite powder may or may not contain rare earth atoms. When hexagonal strontium ferrite powder contains rare earth atoms, it is preferable that the rare earth atoms are present at a concentration of 0.5 to 5.0 atomic percent (bulk concentration) per 100 atomic percent of iron atoms. In one embodiment, hexagonal strontium ferrite powder containing rare earth atoms may exhibit a segregation of rare earth atoms in the surface layer. In the present invention and this specification, "rare earth atom surface layer segregation" means that the rare earth atom content relative to 100% of iron atoms in a solution obtained by partially dissolving hexagonal strontium ferrite powder with acid (hereinafter referred to as "rare earth atom surface layer content" or simply "surface layer content" with respect to rare earth atoms) is different from the rare earth atom content relative to 100% of iron atoms in a solution obtained by completely dissolving hexagonal strontium ferrite powder with acid (hereinafter referred to as "rare earth atom bulk content" or simply "bulk content" with respect to rare earth atoms), Rare earth atom surface content / Rare earth atom bulk content > 1.0 This means that the ratio is satisfied. The rare earth atom content of hexagonal strontium ferrite powder described later is synonymous with the rare earth atom bulk content. In contrast, partial dissolution using acid dissolves the surface layer of the particles constituting the hexagonal strontium ferrite powder, so the rare earth atom content in the solution obtained by partial dissolution is the rare earth atom content in the surface layer of the particles constituting the hexagonal strontium ferrite powder. When the rare earth atom surface layer content satisfies the ratio "rare earth atom surface layer content / rare earth atom bulk content > 1.0", it means that in the particles constituting the hexagonal strontium ferrite powder, rare earth atoms are concentrated in the surface layer (i.e., there are more of them in the surface layer than in the interior). In this invention and specification, the surface layer means a part of the region extending from the surface to the interior of the particles constituting the hexagonal strontium ferrite powder.

[0068] When hexagonal strontium ferrite powder contains rare earth atoms, the rare earth atom content (bulk content) is preferably in the range of 0.5 to 5.0 atomic percent relative to 100 atomic percent of iron atoms. It is believed that containing rare earth atoms at the bulk content within the above range, and having the rare earth atoms unevenly distributed on the surface of the particles constituting the hexagonal strontium ferrite powder, contributes to suppressing the decrease in regeneration output during repeated regeneration. This is presumed to be because the anisotropy constant Ku can be increased by containing rare earth atoms at the bulk content within the above range, and having the rare earth atoms unevenly distributed on the surface of the particles constituting the hexagonal strontium ferrite powder. The higher the value of the anisotropy constant Ku, the more it is possible to suppress the occurrence of a phenomenon called thermal fluctuation (in other words, to improve thermal stability). By suppressing the occurrence of thermal fluctuation, the decrease in regeneration output during repeated regeneration can be suppressed. It is hypothesized that the uneven distribution of rare earth atoms on the surface of hexagonal strontium ferrite powder particles contributes to stabilizing the spin of iron (Fe) sites within the crystal lattice of the surface layer, thereby increasing the anisotropy constant Ku. Furthermore, it is presumed that using hexagonal strontium ferrite powder with a rare-earth atom uneven distribution on the surface as the ferromagnetic powder for the magnetic layer contributes to suppressing wear on the magnetic layer surface due to sliding with the magnetic head. In other words, it is presumed that hexagonal strontium ferrite powder with a rare-earth atom uneven distribution on the surface may also contribute to improving the running durability of the magnetic tape. This is presumed to be because the uneven distribution of rare-earth atoms on the surface of the particles constituting the hexagonal strontium ferrite powder contributes to improved interaction between the particle surface and organic substances (e.g., binders and / or additives) contained in the magnetic layer, resulting in improved strength of the magnetic layer. From the viewpoint of further suppressing the decrease in regeneration output during repeated regeneration and / or further improving running durability, the rare earth atom content (bulk content) is more preferably in the range of 0.5 to 4.5 atomic percent, even more preferably in the range of 1.0 to 4.5 atomic percent, and even more preferably in the range of 1.5 to 4.5 atomic percent.

[0069] The bulk content mentioned above is the content obtained by completely dissolving the hexagonal strontium ferrite powder. In this invention and specification, unless otherwise specified, the content of atoms refers to the bulk content obtained by completely dissolving the hexagonal strontium ferrite powder. The hexagonal strontium ferrite powder containing rare earth atoms may contain only one type of rare earth atom, or it may contain two or more types of rare earth atoms. When two or more types of rare earth atoms are included, the bulk content mentioned above is determined for the sum of the two or more types of rare earth atoms. This also applies to other components in this invention and specification. That is, unless otherwise specified, a certain component may be used alone, or two or more types may be used. When two or more types are used, the content or content refers to the sum of the two or more types.

[0070] When hexagonal strontium ferrite powder contains rare earth atoms, the rare earth atoms included may be one or more of the rare earth atoms. From the viewpoint of further suppressing the decrease in regeneration output during repeated regeneration, preferred rare earth atoms include neodymium atoms, samarium atoms, yttrium atoms, and dysprosium atoms, with neodymium atoms, samarium atoms, and yttrium atoms being more preferred, and neodymium atoms being even more preferred.

[0071] In hexagonal strontium ferrite powder having a rare-earth atom surface segregation, the rare-earth atoms only need to be segregated in the surface layer of the particles constituting the hexagonal strontium ferrite powder, and the degree of segregation is not limited. For example, in hexagonal strontium ferrite powder having a rare-earth atom surface segregation, the ratio of the rare-earth atom surface content obtained by partial dissolution under the dissolution conditions described later to the rare-earth atom bulk content obtained by total dissolution under the dissolution conditions described later, "surface content / bulk content," is greater than 1.0 and can be 1.5 or greater. A "surface content / bulk content" greater than 1.0 means that in the particles constituting the hexagonal strontium ferrite powder, rare-earth atoms are segregated in the surface layer (i.e., there are more of them in the surface layer than in the interior). Furthermore, the ratio of the surface content of rare earth atoms obtained by partial dissolution under the dissolution conditions described later to the bulk content of rare earth atoms obtained by total dissolution under the dissolution conditions described later, "surface content / bulk content," can be, for example, 10.0 or less, 9.0 or less, 8.0 or less, 7.0 or less, 6.0 or less, 5.0 or less, or 4.0 or less. However, in hexagonal strontium ferrite powder having a rare earth atom surface distribution bias, the rare earth atoms only need to be biased towards the surface of the particles constituting the hexagonal strontium ferrite powder, and the above "surface content / bulk content" is not limited to the upper or lower limits exemplified.

[0072] The partial and total dissolution of hexagonal strontium ferrite powder is described below. For hexagonal strontium ferrite powder existing as a powder, the sample powders to be partially and completely dissolved are taken from the same lot of powder. On the other hand, for hexagonal strontium ferrite powder contained in the magnetic layer of a magnetic tape, a portion of the hexagonal strontium ferrite powder extracted from the magnetic layer is subjected to partial dissolution, and another portion is subjected to total dissolution. The extraction of hexagonal strontium ferrite powder from the magnetic layer can be carried out, for example, by the method described in paragraph 0032 of Japanese Patent Application Publication No. 2015-91747. Partial dissolution, as described above, refers to a state where the hexagonal strontium ferrite powder is dissolved to the extent that residual particles can be visually confirmed in the liquid at the end of the dissolution process. For example, partial dissolution can dissolve 10 to 20% by mass of the particles constituting the hexagonal strontium ferrite powder, with the total particles being 100% by mass. On the other hand, total dissolution, as described above, refers to a state where the hexagonal strontium ferrite powder is dissolved to the extent that no residual particles can be visually confirmed in the liquid at the end of the dissolution process. The above-mentioned partial dissolution and surface layer content measurement are performed, for example, by the following method. However, the dissolution conditions such as the amount of sample powder described below are examples only, and any dissolution conditions that enable partial and total dissolution can be arbitrarily adopted. A container (e.g., a beaker) containing 12 mg of sample powder and 10 mL of 1 mol / L hydrochloric acid is held on a hot plate at a set temperature of 70°C for 1 hour. The resulting solution is filtered through a 0.1 μm membrane filter. Elemental analysis of the resulting filtrate is performed using an inductively coupled plasma (ICP) analyzer. In this way, the surface content of rare earth atoms relative to 100% iron atoms can be determined. If multiple types of rare earth atoms are detected by elemental analysis, the total content of all rare earth atoms is taken as the surface content. This is also the case when measuring bulk content. On the other hand, the measurement of total dissolution and bulk content is performed, for example, by the following method. A container (e.g., a beaker) containing 12 mg of sample powder and 10 mL of 4 mol / L hydrochloric acid is held on a hot plate at a set temperature of 80°C for 3 hours. Afterward, the bulk content relative to 100 atomic percent of iron can be determined by performing the same procedure as described above for partial dissolution and surface layer content measurement.

[0073] From the perspective of increasing the playback output when reproducing data recorded on magnetic tape, it is desirable for the mass magnetization σs of the ferromagnetic powder contained in the magnetic tape to be high. In this regard, hexagonal strontium ferrite powder containing rare earth atoms but lacking surface segregation of rare earth atoms tended to have a significantly lower σs compared to hexagonal strontium ferrite powder that does not contain rare earth atoms. In contrast, hexagonal strontium ferrite powder with surface segregation of rare earth atoms is considered preferable in order to suppress such a large decrease in σs. In one embodiment, the σs of hexagonal strontium ferrite powder is 45 A·m 2 It can be 47 A·m or more per kg. 2 It can also be more than / kg. On the other hand, σs is 80 A·m from the viewpoint of noise reduction. 2 Preferably less than / kg, at 60A·m 2 It is more preferable that it be less than or equal to / kg. σs can be measured using a known measuring device capable of measuring magnetic properties, such as a vibrating sample magnetometer. In this invention and specification, unless otherwise specified, the mass magnetization σs is the value measured at a magnetic field strength of 15 kOe. 1 [kOe] = 10 6 It is / 4π[A / m].

[0074] Regarding the constituent atom content (bulk content) of hexagonal strontium ferrite powder, the strontium atom content can be in the range of, for example, 2.0 to 15.0 atomic percent per 100 atomic percent of iron atoms. In one form, hexagonal strontium ferrite powder may contain only strontium atoms as the divalent metal atom. In another form, hexagonal strontium ferrite powder may contain one or more other divalent metal atoms in addition to strontium atoms. For example, it may contain barium atoms and / or calcium atoms. When other divalent metal atoms besides strontium atoms are included, the barium atom content and calcium atom content in the hexagonal strontium ferrite powder can be in the range of, for example, 0.05 to 5.0 atomic percent per 100 atomic percent of iron atoms.

[0075] The known crystal structures of hexagonal ferrites include magnetoplumbite (also called "M-type"), W-type, Y-type, and Z-type. Hexagonal strontium ferrite powder may have any of these crystal structures. The crystal structure can be confirmed by X-ray diffraction analysis. Hexagonal strontium ferrite powder may show a single crystal structure or two or more crystal structures by X-ray diffraction analysis. For example, in one form, hexagonal strontium ferrite powder may show only the M-type crystal structure by X-ray diffraction analysis. For example, M-type hexagonal ferrite is AFe 12 O 19It is represented by the following compositional formula: Here, A represents a divalent metal atom, and if the hexagonal strontium ferrite powder is of type M, A is either only a strontium atom (Sr), or if A contains multiple divalent metal atoms, then as described above, strontium atoms (Sr) make up the largest proportion on an atomic percentage basis. The divalent metal atom content of hexagonal strontium ferrite powder is usually determined by the type of crystal structure of the hexagonal ferrite and is not particularly limited. The same applies to the iron atom content and oxygen atom content. Hexagonal strontium ferrite powder contains at least iron atoms, strontium atoms and oxygen atoms, and may also contain rare earth atoms. Furthermore, hexagonal strontium ferrite powder may or may not contain atoms other than these atoms. As an example, hexagonal strontium ferrite powder may contain aluminum atoms (Al). The aluminum atom content can be, for example, 0.5 to 10.0 atomic percent relative to 100 atomic percent of iron atoms. From the viewpoint of further suppressing the decrease in regeneration output during repeated regeneration, the hexagonal strontium ferrite powder preferably contains iron atoms, strontium atoms, oxygen atoms, and rare earth atoms, and the content of atoms other than these atoms is preferably 10.0 atomic percent or less, more preferably in the range of 0 to 5.0 atomic percent, and may even be 0 atomic percent, relative to 100 atomic percent of iron atoms. That is, in one embodiment, the hexagonal strontium ferrite powder does not need to contain atoms other than iron atoms, strontium atoms, oxygen atoms, and rare earth atoms. The above content expressed in atomic percent is obtained by converting the content of each atom (unit: mass%) obtained by completely dissolving the hexagonal strontium ferrite powder into an atomic percent value using the atomic weight of each atom. Furthermore, in the present invention and this specification, "does not contain" for a certain atom means that the content measured by an ICP analyzer after complete dissolution is 0 mass%. The detection limit of an ICP analyzer is typically 0.01 ppm (parts per million) or less by mass. The term "does not contain" above is used to include the presence of substances in amounts below the detection limit of the ICP analyzer.Hexagonal strontium ferrite powder can, in one form, be bismuth-free (Bi).

[0076] metal powder A preferred specific example of ferromagnetic powder is ferromagnetic metal powder. For details on ferromagnetic metal powder, see, for example, paragraphs 0137-0141 of Japanese Patent Publication No. 2011-216149 and paragraphs 0009-0023 of Japanese Patent Publication No. 2005-251351.

[0077] ε-Iron oxide powder A preferred specific example of a ferromagnetic powder is ε-iron oxide powder. In the present invention and this specification, "ε-iron oxide powder" refers to a ferromagnetic powder in which the crystalline structure of ε-iron oxide is detected as the main phase by X-ray diffraction analysis. For example, if the highest intensity diffraction peak in the X-ray diffraction spectrum obtained by X-ray diffraction analysis is attributed to the crystalline structure of ε-iron oxide, it shall be determined that the crystalline structure of ε-iron oxide has been detected as the main phase. Methods for producing ε-iron oxide powder include methods from goethite and the reverse micelle method. All of the above production methods are publicly known. Furthermore, for methods for producing ε-iron oxide powder in which some of the Fe is substituted with substitution atoms such as Ga, Co, Ti, Al, and Rh, see, for example, J. Jpn. Soc. Powder Metallurgy Vol. 61 Supplement, No. S1, pp. S280-S284, J. Mater. Chem. C, 2013, 1, pp. 5200-5206, etc. However, the method for producing ε-iron oxide powder that can be used as ferromagnetic powder in the magnetic layer of the magnetic tape described above is not limited to the method described herein.

[0078] The activation volume of ε-iron oxide powder is preferably 300 to 1500 nm. 3 The activation volume is within the range described above. Micronized ε-iron oxide powder exhibiting an activation volume within the above range is suitable for the production of magnetic tapes that exhibit excellent electromagnetic conversion properties. The activation volume of the ε-iron oxide powder is preferably 300 nm. 3 That's all, for example, 500nm3 It can also be the above. Furthermore, from the viewpoint of further improving electromagnetic conversion characteristics, the activation volume of ε-iron oxide powder is 1400 nm. 3 The following is more preferable: 1300nm 3 It is even more preferable that the following occur: 1200 nm 3 It is even more preferable that the following conditions be met: 1100 nm 3 The following is even more preferable.

[0079] The anisotropy constant Ku can be cited as an indicator of the reduction of thermal fluctuations, or in other words, the improvement of thermal stability. The ε-iron oxide powder is preferably 3.0 × 10⁻⁶ 4 J / m 3 It can have a Ku of the above, and more preferably 8.0 × 10 4 J / m 3 It can have the above amount of Ku. Also, the amount of Ku in ε-iron oxide powder is, for example, 3.0 × 10⁻⁶. 5 J / m 3 The following values ​​are possible. However, a higher Ku value indicates higher thermal stability, which is preferable, so the values ​​are not limited to those exemplified above.

[0080] From the perspective of increasing the playback output when reproducing data recorded on magnetic tape, it is desirable for the mass magnetization σs of the ferromagnetic powder contained in the magnetic tape to be high. In this regard, in one embodiment, the σs of ε-iron oxide powder is 8 A·m 2 It can be 12 A·m or more / kg. 2 It can also be more than / kg. On the other hand, the σs of ε-iron oxide powder is 40 A·m from the viewpoint of noise reduction. 2 Preferably less than / kg, 35A·m 2 It is more preferable that the amount be less than or equal to / kg.

[0081] In the present invention and this specification, unless otherwise specified, the average particle size of various powders such as ferromagnetic powders shall be the value measured using a transmission electron microscope by the following method. The powder is photographed using a transmission electron microscope at a magnification of 100,000x, and the resulting image is printed onto photographic paper at a total magnification of 500,000x to obtain a photograph of the particles that make up the powder. From the obtained photograph of the particles, the target particles are selected, and their outlines are traced with a digitizer to measure the size of the particles (primary particles). 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 these 500 particles is taken as the average particle size of the powder. As the transmission electron microscope, for example, a Hitachi H-9000 transmission electron microscope can be used. The particle size can be measured using known image analysis software, for example, Carl Zeiss KS-400 image analysis software. Unless otherwise specified, the average particle sizes shown in the examples described later are values ​​measured using a Hitachi H-9000 transmission electron microscope and Carl Zeiss KS-400 image analysis software. In the present invention and this specification, "powder" means a collection of multiple particles. For example, ferromagnetic powder means a collection of multiple ferromagnetic particles. Furthermore, a collection of multiple particles is not limited to a form in which the particles constituting the collection are in direct contact, but also includes forms in which binders, additives, etc., described later, are interposed between the particles. The word "particle" is sometimes used to refer to powder.

[0082] For example, the method described in paragraph 0015 of Japanese Patent Publication No. 2011-048878 can be used to collect sample powder from a magnetic tape for particle size measurement.

[0083] In the present invention and this specification, unless otherwise specified, the size of the particles constituting the powder (particle size) is determined by the shape of the particles observed in the above particle photograph. (1) In the case of needle-shaped, spindle-shaped, columnar (however, the height is greater than the longest diameter of the base), etc., the length of the long axis constituting the particle is expressed as the long axis length, (2) In the case of a plate or column (provided that the thickness or height is less than the longest diameter of the plate or base), it shall be expressed by the longest diameter of the plate or base. (3) If the shape is spherical, polyhedral, irregular, etc., and the major axis constituting the particle cannot be determined from the shape, it shall be represented by the equivalent diameter of a circle. The equivalent diameter of a circle refers to the diameter obtained by the circular projection method.

[0084] Furthermore, the average needle-shape ratio of the powder refers to the arithmetic mean of the values ​​obtained for the 500 particles by measuring the length of the short axis of each particle, i.e., the short axis length, in the above measurement, and determining the (long axis length / short axis length) value for each particle. Here, unless otherwise specified, the short axis length refers to the length of the short axis constituting the particle in the above definition of particle size (1), the thickness or height in the case of (2), and in the case of (3), since there is no distinction between the long axis and the short axis, (long axis length / short axis length) is considered to be 1 for convenience. Unless otherwise specified, when the particle shape is specific, for example, in the case of definition (1) above, the average particle size is the average major axis length, and in the case of definition (2), the average particle size is the average plate diameter. In the case of definition (3), the average particle size is the average diameter (also called the average particle size or average particle diameter).

[0085] The content (filling rate) of ferromagnetic powder in the magnetic layer is preferably in the range of 50 to 90% by mass, and more preferably in the range of 60 to 90% by mass, relative to the total mass of the magnetic layer. A high filling rate of ferromagnetic powder in the magnetic layer is preferable from the viewpoint of improving recording density.

[0086] (Binder) The above magnetic tape can be a coated magnetic tape, and the magnetic layer may contain a binder. The binder is one or more resins. Various resins commonly used as binders for coated magnetic tapes can be used as binders. For example, as a binder, a resin selected from polyurethane resin, polyester resin, polyamide resin, vinyl chloride resin, acrylic resin copolymerized with styrene, acrylonitrile, methyl methacrylate, etc., cellulose resin such as nitrocellulose, epoxy resin, phenoxy resin, polyvinyl acetal, polyvinyl alkylal resin such as polyvinyl butyral can be used alone or in mixture of multiple resins. Among these, polyurethane resin, acrylic resin, cellulose resin, and vinyl chloride resin are preferred. These resins may be homopolymers or copolymers. These resins can also be used as binders in the non-magnetic layer and / or back coat layer described later. For details on the binders mentioned above, please refer to paragraphs 0028 to 0031 of Japanese Patent Publication No. 2010-24113. The average molecular weight of the resin used as a binder can be, for example, 10,000 to 200,000 as a weight-average molecular weight. The binder can be used in an amount of, for example, 1.0 to 30.0 parts by mass per 100.0 parts by mass of ferromagnetic powder.

[0087] (Hardening agent) A curing agent can also be used together with a resin that can be used as a binder. In one form, the curing agent can be a thermosetting compound, which is a compound that undergoes a curing reaction (crosslinking reaction) by heating, and in another form, it can be a photocurable compound, which undergoes a curing reaction (crosslinking reaction) by light irradiation. As the curing reaction progresses during the magnetic layer formation process, at least a portion of the curing agent may be included in the magnetic layer in a state where it has reacted (crosslinked) with other components such as the binder. This also applies to layers formed using a composition that contains a curing agent when the composition used to form other layers contains a curing agent. Preferred curing agents are thermosetting compounds, and polyisocyanates are preferred. For details on polyisocyanates, refer to paragraphs 0124 to 0125 of Japanese Patent Application Publication No. 2011-216149. The curing agent can be used in the magnetic layer forming composition in an amount of, for example, 0 to 80.0 parts by mass, preferably 50.0 to 80.0 parts by mass, per 100.0 parts by mass of the binder.

[0088] (Additives) The magnetic layer may contain one or more additives as needed. Commercially available additives can be appropriately selected and used according to the desired properties. Alternatively, compounds synthesized by known methods can be used as additives. Additives can be used in any amount. An example of an additive is the curing agent mentioned above. Additives that can be included in the magnetic layer include non-magnetic powders (e.g., inorganic powders, carbon black, etc.), lubricants, dispersants, dispersion aids, antifungal agents, antistatic agents, antioxidants, etc. For example, for lubricants, refer to paragraphs 0030 to 0033, 0035 and 0036 of Japanese Patent Application Publication No. 2016-126817. A lubricant may also be included in the non-magnetic layer described later. For lubricants that can be included in the non-magnetic layer, refer to paragraphs 0030, 0031, 0034, 0035 and 0036 of Japanese Patent Application Publication No. 2016-126817. For dispersants, see paragraphs 0061 and 0071 of Japanese Patent Publication No. 2012-133837. Compounds having polyalkylene imine chains and vinyl polymer chains can also act as dispersants to improve the dispersibility of ferromagnetic powders. Furthermore, these 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 back-facing, which will be discussed later. This can contribute to increasing the media lifespan. For compounds having polyalkylene imine chains and vinyl polymer chains, see paragraphs 0024 to 0064 and the examples in Japanese Patent Publication No. 2019-169225. The above compound is preferably present in the magnetic layer at an amount of 0.5 parts by mass or more per 100.0 parts by mass of ferromagnetic powder, more preferably 1.0 part by mass or more, even more preferably 3.0 parts by mass or more, even more preferably 5.0 parts by mass or more, even more preferably 10.0 parts by mass or more, even more preferably 15.0 parts by mass or more, and still more preferably 200 parts by mass or more. Furthermore, the content of the above compound in the magnetic layer can be 40.0 parts by mass or less or 35.0 parts by mass or less per 100.0 parts by mass of ferromagnetic powder. One or more dispersants such as the above compound may be added to the composition for forming the non-magnetic layer.For dispersants that can be added to the composition for forming a non-magnetic layer, see paragraph 0061 of Japanese Patent Application Publication No. 2012-133837. Non-magnetic powders that can be included in the magnetic layer include non-magnetic powders that can function as abrasives, and non-magnetic powders that can function as protrusion-forming agents that form appropriately protruding protrusions on the surface of the magnetic layer (e.g., non-magnetic colloidal particles). For example, for abrasives, see paragraphs 0030-0032 of Japanese Patent Application Publication No. 2004-273070. Colloidal particles are preferred as the protrusion-forming agent; inorganic colloidal particles are preferred from the viewpoint 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 the protrusion-forming agent is preferably in the range of 30-200 nm, and more preferably in the range of 50-100 nm.

[0089] The magnetic layer described above can be provided directly on the surface of a non-magnetic support, or indirectly via a non-magnetic layer.

[0090] <Nonmagnetic layer> Next, the non-magnetic layer will be described. The magnetic tape described above may have a magnetic layer directly on the surface of a non-magnetic support, or it may have a magnetic layer on the surface of a non-magnetic support via a non-magnetic layer containing non-magnetic powder. The non-magnetic powder used in the non-magnetic layer may be an inorganic powder or an organic powder. Carbon black can also be used. Examples of inorganic powders include metals, metal oxides, metal carbonates, metal sulfates, metal nitrides, metal carbides, and metal sulfides. These non-magnetic powders are commercially available and can also be manufactured by known methods. For details, see paragraphs 0146 to 0150 of Japanese Patent Application Publication No. 2011-216149. For carbon black that can be used in the non-magnetic layer, see paragraphs 0040 and 0041 of Japanese Patent Application Publication No. 2010-24113. The content (filling rate) of non-magnetic powder in the non-magnetic layer is preferably in the range of 50 to 90% by mass, and more preferably in the range of 60 to 90% by mass, relative to the total mass of the non-magnetic layer.

[0091] The non-magnetic layer may contain a binder and may also contain additives. For further details regarding the binder, additives, etc., of the non-magnetic layer, known technology relating to non-magnetic layers can be applied. Furthermore, for example, regarding the type and content of the binder, the type and content of the additives, etc., known technology relating to magnetic layers can also be applied.

[0092] In the present invention and this specification, the non-magnetic layer includes a substantially non-magnetic layer containing a small amount of ferromagnetic powder, for example as an impurity or intentionally, along with the non-magnetic powder. A substantially non-magnetic layer is defined as a layer having a remanent magnetic flux density of 10 mT or less, a coercivity of 7.96 kA / m(100 Oe) or less, or a layer having a remanent magnetic flux density of 10 mT or less and a coercivity of 7.96 kA / m(100 Oe) or less. It is preferable that the non-magnetic layer has no remanent magnetic flux density and coercivity.

[0093] <Backcoat layer> The above magnetic tape may or may not have a back coat layer containing non-magnetic powder on the surface side opposite to the surface side having the magnetic layer of the non-magnetic support. For the non-magnetic powder of the back coat layer, refer to the above description regarding the non-magnetic powder of the non-magnetic layer.

[0094] Indentations on the magnetic layer surface can be formed during the manufacturing process of magnetic tape, when the magnetic layer surface and back surface are in contact while the tape is wound in a roll, and the surface shape of the back surface is transferred to the magnetic layer surface (so-called back transfer). The back surface is the surface of the back coat layer if one is present, and the surface of the support if one is absent. If there are many indentations on the magnetic layer surface, and / or if deep indentations are present, it is thought that temperature differences and / or differences in moisture content are likely to occur between different parts of the magnetic tape during storage and / or use. This is presumed to lead to localized large deformation of the magnetic tape, resulting in a reduced media life. Therefore, in order to increase the media life, it is preferable to suppress the occurrence of indentations on the magnetic layer surface. From this point of view, as described above, it is preferable to include compounds having polyalkylene imine chains and vinyl polymer chains in the magnetic layer. Furthermore, as an example of a method for controlling the presence of indentations on the magnetic layer surface, one can select the type of component to add to the composition for forming the back coat layer in order to adjust the surface shape of the back surface. From this point of view, it is preferable that the non-magnetic powder of the back coat layer be a combination of carbon black and a non-magnetic powder other than carbon black, or that carbon black be used (i.e., the non-magnetic powder of the back coat layer consists of carbon black). Examples of non-magnetic powders other than carbon black include the non-magnetic powders exemplified above as those that can be contained in the non-magnetic layer. Regarding the non-magnetic powder of the back coat layer, it is preferable that the proportion of carbon black in 100.0 parts by mass of the total amount of non-magnetic powder be in the range of 50.0 to 100.0 parts by mass, more preferably in the range of 70.0 to 100.0 parts by mass, and even more preferably in the range of 90.0 to 100.0 parts by mass. It is also preferable that the entire amount of non-magnetic powder in the back coat layer be carbon black. The content (filling rate) of non-magnetic powder in the back coat layer is preferably in the range of 50 to 90% by mass, and more preferably in the range of 60 to 90% by mass, relative to the total mass of the back coat layer.

[0095] From the viewpoint of suppressing the occurrence of depressions on the surface of the magnetic layer, in one embodiment, it is preferable to use a non-magnetic powder with an average particle size of 50 nm or less as the non-magnetic powder of the back coat layer. Only one type of non-magnetic powder may be used as the non-magnetic powder of the back coat layer, or two or more types may 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 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 non-magnetic powder contained in the back coat layer is carbon black, and its average particle size is 50 nm or less.

[0096] To suppress the occurrence of depressions on the surface of the magnetic layer, it is preferable that the backcoat layer forming composition contains a component (dispersant) that can improve the dispersibility of the non-magnetic powder contained in the composition. It is more preferable that the backcoat layer forming composition contains a non-magnetic powder with an average particle size of 50 nm or less and a component that can improve the dispersibility of this non-magnetic powder, and it is even more preferable that it contains carbon black with an average particle size of 50 nm or less and a component that can improve the dispersibility of the carbon black.

[0097] As an example of such a dispersant, a compound having an ammonium salt structure of an alkyl ester anion represented by Formula 1 below can be used. Note that "alkyl ester anion" can also be called "alkyl carboxylate anion".

[0098] [ka]

[0099] 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 + This represents an ammonium cation.

[0100] Furthermore, from the viewpoint of improving the dispersibility of carbon black, in one embodiment, two or more components capable of forming the above-mentioned salt structure compound can be used when preparing the backcoat layer forming composition. As a result, when preparing the backcoat layer forming composition, at least some of these components can form the above-mentioned salt structure compound.

[0101] Unless otherwise specified, the groups described below may or may not have substituents. Furthermore, for groups with substituents, "number of carbon atoms" means the number of carbon atoms excluding the substituent unless otherwise specified. In the present invention and this specification, examples of substituents include alkyl groups (e.g., alkyl groups having 1 to 6 carbon atoms), hydroxyl groups, alkoxy groups (e.g., alkoxy groups having 1 to 6 carbon atoms), halogen atoms (e.g., fluorine atoms, chlorine atoms, bromine atoms, etc.), cyano groups, amino groups, nitro groups, acyl groups, carboxyl groups, salts of carboxyl groups, sulfonic acid groups, salts of sulfonic acid groups, and the like.

[0102] The following provides a more detailed explanation of Equation 1.

[0103] 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. A 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, but a linear structure is preferred. The alkyl group or fluorinated alkyl group represented by R may have substituents or be unsubstituted, but it is preferred to be unsubstituted. The alkyl group represented by R is, for example, C n H 2n+1 It can be represented by -, where n is an integer greater than or equal to 7. Also, the alkyl fluoride represented by R is, for example, C n H 2n+1The alkyl group represented by - may have 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 has 7 or more carbon atoms, preferably 8 or more, more preferably 9 or more, even more preferably 10 or more, even more preferably 11 or more, even more preferably 12 or more, and even more preferably 13 or more. Furthermore, the alkyl group or fluorinated alkyl group represented by R has 20 or fewer carbon atoms, more preferably 19 or fewer, and even more preferably 18 or fewer.

[0104] In equation 1, Z + * represents an ammonium cation. The ammonium cation has, in detail, the following structure. In this invention and specification, the asterisk (*) in a formula representing a part of a compound represents the bond position between that part of the structure and adjacent atoms.

[0105] [ka]

[0106] Nitrogen cation of ammonium cation N + and the oxygen anion O in Equation 1 - These can form a salt crosslinking group, creating an ammonium salt structure of an alkyl ester anion represented by formula 1. The presence of a compound having an ammonium salt structure of an alkyl ester anion represented by formula 1 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.

[0107] In one form, Z +The ammonium cation represented by can be obtained, for example, by the nitrogen atom of a nitrogen-containing polymer becoming a cation. A nitrogen-containing polymer means a polymer that contains nitrogen atoms. In this invention and specification, the terms "polymer" and "polymer" are used to encompass both homopolymers and copolymers. Nitrogen atoms can be included in one form as atoms constituting the main chain of the polymer, and in another form as atoms constituting the side chain of the polymer.

[0108] One form of nitrogen-containing polymer is polyalkyleneimines. Polyalkyleneimines are ring-opening polymers of alkyleneimines, and are polymers having multiple repeating units represented by the following formula 2.

[0109] [ka]

[0110] In Equation 2, the nitrogen atom N that makes up the main chain is a nitrogen cation N + And so Z in equation 1 + An ammonium cation represented by [formula] can be obtained. Then, with an alkyl ester anion, it can form an ammonium salt structure, for example, as shown below.

[0111] [ka]

[0112] The following provides a more detailed explanation of Equation 2.

[0113] In formula 2, R 1 and R 2 Each of these independently represents a hydrogen atom or an alkyl group, and n1 represents an integer greater than or equal to 2.

[0114] R 1 or R 2Examples of alkyl groups represented by 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 is preferably an unsubstituted alkyl group. 1 and R 2 The combinations include a form in which one is a hydrogen atom and the other is an alkyl group, a form in which both are hydrogen atoms, and a form in which both are alkyl groups (identical or different alkyl groups), with the form in which both are hydrogen atoms being preferred. As an alkylene imine that yields a polyalkylene imine, the structure with the fewest number of carbon atoms constituting the ring is ethyleneimine, and the number of carbon atoms in the main chain of the alkylene imine (ethyleneimine) obtained by ring-opening of ethyleneimine is 2. 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 polyalkylene imine may be a homopolymer containing only the same structure as the repeating structure represented by formula 2, or it may be a copolymer containing two or more different structures as the repeating structure represented by formula 2. The number-average molecular weight of the polyalkylene imine 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. Furthermore, 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.

[0115] In the present invention and this specification, average molecular weight (weight-average molecular weight and number-average molecular weight) refers to the value obtained by measuring by gel permeation chromatography (GPC) and converting it to standard polystyrene equivalent. Unless otherwise specified, the average molecular weights shown in the examples described below are values ​​obtained by converting the values ​​measured using GPC under the following measurement conditions to standard polystyrene equivalent (polystyrene equivalent value). GPC device: HLC-8220 (manufactured by Tosoh Corporation) Guard Column: TSKguardcolumn Super HZM-H Columns: TSKgel Super HZ 2000, TSKgel Super HZ 4000, TSKgel Super HZ-M (manufactured by Tosoh Corporation, 4.6mm (inner diameter) x 15.0cm, three types of columns connected in series) Eluent: Contains tetrahydrofuran (THF) and 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

[0116] Another form of nitrogen-containing polymer is polyallylamine. Polyallylamine is a polymer of allylamine, having multiple repeating units represented by the following formula 3.

[0117] [ka]

[0118] In Equation 3, the nitrogen atom N constituting the amino group of the side chain is a nitrogen cation N + And so Z in equation 1 + An ammonium cation represented by [formula] can be obtained. Then, with an alkyl ester anion, it can form an ammonium salt structure, for example, as shown below.

[0119] [ka]

[0120] The weight-average molecular weight of the polyallylamine 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 1,000 or more, and more preferably 1,500 or more. Furthermore, the weight-average molecular weight of the above polyallylamine can be, for example, 15,000 or less, preferably 10,000 or less, and more preferably 8,000 or less.

[0121] The presence of compounds having an ammonium salt structure of an alkyl ester anion represented by Formula 1, specifically compounds with structures derived from polyalkylene imines or polyallylamines, in the backcoat layer can be confirmed by analyzing the backcoat layer surface using time-of-flight secondary ion mass spectrometry (TOF-SIMS) or the like.

[0122] Compounds having an ammonium salt structure of an alkyl ester anion represented by Formula 1 can be salts 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, for example, a nitrogen-containing polymer selected from the group consisting of polyalkylene imines 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 replaced with fluorine atoms. For example, the salt formation reaction can easily proceed by mixing the nitrogen-containing polymer and the above fatty acids at room temperature. Room temperature is, for example, about 20-25°C. In one embodiment, one or more nitrogen-containing polymers and one or more of the above fatty acids are used as components of the backcoat layer forming composition, and the salt formation reaction can be carried out by mixing them in the preparation step of the backcoat layer forming composition. Alternatively, in one embodiment, one or more nitrogen-containing polymers and one or more of the above fatty acids can be mixed to form a salt before preparing the backcoat layer forming composition, and this salt can then be used as a component of the backcoat layer forming composition to prepare it. When mixing nitrogen-containing polymers and the above fatty acids to form an ammonium salt of an alkyl ester anion represented by formula 1, the nitrogen atoms constituting the nitrogen-containing polymer may also react with the carboxyl groups of the above fatty acids to form the following structure, and forms including such a structure are also included in the above compound.

[0123] [ka]

[0124] Examples of the above fatty acids include fatty acids having the alkyl group described earlier as R in Formula 1, and fluorinated fatty acids having the fluorinated alkyl group described earlier as R in Formula 1.

[0125] The mixing ratio of the nitrogen-containing polymer used to form the compound having the ammonium salt structure of the alkyl ester anion represented by Formula 1 to the above fatty acids is preferably 10:90 to 90:10, more preferably 20:80 to 85:15, and even more preferably 30:70 to 80:20, as the mass ratio of nitrogen-containing polymer to the above fatty acids. Furthermore, when preparing the composition for forming the back coat layer, the compound having the ammonium salt structure of the alkyl ester anion represented by Formula 1 can be used in an amount of, for example, 1.0 to 20.0 parts by mass, and preferably 1.0 to 10.0 parts by mass, per 100.0 parts by mass of carbon black. Also, when preparing the composition for forming the back coat layer, for example, 0.1 to 10.0 parts by mass of nitrogen-containing polymer can be used per 100.0 parts by mass of carbon black, and preferably 0.5 to 8.0 parts by mass of nitrogen-containing polymer. The above fatty acids can be used in amounts of, for example, 0.05 to 10.0 parts by mass per 100.0 parts by mass of carbon black, and it is preferable to use 0.1 to 5.0 parts by mass.

[0126] Regarding the components that may be included in the backcoat layer, the backcoat layer may include a binder and may also include additives. With regard to the binder and additives of the backcoat layer, prior art relating to backcoat layers may be applied, as may prior art relating to the formulation of magnetic and / or non-magnetic layers. For example, paragraphs 0018 to 0020 of Japanese Patent Application Publication No. 2006-331625 and lines 65 to 38 of column 4 to column 5 of U.S. Patent No. 7,029,774 can be referenced with respect to the backcoat layer.

[0127] <Various thicknesses> Regarding the thickness (total thickness) of magnetic tape, with the enormous increase in the amount of information in recent years, there is a demand for increased recording capacity (higher capacity) in magnetic tape. Means of increasing capacity include reducing the thickness of the magnetic tape (hereinafter also referred to as "thinning") and increasing the length of magnetic tape that can be stored in one magnetic tape cartridge. From this point of view, the thickness (total thickness) of the magnetic tape is preferably 5.6 μm or less, more preferably 5.5 μm or less, more preferably 5.4 μm or less, even more preferably 5.3 μm or less, and even more preferably 5.2 μm or less. Furthermore, from the viewpoint of ease of handling, the thickness of the magnetic tape is preferably 3.0 μm or more, and more preferably 3.5 μm or more.

[0128] The thickness (total thickness) of a magnetic tape can be measured by the following method. Ten tape samples (e.g., 5-10 cm in length) are cut from any part of the magnetic tape, and the thickness of these tape samples is measured by stacking them. The measured thickness is divided by 10 to obtain the value obtained (thickness per tape sample), which is defined as the tape thickness. The above thickness measurement can be performed using a known measuring instrument capable of measuring thickness on the order of 0.1 μm.

[0129] The thickness of the non-magnetic support can be, for example, 3.0 μm or more, and can also be, for example, 5.0 μm or less, 4.8 μm or less, 4.6 μm or less, 4.4 μm or less, or 4.2 μm or less. The thickness of the magnetic layer can be optimized depending on the saturation magnetization of the magnetic head used, the head gap length, the bandwidth of the recording signal, etc., and is generally 0.01 μm to 0.15 μm, preferably 0.02 μm to 0.12 μm, and more preferably 0.03 μm to 0.1 μm from the viewpoint of high-density recording. At least one magnetic layer is sufficient, and the magnetic layer may be separated into two or more layers having different magnetic properties, and known configurations for multilayer magnetic layers can be applied. When separated into two or more layers, the thickness of the magnetic layer is the total thickness of these layers. The thickness of the non-magnetic layer is, for example, 0.1 to 1.5 μm, 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. Various thicknesses, such as the thickness of the magnetic layer, can be determined by the following method. After exposing the cross-section of the magnetic tape in the thickness direction using an ion beam, the exposed cross-section is observed using a scanning electron microscope. Various thicknesses can be determined as the arithmetic mean of the thicknesses obtained at any two points during the cross-sectional observation. Alternatively, various thicknesses can be determined as design thicknesses calculated from manufacturing conditions, etc.

[0130] <Manufacturing process> (Preparation of compositions for each layer) A composition for forming a magnetic layer, a non-magnetic layer, or a backcoat layer typically contains a solvent along with the various components described above. As the solvent, one or more of the solvents commonly used in the manufacture of coated magnetic recording media can be used. The solvent content of each layer-forming composition is not particularly limited. For solvents, refer to paragraph 0153 of Japanese Patent Application Publication No. 2011-216149. The solid content concentration and solvent composition of each layer-forming composition may be appropriately adjusted in accordance with the handling suitability of the composition, the coating conditions, and the thickness of each layer to be formed. The process of preparing a composition for forming a magnetic layer, a non-magnetic layer, or a backcoat layer typically includes at least a kneading step, a dispersion step, and mixing steps provided before or after these steps as needed. Each individual step may be divided into two or more stages. The various components used in the preparation of each layer-forming composition may be added at the beginning or in the middle of any of the steps. Alternatively, individual components may be added in two or more separate steps. For example, a binder may be added in separate steps: a kneading step, a dispersion step, and a mixing step for viscosity adjustment after dispersion. In the manufacturing process of the magnetic tape described above, conventional known manufacturing techniques can be used as some of the steps. In the kneading step, kneaders with strong kneading force, such as open kneaders, continuous kneaders, pressure kneaders, and extruders, can be used. Details of the kneading step are described in Japanese Patent Publication No. 1-106338 and Japanese Patent Publication No. 1-79274. As the disperser, various known dispersers that utilize shear force, such as bead mills, ball mills, sand mills, or homomixers, can be used. Dispersion beads can preferably be used for dispersion. Examples of dispersion beads include ceramic beads and glass beads, with zirconia beads being preferred. Two or more types of beads may be used in combination. The bead diameter (particle size) and bead packing rate of the dispersion beads are not particularly limited and should be set according to the powder to be dispersed. Each layer-forming composition may be filtered by a known method before being subjected to the coating step. Filtration can be performed, for example, by filter filtration. As the filter used for filtration, for example, a filter with a pore size of 0.01 to 3 μm (e.g., a glass fiber filter, a polypropylene filter, etc.) can be used.

[0131] (Coating process) The magnetic layer can be formed by directly applying the magnetic layer-forming composition onto the surface of a non-magnetic support, or by sequentially or simultaneously applying it in layers with the non-magnetic layer-forming composition. The back coat layer can be formed by applying the back coat-forming composition to the surface of the non-magnetic support opposite to the surface having the non-magnetic layer and / or magnetic layer (or to which the non-magnetic layer and / or magnetic layer are subsequently provided). For details on the application for each layer formation, refer to paragraph 0066 of Japanese Patent Application Publication No. 2010-231843.

[0132] (Other processes) For other processes in the manufacture of magnetic tape, known technologies can be applied. For various processes, see, for example, paragraphs 0067 to 0070 of Japanese Patent Publication No. 2010-231843. For example, the coated layer of the magnetic layer forming composition can be subjected to orientation treatment in an orientation zone while the coated layer is wet. For orientation treatment, various known technologies, including those described in paragraph 0052 of Japanese Patent Publication No. 2010-24113, can be applied. For example, vertical orientation treatment can be performed by known methods such as using opposite-polarity opposing magnets. In the orientation zone, the drying rate of the coated layer can be controlled by the temperature and airflow of the drying air and / or the transport speed in the orientation zone. Alternatively, the coated layer may be pre-dried before being transported to the orientation zone. As an example, the magnetic field strength in the vertical orientation treatment can be 0.1 to 1.5 T.

[0133] Regarding magnetic tape, a long roll of raw magnetic tape can be obtained through various processes. The obtained roll of raw magnetic tape is cut (slit) to the width of the magnetic tape to be wound onto a magnetic tape cartridge using a known cutting machine. The above width is determined according to standards, for example, 1 / 2 inch. 1 / 2 inch = 12.65 mm. Typically, a servo pattern is formed on the magnetic tape obtained by slitting. Details on the formation of the servo pattern will be described later.

[0134] (Heat treatment) In one embodiment, the magnetic tape described above may be a magnetic tape manufactured through the following heat treatment. In another embodiment, the magnetic tape may be a magnetic tape manufactured without the following heat treatment. Performing the following heat treatment may contribute to increasing the media lifespan. This is mainly because performing the following heat treatment is thought to contribute to suppressing deformation of the magnetic tape, which mainly occurs due to stress received during storage in a magnetic tape cartridge in an environment exposed to changes in temperature and humidity.

[0135] For heat treatment, the magnetic tape, which has been slit and cut to a width determined according to the standard, can be wound around a core-shaped member, and the heat treatment can be performed while the tape is wound around the member.

[0136] In one embodiment, the above heat treatment is performed with the magnetic tape wound around a core-shaped member for heat treatment (hereinafter referred to as the "heat-treated winding core"), and the heat-treated magnetic tape is wound onto the cartridge reel of a magnetic tape cartridge, thereby producing a magnetic tape cartridge with the magnetic tape wound onto the cartridge reel. The core for heat treatment can be made of metal, resin, paper, etc. From the viewpoint of suppressing winding failures such as spocking, the material of the core for heat treatment is preferably a highly rigid material. For this reason, the core for heat treatment is preferably made of metal or resin. Furthermore, as an indicator of rigidity, the flexural modulus of the material for heat treatment is preferably 0.2 GPa or higher, and more preferably 0.3 GPa or higher. On the other hand, since highly rigid materials are generally expensive, using a core for heat treatment made of a material with rigidity exceeding the rigidity required to suppress winding failures leads to increased costs. Considering the above points, the flexural modulus of the material for heat treatment is preferably 250 GPa or lower. The core for heat treatment can be a solid or hollow core-shaped member. In the case of a hollow core, from the viewpoint of maintaining rigidity, the wall thickness is preferably 2 mm or more. The core for heat treatment may or may not have a flange. It is preferable to prepare a magnetic tape that is at least the length to be ultimately housed in a magnetic tape cartridge (hereinafter referred to as the "final product length") as the magnetic tape to be wound onto the heat treatment core, and to perform heat treatment by winding this magnetic tape onto the heat treatment core and placing it in a heat treatment environment. The length of the magnetic tape wound onto the heat treatment core is at least the final product length, and from the viewpoint of ease of winding onto the heat treatment core, it is preferable to set it to "final product length + α". From the viewpoint of ease of winding, this α is preferably 5 m or more. The tension when 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 when winding onto the heat treatment core is preferably 1.50 N or less, and more preferably 1.00 N or less. The outer diameter of the heat treatment core is preferably 20 mm or more, and more preferably 40 mm or more, from the viewpoint of ease of winding and suppression of coiling (longitudinal curling). Furthermore, the outer diameter of the heat treatment core is preferably 100 mm or less, and more preferably 90 mm or less. The width of the heat treatment core should be greater than or equal to the width of the magnetic tape wound around it. Also, when removing the magnetic tape from the heat treatment core after heat treatment, it is preferable to remove the magnetic tape from the heat treatment core only after the magnetic tape and heat treatment core have cooled sufficiently, in order to prevent unintended tape deformation during the removal operation. It is preferable to first wind the removed magnetic tape onto another core (referred to as a "temporary winding core"), and then wind the magnetic tape from the temporary winding core onto the cartridge reel of the magnetic tape cartridge (generally with an outer diameter of about 40-50 mm). This allows the relationship between the inside and outside of the magnetic tape relative to the heat treatment core during heat treatment to be maintained when winding the magnetic tape onto the cartridge reel of the magnetic tape cartridge. For details of the temporary winding core and the tension when winding the magnetic tape onto this core, please refer to the previous description regarding the heat treatment core. In the configuration in which the above heat treatment is applied to a magnetic tape of a length of "final product length + α", the "+ α" length can be cut off at any stage. For example, in one configuration, the magnetic tape of the final product length is wound from the temporary winding core onto the reel of the magnetic tape cartridge, and the remaining "+ α" length can be cut off.From the standpoint of minimizing the amount that is cut off and discarded, it is preferable that α is 20m or less.

[0137] The specific form of heat treatment performed while the material is wrapped around the core member, as described above, is explained below. The ambient temperature for heat treatment (hereinafter referred to as the "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 used for heat treatment is preferably 0.1 g / kg Dry air or higher, and more preferably 1 g / kg Dry air or higher. An atmosphere with an absolute humidity by weight within the above range is preferable because it can be prepared without using special equipment to reduce moisture. On the other hand, from the viewpoint of suppressing condensation and the resulting decrease in workability, the absolute humidity by weight is preferably 70 g / kg Dry air or lower, and more preferably 66 g / kg Dry air or lower. The heat treatment time is preferably 0.3 hours or longer, and more preferably 0.5 hours or longer. Furthermore, from the viewpoint of production efficiency, the heat treatment time is preferably 48 hours or less.

[0138] (Formation of servo patterns) The magnetic tape described above has multiple servo bands in its magnetic layer. The servo bands are composed of a servo pattern that runs continuously in the longitudinal direction of the magnetic tape. The servo pattern can enable tracking control of the magnetic head in a magnetic recording and playback device, control of the magnetic tape's running speed, and so on. "Formation of the servo pattern" can also be described as "recording of a servo signal." For example, by using the servo signal to acquire dimensional information in the width direction of the running magnetic tape, and adjusting and changing the tension applied to the magnetic tape in the longitudinal direction according to the acquired dimensional information, the width direction of the magnetic tape can be controlled.

[0139] The formation of the servo pattern will be explained below.

[0140] The servo pattern is formed along the longitudinal direction of the magnetic tape. Examples of control methods that utilize servo signals (servo control) include timing-based servo (TBS), amplitude servo, and frequency servo.

[0141] As indicated in ECMA (European Computer Manufacturers Association) - 319 (June 2001), magnetic tapes conforming to the LTO (Linear Tape-Open) standard (commonly called "LTO tapes") employ a timing-based servo system. In this timing-based servo system, the servo pattern is composed of multiple pairs of non-parallel magnetic stripes (also called "servo stripes") arranged continuously 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 specification, "timing-based servo pattern" refers to a servo pattern that enables head tracking in a timing-based servo system. As described above, the reason why the servo pattern is composed of pairs of non-parallel magnetic stripes is to inform the servo signal reading element of its position as it passes over the servo pattern. Specifically, the pair of magnetic stripes described above are formed so that their spacing changes continuously along the width direction of the magnetic tape, and the servo signal reading element can determine the relative position between the servo pattern and the servo signal reading element by reading this spacing. This relative position information enables tracking of the data track. Therefore, multiple servo tracks are typically set up on the servo pattern, aligned with the width of the magnetic tape.

[0142] A servo band is composed of a servo pattern that is continuous in the longitudinal direction of the magnetic tape. The magnetic tape has multiple servo bands in its magnetic layer. For example, in an LTO tape, there are five servo bands. The area between two adjacent servo bands is the data band. The data band consists of multiple data tracks, and each data track corresponds to each servo track.

[0143] In one embodiment, as shown in Japanese Patent Publication No. 2004-318983, each servo band has embedded information indicating the servo band number (also called "servo band ID (identification)" or "UDIM (Unique DataBand Identification Method) information"). This servo band ID is recorded by shifting a specific pair of servo stripes within a servo band so that its position is displaced relative to the longitudinal direction of the magnetic tape. Specifically, the method of shifting a specific pair of servo stripes is changed for each servo band. As a result, the recorded servo band ID is unique for each servo band, so that a servo band can be uniquely identified by reading it with a servo signal reading element.

[0144] Furthermore, one method for uniquely identifying a servo band is the staggered method, as described in ECMA-319 (June 2001). In this staggered method, a group of non-parallel magnetic stripes (servo stripes) arranged continuously along the longitudinal direction of the magnetic tape are recorded in a way that they are shifted along the longitudinal direction of the magnetic tape for each servo band. Since the combination of this shift between adjacent servo bands is unique across the entire magnetic tape, it is possible to uniquely identify a servo band when reading the servo pattern with two servo signal reading elements.

[0145] Furthermore, each servo band typically contains embedded information indicating its position along the longitudinal direction of the magnetic tape (also known as "LPOS (Longitudinal Position) information"), as described in ECMA-319 (June 2001). This LPOS information, like the UDIM information, is recorded by shifting the positions of a pair of servo stripes along the longitudinal direction of the magnetic tape. However, unlike the UDIM information, the same signal is recorded for each servo band in this LPOS information.

[0146] It is also possible to embed information other than the UDIM and LPOS information mentioned above into the servo bands. In this case, the embedded information may be different for each servo band, like the UDIM information, or it may be common to all servo bands, like the LPOS information. Furthermore, methods other than those described above can be used to embed information in the servo bands. For example, a predetermined code may be recorded by thinning out a predetermined pair from a group of servo stripes.

[0147] A servo pattern forming head is called a servo light head. A servo light head typically has a pair of gaps corresponding to the pair of magnetic stripes mentioned above, for each servo band. Typically, a core and a coil are connected to each pair of gaps, and by supplying current pulses to the coils, the magnetic field generated in the core can create a leakage magnetic field in the pair of gaps. When forming a servo pattern, by inputting current pulses while running a magnetic tape over the servo light head, the magnetic patterns corresponding to the pair of gaps are transferred to the magnetic tape, thereby forming the servo pattern. The width of each gap can be appropriately set according to the density of the servo pattern to be formed. For example, the width of each gap can be set to 1 μm or less, 1 to 10 μm, 10 μm or more, etc.

[0148] Before forming a servo pattern on a magnetic tape, it is usually demagnetized (erased). This erasing process can be performed by applying a uniform magnetic field to the magnetic tape using a DC or AC magnet. There are two types of erasing: DC (Direct Current) erasing and AC (Alternating Current) erasing. AC erasing is performed by gradually reducing the strength of the magnetic field while reversing the direction of the magnetic field applied to the magnetic tape. On the other hand, DC erasing is performed by applying a unidirectional magnetic field to the magnetic tape. There are two further methods of DC erasing. The first method is horizontal DC erasing, which applies a unidirectional magnetic field along the longitudinal direction of the magnetic tape. The second method is vertical DC erasing, which applies a unidirectional magnetic field along the thickness direction of the magnetic tape. The erasing process may be performed on the entire magnetic tape or on each servo band of the magnetic tape.

[0149] The direction of the magnetic field of the formed servo pattern is determined according to the direction of the erase. For example, when a magnetic tape is horizontally DC erased, the servo pattern is formed such that the direction of the magnetic field is opposite to the direction of the erase. This makes it possible to increase the output of the servo signal obtained by reading the servo pattern. As shown in Japanese Patent Application Publication No. 2012-53940, when a magnetic pattern using the above gap is transferred to a vertically DC erased magnetic tape, the servo signal obtained by reading the formed servo pattern is in the shape of a single-pole pulse. On the other hand, when a magnetic pattern using the above gap is transferred to a horizontally DC erased magnetic tape, the servo signal obtained by reading the formed servo pattern is in the shape of a double-pole pulse.

[0150] Typically, after the servo pattern is formed, the magnetic tape is wound onto the reel hub of the cartridge reel and housed in a magnetic tape cartridge.

[0151] <Vertical squareness ratio> In one embodiment, the vertical aspect ratio of the magnetic tape can be, for example, 0.55 or more, and preferably 0.60 or more. A vertical aspect ratio of 0.60 or more is preferable from the viewpoint of improving electromagnetic conversion characteristics. In principle, the upper limit of the aspect ratio is 1.00 or less. The vertical aspect ratio of the magnetic tape can be 1.00 or less, and can be 0.95 or less, 0.90 or less, 0.85 or less, or 0.80 or less. A large value for the vertical aspect ratio of the magnetic tape is preferable from the viewpoint of improving electromagnetic conversion characteristics. The vertical aspect ratio of the magnetic tape can be controlled by known methods such as performing a vertical orientation process.

[0152] In the present invention and this specification, "vertical angle ratio" refers to the angle ratio measured in the vertical direction of the magnetic tape. In relation to the angle ratio, "vertical direction" refers to the direction perpendicular to the surface of the magnetic layer, and can also be referred to as the thickness direction. In the present invention and this specification, the vertical angle ratio is determined by the following method. A sample piece of a size suitable for introduction into a vibrating magnetometer is cut from the magnetic tape to be measured. Using a vibrating magnetometer, a magnetic field is applied to this sample piece perpendicular to the sample piece (in the direction perpendicular to the magnetic layer surface) at a maximum applied magnetic field of 3979 kA / m, a measurement temperature of 296 K, and a magnetic field sweep speed of 8.3 kA / m / sec, and the magnetization intensity of the sample piece against the applied magnetic field is measured. The measured magnetization intensity is obtained as a value after demagnetization correction and after subtracting the magnetization of the sample probe of the vibrating magnetometer as background noise. When the magnetization intensity at the maximum applied magnetic field is Ms and the magnetization intensity at zero applied magnetic field is Mr, the squareness ratio SQ is calculated as SQ = Mr / Ms. The measurement temperature refers to the temperature of the sample piece, and the temperature of the sample piece can be set to the measurement temperature by setting the ambient temperature around the sample piece to the measurement temperature, thereby achieving thermal equilibrium.

[0153] [Magnetic head] One aspect of the present invention relates to a magnetic recording and playback device including the magnetic tape cartridge described above. In the present invention and this specification, "magnetic recording and playback device" means a device capable of recording data onto a magnetic tape and playing back data recorded on a magnetic tape. Such a device is generally called a drive and usually includes a magnetic head. A magnetic tape cartridge is inserted into the magnetic recording and playback device, and the magnetic tape is run within the magnetic recording and playback device to record data onto the magnetic tape and / or play back the recorded data using the magnetic head. The magnetic head included in the magnetic recording and playback device may be a recording head capable of recording data onto a magnetic tape, or a playback head capable of playing back data recorded on a magnetic tape. In one embodiment, the magnetic recording and playback device may include both a recording head and a playback head as separate magnetic heads. In another embodiment, the magnetic head included in the magnetic recording and playback device may have a configuration in which both a recording element and a playback element are provided in a single magnetic head. As a playback head, a magnetic head (MR head) that includes a magnetoresistive (MR) element as a playback element capable of sensitively reading information recorded on a magnetic tape is preferred. Various known MR heads (e.g., GMR (Giant Magnetoresistive) heads, TMR (Tunnel Magnetoresistive) heads, etc.) can be used as MR heads. Furthermore, the magnetic head used for recording and / or reproducing data may include a servo pattern reading element. Alternatively, a magnetic head equipped with a servo pattern reading element (servo head) may be included in the magnetic recording and / or reproducing device as a separate head from the magnetic head used for recording and / or reproducing data. For example, a magnetic head used for recording and / or reproducing recorded data (hereinafter also referred to as the "recording and reproducing head") may include two servo signal reading elements, each of which can simultaneously read two adjacent servo bands separated by a data band. One or more data elements can be placed between the two servo signal reading elements.Elements for recording data (recording elements) and elements for reproducing data (reproduction elements) are collectively referred to as "data elements."

[0154] By using a regeneration element with a narrow width as the regeneration element, high-density recorded data can be regenerated with high sensitivity. From this viewpoint, the regeneration element width is preferably 0.8 μm or less. The regeneration element width can be, for example, 0.1 μm or more. However, a value lower than this is also preferable from the above viewpoint. On the other hand, the narrower the playback element width, the more likely it is that playback defects and other phenomena caused by off-track recording will occur. To suppress the occurrence of such phenomena, a magnetic recording and playback device that controls the width dimension of the magnetic tape by adjusting and changing the tension applied to the longitudinal direction of the magnetic tape while it is running is preferable. Here, "regenerative element width" refers to the physical dimension of the regenerative element width. Such physical dimensions can be measured using an optical microscope, a scanning electron microscope, or the like.

[0155] When recording data and / or playing back recorded data, head tracking using servo signals can be performed first. That is, by making the servo signal reading element follow a predetermined servo track, the data element can be controlled to pass over the target data track. The movement of the data track is achieved by changing the servo track read by the servo signal reading element in the tape width direction. Furthermore, the recording / playback head can also record and / or play back data on other data bands. In this case, the servo signal reading element can be moved to a predetermined servo band using the UDIM information described earlier, and tracking for that servo band can be started.

[0156] Figure 5 shows an example of the arrangement of data bands and servo bands. In Figure 5, multiple servo bands 1 are arranged on the magnetic layer of the magnetic tape MT, sandwiched between guide bands 3. Multiple regions 2 sandwiched between two servo bands are the data bands. A servo pattern is a magnetized region, formed by magnetizing a specific region of the magnetic layer with a servo light head. The region magnetized by the servo light head (the position where the servo pattern is formed) is defined by the standard. For example, in the industry standard LTO Ultrium format tape, multiple servo patterns inclined with respect to the tape width direction are formed on the servo bands during magnetic tape manufacturing, as shown in Figure 6. More specifically, in Figure 6, the servo frame SF on the servo band 1 consists of a servo subframe 1 (SSF1) and a servo subframe 2 (SSF2). The servo subframe 1 consists of an A-burst (indicated as A in Figure 6) and a B-burst (indicated as B in Figure 6). The A-burst consists of servo patterns A1 to A5, and the B-burst consists of servo patterns B1 to B5. On the other hand, servo subframe 2 consists of C-bursts (indicated as C in Figure 6) and D-bursts (indicated as D in Figure 6). C-bursts consist of servo patterns C1 to C4, and D-bursts consist of servo patterns D1 to D4. These 18 servo patterns are arranged in sets of 5 and 4 on subframes in a 5, 5, 4, 4 sequence, and are used to identify the servo frames. Figure 6 shows one servo frame for illustrative purposes. However, in reality, in the magnetic layer of magnetic tape where timing-based servo tracking is performed, multiple servo frames are arranged in the direction of travel in each servo band. In Figure 6, the arrows indicate the direction of travel. For example, LTO Ultrium format tape typically has more than 5000 servo frames per meter of tape length in each servo band of the magnetic layer. [Examples]

[0157] The present invention will be described below based on examples. However, the present invention is not limited to the embodiments shown in the examples. Unless otherwise specified, the "parts" and "%" mentioned below refer to "parts by mass" and "mass%". "eq" is equivalent and is a unit that cannot be converted to SI units. Furthermore, unless otherwise specified, the following processes and operations were carried out in an environment with a temperature of 20-25°C and a relative humidity of 40-60%.

[0158] [Nonmagnetic support] In Table 1, "PEN" indicates a polyethylene naphthalate support. The moisture content and Young's modulus in Table 1 are values ​​measured by the method described above.

[0159] [Ferromagnetic powder] In Table 1, "BaFe" in the ferromagnetic powder column refers to hexagonal barium ferrite powder with an average particle size (average plate diameter) of 21 nm.

[0160] In Table 1, "SrFe1" in the ferromagnetic powder column refers to hexagonal strontium ferrite powder prepared as follows. 1707g of SrCO3, 687g of H3BO3, 1120g of Fe2O3, 45g of Al(OH)3, 24g of BaCO3, 13g of CaCO3, and 235g of Nd2O3 were weighed out and mixed in a mixer to obtain a raw material mixture. The obtained raw material mixture was melted in a platinum crucible at a melting temperature of 1390°C. While stirring the molten material, the outlet at the bottom of the platinum crucible was heated, and the molten material was dispensed in a rod shape at approximately 6 g / second. The dispensed material was rolled and rapidly cooled using water-cooled twin rollers to produce an amorphous body. 280g of the prepared amorphous material was placed in an electric furnace and heated to 635°C (crystallization temperature) at a heating rate of 3.5°C / min. The temperature was maintained at this temperature for 5 hours to precipitate (crystallize) hexagonal strontium ferrite particles. Next, the crystalline material obtained above, containing hexagonal strontium ferrite particles, was coarsely ground in a mortar. 1000g of 1mm particle size zirconia beads and 800mL of 1% aqueous acetic acid solution were added to a glass bottle, and the mixture was dispersed in a paint shaker for 3 hours. After that, the resulting dispersion was separated from the beads and placed in a stainless steel beaker. The dispersion was allowed to stand at a liquid temperature of 100°C for 3 hours to dissolve the glass components, then precipitated using a centrifuge, and washed by repeated decantation. Finally, it was dried in a heating furnace at a furnace temperature of 110°C for 6 hours to obtain hexagonal strontium ferrite powder. The average particle size of the hexagonal strontium ferrite powder obtained above was 18 nm, and the activation volume was 902 nm. 3 The anisotropy constant Ku is 2.2 × 10⁻⁶. 5 J / m 3 , mass magnetization σs is 49A m 2 It was / kg. A sample powder of 12 mg was taken from the hexagonal strontium ferrite powder obtained above, and the elemental analysis of the filtrate obtained by partially dissolving this sample powder under the dissolution conditions exemplified earlier was performed using an ICP analyzer to determine the surface layer content of neodymium atoms. Separately, 12 mg of sample powder was taken from the hexagonal strontium ferrite powder obtained above, and the elemental analysis of the filtrate obtained by completely dissolving this sample powder under the dissolution conditions exemplified earlier was performed using an ICP analyzer to determine the bulk content of neodymium atoms. The neodymium atom content (bulk content) relative to 100 atomic percent of iron atoms in the hexagonal strontium ferrite powder obtained above was 2.9 atomic percent. Furthermore, the neodymium atom content in the surface layer was 8.0 atomic percent. The ratio of surface layer content to bulk content, "surface layer content / bulk content," was 2.8, confirming that neodymium atoms were concentrated in the surface layer of the particles.

[0161] The hexagonal ferrite crystal structure of the powder obtained above was confirmed by scanning with CuKα rays at a voltage of 45kV and intensity of 40mA, and measuring the X-ray diffraction pattern under the following conditions (X-ray diffraction analysis). The powder obtained above showed a magnetoplanbite-type (M-type) hexagonal ferrite crystal structure. Furthermore, the crystalline phase detected by X-ray diffraction analysis was a single phase of the magnetoplanbite type. PANalytical X'Pert Pro diffractometer, PIXcel detector Soller slit for incident and diffracted beams: 0.017 radians Fixed angle of dispersion slit: 1 / 4 degree Mask: 10mm Scatter prevention 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

[0162] In Table 1, "SrFe2" in the ferromagnetic powder column refers to hexagonal strontium ferrite powder prepared as follows. 1725g of SrCO3, 666g of H3BO3, 1332g of Fe2O3, 52g of Al(OH)3, 34g of CaCO3, and 141g of BaCO3 were weighed out and mixed in a mixer to obtain a raw material mixture. The obtained raw material mixture was melted in a platinum crucible at a melting point of 1380°C. While stirring the molten material, the outlet at the bottom of the platinum crucible was heated, and the molten material was dispensed in a rod shape at approximately 6 g / second. The dispensed material was rolled and rapidly cooled using water-cooled twin rolls to produce an amorphous body. 280g of the obtained amorphous material was placed in an electric furnace, heated to 645°C (crystallization temperature), and held at the same temperature for 5 hours to precipitate (crystallize) hexagonal strontium ferrite particles. Next, the crystalline material obtained above, containing hexagonal strontium ferrite particles, was coarsely ground in a mortar. 1000g of 1mm particle size zirconia beads and 800mL of 1% aqueous acetic acid solution were added to a glass bottle, and the mixture was dispersed in a paint shaker for 3 hours. After that, the resulting dispersion was separated from the beads and placed in a stainless steel beaker. The dispersion was allowed to stand at a liquid temperature of 100°C for 3 hours to dissolve the glass components, then precipitated using a centrifuge, and washed by repeated decantation. Finally, it was dried in a heating furnace at a furnace temperature of 110°C for 6 hours to obtain hexagonal strontium ferrite powder. The average particle size of the obtained hexagonal strontium ferrite powder was 19 nm, and the activation volume was 1102 nm. 3 The anisotropy constant Ku is 2.0 × 10⁻⁶. 5 J / m 3 , mass magnetization σs is 50A m 2 It was / kg.

[0163] In Table 1, "ε-iron oxide" in the ferromagnetic powder column refers to ε-iron oxide powder prepared as follows. In 90 g of pure water, 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. While stirring with a magnetic stirrer in an air atmosphere at an ambient temperature of 25°C, 4.0 g of a 25% aqueous ammonia solution was added, and the mixture was stirred for 2 hours at the same ambient temperature of 25°C. To the resulting solution, an aqueous citric acid solution obtained by dissolving 1 g of citric acid in 9 g of pure water was added, and the mixture was stirred for 1 hour. After stirring, the precipitated powder was collected by centrifugation, washed with pure water, and dried in a heating furnace at an ambient temperature of 80°C. 800g of pure water was added to the dried powder, and the powder was dispersed in the water again to obtain a dispersion. The obtained 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 the mixture was 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 in a heating furnace at a temperature of 80°C for 24 hours to obtain a precursor of ferromagnetic powder. The obtained ferromagnetic powder precursor was placed in a heating furnace at a temperature of 1000°C under an atmospheric environment and subjected to heat treatment for 4 hours. A heat-treated ferromagnetic powder precursor was added to a 4 mol / L sodium hydroxide (NaOH) aqueous solution, and the solution was stirred for 24 hours while maintaining the temperature at 70°C to remove silicate compounds, which are impurities, from the heat-treated ferromagnetic powder precursor. Subsequently, the ferromagnetic powder, from which the silicate compounds were removed by centrifugation, was collected and washed with pure water to obtain ferromagnetic powder. The composition of the obtained ferromagnetic powder was confirmed by inductively coupled plasma emission spectroscopy (ICP-OES), revealing that it was a Ga, Co, and Ti-substituted ε-iron oxide (ε-Ga 0.28 Co 0.05 Ti 0.05 Fe 1.62 It was O3). Furthermore, X-ray diffraction analysis was performed under the same conditions as described earlier for the hexagonal strontium ferrite powder SrFe1, and from the peaks of the X-ray diffraction pattern, it was confirmed that the obtained ferromagnetic powder has a single-phase crystalline structure of the ε phase (crystalline structure of ε-iron oxide) that does not contain the crystalline structures of the α phase and γ phase. The average particle size of the obtained ε-iron oxide powder was 12 nm, and the activation volume was 746 nm. 3 The anisotropy constant Ku is 1.2 × 10⁻⁶. 5 J / m 3 , mass magnetization σs is 16A m 2 It was / kg.

[0164] The activation volume and anisotropy constant Ku of the hexagonal strontium ferrite powder and ε-iron oxide powder described above were obtained for each ferromagnetic powder using a vibrating sample magnetometer (manufactured by Toei Kogyo Co., Ltd.) and the method described above. Furthermore, the mass magnetization σs was measured using a vibrating sample type magnetometer (manufactured by Toei Kogyo Co., Ltd.) at a magnetic field strength of 1194 kA / m (15 kOe).

[0165] [Example 1] (1) Formulation of a composition for forming a 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 copies Methyl ethyl ketone: 150 parts (Abrasive solution 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 solution B) Diamond abrasive (average particle size: 100nm): 1.0 part Sulfonic acid group-containing polyurethane resin: 0.1 part 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

[0166] The above-mentioned dispersant is a compound (a compound having a polyalkylene imine chain and a vinyl polymer chain) described as a component of the magnetic layer forming composition of Example 1 in Japanese Patent Publication No. 2019-169225. The reaction solution obtained after the synthesis of the above 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 above compound in such reaction solution.

[0167] (2) Formulation of composition for forming a non-magnetic 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 part Cyclohexanone: 300.0 parts Methyl ethyl ketone: 300.0 parts

[0168] (3) Formulation of composition for forming backcoat layer Carbon Black: 100.0 parts Cabot BP-800, average particle size: 17nm SO3Na group-containing polyurethane resin (SO3Na group: 70 eq / ton): 20.0 parts OSO3K group-containing polyvinyl chloride resin (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 Stearamide: 0.1 part

[0169] (4) Production of magnetic tape and magnetic tape cartridge The above components of the magnetic fluid were dispersed for 24 hours using a batch vertical sand mill to prepare a magnetic fluid. As the dispersion beads, zirconia beads with a bead diameter of 0.5 mm were used. Regarding the abrasive liquid, the above components of abrasive liquid A and abrasive liquid B were each dispersed for 24 hours using a batch ultrasonic device (20 kHz, 300 W) to obtain abrasive liquid A and abrasive liquid B. The magnetic fluid, abrasive liquid A, and abrasive liquid B were mixed with the above silica sol and other components, and then subjected to a dispersion treatment for 30 minutes using a batch ultrasonic device (20 kHz, 300 W). Thereafter, filtration was performed using a filter having a pore diameter of 0.5 μm to prepare a composition for forming a magnetic layer. Regarding the composition for forming a non-magnetic layer, the above components were dispersed for 24 hours using a batch vertical sand mill. As the dispersion beads, zirconia beads with a bead diameter of 0.1 mm were used. The obtained dispersion was filtered using a filter having a pore diameter of 0.5 μm to prepare a composition for forming a non-magnetic layer. Regarding the composition for forming a backcoat layer, the above components were kneaded using a continuous kneader and then dispersed using 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 obtained dispersion, and then filtration was performed using a filter having a pore diameter of 1 μm to prepare a composition for forming a backcoat layer. The composition for forming a non-magnetic layer prepared above was applied and dried on the surface of the biaxially stretched support shown in Table 1 with a thickness of 4.1 μm so that the thickness after drying would be 0.7 μm to form a non-magnetic layer. Next, the composition for forming a magnetic layer prepared above was applied on the non-magnetic layer so that the thickness after drying would be 0.1 μm to form a coating layer. Thereafter, while the coating layer of the composition for forming a magnetic layer was in a wet state, a magnetic field with a magnetic field strength of 0.3 T was applied in a direction perpendicular to the surface of the coating layer to perform perpendicular orientation treatment, and then it was dried to form a magnetic layer. Thereafter, the composition for forming a backcoat layer prepared above was applied and dried on the surface of the support opposite to the surface on which the non-magnetic layer and the magnetic layer were formed so that the thickness after drying was 0.3 μm to form a backcoat layer. Thereafter, the long magnetic tape raw web was heat-treated by storing it in a heat treatment furnace at an ambient temperature of 70°C (heat treatment time: 36 hours). After the heat treatment, it was slit into a 1 / 2-inch width to obtain a magnetic tape. By recording a servo signal on the magnetic layer of the obtained magnetic tape using a commercially available servo writer, a magnetic tape having data bands, servo bands, and guide bands in an arrangement according to the LTO (Linear Tape-Open) Ultrium format, and having a servo pattern (timing-based servo pattern) with an arrangement and shape according to the LTO Ultrium format on the servo band was obtained. The servo pattern thus formed is a servo pattern according to the descriptions of JIS (Japanese Industrial Standards) X6175:2006 and Standard ECMA-319 (June 2001). The total number of servo bands is 5, and the total number of data bands is 4. The magnetic tape (length 970 m) after the formation of the above servo pattern was wound around a heat treatment core, and heat treatment was performed in a state of being wound around this core. As the heat treatment core, a solid core member (outer diameter: 50 mm) made of resin with a flexural modulus of 0.8 GPa was used, and the tension during winding was 0.60 N. The heat treatment was performed for 5 hours at the heat treatment temperature shown in Table 1. The absolute humidity by weight of the atmosphere in which the heat treatment was performed was 10 g / kg Dry air. After the heat treatment described above, once the magnetic tape and the heat treatment core had cooled sufficiently, the magnetic tape was removed from the heat treatment core and wound onto a temporary winding core. Then, the final product length (960m) of magnetic tape was wound longitudinally from the temporary winding core onto the reel hub of the magnetic tape cartridge reel, with the tension specified in the "Manufacturing Winding Tension" column of Table 1. The remaining 10m was cut off, and a leader tape conforming to item 9 of Section 3 of Standard ECMA (European Computer Manufacturers Association)-319 (June 2001) was joined to the cut end using commercially available splicing tape. As the temporary winding core, a solid core member made of the same material and having the same outer diameter as the heat treatment core was used. As the magnetic tape cartridge used to house the magnetic tape described above, a single-reel type magnetic tape cartridge with the configuration shown in Figure 2 was used. The reel hub of this magnetic tape cartridge is a single-layer reel hub (thickness: 2.5 mm, outer diameter: 44 mm) made by injection molding of 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 taken, and according to item 6.3.1 (Preparation from molding material) of JIS K 7171:2016, the recommended test piece described in item 6.1.2 of the same JIS was prepared, and the flexural modulus (arithmetic mean of 5 test pieces) was calculated according to the same JIS, resulting in the value shown in Table 1. In the examples and comparative examples described later, the flexural modulus of the reel hub material was also determined by the above method. The flexural modulus of the winding core for heat treatment described above was also determined in the same way. Based on the above, a single-reel type magnetic tape cartridge of Example 1 was fabricated, in which a magnetic tape with a length of 960m was wound onto a reel.

[0170] The presence of a compound containing an ammonium salt structure of an alkyl ester anion represented by Formula 1, formed from polyethyleneimine and stearic acid, in the backcoat layer of the magnetic tape can be confirmed by the following method. A sample is cut out from the magnetic tape, and X-ray photoelectron spectroscopy is performed using an ESCA apparatus on the surface of the backcoat layer (measurement area: 300 μm × 700 μm). Specifically, wide scan measurement is performed using the ESCA apparatus under the following measurement conditions. In the measurement results, peaks are confirmed at the positions of the binding energy of the ester anion and the binding energy of the ammonium cation. Apparatus: AXIS-ULTRA manufactured by Shimadzu Corporation Excitation X-ray source: Monochromatic Al-Kα ray Scan range: 0 - 1200 eV Pass energy: 160 eV Energy resolution: 1 eV / step Integration time: 100 ms / step Number of integrations: 5 Also, a 3 cm long sample piece is cut out from the magnetic tape, and ATR-FT-IR (Attenuated total reflection - fourier transform - infrared spectrometer) measurement (reflection method) is performed on the surface of the backcoat layer. In the measurement results, the wave numbers (1540 cm - or 1430 cm -1 corresponding to the absorption of COO -1 ), and the wave numbers (2400 cm -1 ) corresponding to the absorption of the ammonium cation are confirmed to have absorption.

[0171] [ [Examples 2 - 19, Comparative Examples 1 - 7] Magnetic tape cartridges were produced by the method described for Example 1, except that the items in Table 1 were changed as shown in Table 1. In the comparative examples where "none" is described in the "heat treatment temperature" column in Table 1, a magnetic tape with a final product length of 960 m was housed in a magnetic tape cartridge without performing heat treatment in a state wound around a heat treatment core.

[0172] For the above examples and comparative examples, two magnetic tape cartridges were produced respectively. One was used for the evaluation of the following medium life and tape thickness, and the other was used for the evaluation of the recording and playback performance described later.

[0173] [Evaluation Method] <Media Life> (Measurement of servo band spacing) To allow the magnetic tape cartridge to acclimate to the measurement environment, it was placed in a measurement environment with an ambient temperature of 23°C and a relative humidity of 50% for 5 days. Subsequently, under the above measurement environment, the magnetic tape was run using the magnetic recording and playback device shown in Figure 1 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, separated by a data band, was measured at 1 m intervals along the entire length of the magnetic tape. Measurements were taken for all servo band intervals. The servo band intervals measured in this way were defined as the "servo band interval before storage" at each measurement position. The distance between two adjacent servo bands, separated by a data band, was determined as follows. To determine the spacing between two adjacent servo bands separated by a data band, the dimensions of the servo pattern are necessary. The standard for servo pattern dimensions varies depending on the generation of the LTO. Therefore, first, the average distance AC between the four corresponding stripes of the A-burst and C-burst, and the azimuth angle α of the servo pattern are measured using a magnetic force microscope or similar device. Next, a reel tester and a servo head equipped with two servo signal reading elements (hereinafter referred to as the upper and lower) fixed at an interval perpendicular to the longitudinal direction of the magnetic tape are used to sequentially read the servo pattern formed on the magnetic tape along the longitudinal direction of the tape. The average time between 5 stripes corresponding to A bursts and B bursts over the length of 1 LPOS word is defined as a. The average time between 4 corresponding stripes of A bursts and C bursts over a length of 1 m is defined as b. At this time, the value defined as AC × (1 / 2 - a / b) / (2 × tan(α)) represents the reading position PES in the width direction based on the servo signal obtained by the servo signal reading elements. The reading of the servo pattern is performed simultaneously by the two servo signal reading elements, the upper and the lower. The PES value obtained by the upper servo signal reading element is denoted as PES1, and the PES value obtained by the lower servo signal reading element is denoted as PES2. The interval between two adjacent servo bands separated by a data band can be determined as "PES2 - PES1". This is because the upper and lower servo pattern reading elements are fixed to the servo head and their spacing remains constant. Subsequently, for the magnetic tape cartridges mentioned above, the following values ​​were determined using the method described earlier: "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."

[0174] (Derivation of a linear function) The logarithm of the value of A obtained in the above process and the storage time T (log) e From the value of T, A and log can be obtained using the least squares method. e We derived a linear function with respect to T. The linear function is obtained by setting A to Y and log e Let T be X, then Y = cX + d. c and d are coefficients determined by the least squares method, and both were positive values.

[0175] (Decision B) Measurements were taken in five different 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%, and temperature 32°C, relative humidity 55%) using the following methods. For each measurement environment, the magnetic tape cartridge being measured was placed in the environment for 5 days to allow it to acclimate to the environment. Subsequently, under the measurement conditions, the magnetic tape was run using the magnetic recording and playback device shown in Figure 1, with a tension of 0.70 N applied to the longitudinal direction of the magnetic tape. For the above run, the servo band interval was measured at 1 m intervals in a 100 m area around the outer circumference of the reel, using the method described above, at data band 0 (zero). As previously described, the arithmetic mean of the measured servo band intervals was defined as the servo band interval in that measurement environment. After determining the servo band interval for each of the five environments as described above, the maximum and minimum values ​​among the obtained values ​​were used to calculate the value "B" of the magnetic tape cartridge being measured as "(maximum value - minimum value) × 1 / 2".

[0176] (Calculation of media life) The logarithm of A and T derived above is log e The value of T when A satisfies equation a: A = 1.5 - B was calculated using a linear function of A and T. The media life values ​​obtained for the examples and comparative examples are shown in Table 1.

[0177] <Tape thickness> After the above evaluation, the magnetic tape cartridges were left in an environment of 20-25°C and 40-60% relative humidity for more than 5 days to allow them to acclimate. Subsequently, under the same environment, 10 tape samples (5 cm in length) were cut from arbitrary sections of the magnetic tape removed from the cartridge, and the thickness of these tape samples was measured by stacking them. Thickness was measured using a digital thickness meter consisting of a MARH Millimar 1240 compact amplifier and a Millimar 1301 inductive probe. The measured thickness was divided by 10 to obtain the value obtained (thickness per tape sample), which was defined as the tape thickness. For each magnetic tape, the tape thickness was 5.2 μm.

[0178] <Evaluation of recording and playback performance> (1) Recording data onto magnetic tape before storage and playback of recorded data Recording and playback prior to storage were performed using a magnetic recording and playback device configured as shown in Figure 1. The recording and playback head mounted on the recording and playback head unit has 32 or more channels of playback elements (playback element width: 0.8 μm) and recording elements, and has servo signal reading and playback elements on both sides thereof. For each magnetic tape cartridge, the environment in which recording and playback (described later) were performed was the environment among the five environments described above in which the servoband interval obtained in the measurement to determine B was the maximum value. To allow the magnetic tape cartridge to acclimate to the recording environment, it was placed in the playback environment for five days. After that, recording was performed in the same environment as follows. A magnetic tape cartridge is set in the magnetic recording and playback device, and the magnetic tape is loaded. Next, while performing servo tracking, the recording and playback head unit records pseudo-random data with a specific data pattern onto the magnetic tape. The tension applied in the longitudinal direction of the tape during this process is a constant value of 0.50N. Simultaneously with data recording, the servo band spacing value along the entire length of the tape is measured every 1m along the longitudinal position and recorded in the cartridge memory. Next, while performing servo tracking, the recording and playback head unit plays back the data recorded on the magnetic tape. At this time, while playing back, the value of the servo band interval is measured, and based on the information recorded in the cartridge memory, the tension applied in the tape longitudinal direction is changed 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 playback, the measurement of the servo band interval and the tension control based on it are continuously performed in real time. During such playback, the tension applied in the longitudinal direction of the magnetic tape was changed within the range of 0.50 N to 0.85 N by the control device of the magnetic recording and playback apparatus. Therefore, during the above playback, the maximum value of the tension applied in the longitudinal direction of the magnetic tape is 0.85 N. At the end of the above playback, the entire length of the magnetic tape was wound around the cartridge reel of the magnetic tape cartridge.

[0179] (2) Winding (rewinding) and storage on the cartridge reel Subsequently, in the same environment, in the above magnetic recording and playback apparatus, the magnetic tape was run to wind the entire length of the magnetic tape around the take-up reel of the magnetic recording and playback apparatus. The tension applied in the longitudinal direction of the magnetic tape during this winding was set to a constant value of 0.40 N. Thereafter, with a constant tension of 0.40 N applied in the longitudinal direction of the magnetic tape, the entire length of the magnetic tape was wound around the cartridge reel (also described as "rewinding"). After the above rewinding, the magnetic tape cartridge containing the magnetic tape was stored in a storage environment of an ambient temperature of 23°C and a relative humidity of 50% for 12 hours, and then stored in a storage environment of an ambient temperature of 32°C and a relative humidity of 80% for 24 hours. This was taken as one cycle and subjected to a total of 5 cycles of storage.

[0180] (3) Evaluation of recording and playback performance after storage After the above storage, in order to allow the magnetic tape cartridge to adapt to the playback environment, it was placed for 5 days in the environment among the 5 environments mentioned above where the servo band interval obtained in the measurement to determine B was the maximum value. After that, playback was performed in the same environment as before storage in (1) above. That is, playback was performed by changing the tension applied in the longitudinal direction of the magnetic tape as described above. The number of channels in the above playback was 32. During playback after storage, the recording and playback performance was evaluated as "4" if all 32 channels of data were read correctly, "3" if 31 or 30 channels of data were read correctly, "2" if 29 or 28 channels of data were read correctly, and "1" in all other cases.

[0181] The results are shown in Table 1 (Tables 1-1 to 1-3).

[0182] [Table 1-1]

[0183] [Table 1-2]

[0184] [Table 1-3]

[0185] Regarding the magnetic tape cartridge of Example 1, the recording and playback performance was evaluated using the method described above, except that the winding tension when winding onto the cartridge reel was changed from 0.40N to 0.50N. The evaluation result was "2".

[0186] Except for the fact that vertical alignment processing was not performed during the magnetic tape manufacturing process, the magnetic tape cartridge for Example 1 was manufactured using the method described above. A sample piece was cut from the magnetic tape removed from the magnetic tape cartridge mentioned above. Using a Tamagawa Seisakusho TM-TRVSM5050-SMSL vibrating sample magnetometer, the vertical angular ratio of this sample piece was determined using the method described above, and it was found to be 0.55. A magnetic tape was also removed from the magnetic tape cartridge of Example 1, and the vertical aspect ratio was similarly determined for a sample piece cut from this magnetic tape, which was found to be 0.60.

[0187] The magnetic tapes extracted from the two magnetic tape cartridges described above were each mounted on a 1 / 2-inch reel tester, and their electromagnetic conversion characteristics (SNR: Signal-to-Noise Ratio) were evaluated using the following method. As a result, the magnetic tape extracted from the magnetic tape cartridge of Example 1 showed an SNR value 2 dB higher than that of the magnetic tape manufactured without vertical orientation treatment. Recording and playback were performed in 10 passes under a tension of 0.70 N in the longitudinal direction of the magnetic tape in an environment of 23°C and 50% relative humidity. The relative speed between the magnetic tape and the magnetic head was set to 6 m / s. For recording, a MIG (Metal-in-gap) head (gap length 0.15 μm, track width 1.0 μm) was used as the recording head, and the recording current was set to the optimal recording current for each magnetic tape. For playback, a GMR (Giant-magnetoresistive) head (element thickness 15 nm, shielding gap 0.1 μm, playback element width 0.8 μm) was used as the playback head. A signal with a linear recording density of 300 kfci was recorded, and the playback signal was measured using a spectrum analyzer manufactured by Shibasoku. The unit kfci is the unit of linear recording density (cannot be converted to the SI system). As the signal, the portion where the signal was sufficiently stable after the start of magnetic tape movement was used. [Industrial applicability]

[0188] One aspect of the present invention is useful in the technical field of various data storage, such as archiving.

Claims

1. A magnetic tape cartridge in which magnetic tape is wound and housed on a cartridge reel, The magnetic tape comprises a non-magnetic support and a magnetic layer containing ferromagnetic powder. The non-magnetic support is a polyethylene naphthalate support with a Young's modulus in the width direction of 10,000 MPa or more. The magnetic layer has multiple servo bands, Before performing the following storage, the servo band interval was determined, and the servo band interval was determined after N cycles of storage, where one cycle consisted of 12 hours of storage at 23°C and 50% relative humidity, followed by 12 hours of storage at 32°C and 80% relative humidity. Let A be the maximum absolute value of the difference between these two values, where A is in μm. The logarithm of the total storage time T for N cycles is calculated by taking the value of A obtained for each of N (1, 2, 3, 4, or 5). ｅ The logarithm of A and T derived from the value of T. ｅ The media life calculated by a linear function with respect to T is 3 years or more. The aforementioned media life is A as shown in the following formula a: (Formula a) A = 1.5 - B T is when the conditions are met, The aforementioned B is, Under the following five conditions: Temperature 16℃, relative humidity 20%. Temperature 16℃, relative humidity 80%. Temperature 26℃, relative humidity 80% Temperature 32°C, relative humidity 20% Temperature 32°C, relative humidity 55%. This value is calculated by multiplying the difference between the maximum and minimum values ​​within the servo band intervals obtained by 1 / 2, and its unit is μm, for a magnetic tape cartridge.

2. The magnetic tape cartridge according to claim 1, wherein the media life is 3 years or more and 120 years or less.

3. The magnetic tape cartridge according to claim 1, wherein the Young's modulus in the width direction of the polyethylene naphthalate support is 10,000 MPa or more and 20,000 MPa or less.

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

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

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

8. A magnetic recording and playback apparatus including a magnetic tape cartridge according to any one of claims 1 to 7.

9. The magnetic recording and regeneration apparatus according to claim 8, further comprising a magnetic head having a regeneration element width of 0.8 μm or less.

10. The magnetic tape cartridge and, A reel and Includes, Between the take-up reel and the cartridge reel of the magnetic tape cartridge, the magnetic tape is run with tension applied in the longitudinal direction of the magnetic tape, and the maximum value of the tension is 0.50 N or more, The magnetic recording and playback apparatus according to claim 8, wherein the magnetic tape, after being run under the aforementioned tension, is wound onto the cartridge reel of the magnetic tape cartridge under a tension of 0.40 N or less in the longitudinal direction of the magnetic tape.

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