Recording device, reading device, recording method, recording program, reading method, reading program, and magnetic tape

文档序号：98544 发布日期：2021-10-12 浏览：55次中文

阅读说明：本技术 记录装置、读取装置、记录方法、记录程序、读取方法、读取程序及磁带 (Recording device, reading device, recording method, recording program, reading method, reading program, and magnetic tape ) 是由小泽荣贵近藤理贵宫本健太郎佐野直树于 2020-01-15 设计创作，主要内容包括：信息处理装置具备记录部,所述记录部执行如下处理,即,将包含数据及与数据有关的元数据的多个目标记录于磁记录介质,并且在记录了至少1个目标之后,记录目标中所包含的元数据的集合即第1集合数据。第1集合数据为在记录之前刚刚记录完成的第1集合数据之后所记录的目标中所包含的元数据的集合。磁记录介质在非磁性支撑体上具有包含强磁性粉末及粘结剂的磁性层,在磁性层的表面上进行正己烷清洗后通过光学干涉法在0.5atm及13.5atm的按压下所测量的间距S-(0.5)、S-(13.5)的差分为3.0nm以下。(The information processing apparatus includes a recording unit that executes the following stepsThat is, a plurality of objects including data and metadata related to the data are recorded in the magnetic recording medium, and after at least 1 object is recorded, the 1 st set data which is a set of metadata included in the object is recorded. The 1 st set data is a set of metadata contained in a target recorded immediately before the 1 st set data whose recording is completed is recorded. A magnetic recording medium has a magnetic layer containing ferromagnetic powder and a binder on a nonmagnetic support, and a pitch S measured by an optical interference method at a pressure of 0.5atm and 13.5atm after n-hexane cleaning on the surface of the magnetic layer 0.5 、S 13.5 The difference of (A) is 3.0nm or less.)

1. A recording apparatus includes a recording unit that executes, at each predetermined timing, processing for:

recording a plurality of objects including data and metadata related to the data in a magnetic recording medium, and

after recording at least 1 of the objects, recording a set of the metadata included in the object, that is, 1 st set data, each of the 1 st set data being a set of the metadata included in the object recorded after recording of the 1 st set data which was recorded immediately before, wherein,

the magnetic recording medium has a magnetic layer containing ferromagnetic powder and a binder on a nonmagnetic support, and the magnetic layer has a spacing S measured by an optical interference method at a pressure of 0.5atm after n-hexane cleaning on the surface thereof_0.5And a spacing S measured by optical interference method at a pressure of 13.5atm after n-hexane cleaning on the surface of the magnetic layer_13.5Difference S of_0.5-S_13.5Is 3.0nm or less.

2. The recording apparatus according to claim 1,

the difference is 1.5nm or more and 3.0nm or less.

3. The recording apparatus according to claim 1 or 2, wherein,

said S_0.5In the range of 5.0 to 50.0 nm.

4. The recording apparatus according to any one of claims 1 to 3,

the magnetic layer contains inorganic oxide-based particles.

5. The recording apparatus according to claim 4,

the inorganic oxide particles are composite particles of an inorganic oxide and a polymer.

6. The recording apparatus according to any one of claims 1 to 5,

the magnetic layer contains one or more lubricants selected from the group consisting of fatty acids, fatty acid esters, and fatty acid amides.

7. The recording apparatus according to any one of claims 1 to 6,

a nonmagnetic layer containing nonmagnetic powder and a binder is provided between the nonmagnetic support and the magnetic layer.

8. The recording apparatus according to any one of claims 1 to 7,

the nonmagnetic support has a back coat layer containing a nonmagnetic powder and a binder on the surface side opposite to the surface side having the magnetic layer.

9. The recording apparatus according to any one of claims 1 to 8,

the magnetic recording medium is a magnetic tape.

10. The recording apparatus according to any one of claims 1 to 9,

the recording unit records, after recording at least 1 of the 1 st aggregate data, the 2 nd aggregate data that is the set of the 1 st aggregate data that has been recorded, in the magnetic recording medium.

11. The recording apparatus according to claim 10,

the recording unit overwrites the 2 nd aggregate data to record when the size of the 2 nd aggregate data recorded on the magnetic recording medium is equal to or smaller than a predetermined size and the target is recorded on the magnetic recording medium.

12. The recording apparatus according to claim 10 or 11, wherein,

the magnetic recording medium includes a reference partition and a data partition for recording the object,

the recording unit records the 1 st set data and the 2 nd set data in the data partition, and records the 2 nd set data recorded in the data partition in the reference partition when the size of the 2 nd set data recorded in the data partition exceeds a predetermined size.

13. The recording apparatus according to claim 12, wherein,

the recording unit records the 2 nd set data recorded in the data partition in the reference partition without deleting the 2 nd set data recorded in the data partition, when the 2 nd set data recorded in the data partition is recorded in the reference partition.

14. The recording apparatus according to any one of claims 1 to 13,

the metadata includes identification information unique to the system and identification information unique to the target including the metadata.

15. A reading device is provided with:

a determination section that determines a position on a magnetic recording medium of an object recorded in a data partition of the magnetic recording medium containing the reference partition and an object recording the data partition containing data and metadata related to the data, using at least 1 of 2 nd aggregate data recorded in a reference partition, the 2 nd aggregate data recorded in a data partition, 1 st aggregate data recorded in the data partition, and metadata recorded in the data partition; and

a reading section that reads the target recorded in the position determined by the determination section, wherein,

16. The reading apparatus according to claim 15,

the determination section determines the position with reference to the 2 nd set data recorded in the reference partition, the 2 nd set data recorded in the data partition, the 1 st set data recorded in the data partition, and the metadata recorded in the data partition in this order.

17. A recording method for causing a computer to execute, at each predetermined timing, processing including:

recording a plurality of objects including data and metadata related to the data in a magnetic recording medium, and

18. A recording program for causing a computer to execute, at each predetermined timing, processing of:

recording a plurality of objects including data and metadata related to the data in a magnetic recording medium, and

19. A reading method for causing a computer to execute processing of:

determining a position on a magnetic recording medium of an object recorded in a data partition of a magnetic recording medium including a reference partition and an object recording the data and metadata related to the data, using at least 1 of 2 nd set data recorded in the reference partition, the 2 nd set data recorded in the data partition, 1 st set data recorded in the data partition, and metadata recorded in the data partition, and

reading the recorded object in the determined position, wherein,

20. A reading program for causing a computer to execute processing of:

reading the recorded object in the determined position, wherein,

21. A magnetic tape, which executes the following processing at each predetermined timing:

recording a plurality of objects comprising data and metadata related to said data, an

After recording at least 1 of the objects, recording a set of the metadata included in the object, that is, 1 st set data, each of the 1 st set data being a set of the metadata included in the object recorded after recording of the 1 st set data which was recorded immediately before, wherein,

having a magnetic layer containing a ferromagnetic powder and a binder on a non-magnetic support, and cleaning the surface of the magnetic layer with n-hexane and measuring the distance S by an optical interference method at a pressure of 0.5atm_0.5And a spacing S measured by optical interference method at a pressure of 13.5atm after n-hexane cleaning on the surface of the magnetic layer_13.5Difference S of_0.5-S_13.5Is 3.0nm or less.

Technical Field

The present invention relates to a recording device, a reading device, a recording method, a recording program, a reading method, a reading program, and a magnetic tape.

Background

Conventionally, it has been proposed to control the surface shape of a magnetic layer by forming protrusions on the surface of the magnetic layer (see japanese patent application laid-open nos. 2011-28826 and 2017-168178).

On the other hand, as a File System using a magnetic recording medium such as a magnetic Tape, LTFS (Linear Tape File System) is known. As a technique related to the file system, in japanese patent laid-open No. 2016-4413, a technique of successively writing a plurality of files onto a magnetic tape to form 1 combined file is disclosed. In this technique, after a 1 st index (index) including the start position and size of a combined file on a magnetic tape is written on the magnetic tape, a 2 nd index including the start position and size of each of a plurality of files in the combined file on the magnetic tape is written on the magnetic tape.

Disclosure of Invention

Technical problem to be solved by the invention

In a sliding-type magnetic recording and reproducing apparatus, recording of information on a magnetic recording medium and reproduction of the recorded information are performed by sliding a magnetic layer surface of the magnetic recording medium in contact with a magnetic head. The high friction coefficient when sliding between the magnetic layer surface and the magnetic head causes a reduction in running stability. In contrast, controlling the shape of the surface of the magnetic layer can contribute to reducing the above-described friction coefficient.

In order to record information on the magnetic recording medium and reproduce the recorded information, sliding between the magnetic layer surface and the magnetic head is repeated. In this regard, as proposed in the related art, even if the low friction coefficient can be achieved by controlling the shape of the magnetic layer surface at the initial stage of sliding, there is a possibility that the friction coefficient may increase when sliding is repeated.

However, as shown in fig. 20, the LTFS described above divides the recording area of the tape into an index partition and a data partition. Document data, image data, and other data to be saved by the user are recorded from the beginning of the data partition of the magnetic tape. Further, for example, when the total size of the recorded data exceeds a predetermined size, an index (index 1 in fig. 20) including information indicating the position on the magnetic tape of each recorded data is recorded in the data partition.

When data is recorded in excess of a predetermined size after the index is recorded, a new index is recorded (index 2 in fig. 20). The index includes information indicating the position on the tape of each of all data recorded from the head of the tape.

Therefore, there is a problem that the larger the number of data recorded on the magnetic tape, the larger the size of the index becomes, and there is a possibility that the effective capacity of the magnetic tape or the like is reduced. Here, the effective capacity is a capacity in which data to be saved can be recorded by a user in the magnetic tape.

The technique described in the above-mentioned japanese patent application laid-open No. 2016-.

Further, if the size of the index is increased as described above, the number of times of repeated sliding between the magnetic head and the magnetic recording medium when reading data from the magnetic recording medium may increase. Further, with the recent increase in capacity of magnetic recording media, the amount of data that can be recorded has also increased. Therefore, when data is read from such a large-capacity magnetic recording medium, the number of times of the round trip is further increased, and as a result, the traveling stability of the magnetic recording medium may be significantly lowered.

The present invention has been made in view of the above circumstances, and an object thereof is to suppress an increase in the friction coefficient and improve a decrease in the running stability of a magnetic recording medium.

Means for solving the technical problem

In order to achieve the above object, a recording apparatus of the present invention includes a recording unit that records a plurality of objects including data and metadata related to the data on a magnetic recording medium at predetermined timings, and after at least 1 object is recorded, records 1 st set data that is a set of metadata included in the object, each of the 1 st set data being a set of metadata included in an object recorded immediately before recording the 1 st set data that has been completed,

a magnetic recording medium has a magnetic layer containing a ferromagnetic powder and a binder on a nonmagnetic support, and a pitch S measured by an optical interference method at a pressure of 0.5atm after n-hexane cleaning on the surface of the magnetic layer_0.5And a spacing S measured by optical interference method at a pressure of 13.5atm after n-hexane cleaning on the surface of the magnetic layer_13.5Difference S of_0.5-S_13.5Is 3.0nm or less.

In the recording device of the present invention, the difference may be 1.5nm or more and 3.0nm or less.

In the recording apparatus of the present invention, S_0.5The particle size may be in the range of 5.0 to 50.0 nm.

In the present specification, "to" in a numerical range includes upper and lower limits of numerical values. That is, 5.0 to 50.0nm means 5.0nm to 50.0 nm.

In the recording device of the present invention, the magnetic layer may contain inorganic oxide particles.

In the recording device of the present invention, the inorganic oxide-based particles may be composite particles of an inorganic oxide and a polymer.

In the recording device of the present invention, the magnetic layer may contain at least one lubricant selected from the group consisting of fatty acids, fatty acid esters, and fatty acid amides.

The recording device of the present invention may further include a nonmagnetic layer containing a nonmagnetic powder and a binder between the nonmagnetic support and the magnetic layer.

The recording device of the present invention may further include a back coat layer containing a nonmagnetic powder and a binder on a surface side of the nonmagnetic support opposite to the surface side having the magnetic layer.

In the recording apparatus of the present invention, the magnetic recording medium may be a magnetic tape.

In the recording apparatus of the present invention, the recording unit may record the 2 nd aggregate data, which is an aggregate of the 1 st aggregate data having been recorded, in the magnetic recording medium after recording at least 1 of the 1 st aggregate data.

In the recording apparatus of the present invention, the recording unit may overwrite the 2 nd aggregate data and record the data when the size of the 2 nd aggregate data recorded in the magnetic recording medium is equal to or smaller than a predetermined size and the target data is recorded in the magnetic recording medium.

In the recording apparatus of the present invention, the magnetic recording medium includes a reference partition and a data partition to be recorded, and the recording unit may record the 1 st aggregate data and the 2 nd aggregate data in the data partition, and may record the 2 nd aggregate data recorded in the data partition in the reference partition when a size of the 2 nd aggregate data recorded in the data partition exceeds a predetermined size.

In the recording device of the present invention, when the recording unit records the 2 nd set data recorded in the data partition in the reference partition, the recording unit may record the 2 nd set data recorded in the data partition in the reference partition without deleting the set data.

In the recording apparatus of the present invention, the metadata may include identification information unique to the system and identification information unique to the target including the metadata.

In the recording apparatus of the present invention, the magnetic recording medium may be a magnetic tape.

In order to achieve the above object, a reading apparatus according to the present invention includes: a determination section that determines a position on the magnetic recording medium of an object recorded in a data partition of the magnetic recording medium including the reference partition and a data partition in which an object containing data and metadata related to the data is recorded, using at least 1 of the 2 nd aggregate data recorded in the reference partition, the 2 nd aggregate data recorded in the data partition, the 1 st aggregate data recorded in the data partition, and the metadata recorded in the data partition; and a reading section that reads the object recorded in the position determined by the determining section,

In the reading apparatus of the present invention, the determination unit may determine the position by sequentially referring to the 2 nd aggregate data recorded in the reference partition, the 2 nd aggregate data recorded in the data partition, the 1 st aggregate data recorded in the data partition, and the metadata recorded in the data partition.

In order to achieve the above object, a recording method of the present invention is a recording method in which a computer executes a process of recording a plurality of objects including data and metadata related to the data on a magnetic recording medium at predetermined timings, and after at least 1 object is recorded, 1 st set data which is a set of metadata included in the object is recorded, and each 1 st set data is a set of metadata included in an object recorded immediately after 1 st set data recorded before the recording is completed,

In order to achieve the above object, a recording program of the present invention causes a computer to execute a process of recording a plurality of objects including data and metadata related to the data in a magnetic recording medium at every predetermined timing, and after at least 1 object is recorded, 1 st set data which is a set of metadata included in the object is recorded, and each 1 st set data is a set of metadata included in an object recorded immediately before the recording after the 1 st set data which is completed is recorded,

Further, in order to achieve the above object, in the reading method of the present invention, the computer executes a process of determining a position on the magnetic recording medium of an object recorded in a data partition of the magnetic recording medium including the reference partition and a data partition in which an object containing data and metadata related to the data is recorded, using at least 1 of the 2 nd aggregate data recorded in the reference partition, the 2 nd aggregate data recorded in the data partition, the 1 st aggregate data recorded in the data partition, and the metadata recorded in the data partition, and reading the object recorded in the determined position,

And, in order to achieve the above object, a reading program of the present invention causes a computer to execute a process of determining a position on a magnetic recording medium of an object recorded in a data partition of the magnetic recording medium including a reference partition and a data partition in which an object containing data and metadata related to the data is recorded, using at least 1 of 2 nd set data recorded in the reference partition, 2 nd set data recorded in the data partition, 1 st set data recorded in the data partition, and metadata recorded in the data partition, and reading the object recorded in the determined position,

In order to achieve the above object, a magnetic tape according to the present invention records a plurality of objects including data and metadata related to the data at predetermined timings, records a set of metadata 1, which is a set of 1 st set data, included in the objects after at least 1 object is recorded, and records each 1 st set data as a set of metadata included in an object recorded immediately after the 1 st set data recorded before the recording is completed,

a non-magnetic support having thereon a magnetic layer containing a ferromagnetic powder and a binder, n-hexane cleaning being performed on the surface of the magnetic layer, and the distance S measured by an optical interference method at a pressure of 0.5atm_0.5And a spacing S measured by optical interference method at a pressure of 13.5atm after n-hexane cleaning on the surface of the magnetic layer_13.5Difference S of_0.5-S_13.5Is 3.0nm or less.

Another recording apparatus according to the present invention includes: a memory storing instructions for causing the computer to execute; and

a processor configured to execute the stored instructions,

the processor performs a process of recording a plurality of targets including data and metadata related to the data in the magnetic recording medium at every predetermined timing, and after at least 1 target is recorded, recording 1 st set data which is a set of metadata included in the targets, and every 1 st set data is a set of metadata included in targets recorded immediately after the 1 st set data recorded immediately before the recording is completed,

Another reading apparatus of the present invention includes: a memory storing instructions for causing the computer to execute; and

a processor configured to execute the stored instructions,

the processor performs a process of determining a position of an object recorded in a data partition of the magnetic recording medium including the reference partition and a data partition in which an object containing data and metadata related to the data is recorded, on the magnetic recording medium, using at least 1 of the 2 nd set data recorded in the reference partition, the 2 nd set data recorded in the data partition, the 1 st set data recorded in the data partition, and the metadata recorded in the data partition, and reading the object recorded in the determined position,

Effects of the invention

According to the present invention, a decrease in the running stability of the magnetic recording medium can be improved by suppressing an increase in the friction coefficient.

Drawings

Fig. 1 is a block diagram showing an example of a configuration of a recording and reading system according to each embodiment.

Fig. 2 is a block diagram showing an example of a hardware configuration of the information processing device according to each embodiment.

Fig. 3 is a block diagram showing an example of a functional configuration in a case where a target of the information processing apparatus according to each embodiment is recorded.

Fig. 4 is a diagram showing an example of an initial state of the magnetic tape according to each embodiment.

Fig. 5 is a diagram showing an example of a recording state of the magnetic tape according to each embodiment.

Fig. 6 is a diagram showing an example of a recording state of the magnetic tape according to each embodiment.

Fig. 7 is a diagram showing an example of a recording state of the magnetic tape according to each embodiment.

Fig. 8 is a diagram showing an example of a recording state of the magnetic tape according to each embodiment.

Fig. 9 is a diagram showing an example of a recording state of the magnetic tape according to each embodiment.

Fig. 10 is a flowchart showing an example of the recording process according to each embodiment.

Fig. 11 is a block diagram showing an example of a functional configuration in the case of reading a target of the information processing apparatus according to each embodiment.

Fig. 12 is a flowchart showing an example of metadata storage processing according to each embodiment.

Fig. 13 is a flowchart showing an example of the target reading process according to each embodiment.

Fig. 14 is a schematic diagram showing an example of a case where the magnetic tape according to embodiment 2 is used in another system.

Fig. 15 is a diagram for explaining identification information included in metadata according to embodiment 2.

Fig. 16 is a diagram for explaining a case where identification information unique to a target according to embodiment 2 overlaps.

FIG. 17 is a graph showing the results of the example of the present invention.

Fig. 18 is a diagram schematically showing a method of recording data on each magnetic tape.

FIG. 19 is a graph showing the results of the example of the present invention.

Fig. 20 is a diagram for explaining the recording process of the index in the LTFS.

Detailed Description

Hereinafter, embodiments for implementing the technique of the present invention will be described in detail with reference to the drawings.

[ embodiment 1]

First, a configuration of a recording and reading system 10 according to the present embodiment will be described with reference to fig. 1. As shown in fig. 1, the recording and reading system 10 includes an information processing apparatus 12 and a tape library 14. The tape library 14 is connected to the information processing apparatus 12. The information processing apparatus 12 and the plurality of terminals 16 are connected to the network N and can communicate with each other via the network N.

The tape library 14 includes a plurality of slots (not shown) and a plurality of tape drives 18, and each slot stores a tape T. The magnetic tape T is an example of a magnetic recording medium for writing or reading data by sequential access. Further, as an example of the magnetic Tape T, an LTO (Linear Tape-Open) magnetic Tape may be mentioned.

When data is written or read to or from the magnetic tape T by the information processing device 12, the magnetic tape T to be written or read is loaded from the slot to a predetermined tape drive 18. When writing or reading of the magnetic tape T loaded on the magnetic tape drive 18 by the information processing apparatus 12 is completed, the magnetic tape T is removed from the magnetic tape drive 18 into the slot originally stored.

In the present embodiment, an example in which an object including data to be saved by a user, such as document data and image data, and metadata related to the data is applied as a format (format) of data to be recorded on the magnetic tape T will be described. In addition, the storage system that handles the target is referred to as a target storage system.

Next, a hardware configuration of the information processing device 12 according to the present embodiment will be described with reference to fig. 2. As shown in fig. 2, the information Processing apparatus 12 includes a CPU (Central Processing Unit) 20, a memory 21 as a temporary storage area, and a nonvolatile storage Unit 22. The information processing device 12 includes a display unit 23 such as a liquid crystal display, an input unit 24 such as a keyboard and a mouse, a network I/F (InterFace) 25 connected to the network N, and an external I/F26 connected to the tape library 14. The CPU20, the memory 21, the storage unit 22, the display unit 23, the input unit 24, the network I/F25, and the external I/F26 are connected to the bus 27.

The storage unit 22 is implemented by an HDD (Hard Disk Drive), an SSD (Solid State Drive), a flash memory, or the like. The storage unit 22 as a storage medium stores a recording program 30 and a reading program 32. The CPU20 reads the recording program 30 from the storage unit 22, expands the recording program into the memory 21, and executes the expanded recording program 30. The CPU20 reads the read program 32 from the storage unit 22, expands the read program 32 into the memory 21, and executes the expanded read program 32. Further, as an example of the information processing device 12, a server computer or the like may be mentioned. The information processing device 12 is an example of a recording device that records a target on the magnetic tape T. The information processing device 12 is also an example of a reading device that reads a target recorded on the magnetic tape T.

Next, a functional configuration in a case where a target is recorded on the magnetic tape T of the information processing device 12 according to the present embodiment will be described with reference to fig. 3. As shown in fig. 3, the information processing apparatus 12 includes a receiving unit 40 and a recording unit 42. The CPU20 executes the recording program 30 to function as the receiving unit 40 and the recording unit 42. In addition, a data cache region 44 and a metadata Database (DB)46 are stored in a predetermined storage region of the storage unit 22. A data cache region 44 and a metadata DB46 exist for each tape T.

The reception unit 40 receives data transmitted from the terminal 16 using an API (Application Programming Interface) for processing a target and metadata related to the data via the network I/F25. Further, the receiving unit 40 stores the received data in the data cache region 44, and stores the metadata in the metadata DB 46. The metadata transmitted from the terminal 16 includes identification information such as a data name of the corresponding data, and attribute information indicating an attribute of the data such as a size and a time stamp of the data. The receiving unit 40 adds identification information specific to the target including the received data and metadata to the metadata.

Fig. 4 shows an example of a state in which data is stored in the data cache region 44 and metadata is stored in the metadata DB 46. In fig. 4, the tape T is in a state of being just formatted and having no target recorded.

As shown in fig. 4, data is stored in the data cache region 44, and metadata is stored in the metadata DB46 in association with the data. When the tape T according to the present embodiment is formatted, the tape T is divided into 2 partitions, i.e., a reference partition RP and a data partition DP as a recording target. The reference partition RP and the data partition DP are divided by a guard band GW including a plurality of stripes. A tag is recorded at the head of each of the reference partition RP and the data partition DP. The tag includes identification information of the magnetic tape T, format information regarding a writing format of data to the magnetic tape T, and the like.

The recording unit 42 controls the tape library 14 and loads a target tape T to be recorded on a predetermined tape drive 18. The recording unit 42 records a target including the data stored in the data cache area 44 and the corresponding metadata stored in the metadata DB46 in the data partition DP of the loaded tape T. At this time, the recording unit 42 adds, to the metadata, management information for managing objects such as identification information of the magnetic tape T on which the corresponding object is recorded and information indicating a recording position on the magnetic tape T. Fig. 5 shows an example of a state in which 2 objects are recorded in the data partition DP.

The recording unit 42 records the set of target metadata to be recorded in the data partition DP at predetermined timings. In the following, this set of metadata will be referred to as "1 st set data". In the present embodiment, the recording unit 42 records the 1 st set data, which is a set of metadata of recorded objects, in the data partition DP every time the total size of the recorded objects exceeds a predetermined size. At this time, when the 1 st set data already recorded in the data partition DP exists, the recording unit 42 records the 1 st set data, which is a set of metadata of the target recorded after the 1 st set data before recording, in the data partition DP. That is, the recording unit 42 executes processing for recording the 1 st set data, which is a set of metadata included in the objects, after at least 1 object is recorded, at each predetermined timing. Further, the recording unit 42 executes the above-described processing so that each 1 st set of data becomes a set of metadata included in all targets recorded immediately after the 1 st set of data recorded immediately before the recording is completed. Therefore, each 1 st set data becomes a set of metadata of all targets recorded between the 1 st set data before recording and itself. The above process corresponds to a commit process for ensuring that the recorded target is normally written before the 1 st set of data. The predetermined size at this time is, for example, a value determined in advance to prevent the commit processing from being performed for a long time. In this case, for example, the predetermined size may be a size obtained by multiplying the recording capacity of the magnetic tape T by a predetermined ratio, and may be experimentally determined or changed depending on the recording capacity of the magnetic tape T, the use environment or the use condition of the magnetic tape T, and the like.

The predetermined size at this time may be determined, for example, based on an upper limit value of a time (hereinafter, referred to as "recording time") required when the target is recorded in the data partition DP in a lump by the one-time recording instruction. For example, when the upper limit of the recording time, which is the required performance of the system, is 35 seconds and the recording speed of data on the magnetic tape T is 300MB/sec, the recording time is 35 seconds or less as long as the total value of the sizes of the objects to be recorded is 10GB or less. Therefore, in this case, the predetermined size may be set to 10 GB.

Then, the recording unit 42 records at least 1 of the 1 st set data in the data partition DP, and then records the set of the 1 st set data recorded in the data partition DP. Hereinafter, the set of the 1 st set data is referred to as "2 nd set data" or the like. At this time, when the 2 nd set data already exists in the data partition DP, the recording unit 42 records the 2 nd set data, which is the set of the 1 st set data recorded after the 1 st set data before the set, in the data partition DP. Therefore, each 2 nd set data becomes a set of all 1 st set data recorded between the 2 nd set data before recording and itself.

As shown in fig. 6, when the 1 st set data is not recorded in the data partition DP, the 1 st set data, which is a set of recorded metadata, is recorded in the data partition DP from the beginning of the data partition DP. When the 2 nd set data is not recorded in the data partition DP, the 2 nd set data, which is the set of the 1 st set data that has been recorded, is recorded in the data partition DP from the head of the data partition DP. In fig. 6, the 1 st set data is denoted as "1 st set", and the 2 nd set data is denoted as "2 nd set". The same applies to fig. 7 to 9 described later.

As shown in fig. 6, when the 1 st and 2 nd sets of data are recorded in the data partition DP, the recording unit 42 records file flags before and after the 1 st set of data and before and after the 2 nd set of data. By using the archive flag, the 1 st set data and the 2 nd set data recorded in the data partition DP can be searched.

As shown in fig. 7, when the 1 st set data is recorded in the data partition DP, the 1 st set data, which is a set of metadata of a target recorded after the 1 st set data before recording, is recorded in the data partition DP. When the 2 nd set data is recorded in the data partition DP, the 2 nd set data, which is a set of the 1 st set data recorded after the 2 nd set data before recording, is recorded in the data partition DP. That is, in the present embodiment, since the metadata is not repeatedly included in the plurality of 1 st set data recorded in the data partition DP, a decrease in the effective capacity of the tape T can be suppressed. In the present embodiment, since the 1 st set data is not repeatedly included in the plurality of 2 nd set data recorded in the data partition DP, a decrease in the effective capacity of the tape T can be suppressed.

When recording the target in the data partition DP, if the size of the previous 2 nd set data is equal to or smaller than a predetermined size, the recording unit 42 overwrites the target with the 2 nd set data and records the target. Fig. 7 shows an example of overwriting the 2 nd set data of fig. 6. The predetermined size at this time is predetermined in accordance with, for example, the recording speed of the magnetic tape T. In this case, for example, the predetermined size may be a size obtained by multiplying the recording capacity of the magnetic tape T by a predetermined ratio, and may be experimentally determined or changed depending on the recording capacity of the magnetic tape T, the use environment or the use condition of the magnetic tape T, and the like.

As shown in fig. 8, when the size of the 2 nd set data recorded in the data partition DP exceeds a predetermined size, the recording unit 42 records (copies) the 2 nd set data in the reference partition RP without deleting it. At this time, the recording section 42 also records archive flags before and after the 2 nd set data of the reference partition RP.

As shown in fig. 9, even when the tape T is removed after the data stored in the data cache area 44 is recorded in the data partition DP, the recording unit 42 records the 1 st set data and the 2 nd set data in the data partition DP in the same manner. At this time, the recording unit 42 also records the 2 nd set data in the reference partition RP.

Next, a magnetic recording medium used as the magnetic tape T of the present embodiment will be described.

[ magnetic recording Medium ]

One mode of the magnetic recording medium used in this embodiment relates to a magnetic recording medium having a magnetic layer containing ferromagnetic powder and a binder on a nonmagnetic support, wherein a pitch S measured by an optical interference method at a pressure of 0.5atm after n-hexane cleaning is performed on the surface of the magnetic layer_0.5And a spacing S measured by optical interference method at a pressure of 13.5atm after n-hexane cleaning on the surface of the magnetic layer_13.5Difference (S) of_0.5-S_13.5) Is 3.0nm or less.

In the present embodiment, "n-hexane cleaning" refers to a case where a sample piece cut out from a magnetic recording medium is immersed in fresh n-hexane (200g) at a liquid temperature of 20 to 25 ℃ and subjected to ultrasonic cleaning for 100 seconds (ultrasonic output: 40 kHz). When the magnetic recording medium to be cleaned was a magnetic tape, a sample piece having a length of 5cm was cut out and n-hexane was cleaned. The width of the tape and the width of the coupons cut from the tape are typically 1/2 inches. 1 inch to 0.0254 meters. For the magnetic tape other than the 1/2-inch width, a sample piece having a length of 5cm was cut and n-hexane-washed. When the magnetic recording medium to be cleaned was a magnetic disk, a 5cm × 1.27 cm-sized sample piece was cut out and n-hexane cleaned. The pitch, which will be described in detail below, is measured after the piece subjected to n-hexane washing is left for 24 hours in an environment at a temperature of 23 ℃ and a relative humidity of 50%.

In this embodiment, the meaning of "surface (of) the magnetic layer" of the magnetic recording medium is the same as that of the surface on the magnetic layer side of the magnetic recording medium.

In the present embodiment, the pitch measured by the optical interference method on the surface of the magnetic layer of the magnetic recording medium is set to a value measured by the following method.

In a state where a magnetic recording medium (more specifically, the sample sheet described above is the same hereinafter) and a transparent plate-like member (for example, a glass plate or the like) are stacked so that the surface of the magnetic layer of the magnetic recording medium faces the transparent plate-like member, the pressing member is pressed from the side opposite to the magnetic layer side of the magnetic recording medium at a pressure of 0.5atm or 13.5 atm. In this state, light is irradiated to the surface of the magnetic layer of the magnetic recording medium through the transparent plate-like member (irradiation region: 150000 to 200000 μm)²) And the distance (distance) between the surface of the magnetic layer of the magnetic recording medium and the surface of the transparent plate-like member on the magnetic recording medium side is determined from the intensity of interference light (for example, the contrast of interference fringe images) generated by the optical path difference between the reflected light from the surface of the magnetic layer of the magnetic recording medium and the reflected light from the surface of the transparent plate-like member on the magnetic recording medium side. The light to be irradiated is not particularly limited. In the case where the light to be irradiated has light emission wavelength light over a wide wavelength range, such as white light including light of multiple wavelengths, a member having a function of selectively cutting light of a specific wavelength or light other than the specific wavelength range, such as an interference filter, is disposed between the transparent plate-like member and the light receiving unit that receives the reflected light, and the light of a local wavelength or the light of the local wavelength range in the reflected light is selectively incident on the light receiving unit. In the case where the light to be irradiated is light having a single light emission peak (so-called monochromatic light), the above-described member may not be used. The wavelength of light incident on the light receiving unit may be, for example, in the range of 500 to 700 nm. However, the wavelength of the light incident on the light receiving unit is not limited to the above range. The transparent plate-like member may be a member having transparency enough to allow light to be irradiated to the magnetic recording medium through the member and to allow the irradiated light to pass therethrough to the extent of interference light.

The interference fringe image obtained by the above-described measurement of the pitch was divided into 300000 dots and the pitch of each dot (the distance between the surface of the magnetic layer of the magnetic recording medium and the surface of the magnetic recording medium side of the transparent plate-like member) was found, which was set as a histogram, and the Maximum frequency (Maximum frequency) in the histogram was set as the pitch.

5 pieces of the sample were cut from the same magnetic recording medium, each piece was washed with n-hexane and pressed against a pressing member at a pressure of 0.5atm to determine the pitch S_0.5Further, the pressing member was pressed at a pressure of 13.5atm to determine the pitch S_13.5. Further, the obtained S is calculated_0.5And S_13.5Difference (S) of_0.5-S_13.5). The calculated difference (S) of 5 pieces of sample_0.5-S_13.5) Is the difference (S) of the magnetic recording medium_0.5-S_13.5)。

The measurement can be performed using, for example, a commercially available Tape Spacing Analyzer (TSA; Tape Spacing Analyzer) such as Tape Spacing Analyzer manufactured by Micro Physics. The pitch measurement in the examples was carried out using a Tape Spacing Analyzer manufactured by Micro Physics.

As for the friction coefficient when sliding of the magnetic layer surface and the magnetic head is performed, it can be lowered by forming a protrusion on the magnetic layer surface and reducing a portion in contact with the magnetic head (so-called true contact) on the magnetic layer surface. However, if the height of the protrusion on the surface of the magnetic layer is lowered due to repeated sliding with the magnetic head, the portion of the surface of the magnetic layer that actually contacts the magnetic head increases, and the friction coefficient may increase.

As described above, the inventors of the present invention have made extensive studies, and have found that the pressure applied to the surface of the magnetic layer is not constant when the sliding with the magnetic head is repeated, and that a large pressure may be applied, and that the projections deform or sink into the magnetic layer when a large pressure is applied, thereby lowering the height of the projections, which may cause an increase in the friction coefficient when the sliding with the magnetic head is repeated. The case where a large pressure is applied may be, for example, a case where the pressure is in contact with an edge portion of the magnetic head. In contrast, S is determined by the method described above_0.5And S_13.5Difference (S) of_0.5-S_13.5) As small as 3.0nm or less means that even if a large pressure is applied, the height of the protrusions on the surface of the magnetic layer hardly changes largely. Therefore, even if the sliding with the magnetic head is repeated, the height of the protrusion on the surface of the magnetic layer of the magnetic recording medium having the difference of 3.0nm or less is considered to be less changed. The inventors of the present invention speculate that this is the reason why the increase in the friction coefficient can be suppressed even if the magnetic recording medium is repeatedly slid with the magnetic head. However, the present invention is not limited to the above estimation.

In the present embodiment, 0.5atm is used as an exemplary value of the pressure mainly applied to the surface of the magnetic layer when the magnetic head is slid, 13.5atm is used as an exemplary value of the large pressure applied to the surface of the magnetic layer when the magnetic head is slid, and the pressure applied to the magnetic recording medium when the magnetic head is slid is not limited to the above pressure. As a result of intensive studies, the inventors of the present invention newly found that by controlling the difference obtained by using the pressure, an increase in the friction coefficient can be suppressed even when sliding with the magnetic head is repeated. The control method of the difference will be described later.

The magnetic recording medium will be described in further detail below. Hereinafter, the case where the friction coefficient increases by repeating the sliding between the magnetic layer surface and the magnetic head is simply referred to as "increase in friction coefficient".

< magnetic layer >

(difference (S)_0.5-S_13.5))

Difference (S) of the magnetic recording medium_0.5-S_13.5) Is 3.0nm or less, and is preferably 2.9nm or less, more preferably 2.8nm or less, further preferably 2.7nm or less, further preferably 2.6nm or less, and further preferably 2.5nm or less, from the viewpoint of further suppressing the increase in the friction coefficient. The difference may be, for example, 1.0nm or more, 1.5nm or more, 1.8nm or more, or 2.0nm or more. However, from the viewpoint of suppressing an increase in the friction coefficient, the smaller the difference is, the more preferable the difference is, and therefore, the lower the difference can be, of courseThe lower limits of the examples given above. The difference can be controlled by the type of nonmagnetic filler (hereinafter referred to as "protrusion forming agent") capable of forming a protrusion on the surface of the magnetic layer and the production conditions of the magnetic recording medium. Details of this point will be described later.

S of the magnetic recording medium_0.5And S_13.5As long as difference (S)_0.5-S_13.5) The thickness is not particularly limited as long as it is 3.0nm or less. From the viewpoint of improving the electromagnetic conversion characteristics, S_0.5Preferably 50.0nm or less, more preferably 40.0nm or less, further preferably 30.0nm or less, further preferably 20.0nm or less, further preferably 16.0nm or less, further preferably 15.5nm or less, and further preferably 14.5nm or less. And, from the viewpoint of mainly suppressing the initial friction coefficient with the magnetic head to be low, S_0.5Preferably 5.0nm or more, more preferably 8.0nm or more, further preferably 10.0nm or more, and further preferably 12.0nm or more. Further, S is a reference for maintaining good running stability even if sliding with the magnetic head is repeated_13.5Preferably 5.0nm or more, more preferably 8.0nm or more, and further preferably 10.0nm or more. Further, S is considered to exhibit excellent electromagnetic conversion characteristics even when sliding with the magnetic head is repeated_13.5Preferably 15.0nm or less, more preferably 14.0nm or less, further preferably 13.5nm or less, further preferably 13.0nm or less, and further preferably 12.0nm or less.

(ferromagnetic powder)

As the ferromagnetic powder contained in the magnetic layer, ferromagnetic powder generally used in the magnetic layer of various magnetic recording media can be used. From the viewpoint of improving the recording density of the magnetic recording medium, it is preferable to use a ferromagnetic powder having a small average particle size as the ferromagnetic powder. In this respect, the average particle diameter of the ferromagnetic powder is preferably 50nm or less, more preferably 45nm or less, further preferably 40nm or less, further preferably 35nm or less, further preferably 30nm or less, further preferably 25nm or less, and further preferably 20nm or less. On the other hand, from the viewpoint of the stability of magnetization, the average particle diameter of the ferromagnetic powder is preferably 5nm or more, more preferably 8nm or more, further preferably 10nm or more, further preferably 15nm or more, and further preferably 20nm or more.

A preferred specific example of the ferromagnetic powder is hexagonal ferrite powder. For details of the hexagonal ferrite powder, for example, refer to paragraphs 0012 to 0030 of Japanese patent application laid-open No. 2011-225417, paragraphs 0134 to 0136 of Japanese patent application laid-open No. 2011-216149, paragraphs 0013 to 0030 of Japanese patent application laid-open No. 2012-204726, and paragraphs 0029 to 0084 of Japanese patent application laid-open No. 2015-127985. Hexagonal ferrite powder is particularly preferably hexagonal barium ferrite powder or hexagonal strontium ferrite powder.

A preferable embodiment when hexagonal strontium ferrite powder is used as the ferromagnetic powder is as follows.

The preferred activation volume of the hexagonal strontium ferrite powder is 800-1500 nm³Within the range of (1). The micronized hexagonal strontium ferrite powder having an activation volume within the above range is suitable for the production of a magnetic tape exhibiting excellent electromagnetic conversion characteristics. The preferred activation volume of the hexagonal strontium ferrite powder is 800nm³The wavelength can be, for example, 850nm³The above. Further, from the viewpoint of further improving the electromagnetic conversion characteristics, it is more preferable that the active volume of the hexagonal strontium ferrite powder is 1400nm³Hereinafter, 1300nm is more preferable³Hereinafter, 1200nm is more preferable³The average particle diameter is preferably 1100nm³The following.

The "activation volume" is a unit of magnetization reversal and is an index indicating the magnetic strength of the particle. The activation volume and anisotropy constant Ku described in the present invention and the present specification are values obtained from the following relational expression between Hc and activation volume V, which is obtained by measuring the magnetic field scanning speed (measurement temperature: 23 ℃ C. + -1 ℃ C.) of the coercive force Hc measuring unit for 3 minutes and 30 minutes using a vibration sample type magnetometer. The unit of the anisotropy constant Ku is 1erg/cc — 1.0 × 10^-1J/m³。Hc＝2Ku/Ms{1-[(kT/KuV)ln(At/0.693)]^1/2}

[ in the above formula, Ku: anisotropy constant (unit: J/m)³) Ms: saturation magnetization (unit: kA/m), k: boltzmann constant (Boltzmann constant), T: absolute temperature (unit: K), V: volume of activation (unit: cm)³) And A: spin precession frequency (unit: s)^-1) T: magnetic field reversal time (unit: s)]

As an index of the reduction of thermal shock, in other words, the improvement of thermal stability, anisotropy constant Ku can be cited. The hexagonal strontium ferrite powder is preferably capable of having a size of 1.8 x 10⁵J/m³The Ku may have a value of 2.0 × 10 more preferably⁵J/m³Ku above. The Ku of the hexagonal strontium ferrite powder may be, for example, 2.5 × 10⁵J/m³The following. However, the higher Ku is preferable since the higher Ku is more stable thermally, and thus the Ku is not limited to the above-exemplified values.

From the viewpoint of improving the reproduction output when reproducing data recorded on a magnetic tape, it is desirable that the mass magnetization σ s of ferromagnetic powder contained in the magnetic tape be high. In this regard, it was observed that the hexagonal strontium ferrite powder containing rare earth atoms but not having the property of containing a surface layer portion of rare earth atoms tended to decrease σ s significantly as compared with the hexagonal strontium ferrite powder not containing rare earth atoms. On the other hand, it is considered that hexagonal strontium ferrite powder having a property of localized surface layer portions of rare earth atoms is also preferable in suppressing such a large decrease in σ s. In one embodiment, σ s of the hexagonal strontium ferrite powder may be 45A · m²/kg or more, and may be 47A · m²More than kg. On the other hand, σ s is preferably 80A · m from the viewpoint of noise reduction²Is less than or equal to kg, more preferably 60 A.m²Is less than/kg. As for σ s, measurement can be performed using a known measurement device capable of measuring magnetism, such as a vibration sample type magnetometer. In the present invention and in the present specification, unless otherwise specified, the mass magnetization σ s is set to a value measured at a magnetic field strength of 15 kOe. 1[ kOe ]]＝10⁶/4π[A/m]。

When the magnetic tape contains hexagonal strontium ferrite powder in the magnetic layer, the anisotropic magnetic field Hk of the magnetic layer is preferably 14kOe or more, more preferably 16kOe or more, and still more preferably 18kOe or more. The anisotropic magnetic field Hk of the magnetic layer is preferably 90kOe or less, more preferably 80kOe or less, and still more preferably 70kOe or less.

The anisotropic magnetic field Hk in the present invention and the present specification means a magnetic field in which magnetization is saturated when a magnetic field is applied in the hard axis (hard axis) direction. The anisotropic magnetic field Hk can be measured using a known measuring device capable of measuring magnetism, such as a vibration sample type magnetometer. In the magnetic layer containing the hexagonal strontium ferrite powder, the hard magnetization axis direction of the magnetic layer is the in-plane direction.

As a preferred specific example of the ferromagnetic powder, a metal powder can be cited. For details of the metal powder, for example, reference can be made to paragraphs 0137 to 0141 of Japanese patent application laid-open No. 2011-216149 and paragraphs 0009 to 0023 of Japanese patent application laid-open No. 2005-251351.

As a preferred specific example of the ferromagnetic powder, epsilon-iron oxide powder can also be cited. As a method for producing the epsilon-iron oxide powder, a method for producing goethite (goethite), a reversed micelle method (Reverse micelle method), and the like are known. The above-mentioned production methods are known. Further, as a method for producing an ∈ -iron oxide powder in which a part of Fe is substituted with a substitution atom of Ga, Co, Ti, Al, Rh, or the like, for example, "j.pn.soc.powder metallurgical vol.61supplement, No. S1, pp.s280-S284, j.mater.chem.c,2013,1, pp.5200-5206" or the like can be referred to. However, the method for producing the epsilon-iron oxide powder which can be used as a ferromagnetic powder in the magnetic layer is not limited.

A preferable embodiment when using an ∈ -iron oxide powder as the ferromagnetic powder is as follows.

The preferred activation volume of the epsilon-iron oxide powder is 300-1500 nm³Within the range of (1). The micronized epsilon-iron oxide powder having an activation volume within the above range is suitable for the production of magnetic tapes exhibiting excellent electromagnetic conversion characteristics. The preferred activation volume of the epsilon-iron oxide powder is 300nm³The above can be 500nm, for example³The above. And, from one to anotherMore preferably, the activated volume of the epsilon-iron oxide powder is 1400nm from the viewpoint of enhancing the electromagnetic conversion characteristics³Hereinafter, 1300nm is more preferable³Hereinafter, 1200nm is more preferable³The average particle diameter is preferably 1100nm³The following.

As an index of the reduction of thermal shock, in other words, the improvement of thermal stability, anisotropy constant Ku can be cited. The powder of ε -iron oxide is preferably such that it can have a particle size of 3.0X 10⁴J/m³The Ku may have a value of 8.0 × 10 more preferably⁴J/m³Ku above. Ku of the ε -iron oxide powder may be, for example, 3.0X 10⁵J/m³The following. However, the higher Ku is preferable since the higher Ku is more stable thermally, and thus the Ku is not limited to the above-exemplified values.

From the viewpoint of improving the reproduction output when reproducing data recorded on a magnetic tape, it is desirable that the mass magnetization σ s of ferromagnetic powder contained in the magnetic tape be high. In this regard, in one embodiment, σ s of the ∈ -iron oxide powder may be 8A · m²Is not less than kg, and can be 12 A.m²More than kg. On the other hand, σ s of the ε -iron oxide powder is preferably 40A · m from the viewpoint of noise reduction²Less than kg, more preferably 35 A.m²Is less than/kg.

When the magnetic tape contains the epsilon-iron oxide powder in the magnetic layer, the anisotropic magnetic field Hk of the magnetic layer is preferably 18kOe or more, more preferably 30kOe or more, and still more preferably 38kOe or more. The anisotropic magnetic field Hk of the magnetic layer is preferably 100kOe or less, more preferably 90kOe or less, and still more preferably 75kOe or less. In the magnetic layer containing the epsilon-iron oxide powder, the hard magnetization axis direction of the magnetic layer is the in-plane direction.

In the present embodiment, unless otherwise specified, the average particle diameter of each powder such as a ferromagnetic powder is set to a value measured by the following method using a transmission electron microscope.

The powder was photographed with a transmission electron microscope at a photographing magnification of 100000 times, and printed on photographic paper so that the total magnification thereof becomes 500000 times, thereby obtaining an image of particles constituting the powder. The particle profile is tracked and the size of the particle (primary particle) is measured using a Digitizer (Digitizer) that selects the target particle from the acquired image of the particle. Primary particles refer to individual particles that are not agglomerated.

The above measurements were performed on 500 particles drawn at random. The arithmetic mean of the particle diameters of the 500 particles thus obtained was defined as the average particle diameter of the powder. As the transmission electron microscope, for example, a transmission electron microscope H-9000 model manufactured by Hitachi, ltd. The measurement of the particle diameter can be performed using known image analysis software (e.g., Carl Zeiss co., ltd. image analysis software KS-400). Unless otherwise stated, the average particle diameter shown in the examples described later is a value measured using a transmission electron microscope model H-9000 made by Hitachi, ltd. as a transmission electron microscope and using Carl Zeiss co., ltd. made image analysis software KS-400 as image analysis software. In the present invention and the present specification, the powder refers to an assembly of a plurality of particles. For example, a ferromagnetic powder refers to an aggregate of a plurality of ferromagnetic particles. The aggregate of the plurality of particles is not limited to a mode in which the particles constituting the aggregate are in direct contact with each other, and includes a mode in which a binder, an additive, and the like, which will be described later, are interposed between the particles. The term "particles" is sometimes used to refer to powders.

As a method for collecting the sample powder from the magnetic recording medium for measuring the particle diameter, for example, the method described in paragraph 0015 of japanese patent application laid-open No. 2011-048878 can be employed.

In the present embodiment, as for the size (particle diameter) of the particles constituting the powder, the shape of the particles observed in the above-mentioned particle image sheet is as follows unless otherwise specified

(1) In the case of needle-like, spindle-like, columnar (however, the height is larger than the maximum major axis of the bottom surface), etc., the major axis length which is the length of the major axis constituting the particle,

(2) in the case of a plate-like or columnar shape (however, the thickness or height is smaller than the maximum major axis of the plate surface or bottom surface), as represented by the maximum major axis of the plate surface or bottom surface,

(3) the term "equivalent circle diameter" means a diameter of a sphere, a polyhedron, an unspecified shape, or the like, in which the major axis of the constituent particle cannot be determined from the shape. The equivalent circle diameter is a diameter obtained by a circle projection method.

The average acicular ratio of the powder is obtained by measuring the length of the short axis of the particles in the measurement, that is, the length of the short axis, obtaining the value (length of the long axis/length of the short axis) of each particle, and arithmetically averaging the values obtained for the 500 particles. Here, unless otherwise specified, according to the definition of the particle diameter described above, the minor axis length refers to the length of the minor axis constituting the particle in the case of (1), and similarly refers to the thickness or height, respectively, in the case of (2), and the major axis is not distinguished from the minor axis in the case of (3), and therefore (major axis length/minor axis length) is regarded as 1 for convenience.

Further, unless otherwise specified, when the shape of the particles is specified, for example, in the case where the above definition of the particle diameter is (1), the average particle diameter is the average major axis length, and in the case where the same definition is (2), the average particle diameter is the average plate diameter. When the average particle diameter is defined as (3) in the same manner, the average particle diameter is an average diameter (also referred to as an average particle diameter or an average particle diameter).

The content (filling ratio) of the ferromagnetic powder in the magnetic layer is preferably in the range of 50 to 90 mass%, and more preferably in the range of 60 to 90 mass%. The component other than the ferromagnetic powder of the magnetic layer is at least a binder, and may optionally contain one or more other additives. From the viewpoint of improving the recording density, it is preferable that the filling ratio of the ferromagnetic powder in the magnetic layer is high.

(Binder and curing agent)

The magnetic recording medium is a coating-type magnetic recording medium, and the magnetic layer contains a binder. The binder means one or more resins. As the binder, various resins generally used as binders for coating-type magnetic recording media can be used. For example, as the binder, a resin selected from urethane resin, polyester resin, polyamide resin, vinyl chloride resin, acrylic resin obtained by copolymerizing styrene, acrylonitrile, methyl methacrylate, and the like, cellulose resin such as nitrocellulose, and resin such as epoxy resin, phenoxy resin, polyvinyl acetal, polyvinyl ether resin such as polyvinyl butyral, and the like can be used alone or in combination of a plurality of resins. Among these, polyurethane resins, acrylic resins, cellulose resins, and vinyl chloride resins are preferable. These resins may be homopolymers or copolymers. These resins can also be used as binders in the nonmagnetic layer and/or the back coat layer described later. As for the above binder, reference can be made to paragraphs 0028 to 0031 of Japanese patent application laid-open No. 2010-24113. The binder may be a radiation-curable resin such as an electron beam-curable resin. For the radiation curable resin, reference can be made to paragraphs 0044 to 0045 of japanese patent application laid-open publication No. 2011-048878.

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 a weight average molecular weight. The weight average molecular weight in the present invention and the present specification is a value obtained by using Gel Permeation Chromatography (GPC) and polystyrene conversion of a value measured under the following measurement conditions. The weight average molecular weight of the binder shown in examples described later is a value obtained by converting a value measured under the following measurement conditions into polystyrene.

GPC apparatus: HLC-8120(TOSOH CORPORATION)

Pipe column: TSK gel Multipore HXL-M (manufactured by TOSOH CORPORATION, 7.8mmID (Inner Diameter: Inner Diameter). times.30.0 cm)

Eluent: tetrahydrofuran (THF)

In addition, a curing agent may be used in addition to the binder. The curing agent may be a thermosetting compound which is a compound capable of undergoing a curing reaction (crosslinking reaction) by heating in one formula, and a photocurable compound capable of undergoing a curing reaction (crosslinking reaction) by light irradiation in the other formula. By performing a curing reaction in the production process of the magnetic recording medium, at least a part of the curing agent can be contained in the magnetic layer in a state of being reacted (crosslinked) with other components such as a binder. The curing agent is preferably a thermosetting compound, preferably a polyisocyanate. For the details of the polyisocyanate, refer to paragraphs 0124 to 0125 of Japanese patent application laid-open No. 2011-216149. In the composition for forming a magnetic layer, the curing agent can be used in an amount of, for example, 0 to 80.0 parts by mass with respect to 100.0 parts by mass of the binder, and preferably 50.0 to 80.0 parts by mass from the viewpoint of enhancing the strength of each layer such as a magnetic layer.

(other Components)

The magnetic layer may contain one or more additives, if necessary, in addition to the above-described various components. The additive can be used by appropriately selecting a commercially available product according to the desired properties. Further, a compound synthesized by a known method can be used as an additive. Examples of the additive include the above-mentioned curing agent. Examples of the additives that can be contained in the magnetic layer include a nonmagnetic filler, a lubricant, a dispersant, a dispersion aid, an antibacterial agent, an antistatic agent, an antioxidant, and the like. The nonmagnetic filler means the same as the nonmagnetic particles or the nonmagnetic powder. Examples of the nonmagnetic filler include a nonmagnetic filler (hereinafter, referred to as "polishing agent") capable of functioning as a protrusion-forming agent and a polishing agent. Further, as the additive, known additives such as various polymers described in paragraphs 0030 to 0080 of Japanese patent application laid-open No. 2016 and 051493 can be used.

As the protrusion forming agent of one embodiment of the nonmagnetic filler, particles of an inorganic substance, particles of an organic substance, or composite particles of an inorganic substance and an organic substance can be used. Examples of the inorganic substance include inorganic oxides such as metal oxides, metal carbonates, metal sulfates, metal nitrides, metal carbides, and metal sulfides, and inorganic oxides are preferable. In one embodiment, the protrusion-forming agent may be inorganic oxide-based particles. As used herein, "system" is used in the sense of "comprising". One embodiment of the inorganic oxide-based particles is particles composed of an inorganic oxide. In addition, another embodiment of the inorganic oxide-based particles is composite particles of an inorganic oxide and an organic substance, and specific examples thereof include composite particles of an inorganic oxide and a polymer. Examples of such particles include particles in which a polymer is bonded to the surface of inorganic oxide particles.

S above_0.5The particle diameter of the protrusion-forming agent can be mainly controlled. The average particle diameter of the protrusion-forming agent is, for example, 30 to 300nm, preferably 40 to 200 nm. And, S can be mainly controlled by the manufacturing conditions of the magnetic recording medium_0.5. On the other hand, with respect to S_13.5The particle size of the protrusion-forming agent and the shape of the protrusion-forming agent can be controlled. The closer the shape of the particles is to that of a true sphere, the smaller the pressing resistance generated when a large pressure is applied, and therefore the particles are easily pressed into the magnetic layer, S_13.5It is easy to be small. On the other hand, if the shape of the particles is a shape deviating from a true sphere, for example, a shape called a deformed shape, a large pressing resistance is likely to be generated when a large pressure is applied, and thus it becomes difficult to press the particles into the magnetic layer, and S becomes a shape_13.5It is easy to become large. Further, even if the particle surface is uneven and has low surface smoothness, a large pressing resistance is likely to be generated when a large pressure is applied, and therefore, it becomes difficult to press the inside of the magnetic layer, and S becomes difficult_13.5It is easy to become large. Further, by controlling S_0.5And S_13.5Can correct the difference (S)_0.5-S_13.5) Is set to 3.0nm or less.

The polishing agent as another embodiment of the nonmagnetic filler is preferably a nonmagnetic powder having a mohs hardness of more than 8, and more preferably a nonmagnetic powder having a mohs hardness of 9 or more. On the other hand, the mohs hardness of the protrusion forming agent can be, for example, 8 or less or 7 or less. In addition, the maximum value of the mohs hardness is 10 of diamond. Specifically, alumina (Al) can be mentioned₂O₃) Silicon carbide, boron carbide (B)₄C)、SiO₂TiC, chromium oxide (Cr)₂O₃) Cerium oxide, zirconium oxide (ZrO)₂) And powders of iron oxide, diamond, and the like, and among them, alumina powder such as α -alumina and silicon carbide powder are preferable. The average particle size of the polishing agent is, for example, in the range of 30 to 300nm, preferably in the range of 50 to 200 nm.

The content of the protrusion-forming agent in the magnetic layer is preferably 1.0 to 4.0 parts by mass, and more preferably 1.5 to 3.5 parts by mass, based on 100.0 parts by mass of the ferromagnetic powder, from the viewpoint that the protrusion-forming agent and the polishing agent can more satisfactorily perform their functions. On the other hand, the content of the polishing agent in the magnetic layer is preferably 1.0 to 20.0 parts by mass, more preferably 3.0 to 15.0 parts by mass, and still more preferably 4.0 to 10.0 parts by mass, based on 100.0 parts by mass of the ferromagnetic powder.

Examples of additives that can be used in a magnetic layer containing an abrasive include dispersants described in paragraphs 0012 to 0022 of Japanese patent application laid-open publication No. 2013-131285 as dispersants for improving dispersibility of the abrasive in the composition for forming a magnetic layer. Further, as the dispersant, refer to paragraphs 0061 and 0071 of japanese patent laid-open No. 2012-133837. The dispersant may be contained in the nonmagnetic layer. As for the dispersant that can be contained in the nonmagnetic layer, refer to paragraph 0061 of japanese patent laid-open No. 2012-133837.

As one embodiment of the lubricant that can be contained in the additive of the magnetic layer, one or more lubricants selected from the group consisting of fatty acids, fatty acid esters, and fatty acid amides can be cited. S above_0.5And S_13.5The value measured after n-hexane washing was carried out. If a liquid film of lubricant is present on the surface of the magnetic layer to be pressed at the time of pitch measurement, the measured pitch is narrowed by an amount corresponding to the thickness of the liquid film. On the other hand, it is presumed that the lubricant which can exist as a liquid film at the time of pressing can be removed by washing with n-hexane. Therefore, it is considered that by measuring the pitch after n-hexane cleaning, a measured value of the pitch can be obtained as a value that favorably corresponds to the presence state of the protrusion (height of the protrusion) on the surface of the magnetic layer.

Examples of the fatty acid include lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, behenic acid, erucic acid, and elaidic acid, and stearic acid, myristic acid, and palmitic acid are preferable, and stearic acid is more preferable. The fatty acid may be contained in the magnetic layer in the form of a salt such as a metal salt.

Examples of the fatty acid ester include esters of lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, behenic acid, erucic acid, and elaidic acid. Specific examples thereof include Butyl myristate, Butyl palmitate, Butyl stearate (Butyl stearate), neopentane glycol dioctadecyl stearate, sorbitan monostearate, sorbitan distearate, sorbitan tristearate, oleyl oleate, isodecyl stearate, isotridecyl stearate, octyl stearate, isooctyl stearate, pentyl stearate, butoxyethyl stearate, and the like.

Examples of the fatty acid amide include amides of the above various fatty acids, for example, lauric acid amide, myristic acid amide, palmitic acid amide, stearic acid amide, and the like.

The fatty acid and the fatty acid derivative (amide, ester, etc.) preferably have the same or similar structure as the fatty acid used simultaneously at the site derived from the fatty acid in the fatty acid derivative. For example, when stearic acid is used as the fatty acid, it is preferable to use a stearic acid ester and/or a stearic acid amide.

The fatty acid content of the composition for forming a magnetic layer is, for example, 0 to 10.0 parts by mass, preferably 0.1 to 10.0 parts by mass, and more preferably 1.0 to 7.0 parts by mass, relative to 100.0 parts by mass of the ferromagnetic powder. The content of the fatty acid ester in the composition for forming a magnetic layer is, for example, 0 to 10.0 parts by mass, preferably 0.1 to 10.0 parts by mass, and more preferably 1.0 to 7.0 parts by mass, based on 100.0 parts by mass of the ferromagnetic powder. The content of the fatty acid amide in the composition for forming a magnetic layer is, for example, 0 to 3.0 parts by mass, preferably 0 to 2.0 parts by mass, and more preferably 0 to 1.0 part by mass, based on 100.0 parts by mass of the ferromagnetic powder.

In the case where the magnetic recording medium has a nonmagnetic layer between the nonmagnetic support and the magnetic layer, the fatty acid content of the composition for forming a nonmagnetic layer is, for example, 0 to 10.0 parts by mass, preferably 1.0 to 10.0 parts by mass, and more preferably 1.0 to 7.0 parts by mass, based on 100.0 parts by mass of the nonmagnetic powder. The content of the fatty acid ester in the composition for forming a non-magnetic layer is, for example, 0 to 15.0 parts by mass, preferably 0.1 to 10.0 parts by mass, per 100.0 parts by mass of the non-magnetic powder. The content of the fatty acid amide in the composition for forming a non-magnetic layer is, for example, 0 to 3.0 parts by mass, preferably 0 to 1.0 part by mass, per 100.0 parts by mass of the non-magnetic powder.

< nonmagnetic layer >

Next, the nonmagnetic layer will be described. The magnetic recording medium may have a direct magnetic layer on the nonmagnetic support, or may have a nonmagnetic layer containing nonmagnetic powder and a binder between the nonmagnetic support and the magnetic layer. The nonmagnetic powder used for the nonmagnetic layer may be a powder of an inorganic substance (inorganic powder) or a powder of an organic substance (organic powder). Carbon black and the like can also be used. Examples of the inorganic substance include metals, metal oxides, metal carbonates, metal sulfates, metal nitrides, metal carbides, and metal sulfides. These nonmagnetic powders are commercially available products, and can also be produced by a known method. For details, reference can be made to paragraphs 0146 to 0150 of Japanese patent application laid-open No. 2011-216149. Regarding carbon black that can be used for the nonmagnetic layer, reference can also be made to paragraphs 0040 to 0041 of jp 2010-24113 a. The content (filling ratio) of the nonmagnetic powder in the nonmagnetic layer is preferably in the range of 50 to 90 mass%, and more preferably in the range of 60 to 90 mass%.

As for other details of the binder, additives, and the like of the nonmagnetic layer, known techniques related to the nonmagnetic layer can be applied. For example, the known techniques related to the magnetic layer can be applied to the type and content of the binder, the type and content of the additive, and the like.

The nonmagnetic layer of the magnetic recording medium contains, in addition to the nonmagnetic powder, a substantially nonmagnetic layer containing, for example, an impurity or intentionally a small amount of ferromagnetic powder. The substantially nonmagnetic layer is a layer having a residual magnetic flux density of 10mT or less, a coercive force of 7.96kA/m (100Oe) or less, or a residual magnetic flux density of 10mT or less and a coercive force of 7.96kA/m (100Oe) or less. The nonmagnetic layer preferably has no residual magnetic flux density and coercive force.

< non-magnetic support >

Next, the nonmagnetic support will be described. Examples of the nonmagnetic support (hereinafter also simply referred to as "support") include known materials such as biaxially stretched polyethylene terephthalate, polyethylene naphthalate, polyamide, polyamideimide, and aromatic polyamide. Among these, polyethylene terephthalate, polyethylene naphthalate and polyamide are preferable. These supports may be subjected to corona discharge, plasma treatment, adhesion facilitating treatment, heat treatment, or the like in advance.

< Back coating >

The magnetic recording medium may further include a back coat layer containing a nonmagnetic powder and a binder on a surface side of the nonmagnetic support opposite to the surface side having the magnetic layer. In the back coat layer, one or both of carbon black and inorganic powder are preferably contained. As for the binder contained in the back coat layer and various additives that can be optionally contained, the publicly known techniques relating to the back coat layer can be applied, and the publicly known techniques relating to the formulation of the magnetic layer and/or the nonmagnetic layer can be applied. For example, as for the back coating layer, reference can be made to the descriptions of paragraphs 0018 to 0020 of Japanese patent application laid-open No. 2006-331625 and columns 4, lines 65 to 5, lines 38 of the specification of U.S. Pat. No. 7,029,774.

< various thicknesses >

The thickness of the non-magnetic support is, for example, in the range of 3.0 to 80.0. mu.m, preferably in the range of 3.0 to 50.0. mu.m, and more preferably in the range of 3.0 to 10.0. mu.m.

From the viewpoint of high-density recording which has been demanded in recent years, the thickness of the magnetic layer is preferably 100nm or less. The thickness of the magnetic layer is more preferably in the range of 10nm to 100nm, and still more preferably in the range of 20 to 90 nm. The magnetic layer may have at least one layer, or the magnetic layer may be separated into 2 or more layers having different magnetic properties, and a known structure relating to a multilayer magnetic layer may be applied. The thickness of the magnetic layer when the magnetic layer is separated into 2 or more layers is set as the total thickness of these layers.

The thickness of the nonmagnetic layer is, for example, 0.1 to 1.5 μm, preferably 0.1 to 1.0. mu.m.

The thickness of the back coat layer is preferably 0.9 μm or less, and more preferably in the range of 0.1 to 0.7. mu.m.

The thickness of each layer of the magnetic recording medium and the thickness of the nonmagnetic support can be determined by a known film thickness measurement method. For example, a cross section in the thickness direction of the magnetic recording medium is exposed by a known method such as an ion beam or a microtome, and then the exposed cross section is observed with a scanning electron microscope. In the cross-sectional observation, the thicknesses obtained at 1 site or at a plurality of sites of 2 or more sites randomly extracted, for example, the thicknesses obtained at 2 sites are arithmetically averaged, and various thicknesses can be obtained. The thickness of each layer can be determined as a design thickness calculated from the manufacturing conditions.

< manufacturing method >

(preparation of composition for Forming Each layer)

As for the composition for forming the magnetic layer, the non-magnetic layer or the back coat layer, a solvent is generally contained in addition to the various components previously described. As the solvent, various organic solvents generally used for manufacturing a coating-type magnetic recording medium can be used. Among them, from the viewpoint of solubility of a binder generally used in a coating-type magnetic recording medium, the composition for forming each layer preferably contains one or more ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, cyclohexanone, isophorone, and tetrahydrofuran. The amount of the solvent in the composition for forming each layer is not particularly limited, and can be the same as that of the composition for forming each layer of a general coating-type magnetic recording medium. The step of preparing the composition for forming each layer may generally include at least a kneading step, a dispersing step, and a mixing step provided before and after these steps as needed. Each step may be divided into 2 stages or more. The components used for the preparation of the composition for forming each layer may be added at the beginning or in the middle of any step. Further, each component may be added separately in 2 or more steps. For example, the binder may be separately charged in the kneading step, the dispersing step, and the mixing step for viscosity adjustment after dispersion. In the manufacturing process of the magnetic recording medium, a conventionally known manufacturing technique can be used in a part or all of the processes. In the kneading step, a kneader having a strong kneading power, such as an open kneader (open kneader), a continuous kneader, a pressure kneader, or an extruder, is preferably used. The details of these kneading processes are described in Japanese patent laid-open Nos. H1-106338 and H1-79274. In addition, glass beads and/or other beads can be used for dispersing the composition for forming each layer. As such dispersed beads, zirconia beads, titania beads and steel beads, which are dispersed beads of high specific gravity, are preferable. These dispersed beads are preferably used by optimizing the particle diameter (bead diameter) and the filling ratio. The dispersing machine may be a known dispersing machine. The composition for forming each layer may be filtered by a known method before the coating step. The filtering can be performed by, for example, filter filtering. As the filter used for filtration, for example, a filter having a pore size of 0.01 to 3 μm (for example, a filter made of glass fiber, a filter made of polypropylene, etc.) can be used.

(coating Process)

The magnetic layer can be formed, for example, by directly applying the composition for forming a magnetic layer to the non-magnetic support, or by sequentially or simultaneously applying a plurality of layers of the composition for forming a magnetic layer and the composition for forming a non-magnetic layer to the non-magnetic support. In the aspect of the alignment treatment, when the coating layer of the composition for forming a magnetic layer is in a wet state, the alignment treatment is performed on the coating layer in the alignment region. As for the alignment treatment, various known techniques such as those described in paragraph 0052 of jp 2010-24113 a can be applied. For example, the vertical alignment treatment can be performed by a known method such as a method using opposed pole magnets. In the orientation region, the drying speed of the coating layer can be controlled by the temperature of the drying air, the air volume, and/or the conveyance speed in the orientation region. Also, the coated layer may be dried in advance before being conveyed to the orientation zone.

The back coat layer can be formed by applying the composition for forming a back coat layer to the side of the nonmagnetic support opposite to the side having the magnetic layer (or additionally provided with the magnetic layer). For details of the coating for forming each layer, reference can be made to paragraph 0066 of japanese patent application laid-open No. 2010-231843.

(other steps)

After the coating step, a calendering process is usually performed to improve the surface smoothness of the magnetic recording medium. The more the calendering conditions tend to be intensified, the lower the height of the protrusion of the surface of the magnetic layer formed by the protrusion-forming agent in the manufactured magnetic recording medium becomes. Thereby, for example, S can be set_0.5And decreases. The calendering conditions include the kind and number of the calender roll, the calendering pressure, the calendering temperature (surface temperature of the calender roll), and the calendering speed. The calendering pressure is, for example, 200 to 500kN/m, preferably 250 to 350kN/m, the calendering temperature is, for example, 70 to 120 ℃, preferably 80 to 100 ℃, and the calendering speed is, for example, 50 to 300m/min, preferably 80 to 200 m/min. Further, since the surface of the magnetic layer tends to be smoothed as the number of steps increases as the surface of the roll becomes harder as the calender roll is used, the height of the protrusions on the surface of the magnetic layer can also be adjusted by the combination of the calender rolls and the number of steps.

For other various steps for manufacturing the magnetic recording medium, reference can be made to paragraphs 0067 to 0070 of jp 2010-231843 a.

(formation of Servo Pattern)

In order to realize tracking control of a magnetic head in a magnetic recording/reproducing apparatus and control of a running speed of a magnetic tape, a servo pattern can be formed by a known method on the magnetic tape manufactured as described above. The "formation of servo patterns" can also be referred to as "recording of servo signals" or the like. The following describes the formation of servo patterns.

The servo patterns are typically formed along the long side direction of the tape. Examples of the control (servo control) using the servo signal include a Timing Based Servo (TBS), an amplitude servo, and a frequency servo.

As shown in ECMA (European Computer Manufacturers Association) — 319, a time-based servo system is used for a Tape based on the LTO (Linear Tape-Open: Open Linear Tape) standard (generally referred to as "LTO Tape"). In this time-based servo system, a plurality of servo patterns are formed such that a pair of magnetic stripes (also referred to as "servo stripes") which are not parallel to each other are continuously arranged in the longitudinal direction of the magnetic tape. In the present invention and the present specification, the "time-based servo pattern" refers to a servo pattern that enables head tracking in a servo system of a time-based servo system. As described above, the reason why the servo pattern is formed by the pair of magnetic stripes which are not parallel to each other is to notify the passing position thereof to the servo signal reading element on the passing servo pattern. Specifically, the pair of magnetic stripes are formed such that the interval thereof continuously changes in the width direction of the magnetic tape, and the servo signal reading means reads the interval, whereby the relative position of the servo pattern and the servo signal reading element can be known. The information of the relative position enables to track the data tracks. Therefore, a plurality of servo tracks are generally set in the servo pattern in the width direction of the magnetic tape.

The servo band is composed of servo signals that are continuous in the longitudinal direction of the magnetic tape. Typically, a plurality of such servo bands are provided on a magnetic tape. For example, on an LTO magnetic tape, the number thereof is 5. The area sandwiched between adjacent 2 servo bands is called a data band. The data band is composed of a plurality of data tracks, each corresponding to each servo track.

In one aspect, as shown in japanese patent application laid-open No. 2004-318983, information indicating the number of a servo band (also referred to as "servo band ID (Identification)" or "UDIM (Unique data band Identification Method)" information ") is embedded in each servo band. The servo band ID is recorded by moving a specific pair of a pair of servo stripes having a plurality of servo bands so that the positions of the specific pair of servo stripes are relatively displaced in the longitudinal direction of the magnetic tape. Specifically, the moving method of a specific servo band in a pair of servo stripes having a plurality is changed for each servo band. Thus, the recorded servo band ID is unique for each servo band, and thus the servo band can be uniquely (uniquely) determined only by reading one servo band using the servo signal reading section.

In addition, as a method of uniquely determining a servo band, there is a method using a Staggered (Staggered) system as shown in ECMA-319. In the interleave system, a plurality of sets of a pair of magnetic stripes (servo stripes) which are not parallel to each other are continuously arranged in the longitudinal direction of the magnetic tape and are recorded so as to move in the longitudinal direction of the magnetic tape on a servo band-by-servo band basis. This combination of movement patterns between adjacent servo bands is unique throughout the tape, and thus the servo bands can also be uniquely identified when the servo patterns are read by the 2 servo signal reading elements.

Further, as shown in ECMA-319, information indicating the Position of the tape in the Longitudinal direction (also referred to as "LPOS (Longitudinal Position) information") is usually embedded in each servo band. The LPOS information records the positions of a pair of servo stripes by moving in the longitudinal direction of the magnetic tape, similarly to the UDIM information. However, unlike the UDIM information, the LPOS information records the same signal in each servo band.

Other information than the UDIM information and LPOS information may be embedded in the servo band. In this case, the embedded information may be different for each servo band as in the UDIM information, or may be common for all servo bands as in the LPOS information. As a method of embedding information in the servo band, a method other than the above-described method can be adopted. For example, it may be provided to record a predetermined code by subtracting a predetermined pair from a set of a pair of servo stripes.

The magnetic head for servo pattern formation is called a servo write head. The servo write head has only one pair of gaps corresponding to the pair of magnetic stripes to the extent of the number of servo bands. In general, a core and a coil are connected to each of the pair of gaps, and a leakage magnetic field can be generated between the pair of gaps by supplying a current pulse to the coil. When forming the servo pattern, a magnetic pattern corresponding to a pair of gaps can be transferred onto the magnetic tape by inputting a current pulse while the magnetic tape is running over the servo write head, thereby forming the servo pattern. 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 1 μm or less, 1 to 10 μm, 10 μm or more, and the like, for example.

Prior to forming the servo pattern on the magnetic tape, the magnetic tape is typically subjected to a degaussing (Erase) process. The erasing process can be performed by applying a uniform magnetic field to the magnetic tape using a dc magnet or an ac magnet. In the erasing process, there are a DC (Direct Current) erasing and an AC (Alternating Current) erasing. The AC erase is performed by gradually decreasing the strength of a magnetic field applied to the magnetic tape while reversing the direction of the magnetic field. On the other hand, with respect to DC erasing, it is performed by applying a magnetic field in one direction to the magnetic tape. In the DC erasing, there are further 2 methods. The first method is a horizontal DC erase in which a magnetic field in one direction is applied in the long side direction of the tape. The second method is a perpendicular DC erase in which a magnetic field is applied in one direction in the thickness direction of the tape. The erasing process may be performed for the entire tape or for each servo band of the tape.

The direction of the magnetic field of the formed servo pattern is determined according to the direction of the erasure. For example, when the magnetic tape is subjected to horizontal DC erasing, the servo pattern is formed such that the direction of the magnetic field is opposite to the direction of erasing. This can increase the output of the servo signal obtained by reading the servo pattern. Further, as disclosed in japanese patent application laid-open No. 2012-53940, when a magnetic pattern using the above gap is transferred to a perpendicular DC-erased magnetic tape, a servo signal obtained by reading the formed servo pattern has a unipolar pulse shape. On the other hand, when the magnetic pattern using the gap is transferred to the horizontal DC-erased magnetic tape, the servo signal obtained by reading the formed servo pattern has a bipolar pulse shape.

Next, with reference to fig. 10, an operation in the case of recording a target on the magnetic tape T of the information processing device 12 of the present embodiment will be described. The recording process shown in fig. 10 is executed by the CPU20 executing the recording program 30. The recording process shown in fig. 10 is executed, for example, after the data and the metadata transmitted from the terminal 16 are received by the receiving unit 40 and stored in the data cache 44 and the metadata DB46, respectively. In addition, here, it is assumed that the magnetic tape T of the recording object is loaded into the magnetic tape drive 18.

In step S10 of fig. 10, the recording unit 42 acquires the data stored in the data cache region 44 and the corresponding metadata stored in the metadata DB 46. When this step S10 is repeatedly executed, the recording unit 42 acquires data and metadata that have not been acquired so far.

In step S12, the recording unit 42 determines whether or not the 2 nd set data is recorded at a position immediately adjacent to the recording position of the target on the data partition DP of the magnetic tape T and the size of the 2 nd set data is equal to or smaller than a predetermined size. If the determination is an affirmative determination, the process proceeds to step S16, and if the determination is a negative determination, the process proceeds to step S14.

In step S14, the recording section 42 records the object including the data and the metadata acquired by the processing of step S10 without deleting the 2 nd set data of the data partition DP. On the other hand, in step S16, the recording unit 42 overwrites the object including the data and metadata acquired in the processing of step S10 with the 2 nd set data of a predetermined size or less, and records the object.

In step S18, the recording unit 42 repeatedly performs the processing from step S10 to step S16 to determine whether or not the total of the sizes of the objects recorded in the data partition DP exceeds a predetermined size. If the determination is a negative determination, the process returns to step S10, and if the determination is an affirmative determination, the process proceeds to step S20.

In step S20, as described above, the recording unit 42 records the 1 st set data, which is the set of metadata of the target recorded after the previous 1 st set data recorded in the previous step S20, in the data partition DP. In step S22, as described above, the recording unit 42 records the 2 nd set data, which is the set of the 1 st set data recorded in the data partition DP after the previous 2 nd set data recorded in the previous step S22, in the data partition DP.

In step S24, the recording section 42 determines whether the size of the 2 nd set data recorded by the processing of step S22 exceeds a predetermined size. If the determination is a negative determination, the process proceeds to step S28, and if the determination is an affirmative determination, the process proceeds to step S26. In step S26, the recording section 42 records (copies) the 2 nd set data recorded by the process of step S22 in the reference partition RP.

In step S28, the recording unit 42 determines whether or not all the data stored in the data cache area 44 has been recorded in the data partition DP. If the determination is a negative determination, the process returns to step S10, and if the determination is an affirmative determination, the process proceeds to step S30. In step S30, the recording unit 42 records the 1 st set data and the 2 nd set data in the data partition DP and records the 2 nd set data in the reference partition RP.

In step S32, the recording unit 42 controls the tape library 14 to remove the magnetic tape T from the tape drive 18. When the process of step S32 ends, the recording process ends.

Next, the functional configuration of the information processing device 12 in the case of reading a target from the magnetic tape T on which the target is recorded as described above will be described with reference to fig. 11. As shown in fig. 11, the information processing device 12 includes a reading unit 50, a receiving unit 52, a specifying unit 54, and a transmitting unit 56. The CPU20 executes the reading program 32 to function as the reading unit 50, the receiving unit 52, the specifying unit 54, and the transmitting unit 56.

The administrator of the information processing apparatus 12 loads the tape T to the tape drive 18 at the time of recovery from a failure or the like. When the magnetic tape T is loaded in the magnetic tape drive 18, the reading unit 50 stores the metadata in the metadata DB46 as follows. That is, at this time, the reading section 50 sequentially refers to the 2 nd set data recorded in the reference partition RP, the 2 nd set data recorded in the data partition DP, the 1 st set data recorded in the data partition DP, and the metadata recorded in the data partition DP of the loaded magnetic tape T to store the metadata in the metadata DB 46.

Specifically, the reading section 50 reads the 2 nd set data recorded in the reference partition RP and stores the metadata included in the read 2 nd set data in the metadata DB 46. In addition, in the case where the 2 nd set data does not exist in the reference partition RP, the reading section 50 reads the 2 nd set data recorded in the data partition DP and stores the metadata included in the read 2 nd set data in the metadata DB 46.

When the 2 nd set data is not present in the reference partition RP and the data partition DP, the reading unit 50 reads the 1 st set data recorded in the data partition DP and stores the metadata included in the read 1 st set data in the metadata DB 46.

When the reference partition RP and the data partition DP do not have the 2 nd set data and the 1 st set data, the reading unit 50 reads the metadata recorded in the data partition DP and stores the read metadata in the metadata DB 46. In addition, when reading the metadata recorded on the magnetic tape T, the reading unit 50 may not read the metadata already present in the metadata DB46 by comparison of hash values or the like.

The reading unit 50 reads a target recorded in a position on the magnetic tape T specified by a specifying unit 54 described later.

The receiving unit 52 receives a reading instruction of the target transmitted from the terminal 16 via the network N via the network I/F25. The read instruction includes identification information specific to the target.

The determination section 54 refers to the metadata DB46 and determines the position on the magnetic tape T of the target indicated by the identification information thereof using the metadata containing the identification information received by the reception section 52.

The transmission unit 56 transmits the target read by the reading unit 50 to the terminal 16 via the network I/F25.

Next, an operation in the case of reading a target from the magnetic tape T of the information processing device 12 according to the present embodiment will be described with reference to fig. 12 and 13. The metadata storage processing shown in fig. 12 and the target reading processing shown in fig. 13 are executed by the CPU20 executing the reading program 32. The metadata storage processing shown in fig. 12 is executed, for example, in a case where the magnetic tape T is loaded to the tape drive 18. The object reading process shown in fig. 13 is executed, for example, when the information processing device 12 receives an instruction to read an object transmitted from the terminal 16 via the network N.

In step S40 of fig. 12, the reading section 50 determines whether or not the 2 nd set data is present in the reference partition RP of the loaded magnetic tape T. If the determination is a negative determination, the process proceeds to step S44, and if the determination is an affirmative determination, the process proceeds to step S42. In step S42, the reading section 50 reads the 2 nd set data recorded in the reference partition RP and stores the metadata included in the read 2 nd set data in the metadata DB 46.

In step S44, the reading unit 50 determines whether or not the 2 nd set data is present in the data partition DP of the loaded tape T. If the determination is a negative determination, the process proceeds to step S48, and if the determination is an affirmative determination, the process proceeds to step S46. In step S46, the reading section 50 reads the 2 nd set data recorded in the data partition DP and stores the metadata included in the read 2 nd set data in the metadata DB 46.

In step S48, the reading unit 50 determines whether or not the 1 st set data is present in the data partition DP of the loaded tape T. If the determination is a negative determination, the process proceeds to step S52, and if the determination is an affirmative determination, the process proceeds to step S50. In step S50, the reading section 50 reads the 1 st set data recorded in the data partition DP and stores the metadata included in the read 1 st set data in the metadata DB 46.

In step S52, the reading section 50 reads the metadata recorded in the data partition DP and stores the read metadata in the metadata DB 46. If the processing of step S42, step S46, step S50, or step S52 ends, the metadata storage processing ends.

In step S60 of fig. 13, as described above, the receiving unit 52 receives the reading instruction of the target transmitted from the terminal 16 via the network N via the network I/F25. In step S62, the determination section 54 refers to the metadata DB46 and determines the position on the magnetic tape T of the target indicated by the identification information thereof using the metadata containing the identification information received through the processing of step S60.

In step S64, the reading section 50 reads the target recorded in the position on the magnetic tape T determined by the processing of step S62. In step S66, the transmission section 56 transmits the target read by the process of step S64 to the terminal 16 via the network I/F25. In step S68, the reading unit 50 controls the tape library 14 to remove the magnetic tape T from the tape drive 18. When the process of step S68 ends, the target reading process ends.

As described above, according to the present embodiment, a decrease in the effective capacity of the tape T can be suppressed. Further, according to the present embodiment, since the metadata is recorded in the 2 nd set data in the reference partition RP and the 2 nd set data, the 1 st set data, and the metadata in the data partition DP, it is possible to improve the failure endurance. Further, according to the present embodiment, the increase in the size of the 1 st aggregate data and the 2 nd aggregate data is suppressed by avoiding the duplication of metadata between the 1 st aggregate data and the duplication of metadata between the 2 nd aggregate data in each partition. Therefore, it is possible to suppress an increase in time required for recording the 1 st set data and the 2 nd set data on the magnetic tape T, and thus to suppress a decrease in the effective recording speed. Further, according to the present embodiment, the division into the 2 nd set data does not exceed a predetermined size. Therefore, as a result of suppressing an increase in the size of the 1 st set data and the 2 nd set data recorded once, a decrease in the effective recording speed can be suppressed. The effective recording speed referred to herein is a recording speed from the start of recording of data to be recorded by the user on the magnetic tape T to the end (i.e., a recording speed including metadata). The effective recording speed is obtained by dividing the size of data to be recorded by the user by the time from the start to the end of recording the data on the magnetic tape T.

[ 2 nd embodiment ]

Embodiment 2 of the technique of the present invention will be explained. The configuration of the recording and reading system 10 and the information processing device 12 according to the present embodiment is the same as that of embodiment 1, and therefore, the description thereof is omitted. The operation of the information processing device 12 according to the present embodiment is also the same as that of embodiment 1, and therefore, the description thereof is omitted.

In the present embodiment, as shown in fig. 14, it is assumed that the magnetic tape T to be recorded by the information processing device 12 is transported and used in another system. In embodiment 1, identification information specific to a target is included in metadata, and in this case, if the identification information is unique in a system, it is considered that the same identification information is used in another system. In fig. 14, the identification information unique to the object is denoted by "ObjectID".

Therefore, in the present embodiment, as shown in fig. 15, when generating an object including data and metadata transmitted from the terminal 16, the information processing device 12 includes identification information unique to the system in addition to identification information unique to the object in the metadata. In fig. 15, the identification information specific to the target is denoted by "ObjectID", and the identification information specific to the system is denoted by "SystemID".

As shown in fig. 16, by including identification information unique to the system in the metadata, when the magnetic tape T on which the target is recorded by the information processing device 12 is used in another system, the target can be identified as follows. In other words, even when the identification information of the object overlaps, the object can be identified by using the identification information unique to the system in addition to the identification information unique to the object.

In the above embodiments, the case where the 1 st set data, which is the set of metadata of the recorded objects, is recorded in the data partition DP every time the total size of the recorded objects exceeds a predetermined size has been described, but the present invention is not limited to this. For example, the 1 st set data, which is a set of metadata of recorded objects, may be recorded in the data partition DP whenever the number of recorded objects exceeds a predetermined number. For example, the 1 st set data may be recorded in the data partition DP at a timing when a predetermined time has elapsed after the last recording target.

In the above embodiments, the case where the magnetic tape is applied as the magnetic recording medium has been described, but the present invention is not limited thereto. The magnetic recording medium may be a magnetic recording medium other than a magnetic tape. The magnetic recording medium of the present embodiment is preferably used as various magnetic recording media (magnetic tape, disk-shaped magnetic recording media (magnetic disk), etc.) used in a sliding type magnetic recording and reproducing apparatus. The sliding type device is a device in which a surface of a magnetic layer slides while contacting a magnetic head when recording information on a magnetic recording medium and reading the recorded information.

In the above embodiment, the information processing device 12 and the tape library 14 are described as separate components, but the present invention is not limited thereto. It can also be provided as a magnetic recording and reading apparatus including the information processing apparatus 12 and the magnetic tape library 14.

Also, in the above-described embodiments, various processes performed by executing software (programs) by the CPU may be executed by various processors other than the CPU. Examples of the processor in this case include a dedicated Circuit, which is a processor having a Circuit configuration designed specifically for executing a Specific process, such as a PLD (Programmable Logic Device) or an ASIC (Application Specific Integrated Circuit) whose Circuit configuration can be changed after manufacture, such as an FPGA (Field-Programmable Gate Array). The various processes may be executed by 1 of these various processors, or may be executed by a combination of 2 or more processors of the same kind or different kinds (for example, a plurality of FPGAs, a combination of a CPU and an FPGA, or the like). More specifically, the hardware configuration of these various processors is a circuit in which circuit elements such as semiconductor elements are combined.

In the above embodiment, the recording program 30 and the reading program 32 are previously stored (installed) in the storage unit 22, but the present invention is not limited thereto. The recording program 30 and the reading program 32 may be provided in the form of programs recorded on recording media such as CD-ROM (Compact Disk Read Only Memory), DVD-ROM (Digital Versatile Disk Read Only Memory), and USB (Universal Serial Bus) Memory. The recording program 30 and the reading program 32 may be downloaded from an external device via a network.

Examples

The present invention will be described below with reference to examples. However, the present invention is not limited to the embodiment shown in the examples. The "parts" described below represent "parts by mass". Unless otherwise stated, the steps and evaluations described below were performed in an environment in which the ambient temperature was 23 ℃. + -. 1 ℃. "eq" described below is an equivalent (equivalent) and is a unit that cannot be converted into SI units. First, an example of the magnetic recording medium will be explained.

The protrusion-forming agents used for the production of the magnetic recording media of the examples and comparative examples are as follows. The protrusion-forming agents 1 and 3 are particles having a low surface smoothness of the particle surface. The particle shape of the protrusion forming agent 2 is a cocoon (cocoon) shape. The particle shape of the protrusion-forming agent 4 is a so-called irregular shape. The particle shape of the protrusion-forming agent 5 is a shape close to a true sphere.

Protrusion-forming agent 1: ATLAS (composite particles of silica and polymer) manufactured by Cabot Corporation, average particle diameter 100nm

Protrusion-forming agent 2: TGC6020N (silica particles) manufactured by Cabot Corporation, average particle diameter 140nm

Protrusion-forming agent 3: catalogid (an aqueous dispersion sol of silica particles; as a protrusion-forming agent for preparing a protrusion-forming agent solution described later, a dry substance obtained by heating the aqueous dispersion sol to remove a solvent) manufactured by JGC Catalysts and Chemicals Ltd., and having an average particle diameter of 120nm

Protrusion-forming agent 4: ASAHI CARBON CO, LTD, ASAHI #50 (CARBON black), average particle size 300nm

Protrusion-forming agent 5: PL-10L (aqueous dispersion sol of silica particles; dry matter obtained by heating the aqueous dispersion sol to remove the solvent as a protrusion-forming agent for preparing a protrusion-forming agent solution to be described later) manufactured by LTD, FUSO CHEMICAL CO., LTD, and having an average particle diameter of 130nm

[ example 1]

< composition for forming magnetic layer >

(magnetic liquid)

Ferromagnetic powder (hexagonal barium ferrite powder): 100.0 portion

(coercive force Hc: 196kA/m, average particle diameter (average plate diameter) 24nm)

Oleic acid: 2.0 part by weight

Vinyl chloride copolymer (MR-104 manufactured by KANEKA CORPORATION): 10.0 parts of

Containing SO₃Na-based polyurethane resin: 4.0 part

(weight average molecular weight 70000, SO)₃Na group: 0.07meq/g)

Additive A: 10.0 parts of

Methyl ethyl ketone: 150.0 portion

Cyclohexanone: 150.0 portion

(abrasive liquid)

Alpha-alumina (average particle diameter: 110 nm): 6.0 parts of

Vinyl chloride copolymer (MR 110 manufactured by KANEKA CORPORATION): 0.7 portion of

Cyclohexanone: 20.0 portion

(solution of protrusion-forming agent)

Protrusion forming agent (refer to fig. 17): 1.3 parts of

Methyl ethyl ketone: 9.0 parts of

Cyclohexanone: 6.0 parts of

(Lubricant and curing agent liquid)

Stearic acid: 3.0 parts of

Stearic acid amide: 0.3 part

Butyl stearate: 6.0 parts of

Methyl ethyl ketone: 110.0 portions

Cyclohexanone: 110.0 portions

Polyisocyanate (Coronate (registered trademark) L manufactured by TOSOH CORPORATION): 3.0 parts of

The additive A is a polymer synthesized by the method described in paragraphs 0115 to 0123 of Japanese patent application laid-open No. 2016 & 051493.

< composition for Forming nonmagnetic layer >

Non-magnetic inorganic powder (α -iron oxide): 80.0 parts of

(average particle diameter: 0.15 μm, average needle ratio: 7, BET (Brunauer-Emmett-Teller: Buerts) specific surface area: 52m²/g)

Carbon black (average particle diameter: 20 nm): 20.0 portion

Electron beam curing type vinyl chloride copolymer: 13.0 parts of

Electron beam curing polyurethane resin: 6.0 parts of

Phenyl phosphonic acid: 3.0 parts of

Cyclohexanone: 140.0 parts of

Methyl ethyl ketone: 170.0 parts

Butyl stearate: 2.0 part by weight

Stearic acid: 1.0 part

< composition for Forming Back coating >

Non-magnetic inorganic powder (α -iron oxide): 80.0 parts of

(average particle diameter: 0.15 μm, average needle ratio: 7, BET specific surface area: 52 m)²/g)

Carbon black (average particle diameter: 20 nm): 20.0 portion

Carbon black (average particle diameter: 100 nm): 3.0 parts of

Vinyl chloride copolymer: 13.0 parts of

Sulfonic acid group-containing polyurethane resin: 6.0 parts of

Phenyl phosphonic acid: 3.0 parts of

Cyclohexanone: 140.0 parts of

Methyl ethyl ketone: 170.0 parts

Stearic acid: 3.0 parts of

Polyisocyanate (Coronate made by TOSOH CORPORATION): 5.0 parts of

Methyl ethyl ketone: 400.0 parts of

< preparation of composition for Forming layers >

A composition for forming a magnetic layer was prepared by the following method.

After the components of the magnetic liquid were kneaded and diluted by an open kneader, 12 times of dispersion treatment were performed using zirconia (ZrO2) beads (hereinafter, referred to as "Zr beads") having a particle diameter of 0.5mm by a horizontal bead mill disperser under conditions of a bead filling rate of 80 vol% and a rotor tip circumferential velocity of 10 m/sec with a retention time of 2 minutes each time.

The polishing liquid was prepared by mixing the components of the polishing liquid, then charging the mixture into a vertical mixer disperser together with Zr beads having a particle size of 1mm so that the bead volume/(polishing liquid volume + bead volume) became 60%, and performing a mixer dispersion treatment for 180 minutes to extract the treated liquid, and then performing an ultrasonic dispersion filtration treatment using a flow type ultrasonic dispersion filtration apparatus.

The magnetic liquid, the polishing agent liquid, the protrusion-forming agent liquid, and the lubricant and the curing agent liquid were introduced into a dissolution mixer, and were mixed at a peripheral speed of 10 m/sec for 30 minutes, and then subjected to 3 treatments at a flow rate of 7.5 kg/min by a flow ultrasonic disperser, followed by filtration through a filter having a pore size of 1 μm, to prepare a composition for forming a magnetic layer.

The composition for forming a nonmagnetic layer was prepared by the following method.

The above components except for the lubricant (butyl stearate and stearic acid) were kneaded and diluted with an open kneader, and then subjected to dispersion treatment with a horizontal bead mill disperser. Then, a lubricant (butyl stearate and stearic acid) was added thereto, and the mixture was stirred by a dissolver stirrer to perform mixing treatment, thereby preparing a composition for forming a nonmagnetic layer.

The composition for forming a back coat layer was prepared by the following method.

The above components except for the lubricant (stearic acid), polyisocyanate and methyl ethyl ketone (400.0 parts) were kneaded and diluted with an open kneader, and then dispersed with a horizontal bead mill disperser. Then, a lubricant (stearic acid), polyisocyanate, and methyl ethyl ketone (400.0 parts) were added thereto, and the mixture was stirred by a dissolver stirrer to carry out mixing treatment, thereby preparing a composition for forming a back coat layer.

< manufacture of magnetic tape >

The composition for forming a nonmagnetic layer was applied to a polyethylene naphthalate support having a thickness of 6.0 μm so that the dried thickness became 1.0 μm, and then dried, and then irradiated with an electron beam so that the energy became 40kGy at an acceleration voltage of 125 kV. The magnetic layer-forming composition was applied thereon so that the thickness after drying became 50nm, and when the coating layer was in a wet (non-dried) state, a vertical alignment treatment was performed in which a magnetic field having a magnetic field strength of 0.3T was applied to the surface of the coating layer in the vertical direction, and the coating layer was dried. Further, a back coat layer-forming composition was applied to the surface of the support opposite to the surface on which the nonmagnetic layer and the magnetic layer were formed, so that the dried thickness became 0.5 μm, and dried.

Thereafter, calendering was performed at a calendering speed of 80m/min, a line pressure of 294kN/m and a calendering temperature shown in FIG. 17 using 7-stage calender rolls composed of only metal rolls. Thereafter, the heat treatment was performed for 36 hours in an atmosphere at an ambient temperature of 70 ℃. After the heat treatment, the magnetic tape was cut into 1/2 inches (0.0254 m in 1 inch) in width, and the surface of the magnetic layer was cleaned by a tape cleaning device mounted on a device having a feeding and winding device for the cut product so that the nonwoven fabric and the doctor blade were pressed against the surface of the magnetic layer, thereby obtaining a magnetic tape.

Examples 2 to 7 and comparative examples 1 to 9

A magnetic tape was obtained by the same method as in example 1, except that the kind of the protrusion-forming agent and/or the calendering temperature were changed to the points shown in fig. 17. In fig. 17, the protrusion-forming agent is "none" and means that the protrusion-forming agent is not used. In fig. 17, "recording control" indicates the presence or absence of data recording control according to the present invention.

[ evaluation method ]

(1) Difference (S)_0.5-S_13.5)

Using TSA (Tape Spacing Analyzer (manufactured by Micro Physics), the pitch S after n-hexane cleaning was measured by the following method_0.5And S_13.5And from the measured valuesCalculating the difference (S)_0.5-S_13.5)。

5 pieces of 5 cm-long sample pieces were cut from each of the magnetic tapes of examples and comparative examples, and after n-hexane was washed for each piece by the method described above, S was measured by the following method_0.5And S_13.5。

In a state where a glass plate (model: WG10530) manufactured by Thorlabs, inc.) included in TSA was disposed on the surface of the magnetic layer of the magnetic tape (i.e., the sample sheet), a hemisphere made of urethane included in TSA was used as a pressing member, and the hemisphere was pressed against the back coat surface of the magnetic tape at a pressure of 0.5 atm. In this state, white light is irradiated from a stroboscope provided in the TSA through a glass plate onto a constant region (150000 to 200000 μm) on the surface of the magnetic layer of the magnetic tape²) The obtained reflected light is passed through an interference filter (filter that selectively transmits light having a wavelength of 633 nm) and is reflected by a CCD (Charge-Coupled Device: charge coupled device) to receive light, thereby obtaining an interference fringe image formed in the area.

The image was divided into 300000 dots, the distance (pitch) from the tape-side surface of the glass plate to the magnetic layer surface of the magnetic tape at each dot was determined, this was used as a histogram, and the maximum frequency of the histogram was used as the pitch S_0.5To obtain the final product.

The same sample piece was further pressed, and the pitch S was determined by the same method as described above under a pressure of 13.5atm_13.5。

For the above 5 test pieces, S obtained as described above was calculated_0.5And S_13.5Difference (S) of_0.5-S_13.5) And taking the arithmetic mean of the calculated values as the difference (S)_0.5-S_13.5) Shown in fig. 17.

(2) Coefficient of friction (μ value)

In an environment where the ambient temperature was 23 ℃ and the relative humidity was 50%, a magnetic head detached from an LTO (registered trademark) G5(Linear Tape Generation 5, fifth Generation Open Linear Tape) drive manufactured by IBM was mounted on a Tape running system, and data reading was evaluated as described below while applying a tension of 0.6N (newton), and a magnetic Tape having a Tape length of 20m was cut from the evaluated magnetic Tape. Further, the cut magnetic tape having a length of 20m was fed from the feeding roller and wound on the winding roller, and the magnetic tape was caused to travel at a traveling speed of 4.0m/s while the magnetic layer surface was caused to slide in contact with the magnetic head. In the 1 st run, the friction force with respect to the magnetic head was measured using a Strain gauge (Strain gauge) during the run, and the friction coefficient μ value was obtained from the measured friction force. The value in fig. 17 is a μ value obtained for the 1 st travel, and is therefore represented as "μ value (1 p)".

[ evaluation of data reading ]

A magnetic tape for data reading evaluation was prepared. As the magnetic tape, example 1 of the above-described magnetic recording medium was used.

For evaluation, indexes were recorded on the magnetic tape in the following 2 modes R1 and R2. The mode R2 is a recording mode of the present invention.

Mode R1: every 10 data records, the index of all data so far is recorded.

Mode R2: every 10 data records, 10-share indexes are recorded. The manner of recording the data and the index is shown in fig. 18.

In addition, both modes R1 and R2 record the index of all data at the end of the data. And, the index of 1 data and 1 share of data has 1 unit size. Further, the total data size on the magnetic tape is obtained for each of the data amounts written for the equations R1 and R2.

The total data size when the number of data is d is as follows. Where d mod10 is assumed to be b.

Mode R1 ═ (1/20) × (d)²+30*d+b²-2*b*d+10*b)

Mode R2 ═ 3 × d-b

The results of the total data size for the data amount are shown in fig. 19.

From the results shown in fig. 17, it was confirmed that the magnetic tape of the example had a smaller μ value than the magnetic tape of the comparative example, that is, the increase width of the friction coefficient was small even when the sliding with the magnetic head was repeated. From the results shown in fig. 19, it was confirmed that the total data size of the system R2 with respect to the system R1 was about 46% when the number of data items was 100. At this time, the total moving amount of the magnetic head in the case of sequential reading is reduced by about 54%. Also, it can be confirmed that the reduction rate increases as the number of data increases. In the examples of the present invention, hexagonal barium ferrite powder was used as the ferromagnetic powder, but it was confirmed that even when hexagonal strontium ferrite powder and epsilon-iron oxide powder were used as the ferromagnetic powder, favorable results were obtained as in the case of using hexagonal barium ferrite powder.

The hexagonal strontium ferrite powder used herein had an average particle size of 19nm and an activation volume of 1102nm³Anisotropy constant Ku of 2.0X 10⁵J/m³Mass magnetization σ s of 50A · m²In terms of/kg. The anisotropic magnetic field Hk of the magnetic layer containing the hexagonal strontium ferrite powder was 25 kOe. Similarly, the average particle diameter of the epsilon-iron oxide powder was 12nm, and the activation volume was 746nm³Anisotropy constant Ku of 1.2X 10⁵J/m³The mass magnetization σ s is 16A · m²In terms of/kg. The anisotropic magnetic field Hk of the magnetic layer containing the epsilon-iron oxide powder was 30 kOe.

Description of the symbols

10-record reading system, 12-information processing apparatus, 14-tape library, 16-terminal, 18-tape drive, 20-CPU, 21-memory, 22-storage section, 23-display section, 24-input section, 25-network I/F, 26-external I/F, 27-bus, 30-recording program, 32-reading program, 40, 52-receiving section, 42-recording section, 44-data cache section, 46-metadata DB, 50-reading section, 54-determination section, 56-transmission section, DP-data section, GW-guard band, N-network, RP-reference section, T-tape, R1-mode 1, R2-mode 2.

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