WO2024090286A1

WO2024090286A1 - Magnetic recording cartridge

Info

Publication number: WO2024090286A1
Application number: PCT/JP2023/037503
Authority: WO
Inventors: 実山鹿; 貴広高山; 太佐々木; 泰啓榎本
Original assignee: ソニーグループ株式会社
Priority date: 2022-10-27
Filing date: 2023-10-17
Publication date: 2024-05-02

Abstract

The purpose of the present invention is to provide a magnetic recording cartridge with which, even when driving is performed a plurality of times in high-temperature environments, adhesion of matter does not occur, and damage to a magnetic head is mitigated.　This magnetic recording cartridge comprises a cartridge case, a reel, and a magnetic recording medium accommodated in the cartridge case while being wound on the reel, wherein, when a change in the width of the magnetic recording medium is measured over the entire length after being stored at 65℃ for 360 hours, a symbol Δout representing a change in the width on a winding outer side of the magnetic recording medium is different from a symbol Δin representing a change in the width on a winding inner side of the magnetic recording medium, and the change in the width is 0 ppm at any position in two areas on both sides of a center line of the entire length of the magnetic recording medium when the entire length is divided into four areas, and wherein the magnetic recording medium comprises a magnetic layer, the magnetic recording medium contains a fatty acid, and an extraction rate of the fatty acid defined by a specific formula is 45% or more.

Description

Magnetic Recording Cartridge

This technology relates to magnetic recording cartridges.

As demand for archiving increases, tape-type magnetic recording media with high total capacity are being incorporated into cloud systems. Current tape-type magnetic recording media have a narrower environmental temperature range for actual operation and storage than HDDs (Hard Disk Drives) and semiconductor memory, so there is a demand for expanding the environmental temperature range for actual operation and storage of tape-type magnetic recording media. It is believed that if tape-type magnetic recording media could be used in the same temperature environment as HDDs and semiconductor memory, the range of uses for tape-type magnetic recording media would be greatly expanded.

In tape-type magnetic recording media, if the width dimension of the magnetic recording medium changes significantly due to environmental changes, off-track occurs, making it difficult to ensure stable recording and playback characteristics. Patent Document 1 proposes a tape-type magnetic recording medium that can correct width changes by adjusting the longitudinal tension of the tape-type magnetic recording medium using a recording and playback device, even if the width dimension of the tape-type magnetic recording medium changes due to environmental changes. Furthermore, in order to deal with width changes in tape-type magnetic recording media, Patent Document 2 proposes positioning the data write head at an angle relative to the width direction of the tape-type magnetic recording medium.

JP 2020-173882 A JP 2005-259198 A

The aim of this technology is to provide a magnetic recording cartridge that does not produce adhesions even when run multiple times in a high-temperature environment, and that also reduces damage to the magnetic head.

This technology is
A cartridge case;
Reel and
a magnetic recording medium wound around the reel and housed within the cartridge case;
When the magnetic recording medium was stored at 65° C. for 360 hours in a wound state on the reel, the amount of change in width of the magnetic recording medium was measured over the entire length of the magnetic recording medium.
The sign of the width change amount Δout on the outer side of the magnetic recording medium is different from the sign of the width change amount Δin on the inner side of the magnetic recording medium, and
The amount of change in width is 0 ppm at any one of two regions on either side of a center line of the entire length of the magnetic recording medium when the entire length of the magnetic recording medium is divided into four equal regions, and
The magnetic recording medium has a base layer having a loss modulus of 0.40 GPa or less at 65° C.,
The magnetic recording medium includes a magnetic layer,
The magnetic recording medium contains a fatty acid,
The present invention provides a magnetic recording cartridge having an extractability of 45% or more of a fatty acid defined by the following formula:
Extraction rate of fatty acid (%)=[amount of fatty acid extracted in 5 minutes (mg/m ² )/total amount of fatty acid extracted (mg/m ² )]×100
In accordance with the present technology, a magnetic recording cartridge is provided,
The amount of width change Δin of the magnetic recording medium may be a positive value, and the amount of width change Δout of the magnetic recording medium may be a negative value.
In accordance with the present technology, a magnetic recording cartridge is provided,
When the total length of the magnetic recording medium in the longitudinal direction is taken as 100%, the width change Δ of the magnetic recording medium after storage for 360 hours at 65° C. can be 0 ppm at a position 25% to 75% from the outer end of the magnetic recording medium.
In accordance with the present technology, a magnetic recording cartridge is provided,
The magnetic recording medium may have a width change amount Δin of the magnetic recording medium minus (width change amount Δout of the magnetic recording medium) of 800 ppm or less.
In accordance with the present technology, a magnetic recording cartridge is provided,
The base layer may have a storage modulus at 65° C. of 8.0 GPa or less.
In accordance with the present technology, a magnetic recording cartridge is provided,
The base layer may be formed from PET (polyethylene terephthalate), PEN (polyethylene naphthalate), or PEEK (polyether ether ketone).
In accordance with the present technology, a magnetic recording cartridge is provided,
The magnetic recording medium may have an average thickness _tT of 5.4 μm or less.
In accordance with the present technology, a magnetic recording cartridge is provided,
The base layer may have an average thickness _tB of 4.6 μm or less.
In accordance with the present technology, a magnetic recording cartridge is provided,
The magnetic layer may include magnetic powder.
In accordance with the present technology, a magnetic recording cartridge is provided,
The magnetic layer may contain particles having an abrasive effect, and the average height of protrusions formed by the particles may be 8 nm or less.
In accordance with the present technology, a magnetic recording cartridge is provided,
The 5-minute extractable amount (mg/m ² ) of fatty acids may be 3.0 mg/m ² or more.
In accordance with the present technology, a magnetic recording cartridge is provided,
The total extractable amount of fatty acids (mg/m ² ) may be 5.0 mg/m ² or more.
In accordance with the present technology, a magnetic recording cartridge is provided,
The fatty acid may be stearic acid.
In accordance with the present technology, a magnetic recording cartridge is provided,
The magnetic recording medium may further include a fatty acid ester, and the extraction rate of the fatty acid ester defined by the following formula may be 60% or more.
Extraction rate of fatty acid ester (%)=[amount of fatty acid ester extracted in 5 minutes (mg/m ² )/total amount of fatty acid ester extracted (mg/m ² )]×100
In accordance with the present technology, a magnetic recording cartridge is provided,
The 5-minute extractable amount (mg/m ² ) of fatty acid ester may be 10.0 mg/m ² or more.
The total extractable amount (mg/ ^m2 ) of fatty acid esters may be 12.0 mg/ ^m2 or more.
The fatty acid ester may be butyl stearate.
In accordance with the present technology, a magnetic recording cartridge is provided,
The magnetic layer may have an average thickness of 0.08 μm or less.
In accordance with the present technology, a magnetic recording cartridge is provided,
The magnetic recording medium may further include a non-magnetic layer having an average thickness of 1.0 μm or less.
When the magnetic recording medium was stored at 65° C. for 360 hours in a wound state on the reel, the amount of change in width of the magnetic recording medium was measured over the entire length of the magnetic recording medium.
The sign of the width change amount Δout on the outer side of the magnetic recording medium is different from the sign of the width change amount Δin on the inner side of the magnetic recording medium, and
The amount of change in width is 0 ppm at any one of two regions on either side of a center line of the entire length of the magnetic recording medium when the entire length of the magnetic recording medium is divided into four equal regions, and
A base layer having a loss modulus of 0.40 GPa or less at 65°C,
A magnetic recording medium having a magnetic layer,
The magnetic recording medium contains a fatty acid,
The present invention provides a magnetic recording medium having an extractability of fatty acids defined by the following formula of 45% or more.
Extraction rate of fatty acid (%)=[amount of fatty acid extracted in 5 minutes (mg/m ² )/total amount of fatty acid extracted (mg/m ² )]×100

1 is an exploded perspective view showing an example of the configuration of a magnetic recording cartridge according to a first embodiment. FIG. 1 is a cross-sectional view showing an example of a configuration of a magnetic tape. FIG. 2 is a perspective view showing an example of a particle shape. FIG. 2 is a diagram showing an example of a TEM photograph of a magnetic layer. FIG. 2 is a diagram showing an example of a TEM photograph of a magnetic layer. 1 is a diagram for explaining a method for measuring a servo band pitch using a data recording and reproducing device. 11A and 11B are diagrams for explaining a method of measuring a servo trace line. FIG. 2 is a schematic diagram of a magnetic tape seen from the side. 1 is a schematic diagram of a magnetic tape viewed from above (magnetic layer side). FIG. 1 illustrates a data recording and reproducing device. FIG. 2 is a schematic diagram of a data write head as viewed from below (the back layer side). 13 is a diagram showing the relationship between the angular range Refθ±x° of the azimuth angle of the data write head and the azimuth loss Lθ (recording wavelength: 0.1 μm). 13 is a diagram showing the relationship between the angle range Refθ±x° at the azimuth angle θ of the data write head and the amount of correction for the servo band pitch difference based on the width fluctuation of the magnetic tape. 11 is a diagram showing the amount of correction for the servo band pitch difference based on the width fluctuation of the magnetic tape. FIG. 13 is a diagram showing the relationship between the angle range Refθ±x° of the azimuth angle θ of the data write head and the azimuth loss Lθ (recording wavelength: 0.07 μm). FIG. 1 illustrates a servo recording and reproducing device. 5A and 5B are diagrams showing a servo write head according to embodiment A and a pulse signal input to the servo write head. 4 is an enlarged view of a servo element included in the servo write head according to embodiment A. 11A and 11B are diagrams showing how a servo pattern is written onto a magnetic tape by a servo write head according to embodiment A. 13 is an enlarged view of a servo write head and a servo element included in the servo write head according to embodiment B. 13A and 13B are diagrams showing how a servo pattern is written onto a magnetic tape by a servo write head according to embodiment B. FIG. 13 is a diagram showing a servo write head based on a coordinate system of the servo write head in embodiment B. 11A and 11B are diagrams showing how servo patterns are read by a servo read portion of a data write head in the first comparative example, the second comparative example, and the first embodiment. FIG. 21 is an enlarged view of the diagram on the right side of FIG. 20, showing an example of specific dimensions of the first servo element and the second servo element (based on the XYZ coordinate system). FIG. 23 is an enlarged view of the diagram on the right side of FIG. 22, showing an example of specific dimensions of the first servo element and the second servo element (based on the X"Y"Z" coordinate system). FIG. 11 is a diagram showing a first example of a method for checking whether a magnetic tape is a magnetic tape used in a data recording/reproducing device with a tilted data write head. FIG. 11 is a diagram showing a second example of a method for checking whether a magnetic tape is a magnetic tape used in a data recording/reproducing device with a tilted data write head. FIG. 11 is a cross-sectional view showing an example of a configuration of a magnetic tape according to a second embodiment. FIG. 1 is a schematic diagram showing a configuration of a sputtering apparatus. FIG. 11 is a cross-sectional view showing an example of a configuration of a magnetic tape according to a third embodiment. FIG. 13 is an exploded perspective view showing an example of a configuration of a cartridge according to a modified example of the first embodiment. FIG. 2 is a diagram showing a state in which the entire length of a magnetic tape is divided into four equal regions. FIG. 2 is a graph showing the amount of change in width in the longitudinal direction of the magnetic tape after storage at 65° C. for 360 hours in Example 1. FIG. 13 is a graph showing the amount of change in width in the longitudinal direction of the magnetic tape after storage at 65° C. for 360 hours in Example 2a. FIG. 11 is a graph showing the amount of change in width in the longitudinal direction of the magnetic tape after storage at 65° C. for 360 hours in Example 3. FIG. 13 is a graph showing the amount of change in width in the longitudinal direction of the magnetic tape after storage at 65° C. for 360 hours in Comparative Example 1a. FIG. 13 is a graph showing the amount of change in width in the longitudinal direction of a magnetic tape after storage at 65° C. for 360 hours in Comparative Example 2. FIG. 13 is a graph showing the amount of change in width in the longitudinal direction of a magnetic tape after storage at 65° C. for 360 hours in Comparative Example 3. FIG. 13 is a graph showing the amount of change in width in the longitudinal direction of a magnetic tape after storage at 65° C. for 360 hours in Comparative Example 4. 11 is a schematic diagram for explaining a method of calculating the movement angle of a drive head that is disposed at an angle. FIG. FIG. 2 is a diagram showing an example of a sample mount used for measuring the extraction rate of fatty acids or fatty acid esters. 1 is an image showing an example of a surface shape captured by an AFM. FIG. 13 is a diagram showing an example of a protrusion analysis result by AFM. FIG. 13 is a diagram showing an example of a protrusion height distribution by AFM. 1 is an example of an FE-SEM image. This is a composite image obtained by superimposing an AFM image and a FE-SEM image. This is an enlarged view of a composite image in which an AFM image and a FE-SEM image are superimposed. FIG. 44 is a diagram showing an example of an analysis result of Line 1 in FIG. 43 by AFM. FIG. 1 is a diagram showing a cumulative frequency distribution of the height of protrusions formed by abrasive particles (alumina particles).

Below, we will explain preferred embodiments for implementing this technology. Note that the embodiments described below are representative embodiments of this technology, and the scope of this technology is not limited to these embodiments.

This technology will be described in the following order.
1. Description of the present technology 2. First embodiment (example of magnetic recording cartridge including coated magnetic tape)
(1) Structure of the magnetic recording cartridge (2) Structure of the magnetic tape (3) Manufacturing method of the magnetic tape (4) Description of the data band and servo band of the magnetic tape (5) Function and effect 3. Second embodiment (Example of a magnetic recording cartridge including a vacuum thin film type magnetic tape)
(1) Structure of the magnetic recording cartridge (2) Structure of the magnetic tape (3) Structure of the sputtering device (4) Manufacturing method of the magnetic tape (5) Function and effect 4. Third embodiment (Example of a magnetic recording cartridge including a vacuum thin film type magnetic tape)
(1) Structure of the magnetic recording cartridge (2) Structure of the magnetic tape (3) Function and effect 5. Modifications 6. Examples

1. Description of this technology

There is a demand for a further increase in the recording capacity per magnetic recording cartridge. For example, in order to increase the recording capacity, it is conceivable to make the magnetic recording medium (hereinafter referred to as "magnetic tape") contained in the magnetic recording cartridge thinner (reducing the total thickness) and thereby increase the tape length per magnetic recording cartridge.
However, as the magnetic recording medium becomes thinner, dimensional changes in the track width direction may occur more easily. Dimensional changes in the width direction may cause undesirable phenomena in magnetic recording, such as off-track phenomena. The off-track phenomenon refers to a situation in which the target track does not exist at the track position where the magnetic head should read, or the magnetic head reads the wrong track position.
The magnetic tape contained in a magnetic recording cartridge has a narrower usable temperature range than a HDD, and has been used in a temperature range up to 45° C. By making it possible to use a magnetic recording cartridge in a high-temperature environment of 60° C. or higher, similar to a HDD, it is expected that temperature environment management will become easier when incorporating a magnetic recording cartridge into a data storage system such as a cloud system, and the range of use of tape storage systems will be greatly expanded.
However, when the magnetic tape wound on the reel of a magnetic recording cartridge is stored in a high temperature environment of 60° C. or higher, the portion on the inside of the winding that is subjected to high winding stress expands in the width direction of the magnetic tape, while the portion on the outside of the winding that is pulled in the longitudinal direction by the tension on the magnetic tape narrows in the width direction due to the creep phenomenon, and the difference in width between the inside and outside of the winding tends to become large.

Conventionally, in order to suppress dimensional changes in magnetic tapes, for example, a layer for suppressing dimensional changes in magnetic tapes has been added.
However, the addition of such layers may increase the thickness of the magnetic tape and does not increase the tape length per cartridge product.

Patent Document 1 above proposes a technology for correcting width changes by adjusting the longitudinal tension of a tape-like magnetic recording medium, but this technology does not assume storage or running in a high-temperature environment. Therefore, when a conventional tape-like magnetic recording medium is stored or run in a high-temperature environment, there is a risk that the width change of the tape-like magnetic recording medium will exceed the range that can be corrected by adjusting the running tension, making it difficult to correct the width change.

On the other hand, the present inventors are considering a technology for dealing with deformation in the width direction of a tape-like magnetic recording medium by tilting the head in a tape storage system. However, in a high-temperature environment, the width change is particularly large due to creep characteristics, so when the magnetic head is tilted, the amount of tilt fluctuates greatly, and the tracking ability of the magnetic head may deteriorate. As a result, there is a risk that the width change in a high-temperature environment cannot be adequately dealt with. In addition, when running or storing at high temperatures, the distortion of the stretched tape is relaxed, and the winding is tightened or loosened due to creep. In order to prevent the tape edge from being damaged by the winding slippage caused by this, it is considered to improve the slippage between layers by using, for example, solid lubricant components (carbon particles, etc.). In addition, it is also considered to use components that have an anchor effect in addition to an abrasive effect for magnetic head cleaning (for example, particles with high Mohs hardness, especially alumina, etc.). It is considered that a combination of these two components can prevent an increase in friction force and clean the magnetic head. However, when trying to reduce magnetic head damage using solid lubricant components, adhesion occurs due to the solid lubricant components falling off, which interferes with recording and playback. Increasing the polishing power to remove the deposits can damage the magnetic head itself, or increase the amount of heat and static electricity generated by friction, causing greater damage to the magnetic head.

In light of the above circumstances, the present inventors have studied magnetic recording cartridges with a high recording capacity per cartridge. As a result, the present inventors have found that a magnetic recording cartridge having a specific configuration has a high recording capacity, and that even when stored in a high-temperature environment of 60° C. or higher, the width in the longitudinal direction can be corrected by adjusting the running tension of the tape system or changing the winding direction. In addition, in order to change the winding direction, for example, in a one-reel cartridge, the magnetic tape can be wound on the reel on the drive side, and in a two-reel cartridge, the magnetic tape can be changed by rewinding it on the reel opposite to the stored state. For example, if the magnetic tape has been stored in a state where it is wound on the left reel, it can be changed by rewinding it on the right reel.
That is, the present technology provides a magnetic recording cartridge having a cartridge case, a reel, and a magnetic tape wound on the reel and housed in the cartridge case. The magnetic tape has a base layer having a loss modulus of 0.40 GPa or less at 65° C. When the magnetic tape is wound on the reel and stored at 65° C. for 360 hours, the sign of the width change amount Δout on the outside of the magnetic tape is different from the sign of the width change amount Δin on the inside of the magnetic tape, and the width change amount is 0 ppm at any of two regions sandwiching the center line of the entire length of the magnetic tape when the entire length of the magnetic tape is divided into four equal regions. A method for measuring the width change amount of the magnetic tape will be described below in 2. (2).

The base layer of the magnetic tape included in the magnetic recording cartridge of the present technology may have a loss modulus at 65° C. of 0.40 GPa or less, preferably 0.35 GPa or less, more preferably 0.30 GPa or less, even more preferably 0.25 GPa or less, and even more preferably 0.20 GPa or less. By having the loss modulus at 65° C. of the base layer of the magnetic tape within the above numerical range, even when stored in a high-temperature environment of 60° C. or more, the width in the longitudinal direction can be corrected by adjusting the running tension of the tape system or changing the winding direction.
The lower limit of the loss modulus of the base layer at 65° C. is not particularly limited, but may be, for example, preferably 0.01 GPa or more, more preferably 0.02 GPa or more, and even more preferably 0.03 GPa or more. A method for measuring the loss modulus of the base layer at 65° C. will be described in 2.(2) below.

The storage modulus of the base layer of the magnetic tape included in the magnetic recording cartridge of the present technology may be preferably 8.0 GPa or less, more preferably 7.0 GPa or less, and even more preferably 6.0 GPa or less at 65° C. When the storage modulus of the base layer of the magnetic tape at 65° C. is within the above numerical range, it is possible to provide a magnetic recording cartridge in which the width of the magnetic tape in the longitudinal direction can be corrected by adjusting the running tension of the tape system or changing the winding direction even after storage in a high-temperature environment.
The lower limit of the storage modulus of the base layer at 65° C. is not particularly limited, but may be, for example, preferably 0.01 GPa or more, more preferably 0.02 GPa or more, and further preferably 0.03 GPa or more. A method for measuring the storage modulus of the base layer at 65° C. will be described in 2.(2) below.

In the magnetic recording cartridge of the present technology, when the magnetic tape is wound on a reel and the amount of width change is measured over the entire length of the magnetic tape after storage at 65° C. for 360 hours, the sign of the amount of width change Δout on the outside of the magnetic tape winding is different from the sign of the amount of width change Δin on the inside of the magnetic tape winding. The amount of width change Δ can be expressed by the following formula.
Width change amount Δ=(width change amount after storage at 65°C and 360°C−initial state width change amount)/(initial state width change amount)
When the width change amount Δ is a negative value, it indicates that the width after storage is narrower than the width in the initial state, and when the width change amount Δ is a positive value, it indicates that the width after storage is wider than the width in the initial state.

There are magnetic recording cartridges having one reel and two reels in the cartridge. In either type of magnetic recording cartridge, a magnetic tape is wound around a reel and housed in the magnetic cartridge. As the magnetic tape is wound around the reel during the manufacture of the magnetic cartridge, the magnetic tape is stacked to form a magnetic tape stack. In this specification, the inner side of the magnetic tape refers to the area on the innermost layer side of the magnetic tape stack in a state where the magnetic tape is wound around one reel to form a stack on the reel before the first data is recorded in the magnetic cartridge, and the outer side of the magnetic tape refers to the area on the outermost layer side of the magnetic tape stack. More specifically, the inside of a magnetic tape winding refers to the area starting from the end (hereinafter also referred to as the "inner end" (EOT)) that is attached to a reel inside a magnetic recording cartridge (the reel onto which the magnetic tape is wound before the first data is recorded onto the magnetic cartridge) and extending a predetermined distance from that position toward the end opposite the inner end (hereinafter also referred to as the "outer end" (BOT)).
1, the inside of the magnetic tape refers to the area starting from the end attached to the reel 13 before the first data recording (hereinafter also referred to as the "inner end" (EOT)) and proceeding a predetermined distance from that position toward the end opposite the inner end (hereinafter also referred to as the "outer end" (BOT)). The outside of the magnetic tape refers to the area starting from the outer end of the two ends of the magnetic tape and proceeding a predetermined distance from that position toward the inner end.
17, the inside of the magnetic tape refers to the area starting from the end (hereinafter also referred to as the "inner end" (EOT)) attached to the reel 307 before the first data recording is performed, and proceeding a predetermined distance from that position toward the end opposite the inner end (hereinafter also referred to as the "outer end" (BOT)). The outside of the magnetic tape refers to the area starting from the outer end of the two ends of the magnetic tape, and proceeding a predetermined distance from that position toward the inner end.

The inner side and outer side of the magnetic tape will be described in more detail with reference to Figure 32. Figure 32 is a schematic diagram showing how the entire length of the magnetic tape is divided into four equal parts from the inner end of the roll (EOT) to the outer end of the roll (BOT). As shown in Figure 32, from EOT to BOT, the entire length of the tape is divided into four areas, namely Area D, Area C, Area B, and Area A. In this specification, Area A in Figure 32 is referred to as the outer side of the roll, and Area D is referred to as the inner side of the roll.

In the magnetic recording cartridge of the present technology, the width change is 0 ppm in either of the two regions that sandwich the center line of the entire length of the magnetic tape when the entire length of the magnetic tape is divided into four equal parts. This will be explained with reference to FIG. 32. FIG. 32 is a schematic diagram showing the state in which the entire length of the magnetic tape is divided into four equal parts from the end of the inner side of the winding (EOT) to the end of the outer side of the winding (BOT). As shown in FIG. 32, the entire length of the tape is divided into four regions, namely, region D, region C, region B, and region A, from EOT to BOT. As shown in FIG. 32, the center line of the entire length of the magnetic tape is located between region B and region C, and is the boundary line that separates region B and region C, and the two regions that sandwich the center line are region B and region C. In the magnetic recording cartridge of the present technology, the width change is 0 ppm in either region B or region C.

In the magnetic recording cartridge of the present technology, the amount of width change Δin on the inside of the magnetic tape may be a positive value. Here, the amount of width change Δin on the inside of the magnetic tape means the maximum amount of width change on the inside of the magnetic tape. The amount of width change Δin on the inside of the magnetic tape being a positive value means that the width of the magnetic tape on the inside of the magnetic tape after storage is wider than the width in the initial state.
In the magnetic recording cartridge of the present technology, the amount of width change Δout on the outside of the magnetic tape may be a negative value. Here, the amount of width change Δout on the outside of the magnetic tape means the minimum value of the amount of width change on the outside of the magnetic tape. A negative value for the amount of width change Δout on the outside of the magnetic tape means that the width of the magnetic tape after storage is narrower than the width in the initial state on the outside of the magnetic tape.
Furthermore, when the entire length of the magnetic tape in the longitudinal direction is taken as 100%, preferably at a position 25% to 75% from the outside end (BOT), the width change Δ of the magnetic tape after storage for 360 hours at 65° C. may be 0 ppm. In the magnetic tape shown in FIG 32, the width change Δ of the magnetic tape after storage for 360 hours at 65° C. may be 0 ppm at either region B or region C, which corresponds to a position 25% to 75% from the outside end (BOT).
In addition, in a magnetic tape whose total length is divided into four equal parts as shown in FIG. 32, the average value of the width change Δ in region A, which corresponds to 1/4 of the outer side of the magnetic tape, may be a negative value, and the average value of the width change Δ in region D, which corresponds to 1/4 of the inner side of the magnetic tape, may be a positive value.
In the magnetic tape, (amount of width change Δin on the inside of the magnetic tape roll)−(amount of width change Δout on the outside of the magnetic tape roll) may be 800 ppm or less.

The magnetic tape contained in the magnetic recording cartridge of this technology contains a fatty acid. The magnetic tape may further contain a fatty acid ester. Such fatty acid or fatty acid ester seeps onto the surface of the magnetic tape, and the surface of the abrasive particles is coated with the fatty acid or fatty acid ester, thereby reducing damage to the magnetic head.

In the present technology, the extraction rate of fatty acids defined by the following formula can be 45% or more, preferably 50% or more, more preferably 55% or more, and even more preferably 60% or more. If the extraction rate of fatty acids is less than 45%, friction increases, the magnetic head deteriorates due to frictional heat and electrification, damage to the coating increases, powder fall increases, and durability deteriorates.
Extraction rate of fatty acid (%)=[amount of fatty acid extracted in 5 minutes (mg/m ² )/total amount of fatty acid extracted (mg/m ² )]×100

The upper limit of the fatty acid extraction rate is not particularly limited, but from the viewpoint of preventing the coating film itself from plasticizing, increasing powder fall, and deteriorating durability, it is preferably 75% or less, more preferably 73% or less, and even more preferably 70% or less. The method for measuring the fatty acid extraction rate is explained in 2.(2) below.

Furthermore, the 5-minute extractable amount (mg/ ^m2 ) of the fatty acid may be preferably 3.0 mg/ ^m2 or more, more preferably 3.5 mg/ ^m2 or more, even more preferably 4.0 mg/ ^m2 or more, and even more preferably 4.5 mg/ ^m2 or more.

The upper limit of the 5-minute extractable amount of fatty acids is not particularly limited, but is preferably 14.0 mg/ ^m2 or less, more preferably 13.0 mg/ ^m2 or less, even more preferably 12.0 mg/ ^m2 or less, and even more preferably 10.0 mg/ ^m2 or less. The method for measuring the 5-minute extractable amount of fatty acids will be described in 2.(2) below.

The total extractable amount (mg/m ² ) of the fatty acids may preferably be 5.0 mg/m ² or more, more preferably 7.0 mg/m ² or more, even more preferably 9.0 mg/m ² or more, and even more preferably 10.0 mg/m ² or more.

The upper limit of the total amount of fatty acid extraction is not particularly limited, but is preferably 16.0 mg/ ^m2 or less, more preferably 15.0 mg/ ^m2 or less, even more preferably 14.0 mg/ ^m2 or less, and even more preferably 13.0 mg/ ^m2 or less. The method for measuring the total amount of fatty acid extraction will be described in 2.(2) below.

The magnetic tape included in the magnetic recording cartridge of the present technology further contains a fatty acid ester, and from the viewpoint of suppressing increased friction, deterioration of the magnetic head due to frictional heat and static electricity, increased damage to the coating, increased powder falling, and further deterioration of durability, the extraction rate of the fatty acid ester defined by the following formula can be preferably 60% or more, more preferably 65% or more, even more preferably 70% or more, and even more preferably 75% or more.
Extraction rate of fatty acid ester (%)=[amount of fatty acid ester extracted in 5 minutes (mg/m ² )/total amount of fatty acid ester extracted (mg/m ² )]×100

The upper limit of the extraction rate of the fatty acid ester is not particularly limited, but from the viewpoint of preventing the coating film itself from plasticizing, increasing powder falling, and deteriorating durability, it is preferably 90% or less, more preferably 85% or less, and even more preferably 80% or less. The method for measuring the extraction rate of the fatty acid ester is explained in 2.(2) below.

Furthermore, the 5-minute extractable amount (mg/m ² ) of the fatty acid ester may be preferably 10.0 mg/m ² or more, more preferably 12.0 mg/m ² or more, even more preferably 14.0 mg/m ² or more, and even more preferably 16.0 mg/m ² or more.

The upper limit of the 5-minute extractable amount of the fatty acid ester is not particularly limited, but since there is a risk that the plasticization of the coating film will progress and powder falling will worsen if it exceeds 25.0 mg/ ^m2 , it is preferably 20.0 mg/ ^m2 or less, more preferably 19.0 mg/ ^m2 or less, even more preferably 18.0 mg/ ^m2 or less, and even more preferably 17.0 mg/ ^m2 or less. The method for measuring the 5-minute extractable amount of the fatty acid ester will be explained in 2.(2) below.

The total extractable amount (mg/m ² ) of the fatty acid esters may be preferably 12.0 mg/m ² or more, more preferably 14.0 mg/m ² or more, even more preferably 16.0 mg/m ² or more, and still more preferably 19.0 mg/m ² or more.

The upper limit of the total amount of fatty acid ester extraction is not particularly limited, but is preferably 25.0 mg/ ^m2 or less, more preferably 24.0 mg/ ^m2 or less, even more preferably 23.0 mg/ ^m2 or less, and even more preferably 22.0 mg/ ^m2 or less. The method for measuring the total amount of fatty acid ester extraction will be described in 2.(2) below.

The magnetic tape included in the magnetic recording cartridge of the present technology is preferably a long magnetic tape, and may be, for example, a magnetic recording tape (particularly a long magnetic recording tape).

The magnetic tape included in the magnetic recording cartridge of the present technology may have a magnetic layer, a base layer, and a back layer, and may include other layers in addition to these layers. The other layers may be selected appropriately depending on the type of magnetic tape. The magnetic tape may be, for example, a coated magnetic tape or a vacuum thin-film magnetic tape. The coated magnetic tape will be described in more detail in 2. below. The vacuum thin-film magnetic tape will be described in more detail in 3. below. Please refer to these descriptions for layers included in the magnetic tape other than the above three layers.

The magnetic tape included in the magnetic recording cartridge of the present technology may have, for example, at least one data band and at least two servo bands. The number of data bands may be, for example, 2 to 10, particularly 3 to 6, and more particularly 4 or 5. The number of servo bands may be, for example, 3 to 11, particularly 4 to 7, and more particularly 5 or 6. These servo bands and data bands may be arranged, for example, to extend in the longitudinal direction of the long magnetic tape, particularly to be substantially parallel. The data band and the servo band may be provided on the magnetic layer. An example of a magnetic tape having such a data band and servo band is a magnetic recording tape conforming to the LTO (Linear Tape-Open) standard. That is, the magnetic tape may be a magnetic recording tape conforming to the LTO standard. For example, the magnetic tape may be a magnetic recording tape conforming to the LTO9 standard or a later standard (for example, LTO10, LTO11, or LTO12).
The width of the long magnetic tape (particularly the magnetic recording tape) may be, for example, 5 mm to 30 mm, particularly 7 mm to 25 mm, more particularly 10 mm to 20 mm, and even more particularly 11 mm to 19 mm. The length of the long magnetic tape may be, for example, 500 m to 1500 m. For example, the tape width according to the LTO8 standard is 12.65 mm and the length is 960 m.

2. First embodiment (example of magnetic recording cartridge including coated magnetic tape)

(1) Structure of magnetic recording cartridge

[Magnetic Recording Cartridge]
First, the configuration of a magnetic recording cartridge according to the present technology will be described with reference to Fig. 1. Fig. 1 is an exploded perspective view showing an example of a magnetic recording cartridge 10 according to the present technology. In the description of the present technology, a magnetic recording cartridge conforming to the LTO standard will be taken as an example of the magnetic recording cartridge 10.

The magnetic recording cartridge 10 is a one-reel type cartridge, and includes a cartridge case 12 composed of a lower shell 12A and an upper shell 12B, a reel 13 on which a tape-like magnetic tape MT is wound, a reel lock 14 and a reel spring 15 for locking the rotation of the reel 13, a spider 16 for unlocking the locked state of the reel 13, a slide door 17 for opening and closing a tape outlet 12C provided in the cartridge case 12 across the lower shell 12A and the upper shell 12B, a door spring 18 for biasing the slide door 17 to a closed position of the tape outlet 12C, a write protector 19 for preventing erroneous erasure, and a cartridge memory 11. The reel 13 for winding the magnetic tape MT is substantially disc-shaped with an opening in the center, and is composed of a reel hub 13A and a flange 13B made of a hard material such as plastic. A leader tape LT is connected to the outer peripheral end of the magnetic tape MT. A leader pin 20 is provided at the tip of the leader tape LT.

The magnetic recording cartridge 10 may be a magnetic tape cartridge that complies with the LTO (Linear Tape-Open) standard, or it may be a magnetic tape cartridge that complies with a standard other than the LTO standard.

The cartridge memory 11 is provided near one corner of the magnetic recording cartridge 10. When the magnetic recording cartridge 10 is loaded into the recording and playback device, the cartridge memory 11 faces the reader/writer of the recording and playback device. The cartridge memory 11 communicates with the recording and playback device, specifically the reader/writer, using a wireless communication standard that complies with the LTO standard.

(2) Structure of magnetic tape

2 is a cross-sectional view showing an example of the configuration of the magnetic tape MT. The magnetic tape MT comprises a long base layer 41, an underlayer 42 provided on one main surface (first main surface) of the base layer 41, a magnetic layer 43 provided on the underlayer 42, and a back layer 44 provided on the other main surface (second main surface) of the base layer 41. The underlayer 42 and the back layer 44 are provided as necessary and may be omitted. The magnetic tape MT may be a perpendicular recording type magnetic tape or a longitudinal recording type magnetic tape. From the viewpoint of improving running performance, the magnetic tape MT preferably contains a lubricant. The lubricant may be included in at least one of the underlayer 42 and the magnetic layer 43.

The magnetic tape MT may be one that complies with the LTO standard, or one that complies with a standard other than the LTO standard. The width of the magnetic tape MT may be 1/2 inch, or may be wider than 1/2 inch. If the magnetic tape MT complies with the LTO standard, the width of the magnetic tape MT is 1/2 inch. The magnetic tape MT may have a configuration that allows the width of the magnetic tape MT to be kept constant or nearly constant by adjusting the tension applied to the magnetic tape MT in the longitudinal direction during running using a recording/playback device (drive).

The magnetic tape MT is long and runs in the longitudinal direction during recording and playback. The magnetic tape MT is preferably used in a recording and playback device equipped with a ring-type head as a recording head. The magnetic tape MT is preferably used in a recording and playback device configured to be able to record data with a data track width of 1200 nm or less or 1000 nm or less.

[Base layer]
The base layer 41 is a non-magnetic support that supports the underlayer 42 and the magnetic layer 43. The base layer 41 has a long film shape. The upper limit of the average thickness of the base layer 41 is, for example, preferably 4.6 μm or less, more preferably 4.4 μm or less, 4.2 μm or less, even more preferably 4.0 μm or less, even more preferably 3.8 μm or less, particularly preferably 3.6 μm or less, and most preferably 3.4 μm or less. When the upper limit of the average thickness of the base layer 41 is 4.6 μm or less, the recording capacity that can be recorded in one data cartridge can be increased compared to that of a general magnetic tape. The lower limit of the average thickness of the base layer 41 is preferably 3.0 μm or more, more preferably 3.2 μm or more. When the lower limit of the average thickness of the base layer 41 is 3.0 μm or more, the strength reduction of the base layer 41 can be suppressed.

The average thickness of the base layer 41 is determined as follows. First, the magnetic tape MT contained in the magnetic recording cartridge 10 is unwound, and the magnetic tape MT is cut into lengths of 250 mm from each of the ranges of 10 m to 20 m, 30 m to 40 m, and 50 m to 60 m in the longitudinal direction from the connection 21 between the magnetic tape MT and the leader tape LT to prepare three samples. In this specification, "longitudinal direction" in the "longitudinal direction from the connection 21 between the magnetic tape MT and the leader tape LT" means the direction from one end on the leader tape LT side to the other end on the opposite side.

Then, the layers other than the base layer 41 of each sample (i.e., the undercoat layer 42, the magnetic layer 43, and the back layer 44) are removed with a solvent such as MEK (methyl ethyl ketone) or dilute hydrochloric acid. Next, the thickness of each sample (base layer 41) is measured at five positions using a Mitutoyo Laser Hologram (LGH-110C) as a measuring device, and the average thickness of the base layer 41 is calculated by arithmetically averaging these measurements (a total of 15 sample thicknesses). Note that the five measurement positions are selected randomly from each sample so that they are different positions in the longitudinal direction of the magnetic tape MT.

The base layer 41 contains, for example, at least one of polyesters, polyolefins, cellulose derivatives, vinyl resins, and other polymer resins. When the base layer 41 contains two or more of the above materials, the two or more materials may be mixed, copolymerized, or laminated.

Of the above polymer resins, the base layer 41 preferably contains polyesters. By including polyesters in the base layer 41, the storage modulus E' in the longitudinal direction of the base layer 41 can be reduced to preferably 9.0 GPa or less, more preferably 7.5 GPa or less, even more preferably 6.0 GPa or less, particularly preferably 5.5 GPa or less, and most preferably 4.5 GPa or less. Therefore, by adjusting the longitudinal tension of the magnetic tape MT during running using a recording and playback device, it is particularly easy to control the width of the magnetic tape MT to be constant or nearly constant. A method for measuring the storage modulus E' in the longitudinal direction of the base layer 41 will be described later.

The polyesters include, for example, at least one of PET (polyethylene terephthalate), PEN (polyethylene naphthalate), PBT (polybutylene terephthalate), PBN (polybutylene naphthalate), PCT (polycyclohexylene dimethylene terephthalate), PEB (polyethylene-p-oxybenzoate), and polyethylene bisphenoxycarboxylate. When the base layer 41 includes two or more types of polyesters, the two or more types of polyesters may be mixed, copolymerized, or laminated. At least one of the ends and side chains of the polyesters may be modified. PA (polyamide) may be added to PET (polyethylene terephthalate) to improve the strength of the base layer 41.

The inclusion of polyesters in the base layer 41 can be confirmed, for example, as follows. First, the magnetic tape MT contained in the magnetic recording cartridge 10 is unwound, and the magnetic tape MT is cut out from a range of 30 to 40 m in the longitudinal direction from the connection 21 between the magnetic tape MT and the leader tape LT to prepare a sample, after which all layers of the sample other than the base layer 41 are removed. Next, an IR spectrum of the sample (base layer 41) is obtained by infrared absorption spectrometry (IR). Based on this IR spectrum, it can be confirmed that the base layer 41 contains polyesters.

The polyolefins include, for example, at least one of PE (polyethylene) and PP (polypropylene). The cellulose derivatives include, for example, at least one of cellulose diacetate, cellulose triacetate, CAB (cellulose acetate butyrate) and CAP (cellulose acetate propionate). The vinyl resins include, for example, at least one of PVC (polyvinyl chloride) and PVDC (polyvinylidene chloride).

Other polymeric resins include, for example, at least one of PA (polyamide, nylon), aromatic PA (aromatic polyamide, aramid), PI (polyimide), aromatic PI (aromatic polyimide), PAI (polyamideimide), aromatic PAI (aromatic polyamideimide), PBO (polybenzoxazole, e.g. Zylon (registered trademark)), polyether, PEK (polyetherketone), PEEK (polyetheretherketone), polyetherester, PES (polyethersulfone), PEI (polyetherimide), PSF (polysulfone), PPS (polyphenylene sulfide), PC (polycarbonate), PAR (polyarylate) and PU (polyurethane). In addition, PA (polyamide, nylon), aromatic PA (aromatic polyamide, aramid), PI (polyimide), aromatic PI (aromatic polyimide), PAI (polyamideimide), aromatic PAI (aromatic polyamideimide), PBO (polybenzoxazole, for example Zylon (registered trademark)), polyether, PEK (polyether ketone), and PEEK (polyether ether ketone) can be used alone as a film for the base layer 41.

The base layer 41 may be biaxially stretched in the longitudinal and width directions. The polymer resin contained in the base layer 41 is preferably oriented in a direction oblique to the width direction of the base layer 41.

[Magnetic Layer]
The magnetic layer 43 is a recording layer for recording signals by magnetization patterns. The magnetic layer 43 may be a coating film. The magnetic layer 43 may be a perpendicular recording type recording layer or a longitudinal recording type recording layer. The magnetic layer 43 includes, for example, magnetic powder, a binder, a lubricant, and carbon. The magnetic layer 43 may further include at least one additive selected from antistatic agents, abrasives, hardeners, rust inhibitors, and non-magnetic reinforcing particles, as necessary. The magnetic layer 43 may have a surface having an uneven shape.

The magnetic layer 43 has multiple data bands in which data is written, and multiple servo bands in which servo patterns are written. Details of the data bands and servo bands will be described later.

The magnetic layer 43 is configured so that multiple data tracks can be formed in the data band. From the viewpoint of improving the track recording density and ensuring high recording capacity, the upper limit of the average value of the data track width is preferably 1100 nm or less, more preferably 1000 nm or less, even more preferably 800 nm or less, and particularly preferably 600 nm or less. Taking into account the magnetic particle size, the lower limit of the average value of the data track width W is preferably 20 nm or more.

The average data track width is obtained as follows. First, a magnetic recording cartridge 10 is prepared on which data is recorded over the entire surface of the magnetic tape MT. The magnetic tape MT is unwound from the magnetic recording cartridge 10, and the magnetic tape MT is cut into lengths of 250 mm from the longitudinal range of 10 m to 20 m, 30 m to 40 m, and 50 m to 60 m from the connection 21 between the magnetic tape MT and the leader tape LT to prepare three samples. Next, the data recording pattern of the data band portion of the magnetic layer 43 of each sample is observed using a magnetic force microscope (MFM) to obtain an MFM image. The MFM used is a Dimension3100 manufactured by Digital Instruments and its analysis software. The measurement area of the MFM image is 10 μm x 10 μm, and the measurement area of 10 μm x 10 μm is divided into 512 x 512 (= 262,144) measurement points. For each sample, MFM measurements were performed on a 10 μm x 10 μm measurement area, meaning that three MFM images were obtained. From the three MFM images obtained, the track width was measured at 10 locations using the analysis software provided with the Dimension3100, and the average value (simple average) was calculated. This average value is the average data track width. The measurement conditions for the above MFM were sweep speed: 1 Hz, chip used: MFMR-20, lift height: 20 nm, correction: Flatten order 3.

The upper limit of the average thickness of the magnetic layer 43 is preferably 0.08 μm or less, more preferably 0.07 μm or less, and even more preferably 0.06 μm or less, 0.05 μm or less, or 0.04 μm or less. If the upper limit of the average thickness of the magnetic layer 43 is 0.08 μm or less, when a ring-type head is used as the recording head, the effect of the demagnetizing field can be reduced, and even better electromagnetic conversion characteristics can be obtained.

The lower limit of the average thickness of the magnetic layer 43 is not particularly limited, but is preferably 0.03 μm or more. If the lower limit of the average thickness of the magnetic layer 43 is 0.03 μm or more, output can be ensured when an MR head is used as the reproducing head, and thus even better electromagnetic conversion characteristics can be obtained.

The average thickness of the magnetic layer 43 is obtained as follows. First, the magnetic tape MT housed in the magnetic recording cartridge 10 is unwound, and the magnetic tape MT is cut into 250 mm lengths from the longitudinal range of 10 m to 20 m, 30 m to 40 m, and 50 m to 60 m from the connection 21 between the magnetic tape MT and the leader tape LT to prepare three samples. Next, each sample is processed by the FIB method or the like to be thinned. When the FIB method is used, a carbon layer and a tungsten layer are formed as protective films as a pretreatment for observing the TEM image of the cross section described later. The carbon layer is formed by deposition on the surface of the magnetic tape MT on the magnetic layer 43 side and the surface on the back layer 44 side, and the tungsten layer is further formed on the surface on the magnetic layer 43 side by deposition or sputtering. The thinning is performed along the length direction (longitudinal direction) of the magnetic tape MT. That is, this slicing creates a cross section that is parallel to both the longitudinal and thickness directions of the magnetic tape MT.

The cross section of each of the obtained sliced samples is observed under the following conditions using a transmission electron microscope (TEM) to obtain a TEM image of each sliced sample. Note that the magnification and acceleration voltage may be appropriately adjusted depending on the type of device.
Apparatus: TEM (Hitachi H9000NAR)
Acceleration voltage: 300 kV
Magnification: 100,000 times

Next, using the TEM images of each of the obtained thinned samples, the thickness of the magnetic layer 43 is measured at 10 positions on each thinned sample. The 10 measurement positions on each thinned sample are randomly selected from each sample so that they are different positions in the longitudinal direction of the magnetic tape MT. The average value obtained by arithmetically averaging the measured values of each obtained thinned sample (a total of 30 thicknesses of the magnetic layer 43) is defined as the average thickness [nm] of the magnetic layer 43.

[Magnetic powder]
The magnetic powder includes a plurality of magnetic particles. The magnetic particles are, for example, particles containing a metal oxide (hereinafter referred to as "metal oxide particles"). The metal oxide particles are, for example, particles containing hexagonal ferrite (hereinafter referred to as "hexagonal ferrite particles"), particles containing epsilon-type iron oxide (ε iron oxide) (hereinafter referred to as "ε iron oxide particles"), or particles containing Co-containing spinel ferrite (hereinafter referred to as "cobalt ferrite particles"). It is preferable that the magnetic powder is preferentially crystalline oriented in the perpendicular direction of the magnetic tape MT. In this specification, the perpendicular direction (thickness direction) of the magnetic tape MT means the thickness direction of the magnetic tape MT in a flat state.

[Hexagonal ferrite particles]
The hexagonal ferrite particles have, for example, a plate shape such as a hexagonal plate shape or a column shape such as a hexagonal column shape (however, the thickness or height is smaller than the major axis of the plate surface or bottom surface). In this specification, the hexagonal plate shape includes a substantially hexagonal plate shape. The hexagonal ferrite preferably contains at least one of Ba, Sr, Pb, and Ca, more preferably at least one of Ba and Sr. The hexagonal ferrite may specifically be, for example, barium ferrite or strontium ferrite. The barium ferrite may further contain at least one of Sr, Pb, and Ca in addition to Ba. The strontium ferrite may further contain at least one of Ba, Pb, and Ca in addition to Sr.

More specifically, the hexagonal ferrite has an average composition represented by the general formula MFe ₁₂ O _19. However, M is, for example, at least one metal selected from Ba, Sr, Pb, and Ca, preferably at least one metal selected from Ba and Sr. M may be a combination of Ba and one or more metals selected from the group consisting of Sr, Pb, and Ca. M may also be a combination of Sr and one or more metals selected from the group consisting of Ba, Pb, and Ca. In the above general formula, a part of Fe may be substituted with another metal element.

When the magnetic powder contains hexagonal ferrite particles, the average particle size of the magnetic powder is preferably 13 nm or more and 22 nm or less, more preferably 13 nm or more and 19 nm or less, even more preferably 13 nm or more and 18 nm or less, particularly preferably 14 nm or more and 17 nm or less, and most preferably 14 nm or more and 16 nm or less. When the average particle size of the magnetic powder is 22 nm or less, even better electromagnetic conversion characteristics (e.g., SNR) can be obtained in a high recording density magnetic tape MT. On the other hand, when the average particle size of the magnetic powder is 13 nm or more, the dispersibility of the magnetic powder is further improved, and even better electromagnetic conversion characteristics (e.g., SNR) can be obtained.

When the magnetic powder contains hexagonal ferrite particle powder, the average aspect ratio of the magnetic powder is preferably 1.0 or more and 3.0 or less, more preferably 1.5 or more and 2.8 or less, and even more preferably 1.8 or more and 2.7 or less. When the average aspect ratio of the magnetic powder is within the range of 1.0 or more and 3.0 or less, aggregation of the magnetic powder can be suppressed. In addition, when the magnetic powder is vertically oriented in the process of forming the magnetic layer 43, the resistance applied to the magnetic powder can be suppressed. Therefore, the vertical orientation of the magnetic powder can be improved.

When the magnetic powder contains hexagonal ferrite particles, the average particle size and the average aspect ratio of the magnetic powder are obtained as follows. First, the magnetic tape MT housed in the magnetic recording cartridge 10 is unwound, and the magnetic tape MT is cut out from a range of 30 to 40 m in the longitudinal direction from the connection part 21 between the magnetic tape MT and the leader tape LT. Next, the cut magnetic tape MT is processed by the FIB method or the like to be thinned. When the FIB method is used, a carbon layer and a tungsten layer are formed as protective films as a pretreatment for observing the TEM image of the cross section described later. The carbon layer is formed by deposition on the surface of the magnetic tape MT on the magnetic layer 43 side and the surface on the back layer 44 side, and the tungsten layer is further formed by deposition or sputtering on the surface on the magnetic layer 43 side. The thinning is performed along the length direction (longitudinal direction) of the magnetic tape MT. In other words, the thinning forms a cross section parallel to both the longitudinal direction and the thickness direction of the magnetic tape MT.

The cross section of the obtained thin sample is observed using a transmission electron microscope (Hitachi High-Technologies Corporation H-9500) at an acceleration voltage of 200 kV and a total magnification of 500,000 times in the thickness direction of the magnetic layer 43 so as to include the entire magnetic layer 43, and a TEM photograph is taken. The TEM photographs are prepared in such a way that 50 particles can be extracted that allow the plate diameter DB and plate thickness DA (see Figure 3) shown below to be measured.

In this specification, when the shape of the particle observed in the above TEM photograph is plate-like or columnar (however, the thickness or height is smaller than the major axis of the plate surface or bottom surface) as shown in Figure 3, the major axis of the plate surface or bottom surface of the particle is taken as the plate diameter DB value. The thickness or height of the particle observed in the above TEM photograph is taken as the plate thickness DA value. When the thickness or height of a particle is not constant within a single particle, the thickness or height of the maximum particle is taken as the plate thickness DA.

Next, 50 particles are selected from the TEM photograph based on the following criteria. Particles that are partially outside the field of view of the TEM photograph are not measured, and only particles that have a clear outline and exist in isolation are measured. If there are overlapping particles, those with a clear boundary between them and whose overall shape can be determined are measured as individual particles, but particles with unclear boundaries and whose overall shape cannot be determined are not measured as their shape cannot be determined.

4 and 5 show an example of a TEM photograph. In FIG. 4 and FIG. 5, for example, the particles indicated by the arrows a and d are selected because the plate thickness (thickness or height) DA of the particle can be clearly confirmed. The plate thickness DA of each of the selected 50 particles is measured. The plate thickness DA thus obtained is arithmetically averaged to obtain the average plate thickness DA _ave . The average plate thickness DA _ave is the average particle plate thickness. Next, the plate diameter DB of each magnetic powder is measured. In order to measure the plate diameter DB of the particle, 50 particles whose plate diameter DB of the particle can be clearly confirmed are selected from the TEM photograph taken. For example, in FIG. 4 and FIG. 5, for example, the particles indicated by the arrows b and c are selected because the plate diameter DB can be clearly confirmed. The plate diameter DB of each of the selected 50 particles is measured. The plate diameter DB thus obtained is simply averaged (arithmetic averaged) to obtain the average plate diameter DB _ave . The average plate diameter DB _ave is the average particle size. Then, the average aspect ratio of the particles ( _DBave / _DAave ) is calculated from the average plate thickness _DAave and the average plate diameter _DBave .

When the magnetic powder contains hexagonal ferrite particles, the average particle volume of the magnetic powder is preferably 500 nm3 ^or more and 2500 ^nm3 or less, more preferably 500 ^nm3 or more and 1600 ^nm3 or less, even more preferably 500 ^nm3 or more and 1500 ^nm3 or less, particularly preferably 600 nm3 ^or more and 1200 ^nm3 or less, and most preferably 600 nm3 ^or more and 1000 ^nm3 or less. When the average particle volume of the magnetic powder is 2500 ^nm3 or less, the same effect as when the average particle size of the magnetic powder is 22 nm or less can be obtained. On the other hand, when the average particle volume of the magnetic powder is 500 ^nm3 or more, the same effect as when the average particle size of the magnetic powder is 13 nm or more can be obtained.

The average particle volume of the magnetic powder is calculated as follows. First, the average plate thickness DA _ave and the average plate diameter DB _ave are calculated as described above in relation to the method for calculating the average particle size of the magnetic powder. Next, the average volume V of the magnetic powder is calculated using the following formula.

[ε-iron oxide particles]
The ε-iron oxide particles are hard magnetic particles that can obtain high coercivity even in the case of fine particles. The ε-iron oxide particles are spherical or cubic. In this specification, the term "spherical" includes "approximately spherical". Furthermore, the term "cubic" includes "approximately cubic". Since the ε-iron oxide particles have the above-mentioned shape, when the ε-iron oxide particles are used as the magnetic particles, the contact area between the particles in the thickness direction of the magnetic tape MT can be reduced and the aggregation between the particles can be suppressed compared to when hexagonal plate-shaped barium ferrite particles are used as the magnetic particles. Therefore, the dispersibility of the magnetic particles can be improved, and further excellent electromagnetic conversion characteristics (e.g., SNR) can be obtained.

The ε-iron oxide particles may have a composite particle structure. More specifically, the ε-iron oxide particles include an ε-iron oxide portion and a portion having soft magnetism or a portion having a higher saturation magnetization σs and a smaller coercive force Hc than ε-iron oxide (hereinafter referred to as the "soft magnetic portion, etc.").

The ε-iron oxide portion contains ε-iron oxide. The ε-iron oxide contained in the ε-iron oxide portion preferably has ε-Fe ₂ O ₃ crystals as a main phase, and more preferably is made of single-phase ε-Fe ₂ O ₃ .

The soft magnetic portion is in contact with at least a portion of the ε-iron oxide portion. Specifically, the soft magnetic portion may partially cover the ε-iron oxide portion, or may cover the entire periphery of the ε-iron oxide portion.

The soft magnetic portion (the magnetic portion having a higher saturation magnetization σs and a smaller coercive force Hc than ε-iron oxide) includes, for example, a soft magnetic material such as α-Fe, a Ni-Fe alloy, or an Fe-Si-Al alloy. α-Fe may be obtained by reducing the ε-iron oxide contained in the ε-iron oxide portion.

The portion having soft magnetic properties may contain, for example, Fe ₃ O ₄ , γ-Fe ₂ O ₃ , or spinel ferrite.

By providing the ε-iron oxide particles with a portion having soft magnetic properties as described above, the coercive force Hc of the ε-iron oxide portion alone can be kept high to ensure thermal stability, while the coercive force Hc of the ε-iron oxide particle (composite particle) as a whole can be adjusted to a coercive force Hc suitable for recording.

The ε iron oxide particles may contain an additive instead of the structure of the composite particles, or may have the structure of the composite particles and contain an additive. In this case, part of the Fe in the ε iron oxide particles is replaced with the additive. By containing an additive in the ε iron oxide particles, the coercive force Hc of the ε iron oxide particles as a whole can be adjusted to a coercive force Hc suitable for recording, improving ease of recording. The additive is a metal element other than iron, preferably a trivalent metal element, more preferably at least one selected from the group consisting of Al, Ga and In, and even more preferably at least one selected from the group consisting of Al and Ga.

Specifically, the ε-iron oxide containing the additive is an ε-Fe2 _- _xMxO3 _crystal (wherein M is a metal element other than iron, preferably a trivalent metal element, more preferably at least one selected from the group consisting of Al, Ga and In, and even more preferably at least one selected from the group consisting of Al and Ga; x is, for example, 0<x<1).

When the magnetic particles are ε iron oxide particles, the average particle size of the magnetic particles is preferably 10 nm to 20 nm, more preferably 10 nm to 18 nm, even more preferably 10 nm to 16 nm, particularly preferably 10 nm to 15 nm, and most preferably 10 nm to 14 nm. In magnetic tape MT, the area with a size of 1/2 the recording wavelength becomes the actual magnetization area. Therefore, by setting the average particle size of the magnetic particles to half or less of the shortest recording wavelength, even better electromagnetic conversion characteristics (e.g., SNR) can be obtained. Therefore, when the average particle size of the magnetic particles is 20 nm or less, even better electromagnetic conversion characteristics (e.g., SNR) can be obtained in a high recording density magnetic tape MT (e.g., a magnetic tape MT configured to be able to record signals at the shortest recording wavelength of 40 nm or less). On the other hand, when the average particle size of the magnetic particles is 10 nm or more, the dispersibility of the magnetic particles is further improved, and even better electromagnetic conversion characteristics (e.g., SNR) can be obtained.

When the magnetic particles are ε iron oxide particles, the average aspect ratio of the magnetic particles is preferably 1.0 to 3.0, more preferably 1.0 to 2.5, even more preferably 1.0 to 2.1, and particularly preferably 1.0 to 1.8. When the average aspect ratio of the magnetic particles is within the range of 1.0 to 3.0, aggregation of the magnetic particles can be suppressed. Furthermore, when the magnetic particles are vertically oriented in the process of forming the magnetic layer 43, the resistance applied to the magnetic particles can be suppressed. Therefore, the vertical orientation of the magnetic particles can be improved.

When the magnetic particles are ε iron oxide particles, the average particle size and average aspect ratio of the magnetic particles can be found as follows. First, the magnetic tape MT housed in the magnetic recording cartridge 10 is unwound, and the magnetic tape MT is cut out at a position 30 to 40 m in the longitudinal direction from the connection between the magnetic tape MT and the leader tape. Next, the magnetic tape MT to be measured is processed by the FIB (Focused Ion Beam) method or the like to be thinned. When the FIB method is used, a carbon layer and a tungsten layer are formed as protective layers as a pretreatment for observing the TEM image of the cross section described later. The carbon layer is formed by deposition on the surface of the magnetic tape MT on the magnetic layer 43 side and the surface on the back layer 44 side, and the tungsten layer is further formed on the surface on the magnetic layer 43 side by deposition or sputtering. The thinning is performed along the length direction (longitudinal direction) of the magnetic tape MT. That is, this slicing creates a cross section that is parallel to both the longitudinal and thickness directions of the magnetic tape MT.

The cross section of the obtained thin sample is observed with a transmission electron microscope (H-9500 manufactured by Hitachi High-Technologies Corporation) at an acceleration voltage of 200 kV and a total magnification of 500,000 times so that the entire magnetic layer 43 is included in the thickness direction of the magnetic layer 43, and a TEM image is taken. Next, 50 particles whose particle shape can be clearly confirmed are selected from the taken TEM image, and the long axis length DL and short axis length DS of each particle are measured. Here, the long axis length DL means the maximum distance between two parallel lines drawn from all angles so as to be in contact with the contour of each particle (so-called maximum Feret diameter). On the other hand, the short axis length DS means the maximum length of the particle in the direction perpendicular to the long axis (DL) of the particle. Next, the long axis lengths DL of the measured 50 particles are simply averaged (arithmetic average) to obtain the average long axis length DL _ave . The average long axis length DL _ave thus obtained is the average particle size of the magnetic particles. The minor axis lengths DS of the 50 particles are simply averaged (arithmetic mean) to determine the average minor axis length _DSave . The average aspect ratio of the particles ( _DLave / _DSave ) is then calculated from the average major axis length _DLave and the average minor axis length _DSave .

When the magnetic particles are ε iron oxide particles, the average particle volume of the magnetic particles is preferably 500 nm3 or more and ⁴⁰⁰⁰ ^nm3 or less, more preferably 500 ^nm3 or more and 3000 ^nm3 or less, even more preferably 500 ^nm3 or more and ²⁰⁰⁰ nm3 or less, particularly preferably 600 ^nm3 or more and 1600 ^nm3 or less, and most preferably 600 nm3 ^or more and 1300 ^nm3 or less. Since the noise of a magnetic tape MT is generally inversely proportional to the square root of the number of particles (i.e., proportional to the square root of the particle volume), by making the particle volume smaller, it is possible to obtain even better electromagnetic conversion characteristics (e.g., SNR). Therefore, when the average particle volume of the magnetic particles is 4000 ^nm3 or less, it is possible to obtain even better electromagnetic conversion characteristics (e.g., SNR) in the same way as when the average particle size of the magnetic particles is 20 nm or less. On the other hand, when the average particle volume of the magnetic particles is 500 ^nm3 or more, it is possible to obtain the same effect as when the average particle size of the magnetic particles is 10 nm or more.

When the ε iron oxide particles are spherical, the average particle volume of the magnetic particles is calculated as follows: First, the average major axis length DL _ave is calculated in the same manner as in the above-mentioned method for calculating the average particle size of the magnetic particles. Next, the average volume V of the magnetic particles is calculated by the following formula.
V = (π/6) × DL _ave ³

When the ε iron oxide particles have a cubic shape, the average volume of the magnetic particles is obtained as follows. First, the magnetic tape MT housed in the magnetic recording cartridge 10 is unwound, and the magnetic tape MT is cut out at a position 30 to 40 m in the longitudinal direction from the connection between the magnetic tape MT and the leader tape LT. Next, the cut magnetic tape MT is processed by the FIB (Focused Ion Beam) method or the like to be thinned. When the FIB method is used, a carbon film and a tungsten thin film are formed as protective films as a pretreatment for observing the TEM image of the cross section described later. The carbon film is formed by deposition on the surface of the magnetic tape MT on the magnetic layer 43 side and the surface on the back layer 44 side, and the tungsten thin film is further formed by deposition or sputtering on the surface on the magnetic layer 43 side. The thinning is performed along the length direction (longitudinal direction) of the magnetic tape MT. In other words, the thinning forms a cross section parallel to both the longitudinal direction and the thickness direction of the magnetic tape MT.

The obtained thin sample is observed in cross section in the thickness direction of the magnetic layer 43 at an acceleration voltage of 200 kV and a total magnification of 500,000 times to include the entire magnetic layer 43, and a TEM image is obtained. The magnification and acceleration voltage may be adjusted appropriately depending on the type of device. Next, 50 particles whose particle shapes are clear are selected from the TEM image taken, and the side length DC of each particle is measured. Next, the side lengths DC of the 50 particles measured are simply averaged (arithmetic average) to obtain the average side length DC _ave . Next, the average volume V _ave (particle volume) of the magnetic particles is calculated from the following formula using the average side length DC _ave .
V _ave = DC _ave ³

[Cobalt ferrite particles]
The cobalt ferrite particles preferably have uniaxial crystal anisotropy. The cobalt ferrite particles have uniaxial crystal anisotropy, so that the magnetic powder can be preferentially crystal oriented in the perpendicular direction of the magnetic tape MT. The cobalt ferrite particles have, for example, a cubic shape. In this specification, the cubic shape includes an almost cubic shape. The Co-containing spinel ferrite may further contain at least one of Ni, Mn, Al, Cu, and Zn in addition to Co.

The Co-containing spinel ferrite has, for example, an average composition represented by the following formula.
Co _x M _y Fe ₂ O _Z
(In the formula, M is, for example, at least one metal selected from Ni, Mn, Al, Cu, and Zn. x is a value within the range of 0.4≦x≦1.0. y is a value within the range of 0≦y≦0.3. However, x and y satisfy the relationship of (x+y)≦1.0. z is a value within the range of 3≦z≦4. A part of Fe may be substituted with another metal element.)

When the magnetic powder contains cobalt ferrite particles, the average particle size of the magnetic powder is preferably 8 nm or more and 16 nm or less, more preferably 8 nm or more and 13 nm or less, and even more preferably 8 nm or more and 10 nm or less. When the average particle size of the magnetic powder is 16 nm or less, it is possible to obtain even better electromagnetic conversion characteristics (e.g., SNR) in a high recording density magnetic tape MT. On the other hand, when the average particle size of the magnetic powder is 8 nm or more, the dispersibility of the magnetic powder is further improved, and even better electromagnetic conversion characteristics (e.g., SNR) can be obtained. The method of calculating the average particle size of the magnetic powder is the same as the method of calculating the average particle size of the magnetic powder when the magnetic powder contains ε iron oxide particles.

When the magnetic powder contains cobalt ferrite particles, the average aspect ratio of the magnetic powder is preferably 1.0 to 2.5, more preferably 1.0 to 2.1, and even more preferably 1.0 to 1.8. When the average aspect ratio of the magnetic powder is within the range of 1.0 to 2.5, aggregation of the magnetic powder can be suppressed. In addition, when the magnetic powder is vertically oriented in the process of forming the magnetic layer 43, the resistance applied to the magnetic powder can be suppressed. Therefore, the vertical orientation of the magnetic powder can be improved. The method of calculating the average aspect ratio of the magnetic powder is the same as the method of calculating the average aspect ratio of the magnetic powder when the magnetic powder contains ε iron oxide particles.

When the magnetic powder contains cobalt ferrite particles, the average particle volume of the magnetic powder is preferably 500 nm3 ^or more and 4000 ^nm3 or less, more preferably 600 ^nm3 or more and 2000 ^nm3 or less, and even more preferably 600 ^nm3 or more and 1000 ^nm3 or less. When the average particle volume of the magnetic powder is 4000 ^nm3 or less, the same effect as when the average particle size of the magnetic powder is 16 nm or less can be obtained. On the other hand, when the average particle size of the magnetic powder is 500 ^nm3 or more, the same effect as when the average particle size of the magnetic powder is 8 nm or more can be obtained. The method for calculating the average particle volume of the magnetic component is the same as the method for calculating the average particle volume when the ε iron oxide particles have a cubic shape.

[carbon]
The carbon contained in the magnetic layer 43 may function as an antistatic agent, a solid lubricant, etc. As such carbon, for example, at least one type selected from the group consisting of carbon particles and hybrid particles can be used, and it is preferable to use carbon particles.

As the carbon particles, for example, one or more selected from the group consisting of carbon black, acetylene black, ketjen black, carbon nanotubes, and graphene can be used, and among these carbon particles, it is preferable to use carbon black. As the carbon black, for example, Seast TA manufactured by Tokai Carbon Co., Ltd., Asahi #15, #15HS, etc. manufactured by Asahi Carbon Co., Ltd. can be used.

The hybrid particles include carbon and a material other than carbon. The material other than carbon is, for example, an organic material or an inorganic material. The hybrid particles may be hybrid particles in which carbon is attached to the surface of an inorganic particle. Specifically, for example, the hybrid particles may be hybrid carbon in which carbon is attached to the surface of a silica particle.

For example, when carbon particles are used as the carbon contained in the magnetic layer 43, the carbon particles protrude from the surface of the magnetic layer 43 to form protrusions. When the data write head 60 slides over the magnetic tape MT, the protrusions formed by the carbon particles come into contact with the data write head 60.

[Abrasive]
Some particles of the abrasive contained in the magnetic layer 43 (hereinafter referred to as abrasive particles) protrude from the magnetic surface to form protrusions. When the data write head 60 slides over the magnetic tape MT, the protrusions formed by the abrasive particles come into contact with the data write head 60.

The abrasive particles are particles having an abrasive effect. From the viewpoint of suppressing deformation due to contact with a magnetic head, the Mohs hardness of such abrasive particles is preferably 7 or more, more preferably 7.5 or more, even more preferably 8 or more, and even more preferably 8.5 or more. From the viewpoint of suppressing head wear, the Mohs hardness of the abrasive particles is preferably 9.5 or less. The abrasive particles may preferably be inorganic particles, such as α-Al ₂ O ₃ (α-alumina), β-Al ₂ O ₃ (β-alumina), γ-Al ₂ O ₃ (γ-alumina), silicon carbide, chromium oxide, cerium oxide, α-iron oxide, corundum, silicon nitride, titanium carbide, titanium oxide, silicon dioxide, tin oxide, magnesium oxide, tungsten oxide, zirconium oxide, boron nitride, zinc oxide, calcium carbonate, calcium sulfate, barium sulfate, molybdenum disulfide, acicular α-iron oxide obtained by dehydrating and annealing raw materials of magnetic iron oxide, and those surface-treated with aluminum and/or silica as necessary, diamond powder, etc. The abrasive particles are preferably alumina particles such as α-Al ₂ O ₃ (α-alumina), β-Al ₂ O ₃ (β-alumina), γ-Al ₂ O ₃ (γ-alumina), and silicon carbide. These abrasive particles may be of any shape, such as needle-like, spherical, or cubic, but those having corners in their shape are preferred because they have high abrasiveness.

[Average height of protrusions formed by abrasive particles]
The abrasive particles form protrusions on the surface of the magnetic layer. The average height of the protrusions formed by the abrasive particles is preferably 8 nm or less, more preferably 7.5 nm or less, even more preferably 7.0 nm or less, even more preferably 6.5 nm or less, and even more preferably 6.0 nm or less. By having the average height of the protrusions formed by the abrasive particles of the magnetic tape MT within the above numerical range, the spacing between the data write head and the magnetic tape MT is small, the occurrence of friction increase due to multiple runs is small, and the abrasive force against the data write head can be appropriately maintained.

In addition, the lower limit of the average height of the protrusions formed by the abrasive particles is not particularly limited, but may be, for example, preferably 2.0 nm or more, more preferably 2.5 nm or more, and even more preferably 3.0 nm or more.

[lubricant]
The lubricant contains at least one selected from, for example, a fatty acid and a fatty acid ester, and preferably both a fatty acid and a fatty acid ester. The inclusion of a lubricant in the magnetic layer 43, and in particular the inclusion of both a fatty acid and a fatty acid ester in the magnetic layer 43, contributes to improving the running stability of the magnetic tape MT.

The fatty acid may preferably be a compound represented by the following general formula (1) or (2). For example, the fatty acid may contain either a compound represented by the following general formula (1) or a compound represented by the following general formula (2), or may contain both.

The fatty acid ester may preferably be a compound represented by the following general formula (3) or (4). For example, the fatty acid ester may contain either a compound represented by the following general formula (3) or a compound represented by the following general formula (4), or may contain both.

The lubricant contains either or both of the compound shown in general formula (1) and the compound shown in general formula (2), either or both of the compound shown in general formula (3) and the compound shown in general formula (4), or the compound shown in general formula (5), thereby making it possible to suppress an increase in the dynamic friction coefficient due to repeated recording or playback of the magnetic tape MT.

_CH3 ( _CH2 ) _kCOOH ... (1)
(However, in general formula (1), k is an integer selected from the range of 14 or more and 22 or less, more preferably from the range of 14 or more and 18 or less.)

_CH3 ( _CH2 ) _nCH =CH( _CH2 ) _mCOOH ... (2)
(However, in general formula (2), the sum of n and m is an integer selected from the range of 12 to 20, more preferably from the range of 14 to 18.)

_CH3 ( _CH2 ) _pCOO ( _CH2 ) _qCH3 _... (3)
(However, in general formula (3), p is an integer selected from the range of 14 or more and 22 or less, more preferably 14 or more and 18 or less, and q is an integer selected from the range of 2 or more and 5 or less, more preferably 2 or more and 4 or less.)

_CH3 ( _CH2 ) _rCOO- ( _CH2 ) _sCH ( _CH3 ) ₂ ... (4)
(In the general formula (4), r is an integer selected from the range of 14 or more and 22 or less, and s is an integer selected from the range of 1 or more and 3 or less.)

CH ₃ (CH ₂ ) _t COO-(CH) (CH ₃ ) CH ₂ (CH ₃ ) _u ... (5)
(In the general formula (5), t is an integer selected from the range of 14 or more and 22 or less, and u is an integer selected from the range of 1 or more and 3 or less.)

Specific examples of fatty acids and fatty acid esters include the following: Fatty acids include capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, elaidic acid, linoleic acid, and linolenic acid.

Furthermore, examples of fatty acid esters include butyl caprate, octyl caprylate, ethyl laurate, butyl laurate, octyl laurate, ethyl myristate, butyl myristate, octyl myristate, 2-ethylhexyl myristate, ethyl palmitate, butyl palmitate, octyl palmitate, 2-ethylhexyl palmitate, ethyl stearate, butyl stearate, isobutyl stearate, octyl stearate, 2-ethylhexyl stearate, amyl stearate, isoamyl stearate, 2-ethylpentyl stearate, 2-hexyldecyl stearate, isotridecyl stearate, stearic acid amide, alkyl stearate amide, and butoxyethyl stearate.

[Binding agent]
Examples of the binder include thermoplastic resins, thermosetting resins, and reactive resins. Examples of the thermoplastic resin include vinyl chloride, vinyl acetate, vinyl chloride-vinyl acetate copolymers, vinyl chloride-vinylidene chloride copolymers, vinyl chloride-acrylonitrile copolymers, acrylic acid ester-acrylonitrile copolymers, acrylic acid ester-vinyl chloride-vinylidene chloride copolymers, acrylic acid ester-acrylonitrile copolymers, acrylic acid ester-vinylidene chloride copolymers, methacrylic acid ester-vinylidene chloride copolymers, methacrylic acid ester-vinyl chloride copolymers, methacrylic acid ester-ethylene copolymers, polyvinyl fluoride, vinylidene chloride-acrylonitrile copolymers, acrylonitrile-butadiene copolymers, polyamide resins, polyvinyl butyral, cellulose derivatives (cellulose acetate butyrate, cellulose diacetate, cellulose triacetate, cellulose propionate, nitrocellulose), styrene-butadiene copolymers, polyurethane resins, polyester resins, amino resins, and synthetic rubbers.

Examples of thermosetting resins include phenolic resins, epoxy resins, polyurethane curing resins, urea resins, melamine resins, alkyd resins, silicone resins, polyamine resins, and urea formaldehyde resins.

In order to improve the dispersibility of the magnetic powder, all of the above-mentioned binders may contain polar functional groups such as -SO ₃ M, -OSO ₃ M, -COOM, P=O(OM) ₂ (wherein M represents a hydrogen atom or an alkali metal such as lithium, potassium, or sodium), -NR1R2, -NR1R2R3 ⁺ ^X- having an end group, or >NR1R2 ⁺ ^X- (wherein R1, R2, and R3 represent a hydrogen atom or a hydrocarbon group, and X- represents a halogen element ion such as fluorine, chlorine, bromine, or iodine, an inorganic ion, or an organic ion), -OH, -SH, -CN, or an epoxy group. The amount of these polar functional groups introduced into the binder is preferably 10 ^-1 mol/g or more and 10 ^-8 mol/g or less, and more preferably 10 ^-2 mol/g or more and 10 ^-6 mol/g or less.

[Antistatic Agent]
Examples of the antistatic agent include natural surfactants, nonionic surfactants, and cationic surfactants.

[Curing agent]
Examples of the curing agent include polyisocyanates. Examples of the polyisocyanates include aromatic polyisocyanates such as an adduct of tolylene diisocyanate (TDI) and an active hydrogen compound, and aliphatic polyisocyanates such as an adduct of hexamethylene diisocyanate (HMDI) and an active hydrogen compound. The weight average molecular weight of these polyisocyanates is preferably in the range of 100 to 3,000.

[anti-rust]
Examples of the rust inhibitor include phenols, naphthols, quinones, heterocyclic compounds containing a nitrogen atom, heterocyclic compounds containing an oxygen atom, and heterocyclic compounds containing a sulfur atom.

[Non-magnetic reinforcing particles]
Examples of non-magnetic reinforcing particles include aluminum oxide (α, β or γ alumina), chromium oxide, silicon oxide, diamond, garnet, emery, boron nitride, titanium carbide, silicon carbide, titanium carbide, titanium oxide (rutile or anatase type titanium oxide), and the like.

[Base layer]
The underlayer 42 serves to reduce the unevenness of the surface of the base layer 41 and adjust the unevenness of the surface of the magnetic layer 43. The underlayer 42 is a non-magnetic layer containing non-magnetic powder, a binder, and a lubricant. The underlayer 42 supplies the lubricant to the surface of the magnetic layer 43. The underlayer 42 may further contain at least one additive selected from the group consisting of an antistatic agent, a hardener, and an anti-rust agent, as necessary.

The upper limit of the average thickness of the underlayer 42 is preferably 1.0 μm or less, more preferably 0.9 μm or less, even more preferably 0.8 μm or less, particularly preferably 0.7 μm or less, and most preferably 0.6 μm or less. If the upper limit of the average thickness of the underlayer 42 is 1.0 μm or less, the thickness of the magnetic tape MT can be reduced, so that the recording capacity that can be recorded in one data cartridge can be increased compared to that of a general magnetic tape. If the average thickness of the underlayer 42 is 1.0 μm or less, the elasticity of the magnetic tape MT due to external forces is further increased, so that the width of the magnetic tape MT can be further adjusted by adjusting the tension. The lower limit of the average thickness of the underlayer 42 is preferably 0.3 μm or more. If the lower limit of the average thickness of the underlayer 42 is 0.3 μm or more, the deterioration of the function as the underlayer 42 can be suppressed. The average thickness of the underlayer 42 is determined in the same manner as the average thickness of the magnetic layer 43. However, the magnification of the TEM image is appropriately adjusted according to the thickness of the underlayer 42.

[Non-magnetic powder]
The non-magnetic powder includes at least one of inorganic particle powder and organic particle powder. The non-magnetic powder may also include carbon powder such as carbon black. One type of non-magnetic powder may be used alone, or two or more types of non-magnetic powder may be used in combination. The inorganic particles include, for example, metals, metal oxides, metal carbonates, metal sulfates, metal nitrides, metal carbides, metal sulfides, etc. The shape of the non-magnetic powder may be, for example, various shapes such as needle-like, spherical, cubic, and plate-like, but is not limited to these shapes.

The average particle size of the non-magnetic powder is preferably 10 nm or more and 150 nm or less, more preferably 15 nm or more and 110 nm or less. The average particle size of the non-magnetic powder is determined in the same manner as the average particle size of the magnetic powder described above. The non-magnetic powder may contain non-magnetic powder having two or more particle size distributions.

[Binding agent, lubricant]
The binder and lubricant are the same as those in the magnetic layer 43 described above.

[Additive]
The antistatic agent, hardener and rust inhibitor are the same as those in the magnetic layer 43 described above.

[Back layer]
The back layer 44 contains a binder and a non-magnetic powder. The back layer 44 may further contain at least one additive selected from the group consisting of a lubricant, a hardener, and an antistatic agent, if necessary. The binder and the non-magnetic powder are the same as those in the underlayer 42 described above. The hardener and the antistatic agent are the same as those in the magnetic layer 43 described above.

The upper limit of the average thickness _tb of the back layer 44 is preferably 0.6 μm or less. If the upper limit of the average thickness _tb of the back layer 44 is 0.6 μm or less, the thickness of the underlayer 42 and the base layer 41 can be kept thick even when the average thickness of the magnetic tape MT is 5.3 μm or less, so that the running stability of the magnetic tape MT in a recording and reproducing device can be maintained. The lower limit of the average thickness _tb of the back layer 44 is not particularly limited, but is, for example, 0.2 μm or more.

The average thickness t _b of the back layer 44 is obtained as follows. First, the average thickness t _T of the magnetic tape MT is measured. The method for measuring the average thickness t _T is as described in the "Average Thickness of Magnetic Tape" below. Next, the magnetic tape MT housed in the magnetic recording cartridge 10 is unwound, and the magnetic tape MT is cut into 250 mm lengths from the range of 10 m to 20 m, the range of 30 m to 40 m, and the range of 50 m to 60 m in the longitudinal direction from the connection part 21 between the magnetic tape MT and the leader tape LT, respectively, to prepare three samples. Next, the back layer 44 of each sample is removed with a solvent such as MEK (methyl ethyl ketone) or dilute hydrochloric acid. Next, the thickness of each sample is measured at five positions using a Mitutoyo laser hologram (LGH-110C), and the measured values (total thicknesses of 15 samples) are arithmetically averaged to calculate the average value t _B [μm]. After that, the average thickness t _b [μm] of the back layer 44 is obtained from the following formula. The five measurement positions are selected at random from each sample so that they are different positions in the longitudinal direction of the magnetic tape MT.
_tb [μm]= _tT [μm] _−tB [μm]

[Magnetic tape width change amount Δ]
When the width change amount Δ of the magnetic tape is measured over the entire length of the magnetic tape after storage at 65° C. for 360 hours, the sign of the width change amount Δout on the outer side of the magnetic tape is different from the sign of the width change amount Δin on the inner side of the magnetic tape. By the sign of the width change amount Δout on the outer side of the magnetic tape being different from the sign of the width change amount Δin on the inner side of the magnetic tape, excellent running stability can be obtained even when stored in a high-temperature environment. Furthermore, the width change amount Δ is 0 ppm in any of the two regions sandwiching the center line of the entire length of the magnetic tape when the entire length of the magnetic tape is divided into four equal regions. In this way, by the width change amount Δ being 0 ppm in a specific region in the longitudinal direction of the magnetic tape, excellent running stability can be obtained even when stored in a high-temperature environment. Furthermore, in the longitudinal direction of the magnetic tape, the width change amount Δ is preferably 300 ppm or less, more preferably 250 ppm or less, even more preferably 200 ppm or less, and even more preferably 150 ppm or less in any of the four regions.

The change in width of the magnetic tape, Δ, is measured as follows:

First, the servo band pitch in the longitudinal direction of the magnetic tape in its initial state before storage for 360 hours at 65° C. is measured using the data recording/reproducing device 50. The servo band pitch means the arrangement interval of the servo bands.
In measuring the servo band pitch, the magnetic tape MT is wound into the magnetic recording cartridge 10 with a tension of 0.55 N, and the magnetic tape MT housed in the magnetic recording cartridge 10 is run so as to be wound into the data recording/reproducing device 50 (running in a so-called forward direction) in an environment of 32° C. and 55% RH, and the servo band pitch is measured at each position in the longitudinal direction of the magnetic tape MT over the entire length of the magnetic tape MT. In this measurement, the tension applied to the magnetic tape MT is 0.55 N, and the running speed is 3 to 6 m/s.

Next, the magnetic tape MT is wound into the magnetic recording cartridge 10 with a tension of 0.55 N and stored at 65°C and 40 RH% for 24 hours, then run once back and forth at a tension of 0.55 N in the data recording and reproducing device 50 in an environment of 32°C and 55 RH%, and then stored again for 24 hours in an environment of 65°C and 40 RH%, after which it is run once back and forth at a tension of 0.55 N in the data recording and reproducing device 50 in an environment of 32°C and 55 RH%, repeating this process for a total of 360 hours of storage.

The ratio of the servo band pitch at each position in the longitudinal direction of the magnetic tape MT after storage to the servo band pitch at the corresponding position in the longitudinal direction in the initial state (corresponding positions in the longitudinal direction mean positions having the same length ratio in the entire length) is defined as the width change amount Δ. The portion where the width change amount Δ is minimum and the portion where the width change amount Δ is maximum are identified, and the difference between the maximum width change amount _Δmax and the minimum width change amount _Δmin is calculated.

The method for measuring the servo band pitch will be described in more detail below.
Here, as shown in FIG. 6, an example will be described in which the data write head 60 tracks a data band d0 sandwiched between a servo band s2 and a servo band s3.

As described above, the method of measuring the servo band pitch using the data recording and reproducing device 50 involves running the magnetic tape MT over its entire length using the data recording and reproducing device 50, measuring the numerical values representing the relative positions of the servo trace lines T on each servo band of the two servo read sections 62 with respect to the servo pattern 47, and calculating the servo band pitch from the measured relative positions of each servo trace line T with respect to the servo pattern 47. The spacing between the servo trace lines T shown by solid lines in FIG. 6 indicates the servo band pitch when the width of the magnetic tape MT does not change (the first pitch P1, which is the spacing between the two servo read sections 62 of the data write head 60). The spacing between the servo trace lines T shown by dashed lines in FIG. 6 corresponds to the servo band pitch (P2') when the width of the magnetic tape MT is expanded.

FIG. 7 is a diagram explaining a method for measuring the servo trace line T. The data recording and reproducing device 50 outputs a servo reproduction signal having a waveform according to the position of the servo trace line T relative to the servo pattern 47. Typically, the distance AC between the A burst and the C burst, which are arrays of inclination patterns of the same shape, and the distance AB between the A burst and the B burst, which are arrays of inclination patterns of different shapes, are calculated, and a numerical value representing the relative position of the servo trace line T of each servo lead portion 62 with respect to the servo pattern 47 is calculated using the following formula [Equation 1]. Note that θ is the azimuth angle of each of the inclination patterns, and is set to 12° in this example.

Here, the distance AC may be the distance AC1 between the first slope portions of the A burst and the C burst, the distance AC2 between their second slope portions, the distance AC3 between their third slope portions, or the distance AC4 between their fourth slope portions. These distances AC (AC1 to AC4) refer to the distances between the positions (upper peak positions) that indicate the maximum positive amplitude values in the servo playback waveform.

Similarly, the distance AB may be the distance AB1 between the first inclined portions of the A burst and the B burst, the distance AB2 between their second inclined portions, the distance AB3 between their third inclined portions, or the distance AB4 between their fourth inclined portions. Typically, when distance AC1 is adopted, distance AB1 is adopted, when distance AC2 is adopted, distance AB2 is adopted, when distance AC3 is adopted, distance AB3 is adopted, and when distance AC4 is adopted, distance AB4 is adopted.

Then, the servo band pitch is calculated from the difference in the values representing the position of each servo trace line T on the servo pattern, which is calculated from the ratio of distances AB and AC, using equation 1. Here, of the two servo bands being measured, the difference is taken between the measurement value of the servo band on the tape edge side (servo band s3) and the measurement value of the servo band on the tape center side (servo band s2). The positive or negative value indicates the direction of change in the tape width, with a positive value corresponding to a narrowing of the servo band pitch and a negative value corresponding to a widening of the servo band pitch. If the difference is zero, it means that there is no change in the tape width.

The servo band pitch is preferably determined from the difference between a large number of servo frames, and may be, for example, the average of measured values calculated from the difference between 100 and 100,000 servo frames. The tape tension during measurement is the tension during recording of the servo pattern 47 (reference tension, for example, 0.55 N), and the measurement is performed at a constant tension over the entire length of the magnetic tape MT.

The method of measuring the servo trace line T is not limited to the above example. For example, the distance CA between the C burst and the A burst and the distance CD between the C burst and the D burst may be calculated, and the position of the servo trace line T may be measured using the following formula [Equation 2].

Here, the distance CA may be the distance CA1 between the first inclined portions of the C burst and the A burst, the distance CA2 between their second inclined portions, the distance CA3 between their third inclined portions, or the distance CA4 between their fourth inclined portions. These distances CA (CA1 to CA4) refer to the distances between the positions that indicate the maximum positive amplitude values in the servo playback waveform.

Similarly, the distance CD may be the distance CD1 between the first inclined portions of the C burst and the D burst, the distance CD2 between their second inclined portions, the distance CD3 between their third inclined portions, or the distance CD4 between their fourth inclined portions. Typically, when distance CA1 is adopted, distance CD1 is adopted, when distance CA2 is adopted, distance CD2 is adopted, when distance CA3 is adopted, distance CD3 is adopted, and when distance CA4 is adopted, distance CD4 is adopted.

Furthermore, the servo band pitch may be measured by using the average value of the measurement value using the formula [1] and the measurement value using the formula [2]. Furthermore, the distance between the positions (lower peak positions) showing the maximum negative value of the amplitude in the servo reproduction waveform may be used as the distances AC and AB in the formula [1] and the distances CA and CD in the formula [2]. Alternatively, the average value of the distance between the positions (upper peak positions) showing the maximum positive value of the amplitude in the servo reproduction waveform and the distance between the positions (lower peak positions) showing the maximum negative value may be used as the distances AC and AB in the formula [1] and the distances CA and CD in the formula [2].

As shown in FIG. 6, when the servo trace line T is located at the position indicated by the dashed line, the distance AB is 38.5 μm and the distance AC is 76 μm in the servo band s2, and the distance AB is 37.5 μm and the distance AC is 76 μm in the servo band s3.
In the servo band s2,
(38.5/76) x (76/2 tan 12°) = 90.5641 [μm]
In the servo band s3,
(37.5/76) x (76/2 tan 12°) = 88.2118 [μm]
The difference between these values is
88.2118-90.5641=-2.3523 [μm]
It becomes.
Therefore, the servo band pitch P2 in this case is determined to be a value 2.3523 μm wider than the servo read head pitch P1.

As shown in FIG. 6, when the servo trace line T is at the position indicated by the solid line, the distance AB is 38 μm and the distance AC is 76 μm for both servo band s2 and servo band s3. In this case, the distance is 89.3880 [μm] for both servo band s2 and servo band s3, and the difference between them is 0 [μm]. In other words, the servo band pitch in this case is the same as the servo read head pitch P1.

[Tension control]
The data recording/reproducing device 50 may control the tension of the magnetic tape MT based on the servo pattern pitch measured as described above so that the measured servo pattern pitch becomes equal to the servo read head pitch P1.

In this embodiment, prior to recording data to the magnetic tape MT or reproducing data from the magnetic tape MT, servo signals may be read from two servo bands sandwiching one data band for recording or reproducing data, and it may be determined from each read servo signal whether the pitch of these two servo bands is wider or narrower than the servo read head pitch P1. If the servo band pitch is wider than the servo read head pitch P1, the tension may be increased, and if the servo band pitch is narrower than the servo read head pitch P1, the tension may be decreased. In this way, by adjusting the magnitude of the tension according to the magnitude of the servo band pitch, it is possible to stably perform the desired tracking control for the data band.

The data recording and reproducing device 50 may obtain the relationship between the servo band pitch and tension for one data band by running the tape once back and forth, and record the obtained data in the cartridge memory 11. The data recording and reproducing device 50 may similarly apply the relationship between the servo band pitch and tension measured for the one data band when recording and reproducing data for other data bands.

The amount of width change in the longitudinal direction of the magnetic tape MT can be adjusted, for example, as follows. In order to reduce distortion and creep that occurs in the magnetic tape MT, the material of the base layer, the longitudinal and transverse strength of the base layer (longitudinal and transverse stretching conditions), the type of magnetic layer (coated magnetic layer, vacuum thin-film magnetic layer), and in the case of a coated layer, the Tg of the binder and the amount of hardener, etc. may be appropriately selected. In addition, to relieve distortion, the magnetic tape MT may be stored for a long period of time at a temperature of 65°C or higher before cutting, and further may be stored for a long period of time at a temperature of 55°C or higher before servo writing.

[Loss modulus, storage modulus]
The loss modulus of the base layer 41 at 65° C. can be 0.40 GPa or less, preferably 0.35 GPa or less, more preferably 0.30 GPa or less, even more preferably 0.25 GPa or less, and preferably 0.20 GPa or less. By having the loss modulus within this range, it is possible to provide a magnetic recording cartridge that allows the width of the magnetic tape in the longitudinal direction to be adjusted by adjusting the running tension of the tape system or changing the winding direction, even when stored in a high-temperature environment of 60° C. or more.

The storage modulus of the base layer 41 at 65° C. can be preferably 8.0 GPa or less, more preferably 7.0 GPa or less, and even more preferably 6.0 GPa or less. By having the storage modulus within the above numerical range, it is possible to provide a magnetic recording cartridge in which the width of the magnetic tape in the longitudinal direction can be adjusted by adjusting the running tension of the tape system or changing the winding direction even after storage in a high-temperature environment.
The lower limit of the storage modulus of the base layer at 65° C. is not particularly limited, but may be, for example, preferably 0.01 GPa or more, more preferably 0.02 GPa or more, and even more preferably 0.03 GPa or more.

The loss modulus and storage modulus are measured by dynamic viscoelasticity measurement. The dynamic viscoelasticity measurement is a temperature-dependent measurement, and is specifically performed as follows.

The magnetic tape MT housed in the magnetic recording cartridge 10 is unwound, and cut into 250 mm lengths from three positions, 10 m to 20 m, 30 m to 40 m, and 50 m to 60 m from the connection between the magnetic tape MT and the leader tape LT, and the cut magnetic tape MT is cut into a measuring tape length of 22.0 mm and width of 4.0 mm using a punch to prepare a sample. The layers other than the base layer 41 of the sample (i.e., the non-magnetic layer (undercoat layer) 42, the magnetic layer 43, and the back layer 44) are removed with acetone or ethanol. Both ends of the longitudinal direction of the sample are clamped to the measuring part of a dynamic viscoelasticity measuring device (RSA II, manufactured by TA Instruments). Then, dynamic viscoelasticity measurement is performed under the following measurement conditions. Measurements are performed at five positions for each sample, with n being 3, and the measured values (total of 15 points) are simply averaged (arithmetic average) to calculate the loss modulus and storage modulus. The five measurement positions are selected at random from each sample so that they are different positions in the longitudinal direction of the magnetic tape MT.
Measurement temperature range: -10℃ to 180℃
Temperature rise rate: 2° C./min. Amplitude: Tape is stretched and contracted with an amplitude of 0.1% of the initial length. Measurement frequency: 10 Hz.
Test Type: "Strain-Controlled"
Measurement Type: "Dynamic"
Environment in which the device is placed: Temperature 25°C, humidity 50RH%
Humidity control of the measurement section: None Number of measurements: 3
More detailed settings regarding the measurement conditions of the device are as follows. That is, as described below, in the measurement, the tension is adjusted so that it does not become 0 or less, and the strain is adjusted so that it does not fall below the lower limit of the transducer. The measurement conditions for these adjustments may be appropriately set by those skilled in the art, but for example, the following settings may be adopted for the dynamic viscoelasticity measuring device.
Option settings
Delay Before Test: OFF
Auto Tension (Setting to adjust tension so that it never falls below 0)
Mode Static Force Tracking Dynamic Force
Auto Tension Direction Tension
Initial Static Force 10.0g
Static>Dynamic Force by 5.0%
Minimum Static Force 1.0g
Auto Tension Sensitivity 1.0g
Auto Strain (Setting to adjust the strain so that it does not fall below the lower limit of the transducer)
Max Applied Strain 0.1%
Maximum Allowed Force 100.0g
Min allowed force 2.0g
Strain Adjustment 3.0%
Meas Ops: Default setting

By performing the dynamic viscoelasticity measurement described above on the base layer 41, the loss modulus and storage modulus values at a measurement temperature of 65°C can be obtained.

The loss modulus and storage modulus of the base layer 41 can be adjusted, for example, by the type of material forming the base layer, the stretching state of the base layer in the longitudinal and transverse directions, and/or the coating and drying process, calendaring process, curing process, aging process, etc.

For example, by using PEN, PET, or PEEK as the material forming the base layer, the loss modulus and storage modulus can be reduced compared to other materials.

[Extraction rate of fatty acids and/or fatty acid esters]

<Advance preparations>
(A) Setting the sample mount Cut out four sheets of graph paper and draw 1m marking lines six squares inside both ends so that the center is 1m in size. Figure 41 shows an example of a sample mount used to measure the extraction rate. As shown in Figure 41, an inverted triangle mark is marked 50 cm in the center of the graph paper. Place the graph paper parallel to the desk and fix both ends of the graph paper with double-sided tape. Attach double-sided tape so that it covers the two 1m marking lines and set the sample mount.

(B) Preparation of a mixed solvent of acetonitrile and ultrapure water (acetonitrile:ultrapure water=100:3) Pour 30 mL of ultrapure water into 1000 mL of acetonitrile. After closing the lid, shake gently up and down, and with the lid loosened, degas in an ultrasonic cleaner for 15 minutes.

(C) Preparing the aluminum lid. Set the black lid, white rubber, and aluminum sheet in place.

(D) Preparing the syringe Set the filter on the outer shaft of the syringe. Leave the inner shaft out as well.
(E) Preparation of standard reagent The type of standard reagent varies depending on the fatty acid or fatty acid ester used. The concentration is also optional. As an example, the case of using stearic acid as the fatty acid and butyl stearate as the fatty acid ester is shown below. The standard reagent of stearic acid is prepared as follows. 4.0 mg, 10.0 mg, and 30.0 mg of stearic acid are weighed out, and a solvent of acetonitrile/water = 100/3 is weighed out, and each is diluted to 200 mL. The standard reagent of butyl stearate is prepared as follows. 10.0 mg, 30.0 mg, and 40.0 mg of butyl stearate are weighed out, and a solvent of acetonitrile/water = 100/3 is weighed out, and each is diluted to 200 mL. A standard reagent of stearic acid (manufactured by Junsei Chemical Co., Ltd., purity 95.0%) is prepared. A standard reagent of butyl stearate (manufactured by Junsei Chemical Co., Ltd., purity 95.0%) is prepared.

<Start-up of reversed-phase liquid chromatography>
As a reversed-phase liquid chromatography (HPLC), an Ultimate 3000 (Thermo) (column: ODS-2 5um 4.6×150mm (GL Sciences)) is used. The pump, autosampler, differential refractometer (Shodex RI-101, Showa Denko, set temperature: 30°C), and PC are turned on. The pump is purged for 5 minutes. The autosampler is washed. The software is started. When the flow rate/pressure is increased to 2mL, the liquid starts to flow, so wait for 1 hour or more until it stabilizes. The measurement conditions are set to mobile phase acetonitrile/water = 100/3 (volume ratio), solvent acetonitrile/water = 100/3, column temperature 40°C, measurement time 10 minutes, flow rate 2mL per minute, and injection injection volume 200μL.

<Preparation of standard reagents>
The prepared standard reagent is placed in an ultrasonic cleaner for 15 minutes. When the ultrasonic treatment is finished, insert the syringe with the filter set into the vial and pour the standard reagent directly into the syringe. The standard reagent is packed into the vial. Press the center stem to push the liquid into the vial. When the liquid reaches the top of the vial, close the aluminum lid. The standard reagent remaining in the syringe is returned to the screw cap through the filter.

<Sample collection>
The magnetic tape MT housed in the magnetic recording cartridge 10 is unwound, and the magnetic tape MT is cut out to a length of about 5 m at a position 20 m in the longitudinal direction from the connection part between the magnetic tape MT and the leader tape LT. Using the lines on the graph paper, the magnetic tape is attached to the double-sided tape of the sample mount while overlapping the Mag/Back alternately in parallel. Note that care should be taken not to apply too much tension when attaching the magnetic tape. The P/C surface layer is discarded, and 5 pieces of magnetic tape 1 m long are collected. A ruler is placed on the 1 m mark line of the sample mount, and 1 m of magnetic tape is cut out with a cutter. The five magnetic tapes are gathered together, and the center indicated by the inverted triangle mark is picked up with tweezers, folded in half, and the curled part at the end is grasped and wrinkled. The magnetic tapes are separated one by one and placed in a 120 mL round-bottom flask, and covered with aluminum foil.

(A) 5-minute extraction Measure out 60 mL of hexane into a 100 mL graduated cylinder. Set the stopwatch to 5 minutes. Place the 120 mL screw tube containing the sample in an automatic shaker placed in a 25°C environment, and leave the aluminum lid open. Put the measured 60 mL of hexane into a 120 mL round-bottom flask, put the aluminum lid on, and turn on the stopwatch and the automatic shaker at the same time to start shaking (set the rotation speed of the automatic shaker to 300 rpm). Five minutes after the start of shaking, measure out 50 mL of the sample and transfer it to a 100 mL graduated cylinder. Transfer the sample in the graduated cylinder to an eggplant flask. Insert the eggplant flask containing the sample into the eggplant flask attachment port of the evaporator and fix it. Start the evaporator, set the rotation speed of the eggplant flask to 50 rpm, and rotate the eggplant flask. Start drawing a vacuum to 160 hPa. Submerge the eggplant flask in a hot water bath. The hexane evaporates in about 4 minutes, and only fatty acids or fatty acid esters remain in the eggplant flask. When the hexane is completely gone, remove the recovery flask from the water bath. Release the reduced pressure and release the pressure to atmospheric pressure (approximately 1013 hPa). Stop the evaporator from rotating. Remove the recovery flask and dry it.

(B) Solvent replacement After the hexane has been removed by the evaporator, 5 mL of a mixed solvent of acetonitrile and ultrapure water is pipetted into the dried eggplant flask and poured into the neck. Cover with an aluminum lid and shake while holding the neck of the eggplant flask. Apply ultrasonic waves for 15 minutes. After ultrasonic treatment, shake the eggplant flask again and add all the liquid to the vial with a syringe with a 0.5 μm filter attached. Push in the center shaft, fill the vial with liquid up to the shoulder, close the lid, and discard the liquid remaining in the syringe.

(C) HPLC Measurement After the start-up of reverse phase liquid chromatography (HPLC) is completed, the measurement is started.

<Total Extraction>
The procedures for advance preparation, standard sample preparation, and sample collection are the same as those for the 5-minute extraction, so a detailed explanation is omitted.

Measure out 60 mL of hexane into a 100 mL graduated cylinder. Set the stopwatch to 1 hour. Place the 110 mL screw tube containing the sample in an ultrasonic processor (UT-105HS, SHARP) and leave the aluminum lid open. The ultrasonic processor has a water bath (water temperature: 40-50°C), and fill the water bath with water up to the upper water level line, and set the ultrasonic output to 100%. Place the 60 mL of measured hexane into a 120 mL screw tube, put the aluminum lid on, and turn on the stopwatch and ultrasonic processor at the same time to start extraction. One hour after turning on the ultrasonic processor, use an evaporator to remove hexane from the sample in the 110 mL screw tube using the same method as for the 5-minute extraction. After that, perform solvent replacement in the same manner as for the 5-minute extraction, except that 5 mL of a mixed solvent of acetonitrile and ultrapure water (if the concentration is too high and the HPLC peak area is off, use 10 mL) is added to the sample in the eggplant flask, and then perform measurement.

Data Analysis
Data analysis is carried out according to the following procedure.
(A) Determine the area value of the standard reagent and create a calibration curve (in the form y = ax).
(B) Calculate the area value of the measurement sample and calculate the concentration from the calibration curve (the method of drawing the peak area should be consistent with that of the standard reagent). Then, calculate the amount of fatty acid (mg) or fatty acid ester (mg) in 5 mL (or 10 mL) of acetonitrile solution.
(C) The amount of fatty acid or fatty acid ester is converted into an extractable amount (mg/m ² ) based on the following formula.
Extraction amount = (amount of fatty acid or amount of fatty acid ester * (60/50)) / tape area Amount of fatty acid or amount of fatty acid ester = the value obtained in (2) above Tape area 5m = ^0.06325m2
(1/2 inch x length [m])
*Amount of fatty acids or fatty acid esters was measured in 50 mL of the 60 mL extracted with hexane, so a correction was required.

[Protrusion height]
The height of the protrusions formed by the abrasive particles is measured by performing shape analysis by an atomic force microscope (hereinafter referred to as AFM) and distinguishing the components by image analysis using the brightness difference due to the difference in the amount of secondary electron emission of the carbon particles and the abrasive particles from the FE-SEM images taken by a field emission scanning electron microscope (hereinafter referred to as FE-SEM) of the same location of the measurement sample, as described below. The height of the protrusions can be measured by the AFM, and it is possible to identify whether each protrusion is formed by carbon particles or abrasive particles by the FE-SEM. A composite image is obtained by superimposing the image obtained by the AFM of the same location and the image obtained by the FE-SEM of the certain region, and the type of particles forming each protrusion (whether it is carbon particles or abrasive particles) and the height of each protrusion can be associated from the obtained composite image.
Below, we will explain a method for measuring the height of the protrusions using an AFM, a method for identifying the type of particles that form the protrusions using an FE-SEM, and a method for correlating the height of the protrusions with the type of particles that form the protrusions.

[Method of measuring protrusion height using an atomic force microscope (AFM)]
In this technique, the height of the protrusions formed by the abrasive particles is obtained as follows. First, a measurement sample is prepared by cutting out a size that fits on a sample stage for SEM observation from the magnetic tape MT in the user data area (24 m or more from the leader pin) in the LTO cartridge. Next, marking is performed on the surface of the measurement sample, avoiding the center of the measurement sample. Examples of marking methods include a method of forming linear or dot-shaped recesses on the magnetic tape MT using a manipulator or a nine denter, and a method of forming convex portions on the magnetic tape MT using silver paste or the like. In addition, since the AFM scans the marking portion with a probe, depending on the state of the marking portion, the tip of the probe may become dirty and an accurate shape image may not be obtained, so it is preferable to make the marking small and shallow so that the probe is not contaminated. Next, the marking portion on the surface of the measurement sample is subjected to shape analysis by AFM. Since the marked marking portion is recessed, it is measured with an AFM at a viewing angle of 5 μm × 5 μm so that the marking portion is as close to the edge of the field of view as possible. Note that protrusions on the periphery of the marking portion are not measured. Next, the measurement is performed at a viewing angle of 10 μm×10 μm, a portion to be a mark is determined, and a portion without a marking is measured at a viewing angle of 5 μm×5 μm in accordance with the portion to be a mark. The measurement conditions for the shape analysis are as described below. For abrasive particles, when 20 or more particles can be identified in one AFM viewing field from one measurement sample, one viewing field is measured with the AFM. For abrasive particles, when the number of particles that can be identified in one AFM viewing field is less than 20, multiple viewing fields (e.g., 3 to 5) are measured from one measurement sample. For abrasive particles, 20 points that are identified as particles by binarization processing are secured, and the measured values of the 20 AFM are averaged, and the obtained average value is the height of the protrusions. The shape analysis can provide information on the surface shape, protrusion analysis, and protrusion height distribution. FIG. 42 is an example of an image showing an example of a surface shape captured by the AFM. FIG. 43 is a diagram showing an example of a protrusion analysis result by the AFM. FIG. 44 is a diagram showing an example of a protrusion height distribution. From the information obtained, data such as the number of protrusions formed and the height of the protrusions formed by the particles can be obtained.

<AFM measurement conditions>
Equipment: AFM Dimension 3100 microscope with Nanoscope IV controller (Digital Instruments, USA)
Measurement mode: Tapping frequency during tapping tuning: 200 to 400 kHz
Cantilever: SNL-10 (manufactured by Bruker)
Scan size: 5 μm × 5 μm
Scan rate: 1Hz
Scan lines: 256

<Method of calculating the reference plane when calculating the protrusion height>
The AFM image is divided into 256 × 256 (= 65,536) measurement points, and the height Z(i) (i: measurement point number, i = 1 to 65,536) is measured at each measurement point. The heights Z(i) at each measurement point are simply averaged (arithmetic mean) to determine the average height (reference plane) Z _ave (= (Z(1) + Z(2) + ... + Z(65,536))/65,536).

[Method of identifying the type of particles that form protrusions using FE-SEM]
The marking portion of the measurement sample is imaged using a field emission scanning electron microscope (FE-SEM) under the FE-SEM measurement conditions described below to obtain an FE-SEM image. Figure A in Figure 45 is an example of an FE-SEM image. From the obtained FE-SEM image, the type of particle forming the protrusion can be identified by utilizing the brightness difference due to the difference in the amount of secondary electron emission of the carbon particles and the abrasive particles. Image processing for this identification will be described later. In addition, the positions of the protrusions formed by the carbon particles and the abrasive particles in the FE-SEM image are identified.

<FE-SEM measurement conditions>
Apparatus: HITACHI S-4800 (Hitachi High-Technologies Corporation)
Viewing angle: 5.1 μm x 3.8 μm
Acceleration voltage: 5 kV
Measurement magnification: 25,000 times

The obtained FE-SEM image (Figure A in Figure 45) is binarized using the image processing software Image J under the two processing conditions described below. From the image obtained by the binarization process, information on the number of protrusions formed by the carbon particles and abrasive particles, the average area per protrusion, the total area of the protrusions, and the diameter of the protrusions (Feret diameter) can be obtained. Note that when performing the binarization process, the conditions are changed as follows for the abrasive particles with high brightness (white areas in Figure A in Figure 45) and the carbon particles with low brightness (black areas in Figure A in Figure 45).

Software: Image J Ver 1.44p
Binarization threshold: Threshold (0.65)
Binarization target size: 0.002 μm-infinity

Software: Image J Ver 1.44p
Binarization threshold: Threshold (220, 255)
Binarization target size: 0.001 μm-infinity

Figure 45B shows the position distribution of protrusions formed by abrasive particles (alumina particles) after binarizing the FE-SEM image of Figure 45A under the binarization conditions for abrasive particles (alumina particles). The following information about the abrasive particles was obtained from the resulting image.

Number: 58 Average area: 0.003 ^μm2
Total area: 0.198 ^μm2
Feret diameter: 0.091 μm

Figure C in Figure 45 is an image showing the position distribution of protrusions formed by carbon particles (carbon black particles) after binarizing the FE-SEM image in Figure A in Figure 45 under binarization conditions for carbon particles (carbon black particles). The following information about carbon particles was obtained from the resulting image.

Number: 55 Average area: 0.005 ^μm2
Total area: 0.262 ^μm2
Feret diameter: 0.013 μm

[Method of Corresponding Protrusion Height to Type of Particles Forming the Protrusions]
The obtained AFM image and the FE-SEM image before the binarization process are superimposed to obtain a composite image. Using the composite image, it is determined whether the particles forming each protrusion are carbon particles or abrasive particles. For example, FIG. C in FIG. 46 is a composite image in which an AFM image (FIG. B) and an FE-SEM image (FIG. A) are superimposed so that the positions of the corresponding protrusions coincide with each other. In FIG. 46, different marks are attached at the positions of the protrusions formed by the carbon particles P1 and the abrasive particles P2, which exist in the FE-SEM image (FIG. A) before the image synthesis, so that the positions of the protrusions formed by the carbon particles (carbon black particles) P1 and the abrasive particles P2, which exist in the AFM image (FIG. B) before the image synthesis, can be distinguished. Similarly, different marks are attached at the positions of the protrusions formed by the carbon particles (carbon black particles) P1 and the abrasive particles (alumina particles) P2, which exist in the AFM image (FIG. B) before the image synthesis, so that the positions of the protrusions formed by the abrasive particles P2, which exist in the AFM image (FIG. B) before the image synthesis, can be distinguished. From the composite image in which the AFM image (B) and the FE-SEM image (A) are superimposed so that the positions of the corresponding protrusions coincide, it is possible to determine whether each protrusion is formed from carbon particles P1 or abrasive particles P2. Note that in Fig. 46 (B), the marked portion is measured with an AFM at a viewing angle of 10 μm x 10 μm, and then the portion without the marking is measured at a viewing angle of 5 μm x 5 μm, so no markings are present in the image.

Next, the height of each protrusion in the composite image is measured using AFM analysis software (Dimension 3100 Software version 5.12 Rev. B, Veeco). As described above, the type of particles that form each protrusion (whether it is carbon particles or abrasive particles) is identified, so the identified particle type is associated with the measured height. For example, FIG. 47 is an enlarged view of a composite image in which an AFM image and an FE-SEM image are superimposed. FIG. 48 is a diagram showing the results of AFM analysis (measurement results of protrusion height) for Line 1 (Line 1) set at an arbitrary position in FIG. 47. As shown in FIG. 48, the height of the protrusion formed by the abrasive particles (alumina particles) present on Line 1 can be identified. In this way, the height of the protrusion is identified from the composite image and the AFM analysis results.

[Average height of protrusions]
From the information on the height of the protrusions obtained as described above, the average height of the protrusions formed by the abrasive particles is obtained. The average height of the protrusions can be obtained, for example, from the cumulative frequency distribution of the protrusions formed by the abrasive particles. For example, Fig. 49 is a diagram showing the cumulative frequency distribution of the height of the protrusions formed by the abrasive particles (alumina particles). In Fig. 49, A indicates the frequency and B indicates the cumulative %. Fig. 49 shows that the average height of the protrusions formed by the abrasive particles (alumina particles) is 5.1 nm.

[Attachment]
A so-called full volume test (full length running test) is carried out, in which data is recorded and played back over the entire surface of the magnetic tape. After that, the magnetic head of the drive is observed with an optical microscope to check whether the constituent material of the magnetic layer is attached to the magnetic head. Next, the adhesion of the constituent material of the magnetic layer to the magnetic head after the full length running is evaluated according to the following three-stage criteria.
[standard]
A: No adhesion of the constituent materials of the magnetic layer to the head was observed.
B: Adhesion of the constituent material of the magnetic layer was observed only on the end portion of the head tape running surface where the tape edge runs.
C: Adhesion of the constituent material of the magnetic layer was observed anywhere on the tape running surface of the head.
If the evaluation result is "A" or "B", there will be no problem with the reliability of the magnetic tape. If the evaluation result is "C", short-term head clogging will occur, and the total capacity of the cartridge will be insufficient.

[Output deterioration (head damage)]
The output degradation due to magnetic head damage is evaluated according to the following procedure.
(A) Measure the output (2T, 8T) and head resistance of the drive before evaluation.
(B) Testing is started in an ambient environment. Full-length recording is performed on one cartridge, and when this is complete, the cartridge is replaced with a new one.
(C) Measure the drive output and head resistance every 25 turns to confirm the change in output and head resistance. Check the degree of deterioration (dB) based on the drive output before evaluation. (D) Repeat the above (C) operation up to 50 turns.
Next, the drive output deterioration after 50 windings is evaluated according to the following four-stage criteria.
[standard]
S: Within 2.5 dB A: Within 3 dB B: Over 3 dB C: Over 4 dB If the evaluation result is "B", the capacity loss, rewrite and error rate will worsen. "C" will cause actual damage.

[Arithmetic mean roughness Ra]
The arithmetic mean roughness Ra of the magnetic surface is preferably 2.5 nm or less, and more preferably 2.0 nm or less. If Ra is 2.5 nm or less, a better SNR can be obtained.

The arithmetic mean roughness Ra is determined as follows. First, an AFM (Atomic Force Microscope) (Dimension Icon, manufactured by Bruker) is used to observe the surface on which the magnetic layer 43 is provided, and a cross-sectional profile is obtained. Next, the arithmetic mean roughness Ra is determined from the obtained cross-sectional profile in accordance with JIS B0601:2001.

[Average thickness of magnetic tape t _T ]
The average thickness _tT of the magnetic tape MT is preferably 5.6 μm or less, more preferably 5.4 μm or less, even more preferably 5.0 μm or less, and particularly preferably 4.6 μm or less. When the average thickness _tT of the magnetic tape MT is _tT ≦5.6 μm, the recording capacity that can be recorded in one data cartridge can be increased compared to the conventional case. The lower limit of the average thickness _tT of the magnetic tape MT is not particularly limited, but is, for example, 3.5 μm≦ _tT .

The average thickness _tT of the magnetic tape MT is obtained as follows. First, the magnetic tape MT housed in the magnetic recording cartridge 10 is unwound, and samples are cut out to a length of 250 mm from three positions, 10 m to 20 m, 30 m to 40 m, and 50 m to 60 m from the connection between the magnetic tape MT and the leader tape LT, to prepare samples. Next, the thickness of each sample is measured at five positions using a Mitutoyo Laser Hologram (LGH-110C) as a measuring device, and the measured values (15 points in total) are simply averaged (arithmetic average) to calculate the average thickness _tT [μm]. The five measurement positions are selected randomly from each sample so that they are different positions in the longitudinal direction of the magnetic tape MT.

(3) Manufacturing method of magnetic tape

Next, a method for manufacturing the magnetic tape MT having the above-mentioned configuration will be described. First, a paint for forming the base layer is prepared by kneading and/or dispersing non-magnetic powder, binder, etc. in a solvent. Next, a paint for forming the magnetic layer is prepared by kneading and/or dispersing magnetic powder, binder, etc. in a solvent. The following solvents, dispersing devices, and kneading devices can be used, for example, to prepare the paint for forming the magnetic layer and the paint for forming the base layer.

Solvents used in the preparation of the above-mentioned paints include, for example, ketone-based solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; alcohol-based solvents such as methanol, ethanol, and propanol; ester-based solvents such as methyl acetate, ethyl acetate, butyl acetate, propyl acetate, ethyl lactate, and ethylene glycol acetate; ether-based solvents such as diethylene glycol dimethyl ether, 2-ethoxyethanol, tetrahydrofuran, and dioxane; aromatic hydrocarbon-based solvents such as benzene, toluene, and xylene; and halogenated hydrocarbon-based solvents such as methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, and chlorobenzene. One of these may be used, or a mixture of two or more may be used.

　The kneading device used in the above-mentioned paint preparation may be, for example, a continuous twin-screw kneader, a continuous twin-screw kneader capable of dilution in multiple stages, a kneader, a pressure kneader, a roll kneader, or other kneading device, but is not limited to these devices. In addition, the dispersing device used in the above-mentioned paint preparation may be, for example, a roll mill, a ball mill, a horizontal sand mill, a vertical sand mill, a spike mill, a pin mill, a tower mill, a pearl mill (such as the "DCP Mill" manufactured by Eirich), a homogenizer, or an ultrasonic dispersing machine, but is not limited to these devices.

Next, a paint for forming a base layer is applied to one main surface of the base layer 41 and dried to form a non-magnetic layer (hereinafter also referred to as a base layer) 42. Next, a paint for forming a magnetic layer is applied to this base layer 42 and dried to form a magnetic layer 43 on the base layer 42. During drying, the magnetic powder is magnetically oriented in the thickness direction of the base layer 41, for example, by a solenoid coil. Also, during drying, the magnetic powder may be magnetically oriented in the longitudinal direction (running direction) of the base layer 41, for example, by a solenoid coil, and then magnetically oriented in the thickness direction of the base layer 41. After the magnetic layer 43 is formed, a back layer 44 is formed on the other main surface of the base layer 41. This results in a magnetic tape MT.

Then, the resulting magnetic tape MT is rewound around a large diameter core and undergoes a hardening process. Finally, the magnetic tape MT is calendered and then cut to a specified width (e.g., 1/2 inch width). This results in the desired long, thin magnetic recording tape MT.

(4) Description of data bands and servo bands on magnetic tape

In the magnetic tape MT, a servo recording and reproducing device 70 (servo recording device) (see FIG. 16) is configured to write a servo pattern 47 onto the servo band s of the magnetic tape MT (see FIG. 9) that can be accurately read by a data write head 60 of a data recording and reproducing device 50 (data recording device) (see FIG. 10).

The data write head 60 of the data recording and reproducing device 50 is positioned at an angle with respect to the width direction of the magnetic tape MT (see FIG. 11). Therefore, in this embodiment, a first servo pattern 47a ("/") and a second servo pattern 47b ("\") that are asymmetric with respect to the width direction of the magnetic tape are written in the servo band s (see FIG. 9).

The following describes the configuration of the data recording and reproducing device 50, followed by the configuration of the servo recording and reproducing device 70.

[Data band and servo band overview]
Fig. 8 is a schematic diagram of the magnetic tape MT as viewed from the side, and Fig. 9 is a schematic diagram of the magnetic tape MT as viewed from above (the magnetic layer 43 side). As shown in Fig. 8 and Fig. 9, the magnetic tape MT is configured in the shape of a tape that is long in the longitudinal direction (X-axis direction), short in the width direction (Y-axis direction), and thin in the thickness direction (Z-axis direction).

As shown in FIG. 9, the magnetic layer 43 has a number of data bands d (data bands d0 to d3) in which data is written, and a number of servo bands s (servo bands s0 to s4) in which servo patterns 47 are written. Each of the multiple data bands d and the multiple servo bands s is long in the longitudinal direction (X-axis direction) and short in the width direction (Y-axis direction). The servo bands s are positioned so as to sandwich each data band d in the width direction (Y-axis direction).

In the example shown in FIG. 9, the number of data bands d is four and the number of servo bands s is five. The number of data bands d and the number of servo bands s are 5+4n or more (where n is an integer equal to or greater than 0), preferably 5 or more, and more preferably 9 or more. If the number of servo bands s is 5 or more, the effect of dimensional changes in the width direction of the magnetic tape MT on the servo signal can be suppressed, ensuring stable recording and playback characteristics with less off-track. The upper limit of the number of servo bands SB is not particularly limited, but is, for example, 33 or less.

From the viewpoint of ensuring a high recording capacity, the upper limit of the average value of the servo band width is preferably 98 μm or less, more preferably 60 μm or less, and even more preferably 30 μm or less. The lower limit of the average value of the servo band width WSB is preferably 10 μm or more. It is difficult to manufacture a head unit 56 that can read a servo signal with a servo band width of less than 10 μm.

The ratio of the area of the servo band s to the total surface area of the magnetic layer 43 is, for example, 4.0% or less. The width of the servo band s is, for example, 96 μm or less for a 1/2 inch tape width. The ratio of the area of the servo band s to the total surface area of the magnetic layer 43 can be measured, for example, by developing the magnetic tape MT using a developer such as a ferricolloid developer, and then observing the developed magnetic tape MT with an optical microscope.

The data band d includes a plurality of recording tracks 46 that are long in the longitudinal direction and aligned in the width direction. The number of recording tracks 46 included in one data band d is, for example, about 1000 to 2500. Data is recorded along and within these recording tracks 46. The length of one bit in the longitudinal direction of the data recorded in the data band d is, for example, 48 nm or less.

The width of the recording track 46 (track pitch: Y-axis direction) is, for example, 2.0 μm or less. Note that such a recording track width can be measured, for example, by developing the magnetic layer 43 of the magnetic tape MT using a developing solution such as a ferric colloid developing solution, and then observing the developed magnetic layer 43 of the magnetic tape MT with an optical microscope.

Alternatively, a method using the data write head 60 (see FIG. 11 described later) may be used as a method for measuring the recording track width. In this case, in order to ignore fluctuations during the running of the magnetic tape MT, the data write head 60 is in a recording and reproducing state, and the recording track width can be measured from the change in output when the azimuth angle θ of the data write head 60 is changed. (IEEE_Sept1996_Crosstrack Profiles of Thin Film MR Tape Heads Using the Azimuth Displacement Method)

The servo band s includes a servo pattern 47 of a predetermined shape that is recorded by a servo recording and reproducing device 70 (see FIG. 16) described later. The servo pattern 47 includes a first servo pattern 47a ("/") and a second servo pattern 47b ("\").

In this specification, the symbols "/" and "\" in the first servo pattern 47a and the second servo pattern 47b are used as symbols indicating the inclination direction of the servo pattern when the magnetic tape MT is viewed from below (the back layer side). Therefore, the symbols "/" and "\" in the first servo pattern 47a and the second servo pattern 47b are reversed from the magnetic layer side in FIG. 9. On the other hand, in FIG. 17 to FIG. 25 described later, the first servo element 82a ("/") that writes the first servo pattern 47a ("/"), the second servo element 82b ("\") that writes the second servo pattern 47b ("\"), and the servo patterns 47a and 47b recorded on the magnetic layer by the servo elements 82a and 82b are shown as viewed from the back layer side on the head sliding surface.

In this embodiment, the first servo pattern 47a ("/") and the second servo pattern 47b ("\") are written in the servo band s so as to be asymmetric with respect to the width direction (Y-axis direction) of the magnetic tape MT. Note that in the case of a typical servo pattern, the first servo pattern 47a ("/") and the second servo pattern 47b ("\") are written in the servo band s so as to be symmetric (line symmetric) with respect to the width direction of the magnetic tape MT.

The first servo pattern 47a ("/") is inclined at a first angle θs1 with respect to the width direction of the magnetic tape MT, and the second servo pattern 47b ("\") is inclined at a second angle θs2 different from the first angle θs1 in the opposite direction with respect to the width direction of the magnetic tape MT (see Figures 18 and 20 described below).

A group of first servo patterns 47a ("/") and a group of second servo patterns 47b ("\") are arranged alternately in the longitudinal direction of the magnetic tape MT. The number of first servo patterns 47a ("/") included in a group of first servo patterns 47a ("/") is typically four or five, and similarly, the number of second servo patterns 47b ("\") included in a group of second servo patterns 47b ("\") is typically four or five.

The shape of the servo pattern 47 can be measured, for example, by developing the magnetic layer 43 of the magnetic tape MT using a developer such as a ferric colloid developer, and then observing the developed magnetic layer 43 of the magnetic tape MT with an optical microscope.

Details about the first servo pattern 47a ("/") and the second servo pattern 47b ("\") will be explained in the section explaining the servo write head 80 of the servo recording and reproducing device 70 that writes this servo pattern 47.

Here, the number of recording tracks 46 increases with each generation of LTO-standard magnetic tape MT, dramatically improving recording capacity. As an example, the original LTO-1 had 384 recording tracks 46, but the numbers of recording tracks 46 in LTO-2 to LTO-9 are 512, 704, 896, 1280, 2176, 3584, 6656, and 8960, respectively. Similarly, data recording capacity was 100GB (gigabytes) in LTO-1, but is 200GB, 400GB, 800GB, 1.5TB (terabytes), 2.5TB, 6.0TB, 12TB, and 18TB, respectively, in LTO-2 to LTO-9.

In this embodiment, the number of recording tracks 46 and the recording capacity are not particularly limited and can be changed as appropriate. However, it is advantageous to apply this technology to a magnetic tape MT that has a large number of recording tracks 46 and a large recording capacity (e.g., 6,656 tracks or more, 12 TB or more: LTO8 and later) and is susceptible to variations in the width of the magnetic tape MT.

[Data recording and reproducing device]
10 is a diagram showing a data recording/reproducing device 50. The data recording/reproducing device 50 is capable of recording data on a magnetic tape MT, and is also capable of reproducing the data recorded on the magnetic tape MT.

The data recording and reproducing device 50 is configured so that a magnetic recording cartridge 10 can be loaded into it. The magnetic recording cartridge 10 is configured so that a wound magnetic tape MT can be rotatably accommodated inside it. The data recording and reproducing device 50 may be configured so that one magnetic recording cartridge 10 can be loaded into it, or it may be configured so that multiple magnetic recording cartridges 10 can be loaded into it simultaneously.

The data recording and reproducing device 50 includes a spindle 51, a take-up reel 52, a spindle drive unit 53, a reel drive unit 54, a data write head 60, a control unit 55, a width measuring unit 56, an angle adjustment unit 57, and a number of guide rollers 58.

The spindle 51 is configured so that its rotation can rotate the magnetic tape MT housed inside the magnetic recording cartridge 10. The spindle drive unit 53 rotates the spindle 51 in response to commands from the control unit 55.

The take-up reel 52 is configured to be able to fix the tip of the magnetic tape MT that is pulled out from the magnetic recording cartridge 10 via a tape loading mechanism (not shown). The reel drive device 54 rotates the take-up reel 52 in response to commands from the control device 55.

The multiple guide rollers 58 guide the magnetic tape MT so that the transport path formed between the magnetic recording cartridge 10 and the take-up reel 52 has a predetermined relative positional relationship with the data write head 60.

The data write head 60 is configured to be able to record data to the data band d (recording track 46) of the magnetic tape MT in response to a command from the control device 55 when the magnetic tape MT passes underneath the data write head 60, and is also configured to be able to play back the recorded data.

When data is recorded/played back from the magnetic tape MT by the data write head 60, the spindle 51 and take-up reel 52 are rotated by the spindle drive unit 53 and reel drive unit 54, causing the magnetic tape MT to run. The magnetic tape MT can run back and forth in the forward direction (the direction in which it unwinds from the spindle 51 side to the take-up reel 52 side) indicated by the arrow A1 in FIG. 10, and in the reverse direction (the direction in which it rewinds from the take-up reel 52 side to the spindle 51 side) indicated by the arrow A2.

The data write head 60 is capable of recording/playing back data in both the forward and reverse directions of the magnetic tape MT.

In particular, in this embodiment, the data write head 60 is positioned such that the longitudinal direction (Y'-axis direction) of the data write head 60 is inclined at a predetermined angle θ (first head azimuth angle θ) with respect to the width direction (Y-axis direction) of the magnetic tape MT (see FIG. 11 described below).

In the description of this embodiment, the angle at which the longitudinal direction (Y'-axis direction) of the data write head 60 is inclined with respect to the width direction (Y-axis direction) of the magnetic tape MT is referred to as the azimuth angle θ of the data write head 60. Details of the configuration of the data write head 60 will be described later with reference to FIG. 11 etc.

The width measurement unit 56 is configured to be capable of measuring the width of the magnetic tape MT when the magnetic tape MT passes below the width measurement unit 56. In other words, the width measurement unit 56 is configured to be capable of measuring the width of the magnetic tape MT when the data write head 60 records/plays data on the magnetic tape MT. The width measurement unit 56 measures the width of the magnetic tape MT and transmits it to the control device 55.

The width measurement unit 56 is composed of various sensors, such as an optical sensor. Any sensor capable of measuring the width of the magnetic tape MT may be used as the width measurement unit 56. The width of the magnetic tape MT can also be predicted by reading adjacent servo patterns 47 and determining the difference in position signals. In this case, the width measurement unit 56 can be omitted.

The angle adjustment unit 57 is configured to be able to hold the data write head 60 rotatably around an axis (Z-axis) in the vertical direction. The angle adjustment unit 57 is configured to be able to adjust the azimuth angle θ of the data write head 60 in response to a command from the control device 55.

The control device 55 includes, for example, a control unit, a memory unit, a communication unit, etc. The control unit is composed of, for example, a CPU (Central Processing Unit), etc., and performs overall control of each part of the data recording and playback device 50 according to a program stored in the memory unit.

The storage unit includes a non-volatile memory in which various data and programs are recorded, and a volatile memory used as a working area for the control unit. The above-mentioned various programs may be read from a portable recording medium such as an optical disk or semiconductor memory, or may be downloaded from a server device on a network. The communication unit is configured to be capable of communicating with other devices such as a PC (Personal Computer) or a server device.

In particular, in this embodiment, the control device 55 (control unit) acquires information on the width of the magnetic tape MT from the width measurement unit 56 (or predicts the width of the magnetic tape from the servo signal), and adjusts the azimuth angle θ (see FIG. 11) of the data write head 60 using the angle adjustment unit 57 based on the information on the width of the magnetic tape MT.

In this embodiment, the azimuth angle θ of the data write head 60 is adjusted to accommodate variations in the width of the magnetic tape MT. Typically, when the width of the magnetic tape MT becomes relatively wider, the azimuth angle θ of the data write head 60 is made smaller, and conversely, when the width of the magnetic tape MT becomes relatively narrower, the azimuth angle θ of the data write head 60 is made larger.

The width of the magnetic tape MT may vary for various reasons, such as temperature, humidity, and tension applied to the magnetic tape MT in the longitudinal direction.

[Data Light Head]
Next, a detailed description will be given of the configuration of the data write head 60. Fig. 11 is a schematic diagram of the data write head 60 as viewed from below (the back layer side).

In describing the data write head 60, the longitudinal direction of the data write head 60 is defined as the Y'-axis direction, the width direction of the data write head 60 as the X'-axis direction, and the up-down direction of the data write head 60 as the Z'-axis direction. Additionally, the longitudinal direction (running direction) of the magnetic tape MT is defined as the X-axis direction, the width direction of the magnetic tape MT as the Y-axis direction, and the thickness direction of the magnetic tape MT as the Z-axis direction. Note that the direction of the magnetic tape MT is based on the direction of the magnetic tape MT as it passes under the data write head 60.

As shown in FIG. 11, the data write head 60 includes a first data write head 60a and a second data write head 60b. In the description of this specification, when the two data write heads 60 are not particularly distinguished from each other, they are collectively referred to simply as data write heads 60, and when the two data write heads 60 are particularly distinguished from each other, they are referred to as the first data write head 60a and the second data write head 60b.

The first data write head 60a and the second data write head 60b are configured symmetrically in the width direction (Y' axis direction) of the data write head 60, but are basically configured the same. The first data write head 60a and the second data write head 60b are movable together in the width direction (Y axis direction) of the magnetic tape MT, which allows data to be written to any one of the data bands d out of all data bands d0 to d3.

The first data write head 60a is a head used when the magnetic tape MT is running in the forward direction (direction A1 in FIG. 10). On the other hand, the second data write head 60b is a head used when the magnetic tape MT is running in the reverse direction (direction A2 in FIG. 10).

The data write head 60 has a facing surface 61 that faces the magnetic tape MT. The facing surface 61 is long in the longitudinal direction (Y'-axis direction) of the data write head 60 and short in the width direction (X'-axis direction) of the data write head 60. The facing surface 61 is provided with two servo read sections 62 and multiple data write/read sections 63.

The servo read sections 62 are provided on both ends of the data write head 60 in the longitudinal direction (Y'-axis direction). The servo read sections 62 are configured to be able to reproduce servo signals by reading the magnetic field generated by the servo pattern 47 recorded on the servo band s of the magnetic tape MT using an MR element (MR: Magneto Resistive effect) or the like.

Examples of MR elements that can be used include anisotropic magnetoresistive effect elements (AMR: Anisotropic Magneto Resistive effect), giant magnetoresistive effect elements (GMR: Giant Magneto Resistive effect), and tunnel magnetoresistive effect elements (TMR: Tunnel Magneto Resistive effect).

The data write/read sections 63 are arranged at equal intervals along the longitudinal direction (Y'-axis direction) of the data write head 60. Furthermore, the data write/read sections 63 are arranged at a position sandwiched between two servo read sections 62. The number of data write/read sections 63 is, for example, about 20 to 40, but there is no particular limit to this number.

The data write/read section 63 includes a data write section 64 and a data read section 65. The data write section 64 is configured to be able to record data onto the data band d of the magnetic tape MT by the magnetic field generated from the magnetic gap.

The data read section 65 is also configured to be able to reproduce data signals by reading the magnetic field caused by the data recorded on the data band d of the magnetic tape MT using an MR element or the like. As the MR element, an anisotropic magnetoresistance effect element (AMR), a giant magnetoresistance effect element (GMR), a tunnel magnetoresistance effect element (TMR), or the like is used.

In the first data write head 60a, the data write section 64 is located to the left of the data read section 65 (upstream when the magnetic tape MT flows in the forward direction). On the other hand, in the second data write head 60b, the data write section 64 is located to the right of the data read section 65 (upstream when the magnetic tape MT flows in the reverse direction).

The data read section 65 is capable of reproducing the data signal immediately after the data write section 64 paired with the data read section 65 writes the data to the magnetic tape MT. Alternatively, data written by the data write section 64 of one of the data write heads 60, the first data write head 60a and the second data write head 60b, may be reproduced by the data read section 65 of the other data write head 60.

The magnetic tape MT travels back and forth multiple times, forward and reverse, while data is recorded on the recording track 46 by the first data write head 60a and the second data write head 60b.

The angle adjustment unit 57 (see FIG. 10) is capable of holding the first data write head 60a and the second data write head 60b rotatably around an axis (Z' axis) in the vertical direction. The angle adjustment unit 57 is also capable of rotating the first data write head 60a and the second data write head 60b individually around the axis in the vertical direction.

The angle adjustment unit 57 adjusts the angles of the first data write head 60a and the second data write head 60b so that the longitudinal directions of the first data write head 60a and the second data write head 60b are inclined by the azimuth angle θ with respect to the width direction of the magnetic tape MT.

Here, the positions of the servo read section 62 and data write/read section 63 of the first data write head 60a in the Y-axis direction (width direction of the magnetic tape MT) are the same as the positions of the servo read section 62 and data write/read section 63 of the second data write head 60b in the Y-axis direction. This positional relationship does not change even if the first data write head 60a and the second data write head 60b rotate around the Z-axis.

In other words, the angle adjustment unit 57 can rotate the first data write head 60a and the second data write head 60b individually so that the positions of the servo read section 62 and data write/read section 63 of the first data write head 60a in the Y-axis direction (the width direction of the magnetic tape MT) are the same as the positions of the servo read section 62 and data write/read section 63 of the second data write head 60b in the Y-axis direction.

In this embodiment, a reference angle Refθ is set as a standard for the azimuth angle θ of the data write head 60, and the azimuth angle θ of the data write head 60 is set to an angle range represented by the reference angle Refθ±x°.

The example shown in FIG. 11 shows an example in which the reference angle Refθ is set in a clockwise direction (as viewed from the bottom side of the magnetic tape MT) relative to the width direction of the magnetic tape MT. On the other hand, the reference angle Refθ may be set in a counterclockwise direction (as viewed from the bottom side of the magnetic tape MT) relative to the width direction of the magnetic tape MT.

[Reference angle Refθ and angle range Refθ±x°, etc.]
Next, the reference angle Refθ at the azimuth angle θ of the data write head 60 and the angle range Refθ±x° at the azimuth angle θ of the data write head 60 will be described.

12 is a diagram showing the relationship between the angle range Refθ±x° of the azimuth angle θ of the data write head 60 and the azimuth loss _Lθ (recording wavelength: 0.1 μm). In FIG. 12, the horizontal axis indicates the value of x in the angle range Refθ±x° of the azimuth angle θ of the data write head 60, and the vertical axis indicates the azimuth loss _Lθ .

The azimuth loss L _θ [dB] is expressed by the following formula.
L _θ =−20 Log ₁₀ [sin{(πW/λ) tan θ}/(πW/λ) tan θ] In the formula, W is the reproducing track width, λ is the recording wavelength of data, and θ is the azimuth angle of the data write head 60 .

In Figure 12, five graphs are shown where the reproduction track width W is set to 0.8 μm, 0.5 μm, 0.4 μm, 0.3 μm, and 0.2 μm. In Figure 12, the recording wavelength λ is set to 0.1 μm. Here, the graph where the reproduction track width W is 0.8 μm corresponds to LTO-9, and the graphs where the reproduction track width W is 0.5 μm, 0.4 μm, 0.3 μm, and 0.2 μm correspond to LTO-10 and later (estimated values).

As can be seen from FIG. 12, when the angular range Refθ±x° at the azimuth angle θ of the data write head 60 is the same, the azimuth loss _Lθ is smaller when the reproducing track width W is narrower.

This means that in the case of a configuration in which the azimuth angle θ of the data write head 60 is adjusted to accommodate variations in the width of the magnetic tape MT, as in this embodiment, the greater the number of recording tracks 46 and the narrower the reproduction track width W of the magnetic tape MT (for example, LTO-10 or later) from the viewpoint _of the azimuth loss Lθ, the more advantageous it is.

Here, it is assumed that the allowable value of the azimuth loss _Lθ is 0.05 [dB] or less, and that the reproducing track width W of the magnetic tape MT is 0.5 μm or less (LTO-10 or later (estimated value)).

In this case, as shown by the dotted line in FIG. 12, the angular range of the azimuth angle θ of the data write head 60 is a maximum of Refθ±0.7°. Therefore, in this embodiment, in the angular range of the azimuth angle θ of the data write head 60, the value of x in Refθ±x° is typically set to 0.7° or less.

Figure 13 shows the relationship between the angle range Refθ±x° at the azimuth angle θ of the data write head 60 and the amount of correction for the servo band pitch difference based on the width variation of the magnetic tape MT.

In FIG. 13, the horizontal axis indicates the value of x in the angle range Refθ±x° of the azimuth angle θ of the data write head 60, and the vertical axis indicates the amount of correction for the servo band pitch difference based on the width variation of the magnetic tape MT.

Figure 14 shows the amount of correction for the servo band pitch difference based on the width variation of the magnetic tape MT. As shown in Figure 14, this amount of correction is expressed as a-b.

Here, the value of a is the distance between the two servo read sections 62 in the width direction (Y-axis direction) of the magnetic tape MT when the azimuth angle θ of the data write head 60 is Refθ-x°. On the other hand, the value of b is the distance between the two servo read sections 62 in the width direction (Y-axis direction) of the magnetic tape MT when the azimuth angle θ of the data write head 60 is Refθ+x°.

Returning to Figure 13, six graphs are shown in which the reference angle Refθ at the azimuth angle θ of the data write head 60 is changed to 2.5°, 5°, 7.5°, 10°, 12.5°, and 15°.

From Figure 13, it can be seen that if the angle range Refθ±x° is the same, the amount of correction increases as the reference angle Refθ increases.

As described above, if the azimuth loss _Lθ is 0.05 dB or less and the reproduction track width W is 0.5 μm or less, the angular range of the azimuth angle θ of the data write head 60 is Refθ±0.7° at maximum (see the vertical dashed line in FIG. 13). In addition to this condition, it is further assumed that the correction amount is 10 μm or more (see the horizontal dashed line in FIG. 13).

As can be seen from FIG. 13, in order to satisfy these conditions, a reference angle Refθ of the data write head 60 of 7.5° is slightly insufficient, and a reference angle Refθ of 10° is sufficient. In other words, in order to satisfy the above conditions, the reference angle Refθ should be 8° or more.

Note that the explanation here does not mean that the reference angle Refθ must be 8° or more in this embodiment. In other words, in this embodiment, the reference angle Refθ can be set appropriately to 2.5° or more, 5° or more, 7.5° or more, 8° or more, 10° or more, 12.5° or more, 15° or more, etc.

Fig. 15 is a diagram showing the relationship between the angle range Refθ±x° of the azimuth angle θ of the data write head 60 and the azimuth loss _Lθ (recording wavelength: 0.07 μm). In Fig. 15, the horizontal axis indicates the value of x in the angle range Refθ±x° of the azimuth angle θ of the data write head 60, and the vertical axis indicates the azimuth loss _Lθ . In Fig. 15, the recording wavelength λ of the data is set to 0.07 μm.

The difference between Figure 12 and Figure 15 is that in Figure 12, the data recording wavelength λ is 0.1 μm, whereas in Figure 15, the data recording wavelength λ is 0.07 μm. Note that in LTO-10 and later, it is estimated that the data recording wavelength λ will be 0.1 μm or less, 0.07 μm or less, etc.

As can be seen from a comparison of Figures 12 and 15, the smaller the data recording wavelength λ, the greater the azimuth loss.

In FIG. 15, let us look at the graph where the reproduction track width W is 0.5 μm. When the data recording wavelength λ is 0.07 μm and the reproduction track width W is 0.5 μm, in order to keep the azimuth loss below 0.05 [dB], the value of x in the angle range Refθ±x° of the azimuth angle θ of the data write head 60 should be set to 0.48° or less.

In Figure 13, focus is placed on the point where the x value in the angular range Refθ±x° of the azimuth angle θ of the data write head 60 is 0.48° (see the horizontal axis in Figure 13). When the angular range of the azimuth angle θ of the data write head 60 is Refθ±0.48°, it can be seen that if the above correction amount is 10 μm or more, the reference angle Refθ should be set to 12.5° or more.

Furthermore, in FIG. 15, let us focus on the graph where the reproduction track width W is 0.4 μm. When the data recording wavelength λ is 0.07 μm and the reproduction track width W is 0.4 μm, in order to keep the azimuth loss below 0.05 [dB], the value of x in the angle range Refθ±x° of the azimuth angle θ of the data write head 60 should be set to 0.6° or less.

In Figure 13, focus is placed on the point where the value of x in the angular range Refθ±x° of the azimuth angle θ of the data write head 60 is 0.6° (see the horizontal axis in Figure 13). When the angular range of the azimuth angle θ of the data write head 60 is Refθ±0.6°, it can be seen that if the above correction amount is to be 10 μm or more, the reference angle Refθ should be set to 10° or more.

As will be understood from the explanation here, the angle range Refθ±x° of the azimuth angle θ of the data write head 60 becomes smaller as the data recording wavelength λ becomes smaller. Also, the angle range Refθ±x° of the azimuth angle θ of the data write head 60 becomes larger as the reproduction track width W becomes smaller (see Figures 12 and 15).

Furthermore, the reference angle Refθ at the azimuth angle θ of the data write head 60 becomes larger as the data recording wavelength λ becomes smaller.Furthermore, the reference angle Refθ at the azimuth angle θ of the data write head 60 becomes smaller as the reproduction track width W becomes smaller (see FIG. 13).

As the LTO standard progresses from LTO-9 to LTO-10, LTO-11, etc., it is predicted that the data recording wavelength λ will become smaller and the playback track width W will also become smaller. In response to this, the value of x in the angle range Refθ±x° of the azimuth angle θ of the data write head 60 can be set to an appropriate value (e.g., 0.7° or less, 0.6° or less, 0.5° or less, 0.4° or less, etc.), and the reference angle Refθ of the azimuth angle θ of the data write head 60 can be set to an appropriate value (e.g., 2.5° or more, 5° or more, 7.5° or more, 8° or more, 10° or more, 12.5° or more, 15° or more, etc.).

[Servo recording and reproducing device]
Next, a description will be given of the servo recording and reproducing device 70. FIG.

As shown in FIG. 16, the servo recording and reproducing device 70 includes a feed roller 71, a degaussing unit 72, a servo write head 80, a servo read head 75, a take-up roller 76, and four pairs of capstan rollers 77.

The feed roller 71 is capable of rotatably supporting the rolled magnetic tape MT. The feed roller 71 is rotated in response to the drive of a motor or the like, and feeds out the magnetic tape MT downstream in response to the rotation.

The winding roller 76 is capable of rotatably supporting the rolled magnetic tape MT. The winding roller 76 rotates in response to the drive of a motor or the like, and winds up the magnetic tape MT as it rotates.

The four pairs of capstan rollers 77 are each capable of clamping the magnetic tape MT from both the top and bottom sides. The four pairs of capstan rollers 77 rotate in response to the drive of a motor or the like, and transport the magnetic tape MT along the transport path in response to the rotation.

The feed roller 71, take-up roller 76, and four pairs of capstan rollers 77 are capable of transporting the magnetic tape MT at a constant speed within the transport path.

The servo write head 80 is disposed, for example, on the upper side (magnetic layer 43 side) of the magnetic tape MT. The servo write head 80 applies a magnetic field to the servo band s at a predetermined timing in response to a square wave pulse signal, and records the servo pattern 47 on the servo band s.

The servo write head 80 is capable of recording servo patterns 47 for each of the servo bands s (s0 to s4) when the magnetic tape MT passes underneath the servo write head 80. Details of the configuration of the servo write head 80 will be described later with reference to Figures 17 to 22.

The demagnetizing unit 72 is disposed, for example, upstream of the servo write head 80 and below the magnetic tape MT (toward the base layer 41). The demagnetizing unit 72 is composed, for example, of two permanent magnets 73 and 74. The permanent magnets 73 and 74 apply a magnetic field to the entire magnetic layer 43 using a DC magnetic field, thereby demagnetizing the entire magnetic layer 43 before the servo pattern 47 is recorded by the servo write head 80.

The servo read head 75 is positioned downstream of the servo write head 80 and above the magnetic tape MT (on the magnetic layer 43 side). The servo read head 75 is configured to be able to reproduce the information of the servo pattern 47 by reading the magnetic field generated from the servo pattern 47 recorded on the magnetic tape MT.

The servo read head 75 is capable of reading the servo patterns 47 from all servo bands s (s0 to s4) when the magnetic tape MT passes underneath the servo read head 75. The information on the servo pattern 47 read by the servo read head 75 is used to confirm whether the servo pattern 47 has been recorded accurately.

The types of servo read head 75 include, for example, inductive type, MR type (Magneto Resistive), GMR type (Giant Magneto Resistive), TMR type (Tunnel Magneto Resistive), etc.

Although not shown in the figure, the servo recording and reproducing device 70 is equipped with a control device that comprehensively controls each part of the servo recording and reproducing device 70.

The control device includes, for example, a control unit, a memory unit, a communication unit, etc. The control unit is composed of, for example, a CPU (Central Processing Unit), etc., and performs overall control of each part of the servo recording and reproduction device 70 according to the program stored in the memory unit.

The storage unit includes a non-volatile memory in which various data and programs are recorded, and a volatile memory used as a working area for the control unit. The above-mentioned various programs may be read from a portable recording medium such as an optical disk or semiconductor memory, or may be downloaded from a server device on a network. The communication unit is configured to be capable of communicating with other devices such as a PC or server device.

[Servo write head]
Next, the configuration of the servo write head 80 will be described in detail. As described above, the data write head 60 in the data recording and reproducing device 50 is disposed at an angle with respect to the width direction of the magnetic tape MT. Therefore, the first servo pattern 47a ("/") and the second servo pattern 47b ("\") are written asymmetrically with respect to the width direction of the magnetic tape MT so that the data write head 60 can accurately read the servo patterns 47. The writing of the asymmetric servo patterns 47 is performed by the servo write head 80.

There are two types of servo write head 80 configurations: embodiment A and embodiment B. In embodiment A, the longitudinal direction (Y" axis direction) of servo write head 80a is arranged parallel to the width direction (Y axis direction) of magnetic tape MT (see Figures 17 to 19 described below). On the other hand, in embodiment B, the longitudinal direction (Y" axis direction) of servo write head 80b is arranged at a predetermined angle inclined to the width direction (Y axis direction) of magnetic tape MT (see Figures 20 to 22 described below).

(Embodiment A)
First, an embodiment A of the servo write head 80 will be described. Fig. 17 is a diagram showing the servo write head 80a and a pulse signal input to the servo write head 80a. Fig. 18 is an enlarged view of a servo element 82 of the servo write head 80a. Fig. 19 is a diagram showing a state when the servo write head 80a writes a servo pattern 47 onto the magnetic tape MT. Note that Figs. 17 to 19 show the surface of the servo write head 80a that faces the magnetic tape MT.

As shown in these figures, the servo write head 80a is long in the longitudinal direction (Y" axis direction) and short in the width direction (X" axis direction). In Figures 17 to 19, the longitudinal direction of the servo write head 80a is the Y" axis direction, the width direction of the servo write head 80a is the X" axis direction, and the up-down direction of the servo write head 80a is the Z" axis direction. The longitudinal direction (transport direction) of the magnetic tape MT is the X axis direction, the width direction of the magnetic tape MT is the Y axis direction, and the thickness direction of the magnetic tape MT is the Z axis direction. This is also true in Figures 20 to 22.

In embodiment A, the longitudinal direction (Y" axis direction) of the servo write head 80a coincides with the direction of the magnetic tape MT (Y axis direction), and the width direction (X" axis direction) of the servo write head 80a coincides with the longitudinal direction (X axis direction) of the magnetic tape MT.

The servo write head 80a has a facing surface 81 that faces the magnetic tape MT. The facing surface 81 is long in the longitudinal direction (Y" axis direction) and short in the width direction (X" axis direction).

The servo write head 80a has five pairs of servo elements 82 (magnetic gaps) on the opposing surface 80a. The five pairs of servo elements 82 are arranged at a predetermined interval (servo element pitch: SP) in the longitudinal direction (Y" axis direction) of the servo write head 80a.

In the longitudinal direction (Y" axis direction) of the servo write head 80a (width direction of the magnetic tape MT: Y axis direction), the distance (servo element pitch) between two pairs of adjacent servo elements 82 is, for example, 2858.8 ± 4.6 μm. Note that this value corresponds to the distance (servo band pitch: SP) between two adjacent servo bands s in the width direction (Y axis direction) of the magnetic tape MT.

The pair of servo elements 82 includes a first servo element 82a ("/") and a second servo element 82b ("\") that are configured asymmetrically with respect to the longitudinal direction (Y" axis direction) of the servo write head 80a (width direction of the magnetic tape MT: Y axis direction) (see FIG. 18 in particular).

The first servo element 82a ("/") is inclined at a first angle θs1 relative to the longitudinal direction (Y" axis direction) of the servo write head 80a (width direction of the magnetic tape MT: Y axis direction).The second servo element 82b ("\") is inclined at a second angle θs2 in the opposite direction to the first angle θs1 relative to the longitudinal direction (Y" axis direction) of the servo write head 80a (width direction of the magnetic tape MT: Y axis direction).

The first angle θs1 and the second angle θs2 are related to the reference angle Refθ of the data write head 60, and are expressed by the following equations, respectively.
θs1=Refθ+θa
θs2=Refθ−θa
Here, Refθ is the reference angle Refθ of the data write head 60, and θa is the servo azimuth angle.

If the reference angle Refθ of the data write head 60 is set to 10° and the servo azimuth angle θa is set to 12°, the first angle θs1 of the first servo element 82a ("/") is set to 22°, and the second angle θs2 of the second servo element 82b ("\") is set to 2°.

In the width direction (X" axis direction) of the servo write head 80a (longitudinal direction of the magnetic tape MT: X axis direction), the distance between the first servo element 82a ("/") and the second servo element 82b ("\") is, for example, 38 μm at a position that is 1/2 the width direction component SL of the length of the servo element.

Here, for the first servo element 82a ("/"), the direction along the first angle θs1 (a direction at 22° relative to the width direction of the magnetic tape MT) is defined as the longitudinal direction of the first servo element 82a ("/"). Also, for the second servo element 82b ("\"), the direction along the second angle θs2 (a direction at -2° relative to the width direction of the magnetic tape MT) is defined as the longitudinal direction of the second servo element 82b ("\").

The length of the first servo element 82a ("/") in the longitudinal direction is different from the length of the second servo element 82b ("\") in the longitudinal direction, and in this example, the length of the first servo element 82a ("/") in the longitudinal direction is longer than the length of the second servo element 82b ("\").

On the other hand, the width component SL (Y-axis direction) of the magnetic tape MT in the longitudinal length of the first servo element 82a ("/") is the same as the width component SL (Y-axis direction) of the magnetic tape MT in the longitudinal length of the second servo element 82b ("\"). The width component SL of the length of the servo element 82 is, for example, 96±3 μm.

FIG. 17 shows the pulse signals input to each of the five pairs of servo elements 82. FIG. 19 shows the servo pattern 47 written in the servo band s of the magnetic tape MT by inputting the pulse signals to the five pairs of servo elements 82.

As described above, the data write head 60 is positioned at an inclination of the azimuth angle θ with respect to the width direction of the magnetic tape MT. In this case, assume that pulse signals of the same phase are input to five pairs of servo elements 82 at the same time, and servo patterns 47 of the same phase are written at positions parallel to the width direction of the magnetic tape MT. In this case, the phases of the servo patterns 47 read at the same time by the two servo read portions 62 of the data write head 60 positioned at an angle will be different.

In this embodiment, the phases of the pulse signals input to five pairs of servo elements 82 at the same time are made different, so that servo patterns 47 of the same phase are written non-parallel to the width direction of the magnetic tape MT.

The phase difference between the pulse signals input to two pairs of servo elements 82 adjacent to each other in the longitudinal direction of the servo write head 80a (Y" axis direction: width direction of the magnetic tape MT) corresponds to SP x tan(Refθ). Here, SP (servo band pitch = servo element pitch) is the distance between two adjacent servo bands s in the width direction of the magnetic tape MT, or the distance between two adjacent pairs of servo elements 82 in the width direction of the magnetic tape MT. In addition, Refθ is the reference angle in the data write head 60.

Assume that the value of SP is 2858.8 μm and the reference angle Refθ in the data write head 60 is 10°. In this case, the phase difference between the pulse signals input to two pairs of adjacent servo elements 82 corresponds to 2858.8 μm × tan 10° = 504.08 μm.

Here, the phase differences of the input pulses of the servo elements 82 of servo bands s3, s2, s1, and s0 based on the input pulse of the servo element 82 of servo band s4 correspond to phases of 504.08 μm, 1008.17 μm, 1512.25 μm, and 2016.33 μm, respectively.

For the five pairs of servo elements 82 corresponding to the five servo bands s, the servo element 82 in servo band s0 receives the input pulse with the most advanced phase of the pulse signal input at the same time. The order of the input pulse phase is then the servo element 82 in servo band s1, the servo element 82 in servo band s2, the servo element 82 in servo band s3, and the servo element 82 in servo band s4.

For example, taking the servo element 82 of servo band s0 and the servo element 82 of servo band s1 as an example, at the same time, a pulse signal with a phase that is 504.08 μm ahead of the servo element 82 of servo band s1 is input to the servo element 82 of servo band s0.

Similarly, the phase difference in the width direction (Y-axis direction) of the magnetic tape MT between the servo patterns 47 written in two servo bands s adjacent to each other in the width direction of the magnetic tape MT is expressed as SP x tan(Refθ).

Assume that the value of SP is 2858.8 μm, and the reference angle Refθ in the data write head 60 is 10°. In this case, the phase difference in the width direction (Y-axis direction) of the magnetic tape MT in the servo patterns 47 written to two adjacent servo bands s corresponds to 2858.8 μm × tan 10° = 504.08 μm.

The phase differences of the servo patterns 47 of servo bands s3, s2, s1, and s2 based on the servo pattern 47 of servo band s4 correspond to 504.08 μm, 1008.17 μm, 1512.25 μm, and 2016.33 μm, respectively.

Of the servo patterns 47 written in each of the five servo bands s, the servo pattern 47 in servo band s0 is the one that has the most advanced phase in the width direction (Y-axis direction) of the magnetic tape MT. The order of phases is the servo pattern 47 in servo band s1, the servo pattern 47 in servo band s2, the servo pattern 47 in servo band s3, and the servo pattern 47 in servo band s4.

For example, taking the servo pattern 47 of servo band s0 and the servo pattern 47 of servo band s1 as an example, in the width direction of the magnetic tape MT, the phase of the servo pattern 47 of servo band s0 is set to be ahead of the servo pattern 47 of servo band s1 by a phase corresponding to 504.08 μm.

In the magnetic tape MT, in the direction of the reference angle Refθ (10°) of the data write head 60 relative to the width direction (Y-axis direction) of the magnetic tape MT, the phases of the servo patterns 47 written in the five servo bands s are in phase.

(Embodiment B)
Next, embodiment B of the servo write head 80 will be described. Fig. 20 is an enlarged view of a servo write head 80b according to embodiment B and a servo element 82 that the servo write head 80b has. Fig. 21 is a view showing a state in which a servo pattern 47 is written on a magnetic tape MT by the servo write head 80b according to embodiment B. Figs. 20 and 21 show the surface of the servo write head 80b that faces the magnetic tape MT. Similarly, Figs. 22 to 25 described later also show the surface of the servo write head 80 that faces the magnetic tape MT.

As shown in these figures, the servo write head 80b has a shape that is long in the longitudinal direction (Y" axis direction) and short in the width direction (X" axis direction).

In embodiment B, the longitudinal direction (Y" axis direction) of the servo write head 80b is inclined at a predetermined angle (second head azimuth angle) with respect to the width direction of the magnetic tape MT. The angle at which the longitudinal direction (Y" axis direction) of the servo write head 80b is inclined with respect to the width direction (Y axis direction) of the magnetic tape MT is
It is related to the reference angle Ref θ of the data write head 60 and coincides with the reference angle Ref θ of the data write head 60 (for example, 10°).

The servo write head 80b has a facing surface 81 that faces the magnetic tape MT. The facing surface 81 is long in the longitudinal direction (Y" axis direction) and short in the width direction (X" axis direction).

The servo write head 80b has five pairs of servo elements 82 (magnetic gaps) on the opposing surface 81. The five pairs of servo elements 82 are arranged at a predetermined interval (servo element pitch: SP1) in the width direction (Y-axis direction) of the magnetic tape MT.

The spacing (servo element pitch: SP1) between two pairs of adjacent servo elements 82 in the width direction (Y-axis direction) of the magnetic tape MT is, for example, 2858.8±4.6 μm. This value corresponds to the spacing (servo band pitch: SP1) between two servo bands s that are adjacent to each other in the width direction (Y-axis direction) of the magnetic tape MT.

The difference in position between two pairs of adjacent servo elements 82 in the longitudinal direction (X-axis direction) of the magnetic tape MT is expressed as SP1 x tan(Refθ). Here, SP1 (servo band pitch = servo element pitch) is the distance between two adjacent servo bands s in the width direction of the magnetic tape MT, or the distance between two adjacent pairs of servo elements 82 in the width direction of the magnetic tape MT. Refθ is the reference angle in the data write head 60.

Assume that the value of SP1 is 2858.8 μm, and the reference angle Refθ in the data write head 60 is 10°. In this case, the difference in position between two pairs of adjacent servo elements 82 in the longitudinal direction of the magnetic tape (X-axis direction) is 2858.8 μm × tan 10° = 504.08 μm.

The pair of servo elements 82 includes a first servo element 82a ("/") and a second servo element 82b ("\") that are configured asymmetrically with respect to the width direction (Y-axis direction) of the magnetic tape MT (see particularly the right side of Figure 20).

The first servo element 82a ("/") is inclined at a first angle θs1 relative to the width direction (Y-axis direction) of the magnetic tape MT. The second servo element 82b ("\") is inclined at a second angle θs2 in the opposite direction to the first angle θs1 relative to the width direction (Y-axis direction) of the magnetic tape MT.

In the longitudinal direction (X-axis direction) of the magnetic tape MT, the distance between the first servo element 82a ("/") and the second servo element 82b ("\") is, for example, 38 μm at a position that is 1/2 the width component SL of the length of the servo element 82.

On the other hand, the width component (Y-axis direction) SL1 of the magnetic tape MT in the longitudinal length of the first servo element 82a ("/") is the same as the width component (Y-axis direction) SL1 of the magnetic tape MT in the longitudinal length of the second servo element 82b ("\"). The width component SL1 of the length of the servo element 82 is, for example, 96±3 μm.

FIG. 24 is an enlarged view of the right side of FIG. 20, showing an example of specific dimensions of the first servo element 82a ("/") and the second servo element 82b ("\") (based on the XYZ coordinate system).

As shown in FIG. 24, the length of the first servo element 82a ("/") in the longitudinal direction is 103.5393 μm (= 96 μm/cos 22°). The length of the second servo element 82b ("\") in the longitudinal direction is 96.0585 μm (= 96 μm/cos 2°).

Furthermore, the distance (in the X-axis direction) between the upper end of the first servo element 82a and the upper end of the second servo element 82b is 16.9306 μm (= 38 μm - 48 μm x tan 22° - 48 μm x tan 2° = 38 μm - 19.3932 μm - 1.6762 μm).

Furthermore, the distance (in the X-axis direction) between the bottom end of the first servo element 82a and the bottom end of the second servo element 82b is 59.0695 μm (= 96 μm × tan 22° + 16.9306 μm + 96 μm × tan 2° = 38.7865 μm + 16.9306 μm + 3.3524 μm).

In the above-mentioned embodiment A, a phase difference was set for the pulse signals input to each of the five pairs of servo elements 82. On the other hand, in embodiment B, since the servo write head 80b is arranged at an angle, it is not necessary to set a phase difference for the pulse signals. In other words, pulse signals corresponding to the same phase are input to each of the five pairs of servo elements 82 at the same time.

FIG. 21 shows a servo pattern 47 written in five servo bands s by five pairs of servo elements 82.

The phase difference in the width direction of the magnetic tape MT between the servo patterns 47 written in two servo bands s adjacent to each other in the width direction (Y-axis direction) of the magnetic tape MT is expressed as SP1 x tan(Refθ).

Assume that the value of SP1 is 2858.8 μm, and the reference angle Refθ in the data write head 60 is 10°. In this case, the phase difference between the servo patterns 47 written to two adjacent servo bands s is 2858.8 μm × tan 10° = 504.08 μm.

Note that the phase differences of the servo patterns 47 of servo bands s3, s2, s1, and s2, based on the servo pattern 47 of servo band s4, correspond to 504.08 μm, 1008.17 μm, 1512.25 μm, and 2016.33 μm, respectively.

The above explanation describes the configuration of the servo write head 80b based on the coordinate system of the magnetic tape MT (XYZ coordinate system). In the following, we will explain the configuration of the servo write head 80b based on the coordinate system of the servo write head 80b (X"Y"Z" coordinate system).

FIG. 22 shows the servo write head 80b in embodiment B, based on the coordinate system of the servo write head 80b.

As shown in FIG. 22, the five pairs of servo elements 82 are arranged at a predetermined interval (servo element pitch: SP2) in the longitudinal direction (Y" axis direction) of the servo write head 80b. The interval (servo element pitch: SP2) between two adjacent pairs of -1 servo elements 82 in the longitudinal direction (Y" axis direction) of the servo write head 80b is expressed as SP1 x cos(Refθ).

For example, suppose that the spacing (servo element pitch: SP1) between two adjacent pairs of servo elements 82 in the width direction (Y-axis direction) of the magnetic tape MT is 2858.8 μm, and the reference angle Refθ of the data write head 60 is 10°. In this case, the spacing (servo element pitch: SP2) between two adjacent pairs of servo elements 82 in the longitudinal direction (Y"-axis direction) of the servo write head 80b is 2902.9 μm.

Here, in the above-mentioned embodiment A, the axis of symmetry of the first servo element 82a ("/") and the second servo element 82b ("\") is non-parallel to the width direction (Y-axis direction) of the magnetic tape MT, and is also non-parallel to the longitudinal direction (Y"-axis direction) of the servo write head 80b. On the other hand, in embodiment B, the axis of symmetry of the first servo element 82a ("/") and the second servo element 82b ("\") is non-parallel to the width direction (Y-axis direction) of the magnetic tape MT, but is parallel to the longitudinal direction (Y"-axis direction) of the servo write head 80b.

The first servo element 82a ("/") is inclined at a servo azimuth angle θa relative to the longitudinal direction (Y" axis direction) of the servo write head 80b. On the other hand, the second servo element 82b ("\") is inclined in the opposite direction to the first servo element 82a ("/") at the same servo azimuth angle θa as the first servo element 82a ("/") relative to the longitudinal direction (Y" axis direction) of the servo write head 80b.

Here, for the first servo element 82a ("/"), the direction along the servo azimuth angle θa (a direction at +12° relative to the longitudinal direction of the servo write head 80b) is defined as the longitudinal direction of the first servo element 82a ("/"). Also, for the second servo element 82b ("\"), the direction along the servo azimuth angle θa (a direction at -12° relative to the longitudinal direction of the servo write head 80b) is defined as the longitudinal direction of the second servo element 82b ("\").

Furthermore, the longitudinal component SL21 (Y" axis direction) of the servo write head 80b in the longitudinal length of the first servo element 82a ("/") and the longitudinal component SL22 (Y" axis direction) of the servo write head 80b in the longitudinal length of the second servo element 82b ("\") are also different.

FIG. 25 is an enlarged view of the right side of FIG. 22, showing an example of specific dimensions of the first servo element 82a ("/") and the second servo element 82b ("\") (based on the X"Y"Z" coordinate system).

Let us assume that the width direction component SL1 (Y-axis direction) of the magnetic tape MT in the length of the servo element 82 is 96 μm, the reference angle Refθ of the data write head 60 is 10°, and the servo azimuth angle θa is 12°. In this case, the longitudinal direction component SL21 (Y"-axis direction) of the servo write head 80b in the length of the first servo element 82a ("/") is 101.2767 μm (= 103.5093 μm × cos 12°). Also, in this case, the longitudinal direction component SL22 (Y"-axis direction) of the servo write head 80b in the length of the second servo element 82b ("\") is 93.959 μm (= 96.0585 μm × cos 12°).

In addition, in the width direction (X" axis direction) of the servo write head 80b, the distance between the upper end of the first servo element 82a and the upper end of the second servo element 82b is 16.673 μm (= 16.9306 μm × cos 10°).In addition, in the longitudinal direction (Y" axis direction) of the servo write head 80b, the difference between the position of the upper end of the first servo element 82a ("/") and the position of the upper end of the second servo element 82b ("\") is 2.94 μm (= 16.9306 μm × sin 10°).

In addition, in the width direction (X" axis direction) of the servo write head 80b, the distance between the bottom end of the first servo element 82a and the bottom end of the second servo element 82b is 58.1721 μm (= 59.0695 μm × cos 10°).In addition, in the longitudinal direction (Y" axis direction) of the servo write head 80b, the difference between the position of the bottom end of the first servo element 82a ("/") and the position of the bottom end of the second servo element 82b ("\") is 10.2573 μm (= 59.0695 μm × sin 10°).

In addition, in the width direction (X" axis direction) of the servo write head 80b, the distance (center) between the first servo element 82a ("/") and the second servo element 82b ("\") is, for example, 38.58628253 μm (38 μm x cos10° + (38 μm x sin10°) x tan102° = 37.4227 μm + 6.5986 μm x tan102° = 37.4227 μm + 1.16354026 μm).

Comparison of embodiment A and embodiment B
Next, a comparison between embodiment A and embodiment B will be described.

The right side of Figure 19 shows the servo pattern 47 written by the servo write head 80a in embodiment A being read by the two servo read portions 62 of the data write head 60.

As described above, in the servo write head 80a of embodiment A, the servo write head 80a is positioned without being tilted in the width direction of the magnetic tape MT, and the servo pattern 47 is written by adjusting the phase of the pulse signal input to the servo element 82.

When the servo write head 80a writes the servo pattern 47 onto the magnetic tape MT, the magnetic tape MT may move slightly in the width direction (Y-axis direction).

Let us suppose that in the servo write head 80a of embodiment A, the servo element 82 of servo band s0 writes a servo pattern 47 of a phase ph1 to servo band s0 at a certain time t1. Then, at a later time t2 (the time when the magnetic tape MT has been transported 504.08 μm in the transport direction), the servo element 82 of servo band s1 writes a servo pattern 47 of phase ph1 to servo band s1.

In this case, assume that the magnetic tape MT moves slightly in the width direction between time t1 and time t2. In this case, the distance (in the direction of the reference angle Refθ (10°)) between the position of the servo pattern 47 of phase ph1 in servo band s0 and the position of the servo pattern 47 of phase ph1 in servo band s1 will differ from the default value (the distance between the two servo lead portions 62: in the direction of the reference angle Refθ (10°)).

This can cause errors and prevent the data write head 60 from accurately servo tracing the servo pattern 47.

On the other hand, the right side of Figure 21 shows the servo pattern 47 written by the servo write head 80b in embodiment B being read by the two servo read portions 62 of the data write head 60.

In the servo write head 80b of embodiment B, the servo write head 80b is positioned at an angle to the width direction of the magnetic tape MT, and the servo pattern 47 is written with the same phase of the pulse signal input to the servo element 82.

Assume that in the servo write head 80b of embodiment B, the servo element 82 of servo band s0 and the servo element 82 of servo band s1 write servo patterns 47 of the same phase ph1 to servo band s0 and servo band s1 at the same time t1.

Then, the servo element 82 of servo band s0 and the servo element 82 of servo band s1 write servo patterns 47 of the same phase ph2 to servo bands s0 and s1 at the same time t2.

In this case, assume that the magnetic tape MT moves slightly in the width direction between time t1 and time t2. In this case, the distance (in the direction of reference angle Refθ (10°)) between the position of servo pattern 47 of phase ph1 in servo band s0 and the position of servo pattern 47 of phase ph1 in servo band s1 is the same as the distance between the position of servo pattern 47 of phase ph2 in servo band s0 and the position of servo pattern 47 of phase ph2 in servo band s1. These distances are the same as the default value (distance between two servo lead portions 62: in the direction of reference angle Refθ (10°)), and are constant.

In other words, in embodiment B, the spacing (in the direction of the reference angle Refθ) between servo patterns 47 of the same phase in adjacent servo bands s can be made constant, regardless of slight movement in the width direction of the magnetic tape MT when writing the servo patterns 47. This allows the data write head 60 to accurately servo trace the servo patterns 47.

As will be understood from the explanation here, in terms of slight movement in the width direction of the magnetic tape MT when writing the servo pattern 47, embodiment B is more advantageous than embodiment A. However, this is not intended to mean that the method of embodiment A cannot be adopted, and embodiment A is also included as an example of the present technology. For example, if the slight movement in the width direction of the magnetic tape MT when writing the servo pattern 47 is at a negligible level, or if the slight movement in the width direction of the magnetic tape MT when writing the servo pattern 47 can be suppressed to a negligible level, the method of embodiment A may be adopted.

[Effects, etc.]
As described above, in the first embodiment, the servo write head 80 can write the first servo pattern 47a ("/") and the second servo pattern 47b ("\") that are asymmetric with respect to the width direction of the magnetic tape MT to each of the servo bands s0 to s4. This allows the data write head 60 to accurately read the servo pattern 47 when the data write head 60 is disposed at an angle with respect to the width direction of the magnetic tape MT.

FIG. 23 is a diagram showing the state when the servo pattern 47 is read by the servo read portion 62 of the data write head 60 in the first comparative example, the second comparative example, and the first embodiment.

Referring to the left side of FIG. 23, in the first comparative example, the first servo pattern 47a ("/") and the second servo pattern 47b ("\") are symmetrical with respect to the width direction of the magnetic tape MT. In addition, the longitudinal direction of the data write head 60 is parallel to the width direction of the magnetic tape MT.

In the first comparative example, the azimuth loss of the servo patterns 47 relative to the servo read portion 62 of the data write head 60 is the same for each group of servo patterns 47. Therefore, when the servo patterns 47 are read by the servo read portion 62 of the servo write head 80, the output of the servo signal is the same for each servo burst corresponding to the group of servo patterns 47.

Referring to the center of FIG. 23, in the second comparative example, the first servo pattern 47a ("/") and the second servo pattern 47b ("\") are symmetrical with respect to the width direction of the magnetic tape MT. On the other hand, the longitudinal direction of the data write head 60 is arranged at an angle with respect to the width direction of the magnetic tape MT.

In the second comparative example, the azimuth loss of the servo patterns 47 relative to the servo read section 62 of the data write head 60 differs for each group of servo patterns 47. Therefore, when the servo patterns 47 are read by the servo read section 62 of the servo write head 80, the output of the servo burst in the servo signal corresponding to the group of servo patterns 47 with less azimuth loss is large, while the output of the servo burst corresponding to the group of servo patterns 47 with more azimuth loss is small. This can cause an error in the tracking reference position.

Referring to the right side of FIG. 23, in the first embodiment, the first servo pattern 47a ("/") and the second servo pattern 47b ("\") on the magnetic tape MT are asymmetric with respect to the width direction of the magnetic tape MT. In addition, the longitudinal direction of the data write head 60 is non-parallel to the width direction of the magnetic tape MT.

In the first embodiment, the azimuth loss of the servo patterns 47 relative to the servo read portion 62 of the data write head 60 is the same for each group of servo patterns 47. Therefore, when the servo patterns 47 are read by the servo read portion 62 of the servo write head 80, the output of the servo signal is the same for each servo burst corresponding to the group of servo patterns 47.

In this way, in the first embodiment, the first servo pattern 47a ("/") and the second servo pattern 47b ("\") are asymmetric with respect to the width direction of the magnetic tape MT, so that when the data write head 60 is positioned at an angle with respect to the width direction of the magnetic tape MT, the data write head 60 can accurately read the servo pattern 47.

In the first embodiment, the longitudinal direction of the data write head 60 in the data recording and reproducing device 50 is inclined at an azimuth angle θ with respect to the width direction of the magnetic tape MT, and the azimuth angle θ is adjusted. This makes it possible to accommodate variations in the width of the magnetic tape MT.

In the first embodiment, the azimuth angle θ of the data write head 60 in the data recording and reproducing device 50 is adjusted within the range of the reference angle Refθ±x°.

In this case, by setting the value of x to 0.7° or less, it is possible to reduce the azimuth loss Lθ while accommodating magnetic tapes MT with small playback track widths W (e.g., 0.5 μm or less). Also, by setting the reference angle Refθ to 8° or more, the above correction amount can be increased (e.g., 10 μm or more).

Also, in the first embodiment, in the servo recording and reproducing device 70, the first servo element 82a ("/") and the second servo element 82b ("\") are provided in the servo write head 80 so as to be asymmetric with respect to the width direction of the magnetic tape MT. This makes it possible to properly write a servo pattern 47 that is asymmetric with respect to the width direction of the magnetic tape MT by the first servo element 82a ("/") and the second servo element 82b ("\").

In addition, in the first embodiment, the first servo element 82a ("/") is inclined at a first angle θs1 with respect to the width direction of the magnetic tape MT, and the second servo element 82b ("\") is inclined at a second angle θs2, which is different from the first angle θs1, in the opposite direction to the first angle θs1 with respect to the width direction of the magnetic tape MT.

In the first embodiment, the first angle θs1 and the second angle θs2 are related to the reference angle Refθ of the data write head 60. This allows the first servo element 82a ("/") and the second servo element 82b ("\") to properly write an asymmetric servo pattern 47 that can be accurately read by the data write head 60.

In addition, in the first embodiment, the length of the first servo element 82a ("/") in the longitudinal direction is different from the length of the first servo element 82a ("/") in the longitudinal direction, but the component of the length of the first servo element 82a ("/") in the width direction of the magnetic tape MT is the same as the component of the length of the second servo element 82b ("\") in the width direction of the magnetic tape MT. This makes it possible to align the lengths of the first servo pattern 47a ("/") and the second servo pattern 47b ("\") written by the first servo element 82a ("/") and the second servo element 82b ("\") in the width direction of the magnetic tape MT.

Furthermore, in the first embodiment, the longitudinal direction of the servo write head 80 may be arranged so as to be inclined at a predetermined angle with respect to the width direction of the magnetic tape MT (see embodiment B). In this case, it is possible to appropriately respond to slight movements in the width direction of the magnetic tape MT when writing the servo pattern 47.

Also, in the first embodiment, the angle at which the longitudinal direction of the servo write head 80 is tilted with respect to the width direction of the magnetic tape MT may be related to the reference angle Refθ of the data write head 60, and this angle may coincide with the reference angle Refθ of the data write head 60. This makes it possible to properly write an asymmetric servo pattern 47 that can be accurately read by the tilted data write head 60.

Furthermore, in the magnetic tape MT according to the first embodiment, the phase difference in the width direction of the magnetic tape MT between the servo patterns 47 in adjacent servo bands s is related to the reference angle Refθ of the servo write head 80 and is expressed as SP×tan(Refθ). This allows the servo patterns 47 to be accurately read by the data write head 60, which is positioned at an angle.

[Method of checking whether a magnetic tape is a magnetic tape used in a data recording/reproducing device with a tilted data write head]
Next, a method for checking whether the magnetic tape MT is a magnetic tape MT used in a data recording/reproducing device 50 of the type in which the data write head 60 is positioned at an angle with respect to the width direction (Y-axis direction) of the magnetic tape MT will be described.

[Confirmation method: First example]
26 is a diagram showing a first example of a method for checking whether or not a magnetic tape MT is a magnetic tape MT used in a data write head tilt type data recording and reproducing device 50. In the first example, the following check is performed based on the angle (first angle θs1) at which the first servo pattern 47a ("/") is tilted with respect to the width direction (Y-axis direction) of the magnetic tape MT, and the angle (second angle θs2) at which the second servo pattern 47b ("\") is tilted with respect to the width direction of the magnetic tape.

Note that Figure 26 shows the magnetic tape MT as seen from the top (magnetic layer side) (therefore, in the first servo pattern 47a ("/") and the second servo pattern 47b ("\"), the signs "/" and "\" are reversed from appearance).

As shown in FIG. 26, first, a developer such as a ferricolloid developer (e.g., Sigmarca Q (registered trademark) manufactured by Sigma High Chemical Co.) is applied to the magnetic layer 43 of the magnetic tape MT to perform development. After that, the developed magnetic layer 43 of the magnetic tape MT is observed with an optical microscope to confirm the shape of the servo pattern 47.

At this time, first, the upper and lower ends of the first servo pattern 47a ("/") and the upper and lower ends of the second servo pattern 47b ("\") are measured as measurement points. Then, the distance a (corresponding to the servo band width) between the upper and lower ends of the servo pattern 47 in the width direction (Y-axis direction) of the magnetic tape MT is measured.

Furthermore, in the longitudinal direction (X-axis direction) of the magnetic tape MT, the distance b between the upper end and the lower end of the first servo pattern 47a ("/") is measured. Further, in the longitudinal direction (X-axis direction) of the magnetic tape MT, the distance c between the upper end and the lower end of the second servo pattern 47b ("\") is measured.

In this case, the angle (first angle θs1) at which the first servo pattern 47a ("/") is inclined with respect to the width direction (Y-axis direction) of the magnetic tape MT is calculated by tan ^-1 (b/a). Also, the angle (second angle θs2) at which the second servo pattern 47b ("\") is inclined with respect to the width direction (Y-axis direction) of the magnetic tape MT is calculated by tan ^-1 (c/a).

For example, suppose that the value of a is 96 μm, the value of b is 39 μm, and the value of c is 3 μm. In this case, the angle (first angle θs1) at which the first servo pattern 47a ("/") is inclined with respect to the width direction (Y-axis direction) of the magnetic tape MT is tan ^-1 (39/96) = 21.59°, which is approximately 22°. Also, the angle (second angle θs2) at which the second servo pattern 47b ("\") is inclined with respect to the width direction (Y-axis direction) of the magnetic tape MT is tan ^-1 (3/96) = 1.79°, which is approximately 2°.

Next, the predetermined angle is calculated by (the inclination angle (first angle θs1) of the first servo pattern 47a ("/") - the inclination angle (second angle θs2) of the second servo pattern 47b ("\"))/2 ((22-2)/2 = 10°). The angle calculated at this time corresponds to the angle at which the symmetry axes of the first servo pattern 47a and the second servo pattern 47b are inclined with respect to the width direction (Y-axis direction) of the magnetic tape MT.

Let us assume that the angle calculated by (first angle θs1 - second angle θs2)/2 coincides with the angle (reference angle) at which the data write head 60 is tilted with respect to the width direction (Y-axis direction) of the magnetic tape MT (θs1 - θs2)/2 = refθ) (this may include a certain degree of error).

In this case, as already explained with reference to the right side of FIG. 23, the azimuth loss of the servo patterns 47 relative to the servo read portion 62 of the data write head 60 is the same for each group of servo patterns 47. As a result, when the servo patterns 47 are read by the servo read portion 62 of the servo write head 80, the output of the servo signal is the same for each servo burst corresponding to the group of servo patterns 47.

Therefore, if the angle calculated by (θs1-θs2)/2 coincides with the angle (reference angle) at which the data write head 60 is tilted with respect to the width direction (Y-axis direction) of the magnetic tape MT, this magnetic tape MT can be considered to be a magnetic tape MT used in a data recording and playback device 50 of a type in which the data write head 60 is positioned at an angle with respect to the width direction (Y-axis direction) of the magnetic tape MT.

[Confirmation method: second example]
27 is a diagram showing a second example of a method for checking whether a magnetic tape MT is a magnetic tape MT used in a data recording/reproducing device 50 with a tilted data write head. In the second example, the above checking is performed based on a phase difference between the servo patterns 47 in adjacent servo bands.

In this second example, a data recording and reproducing device is used, in which the data write head 60 is positioned parallel to the width direction (Y-axis direction) of the magnetic tape MT.

First, the two servo read sections 62 of the data write head 60 read the servo patterns 47 in the adjacent servo bands, and reproduce the servo signals.

The phase of the servo signal reproduced by the lower servo read section 62 is ahead of the phase of the servo signal reproduced by the upper servo read section 62, resulting in a phase difference. At this time, the difference in time at which the same LPOS (Longitudinal Position) information is read between the servo signal reproduced by the lower servo read section 62 and the servo signal reproduced by the upper servo read section 62 is found. This time difference is then converted into distance to find the phase difference d in the longitudinal direction of the magnetic tape (for example, 0.505 μm).

Next, based on the obtained phase difference d (eg, 0.505 μm) and the servo band pitch SP (known) (eg, 2.8588 μm), a predetermined angle is obtained by tan ⁻¹ (d/SP) (tan ⁻¹ (0.505/2.8588)=10.017°).

The angle found in this case corresponds to the angle that a straight line connecting the positions where in-phase information is written in the servo pattern 47 of one servo band and the servo pattern 47 of the other servo band makes with respect to the width direction of the magnetic tape.

Let us assume that the angle calculated by tan ^-1 (d/SP) coincides with the angle (reference angle) at which the data write head 60 is tilted with respect to the width direction (Y-axis direction) of the magnetic tape MT (tan ^-1 (d/SP) = ref θ) (some degree of error may be included). In this case, the magnetic tape MT can be regarded as a magnetic tape MT used in a data recording/reproducing device 50 of the type in which the data write head 60 is disposed at an angle with respect to the width direction (Y-axis direction) of the magnetic tape MT.

(5) Effects

As explained in (2) of 2. above, in the magnetic tape MT according to the first embodiment, when the width change Δ of the magnetic tape MT is measured over the entire length of the magnetic tape MT after storage at 65° C. for 360 hours, the sign of the width change Δout on the outer side of the magnetic tape MT is different from the sign of the width change Δin on the inner side of the magnetic tape MT. Since the sign of the width change Δout on the outer side of the magnetic tape MT is different from the sign of the width change Δin on the inner side of the magnetic tape MT, excellent running stability can be obtained even when stored in a high-temperature environment. Furthermore, the width change Δ is 0 ppm in either of the two regions that sandwich the center line of the entire length of the magnetic tape when the entire length of the magnetic tape is divided into four equal regions. This allows excellent running stability to be obtained even when stored in a high-temperature environment. Furthermore, in the longitudinal direction of the magnetic tape, the width change Δ is 300 ppm or less in any of the four regions. This allows the azimuth angle θ of the data write head to be adjusted to accommodate changes in shape due to changes in temperature and humidity, even if the width of the magnetic tape MT1 changes in a high-temperature environment.

As explained in (4) of 2. above, the magnetic tape MT according to the first embodiment has a plurality of servo bands s in which servo patterns 47 including a first servo pattern 47a and a second servo pattern 47b asymmetrical with respect to the width direction are written, and the servo patterns 47 in the servo bands s adjacent to each other have a phase difference. Therefore, the magnetic tape MT according to the first embodiment can be used in a data recording and reproducing device 50 that can respond to a change in the width of the magnetic tape MT by adjusting the azimuth angle θ of the data write head 60. In the data recording and reproducing device 50, typically, when the width of the magnetic tape MT becomes relatively wide, the azimuth angle θ of the data write head 60 is made small, and conversely, when the width of the magnetic tape MT becomes relatively narrow, the azimuth angle θ of the data write head 60 is made large. As a result, the servo patterns 47 of the magnetic tape MT can be accurately read even when the width of the magnetic tape MT changes.
Therefore, even if the temperature of the magnetic tape MT changes in a high temperature environment, the azimuth angle θ of the data write head 60 can be adjusted to accommodate the change in width.

As described above, the magnetic tape MT according to the first embodiment is capable of dealing with width changes that may occur in high-temperature environments. Therefore, the magnetic tape MT according to the first embodiment is suitable for storage and running in high-temperature environments.

3. Second embodiment (example of magnetic recording cartridge including vacuum thin-film magnetic tape)

(1) Structure of magnetic recording cartridge

The magnetic recording cartridge of this embodiment is the same as the magnetic recording cartridge 10 described in 2. "(1) Configuration of the magnetic cartridge" above, except that it includes a vacuum thin-film type magnetic tape MT1 instead of a coating type magnetic tape MT. The vacuum thin-film type magnetic tape MT1 is described below.

(2) Structure of magnetic tape

In the above first embodiment, the magnetic tape MT is a coated magnetic tape in which the underlayer and magnetic layer are produced by a coating process (wet process), but the magnetic tape may be a vacuum thin-film type magnetic tape in which the underlayer and magnetic layer are produced by a vacuum thin-film production technique (dry process) such as sputtering.

Figure 28 is a cross-sectional view showing an example of the configuration of a vacuum thin-film type magnetic tape MT1 according to a second embodiment of the present technology. The magnetic tape MT1 is a perpendicular recording type magnetic recording medium, and includes a film-like base layer 111, a soft magnetic underlayer (hereinafter referred to as "SUL") 112, a first seed layer 113A, a second seed layer 113B, a first underlayer 114A, a second underlayer 114B, and a magnetic layer 115 as a recording layer. The SUL 112, the first and second seed layers 113A and 113B, the first and second underlayers 114A and 114B, and the magnetic layer 115 are vacuum thin films such as sputtered films.

The SUL 112, the first and second seed layers 113A, 113B, and the first and second underlayers 114A, 114B are provided between one major surface (hereinafter referred to as the "surface") of the base layer 111 and the magnetic layer 115, and are stacked in the following order from the base layer 111 toward the magnetic layer 115: SUL 112, first seed layer 113A, second seed layer 113B, first underlayer 114A, second underlayer 114B.

The magnetic tape MT1 may further include a protective layer 116 provided on the magnetic layer 115 and a lubricating layer 117 provided on the protective layer 116, if necessary. The magnetic tape MT1 may further include a back layer 118 provided on the other main surface (hereinafter referred to as the "back surface") of the base layer 111, if necessary.

Hereinafter, the longitudinal direction of the magnetic tape MT1 (the longitudinal direction of the base layer 111) is referred to as the MD (machine direction). Here, the MD direction refers to the relative movement direction of the recording and reproducing heads with respect to the magnetic tape MT1, i.e., the direction in which the magnetic tape MT1 runs during recording and reproducing.

The magnetic tape MT1 according to the second embodiment is suitable for use as a storage medium for data archives, the demand of which is expected to increase in the future. This magnetic tape MT1 can achieve an areal recording density of 50 Gb/ ⁱⁿ² or more, which is 10 times or more than that of current coating-type magnetic recording media for storage. When a general linear recording type data cartridge is configured using the magnetic tape MT1 having such an areal recording density, a large capacity recording capacity of 100 TB or more can be achieved per data cartridge.

The magnetic tape MT1 according to the second embodiment is suitable for use in a recording and reproducing device (a recording and reproducing device for recording and reproducing data) having a ring-type recording head and a Giant Magnetoresistive (GMR) type or Tunneling Magnetoresistive (TMR) type reproducing head. The magnetic tape MT1 according to the second embodiment preferably uses a ring-type recording head as a servo signal writing head. A data signal is recorded perpendicularly on the magnetic layer 115, for example, by a ring-type recording head. A servo signal is recorded perpendicularly on the magnetic layer 115, for example, by a ring-type recording head.

The average thickness t _T , width change, storage modulus, loss modulus, etc. of the magnetic tape MT1 in the second embodiment are similar to those in the first embodiment.

[Base layer]
The base layer 111 is similar to the base layer 41 in the first embodiment.

[SUL]
The SUL 112 includes a soft magnetic material in an amorphous state. The soft magnetic material includes at least one of a Co-based material and an Fe-based material. The Co-based material includes, for example, CoZrNb, CoZrTa, or CoZrTaNb. The Fe-based material includes, for example, FeCoB, FeCoZr, or FeCoTa.

SUL 112 is a single layer SUL and is provided directly on base layer 111. The average thickness of SUL 112 is preferably 10 nm or more and 50 nm or less, and more preferably 20 nm or more and 30 nm or less.

The average thickness of the SUL 112 is determined in the same manner as the magnetic layer 43 in the first embodiment. The average thicknesses of the layers other than the SUL 112 (i.e., the average thicknesses of the first and second seed layers 113A, 113B, the first and second underlayers 114A, 114B, and the magnetic layer 115), which will be described later, are also determined in the same manner as the magnetic layer 43 in the first embodiment. However, the magnification of the TEM image is appropriately adjusted according to the thickness of each layer.

[First and second seed layers]
The first seed layer 113A includes an alloy containing Ti and Cr, and is in an amorphous state. The alloy may further include O (oxygen). The oxygen may be impurity oxygen contained in a small amount in the first seed layer 113A when the first seed layer 113A is formed by a film forming method such as a sputtering method.

Here, "alloy" refers to at least one of a solid solution, a eutectic, and an intermetallic compound containing Ti and Cr. "Amorphous state" means that a halo is observed by X-ray diffraction or electron beam diffraction, etc., and the crystal structure cannot be identified.

The atomic ratio of Ti to the total amount of Ti and Cr contained in the first seed layer 113A is preferably in the range of 30 atomic % or more and less than 100 atomic %, and more preferably 50 atomic % or more and less than 100 atomic %. If the atomic ratio of Ti is less than 30%, the (100) plane of the body-centered cubic lattice (bcc) structure of Cr will become oriented, and there is a risk that the orientation of the first and second underlayers 114A and 114B formed on the first seed layer 113A will decrease.

The atomic ratio of Ti is determined as follows. While ion milling the magnetic tape MT1 from the magnetic layer 115 side, a depth profile analysis (depth profile measurement) of the first seed layer 113A is performed by Auger Electron Spectroscopy (AES). Next, the average composition (average atomic ratio) of Ti and Cr in the film thickness direction is determined from the obtained depth profile. Next, the atomic ratio of Ti is determined using the obtained average composition of Ti and Cr.

When the first seed layer 113A contains Ti, Cr and O, the atomic ratio of O to the total amount of Ti, Cr and O contained in the first seed layer 113A is preferably 15 atomic % or less, more preferably 10 atomic % or less. If the atomic ratio of O exceeds 15 atomic %, TiO2 crystals are generated, which may affect the crystal nucleation of the first and second underlayers 114A and 114B formed on the first seed layer 113A, and may reduce the orientation of the first and second underlayers 114A and 114B. The atomic ratio of O is determined using the same analytical method as the atomic ratio of Ti.

The alloy contained in the first seed layer 113A may further contain an element other than Ti and Cr as an additive element. The additive element may be, for example, one or more elements selected from the group consisting of Nb, Ni, Mo, Al, W, etc.

The average thickness of the first seed layer 113A is preferably 2 nm or more and 15 nm or less, and more preferably 3 nm or more and 10 nm or less.

The second seed layer 113B contains, for example, NiW or Ta, and has a crystalline state. The average thickness of the second seed layer 113B is preferably 3 nm or more and 20 nm or less, more preferably 5 nm or more and 15 nm or less.

The first and second seed layers 113A and 113B have a crystal structure similar to that of the first and second underlayers 114A and 114B, and are not seed layers provided for the purpose of crystal growth, but are seed layers that improve the vertical orientation of the first and second underlayers 114A and 114B due to the amorphous state of the first and second seed layers 113A and 113B.

[First and second underlayers]
The first and second underlayers 114A and 114B preferably have the same crystal structure as the magnetic layer 115. When the magnetic layer 115 contains a Co-based alloy, the first and second underlayers 114A and 114B preferably contain a material having a hexagonal close-packed (hcp) structure similar to the Co-based alloy, and the c-axis of the structure is preferably oriented perpendicular to the film surface (i.e., in the film thickness direction). This is because it enhances the orientation of the magnetic layer 115 and can relatively well match the lattice constants of the second underlayer 114B and the magnetic layer 115. As the material having the hexagonal close-packed (hcp) structure, it is preferable to use a material containing Ru, and specifically, Ru alone or a Ru alloy is preferable. As the Ru alloy, for example, Ru alloy oxides such as Ru-SiO ₂ , Ru-TiO ₂ or Ru-ZrO ₂ can be mentioned.

As described above, the first and second underlayers 114A and 114B can be made of similar materials. However, the intended effects of the first and second underlayers 114A and 114B are different. Specifically, the second underlayer 114B has a film structure that promotes the granular structure of the magnetic layer 115 that is the layer above it, and the first underlayer 114A has a film structure with high crystal orientation. To obtain such a film structure, it is preferable to use different film formation conditions, such as sputtering conditions, for the first and second underlayers 114A and 114B.

The average thickness of the first underlayer 114A is preferably 3 nm to 15 nm, more preferably 5 nm to 10 nm. The average thickness of the second underlayer 114B is preferably 7 nm to 40 nm, more preferably 10 nm to 25 nm.

[Magnetic Layer]
The magnetic layer 115 is a perpendicular magnetic recording layer in which the magnetic material is oriented perpendicularly. The magnetic layer 115 may be a vacuum thin film such as a sputtered film. From the viewpoint of improving the recording density, the magnetic layer 115 is preferably a granular magnetic layer containing a Co-based alloy. This granular magnetic layer is composed of ferromagnetic crystal grains containing a Co-based alloy and non-magnetic grain boundaries (non-magnetic material) surrounding the ferromagnetic crystal grains. More specifically, this granular magnetic layer is composed of columns (columnar crystals) containing a Co-based alloy and non-magnetic grain boundaries (e.g., oxides such as _SiO2 ) surrounding the columns and magnetically separating each column. In this structure, the magnetic layer 115 can be formed with a structure in which each column is magnetically separated.

The Co-based alloy has a hexagonal close-packed (hcp) structure, with its c-axis oriented perpendicular to the film surface (film thickness direction). As the Co-based alloy, it is preferable to use a CoCrPt-based alloy containing at least Co, Cr, and Pt. The CoCrPt-based alloy is not particularly limited, and the CoCrPt alloy may further contain an additive element. Examples of the additive element include one or more elements selected from the group consisting of Ni, Ta, etc.

The non-magnetic grain boundaries surrounding the ferromagnetic crystal grains contain a non-magnetic metal material. Here, the metal includes a semi-metal. For example, at least one of a metal oxide and a metal nitride can be used as the non-magnetic metal material, and from the viewpoint of maintaining the granular structure more stably, it is preferable to use a metal oxide. As the metal oxide, there is a metal oxide containing at least one element selected from the group consisting of Si, Cr, Co, Al, Ti, Ta, Zr, Ce, Y, and Hf, and a metal oxide containing at least Si oxide (i.e., SiO ₂ ) is preferable. Specific examples of the metal oxide include SiO ₂ , Cr ₂ O ₃ , CoO, Al ₂ O ₃ , TiO ₂ , Ta ₂ O ₅ , ZrO ₂ , or HfO ₂ . As the metal nitride, there is a metal nitride containing at least one element selected from the group consisting of Si, Cr, Co, Al, Ti, Ta, Zr, Ce, Y, and Hf. Specific examples of metal nitrides include SiN, TiN, and AlN.

It is preferable that the CoCrPt alloy contained in the ferromagnetic crystal grains and the Si oxide contained in the non-magnetic grain boundaries have an average composition shown in the following formula (5), because this can suppress the influence of the demagnetizing field and realize a saturation magnetization Ms that can ensure sufficient reproduction output, thereby achieving further improvement in the recording and reproduction characteristics.
( _CoxPtyCr100 _-x-y ) _100-z- ( _SiO2 ) _z ... ₍ 5)
(In formula (5), x, y, and z are values within the ranges of 69≦X≦75, 10≦y≦16, and 9≦Z≦12, respectively.)

The above composition can be determined as follows. While ion milling the magnetic tape MT1 from the magnetic layer 115 side, AES is used to perform a depth direction analysis of the magnetic layer 115, and the average composition (average atomic ratio) of Co, Pt, Cr, Si, and O in the film thickness direction is determined.

The upper limit of the average thickness of the magnetic layer 115 is, for example, 90 nm or less, preferably 80 nm or less, more preferably 70 nm or less, even more preferably 60 nm or less, and particularly preferably 50 nm or less, 20 nm or less, or 15 nm or less. The lower limit of the average thickness of the magnetic layer 115 is preferably 9 nm or more. When the average thickness of the magnetic layer 115 is 9 nm or more and 90 nm or less, the electromagnetic conversion characteristics can be improved.

The magnetic layer 115 has multiple data bands in which data is written, and multiple servo bands in which servo patterns are written. For details of the data bands and servo bands of the magnetic layer 115, the explanation of the data bands and servo bands in the first embodiment described in 1. (2) above applies. Therefore, the explanation of the data bands and servo bands of the magnetic layer 115 is omitted.

[Protective Layer]
The protective layer 116 contains, for example, a carbon material or silicon dioxide (SiO ₂ ), and preferably contains a carbon material from the viewpoint of the film strength of the protective layer 116. Examples of the carbon material include graphite, diamond-like carbon (DLC), diamond, and the like.

[Lubricant layer]
The lubricating layer 117 includes at least one lubricant. The lubricating layer 117 may further include various additives, such as a rust inhibitor, as necessary. Examples of the lubricant include the same lubricant as that used in the magnetic layer 43 in the first embodiment.

The lubricant may not only be held as a lubricating layer 117 on the surface of the magnetic tape MT1 as described above, but may also be contained and held in layers such as the magnetic layer 115 and protective layer 116 that make up the magnetic tape MT1.

[Back layer]
The back layer 118 is similar to the back layer 44 in the first embodiment.

(3) Configuration of the sputtering device

Below, with reference to FIG. 29, an example of the configuration of the sputtering device 120 used in the manufacture of the magnetic tape MT1 according to the second embodiment will be described. The sputtering device 120 is a continuous winding type sputtering device used to deposit the SUL 112, the first seed layer 113A, the second seed layer 113B, the first underlayer 114A, the second underlayer 114B, and the magnetic layer 115, and includes a deposition chamber 121, a drum 122 which is a metal can (rotating body), cathodes 123a to 123f, a supply reel 124, a take-up reel 125, and a number of guide rolls 127a to 127c, 128a to 128c. The sputtering device 120 is, for example, a DC (direct current) magnetron sputtering type device, but the sputtering type is not limited to this type.

The film-forming chamber 121 is connected to a vacuum pump (not shown) via an exhaust port 126, and the atmosphere in the film-forming chamber 121 is set to a predetermined vacuum level by the vacuum pump. Inside the film-forming chamber 121, a rotatable drum 122, a supply reel 124, and a take-up reel 125 are arranged. Inside the film-forming chamber 121, a plurality of guide rolls 127a-127c are provided for guiding the transport of the base layer 111 between the supply reel 124 and the drum 122, and a plurality of guide rolls 128a-128c are provided for guiding the transport of the base layer 111 between the drum 122 and the take-up reel 125. During sputtering, the base layer 111 unwound from the supply reel 124 is wound onto the take-up reel 125 via the guide rolls 127a-127c, the drum 122, and the guide rolls 128a-128c. The drum 122 has a cylindrical shape, and the long base layer 111 is transported along the cylindrical peripheral surface of the drum 122. The drum 122 is provided with a cooling mechanism (not shown), and is cooled to, for example, about −20° C. during sputtering. Inside the film-forming chamber 121, a plurality of cathodes 123a to 123f are arranged facing the peripheral surface of the drum 122. Targets are set on each of these cathodes 123a to 123f. Specifically, targets for forming the SUL 112, the first seed layer 113A, the second seed layer 113B, the first underlayer 114A, the second underlayer 114B, and the magnetic layer 115 are set on the cathodes 123a, 123b, 123c, 123d, 123e, and 123f, respectively. These cathodes 123a-123f simultaneously deposit multiple types of films, namely, SUL 112, first seed layer 113A, second seed layer 113B, first underlayer 114A, second underlayer 114B, and magnetic layer 115.

In the sputtering apparatus 120 having the above configuration, the SUL 112, the first seed layer 113A, the second seed layer 113B, the first underlayer 114A, the second underlayer 114B and the magnetic layer 115 can be continuously formed by the roll-to-roll method.

(4) Manufacturing method of magnetic tape

The magnetic tape MT1 according to the second embodiment can be manufactured, for example, as follows.

First, using the sputtering device 120 shown in FIG. 29, the SUL 112, the first seed layer 113A, the second seed layer 113B, the first underlayer 114A, the second underlayer 114B, and the magnetic layer 115 are sequentially deposited on the surface of the base layer 111. Specifically, the deposition is performed as follows. First, the deposition chamber 121 is evacuated to a predetermined pressure. Then, while introducing a process gas such as Ar gas into the deposition chamber 121, the targets set on the cathodes 123a to 123f are sputtered. As a result, the SUL 112, the first seed layer 113A, the second seed layer 113B, the first underlayer 114A, the second underlayer 114B, and the magnetic layer 115 are sequentially deposited on the surface of the running base layer 111.

The atmosphere in the film formation chamber 121 during sputtering is set to, for example, about 1×10 ⁻⁵ Pa to 5×10 ⁻⁵ Pa. The film thickness and characteristics of the SUL 112, the first seed layer 113A, the second seed layer 113B, the first underlayer 114A, the second underlayer 114B and the magnetic layer 115 can be controlled by adjusting the tape line speed for winding up the base layer 111, the pressure of the process gas such as Ar gas introduced during sputtering (sputtering gas pressure), the input power, and the like.

Next, the protective layer 116 is formed on the magnetic layer 115. The protective layer 116 can be formed by, for example, chemical vapor deposition (CVD) or physical vapor deposition (PVD).

Next, a paint for forming the back layer is prepared by kneading and dispersing a binder, inorganic particles, a lubricant, etc. in a solvent. Next, the paint for forming the back layer is applied to the back surface of the base layer 111 and dried, thereby forming the back layer 118 on the back surface of the base layer 111.

Next, for example, a lubricant is applied onto the protective layer 116 to form the lubricant layer 117. As a method for applying the lubricant, various application methods such as gravure coating and dip coating can be used. Next, if necessary, the magnetic tape MT1 is cut to a predetermined width. In this manner, the magnetic tape MT1 shown in FIG. 28 is obtained.

(5) Effects The description of the effects described in (5) of 2 above also applies to the second embodiment. That is, in the magnetic tape MT1 according to the second embodiment, even if the magnetic tape MT1 is stored or run in a high-temperature environment for a long period of time (for example, 10 years), the magnetic tape MT1 can correct the width change of the magnetic tape MT1 by adjusting the running tension of the magnetic tape MT1, as in the first embodiment. Also, even if the width of the magnetic tape MT1 changes in a high-temperature environment, the width change can be accommodated by adjusting the azimuth angle θ of the data write head. Thus, the magnetic tape MT1 according to the second embodiment can handle the width change that may occur in a high-temperature environment, so the magnetic tape MT1 according to the second embodiment is suitable for storage and running in a high-temperature environment.

4. Third embodiment (example of magnetic recording cartridge including vacuum thin-film magnetic tape)

(1) Structure of magnetic recording cartridge

The magnetic recording cartridge of this embodiment is the same as the magnetic recording cartridge 10 described in "(1) Configuration of the magnetic cartridge" in 2. above, except that it includes a vacuum thin-film type magnetic tape MT2 instead of the coated magnetic tape MT. The vacuum thin-film type magnetic tape MT2 is described below.

(2) Structure of magnetic tape

FIG. 30 is a cross-sectional view showing an example of the configuration of a vacuum thin-film magnetic tape MT2 according to a third embodiment of the present technology. The magnetic tape MT2 includes a base layer 111, an SUL 112, a seed layer 131, a first underlayer 132A, a second underlayer 132B, and a magnetic layer 115. Note that in the third embodiment, parts that are the same as those in the second embodiment are given the same reference numerals and will not be described.

The SUL 112, seed layer 131, first and second underlayers 132A and 132B are provided between one major surface of the base layer 111 and the magnetic layer 115, and are stacked in the order of SUL 112, seed layer 131, first underlayer 132A, and second underlayer 132B from the base layer 111 toward the magnetic layer 115.

[Seed layer]
The seed layer 131 contains Cr, Ni, and Fe, has a face-centered cubic lattice (fcc) structure, and is preferentially oriented so that the (111) plane of this face-centered cubic structure is parallel to the surface of the base layer 111. Here, the preferential orientation means a state in which the diffraction peak intensity from the (111) plane of the face-centered cubic lattice structure is greater than the diffraction peaks from other crystal planes in a θ-2θ scan of an X-ray diffraction method, or a state in which only the diffraction peak intensity from the (111) plane of the face-centered cubic lattice structure is observed in a θ-2θ scan of an X-ray diffraction method.

From the viewpoint of improving the SNR, the intensity ratio of the X-ray diffraction of the seed layer 131 is preferably 60 cps/nm or more, more preferably 70 cps/nm or more, and even more preferably 80 cps/nm or more. Here, the intensity ratio of the X-ray diffraction of the seed layer 131 is a value (I/D (cps/nm)) obtained by dividing the intensity I (cps) of the X-ray diffraction of the seed layer 131 by the average thickness D (nm) of the seed layer 131.

The Cr, Ni, and Fe contained in the seed layer 131 preferably have an average composition represented by the following formula (6).
_CrX ( _NiYFe100 _-Y ) _100-X ... (6)
(In formula (6), X is within the range of 10≦X≦45, and Y is within the range of 60≦Y≦90.)
When X is within the above range, the (111) orientation of the face-centered cubic lattice structure of Cr, Ni, and Fe is improved, and a better SNR can be obtained. Similarly, when Y is within the above range, the (111) orientation of the face-centered cubic lattice structure of Cr, Ni, and Fe is improved, and a better SNR can be obtained.

The average thickness of the seed layer 131 is preferably 5 nm or more and 40 nm or less. By setting the average thickness of the seed layer 131 within this range, the (111) orientation of the face-centered cubic lattice structure of Cr, Ni, and Fe can be improved, and a better SNR can be obtained. The average thickness of the seed layer 131 is determined in the same manner as the magnetic layer 43 in the first embodiment. However, the magnification of the TEM image is appropriately adjusted according to the thickness of the seed layer 131.

[First and second underlayers]
The first underlayer 132A contains Co and O having a face-centered cubic lattice structure, and has a columnar (columnar crystal) structure. The first underlayer 132A containing Co and O has substantially the same effect (function) as the second underlayer 132B containing Ru. The concentration ratio of the average atomic concentration of O to the average atomic concentration of Co ((average atomic concentration of O)/(average atomic concentration of Co)) is 1 or more. When the concentration ratio is 1 or more, the effect of providing the first underlayer 132A is improved, and a better SNR can be obtained.

From the viewpoint of improving the SNR, it is preferable that the column structure is inclined. The direction of the inclination is preferably the longitudinal direction of the long magnetic tape MT2. The longitudinal direction is preferable for the following reasons. The magnetic tape MT2 according to this embodiment is a magnetic recording medium for so-called linear recording, and the recording tracks are parallel to the longitudinal direction of the magnetic tape MT2. The magnetic tape MT2 according to this embodiment is also a so-called perpendicular magnetic recording medium, and from the viewpoint of recording characteristics, it is preferable that the crystal orientation axis of the magnetic layer 115 is vertical, but the influence of the inclination of the column structure of the first underlayer 132A may cause the crystal orientation axis of the magnetic layer 115 to be inclined. In the magnetic tape MT2 for linear recording, in relation to the head magnetic field during recording, a configuration in which the crystal orientation axis of the magnetic layer 115 is inclined in the longitudinal direction of the magnetic tape MT2 can reduce the influence of the inclination of the crystal orientation axis on the recording characteristics compared to a configuration in which the crystal orientation axis of the magnetic layer 115 is inclined in the width direction of the magnetic tape MT2. In order to tilt the crystal orientation axis of the magnetic layer 115 in the longitudinal direction of the magnetic tape MT2, it is preferable to set the tilt direction of the column structure of the first underlayer 132A to the longitudinal direction of the magnetic tape MT2 as described above.

The inclination angle of the column structure is preferably greater than 0° and equal to or less than 60°. When the inclination angle is in the range of greater than 0° and equal to or less than 60°, the change in the tip shape of the columns contained in the first underlayer 132A is large and becomes approximately triangular, which tends to enhance the effect of the granular structure, reduce noise, and improve the SNR. On the other hand, when the inclination angle exceeds 60°, the change in the tip shape of the columns contained in the first underlayer 132A is small and it is difficult to obtain an approximately triangular shape, which tends to weaken the low-noise effect.

The average grain size of the columnar structure is 3 nm or more and 13 nm or less. If the average grain size is less than 3 nm, the average grain size of the columnar structure contained in the magnetic layer 115 will be small, and there is a risk that the ability of current magnetic materials to retain records will decrease. On the other hand, if the average grain size is 13 nm or less, noise can be suppressed and a better SNR can be obtained.

The average thickness of the first underlayer 132A is preferably 10 nm or more and 150 nm or less. If the average thickness of the first underlayer 132A is 10 nm or more, the (111) orientation of the face-centered cubic lattice structure of the first underlayer 132A is improved, and a better SNR can be obtained. On the other hand, if the average thickness of the first underlayer 132A is 150 nm or less, the column particle size can be prevented from increasing. Therefore, noise can be suppressed and a better SNR can be obtained. The average thickness of the first underlayer 132A is determined in the same manner as the magnetic layer 43 in the first embodiment. However, the magnification of the TEM image is appropriately adjusted according to the thickness of the first underlayer 132A.

The second underlayer 132B preferably has the same crystal structure as the magnetic layer 115. When the magnetic layer 115 contains a Co-based alloy, the second underlayer 132B preferably contains a material having a hexagonal close-packed (hcp) structure similar to the Co-based alloy, and the c-axis of the structure is preferably oriented perpendicular to the film surface (i.e., in the film thickness direction). This is because it can increase the orientation of the magnetic layer 115 and relatively well match the lattice constants of the second underlayer 132B and the magnetic layer 115. As a material having a hexagonal close-packed structure, it is preferable to use a material containing Ru, and specifically, Ru alone or a Ru alloy is preferable. As the Ru alloy, for example, Ru alloy oxides such as Ru-SiO ₂ , Ru-TiO ₂ , or Ru-ZrO ₂ can be mentioned.

The average thickness of the second underlayer 132B may be thinner than that of an underlayer in a typical magnetic recording medium (e.g., an underlayer containing Ru), and can be, for example, 1 nm or more and 5 nm or less. Since the seed layer 131 and the first underlayer 132A having the above-mentioned configuration are provided under the second underlayer 132B, a good SNR can be obtained even if the average thickness of the second underlayer 132B is as thin as described above. The average thickness of the second underlayer 132B is determined in the same manner as the magnetic layer 43 in the first embodiment. However, the magnification of the TEM image is appropriately adjusted according to the thickness of the second underlayer 132B.

The average thickness t _T , the width change, and the loss modulus of the base layer 111 of the magnetic tape MT2 in the third embodiment are similar to those in the first embodiment.

The data band and servo band of the magnetic layer 115 in the third embodiment are the same as those in the first embodiment. That is, the details of the data band and servo band of the magnetic layer 115 in the third embodiment are as described in 2. (2) above.

(3) Effects

The explanation of the effects described in (5) of 2 above also applies to the third embodiment. That is, in the magnetic tape MT2 according to the third embodiment, as in the first embodiment, even if the magnetic tape MT2 is stored or run in a high-temperature environment for a long period of time (for example, 10 years), the width change of the magnetic tape MT2 can be corrected by adjusting the running tension of the magnetic tape MT2. Also, even if the width of the magnetic tape MT2 changes in a high-temperature environment, the width change can be accommodated by adjusting the azimuth angle θ of the data write head. Thus, the magnetic tape MT2 according to the third embodiment can accommodate width changes that may occur in a high-temperature environment, and therefore the magnetic tape MT2 according to the third embodiment is suitable for storage and running in a high-temperature environment.

The magnetic tape MT2 according to the third embodiment includes a seed layer 131 and a first underlayer 132A between a base layer 111 and a second underlayer 132B. The seed layer 131 contains Cr, Ni, and Fe, has a face-centered cubic lattice structure, and is preferentially oriented so that the (111) plane of this face-centered cubic structure is parallel to the surface of the base layer 111. The first underlayer 132A contains Co and O, and has a columnar structure in which the ratio of the average atomic concentration of O to the average atomic concentration of Co is 1 or more, and the average grain size is 3 nm or more and 13 nm or less. This makes it possible to realize a magnetic layer 115 with good crystal orientation and high coercivity by reducing the thickness of the second underlayer 132B and using as little Ru, which is an expensive material, as possible.

The Ru contained in the second underlayer 132B has the same hexagonal close-packed lattice structure as Co, the main component of the magnetic layer 115. Therefore, Ru has the effect of improving the crystal orientation of the magnetic layer 115 and promoting granularity at the same time. In addition, in order to further improve the crystal orientation of the Ru contained in the second underlayer 132B, the first underlayer 132A and the seed layer 131 are provided under the second underlayer 132B. In the magnetic tape MT2 according to the third embodiment, the first underlayer 132A containing inexpensive CoO with a face-centered cubic lattice structure achieves almost the same effect (function) as the second underlayer 132B containing Ru. Therefore, the thickness of the second underlayer 132B can be made thin. In addition, in order to improve the crystal orientation of the first underlayer 132A, the seed layer 131 containing Cr, Ni and Fe is provided.

5. Modifications

[Modification 1]
In the above first embodiment, the magnetic tape cartridge 10 is a one-reel type cartridge, but it may be a two-reel type cartridge.

Figure 31 is an exploded perspective view showing an example of the configuration of a two-reel type cartridge 321. The cartridge 321 comprises an upper half 302 made of synthetic resin, a transparent window member 323 that fits into and is fixed to a window portion 302a opened on the upper surface of the upper half 302, a reel holder 322 that is fixed to the inside of the upper half 302 and prevents the reels 306 and 307 from floating up, a lower half 305 that corresponds to the upper half 302, the reels 306 and 307 that are stored in the space formed by combining the upper half 302 and the lower half 305, the magnetic tape MT wound on the reels 306 and 307, a front lid 309 that closes the front opening formed by combining the upper half 302 and the lower half 305, and a back lid 309A that protects the magnetic tape MT exposed at this front opening.

Reels 306 and 307 are used to wind magnetic tape MT. Reel 306 comprises a lower flange 306b having a cylindrical hub portion 306a in the center around which magnetic tape MT is wound, an upper flange 306c of approximately the same size as lower flange 306b, and a reel plate 311 sandwiched between hub portion 306a and upper flange 306c. Reel 307 has the same configuration as reel 306.

The window member 323 has mounting holes 323a at positions corresponding to the reels 306 and 307 for attaching reel holders 322, which are reel holding means for preventing the reels from floating up. The magnetic tape MT is the same as the magnetic tape MT in the first embodiment.

[Modification 2]
The magnetic tape MT1 according to the second embodiment may further include an underlayer between the base layer 111 and the SUL 112. Since the SUL 112 has an amorphous state, it does not play a role in promoting epitaxial growth of the layer formed on the SUL 112, but it is required not to disturb the crystal orientation of the first and second underlayers 114A and 114B formed on the SUL 112. For this purpose, it is preferable that the soft magnetic material has a fine structure that does not form columns, but if the influence of degassing such as moisture from the base layer 111 is large, the soft magnetic material may become coarse and disturb the crystal orientation of the first and second underlayers 114A and 114B formed on the SUL 112. In order to suppress the influence of degassing such as moisture from the base layer 111, it is preferable to provide an underlayer having an amorphous state, which contains an alloy containing Ti and Cr, between the base layer 111 and the SUL 112, as described above. As a specific configuration of this underlayer, a configuration similar to that of the first seed layer 113A of the second embodiment can be adopted.

The magnetic tape MT1 does not have to include at least one of the second seed layer 113B and the second underlayer 114B. However, from the viewpoint of improving the SNR, it is more preferable to include both the second seed layer 113B and the second underlayer 114B.

The magnetic tape MT1 may be provided with an APC-SUL (Antiparallel Coupled SUL) instead of a single-layer SUL.

6. Example

　Below, the present technology will be explained in detail using examples, but the present technology is not limited to these examples.

In the following examples and comparative examples, the loss modulus of the base layer of the magnetic tape is a value determined by the measurement method described in the first embodiment.

[Width change amount]
The amount of change in width was determined by the measurement method described in the first embodiment.

[Method of calculating the movement angle of a drive head arranged at an angle]
40 is a schematic diagram for explaining a method for calculating the movement angle of a tilted drive head, which is the movement angle of the drive head required to deal with width changes assumed when the disk is stored in a high-temperature environment.
The left side of Fig. 40 shows the distance (h) between the two servo read heads of the drive head, the servo band pitch (SP), and the tilt angle (10°) of the drive head for the initial (before width change) magnetic tape. In the case of the left side of Fig. 34, Cos10°=SP/h.
The right side of Figure 40 shows the servo band pitch (SP-ΔSP), the drive head movement angle (α), and the tilt angle (10°+α) after the drive head moves on the magnetic tape after the servo band pitch has narrowed (after the width has changed). In the case on the right side of Figure 40, Cos(10°+α)=(SP-ΔSP)/h. From this formula, the drive head movement angle (α) is calculated as follows:
10° + α = Cos-1 [(SP-ΔSP)/h]
α=Cos−1[(SP−ΔSP)/h]−10°

[Running characteristics after rewinding and long-term storage]
After storing the magnetic recording cartridge for two weeks at 65°C and 40% RH, the magnetic tape was wound around the take-up reel 52 of the data recording and reproducing device 50, and the magnetic tape was reversed inward and outward while being stored for another two weeks. After that, the magnetic tape was recorded and reproduced over the entire surface using the data recording and reproducing device 50, and the running characteristics were given a judgment value based on the following three-level criteria. The evaluations "B" and "C" indicate undesirable judgment results. When the magnetic tape was able to be recorded and reproduced over the entire surface, the amount of change in width in the data band at the center of the width of the magnetic tape from before storage was measured, and the difference between the part with the smallest width and the part with the largest width was calculated.
A: No abnormality occurred (no failure occurred).
B: After several runs, the servo cannot be read and the system stops due to an error.
C: The servo cannot be read and a system error occurs, causing an immediate stop.

[Example 1]
(Preparation process of paint for forming magnetic layer)
The magnetic layer coating material was prepared as follows. First, the first composition having the following composition was mixed with an extruder. Next, the mixed first composition and the second composition having the following composition were added to a stirring tank equipped with a disperser and premixed. Then, the mixture was further mixed with a sand mill and filtered to prepare the magnetic layer coating material.

(First composition)
Barium ferrite ( _BaFe12O19 ) magnetic powder (hexagonal plate shape, average aspect ratio 3.0, average particle volume ^{1500 nm3} ₎ : 100 parts by mass Vinyl chloride resin (cyclohexanone solution 30% by mass): 35 parts by mass (vinyl chloride resin: degree of polymerization 300, number average molecular weight Mn = 10,000, contains _OSO3K = 0.07 mmol/g and secondary OH = 0.3 mmol/g as polar groups)
Polyurethane resin (resin solution: polyurethane resin content 30% by mass, cyclohexanone content 70% by mass): 10 parts by mass (polyurethane resin: number average molecular weight Mn=25,000, glass transition temperature Tg=110° C.) Aluminum oxide powder: 7.5 parts by mass (α-Al ₂ O ₃ , average particle size 80 μm)

(Second Composition)
Carbon black: 2.0 parts by mass (manufactured by Tokai Carbon Co., Ltd., product name: Seast S, arithmetic mean particle diameter 70 nm)
Polyurethane resin (resin solution: polyurethane resin content 30% by mass, cyclohexanone content 70% by mass): 5.0 parts by mass (polyurethane resin: number average molecular weight Mn = 25,000, glass transition temperature Tg = 110°C) n-Butyl stearate: 2 parts by mass Methyl ethyl ketone: 121.0 parts by mass Toluene: 121.0 parts by mass Cyclohexanone: 116.0 parts by mass

To the magnetic layer-forming paint prepared as above, 3.3 parts by mass of polyisocyanate (product name: Coronate L, manufactured by Tosoh Corporation) and 2 parts by mass of stearic acid were added as a curing agent.

(Preparation process of paint for forming base layer)
The paint for forming the undercoat layer was prepared as follows. First, the third composition having the following composition was mixed with an extruder. Next, the mixed third composition and the fourth composition having the following composition were added to a stirring tank equipped with a disperser and premixed. Then, further mixing was performed with a dyno mill and filtering was performed to prepare the paint for forming the undercoat layer.

(Third Composition)
Acicular iron oxide powder: 100 parts by mass (α-Fe ₂ O ₃ , average major axis length 0.11 μm)
Vinyl chloride resin (cyclohexanone solution 30% by mass): 46 parts by mass (vinyl chloride resin: degree of polymerization 300, number average molecular weight Mn = 10,000, contains OSO ₃ K = 0.07 mmol/g and secondary OH = 0.3 mmol/g as polar groups)
Aluminum oxide powder: 3 parts by mass (α-Al ₂ O ₃ , average particle size 0.1 μm)

(Fourth Composition)
Carbon black: 30 parts by weight (manufactured by Asahi Carbon Co., Ltd., product name: #80)
Polyurethane resin (resin solution: polyurethane resin content 30% by mass, cyclohexanone content 70% by mass): 40 parts by mass (polyurethane resin: number average molecular weight Mn = 25,000, glass transition temperature Tg = 110°C) n-Butyl stearate: 2 parts by mass Methyl ethyl ketone: 108.2 parts by mass Toluene: 108.2 parts by mass Cyclohexanone: 100.0 parts by mass

To the base layer forming paint prepared as above, 1.5 parts by mass of polyisocyanate (product name: Coronate L, manufactured by Tosoh Corporation) and 2.0 parts by mass of stearic acid were added as a curing agent.

(Preparation of paint for forming back layer)
The paint for forming the back layer was prepared as follows. The following raw materials were mixed in a stirring tank equipped with a disperser and filtered to prepare the paint for forming the back layer. Carbon black (manufactured by Asahi Carbon Co., Ltd., product name: #80): 100 parts by mass Polyester polyurethane: 100 parts by mass (manufactured by Nippon Polyurethane Co., Ltd., product name: N-2304)
Methyl ethyl ketone: 500 parts by weight Toluene: 400 parts by weight Cyclohexanone: 100 parts by weight Polyisocyanate (product name: Coronate L, manufactured by Tosoh Corporation): 10 parts by weight

(Film forming process)
Using the coating material prepared as described above, an underlayer and a magnetic layer were formed on one main surface of a long polymer film serving as a non-magnetic support in the following manner.

First, the base layer was formed by applying the paint for forming the base layer onto the polymer film that would become the base layer and drying it. The application conditions were adjusted so that the average thickness of the base layer after calendaring would be 0.82 μm. The polymer film used was reinforced PET (trade name "SPALTAN" (registered trademark), manufactured by Toray Industries, Inc.) with an average thickness of 4.0 μm.

Next, the magnetic layer-forming paint was applied onto the underlayer and dried to form a magnetic layer on the underlayer. The application conditions were adjusted so that the average thickness of the magnetic layer after calendaring would be 0.08 μm. When the magnetic layer-forming paint was dried, the magnetic powder was magnetically oriented in the thickness direction of the polymer film by a neodymium magnet. The drying conditions (drying temperature and drying time) of the magnetic layer-forming paint were adjusted, and the squareness ratio in the longitudinal direction was set to 34%.

Next, a back layer was formed by applying a paint for forming a back layer to the other main surface of the reinforced PET film on which the undercoat layer and magnetic layer were formed, and then drying it. At this time, the application conditions were adjusted so that the average thickness of the back layer after calendaring was 0.3 μm. In this way, a magnetic tape was obtained.

(Curing process)
Next, the magnetic tape was wound into a roll, and then subjected to a heat treatment in this state to harden the underlayer and the magnetic layer.

(Calendar process)
The magnetic tape thus obtained was then subjected to a calendar treatment to smooth the surface of the magnetic layer.

(Cutting process)
The magnetic tape obtained as described above was cut to a width of 1/2 inch (12.65 mm). As a result, the desired long magnetic tape (average thickness 5.2 μm) was obtained. The magnetic tape obtained as described above had the properties shown in Tables 1 and 2. For example, the loss modulus of the base layer of the magnetic tape at 65° C. was 0.07 GPa.

(Demagnetization process and servo pattern writing process)
The 1/2 inch wide magnetic tape was wound around a reel provided in a cartridge case to obtain a magnetic recording cartridge. After demagnetizing the magnetic tape, a servo pattern was written on the magnetic tape. The servo pattern included a first servo pattern and a second servo pattern that were asymmetric with respect to the width direction of the magnetic tape. In addition, the servo patterns in the adjacent servo bands had a phase difference. After storing the magnetic tape at 65°C, 40 RH% for 360 hours in a state where the magnetic tape was wound into the magnetic recording cartridge with a tension of 0.55 N, the magnetic tape housed in the magnetic recording cartridge was run so as to be wound into a magnetic recording and reproducing device (running in the so-called forward direction) and the servo band pitch was measured. In addition, the servo band pitch in the longitudinal direction was also measured for the magnetic tape housed in the magnetic recording cartridge in the initial state before storage, and the width change amount represented by the ratio of the servo band pitch after storage to the servo band pitch in the initial state was calculated. The results are shown in FIG. 33. In FIG. 33, the horizontal axis indicates the position in the longitudinal direction of the magnetic tape. In FIG. 33, the position of the end (BOT) on the outer periphery side (outside of the winding) of the magnetic tape wound on the tape reel is set to 0, and the position of the end (hereinafter also referred to as EOT) on the inner periphery side (inside of the winding) of the magnetic tape wound on the tape reel is set to 84, and the total length of the magnetic tape is divided into 84 equal parts. In FIG. 33, the vertical axis indicates the amount of width change after storage at 65° C., 40 RH%, and 360 hours, and indicates width after storage/width before storage. In FIG. 33, when the amount of width change indicates a negative value, it means that the width of the magnetic tape is narrower after storage than before storage, and when the amount of width change indicates a positive value, it means that the width of the magnetic tape is wider after storage than before storage. Note that the explanation of FIG. 33 applies to the horizontal and vertical axes in FIGS. 34 to 42 as well. As shown in FIG. 33, the amount of width change on the outer side of the winding at positions 0 to 20 is a negative value, the amount of width change on the inner side of the winding at positions 60 to 84 is a positive value, and the amount of width change is 0 ppm between positions 55 and 56.

[Example 2a]
A magnetic tape was obtained in the same manner as in Example 1, except that a polyethylene naphthalate film (hereinafter referred to as "PEN film") was used as the base layer material, the average thickness of the magnetic layer was 0.06 μm, and the average thickness of the underlayer was 0.84 μm. As in Example 1, a magnetic recording cartridge was manufactured using the magnetic tape, and a servo pattern was recorded on the magnetic tape. The results of the width change in the longitudinal direction of the magnetic tape are shown in FIG. 34. As shown in FIG. 34, the width change on the outside of the winding at positions 0 to 20 was a negative value, the width change on the inside of the winding at positions 60 to 84 was a positive value, and the width change was 0 ppm between positions 59 and 60.

Example 2b
A magnetic tape was obtained in the same manner as in Example 2, except that the calendering temperature was low, the average thickness of the magnetic layer was 0.07 μm, and the average thickness of the underlayer was 0.83 μm. In the same manner as in Example 1, a magnetic recording cartridge was manufactured using the magnetic tape, and a servo pattern was recorded on the magnetic tape.

[Example 2c]
A magnetic tape was obtained in the same manner as in Example 2, except that the drying temperature during coating was lowered by 5° C., the average thickness of the magnetic layer was 0.07 μm, and the average thickness of the underlayer was 0.83 μm. In the same manner as in Example 1, a magnetic recording cartridge was manufactured using the magnetic tape, and a servo pattern was recorded on the magnetic tape.

[Example 2d]
A magnetic tape was obtained in the same manner as in Example 2, except that the drying temperature during coating was lowered by 10° C., the average thickness of the magnetic layer was 0.05 μm, the average thickness of the underlayer was 0.45 μm, and the average thickness of the base layer was 4.40 μm. In the same manner as in Example 1, a magnetic recording cartridge was manufactured using the magnetic tape, and a servo pattern was recorded on the magnetic tape.

[Example 3]
A magnetic tape was obtained in the same manner as in Example 1, except that a polyether ether ketone film (hereinafter referred to as "PEEK film") was used as the base layer material, the average thickness of the back layer was 0.4 μm, the average thickness of the magnetic layer was 0.07 μm, the average thickness of the underlayer was 0.83 μm, and the average total thickness was 5.3 μm. As in Example 1, a magnetic recording cartridge was manufactured using the magnetic tape, and a servo pattern was recorded on the magnetic tape. The results of the width change in the longitudinal direction of the magnetic tape are shown in FIG. 35. As shown in FIG. 35, the width change on the outer side of the winding at positions 0 to 20 was a negative value, the width change on the inner side of the winding at positions 60 to 84 was a positive value, and the width change was 0 ppm between positions 37 and 38.

[Comparative Example 1a]
A magnetic tape was obtained in the same manner as in Example 2, except that a polyurethane resin with a Tg of 70°C was used as the resin blended in the paint for forming the magnetic layer and the paint for forming the undercoat layer, the amount of n-butyl stearate added to the magnetic layer was 1.5 parts by mass, and no polyisocyanate was added as a hardener to the paint for forming the undercoat layer. A magnetic recording cartridge was manufactured using the magnetic tape in the same manner as in Example 2, and a servo pattern was recorded on the magnetic tape. The results of the width change in the longitudinal direction of the magnetic tape are shown in FIG. 36. As shown in FIG. 36, the width change on the outer side of the winding at positions 0 to 20 was a positive value, and the width change on the inner side of the winding at positions 60 to 84 was also a positive value.

[Comparative Example 1b]
A tape was obtained in the same manner as in Comparative Example 1, except that the calendering temperature was 10° C. lower than that in Comparative Example 1.

[Comparative Example 2]
The average thickness of the base layer was 4.0 μm, the average thickness of the magnetic layer and the undercoat layer was 1.2 μm, the average thickness of the back layer was 0.4 μm, the average total thickness was 5.6 μm, a polyurethane resin with a Tg of 70° C. was used as the resin blended in the paint for forming the magnetic layer and the paint for forming the undercoat layer was used, and 1.7 parts by mass of polyisocyanate (product name: Coronate L, manufactured by Tosoh Corporation) was added as a hardener to the paint for forming the magnetic layer, and 0.75 parts by mass of polyisocyanate (product name: Coronate L, manufactured by Tosoh Corporation) was added as a hardener to the paint for forming the undercoat layer. A magnetic tape was manufactured in the same manner as in Example 1. A magnetic recording cartridge was manufactured using the magnetic tape in the same manner as in Example 1, and a servo pattern was recorded on the magnetic tape. The results of the width change in the longitudinal direction of the magnetic tape are shown in FIG. 37. As shown in FIG. 37, the width change on the outer side of the winding at positions 0 to 20 was a positive value, and the width change on the inner side of the winding at positions 60 to 84 was also a positive value.

[Comparative Example 3]
A magnetic tape was obtained in the same manner as in Example 2, except that a polyurethane resin with a Tg of 70° C. was used as the resin blended in the paint for forming the magnetic layer and the paint for forming the undercoat layer, and polyisocyanate was not added as a curing agent to the paint for forming the undercoat layer. A magnetic recording cartridge was manufactured using the magnetic tape in the same manner as in Example 2, and a servo pattern was recorded on the magnetic tape. The results of the width change in the longitudinal direction of the magnetic tape are shown in FIG. 38. As shown in FIG. 38, the width change on the outer side of the winding at positions 0 to 20 was a negative value, and the width change on the inner side of the winding at positions 60 to 84 was also a negative value.

[Comparative Example 4]
A magnetic tape was obtained in the same manner as in Example 2, except that an aramid film (hereinafter referred to as "ARAMID film") was used as the base layer, a polyurethane resin with a Tg of 70°C was used as the resin blended in the paint for forming the magnetic layer and the paint for forming the undercoat layer, and no polyisocyanate was added as a hardener to the paint for forming the undercoat layer. A magnetic recording cartridge was manufactured using the magnetic tape in the same manner as in Example 2, and a servo pattern was recorded on the magnetic tape. The results of the width change in the longitudinal direction of the magnetic tape are shown in Figure 39.

[Comparative Example 5]
A magnetic tape was obtained in the same manner as in Example 2, except that the average thickness of the base layer was 4.0 μm, the average thickness of the magnetic layer and the undercoat layer was 1.2 μm, the average thickness of the back layer was 0.4 μm, the average total thickness was 5.6 μm, a polyurethane resin with a Tg of 70° C. was used for the coating material for forming the magnetic layer and the coating material for forming the undercoat layer, and no polyisocyanate was added as a curing agent to the coating material for forming the undercoat layer. A magnetic recording cartridge was manufactured using the magnetic tape in the same manner as in Example 2, and a servo pattern was recorded on the magnetic tape.

Tables 1 and 2 show the configurations and evaluation results of the magnetic tapes of Examples 1 to 3 and Comparative Examples 1 to 5. Also, Figures 33 to 41 show the amount of width change in the longitudinal direction of each of the magnetic tapes of Examples 1 to 3 and Comparative Examples 1 to 4.

The results shown in Table 1 reveal the following:

All of the magnetic tapes of Examples 1 to 3 were stored for two weeks in an environment of 65°C and 40% RH, then rewound so that the outside and inside of the winding were reversed, and after another two weeks of storage in the same environment, the entire tape was played back using a magnetic recording and playback device. The running characteristics were rated A, with no Fails occurring, and good running characteristics were observed. This shows that the magnetic recording cartridge according to this technology is suitable for storage and use in high-temperature environments of 60°C or higher.

The results of the change in tape width in the longitudinal direction for Example 2b and Comparative Example 3 show that the sign of the width change Δout on the outside of the magnetic tape roll is different from the sign of the width change Δin on the inside of the magnetic tape roll, and therefore the magnetic recording tape can improve its running characteristics when rewound and stored for a long period of time.

Comparing Example 2b with Comparative Example 3, it can be seen that if (width change on the inside of the magnetic tape roll Δin) - (width change on the outside of the magnetic tape roll Δout) after storage for 360 hours at 65°C is 800 ppm or less, the running characteristics after rewinding and long-term storage can be improved.

Comparing Example 1 and Comparative Example 2, it can be seen that in region C, which is the two parts sandwiching the center line of the entire length of the magnetic tape when the entire length of the magnetic tape is divided into four equal parts, the width change Δ of the magnetic tape after storage at 65°C for 360 hours is 0 ppm, which means that the running characteristics can be improved by rewinding and storing for a long period of time.

Comparing Example 2b with Comparative Example 4, it can be seen that by having a base layer with a loss modulus of 0.40 GPa or less at 65°C, the running characteristics can be improved after rewinding and long-term storage.

Comparing Example 2a with Comparative Example 1b, it can be seen that with a fatty acid extraction rate of 45% or more, adhesion to the magnetic head is smooth and head damage is minimal.

　Although the embodiments and examples of the present technology have been specifically described above, the present technology is not limited to the above-mentioned embodiments and examples, and various modifications based on the technical concept of the present technology are possible.

For example, the configurations, methods, steps, shapes, materials, and values given in the above-mentioned embodiments and examples are merely examples, and different configurations, methods, steps, shapes, materials, and values may be used as necessary. In addition, the chemical formulas of compounds, etc. are representative, and are not limited to the valences, etc. given as long as they are general names of the same compounds.

Furthermore, the configurations, methods, processes, shapes, materials, and numerical values of the above-mentioned embodiments and examples can be combined with each other without departing from the spirit of this technology.

In addition, in this specification, a numerical range indicated using "~" indicates a range that includes the numerical values before and after "~" as the minimum and maximum values, respectively. In numerical ranges described in stages in this specification, the upper or lower limit of a numerical range of a certain stage may be replaced with the upper or lower limit of a numerical range of another stage. Unless otherwise specified, the materials exemplified in this specification may be used alone or in combination of two or more types.

The present technology can also be configured as follows.
[1]
A cartridge case;
Reel and
a magnetic recording medium wound around the reel and housed within the cartridge case;
When the magnetic recording medium was stored wound on the reel at 65° C. for 360 hours, the amount of change in width of the magnetic recording medium was measured over the entire length.
The sign of the width change amount Δout on the outer side of the magnetic recording medium is different from the sign of the width change amount Δin on the inner side of the magnetic recording medium, and
The amount of change in width is 0 ppm at any one of two regions on either side of a center line of the entire length of the magnetic recording medium when the entire length of the magnetic recording medium is divided into four equal regions, and
The magnetic recording medium has a base layer having a loss modulus of 0.40 GPa or less at 65° C.,
The magnetic recording medium includes a magnetic layer,
The magnetic recording medium contains a fatty acid,
A magnetic recording cartridge having an extraction rate of fatty acids defined by the following formula of 45% or more.
Extraction rate of fatty acid (%)=[amount of fatty acid extracted in 5 minutes (mg/m ² )/total amount of fatty acid extracted (mg/m ² )]×100
[2]
2. The magnetic recording cartridge according to claim 1, wherein the amount of width change Δin of the magnetic recording medium is a positive value, and the amount of width change Δout of the magnetic recording medium is a negative value.
[3]
The magnetic recording cartridge according to [1] or [2], wherein, when the total length of the magnetic recording medium in the longitudinal direction is taken as 100%, the amount of width change Δ of the magnetic recording medium after storage for 360 hours at 65° C. is 0 ppm at a position 25% to 75% from the outer end of the magnetic recording medium.
[4]
The magnetic recording cartridge according to any one of [1] to [3], wherein the magnetic recording medium has a width change amount Δin of the magnetic recording medium minus (width change amount Δout of the magnetic recording medium) of 800 ppm or less.
[5]
The magnetic recording cartridge according to any one of [1] to [4], wherein the storage modulus of the base layer at 65° C. is 8.0 GPa or less.
[6]
6. The magnetic recording cartridge according to any one of claims 1 to 5, wherein the base layer is made of PET (polyethylene terephthalate), PEN (polyethylene naphthalate), or PEEK (polyether ether ketone).
[7]
The magnetic recording cartridge according to any one of [1] to [6], wherein the average thickness _tT of the magnetic recording medium is 5.4 μm or less.
[8]
The magnetic recording cartridge according to any one of [1] to [7], wherein the average thickness t _B of the base layer is 4.6 μm or less.
[9]
The magnetic recording cartridge according to any one of claims 1 to 8, wherein the magnetic layer contains magnetic powder.
[10]
The magnetic recording cartridge according to any one of [1] to [9], wherein the magnetic layer contains particles having an abrasive effect, and the average height of protrusions formed by the particles is 8 nm or less.
The magnetic recording cartridge according to any one of [1] to [10], wherein the 5-minute extractable amount (mg/m ² ) of fatty acids is 3.0 mg/m ² or more.
[12]
The magnetic recording cartridge according to any one of [1] to [11], wherein the total amount of fatty acid extraction (mg/m ² ) is 5.0 mg/m ² or more.
[13]
13. The magnetic recording cartridge according to any one of claims 1 to 12, wherein the fatty acid is stearic acid.
[14]
The magnetic recording cartridge according to any one of [1] to [13], wherein the magnetic recording medium further contains a fatty acid ester, and the extraction rate of the fatty acid ester defined by the following formula is 60% or more.
Extraction rate of fatty acid ester (%)=[amount of fatty acid ester extracted in 5 minutes (mg/m ² )/total amount of fatty acid ester extracted (mg/m ² )]×100
[15]
The magnetic recording cartridge according to claim 14, wherein the 5-minute extractable amount (mg/m ² ) of the fatty acid ester is 10.0 mg/m ² or more.
[16]
The magnetic recording cartridge according to [14] or [15], wherein the total amount of fatty acid ester extract (mg/m ² ) is 12.0 mg/m ² or more.
[17]
17. The magnetic recording cartridge according to any one of claims 14 to 16, wherein the fatty acid ester is butyl stearate.
[18]
The magnetic recording cartridge according to any one of [1] to [17], wherein the average thickness of the magnetic layer is 0.08 μm or less.
[19]
The magnetic recording cartridge according to any one of [1] to [18], wherein the magnetic recording medium further comprises a non-magnetic layer having an average thickness of 1.0 μm or less.
[20]
A magnetic recording medium wound on a reel of a magnetic recording cartridge and accommodated in a cartridge case of the magnetic recording cartridge,
When the magnetic recording medium was stored wound on the reel at 65° C. for 360 hours, the amount of change in width of the magnetic recording medium was measured over the entire length.
The sign of the width change amount Δout on the outer side of the magnetic recording medium is different from the sign of the width change amount Δin on the inner side of the magnetic recording medium, and
The amount of change in width is 0 ppm at any one of two regions on either side of a center line of the entire length of the magnetic recording medium when the entire length of the magnetic recording medium is divided into four equal regions, and
A base layer having a loss modulus of 0.40 GPa or less at 65°C,
A magnetic recording medium having a magnetic layer,
The magnetic recording medium contains a fatty acid,
A magnetic recording medium having an extraction rate of fatty acids defined by the following formula of 45% or more.
Extraction rate of fatty acid (%)=[amount of fatty acid extracted in 5 minutes (mg/m ² )/total amount of fatty acid extracted (mg/m ² )]×100

MT magnetic tape 10 magnetic recording cartridge 13 reel 41 base layer 42 undercoat layer 43 magnetic layer 44 back layer

Claims

A cartridge case;
Reel and
a magnetic recording medium wound around the reel and housed within the cartridge case;
When the magnetic recording medium was stored at 65° C. for 360 hours in a wound state on the reel, the amount of change in width of the magnetic recording medium was measured over the entire length of the magnetic recording medium.
The sign of the width change amount Δout on the outer side of the magnetic recording medium is different from the sign of the width change amount Δin on the inner side of the magnetic recording medium, and
The amount of change in width is 0 ppm at any one of two regions on either side of a center line of the entire length of the magnetic recording medium when the entire length of the magnetic recording medium is divided into four equal regions, and
The magnetic recording medium has a base layer having a loss modulus of 0.40 GPa or less at 65° C.,
The magnetic recording medium includes a magnetic layer,
The magnetic recording medium contains a fatty acid,
A magnetic recording cartridge having an extraction rate of fatty acids defined by the following formula of 45% or more.
Extraction rate of fatty acid (%)=[amount of fatty acid extracted in 5 minutes (mg/m 2 )/total amount of fatty acid extracted (mg/m 2 )]×100
The magnetic recording cartridge of claim 1, wherein the width change amount Δin of the magnetic recording medium is a positive value, and the width change amount Δout of the magnetic recording medium is a negative value.
The magnetic recording cartridge according to claim 1, in which the width change Δ of the magnetic recording medium after storage for 360 hours at 65°C is 0 ppm at a position 25% to 75% from the outer end of the magnetic recording medium when the total length of the magnetic recording medium in the longitudinal direction is 100%.
The magnetic recording cartridge according to claim 1, wherein the magnetic recording medium has a width change amount Δin of the magnetic recording medium minus a width change amount Δout of the magnetic recording medium of 800 ppm or less.
The magnetic recording cartridge of claim 1, wherein the storage modulus of the base layer at 65°C is 8.0 GPa or less.
The magnetic recording cartridge of claim 1, wherein the base layer is formed from PET (polyethylene terephthalate), PEN (polyethylene naphthalate), or PEEK (polyether ether ketone).
2. The magnetic recording cartridge of claim 1, wherein the average thickness tT of said magnetic recording medium is 5.4 [mu]m or less.
2. The magnetic recording cartridge of claim 1, wherein the base layer has an average thickness, tB , of 4.6 [mu]m or less.
The magnetic recording cartridge of claim 1, wherein the magnetic layer includes magnetic powder.
The magnetic recording cartridge of claim 1, wherein the magnetic layer contains particles with an abrasive effect, and the average height of the protrusions formed by the particles is 8 nm or less.
2. The magnetic recording cartridge of claim 1, wherein the 5-minute extractable amount (mg/ m2 ) of fatty acids is 3.0 mg/ m2 or more.
2. The magnetic recording cartridge of claim 1, wherein the total fatty acid extractables (mg/ m2 ) is 5.0 mg/ m2 or greater.
The magnetic recording cartridge of claim 1, wherein the fatty acid is stearic acid.
2. The magnetic recording cartridge according to claim 1, wherein the magnetic recording medium further contains a fatty acid ester, and the extraction rate of the fatty acid ester defined by the following formula is 60% or more.
Extraction rate of fatty acid ester (%)=[amount of fatty acid ester extracted in 5 minutes (mg/m 2 )/total amount of fatty acid ester extracted (mg/m 2 )]×100
15. The magnetic recording cartridge of claim 14, wherein the 5-minute extractable amount (mg/ m2 ) of fatty acid ester is 10.0 mg/ m2 or more.
15. The magnetic recording cartridge of claim 14, wherein the total extractable amount (mg/ m2 ) of fatty acid esters is 12.0 mg/ m2 or greater.
The magnetic recording cartridge of claim 14, wherein the fatty acid ester is butyl stearate.
The magnetic recording cartridge of claim 1, wherein the average thickness of the magnetic layer is 0.08 μm or less.
The magnetic recording cartridge of claim 1, wherein the magnetic recording medium further has a non-magnetic layer having an average thickness of 1.0 μm or less.
A magnetic recording medium wound on a reel of a magnetic recording cartridge and accommodated in a cartridge case of the magnetic recording cartridge,
When the magnetic recording medium was stored at 65° C. for 360 hours in a wound state on the reel, the amount of change in width of the magnetic recording medium was measured over the entire length of the magnetic recording medium.
The sign of the width change amount Δout on the outer side of the magnetic recording medium is different from the sign of the width change amount Δin on the inner side of the magnetic recording medium, and
The amount of change in width is 0 ppm at any one of two regions on either side of a center line of the entire length of the magnetic recording medium when the entire length of the magnetic recording medium is divided into four equal regions, and
A base layer having a loss modulus of 0.40 GPa or less at 65°C,
A magnetic recording medium having a magnetic layer,
The magnetic recording medium contains a fatty acid,
A magnetic recording medium having an extraction rate of fatty acids defined by the following formula of 45% or more.
Extraction rate of fatty acid (%)=[amount of fatty acid extracted in 5 minutes (mg/m 2 )/total amount of fatty acid extracted (mg/m 2 )]×100