WO2023100879A1

WO2023100879A1 - Magnetic tape, magnetic tape cartridge, and magnetic tape device

Info

Publication number: WO2023100879A1
Application number: PCT/JP2022/043993
Authority: WO
Inventors: 成人笠田
Original assignee: 富士フイルム株式会社
Priority date: 2021-12-02
Filing date: 2022-11-29
Publication date: 2023-06-08

Abstract

Provided is a magnetic tape having a non-magnetic support and a magnetic layer containing a ferromagnetic powder. The non-magnetic support is a polyethylene naphthalate support that has a Young's modulus of at least 10,000 MPa in the width direction. The ratio (AlFeSil wear value 2 / AlFeSil wear value 1) of the change in the AlFeSil wear value before and after storing of the tape, as measured for the surface of the magnetic layer in an environment having a temperature of 23°C and a relative humidity of 50%, is at least 0.7. Also provided are a magnetic tape cartridge and a magnetic tape device that include the magnetic tape.

Description

Magnetic tapes, magnetic tape cartridges and magnetic tape devices

The present invention relates to magnetic tapes, magnetic tape cartridges, and magnetic tape devices.

Magnetic recording media include tape-shaped and disk-shaped magnetic recording media. Tape-shaped magnetic recording media, that is, magnetic tapes, are mainly used for data storage applications such as data backups and archives (see, for example, Patent Documents 1).

Patent No. 6635216

Data is recorded on a magnetic tape by running the magnetic tape inside a magnetic tape device (generally called a "drive") and making the magnetic head follow the data band of the magnetic tape to record data on the data band. It is done by A data track is thereby formed in the data band. When reproducing the recorded data, the magnetic tape is run in the magnetic tape device and the magnetic head follows the data band of the magnetic tape to read the data recorded on the data band.

In order to improve the accuracy with which the magnetic head follows the data band of the magnetic tape during recording and/or reproduction as described above, a system (hereinafter referred to as "servo system") that performs head tracking using a servo signal is employed. has been put into practical use.
Furthermore, by using a servo signal to acquire dimension information in the width direction of the running magnetic tape and adjusting the tension applied in the longitudinal direction of the magnetic tape according to the acquired dimension information, (see, for example, paragraph 0117 of Patent Document 1). The above tension adjustment causes the magnetic head for recording or reproducing data to deviate from the intended track position due to the width deformation of the magnetic tape during recording or reproduction, causing phenomena such as overwriting of recorded data and defective reproduction. It is thought that it can contribute to suppressing the fact that For magnetic recording, it is required to obtain excellent electromagnetic conversion characteristics. It is desirable that the deterioration of the electromagnetic conversion characteristics is small.

One aspect of the present invention is to provide a magnetic tape whose electromagnetic conversion characteristics are less degraded when recording and/or reproducing is performed by controlling the dimension in the width direction of the magnetic tape by adjusting the tension applied in the longitudinal direction of the magnetic tape. The main purpose is to provide

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 non-magnetic support is a polyethylene naphthalate support having a Young's modulus in the width direction of 10,000 MPa or more, and stores the AlFeSil wear value measured on the surface of the magnetic layer in an environment with a temperature of 23° C. and a relative humidity of 50%. The rate of change before and after, AlFeSil wear value 2/AlFeSil wear value 1, is 0.7 or more,
The AlFeSil abrasion value 1 is an AlFeSil abrasion value measured by applying a tension of 2.0 N (Newton) in the longitudinal direction of the magnetic tape,
The AlFeSil abrasion value 2 is obtained by sliding the magnetic tape after the measurement of the AlFeSil abrasion value 1 back and forth against an LTO (registered trademark: Linear Tape-Open) 8 head 1500 times, and then storing the magnetic tape for 24 hours. Magnetic tape, AlFeSil abrasion value measured under 2.0 N tension in the longitudinal direction.
[2] The magnetic tape according to [1], wherein the AlFeSil wear value 2/AlFeSil wear value 1 is 0.7 or more and 1.0 or less.
[3] The magnetic tape of [1] or [2], wherein the magnetic layer further contains one or more non-magnetic powders.
[4] The magnetic tape according to [3], wherein the non-magnetic powder contains alumina powder.
[5] The magnetic tape according to any one of [1] to [4], further comprising a nonmagnetic layer containing nonmagnetic powder between the nonmagnetic support and the magnetic layer.
[6] The magnetic field according to any one of [1] to [5], further comprising a back coat layer containing a non-magnetic powder on the surface side opposite to the surface side having the magnetic layer of the non-magnetic support. tape.
[7] The magnetic tape according to any one of [1] to [6], which has a tape thickness of 5.2 μm or less.
[8] The magnetic tape according to any one of [1] to [7], wherein the polyethylene naphthalate support has a Young's modulus in the width direction of 10000 MPa or more and 20000 MPa or less.
[9] The magnetic tape according to any one of [1] to [8], which has a vertical squareness ratio of 0.60 or more.
[10] A magnetic tape cartridge containing the magnetic tape according to any one of [1] to [9].
[11] A magnetic tape device including the magnetic tape according to any one of [1] to [9].
[12] The magnetic tape device according to [11], which has a tension adjusting mechanism capable of adjusting the tension applied to the magnetic tape running in the magnetic tape device in the longitudinal direction.

According to one aspect of the present invention, when recording and/or reproducing is performed by controlling the dimension in the width direction of the magnetic tape by adjusting the tension applied in the longitudinal direction of the magnetic tape, the electromagnetic conversion characteristics are less deteriorated. A tape can be provided. Further, according to one aspect of the present invention, it is possible to provide a magnetic tape cartridge and a magnetic tape device containing the above magnetic tape.

An example arrangement of data bands and servo bands is shown. An example of servo pattern arrangement for an LTO Ultrium format tape is shown. 1 is a schematic diagram showing an example of a magnetic tape device; FIG.

[Magnetic tape]
One aspect of the present invention relates to a magnetic tape having a non-magnetic support and a magnetic layer containing ferromagnetic powder. The non-magnetic support is a polyethylene naphthalate support having a Young's modulus of 10000 MPa or more in the width direction. In an environment with a temperature of 23° C. and a relative humidity of 50%, the change rate of the AlFeSil wear value measured on the surface of the magnetic layer before and after storage (AlFeSil wear value 2/AlFeSil wear value 1) is 0.7 or more. In the present invention and this specification, the term "(the) surface of the magnetic layer" is synonymous with the magnetic layer side surface of the magnetic tape. The AlFeSil abrasion value 1 is an AlFeSil abrasion value measured by applying a tension of 2.0 N in the longitudinal direction of the magnetic tape. The above AlFeSil abrasion value 2 was obtained by sliding the magnetic tape after the measurement of the above AlFeSil abrasion value 1 back and forth against an LTO8 head 1500 times, storing the magnetic tape for 24 hours, and then applying a tension of 2.0 N in the longitudinal direction of the magnetic tape. is the AlFeSil wear value measured by

In a magnetic tape device that controls the widthwise dimension of a magnetic tape by adjusting the tension applied in the longitudinal direction of the magnetic tape, the greater the tension applied to the magnetic tape in the longitudinal direction, the greater the widthwise dimension of the magnetic tape. It can be shrunk more (i.e. narrower), and the less the tension, the less it shrunk. By adjusting the tension applied in the longitudinal direction of the magnetic tape in this manner, the dimension of the magnetic tape in the width direction can be controlled.
On the other hand, the recording of data on the magnetic tape and the reproduction of the recorded data are usually performed by bringing the surface of the magnetic layer of the magnetic tape and the magnetic head into contact with each other and sliding them. The inventor of the present invention considered that when the tension is adjusted as described above, a large tension applied in the longitudinal direction of the magnetic tape may be a factor in the deterioration of the electromagnetic conversion characteristics. In detail, the present inventor considered as follows. Repeated running of the magnetic tape tends to reduce the polishing force of the surface of the magnetic tape (specifically, the surface of the magnetic layer), and this tendency is more pronounced as greater tension is applied to the magnetic tape in its longitudinal direction while the magnetic tape is running. can be A decrease in the abrasiveness of the surface of the magnetic tape leads to a decrease in the head cleaning ability of the magnetic tape. When the head cleaning force of the magnetic tape is lowered, foreign matter (generally called "debris") adhered to the magnetic head due to sliding against the magnetic tape tends to remain on the magnetic head, and the existence of this foreign matter. Due to this, spacing loss occurs and the electromagnetic conversion characteristics deteriorate.
In the course of repeated studies, the inventors of the present invention have found that if it is possible to bring the polishing force, which has decreased due to the above repeated running, closer to the state before the decrease in a short period of time (hereinafter also referred to as "early recovery of polishing characteristics"), the repeated running can be performed. The inventors thought that it would be possible to improve the reduced polishing power at an early stage, and further conducted intensive studies. If the polishing characteristics can be recovered early, for example, even if the interval from the end of recording to the next recording or the interval from the end of recording to reproduction is shortened, the deterioration of the electromagnetic conversion characteristics can be suppressed.
As a result of such intensive studies, the present inventors have found the rate of change in the AlFeSil wear value measured on the surface of the magnetic layer in an environment of 23° C. and 50% relative humidity before and after storage (AlFeSil wear value 2/AlFeSil wear value 1). is 0.7 or more, it is possible to quickly recover the polishing characteristics, and by adjusting the tension applied in the longitudinal direction of the magnetic tape, the dimension in the width direction of the magnetic tape can be controlled for recording and/or recording. Alternatively, the present inventors have newly found that the electromagnetic conversion characteristics, which have deteriorated due to repeated running, can be brought close to the state before deterioration in a short period of time during reproduction. The temperature and humidity of the measurement environment are adopted as exemplary values of the temperature and humidity of the environment in which the magnetic tape is used. Therefore, the environment in which data is recorded on the magnetic tape and the recorded data is reproduced is not limited to the temperature and humidity environment described above. The tension applied in the longitudinal direction of the magnetic tape when measuring the AlFeSil abrasion value was also adopted as an exemplary value of the large tension that can be applied in the longitudinal direction of the magnetic tape when the tension adjustment is performed as described above. be. Therefore, the tension applied in the longitudinal direction of the magnetic tape when recording data on the magnetic tape and reproducing the recorded data is not limited to the tension described above.
Furthermore, the present inventor believes that the magnetic tape includes a polyethylene naphthalate support having a Young's modulus in the width direction of 10000 MPa or more as a non-magnetic support, by adjusting the tension applied in the longitudinal direction of the magnetic tape. It is thought that it can contribute to enabling good recording and/or reproduction by controlling the dimension in the width direction.
However, the present invention is not limited by the conjectures of the inventors described herein.

In the present invention and this specification, the AlFeSil abrasion value 1 is a value measured by the following method in an environment of temperature 23° C. and relative humidity 50%.
The wear width of the AlFeSil prism is measured when the magnetic tape to be measured is run under the following running condition A using a reel tester. The AlFeSil prism is a prism made of AlFeSil, which is a sendust-based alloy. AlFeSil prisms defined in ECMA (European Computer Manufacturers Association)-288/AnnexH/H2 are used for the evaluation. The wear width of the AlFeSil prism is obtained by observing the edge of the AlFeSil prism from above using an optical microscope and obtaining the wear width described in paragraph 0015 of JP-A-2007-026564 based on FIG. 1 of the same publication.
(Running condition A)
In an environment with a temperature of 23° C. and a relative humidity of 50%, the surface of the magnetic layer of the magnetic tape is applied in the longitudinal direction of the magnetic tape so that one edge of the AlFeSil prism is perpendicular to the longitudinal direction of the AlFeSil prism with a wrap angle of 12°. The contact is made with a tension of 2.0N. In this state, a portion of the magnetic tape to be measured over a length of 580 m in the longitudinal direction is run at a speed of 3 m/sec to make one reciprocation.
The wear width of the AlFeSil prism after running is defined as an AlFeSil wear value of 1.

In the present invention and this specification, the AlFeSil abrasion value 2 is a value measured by the following method in an environment of temperature 23° C. and relative humidity 50%.
Using a reel tester, the magnetic tape after measuring the AlFeSil abrasion value 1 is run under the following running condition B.
(Driving condition B)
In an environment with a temperature of 23°C and a relative humidity of 50%, the magnetic layer surface of the magnetic tape is brought into contact with the LTO8 head at a wrap angle of 4°, and a tension of 2.0 N is applied in the longitudinal direction of the magnetic tape. The head is reciprocatingly slid 1500 times at a speed of 4 m/sec. In such reciprocating sliding, a portion of the magnetic tape to be measured, which includes at least the portion that was run to obtain an AlFeSil wear value of 1 (a portion extending over a length of 580 m in the longitudinal direction), is slid against the LTO8 head.
The magnetic tape after reciprocating sliding was run in the same environment (temperature 23 ° C. relative humidity 50%) to obtain at least an AlFeSil wear value of 1 (a portion extending over a length of 580 m in the longitudinal direction) on the reel. Store rolled up for 24 hours. Within 1 hour after the storage, the portion of the magnetic tape that was run to obtain the AlFeSil abrasion value of 1 (the portion extending over a length of 580 m in the longitudinal direction) was run under the same environment (temperature 23 ° C. relative humidity 50%). Run with A.
The wear width of the AlFeSil prism after running is defined as an AlFeSil wear value 2 .

In the present invention and this specification, the rate of change in the AlFeSil abrasion value before and after storage (AlFeSil abrasion value 2/AlFeSil abrasion value 1) measured on the surface of the magnetic layer of the magnetic tape in an environment with a temperature of 23° C. and a relative humidity of 50%. is calculated from the AlFeSil wear value 1 and the AlFeSil wear value 2 obtained by the above method. Hereinafter, the rate of change (AlFeSil wear value 2/AlFeSil wear value 1) is also referred to as "AlFeSil wear value change rate before and after storage (AlFeSil wear value 2/AlFeSil wear value 1)".

In the present invention and this specification, an "LTO8 head" is a magnetic head conforming to the LTO8 standard. As the LTO8 head, a magnetic head mounted on the LTO8 drive may be taken out and used, or a magnetic head commercially available as a magnetic head for the LTO8 drive may be used. Here, the LTO8 drive is a drive (magnetic tape device) conforming to the LTO8 standard. An LTO9 drive is a drive conforming to the LTO9 standard, and the same applies to drives of other Generations. Also, in running the magnetic tape under the running condition B, it is assumed that a new (that is, unused) LTO8 head is used for each magnetic tape to be measured. Considering that the LTO8 standard is a standard that can cope with recent high-density recording, LTO8 is adopted as the magnetic head used for running the magnetic tape under the running condition B. Tapes are not limited to those used in LTO8 drives. The magnetic tape may be used for recording and/or reproducing data in an LTO8 drive, may be used for recording and/or reproducing data in an LTO9 drive or a further next generation drive, or may be used for LTO8 such as LTO7. Data may be recorded and/or played back on earlier generation drives.

<AlFeSil wear value change rate before and after storage (AlFeSil wear value 2/AlFeSil wear value 1)>
With respect to the polishing characteristics of the magnetic tape, from the viewpoint of suppressing the deterioration of the electromagnetic conversion characteristics when recording and/or reproducing by controlling the dimension in the width direction of the magnetic tape by adjusting the tension applied in the longitudinal direction of the magnetic tape. The AlFeSil wear value change rate before and after storage (AlFeSil wear value 2/AlFeSil wear value 1) is 0.7 or more, preferably 0.8 or more, and more preferably 0.9 or more. The AlFeSil abrasion value change rate before and after storage (AlFeSil abrasion value 2/AlFeSil abrasion value 1) can be, for example, 1.0 or less, 1.0 or less, or 0.9 or less. The fact that the AlFeSil abrasion value change rate before and after storage (AlFeSil abrasion value 2/AlFeSil abrasion value 1) is closer to 1.0 means that the polishing force on the surface of the magnetic tape, which has decreased due to repeated running, can be reduced in a short period of time by the state before the decrease. It is preferable because it can mean that it can be brought closer. AlFeSil wear value 1 and AlFeSil wear value 2 can be, for example, ≧8 μm or ≧10 μm, and ≦25 μm or ≦22 μm, respectively. The abrasive properties of the magnetic tape can be adjusted by, for example, the type of components used for forming the magnetic layer, the preparation method of the composition for forming the magnetic layer, and the like. Details of this point will be described later.

<Vertical squareness ratio>
In one form, the vertical squareness ratio of the magnetic tape can be, for example, 0.55 or more, preferably 0.60 or more. It is preferable from the viewpoint of improving the electromagnetic conversion characteristics that the vertical squareness ratio of the magnetic tape is 0.60 or more. The upper limit of the squareness ratio is, in principle, 1.00 or less. The vertical squareness ratio of the magnetic tape may be 1.00 or less, 0.95 or less, 0.90 or less, 0.85 or less, or 0.80 or less. A magnetic tape having a large squareness ratio in the vertical direction is preferable from the viewpoint of improving electromagnetic conversion characteristics. The perpendicular squareness ratio of the magnetic tape can be controlled by a known method such as performing a perpendicular orientation treatment.

In the present invention and herein, the "vertical squareness ratio" is the squareness ratio measured in the perpendicular direction of the magnetic tape. The "perpendicular direction" described with respect to the squareness ratio is the direction orthogonal to the surface of the magnetic layer, and can also be called the thickness direction. In the present invention and this specification, the vertical squareness ratio is obtained by the following method.
A sample piece of a size that can be introduced into the vibrating sample magnetometer is cut out from the magnetic tape to be measured. Using a vibrating sample magnetometer, this sample piece was measured at a maximum applied magnetic field of 3979 kA/m, a measurement temperature of 296 K, and a magnetic field sweep rate of 8.3 kA/m/sec. direction) and measure the magnetization strength of the sample piece with respect to the applied magnetic field. The measured value of the magnetization intensity shall be obtained as a value after demagnetization correction and as a value obtained by subtracting the magnetization of the sample probe of the vibrating sample magnetometer as background noise. The squareness ratio SQ is a value calculated as SQ=Mr/Ms, where Ms is the magnetization intensity at the maximum applied magnetic field and Mr is the magnetization intensity at zero applied magnetic field. The measurement temperature refers to the temperature of the sample piece, and by setting the ambient temperature around the sample piece to the measurement temperature, the temperature equilibrium is established, whereby the temperature of the sample piece can be made the measurement temperature.

The magnetic tape will be described in more detail below.

<Magnetic layer>
(ferromagnetic powder)
As the ferromagnetic powder contained in the magnetic layer, one or a combination of two or more ferromagnetic powders known as ferromagnetic powders used in the magnetic layers of various magnetic recording media can be used. From the viewpoint of improving the recording density, it is preferable to use ferromagnetic powder having a small average particle size. From this point, 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, and 30 nm or less. It is 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, still more preferably 10 nm or more, and 15 nm or more. is more preferable, and 20 nm or more is even more preferable.

Hexagonal Ferrite Powder A preferred specific example of the ferromagnetic powder is hexagonal ferrite powder. For details of the hexagonal ferrite powder, for example, paragraphs 0012 to 0030 of JP-A-2011-225417, paragraphs 0134-0136 of JP-A-2011-216149, paragraphs 0013-0030 of JP-A-2012-204726 and Paragraphs 0029 to 0084 of JP-A-2015-127985 can be referred to.

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

The hexagonal strontium ferrite powder, which is one form of the hexagonal ferrite powder, will be described in more detail below.

The activated volume of the hexagonal strontium ferrite powder is preferably in the range of 800-1600 nm ³ . A finely divided hexagonal strontium ferrite powder exhibiting an activation volume within the above range is suitable for making a magnetic tape exhibiting excellent electromagnetic conversion characteristics. The activated volume of the hexagonal strontium ferrite powder is preferably greater than or equal to 800 nm ³ , for example it may be greater than or equal to 850 nm ³ . Further, from the viewpoint of further improving electromagnetic conversion characteristics, the activated volume of the hexagonal strontium ferrite powder is more preferably 1500 nm ³ or less, further preferably 1400 nm ³ or less, and 1300 nm ³ or less. is more preferable, 1200 nm ³ or less is even more preferable, and 1100 nm ³ or less is even more preferable. The same is true for the activation volume of hexagonal barium ferrite powder.

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

An anisotropic constant Ku can be cited as an index for reducing thermal fluctuation, in other words, improving thermal stability. The hexagonal strontium ferrite powder can preferably have a Ku of 1.8×10 ⁵ J/m ³ or more, more preferably 2.0×10 ⁵ J/m ³ or more. Also, Ku of the hexagonal strontium ferrite powder can be, for example, 2.5×10 ⁵ J/m ³ or less. However, the higher the Ku value, the higher the thermal stability, which is preferable.

The hexagonal strontium ferrite powder may or may not contain rare earth atoms. When the hexagonal strontium ferrite powder contains rare earth atoms, it preferably contains 0.5 to 5.0 atomic % of rare earth atoms (bulk content) with respect to 100 atomic % of iron atoms. In one form, the hexagonal strontium ferrite powder containing rare earth atoms can have uneven distribution of rare earth atoms on the surface layer. In the present invention and in this specification, the term "rare earth atom surface uneven distribution" refers to the rare earth atom content ratio (hereinafter referred to as "Rare earth atom surface layer content" or simply "surface layer content" with respect to rare earth atoms.) is 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), and
Rare earth atom surface layer content/rare earth atom bulk content>1.0
means that the ratio of The rare earth atom content rate of the hexagonal strontium ferrite powder described later is synonymous with the rare earth atom bulk content rate. On the other hand, since partial dissolution using an acid dissolves the surface layer of the particles constituting the hexagonal strontium ferrite powder, the content of rare earth atoms in the solution obtained by partial dissolution is It is the rare earth atom content rate in the surface layer of the particles. The rare earth atom surface layer portion content ratio satisfies the ratio of "rare earth atom surface layer portion content/rare earth atom bulk content ratio >1.0" means that the rare earth atoms are present in the surface layer portion of the particles constituting the hexagonal strontium ferrite powder. It means that it is unevenly distributed (that is, it exists more than inside). In the present invention and in this specification, the term "surface layer portion" means a partial region extending from the surface toward the inside of a particle that constitutes the hexagonal strontium ferrite powder.

When the hexagonal strontium ferrite powder contains rare earth atoms, the rare earth atom content (bulk content) is preferably in the range of 0.5 to 5.0 atomic % with respect to 100 atomic % of iron atoms. The fact that the rare earth atoms are contained in the bulk content in the above range and that the rare earth atoms are unevenly distributed in the surface layer of the particles constituting the hexagonal strontium ferrite powder contributes to suppressing the decrease in reproduction output during repeated reproduction. Conceivable. This is because the hexagonal strontium ferrite powder contains rare earth atoms with a bulk content within the above range, and the rare earth atoms are unevenly distributed in the surface layers of the particles constituting the hexagonal strontium ferrite powder. This is presumed to be due to the fact that The higher the anisotropy constant Ku, the more the occurrence of a phenomenon called thermal fluctuation can be suppressed (in other words, the thermal stability can be improved). By suppressing the occurrence of thermal fluctuation, it is possible to suppress a decrease in reproduction output in repeated reproduction. The uneven distribution of rare earth atoms in the particle surface layer of the hexagonal strontium ferrite powder contributes to stabilizing the spin of the iron (Fe) site in the crystal lattice of the surface layer, thereby increasing the anisotropy constant Ku. It is speculated that it will increase.
In addition, it is speculated that the use of hexagonal strontium ferrite powder, which has rare earth atoms unevenly distributed in the surface layer, as the ferromagnetic powder for the magnetic layer contributes to suppressing abrasion of the magnetic layer surface due to sliding against the magnetic head. be. That is, it is presumed that the hexagonal strontium ferrite powder having rare earth atoms unevenly distributed on the surface layer can contribute to the improvement of the running durability of the magnetic tape. This is because the uneven distribution of rare earth atoms on the surfaces of the particles that make up the hexagonal strontium ferrite powder improves the interaction between the particle surfaces and organic substances (e.g., binders and/or additives) contained in the magnetic layer. and as a result, the strength of the magnetic layer is improved.
From the viewpoint of suppressing a decrease in reproduction output in repeated reproduction and/or from the viewpoint of further improving running durability, the rare earth atom content (bulk content) is in the range of 0.5 to 4.5 atomic %. is more preferably in the range of 1.0 to 4.5 atomic %, and even more preferably in the range of 1.5 to 4.5 atomic %.

The above bulk content is the content obtained by completely dissolving the hexagonal strontium ferrite powder. In the present invention and this specification, unless otherwise specified, the atomic content 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 kind of rare earth atoms as rare earth atoms, or may contain two or more kinds of rare earth atoms. When two or more rare earth atoms are contained, the bulk content is obtained for the total of two or more rare earth atoms. This point also applies to the present invention and other components in this specification. That is, unless otherwise specified, only one component may be used, or two or more components may be used. When two or more are used, the content or content refers to the total of two or more.

When the hexagonal strontium ferrite powder contains rare earth atoms, the contained rare earth atoms may be any one or more rare earth atoms. Preferred rare earth atoms from the viewpoint of suppressing a decrease in reproduction output in repeated reproduction include neodymium atoms, samarium atoms, yttrium atoms and dysprosium atoms, more preferably neodymium atoms, samarium atoms and yttrium atoms, and neodymium atoms. More preferred.

In the hexagonal strontium ferrite powder having rare earth atoms unevenly distributed on the surface layer, the rare earth atoms need only be unevenly distributed on the surface layer of the particles constituting the hexagonal strontium ferrite powder, and the degree of uneven distribution is not limited. For example, for a hexagonal strontium ferrite powder having rare earth atoms unevenly distributed in the surface layer, the surface layer content of rare earth atoms obtained by partially dissolving under the dissolving conditions described later and the rare earth elements obtained by completely dissolving under the dissolving conditions described later The ratio of atoms to the bulk content, "surface layer content/bulk content", is greater than 1.0 and can be 1.5 or more. When the "surface layer content/bulk content" is greater than 1.0, it means that the rare earth atoms are unevenly distributed in the surface layer (ie, more present than in the interior) in the particles constituting the hexagonal strontium ferrite powder. do. In addition, the ratio between the surface layer content of rare earth atoms obtained by partial dissolution under the dissolution conditions described later and the bulk content of rare earth atoms obtained by complete dissolution under the dissolution conditions described later, "surface layer content/ The "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 the hexagonal strontium ferrite powder having rare earth atoms unevenly distributed in the surface layer portion, the rare earth atoms should be unevenly distributed in the surface layer portion of the particles constituting the hexagonal strontium ferrite powder. "Ratio" is not limited to the exemplified upper or lower limits.

Partial dissolution and total dissolution of hexagonal strontium ferrite powder are described below. For hexagonal strontium ferrite powders present as powders, sample powders for partial dissolution and total dissolution are taken from the same lot of powder. On the other hand, as for the hexagonal strontium ferrite powder contained in the magnetic layer of the magnetic tape, part of the hexagonal strontium ferrite powder taken out from the magnetic layer is subjected to partial melting, and the other part is subjected to complete melting. The hexagonal strontium ferrite powder can be extracted from the magnetic layer, for example, by the method described in paragraph 0032 of JP-A-2015-91747.
The partial dissolution means dissolution to such an extent that residual hexagonal strontium ferrite powder can be visually confirmed in the liquid at the end of dissolution. For example, by partial dissolution, a region of 10 to 20% by mass of the particles constituting the hexagonal strontium ferrite powder can be dissolved out of 100% by mass of the entire particles. On the other hand, the above-mentioned complete dissolution means that the hexagonal strontium ferrite powder is dissolved to the point where no residue of the hexagonal strontium ferrite powder remains in the liquid at the end of dissolution.
The partial dissolution and the measurement of the surface layer content are performed, for example, by the following methods. However, the dissolution conditions such as the amount of sample powder described below are examples, and dissolution conditions that allow partial dissolution and complete dissolution can be arbitrarily adopted.
A container (for example, a beaker) containing 12 mg of sample powder and 10 mL of 1 mol/L hydrochloric acid is held on a hot plate with a set temperature of 70° C. for 1 hour. The resulting solution is filtered through a 0.1 μm membrane filter. Elemental analysis of the filtrate thus obtained is performed by an inductively coupled plasma (ICP) analyzer. In this way, the surface layer portion content of rare earth atoms relative to 100 atomic % of iron atoms can be obtained. When multiple types of rare earth atoms are detected by elemental analysis, the total content of all rare earth atoms is taken as the surface layer portion content. This point also applies to the measurement of the bulk content.
On the other hand, the measurement of the total dissolution and bulk content is carried out, for example, by the following method.
A container (for example, a beaker) containing 12 mg of sample powder and 10 mL of 4 mol/L hydrochloric acid is held on a hot plate with a set temperature of 80° C. for 3 hours. After that, the partial dissolution and the measurement of the surface layer portion content are carried out in the same manner as described above, and the bulk content with respect to 100 atom % of iron atoms can be obtained.

From the viewpoint of increasing the reproduction output when reproducing data recorded on the magnetic tape, it is desirable that the ferromagnetic powder contained in the magnetic tape have a high mass magnetization σs. In this regard, hexagonal strontium ferrite powders containing rare earth atoms but not unevenly distributed in the surface layer of rare earth atoms tended to have a significantly lower σs compared to hexagonal strontium ferrite powders containing no rare earth atoms. On the other hand, hexagonal strontium ferrite powder having rare earth atoms unevenly distributed in the surface layer is considered preferable in terms of suppressing such a large decrease in σs. In one form, the σs of the hexagonal strontium ferrite powder can be 45 A·m ² /kg or greater, and can also be 47 A·m ² /kg or greater. On the other hand, from the viewpoint of noise reduction, σs is preferably 80 A·m ² /kg or less, more preferably 60 A·m ² /kg or less. σs can be measured using a known measuring device capable of measuring magnetic properties, such as a vibrating sample magnetometer. In the present invention and this specification, unless otherwise specified, mass magnetization σs is a value measured at a magnetic field strength of 15 kOe. 1 [kOe]=10 ⁶ /4π [A/m].

With respect to the content of constituent atoms (bulk content) of the hexagonal strontium ferrite powder, the strontium atom content can be, for example, in the range of 2.0 to 15.0 atomic % with respect to 100 atomic % of iron atoms. . In one form, the hexagonal strontium ferrite powder can have strontium atoms as the only divalent metal atoms contained in the powder. In yet another form, the hexagonal strontium ferrite powder can also contain one or more other divalent metal atoms in addition to the strontium atoms. For example, it can contain barium atoms and/or calcium atoms. When other divalent metal atoms other than strontium atoms are contained, the barium atom content and calcium atom content in the hexagonal strontium ferrite powder are, for example, 0.05 to 5 atoms per 100 atomic percent of iron atoms. can be in the range of .0 atomic %.

As crystal structures of hexagonal ferrite, magnetoplumbite type (also called “M type”), W type, Y type and Z type are known. The hexagonal strontium ferrite powder may have any crystal structure. The crystal structure can be confirmed by X-ray diffraction analysis. The hexagonal strontium ferrite powder can have a single crystal structure or two or more crystal structures detected by X-ray diffraction analysis. For example, in one form, a hexagonal strontium ferrite powder can be one in which only the M-type crystal structure is detected by X-ray diffraction analysis. For example, M-type hexagonal ferrite is represented by a composition formula of AFe ₁₂ O ₁₉ . Here, A represents a divalent metal atom, and if the hexagonal strontium ferrite powder is M-type, A is only a strontium atom (Sr), or if A contains a plurality of divalent metal atoms, , as described above, strontium atoms (Sr) account for the largest amount on an atomic % basis. The divalent metal atom content of the 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 the oxygen atom content. The hexagonal strontium ferrite powder contains at least iron atoms, strontium atoms and oxygen atoms, and may also contain rare earth atoms. Furthermore, the hexagonal strontium ferrite powder may or may not contain atoms other than these atoms. As an example, the hexagonal strontium ferrite powder may contain aluminum atoms (Al). The content of aluminum atoms can be, for example, 0.5 to 10.0 atomic % with respect to 100 atomic % of iron atoms. From the viewpoint of suppressing a decrease in reproduction output in repeated reproduction, the hexagonal strontium ferrite powder contains iron atoms, strontium atoms, oxygen atoms and rare earth atoms, and the content of atoms other than these atoms is 100 atomic % iron atoms. On the other hand, it is preferably 10.0 atomic % or less, more preferably in the range of 0 to 5.0 atomic %, and may be 0 atomic %. That is, in one form, the hexagonal strontium ferrite powder may contain no atoms other than iron atoms, strontium atoms, oxygen atoms and rare earth atoms. The content expressed in atomic % above is the content of each atom (unit: mass %) obtained by completely dissolving the hexagonal strontium ferrite powder, and converted to the value expressed in atomic % using the atomic weight of each atom. It is required by conversion. Moreover, in the present invention and this specification, the phrase "not containing" an atom means that the content of the atom is 0% by mass as measured by an ICP analyzer after being completely dissolved. The detection limit of an ICP analyzer is usually 0.01 ppm (parts per million) or less on a mass basis. The above "does not contain" shall be used in the sense of containing in an amount below the detection limit of the ICP analyzer. The hexagonal strontium ferrite powder, in one form, can be free of bismuth atoms (Bi).

Metal powder Ferromagnetic metal powder is also a preferred specific example of the ferromagnetic powder. For details of the ferromagnetic metal powder, for example, paragraphs 0137 to 0141 of JP-A-2011-216149 and paragraphs 0009-0023 of JP-A-2005-251351 can be referred to.

ε-iron oxide powder A preferred specific example of the ferromagnetic powder is ε-iron oxide powder. In the present invention and the specification, "ε-iron oxide powder" means a ferromagnetic powder in which the crystal structure of ε-iron oxide is detected as the main phase by X-ray diffraction analysis. For example, when the highest intensity diffraction peak in the X-ray diffraction spectrum obtained by X-ray diffraction analysis is attributed to the crystal structure of ε-iron oxide, it is determined that the crystal structure of ε-iron oxide has been detected as the main phase. shall be As a method for producing ε-iron oxide powder, a method of producing from goethite, a reverse micelle method, and the like are known. All of the above manufacturing methods are known. Also, a method for producing ε-iron oxide powder in which a part of Fe is substituted with substitution atoms such as Ga, Co, Ti, Al, and Rh is described in J. Am. Jpn. Soc. Powder Metallurgy Vol. 61 Supplement, No. S1, pp. S280-S284, J.P. Mater. Chem. C, 2013, 1, pp. 5200-5206 and the like. However, the method for producing the ε-iron oxide powder that can be used as the ferromagnetic powder in the magnetic layer of the magnetic tape is not limited to the methods mentioned here.

The activated volume of the ε-iron oxide powder is preferably in the range of 300-1500 nm ³ . A finely divided ε-iron oxide powder exhibiting an activation volume in the above range is suitable for making a magnetic tape exhibiting excellent electromagnetic conversion properties. The activated volume of the ε-iron oxide powder is preferably greater than or equal to 300 nm ³ and may eg be greater than or equal to 500 nm ³ . Further, from the viewpoint of further improving the electromagnetic conversion characteristics, the activated volume of the ε-iron oxide powder is more preferably 1400 nm ³ or less, further preferably 1300 nm ³ or less, and 1200 nm ³ or less. is more preferable, and 1100 nm ³ or less is even more preferable.

An anisotropic constant Ku can be cited as an index for reducing thermal fluctuation, in other words, improving thermal stability. The ε-iron oxide powder can preferably have a Ku of 3.0×10 ⁴ J/m ³ or more, more preferably 8.0×10 ⁴ J/m ³ or more. Also, Ku of the ε-iron oxide powder can be, for example, 3.0×10 ⁵ J/m ³ or less. However, a higher Ku means a higher thermal stability, which is preferable, and thus is not limited to the values exemplified above.

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

In the present invention and this specification, unless otherwise specified, the average particle size of various powders such as ferromagnetic powder is a value measured by the following method using a transmission electron microscope.
The powder is photographed using a transmission electron microscope at a magnification of 100,000 times, and printed on photographic paper or displayed on a display so that the total magnification is 500,000 times to obtain a photograph of the particles that make up the powder. . The particles of interest are selected from the photograph of the particles obtained, and the contours of the particles are traced with a digitizer to measure the size of the particles (primary particles). Primary particles refer to individual particles without agglomeration.
The above measurements are performed on 500 randomly selected particles. The arithmetic mean of the particle sizes of the 500 particles thus obtained is taken as the average particle size of the powder. As the transmission electron microscope, for example, Hitachi's H-9000 transmission electron microscope can be used. Further, the particle size can be measured using known image analysis software such as Carl Zeiss image analysis software KS-400. Unless otherwise specified, the average particle size shown in the examples below was measured using a transmission electron microscope H-9000 manufactured by Hitachi, and image analysis software KS-400 manufactured by Carl Zeiss as image analysis software. value. In the present invention and herein, powder means a collection of particles. For example, ferromagnetic powder means an aggregate of ferromagnetic particles. In addition, the aggregation of a plurality of particles is not limited to the form in which the particles constituting the aggregation are in direct contact, but also includes the form in which a binder, an additive, etc., which will be described later, is interposed between the particles. be. The term particles is sometimes used to describe powders.

As a method for collecting sample powder from a magnetic tape for particle size measurement, for example, the method described in paragraph 0015 of JP-A-2011-048878 can be adopted.

In the present invention and this specification, unless otherwise specified, the size of the particles constituting the powder (particle size) is the shape of the particles observed in the above particle photographs.
(1) In the case of needle-like, spindle-like, columnar (however, the height is greater than the maximum major diameter of the bottom surface), etc., the length of the major axis constituting the particle, that is, the major axis length,
(2) In the case of a plate-like or columnar shape (where the thickness or height is smaller than the maximum major diameter of the plate surface or bottom surface), it is expressed by the maximum major diameter of the plate surface or bottom surface,
(3) If the particle is spherical, polyhedral, irregular, or the like, and the major axis of the particle cannot be specified from the shape, it is represented by the equivalent circle diameter. The equivalent circle diameter is obtained by the circular projection method.

In addition, the average acicular ratio of the powder is obtained by measuring the length of the minor axis of the particles in the above measurement, that is, the minor axis length, and obtaining the value of (long axis length / minor axis length) of each particle. It refers to the arithmetic mean of the values obtained for the particles. Here, unless otherwise specified, the minor axis length is the length of the minor axis constituting the particle in the case of (1) in the definition of the particle size, and the thickness or height in the case of (2). In the case of (3), since there is no distinction between the major axis and the minor axis, (long axis length/short axis length) is regarded as 1 for convenience.
Unless otherwise specified, when the particle shape is specific, for example, in the case of the definition (1) of the particle size, the average particle size is the average major axis length, and in the case of the definition (2), the average particle size is Average plate diameter. In the case of the same definition (3), the average particle size is the average diameter (also referred to as average particle size or average particle size).

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

(Binder)
The magnetic tape may be a coated magnetic tape, and the magnetic layer may contain a binder. A binder is one or more resins. As the binder, various resins commonly used as binders for coating-type magnetic recording media can be used. Examples of binders include polyurethane resins, polyester resins, polyamide resins, vinyl chloride resins, acrylic resins obtained by copolymerizing styrene, acrylonitrile, methyl methacrylate, etc., cellulose resins such as nitrocellulose, epoxy resins, phenoxy resins, polyvinyl acetal, A resin selected from polyvinyl alkylal resins such as polyvinyl butyral can be used singly, or a plurality of resins can be mixed and used. Preferred among these are polyurethane resins, acrylic resins, cellulose resins, and vinyl chloride resins. These resins may be homopolymers or copolymers. These resins can also be used as binders in the non-magnetic layer and/or backcoat layer, which will be described later. Paragraphs 0028 to 0031 of JP-A-2010-24113 can be referred to for the above binders. The binder may also be a radiation-curable resin such as an electron beam-curable resin. Regarding the radiation curable resin, paragraphs 0044 to 0045 of JP-A-2011-048878 can be referred to.
The weight-average molecular weight of the resin used as the binder can be, for example, 10,000 or more and 200,000 or less. The binder can be used in an amount of, for example, 1.0 to 30.0 parts by weight per 100.0 parts by weight of the ferromagnetic powder.

(curing agent)
A hardening agent can also be used with the binder. The curing agent can be, in one form, a thermosetting compound which is a compound in which a curing reaction (crosslinking reaction) proceeds by heating, and in another form, a photocuring compound in which a curing reaction (crosslinking reaction) proceeds by light irradiation. can be a chemical compound. The curing agent can be contained in the magnetic layer in a state in which at least a portion thereof has reacted (crosslinked) with other components such as a binder as the curing reaction progresses during the manufacturing process of the magnetic tape. Preferred curing agents are thermosetting compounds, preferably polyisocyanates. For details of the polyisocyanate, paragraphs 0124 to 0125 of JP-A-2011-216149 can be referred to. The curing agent is contained in the composition for forming the magnetic layer in an amount of, for example, 0 to 80.0 parts by weight per 100.0 parts by weight of the binder. It can be used in an amount of 80.0 parts by weight.

(Additive)
The magnetic layer may optionally contain one or more additives. Examples of additives include the curing agents described above. Additives contained in the magnetic layer include nonmagnetic powders, lubricants, dispersants, dispersing aids, antifungal agents, antistatic agents, antioxidants, and the like.

Examples of the dispersant that can be added to the composition for forming the magnetic layer include known dispersants for enhancing the dispersibility of ferromagnetic powder such as carboxy group-containing compounds and nitrogen-containing compounds. For example, the nitrogen-containing compound may be any of a primary amine represented by _NH2R , a secondary amine represented by _NHR2 , and a tertiary amine represented by _NR3 . In the above, R represents an arbitrary structure constituting the nitrogen-containing compound, and multiple Rs may be the same or different. The nitrogen-containing compound may be a compound (polymer) having multiple repeating structures in its molecule. The reason why the nitrogen-containing compound can work as a dispersing agent is considered to be that the nitrogen-containing portion of the nitrogen-containing compound functions as an adsorption portion to the particle surface of the ferromagnetic powder. Examples of carboxy group-containing compounds include fatty acids such as oleic acid. As for the carboxy group-containing compound, the reason why the carboxy group-containing compound can work as a dispersing agent is considered to be that the carboxy group functions as an adsorption site on the particle surface of the ferromagnetic powder. It is also preferable to use a carboxy group-containing compound and a nitrogen-containing compound in combination. The amount of these dispersants to be used can be set appropriately.

A dispersant may be added to the composition for forming the non-magnetic layer. See paragraph 0061 of JP-A-2012-133837 for the dispersant that can be added to the composition for forming a non-magnetic layer.

Examples of additives that can be added to the magnetic layer include polyalkyleneimine-based polymers described in JP-A-2016-51493. For such a polyalkyleneimine-based polymer, reference can be made to paragraphs 0035 to 0077 of JP-A-2016-51493 and the examples in the same publication.

The non-magnetic powder that can be contained in the magnetic layer includes a non-magnetic powder that can function as an abrasive, a non-magnetic powder that can function as a protrusion-forming agent that forms moderately protruding protrusions on the surface of the magnetic layer, and the like. mentioned.

As the abrasive, a non-magnetic powder having a Mohs hardness of more than 8 is preferable, and a non-magnetic powder having a Mohs hardness of 9 or more is more preferable. The maximum value of Mohs hardness is 10. The abrasive can be a powder of inorganic material or can be a powder of organic material. The abrasive can be an inorganic or organic oxide powder or carbide powder. Examples of carbide include boron carbide (eg, B ₄ C), titanium carbide (eg, TiC), and the like. Diamond can also be used as the abrasive. In one form, the abrasive is preferably an inorganic oxide powder. Specifically, examples of inorganic oxides include alumina (e.g. Al ₂ O ₃ ), titanium oxide (e.g. TiO ₂ ), cerium oxide (e.g. CeO ₂ ), zirconium oxide (e.g. ZrO ₂ ), and the like. Among them, alumina is preferred. Alumina has a Mohs hardness of about 9. Regarding alumina powder, paragraph 0021 of JP-A-2013-229090 can also be referred to. Further, as an index of the particle size of the abrasive, the specific surface area can be used. It can be considered that the larger the specific surface area, the smaller the particle size of the primary particles constituting the abrasive. As the abrasive, it is preferable to use an abrasive having a specific surface area measured by the BET (Brunauer-Emmett-Teller) method (hereinafter referred to as "BET specific surface area") of 14 m ² /g or more. From the viewpoint of dispersibility, it is preferable to use a polishing agent having a BET specific surface area of 40 m ² /g or less. The content of the abrasive in the magnetic layer is preferably 1.0 to 20.0 parts by mass, more preferably 1.0 to 15.0 parts by mass, per 100.0 parts by mass of the ferromagnetic powder. preferable. As the abrasive, only one type of non-magnetic powder can be used, or two or more types of non-magnetic powders having different compositions and/or physical properties (for example, size) can be used. When two or more kinds of non-magnetic powders are used as abrasives, the content of abrasives means the total content of these two or more kinds of non-magnetic powders. The above points also apply to the content of various components in the present invention and the present specification. The abrasive is preferably dispersed separately from the ferromagnetic powder (separate dispersion), and more preferably dispersed separately from the protrusion forming agent described later (separate dispersion). When preparing the composition for forming the magnetic layer, preparing two or more types of dispersions with different components and/or dispersion conditions as abrasive dispersions (hereinafter also referred to as "abrasive liquids") is It is preferable for controlling the polishing properties of the magnetic tape.

A dispersant can also be used to adjust the dispersion state of the abrasive liquid. A compound that can function as a dispersant for enhancing the dispersibility of the abrasive includes an aromatic hydrocarbon compound having a phenolic hydroxy group. A "phenolic hydroxy group" refers to a hydroxy group directly attached to an aromatic ring. The aromatic ring contained in the aromatic hydrocarbon compound may be monocyclic, polycyclic, or condensed. From the viewpoint of improving the dispersibility of the abrasive, aromatic hydrocarbon compounds containing a benzene ring or a naphthalene ring are preferred. Moreover, the aromatic hydrocarbon compound may have a substituent other than the phenolic hydroxy group. Examples of substituents other than phenolic hydroxy groups include halogen atoms, alkyl groups, alkoxy groups, amino groups, acyl groups, nitro groups, nitroso groups, hydroxyalkyl groups and the like. Alkoxy groups, amino groups and hydroxyalkyl groups are preferred. The number of phenolic hydroxy groups contained in one molecule of the aromatic hydrocarbon compound may be one, two, three or more.

A preferred form of the aromatic hydrocarbon compound having a phenolic hydroxy group is the compound represented by the following formula 100.

[In Formula 100, two of X ¹⁰¹ to X ¹⁰⁸ are hydroxy groups, and the other six each independently represent a hydrogen atom or a substituent. ]

In the compound represented by Formula 100, the substitution positions of the two hydroxy groups (phenolic hydroxy groups) are not particularly limited.

In Formula 100, two of X ¹⁰¹ to X ¹⁰⁸ are hydroxy groups (phenolic hydroxy groups), and the other 6 each independently represent a hydrogen atom or a substituent. In addition, among X ¹⁰¹ to X ¹⁰⁸ , all of the portions other than the two hydroxy groups may be hydrogen atoms, or some or all of them may be substituents. As the substituent, the substituents described above can be exemplified. One or more phenolic hydroxy groups may be included as substituents other than the two hydroxy groups. From the viewpoint of improving the dispersibility of the abrasive, it is preferable that the hydroxy groups other than two among X ¹⁰¹ to X ¹⁰⁸ are not phenolic hydroxy groups. That is, the compound represented by formula 100 is preferably dihydroxynaphthalene or a derivative thereof, more preferably 2,3-dihydroxynaphthalene or a derivative thereof. Preferable substituents as the substituents represented by X ¹⁰¹ to X ¹⁰⁸ include halogen atoms (eg, chlorine atom, bromine atom), amino groups, alkyl groups having 1 to 6 carbon atoms (preferably 1 to 4), and methoxy groups. and ethoxy, acyl, nitro and nitroso groups, and —CH ₂ OH groups.

In addition, paragraphs 0024 to 0028 of JP-A-2014-179149 can also be referred to for the dispersant for enhancing the dispersibility of the abrasive.

The dispersant for enhancing the dispersibility of the abrasive is, for example, when preparing the abrasive liquid (for each abrasive liquid when preparing a plurality of abrasive liquids), per 100.0 parts by mass of the abrasive: For example, it can be used in a proportion of 0.5 to 20.0 parts by mass, preferably in a proportion of 1.0 to 10.0 parts by mass.

One form of protrusion-forming agent is carbon black. The average particle size of carbon black is preferably in the range of 5-200 nm, more preferably in the range of 10-150 nm. The BET specific surface area of carbon black is preferably 10 m ² /g or more, more preferably 15 m ² /g or more. The BET specific surface area of carbon black is preferably 50 m ² /g or less, more preferably 40 m ² /g or less, from the viewpoint of ease of improving dispersibility. Moreover, colloidal particles can be mentioned as another form of the projection forming agent. The colloidal particles are preferably inorganic colloidal particles, more preferably inorganic oxide colloidal particles, and still more preferably silica colloidal particles (colloidal silica) from the viewpoint of availability. In the present invention and the specification, the term "colloidal particles" means methyl ethyl ketone, cyclohexanone, toluene or ethyl acetate, or at least one mixed solvent containing two or more of the above solvents in an arbitrary mixing ratio. A particle is defined as a particle that, when dispersed, does not settle but can disperse to provide a colloidal dispersion. The average particle size of the colloidal particles can be, for example, 30-300 nm, preferably 40-200 nm. The content of the protrusion-forming agent in the magnetic layer is preferably 0.5 to 4.0 parts by mass, more preferably 0.5 to 3.5 parts by mass, per 100.0 parts by mass of the ferromagnetic powder. is more preferred. The protrusion-forming agent is preferably dispersed separately from the ferromagnetic powder, and more preferably dispersed separately from the abrasive. When preparing the composition for forming the magnetic layer, prepare two or more dispersions with different components and/or dispersion conditions as a dispersion of the protrusion-forming agent (hereinafter also referred to as "protrusion-forming agent liquid"). can also

In addition, one form of additive that can be contained in the magnetic layer is a compound having an ammonium salt structure of an alkyl ester anion represented by Formula 1 below.

(In Formula 1, R represents an alkyl group having 7 or more carbon atoms or a fluorinated alkyl group having 7 or more carbon atoms, and Z ⁺ represents an ammonium cation.)

The inventor believes that the compounds can function as lubricants. This point will be further explained below.
Lubricants can be broadly classified into fluid lubricants and boundary lubricants. The present inventor believes that the compound having the ammonium salt structure of the alkyl ester anion represented by Formula 1 above can function as a fluid lubricant. It is believed that the fluid lubricant itself can play a role in providing lubricity to the magnetic layer by forming a liquid film on the surface of the magnetic layer. In order to control the polishing characteristics of the magnetic tape, it is presumed that it is desirable for the fluid lubricant to form a liquid film on the surface of the magnetic layer. Regarding the liquid film of the fluid lubricant, it is considered desirable to use an appropriate amount of the fluid lubricant forming the liquid film on the surface of the magnetic layer from the viewpoint of enabling more stable sliding. In this regard, it is believed that the compounds containing the ammonium salt structure of the alkyl ester anion represented by Formula 1 can play an excellent role as fluid lubricants even in relatively small amounts. Therefore, it is considered that the inclusion of the above compound in the magnetic layer leads to improved sliding stability between the magnetic layer surface of the magnetic tape and the magnetic head.

The above compounds will be described in more detail below.

In the present invention and this specification, unless otherwise specified, the groups described may have a substituent or may be unsubstituted. In addition, the “carbon number” of a group having a substituent means the number of carbon atoms not including the number of carbon atoms of the substituent unless otherwise specified. In the present invention and the specification, substituents include, for example, alkyl groups (eg alkyl groups having 1 to 6 carbon atoms), hydroxy groups, alkoxy groups (eg alkoxy groups having 1 to 6 carbon atoms), halogen atoms (eg fluorine atom, chlorine atom, bromine atom, etc.), a cyano group, an amino group, a nitro group, an acyl group, a carboxy group, a salt of a carboxy group, a sulfonic acid group, a salt of a sulfonic acid group, and the like.

At least part of the compound having an ammonium salt structure of an alkyl ester anion represented by formula 1 is contained in the magnetic layer and is capable of forming a liquid film on the surface of the magnetic layer. It is also possible to form a liquid film by moving to the surface of the magnetic layer during sliding with the head. Also, part of it can be contained in a non-magnetic layer, which will be described later, and can also migrate to the magnetic layer and then to the surface of the magnetic layer to form a liquid film. The "alkylester anion" can also be called an "alkylcarboxylate anion".

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, may have a branched structure, may be a cyclic alkyl group or fluorinated alkyl group, and has a linear structure. is preferred. The alkyl group or fluorinated alkyl group represented by R may have a substituent or may be unsubstituted, and is preferably unsubstituted. An alkyl group represented by R can be represented by, for example, C _n H _2n+1 -. Here, n represents an integer of 7 or more. Further, the fluorinated alkyl group represented by R can have a structure in which, for example, some or all of the hydrogen atoms constituting the alkyl group represented by C _n H _2n+1 - are substituted with fluorine atoms. The number of carbon atoms in the alkyl group or fluorinated alkyl group represented by R is 7 or more, preferably 8 or more, more preferably 9 or more, further preferably 10 or more, and 11 or more. more preferably, 12 or more, and even more preferably 13 or more. The number of carbon atoms in the alkyl group or fluorinated alkyl group represented by R is preferably 20 or less, more preferably 19 or less, and even more preferably 18 or less.

In Formula 1, Z ⁺ represents an ammonium cation. The ammonium cation specifically has the following structure. In the present invention and this specification, "*" in formulas representing part of a compound represents the bonding position between the structure of that part and an adjacent atom.

The nitrogen cation N ⁺ of the ammonium cation and the oxygen anion O 2 ⁻ in formula 1 can form a salt bridging group to form the ammonium salt structure of the alkyl ester anion represented by formula 1. The presence of the compound having the ammonium salt structure of the alkyl ester anion represented by Formula 1 in the magnetic layer can be confirmed by X-ray photoelectron spectroscopy (ESCA) and infrared spectroscopy (IR) for the magnetic tape. It can be confirmed by analyzing by infrared spectroscopy) or the like.

In one form, an ammonium cation represented by Z ⁺ can be provided, for example, by a nitrogen atom of a nitrogen-containing polymer becoming a cation. A nitrogen-containing polymer means a polymer containing nitrogen atoms. In the present invention and the specification, the terms "polymer" and "polymer" are used in the sense of including homopolymers and copolymers. A nitrogen atom can be contained as an atom constituting a main chain of a polymer in one form, and can be contained as an atom constituting a side chain of a polymer in one form.

One form of nitrogen-containing polymer is polyalkyleneimine. Polyalkyleneimine is a ring-opening polymer of alkyleneimine, and is a polymer having a plurality of repeating units represented by formula 2 below.

The nitrogen atom N constituting the main chain in Formula 2 can become a nitrogen cation N ⁺ to provide an ammonium cation represented by Z ⁺ in Formula 1. and can form an ammonium salt structure with an alkyl ester anion, for example as follows.

Formula 2 will be described in more detail below.

In Formula 2, R ¹ and R ² each independently represent a hydrogen atom or an alkyl group, and n1 represents an integer of 2 or more.

The alkyl group represented by R ¹ or R ² includes, for example, an alkyl group having 1 to 6 carbon atoms, preferably an alkyl group having 1 to 3 carbon atoms, more preferably a methyl group or an ethyl group. group, more preferably a methyl group. The alkyl group represented by R ¹ or R ² is preferably an unsubstituted alkyl group. The combination of R ¹ and R ² in Formula 2 includes a mode in which one is a hydrogen atom and the other is an alkyl group, a mode in which both are hydrogen atoms, and a mode in which both are alkyl groups (same or different alkyl groups). There is a form, preferably a form in which both are hydrogen atoms. As the alkyleneimine leading to polyalkyleneimine, the structure with the smallest number of carbon atoms constituting the ring is ethyleneimine, and the main chain of the alkyleneimine obtained by ring opening of ethyleneimine (ethyleneimine) has 2 carbon atoms. . Therefore, n1 in Formula 2 is 2 or more. n1 in Formula 2 can be, for example, 10 or less, 8 or less, 6 or less, or 4 or less. The polyalkyleneimine may be a homopolymer containing only the same structure as the repeating structure represented by Formula 2, or 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 polyalkyleneimine that can be used to form the compound having the ammonium salt structure of the alkyl ester anion represented by Formula 1 can be, for example, 200 or more, preferably 300 or more, 400 or more is more preferable. The number average molecular weight of the polyalkyleneimine may be, for example, 10,000 or less, preferably 5,000 or less, and more preferably 2,000 or less.

In the present invention and this specification, the average molecular weight (weight average molecular weight and number average molecular weight) is measured by gel permeation chromatography (GPC: Gel Permeation Chromatography) and refers to a value determined by standard polystyrene conversion. Unless otherwise specified, the average molecular weight shown in the examples below is a value obtained by converting the value measured under the following measurement conditions using GPC into standard polystyrene (polystyrene conversion value).
GPC device: HLC-8220 (manufactured by Tosoh Corporation)
Guard column: TSKguardcolumn Super HZM-H
Column: TSKgel Super HZ 2000, TSKgel Super HZ 4000, TSKgel Super HZ-M (manufactured by Tosoh Corporation, 4.6 mm (inner diameter) × 15.0 cm, 3 types of columns connected in series)
Eluent: Tetrahydrofuran (THF) containing stabilizer (2,6-di-t-butyl-4-methylphenol) Eluent flow rate: 0.35 mL/min Column temperature: 40°C
Inlet temperature: 40°C
Refractive index (RI: Refractive Index) measurement temperature: 40 ° C.
Sample concentration: 0.3% by mass
Sample injection volume: 10 μL

Another form of nitrogen-containing polymer is polyallylamine. Polyallylamine is a polymer of allylamine and is a polymer having a plurality of repeating units represented by Formula 3 below.

The nitrogen atom N constituting the amino group of the side chain in Formula 3 can become a nitrogen cation N ⁺ to provide an ammonium cation represented by Z ⁺ in Formula 1. and can form an ammonium salt structure with an alkyl ester anion, for example, as follows.

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

The inclusion of a compound having a structure derived from polyalkyleneimine or polyallylamine as a compound having an ammonium salt structure of an alkyl ester anion represented by Formula 1 is useful for the magnetic layer surface to be analyzed by time-of-flight secondary ion mass spectrometry ( It can be confirmed by analysis using TOF-SIMS: Time-of-Flight Secondary Ion Mass Spectrometry) or the like.

The compound having an ammonium salt structure of an alkyl ester anion represented by Formula 1 is a nitrogen-containing polymer and at least one fatty acid selected from the group consisting of fatty acids having 7 or more carbon atoms and fluorinated fatty acids having 7 or more carbon atoms. can be a salt of The salt-forming nitrogen-containing polymer can be one or more nitrogen-containing polymers, such as nitrogen-containing polymers selected from the group consisting of polyalkyleneimines and polyallylamines. Fatty acids that form salts 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. A fluorinated fatty acid has a structure in which some or all of the hydrogen atoms constituting the alkyl group bonded to the carboxyl group COOH in the fatty acid are substituted with fluorine atoms. For example, by mixing the nitrogen-containing polymer and the fatty acid at room temperature, the salt formation reaction can proceed easily. Room temperature is, for example, about 20 to 25.degree. In one embodiment, one or more nitrogen-containing polymers and one or more fatty acids are used as components of the composition for forming the magnetic layer, and these are mixed in the process of preparing the composition for forming the magnetic layer to form a salt. Allow the reaction to proceed. In one embodiment, before preparing the magnetic layer-forming composition, one or more nitrogen-containing polymers and one or more fatty acids are mixed to form a salt, and then the salt is added to the magnetic layer-forming composition. A composition for forming a magnetic layer can be prepared by using it as a component of a material. This point also applies to the formation of a non-magnetic layer containing a compound having an ammonium salt structure of an alkyl ester anion represented by formula (1). For example, for the magnetic layer, 0.1 to 10.0 parts by weight of nitrogen-containing polymer can be used per 100.0 parts by weight of ferromagnetic powder, and 0.5 to 8.0 parts by weight of nitrogen-containing polymer can be used. It is preferred to use For example, 0.05 to 10.0 parts by weight, preferably 0.1 to 5.0 parts by weight, of the fatty acid can be used per 100.0 parts by weight of the ferromagnetic powder. Further, when preparing the composition for forming the magnetic layer, the abrasive can be dispersed separately from the ferromagnetic powder, and can also be dispersed separately from the protrusion-forming agent. In such a separate dispersion, a compound having an ammonium salt structure of an alkyl ester anion represented by Formula 1 is added to the abrasive by mixing the abrasive with one or more nitrogen-containing polymers and one or more fatty acids. It can also be efficiently adsorbed to. For example, 0.01 to 1.0 parts by mass of a nitrogen-containing polymer and 0.01 to 1.0 parts by mass of fatty acids can be mixed with 1.0 parts by mass of the abrasive. In one embodiment, one or more nitrogen-containing polymers and one or more fatty acids are mixed to form a salt, and then the salt can be mixed with the abrasive in the separate dispersion. For example, 0.03 to 3.0 parts by mass of such a salt can be mixed with 1.0 part by mass of the abrasive. The present inventor believes that dispersing the abrasive separately together with the above components is preferable for controlling the rate of change in AlFeSil wear value before and after storage (AlFeSil wear value 2/AlFeSil wear value 1) to 0.7 or more. there is More specifically, by separately dispersing the abrasive together with the above components, the abrasive can be coated with the above salt, so that the component capable of functioning as a lubricant, such as the above salt, can be transferred from the inside of the magnetic layer to the surface. The inventor believes that it will be easier to supply to the early stage. The present inventors speculate that this contributes to making it possible to bring the polishing force on the surface of the magnetic tape, which has decreased due to repeated running, closer to the state before the decrease in a short period of time. Regarding the 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 0.5 to 8.0 parts by mass of nitrogen-containing polymer can be used. It is preferred to use nitrogen polymers. The above fatty acid can be used, for example, in an amount of 0.05 to 10.0 parts by mass, preferably 0.1 to 5.0 parts by mass, per 100.0 parts by mass of the non-magnetic powder. When the nitrogen-containing polymer and the fatty acid are mixed to form the ammonium salt of the alkyl ester anion represented by the formula 1, the nitrogen atom constituting the nitrogen-containing polymer and the carboxy group of the fatty acid are also The following structures may be formed upon reaction, and forms containing such structures are also included in the above compounds.

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

The mixing ratio of the nitrogen-containing polymer and the fatty acid used to form the compound having the ammonium salt structure of the alkyl ester anion represented by Formula 1 is 10:10 as a mass ratio of the nitrogen-containing polymer:the fatty acid. It is preferably from 90 to 90:10, more preferably from 20:80 to 85:15, even more preferably from 30:70 to 80:20. The compound having an ammonium salt structure of an alkyl ester anion represented by Formula 1 is preferably contained in the magnetic layer in an amount of 0.01 parts by weight or more, preferably 0.1 parts by weight, per 100.0 parts by weight of the ferromagnetic powder. It is more preferable to contain 1 part or more, and it is still more preferable to contain 0.5 parts by mass or more. Here, the content of the compound in the magnetic layer means the sum of the amount forming the liquid film on the surface of the magnetic layer and the amount contained inside the magnetic layer. On the other hand, a high content of ferromagnetic powder in the magnetic layer is preferable from the viewpoint of high-density recording. Therefore, from the viewpoint of high-density recording, it is preferable that the content of components other than the ferromagnetic powder is small. From this viewpoint, the content of the compound in the magnetic layer is preferably 15.0 parts by mass or less, more preferably 10.0 parts by mass or less, relative to 100.0 parts by mass of the ferromagnetic powder. It is more preferably 8.0 parts by mass or less. The same applies to the preferred range of the content of the above compounds in the composition for forming the magnetic layer used to form the magnetic layer.

The magnetic layer may contain one or more additional components that can function as lubricants. Examples of components that can function as lubricants include fatty acid esters and fatty acid amides. Examples of fatty acid esters include esters of lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, behenic acid, erucic acid and elaidic acid. Specific examples include butyl myristate, butyl palmitate, butyl stearate, neopentyl glycol dioleate, sorbitan monostearate, sorbitan distearate, sorbitan tristearate, oleyl oleate, isocetyl stearate, and stearin. Examples include isotridecyl stearate, octyl stearate, isooctyl stearate, amyl stearate, butoxyethyl stearate and the like. The fatty acid ester content in the composition for forming the magnetic layer or in the magnetic layer is, for example, 0.1 to 10.0 parts by weight, preferably 1.0 to 7.0 parts by weight, per 100.0 parts by weight of the ferromagnetic powder. is. Examples of fatty acid amides include amides of various fatty acids such as lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, behenic acid, erucic acid, and elaidic acid, specifically lauric acid amide. , myristic acid amide, palmitic acid amide, stearic acid amide, and the like. The fatty acid amide content of the magnetic layer is, for example, 0 to 3.0 parts by weight, preferably 0 to 2.0 parts by weight, more preferably 0 to 1.0 parts by weight, per 100.0 parts by weight of the ferromagnetic powder. part by mass. In addition, the non-magnetic layer may also contain one or more components capable of functioning as a lubricant. For example, the non-magnetic layer may contain one or more components selected from the group consisting of fatty acids, fatty acid esters and fatty acid amides. The fatty acid content in the composition for forming the nonmagnetic layer or in the nonmagnetic layer is, for example, 0 to 10.0 parts by mass, preferably 1.0 to 10.0 parts by mass, per 100.0 parts by mass of the nonmagnetic powder. Yes, more preferably 1.0 to 7.0 parts by mass. The fatty acid ester content in the composition for forming the non-magnetic layer or the non-magnetic layer is, for example, 0 to 10.0 parts by weight, preferably 0.1 to 8.0 parts by weight, per 100.0 parts by weight of the non-magnetic powder. is. The fatty acid amide content of the composition for forming the nonmagnetic layer or the nonmagnetic layer is, for example, 0 to 3.0 parts by weight, preferably 0 to 1.0 parts by weight, per 100.0 parts by weight of the nonmagnetic powder. . Regarding the dispersant, paragraphs 0061 and 0071 of JP-A-2012-133837 can be referred to. A dispersant may be added to the non-magnetic layer forming composition. See paragraph 0061 of JP-A-2012-133837 for the dispersant that can be added to the composition for forming a non-magnetic layer.

<Non-Magnetic Layer>
Next, the nonmagnetic layer will be explained. The magnetic tape may have a magnetic layer directly on a non-magnetic support, or may have a non-magnetic layer containing non-magnetic powder between the non-magnetic support and the magnetic layer. The non-magnetic powder used in the non-magnetic layer may be inorganic powder (inorganic powder) or organic powder (organic powder). Carbon black or the like can also be used. Examples of inorganic substances include metals, metal oxides, metal carbonates, metal sulfates, metal nitrides, metal carbides, and metal sulfides. These non-magnetic powders are commercially available and can be produced by known methods. For details, paragraphs 0146 to 0150 of JP-A-2011-216149 can be referred to. For carbon black that can be used in the non-magnetic layer, see paragraphs 0040 to 0041 of JP-A-2010-24113. The nonmagnetic powder content (filling rate) in the nonmagnetic layer is preferably in the range of 50 to 90% by mass, more preferably in the range of 60 to 90% by mass, relative to the total mass of the nonmagnetic layer. .

The non-magnetic layer can contain a binder and can also contain additives. Known techniques for nonmagnetic layers can be applied to other details such as binders and additives for the nonmagnetic layer. Also, for example, the type and content of the binder, the type and content of the additive, etc., can be applied to known techniques relating to the magnetic layer.

The non-magnetic layer of the magnetic tape includes, in addition to non-magnetic powder, a substantially non-magnetic layer containing a small amount of ferromagnetic powder, for example, as an impurity or intentionally. Here, the substantially non-magnetic layer means that the residual magnetic flux density of this layer is 10 mT or less, the coercive force is 7.96 kA/m (100 Oe) or less, or the residual magnetic flux density is 10 mT or less. and a coercive force of 7.96 kA/m (100 Oe) or less. The non-magnetic layer preferably has no residual magnetic flux density and no coercive force.

<Nonmagnetic support>
Next, the non-magnetic support will be described. The magnetic tape includes a polyethylene naphthalate support having a Young's modulus in the width direction of 10000 MPa (megapascal) or more as a non-magnetic support (hereinafter also simply referred to as "support").

Polyethylene naphthalate (PEN) is a resin containing a naphthalene ring and a plurality of ester bonds (that is, a polyester containing a naphthalene ring). It is a resin that can be obtained by subjecting a transesterification reaction and a polycondensation reaction to In the present invention and herein, "polyethylene naphthalate" has a structure having one or more other components (e.g., copolymer components, components introduced into terminals or side chains, etc.) in addition to the above components. is also included. In the present invention and herein, "polyethylene naphthalate support" means a support comprising at least one layer of polyethylene naphthalate film. The term "polyethylene naphthalate film" refers to a film in which polyethylene naphthalate is the most abundant component on a mass basis among the components constituting this film. The "polyethylene naphthalate support" in the present invention and the specification includes those in which all the resin films contained in this support are polyethylene naphthalate films, and those in which polyethylene naphthalate films and other resin films are included. is included. Specific forms of the polyethylene naphthalate support include a single-layer polyethylene naphthalate film, a laminated film of two or more layers of polyethylene naphthalate films having the same constituents, and a laminate of two or more layers of polyethylene naphthalate films having different constituents. Films, laminated films containing one or more layers of polyethylene naphthalate films and one or more layers of resin films other than polyethylene naphthalate films, and the like can be mentioned. An adhesive layer or the like may optionally be included between two adjacent layers in the laminated film. The polyethylene naphthalate support may also optionally include a metal film and/or a metal oxide film formed by vapor deposition or the like on one or both surfaces.

In addition, the non-magnetic support can be a biaxially stretched film, and may be a film subjected to corona discharge, plasma treatment, easy adhesion treatment, heat treatment, or the like.

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 modulus shown in the table below is a value determined by the following method using Tensilon manufactured by Toyo Baldwin Co., Ltd. as a universal tensile tester.
A sample piece cut out from a non-magnetic support to be measured is pulled by a universal tensile tester under the conditions of a distance between chucks of 100 mm, a tensile speed of 10 mm/min and a chart speed of 500 mm/min. As the universal tensile tester, for example, a commercially available universal tensile tester such as Tensilon manufactured by Toyo Baldwin Co., Ltd. or a universal tensile tester with a known configuration can be used. The Young's modulus in the longitudinal direction and width direction of the sample piece is calculated from the tangent to the rising portion of the load-elongation curve thus obtained. Here, the longitudinal direction and width direction of the sample piece mean the longitudinal direction and width direction when this sample piece is included in the magnetic tape.
For example, after removing portions other than the non-magnetic support, such as the magnetic layer, from the magnetic tape by a known method (e.g., film removal using an organic solvent, etc.), the longitudinal direction and width direction of the non-magnetic support are removed by the above method. Young's modulus can also be obtained.

The Young's modulus of the polyethylene naphthalate support in the width direction is 10000 MPa or more. This is the reason why the above-mentioned magnetic tape makes it possible to control the dimension of the magnetic tape in the width direction by adjusting the tension applied to the magnetic tape in the longitudinal direction and to perform good recording and/or reproduction. The inventor thinks The widthwise Young's modulus of the polyethylene naphthalate support may be, for example, 11000 MPa or more. The widthwise Young's modulus 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, or may exceed the values exemplified here.

The polyethylene naphthalate support may have a Young's modulus of 10000 MPa or more in the width direction, and the Young's modulus in the longitudinal direction is not particularly limited. In one form, the longitudinal Young's modulus of the polyethylene naphthalate support is preferably 2500 MPa or more, more preferably 3000 MPa or more. The longitudinal Young's modulus of the polyethylene naphthalate support may be, for example, 10000 MPa or less, 9000 MPa or less, 8000 MPa or less, 7000 MPa or less, or 6000 MPa or less. When manufacturing a magnetic tape, a non-magnetic support is generally used with the MD (machine direction) of the film as the longitudinal direction and the TD (transverse direction) as the width direction. 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 in one form, and can be different values in another form. In one form, the Young's modulus in the width direction of the polyethylene naphthalate support may be larger than the Young's modulus in the longitudinal direction. The Young's modulus of the non-magnetic support can be controlled by the types and mixing ratios of the components constituting the support, manufacturing conditions of the support, and the like. For example, the Young's modulus in the longitudinal direction and the Young's modulus in the width direction can be controlled by adjusting the draw ratio in each direction in the biaxial stretching process.

<Back coat layer>
The tape may or may not have a backcoat layer containing nonmagnetic powder on the surface of the nonmagnetic support opposite to the surface having the magnetic layer. The backcoat layer preferably contains one or both of carbon black and inorganic powder. The backcoat layer may contain a binder and may also contain additives. For the details of the non-magnetic powder, binders, additives, etc. of the back coat layer, known techniques for the back coat layer can be applied, and known techniques for the magnetic layer and/or the non-magnetic layer can also be applied. For example, paragraphs 0018 to 0020 of JP-A-2006-331625 and US Pat. .

<Various thicknesses>
As for the thickness (total thickness) of magnetic tapes, with the enormous increase in the amount of information in recent years, magnetic tapes are required to have a higher recording capacity (higher capacity). Means for increasing the capacity include reducing the thickness of the magnetic tape and increasing the length of the magnetic tape that can be accommodated in one roll of the magnetic tape cartridge. From this point, 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, and more preferably 5.3 μm. It is more preferably 5.2 μm or less, and even more preferably 5.2 μm or less. From the viewpoint of ease of handling, the thickness of the magnetic tape is preferably 3.0 μm or more, more preferably 3.5 μm or more.

The thickness (total thickness) of the magnetic tape can be measured by the following method.
Ten tape samples (for example, 5 to 10 cm in length) are cut out from an arbitrary portion of the magnetic tape, these tape samples are overlapped, and the thickness is measured. The value (thickness per tape sample) obtained by dividing the measured thickness by 1/10 is taken as the tape thickness. The thickness measurement can be performed using a known measuring instrument capable of measuring thickness on the order of 0.1 μm.

The thickness of the nonmagnetic support can be, for example, 3.0 μm or more, and can 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. can.
The thickness of the magnetic layer can be optimized according to the saturation magnetization amount of the magnetic head to be used, the head gap length, the recording signal band, etc., and is generally 0.01 μm to 0.15 μm. From the point of view, it is preferably 0.02 μm to 0.12 μm, more preferably 0.03 μm to 0.1 μm. At least one magnetic layer is sufficient, and the magnetic layer may be separated into two or more layers having different magnetic properties, and a known multilayer magnetic layer structure can be applied. The thickness of the magnetic layer when separated into two or more layers is the total thickness of these layers.
The thickness of the nonmagnetic layer is, for example, 0.1 to 1.5 μm, preferably 0.1 to 1.0 μm.
The thickness of the backcoat layer is preferably 0.9 μm or less, more preferably 0.1 to 0.7 μm.
Various thicknesses such as the thickness of the magnetic layer can be obtained, for example, by the following methods.
After exposing a section of the magnetic tape in the thickness direction with an ion beam, the exposed section is observed with a scanning electron microscope or a transmission electron microscope. Various thicknesses can be determined as the arithmetic mean of the thicknesses determined at two arbitrary locations in cross-sectional observation. Alternatively, various thicknesses can be obtained as design thicknesses calculated from manufacturing conditions and the like.

<Manufacturing method>
(Preparation of each layer-forming composition)
A composition for forming a magnetic layer, a non-magnetic layer, or a backcoat layer usually contains a solvent along with the various components described above. As the solvent, various organic solvents generally used for producing coating type magnetic recording media can be used. Among them, from the viewpoint of the solubility of binders commonly used in coating-type magnetic recording media, each layer-forming composition contains ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, cyclohexanone, isophorone, and tetrahydrofuran. It is preferable that one or more of The amount of solvent in each layer-forming composition is not particularly limited, and can be the same as in each layer-forming composition for a conventional coating type magnetic recording medium. In addition, the step of preparing each layer-forming composition can usually include at least a kneading step, a dispersing step, and a mixing step provided before or after these steps as required. Each step may be divided into two or more stages. The components used for preparing each layer-forming composition may be added at the beginning or in the middle of any step. Individual ingredients may be added in portions in two or more steps. For example, the binder may be added separately in the kneading process, the dispersing process, and the mixing process for adjusting the viscosity after dispersion. As described above, one or more nitrogen-containing polymers and one or more of the above fatty acids are used as components of the composition for forming the magnetic layer, and these are used in the preparation process of the composition for forming the magnetic layer. By mixing, the salt-forming reaction can proceed. In one embodiment, before preparing the magnetic layer-forming composition, one or more nitrogen-containing polymers and one or more fatty acids are mixed to form a salt, and then the salt is added to the magnetic layer-forming composition. A composition for forming a magnetic layer can be prepared by using it as a component of a material. This point also applies to the process of preparing the composition for forming the non-magnetic layer. In one embodiment, in the step of preparing a composition for forming a magnetic layer, after preparing a dispersion containing a protrusion-forming agent (hereinafter referred to as "protrusion-forming agent liquid"), this protrusion-forming agent liquid is added to a magnetic It can be mixed with one or more other components of the layer-forming composition. During the separate dispersion of the abrasive (ie, during the preparation of the abrasive liquid), the ingredients previously described can also be mixed. Moreover, you may filter after a dispersion|distribution process. The following description can be referred to for the filter used for filtration.

In the manufacturing process of the magnetic tape, conventional known manufacturing techniques can be used in part or all of the process. In the kneading step, it is preferable to use a kneader having a strong kneading force such as an open kneader, continuous kneader, pressure kneader, extruder or the like. Details of these kneading treatments are described in Japanese Patent Application Laid-Open Nos. 1-106338 and 1-79274. Also, glass beads and/or other beads can be used to disperse each layer forming composition. As such dispersing beads, zirconia beads, titania beads, and steel beads, which are high specific gravity dispersing beads, are suitable. It is preferable to optimize the particle diameter (bead diameter) and the packing rate of these dispersed beads. A known disperser can be used. Each layer-forming composition may be filtered by a known method before being applied to the coating step. Filtration can be performed, for example, by filter filtration. As a filter used for filtration, for example, a filter having a pore size of 0.01 to 3 μm (eg, glass fiber filter, polypropylene filter, etc.) can be used.

(Coating process)
The magnetic layer can be formed, for example, by directly coating the magnetic layer-forming composition on the non-magnetic support, or by sequentially or simultaneously coating the magnetic layer-forming composition with the non-magnetic layer-forming composition. When the orientation treatment is performed, the orientation treatment is applied to the coating layer of the composition for forming the magnetic layer in the orientation zone while the coating layer is in a wet state. Various known techniques including those described in paragraph 0052 of JP-A-2010-24113 can be applied to the alignment treatment. For example, the vertical alignment treatment can be performed by a known method such as a method using opposed magnets with different poles. In the orientation zone, the drying speed of the coating layer can be controlled by the temperature and air volume of the drying air and/or the conveying speed in the orientation zone. Also, the coated layer may be pre-dried before being conveyed to the orientation zone.
The backcoat layer can be formed by coating a composition for forming a backcoat layer on the opposite side of the non-magnetic support from the side having the magnetic layer (or the side on which the magnetic layer is to be provided later). For details of coating for forming each layer, paragraph 0066 of JP-A-2010-231843 can be referred to.

(Other processes)
After performing the coating step, the magnetic tape may be subjected to calendering treatment to increase the surface smoothness. With respect to the calender conditions, the calender pressure is for example 200-500 kN/m, preferably 250-350 kN/m, the calender temperature is for example 70-120° C., preferably 80-100° C., and the calender speed is for example 50 ~300 m/min, preferably 80-200 m/min. In addition, the surface of the magnetic layer tends to become smoother as a roll with a harder surface is used as the calender roll and as the number of stages is increased.
For various other steps for manufacturing the magnetic tape, paragraphs 0067 to 0070 of JP-A-2010-231843 can be referred to.
Through various processes, a long magnetic tape raw material can be obtained. The obtained magnetic tape material is cut (slit) to the width of the magnetic tape to be accommodated in the magnetic tape cartridge by a known cutting machine. The above width can be determined according to standards and is typically 1/2 inch. 1/2 inch = 12.65 mm.
Servo patterns are usually formed on the magnetic tape obtained by slitting.

(Formation of servo pattern)
"Formation of servo patterns" can also be called "recording of servo signals." Formation of the servo pattern will be described below.

A servo pattern is usually formed along the longitudinal direction of the magnetic tape. Methods of control using servo signals (servo control) include timing-based servo (TBS), amplitude servo, frequency servo, and the like.

As shown in ECMA (European Computer Manufacturers Association)-319 (June 2001), a magnetic tape conforming to the LTO (Linear Tape-Open) standard (generally called "LTO tape") adopts a timing-based servo system. ing. In this timing-based servo system, a servo pattern is composed of a plurality of non-parallel pairs of magnetic stripes (also called "servo stripes") arranged continuously in the longitudinal direction of the magnetic tape. In the present invention and in this specification, the term "timing-based servo pattern" refers to a servo pattern that enables head tracking in a timing-based servo system servo system. The reason why the servo pattern is composed of a pair of non-parallel magnetic stripes is to inform the servo signal reading element passing over the servo pattern of its passing position. Specifically, the pair of magnetic stripes are formed so that the interval between them changes continuously along the width direction of the magnetic tape. and the relative position of the servo signal reading element. This relative position information enables tracking of the data tracks. For this reason, a plurality of servo tracks are usually set on the servo pattern along the width direction of the magnetic tape.

A servo band is composed of servo patterns that are continuous in the longitudinal direction of the magnetic tape. A plurality of servo bands are usually provided on the magnetic tape. For example, in LTO tape, the number is five. A data band is an area sandwiched between two adjacent servo bands. The data band is composed of a plurality of data tracks, each data track corresponding to each servo track.

In one form, as disclosed in JP-A-2004-318983, each servo band includes information indicating the number of the servo band ("servo band ID (identification)" or "UDIM (Unique Data Band Identification)"). Method (also called information) is embedded. This servo band ID is recorded by shifting a specific one of a plurality of pairs of servo stripes in the servo band so that the position thereof is relatively displaced in the longitudinal direction of the magnetic tape. Specifically, the method of shifting a specific one of a plurality of pairs 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 one servo band can be uniquely specified only by reading one servo band with a servo signal reading element.

It should be noted that as a method for uniquely specifying a servo band, there is also a method using a staggered method as shown in ECMA-319 (June 2001). In this staggered method, groups of non-parallel pairs of magnetic stripes (servo stripes) arranged continuously in the longitudinal direction of the magnetic tape are recorded so as to be shifted in the longitudinal direction of the magnetic tape for each servo band. do. Since this combination of shifts between adjacent servo bands is unique for the entire magnetic tape, the servo band can be uniquely identified when reading the servo pattern with two servo signal reading elements. It is possible.

In each servo band, information indicating the position in the longitudinal direction of the magnetic tape (also called "LPOS (Longitudinal Position) information") is also usually embedded as indicated in ECMA-319 (June 2001). ing. Like the UDIM information, this LPOS information is also recorded by shifting the positions of a pair of servo stripes in the longitudinal direction of the magnetic tape. However, unlike the UDIM information, the same signal is recorded in each servo band in this LPOS information.

Other information different from the above UDIM and LPOS information can also be embedded in the servo band. In this case, the embedded information may be different for each servo band, such as UDIM information, or common to all servo bands, such as LPOS information.
Also, as a method of embedding information in the servo band, it is possible to adopt a method other than the above. For example, a predetermined code may be recorded by thinning out a predetermined pair from a group of paired servo stripes.

The servo pattern forming head is called a servo write head. A servo write head normally has a pair of gaps corresponding to the pair of magnetic stripes as many as the number of servo bands. Normally, a core and a coil are connected to each pair of gaps, and by supplying current pulses to the coils, a magnetic field generated in the core can generate a leakage magnetic field in the pair of gaps. When forming the servo pattern, the magnetic pattern corresponding to the pair of gaps is transferred onto the magnetic tape by inputting a current pulse while the magnetic tape is running over the servo write head, thereby forming the servo pattern. can be done. The width of each gap can be appropriately set according to the density of the servo pattern to be formed. The width of each gap can be set to, for example, 1 μm or less, 1 to 10 μm, or 10 μm or more.

Before forming the servo pattern on the magnetic tape, the magnetic tape is usually demagnetized (erase). This erasing process can be performed by applying a uniform magnetic field to the magnetic tape using a DC magnet or an AC magnet. The erase process includes DC (Direct Current) erase and AC (Alternating Current) erase. AC erase is performed by gradually decreasing the strength of the magnetic field while reversing the direction of the magnetic field applied to the magnetic tape. DC erase, on the other hand, is performed by applying a unidirectional magnetic field to the magnetic tape. There are two methods of DC erase. The first method is a horizontal DC erase that applies a unidirectional magnetic field along the length of the magnetic tape. The second method is perpendicular DC erase, in which a unidirectional magnetic field is applied along the thickness of the magnetic tape. The erase process may be performed on the entire magnetic tape, or may be performed on each servo band of the magnetic tape.

The direction of the magnetic field of the formed servo pattern is determined according to the erase direction. For example, when horizontal DC erasing is performed on a magnetic tape, the servo pattern is formed so that the direction of the magnetic field is opposite to the direction of erasing. As a result, the output of the servo signal obtained by reading the servo pattern can be increased. Incidentally, as disclosed in Japanese Patent Application Laid-Open No. 2012-53940, when a magnetic pattern is transferred to a perpendicular DC-erased magnetic tape using the gap, the formed servo pattern is read and obtained. The servo signal has a unipolar pulse shape. On the other hand, when a magnetic pattern is transferred to a magnetic tape that has been horizontally DC-erased using the gap, a servo signal obtained by reading the formed servo pattern has a bipolar pulse shape.

[Magnetic tape cartridge]
One aspect of the present invention relates to a magnetic tape cartridge including the above magnetic tape.

The details of the magnetic tape included in the magnetic tape cartridge are as described above.

A magnetic tape cartridge generally contains a magnetic tape wound on a reel inside the cartridge body. The reel is rotatably provided inside the cartridge body. As magnetic tape cartridges, a single reel type magnetic tape cartridge having one reel inside the cartridge body and a dual reel type magnetic tape cartridge having two reels inside the cartridge body are widely used. When a single-reel type magnetic tape cartridge is mounted on a magnetic tape device for recording and/or reproducing data on the magnetic tape, the magnetic tape is pulled out from the magnetic tape cartridge and wound on the reel of the magnetic tape device. be taken. A magnetic head is arranged in the magnetic tape transport path from the magnetic tape cartridge to the take-up reel. The magnetic tape is fed out and taken up between the reel (supply reel) of the magnetic tape cartridge and the reel (take-up reel) of the magnetic tape device. During this time, data is recorded and/or reproduced by contact and sliding between the magnetic head and the surface of the magnetic layer of the magnetic tape. On the other hand, a twin-reel type magnetic tape cartridge has both a supply reel and a take-up reel inside the magnetic tape cartridge.

In one form, the magnetic tape cartridge can include a cartridge memory. The cartridge memory can be, for example, a non-volatile memory, and can be a memory in which tension adjustment information is already recorded, or a memory in which tension adjustment information is recorded. The tension adjustment information is information for adjusting the tension applied to the magnetic tape in the longitudinal direction. Regarding the cartridge memory, reference can also be made to the later description.

The above magnetic tape and magnetic tape cartridge are preferably used in a magnetic tape device (in other words, a magnetic recording/reproducing system) that controls the widthwise dimension of the magnetic tape by adjusting the tension applied to the magnetic tape in the longitudinal direction. obtain.

[Magnetic tape device]
One aspect of the present invention relates to a magnetic tape device including the above magnetic tape. In the above magnetic tape device, data recording on the magnetic tape and/or reproduction of data recorded on the magnetic tape can be performed by bringing the surface of the magnetic layer of the magnetic tape and the magnetic head into contact with each other and sliding the magnetic head. . The magnetic tape device can detachably include the magnetic tape cartridge according to one aspect of the present invention.

The magnetic tape cartridge can be mounted on a magnetic tape device having a magnetic head and used to record and/or reproduce data. In the present invention and in this specification, the term "magnetic tape device" means a device capable of at least one of recording data on a magnetic tape and reproducing data recorded on the magnetic tape. Such devices are commonly called drives. The magnetic head included in the magnetic tape device can be a recording head capable of recording data on the magnetic tape, and a reproducing head capable of reproducing data recorded on the magnetic tape. can also In one form, the magnetic tape device can include both a recording head and a reproducing head as separate magnetic heads. In another form, the magnetic head included in the magnetic tape device may have a configuration in which both the recording element and the reproducing element are provided in one magnetic head. As a reproducing head, a magnetic head (MR head) including a magnetoresistive (MR) element capable of reading information recorded on a magnetic tape with high sensitivity as a reproducing element is preferable. As the MR head, various known MR heads (for example, GMR (Giant Magnetoresistive) head, TMR (Tunnel Magnetoresistive) head, etc.) can be used. A magnetic head for recording and/or reproducing data may also include a servo signal reading element. Alternatively, the magnetic tape device may include a magnetic head (servo head) having a servo signal reading element as a separate head from the magnetic head for recording and/or reproducing data. For example, a magnetic head for recording data and/or reproducing recorded data (hereinafter also referred to as a "recording/reproducing head") may include two servo signal reading elements. can simultaneously read two adjacent servo bands across the data band. One or more data elements can be positioned between the two servo signal read elements. An element for recording data (recording element) and an element for reproducing data (reading element) are collectively referred to as a "data element".

By reproducing data using a reproducing element having a narrow reproducing element width as a reproducing element, data recorded at a high density can be reproduced with high sensitivity. From this point of view, the read element width of the read element is preferably 0.8 μm or less. The read element width of the read element can be, for example, 0.3 μm or more. However, falling below this value is also preferable from the above viewpoint.
On the other hand, the narrower the width of the reproducing element, the more likely it is that phenomena such as poor reproduction due to off-track will occur. In order to suppress the occurrence of such a phenomenon, a magnetic tape device that controls the widthwise dimension of the magnetic tape by adjusting the tension applied to the magnetic tape in the longitudinal direction is preferable.
Here, the "reproducing element width" means the physical dimension of the reproducing element width. Such physical dimensions can be measured with an optical microscope, scanning electron microscope, or the like.

When recording data and/or reproducing recorded data, first, tracking using a servo signal can be performed. That is, by causing the servo signal reading element to 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 performed by changing the servo track read by the servo signal reading element in the tape width direction.
The record/playback head can also record and/or play back other data bands. In this case, the above-described UDIM information is used to move the servo signal reading element to a predetermined servo band, and tracking for that servo band can be started.

Fig. 1 shows an example of the arrangement of data bands and servo bands. In FIG. 1, a plurality of servo bands 1 are sandwiched between guide bands 3 on the magnetic layer of the magnetic tape MT. A plurality of areas 2 sandwiched between two servo bands are data bands. A servo pattern is a magnetized region formed by magnetizing a specific region of a magnetic layer with a servo write head. The area magnetized by the servo write head (the position where the servo pattern is formed) is defined by standards. For example, in the industry standard LTO Ultrium format tape, a plurality of servo patterns inclined with respect to the tape width direction as shown in FIG. 2 are formed on the servo band when the magnetic tape is manufactured. Specifically, in FIG. 2, the servo frame SF on servo band 1 is composed of servo subframe 1 (SSF1) and servo subframe 2 (SSF2). A servo subframe 1 is composed of an A burst (symbol A in FIG. 2) and a B burst (symbol B in FIG. 2). The A burst is composed of servo patterns A1 to A5, and the B burst is composed of servo patterns B1 to B5. On the other hand, servo subframe 2 is composed of a C burst (symbol C in FIG. 2) and a D burst (symbol D in FIG. 2). The C burst is composed of servo patterns C1 to C4, and the D burst is composed of servo patterns D1 to D4. Such 18 servo patterns are arranged in sets of 5 and 4 in subframes arranged in an array of 5, 5, 4, 4, and are used to identify servo frames. FIG. 2 shows one servo frame for explanation. In practice, however, a plurality of servo frames are arranged in the running direction in each servo band on the magnetic layer of the magnetic tape on which the head tracking of the timing-based servo system is performed. In FIG. 2, arrows indicate the direction of travel. For example, an LTO Ultrium format tape typically has 5000 or more servo frames per meter of tape length in each servo band of the magnetic layer.

The magnetic tape device can have a tension adjustment mechanism that can adjust the tension applied to the magnetic tape running in the magnetic tape device in the longitudinal direction. Such a tension adjusting mechanism can variably control the tension applied to the magnetic tape in the longitudinal direction, and preferably controls the widthwise dimension of the magnetic tape by adjusting the tension applied in the longitudinal direction of the magnetic tape. be able to. In the tension adjustment described above, the tension applied to the magnetic tape in the longitudinal direction can be changed. An example of such a magnetic tape device will be described below with reference to FIG. However, the present invention is not limited to the example shown in FIG.

<Configuration of magnetic tape device>
The magnetic tape device 10 shown in FIG. 3 controls the recording/reproducing head unit 12 according to commands from the control device 11 to record and reproduce data on the magnetic tape MT.
The magnetic tape device 10 has a structure capable of detecting and adjusting the tension applied in the longitudinal direction of the magnetic tape from spindle motors 17A and 17B that control the rotation of the magnetic tape cartridge reel and take-up reel, and their drive devices 18A and 18B. are doing.
The magnetic tape device 10 has a configuration in which a magnetic tape cartridge 13 can be loaded.
The magnetic tape device 10 has a cartridge memory read/write device 14 capable of reading from and writing to the cartridge memory 131 in the magnetic tape cartridge 13 .
From the magnetic tape cartridge 13 mounted on the magnetic tape device 10 , the end of the magnetic tape MT or the leader pin is pulled out by an automatic loading mechanism or manually, and the magnetic layer surface of the magnetic tape MT is recorded by the recording/reproducing head unit 12 . The magnetic tape MT is wound onto the take-up reel 16 by passing over the recording/reproducing head through the guide rollers 15A and 15B so as to contact the surface of the reproducing head.
A signal from the controller 11 controls the rotation and torque of the spindle motors 17A and 17B to run the magnetic tape MT at an arbitrary speed and tension. A servo pattern preformed on the magnetic tape can be used to control the tape speed. A tension detection mechanism may be provided between the magnetic tape cartridge 13 and the take-up reel 16 to detect tension. Tension control may be performed using guide rollers 15A and 15B in addition to control by spindle motors 17A and 17B.
The cartridge memory read/write device 14 is configured to be able to read and write information from the cartridge memory 131 according to commands from the control device 11 . As a communication method between the cartridge memory read/write device 14 and the cartridge memory 131, for example, the ISO (International Organization for Standardization) 14443 method can be adopted.

The control device 11 includes, for example, a control section, a storage section, a communication section, and the like.

The recording/reproducing head unit 12 is composed of, for example, a recording/reproducing head, a servo tracking actuator for adjusting the position of the recording/reproducing head in the track width direction, a recording/reproducing amplifier 19, a connector cable for connecting to the control device 11, and the like. A recording/reproducing head is composed of, for example, a recording element for recording data on a magnetic tape, a reproducing element for reproducing data from the magnetic tape, and a servo signal reading element for reading a servo signal recorded on the magnetic tape. For example, one or more recording elements, one or more reproducing elements, and one or more servo signal reading elements are mounted in one magnetic head. Alternatively, each element may be separately provided in a plurality of magnetic heads corresponding to the traveling direction of the magnetic tape.

The recording/reproducing head unit 12 is configured to be able to record data on the magnetic tape MT according to commands from the control device 11 . Further, according to a command from the control device 11, the data recorded on the magnetic tape MT can be reproduced.

The controller 11 determines the running position of the magnetic tape from the servo signal read from the servo band while the magnetic tape MT is running, and controls the servo so that the recording element and/or the reproducing element are positioned at the target running position (track position). It has a mechanism for controlling the tracking actuator. This track position control is performed, for example, by feedback control.
The control device 11 has a mechanism for obtaining a servo band interval from servo signals read from two adjacent servo bands while the magnetic tape MT is running. It also has a mechanism for controlling the tension in the longitudinal direction of the magnetic tape by controlling the torque of the spindle motor 17A and the spindle motor 17B and/or the guide rollers 15A and 15B so that the servo band interval becomes a target value. . This tension control is performed, for example, by feedback control. Further, the control device 11 can store the obtained servo band interval information in a storage unit inside the control device 11, the cartridge memory 131, an external connected device, or the like.

The present invention will be described below based on examples. However, the present invention is not limited to the embodiments shown in Examples. Unless otherwise specified, "parts" and "%" described below indicate "mass parts" and "mass%". The processes and evaluations described below were performed in an environment at a temperature of 23°C ± 1°C unless otherwise specified. Also, "eq" described below indicates an equivalent, which is a unit that cannot be converted into the SI unit system.

[Nonmagnetic support]
In Table 2, "PEN" indicates polyethylene naphthalate support. Young's modulus in Table 2 is a value measured by the method described above.

[Ferromagnetic powder]
In Table 2, "BaFe" is hexagonal barium ferrite powder with an average particle size (average plate diameter) of 21 nm.

In Table 2, "SrFe1" is hexagonal strontium ferrite powder produced by the following method.
1707 _g of SrCO3, 687 _g of _H3BO3 , 1120 g of _Fe2O3 , 45 g of Al(OH) ₃ , 24 g of _BaCO3 , 13 g of _CaCO3 , and 235 g _of _Nd2O3 were weighed and mixed in _a mixer. A raw material mixture was obtained by mixing.
The obtained raw material mixture was melted in a platinum crucible at a melting temperature of 1390° C., and while the melt was being stirred, a tap hole provided at the bottom of the platinum crucible was heated, and the melt was tapped in a rod shape at a rate of about 6 g/sec. . The tapped liquid was rolled and quenched with a water-cooled twin roller to prepare an amorphous body.
280 g of the produced amorphous material was placed in an electric furnace, heated to 635° C. (crystallization temperature) at a heating rate of 3.5° C./min, and held at the same temperature for 5 hours to produce hexagonal strontium ferrite particles. Precipitated (crystallized).
Next, the crystallized product obtained above containing hexagonal strontium ferrite particles was coarsely pulverized in a mortar, and 1000 g of zirconia beads having a particle size of 1 mm and 800 ml of a 1% concentration aqueous solution of acetic acid were added to a glass bottle and dispersed for 3 hours using a paint shaker. did After that, the resulting dispersion was separated from the beads and placed in a stainless steel beaker. After the dispersion liquid was allowed to stand at a liquid temperature of 100°C for 3 hours to dissolve the glass component, it was precipitated in a centrifuge and washed by repeating decantation. After drying for a few hours, hexagonal strontium ferrite powder was obtained.
The average particle size of the hexagonal strontium ferrite powder obtained above is 18 nm, the activation volume is 902 nm ³ , the anisotropy constant Ku is 2.2×10 ⁵ J/m ³ , and the mass magnetization σs is 49 A·m ² /. kg.
12 mg of sample powder was taken from the hexagonal strontium ferrite powder obtained above, and the sample powder was partially dissolved under the dissolution conditions exemplified above. The surface layer content was determined.
Separately, 12 mg of sample powder was taken from the hexagonal strontium ferrite powder obtained above, and the sample powder was completely dissolved under the dissolution conditions exemplified above. Atomic bulk content was determined.
The content of neodymium atoms (bulk content) with respect to 100 atomic % of iron atoms in the hexagonal strontium ferrite powder obtained above was 2.9 atomic %. The content of neodymium atoms in the surface layer was 8.0 atomic %. The ratio of the surface layer portion content rate to the bulk content rate, "surface layer portion content rate/bulk content rate", was 2.8, confirming that neodymium atoms were unevenly distributed in the surface layer of the particles.
The fact that the powder obtained above exhibits the crystal structure of hexagonal ferrite is confirmed by scanning CuKα rays under the conditions of a voltage of 45 kV and an intensity of 40 mA and measuring the X-ray diffraction pattern under the following conditions (X-ray diffraction analysis). confirmed. The powder obtained above exhibited a crystal structure of magnetoplumbite-type (M-type) hexagonal ferrite. The crystal phase detected by X-ray diffraction analysis was a magnetoplumbite single phase.
PANalytical X'Pert Pro diffractometer, PIXcel detector Soller slits for incident and diffracted beams: 0.017 radians Fixed divergence slit angle: ¼ degree Mask: 10 mm
Anti-scattering slit: 1/4 degree Measurement mode: continuous Measurement time per step: 3 seconds Measurement speed: 0.017 degree per second Measurement step: 0.05 degree

In Table 2, "SrFe2" is hexagonal strontium ferrite powder produced by the following method.
1725 _g of SrCO3, 666 _g of _H3BO3 , 1332 g of _Fe2O3 , 52 g of Al(OH) ₃ , 34 g of _CaCO3 and 141 _g of _BaCO3 were weighed and mixed in a mixer to obtain a raw material mixture.
The obtained raw material mixture was melted in a platinum crucible at a melting temperature of 1380° C., and while the melt was being stirred, a tap hole provided at the bottom of the platinum crucible was heated, and the melt was tapped in a rod shape at a rate of about 6 g/sec. . The tapped liquid was rolled and quenched with water-cooled twin rolls to prepare an amorphous body.
280 g 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 crystallized product obtained above containing hexagonal strontium ferrite particles was coarsely pulverized in a mortar, and 1000 g of zirconia beads having a particle size of 1 mm and 800 ml of a 1% concentration aqueous solution of acetic acid were added to a glass bottle and dispersed for 3 hours using a paint shaker. did After that, the resulting dispersion was separated from the beads and placed in a stainless steel beaker. After the dispersion liquid was allowed to stand at a liquid temperature of 100°C for 3 hours to dissolve the glass component, it was precipitated in a centrifuge, washed by repeating decantation, and placed in a heating furnace at a temperature of 110°C for 6 hours. After drying for a few hours, hexagonal strontium ferrite powder was obtained.
The obtained hexagonal strontium ferrite powder had an average particle size of 19 nm, an activated volume of 1102 nm ³ , an anisotropy constant Ku of 2.0×10 ⁵ J/m ³ , and a mass magnetization σs of 50 A·m ² /kg. there were.

In Table 2, "ε-iron oxide" is ε-iron oxide powder prepared by the following method.
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 4.0 g of an aqueous ammonia solution having a concentration of 25% was added to a solution of 1.5 g of polyvinylpyrrolidone (PVP) in an air atmosphere at an ambient temperature of 25° C. while stirring using a magnetic stirrer. , and the mixture was stirred for 2 hours while maintaining the ambient temperature of 25°C. A citric acid solution obtained by dissolving 1 g of citric acid in 9 g of pure water was added to the obtained solution, and the mixture was stirred for 1 hour. The powder precipitated after stirring was collected by centrifugation, washed with pure water, and dried in a heating furnace with an internal furnace temperature of 80°C.
800 g of pure water was added to the dried powder, and the powder was dispersed again in water to obtain a dispersion liquid. The obtained dispersion was heated to a liquid temperature of 50° C., and 40 g of a 25% concentration aqueous ammonia solution was added dropwise while stirring. After stirring for 1 hour while maintaining the temperature at 50° C., 14 mL of tetraethoxysilane (TEOS) was added dropwise and the mixture was stirred for 24 hours. 50 g of ammonium sulfate was added to the obtained reaction solution, and the precipitated powder was collected by centrifugation, washed with pure water, and dried in a heating furnace at an internal temperature of 80°C for 24 hours to obtain a ferromagnetic powder precursor. Obtained.
The obtained ferromagnetic powder precursor was placed in a heating furnace with an internal temperature of 1000° C. in an air atmosphere, and heat-treated for 4 hours.
The heat-treated ferromagnetic powder precursor was put into a 4 mol/L sodium hydroxide (NaOH) aqueous solution, and the liquid temperature was maintained at 70° C. and stirred for 24 hours to obtain the heat-treated ferromagnetic powder. A silicic acid compound as an impurity was removed from the precursor.
After that, the ferromagnetic powder from which the silicic acid compound was removed was collected by centrifugal separation and washed with pure water to obtain the ferromagnetic powder.
When the composition of the obtained ferromagnetic powder was confirmed by high-frequency inductively coupled plasma-optical emission spectrometry (ICP-OES), Ga, Co and Ti-substituted ε-iron oxide (ε-Ga _{0 .28} Co _0.05 Ti _0.05 Fe _1.62 O ₃ ). In addition, X-ray diffraction analysis was performed under the same conditions as those described above for SrFe1, and from the peaks of the X-ray diffraction pattern, it was confirmed that the obtained ferromagnetic powder did not contain the crystal structure of α phase and γ phase, ε It was confirmed to have a single-phase crystal structure (ε-iron oxide crystal structure).
The resulting ε-iron oxide powder had an average particle size of 12 nm, an activated volume of 746 nm ³ , an anisotropy constant Ku of 1.2×10 ⁵ J/m ³ and a mass magnetization σs of 16 A·m ² /kg. there were.

The activation volume and anisotropy constant Ku of the above hexagonal strontium ferrite powder and ε-iron oxide powder were obtained using a vibrating sample magnetometer (manufactured by Toei Kogyo Co., Ltd.) for each ferromagnetic powder, as previously described. It is a value obtained by the method of
Also, the mass magnetization σs is a value measured at a magnetic field strength of 15 kOe using a vibrating sample magnetometer (manufactured by Toei Industry Co., Ltd.).

[Preparation of abrasive liquid]
<Preparation of abrasive liquid A1>
For 100.0 parts of the abrasive (alumina powder) shown in Table 1, the amount shown in Table 1 of 2,3-dihydroxynaphthalene (manufactured by Tokyo Kasei Co., Ltd.), the amount shown in Table 1 of polyethyleneimine (manufactured by Nippon Shokubai Co., Ltd., number average molecular weight 300), stearic acid in the amount shown in Table 1, and a polyester polyurethane resin having an SO _Na group as a polar group (UR-4800 manufactured by Toyobo Co., Ltd. (polar group weight: 80 meq/kg)) 32% solution (solvent is a mixed solvent of methyl ethyl ketone and toluene), and 570.0 parts of a mixture of methyl ethyl ketone and cyclohexanone (1:1 mass ratio) as a solvent are mixed, and in the presence of zirconia beads (bead diameter: 0.1 mm), Dispersed with a paint shaker for the time shown in Table 1 (bead dispersion time).
After dispersion, the dispersion obtained by separating the dispersion and the beads with a mesh was subjected to centrifugal separation. In the centrifugation process, CS150GXL manufactured by Hitachi Koki Co., Ltd. (rotor used is S100AT6 manufactured by Hitachi Koki Co., Ltd.) is used as a centrifuge, and the rotation speed (rpm: rotation per minute) shown in Table 1 is used for the time shown in Table 1 (centrifugation time ),carried out. By this centrifugation treatment, particles having a relatively large particle size are precipitated, and particles having a relatively small particle size are dispersed in the supernatant liquid.
After that, the supernatant was collected by decantation. This collected liquid is called "abrasive liquid A1".

<Preparation of Abrasive Liquids A2, B1, B2, C1 and C2>
Abrasive liquids A2 to C2 were prepared in the same manner as for abrasive liquid A1, except that various items were changed as shown in Table 1.

[Example A1]
<Preparation of Composition for Forming Magnetic Layer>
(Magnetic liquid)
Ferromagnetic powder (see Table 2): 100.0 parts Oleic acid: 2.0 parts Vinyl chloride copolymer (MR-104 manufactured by Zeon Corporation): 10.0 parts SO ₃ Na group-containing polyurethane resin: 4.0 parts (Weight average molecular weight 70000, SO ₃ Na group: 0.07 meq/g)
Polyalkyleneimine polymer (synthetic product obtained by the method described in paragraphs 0115 to 0123 of JP-A-2016-51493): 6.0 parts methyl ethyl ketone: 150.0 parts cyclohexanone: 150.0 parts (abrasive liquid )
Use the abrasive liquid shown in Table 2 so that the amount of abrasive in the abrasive liquid is the amount shown in Table 2 (other components)
Carbon black (average particle size: 20 nm): 0.7 parts Polyethyleneimine (manufactured by Nippon Shokubai Co., Ltd., number average molecular weight 300): See Table 2 Stearic acid: See Table 2 Stearamide: 0.3 parts Butyl stearate: 6 .0 part Methyl ethyl ketone: 110.0 parts Cyclohexanone: 110.0 parts Polyisocyanate (Coronate (registered trademark) L manufactured by Tosoh Corporation): 3.0 parts

(Preparation method)
Various components of the above magnetic liquid were dispersed for 24 hours using zirconia beads (first dispersion beads, density 6.0 g/cm ³ ) with a bead diameter of 0.5 mm in a batch-type vertical sand mill (first stage ), followed by filtration using a filter with a pore size of 0.5 μm to prepare Dispersion A. The zirconia beads were used in an amount 10 times the mass of the ferromagnetic powder.
After that, the dispersion liquid A was dispersed in a batch-type vertical sand mill using diamond beads with a bead diameter of 500 nm (second dispersion beads, density 3.5 g/cm ³ ) for 1 hour (second step), followed by centrifugation. A dispersion liquid (dispersion liquid B) was prepared by separating the diamond beads using a vessel. The amount of diamond beads used was 10 times the mass of the ferromagnetic powder.
Dispersion B obtained above, the abrasive liquid and the above-mentioned other components were introduced into a dissolver stirrer and stirred for 360 minutes at a peripheral speed of 10 m/sec. Then, after performing ultrasonic dispersion treatment for 60 minutes at a flow rate of 7.5 kg/min using a flow-type ultrasonic disperser, the mixture was filtered three times through a filter with a pore size of 0.3 μm to prepare a composition for forming a magnetic layer.

<Preparation of composition for forming non-magnetic layer>
Various components of the following composition for forming a non-magnetic layer were dispersed for 24 hours in a batch-type vertical sand mill using zirconia beads with a bead diameter of 0.1 mm, and then filtered using a filter with a pore diameter of 0.5 μm. A composition for forming a non-magnetic layer was prepared by filtration.

Non-magnetic inorganic powder α-iron oxide: 100.0 parts (average particle size 10 nm, BET specific surface area 75 m ² /g)
Carbon black: 25.0 parts (average particle size 20 nm)
SO ₃ Na group-containing polyurethane resin: 18.0 parts (weight average molecular weight 70000, SO ₃ Na group content 0.2 meq/g)
Stearic acid: 1.0 parts Cyclohexanone: 300.0 parts Methyl ethyl ketone: 300.0 parts

<Preparation of Composition for Forming Backcoat Layer>
Of the various components of the composition for forming a backcoat layer described below, components other than lubricants (stearic acid and butyl stearate), polyisocyanate and 200.0 parts of cyclohexanone were kneaded and diluted in an open kneader, and then dispersed in a horizontal bead mill. Using zirconia beads with a bead diameter of 1 mm, 12 passes of dispersion treatment were performed with a bead filling rate of 80% by volume, a rotor tip peripheral speed of 10 m/sec, and a residence time of 2 minutes per pass. Thereafter, the remaining components were added and stirred with a dissolver, and the resulting dispersion was filtered through a filter having a pore size of 1 μm to prepare a composition for forming a backcoat layer.

Non-magnetic inorganic powder α-iron oxide: 80.0 parts (average particle size 0.15 μm, BET specific surface area 52 m ² /g)
Carbon black: 20.0 parts (average particle size 20 nm)
Vinyl chloride copolymer: 13.0 parts Sulfonic acid group-containing polyurethane resin: 6.0 parts Phenylphosphonic acid: 3.0 parts Cyclohexanone: 155.0 parts Methyl ethyl ketone: 155.0 parts Stearic acid: 3.0 parts Stearic acid Butyl: 3.0 parts Polyisocyanate: 5.0 parts Cyclohexanone: 200.0 parts

<Production of magnetic tape and magnetic tape cartridge>
On the surface of the biaxially stretched support shown in Table 2 having a thickness of 4.2 μm, the non-magnetic layer-forming composition prepared above was coated and dried so as to give a thickness of 0.6 μm after drying. A non-magnetic layer was formed.
Next, the composition for forming a magnetic layer prepared above was coated on the non-magnetic layer so that the thickness after drying was 0.1 μm to form a coating layer.
Thereafter, while the coating layer of the composition for forming the magnetic layer is in a wet state, a magnetic field with a magnetic field strength of 0.3 T is applied in a direction perpendicular to the surface of the coating layer to perform a vertical alignment treatment, followed by drying. A magnetic layer was formed.
After that, the composition for forming a backcoat layer prepared above was coated on the surface of the support opposite to the surface on which the non-magnetic layer and the magnetic layer were formed, and dried so as to give a thickness of 0.3 μm after drying. to form a back coat layer.
After that, using a calender roll composed only of metal rolls, the surface is smoothed (calendered) at a speed of 100 m / min, a linear pressure of 294 kN / m, and a calender temperature of 90 ° C. (surface temperature of the calender roll). did Thus, a long magnetic tape raw material was obtained.
Then, after performing heat treatment for 36 hours at an ambient temperature of 70° C., the long magnetic tape original was slit into 1/2 inch width to obtain a magnetic tape.
By recording a servo signal on the magnetic layer of the obtained magnetic tape with a commercially available servo writer, a data band, a servo band, and a guide band are arranged in accordance with the LTO (Linear Tape-Open) Ultrium format, and the servo A magnetic tape having a servo pattern (timing-based servo pattern) arranged and shaped according to the LTO Ultrium format on the band was obtained. The servo pattern thus formed is a servo pattern according to the descriptions of JIS (Japanese Industrial Standards) X6175:2006 and Standard ECMA-319 (June 2001). The total number of servo bands is five, and the total number of data bands is four.
The magnetic tape (length 960 m) on which the servo signals were thus recorded was wound around the reel of a magnetic tape cartridge (LTO Ultrium 8 data cartridge).
In this way, a magnetic tape cartridge of Example A1 in which the magnetic tape was wound around the reel was produced.

It can be confirmed by the following method that the magnetic layer of the magnetic tape contains the compound containing the ammonium salt structure of the alkyl ester anion represented by the formula 1 formed by polyethyleneimine and stearic acid.
A sample is cut out from the magnetic tape, and X-ray photoelectron spectroscopic analysis is performed on the surface of the magnetic layer (measurement area: 300 μm×700 μm) using an ESCA device. Specifically, wide scan measurement is performed with an ESCA device under the following measurement conditions. In the measurement results, peaks are confirmed at the positions of the binding energy of the ester anion and the binding energy of the ammonium cation.
Apparatus: Shimadzu AXIS-ULTRA
Excitation X-ray source: Monochromatic Al-Kα ray Scan range: 0 to 1200 eV
Pass energy: 160 eV
Energy resolution: 1 eV/step
Acquisition time: 100ms/step
Cumulative count: 5
In addition, a sample piece with a length of 3 cm was cut from the magnetic tape, and the surface of the magnetic layer was subjected to ATR-FT-IR (attenuated total reflection-fourier transform-infrared spectrometer) measurement ( ^reflection method). (1540 cm ⁻¹ or 1430 cm ⁻¹ ) and a wave number (2400 cm ⁻¹ ) corresponding to the absorption of ammonium cations.

[Examples A2 to A12, Examples B1 to B11]
A magnetic tape and a magnetic tape cartridge were obtained by the method described for Example A1, except that the items shown in Table 2 were changed as shown in Table 2.
In Examples A2 to A12, Examples B2 to B4 and B6 to B11, polyethyleneimine and stearic acid were added as other components in the preparation of the magnetic layer forming compositions in the same manner as in Example A1. In Examples B1 and B5, stearic acid was added as another component in the preparation of the magnetic layer-forming composition in the same manner as in Example A1, but polyethyleneimine was not added. In Examples B1 to B8, magnetic layer-forming compositions were prepared using abrasive solutions prepared without adding polyethylenimine and stearic acid.

For each of the above examples, three magnetic tape cartridges were produced, one was used for the evaluation of deterioration in electromagnetic conversion characteristics described below, one was used for the evaluation of recording and reproduction performance described below, and the other was used for evaluation. was used to evaluate the following magnetic tapes.

[Evaluation regarding deterioration of electromagnetic conversion characteristics (SNR (Signal-to-Noise-Ratio) reduction amount)]
The amount of SNR decrease was obtained as an evaluation of the decrease in electromagnetic conversion characteristics by the following method. The following recording and reproduction were performed using a 1/2 inch reel tester with a fixed magnetic head.
The magnetic tape (total length of magnetic tape: 960 m) of each example was subjected to 1,500 passes of recording and reproduction by applying a tension of 2.0 N in the longitudinal direction of the magnetic tape in an environment of a temperature of 23° C. and a relative humidity of 50%. The relative speed between the magnetic tape and the magnetic head was 8 m/sec, and recording was performed using a MIG (Metal-in-gap) head (gap length 0.15 μm, track width 1.0 μm) as the recording head, and recording current was The optimum recording current was set for each magnetic tape. Reproduction was performed using a GMR (Giant-Magnetoresistive) head (element thickness: 15 nm, shield interval: 0.1 μm, reproduction element width: 0.8 μm). A signal with a linear recording density of 300 kfci was recorded, and the reproduced signal was measured with a spectrum analyzer manufactured by Shibasoku. The unit kfci is the unit of linear recording density (cannot be converted to the SI unit system). As the signal, a portion where the signal was sufficiently stabilized after the magnetic tape started running was used.
After running, the magnetic tape was stored for 24 hours in an environment with a temperature of 23° C. and a relative humidity of 50%, and then recording and reproduction were performed under the same conditions as above within 1 hour.
The difference between the SNR of the 100th pass before storage and the SNR of the 100th pass after storage (SNR of 100th pass before storage - SNR of 100th pass after storage) was calculated and used as the SNR decrease amount.

[Evaluation of recording/playback performance]
Evaluation of recording/reproducing performance was performed using a magnetic tape device having the configuration shown in FIG. The recording/reproducing head mounted on the recording/reproducing head unit 12 has 32 or more channels of reproducing elements (reproducing element width: 0.8 μm) and recording elements, and has servo signal reading elements on both sides thereof.
The magnetic tape cartridge of each example was placed in an environment with an ambient temperature of 23° C. and a relative humidity of 50% for 5 days or more. After acclimatizing to the environment in this way, data was recorded as follows in the same environment.
Set the magnetic tape cartridge in the magnetic tape device and load the magnetic tape. Next, pseudo-random data having a specific data pattern is recorded on the magnetic tape by the recording/reproducing head unit while performing servo tracking. At that time, the tension applied in the longitudinal direction of the tape is 0.7N. In data recording, three or more reciprocations are performed so that the difference in the value of (PES1+PES2)/2 between adjacent tracks is 1.16 μm. Simultaneously with data recording, the value of the servo band interval over the entire length of the tape is measured every 1 m of the longitudinal position and recorded in the cartridge memory.
The magnetic tape cartridge on which data was recorded as described above was placed in a storage environment with an ambient temperature of 60° C. and a relative humidity of 20% for 72 hours.
After that, the magnetic tape cartridge was placed in an environment with an ambient temperature of 23° C. and a relative humidity of 50% for 5 days or longer. After acclimatization to the environment, the data was reproduced in the same environment as follows.
Set the magnetic tape cartridge in the magnetic tape device and load the magnetic tape. Next, while performing servo tracking, the data recorded on the magnetic tape is reproduced by the recording/reproducing head unit. At that time, the value of the servo band interval is measured at the same time as the reproduction. Adjust the tension in the direction. During playback, measurement of the servo band interval and adjustment of tension based thereon are continuously performed in real time. In each example, the tension values used by the controller 11 for the above tension adjustments ranged from 0.2 to 1.2N.
The number of channels in the above playback is 32 channels, and the recording/playback performance is evaluated as "3" when the data of all 32 channels are correctly read during playback, and the recording is performed when the data of the 31st to 28th channels are correctly read. The reproduction performance was evaluated as "2", and the other cases were evaluated as the recording and reproduction performance as "1".

[Evaluation of magnetic tape]
(1) AlFeSil wear value 1, AlFeSil wear value 2, AlFeSil wear value change rate before and after storage (AlFeSil wear value 2/AlFeSil wear value 1)
The magnetic tape was taken out from the magnetic tape cartridge of each example, and the AlFeSil abrasion value 1 and the AlFeSil abrasion value 2 were determined in an environment of temperature 23° C. and relative humidity 50% by the method described above. As the LTO8 head, a commercially available LTO8 head (manufactured by IBM) was used. From the obtained AlFeSil wear value 1 and AlFeSil wear value 2, the rate of change in AlFeSil wear value before and after storage (AlFeSil wear value 2/AlFeSil wear value 1) was calculated.

(2) Tape thickness Ten tape samples (5 cm in length) were cut out from an arbitrary portion of the magnetic tape taken out from the magnetic tape cartridge of each example, and these tape samples were stacked to measure the thickness. Thickness measurements were made using a MARH Millimar 1240 compact amplifier and a Millimar 1301 inductive probe digital thickness gauge. The value (thickness per tape sample) obtained by dividing the measured thickness by 1/10 was taken as the tape thickness. Each magnetic tape had a tape thickness of 5.2 μm.

The above results are shown in Table 2 (Tables 2-1 and 2-2).

From the results shown in Table 2, the following points can be confirmed.
The magnetic tapes of Examples A1 to A12 and B9 to B11 in which the AlFeSil abrasion value change rate (AlFeSil abrasion value 2/AlFeSil abrasion value 1) before and after storage is 0.7 or more adjusts the tension applied to the magnetic tape in the longitudinal direction. Therefore, it can be confirmed that the magnetic tape can suppress the deterioration of the electromagnetic conversion characteristics in the magnetic tape device for controlling the dimension of the magnetic tape in the width direction. This result is due to the fact that in the magnetic tapes of Examples A1 to A24 and Examples B9 to B11, the polishing force on the surface of the magnetic tape, which had decreased due to repeated running, could be brought close to the state before the decrease in a short period of time. The inventor of the present invention conjectures that
From the comparison between Examples A1 to A12 and Examples B1 to B11, the magnetic tape including a polyethylene naphthalate support having a Young's modulus in the width direction of 10000 MPa or more as a non-magnetic support adjusts the tension applied in the longitudinal direction of the magnetic tape. Therefore, it can be confirmed that the magnetic tape can be suitably used in a magnetic tape device for controlling the dimension in the width direction of the magnetic tape.

A magnetic tape cartridge was produced in the same manner as in Example A1, except that no vertical alignment treatment was performed during the production of the magnetic tape.
A sample piece was cut out from the magnetic tape taken out from the magnetic tape cartridge. The squareness ratio in the vertical direction of this sample piece was found to be 0.55 by using the TM-TRVSM5050-SMSL model manufactured by Tamagawa Seisakusho as a vibrating sample magnetometer by the method described above.
A magnetic tape was taken out from the magnetic tape cartridge of Example A1, and the vertical squareness ratio of a sample piece cut out from this magnetic tape was similarly determined to be 0.60.

The magnetic tapes taken out from the above two magnetic tape cartridges were each attached to a 1/2 inch reel tester, and the electromagnetic conversion characteristics (SNR: Signal-to-Noise Ratio) were evaluated by the following method. As a result, a 2 dB higher SNR value was obtained for the magnetic tape taken out from the magnetic tape cartridge of Example A1 than for the magnetic tape produced without the perpendicular orientation treatment.
Ten passes of recording and reproduction were performed by applying a tension of 0.7 N in the longitudinal direction of the magnetic tape in an environment of 23° C. and 50% relative humidity. The relative speed between the magnetic tape and the magnetic head was 6 m/sec, and recording was performed using a MIG (Metal-in-gap) head (gap length 0.15 μm, track width 1.0 μm) as a recording head, and recording current. The optimum recording current was set for each magnetic tape. Reproduction was performed using a GMR (Giant-Magnetoresistive) head (element thickness: 15 nm, shield interval: 0.1 μm, reproduction element width: 0.8 μm). A signal with a linear recording density of 300 kfci was recorded, and the reproduced signal was measured with a spectrum analyzer manufactured by Shibasoku. The unit kfci is the unit of linear recording density (cannot be converted to the SI unit system). As the signal, a portion where the signal was sufficiently stabilized after the magnetic tape started running was used.

One aspect of the present invention is useful in various data storage technical fields.

Claims

A magnetic tape having a non-magnetic support and a magnetic layer containing ferromagnetic powder,
The non-magnetic support is a polyethylene naphthalate support having a Young's modulus in the width direction of 10,000 MPa or more, and stores the AlFeSil wear value measured on the surface of the magnetic layer in an environment with a temperature of 23° C. and a relative humidity of 50%. The rate of change before and after, AlFeSil wear value 2/AlFeSil wear value 1, is 0.7 or more,
The AlFeSil abrasion value 1 is an AlFeSil abrasion value measured by applying a tension of 2.0 N in the longitudinal direction of the magnetic tape,
The AlFeSil abrasion value 2 was obtained by sliding the magnetic tape after the measurement of the AlFeSil abrasion value 1 back and forth against an LTO8 head 1500 times, storing the magnetic tape for 24 hours, and applying a tension of 2.0 N in the longitudinal direction of the magnetic tape. magnetic tape, which is an AlFeSil wear value measured by
2. The magnetic tape according to claim 1, wherein said AlFeSil wear value 2/AlFeSil wear value 1 is 0.7 or more and 1.0 or less.
2. The magnetic tape of claim 1, wherein the magnetic layer further comprises one or more non-magnetic powders.
4. The magnetic tape of claim 3, wherein the non-magnetic powder includes alumina powder.
2. The magnetic tape according to claim 1, further comprising a non-magnetic layer containing non-magnetic powder between said non-magnetic support and said magnetic layer.
2. The magnetic tape according to claim 1, further comprising a back coat layer containing a non-magnetic powder on the surface side opposite to the surface side having the magnetic layer of the non-magnetic support.
2. The magnetic tape according to claim 1, wherein the tape thickness is 5.2 [mu]m or less.
2. The magnetic tape according to claim 1, wherein the polyethylene naphthalate support has a Young's modulus in the width direction of 10000 MPa or more and 20000 MPa or less.
2. The magnetic tape of claim 1, having a vertical squareness ratio of 0.60 or more.
A magnetic tape cartridge containing the magnetic tape according to any one of claims 1 to 9.
A magnetic tape device comprising the magnetic tape according to any one of claims 1 to 9.
12. The magnetic tape device according to claim 11, further comprising a tension adjusting mechanism capable of adjusting tension applied to the magnetic tape running in the magnetic tape device in the longitudinal direction.