JP6729780B1 - Magnetic recording medium and cartridge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic recording medium having both excellent running stability and electromagnetic conversion characteristics. In a recording/reproducing system, a magnetic tape MT is a tape-shaped magnetic recording medium, and includes a substrate 41, an underlayer 42 provided on the substrate, and a magnetic layer 43 provided on the underlayer. Equipped with. The substrate contains polyester, the underlayer and the magnetic layer contain a lubricant, the magnetic layer has a surface provided with a large number of holes 43A, and the arithmetic average roughness Ra of the surface is 2.5 nm or less. The BET specific surface area of the entire magnetic recording medium measured in a state where the magnetic recording medium was washed and dried was 3.5 m2/g or more and 7.0 m2/g or less, and the BET specific surface area in the perpendicular direction of the magnetic layer was The squareness ratio is 65% or more, the average thickness of the magnetic layer is 80 nm or less, the average thickness of the magnetic recording medium is 5.6 μm or less, and the servo pattern is recorded on the magnetic layer. The statistical value σ SW indicating non-linearity is 24 nm or less. [Selection diagram] Fig. 4

Description

The present disclosure relates to magnetic recording media and cartridges.

Tape-shaped magnetic recording media are widely used for storing electronic data. In this magnetic recording medium, various improvements in characteristics have been studied.

In Patent Document 1, in order to achieve both excellent running stability and electromagnetic conversion characteristics, the root mean square surface roughness (Rq) of the surface of the magnetic layer forming surface is set to 4.0 nm or less, and the surface profile of the magnetic layer forming surface is It is described that the skewness (Sk: Skewness) is -1 or more and +1 or less.

JP, 2006-69553, A

The tape-shaped magnetic recording medium is usually housed in a cartridge case. In order to further increase the recording capacity of the cartridge, it is conceivable to make the magnetic recording medium contained in the cartridge thinner (to reduce the total thickness) and increase the tape length of the cartridge. However, a magnetic recording medium having a small total thickness may be inferior in running stability. In particular, when recording and/or reproducing repeatedly, the magnetic recording medium having a small total thickness may change its surface condition, particularly the surface condition relating to friction, and may deteriorate running stability.

An object of the present disclosure is to provide a magnetic recording medium and a cartridge that can achieve both excellent running stability and electromagnetic conversion characteristics even when the total thickness of the magnetic recording medium is thin.

In order to solve the above-mentioned problems, a first disclosure is a tape-shaped magnetic recording medium, which comprises a substrate, an underlayer provided on the substrate, a magnetic layer provided on the underlayer, and a substrate. And a back layer provided on the surface opposite to the underlayer , the substrate includes polyester, the average thickness of the substrate is 4.2 μm or less, and the underlayer and the magnetic layer include a lubricant. arithmetic average roughness Ra of the magnetic layer table surface is at 2.5nm or less, the magnetic recording medium is cleaned, was measured in a dry state, the whole of the BET specific surface area of the magnetic recording medium is 3.5 m ² / g or more and 7.0 m ² /g or less, the squareness ratio of the magnetic layer in the vertical direction is 65% or more, the average thickness of the magnetic layer is 80 nm or less, and the average thickness of the magnetic recording medium is 5. The magnetic recording medium has a thickness of 6 μm or less, a servo pattern is recorded on the magnetic layer, and a statistical value σ _SW indicating the nonlinearity of the servo pattern is 24 nm or less.
A second disclosure is a tape-shaped magnetic recording medium, comprising a substrate, an underlayer provided on the substrate, a magnetic layer provided on the underlayer, and a surface of the substrate opposite to the underlayer. The backing layer provided on the magnetic recording medium, the substrate containing polyester, the underlayer and the magnetic layer containing a lubricant, and the arithmetic average roughness Ra of the surface of the magnetic layer is 2.5 nm or less. The BET specific surface area of the entire magnetic recording medium measured in the washed and dried state is 4.5 m ² /g or more and 7.0 m ² /g or less, and the squareness ratio of the magnetic layer in the perpendicular direction is 65% or more, the average thickness of the magnetic layer is 80 nm or less, the average thickness of the magnetic recording medium is 5.6 μm or less, the servo pattern is recorded on the magnetic layer, and the nonlinearity of the servo pattern is reduced. The statistical value σ _SW shown is a magnetic recording medium of 24 nm or less.

A third disclosure is a cartridge including the magnetic recording medium of the first or second disclosure, and a storage unit having an area for writing adjustment information for adjusting a tension applied in the longitudinal direction of the magnetic recording medium.

FIG. 1 is a schematic diagram showing an example of the configuration of a recording/reproducing system according to the first embodiment of the present disclosure. FIG. 2 is an exploded perspective view showing an example of the configuration of the cartridge. FIG. 3 is a block diagram showing an example of the configuration of the cartridge memory. FIG. 4 is a cross-sectional view showing an example of the structure of the magnetic tape. FIG. 5 is a schematic diagram showing an example of a layout of data bands and servo bands. FIG. 6 is an enlarged view showing an example of the structure of the data band. FIG. 7 is an enlarged view showing an example of the configuration of the servo band. FIG. 8 is a schematic diagram of a head unit used for measuring the statistical value σ _SW . 9A and 9B are diagrams showing examples of TEM photographs of the magnetic layer. 10A and 10B are schematic diagrams for explaining a method of measuring the coefficient of friction between the magnetic surface and the magnetic head, respectively. FIG. 11 is a schematic diagram showing an example of the configuration of the servo writer. FIG. 12A is a perspective view showing an example of the configuration of a servo signal write head. 12B is a sectional view taken along line XIIB-XIIB of FIG. 12A. FIG. 13 is a flow chart for explaining an example of the operation of the recording/reproducing apparatus at the time of recording data. FIG. 14 is a flow chart for explaining an example of the operation of the recording/reproducing apparatus during data reproduction. FIG. 15 is a schematic diagram showing an example of the configuration of a recording/reproducing system according to the second embodiment of the present disclosure. FIG. 16 is a flow chart for explaining an example of the operation of the recording/reproducing apparatus at the time of recording data. FIG. 17 is a flow chart for explaining an example of the operation of the recording/reproducing apparatus during data reproduction.

The embodiments of the present disclosure will be described in the following order. In all the drawings of the following embodiments, the same or corresponding parts are designated by the same reference numerals.
1 1st Embodiment 2 2nd Embodiment 3 Modification

<1 First Embodiment>
[Structure of recording/playback system]
FIG. 1 is a schematic diagram showing an example of the configuration of a recording/reproducing system 100 according to the first embodiment of the present disclosure. The recording/reproducing system 100 is a magnetic tape recording/reproducing system, and includes a cartridge 10 and a recording/reproducing device 50 configured to load and unload the cartridge 10.

[Cartridge configuration]
FIG. 2 is an exploded perspective view showing an example of the configuration of the cartridge 10. The cartridge 10 is a magnetic tape cartridge conforming to the LTO (Linear Tape-Open) standard, and a magnetic tape (tape-shaped magnetic recording medium) is provided inside a cartridge case 12 composed of a lower shell 12A and an upper shell 12B. The reel 13 around which the MT is wound, the reel lock 14 and the reel spring 15 for locking the rotation of the reel 13, the spider 16 for releasing the locked state of the reel 13, the lower shell 12A and the upper shell 12B. Slide door 17 that opens and closes the tape outlet 12C provided in the cartridge case 12, a door spring 18 that urges the slide door 17 to the closed position of the tape outlet 12C, and a write protect 19 that prevents erroneous erasing. And a cartridge memory 11. The reel 13 has a substantially disc shape having an opening in the center and is composed of a reel hub 13A made of a hard material such as plastic and a flange 13B. A leader pin 20 is provided at one end of the magnetic tape MT.

The cartridge memory 11 is provided near one corner of the cartridge 10. When the cartridge 10 is loaded in the recording/reproducing apparatus 50, the cartridge memory 11 faces the reader/writer 57 of the recording/reproducing apparatus 50. The cartridge memory 11 communicates with the recording/reproducing device 50, specifically, the reader/writer 57, according to the wireless communication standard conforming to the LTO standard.

[Cartridge memory configuration]
FIG. 3 is a block diagram showing an example of the configuration of the cartridge memory 11. The cartridge memory 11 uses an induced electromotive force to generate and rectify an electric power from an antenna coil (communication unit) 31 that communicates with the reader/writer 57 according to a prescribed communication standard, and an electric wave received by the antenna coil 31. A rectification/power supply circuit 32, a clock circuit 33 that similarly generates a clock from an electric wave received by the antenna coil 31 using an induced electromotive force, a detection of an electric wave received by the antenna coil 31, and a signal transmitted by the antenna coil 31. A detection/modulation circuit 34 that performs modulation, and a controller (control unit) 35 configured by a logic circuit or the like for distinguishing commands and data from the digital signal extracted from the detection/modulation circuit 34 and processing the data. , A memory (storage unit) 36 for storing information. Further, the cartridge memory 11 includes a capacitor 37 connected in parallel to the antenna coil 31, and the antenna coil 31 and the capacitor 37 form a resonance circuit.

The memory 36 stores information related to the cartridge 10. The memory 36 is a non-volatile memory (Non Volatile Memory: NVM). The storage capacity of the memory 36 is preferably about 32 KB or more.

The memory 36 has a first storage area 36A and a second storage area 36B. The first storage area 36A corresponds to the storage area of the cartridge memory of the LTO standard before LTO8 (hereinafter referred to as "conventional cartridge memory"), and is used for storing information compliant with the LTO standard before LTO8. Area. The information based on the LTO standard prior to LTO8 is, for example, manufacturing information (for example, the unique number of the cartridge 10), usage history (for example, the tape pull-out count (Thread Count), etc.).

The second storage area 36B corresponds to an extended storage area with respect to the storage area of the conventional cartridge memory. The second storage area 36B is an area for storing additional information. Here, the additional information means information related to the cartridge 10, which is not defined by the LTO standard prior to LTO8. Examples of the additional information include tension adjustment information, management ledger data, Index information, thumbnail information of moving images stored on the magnetic tape MT, and the like, but are not limited to these data. The tension adjustment information is information for adjusting the tension applied in the longitudinal direction of the magnetic tape MT. The tension adjustment information includes a distance between adjacent servo bands (a distance between servo patterns recorded in adjacent servo bands) when recording data on the magnetic tape MT. The distance between the adjacent servo bands is an example of width-related information related to the width of the magnetic tape MT. Details of the distance between the servo bands will be described later. In the following description, the information stored in the first storage area 36A may be referred to as "first information", and the information stored in the second storage area 36B may be referred to as "second information".

The memory 36 may have a plurality of banks. In this case, some of the plurality of banks may form the first storage area 36A, and the remaining banks may form the second storage area 36B.

The antenna coil 31 induces an induced voltage by electromagnetic induction. The controller 35 communicates with the recording/reproducing device 50 via the antenna coil 31 according to a prescribed communication standard. Specifically, for example, mutual authentication, command transmission/reception, data exchange, etc. are performed.

The controller 35 stores in the memory 36 the information received from the recording/reproducing device 50 via the antenna coil 31. For example, the tension adjustment information received from the recording/reproducing device 50 via the antenna coil 31 is stored in the second storage area 36B of the memory 36. The controller 35 reads information from the memory 36 in response to a request from the recording/reproducing device 50, and transmits the information to the recording/reproducing device 50 via the antenna coil 31. For example, in response to a request from the recording/reproducing device 50, the tension adjustment information is read from the second storage area 36B of the memory 36 and transmitted to the recording/reproducing device 50 via the antenna coil 31.

[Structure of magnetic tape]
FIG. 4 is a sectional view showing an example of the structure of the magnetic tape MT. The magnetic tape MT is a tape-shaped magnetic recording medium, and includes a long base 41, a base layer 42 provided on one main surface (first main surface) of the base 41, and a base layer 42. And a back layer 44 provided on the other main surface (second main surface) of the base 41. The base layer 42 and the back layer 44 are provided as needed and may be omitted. The magnetic tape MT may be a perpendicular recording type magnetic recording medium or a longitudinal recording type magnetic recording medium.

The magnetic tape MT has a long tape shape and is run in the longitudinal direction during recording and reproduction. The surface of the magnetic layer 43 is the surface on which the magnetic head 56 of the recording/reproducing device 50 runs. The magnetic tape MT is preferably used in a recording/reproducing apparatus having a ring type head as a recording head. The magnetic tape MT is preferably used in a recording/reproducing apparatus configured to record data with a data track width of 1500 nm or less or 1000 nm or less.

(Base)
The base 41 is a non-magnetic support that supports the underlayer 42 and the magnetic layer 43. The base 41 has a long film shape. The upper limit of the average thickness of the substrate 41 is preferably 4.2 μm or less, more preferably 3.8 μm or less, and even more preferably 3.4 μm or less. When the upper limit of the average thickness of the substrate 41 is 4.2 μm or less, the recording capacity that can be recorded in one data cartridge can be made higher than that of a general magnetic tape. The lower limit of the average thickness of the base body 41 is preferably 3 μm or more, more preferably 3.2 μm or more. When the lower limit of the average thickness of the base 41 is 3 μm or more, the strength reduction of the base 41 can be suppressed.

The average thickness of the base 41 is obtained as follows. First, a magnetic tape MT having a width of ½ inch is prepared and cut into a length of 250 mm to prepare a sample. Subsequently, the layers other than the substrate 41 (that is, the underlayer 42, the magnetic layer 43, and the back layer 44) of the sample are removed with a solvent such as MEK (methyl ethyl ketone) or dilute hydrochloric acid. Next, using a Mitutoyo laser hog gauge (LGH-110C) as a measuring device, the thickness of the sample (base 41) was measured at five or more positions, and the measured values were simply averaged (arithmetic mean). Then, the average thickness of the base 41 is calculated. The measurement position shall be randomly selected from the sample.

The base 41 includes polyester. Since the base 41 contains polyester, the Young's modulus in the longitudinal direction of the base 41 can be reduced. Therefore, by adjusting the tension in the longitudinal direction of the magnetic tape MT during traveling by the recording/reproducing device 50, the width of the magnetic tape MT can be kept constant or almost constant.

Examples of the polyester include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polybutylene terephthalate (PBT), polybutylene naphthalate (PBN), polycyclohexylene dimethylene terephthalate (PCT), and polyethylene-p-oxybenzoate ( PEB) and at least one of polyethylene bisphenoxycarboxylate. When the substrate 41 contains two or more kinds of polyester, these two or more kinds of polyester may be mixed, may be copolymerized, or may be laminated. At least one of the terminal and side chains of the polyester may be modified.

The fact that the substrate 41 contains polyester is confirmed, for example, as follows. First, the layers other than the substrate 41 of the sample are removed in the same manner as the method of measuring the average thickness of the substrate 41. Next, the IR spectrum of the sample (base 41) is acquired by infrared absorption spectroscopy (IR). Based on this IR spectrum, it can be confirmed that the substrate 41 contains polyester.

The substrate 41 may further include at least one of polyamide, polyimide, and polyamideimide in addition to polyester, and may include polyamide, polyimide, polyamideimide, polyolefins, cellulose derivatives, vinyl resins, and others. It may further contain at least one of the above polymer resins. The polyamide may be an aromatic polyamide (aramid). The polyimide may be an aromatic polyimide. The polyamideimide may be an aromatic polyamideimide.

When the base 41 includes a polymer resin other than polyester, the base 41 preferably contains polyester as a main component. Here, the main component means a component having the largest content (mass ratio) among the polymer resins contained in the base 41. When the substrate 41 contains a polymer resin other than polyester, the polyester and the polymer resin other than polyester may be mixed or may be copolymerized.

The base body 41 may be biaxially stretched in the longitudinal direction and the width direction. The polymer resin contained in the base 41 is preferably oriented obliquely with respect to the width direction of the base 41.

(Magnetic layer)
The magnetic layer 43 is a recording layer for recording a signal with a magnetization pattern. The magnetic layer 43 may be a perpendicular recording type recording layer or a longitudinal recording type recording layer. The magnetic layer 43 contains, for example, magnetic powder, a binder and a lubricant. The magnetic layer 43 may further contain at least one additive selected from an antistatic agent, an abrasive, a curing agent, a rust preventive, non-magnetic reinforcing particles and the like, if necessary.

The magnetic layer 43 has a surface provided with a large number of holes 43A. A lubricant is stored in these many holes 43A. It is preferable that the large number of holes 43A extend in a direction perpendicular to the surface of the magnetic layer 43. This is because it is possible to improve the supply of the lubricant to the surface of the magnetic layer 43. Note that a part of the large number of holes 43A may be extended in the vertical direction.

The arithmetic average roughness Ra of the surface of the magnetic layer 43 is 2.5 nm or less, preferably 2.2 nm or less, more preferably 1.9 nm or less. When the arithmetic average roughness Ra is 2.5 nm or less, output reduction due to spacing loss can be suppressed, and thus excellent electromagnetic conversion characteristics can be obtained. The lower limit of the arithmetic average roughness Ra of the surface of the magnetic layer 43 is preferably 1.0 nm or more, more preferably 1.2 nm or more, and even more preferably 1.4 nm or more. When the lower limit value of the arithmetic average roughness Ra of the surface of the magnetic layer 43 is 1.0 nm or more, it is possible to suppress a decrease in running property due to an increase in friction.

The arithmetic average roughness Ra is obtained as follows. First, the surface of the magnetic layer 43 is observed by an AFM (Atomic Force Microscope) to obtain an AFM image of 40 μm×40 μm. The AFM is Nano Scope IIIa D3100 manufactured by Digital Instruments, and the cantilever is made of silicon single crystal (Note 1), and the tapping frequency is tuned at 200 to 400 Hz. Next, the AFM image is divided into 512×512 (=262,144) measurement points, and the height Z(i) (i: measurement point number, i=1 to 262,144) is obtained at each measurement point. The heights Z(i) of the measurement points measured are simply averaged (arithmetic mean) to obtain the average height (average surface) Zave (=(Z(1)+Z(2)+...+Z( 262,144))/262,144) is calculated. Subsequently, the deviation Z″(i) (=Z(i)−Zave) from the average center line at each measurement point is obtained, and the arithmetic average roughness Ra [nm](=(Z″(1)+Z″( 2) +...+Z"(262,144))/262,144) is calculated. At this time, as the image processing, data subjected to filtering processing by Flatten order 2 and planefit order 3 XY is used as data.
(Note 1) Nano World SPM probe NCH normal type PointProbe L (cantilever length) = 125 μm

The lower limit of the total BET specific surface area of the magnetic tape MT measured in a state where the magnetic tape MT is washed and dried is 3.5 m ² /g or more, preferably 4 m ² /g or more, more preferably 4. It is 5 m ² /g or more, and more preferably 5 m ² /g or more. When the lower limit of the BET specific surface area is 3.5 m ² /g or more, even after repeated recording or reproduction (that is, even after the magnetic head 56 is brought into contact with the surface of the magnetic tape MT and repeatedly run). Therefore, it is possible to suppress a decrease in the supply amount of the lubricant between the surface of the magnetic layer 43 and the magnetic head 56. Therefore, an increase in the dynamic friction coefficient can be suppressed. Therefore, excellent running stability can be obtained.

The upper limit value of the entire BET specific surface area of the magnetic tape MT measured in a state where the magnetic tape MT is washed and dried is 7 m ² /g or less, preferably 6 m ² /g or less, more preferably 5.5 m ² /G or less. When the upper limit value of the BET specific surface area is 7 m ² /g or less, the lubricant can be sufficiently supplied without running out even after running many times. Therefore, an increase in the dynamic friction coefficient can be suppressed. Therefore, excellent running stability can be obtained.

The average pore diameter of the entire magnetic tape MT measured in a washed and dried state of the magnetic tape MT is 6 nm or more and 11 nm or less, preferably 7 nm or more and 10 nm or less, more preferably 7.5 nm or more and 10 nm or less. .. When the average pore diameter is 6 nm or more and 11 nm or less, the effect of suppressing the increase in the dynamic friction coefficient described above can be further improved. Therefore, more excellent running stability can be obtained.

The entire BET specific surface area of the magnetic tape MT and the entire pore distribution of the magnetic tape MT (pore volume and average pore diameter (maximum pore volume during desorption) measured in a state where the magnetic tape MT was washed and dried) Is the pore diameter of))) is determined as follows. First, a magnetic tape MT having a size about 10% larger than an area of 0.1265 m ² is dipped in hexane (a sufficient amount of the magnetic tape MT, for example, 150 mL) for 24 hours, and then naturally dried to have an area of 0.1265 m 2. ^A measurement sample is prepared by cutting out into a size of ² (for example, 50 cm at both ends of the dried magnetic tape MT is cut off to prepare a tape width of 10 m). Next, the BET specific surface area is determined using a specific surface area/pore distribution measuring device. Further, the pore size distribution (pore volume and average pore diameter) is determined by the BJH method using a specific surface area/pore distribution measuring device. The measuring device and the measuring conditions are shown below. In this way, the average diameter of the pores is measured.
Measuring environment: Room temperature Measuring device: 3FLEX manufactured by Micromeritics
Measured adsorbate: N ₂ gas Measured pressure range (P/P ₀ (relative pressure)): _{0 to} 0.995
For the measured pressure range, the pressure is varied as shown in Table 1 below. The pressure values in Table 1 below are relative pressures P/P ₀ . In Table 1 below, for example, in step 1, the pressure is changed from the starting pressure of 0.000 to the ultimate pressure of 0.010 by 0.001 per 10 seconds. When the pressure reaches the ultimate pressure, the pressure change in the next step is performed. The same applies to steps 2 to 10. However, in each step, if the pressure does not reach equilibrium, the apparatus waits for the pressure to reach equilibrium before proceeding to the next step.

As shown in FIG. 5, the magnetic layer 43 has a plurality of servo bands SB and a plurality of data bands DB in advance. The plurality of servo bands SB are provided at equal intervals in the width direction of the magnetic tape MT. A data band DB is provided between the adjacent servo bands SB. The servo band SB is for guiding the magnetic head 56 (specifically, the servo read heads 56A and 56B) when recording or reproducing data. A servo pattern (servo signal) for performing tracking control of the magnetic head 56 is written in the servo band SB in advance. User data is recorded in the data band DB.

The upper limit of the proportion of the total area S _SB of the servo band _{SB R S (= (S SB} / S) × 100) to the area S of the surface of the magnetic layer 43, in order to ensure a high recording capacity, preferably 4. It is 0% or less, more preferably 3.0% or less, and even more preferably 2.0% or less. On the other hand, the lower limit value of the ratio R _S of the total area S _SB of the servo band SB to the surface area S of the magnetic layer 43 is preferably 0.8% or more from the viewpoint of securing the servo band SB of 5 or more.

The ratio R _S of the total area S _SB of the servo band SB to the area S of the entire surface of the magnetic layer 43 is obtained as follows. The magnetic tape MT is developed using a ferri colloid developer (Sigma Marker Q manufactured by Sigma High Chemical Co., Ltd.), and then the developed magnetic tape MT is observed with an optical microscope to determine the servo band width _WSB and servo band SB. Measure the number of. Next, the ratio R _S is calculated from the following formula.
Ratio R _S [%]=(((servo band width W _SB )×(number of servo bands SB))/(width of magnetic tape MT))×100

The number of servo bands SB is preferably 5 or more, more preferably 5+4n (where n is a positive integer) or more. When the number of servo bands SB is 5 or more, the influence on the servo signal due to the dimension change of the magnetic tape MT in the width direction is suppressed, and stable recording/reproducing characteristics with less off-track can be secured. The upper limit of the number of servo bands SB is not particularly limited, but is 33 or less, for example.

The number of servo bands SB is obtained in the same manner as the above-described method of calculating the ratio R _S.

The upper limit of the servo band width W _SB, in order to ensure a high recording capacity, preferably 95μm or less, more preferably 60μm or less, even more preferably 30μm or less. The lower limit value of the servo bandwidth _WSB is preferably 10 μm or more. It is difficult to manufacture the recording head 56 capable of reading a servo signal having a servo bandwidth W _SB of less than 10 μm.

The width of the servo band width W _SB is obtained in the same manner as the above-described method of calculating the ratio R _S.

As shown in FIG. 6, the magnetic layer 43 is configured to be able to form a plurality of data tracks Tk in the data band DB. The upper limit of the data track width W is preferably 2000 nm or less, more preferably 1500 nm or less, still more preferably 1000 nm or less from the viewpoint of improving track recording density and ensuring high recording capacity. The lower limit of the data track width W is preferably 20 nm or more in consideration of the magnetic particle size.

From the viewpoint of ensuring a high recording capacity, the magnetic layer 43 can record data such that the minimum value L of the distance between magnetization reversals is preferably 48 nm or less, more preferably 44 nm or less, and even more preferably 40 nm or less. It is configured. The lower limit of the minimum value L of the distance between magnetization reversals is preferably 20 nm or more in consideration of the magnetic particle size.

In the magnetic layer 43, the minimum value L of the distance between magnetization reversals and the data track width W are preferably W/L≦35, more preferably W/L≦30, and even more preferably or W/L≦25. It is configured to record data. When the minimum value L of the distance between magnetization reversals is a constant value and the minimum value L of the distance between magnetization reversals and the track width W are W/L>35 (that is, the track width W is large), the track recording density is increased. Therefore, there is a possibility that a sufficient recording capacity cannot be secured. Further, if the track width W is a constant value and the minimum value L of the magnetization reversal distance and the track width W are W/L>35 (that is, the minimum value L of the magnetization reversal distance is small), the bit length Becomes smaller and the linear recording density increases, but the electromagnetic conversion characteristics (eg SNR (Signal-to-Noise Ratio)) may be significantly deteriorated due to the effect of spacing loss. Therefore, in order to suppress the deterioration of the electromagnetic conversion characteristics (for example, SNR) while ensuring the recording capacity, it is preferable that W/L is in the range of W/L≦35 as described above. The lower limit of W/L is not particularly limited, but for example, 1≦W/L.

The data track width W is obtained as follows. A magnetic tape MT having data recorded on the entire surface is prepared, and the data recording pattern of the data band DB portion of the magnetic layer 43 is observed using a magnetic force microscope (MFM) to obtain an MFM image. As the MFM, Dimension3100 manufactured by Digital Instruments and its analysis software are used. The measurement area of the MFM image is 10 μm×10 μm, and the measurement area of 10 μm×10 μm is divided into 512×512 (=262,144) measurement points. MFM measurement is performed on three 10 μm×10 μm measurement regions at different locations, that is, three MFM images are obtained. From the three obtained MFM images, the track width is measured at 10 points using the analysis software attached to Dimension3100, and the average value (simple average) is taken. The average value is the data track width W. The measurement conditions of the MFM are: sweep rate: 1 Hz, used chip: MFMR-20, lift height: 20 nm, and correction: Flatten order 3.

The minimum value L of the distance between magnetization reversals is obtained as follows. A magnetic tape MT having data recorded on the entire surface is prepared, and the data recording pattern of the data band DB portion of the magnetic layer 43 is observed using a magnetic force microscope (MFM) to obtain an MFM image. As the MFM, Dimension3100 manufactured by Digital Instruments and its analysis software are used. The measurement area of the MFM image is 2 μm×2 μm, and the measurement area of 2 μm×2 μm is divided into 512×512 (=262,144) measurement points. MFM measurement is performed on three 2 μm×2 μm measurement regions at different locations, that is, three MFM images are obtained. Fifty bit distances are measured from the obtained two-dimensional unevenness chart of the recording pattern of the MFM image. The measurement of the bit distance is performed using the analysis software attached to Dimension3100. The value that is the greatest common divisor of the measured 50 bit distances is the minimum value of the magnetization reversal distance L. The measurement conditions are sweep rate: 1 Hz, used chip: MFMR-20, lift height: 20 nm, and correction: Flatten order 3.

The servo pattern is a magnetized area and is formed by magnetizing a specific area of the magnetic layer 43 in a specific direction by a servo write head during manufacturing of the magnetic tape. A region of the servo band SB where the servo pattern is not formed (hereinafter referred to as “non-pattern region”) may be a magnetized region in which the magnetic layer 43 is magnetized, or the magnetic layer 43 is not magnetized. It may be a non-magnetized region. When the non-patterned area is a magnetized area, the servo pattern forming area and the non-patterned area are magnetized in different directions (for example, opposite directions).

According to the LTO standard, as shown in FIG. 7, a servo pattern including a plurality of servo stripes (linear magnetized regions) 113 inclined with respect to the width direction of the magnetic tape MT is formed in the servo band SB.

The servo band SB includes a plurality of servo frames 110. Each servo frame 110 is composed of 18 servo stripes 113. Specifically, each servo frame 110 is composed of a servo subframe 1 (111) and a servo subframe 2 (112).

Servo subframe 1 (111) is composed of A burst 111A and B burst 111B. The B burst 111B is arranged adjacent to the A burst 111A. The A burst 111A includes five servo stripes 113 that are inclined at a predetermined angle φ with respect to the width direction of the magnetic tape MT and are formed at regular intervals. In FIG. 7, symbols A ₁ , A ₂ , A ₃ , A ₄ , A ₅ are assigned to these five servo stripes 113 from the EOT (End Of Tape) of the magnetic tape MT toward the BOT (Beginning Of Tape). It is attached. Similar to the A burst 111A, the B burst 111B includes five servo stripes 113 that are inclined at a predetermined angle φ with respect to the width direction of the magnetic tape MT and are formed at regular intervals. In FIG. 7, these five servo stripes 113 are shown with reference numerals B ₁ , B ₂ , B ₃ , B ₄ , and B ₅ from the EOT to the BOT of the magnetic tape MT. The servo stripe 113 of the B burst 111B is inclined in the opposite direction to the servo stripe 113 of the A burst 111A. That is, the servo stripe 113 of the A burst 111A and the servo stripe 113 of the B burst 111B are arranged in a V shape.

Servo subframe 2 (112) is composed of C burst 112C and D burst 112D. The D burst 112D is arranged adjacent to the C burst 112C. The C burst 112C includes four servo stripes 113 that are inclined at a predetermined angle φ with respect to the tape width direction and are formed at regular intervals. In FIG. 7, these four servo stripes 113 are shown with reference numerals C ₁ , C ₂ , C ₃ and C ₄ from the EOT to the BOT of the magnetic tape MT. Similar to the C burst 112C, the D burst 112D includes four servo stripes 113 that are inclined at a predetermined angle φ with respect to the tape width direction and are formed at regular intervals. In FIG. 7, these four servo stripes 113 are indicated by reference numerals D ₁ , D ₂ , D ₃ and D ₄ from the EOT to the BOT of the magnetic tape MT. The servo stripe 113 of the D burst 112D is inclined in the opposite direction to the servo stripe 113 of the C burst 112C. That is, the servo stripe 113 of the C burst 112C and the servo stripe 113 of the D burst 112D are arranged in a V shape.

The predetermined angle φ of the servo stripe 113 in the A burst 111A, B burst 111B, C burst 112C, and D burst 112D can be, for example, 5° or more and 25° or less, and particularly 11° or more and 25° or less.

By reading the servo band SB with the magnetic head 56, information for obtaining the tape speed and the vertical position of the magnetic head can be obtained. Tape speed is calculated from the time between four timing signals (A1-C1, A2-C2, A3-C3, A4-C4). The head position is calculated from the time between the above-mentioned four timing signals and the time between the other four timing signals (A1-B1, A2-B2, A3-B3, A4-B4).

As shown in FIG. 7, the servo patterns (that is, the plurality of servo stripes 113) are preferably linearly arranged in the longitudinal direction of the magnetic tape MT. That is, it is preferable that the servo band SB has a linear shape in the longitudinal direction.

The statistical value σ _SW indicating the non-linearity of the arrangement of the servo patterns (non-linearity of the servo band SB) is 24 nm or less, preferably 23 nm or less, more preferably 20 nm or less, still more preferably 15 nm or less. When the statistical value σ _SW is 24 nm or less, it is possible to suppress the servo pattern from swinging in the width direction of the magnetic tape MT. That is, an array of servo patterns (servo band SB) having excellent linearity can be obtained. Therefore, the magnetic head 56 can be properly guided by the servo pattern (servo band SB) to the position where the data is written on the magnetic tape MT, so that excellent running stability can be obtained. Therefore, it is possible to suppress the occurrence of an error when reading data.

The statistical value σ _SW indicating the non-linearity of the arrangement of the servo patterns (non-linearity of the servo band SB) is preferably as small as possible from the viewpoint of improving running stability, and is, for example, 0 or more.

The statistical value σ _SW indicating the non-linearity of the servo band is a tape running device (Tape Transportation (Mountain Engineering II, Tape Engineering) which has a magnetic head for reading a servo pattern recorded on the surface of the magnetic layer 43 of the magnetic tape MT. Inc.)). The magnetic head may be one used in a commercially available LTO8 full height drive. The magnetic head is used while being fixed to the tape running device.

Using the tape running device, the magnetic tape MT is run at 2 m/s so that the surface of the magnetic layer 43 side slides on the surface of the magnetic head. The reading element on the surface of the magnetic head is used to read the reproduced waveform of the servo signal from the servo pattern of the magnetic tape MT using a digital oscilloscope. That is, the magnetic servo pattern is converted into an electric servo signal. In order to acquire the reproduced waveform of the servo signal with sufficient accuracy, the sampling rate of the digital oscilloscope shall be 20,000,000 or more per second.

In order to read the servo pattern recorded in one servo band, two reading elements arranged side by side in the longitudinal direction of the magnetic tape MT are used. The two reading elements are included in the magnetic head unit used in the LTO8 full height drive. The two reading elements will be described below with reference to FIG.

FIG. 8 is a schematic diagram of the magnetic head unit. The head unit 300 shown in FIG. 8 has three head portions 300A, 300B, and 300C arranged side by side along the longitudinal direction of the magnetic tape MT. The head unit 300A has two servo heads 320A1 and 320A2 and a plurality of recording heads 340. An ellipse-like point in the head portion 300A means that the recording heads 340 are lined up. The head unit 300B has two servo heads 320B1 and 320B2 and a plurality of reproducing heads 350. An ellipse-like point in the head portion 300B means that the reproducing heads 350 are arranged side by side. The head unit 300C has two servo heads 320C1 and 320C2 and a plurality of recording heads 340. An ellipse-like point in the head portion 300C means that the recording heads 340 are lined up.

The two reading elements used to obtain the statistical value σ _SW are only the servo head 320A1 included in the head unit 300A and the servo head 320B1 included in the head unit 300B. No other servo head is used. Of the two reading elements, the unwinding side reading element (servo head 320A1) is referred to as a reading element a, and the winding side reading element (servo head 320B1) is also referred to as a reading element b.

The reproduced waveform of the servo signal obtained by each reading element is acquired by a digital oscilloscope or the like. The "relative difference p between the center line of the servo pattern and the actual passing position of the reading element on the servo pattern" is calculated based on the acquired reproduced waveform of each servo signal. Specifically, the relative difference p is calculated using the shape of the reproduced waveform of the obtained servo signal and the shape of the servo pattern itself.

The relative difference p is calculated by the following calculation formula.

The above formula for calculating the relative difference p will be described below with reference to FIG. 7. The difference (B _a1 −A _a1 ) in the above formula is the difference [sec] between the time when the stripe B ₁ is read by the reading element a and the time when the stripe A ₁ is read by the reading element a. Yes, it is obtained from the interval between the signal peak due to the stripe A ₁ and the signal peak due to the stripe B ₁ and the tape running speed (m/s). The interval between the two signal peaks is obtained from the shape of the reproduced waveform of the servo signal obtained above. The difference (B _a1 −A _a1 ) corresponds to the difference between the timings at which both stripes are read at the actual traveling position (actual pass in FIG. 7) on the servo pattern of the reading element. Similarly, the other difference terms are obtained from the interval between the signal peaks caused by the corresponding two stripes and the tape running speed. Further, the relative difference p is similarly calculated based on the signal peak obtained by the reading element b.

The azimuth angle φ in the above equation can be obtained from the shape of the servo pattern itself. For the azimuth angle φ, the magnetic tape MT is developed with a ferri colloid developer (Sigma High Chemical Co., Sigma Car Q), and a universal tool microscope (TOPCON TUM-220ES) and data processor (TOPCON CA-1B) are used. Required by using. From the shape of the servo pattern itself, the distance between the stripe A ₁ and the stripe B ₁ (X in the calculation formula in FIG. 7) at the center of the servo band (center line in FIG. 7) and the stripes A ₁ and C ₁ And the distance (Y in FIG. 7 and the above calculation formula) are obtained. Fifty servo frames are selected at arbitrary points in the tape length direction, X and Y are calculated in each servo frame, and a simple average of 50 data is used as X and Y in the above calculation formula. To do.

The relative difference p is calculated for each of 1024 continuous servo sub-frames along the longitudinal direction of the magnetic tape MT. That is, 1024 relative differences p are acquired. For example, when the interval between the servo sub-frames is 76 μm, the relative difference p is acquired every 76 μm. The 1024 relative differences p calculated based on the servo signals read by the reading element a are referred to as pa ₀ , pa ₁ ,..., And pa ₁₀₂₃ . The 1024 relative differences p calculated based on the servo signals read by the reading element b are referred to as pb ₀ , pb ₁ ,..., And pb ₁₀₂₃ .

In order to eliminate the influence of the movement of the magnetic tape MT in the width direction on the magnetic head, the difference between pa and pb at each position n is calculated and is set to Δp. That is, Δp _n = pa _n -pb _n. Here, n=0, 1,..., And 1023. A discrete FFT (Fourier transform) is performed on the obtained Δp _n to obtain ΔP _n (n=0...1023), that is, ΔP(f) (where f=wavenumber [cycle/m]). obtain. Here, in _order to remove the DC component of ΔP _n (that is, n=0), in other words, ΔP(∞), ΔP ₀ is replaced with a value close to ₀ , such as 10 ⁻¹⁰⁰ .

Further, the FFT is performed so that the unit of ΔP(f) is [nm ² /Hz].
The process of obtaining ΔP(f) is repeated over 500 m or more in the longitudinal direction of the magnetic tape MT to obtain ΔP(f) ₁ ... ΔP(f) _m . In order to remove measurement noise, ΔP(f) ₁ ... ΔP(f) _m are averaged on the frequency axis to obtain ΔP(f) _ave . After that, in order to estimate the behavior WIP(f) of the displacement difference in the actual drive, a general second-order closed-loop response filter CLF(f) is applied to ΔP(f) _ave . That is, WIP(f)=|CLF(f)| ² ×ΔP(f) _ave . CLF(f) will be described later.

By using the above WIP(f), the calculation of the following formula (1) is performed to obtain σ _SW . The df in the following calculation will also be described later.

A general second-order closed loop response CLF(s) can be expressed by the following equation (2).

By using the bilinear Z transform, CLF(z) can be expressed by the following equation (3).

From the relationship of z=e ^{j ωTs} and ω=2πf, CLF(f) can be expressed by the following equation (4).

The meaning of each term in the above formulas is as follows.

The upper limit of the average thickness t _m of the magnetic layer 43 is 80 nm or less, preferably 70 nm or less, more preferably 50 nm or less. When the upper limit of the average thickness t _m of the magnetic layer 43 is 80 nm or less, when a ring type head is used as the recording head, the influence of the demagnetizing field can be reduced, so that more excellent electromagnetic conversion characteristics can be obtained. it can.

The lower limit of the average thickness t _m of the magnetic layer 43 is preferably 35 nm or more. When the lower limit value of the average thickness t _m of the magnetic layer 43 is 35 nm or more, when an MR type head is used as the reproducing head, output can be secured, and thus more excellent electromagnetic conversion characteristics can be obtained.

The average thickness t _m of the magnetic layer 43 is obtained as follows. First, the magnetic tape MT to be measured is processed into thin pieces by the FIB method or the like. When the FIB method is used, a carbon layer and a tungsten layer are formed as protective films as a pretreatment for observing a TEM image of a cross section described later. The carbon layer is formed on the magnetic layer 43 side surface and the back layer 44 side surface of the magnetic tape MT by a vapor deposition method, and the tungsten layer is further formed on the magnetic layer 43 side surface by a vapor deposition method or a sputtering method. It The thinning is performed along the length direction (longitudinal direction) of the magnetic tape MT. That is, by the thinning, a cross section parallel to both the longitudinal direction and the thickness direction of the magnetic tape MT is formed.

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

Next, using the obtained TEM image, the thickness of the magnetic layer 43 is measured at at least 10 positions in the longitudinal direction of the magnetic tape MT. The average value obtained by simply averaging the obtained measured values (arithmetic average) is defined as the average thickness t _m [nm] of the magnetic layer 43. The position at which the above measurement is performed shall be randomly selected from the test pieces.

(Magnetic powder)
The magnetic powder contains a plurality of magnetic particles. The magnetic particles include, for example, particles containing hexagonal ferrite (hereinafter referred to as “hexagonal ferrite particles”), particles containing epsilon-type iron oxide (ε iron oxide) (hereinafter referred to as “ε iron oxide particles”), or Co-containing particles. Particles containing spinel ferrite (hereinafter referred to as "cobalt ferrite particles"). It is preferable that the magnetic powder is preferentially crystallized in the thickness direction (vertical direction) of the magnetic tape MT.

(Hexagonal ferrite particles)
The hexagonal ferrite particles have a plate shape such as a hexagonal plate shape. In the present specification, the hexagonal slope shape includes almost hexagonal slope shape. The hexagonal ferrite preferably comprises at least one of Ba, Sr, Pb and Ca, more preferably at least one of Ba and Sr. The hexagonal ferrite may be, for example, barium ferrite or strontium ferrite. The barium ferrite may further contain at least one of Sr, Pb and Ca in addition to Ba. The strontium ferrite may further contain at least one of Ba, Pb, and Ca in addition to Sr.

More specifically, the hexagonal ferrite has an average composition represented by the general formula MFe ₁₂ O ₁₉ . However, M is, for example, at least one metal selected from Ba, Sr, Pb, and Ca, and preferably at least one metal selected from Ba and Sr. M may be a combination of Ba and one or more metals selected from the group consisting of Sr, Pb and Ca. Further, M may be a combination of Sr and one or more metals selected from the group consisting of Ba, Pb and Ca. In the above general formula, part of Fe may be replaced with another metal element.

When the magnetic powder includes hexagonal ferrite particle powder, the average particle size of the magnetic powder is preferably 30 nm or less, more preferably 12 nm or more and 25 nm or less, even more preferably 15 nm or more and 22 nm or less, particularly preferably 15 nm or more and 20 nm or less, Most preferably, it is 15 nm or more and 18 nm or less. When the average particle size of the magnetic powder is 30 nm or less, more excellent electromagnetic conversion characteristics (for example, SNR) can be obtained in the high recording density magnetic tape MT. On the other hand, when the average particle size of the magnetic powder is 12 nm or more, the dispersibility of the magnetic powder is further improved, and more excellent electromagnetic conversion characteristics (for example, SNR) can be obtained.

The average aspect ratio of the magnetic powder is preferably 1.0 or more and 2.5 or less, more preferably 1.0 or more and 2.1 or less, and even more preferably 1.0 or more and 1.8 or less. When the average aspect ratio of the magnetic powder is in the range of 1.0 or more and 2.5 or less, aggregation of the magnetic powder can be suppressed. Further, when the magnetic powder is vertically oriented in the process of forming the magnetic layer 43, the resistance applied to the magnetic powder can be suppressed. Therefore, the vertical orientation of the magnetic powder can be improved.

When the magnetic powder contains hexagonal ferrite particle powder, the average particle size and the average aspect ratio of the magnetic powder are determined as follows. First, the magnetic tape MT to be measured is processed into thin pieces by the FIB method or the like. When the FIB method is used, a carbon layer and a tungsten layer are formed as protective films as a pretreatment for observing a TEM image of a cross section described later. The carbon layer is formed on the magnetic layer 43 side surface and the back layer 44 side surface of the magnetic tape MT by a vapor deposition method, and the tungsten layer is further formed on the magnetic layer 43 side surface by a vapor deposition method or a sputtering method. It The thinning is performed along the length direction (longitudinal direction) of the magnetic tape MT. That is, by the thinning, a cross section parallel to both the longitudinal direction and the thickness direction of the magnetic tape MT is formed.

Using a transmission electron microscope (H-9500 manufactured by Hitachi High-Technologies Corporation), the above cross section of the obtained thin sample was subjected to an acceleration voltage of 200 kV and an overall magnification of 500,000 times with respect to the thickness direction of the magnetic layer 43 as a whole. Cross-section observation is performed so as to include, and a TEM photograph is taken. Next, from the photographed TEM photograph, 50 particles whose side faces are oriented toward the observation surface and whose thickness can be clearly confirmed are selected. For example, FIGS. 9A and 9B show examples of TEM photographs. In FIGS. 9A and 9B, for example, the particles indicated by arrows a and d are selected because their thickness can be clearly confirmed. The maximum plate thickness DA of each of the selected 50 particles is measured. The maximum plate thickness DA thus obtained is simply averaged (arithmetic average) to obtain the average maximum plate thickness DA _ave . Then, the plate diameter DB of each magnetic powder is measured. In order to measure the plate diameter DB of the particles, 50 particles whose plate diameters can be clearly confirmed are selected from the taken TEM photographs. For example, in FIGS. 9A and 9B, the particles indicated by arrows b and c are selected because their plate diameters can be clearly confirmed. The plate diameter DB of each of the selected 50 particles is measured. The plate diameter DB thus obtained is simply averaged (arithmetic average) to obtain an average plate diameter DB _ave . The average plate diameter DB _ave is the average particle size. Then, the average aspect ratio (DB _ave /DA _ave ) of the particles is obtained from the average maximum plate thickness DA _ave and the average plate diameter DB _ave .

If the magnetic powder contains a hexagonal ferrite particles powder, average particle volume of the magnetic powder is preferably 5900Nm ³ or less, more preferably 500 nm ³ or more 3400 nm ³ or less, still more preferably 1000 nm ³ or more 2500 nm ³ or less, particularly preferably 1000 nm ³ or more 1800 nm ³ or less, and most preferably 1000 nm ³ or more 1500 nm ³ or less. When the average particle volume of the magnetic powder is 5900 nm ³ or less, the same effect as when the average particle size of the magnetic powder is 30 nm or less is obtained. On the other hand, when the average particle volume of the magnetic powder is 500 nm ³ or more, the same effect as when the average particle size of the magnetic powder is 12 nm or more is obtained.

The average particle volume of the magnetic powder is obtained as follows. First, the average major axis length DA _ave and the average plate diameter DB _ave are obtained as described above regarding the method for calculating the average particle size of the magnetic powder. Next, the average volume V of the magnetic powder is calculated by the following formula.

(Ε iron oxide particles)
The ε iron oxide particles are hard magnetic particles that can obtain high coercive force even when they are fine particles. The ε iron oxide particles have a spherical shape or a cubic shape. In the present specification, the spherical shape includes almost spherical shape. In addition, the cubic shape includes almost a cubic shape. Since the ε iron oxide particles have the above-described shape, when the ε iron oxide particles are used as the magnetic particles, the magnetic tape MT can be used as compared with the case where the hexagonal plate-shaped barium ferrite particles are used as the magnetic particles. It is possible to reduce the contact area between the particles in the thickness direction and suppress the aggregation of the particles. Therefore, the dispersibility of the magnetic powder can be enhanced, and more excellent electromagnetic conversion characteristics (for example, SNR) can be obtained.

The ε iron oxide particles have a core-shell structure. Specifically, the ε iron oxide particles include a core portion and a shell portion having a two-layer structure provided around the core portion. The shell part having a two-layer structure includes a first shell part provided on the core part and a second shell part provided on the first shell part.

The core portion contains ε iron oxide. The ε iron oxide contained in the core portion preferably has ε-Fe ₂ O ₃ crystal as a main phase, and more preferably ε-Fe ₂ O _{3 in} a single phase.

The first shell portion covers at least a part of the periphery of the core portion. Specifically, the first shell portion may partially cover the periphery of the core portion or may cover the entire periphery of the core portion. From the viewpoint of making sufficient exchange coupling between the core portion and the first shell portion and improving the magnetic characteristics, it is preferable to cover the entire surface of the core portion.

The first shell portion is a so-called soft magnetic layer, and includes, for example, a soft magnetic material such as α-Fe, Ni-Fe alloy, or Fe-Si-Al alloy. α-Fe may be obtained by reducing ε iron oxide contained in the core part.

The second shell portion is an oxide film as an antioxidant layer. The second shell portion contains α-iron oxide, aluminum oxide or silicon oxide. The α-iron oxide includes, for example, at least one iron oxide selected from Fe ₃ O ₄ , Fe ₂ O ₃ and FeO. When the first shell portion contains α-Fe (soft magnetic material), the α-iron oxide may be obtained by oxidizing α-Fe contained in the first shell portion.

Since the ε iron oxide particles have the first shell portion as described above, the ε iron oxide particles (core shell particles) as a whole are maintained while maintaining a large coercive force Hc of the core portion alone to ensure thermal stability. Can be adjusted to a coercive force Hc suitable for recording. Further, since the ε iron oxide particles have the second shell portion as described above, the ε iron oxide particles are exposed to the air in the manufacturing process of the magnetic tape MT and before the process, and the surface of the particles is rusted or the like. It is possible to prevent the characteristics of the ε iron oxide particles from being deteriorated due to the occurrence of. Therefore, the characteristic deterioration of the magnetic tape MT can be suppressed.

The ε iron oxide particles may have a shell portion having a single layer structure. In this case, the shell part has the same configuration as the first shell part. However, from the viewpoint of suppressing the characteristic deterioration of the ε iron oxide particles, as described above, it is preferable that the ε iron oxide particles have a shell portion having a two-layer structure.

The ε iron oxide particles may contain an additive instead of the core-shell structure, or may have an additive together with the core-shell structure. In this case, part of Fe in the ε iron oxide particles is replaced with the additive. Even if the ε iron oxide particles include the additive, the coercive force Hc of the ε iron oxide particles as a whole can be adjusted to a coercive force Hc suitable for recording, so that the ease of recording can be improved. The additive is a metal element other than iron, preferably a trivalent metal element, more preferably at least one of Al, Ga and In, and even more preferably at least one of Al and Ga.

Specifically, ε-iron oxide containing an additive is an ε-Fe _2-x M _x O ₃ crystal (where M is a metal element other than iron, preferably a trivalent metal element, more preferably Al or Ga). And at least one of In and even more preferably at least one of Al and Ga. x is, for example, 0<x<1.

The average particle size (average maximum particle size) of the magnetic powder is, for example, 22.5 nm or less. The average particle size (average maximum particle size) of the magnetic powder is preferably 22 nm or less, more preferably 8 nm or more and 22 nm or less, even more preferably 12 nm or more and 22 nm or less, particularly preferably 12 nm or more and 15 nm or less, most preferably 12 nm or more and 14 nm. It is as follows. In the magnetic tape MT, an area having a size of 1/2 the recording wavelength is the actual magnetized area. Therefore, by setting the average particle size of the magnetic powder to be half or less of the shortest recording wavelength, it is possible to obtain more excellent electromagnetic conversion characteristics (for example, SNR). Therefore, when the average particle size of the magnetic powder is 22 nm or less, a more excellent electromagnetic conversion is achieved in the high recording density magnetic tape MT (for example, the magnetic tape MT configured to record a signal at the shortest recording wavelength of 44 nm or less). A property (eg SNR) can be obtained. On the other hand, when the average particle size of the magnetic powder is 8 nm or more, the dispersibility of the magnetic powder is further improved, and more excellent electromagnetic conversion characteristics (for example, SNR) can be obtained.

The average aspect ratio of the magnetic powder is preferably 1.0 or more and 3.0 or less, more preferably 1.0 or more and 2.5 or less, still more preferably 1.0 or more and 2.1 or less, and particularly preferably 1.0. The above is 1.8 or less. When the average aspect ratio of the magnetic powder is in the range of 1.0 or more and 3.0 or less, aggregation of the magnetic powder can be suppressed. Further, when the magnetic powder is vertically oriented in the process of forming the magnetic layer 43, the resistance applied to the magnetic powder can be suppressed. Therefore, the vertical orientation of the magnetic powder can be improved.

When the magnetic powder contains ε iron oxide particle powder, the average particle size and the average aspect ratio of the magnetic powder are determined as follows. First, the magnetic tape MT to be measured is processed into thin pieces by processing by the FIB (Focused Ion Beam) method or the like. When the FIB method is used, a carbon layer and a tungsten layer are formed as protective layers as a pretreatment for observing a TEM image of a cross section described later. The carbon layer is formed on the magnetic layer 43 side surface and the back layer 44 side surface of the magnetic tape MT by a vapor deposition method, and the tungsten layer is further formed on the magnetic layer 43 side surface by a vapor deposition method or a sputtering method. It The thinning is performed along the length direction (longitudinal direction) of the magnetic tape MT. That is, by the thinning, a cross section parallel to both the longitudinal direction and the thickness direction of the magnetic tape MT is formed.

Using a transmission electron microscope (H-9500 manufactured by Hitachi High-Technologies Corporation), the above cross section of the obtained thin sample was subjected to an acceleration voltage of 200 kV and an overall magnification of 500,000 times with respect to the thickness direction of the magnetic layer 43 as a whole. Cross-section observation is performed so as to include, and a TEM photograph is taken. Next, from the photographed TEM photograph, 50 particles whose shape can be clearly confirmed are selected, and the major axis length DL and the minor axis length DS of each particle are measured. Here, the major axis length DL means the maximum distance (so-called maximum Feret diameter) of the distance between two parallel lines drawn from any angle so as to be in contact with the contour of each particle. On the other hand, the minor axis length DS means the maximum length of the particles in the direction orthogonal to the major axis (DL) of the particles. Subsequently, the measured major axis lengths DL of 50 particles are simply averaged (arithmetic average) to obtain an average major axis length DL _ave . The average major axis length DL _ave determined in this way is the average particle size of the magnetic powder. In addition, the measured minor axis length DS of 50 particles is simply averaged (arithmetic average) to obtain the average minor axis length DS _ave . Then, the average aspect ratio (DL _ave /DS _ave ) of the particles is obtained from the average major axis length DLave and the average minor axis length DS _ave .

The average particle volume of the magnetic powder is preferably 5600Nm ³ or less, more preferably 250 nm ³ or more 5600Nm ³ or less, still more preferably 900 nm ³ or more 5600Nm ³ or less, particularly preferably 900 nm ³ or more 1800 nm ³ or less, and most preferably 900 nm ³ It is 1500 nm ³ or less. Generally, the noise of the magnetic tape MT is inversely proportional to the square root of the number of particles (that is, proportional to the square root of the particle volume). Therefore, by making the particle volume smaller, more excellent electromagnetic conversion characteristics (for example, SNR) can be obtained. it can. Therefore, when the average particle volume of the magnetic powder is 5600 nm ³ or less, more excellent electromagnetic conversion characteristics (for example, SNR) can be obtained as in the case where the average particle size of the magnetic powder is 22 nm or less. On the other hand, when the average particle volume of the magnetic powder is 250 nm ³ or more, the same effect as when the average particle size of the magnetic powder is 8 nm or more is obtained.

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

When the ε iron oxide particles have a cubic shape, the average volume of the magnetic powder is determined as follows. The magnetic tape MT is processed into thin pieces by processing by the FIB (Focused Ion Beam) method or the like. When the FIB method is used, a carbon film and a tungsten thin film are formed as protective films as a pretreatment for observing a TEM image of a cross section described later. The carbon film is formed on the magnetic layer 43 side surface and the back layer 44 side surface of the magnetic tape MT by an evaporation method, and the tungsten thin film is further formed on the magnetic layer 43 side surface by an evaporation method or a sputtering method. It The thinning is performed along the length direction (longitudinal direction) of the magnetic tape MT. That is, by the thinning, a cross section parallel to both the longitudinal direction and the thickness direction of the magnetic tape MT is formed.

Using a transmission electron microscope (H-9500 manufactured by Hitachi High-Technologies Corp.), the obtained thin section sample has an accelerating voltage of 200 kV and a total magnification of 500,000 times so that the entire magnetic layer 43 is included in the thickness direction of the magnetic layer 43. The cross-section is observed to obtain a TEM photograph. Note that the magnification and the acceleration voltage may be appropriately adjusted according to the type of device. Next, 50 particles whose particle shapes are clear are selected from the photographed TEM photograph, and the side length DC of each particle is measured. Then, the measured side lengths DC of 50 particles are simply averaged (arithmetic average) to obtain an average side length DC _ave . Next, using the average side length DC _ave , the average volume V _ave (particle volume) of the magnetic powder is calculated from the following equation.
V _ave =DC _ave ³

(Cobalt ferrite particles)
The cobalt ferrite particles preferably have uniaxial crystal anisotropy. Since the cobalt ferrite particles have uniaxial crystal anisotropy, the magnetic powder can be preferentially crystallized in the thickness direction (vertical direction) of the magnetic tape MT. The cobalt ferrite particles have, for example, a cubic shape. In the present specification, the cubic shape substantially includes a cubic shape. The Co-containing spinel ferrite may further contain at least one of Ni, Mn, Al, Cu and Zn in addition to Co.

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

When the magnetic powder contains cobalt ferrite particle powder, the average particle size of the magnetic powder is preferably 25 nm or less, more preferably 8 nm or more and 23 nm or less, still more preferably 8 nm or more and 12 nm or less, particularly preferably 8 nm or more and 11 nm or less. .. When the average particle size of the magnetic powder is 25 nm or less, more excellent electromagnetic conversion characteristics (for example, SNR) can be obtained in the high recording density magnetic tape MT. On the other hand, when the average particle size of the magnetic powder is 8 nm or more, the dispersibility of the magnetic powder is further improved, and more excellent electromagnetic conversion characteristics (for example, SNR) can be obtained. The method for calculating the average particle size of the magnetic powder is the same as the method for calculating the average particle size of the magnetic powder when the magnetic powder contains ε iron oxide particle powder.

The average aspect ratio of the magnetic powder is preferably 1.0 or more and 3.0 or less, more preferably 1.0 or more and 2.5 or less, still more preferably 1.0 or more and 2.1 or less, and particularly preferably 1.0. The above is 1.8 or less. When the average aspect ratio of the magnetic powder is in the range of 1.0 or more and 3.0 or less, aggregation of the magnetic powder can be suppressed. Further, when the magnetic powder is vertically oriented in the process of forming the magnetic layer 43, the resistance applied to the magnetic powder can be suppressed. Therefore, the vertical orientation of the magnetic powder can be improved. The method for calculating the average aspect ratio of the magnetic powder is the same as the method for calculating the average aspect ratio of the magnetic powder when the magnetic powder contains ε iron oxide particle powder.

The average particle volume of the magnetic powder is preferably 15000 nm ³ or less, more preferably 500 nm ³ or more 12000 nm ³ or less, particularly preferably 500 nm ³ or more 1800 nm ³ or less, and most preferably 500 nm ³ or more 1500 nm ³ or less. When the average particle volume of the magnetic powder is 15000 nm ³ or less, the same effect as when the average particle size of the magnetic powder is 25 nm or less is obtained. On the other hand, when the average particle volume of the magnetic powder is 500 nm ³ or more, the same effect as when the average particle size of the magnetic powder is 8 nm or more is obtained. The method for calculating the average particle volume of the magnetic component is the same as the method for calculating the average particle volume when the ε iron oxide particles have a cubic shape.

(Binder)
Examples of the binder include thermoplastic resins, thermosetting resins, reactive resins, and the like. Examples of the thermoplastic resin include vinyl chloride, vinyl acetate, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, acrylic ester-acrylonitrile copolymer, and acrylic. Acid ester-vinyl chloride-vinylidene chloride copolymer, acrylic acid ester-acrylonitrile copolymer, acrylic acid ester-vinylidene chloride copolymer, methacrylic acid ester-vinylidene chloride copolymer, methacrylic acid ester-vinyl chloride copolymer , Methacrylic acid ester-ethylene copolymer, polyvinyl fluoride, vinylidene chloride-acrylonitrile copolymer, acrylonitrile-butadiene copolymer, polyamide resin, polyvinyl butyral, cellulose derivative (cellulose acetate butyrate, cellulose diacetate, cellulose triacetate, Cellulose propionate, nitrocellulose), styrene-butadiene copolymer, polyurethane resin, polyester resin, amino resin, synthetic rubber and the like.

Examples of the thermosetting resin include phenol resin, epoxy resin, polyurethane curable resin, urea resin, melamine resin, alkyd resin, silicone resin, polyamine resin, urea formaldehyde resin and the like.

All of the binder described above, for the purpose of improving the dispersibility of the magnetic _{powder, -SO 3 M, -OSO 3 M} , -COOM, P = O (OM) 2 ( where formula, M is a hydrogen atom or lithium, potassium, an alkali metal such as sodium) or, -NR1R2, -NR1R2R3 ⁺ X ^- side chain amine having a terminal group represented by,> NR1R2 ⁺ X ^- represented by main-chain amine ( However, in the formula, R1, R2, and R3 represent a hydrogen atom or a hydrocarbon group, X ⁻ represents a halogen element ion such as fluorine, chlorine, bromine, or iodine, an inorganic ion or an organic ion), and —OH or —. A polar functional group such as SH, —CN or an epoxy group may be introduced. The amount of these polar functional groups introduced into the binder is preferably 10 ^-1 to 10 ^-8 mol/g, more preferably 10 ^-2 to 10 ^-6 mol/g.

(lubricant)
The lubricant contains, for example, at least one selected from fatty acids and fatty acid esters, preferably both fatty acids and fatty acid esters. The fact that the magnetic layer 43 contains a lubricant, especially the fact that the magnetic layer 43 contains both fatty acid and fatty acid ester contributes to the improvement of running stability of the magnetic tape MT. More particularly, when the magnetic layer 43 contains a lubricant and has pores, good running stability is achieved. It is considered that the improvement of the running stability is because the dynamic friction coefficient of the surface of the magnetic tape MT on the magnetic layer 43 side is adjusted to a value suitable for running the magnetic tape MT by the lubricant.

The fatty acid may preferably be a compound represented by the following general formula (1) or (2). For example, one of the compound represented by the following general formula (1) and the compound represented by the following general formula (2) may be contained as the fatty acid, or both may be contained.

Further, the fatty acid ester may be preferably a compound represented by the following general formula (3) or (4). For example, as the fatty acid ester, one of the compound represented by the following general formula (3) and the compound represented by the following general formula (4) may be contained, or both may be contained.

The lubricant is one or both of the compound represented by the general formula (1) and the compound represented by the general formula (2), the compound represented by the general formula (3) and the compound represented by the general formula (4). By including either one or both of them, it is possible to suppress an increase in the dynamic friction coefficient due to repeated recording or reproduction of the magnetic tape MT.

CH ₃ (CH ₂ ) _k COOH (1)
(However, in the general formula (1), k is an integer selected from the range of 14 or more and 22 or less, more preferably the range of 14 or more and 18 or less.)

_{CH 3 (CH 2) n CH} = CH (CH 2) m COOH ··· (2)
(However, in the general formula (2), the sum of n and m is an integer selected from the range of 12 or more and 20 or less, more preferably the range of 14 or more and 18 or less.)

_{CH 3 (CH 2) p COO} (CH 2) q CH 3 ··· (3)
(However, in the general formula (3), p is an integer selected from the range of 14 or more and 22 or less, more preferably 14 or more and 18 or less, and q is the range of 2 or more and 5 or less, more preferably 2 or more and 4 or less. It is an integer selected from the following range.)

_{CH 3 (CH 2) r COO-} (CH 2) s CH (CH 3) 2 ··· (4)
(However, in general formula (4), r is an integer selected from the range of 14 or more and 22 or less, and s is an integer selected from the range of 1 or more and 3 or less.)

(Antistatic agent)
Examples of the antistatic agent include carbon black, natural surfactants, nonionic surfactants, and cationic surfactants.

(Abrasive)
As the abrasive, for example, α-alumina, β-alumina, γ-alumina, α-alumina having a conversion rate of 90% or more, silicon carbide, chromium oxide, cerium oxide, α-iron oxide, corundum, silicon nitride, titanium carbide, oxidation. Needle-shaped α obtained by dehydrating and annealing raw materials of titanium, silicon dioxide, tin oxide, magnesium oxide, tungsten oxide, zirconium oxide, boron nitride, zinc oxide, calcium carbonate, calcium sulfate, barium sulfate, molybdenum disulfide, and magnetic iron oxide. Examples thereof include iron oxide, and optionally those surface-treated with aluminum and/or silica.

(Curing agent)
Examples of the curing agent include polyisocyanate and the like. Examples of the polyisocyanate include aromatic polyisocyanates such as adducts of tolylene diisocyanate (TDI) and an active hydrogen compound, and aliphatic polyisocyanates such as adducts of hexamethylene diisocyanate (HMDI) and an active hydrogen compound. Can be mentioned. The weight average molecular weight of these polyisocyanates is preferably in the range of 100 to 3000.

(anti-rust)
Examples of the rust preventive agent include phenols, naphthols, quinones, nitrogen atom-containing heterocyclic compounds, oxygen atom-containing heterocyclic compounds, and sulfur atom-containing heterocyclic compounds.

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

(Underlayer)
The underlayer 42 serves to reduce irregularities on the surface of the base 41 and adjust irregularities on the surface of the magnetic layer 43. The underlayer 42 is a nonmagnetic layer containing nonmagnetic powder, a binder and a lubricant. The underlayer 42 supplies a lubricant to the surface of the magnetic layer 43. The base layer 42 may further include at least one additive selected from an antistatic agent, a curing agent, an anticorrosive agent, and the like, if necessary.

The average thickness of the underlayer 42 is preferably 0.3 μm or more and 2.0 μm or less, more preferably 0.5 μm or more and 1.4 μm or less. The average thickness of the underlayer 42 is obtained in the same manner as the average thickness of the magnetic layer 43. However, the magnification of the TEM image is appropriately adjusted according to the thickness of the underlayer 42. When the average thickness of the underlayer 42 is 2.0 μm or less, the elasticity of the magnetic tape MT due to an external force is further enhanced, and therefore the width of the magnetic tape MT can be adjusted more easily by adjusting the tension.

The underlayer 42 preferably has a large number of holes. The lubricant is stored in these many holes, so that the magnetic layer can be recorded even after repeated recording or reproduction (that is, even after the magnetic head 56 is brought into contact with the surface of the magnetic tape MT to repeatedly run). It is possible to further suppress a decrease in the supply amount of the lubricant between the surface of 43 and the magnetic head. Therefore, the increase in the dynamic friction coefficient can be further suppressed. That is, it is possible to obtain more excellent running stability.

From the viewpoint of suppressing the decrease in the dynamic friction coefficient after repeated recording or reproduction, it is preferable that the hole portion of the underlayer 42 and the hole portion 43A of the magnetic layer 43 are connected. Here, the fact that the holes of the underlayer 42 and the holes 43A of the magnetic layer 43 are connected means that some of the many holes of the underlayer 42 and the many holes of the magnetic layer 43 are connected. It is assumed to include a state in which some of 43A are connected.

From the viewpoint of improving the supply of the lubricant to the surface of the magnetic layer 43, it is preferable that the multiple holes include those extending in the direction perpendicular to the surface of the magnetic layer 43. From the viewpoint of improving the supply of the lubricant to the surface of the magnetic layer 43, the holes of the underlayer 42 extending in the direction perpendicular to the surface of the magnetic layer 43 and the surface of the magnetic layer 43 are It is preferable that the holes 43A of the magnetic layer 43 extending in the vertical direction are connected to each other.

(Non-magnetic powder)
The non-magnetic powder contains, for example, at least one kind of inorganic particle powder and organic particle powder. The non-magnetic powder may contain carbon powder such as carbon black. In addition, one type of non-magnetic powder may be used alone, or two or more types of non-magnetic powder may be used in combination. The inorganic particles include, for example, metal, metal oxide, metal carbonate, metal sulfate, metal nitride, metal carbide or metal sulfide. Examples of the shape of the non-magnetic powder include various shapes such as a needle shape, a spherical shape, a cubic shape, and a plate shape, but are not limited to these shapes.

(Binder, lubricant)
The binder and the lubricant are the same as those of the magnetic layer 43 described above.

(Additive)
The antistatic agent, the curing agent and the rust preventive agent are the same as those of the magnetic layer 43 described above.

(Back layer)
The back layer 44 contains a binder and non-magnetic powder. The back layer 44 may further include at least one additive selected from a lubricant, a curing agent, an antistatic agent, and the like, if necessary. The binder and the non-magnetic powder are the same as those of the underlayer 42 described above.

The average particle size of the non-magnetic powder is preferably 10 nm or more and 150 nm or less, more preferably 15 nm or more and 110 nm or less. The average particle size of the non-magnetic powder is determined in the same manner as the average particle size of the above magnetic powder. The non-magnetic powder may include non-magnetic powder having a particle size distribution of 2 or more.

The upper limit of the average thickness of the back layer 44 is preferably 0.6 μm or less. When the upper limit of the average thickness of the back layer 44 is 0.6 μm or less, the thicknesses of the underlayer 42 and the base 41 can be kept thick even when the average thickness of the magnetic tape MT is 5.6 μm or less. The running stability of the magnetic tape MT in the recording/reproducing apparatus 50 can be maintained. The lower limit of the average thickness of the back layer 44 is not particularly limited, but is 0.2 μm or more, for example.

The average thickness t _b of the back layer 44 is obtained as follows. First, the average thickness t _T of the magnetic tape MT is measured. The method for measuring the average thickness t _T is as described in "Average thickness of magnetic tape" below. Subsequently, the back layer 44 of the sample is removed with a solvent such as MEK (methyl ethyl ketone) or dilute hydrochloric acid. Next, the thickness of the sample is measured at five or more positions using a laser hologage (LGH-110C) manufactured by Mitutoyo, and these measured values are simply averaged (arithmetic mean) to obtain an average value t _B. Calculate [μm]. Then, the average thickness t _b [μm] of the back layer 44 is calculated by the following formula. The measurement position shall be randomly selected from the sample.
t _b [μm]=t _T [μm]−t _B [μm]

The back layer 44 has a surface provided with a large number of protrusions 44A. The large number of protrusions 44A are for forming a large number of holes 43A on the surface of the magnetic layer 43 when the magnetic tape MT is wound into a roll. The large number of holes 43A are composed of, for example, a large number of non-magnetic particles protruding from the surface of the back layer 44.

(Average thickness of magnetic tape)
The upper limit of the average thickness (average total thickness) t _T of the magnetic tape MT is 5.6 μm or less, preferably 5.0 μm or less, more preferably 4.6 μm or less, and even more preferably 4.4 μm or less. When the average thickness t _T of the magnetic tape MT is 5.6 μm or less, the recording capacity that can be recorded in one data cartridge can be increased as compared with a general magnetic tape. The lower limit of the average thickness t _T of the magnetic tape MT is not particularly limited, but is 3.5 μm or more, for example.

The average thickness t _T of the magnetic tape MT is obtained as follows. First, a magnetic tape MT having a width of ½ inch is prepared and cut into a length of 250 mm to prepare a sample. Next, the thickness of the sample is measured at 5 or more positions using a laser hologage (LGH-110C) manufactured by Mitutoyo as a measuring device, and the measured values are simply averaged (arithmetic average) to obtain the average. The value t _T [μm] is calculated. The measurement position shall be randomly selected from the sample.

(Coercive force Hc)
The upper limit of the coercive force Hc2 of the magnetic layer 43 in the longitudinal direction of the magnetic tape MT is preferably 2000 Oe or less, more preferably 1900 Oe or less, and even more preferably 1800 Oe or less. When the coercive force Hc2 of the magnetic layer 43 in the longitudinal direction is 2000 Oe or less, sufficient electromagnetic conversion characteristics can be obtained even at high recording density.

The lower limit of the coercive force Hc2 of the magnetic layer 43 measured in the longitudinal direction of the magnetic tape MT is preferably 1000 Oe or more. When the coercive force Hc2 of the magnetic layer 43 measured in the longitudinal direction is 1000 Oe or more, demagnetization due to leakage magnetic flux from the recording head can be suppressed.

The above coercive force Hc2 is obtained as follows. First, three magnetic tapes MT are laminated with double-sided tape, and then punched with a φ6.39 mm punch to prepare a measurement sample. At this time, marking is performed with an arbitrary ink having no magnetism so that the longitudinal direction (traveling direction) of the magnetic tape MT can be recognized. Then, the MH loop of the measurement sample (entire magnetic tape MT) corresponding to the longitudinal direction (traveling direction) of the magnetic tape MT is measured using a vibrating sample magnetometer (VSM). Next, the coating film (the underlayer 42, the magnetic layer 43, the back layer 44, etc.) is wiped with acetone or ethanol or the like, and only the base 41 is left. Then, three obtained bases 41 are overlapped with a double-sided tape and then punched with a φ6.39 mm punch to prepare a sample for background correction (hereinafter, simply “correction sample”). After that, the M-H loop of the correction sample (base 41) corresponding to the vertical direction of the base 41 (the vertical direction of the magnetic tape MT) is measured using VSM.

In the measurement of the MH loop of the measurement sample (entire magnetic tape MT) and the MH loop of the correction sample (base 41), a high-sensitivity vibration sample magnetometer "VSM-P7-" manufactured by Toei Industry Co., Ltd. Type 15" is used. The measurement conditions are: measurement mode: full loop, maximum magnetic field: 15 kOe, magnetic field step: 40 bit, Time constant of Locking amp: 0.3 sec, Waiting time: 1 sec, MH average number: 20.

After the MH loop of the measurement sample (entire magnetic tape MT) and the MH loop of the correction sample (base 41) are obtained, correction is performed from the MH loop of the measurement sample (entire magnetic tape MT). Background correction is performed by subtracting the MH loop of the sample (base 41), and the MH loop after background correction is obtained. A measurement/analysis program attached to "VSM-P7-15 type" is used for the calculation of the background correction. The coercive force Hc2 is obtained from the obtained MH loop after background correction. A measurement/analysis program attached to the "VSM-P7-15 type" is used for this calculation. In addition, the measurement of the above-mentioned MH loop shall be performed at 25 degreeC. In addition, "diamagnetic field correction" when measuring the MH loop in the longitudinal direction of the magnetic tape MT is not performed.

(Squareness ratio)
The squareness S1 of the magnetic layer 43 in the perpendicular direction (thickness direction) of the magnetic tape MT is preferably 65% or more, more preferably 70% or more, even more preferably 75% or more, particularly preferably 80% or more, most preferably Is 85% or more. When the squareness ratio S1 is 65% or more, the vertical orientation of the magnetic powder becomes sufficiently high, so that more excellent electromagnetic conversion characteristics (for example, SNR) can be obtained.

The squareness S1 in the vertical direction is obtained as follows. First, three magnetic tapes MT are laminated with double-sided tape, and then punched with a φ6.39 mm punch to prepare a measurement sample. At this time, marking is performed with an arbitrary ink having no magnetism so that the longitudinal direction (traveling direction) of the magnetic tape MT can be recognized. Then, the MH loop of the measurement sample (the entire magnetic tape MT) corresponding to the vertical direction (thickness direction) of the magnetic tape MT is measured using the VSM. Next, the coating film (the underlayer 12, the magnetic layer 43, the back layer 44, etc.) is wiped using acetone, ethanol, or the like, and only the base 41 is left. Then, three obtained bases 41 are laminated with double-sided tape and punched with a φ6.39 mm punch to obtain a sample for background correction (hereinafter, simply “correction sample”). After that, the M-H loop of the correction sample (base 41) corresponding to the vertical direction of the base 41 (the vertical direction of the magnetic tape MT) is measured using VSM.

In the measurement of the MH loop of the measurement sample (entire magnetic tape MT) and the MH loop of the correction sample (base 41), a high-sensitivity vibration sample magnetometer "VSM-P7-" manufactured by Toei Industry Co., Ltd. Type 15" is used. The measurement conditions are: measurement mode: full loop, maximum magnetic field: 15 kOe, magnetic field step: 40 bit, Time constant of Locking amp: 0.3 sec, Waiting time: 1 sec, MH average number: 20.

After the MH loop of the measurement sample (entire magnetic tape MT) and the MH loop of the correction sample (base 41) are obtained, correction is performed from the MH loop of the measurement sample (entire magnetic tape MT). Background correction is performed by subtracting the MH loop of the sample (base 41), and the MH loop after background correction is obtained. A measurement/analysis program attached to "VSM-P7-15 type" is used for the calculation of the background correction.

The saturation magnetization Ms(emu) and the residual magnetization Mr(emu) of the obtained MH loop after background correction are substituted into the following formula to calculate the squareness ratio S1(%). In addition, the measurement of the above-mentioned MH loop shall be performed at 25 degreeC. In addition, "diamagnetic field correction" when measuring the MH loop in the vertical direction of the magnetic tape MT is not performed. A measurement/analysis program attached to the "VSM-P7-15 type" is used for this calculation.
Squareness ratio S1(%)=(Mr/Ms)×100

The squareness S2 of the magnetic layer 43 in the longitudinal direction (running direction) of the magnetic tape MT is preferably 35% or less, more preferably 30% or less, even more preferably 25% or less, particularly preferably 20% or less, most preferably Is 15% or less. When the squareness ratio S2 is 35% or less, the vertical orientation of the magnetic powder becomes sufficiently high, so that more excellent electromagnetic conversion characteristics (for example, SNR) can be obtained.

The squareness ratio S2 in the longitudinal direction is obtained in the same manner as the squareness ratio S1 except that the MH loop is measured in the longitudinal direction (running direction) of the magnetic tape MT and the base 41.

(Hc2/Hc1)
The ratio Hc2/Hc1 of the coercive force Hc1 of the magnetic layer 43 in the vertical direction and the coercive force Hc2 of the magnetic layer 43 in the longitudinal direction is Hc2/Hc1≦0.8, preferably Hc2/Hc1≦0.75, and more preferably Hc2/Hc1≦0.7, even more preferably Hc2/Hc1≦0.65, and particularly preferably Hc2/Hc1≦0.6. When the coercive forces Hc1 and Hc2 satisfy the relationship of Hc2/Hc1≦0.8, the degree of vertical orientation of the magnetic powder can be increased. Therefore, the magnetization transition width can be reduced, and a high-output signal can be obtained at the time of signal reproduction, so that more excellent electromagnetic conversion characteristics (for example, SNR) can be obtained. As described above, when Hc2 is small, the magnetic field in the vertical direction from the recording head causes the magnetization to react with good sensitivity, so that a good recording pattern can be formed.

When the ratio Hc2/Hc1 is Hc2/Hc1≦0.8, it is particularly effective that the average thickness of the magnetic layer 43 is 90 nm or less. When the average thickness of the magnetic layer 43 exceeds 90 nm, when a ring type head is used as the recording head, the lower region (the region on the side of the underlayer 42) of the magnetic layer 43 is magnetized in the longitudinal direction, and the magnetic layer 43. May not be magnetized uniformly in the thickness direction. Therefore, even if the ratio Hc2/Hc1 is set to Hc2/Hc1≦0.8 (that is, even if the vertical orientation degree of the magnetic powder is increased), there is a possibility that further excellent electromagnetic conversion characteristics (for example, SNR) may not be obtained.

The lower limit of Hc2/Hc1 is not particularly limited, but is 0.5≦Hc2/Hc1, for example. Hc2/Hc1 represents the degree of vertical orientation of magnetic powder, and the smaller Hc2/Hc1, the higher the degree of vertical orientation of magnetic powder.

The method of calculating the coercive force Hc2 of the magnetic layer 43 in the longitudinal direction is as described above. The coercive force Hc1 of the magnetic layer 43 in the perpendicular direction is the same as the coercive force Hc2 of the magnetic layer 43 in the longitudinal direction except that the MH loop is measured in the perpendicular direction (thickness direction) of the magnetic tape MT and the base 41. Desired.

(Activation volume V _act )
Activation volume V _act is preferably 8000 nm ³ or less, more preferably 6000 nm ³ or less, still more preferably 5000 nm ³ or less, particularly preferably 4000 nm ³ or less, most preferably 3000 nm ³ or less. When the activation volume V _act is 8000 nm ³ or less, the dispersion state of the magnetic powder becomes good, so that the bit inversion region can be made steep, and the magnetic field leaked from the recording head recorded on the adjacent track. It is possible to suppress deterioration of the magnetization signal. Therefore, there is a possibility that further excellent electromagnetic conversion characteristics (for example, SNR) may not be obtained.

The above-mentioned activation volume V _act is obtained by the following equation derived by Street & Woolley.
V _act (nm ³ )=k _B ×T×Δ _irr /(μ ₀ ×Ms×S)
(However, k _B : Boltzmann constant (1.38×10 ⁻²³ J/K), T: temperature (K), Χ _irr : irreversible magnetic susceptibility, μ ₀ : magnetic permeability of vacuum, S: magnetic viscosity coefficient, Ms: saturation magnetization (emu/cm ³ ))

The irreversible magnetic susceptibility Χ _irr , the saturation magnetization Ms, and the magnetic viscosity coefficient S, which are substituted into the above equation, are obtained as follows using VSM. The measurement direction by VSM is the thickness direction (vertical direction) of the magnetic tape MT. Further, the measurement by VSM is performed at 25° C. on the measurement sample cut out from the long magnetic tape MT. In addition, "diamagnetic field correction" when measuring the MH loop in the thickness direction (vertical direction) of the magnetic tape MT is not performed.

(Irreversible magnetic susceptibility Χ _irr )
The irreversible magnetic susceptibility Χ _irr is defined as the gradient of the residual magnetization curve (DCD curve) near the residual coercive force Hr. First, a magnetic field of -1193 kA/m (15 kOe) is applied to the entire magnetic tape MT to return the magnetic field to zero and bring it to a remanent magnetization state. After that, a magnetic field of about 15.9 kA/m (200 Oe) is applied in the opposite direction to return it to zero again and measure the residual magnetization. After that, similarly, a magnetic field 15.9 kA/m larger than the applied magnetic field is applied and the measurement for returning to zero is repeated, and the residual magnetization is plotted against the applied magnetic field to measure the DCD curve. From the obtained DCD curve, the point at which the magnetization amount is zero is set as the residual coercive force Hr, and the DCD curve is further differentiated to obtain the slope of the DCD curve in each magnetic field. In the slope of this DCD curve, the slope in the vicinity of the residual coercive force Hr is _πirr .

(Saturation magnetization Ms)
First, the MH loop after background correction is obtained in the same manner as the method of measuring the squareness ratio S1 described above. Next, Ms(emu/cm ³ ) is calculated from the value of the saturation magnetization Ms(emu) of the obtained MH loop and the volume (cm ³ ) of the magnetic layer 43 in the measurement sample. The volume of the magnetic layer 43 is obtained by multiplying the area of the measurement sample by the average thickness of the magnetic layer 43. The method for calculating the average thickness of the magnetic layer 43 necessary for calculating the volume of the magnetic layer 43 is as described above.

(Magnetic viscosity coefficient S)
First, a magnetic field of -1193 kA/m (15 kOe) is applied to the entire magnetic tape MT (measurement sample) to return the magnetic field to zero and bring it to a remanent magnetization state. Then, in the opposite direction, a magnetic field equivalent to the value of the residual coercive force Hr obtained from the DCD curve is applied. With the magnetic field applied, the magnetization amount is continuously measured at regular time intervals for 1000 seconds. The relationship between the time t and the magnetization amount M(t) thus obtained is compared with the following formula to calculate the magneto-viscosity coefficient S.
M(t)=M0+S×ln(t)
(However, M(t): magnetization amount at time t, M0: initial magnetization amount, S: magnetic viscosity coefficient, ln(t): natural logarithm of time)

(Back surface roughness R _b )
The surface roughness R _b of the back surface (surface roughness of the back layer 44) is preferably R _b ≦6.0 [nm]. When the surface roughness R _b of the back surface is within the above range, more excellent electromagnetic conversion characteristics can be obtained.

上述のようにして、長手方向で少なくとも５点以上の位置にて面粗度を測定したのち、
各位置で得られた表面プロファイルから自動計算されたそれぞれの算術平均粗さＳ_a（ｎｍ）の平均値をバック面の表面粗度Ｒ_b（ｎｍ）とする。 The surface roughness R _b of the back surface is obtained as follows. First, a magnetic tape MT having a width of 12.65 mm is prepared and cut into a length of 100 mm to prepare a sample. Then, the sample is placed on a slide glass so that the surface to be measured (surface on the magnetic layer side) faces up, and the end of the sample is fixed with a mending tape. The surface shape is measured using a VertScan (50 times objective lens) as a measuring device, and the surface roughness R _b of the back surface is obtained from the following formula based on the ISO 25178 standard.
Equipment: Non-contact roughness meter using optical interference (Ryoka System Co., Ltd. non-contact surface/layer cross-section shape measurement system VertScan R5500GL-M100-AC)
Objective lens: 20 times Measurement area: 640×480 pixels (field of view: approximately 237 μm×178 μm field of view)
Measurement mode: phase
Wavelength filter: 520nm
CCD: 1/3 lens Noise removal filter: Smoothing 3×3
Surface correction: Corrected by the second-order polynomial approximation surface Measurement software: VS-Measure Version5.5.2
Analysis software: VS-viewer Version5.5.5

As described above, after measuring the surface roughness at the positions of at least 5 points in the longitudinal direction,
The average value of the arithmetic average roughness S _a (nm) automatically calculated from the surface profile obtained at each position is defined as the surface roughness R _b (nm) of the back surface.

(Young's modulus in the longitudinal direction of the magnetic tape)
The Young's modulus in the longitudinal direction of the magnetic tape MT is preferably 8.0 GPa or less, more preferably 7.9 GPa or less, even more preferably 7.5 GPa or less, and particularly preferably 7.1 GPa or less. When the Young's modulus in the longitudinal direction of the magnetic tape MT is 8.0 GPa or less, the elasticity of the magnetic tape MT is further enhanced by an external force, and thus the width of the magnetic tape MT can be adjusted more easily by adjusting the tension. Therefore, the off-track can be suppressed more appropriately, and the data recorded on the magnetic tape MT can be reproduced more accurately.

The Young's modulus in the longitudinal direction of the magnetic tape MT is a value indicating the difficulty of expansion/contraction in the longitudinal direction of the magnetic tape MT due to an external force. The larger this value is, the more difficult it is for the magnetic tape MT to expand/contract in the longitudinal direction. The smaller the value, the easier the magnetic tape MT expands and contracts in the longitudinal direction due to the external force.

Although the Young's modulus in the longitudinal direction of the magnetic tape MT is a value in the longitudinal direction of the magnetic tape MT, it also correlates with the difficulty of expansion and contraction in the width direction of the magnetic tape MT. That is, the larger this value is, the harder the magnetic tape MT expands and contracts in the width direction by the external force, and the smaller this value, the easier the magnetic tape MT expands and contracts in the width direction by the external force. Therefore, from the viewpoint of tension adjustment, it is advantageous that the Young's modulus of the magnetic tape MT in the longitudinal direction is small.

A tensile tester (AG-100D, manufactured by Shimadzu Corp.) is used to measure the Young's modulus. When it is desired to measure the Young's modulus in the tape longitudinal direction, the tape is cut into a length of 180 mm to prepare a measurement sample. A jig capable of fixing the width (1/2 inch) of the tape is attached to the tensile tester and the upper and lower sides of the tape width are fixed. The distance (length of tape between chucks) is 100 mm. After chucking the tape sample, stress is gradually applied in the direction of pulling the sample. The pulling speed is 0.1 mm/min. The Young's modulus is calculated from the change in stress and the amount of elongation at this time using the following formula.
E(N/m ² )=((ΔN/S)/(Δx/L))×10 ⁶
ΔN: Change in stress (N)
S: Cross-sectional area of test piece (mm ² )
Δx: Elongation (mm)
L: Distance between gripping jigs (mm)
The stress range is 0.5 N to 1.0 N, and the stress change (ΔN) and the elongation amount (Δx) at this time are used for the calculation.

(Young's modulus in the longitudinal direction of the substrate)
The Young's modulus in the longitudinal direction of the base body 41 is preferably 7.5 GPa or less, more preferably 7.4 GPa or less, even more preferably 7.0 GPa or less, and particularly preferably 6.6 GPa or less. When the Young's modulus of the base body 41 in the longitudinal direction is 7.5 GPa or less, the elasticity of the magnetic tape MT is further enhanced by an external force, so that the width of the magnetic tape MT can be adjusted more easily by adjusting the tension. Therefore, the off-track can be suppressed more appropriately, and the data recorded on the magnetic tape MT can be reproduced more accurately.

The Young's modulus of the base body 41 in the longitudinal direction is obtained as follows. First, the base layer 42, the magnetic layer 43, and the back layer 44 are removed from the magnetic tape MT to obtain the base 41. Using this substrate 41, the Young's modulus in the longitudinal direction of the substrate 41 is obtained in the same procedure as the Young's modulus in the longitudinal direction of the magnetic tape MT.

The thickness of the base 41 occupies more than half of the total thickness of the magnetic tape MT. Therefore, the Young's modulus in the longitudinal direction of the base 41 correlates with the difficulty of expansion/contraction of the magnetic tape MT due to an external force. The larger this value, the more difficult the magnetic tape MT expands/contracts in the width direction. The tape MT easily expands and contracts in the width direction by an external force.

Although the Young's modulus in the longitudinal direction of the base body 41 is a value in the longitudinal direction of the magnetic tape MT, it also correlates with the difficulty of expansion and contraction in the width direction of the magnetic tape MT. That is, the larger this value is, the harder the magnetic tape MT expands and contracts in the width direction by the external force, and the smaller this value, the easier the magnetic tape MT expands and contracts in the width direction by the external force. Therefore, from the viewpoint of tension adjustment, it is advantageous that the Young's modulus of the base body 41 in the longitudinal direction is small.

(Dynamic friction coefficient)
The dynamic friction coefficient μ _A between the surface of the magnetic layer 43 and the magnetic head 56 when the tension applied to the magnetic tape MT is 1.2 N, and the dynamic friction coefficient μ _A of the magnetic layer 43 when the tension applied to the magnetic tape MT is 0.4 N. The friction coefficient ratio (μ _B /μ _A ) of the dynamic friction coefficient μ _B between the surface and the magnetic head 56 is preferably 1.0 or more and 2.0 or less, more preferably 1.0 or more and 1.5 or less. .. When the friction coefficient ratio (μ _B /μ _A ) is 1.0 or more and 2.0 or less, the change of the dynamic friction coefficient due to the tension change during running can be reduced, so that the tension of the magnetic tape MT during running of the magnetic tape MT can be reduced. Even when adjustment is performed, excellent running stability can be obtained.

The dynamic friction coefficient μ _A and the dynamic friction coefficient μ _B for calculating the friction coefficient ratio (μ _B /μ _A ) are calculated as follows. First, as shown in FIG. 10A, a magnetic surface of a magnetic tape MT having a width of 1/2 inch comes into contact with two cylindrical guide rolls 73A and 73B having a diameter of 1 inch and spaced apart from each other and arranged in parallel. To put. The two guide rolls 73A and 73B are fixed to a hard plate-shaped member 76, so that their positional relationship is fixed.

Next, the magnetic tape MT is brought into contact with the head block (for recording/playback) 74 mounted on the LTO5 drive so that the magnetic surface comes into contact and the holding angle θ ₁ (°)=5.6°. Let The head block 74 is arranged substantially at the center of the guide rolls 73A and 73B. The head block 74 is movably attached to the plate member 76 so that the holding angle θ ₁ can be changed. However, when the holding angle θ ₁ (°) reaches 5.6°, the position of the head block 74 changes. The head block 74 is fixed with respect to the plate-like member 76, so that the positional relationship between the guide rolls 73A and 73B and the head block 74 is also fixed.

One end of the magnetic tape MT is connected to the movable strain gauge 71 via a jig 72. The magnetic tape MT is fixed to the jig 72 as shown in FIG. 10B. A weight 75 is connected to the other end of the magnetic tape MT. The weight 75 applies a tension of _0.4 N (T ₀ [N]) in the longitudinal direction of the magnetic tape MT. The movable strain gauge 71 is fixed on a base 77. The positional relationship between the table 77 and the plate-shaped member 76 is also fixed, whereby the positional relationship among the guide rolls 73A and 73B, the head block 74, and the movable strain gauge 71 is fixed.

By the movable strain gauge 71, the magnetic tape MT is slid on the head block 74 by 60 mm so that the magnetic tape MT moves toward the movable strain gauge 71 at 10 mm/s. The output value (voltage) of the movable strain gauge 71 at the time of sliding is converted into T[N] based on the linear relationship (described later) between the output value and the load that are acquired in advance. Acquire T[N] 13 times from the start of sliding of the above 60 mm sliding to the stop of sliding, and simply average 11 T[N] excluding the first and last two times. _Gives T _ave [N].

Then, determine the dynamic friction coefficient μ _A from the following formula.

The above linear relationship is obtained as follows. That is, the output value (voltage) of the movable strain gauge 71 is obtained when the load of 0.4 N is applied to the movable strain gauge 71 and when the load of 1.5 N is applied. A linear relationship between the output value and the load is obtained from the obtained two output values and the above two loads. Using the linear relationship, as described above, the output value (voltage) by the movable strain gauge 71 during sliding is converted into T[N].

The dynamic friction coefficient μ _B is measured by the same method as the method of measuring the dynamic friction coefficient μ _A , except that the tension T ₀ [N] applied to the other end is 1.2N.

The friction coefficient ratio (μ _B /μ _A ) is calculated from the dynamic friction coefficient μ _A and the dynamic friction coefficient μ _B measured as described above.

Assuming that the dynamic friction coefficient between the surface of the magnetic layer 43 and the magnetic head 56 when the tension applied to the magnetic tape MT is 0.6 N is μ _C , the dynamic friction coefficient μ _C (5) in the fifth run and the 1,000th run The friction coefficient ratio (μ _C (1000)/μ _C (5)) to the dynamic friction coefficient μ _C (1000) is preferably 1.0 or more and 2.0 or less, more preferably 1.0 or more and 1.5 or less. Is. When the friction coefficient ratio (μ _C (1000)/μ _C (5)) is 1.0 or more and 2.0 or less, the change in the dynamic friction coefficient after 1000 times of running can be reduced, so that even after 1,000 times of running It is possible to obtain excellent running stability. Here, as the magnetic head 56, a drive corresponding to the magnetic tape MT is used.

上記直線関係は以下のとおりに得られる。すなわち、可動式ストレインゲージ７１に０．４Ｎの荷重をかけた場合と１．５Ｎの荷重をかけた場合のそれぞれについて、可動式ストレインゲージ７１の出力値（電圧）を得る。得られた２つの出力値と上記２つの荷重とから、出力値と荷重との直線関係が得られる。当該直線関係を用いて、上記のとおり、摺動時の可動式ストレインゲージ７１による出力値（電圧）がＴ［Ｎ］に変換される。 The dynamic friction coefficient μ _C (5) and the dynamic friction coefficient μ _C (1000) for calculating the friction coefficient ratio (μ _C (1000)/μ _C (5)) are calculated as follows. The magnetic tape MT is connected to the movable strain gauge 71 in the same manner as the method for measuring the dynamic friction coefficient μ _A , except that the tension T ₀ [N] applied to the other end of the magnetic tape MT is set to 0.6N. .. Then, the magnetic tape MT is slid with respect to the head block 74 at a rate of 10 mm/s toward the movable strain gauge by 60 mm (outward path) and away from the movable strain gauge by 60 mm (return path). This reciprocating operation is repeated 1000 times. Of the 1000 reciprocating motions, the output value (voltage) of the strain gauge was acquired 13 times between the sliding start and the sliding stop of the 5th forward 60 mm sliding, and the dynamic friction coefficient μ _A was obtained. Based on the obtained linear relationship between the output value and the load (which will be described later), it is converted into T[N]. T _ave [N] is obtained by simply averaging 11 pieces except the first and last two times. The dynamic friction coefficient μ _C (5) is calculated by the following formula.

The above linear relationship is obtained as follows. That is, the output value (voltage) of the movable strain gauge 71 is obtained when the load of 0.4 N is applied to the movable strain gauge 71 and when the load of 1.5 N is applied. A linear relationship between the output value and the load is obtained from the obtained two output values and the above two loads. As described above, the output value (voltage) by the movable strain gauge 71 during sliding is converted into T[N] using the linear relationship.

Further, the dynamic friction coefficient μ _C (1000) is obtained in the same manner as the dynamic friction coefficient μ _C (5) except that the 1000th forward trip is measured.

A friction coefficient ratio μ _C (1000)/μ _C (5) is calculated from the dynamic friction coefficient μ _C (5) and the dynamic friction coefficient μ _C (1000) measured as described above.

[Configuration of servo writer]
Next, an example of the configuration of the servo writer 210 used for writing the above-mentioned servo pattern will be described with reference to FIGS. 11, 12A, and 12B.

The servo writer 210 has the same configuration as that of the servo writer described in WO 2019/093469 (specifically, the servo writer described with reference to FIG. 1 of the same document) except for the servo signal write head 219. Have. As the servo signal write head 219, the servo signal write head described in Japanese Patent Laid-Open No. 2006-127730 (in particular, the servo signal write head described with reference to FIG. 26 of the same document) is used.

As shown in FIG. 11, the servo track writer 210 includes a delivery reel 211, a take-up reel 212, capstans 213A and 214A, pinch rollers 213B and 214B, guide rollers 215A and 215B, and a polishing section 216. The dusting unit 217, the tension adjusting unit 218, the servo signal writing head 219, the servo signal reading head 220, the preamplifier 221, the control device 222, the pulse generating circuit 223, and the driving device 224 are provided. The servo track writer 210 is a device for writing a servo signal in the servo band of the long magnetic tape MT. The tension adjusting portion 218 includes a tension arm 218A and a pair of supporting portions 218B.

As shown in FIG. 12A, the servo signal writing head 219 has a head chip 232, and a sliding surface 234 for a linear magnetic tape (not shown) on the upper surface of the head chip 232. In the moving surface 234, at least a part of a magnetic head portion 235, which is a recording element for recording servo signals, and a bottomed cavity 236 whose periphery is closed are formed.

As shown in FIG. 12B, at least a part of the sliding surface 234 of the servo signal writing head 219 is a flat surface, and a linear magnetic tape (not shown) arranged to face the sliding surface 234 is At the time of traveling, air in the vicinity is scraped off by the edge portion of the magnetic head sliding surface 234, and the pressure is reduced in the bottomed cavity 236, so that the spacing with the sliding surface 234 is made smaller.

The servo signal writing head 219 having a cavity mounted on the servo track writer 210 and the distance between the guide rollers 215A and 215B adjacent to the head are adjusted, and the tape penetration angle to the servo signal writing head 219 is adjusted. By doing so, it is possible to adjust the friction between the servo signal writing head 219 and the magnetic tape MT when recording the servo pattern. By adjusting the friction in this way, it is possible to adjust σ _sw of the magnetic tape MT. Σ _SW tends to decrease as the friction between the servo signal writing head 219 and the magnetic tape MT during recording the servo pattern decreases.

[Magnetic tape manufacturing method]
Next, an example of a method of manufacturing the magnetic tape MT having the above configuration will be described.

(Paint preparation process)
First, a non-magnetic powder, a binder and the like are kneaded and dispersed in a solvent to prepare a base layer forming coating material. Next, the magnetic powder, the binder and the like are kneaded and dispersed in a solvent to prepare a magnetic layer forming coating material. For the preparation of the magnetic layer-forming coating material and the underlayer-forming coating material, for example, the following solvent, dispersing device and kneading device can be used.

Examples of the solvent used for preparing the above-mentioned paint include acetone, methyl ethyl ketone, methyl isobutyl ketone, ketone solvents such as cyclohexanone, alcohol solvents such as methanol, ethanol and propanol, methyl acetate, ethyl acetate, butyl acetate, propyl acetate. , Ethyl lactate, ester solvents such as ethylene glycol acetate, diethylene glycol dimethyl ether, 2-ethoxyethanol, tetrahydrofuran, ether solvents such as dioxane, benzene, toluene, aromatic hydrocarbon solvents such as xylene, methylene chloride, ethylene chloride, Examples thereof include halogenated hydrocarbon solvents such as carbon tetrachloride, chloroform and chlorobenzene. These may be used alone or in an appropriate mixture.

As the kneading device used for the above-mentioned paint preparation, for example, a kneading device such as a continuous biaxial kneading machine, a continuous biaxial kneading machine capable of diluting in multiple stages, a kneader, a pressure kneader, or a roll kneader can be used. However, it is not particularly limited to these devices. Further, as the dispersing device used for the above-mentioned coating preparation, for example, a roll mill, a ball mill, a horizontal sand mill, a vertical sand mill, a spike mill, a pin mill, a tower mill, a pearl mill (for example, "DCP mill" manufactured by Erich Co., Ltd.), a homogenizer, and A dispersion device such as a sonic disperser can be used, but the device is not particularly limited to these devices.

(Coating process)
Next, the underlayer-forming coating material is applied to one main surface of the substrate 41 and dried to form the underlayer 42. Subsequently, the magnetic layer 43 is formed on the underlayer 42 by applying a coating material for forming a magnetic layer on the underlayer 42 and drying it. In addition, at the time of drying, the magnetic powder is magnetically oriented in the thickness direction of the base 41 by, for example, a solenoid coil. Further, during drying, the magnetic powder may be magnetically oriented in the traveling direction (longitudinal direction) of the base 41 by using, for example, a solenoid coil, and then magnetic field oriented in the thickness direction of the base 41. By thus performing the treatment for temporarily orienting the magnetic powder in the longitudinal direction, the degree of vertical orientation of the magnetic powder (that is, the squareness ratio S1) can be further improved. After forming the magnetic layer 43, the back layer 44 is formed on the other main surface of the base 41. Thereby, the magnetic tape MT is obtained.

The squareness ratios S1 and S2 are, for example, the strength of the magnetic field applied to the coating film of the magnetic layer-forming coating material, the concentration of solids in the magnetic layer-forming coating material, and the drying conditions (drying conditions) of the magnetic layer-forming coating material. It is set to a desired value by adjusting the temperature and the drying time). The strength of the magnetic field applied to the coating film is preferably 2 times or more and 3 times or less the coercive force of the magnetic powder. In order to further increase the squareness ratio S1 (that is, to further reduce the squareness ratio S2), it is preferable to improve the dispersion state of the magnetic powder in the magnetic layer-forming coating material. In order to further increase the squareness S1, it is effective to magnetize the magnetic powder before the magnetic layer-forming coating material enters the orienting device for orienting the magnetic powder in the magnetic field. The methods for adjusting the squareness ratios S1 and S2 may be used alone or in combination of two or more.

(Calendar process, transfer process)
Then, the obtained magnetic tape MT is calendered to smooth the surface of the magnetic layer 43. Next, the calendered magnetic tape MT is wound into a roll, and then the magnetic tape MT is heated in this state, so that the large number of protrusions 44A on the surface of the back layer 44 are covered with the magnetic layer 43. Transfer to the surface of. As a result, a large number of holes 43A are formed on the surface of the magnetic layer 43.

The temperature of the heat treatment is preferably 55° C. or higher and 75° C. or lower. When the temperature of the heat treatment is 55° C. or higher, good transferability can be obtained. On the other hand, if the temperature of the heat treatment exceeds 75° C., the amount of pores becomes too large, and the lubricant on the surface of the magnetic layer 43 may be excessive. Here, the temperature of the heat treatment is the temperature of the atmosphere holding the magnetic tape MT.

The heat treatment time is preferably 15 hours or more and 40 hours or less. When the heat treatment time is 15 hours or more, good transferability can be obtained. On the other hand, when the heat treatment time is 40 hours or less, a decrease in productivity can be suppressed.

(Cutting process)
Finally, the magnetic tape MT is cut into a predetermined width (for example, 1/2 inch width). From the above, the magnetic tape MT is obtained.

(Servo pattern writing process)
The servo writer 210 described above writes a servo pattern on the magnetic tape MT. At this time, the statistical value σ _sw of the magnetic tape MT is adjusted to 24 nm or less by adjusting the friction between the servo signal writing head 119 and the magnetic tape MT when writing the servo pattern as described above. It is possible.

[Structure of recording/reproducing apparatus]
The recording/reproducing device 50 records and reproduces the magnetic tape MT having the above-mentioned configuration. The recording/reproducing device 50 has a configuration capable of adjusting the tension applied in the longitudinal direction of the magnetic tape MT. Further, the recording/reproducing device 50 has a configuration in which the cartridge 10 can be loaded. Here, for ease of explanation, a case will be described in which the recording/reproducing device 50 has a configuration in which one cartridge 10 can be loaded, but the recording/reproducing device 50 can load a plurality of cartridges 10. It may have various configurations.

The recording/reproducing device 50 is connected to an information processing device such as a server 61 and a personal computer (hereinafter referred to as “PC”) 62 via a network 60, and the data supplied from these information processing devices is stored in the cartridge 10. It is configured to be recordable. Further, in response to a request from these information processing devices, the data can be reproduced from the cartridge 10 and supplied to these information processing devices. The shortest recording wavelength of the recording/reproducing device 50 is preferably 96 nm or less, more preferably 88 nm or less, even more preferably 80 nm or less.

As shown in FIG. 1, the recording/reproducing device 50 includes a spindle 51, a reel 52 on the recording/reproducing device 50 side, a spindle driving device 53, a reel driving device 54, a plurality of guide rollers 55, a magnetic head (head). A unit) 56, a reader/writer 57 as a communication unit, a communication interface (hereinafter, I/F) 58, and a control device 59.

The spindle 51 is configured so that the cartridge 10 can be mounted therein. On the magnetic tape MT, a V-shaped servo pattern is recorded in advance as a servo signal. The reel 52 is configured to be capable of fixing the tip (leader pin 20) of the magnetic tape MT pulled out from the cartridge 10 via a tape loading mechanism (not shown).

The spindle drive device 53 rotates the spindle 51 in response to a command from the control device 59. The reel drive device 54 rotates the reel 52 in response to a command from the control device 59. The plurality of guide rollers 55 guide the traveling of the magnetic tape MT so that the tape path formed between the cartridge 10 and the reel 52 has a predetermined relative positional relationship with the magnetic head 56.

When data is recorded on the magnetic tape MT, or when data is reproduced from the magnetic tape MT, the spindle 51 and the reel 52 are rotationally driven by the spindle drive device 53 and the reel drive device 54, The magnetic tape MT runs. The running direction of the magnetic tape MT can be reciprocated in a forward direction (direction flowing from the cartridge 10 side to the reel 52 side) and a reverse direction (direction flowing from the reel 52 side to the cartridge 10 side).

In this embodiment, by controlling the rotation of the spindle 51 by the spindle drive device 53 and the rotation of the reel 52 by the reel drive device 54, the longitudinal tension of the magnetic tape MT during data recording or data reproduction can be adjusted. It is said that The tension adjustment of the magnetic tape MT may be performed by controlling the movement of the guide roller 55 instead of or in addition to the control of the rotation of the spindle 51 and the reel 52.

The reader/writer 57 is configured to be able to write the first information and the second information to the cartridge memory 11 in response to a command from the control device 59. Further, the reader/writer 57 is configured to be able to read the first information and the second information from the cartridge memory 11 in response to a command from the control device 59. As a communication method between the reader/writer 57 and the cartridge memory 11, for example, the ISO14443 method is adopted. The second information includes tension adjustment information. The tension adjustment information is an example of data recording information.

The control device 59 includes, for example, a control unit, a storage unit, a communication unit, and the like. The control unit is composed of, for example, a CPU (Central Processing Unit), etc., and controls each unit of the recording/reproducing device 50 according to a program stored in the storage unit. For example, the control device 59 records a data signal supplied from the information processing device on the magnetic tape MT by the magnetic head 56 in response to a request from the information processing device such as the server 61 and the PC 62. Further, the control device 59 reproduces the data signal recorded on the magnetic tape MT by the magnetic head 56 in response to a request from the information processing device such as the server 61 and the PC 62, and supplies it to the information processing device.

The storage unit includes a non-volatile memory in which various data and various programs are recorded, and a volatile memory used as a work area of the control unit. The various programs may be read from a portable recording medium such as an optical disk or a portable storage device such as a semiconductor memory, or may be downloaded from a server device on the network.

The controller 59 causes the magnetic head 56 to read the servo signals recorded in the two adjacent servo bands SB when recording data on the magnetic tape MT or reproducing data from the magnetic tape MT. The controller 59 uses the servo signals read from the two servo bands SB to control the position of the magnetic head 56 so that the magnetic head 56 follows the servo pattern.

When recording data on the magnetic tape MT, the controller 59 determines the distance between the two adjacent servo bands SB (the width direction of the magnetic tape MT from the reproduced waveform of the servo signal read from the two adjacent servo bands SB). The distance) d1 is calculated. Then, the obtained distance is written in the memory 36 by the reader/writer 57.

At the time of reproducing the data from the magnetic tape MT, the controller 59 determines the distance between the two adjacent servo bands SB (the width of the magnetic tape MT from the reproduced waveform of the servo signal read from the two adjacent servo bands SB). The distance in the direction) d2 is calculated. At the same time, the control device 59 reads the distance d1 between the two adjacent servo bands SB, which is obtained when the data is recorded on the magnetic tape MT, from the memory 36 by the reader/writer 57. The control device 59 controls the difference Δd between the distance d1 between the servo bands SB obtained when the data is recorded on the magnetic tape MT and the distance d2 between the servo bands SB obtained when the data is reproduced from the magnetic tape MT within a specified range. The rotation of the spindle drive device 53 and the reel drive device 54 is controlled so that the inside of the magnetic tape MT is kept inside, and the tension applied in the longitudinal direction of the magnetic tape MT is adjusted. This tension adjustment control is performed by feedback control, for example.

The magnetic head 56 is configured to be able to record data on the magnetic tape MT according to a command from the control device 59. Further, the magnetic head 56 is configured to be able to reproduce the data recorded on the magnetic tape MT according to a command from the control device 59. The magnetic head 56 has, for example, two servo read heads 56A and 56B and a plurality of data write/read heads.

The servo read heads 56A and 56B are configured to be able to reproduce the servo signal by reading the magnetic field generated from the servo signal recorded on the magnetic tape MT with an MR element (MR: Magneto Resistive) or the like. The distance between the two servo read heads 56A and 56B in the width direction is substantially the same as the distance between the two adjacent servo bands SB.

The data write/read heads are arranged at positions sandwiched by the two servo read heads 56A and 56B at equal intervals along the direction from one servo read head 56A, 56B toward the other servo read head 56A, 56B. There is. The data write/read head is configured to be able to record data on the magnetic tape MT by the magnetic field generated from the magnetic gap. Further, the data write/read head is configured to be able to reproduce the data by reading the magnetic field generated from the data recorded on the magnetic tape MT with the MR element or the like.

The communication I/F 58 is for communicating with an information processing device such as the server 61 and the PC 62, and is connected to the network 60.

[Operation of recording/reproducing apparatus during data recording]
An example of the operation of the recording/reproducing device 50 at the time of recording data will be described below with reference to FIG.

First, the control device 59 loads the cartridge 10 into the recording/reproducing device 50 (step S11). Next, the control device 59 controls the rotation of the spindle 51 and the reel 52, and runs the magnetic tape MT while applying a specified tension in the longitudinal direction of the magnetic tape MT. Then, the controller 59 reads the servo signal by the servo read heads 56A and 56B of the magnetic head 56 and records the data on the magnetic tape MT by the data write/read head of the magnetic head 56 (step S12).

At this time, the magnetic head 56 traces two adjacent servo bands SB by the two servo read heads 56A and 56B of the magnetic head 56, and the data write/read head of the magnetic head 56 is used for the data band DB. Record the data.

Next, the control device 59 obtains the distance d1 between two adjacent servo bands SB at the time of data recording from the reproduced waveform of the servo signal read by the servo read heads 56A and 56B of the magnetic head 56 (step S13). Next, the controller 59 writes the distance d1 between the servo bands SB at the time of data recording in the cartridge memory 11 by the reader/writer 57 (step S14). The controller 59 may continuously measure the distance d1 between the servo bands SB and write it in the cartridge memory 11, or may measure the distance d1 between the servo bands SB at regular intervals and write it in the cartridge memory 11. When the distance d1 between the servo bands SB is measured at regular intervals and written in the cartridge memory 11, the amount of information written in the memory 36 can be reduced.

[Operation of recording/reproducing apparatus during data reproduction]
An example of the operation of the recording/reproducing device 50 at the time of reproducing data will be described below with reference to FIG.

First, the control device 59 loads the cartridge 10 into the recording/reproducing device 50 (step S21). Next, the controller 59 reads the distance d1 between the servo bands at the time of recording from the cartridge memory 11 by the reader/writer 57 (step S22).

Next, the control device 59 controls the rotation of the spindle 51 and the reel 52, and runs the magnetic tape MT while applying a specified tension in the longitudinal direction of the magnetic tape MT. Then, the controller 59 reads the servo signals by the servo read heads 56A and 56B of the magnetic head 56, and reproduces the data from the magnetic tape MT by the data write/read head of the magnetic head 56 (step S23).

Next, the control device 59 calculates the distance d2 between two adjacent servo bands SB during data reproduction from the reproduction waveform of the servo signal read by the servo read heads 56A and 56B of the magnetic head 56 ( Step S24).

Next, the control device 59 determines whether or not the difference Δd between the distance d1 between the servo bands read in step S22 and the distance d2 between the servo bands SB calculated in step S24 is within a specified value ( Step S25).

When it is determined in step S25 that the difference Δd is within the specified value, the control device 59 controls the rotation of the spindle 51 and the reel 52 so that the specified tension is maintained (step S26).

On the other hand, when it is determined in step S25 that the difference Δd is not within the specified value, the control device 59 controls the rotation of the spindle 51 and the reel 52 so that the difference Δd becomes small, and the running magnetic tape MT. The tension applied to is adjusted and the process returns to step S24 (step S27).

[effect]
As described above, in the magnetic tape MT according to the first embodiment, the entire BET specific surface area of the magnetic tape MT measured in the washed and dried state of the magnetic tape MT is 3.5 m ² /g or more. Since it is 7.0 m ² /g or less and the statistical value σ _SW indicating the nonlinearity of the servo pattern is 24 nm, excellent running stability can be obtained even when the total thickness of the magnetic tape MT is thin. You can Further, the arithmetic average roughness Ra of the surface of the magnetic layer 43 is 2.5 nm or less, the squareness ratio of the magnetic layer 43 in the vertical direction is 65%, and the average thickness of the magnetic layer 43 is 80 nm, which is excellent. Electromagnetic conversion characteristics can be obtained. Therefore, it is possible to achieve both excellent running stability and electromagnetic conversion characteristics.

Furthermore, in the magnetic tape MT according to the first embodiment, the base body 41 contains polyester. As a result, when the width of the magnetic tape MT that changes the environmental temperature or humidity around the magnetic tape MT (cartridge 10) on which data is recorded with the above-described data track width changes, the length of the magnetic tape MT during running is increased. By adjusting the tension in the direction by the recording/reproducing device 50, the width of the magnetic tape MT can be kept constant or almost constant. Therefore, off-track due to changes in environmental temperature and humidity can be suppressed.

<2 Second Embodiment>
[Structure of recording/reproducing apparatus]
FIG. 15 is a schematic diagram showing an example of the configuration of a recording/reproducing system 100A according to the second embodiment of the present disclosure. The recording/reproducing system 100A includes a cartridge 10 and a recording/reproducing device 50A.

The recording/reproducing device 50A further includes a thermometer 63 and a hygrometer 64. The thermometer 63 measures the temperature around the magnetic tape MT (cartridge 10) and outputs it to the controller 59. Further, the hygrometer 64 measures the humidity around the magnetic tape MT (cartridge 10) and outputs it to the control device 59.

The controller 59 measures the temperature Tm1 and the humidity H1 around the magnetic tape MT (cartridge 10) with the thermometer 63 and the hygrometer 64 at the time of recording data on the magnetic tape MT, and the cartridge memory via the reader/writer 57. Write to 11. The temperature Tm1 and the humidity H1 are examples of environmental information around the magnetic tape MT.

At the time of recording data on the magnetic tape MT, the control device 59 obtains the tension Tn1 applied in the longitudinal direction of the magnetic tape MT based on the drive data of the spindle 51 and the reel 52, and the cartridge memory 11 via the reader/writer 57. Write in.

The controller 59 obtains the distance d1 between the two adjacent servo bands SB from the reproduced waveform of the servo signal read from the two adjacent servo bands SB when recording the data on the magnetic tape MT. Then, based on this distance d1, the width W1 of the magnetic tape MT at the time of data recording is calculated and written in the memory 36 by the reader/writer 57.

The controller 59 measures the temperature Tm2 and the humidity H2 around the magnetic tape MT (cartridge 10) by the thermometer 63 and the hygrometer 64 when reproducing the data from the magnetic tape MT.

The controller 59 obtains the tension Tn2 applied in the longitudinal direction of the magnetic tape MT based on the drive data of the spindle 51 and the reel 52 when reproducing the data from the magnetic tape MT.

The controller 59 obtains the distance d2 between the two adjacent servo bands SB from the reproduced waveform of the servo signal read from the two adjacent servo bands SB when reproducing the data from the magnetic tape MT. Then, based on this distance d2, the width W2 of the magnetic tape MT during data reproduction is calculated.

The controller 59 reads the temperature Tm1, the humidity H1, the tension Tn1 and the width W1 written at the time of data recording from the cartridge memory 11 via the reader/writer 57 at the time of reproducing the data from the magnetic tape MT. Then, the control device 59 uses the temperature Tm1, the humidity H1, the tension Tn1 and the width W1 at the time of recording the data, and the temperature Tm2, the humidity H2, the tension Tn2 and the width W2 at the time of the data reproduction to determine the magnetic field at the time of the data reproduction. The tension applied to the magnetic tape MT is controlled so that the width W2 of the tape MT is equal or almost equal to the width W1 of the magnetic tape during data recording.

The controller 35 of the cartridge memory 11 stores the temperature Tm1, the humidity H1, the tension Tn1 and the width W1 received from the recording/reproducing device 50A via the antenna coil 31 in the second storage area 36B of the memory 36. The controller 35 of the cartridge memory 11 reads the temperature Tm1, the humidity H1, the tension Tn1 and the width W1 from the memory 36 in response to a request from the recording/reproducing apparatus 50A, and transmits them to the recording/reproducing apparatus 50A via the antenna coil 31.

[Operation of recording/reproducing apparatus during data recording]
Hereinafter, an example of the operation of the recording/reproducing device 50A at the time of recording data will be described with reference to FIG.

First, the control device 59 loads the cartridge 10 into the recording/reproducing device 50A (step S101). Next, the control device 59 controls the rotation of the spindle 51 and the reel 52, and runs the magnetic tape MT while applying a specified tension in the longitudinal direction of the magnetic tape MT. Then, the control device 59 records data on the magnetic tape MT by the magnetic head 56 (step S102).

Next, the control device 59 acquires the temperature Tm1 and the humidity H1 (environmental information) around the magnetic tape MT during data recording from the thermometer 63 and the hygrometer 64 (step S103).

Next, the control device 59 calculates the tension Tn1 applied in the longitudinal direction of the magnetic tape MT during data recording, based on the drive data of the spindle 51 and the reel 52 during data recording (step S104).

Next, the controller 59 obtains the distance d1 between two adjacent servo bands SB from the reproduced waveform of the servo signal read by the servo read heads 56A and 56B of the magnetic head 56. Next, the control device 59 calculates the width W1 of the magnetic tape MT during data recording based on this distance d1 (step S105).

Next, the controller 59 writes the temperature Tm1, the humidity H1, the tension Tn1 and the width W1 of the magnetic tape MT to the cartridge memory 11 as data recording information by the reader/writer 57 (step S106).

[Operation of recording/reproducing apparatus during data reproduction]
An example of the operation of the recording/reproducing device 50A during data reproduction will be described below with reference to FIG.

First, the control device 59 loads the cartridge 10 into the recording/reproducing device 50A (step S111). Next, the control device 59 reads the data recording information (the temperature Tm1, the humidity H1, the tension Tn1, and the width W1 of the magnetic tape MT) written in the cartridge memory 11 from the cartridge memory 11 by the reader/writer 57 and acquires the information. (Step S112). Next, the controller 59 uses the thermometer 63 and the hygrometer 64 to acquire the information on the current temperature Tm2 and the humidity H2 around the magnetic tape MT at the time of data reproduction (step S113).

Next, the control device 59 calculates a temperature difference TmD (TmD=Tm2-Tm1) between the temperature Tm1 during data recording and the temperature Tm2 during data reproduction (step S114). Further, the control device 59 calculates a humidity difference HD (HD=H2-H1) between the humidity H1 during data recording and the humidity H2 during data reproduction (step S115).

Next, the controller 59 multiplies the temperature difference TmD by the coefficient α (TmD×α) and multiplies the humidity difference HD by the coefficient β (HD×β) (step S116). The coefficient α is a value indicating how much the tension of the magnetic tape MT should be changed as compared with the tension Tn1 at the time of data recording per 1° C. of temperature difference. The coefficient β is a value indicating how much the tension of the magnetic tape MT should be changed with respect to the tension Tn1 at the time of data recording per humidity difference of 1%.

Next, the control device 59 adds the value of TmD×α and the value of HD×β to the tension Tn1 at the time of data recording, so that the length of the magnetic tape MT is at the time of data reproduction (current). The tension Tn2 to be applied in the direction is calculated (step S117).
Tn2=Tn1+TmD×α+HD×β

After determining the tension Tn2 of the magnetic tape MT at the time of data reproduction, the controller 59 controls the rotation of the spindle 51 and the reel 52, and controls the running of the magnetic tape MT so that the magnetic tape MT runs at the tension Tn2. To do. Then, the controller 59 reads the servo signal of the servo band SB by the servo read heads 56A and 56B of the magnetic head 56, and reproduces the data recorded in the data track Tk by the data write/read head of the magnetic head 56. Perform (step S118).

At this time, since the width of the magnetic tape MT is adjusted to the width at the time of data recording by adjusting the tension of the magnetic tape MT, the data write/read head of the magnetic head 56 is accurately positioned with respect to the data track Tk. Can be matched. As a result, even if the width of the magnetic tape MT fluctuates due to some cause (for example, fluctuations in temperature and humidity), the data recorded on the magnetic tape MT can be accurately reproduced.

The value of the tension Tn2 to be applied to the magnetic tape MT at the time of data reproduction (current) is higher if the temperature at the time of data reproduction is higher than the temperature at the time of data recording. Therefore, when the temperature rises and the width of the magnetic tape MT becomes wider than that during data recording, the width of the magnetic tape MT can be narrowed to reproduce the same width as during data reproduction.

On the contrary, at the time of data reproduction (current), the value of the tension Tn2 to be applied to the magnetic tape MT becomes lower if the temperature at the time of data reproduction is lower than the temperature at the time of data recording. Therefore, when the temperature becomes lower and the width of the magnetic tape MT becomes narrower than that at the time of data recording, the width of the magnetic tape MT can be widened to reproduce the same width as at the time of data reproduction.

The value of the tension Tn2 to be applied to the magnetic tape MT at the time of data reproduction (current) becomes higher if the humidity at the time of data reproduction is higher than the humidity at the time of data recording. Therefore, when the humidity becomes high and the width of the magnetic tape MT becomes wider than that at the time of data recording, the width of the magnetic tape MT can be narrowed to reproduce the same width as at the time of data reproduction.

On the contrary, at the time of data reproduction (current), the value of the tension Tn2 to be applied to the magnetic tape MT becomes lower if the humidity at the time of data reproduction is lower than the humidity at the time of data recording. Therefore, when the humidity becomes low and the width of the magnetic tape MT becomes narrower than that at the time of data recording, the width of the magnetic tape MT can be widened to reproduce the same width as at the time of data reproduction.

Here, in order to obtain the tension Tn2 to be applied to the magnetic tape MT during data reproduction, in addition to the temperature Tm1 during recording of data, the humidity H1, and the tension Tn1 of the magnetic tape MT (or instead of the tension Tn1), Further, information on the width W1 of the magnetic tape MT at the time of recording data may be used.

In this case as well, the control device 59 similarly calculates the temperature difference TmD (TmD=Tm2-Tm1) and the humidity difference HD (HD=H2-H1). Then, the control device 59 multiplies the temperature difference TmD by the coefficient γ (TmD×γ) and the humidity difference HD by the coefficient δ (HD×δ) (step S116).

Here, the coefficient γ is a value (a value indicating an expansion coefficient per unit length (width direction) based on temperature) indicating how much the width of the magnetic tape MT varies per 1° C. of temperature difference. Further, the coefficient δ is a value (a value indicating an expansion coefficient per unit length (width direction) based on humidity) indicating how much the width of the magnetic tape MT fluctuates per humidity difference of 1%.

Next, the control device 59 predicts the current width w2 of the magnetic tape MT at the time of data reproduction based on the width W1 of the past magnetic tape MT at the time of data recording by the following formula.
W2=W1 (1+TmD×γ+HD2×δ)

Next, the control device 59 calculates the difference WD between the current width w2 of the magnetic tape MT during data reproduction and the width W1 of the past magnetic tape MT during data recording (WD=W2-W1=W1( TmD×γ+HD2×δ))).

Then, the controller 59 adds the value obtained by multiplying the width difference WD by the coefficient ε to the tension Tn1 of the magnetic tape MT during data recording to calculate the tension Tn2 of the magnetic tape MT during data reproduction Tn2= Tn1+WD×ε

Here, the coefficient ε is a value representing the tension in the longitudinal direction of the magnetic tape MT, which is necessary to change the width of the magnetic tape MT by a unit distance.

After determining the tension Tn2 of the magnetic tape MT at the time of data reproduction, the controller 59 controls the rotation of the spindle 51 and the reel 52, and controls the running of the magnetic tape MT so that the magnetic tape MT runs at the tension Tn2. To do. Then, the controller 59 reads the servo signal of the servo band SB by the servo read heads 56A and 56B of the magnetic head 56, and reproduces the data recorded in the data track Tk by the data write/read head of the magnetic head 56. To do.

Even when the tension Tn2 is determined by such a method, if the width of the magnetic tape MT changes due to some cause (for example, changes in temperature and humidity), the data recorded on the magnetic tape MT is changed. Can be reproduced accurately.

[effect]
As described above, in the second embodiment, the data recording information of the magnetic tape MT is stored in the cartridge memory 11. Therefore, by using this information during the data reproduction, the width of the magnetic tape MT can be properly adjusted. Can be adjusted to. Therefore, even if the width of the magnetic tape MT changes for some reason, the data recorded on the magnetic tape MT can be accurately reproduced.

Further, in the present embodiment, the temperature Tm1 and the humidity H1 (environmental information) around the magnetic tape MT at the time of data recording are written as the data recording information. Therefore, variations in the width of the magnetic tape MT and the width of the data track Tk due to variations in temperature and humidity can be appropriately dealt with.

<3 modification>
(Modification 1)
In the first and second embodiments described above, the case where the tension adjustment information is stored in the cartridge memory 11 has been described, but the tension adjustment information may be stored in the control device 59 of the recording/reproducing devices 50 and 50A. .. In this case, the control device 59 controls the rotation of the spindle drive device 53 and the reel drive device 54 based on the tension adjustment information stored in the control device 59, and adjusts the tension applied in the longitudinal direction of the magnetic tape MT.

(Modification 2)
The magnetic tape MT may be used in the library device. In this case, the library device has a configuration in which the tension applied in the longitudinal direction of the magnetic tape MT can be adjusted, and a plurality of recording/reproducing devices 50 in the first embodiment or recording/reproducing devices 50A in the second embodiment are used. It may be provided.

(Modification 3)
The servo writer may keep the width of the magnetic tape MT constant or almost constant by adjusting the tension in the longitudinal direction of the magnetic tape MT when recording a servo signal or the like. In this case, the servo writer may include a detection device that detects the width of the magnetic tape MT, and the tension in the longitudinal direction of the magnetic tape MT may be adjusted based on the detection result of this detection device.

(Modification 4)
The magnetic tape MT is not limited to the perpendicular recording type magnetic tape, but may be a horizontal recording type magnetic tape. In this case, acicular magnetic powder such as metal magnetic powder may be used as the magnetic powder.

(Modification 5)
In the above-described first embodiment, the case where the distance between the servo bands SB is used as the width-related information related to the magnetic tape at the time of data recording has been described, but the width of the magnetic tape MT may be used.

In this case, the controller 59 calculates the width W1 of the magnetic tape MT from the distance d1 between the servo bands SB at the time of data recording, and writes this width W1 in the cartridge memory 11 by the reader/writer 57.

The controller 59 reads the width W1 of the magnetic tape MT at the time of data recording from the cartridge memory 11 at the time of data reproduction, and at the same time, reads the magnetic tape MT at the time of data reproduction from the distance d2 between the servo bands SB at the time of data reproduction. The width W2 of Then, the control device 59 calculates the difference ΔW between the width W1 of the magnetic tape MT during data recording and the width W2 of the magnetic tape MT during data reproduction, and determines whether the difference ΔW is within a specified value. To do.

When the difference Δd is within the specified value, the control device 59 controls the rotational drive of the spindle 51 and the reel 52 so that the specified tension is maintained. On the other hand, when the difference Δd is not within the specified value, the rotational drive of the spindle 51 and the reel 52 is controlled and the tension applied to the traveling magnetic tape MT is adjusted so that the difference Δd falls within the specified value.

(Modification 6)
In the above-described second embodiment, the case where all of the temperatures Tm1, Tm2, the humidity H1, H2, the tensions Tn1, Tn2, and the widths W1, W2 are used as the data recording time information has been described. , Temperature Tm1, Tm2, humidity H1, H2, tensions Tn1, Tn2, and widths W1, W2, or a combination of any two or three.

Information (temperature Tm2, humidity H2, tension Tn2, width W2) at the time of data reproduction is stored in the cartridge memory 11 as well as information (temperature Tm1, humidity H1, tension Tn1, width W1) at the time of data recording. May be. For example, this information at the time of data reproduction is used when the data in the magnetic tape MT is reproduced at another occasion after the data is reproduced.

(Modification 7)
In the first and second embodiments described above, by transferring the large number of protrusions 44A provided on the surface of the back layer 44 to the surface of the magnetic layer 43, a large number of holes 43A are formed on the surface of the magnetic layer 43. However, the method of forming the large number of holes 43A is not limited to this. For example, a large number of holes 43A may be formed on the surface of the magnetic layer 43 by adjusting the type of solvent contained in the magnetic layer-forming coating material and the drying conditions of the magnetic layer-forming coating material.

Hereinafter, the present disclosure will be specifically described with reference to examples, but the present disclosure is not limited to these examples.

In the following examples and comparative examples, the average thickness of the magnetic tape, the arithmetic average roughness Ra of the surface of the magnetic layer, the squareness ratio in the vertical direction, the average thickness of the magnetic layer, the BET specific surface area, the pore distribution (the maximum fineness during desorption). The pore diameter of the pore volume) and the statistical value σ _SW indicating the non-linearity of the servo pattern are values obtained by the measuring method described in the first embodiment.

[Example 1]
(Preparation process of paint for forming magnetic layer)
A magnetic layer-forming coating material was prepared as follows. First, the first composition having the following composition was kneaded with an extruder. Then, the kneaded first composition and the second composition having the following composition were added to a stirring tank equipped with a disper, and premixed. Subsequently, sand mill mixing was further performed and filter treatment was performed to prepare a magnetic layer-forming coating material.

(First composition)
Powder of barium ferrite (BaFe ₁₂ O ₁₉ ) particles (hexagonal plate shape, average aspect ratio 2.8, average particle volume 1600 nm ³ ): 100 parts by mass Vinyl chloride resin (resin solution: resin content 30% by mass, cyclohexanone 70% by mass) %): 42 parts by mass (including solvent)
(The degree of polymerization is 300, Mn=10000, and OSO ₃ K=0.07 mmol/g as a polar group, and secondary OH=0.3 mmol/g is contained.)
Aluminum oxide powder: 5 parts by mass (α-Al ₂ O ₃ , average particle size 0.1 μm)
Carbon black: 2 parts by mass (manufactured by Tokai Carbon Co., Ltd., product name: Seast TA)

(Second composition)
Vinyl chloride resin: 3 parts by mass (including solvent)
(Resin solution: resin content 30% by mass, cyclohexanone 70% by mass)
n-Butyl stearate: 2 parts by mass Methyl ethyl ketone: 121.3 parts by mass Toluene: 121.3 parts by mass Cyclohexanone: 60.7 parts by mass

Finally, in the magnetic layer-forming coating material prepared as described above, 4 parts by mass of polyisocyanate (trade name: Coronate L, Tosoh Corporation) as a curing agent and 2 parts by mass of stearic acid as a lubricant are added. Was added.

(Preparation process of paint for forming underlayer)
A base layer-forming coating material was prepared as follows. First, the third composition having the following composition was kneaded with an extruder. Next, the kneaded third composition and the fourth composition having the following composition were added to a stirring tank equipped with a disper and premixed. Subsequently, sand mill mixing was further performed and filter treatment was performed to prepare a coating material for forming an underlayer.

(Third composition)
Needle-shaped iron oxide powder: 100 parts by mass (α-Fe ₂ O ₃ , average major axis length 0.15 μm)
Vinyl chloride resin: 60.6 parts by mass (including solvent)
(Resin solution: resin content 30% by mass, cyclohexanone 70% by mass)
Carbon black: 10 parts by mass (average particle size 20 nm)

(Fourth composition)
Polyurethane resin UR8200 (manufactured by Toyobo): 18.5 parts by mass n-butyl stearate: 2 parts by mass Methyl ethyl ketone: 108.2 parts by mass Toluene: 108.2 parts by mass Cyclohexanone: 18.5 parts by mass

Finally, in the undercoat-forming coating material prepared as described above, 4 parts by mass of polyisocyanate (trade name: Coronate L, Tosoh Corporation) as a curing agent and 2 parts by mass of stearic acid as a lubricant are added. Was added.

(Preparation process of back layer paint)
The back layer forming coating material was prepared as follows. The following raw materials were mixed in a stirring tank equipped with a disper and filtered to prepare a back layer-forming coating material.
Small particle size carbon black powder (average particle size (D50) 20 nm): 90 parts by mass Large particle size carbon black powder (average particle size (D50) 270 nm): 10 parts by mass Polyester polyurethane: 100 parts by mass (Tosoh Corporation Co., Ltd., product name: N-2304)
Methyl ethyl ketone: 500 parts by mass Toluene: 400 parts by mass Cyclohexanone: 100 parts by mass

(Coating process)
Using the magnetic layer-forming coating material and the underlayer-forming coating material prepared as described above, a non-magnetic support having an average thickness of 4.2 μm and a long polyethylene naphthalate film (hereinafter referred to as “PEN film”) An underlayer and a magnetic layer were formed on one of the main surfaces as follows. First, a base layer-forming coating material was applied onto one main surface of a PEN film and dried to form a base layer having an average thickness of 0.9 μm after calendaring. Next, a magnetic layer-forming coating material was applied onto the underlayer and dried to form a magnetic layer having an average thickness of 80 nm after calendering. When the coating material for forming the magnetic layer was dried, the magnetic powder was magnetically oriented in the thickness direction of the film with a solenoid coil. Further, the drying conditions (drying temperature and drying time) of the magnetic layer-forming coating material were adjusted, and the squareness ratio S1 in the thickness direction (vertical direction) of the magnetic tape was set to 65%. Subsequently, the back layer-forming coating material was applied onto the other main surface of the PEN film and dried to form a back layer having an average thickness of 0.4 μm after calendering. Thereby, a magnetic tape was obtained.

(Calendar process, transfer process)
First, calendering was performed to smooth the surface of the magnetic layer. At this time, the calendering conditions were adjusted to set the arithmetic average roughness Ra of the surface of the magnetic layer to 2.5 nm. Next, the obtained magnetic tape was wound into a roll, and in this state, the magnetic tape was subjected to the first heat treatment at 60° C. for 10 hours. Then, the magnetic tape is rewound in a roll shape so that the end portion located on the inner peripheral side is located opposite to the outer peripheral side, and in this state, the magnetic tape is subjected to the second heating at 60° C. for 10 hours. Processed. As a result, many protrusions on the surface of the back layer were transferred to the surface of the magnetic layer, and many holes were formed on the surface of the magnetic layer. The BET specific surface area of the entire magnetic tape was 4.5 m ² /g. The average pore diameter of the entire magnetic tape MT was 8.0 nm.

(Cutting process)
The magnetic tape obtained as described above was cut into ½ inch (12.65 mm) widths. As a result, a long magnetic tape having an average thickness of 5.6 μm was obtained.

(Servo pattern writing process)
Five servo bands were formed by writing a servo pattern on the magnetic tape obtained as described above using a servo writer. The servo pattern was made to comply with the LTO-8 standard. As the servo writer, the one having the configuration described in the first embodiment was used (see FIGS. 11, 12A, and 12B).

By adjusting the distance between the servo signal writing head and the guide roller, and adjusting the tape penetration angle into the servo signal writing head, between the servo signal writing head and the magnetic tape when recording the servo pattern. The friction coefficient of was adjusted. As a result, the σ _sw of the magnetic tape was adjusted to 23 nm. As described above, the magnetic tape on which the servo pattern was written was obtained.

[Example 2]
In the coating step, a magnetic pattern having an average thickness of 5.1 μm in which a servo pattern was written was formed in the same manner as in Example 1 except that the PEN film had an average thickness of 4.0 μm and the underlayer had an average thickness of 0.6 μm. Got the tape.

[Example 3]
In the calendering step, a magnetic tape on which a servo pattern was written was prepared in the same manner as in Example 1 except that the calendering conditions were adjusted to set the arithmetic average roughness Ra of the surface of the magnetic layer to 2.2 nm. Obtained.

[Example 4]
A servo pattern was obtained in the same manner as in Example 1 except that the drying conditions (drying temperature and drying time) of the magnetic layer-forming coating material were adjusted and the squareness ratio in the thickness direction (vertical direction) of the magnetic tape was set to 70%. A magnetic tape on which is written is obtained.

[Example 5]
In the coating step, in the same manner as in Example 1 except that the average thickness of the PEN film was 4.2 μm, the average thickness of the underlayer after calendering was 0.9 μm, and the average thickness of the magnetic layer after calendering was 70 nm. A magnetic tape having an average thickness of 5.6 μm, on which a servo pattern was written, was obtained.

[Example 6]
In the coating step, the same procedure as in Example 1 was repeated except that the average thickness of the PEN film was 4.2 μm, the average thickness of the underlayer after calendaring was 0.9 μm, and the average thickness of the magnetic layer after calendaring was 50 nm. A magnetic tape having an average thickness of 5.6 μm, on which a servo pattern was written, was obtained.

[Example 7]
In the transfer step, the BET specific surface area was set to 3.5 m ² /g by setting the temperature of the first and second heat treatments to 55° C. and the time of the first and second heat treatments to 10 hours. A magnetic tape on which a servo pattern was written was obtained in the same manner as in Example 1 except for the above.

[Example 8]
In the transfer step, the BET specific surface area is 7.0 m ² /g and the average fineness is set by setting the temperature of the first and second heat treatments to 70° C. and setting the time of the first and second heat treatments to 10 hours. A magnetic tape on which a servo pattern was written was obtained in the same manner as in Example 1 except that the hole diameter was 6.0 nm.

[Example 9]
In the step of writing the servo pattern, the coefficient of friction between the servo signal writing head and the magnetic tape is reduced as compared with the first embodiment, and thus the statistical value σ _SW indicating the nonlinearity of the servo pattern is set to 20 nm. A magnetic tape on which a servo pattern was written was obtained in the same manner as in Example 1 except for the above.

[Example 10]
In the step of writing the servo pattern, the coefficient of friction between the servo signal writing head and the magnetic tape was reduced as compared with that in Example 9 to set the statistical value σ _SW indicating the nonlinearity of the servo pattern to 15 nm. A magnetic tape on which a servo pattern was written was obtained in the same manner as in Example 1 except for the above.

[Example 11]
A servo pattern was obtained in the same manner as in Example 1 except that powder of strontium ferrite particles (hexagonal plate shape, aspect ratio 2.9, particle volume 1600 nm ³ ) was used as the magnetic powder in the step of preparing the coating material for forming the magnetic layer. A magnetic tape on which is written is obtained.

[Example 12]
A servo pattern was obtained in the same manner as in Example 1 except that ε iron oxide particle powder (spherical shape, aspect ratio 1.1, particle volume 1800 nm ³ ) was used as the magnetic powder in the process of preparing the coating for forming the magnetic layer. A written magnetic tape was obtained.

[Example 13]
A servo pattern was written in the same manner as in Example 1 except that cobalt ferrite powder (cubic shape, aspect ratio 1.7, particle volume 2000 nm ³ ) was used as the magnetic powder in the process of preparing the magnetic layer-forming coating material. Obtained magnetic tape.

[Example 14]
The drying conditions (drying temperature and drying time) of the magnetic layer-forming coating material were adjusted to set the squareness ratio in the thickness direction (vertical direction) of the magnetic tape to 70%, and in the transfer step, the first and second Except that the BET specific surface area was 3.5 m ² /g and the average pore diameter was 8.0 nm by setting the temperature of the heat treatment to 55° C. and the time of the first and second heat treatments to 10 hours. In the same manner as in Example 3, a magnetic tape having a servo pattern written therein was obtained.

[Example 15]
In the transfer step, the BET specific surface area is 7.0 m ² /g and the average fineness is set by setting the temperature of the first and second heat treatments to 70° C. and setting the time of the first and second heat treatments to 10 hours. A magnetic tape on which a servo pattern was written was obtained in the same manner as in Example 14 except that the hole diameter was 6.0 nm.

[Comparative Example 1]
In the servo pattern writing process, the tension of the magnetic tape is made higher than that in the first embodiment, and the coefficient of friction between the servo signal writing head and the magnetic tape is increased to show a statistical value indicating the non-linearity of the servo pattern. A magnetic tape on which a servo pattern was written was obtained in the same manner as in Example 1 except that σ _SW was set to 25 nm.

[Comparative example 2]
In the calendering step, a magnetic tape on which a servo pattern was written was prepared in the same manner as in Example 1 except that the calendering conditions were adjusted to set the arithmetic average roughness Ra of the surface of the magnetic layer to 3.0 nm. Obtained.

[Comparative Example 3]
A servo pattern was obtained in the same manner as in Example 1 except that the drying conditions (drying temperature and drying time) of the magnetic layer-forming coating material were adjusted and the squareness ratio in the thickness direction (vertical direction) of the magnetic tape was set to 60%. A magnetic tape on which is written is obtained.

[Comparative Example 4]
In the coating step, in the same manner as in Example 1 except that the average thickness of the PEN film was 4.2 μm, the average thickness of the underlayer after calendaring was 0.9 μm, and the average thickness of the magnetic layer after calendaring was 90 nm. A magnetic tape having an average thickness of 5.6 μm, on which a servo pattern was written, was obtained.

[Comparative Example 5]
In the transfer step, the temperature of the first and second heat treatments was set to 55° C., and the time of the first and second heat treatments was set to 10 hours, so that the BET specific surface area was 3.2 m ² /g and the average fineness. A magnetic tape on which a servo pattern was written was obtained in the same manner as in Example 1 except that the hole diameter was 9.0 nm.

[Comparative Example 6]
In the transfer step, first, the temperature of the second heat treatment and 70 ° C., first, by which the time of the second heat treatment is 20 hours, the BET specific surface area of 8.0 m ² / g, an average pore A magnetic tape on which a servo pattern was written was obtained in the same manner as in Example 1 except that the hole diameter was 6.0 nm.

[Evaluation]
(SNR)
The SNRs of the magnetic tapes of Examples 1 to 15 and Comparative Examples 1 to 6 (magnetic tape after writing the servo pattern) were evaluated as follows. The SNR (electromagnetic conversion characteristics) of the magnetic tape in a 25° C. environment was measured using a 1/2 inch tape running device (MTS Transport, manufactured by Mountain Engineering II) equipped with a recording/reproducing head and a recording/reproducing amplifier. A ring head having a gap length of 0.2 μm was used as the recording head, and a GMR head having a shield distance of 0.1 μm was used as the reproducing head. The relative speed was 6 m/s, the recording clock frequency was 160 MHz, and the recording track width was 2.0 μm. The SNR was calculated based on the method described in the following document. The results are shown in Table 2 as relative values with the SNR of Example 1 being 0 dB.
Y.Okazaki: “An Error Rate Emulation System.”, IEEE Trans. Man., 31, pp.3093-3095 (1995)

(Friction coefficient ratio)
The friction coefficient ratios (μ _B /μ _A ) and the friction coefficient ratios (μ _C (1000)/μ _C (5)) of the magnetic tapes of Examples 1 to 15 and Comparative Examples 1 to 6 were determined by the above-mentioned first embodiment. It evaluated by the evaluation method demonstrated in the form.

(Running stability (1))
The running stability of the magnetic tapes of Examples 1 to 15 and Comparative Examples 1 to 6 (magnetic tape after writing the servo pattern) was evaluated as follows. The magnetic tape was incorporated into the LTO cartridge. A so-called full volume test was performed on the LTO cartridge, in which data was recorded and reproduced on the entire surface of the magnetic tape by using an LTO drive connected to a server and a PC via SCSI and fiber channel. In the full volume test, the recording state of data was sequentially monitored, and when a problem occurred, information on the problem was recorded.

In the full volume test, if the running state of the magnetic tape is unstable, the drive automatically performs a so-called stop light to temporarily stop recording. When the stop write is performed, the data transfer rate drops. Further, in the full volume test, when the running state of the magnetic tape becomes further unstable, the drive automatically stops recording completely and becomes a so-called fail state.

For each of the magnetic tapes of Examples 1 to 15 and Comparative Examples 1 to 6, the full volume test was repeated 5 times in succession, and the "relative value of the transfer rate at the 5th full volume test" and "presence/absence of fail" were Was recorded. The relative value of the transfer rate in the full volume test is the ratio of the average transfer rate per full volume test to the transfer rate when the drive used for evaluation exhibited the maximum performance. The case where the maximum performance of the drive is demonstrated is 100%. For example, when the LTO8 drive is connected to the server via a fiber channel and recording is performed in the LTO8 format, the transfer rate when the LTO8 drive exhibits the maximum performance is 350 MB/sec. The “presence/absence of fail” is whether or not the above-mentioned fail state has occurred.

Each magnetic tape was evaluated according to the four-step evaluation criteria shown in Table 2 below. As shown in Table 2, level 4 means that it has the best driving stability and level 1 means that it has the worst driving stability. For example, when the relative value of the transfer rate of the magnetic tape is 95% or more and 100% or less in all of the fifth full volume tests and there is no failure, the magnetic tape is evaluated as level 4. Evaluation of Level 4 or 3 (that is, the transfer rate of the magnetic tape at the fifth time of the full volume test is 80% or more) is desirable from the viewpoint of good running stability of the magnetic tape.
The evaluation results of the running stability of each magnetic tape are shown in the column of "Running stability (1)" in Table 3.

Table 2 shows the details of the four criteria for judging the running stability.

(Running stability (2))
The running stability of the magnetic tapes of Examples 1 to 15 and Comparative Examples 1 to 6 (magnetic tape after writing the servo pattern) was evaluated as follows. First, as a cartridge, a cartridge memory is provided which has a memory area for writing tension adjustment information in a memory, and which is capable of writing tension adjustment information to the area and reading tension adjustment information from the area by a controller. Prepared. The size of this cartridge was the same size (102 mm×105 mm×22 mm) as the cartridge used in the evaluation of running stability (1).

Next, a full volume test was performed in the same manner as in "Running stability (1)" above, except that the tension in the longitudinal direction of the magnetic tape was adjusted when recording and reproducing data on the entire surface of the magnetic tape. Next, the running stability was evaluated in four levels of Levels 1 to 4 in the same manner as in the above "Running stability (1)".
The evaluation results of the running stability of each magnetic tape are shown in the column of "Running stability (2)" in Table 3.

The tension adjustment in the longitudinal direction of the magnetic tape was performed as follows. That is, while reciprocating the magnetic tape by the recording/reproducing apparatus, two or more rows of servo bands (servo tracks) are reproduced at the same time, and the reproduced waveform shape of each C-shaped servo pattern row (servo signal) of those servo bands is reproduced. From this, the intervals of the servo pattern trains during running were continuously measured (at each point having servo position information (specifically, about every 6 mm)). Then, the rotational drive of the spindle drive device and the reel drive device is controlled based on the measured distance information of the servo pattern train, and the tension in the longitudinal direction of the magnetic tape is adjusted so that the space between the servo pattern trains approaches the specified width. Was adjusted automatically. Here, the “specified width” means a distance between two servo read heads included in the recording/reproducing apparatus. When the magnetic tape is running, the two servo read heads are respectively located in the two servo bands located above and below the data band.

(Young's modulus)
The Young's modulus of the magnetic tapes of Examples 1 to 15 and Comparative Examples 1 to 6 were measured by the Young's modulus measuring method described in the first embodiment.

ＰＥＮ：ポレエチレンナフタレート
ＴＣ：Tension control Table 3 shows the configurations and evaluation results of the magnetic tapes of Examples 1 to 15 and Comparative Examples 1 to 6.

PEN: Polyethylene naphthalate TC: Tension control

The results of the above evaluation reveal the following.
When the total BET specific surface area of the magnetic tape measured in a state where the magnetic tape is washed and dried is out of the range of 3.5 m ² /g or more and 7.0 m ² /g or less, running stability decreases ( Examples 1, 7, 8 and Comparative Examples 5, 6).
When the statistical value σ _SW indicating the non-linearity of the servo pattern string (servo band) exceeds 24 nm, the running stability decreases (Examples 1, 9, 10 and Comparative Example 1).
When the arithmetic average roughness Ra of the surface of the magnetic layer exceeds 2.5 nm, the electromagnetic conversion characteristics (SNR) deteriorate (Examples 1, 3 and Comparative Example 2).
If the squareness ratio of the magnetic layer in the vertical direction is less than 65%, the electromagnetic conversion characteristics (SNR) deteriorate (Examples 1, 4 and Comparative Example 3).
When the average thickness of the magnetic layer exceeds 80 nm, the electromagnetic conversion characteristics (SNR) deteriorate (Examples 1, 5, 6 and Comparative Example 4).

Therefore, in order to achieve both excellent running stability and electromagnetic conversion characteristics in a magnetic tape having an average thickness of 5.6 μm or less, the entire BET specific surface area of the magnetic tape is 3.5 m ² /g or more and 7.0 m or less. ² /g or less, the statistic value σ _SW indicating the non-linearity of the servo pattern is 24 nm or less, the arithmetic average roughness Ra of the surface of the magnetic layer is 2.5 nm or less, and the rectangular shape of the magnetic layer in the vertical direction. The ratio is 65% or more, and the average thickness of the magnetic layer is 80 nm or less.

Even if strontium ferrite particle powder is used instead of barium ferrite particle powder as the magnetic powder, the BET specific surface area, statistical value σ _SW, arithmetic mean roughness Ra, squareness ratio and average thickness of the magnetic layer satisfy the above numerical range. In a magnetic tape having an average thickness of 5.6 μm or less, excellent running stability and electromagnetic conversion characteristics can both be achieved (Examples 1 and 11).

Even when ε iron oxide particle powder or cobalt ferrite particle powder is used instead of hexagonal ferrite particle powder (barium ferrite particle powder, strontium ferrite particle powder) as magnetic powder, BET specific surface area, statistical value σ _SW, arithmetic When the average roughness Ra, the squareness ratio, and the average thickness of the magnetic layer satisfy the above numerical ranges, the magnetic tape having an average thickness of 5.6 μm or less can have both excellent running stability and electromagnetic conversion characteristics. Yes (Examples 1, 12, 13).

When the BET specific surface area, the statistical value σ _{SW, the} arithmetic average roughness Ra, the squareness ratio and the average thickness of the magnetic layer satisfy the above numerical ranges, the average thickness is 5.6 μm even when the tension of the magnetic tape is adjusted. It is the following, and it is possible to achieve both excellent running stability and electromagnetic conversion characteristics in the magnetic tape (Example 1).

In order to obtain more excellent running stability in a magnetic tape having an average thickness of 5.6 μm or less, it is preferable that the statistical value σ _SW indicating the nonlinearity of the servo pattern string (servo band) is 20 nm or less. (Examples 1, 9, 10).
In order to obtain more excellent electromagnetic conversion characteristics, it is preferable that the arithmetic average roughness Ra of the surface of the magnetic layer is 2.2 nm or less (Examples 1 and 3).
In order to obtain more excellent electromagnetic conversion characteristics, it is preferable that the squareness ratio of the magnetic layer in the vertical direction is 70% or more (Examples 1 and 4).

When the friction coefficient ratio (μ _B /μ _A ) is in the range of 1.0 or more and 2.0 or less, excellent running stability can be obtained even when tension control is applied to a magnetic tape having an average thickness of 5.6 μm or less. (Examples 1, 8, 14, 15 and Comparative Examples 5, 6).
When the friction coefficient ratio (μ _C (1000)/μ _C (5) is in the range of 1.0 or more and 2.0 or less, a full volume test is performed 5 times on a magnetic tape having an average thickness of 5.6 μm or less. After running (that is, even after passing a magnetic tape having an average thickness of 5.6 μm or less more than 1000 times), excellent running stability is obtained (Examples 1, 3, 7, 14, 15 and comparison). Examples 5, 6).

Although the embodiment and the modified example of the present disclosure have been specifically described above, the present disclosure is not limited to the above-described embodiment and the modified example, and various modifications based on the technical idea of the present disclosure are possible. Is. For example, the configurations, methods, steps, shapes, materials, numerical values, and the like described in the above-described embodiments and modifications are merely examples, and configurations, methods, steps, shapes, materials, numerical values, etc. different from these may be used as necessary. May be used. The configurations, methods, steps, shapes, materials, numerical values, and the like of the above-described embodiments and modified examples can be combined with each other without departing from the gist of the present disclosure.

The chemical formulas of the compounds and the like exemplified in the above-described embodiments and modified examples are representative ones, and the valences and the like described are not limited as long as they are common names of the same compounds. In the numerical ranges described stepwise in the above-described embodiments and modifications, the upper limit value or the lower limit value of the numerical range of a certain stage may be replaced with the upper limit value or the lower limit value of the numerical range of another stage. The materials exemplified in the above-described embodiments and modifications can be used alone or in combination of two or more unless otherwise specified.

Further, the present disclosure may also adopt the following configurations.
(1)
A tape-shaped magnetic recording medium,
A substrate,
A base layer provided on the base,
A magnetic layer provided on the underlayer,
The substrate comprises polyester,
The underlayer and the magnetic layer include a lubricant,
The magnetic layer has a surface provided with a large number of holes,
The arithmetic average roughness Ra of the surface is 2.5 nm or less,
The BET specific surface area of the entire magnetic recording medium measured in a state where the magnetic recording medium is washed and dried is 3.5 m ² /g or more and 7.0 m ² /g or less,
The squareness ratio of the magnetic layer in the vertical direction is 65% or more,
The average thickness of the magnetic layer is 80 nm or less,
The average thickness of the magnetic recording medium is 5.6 μm or less,
A magnetic recording medium in which a servo pattern is recorded on the magnetic layer, and a statistical value σ _SW indicating the nonlinearity of the servo pattern is 24 nm or less.
(2)
The magnetic recording medium according to (1), wherein the statistical value σ _SW is 23 nm or less.
(3)
The magnetic recording medium according to (1), wherein the statistical value σ _SW is 20 nm or less.
(4)
The magnetic recording medium according to any one of (1) to (3), wherein the squareness ratio is 70% or more.
(5)
The magnetic recording medium according to any one of (1) to (4), wherein the arithmetic average roughness Ra is 2.2 nm or less.
(6)
Coefficient of dynamic friction μ _A between the surface of the magnetic layer and the magnetic head when the tension applied to the magnetic recording medium is 1.2 N, and the magnetic layer when the tension applied to the magnetic recording medium is 0.4 N The friction coefficient ratio (μ _B /μ _A ) between the surface of the magnetic head and the dynamic friction coefficient μ _B between the magnetic head and the magnetic head is 1.0 or more and 2.0 or less. (1) to (5) Magnetic recording medium.
(7)
Regarding the dynamic friction coefficient μ _C between the surface of the magnetic layer and the magnetic head when the tension applied to the magnetic recording medium is 0.6 N, the dynamic friction coefficient μ _C (5) at the fifth running time and the dynamic friction coefficient at the 1,000th running time mu _C (1000) and the friction coefficient ratio _{(μ C (1000) / μ} C (5)) , the magnetic recording according to any one of 1.0 to 2.0 (1) (6) Medium.
(8)
The magnetic recording medium according to any one of (1) to (7), wherein the entire average pore diameter of the magnetic recording medium measured in a state where the magnetic recording medium is washed and dried is 6 nm or more and 11 nm or less. Medium.
(9)
The magnetic recording medium according to any one of (1) to (8), wherein the coercive force Hc of the magnetic layer in the longitudinal direction is 2000 Oe or less.
(10)
The magnetic recording medium according to any one of (1) to (9), wherein the magnetic layer has five or more servo bands.
(11)
The magnetic recording medium according to (10), wherein the ratio of the total area of the servo band to the area of the surface is 4.0% or less.
(12)
The width of the servo band is the magnetic recording medium according to (10) or (11), which is 95 μm or less.
(13)
The magnetic layer is configured to form a plurality of data tracks,
The magnetic recording medium according to any one of (1) to (12), wherein the width of the data track is 2.0 μm or less.
(14)
The magnetic recording medium according to any one of (1) to (13), wherein the magnetic layer is capable of recording data such that the minimum value of the inter-reversal distance L is 48 nm or less.
(15)
The magnetic recording medium according to any one of (1) to (14), wherein the average thickness of the substrate is 4.2 μm or less.
(16)
The lubricant contains at least one selected from fatty acids and fatty acid esters,
(1) to (15), wherein the fatty acid contains a compound represented by the following general formula (1) or (2), and the fatty acid ester contains a compound represented by the following general formula (3) or (4) The magnetic recording medium according to any one of the above.
CH ₃ (CH ₂ ) _k COOH (1)
(However, in the general formula (1), k is an integer selected from the range of 14 or more and 22 or less.)
_{CH 3 (CH 2) n CH} = CH (CH 2) m COOH ··· (2)
(However, in the general formula (2), the sum of n and m is an integer selected from the range of 12 or more and 20 or less.)
_{CH 3 (CH 2) p COO} (CH 2) q CH 3 ··· (3)
(However, in the general formula (3), p is an integer selected from the range of 14 to 22 and q is an integer selected from the range of 2 to 5).
_{CH 3 (CH 2) r COO-} (CH 2) s CH (CH 3) 2 ··· (4)
(However, in the general formula (4), r is an integer selected from the range of 14 to 22 and s is an integer selected from the range of 1 to 3).
(17)
The magnetic layer contains magnetic powder,
The magnetic recording medium according to any one of (1) to (16), wherein the magnetic powder contains hexagonal ferrite, ε iron oxide, or Co-containing spinel ferrite.
(18)
The hexagonal ferrite contains at least one of Ba and Sr,
The magnetic recording medium according to (17), wherein the ε iron oxide contains at least one of Al and Ga.
(19)
The magnetic recording medium according to any one of (1) to (18),
A storage unit having an area for writing adjustment information for adjusting the tension applied in the longitudinal direction of the magnetic recording medium.
(20)
A communication unit that communicates with the recording/reproducing device,
The adjustment information received from the recording/reproducing apparatus via the communication unit is stored in the area, and the adjustment information is read from the area in response to a request from the recording/reproducing apparatus, and is transmitted via the communication unit. The cartridge according to (19), further comprising: a control unit for transmitting to the recording/reproducing apparatus.

10 Cartridge 11 Cartridge Memory 31 Antenna Coil 32 Rectification/Power Supply Circuit 33 Clock Circuit 34 Detection/Modulation Circuit 35 Controller 36 Memory 36A First Storage Area 36B Second Storage Area 41 Base Body 42 Underlayer 43 Magnetic Layer 44 Back Layer 50, 50A recording/reproducing apparatus 51 spindle 51
52 reel 52
53 spindle drive device 54 reel drive device 55 guide roller 56 magnetic head 57 reader/writer 58 communication interface 59 controller 60 network 61 hygrometer 61
62 PC
63 thermometer 64 hygrometer 100, 100A recording/reproducing system 110 servo frame 111 servo sub-frame 1
111A A burst 111B B burst 112 Servo subframe 2
112C C burst 112C C burst 113 Servo stripe MT Magnetic tape SB Servo band DB Data bind

Claims (36)

A tape-shaped magnetic recording medium,
A substrate,
A base layer provided on the base,
A magnetic layer provided on the underlayer ,
A back layer provided on the surface of the base opposite to the base layer ,
The substrate contains polyester, and the average thickness of the substrate is 4.2 μm or less,
The underlayer and the magnetic layer include a lubricant,
Arithmetic average roughness Ra of the magnetic layer table surface is at 2.5nm or less,
The BET specific surface area of the entire magnetic recording medium measured in a state where the magnetic recording medium is washed and dried is 3.5 m ² /g or more and 7.0 m ² /g or less,
The squareness ratio of the magnetic layer in the vertical direction is 65% or more,
The average thickness of the magnetic layer is 80 nm or less,
The average thickness of the magnetic recording medium is 5.6 μm or less,
A magnetic recording medium in which a servo pattern is recorded on the magnetic layer, and a statistical value σ _SW indicating the nonlinearity of the servo pattern is 24 nm or less. A tape-shaped magnetic recording medium,
A substrate,
A base layer provided on the base,
A magnetic layer provided on the underlayer ,
A back layer provided on the surface of the base opposite to the base layer ,
The substrate comprises polyester,
The underlayer and the magnetic layer include a lubricant,
Arithmetic average roughness Ra of the magnetic layer table surface is at 2.5nm or less,
The BET specific surface area of the entire magnetic recording medium measured in a state where the magnetic recording medium is washed and dried is 4.5 m ² /g or more and 7.0 m ² /g or less,
The squareness ratio of the magnetic layer in the vertical direction is 65% or more,
The average thickness of the magnetic layer is 80 nm or less,
The average thickness of the magnetic recording medium is 5.6 μm or less,
A magnetic recording medium in which a servo pattern is recorded on the magnetic layer, and a statistical value σ _SW indicating the nonlinearity of the servo pattern is 24 nm or less. The statistical value sigma _SW to a magnetic recording medium according to claim 1 or 2 or less 23 nm. The statistical value sigma _SW to a magnetic recording medium according to claim 1 or 2 is 20nm or less. The squareness ratio, the magnetic recording medium according to claim 1 or 2 is 70% or more. The arithmetic average roughness Ra, a magnetic recording medium according to claim 1 or 2 or less 2.2 nm. Coefficient of dynamic friction μ _A between the surface of the magnetic layer and the magnetic head when the tension applied to the magnetic recording medium is 1.2 N, and the magnetic layer when the tension applied to the magnetic recording medium is 0.4 N 3. The magnetic recording medium according to claim 1, wherein a friction coefficient ratio (μ _B /μ _A ) between the surface of the magnetic head and the dynamic friction coefficient μ _B between the magnetic head and the magnetic head is 1.0 or more and 2.0 or less. Regarding the dynamic friction coefficient μ _C between the surface of the magnetic layer and the magnetic head when the tension applied to the magnetic recording medium is 0.6 N, the dynamic friction coefficient μ _C (5) at the fifth running time and the dynamic friction coefficient at the 1,000th running time mu _C (1000) and the friction coefficient ratio _{(μ C (1000) / μ} C (5)) , the magnetic recording medium according to claim 1 or 2 is 1.0 or more and 2.0 or less. The magnetic recording medium according to claim 1 or 2 , wherein an average pore diameter of the entire magnetic recording medium measured in a state where the magnetic recording medium is washed and dried is 6 nm or more and 11 nm or less. The magnetic coercive force Hc of the magnetic layer in the longitudinal direction of the recording medium, a magnetic recording medium according to claim 1 or 2 or less 2000 Oe. The magnetic layer, the magnetic recording medium according to claim 1 or 2 having five or more servo bands. The magnetic recording medium according to claim 11 , wherein the ratio of the total area of the servo bands to the area of the surface of the magnetic layer is 4.0% or less. The magnetic recording medium according to claim 11 , wherein the width of the servo band is 95 μm or less. The magnetic layer is configured to form a plurality of data tracks,
The width of the data track, magnetic recording medium according to claim 1 or 2 is 2000nm or less. The magnetic recording medium according to claim 1 or 2 , wherein the magnetic layer is configured to record data such that the minimum value of the distance L between magnetization reversals is 48 nm or less. The average thickness of the back layer, the magnetic recording medium according to claim 1 or 2 is 0.6μm or less. The lubricant contains at least one selected from fatty acids and fatty acid esters,
It includes compounds wherein the fatty acid is represented by the following general formula (1) or (2), and, wherein the fatty acid ester according to claim 1 or 2 comprising a compound represented by the following general formula (3) or (4) Magnetic recording medium.
CH ₃ (CH ₂ ) _k COOH (1)
(However, in the general formula (1), k is an integer selected from the range of 14 or more and 22 or less.)
_{CH 3 (CH 2) n CH} = CH (CH 2) m COOH ··· (2)
(However, in the general formula (2), the sum of n and m is an integer selected from the range of 12 or more and 20 or less.)
_{CH 3 (CH 2) p COO} (CH 2) q CH 3 ··· (3)
(However, in the general formula (3), p is an integer selected from the range of 14 to 22 and q is an integer selected from the range of 2 to 5).
_{CH 3 (CH 2) r COO-} (CH 2) s CH (CH 3) 2 ··· (4)
(However, in the general formula (4), r is an integer selected from the range of 14 to 22 and s is an integer selected from the range of 1 to 3). The magnetic layer contains magnetic powder,
The magnetic powder, the magnetic recording medium according to claim 1 or 2 comprising a hexagonal ferrite, epsilon iron oxide or Co-containing spinel ferrite. The hexagonal ferrite contains at least one of Ba and Sr,
The magnetic recording medium according to claim 18 , wherein the ε iron oxide contains at least one of Al and Ga. The magnetic recording medium according to claim 1, wherein the average thickness of the magnetic recording medium is 5.1 μm or less. The magnetic recording medium according to claim 1, wherein the average thickness of the magnetic recording medium is 5.0 μm or less. The magnetic recording medium according to claim 1, wherein the average thickness of the magnetic recording medium is 4.6 μm or less. The magnetic recording medium according to claim 1, wherein the average thickness of the magnetic layer is 35 nm or more and 50 nm or less. The entire BET specific surface area of the magnetic recording medium is 4.0 m. ^Two /G or more 7.0m ^Two The magnetic recording medium according to claim 1, which is equal to or less than /g. The BET specific surface area of the entire magnetic recording medium is 4.5 m ^Two /G or more 7.0m ^Two The magnetic recording medium according to claim 1, which is equal to or less than /g. The BET specific surface area of the entire magnetic recording medium is 5.0 m ^Two /G or more 7.0m ^Two /G or less, The magnetic recording medium according to claim 1 or 2. The magnetic recording medium according to claim 1 or 2, wherein the average pore diameter of the entire magnetic recording medium measured in a state where the magnetic recording medium is washed and dried is 7 nm or more and 10 nm or less. The magnetic recording medium according to claim 2, wherein the average thickness of the substrate is 4.2 μm or less. The magnetic recording medium according to claim 1, wherein the average thickness of the substrate is 3.8 μm or less. The magnetic recording medium according to claim 1, wherein the average thickness of the substrate is 3.4 μm or less. The magnetic layer contains magnetic powder,
The magnetic recording medium according to claim 1, wherein the average particle size of the magnetic powder is 12 nm or more and 25 nm or less. The magnetic recording medium according to claim 31, wherein the average particle size of the magnetic powder is 15 nm or more and 22 nm or less. The magnetic recording medium according to claim 31, wherein the average particle size of the magnetic powder is 15 nm or more and 20 nm or less. The magnetic recording medium according to claim 31, wherein the average particle size of the magnetic powder is 15 nm or more and 18 nm or less. The magnetic recording medium according to any one of claims 1 to 34 ,
A storage unit having an area for writing adjustment information for adjusting the tension applied in the longitudinal direction of the magnetic recording medium. A communication unit that communicates with the recording/reproducing device,
The adjustment information received from the recording/reproducing apparatus via the communication unit is stored in the area, and the adjustment information is read from the area in response to a request from the recording/reproducing apparatus, and is transmitted via the communication unit. 36. The cartridge according to claim 35 , further comprising: a control unit for transmitting to the recording/reproducing apparatus.

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