JP6898962B2 - Magnetic tape device - Google Patents

Description

The present invention relates to a magnetic tape device.

A magnetic recording / reproducing device that records data on a magnetic recording medium and / or reads (reproduces) the recorded data is roughly classified into a magnetic disk device and a magnetic tape device. A typical example of a magnetic disk device is an HDD (Hard Disk Drive). In a magnetic disk device, a magnetic disk is used as a magnetic recording medium. On the other hand, in a magnetic tape device, a magnetic tape is used as a magnetic recording medium.

In both the magnetic disk device and the magnetic tape device, narrowing the recording track width is preferable for increasing the recording capacity (increasing the capacity). On the other hand, as the recording track width is narrowed, the signal of the adjacent track is likely to be mixed with the signal of the track to be read during reproduction, so that it is difficult to maintain the reproduction quality such as SNR (Signal-to-Noise Ratio). Become. In this regard, in recent years, it has been proposed to improve the reproduction quality by two-dimensionally reading the signal of the recording track by a plurality of reading elements (also referred to as “reproduction elements”) (for example, Patent Document 1). See ~ 3). If the reproduction quality can be improved in this way, the reproduction quality can be maintained even if the recording track width is narrowed, so that the recording capacity can be increased by narrowing the recording track width.

Japanese Unexamined Patent Publication No. 2016-110680 Japanese Unexamined Patent Publication No. 2011-134372 U.S. Pat. No. 7,755,863

Patent Documents 1 and 2 study a magnetic disk device. On the other hand, magnetic tape has recently attracted attention as a data storage medium for storing a large amount of data for a long period of time. However, the magnetic tape device is generally a sliding type device in which data reading (reproduction) is performed by contacting and sliding the magnetic tape and the reading element. Therefore, the relative position between the reading element and the track to be read tends to fluctuate during reproduction, and improvement of reproduction quality tends to be more difficult than that of a magnetic disk device. Although Patent Document 3 describes a magnetic tape device (tape drive), it does not show a specific means for improving the reproduction quality of the magnetic tape device.

One aspect of the present invention provides a magnetic tape device capable of improving reproduction quality.

One aspect of the present invention is
With magnetic tape
With the reading element unit
Extractor and
Including
The magnetic tape has a magnetic layer containing a ferromagnetic powder and a binder on a non-magnetic support.
The magnetic layer has a servo pattern and has a servo pattern.
The above ferromagnetic powder is a hexagonal ferrite powder.
Peak intensity of the diffraction peak on the (114) plane of the hexagonal ferrite crystal structure obtained by X-ray diffraction analysis of the magnetic layer using the In-Plane method Int (114) with respect to the peak intensity Int of the diffraction peak on the (110) plane. The intensity ratio of (110) (Int (110) / Int (114); hereinafter, also referred to as “XRD (X-ray diffraction) intensity ratio”) is 0.5 or more and 4.0 or less.
The vertical angular ratio of the magnetic tape is 0.65 or more and 1.00 or less.
The reading element unit has a plurality of reading elements that read data from a specific track area including a track to be read among the track areas included in the magnetic tape by a linear scan method.
The extraction unit performs waveform equalization processing on each of the reading results for each reading element according to the amount of displacement between the magnetic tape and the reading element unit. Extract the data derived from the track to be read and
The amount of deviation is determined according to the result obtained by reading the servo pattern of the magnetic layer of the magnetic tape by the servo element.
Regarding.

In one aspect, some of the plurality of reading elements may overlap each other in the traveling direction of the magnetic tape.

In one aspect, the specific track region can be a region including the read target track and an adjacent track adjacent to the read target track, and each of the plurality of reading elements is connected to the magnetic tape. When the positional relationship changes, both the read target track and the adjacent track can be straddled.

In one aspect, the plurality of reading elements can be arranged side by side in close proximity to each other in the width direction of the magnetic tape.

In one aspect, the plurality of reading elements can be contained within the reading target track in the width direction of the magnetic tape.

In one aspect, the waveform equalization process can be performed using a tap coefficient determined according to the deviation amount.

In one aspect, for each of the plurality of reading elements, the ratio of the overlapping area with the reading target track and the overlapping area with the adjacent track adjacent to the reading target track can be specified from the deviation amount. The tap coefficient can be determined according to the specified ratio.

In one aspect, the reading operation of the reading element unit can be performed in synchronization with the reading operation performed by the servo element.

In one aspect, the extraction unit can have a two-dimensional FIR (Finite Impulse Response) filter, and the two-dimensional FIR filter performs the waveform equalization processing on each of the reading results for each reading element. By synthesizing each of the obtained results, data derived from the read target track can be extracted from the read result.

In one aspect, the plurality of reading elements can be a pair of reading elements.

In one aspect, the vertical angular ratio of the magnetic tape can be 0.65 or more and 0.90 or less.

In one aspect, the activated volume of the hexagonal ferrite powder ^{can be 1600 nm 3} or less.

According to one aspect of the present invention, it is possible to provide a magnetic tape device capable of reproducing data recorded on a magnetic tape with high reproduction quality.

It is a schematic block diagram which shows an example of the whole structure of a magnetic tape reader. It is a schematic plan view which shows an example of the schematic structure of the reading head included in the magnetic tape reader, and the magnetic tape in a plan view. It is a schematic plan view which shows an example of the schematic structure of the reading element unit and a magnetic tape in a plan view. It is a schematic plan view which shows an example of the schematic structure of the track area and a pair of reading elements in a plan view. It is a graph which shows an example of the correlation of the SNR and the track offset about each of the single reading element data and the 1st composite data under the 1st condition. It is a graph which shows an example of the correlation of the SNR and the track offset about each of the single reading element data and the 2nd composite data under the 2nd condition. It is a block diagram which shows an example of the main part structure of the electric system hardware of a magnetic tape reader. It is a conceptual diagram provided for the explanation of the calculation method of the deviation amount. It is a flowchart which shows an example of the flow of a magnetic tape reading process. It is a conceptual diagram which provides the explanation of the processing performed by the 2D FIR filter of the extraction part. It is a schematic plan view which shows an example of the state which the reading element unit straddles a reading target track and a 2nd noise mixing source track. It is a schematic plan view which shows the 1st modification of a reading element unit. It is a schematic plan view which shows the 2nd modification of a reading element unit. An example of arranging the servo pattern of the LTO (Linear-Tape-Open) Ultram format tape is shown. It is explanatory drawing of the angle α about the edge shape of a servo pattern. It is explanatory drawing of the angle α about the edge shape of a servo pattern. An example of the edge shape of the servo pattern is shown. An example of the servo pattern is shown. An example of the servo pattern is shown. An example of the servo pattern is shown. It is a conceptual diagram provided for the explanation of the 1st conventional example. It is a conceptual diagram which provides the explanation of the 2nd prior art example. It is a figure which shows an example of the 2D image of the reproduction signal obtained from a single reading element.

The magnetic tape device according to one aspect of the present invention includes a magnetic tape, a reading element unit, and an extraction unit.

Regarding the reading of data from the magnetic tape, in the conventional example shown in FIG. 21, the elongated reading head 200 includes a plurality of reading elements 202 along the longitudinal direction. A plurality of tracks 206 are formed on the magnetic tape 204. The reading head 200 is arranged so that the longitudinal direction coincides with the width direction of the magnetic tape 204. Further, each of the plurality of reading elements 202 is assigned to each of the plurality of tracks 206 in a one-to-one relationship, and data is read from the tracks 206 at opposite positions.

However, the magnetic tape 204 usually expands and contracts due to changes in time, environment, tension, and the like. When the magnetic tape expands and contracts in the width direction of the magnetic tape 204, the centers of the reading elements 202 arranged at both ends in the longitudinal direction of the reading head 200 deviate from the center of the track 206. When the magnetic tape 204 is deformed by expanding and contracting in the width direction, in particular, among the plurality of reading elements 202, the reading element 202 closer to both ends of the reading head 200 is greatly affected by off-track. In order to reduce the influence of off-track, for example, a method of allowing a margin in the width of the track 206 can be considered. However, the wider the width of the track 206, the smaller the recording capacity of the magnetic tape 204.

Further, as an example, as in the conventional example shown in FIG. 22, the reading head 200 is usually provided with the servo element 208. The servo pattern given in advance to the magnetic tape 204 along the traveling direction of the magnetic tape 204 is read by the servo element 208. Then, from the servo signal obtained by reading the servo pattern by the servo element 208, the reading element 202 travels on the magnetic tape 204 by a control device (not shown), for example, at regular time intervals. Is identified. As a result, the PES (Position Error Signal) in the width direction of the magnetic tape 204 is detected by the control device.

In this way, when the traveling position of the reading element 202 is specified by the control device, the control device performs feedback control on the actuator for the reading head (not shown) based on the specified traveling position. As a result, tracking of the magnetic tape 204 in the width direction is realized.

However, even if tracking is performed, steep vibrations, high-frequency components of jitter, and the like cause an increase in PES, which leads to deterioration in reproduction quality of data read from the track to be read.
On the other hand, in the magnetic tape device according to one aspect of the present invention, the reading element unit reads data from a specific track area including a read target track among the track areas included in the magnetic tape by a linear scan method. The extraction unit has a reading element, and the extraction unit performs waveform equalization processing on each of the reading results for each reading element according to the amount of displacement between the magnetic tape and the reading element unit. From the reading result, data derived from the reading target track is extracted. As a result, according to the magnetic tape device, it is possible to improve the reproduction quality of the data read from the read target track as compared with the case where the data is read from the read target track by only a single reading element by the linear scan method. As a result, it is possible to increase the allowable amount of deviation (track offset amount) that can ensure good reproduction quality.
Further, the above deviation amount is detected by reading the servo pattern. However, if the error between the amount of deviation detected by reading the servo pattern and the amount of deviation actually occurring is large, the waveform or the like corresponding to the above amount of deviation will be obtained with respect to the reading result read at each part of the magnetic tape. The conversion process may not always be the optimum waveform equalization process. On the other hand, if the error between the amount of deviation detected by reading the servo pattern and the amount of deviation actually occurring can be reduced, the waveform equalization more suitable for the reading result read at each location can be achieved. It becomes possible to perform processing. As a result, it is possible to increase the allowable amount of deviation that can ensure good reproduction quality by the above waveform equalization processing.
As described above, the fact that the permissible amount of deviation that can ensure good reproduction quality can be increased means that high reproduction quality (for example, high SNR, low error rate, etc.) can be achieved even if the track margin (recording track width-reproduction element width) is reduced. ) Can contribute to enabling reproduction. The fact that the track margin can be reduced can contribute to reducing the recording track width and increasing the number of recording tracks that can be arranged in the width direction of the magnetic tape, that is, increasing the capacity.
Regarding the above points, the XRD intensity ratio of the magnetic tape on which data is read by the magnetic tape device is 0.5 or more and 4.0 or less, and the vertical square type ratio is 0.65 or more and 1.00 or less. It is considered that this contributes to improving the accuracy of reading the servo pattern and identifying the position of the reading element. It is presumed that this leads to reducing the error between the amount of deviation detected by reading the servo pattern and the amount of deviation actually occurring. This point will be described later.

Hereinafter, the magnetic tape device will be described in more detail. Hereinafter, the magnetic tape device may be described with reference to the drawings. However, the magnetic tape device is not limited to the mode shown in the drawings.

[Structure of magnetic tape device and magnetic tape reading process]
As an example, as shown in FIG. 1, the magnetic tape device 10 includes a magnetic tape cartridge 12, a transport device 14, a reading head 16, and a control device 18.

The magnetic tape device 10 is a device that pulls out the magnetic tape MT from the magnetic tape cartridge 12 and reads data from the pulled out magnetic tape MT by a linear scan method using a reading head 16. Reading data can also be referred to as playing back data.

The control device 18 controls the entire magnetic tape device 10. In one aspect, the control performed by the control device 18 can be realized by an ASIC (Application Specific Integrated Circuit). Further, in one aspect, the control performed by the control device 18 can be realized by an FPGA (Field-Programmable Gate Array). Further, the control performed by the control device 18 may be realized by a computer including a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory). Further, the above control may be realized by a combination of two or more of AISC, FPGA, and a computer.

The transport device 14 is a device that selectively transports the magnetic tape MT in the forward direction and the reverse direction, and includes a delivery motor 20, a take-up reel 22, a take-up motor 24, a plurality of guide rollers GR, and a control device 18. ing.

A cartridge reel CR is provided in the magnetic tape cartridge 12. A magnetic tape MT is wound around the cartridge reel CR. The delivery motor 20 rotates and drives the cartridge reel CR in the magnetic tape cartridge 12 under the control of the control device 18. The control device 18 controls the delivery motor 20 to control the rotation direction, rotation speed, rotation torque, and the like of the cartridge reel CR.

When the magnetic tape MT is wound by the take-up reel 22, the control device 18 rotates the delivery motor 20 so that the magnetic tape MT travels in the forward direction. The rotation speed, rotation torque, and the like of the delivery motor 20 are adjusted according to the speed of the magnetic tape MT wound by the take-up reel 22.

The take-up motor 24 rotates the take-up reel 22 under the control of the control device 18. The control device 18 controls the take-up motor 24 to control the rotation direction, rotation speed, rotation torque, and the like of the take-up reel 22.

When the magnetic tape MT is wound by the take-up reel 22, the control device 18 rotates the take-up motor 24 so that the magnetic tape MT travels in the forward direction. The rotation speed, rotation torque, and the like of the take-up motor 24 are adjusted according to the speed of the magnetic tape MT taken up by the take-up reel 22.

By adjusting the rotation speed, rotation torque, and the like of each of the delivery motor 20 and the take-up motor 24 in this way, tension within a predetermined range is applied to the magnetic tape MT. Here, the “within the predetermined range” refers to, for example, a range of tension obtained by computer simulation and / or an actual machine test as a range of tension in which data can be read from the magnetic tape MT by the reading head 16.

When the magnetic tape MT is rewound to the cartridge reel CR, the control device 18 rotates the delivery motor 20 and the take-up motor 24 so that the magnetic tape MT travels in the opposite direction.

In one aspect, the tension of the magnetic tape MT is controlled by controlling the rotational speed, rotational torque, and the like of the delivery motor 20 and the take-up motor 24. Further, in one aspect, the tension of the magnetic tape MT may be controlled by using a dancer roller or by drawing the magnetic tape MT into the vacuum chamber.

Each of the plurality of guide rollers GR is a roller that guides the magnetic tape MT. The traveling path of the magnetic tape MT is defined by arranging a plurality of guide rollers GR separately at positions straddling the reading head 16 between the magnetic tape cartridge 12 and the take-up reel 22.

The reading head 16 includes a reading unit 26 and a holder 28. The reading unit 26 is held by the holder 28 so as to come into contact with the traveling magnetic tape MT.

As an example, as shown in FIG. 2, the magnetic tape MT includes a track region 30 and a servo pattern 32. The servo pattern 32 is a pattern used for detecting the position of the reading head 16 with respect to the magnetic tape MT. In the servo pattern 32, a first diagonal line 32A having a first predetermined angle (for example, 95 degrees) and a second diagonal line 32B having a second predetermined angle (for example, 85 degrees) are magnetic tape MT at both ends in the tape width direction. It is a pattern that is alternately arranged at a constant pitch (cycle) along the traveling direction of. The "tape width direction" referred to here refers to the width direction of the magnetic tape MT.

The track area 30 is an area in which data to be read is written, and is formed in the central portion of the magnetic tape MT in the tape width direction. The "central portion in the tape width direction" referred to here refers to, for example, a region between the servo pattern 32 at one end of the magnetic tape MT in the tape width direction and the servo pattern 32 at the other end. Hereinafter, for convenience of explanation, the "traveling direction of the magnetic tape MT" is simply referred to as the "traveling direction".

The reading unit 26 includes a servo element pair 36 and a plurality of reading element units 38. The holder 28 is formed in an elongated shape in the tape width direction, and the total length of the holder 28 in the longitudinal direction is longer than the width of the magnetic tape MT. The servo element pair 36 is arranged at both ends in the longitudinal direction of the holder 28, and the plurality of reading element units 38 are arranged at the central portion in the longitudinal direction of the holder 28.

The servo element pair 36 includes servo elements 36A and 36B. The servo element 36A is arranged at a position facing the servo pattern 32 at one end of the magnetic tape MT in the tape width direction, and the servo element 36B is attached to the servo pattern 32 at the other end of the magnetic tape MT in the tape width direction. It is located at the opposite position.

In the holder 28, a plurality of reading element units 38 are arranged along the tape width direction between the servo element 36A and the servo element 36B. The track area 30 includes a plurality of tracks at equal intervals in the tape width direction, and in a default state of the magnetic tape device 10, each of the plurality of reading element units 38 faces each track in the track area 30. Have been placed.

Therefore, the reading unit 26 and the magnetic tape MT move relative to each other in a straight line along the longitudinal direction of the magnetic tape MT, so that the data of each track in the track region 30 is the position among the plurality of reading element units 38. Is read by each of the corresponding reading element units 38 in a linear scan method. Further, in the linear scan method, the servo pattern 32 is read by the servo element pair 36 in synchronization with the reading operation of the reading element unit 38. That is, in one aspect of the linear scan method, the reading of the magnetic tape MT is performed in parallel by the plurality of reading element units 38 and the servo element pair 36.

Here, the above-mentioned "each track in the track area 30" refers to a track included in "each of a plurality of specific track areas including each track to be read among the track areas included in the magnetic tape".

The above-mentioned "default state of the magnetic tape device 10" refers to a state in which the magnetic tape MT is not deformed and the positional relationship between the magnetic tape MT and the reading head 16 is correct. Here, the "correct positional relationship" refers to, for example, a positional relationship in which the center of the magnetic tape MT in the tape width direction and the center of the reading head 16 in the longitudinal direction coincide with each other.

In one aspect, each of the plurality of reading element units 38 has the same configuration. Hereinafter, for convenience of explanation, one of the plurality of reading element units 38 will be described as an example. As an example, as shown in FIG. 3, the reading element unit 38 includes a pair of reading elements. In the example shown in FIG. 3, the "pair of reading elements" refers to the first reading element 40 and the second reading element 42. Each of the first reading element 40 and the second reading element 42 reads data from the specific track area 31 including the reading target track 30A in the track area 30.

In the example shown in FIG. 3, one specific track area 31 is shown for convenience of explanation. Actually, usually, a plurality of specific track areas 31 exist in the track area 30, and each specific track area 31 includes a read target track 30A. Then, one reading element unit 38 is assigned to each of the plurality of specific track regions 31. Specifically, one reading element unit 38 is assigned to each reading target track 30A of the plurality of specific track areas 31.

The specific track area 31 refers to three adjacent tracks. The first track of the three adjacent tracks is the read target track 30A in the track area 30. The second of the three adjacent tracks is the first noise mixing source track 30B, which is one of the adjacent tracks adjacent to the read target track 30A. The third of the three adjacent tracks is the second noise mixing source track 30C, which is one of the adjacent tracks adjacent to the read target track 30A. The reading target track 30A is a track at a position facing the reading element unit 38 in the track area 30. That is, the read target track 30A, in other words, refers to the track for which the data of the reading element unit 38 is read.

The first noise mixing source track 30B is adjacent to one side in the tape width direction with respect to the reading target track 30A, and is a track that becomes a mixing source of noise mixed in the data read from the reading target track 30A. is there. The second noise mixing source track 30C is adjacent to the other side in the tape width direction with respect to the reading target track 30A, and is a track that becomes a mixing source of noise mixed in the data read from the reading target track 30A. is there. Hereinafter, for convenience of explanation, when it is not necessary to distinguish between the first noise mixing source track 30B and the second noise mixing source track 30C, they are referred to as “adjacent tracks” without reference numerals.

In one aspect, in the track area 30, a plurality of specific track areas 31 are arranged at regular intervals in the tape width direction. For example, in the track area 30, 32 specific track areas 31 are arranged at regular intervals in the tape width direction, and one reading element unit 38 is assigned to each specific track area 31.

The first reading element 40 and the second reading element 42 are arranged in a state of being close to each other in the traveling direction and at a position where a part of the first reading element 40 overlaps in the traveling direction. In the default state of the magnetic tape device 10, the first reading element 40 is arranged at a position straddling the reading target track 30A and the first noise mixing source track 30B. In the default state of the magnetic tape device 10, the second reading element 42 is arranged at a position straddling the reading target track 30A and the first noise mixing source track 30B.

In the default state of the magnetic tape device 10, the area of the portion of the first reading element 40 facing the read target track 30A in a plan view is the first noise mixing source of the first reading element 40. It is larger than the area of the portion facing the truck 30B. On the other hand, in the default state of the magnetic tape device 10, the area of the portion of the second reading element 42 facing the first noise mixing source track 30B in the plan view is the area of the first reading element 40. It is larger than the area of the portion facing the read target track 30A.

The data read by the first reading element 40 is subjected to waveform equalization processing by the first equalizer 70 (see FIG. 7) described later. The data read by the second reading element 42 is subjected to waveform equalization processing by the second equalizer 72 (see FIG. 7) described later. Each of the data obtained by performing the waveform equalization processing by each of the first equalizer 70 and the second equalizer 72 is combined by being added by the adder 44.

In FIG. 3, a mode in which the reading element unit 38 has the first reading element 40 and the second reading element 42 is described as an example. However, for example, even if only one reading element of the pair of reading elements (hereinafter, also referred to as a single reading element) is used, a signal corresponding to the reproduced signal obtained from the reading element unit 38 can be obtained.

In this case, for example, as shown in FIG. 8 as an example, the plane position on the track calculated from the servo signal acquired by the servo element pair 36 in synchronization with the reproduction signal of the reproduction signal obtained from the single reading element. Assign to. Then, by repeating this while moving the single reading element in the tape width direction, a two-dimensional image of the reproduced signal (hereinafter, simply referred to as "two-dimensional image") is obtained. Here, the two-dimensional image or the reproduction signal forming a part of the two-dimensional image (for example, the reproduction signal corresponding to the positions of a plurality of tracks) is a signal corresponding to the reproduction signal obtained from the reading element unit 38. is there.

FIG. 23 shows an example of a two-dimensional image of a reproduced signal obtained by using a loop tester on a looped magnetic tape MT (hereinafter, also referred to as “loop tape”). Here, the loop tester refers to, for example, a device that conveys a loop tape in a state of being repeatedly brought into contact with a single reading element. In order to obtain a two-dimensional image as in the loop tester, a reel tester may be used, or an actual tape drive may be used. The "reel tester" referred to here refers to, for example, a device that conveys a magnetic tape MT in a reel form.

As described above, even if a conventional magnetic tape head that does not have a reading element unit in which a plurality of reading elements are mounted at close positions is used, the effect of the technique described in the present specification is quantitatively evaluated. be able to. Examples of an index for quantitatively evaluating the effect of the technique described in the present specification include SNR, error rate, and the like.

4 to 6 show the results obtained by the present inventors in an experiment. As an example, as shown in FIG. 4, a reading element pair 50 is arranged on the track region 49. The track area 49 includes a first track 49A, a second track 49B, and a third track 49C that are adjacent in the tape width direction. The reading element pair 50 includes a first reading element 50A and a second reading element 50B. The first reading element 50A and the second reading element 50B are arranged at positions close to each other in the tape width direction. Further, the first reading element 50A is arranged so as to face the second track 49B, which is the reading target track, and to fit in the second track 49B. Further, the second reading element 50B is arranged so as to face the first track 49A adjacent to one side of the second track 49B and to fit in the first track 49A.

FIG. 5 shows an example of the correlation between the SNR and the track offset for each of the single reading element data and the first composite data under the first condition. Further, FIG. 6 shows an example of the correlation between the SNR and the track offset for each of the single reading element data and the second composite data under the second condition.

Here, the single reading element data is the data obtained by subjecting the data read by the first reading element 50A to waveform equalization processing, similarly to the first reading element 40 shown in FIG. Point to. The first condition refers to a condition that the reading element pitch is 700 nm (nanometers). The second condition refers to a condition in which the reading element pitch is 500 nm. The reading element pitch refers to the pitch of the first reading element 50A and the second reading element 50B in the tape width direction, as shown in FIG. 4 as an example. As shown in FIG. 4, the track offset refers to the amount of deviation between the center of the second track 49B in the tape width direction and the center of the first reading element 50A in the track width direction.

The first composite data refers to data synthesized by adding the first waveform equalization processed data and the second waveform equalization processed data obtained under the first condition. The first waveform equalization processed data is the data obtained by subjecting the data read by the first reading element 50A to the waveform equalization processing, similarly to the first reading element 40 shown in FIG. Point to. The second waveform equalization processed data is the data obtained by subjecting the data read by the second reading element 50B to the waveform equalization processing, similarly to the second reading element 42 shown in FIG. Point to. The second composite data refers to data synthesized by adding the first waveform equalization processed data and the second waveform equalization processed data obtained under the second condition.

Comparing the SNR of the first composite data shown in FIG. 5 with the SNR of the second composite data shown in FIG. 6, the SNR of the first composite data has a track offset of about −0.4 μm (micrometer) to 0.2 μm. The SNR of the second composite data does not drop sharply in the middle as in the graph of the SNR of the first composite data, whereas the SNR of the second composite data drops sharply in the middle of the graph. Each of the SNR of the first composite data and the SNR of the second composite data is higher than the SNR of the single read element data, and in particular, the SNR of the second composite data is the single read element data in the entire range of the track offset. Higher than the SNR of.

From the experimental results shown in FIGS. 5 and 6, the present inventors have compared the first reading element 50A and the second reading element 50B in the tape width direction as compared with the case where the data is read only by the first reading element 50A. It was found that it is preferable to read the data in a state of being close to the device. The term "closed state" as used herein means, for example, that the first reading element 50A and the second reading element 50B do not come into contact with each other, and the SNR is higher than the SNR of the single reading element data in the entire range of the track offset. Refers to the state in which they are arranged side by side in the tape width direction so that

In one aspect, as shown in FIG. 3 as an example, in the reading element unit 38, the first reading element 40 and the second reading element 42 overlap each other with respect to the traveling direction, thereby causing the magnetic tape MT. Achieves high density of trucks included in.

As an example, as shown in FIG. 7, the magnetic tape device 10 includes an actuator 60, an extraction unit 62, an A / D (Analog / Digital) converter 64, 66, 68, a decoding unit 69, and a computer 73.

The control device 18 is connected to the servo element pair 36 via an A / D (Analog-to-digital) converter 68. The A / D converter 68 transmits the servo signal obtained by converting the analog signal obtained by reading the servo pattern 32 by the servo elements 36A and 36B included in the servo element pair 36 into a digital signal to the control device 18. Output.

The control device 18 is connected to the actuator 60. The actuator 60 is attached to the reading head 16 and causes the reading head 16 to fluctuate in the tape width direction by applying power to the reading head 16 under the control of the control device 18. The actuator 60 includes, for example, a voice coil motor, and the power applied to the reading head 16 is obtained by converting electrical energy based on the current flowing through the coil into kinetic energy using the energy of a magnet as a medium. It is power.

Here, the mode in which the voice coil motor is mounted on the actuator 60 is mentioned. However, the magnetic tape device is not limited to this mode, and for example, a piezoelectric element can be adopted instead of the voice coil motor. It is also possible to use a voice coil motor and a piezoelectric element together.

The amount of misalignment between the magnetic tape MT and the reading element unit 38 is determined according to the servo signal obtained by reading the servo pattern 32 by the servo element pair 36. By controlling the actuator 60, the control device 18 applies power to the reading head 16 according to the amount of displacement between the magnetic tape MT and the reading element unit 38, so that the reading head 16 fluctuates in the tape width direction. Then, the position of the reading head 16 is adjusted to a normal position. Here, the normal position refers to the position of the reading head 16 in the default state of the magnetic tape device 10, for example, as shown in FIG.

Hereinafter, for convenience of explanation, the amount of displacement between the magnetic tape MT and the reading element unit 38 is simply referred to as “amount of displacement”. The amount of deviation is calculated based on the ratio of the distance A to the distance B, for example, as shown in FIG. The distance A refers to a distance calculated from the result obtained by reading the adjacent first diagonal line 32A and the second diagonal line 32B by the servo element 36A. The distance B refers to a distance calculated from the result obtained by reading two adjacent first diagonal lines 32A by the servo element 36A.

The extraction unit 62 includes a control device 18 and a two-dimensional FIR filter 71. The two-dimensional FIR filter 71 includes an adder 44, a first equalizer 70, and a second equalizer 72.

The first equalizer 70 is connected to the first reading element 40 via an A / D converter 64. Further, the first equalizer 70 is connected to each of the control device 18 and the adder 44. The data read from the specific track area 31 by the first reading element 40 is an analog signal, and the A / D converter 64 converts the data read from the specific track area 31 by the first reading element 40 into a digital signal. The first read signal thus obtained is output to the first equalizer 70.

The second equalizer 72 is connected to the second reading element 42 via the A / D converter 66. Further, the second equalizer 72 is connected to each of the control device 18 and the adder 44. The data read from the specific track area 31 by the second reading element 42 is an analog signal, and the A / D converter 66 converts the data read from the specific track area 31 by the second reading element 42 into a digital signal. The second read signal thus obtained is output to the second equalizer 72. The first read signal and the second read signal are examples of "reading results for each reading element".

The first equalizer 70 performs waveform equalization processing on the input first read signal. For example, the first equalizer 70 convolves the tap coefficient with respect to the input first read signal, and outputs the first arithmetically processed signal which is the signal after the arithmetic processing.

The second equalizer 72 performs waveform equalization processing on the input second read signal. For example, the second equalizer 72 convolves the tap coefficient with respect to the input second read signal, and outputs the second arithmetically processed signal which is the signal after the arithmetic processing.

Each of the first equalizer 70 and the second equalizer 72 outputs the first arithmetically processed signal and the second arithmetically processed signal to the adder 44. The adder 44 synthesizes the first arithmetically processed signal input from the first equalizer 70 and the second arithmetically processed signal input from the second equalizer 72 by adding them together. The synthesized data obtained by the synthesis is output to the decoding unit 69.

Each of the first equalizer 70 and the second equalizer 72 is a one-dimensional FIR filter.

In one aspect, the FIR filter itself is a series of real values including positive and negative, the number of rows in the series is referred to as the number of taps, and the numerical value itself is referred to as the tap coefficient. In one aspect, waveform equalization refers to a process of convolving (multiply-accumulate) the above-mentioned series of real values, that is, tap coefficients, with respect to the read signal. The term "read signal" as used herein refers to a general term for the first read signal and the second read signal. Further, in one aspect, the equalizer refers to a circuit that executes a process of convolving a tap coefficient with respect to a read signal or other input signal and outputting a signal after the calculation process. In one aspect, the adder simply refers to a circuit that adds two sequences. The weighting of the two series is reflected in the numerical value of the FIR filter used in the first equalizer 70 and the second equalizer 72, that is, the tap coefficient.

The control device 18 sets the tap coefficient according to the amount of deviation for each FIR filter of the first equalizer 70 and the second equalizer 72, thereby setting the first equalizer 70 and the second equalizer 70 and the second equalizer. Each of the chemical devices 72 is subjected to a waveform equalization process according to the amount of deviation.

The control device 18 includes a corresponding table 18A. In the correspondence table 18A, the tap coefficient and the deviation amount are associated with each of the first equalizer 70 and the second equalizer 72. The combination of the tap coefficient and the deviation amount is, for example, the combination of the tap coefficient and the deviation amount for which the adder 44 obtains the best synthetic data based on the results of at least one of the tests and simulations of the actual machine. It is a combination obtained in advance as. The "best composite data" referred to here refers to data corresponding to the track data to be read.

Here, the "reading target track data" refers to "data derived from the reading target track 30A". In other words, the “data derived from the read target track 30A” refers to data corresponding to the data written in the read target track 30A. As an example of the data corresponding to the data written in the read target track 30A, there is data read from the read target track 30A without the noise component from the adjacent track being mixed.

In the above, the corresponding table 18A is illustrated. In another aspect, an arithmetic expression may be adopted instead of the corresponding table 18A. The "calculation formula" referred to here refers to, for example, a calculation formula in which the independent variable is the deviation amount and the dependent variable is the tap coefficient.

In the above, the mode in which the tap coefficient is derived from the corresponding table 18A in which the combination of the tap coefficient and the deviation amount is defined is mentioned. In another aspect, for example, the tap coefficient may be derived from a corresponding table or arithmetic expression in which the combination of the tap coefficient and the ratio is defined. The “ratio” referred to here refers to the ratio of the overlapping region with the reading target track 30A and the overlapping region with the adjacent track for each of the first reading element 40 and the second reading element 42. The ratio is specified by the control device 18 by calculating from the deviation amount, and the tap coefficient is determined according to the specified ratio.

The decoding unit 69 decodes the composite data input from the adder 44, and outputs the decoded signal obtained by decoding to the computer 73. The computer 73 performs various processes on the decoding signal input from the decoding unit 69.

Next, the magnetic tape reading process executed by the extraction unit 62 will be described with reference to FIG. Hereinafter, for convenience of explanation, it will be described on the premise that the servo signal is input to the control device 18 when the sampling time comes. Here, sampling means not only sampling of servo signals but also sampling of read signals. That is, in one aspect, since the track region 30 is formed in parallel with the servo pattern 32 along the traveling direction, the reading operation of the reading element unit 38 is performed in synchronization with the reading operation of the servo element pair 36.

In the process shown in FIG. 9, first, in step 100, the control device 18 determines whether or not the sampling time has come. In step 100, when the sampling time has come, the determination is affirmed, and the magnetic tape reading process shifts to step 102. If the sampling time has not arrived in step 100, the determination is denied and the determination in step 100 is performed again.

In step 102, the first equalizer 70 acquires the first read signal, the second equalizer 72 acquires the second read signal, and then the magnetic tape reading process shifts to step 104.

In step 104, the control device 18 acquires the servo signal, calculates the deviation amount from the acquired servo signal, and then the magnetic tape reading process shifts to step 106.

In step 106, the control device 18 sets a tap coefficient corresponding to the deviation amount calculated in the process of step 104 for each of the first to third taps of the first equalizer 70 and the second equalizer 72. Derived from 18A. That is, by executing the process of this step 106, the optimum combination of the one-dimensional FIR filter which is an example of the first equalizer 70 and the one-dimensional filter which is an example of the second equalizer 72 can be obtained. It is decided. The "optimal combination" referred to here refers to, for example, a combination in which the composite data output by executing the process of step 112 described later is converted into data corresponding to the track data to be read.

In the next step 108, the control device 18 sets the tap coefficient derived in the process of step 106 for each of the first equalizer 70 and the second equalizer 72, and then the magnetic tape reading process is performed in step. Move to 110.

In step 110, the first equalizer 70 generates a first arithmetically processed signal by performing waveform equalization processing on the first read signal acquired in the process of step 102. The first equalizer 70 outputs the generated first arithmetically processed signal to the adder 44. The second equalizer 72 generates a second arithmetically processed signal by performing waveform equalization processing on the second read signal acquired in the process of step 102. The second equalizer 72 outputs the generated second arithmetically processed signal to the adder 44.

In the next step 112, the adder 44 uses the first arithmetically processed signal input from the first equalizer 70 and the second equalizer 72 input from the second equalizer 72, as shown in FIG. 10 as an example. It is synthesized by adding the arithmetically processed signal of 2. Then, the adder 44 outputs the synthesized data obtained by the synthesis to the decoding unit 69.

When the reading element unit 38 is arranged on the specific track area 31 as in the example shown in FIG. 3, by executing the process of this step 112, the composite data is obtained from the first noise mixing source track 30B. Data corresponding to the read target track data from which the noise component of the above has been removed is output. That is, by executing the processes of steps 102 to 112, the extraction unit 62 extracts only the data derived from the read target track 30A.

When the tape width direction of the magnetic tape MT expands or contracts, or when vibration is applied to at least one of the magnetic tape MT and the reading head 16, the reading element unit 38 moves from the position shown in FIG. 3 as an example to FIG. It may be displaced to the position shown in. In the example shown in FIG. 11, the first reading element 40 and the second reading element 42 are arranged at positions straddling both the reading target track 30A and the second noise mixing source track 30C. In this case, by executing the processes of steps 102 to 112, the data corresponding to the read target track data from which the noise component is removed from the second noise mixing source track 30C is output to the decoding unit 69 as composite data. Will be done.

In the next step 114, the control device 18 determines whether or not the condition for terminating the magnetic tape reading process (hereinafter, referred to as “end condition”) is satisfied. The end condition refers to, for example, a condition that all of the magnetic tape MT is wound by the take-up reel 22, a condition that an instruction to forcibly end the magnetic tape reading process is given from the outside, and the like.

If the end condition is not satisfied in step 114, the determination is denied and the magnetic tape reading process proceeds to step 100. If the end condition is satisfied in step 114, the determination is affirmed and the magnetic tape reading process ends.

As described above, in one aspect of the magnetic tape device 10, data is read from the specific track region 31 by the first reading element 40 and the second reading element 42 arranged in close proximity to each other. Then, the extraction unit 62 performs waveform equalization processing according to the amount of deviation on each of the first reading element 40 and the second reading element 42, so that the first reading signal and the second reading signal are separated from each other. , Data derived from the read target track 30A is extracted. Therefore, the magnetic tape device 10 reduces the reproduction quality of the data read from the read target track 30A by the linear scan method as compared with the case where the data is read from the read target track 30A by the linear scan method using only a single reading element. It can be suppressed.

Further, in one aspect of the magnetic tape device 10, a part of the first reading element 40 and the second reading element 42 overlap each other in the traveling direction. Therefore, the magnetic tape device 10 can improve the reproduction quality of the data read from the read target track 30A by the linear scan method, as compared with the case where the entire plurality of reading elements overlap each other in the traveling direction.

Further, in one aspect of the magnetic tape device 10, the specific track region 31 includes a read target track 30A, a first noise mixing source track 30B, and a second noise mixing source track 30C, and includes a first reading element 40 and a first noise mixing source track 30C. Each of the two reading elements 42 straddles both the reading target track 30A and the adjacent track when the positional relationship with the magnetic tape MT changes. Therefore, the magnetic tape device 10 first reads data by entering the adjacent track from the reading target track 30A in the tape width direction, as compared with the case where data is read from the reading target track 30A by only a single reading element by the linear scanning method. The noise component generated in one of the element 40 and the second reading element 42 is reduced by utilizing the reading result of the other reading element entering the adjacent track from the reading target track 30A in the tape width direction. Can be done.

Further, in one aspect of the magnetic tape device 10, the tap coefficient used in the waveform equalization processing is determined according to the amount of deviation. Therefore, the magnetic tape device 10 magnetically removes the noise component generated by entering the read target track 30A from the adjacent track in the tape width direction, as compared with the case where the tap coefficient is determined according to a parameter unrelated to the deviation amount. It can be immediately reduced by following the change in the positional relationship between the tape MT and the reading element unit 38.

Further, in one aspect of the magnetic tape device 10, for each of the first reading element 40 and the second reading element 42, the ratio of the overlapping region with the reading target track 30A and the overlapping region with the adjacent track is specified from the deviation amount. , The tap coefficient is determined according to the specified ratio. As a result, in the magnetic tape device 10, the tap coefficient is determined according to a parameter that is not related to the ratio of the overlapping area with the reading target track 30A and the overlapping area with the adjacent track for each of the plurality of reading elements. Compared with the case, even if the positional relationship between the magnetic tape MT and the reading element unit 38 changes, the noise component can be accurately reduced.

Further, in one aspect of the magnetic tape device 10, the deviation amount is determined according to the result obtained by reading the servo pattern 32 by the servo element pair 36. As a result, the magnetic tape device 10 can easily determine the deviation amount as compared with the case where the servo pattern 32 is not applied to the magnetic tape MT.

Further, in one aspect of the magnetic tape device 10, the reading operation of the reading element unit 38 is performed in synchronization with the reading operation of the servo element pair 36. As a result, the magnetic tape device 10 enters the reading target track from the adjacent track in the width direction of the magnetic tape, as compared with the magnetic disk and the helical scan type magnetic tape which cannot read the servo pattern and the data in synchronization. The generated noise component can be reduced immediately.

Further, in one aspect of the magnetic tape device 10, the extraction unit 62 has a two-dimensional FIR filter 71. Then, the first read signal and the first read signal are combined by synthesizing the results obtained by subjecting each of the first read signal and the second read signal to waveform equalization processing by the two-dimensional FIR filter 71. 2 Data derived from the read target track 30A is extracted from the read signal. As a result, the magnetic tape device 10 can quickly extract data derived from the read target track 30A from the first read signal and the second read signal as compared with the case where only the one-dimensional FIR filter is used. Further, the magnetic tape device 10 can realize the calculation with a smaller amount of calculation as compared with the case of performing the matrix calculation.

Further, in one aspect of the magnetic tape device 10, the first reading element 40 and the second reading element 42 are adopted as a pair of reading elements. As a result, the magnetic tape device 10 can contribute to the miniaturization of the reading element unit 38 as compared with the case where three or more reading elements are used. As the reading element unit 38 is miniaturized, the reading unit 26 and the reading head 16 can also be miniaturized. Further, the magnetic tape device 10 can suppress the occurrence of a situation in which adjacent reading element units 38 come into contact with each other.

Further, in one aspect of the magnetic tape device 10, data is read by each of the plurality of reading element units 38 from the corresponding reading target tracks 30A included in each of the plurality of specific track areas 31 by a linear scan method. As a result, the magnetic tape device 10 quickly completes the reading of the data from the plurality of reading target tracks 30A as compared with the case where the data is read from each of the plurality of reading target tracks 30A only by the single reading element unit 38. can do.

In the above embodiment, with the magnetic tape device 10 in the default state, each of the first reading element 40 and the second reading element 42 is used for both the reading target track 30A and the first noise mixing source track 30B. The magnetic tape device is provided so as to straddle, but the magnetic tape device is not limited to such an embodiment. In the example shown in FIG. 12, the reading element unit 138 is adopted instead of the reading element unit 38 described above. The reading element unit 138 includes a first reading element 140 and a second reading element 142. In the default state of the magnetic tape device 10, the center of the first reading element 140 in the tape width direction coincides with the center CL of the reading target track 30A in the tape width direction. Further, in the default state of the magnetic tape device 10, the first reading element 140 and the second reading element 142 read without protruding into the first noise mixing source track 30B and the second noise mixing source track 30C. It fits in the target truck 30A. Further, in the default state of the magnetic tape device 10, each of the first reading element 140 and the second reading element 142 has a traveling direction, similarly to the first reading element 40 and the second reading element 42 described in the above embodiment. It is provided so that parts of each other overlap each other.

As an example, as shown in FIG. 12, even when the first reading element 140 and the second reading element 142 face the reading target track 30A without protruding from the reading target track 30A, the reading element unit 138 The positional relationship with the magnetic tape MT may change. That is, the reading element unit 138 may straddle the reading target track 30A and the first noise mixing source track 30B, or the reading element unit 138 may straddle the reading target track 30A and the second noise mixing source track 30C. .. Even in these cases, by executing the processes of steps 102 to 112 described above, the noise component removed from the first noise mixing source track 30B or the second noise mixing source track 30C is removed. It is possible to obtain data corresponding to the target track data.

Further, since the first reading element 140 and the second reading element 142 are arranged at positions where parts of the first reading element 140 and the second reading element 142 overlap each other in the traveling direction, the portion of the track 30A to be read that cannot be read by the first reading element 140 The second reading element 142 can read the data. As a result, the reliability of the read target track data can be improved as compared with the case where the first reading element 140 is used alone to read the data from the read target track 30A.

Further, as shown in FIG. 11, as an example, in the default state of the magnetic tape device 10, each of the first reading element 40 and the second reading element 42 of the reading target track 30A and the second noise mixing source track 30C. It may be arranged at a position straddling both of them.

Further, in the above, the reading element unit 38 including the first reading element 40 and the second reading element 42 has been exemplified. However, the magnetic tape device is not limited to such an embodiment. In the example shown in FIG. 13, the reading element unit 238 is adopted instead of the reading element unit 38. The reading element unit 238 is different from the reading element unit 38 in that it has a third reading element 244. In the default state of the magnetic tape device 10, the third reading element 244 is arranged at a position where a part of the third reading element 244 overlaps with the first reading element 40 in the traveling direction. Further, in the default state of the magnetic tape device 10, the third reading element 244 is arranged at a position straddling the reading target track 30A and the second noise mixing source track 30C.

In this case, the first equalizer 70 is assigned to the first reading element 40, and the second equalizer 72 is assigned to the second reading element 42 as well as the third reading element 244. Allocate a 3 equalizer (not shown). The third equalizer also has the same function as the first equalizer and the second equalizer described above, and with respect to the third read signal read by the third reading element 244. And perform waveform equalization processing. Then, the third equalizer convolves, for example, the tap coefficient with respect to the third read signal, and outputs the third arithmetically processed signal, which is the signal after the arithmetic processing. The adder 44 has a first arithmetically processed signal corresponding to the first read signal, a second arithmetically processed signal corresponding to the second read signal, and a third arithmetically processed signal corresponding to the third read signal. It is synthesized by adding the signal, and the synthesized data obtained by the synthesis is output to the decoding unit 69.

In the example shown in FIG. 13, the magnetic tape device 10 is in the default state, and the third reading element 244 is arranged at a position straddling the reading target track 30A and the second noise mixing source track 30C. Technology is not limited to this. In the default state of the magnetic tape device 10, the third reading element 244 may be arranged at a position facing the reading target track 30A without protruding from the reading target track 30A.

Moreover, in the above, the reading element unit 38 was illustrated. However, the magnetic tape device is not limited to such an embodiment. For example, instead of the reading element unit 38, the reading element pair 50 shown in FIG. 4 may be adopted. In this case, the first reading element 50A and the second reading element 50B are arranged at positions close to each other in the tape width direction. Further, the first reading element 50A and the second reading element 50B do not come into contact with each other, and as shown in FIG. 6 as an example, the SNR is higher than the SNR of the single reading element data in the entire range of the track offset. So that they are arranged side by side in the tape width direction.

In the example shown in FIG. 4, for example, the first reading element 50A is housed in the second track 49B in a plan view, and the second reading element 50B is housed in the first track 49A in a plan view.

Moreover, in the above, the servo element pair 36 was illustrated. However, the magnetic tape device is not limited to such an embodiment. For example, one of the servo elements 36A and 36B may be adopted instead of the servo element pair 36.

Further, in the above description, a mode in which a plurality of specific track areas 31 are arranged at regular intervals in the tape width direction in the track area 30 has been described. However, the magnetic tape device is not limited to such an embodiment. For example, in two adjacent specific track areas 31 among a plurality of specific track areas 31, one specific track area 31 and the other specific track area 31 overlap by one track in the tape width direction. It may be arranged in the direction. In this case, one adjacent track (for example, the first noise mixing source track 30B) included in one specific track area 31 becomes the read target track 30A in the other specific track area 31. Further, the read target track 30A included in one specific track area 31 becomes an adjacent track area (for example, a second noise mixing source track 30C) in the other specific track area 31.

The configuration of the magnetic tape device and the magnetic tape reading process described above are merely examples. Therefore, it goes without saying that it is possible to delete unnecessary steps, add new steps, change the processing order, and the like within a range that does not deviate from the purpose.
Further, the magnetic tape device can read (reproduce) the data recorded on the magnetic tape, and can also have a configuration for recording the data on the magnetic tape.

[Magnetic tape]
Next, the details of the magnetic tape on which data is read in the magnetic tape device will be described.

<XRD intensity ratio, vertical angle type ratio>
The XRD intensity ratio and the vertical angular type ratio will be described below.
The ferromagnetic powder contained in the magnetic layer of the magnetic tape is hexagonal ferrite powder. Among the hexagonal ferrite powders contained in the magnetic layer, there are particles that affect the magnetic properties of the hexagonal ferrite powder (aggregate of particles) (hereinafter, also referred to as "former particles"), and whether or not they have an effect. It is presumed that particles that are considered to have little effect (hereinafter, also referred to as "the latter particles") are included. The latter particles are considered to be fine particles generated by, for example, partial chipping (chipping) of the particles due to the dispersion treatment performed at the time of preparing the composition for forming a magnetic layer. Among the particles constituting the hexagonal ferrite powder contained in the magnetic layer, the former particles are considered to be particles that cause diffraction peaks in X-ray diffraction analysis using the In-Plane method, while the latter particles are. Since it is fine, it is considered that the diffraction peak is not caused or the influence on the diffraction peak is small. Therefore, based on the intensity of the diffraction peak brought about by the X-ray diffraction analysis of the magnetic layer using the In-Plane method, it is possible to control the presence state of the particles in the magnetic layer, which affects the magnetic properties of the hexagonal ferrite powder. It is presumed that it can be done. The XRD intensity ratio is considered to be an index in this regard.
On the other hand, the vertical angular ratio is the ratio of the residual magnetization to the saturation magnetization measured in the direction perpendicular to the surface of the magnetic layer, and the smaller the residual magnetization, the smaller the value. Since the latter particles are considered to be fine and difficult to maintain magnetization, it is presumed that the more the latter particles are contained in the magnetic layer, the smaller the vertical angular ratio tends to be. Therefore, it is considered that the vertical angular ratio can be an index of the abundance of the latter particles (fine particles) in the magnetic layer.
It is considered that the reason why the accuracy of reading the servo pattern and identifying the position of the reading element is lowered is that when the servo light head magnetizes (forms the servo pattern), an unintended part on the magnetic layer is also magnetized. .. Then, it is presumed that the magnetization of the above-mentioned unintended portion is likely to occur due to the occurrence of magnetic strain in the magnetic layer. On the other hand, setting the XRD intensity ratio to 0.5 or more and 4.0 or less and setting the vertical azimuth ratio to 0.65 or more and 1.00 or less are magnetic in the magnetic layer as follows. It is speculated that it may contribute to suppressing the occurrence of various strains.
It is considered that the XRD intensity ratio of 0.5 or more and 4.0 or less means that the former particles are appropriately aligned in the magnetic layer, and this is the occurrence of magnetic strain in the magnetic layer. It is presumed to contribute to suppression. Further, since the latter particles are fine, it is considered that the magnetization is easily reversed. The vertical angular ratio of 0.65 or more and 1.00 or less is considered to mean that the abundance of the latter particles, which are easily reversed in magnetization, is small, and this also causes magnetic strain in the magnetic layer. It is presumed that it contributes to the suppression of.
From the above, if the accuracy of reading the servo pattern and identifying the position of the reading element can be improved, it is possible to reduce the error between the amount of deviation detected by reading the servo pattern and the amount of deviation actually occurring. It is inferred that it will be. However, the above is a guess and does not limit the present invention in any way.

(XRD intensity ratio)
The magnetic tape contains hexagonal ferrite powder in the magnetic layer. The XRD intensity ratio is determined by X-ray diffraction analysis of a magnetic layer containing hexagonal ferrite powder using the In-Plane method. In the following, the X-ray diffraction analysis performed by using the In-Plane method will also be referred to as "In-Plane XRD". In-Plane XRD shall be performed by irradiating the surface of the magnetic layer with X-rays under the following conditions using a thin film X-ray diffractometer. The measurement direction is the longitudinal direction of the magnetic tape.
Uses Cu radiation source (output 45 kV, 200 mA)
Scan condition: The range of 20 to 40 degrees is 0.05 degree / step, 0.1 degree / min.
Optical system used: Parallel optical system Measurement method :: 2θχ scan (X-ray incident angle 0.25 °)
The above conditions are set values in the thin film X-ray diffractometer. As the thin film X-ray diffractometer, a known device can be used. As an example of the thin film X-ray diffractometer, a SmartLab manufactured by Rigaku Corporation can be mentioned. The sample to be analyzed for In-Plane XRD is a tape sample cut out from the magnetic tape to be measured, and the size and shape thereof are not limited as long as the diffraction peak described later can be confirmed.

Examples of the X-ray diffraction analysis method include thin film X-ray diffraction and powder X-ray diffraction. While powder X-ray diffraction measures the X-ray diffraction of a powder sample, thin film X-ray diffraction can measure the X-ray diffraction of a layer or the like formed on a substrate. Thin film X-ray diffraction is classified into an In-Plane method and an Out-Of-Plane method. The X-ray incident angle at the time of measurement is in the range of 5.00 to 90.00 ° in the Out-Of-Plane method, whereas it is usually in the range of 0.20 to 0.50 ° in the In-Plane method. .. In the In-Plane XRD of the present invention and the present specification, the X-ray incident angle is 0.25 ° as described above. The In-Plane method has a smaller X-ray incident angle than the Out-Of-Plane method, and therefore has a shallower penetration depth of X-rays. Therefore, according to the X-ray diffraction analysis (In-Plane XRD) using the In-Plane method, it is possible to perform the X-ray diffraction analysis of the surface layer portion of the sample to be measured. For tape samples, according to In-Plane XRD, X-ray diffraction analysis of the magnetic layer can be performed. The above XRD intensity ratio is the (110) plane of the diffraction peak of the (114) plane of the hexagonal ferrite crystal structure with respect to the peak intensity Int (114) in the X-ray diffraction spectrum obtained by the In-Plane XRD. It is the intensity ratio (Int (110) / Int (114)) of the peak intensity Int (110) of the diffraction peak of. Int is used as an abbreviation for Intensity. In the X-ray diffraction spectrum (vertical axis: Integrity, horizontal axis: diffraction angle 2θχ (degree)) obtained by In-Plane XRD, the diffraction peak of the (114) plane is a peak in which 2θχ is detected in the range of 33 to 36 degrees. The diffraction peak of the (110) plane is a peak in which 2θχ is detected in the range of 29 to 32 degrees.

Among the diffraction planes, the (114) plane of the hexagonal ferrite crystal structure is located near the easily magnetized axial direction (c-axis direction) of the hexagonal ferrite powder particles (hexagonal ferrite particles). Further, the (110) plane of the hexagonal ferrite crystal structure is located in a direction orthogonal to the easy magnetization axial direction.
In the X-ray diffraction spectrum obtained by In-Plane XRD, the peak intensity of the diffraction peak on the (114) plane of the hexagonal ferrite crystal structure, the peak intensity of the diffraction peak on the (110) plane, Int (110) with respect to Int (114). The larger the ratio (Int (110) / Int (114); XRD intensity ratio), the more the former particles existing in a state in which the direction orthogonal to the easy-diffraction axial direction is closer to the surface of the magnetic layer becomes the magnetic layer. On the other hand, it is considered that the smaller the XRD intensity ratio is, the less the former particles existing in such a state are in the magnetic layer. The state in which the XRD intensity ratio is 0.5 or more and 4.0 or less is considered to mean that the former particles are in a state of being appropriately aligned in the magnetic layer. It is presumed that this contributes to the suppression of the occurrence of magnetic strain in the magnetic layer. The XRD intensity ratio is preferably 3.5 or less from the viewpoint of further suppressing the magnetization of unintended parts on the magnetic layer when magnetizing (forming a servo pattern) by the servo light head. More preferably, it is 0.0 or less. From the same viewpoint, the XRD intensity ratio is preferably 0.7 or more, and more preferably 1.0 or more. The XRD intensity ratio can be controlled, for example, by the processing conditions of the orientation treatment performed in the manufacturing process of the magnetic tape. As the orientation treatment, it is preferable to perform a vertical orientation treatment. The vertical alignment treatment can preferably be performed by applying a magnetic field perpendicular to the surface of the coating layer of the composition for forming a magnetic layer in a wet state (undried state). The stronger the orientation condition, the larger the value of the XRD intensity ratio tends to be. Examples of the treatment condition for the alignment treatment include the magnetic field strength in the alignment treatment. The treatment conditions for the orientation treatment are not particularly limited. The processing conditions for the orientation treatment may be set so that an XRD intensity ratio of 0.5 or more and 4.0 or less can be realized. As an example, the magnetic field strength in the vertical alignment treatment can be 0.10 to 0.80T, or can be 0.10 to 0.60T. The higher the dispersibility of the hexagonal ferrite powder in the composition for forming a magnetic layer, the larger the value of the XRD intensity ratio tends to be due to the vertical alignment treatment.

(Vertical square ratio)
The vertical square ratio is a square ratio measured in the vertical direction of the magnetic tape. The "vertical direction" described with respect to the square ratio means a direction orthogonal to the surface of the magnetic layer. The vertical azimuth ratio is measured using a vibrating sample magnetometer. Specifically, the vertical angular ratio in the present invention and the present specification is a maximum external magnetic field of 1194 kA / m (15 kOe) on the magnetic tape at a measurement temperature of 23 ° C. ± 1 ° C. in a vibrating sample magnetometer. It is a value obtained by sweeping under the condition of a scan speed of 4.8 kA / m / sec (60 Oe / sec), and is a value after demagnetic field correction. The measured value shall be obtained as the value obtained by subtracting the magnetization of the sample probe of the vibrating sample magnetometer as background noise.

The vertical angle ratio of the tape is 0.65 or more and 1.00 or less. It is presumed that the vertical azimuth ratio of the magnetic tape can be an index of the abundance of the latter particles (fine particles) described above. It is considered that the abundance of such fine particles is small in the magnetic layer in which the vertical angular ratio of the magnetic tape is 0.65 or more and 1.00 or less. It is presumed that this contributes to the suppression of the occurrence of magnetic strain in the magnetic layer. The vertical angular ratio is preferably 0.68 or more from the viewpoint of further suppressing magnetization of unintended parts on the magnetic layer when magnetizing (forming a servo pattern) by the servo light head. , 0.70 or more, more preferably 0.73 or more, and even more preferably 0.75 or more. In principle, the square ratio is 1.00 at the maximum. Therefore, the vertical angular ratio of the magnetic tape is 1.00 or less. The vertical angular ratio may be, for example, 0.95 or less, 0.90 or less, 0.87 or less, or 0.85 or less. It is considered that the larger the value of the vertical angular ratio, the smaller the number of the latter particles (fine particles) in the magnetic layer, which is preferable from the viewpoint of suppressing the occurrence of magnetic strain in the magnetic layer. Therefore, the vertical azimuth ratio may exceed the above-exemplified value.

In order to make the vertical angular ratio of 0.65 or more and 1.00 or less, it is necessary that fine particles are generated due to partial chipping (chipping) of particles in the step of preparing the composition for forming a magnetic layer. It is considered preferable to suppress it. Specific means for suppressing the occurrence of chipping will be described later.

Next, the magnetic layer and the like included in the magnetic tape will be described in more detail.

<Magnetic layer>
(Ferromagnetic powder)
The ferromagnetic powder contained in the magnetic layer is hexagonal ferrite powder. As an index of the particle size of the hexagonal ferrite powder, the activated volume, which is a unit of magnetization reversal, can be adopted. In one aspect, the activated volume of the hexagonal ferrite powder contained in the magnetic layer ^{can be 1600 nm 3} or less, and may be 1500 nm ³ or less or 1400 nm ³ or less. In general, it can be said that the smaller the activated volume, the more suitable for high-density recording. On the other hand, from the viewpoint of magnetization stability, the activated volume of the hexagonal ferrite powder ^{is preferably 800 nm 3} or more, more preferably 1000 nm ³ or more, and ^{further preferably 1200 nm 3} or more. ..

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

The activation volume described above can be determined by using the powder itself as a measurement sample for the hexagonal ferrite powder existing as a powder. On the other hand, with respect to the hexagonal ferrite powder contained in the magnetic layer of the magnetic tape, the powder can be collected from the magnetic layer to obtain a sample for measurement. The measurement sample can be collected by, for example, the following method.
1. 1. The surface of the magnetic layer is surface-treated with a plasma reactor manufactured by Yamato Scientific Co., Ltd. for 1 to 2 minutes to incinerate and remove organic components (binders, etc.) on the surface of the magnetic layer.
2. A filter paper soaked with an organic solvent such as cyclohexanone or acetone is attached to the edge of the metal rod, and then the above 1. The surface of the magnetic layer after the treatment is rubbed, and the magnetic layer component is transferred from the magnetic tape to the filter paper and peeled off.
3. 3. Above 2. Shake off the exfoliated component in an organic solvent such as cyclohexanone or acetone (put the filter paper in an organic solvent and shake it off with an ultrasonic disperser), dry the organic solvent, and take out the exfoliated component.
4. Above 3. The components shaken off in step 2 are placed in a thoroughly washed glass test tube, and about 20 ml of n-butylamine is added thereto to seal the glass test tube. (Add an amount of n-butylamine that can decompose the residual organic component without ashing.)
5. The glass test tube is heated at an internal temperature of 170 ° C. for 20 hours or more to decompose organic components.
6. 5. Above. After the decomposition of the above, the precipitate is thoroughly washed with pure water and dried, and the powder is taken out.
7. 6. Above. The neodymium magnet is brought close to the powder collected in step 1 and the adsorbed powder (that is, hexagonal ferrite powder) is taken out.
By the above steps, hexagonal ferrite powder for measuring the activated volume can be collected from the magnetic layer. Since the hexagonal ferrite powder is hardly damaged by the above treatment, the activated volume of the hexagonal ferrite powder contained in the magnetic layer can be measured by the above method.

In the present invention and the present specification, the ferromagnetic powder means an aggregate of a plurality of ferromagnetic particles, and the aggregate is not limited to a mode in which the particles constituting the aggregate are in direct contact with each other, and the binder is used. , Additives and the like are also included in the manner in which the particles are interposed between the particles. The above points also apply to various powders of the present invention and the present specification, such as non-magnetic powders. The particles constituting the hexagonal ferrite powder (hexagonal ferrite particles) are also referred to as "hexagonal ferrite particles" or simply "particles". For details of the hexagonal ferrite powder, for example, paragraphs 0012 to 0030 of JP2011-225417A, paragraphs 0134 to 0136 of JP2011-216149A, paragraphs 0013 to 0030 of JP2012-204726 and the like. References can be made to paragraphs 0029 to 0084 of JP-A-2015-127985.

Regarding the hexagonal ferrite powder, as the crystal structure of the hexagonal ferrite, a magnetoplumbite type (also referred to as "M type"), a W type, a Y type, and a Z type are known. The hexagonal ferrite powder contained in the magnetic layer may have any crystal structure. Further, the crystal structure of hexagonal ferrite includes an iron atom and a divalent metal atom as constituent atoms. The divalent metal atom is a metal atom that can be a divalent cation as an ion, and examples thereof include an alkaline earth metal atom such as a barium atom, a strontium atom and a calcium atom, and a lead atom. For example, a hexagonal ferrite containing a barium atom as a divalent metal atom is a barium ferrite, and a hexagonal ferrite containing a strontium atom is a strontium ferrite. Further, the hexagonal ferrite may be a mixed crystal of two or more types of hexagonal ferrite. As an example of the mixed crystal, a mixed crystal of barium ferrite and strontium ferrite can be mentioned.

The shape of the particles constituting the hexagonal ferrite powder is a particle photograph obtained by photographing the hexagonal ferrite powder with a transmission electron microscope at an imaging magnification of 100,000 times and printing it on photographic paper so as to have a total magnification of 500,000 times. In, the contour of the particle (primary particle) is traced and specified by the digitizer. Primary particles are independent particles without agglomeration. Photography using a transmission electron microscope shall be performed by a direct method using a transmission electron microscope at an acceleration voltage of 300 kV. Observation and measurement with a transmission electron microscope can be performed using, for example, a transmission electron microscope H-9000 manufactured by Hitachi and an image analysis software KS-400 manufactured by Carl Zeiss. Regarding the shape of the particles constituting the hexagonal ferrite powder, the “plate-like” means a shape having two opposing plate surfaces. On the other hand, among the particle shapes that do not have such a plate surface, the shape that distinguishes between the major axis and the minor axis is the "elliptical shape". The major axis is determined as the axis (straight line) that can take the longest particle length. On the other hand, the minor axis is determined as the axis having the longest particle length when the particle length is taken by a straight line orthogonal to the major axis. A shape in which there is no distinction between a major axis and a minor axis, that is, a shape in which the major axis length = the minor axis length is "spherical". A shape in which the long axis and the short axis cannot be specified from the shape is called an indeterminate form. Imaging using a transmission electron microscope for identifying the particle shape is performed without orienting the powder to be photographed. The shape of the raw material powder used for preparing the composition for forming the magnetic layer and the hexagonal ferrite powder contained in the magnetic layer may be plate-shaped, elliptical, spherical or amorphous.

The average particle size for the various powders described in the present invention and the present specification is the arithmetic mean of the values obtained for 500 randomly selected particles using the particle photographs taken as described above. The average particle size shown in the examples described later is a value obtained by using a transmission electron microscope H-9000 manufactured by Hitachi as a transmission electron microscope and an image analysis software KS-400 manufactured by Carl Zeiss as an image analysis software.

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

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

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

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

When the hexagonal strontium ferrite powder contains rare earth atoms, the rare earth atom content (bulk content) is preferably in the range of 0.5 to 5.0 atom% with respect to 100 atom% of iron atoms. The fact that the rare earth atoms are contained in the bulk content in the above range and the rare earth atoms are unevenly distributed on the surface layer of the particles constituting the hexagonal strontium ferrite powder contributes to suppressing the decrease in the regeneration output in the repeated regeneration. Conceivable. This is because the hexagonal strontium ferrite powder contains rare earth atoms at a bulk content in the above range, and the rare earth atoms are unevenly distributed on the surface layer of the particles constituting the hexagonal strontium ferrite powder. It is presumed that this is because it can be enhanced. The higher the value of the anisotropy constant Ku, the more the occurrence of a phenomenon called thermal fluctuation can be suppressed (in other words, the thermal stability can be improved). By suppressing the occurrence of thermal fluctuation, it is possible to suppress a decrease in the reproduction output during repeated reproduction. The uneven distribution of rare earth atoms on the surface layer of the hexagonal strontium ferrite powder contributes to stabilizing the spin of iron (Fe) sites in the crystal lattice of the surface layer, which results in anisotropy constant Ku. It is speculated that it will increase.
In addition, it is presumed that the use of hexagonal strontium ferrite powder, which has uneven distribution on the surface layer of rare earth atoms, as the ferromagnetic powder of the magnetic layer also contributes to suppressing the surface of the magnetic layer from being scraped by sliding with the magnetic head. To. That is, it is presumed that the hexagonal strontium ferrite powder having uneven distribution on the surface layer of rare earth atoms can also contribute to the improvement of the running durability of the magnetic tape. This is because the uneven distribution of rare earth atoms on the surface of the particles constituting the hexagonal strontium ferrite powder improves the interaction between the particle surface and the organic substances (for example, binder and / or additive) contained in the magnetic layer. As a result, it is presumed that the strength of the magnetic layer is improved.
The rare earth atom content (bulk content) is in the range of 0.5 to 4.5 atomic% from the viewpoint of further suppressing the decrease in the reproduction output in the repeated regeneration and / or further improving the running durability. It is more preferably in the range of 1.0 to 4.5 atomic%, further preferably in the range of 1.5 to 4.5 atomic%.

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

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

In the hexagonal strontium ferrite powder having uneven distribution on the surface layer of rare earth atoms, the rare earth atoms may be unevenly distributed on the surface layer of the particles constituting the hexagonal strontium ferrite powder, and the degree of uneven distribution is not limited. For example, a hexagonal strontium ferrite powder having uneven distribution on the surface layer of a rare earth atom is partially melted under the melting conditions described later and the content of the surface layer of the rare earth atom and the rare earth obtained by completely melting under the melting conditions described later. The ratio of atoms to the bulk content, "surface layer content / bulk content", is more than 1.0 and can be 1.5 or more. When the "surface layer content / bulk content" is larger than 1.0, it means that the rare earth atoms are unevenly distributed (that is, more than the inside) in the particles constituting the hexagonal strontium ferrite powder. To do. In addition, the ratio of the surface layer content of rare earth atoms obtained by partial melting under the dissolution conditions described later to the bulk content of rare earth atoms obtained by total dissolution under the dissolution conditions described later, "Surface layer content / The "bulk content" can be, for example, 10.0 or less, 9.0 or less, 8.0 or less, 7.0 or less, 6.0 or less, 5.0 or less, or 4.0 or less. However, in the hexagonal strontium ferrite powder having uneven distribution on the surface layer of rare earth atoms, the rare earth atoms need only be unevenly distributed on the surface layer of the particles constituting the hexagonal strontium ferrite powder. The "rate" is not limited to the upper or lower limit illustrated.

Partial and total melting of hexagonal strontium ferrite powder will be described below. For hexagonal strontium ferrite powder that exists as a powder, the sample powder that is partially or completely dissolved is collected from the same lot of powder. On the other hand, regarding the hexagonal strontium ferrite powder contained in the magnetic layer of the magnetic tape, a part of the hexagonal strontium ferrite powder taken out from the magnetic layer is subjected to partial dissolution, and the other part is subjected to total dissolution. The hexagonal strontium ferrite powder can be taken out from the magnetic layer by, for example, the method described in paragraph 0032 of Japanese Patent Application Laid-Open No. 2015-91747.
The above partial dissolution means that the hexagonal strontium ferrite powder is dissolved in the liquid to the extent that the residue can be visually confirmed at the end of the dissolution. For example, partial melting can dissolve a region of 10 to 20% by mass of the particles constituting the hexagonal strontium ferrite powder, with the entire particles as 100% by mass. On the other hand, the above-mentioned total dissolution means that the hexagonal strontium ferrite powder is dissolved in the liquid until the residue is not visually confirmed at the end of the dissolution.
The partial melting and the measurement of the surface layer content are carried out by, for example, the following methods. However, the following dissolution conditions such as the amount of sample powder are examples, and dissolution conditions capable of partial dissolution and total dissolution can be arbitrarily adopted.
A container (for example, a beaker) containing 12 mg of sample powder and 10 mL of 1 mol / L hydrochloric acid is held on a hot plate at a set temperature of 70 ° C. for 1 hour. The obtained solution is filtered through a 0.1 μm membrane filter. Elemental analysis of the filtrate thus obtained is performed by an inductively coupled plasma (ICP) analyzer. In this way, the surface layer content of rare earth atoms with respect to 100 atomic% of iron atoms can be determined. When a plurality of rare earth atoms are detected by elemental analysis, the total content of all rare earth atoms is defined as the surface layer content. This point is the same in the measurement of bulk content.
On the other hand, the total dissolution and the measurement of the bulk content are carried out by, for example, the following methods.
A container (for example, a beaker) containing 12 mg of sample powder and 10 mL of 4 mol / L hydrochloric acid is held on a hot plate at a set temperature of 80 ° C. for 3 hours. After that, the bulk content with respect to 100 atomic% of iron atoms can be obtained by performing the same procedure as the above-mentioned partial melting and measurement of the surface layer content.

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

Regarding the content of constituent atoms (bulk content) of the hexagonal strontium ferrite powder, the strontium atom content can be in the range of, for example, 2.0 to 15.0 atom% with respect to 100 atom% of iron atoms. .. In one aspect, the hexagonal strontium ferrite powder can contain only strontium atoms as divalent metal atoms contained in the powder. In another aspect, the hexagonal strontium ferrite powder can also contain one or more other divalent metal atoms in addition to the strontium atom. For example, it can contain barium and / or calcium atoms. When a divalent metal atom other than the strontium atom is contained, the barium atom content and the calcium atom content in the hexagonal strontium ferrite powder are, for example, 0.05 to 5 with respect to 100 atomic% of iron atoms, respectively. It can be in the range of 0.0 atomic%.

As the crystal structure of hexagonal ferrite, magnetoplumbite type (also referred to as "M type"), W type, Y type and Z type are known. The hexagonal strontium ferrite powder may have any crystal structure. The crystal structure can be confirmed by X-ray diffraction analysis. Hexagonal strontium ferrite powder can be one in which a single crystal structure or two or more kinds of crystal structures are detected by X-ray diffraction analysis. For example, in one aspect, the hexagonal strontium ferrite powder can be such that only the M-type crystal structure is detected by X-ray diffraction analysis. For example, M-type hexagonal ferrite is represented by the composition formula of _{AFe 12} O _19. Here, A represents a divalent metal atom, and when the hexagonal strontium ferrite powder is M-type, A is only a strontium atom (Sr), or when A contains a plurality of divalent metal atoms. As mentioned above, the strontium atom (Sr) occupies the largest amount on the basis of atomic%. The divalent metal atom content of the hexagonal strontium ferrite powder is usually determined by the type of crystal structure of the hexagonal ferrite, and is not particularly limited. The same applies to the iron atom content and the oxygen atom content. The hexagonal strontium ferrite powder contains at least iron atoms, strontium atoms and oxygen atoms, and can also contain rare earth atoms. Further, the hexagonal strontium ferrite powder may or may not contain atoms other than these atoms. As an example, the hexagonal strontium ferrite powder may contain an aluminum atom (Al). The content of aluminum atoms can be, for example, 0.5 to 10.0 atomic% with respect to 100 atomic% of iron atoms. From the viewpoint of further suppressing the decrease in regeneration output during repeated regeneration, the hexagonal strontium ferrite powder contains iron atoms, strontium atoms, oxygen atoms and rare earth atoms, and the content of atoms other than these atoms is 100 iron atoms. % Is preferably 10.0 atomic% or less, more preferably in the range of 0 to 5.0 atomic%, and may be 0 atomic%. That is, in one aspect, the hexagonal strontium ferrite powder does not have to contain atoms other than iron atoms, strontium atoms, oxygen atoms and rare earth atoms. The content expressed in atomic% above is the content (unit: mass%) of each atom obtained by completely dissolving the hexagonal strontium ferrite powder, and is converted to the value expressed in atomic% using the atomic weight of each atom. Calculated by conversion. Further, in the present invention and the present specification, "not contained" for a certain atom means that the content is completely dissolved and the content measured by an ICP analyzer is 0% by mass. The detection limit of an ICP analyzer is usually 0.01 ppm (parts per million) or less on a mass basis. The above-mentioned "not included" is used in the sense of including the inclusion in an amount less than the detection limit of the ICP analyzer. The hexagonal strontium ferrite powder can, in one aspect, be free of bismuth atoms (Bi).

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

(Binder)
The magnetic tape is a coating type magnetic tape, and the magnetic layer contains a binder. A binder is one or more resins. The resin may be a homopolymer or a copolymer. Examples of the binder contained in the magnetic layer include polyurethane resin, polyester resin, polyamide resin, vinyl chloride resin, styrene, acrylonitrile, acrylic resin obtained by copolymerizing methyl methacrylate and the like, cellulose resin such as nitrocellulose, epoxy resin and phenoxy resin. A resin selected from polyvinyl archylal resins such as polyvinyl acetal and polyvinyl butyral can be used alone, or a plurality of resins can be mixed and used. Of these, polyurethane resins, acrylic resins, cellulose resins and vinyl chloride resins are preferred. These resins can also be used as binders in the non-magnetic layer and / or the backcoat layer described later. For the above binder, paragraphs 0029 to 0031 of JP-A-2010-24113 can be referred to. The average molecular weight of the resin used as the binder can be, for example, 10,000 or more and 200,000 or less as the weight average molecular weight. The weight average molecular weight in the present invention and the present specification is a value obtained by converting a value measured by gel permeation chromatography (GPC) into polystyrene. The following conditions can be mentioned as the measurement conditions. The weight average molecular weight shown in Examples described later is a value obtained by converting a value measured under the following measurement conditions into polystyrene.
GPC device: HLC-8120 (manufactured by Tosoh)
Column: TSK gel Multipore HXL-M (manufactured by Tosoh Corporation, 7.8 mm ID (Inner Diameter (inner diameter)) x 30.0 cm)
Eluent: tetrahydrofuran (THF)

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

(Additive)
The magnetic layer contains a ferromagnetic powder and a binder, and may contain one or more additives, if necessary. Examples of the additive include the above-mentioned curing agent. Examples of the additive contained in the magnetic layer include non-magnetic powder (for example, inorganic powder, carbon black, etc.), lubricant, dispersant, dispersion aid, fungicide, antistatic agent, antioxidant, and the like. Can be done. The non-magnetic powder includes a non-magnetic powder that can function as an abrasive, and a non-magnetic powder that can function as a protrusion-forming agent that forms protrusions that appropriately project on the surface of the magnetic layer (for example, non-magnetic colloidal particles). Etc.) etc. The average particle size of colloidal silica (silica colloidal particles) shown in Examples described later is a value obtained by the method described as a method for measuring the average particle size in paragraph 0015 of JP2011-048878A. .. As the additive, a commercially available product can be appropriately selected according to the desired properties, or the additive can be produced by a known method and used in an arbitrary amount. As an example of an additive that can be used for a magnetic layer containing an abrasive, the dispersants described in paragraphs 0012 to 0022 of JP2013-131285A are mentioned as dispersants for improving the dispersibility of the abrasive. be able to. For example, for lubricants, paragraphs 0030 to 0033, 0035 and 0036 of JP2016-126817A can be referred to. The non-magnetic layer may contain a lubricant. For the lubricants that can be contained in the non-magnetic layer, reference can be made to paragraphs 0030, 0031, 0034, 0035 and 0036 of JP2016-126817A. For the dispersant, paragraphs 0061 and 0071 of JP2012-133387A can be referred to. The dispersant may be contained in the non-magnetic layer. For the dispersant that can be contained in the non-magnetic layer, paragraph 0061 of JP2012-133387A can be referred to.

Further, as the dispersant which is an example of the additive, a known dispersant such as a carboxy group-containing compound and a nitrogen-containing compound can be used. For example, the nitrogen-containing compound may be any of a primary amine represented by _{NH 2 R, a secondary amine represented by NHR 2} , and a tertiary amine represented by _{NR 3.} In the above, R indicates an arbitrary structure constituting the nitrogen-containing compound, and a plurality of Rs existing may be the same or different. The nitrogen-containing compound may be a compound (polymer) having a plurality of repeating structures in the molecule. It is considered that the reason why the nitrogen-containing compound can act as a dispersant is that the nitrogen-containing portion of the nitrogen-containing compound functions as an adsorption portion of the hexagonal ferrite powder on the particle surface. Examples of the carboxy group-containing compound include fatty acids such as oleic acid. Regarding the carboxy group-containing compound, it is considered that the carboxy group functions as an adsorption portion of the hexagonal ferrite powder on the particle surface, which is the reason why the carboxy group-containing compound can act as a dispersant. It is also preferable to use a carboxy group-containing compound and a nitrogen-containing compound in combination.

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

<Non-magnetic layer>
Next, the non-magnetic layer will be described. The magnetic tape may have a magnetic layer directly on the non-magnetic support, or may have a non-magnetic layer containing a non-magnetic powder and a binder between the non-magnetic support and the magnetic layer. Good. The non-magnetic powder used for the non-magnetic layer may be an inorganic substance powder or an organic substance powder. In addition, carbon black or the like can also be used. Examples of the inorganic substance include metals, metal oxides, metal carbonates, metal sulfates, metal nitrides, metal carbides, metal sulfides and the like. These non-magnetic powders are commercially available and can also be produced by known methods. For details thereof, refer to paragraphs 0146 to 0150 of JP2011-216149A. For carbon black that can be used for the non-magnetic layer, paragraphs 0040 to 0041 of JP2010-24113A can also be referred to. The content (filling rate) of the non-magnetic powder in the non-magnetic layer is preferably in the range of 50 to 90% by mass, and more preferably in the range of 60 to 90% by mass.

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

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

<Non-magnetic support>
Next, the non-magnetic support will be described. Examples of the non-magnetic support (hereinafter, also simply referred to as “support”) include known biaxially stretched polyethylene terephthalates, polyethylene naphthalates, polyamides, polyamideimides, aromatic polyamides and the like. Among these, polyethylene terephthalate, polyethylene naphthalate, and polyamide are preferable. These supports may be subjected to corona discharge, plasma treatment, easy adhesion treatment, heat treatment and the like in advance.

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

<Various thickness>
The thickness of the non-magnetic support is preferably 3.0 to 6.0 μm.
The thickness of the magnetic layer is preferably 0.15 μm or less, and more preferably 0.1 μm or less, from the viewpoint of high-density recording that has been demanded in recent years. The thickness of the magnetic layer is more preferably in the range of 0.01 to 0.1 μm. The magnetic layer may be at least one layer, and the magnetic layer may be separated into two or more layers having different magnetic characteristics, and a known configuration relating to a multi-layer magnetic layer can be applied. The thickness of the magnetic layer when separated into two or more layers is the total thickness of these layers.

The thickness of the non-magnetic layer is, for example, 0.1 to 1.5 μm, preferably 0.1 to 1.0 μm.

The thickness of the backcoat layer is preferably 0.9 μm or less, more preferably 0.1 to 0.7 μm.

The thickness of each layer of the magnetic tape and the non-magnetic support can be determined by a known film thickness measuring method. As an example, for example, a cross section in the thickness direction of a magnetic tape is exposed by a known method such as an ion beam or a microtome, and then the cross section is observed using a scanning electron microscope in the exposed cross section. Various thicknesses can be obtained as the arithmetic mean of the thickness obtained at one location in the thickness direction in the cross-sectional observation, or at two or more randomly selected locations, for example, two locations. Alternatively, the thickness of each layer may be obtained as a design thickness calculated from the manufacturing conditions.

<Manufacturing process>
(Preparation of composition for forming each layer)
The composition for forming the magnetic layer, the non-magnetic layer or the backcoat layer usually contains a solvent together with the various components described above. As the solvent, various organic solvents generally used for producing a coating type magnetic recording medium can be used. Above all, from the viewpoint of solubility of a binder usually used for a coating type magnetic recording medium, each layer-forming composition contains a ketone solvent such as acetone, methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, cyclohexanone, isophorone, and tetrahydrofuran. It is preferable that one or more of the above is contained. The amount of the solvent in each layer-forming composition is not particularly limited, and can be the same as that of each layer-forming composition of a normal coating type magnetic recording medium. In addition, the step of preparing each layer-forming composition can usually include at least a kneading step, a dispersion step, and a mixing step provided before and after these steps as necessary. Each step may be divided into two or more steps. The components used in the preparation of each layer-forming composition may be added at the beginning or in the middle of any step. Further, each raw material may be added separately in two or more steps. For example, the binder may be divided and added in a kneading step, a dispersion step, and a mixing step for adjusting the viscosity after dispersion. Conventionally known manufacturing techniques can be used in various steps to manufacture magnetic tapes. In the kneading step, it is preferable to use a kneader having a strong kneading force such as an open kneader, a continuous kneader, a pressurized kneader, and an extruder. Details of these kneading treatments are described in JP-A-1-106338 and JP-A-1-79274. A known disperser can be used. Each layer-forming composition may be filtered by a known method before being subjected to the coating step. Filtration can be performed, for example, by filter filtration. As the filter used for filtration, for example, a filter having a pore size of 0.01 to 3 μm (for example, a glass fiber filter, a polypropylene filter, etc.) can be used.

Regarding the dispersion treatment of the composition for forming a magnetic layer, it is preferable to suppress the occurrence of chipping as described above. For that purpose, in the step of preparing the composition for forming a magnetic layer, the hexagonal ferrite powder is dispersed by a two-step dispersion treatment, and the coarse agglomerates of the hexagonal ferrite powder are formed by the first-step dispersion treatment. After crushing, it is preferable to perform a second-stage dispersion treatment in which the collision energy applied to the particles of the hexagonal ferrite powder by collision with the dispersed beads is smaller than that of the first dispersion treatment. According to such a dispersion treatment, it is possible to improve the dispersibility of the hexagonal ferrite powder and suppress the occurrence of chipping at the same time.

Preferred embodiments of the above two-step dispersion treatment include a first step of obtaining a dispersion liquid by dispersing the hexagonal ferrite powder, a binder and a solvent in the presence of the first dispersion beads. A second step of dispersing the dispersion obtained in the above step in the presence of a second dispersed bead having a smaller bead diameter and density than the first dispersed bead can be mentioned. The dispersion treatment of the above-mentioned preferable embodiment will be further described below.

In order to enhance the dispersibility of the hexagonal ferrite powder, it is preferable that the first step and the second step described above are performed as a dispersion treatment before mixing the hexagonal ferrite powder with other powder components. For example, when forming a magnetic layer containing the non-magnetic filler, a liquid (magnetic liquid) containing a hexagonal ferrite powder, a binder, a solvent and an additive optionally added before being mixed with the non-magnetic filler. As the distributed treatment, it is preferable to carry out the first step and the second step described above.

The bead diameter of the second dispersed beads is preferably 1/100 or less, more preferably 1/500 or less of the bead diameter of the first dispersed beads. Further, the bead diameter of the second dispersed beads can be, for example, 1/10000 or more of the bead diameter of the first dispersed beads. However, it is not limited to this range. For example, the bead diameter of the second dispersed beads is preferably in the range of 80 to 1000 nm. On the other hand, the bead diameter of the first dispersed beads can be in the range of, for example, 0.2 to 1.0 mm.
The bead diameter in the present invention and the present specification is a value measured by the same method as the method for measuring the average particle size of the powder described above.

The second step described above is preferably performed under the condition that the second dispersed beads are present in an amount of 10 times or more that of the hexagonal ferrite powder on a mass basis, and is present in an amount of 10 to 30 times. It is more preferable to carry out under the conditions.
On the other hand, the amount of the first dispersed beads in the first step is also preferably in the above range.

The second dispersed beads are beads having a lower density than the first dispersed beads. The "density" is obtained by dividing the mass (unit: g) of the dispersed beads by the volume (unit: cm ^3). The measurement is performed by the Archimedes method. The density of the second dispersed beads is preferably 3.7 g / cm ³ or less, and more preferably 3.5 g / cm ³ or less. The density of the second dispersed beads may be, for example, 2.0 g / cm ³ or more, or less than ^{2.0 g / cm 3.} Examples of the second dispersed beads preferable from the viewpoint of density include diamond beads, silicon carbide beads, silicon nitride beads and the like, and examples of the second dispersed beads preferable from the viewpoint of density and hardness include diamond beads. Can be done.
On the other hand, the first dispersion beads, preferably density is 3.7 g / cm ³ greater than the dispersion beads, density is 3.8 g / cm ³ or more dispersing beads more preferably, 4.0 g / cm ³ or more dispersion Beads are more preferred. The density of the first dispersed beads may be, for example, 7.0 g / cm ³ or less, or more than 7.0 g / cm ³ . As the first dispersed beads, it is preferable to use zirconia beads, alumina beads and the like, and it is more preferable to use zirconia beads.

The dispersion time is not particularly limited, and may be set according to the type of the disperser to be used.

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

(Other processes)
For other various steps for manufacturing the magnetic tape, paragraphs 0067 to 0070 of JP2010-231843A can be referred to. It is preferable that the coating layer of the composition for forming a magnetic layer is subjected to an orientation treatment while the coating layer is in a wet (undried) state. For the orientation treatment, various known techniques such as the description in paragraph 0067 of JP-A-2010-231843 can be applied. As described above, it is preferable to perform the vertical alignment treatment as the orientation treatment from the viewpoint of controlling the XRD intensity ratio. Regarding the orientation treatment, the above description can also be referred to. For example, the vertical alignment treatment can be performed by a known method such as a method using a magnet opposite to the opposite pole. In the alignment zone, the drying rate of the coating layer can be controlled by the temperature of the drying air, the air volume, and / or the transport rate of the magnetic tape in the alignment zone. Alternatively, the coating layer may be pre-dried before being transported to the alignment zone.

The above-mentioned method for manufacturing a magnetic tape is an example, and the XRD intensity ratio and the vertical azimuth ratio can be controlled within the above ranges by any means capable of adjusting the XRD intensity ratio and the vertical azimuth ratio, respectively. , Such aspects are also included in the present invention.

A servo pattern is formed on the magnetic layer of the magnetic tape. The formation of a servo pattern on the magnetic layer is performed by magnetizing a specific position of the magnetic layer with a servo pattern recording head (also referred to as a "servo write head"). The shape of the servo pattern and the arrangement in the magnetic layer for enabling tracking are known, and the region magnetized by the servo light head (the position where the servo pattern is formed) is defined by the standard. A known technique can be applied to the servo pattern of the magnetic layer of the magnetic tape. For example, as a tracking method, a timing-based servo method and an amplitude-based servo method are known. The servo pattern that can be formed on the magnetic layer of the magnetic tape may be a servo pattern that enables tracking of any method. Further, a servo pattern that enables tracking by the timing-based servo method and a servo pattern that enables tracking by the amplitude-based servo method may be formed on the magnetic layer.

With magnetic tape, the data is usually recorded on the data band of the magnetic tape. This forms a track in the data band. Specifically, the magnetic tape usually has a plurality of regions having a servo pattern (referred to as "servo bands") along the longitudinal direction. The data band is an area sandwiched between two servo bands. For example, the track area 30 in FIG. 2 is a data band. Data recording is performed on the data band, and a plurality of tracks are formed along the longitudinal direction in the data band. As an example, for example, the LTO (Linear-Tape-Open) Ultram format tape, which is an industry standard, is formed with a servo pattern capable of tracking by a timing-based servo method. For tracking by the timing-based servo method, a plurality of servo patterns having two or more different shapes are formed on the magnetic layer. The position of the servo head is recognized by the time interval in which the servo head reproduces (reads) two servo patterns having different shapes and the time interval in which the servo head reproduces two servo patterns having the same shape. Tracking is performed based on the position of the servo head recognized in this way. Specifically, when the LTO Ultra format tape is manufactured, a plurality of servo patterns inclined with respect to the tape width direction are formed on the servo band as shown in FIG. In FIG. 14, the servo frame SF on the servo band is composed of the servo subframe 1 (SSF1) and the servo subframe 2 (SSF2). The servo subframe 1 is composed of an A burst (reference numeral A in FIG. 14) and a B burst (reference numeral B in FIG. 14). The A burst is composed of servo patterns A1 to A5, and the B burst is composed of servo patterns B1 to B5. On the other hand, the servo subframe 2 is composed of a C burst (reference numeral C in FIG. 14) and a D burst (reference numeral D in FIG. 14). The C burst is composed of servo patterns C1 to C4, and the D burst is composed of servo patterns D1 to D4. Such 18 servo patterns are arranged in a set of 5 and 4 in subframes arranged in an array of 5, 5, 4, 4, and used to identify the servo frames. FIG. 14 shows one servo frame for illustration. However, in reality, in the magnetic layer of the magnetic tape on which the timing-based servo type tracking is performed, a plurality of servo frames are arranged in the traveling direction in each servo band. In FIG. 14, the arrow indicates the traveling direction. For example, an LTO Ultra format tape usually has 5000 or more servo frames per 1 m of tape length in each servo band of the magnetic layer. The servo element sequentially reads the servo pattern in a plurality of servo frames while contacting and sliding on the surface of the magnetic layer of the magnetic tape conveyed in the magnetic tape device. Hereinafter, a servo pattern capable of tracking by the timing-based servo method is referred to as a "timing-based servo pattern".

It is suppressed that unintended parts on the magnetic layer are also magnetized when magnetized (forming a servo pattern) by the servo light head, for example, the edge specified by the magnetic force microscope observation of the timing-based servo pattern. Difference between the _{cumulative distribution function L 99.9} of the position deviation width from the ideal shape in the longitudinal direction of the magnetic tape of the shape L _{99.9 and the value L 0.1} of the above cumulative distribution function 0.1% _{(L 99)} It can be evaluated by _.9- L _0.1 ) (hereinafter, also simply referred to as "difference (L _99.9- L _0.1)"). The timing-based servo pattern is formed on the magnetic layer as a plurality of servo patterns having two or more different shapes. In one example, a plurality of servo patterns having two or more different shapes are continuously arranged at regular intervals for each of a plurality of servo patterns having the same shape. In another example, different types of servo patterns are arranged alternately. Regarding the fact that the servo patterns have the same shape, the positional deviation of the edge shape of the servo pattern does not matter. The shape of the servo pattern that can be tracked by the timing-based servo method and the arrangement on the servo band are known, and the servo pattern shown in FIG. 14 is a specific example. In the present invention and the present specification, the edge shape specified by the magnetic force microscope observation of the timing-based servo pattern is also described as the magnetic tape traveling direction (hereinafter, simply referred to as "traveling direction") when recording a magnetic signal (data). The shape of the edge is located on the downstream side with respect to.). For example, in FIG. 14, the traveling direction side of the arrow is the upstream side, and the opposite side is the downstream side.

Below, the edge shape specified by the magnetic force microscope observation of the timing-based servo pattern, and the cumulative distribution function of the position deviation width from the ideal shape in the longitudinal direction of the magnetic tape of this edge shape L _{99.9% value L 99.9} The difference between the cumulative distribution function 0.1% and the value L _0.1 (L _99.9- L _0.1 ), and the ideal shape will be described.
In the following, a linear servo pattern that extends continuously from one side in the width direction of the magnetic tape toward the other and is inclined at an angle α with respect to the width direction of the magnetic tape will be mainly described as an example. The above angle α is a line segment connecting two ends in the tape width direction of the edge of the servo pattern located on the downstream side of the traveling direction of the magnetic tape when recording a magnetic signal (data) and the magnetic tape. It means the angle formed by the width direction of. Including this point, it will be further described below.

15 and 16 are explanatory views of the angle α. In the servo pattern shown in FIG. 14, the servo pattern A1 to A5, for servo pattern which is inclined toward the upstream side in the running direction as C1 -C4, connecting the ends two locations on the downstream side of the edge E _L The angle formed by the line segment (broken line L1 in FIG. 15) and the tape width direction (broken line L2 in FIG. 15) is defined as the angle α. On the other hand, the servo pattern B1 to B5, the servo pattern which is inclined toward the downstream side in the traveling direction as shown in D1 to D4, the line segment connecting the ends two locations on the downstream side of the edge E _L (in FIG. 16 , The angle formed by the broken line L1) and the tape width direction (broken line L2 in FIG. 16) is defined as an angle α. This angle α is generally called an azimuth angle, and is determined by the setting of the servo light head when forming a magnetization region (servo pattern) on the servo band.

If the servo pattern is ideally formed when the magnetization region (servo pattern) is formed on the servo band, the edge shape of the servo pattern inclined at an angle α with respect to the width direction of the magnetic tape is as described above. It matches the shape of the line segment (broken line L1 in FIGS. 15 and 16) connecting the two edge ends of the above. That is, it becomes a straight line. Therefore, at each location on the edge, the misalignment width from the ideal shape in the longitudinal direction of the magnetic tape (hereinafter, also simply referred to as “misalignment width”) becomes zero. However, as shown in FIG. 17, the edge shape of the servo pattern deviates from the ideal shape, and the large variation in the misalignment width and the large variation in the value of the misalignment width at each edge are the servo patterns. It is considered to be a factor that lowers the accuracy of identifying the position of the reading element by reading. On the other hand, the above difference (L _99.9- L _0.1 ) shows that the displacement width from the ideal shape is small at each edge position of the servo pattern, and the value of the displacement width is different at each edge location. Is a value that can be an indicator that is small.

The difference (L _99.9- L _0.1 ) is a value obtained by the following method.
The surface of the magnetic layer of the magnetic tape on which the servo pattern is formed is observed with a magnetic force microscope (MFM; Magnetic Force Microscope). The measurement range is a range that includes five servo patterns. For example, in the LTO Ultra format tape, by setting the measurement range to 90 μm × 90 μm, five servo patterns of A burst or B burst can be observed. The servo pattern (magnetization region) is extracted by measuring the measurement range at a pitch of 100 nm (coarse measurement).
Then, in order to detect the boundary between the magnetized region and the non-magnetized region at the edge of the servo pattern located downstream with respect to the traveling direction, measurement is performed at a pitch of 5 nm in the vicinity of the boundary to obtain a magnetic profile. When the obtained magnetic profile is tilted by an angle α with respect to the width direction of the magnetic tape, rotation correction is performed by analysis software along the width direction of the magnetic tape (so that α = 0 °). After that, the position coordinates of the peak value of each profile measured at a pitch of 5 nm are calculated by the analysis software. The position coordinates of this peak value indicate the position of the boundary between the magnetized region and the non-magnetized region. The position coordinates are specified by, for example, an xy coordinate system in which the traveling direction is the x coordinate and the width direction is the y coordinate.
Taking the case where the ideal shape is a straight line and the position coordinates of a certain position on the straight line are (x, y) = (a, b), the actually obtained edge shape (position coordinates of the boundary) is taken. If is consistent with the ideal shape, the calculated position coordinates are (x, y) = (a, b). In this case, the misalignment width is zero. On the other hand, if the actually obtained edge shape deviates from the ideal shape, the x-coordinate of the position of y = b at the boundary becomes x = a + c or x = a-c. For example, x = a + c means that the width c is deviated to the upstream side with respect to the traveling direction, and x = a−c means, for example, the width c (that is, based on the upstream side) to the downstream side with respect to the traveling direction. Then -c) is the case where there is a deviation. Here, c is the misalignment width. That is, the absolute value of the displacement width of the x-coordinate from the ideal shape is the displacement width from the ideal shape in the longitudinal direction of the magnetic tape. In this way, the misalignment width at each point on the downstream side in the traveling direction obtained by the measurement at the pitch of 5 nm is obtained.
From the values obtained for each servo pattern, the cumulative distribution function is obtained by analysis software. From the obtained cumulative distribution function, the cumulative distribution function 99.9% value L _99.9 and the 0.1% value L _{0.1 were obtained, and the difference (L 99.)} was obtained for each servo pattern from the obtained values. _9- L _0.1 ) is calculated.
The above measurement is performed in three different measurement ranges (measurement number N = 3).
_{The arithmetic mean of the difference (L 99.9-} L _0.1 ) obtained for each servo pattern is defined as the above difference (L _99.9- L _{0.1) for the magnetic tape.}

The "ideal shape" of the edge shape of the servo pattern in the present specification means the edge shape when the servo pattern is formed without misalignment. For example, in one aspect, the servo pattern is a linear servo pattern that extends continuously or discontinuously from one side to the other in the width direction of the magnetic tape. The "straight line" of the servo pattern means that the pattern shape does not include a curved portion regardless of the positional deviation of the edge shape. "Continuous" means extending from one side in the tape width direction toward the other without any inflection point and uninterrupted tilt angle. An example of a servo pattern that continuously extends from one side to the other in the width direction of the magnetic tape is the servo pattern shown in FIG. On the other hand, "discontinuity" means that there is one or more inflection points of the inclination angle and / or that the inclination angle is interrupted and extended at one or more points. The shape that has an inflection point of the inclination angle but extends without interruption is a so-called polygonal line shape. An example of a discontinuous servo pattern in which one inflection point of the inclination angle extends from one side in the tape width direction toward the other without interruption is the servo pattern shown in FIG. On the other hand, an example of a discontinuous servo pattern that is interrupted at one point without an inflection point of the inclination angle and extends from one side in the tape width direction toward the other is the servo pattern shown in FIG. Further, an example of a discontinuous servo pattern in which the inclination angle has one inflection point and is interrupted at one point and extends from one side in the tape width direction toward the other is the servo pattern shown in FIG.
For a linear servo pattern that extends continuously from one side in the tape width direction to the other, the "ideal shape" of the edge shape connects two ends of the edge on the downstream side in the traveling direction of the linear servo pattern. It is the shape of a line segment (straight line shape). For example, the linear servo pattern shown in FIG. 14 has a linear shape shown by L1 in FIG. 15 or 16. On the other hand, for a linear servo pattern that extends discontinuously, the ideal shape is the shape of a line segment connecting one end to the other end of a portion having the same inclination angle (straight shape) for a shape having an inflection point of the inclination angle. Is. Further, the shape that is interrupted and extended at one or more points is the shape of a line segment (straight line shape) that connects one end to the other end of each continuously extending portion. For example, the servo pattern shown in FIG. 18 is a line segment connecting e1 and e2 and a line segment connecting e2 and e3. The servo pattern shown in FIG. 19 is a line segment connecting e4 and e5 and a line segment connecting e6 and e7. The servo pattern shown in FIG. 20 is a line segment connecting e8 and e9 and a line segment connecting e10 and e11.

In the above, the linear servo pattern has been described as an example. However, the servo pattern may be a servo pattern in which the ideal edge shape is a curved shape. For example, for a servo pattern whose edge shape on the downstream side with respect to the traveling direction is ideally a partial arc shape, a magnetic force microscope with an edge shape on the downstream side with respect to the traveling direction is used with respect to the position coordinates of this partial arc. _{The difference (L 99.9-} L _0.1 ) can be obtained from the position deviation width obtained from the obtained position coordinates.

As the magnetic force microscope used in the above measurement, a commercially available magnetic force microscope having a known configuration is used in the frequency modulation (FM) mode. As the probe of the magnetic force microscope, for example, SSS-MFMR (nominal radius of curvature of 15 nm) manufactured by Nowold can be used. The distance between the surface of the magnetic layer and the tip of the probe when observed with a magnetic force microscope shall be in the range of 20 to 50 nm.
Further, as the analysis software, commercially available analysis software or analysis software incorporating a known arithmetic expression can be used.

The above difference (L _99.9- L _0.1 ) can be 180 nm or less, 170 nm or less, 160 nm or less, 150 nm or less, 140 nm or less, 130 nm or less, 120 nm or less, 110 nm or less, or 100 nm or less. be able to. The difference (L _99.9- L _0.1 ) can be, for example, 50 nm or more, 60 nm or more, or 70 nm or more. The difference (L _99.9- L _0.1 ) can be controlled by the type of servo light head (specifically, the leakage magnetic field) used to form the servo pattern. As the servo light head, for example, a servo light head having a leakage magnetic field in the range of 150 to 400 kA / m, preferably 200 to 400 kA / m can be used. However, as the activated volume of the hexagonal ferrite powder contained in the magnetic layer becomes smaller, it tends to be difficult to reduce the _{difference (L 99.9-} L _{0.1) only by increasing the capacity of the servo light head.} There is. It is presumed that this is because the arrangement of the hexagonal ferrite powder particles in the magnetic layer is easily distorted due to the small activated volume, and magnetic distortion is likely to occur in the magnetic layer. However, it is just a guess. On the other hand, the magnetic tape having the XRD intensity ratio and the vertical angular ratio in the above range has a difference (L _99.9- L _{0.) Even if the activated volume of the hexagonal ferrite powder contained in the magnetic layer is small. It is easy to reduce 1} ), for example, to 180 nm or less. This point may also apply to servo patterns other than the timing-based servo pattern. That is, the fact that the XRD intensity ratio and the vertical azimuth ratio are in the ranges described above suppresses that an unintended portion on the magnetic layer is also magnetized when being magnetized (forming a servo pattern) by the servo light head. Can contribute to doing so.

In a timing-based servo system, for example, a pair of servo patterns (also referred to as "servo stripes") that are not parallel to each other and are continuously arranged in a plurality in the longitudinal direction of a magnetic tape are read by a servo element to obtain a servo signal. Is obtained.

In one aspect, as shown in Japanese Patent Application Laid-Open No. 2004-318983, each servo band has information indicating the number of the servo band (“servo band ID (identification)” or “UDIM (Unique DataBand Identification Method)”. Also called "information") is embedded. The servo band ID is recorded by shifting a specific one of a plurality of pairs of servo patterns in the servo band so that the position thereof is displaced relative to the longitudinal direction of the magnetic tape. Specifically, the method of shifting a specific one of a plurality of pairs of servo patterns is changed for each servo band. As a result, the recorded servo band ID becomes unique for each servo band, so that the servo band can be uniquely identified by simply reading one servo band with the servo element.

As a method for uniquely specifying the servo band, there is also a method using a staggered method as shown in ECMA (European Computer Manufacturers Association) -319. In this staggered method, a group of a pair of servo patterns (servo stripes) that are continuously arranged in the longitudinal direction of the magnetic tape and are not parallel to each other are recorded so as to be shifted in the longitudinal direction of the magnetic tape for each servo band. To do. This combination of shifting methods between adjacent servo bands is unique to the entire magnetic tape, so it is possible to uniquely identify the servo band when reading the servo pattern with two servo elements. It has become.

Further, as shown in ECMA-319, information indicating the position of the magnetic tape in the longitudinal direction (also referred to as "LPOS (Longitorial Position) information") is usually embedded in each servo band. This LPOS information, like the UDIM information, is also recorded by shifting the positions of the pair of servo patterns in the longitudinal direction of the magnetic tape. However, unlike the UDIM information, in this LPOS information, the same signal is recorded in each servo band.

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

The servo light head has a pair of gaps corresponding to the pair of servo patterns as many as the number of servo bands. Normally, a core and a coil are connected to each pair of gaps, and by supplying a current pulse to the coil, a magnetic field generated in the core can generate a leakage magnetic field in the pair of gaps. When forming the servo pattern, the magnetic pattern corresponding to the pair of gaps is transferred to the magnetic tape by inputting a current pulse while running the magnetic tape on the servo light head to form the servo pattern. Can be done. The width of each gap can be appropriately set according to the density of the formed servo pattern. The width of each gap can be set to, for example, 1 μm or less, 1 to 10 μm, 10 μm or more, and the like.

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

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

The magnetic tape described above is usually housed in a magnetic tape cartridge, and the magnetic tape cartridge is mounted on the magnetic tape device. The configuration of the magnetic tape cartridge is known.

According to one aspect, the following magnetic tapes are also provided.
Having a magnetic layer containing ferromagnetic powder and binder on a non-magnetic support,
The magnetic layer has a servo pattern and
The ferromagnetic powder is a hexagonal ferrite powder,
Peak intensity of the diffraction peak on the (114) plane of the hexagonal ferrite crystal structure obtained by X-ray diffraction analysis of the magnetic layer using the In-Plane method Int. Peak intensity Int of the diffraction peak on the (110) plane with respect to Int (114). The intensity ratio (Int (110) / Int (114)) of (110) is 0.5 or more and 4.0 or less, and the vertical angular type ratio of the magnetic tape is 0.65 or more and 1.00 or less. tape.

According to one aspect, the following magnetic tapes are also provided.
A magnetic tape used to record data and read recorded data.
Having a magnetic layer containing ferromagnetic powder and binder on a non-magnetic support,
The magnetic layer has a servo pattern and
The ferromagnetic powder is a hexagonal ferrite powder,
Peak intensity of the diffraction peak on the (114) plane of the hexagonal ferrite crystal structure obtained by X-ray diffraction analysis of the magnetic layer using the In-Plane method Int. Peak intensity Int of the diffraction peak on the (110) plane with respect to Int (114). The intensity ratio (Int (110) / Int (114)) of (110) is 0.5 or more and 4.0 or less, and the vertical angular type ratio of the magnetic tape is 0.65 or more and 1.00 or less. tape.
In one aspect, the reading of the data can be performed by the reading element unit.
In one aspect, the reading element unit can have a plurality of reading elements that read data from a specific track area including a reading target track in the track area included in the magnetic tape by a linear scan method.
In one aspect, the reading result for each reading element can be extracted by the extraction unit.
In one aspect, the extraction unit can extract data derived from the reading target track from the reading result for each reading element.
In one aspect, the extraction unit performs waveform equalization processing on each of the reading results for each reading element according to the amount of displacement between the magnetic tape and the reading element unit, thereby reading the reading. From the result, the data derived from the read target track can be extracted.

The above description can be referred to for specific embodiments that the magnetic tape, the reading element unit, and the extraction unit can take.

Hereinafter, the present invention will be described based on examples. However, the present invention is not limited to the embodiments shown in the examples. Unless otherwise specified, the indications of "part" and "%" described below indicate "parts by mass" and "% by mass". The "eq" described below is an equivalent and is a unit that cannot be converted into SI units. Further, unless otherwise specified, the steps and evaluations described below were performed in an environment with an atmospheric temperature of 23 ° C. ± 1 ° C.

1. 1. Fabrication of Magnetic Tape [Example 1]
The formulation of each layer-forming composition is shown below.

<Prescription of composition for forming magnetic layer>
(Magnetic liquid)
Plate-shaped hexagonal ferrite powder (M-type barium ferrite): 10.0 parts Oleic acid: 2.0 parts Vinyl chloride copolymer (MR-104 manufactured by Kaneka Co., Ltd.): 10.0 parts SO ₃ Na group-containing polyurethane resin: 4.0 parts (weight average molecular weight: 70,000, SO ₃ Na group: 0.07 meq / g)
Amine-based polymer (DISPERBYK-102 manufactured by Big Chemie): 6.0 parts Methyl ethyl ketone: 150.0 parts Cyclohexanone: 150.0 parts (abrasive solution)
α-Alumina: 6.0 parts (BET (Brunauer-Emmett-Teller) specific surface area: 19 m ² / g, Mohs hardness: 9)
SO ₃ Na group-containing polyurethane resin: 0.6 parts (weight average molecular weight: 70,000, SO ₃ Na group: 0.1 meq / g)
2,3-Dihydroxynaphthalene: 0.6 parts Cyclohexanone: 23.0 parts (protrusion forming agent solution)
Colloidal silica: 2.0 parts (average particle size: 80 nm)
Methyl ethyl ketone: 8.0 parts (lubricant and curing agent solution)
Stearic acid: 3.0 parts Stearic acid amide: 0.3 parts Butyl stearate: 6.0 parts Methyl ethyl ketone: 110.0 parts Cyclohexanone: 110.0 parts Polyisocyanate (Tosoh Coronate (registered trademark) L): 3 .0 copies

<Prescription of non-magnetic layer forming composition>
Non-magnetic inorganic powder α-iron oxide: 100.0 parts (average particle size: 10 nm, BET specific surface area: 75 m ² / g)
Carbon black: 25.0 parts (average particle size: 20 nm)
SO ₃ Na group-containing polyurethane resin: 18.0 parts (weight average molecular weight: 70,000, SO ₃ Na group content: 0.2 meq / g)
Stearic acid: 1.0 parts Cyclohexanone: 300.0 parts Methyl ethyl ketone: 300.0 parts

<Prescription of composition for forming back coat layer>
Non-magnetic inorganic powder α-iron oxide: 80.0 parts (average particle size: 0.15 μm, BET specific surface area: 52 m ² / g)
Carbon black: 20.0 parts (average particle size: 20 nm)
Vinyl chloride copolymer: 13.0 parts Sulfonic acid base-containing polyurethane resin: 6.0 parts Phenylphosphonic acid: 3.0 parts Cyclohexanone: 155.0 parts Methyl ethyl ketone: 155.0 parts Stealic acid: 3.0 parts Steric acid Butyl: 3.0 parts Polyisocyanate: 5.0 parts Cyclohexanone: 200.0 parts

<Preparation of composition for forming magnetic layer>
The composition for forming a magnetic layer was prepared by the following method.
Various components of the above magnetic liquid were dispersed for 24 hours using zirconia beads (first dispersed beads, density 6.0 g / cm ^{3) having a bead diameter of 0.5 mm by a batch type vertical sand mill (first step).} ), Then, the dispersion liquid A was prepared by filtering using a filter having a pore size of 0.5 μm. The amount of zirconia beads used was 10 times the amount of hexagonal barium ferrite powder on a mass basis.
Then, the dispersion liquid A was dispersed for 1 hour by using a batch type vertical sand mill using diamond beads having the bead diameter shown in Table 1 (second dispersion beads, density 3.5 g / cm ^{3) (second step).} , A dispersion liquid (dispersion liquid B) from which diamond beads were separated was prepared using a centrifuge. The following magnetic liquid is the dispersion liquid B thus obtained. The diamond beads were used in a prescription amount 10 times the mass of the hexagonal barium ferrite powder.
The abrasive liquid is a mixture of various components of the above abrasive liquid and placed in a horizontal bead mill disperser together with zirconia beads having a bead diameter of 0.3 mm, so that the bead volume / (abrasive liquid volume + bead volume) becomes 80%. The bead mill dispersion treatment was performed for 120 minutes, the liquid after the treatment was taken out, and the ultrasonic dispersion filtration treatment was performed using a flow-type ultrasonic dispersion filtration device. In this way, the abrasive liquid was prepared.
The prepared magnetic solution, abrasive solution, and the remaining components were introduced into the dissolver, stirred at a peripheral speed of 10 m / sec for 30 minutes, and then treated with a flow type ultrasonic disperser at a flow rate of 7.5 kg / min for 3 passes. , A composition for forming a magnetic layer was prepared by filtering with a filter having a pore size of 1 μm.

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

<Preparation of composition for backcoat layer formation>
Of the various components of the backcoat layer forming composition described above, the components excluding the lubricant (stearic acid and butyl stearate), polyisocyanate and 200.0 parts of cyclohexanone are kneaded and diluted with an open kneader, and then dispersed in a horizontal bead mill. Using a zirconia bead having a bead diameter of 1 mm by a machine, the bead filling rate was 80% by volume, the rotor tip peripheral speed was 10 m / sec, the residence time per pass was set to 2 minutes, and 12 passes were subjected to the dispersion treatment. Then, the remaining components described above were added and stirred with a dissolver, and the obtained dispersion was filtered using a filter having a pore size of 1 μm to prepare a composition for forming a back coat layer.

<How to make magnetic tape>
On the surface of a polyethylene naphthalate support having a thickness of 5.0 μm, the composition for forming a non-magnetic layer prepared above so as to have a thickness of 1.0 μm after drying is applied and dried to form a non-magnetic layer. did. A coating layer was formed by applying the composition for forming a magnetic layer prepared above so that the thickness after drying would be 0.1 μm on the surface of the formed non-magnetic layer. While the coating layer of the composition for forming a magnetic layer was in a wet (undried) state, a magnetic field having the strength shown in Table 1 was applied in the direction perpendicular to the surface of the coating layer to perform a vertical alignment treatment. Then, the coating layer was dried to form a magnetic layer.
Then, the backcoat layer forming composition prepared above was applied onto the surface of the support opposite to the surface on which the non-magnetic layer and the magnetic layer were formed so that the thickness after drying would be 0.4 μm. It was dried.
The magnetic tape thus obtained is calendared (surface smoothing) at a speed of 100 m / min, a linear pressure of 300 kg / cm (294 kN / m), and a calendar roll surface temperature of 90 ° C. by a calendar roll composed of only metal rolls. Then, the heat treatment was performed for 36 hours in an environment having an ambient temperature of 70 ° C. After the heat treatment, slits were made to a width of 1/2 inch (0.0127 m) to prepare a magnetic tape. With the magnetic layer of the produced magnetic tape degaussed, a servo light head (leakage magnetic field: see Table 1) was used to form a servo pattern of arrangement and shape according to the LTO Ultra format on the magnetic layer. As a result, the magnetic layer has a data band, a servo band, and a guide band in an arrangement according to the LTO Ultra format, and a servo pattern (timing-based servo pattern) having an arrangement and a shape according to the LTO Ultra format is provided on the servo band. Obtained a magnetic tape to have.

[Examples 2 to 5, Comparative Examples 1 to 8]
A magnetic tape was produced in the same manner as in Example 1 except that the various items shown in Table 1 were changed as shown in Table 1.
For the comparative examples in which "None" is described in the column of dispersed beads and the column of time in Table 1, a composition for forming a magnetic layer was prepared without carrying out the second step in the magnetic liquid dispersion treatment.
In Table 1, for the comparative example in which “None” is described in the column of the vertical alignment treatment magnetic field strength, the magnetic layer was formed without the orientation treatment.
It can be said that the larger the value of the leakage magnetic field of the servo light head, the higher the ability to record the servo pattern. In the examples and comparative examples, two types of servo light heads having different leakage magnetic fields were used.

[Evaluation method]
(1) Activated volume A part of each magnetic tape of Examples and Comparative Examples was cut out, and hexagonal ferrite powder was collected from the magnetic layer by the method exemplified above as a method for collecting a sample for measurement. The collected hexagonal ferrite powder was measured to determine the activated volume. The measurement was performed using a vibration sample type magnetic flux meter (manufactured by Toei Kogyo Co., Ltd.) at magnetic field sweep speeds of 3 minutes and 30 minutes in the coercive force Hc measuring unit, and the activated volume was calculated from the relational expression described above. The measurement was performed in an environment of 23 ° C. ± 1 ° C. The measured activation volumes were all 1600 nm ³ .

(2) XRD intensity ratio A tape sample was cut out from the produced magnetic tape.
The cut-out tape sample was subjected to In-Plane XRD by the method described above by injecting X-rays on the surface of the magnetic layer using a thin film X-ray diffractometer (SmartLab manufactured by Rigaku Co., Ltd.).
From the X-ray diffraction spectrum obtained by In-Plane XRD, the peak intensity Int (114) of the diffraction peak on the (114) plane and the peak intensity Int (110) of the diffraction peak on the (110) plane of the hexagonal ferrite crystal structure can be obtained. The XRD intensity ratio (Int (110) / Int (114)) was calculated.

(3) Vertical azimuth ratio For the produced magnetic tape, the vertical azimuth ratio was determined by the method described above using a vibration sample type magnetic flux meter (manufactured by Toei Kogyo Co., Ltd.).

(4) For each of the magnetic tapes of the measurement and calculation examples and comparative examples of the difference _(L 99.9 _{-L 0.1),} was determined difference _(L 99.9 _{-L 0.1)} by the following method.
90 μm × 90 μm of the magnetic layer surface of the magnetic tape on which the servo pattern was formed using Bruker's Dimensions 3100 as a magnetic force microscope in frequency modulation mode and Nanold's SSS-MFMR (nominal radius of curvature 15 nm) as a probe. A servo pattern (magnetization region) was extracted by performing a rough measurement at a pitch of 100 nm in the measurement range of. The distance between the surface of the magnetic layer and the tip of the probe when observed with a magnetic force microscope was 20 nm. Since the measurement range includes five A-burst servo patterns formed according to the LTO Ultra format, these five servo patterns were extracted.
Using the above magnetic force microscope and probe, the vicinity of the boundary between the magnetized region and the non-magnetized region was measured at a pitch of 5 nm for the edge on the downstream side with respect to the traveling direction of each servo pattern to obtain a magnetic profile. Since the obtained magnetic profile was tilted at an angle α = 12 °, rotation correction was performed by analysis software so that the angle α = 0 °.
The measurement was performed at three different locations on the surface of the magnetic layer. Each measurement range contained five A-burst servo patterns.
_{Then, the difference (L 99.9-} L _0.1 ) was obtained by the method described above using analysis software. As the analysis software, MATLAB manufactured by MathWorks was used. The difference (L _99.9- L _0.1 ) thus obtained is shown in Table 2.

(5) Performance evaluation (i) For the magnetic layer of each of the magnetic tapes of Examples and Comparative Examples, a recording / playback head mounted on an IBM TS1155 tape drive was used to record lines at a speed of 6 m / s. Data was recorded under recording conditions of density: 600 kbps (255 bit PRBS) and track pitch: 2 μm. The above-mentioned unit kbpi is a unit of line recording density (cannot be converted into SI unit system). The above PRBS is an abbreviation for Pseudo Random Bit Sequence.
According to the above recording, the magnetic layer of each magnetic tape has a specific track area in which the track to be read is located between two adjacent tracks, that is, between the first noise mixing source track and the second noise mixing source track. It is formed.
(Ii) The following data reading was performed as a model experiment in which data reading was performed using a reading element unit having two reading elements arranged in close proximity to each other. In the following model experiment, data reading was performed by contacting and sliding the surface of the magnetic layer and the reading element.
Reading is started with the magnetic head having a single reading element arranged so that the center of the track to be read in the tape width direction and the center of the reading element in the track width direction coincide with each other, and the first data reading is performed. went. During this first data reading, the servo pattern was read by the servo element, and the tracking of the timing-based servo method was also performed. Further, the data reading operation was performed by the reading element in synchronization with the servo pattern reading operation.
Next, the same magnetic head was shifted by 500 nm in the tape width direction (one adjacent track side), and the second data reading was performed in the same manner as the first data reading. The above two data readings were performed under reading conditions of a reproduction element width: 0.2 μm, a speed: 4 m / s, and a sampling rate: 1.25 times the bit rate.
The read signal obtained in the first data reading was input to the equalizer, and waveform equalization processing was performed according to the amount of displacement between the magnetic tape and the magnetic head (reading element) in the first data reading. .. This waveform equalization process is a process performed as follows. The ratio of the overlapping area between the reading element and the track to be read and the overlapping area between the reading element and the adjacent track is calculated from the amount of position deviation obtained by reading the servo pattern formed at a fixed cycle by the servo element. Identify. Waveform equalization processing is performed by convolving the tap coefficient derived from this specified ratio using an arithmetic expression with respect to the read signal. The above calculation formula is a calculation formula using EPR4 (Exted Partial Response class 4) as a basic waveform (target). The read signal obtained by the second data reading was also subjected to waveform equalization processing in the same manner.
By performing the phase matching processing (hereinafter, referred to as "two-dimensional signal processing") of the two read signals subjected to the above waveform equalization processing, the two reading elements (reading) arranged in close proximity to each other are performed. A reading signal would be obtained by a reading element unit having an element pitch = 500 nm). For the read signal thus obtained, the SNR at the signal detection point was calculated.
(Iii) In the above (ii), the position of the reading element at the start of the first data reading is set to the first noise mixing source track side and the second noise mixing source track side at intervals of 0.1 μm from the center in the tape width direction of the track to be read. The SNR envelope with respect to the track position was obtained by repeating the process while offsetting each track to the noise mixing source track side.
In Table 2, for Examples and Comparative Examples in which “Yes” is described in the “Two-dimensional signal processing” column, an SNR envelope was obtained by the above method.
In Table 2, for the comparative example in which “None” is described in the column of “Two-dimensional signal processing”, the result of the first data reading (that is, only with a single element) without performing the above-mentioned second data reading. The envelope of SNR was obtained with respect to the data reading result).
(Iv) The envelope of the SNR of Comparative Example 1 was used as the reference envelope, and the place where the SNR decreased by -3 dB from the SNR of the track center in the reference envelope was set as the lower limit of the SNR. For each envelope, the maximum track offset amount above this lower limit was defined as the allowable track offset amount. For each of the Examples and Comparative Examples, the rate of increase in the allowable track offset amount with respect to the allowable track offset amount in Comparative Example 1 was determined as the “allowable track offset amount increase rate”.

The above results are shown in Table 2.

As shown in Table 2, according to the examples, an allowable track offset amount increase rate of 20% or more could be realized.
A large allowable track offset amount required by the above method is advantageous in enabling reproduction with high reproduction quality even if the track margin is reduced. From this point, it is preferable that the allowable track offset amount increase rate is 20% or more.

One aspect of the present invention is useful in magnetic recording applications where it is desired to reproduce high density recorded data with high reproduction quality.

Claims (12)

With magnetic tape
With the reading element unit
Extractor and
Including
The magnetic tape has a magnetic layer containing a ferromagnetic powder and a binder on a non-magnetic support.
The magnetic layer has a servo pattern and has a servo pattern.
The ferromagnetic powder is a hexagonal ferrite powder.
Peak intensity of the diffraction peak on the (114) plane of the hexagonal ferrite crystal structure obtained by X-ray diffraction analysis of the magnetic layer using the In-Plane method Int Peak intensity of the diffraction peak on the (110) plane with respect to Int (114) The intensity ratio of (110), Int (110) / Int (114), is 0.5 or more and 4.0 or less.
The vertical angular ratio of the magnetic tape is 0.65 or more and 1.00 or less.
The reading element unit has a plurality of reading elements that read data from a specific track area including a track to be read among the track areas included in the magnetic tape by a linear scan method.
The extraction unit performs waveform equalization processing on each of the reading results for each reading element according to the amount of displacement between the magnetic tape and the reading element unit, and from the reading results, the above-mentioned Extract the data derived from the track to be read and
The amount of deviation is determined according to the result obtained by reading the servo pattern of the magnetic layer of the magnetic tape by the servo element. The magnetic tape device according to claim 1, wherein some of the plurality of reading elements overlap each other in the traveling direction of the magnetic tape. The specific track area is an area including the read target track and an adjacent track adjacent to the read target track.
The magnetic tape device according to claim 2, wherein each of the plurality of reading elements straddles both the reading target track and the adjacent track when the positional relationship with the magnetic tape changes. .. The magnetic tape device according to claim 1, wherein the plurality of reading elements are arranged side by side in a state of being close to each other in the width direction of the magnetic tape. The magnetic tape device according to any one of claims 1 to 4, wherein the plurality of reading elements are housed in the reading target track in the width direction of the magnetic tape. The magnetic tape device according to any one of claims 1 to 5, wherein the waveform equalization process is performed using a tap coefficient determined according to the deviation amount. For each of the plurality of reading elements, the ratio of the overlapping area with the reading target track and the overlapping area with the adjacent track adjacent to the reading target track is specified from the deviation amount, and the specified ratio is obtained. The magnetic tape device according to claim 6, wherein the tap coefficient is determined accordingly. The magnetic tape device according to any one of claims 1 to 7, wherein the reading operation of the reading element unit is performed in synchronization with the reading operation performed by the servo element. The extraction unit has a two-dimensional FIR filter and has a two-dimensional FIR filter.
The two-dimensional FIR filter derives from the reading result from the reading target track by synthesizing each result obtained by performing the waveform equalization processing on each of the reading results for each reading element. The magnetic tape device according to any one of claims 1 to 8, wherein the data is extracted. The magnetic tape device according to any one of claims 1 to 9, wherein the plurality of reading elements are a pair of reading elements. The magnetic tape device according to any one of claims 1 to 10, wherein the vertical square ratio of the magnetic tape is 0.65 or more and 0.90 or less. The magnetic tape device according to any one of claims 1 to 11, wherein the activated volume of the hexagonal ferrite powder is 1600 nm ^{3 or less.}

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