JP7357745B2 - magnetic tape cartridge - Google Patents

Description

The present invention relates to magnetic tape cartridges.

There are two types of magnetic recording media: tape-shaped and disk-shaped. Tape-shaped magnetic recording media, that is, magnetic tape, are mainly used for data storage applications such as data backup and archiving (for example, patent documents (see 1).

To record and reproduce signals on magnetic tape, a magnetic tape cartridge containing magnetic tape wound on a reel is usually set in a magnetic tape device called a drive, and the magnetic tape is run within the magnetic tape device to create a tape. This is performed by bringing the surface (magnetic layer surface) and the magnetic head into contact and sliding them.

Japanese Patent Application Publication No. 2005-346865

Information is usually recorded on a magnetic tape by recording magnetic signals on a data band of the magnetic tape. As a result, data tracks are formed in the data band.
On the other hand, when reproducing recorded information, a magnetic tape is run within a magnetic tape device, a magnetic head is made to follow a data track of the magnetic tape, and information recorded on the data track is read. If the precision with which the magnetic head follows the data track is low, reproduction errors are likely to occur.

Incidentally, with the enormous increase in the amount of information in recent years, magnetic tapes are required to have an increased recording capacity (higher capacity). Means for increasing the capacity include reducing the thickness of the magnetic tape (hereinafter also referred to as "thinning") and increasing the length of the magnetic tape accommodated in each magnetic tape cartridge. However, according to studies conducted by the present inventors, it has been found that when the thickness of a magnetic tape is made thinner, reproduction errors are more likely to occur.

SUMMARY OF THE INVENTION An object of the present invention is to make it possible to simultaneously reduce the thickness of a magnetic tape and suppress the occurrence of playback errors.

One aspect of the present invention is
A single-reel type magnetic tape cartridge in which magnetic tape is wound on a reel,
The above magnetic tape is
having a magnetic layer containing ferromagnetic powder and a binder on a non-magnetic support;
The tape thickness is 5.2 μm or less, and the tape width difference (B-A) between tape width A at a position of 10 m ± 1 m from the outside end of the tape and tape width B at a position of 50 m ± 1 m from the inside end of the tape is A magnetic tape cartridge, which is 2.4 μm or more and 12.0 μm or less, and the tape width A and the tape width B are values on the 100th day from the date of manufacture of the magnetic tape cartridge;
Regarding.

In one embodiment, the magnetic tape is stored in a dry environment at a temperature of 52° C. for 24 hours with a load of 100 g applied in the longitudinal direction of the tape, and then the tape width deformation is measured within 20 minutes after the load is removed. The rate can be 400 ppm or less. The above-mentioned tape width deformation rate is a value obtained when the above-mentioned storage was started on the 100th day from the date of manufacture of the magnetic tape cartridge.

In one embodiment, the magnetic tape may have a nonmagnetic layer containing a nonmagnetic powder and a binder between the nonmagnetic support and the magnetic layer.

In one aspect, the magnetic tape may have a back coat layer containing nonmagnetic powder and a binder on the surface side of the nonmagnetic support opposite to the surface side having the magnetic layer.

In one aspect, the non-magnetic support can be a polyethylene naphthalate support.

In one aspect, the nonmagnetic support can be an aromatic polyamide support.

In one aspect, the non-magnetic support can be a polyethylene terephthalate support.

According to one aspect of the present invention, there is provided a magnetic tape cartridge including a thinned magnetic tape having a tape thickness of 5.2 μm or less, the magnetic tape cartridge capable of suppressing the occurrence of reproduction errors during reproduction of information recorded on the magnetic tape. A tape cartridge can be provided.

[Magnetic tape cartridge]
One aspect of the present invention is a single-reel magnetic tape cartridge in which a magnetic tape is wound on a reel, the magnetic tape having a magnetic layer containing ferromagnetic powder and a binder on a non-magnetic support. However, the tape thickness is 5.2 μm or less, and the tape width difference (B-A ) is 2.4 μm or more and 12.0 μm or less, and the tape width A and the tape width B are values on the 100th day from the date of manufacture of the magnetic tape cartridge.

One of the causes of playback errors when playing back information recorded on magnetic tape is that the widthwise dimension of the magnetic tape changes over time between the time information is recorded on the magnetic tape and the time it is played back. can be mentioned. Regarding dimensional changes in the width direction of a magnetic tape, Patent Document 1 (Japanese Unexamined Patent Application Publication No. 2005-346865) mentioned above proposes increasing dimensional stability by providing a reinforcing layer (for example, Patent Document 1) 1, paragraphs 0014 and 0054). This proposal can be said to be aimed at providing a magnetic tape that is difficult to deform.
In response to this, the inventors of the present invention have made the following new findings as a result of intensive studies on dimensional changes of magnetic tapes housed in magnetic tape cartridges.
A magnetic tape cartridge is manufactured by slitting a long magnetic tape material into a predetermined width and winding and storing the magnetic tape on a reel of the magnetic tape cartridge. Cartridge configurations include a single reel type with one reel and a twin reel type with two reels, and single reel type magnetic tape cartridges have been widely used in recent years. The inventors of the present invention conducted extensive studies on the deformation of magnetic tape over time within a single-reel magnetic tape cartridge, and found that the part near the reel (inner part) becomes wider than it was initially due to compressive stress in the tape thickness direction. The thinner magnetic tape (specifically, tape It has become clear that this problem occurs significantly when the thickness is 5.2 μm or less. The reason for this is that as the magnetic tape becomes thinner, even if the tension applied to the magnetic tape is the same, the compressive stress or tensile stress applied to each position of the magnetic tape becomes larger; As a result, it is speculated that deformation to become wider or narrower than the above-mentioned initial stage is likely to occur. Further, as magnetic tapes are made thinner to increase capacity and the length of magnetic tape accommodated in one magnetic tape cartridge becomes longer, the number of turns of magnetic tape in a magnetic tape cartridge increases. As a result, the inner part of the magnetic tape (the part closer to the reel) is thought to be compressed more strongly, and as a result, the above-mentioned phenomenon of the inner part deforming into a wider width than initially occurs will occur more noticeably. It is inferred.
Based on the above findings, the present inventors discovered that the magnetic tape deforms differently depending on the position as described above from the time of recording (data track formation), which makes it difficult to make the magnetic head follow the data track. I came to think that this was the cause of the playback error.
Therefore, the inventors of the present invention have proposed that if the deformation that can occur over time in a magnetic tape cartridge between recording and playback can be caused in advance, deformation that can occur over time between recording and playback can occur on a thinned magnetic tape. We thought that it would be possible to suppress the occurrence of reproduction errors caused by the above-mentioned deformation, and we conducted further intensive studies. This study was based on a technical idea that was clearly different from the conventional technical idea, which was aimed at providing a magnetic tape that was difficult to deform. As a result, the present inventors deformed the magnetic tape cartridge in advance so that the tape width difference (B-A) was 2.4 μm or more and 12.0 μm or less on the 100th day from the manufacturing date of the magnetic tape cartridge. The inventors have discovered that it is possible to suppress the occurrence of reproduction errors when reproducing information recorded on a thin magnetic tape having a tape thickness of 5.2 μm or less, and have completed one aspect of the present invention. The reason why the 100th day from the manufacturing date of the magnetic tape cartridge was adopted as the reference date is that in conventional magnetic tape cartridges, the above tape width difference (B-A) is 2.4 μm as of 100 days from the manufacturing date of the magnetic tape cartridge. This is because such deformation as above does not occur.
However, the above description includes speculations made by the present inventors. In addition, the descriptions below also include speculations made by the present inventors. The present invention is not limited to such speculation.
The magnetic tape cartridge will be explained below.

<Configuration of magnetic tape cartridge>
The above magnetic tape cartridge is a single reel type magnetic tape cartridge. In a single-reel magnetic tape cartridge, magnetic tape is wound around a single reel. As for the configuration of the magnetic tape cartridge, known techniques related to single-reel type magnetic tape cartridges can be applied.

<Magnetic tape>
(Tape width difference (B-A))
The magnetic tape included in the magnetic tape cartridge has a tape width difference (B-A) of 2 between the tape width A at a position of 10 m±1 m from the outer end of the tape and the tape width B at a position of 50 m±1 m from the inner end of the tape. .4 μm or more and 12.0 μm or less. The above tape width A and tape width B are the values on the 100th day from the date of manufacture of the magnetic tape cartridge.
Individual identification information (ID (identification) information) such as the manufacturing date is recorded on the magnetic tape cartridge for product management. In the present invention and this specification, the "magnetic tape cartridge manufacturing date" refers to the manufacturing date recorded on the magnetic tape cartridge. Such information is usually recorded on an RFID (Radio Frequency Identifier) tag inside the cartridge, and by reading the RFID tag, the manufacturing date (usually recorded as the "Date of Manufacturer") can be recognized. be able to. For a magnetic tape cartridge whose tape width difference (B-A) on the 100th day from the date of manufacture of the magnetic tape cartridge is within the above range, recording of information on the magnetic tape contained in this magnetic tape cartridge and recorded information Regeneration may be performed on any day less than 100 days, on the 100th day, or on any day greater than 100 days from the date of manufacture of the magnetic tape cartridge. Magnetic tape cartridges with the same product lot number are usually manufactured using the same raw materials and under the same manufacturing conditions, so the tape width difference (B- A) can be considered to have the same value. The above points also apply to various physical properties described below.
In addition, the part of the magnetic tape on which various physical properties such as tape width difference (B-A) are measured is joined to the area where information is recorded and/or reproduced by a joining means such as splicing tape. parts shall not be taken into account. For example, a leader tape may be attached to the outer tape end of a magnetic tape for withdrawing and winding the magnetic tape from a magnetic tape cartridge. In such a case, the leader tape is not considered as part of the magnetic tape on which various physical properties such as tape width difference (BA) are measured. Therefore, when the leader tape is spliced, the tape outer end of the magnetic tape is the end of the magnetic tape on the side to which the leader tape is spliced.

The outer end of the tape mentioned above is the end of the magnetic tape wound on the reel that is farthest from the reel, and the tape width A at a position 10 m ± 1 m from the outer end of the tape becomes stronger over time and becomes wider than the initial width. It represents the tape width at the part where it deforms. On the other hand, the inner end of the tape mentioned above is the end of the starting point for winding onto the reel, and the tape width B at a position 50 m ± 1 m from the inner end of the tape is strongly compressed over time and deforms to be wider than the initial position. It represents the tape width of the section.
A magnetic tape cartridge is manufactured by slitting a long magnetic tape material into a specified width, winding the resulting magnetic tape onto a reel, and storing the tape in a magnetic tape cartridge. The specified width is typically 1/2 inch (0.0127 meters), and the width of the slit magnetic tape is the same at each location. For equal widths, manufacturing errors that normally occur in the slitting process are allowed. On the other hand, as described above, it is thought that the magnetic tape undergoes different deformations depending on the position over time during the period from recording to reproduction. However, in conventional magnetic tape cartridges, on the 100th day from the date of manufacture of the magnetic tape cartridge, the tape width difference (B-A) between tape width A and tape width B is 2.4 μm or more. No deformation occurs. In contrast, by causing deformation in advance such that the tape width difference (B-A) becomes 2.4 μm or more on the 100th day from the date of manufacture of the magnetic tape cartridge, the magnetic tape can be deformed between recording and playback. It is thought that it is possible to suppress the occurrence of reproduction errors caused by the deformation that occurs depending on the position as described above over time. On the other hand, if the difference in tape width between the inner and outer portions of a magnetic tape before information is recorded is too large, errors are likely to occur during recording. On the other hand, if the tape width difference (B-A) is 12.0 μm or less on the 100th day from the date of manufacture of the magnetic tape cartridge, information can be easily recorded over the entire length of the magnetic tape housed in the magnetic tape cartridge. can be done. From the viewpoint of further suppressing the occurrence of reproduction errors, the tape width difference (BA) is preferably 3.0 μm or more, more preferably 5.0 μm or more. On the other hand, from the viewpoint of further suppressing the occurrence of errors during recording, the tape width difference (BA) is preferably 11.0 μm or less.

The above tape width difference (BA) is a value determined by the following method. The following operations and measurements are performed in an environment with a temperature of 20-25° C. and a relative humidity of 40-60%.
A magnetic tape wound on a reel was removed from a magnetic tape cartridge 100 days after the manufacturing date of the magnetic tape cartridge, and a tape sample with a length of 20 cm including a position 10 m ± 1 m from the outer end of the tape and 50 m from the inner end of the tape was obtained. Cut out a tape sample with a length of 20 cm including positions of ±1 m. The tape width of each tape sample is measured at the center in the longitudinal direction of the tape sample while being sandwiched between plate-like members (for example, glass slides) in order to eliminate the influence of curl. The tape width can be measured using a known measuring device capable of measuring dimensions with an accuracy of 0.1 μm order. Further, the measurement is performed within 20 minutes after removing the magnetic tape from the magnetic tape cartridge. For each tape sample above, the tape width was measured seven times (N = 7), and the arithmetic mean of the five measured values excluding the maximum and minimum values obtained from the seven measurements was calculated. demand. If the total length of the magnetic tape housed in the magnetic tape cartridge is 950 m, the arithmetic mean thus determined is taken as the tape width at each position (tape width A or tape width B). On the other hand, if the total length of the magnetic tape housed in the magnetic tape cartridge is other than 950 m, the following formula is obtained, where the total length of the magnetic tape is L1 (unit: m) and the arithmetic mean obtained above is W1:
W=(950/L1)×W1
Let W determined by the above be the tape width (tape width A or tape width B) at each position. The tape width difference (BA) can be controlled by heat treatment. Details of the heat treatment will be described later.

(Tape width deformation rate)
As mentioned above, the magnetic tape having a tape width difference (B-A) of 2.4 μm or more and 12.0 μm or less on the 100th day from the date of manufacture of the magnetic tape cartridge preferably has a tape width deformation rate determined by the following method. It can be 400 ppm (parts per million) or less, more preferably 390 ppm or less, even more preferably 380 ppm or less, even more preferably 370 ppm or less, even more preferably 360 ppm or less, It is even more preferable that the content is 350 ppm or less. The tape width deformation rate can be, for example, 10 ppm or more, 100 ppm or more, 150 ppm or more, 200 ppm or more, or 250 ppm or more. It is considered that the smaller the tape width deformation rate, the smaller the dimensional change in the width direction of the magnetic tape during the period from recording information to the magnetic tape to reproducing it. Therefore, from the viewpoint of further suppressing the occurrence of reproduction errors caused by changes in tape width between recording and reproduction, the magnetic tape width deformation rate is preferably as small as possible, and may be 0 ppm. The above tape width deformation rate can also be controlled by heat treatment, which will be described in detail later.

The above tape width deformation rate is a value determined by the following method. The following operations and measurements are performed in an environment with a temperature of 20 to 25° C. and a relative humidity of 40 to 60%, except for the storage described below.
Take out the magnetic tape wound on a reel from a magnetic tape cartridge 100 days after the manufacturing date of the magnetic tape cartridge, cut out a tape sample with a length of 20 cm including a position 10 m ± 1 m from the outer end of the tape, and cut the tape by the above method. Find the width. This tape width is defined as the tape width before storage. This tape width before storage is the value of the tape sample used to determine the tape width difference (B-A) (that is, the tape width A determined above) or the tape width difference (B-A). ) is the value determined for a tape sample cut out from the same magnetic tape as the tape sample used to determine the distance 10 m±1 m from the outer end of the tape.
A tape sample with a length of 20 cm for which the tape width before storage was determined was held at one end of the tape sample and a 100 g weight was suspended from the other end to apply a load of 100 g in the longitudinal direction of the tape. Store in a dry environment at a temperature of 52°C for 24 hours. A dry environment is an environment with a relative humidity of 10% or less. The storage begins on the 100th day from the date of manufacture of the magnetic tape cartridge. After storage and within 20 minutes after removing the load, measure the tape width (arithmetic mean of 5 measurements excluding the maximum and minimum values obtained in 7 measurements) using the same method as above. demand. This tape width is defined as the tape width after storage.
The value obtained by dividing the difference in tape width before and after storage (tape width before storage - tape width after storage) by the tape width before storage x 10 ⁶ (unit: ppm) is defined as the tape width deformation rate.

The magnetic tape included in the magnetic tape cartridge will be described in more detail below.

(tape thickness)
The thickness (total thickness) of the magnetic tape is 5.2 μm or less. It is preferable to make the magnetic tape thinner because it leads to higher capacity. However, magnetic tapes that have been thinned to a thickness of 5.2 μm or less tend to deform differently depending on the position within the magnetic tape cartridge over time if no measures are taken, as described above. The inventors believe that this is the cause of playback errors. On the other hand, the above-mentioned magnetic tapes with a tape width difference (B-A) of 2.4 μm or more and 12.0 μm or less on the 100th day from the magnetic tape cartridge manufacturing date are It can be said to be a magnetic tape that has undergone deformation that may occur over time. This makes it possible to suppress the occurrence of reproduction errors when reproducing information recorded on a thin magnetic tape having a tape thickness of 5.2 μm or less. From the viewpoint of further increasing capacity, the thickness of the magnetic tape is preferably 5.0 μm or less, more preferably 4.8 μm or less. Further, 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 above tape thickness is a value determined by the following method.
Take out the magnetic tape wound on a reel from a magnetic tape cartridge 100 days after the manufacturing date of the magnetic tape cartridge, cut out 10 tape samples (for example, 5 to 10 cm in length) from any part of this magnetic tape, and cut them out. Stack the tape samples and measure the thickness. The value obtained by dividing the measured thickness by one-tenth (thickness per tape sample) is defined as the tape thickness. The thickness measurement described above can be performed using a known measuring device capable of measuring thickness on the order of 0.1 μm. This tape thickness may be determined using the magnetic tape used to determine the tape width difference (B-A) and/or the tape width deformation rate, or the tape width difference (B-A) and/or the tape width deformation rate. Alternatively, the tape width deformation rate may be determined using a magnetic tape taken out from a magnetic tape cartridge that has the same product lot number as the magnetic tape cartridge containing the magnetic tape used to determine the tape width deformation rate.
Further, various thicknesses such as the thickness of the magnetic layer can be determined by the following method.
After exposing a cross section of the magnetic tape in the thickness direction with an ion beam, the exposed cross section is observed using a scanning electron microscope. Various thicknesses can be determined as the arithmetic mean of the thicknesses determined at any two locations during cross-sectional observation. Alternatively, various thicknesses can also be determined as design thicknesses calculated from manufacturing conditions and the like.

(Non-magnetic support)
The magnetic tape has at least a nonmagnetic support and a magnetic layer. Examples of the nonmagnetic support (hereinafter also simply referred to as "support") include polyethylene naphthalate supports, polyamide supports, polyethylene terephthalate supports, polyamideimide supports, and the like. These supports are available as commercial products or can be manufactured by known methods. As the support, polyethylene naphthalate supports, polyamide supports, and polyethylene terephthalate supports are preferred from the viewpoints of strength, flexibility, and the like. A polyethylene naphthalate support means a support containing at least a polyethylene naphthalate layer, and includes a support consisting of a single layer or two or more polyethylene naphthalate layers, and a support comprising one or more other layers in addition to the polyethylene naphthalate layer. Includes what is included. This point also applies to other supports. Moreover, the polyamide can contain an aromatic skeleton and/or an aliphatic skeleton, and polyamide containing an aromatic skeleton (aromatic polyamide) is preferable, and aramid is more preferable. The support may be subjected to corona discharge, plasma treatment, adhesive treatment, heat treatment, etc. in advance.

(magnetic layer)
Ferromagnetic Powder The magnetic layer includes ferromagnetic powder and a binder. As the ferromagnetic powder contained in the magnetic layer, ferromagnetic powders known as ferromagnetic powders used in the magnetic layers of various magnetic recording media can be used. It is preferable to use ferromagnetic powder with a small average particle size from the viewpoint of improving recording density. From this point of view, 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 preferable that the particle diameter is 25 nm or less, even more preferably 20 nm or less. On the other hand, from the viewpoint of magnetization stability, the average particle size of the ferromagnetic powder is preferably 5 nm or more, more preferably 8 nm or more, even more preferably 10 nm or more, and still more preferably 15 nm or more. is more preferable, and even more preferably 20 nm or more.

-Hexagonal ferrite powder-
A preferred example of the ferromagnetic powder is hexagonal ferrite powder. For details on the hexagonal ferrite powder, see, for example, paragraphs 0012 to 0030 of JP2011-225417A, paragraphs 0134 to 0136 of JP2011-216149A, paragraphs 0013 to 0030 of JP2012-204726A, and Paragraphs 0029 to 0084 of Japanese Patent Application Publication No. 2015-127985 can be referred to.

In the present invention and this specification, "hexagonal ferrite powder" refers to a ferromagnetic powder in which a hexagonal ferrite type crystal structure is detected as the main phase by X-ray diffraction analysis. The main phase refers to a structure to which the most intense diffraction peak belongs in an X-ray diffraction spectrum obtained by X-ray diffraction analysis. For example, if the most intense diffraction peak in an X-ray diffraction spectrum obtained by X-ray diffraction analysis is attributed to a hexagonal ferrite crystal structure, it is determined that a hexagonal ferrite crystal structure has been detected as the main phase. shall be taken as a thing. When only a single structure is detected by X-ray diffraction analysis, this detected structure is taken as the main phase. The hexagonal ferrite type crystal structure includes at least iron atoms, divalent metal atoms, and oxygen atoms as constituent atoms. The divalent metal atom is a metal atom that can become a divalent cation as an ion, and includes alkaline earth metal atoms such as strontium atom, barium atom, and calcium atom, lead atom, and the like. In the present invention and this specification, hexagonal strontium ferrite powder refers to powder in which the main divalent metal atoms contained are strontium atoms, and hexagonal barium ferrite powder refers to powder in which the main divalent metal atoms contained in this powder are strontium atoms. The divalent metal atom is a barium atom. The main divalent metal atoms are the divalent metal atoms that account for the largest percentage on an atomic percent basis among the divalent metal atoms contained in this powder. However, the divalent metal atoms mentioned above do not include rare earth atoms. A "rare earth atom" in the present invention and herein is selected from the group consisting of scandium atom (Sc), yttrium atom (Y), and lanthanide atom. Lanthanoid atoms include lanthanum atom (La), cerium atom (Ce), praseodymium atom (Pr), neodymium atom (Nd), promethium atom (Pm), samarium atom (Sm), europium atom (Eu), and 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). Ru.

Below, hexagonal strontium ferrite powder, which is one embodiment of hexagonal ferrite powder, will be explained in more detail.

The activation volume of the hexagonal strontium ferrite powder is preferably in the range of 800 to 1500 nm ³ . Finely divided hexagonal strontium ferrite powder exhibiting an activation volume in the above range is suitable for producing a magnetic tape exhibiting excellent electromagnetic conversion characteristics. The activation volume of the hexagonal strontium ferrite powder is preferably 800 nm ³ or more, and can also be, for example, 850 nm ³ or more. Further, from the viewpoint of further improving electromagnetic conversion characteristics, the activated volume of the hexagonal strontium ferrite powder is more preferably 1400 nm ³ or less, even more preferably 1300 nm ³ or less, and 1200 nm ³ or less. is more preferable, and even more preferably 1100 nm ³ or less.

"Activation volume" is a unit of magnetization reversal and is an index indicating the magnetic size of a particle. The activation volume described in the present invention and this specification and the anisotropy constant Ku described later are measured using a vibrating sample magnetometer at magnetic field sweep speeds of 3 minutes and 30 minutes in the coercive force Hc measurement section (measurement Temperature: 23° C.±1° C.), a value determined from the following relational expression between Hc and activation volume V. Note that the unit of the anisotropy constant Ku is 1erg/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)]

The anisotropy constant Ku can be cited as an index of reduction in thermal fluctuation, in other words, improvement in 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. Moreover, Ku of the hexagonal strontium ferrite powder can be, for example, 2.5×10 ⁵ J/m ³ or less. However, since a higher Ku means higher thermal stability and is preferable, it is not limited to the values exemplified above.

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

When the hexagonal ferrite powder contains rare earth atoms, the rare earth atom content (bulk content) is preferably in the range of 0.5 to 5.0 atom % based on 100 atom % of iron atoms. It is believed that the uneven distribution of rare earth atoms in the surface layer of the particles constituting the hexagonal strontium ferrite powder, which contains rare earth atoms at a bulk content in the above range, contributes to suppressing the reduction in reproduction output during repeated reproduction. Conceivable. This is due to the fact that the hexagonal strontium ferrite powder contains rare earth atoms in the bulk content within 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. It is presumed that this is because it can increase the The higher the value of the anisotropy constant Ku, the more the phenomenon called thermal fluctuation can be suppressed (in other words, the thermal stability can be improved). By suppressing the occurrence of thermal fluctuations, it is possible to suppress a decrease in reproduction output during repeated reproduction. The uneven distribution of rare earth atoms in the particle surface of hexagonal strontium ferrite powder contributes to stabilizing the spin of iron (Fe) sites in the crystal lattice in the surface layer, which increases the anisotropy constant Ku. It is speculated that this will increase.
In addition, it is assumed that using hexagonal strontium ferrite powder, which has rare earth atoms unevenly distributed in the surface layer, as the ferromagnetic powder for the magnetic layer also contributes to suppressing the surface of the magnetic layer from being scraped by sliding with the magnetic head. Ru. That is, it is surmised that the hexagonal strontium ferrite powder having rare earth atoms unevenly distributed in the surface layer may also contribute to improving the running durability of the magnetic tape. This is due to the uneven distribution of rare earth atoms on the surface of the particles constituting the hexagonal strontium ferrite powder, which improves the interaction between the particle surface and the organic substances (e.g. binders and/or additives) contained in the magnetic layer. It is presumed that this is because the magnetic layer contributes to the strength of the magnetic layer, and as a result, the strength of the magnetic layer is improved.
From the viewpoint of further suppressing the decline in reproduction output during repeated reproduction and/or further improving running durability, the rare earth atom content (bulk content) is in the range of 0.5 to 4.5 at%. It is more preferably in the range of 1.0 to 4.5 atom %, even more preferably in the range of 1.5 to 4.5 atom %.

The above bulk content is the content determined by completely melting the hexagonal strontium ferrite powder. In the present invention and this specification, unless otherwise specified, the atomic content refers to the bulk content determined 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, or may contain two or more kinds of rare earth atoms. The above-mentioned bulk content when two or more types of rare earth atoms are included is calculated for the total of two or more types of rare earth atoms. This point also applies to other components in the present invention and this specification. That is, unless otherwise specified, one kind of a certain component may be used, or two or more kinds thereof may be used. When two or more types are used, the content or content rate refers to the total of the two or more types.

When the hexagonal strontium ferrite powder contains rare earth atoms, the rare earth atoms contained may be at least one kind of rare earth atoms. Preferred rare earth atoms from the viewpoint of further suppressing a decrease in reproduction output during repeated reproduction include neodymium atoms, samarium atoms, yttrium atoms, and dysprosium atoms, with neodymium atoms, samarium atoms, and yttrium atoms being more preferred; Atom is more preferred.

In the hexagonal strontium ferrite powder having rare earth atoms unevenly distributed in the surface layer, it is sufficient that the rare earth atoms are unevenly distributed in 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 that has rare earth atoms unevenly distributed in the surface layer, the surface layer content of rare earth atoms determined by partial melting under the melting conditions described below and the rare earth content determined by completely melting under the melting conditions described below. The ratio of atoms to the bulk content, "surface layer content/bulk content" is more than 1.0, and can be 1.5 or more. When the "surface layer content ratio/bulk content ratio" is larger than 1.0, it means that rare earth atoms are unevenly distributed in the surface layer (that is, more present than in the interior) in the particles that make up the hexagonal strontium ferrite powder. do. In addition, the ratio of the surface layer content of rare earth atoms determined by partial dissolution under the dissolution conditions described below and the bulk content of rare earth atoms determined by total dissolution under the dissolution conditions described below, ``surface layer content/ Bulk content" can be, for example, 10.0 or less, 9.0 or less, 8.0 or less, 7.0 or less, 6.0 or less, 5.0 or less, or 4.0 or less. However, in a hexagonal strontium ferrite powder having rare earth atoms unevenly distributed in the surface layer, it is sufficient that the rare earth atoms are unevenly distributed in the surface layer of the particles constituting the hexagonal strontium ferrite powder, and the above "surface layer content/bulk content" is sufficient. The "rate" is not limited to the illustrated upper or lower limits.

Partial and total dissolution of hexagonal strontium ferrite powder will be explained below. For hexagonal strontium ferrite powders that are present as powders, the partially dissolved and fully dissolved sample powders are taken from the same lot of powder. On the other hand, regarding 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 total melting. The hexagonal strontium ferrite powder can be taken out from the magnetic layer by, for example, the method described in paragraph 0032 of JP-A-2015-91747.
The above-mentioned partial dissolution means that the hexagonal strontium ferrite powder is dissolved 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, it is possible to dissolve a region of 10 to 20 mass % of the particles constituting the hexagonal strontium ferrite powder, assuming that the entire particle is 100 mass %. On the other hand, the above-mentioned complete dissolution means that the hexagonal strontium ferrite powder is dissolved to a state where no residual hexagonal strontium ferrite powder is visually confirmed in the liquid upon completion of dissolution.
The above-mentioned partial dissolution and measurement of the surface layer content are performed, for example, by the following method. However, the dissolution conditions such as the amount of sample powder described below are merely examples, and any dissolution conditions that allow partial dissolution and complete dissolution can be adopted as desired.
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 at a set temperature of 70° C. for 1 hour. The obtained solution is filtered through a 0.1 μm membrane filter. Elemental analysis of the filtrate thus obtained is performed using an inductively coupled plasma (ICP) analyzer. In this way, the content of rare earth atoms in the surface layer relative to 100 atom % of iron atoms can be determined. 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 content. This point also applies to the measurement of bulk content.
On the other hand, the measurement of the total dissolution and bulk content is performed, 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 at a set temperature of 80° C. for 3 hours. Thereafter, it is possible to determine the bulk content relative to 100 atom % of iron atoms by performing the same steps as the above-described partial dissolution and measurement of the surface layer content.

From the viewpoint of increasing reproduction output when reproducing information recorded on a magnetic tape, it is desirable that the mass magnetization σs of the ferromagnetic powder contained in the magnetic tape is high. In this regard, a hexagonal strontium ferrite powder that contains rare earth atoms but does not have rare earth atoms unevenly distributed in the surface layer tends to have a significantly lower σs than a hexagonal strontium ferrite powder that does not contain rare earth atoms. On the other hand, a hexagonal strontium ferrite powder having rare earth atoms unevenly distributed in the surface layer is considered to be preferable in order to suppress such a large decrease in σs. In one embodiment, the σs of the hexagonal strontium ferrite powder can be 45 A·m ² /kg or more, and can also be 47 A·m ² /kg or more. On the other hand, from the viewpoint of noise reduction, σs is preferably 80 A·m ² /kg or less, 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 1194 kA/m (15 kOe).

Regarding the content of the constituent atoms (bulk content) of the hexagonal ferrite powder, the strontium atom content can be in the range of, for example, 2.0 to 15.0 atom % based on 100 atom % of iron atoms. In one embodiment, the hexagonal strontium ferrite powder may contain only strontium atoms as divalent metal atoms. In another aspect, the hexagonal strontium ferrite powder can also contain one or more other divalent metal atoms in addition to strontium atoms. For example, it can contain barium atoms and/or calcium atoms. When divalent metal atoms other than strontium atoms are included, the barium atom content and calcium atom content in the hexagonal strontium ferrite powder are, for example, 0.05 to 5, respectively, relative to 100 at% of iron atoms. It can be in the range of .0 at.%.

As the crystal structure 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. Crystal structure can be confirmed by X-ray diffraction analysis. The hexagonal strontium ferrite powder may have a single crystal structure or two or more types of crystal structures detected by X-ray diffraction analysis. For example, in one embodiment, the hexagonal strontium ferrite powder can have only an M-type crystal structure detected by X-ray diffraction analysis. For example, M-type hexagonal ferrite is represented by the composition formula 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 multiple divalent metal atoms, As mentioned above, strontium atoms (Sr) account for the largest amount on an atomic percent 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 further suppressing the reduction in playback output during repeated playback, 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 iron atoms. %, it is preferably 10.0 atom % or less, more preferably in the range of 0 to 5.0 atom %, and may be 0 atom %. That is, in one embodiment, the hexagonal strontium ferrite powder may not contain 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 melting the hexagonal strontium ferrite powder, and is converted to the value expressed in atomic % using the atomic weight of each atom. It can be calculated by converting. Furthermore, in the present invention and this specification, "not containing" an atom means that the content thereof as measured by an ICP analyzer after being completely dissolved is 0% by mass. The detection limit of an ICP analyzer is usually 0.01 ppm (parts per million) or less on a mass basis. The above-mentioned "does not contain" is used to mean that it is contained in an amount below the detection limit of the ICP analyzer. In one embodiment, the hexagonal strontium ferrite powder can be free of bismuth atoms (Bi).

-Metal powder-
A preferable specific example of the ferromagnetic powder is a ferromagnetic metal powder. For details of the ferromagnetic metal powder, reference can be made to, for example, paragraphs 0137 to 0141 of JP-A No. 2011-216149 and paragraphs 0009 to 0023 of JP-A No. 2005-251351.

-ε-Iron oxide powder-
A preferred example of the ferromagnetic powder is ε-iron oxide powder. In the present invention and this specification, "ε-iron oxide powder" refers to a ferromagnetic powder in which an ε-iron oxide type crystal structure is detected as the main phase by X-ray diffraction analysis. For example, if the most intense diffraction peak in an X-ray diffraction spectrum obtained by X-ray diffraction analysis is attributed to the ε-iron oxide type crystal structure, it is assumed that the ε-iron oxide type crystal structure has been detected as the main phase. shall judge. Known methods for producing ε-iron oxide powder include a method for producing it from goethite, a reverse micelle method, and the like. All of the above manufacturing methods are publicly known. Further, regarding 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, Rh, etc., see, for example, J. Jpn. Soc. Powder Metallurgy Vol. 61 Supplement, No. S1, pp. S280-S284, J. Mater. Chem. C, 2013, 1, pp. 5200-5206 etc. can be referred to. 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 method mentioned above.

The activated volume of the ε-iron oxide powder is preferably in the range of 300 to 1500 nm ³ . Finely divided ε-iron oxide powder exhibiting an activation volume within the above range is suitable for producing a magnetic tape exhibiting excellent electromagnetic conversion characteristics. The activated volume of the ε-iron oxide powder is preferably 300 nm ³ or more, and can also be, for example, 500 nm ³ or more. Further, from the viewpoint of further improving electromagnetic conversion characteristics, the activated volume of the ε-iron oxide powder is more preferably 1400 nm ³ or less, even more preferably 1300 nm ³ or less, and 1200 nm ³ or less. is more preferable, and even more preferably 1100 nm ³ or less.

The anisotropy constant Ku can be cited as an index of reduction in thermal fluctuation, in other words, improvement in 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. Further, Ku of the ε-iron oxide powder can be, for example, 3.0×10 ⁵ J/m ³ or less. However, since a higher Ku means higher thermal stability, which is preferable, it is not limited to the values exemplified above.

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

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 at a total magnification of 500,000 times to obtain a photograph of the particles constituting the powder. Select the target particle from the obtained particle photo, trace the outline of the particle with a digitizer, and measure the size of the particle (primary particle). Primary particles refer to independent particles without agglomeration.
The above measurements are performed on 500 randomly extracted particles. The arithmetic mean of the particle sizes of the 500 particles thus obtained is defined as the average particle size of the powder. As the transmission electron microscope, for example, a transmission electron microscope model H-9000 manufactured by Hitachi may be used. Furthermore, 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 model manufactured by Hitachi as a transmission electron microscope and image analysis software KS-400 manufactured by Carl Zeiss as image analysis software. It is a value. In the present invention and herein, powder refers to a collection of particles. For example, ferromagnetic powder means a collection of multiple ferromagnetic particles. Furthermore, an aggregate of multiple particles is not limited to an embodiment in which the particles constituting the aggregate are in direct contact with each other, but also includes an embodiment in which a binder, an additive, etc., which will be described later, are interposed between the particles. Ru. The term particle is sometimes used to refer to powder.

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 No. 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 as follows:
(1) If the particle is needle-shaped, spindle-shaped, columnar (however, the height is larger than the maximum major axis of the bottom surface), etc., it is expressed by the length of the major axis that makes up the particle, that is, the major axis length,
(2) If it is plate-shaped or columnar (however, the thickness or height is smaller than the maximum major axis of the plate surface or bottom surface), it is expressed by the maximum major axis of the plate surface or bottom surface,
(3) If the particle is spherical, polyhedral, unspecified, etc., and the long axis constituting the particle cannot be determined from the shape, it is expressed by an equivalent circle diameter. The equivalent circle diameter refers to what is determined by the circular projection method.

In addition, the average acicular ratio of the powder can be determined by measuring the short axis length of the particles in the above measurement, determining the value of (major axis length / short axis length) of each particle, and calculating the average acicular ratio of the 500 particles. Refers to the arithmetic mean of the values obtained for the particles. Here, unless otherwise specified, the short axis length refers to the length of the short axis constituting the particle in the case of (1) in the above particle size definition, and the thickness or height in the case of (2). In the case of (3), there is no distinction between the major axis and the minor axis, so (major axis length/minor axis length) is regarded as 1 for convenience.
Unless otherwise specified, when the particle shape is specific, for example, in the case of the above definition (1) of particle size, the average particle size is the average major axis length, and in the case of the same definition (2), the average particle size is This is the 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 diameter or average particle diameter).

The content (filling rate) of the ferromagnetic powder 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. Components other than the ferromagnetic powder of the magnetic layer are at least a binder, and optionally one or more additional additives may be included. It is preferable that the filling rate of ferromagnetic powder in the magnetic layer is high from the viewpoint of improving recording density.

Binder, Curing Agent The above magnetic tape is a coated magnetic tape and contains a binder in the magnetic layer. The binder is one or more resins. As the binder, various resins commonly used as binders for coated magnetic recording media can be used. For example, binders include polyurethane resins, polyester resins, polyamide resins, vinyl chloride resins, acrylic resins copolymerized with styrene, acrylonitrile, methyl methacrylate, etc., cellulose resins such as nitrocellulose, epoxy resins, phenoxy resins, polyvinyl acetals, A resin selected from polyvinyl alkyral resins such as polyvinyl butyral can be used alone, or a plurality of resins can be used in combination. Among these, preferred 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 a binder in the nonmagnetic layer and/or back coat layer described below.
Regarding the above binders, reference can be made to paragraphs 0028 to 0031 of JP-A No. 2010-24113. The average molecular weight of the resin used as the binder can be, for example, 10,000 or more and 200,000 or less in terms of weight average molecular weight. The weight average molecular weight in the present invention and this specification is a value determined by gel permeation chromatography (GPC) under the following measurement conditions in terms of polystyrene. The weight average molecular weight of the binder shown in the Examples below is a value determined by converting the value measured under the following measurement conditions into polystyrene.
GPC device: HLC-8120 (manufactured by Tosoh Corporation)
Column: TSK gel Multipore HXL-M (manufactured by Tosoh Corporation, 7.8 mm ID (Inner Diameter) x 30.0 cm)
Eluent: Tetrahydrofuran (THF)

A curing agent can also be used in conjunction with a resin that can be used as a binder. In one embodiment, the curing agent can be a thermosetting compound, which is a compound in which a curing reaction (crosslinking reaction) proceeds by heating, and in another embodiment, a photocuring compound, in which a curing reaction (crosslinking reaction) proceeds by light irradiation. It can be a chemical compound. As a curing reaction progresses during the magnetic layer forming process, at least a portion of the curing agent may be contained in the magnetic layer in a reacted (crosslinked) state with other components such as a binder. This point also applies to layers formed using the composition when the composition used to form the other layer contains a curing agent. Preferred curing agents are thermosetting compounds, with polyisocyanates being preferred. For details of the polyisocyanate, paragraphs 0124 to 0125 of JP-A No. 2011-216149 can be referred to. The content of the curing agent in the composition for forming a magnetic layer can be, for example, 0 to 80.0 parts by mass based on 100.0 parts by mass of the binder, and from the viewpoint of improving the strength of the magnetic layer, it is 50.0 parts by mass. ~80.0 parts by mass.

Additives The magnetic layer contains a ferromagnetic powder and a binder, and may contain one or more additives as necessary. Examples of the additives include the above-mentioned curing agents. In addition, examples of additives included in the magnetic layer include non-magnetic powder (for example, inorganic powder, carbon black, etc.), lubricant, dispersant, dispersion aid, fungicide, antistatic agent, antioxidant, etc. Can be done. For example, regarding the lubricant, paragraphs 0030 to 0033, 0035, and 0036 of JP 2016-126817A can be referred to. A lubricant may be included in the nonmagnetic layer described below. Regarding the lubricant that can be included in the nonmagnetic layer, paragraphs 0030 to 0031, 0034, 0035, and 0036 of JP 2016-126817A can be referred to. Regarding the dispersant, paragraphs 0061 and 0071 of JP 2012-133837A can be referred to. A dispersant may be added to the composition for forming a nonmagnetic layer. Regarding the dispersant that can be added to the composition for forming a non-magnetic layer, paragraph 0061 of JP-A-2012-133837 can be referred to. In addition, examples of the non-magnetic powder that can be included in the magnetic layer include non-magnetic powder that can function as an abrasive, and non-magnetic powder that can function as a protrusion-forming agent that forms protrusions that appropriately protrude on the surface of the magnetic layer. (for example, non-magnetic colloid particles, etc.). Note that the average particle size of colloidal silica (silica colloidal particles) shown in the Examples below is a value determined by the method described in paragraph 0015 of JP 2011-048878A as the method for measuring the average particle size. . The additives can be used in any amount by appropriately selecting commercially available products or by manufacturing them by known methods, depending on the desired properties. Examples of additives that can be used to improve the dispersibility of the abrasive in the magnetic layer containing the abrasive include the dispersants described in paragraphs 0012 to 0022 of JP-A No. 2013-131285.

The magnetic layer described above can be provided directly on the surface of the nonmagnetic support or indirectly via the nonmagnetic layer.

(Nonmagnetic layer)
Next, the nonmagnetic layer will be explained. The magnetic tape may have a magnetic layer directly on the surface of a non-magnetic support, or may have a magnetic layer on the surface of a non-magnetic support via a non-magnetic layer containing non-magnetic powder and a binder. You can. The nonmagnetic powder used in the nonmagnetic layer may be an inorganic powder or an organic powder. Further, carbon black or the like can also be used. Examples of the inorganic powder include powders of metals, metal oxides, metal carbonates, metal sulfates, metal nitrides, metal carbides, metal sulfides, and the like. These nonmagnetic powders are available as commercial products, and can also be produced by known methods. For details thereof, paragraphs 0146 to 0150 of JP-A No. 2011-216149 can be referred to. Regarding carbon black that can be used in the nonmagnetic layer, paragraphs 0040 to 0041 of JP-A No. 2010-24113 can also be referred to. The content (filling rate) of the nonmagnetic powder 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.

For other details such as the binder and additives of the nonmagnetic layer, known techniques regarding nonmagnetic layers can be applied. Further, for example, regarding the type and content of the binder, the type and content of the additive, and the like, known techniques regarding the magnetic layer can also be applied.

In the present invention and herein, a non-magnetic layer is intended to include a substantially non-magnetic layer containing a small amount of ferromagnetic powder, for example as an impurity or intentionally, along with the non-magnetic powder. Here, a substantially non-magnetic layer means that this layer has a residual magnetic flux density of 10 mT or less, a coercive force of 7.96 kA/m (100 Oe) or less, or a residual magnetic flux density of 10 mT or less. A layer having a coercive force of 7.96 kA/m (100 Oe) or less. Preferably, the nonmagnetic layer has no residual magnetic flux density and no coercive force.

(back coat layer)
The above magnetic tape may also have a back coat layer containing nonmagnetic powder and a binder on the surface side of the nonmagnetic support opposite to the surface side having the magnetic layer. The back coat layer preferably contains one or both of carbon black and inorganic powder. Regarding the binder and various additives that may be optionally included in the back coat layer, known techniques regarding the back coat layer can be applied, and known techniques regarding the formulation of the magnetic layer and/or nonmagnetic layer can be applied. You can also do it. For example, the descriptions in paragraphs 0018 to 0020 of JP-A No. 2006-331625 and in column 4, line 65 to column 5, line 38 of U.S. Patent No. 7,029,774 can be referred to regarding the back coat layer. .

(Various thicknesses)
The thickness (total thickness) of the magnetic tape is as described above.
The thickness of the nonmagnetic support is preferably 3.0 to 5.0 μm.
The thickness of the magnetic layer can be optimized depending on the saturation magnetization of the magnetic head used, the head gap length, the recording signal band, etc., and is generally 0.01 μm to 0.15 μm, from the viewpoint of high-density recording. , preferably 0.02 μm to 0.12 μm, more preferably 0.03 μm to 0.1 μm. It is sufficient that there is at least one magnetic layer, and the magnetic layer may be separated into two or more layers having different magnetic properties, and a structure related to a known multilayer magnetic layer can be applied. The thickness of the magnetic layer when it is 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 back coat layer is preferably 0.9 μm or less, more preferably 0.1 to 0.7 μm.

<Manufacturing process>
(Preparation of composition for forming each layer)
The process of preparing a composition for forming a magnetic layer, a nonmagnetic layer, or a backcoat layer usually includes at least a kneading process, a dispersion process, and a mixing process provided before and after these processes as necessary. Each individual process may be divided into two or more stages. The components used to prepare each layer-forming composition may be added at the beginning or middle of any step. As the solvent, one or more of various solvents commonly used in manufacturing coated magnetic recording media can be used. Regarding the solvent, reference can be made to, for example, paragraph 0153 of JP-A No. 2011-216149. Further, the individual components may be added in divided portions in two or more steps. For example, the binder may be added in portions during the kneading step, the dispersion step, and the mixing step for adjusting the viscosity after dispersion. In order to manufacture the above magnetic tape, known manufacturing techniques can be used in various steps. In the kneading step, it is preferable to use an open kneader, continuous kneader, pressure kneader, extruder, or other device with strong kneading power. For details of the kneading process, reference can be made to JP-A-1-106338 and JP-A-1-79274. A known disperser can be used. At any stage of preparing each layer-forming composition, filtration may be performed by a known method. Filtration can be performed, for example, by filter filtration. As the filter used for filtration, for example, a filter with a pore size of 0.01 to 3 μm (eg, a glass fiber filter, a polypropylene filter, etc.) can be used.

(Coating process)
The magnetic layer can be formed by applying the composition for forming a magnetic layer directly onto the surface of a non-magnetic support, or by applying a multilayer coating with the composition for forming a non-magnetic layer, either sequentially or simultaneously. The back coat layer is formed by applying the composition for forming a back coat layer to the surface of the non-magnetic support opposite to the surface having the non-magnetic layer and/or magnetic layer (or on which the non-magnetic layer and/or magnetic layer is subsequently provided). It can be formed by applying it to the surface. For details of coating for forming each layer, reference can be made to paragraph 0066 of JP-A No. 2010-231843.

(Other processes)
Known techniques can be applied to other various steps for manufacturing the magnetic tape. Regarding various steps, for example, paragraphs 0067 to 0070 of JP-A No. 2010-231843 can be referred to. For example, the coating layer of the composition for forming a magnetic layer can be subjected to an orientation treatment while the coating layer is in a wet (undried) state. Regarding the alignment treatment, various known techniques such as the one described in paragraph 0067 of JP-A No. 2010-231843 can be applied.
By going through various steps, a long magnetic tape material can be obtained. The obtained magnetic tape original is cut (slit) into the width of the magnetic tape to be wound around a magnetic tape cartridge using a known cutting machine. The above widths are determined according to standards and are typically 1/2 inch (0.0127 meters).
A servo pattern can be formed on the magnetic tape obtained by slitting by a known method in order to enable head tracking servo in a magnetic tape device (drive). For example, the servo pattern can be formed on a DC (Direct Current) demagnetized magnetic layer. The direction of demagnetization can be longitudinal or perpendicular to the magnetic tape. Furthermore, the direction of magnetization when forming the servo pattern (that is, the magnetized region) can be in the longitudinal direction or perpendicular direction of the magnetic tape.

(Heat treatment)
As described above, the tape width difference (B-A) can be controlled within the above range by generating in advance the deformation that may occur over time in the magnetic tape cartridge between recording and playback. Can be done. For this purpose, it is preferable to wind the magnetic tape cut to the above-mentioned width around a core-like member and heat-treat it in the wound state. By this heat treatment, deformation that may occur over time in the magnetic tape wound on a reel within the magnetic tape cartridge can be caused in advance between recording and reproduction.

In one embodiment, the above heat treatment is performed with the magnetic tape wrapped around a core member for heat treatment (hereinafter referred to as "core for heat treatment"), and the magnetic tape after heat treatment is wound onto a reel of a magnetic tape cartridge. , it is possible to produce a magnetic tape cartridge in which magnetic tape is wound on a reel.
The core for heat treatment can be made of metal, resin, paper, or the like. The material of the core for heat treatment is preferably a material with high rigidity from the viewpoint of suppressing the occurrence of winding failures such as spokes. From this point of view, the core for heat treatment is preferably made of metal or resin. Further, as an index of rigidity, the bending elastic modulus of the material of the core for heat treatment is preferably 0.2 GPa or more, more preferably 0.3 GPa or more. On the other hand, since high-rigidity materials are generally expensive, using a core for heat treatment that is made of a material whose rigidity exceeds the rigidity that can suppress the occurrence of winding failures leads to increased costs. Considering the above points, the bending elastic modulus of the material of the core for heat treatment is preferably 250 GPa or less. The flexural modulus is a value measured according to ISO (International Organization for Standardization) 178, and the flexural modulus of various materials is known. Further, the core for heat treatment can be a solid or hollow core member. In the case of a hollow shape, the wall thickness is preferably 2 mm or more from the viewpoint of maintaining rigidity. Further, the core for heat treatment may or may not have a flange.
Prepare a magnetic tape with a length longer than that to be finally accommodated in a magnetic tape cartridge (hereinafter referred to as "final product length") as a magnetic tape to be wound around a core for heat treatment, and wrap this magnetic tape around a core for heat treatment. It is preferable to carry out the heat treatment by placing the film in a heat treatment environment in a state where the material is in the same state as before. The length of the magnetic tape wound around the core for heat treatment is equal to or longer than the length of the final product, and from the viewpoint of ease of winding onto the core for heat treatment, it is preferably "length of the final product + α". This α is preferably 5 m or more from the viewpoint of ease of winding. The tension at the time of winding onto the core for heat treatment is preferably 0.1 N (Newton) or more from the viewpoints of ease of winding, ease of adjusting the tape width difference (B-A) by heat treatment, and manufacturing suitability. . Further, from the viewpoint of suppressing excessive deformation, the tension during winding onto the core for heat treatment is preferably 1.5 N or less, more preferably 1.0 N or less. The outer diameter of the core for heat treatment is preferably 20 mm or more, more preferably 40 mm or more, from the viewpoint of ease of winding and suppression of coiling (curl in the longitudinal direction). On the other hand, from the viewpoint of ease of adjusting the tape width difference (BA) within the above range, the outer diameter of the core for heat treatment is preferably 100 mm or less, more preferably 90 mm or less. The width of the core for heat treatment may be at least the width of the magnetic tape wound around the core. In addition, when removing the magnetic tape from the heat treatment core after heat treatment, in order to prevent unintentional tape deformation during the removal operation, the magnetic tape and the heat treatment core must be cooled sufficiently before the magnetic tape is removed from the heat treatment core. It is preferable to remove the core from the core for heat treatment. The removed magnetic tape is once wound onto another core (referred to as the "temporary winding core"), and then the temporary winding core is reeled into a magnetic tape cartridge (generally with an outer diameter of 40 to 50 mm). It is preferable to wind up the magnetic tape to a certain degree. Thereby, the magnetic tape can be wound onto the reel of the magnetic tape cartridge while maintaining the relationship between the inside and outside of the magnetic tape with respect to the heat treatment core during heat treatment. For details of the temporary winding core and the tension when winding the magnetic tape onto this core, the above description regarding the heat treatment core can be referred to. In an embodiment in which the heat treatment is applied to a magnetic tape having a length of "final product length + α", the length of "+α" may be cut off at an arbitrary stage. For example, in one embodiment, the magnetic tape may be wound for the length of the final product from the temporary winding core onto the reel of the magnetic tape cartridge, and the remaining length "+α" may be cut off. From the viewpoint of reducing the portion to be cut and discarded, the above α is preferably 20 m or less.

A specific aspect of the heat treatment performed while the core member is wound as described above will be described below.
The ambient temperature at which the heat treatment is performed (hereinafter referred to as "heat treatment temperature") is preferably 40°C or higher, more preferably 50°C or higher. On the other hand, from the viewpoint of suppressing excessive deformation, the heat treatment temperature is preferably 75°C or lower, more preferably 70°C or lower, and even more preferably 65°C or lower.
The weight absolute humidity of the atmosphere in which the heat treatment is performed is preferably 0.1 g/kg dry air or more, more preferably 1 g/kg dry air or more. An atmosphere in which the weight absolute humidity is within the above range is preferable because it can be prepared without using any special equipment for reducing moisture. On the other hand, the weight absolute humidity is preferably 70 g/kg dry air or less, more preferably 66 g/kg dry air or less, from the viewpoint of suppressing the deterioration of workability due to dew condensation. The heat treatment time is preferably 0.3 hours or more, more preferably 0.5 hours or more. Further, the heat treatment time is preferably 48 hours or less from the viewpoint of production efficiency.

By performing heat treatment as explained above, a magnetic tape cartridge equipped with a magnetic tape having a tape width difference (B-A) of 2.4 μm or more and 12.0 μm or less as a value on the 100th day from the magnetic tape cartridge manufacturing date can be produced. It can be made. The tape width of the magnetic tape subjected to the above-described heat treatment usually becomes gradually wider from the outer end of the tape toward the inner end. Therefore, if the tape width is measured for a tape sample taken from an arbitrary position between the measurement position of tape width A and the measurement position of tape width B, the tape width will exceed A as the value on the 100th day from the date of manufacture of the magnetic tape cartridge. Usually, the value is less than the tape width B.

That is, according to one aspect, a method for manufacturing a magnetic tape cartridge according to one aspect of the present invention can be provided. In this manufacturing method, a magnetic tape of equal width is cut out from a magnetic tape original roll, and the cut out magnetic tape is heat-treated while being wound around a core-like member. It is possible to cause a deformation in which the tape width difference (B-A) is 2.4 μm or more and 12.0 μm or less. The details of the above manufacturing method are as described above.

In one aspect, the shipping date of the magnetic tape cartridge (the date on which it is shipped as a product from a manufacturing factory) can be any day within a period from the manufacturing date of the magnetic tape cartridge to the 100th day. The above-mentioned magnetic tape cartridge shipped within the above-mentioned period can suppress the occurrence of playback errors even if it is used early after shipment. It is preferable to ship the magnetic tape cartridge within the 100th day from the date of manufacture of the magnetic tape cartridge, since long-term inventory storage is not required.

The above magnetic tape cartridge can be attached to a magnetic tape device equipped with a magnetic head and used for recording and/or reproducing information. In the present invention and this specification, a "magnetic tape device" refers to a device that can perform at least one of recording information on a magnetic tape and reproducing information recorded on a magnetic tape. Such devices are commonly referred to as drives. The magnetic head included in the magnetic tape device may be a recording head capable of recording information on the magnetic tape, and a reproduction head capable of reproducing information recorded on the magnetic tape. You can also do it. Further, in one aspect, the magnetic tape device can include both a recording head and a reproducing head as separate magnetic heads. In another aspect, the magnetic head included in the magnetic tape device may have a configuration in which one magnetic head includes both a recording element and a reproducing element. The reproducing head is preferably a magnetic head (MR head) that includes a magnetoresistive (MR) element as a reproducing element that can read information recorded on a magnetic tape with high sensitivity. As the MR head, various known MR heads (for example, a GMR (Giant Magnetoresistive) head, a TMR (Tunnel Magnetoresistive) head, etc.) can be used. Further, a magnetic head that records information and/or reproduces information may include a servo pattern reading element. Alternatively, the magnetic tape device may include a magnetic head (servo head) equipped with a servo pattern reading element as a head separate from the magnetic head that records and/or reproduces information.

In the above magnetic tape device, recording of information on the magnetic tape and/or reproduction of information 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 described above can removably include the magnetic tape cartridge according to one aspect of the present invention, and known techniques can be applied to the other components.

The magnetic tape device includes a magnetic tape cartridge according to one aspect of the present invention. Therefore, it is possible to suppress reproduction errors from occurring when reproducing information recorded on a magnetic tape.

One aspect of the present invention will be described below based on Examples. However, the present invention is not limited to the embodiments shown in the examples. "Parts" and "%" described below indicate "parts by mass" and "% by mass" unless otherwise specified. "eq" is equivalent and is a unit that cannot be converted into SI units.
Further, the following various steps and operations were performed in an environment with a temperature of 20 to 25°C and a relative humidity of 40 to 60% unless otherwise specified.

In Table 1, "BaFe" indicates hexagonal barium ferrite powder, "SrFe" indicates hexagonal strontium ferrite powder, "ε-iron oxide" indicates ε-iron oxide powder, and "PEN" indicates polyethylene naphthalate powder. Supports are indicated, "PA" indicates an aromatic polyamide support, and "PET" indicates a polyethylene terephthalate support.

[Example 1]
(1) Preparation of alumina dispersion For 100.0 parts of alumina powder (HIT-80 manufactured by Sumitomo Chemical Co., Ltd.) with a pregelatinization rate of about 65% and a BET (Brunauer-Emmett-Teller) specific surface area of 20 m ² /g, 3. 0 parts of 2,3-dihydroxynaphthalene (manufactured by Tokyo Kasei Co., Ltd.), a 32% solution of polyester polyurethane resin (manufactured by Toyobo Co., Ltd. UR-4800 (polar group amount: 80 meq/kg)) having an SO ₃ Na group as a polar group ( Mix 31.3 parts of a mixed solvent of methyl ethyl ketone and toluene as a solvent and 570.0 parts of a mixed solution of methyl ethyl ketone and cyclohexanone 1:1 (mass ratio) as a solvent, and disperse in a paint shaker for 5 hours in the presence of zirconia beads. I let it happen. After dispersion, the dispersion liquid and beads were separated using a mesh to obtain an alumina dispersion.

(2) Composition formulation for magnetic layer formation (magnetic liquid)
Ferromagnetic powder 100.0 parts Hexagonal barium ferrite powder with average particle size (average plate diameter) 21 nm SO ₃ Na group-containing polyurethane resin 14.0 parts Weight average molecular weight: 70,000, SO ₃ Na group: 0.2 meq/ g
Cyclohexanone 150.0 parts Methyl ethyl ketone 150.0 parts (abrasive liquid)
6.0 parts of alumina dispersion prepared in (1) above (silica sol (projection forming agent liquid))
Colloidal silica (average particle size 120 nm) 2.0 parts Methyl ethyl ketone 1.4 parts (other ingredients)
Stearic acid 2.0 parts Stearic acid amide 0.2 parts Butyl stearate 2.0 parts Polyisocyanate (Coronate (registered trademark) L manufactured by Tosoh Corporation) 2.5 parts (finishing solvent)
Cyclohexanone 200.0 parts Methyl ethyl ketone 200.0 parts

(3) Non-magnetic layer forming composition formulation Non-magnetic inorganic powder: α-iron oxide 100.0 parts Average particle size (average major axis length): 0.15 μm
Average acicular ratio: 7
BET specific surface area: 52m ² /g
Carbon black 20.0 parts Average particle size: 20nm
SO ₃ Na group-containing polyurethane resin 18.0 parts Weight average molecular weight: 70,000, SO ₃ Na group: 0.2 meq/g
Stearic acid 2.0 parts Stearamide 0.2 parts Butyl stearate 2.0 parts Cyclohexanone 300.0 parts Methyl ethyl ketone 300.0 parts

(4) Composition formulation for back coat layer formation Carbon black 100.0 parts DBP (Dibutyl phthalate) oil absorption 74 cm ³ /100 g
Nitrocellulose 27.0 parts Polyester polyurethane resin containing sulfonic acid group and/or its salt
62.0 parts Polyester resin 4.0 parts Alumina powder (BET specific surface area: 17 m ² /g) 0.6 parts Methyl ethyl ketone 600.0 parts Toluene 600.0 parts Polyisocyanate (Coronate L manufactured by Tosoh Corporation) 15.0 parts

(5) Preparation of each layer-forming composition A magnetic layer-forming composition was prepared by the following method. The above magnetic liquid was prepared by dispersing each component for 24 hours (bead dispersion) using a batch type vertical sand mill. Zirconia beads with a bead diameter of 0.5 mm were used as the dispersion beads. Using the above sand mill, mix the prepared magnetic liquid, the above polishing agent liquid, and other components (silica sol, other components, and finishing additive solvent), disperse the beads for 5 minutes, and then use a batch type ultrasonic device (20 kHz, 300 W). Treatment (ultrasonic dispersion) was performed for 0.5 minutes. Thereafter, filtration was performed using a filter having a pore size of 0.5 μm to prepare a composition for forming a magnetic layer.
A composition for forming a nonmagnetic layer was prepared by the following method. The above components except for the lubricant (stearic acid, stearamide, and butyl stearate) were kneaded and diluted using an open kneader, and then dispersed using a horizontal bead mill disperser. Thereafter, a lubricant (stearic acid, stearamide, and butyl stearate) was added, and the mixture was stirred and mixed using a dissolver stirrer to prepare a composition for forming a nonmagnetic layer.
A composition for forming a back coat layer was prepared by the following method. The above components except for polyisocyanate were introduced into a dissolver stirrer and stirred at a peripheral speed of 10 m/sec for 30 minutes, followed by dispersion treatment using a horizontal bead mill disperser. Thereafter, polyisocyanate was added and stirred and mixed using a dissolver stirrer to prepare a composition for forming a back coat layer.

(6) Method for producing magnetic tapes and magnetic tape cartridges On the surface of a support of the type and thickness listed in Table 1, the tape prepared in (5) above was placed so that the thickness after drying would be the thickness listed in Table 1. A nonmagnetic layer was formed by applying and drying the composition for forming a nonmagnetic layer. Next, the magnetic layer forming composition prepared in (5) above was applied onto the nonmagnetic layer so that the thickness after drying would be as shown in Table 1 to form a coating layer. Thereafter, while the coated layer of the magnetic layer forming composition is still in an undried state, a magnetic field with a magnetic field strength of 0.3 T is applied perpendicularly to the surface of the coated layer to perform a vertical alignment treatment, and then dried. Then, a magnetic layer was formed. Thereafter, on the surface of the support listed in Table 1 opposite to the surface on which the non-magnetic layer and magnetic layer were formed, the solution prepared in (5) above was applied so that the thickness after drying would be the thickness listed in Table 1. A back coat layer was formed by applying and drying the composition for forming a back coat layer.
Thereafter, the surface was smoothed using a calender roll consisting only of metal rolls at a speed of 100 m/min, a linear pressure of 294 kN/m (300 kg/cm), and a calender temperature of 90°C (surface temperature of the calender roll). Processing (calendar processing) was performed.
Thereafter, heat treatment was performed by storing the long magnetic tape material in a heat treatment furnace at an ambient temperature of 70° C. (heat treatment time: 36 hours). After the heat treatment, the tape was slit into a 1/2 inch (0.0127 meter) width to obtain a magnetic tape. By recording a servo signal on the magnetic layer of the obtained magnetic tape using a commercially available servo writer, the resulting magnetic tape has a data band, a servo band, and a guide band arranged in accordance with the LTO (Linear-Tape-Open) Ultrium format, and A magnetic tape having a servo pattern (timing-based servo pattern) arranged and shaped according to the LTO Ultrium format on a servo band was obtained.
The magnetic tape (length: 960 m) after recording the servo signal was wound around a core for heat treatment, and heat treated while being wound around the core. As the winding core for heat treatment, a solid core member made of resin (outer diameter: 50 mm) with a bending elastic modulus of 0.8 GPa was used, and the tension at the time of winding was 0.6 N. The heat treatment was performed at the heat treatment temperature shown in Table 1 for 5 hours. The weight absolute humidity of the atmosphere in which the heat treatment was performed was 10 g/kg dry air.
After the above heat treatment, the magnetic tape and the heat treatment core are sufficiently cooled, and then the magnetic tape is removed from the heat treatment core and wound onto the temporary winding core, and then the magnetic tape cartridge ( Wind the final product length (950 m) of magnetic tape onto the reel (reel outer diameter: 44 mm) of LTO Ultrium 7 data cartridge, cut off the remaining 10 m, and attach Standard ECMA to the cut end using commercially available splicing tape. (European Computer Manufacturers Association)-319 (June 2001) Leader tape according to Section 3, Item 9 was joined. As the temporary winding core, a solid core member made of the same material and having the same outer diameter as the heat treatment core was used, and the tension during winding was 0.6N.
As described above, a single-reel type magnetic tape cartridge of Example 1 in which a magnetic tape having a length of 950 m was wound around a reel was manufactured.
For each Example, each Comparative Example, and each Reference Example, two magnetic tape cartridges were produced, one of which was used for the evaluation described below, and the other used for the recording/reproduction test described below. The date when the magnetic tape was placed in the magnetic tape cartridge was recorded on the RFID tag inside each magnetic tape cartridge as the date of manufacture of the magnetic tape cartridge.

[Examples 2 to 6]
A magnetic tape cartridge was produced in the same manner as in Example 1, except that the heat treatment performed while the magnetic tape was wound around the core for heat treatment was performed at the heat treatment temperature shown in Table 1.

[Example 7]
A magnetic tape cartridge was prepared in the same manner as in Example 1, except that the support shown in Table 1 was used as the support, and the heat treatment was performed with the magnetic tape wound around the heat treatment core at the heat treatment temperature shown in Table 1. was created.

[Example 8]
A magnetic tape cartridge was produced in the same manner as in Example 7, except that the heat treatment performed while the magnetic tape was wound around the core for heat treatment was performed at the heat treatment temperature shown in Table 1.

[Example 9]
A magnetic tape cartridge was prepared in the same manner as in Example 1, except that the support shown in Table 1 was used as the support, and the heat treatment was performed with the magnetic tape wound around the heat treatment core at the heat treatment temperature shown in Table 1. was created.

[Example 10]
A magnetic tape cartridge was produced in the same manner as in Example 9, except that the heat treatment performed while the magnetic tape was wound around the core for heat treatment was performed at the heat treatment temperature shown in Table 1.

[Example 11]
A magnetic tape cartridge was produced in the same manner as in Example 1, except that the ferromagnetic powder was changed to hexagonal strontium ferrite powder obtained by the method shown below.
(Method for producing hexagonal strontium ferrite powder)
We weighed 1707 g of SrCO ₃ , 687 g of H ₃ BO ₃ , 1120 g of Fe ₂ O ₃ , 45 g of Al(OH) ₃ , 24 g of BaCO ₃ , 13 g of CaCO ₃ , and 235 g of Nd ₂ O ₃ and mixed them in a mixer. The mixture was mixed to obtain a raw material mixture.
The obtained raw material mixture was melted in a platinum crucible at a melting temperature of 1390°C, and while stirring the melt, the tap hole provided at the bottom of the platinum crucible was heated, and the melt was tapped in the form of a rod at a rate of about 6 g/sec. . The tapped liquid was rapidly cooled by rolling with water-cooled twin rollers to produce an amorphous body.
280g of the prepared 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 form hexagonal strontium ferrite particles. Precipitated (crystallized).
Next, the crystallized product obtained above containing hexagonal strontium ferrite particles was coarsely ground in a mortar, 1000 g of zirconia beads with a particle size of 1 mm and 800 ml of 1% acetic acid were added to a glass bottle, and dispersed for 3 hours in a paint shaker. went. Thereafter, the resulting dispersion was separated from the beads and placed in a stainless steel beaker. The dispersion was allowed to stand at a liquid temperature of 100°C for 3 hours to dissolve the glass components, then precipitated in a centrifuge, washed by repeated decantation, and then heated in a heating furnace at an internal temperature of 110°C for 6 hours. After drying for several hours, hexagonal strontium ferrite powder was obtained.
The hexagonal strontium ferrite powder obtained above has an average particle size of 18 nm, an activation volume of 902 nm ³ , an anisotropy constant Ku of 2.2×10 ⁵ J/m ³ , and a mass magnetization σs of 49 A·m ² / It was kg.
12 mg of sample powder was collected from the hexagonal strontium ferrite powder obtained above, and the sample powder was partially dissolved under the dissolution conditions exemplified above. The obtained filtrate was subjected to elemental analysis using an ICP analyzer, and the neodymium atoms were analyzed using an ICP analyzer. The surface layer content was determined.
Separately, 12 mg of sample powder was collected from the hexagonal strontium ferrite powder obtained above, and this sample powder was completely dissolved under the dissolution conditions exemplified above. The elemental analysis of the obtained filtrate was performed using an ICP analyzer. The bulk content of atoms was determined.
The content of neodymium atoms (bulk content) with respect to 100 atom % of iron atoms in the hexagonal strontium ferrite powder obtained above was 2.9 atom %. Further, the content of neodymium atoms in the surface layer was 8.0 at %. The ratio of the surface layer content to the bulk content, "surface layer content/bulk content," was 2.8, and it was confirmed that neodymium atoms were unevenly distributed in the surface layer of the particles.

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

[Example 12]
A magnetic tape cartridge was produced in the same manner as in Example 1, except that the ferromagnetic powder was changed to hexagonal strontium ferrite powder obtained by the method shown below.
(Method for producing hexagonal strontium ferrite powder)
1725 g of SrCO ₃ , 666 g of H ₃ BO ₃ , 1332 g of Fe ₂ O ₃ , 52 g of Al(OH) ₃ , 34 g of CaCO ₃ and 141 g of BaCO ₃ 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 stirring the melt, the tap hole provided at the bottom of the platinum crucible was heated, and the melt was tapped in the form of a rod at a rate of about 6 g/sec. . The tapped liquid was rapidly cooled and rolled using water-cooled twin rolls to produce 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 ground in a mortar, 1000 g of zirconia beads with a particle size of 1 mm and 800 ml of 1% acetic acid were added to a glass bottle, and dispersed for 3 hours in a paint shaker. went. Thereafter, the resulting dispersion was separated from the beads and placed in a stainless steel beaker. The dispersion was allowed to stand at a liquid temperature of 100°C for 3 hours to dissolve the glass components, then precipitated in a centrifuge, washed by repeated decantation, and then heated in a heating furnace at an internal temperature of 110°C for 6 hours. After drying for several hours, hexagonal strontium ferrite powder was obtained.
The average particle size of the obtained hexagonal strontium ferrite powder was 19 nm, the activation volume was 1102 nm ³ , the anisotropy constant Ku was 2.0×10 ⁵ J/m ³ , and the mass magnetization σs was 50 A·m ² /kg. there were.

[Example 13]
A magnetic tape cartridge was produced in the same manner as in Example 1, except that the ferromagnetic powder was changed to ε-iron oxide powder obtained by the method shown below.
(Method for producing ε-iron oxide powder)
90 g of pure water, 8.3 g of iron (III) nitrate nonahydrate, 1.3 g of gallium (III) nitrate octahydrate, 190 mg of cobalt (II) nitrate hexahydrate, 150 mg of titanium (IV) sulfate, and To a solution of 1.5 g of polyvinylpyrrolidone (PVP), while stirring using a magnetic stirrer, 4.0 g of an ammonia aqueous solution with a concentration of 25% was added in the atmosphere at an ambient temperature of 25°C. The mixture was stirred for 2 hours while maintaining the ambient temperature at 25°C. A citric acid solution obtained by dissolving 1 g of citric acid in 9 g of pure water was 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 temperature of 80°C.
800 g of pure water was added to the dried powder and the powder was again dispersed in water to obtain a dispersion. The temperature of the resulting dispersion was raised to 50° C., and 40 g of a 25% ammonia aqueous 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 resulting 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 loaded into a heating furnace with an internal temperature of 1000° C. under an air atmosphere, and heat-treated for 4 hours.
The heat-treated ferromagnetic powder was prepared by pouring the heat-treated ferromagnetic powder precursor into a 4 mol/L sodium hydroxide (NaOH) aqueous solution, maintaining the liquid temperature at 70°C, and stirring for 24 hours. The impurity silicic acid compound was removed from the precursor.
Thereafter, the ferromagnetic powder from which the silicic acid compound had been removed was collected by centrifugation and washed with pure water to obtain ferromagnetic powder.
When the composition of the obtained ferromagnetic powder was confirmed by high-frequency inductively coupled plasma-optical emission spectrometry (ICP-OES), it was found to be Ga, Co and Ti substituted ε-iron oxide (ε-Ga _0.58 Fe _1.42 O ₃ ). In addition, X-ray diffraction analysis was performed under the same conditions as described for Example 11, and the peaks of the X-ray diffraction pattern showed that the obtained ferromagnetic powder did not contain α-phase and γ-phase crystal structures. It was confirmed that the material had a single-phase crystal structure of the ε phase (ε-iron oxide type crystal structure).
The average particle size of the obtained ε-iron oxide powder was 12 nm, the activation volume was 746 nm ³ , the anisotropy constant Ku was 1.2×10 ⁵ J/m ³ , and the mass magnetization σs was 16 A·m ² /kg. there were.

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

[Reference example 1]
The process was the same as in Example 1, except that each layer with the thickness shown in Table 1 was formed using a support with the thickness shown in Table 1, and the heat treatment was not performed while the magnetic tape was wound around the heat treatment core. A magnetic tape cartridge was manufactured.

[Comparative example 1]
A magnetic tape cartridge was produced in the same manner as in Example 1, except that the magnetic tape was not heat-treated while being wound around the heat-treating core.

[Comparative Examples 2 and 3]
A magnetic tape cartridge was produced in the same manner as in Example 1, except that the heat treatment performed while the magnetic tape was wound around the core for heat treatment was performed at the heat treatment temperature shown in Table 1.

[Comparative example 4]
A magnetic tape cartridge was produced in the same manner as in Example 7, except that the magnetic tape was not heat-treated while being wound around the heat-treating core.

[Comparative example 5]
A magnetic tape cartridge was produced in the same manner as in Example 9, except that the magnetic tape was not heat-treated while being wound around the heat-treating core.

[Evaluation of magnetic tape]
The magnetic tapes were taken out from each of the magnetic tape cartridges of Examples and Comparative Examples on the 100th day from the date of manufacture of the magnetic tape cartridges, and the following evaluations were performed on the taken out magnetic tapes.

(1) Tape width difference (B-A)
After removing the leader tape that was joined to the outer end of the tape, a tape sample of length 20 cm including a position 10 m ± 1 m from the outer end of the tape and a tape length of 20 cm including a position 50 m ± 1 m from the inner end of the tape was prepared. A sample was cut out. The tape width of each tape sample was measured at the center in the longitudinal direction of the tape sample while being sandwiched between two glass slides to eliminate the influence of curl. The tape width was measured within 20 minutes after the magnetic tape was taken out from the magnetic tape cartridge using a laser high-precision dimension measuring device LS-7030 manufactured by KEYENCE. For each of the above tape samples, the tape width was measured seven times (N = 7), and the arithmetic mean of the five measured values excluding the maximum and minimum values obtained from the seven measurements was calculated. I asked for it. The arithmetic mean thus obtained was used as the tape width at each position (tape width A or tape width B) to calculate the tape width difference (BA).

(2) Tape Width Deformation Rate The tape width A determined in (1) above was taken as the tape width before storage.
After measuring a tape sample with a length of 20 cm including a position 10 m ± 1 m from the outer end of the tape in (1) above, hold one end of this tape sample and suspend a 100 g weight from the other end. The tape was stored for 24 hours in a dry environment at a temperature of 52° C. under a load of 100 g in the longitudinal direction of the tape. After the storage, the tape width was determined within 20 minutes after the load was removed in the same manner as in (1) above, and this tape width was taken as the tape width after storage.
The difference in tape width before and after storage (tape width before storage - tape width after storage) divided by the tape width before storage x 10 ⁶ (unit: ppm) was calculated and used as the tape width deformation rate.

(3) Tape Thickness Ten tape samples (5 cm in length) were cut out from any part of the magnetic tape taken out from the magnetic tape cartridge in (1) above, and these tape samples were stacked and the thickness was measured. Thickness measurements were made using a MARH Millimar 1240 compact amplifier and Millimar 1301 inductive probe digital thickness gauge. The value obtained by dividing the measured thickness by one-tenth (thickness per tape sample) was defined as the tape thickness.
The thickness of each layer shown in Table 1 is the design thickness calculated from the manufacturing conditions, and the thickness of the support is the manufacturer's value.

[Recording and playback test]
After storing a magnetic tape cartridge with a specified amount of data recorded on the magnetic tape in an environment at a temperature of 40 degrees Celsius and relative humidity of 80% for three months, we evaluated whether or not all recorded data could be played back (read). . Recording and playback were performed using an LTO Ultrium7 (LTO7) drive. The specified capacity is 6.0 TB (terabyte).
Data was recorded on the 100th day from the date of manufacture of the magnetic tape cartridge, after the magnetic tape cartridge was placed in an evaluation environment and allowed to stand for at least one day to acclimatize to the environment. If an error occurred during recording and the specified capacity could not be recorded, that cartridge was not used for subsequent evaluation, and was indicated in Table 1 as ``Evaluation not possible.'' Specifically, the case where the above evaluation cannot be performed means that even if the servo head of the drive reads the servo pattern and performs head tracking, the magnetic head cannot be aligned to the recording position and the drive generates an error signal. This is the case when the engine starts and stops.
After the above-mentioned storage, playback was performed under the same temperature and humidity environment as the environment in which recording was performed, and this playback was performed using the same individual drive as used during recording. Reproduction was also performed after the magnetic tape cartridge was left in the evaluation environment for one day or more to become accustomed to the same environment. When all data recorded on the magnetic tape in the magnetic tape cartridge has been completely reproduced without any error, it is indicated as "reproducible" in Table 1. If the SNR (signal-to-noise-ratio) of the playback signal was poor during playback, data could not be read correctly from the playback signal, and an error occurred during playback and playback of all data was not completed. , was written as "unreproducible" in Table 1.

The above results are shown in Table 1 (Table 1-1 to Table 1-3).

Regarding the magnetic tape cartridge produced in the same manner as Comparative Example 1, the tape width difference (B-A) was determined on the 360th day from the date of manufacture of the magnetic tape cartridge, and it was found to be 4.5 μm, and the tape width deformation rate was 400 ppm. . Comparing this result and the evaluation results of Examples 1 to 13 with Comparative Examples 1, 4, and 5, which were wound around the core for heat treatment without heat treatment, it was found that by performing heat treatment as in Examples 1 to 13, , it can be confirmed that the deformation that occurs over time within the magnetic tape cartridge could be prevented in advance.
In each of the magnetic tape cartridges of Examples 1 to 13, recording and reproduction could be performed while suppressing the occurrence of errors.
On the other hand, from a comparison between Reference Example 1 and Comparative Examples 1, 2, 4, and 5, it can be confirmed that reproduction errors are more likely to occur when the tape thickness is reduced to 5.2 μm or less. In Comparative Examples 1, 2, 4, and 5, the occurrence of reproduction errors could not be suppressed, and reproduction of all data could not be completed.
The reason why Comparative Example 3 could not be evaluated is considered to be that a recording error occurred because the tape width differed depending on the position of the tape, so that the tape width difference (BA) exceeded 12.0 μm.

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

Claims (12)

A single-reel type magnetic tape cartridge in which magnetic tape is wound on a reel,
The magnetic tape is
It has a magnetic layer containing ferromagnetic powder on a non-magnetic support,
A non-magnetic layer containing non-magnetic powder is provided between the non-magnetic support and the magnetic layer,
The thickness of the non-magnetic layer is 0.1 μm or more and 1.5 μm or less,
The tape thickness is 5.2 μm or less, and the tape width difference, B-A, between the tape width A at a position 10 m ± 1 m from the tape outer end and the tape width B at a position 50 m ± 1 m from the tape inner end is A magnetic tape cartridge, wherein the tape width A and the tape width B are 2.4 μm or more and 12.0 μm or less, and the tape width A and the tape width B are values on the 100th day from the date of manufacture of the magnetic tape cartridge. The magnetic tape has a tape width deformation rate of 400 ppm or less measured within 20 minutes after the load is removed after being stored in a dry environment at a temperature of 52° C. for 24 hours with a load of 100 g applied in the longitudinal direction of the tape. 2. The magnetic tape cartridge according to claim 1, wherein the tape width deformation rate is a value obtained when the storage is started on the 100th day from the date of manufacture of the magnetic tape cartridge. The magnetic tape cartridge according to claim 1 or 2, wherein the ferromagnetic powder has an average particle size of 10 nm or more and 45 nm or less. The magnetic tape cartridge according to claim 1, wherein the ferromagnetic powder has an average particle size of 15 nm or more and 40 nm or less. The magnetic tape cartridge according to claim 1, wherein the ferromagnetic powder has an average particle size of 15 nm or more and 30 nm or less. The magnetic tape cartridge according to claim 1, wherein the ferromagnetic powder has an average particle size of 15 nm or more and 25 nm or less. The magnetic tape cartridge according to any one of claims 1 to 6, wherein the thickness of the nonmagnetic layer is 0.1 μm or more and 1.0 μm or less. The magnetic tape according to any one of claims 1 to 7, wherein the magnetic tape has a back coat layer containing nonmagnetic powder on a surface side of the nonmagnetic support opposite to the surface side having the magnetic layer. magnetic tape cartridge. The magnetic tape cartridge according to claim 1, wherein the non-magnetic support is a polyethylene naphthalate support. The magnetic tape cartridge according to claim 1, wherein the nonmagnetic support is an aromatic polyamide support. The magnetic tape cartridge according to claim 1, wherein the non-magnetic support is a polyethylene terephthalate support. The magnetic tape cartridge according to any one of claims 1 to 11, wherein the tape width difference, BA, is 5.0 μm or more and 12.0 μm or less.