JP6883053B2 - Magnetic tape cartridge - Google Patents

Description

The present invention relates to a magnetic tape cartridge.

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

To record and reproduce a signal on a magnetic tape, a magnetic tape cartridge containing the magnetic tape wound on a reel is usually set in a magnetic tape device called a drive, and the magnetic tape is run in the magnetic tape device to tape the tape. This is done by bringing the surface (the surface of the magnetic layer) and the magnetic head into contact with each other and sliding them.

Japanese Unexamined Patent Publication No. 2005-346856

Recording of information on a magnetic tape is usually performed by recording a magnetic signal in the data band of the magnetic tape. As a result, a data track is formed in the data band.
On the other hand, when the recorded information is reproduced, the magnetic tape is run in the magnetic tape device, and the magnetic head is made to follow the data track of the magnetic tape to read the information recorded in the data track. Here, if the accuracy with which the magnetic head follows the data track is low, a reproduction error is likely to occur.

By the way, with the enormous increase in the amount of information in recent years, magnetic tapes are required to have a higher recording capacity (higher capacity). As a means for increasing the capacity, it is possible to reduce the thickness of the magnetic tape (hereinafter, also referred to as “thinning”) and increase the length of the magnetic tape accommodated in one roll of the magnetic tape cartridge. However, according to the study by the present inventors, a phenomenon is observed in which a reproduction error is likely to occur when the thickness of the magnetic tape is reduced.

Therefore, an object of the present invention is to make it possible to reduce the thickness of the magnetic tape and suppress the occurrence of reproduction 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
Having a magnetic layer containing ferromagnetic powder and binder on a non-magnetic support,
The tape width difference (BA) 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 is 5.2 μm or less. The 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 aspect, the magnetic tape is stored for 24 hours in a dry environment at a temperature of 52 ° C. 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 tape width deformation rate is a value obtained by starting the storage on the 100th day from the date of manufacture of the magnetic tape cartridge.

In one aspect, the magnetic tape can have a non-magnetic layer containing a non-magnetic powder and a binder between the non-magnetic support and the magnetic layer.

In one aspect, the magnetic tape may have a backcoat layer containing a non-magnetic powder and a binder on the surface side of the non-magnetic 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 non-magnetic 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, a magnetic tape cartridge containing a thin magnetic tape having a tape thickness of 5.2 μm or less, which can suppress the occurrence of a reproduction error in reproduction of information recorded on the magnetic tape. Tape cartridges can be provided.

[Magnetic tape cartridge]
One aspect of the present invention is a single reel type magnetic tape cartridge in which a magnetic tape is wound on a reel, and the magnetic tape has a magnetic layer containing a ferromagnetic powder and a binder on a non-magnetic support. However, the tape width difference (BA) between the tape width A at a position where the tape thickness is 5.2 μm or less and 10 m ± 1 m from the outer end of the tape and the tape width B at a position 50 m ± 1 m from the inner end of the tape. ) 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, relating to the magnetic tape cartridge.

One of the causes of playback errors when playing back information recorded on magnetic tape is that the widthwise dimensions of the magnetic tape change over time between recording and playing back the information on the magnetic tape. Can be mentioned. Regarding the dimensional change in the width direction of the magnetic tape, Patent Document 1 (Japanese Unexamined Patent Publication No. 2005-346856) described above proposes to improve the dimensional stability by providing a reinforcing layer (for example, Patent Document). See paragraph 0014 and paragraph 0054 of paragraph 1). It can be said that this proposal aims to provide a magnetic tape that is not easily deformed.
On the other hand, the present inventors have obtained the following new findings as a result of intensive studies on the dimensional change of the magnetic tape housed in the magnetic tape cartridge.
The magnetic tape cartridge is manufactured by winding and accommodating a magnetic tape obtained by slitting a long magnetic tape original fabric into a predetermined width on a reel of the magnetic tape cartridge. There are two types of cartridges, a single reel type having one reel and a twin reel type having two reels. In recent years, a single reel type magnetic tape cartridge has been widely used. While the present inventors have been diligently studying the deformation of the magnetic tape over time in the single reel type magnetic tape cartridge, the portion close to the reel (inner portion) becomes wider than the initial stage due to the compressive stress in the tape thickness direction. On the other hand, the part far from the reel (outer part) is deformed to be narrower than the initial width due to the tensile stress in the longitudinal direction of the tape. It was clarified that it occurs remarkably when the thickness is 5.2 μm or less). For the reason, the present inventors, when the magnetic tape is thinned, the compressive stress or the tensile stress applied to each position of the magnetic tape becomes larger even if the tension applied to the magnetic tape is the same. As a result, it is speculated that deformation that becomes wider or narrower than the initial stage is likely to occur. Further, when the magnetic tape is thinned to increase the capacity and the length of the magnetic tape accommodated in one roll of the magnetic tape cartridge is increased, the number of turns of the magnetic tape in the magnetic tape cartridge is increased. As a result, it is considered that the inner part of the magnetic tape (the part close to the reel) is compressed more strongly, and as a result, the phenomenon that the inner part is deformed wider than the initial state becomes more remarkable. Inferred.
Based on the above findings, the present inventors have difficulty in causing the magnetic head to follow the data track because the magnetic tape undergoes different deformations over time depending on the position as described above from the time of recording (when the data track is formed). I came to think that this causes a playback error.
Therefore, if the present inventors generate in advance the deformation that may occur in the magnetic tape cartridge with time between recording and reproduction, the deformation occurs with time between recording and reproduction in the thinned magnetic tape. Considering that it will be possible to suppress the occurrence of reproduction errors due to the above deformation, further diligent studies were conducted. This was a study based on a technical idea that was clearly different from the conventional technical idea that aimed to provide a magnetic tape that was not easily deformed. As a result, the present inventors preliminarily deform the tape width difference (BA) to be 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. We have found that it is possible to suppress the occurrence of a reproduction error when reproducing information recorded on a thin magnetic tape having a tape thickness of 5.2 μm or less, and completed the above-mentioned aspect of the present invention. The reason why the 100th day from the date of manufacture of the magnetic tape cartridge was adopted as the reference date is that, in the conventional magnetic tape cartridge, the above tape width difference (BA) is 2.4 μm at the time of 100 days from the date of manufacture of the magnetic tape cartridge. This is because the above-mentioned deformation does not occur.
However, the above description includes the inferences of the present inventors. In addition, the description below also includes the inferences of the present inventors. The present invention is not limited to such inference.
Hereinafter, the magnetic tape cartridge will be described.

<Structure of magnetic tape cartridge>
The magnetic tape cartridge is a single reel type magnetic tape cartridge. In the single reel type magnetic tape cartridge, the magnetic tape is wound on a single reel. As for the configuration of the magnetic tape cartridge, a known technique relating to a single reel type magnetic tape cartridge can be applied.

<Magnetic tape>
(Tape width difference (BA))
The magnetic tape contained in the magnetic tape cartridge has a tape width difference (BA) 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. It is 4 μm or more and 12.0 μm or less. 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.
Individual identification information (ID (identification) information) such as a manufacturing date is recorded in the magnetic tape cartridge for product management. In the present invention and the present specification, the "magnetic tape cartridge manufacturing date" shall mean the manufacturing date recorded on the magnetic tape cartridge. Such information is usually recorded on an RFID (Radio Frequency Identification) tag inside the cartridge, and the date of manufacture (usually the date recorded as "Date of Manufacturer") is recognized by reading the RFID tag. be able to. For a magnetic tape cartridge in which the tape width difference (BA) on the 100th day from the date of manufacture of the magnetic tape cartridge is within the above range, information is recorded on the magnetic tape contained in the magnetic tape cartridge and the recorded information is recorded. Regeneration may occur on any day less than 100 days from the date of manufacture of the magnetic tape cartridge, on the 100th day, or on any day greater than 100 days. Since the magnetic tape cartridges with the same product lot number are usually manufactured using the same raw materials under the same manufacturing conditions, the tape width difference (B-) on the 100th day from the manufacturing date of the magnetic tape cartridge. A) can be considered to have the same value. The above points are the same for various physical properties described later.
Further, as a part of the magnetic tape on which various physical properties such as the tape width difference (BA) are measured, it is bonded to the region where information is recorded and / or reproduced by a bonding means such as a splicing tape. The part shall not be considered. For example, a leader tape may be attached to the outer end of the tape for pulling out and winding the magnetic tape from the magnetic tape cartridge. In such a case, the leader tape is not considered as a part of the magnetic tape for which various physical properties such as the tape width difference (BA) are measured. Therefore, when the leader tape is joined, the tape outer end of the magnetic tape is the end of the magnetic tape on the side to which the leader tape is joined.

The outer end of the tape is the end farthest from the reel of the magnetic tape wound on the reel, and the tape width A at a position of 10 m ± 1 m from the outer end of the tape is strongly tensioned over time and is wider than the initial stage. It represents the tape width of the narrowly deformed part. On the other hand, the inner end of the tape is the end of the starting point of winding on the reel, and the tape width B at a position of 50 m ± 1 m from the inner end of the tape is strongly compressed with time and deformed wider than the initial stage. It represents the tape width of the part.
The magnetic tape cartridge is manufactured by winding a magnetic tape obtained by slitting a long magnetic tape original fabric into a predetermined width on a reel and accommodating it in the magnetic tape cartridge. The width specified above is typically 1/2 inch (0.0127 meters), and the width of the slit magnetic tape is equal at each position. For monospaced fonts, manufacturing errors that can normally occur in the slit process are acceptable. On the other hand, as described above, it is considered that the magnetic tape undergoes different deformations over time depending on the position during the period from recording to reproduction. However, in the conventional magnetic tape cartridge, the tape width difference (BA) between the tape width A and the tape width B becomes 2.4 μm or more on the 100th day from the date of manufacture of the magnetic tape cartridge. No deformation occurs. On the other hand, the magnetic tape is deformed so that the tape width difference (BA) becomes 2.4 μm or more on the 100th day from the manufacturing date of the magnetic tape cartridge, so that the magnetic tape can be recorded and reproduced. However, it is considered that the occurrence of a reproduction error caused by causing different deformations depending on the position as described above over time can be suppressed. On the other hand, if the tape width difference between the inner portion and the outer portion of the magnetic tape before the information is recorded is too large, an error is likely to occur during recording. On the other hand, if the tape width difference (BA) is 12.0 μm or less on the 100th day from the date of manufacture of the magnetic tape cartridge, it is easy to record information over the entire length of the magnetic tape contained 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, and 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 tape width difference (BA) is a value obtained 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%.
Magnetic Tape Cartridge Take out the magnetic tape wound on the reel from the magnetic tape cartridge 100 days from the date of manufacture, a 20 cm long tape sample including a position 10 m ± 1 m from the outer end of the tape, and 50 m from the inner end of the tape. Cut out a tape sample with a length of 20 cm including the position of ± 1 m. The tape width of each tape sample is measured at the center of the tape sample in the longitudinal direction while being sandwiched between plate-shaped members (for example, slide glass) in order to remove the influence of curl. The tape width can be measured using a known measuring instrument capable of measuring dimensions with an accuracy on the order of 0.1 μm. The measurement is performed within 20 minutes after removing the magnetic tape from the magnetic tape cartridge. In each of the above tape samples, the tape width was measured 7 times (N = 7), and the arithmetic mean of the 5 measured values excluding the maximum and minimum values obtained in the 7 measurements was calculated. Ask. When the total length of the magnetic tape contained in the magnetic tape cartridge is 950 m, the arithmetic mean thus obtained is defined as the tape width (tape width A or tape width B) at each position. On the other hand, when the total length of the magnetic tape contained in the magnetic tape cartridge is a length other than 950 m, the total length of the magnetic tape is L1 (unit: m), and the arithmetic mean obtained above is W1.
W = (950 / L1) x W1
Let W obtained 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 performing heat treatment. The details of the heat treatment will be described later.

(Tape width deformation rate)
As described above, a magnetic tape having a tape width difference (BA) 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 obtained by the following method. It can be 400 ppm (parts per million) or less, more preferably 390 ppm or less, further preferably 380 ppm or less, further preferably 370 ppm or less, still more preferably 360 ppm or less. It is even more preferably 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 from the recording of the information on the magnetic tape to the reproduction. Therefore, from the viewpoint of further suppressing the occurrence of reproduction errors due to changes in the tape width between recording and reproduction, the smaller the magnetic tape width deformation rate is, the more preferable it is, and it may be 0 ppm. The tape width deformation rate can also be controlled by heat treatment described in detail later.

The tape width deformation rate is a value obtained 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%, except for the storage described below.
The magnetic tape wound on the reel is taken out from the magnetic tape cartridge 100 days from the date of manufacture of the magnetic tape cartridge, and a tape sample having a length of 20 cm including a position of 10 m ± 1 m from the outer end of the tape is cut out and taped by the above method. Find the width. This tape width is defined as the tape width before storage. The tape width before storage is the value of the tape sample used to obtain the tape width difference (BA) (that is, the tape width A obtained above), or the tape width difference (BA). ) Is the value obtained for the tape sample cut out from the same magnetic tape as the tape sample used for obtaining) so as to include a position of 10 m ± 1 m from the outer end of the tape.
A 20 cm long tape sample for which the width of the tape before storage was obtained was loaded with a load of 100 g in the longitudinal direction of the tape by holding one end of the tape sample and hanging a weight of 100 g on the other end. In this state, it is stored for 24 hours in a dry environment at a temperature of 52 ° C. The dry environment is an environment with a relative humidity of 10% or less. The storage starts on the 100th day from the date of manufacture of the magnetic tape cartridge. Within 20 minutes after the load is removed after the above storage, the tape width (arithmetic mean of 5 measured values excluding the maximum and minimum values obtained in 7 measurements) is measured in the same manner as in the above method. Ask. This tape width is defined as the tape width after storage.
The difference in the tape width of before and after storage - value × 10 ⁶ divided by (before storage tape width after storage tape width) and before storage tape width (unit: ppm), and the tape width deformation ratio.

Hereinafter, the magnetic tape included in the magnetic tape cartridge will be described in more detail.

(Tape thickness)
The thickness (total thickness) of the magnetic tape is 5.2 μm or less. It is preferable to reduce the thickness of the magnetic tape because it leads to an increase in capacity. However, a magnetic tape thinned to a thickness of 5.2 μm or less tends to deform depending on the position over time in the magnetic tape cartridge as described above if no measures are taken. The present inventors consider that is a cause of a reproduction error. On the other hand, the magnetic tape having a tape width difference (BA) 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 is contained in the magnetic tape cartridge during the period from recording to reproduction. It can be said that it is a magnetic tape in which deformation that can occur over time is generated in advance. This makes it possible to suppress the occurrence of a reproduction error when reproducing the information recorded on the thin magnetic tape having a tape thickness of 5.2 μm or less. From the viewpoint of further increasing the capacity, the thickness of the magnetic tape is preferably 5.0 μm or less, and 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, and more preferably 3.5 μm or more.

The tape thickness is a value obtained by the following method.
Magnetic tape cartridge From the magnetic tape cartridge 100 days after the date of manufacture, the magnetic tape wound on the reel is taken out, and 10 tape samples (for example, 5 to 10 cm in length) are cut out from any part of the magnetic tape, and these are cut out. Stack tape samples and measure the thickness. The value obtained by 1/10 of the measured thickness (thickness per tape sample) is defined as the tape thickness. The thickness measurement can be performed using a known measuring device capable of measuring the thickness on the order of 0.1 μm. This tape thickness may be determined using the above-mentioned tape width difference (BA) and / or the magnetic tape used for determining the tape width deformation rate, and the above-mentioned tape width difference (BA) and / or the above-mentioned tape width difference (BA) and /. Alternatively, the magnetic tape taken out from the magnetic tape cartridge having the same product lot number as the magnetic tape cartridge containing the magnetic tape used to obtain the tape width deformation rate may be used.
Further, various thicknesses such as the thickness of the magnetic layer can be obtained by the following methods.
After exposing the cross section of the magnetic tape in the thickness direction with an ion beam, the cross section of the exposed cross section is observed with a scanning electron microscope. Various thicknesses can be obtained as the arithmetic mean of the thicknesses obtained at any two points in the cross-sectional observation. Alternatively, various thicknesses can be obtained as design thicknesses calculated from manufacturing conditions and the like.

(Non-magnetic support)
The magnetic tape has at least a non-magnetic support and a magnetic layer. Examples of the non-magnetic support (hereinafter, also simply referred to as “support”) include a polyethylene naphthalate support, a polyamide support, a polyethylene terephthalate support, a polyamide-imide support and the like. These supports are commercially available or can be manufactured by known methods. As the support, a polyethylene naphthalate support, a polyamide support and a polyethylene terephthalate support are preferable from the viewpoint of strength, flexibility and the like. The polyethylene naphthalate support means a support including at least a polyethylene naphthalate layer, which comprises a single layer or two or more polyethylene naphthalate layers and one or more other layers in addition to the polyethylene naphthalate layer. What is included is included. This point is the same for other supports. Further, the polyamide can include an aromatic skeleton and / or an aliphatic skeleton, and a polyamide containing an aromatic skeleton (aromatic polyamide) is preferable, and aramid is more preferable. The support may be subjected to corona discharge, plasma treatment, easy adhesion treatment, heat treatment or the like in advance.

(Magnetic layer)
Ferromagnetic powder The magnetic layer contains a ferromagnetic powder and a binder. As the ferromagnetic powder contained in the magnetic layer, a ferromagnetic powder known as the ferromagnetic powder used in the magnetic layer of various magnetic recording media can be used. It is preferable to use a ferromagnetic powder having a small average particle size from the viewpoint of improving the recording density. From this point, the average particle size of the ferromagnetic powder is preferably 50 nm or less, more preferably 45 nm or less, further preferably 40 nm or less, further preferably 35 nm or less, and more preferably 30 nm or less. It is even more preferably 25 nm or less, and even more preferably 20 nm or less. On the other hand, from the viewpoint of magnetization stability, the average particle size of the ferromagnetic powder is preferably 5 nm or more, more preferably 8 nm or more, further preferably 10 nm or more, and further preferably 15 nm or more. Is even more preferable, and 20 nm or more is even more preferable.

− Hexagonal ferrite powder −
A preferred specific example of the ferromagnetic powder is a hexagonal ferrite powder. For details of the hexagonal ferrite powder, for example, paragraphs 0012 to 0030 of JP2011-225417A, paragraphs 0134 to 0136 of JP2011-216149A, paragraphs 0013 to 0030 of JP2012-204726A, and References can be made to paragraphs 0029 to 0084 of JP-A-2015-127985.

In the present invention and the present specification, the "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 highest intensity diffraction peak belongs in the X-ray diffraction spectrum obtained by X-ray diffraction analysis. For example, when the highest intensity diffraction peak in the X-ray diffraction spectrum obtained by X-ray diffraction analysis belongs to the hexagonal ferrite type crystal structure, it is determined that the hexagonal ferrite type crystal structure is detected as the main phase. It shall be. When only a single structure is detected by X-ray diffraction analysis, this detected structure is used as the main phase. The hexagonal ferrite type crystal structure contains at least iron atoms, divalent metal atoms and oxygen atoms as constituent atoms. The divalent metal atom is a metal atom that can be a divalent cation as an ion, and examples thereof include alkaline earth metal atoms such as strontium atom, barium atom and calcium atom, and lead atom. In the present invention and the present specification, the hexagonal strontium ferrite powder means that the main divalent metal atom contained in this powder is a strontium atom, and the hexagonal barium ferrite powder is the main contained in this powder. A divalent metal atom is a barium atom. The main divalent metal atom is a divalent metal atom that occupies the largest amount on an atomic% basis among the divalent metal atoms contained in this powder. However, rare earth atoms are not included in the above divalent metal atoms. The "rare earth atom" in the present invention and the present specification is selected from the group consisting of a scandium atom (Sc), a yttrium atom (Y), and a lanthanoid atom. The lanthanoid atom is a lanthanum atom (La), a cerium atom (Ce), a placeodim atom (Pr), a neodymium atom (Nd), a promethium atom (Pm), a samarium atom (Sm), a gadolinium atom (Eu), and a gadolinium atom (Gd). ), Terbium atom (Tb), dysprosium atom (Dy), formium atom (Ho), erbium atom (Er), samarium atom (Tm), ytterbium atom (Yb), and lutetium atom (Lu). To.

Hereinafter, the hexagonal strontium ferrite powder, which is one aspect of the hexagonal ferrite powder, will be described in more detail.

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

The "activated volume" is a unit of magnetization reversal and is an index indicating the magnetic size of a particle. The activated volume described in the present invention and the present specification and the anisotropic 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 measuring unit (measurement). Temperature: 23 ° C ± 1 ° C), which is a value obtained from the following relational expression between Hc and activated volume V. Regarding the unit of the anisotropy constant Ku, 1 erg / cc = 1.0 × 10 ^-1 J / m ³ .
Hc = 2Ku / Ms {1-[(kT / KuV) ln (At / 0.693)] ^1/2 }
[In the above formula, Ku: anisotropic 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 lag frequency (unit: s ^-1 ), t: magnetic field reversal time (unit: s)]

Anisotropy constant Ku can be mentioned as an index for reducing thermal fluctuation, in other words, improving thermal stability. Hexagonal strontium ferrite powder can preferably have 1.8 × 10 ⁵ J / m ³ or more Ku, more preferably have a 2.0 × 10 ⁵ J / m ³ or more Ku. Also, Ku of hexagonal strontium ferrite powder can be, for example, not 2.5 × 10 ⁵ J / m ³ or less. However, the higher the Ku, the higher the thermal stability, which is preferable, and therefore, the value is not limited to the above-exemplified value.

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 hexagonal strontium ferrite powder contains rare earth atoms at a content rate (bulk content) of 0.5 to 5.0 atom% with respect to 100 atom% of iron atoms. In one aspect, the hexagonal strontium ferrite powder containing rare earth atoms can have uneven distribution on the surface layer of rare earth atoms. The term "rare earth atomic surface uneven distribution" as used in the present invention and the present specification refers to the rare earth atom content with respect to 100 atomic% of iron atoms in the solution obtained by partially dissolving hexagonal strontium ferrite powder with an acid (hereinafter referred to as "rare earth atom content"). “Rare earth atom surface layer 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 an acid. Rare earth atom content (hereinafter referred to as "rare earth atom bulk content" or simply referred to as "bulk content" for rare earth atoms).
Rare earth atom surface layer content / Rare earth atom bulk content> 1.0
Means that the ratio of The rare earth atom content of the hexagonal ferrite powder described later 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. Therefore, the rare earth atom content in the solution obtained by the partial dissolution constitutes the hexagonal strontium ferrite powder. It is the rare earth atom content in the surface layer of the particles. The fact that the rare earth atom surface layer content satisfies the ratio of "rare earth atom surface layer content / rare earth atom bulk content>1.0" means that the rare earth atom is present in the surface layer of the particles constituting the hexagonal strontium ferrite powder. It means that it is unevenly distributed (that is, it exists more than inside). The surface layer portion in the present invention and the present specification means a partial region from the surface to the inside of the particles constituting the hexagonal strontium ferrite powder.

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 atomic% with respect to 100 atomic% of iron atoms. The fact that the rare earth atoms are contained in the bulk content in the above range and the rare earth atoms are unevenly distributed on the surface layer of the particles constituting the hexagonal strontium ferrite powder contributes to suppressing the decrease in the regeneration output in the repeated regeneration. Conceivable. This is because the hexagonal strontium ferrite powder contains rare earth atoms at a bulk content in the above range, and the rare earth atoms are unevenly distributed on the surface layer of the particles constituting the hexagonal strontium ferrite powder. It is presumed that this is because it can be enhanced. The higher the value of the anisotropy constant Ku, the more the occurrence of a phenomenon called thermal fluctuation can be suppressed (in other words, the thermal stability can be improved). By suppressing the occurrence of thermal fluctuation, it is possible to suppress a decrease in the reproduction output during repeated reproduction. The uneven distribution of rare earth atoms on the surface layer of the hexagonal strontium ferrite powder contributes to stabilizing the spin of iron (Fe) sites in the crystal lattice of the surface layer, which results in anisotropy constant Ku. It is speculated that it will increase.
In addition, it is presumed that the use of hexagonal strontium ferrite powder, which has uneven distribution on the surface layer of rare earth atoms, as the ferromagnetic powder of the magnetic layer also contributes to suppressing the surface of the magnetic layer from being scraped by sliding with the magnetic head. To. That is, it is presumed that the hexagonal strontium ferrite powder having uneven distribution on the surface layer of rare earth atoms can also contribute to the improvement of the running durability of the magnetic tape. This is because the uneven distribution of rare earth atoms on the surface of the particles constituting the hexagonal strontium ferrite powder improves the interaction between the particle surface and the organic substances (for example, binder and / or additive) contained in the magnetic layer. As a result, it is presumed that the strength of the magnetic layer is improved.
The rare earth atom content (bulk content) is in the range of 0.5 to 4.5 atomic% from the viewpoint of further suppressing the decrease in the reproduction output in the repeated regeneration and / or further improving the running durability. It is more preferably in the range of 1.0 to 4.5 atomic%, further preferably in the range of 1.5 to 4.5 atomic%.

The bulk content is a content obtained by completely dissolving the hexagonal strontium ferrite powder. Unless otherwise specified, in the present invention and the present specification, the content of atoms means the bulk content obtained by completely dissolving hexagonal strontium ferrite powder. The hexagonal strontium ferrite powder containing a rare earth atom may contain only one kind of rare earth atom as a rare earth atom, or may contain two or more kinds of rare earth atoms. The bulk content when two or more kinds of rare earth atoms are contained is determined for the total of two or more kinds of rare earth atoms. This point is the same for the present invention and other components in the present specification. That is, unless otherwise specified, a certain component may be used alone or in combination of two or more. The content or content rate when two or more types are used shall mean the total of two or more types.

When the hexagonal strontium ferrite powder contains a rare earth atom, the rare earth atom contained may be any one or more of the rare earth atoms. Examples of the rare earth atom preferable from the viewpoint of further suppressing the decrease in the reproduction output in the repeated regeneration include a neodymium atom, a samarium atom, an ythrium atom and a dysprosium atom, and a neodymium atom, a samarium atom and an yttrium atom are more preferable. Atoms are more preferred.

In the hexagonal strontium ferrite powder having uneven distribution on the surface layer of rare earth atoms, the rare earth atoms may be unevenly distributed on the surface layer of the particles constituting the hexagonal strontium ferrite powder, and the degree of uneven distribution is not limited. For example, a hexagonal strontium ferrite powder having uneven distribution on the surface layer of a rare earth atom is partially dissolved under the dissolution conditions described later, and the content of the surface layer of the rare earth atom is completely dissolved under the dissolution conditions described later. The ratio of the atom 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 / bulk content" is larger than 1.0, it means that the rare earth atoms are unevenly distributed (that is, more than the inside) in the particles constituting the hexagonal strontium ferrite powder. To do. In addition, the ratio of the surface layer content of rare earth atoms obtained by partial dissolution under the dissolution conditions described later to the bulk content of rare earth atoms obtained by total dissolution under the dissolution conditions described later, "Surface layer content / The "bulk content" can be, for example, 10.0 or less, 9.0 or less, 8.0 or less, 7.0 or less, 6.0 or less, 5.0 or less, or 4.0 or less. However, in the hexagonal strontium ferrite powder having uneven distribution on the surface layer of rare earth atoms, the rare earth atoms need only be unevenly distributed on the surface layer of the particles constituting the hexagonal strontium ferrite powder. The "rate" is not limited to the upper or lower limit illustrated.

The partial dissolution and total dissolution of the hexagonal strontium ferrite powder will be described below. For the hexagonal strontium ferrite powder that exists as a powder, the sample powder that is partially or completely dissolved is collected 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, a part of the hexagonal strontium ferrite powder taken out from the magnetic layer is subjected to partial dissolution, and the other part is subjected to total dissolution. The hexagonal strontium ferrite powder can be taken out from the magnetic layer by, for example, the method described in paragraph 0032 of JP2015-91747A.
The above-mentioned partial dissolution means that the hexagonal strontium ferrite powder is dissolved in the liquid to the extent that the residue can be visually confirmed at the end of the dissolution. For example, by partial dissolution, 10 to 20% by mass of the particles constituting the hexagonal strontium ferrite powder can be dissolved with the whole particles as 100% by mass. On the other hand, the above-mentioned total dissolution means that the hexagonal strontium ferrite powder is dissolved in the liquid until the residue is not visually confirmed at the end of the dissolution.
The partial dissolution and the measurement of the surface layer content are carried out by, for example, the following methods. However, the following dissolution conditions such as the amount of sample powder are examples, and dissolution conditions capable of partial dissolution and total dissolution can be arbitrarily adopted.
A container (for example, a beaker) containing 12 mg of sample powder and 10 ml of 1 mol / L hydrochloric acid is held on a hot plate 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 by an inductively coupled plasma (ICP) analyzer. In this way, the surface layer content of rare earth atoms with respect to 100 atomic% of iron atoms can be determined. When a plurality of rare earth atoms are detected by elemental analysis, the total content of all rare earth atoms is defined as the surface layer content. This point is the same in the measurement of bulk content.
On the other hand, the total dissolution and the measurement of the bulk content are carried out by, for example, the following methods.
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. After that, the same procedure as the above-mentioned partial dissolution and measurement of the surface layer content can be performed to determine the bulk content with respect to 100 atomic% of iron atoms.

From the viewpoint of increasing the reproduction output when reproducing the information recorded on the magnetic tape, it is desirable that the mass magnetization σs of the ferromagnetic powder contained in the magnetic tape is high. In this regard, the hexagonal strontium ferrite powder containing rare earth atoms but not having uneven distribution on the surface layer of rare earth atoms tended to have a significantly lower σs than the hexagonal strontium ferrite powder containing no rare earth atoms. On the other hand, hexagonal strontium ferrite powder having uneven distribution on the surface layer of rare earth atoms is considered to be preferable in order to suppress such a large decrease in σs. In one aspect, 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.} Meanwhile, [sigma] s from the viewpoint of noise reduction, is preferably not more than 80A · m ² / kg, more preferably not more than 60A · m ² / kg. σs can be measured using a known measuring device capable of measuring magnetic characteristics such as a vibrating sample magnetometer. Unless otherwise specified, in the present invention and the present specification, the mass magnetization σs is a value measured at a magnetic field strength of 1194 kA / m (15 kOe).

Regarding the content of 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% with respect to 100 atom% of iron atoms. In one aspect, the hexagonal strontium ferrite powder can contain only strontium atoms as divalent metal atoms contained in the powder. In another aspect, the hexagonal strontium ferrite powder can also contain one or more other divalent metal atoms in addition to the strontium atom. For example, it can contain barium and / or calcium atoms. When a divalent metal atom other than the strontium atom is contained, the barium atom content and the calcium atom content in the hexagonal strontium ferrite powder are, for example, 0.05 to 5 with respect to 100 atomic% of iron atoms, respectively. It can be in the range of 0.0 atomic%.

As the crystal structure of hexagonal ferrite, magnetoplumbite type (also referred to as "M type"), W type, Y type and Z type are known. The hexagonal strontium ferrite powder may have any crystal structure. The crystal structure can be confirmed by X-ray diffraction analysis. The hexagonal strontium ferrite powder can be one in which a single crystal structure or two or more kinds of crystal structures are detected by X-ray diffraction analysis. For example, in one aspect, the hexagonal strontium ferrite powder can be such that only the M-type crystal structure is detected by X-ray diffraction analysis. For example, M-type hexagonal ferrite is represented by the composition formula of _{AFe 12} O _19. Here, A represents a divalent metal atom, and when the hexagonal strontium ferrite powder is M-type, A is only a strontium atom (Sr), or when A contains a plurality of divalent metal atoms. As mentioned above, the strontium atom (Sr) occupies the largest amount on the basis of atomic%. 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 can also contain rare earth atoms. Further, 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 an aluminum atom (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 decrease in regeneration output during repeated regeneration, 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. % Is preferably 10.0 atomic% or less, more preferably in the range of 0 to 5.0 atomic%, and may be 0 atomic%. That is, in one aspect, the hexagonal strontium ferrite powder does not have to contain atoms other than iron atoms, strontium atoms, oxygen atoms and rare earth atoms. The content expressed in atomic% above is the content (unit: mass%) of each atom obtained by completely dissolving the hexagonal strontium ferrite powder, and is converted to the value expressed in atomic% using the atomic weight of each atom. Calculated by conversion. Further, in the present invention and the present specification, "not contained" for a certain atom means that the content is completely dissolved and the content measured by an ICP analyzer 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 "not included" is used in the sense of including the inclusion in an amount less than the detection limit of the ICP analyzer. In one aspect, the hexagonal strontium ferrite powder can be free of bismuth atoms (Bi).

-Metal powder-
As a preferable specific example of the ferromagnetic powder, a ferromagnetic metal powder can also be mentioned. For details of the ferromagnetic metal powder, for example, paragraphs 0137 to 0141 of JP2011-216149A and paragraphs 0009 to 0023 of JP2005-251351 can be referred to.

-Ε-Iron oxide powder-
As a preferable specific example of the ferromagnetic powder, ε-iron oxide powder can also be mentioned. In the present invention and the present specification, the "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, when the highest intensity diffraction peak in the X-ray diffraction spectrum obtained by X-ray diffraction analysis is assigned to the ε-iron oxide type crystal structure, the ε-iron oxide type crystal structure is detected as the main phase. Judgment shall be made. As a method for producing ε-iron oxide powder, a method for producing from goethite, a reverse micelle method, and the like are known. All of the above manufacturing methods are known. Regarding the method for producing ε-iron oxide powder in which a part of Fe is substituted with a substituted atom such as Ga, Co, Ti, Al, Rh, for example, J.I. Jpn. Soc. Powder Metallurgy Vol. 61 Supplement, No. S1, pp. S280-S284, J. Mol. Mater. Chem. C, 2013, 1, pp. 5200-5206 and the like can be referred to. However, the method for producing ε-iron oxide powder that can be used as a ferromagnetic powder in the magnetic layer of the magnetic tape is not limited to the methods listed here.

The activated volume of the ε-iron oxide powder is preferably in the range of ^{300-1500 nm 3.} The finely divided ε-iron oxide powder exhibiting an activated volume in 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 be, for example, 500 nm ³ or more. Further, from the viewpoint further improvement of the electromagnetic conversion characteristics, .epsilon. activation volume of the iron oxide powder is more preferably 1400 nm ³ or less, further preferably 1300 nm ³ or less, and 1200 nm ³ or less Is even more preferable, and 1100 nm ³ or less is even more preferable.

Anisotropy constant Ku can be mentioned as an index for reducing thermal fluctuation, in other words, improving thermal stability. The ε-iron oxide powder can preferably have ^{Ku of 3.0 × 10 4} J / m ³ or more, and more preferably 8.0 × 10 ⁴ J / m ³ or more. Further, .epsilon. Ku iron oxide powder can be, for example, not 3.0 × 10 ⁵ J / m ³ or less. However, the higher the Ku, the higher the thermal stability, which is preferable, and therefore, the value is not limited to the above-exemplified value.

From the viewpoint of increasing the reproduction output when reproducing the information recorded on the 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 8 A · m 2} / kg or more, and can also be 12 A · m ^{2 / kg or more.} On the other hand, the σs of the ε-iron oxide powder ^{is preferably 40 A · m 2} / kg or less, and more preferably 35 A · m ² / kg or less, from the viewpoint of noise reduction.

Unless otherwise specified in the present invention and the present specification, the average particle size of various powders such as ferromagnetic powders is a value measured by the following method using a transmission electron microscope.
The powder is photographed using a transmission electron microscope at an imaging magnification of 100,000 times, and printed on photographic paper so as to have a total magnification of 500,000 times to obtain a photograph of the particles constituting the powder. Select the target particle from the obtained photograph of the particle, trace the outline of the particle with a digitizer, and measure the size of the particle (primary particle). Primary particles are independent particles without agglomeration.
The above measurements are performed on 500 randomly sampled particles. The arithmetic mean of the particle sizes of the 500 particles thus obtained is taken as the average particle size of the powder. As the transmission electron microscope, for example, Hitachi's transmission electron microscope H-9000 can be used. Further, the particle size can be measured by using a known image analysis software, for example, an image analysis software KS-400 manufactured by Carl Zeiss. Unless otherwise specified, the average particle size shown in the examples described later was measured using a transmission electron microscope H-9000 manufactured by Hitachi as a transmission electron microscope and a Carl Zeiss image analysis software KS-400 as an image analysis software. The value. In the present invention and the present specification, the powder means an aggregate of a plurality of particles. For example, a ferromagnetic powder means a collection of a plurality of ferromagnetic particles. Further, the set of a plurality of particles is not limited to a mode in which the particles constituting the set are in direct contact with each other, and also includes a mode in which a binder, an additive, etc., which will be described later, are interposed between the particles. To. The term particle is sometimes used to describe powder.

As a method for collecting the sample powder from the magnetic tape for measuring the particle size, for example, the method described in paragraph 0015 of JP2011-048878A can be adopted.

Unless otherwise specified in the present invention and the present specification, the size (particle size) of the particles constituting the powder is the shape of the particles observed in the above particle photograph.
(1) In the case of needle-shaped, spindle-shaped, columnar (however, the height is larger than the maximum major axis of the bottom surface), it is represented by the length of the major axis constituting 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 represented by the maximum major axis of the plate surface or bottom surface.
(3) When the shape is spherical, polyhedral, unspecified, etc., and the long axis constituting the particles cannot be specified from the shape, it is represented by the diameter equivalent to a circle. The equivalent diameter of a circle is what is obtained by the circular projection method.

Further, for the average needle-like ratio of the powder, the length of the minor axis of the particles, that is, the minor axis length is measured in the above measurement, and the value of (major axis length / minor axis length) of each particle is obtained. Refers to the arithmetic average of the values obtained for a particle. Here, unless otherwise specified, the minor axis length is the length of the minor axis constituting the particle in the case of (1) in the above definition of the particle size, and the thickness or height in the case of the same (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 shape of the particles is specific, for example, in the case of the above definition of particle size (1), the average particle size is the average major axis length, and in the case of the same definition (2), the average particle size is Average plate diameter. In the case of the same definition (3), the average particle size is an average diameter (also referred to as an average particle size or an average particle size).

The content (filling rate) of the ferromagnetic powder in the magnetic layer is preferably in the range of 50 to 90% by mass, and more preferably in the range of 60 to 90% by mass. The components of the magnetic layer other than the ferromagnetic powder are at least a binder and may optionally include one or more additional additives. A high filling rate of the ferromagnetic powder in the magnetic layer is preferable from the viewpoint of improving the recording density.

Binder, Hardener The magnetic tape is a coating type magnetic tape, and the magnetic layer contains a binder. The binder is one or more resins. As the binder, various resins usually used as a binder for a coating type magnetic recording medium can be used. For example, as the binder, polyurethane resin, polyester resin, polyamide resin, vinyl chloride resin, styrene, acrylonitrile, acrylic resin obtained by copolymerizing methyl methacrylate and the like, cellulose resin such as nitrocellulose, epoxy resin, phenoxy resin, polyvinyl acetal, etc. A resin selected from a polyvinyl alkyral resin such as polyvinyl butyral can be used alone, or a plurality of resins can be mixed and used. Of these, polyurethane resins, acrylic resins, cellulose resins, and vinyl chloride resins are preferred. These resins may be homopolymers or copolymers. These resins can also be used as binders in the non-magnetic layer and / or the backcoat layer described later.
For the above binder, paragraphs 0028 to 0031 of JP-A-2010-24113 can be referred to. The average molecular weight of the resin used as the binder can be, for example, 10,000 or more and 200,000 or less as the weight average molecular weight. The weight average molecular weight in the present invention and the present specification is a value obtained by converting a value measured by gel permeation chromatography (GPC) under the following measurement conditions into polystyrene. The weight average molecular weight of the binder shown in Examples described later is a value obtained by converting a value measured under the following measurement conditions into polystyrene.
GPC device: HLC-8120 (manufactured by Tosoh)
Column: TSK gel Multipore HXL-M (manufactured by Tosoh, 7.8 mm ID (Inner Diameter) x 30.0 cm)
Eluent: tetrahydrofuran (THF)

Further, a curing agent can be used together with a resin that can be used as a binder. The curing agent can be a thermosetting compound which is a compound in which a curing reaction (crosslinking reaction) proceeds by heating in one aspect, and a photocuring agent in which a curing reaction (crosslinking reaction) proceeds by light irradiation in another aspect. It can be a sex compound. As the curing reaction proceeds in the process of forming the magnetic layer, at least a part of the curing agent can be contained in the magnetic layer in a state of reacting (crosslinking) with other components such as a binder. This point is the same for the layer formed by using this composition when the composition used for forming another layer contains a curing agent. Preferred curing agents are thermosetting compounds, with polyisocyanates being preferred. For details of the polyisocyanate, refer to paragraphs 0124 to 0125 of JP2011-216149A. The content of the curing agent in the composition for forming the magnetic layer can be, for example, 0 to 80.0 parts by mass with respect to 100.0 parts by mass of the binder, and 50.0 from the viewpoint of improving the strength of the magnetic layer. It can be ~ 80.0 parts by mass.

Additives The magnetic layer contains a ferromagnetic powder and a binder and may contain one or more additives, if desired. Examples of the additive include the above-mentioned curing agent. Examples of the additive contained in the magnetic layer include non-magnetic powder (for example, inorganic powder, carbon black, etc.), lubricant, dispersant, dispersion aid, fungicide, antistatic agent, antioxidant, and the like. Can be done. For example, for lubricants, paragraphs 0030 to 0033, 0035 and 0036 of JP2016-126817A can be referred to. A lubricant may be contained in the non-magnetic layer described later. For the lubricants that can be contained in the non-magnetic layer, reference can be made to paragraphs 0030 to 0031, 0034, 0035 and 0036 of JP2016-126817A. For the dispersant, paragraphs 0061 and 0071 of JP2012-133387A can be referred to. A dispersant may be added to the composition for forming a non-magnetic layer. For the dispersant that can be added to the composition for forming a non-magnetic layer, paragraph 0061 of Japanese Patent Application Laid-Open No. 2012-1333837 can be referred to. Further, as the non-magnetic powder that can be contained in the magnetic layer, a non-magnetic powder that can function as a polishing agent and a 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 colloidal particles, etc.) and the like. The average particle size of colloidal silica (silica colloidal particles) shown in Examples described later is a value obtained by the method described as a method for measuring the average particle size in paragraph 0015 of JP2011-048878A. .. As the additive, a commercially available product can be appropriately selected according to the desired properties, or the additive can be produced by a known method and used in an arbitrary amount. Examples of the additive 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 JP2013-131285.

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

(Non-magnetic layer)
Next, the non-magnetic layer will be described. The magnetic tape may have a magnetic layer directly on the surface of the non-magnetic support, and has a magnetic layer on the surface of the non-magnetic support via a non-magnetic layer containing a non-magnetic powder and a binder. You may. The non-magnetic powder used for the non-magnetic layer may be an inorganic powder or an organic powder. In addition, 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 non-magnetic powders are commercially available and can also be produced by known methods. For details thereof, refer to paragraphs 0146 to 0150 of JP2011-216149A. For carbon black that can be used for the non-magnetic layer, paragraphs 0040 to 0041 of JP2010-24113A can also be referred to. The content (filling rate) of the non-magnetic powder in the non-magnetic layer is preferably in the range of 50 to 90% by mass, and more preferably in the range of 60 to 90% by mass.

For other details such as binders and additives of the non-magnetic layer, known techniques relating to the non-magnetic layer can be applied. Further, for example, with respect to the type and content of the binder, the type and content of the additive, and the like, known techniques relating to the magnetic layer can also be applied.

In the present invention and the present specification, the non-magnetic layer includes not only the non-magnetic powder but also a substantially non-magnetic layer containing a small amount of ferromagnetic powder, for example, as an impurity or intentionally. Here, the substantially non-magnetic layer means that the residual magnetic flux density of this layer is 10 mT or less, the coercive force is 7.96 kA / m (100 Oe) or less, or the residual magnetic flux density is 10 mT or less. It refers to a layer having a coercive force of 7.96 kA / m (100 Oe) or less. The non-magnetic layer preferably has no residual magnetic flux density and coercive force.

(Back coat layer)
The magnetic tape may also have a backcoat layer containing a non-magnetic powder and a binder on the surface side opposite to the surface side having the magnetic layer of the non-magnetic support. The backcoat layer preferably contains one or both of carbon black and inorganic powder. For the binder contained in the backcoat layer and various additives that may be optionally contained, the known technique relating to the backcoat layer can be applied, and the known technique relating to the formulation of the magnetic layer and / or the non-magnetic layer shall be applied. You can also. For example, paragraphs 0018 to 0020 of JP-A-2006-331625 and the description of US Pat. No. 7,029,774, column 4, line 65 to column 5, line 38 can be referred to for the backcoat layer. ..

(Various thickness)
The thickness (total thickness) of the magnetic tape is as described above.
The thickness of the non-magnetic support is preferably 3.0 to 5.0 μm.
The thickness of the magnetic layer can be optimized by the saturation magnetization amount of the magnetic head used, the head gap length, the band of the recording signal, etc., and is generally 0.01 μm to 0.15 μm, from the viewpoint of high-density recording. It is preferably 0.02 μm to 0.12 μm, and more preferably 0.03 μm to 0.1 μm. The magnetic layer may be at least one layer, and the magnetic layer may be separated into two or more layers having different magnetic characteristics, and a known configuration relating to a multi-layer magnetic layer can be applied. The thickness of the magnetic layer when separated into two or more layers is the total thickness of these layers.
The thickness of the non-magnetic layer is, for example, 0.1 to 1.5 μm, preferably 0.1 to 1.0 μm.
The thickness of the backcoat layer is preferably 0.9 μm or less, more preferably 0.1 to 0.7 μm.

<Manufacturing process>
(Preparation of composition for forming each layer)
The step of preparing the composition for forming the magnetic layer, the non-magnetic layer or the backcoat layer usually includes at least a kneading step, a dispersion step, and a mixing step provided before and after these steps as necessary. Each process may be divided into two or more steps. The components used in the preparation of each layer-forming composition may be added at the beginning or in the middle of any step. As the solvent, one or more of various solvents usually used for producing a coating type magnetic recording medium can be used. For the solvent, for example, paragraph 0153 of JP2011-216149A can be referred to. Further, each component may be added separately in two or more steps. For example, the binder may be divided and added in a kneading step, a dispersion step, and a mixing step for adjusting the viscosity after dispersion. In order to manufacture the magnetic tape, known manufacturing techniques can be used in various steps. In the kneading step, it is preferable to use an open kneader, a continuous kneader, a pressurized kneader, an extruder or the like having a strong kneading force. For details of the kneading process, Japanese Patent Application Laid-Open No. 1-106338 and JP-A-1-79274 can be referred to. A known disperser can be used. Filtration may be performed by a known method at any stage of preparing each layer-forming composition. Filtration can be performed, for example, by filter filtration. As the filter used for filtration, for example, a filter having a pore size of 0.01 to 3 μm (for example, a glass fiber filter, a polypropylene filter, etc.) can be used.

(Applying process)
The magnetic layer can be formed by directly applying the composition for forming a magnetic layer on the surface of a non-magnetic support, or by applying multiple layers sequentially or simultaneously with the composition for forming a non-magnetic layer. In the backcoat layer, the composition for forming the backcoat layer is placed on the side opposite to the surface having the non-magnetic layer and / or the magnetic layer of the non-magnetic support (or the non-magnetic layer and / or the magnetic layer is additionally provided). It can be formed by applying it to the surface. For details of the coating for forming each layer, refer to paragraph 0066 of Japanese Patent Application Laid-Open No. 2010-231843.

(Other processes)
Known techniques can be applied to various other steps for the production of magnetic tapes. For various steps, for example, paragraphs 0067 to 0070 of JP2010-231843A 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. For the orientation treatment, various known techniques such as the description in paragraph 0067 of JP-A-2010-231843 can be applied.
By going through various steps, a long magnetic tape raw fabric can be obtained. The obtained magnetic tape raw fabric is cut (slit) to the width of the magnetic tape to be wound around the magnetic tape cartridge by a known cutting machine. The above width is determined according to the standard and is usually 1/2 inch (0.0127 meters).
A servo pattern can also be formed on the magnetic tape obtained by slitting by a known method in order to enable head tracking servo to be performed in the magnetic tape device (drive). For example, the servo pattern can be formed on a DC (Direct Current) degaussed magnetic layer. The degaussing direction can be the longitudinal or vertical direction of the magnetic tape. Further, the direction of magnetization when forming the servo pattern (that is, the magnetization region) can be the longitudinal direction or the vertical direction of the magnetic tape.

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

In one aspect, the heat treatment is performed in a state where the magnetic tape is wound around a core-shaped member for heat treatment (hereinafter, referred to as “core for heat treatment”), and the magnetic tape after the heat treatment is wound around a reel of a magnetic tape cartridge. , A magnetic tape cartridge in which a magnetic tape is wound on a reel can be produced.
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 having high rigidity from the viewpoint of suppressing the occurrence of winding failure such as spoking. From this point of view, the heat treatment winding core is preferably made of metal or resin. Further, as an index of rigidity, the flexural 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 a high-rigidity material is generally expensive, using a heat-treating winding core of a material having a rigidity exceeding the rigidity capable of suppressing the occurrence of winding failure leads to an increase in cost. Considering the above points, the flexural modulus of the material of the heat treatment core 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 heat treatment winding core can be a solid or hollow core-like 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 heat treatment winding core may or may not have a flange.
As a magnetic tape to be wound around the heat treatment core, prepare a magnetic tape having a length longer than the length finally accommodated in the magnetic tape cartridge (hereinafter referred to as "final product length"), and wind this magnetic tape around the heat treatment core. It is preferable to perform the heat treatment by placing the magnet in a heat treatment environment. The length of the magnetic tape wound around the heat treatment core is equal to or longer than the final product length, and from the viewpoint of ease of winding around the heat treatment core or the like, it is preferably "final product length + α". This α is preferably 5 m or more from the viewpoint of ease of winding. The tension at the time of winding on the heat treatment core is preferably 0.1 N (Newton) or more from the viewpoints of ease of winding, ease of adjusting the tape width difference (BA) by heat treatment, and manufacturing suitability. .. Further, from the viewpoint of suppressing the occurrence of excessive deformation, the tension at the time of winding around the heat treatment winding core is preferably 1.5 N or less, more preferably 1.0 N or less. The outer diameter of the heat treatment winding core 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) to the above range, the outer diameter of the heat treatment core is preferably 100 mm or less, more preferably 90 mm or less. The width of the heat treatment core may be equal to or greater than the width of the magnetic tape wound around the core. Further, when removing the magnetic tape from the heat treatment core after the heat treatment, the magnetic tape and the heat treatment core are sufficiently cooled before the magnetic tape is sufficiently cooled in order to prevent unintended tape deformation during the removal operation. Is preferably removed from the heat treatment core. The removed magnetic tape is once wound on another winding core (referred to as "temporary winding core"), and then from the temporary winding core to the reel of the magnetic tape cartridge (generally, the outer diameter is 40 to 50 mm). It is preferable to wind the magnetic tape around the reel. As a result, the magnetic tape can be wound around the reel of the magnetic tape cartridge while maintaining the relationship between the inside and the outside of the magnetic tape with respect to the heat treatment core during the heat treatment. For details of the temporary winding core and the tension when winding the magnetic tape around the winding core, the above description regarding the heat treatment winding core can be referred to. In the embodiment in which the above 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 for the final product length may be wound from the temporary winding core to the reel of the magnetic tape cartridge, and the remaining “+ α” length may be cut off. From the viewpoint of reducing the portion to be cut and discarded, the α is preferably 20 m or less.

A specific mode of the heat treatment performed in the state of being wound around the core-shaped member as described above will be described below.
The atmospheric 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, and more preferably 1 g / kg Dry air or more. An atmosphere having a weight absolute humidity in the above range is preferable because it can be prepared without using a special device for reducing moisture. On the other hand, the absolute weight humidity is preferably 70 g / kg Dry air or less, and more preferably 66 g / kg Dry air or less, from the viewpoint of suppressing the occurrence of dew condensation and deterioration of workability. The heat treatment time is preferably 0.3 hours or more, more preferably 0.5 hours or more. The heat treatment time is preferably 48 hours or less from the viewpoint of production efficiency.

By performing the heat treatment as described above, a magnetic tape cartridge provided with a magnetic tape having a tape width difference (BA) of 2.4 μm or more and 12.0 μm or less as a value on the 100th day from the date of manufacture of the magnetic tape cartridge can be obtained. Can be made. The tape width of the magnetic tape subjected to the heat treatment is usually gradually widened from the outer end to the inner end of the tape. Therefore, when the tape width is measured for a tape sample collected from an arbitrary position between the measurement position of the tape width A and the measurement position of the tape width B, the tape width exceeds A as the value on the 100th day from the date of manufacture of the magnetic tape cartridge. The value is usually less than the tape width B.

That is, according to one aspect, it is possible to provide a method for manufacturing a magnetic tape cartridge according to one aspect of the present invention. In such a manufacturing method, a magnetic tape having the same width is cut out from the original magnetic tape, and the cut out magnetic tape is wound around a core member and heat-treated to obtain a magnetic tape on the 100th day from the date of manufacture of the magnetic tape cartridge. As a value of, the tape width difference (BA) can be deformed to be 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 of shipment as a product from the manufacturing factory) can be any day within the period from the manufacturing date of the magnetic tape cartridge to the 100th day. The magnetic tape cartridge shipped within the above period can suppress the occurrence of reproduction errors even if it is used early after shipment. It is preferable to ship the magnetic tape cartridge within the period from the manufacturing date of the magnetic tape cartridge to the 100th day because it does not require long-term inventory storage.

The magnetic tape cartridge can be attached to a magnetic tape device provided with a magnetic head and used for recording and / or reproducing information. In the present invention and the present specification, the "magnetic tape device" means a device capable of recording information on a magnetic tape and reproducing the information recorded on the magnetic tape. Such a device is commonly referred to as a drive. The magnetic head included in the magnetic tape device can be a recording head capable of recording information on the magnetic tape, and can be a reproduction head capable of reproducing the information recorded on the magnetic tape. You can also. 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 both a recording element and a reproducing element are provided in one magnetic head. As the reproduction head, a magnetic head (MR head) including a magnetoresistive (MR) element capable of reading information recorded on a magnetic tape with high sensitivity as a reproduction element is preferable. As the MR head, various known MR heads (for example, GMR (Giant Magnetoresistive) head, TMR (Tunnel Magnetoristive) head, etc.) can be used. Further, the 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) provided with a servo pattern reading element as a head separate from the magnetic head that records and / or reproduces information.

In the magnetic tape device, the recording of information on the magnetic tape and / or the reproduction of the 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 them. .. The magnetic tape device can include the magnetic tape cartridge according to one aspect of the present invention in a detachable manner, and known techniques can be applied to others.

The magnetic tape device includes a magnetic tape cartridge according to an aspect of the present invention. Therefore, it is possible to suppress the occurrence of a reproduction error when reproducing the information recorded on the magnetic tape.

Hereinafter, one aspect of the present invention will be described based on examples. However, the present invention is not limited to the embodiments shown in the examples. Unless otherwise specified, the indications of "part" and "%" described below indicate "parts by mass" and "% by mass". “Eq” is an equivalent and is a unit that cannot be converted into SI units.
Unless otherwise specified, 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%.

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 terephthalate. "PA" indicates an aromatic polyamide support, and "PET" indicates a polyethylene terephthalate support.

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

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

(3) Composition for forming a non-magnetic layer Non-magnetic inorganic powder: α-iron oxide 100.0 parts Average particle size (average major axis length): 0.15 μm
Average needle-like ratio: 7
BET specific surface area: 52 m ² / g
Carbon black 20.0 parts Average particle size: 20 nm
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 Stearic acid amide 0.2 parts Butyl stearate 2.0 parts Cyclohexanone 300.0 parts Methyl ethyl ketone 300.0 parts

(4) a back coat layer forming composition formulations Carbon black 100.0 parts DBP (Dibutyl phthalate) oil absorption of 74cm ^3/100 g
Nitrocellulose 27.0 parts Polyester polyurethane resin containing a sulfonic acid group and / or a salt thereof
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 (Tosoh Coronate L) 15.0 parts

(5) Preparation of composition for forming each layer A composition for forming a magnetic layer 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. As the dispersed beads, zirconia beads having a bead diameter of 0.5 mm were used. Using the above sand mill, the prepared magnetic solution, the above abrasive solution and other components (silica sol, other components and finish addition solvent) are mixed and bead-dispersed for 5 minutes, and then a batch type ultrasonic device (20 kHz, 300 W). The treatment (ultrasonic dispersion) was carried out for 0.5 minutes. Then, 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 non-magnetic layer was prepared by the following method. The above components excluding the lubricants (stearic acid, stearic acid amide and butyl stearate) were kneaded and diluted with an open kneader, and then dispersed with a horizontal bead mill disperser. Then, a lubricant (stearic acid, stearic acid amide and butyl stearate) was added, and the mixture was stirred and mixed with a dissolver stirrer to prepare a composition for forming a non-magnetic layer.
A composition for forming a backcoat layer was prepared by the following method. The above components excluding polyisocyanate were introduced into a dissolver stirrer, stirred at a peripheral speed of 10 m / sec for 30 minutes, and then dispersed by a horizontal bead mill disperser. Then, polyisocyanate was added, and the mixture was stirred and mixed with a dissolver stirrer to prepare a composition for forming a backcoat layer.

(6) Method for Producing Magnetic Tape and Magnetic Tape Cartridge Prepared in (5) above so that the thickness after drying is the thickness shown in Table 1 on the surface of the support of the type and thickness shown in Table 1. The composition for forming a non-magnetic layer was applied and dried to form a non-magnetic layer. Next, the composition for forming a magnetic layer prepared in (5) above was applied onto the non-magnetic layer so that the thickness after drying would be the thickness shown in Table 1 to form a coating layer. After that, while the coating layer of the composition for forming a magnetic layer is in an undried state, a magnetic field having a magnetic field strength of 0.3T is applied in the direction perpendicular to the surface of the coating layer to perform a vertical alignment treatment, and then drying. To form a magnetic layer. Then, the non-magnetic layer of the support shown in Table 1 and the surface opposite to the surface on which the magnetic layer was formed were prepared in (5) above so that the thickness after drying would be the thickness shown in Table 1. The backcoat layer forming composition was applied and dried to form a backcoat layer.
Then, using a calendar roll composed only of a metal roll, the surface is smoothed at a speed of 100 m / min, a linear pressure of 294 kN / m (300 kg / cm), and a calendar temperature of 90 ° C. (the surface temperature of the calendar roll). Processing (calendar processing) was performed.
Then, the long magnetic tape raw fabric was stored in a heat treatment furnace having an atmospheric temperature of 70 ° C. to perform heat treatment (heat treatment time: 36 hours). After the heat treatment, slits were made to a width of 1/2 inch (0.0127 m) to obtain a magnetic tape. By recording a servo signal on the magnetic layer of the obtained magnetic tape with a commercially available servo writer, it has a data band, a servo band, and a guide band in an arrangement according to the LTO (Linear-Tape-Open) Ultra format, and has a data band, a servo band, and a guide band. A magnetic tape having a servo pattern (timing-based servo pattern) arranged and shaped according to the LTO Ultra format on the servo band was obtained.
The magnetic tape (length 960 m) after recording the servo signal was wound around a core for heat treatment, and the heat treatment was performed in a state of being wound around the core. As the core for heat treatment, a resin-made solid core member (outer diameter: 50 mm) having a flexural 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 heat-treated atmosphere was 10 g / kg Dry air.
After the above heat treatment, after the magnetic tape and the heat treatment core have been sufficiently cooled, the magnetic tape is removed from the heat treatment core, wound around the temporary winding core, and then the magnetic tape cartridge (from the temporary winding core). Wind the magnetic tape for the final product length (950 m) around the reel (reel outer diameter: 44 mm) of the LTO Ultra7 data cartridge, cut off the remaining 10 m, and use a commercially available splicing tape at the end of the cut side to use Standard ECMA. (European Computer Manufacturers Association)-319 (June 2001) Leader tapes were joined according to item 9 of Section 3. As the winding core for temporary winding, a solid core-shaped member made of the same material as the winding core for heat treatment and having the same outer diameter was used, and the tension at the time of 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 on a reel was produced.
For each Example, each Comparative Example and Reference Example, two magnetic tape cartridges were made, one used for the evaluation described below and the other used for the recording and reproduction test described below. On the RFID tag inside each magnetic tape cartridge, the date when the magnetic tape was stored in the magnetic tape cartridge was recorded as the date of manufacture of the magnetic tape cartridge (Date of Manufacturer).

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

[Example 7]
The magnetic tape cartridge is the same as in Example 1 except that the support shown in Table 1 is used as the support and the heat treatment is performed with the magnetic tape wound around the core for heat treatment at the heat treatment temperature shown in Table 1. Was produced.

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

[Example 9]
The magnetic tape cartridge is the same as in Example 1 except that the support shown in Table 1 is used as the support and the heat treatment is performed with the magnetic tape wound around the core for heat treatment at the heat treatment temperature shown in Table 1. Was produced.

[Example 10]
A magnetic tape cartridge was produced in the same manner as in Example 9 except that the heat treatment performed with the magnetic tape 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 the hexagonal strontium ferrite powder obtained by the method shown below.
(Method for producing hexagonal strontium ferrite powder)
The SrCO ₃ 1707g, H ₃ BO ₃ and 687 g, Fe ₂ O ₃ to 1120g, Al (OH) ₃ to 45 g, the BaCO ₃ 24 g, 13 g of CaCO _3, and Nd ₂ O ₃ and 235g weighed, with 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 the hot water outlet provided at the bottom of the platinum crucible was heated while stirring the melt, so that the melt was discharged into a rod shape at about 6 g / sec. .. The hot water was rolled and rapidly cooled with a water-cooled twin roller to prepare an amorphous body.
280 g of the produced amorphous body was charged into an electric furnace, the temperature was raised to 635 ° C (crystallization temperature) at a heating rate of 3.5 ° C / min, and the temperature was maintained at the same temperature for 5 hours to obtain hexagonal strontium ferrite particles. It was precipitated (crystallized).
Next, the crystallized product obtained above containing hexagonal strontium ferrite particles was roughly pulverized in a mortar, 1000 g of zirconia beads having a particle size of 1 mm and 800 ml of acetic acid having a 1% concentration were added to a glass bottle, and the mixture was dispersed in a paint shaker for 3 hours. went. Then, the obtained dispersion was separated from the beads and placed in a stainless beaker. The dispersion is allowed to stand at a liquid temperature of 100 ° C. for 3 hours to dissolve the glass components, then precipitated by a centrifuge and repeatedly decanted for cleaning, and then in a heating furnace having a furnace temperature of 110 ° C. 6 It was dried for a time to obtain a hexagonal strontium ferrite powder.
The average particle size of the hexagonal strontium ferrite powder obtained above 18 nm, activation volume 902nm ^3, the anisotropy constant Ku is ^{2.2 × 10 5 J / m 3} , the mass magnetization σs is 49A · m ² / It was kg.
12 mg of a 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, and the elemental analysis of the obtained filtrate was performed by an ICP analyzer to obtain neodymium atoms. The content of the surface layer was determined.
Separately, 12 mg of a sample powder was collected from the hexagonal strontium ferrite powder obtained above, and the sample powder was completely dissolved under the dissolution conditions exemplified above to perform elemental analysis of the filtrate obtained by using an ICP analyzer. The bulk content of the atoms was determined.
The content of neodymium atoms (bulk content) with respect to 100 atomic% of iron atoms of the hexagonal strontium ferrite powder obtained above was 2.9 atomic%. The surface layer content of neodymium atoms was 8.0 atomic%. The ratio of the surface layer content to the bulk content, "surface layer content / bulk content" was 2.8, and it was confirmed that the neodymium atoms were unevenly distributed on the surface layer of the particles.

To show the crystal structure of hexagonal ferrite in the powder obtained above, CuKα rays are scanned under the conditions of a voltage of 45 kV and an intensity of 40 mA, and the X-ray diffraction pattern is measured under the following conditions (X-ray diffraction analysis). confirmed. The powder obtained above showed a magnetoplumbite-type (M-type) hexagonal ferrite crystal structure. The crystal phase detected by X-ray diffraction analysis was a magnetoplumbite-type single phase.
PANALITICAL X'Pert Pro Diffractometer, PIXcel Detector Singler slit of incident beam and diffracted beam: 0.017 Radian dispersion slit fixed angle: 1/4 degree Mask: 10 mm
Anti-scattering 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 the hexagonal strontium ferrite powder obtained by the method shown below.
(Method for producing hexagonal strontium ferrite powder)
The SrCO ₃ 1725 g, 666 g of H ₃ BO _3, 1332g of _{Fe 2 O 3, Al (OH} ) 3 to 52 g, the CaCO ₃ 34g, the BaCO ₃ was 141g weighed to give a mixing in a mixer starting mixture.
The obtained raw material mixture was melted in a platinum crucible at a melting temperature of 1380 ° C., and the hot water outlet provided at the bottom of the platinum crucible was heated while stirring the melt, so that the melt was discharged into a rod shape at about 6 g / sec. .. The hot water was rapidly cooled and rolled with a water-cooled twin roll to prepare an amorphous body.
280 g of the obtained amorphous material was charged into an electric furnace, heated to 645 ° C. (crystallization temperature), and kept 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 roughly pulverized in a mortar, 1000 g of zirconia beads having a particle size of 1 mm and 800 ml of acetic acid having a 1% concentration were added to a glass bottle, and the mixture was dispersed in a paint shaker for 3 hours. went. Then, the obtained dispersion was separated from the beads and placed in a stainless beaker. The dispersion is allowed to stand at a liquid temperature of 100 ° C. for 3 hours to dissolve the glass components, then precipitated by a centrifuge and repeatedly decanted for cleaning, and then in a heating furnace having a furnace temperature of 110 ° C. 6 It was dried for a time to obtain a hexagonal strontium ferrite powder.
The average particle size of the resulting hexagonal strontium ferrite powder 19 nm, activation volume 1102nm ^3, the anisotropy constant Ku is ^{2.0 × 10 5 J / m 3} , the mass magnetization σs at 50A · 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 the ε-iron oxide powder obtained by the method shown below.
(Method of producing ε-iron oxide powder)
In 90 g of pure water, 8.3 g of iron (III) nitrate 9 hydrate, 1.3 g of gallium nitrate (III) octahydrate, 190 mg of cobalt (II) nitrate hexahydrate, 150 mg of titanium (IV) sulfate, and A solution of 1.5 g of polyvinylpyrrolidone (PVP) is stirred with a magnetic stirrer, and 4.0 g of an aqueous ammonia solution having a concentration of 25% is added in an atmospheric atmosphere under the condition of an atmospheric temperature of 25 ° C. The mixture was stirred for 2 hours under the temperature condition of 25 ° C. To the obtained solution, a citric acid solution obtained by dissolving 1 g of citric acid in 9 g of pure water was added, and the mixture was stirred for 1 hour. The powder precipitated after stirring was collected by centrifugation, washed with pure water, and dried in a heating furnace having a furnace temperature of 80 ° C.
800 g of pure water was added to the dried powder, and the powder was dispersed again in water to obtain a dispersion liquid. The obtained dispersion was heated to a liquid temperature of 50 ° C., and 40 g of a 25% aqueous ammonia solution was added dropwise with stirring. After stirring for 1 hour while maintaining the temperature of 50 ° C., 14 mL of tetraethoxysilane (TEOS) was added dropwise, and the mixture was stirred for 24 hours. 50 g of ammonium sulfate was added to the obtained reaction solution, and the precipitated powder was collected by centrifugation, washed with pure water, and dried in a heating furnace at a furnace temperature of 80 ° C. for 24 hours to prepare a precursor of the ferromagnetic powder. Obtained.
The obtained precursor of the ferromagnetic powder was loaded into a heating furnace having a furnace temperature of 1000 ° C. under an air atmosphere, and heat-treated for 4 hours.
The precursor of the heat-treated ferromagnetic powder was put into a 4 mol / L aqueous solution of sodium hydroxide (NaOH), and the temperature was maintained at 70 ° C. and stirred for 24 hours to heat-treat the ferromagnetic powder. The silicic acid compound, which is an impurity, was removed from the precursor of.
Then, the ferromagnetic powder from which the silicic acid compound was removed was collected by centrifugation and washed with pure water to obtain a ferromagnetic powder.
The composition of the obtained ferromagnetic powder was confirmed by high frequency inductively coupled plasma emission spectroscopy (ICP-OES; Inductively Coupled Plasma-Optical Mission Spectrometry) and found to be Ga, Co and Ti-substituted ε-iron oxide (ε-Ga _0.58). It was Fe _1.42 O ₃ ). Further, the X-ray diffraction analysis was performed under the same conditions as those described in Example 11 above, and the ferromagnetic powder obtained from the peak of the X-ray diffraction pattern does not contain the α-phase and γ-phase crystal structures. , Ε phase single phase crystal structure (ε-iron oxide type crystal structure) was confirmed.
The resulting ε- average particle size of the iron oxide powder is 12 nm, activation volume 746 nm ^3, the anisotropy constant Ku is ^{1.2 × 10 5 J / m 3} , the mass magnetization σs at 16A · m ² / kg there were.

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

[Reference example 1]
Similar to Example 1, except that the support having the thickness shown in Table 1 was used to form each layer having the thickness shown in Table 1 and the heat treatment was not performed with the magnetic tape wound around the core for heat treatment. A magnetic tape cartridge was produced.

[Comparative Example 1]
A magnetic tape cartridge was produced in the same manner as in Example 1 except that the heat treatment was not performed with the magnetic tape wound around the core for heat treatment.

[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 with the magnetic tape wound around the core for heat treatment was performed at the heat treatment temperatures shown in Table 1.

[Comparative Example 4]
A magnetic tape cartridge was produced in the same manner as in Example 7, except that the heat treatment was not performed with the magnetic tape wound around the core for heat treatment.

[Comparative Example 5]
A magnetic tape cartridge was produced in the same manner as in Example 9, except that the heat treatment was not performed with the magnetic tape wound around the core for heat treatment.

[Evaluation of magnetic tape]
The magnetic tape was 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 cartridge, and the taken out magnetic tape was evaluated as follows.

(1) Tape width difference (BA)
After removing the leader tape bonded to the outer end of the tape, a 20 cm long tape sample including a position 10 m ± 1 m from the outer end of the tape and a 20 cm long tape including a position 50 m ± 1 m from the inner end of the tape. A sample was cut out. The tape width of each tape sample was measured at the center of the tape sample in the longitudinal direction while being sandwiched between two slide glasses in order to eliminate the influence of curl. The tape width was measured within 20 minutes after removing the magnetic tape from the magnetic tape cartridge using a laser high-precision dimensional measuring instrument LS-7030 manufactured by KEYENCE. In each of the above tape samples, the tape width was measured 7 times (N = 7), and the arithmetic mean of the 5 measured values excluding the maximum and minimum values obtained in the 7 measurements was calculated. I asked. The tape width difference (BA) was calculated by using the arithmetic mean thus obtained as the tape width (tape width A or tape width B) at each position.

(2) Tape Width Deformation Rate The tape width A obtained in (1) above was defined as the tape width before storage.
A tape sample having a length of 20 cm including a position of 10 m ± 1 m from the outer end of the tape is measured in (1) above, and then one end of the tape sample is held and a weight of 100 g is hung on 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. Within 20 minutes after the load was removed after the storage, the tape width was determined in the same manner as in the method (1) above, and this tape width was defined as the tape width after storage.
The difference in the tape width before and after the storage (before storage tape width - after storage tape width) and before storage value × 10 ⁶ divided by the tape width (unit: ppm) was calculated, and the tape width deformation ratio.

(3) Tape Thickness Ten tape samples (length 5 cm) were cut out from an arbitrary 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. The thickness was measured using a Mallimar 1240 compact amplifier manufactured by MARH and a digital thickness gauge of a Millimar 1301 lead probe. The value obtained by 1/10 of the measured thickness (thickness per tape sample) was defined as the tape thickness.
The thickness of each layer shown in Table 1 is a design thickness calculated from the manufacturing conditions, and the thickness of the support is a manufacturer's value.

[Recording / playback test]
After storing the magnetic tape cartridge in which the specified capacity of data was recorded on the magnetic tape in an environment with a temperature of 40 ° C. and a relative humidity of 80% for 3 months, it was evaluated whether or not all the recorded data could be reproduced (read). .. Recording and playback was performed using an LTO Ultram7 (LTO7) drive. The specified capacity is 6.0 TB (terabyte).
The 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 the evaluation environment and left for 1 day or more to acclimatize to the same environment. If an error occurred during recording and the specified capacity could not be recorded, the cartridge was not used for subsequent evaluation, and Table 1 marked "Unevaluable". In the above case where evaluation is not possible, more specifically, even if the servo pattern of the above drive is read by the servo head and head tracking is performed, the magnetic head cannot be aligned with the position to be recorded and the drive gives an error signal. This is the case when the signal is emitted and stopped.
After the above storage, reproduction was performed in an environment of the same temperature and humidity as the environment in which the recording was performed, and this reproduction was performed using the same individual drive as at the time of recording. Reproduction was also performed after the magnetic tape cartridge was left in the evaluation environment for 1 day or more to acclimatize to the same environment. When the reproduction of all the data recorded on the magnetic tape in the magnetic tape cartridge was completed without the occurrence of an error, Table 1 shows "reproducible". When the data cannot be read correctly from the playback signal because the SNR (signal-to-noise-ratio) of the playback signal is bad during playback, and an error occurs during playback and the playback of all data is not completed. , Table 1 shows "non-reproducible".

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

For the magnetic tape cartridge produced in the same manner as in Comparative Example 1, the tape width difference (BA) was determined 360 days from the date of manufacture of the magnetic tape cartridge and found to be 4.5 μm, and the tape width deformation rate was 400 ppm. .. From this result and the comparison between Comparative Examples 1, 4 and 5 without heat treatment in the state of being wound around the core for heat treatment and the evaluation results of Examples 1 to 13, the heat treatment was performed as in Examples 1 to 13. It can be confirmed that the deformation that occurs over time in the magnetic tape cartridge can be generated 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 the comparison between Reference Example 1 and Comparative Examples 1, 2, 4 and 5, it can be confirmed that when the tape thickness is reduced to 5.2 μm or less, a reproduction error is likely to occur. In Comparative Examples 1, 2, 4 and 5, the occurrence of reproduction errors could not be suppressed, and the reproduction of all data could not be completed.
It is considered that the reason why the evaluation was not possible in Comparative Example 3 was that a recording error occurred because the width differs depending on the position of the tape so that the tape width difference (BA) exceeds 12.0 μm.

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

Claims (8)

A single reel type magnetic tape cartridge in which magnetic tape is wound on a reel.
The magnetic tape is
Having a magnetic layer containing ferromagnetic powder and binder on a non-magnetic support,
The tape width difference between the tape width A at a position where the tape thickness is 5.2 μm or less and 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, BA. A magnetic tape cartridge having a value of 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 for 24 hours in a dry environment at a temperature of 52 ° C. with a load of 100 g applied in the longitudinal direction of the tape. The magnetic tape cartridge according to claim 1, wherein the tape width deformation rate is a value obtained by starting the storage 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 magnetic tape has a non-magnetic layer containing a non-magnetic powder and a binder between the non-magnetic support and the magnetic layer. Any one of claims 1 to 3, wherein the magnetic tape has a backcoat layer containing a non-magnetic powder and a binder on the surface side of the non-magnetic support opposite to the surface side having the magnetic layer. The magnetic tape cartridge described in. The magnetic tape cartridge according to any one of claims 1 to 4, wherein the non-magnetic support is a polyethylene naphthalate support. The magnetic tape cartridge according to any one of claims 1 to 4, wherein the non-magnetic support is an aromatic polyamide support. The magnetic tape cartridge according to any one of claims 1 to 4, wherein the non-magnetic support is a polyethylene terephthalate support. The magnetic tape cartridge according to any one of claims 1 to 7, wherein the tape width difference, BA, is 5.0 μm or more and 12.0 μm or less.