Magnetic recording media and cartridges

Abstract

Provided is a tape-form magnetic recording medium with which it is possible to correct any change in the width of the magnetic recording medium by adjusting the transport tension of the magnetic recording medium, even when the magnetic recording medium is stored or transported in a high-temperature environment.　In this tape-form magnetic recording medium, the average amount of change in the width of the magnetic recording medium before and after the magnetic recording medium is allowed to stand for 40 hours in an environment having a temperature of 50°C and a relative humidity of 40% RH while 0.55 N of tension is applied in the longitudinal direction is 170 ppm or less, and the average tension responsiveness with respect to longitudinal-direction tension in an environment having a temperature of 50°C and a relative humidity of 40% RH is 700 ppm / N or greater.

Description

[Technical Field]

[0001] The present disclosure relates to a magnetic recording medium and a cartridge including the same. [Background technology]

[0002] As demand for archiving increases, tape-type magnetic recording media with high total capacity are being incorporated into cloud systems. Current tape-type magnetic recording media have a narrower environmental temperature range for running and storing data than hard disk drives (HDDs) and semiconductor memories. Therefore, it is desirable to expand the environmental temperature range for running and storing tape-type magnetic recording media. It is believed that if tape-type magnetic recording media could be used in the same temperature environment as HDDs and semiconductor memories, the range of uses for tape-type magnetic recording media would be greatly expanded.

[0003] In tape-type magnetic recording media, if the width dimension of the magnetic recording medium changes significantly due to environmental changes, off-track occurs, making it difficult to ensure stable recording and reproduction characteristics. Patent Document 1 proposes a tape-type magnetic recording medium that can correct width changes by adjusting the longitudinal tension of the tape-type magnetic recording medium using a recording and reproduction device, even if the width dimension of the tape-type magnetic recording medium changes due to environmental changes. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-173882 Summary of the Invention [Problem to be solved by the invention]

[0005] For HDDs, the upper limit temperature for guaranteed operation is generally assumed to be 50°C, but conventional tape-type magnetic recording media are not assumed to be stored or run in such high-temperature environments. Patent Document 1 also does not assume storage or running in such high-temperature environments. For this reason, if conventional tape-type magnetic recording media are stored or run in high-temperature environments, there is a risk that the width change of the tape will exceed the range that can be corrected by adjusting the running tension, making it difficult to correct the width change.

[0006] The object of the present disclosure is to provide a tape-shaped magnetic recording medium and a cartridge equipped with the same that can correct changes in the width of the magnetic recording medium by adjusting the running tension of the magnetic recording medium, even when the magnetic recording medium is stored or run in a high-temperature environment. [Means for solving the problem]

[0007] In order to solve the above problems, the first disclosure is: A tape-shaped magnetic recording medium, This magnetic recording medium has an average width change of 170 ppm or less before and after being left standing for 40 hours in an environment of 50°C temperature and 40% RH relative humidity with a tension of 0.55 N applied in the longitudinal direction, and also has an average tension response to longitudinal tension in an environment of 50°C temperature and 40% RH relative humidity of 700 ppm / N or more.

[0008] The second disclosure is: the magnetic recording medium of the first disclosure; a storage unit configured to be able to write adjustment information for adjusting the tension applied to the magnetic recording medium in the longitudinal direction; A cartridge comprising: [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is an exploded perspective view showing an example of the configuration of a cartridge according to a first embodiment of the present disclosure. [Figure 2] FIG. 2 is a block diagram showing an example of the configuration of the cartridge memory. [Figure 3] FIG. 3 is a cross-sectional view showing an example of the configuration of a magnetic tape. [Figure 4] FIG. 4 is a schematic diagram showing an example of the layout of the data band and the servo band. [Figure 5] FIG. 5 is an enlarged view showing an example of the configuration of a data band. [Figure 6] FIG. 6 is an enlarged view showing an example of the configuration of a servo band. [Figure 7] FIG. 7 is a perspective view showing an example of the shape of a particle. [Figure 8] FIG. 8 is a diagram showing an example of a TEM photograph of the magnetic layer. [Figure 9] FIG. 9 is a diagram showing an example of a TEM photograph of the magnetic layer. [Figure 10] FIG. 10 is a perspective view showing the configuration of the measuring device. [Figure 11] FIG. 11 is a schematic diagram showing an example of the configuration of a recording and reproducing system. [Figure 12] FIG. 12 is a flowchart for explaining an example of the operation of the recording / reproducing device when recording data. [Figure 13] FIG. 13 is a flowchart for explaining an example of the operation of the recording / reproducing device when reproducing data. [Figure 14] FIG. 14 is a cross-sectional view showing an example of the configuration of a magnetic tape according to the second embodiment of the present disclosure. [Figure 15] FIG. 15 is a schematic diagram showing the configuration of a sputtering apparatus. [Figure 16] FIG. 16 is a cross-sectional view showing an example of the configuration of a magnetic tape according to the third embodiment of the present disclosure. [Figure 17] FIG. 17 is an exploded perspective view showing an example of the configuration of a cartridge according to a modified example of the first embodiment of the present disclosure. [Figure 18] FIG. 18 is a graph showing the measurement results of the amount of change in width of the magnetic tapes according to Examples 1 to 3 and Comparative Examples 1 to 3. [Figure 19]FIG. 19 is a graph showing the measurement results of the amount of change in width of the magnetic tape according to Example 1. [Figure 20] FIG. 20 is a graph showing the results of measuring the storage modulus E′ of a reinforced PET film and a PEN film. DETAILED DESCRIPTION OF THE INVENTION

[0010] The embodiments of the present disclosure will be described in the following order. 1. First embodiment (example of coated magnetic tape) 1.1 Cartridge Configuration 1.2 Cartridge Memory Configuration 1.3 Magnetic Tape Configuration 1.4 Magnetic tape manufacturing method 1.5 Effects 2. Second embodiment (example of vacuum thin film magnetic tape) 2.1 Magnetic Tape Structure 2.2 Configuration of the sputtering equipment 2.3 Magnetic tape manufacturing method 2.4 Effects 3 Third embodiment (example of vacuum thin film magnetic tape) 3.1 Magnetic Tape Structure 3.2 Effects 4. Variations

[0011] In this specification, unless a measurement environment is specifically stated in the description of the measurement method, measurements are performed in an environment of 25°C ± 2°C and 50% RH ± 5% RH. Furthermore, in this specification, numerical ranges indicated using "from" indicate ranges that include the numerical values ​​before and after "from" as the minimum and maximum values, respectively.

[0012] <1 First Embodiment> [1.1 Cartridge configuration] 1 is an exploded perspective view showing an example of the configuration of a cartridge 10. The cartridge 10 is a single-reel cartridge, and includes a cartridge case 12 composed of a lower shell 12A and an upper shell 12B, a reel 13 on which a tape-like magnetic recording medium (hereinafter referred to as "magnetic tape") MT is wound, a reel lock 14 and a reel spring 15 for locking the rotation of the reel 13, a spider 16 for unlocking the locked state of the reel 13, a sliding door 17 for opening and closing a tape outlet 12C provided in the cartridge case 12 across the lower shell 12A and the upper shell 12B, a door spring 18 for biasing the sliding door 17 to a closed position of the tape outlet 12C, a write protect 19 for preventing accidental erasure, and a cartridge memory 11. The reel 13 for winding the magnetic tape MT is generally disc-shaped with an opening in the center, and is composed of a reel hub 13A and a flange 13B made of a hard material such as plastic. A leader tape LT is connected to the outer peripheral end of the magnetic tape MT, and a leader pin 20 is provided at the tip of the leader tape LT.

[0013] The cartridge 10 may be a magnetic tape cartridge that conforms to the LTO (Linear Tape-Open) standard, or may be a magnetic tape cartridge that conforms to a standard other than the LTO standard.

[0014] The cartridge memory 11 is provided near one corner of the cartridge 10. When the cartridge 10 is loaded into the recording / playback device, the cartridge memory 11 faces the reader / writer of the recording / playback device. The cartridge memory 11 communicates with the recording / playback device, specifically the reader / writer, using a wireless communication standard that complies with the LTO standard.

[0015] [1.2 Cartridge Memory Configuration] 2 is a block diagram showing an example of the configuration of the cartridge memory 11. The cartridge memory 11 includes an antenna coil (communication unit) 31 that communicates with a reader / writer using a specified communication standard; a rectification / power circuit 32 that generates power by rectifying and generating electricity from radio waves received by the antenna coil 31 using induced electromotive force; a clock circuit 33 that generates a clock from the radio waves received by the antenna coil 31 using induced electromotive force; a detection / modulation circuit 34 that detects the radio waves received by the antenna coil 31 and modulates the signal to be transmitted by the antenna coil 31; a controller (control unit) 35 that is composed of logic circuits and the like for identifying and processing commands and data from the digital signal extracted from the detection / modulation circuit 34; and a memory (storage unit) 36 that stores information. The cartridge memory 11 also includes a capacitor 37 connected in parallel to the antenna coil 31, and the antenna coil 31 and capacitor 37 form a resonant circuit.

[0016] The memory 36 stores information related to the cartridge 10. The memory 36 is a non-volatile memory (NVM). The memory 36 preferably has a storage capacity of approximately 32 KB or more.

[0017] The memory 36 may have a first memory area 36A and a second memory area 36B. The first memory area 36A is an area for storing first information. The first information includes, for example, at least one type selected from the group consisting of manufacturing information of the cartridge 10 (e.g., a unique number of the cartridge 10) and a usage history of the cartridge 10 (e.g., the number of times the magnetic tape MT has been pulled out (thread count)). The second memory area 36B is an area for storing second information. The second information includes, for example, at least one type selected from the group consisting of tension adjustment information, management ledger data, index information, thumbnail information, etc.

[0018] The tension adjustment information is information for adjusting the tension applied to the magnetic tape MT in the longitudinal direction. The tension adjustment information includes, for example, at least one type of information selected from the group consisting of information obtained by intermittently measuring the width between servo bands in the longitudinal direction of the magnetic tape MT, tension information of the recording / playback device, and temperature and humidity information of the recording / playback device. This information may be managed in conjunction with information on the usage status of the cartridge 10. The tension adjustment information is preferably obtained when recording data to the magnetic tape MT or before recording data. The tension information of the recording / playback device means information on the tension applied to the magnetic tape MT in the longitudinal direction.

[0019] The management ledger data is data that includes at least one of the following: the capacity, creation date, edit date, and storage location of the data file recorded on the magnetic tape MT. The index information is metadata, etc., for searching the contents of the data file. The thumbnail information is a thumbnail of the video or still image stored on the magnetic tape MT. In the following description, the information stored in the first memory area 36A may be referred to as "first information," and the information stored in the second memory area 36B may be referred to as "second information."

[0020] The memory 36 may have a plurality of banks. In this case, some of the plurality of banks may constitute a first storage area 36A, and the remaining banks may constitute a second storage area 36B.

[0021] The antenna coil 31 induces an induced voltage by electromagnetic induction. The controller 35 communicates with the recording / playback device in accordance with a specified communication standard via the antenna coil 31. Specifically, for example, mutual authentication, sending and receiving of commands, data exchange, etc. are performed.

[0022] The controller 35 stores information received from the recording / playback device via the antenna coil 31 in the memory 36. For example, the controller 35 stores tension adjustment information received from the recording / playback device via the antenna coil 31 in the second storage area 36B of the memory 36. In response to a request from the recording / playback device, the controller 35 reads information from the memory 36 and transmits the information to the recording / playback device via the antenna coil 31. For example, in response to a request from the recording / playback device, the controller 35 reads tension adjustment information from the second storage area 36B of the memory 36 and transmits the information to the recording / playback device via the antenna coil 31.

[0023] 1.3 Magnetic Tape Structure FIG. 3 is a cross-sectional view showing an example of the configuration of a magnetic tape MT. The magnetic tape MT includes a long substrate 41, an underlayer 42 provided on one main surface (first main surface) of the substrate 41, a magnetic layer 43 provided on the underlayer 42, and a back layer 44 provided on the other main surface (second main surface) of the substrate 41. The underlayer 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 preferably contains a lubricant from the viewpoint of improving running performance. The lubricant may be contained in at least one of the underlayer 42 and the magnetic layer 43.

[0024] The magnetic tape MT may conform to the LTO standard, or may conform to a standard other than the LTO standard. The width of the magnetic tape MT may be 1 / 2 inch, or may be wider than 1 / 2 inch. If the magnetic tape MT conforms to the LTO standard, the width of the magnetic tape MT is 1 / 2 inch. The magnetic tape MT may be configured to be able to keep the width of the magnetic tape MT constant or approximately constant by adjusting the tension applied to the magnetic tape MT in the longitudinal direction during running using a recording / playback device (drive).

[0025] The magnetic tape MT is long and runs longitudinally during recording and playback. The magnetic tape MT is preferably used in a recording and playback device equipped with a ring-type head as a recording head. The magnetic tape MT is preferably used in a recording and playback device configured to be able to record data with a data track width of 1500 nm or less or 1000 nm or less.

[0026] (Base) The substrate 41 is a non-magnetic support that supports the underlayer 42 and the magnetic layer 43. The substrate 41 has the shape of a long film. The upper limit of the average thickness of the substrate 41 is, for example, 4.4 μm or less, preferably 4.2 μm or less, more preferably 4.0 μm or less, even more preferably 3.8 μm or less, particularly preferably 3.6 μm or less, and most preferably 3.4 μm or less. If the upper limit of the average thickness of the substrate 41 is 4.4 μm or less, the recording capacity that can be recorded in one data cartridge can be increased compared to that of general magnetic tape. The lower limit of the average thickness of the substrate 41 is preferably 3 μm or more, more preferably 3.2 μm or more. If the lower limit of the average thickness of the substrate 41 is 3 μm or more, a decrease in the strength of the substrate 41 can be suppressed.

[0027] The average thickness of the substrate 41 is determined as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and three 250 mm lengths of the magnetic tape MT are cut out from the longitudinal range of 10 m to 20 m, 30 m to 40 m, and 50 m to 60 m from the joint 21 between the magnetic tape MT and the leader tape LT, to prepare three samples. In this specification, the "longitudinal direction" in the "longitudinal direction from the joint 21 between the magnetic tape MT and the leader tape LT" refers to the direction from one end on the leader tape LT side to the other end on the opposite side.

[0028] Next, the layers other than the substrate 41 of each sample (i.e., the underlayer 42, magnetic layer 43, and back layer 44) are removed with a solvent such as MEK (methyl ethyl ketone) or dilute hydrochloric acid. Next, using a Mitutoyo Laser Hologram (LGH-110C) as a measuring device, the thickness of each sample (substrate 41) is measured at five positions, and the measured values ​​(a total of 15 sample thicknesses) are arithmetically averaged to calculate the average thickness of the substrate 41. The five measurement positions are selected randomly from each sample so that they are different positions in the longitudinal direction of the magnetic tape MT.

[0029] The substrate 41 includes, for example, at least one of polyesters, polyolefins, cellulose derivatives, vinyl resins, and other polymer resins. When the substrate 41 includes two or more of the above materials, the two or more materials may be mixed, copolymerized, or laminated.

[0030] Of the above polymer resins, the substrate 41 preferably contains polyesters. By including polyesters in the substrate 41, the storage modulus E' of the substrate 41 in the longitudinal direction can be reduced to preferably 9.0 GPa or less, more preferably 7.5 GPa or less, even more preferably 6.0 GPa or less, particularly preferably 5.5 GPa or less, and most preferably 4.5 GPa or less. Therefore, by adjusting the longitudinal tension of the magnetic tape MT during running using a recording / playback device, it is particularly easy to control the width of the magnetic tape MT to be constant or approximately constant. A method for measuring the storage modulus E' of the substrate 41 in the longitudinal direction will be described later.

[0031] The polyesters include, for example, at least one of PET (polyethylene terephthalate), PEN (polyethylene naphthalate), PBT (polybutylene terephthalate), PBN (polybutylene naphthalate), PCT (polycyclohexylene dimethylene terephthalate), PEB (polyethylene-p-oxybenzoate), and polyethylene bisphenoxycarboxylate. When the base 41 includes two or more polyesters, the two or more polyesters may be mixed, copolymerized, or laminated. At least one of the terminals and side chains of the polyesters may be modified. To improve the strength of the base 41, PA (polyamide) may be added to PET (polyethylene terephthalate).

[0032] The inclusion of polyesters in the substrate 41 can be confirmed, for example, as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and a section of the magnetic tape MT is cut out from the joint 21 between the magnetic tape MT and the leader tape LT in the longitudinal direction, ranging from 30 to 40 m, to prepare a sample. After that, the layers of the sample other than the substrate 41 are removed. Next, an IR spectrum of the sample (substrate 41) is obtained by infrared absorption spectrometry (IR). Based on this IR spectrum, it can be confirmed that the substrate 41 contains polyesters.

[0033] The polyolefins include, for example, at least one of PE (polyethylene) and PP (polypropylene). The cellulose derivatives include, for example, at least one of cellulose diacetate, cellulose triacetate, CAB (cellulose acetate butyrate), and CAP (cellulose acetate propionate). The vinyl resins include, for example, at least one of PVC (polyvinyl chloride) and PVDC (polyvinylidene chloride).

[0034] Examples of other polymer resins include at least one of PA (polyamide, nylon), aromatic PA (aromatic polyamide, aramid), PI (polyimide), aromatic PI (aromatic polyimide), PAI (polyamideimide), aromatic PAI (aromatic polyamideimide), PBO (polybenzoxazole, such as Zylon (registered trademark)), polyether, PEK (polyetherketone), PEEK (polyetheretherketone), polyetherester, PES (polyethersulfone), PEI (polyetherimide), PSF (polysulfone), PPS (polyphenylene sulfide), PC (polycarbonate), PAR (polyarylate), and PU (polyurethane).

[0035] The substrate 41 may be biaxially stretched in the longitudinal direction and the width direction. The polymer resin contained in the substrate 41 is preferably oriented in a direction oblique to the width direction of the substrate 41.

[0036] (magnetic layer) The magnetic layer 43 is a recording layer for recording signals using a magnetization pattern. The magnetic layer 43 may be a coating film. The magnetic layer 43 may be a recording layer for perpendicular recording or a recording layer for longitudinal recording. The magnetic layer 43 contains, for example, magnetic powder, a binder, a lubricant, and carbon. If necessary, the magnetic layer 43 may further contain at least one additive selected from the group consisting of an antistatic agent, an abrasive, a hardener, an anticorrosive agent, and non-magnetic reinforcing particles. The magnetic layer 43 may have an uneven surface.

[0037] As shown in FIG. 4, the magnetic layer 43 may have 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 adjacent servo bands SB. The servo bands SB are used to guide the head unit 56 (specifically, servo read heads 56A and 56B) when recording or reproducing data. A servo pattern (servo signal) for tracking control of the head unit 56 is written in advance in the servo bands SB. User data is recorded in the data bands DB.

[0038] The total area S of multiple servo bands SB relative to the area S of the magnetic surface SB The ratio of RS(=(S SB From the viewpoint of ensuring a high recording capacity, the upper limit of the average value of (S / S)×100) is preferably 4.0% or less, more preferably 3.0% or less, and even more preferably 2.0% or less. SB The lower limit of the average value of the ratio RS is preferably 0.8% or more, from the viewpoint of ensuring 5 or more servo bands SB.

[0039] The total area S of the plurality of servo bands SB relative to the area S of the entire surface of the magnetic layer 43 SB Ratio R S The average value of is found as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and the magnetic tape MT is cut into 250 mm lengths from the longitudinal range of 10 m to 20 m, 30 m to 40 m, and 50 m to 60 m from the joint 21 between the magnetic tape MT and the leader tape LT, to prepare three samples. Next, each sample is developed using a ferricolloid developer (Sigma Marker Q, manufactured by Sigma High Chemical Co., Ltd.), and then each developed sample is observed under an optical microscope to determine the servo bandwidth W SB The number of servo bands SB is measured. Next, the ratio RS of each sample is calculated using the following formula. Ratio RS [%] = (((Servo bandwidth WSB ) x (number of servo bands SB)) / (width of magnetic tape MT)) x 100 Next, the ratios RS of the three samples are arithmetically averaged to calculate the average value of the ratio RS.

[0040] The number of servo bands SB is, for example, 5+4n or more (where n is an integer greater than or equal to 0). The number of servo bands SB is preferably 5 or more, and more preferably 9 or more. If the number of servo bands SB is 5 or more, the effect of dimensional changes in the width direction of the magnetic tape MT on the servo signal can be suppressed, ensuring stable recording and reproduction characteristics with less off-track. The upper limit of the number of servo bands SB is not particularly limited, but is, for example, 33 or less.

[0041] The number of servo bands SB is determined as follows: First, the magnetic tape MT housed in the cartridge 10 is unwound, and a sample of 250 mm is cut from the magnetic tape MT in a range of 30 m to 40 m in the longitudinal direction from the joint 21 between the magnetic tape MT and the leader tape LT. Next, the ratio R S In the same manner as in the calculation of (1), the sample is developed and the number of servo bands SB is measured.

[0042] Servo Bandwidth W SB From the viewpoint of ensuring a high recording capacity, the upper limit of the average value of is preferably 95 μm or less, more preferably 60 μm or less, and even more preferably 30 μm or less. SB The lower limit of the average value of is preferably 10 μm or more. SB It is difficult to manufacture a head unit 56 that can read such servo signals.

[0043] Servo Bandwidth W SB The average value of the above ratio R S The servo bandwidth W of the three samples is calculated in the same way as SB Next, the servo bandwidth W of the three samples is calculated. SB The servo bandwidth W is calculated by arithmetically averagingSB Calculate the average value of

[0044] 5, the magnetic layer 43 is configured so that multiple data tracks Tk can be formed on the data band DB. From the viewpoint of improving track recording density and ensuring high recording capacity, the upper limit of the average value of the data track width W is preferably 1500 nm or less, more preferably 1000 nm or less, even more preferably 800 nm or less, and particularly preferably 600 nm or less. Taking into account the magnetic grain size, the lower limit of the average value of the data track width W is preferably 20 nm or more.

[0045] To ensure a high recording capacity, the magnetic layer 43 is configured to record data such that the minimum distance L between magnetization reversals is preferably 40 nm or less, more preferably 36 nm or less, and even more preferably 32 nm or less. Taking the magnetic grain size into consideration, the lower limit of the minimum distance L between magnetization reversals is preferably 20 nm or more.

[0046] The average data track width W is calculated as follows. First, a cartridge 10 is prepared with data recorded on the entire surface of the magnetic tape MT. The magnetic tape MT is unwound from the cartridge 10. Three 250 mm lengths of the magnetic tape MT are cut from the longitudinal ranges of 10 to 20 m, 30 to 40 m, and 50 to 60 m from the joint 21 between the magnetic tape MT and the leader tape LT, to create three samples. Next, the data recording pattern in the data band DB portion of the magnetic layer 43 of each sample is observed using a magnetic force microscope (MFM) to obtain an MFM image. A Digital Instruments Dimension3100 and its analysis software are used for the MFM. The measurement area of ​​the MFM image is 10 μm × 10 μm, and this 10 μm × 10 μm measurement area is divided into 512 × 512 (= 262,144) measurement points. For each sample, MFM measurements were performed on a 10 μm × 10 μm measurement area, resulting in three MFM images. Using the analysis software provided with the Dimension3100, the track width was measured at 10 locations and the average (simple average) was calculated from the three MFM images. This average value was the average data track width W. The MFM measurement conditions were: sweep speed: 1 Hz, tip used: MFMR-20, lift height: 20 nm, and correction: Flatten order 3.

[0047] The minimum distance L between magnetization reversals is calculated as follows. First, a cartridge 10 is prepared with data recorded on the entire surface of the magnetic tape MT. The magnetic tape MT is unwound from the cartridge 10. Three 250 mm lengths of the magnetic tape MT are cut from the connection 21 between the magnetic tape MT and the leader tape LT, ranging from 10 to 20 m, 30 to 40 m, and 50 to 60 m in the longitudinal direction, to prepare three samples. Next, the data recording pattern in the data band DB portion of the magnetic layer 43 of each sample is observed using a magnetic force microscope (MFM) to obtain an MFM image. A Digital Instruments Dimension3100 and its analysis software are used for the MFM. The measurement area of ​​the MFM image is 2 μm × 2 μm, and this 2 μm × 2 μm measurement area is divided into 512 × 512 (= 262,144) measurement points. For each sample, MFM measurements were performed on a 2 μm x 2 μm measurement area, resulting in three MFM images. Fifty inter-bit distances were measured from a two-dimensional concavo-convex chart of the recording pattern of the obtained MFM image. The inter-bit distance measurements were performed using the analysis software provided with the Dimension3100. The value that is approximately the greatest common denominator of the 50 measured inter-bit distances was taken as the minimum value L of the distance between magnetization reversals. The measurement conditions were: sweep speed: 1 Hz, tip used: MFMR-20, lift height: 20 nm, and correction: Flatten order 3.

[0048] The servo patterns are magnetized regions, and are formed by magnetizing specific regions of the magnetic layer 43 in specific directions using a servo write head during magnetic tape manufacturing. The regions of the servo band SB where no servo patterns are formed (hereinafter referred to as "non-pattern regions") may be magnetized regions where the magnetic layer 43 is magnetized, or may be non-magnetized regions where the magnetic layer 43 is not magnetized. When the non-pattern regions are magnetized regions, the servo pattern forming regions and the non-pattern regions are magnetized in different directions (for example, opposite directions).

[0049] In the LTO standard, a servo pattern consisting of a plurality of servo stripes (linear magnetized regions) 113 inclined with respect to the width direction of the magnetic tape MT is formed on the servo band SB, as shown in FIG.

[0050] The servo band SB includes a plurality of servo frames 100. Each servo frame 100 is made up of 18 servo stripes 103. Specifically, each servo frame 100 is made up of a servo subframe 1 (101) and a servo subframe 2 (102).

[0051] Servo subframe 1 (101) is composed of an A burst 101A and a B burst 101B. The B burst 101B is located adjacent to the A burst 101A. The A burst 101A has five servo stripes 103 formed at regular intervals and inclined at a predetermined angle φ with respect to the width direction of the magnetic tape MT. In FIG. 6, these five servo stripes 103 are denoted by symbols A1, A2, A3, A4, and A5 from the EOT (End of Tape) to the BOT (Beginning of Tape) of the magnetic tape MT. Like the A burst 101A, the B burst 101B has five servo pulses 63 formed at regular intervals and inclined at a predetermined angle φ with respect to the width direction of the magnetic tape MT. In FIG. 6, these five servo stripes 103 are denoted by symbols B1, B2, B3, B4, and B5 from the EOT to the BOT of the magnetic tape MT. The servo stripes 103 of the B burst 101B are inclined in the opposite direction to the servo stripes 103 of the A burst 101A. That is, the servo stripes 103 of the A burst 101A and the servo stripes 103 of the B burst 101B are arranged in a V-shape.

[0052] Servo subframe 2 (102) is composed of a C burst 102C and a D burst 102D. The D burst 102D is located adjacent to the C burst 102C. The C burst 102C has four servo stripes 103 formed at a specified interval and inclined at a specified angle φ with respect to the tape width direction. In FIG. 6, these four servo stripes 103 are denoted by symbols C1, C2, C3, and C4 from the EOT to the BOT of the magnetic tape MT. Like the C burst 102C, the D burst 102D has four servo pulses 63 formed at a specified interval and inclined at a specified angle φ with respect to the tape width direction. In FIG. 6, these four servo stripes 103 are denoted by symbols D1, D2, D3, and D4 from the EOT to the BOT of the magnetic tape MT. The servo stripes 103 of the D burst 102D are inclined in the opposite direction to the servo stripes 103 of the C burst 102C. That is, the servo stripes 103 of the C burst 102C and the servo stripes 103 of the D burst 102D are arranged in a V-shape.

[0053] The above-mentioned predetermined angle φ of the servo stripe 103 in the A burst 101A, the B burst 101B, the C burst 102C, and the D burst 102D can be, for example, 11° or more and 40° or less, preferably 11° or more and 36° or less, more preferably 11° or more and 25° or less, and even more preferably 17° or more and 25° or less.

[0054] Reading the servo band SB with the head unit 56 provides information for determining the tape speed and the longitudinal position of the head unit 56. The tape speed is calculated from the time between four timing signals (A1-C1, A2-C2, A3-C3, A4-C4). The position of the head unit 56 is calculated from the time between the aforementioned four timing signals and the time between another four timing signals (A1-B1, A2-B2, A3-B3, A4-B4). The servo pattern may be a shape containing two parallel lines.

[0055] 6, the servo patterns (i.e., the plurality of servo stripes 103) are preferably arranged linearly in the longitudinal direction of the magnetic tape MT. That is, the servo bands SB preferably have a linear shape in the longitudinal direction of the magnetic tape MT.

[0056] The upper limit of the average thickness of magnetic layer 43 is preferably 90 nm or less, more preferably 80 nm or less, even more preferably 70 nm or less, particularly preferably 60 nm or less, and most preferably 50 nm or less. If the upper limit of the average thickness of magnetic layer 43 is 90 nm or less, when a ring-type head is used as the recording head, the influence of the demagnetizing field can be reduced, thereby achieving even better electromagnetic conversion characteristics.

[0057] The lower limit of the average thickness of the magnetic layer 43 is preferably 35 nm or more. If the lower limit of the average thickness of the magnetic layer 43 is 35 nm or more, output can be ensured when an MR head is used as the reproducing head, and therefore even better electromagnetic conversion characteristics can be obtained.

[0058] The average thickness of the magnetic layer 43 is determined as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and three 250 mm lengths of the magnetic tape MT are cut from the connection 21 between the magnetic tape MT and the leader tape LT in the longitudinal direction, from 10 to 20 m, 30 to 40 m, and 50 to 60 m, to prepare three samples. Next, each sample is thinned using a FIB method or other processing. When using the FIB method, a carbon layer and a tungsten layer are formed as protective films as a pretreatment for observing the cross-sectional TEM image described below. The carbon layer is formed by vapor deposition on the surface of the magnetic tape MT facing the magnetic layer 43 and the surface facing the back layer 44, and the tungsten layer is further formed by vapor deposition or sputtering on the surface facing the magnetic layer 43. The thinning is performed along the longitudinal direction of the magnetic tape MT. That is, the thinning results in a cross section parallel to both the longitudinal and thickness directions of the magnetic tape MT.

[0059] The cross section of each obtained sliced ​​sample is observed under a transmission electron microscope (TEM) under the following conditions to obtain a TEM image of each sliced ​​sample. Note that the magnification and acceleration voltage may be adjusted appropriately depending on the type of device. Apparatus: TEM (Hitachi H9000NAR) Accelerating voltage: 300 kV Magnification: 100,000x

[0060] Next, using the TEM image of each thinned sample, the thickness of the magnetic layer 43 is measured at 10 positions on each thinned sample. The 10 measurement positions on each thinned sample are randomly selected from each sample so that they are different positions in the longitudinal direction of the magnetic tape MT. The arithmetic mean of the measured values ​​of each thinned sample (a total of 30 thicknesses of the magnetic layer 43) is taken as the average thickness [nm] of the magnetic layer 43.

[0061] (magnetic powder) The magnetic powder includes a plurality of magnetic particles. The magnetic particles are, for example, particles containing a metal oxide (hereinafter referred to as "metal oxide particles"). The metal oxide particles are, for example, particles containing hexagonal ferrite (hereinafter referred to as "hexagonal ferrite particles"), particles containing epsilon-type iron oxide (ε-iron oxide) (hereinafter referred to as "ε-iron oxide particles"), or particles containing Co-containing spinel ferrite (hereinafter referred to as "cobalt ferrite particles"). It is preferable that the magnetic powder has a crystal orientation preferentially in the perpendicular direction of the magnetic tape MT. In this specification, the perpendicular direction (thickness direction) of the magnetic tape MT means the thickness direction of the magnetic tape MT in a flat state.

[0062] (Hexagonal ferrite particles) Hexagonal ferrite particles have, for example, a plate shape such as a hexagonal plate or a columnar shape such as a hexagonal column (however, the thickness or height is smaller than the major axis of the plate surface or base). In this specification, hexagonal plate shape includes a substantially hexagonal plate shape. Hexagonal ferrite preferably contains at least one of Ba, Sr, Pb, and Ca, more preferably at least one of Ba and Sr. Specifically, the hexagonal ferrite may be, for example, barium ferrite or strontium ferrite. Barium ferrite may further contain at least one of Sr, Pb, and Ca in addition to Ba. Strontium ferrite may further contain at least one of Ba, Pb, and Ca in addition to Sr.

[0063] More specifically, hexagonal ferrites have the general formula MFe 12 O 19 The alloy has an average composition represented by the formula: where M is, for example, at least one metal selected from Ba, Sr, Pb, and Ca, preferably at least one metal selected from Ba and Sr. M may be a combination of Ba and one or more metals selected from the group consisting of Sr, Pb, and Ca. M may also be a combination of Sr and one or more metals selected from the group consisting of Ba, Pb, and Ca. In the above general formula, part of Fe may be substituted with another metal element.

[0064] When the magnetic powder contains hexagonal ferrite particles, the average particle size of the magnetic powder is preferably 13 nm to 22 nm, more preferably 13 nm to 19 nm, even more preferably 13 nm to 18 nm, particularly preferably 14 nm to 17 nm, and most preferably 14 nm to 16 nm. When the average particle size of the magnetic powder is 22 nm or less, even better electromagnetic conversion characteristics (e.g., SNR) can be obtained in high-recording-density magnetic tapes MT. On the other hand, when the average particle size of the magnetic powder is 13 nm or more, the dispersibility of the magnetic powder is further improved, and even better electromagnetic conversion characteristics (e.g., SNR) can be obtained.

[0065] When the magnetic powder contains hexagonal ferrite particles, the average aspect ratio of the magnetic powder is preferably 1.0 or more and 3.0 or less, more preferably 1.5 or more and 2.8 or less, and even more preferably 1.8 or more and 2.7 or less. When the average aspect ratio of the magnetic powder is within the range of 1.0 or more and 3.0 or less, aggregation of the magnetic powder can be suppressed. Furthermore, 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.

[0066] When the magnetic powder contains hexagonal ferrite particles, the average particle size and average aspect ratio of the magnetic powder can be determined as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and a section of the magnetic tape MT is cut out from the connection 21 between the magnetic tape MT and the leader tape LT in the longitudinal direction, approximately 30 to 40 meters in length. The cut magnetic tape MT is then processed and thinned using a FIB method or similar. When using the FIB method, a carbon layer and a tungsten layer are formed as protective films as a pretreatment for observing the cross-sectional TEM image described below. The carbon layer is formed by vapor deposition on the surface of the magnetic tape MT facing the magnetic layer 43 and the surface facing the back layer 44, and the tungsten layer is further formed by vapor deposition or sputtering on the surface facing the magnetic layer 43. The thinning is performed along the length (longitudinal direction) of the magnetic tape MT. That is, the thinning results in a cross section parallel to both the longitudinal and thickness directions of the magnetic tape MT.

[0067] The cross section of the obtained thin sample is observed using a transmission electron microscope (H-9500 manufactured by Hitachi High-Technologies Corporation) at an acceleration voltage of 200 kV and a total magnification of 500,000 times, so as to include the entire magnetic layer 43 in the thickness direction of the magnetic layer 43, and a TEM photograph is taken. The number of TEM photographs prepared is such that 50 particles can be extracted that can measure the plate diameter DB and plate thickness DA (see Figure 7) shown below.

[0068] In this specification, when the shape of the particle observed in the above TEM photograph is plate-like or columnar (however, the thickness or height is smaller than the major axis of the plate surface or base), as shown in Figure 7, the major axis of the plate surface or base of the particle is taken as the plate diameter DB value. The thickness or height of the particle observed in the above TEM photograph is taken as the plate thickness DA value. When the plate surface or base of the particle observed in the TEM photograph is hexagonal, the major axis means the longest diagonal distance. When the thickness or height of a particle is not constant within a single particle, the thickness or height of the largest particle is taken as the plate thickness DA.

[0069] Next, 50 particles are selected from the TEM photograph based on the following criteria. Particles with parts outside the field of view of the TEM photograph are not measured, and only particles with a clear outline and that exist independently are measured. If particles overlap, those with a clear boundary between them and whose overall shape can be determined are measured as individual particles, but particles with unclear boundaries and whose overall shape cannot be determined are not measured as their shape cannot be determined.

[0070] Examples of TEM photographs are shown in Figures 8 and 9. In Figures 8 and 9, the particles indicated by arrows a and d are selected because their plate thickness (thickness or height) DA can be clearly confirmed. The plate thickness DA of each of the selected 50 particles is measured. The plate thicknesses DA thus obtained are arithmetically averaged to obtain the average plate thickness DA. ave Average plate thickness DA ave is the average particle plate thickness. Next, the plate diameter DB of each magnetic powder is measured. In order to measure the particle plate diameter DB, 50 particles whose particle plate diameter DB can be clearly confirmed are selected from the TEM photograph. For example, in Figures 8 and 9, the particles indicated by arrows b and c are selected because their plate diameter DB can be clearly confirmed. The plate diameter DB of each of the selected 50 particles is measured. The plate diameters DB thus determined are simply averaged (arithmetic average) to obtain the average plate diameter DB. ave Average plate diameter DB ave is the average grain size. And the average plate thickness DA aveand average plate diameter DB ave The average aspect ratio of the particles (DB ave / DA ave ) is found.

[0071] When the magnetic powder includes hexagonal ferrite particles, the average particle volume of the magnetic powder is preferably 500 nm 3 More than 2500nm 3 Less than 500 nm, more preferably 3 More than 1600nm 3 Less than 500 nm, more preferably 3 More than 1500nm 3 Below 600 nm, particularly preferably 3 More than 1200nm 3 Below 600 nm, most preferably 3 More than 1000nm 3 The average particle volume of the magnetic powder is 2500 nm or less. 3 When the average particle size of the magnetic powder is 22 nm or less, the same effect as when the average particle volume of the magnetic powder is 500 nm or less can be obtained. 3 If the average particle size of the magnetic powder is 13 nm or more, the same effect as that obtained when the average particle size of the magnetic powder is 13 nm or more can be obtained.

[0072] The average particle volume of the magnetic powder can be calculated as follows: First, as described above in relation to the method for calculating the average particle size of the magnetic powder, the average plate thickness DA ave and average plate diameter DB ave Next, calculate the average volume V of the magnetic powder using the following formula:

number

[0073] (ε iron oxide particles) ε-iron oxide particles are hard magnetic particles that can achieve high coercivity even in the form of fine particles. ε-iron oxide particles have a spherical or cubic shape. In this specification, spherical includes nearly spherical. Furthermore, cubic includes nearly cubic. Because ε-iron oxide particles have the above-described shape, when ε-iron oxide particles are used as magnetic particles, the contact area between particles in the thickness direction of the magnetic tape MT can be reduced and particle aggregation can be suppressed compared to when hexagonal plate-shaped barium ferrite particles are used as magnetic particles. This improves the dispersibility of the magnetic powder and allows for even better electromagnetic conversion characteristics (e.g., SNR).

[0074] The ε-iron oxide particles have a core-shell structure. Specifically, the ε-iron oxide particles have a core and a two-layer shell structure surrounding the core. The two-layer shell structure includes a first shell portion provided on the core and a second shell portion provided on the first shell portion.

[0075] The core portion contains ε-iron oxide. The ε-iron oxide contained in the core portion preferably has ε-Fe2O3 crystals as a main phase, and more preferably is composed of a single phase ε-Fe2O3.

[0076] The first shell portion covers at least a portion of the periphery of the core portion. Specifically, the first shell portion may cover a portion of the periphery of the core portion, or may cover the entire periphery of the core portion. From the viewpoint of ensuring sufficient exchange coupling between the core portion and the first shell portion and improving magnetic properties, it is preferable that the first shell portion covers the entire surface of the core portion.

[0077] The first shell portion is a so-called soft magnetic layer and includes a soft magnetic material such as α-Fe, a Ni-Fe alloy, or an Fe-Si-Al alloy. The α-Fe may be obtained by reducing ε-iron oxide contained in the core portion.

[0078] The second shell portion is an oxide coating serving as an anti-oxidation layer. The second shell portion contains α-iron oxide, aluminum oxide, or silicon oxide. The α-iron oxide includes at least one iron oxide selected from Fe3O4, Fe2O3, and FeO. When the first shell portion contains α-Fe (soft magnetic material), the α-iron oxide may be obtained by oxidizing the α-Fe contained in the first shell portion.

[0079] By having the first shell portion as described above, the coercivity Hc of the core portion alone can be maintained at a high value to ensure thermal stability, while the coercivity Hc of the entire ε-iron oxide particle (core-shell particle) can be adjusted to a coercivity Hc suitable for recording. Furthermore, by having the second shell portion as described above, the ε-iron oxide particles can be prevented from deteriorating in their properties due to exposure to air during and before the manufacturing process of the magnetic tape MT, which can lead to rust and other damage to the particle surface. Therefore, deterioration of the properties of the magnetic tape MT can be prevented.

[0080] The ε-iron oxide particles may have a shell part with 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 deterioration of the properties of the ε-iron oxide particles, it is preferable that the ε-iron oxide particles have a shell part with a two-layer structure as described above.

[0081] The ε-iron oxide particles may contain an additive instead of the core-shell structure, or may have a core-shell structure and contain an additive. In this case, part of the Fe in the ε-iron oxide particles is substituted with the additive. By containing the additive in the ε-iron oxide particles, the coercivity Hc of the entire ε-iron oxide particles can be adjusted to a coercivity Hc suitable for recording, thereby improving ease of recording. 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.

[0082] Specifically, the ε-iron oxide containing additives is ε-Fe 2-x Mx O crystal (wherein M 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. x is, for example, 0 <x<1である。)である。

[0083] When the magnetic powder contains ε-iron oxide particles, the average particle size of the magnetic powder is preferably 10 nm to 20 nm, more preferably 10 nm to 18 nm, even more preferably 10 nm to 16 nm, particularly preferably 10 nm to 15 nm, and most preferably 10 nm to 14 nm. In magnetic tape MT, the actual magnetization region is a region half the size of the recording wavelength. Therefore, by setting the average particle size of the magnetic powder to less than half the shortest recording wavelength, even better electromagnetic conversion characteristics (e.g., SNR) can be obtained. Therefore, when the average particle size of the magnetic powder is 20 nm or less, even better electromagnetic conversion characteristics (e.g., SNR) can be obtained in high-recording-density magnetic tape MT (e.g., magnetic tape MT configured to record signals at the shortest recording wavelength of 40 nm or less). On the other hand, when the average particle size of the magnetic powder is 10 nm or more, the dispersibility of the magnetic powder is further improved, and even better electromagnetic conversion characteristics (e.g., SNR) can be obtained.

[0084] When the magnetic powder contains ε-iron oxide particles, 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, even more preferably 1.0 or more and 2.1 or less, and particularly preferably 1.0 or more and 1.8 or less. When the average aspect ratio of the magnetic powder is within the range of 1.0 or more and 3.0 or less, aggregation of the magnetic powder can be suppressed. Furthermore, 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.

[0085] When the magnetic powder contains ε-iron oxide particles, the average particle size and average aspect ratio of the magnetic powder can be determined as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and a section of the magnetic tape MT is cut out from a range of 30 to 40 meters in the longitudinal direction from the joint 21 between the magnetic tape MT and the leader tape LT. Next, the cut magnetic tape MT is processed and thinned using a method such as FIB (Focused Ion Beam). When using the FIB method, a carbon layer and a tungsten layer are formed as protective layers as a pretreatment for observing the cross-sectional TEM image described below. The carbon layer is formed by vapor deposition on the surface of the magnetic tape MT facing the magnetic layer 43 and the surface facing the back layer 44, and the tungsten layer is further formed by vapor deposition or sputtering on the surface facing the magnetic layer 43. The thinning is performed along the length (longitudinal direction) of the magnetic tape MT. That is, the thinning results in a cross section parallel to both the longitudinal and thickness directions of the magnetic tape MT.

[0086] The cross section of the obtained thin sample was observed using a transmission electron microscope (H-9500, manufactured by Hitachi High-Technologies Corporation) at an acceleration voltage of 200 kV and a total magnification of 500,000 times, so as to include the entire magnetic layer 43 in the thickness direction of the magnetic layer 43, and a TEM photograph was taken. Next, 50 particles whose particle shape could be clearly confirmed were selected from the TEM photograph, and the long axis length DL and short axis length DS of each particle were measured. Here, the long axis length DL refers to the longest distance between two parallel lines drawn from all angles so as to be tangent to the outline of each particle (the so-called maximum Feret diameter). Meanwhile, the short axis length DS refers to the longest length of the particle in the direction perpendicular to the long axis (DL) of the particle. Next, the long axis lengths DL of the measured 50 particles were arithmetically averaged to obtain the average long axis length DL. ave The average major axis length DL ave is the average particle size of the magnetic powder. The minor axis lengths DS of the 50 particles measured are arithmetically averaged to obtain the average minor axis length DS ave Then, calculate the average major axis length DL ave and mean minor axis length DS aveThe average aspect ratio of the particles (DL ave / DS ave ) is found.

[0087] When the magnetic powder comprises ε iron oxide particles, the average particle volume of the magnetic powder is preferably 500 nm 3 More than 4000nm 3 Less than 500 nm, more preferably 3 More than 3000nm 3 less than or equal to 500 nm, and even more preferably 3 More than 2000nm 3 Below 600 nm, particularly preferably 3 More than 1600nm 3 Below 600 nm, most preferably 3 More than 1300nm 3 Generally, the noise of magnetic tape MT is inversely proportional to the square root of the number of particles (i.e., proportional to the square root of the particle volume), so by making the particle volume smaller, it is possible to obtain even better electromagnetic conversion characteristics (for example, SNR). Therefore, when the average particle volume of the magnetic powder is 4000 nm 3 When the average particle size of the magnetic powder is 500 nm or less, it is possible to obtain even better electromagnetic conversion characteristics (for example, SNR), similar to when the average particle size of the magnetic powder is 20 nm or less. 3 If the average particle size of the magnetic powder is 10 nm or more, the same effect as that obtained when the average particle size of the magnetic powder is 10 nm or more can be obtained.

[0088] When the ε-iron oxide particles are spherical, the average particle volume of the magnetic powder can be calculated as follows: First, the average major axis length DL is calculated in the same manner as in the above-mentioned method for calculating the average particle size of the magnetic powder. ave Next, calculate the average volume V of the magnetic powder using the following formula: V=(π / 6)×DL ave 3

[0089] When the ε-iron oxide particles have a cubic shape, the average volume of the magnetic powder is calculated as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and a section of the magnetic tape MT is cut out from a range of 30 to 40 m in the longitudinal direction from the joint 21 between the magnetic tape MT and the leader tape LT. Next, the cut magnetic tape MT is processed and thinned using a method such as FIB (Focused Ion Beam). When using the FIB method, a carbon film and a tungsten thin film are formed as protective films as a pretreatment for observing the cross-sectional TEM image described below. The carbon film is formed by vapor deposition on the surface of the magnetic tape MT facing the magnetic layer 43 and the surface facing the back layer 44, and the tungsten thin film is further formed by vapor deposition or sputtering on the surface facing the magnetic layer 43. The thinning is performed along the length (longitudinal direction) of the magnetic tape MT. In other words, the thinning results in a cross section parallel to both the longitudinal and thickness directions of the magnetic tape MT.

[0090] The obtained thin film sample is observed using a transmission electron microscope (H-9500 manufactured by Hitachi High-Technologies Corporation) at an acceleration voltage of 200 kV and a total magnification of 500,000 times to observe the cross section of the magnetic layer 43 in the thickness direction of the magnetic layer 43 so as to include the entire magnetic layer 43, and a TEM photograph is obtained. Note that the magnification and acceleration voltage may be adjusted appropriately depending on the type of device. Next, 50 particles whose particle shape is clear are selected from the TEM photograph, and the side length DC of each particle is measured. Next, the side lengths DC of the measured 50 particles are arithmetically averaged to obtain the average side length DC. ave Next, calculate the average side length DC ave Using the following formula, the average volume of the magnetic powder V ave (particle volume) is calculated. V ave =DC ave 3

[0091] (cobalt ferrite particles) The cobalt ferrite particles preferably have uniaxial crystal anisotropy. The uniaxial crystal anisotropy of the cobalt ferrite particles allows the magnetic powder to be preferentially crystalline oriented in the direction perpendicular to the magnetic tape MT. The cobalt ferrite particles may have, for example, a cubic shape. In this specification, the term "cubic shape" includes a substantially cubic shape. The Co-containing spinel ferrite may further contain at least one of Ni, Mn, Al, Cu, and Zn in addition to Co.

[0092] The Co-containing spinel ferrite has an average composition represented by the following formula, for example. Co x M y FeO Z (In the formula, M is at least one metal selected from the group consisting of Ni, Mn, Al, Cu, and Zn. x is a value within the range of 0.4≦x≦1.0. y is a value within the range of 0≦y≦0.3. However, x and y satisfy the relationship (x+y)≦1.0. z is a value within the range of 3≦z≦4. A portion of Fe may be substituted with another metal element.)

[0093] When the magnetic powder contains cobalt ferrite particles, the average particle size of the magnetic powder is preferably 8 nm to 16 nm, more preferably 8 nm to 13 nm, and even more preferably 8 nm to 10 nm. When the average particle size of the magnetic powder is 16 nm or less, even better electromagnetic conversion characteristics (e.g., SNR) can be obtained in high-recording-density magnetic tapes MT. On the other hand, when the average particle size of the magnetic powder is 8 nm or more, the dispersibility of the magnetic powder is further improved, and even better electromagnetic conversion characteristics (e.g., SNR) can be obtained. The method 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 particles.

[0094] When the magnetic powder contains cobalt ferrite particles, the average aspect ratio of the magnetic powder is preferably 1.0 to 2.5, more preferably 1.0 to 2.1, and even more preferably 1.0 to 1.8. When the average aspect ratio of the magnetic powder is within the range of 1.0 to 2.5, aggregation of the magnetic powder can be suppressed. Furthermore, 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 particles.

[0095] When the magnetic powder includes cobalt ferrite particles, the average particle volume of the magnetic powder is preferably 500 nm 3 More than 4000nm 3 Less than 600 nm, more preferably 3 More than 2000nm 3 or less, even more preferably 600 nm 3 More than 1000nm 3 The average particle volume of the magnetic powder is 4000 nm or less. 3 If the average particle size of the magnetic powder is 16 nm or less, the same effect as when the average particle volume of the magnetic powder is 500 nm or less can be obtained. 3 This produces the same effect as when the average particle size of the magnetic powder is 8 nm or more. 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.

[0096] (binder) Examples of binders include thermoplastic resins, thermosetting resins, reactive resins, etc. Examples of thermoplastic resins include vinyl chloride, vinyl acetate, vinyl chloride-vinyl acetate copolymers, vinyl chloride-vinylidene chloride copolymers, vinyl chloride-acrylonitrile copolymers, acrylic acid ester-acrylonitrile copolymers, acrylic acid ester-vinyl chloride-vinylidene chloride copolymers, acrylic acid ester-acrylonitrile copolymers, acrylic acid ester-vinylidene chloride copolymers, methacrylic acid ester-vinylidene chloride copolymers, methacrylic acid ester-vinyl chloride copolymers, methacrylic acid ester-ethylene copolymers, polyvinyl fluoride, vinylidene chloride-acrylonitrile copolymers, acrylonitrile-butadiene copolymers, polyamide resins, polyvinyl butyral, cellulose derivatives (cellulose acetate butyrate, cellulose diacetate, cellulose triacetate, cellulose propionate, nitrocellulose), styrene-butadiene copolymers, polyurethane resins, polyester resins, amino resins, and synthetic rubbers.

[0097] Examples of thermosetting resins include phenolic resins, epoxy resins, polyurethane curing resins, urea resins, melamine resins, alkyd resins, silicone resins, polyamine resins, and urea formaldehyde resins.

[0098] All of the above binders may contain -SO3M, -OSO3M, -COOM, P=O(OM)2 (where M represents a hydrogen atom or an alkali metal such as lithium, potassium, or sodium), -NR1R2, -NR1R2R3, etc., in order to improve the dispersibility of the magnetic powder. + X - A side chain amine having a terminal group represented by the formula: >NR1R2 + X - (wherein R1, R2, and R3 represent a hydrogen atom or a hydrocarbon group, and X -represents a halogen element ion such as fluorine, chlorine, bromine, or iodine, or an inorganic ion or an organic ion.) Furthermore, polar functional groups such as -OH, -SH, -CN, and epoxy groups may be introduced. The amount of these polar functional groups introduced into the binder is 10 -1 mol / g or more 10 -8 It is preferably 10 mol / g or less. -2 mol / g or more 10 -6 It is more preferably mol / g or less.

[0099] (lubricant) The lubricant contains at least one selected from, for example, a fatty acid and a fatty acid ester, and preferably both a fatty acid and a fatty acid ester. The inclusion of a lubricant in magnetic layer 43, and particularly the inclusion of both a fatty acid and a fatty acid ester in magnetic layer 43, contributes to improving the running stability of magnetic tape MT.

[0100] The fatty acid may preferably be a compound represented by the following general formula (1) or (2). For example, the fatty acid may contain either or both of the compound represented by the following general formula (1) and the compound represented by the general formula (2).

[0101] The fatty acid ester may preferably be a compound represented by the following general formula (3) or (4). For example, the fatty acid ester may contain either or both of the compound represented by the following general formula (3) and the compound represented by the general formula (4).

[0102] By including in the lubricant either one or both of the compound represented by general formula (1) and the compound represented by general formula (2), and either one or both of the compound represented by general formula (3) and the compound represented by general formula (4), it is possible to suppress an increase in the dynamic friction coefficient of the magnetic tape MT due to repeated recording or playback.

[0103] CH3(CH2) k COOH (1) (However, in general formula (1), k is an integer selected from the range of 14 or more and 22 or less, more preferably from the range of 14 or more and 18 or less.)

[0104] CH3(CH2) n CH=CH(CH2) m COOH (2) (However, in general formula (2), the sum of n and m is an integer selected from the range of 12 to 20, more preferably from the range of 14 to 18.)

[0105] CH3(CH2) p COO(CH2) q CH3···(3) (However, in general formula (3), p is an integer selected from the range of 14 or more and 22 or less, more preferably 14 or more and 18 or less, and q is an integer selected from the range of 2 or more and 5 or less, more preferably 2 or more and 4 or less.)

[0106] CH3(CH2) r COO-(CH2) s CH(CH3)2 (4) (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.)

[0107] (carbon) The carbon contained in the magnetic layer 43 may function as an antistatic agent, a lubricant, etc. A portion of the carbon contained in the magnetic layer 43 is exposed from the surface of the magnetic layer 43. The unevenness on the surface of the magnetic layer 43 may be formed by carbon, an abrasive, etc.

[0108] The carbon is specifically carbon particles, and the carbon particles include, for example, one or more selected from the group consisting of carbon black, acetylene black, ketjen black, carbon nanotubes, and graphene.

[0109] (antistatic agent) Examples of antistatic agents include natural surfactants, nonionic surfactants, and cationic surfactants.

[0110] (abrasive) Examples of abrasives include acicular α-iron oxide obtained by dehydrating and annealing raw materials such as α-alumina with an α-conversion rate of 90% or more, β-alumina, γ-alumina, silicon carbide, chromium oxide, cerium oxide, α-iron oxide, corundum, silicon nitride, titanium carbide, titanium oxide, silicon dioxide, tin oxide, magnesium oxide, tungsten oxide, zirconium oxide, boron nitride, zinc oxide, calcium carbonate, calcium sulfate, barium sulfate, molybdenum disulfide, and magnetic iron oxide, and, if necessary, surface-treated with aluminum and / or silica.

[0111] (hardening agent) Examples of the curing agent include polyisocyanates. Examples of polyisocyanates include aromatic polyisocyanates such as an adduct of tolylene diisocyanate (TDI) and an active hydrogen compound, and aliphatic polyisocyanates such as an adduct of hexamethylene diisocyanate (HMDI) and an active hydrogen compound. The weight-average molecular weight of these polyisocyanates is preferably in the range of 100 to 3,000.

[0112] (rust inhibitor) Examples of the rust inhibitor include phenols, naphthols, quinones, heterocyclic compounds containing a nitrogen atom, heterocyclic compounds containing an oxygen atom, and heterocyclic compounds containing a sulfur atom.

[0113] (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, and titanium oxide (rutile or anatase titanium oxide).

[0114] (base layer) The underlayer 42 serves to reduce the unevenness of the surface of the substrate 41 and adjust the unevenness of the surface of the magnetic layer 43. The underlayer 42 is a non-magnetic layer containing non-magnetic powder, a binder, and a lubricant. The underlayer 42 supplies the lubricant to the surface of the magnetic layer 43. If necessary, the underlayer 42 may further contain at least one additive selected from the group consisting of an antistatic agent, a hardener, and an anti-rust agent.

[0115] The upper limit of the average thickness of the underlayer 42 is preferably 1.0 μm or less, more preferably 0.9 μm or less, even more preferably 0.8 μm or less, particularly preferably 0.7 μm or less, and most preferably 0.6 μm or less. When the upper limit of the average thickness of the underlayer 42 is 1.0 μm or less, the thickness of the magnetic tape MT can be reduced, thereby increasing the recording capacity that can be recorded in one data cartridge compared to general magnetic tape. Furthermore, when the average thickness of the underlayer 42 is 1.0 μm or less, the magnetic tape MT is more elastic due to external forces, making it easier to adjust the width of the magnetic tape MT by adjusting the tension. The lower limit of the average thickness of the underlayer 42 is preferably 0.3 μm or more. When the lower limit of the average thickness of the underlayer 42 is 0.3 μm or more, deterioration of the functionality of the underlayer 42 can be suppressed. The average thickness of the underlayer 42 is determined in the same manner as the average thickness of the magnetic layer 43. The magnification of the TEM image is adjusted appropriately depending on the thickness of the underlayer 42.

[0116] (Non-magnetic powder) The non-magnetic powder includes, for example, at least one of inorganic particle powder and organic particle powder. The non-magnetic powder may also include carbon powder such as carbon black. One type of non-magnetic powder may be used alone, or two or more types of non-magnetic powder may be used in combination. The inorganic particles include, for example, metals, metal oxides, metal carbonates, metal sulfates, metal nitrides, metal carbides, or metal sulfides. The shape of the non-magnetic powder may be, for example, acicular, spherical, cubic, plate-like, or other various shapes, but is not limited to these shapes.

[0117] (binder, lubricant) The binder and lubricant are the same as those used in the magnetic layer 43 described above.

[0118] (additives) The antistatic agent, hardener, and anticorrosive agent are the same as those in the magnetic layer 43 described above.

[0119] (Back layer) The back layer 44 contains a binder and a non-magnetic powder. If necessary, the back layer 44 may further contain at least one additive selected from the group consisting of a lubricant, a hardener, and an antistatic agent. The binder and non-magnetic powder are the same as those in the underlayer 42 described above. The hardener and antistatic agent are the same as those in the magnetic layer 43 described above.

[0120] The average particle size of the non-magnetic powder is preferably 10 nm or more and 150 nm or less, more preferably 15 nm or more and 110 nm or less. The average particle size of the non-magnetic powder is determined in the same manner as the average particle size of the magnetic powder. The non-magnetic powder may contain non-magnetic powder having two or more particle size distributions.

[0121] The upper limit of the average thickness of the back layer 44 is preferably 0.6 μm or less. If the upper limit of the average thickness of the back layer 44 is 0.6 μm or less, the thickness of the underlayer 42 and the substrate 41 can be maintained large even when the average thickness of the magnetic tape MT is 5.3 μm or less, thereby maintaining running stability of the magnetic tape MT within a recording / reproducing device. The lower limit of the average thickness of the back layer 44 is not particularly limited, but is, for example, 0.2 μm or more.

[0122] The average thickness t of the back layer 44 b can be calculated as follows: First, the average thickness t of the magnetic tape MT T Measure the average thickness t TThe measurement method for is as described in "Average Thickness of Magnetic Tape" below. Next, the magnetic tape MT housed in the cartridge 10 is unwound, and the magnetic tape MT is cut into lengths of 250 mm from the longitudinal range of 10 m to 20 m, 30 m to 40 m, and 50 m to 60 m from the joint 21 between the magnetic tape MT and the leader tape LT, to prepare three samples. Next, the back layer 44 of each sample is removed with a solvent such as MEK (methyl ethyl ketone) or dilute hydrochloric acid. Next, the thickness of each sample is measured at five positions using a Mitutoyo Laser Hologram Gauge (LGH-110C), and these measurements (a total of 15 sample thicknesses) are arithmetically averaged to obtain the average thickness t B Then, the average thickness t of the back layer 44 is calculated using the following formula: b The five measurement positions are selected randomly from each sample so that they are different positions in the longitudinal direction of the magnetic tape MT. t b [μm]=t T [μm]-t B [μm]

[0123] (Average width change ΔA) The average width change ΔA of the magnetic tape MT before and after being left stationary for 40 hours in an environment with a temperature of 50°C and a relative humidity of 40% RH under a longitudinal tension of 0.55 N is 0 ppm to 170 ppm, preferably 0 ppm to 140 ppm, more preferably 0 ppm to 70 ppm, and even more preferably 0 ppm to 30 ppm. If the average width change ΔA of the magnetic tape MT exceeds 170 ppm, the creep change of the magnetic tape MT when the magnetic tape MT wound in the cartridge 10 is stored in a high-temperature environment for a long period of time and when the magnetic tape MT is run in a high-temperature environment for a long period of time becomes large. Therefore, the width change of the magnetic tape MT wound in the cartridge 10 and stored in a high-temperature environment for a long period of time and the magnetic tape MT run in a high-temperature environment for a long period of time exceeds the range that can be corrected by adjusting the longitudinal running tension. Therefore, it becomes difficult to correct the width change by adjusting the longitudinal running tension. In this specification, a high temperature environment refers to an environment of 35°C or higher and 50°C or lower.

[0124] Conventional magnetic tapes undergo significant shape changes due to creep in high-temperature environments. This makes it difficult to correct width changes by adjusting the running tension of the magnetic tape. In contrast, the magnetic tape MT according to the first embodiment has an average width change ΔA of 170 ppm or less, reducing not only environmentally induced deformation of the magnetic tape MT but also creep deformation in high-temperature environments. Therefore, width changes of the magnetic tape MT can be corrected by adjusting the running tension of the magnetic tape MT.

[0125] The average width change ΔA may be set to a desired value by selecting at least one of the substrate 41 and the underlayer 42. For example, the average width change ΔA may be set to a desired value by selecting at least one of the thickness of the substrate 41 and the material of the substrate 41. The average width change ΔA may also be set to a desired value by adjusting the stretching strength of the substrate 41 in the width direction and longitudinal direction. The average width change ΔA may also be set to a desired value by selecting the type of magnetic layer 43 from a coated film and a sputtered film.

[0126] Alternatively, the average width change ΔA may be set to a desired value by providing a strain relaxation process after the calendaring process and before the cutting process, and adjusting the environmental temperature and storage time in the strain relaxation process (for example, storing for 48 hours in an environment at a temperature of 65° C.). Alternatively, the average width change ΔA may be set to a desired value by providing a strain relaxation process after the demagnetizing process and before the servo pattern writing process, and adjusting the environmental temperature and storage time in the strain relaxation process (for example, storing for 48 hours in an environment at a temperature of 55° C.).

[0127] In addition, by selecting one of the above multiple selection examples, the average width change amount ΔA may be set to a desired value, or by selecting two or more, the average width change amount ΔA may be set to a desired value.

[0128] The average width change ΔA of the magnetic tape MT is calculated as follows: First, the magnetic tape MT housed in the cartridge 10 is unwound, and three 250 mm samples are obtained by cutting the magnetic tape MT from the connection 21 between the magnetic tape MT and the leader tape LT in the longitudinal direction, from the range of 10 m to 20 m, the range of 30 m to 40 m, and the range of 50 m to 60 m.

[0129] Next, the width change ΔA of each of the three samples is determined as follows. First, a measuring device as shown in FIG. 10 is prepared, incorporating a Keyence LS-7000 digital dimension measuring instrument. A sample 10S is set in the measuring device. Specifically, one end of a long sample (magnetic tape MT) 10S is fixed by a fixing portion 231. Next, as shown in FIG. 10, the sample 10S is placed on five support members 2321-2325, each of which is substantially cylindrical and rod-like. The sample 10S is placed on these support members 2321-2325 so that its back surface is in contact with the five support members 2321-2325. All five support members 2321-2325 (particularly their surfaces) are made of stainless steel SUS304, and their surface roughness Rz (maximum height) is 0.15 μm to 0.3 μm.

[0130] The arrangement of the five rod-shaped support members 2321-2325 will be described with reference to FIG. 10. As shown in FIG. 10, the sample 10S is placed on the five support members 2321-2325. The five support members 2321-2325 will be referred to hereinafter, starting from the one closest to the fixed portion 231, as the "first support member 2321," the "second support member 2322," the "third support member 2323" (having the slit 232A), the "fourth support member 2324," and the "fifth support member 2325" (closest to the weight 233). The diameter of each of these five support members 2321-2325 is 7 mm. The distance d1 between the first support member 2321 and the second support member 2322 (particularly, the distance between the central axes of these support members) is 20 mm. The distance d2 between the second support member 2322 and the third support member 2323 is 30 mm. The distance d3 between the third support member 2323 and the fourth support member 2324 is 30 mm. The distance d4 between the fourth support member 2324 and the fifth support member 2325 is 20 mm.

[0131] The three support members 2322-2324 are arranged so that the portion of the sample 10S resting between the second support member 2322, the third support member 2323, and the fourth support member 2324 forms a plane that is approximately perpendicular to the direction of gravity. The first support member 2321 and the second support member 2322 are arranged so that the sample 10S forms an angle of θ1 = 30° with respect to the approximately perpendicular plane between the first support member 2321 and the second support member 2322. The fourth support member 2324 and the fifth support member 2325 are arranged so that the sample 10S forms an angle of θ2 = 30° with respect to the approximately perpendicular plane between the fourth support member 2324 and the fifth support member 2325. Of the five first to fifth support members 2321 to 2325, the third support member 2323 is fixed so as not to rotate, but the other four, the first, second, fourth, and fifth support members 2321, 2322, 2324, and 2325, are all rotatable. Because the support member 2323 is fixed so as not to rotate as described above, the contact angle between the support 2323 and the sample 10S is made shallow in consideration of reducing friction between the support 2323 and the sample 10S.

[0132] The sample 10S is held on the support members 2321 to 2325 so as not to move in the width direction of the sample 10S. Among the support members 2321 to 2325, a support member 2323 is located between the light emitter 234 and the light receiver 235 and is located approximately in the center between the fixing part 231 and the part where a load is applied, and is provided with a slit 232A. Light L is irradiated from the light emitter 234 to the light receiver 235 through the slit 232A. The slit width of the slit 232A is 1 mm, and the light L can pass through the slit 232A without being blocked by the frame of the slit 232A.

[0133] Next, the measurement device is placed in a chamber at room temperature (temperature 25°C, relative humidity 50%RH), and a weight 233 is attached to the other end of the sample 10S to apply a load of 0.55 N. The sample 10S is then left to stand in the room temperature environment for 30 minutes. After standing for 30 minutes, the temperature inside the chamber is raised, and measurement of the width of the sample 10S begins when the chamber reaches the specified environment (temperature 50°C, relative humidity 40%RH). While maintaining the specified environment inside the chamber (temperature 50°C, relative humidity 40%RH), measurement of the width of the sample 10S continues for 40 hours from the start of the measurement.

[0134] The measuring device irradiates light L from the light emitter 234 to the light receiver 235 under a load of 0.55 N in the specified environment, and measures the width of the sample 10S to which a load is applied in the longitudinal direction. The width measurement is performed when the sample 10S is not curled. The light emitter 234 and the light receiver 235 are provided in a digital dimension measuring instrument LS-7000.

[0135] Next, using the width measurement results of the sample 10S obtained as described above, the width of the sample 10S at the start of the measurement (i.e., the time when the chamber interior reaches the specified environment) is used as a reference, and the width change Δa of the sample 10S 40 hours after the start of the measurement is calculated. Next, the width change Δa of the three samples 10S calculated as described above is arithmetically averaged to obtain the average width change ΔA of the magnetic tape MT.

[0136] (Average tension response ΔW) The lower limit of the average tension response ΔW to longitudinal tension in an environment of 50°C temperature and 40% RH is 700 ppm / N or more, preferably 715 ppm / N or more, more preferably 750 ppm / N or more, and even more preferably 800 ppm / N or more. If the average tension response ΔW is less than 700 ppm / N, the average tension response ΔW in a high-temperature environment is low, making it difficult to correct creep changes in the magnetic tape MT when the magnetic tape MT wound into the cartridge 10 is stored in a high-temperature environment for a long period of time, and when the magnetic tape MT is run in a high-temperature environment for a long period of time, by adjusting the running tension. As mentioned above, in this specification, a high-temperature environment refers to an environment of 35°C or more and 50°C or less.

[0137] The upper limit of the average tension response ΔW is, for example, 1,700,000 ppm / N or less or 20,000 ppm / N or less, preferably 15,000 ppm / N or less, more preferably 8,000 ppm / N or less, 5,000 ppm / N or less, 4,000 ppm / N or less, 3,000 ppm / N or less, or 2,000 ppm / N or less. If the average tension response ΔW is 15,000 ppm / N or less, even if there is variation in the tension control of the recording / reproducing device, the amount of change in the width of the magnetic tape MT due to the variation can be reduced.

[0138] The average tension response ΔW may be set to a desired value by selecting at least one of the substrate 41 and the underlayer 42. For example, the average tension response ΔW may be set to a desired value by selecting at least one of the thickness of the substrate 41 and the material of the substrate 41. The average tension response ΔW may also be set to a desired value by adjusting the stretching strength of the substrate 41 in the width direction and the length direction. For example, by increasing the stretching strength of the substrate 41 in the width direction, the average tension response ΔW decreases, and conversely, by increasing the stretching strength of the substrate 41 in the length direction, the average tension response ΔW increases. The average tension response ΔW may also be set to a desired value by selecting the type of magnetic layer 43 from a coated film and a sputtered film.

[0139] The average tension response ΔW may be set to a desired value by providing a strain relaxation process after the calendaring process and before the cutting process, and adjusting the environmental temperature and storage time in the strain relaxation process (for example, storing for 48 hours in an environment at a temperature of 65° C.).The average tension response ΔW may be set to a desired value by providing a strain relaxation process after the demagnetizing process and before the servo pattern writing process, and adjusting the environmental temperature and storage time in the strain relaxation process (for example, storing for 48 hours in an environment at a temperature of 55° C.).

[0140] In addition, by selecting one of the above multiple selection examples, the average tension responsiveness ΔW may be set to a desired value, or by selecting two or more, the average tension responsiveness ΔW may be set to a desired value.

[0141] The average tension response ΔW is calculated as follows: First, the ½-inch wide magnetic tape MT housed in the cartridge 10 is unwound, and three 250 mm samples are obtained by cutting the magnetic tape MT from the joint 21 between the magnetic tape MT and the leader tape LT in the longitudinal direction, from 10 m to 20 m, 30 m to 40 m, and 50 m to 60 m.

[0142] Next, the tension response Δw of the three samples is calculated as follows. Loads of 0.2 N, 0.6 N, and 1.0 N are applied in the longitudinal direction of sample 10S, in that order, and the width of sample 10S is measured at loads of 0.2 N, 0.6 N, and 1.0 N. Next, the tension response Δw is calculated using the following formula. Note that the measurement when a load of 0.6 N is applied is performed to check for any abnormalities in the measurement (especially to check that these three measurement results are linear), and this measurement result is not used in the following formula.

number

[0143] Next, the tension responses Δw of the three samples obtained as described above are arithmetically averaged to obtain an average tension response ΔW.

[0144] The width of the sample 10S when each load is applied is measured as follows. First, a measuring device shown in FIG. 10 is prepared, incorporating a Keyence LS-7000 digital dimension measuring instrument, and the sample 10S is set in this measuring device. The specific configuration of the measuring device is the same as that of the method for measuring the average width change ΔA described above. Furthermore, the specific procedure for setting the sample 10S in the measuring device is also the same as that of the method for measuring the average width change ΔA described above.

[0145] Next, the measurement device is placed in a chamber controlled to a constant temperature of 50°C and relative humidity of 40%RH. A weight 233 for applying a 0.2 N load is attached to the other end of the sample 10S, and the sample 10S is left to stand in the above environment for two hours. After standing for two hours, the width of the sample 10S is measured. Next, the weight for applying the 0.2 N load is changed to a weight 233 for applying a 0.6 N load, and the width of the sample 10S is measured five minutes after the change. Finally, the weight 233 is changed to a weight for applying a 1.0 N load, and the width of the sample 10S is measured five minutes after the change.

[0146] As described above, the load applied to the sample 10S in the longitudinal direction can be changed by adjusting the weight of the weight 233. With each load applied in a constant environment of 50°C temperature and 40% RH, light L is irradiated from the light emitter 234 to the light receiver 235, and the width of the sample 10S to which the load is applied in the longitudinal direction is measured. The width measurement is performed when the sample 10S is not curled. The light emitter 234 and the light receiver 235 are provided in the digital dimension measuring instrument LS-7000.

[0147] (Average storage modulus in the longitudinal direction of the substrate) The upper limit of the average storage modulus in the longitudinal direction of the substrate 41 in an environment at a temperature of 50° C. is preferably 9.0 GPa or less, more preferably 7.5 GPa or less, even more preferably 6.0 GPa or less, particularly preferably 5.5 GPa or less, and most preferably 4.5 GPa or less. When the upper limit of the storage modulus is 9.0 GPa or less, the magnetic tape MT has high elasticity in response to tension in the longitudinal direction in a high-temperature environment, and therefore the average tension response ΔW can be improved.

[0148] The lower limit of the average storage modulus in the longitudinal direction of the substrate 41 in an environment at a temperature of 50°C is preferably 3.0 GPa or more, more preferably 3.5 GPa or more. If the upper limit of the storage modulus is 3.0 GPa or more, it is possible to prevent the magnetic tape MT from becoming excessively stretchable in response to tension in the longitudinal direction, thereby preventing a decrease in running stability.

[0149] The average longitudinal storage modulus of the magnetic tape MT is a value that indicates the resistance of the magnetic tape MT to longitudinal expansion and contraction due to external forces; the larger this value, the more difficult it is for the magnetic tape MT to longitudinally expand and contract due to external forces, and the smaller this value, the more easily the magnetic tape MT expands and contracts due to external forces in the longitudinal direction.

[0150] The average storage modulus in the longitudinal direction of the magnetic tape MT is a value related to the longitudinal direction of the magnetic tape MT, but it also correlates with the resistance to expansion and contraction in the width direction of the magnetic tape MT. In other words, the larger this value, the less likely the magnetic tape MT is to expand and contract in the width direction due to external forces, and the smaller this value, the more likely the magnetic tape MT is to expand and contract in the width direction due to external forces. Therefore, from the perspective of tension adjustment, it is advantageous for the average storage modulus in the longitudinal direction of the magnetic tape MT to be small, as described above, 9.0 GPa or less.

[0151] The average storage modulus of the magnetic tape MT in the longitudinal direction is determined as follows. First, the 1 / 2-inch-wide magnetic tape MT housed in the cartridge 10 is unwound, and three samples are punched out to the specified size from the ranges of 10 to 20 m, 30 to 40 m, and 50 to 60 m in the longitudinal direction from the joint 21 between the magnetic tape MT and the leader tape LT. Next, the storage modulus E' of the substrate 41 in the longitudinal direction at a temperature of 50°C is measured for each of the three samples. Next, the average storage modulus E' of the substrate 41 in the longitudinal direction at a temperature of 50°C is determined by arithmetically averaging the measured storage moduli E' of the three samples.

[0152] The storage modulus E' is measured by dynamic viscoelasticity measurement, which is a temperature-dependent measurement, and is specifically carried out as follows. The magnetic tape MT is punched out using a punching tool to obtain a sample having a length of 22.0 mm in the longitudinal direction of the tape and a width of 4.0 mm in the transverse direction. Both longitudinal ends of the sample are clamped to the measuring section of a dynamic viscoelasticity measuring device (RSAII, manufactured by TA Instruments). Dynamic viscoelasticity measurement is then performed under the following measurement conditions. Measurement temperature range: -10℃ to 140℃ Heating rate: 2°C / min Amplitude: Stretched and contracted with an amplitude of 0.1% of the initial tape length Measurement frequency: 10Hz Test Type: “Strain-Controlled” Measurement Type: "Dynamic" Environment in which the device is placed: Temperature 25°C, relative humidity 50% Humidity control of the measurement section: None More detailed settings regarding the measurement conditions of the above-mentioned device are as follows. That is, as described below, in the above measurement, the tension is adjusted so that it does not become 0 or less, and the strain is adjusted so that it does not fall below the lower limit of the transducer. The measurement conditions for these adjustments may be appropriately set by those skilled in the art, but for example, the following settings may be adopted for the above-mentioned dynamic viscoelasticity measuring device. Option settings Delay Before Test: OFF Auto Tension Mode Static Force Tracking Dynamic Force Auto Tension Direction Tension Initial Static Force 10.0g Static>Dynamic Force by 5.0% Minimum Static Force 1.0g Auto Tension Sensitivity 1.0g Auto Strain Max Applied Strain 0.1% Maximum Allowed Force 100.0g Min allowed force 2.0g Strain Adjustment 3.0% Meas Ops: Default setting

[0153] By subjecting the sample to the dynamic viscoelasticity measurement described above, the storage modulus E' value at each measurement temperature can be obtained. The storage modulus E' at a measurement temperature of 50°C can also be obtained. By plotting the storage modulus E' values ​​obtained at each measurement temperature against the measurement temperature, the tendency of changes in the storage modulus E' with temperature can be determined. An example of the measurement results of the storage modulus E' is shown in FIG. 20.

[0154] The storage modulus E' of the magnetic tape MT can be adjusted, for example, by changing the type of material forming the substrate 41 and / or the composition and combination of the magnetic layer 43, underlayer 42, and back layer 44 (especially the underlayer 42, which is often the thickest of these three layers).

[0155] For example, the storage modulus E' can be adjusted by using PEN, PET, or PEEK as the material for forming the base 41. Furthermore, the shape of a graph plotting the storage modulus E' against temperature changes can be changed depending on the selection of these resins.

[0156] Furthermore, the storage modulus E' can be adjusted, for example, by changing the type of resin component contained in the coating material forming the magnetic layer 43, the underlayer 42, and the back layer 44 (particularly the underlayer 42) and / or adjusting the resin composition. For example, the storage modulus E' can be adjusted by adjusting the glass transition temperature Tg of the binder contained in these layers. From the viewpoint of ease of adjusting the glass transition temperature Tg, the binder contains, for example, a polyurethane-based resin. More preferably, the underlayer 42 contains a polyurethane-based resin, which facilitates adjustment of the storage modulus E'. Even more preferably, the glass transition temperature Tg of the polyurethane-based resin contained in the underlayer 42 is preferably 10°C or higher and 140°C or lower, more preferably 30°C or higher and 130°C or lower, even more preferably 30°C or higher and 120°C or lower, and particularly preferably 55°C or higher and 120°C or lower. If the glass transition temperature Tg is too low, adhesion may occur during storage at high temperatures. If the glass transition temperature Tg is too high, surface smoothing (calendering) may be difficult.

[0157] (average thickness of magnetic tape) Average thickness of magnetic tape MT (average total thickness) t T The upper limit of the average thickness t of the magnetic tape MT is preferably 5.2 μm or less, more preferably 5.1 μm or less, even more preferably 4.9 μm or less, particularly preferably 4.6 μm or less, and most preferably 4.4 μm or less. T If the average thickness t of the magnetic tape MT is 5.3 μm or less, the recording capacity that can be recorded in one data cartridge can be increased compared to that of general magnetic tape. T The lower limit is not particularly limited, but is, for example, 3.5 μm or more.

[0158] Average thickness t of magnetic tape MT Tis obtained as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and the magnetic tape MT is cut into 250 mm lengths from the longitudinal range of 10 m to 20 m, 30 m to 40 m, and 50 m to 60 m from the joint 21 between the magnetic tape MT and the leader tape LT, to prepare three samples. Next, the thickness of each sample is measured at five positions using a Mitutoyo Laser Hologram (LGH-110C) as a measuring device, and the arithmetic average of these measurements (a total of 15 sample thicknesses) is calculated to obtain the average thickness t T The five measurement positions are selected randomly from each sample so that they are different positions in the longitudinal direction of the magnetic tape MT.

[0159] (Arithmetic mean roughness Ra of the magnetic layer surface) The average value of the arithmetic mean roughness Ra of the surface of the magnetic layer 43 is 1.9 nm or less, preferably 1.6 nm or less, and more preferably 1.3 nm or less. When the average value of the arithmetic mean roughness Ra is 1.9 nm or less, output reduction due to spacing loss can be suppressed, thereby obtaining excellent electromagnetic conversion characteristics. The lower limit of the average value of the arithmetic mean roughness Ra of the surface of the magnetic layer 43 is preferably 1.0 nm or more, and more preferably 1.2 nm or more. When the lower limit of the average value of the arithmetic mean roughness Ra of the surface of the magnetic layer 43 is 1.0 nm or more, deterioration of running performance due to increased friction can be suppressed.

[0160] The average value of the arithmetic mean roughness Ra is calculated as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and three 250 mm lengths of the magnetic tape MT are cut from the connection 21 between the magnetic tape MT and the leader tape LT in the longitudinal direction, from 10 to 20 m, 30 to 40 m, and 50 to 60 m, to prepare three samples. Next, the surface of the magnetic layer 43 of each sample is observed using an AFM (Atomic Force Microscope), and a 40 μm × 40 μm AFM image is obtained. The AFM used is a Digital Instruments Nano Scope IIIa D3100, with a silicon single crystal cantilever (Note 1), and measurements are performed with a tapping frequency tuning of 200 Hz to 400 Hz. Next, each AFM image is divided into 512 x 512 (= 262,144) measurement points, and the height Z(i) (i: measurement point number, i = 1 to 262,144) is measured at each measurement point. The heights Z(i) at each measurement point are arithmetically averaged to determine the average height (average surface) Zave (= (Z(1) + Z(2) + ··· + Z(262,144)) / 262,144). Next, the deviation Z"(i) (= Z(i) - Zave) from the average center line at each measurement point is calculated, and the arithmetic mean roughness Ra [nm] (= (Z"(1) + Z"(2) + ··· + Z"(262,144)) / 262,144) is calculated. In this case, the image is filtered using Flatten order 2 and planefit order 3 XY before being used as data. (Note 1) Nano World SPM probe NCH normal type PointProbe L (cantilever length) = 125 μm Next, the arithmetic mean roughnesses Ra of the three samples are arithmetically averaged to calculate the average value of the arithmetic mean roughnesses Ra.

[0161] (Surface roughness R b ) Surface roughness of the back surface (surface roughness of the back layer 44) R b The average value of R b The surface roughness R of the back surface is preferably ≦6.0 [nm]. bWhen the average value is within the above range, even better electromagnetic conversion characteristics can be obtained.

[0162] Back surface roughness R b The average value of is calculated as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and the magnetic tape MT is cut into 100 mm lengths from the junction 21 between the magnetic tape MT and the leader tape LT in the longitudinal direction in the ranges of 10 m to 20 m, 30 m to 40 m, and 50 m to 60 m, respectively, to prepare three samples. Next, the sample is placed on a slide glass with the surface to be measured (the surface on the magnetic layer side) facing up, and the edges of the sample are fixed with mending tape. The surface shape is measured using a VertScan measuring device, and the surface roughness R of the back surface is calculated from the following formula based on the ISO 25178 standard: b Ask for. The measurement conditions are as follows. Equipment: Non-contact roughness meter using optical interference (Ryoka Systems Corporation's non-contact surface and layer cross-sectional shape measurement system, VertScan R5500GL-M100-AC) Objective lens: 20x Measurement area: 640 x 480 pixels (field of view: approximately 237 μm x 178 μm) Measurement mode: phase Wavelength filter: 520nm CCD: 1 / 3 inch Noise Reduction Filter: Smoothing 3x3 Surface correction: Correction using a quadratic polynomial approximation surface Measurement software: VS-Measure Version 5.5.2 Analysis software: VS-viewer Version 5.5.5

number

[0163] (Average value of coercive force Hc2) The upper limit of the average value of the coercive force Hc2 of the magnetic layer 43 in the longitudinal direction of the magnetic tape MT is preferably 3000 Oe or less, more preferably 2000 Oe or less, even more preferably 1900 Oe or less, and particularly preferably 1800 Oe or less. If the average value of the coercive force Hc2 of the magnetic layer 43 in the longitudinal direction of the magnetic tape MT is 3000 Oe or less, sufficient electromagnetic conversion characteristics can be obtained even at high recording densities.

[0164] The lower limit of the average value 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 average value of the coercive force Hc2 of the magnetic layer 43 measured in the longitudinal direction of the magnetic tape MT is 1000 Oe or more, demagnetization due to leakage flux from the recording head can be suppressed.

[0165] The average value of the coercive force Hc2 is calculated as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and 250 mm lengths of magnetic tape MT are cut out from the longitudinal ranges of 10 m to 20 m, 30 m to 40 m, and 50 m to 60 m from the joint 21 between the magnetic tape MT and the leader tape LT. Three of the cut magnetic tape MTs are stacked with double-sided tape so that the longitudinal direction of the magnetic tape MT is the same, and then punched out with a φ6.39 mm punch to prepare measurement samples. At this time, markings are made with any nonmagnetic ink so that the longitudinal direction (running direction) of the magnetic tape MT can be identified. Then, the MH loop of the measurement sample (the entire magnetic tape MT) corresponding to the longitudinal direction (running direction) of the magnetic tape MT is measured using a vibrating sample magnetometer (VSM). Next, the coatings (underlayer 42, magnetic layer 43, back layer 44, etc.) of the magnetic tape MT cut out above are wiped off using acetone, ethanol, or the like, leaving only the substrate 41. Three of the obtained substrates 41 are then stacked together with double-sided tape and punched out with a φ6.39 mm punch to prepare a sample for background correction (hereinafter simply referred to as the "correction sample"). Thereafter, the MH loop of the correction sample (substrate 41) corresponding to the longitudinal direction of the substrate 41 (the longitudinal direction of the magnetic tape MT) is measured using a VSM.

[0166] The MH loop of the measurement sample (the entire magnetic tape MT) and the MH loop of the correction sample (substrate 41) are measured using a high-sensitivity vibrating sample magnetometer, model VSM-P7-15, manufactured by Toei Kogyo Co., Ltd. The measurement conditions are as follows: measurement mode: full loop, maximum magnetic field: 15 kOe, magnetic field step: 40 bits, time constant of locking amp: 0.3 sec, waiting time: 1 sec, number of MH averages: 20.

[0167] After obtaining the MH loop of the measurement sample (the entire magnetic tape MT) and the MH loop of the correction sample (substrate 41), background correction is performed by subtracting the MH loop of the correction sample (substrate 41) from the MH loop of the measurement sample (the entire magnetic tape MT), resulting in a background-corrected MH loop. This background correction calculation is performed using the measurement and analysis program included with the VSM-P7-15. The coercive force Hc2 is calculated from the background-corrected MH loop. This calculation is performed using the measurement and analysis program included with the VSM-P7-15. All of the above MH loop measurements are performed in an environment of 25°C ± 2°C and 50% RH ± 5% RH. Furthermore, no "demagnetization field correction" is performed when measuring the MH loop in the longitudinal direction of the magnetic tape MT. Next, the coercive forces Hc2 of the three samples are arithmetically averaged to calculate the average coercive force Hc2.

[0168] (Average value of squareness ratios S1 and S2) The average squareness ratio S1 of the magnetic layer 43 in the perpendicular 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, and most preferably 85% or more. When the average squareness ratio S1 is 65% or more, the perpendicular orientation of the magnetic powder is sufficiently high, resulting in even better electromagnetic conversion characteristics.

[0169] The average squareness ratio S1 in the perpendicular direction of the magnetic tape MT is calculated as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and 250 mm lengths of magnetic tape MT are cut out from the longitudinal ranges of 10 to 20 m, 30 to 40 m, and 50 to 60 m from the joint 21 between the magnetic tape MT and the leader tape LT. Three of the cut magnetic tape MTs are stacked with double-sided tape so that the longitudinal direction of the magnetic tape MT is the same, and then punched out with a φ6.39 mm punch to prepare measurement samples. At this time, markings are made with any nonmagnetic ink so that the longitudinal direction (running direction) of the magnetic tape MT can be identified. Then, the MH loop of the measurement sample (the entire magnetic tape MT) corresponding to the perpendicular direction (thickness direction) of the magnetic tape MT is measured using a VSM. Next, the coatings (underlayer 42, magnetic layer 43, back layer 44, etc.) of the magnetic tape MT cut out above are wiped off using acetone, ethanol, or the like, leaving only the substrate 41. Three of the obtained substrates 41 are then stacked together with double-sided tape and punched out with a φ6.39 mm punch to prepare a sample for background correction (hereinafter simply referred to as the "correction sample"). Thereafter, the MH loop of the correction sample (substrate 41) corresponding to the perpendicular direction of the substrate 41 (the perpendicular direction of the magnetic tape MT) is measured using a VSM.

[0170] The MH loop of the measurement sample (the entire magnetic tape MT) and the MH loop of the correction sample (substrate 41) are measured using a high-sensitivity vibrating sample magnetometer, model VSM-P7-15, manufactured by Toei Kogyo Co., Ltd. The measurement conditions are as follows: measurement mode: full loop, maximum magnetic field: 15 kOe, magnetic field step: 40 bits, time constant of locking amp: 0.3 sec, waiting time: 1 sec, number of MH averages: 20.

[0171] After obtaining the MH loop of the measurement sample (the entire magnetic tape MT) and the MH loop of the correction sample (substrate 41), background correction is performed by subtracting the MH loop of the correction sample (substrate 41) from the MH loop of the measurement sample (the entire magnetic tape MT), and the MH loop after background correction is obtained. This background correction calculation is performed using the measurement and analysis program included with the "VSM-P7-15 model."

[0172] The saturation magnetization Ms (emu) and residual magnetization Mr (emu) of the MH loop after background correction are substituted into the following equation to calculate the squareness ratio S1 (%). Note that all of the above MH loop measurements are performed in an environment of 25°C ± 2°C and 50% RH ± 5% RH. Furthermore, no "demagnetizing field correction" is performed when measuring the MH loop in the perpendicular direction to the magnetic tape MT. Note that this calculation uses the measurement and analysis program included with the "VSM-P7-15 model." Squareness ratio S1(%)=(Mr / Ms)×100 Next, the squareness ratios S1 of the three samples are arithmetically averaged to calculate the average squareness ratio S1.

[0173] The average squareness ratio 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, and most preferably 15% or less. When the average squareness ratio S2 is 35% or less, the magnetic powder has a sufficiently high perpendicular orientation, resulting in even better electromagnetic conversion characteristics.

[0174] The average squareness ratio S2 in the longitudinal direction of the magnetic tape MT is determined in the same manner as the average squareness ratio S1, except that the MH loop is measured in the longitudinal direction (running direction) of the magnetic tape MT and the substrate 41.

[0175] (Average Young's modulus in the longitudinal direction of magnetic tape) The upper limit of the average Young's modulus in the longitudinal direction of the magnetic tape MT is preferably 9.0 GPa or less, more preferably 8.0 GPa or less, even more preferably 7.5 GPa or less, and particularly preferably 7.1 GPa or less. When the average Young's modulus in the longitudinal direction of the magnetic tape MT is 9.0 GPa or less, the magnetic tape MT becomes more elastic due to external forces, making it easier to adjust the width of the magnetic tape MT by adjusting the tension. Therefore, off-track can be more appropriately suppressed, and data recorded on the magnetic tape MT can be more accurately reproduced. The lower limit of the average Young's modulus in the longitudinal direction of the magnetic tape MT is preferably 3.0 GPa or more, more preferably 4.0 GPa or more. When the lower limit of the average Young's modulus in the longitudinal direction of the magnetic tape MT is 3.0 GPa or more, deterioration of running stability can be suppressed.

[0176] The average Young's modulus in the longitudinal direction of the magnetic tape MT is a value that indicates the resistance of the magnetic tape MT to expansion and contraction in the longitudinal direction due to external forces; the larger this value, the more difficult it is for the magnetic tape MT to expand and contract in the longitudinal direction due to external forces, and the smaller this value, the more easily the magnetic tape MT expands and contracts in the longitudinal direction due to external forces.

[0177] The average Young's modulus in the longitudinal direction of the magnetic tape MT is a value related to the longitudinal direction of the magnetic tape MT, but it also correlates with the resistance to expansion and contraction in the width direction of the magnetic tape MT. In other words, the larger this value, the less likely the magnetic tape MT is to expand and contract in the width direction due to external forces, and the smaller this value, the more likely the magnetic tape MT is to expand and contract in the width direction due to external forces. Therefore, from the perspective of tension adjustment, it is advantageous for the average Young's modulus in the longitudinal direction of the magnetic tape MT to be small, as described above, 9.0 GPa or less.

[0178] The average Young's modulus in the longitudinal direction of the magnetic tape MT is determined as follows: First, the magnetic tape MT housed in the cartridge 10 is unwound, and three 180 mm samples are obtained by cutting the magnetic tape MT from the longitudinal range of 10 to 20 m, 30 to 40 m, and 50 to 60 m from the joint 21 between the magnetic tape MT and the leader tape LT. Next, the Young's modulus in the longitudinal direction of each of the three samples is measured, and the average Young's modulus in the longitudinal direction of the magnetic tape MT is determined by arithmetically averaging these measurements.

[0179] The Young's modulus of each sample is measured using a tensile tester (Shimadzu Corporation, AG-100D) as follows: A jig capable of fixing the tape width (1 / 2 inch) is attached to the tensile tester, and the top and bottom of the tape width are fixed. The distance (length of the tape between the chucks) is set to 100 mm. After the tape sample is chucked, stress is gradually applied in the direction in which the sample is pulled (longitudinal direction of the sample). The pulling speed is set to 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(GPa)=((ΔN / S) / (Δx / L))×10 -3 ΔN: Change in stress (N) S: Cross-sectional area of ​​the test piece (mm 2 ) Δx: Elongation (mm) L: Distance between gripping jigs (mm) The cross-sectional area S of the measurement sample is the cross-sectional area before the tensile operation, and is calculated by multiplying the width (1 / 2 inch) of the measurement sample by the thickness of the measurement sample. The range of tensile stress during measurement is set to the linear region of tensile stress depending on the thickness of the magnetic tape MT, etc. In this case, the stress range is set to 0.5 N to 1.0 N, and the change in stress (ΔN) and elongation (Δx) at this time are used for calculation. The above Young's modulus measurement is performed at 25°C ± 2°C and 50% RH ± 5% RH.

[0180] (Average Young's modulus in the longitudinal direction of the substrate) The average Young's modulus in the longitudinal direction of the substrate 41 is preferably 7.8 GPa or less, more preferably 7.0 GPa or less, even more preferably 6.6 GPa or less, and particularly preferably 6.4 GPa or less. When the average Young's modulus in the longitudinal direction of the substrate 41 is 7.8 GPa or less, the magnetic tape MT becomes more elastic due to external forces, making it easier to adjust the width of the magnetic tape MT by adjusting the tension. Therefore, off-track can be more appropriately suppressed, and data recorded on the magnetic tape MT can be more accurately reproduced. The lower limit of the average Young's modulus in the longitudinal direction of the substrate 41 is preferably 2.5 GPa or more, more preferably 3.0 GPa or more. When the lower limit of the average Young's modulus in the longitudinal direction of the substrate 41 is 2.5 GPa or more, deterioration of running stability can be suppressed.

[0181] The average Young's modulus in the longitudinal direction of the substrate 41 is determined as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and the magnetic tape MT is cut into 180 mm lengths from the joint 21 between the magnetic tape MT and the leader tape LT in the longitudinal direction in ranges of 10 to 20 m, 30 to 40 m, and 50 to 60 m, respectively, to prepare three samples. Next, the underlayer 42, magnetic layer 43, and back layer 44 are removed from each cut sample to obtain the substrate 41. Using the substrates 41 of these three samples, the average Young's modulus in the longitudinal direction of the substrate 41 is determined using the same procedure as for the average Young's modulus in the longitudinal direction of the magnetic tape MT.

[0182] The thickness of the substrate 41 accounts for more than half of the overall thickness of the magnetic tape MT. Therefore, the average Young's modulus in the longitudinal direction of the substrate 41 correlates with the resistance of the magnetic tape MT to expansion and contraction due to external force, and the larger this value, the less the magnetic tape MT is able to expand and contract in the width direction due to external force, and the smaller this value, the more the magnetic tape MT is able to expand and contract in the width direction due to external force.

[0183] The average Young's modulus in the longitudinal direction of the substrate 41 is a value related to the longitudinal direction of the magnetic tape MT, but it also correlates with the resistance to expansion and contraction in the width direction of the magnetic tape MT. In other words, the larger this value, the less likely the magnetic tape MT is to expand and contract in the width direction due to external force, and the smaller this value, the more likely the magnetic tape MT is to expand and contract in the width direction due to external force. Therefore, from the perspective of tension adjustment, it is advantageous for the average Young's modulus in the longitudinal direction of the substrate 41 to be small, as described above, 7.8 GPa or less.

[0184] [1.4 Magnetic tape manufacturing method] Next, an example of a method for manufacturing the magnetic tape MT having the above-described configuration will be described.

[0185] (Paint preparation process) First, a paint for forming the base layer is prepared by kneading and dispersing non-magnetic powder, binder, etc. in a solvent. Next, a paint for forming the magnetic layer is prepared by kneading and dispersing magnetic powder, binder, lubricant, carbon, etc. in a solvent. The following solvents, dispersing devices, and kneading devices can be used to prepare the paint for forming the magnetic layer and the paint for forming the base layer.

[0186] Examples of solvents used in preparing the coating material include ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone, alcohol solvents such as methanol, ethanol, and propanol, ester solvents such as methyl acetate, ethyl acetate, butyl acetate, propyl acetate, ethyl lactate, and ethylene glycol acetate, ether solvents such as diethylene glycol dimethyl ether, 2-ethoxyethanol, tetrahydrofuran, and dioxane, aromatic hydrocarbon solvents such as benzene, toluene, and xylene, and halogenated hydrocarbon solvents such as methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, and chlorobenzene. These may be used alone or in appropriate mixtures.

[0187] Examples of kneading devices used in preparing the above coating materials include, but are not limited to, continuous twin-screw kneaders, continuous twin-screw kneaders capable of multi-stage dilution, kneaders, pressure kneaders, roll kneaders, etc. Examples of dispersing devices used in preparing the above coating materials include, but are not limited to, roll mills, ball mills, horizontal sand mills, vertical sand mills, spike mills, pin mills, tower mills, pearl mills (e.g., Eirich's "DCP Mill"), homogenizers, ultrasonic dispersers, etc.

[0188] (coating process) Next, a base layer forming paint is applied to one main surface of the substrate 41 and dried to form the base layer 42. Subsequently, a magnetic layer forming paint is applied to the base layer 42 and dried to form the magnetic layer 43 on the base layer 42. During drying, the magnetic powder may be magnetically oriented in the thickness direction of the substrate 41, for example, using a solenoid coil. Furthermore, during drying, the magnetic powder may be magnetically oriented in the running direction (longitudinal direction) of the substrate 41, for example, using a solenoid coil, and then magnetically oriented in the thickness direction of the substrate 41. By performing a process to orient the magnetic powder in the longitudinal direction in this manner, the degree of perpendicular orientation of the magnetic powder (i.e., the squareness ratio S1) can be further improved. After the magnetic layer 43 is formed, a back layer 44 is formed on the other main surface of the substrate 41. This results in a magnetic tape MT.

[0189] The squareness ratios S1 and S2 can be set to desired values ​​by, for example, adjusting the strength of the magnetic field applied to the coating film of the magnetic layer-forming paint, the concentration of solids in the magnetic layer-forming paint, and the drying conditions (drying temperature and drying time) of the coating film of the magnetic layer-forming paint. The strength of the magnetic field applied to the coating film is preferably between two and three times the coercive force of the magnetic powder. To further increase the squareness ratio S1 (i.e., to further reduce the squareness ratio S2), it is preferable to improve the dispersion state of the magnetic powder in the magnetic layer-forming paint. To further increase the squareness ratio S1, it is also effective to magnetize the magnetic powder before the magnetic layer-forming paint enters an orientation device that magnetically orients the magnetic powder. The above methods for adjusting the squareness ratios S1 and S2 may be used alone or in combination.

[0190] (hardening process) Next, the magnetic tape MT is wound into a roll, and then the magnetic tape MT is subjected to a heat treatment in this state, thereby hardening the underlayer 42 and the magnetic layer 43.

[0191] (calendering process) Next, the obtained magnetic tape MT is subjected to a calendering process to smooth the surface of the magnetic layer 43.

[0192] (Cutting process) Next, the magnetic tape MT is cut to a predetermined width (for example, 1 / 2 inch width). In this way, the magnetic tape MT is obtained.

[0193] (Demagnetization process and servo pattern writing process) Next, if necessary, the magnetic tape MT may be demagnetized and then a servo pattern may be written onto the magnetic tape MT.

[0194] [1.5 Recording and playback system configuration] 11 is a schematic diagram showing an example of the configuration of a recording and playback system 60. The recording and playback system 60 is a magnetic tape recording and playback system, and includes a cartridge 10 and a recording and playback device 50 configured to be able to load and unload the cartridge 10.

[0195] [1.6 Configuration of recording / playback device] The recording / reproducing device 50 records to and reproduces from the magnetic tape MT having the above-described configuration. The recording / reproducing device 50 is configured to be able to adjust the tension applied to the magnetic tape MT in the longitudinal direction. The recording / reproducing device 50 is also configured to be able to load a cartridge 10. Here, for ease of explanation, the recording / reproducing device 50 is described as being configured to be able to load one cartridge 10, but the recording / reproducing device 50 may also be configured to be able to load multiple cartridges 10.

[0196] The recording / playback device 50 is connected to information processing devices such as a server 71 and a personal computer (hereinafter referred to as "PC") 72 via a network 70, and is configured to be able to record data supplied from these information processing devices onto the cartridge 10. It is also configured to be able to reproduce data from the cartridge 10 and supply it to these information processing devices in response to a request from these information processing devices. The shortest recording wavelength of the recording / playback device 50 is preferably 100 nm or less, more preferably 75 nm or less, even more preferably 60 nm or less, and particularly preferably 50 nm or less.

[0197] As shown in FIG. 11, the recording / playback device 50 includes a spindle 51, a reel 52 on the recording / playback device 50 side, a spindle drive device 53, a reel drive device 54, a plurality of guide rollers 55, a head unit 56, a reader / writer 57 as a communication unit, a communication interface (hereinafter, I / F) 58, and a control device 59.

[0198] The spindle 51 is configured so that the cartridge 10 can be attached thereto. A V-shaped servo pattern is pre-recorded on the magnetic tape MT as a servo signal. The reel 52 is configured so that the leading end (leader pin 22) of the magnetic tape MT pulled out from the cartridge 10 via a tape loading mechanism (not shown) can be fixed thereto.

[0199] The spindle drive unit 53 rotates the spindle 51 in response to commands from the control unit 59. The reel drive unit 54 rotates the reel 52 in response to commands from the control unit 59. A plurality of guide rollers 55 guide the running 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 head unit 56.

[0200] When data is recorded on the magnetic tape MT or when data is reproduced from the magnetic tape MT, the spindle 51 and reel 52 are rotated and run by the spindle drive device 53 and reel drive device 54. The magnetic tape MT can run in both the forward direction (from the cartridge 10 side to the reel 52 side) and the reverse direction (from the reel 52 side to the cartridge 10 side).

[0201] In this embodiment, the tension of the magnetic tape MT in the longitudinal direction during data recording or data playback can be adjusted 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. Note that the tension of the magnetic tape MT may be adjusted by controlling the movement of the guide roller 55 instead of or in addition to controlling the rotation of the spindle 51 and the reel 52.

[0202] The reader / writer 57 is configured to be able to write first information and second information to the cartridge memory 11 in response to a command from the control device 59. The reader / writer 57 is also configured to be able to read the first information and second information from the cartridge memory 11 in response to a command from the control device 59. The communication method between the reader / writer 57 and the cartridge memory 11 may be, for example, the ISO14443 method. The second information includes tension adjustment information. The tension adjustment information is an example of data recording information.

[0203] The control device 59 includes, for example, a control unit, a storage unit, a communication unit, etc. The control unit is configured with, for example, a CPU (Central Processing Unit), etc., and controls each unit of the recording / playback device 50 in accordance with a program stored in the storage unit. For example, the control device 59 records data signals supplied from information processing devices such as the server 71 and the PC 72 onto the magnetic tape MT by the head unit 56 in response to requests from the information processing devices. Furthermore, the control device 59 reproduces the data signals recorded on the magnetic tape MT by the head unit 56 in response to requests from the information processing devices such as the server 71 and the PC 72, and supplies the reproduced data signals to the information processing devices.

[0204] The storage unit includes a non-volatile memory for storing various data and programs, and a volatile memory used as a work area for 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 a network.

[0205] When recording data onto the magnetic tape MT or reproducing data from the magnetic tape MT, the control device 59 reads the servo signals recorded on two adjacent servo bands SB by the head unit 56. Using the servo signals read from the two servo bands SB, the control device 59 controls the position of the head unit 56 so that the head unit 56 follows the servo pattern.

[0206] When recording data on the magnetic tape MT, the control device 59 calculates the distance d1 between two adjacent servo bands SB (the distance in the width direction of the magnetic tape MT) from the reproduced waveforms of the servo signals read from the two adjacent servo bands SB, and then writes the calculated distance into the memory 36 by the reader / writer 57.

[0207] When reproducing data from the magnetic tape MT, the control device 59 determines the distance d2 between two adjacent servo bands SB (the distance in the width direction of the magnetic tape MT) from the reproduced waveforms of the servo signals read from the two adjacent servo bands SB. At the same time, the control device 59 reads the distance d1 between the two adjacent servo bands SB, which was determined when data was recorded on the magnetic tape MT, from the memory 36 using the reader / writer 57. The control device 59 controls the rotation of the spindle drive device 53 and the reel drive device 54 to adjust the tension applied to the magnetic tape MT in the longitudinal direction so that the difference Δd between the distance d1 between the servo bands SB, which was determined when data was recorded on the magnetic tape MT, and the distance d2 between the servo bands SB, which was determined when data was reproduced from the magnetic tape MT, falls within a specified range. This tension adjustment is controlled by, for example, feedback control.

[0208] The head unit 56 is configured to be able to record data on the magnetic tape MT in response to commands from the control device 59. The head unit 56 is also configured to be able to play back data recorded on the magnetic tape MT in response to commands from the control device 59. The head unit 56 has, for example, two servo read heads and a plurality of data write / read heads.

[0209] The servo read head is 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 using an MR element (MR: Magneto Resistive) etc. The widthwise spacing between the two servo read heads is approximately the same as the distance between two adjacent servo bands SB.

[0210] The data write / read heads are positioned between the two servo read heads, at equal intervals along the direction from one servo read head to the other. The data write / read heads are configured to be able to record data onto the magnetic tape MT using a magnetic field generated from a magnetic gap. The data write / read heads are also configured to be able to reproduce data by reading the magnetic field generated from the data recorded on the magnetic tape MT using an MR element or the like.

[0211] The communication I / F 58 is for communicating with information processing devices such as a server 71 and a PC 72, and is connected to a network .

[0212] 1.7 Operation of the recording / playback device when recording data An example of the operation of the recording / reproducing device 50 when recording data will now be described with reference to FIG.

[0213] 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 control device 59 reads the servo signal with the servo read head of the head unit 56, and records data on the magnetic tape MT with the data write / read head of the head unit 56 (step S12).

[0214] At this time, the head unit 56 records data onto the data band DB with the data write / read head of the head unit 56 while tracing two adjacent servo bands SB with the two servo read heads of the head unit 56 .

[0215] Next, the control device 59 determines the distance d1 between two adjacent servo bands SB during data recording from the reproduced waveform of the servo signal read by the servo read head of the head unit 56 (step S13). Next, the control device 59 uses the reader / writer 57 to write the distance d1 between the servo bands SB during data recording to the cartridge memory 11 (step S14). The control device 59 may continuously measure the distance d1 between the servo bands SB and write it to the cartridge memory 11, or may measure the distance d1 between the servo bands at regular intervals and write it to the cartridge memory 11. When the distance d1 between the servo bands SB is measured at regular intervals and written to the cartridge memory 11, the amount of information written to the memory 36 can be reduced.

[0216] [1.8 Operation of the recording / playback device during data playback] An example of the operation of the recording / reproducing device 50 when reproducing data will now be described with reference to FIG.

[0217] First, the control device 59 loads the cartridge 10 into the recording / reproducing device 50 (step S21). Next, the control device 59 reads the distance d1 between the servo bands at the time of recording from the cartridge memory 11 using the reader / writer 57 (step S22).

[0218] 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 reads the servo signal with the servo read head of the head unit 56, and reproduces data from the magnetic tape MT with the data write / read head of the head unit 56 (step S23).

[0219] Next, the control device 59 calculates the distance d2 between two adjacent servo bands SB during data reproduction from the reproduced waveform of the servo signal read by the servo read head of the head unit 56 (step S24).

[0220] Next, the control device 59 determines whether the difference Δd between the distance d1 between the servo bands read out in step S22 and the distance d2 between the servo bands SB calculated in step S24 is within a specified value (step S25).

[0221] If 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).

[0222] On the other hand, if 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 as to reduce the difference Δd, adjusts the tension applied to the running magnetic tape MT, and returns the process to step S24 (step S27).

[0223] [1.5 Action and Effects] As described above, in the magnetic tape MT according to the first embodiment, the average width change ΔA of the magnetic tape MT before and after being left standing for 40 hours in an environment of 50°C and 40%RH with a tension of 0.55N applied in the longitudinal direction is 170 ppm or less, so that in addition to deformation of the magnetic tape MT due to the environment, creep deformation of the magnetic tape MT in a high-temperature environment can be sufficiently suppressed over a long period (e.g., 10 years). As a result, even when the magnetic tape MT is stored or run in a high-temperature environment for a long period (e.g., 10 years), width change of the magnetic tape MT can be suppressed. Furthermore, since the average tension response to longitudinal tension is 700 ppm / N or more in an environment of a temperature of 50°C and a relative humidity of 40% RH, width changes of the magnetic tape MT can be effectively corrected in a high-temperature environment. Therefore, even if the magnetic tape MT is stored or run in a high temperature environment for a long period of time (for example, 10 years), the change in width of the magnetic tape MT can be corrected by adjusting the running tension of the magnetic tape MT.

[0224] <2. Second embodiment> In the above first embodiment, the magnetic tape MT is described as a coated magnetic tape in which the base layer, magnetic layer, etc. are produced by a coating process (wet process), but it may also be a vacuum thin-film magnetic tape in which the base layer, magnetic layer, etc. are produced by a vacuum thin-film production technique (dry process) such as sputtering.

[0225] 2.1 Magnetic Tape Structure 14 is a cross-sectional view showing an example of the configuration of a vacuum thin-film magnetic tape MT1 according to a second embodiment of the present disclosure. The magnetic tape MT1 is a perpendicular recording magnetic recording medium and includes a film-like substrate 111, a soft magnetic underlayer (hereinafter referred to as "SUL") 112, a first seed layer 113A, a second seed layer 113B, a first underlayer 114A, a second underlayer 114B, and a magnetic layer 115 as a recording layer. The SUL 112, the first and second seed layers 113A and 113B, the first and second underlayers 114A and 114B, and the magnetic layer 115 are vacuum thin films such as sputtered films.

[0226] SUL 112, first and second seed layers 113A, 113B, and first and second underlayers 114A, 114B are provided between one major surface (hereinafter referred to as the "surface") of substrate 111 and magnetic layer 115, and are stacked in the order of SUL 112, first seed layer 113A, second seed layer 113B, first underlayer 114A, and second underlayer 114B from substrate 111 toward magnetic layer 115.

[0227] If necessary, the magnetic tape MT1 may further include a protective layer 116 provided on the magnetic layer 115 and a lubricating layer 117 provided on the protective layer 116. Furthermore, if necessary, the magnetic tape MT1 may further include a back layer 118 provided on the other main surface (hereinafter referred to as the "back surface") of the substrate 111.

[0228] Hereinafter, the longitudinal direction of the magnetic tape MT1 (the longitudinal direction of the substrate 111) is referred to as the MD (Machine Direction) direction. Here, the machine direction refers to the direction of relative movement of the recording and reproducing heads with respect to the magnetic tape MT1, i.e., the direction in which the magnetic tape MT1 runs during recording and reproduction.

[0229] The magnetic tape MT1 according to the second embodiment is suitable for use as a storage medium for data archives, a field recording density of which is expected to increase in the future. This magnetic tape MT1 has an areal recording density of 50 Gb / in, which is 10 times or more that of current coated magnetic recording media for storage. 2 When a data cartridge using a general linear recording method is constructed using magnetic tape MT1 with such an areal recording density, a large capacity of 100 TB or more can be recorded per data cartridge.

[0230] The magnetic tape MT1 according to the second embodiment is suitable for use in a recording / reproducing device (a recording / reproducing device for recording and reproducing data) having a ring-type recording head and a giant magnetoresistive (GMR) or tunneling magnetoresistive (TMR) reproducing head. The magnetic tape MT1 according to the second embodiment preferably uses a ring-type recording head as a servo signal write head. A data signal is perpendicularly recorded on the magnetic layer 115 by, for example, a ring-type recording head. A servo signal is perpendicularly recorded on the magnetic layer 115 by, for example, a ring-type recording head.

[0231] The average thickness t of the magnetic tape MT1 in the second embodiment T The average width change ΔA, the average tension response, the average storage modulus of the base 111, etc. are the same as those in the first embodiment.

[0232] (Base) The base 111 is similar to the base 41 in the first embodiment.

[0233] (SUL) The SUL 112 includes a soft magnetic material in an amorphous state. The soft magnetic material includes, for example, at least one of a Co-based material and an Fe-based material. The Co-based material includes, for example, CoZrNb, CoZrTa, or CoZrTaNb. The Fe-based material includes, for example, FeCoB, FeCoZr, or FeCoTa.

[0234] The SUL 112 is a single layer SUL, and is provided directly on the substrate 111. The average thickness of the SUL 112 is preferably 10 nm or more and 50 nm or less, and more preferably 20 nm or more and 30 nm or less.

[0235] The average thickness of the SUL 112 is determined in the same manner as for the magnetic layer 43 in the first embodiment. The average thicknesses of the layers other than the SUL 112 (i.e., the average thicknesses of the first and second seed layers 113A and 113B, the first and second underlayers 114A and 114B, and the magnetic layer 115), which will be described later, are also determined in the same manner as for the magnetic layer 43 in the first embodiment. However, the magnification of the TEM image is adjusted appropriately depending on the thickness of each layer.

[0236] (First and second seed layers) The first seed layer 113A includes an alloy containing Ti and Cr and is in an amorphous state. The alloy may further include O (oxygen). The oxygen may be impurity oxygen contained in trace amounts in the first seed layer 113A when the first seed layer 113A is formed by a film formation method such as sputtering.

[0237] Here, "alloy" refers to at least one of a solid solution, a eutectic, an intermetallic compound, etc. containing Ti and Cr. "Amorphous state" refers to a state in which a halo is observed by X-ray diffraction or electron diffraction, etc., and the crystal structure cannot be identified.

[0238] The atomic ratio of Ti to the total amount of Ti and Cr contained in first seed layer 113A is preferably within a range of 30 atomic % or more and less than 100 atomic %, more preferably 50 atomic % or more and less than 100 atomic %. If the atomic ratio of Ti is less than 30%, the (100) plane of the body-centered cubic lattice (bcc) structure of Cr will become oriented, and there is a risk that the orientation of first and second underlayers 114A and 114B formed on first seed layer 113A will be reduced.

[0239] The atomic ratio of Ti is determined as follows. While ion milling the magnetic tape MT1 from the magnetic layer 115 side, a depth profile analysis (depth profile measurement) of the first seed layer 113A is performed by Auger Electron Spectroscopy (hereinafter referred to as "AES"). Next, the average composition (average atomic ratio) of Ti and Cr in the film thickness direction is determined from the obtained depth profile. Next, the atomic ratio of Ti is determined using the determined average composition of Ti and Cr.

[0240] When first seed layer 113A contains Ti, Cr, and O, the atomic ratio of O to the total amount of Ti, Cr, and O contained in first seed layer 113A is preferably 15 atomic % or less, more preferably 10 atomic % or less. If the atomic ratio of O exceeds 15 atomic %, TiO crystals are generated, which may affect the crystal nucleation of first and second underlayers 114A and 114B formed on first seed layer 113A, and may reduce the orientation of first and second underlayers 114A and 114B. The atomic ratio of O is determined using the same analytical method as for the atomic ratio of Ti.

[0241] The alloy contained in first seed layer 113A may further contain an element other than Ti and Cr as an additive element, such as one or more elements selected from the group consisting of Nb, Ni, Mo, Al, W, etc.

[0242] The average thickness of first seed layer 113A is preferably 2 nm or more and 15 nm or less, and more preferably 3 nm or more and 10 nm or less.

[0243] Second seed layer 113B contains, for example, NiW or Ta, and is in a crystalline state. The average thickness of second seed layer 113B is preferably 3 nm or more and 20 nm or less, and more preferably 5 nm or more and 15 nm or less.

[0244] The first and second seed layers 113A and 113B have a crystalline structure similar to that of the first and second base layers 114A and 114B, and are not seed layers provided for the purpose of crystal growth, but rather seed layers that improve the vertical orientation of the first and second base layers 114A and 114B due to the amorphous state of the first and second seed layers 113A and 113B.

[0245] (First and second base layers) The first and second underlayers 114A and 114B preferably have the same crystal structure as the magnetic layer 115. When the magnetic layer 115 contains a Co-based alloy, the first and second underlayers 114A and 114B preferably contain a material with a hexagonal close-packed (hcp) structure similar to that of the Co-based alloy, with the c-axis of the structure oriented perpendicular to the film surface (i.e., in the film thickness direction). This is because it enhances the orientation of the magnetic layer 115 and can achieve relatively good lattice constant matching between the second underlayer 114B and the magnetic layer 115. As a material with a hexagonal close-packed (hcp) structure, a material containing Ru is preferably used, and specifically, Ru alone or a Ru alloy is preferably used. Examples of Ru alloys include Ru alloy oxides such as Ru-SiO2, Ru-TiO2, and Ru-ZrO2.

[0246] As described above, the first and second underlayers 114A and 114B can be made of the same material. However, the first and second underlayers 114A and 114B have different intended effects. Specifically, the second underlayer 114B has a film structure that promotes the granular structure of the magnetic layer 115 that is the layer thereover, while the first underlayer 114A has a film structure that has high crystal orientation. To achieve such film structures, it is preferable to use different film formation conditions, such as sputtering conditions, for the first and second underlayers 114A and 114B.

[0247] The average thickness of the first underlayer 114A is preferably 3 nm to 15 nm, more preferably 5 nm to 10 nm. The average thickness of the second underlayer 114B is preferably 7 nm to 40 nm, more preferably 10 nm to 25 nm.

[0248] (magnetic layer) The magnetic layer 115 is a perpendicular magnetic recording layer in which a magnetic material is perpendicularly oriented. The magnetic layer 115 may be a vacuum thin film such as a sputtered film. From the viewpoint of improving recording density, the magnetic layer 115 is preferably a granular magnetic layer containing a Co-based alloy. This granular magnetic layer is composed of ferromagnetic crystal grains containing a Co-based alloy and nonmagnetic grain boundaries (nonmagnetic material) surrounding the ferromagnetic crystal grains. More specifically, this granular magnetic layer is composed of columns (columnar crystals) containing a Co-based alloy and nonmagnetic grain boundaries (e.g., oxides such as SiO2) surrounding the columns and magnetically separating them. This structure allows the magnetic layer 115 to be configured so that each column is magnetically separated.

[0249] The Co-based alloy has a hexagonal close-packed (hcp) structure, with its c-axis oriented perpendicular to the film surface (thickness direction). The Co-based alloy is preferably a CoCrPt-based alloy containing at least Co, Cr, and Pt. The CoCrPt-based alloy is not particularly limited, and the CoCrPt alloy may further contain an additive element. The additive element may be, for example, one or more elements selected from the group consisting of Ni, Ta, etc.

[0250] The nonmagnetic grain boundaries surrounding the ferromagnetic crystal grains contain a nonmagnetic metal material. Here, metal includes semimetal. Examples of the nonmagnetic metal material include at least one of a metal oxide and a metal nitride. From the viewpoint of maintaining a more stable granular structure, a metal oxide is preferable. Examples of metal oxides include metal oxides containing at least one element selected from the group consisting of Si, Cr, Co, Al, Ti, Ta, Zr, Ce, Y, and Hf. Metal oxides containing at least Si oxide (i.e., SiO2) are preferred. Specific examples of metal oxides include SiO2, Cr2O3, CoO, Al2O3, TiO2, Ta2O5, ZrO2, and HfO2. Examples of metal nitrides include metal nitrides containing at least one element selected from the group consisting of Si, Cr, Co, Al, Ti, Ta, Zr, Ce, Y, and Hf. Specific examples of metal nitrides include SiN, TiN, and AlN.

[0251] It is preferable that the CoCrPt alloy contained in the ferromagnetic crystal grains and the Si oxide contained in the non-magnetic grain boundaries have an average composition as shown in the following formula (1), because this can suppress the influence of the demagnetizing field and realize a saturation magnetization Ms that can ensure sufficient reproduction output, thereby further improving the recording and reproduction characteristics. (Co x Pt y Cr 100-x-y ) 100-z -(SiO2) z ···(1) (In formula (1), x, y, and z are values ​​within the ranges of 69≦X≦75, 10≦y≦16, and 9≦Z≦12, respectively.)

[0252] The above composition can be determined as follows: While ion milling the magnetic tape MT1 from the magnetic layer 115 side, depth direction analysis of the magnetic layer 115 is performed by AES to determine the average composition (average atomic ratio) of Co, Pt, Cr, Si, and O in the film thickness direction.

[0253] The upper limit of the average thickness of magnetic layer 115 is, for example, 90 nm or less, preferably 80 nm or less, more preferably 70 nm or less, even more preferably 60 nm or less, and particularly preferably 50 nm or less, 20 nm or less, or 15 nm or less. The lower limit of the average thickness of magnetic layer 115 is preferably 9 nm or more. When the average thickness of magnetic layer 43 is 9 nm or more and 90 nm or less, the electromagnetic conversion characteristics can be improved.

[0254] (protective layer) The protective layer 116 includes, for example, a carbon material or silicon dioxide (SiO2), and preferably includes a carbon material from the viewpoint of the film strength of the protective layer 116. Examples of the carbon material include graphite, diamond-like carbon (DLC), and diamond.

[0255] (lubricating layer) The lubricating layer 117 contains at least one lubricant. The lubricating layer 117 may further contain various additives, such as a rust inhibitor, as necessary. Examples of lubricants include those similar to those used in the magnetic layer 43 of the first embodiment.

[0256] The lubricant may not only be held on the surface of the magnetic tape MT1 as the lubricating layer 117 as described above, but may also be contained and held in layers such as the magnetic layer 115 and protective layer 116 that make up the magnetic tape MT1.

[0257] (Back layer) The back layer 118 is similar to the back layer 44 in the first embodiment.

[0258] [2.2 Sputtering equipment configuration] 15, an example of the configuration of a sputtering apparatus 120 used in manufacturing the magnetic tape MT1 according to the second embodiment will be described. This sputtering apparatus 120 is a continuous winding sputtering apparatus used to deposit the SUL 112, first seed layer 113A, second seed layer 113B, first underlayer 114A, second underlayer 114B, and magnetic layer 115, and includes a deposition chamber 121, a drum 122 which is a metal can (rotating body), cathodes 123a-123f, a supply reel 124, a take-up reel 125, and a plurality of guide rolls 127a-127c and 128a-128c. The sputtering apparatus 120 is, for example, a DC (direct current) magnetron sputtering apparatus, but the sputtering method is not limited to this.

[0259] The film formation chamber 121 is connected to a vacuum pump (not shown) via an exhaust port 126, and the atmosphere inside the film formation chamber 121 is set to a predetermined vacuum level by this vacuum pump. A rotatable drum 122, a supply reel 124, and a take-up reel 125 are arranged inside the film formation chamber 121. A plurality of guide rolls 127a to 127c are provided inside the film formation chamber 121 to guide the transport of the substrate 111 between the supply reel 124 and the drum 122, and a plurality of guide rolls 128a to 128c are provided inside the film formation chamber 121 to guide the transport of the substrate 111 between the drum 122 and the take-up reel 125. During sputtering, the substrate 111 is unwound from the supply reel 124 and wound onto the take-up reel 125 via the guide rolls 127a to 127c, the drum 122, and the guide rolls 128a to 128c. The drum 122 has a cylindrical shape, and the elongated substrate 111 is transported along the cylindrical circumferential surface of the drum 122. The drum 122 is provided with a cooling mechanism (not shown), and is cooled to, for example, about −20° C. during sputtering. A plurality of cathodes 123 a to 123 f are arranged inside the film formation chamber 121, facing the circumferential surface of the drum 122. Targets are set on each of these cathodes 123 a to 123 f. Specifically, targets for forming the SUL 112, the first seed layer 113A, the second seed layer 113B, the first underlayer 114A, the second underlayer 114B, and the magnetic layer 115 are set on the cathodes 123 a, 123 b, 123 c, 123 d, 123 e, and 123 f, respectively. These cathodes 123a to 123f simultaneously deposit a plurality of types of films, namely SUL 112, first seed layer 113A, second seed layer 113B, first underlayer 114A, second underlayer 114B, and magnetic layer 115.

[0260] In the sputtering apparatus 120 having the above configuration, the SUL 112, the first seed layer 113A, the second seed layer 113B, the first underlayer 114A, the second underlayer 114B, and the magnetic layer 115 can be continuously deposited by a roll-to-roll method.

[0261] [2.3 Magnetic tape manufacturing method] The magnetic tape MT1 according to the second embodiment can be manufactured, for example, as follows.

[0262] First, using the sputtering apparatus 120 shown in FIG. 15, the SUL 112, the first seed layer 113A, the second seed layer 113B, the first underlayer 114A, the second underlayer 114B, and the magnetic layer 115 are sequentially deposited on the surface of the substrate 111. Specifically, the deposition is performed as follows. First, the deposition chamber 121 is evacuated to a predetermined pressure. Then, while a process gas such as Ar gas is introduced into the deposition chamber 121, the targets set on the cathodes 123a to 123f are sputtered. As a result, the SUL 112, the first seed layer 113A, the second seed layer 113B, the first underlayer 114A, the second underlayer 114B, and the magnetic layer 115 are sequentially deposited on the surface of the traveling substrate 111.

[0263] The atmosphere in the film forming chamber 121 during sputtering is, for example, 1×10 -5 Pa to 5 x 10 -5 The pressure is set to about Pa. The film thickness and characteristics of SUL 112, first seed layer 113A, second seed layer 113B, first underlayer 114A, second underlayer 114B, and magnetic layer 115 can be controlled by adjusting the tape line speed for winding up substrate 111, the pressure of process gas such as Ar gas introduced during sputtering (sputtering gas pressure), input power, etc.

[0264] Next, the protective layer 116 is formed on the magnetic layer 115. The protective layer 116 can be formed by, for example, chemical vapor deposition (CVD) or physical vapor deposition (PVD).

[0265] Next, a coating material for forming the back layer is prepared by kneading and dispersing a binder, inorganic particles, a lubricant, etc. in a solvent. Next, the coating material for forming the back layer is applied to the rear surface of the substrate 111 and dried, thereby forming the back layer 118 on the rear surface of the substrate 111.

[0266] Next, for example, a lubricant is applied onto the protective layer 116 to form a lubricating layer 117. Various methods, such as gravure coating and dip coating, can be used to apply the lubricant. Next, the magnetic tape MT1 is cut to a predetermined width as needed. This completes the magnetic tape MT1 shown in FIG. 14.

[0267] [2.4 Action and Effects] In the magnetic tape MT1 of the second embodiment, as in the first embodiment, even if the magnetic tape MT1 is stored or run in a high-temperature environment for a long period of time (e.g., 10 years), the change in width of the magnetic tape MT1 can be corrected by adjusting the running tension of the magnetic tape MT1.

[0268] <3 Third embodiment> 3.1 Magnetic Tape Structure 16 is a cross-sectional view showing an example of the configuration of a vacuum thin-film magnetic tape MT2 according to a third embodiment of the present disclosure. The magnetic tape MT2 includes a substrate 111, an SUL 112, a seed layer 131, a first underlayer 132A, a second underlayer 132B, and a magnetic layer 115. Note that in the third embodiment, parts that are the same as those in the second embodiment are designated by the same reference numerals, and descriptions thereof will be omitted.

[0269] The SUL 112, seed layer 131, first and second underlayers 132A and 132B are provided between one major surface of the substrate 111 and the magnetic layer 115, and are stacked in the order of SUL 112, seed layer 131, first underlayer 132A, and second underlayer 132B from the substrate 111 toward the magnetic layer 115.

[0270] (seed layer) The seed layer 131 contains Cr, Ni, and Fe, and has a face-centered cubic lattice (fcc) structure, with the (111) plane of this face-centered cubic structure preferentially oriented so that it is parallel to the surface of the substrate 111. Here, preferred orientation refers to a state in which the diffraction peak intensity from the (111) plane of the face-centered cubic lattice structure is greater than the diffraction peaks from other crystal planes in a θ-2θ scan of an X-ray diffraction method, or a state in which only the diffraction peak intensity from the (111) plane of the face-centered cubic lattice structure is observed in a θ-2θ scan of an X-ray diffraction method.

[0271] From the viewpoint of improving the SNR, the intensity ratio of the X-ray diffraction of the seed layer 131 is preferably 60 cps / nm or more, more preferably 70 cps / nm or more, and even more preferably 80 cps / nm or more. Here, the intensity ratio of the X-ray diffraction of the seed layer 131 is a value (I / D (cps / nm)) obtained by dividing the intensity I (cps) of the X-ray diffraction of the seed layer 131 by the average thickness D (nm) of the seed layer 131.

[0272] The Cr, Ni, and Fe contained in the seed layer 131 preferably have an average composition represented by the following formula (2). Cr X (Ni Y Fe 100-Y ) 100-X ···(2) (However, in formula (2), X is within the range of 10≦X≦45, and Y is within the range of 60≦Y≦90.) When X is within the above range, the (111) orientation of the face-centered cubic lattice structure of Cr, Ni, and Fe is improved, resulting in a better SNR. Similarly, when Y is within the above range, the (111) orientation of the face-centered cubic lattice structure of Cr, Ni, and Fe is improved, resulting in a better SNR.

[0273] The average thickness of the seed layer 131 is preferably 5 nm or more and 40 nm or less. By setting the average thickness of the seed layer 131 within this range, the (111) orientation of the face-centered cubic lattice structure of Cr, Ni, and Fe can be improved, resulting in a better SNR. The average thickness of the seed layer 131 is determined in the same manner as for the magnetic layer 43 in the first embodiment. However, the magnification of the TEM image is adjusted appropriately depending on the thickness of the seed layer 131.

[0274] (First and second base layers) The first underlayer 132A contains Co and O having a face-centered cubic lattice structure and has a columnar (columnar crystal) structure. The first underlayer 132A containing Co and O provides substantially the same effect (function) as the second underlayer 132B containing Ru. The concentration ratio of the average atomic concentration of O to the average atomic concentration of Co ((average atomic concentration of O) / (average atomic concentration of Co)) is 1 or more. When the concentration ratio is 1 or more, the effect of providing the first underlayer 132A is improved, and a better SNR can be obtained.

[0275] From the viewpoint of improving the SNR, the columnar structure is preferably tilted. The tilt direction is preferably the longitudinal direction of the long magnetic tape MT2. The longitudinal direction is preferred for the following reasons: The magnetic tape MT2 according to this embodiment is a magnetic recording medium for so-called linear recording, and the recording tracks are parallel to the longitudinal direction of the magnetic tape MT2. The magnetic tape MT2 according to this embodiment is also a so-called perpendicular magnetic recording medium. From the viewpoint of recording characteristics, it is preferable that the crystalline orientation axis of the magnetic layer 115 is vertical. However, the tilt of the columnar structure of the first underlayer 132A may cause the crystalline orientation axis of the magnetic layer 115 to tilt. In the magnetic tape MT2 for linear recording, a configuration in which the crystalline orientation axis of the magnetic layer 115 is tilted in the longitudinal direction of the magnetic tape MT2 in relation to the head magnetic field during recording can reduce the impact of the tilt of the crystalline orientation axis on recording characteristics compared to a configuration in which the crystalline orientation axis of the magnetic layer 115 is tilted in the width direction of the magnetic tape MT2. In order to tilt the crystal orientation axis of the magnetic layer 115 in the longitudinal direction of the magnetic tape MT2, it is preferable to set the tilt direction of the columnar structure of the first underlayer 132A in the longitudinal direction of the magnetic tape MT2 as described above.

[0276] The tilt angle of the columnar structure is preferably greater than 0° and not greater than 60°. When the tilt angle is greater than 0° and not greater than 60°, the tip shapes of the columns included in the first underlayer 132A change significantly, becoming roughly triangular mountain-shaped, which tends to enhance the effect of the granular structure, reduce noise, and improve SNR. On the other hand, when the tilt angle exceeds 60°, the tip shapes of the columns included in the first underlayer 132A change slightly, making it difficult for them to become roughly triangular mountain-shaped, which tends to weaken the low-noise effect.

[0277] The average grain size of the columnar structure is 3 nm or more and 13 nm or less. If the average grain size is less than 3 nm, the average grain size of the columnar structure included in the magnetic layer 115 will be small, which may reduce the ability of current magnetic materials to retain data. On the other hand, if the average grain size is 13 nm or less, noise can be suppressed and a better SNR can be obtained.

[0278] The average thickness of the first underlayer 132A is preferably 10 nm or more and 150 nm or less. When the average thickness of the first underlayer 132A is 10 nm or more, the (111) orientation of the face-centered cubic lattice structure of the first underlayer 132A is improved, resulting in a better SNR. On the other hand, when the average thickness of the first underlayer 132A is 150 nm or less, the columnar grain size can be prevented from increasing. Therefore, noise can be suppressed, resulting in a better SNR. The average thickness of the first underlayer 132A is determined in the same manner as the magnetic layer 43 in the first embodiment. However, the magnification of the TEM image is appropriately adjusted depending on the thickness of the first underlayer 132A.

[0279] The second underlayer 132B preferably has the same crystal structure as the magnetic layer 115. When the magnetic layer 115 contains a Co-based alloy, the second underlayer 132B preferably contains a material with a hexagonal close-packed (hcp) structure similar to that of the Co-based alloy, with the c-axis of the structure oriented perpendicular to the film surface (i.e., in the film thickness direction). This is because it enhances the orientation of the magnetic layer 115 and can achieve relatively good lattice constant matching between the second underlayer 132B and the magnetic layer 115. As a material with a hexagonal close-packed structure, a material containing Ru is preferably used, and specifically, Ru alone or a Ru alloy is preferably used. Examples of Ru alloys include Ru alloy oxides such as Ru-SiO2, Ru-TiO2, and Ru-ZrO2.

[0280] The average thickness of the second underlayer 132B may be thinner than that of an underlayer in a typical magnetic recording medium (e.g., an underlayer containing Ru), and can be, for example, 1 nm to 5 nm. Because the seed layer 131 and the first underlayer 132A having the above-described configuration are provided under the second underlayer 132B, a good SNR can be obtained even if the average thickness of the second underlayer 132B is as thin as described above. The average thickness of the second underlayer 132B is determined in the same manner as the magnetic layer 43 in the first embodiment. However, the magnification of the TEM image is appropriately adjusted depending on the thickness of the second underlayer 132B.

[0281] The average thickness t of the magnetic tape MT2 in the third embodiment T The average width change ΔA, the average tension response, the average storage modulus of the base 111, etc. are the same as those in the first embodiment.

[0282] [3.2 Action and Effects] In the magnetic tape MT2 of the third embodiment, as in the first embodiment, even if the magnetic tape MT2 is stored or run in a high-temperature environment for a long period of time (e.g., 10 years), the change in width of the magnetic tape MT2 can be corrected by adjusting the running tension of the magnetic tape MT2.

[0283] The magnetic tape MT2 according to the third embodiment includes a seed layer 131 and a first underlayer 132A between a substrate 111 and a second underlayer 132B. The seed layer 131 contains Cr, Ni, and Fe and has a face-centered cubic lattice structure, with the (111) plane of this face-centered cubic structure preferentially oriented parallel to the surface of the substrate 111. The first underlayer 132A contains Co and O, and has a columnar structure in which the ratio of the average atomic concentration of O to the average atomic concentration of Co is 1 or greater and the average grain size is 3 nm or greater and 13 nm or less. This allows the second underlayer 132B to be thinned to minimize the use of Ru, an expensive material, and realizes a magnetic layer 115 with good crystal orientation and high coercivity.

[0284] The Ru contained in the second underlayer 132B has the same hexagonal close-packed lattice structure as Co, the main component of the magnetic layer 115. Therefore, Ru has the effect of simultaneously improving the crystalline orientation and granularity of the magnetic layer 115. To further improve the crystalline orientation of the Ru contained in the second underlayer 132B, the first underlayer 132A and the seed layer 131 are provided below the second underlayer 132B. In the magnetic tape MT2 according to the third embodiment, the first underlayer 132A containing inexpensive CoO and having a face-centered cubic lattice structure achieves substantially the same effect (function) as the second underlayer 132B containing Ru. This allows the thickness of the second underlayer 132B to be reduced. To enhance the crystalline orientation of the first underlayer 132A, the seed layer 131 containing Cr, Ni, and Fe is provided.

[0285] <4 Variations> (Variation 1) In the first embodiment described above, the magnetic tape cartridge is a one-reel type cartridge 10, but it may also be a two-reel type cartridge.

[0286] 17 is an exploded perspective view showing an example of the configuration of a two-reel type cartridge 321. Cartridge 321 comprises an upper half 302 made of synthetic resin, a transparent window member 323 fitted into and fixed to a window 302a opened in the top surface of upper half 302, a reel holder 322 fixed to the inside of upper half 302 to prevent reels 306 and 307 from floating up, a lower half 305 corresponding to upper half 302, reels 306 and 307 stored in a space formed when upper half 302 and lower half 305 are joined together, magnetic tape MT wound on reels 306 and 307, a front lid 309 that closes a front opening formed when upper half 302 and lower half 305 are joined together, and a back lid 309A that protects the magnetic tape MT exposed in this front opening.

[0287] Reels 306 and 307 are used to wind magnetic tape MT. Reel 306 includes a lower flange 306b having a cylindrical hub portion 306a in the center around which magnetic tape MT is wound, an upper flange 306c having approximately the same size as lower flange 306b, and a reel plate 311 sandwiched between hub portion 306a and upper flange 306c. Reel 307 has the same configuration as reel 306.

[0288] The window member 323 is provided with mounting holes 323a at positions corresponding to the reels 306 and 307, respectively, for assembling reel holders 322, which are reel holding means for preventing these reels from floating up. The magnetic tape MT is the same as the magnetic tape MT in the first embodiment.

[0289] (Variation 2) The magnetic tape MT1 according to the second embodiment may further include an underlayer between the substrate 111 and the SUL 112. Because the SUL 112 is amorphous, it does not promote epitaxial growth of layers formed on the SUL 112. However, it is required that the SUL 112 does not disturb the crystalline orientation of the first and second underlayers 114A and 114B formed on the SUL 112. To achieve this, it is preferable that the soft magnetic material have a fine structure that does not form columns. However, if the influence of degassing, such as moisture, from the substrate 111 is significant, the soft magnetic material may become coarse, disturbing the crystalline orientation of the first and second underlayers 114A and 114B formed on the SUL 112. To suppress the influence of degassing, such as moisture, from the substrate 111, it is preferable to provide an amorphous underlayer containing an alloy containing Ti and Cr between the substrate 111 and the SUL 112, as described above. As a specific configuration of this underlayer, the same configuration as that of the first seed layer 113A of the second embodiment can be adopted.

[0290] The magnetic tape MT1 does not necessarily have to include at least one of the second seed layer 113B and the second underlayer 114B, but from the viewpoint of improving the SNR, it is more preferable to include both the second seed layer 113B and the second underlayer 114B.

[0291] The magnetic tape MT1 may be provided with an APC-SUL (Antiparallel Coupled SUL) instead of a single-layer SUL. [Example]

[0292] The present disclosure will be specifically described below using examples, but the present disclosure is not limited to these examples.

[0293] In the following examples and comparative examples, the average width change ΔA, the average tension response ΔW, the average storage modulus of the substrate in the longitudinal direction, the average Young's modulus of the substrate in the longitudinal direction, the average thickness of the substrate, the average thickness of the magnetic tape, the average thickness of the magnetic layer, the average thickness of the underlayer, the average thickness of the back layer, and the squareness ratios S1 and S2 are values ​​determined by the measurement method described in the first embodiment.

[0294] [Example 1] (SUL film formation process) First, a CoZrNb layer (SUL) with an average thickness of 10 nm was formed on one main surface of a long polymer film serving as a non-magnetic support under the following film-forming conditions: The polymer film used was a PEN film with an average thickness of 3.8 μm, an average longitudinal storage modulus of 5.5 GPa at 50°C, and an average longitudinal Young's modulus of 6.3 GPa. Film formation method: DC magnetron sputtering method Target: CoZrNb target Gas type: Ar Gas pressure: 0.1 Pa

[0295] (First seed layer formation process) Next, a TiCr layer (first seed layer) having an average thickness of 5 nm was formed on the CoZrNb layer under the following film formation conditions. Sputtering method: DC magnetron sputtering method Target: TiCr target Ultimate vacuum: 5×10 -5Pa Gas type: Ar Gas pressure: 0.5 Pa

[0296] (Second seed layer formation process) Next, a NiW layer (second seed layer) having an average thickness of 10 nm was formed on the TiCr layer under the following film formation conditions. Sputtering method: DC magnetron sputtering method Target: NiW target Ultimate vacuum: 5×10 -5 Pa Gas type: Ar Gas pressure: 0.5 Pa

[0297] (First Underlayer Forming Process) Next, a Ru layer (first underlayer) having an average thickness of 10 nm was formed on the NiW layer under the following film formation conditions. Sputtering method: DC magnetron sputtering method Target: Ru target Gas type: Ar Gas pressure: 0.5 Pa

[0298] (Second Underlayer Forming Process) Next, a Ru layer (second underlayer) having an average thickness of 20 nm was formed on the Ru layer under the following film formation conditions. Sputtering method: DC magnetron sputtering method Target: Ru target Gas type: Ar Gas pressure: 1.5Pa

[0299] (Magnetic layer deposition process) Next, a (CoCrPt)-(SiO2) layer (magnetic layer) having an average thickness of 9 nm was formed on the Ru layer under the following film formation conditions. Film formation method: DC magnetron sputtering method Target: (CoCrPt)-(SiO2) target Gas type: Ar Gas pressure: 1.5Pa

[0300] (Protective layer deposition process) Next, a carbon layer (protective layer) having an average thickness of 5 nm was formed on the magnetic layer under the following film formation conditions. Film formation method: DC magnetron sputtering method Target: Carbon target Gas type: Ar Gas pressure: 1.0 Pa

[0301] (Lubrication layer formation process) Next, a lubricant was applied onto the protective layer to form a lubricating layer.

[0302] (Back layer deposition process) Next, a coating material for forming a back layer was applied to the other main surface of the polymer film and dried to form a back layer having an average thickness tb of 0.3 μm. T A magnetic tape with a thickness of 4.0 μm was obtained.

[0303] (Cutting process) The magnetic tape obtained as described above was cut into a width of 1 / 2 inch (12.65 mm). As a result, the desired long magnetic tape (average thickness 4.2 μm) was obtained.

[0304] In Example 1, a sputtered film was used as the magnetic layer, a PEN film was used as the polymer film, and the average width change ΔA and average tension response ΔW were set to the values ​​shown in Table 1 by adjusting the stretching strength of the PEN film in the width and length directions.

[0305] [Example 2] The polymer film used was a reinforced PET film having an average thickness of 3.8 μm, an average longitudinal storage modulus of 3.9 GPa at a temperature of 50° C., and an average longitudinal Young's modulus of 4.6 GPa. Here, the reinforced PET film means a PET film reinforced by adding polyamide. A sputtered film was used as the magnetic layer, and a reinforced PET film was used as the polymer film. By adjusting the stretching strength of the reinforced PET film in the width and length directions, the average width change ΔA and average tension response ΔW were set to the values ​​shown in Table 1. Other than the above, the same procedure as in Example 1 was carried out to obtain a magnetic tape having an average thickness of 4.2 μm.

[0306] [Example 3] (Preparation process of paint for forming magnetic layer) The magnetic layer-forming paint was prepared as follows. First, a first composition having the following formulation was kneaded using an extruder. Next, the kneaded first composition and a second composition having the following formulation were added to a stirring tank equipped with a disperser and premixed. Subsequently, further sand mill mixing was performed and filtering was carried out to prepare the magnetic layer-forming paint.

[0307] (First composition) Barium ferrite (BaFe 12 O 19 ) Magnetic powder (hexagonal plate shape, average aspect ratio 3.0, average particle volume 2500nm 3 ):100 parts by mass Resin solution in which vinyl chloride resin is dispersed in cyclohexanone (resin solution: vinyl chloride resin content 30% by mass, cyclohexanone content 70% by mass): 52 parts by mass (Vinyl chloride resin: degree of polymerization 300, number average molecular weight Mn=10,000, polar groups OSO3K=0.07 mmol / g, secondary OH=0.3 mmol / g) Aluminum oxide powder: 5 parts by mass (α-Al2O3, average particle size 0.2μm) Carbon black: 2 parts by mass (manufactured by Tokai Carbon Co., Ltd., product name: Seest TA)

[0308] (Second composition) Resin solution in which vinyl chloride resin is dispersed in cyclohexanone (resin solution: vinyl chloride resin content 30% by mass, cyclohexanone content 70% by mass): 3.5 parts by mass (Vinyl chloride resin: degree of polymerization 300, number average molecular weight Mn=10,000, polar groups OSO3K=0.07 mmol / g, secondary OH=0.3 mmol / g) 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

[0309] Finally, 4 parts by mass of polyisocyanate (trade name: Coronate L, manufactured by Tosoh Corporation) and 2 parts by mass of myristic acid were added as a curing agent to the magnetic layer-forming coating material prepared as described above.

[0310] (Preparation process of paint for forming base layer) The paint for forming the primer layer was prepared as follows. First, the third composition having the following composition was kneaded using an extruder. Next, the kneaded third composition and the fourth composition having the following composition were added to a stirring tank equipped with a disperser and premixed. Subsequently, further mixing was performed using a sand mill and filtering was performed to prepare the paint for forming the primer layer.

[0311] (Third composition) Acicular iron oxide powder: 100 parts by mass (α-Fe2O3, average major axis length 0.15μm) Vinyl chloride resin: 55.6 parts by mass (Resin solution: 30% resin by mass, 70% cyclohexanone by mass) Carbon black: 10 parts by mass (Average particle size 20nm)

[0312] (4th composition) Polyurethane resin UR8200 (manufactured by Toyobo): 18.5 parts by weight 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

[0313] Finally, 4 parts by mass of polyisocyanate (trade name: Coronate L, manufactured by Tosoh Corporation) as a curing agent and 2 parts by mass of myristic acid were added to the coating material for forming the undercoat layer prepared as described above.

[0314] (Preparation process of paint for forming back layer) The coating material for forming a back layer was prepared as follows: The following raw materials were mixed in a stirring tank equipped with a disperser, and the mixture was filtered to prepare the coating material for forming a back layer. Carbon black (manufactured by Asahi Carbon Co., Ltd., product name: #80): 100 parts by mass Polyester polyurethane: 100 parts by mass (Nippon Polyurethane Co., Ltd., product name: N-2304) Methyl ethyl ketone: 500 parts by mass Toluene: 400 parts by mass Cyclohexanone: 100 parts by mass

[0315] (Film forming process) Using the coating material prepared as described above, an underlayer and a magnetic layer were formed on one main surface of a long polymer film serving as a non-magnetic support in the following manner.

[0316] First, a primer layer was formed by applying a primer coating to a reinforced PET film and drying it. The coating conditions were adjusted so that the average thickness of the primer layer after calendering would be 0.8 μm. The polymer film used was a reinforced PET film with an average thickness of 4.0 μm, an average longitudinal storage modulus of 3.9 GPa at 50°C, and an average longitudinal Young's modulus of 4.6 GPa.

[0317] Next, a magnetic layer-forming paint was applied to the underlayer and dried to form a magnetic layer on the underlayer. The application conditions were adjusted so that the average thickness of the magnetic layer after calendering would be 0.08 μm. As the magnetic layer-forming paint dried, a neodymium magnet magnetically oriented the magnetic powder in the thickness direction of the polymer film. The drying conditions (drying temperature and drying time) for the magnetic layer-forming paint were adjusted to set the squareness ratio S1 in the thickness direction (perpendicular direction) of the magnetic tape to 65% and the squareness ratio S2 in the longitudinal direction to 35%.

[0318] Next, a back layer was formed by applying a coating material for forming a back layer to the other main surface of the reinforced PET film on which the underlayer and magnetic layer had been formed, and then drying the coating material. The coating conditions were adjusted so that the average thickness of the back layer after calendering was 0.32 μm. This resulted in the production of a magnetic tape.

[0319] (hardening process) Next, the magnetic tape was wound into a roll, and then subjected to a heat treatment in this state to harden the underlayer and the magnetic layer.

[0320] (calendering process) Next, the obtained magnetic tape MT was subjected to a calendering process to smooth the surface of the magnetic layer.

[0321] (Cutting process) The magnetic tape obtained as described above was cut into a width of 1 / 2 inch (12.65 mm), thereby obtaining the desired long magnetic tape (average thickness 5.2 μm).

[0322] In Example 3, a coating film was used as the magnetic layer, a reinforced PET film was used as the polymer film, and the average width change ΔA and average tension response ΔW were set to the values ​​shown in Table 1 by adjusting the stretching strength of the PET film in the width and length directions.

[0323] [Comparative Example 1] The polymer film used was a PET film having an average thickness of 4.8 μm, an average storage modulus in the longitudinal direction at a temperature of 50° C. of 3.9 GPa, and an average Young's modulus in the longitudinal direction of 4.7 GPa. A sputtered film was used as the magnetic layer, and a PET film was used as the polymer film. By adjusting the stretching strength of the PET film in the width and length directions, the average width change ΔA and average tension response ΔW were set to the values ​​shown in Table 1. Other than the above, the same procedure as in Example 1 was carried out to obtain a magnetic tape having an average thickness of 5.2 μm.

[0324] Comparative Example 2 The polymer film used was a PEN film having an average thickness of 4.0 μm, an average storage modulus in the longitudinal direction of 5.5 GPa in an environment at a temperature of 50° C., and an average Young's modulus in the longitudinal direction of 6.3 GPa. The barium ferrite (BaFe 12 O 19 ) Magnetic powder, hexagonal plate shape, average aspect ratio 3.0, average particle volume 1600nm 3 The following was used. A coating film was used as the magnetic layer, and a PEN film was used as the polymer film. By adjusting the stretching strength of the PEN film in the width and length directions, the average width change ΔA and average tension response ΔW were set to the values ​​shown in Table 1. Other than the above, the same procedure as in Example 3 was carried out to obtain a magnetic tape having an average thickness of 5.2 μm.

[0325] Comparative Example 3 The polymer film used was a reinforced PET film having an average thickness of 4.6 μm, an average storage modulus in the longitudinal direction of 3.9 GPa in an environment at a temperature of 50° C., and an average Young's modulus in the longitudinal direction of 4.6 GPa. The average thickness of the magnetic layer after the calendering treatment was set to 0.08 μm, and the average thickness of the underlayer after the calendering treatment was set to 0.8 μm. The barium ferrite (BaFe 12 O 19) Magnetic powder, hexagonal plate shape, average aspect ratio 3.0, average particle volume 1600nm 3 The following was used. A coating film was used as the magnetic layer, and a reinforced PET film was used as the polymer film. By adjusting the stretching strength of the reinforced PET film in the width and length directions, the average width change ΔA and average tension response ΔW were set to the values ​​shown in Table 1. Other than the above, the same procedure as in Example 3 was carried out to obtain a magnetic tape having an average thickness of 5.6 μm.

[0326] (Average width change ΔA) Fig. 18 is a graph showing the measurement results of the amount of width change of the magnetic tapes according to Examples 1 to 3 and Comparative Examples 1 to 3. Fig. 19 is a graph showing the measurement results of the amount of width change of the magnetic tape according to Example 1.

[0327] (Method for measuring the tension required to adjust for width changes over a 10-year period) The measurement environment for the LTO7 Drive is fixed at 32°C and 55% humidity. The cartridges are stored with the wire wound into the cartridge at a tension of 0.55 N. Measurements are started after one hour in each environment. Measurements will be performed once a day for 14 days. The measurement band measures the DB0 part in normal creep evaluation. Expectations for 10 years from now The creep rate was calculated using an approximate formula based on the storage time and creep change amount from the start of measurement and the point after 14 days (336 hours). This creep rate is used to calculate the rate 10 years from now (87,600 hours). Creep change after 10 years / tension response = the tension required to adjust the width change over an assumed 10-year period.

[0328] The bandwidth measurement is performed as follows. The method for measuring servo band pitch using a tape drive device involves running the magnetic tape using the tape drive device, measuring the servo trace lines T on each servo band of the two servo read heads, and then measuring the servo band pitch from the relative position of each measured servo trace line T to the servo pattern. The spacing between the servo trace lines T indicates the servo band pitch (the spacing between the two servo read heads of the drive head) when the width of the magnetic tape is not changing.

[0329] The tape drive device outputs a servo reproduction signal having a waveform corresponding to the position of the servo trace line T relative to the servo pattern. Typically, the distance AC between the A burst and the C burst, which are arrays of inclined patterns of the same shape, and the distance AB between the A burst and the B burst, which are arrays of inclined patterns of different shapes, are calculated, and the position of the servo trace line T of each servo read head 132 is measured using the following formula (1). Note that θ is the azimuth angle of each of the inclined patterns, which corresponds to the angle φ in Figure 6, and is set to 12° in this example.

[0330]

number

[0331] Here, the distance AC may be the distance A1-C1 between the first slopes of the A burst and the C burst, the distance A2-C2 between their second slopes, the distance A3-C3 between their third slopes, or the distance A4-C4 between their fourth slopes. These distances AC (AC1 to AC4) refer to the distances between positions (upper peak positions) showing the maximum positive amplitude in the servo reproduction waveform. Similarly, the distance AB may be the distance A1-B1 between the first inclined portions of the A burst and the B burst, the distance A2-B2 between the second inclined portions thereof, the distance A3-B3 between the third inclined portions thereof, or the distance A4-B4 between the fourth inclined portions thereof. Typically, when the distance A1-C1 is used, the distance A1-B1 is used, when the distance A2-C2 is used, the distance A2-B2 is used, when the distance A3-C3 is used, the distance A3-B3 is used, and when the distance A4-C4 is used, the distance A4-B4 is used. The servo band pitch is then calculated from the difference between the values ​​representing the position of each servo trace line T on the servo pattern, which is calculated from the ratio of distance AB to distance AC, calculated using equation [4]. Here, of the two servo bands being measured, the difference is taken between the measurement value of the servo band on the tape edge side (servo band s3) and the measurement value of the servo band on the tape center side (servo band s2). Whether this value is positive or negative indicates the direction of change in tape width; a positive value corresponds to a narrowing of the servo band pitch, and a negative value corresponds to a widening of the servo band pitch. If the difference is zero, it means that there is no change in tape width. The servo band pitch is preferably determined from the difference between many servo frames, and may be the average value of the measured values ​​calculated from the difference between 100 to 100,000 servo frames. The tape tension during measurement is 0.55 N, and the measurement is performed at a constant tension over the entire length of the magnetic tape MT.

[0332] [Table 1]

[0333] If the tension (N) required to adjust the average width change ΔA is 0.25 or more, the tension (N) required to adjust the width change over an estimated 10 years will exceed 0.75 N, making tension adjustment difficult in an actual drive.

[0334] Although the embodiments and modifications of the present disclosure have been specifically described above, the present disclosure is not limited to the above embodiments and modifications, and various modifications based on the technical concepts of the present disclosure are possible. For example, the configurations, methods, steps, shapes, materials, and numerical values ​​described in the above embodiments and modifications are merely examples, and different configurations, methods, steps, shapes, materials, and numerical values ​​may be used as necessary. The configurations, methods, steps, shapes, materials, and numerical values ​​of the above embodiments and modifications can be combined with each other as long as they do not deviate from the spirit of the present disclosure.

[0335] The chemical formulas of the compounds exemplified in the above embodiments and modifications are representative, and are not limited to the valences described, etc., as long as they are the general names of the same compounds. In the numerical ranges described in stages in the above embodiments and modifications, the upper or lower limit of a numerical range in one stage may be replaced with the upper or lower limit of a numerical range in another stage. Unless otherwise specified, the materials exemplified in the above embodiments and modifications can be used alone or in combination of two or more.

[0336] The present disclosure may also employ the following configuration. (1) A tape-shaped magnetic recording medium, A magnetic recording medium in which the average width change before and after being left standing for 40 hours in an environment of 50°C temperature and 40% RH with a tension of 0.55 N applied in the longitudinal direction is 170 ppm or less, and the average tension responsiveness to longitudinal tension in an environment of 50°C temperature and 40% RH is 700 ppm / N or more. (2) 2. The magnetic recording medium according to claim 1, wherein the average tension response is 715 ppm / N or more and 15,000 ppm / N or less. (3) The magnetic recording medium according to (1) or (2), wherein the average width change is 140 ppm or less. (4) A substrate, an underlayer, and a magnetic layer are sequentially provided, The magnetic recording medium according to any one of (1) to (3), wherein the substrate has an average storage modulus in the longitudinal direction of 3.0 GPa or more and 9.0 GPa or less in an environment at a temperature of 50°C. (5) The magnetic recording medium according to (4), wherein the average storage modulus is 3.5 GPa or more and 6.0 GPa or less. (6) The magnetic recording medium according to (4) or (5), wherein the substrate contains polyesters. (7) The magnetic recording medium according to (6), wherein the polyesters include at least one selected from the group consisting of polyethylene terephthalate and polyethylene naphthalate. (8) The magnetic recording medium according to any one of (4) to (7), wherein the substrate has an average thickness of 4.4 μm or less. (9) The magnetic recording medium according to any one of (4) to (8), wherein the magnetic layer is a vacuum thin film. (10) The magnetic recording medium according to any one of (4) to (8), wherein the magnetic layer is a coating film. (11) The magnetic recording medium according to any one of (4) to (8) and (10), wherein the magnetic layer contains magnetic powder. (12) The magnetic recording medium according to (11), wherein the magnetic powder includes ε-iron oxide magnetic powder, hexagonal ferrite magnetic powder, or Co-containing spinel ferrite magnetic powder. (13) The magnetic recording medium according to any one of (4) to (12), wherein the average thickness of the magnetic layer is 90 nm or less. (14) The magnetic recording medium according to any one of (4) to (12), wherein the underlayer has an average thickness of 1.0 μm or less. (15) The magnetic recording medium according to any one of (4) to (14), wherein the average thickness of the magnetic recording medium is 5.2 μm or less. (16) The magnetic recording medium according to any one of (4) to (15), wherein the squareness of the magnetic layer in the perpendicular direction of the magnetic recording medium is 65% or more. (17) The magnetic recording medium according to any one of (4) to (16), wherein the magnetic layer has five or more servo bands. (18) The magnetic recording medium according to (17), wherein the width of the servo band is 95 μm or less. (19) the magnetic layer is configured to be able to form a plurality of data tracks; The magnetic recording medium according to any one of (4) to (18), wherein the width of the data track is 1500 nm or less. (20) A magnetic recording medium according to any one of (1) to (19), a storage unit configured to be able to write adjustment information for adjusting the tension applied in the longitudinal direction of the magnetic recording medium; A cartridge comprising: [Explanation of symbols]

[0337] 10 cartridges 11 Cartridge Memory 31 Antenna coil 32 Rectification / power supply circuit 33 Clock Circuit 34 Detection and modulation circuit 35 Controller 36 memory 36A First storage area 36B Second storage area 41 Base 42 Base layer 43 Magnetic layer 44 Back layer 56 Head Unit 56A, 56B servo readhead 100 servo frames 101 Servo subframe 1 101A A Burst 101B B Burst 102 Servo subframe 2 102C C Burst 102D D Burst 103 Servo Stripe MT magnetic tape SB servo band DB Data Binding

Claims

1. A tape-shaped magnetic recording medium, A magnetic recording medium in which the average width change before and after being left standing for 40 hours in an environment of 50°C temperature and 40% RH with a tension of 0.55 N applied in the longitudinal direction is 170 ppm or less, and the average tension response to longitudinal tension in an environment of 50°C temperature and 40% RH is 700 ppm / N or more.

2. 2. The magnetic recording medium according to claim 1, wherein the average tension response is 715 ppm / N or more and 15,000 ppm / N or less.

3. 2. The magnetic recording medium according to claim 1, wherein the average width change is 140 ppm or less.

4. A substrate, an underlayer, and a magnetic layer are sequentially provided, 2. The magnetic recording medium according to claim 1, wherein the substrate has an average storage modulus in the longitudinal direction in an environment at a temperature of 50° C. of 3.0 GPa or more and 9.0 GPa or less.

5. 5. The magnetic recording medium according to claim 4, wherein the average storage modulus is 3.5 GPa or more and 6.0 GPa or less.

6. 5. The magnetic recording medium according to claim 4, wherein the substrate comprises polyesters.

7. 7. The magnetic recording medium according to claim 6, wherein the polyesters include at least one selected from the group consisting of polyethylene terephthalate and polyethylene naphthalate.

8. 5. The magnetic recording medium according to claim 4, wherein the average thickness of the substrate is 4.4 [mu]m or less.

9. 5. The magnetic recording medium according to claim 4, wherein the magnetic layer is a vacuum thin film.

10. 5. The magnetic recording medium according to claim 4, wherein the magnetic layer is a coating film.

11. The magnetic recording medium according to claim 4 , wherein the magnetic layer contains magnetic powder.

12. 12. The magnetic recording medium according to claim 11, wherein the magnetic powder includes ε-iron oxide magnetic powder, hexagonal ferrite magnetic powder, or Co-containing spinel ferrite magnetic powder.

13. 5. The magnetic recording medium according to claim 4, wherein the average thickness of the magnetic layer is 90 nm or less.

14. 5. The magnetic recording medium according to claim 4, wherein the average thickness of the underlayer is 1.0 [mu]m or less.

15. 2. The magnetic recording medium according to claim 1, wherein the average thickness of the magnetic recording medium is 5.2 [mu]m or less.

16. 5. The magnetic recording medium according to claim 4, wherein the squareness ratio of the magnetic layer in the perpendicular direction of the magnetic recording medium is 65% or more.

17. 5. The magnetic recording medium according to claim 4, wherein the magnetic layer has five or more servo bands.

18. 18. The magnetic recording medium according to claim 17, wherein the width of the servo band is 95 [mu]m or less.

19. the magnetic layer is configured to be able to form a plurality of data tracks; 5. The magnetic recording medium according to claim 4, wherein the width of the data track is 1500 nm or less.

20. The magnetic recording medium according to claim 1; a storage unit configured to be able to write adjustment information for adjusting the tension applied in the longitudinal direction of the magnetic recording medium; A cartridge comprising:

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