Magnetic tape and magnetic tape housing

Abstract

The present invention provides a magnetic tape having a non-magnetic support and a magnetic layer containing ferromagnetic powder. The amount of dimensional change Δw in the width direction in relation to a tension change in the longitudinal direction is between 400 ppm / N and 900 ppm / N (both inclusive), the non-magnetic support is a polyethylene naphthalate support with the Young's modulus in the width direction being 10000 MPa or more, the magnetic layer includes a plurality of servo bands, and a variation coefficient CV calculated from equation A: CV = (σG / Δw) × 100 is 10% or less, where σG represents a standard deviation of servo band intervals as measured in an area extending over 100 meters in the longitudinal direction of the magnetic tape with a tension of 0.6 N applied thereon in the longitudinal direction.

Description

Technical Field

[0001] The present invention relates to a magnetic tape and a magnetic tape container.

Background Art

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

Prior Art Documents

Patent Documents

[0003] [[ID=2②]]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Recording of data on a magnetic tape and reproduction of the recorded data are usually performed while running the magnetic tape in a magnetic recording and reproducing apparatus (generally called a drive) by repeating the operation of pulling out the magnetic tape wound around one reel and winding it around the other reel between two reels. For the magnetic tape running in this way, recording of data and reproduction of the recorded data are performed by a magnetic head in the drive.

[0005] Magnetic tape is generally considered to be cost-effective compared to other recording media due to its low cost per unit of data recorded and low power consumption during data storage. The cost advantage increases as the amount of data recorded increases. For this reason, magnetic tape has been attracting attention as a high-capacity data storage medium in recent years. If the data transfer rate (write speed and / or read speed) remains constant, the time required to record and play back data increases as the amount of data recorded increases. Therefore, in order to further increase the amount of data recorded on magnetic tape, it is desirable to increase the data transfer rate (write speed and / or read speed) of the magnetic tape.

[0006] One aspect of the present invention primarily aims to enable improved transfer rates in recording data onto magnetic tape and / or reproducing data recorded on magnetic tape. [Means for solving the problem]

[0007] One aspect of the present invention is as follows: [1] A magnetic tape having a non-magnetic support and a magnetic layer containing ferromagnetic powder, The change in widthwise dimension Δw in response to a change in tension in the longitudinal direction is between 400 ppm / N and 900 ppm / N. The above non-magnetic support is a polyethylene naphthalate support with a Young's modulus in the width direction of 10,000 MPa or more, and The above magnetic layer has multiple servo bands, Formula A below: CV = (σG / Δw) × 100 The coefficient of variation CV calculated by this method is 10% or less. The above σG is the standard deviation of the servoband spacing measured over a 100m longitudinal region of the magnetic tape under a tension of 0.6N in the longitudinal direction. (Note that "ppm" is an abbreviation for parts per million, and "CV" is an abbreviation for Coefficient of Variation.) [2] The magnetic tape described in [1], wherein the coefficient of variation CV is 1% or more and 10% or less. [3] The magnetic tape according to [1] or [2], wherein the Young's modulus in the width direction of the polyethylene naphthalate support is 10,000 MPa or more and 20,000 MPa or less. [4] A magnetic tape as described in any of [1] to [3], wherein the tape thickness is 5.2 μm or less. [5] A magnetic tape according to any one of [1] to [4], further comprising a non-magnetic layer containing non-magnetic powder between the non-magnetic support and the magnetic layer. [6] The magnetic tape according to any one of [1] to [5], further comprising a back coat layer containing non-magnetic powder on the surface side of the non-magnetic support opposite to the surface side having the magnetic layer. [7] The magnetic tape described in any of [1] to [6], wherein the vertical aspect ratio of the magnetic tape is 0.60 or greater. A magnetic tape housing including a core around which the magnetic tape described in any of [8][1] to [7] is wound. [9] A magnetic tape cartridge, which is the magnetic tape housing described in [8].

[10] A magnetic tape housing according to [8], further comprising a magnetic head, which is a magnetic recording and playback device.

[11] The magnetic tape housing according to

[10] , wherein the magnetic head includes a regenerating element having a regenerating element width of 0.8 μm or less.

[12] A magnetic tape housing according to

[10] or

[11] , having a tension adjustment mechanism capable of adjusting the tension applied in the longitudinal direction of a magnetic tape running inside a magnetic recording and playback device.

[13] A magnetic tape housing according to any one of [8] to

[12] , wherein the roundness of the trajectory traced by the magnetic tape for one rotation when the wound magnetic tape is pulled out from the winding core is 120 μm or less as the arithmetic mean of the measurements taken at three locations in the width direction of the magnetic tape. [Effects of the Invention]

[0008] According to one aspect of the present invention, it is possible to improve the transfer rate in recording data onto magnetic tape and / or reproducing data recorded on magnetic tape. [Brief explanation of the drawing]

[0009] [Figure 1] This is a perspective view of an example of a magnetic tape cartridge. [Figure 2] This is a perspective view of the moment when magnetic tape is being wound onto a reel. [Figure 3] This is a perspective view of the reel after the magnetic tape has been wound onto it. [Figure 4] This diagram shows a schematic example of a magnetic recording and playback device with a magnetic tape cartridge inserted. [Figure 5] A schematic diagram of an example of a magnetic recording and playback device is shown. [Figure 6] Figure 4 shows a schematic diagram of a magnetic tape cartridge, with an opening formed in its case, mounted in the magnetic recording and playback device shown. [Figure 7] An example of the arrangement of data bands and servo bands is shown. [Figure 8] This shows an example of a servo pattern arrangement for an LTO (Linear Tape-Open) Ultrium format tape. [Modes for carrying out the invention]

[0010] One aspect of the present invention relates to a magnetic tape having a non-magnetic support and a magnetic layer containing ferromagnetic powder. The change in width Δw of the magnetic tape with respect to a change in tension in the longitudinal direction is 400 ppm / N or more and 900 ppm / N or less. The non-magnetic support is a polyethylene naphthalate support with a Young's modulus in the width direction of 10,000 MPa or more. The magnetic layer has a plurality of servo bands, and the coefficient of variation CV calculated by formula A: CV = (σG / Δw) × 100 is 10% or less. σG is the standard deviation of the servo band spacing measured over a 100 m longitudinal region of the magnetic tape when a tension of 0.6 N is applied in the longitudinal direction.

[0011] Furthermore, one aspect of the present invention relates to a magnetic tape housing that includes a core around which the magnetic tape is wound. In a magnetic recording and playback device that uses magnetic tape as a magnetic recording medium, the magnetic head is usually built into the magnetic recording and playback device, while the magnetic tape is treated as a removable medium (a so-called interchangeable medium). For example, a magnetic tape cartridge containing magnetic tape is inserted into the magnetic recording and playback device, and the magnetic tape is run between the reel of the magnetic tape cartridge and the take-up reel built into the magnetic recording and playback device to record data onto the magnetic tape and / or to play back data recorded on the magnetic tape. After that, the magnetic tape is placed back into the magnetic tape cartridge, and the magnetic tape cartridge is removed from the magnetic recording and playback device together with the magnetic tape cartridge. In this configuration, the magnetic tape cartridge can be the magnetic tape housing, and the winding core can be the reel provided in the magnetic tape cartridge. In another embodiment, the magnetic tape is not treated as a replaceable medium, and the magnetic tape is housed in a magnetic recording and playback device equipped with a magnetic head. In this embodiment, the magnetic recording and playback device can be the magnetic tape housing, and the winding core can be a reel provided within the magnetic recording and playback device. The configuration of the magnetic tape cartridge and magnetic recording / reproducing device will be described further later.

[0012] In the present invention and this specification, "Δw" is a value obtained by the method described in paragraphs 0093 to 0097 of Japanese Patent No. 6590102 (Patent Document 1).

[0013] In the present invention and this specification, "σG" is a value obtained by the following method. Measurements are performed in an environment with an ambient temperature of 25°C and a relative humidity of 50%. The magnetic tape housing containing the magnetic tape to be measured is placed in the measurement environment for at least 5 days to allow it to acclimate. Then, in this measurement environment, the magnetic tape is run in a magnetic recording and playback device equipped with a tension adjustment mechanism that applies tension in the longitudinal direction of the magnetic tape, with a tension of 0.6N (the tension setting value set in the magnetic recording and playback device) applied in the longitudinal direction of the magnetic tape. If the magnetic tape housing is a magnetic recording and playback device, the magnetic tape is run within this device. If the magnetic tape housing is a magnetic tape cartridge, this magnetic tape cartridge is mounted in the magnetic recording and playback device and the magnetic tape is run. With the magnetic tape run under the above tension, the interval between two adjacent servo bands on either side of the data band is determined for each LPOS (Longitudinal Position) word. At any point on the magnetic tape, the servo band interval is determined every 1m for all LPOS words obtained for the entire longitudinal range of the 100m tape length, and if there are multiple servo band intervals, the servo band interval is determined every 1m for all servo band intervals. The area between two adjacent servo bands is called the data band. The number of servo band intervals is the same as the number of data bands. For example, if the total number of data bands is 4, the number of servo band intervals is also 4. If the number of servo band intervals is "n", then by determining the servo band intervals every 1m over a 100m longitudinal region as described above, "100 × n" measurements can be obtained. The standard deviation σ (i.e., the positive square root of the variance) calculated using these "100 × n" servo band interval measurements is defined as "σG". The interval between two adjacent servo bands separated by a data band can be determined, for example, using the PES (Position Error Signal) obtained from the servo signal acquired by reading the servo pattern with a servo signal reading element. For details, please refer to the description of the embodiment below. In the above measurement, a tension of 0.6N is used as an example of the tension that can be applied in the longitudinal direction to a magnetic tape running in a magnetic recording and playback device. However, this is merely an example, and the tension that can be applied in the longitudinal direction to the magnetic tape during its movement is not limited.

[0014] The coefficient of variation CV can be calculated from equation A below using Δw and σG obtained by the above method. Equation A: CV = (σG / Δw) × 100

[0015] As previously mentioned, recording data to and playing back recorded data on magnetic tape is typically done by repeatedly pulling the magnetic tape from one reel and winding it onto the other, thereby moving the magnetic tape within the magnetic recording and playback device. More specifically, data recording to magnetic tape is typically done by running the magnetic tape within the magnetic recording and playback device and recording data on the data bands by having the magnetic head follow the data bands of the magnetic tape. This creates data tracks on the data bands. During playback of recorded data, the magnetic tape is run within the magnetic recording and playback device, and the magnetic head follows the data bands of the magnetic tape to read the data recorded on the data bands. To improve the accuracy of the magnetic head following the data bands of the magnetic tape during such recording and / or playback, systems that use servo signals to perform head tracking (hereinafter referred to as "servo systems") have been put into practical use. Furthermore, the dimensions of the magnetic tape in the width direction are controlled by using servo signals to acquire widthwise dimensional information of the magnetic tape while it is in motion, and by adjusting the tension applied to the longitudinal direction of the magnetic tape according to the acquired dimensional information (see, for example, paragraph 0171 of Patent Document 1 (Japanese Patent No. 6590102)). The above tension adjustment is thought to contribute to suppressing phenomena such as overwriting of recorded data and playback failures, which can occur when the magnetic head for recording or playing back data is misaligned from the target track position due to width deformation of the magnetic tape during recording or playback. Regarding misalignment in the width direction of magnetic tape, the inventors, while conducting research to improve the transfer rate (hereinafter simply referred to as "transfer rate") in recording data on magnetic tape and / or reproducing data recorded on magnetic tape, considered that suppressing the occurrence of the aforementioned phenomenon by the tension adjustment described above would lead to an improvement in the transfer rate. Furthermore, the inventors speculated that when unwinding the wound magnetic tape, misalignment in the width direction of the magnetic tape occurring at a shorter cycle than the cycle in which the tension adjustment described above is performed could be a cause of a decrease in the transfer rate. Specifically, the inventors speculated that such short-cycle misalignment in the width direction of the magnetic tape could increase the frequency with which the magnetic recording and playback device performs "start / stop" or "repositioning," which involves temporarily stopping the movement of the magnetic tape and reversing the magnetic tape to write or read data again. The more frequently "start / stop" and / or "repositioning" operations are performed, the longer the time required to write and / or read data, resulting in a decrease in the transfer rate. After further intensive research, the inventors concluded that both Δw and the coefficient of variation CV should be controlled in order to suppress the occurrence of positional misalignment in the width direction at the short period described above. The inventors have now discovered that by controlling Δw and the coefficient of variation CV to the ranges described above, it is possible to improve the transfer rate in recording data to magnetic tape and / or playing back recorded data. It should be noted that while Patent Document 1 (Japanese Patent No. 6590102) mentioned above contains a description of Δw, it does not suggest that the coefficient of variation CV, which is obtained as described above, should be controlled. In response to this, the inventors surmise that a small value for the coefficient of variation CV means that variations in widthwise dimensional changes that occur when the magnetic tape is subjected to tension in the longitudinal direction are suppressed, and that setting this value to 10% or less contributes to suppressing the occurrence of widthwise positional deviations over short periods. Furthermore, the inventors believe that including a polyethylene naphthalate support with a Young's modulus of 10,000 MPa or more in the width direction as a non-magnetic support can contribute to controlling the width dimension of the magnetic tape by adjusting the tension applied in the longitudinal direction of the magnetic tape, thereby enabling good recording and / or playback. However, the present invention is not limited to the inferences described herein, including the inferences mentioned above.

[0016] The magnetic tape and the magnetic tape housing described above will be explained in more detail below.

[0017] [Magnetic tape] <Δw> The Δw of the above magnetic tape is between 400 ppm / N and 900 ppm / N. Magnetic tapes with a large Δw value exhibit larger dimensional changes in the width direction in response to changes in tension in the longitudinal direction. This is preferable from the viewpoint of easily suppressing phenomena such as overwriting of recorded data or playback failures, which can occur when the magnetic head for recording or playing back data is misaligned from the target track position due to width deformation of the magnetic tape during recording or playback, by adjusting the tension. From this viewpoint, the Δw of the above magnetic tape is preferably 450 ppm / N or more, more preferably 500 ppm / N or more, even more preferably 550 ppm / N or more, and even more preferably 600 ppm / N or more. Furthermore, large deformation in the width direction of the magnetic tape due to tension adjustment can cause errors. Suppressing such errors is preferable from the viewpoint of improving the transfer rate. From this viewpoint, the Δw of the magnetic tape is preferably 900 ppm / N or less, more preferably 850 ppm / N or less, more preferably 800 ppm / N or less, even more preferably 750 ppm / N or less, and even more preferably 700 ppm / N or less. The method for controlling Δw will be described later.

[0018] <Coefficient of variation CV> The coefficient of variation CV calculated by formula A described above for the magnetic tape is preferably 10% or less, and more preferably 9% or less, in the order of 8% or less, 7% or less, 6% or less, 5% or less, 4% or less, 3% or less, 2% or less, and 1% or less, from the viewpoint of improving the transfer rate. The coefficient of variation CV can be, for example, 0%, 0% or more, greater than 0%, or 1% or more. From the viewpoint of improving the transfer rate, a smaller value for the coefficient of variation CV is preferable. The method for controlling the coefficient of variation CV will be described later.

[0019] <Nonmagnetic support> The above magnetic tape includes a polyethylene naphthalate support as a non-magnetic support (hereinafter also simply referred to as "support"), with a Young's modulus in the width direction of 10,000 MPa (megapascals) or more.

[0020] Polyethylene naphthalate (PEN) is a resin containing a naphthalene ring and multiple ester bonds (i.e., a polyester containing a naphthalene ring), which can be obtained by esterification of 2,6-naphthalenedicarboxylate dimethyl with ethylene glycol, followed by transesterification and polycondensation reactions. In this invention and specification, "polyethylene naphthalate" also includes structures having one or more other components in addition to the above components (e.g., copolymer components, components introduced into terminals or side chains, etc.). In this invention and specification, "polyethylene naphthalate support" means a support containing at least one layer of polyethylene naphthalate film. "Polyethylene naphthalate film" means a film in which polyethylene naphthalate is the most abundant component by mass among the components constituting the film. In this invention and specification, "polyethylene naphthalate support" includes supports in which all resin films contained in the support are polyethylene naphthalate films, and supports containing polyethylene naphthalate films and other resin films. Specific forms of polyethylene naphthalate supports include single-layer polyethylene naphthalate films, laminated films of two or more polyethylene naphthalate films with the same constituent components, laminated films of two or more polyethylene naphthalate films with different constituent components, and laminated films containing one or more polyethylene naphthalate films and one or more resin films other than polyethylene naphthalate films. In laminated films, an adhesive layer or the like may be optionally included between two adjacent layers. Furthermore, the polyethylene naphthalate support may optionally include a metal film and / or a metal oxide film formed by vapor deposition or the like on one or both surfaces.

[0021] Furthermore, the non-magnetic support can be a biaxially oriented film, and may be a film that has been subjected to corona discharge, plasma treatment, easy adhesion treatment, heat treatment, etc.

[0022] In the present invention and this specification, the Young's modulus of a non-magnetic support is a value measured by the following method in a measurement environment of 23°C and 50% relative humidity. The Young's moduli shown in the table below are values ​​obtained by the following method using a Tensilon universal tensile testing device manufactured by Toyo Baldwin Co., Ltd. A sample piece cut from the non-magnetic support to be measured is pulled using a universal tensile testing apparatus under the conditions of a chuck distance of 100 mm, a tensile speed of 10 mm / min, and a chart speed of 500 mm / min. As the universal tensile testing apparatus, commercially available universal tensile testing apparatuses such as the Tensilon manufactured by Toyo Baldwin Co., Ltd., or universal tensile testing apparatuses with known configurations can be used. From the tangents of the rising portion of the load-elongation curve thus obtained, the Young's modulus in the longitudinal and width directions of the sample piece is calculated, respectively. Here, the longitudinal and width directions of the sample piece refer to the longitudinal and width directions when the sample piece was contained in a magnetic tape. For example, after removing parts other than the non-magnetic support, such as the magnetic layer, from the magnetic tape using a known method (e.g., defilm removal using an organic solvent), the Young's modulus in the longitudinal and width directions of the non-magnetic support can be determined using the method described above.

[0023] The Young's modulus in the width direction of the polyethylene naphthalate support is 10,000 MPa or higher. The inventors believe this is why the magnetic tape allows for good recording and / or playback by controlling the width dimension of the magnetic tape by adjusting the tension applied in the longitudinal direction of the magnetic tape. The Young's modulus in the width direction of the polyethylene naphthalate support can also be, for example, 11,000 MPa or higher. Furthermore, the Young's modulus in the width direction of the polyethylene naphthalate support may be, for example, 20,000 MPa or less, 18,000 MPa or less, 16,000 MPa or less, or 14,000 MPa or less, and may exceed the values ​​exemplified herein.

[0024] The polyethylene naphthalate support described above only needs to have a Young's modulus of 10,000 MPa or more in the width direction, and the Young's modulus in the longitudinal direction is not particularly limited. In one embodiment, the Young's modulus in the longitudinal direction of the polyethylene naphthalate support is preferably 2,500 MPa or more, and more preferably 3,000 MPa or more. Furthermore, the Young's modulus in the longitudinal direction of the polyethylene naphthalate support can be, for example, 10,000 MPa or less, 9,000 MPa or less, 8,000 MPa or less, 7,000 MPa or less, or 6,000 MPa or less. A larger Young's modulus in the longitudinal direction of the non-magnetic support tends to result in a smaller Δw. Similarly, a larger Young's modulus in the width direction of the non-magnetic support tends to result in a smaller Δw. When manufacturing magnetic tape, the non-magnetic support is usually used with the MD direction (Machine direction) of the film as the longitudinal direction and the TD direction (Transverse direction) as the width direction. In one embodiment, the Young's modulus in the longitudinal direction and the Young's modulus in the width direction of the non-magnetic support can be the same value, while in another embodiment, they can be different values. In one embodiment, the Young's modulus in the width direction of the polyethylene naphthalate support can be greater than the Young's modulus in the longitudinal direction. The Young's modulus of a non-magnetic support can be controlled by the type and mixing ratio of the components constituting the support, the manufacturing conditions of the support, etc. For example, by adjusting the stretching ratio in each direction during the biaxial stretching process, the Young's modulus in the longitudinal direction and the Young's modulus in the width direction can be controlled, respectively.

[0025] <Magnetic layer> (Ferromagnetic powder) As the ferromagnetic powder contained in the magnetic layer, one or more known ferromagnetic powders used in the magnetic layers of various magnetic recording media can be used in combination. Using a ferromagnetic powder with a small average particle size is preferable from the viewpoint of improving recording density. From this viewpoint, the average particle size of the ferromagnetic powder is preferably 50 nm or less, more preferably 45 nm or less, even more preferably 40 nm or less, even more preferably 35 nm or less, even more preferably 30 nm or less, even more preferably 25 nm or less, and even more preferably 20 nm or less. On the other hand, from the viewpoint of magnetization stability, the average particle size of the ferromagnetic powder is preferably 5 nm or more, more preferably 8 nm or more, even more preferably 10 nm or more, even more preferably 15 nm or more, and even more preferably 20 nm or more.

[0026] Hexagonal ferrite powder A preferred example of ferromagnetic powder is hexagonal ferrite powder. For details on hexagonal ferrite powder, see, for example, paragraphs 0012 to 0030 of Japanese Patent Publication No. 2011-225417, paragraphs 0134 to 0136 of Japanese Patent Publication No. 2011-216149, paragraphs 0013 to 0030 of Japanese Patent Publication No. 2012-204726, and paragraphs 0029 to 0084 of Japanese Patent Publication No. 2015-127985.

[0027] In the present invention and this specification, "hexagonal ferrite powder" refers to a ferromagnetic powder in which a hexagonal ferrite crystal structure is detected as the main phase by X-ray diffraction analysis. The main phase refers to the structure to which the highest intensity diffraction peak in the X-ray diffraction spectrum obtained by X-ray diffraction analysis belongs. For example, if the highest intensity diffraction peak in the X-ray diffraction spectrum obtained by X-ray diffraction analysis is attributed to the hexagonal ferrite crystal structure, it shall be determined that the hexagonal ferrite crystal structure has been detected as the main phase. If only a single structure is detected by X-ray diffraction analysis, this detected structure shall be considered the main phase. The hexagonal ferrite crystal structure contains at least iron atoms, divalent metal atoms, and oxygen atoms as constituent atoms. Divalent metal atoms are metal atoms that can become divalent cations as ions, and examples include strontium atoms, barium atoms, alkaline earth metal atoms such as calcium atoms, and lead atoms. In the present invention and this specification, hexagonal strontium ferrite powder refers to powder in which the main divalent metal atom contained is strontium, and hexagonal barium ferrite powder refers to powder in which the main divalent metal atom contained is barium. The main divalent metal atom refers to the divalent metal atom that accounts for the largest proportion on an atomic percentage basis among the divalent metal atoms contained in the powder. However, rare earth atoms are not included in the above divalent metal atoms. In the present invention and this specification, "rare earth atoms" are selected from the group consisting of scandium atoms (Sc), yttrium atoms (Y), and lanthanide atoms. Lanthanide atoms are selected from the group consisting of lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu).

[0028] Below, we will describe hexagonal strontium ferrite powder, a form of hexagonal ferrite powder, in more detail.

[0029] The activation volume of the hexagonal strontium ferrite powder is preferably in the range of 800 to 1600 nm 3 The particulate hexagonal strontium ferrite powder showing an activation volume within the above range is suitable for producing a magnetic tape that exhibits excellent electromagnetic conversion characteristics. The activation volume of the hexagonal strontium ferrite powder is preferably 800 nm 3 or more, for example, 850 nm 3 or more. Also, from the viewpoint of further improving the electromagnetic conversion characteristics, the activation volume of the hexagonal strontium ferrite powder is more preferably 1500 nm 3 or less, still more preferably 1400 nm 3 or less, even more preferably 1300 nm 3 or less, still even more preferably 1200 nm 3 or less, yet still even more preferably 1100 nm 3 or less, and yet still even more preferably. The same applies to the activation volume of the hexagonal barium ferrite powder.

[0030] The "activation volume" is a unit of magnetization reversal and is an index indicating the magnetic size of particles. The activation volume described in the present invention and this specification and the anisotropy constant Ku described later are measured using a vibrating sample magnetometer at magnetic field sweep rates of 3 minutes and 30 minutes in the coercive force Hc measurement section (measurement temperature: 23°C ± 1°C), and are values obtained from the following relational expression between Hc and the activation volume V. Regarding the unit of the anisotropy constant Ku, 1 erg / cc = 1.0×10 -1 J / m 3 is. Hc = 2Ku / Ms{×1 - [(kT / KuV)ln(At / 0.693)] 1 / 2} [In the above formula, Ku: anisotropy constant (unit: J / m 3 ), Ms: saturation magnetization (unit: kA / m), k: Boltzmann constant, T: absolute temperature (unit: K), V: activation volume (unit: cm 3 ), A: spin precession frequency (unit: s -1 ), t: magnetic field reversal time (unit: s)]

[0031] As an indicator of the reduction of thermal fluctuations, or in other words, the improvement of thermal stability, the anisotropy constant Ku can be cited. The hexagonal strontium ferrite powder is preferably 1.8 × 10⁻⁶ 5 J / m 3 It can have a Ku of the above, and more preferably 2.0 × 10 5 J / m 3 It can have a Ku content of the above. Also, the Ku content of hexagonal strontium ferrite powder is, for example, 2.5 × 10⁻⁶. 5 J / m 3 The following values ​​are possible. However, since a higher Ku value is preferable as it indicates higher thermal stability, the values ​​are not limited to those exemplified above.

[0032] Hexagonal strontium ferrite powder may or may not contain rare earth atoms. When hexagonal strontium ferrite powder contains rare earth atoms, it is preferable that the rare earth atoms are present at a concentration of 0.5 to 5.0 atomic percent (bulk concentration) per 100 atomic percent of iron atoms. In one embodiment, hexagonal strontium ferrite powder containing rare earth atoms may exhibit a segregation of rare earth atoms in the surface layer. In the present invention and this specification, "rare earth atom surface layer segregation" means that the content of rare earth atoms relative to 100% of iron atoms in a solution obtained by partially dissolving hexagonal strontium ferrite powder with acid (hereinafter referred to as "rare earth atom surface layer content" or simply "surface layer content" with respect to rare earth atoms) is different from the content of rare earth atoms relative to 100% of iron atoms in a solution obtained by completely dissolving hexagonal strontium ferrite powder with acid (hereinafter referred to as "rare earth atom bulk content" or simply "bulk content" with respect to rare earth atoms), Rare earth atom surface content / Rare earth atom bulk content > 1.0 This means that the ratio is satisfied. The rare earth atom content of hexagonal strontium ferrite powder described later is synonymous with the rare earth atom bulk content. In contrast, partial dissolution using acid dissolves the surface layer of the particles constituting the hexagonal strontium ferrite powder, so the rare earth atom content in the solution obtained by partial dissolution is the rare earth atom content in the surface layer of the particles constituting the hexagonal strontium ferrite powder. When the rare earth atom surface layer content satisfies the ratio "rare earth atom surface layer content / rare earth atom bulk content > 1.0", it means that in the particles constituting the hexagonal strontium ferrite powder, rare earth atoms are concentrated in the surface layer (i.e., there are more of them in the surface layer than in the interior). In this invention and specification, the surface layer means a part of the region extending from the surface to the interior of the particles constituting the hexagonal strontium ferrite powder.

[0033] When hexagonal strontium ferrite powder contains rare earth atoms, the rare earth atom content (bulk content) is preferably in the range of 0.5 to 5.0 atomic percent relative to 100 atomic percent of iron atoms. It is believed that containing rare earth atoms at the bulk content within the above range, and having the rare earth atoms unevenly distributed on the surface of the particles constituting the hexagonal strontium ferrite powder, contributes to suppressing the decrease in regeneration output during repeated regeneration. This is presumed to be because the anisotropy constant Ku can be increased by containing rare earth atoms at the bulk content within the above range, and having the rare earth atoms unevenly distributed on the surface of the particles constituting the hexagonal strontium ferrite powder. The higher the value of the anisotropy constant Ku, the more it is possible to suppress the occurrence of a phenomenon called thermal fluctuation (in other words, to improve thermal stability). By suppressing the occurrence of thermal fluctuation, the decrease in regeneration output during repeated regeneration can be suppressed. It is speculated that the uneven distribution of rare earth atoms on the surface of hexagonal strontium ferrite powder particles contributes to stabilizing the spin of iron (Fe) sites within the crystal lattice of the surface layer, thereby increasing the anisotropy constant Ku. Furthermore, it is presumed that using hexagonal strontium ferrite powder with a rare-earth atom uneven distribution on the surface as the ferromagnetic powder for the magnetic layer contributes to suppressing wear on the magnetic layer surface due to sliding with the magnetic head. In other words, it is presumed that hexagonal strontium ferrite powder with a rare-earth atom uneven distribution on the surface may also contribute to improving the running durability of the magnetic tape. This is presumed to be because the uneven distribution of rare-earth atoms on the surface of the particles constituting the hexagonal strontium ferrite powder contributes to improved interaction between the particle surface and organic substances (e.g., binders and / or additives) contained in the magnetic layer, resulting in improved strength of the magnetic layer. From the viewpoint of further suppressing the decrease in regeneration output during repeated regeneration and / or further improving running durability, the rare earth atom content (bulk content) is more preferably in the range of 0.5 to 4.5 atomic percent, even more preferably in the range of 1.0 to 4.5 atomic percent, and even more preferably in the range of 1.5 to 4.5 atomic percent.

[0034] The bulk content mentioned above is the content obtained by completely dissolving the hexagonal strontium ferrite powder. In this invention and specification, unless otherwise specified, the content of atoms refers to the bulk content obtained by completely dissolving the hexagonal strontium ferrite powder. The hexagonal strontium ferrite powder containing rare earth atoms may contain only one type of rare earth atom, or it may contain two or more types of rare earth atoms. When two or more types of rare earth atoms are included, the bulk content mentioned above is determined for the sum of the two or more types of rare earth atoms. This also applies to other components in this invention and specification. That is, unless otherwise specified, a certain component may be used alone, or two or more types may be used. When two or more types are used, the content or content refers to the sum of the two or more types.

[0035] When hexagonal strontium ferrite powder contains rare earth atoms, the rare earth atoms included may be one or more of the rare earth atoms. From the viewpoint of further suppressing the decrease in regeneration output during repeated regeneration, preferred rare earth atoms include neodymium atoms, samarium atoms, yttrium atoms, and dysprosium atoms, with neodymium atoms, samarium atoms, and yttrium atoms being more preferred, and neodymium atoms being even more preferred.

[0036] In hexagonal strontium ferrite powder having a rare-earth atom surface segregation, the rare-earth atoms only need to be segregated in the surface layer of the particles constituting the hexagonal strontium ferrite powder, and the degree of segregation is not limited. For example, in hexagonal strontium ferrite powder having a rare-earth atom surface segregation, the ratio of the rare-earth atom surface content obtained by partial dissolution under the dissolution conditions described later to the rare-earth atom bulk content obtained by total dissolution under the dissolution conditions described later, "surface content / bulk content," is greater than 1.0 and can be 1.5 or greater. A "surface content / bulk content" greater than 1.0 means that in the particles constituting the hexagonal strontium ferrite powder, rare-earth atoms are segregated in the surface layer (i.e., there are more of them in the surface layer than in the interior). Furthermore, the ratio of the surface content of rare earth atoms obtained by partial dissolution under the dissolution conditions described later to the bulk content of rare earth atoms obtained by total dissolution under the dissolution conditions described later, "surface content / bulk content," can be, for example, 10.0 or less, 9.0 or less, 8.0 or less, 7.0 or less, 6.0 or less, 5.0 or less, or 4.0 or less. However, in hexagonal strontium ferrite powder having a rare earth atom surface distribution bias, the rare earth atoms only need to be biased towards the surface of the particles constituting the hexagonal strontium ferrite powder, and the above "surface content / bulk content" is not limited to the upper or lower limits exemplified.

[0037] The partial and total dissolution of hexagonal strontium ferrite powder is described below. For hexagonal strontium ferrite powder existing as a powder, the sample powders to be partially and completely dissolved are taken from the same lot of powder. On the other hand, for hexagonal strontium ferrite powder contained in the magnetic layer of a magnetic tape, a portion of the hexagonal strontium ferrite powder extracted from the magnetic layer is subjected to partial dissolution, and another portion is subjected to total dissolution. The extraction of hexagonal strontium ferrite powder from the magnetic layer can be carried out, for example, by the method described in paragraph 0032 of Japanese Patent Application Publication No. 2015-91747. Partial dissolution, as described above, refers to a state where the hexagonal strontium ferrite powder is dissolved to the extent that residual particles can be visually confirmed in the liquid at the end of the dissolution process. For example, partial dissolution can dissolve 10 to 20% by mass of the particles constituting the hexagonal strontium ferrite powder, with the total particles being 100% by mass. On the other hand, total dissolution, as described above, refers to a state where the hexagonal strontium ferrite powder is dissolved to the extent that no residual particles can be visually confirmed in the liquid at the end of the dissolution process. The above-mentioned partial dissolution and surface layer content measurement are performed, for example, by the following method. However, the dissolution conditions such as the amount of sample powder described below are examples only, and any dissolution conditions that enable partial and total dissolution can be arbitrarily adopted. A container (e.g., a beaker) containing 12 mg of sample powder and 10 mL of 1 mol / L hydrochloric acid is held on a hot plate at a set temperature of 70°C for 1 hour. The resulting solution is filtered through a 0.1 μm membrane filter. Elemental analysis of the resulting filtrate is performed using an inductively coupled plasma (ICP) analyzer. In this way, the surface content of rare earth atoms relative to 100% iron atoms can be determined. If multiple types of rare earth atoms are detected by elemental analysis, the total content of all rare earth atoms is taken as the surface content. This is also the case when measuring bulk content. On the other hand, the measurement of total dissolution and bulk content is performed, for example, by the following method. A container (e.g., a beaker) containing 12 mg of sample powder and 10 mL of 4 mol / L hydrochloric acid is held on a hot plate at a set temperature of 80°C for 3 hours. Afterward, the bulk content relative to 100 atomic percent of iron can be determined by performing the same procedure as described above for partial dissolution and surface layer content measurement.

[0038] From the perspective of increasing the playback output when reproducing data recorded on magnetic tape, it is desirable for the mass magnetization σs of the ferromagnetic powder contained in the magnetic tape to be high. In this regard, hexagonal strontium ferrite powder containing rare earth atoms but lacking surface segregation of rare earth atoms tended to have a significantly lower σs compared to hexagonal strontium ferrite powder that does not contain rare earth atoms. In contrast, hexagonal strontium ferrite powder with surface segregation of rare earth atoms is considered preferable in order to suppress such a large decrease in σs. In one embodiment, the σs of hexagonal strontium ferrite powder is 45 A·m 2 It can be 47 A·m or more per kg. 2 It can also be more than / kg. On the other hand, σs is 80 A·m from the viewpoint of noise reduction. 2 Preferably less than / kg, at 60A·m 2 It is more preferable that it be less than or equal to / kg. σs can be measured using a known measuring device capable of measuring magnetic properties, such as a vibrating sample magnetometer. In this invention and specification, unless otherwise specified, the mass magnetization σs is the value measured at a magnetic field strength of 15 kOe. 1 [kOe] = 10 6 It is / 4π[A / m].

[0039] Regarding the constituent atom content (bulk content) of hexagonal strontium ferrite powder, the strontium atom content can be in the range of, for example, 2.0 to 15.0 atomic percent per 100 atomic percent of iron atoms. In one form, hexagonal strontium ferrite powder may contain only strontium atoms as the divalent metal atom. In another form, hexagonal strontium ferrite powder may contain one or more other divalent metal atoms in addition to strontium atoms. For example, it may contain barium atoms and / or calcium atoms. When other divalent metal atoms besides strontium atoms are included, the barium atom content and calcium atom content in the hexagonal strontium ferrite powder can be in the range of, for example, 0.05 to 5.0 atomic percent per 100 atomic percent of iron atoms.

[0040] The known crystal structures of hexagonal ferrites include magnetoplumbite (also called "M-type"), W-type, Y-type, and Z-type. Hexagonal strontium ferrite powder may exhibit any of these crystal structures. The crystal structure can be confirmed by X-ray diffraction analysis. Hexagonal strontium ferrite powder may exhibit a single crystal structure or two or more crystal structures as detected by X-ray diffraction analysis. For example, in one form, hexagonal strontium ferrite powder may exhibit only the M-type crystal structure as detected by X-ray diffraction analysis. For example, M-type hexagonal ferrite is AFe 12 O 19It is represented by the following compositional formula: Here, A represents a divalent metal atom, and if the hexagonal strontium ferrite powder is of type M, A is either only a strontium atom (Sr), or if A contains multiple divalent metal atoms, then as described above, strontium atoms (Sr) make up the largest proportion on an atomic percentage basis. The divalent metal atom content of hexagonal strontium ferrite powder is usually determined by the type of crystal structure of the hexagonal ferrite and is not particularly limited. The same applies to the iron atom content and oxygen atom content. Hexagonal strontium ferrite powder contains at least iron atoms, strontium atoms and oxygen atoms, and may also contain rare earth atoms. Furthermore, hexagonal strontium ferrite powder may or may not contain atoms other than these atoms. As an example, hexagonal strontium ferrite powder may contain aluminum atoms (Al). The aluminum atom content can be, for example, 0.5 to 10.0 atomic percent relative to 100 atomic percent of iron atoms. From the viewpoint of further suppressing the decrease in regeneration output during repeated regeneration, the hexagonal strontium ferrite powder preferably contains iron atoms, strontium atoms, oxygen atoms, and rare earth atoms, and the content of atoms other than these atoms is preferably 10.0 atomic percent or less, more preferably in the range of 0 to 5.0 atomic percent, and may even be 0 atomic percent, relative to 100 atomic percent of iron atoms. That is, in one embodiment, the hexagonal strontium ferrite powder does not need to contain atoms other than iron atoms, strontium atoms, oxygen atoms, and rare earth atoms. The above content expressed in atomic percent is obtained by converting the content of each atom (unit: mass%) obtained by completely dissolving the hexagonal strontium ferrite powder into an atomic percent value using the atomic weight of each atom. Furthermore, in the present invention and this specification, "does not contain" for a certain atom means that the content measured by an ICP analyzer after complete dissolution is 0 mass%. The detection limit of an ICP analyzer is typically 0.01 ppm (parts per million) or less by mass. The term "does not contain" above is used to include the presence of substances in amounts below the detection limit of the ICP analyzer.Hexagonal strontium ferrite powder can, in one form, be bismuth-free (Bi).

[0041] metal powder A preferred specific example of ferromagnetic powder is ferromagnetic metal powder. For details on ferromagnetic metal powder, see, for example, paragraphs 0137-0141 of Japanese Patent Publication No. 2011-216149 and paragraphs 0009-0023 of Japanese Patent Publication No. 2005-251351.

[0042] ε-Iron oxide powder A preferred specific example of a ferromagnetic powder is ε-iron oxide powder. In the present invention and this specification, "ε-iron oxide powder" refers to a ferromagnetic powder in which the crystalline structure of ε-iron oxide is detected as the main phase by X-ray diffraction analysis. For example, if the highest intensity diffraction peak in the X-ray diffraction spectrum obtained by X-ray diffraction analysis is attributed to the crystalline structure of ε-iron oxide, it shall be determined that the crystalline structure of ε-iron oxide has been detected as the main phase. Methods for producing ε-iron oxide powder include methods from goethite and the reverse micelle method. All of the above production methods are publicly known. Furthermore, for methods for producing ε-iron oxide powder in which some of the Fe is substituted with substitution atoms such as Ga, Co, Ti, Al, and Rh, see, for example, J. Jpn. Soc. Powder Metallurgy Vol. 61 Supplement, No. S1, pp. S280-S284, J. Mater. Chem. C, 2013, 1, pp. 5200-5206, etc. However, the method for producing ε-iron oxide powder that can be used as ferromagnetic powder in the magnetic layer of the magnetic tape described above is not limited to the method described herein.

[0043] The activation volume of ε-iron oxide powder is preferably 300 to 1500 nm. 3 The activation volume is within the range described above. Micronized ε-iron oxide powder exhibiting an activation volume within the above range is suitable for the production of magnetic tapes that exhibit excellent electromagnetic conversion properties. The activation volume of the ε-iron oxide powder is preferably 300 nm. 3 That's all, for example, 500nm3 It can also be the above. Furthermore, from the viewpoint of further improving electromagnetic conversion characteristics, the activation volume of ε-iron oxide powder is 1400 nm. 3 The following is more preferable: 1300nm 3 It is even more preferable that the following occur: 1200 nm 3 It is even more preferable that the following conditions be met: 1100 nm 3 The following is even more preferable.

[0044] The anisotropy constant Ku can be cited as an indicator of the reduction of thermal fluctuations, or in other words, the improvement of thermal stability. The ε-iron oxide powder is preferably 3.0 × 10⁻⁶ 4 J / m 3 It can have a Ku of the above, and more preferably 8.0 × 10 4 J / m 3 It can have the above amount of Ku. Also, the amount of Ku in ε-iron oxide powder is, for example, 3.0 × 10⁻⁶. 5 J / m 3 The following values ​​are possible. However, a higher Ku value indicates higher thermal stability, which is preferable, so the values ​​are not limited to those exemplified above.

[0045] From the perspective of increasing the playback output when reproducing data recorded on magnetic tape, it is desirable for the mass magnetization σs of the ferromagnetic powder contained in the magnetic tape to be high. In this regard, in one embodiment, the σs of ε-iron oxide powder is 8 A·m 2 It can be 12A·m or more / kg. 2 It can also be more than / kg. On the other hand, the σs of ε-iron oxide powder is 40 A·m from the viewpoint of noise reduction. 2 Preferably less than / kg, 35A·m 2 It is more preferable that the amount be less than or equal to / kg.

[0046] In the present invention and this specification, unless otherwise specified, the average particle size of various powders such as ferromagnetic powders shall be the value measured using a transmission electron microscope by the following method. The powder is photographed using a transmission electron microscope at a magnification of 100,000x, and the resulting image is printed on photographic paper or displayed on a screen to obtain a total magnification of 500,000x, thereby obtaining a photograph of the particles that make up the powder. From the obtained photographs of the particles, the target particles are selected, and their contours are traced with a digitizer to measure the size of the particles (primary particles). Primary particles are defined as independent particles that do not aggregate. The above measurements are performed on 500 randomly selected particles. The arithmetic mean of the particle sizes of these 500 particles is taken as the average particle size of the powder. As the transmission electron microscope, for example, a Hitachi H-9000 transmission electron microscope can be used. The particle size can be measured using known image analysis software, for example, Carl Zeiss KS-400 image analysis software. Unless otherwise specified, the average particle sizes shown in the examples described later are values ​​measured using a Hitachi H-9000 transmission electron microscope and Carl Zeiss KS-400 image analysis software. In the present invention and this specification, "powder" means a collection of multiple particles. For example, ferromagnetic powder means a collection of multiple ferromagnetic particles. Furthermore, a collection of multiple particles is not limited to a form in which the particles constituting the collection are in direct contact, but also includes forms in which binders, additives, etc., described later, are interposed between the particles. The word "particle" is sometimes used to refer to powder.

[0047] For example, the method described in paragraph 0015 of Japanese Patent Publication No. 2011-048878 can be used to collect sample powder from a magnetic tape for particle size measurement.

[0048] In the present invention and this specification, unless otherwise specified, the size of the particles constituting the powder (particle size) is determined by the shape of the particles observed in the above particle photograph. (1) In the case of needle-shaped, spindle-shaped, columnar (however, the height is greater than the longest diameter of the base), etc., the length of the long axis constituting the particle is expressed as the long axis length, (2) In the case of a plate or column (provided that the thickness or height is less than the longest diameter of the plate or base), it shall be expressed by the longest diameter of the plate or base. (3) If the shape is spherical, polyhedral, irregular, etc., and the major axis constituting the particle cannot be determined from the shape, it shall be represented by the equivalent diameter of a circle. The equivalent diameter of a circle refers to the diameter obtained by the circular projection method.

[0049] Furthermore, the average needle-shape ratio of the powder refers to the arithmetic mean of the values ​​obtained for the 500 particles by measuring the length of the short axis of each particle, i.e., the short axis length, in the above measurement, and determining the (long axis length / short axis length) value for each particle. Here, unless otherwise specified, the short axis length refers to the length of the short axis constituting the particle in the above definition of particle size (1), the thickness or height in the case of (2), and in the case of (3), since there is no distinction between the long axis and the short axis, (long axis length / short axis length) is considered to be 1 for convenience. Unless otherwise specified, when the particle shape is specific, for example, in the case of definition (1) above, the average particle size is the average major axis length, and in the case of definition (2), the average particle size is the average plate diameter. In the case of definition (3), the average particle size is the average diameter (also called the average particle size or average particle diameter).

[0050] The content (filling rate) of ferromagnetic powder in the magnetic layer is preferably in the range of 50 to 90% by mass, and more preferably in the range of 60 to 90% by mass, relative to the total mass of the magnetic layer. A high filling rate of ferromagnetic powder in the magnetic layer is preferable from the viewpoint of improving recording density.

[0051] (Binder) The above magnetic tape can be a coated magnetic tape, and the magnetic layer may contain a binder. The binder is one or more resins. Various resins commonly used as binders for coated magnetic recording media can be used as binders. For example, as a binder, a resin selected from polyurethane resin, polyester resin, polyamide resin, vinyl chloride resin, acrylic resin copolymerized with styrene, acrylonitrile, methyl methacrylate, etc., cellulose resin such as nitrocellulose, epoxy resin, phenoxy resin, polyvinyl acetal, polyvinyl alkylal resin such as polyvinyl butyral can be used alone or in mixture of multiple resins. Among these, polyurethane resin, acrylic resin, cellulose resin, and vinyl chloride resin are preferred. These resins may be homopolymers or copolymers. These resins can also be used as binders in the non-magnetic layer and / or back coat layer described later. For details on the binders mentioned above, please refer to paragraphs 0028 to 0031 of Japanese Patent Publication No. 2010-24113. The average molecular weight of the resin used as a binder can be, for example, 10,000 to 200,000 as a weight-average molecular weight. The binder can be used in an amount of, for example, 1.0 to 30.0 parts by mass per 100.0 parts by mass of ferromagnetic powder.

[0052] (Hardening agent) A curing agent can also be used together with a resin that can be used as a binder. In one form, the curing agent can be a thermosetting compound, which is a compound that undergoes a curing reaction (crosslinking reaction) by heating, and in another form, it can be a photocurable compound, which undergoes a curing reaction (crosslinking reaction) by light irradiation. As the curing reaction progresses during the magnetic layer formation process, at least a portion of the curing agent may be included in the magnetic layer in a state where it has reacted (crosslinked) with other components such as the binder. This also applies to layers formed using a composition that contains a curing agent when the composition used to form other layers contains a curing agent. Preferred curing agents are thermosetting compounds, and polyisocyanates are preferred. For details on polyisocyanates, refer to paragraphs 0124 to 0125 of Japanese Patent Application Publication No. 2011-216149. The curing agent can be used in the magnetic layer forming composition in an amount of, for example, 0 to 80.0 parts by mass, preferably 50.0 to 80.0 parts by mass, per 100.0 parts by mass of the binder.

[0053] (Additives) The magnetic layer may contain one or more additives as needed. An example of an additive is the curing agent mentioned above. Other additives that can be included in the magnetic layer include non-magnetic powders (e.g., inorganic powders, carbon black, etc.), lubricants, dispersants, dispersion aids, antifungal agents, antistatic agents, antioxidants, etc. For example, regarding lubricants, see paragraphs 0030-0033, 0035, and 0036 of Japanese Patent Application Publication No. 2016-126817. A lubricant may also be included in the non-magnetic layer, as described later. For lubricants that can be included in the non-magnetic layer, see paragraphs 0030, 0031, and 0034-0036 of Japanese Patent Application Publication No. 2016-126817. For dispersants, see paragraphs 0061 and 0071 of Japanese Patent Application Publication No. 2012-133837. A dispersant may also be added to the composition for forming the non-magnetic layer. For dispersants that can be added to the composition for forming a non-magnetic layer, refer to paragraph 0061 of Japanese Patent Application Publication No. 2012-133837. Examples of non-magnetic powders that can be included in the magnetic layer include non-magnetic powders that can function as abrasives, and non-magnetic powders that can function as protrusion-forming agents that form appropriately protruding protrusions on the surface of the magnetic layer (e.g., non-magnetic colloidal particles). The average particle size of the colloidal silica (silica colloidal particles) shown in the examples below was determined by the method described in paragraph 0015 of Japanese Patent Application Publication No. 2011-048878 for measuring average particle size. Additives can be used in any amount, either by appropriately selecting commercially available products according to the desired properties, or by manufacturing them by known methods. An example of an additive that can be used to improve the dispersibility of abrasives in a magnetic layer containing abrasives is the dispersant described in paragraphs 0012-0022 of Japanese Patent Application Publication No. 2013-131285.

[0054] The magnetic layer described above can be provided directly on the surface of a non-magnetic support, or indirectly via a non-magnetic layer.

[0055] <Nonmagnetic layer> Next, the non-magnetic layer will be described. The magnetic tape described above may have a magnetic layer directly on the surface of a non-magnetic support, or it may have a magnetic layer on the surface of a non-magnetic support via a non-magnetic layer containing non-magnetic powder. The non-magnetic powder used in the non-magnetic layer may be an inorganic powder or an organic powder. Carbon black can also be used. Examples of inorganic powders include metals, metal oxides, metal carbonates, metal sulfates, metal nitrides, metal carbides, and metal sulfides. These non-magnetic powders are commercially available and can also be manufactured by known methods. For details, see paragraphs 0146 to 0150 of Japanese Patent Application Publication No. 2011-216149. For carbon black that can be used in the non-magnetic layer, see paragraphs 0040 and 0041 of Japanese Patent Application Publication No. 2010-24113. The content (filling rate) of non-magnetic powder in the non-magnetic layer is preferably in the range of 50 to 90% by mass, and more preferably in the range of 60 to 90% by mass, relative to the total mass of the non-magnetic layer.

[0056] Regarding the coefficient of variation CV mentioned above, the inventors believe that reducing the thickness variation of the magnetic tape (difference in thickness depending on the position) leads to a smaller value of the coefficient of variation CV. One way to reduce the thickness variation of the magnetic tape is to improve the dispersibility of the non-magnetic powder in the non-magnetic layer. From this point of view, it is preferable that the composition for forming the non-magnetic layer contains a component (dispersant) that can improve the dispersibility of the non-magnetic powder contained in the composition. As an example of such a dispersant, a compound having an ammonium salt structure of an alkyl ester anion represented by the following formula 1 can be used. Note that "alkyl ester anion" can also be called "alkyl carboxylate anion".

[0057] [ka]

[0058] In Formula 1, R represents an alkyl group having 7 or more carbon atoms or a fluorinated alkyl group having 7 or more carbon atoms, and Z + This represents an ammonium cation.

[0059] Furthermore, from the viewpoint of improving the dispersibility of non-magnetic powders, in one embodiment, two or more components capable of forming the above-mentioned salt structure compound can be used when preparing the non-magnetic layer forming composition. As a result, when preparing the non-magnetic layer forming composition, at least some of these components can form the above-mentioned salt structure compound.

[0060] Unless otherwise specified, the groups described below may or may not have substituents. Furthermore, for groups with substituents, "number of carbon atoms" means the number of carbon atoms excluding the substituent unless otherwise specified. In the present invention and this specification, examples of substituents include alkyl groups (e.g., alkyl groups having 1 to 6 carbon atoms), hydroxyl groups, alkoxy groups (e.g., alkoxy groups having 1 to 6 carbon atoms), halogen atoms (e.g., fluorine atoms, chlorine atoms, bromine atoms, etc.), cyano groups, amino groups, nitro groups, acyl groups, carboxyl groups, salts of carboxyl groups, sulfonic acid groups, salts of sulfonic acid groups, and the like.

[0061] The following provides a more detailed explanation of Equation 1.

[0062] In Formula 1, R represents an alkyl group having 7 or more carbon atoms or a fluorinated alkyl group having 7 or more carbon atoms. A fluorinated alkyl group has a structure in which some or all of the hydrogen atoms constituting the alkyl group are substituted with fluorine atoms. The alkyl group or fluorinated alkyl group represented by R may have a linear structure, a branched structure, or a cyclic alkyl group or fluorinated alkyl group, but a linear structure is preferred. The alkyl group or fluorinated alkyl group represented by R may have substituents or be unsubstituted, but it is preferred to be unsubstituted. The alkyl group represented by R is, for example, C n H 2n+1 It can be represented by -, where n is an integer greater than or equal to 7. Also, the alkyl fluoride represented by R is, for example, C n H 2n+1The alkyl group represented by - may have a structure in which some or all of the hydrogen atoms constituting the alkyl group are substituted with fluorine atoms. The alkyl group or fluorinated alkyl group represented by R has 7 or more carbon atoms, preferably 8 or more, more preferably 9 or more, even more preferably 10 or more, even more preferably 11 or more, even more preferably 12 or more, and even more preferably 13 or more. Furthermore, the alkyl group or fluorinated alkyl group represented by R has 20 or fewer carbon atoms, more preferably 19 or fewer, and even more preferably 18 or fewer.

[0063] In equation 1, Z + * represents an ammonium cation. The ammonium cation has, in detail, the following structure. In this invention and specification, the asterisk (*) in a formula representing a part of a compound represents the structure of that part and the bond position with an adjacent atom.

[0064] [ka]

[0065] Nitrogen cation of ammonium cation N + and the oxygen anion O in Equation 1 - These can form a salt crosslinking group, creating an ammonium salt structure of an alkyl ester anion represented by formula 1. The presence of a compound having an ammonium salt structure of an alkyl ester anion represented by formula 1 in the non-magnetic layer can be confirmed by analyzing the magnetic tape using X-ray photoelectron spectroscopy (ESCA: Electron Spectroscopy for Chemical Analysis), infrared spectroscopy (IR: infrared spectroscopy), etc. The presence of a compound having an ammonium salt structure of an alkyl ester anion represented by formula 1 in the back coat layer, described later, can also be confirmed by the same method.

[0066] In one form, Z +The ammonium cation represented by can be obtained, for example, by the nitrogen atom of a nitrogen-containing polymer becoming a cation. A nitrogen-containing polymer means a polymer that contains nitrogen atoms. In this invention and specification, the terms "polymer" and "polymer" are used to encompass both homopolymers and copolymers. Nitrogen atoms can be included in one form as atoms constituting the main chain of the polymer, and in another form as atoms constituting the side chain of the polymer.

[0067] One form of nitrogen-containing polymer is polyalkyleneimines. Polyalkyleneimines are ring-opening polymers of alkyleneimines, and are polymers having multiple repeating units represented by the following formula 2.

[0068] [ka]

[0069] In Equation 2, the nitrogen atom N that makes up the main chain is a nitrogen cation N + And so Z in equation 1 + An ammonium cation represented by [formula] can be obtained. Then, with an alkyl ester anion, it can form an ammonium salt structure, for example, as shown below.

[0070] [ka]

[0071] The following provides a more detailed explanation of Equation 2.

[0072] In formula 2, R 1 and R 2 Each of these independently represents a hydrogen atom or an alkyl group, and n1 represents an integer greater than or equal to 2.

[0073] R 1 or R 2Examples of alkyl groups represented by include alkyl groups having 1 to 6 carbon atoms, preferably alkyl groups having 1 to 3 carbon atoms, more preferably a methyl group or an ethyl group, and even more preferably a methyl group. 1 or R 2 The alkyl group represented by is preferably an unsubstituted alkyl group. 1 and R 2 The combinations include a form in which one is a hydrogen atom and the other is an alkyl group, a form in which both are hydrogen atoms, and a form in which both are alkyl groups (identical or different alkyl groups), with the form in which both are hydrogen atoms being preferred. As an alkylene imine that yields a polyalkylene imine, the structure with the fewest number of carbon atoms constituting the ring is ethyleneimine, and the number of carbon atoms in the main chain of the alkylene imine (ethyleneimine) obtained by ring-opening of ethyleneimine is 2. Therefore, n1 in formula 2 is 2 or more. n1 in formula 2 can be, for example, 10 or less, 8 or less, 6 or less, or 4 or less. The polyalkylene imine may be a homopolymer containing only the same structure as the repeating structure represented by formula 2, or it may be a copolymer containing two or more different structures as the repeating structure represented by formula 2. The number-average molecular weight of the polyalkylene imine that can be used to form a compound having an ammonium salt structure of an alkyl ester anion represented by formula 1 can be, for example, 200 or more, preferably 300 or more, and more preferably 400 or more. Furthermore, the number-average molecular weight of the polyalkyleneimine can be, for example, 10,000 or less, preferably 5,000 or less, and more preferably 2,000 or less.

[0074] In the present invention and this specification, average molecular weight (weight-average molecular weight and number-average molecular weight) refers to the value obtained by measuring by gel permeation chromatography (GPC) and converting it to standard polystyrene equivalent. Unless otherwise specified, the average molecular weights shown in the examples described below are values ​​obtained by converting the values ​​measured using GPC under the following measurement conditions to standard polystyrene equivalent (polystyrene equivalent value). GPC device: HLC-8220 (manufactured by Tosoh Corporation) Guard Column: TSKguardcolumn Super HZM-H Columns: TSKgel Super HZ 2000, TSKgel Super HZ 4000, TSKgel Super HZ-M (manufactured by Tosoh Corporation, 4.6mm (inner diameter) x 15.0cm, three types of columns connected in series) Eluent: Contains tetrahydrofuran (THF) and stabilizer (2,6-di-t-butyl-4-methylphenol). Eluent flow rate: 0.35mL / min Column temperature: 40℃ Inlet temperature: 40℃ Refractive Index (RI) measurement temperature: 40℃ Sample concentration: 0.3% by mass Sample injection volume: 10 μL

[0075] Another form of nitrogen-containing polymer is polyallylamine. Polyallylamine is a polymer of allylamine, having multiple repeating units represented by the following formula 3.

[0076] [ka]

[0077] In Equation 3, the nitrogen atom N constituting the amino group of the side chain is a nitrogen cation N + And so Z in equation 1 + An ammonium cation represented by [formula] can be obtained. Then, with an alkyl ester anion, it can form an ammonium salt structure, for example, as shown below.

[0078] [ka]

[0079] The weight-average molecular weight of the polyallylamine that can be used to form a compound having an ammonium salt structure of an alkyl ester anion represented by Formula 1 can be, for example, 200 or more, preferably 1,000 or more, and more preferably 1,500 or more. Furthermore, the weight-average molecular weight of the above polyallylamine can be, for example, 15,000 or less, preferably 10,000 or less, and more preferably 8,000 or less.

[0080] The presence of compounds having an ammonium salt structure of an alkyl ester anion represented by Equation 1, specifically compounds derived from polyalkylene imines or polyallylamines, in the non-magnetic layer can be confirmed by analyzing the surface of the non-magnetic layer using time-of-flight secondary ion mass spectrometry (TOF-SIMS). The presence of compounds having an ammonium salt structure of an alkyl ester anion represented by Equation 1 in the backcoat layer, described later, can also be confirmed by a similar method.

[0081] Compounds having an ammonium salt structure of an alkyl ester anion represented by Formula 1 can be salts of a nitrogen-containing polymer and one or more fatty acids selected from the group consisting of fatty acids having 7 or more carbon atoms and fluorinated fatty acids having 7 or more carbon atoms. The nitrogen-containing polymer that forms the salt can be one or more nitrogen-containing polymers, for example, a nitrogen-containing polymer selected from the group consisting of polyalkylene imines and polyallylamines. The fatty acids that form the salt can be one or more fatty acids selected from the group consisting of fatty acids having 7 or more carbon atoms and fluorinated fatty acids having 7 or more carbon atoms. Fluorinated fatty acids have a structure in which some or all of the hydrogen atoms constituting the alkyl group bonded to the carboxyl group COOH in the fatty acid are replaced with fluorine atoms. For example, the salt formation reaction can easily proceed by mixing the nitrogen-containing polymer and the above fatty acids at room temperature. Room temperature is, for example, about 20-25°C. In one embodiment, one or more nitrogen-containing polymers and one or more of the above fatty acids are used as components of the non-magnetic layer-forming composition, and the salt formation reaction can be carried out by mixing them in the preparation step of the non-magnetic layer-forming composition. Alternatively, in one embodiment, one or more nitrogen-containing polymers and one or more of the above fatty acids can be mixed to form a salt before preparing the non-magnetic layer-forming composition, and this salt can then be used as a component of the non-magnetic layer-forming composition to prepare it. When mixing nitrogen-containing polymers and the above fatty acids to form an ammonium salt of an alkyl ester anion represented by formula 1, the nitrogen atoms constituting the nitrogen-containing polymer and the carboxyl groups of the above fatty acids may also react to form the following structure, and forms including such a structure are also included in the above compound.

[0082] [ka]

[0083] Examples of the above fatty acids include fatty acids having the alkyl group described earlier as R in Formula 1, and fluorinated fatty acids having the fluorinated alkyl group described earlier as R in Formula 1.

[0084] The mixing ratio of the nitrogen-containing polymer used to form the compound having the ammonium salt structure of the alkyl ester anion represented by Formula 1 to the above fatty acids is preferably 10:90 to 90:10, more preferably 20:80 to 85:15, and even more preferably 30:70 to 80:20, as the mass ratio of nitrogen-containing polymer to the above fatty acids. Furthermore, when preparing the composition for forming a non-magnetic layer, the compound having the ammonium salt structure of the alkyl ester anion represented by Formula 1 can be used in an amount of, for example, 1.0 to 20.0 parts by mass, and preferably 1.0 to 10.0 parts by mass, per 100.0 parts by mass of non-magnetic powder. Also, when preparing the composition for forming a non-magnetic layer, for example, 0.1 to 10.0 parts by mass of nitrogen-containing polymer can be used per 100.0 parts by mass of non-magnetic powder, and preferably 0.5 to 8.0 parts by mass of nitrogen-containing polymer. The above fatty acids can be used in amounts of, for example, 0.05 to 10.0 parts by mass per 100.0 parts by mass of non-magnetic powder, and it is preferable to use 0.1 to 5.0 parts by mass.

[0085] The non-magnetic layer may contain a binder and may also contain additives. For further details regarding the binder, additives, etc., of the non-magnetic layer, known technology relating to non-magnetic layers can be applied. Furthermore, for example, regarding the type and content of the binder, the type and content of the additives, etc., known technology relating to magnetic layers can also be applied.

[0086] In the present invention and this specification, the non-magnetic layer includes a substantially non-magnetic layer containing a small amount of ferromagnetic powder, for example as an impurity or intentionally, along with the non-magnetic powder. A substantially non-magnetic layer is defined as a layer having a remanent magnetic flux density of 10 mT or less, a coercivity of 7.96 kA / m(100 Oe) or less, or a layer having a remanent magnetic flux density of 10 mT or less and a coercivity of 7.96 kA / m(100 Oe) or less. It is preferable that the non-magnetic layer has no remanent magnetic flux density and coercivity.

[0087] <Backcoat layer> The above magnetic tape may or may not have a back coat layer containing non-magnetic powder on the surface side opposite to the surface side having the magnetic layer of the non-magnetic support. For the non-magnetic powder of the back coat layer, refer to the previous description regarding the non-magnetic powder of the non-magnetic layer. The content (filling rate) of non-magnetic powder in the back coat layer is preferably in the range of 50 to 90% by mass, and more preferably in the range of 60 to 90% by mass, relative to the total mass of the back coat layer.

[0088] Regarding the coefficient of variation CV mentioned above, one means of reducing the thickness variation of the magnetic tape is to improve the dispersibility of the non-magnetic powder in the back coat layer. From this point of view, it is preferable that the back coat layer forming composition contains a component (dispersant) that can improve the dispersibility of the non-magnetic powder contained in the composition. As an example of such a dispersant, a compound having an ammonium salt structure of an alkyl ester anion represented by Formula 1 can be used. For details of the back coat layer forming composition containing such a compound, refer to the previous description of the non-magnetic layer forming composition. The mixing ratio of the nitrogen-containing polymer used to form the compound having an ammonium salt structure of an alkyl ester anion represented by Formula 1 and the above fatty acids is preferably 10:90 to 90:10, more preferably 20:80 to 85:15, and even more preferably 30:70 to 80:20 as the mass ratio of nitrogen-containing polymer to the above fatty acids. Furthermore, when preparing the composition for forming the backcoat layer, for example, 1.0 to 20.0 parts by mass of the alkyl ester anion ammonium salt structure represented by Formula 1 can be used per 100.0 parts by mass of the non-magnetic powder, and it is preferable to use 1.0 to 10.0 parts by mass. Also, when preparing the composition for forming the backcoat layer, for example, 0.1 to 10.0 parts by mass of nitrogen-containing polymer can be used per 100.0 parts by mass of the non-magnetic powder, and it is preferable to use 0.5 to 8.0 parts by mass of nitrogen-containing polymer. The above fatty acids can be used per 100.0 parts by mass of the non-magnetic powder, for example, 0.05 to 10.0 parts by mass, and it is preferable to use 0.1 to 5.0 parts by mass.

[0089] Regarding the components that may be included in the backcoat layer, the backcoat layer may include a binder and may also include additives. With regard to the binder and additives of the backcoat layer, prior art relating to backcoat layers may be applied, as may prior art relating to the formulation of magnetic and / or non-magnetic layers. For example, paragraphs 0018 to 0020 of Japanese Patent Application Publication No. 2006-331625 and lines 65 to 38 of column 4 to column 5 of U.S. Patent No. 7,029,774 can be referenced with respect to the backcoat layer.

[0090] <Various thicknesses> Regarding the thickness (total thickness) of magnetic tape, with the enormous increase in the amount of information in recent years, there is a demand for increased recording capacity (higher capacity) in magnetic tape. Means of increasing capacity include reducing the thickness of the magnetic tape (hereinafter also referred to as "thinning") and increasing the length of magnetic tape that can be accommodated in one magnetic tape cartridge. From this point of view, the thickness (total thickness) of the magnetic tape is preferably 5.6 μm or less, more preferably 5.5 μm or less, more preferably 5.4 μm or less, even more preferably 5.3 μm or less, and even more preferably 5.2 μm or less. Furthermore, from the viewpoint of ease of handling, the thickness of the magnetic tape is preferably 3.0 μm or more, and more preferably 3.5 μm or more. Regarding the thickness of the magnetic tape, the value of Δw tends to increase as the thickness decreases.

[0091] The thickness (total thickness) of a magnetic tape can be measured by the following method. Ten tape samples (e.g., 5-10 cm in length) are cut from any part of the magnetic tape, and the thickness of these tape samples is measured by stacking them. The measured thickness is divided by 10 to obtain the value obtained (thickness per tape sample), which is defined as the tape thickness. The above thickness measurement can be performed using a known measuring instrument capable of measuring thickness on the order of 0.1 μm.

[0092] The thickness of the non-magnetic support can be, for example, 3.0 μm or more, and can also be, for example, 5.0 μm or less, 4.8 μm or less, 4.6 μm or less, 4.4 μm or less, or 4.2 μm or less. The thickness of the magnetic layer can be optimized depending on the saturation magnetization of the magnetic head used, the head gap length, the bandwidth of the recording signal, etc., and is generally 0.01 μm to 0.15 μm, preferably 0.02 μm to 0.12 μm, and more preferably 0.03 μm to 0.1 μm from the viewpoint of high-density recording. At least one magnetic layer is sufficient, and the magnetic layer may be separated into two or more layers having different magnetic properties, and known configurations for multilayer magnetic layers can be applied. When separated into two or more layers, the thickness of the magnetic layer is the total thickness of these layers. The thickness of the non-magnetic layer is, for example, 0.1 to 1.5 μm, and preferably 0.1 to 1.0 μm. The thickness of the backcoat layer is preferably 0.9 μm or less, and more preferably 0.1 to 0.7 μm. Various thicknesses, such as the thickness of the magnetic layer, can be determined by the following method. After exposing the cross-section of the magnetic tape in the thickness direction using an ion beam, the exposed cross-section is observed using a scanning electron microscope or a transmission electron microscope. Various thicknesses can be determined as the arithmetic mean of the thicknesses obtained at any two locations during the cross-sectional observation. Alternatively, various thicknesses can be determined as design thicknesses calculated from manufacturing conditions, etc.

[0093] <Manufacturing process> (Preparation of compositions for each layer) The process of preparing a composition for forming a magnetic layer, a non-magnetic layer, or a backcoat layer typically includes at least a kneading step, a dispersion step, and mixing steps provided before or after these steps as needed. Each individual step may be divided into two or more stages. The components used in preparing each layer-forming composition may be added at the beginning or in the middle of any of the steps. As the solvent, one or more of the various solvents commonly used in the manufacture of coated magnetic recording media can be used. For solvents, see, for example, paragraph 0153 of Japanese Patent Publication No. 2011-216149. In addition, individual components may be added in two or more separate steps. For example, a binder may be added in separate steps: a kneading step, a dispersion step, and a mixing step for viscosity adjustment after dispersion. Known manufacturing techniques can be used in various steps to manufacture the above magnetic tape. In the kneading step, it is preferable to use a kneader with strong kneading force, such as an open kneader, a continuous kneader, a pressure kneader, or an extruder. For details of the kneading process, please refer to Japanese Patent Publication No. 1-106338 and Japanese Patent Publication No. 1-79274. Known dispersers can be used. Filtration may be performed by known methods at any stage in preparing each layer-forming composition. Filtration can be performed, for example, by filter filtration. As filters used for filtration, for example, filters with a pore size of 0.01 to 3 μm (e.g., glass fiber filters, polypropylene filters, etc.) can be used.

[0094] (Coating process) The magnetic layer can be formed by directly applying the magnetic layer-forming composition onto the surface of a non-magnetic support, or by sequentially or simultaneously applying it in layers with the non-magnetic layer-forming composition. The back coat layer can be formed by applying the back coat-forming composition to the surface of the non-magnetic support opposite to the surface having the non-magnetic layer and / or magnetic layer (or to which the non-magnetic layer and / or magnetic layer are subsequently provided). For details on the application for each layer formation, refer to paragraph 0066 of Japanese Patent Application Publication No. 2010-231843.

[0095] (Other processes) For other processes in the manufacture of magnetic tape, known techniques can be applied. For details on these processes, see, for example, paragraphs 0067 to 0070 of Japanese Patent Publication No. 2010-231843. For example, the coated layer of a magnetic layer-forming composition can be subjected to orientation treatment in an orientation zone while the coated layer is still wet. Various known techniques, including those described in paragraph 0052 of Japanese Patent Application Publication No. 2010-24113, can be applied to the orientation treatment. For example, vertical orientation treatment can be performed by known methods such as using opposing magnets of opposite poles. In the orientation zone, the drying rate of the coated layer can be controlled by the temperature and airflow of the drying air and / or the transport speed in the orientation zone. Alternatively, the coated layer may be pre-dried before being transported to the orientation zone. Regarding the calendering process, strengthening the calendering conditions can contribute to reducing variations in the thickness of the magnetic tape. Reducing variations in the thickness of the magnetic tape can lead to a smaller coefficient of variation (CV). Examples of calendering conditions include calendering pressure, calendering temperature (surface temperature of the calender roll), and calendering speed. The calendering process is strengthened as the values ​​of calendering pressure and calendering temperature increase, and the calendering process is strengthened as the calendering speed decreases. For example, the calendering pressure (linear pressure) can be in the range of 200 to 500 kg / cm, and is preferably in the range of 250 to 350 kg / cm. The calendering temperature (surface temperature of the calender roll) can be in the range of 85 to 120°C, and is preferably in the range of 90 to 110°C. The calendering speed can be in the range of 50 to 300 m / min, and is preferably in the range of 50 to 200 m / min. Through various processes, a long roll of magnetic tape raw material can be obtained. The obtained magnetic tape raw material is then cut (slit) to the width of the magnetic tape to be wound onto a magnetic tape cartridge using a known cutting machine. The above width is determined according to standards and is usually 1 / 2 inch. 1 / 2 inch = 12.65 mm. A servo pattern is formed on the magnetic tape obtained by slitting. Details about the servo pattern will be described later.

[0096] (Heat treatment) In one embodiment, the magnetic tape described above may be a magnetic tape manufactured through the following heat treatment. Performing the following heat treatment may contribute to reducing the value of the coefficient of variation CV. Furthermore, when performing such heat treatment, strengthening the heat treatment conditions (for example, increasing the heat treatment temperature) may contribute to reducing the value of the coefficient of variation CV.

[0097] For heat treatment, the magnetic tape, which has been slit and cut to a width determined according to the standard, can be wrapped around a core-shaped member, and the heat treatment can be performed while the tape is still wrapped around the member.

[0098] In one embodiment, the above heat treatment is performed with the magnetic tape wound around a core-shaped member for heat treatment (hereinafter referred to as the "heat-treated winding core"), and the heat-treated magnetic tape is wound onto a reel of a magnetic tape cartridge to produce a magnetic tape cartridge with the magnetic tape wound on a reel. The core for heat treatment can be made of metal, resin, paper, etc. From the viewpoint of suppressing winding failures such as spocking, the material of the core for heat treatment is preferably a highly rigid material. For this reason, the core for heat treatment is preferably made of metal or resin. Furthermore, as an indicator of rigidity, the flexural modulus of the material for heat treatment is preferably 0.2 GPa or higher, and more preferably 0.3 GPa or higher. On the other hand, since highly rigid materials are generally expensive, using a core for heat treatment made of a material with rigidity exceeding the rigidity required to suppress winding failures leads to increased costs. Considering the above points, the flexural modulus of the material for heat treatment is preferably 250 GPa or lower. The core for heat treatment can be a solid or hollow core-shaped member. In the case of a hollow core, from the viewpoint of maintaining rigidity, the wall thickness is preferably 2 mm or more. The core for heat treatment may or may not have a flange. It is preferable to prepare a magnetic tape that is longer than the length to be ultimately housed in a magnetic tape cartridge (hereinafter referred to as the "final product length") as the magnetic tape to be wound onto the heat treatment core, and to perform heat treatment by winding this magnetic tape onto the heat treatment core and placing it in a heat treatment environment. The length of the magnetic tape wound onto the heat treatment core is greater than or equal to the final product length, and from the viewpoint of ease of winding onto the heat treatment core, it is preferable to set it to "final product length + α". From the viewpoint of ease of winding, this α is preferably 5m or more. The tension when winding onto the heat treatment core is preferably 0.1N (Newtons) or more. Furthermore, from the viewpoint of suppressing excessive deformation, the tension when winding onto the heat treatment core is preferably 1.5N or less, and more preferably 1.0N or less. The outer diameter of the heat treatment core is preferably 20mm or more, and more preferably 40mm or more, from the viewpoint of ease of winding and suppression of coiling (longitudinal curling). Furthermore, the outer diameter of the heat treatment core is preferably 100 mm or less, and more preferably 90 mm or less. The width of the heat treatment core should be greater than or equal to the width of the magnetic tape wound around it. Also, when removing the magnetic tape from the heat treatment core after heat treatment, it is preferable to remove the magnetic tape from the heat treatment core only after the magnetic tape and the heat treatment core have cooled sufficiently, in order to prevent unintended tape deformation during the removal operation. It is preferable to first wind the removed magnetic tape onto another core (referred to as a "temporary winding core"), and then wind the magnetic tape from the temporary winding core onto a reel of a magnetic tape cartridge (generally with an outer diameter of about 40-50 mm). This allows the relationship between the inside and outside of the magnetic tape relative to the heat treatment core during heat treatment to be maintained when winding the magnetic tape onto the reel of the magnetic tape cartridge. For details of the temporary winding core and the tension when winding the magnetic tape onto this core, please refer to the previous description regarding the heat treatment core. In the configuration in which the above heat treatment is applied to a magnetic tape of a length of "final product length + α", the "+ α" length can be cut off at any stage. For example, in one configuration, the magnetic tape of the final product length can be wound from the temporary winding core onto the reel of the magnetic tape cartridge, and the remaining "+ α" length can be cut off.From the standpoint of minimizing the amount that is cut off and discarded, it is preferable that α is 20m or less.

[0099] The specific form of heat treatment performed while the material is wrapped around the core member, as described above, is explained below. The ambient temperature for heat treatment (hereinafter referred to as the "heat treatment temperature") is preferably 40°C or higher, and more preferably 50°C or higher. On the other hand, from the viewpoint of suppressing excessive deformation, the heat treatment temperature is preferably 75°C or lower, more preferably 70°C or lower, and even more preferably 65°C or lower. The absolute humidity by weight of the atmosphere used for heat treatment is preferably 0.1 g / kg Dry air or higher, and more preferably 1 g / kg Dry air or higher. An atmosphere with an absolute humidity by weight within the above range is preferable because it can be prepared without using special equipment to reduce moisture. On the other hand, from the viewpoint of suppressing condensation and the resulting decrease in workability, the absolute humidity by weight is preferably 70 g / kg Dry air or lower, and more preferably 66 g / kg Dry air or lower. The heat treatment time is preferably 0.3 hours or longer, and more preferably 0.5 hours or longer. Furthermore, from the viewpoint of production efficiency, the heat treatment time is preferably 48 hours or less.

[0100] (Formation of servo patterns) "Forming a servo pattern" can also be described as "recording a servo signal." The formation of a servo pattern is explained below.

[0101] Servo patterns are typically formed along the longitudinal direction of the magnetic tape. Examples of control methods that utilize servo signals (servo control) include timing-based servo (TBS), amplitude servo, and frequency servo.

[0102] As indicated in ECMA (European Computer Manufacturers Association) - 319 (June 2001), magnetic tapes conforming to the LTO (Linear Tape-Open) standard (commonly called "LTO tapes") employ a timing-based servo system. In this timing-based servo system, the servo pattern is composed of multiple pairs of non-parallel magnetic stripes (also called "servo stripes") arranged continuously along the longitudinal direction of the magnetic tape. In this invention and specification, "timing-based servo pattern" refers to a servo pattern that enables head tracking in a timing-based servo system. The reason the servo pattern is composed of pairs of non-parallel magnetic stripes, as described above, is to inform the servo signal reading element of its position as it passes over the servo pattern. Specifically, the pair of magnetic stripes described above are formed such that their spacing changes continuously along the width direction of the magnetic tape, and the servo signal reading element can determine the relative position between the servo pattern and the servo signal reading element by reading this spacing. This relative position information enables tracking of the data track. Therefore, multiple servo tracks are typically set up on the servo pattern, aligned with the width of the magnetic tape.

[0103] A servo band consists of a servo pattern that runs continuously along the longitudinal direction of the magnetic tape. Typically, multiple servo bands are provided on a magnetic tape. For example, in an LTO tape, there are five. The area between two adjacent servo bands is the data band. A data band consists of multiple data tracks, each corresponding to a servo track.

[0104] In one embodiment, as shown in Japanese Patent Publication No. 2004-318983, each servo band has embedded information indicating the servo band number (also called "servo band ID (identification)" or "UDIM (Unique DataBand Identification Method) information"). This servo band ID is recorded by shifting a specific pair of servo stripes within a servo band so that its position is displaced relative to the longitudinal direction of the magnetic tape. Specifically, the method of shifting a specific pair of servo stripes is changed for each servo band. As a result, the recorded servo band ID is unique for each servo band, so that a servo band can be uniquely identified by reading it with a servo signal reading element.

[0105] Furthermore, one method for uniquely identifying a servo band is the staggered method, as described in ECMA-319 (June 2001). In this staggered method, a group of non-parallel magnetic stripes (servo stripes) arranged continuously along the longitudinal direction of the magnetic tape are recorded in a way that they are shifted along the longitudinal direction of the magnetic tape for each servo band. Since the combination of this shift between adjacent servo bands is unique across the entire magnetic tape, it is possible to uniquely identify a servo band when reading the servo pattern with two servo signal reading elements.

[0106] Furthermore, each servo band typically contains embedded information indicating its position along the longitudinal direction of the magnetic tape (also known as "LPOS (Longitudinal Position) information"), as described in ECMA-319 (June 2001). This LPOS information, like the UDIM information, is recorded by shifting the positions of a pair of servo stripes along the longitudinal direction of the magnetic tape. However, unlike the UDIM information, the same signal is recorded for each servo band in this LPOS information.

[0107] It is also possible to embed information other than the UDIM and LPOS information mentioned above into the servo bands. In this case, the embedded information may be different for each servo band, like the UDIM information, or it may be common to all servo bands, like the LPOS information. Furthermore, methods other than those described above can be used to embed information in the servo bands. For example, a predetermined code may be recorded by thinning out a predetermined pair from a group of servo stripes.

[0108] A servo pattern forming head is called a servo light head. A servo light head typically has a pair of gaps corresponding to the pair of magnetic stripes mentioned above, for each servo band. Typically, a core and a coil are connected to each pair of gaps, and by supplying current pulses to the coils, the magnetic field generated in the core can create a leakage magnetic field in the pair of gaps. When forming a servo pattern, by inputting current pulses while running a magnetic tape over the servo light head, the magnetic patterns corresponding to the pair of gaps are transferred to the magnetic tape, thereby forming the servo pattern. The width of each gap can be appropriately set according to the density of the servo pattern to be formed. For example, the width of each gap can be set to 1 μm or less, 1 to 10 μm, 10 μm or more, etc.

[0109] Before forming a servo pattern on a magnetic tape, it is usually demagnetized (erased). This erasing process can be performed by applying a uniform magnetic field to the magnetic tape using a DC or AC magnet. There are two types of erasing: DC (Direct Current) erasing and AC (Alternating Current) erasing. AC erasing is performed by gradually reducing the strength of the magnetic field while reversing the direction of the magnetic field applied to the magnetic tape. On the other hand, DC erasing is performed by applying a unidirectional magnetic field to the magnetic tape. There are two further methods of DC erasing. The first method is horizontal DC erasing, which applies a unidirectional magnetic field along the longitudinal direction of the magnetic tape. The second method is vertical DC erasing, which applies a unidirectional magnetic field along the thickness direction of the magnetic tape. The erasing process may be performed on the entire magnetic tape or on each servo band of the magnetic tape.

[0110] The direction of the magnetic field of the formed servo pattern is determined according to the direction of the erase. For example, when a magnetic tape is horizontally DC erased, the servo pattern is formed such that the direction of the magnetic field is opposite to the direction of the erase. This makes it possible to increase the output of the servo signal obtained by reading the servo pattern. As shown in Japanese Patent Application Publication No. 2012-53940, when a magnetic pattern using the above gap is transferred to a vertically DC erased magnetic tape, the servo signal obtained by reading the formed servo pattern is in the shape of a single-pole pulse. On the other hand, when a magnetic pattern using the above gap is transferred to a horizontally DC erased magnetic tape, the servo signal obtained by reading the formed servo pattern is in the shape of a double-pole pulse.

[0111] <Vertical squareness ratio> In one embodiment, the vertical aspect ratio of the magnetic tape can be, for example, 0.55 or more, and preferably 0.60 or more. A vertical aspect ratio of 0.60 or more is preferable from the viewpoint of improving electromagnetic conversion characteristics. In principle, the upper limit of the aspect ratio is 1.00 or less. The vertical aspect ratio of the magnetic tape can be 1.00 or less, and can be 0.95 or less, 0.90 or less, 0.85 or less, or 0.80 or less. A large value for the vertical aspect ratio of the magnetic tape is preferable from the viewpoint of improving electromagnetic conversion characteristics. The vertical aspect ratio of the magnetic tape can be controlled by known methods such as performing a vertical orientation process.

[0112] In the present invention and this specification, "vertical angle ratio" refers to the angle ratio measured in the vertical direction of the magnetic tape. In relation to the angle ratio, "vertical direction" refers to the direction perpendicular to the surface of the magnetic layer, and can also be referred to as the thickness direction. In the present invention and this specification, the vertical angle ratio is determined by the following method. A sample piece of a size suitable for introduction into a vibrating magnetometer is cut from the magnetic tape to be measured. Using a vibrating magnetometer, a magnetic field is applied to this sample piece perpendicular to the sample piece (in the direction perpendicular to the magnetic layer surface) at a maximum applied magnetic field of 3979 kA / m, a measurement temperature of 296 K, and a magnetic field sweep speed of 8.3 kA / m / sec, and the magnetization intensity of the sample piece against the applied magnetic field is measured. The measured magnetization intensity is obtained as a value after demagnetization correction and after subtracting the magnetization of the sample probe of the vibrating magnetometer as background noise. When the magnetization intensity at the maximum applied magnetic field is Ms and the magnetization intensity at zero applied magnetic field is Mr, the squareness ratio SQ is calculated as SQ = Mr / Ms. The measurement temperature refers to the temperature of the sample piece, and the temperature of the sample piece can be set to the measurement temperature by setting the ambient temperature around the sample piece to the measurement temperature, thereby achieving thermal equilibrium.

[0113] [Magnetic tape housing] One aspect of the present invention relates to a magnetic tape housing that includes a core around which the magnetic tape is wound.

[0114] <A form of magnetic tape housing (magnetic tape cartridge)> One form of the magnetic tape housing described above is a magnetic tape cartridge.

[0115] A magnetic tape cartridge (hereinafter also simply referred to as "cartridge") houses a magnetic tape wound around a reel (core) inside the cartridge body. The core around which the magnetic tape is wound in the magnetic tape housing, such as the reel of the cartridge, consists of at least a hub, and usually flanges are provided at both ends of the hub. The core of the magnetic tape housing is rotatably mounted inside the magnetic tape housing. As magnetic tape cartridges, single-reel type magnetic tape cartridges, which have one reel inside the cartridge body, and double-reel type magnetic tape cartridges, which have two reels inside the cartridge body, are widely used. When a single-reel type magnetic tape cartridge is installed in a magnetic recording and / or playback device for recording and / or playing back data on magnetic tape, the magnetic tape is pulled out from the magnetic tape cartridge and wound onto a reel (hereinafter also referred to as "take-up reel") provided in the magnetic recording and playback device. A magnetic head is positioned in the magnetic tape transport path from the magnetic tape cartridge to the take-up reel. In a magnetic tape cartridge, the magnetic tape is drawn out and wound up between the reel (supply reel) of the magnetic tape cartridge and the reel (take-up reel) of the magnetic recording and playback device. During this time, data is recorded and / or reproduced by contact and sliding between, for example, the magnetic head and the magnetic layer surface of the magnetic tape. In contrast, a dual-reel magnetic tape cartridge has both the supply reel and the take-up reel housed inside the magnetic tape cartridge. The magnetic tape housing can be a single-reel magnetic tape cartridge in one form, or a dual-reel magnetic tape cartridge in another form. When the magnetic tape housing is a dual-reel magnetic tape cartridge, the core from which the magnetic tape is drawn for the measurement of roundness, which will be described in detail later, refers to the reel on which the larger portion of the magnetic tape is wound when the magnetic tape cartridge is unused. For single-reel and dual-reel magnetic tape cartridges, the measurement of roundness, which will be described in detail later, shall be performed using an unused magnetic tape cartridge.In the present invention and this specification, "unused" with respect to a magnetic tape housing (e.g., a magnetic tape cartridge or a magnetic recording / reproducing device) means that the magnetic tape housed in the magnetic tape housing has not been run since it was provided as a product. In one embodiment, the magnetic tape housing is preferably a single-reel type magnetic tape cartridge, which has been mainly adopted in the data storage field in recent years.

[0116] The hub of the winding core is a cylindrical member that constitutes the central axis around which the magnetic tape is wound. The hub of the winding core can be a single-layer cylindrical member, or it can be a multi-layer cylindrical member with two or more layers. From the viewpoint of manufacturing cost and ease of manufacturing, it is preferable that the hub of the winding core be a single-layer cylindrical member.

[0117] The flexural modulus of the material constituting at least the outer surface layer of the hub can be, for example, 3 GPa (gigapascals) or higher. The inventors believe that high rigidity of the hub of the winding core around which the magnetic tape is wound can contribute to suppressing the positional displacement in the width direction at the short period described above when the wound magnetic tape is pulled out. The inventors surmise that this is desirable from the viewpoint of further improving the transfer rate. From this viewpoint, in one embodiment, the flexural modulus of the material constituting at least the outer surface layer of the hub is preferably 5 GPa (gigapascals) or higher, more preferably 6 GPa or higher, even more preferably 7 GPa or higher, and even more preferably 8 GPa or higher. The above flexural modulus can be, for example, 20 GPa or less, 15 GPa or less, or 10 GPa or less. However, a high flexural modulus is considered desirable in suppressing the positional displacement in the width direction at the short period described above. Therefore, the above flexural modulus may exceed the values ​​exemplified here.

[0118] The above flexural modulus is the flexural modulus of the material constituting the cylindrical member when the hub of the winding core is a single-layer cylindrical member. On the other hand, when the hub is a multilayer cylindrical member with two or more layers, the above flexural modulus is the flexural modulus of the material constituting at least the outer surface layer of the hub. In the present invention and this specification, "flexural modulus" is a value obtained in accordance with JIS (Japanese Industrial Standards) K 7171:2016. JIS K 7171:2016 is a Japanese Industrial Standard created without changing the technical content, based on ISO (International Organization for Standardization) 178 and Amendment 1:2013, which were published as the 5th edition in 2010. The test specimen used to measure the flexural modulus is prepared in accordance with item 6 "Test specimen" of JIS K 7171:2016.

[0119] Materials that can constitute the hub of the winding core of a magnetic tape cartridge reel include resin and metal. Examples of metals include aluminum. From the viewpoint of cost and productivity, resin is preferred. Examples of resins include fiber-reinforced resins. Examples of fiber-reinforced resins include glass fiber reinforced resins and carbon fiber reinforced resins. Fiber-reinforced polycarbonate is preferred as such a fiber-reinforced resin. This is because polycarbonate is readily available and can be molded with high precision and at low cost using general-purpose molding machines such as injection molding machines. Furthermore, in glass fiber reinforced resins, the glass fiber content can be, for example, 10% by mass or more, and preferably 15% by mass or more. The higher the glass fiber content, the higher the flexural modulus of the glass fiber reinforced resin tends to be. As an example, the glass fiber content of a glass fiber reinforced resin can be 50% by mass or less, or 40% by mass or less. In one embodiment, glass fiber reinforced polycarbonate is preferred as the resin constituting the hub. Other resins constituting the hub can include high-strength resins generally known as super engineering plastics. One example of a super engineering plastic is polyphenylene sulfide (PPS).

[0120] The thickness of the hub described above is preferably in the range of 2.0 to 3.0 mm, from the viewpoint of achieving both hub strength and dimensional accuracy during molding. The thickness of the hub refers to the total thickness of the multilayer structure in the case of a hub with two or more layers. The outer diameter of the hub is usually determined by the specifications of the magnetic recording and playback device, and can be in the range of, for example, 20 to 60 mm.

[0121] The configuration of the magnetic tape cartridge will be described below with reference to the drawings. However, the configurations shown in the drawings are illustrative, and the present invention is not limited to such examples.

[0122] Figure 1 is a perspective view of an example of a magnetic tape cartridge. Figure 1 shows a single-reel magnetic tape cartridge.

[0123] The magnetic tape cartridge 10 shown in Figure 1 has a case 12. The case 12 is formed in the shape of a rectangular box. The case 12 is usually made of a resin such as polycarbonate. Inside the case 12, a single reel 20 is rotatably housed.

[0124] Figure 2 is a perspective view of the reel as the magnetic tape is being wound. Figure 3 is a perspective view of the reel after the magnetic tape has been fully wound.

[0125] The reel 20 has a cylindrical reel hub 22 that forms the axial center. The reel hub has been described in detail earlier.

[0126] The reel hub 22 is provided with flanges (lower flange 24 and upper flange 26) that extend radially outward from the lower and upper ends of the reel hub 22, respectively. Here, "upper" refers to the side located above the magnetic tape cartridge when it is mounted on a magnetic recording and playback device, and "lower" refers to the side located below it. It is preferable that one or both of the lower flange 24 and the upper flange 26 are integrally configured with the reel hub 22 from the viewpoint of reinforcing the upper and / or lower end sides of the reel hub 22. Integral configuration means that they are configured as a single component rather than separate components. In the first embodiment, the reel hub 22 and the upper flange 26 are configured as a single component, and this component is joined to the lower flange 24, which is configured as a separate component, in a known manner. In the second embodiment, the reel hub 22 and the lower flange 24 are configured as a single component, and this component is joined to the upper flange 26, which is configured as a separate component, in a known manner. The reels of the magnetic tape cartridge described above may take any form. Each component can be manufactured by known molding methods such as injection molding.

[0127] The magnetic tape T is wound around the outer circumference of the reel hub 22, starting from the inner end Tf of the tape (see Figure 2). The tension applied in the longitudinal direction of the magnetic tape when winding it around the reel hub is preferably 1.5 N (Newtons) or less, more preferably 1.0 N or less, and it is also preferable to have no tension at all.

[0128] The side wall of the case 12 has an opening 14 for pulling out the magnetic tape T wound on the reel 20, and a leader pin 16 is fixed to the outer end Te of the magnetic tape T pulled out from this opening 14, which is pulled out while being locked in place by a pull-out member (not shown) of a magnetic recording and playback device (not shown).

[0129] Furthermore, the opening 14 is opened and closed by a door 18. The door 18 is formed in the shape of a rectangular plate large enough to close the opening 14, and is biased in the direction of closing the opening 14 by a biasing member (not shown). The door 18 is then opened against the biasing force of the biasing member when the magnetic tape cartridge 10 is installed in the magnetic recording and playback device.

[0130] For further details regarding magnetic tape cartridges, publicly known technologies relating to magnetic tape cartridges can be applied.

[0131] In the above configuration, the magnetic tape is treated as a removable medium (a so-called interchangeable medium), and a magnetic tape cartridge (magnetic tape housing) containing the magnetic tape can be inserted into a magnetic recording and playback device, and the magnetic tape cartridge containing the magnetic tape can be removed from the magnetic recording and playback device.

[0132] Figure 4 shows a schematic diagram of an example of a magnetic recording and playback device with a magnetic tape cartridge inserted. In Figure 4, the magnetic tape cartridge 10 is inserted into the housing H of the magnetic recording and playback device 60, the magnetic tape T is pulled out from within the housing H, and wound onto the take-up reel 606. The housing H can be made of, for example, metal, resin, etc. For details regarding the magnetic tape cartridge 10, please refer to the previous description concerning single-reel type magnetic tape cartridges. Recording and playback of data onto magnetic tape T is performed by controlling the recording / playback head unit 602 by commands from the control device 601. The magnetic recording and playback device 60 has a configuration that allows for the detection and adjustment of tension applied in the longitudinal direction of the magnetic tape from the spindle motors 607A, 607B and their drive units 608A, 608B that control the rotation of the cartridge reel 20 and the take-up reel 606. The magnetic recording and playback device 60 has a configuration that allows a magnetic tape cartridge 10 to be installed. The magnetic recording and playback device 60 has a cartridge memory read / write device 604 that can read from and write to the cartridge memory 27 in the magnetic tape cartridge 10. The cartridge memory can be, for example, a non-volatile memory, and in one embodiment, information regarding tension adjustment, which will be described later, is already recorded or will be recorded. The information regarding tension adjustment is information for adjusting the tension applied in the longitudinal direction of the magnetic tape. In the magnetic tape cartridge 10 inserted into the housing H of the magnetic recording and playback device 60, one end of the magnetic tape T or the leader pin is pulled out by an automatic loading mechanism or manually, and the magnetic tape T passes over the recording and playback head through guide rollers 605A and 605B with the magnetic layer surface of the magnetic tape T in contact with the recording and playback head surface of the recording and playback head unit 602, and the magnetic tape T is wound onto the take-up reel 606. In one embodiment, when recording data to the magnetic tape and / or playing back data recorded on the magnetic tape in the magnetic recording and playback device, the magnetic head contacts and slides against the magnetic layer surface of the magnetic tape. Such a magnetic recording and playback device is generally called a sliding drive or contact sliding drive. In another embodiment, in the magnetic recording and playback device, the magnetic head records data to the magnetic tape and / or plays back data recorded on the magnetic tape in a non-contact state, except when it is in accidental contact with the magnetic layer surface. Such a magnetic recording and playback device is generally called a floating drive. The rotation and torque of spindle motors 607A and 607B are controlled by signals from the control device 601, so that the magnetic tape T runs at a desired speed and tension. A servo pattern pre-formed on the magnetic tape can be used to control the tape speed. A tension detection mechanism may be provided between the magnetic tape cartridge 10 and the take-up reel 606 for tension detection. In addition to the control performed by spindle motors 607A and 607B, tension adjustment may also be performed using guide rollers 605A and 605B. The cartridge memory read / write device 604 is configured to read and write information to the cartridge memory 27 in response to commands from the control device 601. For example, the ISO (International Organization for Standardization) 14443 standard can be used as the communication method between the cartridge memory read / write device 604 and the cartridge memory 27.

[0133] The control device 601 includes, for example, a control unit, a storage unit, a communication unit, and the like.

[0134] The recording / playback head unit 602 consists of, for example, a recording / playback head, a servo tracking actuator for adjusting the position of the recording / playback head in the track width direction, a recording / playback amplifier 609, and a connector cable for connecting to the control device 601. The recording / playback head consists of, for example, a recording element for recording data on the magnetic tape, a playback element for reproducing the data on the magnetic tape, and a servo signal reading element for reading the servo signals recorded on the magnetic tape. Within a single magnetic head, for example, one or more recording elements, playback elements, and servo signal reading elements are mounted. Alternatively, each element may be separately contained in multiple magnetic heads corresponding to the direction in which the magnetic tape travels.

[0135] The recording / playback head unit 602 is configured to record data onto the magnetic tape T in response to commands from the control device 601. It is also configured to play back data recorded on the magnetic tape T in response to commands from the control device 601.

[0136] The control device 601 has a mechanism to determine the running position of the magnetic tape T from the servo signals read from the servo bands when the magnetic tape T is running, and to control the servo tracking actuator so that the recording element and / or playback element are positioned at the target running position (track position). This track position control is performed, for example, by feedback control. The control device 601 also has a mechanism to determine the servo band interval from the servo signals read from two adjacent servo bands when the magnetic tape T is running. It also has a mechanism to adjust and change the tension applied to the longitudinal direction of the magnetic tape by controlling the torque of spindle motors 607A and 607B and / or guide rollers 605A and 605B so that the servo band interval becomes a target value. This tension adjustment is performed, for example, by feedback control. Furthermore, the control device 601 can store the obtained servoband interval information in the internal storage unit of the control device 601 located within the housing H of the magnetic recording and playback device 60, in a separate storage device (not shown) located within the housing H, in the cartridge memory 27, or in an external storage device (not shown) located outside the housing H.

[0137] In the magnetic recording and playback device 60, tension can be applied to the magnetic tape in the longitudinal direction during recording and / or playback. The tension applied to the magnetic tape in the longitudinal direction is a constant value in one configuration and varies in another configuration. For example, as described above, in Figure 4, a tension detection mechanism can be provided between the magnetic tape cartridge 10 and the take-up reel 606 to detect the tension. Furthermore, the magnetic recording and playback device's control device can be used to control the tension so that, for example, the minimum tension does not fall below a value specified or recommended by standards, and / or the maximum tension does not exceed a value specified or recommended by standards. For example, the tension applied to the magnetic tape in the longitudinal direction can be variably controlled by a tension adjustment mechanism that can adjust the tension applied to the magnetic tape running within the magnetic recording and playback device. Preferably, the width dimension of the magnetic tape can be controlled by adjusting the tension applied to the magnetic tape in the longitudinal direction. In the above tension adjustment, the tension applied to the magnetic tape in the longitudinal direction can change.

[0138] Data is recorded onto the magnetic tape while the magnetic tape T is moved between the take-up reel 606 and the cartridge reel 20. Data recorded on the magnetic tape is also played back while the magnetic tape T is moved between the take-up reel 606 and the cartridge reel 20. After recording and / or playback is complete, the magnetic tape T is usually wound onto the cartridge reel 20 of the magnetic tape cartridge 10, and the entire length of the magnetic tape T is housed within the magnetic tape cartridge 10. The magnetic tape cartridge 10 containing the magnetic tape T is, in one configuration, held within the housing H of the magnetic recording and playback device 60, and in another configuration, removed from the housing H. A thermometer / hygrometer 610 can optionally be placed inside the housing H of the magnetic recording and playback device 60. The thermometer / hygrometer 610 allows for the measurement and monitoring of the temperature and humidity inside the housing H of the magnetic recording and playback device 60.

[0139] [Another form of magnetic tape housing (magnetic recording and playback device)] Another form of the magnetic tape housing described above is a magnetic recording and playback device. In this form, the magnetic tape is not treated as a replaceable medium, and the magnetic tape and magnetic head are housed within the magnetic tape housing (magnetic recording and playback device). In this form, the core from which the magnetic tape is pulled for the measurement of roundness, which will be described in detail later, refers to the reel in which the larger portion of the magnetic tape is wound, among the two reels in an unused magnetic recording and playback device. Furthermore, in this form, the measurement of roundness, which will be described in detail later, is performed using an unused magnetic recording and playback device.

[0140] Figure 5 shows a schematic diagram of an example of the above configuration in which a reel on which magnetic tape is wound and a magnetic recording and playback device are integrated. In Figure 5, tape reels 911A and 911B are fixed within the housing H of the magnetic recording and playback device 90, and the magnetic tape T is not treated as a replaceable medium. Data is recorded onto the magnetic tape by running the magnetic tape T between tape reels 911A and 911B. Data recorded on the magnetic tape is also played back by running the magnetic tape T between tape reels 911A and 911B. After recording and / or playback is complete, the magnetic tape T is usually stored in the magnetic recording and playback device 90 with most of it wound onto tape reel 911A or tape reel 911B.

[0141] For the housing H, control device 901, recording / playback head unit 902, guide rollers 905A, 905B, spindle motors 907A, 907B, drive units 908A, 908B, recording / playback amplifier 909, and temperature / hygrometer 910 in Figure 5, refer to the descriptions of each part in Figure 4. For the tape reels 911A and 911B, refer to the descriptions of each part in Figures 2, 3, and 4, respectively.

[0142] The magnetic recording and playback device 90 includes a storage device 912 housed within the housing H and an external storage device 913 located outside the housing H. The control device 901 can store, for example, the servo band interval information obtained as previously described with respect to Figure 4 in the storage device 912 and / or the external storage device 913.

[0143] In any configuration, the total length of the magnetic tape housed in the magnetic tape housing is not particularly limited and can be, for example, 200m or more, or 800m or more (for example, in the range of approximately 800m to 2500m). The longer the total length of the tape housed in a single magnetic tape housing, the more preferable it is from the viewpoint of increasing the capacity of the magnetic tape housing.

[0144] <Roundness> With respect to the magnetic tape housed in the above-mentioned magnetic tape housing, the roundness of the trajectory traced by the magnetic tape for one rotation when the magnetic tape wound around the core is pulled out from the core can be, for example, 120 μm or less, and preferably 100 μm or less, as the arithmetic mean of measurements taken at three locations in the width direction of the magnetic tape. The inventors believe that a roundness of 100 μm or less is preferable from the viewpoint of further improving the transfer rate. From the viewpoint of further improving the transfer rate, the roundness is more preferably 95 μm or less, even more preferably 90 μm or less, even more preferably 85 μm or less, even more preferably 80 μm or less, even more preferably 75 μm or less, and even more preferably 70 μm or less. Furthermore, the roundness can be, for example, 30 μm or more, 35 μm or more, 40 μm or more, or 45 μm or more, and can also be lower than the values ​​exemplified herein. A smaller value of roundness is preferable from the viewpoint of further improving the transfer rate. The degree of roundness tends to decrease as the flexural modulus of the core hub increases.

[0145] The "roundness" as used in the present invention and this specification is a value determined by the following method. The following measurements will be performed in a measurement environment where the ambient temperature is in the range of 20-25°C and the relative humidity is in the range of 40-60%. To allow the equipment and the magnetic tape housing to acclimate to the measurement environment, the measurements will be performed after they have been left in the environment for at least one day. The measurement method will be explained below, using the example of a single-reel magnetic tape cartridge as the magnetic tape housing to be measured. To extract the magnetic tape from the reel (core) of the magnetic tape cartridge, a magnetic recording and playback device (drive) capable of attaching and detaching the magnetic tape cartridge is used. To observe the surface of the magnetic tape extracted from the reel (core) and the upper surface of the upper flange of the reel within the case of the magnetic tape cartridge while it is set in the drive, the following processing is performed on the magnetic tape cartridge. After leaving the magnetic tape cartridge to be measured in the above measurement environment for more than one day, the reel with the magnetic tape wound around it is removed from the case of the magnetic tape cartridge. The removal of the reel is performed in the above measurement environment. If the magnetic tape wound around the reel has a leader tape and / or leader pins attached, the above removal is performed with them attached. The reel (with the magnetic tape wound around it) thus removed is left in the above measurement environment until it is transferred to a case with an opening. If the magnetic tape cartridge contains cartridge memory, the cartridge memory is also removed. The removed reel and cartridge memory are transferred to a cartridge case that has an opening so that the upper surface of the reel's upper flange and the magnetic tape surface can be observed from outside the case using an optical discriminant sensor and a laser displacement meter, respectively. The transfer to the case with the opening is performed in the above measurement environment. Alternatively, the case of the magnetic tape cartridge to be measured may be processed to form the above opening. The processing to form the opening can be performed with the reel, with the magnetic tape wound around it, still housed in the case, or after the reel, with the magnetic tape wound around it, has been temporarily removed from the case. The removal of the reel is performed in the above measurement environment after the magnetic tape cartridge to be measured has been left in the above measurement environment for at least one day. If the magnetic tape wound around the reel has a leader tape and / or leader pins attached, the removal is performed with them attached. The reel (with the magnetic tape wound around it) thus removed is left in the above measurement environment until it is put back into the case after the opening has been formed.When the process for forming the opening is carried out with the reel, on which the magnetic tape is wound, still housed in its case, the magnetic tape cartridge to be measured is left in the above-mentioned measurement environment for at least one day, and then the opening is formed in the same measurement environment. The opening can be formed by known methods. The rotation period of the magnetic tape cartridge reel (winding core) is detected by attaching a light-reflective sticker or similar to the upper surface of the reel's upper flange and detecting it with a light discrimination sensor during measurement. As the light discrimination sensor, for example, a light discrimination sensor capable of emitting light with a spot diameter of about 5 mm and outputting an electrical signal synchronized with the index can be used. Specific examples include the KEYENCE CZ-H35S and CZ-C21A. For measuring the surface displacement of magnetic tape pulled from a reel (core), a laser displacement meter should have a laser spot diameter of 1.5 mm or less, a displacement resolution of 0.5 μm or less, a time resolution of 50 μs or less, and be capable of outputting an electrical signal corresponding to the amount of displacement. Specific examples of usable laser displacement meters include, for example, the KEYENCE LK-G85 and LK-GD500. The magnetic tape cartridge is inserted into the magnetic recording and playback device, and the magnetic tape is loaded. The magnetic recording and playback device used for measurement can be of any standard or generation, as long as it is capable of mounting the magnetic tape cartridge and running the magnetic tape contained in the magnetic tape cartridge. If the reel (on which the magnetic tape is wound) and cartridge memory of the magnetic tape cartridge to be measured are transferred to another magnetic tape cartridge with an opening in the case, the magnetic tape loading is performed according to the information recorded in the transferred cartridge memory. Figure 6 shows a schematic diagram of a magnetic tape cartridge with an opening formed in its case mounted on the magnetic recording and playback device shown in Figure 4. The top of the magnetic recording and playback device may be left open, or an opening may be provided in the housing H of the magnetic recording and playback device, so that the displacement of the surface of the magnetic tape can be measured by a laser displacement meter. For example, as shown in Figure 6, the position where the displacement of the surface of the magnetic tape is measured by the laser displacement meter is the rotational angle position where the magnetic tape is not completely unwound from the reel (core) of the magnetic tape cartridge. In Figure 6, the dotted line extending from the laser displacement meter schematically represents the laser beam. The measurement points for the width direction of the magnetic tape surface are three locations: the center of the tape in the width direction, 1 mm below the top edge, and 1 mm above the bottom edge. The width of the magnetic tape is determined according to the standard, for example, 1 / 2 inch. 1 / 2 inch = 12.65 mm. However, even for magnetic tapes with widths other than 1 / 2 inch, the measurement points for the width direction are the three locations described above. During measurement, a digital oscilloscope, data logger, etc., is used to continuously measure the electrical signal of the magnetic tape surface displacement obtained by the laser displacement meter and the electrical signal of the reel rotation index obtained by the optical discrimination sensor. The measurement pitch is finer than 1° of the reel rotation angle. In a magnetic recording and playback device, after loading the magnetic tape, the tape is wound onto the reel of the magnetic recording and playback device (in the example shown in Figure 6, the take-up reel 606) at a constant speed in the range of 2 m / s to 8 m / s while a tension of 0.3 N (Newtons) to 1.1 N is applied to the tape in the longitudinal direction. The electrical signals of the displacement of the magnetic tape surface and the electrical signals of the reel's rotation index are measured and stored using a digital oscilloscope, data logger, etc., as described above. The tension and speed values ​​are set to the values ​​in the magnetic recording and playback device. The electrical displacement signal is converted to displacement (unit: μm) using a coefficient specified for the laser displacement meter used to convert the electrical displacement signal (voltage value) to displacement. This coefficient is listed, for example, in the laser displacement meter's spec sheet. Using the electrical signal of the reel's rotation index obtained in the above measurement, the measurement results used to calculate the roundness are extracted from the displacement measurement results. Specifically, in the state in which the magnetic tape cartridge was wound on the reel (core), the end of the magnetic tape on the reel side is called the inner end, and the other end is called the outer end. One rotation of the core is considered one period, and the measurement results for three consecutive rotations (three periods) after approximately 50m of the magnetic tape from the outer end has been wound onto the reel of the magnetic recording and playback device are extracted. Using the extracted measurement results (displacement), the roundness of the trajectory of the magnetic tape pulled from the core is calculated for each rotation (1 period). At three measurement points in the width direction, the roundness of the trajectory for one rotation is determined by taking the arithmetic mean of three rotations (3 periods) at each point. The arithmetic mean of the values ​​obtained at each of the three points is taken as the value of the roundness of the trajectory of the magnetic tape for one rotation in the magnetic tape cartridge (magnetic tape housing) being measured. The calculation of roundness is performed using the method specified in JIS B0621:1984 (minimum area center method). Roundness, as specified in item 4.3 of JIS B0621:1984, refers to the degree of deviation of a circular shape from a geometrically correct circle (called a geometric circle). Roundness, as specified in item 5.3 of the same JIS, is expressed as the difference in radii between two concentric geometric circles when the distance between the two concentric circles is minimized when the circular shape is enclosed by two concentric geometric circles. If the trajectory of the magnetic tape pulled from the core for one rotation is a geometric circle, the distance between the laser displacement meter and the measurement position on the magnetic tape surface, as measured by the laser displacement meter, will always be the same value (hereinafter referred to as X) throughout the rotation. However, if the trajectory deviates from a geometric circle, the distance between the laser displacement meter and the measurement position on the magnetic tape surface, as measured by the laser displacement meter, will become shorter or longer than X. The difference between this distance and X is the amount of displacement measured by the laser displacement meter, and from this amount of displacement, the trajectory of the magnetic tape pulled from the core for one rotation can be drawn. The roundness of the drawn trajectory is then determined as described above.

[0146] If the magnetic tape housing is a magnetic recording and playback device, the top of the magnetic recording and playback device is left open, or an opening is provided in the housing of the magnetic recording and playback device, so that the upper surface of the reel flange and the surface of the magnetic tape can be observed from outside the device using an optical discrimination sensor and a laser displacement meter, respectively. Using an unused magnetic recording and playback device, the roundness is determined by the method described above, except that the magnetic tape housing is a single-reel type magnetic tape cartridge, and the magnetic tape is wound from one reel (winding core) to the other by running the magnetic tape through the magnetic recording and playback device.

[0147] When the magnetic tape housing is a dual-reel magnetic tape cartridge, an opening is provided in the magnetic tape cartridge so that the upper surface of the reel flange and the surface of the magnetic tape can be observed from outside the case using an optical discriminant sensor and a laser displacement meter, respectively. The roundness is determined by the method described above, using the case where the magnetic tape housing is a single-reel magnetic tape cartridge as an example, except that an unused dual-reel magnetic tape cartridge is mounted in a magnetic recording and playback device and the magnetic tape is wound from one reel (winding core) to the other reel of the magnetic tape cartridge.

[0148] Typically, after the servo pattern is formed, the magnetic tape is wound onto the core of a magnetic tape housing and then housed in the magnetic tape housing. As previously described, the magnetic tape housing is in one form a magnetic tape cartridge, and in another form a magnetic recording and playback device including a magnetic head.

[0149] <Magnetic head> In the present invention and this specification, “magnetic recording and playback device” means a device capable of recording data onto a magnetic tape and playback of data recorded on a magnetic tape. Such a device is generally called a drive and may be a tape drive for recording digital data. The magnetic tape housing may be a magnetic tape cartridge in one embodiment, or a magnetic recording and playback device including a magnetic head in another embodiment. The magnetic tape cartridge is inserted into the magnetic recording and playback device, and the magnetic tape is run within the magnetic recording and playback device to record data onto the magnetic tape and / or play back the recorded data using the magnetic head. The magnetic head included in the magnetic recording and playback device may be a recording head capable of recording data onto a magnetic tape, or a playback head capable of playing back data recorded on the magnetic tape. In one embodiment, the magnetic recording and playback device may include both a recording head and a playback head as separate magnetic heads. In another embodiment, the magnetic head included in the magnetic recording and playback device may have a configuration in which both the recording element and the playback element are provided on a single magnetic head. As the playback head, a magnetic head (MR head) that includes a magnetoresistive (MR) element as a playback element capable of sensitively reading information recorded on magnetic tape is preferred. Various known MR heads (e.g., GMR (Giant Magnetoresistive) head, TMR (Tunnel Magnetoresistive) head, etc.) can be used as the MR head. In addition, the magnetic head that records and / or plays back data may include a servo pattern reading element. Alternatively, a magnetic head (servo head) equipped with a servo pattern reading element may be included in the magnetic recording and / or playback device as a separate head from the magnetic head that records and / or plays back data.For example, a magnetic head that records and / or reproduces recorded data (hereinafter also referred to as the "recording / reproduction head") may include two servo signal reading elements, each of which can simultaneously read two adjacent servo bands separated by a data band. One or more data elements may be placed between the two servo signal reading elements. Elements for recording data (recording elements) and elements for reproducing data (reproduction elements) are collectively referred to as "data elements."

[0150] By using a regeneration element with a narrow width as the regeneration element, high-density recorded data can be regenerated with high sensitivity. From this viewpoint, the regeneration element width is preferably 0.8 μm or less. The regeneration element width can be, for example, 0.1 μm or more. However, a value lower than this is also preferable from the above viewpoint. On the other hand, the narrower the playback element width, the more likely it is that playback defects and other phenomena caused by off-track recording will occur. To suppress the occurrence of such phenomena, a magnetic recording and playback device that controls the width dimension of the magnetic tape by adjusting and changing the tension applied to the longitudinal direction of the magnetic tape while it is running is preferable. Here, "regenerative element width" refers to the physical dimension of the regenerative element width. Such physical dimensions can be measured using an optical microscope, a scanning electron microscope, or the like.

[0151] When recording data and / or playing back recorded data, head tracking using servo signals can be performed first. That is, by making the servo signal reading element follow a predetermined servo track, the data element can be controlled to pass over the target data track. The movement of the data track is achieved by changing the servo track read by the servo signal reading element in the tape width direction. Furthermore, the recording / playback head can also record and / or play back data for other data bands. In this case, the servo signal reading element can be moved to a predetermined servo band using the UDIM information described earlier, and tracking for that servo band can be started.

[0152] Figure 7 shows an example of the arrangement of data bands and servo bands. In Figure 7, multiple servo bands 1 are arranged on the magnetic layer of the magnetic tape T, sandwiched between guide bands 3. Multiple regions 2 sandwiched between two servo bands are the data bands. A servo pattern is a magnetized region, formed by magnetizing a specific region of the magnetic layer with a servo light head. The region magnetized by the servo light head (the position where the servo pattern is formed) is defined by the standard. For example, in the industry standard LTO Ultrium format tape, multiple servo patterns inclined with respect to the tape width direction are formed on the servo bands during magnetic tape manufacturing, as shown in Figure 8. More specifically, in Figure 8, the servo frame SF on the servo band 1 consists of a servo subframe 1 (SSF1) and a servo subframe 2 (SSF2). The servo subframe 1 consists of an A-burst (indicated as A in Figure 8) and a B-burst (indicated as B in Figure 8). The A-burst consists of servo patterns A1 to A5, and the B-burst consists of servo patterns B1 to B5. On the other hand, servo subframe 2 consists of C-bursts (indicated as C in Figure 8) and D-bursts (indicated as D in Figure 8). C-bursts consist of servo patterns C1 to C4, and D-bursts consist of servo patterns D1 to D4. These 18 servo patterns are arranged in sets of 5 and 4 on subframes in a 5, 5, 4, 4 sequence, and are used to identify the servo frames. Figure 8 shows one servo frame for illustrative purposes. However, in reality, in the magnetic layer of a magnetic tape where timing-based servo head tracking is performed, multiple servo frames are arranged in the direction of travel in each servo band. In Figure 8, the arrows indicate the direction of travel. For example, LTO Ultrium format tape typically has more than 5000 servo frames per meter of tape length in each servo band of the magnetic layer. [Examples]

[0153] An embodiment of the present invention will be described below based on an example. However, the present invention is not limited to the embodiment shown in the example. Unless otherwise specified, the terms "parts" and "%" below refer to "parts by mass" and "mass%". "eq" is equivalent and is a unit that cannot be converted to SI units. Furthermore, unless otherwise specified, the following processes and operations were carried out in an environment with a temperature of 20-25°C and a relative humidity of 40-60%.

[0154] [Non-magnetic support] In Table 1, "PEN" indicates a polyethylene naphthalate support. The Young's modulus in Table 1 is the value measured by the method described above.

[0155] [Ferromagnetic powder] In Table 1, "BaFe" in the ferromagnetic powder column refers to hexagonal barium ferrite powder with an average particle size (average plate diameter) of 21 nm.

[0156] In Table 1, "SrFe1" in the ferromagnetic powder column refers to hexagonal strontium ferrite powder prepared as follows. 1707g of SrCO3, 687g of H3BO3, 1120g of Fe2O3, 45g of Al(OH)3, 24g of BaCO3, 13g of CaCO3, and 235g of Nd2O3 were weighed out and mixed in a mixer to obtain a raw material mixture. The obtained raw material mixture was melted in a platinum crucible at a melting temperature of 1390°C. While stirring the molten material, the outlet at the bottom of the platinum crucible was heated, and the molten material was dispensed in a rod shape at approximately 6 g / second. The dispensed material was rolled and rapidly cooled using water-cooled twin rollers to produce an amorphous body. 280g of the prepared amorphous material was placed in an electric furnace and heated to 635°C (crystallization temperature) at a heating rate of 3.5°C / min. The temperature was maintained at this temperature for 5 hours to precipitate (crystallize) hexagonal strontium ferrite particles. Next, the crystalline material obtained above, containing hexagonal strontium ferrite particles, was coarsely ground in a mortar. 1000g of 1mm particle size zirconia beads and 800mL of 1% aqueous acetic acid solution were added to a glass bottle, and the mixture was dispersed in a paint shaker for 3 hours. After that, the resulting dispersion was separated from the beads and placed in a stainless steel beaker. The dispersion was allowed to stand at a liquid temperature of 100°C for 3 hours to dissolve the glass components, then precipitated using a centrifuge, and washed by repeated decantation. Finally, it was dried in a heating furnace at a furnace temperature of 110°C for 6 hours to obtain hexagonal strontium ferrite powder. The average particle size of the hexagonal strontium ferrite powder obtained above was 18 nm, and the activation volume was 902 nm. 3 The anisotropy constant Ku is 2.2 × 10⁻⁶. 5 J / m 3 , mass magnetization σs is 49A m 2 It was / kg. A sample powder of 12 mg was taken from the hexagonal strontium ferrite powder obtained above, and the elemental analysis of the filtrate obtained by partially dissolving this sample powder under the dissolution conditions exemplified earlier was performed using an ICP analyzer to determine the surface layer content of neodymium atoms. Separately, 12 mg of sample powder was taken from the hexagonal strontium ferrite powder obtained above, and the elemental analysis of the filtrate obtained by completely dissolving this sample powder under the dissolution conditions exemplified earlier was performed using an ICP analyzer to determine the bulk content of neodymium atoms. The neodymium atom content (bulk content) relative to 100 atomic percent of iron atoms in the hexagonal strontium ferrite powder obtained above was 2.9 atomic percent. Furthermore, the neodymium atom content in the surface layer was 8.0 atomic percent. The ratio of surface layer content to bulk content, "surface layer content / bulk content," was 2.8, confirming that neodymium atoms were concentrated in the surface layer of the particles.

[0157] The hexagonal ferrite crystal structure of the powder obtained above was confirmed by scanning with CuKα rays at a voltage of 45kV and intensity of 40mA, and measuring the X-ray diffraction pattern under the following conditions (X-ray diffraction analysis). The powder obtained above showed a magnetoplanbite-type (M-type) hexagonal ferrite crystal structure. Furthermore, the crystalline phase detected by X-ray diffraction analysis was a single phase of the magnetoplanbite type. PANalytical X'Pert Pro diffractometer, PIXcel detector Soller slit for incident and diffracted beams: 0.017 radians Fixed angle of dispersion slit: 1 / 4 degree Mask: 10mm Scatter prevention slit: 1 / 4 degree Measurement mode: Continuous Measurement time per step: 3 seconds Measurement speed: 0.017 degrees per second Measurement step: 0.05 degrees

[0158] In Table 1, "SrFe2" in the ferromagnetic powder column refers to hexagonal strontium ferrite powder prepared as follows. 1725g of SrCO3, 666g of H3BO3, 1332g of Fe2O3, 52g of Al(OH)3, 34g of CaCO3, and 141g of BaCO3 were weighed out and mixed in a mixer to obtain a raw material mixture. The obtained raw material mixture was melted in a platinum crucible at a melting point of 1380°C. While stirring the molten material, the outlet at the bottom of the platinum crucible was heated, and the molten material was dispensed in a rod shape at approximately 6 g / second. The dispensed material was rolled and rapidly cooled using water-cooled twin rolls to produce an amorphous body. 280g of the obtained amorphous material was placed in an electric furnace, heated to 645°C (crystallization temperature), and held at the same temperature for 5 hours to precipitate (crystallize) hexagonal strontium ferrite particles. Next, the crystalline material obtained above, containing hexagonal strontium ferrite particles, was coarsely ground in a mortar. 1000g of 1mm particle size zirconia beads and 800mL of 1% aqueous acetic acid solution were added to a glass bottle, and the mixture was dispersed in a paint shaker for 3 hours. After that, the resulting dispersion was separated from the beads and placed in a stainless steel beaker. The dispersion was allowed to stand at a liquid temperature of 100°C for 3 hours to dissolve the glass components, then precipitated using a centrifuge, and washed by repeated decantation. Finally, it was dried in a heating furnace at a furnace temperature of 110°C for 6 hours to obtain hexagonal strontium ferrite powder. The average particle size of the obtained hexagonal strontium ferrite powder was 19 nm, and the activation volume was 1102 nm. 3 The anisotropy constant Ku is 2.0 × 10⁻⁶. 5 J / m 3 , mass magnetization σs is 50A m 2 It was / kg.

[0159] In Table 1, "ε-iron oxide" in the ferromagnetic powder column refers to ε-iron oxide powder prepared as follows. In 90 g of pure water, 8.3 g of iron(III) nitrate nonahydrate, 1.3 g of gallium(III) nitrate octahydrate, 190 mg of cobalt(II) nitrate hexahydrate, 150 mg of titanium(IV) sulfate, and 1.5 g of polyvinylpyrrolidone (PVP) were dissolved. While stirring with a magnetic stirrer in an air atmosphere at an ambient temperature of 25°C, 4.0 g of a 25% aqueous ammonia solution was added, and the mixture was stirred for 2 hours at the same ambient temperature of 25°C. To the resulting solution, an aqueous citric acid solution obtained by dissolving 1 g of citric acid in 9 g of pure water was added, and the mixture was stirred for 1 hour. After stirring, the precipitated powder was collected by centrifugation, washed with pure water, and dried in a heating furnace at an ambient temperature of 80°C. 800g of pure water was added to the dried powder, and the powder was dispersed in the water again to obtain a dispersion. The obtained dispersion was heated to 50°C, and 40g of a 25% aqueous ammonia solution was added dropwise while stirring. After stirring for 1 hour while maintaining the temperature at 50°C, 14mL of tetraethoxysilane (TEOS) was added dropwise, and the mixture was stirred for 24 hours. 50g of ammonium sulfate was added to the resulting reaction solution, and the precipitated powder was collected by centrifugation, washed with pure water, and dried in a heating furnace at a temperature of 80°C for 24 hours to obtain a precursor of ferromagnetic powder. The obtained ferromagnetic powder precursor was placed in a heating furnace at a temperature of 1000°C under an atmospheric environment and subjected to heat treatment for 4 hours. A heat-treated ferromagnetic powder precursor was added to a 4 mol / L sodium hydroxide (NaOH) aqueous solution, and the solution was stirred for 24 hours while maintaining the temperature at 70°C to remove silicate compounds, which are impurities, from the heat-treated ferromagnetic powder precursor. Subsequently, the ferromagnetic powder, from which the silicate compounds were removed by centrifugation, was collected and washed with pure water to obtain ferromagnetic powder. The composition of the obtained ferromagnetic powder was confirmed by inductively coupled plasma emission spectroscopy (ICP-OES), revealing that it was a Ga, Co, and Ti-substituted ε-iron oxide (ε-Ga 0.28 Co 0.05 Ti 0.05 Fe 1.62 It was O3). Furthermore, X-ray diffraction analysis was performed under the same conditions as described earlier for the hexagonal strontium ferrite powder SrFe1, and from the peaks of the X-ray diffraction pattern, it was confirmed that the obtained ferromagnetic powder has a single-phase crystalline structure of the ε phase (crystalline structure of ε-iron oxide) that does not contain the crystalline structures of the α phase and γ phase. The average particle size of the obtained ε-iron oxide powder was 12 nm, and the activation volume was 746 nm. 3 The anisotropy constant Ku is 1.2 × 10⁻⁶. 5 J / m 3 , mass magnetization σs is 16A m 2 It was / kg.

[0160] The activation volume and anisotropy constant Ku of the hexagonal strontium ferrite powder and ε-iron oxide powder described above were obtained for each ferromagnetic powder using a vibrating sample magnetometer (manufactured by Toei Kogyo Co., Ltd.) and the method described above. Furthermore, the mass magnetization σs was measured using a vibrating sample type magnetometer (manufactured by Toei Kogyo Co., Ltd.) at a magnetic field strength of 1194 kA / m (15 kOe).

[0161] [Example A1] (1) Preparation of alumina dispersion Alpha conversion rate approximately 65%, BET (Brunauer-Emmett-Teller) specific surface area 20m 2 100.0 parts of alumina powder (HIT-80, manufactured by Sumitomo Chemical Co., Ltd.) at a concentration of 1 / g was mixed with 3.0 parts of 2,3-dihydroxynaphthalene (manufactured by Tokyo Chemical Co., Ltd.), 31.3 parts of a 32% solution of polyester polyurethane resin having SO3Na groups as polar groups (UR-4800, manufactured by Toyobo Co., Ltd. (polar group amount: 80 meq / kg)) (solvent: mixed solvent of methyl ethyl ketone and toluene), and 570.0 parts of a mixed solution of methyl ethyl ketone and cyclohexanone in a 1:1 (mass ratio) solvent. The mixture was dispersed in the presence of zirconia beads using a paint shaker for 5 hours. After dispersion, the dispersion and beads were separated using a mesh to obtain an alumina dispersion.

[0162] (2) Composition formulation for forming a magnetic layer (Magnetic liquid) Ferromagnetic powder (see Table 1) 100.0 parts SO3Na group-containing polyurethane resin 14.0 parts Weight average molecular weight: 70,000, SO3Na group: 0.2meq / g Cyclohexanone 150.0 parts Methyl ethyl ketone 150.0 parts (Abrasive solution) 6.0 parts of the alumina dispersion prepared in (1) above. (Silica sol (protrusion-forming agent liquid)) Colloidal silica (average particle size 120 nm) 2.0 parts Methyl ethyl ketone 1.4 parts (Other ingredients) Stearic acid 2.0 parts Stearic acid amide 0.2 parts Butyl stearate 2.0 parts Polyisocyanate (Tosoh Corporation's Coronate® L) 2.5 parts (Finishing solvent) Cyclohexanone 200.0 parts Methyl ethyl ketone 200.0 parts

[0163] (3) Composition formulation for forming a non-magnetic layer Non-magnetic inorganic powder: α-iron oxide 100.0 parts Average particle size (average major axis length): 0.15μm Average acicular ratio: 7 BET specific surface area: 52m 2 / g Carbon Black 20.0 parts Average particle size: 20nm SO3Na group-containing polyurethane resin 18.0 parts Weight average molecular weight: 70,000, SO3Na group: 0.2meq / g Polyethyleneimine (manufactured by Nippon Shokubai Co., Ltd., number average molecular weight 600) See Table 1. See Table 1 for stearic acid. Stearic acid amide 0.2 parts Butyl stearate 2.0 parts Cyclohexanone 300.0 parts Methyl ethyl ketone 300.0 parts

[0164] (4) Composition formulation for forming a back coat layer Carbon black 100.0 parts DBP (Dibutyl phthalate) oil absorption 74cm 3 / 100g Nitrocellulose 27.0 parts 62.0 parts of polyester polyurethane resin containing sulfonic acid groups and / or salts thereof Polyester resin 4.0 parts Alumina powder (BET specific surface area: 17m²) 2 / g) 0.6 parts Polyethyleneimine (manufactured by Nippon Shokubai Co., Ltd., number average molecular weight 600) See Table 1. See Table 1 for stearic acid. Methyl ethyl ketone 600.0 parts Toluene 600.0 parts Polyisocyanate (Tosoh Corporation's Coronate® L) 15.0 parts

[0165] (5) Preparation of compositions for forming each layer A composition for forming a magnetic layer was prepared by the following method. The magnetic solution was prepared by dispersing each component for 24 hours using a batch-type vertical sand mill (bead dispersion). Zirconia beads with a diameter of 0.5 mm were used as the dispersion beads. The prepared magnetic solution, the polishing solution, silica sol, other components, and finishing solvent were mixed using the sand mill and dispersed for 5 minutes. Then, the mixture was treated for 0.5 minutes using a batch-type ultrasonic device (20 kHz, 300 W) (ultrasonic dispersion). After that, the mixture was filtered using a filter with a pore size of 0.5 μm to prepare the composition for forming a magnetic layer. A composition for forming a non-magnetic layer was prepared by the following method: The above components, excluding stearic acid, stearic acid amide, and butyl stearate, were kneaded and diluted using an open kneader, and then dispersed using a horizontal bead mill disperser. Subsequently, stearic acid, stearic acid amide, and butyl stearate were added, and the mixture was stirred and mixed using a dissolver stirrer to prepare a composition for forming a non-magnetic layer. A composition for forming a backcoat layer was prepared by the following method. The above components, excluding polyisocyanate, were introduced into a dissolver stirrer and stirred at a peripheral speed of 10 m / sec for 30 minutes, after which dispersion was performed using a horizontal bead mill disperser. Subsequently, polyisocyanate was added and stirred and mixed using a dissolver stirrer to prepare a composition for forming a backcoat layer.

[0166] (6) Method for manufacturing magnetic tape and magnetic tape cartridge A non-magnetic layer was formed on the surface of a biaxially stretched support of the type and thickness described in Table 1 by applying and drying the non-magnetic layer-forming composition prepared in (5) above so that the thickness after drying would be the thickness described in Table 1. Next, a coating layer was formed on the non-magnetic layer by applying the magnetic layer-forming composition prepared in (5) above so that the thickness after drying would be the thickness described in Table 1. After that, while the coating layer of the magnetic layer-forming composition was still wet, a magnetic field of strength 0.3T was applied perpendicular to the surface of the coating layer to perform a vertical orientation treatment, and then it was dried to form a magnetic layer. Subsequently, a back coat layer was formed on the surface of the support opposite to the surface on which the non-magnetic layer and magnetic layer were formed by applying and drying the back coat layer-forming composition prepared in (5) above so that the thickness after drying would be the thickness described in Table 1. Subsequently, a surface smoothing treatment (calendering treatment) was performed using a calendering roll consisting solely of metal rolls, at the calendering speed, calendering pressure (linear pressure), and calendering temperature (surface temperature of the calendering roll) listed in Table 1. Subsequently, the long roll of magnetic tape raw material was heat-treated by storing it in a heat treatment furnace at an ambient temperature of 70°C (heat treatment time: 36 hours). After heat treatment, it was slit into 1 / 2-inch widths to obtain magnetic tape. By recording servo signals on the magnetic layer of the obtained magnetic tape using a commercially available servo writer, a magnetic tape was obtained having data bands, servo bands, and guide bands arranged according to the LTO (Linear Tape-Open) Ultrium format, and having a servo pattern (timing-based servo pattern) on the servo bands arranged and shaped according to the LTO Ultrium format. The servo pattern thus formed is a servo pattern that conforms to the descriptions in JIS (Japanese Industrial Standards) X6175:2006 and Standard ECMA-319 (June 2001). The total number of servo bands is 5, and the total number of data bands is 4. The magnetic tape (970m in length) with the servo pattern formed as described above was wound onto a heat treatment core, and heat treatment was performed while the tape was wound onto this core. A solid core made of resin with a bending modulus of 0.8 GPa (outer diameter: 50 mm) was used as the heat treatment core, and the tension during winding was 0.6 N. The heat treatment was performed for 5 hours at the heat treatment temperatures shown in Table 1. The absolute humidity by weight of the atmosphere during heat treatment was 10 g / kg dry air. After the heat treatment described above, once the magnetic tape and the heat treatment core had cooled sufficiently, the magnetic tape was removed from the heat treatment core and wound onto a temporary winding core. Then, the final product length (960m) of magnetic tape was wound from the temporary winding core onto a reel (reel outer diameter: 44mm) of a magnetic tape cartridge (LTO Ultrium7 data cartridge). The remaining 10m was cut off, and a leader tape was joined to the cut end using commercially available splicing tape, in accordance with item 9 of Section 3 of Standard ECMA (European Computer Manufacturers Association)-319 (June 2001). As the temporary winding core, a solid core member made of the same material and having the same outer diameter as the heat treatment core was used, and the tension during winding was set to 0.6N. As the magnetic tape cartridge used to house the magnetic tape described above, a single-reel type magnetic tape cartridge with the configuration shown in Figure 1 was used. The reel hub of this magnetic tape cartridge is a single-layer reel hub (thickness: 2.5 mm, outer diameter: 44 mm) made by injection molding of glass fiber reinforced polycarbonate. The glass fiber content of this glass fiber reinforced polycarbonate is the value shown in Table 1. A portion of the glass fiber reinforced polycarbonate for injection molding was taken, and according to item 6.3.1 (Preparation from molding material) of JIS K 7171:2016, the recommended test piece described in item 6.1.2 of the same JIS was prepared, and the flexural modulus (arithmetic mean of 5 test pieces) was calculated according to the same JIS, resulting in the value shown in Table 1. For each example described below, the flexural modulus of the reel hub material was also determined by the above method. The flexural modulus of the winding core for heat treatment described above was also determined in the same way. The magnetic tape was wound onto the reel hub of the magnetic tape cartridge while applying a tension of 1.0N or less in the longitudinal direction of the tape, and the magnetic tape was then housed in the magnetic tape cartridge. Based on the above, a single-reel type magnetic tape cartridge, Example A1, was fabricated, in which a 960m long magnetic tape was wound onto a reel.

[0167] The presence of a compound containing an ammonium salt structure of an alkyl ester anion represented by Formula 1, formed from polyethyleneimine and stearic acid, in the magnetic tape can be confirmed by the method described above. For example, the presence of a compound containing an ammonium salt structure of an alkyl ester anion represented by Formula 1, formed from polyethyleneimine and stearic acid, in the back coat layer can be confirmed by the following method. A sample is cut from the magnetic tape, and X-ray photoelectron spectroscopy analysis is performed on the backcoat layer surface (measurement area: 300 μm × 700 μm) using an ESCA instrument. For details, wide-scan measurements are performed using the ESCA instrument under the measurement conditions described below. In the measurement results, peaks are observed at the bond energy positions of the ester anion and the ammonium cation. Equipment: Shimadzu Corporation AXIS-ULTRA Excitation X-ray source: Monochromatic Al-Kα rays Scan range: 0~1200eV Pass energy: 160 eV Energy resolution: 1 eV / step Data acquisition time: 100ms / step Total number of times: 5 Furthermore, when a 3cm long sample piece was cut from the magnetic tape and ATR-FT-IR (Attenuated total reflection-fourier transform-infrared spectrometer) measurement (reflection method) was performed on the surface of the backcoat layer, the measurement results showed that COO - Wavefrequency corresponding to absorption (1540 cm) -1 or 1430cm -1 ), and the wavenumber corresponding to the absorption of ammonium cations (2400 cm²).-1 Absorption is confirmed in ).

[0168] The above process was repeated to produce five magnetic tape cartridges. One of the five magnetic tape cartridges was used for (7) and (8) below, another for (9) below, another for (10) below, another for (11) below, and the remaining magnetic tape cartridge was used for (12) below.

[0169] (7) Tape thickness Ten tape samples (5 cm in length) were cut from an arbitrary section of magnetic tape, and the thickness of these samples was measured by stacking them. The thickness was measured using a digital thickness meter consisting of a MARH Millimar 1240 compact amplifier and a Millimar 1301 inductive probe. The measured thickness was divided by 10 to obtain the value obtained (thickness per tape sample), which was defined as the tape thickness. The tape thicknesses are shown in Table 1.

[0170] (8) Measurement of Δw Δw was calculated for the magnetic tape removed from the magnetic tape cartridge using the method described above.

[0171] (9) Measurement of σG and calculation of coefficient of variation CV The magnetic tape cartridge containing the magnetic tape to be measured was left in the measurement environment (ambient temperature 25°C, relative humidity 50%) for more than 5 days to allow it to acclimate. Subsequently, in that measurement environment, the magnetic tape was run using the magnetic recording and playback device shown in Figure 4 with a tension of 0.6N applied in the longitudinal direction of the magnetic tape, and σG was determined using the method described above. The spacing between two adjacent servo bands separated by a data band was determined as follows. In order to determine the distance between two adjacent servo bands sandwiching a data band, the dimensions of the servo pattern are required. The standards for the dimensions of the servo pattern vary depending on the generation of LTO. Therefore, first, using a magnetic force microscope or the like, measure the average distance AC between the corresponding four stripes of the A burst and the C burst, and the azimuth angle α of the servo pattern. Next, using a reel tester and a servo head equipped with two servo signal reading elements (hereinafter, one is called the upper side and the other is called the lower side) fixed at intervals in a direction orthogonal to the longitudinal direction of the magnetic tape, the servo pattern formed on the magnetic tape is sequentially read along the tape longitudinal direction. Define the average time a between the five stripes corresponding to the A burst and the B burst over the length of 1 LPOS word. Define the average time b between the corresponding four stripes of the A burst and the C burst over the length of 1 LPOS word. At this time, the value defined by AC×(1 / 2 - a / b) / (2×tan(α)) represents the reading position PES in the width direction based on the servo signal obtained by the servo signal reading element over the length of 1 LPOS word. The reading of the servo pattern for 1 LPOS word is performed simultaneously by the two servo signal reading elements on the upper side and the lower side. Let the value of PES obtained by the upper servo signal reading element be PES1, and the value of PES obtained by the lower servo signal reading element be PES2. As "PES2 - PES1", for 1 LPOS word, the distance between two adjacent servo bands sandwiching the data band can be obtained. This is because the upper and lower servo pattern reading elements are fixed to the servo head and their distance does not change. From the Δw and σG obtained above, the coefficient of variation CV was calculated by the formula A shown above.

[0172] (10) Measurement of roundness The LK-G85 and LK-GD500 manufactured by KEYENCE were used as laser displacement meters, and the CZ-H35S and CZ-C21A manufactured by KEYENCE were used as optical discrimination sensors. By the method described above, the roundness of the trajectory for one rotation drawn by the magnetic tape when pulling the magnetic tape wound around the reel (spool) of the magnetic tape cartridge out of the spool was determined. The above measurement was carried out by taking out the reel with the magnetic tape wound around it from the case of the magnetic tape cartridge and transferring this reel to the cartridge case with an opening formed as described above.

[0173] (11) Measurement of transfer rate The magnetic tape cartridge was inserted into the magnetic recording and reproducing apparatus, and data was recorded on the magnetic tape and the recorded data was reproduced. As the magnetic recording and reproducing apparatus, a magnetic recording and reproducing apparatus having the configuration shown in FIG. 4 and including a reproducing element unit having a reproducing element with a reproducing element width of 0.8 μm and 32 or more recording elements and servo signal reading elements on both sides thereof was used. After acclimating the magnetic tape cartridge and the magnetic recording and reproducing apparatus to the measurement environment (ambient temperature 20 to 25°C, relative humidity 40 to 60%) for one day or more, recording and reproduction were performed over the entire length and width of the tape. At the time of the above recording and reproduction, the maximum capacity of the magnetic tape was recorded and reproduced using drive control software. Also, at the time of the above recording and reproduction, the tension applied in the longitudinal direction of the magnetic tape changed due to the tension adjustment performed by the control device of the magnetic recording and reproducing apparatus. Regarding the above recording and reproduction, the transfer rate was calculated as the capacity recorded or reproduced per unit time (MB (megabyte) / second) by dividing the "recorded or reproduced capacity" by the "time required for recording or reproduction". When the value calculated by dividing the recorded capacity by the time required for recording and the value obtained by dividing the reproduced capacity by the time required for reproduction were different, the lower value was adopted as the transfer rate. In Table 1, the transfer rate is shown as a relative value with the maximum transfer rate in the combination of the magnetic recording and reproducing apparatus and the magnetic tape being 100.0%. The above maximum transfer rate is obtained, for example, by the following method. Using LTO-G8 (Generation 8) media, an LTO-8 drive, and IBM's free software (IBM Tape Diagnostic Tool - Graphical Edition), the "Read And Write Tests" command is used to record and play back the maximum capacity, and the "DataRate" can be obtained by reading the resulting log data file. For LTO-G8 media (uncompressed, full-height drive), a transfer rate of 100.0% = 360 MB / second can be obtained.

[0174] (12) Evaluation of recording and playback performance The recording and playback performance was evaluated using a magnetic recording and playback device with the configuration shown in Figure 4. The recording and playback head mounted on the recording and playback head unit 602 has 32 or more channels of playback elements (playback element width: 0.8 μm) and recording elements, and has servo signal reading elements on both sides thereof. Each magnetic tape cartridge in Example A1 was placed in an environment with an ambient temperature of 23°C and a relative humidity of 50% for more than 5 days. After acclimatizing to the environment, data was recorded in the same environment as follows. A magnetic tape cartridge is set in the magnetic recording and playback device, and the magnetic tape is loaded. Next, while performing servo tracking, the recording and playback head unit records pseudo-random data with a specific data pattern onto the magnetic tape. The tension applied in the longitudinal direction of the tape is set to 0.7N. During data recording, recording is performed for three or more passes so that the difference in the value of (PES1 + PES2) / 2 between adjacent tracks is 1.16 μm. Simultaneously with data recording, the servo band spacing value along the entire length of the tape is measured every 1m along the longitudinal position and recorded in the cartridge memory. The magnetic tape cartridges on which the data was recorded as described above were placed in a storage environment with an ambient temperature of 60°C and a relative humidity of 20% for 72 hours. Subsequently, the magnetic tape cartridge of Example A1 was placed in an environment with an ambient temperature of 23°C and a relative humidity of 50% for more than 5 days. After allowing it to acclimate to the environment, data playback was performed in the same environment as follows. A magnetic tape cartridge is set in the magnetic recording and playback device, and the magnetic tape is loaded. Next, the recording and playback head unit plays back the data recorded on the magnetic tape while performing servo tracking. At the same time as playback, the servo band interval value is measured, and based on the information recorded in the cartridge memory, the tension applied in the longitudinal direction of the tape is adjusted so that the absolute value of the difference between the servo band interval at the same longitudinal position and the servo band interval at the time of recording approaches 0. During playback, the measurement of the servo band interval and the tension adjustment based on it are performed continuously in real time. In Example A1 and the examples described later, the tension value used by the control device 601 for the above tension adjustment was in the range of 0.2 to 1.2 N. The number of channels in the above playback was 32. During playback, the recording and playback performance was evaluated as "3" if all 32 channels of data were read correctly, as "2" if channels 31 to 28 were read correctly, and as "1" in all other cases.

[0175] [Example A2~A23, Example B1~B18] Aside from the changes made to the items in Table 1 as shown in Table 1, the magnetic tape cartridge was manufactured and various evaluations were performed as described for Example A1. In Table 1, in the cases where "None" is written in the "Heat Treatment Temperature" column, heat treatment was not performed while the material was wound onto the heat treatment core.

[0176] The results are shown in Table 1 (Tables 1-1 to 1-9).

[0177] [Table 1-1]

[0178] [Table 1-2]

[0179] [Table 1-3]

[0180]

Table 1-4

[0181]

Table 1-5

[0182]

Table 1-6

[0183]

Table 1-7

[0184]

Table 1-8

[0185]

Table 1-9

[0186] From the results shown in Table 1, the following points can be confirmed. From the comparison between Examples A1 to A23 and Examples B15 to B18 and Examples B1 to B14, it can be confirmed that Δw and CV of the magnetic tape being within the previously described ranges contribute to enabling recording and reproduction at a high transfer rate. From the comparison between Examples A1 to A23 and Examples B1 to B18, it can be confirmed that a magnetic tape including a polyethylene naphthalate support having a Young's modulus in the width direction of 10,000 MPa or more as a non-magnetic support is a magnetic tape that can be suitably used in a magnetic recording and reproducing apparatus that controls the dimensions in the width direction of the magnetic tape by adjusting the tension applied in the longitudinal direction of the magnetic tape.

[0187] Except for the fact that vertical alignment processing was not performed during the magnetic tape manufacturing process, the magnetic tape cartridge for Example A1 was manufactured using the method described above. A sample piece was cut from the magnetic tape removed from the magnetic tape cartridge mentioned above. Using a Tamagawa Seisakusho TM-TRVSM5050-SMSL vibrating sample magnetometer, the vertical angular ratio of this sample piece was determined using the method described above, and it was found to be 0.55. A magnetic tape was also extracted from the magnetic tape cartridge of Example A1, and the vertical aspect ratio was similarly determined for a sample piece cut from this magnetic tape, which was found to be 0.60.

[0188] The magnetic tapes extracted from the two magnetic tape cartridges described above were each mounted on a 1 / 2-inch reel tester, and their electromagnetic conversion characteristics (SNR: Signal-to-Noise Ratio) were evaluated using the following method. As a result, the magnetic tape extracted from the magnetic tape cartridge of Example A1 showed an SNR value 2 dB higher than that of the magnetic tape manufactured without vertical orientation treatment. Recording and playback were performed in 10 passes under a tension of 0.7N in the longitudinal direction of the magnetic tape in an environment of 23°C and 50% relative humidity. The relative speed between the magnetic tape and the magnetic head was set to 6 m / s. For recording, a MIG (Metal-in-gap) head (gap length 0.15 μm, track width 1.0 μm) was used as the recording head, and the recording current was set to the optimal recording current for each magnetic tape. For playback, a GMR (Giant-magnetoresistive) head (element thickness 15 nm, shielding gap 0.1 μm, playback element width 0.8 μm) was used as the playback head. A signal with a linear recording density of 300 kfci was recorded, and the playback signal was measured using a spectrum analyzer manufactured by Shibasoku. The unit kfci is the unit of linear recording density (cannot be converted to the SI system). As the signal, the portion where the signal was sufficiently stable after the start of magnetic tape movement was used. [Industrial applicability]

[0189] One aspect of the present invention is useful in the technical field of various data storage, such as backup and archiving.

Claims

1. A magnetic tape comprising a non-magnetic support and a magnetic layer containing ferromagnetic powder, The change in widthwise dimension Δw in response to a change in tension in the longitudinal direction is 400 ppm / N or more and 900 ppm / N or less. The non-magnetic support is a polyethylene naphthalate support with a Young's modulus in the width direction of 10,000 MPa or more, and The magnetic layer has multiple servo bands, Formula A below: CV=(σG / Δw)×100 The coefficient of variation CV calculated by this method is 10% or less. The aforementioned σG is the standard deviation of the servoband spacing measured over a 100 m longitudinal region of the magnetic tape under a tension of 0.6 N in the longitudinal direction, wherein the magnetic tape is a magnetic tape.

2. The magnetic tape according to claim 1, wherein the coefficient of variation CV is 1% or more and 10% or less.

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

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

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

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

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

8. A magnetic tape housing including a core around which the magnetic tape described in any one of claims 1 to 7 is wound.

9. A magnetic tape container according to claim 8, which is a magnetic tape cartridge.

10. A magnetic tape housing according to claim 8, which is a magnetic recording and playback device, further comprising a magnetic head.

11. The magnetic tape housing according to claim 10, wherein the magnetic head includes a regeneration element having a regeneration element width of 0.8 μm or less.

12. The magnetic tape housing according to claim 10, further comprising a tension adjustment mechanism capable of adjusting the tension applied in the longitudinal direction of a magnetic tape traveling within a magnetic recording and playback device.

13. The magnetic tape housing according to claim 8, wherein the roundness of the trajectory traced by the magnetic tape for one rotation when the wound magnetic tape is pulled out from the winding core is 120 μm or less as the arithmetic mean of measurements taken at three locations in the width direction of the magnetic tape.

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