Tape, tape cartridge, and tape device

Abstract

The present invention addresses the problem of providing a tape having excellent tape running stability when a magnetic head is tilted in a low-temperature, high-humidity environment to perform recording and / or playback. The magnetic tape has a friction absolute value of 0.10 nN or less as measured by a horizontal force microscope in a 3 [mu] m * 3 [mu] m measurement region on the surface of a magnetic layer before the magnetic tape slides back and forth 500 times with respect to an LTO8 magnetic head at a magnetic head inclination angle of 15 degrees in an environment having a temperature of 15 DEG C and a relative humidity of 80%. And the reduction rate of the standard deviation of the friction distribution measured by a horizontal force microscope in a 3 [mu] m * 3 [mu] m measurement region on the surface of the magnetic layer before and after 500 times of reciprocating sliding with respect to the LTO8 magnetic head at a magnetic head inclination angle of 15 degrees in an environment at a temperature of 15 DEG C and a relative humidity of 80% is 20% or more. A tape cartridge and a tape device including the tape are provided.

Description

Technical Field

[0001] This invention relates to a magnetic tape, a magnetic tape cassette, and a magnetic tape device. Background Technology

[0002] Magnetic recording media are available in tape and disc formats. Tape magnetic recording media, i.e. magnetic tape, are mainly used for data storage purposes such as data backup and archiving (e.g., see Patent Documents 1-3).

[0003] Patent Document 1: Japanese Patent Publication No. 2016-524774

[0004] Patent Document 2: US2019 / 0164573A1

[0005] Patent Document 3: Description of Japanese Patent No. 6590104

[0006] Data recording on magnetic tape is typically performed as follows: the magnetic tape travels within the tape drive, and a read / write head follows the data track of the tape to record data. This creates data tracks on the data track. Furthermore, when playing back the recorded data, the magnetic tape travels within the tape drive, and the read / write head follows the data track to read the data recorded on the data track.

[0007] To improve the accuracy of the magnetic head following the data tape during recording and / or playback as described above, systems that utilize servo signals for head tracking (hereinafter referred to as "servo systems") have been put into practical use.

[0008] Furthermore, the following was proposed: A servo signal is used to acquire the dimensional information (shrinkage, elongation, etc.) of the magnetic tape in the width direction during tape transport, and the angle at which the axis of the magnetic head module is tilted relative to the width direction of the magnetic tape (hereinafter also referred to as the "head tilt angle") is changed based on the acquired dimensional information (refer to Patent Documents 1 and 2, for example, paragraphs 0059-0067 and 0084 of Patent Document 1). During recording or playback, if the magnetic head used for recording or playing data deviates from the target track position due to the width deformation of the magnetic tape, phenomena such as overwriting of recorded data and poor playback will occur. The inventors believe that one solution to suppress this phenomenon is to change the head tilt angle as described above.

[0009] For example, assuming the head tilt angle is changed as described above, when recording and / or playing data by tilting the axis of the head module relative to the width direction of the magnetic tape (i.e., tilting the head), high tape transport stability is preferable. This is because high tape transport stability is thought to potentially help further suppress the aforementioned phenomena.

[0010] In recent years, magnetic tapes have sometimes been used in data centers where temperature and humidity are managed.

[0011] On the other hand, data centers require energy conservation to reduce costs. To save energy, it is preferable to make the management conditions of the tape usage environment within the data center more relaxed than they are now, or even to eliminate the need for management altogether.

[0012] However, if the management conditions of the usage environment are relaxed or not managed at all, the situation of using magnetic tape in environments such as low temperature and high humidity must be considered. Therefore, a magnetic tape with excellent tape transport stability when recording and / or playing data with a tilted magnetic head in low temperature and high humidity environments is preferred. Summary of the Invention

[0013] One objective of this invention is to provide a magnetic tape with excellent tape transport stability when recording and / or playing back with a tilted magnetic head in a low-temperature and high-humidity environment.

[0014] One aspect of the present invention is as follows.

[0015] [1] A magnetic tape having a non-magnetic support and a magnetic layer containing strongly magnetic powder, wherein the absolute value of friction on the surface of the magnetic layer, measured using a horizontal force microscope in a 3μm × 3μm measurement area, is less than 0.10 nN (nano-Newtons) before the magnetic head slides back and forth 500 times relative to an LTO (Linear Tape-Open) 8 magnetic head at a tilt angle of 15° at an environment of 15° and 80% relative humidity.

[0016] The standard deviation of the friction distribution on the surface of the magnetic layer, measured using a horizontal force microscope in a 3μm×3μm measurement area before and after 500 reciprocating slides relative to the LTO8 magnetic head at a 15° tilt angle under an environment of 15° temperature and 80% relative humidity, decreased by more than 20%.

[0017] [2] According to the magnetic tape described in [1], the kinetic friction force F (hereinafter also referred to as "kinetic friction force F") on the 500th path in the above 500 reciprocating slides is 15gf or less.

[0018] [3] The magnetic tape according to [1] or [2], wherein the absolute value of the friction is 0.02nN or more and 0.10nN or less.

[0019] [4] The magnetic tape according to any one of [1] to [3], wherein the reduction rate is more than 20% and less than 25%.

[0020] [5] The magnetic tape according to any one of [1] to [4] further comprises a non-magnetic layer containing non-magnetic powder between the non-magnetic support and the magnetic layer.

[0021] [6] The magnetic tape according to any one of [1] to [5] further has a back coating containing non-magnetic powder on the surface side of the non-magnetic support opposite to the surface side having the magnetic layer.

[0022] [7] The magnetic tape according to any one of [1] to [6], wherein the magnetic tape thickness is 5.0 μm or less.

[0023] [8] The magnetic tape according to any one of [1] to [7], wherein the vertical rectangularity ratio of the magnetic tape is 0.60 or more.

[0024] [9] The magnetic tape according to any one of [1] to [8], wherein the vertical rectangularity ratio of the magnetic tape is 0.65 or more.

[0025]

[10] The magnetic tape according to any one of [1] to [9], wherein the non-magnetic support is an aromatic polyamide support.

[0026]

[11] According to the magnetic tape described in [1], the dynamic friction force F on the 500th path in the above-mentioned 500 reciprocating slides is less than 15gf.

[0027] The absolute value of the aforementioned friction is above 0.02 nN and below 0.10 nN.

[0028] The reduction rate mentioned above is between 20% and 25%.

[0029] The magnetic tape also has a non-magnetic layer containing non-magnetic powder between the aforementioned non-magnetic support and the aforementioned magnetic layer.

[0030] On the surface of the non-magnetic support opposite to the surface with the magnetic layer, there is also a back coating containing non-magnetic powder.

[0031] The magnetic tape thickness is less than 5.0 μm, and

[0032] The vertical rectangularity ratio of the aforementioned magnetic tape is 0.60 or higher.

[0033]

[12] A magnetic tape cassette comprising any one of [1] to

[11] .

[0034]

[13] A magnetic tape device comprising any one of [1] to

[11] .

[0035]

[14] The magnetic tape device according to

[13] further includes a magnetic head,

[0036] The aforementioned magnetic head has a module comprising an array of multiple head elements between a pair of servo signal readout elements, and

[0037] The aforementioned magnetic tape device changes the angle θ between the axis of the aforementioned element array and the width direction of the aforementioned magnetic tape when the magnetic tape travels within the aforementioned magnetic tape device.

[0038] Invention Effects

[0039] According to one aspect of the present invention, a magnetic tape with excellent tape transport stability can be provided when the magnetic head is tilted for data recording and / or playback in low temperature and high humidity environments. Furthermore, according to one aspect of the present invention, a magnetic tape cassette and a magnetic tape device comprising the aforementioned magnetic tape can be provided. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of an example of a module representing a magnetic head.

[0041] Figure 2 This is an illustration of the relative positional relationship between the module and the magnetic tape as the magnetic tape travels within the magnetic tape device.

[0042] Figure 3 This is an explanatory diagram related to the change in angle θ during tape travel.

[0043] Figure 4 This shows a configuration example for the data band and servo band.

[0044] Figure 5 This represents a servo pattern configuration example for LTO Ultrium format magnetic tape.

[0045] Figure 6 This is an explanatory diagram illustrating the method for measuring the angle θ during magnetic tape transport.

[0046] Figure 7 This is a schematic diagram illustrating an example of a magnetic tape device. Detailed Implementation

[0047] [Cassette tape]

[0048] One aspect of the present invention relates to a magnetic tape having a non-magnetic support and a magnetic layer containing strongly magnetic powder. Before the magnetic tape is slid back and forth 500 times relative to an LTO8 magnetic head at a head tilt angle of 15° at an environment of 15°C and 80% relative humidity, the absolute value of friction on the surface of the magnetic layer within a 3μm × 3μm measurement area measured using a horizontal force microscope (LFM) is 0.10 nN or less. Furthermore, the reduction rate of the standard deviation of the friction distribution on the surface of the magnetic layer within a 3μm × 3μm measurement area before and after 500 slids of the magnetic tape relative to an LTO8 magnetic head at a head tilt angle of 15° at an environment of 15°C and 80% relative humidity is 20% or more. The aforementioned absolute value of friction is also referred to as the "absolute value of friction before sliding." The aforementioned reduction rate is also referred to as the "LFM reduction rate."

[0049] <Head tilt angle>

[0050] Before explaining the head tilt angle mentioned above, the LTO8 head will be explained first. Furthermore, the reasons why it is believed that tilting the axis of the head module relative to the width direction of the tape during tape transport can suppress the phenomena that occur during recording or playback.

[0051] In this invention and specification, "LTO8 head" refers to a magnetic head conforming to the LTO8 standard. As an LTO8 head, a head mounted on an LTO8 drive can be removed for use, or a commercially available head for LTO8 drives can be used. Here, LTO8 drive refers to a drive (magnetic tape device) conforming to the LTO8 standard. LTO9 drive refers to a drive conforming to the LTO9 standard, and this also applies to next-generation drives. Furthermore, when multiple magnetic tapes to be tested are slid back and forth relative to an LTO8 head at a head tilt angle of 15°, it is assumed that a new (i.e., unused) LTO8 head is used for testing each magnetic tape. Additionally, considering that the LTO8 standard is capable of handling the high-density recording of recent years, and LTO8 is used as the head, the aforementioned magnetic tape is not limited to the magnetic tape used in an LTO8 drive. The aforementioned tapes can be used for data recording and / or playback on LTO8 drives, LTO9 drives or next-generation drives, or LTO7 drives and earlier generations of drives.

[0052] The LTO8 head has three modules, each comprising an array of head elements between a pair of servo signal readout elements. These three modules are configured in a “recording module - playback module - recording module” configuration (total number of modules: 3) within the LTO8 head.

[0053] Each module includes an array of 32 magnetic head elements between a pair of servo signal readout elements, i.e., the arrangement of the elements. A module with recording elements as magnetic head elements is a recording module for recording data onto magnetic tape. A module with playback elements as magnetic head elements is a playback module for playing back data recorded on magnetic tape. In the LTO8 head, the three modules are configured such that the axes of the element arrays of each module are oriented parallel to each other. This "parallelism" does not necessarily mean parallelism in a strict sense, but includes a range of errors generally permissible in the art to which this invention pertains. The range of errors can, for example, represent a strict parallelism within ±10°.

[0054] The head tilt angle during 500 reciprocating slides is set to the head tilt angle in the playback module of the LTO8 head.

[0055] In each element array, a pair of servo signal readout elements and multiple magnetic head elements (i.e., recording elements or playback elements) are arranged linearly apart. Here, "linearly arranged" means that each magnetic head element is arranged on a straight line connecting the central portion of one servo signal readout element and the central portion of another servo signal readout element. Furthermore, the "axis of the element array" in this invention and specification refers to the straight line connecting the central portion of one servo signal readout element and the central portion of another servo signal readout element.

[0056] Next, the structure of the module will be further described with reference to the accompanying drawings. However, the embodiments shown in the drawings are merely examples and do not limit the present invention.

[0057] Figure 1 This is a schematic diagram of an example of a module representing a magnetic head. Figure 1 The module shown has multiple head elements between a pair of servo signal readout elements (servo signal readout elements 1 and 2). These head elements are also referred to as "channels". "Ch" in the diagram is an abbreviation for Channel. Figure 1 The module shown has a total of 32 head elements, from Ch0 to Ch31. The playback module for the LTO8 head has a total of 32 playback elements, from Ch0 to Ch31.

[0058] Figure 1 In this context, "L" represents the distance between a pair of servo signal reading elements, that is, the distance between one servo signal reading element and another. Figure 1In the module shown, "L" represents the distance between servo signal reading element 1 and servo signal reading element 2. More specifically, it is the distance between the central portion of servo signal reading element 1 and the central portion of servo signal reading element 2. This distance can be measured, for example, using an optical microscope.

[0059] Figure 2 This is an illustration of the relative positional relationship between the module and the magnetic tape as the magnetic tape travels within the magnetic tape device. Figure 2 In the diagram, dotted line A represents the width direction of the magnetic tape. Dotted line B represents the axis of the element array. Angle θ can be described as the tilt angle of the read / write head during tape transport, and is the angle between dotted line A and dotted line B. When angle θ is 0° during tape transport, the distance in the width direction of the magnetic tape between one servo signal read / write element and another in the element array (hereinafter also referred to as the "effective distance between servo signal read / write elements") is "L". Conversely, when angle θ exceeds 0°, the effective distance between servo signal read / write elements is "Lcosθ", where Lcosθ is less than L. That is, "Lcosθ < L".

[0060] As described above, during recording or playback, if the magnetic head used for recording or playing data deviates from the target track position due to the deformation of the magnetic tape width, phenomena such as overwriting of recorded data and poor playback will occur. For example, if the width of the magnetic tape shrinks or stretches, the magnetic head element that should be recording or playing data at the target track position may be recording or playing data at a different track position. Furthermore, if the width of the magnetic tape stretches, the effective distance between the servo signal readout elements will become shorter than the interval between two adjacent servo tapes sandwiching the data tape (also called "servo tape interval" or "servo tape spacing." Specifically, it is the distance between the two servo tapes in the width direction of the magnetic tape), which may result in the portion of the tape near the edge not recording or playing data.

[0061] In contrast, if the element array is tilted at an angle θ greater than 0°, then, as mentioned above, the effective distance between the servo signal readout elements will become "Lcosθ". The larger the value of θ, the smaller the value of Lcosθ, and vice versa. Therefore, by changing the value of θ according to the degree of dimensional change (i.e., shrinkage or elongation) in the width direction of the magnetic tape, it is possible to make the effective distance between the servo signal readout elements close to or consistent with the spacing of the servo tape. This prevents the magnetic head used for recording or playing back data from deviating from the target track position due to the width deformation of the magnetic tape during recording or playback, thus avoiding phenomena such as overwriting of recorded data or poor playback, or reducing the frequency of such phenomena.

[0062] Figure 3This is an explanatory diagram related to the change in angle θ during tape travel.

[0063] θ is the angle θ at the start of the tape movement. initial For example, it can be set to above 0° or greater than 0°.

[0064] Figure 3 In the middle, the diagram shows the state of the module when the conveyor belt starts moving.

[0065] Figure 3 The middle and right figures show that the angle θ is set to be greater than θ. initial Angle of angle θ c The module's status at that time. The effective distance Lcosθ between servo signal reading elements. c Become less than Lcosθ when the tape starts to travel. initial The value of this angle is preferred when the width of the magnetic tape is contracted during tape transport.

[0066] on the other hand, Figure 3 In the middle, the left figure shows that the angle θ is set to be less than θ. initial Angle of angle θ e The module's status at that time. The effective distance Lcosθ between servo signal reading elements. e Become greater than Lcosθ when the tape starts to travel. initial The value of this angle is preferred when the width of the magnetic tape expands during tape travel.

[0067] As mentioned above, changing the tilt angle of the magnetic head during tape transport can help prevent the magnetic head used for recording or playing data from deviating from the target track position due to the width deformation of the magnetic tape, which could lead to overwriting of recorded data, poor playback, or reduce the frequency of such occurrences.

[0068] On the other hand, data recording and playback of magnetic tape are typically performed by sliding the magnetic head against the magnetic layer surface as the tape is moved. The inventors believe that if the magnetic head is tilted during recording and / or playback, the contact state between the magnetic head and the magnetic layer surface becomes unstable, which could be a major cause of decreased tape movement stability.

[0069] Based on the above speculation, the inventors conducted repeated and in-depth research. As a result, the inventors rediscovered that magnetic tapes with an absolute friction value of 0.10 nN or less before reciprocating sliding and an LFM reduction rate of 20% or more exhibit excellent tape-running stability when recording and / or playing data with a tilted magnetic head in a low-temperature, high-humidity environment. Furthermore, the temperature and humidity of the measured environment were used as exemplary values ​​for the temperature and humidity of the low-temperature, high-humidity environment. Therefore, the environment for recording data on the aforementioned magnetic tape and playing back the recorded data is not limited to the aforementioned temperature and humidity conditions. Regarding the magnetic head tilt angle, an exemplary value was also used as an angle that can be used when changing the magnetic head tilt angle during tape transport to record and / or play back data. Therefore, the magnetic head tilt angle for recording data on the aforementioned magnetic tape and playing back the recorded data is not limited to the aforementioned angle. Furthermore, the present invention is not limited to the inventors' speculations described in this specification.

[0070] In this specification, the tape transport stability during data recording and / or playback when the magnetic head is tilted during tape transport in a low-temperature, high-humidity environment is also referred to as "tape transport stability." Furthermore, a low-temperature, high-humidity environment can be, for example, an environment with a temperature of approximately 0°C to 20°C. As for the relative humidity, the humidity of this environment can be, for example, approximately 70% to 100%. In this invention and this specification, the temperature and humidity described regarding the environment refer to the ambient temperature and relative humidity of that environment.

[0071] In this invention and this specification, the magnetic tape used as the test object is subjected to 500 reciprocating slides relative to the LTO8 magnetic head at a magnetic head tilt angle of 15° under an environment of 15° temperature and 80% relative humidity by the following method.

[0072] Furthermore, the head tilt angle (15°) refers to the angle between the axis of the element array of the LTO8 head's playback module and a direction orthogonal to the sliding direction on the first path of the following 500 reciprocating slides. This angle is used to... Figure 2 In this context, A is referred to as the direction orthogonal to the sliding direction, and the angle θ between A and B is defined. During 500 reciprocating slides, the tilt angle of the magnetic head remains constant.

[0073] The magnetic tape to be measured is placed on two cylindrical guide rollers, each 1 inch in diameter (1 inch = 2.54 cm), spaced parallel to each other, in such a way that the surface of the magnetic layer is in contact with them. Before starting the reciprocating sliding, it is placed for at least 24 hours to allow it to acclimatize to the environment (temperature 15°C, relative humidity 80%), with the magnetic tape to be measured placed on the guide rollers as described above.

[0074] In a randomly selected section of the magnetic tape used for testing, the magnetic head tilt angle was set to 15°, and the magnetic layer surface of the tape was slid relative to the LTO8 magnetic head for 500 reciprocating slides. Regarding the sliding conditions, the winding angle θ was set to 6°, and the sliding speed was set to 30 mm / s. During sliding, the tension applied along the length of the tape was set to 0.55 N. The sliding distance for both the outgoing and returning paths was set to 5 cm. One end of the tape along its length was connected to a strain gauge, and a tension of 0.20 N was applied to the other end. When measuring the kinetic friction force F, the resistance generated during sliding was detected using a strain gauge. The applied tension was set to T0 (unit: N), the resistance detected by the strain gauge was set to T (unit: N), and the kinetic friction force F was calculated using the following formula. That is, here, the kinetic friction force F is calculated with T0 = 0.20. The kinetic friction force on the 500th outgoing path is defined as "kinetic friction force F". Regarding the unit of kinetic friction F, "gf" represents gram force, and 1 N (Newton) is approximately 102 gf.

[0075] [Formula 1]

[0076] F = T - T0

[0077] <Absolute value of friction before reciprocating sliding, LFM reduction rate>

[0078] In the aforementioned magnetic tape, the absolute value of friction (absolute value of friction before reciprocating sliding) on ​​the surface of the magnetic layer within a 3μm×3μm measurement area measured using a horizontal force microscope at a temperature of 15°C and relative humidity of 80% is less than 0.10 nN. Furthermore, the reduction rate of the standard deviation of the friction distribution within a 3μm×3μm measurement area on the surface of the magnetic layer before and after the aforementioned magnetic tape has reciprocated sliding relative to the LTO8 head 500 times at a 15°C and relative humidity environment is more than 20%.

[0079] In this invention and specification, the absolute value of friction and the standard deviation of friction distribution are measured using a horizontal force microscope (LFM), one of the measurement modes of an atomic force microscope (AFM). For example, the BRUKER Nanoscope 5 (measurement mode: LFM) can be cited as a horizontal force microscope.

[0080] Before performing measurements using a horizontal force microscope (LFM), the LFM and probe must be calibrated. Calibration of the LFM and probe can be performed, for example, using commercially available calibration samples (e.g., Tokyo Instruments, Inc. TGG1) and known methods. One example of a known method is the wedge method. For information on the wedge method, see, for example, Rev. Sci. Instrum., Vol. 67, No. 9, September 1996. Under the following measurement conditions, the LFM output (in mV) was measured for three measurement areas of the magnetic layer surface that had undergone the aforementioned 500 reciprocating slides and three measurement areas of the magnetic layer surface that had not undergone the same reciprocating slides. The resulting output distribution was then normalized (Min-MaxNormalization), and the standard deviation was calculated. "Min" is an abbreviation for "minimum," and "Max" is an abbreviation for "maximum." The standard deviation obtained by measurement on the surface of the magnetic layer after 500 reciprocating slides is set as the "measured value after reciprocating slides", and the standard deviation obtained by measurement on the surface of the magnetic layer before reciprocating slides is set as the "measured value before reciprocating slides". The LFM reduction rate is calculated by the following formula.

[0081] LFM reduction rate = 100 × (measured value before reciprocating sliding - measured value after reciprocating sliding) / measured value before reciprocating sliding

[0082] Furthermore, in this invention and this specification, the meaning of "the surface of the magnetic layer" is the same as the meaning of the magnetic layer side surface of the magnetic tape.

[0083] (Measurement conditions)

[0084] Measurement environment: temperature 23℃, relative humidity 50%

[0085] Measurement area: 3μm × 3μm

[0086] Measurement surface: Magnetic layer surface

[0087] Resolution: 512 pixels × 512 pixels

[0088] Scan Rate: 3μm / second

[0089] Set Point: 100nN

[0090] AFM probe: SI-AF01 (manufactured by Hitachi High-Tech Corporation)

[0091] Number of measurements: N = 3

[0092] If the measurement for determining the LFM output is performed as described above, in addition to the LFM output, the absolute friction value can also be calculated for each pixel within the measurement area (3μm × 3μm). Therefore, for each measurement location, a total of 262,144 (512 × 512) absolute friction values ​​can be obtained. The arithmetic mean of the 262,144 absolute friction values ​​is taken as the absolute friction value for that measurement location. The arithmetic mean of the absolute friction values ​​calculated for the three measurement areas of the magnetic layer surface that did not undergo the above reciprocating sliding is taken as the absolute friction value before reciprocating sliding.

[0093] The magnetic tapes described above, with an absolute value of friction before reciprocating sliding of 0.10 nN or less and an LFM reduction rate of 20% or more, exhibit excellent tape-running stability when recording and / or playing back using a tilted magnetic head in low-temperature and high-humidity environments. The inventors speculate that this excellent tape-running stability is due to the fact that the magnetic tapes with an absolute value of friction before reciprocating sliding of 0.10 nN or less and an LFM reduction rate of 20% or more can suppress the increase in dynamic friction force F during repeated tape-running with a tilted magnetic head. The reason for setting the absolute value of friction before reciprocating sliding of the aforementioned magnetic tape to 0.10 nN or less and the LFM reduction rate to 20% or more is that, during repeated in-depth research, the inventors confirmed the following phenomenon: if the absolute value of friction before reciprocating sliding exceeds 0.10 nN and / or the LFM reduction rate is less than 20%, the increase in dynamic friction force F during repeated tape-running with a tilted magnetic head becomes significant. The inventors believe that the larger the LFM reduction rate, the more effectively the increase in dynamic friction force F is suppressed, because the larger the LFM reduction rate, the easier it is for the uneven distribution of lubricant on the magnetic layer surface to become uniform due to contact with the magnetic head. Furthermore, the inventors hypothesize that a small absolute value of friction before reciprocating sliding indicates that the formation of meniscus droplet adhesion caused by the lubricant is suppressed. The inventors also believe that this can help suppress the increase in kinetic friction force F.

[0094] (Absolute value of friction before reciprocating sliding)

[0095] The absolute value of the friction before reciprocating sliding of the aforementioned magnetic tape is 0.10 nN or less. From the viewpoint of further suppressing the increase of kinetic friction F and thus further improving tape transport stability, it is preferably 0.09 nN or less, and more preferably 0.08 nN or less, 0.07 nN or less, and 0.06 nN or less. The absolute value of the friction before reciprocating sliding can, for example, be 0.01 nN or more or 0.02 nN or more. The inventors believe that, from the viewpoint of improving tape transport stability, the smaller the absolute value of the friction before reciprocating sliding, the more preferred. Therefore, the absolute value of the friction before reciprocating sliding can also be lower than the above range.

[0096] (LFM reduction rate)

[0097] The aforementioned magnetic tape has an LFM reduction rate of 20% or more. From the viewpoint of further suppressing the increase of kinetic friction F and thus further improving tape transport stability, the LFM reduction rate is preferably 21% or more, and more preferably 22%, 23%, or 24% or more. The LFM reduction rate can, for example, be 30% or less, 29% or less, 28% or less, 27% or less, 26% or less, or 25% or less. The inventors believe that, from the viewpoint of improving tape transport stability, a higher LFM reduction rate is more preferred. Therefore, the LFM reduction rate can also exceed the above range.

[0098] <Kinetic friction force F>

[0099] The dynamic friction force F in the 500th path of the aforementioned 500 reciprocating slides of the magnetic tape is preferably 15 gf or less, more preferably 12 gf or less, and even more preferably 10 gf or less, 8 gf or less, and 6 gf or less. The dynamic friction force F can be, for example, 4 gf or more, or lower than the value exemplified here.

[0100] By controlling the absolute value of friction before reciprocating sliding to below 0.10 nN and the LFM reduction rate to above 20%, the dynamic friction force F can be controlled to below 15 gf. Specific examples of schemes for controlling the absolute value of friction before reciprocating sliding and controlling the LFM reduction rate will be described later.

[0101] The following is a more detailed explanation of the aforementioned magnetic tape.

[0102] <Magnetic Layer>

[0103] (Strongly magnetic powder)

[0104] As the strongly magnetic powder contained in the magnetic layer, one or more strongly magnetic powders known to be used in the magnetic layers of various magnetic recording media can be used in combination. From the viewpoint of improving recording density, strongly magnetic powders with small average particle size are preferred. From this point of view, the average particle size of the strongly magnetic powder is preferably 50 nm or less, more preferably 45 nm or less, even more preferably 40 nm or less, even more preferably 35 nm or less, even more preferably 30 nm or less, even more preferably 25 nm or less, and even more preferably 20 nm or less. On the other hand, from the viewpoint of magnetization stability, the average particle size of the strongly magnetic 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.

[0105] Hexagonal ferrite powder

[0106] As a preferred specific example of a strongly magnetic powder, hexagonal ferrite powder can be cited. For details regarding hexagonal ferrite powder, see, for example, paragraphs 0012 to 0030 of Japanese Patent Application Publication No. 2011-225417, paragraphs 0134 to 0136 of Japanese Patent Application Publication No. 2011-216149, paragraphs 0013 to 0030 of Japanese Patent Application Publication No. 2012-204726, and paragraphs 0029 to 0084 of Japanese Patent Application Publication No. 2015-127985.

[0107] In this invention and specification, "hexagonal ferrite powder" refers to a strongly magnetic powder whose crystal structure as a hexagonal ferrite can be 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 belongs to the crystal structure of a hexagonal ferrite, then the crystal structure of the hexagonal ferrite is determined to be the main phase. If only a single structure is detected by X-ray diffraction analysis, that detected structure is considered the main phase. As constituent atoms, the crystal structure of a hexagonal ferrite contains at least iron atoms, divalent metal atoms, and oxygen atoms. Divalent metal atoms refer to metal atoms that can become divalent cations as ions; examples include alkaline earth metal atoms such as strontium, barium, and calcium, as well as lead atoms. In this invention and specification, hexagonal strontium ferrite powder refers to a hexagonal ferrite in which the predominant divalent metal atom is strontium, and hexagonal barium ferrite powder refers to a hexagonal ferrite in which the predominant divalent metal atom is barium. The predominant divalent metal atom refers to the divalent metal atom that constitutes the largest proportion of the divalent metal atoms in the powder, based on an atomic percentage. However, rare earth atoms are not included in the aforementioned divalent metal atoms. In this invention and specification, "rare earth atoms" are selected from the group consisting of scandium (Sc), yttrium (Y), and lanthanides. The 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).

[0108] The following is a more detailed description of hexagonal strontium ferrite powder as one type of hexagonal ferrite powder.

[0109] The activation volume of hexagonal strontium ferrite powder is preferably in the range of 800–1600 nm. 3Within the aforementioned range, micronized hexagonal strontium ferrite powder with an activation volume within this range is suitable for manufacturing magnetic tapes that exhibit excellent electromagnetic conversion properties. The preferred activation volume of the hexagonal strontium ferrite powder is 800 nm. 3 The above, for example, could also be 850nm. 3 That's all. Furthermore, from the viewpoint of further improving electromagnetic conversion characteristics, the activation volume of hexagonal strontium ferrite powder is more preferably 1500 nm. 3 Hereinafter, 1400nm is further preferred. 3 The following is a further preferred option: 1300nm 3 The following is a further preferred option: 1200nm 3 Hereinafter, 1100nm is further preferred. 3 The activation volume of this pair of hexagonal barium ferrite powders is also the same.

[0110] "Activation volume" is the unit of magnetization reversal and is an indicator of the magnetic strength of a particle. The activation volume and anisotropy constant Ku described in this invention and specification were determined using a vibrating sample type magnetometer at a magnetic field scanning speed of 3 minutes and 30 minutes (measurement temperature: 23℃±1℃) using the coercivity Hc measuring unit, and calculated according to the following relationship between Hc and activation volume V. Regarding the unit of the anisotropy constant Ku, 1 erg / cc = 1.0 × 10⁻⁶. -1 J / m 3 .

[0111] Hc=2Ku / Ms{1-[(kT / KuV)ln(At / 0.693)] 1 / 2}

[0112] In the above formula, Ku: anisotropy constant (unit: J / m) 3 Ms: saturation magnetization (kA / m), k: Boltzmann constant, T: absolute temperature (K), V: activation volume (cm³) 3 A: Spin precession frequency (unit: s) -1 ), t: magnetic field reversal time (unit: s)

[0113] An anisotropy constant Ku can be cited as an indicator of reduced thermal fluctuations (in other words, improved thermal stability). Hexagonal strontium ferrite powder preferably has a Ku value of 1.8 × 10⁻⁶. 5 J / m 3 The above-mentioned Ku, more preferably, can have 2.0 × 10 5 J / m 3 The above refers to the Ku value. Furthermore, the Ku value of hexagonal strontium ferrite powder can, for example, be 2.5 × 10⁻⁶. 5 J / m 3However, a higher Ku value indicates higher thermal stability and is therefore preferred; it is not limited to the values ​​exemplified above.

[0114] 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 it contains rare earth atoms at a content of 0.5 to 5.0 atomic% (bulk content) relative to 100 atomic% of iron atoms. In one embodiment, the hexagonal strontium ferrite powder containing rare earth atoms may have a rare earth atom surface bias. In this invention and this specification, "rare earth atom surface layer bias" refers to the rare earth atom content (hereinafter referred to as "rare earth atom surface layer content" or simply "surface layer content") in the solution obtained by partially dissolving hexagonal strontium ferrite powder with acid relative to 100 atomic percent of iron atoms, and the rare earth atom content (hereinafter referred to as "rare earth atom bulk content" or simply "bulk content") in the solution obtained by completely dissolving hexagonal strontium ferrite powder with acid relative to 100 atomic percent of iron atoms, satisfying the following ratio:

[0115] The ratio of rare earth atoms in the surface layer to rare earth atoms in the bulk layer is greater than 1.0.

[0116] The meaning of the rare earth atom content of hexagonal strontium ferrite powder, as described later, is the same as the meaning of the rare earth atom bulk content. In contrast, the partial dissolution using acid dissolves the surface portion of the particles constituting the hexagonal strontium ferrite powder; therefore, the rare earth atom content in the solution obtained through partial dissolution refers to the rare earth atom content in the surface portion of the particles constituting the hexagonal strontium ferrite powder. A rare earth atom surface portion content that satisfies the ratio "rare earth atom surface portion content / rare earth atom bulk content > 1.0" indicates that rare earth atoms are predominantly present in the surface portion (i.e., in greater quantities than in the interior) of the particles constituting the hexagonal strontium ferrite powder. In this invention and this specification, the surface portion refers to a region extending from the surface of the particles constituting the hexagonal strontium ferrite powder towards the interior.

[0117] When hexagonal strontium ferrite powder contains rare earth atoms, the rare earth atom content (bulk content) relative to 100 atomic% of iron atoms is preferably in the range of 0.5 to 5.0 atomic%. It is believed that containing rare earth atoms at a bulk content within the above range, with the rare earth atoms predominantly located on the surface of the particles constituting the hexagonal strontium ferrite powder, helps to suppress the decrease in playback output during repeated playback. This is presumably because containing rare earth atoms at a bulk content within the above range, with the rare earth atoms predominantly located on the surface of the particles constituting the hexagonal strontium ferrite powder, can increase the anisotropy constant Ku. A higher anisotropy constant Ku value better suppresses the phenomenon known as thermal fluctuation (in other words, it improves thermal stability). By suppressing thermal fluctuations, the decrease in playback output during repeated playback can be suppressed. It is speculated that the rare earth atoms biased towards the surface of hexagonal strontium ferrite powder particles help stabilize the spin of the iron (Fe) position within the lattice of the surface layer, thereby increasing the anisotropy constant Ku.

[0118] Furthermore, it is speculated that using hexagonal strontium ferrite powder with rare-earth atom surface bias as a strong magnetic powder for the magnetic layer can also help suppress the wear of the magnetic layer surface due to slippage with the magnetic head. That is, it is speculated that hexagonal strontium ferrite powder with rare-earth atom surface bias can also help improve the tape travel durability. This is speculated because the rare-earth atom bias on the surface of the particles constituting the hexagonal strontium ferrite powder helps to enhance the interaction between the particle surface and the organic matter (e.g., binders and / or additives) contained in the magnetic layer, resulting in increased strength of the magnetic layer.

[0119] From the viewpoint of suppressing the decline in playback output during repeated playback and / or further improving the durability of the conveyor belt, the rare earth atom content (bulk content) is more preferably in the range of 0.5 to 4.5 atomic%, more preferably in the range of 1.0 to 4.5 atomic%, and even more preferably in the range of 1.5 to 4.5 atomic%.

[0120] The aforementioned bulk content rate is the content rate obtained by completely dissolving hexagonal strontium ferrite powder. In this invention and specification, unless otherwise specified, the content rate refers to the bulk content rate obtained by completely dissolving hexagonal strontium ferrite powder. As rare earth atoms, the hexagonal strontium ferrite powder containing rare earth atoms may contain only one type of rare earth atom or two or more types. The aforementioned bulk content rate when containing two or more rare earth atoms is calculated based on the sum of the two or more rare earth atoms. This also applies to other components in this invention and specification. That is, unless otherwise specified, a component may use only one type or two or more types. The content or content rate when using two or more types is based on the sum of the two or more types.

[0121] When hexagonal strontium ferrite powder contains rare earth atoms, the rare earth atoms can be any one or more of the rare earth atoms. From the viewpoint of suppressing the decrease in playback output during repeated playback, preferred rare earth atoms include neodymium atoms, samarium atoms, yttrium atoms, and dysprosium atoms, more preferably neodymium atoms, samarium atoms, and yttrium atoms, and even more preferably neodymium atoms.

[0122] In hexagonal strontium ferrite powder exhibiting a surface-partial predominance of rare earth atoms, the rare earth atoms only need to be present in the surface portion of the particles constituting the hexagonal strontium ferrite powder, and the degree of predominance is not limited. For example, regarding hexagonal strontium ferrite powder exhibiting a surface-partial predominance of rare earth atoms, the ratio of the surface portion 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 complete dissolution under the dissolution conditions described later, "surface portion content / bulk content," exceeds 1.0, and can be 1.5 or more. A "surface portion content / bulk content" greater than 1.0 indicates that rare earth atoms are predominantly present in the surface portion (i.e., their quantity is greater than that in the interior) of the particles constituting the hexagonal strontium ferrite powder. Furthermore, the ratio of the surface portion 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 complete dissolution under the dissolution conditions described later, "surface portion 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 with a rare earth atom surface portion bias, the rare earth atoms only need to be biased in the surface portion of the particles constituting the hexagonal strontium ferrite powder, and the above-mentioned "surface portion content / bulk content" is not limited to the upper or lower limit shown.

[0123] The partial and complete dissolution of hexagonal strontium ferrite powder will be described below. For hexagonal strontium ferrite powder existing in powder form, the partially and completely dissolved sample powders are collected from the same batch 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 removed from the magnetic layer is used for partial dissolution, and another portion is used for complete dissolution. When removing the hexagonal strontium ferrite powder from the magnetic layer, the method described, for example, in paragraph 0032 of Japanese Patent Application Publication No. 2015-91747 can be used.

[0124] The aforementioned partial dissolution refers to the degree to which dissolution is complete, to the point where the hexagonal strontium ferrite powder residue can be visually confirmed in the liquid. For example, through partial dissolution, 10 to 20% by mass of the particles constituting the hexagonal strontium ferrite powder can be dissolved, based on a particle mass percentage of 100%. On the other hand, the aforementioned complete dissolution refers to the state to which dissolution is complete, to the point where the hexagonal strontium ferrite powder residue cannot be visually confirmed in the liquid.

[0125] The determination of partial dissolution and surface layer content mentioned above is performed, for example, by the following method. However, the dissolution conditions, such as the amount of sample powder described below, are merely examples, and any dissolution conditions capable of partial and complete dissolution can be used.

[0126] A container (e.g., a beaker) containing 12 mg of sample powder and 10 mL of 1 mol / L hydrochloric acid is kept 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 filtrate is performed using an inductively coupled plasma (ICP) analyzer. This allows the determination of the surface portion content of rare earth atoms relative to 100 atomic percent of iron atoms. If multiple rare earth atoms are detected by elemental analysis, the total content of all rare earth atoms is taken as the surface portion content. This is also applied to the determination of bulk content.

[0127] On the other hand, the determination of complete dissolution and bulk content is carried out, for example, by the following method.

[0128] A container (e.g., a beaker) containing 12 mg of sample powder and 10 mL of 4 mol / L hydrochloric acid is kept on a hot plate at a set temperature of 80°C for 3 hours. Then, the same steps as those described above for determining partial dissolution and surface content are performed to determine the bulk content relative to 100 atomic percent of iron atoms.

[0129] From the viewpoint of improving playback output when playing data recorded on magnetic tape, it is preferable that the magnetic tape contains a strongly magnetic powder with a high mass magnetization σs. In this regard, hexagonal strontium ferrite powder containing rare-earth atoms but lacking a rare-earth atom surface bias tends to exhibit a significantly lower σs compared to hexagonal strontium ferrite powder without rare-earth atoms. Therefore, to suppress this significant decrease in σs, hexagonal strontium ferrite powder with a rare-earth atom surface bias is considered preferable. In one embodiment, the σs of the hexagonal strontium ferrite powder can be 45 A·m. 2 / kg or above, or 47A·m 2 / kg or more. On the other hand, from the viewpoint of noise reduction, σs is preferably 80 A·m. 2 / kg or less, preferably 60A·m2 / kg or less. σs can be measured using a known measuring device capable of measuring magnetic properties, such as a vibrating sample type magnetometer. In this invention and specification, unless otherwise specified, the mass magnetization σs is the value measured with a magnetic field strength of 15 kOe. 1 [kOe] = 10 6 / 4π[A / m].

[0130] Regarding the atomic content (bulk content) of the hexagonal strontium ferrite powder, the strontium atom content relative to 100 atomic% of iron atoms can, for example, be in the range of 2.0 to 15.0 atomic% (100 atomic% of iron atoms). In one embodiment, the hexagonal strontium ferrite powder may contain only strontium atoms as divalent metal atoms in the powder. Furthermore, in another embodiment, the hexagonal strontium ferrite powder may also contain one or more other divalent metal atoms besides strontium atoms. For example, it may contain barium atoms and / or calcium atoms. In the case of containing divalent metal atoms other than strontium atoms, the barium atom content and calcium atom content in the hexagonal strontium ferrite powder can, for example, be in the range of 0.05 to 5.0 atomic% (100 atomic% of iron atoms), respectively.

[0131] As for the crystal structures of hexagonal ferrites, the known types are magnetoplumbide (also known as "M-type"), W-type, Y-type, and Z-type. Hexagonal strontium ferrite powder can adopt any crystal structure. The crystal structure can be confirmed by X-ray diffraction analysis. Hexagonal strontium ferrite powder can be detected by X-ray diffraction analysis to have a single crystal structure or two or more crystal structures. For example, in one embodiment, hexagonal strontium ferrite powder can be detected by X-ray diffraction analysis to have only an M-type crystal structure. For example, M-type hexagonal ferrite is made from AFe... 12 O 19The composition is represented by the formula. Here, A represents a divalent metal atom. In the case of hexagonal strontium ferrite powder of type M, A is only a strontium atom (Sr), or when A contains multiple divalent metal atoms, as mentioned above, the strontium atom (Sr) accounts for the largest proportion on an atomic percentage basis. The divalent metal atom content of hexagonal strontium ferrite powder is usually determined according to the type of crystal structure of 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 contain atoms other than these atoms, or it may not contain atoms other than these atoms. As an example, hexagonal strontium ferrite powder may contain aluminum atoms (Al). The aluminum atom content relative to 100 atomic percent of iron atoms may be, for example, 0.5 to 10.0 atomic percent. From the viewpoint of suppressing the decline in playback output during repeated playback, 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 10.0 atomic% or less relative to 100 atomic% of iron atoms, more preferably in the range of 0 to 5.0 atomic%, and may also be 0 atomic%. That is, in one embodiment, hexagonal strontium ferrite powder may be free of atoms other than iron atoms, strontium atoms, oxygen atoms, and rare earth atoms. The content expressed as atomic% is obtained by converting the content of each atom (unit: mass%) obtained by completely dissolving the hexagonal strontium ferrite powder into a value expressed as atomic% using the atomic weight of each atom. Furthermore, in this invention and this specification, "free of" for a certain atom means that the content obtained by complete dissolution and measurement by an ICP analyzer is 0 mass%. The detection limit of the ICP analyzer is generally 0.01 ppm (parts per million) or less on a mass basis. The term "excluding" is used to include cases where the content is less than the detection limit of the ICP analyzer. In one embodiment, the hexagonal strontium ferrite powder may be bismuth-free (Bi).

[0132] Metal powder

[0133] As a preferred specific example of a strongly magnetic powder, strongly magnetic metal powder can be cited. For details regarding strongly magnetic metal powder, see, for example, paragraphs 0137 to 0141 of Japanese Patent Application Publication No. 2011-216149 and paragraphs 0009 to 0023 of Japanese Patent Application Publication No. 2005-251351.

[0134] ε-iron oxide powder

[0135] As a preferred specific example of a strongly magnetic powder, ε-iron oxide powder can be cited. In this invention and this specification, "ε-iron oxide powder" refers to a strongly magnetic powder whose crystal structure of ε-iron oxide is detected as the main phase by X-ray diffraction analysis. For example, if the highest intensity diffraction peak in the X-ray diffraction spectrum obtained by X-ray diffraction analysis belongs to the crystal structure of ε-iron oxide, then the crystal structure of ε-iron oxide is determined to be the main phase. Methods for manufacturing ε-iron oxide powder include methods using goethite, reverse micelle methods, etc. These manufacturing methods are all well known. Furthermore, regarding methods for manufacturing ε-iron oxide powder in which a portion of Fe is replaced by substituted atoms such as Ga, Co, Ti, Al, Rh, etc., for example, see 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 manufacturing ε-iron oxide powder, which can be used as a strong magnetic powder in the magnetic layer of the magnetic tape described above, is not limited to the methods listed herein.

[0136] The activation volume of ε-iron oxide powder is preferably in the range of 300–1500 nm. 3 Within the aforementioned range, micronized ε-iron oxide powder with an activation volume within this range is suitable for manufacturing magnetic tapes that exhibit excellent electromagnetic conversion properties. The preferred activation volume of the ε-iron oxide powder is 300 nm. 3 The above, for example, could also be 500nm. 3 That's all. Furthermore, from the viewpoint of further improving electromagnetic conversion characteristics, the activation volume of ε-iron oxide powder is more preferably 1400 nm. 3 The following is a further preferred option: 1300nm 3 The following is a further preferred option: 1200nm 3 Hereinafter, 1100nm is further preferred. 3 the following.

[0137] An anisotropy constant Ku can be cited as an indicator of reduced thermal fluctuations (in other words, improved thermal stability). ε-iron oxide powder preferably has a Ku value of 3.0 × 10⁻⁶. 4 J / m 3 The above-mentioned Ku, more preferably, can have 8.0 × 10 4 J / m 3 The above refers to the Ku. Furthermore, the Ku of ε-iron oxide powder can, for example, be 3.0 × 10⁻⁶. 5 J / m 3 However, a higher Ku value indicates higher thermal stability and is therefore preferred; it is not limited to the values ​​exemplified above.

[0138] From the viewpoint of improving playback output when playing back data recorded on magnetic tape, it is preferable that the magnetic tape contains strongly magnetic powder with a high mass magnetization σs. In this regard, in one embodiment, the σs of the ε-iron oxide powder can be 8 A·m. 2 / kg or above, or 12A·m 2 / kg or more. On the other hand, from the viewpoint of noise reduction, the σs of ε-iron oxide powder is preferably 40 A·m. 2 Below / kg, preferably 35A·m 2 / kg or less.

[0139] Unless otherwise specified in this invention and specification, the average particle size of various powders, such as strongly magnetic powders, is the value determined using a transmission electron microscope by the following method.

[0140] The powder was photographed at 100,000x magnification using a transmission electron microscope, and then printed at a total magnification of 500,000x on photographic paper or displayed on a monitor to obtain photographs of the particles that make up the powder. Target particles were selected from the obtained particle photographs, and their outlines were traced using a digitizer to determine the size of the particles (primary particles). Primary particles refer to unaggregated, independent particles.

[0141] The above measurements were performed on 500 randomly selected particles. The arithmetic mean of the particle sizes of these 500 particles was taken as the average particle size of the powder. For example, a Hitachi, Ltd. H-9000 transmission electron microscope can be used as the transmission electron microscope described above. Furthermore, the particle size can be measured using known image analysis software (e.g., Carl Zeiss AG KS-400 image analysis software). Unless otherwise specified, the average particle size shown in the embodiments described below refers to the value measured using a Hitachi, Ltd. H-9000 transmission electron microscope as a transmission electron microscope and Carl Zeiss AG KS-400 image analysis software as image analysis software. In this invention and specification, "powder" refers to a collection of multiple particles. For example, "strong magnetic powder" refers to a collection of multiple strongly magnetic particles. Furthermore, the collection of multiple particles is not limited to the particles constituting the collection being in direct contact, but also includes the presence of binders, additives, etc., between the particles, as described later. The term "particle" is sometimes also used to refer to powder.

[0142] As a method for collecting sample powder from magnetic tape to determine particle size, the method described in paragraph 0015 of Japanese Patent Application Publication No. 2011-048878 can be used, for example.

[0143] Unless otherwise specified in this invention and specification, the size of the particles constituting the powder (particle size) and the shape of the particles observed in the above particle photographs are as follows:

[0144] (1) In the cases of needle-like, spindle-shaped, and columnar (where the height is greater than the maximum major diameter of the base), the length is represented by the length of the major axis constituting the particle (i.e., the length of the major axis).

[0145] (2) In the case of plate-shaped or columnar (where the thickness or height is less than the maximum major diameter of the plate surface or bottom surface), the major diameter is represented by the maximum major diameter of the plate surface or bottom surface.

[0146] (3) In cases where the shape is spherical, polyhedral, irregular, etc., and the major axis of the constituent particles cannot be determined based on the shape, it is represented by the equivalent diameter of the circle. The equivalent diameter of the circle is obtained by the circular projection method.

[0147] Furthermore, the average needle-like ratio of the powder refers to the arithmetic mean of the values ​​obtained for the 500 particles, obtained by measuring the length of the minor axis (i.e., minor axis length) of each particle in the above-mentioned measurement and calculating the (major axis length / minor axis length) of each particle. Here, unless otherwise specified, in the definition of particle size (1) above, the minor axis length refers to the length of the minor axis constituting the particle, and in the definition of particle size (2) above, the minor axis length refers to the thickness or height, respectively.

[0148] In the case of (3), since the major axis and minor axis are not distinguished, for convenience, (major axis length / minor axis length) is considered as 1.

[0149] Furthermore, unless otherwise specified, when the particles have a specific shape, for example, in the case of the above definition of particle size (1), the average particle size is the average major axis length; in the case of the above definition of particle size (2), the average particle size is the average plate diameter; and in the case of the above definition of particle size (3), the average particle size is the average diameter (also referred to as the average particle size).

[0150] The content (filling rate) of the strongly magnetic powder in the magnetic layer relative to the total mass of the magnetic layer is preferably in the range of 50 to 90% by mass, more preferably in the range of 60 to 90% by mass. From the viewpoint of increasing recording density, a high filling rate of the strongly magnetic powder in the magnetic layer is preferred.

[0151] (Adhesive)

[0152] The aforementioned magnetic tape can be a coated magnetic tape and may contain an adhesive in the magnetic layer. The adhesive is one or more resins. Various resins commonly used as adhesives in coated magnetic recording media can be used as adhesives. For example, resins selected from polyurethane resins, polyester resins, polyamide resins, vinyl chloride resins, copolystyrene, acrylonitrile, methyl methacrylate, etc., acrylic resins, cellulose resins such as nitrocellulose, epoxy resins, phenoxy resins, polyvinyl acetal, polyvinyl butyral, etc., can be used alone as adhesives, or a mixture of multiple resins can be used. Polyurethane resins, acrylic resins, cellulose resins, and vinyl chloride resins are preferred. These resins can be homopolymers or copolymers. These resins can also be used as adhesives in the non-magnetic layer and / or back coating layer described later. For more information on the above adhesives, please refer to paragraphs 0028 to 0031 of Japanese Patent Application Publication No. 2010-24113. Furthermore, the adhesive can also be a radiation-curable resin such as an electron beam-curable resin. For information on radiation-curable resins, please refer to paragraphs 0044 to 0045 of Japanese Patent Application Publication No. 2011-048878.

[0153] The average molecular weight of the resin used as a binder, based on its weight-average molecular weight, can be, for example, 10,000 or more and 200,000 or less. The weight-average molecular weight in this invention and specification refers to a value obtained by converting a value measured by gel permeation chromatography (GPC) under the following testing conditions into polystyrene. The weight-average molecular weight of the binder shown in the examples described later is a value obtained by converting a value measured under the following testing conditions into polystyrene. The binder can be used, for example, in an amount of 1.0 to 30.0 parts by weight relative to 100.0 parts by weight of the strongly magnetic powder.

[0154] GPC Unit: HLC-8120 (manufactured by Tosoh Corporation)

[0155] Column: TSK gel Multipore HXL-M (manufactured by TOSOH CORPORATION, 7.8mm ID (inner diameter) × 30.0cm)

[0156] Eluent: Tetrahydrofuran (THF)

[0157] (Curing agent)

[0158] A curing agent can also be used in conjunction with an adhesive. Regarding the curing agent, in one approach, it can be a compound that undergoes a curing reaction (crosslinking reaction) by heating (i.e., a thermosetting compound); in another approach, it can be a photocuring compound that undergoes a curing reaction (crosslinking reaction) by light irradiation. The curing agent undergoes a curing reaction during the magnetic tape manufacturing process, and at least a portion of it can be included in the magnetic layer in a state of reaction (crosslinking) with other components such as the adhesive. A thermosetting compound is preferred as the curing agent, and polyisocyanate is suitable. For details regarding polyisocyanate, please refer to paragraphs 0124-0125 of Japanese Patent Application Publication No. 2011-216149. In the composition for forming the magnetic layer, the curing agent can be used, for example, in an amount of 0 to 80 parts by weight relative to 100.0 parts by weight of the adhesive; from the viewpoint of improving the strength of each layer, including the magnetic layer, it is preferable to use an amount of 50.0 to 80.0 parts by weight.

[0159] (Other ingredients)

[0160] The magnetic layer may contain one or more additives as needed. Commercially available additives may be selected based on the desired properties. Alternatively, compounds synthesized by known methods may be used as additives. Examples of additives include the aforementioned curing agent. Furthermore, additives that may be included in the magnetic layer include non-magnetic fillers, lubricants, dispersants, dispersing aids, mildew inhibitors, antistatic agents, and antioxidants. The term "non-magnetic filler" is synonymous with "non-magnetic particle" or "non-magnetic powder." Examples of non-magnetic fillers include those capable of functioning as protrusion-forming agents and those capable of functioning as abrasives. Furthermore, known additives such as the various polymers described in paragraphs 0030 to 0080 of Japanese Patent Application Publication No. 2016-051493 may also be used as additives.

[0161] As a protrusion forming agent (a type of non-magnetic filler), inorganic particles, organic particles, or composite particles of inorganic and organic substances can be used. Carbon black can also be used. Examples of inorganic substances include inorganic oxides such as metal oxides, metal carbonates, metal sulfates, metal nitrides, metal carbides, and metal sulfides, with inorganic oxides being preferred. In one embodiment, the protrusion forming agent can be inorganic oxide-based particles. Here, "based" is used to mean "containing". One type of inorganic oxide-based particles is particles composed of inorganic oxides. Another type of inorganic oxide-based particles is composite particles of inorganic oxides and organic substances; as a specific example, composite particles of inorganic oxides and polymers can be given. Examples of such particles include particles with polymers bonded to the surface of inorganic oxide particles.

[0162] The average particle size of the protrusion forming agent can be, for example, 30–300 nm, preferably 40–200 nm. Furthermore, regarding the shape of the protrusion forming agent, it is believed that the closer the shape of the particles of the protrusion forming agent contained in the magnetic layer is to that of a true sphere, the easier it is for the LFM reduction rate to decrease. This is believed to be because the closer the particle shape is to that of a true sphere, the smaller the indentation resistance that exerts its effect when pressure is applied. Conversely, it is speculated that if the particle shape is different from that of a true sphere, for example, a so-called irregular shape, it is easier to exert a large indentation resistance when pressure is applied, which helps to suppress the protrusion forming agent from penetrating into the magnetic layer due to reciprocating sliding. This is believed to help increase the LFM reduction rate. Furthermore, it is speculated that particles with heterogeneous surfaces and low surface smoothness tend to exert a large indentation resistance when pressure is applied, which helps to suppress the protrusion forming agent from penetrating into the magnetic layer due to reciprocating sliding. Therefore, the inventors believe that using a protrusion-forming agent with a particle shape different from that of a true sphere and / or using a protrusion-forming agent with a non-homogeneous particle surface and low surface smoothness can help achieve an LFM reduction rate of 20% or more. Furthermore, in one embodiment, a substance with a so-called irregular shape can also be used as the protrusion-forming agent.

[0163] As another type of non-magnetic filler, the abrasive is preferably a non-magnetic powder with a Mohs hardness greater than 8, more preferably a non-magnetic powder with a Mohs hardness of 9 or greater. In contrast, the Mohs hardness of the protrusion forming agent can be, for example, 8 or less or 7 or less. The maximum Mohs hardness is 10 of that of diamond. Specifically, examples of abrasives include powders of alumina (e.g., Al2O3), silicon carbide, boron carbide (e.g., B4C), SiO2, TiC, chromium oxide (Cr2O3), cerium oxide, zirconium oxide (e.g., ZrO2), iron oxide, and diamond, among which alumina powder such as α-alumina and silicon carbide powder are preferred. Furthermore, the average particle size of the abrasive can be, for example, in the range of 30 to 300 nm, preferably in the range of 50 to 200 nm.

[0164] Furthermore, from the viewpoint that the protrusion forming agent and the abrasive can perform their functions better, the content of the protrusion forming agent in the magnetic layer is preferably 0.1 to 4.0 parts by weight relative to 100.0 parts by weight of the strong magnetic powder, more preferably 0.3 to 3.5 parts by weight, and even more preferably 0.5 to 2.5 parts by weight. On the other hand, regarding the abrasive, the content in the magnetic layer is preferably 1.0 to 20.0 parts by weight relative to 100.0 parts by weight of the strong magnetic powder, more preferably 3.0 to 15.0 parts by weight, and even more preferably 4.0 to 10.0 parts by weight.

[0165] As an example of an additive that can be used in a magnetic layer containing an abrasive, the dispersant described in paragraphs 0012 to 0022 of Japanese Patent Application Publication No. 2013-131285 is cited as a dispersant for improving the dispersibility of the abrasive in the composition for forming the magnetic layer. Furthermore, regarding dispersants, paragraphs 0061 and 0071 of Japanese Patent Application Publication No. 2012-133837 can be referenced. The dispersant can be included in the non-magnetic layer. Regarding dispersants that may be included in the non-magnetic layer, paragraph 0061 of Japanese Patent Application Publication No. 2012-133837 can be referenced.

[0166] In one embodiment, the magnetic tape may contain one or more fatty acid compounds selected from the group consisting of fatty acids, fatty acid esters, and fatty acid amides in the magnetic layer side portion on the non-magnetic support. In this invention and specification, regarding a magnetic recording medium having a magnetic layer directly on a non-magnetic support, "the magnetic layer side portion on the non-magnetic support" refers to the magnetic layer; regarding a magnetic recording medium having a non-magnetic layer between a non-magnetic support and a magnetic layer, "the magnetic layer side portion on the non-magnetic support" refers to both the magnetic layer and / or the non-magnetic layer. "The magnetic layer side portion on the non-magnetic support" is also simply referred to as "the magnetic layer side portion." The presence of a component on the surface of the magnetic layer side of the magnetic tape is also included in the portion containing that component on the magnetic layer side. The aforementioned fatty acid compounds can function as lubricants. The magnetic layer side portion may contain only one fatty acid compound selected from the group consisting of fatty acids, fatty acid esters, and fatty acid amides, or it may contain two or more. Furthermore, as fatty acids, it may contain only one or two or more fatty acids. This also applies to fatty acid esters and fatty acid amides.

[0167] Examples of fatty acids include lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, behenic acid, erucic acid, and transoleic acid, with stearic acid, myristic acid, and palmitic acid being preferred, and stearic acid being more preferred. Fatty acids may also be contained in the magnetic layer in the form of salts such as metal salts.

[0168] Examples of fatty acid esters include butyl hexanoate, butyl octanoate, butyl decanoate, butyl laurate, butyl myristate, and butyl palmitate. The inventors hypothesize that using fatty acid esters with fewer carbon atoms in the fatty acid moiety can help suppress the formation of meniscus-shaped droplet adhesion caused by lubricants. This could potentially help reduce the absolute value of friction before reciprocating sliding.

[0169] Furthermore, the inventors hypothesize that using a fatty acid ester with a low number of carbon atoms in its fatty acid moiety can help to uniformly distribute the lubricant (e.g., fatty acid) due to contact with the magnetic head. This could potentially contribute to increasing the LFM reduction rate. Based on the above viewpoint, a fatty acid ester with 16 or fewer carbon atoms in its fatty acid moiety is preferred. For example, butyl palmitate has 16 carbon atoms in its fatty acid moiety. The number of carbon atoms in the aforementioned fatty acid moiety can, for example, be 6 or more and 16 or less.

[0170] Examples of fatty acid amides include the various fatty acid amides described above. Specific examples include lauryl amide, myristyl amide, palmitamide, stearyl amide, etc.

[0171] In one embodiment, a magnetic recording medium containing one or more fatty acid compounds selected from the group consisting of fatty acids, fatty acid esters, and fatty acid amides in the magnetic layer side portion can be manufactured by forming a magnetic layer using a magnetic layer forming composition containing one or more of the aforementioned fatty acid compounds. Furthermore, in another embodiment, a magnetic recording medium containing one or more of the aforementioned fatty acid compounds in the magnetic layer side portion can be manufactured by forming a non-magnetic layer using a non-magnetic layer forming composition containing one or more of the aforementioned fatty acid compounds. Also, in another embodiment, a magnetic recording medium containing one or more of the aforementioned fatty acid compounds in the magnetic layer side portion can be manufactured by forming a non-magnetic layer using a non-magnetic layer forming composition containing one or more of the aforementioned fatty acid compounds and forming a magnetic layer using a magnetic layer forming composition containing one or more of the aforementioned fatty acid compounds. The non-magnetic layer can retain components such as fatty acids, fatty acid esters, and fatty acid amides that function as lubricants and supply them to the magnetic layer. The fatty acids, fatty acid esters, and fatty acid amides contained in the non-magnetic layer can be transferred to the magnetic layer and exist within the magnetic layer.

[0172] The content of fatty acids in the magnetic layer or the composition for forming the magnetic layer is, for example, 0 to 3.0 parts by weight relative to 100.0 parts by weight of the strong magnetic powder, preferably 0.5 to 3.0 parts by weight.

[0173] The content of fatty acid esters in the magnetic layer or the composition for forming the magnetic layer is, for example, 0.1 to 10.0 parts by weight relative to 100.0 parts by weight of the strong magnetic powder, preferably 0.3 to 7.0 parts by weight, and more preferably 0.5 to 5.0 parts by weight. According to the inventors' research, when compared with cases using the same type of fatty acid ester, a trend was observed that the higher the content of the fatty acid ester, the greater the LFM reduction rate. Furthermore, when compared with cases using the same amount of fatty acid ester, a trend was observed that the fewer carbon atoms in the fatty acid portion of the fatty acid ester, the greater the LFM reduction rate.

[0174] The content of fatty acid amide in the magnetic layer or the composition for forming the magnetic layer is, for example, 0 to 1.0 parts by weight relative to 100.0 parts by weight of the strong magnetic powder, preferably 0.1 to 1.0 parts by weight.

[0175] Regarding the content of fatty acids, fatty acid esters, and fatty acid amides in the composition for forming a non-magnetic layer, the aforementioned strongly magnetic powder can be replaced with non-magnetic powder, and the above description applies.

[0176] <Non-magnetic layer>

[0177] Next, the non-magnetic layer will be described. The magnetic tape described above can have a magnetic layer directly on a non-magnetic support, or a non-magnetic layer containing non-magnetic powder can be formed between the non-magnetic support and the magnetic layer. The non-magnetic powder used in the non-magnetic layer can be an inorganic powder (inorganic powder) or an organic powder (organic powder). Carbon black can also be used. Examples of inorganic materials include metals, metal oxides, metal carbonates, metal sulfates, metal nitrides, metal carbides, and metal sulfides. These non-magnetic powders can be obtained commercially available or manufactured using known methods. For details, please refer to paragraphs 0146 to 0150 of Japanese Patent Application Publication No. 2011-216149. For information on carbon black that can be used in the non-magnetic layer, please refer to paragraphs 0040 to 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 relative to the total mass of the non-magnetic layer, and more preferably in the range of 60 to 90% by mass.

[0178] The non-magnetic layer may contain an adhesive or additives. Further details regarding the adhesives, additives, etc., of the non-magnetic layer can be found in known techniques related to non-magnetic layers. Furthermore, for example, details regarding the type and content of the adhesive, and the type and content of the additives, can also be found in known techniques related to magnetic layers.

[0179] The dispersant can also be added to the composition for forming a non-magnetic layer. For information on dispersants that can be added to the composition for forming a non-magnetic layer, please refer to paragraph 0061 of Japanese Patent Application Publication No. 2012-133837.

[0180] The non-magnetic layer of the aforementioned magnetic tape also includes a substantially non-magnetic layer that, along with the non-magnetic powder, contains, for example, in the form of impurities or intentionally in small amounts of strongly magnetic powder. Here, a substantially non-magnetic layer refers to a layer with a remanent magnetic flux density of 10 mT or less, a magnetic retention force of 7.96 kA / m (100 Oe) or less, or a layer with a remanent magnetic flux density of 10 mT or less and a magnetic retention force of 7.96 kA / m (100 Oe) or less. Preferably, the non-magnetic layer does not have remanent magnetic flux density or magnetic retention force.

[0181] <Non-magnetic support>

[0182] Next, the non-magnetic support will be described. Examples of non-magnetic supports (hereinafter referred to simply as "support") include biaxially stretched polyethylene terephthalate, polyethylene naphthalate, polyamide, polyamide-imide, and aromatic polyamide. Among these, polyethylene terephthalate, polyethylene naphthalate, and polyamide are preferred. These supports can be pre-treated with corona discharge, plasma treatment, easy-bonding treatment, heat treatment, etc.

[0183] In one embodiment, the non-magnetic support of the magnetic tape can be an aromatic polyester support. In this invention and specification, "aromatic polyester" refers to a resin containing an aromatic backbone and multiple ester bonds, and "aromatic polyester support" refers to a support containing at least one layer of aromatic polyester film. "Aromatic polyester film" refers to a film in which aromatic polyester constitutes the largest component by mass. In this invention and specification, "aromatic polyester support" includes supports in which all resin films are aromatic polyester films, and supports that include aromatic polyester films and other resin films. Specific examples of aromatic polyester supports include single-layer aromatic polyester films, laminated films with two or more aromatic polyester films of the same composition, laminated films with two or more aromatic polyester films of different compositions, and laminated films including one or more aromatic polyester films and one or more resin films other than aromatic polyester films. An adhesive layer may also be arbitrarily included between adjacent layers in the laminated film. Furthermore, the aromatic polyester support may also optionally include a metal film and / or a metal oxide film formed on one or both surfaces by vapor deposition or the like. The same applies to the "polyethylene terephthalate support" and "polyethylene naphthalate support" in this invention and specification.

[0184] There are no particular limitations on the aromatic rings contained in the aromatic skeleton of aromatic polyesters. Specific examples of aromatic rings include benzene rings and naphthalene rings.

[0185] For example, polyethylene terephthalate (PET) is a polyester containing benzene rings and is a resin obtained by polycondensation of ethylene glycol with terephthalic acid and / or dimethyl terephthalate. The term "polyethylene terephthalate" in this invention and specification also includes polyethylene terephthalate having a structure containing one or more other components (e.g., copolymer components, components introduced into the ends or side chains, etc.) in addition to the components described above.

[0186] Polyethylene naphthalate (PEN) is a polyester containing a naphthalene ring, and is a resin obtained by esterification of dimethyl 2,6-naphthalenedicarboxylate with ethylene glycol, followed by transesterification and polycondensation. The term "polyethylene naphthalate" in this invention and specification also includes polyethylene naphthalate with a structure having one or more other components (e.g., copolymer components, components introduced into the ends or side chains, etc.) in addition to the above-mentioned components.

[0187] Furthermore, in one embodiment, the non-magnetic support of the aforementioned magnetic tape can be an aromatic polyamide support. In this invention and specification, "aromatic polyamide" refers to a resin containing an aromatic backbone and multiple amide bonds. The aromatic rings contained in the aromatic backbone of the aromatic polyamide are not particularly limited. Specific examples of aromatic rings include, for example, benzene rings. "Aromatic polyamide support" refers to a support comprising at least one layer of aromatic polyamide film. "Aromatic polyamide film" refers to a film in which aromatic polyamide constitutes the largest component by mass. In this invention and specification, "aromatic polyamide support" includes supports in which all resin films comprised of aromatic polyamide films, and supports comprising aromatic polyamide films and other resin films. Specific examples of aromatic polyamide supports include single-layer aromatic polyamide films, laminated films consisting of two or more aromatic polyamide films with the same composition, laminated films consisting of two or more aromatic polyamide films with different compositions, and laminated films comprising one or more aromatic polyamide films and one or more resin films other than aromatic polyamide films. An adhesive layer may also be arbitrarily included between adjacent layers in the laminated film. Furthermore, the aromatic polyamide support may arbitrarily include metal films and / or metal oxide films formed on one or both surfaces by vapor deposition or the like.

[0188] Furthermore, as mentioned above, the non-magnetic support can be a biaxially stretched membrane, or a membrane subjected to corona discharge, plasma treatment, easy bonding treatment, heat treatment, etc.

[0189] As an indicator of the physical properties of a nonmagnetic support, moisture content can be cited as an example. In this invention and this specification, the moisture content of the nonmagnetic support is a value obtained by the following method.

[0190] A sample piece (e.g., a few grams) cut from a non-magnetic support used to determine the moisture content is dried in a vacuum desiccator at a temperature of 180°C and a pressure below 100 Pa until it reaches a constant weight. The mass of this dried sample piece is designated as W1. W1 is the value measured within 30 seconds after removal from the vacuum desiccator at a temperature of 23°C and a relative humidity of 50%. Next, the mass of the sample piece after being placed at a temperature of 25°C and a relative humidity of 75% for 48 hours is designated as W2. W2 is the value measured within 30 seconds after removal from the aforementioned environment at a temperature of 23°C and a relative humidity of 50%. The moisture content is calculated using the following formula.

[0191] Moisture content (%) = [(W2-W1) / W1] × 100

[0192] For example, the moisture content of the non-magnetic support can be determined by the above method after removing the non-magnetic support, such as the magnetic layer, from the magnetic tape using known methods (e.g., stripping with organic solvents).

[0193] In one embodiment, the moisture content of the non-magnetic support of the magnetic tape is preferably 2.0% or less, more preferably 1.8% or less, even more preferably 1.6% or less, even more preferably 1.4% or less, even more preferably 1.2% or less, and even more preferably 1.0% or less. Furthermore, the moisture content of the non-magnetic support of the magnetic tape can be 0%, 0% or more, more than 0%, or 0.1% or more.

[0194] Young's modulus can also be cited as an indicator of the physical properties of non-magnetic supports. In this invention and this specification, the Young's modulus of the non-magnetic support is a value determined by the following method under a measurement environment of 23°C and 50% relative humidity.

[0195] Under conditions of a clamp spacing of 100 mm, a tensile speed of 10 mm / min, and a plotting speed of 500 mm / min, a specimen cut from a non-magnetic support, which is the object of the test, is stretched using a universal tensile testing apparatus. As a universal tensile testing apparatus, commercially available universal tensile testing apparatuses such as those manufactured by TOYO BALDWIN CO.Ltd. (TENSILO N) or those with known structures can be used. The Young's modulus of the specimen in the length and width directions is calculated based on the tangent of the rising portion of the load-elongation curve obtained in this way. Here, the length and width directions of the specimen refer to the length and width directions when the specimen is contained within the magnetic tape.

[0196] For example, after removing the portion other than the non-magnetic support, such as the magnetic layer, from the magnetic tape using known methods (e.g., stripping with organic solvents), the Young's modulus in the length and width directions of the non-magnetic support can be determined using the methods described above.

[0197] In one embodiment, the Young's modulus of the non-magnetic support of the magnetic tape in the longitudinal direction is preferably 3000 MPa or more, more preferably 4000 MPa or more, even more preferably 5000 MPa or more, and even more preferably 6000 MPa or more. Furthermore, the Young's modulus of the non-magnetic support of the magnetic tape in the longitudinal direction can be 15000 MPa or less, 13000 MPa or less, or 12000 MPa or less. Regarding the width direction, the Young's modulus of the non-magnetic support of the magnetic tape in the width direction is preferably 2000 MPa or more, more preferably 3000 MPa or more, even more preferably 4000 MPa or more, and even more preferably 5000 MPa or more. Furthermore, the Young's modulus of the non-magnetic support of the magnetic tape in the width direction can be 12000 MPa or less, 11000 MPa or less, or 10000 MPa or less. In the manufacture of magnetic tapes, the non-magnetic support typically uses the machine direction (MD) of the film as its length direction and the traverse direction (TD) as its width direction. Furthermore, in one embodiment, it is preferable that the Young's modulus in the length direction is greater than the Young's modulus in the width direction; more preferably, the difference (Young's modulus in the length direction - Young's modulus in the width direction) is in the range of 800–3000 MPa.

[0198] The moisture content and Young's modulus of a non-magnetic support can be controlled based on the types and mixing ratios of the components constituting the support, as well as the manufacturing conditions of the support. For example, by adjusting the stretching ratio in each direction during biaxial stretching, the Young's modulus in the length direction and the Young's modulus in the width direction can be controlled separately.

[0199] <Back Coating>

[0200] The aforementioned magnetic tape may or may not have a back coating containing non-magnetic powder on the surface of the non-magnetic support opposite to the surface with the magnetic layer. Preferably, the back coating contains one or both of carbon black and inorganic powder. The back coating may contain a binder and additives. Details regarding the non-magnetic powder, binder, additives, etc., of the back coating can be found in known technologies related to the back coating, as well as known technologies related to the magnetic layer and / or non-magnetic layer. For example, regarding the back coating, reference can be made to paragraphs 0018-0020 of Japanese Patent Application Publication No. 2006-331625 and lines 65-38 of column 4 of the specification of U.S. Patent No. 7,029,774.

[0201] <Various Thicknesses>

[0202] Regarding the thickness (total thickness) of magnetic tape, with the tremendous increase in information volume in recent years, there is a demand for increased recording capacity (increased capacity) of magnetic tape. As a means of increasing capacity, examples include reducing the thickness of the magnetic tape and increasing the length of the tape contained in each tape reel. From this perspective, the thickness (total thickness) of the aforementioned magnetic tape is preferably 5.6 μm or less, more preferably 5.5 μm or less, even more preferably 5.4 μm or less, further preferably 5.3 μm or less, even more preferably 5.2 μm or less, and even more preferably 5.0 μm or less. Furthermore, from the viewpoint of ease of operation, the thickness of the magnetic tape is preferably 3.0 μm or more, more preferably 3.5 μm or more.

[0203] The thickness (total thickness) of the magnetic tape can be determined by the following methods.

[0204] Ten magnetic tape samples (e.g., 5–10 cm in length) are cut from any portion of the magnetic tape and overlapped to measure the thickness. The thickness of each magnetic tape sample is taken as the thickness of the tape by dividing the measured thickness by 10. The thickness measurement described above can be performed using a known measuring instrument capable of measuring thicknesses in the 0.1 μm range.

[0205] The thickness of the non-magnetic support is preferably 2.0 to 5.0 μm, more preferably 3.0 to 5.0 μm.

[0206] The thickness of the magnetic layer can be optimized based on factors such as the saturation magnetization of the magnetic head, the head gap length, and the frequency band of the recorded signal. It is typically 0.01 μm to 0.15 μm, and from the viewpoint of high-density recording, 0.02 μm to 0.12 μm is preferred, and 0.03 μm to 0.1 μm is even more preferred. At least one magnetic layer is required; the magnetic layer can be divided into two or more magnetic layers with different magnetic properties, and known structures related to multilayer magnetic layers can be applied. When divided into two or more magnetic layers, the thickness of the magnetic layer refers to the total thickness of these layers.

[0207] The thickness of the non-magnetic layer is, for example, 0.1 to 1.5 μm, preferably 0.1 to 1.0 μm, and more preferably 0.1 to 0.7 μm.

[0208] The thickness of the back coating is preferably less than 0.9 μm, and more preferably 0.1 to 0.7 μm.

[0209] The thickness of the magnetic layer and other thicknesses can be determined using the following methods.

[0210] After exposing a cross-section of the magnetic tape along its thickness using an ion beam, the exposed cross-section is observed using a scanning electron microscope or a transmission electron microscope. Various thicknesses can be calculated as the arithmetic mean of the thicknesses obtained at any two points during the cross-sectional observation. Alternatively, various thicknesses can be calculated as design thicknesses based on manufacturing conditions, etc.

[0211] <Manufacturing Method>

[0212] (Preparation of the composition for forming each layer)

[0213] The compositions used to form magnetic layers, non-magnetic layers, or back coatings typically contain solvents along with the aforementioned components. Various organic solvents commonly used in the manufacture of coated magnetic recording media can be used as solvents. From the viewpoint of the solubility of binders commonly used in coated magnetic recording media, it is preferable that each layer-forming composition contains one or more ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, cyclohexanone, isophorone, and tetrahydrofuran. The amount of solvent in each layer-forming composition is not particularly limited and can be the same as that in typical coated magnetic recording media layer-forming compositions. Furthermore, the process of preparing each layer-forming composition typically includes at least a mixing process, a dispersion process, and a mixing process set up before and after these processes as needed. Each process can be divided into two or more stages. Components used in the preparation of each layer-forming composition can be added at the initial stage or midway through any process. Components can also be added in two or more processes. For example, the binder can be added in stages during the mixing process, the dispersion process, and the mixing process for adjusting viscosity after dispersion. In one approach, during the preparation of the magnetic layer forming composition, the protrusion forming agent solution (hereinafter referred to as "protrusion forming agent solution") can be mixed with one or more other components of the magnetic layer forming composition after the preparation of a dispersion containing a protrusion forming agent. For example, the protrusion forming agent solution can be prepared using a known dispersion treatment such as ultrasonic treatment. Ultrasonic treatment, for example, can be performed at a concentration of 200 cc (1 cc = 1 cm). 3 The ultrasonic output is approximately 10–2000 watts for about 1–300 minutes. Furthermore, filtration can be performed after dispersion treatment. For information on the filter used for filtration, please refer to the following description.

[0214] In the aforementioned magnetic tape manufacturing process, conventionally known manufacturing techniques can be used in some or all of the processes. In the mixing process, kneaders with strong mixing power, such as open-type kneaders, continuous kneaders, pressure kneaders, and extruders, are preferred. Details regarding these mixing processes are described in Japanese Patent Application Publication Nos. 1-106338 and 1-79274. Furthermore, glass beads and / or other beads can be used to disperse the compositions for forming each layer. High-density dispersed beads, such as zirconia beads, titanium dioxide beads, and steel beads, are preferred. These dispersed beads are preferably used with optimized particle size (bead diameter) and filling rate. Known dispersers can be used. According to the inventors' research, a trend has been observed where a longer dispersion time for the composition for forming the non-magnetic layer results in a greater LFM reduction rate. It is speculated that by extending the dispersion time of the composition for forming the non-magnetic layer, a denser non-magnetic layer can be formed, thereby suppressing the penetration of the protrusion forming agent into the magnetic layer due to reciprocating sliding. This is believed to help increase the LFM reduction rate. The composition for forming each layer can be filtered using known methods before being used in the coating process. Filtration can be performed, for example, by using a filter. As a filter 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.

[0215] (Coating process)

[0216] A magnetic layer can be formed by directly coating a magnetic layer forming composition onto a non-magnetic support, or by sequentially or simultaneously coating it with a non-magnetic layer forming composition in multiple layers. In the case of an alignment process, the coating layer is oriented within an alignment zone while the magnetic layer forming composition is still wet. Various known techniques, such as those described in paragraph 0052 of Japanese Patent Application Publication No. 2010-24113, can be applied to the alignment process. For example, vertical alignment can be performed using known methods such as the use of opposite-pole magnets. In the alignment zone, the drying speed of the coating layer can be controlled based on the temperature and flow rate of the drying air and / or the conveying speed within the alignment zone. Furthermore, the coating layer can be pre-dried before being conveyed to the alignment zone.

[0217] The back coating can be formed by applying a back coating forming composition to the side of a non-magnetic support opposite to the side having a magnetic layer (or with an additional magnetic layer). For details regarding the coating used to form each layer, please refer to paragraph 0066 of Japanese Patent Application Publication No. 2010-231843.

[0218] (Other processes)

[0219] After the coating process described above, calendering is typically performed to improve the surface smoothness of the magnetic tape. It is speculated that by intensifying the calendering conditions, a denser non-magnetic layer can be formed, thereby suppressing the penetration of the protrusion-forming agent into the magnetic layer due to reciprocating sliding. This is believed to contribute to increasing the LFM reduction rate. Intensifying the calendering conditions includes, for example, increasing the calendering pressure, increasing the calendering temperature, decreasing the calendering speed, and increasing the number of calendering passes. Regarding the calendering conditions, the calendering pressure is, for example, 200–500 kN / m, preferably 250–350 kN / m; the calendering temperature is preferably 90–120°C, more preferably 100–120°C; and the calendering speed is, for example, 50–300 m / min, preferably 80–200 m / min. The number of calendering passes is preferably 2 or more, for example, 2 to 4 passes.

[0220] For details on other processes used in the manufacture of magnetic tapes, please refer to paragraphs 0067 to 0070 of Japanese Patent Application Publication No. 2010-231843.

[0221] Through various processes, a long strip of raw magnetic tape can be obtained. The obtained raw magnetic tape is then cut (sliced) using a known cutting machine, for example, to the width required to fit into a tape cassette. This width can be determined according to standards, but is typically 1 / 2 inch.

[0222] Servo patterns are typically formed on the cut magnetic tape.

[0223] (Formation of servo patterns)

[0224] The formation of servo patterns can also be called the recording of servo signals. The formation of servo patterns will be explained below.

[0225] Servo patterns are typically formed along the length of the magnetic tape. Examples of control methods that utilize servo signals (servo control) include time-based servo (TBS), amplitude servo, and frequency servo.

[0226] As shown in ECMA (European Computer Manufacturers Association)-319 (June 2001), time-based servoing is used in LTO (Linear Tape-Open) compliant magnetic tapes (commonly referred to as "LTO tapes"). In this time-based servoing method, the servo pattern is constructed by continuously arranging multiple pairs of non-parallel magnetic strips (also referred to as "servo strips") along the length of the tape. In this invention and specification, "time-based servo pattern" refers to a servo pattern capable of head tracking in a time-based servoing servo system. As described above, the reason for constructing the servo pattern with a pair of non-parallel magnetic strips is to notify the servo signal readout element passing over the servo pattern of its position. Specifically, the pair of magnetic strips is formed such that the interval changes continuously along the width of the tape, and the servo signal readout element can determine the relative position of the servo pattern and the servo signal readout element by reading this interval. This relative position information makes data track tracking possible. Therefore, multiple servo tracks are typically arranged along the width of the tape on the servo pattern.

[0227] The servo tape consists of a continuous servo pattern along the length of the magnetic tape. Multiple servo tapes are typically present on the tape. For example, in an LTO tape, there are five. The area between two adjacent servo tapes is the data tape. The data tape consists of multiple data tracks, each corresponding to a servo track.

[0228] Furthermore, in one approach, as shown in Japanese Patent Application Publication No. 2004-318983, each servo tape contains embedded information indicating the servo tape's number (also referred to as "servo tape ID (identification)" or "UDIM (Unique Data Band Identification Method) information"). This servo tape ID is recorded by moving a specific pair of servo magnetic strips from a pair of servo magnetic strips present in the servo tape, causing their positions to shift relative to each other along the length of the magnetic tape. Specifically, the movement of a specific pair of servo magnetic strips from a pair of servo magnetic strips is changed for each servo tape. Therefore, the recorded servo tape ID is unique for each servo tape, and thus, by reading a single servo tape using a servo signal reading element, the servo tape can be uniquely identified.

[0229] Another method for uniquely identifying servo tapes is the interleaving method shown in ECMA-319 (June 2001). In this interleaving method, each servo tape is recorded by moving a group of multiple pairs of non-parallel magnetic strips arranged consecutively along the length of the magnetic tape (servo strips). Since this combination of movement patterns between adjacent servo tapes is unique throughout the entire magnetic tape, the servo tape can also be uniquely identified when reading the servo pattern using two servo signal readout elements.

[0230] Furthermore, as shown in ECMA-319 (June 2001), information indicating the position of the magnetic tape along its length (also known as "LPOS (Longitudinal Position) information") is typically embedded in each servo tape. Similar to UDIM information, this LPOS information is recorded by shifting the position of a pair of servo strips along the length of the tape. However, unlike UDIM information, the same signal is recorded in each servo tape in this LPOS information.

[0231] Other information, different from the UDIM and LPOS information mentioned above, can also be embedded into the server tape. In this case, the embedded information can vary depending on the server tape, like the UDIM information, or it can be universal across all server tapes, like the LPOS information.

[0232] Furthermore, other methods besides those mentioned above can also be used as a way to embed information in the servo strip. For example, a specified code can be recorded by pulling a specified pair from the middle of a pair of servo magnetic strips.

[0233] The magnetic head used for servo pattern formation is called a servo write head. A servo write head typically has a pair of gaps corresponding to the aforementioned pair of magnetic strips, and the number of these gaps is the same as the number of servo tapes. Generally, each pair of gaps is connected to a magnetic core and a coil. By supplying current pulses to the coils, the magnetic field generated in the magnetic core produces a leakage magnetic field in the pair of gaps. During servo pattern formation, by feeding the magnetic tape onto the servo write head while simultaneously inputting current pulses, the magnetic pattern corresponding to the pair of gaps can be transferred onto the magnetic tape, thereby forming a servo pattern. The width of each gap can be appropriately set according to the density of the formed servo pattern. For example, the width of each gap can be set to less than 1 μm, 1–10 μm, or more than 10 μm.

[0234] Before forming servo patterns on the magnetic tape, the tape is typically demagnetized (erased). This erasure process can be performed by applying a uniform magnetic field to the tape using a DC or AC magnet. Erasure processes include DC (Direct Current) erasure and AC (Alternating Current) erasure. AC erasure is performed by gradually reducing the strength of the magnetic field while reversing the direction applied to the tape. On the other hand, DC erasure is performed by applying a unidirectional magnetic field to the tape. DC erasure includes two methods. The first method is horizontal DC erasure, which applies a unidirectional magnetic field along the length of the tape. The second method is vertical DC erasure, which applies a unidirectional magnetic field along the thickness of the tape. Erasure processes can be performed on the entire tape or on each servo section of the tape.

[0235] The orientation of the magnetic field in the formed servo pattern depends on the erasure orientation. For example, when performing horizontal DC erasure on a magnetic tape, the servo pattern is formed with the magnetic field orientation opposite to the erasure orientation. This increases the output of the servo signal obtained by reading the servo pattern. Furthermore, as shown in Japanese Patent Application Publication No. 2012-53940, when a magnetic pattern using the aforementioned gap is transferred to a magnetic tape that has been vertically DC erased, the servo signal obtained by reading the formed servo pattern is a unipolar pulse shape. On the other hand, when a magnetic pattern using the aforementioned gap is transferred to a magnetic tape that has been horizontally DC erased, the servo signal obtained by reading the formed servo pattern is a bipolar pulse shape.

[0236] <Vertical Rectangular Ratio>

[0237] In one embodiment, the vertical aspect ratio of the magnetic tape can be, for example, 0.55 or higher, and from the viewpoint of improving electromagnetic conversion characteristics, preferably 0.60 or higher, more preferably 0.65 or higher. In principle, the upper limit of the aspect ratio is 1.00 or lower. The vertical aspect ratio of the magnetic tape can be 1.00 or lower, and can be 0.95 or lower, 0.90 or lower, 0.85 or lower, or 0.80 or lower. From the viewpoint of improving electromagnetic conversion characteristics, a larger value for the vertical aspect ratio of the magnetic tape is preferred. The vertical aspect ratio of the magnetic tape can be controlled by known methods such as implementing vertical orientation processing.

[0238] In this invention and this specification, "vertical rectangularity ratio" refers to the rectangularity ratio measured in the vertical direction of the magnetic tape. The "vertical direction" mentioned in the rectangularity ratio refers to the direction orthogonal to the surface of the magnetic layer, and can also be called the thickness direction. In this invention and this specification, the vertical rectangularity ratio is determined by the following method.

[0239] A sample piece of the required size for importing into a vibrating sample magnetometer was cut from the magnetic tape to be measured. Using the vibrating sample magnetometer, a magnetic field was applied to the sample piece in the direction perpendicular to the magnetic layer surface (orthogonal to the magnetic layer surface) at a maximum applied magnetic field of 3979 kA / m, a measurement temperature of 296 K, and a magnetic field scan speed of 8.3 kA / m / s. The magnetization of the sample piece relative to the applied magnetic field was measured. The measured value of the magnetization was obtained as a demagnetization correction value, and was obtained by subtracting the magnetization of the sample probe of the vibrating sample magnetometer as background noise. When the magnetization at the maximum applied magnetic field is set as Ms, and the magnetization at zero applied magnetic field is set as Mr, the squareness ratio SQ (Squareness Ratio) is calculated by SQ = Mr / Ms. The measurement temperature refers to the temperature of the sample piece. By setting the ambient temperature around the sample piece as the measurement temperature, the temperature of the sample piece can be made the measurement temperature by achieving temperature equilibrium.

[0240] [Cassette Tape Case]

[0241] One aspect of the present invention relates to a magnetic tape cassette comprising the aforementioned magnetic tape.

[0242] The details of the magnetic tapes included in the aforementioned cassette are as described above.

[0243] In a magnetic tape cassette, the magnetic tape is typically housed inside the cassette body while being wound onto a reel. The reel is configured to rotate within the cassette body. Single-reel cassettes, with one reel inside the cassette body, and double-reel cassettes, with two reels inside the cassette body, are widely used. When a single-reel cassette is installed on a tape drive for recording and / or playing data from the tape, the tape is pulled from the cassette and wound onto a reel on the tape drive side. A magnetic head is positioned along the tape transport path from the cassette to the take-up reel. Tape feeding and winding occur between the reel on the cassette side (feed reel) and the reel on the tape drive side (take-up reel). During this process, the magnetic head contacts and slides against the magnetic layer surface of the tape, thereby recording and / or playing back data. In contrast, a double-reel cassette has both a feed reel and a take-up reel inside the cassette.

[0244] In one embodiment, the aforementioned magnetic tape cassette may include a cartridge memory. The cartridge memory may be, for example, a non-volatile memory that has recorded head tilt angle adjustment information or records head tilt angle adjustment information. The head tilt angle adjustment information is information used to adjust the head tilt angle when the magnetic tape travels within the magnetic tape device. For example, as head tilt angle adjustment information, the value of the servo tape interval at various positions along the length of the magnetic tape during data recording may be recorded. For example, when playing back data recorded on the magnetic tape, the value of the servo tape interval can be measured during playback, and the head tilt angle can be changed by the control device of the magnetic tape device to make the absolute value of the difference between the servo tape interval at the same length position recorded in the cartridge memory and that at the same position approach 0. The head tilt angle may be, for example, the aforementioned angle θ. When the head is tilted to record and / or play back data, the aforementioned angle θ may exceed 0°, and may be less than 45°, less than 40°, or less than 35°.

[0245] The aforementioned magnetic tape and cassette can be used in magnetic tape devices (in other words, magnetic recording playback systems) that record and / or play data by changing the tilt angle of the magnetic head during tape transport. In this usage, since the recording and / or playback of data includes the period when the magnetic head is tilted, magnetic tapes with high transport stability during data recording and / or playback by tilting the magnetic head are preferred.

[0246] However, the aforementioned magnetic tapes and cassettes are not limited to those used in this magnetic tape apparatus. For example, it is also possible to use them in a manner where the head tilt angle is fixed throughout each recording or playback cycle, based on changes made to the head tilt angle during a particular recording or playback cycle and subsequent recordings or playback cycles. In this usage, the head tilt is included during data recording and / or playback, therefore, a magnetic tape with high tape transport stability during data recording and / or playback is preferred when the head is tilted.

[0247] [Magnetic tape device]

[0248] One aspect of the present invention relates to a magnetic tape device comprising the aforementioned magnetic tape. In the magnetic tape device, data recording on the magnetic tape and / or playback of data recorded on the magnetic tape can be performed, for example, by contacting and sliding the magnetic layer surface of the magnetic tape against a magnetic head. The magnetic tape device may detachably include the magnetic tape cassette according to one aspect of the present invention.

[0249] The aforementioned magnetic tape cassette can be mounted onto a magnetic tape device equipped with magnetic heads for data recording and / or playback. In this invention and specification, "magnetic tape device" refers to a device capable of at least one of recording data onto a magnetic tape and playing back data recorded on the magnetic tape. This device is commonly referred to as a drive.

[0250] <Magnetic head>

[0251] The aforementioned magnetic tape device may include a magnetic head. Regarding the structure of the magnetic head and the angle θ that serves as the tilt angle of the magnetic head, please refer to the above. Figures 1-3 The magnetic head included in the aforementioned magnetic tape device can be an LTO8 head in one embodiment, a different generation of LTO head in another embodiment, or a head other than an LTO head in yet another embodiment. When the magnetic head includes a playback element, a magnetoresistive (MR) element capable of sensitively reading information recorded on the magnetic tape is preferred as the playback element. Various known MR elements can be used as the MR element (e.g., GMR (Giant Magnetoresistive) element, TMR (Tunnel Magnetoresistive) element, etc.). Hereinafter, the magnetic head that records data and / or plays back the recorded data will also be referred to as a "recording and playback head". The element used for recording data (recording element) and the element used for playing back data (playback element) are collectively referred to as the "head element".

[0252] When recording and / or playing back recorded data, the first step is to track the data using servo signals. That is, by making the servo signal read element follow a specified servo track, the read / write head can be controlled to move along the target data track. Movement of the data track is achieved by changing the servo track read by the servo signal read element in the width direction of the magnetic tape.

[0253] Furthermore, the recording and playback head can also record and / or play back other data tapes. In this case, simply use the aforementioned UDIM information to move the servo signal readout element to the specified servo tape to begin tracking that servo tape.

[0254] Figure 4 The diagram shows an example of the configuration of the data band and the servo band. Figure 4 In this design, multiple servo tapes 1 are arranged on the magnetic layer of the magnetic tape MT, sandwiched between guide tapes 3. Multiple regions 2 sandwiched between two servo tapes are data tapes. The servo pattern is a magnetized region, formed by magnetizing specific areas of the magnetic layer using a servo writing head. The region magnetized by the servo writing head (the location where the servo pattern is formed) is determined according to a standard. For example, in the LTUltrium format magnetic tape, which is an industry standard specification, when manufacturing the tape, such as... Figure 5 As shown, multiple servo patterns tilted relative to the bandwidth direction are formed on the servo strip. Specifically, in Figure 5 In the context of servo frame SF on servo band 1, it consists of servo subframe 1 (SSF1) and servo subframe 2 (SSF2). Servo subframe 1 is composed of A bursts (...). Figure 5The symbols A and B are in the middle. Figure 5 The A burst consists of servo patterns A1 to A5, and the B burst consists of servo patterns B1 to B5. On the other hand, servo subframe 2 consists of the C burst (…). Figure 5 The symbol C) and D burst ( Figure 5 The middle part is composed of the symbol D). The C burst consists of servo patterns C1 to C4, and the D burst consists of servo patterns D1 to D4. These 18 servo patterns are configured in combinations of 5 and 4 on subframes arranged in an array of 5, 5, 4, 4, used to identify servo frames. Figure 5 For illustrative purposes, a single servo frame is shown. However, in reality, in the magnetic layer of a magnetic tape performing time-based servo head tracking, multiple servo frames are arranged along the tape travel direction on each servo tape. Figure 5 In the image, the arrow indicates the direction of tape travel. For example, LTO Ul trium format tapes typically have more than 5,000 servo frames per 1m of tape length on each servo tape of the magnetic layer.

[0255] In the aforementioned magnetic tape apparatus, the tilt angle of the magnetic head can be changed as the magnetic tape travels within the apparatus. The tilt angle is, for example, the angle θ formed by the axis of the element array and the width direction of the magnetic tape. Regarding the angle θ, as described above, for example, by providing an angle adjustment unit in the recording / playback head unit of the magnetic head to adjust the angle of the head module, the angle θ can be variably adjusted during magnetic tape travel. This angle adjustment unit may, for example, include a rotation mechanism that rotates the module. Known techniques can be applied to the angle adjustment unit.

[0256] Regarding the tilt angle of the magnetic head during tape transport, when the magnetic head consists of multiple modules, a reference can be used to define the angle for a randomly selected module. Figures 1-3 The angle θ is used to describe the angle θ at which the tape begins to move. initial It can be set to 0° or above 0°. θ initial The larger the value of θ, the greater the change in the effective distance between the servo signal readout elements relative to the change in angle θ. Therefore, from the viewpoint of adjusting the ability to adjust the effective distance between the servo signal readout elements in accordance with the dimensional change in the width direction of the magnetic tape, this is preferable. From this perspective, θ initialPreferably, the angle is 1° or more, more preferably 5° or more, and even more preferably 10° or more. On the other hand, regarding the angle (generally referred to as the "winding angle") between the magnetic layer surface and the contact surface of the magnetic head when the magnetic tape travels and contacts the magnetic head, keeping the deviation related to the tape width direction small is effective in improving the uniformity of friction in the tape width direction caused by the contact between the magnetic head and the tape during tape travel. Furthermore, from the viewpoint of head position tracking and tape travel stability, it is preferable to improve the uniformity of the aforementioned friction in the tape width direction. From the viewpoint of reducing the deviation in the tape width direction of the aforementioned winding angle, θ initial Preferably, the angle is 45° or less, more preferably 40° or less, and even more preferably 35° or less.

[0257] Regarding the change in angle θ during tape transport, the angle θ of the magnetic head during the tape transport within the tape drive changes from θ at the start of transport. initial In cases where changes occur to the data recorded onto and / or played back on the tape, the maximum change Δθ in the angle θ during tape travel is calculated using the following formula: max and Δθ min The larger value in the middle. The maximum value of the angle θ during tape travel is θ. max The minimum value is θ min Additionally, "max" is an abbreviation for maximum, and "min" is an abbreviation for mini mum.

[0258] Δθ max =θ max -θ initial

[0259] Δθ min =θ initial -θ min

[0260] In one embodiment, Δθ can exceed 0.000°. From the viewpoint of adjusting the effective distance between servo signal reading elements in accordance with dimensional changes in the width direction of the magnetic tape, it is preferably 0.001° or more, more preferably 0.010° ​​or more. Furthermore, from the viewpoint of facilitating the synchronization of recorded and / or played data among multiple magnetic head elements during data recording and / or data playback, Δθ is preferably 1.000° or less, more preferably 0.900° or less, further preferably 0.800° or less, even more preferably 0.700° or less, and even more preferably 0.600° or less.

[0261] exist Figure 2 and Figure 3In the example shown, the axis of the element array is inclined toward the direction of magnetic tape transport. However, the invention is not limited to this example. Embodiments in the above-described magnetic tape apparatus where the axis of the element array is inclined in the opposite direction to the direction of magnetic tape transport are also included in the invention.

[0262] θ is the tilt angle of the magnetic head when the magnetic tape starts to move. initial It can be set through the control device of the magnetic tape device, etc.

[0263] Regarding the tilt angle of the magnetic head during magnetic tape transport. Figure 6 This is an explanatory diagram of the method for measuring the angle θ during magnetic tape travel. The angle θ during magnetic tape travel can be determined, for example, by the following method. When the angle θ during magnetic tape travel is determined by the following method, the angle θ changes within the range of 0 to 90° during magnetic tape travel. That is, if the axis of the component array is tilted towards the direction of magnetic tape travel when the tape begins to travel, then during magnetic tape travel, the component array will not tilt so that its axis is tilted in the opposite direction to the direction of magnetic tape travel when the tape begins to travel; conversely, if the axis of the component array is tilted in the opposite direction to the direction of magnetic tape travel when the tape begins to travel, then during magnetic tape travel, the component array will not tilt so that its axis is tilted towards the direction of magnetic tape travel when the tape begins to travel.

[0264] The phase difference (i.e., time difference) ΔT of the playback signals from a pair of servo signal reading elements 1 and 2 is measured. ΔT can be measured using a measuring unit installed in the magnetic tape drive. The structure of this measuring unit is known. The distance L between the center of servo signal reading element 1 and the center of servo signal reading element 2 can be measured using an optical microscope or the like. When the magnetic tape travels at a speed v, the distance between the center of the two servo signal reading elements in the magnetic tape travel direction is Lsinθ, and the relationship Lsinθ = v × ΔT holds. Therefore, the angle θ during magnetic tape travel can be calculated using the formula "θ = arcsin(vΔT / L)". Furthermore, Figure 6 The right figure shows an example where the axis of the element array is tilted towards the direction of the magnetic tape transport. In this example, the phase difference (i.e., time difference) ΔT between the phase of the playback signal from servo signal readout element 2 and the phase of the playback signal from servo signal readout element 1 is measured. When the axis of the element array is tilted in the opposite direction to the direction of the magnetic tape transport, ΔT is measured as the phase difference (i.e., time difference) between the phase of the playback signal from servo signal readout element 1 and the phase of the playback signal from servo signal readout element 2. Otherwise, θ can be calculated using the method described above.

[0265] Furthermore, the measurement interval of angle θ (i.e., the measurement interval of angle θ related to the length direction of the magnetic tape) can be selected based on the frequency of bandwidth deformation related to the length direction of the magnetic tape. As an example, the measurement interval can be set to 250 μm.

[0266] <Structure of magnetic tape device>

[0267] Figure 7 The magnetic tape device 10 shown controls the recording and playback head unit 12 according to the command from the control device 11 to record and play data for the magnetic tape MT.

[0268] The magnetic tape device 10 has a structure capable of detecting and adjusting the tension applied to the magnetic tape in the length direction by the spindle motors 17A, 17B and their drive devices 18A, 18B from the rotating control tape cassette reel and take-up reel.

[0269] The magnetic tape device 10 has a structure capable of loading magnetic tape cartridges 13.

[0270] The magnetic tape device 10 has a cartridge memory read / write device 14 capable of reading and writing to the cartridge memory 131 inside the magnetic tape cartridge 13.

[0271] The magnetic tape MT is pulled out from the end of the tape cassette 13 installed in the magnetic tape device 10 by an automatic loading mechanism or by manual pulling out of the guide pin, with the magnetic layer surface of the tape MT in contact with the recording and playback head surface of the recording and playback head unit 12, so that it passes through the guide rollers 15A and 15B and the recording and playback head, thereby winding the tape MT onto the take-up reel 16.

[0272] The rotation and torque of spindle motors 17A and 17B are controlled based on signals from control device 11, allowing the magnetic tape MT to travel at any speed and tension. Control of tape speed and head tilt angle can be achieved using a servo pattern pre-formed on the tape. A tension detection mechanism can be installed between the tape cassette 13 and the take-up reel 16 to detect tension. In addition to control by spindle motors 17A and 17B, tension control can also be achieved using guide rollers 15A and 15B.

[0273] The cartridge memory read / write device 14 is configured to read and write information from the cartridge memory 131 according to commands from the control device 11. The communication method between the cartridge memory read / write device 14 and the cartridge memory 131 can, for example, employ ISO (International Organization for Standardization) 14443.

[0274] The control device 11 includes, for example, a control unit, a storage unit, and a communication unit.

[0275] The recording and playback head unit 12 comprises, for example, a recording and playback head, a servo tracking actuator for adjusting the position of the recording and playback head in the track width direction, a recording and playback amplifier 19, and a connector cable for connecting to the control device 11. The recording and playback head comprises, for example, a recording element for recording data on the magnetic tape, a playback element for playing back the data on the magnetic tape, and a servo signal reading element for reading the servo signals recorded on the magnetic tape. For example, one or more recording elements, playback elements, and servo signal reading elements may be mounted within a single head. Alternatively, each element may be individually housed within multiple heads corresponding to the magnetic tape's travel direction.

[0276] The recording and playback head unit 12 is configured to record data onto the magnetic tape MT according to commands from the control device 11. Furthermore, it is configured to play back the data recorded on the magnetic tape MT according to commands from the control device 11.

[0277] The control device 11 has a mechanism that determines the tape travel position based on servo signals read from servo tapes during tape travel and controls a servo tracking actuator to position the recording element and / or playback element at a target tape travel position (track position). This track position control is performed, for example, through feedback control. The control device 11 also has a mechanism that determines the servo tape interval based on servo signals read from two adjacent servo tapes during tape travel. The control device 11 can store the determined servo tape interval information in its internal storage unit, cartridge memory 131, or external connection devices. Furthermore, the control device 11 can change the head tilt angle based on the tape width dimension information during tape travel. This allows the effective distance between servo signal reading elements to be close to or consistent with the servo tape interval. This dimension information can be obtained using a servo pattern pre-formed on the tape. For example, the angle θ between the axis of the element array and the tape width direction during tape travel can be changed based on the tape width dimension information obtained during tape travel within the tape drive. The tilt angle of the magnetic head can be adjusted, for example, through feedback control. Furthermore, the tilt angle of the magnetic head can also be adjusted, for example, by the methods described in Japanese Patent Publication No. 2016-524774 (Patent Document 1) or US2019 / 0164573A1 (Patent Document 2).

[0278] Example

[0279] The present invention will now be described with reference to embodiments. However, the present invention is not limited to the embodiments shown in the examples. The term "parts" as used below refers to "parts by mass". Furthermore, unless otherwise specified, the processes and evaluations described below are performed at a temperature of 23°C ± 1°C. The term "eq" as used below refers to equivalent, a unit that cannot be converted to SI units.

[0280] [Protrusion-forming agent]

[0281] The protrusion forming agents used in the preparation of the magnetic layer forming composition for making the magnetic tapes of the embodiments or comparative examples are as follows. The particle shapes of protrusion forming agents A and B are so-called irregular shapes.

[0282] Protrusion forming agent A: ASAHI #50 (carbon black) manufactured by ASAHI CARBON CO.,LTD., with an average particle size of 60nm.

[0283] Protrusion forming agent B: #45L (carbon black) manufactured by Mitsubishi Chemical Corporation, average particle size 60nm

[0284] [Fatty acid esters]

[0285] The following fatty acid esters are used in the preparation of magnetic layer forming compositions and non-magnetic layer forming compositions for the production of magnetic tapes of the examples or comparative examples.

[0286] Fatty acid ester A: Stearic acid sec (secondary) butyl ester

[0287] Fatty acid ester B: Butyl palmitate

[0288] Fatty acid ester C: Butyl myristate

[0289] Fatty acid ester D: Butyl laurate

[0290] Fatty acid ester E: Butyl decanoate

[0291] Fatty acid ester F: Butyl octanoate

[0292] Fatty acid ester G: Butyl hexanoate

[0293] [Strongly magnetic powder]

[0294] In Table 1, “BaFe” refers to hexagonal barium ferrite powder (magnetic force Hc: 196kA / m, average particle size (average plate diameter) 24nm).

[0295] In Table 1, “SrFe1” refers to hexagonal strontium ferrite powder produced by the following method.

[0296] Weigh out 1707g of SrCO3, 687g of H3BO3, 1120g of Fe2O3, 45g of Al(OH)3, 24g of BaCO3, 13g of CaCO3 and 235g of Nd2O3, and mix them in a mixer to obtain a raw material mixture.

[0297] The obtained raw material mixture was melted in a platinum crucible at a melting temperature of 1390°C. While stirring the melt, the melt outlet located at the bottom of the platinum crucible was heated, and the melt was discharged into a rod shape at a rate of approximately 6 g / s. The discharged melt was then rapidly cooled by rolling using water-cooled twin rollers to produce an amorphous substance.

[0298] 280g of the prepared amorphous material was placed in an electric furnace and heated to 635℃ (crystallization temperature) at a heating rate of 3.5℃ / min, and kept at the same temperature for 5 hours to allow hexagonal strontium ferrite particles to precipitate (crystallize).

[0299] Next, the crystals obtained above, containing hexagonal strontium ferrite particles, were coarsely pulverized in a mortar. Then, 1000g of 1mm zirconium oxide beads and 800ml of a 1% acetic acid aqueous solution were added to a glass bottle containing the contents, and the mixture was dispersed using a paint stirrer for 3 hours. The resulting dispersion was then separated from the beads and placed in a stainless steel beaker. After dissolving the glass components by standing the dispersion at 100°C for 3 hours, it was precipitated using a centrifuge and repeatedly decanted for washing. Finally, it was dried in a furnace at 110°C for 6 hours to obtain hexagonal strontium ferrite powder.

[0300] The hexagonal strontium ferrite powder obtained above has an average particle size of 18 nm and an activation volume of 902 nm. 3 The anisotropy constant Ku is 2.2 × 10⁻⁶. 5 J / m 3 The mass magnetization σs is 49 A·m 2 / kg.

[0301] 12 mg of sample powder was collected from the hexagonal strontium ferrite powder obtained above. The elemental composition of the filtrate obtained by partially dissolving the sample powder under the above-described dissolution conditions was determined by an ICP analyzer.

[0302] In addition, 12 mg of sample powder was collected from the hexagonal strontium ferrite powder obtained above, and the elemental analysis of the filtrate obtained by completely dissolving the sample powder under the above-described dissolution conditions was performed using an ICP analysis device to determine the bulk content of neodymium atoms.

[0303] In the hexagonal strontium ferrite powder obtained above, the content of neodymium atoms relative to 100 atomic% of iron atoms (bulk content) is 2.9 atomic%. Furthermore, the surface portion of neodymium atoms contains 8.0 atomic%. The ratio of surface portion content to bulk content, "surface portion content / bulk content", is 2.8, confirming that neodymium atoms are predominantly located on the surface of the particles.

[0304] By scanning CuKα rays at a voltage of 45 kV and an intensity of 40 mA, and measuring the X-ray diffraction pattern under the following conditions (X-ray diffraction analysis), it was confirmed that the powder obtained above exhibits a hexagonal ferrite crystal structure. The powder obtained above exhibits a magnetoplumbleite-type (M-type) hexagonal ferrite crystal structure. Furthermore, the crystal phase detected by X-ray diffraction analysis is a magnetoplumbleite-type single phase.

[0305] PANalytical X'Pert Pro diffractometer, PIXcel detector

[0306] Soller slit for incident and diffracted beams: 0.017 radians

[0307] Fixed angle of the dispersing slit: 1 / 4 degree

[0308] Mask: 10mm

[0309] Slit prevention for scattering: 1 / 4 degree

[0310] Measurement mode: Continuous

[0311] Measurement time for each stage: 3 seconds

[0312] Measurement speed: 0.017 degrees per second

[0313] Measurement step size: 0.05 degrees

[0314] In Table 1, “SrFe2” refers to hexagonal strontium ferrite powder produced by the following method.

[0315] Weigh out 1725g of SrCO3, 666g of H3BO3, 1332g of Fe2O3, 52g of Al(OH)3, 34g of CaCO3, and 141g of BaCO3, and mix them in a mixer to obtain a raw material mixture.

[0316] The obtained raw material mixture was melted in a platinum crucible at a melting temperature of 1380°C. While stirring the melt, the melt outlet located at the bottom of the platinum crucible was heated, and the melt was discharged into a rod shape at a rate of approximately 6 g / s. The discharged melt was then subjected to calendering and rapid cooling using water-cooled twin rollers to produce an amorphous substance.

[0317] The obtained amorphous body of 280g was placed in an electric furnace and heated to 645℃ (crystallization temperature). The temperature was maintained at the same temperature for 5 hours to allow hexagonal strontium ferrite particles to precipitate (crystallize).

[0318] Next, the crystals obtained above, containing hexagonal strontium ferrite particles, were coarsely pulverized in a mortar. Then, 1000g of 1mm zirconium oxide beads and 800ml of a 1% acetic acid aqueous solution were added to a glass bottle containing the contents, and the mixture was dispersed using a paint stirrer for 3 hours. The resulting dispersion was then separated from the beads and placed in a stainless steel beaker. After dissolving the glass components by standing the dispersion at 100°C for 3 hours, it was precipitated using a centrifuge and repeatedly decanted for washing. Finally, it was dried in a furnace at 110°C for 6 hours to obtain hexagonal strontium ferrite powder.

[0319] The obtained hexagonal strontium ferrite powder has an average particle size of 19 nm and an activation volume of 1102 nm. 3 The anisotropy constant Ku is 2.0 × 10⁻⁶. 5 J / m 3 The mass magnetization σs is 50 A·m 2 / kg.

[0320] In Table 1, “ε-iron oxide” refers to ε-iron oxide powder produced by the following method.

[0321] A solution obtained by dissolving 8.3 g of ferric(III) nonahydrate, 1.3 g of gallium(III) octahydrate, 190 mg of cobalt(II) hexahydrate, 150 mg of titanium(IV) sulfate, and 1.5 g of polyvinylpyrrolidone (PVP) in 90 g of pure water was stirred using a magnetic stirrer. Simultaneously, 4.0 g of a 25% ammonia solution was added to the solution under atmospheric conditions and an ambient temperature of 25°C. The mixture was stirred for 2 hours while maintaining the ambient temperature at 25°C. A citric acid solution obtained by dissolving 1 g of citric acid in 9 g of pure water was then added to the resulting solution, and the mixture was stirred for 1 hour. The precipitated powder was collected by centrifugation, washed with pure water, and dried in a furnace at 80°C.

[0322] 800g of pure water was added to the dried powder to redisperse it, yielding a dispersion. The dispersion was heated to 50°C, and 40g of a 25% ammonia solution was added dropwise while stirring. After stirring at 50°C for 1 hour, 14mL of tetraethoxysilane (TEOS) was added, and stirring continued for 24 hours. 50g of ammonium sulfate was added to the resulting reaction solution. The precipitated powder was collected by centrifugation, washed with pure water, and dried in an oven at 80°C for 24 hours to obtain a precursor for the strongly magnetic powder.

[0323] The obtained strong magnetic powder precursor was placed in a heating furnace at a temperature of 1000℃ under atmospheric conditions and subjected to heating treatment for 4 hours.

[0324] The precursor of the heat-treated strong magnetic powder was added to a 4 mol / L sodium hydroxide (NaOH) aqueous solution, and the solution temperature was maintained at 70°C and stirred for 24 hours, thereby removing the silica compound as an impurity from the precursor of the heat-treated strong magnetic powder.

[0325] Then, the strongly magnetic powder after removing the silica compounds was collected by centrifugation and washed with pure water to obtain the strongly magnetic powder.

[0326] The composition of the strongly magnetic powder, confirmed by high-frequency inductively coupled plasma-optical emission spectrometry (ICP-OES), was Ga, Co, and Ti-substituted ε-iron oxide (ε-Ga). 0.28 Co 0.05 Ti 0.05 Fe 1.62 O3). Furthermore, under the same conditions as those described above for SrFe1, X-ray diffraction analysis was performed, and the peaks of the X-ray diffraction pattern confirmed that the obtained strongly magnetic powder has a single-phase ε-phase crystal structure (the crystal structure of ε-iron oxide) that does not contain α-phase or γ-phase crystal structures.

[0327] The obtained ε-iron oxide powder had an average particle size of 12 nm and an activation volume of 746 nm. 3 The anisotropy constant Ku is 1.2 × 10⁻⁶. 5 J / m 3 The mass magnetization σs is 16 A·m 2 / kg.

[0328] The activation volume and anisotropy constant Ku of the hexagonal strontium ferrite powder and ε-iron oxide powder mentioned above were obtained by using a vibrating sample magnetometer (manufactured by TOEI INDUSTRY CO.,LTD.) for each strongly magnetic powder using the above method.

[0329] Furthermore, the mass magnetization σs was measured using a vibrating sample type magnetometer (manufactured by TOEI INDUSTRY CO.,LTD.) at a magnetic field strength of 15 kOe.

[0330] [Non-magnetic support]

[0331] In Table 1, “PEN” represents polyethylene naphthalate support and “PA” represents aromatic polyamide support.

[0332] [Example 1]

[0333] <Composition for forming magnetic layers>

[0334] (Magnetic fluid)

[0335] Strongly magnetic powder (refer to Table 1): 100.0 parts

[0336] Oleic acid: 2.0 parts

[0337] Vinyl chloride copolymer (KANEKA CORPORATION MR-104): 10.0 parts

[0338] Polyurethane resin containing SO3Na groups: 4.0 parts

[0339] (Weight-average molecular weight 70,000, SO3Na group: 0.07 meq / g)

[0340] Additive A: 10.0 parts

[0341] Methyl ethyl ketone: 150.0 parts

[0342] Cyclohexanone: 150.0 parts (grinding solution)

[0343] α-Alumina (average particle size: 110 nm): 6.0 parts

[0344] Vinyl chloride copolymer (KANEKA CORPORATION MR110): 0.7 parts

[0345] Cyclohexanone: 20.0 parts

[0346] (Protrusion-forming agent solution)

[0347] Protrusion forming agents (refer to Table 1): Refer to Table 1

[0348] Methyl ethyl ketone: 9.0 parts

[0349] Cyclohexanone: 6.0 parts

[0350] (Other ingredients)

[0351] Stearic acid: 1.0 part

[0352] Stearamide: 0.3 parts

[0353] Fatty acid esters (refer to Table 1): Refer to Table 1

[0354] Methyl ethyl ketone: 110.0 parts

[0355] Cyclohexanone: 110.0 parts

[0356] Polyisocyanate (TOSOH CORPORATION CORONATE (registered trademark) L): 3.0 parts

[0357] The additive A mentioned above is a polymer synthesized by the method described in paragraphs 0115 to 0123 of Japanese Patent Application Publication No. 2016-051493.

[0358] <Composition for forming non-magnetic layers>

[0359] Non-magnetic inorganic powder (α-iron oxide): 80.0 parts

[0360] (Average particle size: 0.15 μm, average needle ratio: 7, BET (Brunauer-Emmett-Teller) specific surface area: 52 m²) 2 / g)

[0361] Carbon black (average particle size: 20 nm): 20.0 parts

[0362] Electron beam cured vinyl chloride copolymer: 13.0 parts

[0363] Electron beam cured polyurethane resin: 6.0 parts

[0364] Phenylated phosphonic acid: 3.0 parts

[0365] Cyclohexanone: 140.0 parts

[0366] Methyl ethyl ketone: 170.0 parts

[0367] Fatty acid esters of the same type as those added to the composition for forming the magnetic layer: 2.0 parts; stearic acid: 1.0 part

[0368] <Composition for forming back coating>

[0369] Non-magnetic inorganic powder (α-iron oxide): 80.0 parts

[0370] (Average particle size: 0.15 μm, average needle ratio: 7, BET specific surface area: 52 m²) 2 / g)

[0371] Carbon black (average particle size: 20 nm): 20.0 parts

[0372] Carbon black (average particle size: 100 nm): 3.0 parts

[0373] Vinyl chloride copolymer: 13.0 parts

[0374] Polyurethane resin containing sulfonic acid groups: 6.0 parts

[0375] Phenylated phosphonic acid: 3.0 parts

[0376] Cyclohexanone: 140.0 parts

[0377] Methyl ethyl ketone: 170.0 parts

[0378] Stearic acid: 3.0 parts

[0379] Polyisocyanate (TOSOH CORPORATION CORONATE (registered trademark) L): 5.0 parts; Methyl ethyl ketone: 400.0 parts

[0380] <Preparation of the composition for forming each layer>

[0381] The composition for forming a magnetic layer is prepared by the following method.

[0382] After the magnetic liquid was mixed and diluted using an open kneader, it was dispersed 12 times using a horizontal bead mill disperser with 0.5 mm zirconium oxide (ZrO2) beads (hereinafter referred to as "Zr beads") at a bead filling rate of 80% by volume and a rotor front end circumferential speed of 10 m / s. The residence time for each time was set to 2 minutes.

[0383] Regarding the grinding agent solution, after mixing the components of the grinding agent solution, it was placed together with Zr beads with a particle size of 1mm into a vertical sand mill disperser. The solution was adjusted to 100 × bead volume / (grind agent solution volume + bead volume) = 60%, and the mixture was sand milled and dispersed for 180 minutes. The treated liquid was then removed and subjected to ultrasonic dispersion and filtration using a flow-type ultrasonic dispersion and filtration device.

[0384] After mixing the components of the protrusion-forming agent solution, the solution was ultrasonically treated (dispersion treatment) for 60 minutes using a horn-type ultrasonic disperser with an ultrasonic output of 500 watts per 200cc to obtain a dispersion. The dispersion was then filtered through a filter with a pore size of 0.5μm to prepare the protrusion-forming agent solution.

[0385] The magnetic fluid, abrasive fluid, protrusion forming agent fluid, and other components were introduced into a dissolving mixer and stirred at a circumferential speed of 10 m / s for 30 minutes. After being processed three times using a flow ultrasonic disperser at a flow rate of 7.5 kg / min, the mixture was filtered through a filter with a pore size of 1 μm to prepare a composition for forming a magnetic layer.

[0386] The composition for forming a nonmagnetic layer is prepared by the following method.

[0387] After mixing and diluting the above-mentioned components (excluding lubricants (fatty acid esters and stearic acid)) using an open kneader, dispersion was carried out for 360 minutes using a horizontal bead mill disperser. Then, lubricants (fatty acid esters and stearic acid) were added, and the mixture was stirred using a dissolving mixer to prepare a composition for forming a non-magnetic layer.

[0388] The composition for forming the back coating is prepared by the following method.

[0389] The above-mentioned components, excluding lubricant (stearic acid), polyisocyanate, and methyl ethyl ketone (400.0 parts), were mixed and diluted using an open kneader, and then dispersed using a horizontal bead mill disperser. Next, lubricant (stearic acid), polyisocyanate, and methyl ethyl ketone (400.0 parts) were added, and the mixture was stirred using a dissolving mixer to prepare a composition for forming a back coating.

[0390] <Making of Magnetic Tapes and Cassette Cases>

[0391] On a biaxially stretched nonmagnetic support with the thicknesses shown in Table 1 (types: refer to Table 1), a nonmagnetic layer forming composition was coated to a thickness of 0.6 μm after drying. After drying, the support was irradiated with an electron beam at an accelerating voltage of 125 kV to achieve an energy of 40 kGy. A magnetic layer forming composition was then coated to a thickness of 0.1 μm after drying to form a coating layer. While the coating layer was still wet, a magnetic field with a strength of 0.5 T was applied to the surface of the coating layer of the magnetic layer forming composition in a vertical direction within the alignment region to perform vertical alignment treatment. After drying, the coating layer was then dried. Subsequently, a back coating forming composition was coated to a thickness of 0.3 μm after drying on the surface of the support opposite to the surfaces where the nonmagnetic and magnetic layers were formed, and then dried.

[0392] Then, using a 7-segment calendering roll consisting only of metal rollers, two calendering processes were performed at a calendering speed of 80 m / min, a linear pressure of 294 kN / m, and a calendering temperature (surface temperature of the calendering rolls) of 100°C. Following this, a heat treatment was performed for 36 hours at an ambient temperature of 70°C. After the heat treatment, the magnetic tape was cut into 1 / 2-inch widths and cleaned using a magnetic tape cleaning device mounted on a feed and take-up mechanism with a non-woven fabric and scraper against the magnetic layer surface, thus obtaining a magnetic tape.

[0393] By using a commercially available servo writer to record servo signals on the magnetic layer of the obtained magnetic tape, a magnetic tape is obtained with a configuration based on the LTO (Linear Tape-Open) Ultrium format, consisting of a data tape, a servo tape, and a guide tape, and with a servo pattern (timing-based servo pattern) on the servo tape based on the LTO Ultrium format configuration and shape. The servo pattern thus formed conforms to the servo pattern described in JIS (Japanese Industrial Standards) X6175:2006 and Standard ECMA-319 (June 2001). The total number of servo tapes is 5, and the total number of data tapes is 4.

[0394] The magnetic tape (960m in length) containing the servo signals is wound onto the reel of the tape cassette (LTO Ultrium 8 data cassette).

[0395] In this way, a cassette tape was made that contained the tape reel on a reel.

[0396] [Examples 2-20, Comparative Examples 1-15]

[0397] As shown in Table 1, the items in Table 1 were changed. Apart from that, the magnetic tape and magnetic tape cassette were obtained by the method described in Example 1.

[0398] Regarding the above embodiments and comparative examples, three magnetic tape cassettes were made, one for evaluating the following tape transport stability, and the other two for evaluating the following magnetic tapes (1) and (2), respectively.

[0399] [Evaluation of conveyor belt stability]

[0400] The stability of the conveyor belt was evaluated using the following methods at an environment of 15℃ and 80% relative humidity.

[0401] Each magnetic tape cassette used in the embodiments and comparative examples, and used Figure 7The magnetic tape device shown performs data recording and playback. The modules included in the recording and playback head unit are configured in the order of "recording module - playback module - recording module" (total number of modules: 3). Each module contains 32 head elements (Ch0 to Ch31), which are sandwiched between a pair of servo signal readout elements to form an element array.

[0402] The head tilt angle was set to 15°, and data recording, playback, and evaluation of tape transport stability during playback were performed using the following method. The head tilt angle is the angle θ formed by the axis of the playback module's element array and the width direction of the magnetic tape at the start of tape transport. Angle θ is set by the tape drive's control device at the start of tape transport, and the head tilt angle remains fixed during tape transport.

[0403] A tape cassette is installed in the tape drive, and a tape is loaded. Then, while performing servo tracking, a recording / playback head unit records pseudo-random data with a specific data pattern onto the tape. The tension applied along the length of the tape is kept constant. Simultaneously with data recording, the servo tape interval of the entire tape is measured every 1 meter along its long side and recorded in the cassette memory.

[0404] Next, while performing servo tracking, the data recorded on the magnetic tape is played back using the recording and playback head unit. At this time, the tension applied along the length of the magnetic tape is set to a constant value.

[0405] In the aforementioned playback, the belt transport stability was evaluated using the standard deviation (hereinafter referred to as "σPES") of the read position PES (Position Error Signal) in the width direction of the servo signal obtained by the servo signal readout element as an indicator.

[0406] PES is obtained using the following method.

[0407] To determine the PES, the dimensions of the servo pattern are needed. The standard for the servo pattern dimensions varies depending on the generation of the LTO. Therefore, firstly, the average distance AC between the four corresponding magnetic strips of the A and C bursts and the azimuth angle α of the servo pattern are measured using a magnetic force microscope or similar instrument.

[0408] The average time between the five stripes corresponding to bursts A and B, covering a length of 1 LPOS word, is defined as 'a'. The average time between the four stripes corresponding to bursts A and C, covering a length of 1 LPOS word, is defined as 'b'. The value defined by AC×(1 / 2-a / b) / (2×tan(α)) is the read position PES (Position Error Signal) in the width direction of the servo signal obtained by the servo signal read element covering a length of 1 LPOS word. Regarding the magnetic tape, the end on one side of the reel wound onto the tape cassette is called the inner end, and the end on the opposite side is called the outer end. The outer end is set to 0m. For a region covering a length of 30m to 200m along the length of the magnetic tape, the standard deviation (σPES) of the PES obtained by the above method is calculated.

[0409] The σPES values ​​obtained for the embodiments and comparative examples are shown in Table 1 as relative values ​​to the σPES obtained for Comparative Example 1. That is, "σPES (relative value) = σPES of the embodiment or comparative example to which the relative value is calculated / σPES of Comparative Example 1". If the σPES (relative value) obtained in this way is 0.50 or less, it can be judged that the conveyor belt stability is excellent.

[0410] [Cassette tape review]

[0411] (1) Absolute value of friction before reciprocating sliding, LFM reduction rate, dynamic friction force F

[0412] Tapes were removed from each tape cassette of the examples and comparative examples, and subjected to 500 reciprocating slides using the method described above at 15°C and 80% relative humidity. The LFM output (unit: mV) after the reciprocating slides was measured. The output distribution was then normalized (Min-Max Normalization), and the standard deviation (measured value after reciprocating slides) was calculated. For the portion of the tape that did not undergo 500 reciprocating slides, the LFM output (unit: mV) was measured using the method described above, and the output distribution was normalized (Min-Max Normalization), and the standard deviation (measured value before reciprocating slides) was calculated. Based on the measured values ​​before and after reciprocating slides obtained in this way, the LFM reduction rate was calculated using the above formula.

[0413] Furthermore, as described above, the absolute value of friction before reciprocating sliding was calculated based on the absolute value of friction obtained in the measurement before reciprocating sliding.

[0414] As a horizontal force microscope, a BRUKER Nanoscope 5 (measurement mode: LF M) was used. The horizontal force microscope and probe were calibrated using a commercially available calibration sample (Tokyo Instruments, Inc. TGG1) following the description in Rev. Sci. Instrum., Vol. 67, No. 9, September 1996, via the wedge method.

[0415] Furthermore, using the above method, the kinetic friction force F on the 500th path in 500 reciprocating slides was calculated.

[0416] As an LTO8 head, a commercially available LTO8 head (manufactured by IBM) was used.

[0417] (2) Magnetic tape thickness

[0418] Ten tape samples (5 cm in length) were cut from any portion of the tape taken from each tape cassette of the Examples and Comparative Examples, and the thickness of these samples was measured by overlapping them. The thickness was measured using a digital thickness gauge with a Millimar 1240 compact amplifier and a Millimar 1301 inductive probe manufactured by MARH. The thickness of each tape sample was taken as the tape thickness by dividing the measured thickness by 10. For each tape of Examples 1-17 and Comparative Examples 1-15, the tape thickness was 5.0 μm. The tape thicknesses of each tape of Examples 18-20 are as follows: Example 18: 4.6 μm, Example 19: 4.0 μm, Example 20: 3.4 μm.

[0419] The results are shown in Table 1 (Table 1-1 to Table 1-7).

[0420] [Table 1-1]

[0421]

[0422] [Table 1-2]

[0423]

[0424] [Table 1-3]

[0425]

[0426] [Table 1-4]

[0427]

[0428] [Table 1-5]

[0429]

[0430] [Table 1-6]

[0431]

[0432] [Table 1-7]

[0433]

[0434] The results shown in Table 1 confirm that the magnetic tapes of the embodiments with an absolute friction value of less than 0.10 nN before reciprocating sliding and an LFM reduction rate of more than 20% exhibit excellent tape-running stability when the magnetic head is tilted in a low temperature and high humidity environment.

[0435] The magnetic tape was manufactured without vertical orientation treatment, but otherwise, the magnetic tape was manufactured using the method described in Example 1.

[0436] Sample pieces were cut from the aforementioned magnetic tape. A TM-TRVSM5050-SMSL type magnetometer manufactured by TAMAKAWA CO.,LTD was used as the vibration-test type magnetometer. The vertical rectangle ratio of the sample piece was determined to be 0.55 using the method described above.

[0437] Similarly, the vertical rectangle ratio of the sample piece cut from the magnetic tape of Example 1 was 0.65.

[0438] The two magnetic tapes were mounted onto a 1 / 2-inch reel testing machine, and their electromagnetic conversion characteristics (SNR: Signal-to-Noise Ratio) were evaluated using the following method. As a result, the magnetic tape of Example 1 achieved an SNR value 4 dB higher than that of the magnetic tape manufactured without vertical orientation treatment.

[0439] Ten recording and playback cycles were performed under an environment of 23°C and 50% relative humidity, with a tension of 0.7 N applied along the length of the magnetic tape. The relative speed between the tape and the magnetic head was set to 6 m / s. A MIG (Metal-in-Gap) head (0.15 μm gap length, 1.0 μm track width) was used as the recording head, and the recording current was set to the optimal recording current for each tape. A GMR (Giant-magnetoresistive) head (15 nm element thickness, 0.1 μm shielding spacing, 0.8 μm playback element width) was used as the playback head. The head tilt angle was set to 0°. A signal with a line recording density of 300 kfci was recorded, and the playback signal was measured using a spectrum analyzer manufactured by Shibasoku Co., Ltd. The unit kfci is the unit of line recording density (cannot be converted to SI units).

[0440] (Control). As a signal, the portion of the signal that is sufficiently stable after the tape begins to move is used.

[0441] Industrial availability

[0442] One aspect of the present invention is useful in the field of various data storage technologies.

Claims

1. A magnetic tape having a non-magnetic support and a magnetic layer containing strongly magnetic powder, The absolute value of friction on the surface of the magnetic layer of the magnetic tape, measured using a horizontal force microscope within a 3μm × 3μm measurement area, was less than 0.10 nN before the magnetic head slid back and forth 500 times relative to the LTO8 magnetic head at a 15° tilt angle under an environment of 15° temperature and 80% relative humidity. The standard deviation of the friction distribution on the surface of the magnetic layer, measured using a horizontal force microscope in a 3μm×3μm measurement area before and after 500 reciprocating slides relative to the LTO8 magnetic head at a 15° tilt angle under an environment of 15° temperature and 80% relative humidity, decreased by more than 20%.

2. The magnetic tape according to claim 1, wherein, The kinetic friction force F on the path of the 500th reciprocating slide in the 500th reciprocating slide is less than 15gf.

3. The magnetic tape according to claim 1, wherein, The absolute value of the friction is greater than 0.02nN and less than 0.10nN.

4. The magnetic tape according to claim 1, wherein, The reduction rate is above 20% and below 25%.

5. The magnetic tape according to claim 1, wherein, Between the non-magnetic support and the magnetic layer, there is also a non-magnetic layer containing non-magnetic powder.

6. The magnetic tape according to claim 1, wherein, The non-magnetic support also has a back coating containing non-magnetic powder on the side opposite to the side with the magnetic layer.

7. The magnetic tape according to claim 1, wherein, The magnetic tape has a thickness of less than 5.0 μm.

8. The magnetic tape according to claim 1, wherein, The vertical rectangularity ratio of the magnetic tape is 0.60 or higher.

9. The magnetic tape according to claim 1, wherein, The vertical rectangularity ratio of the magnetic tape is 0.65 or higher.

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

11. The magnetic tape according to claim 1, wherein, The kinetic friction force F on the path of the 500th reciprocating slide in the 500th reciprocating slide is less than 15gf. The absolute value of the friction is greater than or equal to 0.02 nN and less than or equal to 0.10 nN. The reduction rate is above 20% and below 25%. The magnetic tape also has a non-magnetic layer containing non-magnetic powder between the non-magnetic support and the magnetic layer. The non-magnetic support also has a back coating containing non-magnetic powder on the surface opposite to the surface with the magnetic layer. The magnetic tape thickness is less than 5.0 μm, and The vertical rectangularity ratio of the magnetic tape is 0.60 or higher.

12. A magnetic tape cassette comprising the magnetic tape according to any one of claims 1 to 11.

13. A magnetic tape device comprising the magnetic tape according to any one of claims 1 to 11.

14. The magnetic tape device according to claim 13, wherein, Also includes the magnetic head, The magnetic head has a module comprising an array of elements having a plurality of head elements between a pair of servo signal readout elements, and In the magnetic tape device, as the magnetic tape travels within the device, the angle θ between the axis of the element array and the width direction of the magnetic tape is changed.

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