Magnetic tape, magnetic tape cassette and magnetic tape apparatus

Abstract

The present application provides a magnetic tape having a non-magnetic support and a magnetic layer containing a ferromagnetic powder, wherein the reduction rate of the standard deviation of the friction distribution measured by a lateral force microscope in a 3 μm x 3 μm measurement area on the surface of the magnetic layer before and after reciprocating sliding 500 times at a head tilt angle of 15° with respect to an LTO8 magnetic head in an environment at a temperature of 15°C and a relative humidity of 80% is 20% or more.

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 (for example, see Patent Documents 1-3).

[0003] Previous technical documents Patent documents Patent Document 1: Japanese Patent Publication No. 2016-524774 Patent Document 2: US2019 / 0164573A1 Patent Document 3: Description of Japanese Patent No. 6590104 Summary of the Invention

[0004] The technical problem to be solved by the invention 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 reproducing 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.

[0005] 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.

[0006] The following is also proposed: Servo signals are used to acquire the dimensional information (shrinkage, elongation, etc.) of the magnetic tape in the width direction during the 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 (see Patent Documents 1 and 2, for example, paragraphs 0059-0067 and 0084 of Patent Document 1). If, during recording or playback, the magnetic head used for recording or playback 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 changing the head tilt angle as described above is one method to suppress the occurrence of this phenomenon.

[0007] For example, assuming the head tilt angle changes as described above, it is preferable to perform data recording and / or playback by tilting the axial direction of the head module relative to the width direction of the magnetic tape (i.e., tilting the head), which results in high tape transport stability. This is because high tape transport stability is believed to help, for example, further suppress the occurrence of the aforementioned phenomena.

[0008] In recent years, magnetic tapes have sometimes been used in data centers where temperature and humidity are controlled.

[0009] On the other hand, data centers require energy efficiency to reduce costs. To achieve energy efficiency, it is preferable to relax the management conditions of the tape usage environment within the data center, or even eliminate the need for management altogether.

[0010] However, if the management conditions of the usage environment are relaxed or not managed at all, it is foreseeable that the magnetic tape will be used in environments such as low temperature and high humidity. Therefore, it is preferable to have a magnetic tape with excellent tape transport stability when recording and / or reproducing data by tilting the magnetic head in low temperature and high humidity environments.

[0011] One objective of this invention is to provide a magnetic tape with excellent tape transport stability when recording and / or reproducing with a tilted magnetic head in a low-temperature and high-humidity environment.

[0012] means for solving technical problems One aspect of the present invention is described below.

[0013] [1] A magnetic tape having a non-magnetic support and a magnetic layer comprising strongly magnetic powder, wherein, In an environment of 15°C and 80% relative humidity, the standard deviation of the friction distribution measured by a transverse force microscope in a 3μm×3μm measurement area on the surface of the magnetic layer before and after 500 reciprocating slides of the LTO (Linear Tape-Open) 8 magnetic head at a head tilt angle of 15°, was reduced by more than 20%.

[0014] [2] According to the magnetic tape described in [1], wherein, The dynamic friction force F (hereinafter also referred to as "dynamic friction force F") in the 500th stroke of the above 500 reciprocating sliding motion is less than 15gf.

[0015] [3] According to the magnetic tape described in [1] or [2], wherein, The aforementioned reduction rate is between 20% and 30%.

[0016] [4] The magnetic tape according to any one of [1] to [3], wherein, The aforementioned reduction rate is between 22% and 30%.

[0017] [5] The magnetic tape according to any one of [1] to [4], wherein, The aforementioned reduction rate is between 24% and 30%.

[0018] [6] The magnetic tape according to any one of [1] to [5], wherein, Between the aforementioned non-magnetic support and the aforementioned magnetic layer, there is also a non-magnetic layer containing non-magnetic powder.

[0019] [7] The magnetic tape according to any one of [1] to [6], wherein, The non-magnetic support has a back coating containing non-magnetic powder on the side opposite to the side with the magnetic layer.

[0020] [8] The magnetic tape according to any one of [1] to [7], wherein, The magnetic tape thickness is less than 5.0 μm.

[0021] [9] The magnetic tape according to any one of [1] to [8], wherein, The vertical rectangle ratio of the aforementioned magnetic tape is 0.60 or higher.

[0022]

[10] The magnetic tape according to any one of [1] to [9], wherein, The vertical rectangularity ratio of the aforementioned magnetic tape is 0.65 or higher.

[0023]

[11] The magnetic tape according to any one of [1] to

[10] , wherein, The aforementioned non-magnetic support is an aromatic polyamide support.

[0024]

[12] According to the magnetic tape described in [1], wherein, The dynamic friction force F in the 500th stroke of the above 500 reciprocating sliding motion is less than 15gf. Between the aforementioned non-magnetic support and the aforementioned magnetic layer, there is also a non-magnetic layer containing non-magnetic powder. 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 aforementioned magnetic tape is 0.60 or higher.

[0025]

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

[12] .

[0026]

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

[12] .

[0027]

[15] The magnetic tape device according to

[14] further includes a magnetic head. The aforementioned magnetic head has a module, the module comprising an array of elements having a plurality of magnetic head elements between a pair of servo signal readout elements, and 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.

[0028] Invention Effects 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 a low-temperature and high-humidity environment. Furthermore, according to one aspect of the present invention, a magnetic tape cassette and a magnetic tape assembly comprising the aforementioned magnetic tape can be provided. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of an example of a module representing a magnetic head.

[0030] Figure 2 This is an illustration of the relative positional relationship between the modules and the magnetic tape during its transport within the magnetic tape device.

[0031] Figure 3 This is an explanatory diagram related to the change of angle θ during magnetic tape transport.

[0032] Figure 4 This shows a configuration example for the data band and servo band.

[0033] Figure 5 This represents a servo pattern configuration example for LTO Ultrium format magnetic tape.

[0034] Figure 6 This is an explanatory diagram illustrating the method for measuring the angle θ during magnetic tape transport.

[0035] Figure 7 This is a schematic diagram illustrating an example of a magnetic tape device. Detailed Implementation

[0036] [Cassette tape] One aspect of the present invention relates to a magnetic tape having a non-magnetic support and a magnetic layer containing strongly magnetic powder. Under conditions of 15°C and 80% relative humidity, after the magnetic tape is slid back and forth 500 times with a head tilt angle of 15° relative to an LTO8 magnetic head, the standard deviation of the friction distribution on the surface of the magnetic layer, measured by a lateral force microscope (LFM) within a 3μm × 3μm measurement area, shows a reduction rate of 20% or more. This reduction rate is also referred to as the "LFM reduction rate".

[0037] <Head tilt angle> Before explaining the head tilt angle mentioned above, the LTO8 magnetic head will be explained first. Furthermore, the reasons why it is believed that tilting the axis of the magnetic head module relative to the width direction of the magnetic tape during tape transport can suppress the phenomena that occur during recording or playback.

[0038] 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 applies to other generations of drives as well. Furthermore, when multiple magnetic tapes to be tested are slid back and forth relative to the LTO8 head at a 15° head tilt angle, it is assumed that a new (i.e., unused) LTO8 head is used for each tape test. 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 tapes used in LTO8 drives. The aforementioned magnetic tapes can record and / or reproduce data in LTO8 drives, LTO9 drives or next-generation drives, or even LTO7 and other drives prior to LTO8.

[0039] 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.

[0040] Each module includes an array of 32 head elements between a pair of servo signal readout elements, i.e., the arrangement of the elements. A module with recording elements as head elements is a recording module for recording data onto magnetic tape. A module with playback elements as head elements is a playback module for reproducing 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. For example, the range of errors can represent strict parallelism within a range of less than ±10°.

[0041] The head tilt angle during 500 reciprocating slides is set as the head tilt angle in the regeneration module of the LTO8 magnetic head.

[0042] 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 in a straight line with spacing. Here, "arranged in a straight line" 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 this 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.

[0043] 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.

[0044] 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 regeneration module for the LTO8 head has a total of 32 regeneration elements, from Ch0 to Ch31.

[0045] 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 1 In 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.

[0046] Figure 2 This is an illustration of the relative positional relationship between the modules and the magnetic tape during its transport 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 head tilt angle during tape transport, which 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 element and another in the element array (hereinafter also referred to as the "effective distance between servo signal read elements") is "L". Conversely, when angle θ exceeds 0°, the effective distance between servo signal read elements is "Lcosθ", where Lcosθ is less than L. That is, "Lcosθ < L".

[0047] As described above, during recording or playback, if the magnetic head used for recording or playback 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. For example, if the width of the magnetic tape shrinks or stretches, it is possible that the magnetic head element that should record or play data at the target track position may record or play 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 known as "servo tape spacing" or "servo tape interval." Specifically, this refers to the distance between the two servo tapes in the width direction of the magnetic tape), which may result in data not being recorded or played back near the edge of the magnetic tape.

[0048] In contrast, if the element array is tilted at an angle θ greater than 0°, the effective distance between the servo signal readout elements becomes "Lcosθ", as described above. The larger the value of θ, the smaller the value of Lcosθ; conversely, the smaller the value of θ, the larger the value of Lcosθ. Therefore, by changing the value of θ according to the degree of dimensional change (i.e., shrinkage or elongation) in the width direction of the magnetic tape, the effective distance between the servo signal readout elements can be made close to or consistent with the spacing of the servo tape. This prevents the magnetic head used for recording or reproducing data from deviating from the target track position due to tape width deformation during recording or reproduction, thus avoiding overwriting of recorded data, poor reproduction, or reducing the frequency of such occurrences.

[0049] Figure 3 This is an explanatory diagram related to the change of angle θ during magnetic tape transport.

[0050] 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°.

[0051] Figure 3 In the middle, the diagram shows the state of the module when the conveyor belt starts moving.

[0052] Figure 3 In the middle, the right figure shows that the angle θ is set to be greater than θ. initial（初始角度） 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 contracts during tape transport.

[0053] on the other hand, Figure 3 In the middle, the left figure shows that the angle θ is set to be less than θ. initialAngle 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.

[0054] As mentioned above, changing the head tilt angle during tape transport can help prevent the magnetic head used for recording or reproducing 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 reproduction, or reduce the frequency of such occurrences.

[0055] 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.

[0056] Based on the above speculation, the inventors conducted repeated and in-depth research. As a result, the inventors discovered that magnetic tapes with a previously described LFM reduction rate of 20% or more exhibit excellent tape-running stability when recording and / or reproducing data by tilting the 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 and reproducing data on the aforementioned magnetic tape is not limited to the aforementioned temperature and humidity conditions. Regarding the head tilt angle, an exemplary value was also used as an angle that can be used when changing the head tilt angle during tape transport to record and / or reproduce data. Therefore, the head tilt angle for recording and reproducing data on the aforementioned magnetic tape is not limited to the aforementioned angle. Furthermore, the present invention is not limited to the inventors' speculations described in this specification.

[0057] In this specification, the tape transport stability during data recording and / or regeneration 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.

[0058] In this invention and this specification, the magnetic tape of the test object is subjected to 500 reciprocating slides relative to the LTO8 magnetic head at a head tilt angle of 15° in an environment of 15° temperature and 80% relative humidity by the following method.

[0059] Furthermore, the head tilt angle (15°) refers to the angle between the axis of the element array of the LTO8 head's regeneration module and the direction orthogonal to the sliding direction during the first stroke of the following 500 reciprocating slides. This angle is used to... Figure 2 In this context, A is renamed to be the direction orthogonal to the sliding direction, and the angle θ between A and B is defined. During 500 reciprocating slides, the head tilt angle remains constant.

[0060] The magnetic tape to be measured is placed on two cylindrical guide rollers, each 1 inch in diameter (1 inch = 2.54 cm), spaced apart and arranged in parallel, in such a way that the surface of the magnetic layer is in contact with them. Before measurement, in order to acclimate it to the measurement environment (temperature 15°C, relative humidity 80%), the magnetic tape to be measured is placed on the guide rollers in the above manner and left to stand for more than 24 hours.

[0061] In a randomly selected section of the magnetic tape used for testing, the head tilt angle was set to 15°, and the magnetic layer surface of the tape was slid relative to the LTO8 head for 500 reciprocating slides. Regarding the testing conditions, the wrap 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 forward and return strokes 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 according to the following formula. That is, here, the kinetic friction force F is calculated with T0 = 0.20. The kinetic friction force in the 500th forward stroke 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.

[0062] [Formula 1] <LFM Reduction Rate> In an environment with a temperature of 15°C and a relative humidity of 80%, the reduction rate of the standard deviation of the friction distribution (LFM reduction rate) of the magnetic layer surface of the above magnetic tape in a 3μm×3μm measurement area before and after sliding back and forth 500 times relative to the LTO8 magnetic head at a head tilt angle of 15° is more than 20% as measured by a transverse force microscope.

[0063] In this invention and specification, the standard deviation of the friction distribution is measured using one of the measurement modes of atomic force microscopy (AFM), namely, lateral force microscopy (LFM). For example, the Bruker Nanoscope 5 (measurement mode: LFM) can be used as a lateral force microscope. Under the following measurement conditions, the LFM output (unit: mV) was measured for three measurement areas on the magnetic layer surface that had undergone the aforementioned 500 reciprocating slides and three measurement areas on the magnetic layer surface that had not undergone such reciprocating slides. The obtained output distribution was normalized (Min-Max Normalization), and the standard deviation was calculated. "Min" is an abbreviation for "minimum," and "Max" is an abbreviation for "maximum." The standard deviation obtained from the measurement on the magnetic layer surface that had undergone 500 reciprocating slides is defined as the "measured value after reciprocating slides," and the standard deviation obtained from the measurement on the magnetic layer surface that had not undergone such reciprocating slides is defined as the "measured value before reciprocating slides." The LFM reduction rate was calculated using the following formula.

[0064] LFM reduction rate = (Measurement value before reciprocating sliding - Measurement value after reciprocating sliding) / Measurement value before reciprocating sliding × 100 In addition, 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.

[0065] (Measurement conditions) Measurement environment: Temperature 23℃, relative humidity 50% Measurement area: 3μm × 3μm Measurement surface: Magnetic layer surface Resolution: 512 pixels × 512 pixels Scan Rate: 3μm / second Set Point: 100nN AFM probe: SI-AF01 (manufactured by Hitachi High-Tech Corporation) Number of measurements: N=3 The aforementioned magnetic tapes with an LFM reduction rate of 20% or higher exhibit excellent transport stability when recording and / or reproducing with a tilted magnetic head under low temperature and high humidity conditions. The inventors speculate that this excellent transport stability is due to the fact that magnetic tapes with an LFM reduction rate of 20% or higher can suppress the increase in dynamic friction force F during repeated transport with a tilted magnetic head. The reason for setting the LFM reduction rate of the aforementioned magnetic tape to 20% or higher is that, through repeated in-depth research, the inventors confirmed that if the LFM reduction rate is lower than 20%, the increase in dynamic friction force F during repeated transport with a tilted magnetic head becomes significant. The reason why a higher LFM reduction rate further suppresses the increase in dynamic friction force F is that the inventors believe that a higher LFM reduction rate makes it easier for the uneven distribution of lubricant on the magnetic layer surface to become uniform through contact with the magnetic head. From the viewpoint of further suppressing the increase in dynamic friction force F and further improving transport stability, the LFM reduction rate is preferably 22% or higher, and more preferably 24% or higher. The LFM reduction rate can be, for example, below 30%, below 29%, below 28%, below 27%, below 26%, or below 25%. The inventors believe that, from the viewpoint of improving belt transport stability, a higher LFM reduction rate is preferable. Therefore, the LFM reduction rate can also exceed the above ranges.

[0066] <Kinetic friction force F> The dynamic friction force F in the 500th stroke of the 500 reciprocating slides of the aforementioned 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.

[0067] By controlling the LFM reduction rate to above 20%, the dynamic friction force F can be controlled to below 15gf. Specific examples of methods for controlling the LFM reduction rate to above 20% will be described later.

[0068] The following is a more detailed explanation of the aforementioned magnetic tape.

[0069] <Magnetic Layer> (Strongly magnetic powder) 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, it is preferable to use a strongly magnetic powder with a small average particle size. Considering this, 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 still 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.

[0070] Hexagonal ferrite powder Hexagonal ferrite powder is a preferred specific example of a strongly magnetic powder. For details regarding hexagonal ferrite powder, see, for example, paragraphs 0012-0030 of Japanese Patent Application Publication No. 2011-225417, paragraphs 0134-0136 of Japanese Patent Application Publication No. 2011-216149, paragraphs 0013-0030 of Japanese Patent Application Publication No. 2012-204726, and paragraphs 0029-0084 of Japanese Patent Application Publication No. 2015-127985.

[0071] 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. The crystal structure of a hexagonal ferrite contains at least iron atoms, divalent metal atoms, and oxygen atoms as constituent atoms. Divalent metal atoms refer to metal atoms that can become divalent cations as ions, such as strontium atoms, barium atoms, calcium atoms, and lead atoms. In this invention and specification, hexagonal strontium ferrite powder refers to powder in which the predominant divalent metal atom is strontium, and hexagonal barium ferrite powder refers to powder in which the predominant divalent metal atom is barium. The predominant divalent metal atom refers to the divalent metal atom that occupies the largest proportion of the divalent metal atoms in the powder, based on an atomic percentage. 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).

[0072] The following is a more detailed description of hexagonal strontium ferrite powder as one type of hexagonal ferrite powder.

[0073] The activation volume of hexagonal strontium ferrite powder is preferably in the range of 800–1600 nm. 3 Within 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 3The following is a further preferred option: 1200nm 3 Hereinafter, 1100nm is further preferred. 3 The activation volume of hexagonal barium ferrite powder is also the same.

[0074] "Activation volume" is a unit of magnetization reversal and 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. The unit of the anisotropy constant Ku is 1 erg / cc = 1.0 × 10⁻¹⁰. -1 J / m 3 .

[0075] Hc=2Ku / Ms{1-[(kT / KuV)ln(At / 0.693)] 1 / 2} In the above formula, Ku: anisotropy constant (unit: J / m) 3 Ms: saturation magnetization (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) 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 3 However, a higher Ku value indicates higher thermal stability and is therefore preferred; it is not limited to the values ​​exemplified above.

[0076] Hexagonal strontium ferrite powder may or may not contain rare earth atoms. When hexagonal strontium ferrite powder contains rare earth atoms, it is preferable that the rare earth atoms are contained 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 exhibit rare earth atom segregation on the surface layer. In this invention and this specification, "rare earth atom surface layer segregation" refers to the ratio of the rare earth atom content (hereinafter, "rare earth atom surface layer content" or rare earth atoms) in a solution obtained by partially dissolving hexagonal strontium ferrite powder with acid to the rare earth atom content (hereinafter, "rare earth atom surface layer content" or rare earth atoms are simply referred to as "surface layer content") in a solution obtained by completely dissolving hexagonal strontium ferrite powder with acid to the rare earth atom content (hereinafter, "rare earth atom bulk content" or rare earth atoms are simply referred to as "bulk content") satisfying the condition that the rare earth atom surface layer content / rare earth atom bulk content > 1.0.

[0077] 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, since partial dissolution with acid dissolves only the surface portion of the particles constituting the hexagonal strontium ferrite powder, 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 concentrated in the surface portion (i.e., present 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 toward the interior.

[0078] 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 clustered in the surface layer of the particles constituting the hexagonal strontium ferrite powder, helps to suppress the decrease in regeneration output during repeated regeneration. This is presumably because by containing rare earth atoms at a bulk content within the above range and with the rare earth atoms clustered in the surface layer of the particles constituting the hexagonal strontium ferrite powder, the anisotropy constant Ku can be increased. A higher value of the anisotropy constant Ku is more effective in suppressing the phenomenon known as thermal fluctuation (in other words, it improves thermal stability). By suppressing thermal fluctuation, the decrease in regeneration output during repeated regeneration can be suppressed. It is speculated that the segregation of rare earth atoms in the surface layer of hexagonal strontium ferrite powder particles helps to stabilize the spin of iron (Fe) sites in the lattice of the surface layer, thereby increasing the anisotropy constant Ku.

[0079] Furthermore, it is speculated that using hexagonal strontium ferrite powder with rare-earth atom segregation on the surface as a strong magnetic powder in the magnetic layer also helps to suppress 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 segregation on the surface can also help improve the tape travel durability. This is speculated because the segregation of rare-earth atoms 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.

[0080] From the viewpoint of suppressing the decline in regeneration output during repeated regeneration 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%.

[0081] The above-mentioned bulk content rate is the content rate obtained by completely dissolving hexagonal strontium ferrite powder. In this invention and this specification, unless otherwise specified, the content rate for atoms 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 may contain two or more types of rare earth atoms. The above-mentioned 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 this 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 refers to the sum of the two or more types.

[0082] When hexagonal strontium ferrite powder contains rare earth atoms, the rare earth atoms contained can be any one or more of the rare earth atoms. From the viewpoint of suppressing the decrease in regeneration output during repeated regeneration, 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.

[0083] In hexagonal strontium ferrite powder exhibiting rare-earth atom segregation on the surface, the rare-earth atoms only need to be segregated on the surface of the particles constituting the hexagonal strontium ferrite powder, and the degree of segregation is not limited. For example, regarding hexagonal strontium ferrite powder exhibiting rare-earth atom segregation on the surface, the ratio of the surface content of rare-earth atoms obtained by partial dissolution under the dissolution conditions described later to the bulk content of rare-earth atoms obtained by complete dissolution under the dissolution conditions described later, "surface content / bulk content", exceeds 1.0, and can be 1.5 or more. A "surface content / bulk content" greater than 1.0 indicates that rare-earth atoms are segregated on the surface of the particles constituting the hexagonal strontium ferrite powder (i.e., their presence is greater than that in the interior). 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 rare earth atom surface portion segregation, the rare earth atoms only need to be segregated 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.

[0084] 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. The removal of the hexagonal strontium ferrite powder from the magnetic layer can be performed, for example, by the method described in paragraph 0032 of Japanese Patent Application Publication No. 2015-91747.

[0085] The aforementioned partial dissolution refers to the point at which dissolution is complete, to the point where it is visually identifiable that hexagonal strontium ferrite powder remains in the liquid. For example, partial dissolution can dissolve 10-20% by mass (with the total number of particles as 100% by mass) of the particles constituting the hexagonal strontium ferrite powder. On the other hand, the aforementioned complete dissolution refers to the point at which dissolution is complete, to the point where it is no longer visually identifiable that hexagonal strontium ferrite powder remains in the liquid.

[0086] 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.

[0087] 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. In cases where 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.

[0088] On the other hand, the determination of complete dissolution and bulk content is carried out, for example, by the following method.

[0089] 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 determination of partial dissolution and surface content is carried out in the same manner as described above, and the bulk content relative to 100 atomic% of iron atoms can be determined.

[0090] From the viewpoint of improving the playback output when reproducing data recorded onto the magnetic tape, it is preferable that the magnetic powder contained in the magnetic tape has a high mass magnetization σs. In this regard, hexagonal strontium ferrite powder containing rare-earth atoms but lacking rare-earth atom surface segregation tends to show a significant decrease in σs compared to hexagonal strontium ferrite powder without rare-earth atoms. Therefore, in terms of suppressing this significant decrease in σs, hexagonal strontium ferrite powder with rare-earth atom surface segregation is also 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·m 2 / kg or less. σs can be measured using a known measuring device capable of measuring the magnetic properties of vibrating sample type magnetometers, etc. In this invention and this specification, unless otherwise specified, the mass magnetization σs is a value measured with a magnetic field strength of 15 kOe. 1 [kOe] = 10 6 / 4π[A / m].

[0091] 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%. 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. When it contains 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% relative to 100 atomic% of iron atoms.

[0092] As for the crystal structures of hexagonal ferrites, the known types include magnetoplumbleite (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. Moreover, 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% of iron atoms may be, for example, 0.5 to 10.0 atoms. From the viewpoint of suppressing the decrease in regeneration output during repeated regeneration, 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 not contain 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, for a certain atom, "not containing" means that the content obtained by complete dissolution and determination 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 mean including amounts less than the detection limit of the ICP analyzer. In one embodiment, the hexagonal strontium ferrite powder may be free of bismuth atoms (Bi).

[0093] Metal powder As a preferred specific example of a strongly magnetic powder, strongly magnetic metal powder can also be cited. For details regarding strongly magnetic metal powder, please refer to 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.

[0094] ε-iron oxide powder 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, it is determined that the crystal structure of ε-iron oxide is detected as 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, refer to J.Jpn.Soc.Powder Metallurgy Vol.61 Supplement, No S1, pp S280-S284, JMater.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.

[0095] The activation volume of ε-iron oxide powder is preferably in the range of 300–1500 nm. 3 Within the range described above, micronized ε-iron oxide powder exhibiting 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 The preferred option is 1100nm. 3 the following.

[0096] An anisotropy constant Ku can be cited as an indicator of reduced thermal fluctuations, or 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, has 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.

[0097] From the viewpoint of improving the playback output when reproducing data recorded onto the 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.

[0098] 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.

[0099] The powder was photographed using a transmission electron microscope at a magnification of 100,000, and then printed on photographic paper or displayed on a monitor at a total magnification of 500,000 to obtain photographs of the particles constituting 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.

[0100] 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 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, such as Carl Zeiss KS-400 image analysis software. Unless otherwise specified, the average particle size shown in the following embodiments is the value obtained by using a Hitachi H-9000 transmission electron microscope as the transmission electron microscope and Carl Zeiss KS-400 image analysis software as the image analysis software. In this invention and specification, "powder" refers to a collection of multiple particles. For example, strongly 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.

[0101] 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.

[0102] Unless otherwise specified in this invention and specification, the size of the particles constituting the powder (particle size) refers to the shape of the particles observed in the aforementioned particle photographs. (1) In the cases of needle-like, spindle-shaped, and columnar shapes (where the height is greater than the maximum major diameter of the base), the length of the major axis constituting the particle is used, i.e., the length of the major axis. (2) In the case of a plate or column (where the thickness or height is less than the maximum major diameter of the plate surface or bottom surface), the maximum major diameter of the plate surface or bottom surface shall be used. (3) When 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 refers to the diameter obtained by using the circular projection method.

[0103] Furthermore, the average aspect ratio of the powder refers to the arithmetic mean of the values ​​obtained from the above measurements of the minor axis length of the particles, i.e., the minor axis length, and the (major axis length / minor axis length) of each particle. Here, unless otherwise specified, the so-called minor axis length, in the definition of particle size above (1), refers to the length of the minor axis constituting the particle; similarly, in (2), it refers to the thickness or height; and in (3), since there is no difference between the major axis and the minor axis, for convenience, (major axis length / minor axis length) is regarded as 1.

[0104] 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).

[0105] The content (filling rate) of the strongly magnetic powder in the magnetic layer is preferably in the range of 50 to 90% by mass relative to the total mass of the magnetic layer, and 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.

[0106] (Adhesive) 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 multiple resins can be used in combination. Among these, 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 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.

[0107] 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 binder can be used in amounts of, for example, 1.0 to 30.0 parts by weight relative to 100.0 parts by weight of the strong magnetic powder.

[0108] (Curing agent) 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 photocurable 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 more preferred. 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.

[0109] (Other ingredients) 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 that function as protrusion forming agents and those that function as abrasives. Furthermore, known additives such as the polymers described in paragraphs 0030 to 0080 of Japanese Patent Application Publication No. 2016-051493 may also be used.

[0110] 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. For example, particles with polymers bonded to the surface of inorganic oxide particles can be used as such particles.

[0111] 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 sinking 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 uneven particle 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 sinking 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 an uneven particle surface and low surface smoothness can help to 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.

[0112] 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 for 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.

[0113] 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.

[0114] 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 can be 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.

[0115] Furthermore, as an additive that can be included in the magnetic layer, a compound having an ammonium salt structure of an alkyl ester anion represented by the following Formula 1 can be cited.

[0116] [Chemical Formula 1] (In Formula 1, R represents an alkyl group with 7 or more carbon atoms or a fluorinated alkyl group with 7 or more carbon atoms, Z) + (This indicates an ammonium cation.) The inventors believe that the above-mentioned compound can function as a lubricant. This will be further explained below.

[0117] Lubricants can be broadly classified into fluid lubricants and boundary lubricants. The inventors believe that compounds having an ammonium salt structure of an alkyl ester anion represented by Formula 1 above can function as fluid lubricants. It is believed that the fluid lubricant itself forms a liquid film on the surface of the magnetic layer, thereby imparting lubricity to the magnetic layer. It is speculated that, in order to increase the LFM reduction rate, the distribution of the fluid lubricant present on the surface of the magnetic layer should be easily homogenized due to contact with the magnetic head.

[0118] Regarding the above aspects, the aforementioned compounds contain an ammonium salt structure of an alkyl ester anion represented by Formula 1. It is believed that the distribution of compounds containing this structure on the surface of the magnetic layer is easily homogenized due to contact with the magnetic head. Therefore, it is believed that the presence of the aforementioned compounds in the magnetic layer can help control the LFM reduction rate.

[0119] The above compounds will now be described in further detail.

[0120] In this invention and this specification, unless otherwise stated, the described groups may have substituents or not. Furthermore, regarding substituent groups, unless specifically stated otherwise, "number of carbon atoms" refers to the number of carbon atoms excluding the substituents. In this invention and this specification, examples of substituents include alkyl groups (e.g., alkyl groups with 1 to 6 carbon atoms), hydroxyl groups, alkoxy groups (e.g., alkoxy groups with 1 to 6 carbon atoms), halogen atoms (e.g., fluorine atoms, chlorine atoms, bromine atoms, etc.), cyano groups, amino groups, nitro groups, acyl groups, carboxyl groups, salts of carboxyl groups, sulfonic acid groups, and salts of sulfonic acid groups.

[0121] In compounds having an ammonium salt structure of an alkyl ester anion represented by Formula 1, at least a portion contained in the magnetic layer can form a liquid film on the surface of the magnetic layer, and a portion contained within the magnetic layer can move to the surface of the magnetic layer and form a liquid film when sliding with a magnetic head. Furthermore, a portion can be contained in the non-magnetic layer (described later) and can also move into the magnetic layer, and subsequently to the surface of the magnetic layer to form a liquid film. Additionally, "alkyl ester anion" can also be referred to as "alkyl carboxylate anion".

[0122] In Formula 1, R represents an alkyl group having 7 or more carbon atoms or a fluoroalkyl group having 7 or more carbon atoms. The fluoroalkyl group has a structure in which some or all of the hydrogen atoms constituting the alkyl group are replaced by fluorine atoms. The alkyl or fluoroalkyl group represented by R can be a straight-chain structure, a branched structure, or a cyclic alkyl or fluoroalkyl group, preferably a straight-chain structure. The alkyl or fluoroalkyl group represented by R can have substituents or be unsubstituted, preferably unsubstituted. The alkyl group represented by R can, for example, be formed from C... n H 2n+1 - indicates. Here, n represents an integer greater than 7. Furthermore, the fluoroalkyl group represented by R can, for example, have the structure of C n H 2n+1 - indicates a structure in which some or all of the hydrogen atoms of the alkyl group are replaced by fluorine atoms. The alkyl or fluoroalkyl group represented by R has 7 or more carbon atoms, preferably 8 or more, more preferably 9 or more, even more preferably 10 or more, even more preferably 11 or more, even more preferably 12 or more, and even more preferably 13 or more. Furthermore, the alkyl or fluoroalkyl group represented by R preferably has 20 or fewer carbon atoms, more preferably 19 or fewer, and even more preferably 18 or fewer.

[0123] In Equation 1, Z + This indicates an ammonium cation. Specifically, the ammonium cation has the following structure. In this invention and specification, the asterisk in the formula representing a portion of a compound indicates the bonding position of that portion of the structure with adjacent atoms.

[0124] [Chemical Formula 2] The nitrogen cation of ammonium cation N + With the oxygen anion O in Formula 1 - A salt bridging group is formed, thereby enabling the formation of an ammonium salt structure of an alkyl ester anion represented by Formula 1. The presence of compounds with an ammonium salt structure of an alkyl ester anion represented by Formula 1 within a magnetic layer can be confirmed by analyzing the magnetic tape using X-ray photoelectron spectroscopy (ESCA) or infrared spectroscopy (IR).

[0125] In one approach, by Z + The ammonium cation represented can be generated, for example, by the nitrogen atom of a nitrogen-containing polymer becoming a cation. A nitrogen-containing polymer refers to a polymer containing nitrogen atoms. In this invention and specification, the terms "polymer" and "polymer" are used to encompass both homopolymers and copolymers. In one embodiment, the nitrogen atom may be included as an atom constituting the main chain of the polymer, and in another embodiment, it may be included as an atom constituting the side chain of the polymer.

[0126] One example of a nitrogen-containing polymer is polyalkylene imide. Polyalkylene imide is a ring-opening polymer of alkylene imide and is a polymer having a plurality of repeating units represented by the following Formula 2.

[0127] [Chemical Formula 3] In Formula 2, the nitrogen atom N in the main chain becomes a nitrogen cation N. + Thus, Z in Equation 1 can be generated. + The ammonium cation is represented. Furthermore, alkyl ester anions can, for example, form ammonium salt structures as follows.

[0128] [Chemical Formula 4] The following is a more detailed explanation of Equation 2.

[0129] In Equation 2, R 1 and R 2 Each can be used to independently represent a hydrogen atom or an alkyl group, and n1 represents an integer greater than 2.

[0130] As R 1 or R 2 The alkyl group represented, for example, includes alkyl groups having 1 to 6 carbon atoms, preferably alkyl groups having 1 to 3 carbon atoms, more preferably methyl or ethyl, and even more preferably methyl. R 1 or R 2The alkyl group represented is preferably an unsubstituted alkyl group. As R in Formula 2 1 and R 2 The combination can be in the form of one being a hydrogen atom and the other being an alkyl group, in the form of both being hydrogen atoms, or in the form of both being alkyl groups (the same or different alkyl groups), with the form of both being hydrogen atoms being preferred. As the alkylimide that brings about the polyalkylimide, the structure with the fewest carbon atoms forming the ring is ethyleneimide, and the alkylimide (ethyleneimide) obtained by ring-opening ethyleneimide has a main chain with 2 carbon atoms. Therefore, n1 in Formula 2 is 2 or more. n1 in Formula 2 can, for example, be 10 or less, 8 or less, 6 or less, or 4 or less. The polyalkylimide can be a homopolymer containing only the same structure as a repeating structure represented by Formula 2, or it can be a copolymer containing two or more different structures as repeating structures represented by Formula 2. The number average molecular weight of the polyalkylimide that can be used to form a compound having an ammonium salt structure of an alkyl ester anion represented by Formula 1 can, for example, be 200 or more, preferably 300 or more. Furthermore, the number average molecular weight of the aforementioned polyalkylimide can be, for example, 10,000 or less, preferably 5,000 or less, and more preferably 2,000 or less.

[0131] In this invention and specification, the average molecular weight (weight-average molecular weight and number-average molecular weight) refers to the value determined by gel permeation chromatography (GPC) and converted to standard polystyrene. Unless otherwise stated, the average molecular weight shown in the examples described below is the value obtained by converting the value obtained by using GPC and according to the following measurement conditions to standard polystyrene (polystyrene conversion value).

[0132] GPC Unit: HLC-8220 (manufactured by TOSOH CORPORATION) Protective column: TSKguardcolumn Super HZM-H Tubes: TSKgel Super HZ 2000, TSKgel Super HZ 4000, TSKgel Super HZ-M (manufactured by TOSOH CORPORATION, 4.6mm (inner diameter) × 15.0cm, three types of tubes connected in series) Eluent: Contains tetrahydrofuran (THF) and stabilizer (2,6-di-tert-butyl-4-methylphenol) Elution buffer flow rate: 0.35 mL / min Column temperature: 40℃ Inlet temperature: 40℃ Refractive index (RI) measurement temperature: 40℃ Sample concentration: 0.3% by mass Sample injection volume: 10 μL Furthermore, polyallylamine can be cited as another example of a nitrogen-containing polymer. Polyallylamine is a polymer of allylamine and is a polymer having a plurality of repeating units represented by Formula 3 below.

[0133] [Chemical Formula 5] In Formula 3, the nitrogen atom N of the amino group constituting the side chain becomes a nitrogen cation N. + Thus, Z in Equation 1 can be generated. + The ammonium cation is represented. Furthermore, alkyl ester anions can, for example, form ammonium salt structures as follows.

[0134] [Chemical Formula 6] The weight-average molecular weight of the polyallylamine capable of forming a compound having an ammonium salt structure of an alkyl ester anion represented by Formula 1 can be, for example, 200 or more, preferably 1,000 or more, and more preferably 1,500 or more. Furthermore, the weight-average molecular weight of the aforementioned polyallylamine can be, for example, 15,000 or less, preferably 10,000 or less, and more preferably 8,000 or less.

[0135] As compounds having an ammonium salt structure of an alkyl ester anion represented by Formula 1, including compounds having a structure derived from polyalkylimide or polyallylamine, these compounds can be identified, for example, by analyzing the surface of the magnetic layer using methods such as Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS).

[0136] Compounds having an ammonium salt structure of an alkyl ester anion represented by Formula 1 can be salts of one or more fatty acids selected from the group consisting of a nitrogen-containing polymer and fatty acids having seven or more carbon atoms and fluorinated fatty acids having seven or more carbon atoms. The nitrogen-containing polymer forming the salt can be one or more nitrogen-containing polymers, for example, nitrogen-containing polymers selected from the group consisting of polyalkylimides and polyallylamines. The fatty acids forming the salt can be one or more fatty acids selected from the group consisting of fatty acids having seven or more carbon atoms and fluorinated fatty acids having seven or more carbon atoms. The fluorinated fatty acids have a structure in which part or all of the hydrogen atoms of the alkyl group bonded to the COOH group in the fatty acid are replaced by fluorine atoms. For example, a salt-forming reaction can be readily carried out by mixing the nitrogen-containing polymer and the aforementioned fatty acids at room temperature. Room temperature is, for example, around 20–25°C. In one embodiment, as components of a composition for forming a magnetic layer, one or more nitrogen-containing polymers and one or more fatty acids are used, and these are mixed in the preparation step of the composition for forming a magnetic layer, thereby enabling a salt-forming reaction. Furthermore, in one embodiment, before preparing the magnetic layer forming composition, after mixing one or more nitrogen-containing polymers and one or more fatty acids to form a salt, the salt can be used as a component of the magnetic layer forming composition to prepare the magnetic layer forming composition. This also applies to the case of forming a non-magnetic layer comprising a compound having an ammonium salt structure having an alkyl ester anion represented by Formula 1. For example, regarding the magnetic layer, 0.1 to 10.0 parts by weight of the nitrogen-containing polymer can be used per 100.0 parts by weight of strongly magnetic powder, preferably 0.5 to 8.0 parts by weight of the nitrogen-containing polymer. The aforementioned fatty acid can be used, for example, 0.05 to 10.0 parts by weight of the strongly magnetic powder, preferably 0.1 to 5.0 parts by weight. Furthermore, regarding the non-magnetic layer, 0.1 to 10.0 parts by weight of the nitrogen-containing polymer can be used per 100.0 parts by weight of non-magnetic powder, preferably 0.5 to 8.0 parts by weight of the nitrogen-containing polymer. The aforementioned fatty acids can be used in amounts of, for example, 0.05 to 10.0 parts by weight of non-magnetic powder per 100.0 parts by weight, preferably 0.1 to 5.0 parts by weight. Furthermore, when mixing the nitrogen-containing polymer and the aforementioned fatty acids to form an ammonium salt of the alkyl ester anion represented by Formula 1, sometimes the nitrogen atoms constituting the nitrogen-containing polymer react with the carboxyl groups of the aforementioned fatty acids to form the following structure, and this structure is also included in the aforementioned compounds.

[0137] [Chemical Formula 7] Examples of the aforementioned fatty acids include fatty acids in which R in Formula 1 is described as an alkyl group and fluorinated fatty acids in which R in Formula 1 is described as a fluorinated alkyl group.

[0138] The mixing ratio of the nitrogen-containing polymer and the aforementioned fatty acids used to form the compound having the ammonium salt structure of the alkyl ester anion represented by Formula 1 is preferably 10:90 to 90:10, more preferably 20:80 to 85:15, and even more preferably 30:70 to 80:20, in terms of the mass ratio of nitrogen-containing polymer to the aforementioned fatty acids. Furthermore, the compound having the ammonium salt structure of the alkyl ester anion represented by Formula 1 preferably contains at least 0.01 parts by mass relative to 100.0 parts by mass of the strongly magnetic powder in the magnetic layer, more preferably at least 0.1 parts by mass, and even more preferably at least 0.5 parts by mass. Here, the content of the aforementioned compound in the magnetic layer refers to the total amount of the liquid film formed on the surface of the magnetic layer and the amount contained within the magnetic layer. On the other hand, from the viewpoint of high-density recording, it is preferable that the content of the strongly magnetic powder in the magnetic layer is high. Therefore, from the viewpoint of high-density recording, it is preferable that the content of components other than the strongly magnetic powder is low. From this perspective, the content of the aforementioned compound in the magnetic layer is preferably 15.0 parts by weight or less, more preferably 10.0 parts by weight or less, and even more preferably 8.0 parts by weight or less, relative to 100.0 parts by weight of the strongly magnetic powder. Furthermore, the preferred range for the content of the aforementioned compound in the magnetic layer forming composition used to form the magnetic layer is also the same.

[0139] As a lubricant, esters and / or amides of fatty acids such as lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, behenic acid, erucic acid, and transoleic acid can also be used.

[0140] Specific examples of fatty acid esters include butyl myristate, butyl palmitate, butyl stearate, neopentyl glycol dioleate, sorbitol monostearate, sorbitol distearate, sorbitol tristearate, oleate, isohexadecanyl stearate, isothiazyl stearate, octyl stearate, isooctyl stearate, pentyl stearate, and butoxyethyl stearate.

[0141] Specific examples of fatty acid amides include laurylamide, myristylamide, palmitamide, stearamide, etc.

[0142] The content of fatty acid esters in the magnetic layer or the composition for forming the magnetic layer is, for example, 0 to 10.0 parts by weight relative to 100.0 parts by weight of the strong magnetic powder, preferably 0.5 to 7.0 parts by weight.

[0143] 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.

[0144] Regarding the content of 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 can be applied.

[0145] 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.

[0146] <Non-magnetic layer> 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 it can have a non-magnetic layer containing non-magnetic powder between the non-magnetic support and the magnetic layer. The non-magnetic powder used in the non-magnetic layer can be an inorganic powder (inorganic powder) or an organic powder (organic powder). Furthermore, 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 as commercially available products 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 the 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.

[0147] The non-magnetic layer may contain an adhesive or additives. Further details regarding the adhesives, additives, etc., of the non-magnetic layer can be obtained using known techniques related to non-magnetic layers. Furthermore, for example, known techniques related to magnetic layers can also be applied regarding the type and content of the adhesive, the type and content of the additives, etc.

[0148] 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, as an impurity or intentionally in the form of a small amount 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 and a coercivity of 7.96 kA / m (100 Oe) or less, or a remanent magnetic flux density of 10 mT or less and a coercivity 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.

[0149] <Non-magnetic support> 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.

[0150] 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 aromatic polyester supports in which all resin films are aromatic polyester films, and aromatic polyester 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 layers of aromatic polyester films having the same composition, laminated films with two or more layers of aromatic polyester films having different compositions, and laminated films containing one or more layers of aromatic polyester films and one or more layers of resin films other than aromatic polyester films. An adhesive layer may also be arbitrarily included between adjacent layers in a laminated film. Furthermore, the aromatic polyester support may also optionally contain 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.

[0151] 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.

[0152] 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 compounds 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.

[0153] Polyethylene naphthalate (PEN) is a polyester containing a naphthalene ring, and is a resin obtained by esterification of dimethyl 2,6-naphthalate with ethylene glycol followed by transesterification and polycondensation. The term "polyethylene naphthalate" in this invention and specification also includes compounds having a structure containing one or more other components besides those described above (e.g., copolymer components, components introduced into the ends or side chains, etc.).

[0154] 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 comprising 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 aromatic polyamide supports in which all resin films comprising the support are aromatic polyamide films, and aromatic polyamide 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 a metal film and / or a metal oxide film formed on one or both surfaces by vapor deposition or the like.

[0155] 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.

[0156] 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.

[0157] A sample piece (e.g., a few grams) cut from the non-magnetic support of the object from which the moisture content is to be measured is dried to constant weight in a vacuum desiccator at a temperature of 180°C and a pressure of 100 Pa. 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 in an environment at 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 above environment at a temperature of 23°C and a relative humidity of 50%. The moisture content is calculated using the following formula.

[0158] Moisture content (%) = [(W2-W1) / W1] × 100 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).

[0159] 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.

[0160] Young's modulus can also be cited as an indicator of the physical properties of non-magnetic supports. In this invention and 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.

[0161] Under conditions of a clamp spacing of 100 mm, a tensile speed of 10 mm / min, and a recording paper speed of 500 mm / min, a specimen cut from a non-magnetic support of the test object is stretched using a universal tensile testing apparatus. For example, commercially available universal tensile testing apparatuses such as the Tensilon apparatus manufactured by TOYO BALDWIN CO.Ltd., or universal tensile testing apparatuses with known structures can be used. Based on the tangent of the initial rising portion of the load-elongation curve thus obtained, the Young's modulus in the length and width directions of the specimen is calculated, respectively. 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.

[0162] 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.

[0163] 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, further 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, further 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 manufacturing magnetic tapes, the non-magnetic support typically uses the machine direction (MD) of the film as the longitudinal direction and the transverse direction (TD) as the width direction. Furthermore, in one embodiment, it is preferable that the Young's modulus in the length direction is greater than that in the width direction, and more preferably the difference (Young's modulus in the length direction - Young's modulus in the width direction) is in the range of 800 to 3000 MPa.

[0164] 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.

[0165] <Back Coating> The aforementioned magnetic tape may have a back coating containing non-magnetic powder on the surface of the non-magnetic support opposite to the surface with the magnetic layer, or it may not have such a back coating. Preferably, the back coating contains one or both of carbon black and inorganic powder. The back coating may contain a binder or additives. Details regarding the non-magnetic powder, binder, additives, etc., of the back coating can be obtained using known techniques related to the back coating, as well as known techniques related to the magnetic layer and / or non-magnetic layer. For example, regarding the back coating, reference can be made to paragraphs 0018 to 0020 of Japanese Patent Application Publication No. 2006-331625 and lines 65 to 38 of column 4 of the specification of U.S. Patent No. 7,029,774.

[0166] <Various Thicknesses> 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 (high capacity) of magnetic tape. As a solution to increase 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.

[0167] The thickness (total thickness) of the magnetic tape can be determined using the following methods.

[0168] 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 obtained 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.

[0169] The thickness of the non-magnetic support is preferably 2.0 to 5.0 μm, more preferably 3.0 to 5.0 μm.

[0170] 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.

[0171] 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.

[0172] The thickness of the back coating is preferably less than 0.9 μm, and more preferably 0.1 to 0.7 μm.

[0173] The thickness of the magnetic layer and other thicknesses can be determined using the following methods.

[0174] After exposing a cross-section of the magnetic tape along its thickness direction using an ion beam, cross-sectional observation is performed on the exposed section using a scanning electron microscope or a transmission electron microscope. Various thicknesses can be calculated as the arithmetic mean of the thicknesses obtained from any two locations in the cross-sectional observation. Alternatively, various thicknesses can also be calculated as design thicknesses based on manufacturing conditions, etc.

[0175] <Manufacturing Method> (Preparation of the composition for forming each layer) 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 typically 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 for preparing each layer-forming composition typically includes at least a mixing process, a dispersion process, and a mixing process provided 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 separately 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. Furthermore, as described above, when one or more nitrogen-containing polymers and one or more fatty acids are used as components of the magnetic layer forming composition, they are mixed during the preparation step of the magnetic layer forming composition, thereby enabling a salt formation reaction. In another embodiment, before preparing the magnetic layer forming composition, one or more nitrogen-containing polymers and one or more fatty acids are mixed to form a salt, and then this salt can be used as a component of the magnetic layer forming composition. This also applies to the preparation step of non-magnetic layer forming compositions. In one embodiment, during the preparation step of the magnetic layer forming composition, after preparing a dispersion containing a protrusion forming agent (hereinafter referred to as "protrusion forming agent liquid"), the protrusion forming agent liquid can be mixed with one or more other components of the magnetic layer forming composition. For example, the protrusion forming agent liquid can be prepared by 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, and the treatment lasts for approximately 1–300 minutes. Furthermore, filtration can be performed after dispersion treatment. For information on the filters used for filtration, please refer to the following description.

[0176] 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 Publications Nos. 1-106338 and 1-79274. Furthermore, glass beads and / or other beads can be used to disperse the compositions for forming each layer. Zirconia beads, titanium dioxide beads, and steel beads, which have high specific gravity, are preferred as such dispersing beads. These dispersing beads are preferably used with optimized particle size (bead diameter) and filling rate. Known dispersing machines 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 sinking 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.

[0177] (Coating process) The magnetic layer can be formed by directly coating a magnetic layer forming composition onto a non-magnetic support, or by sequentially or simultaneously coating multiple layers with the non-magnetic layer forming composition. In the case of an alignment process, the coating layer in the alignment region is aligned while the coating layer of the magnetic layer forming composition is wet. Various known techniques, including those described in paragraph 0052 of Japanese Patent Application Publication No. 2010-24113, can be applied for the alignment process. For example, vertical alignment can be performed using known methods such as the method using opposite-pole magnets. In the alignment region, 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 in the alignment region. Furthermore, the coating layer can be pre-dried before being conveyed to the alignment region.

[0178] 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.

[0179] (Other processes) 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 inhibiting the deposition 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 two or more, for example, two to four passes.

[0180] 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.

[0181] Through various processes, a long, thin magnetic tape roll can be obtained. The resulting roll is then cut (divided) 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.

[0182] Servo patterns are typically formed in the resulting magnetic tape after splitting.

[0183] (Formation of servo patterns) The formation of servo patterns can also be called the recording of servo signals. The formation of servo patterns will be explained below.

[0184] Servo patterns are typically formed along the length of the magnetic tape. Examples of control methods utilizing servo signals (servo control) include time-based servo (TBS), amplitude servo, and frequency servo.

[0185] As shown in ECMA (European Computer Manufacturers Association) 319 (June 2001), time-based servoing is used in magnetic tapes conforming to the LTO (Linear Tape-Open) standard (generally 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 stripes (also referred to as "servo stripes") 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 mentioned above, the servo pattern is constructed by a pair of non-parallel magnetic stripes to notify the servo signal readout element passing over the servo pattern of its position. Specifically, the pair of magnetic stripes are formed with their interval continuously varying along the width of the tape. By reading this interval by the servo signal readout element, the relative position of the servo pattern and the servo signal readout element can be determined. This information of the relative position enables tracking of the tracking data track. Therefore, multiple servo tracks are typically arranged along the width of the tape on the servo pattern.

[0186] The servo tape consists of a continuous servo pattern along the length of the magnetic tape. Multiple servo tapes are typically arranged on the tape. For example, in an LTO tape, there are five servo tapes. 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.

[0187] Furthermore, in one approach, as shown in Japanese Patent Application Publication No. 2004-318983, information indicating the serial number of the servo band is embedded in each servo band (also referred to as "servo band ID (identification)" or "UDIM (Unique Data Band Identification Method) information"). This servo band ID is recorded by offsetting specific servo stripes in a pair of servo stripes that exist multiple times within the servo band, by relative displacement of their positions along the length of the magnetic tape. Specifically, the offsetting method of specific servo stripes in a pair of servo stripes that exist multiple times is changed for each servo band. Therefore, the recorded servo band ID is unique for each servo band, and thus, by reading a single servo band using a servo signal reading element, the servo band can be uniquely identified.

[0188] Another method for uniquely identifying servo strips is the interleaving method shown in ECMA-319 (June 2001). In this interleaving method, multiple pairs of non-parallel magnetic stripes are arranged consecutively along the length of the magnetic tape and recorded in a manner that each servo strip is staggered along the length of the tape. The combination of this staggering method between adjacent servo strips is unique throughout the entire magnetic tape, thus allowing for unique identification of the servo strip when the servo pattern is read using two servo signal readout elements.

[0189] Furthermore, as shown in ECMA-319 (June 2001), information indicating the position along the length of the magnetic tape (also known as "LPOS (Longitudinal Position) information") is typically embedded in each servo tape. Similar to UDIM information, this LPOS information is recorded by offsetting the positions of a pair of servo stripes along the length of the tape. However, unlike UDIM information, the same signal is recorded in each servo tape in this LPOS information.

[0190] 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 for each server tape, like the UDIM information, or it can be universal across all server tapes, like the LPOS information.

[0191] Furthermore, other methods besides those described 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 stripes.

[0192] 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. A core and a coil are usually connected to each pair of gaps. By supplying current pulses to the coils, the magnetic field generated in the core produces a leakage magnetic field in the pair of gaps. During servo pattern formation, by inputting current pulses while the magnetic tape is being fed onto the servo write head, the magnetic pattern corresponding to the pair of gaps can be transferred onto the magnetic tape to form the 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.

[0193] Before forming servo patterns on the magnetic tape, the tape is typically demagnetized (erased). This erasure process can be performed by applying the same magnetic field to the tape using either a DC or AC magnet. There are two types of erasure: DC (Direct Current) erasure and AC (Alternating Current) erasure. AC erasure is performed by gradually reducing the strength of the magnetic field while reversing its direction. DC erasure, on the other hand, is performed by applying a directional magnetic field to the tape. DC erasure has two further methods. The first method is horizontal DC erasure, which applies a directional magnetic field along the length of the tape. The second method is vertical DC erasure, which applies a directional magnetic field along the thickness of the tape. Erasure can be performed on the entire tape or on each servo section of the tape.

[0194] The orientation of the magnetic field of the formed servo pattern depends on the erasure orientation. For example, when a horizontal DC erasure is applied to the 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 is transferred to a magnetic tape that has been vertically DC erased using the aforementioned gap, the servo signal obtained by reading the formed servo pattern is a unipolar pulse shape. On the other hand, when a magnetic pattern is transferred to a magnetic tape that has been horizontally DC erased using the aforementioned gap, the servo signal obtained by reading the formed servo pattern is a bipolar pulse shape.

[0195] <Vertical Rectangular Ratio> 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.

[0196] 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.

[0197] 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 is the value 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.

[0198] [Cassette Tape Case] One aspect of the present invention relates to a magnetic tape cassette comprising the aforementioned magnetic tape.

[0199] The details of the magnetic tapes included in the aforementioned cassette are as described above.

[0200] 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 in a tape drive for recording and / or reproducing data on the magnetic tape, the magnetic tape is pulled out of the cassette and wound onto a reel on the tape drive side. A magnetic head is positioned along the magnetic tape transport path from the cassette to the take-up reel. Magnetic 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 magnetic tape, thereby recording and / or reproducing data. For this purpose, a double-reel cassette has both a feed reel and a take-up reel inside the cassette.

[0201] 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 reproducing data recorded on the magnetic tape, the value of the servo tape interval may be measured during reproduction, and the head tilt angle may be changed by a control device of the magnetic tape device so that the absolute value of the difference between the servo tape interval recorded at the same length position in the cartridge memory and that recorded therein is close to 0. The head tilt angle may be, for example, the aforementioned angle θ. When the tilted head performs data recording and / or reproduction, the aforementioned angle θ may exceed 0°, and may be less than 45°, less than 40°, or less than 35°.

[0202] The aforementioned magnetic tape and cassette can be applied to magnetic tape devices (in other words, magnetic recording and playback systems) that record and / or reproduce data by changing the head tilt angle during tape transport. In this application, since the head tilt is included during data recording and / or data playback, a magnetic tape with high transport stability during data recording and / or playback with a tilted head is preferred.

[0203] However, the aforementioned magnetic tapes and cassettes are not limited to those used in this magnetic tape apparatus. For example, it can also be used in a manner where the head tilt angle is fixed during each recording or playback process, based on changes made to the head tilt angle during a particular recording or playback operation and subsequent recording or playback operations. In this mode of use, the tilting of the magnetic head is included during data recording and / or data playback; therefore, magnetic tapes with high tape transport stability during data recording and / or playback are preferred when the magnetic head is tilted.

[0204] [Magnetic tape device] One aspect of the present invention relates to a magnetic tape apparatus comprising the aforementioned magnetic tape. In the magnetic tape apparatus, data recording to 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 aforementioned magnetic tape apparatus may detachably include the magnetic tape cassette according to one aspect of the present invention.

[0205] The aforementioned magnetic tape cartridge 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 means capable of at least one of recording data onto a magnetic tape and playing back data recorded onto the magnetic tape. This means is commonly referred to as a drive.

[0206] <Magnetic head> The aforementioned magnetic tape device may include a magnetic head. Regarding the structure of the magnetic head and the angle θ, which serves as the head tilt angle, 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, and 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 performs data recording and / or playback of 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 playback data (playback element) are collectively referred to as "head element".

[0207] When recording and / or reproducing 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 along the width of the magnetic tape.

[0208] Furthermore, the recording and reproducing head can also record and / or reproduce other data tapes. In this case, the servo signal readout element is moved towards the specified servo tape using the UDIM information described above to begin tracking that servo tape.

[0209] 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 conductor 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 specifications. For example, in the LTO Ultrium 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 width direction, are formed on the servo strip. Specifically, in Figure 5 In the context of server band 1, the server frame SF consists of server subframe 1 (SSF1) and server subframe 2 (SSF2). Server subframe 1 is composed of A burst ( Figure 5 The symbols A and B are in the middle. Figure 5The 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 is in the middle and D bursts ( Figure 5 The symbol D is used to represent the servo pattern. A C burst consists of servo patterns C1 to C4, and a D burst consists of servo patterns D1 to D4. These 18 servo patterns are arranged in groups of 5 and 4 in subframes arranged in a 5, 5, 4, 4 pattern to identify servo frames. Figure 5 For illustrative purposes, only one 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 in each servo tape. Figure 5 In the diagram, the arrows indicate the direction of tape travel. For example, LTO Ultrium format tapes typically have more than 5,000 servo frames per 1 meter of tape length in each servo tape of the magnetic layer.

[0210] In the aforementioned magnetic tape apparatus, the head tilt angle can be changed as the magnetic tape travels within the apparatus. The head 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 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 magnetic head module, 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.

[0211] Regarding the head tilt angle during tape transport, when the magnetic head comprises multiple modules, a reference can be used to define the angle for a randomly selected module. Figures 1-3 The angle θ is the angle at the start of tape feeding. initial It can be set to 0° or higher than 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, it is preferable from the viewpoint of adjusting the effective distance between the servo signal readout elements according to the dimensional change in the width direction of the magnetic tape. From this point of view, θ initial Preferably, 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 "wrapping angle") formed by 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 magnetic tape during tape travel. Furthermore, from the viewpoint of magnetic 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 wrap angle, θ initialPreferably, the angle is 45° or less, more preferably 40° or less, and even more preferably 35° or less.

[0212] Regarding the change of angle θ during tape transport, the angle θ of the magnetic head changes from θ at the start of tape transport during the tape's journey within the tape drive. initial In cases where changes occur to the data recorded onto and / or reproduced on the magnetic tape, the maximum change in angle θ during tape transport, Δθ, is calculated according to the following formula: max and Δθ min The larger value in the middle. The maximum value of the angle θ during tape transport is θ. max The minimum value is θ min Additionally, "max" is an abbreviation for maximum, and "min" is an abbreviation for minimum.

[0213] Δθ max =θ max -θ initial Δθ min =θ initial -θ min In one embodiment, Δθ can exceed 0.000°. From the viewpoint of adjusting the effective distance between servo signal readout 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 reproduced data among multiple magnetic head elements during data recording and / or data reproduction, Δθ is preferably 1.000° or less, more preferably 0.900° or less, further preferably 0.800° or less, more preferably 0.700° or less, and even more preferably 0.600° or less.

[0214] exist Figure 2 and Figure 3 In 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.

[0215] θ is the head tilt angle when the tape starts to move. initial It can be set through the control device of the magnetic tape device, etc.

[0216] Regarding the head tilt angle during tape transport. Figure 6This is an explanatory diagram illustrating the method for measuring the angle θ during magnetic tape transport. The angle θ during magnetic tape transport can be determined, for example, by the following method. When determining the angle θ during magnetic tape transport using this method, it is assumed that the angle θ varies within the range of 0 to 90° during tape transport. That is, if the axis of the component array is tilted towards the tape transport direction at the start of tape transport, then during tape transport, the component array will not tilt so that its axis is tilted in the opposite direction to the initial tape transport direction; conversely, if the axis of the component array is tilted in the opposite direction to the initial tape transport direction at the start of tape transport, then during tape transport, the component array will not tilt so that its axis is tilted in the initial tape transport direction.

[0217] The phase difference (i.e., time difference) ΔT of the regenerated signals from a pair of servo signal readout elements 1 and 2 is measured. The measurement of ΔT can be performed by a measuring unit installed in the magnetic tape device. The structure of this measuring unit is known. The distance L between the central portion of servo signal readout element 1 and the central portion of servo signal readout element 2 can be measured using an optical microscope or the like. When the magnetic tape travel speed is v, the distance between the central portions of the two servo signal readout 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 travel. In this example, the phase difference (i.e., time difference) ΔT between the phase of the regenerated signal of servo signal readout element 2 and the phase of the regenerated signal of 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 travel, ΔT is measured as the phase difference (i.e., time difference) between the phase of the regenerated signal of servo signal readout element 1 and the phase of the regenerated signal of servo signal readout element 2. Otherwise, θ can be obtained using the method described above.

[0218] 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.

[0219] <Structure of magnetic tape device> Figure 7 The magnetic tape device 10 shown controls the recording and playback head unit 12 according to commands from the control device 11 to record and play back data for the magnetic tape MT.

[0220] 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.

[0221] The magnetic tape device 10 has a structure capable of loading magnetic tape cartridges 13.

[0222] 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.

[0223] 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.

[0224] 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. Tape speed and head tilt angle can be controlled 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 via spindle motors 17A and 17B, tension control can also be achieved using guide rollers 15A and 15B.

[0225] 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 be, for example, ISO (International Organization for Standardization) 14443.

[0226] The control device 11 includes, for example, a control unit, a storage unit, and a communication unit.

[0227] The recording / reproducing head unit 12 comprises, for example, a recording / reproducing magnetic head, a servo tracking actuator for adjusting the position of the recording / reproducing magnetic head in the track width direction, a recording / reproducing amplifier 19, and a connector cable for connecting to the control device 11. The recording / reproducing magnetic head comprises, for example, a recording element for recording data on the magnetic tape, a reproducing element for reproducing data on the magnetic tape, and a servo signal reading element for reading servo signals recorded on the magnetic tape. For example, one or more recording elements, reproducing elements, and servo signal reading elements may be mounted in a single magnetic head. Alternatively, each element may be individually housed in multiple magnetic heads corresponding to the magnetic tape's travel direction.

[0228] 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 reproduce the data recorded on the magnetic tape MT according to commands from the control device 11.

[0229] 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 dimensional information in the width direction of the tape during travel. This allows the effective distance between servo signal reading elements to be close to or consistent with the servo tape interval. This dimensional 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 width direction of the tape can be changed based on the dimensional information in the width direction of the tape obtained during travel. The head tilt angle can be adjusted, for example, through feedback control. Furthermore, the head tilt angle can also be adjusted, for example, by the methods described in Japanese Patent Application Publication No. 2016-524774 (Patent Document 1) or US2019 / 0164573A1 (Patent Document 2).

[0230] Example The present invention will now be described based on embodiments. However, the present invention is not limited to the embodiments shown. 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.

[0231] [Protrusion-forming agent] The protrusion forming agents used in the preparation of the magnetic layer forming composition for the production of magnetic tapes in the examples or comparative examples are as follows. Protrusion forming agent B consists of particles with low surface smoothness. The particle shapes of protrusion forming agents A and C are so-called irregular shapes.

[0232] Protrusion forming agent A: ASAHI #50 (carbon black) manufactured by ASAHI CARBON CO.,LTD., with an average particle size of 60nm. Protrusion forming agent B: ATLAS (a composite particle of silica and polymer) manufactured by Cabot Corporation, with an average particle size of 100 nm. Protrusion forming agent C: #45L (carbon black) manufactured by Mitsubishi Chemical Corporation, with an average particle size of 60 nm. [Strongly magnetic powder] In Table 1, “BaFe” is hexagonal barium ferrite powder (magnetic force Hc: 196kA / m, average particle size (average plate diameter) 24nm).

[0233] In Table 1, “SrFe1” refers to hexagonal strontium ferrite powder produced by the following method.

[0234] 1707g of SrCO3, 687g of H3BO3, 1120g of Fe2O3, 45g of Al(OH)3, 24g of BaCO3, 13g of CaCO3, and 235g of Nd2O3 were weighed and mixed in a mixer to obtain a raw material mixture.

[0235] 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.

[0236] 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. The temperature was then maintained at the same temperature for 5 hours to allow hexagonal strontium ferrite particles to precipitate (crystallize).

[0237] 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, repeatedly decanted, washed, and dried in a furnace at 110°C for 6 hours to obtain hexagonal strontium ferrite powder.

[0238] 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 3The mass magnetization σs is 49 A·m 2 / kg.

[0239] 12 mg of sample powder was collected from the hexagonal strontium ferrite powder obtained above. The elemental analysis of the filtrate obtained by partially dissolving the sample powder under the dissolution conditions illustrated above was performed using an ICP analyzer to determine the surface content of neodymium atoms.

[0240] 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.

[0241] 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%. It was confirmed that the ratio of surface portion content to bulk content, "surface portion content / bulk content", is 2.8, indicating that neodymium atoms are concentrated on the surface of the particles.

[0242] The powder obtained above was confirmed to exhibit a hexagonal ferrite crystal structure by scanning CuKα rays under a voltage of 45 kV and an intensity of 40 mA, and by measuring the X-ray diffraction pattern under the following conditions (X-ray diffraction analysis). The powder obtained above exhibits a magnetoplumbite (M-type) hexagonal ferrite crystal structure. Furthermore, the crystal phase detected by X-ray diffraction analysis is a magnetoplumbite type single phase.

[0243] PANalytical X'Pert Pro diffractometer, PIXcel detector Soller slit for incident and diffracted beams: 0.017 radians Fixed angle of the dispersing slit: 1 / 4 degree Mask: 10mm Slit prevention for scattering: 1 / 4 degree Measurement mode: Continuous Measurement time for each stage: 3 seconds Measurement speed: 0.017 degrees per second Measurement step size: 0.05 degrees In Table 1, “SrFe2” refers to hexagonal strontium ferrite powder produced by the following method.

[0244] 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.

[0245] 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.

[0246] 280g of the obtained amorphous body 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).

[0247] 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, repeatedly decanted, washed, and dried in a furnace at 110°C for 6 hours to obtain hexagonal strontium ferrite powder.

[0248] 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.

[0249] In Table 1, “ε-iron oxide” refers to ε-iron oxide powder produced by the following method.

[0250] A solution of 8.3 g of ferric nitrate (III) nonahydrate, 1.3 g of gallium nitrate (III) octahydrate, 190 mg of cobalt nitrate (II) hexahydrate, 150 mg of titanium sulfate (IV), and 1.5 g of polyvinylpyrrolidone (PVP) dissolved 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 (1 g of citric acid dissolved 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 an oven at 80°C.

[0251] 800g of pure water was added to the dried powder to redisperse it, yielding a dispersion. While stirring the dispersion at 50°C, 40g of a 25% ammonia solution was added dropwise. After stirring for 1 hour at 50°C, 14mL of tetraethoxysilane (TEOS) was added, and stirring continued for 24 hours. 50g of ammonium sulfate was added to the resulting reaction solution, and the precipitated powder was collected by centrifugation, washed with pure water, and dried in an oven at 80°C for 24 hours to obtain the precursor of the strongly magnetic powder.

[0252] 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.

[0253] 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.

[0254] Then, the strong magnetic powder with silica compounds removed was collected by centrifugation and washed with pure water to obtain the strong magnetic powder.

[0255] The composition of the obtained 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 in the X-ray diffraction pattern confirmed that the obtained strongly magnetic powder has an ε-phase single-phase crystal structure (the crystal structure of ε-iron oxide) that does not contain α-phase or γ-phase crystal structures.

[0256] The obtained ε-iron oxide powder has 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.

[0257] The activation volume and anisotropy constant Ku of the above-mentioned hexagonal strontium ferrite powder and ε-iron oxide powder were obtained by using a vibrating sample magnetometer (manufactured by TOEI INDUSTRY CO.,LTD.) on each strongly magnetic powder and by the method described above.

[0258] 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.

[0259] [Non-magnetic support] In Table 1, “PEN” represents polyethylene naphthalate support and “PA” represents aromatic polyamide support.

[0260] [Example 1] <Composition for forming magnetic layers> (Magnetic fluid) Strongly magnetic powder (refer to Table 1): 100.0 parts Oleic acid: 2.0 parts Vinyl chloride copolymer (MR-104 manufactured by KANEKA CORPORATION): 10.0 parts Polyurethane resin containing SO3Na groups: 4.0 parts (Weight-average molecular weight 70,000, SO3Na group: 0.07 meq / g) Additive A: 10.0 parts Methyl ethyl ketone: 150.0 parts Cyclohexanone: 150.0 parts (Grinding agent solution) α-Alumina (average particle size: 110 nm): 6.0 parts Vinyl chloride copolymer (MR110 manufactured by KANEKA CORPORATION): 0.7 parts Cyclohexanone: 20.0 parts (Protrusion-forming agent liquid) Protrusion forming agents (refer to Table 1): Refer to Table 1 Methyl ethyl ketone: 9.0 parts Cyclohexanone: 6.0 parts (Other ingredients) Polyethyleneimine (manufactured by NIPPON SHOKUBAI CO., LTD., number average molecular weight 300): Refer to Table 1 Stearic acid: Refer to Table 1 Stearamide: 0.3 parts Butyl stearate: 6.0 parts Methyl ethyl ketone: 110.0 parts Cyclohexanone: 110.0 parts Polyisocyanate (TOSOH CORPORATION CORONATE (registered trademark) L): 3.0 parts 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.

[0261] <Composition for forming non-magnetic layers> Non-magnetic inorganic powder (α-iron oxide): 80.0 parts (Average particle size: 0.15 μm, average aspect ratio: 7, BET (Brunauer-Emmett-Teller) specific surface area: 52 m²) 2 / g) Carbon black (average particle size: 20 nm): 20.0 parts Electron beam cured vinyl chloride copolymer: 13.0 parts Electron beam cured polyurethane resin: 6.0 parts Phenylated phosphonic acid: 3.0 parts Cyclohexanone: 140.0 parts Methyl ethyl ketone: 170.0 parts Butyl stearate: 2.0 parts Stearic acid: 1.0 part <Composition for forming back coating> Non-magnetic inorganic powder (α-iron oxide): 80.0 parts (Average particle size: 0.15μm, average aspect ratio: 7, BET specific surface area: 52m²) 2 / g) Carbon black (average particle size: 20 nm): 20.0 parts Carbon black (average particle size: 100nm): 3.0 parts Vinyl chloride copolymer: 13.0 parts Polyurethane resin containing sulfonic acid groups: 6.0 parts Phenylated phosphonic acid: 3.0 parts Cyclohexanone: 140.0 parts Methyl ethyl ketone: 170.0 parts Stearic acid: 3.0 parts Polyisocyanate (TOSOH CORPORATION CORONATE (registered trademark) L): 5.0 parts Methyl ethyl ketone: 400.0 parts <Preparation of the composition for forming each layer> A composition for forming magnetic layers was prepared by the following method.

[0262] After mixing and diluting the components of the above magnetic liquid using an open kneader, a horizontal bead mill disperser was used to disperse the liquid 12 times using zirconia (ZrO2) beads (hereinafter referred to as "Zr beads") with a particle size of 0.5 mm 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.

[0263] Regarding the grinding agent liquid, after mixing the above-mentioned components of the grinding agent liquid, it was placed together with Zr beads with a particle size of 1mm into a vertical sand mill disperser. The ratio of bead volume to (grind agent liquid volume + bead volume) was adjusted to 60%, and the sand mill dispersion treatment was carried out for 180 minutes. The treated liquid was then removed and ultrasonically dispersed and filtered using a flow ultrasonic dispersion filtration device.

[0264] After mixing the components of the above-mentioned 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 with a filter with a pore size of 0.5μm to prepare the protrusion-forming agent solution.

[0265] 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.

[0266] A composition for forming a nonmagnetic layer was prepared by the following method.

[0267] After the above-mentioned components, excluding the lubricant (butyl stearate and stearic acid), were mixed and diluted using an open kneader, they were dispersed using a horizontal bead mill disperser for the dispersion times listed in Table 1. Then, the lubricant (butyl stearate and stearic acid) was added, and the mixture was stirred using a dissolving mixer to prepare a composition for forming a non-magnetic layer.

[0268] The composition for forming a back coating was prepared by the following method.

[0269] After mixing and diluting the above-mentioned components, excluding the lubricant (stearic acid), polyisocyanate, and methyl ethyl ketone (400.0 parts), using an open kneader, dispersion was carried out using a horizontal bead mill disperser. Then, the 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 back coating formation.

[0270] <Making of Magnetic Tapes and Cassette Cases> On a biaxially stretched nonmagnetic support with the thicknesses shown in Table 1 (type: 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.

[0271] Then, using a 7-segment calendering roll consisting only of metal rolls, calendering was performed the number of times listed in Table 1 at a calendering speed of 80 m / min, a linear pressure of 294 kN / m, and the calendering temperature (surface temperature of the calendering rolls) listed in Table 1. Next, 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 device with a feed and take-up mechanism for the cut pieces, with a non-woven fabric and a scraper pressed against the surface of the magnetic layer.

[0272] By using a commercially available servo writer to record servo signals on the magnetic layer of the obtained magnetic tape, a magnetic tape is produced with a configuration based on LTO (Linear Tape-Open) Ultrium format, consisting of data tape, servo tape, and guide tape, and with a servo pattern (time-base servo pattern) on the servo tape based on the LTO Ultrium format configuration and shape. The resulting servo pattern conforms to 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.

[0273] The magnetic tape (960m in length) containing the servo signals is wound onto the reel of the tape cassette (LTO Ultrium 8 data cassette).

[0274] In this way, a cassette tape was made that contained the tape reel on the reel.

[0275] Compounds containing an ammonium salt structure of an alkyl ester anion represented by Formula 1, formed from polyethyleneimine and stearic acid, in the magnetic layer of magnetic tape can be identified by the following method.

[0276] Samples were cut from magnetic tape and X-ray photoelectron spectroscopy (ESCA) was performed on the magnetic layer surface (measurement area: 300 μm × 700 μm) using an ESCA apparatus. Specifically, wide-scan measurements were performed using the ESCA apparatus under the following conditions. Peaks were identified at the binding energies of the ester anion and the ammonium cation in the measurement results.

[0277] Device: AXIS-ULTRA manufactured by SHIMADZU CORPORATION Excitation X-ray source: Monochromatic Al-Kα rays Scan range: 0–1200 eV Energy consumption: 160eV Energy resolution: 1 eV / step Read-in time: 100ms / step Total number of times: 5 Furthermore, a 3cm sample was cut from the magnetic tape, and ATR-FT-IR (Attenuated Total Reflection-Fourier Transform-Infrared Spectrometer) measurements (reflectance method) were performed on the surface of the magnetic layer. In the measurement results, [the results were compared with COO]. - The absorption wavenumber corresponding to (1540cm) -1 Or 1430cm -1 ) and the wavenumber corresponding to the absorption of ammonium cations (2400 cm⁻¹) -1 Absorption was confirmed.

[0278] [Examples 2-14, Comparative Examples 1-6] 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.

[0279] 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.

[0280] [Evaluation of conveyor belt stability] The stability of the conveyor belt was evaluated using the following methods at an environment of 15℃ and 80% relative humidity.

[0281] 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.

[0282] By setting the head tilt angle to 15°, the following steps were performed to record and replay data and evaluate the tape travel stability during the replay process. The head tilt angle is the angle θ formed by the axis of the element array of the replay module and the width direction of the magnetic tape at the start of tape travel. Angle θ is set by the tape drive control device at the start of tape travel, and the head tilt angle remains fixed during tape travel.

[0283] A tape cassette is installed in the tape drive, and a tape is loaded. Then, while performing servo tracking, pseudo-random data with a specific data pattern is recorded on the tape via a recording and playback head unit. The tension along the tape length is set to a constant value at this time. Simultaneously with data recording, the servo tape interval is measured every 1m along the entire tape length and recorded in the cassette memory.

[0284] Next, while performing servo tracking, the data recorded on the magnetic tape is reproduced through the recording and playback head unit. The tension along the tape length is set to a constant value at this time.

[0285] 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 during the above-mentioned regeneration process.

[0286] PES is obtained using the following method.

[0287] To determine the PES, the dimensions of the servo pattern are needed. The servo pattern dimensions vary depending on the generation of the LTO. Therefore, firstly, using a magnetic force microscope or similar instrument, the average distance AC between the four corresponding fringes of the A-burst and C-burst, as well as the azimuth angle α of the servo pattern, are measured.

[0288] The average time between the 5 stripes corresponding to bursts A and B over a length of 1 LPOS word is defined as 'a'. The average time between the 4 stripes corresponding to bursts A and C over 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 across the 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 along the length of the magnetic tape spanning 30m to 200m, the standard deviation (σPES) of the PES obtained by the above method is calculated. If the σPES obtained in this way is below 50nm, it can be judged that the tape travel stability is excellent.

[0289] [Cassette tape review] (1) LFM reduction rate, dynamic friction force F 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, and the standard deviation (measured value after reciprocating slides) was calculated after normalizing the output distribution (Min-Max Normalization). 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 standard deviation (measured value before reciprocating slides) was calculated after normalizing the output distribution (Min-Max Normalization). Based on the measured values ​​before and after reciprocating slides, the LFM reduction rate was calculated using the above formula. A Bruker Nanoscope 5 (measurement mode: LFM) was used as the transverse force microscope.

[0290] Furthermore, using the above method, the kinetic friction force F in the 500th forward stroke out of 500 reciprocating slides was calculated. A commercially available LTO8 head (manufactured by IBM) was used as the LTO8 head.

[0291] (2) Magnetic tape thickness Ten magnetic tape samples (5 cm in length) were cut from arbitrary portions of the magnetic tapes taken from each 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 Mahr GmbH. The thickness of each magnetic tape sample was taken as the thickness of the tape sample by dividing the measured thickness by 10. For each magnetic tape of Examples 1-11 and Comparative Examples 1-6, the magnetic tape thickness was 5.0 μm. The magnetic tape thicknesses of Examples 12-14 are as follows: Example 12: 4.6 μm, Example 13: 4.0 μm, Example 14: 3.4 μm.

[0292] The results are shown in Table 1 (Table 1-1 to Table 1-4).

[0293] [Table 1-1]

[0294] [Table 1-2]

[0295] [Table 1-3]

[0296] [Table 1-4]

[0297] The results shown in Table 1 confirm that the magnetic tapes of the embodiments with an LFM reduction rate of over 20% exhibit excellent tape-running stability when the magnetic head is tilted in a low-temperature and high-humidity environment.

[0298] The magnetic tape was not vertically oriented during its production; otherwise, it was produced using the method described in Example 1.

[0299] 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.

[0300] Similarly, the vertical rectangle ratio of the sample piece cut from the magnetic tape of Example 1 was 0.65.

[0301] The two magnetic tapes were mounted onto a 1 / 2-inch reel tester, and their electromagnetic conversion characteristics (SNR: Signal-to-Noise Ratio) were evaluated using the following method. As a result, the magnetic tape of Example 1 achieved an SNR value 4 dB higher than that of the magnetic tape produced without vertical orientation treatment.

[0302] 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 (gap length 0.15 μm, track width 1.0 μm) was used as the recording head, and the recording current was set to the optimal recording current for each tape. A GMR (Giant-magnetoresistive) head (element thickness 15 nm, shielding spacing 0.1 μm, playback element width 0.8 μm) was used as the playback head for playback. 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 refers to the unit of line recording density (which cannot be converted to SI units). The portion of the signal that was sufficiently stable after the tape began to move was used as the signal.

[0303] Industrial availability One aspect of the present invention is applicable to various data storage technologies.

Claims

1. A magnetic tape having a non-magnetic support and a magnetic layer comprising strongly magnetic powder, wherein, The standard deviation of the friction distribution on the surface of the magnetic layer, measured by a transverse force microscope in a 3μm×3μm measurement area before and after 500 reciprocating slides relative to the LTO8 magnetic head at a head tilt angle of 15° 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 dynamic friction force F in the 500th forward stroke of the 500 reciprocating slides is less than 15gf.

3. The magnetic tape according to claim 1, wherein, The reduction rate is above 20% and below 30%.

4. The magnetic tape according to claim 1, wherein, The reduction rate is above 22% and below 30%.

5. The magnetic tape according to claim 1, wherein, The reduction rate is above 24% and below 30%.

6. 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.

7. 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.

8. The magnetic tape of claim 1, wherein, The magnetic tape thickness is less than 5.0 μm.

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

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

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

12. The magnetic tape according to claim 1, wherein, The dynamic friction force F in the 500th stroke of the 500 reciprocating sliding motion is less than 15gf. Between the non-magnetic support and the magnetic layer, there is also a non-magnetic layer containing non-magnetic powder. 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.

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

14. A magnetic tape device comprising the magnetic tape according to any one of claims 1 to 12.

15. The magnetic tape device of claim 14, further comprising a magnetic head, The magnetic head has a module including an array of elements, the array having multiple head elements between a pair of servo signal readout elements, and The magnetic tape device changes the angle θ between the axis of the element array and the width direction of the magnetic tape as the magnetic tape travels within the device.

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