Magnetic recording media and cartridges

Abstract

The present invention provides a magnetic recording medium having excellent electromagnetic conversion characteristics. 　This magnetic recording medium being tape-shaped comprises a base body, an undercoat layer, and a magnetic layer, in order. The magnetic layer contains hexagonal ferrite particles. The crystallite size calculated from a peak derived from the (1, 1, 0) plane of hexagonal ferrite, which has been obtained by measuring the magnetic layer using an oblique-incidence X-ray diffraction method, is from 11.0 to 15.0 nm.

Description

[Technical Field]

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

[0002] In recent years, with the development of information technology (IT), there has been an increasing demand for higher recording density in tape-type magnetic recording media used as data storage media. To meet this demand, there is a need for smaller particle sizes of hexagonal ferrite magnetic powder. For example, Patent Document 1 discloses hexagonal strontium ferrite magnetic powder with an average particle size ranging from 10 to 25 nm. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-127985 Summary of the Invention [Problem to be solved by the invention]

[0004] However, even if the particle size of the powdered hexagonal ferrite magnetic powder is specified before the tape-shaped magnetic recording medium is produced, it is difficult to obtain excellent electromagnetic conversion characteristics, and there is room for improvement.

[0005] An object of the present disclosure is to provide a magnetic recording medium having excellent electromagnetic conversion characteristics and a cartridge including the same. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems, the first disclosure provides: A tape-shaped magnetic recording medium, A substrate, an underlayer, and a magnetic layer are sequentially provided, the magnetic layer includes hexagonal ferrite particles; Using grazing incidence X-ray diffraction , in the state of the magnetic recording mediumIn the magnetic recording medium, the crystallite size calculated from the peak derived from the (1,1,0) plane of hexagonal ferrite obtained by measuring the magnetic layer is 11.0 nm or more and 15.0 nm or less.

[0007] The second disclosure is a cartridge including the magnetic recording medium of the first disclosure. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is an exploded perspective view showing an example of the configuration of a cartridge according to an 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. 10A is a plan view of a sample for X-ray diffraction measurement, and Fig. 10B is a cross-sectional view taken along line XB-XB in Fig. 10A. [Figure 11] FIG. 11 is an exploded perspective view showing an example of the configuration of a cartridge according to a modified example of an embodiment of the present disclosure. [Figure 12] FIG. 12 is a graph showing the relationship between the crystallite size calculated from the diffraction peaks of grazing incidence X-ray diffraction and the SNR. DETAILED DESCRIPTION OF THE INVENTION

[0009] The embodiments of the present disclosure will be described in the following order. 1. Overview 2 Cartridge Configuration 3 Cartridge Memory Configuration 4 Magnetic Tape Configuration 5. Magnetic tape manufacturing method 6. Effects 7 Variations

[0010] 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.

[0011] [1 Overview] The present inventors have conducted extensive research to obtain excellent electromagnetic conversion characteristics, and as a result have found that simply specifying the particle size of the hexagonal ferrite magnetic powder before producing a tape-type magnetic recording medium does not sufficiently improve the electromagnetic conversion characteristics, and that it is necessary to specify the size of the hexagonal ferrite crystallites on the surface of the magnetic layer in the state of the tape-type magnetic recording medium.

[0012] Therefore, the inventors attempted to calculate the crystallite size of hexagonal ferrite in the magnetic layer of a magnetic recording medium using diffraction peaks obtained by 2θ / θ X-ray diffraction measurement (specifically, peaks belonging to the (1,1,0) plane of hexagonal ferrite). However, the 2θ / θ method had the problem that the peaks originating from the hexagonal ferrite in the magnetic layer could not be detected due to the influence of diffraction peaks originating from the base material of the magnetic recording medium.

[0013] As a result of further intensive research to solve the above problems, the inventors discovered a method for calculating the hexagonal ferrite crystallite size of the magnetic layer from the diffraction peaks obtained using oblique incidence X-ray diffraction (specifically, the peaks derived from the (1,1,0) plane of hexagonal ferrite).

[0014] [2 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.

[0015] 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.

[0016] The cartridge memory 11 is provided near one corner of the cartridge 10. When the cartridge 10 is loaded into a recording / playback device (drive), the cartridge memory 11 faces a 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.

[0017] [3 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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] The management ledger data includes at least one type of data selected from the group consisting of the capacity, creation date, edit date, and storage location of the data files recorded on the magnetic tape MT. The index information is metadata for searching the contents of the data files. The thumbnail information is a thumbnail of the video or still image stored on the magnetic tape MT.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] [4 Magnetic Tape Configuration] 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.

[0026] 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.

[0027] 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.

[0028] (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.

[0029] 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 positions 10 m to 20 m, 30 m to 40 m, and 50 m to 60 m in the longitudinal direction 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.

[0030] 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 these measurements (15 positions in total) are simply averaged (arithmetic mean) to calculate the average thickness of the substrate 41. Note that the five measurement positions are selected randomly from the sample so that they are each different from the others in the longitudinal direction of the magnetic tape MT.

[0031] The base 41 includes at least one material selected from the group consisting of, for example, polyesters, polyolefins, cellulose derivatives, vinyl resins, other polymer resins, etc. When the base 41 includes two or more materials among the above, the two or more materials may be mixed, copolymerized, or laminated.

[0032] Of the above polymer resins, the substrate 41 preferably contains polyesters. By including polyesters in the substrate 41, the average Young's modulus in the longitudinal direction of the substrate 41 can be reduced to preferably 2.5 GPa or more and 7.8 GPa or less, more preferably 3.0 GPa or more and 7.0 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 almost constant. A method for measuring the average Young's modulus in the longitudinal direction of the substrate 41 will be described later.

[0033] The polyesters include, for example, at least one selected from the group consisting 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.

[0034] 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.

[0035] The polyolefins include, for example, at least one selected from the group consisting of PE (polyethylene) and PP (polypropylene). The cellulose derivatives include, for example, at least one selected from the group consisting of cellulose diacetate, cellulose triacetate, CAB (cellulose acetate butyrate), and CAP (cellulose acetate propionate). The vinyl resins include, for example, at least one selected from the group consisting of PVC (polyvinyl chloride) and PVDC (polyvinylidene chloride).

[0036] Examples of other polymer resins include at least one selected from the group consisting 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).

[0037] 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.

[0038] (magnetic layer) The magnetic layer 43 is a recording layer for recording signals using a magnetization pattern. 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 and a binder. If necessary, the magnetic layer 43 may further contain at least one additive selected from the group consisting of lubricants, carbon, dispersants, antistatic agents, abrasives, hardeners, rust inhibitors, and non-magnetic reinforcing particles. The magnetic layer 43 may have an uneven surface.

[0039] 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 56 (specifically, servo read heads 56A and 56B) when recording or reproducing data. A servo pattern (servo signal) for tracking control of the head 56 is written in advance in the servo bands SB. User data is recorded in the data bands DB.

[0040] The total area S of multiple servo bands SB relative to the area S of the magnetic surface SB The ratio R S (=(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 ratio R S The lower limit of the average value is preferably 0.8% or more, from the viewpoint of ensuring 5 or more servo bands SB.

[0041] 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 positions 10 m to 20 m, 30 m to 40 m, and 50 m to 60 m in the longitudinal direction from the joint 21 between the magnetic tape MT and the leader tape LT, respectively, 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 and the number of servo bands SB. Next, calculate the ratio R of each sample using the following formula: S Ask for. Ratio R S [%]=(((Servo bandwidth W SB ) x (number of servo bands SB)) / (width of magnetic tape MT)) x 100 Next, the proportion of the three samples, R S The arithmetic mean is the ratio R S Calculate the average value of

[0042] 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.

[0043] 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.

[0044] 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 56 that can read such servo signals.

[0045] 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 SBNext, the servo bandwidth W of the three samples is calculated. SB The servo bandwidth W is calculated by arithmetically averaging SB Calculate the average value of

[0046] 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.

[0047] 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.

[0048] 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 positions 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.

[0049] The minimum distance L between magnetic 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, and three 250 mm lengths of the magnetic tape MT are cut out from positions 10 to 20 m, 30 to 40 m, and 50 to 60 m longitudinally from the joint 21 between the magnetic tape MT and the leader tape LT 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.

[0050] 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).

[0051] 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.

[0052] The servo band SB includes a plurality of servo frames 110. Each servo frame 110 is made up of 18 servo stripes 113. Specifically, each servo frame 110 is made up of a servo subframe 1 (111) and a servo subframe 2 (112).

[0053] Servo subframe 1 (111) is composed of an A burst 111A and a B burst 111B. The B burst 111B is located adjacent to the A burst 111A. The A burst 111A has five servo stripes 113 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 113 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 111A, the B burst 111B 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 113 are denoted by symbols B1, B2, B3, B4, and B5 from the EOT to the BOT of the magnetic tape MT. The servo stripes 113 of the B burst 111B are inclined in the opposite direction to the servo stripes 113 of the A burst 111A. That is, the servo stripes 113 of the A burst 111A and the servo stripes 113 of the B burst 111B are arranged in a V-shape.

[0054] Servo subframe 2 (112) is composed of a C burst 112C and a D burst 112D. The D burst 112D is located adjacent to the C burst 112C. The C burst 112C has four servo stripes 113 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 113 are denoted by symbols C1, C2, C3, and C4 from the EOT to the BOT of the magnetic tape MT. Like the C burst 112C, the D burst 112D 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 113 are denoted by symbols D1, D2, D3, and D4 from the EOT to the BOT of the magnetic tape MT. The servo stripes 113 of the D burst 112D are inclined in the opposite direction to the servo stripes 113 of the C burst 112C. That is, the servo stripes 113 of the C burst 112C and the servo stripes 113 of the D burst 112D are arranged in a V-shape.

[0055] The above-mentioned predetermined angle φ of the servo stripe 113 in the A burst 111A, the B burst 111B, the C burst 112C, and the D burst 112D 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.

[0056] Reading the servo band SB with the head 56 provides information for determining the tape speed and the longitudinal position of the head 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 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.

[0057] 6, the servo patterns (i.e., the plurality of servo stripes 113) 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.

[0058] The upper limit of the average thickness of magnetic layer 43 is 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. If the upper limit of the average thickness of magnetic layer 43 is 80 nm or less, when a ring-type head is used as the recording head, the influence of the demagnetizing field can be reduced, thereby achieving even better electromagnetic conversion characteristics.

[0059] 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.

[0060] 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 samples are cut from the magnetic tape MT at positions 10 to 20 m, 30 to 40 m, and 50 to 60 m from the connection 21 between the magnetic tape MT and the leader tape LT in the longitudinal direction. Each sample is then thinned using a FIB method or other suitable process. 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. The tungsten layer is then further formed by vapor deposition or sputtering on the surface facing the magnetic layer 43. This thinning is performed along the longitudinal direction of the magnetic tape MT. That is, this thinning results in a cross section parallel to both the longitudinal and thickness directions of the magnetic tape MT.

[0061] 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

[0062] 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 measured values ​​of each thinned sample (thickness of the magnetic layer 43 at a total of 30 points) are simply averaged (arithmetic mean) to obtain the average thickness [nm] of the magnetic layer 43.

[0063] (magnetic powder) The magnetic powder contains hexagonal ferrite particles. The magnetic powder preferably 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.

[0064] The 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, the term "hexagonal plate" includes a substantially hexagonal plate shape. The hexagonal ferrite preferably contains at least one element selected from the group consisting of Ba, Sr, Pb, and Ca, more preferably at least one element selected from the group consisting of Ba and Sr. Specifically, the hexagonal ferrite may be, for example, barium ferrite or strontium ferrite. Barium ferrite may contain at least one element selected from the group consisting of Sr, Pb, and Ca in addition to Ba. Strontium ferrite may contain at least one element selected from the group consisting of Ba, Pb, and Ca in addition to Sr.

[0065] 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 the group consisting of Ba, Sr, Pb, and Ca, preferably at least one metal selected from the group consisting of Ba and Sr. M may be a combination of Ba and at least one metal selected from the group consisting of Sr, Pb, and Ca. M may also be a combination of Sr and at least one metal 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.

[0066] The average particle size of the magnetic powder determined from the state of the magnetic tape MT is, for example, 13 nm to 22 nm, 13 nm to 19 nm, 13 nm to 18 nm, 14 nm to 17 nm, or 14 nm to 16 nm.

[0067] The average aspect ratio of the magnetic powder determined from the state of the magnetic tape MT 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.

[0068] The average particle size and average aspect ratio of the magnetic powder are determined as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound and cut out at a position 30 m longitudinally from the connection 21 between the magnetic tape MT and the leader tape LT. Next, the magnetic tape MT to be measured is processed and thinned using a FIB method or the like. 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. In other words, the thinning results in a cross section parallel to both the longitudinal and thickness directions of the magnetic tape MT.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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 simply averaged (arithmetic mean) 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 ave and average plate diameter DB ave The average aspect ratio of the particles (DB ave / DA ave ) is found.

[0073] The average particle volume of the magnetic powder determined from the state of the magnetic tape MT is, for example, 500 nm 3 More than 2500nm 3 Below, 500nm 3 More than 1600nm 3 Below, 500nm 3 More than 1500nm 3 Below, 600nm 3More than 1200nm 3 or below 600nm 3 More than 1000nm 3 The following is the result.

[0074] 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

[0075] (Crystalline size of hexagonal ferrite in magnetic tape) The hexagonal ferrite particles are composed of one or more crystallites. The crystallites may be plate-shaped, such as a hexagonal plate, or columnar, such as a hexagonal column (provided that the thickness or height is smaller than the major axis of the plate or base). The crystallite size calculated from the peak derived from the (1,1,0) plane of the hexagonal ferrite obtained by measuring the magnetic surface of the magnetic tape MT using Grazing Incidence X-ray Diffraction (GIXD) (hereinafter referred to as the "XRD crystallite size in the magnetic tape state") is 11 nm or more and 15 nm or less, preferably 12 nm or more and 14 nm or less. When the XRD crystallite size in the magnetic tape state is 11 nm or more, sufficient magnetic thermal stability can be maintained, ensuring long-term storage reliability of magnetic recording. On the other hand, when the XRD crystallite size in the magnetic tape state is 15 nm or less, further improvements in areal recording density can be expected. Therefore, when the XRD crystallite size in the magnetic tape state is 11 nm or more and 15 nm or less, excellent electromagnetic conversion characteristics can be obtained.

[0076] The XRD crystallite size in the magnetic tape state differs from the particle size measured from the cross-sectional TEM image of the magnetic tape MT. While the cross-sectional TEM image shows the apparent size of the magnetic particles, the XRD crystallite size indicates the size of the crystalline portion inside the magnetic particles. The surface of the magnetic particles is chemically unstable, so it does not contribute to the effective particle volume that functions as a magnet. On the other hand, the crystallite size measured by XRD can be considered the effective particle size that functions as a magnet.

[0077] Even if the particle size measured from a cross-sectional TEM image of magnetic tape MT or the crystallite size measured by XRD in the magnetic powder state is specified, it is difficult to determine the XRD crystallite size in the magnetic tape state. During the magnetic tape MT manufacturing process (mainly the preparation process of the coating material for forming the magnetic layer), magnetic particles may be damaged by dispersion media such as beads. While major damage, such as a magnetic particle breaking in half, can be observed using an electron microscope such as a TEM, minute changes such as a single molecule's worth of surface wear or internal defects are difficult to identify by external observation using an electron microscope such as a TEM. Measuring the XRD crystallite size in the magnetic tape state allows us to determine the effective magnetic particle size that will ultimately function as a magnet after the magnetic tape MT manufacturing process.

[0078] Even if the particle size measured from a cross-sectional TEM image of the magnetic tape MT or the crystallite size measured by XRD in the magnetic powder state is set within a specified range, it is difficult to obtain excellent electromagnetic conversion characteristics. In contrast, in this embodiment, excellent electromagnetic conversion characteristics can be obtained by setting the XRD crystallite size in the magnetic tape state within a specified range. This is because the XRD crystallite size in the magnetic tape state is the size of magnetic particles that effectively behave as a magnet, taking into account damage to the magnetic particles during the dispersion process, and is a parameter that is directly related to the actual recording and playback of the magnetic tape MT.

[0079] The XRD crystallite size in the magnetic tape state is determined as follows: First, the magnetic tape MT housed in the cartridge 10 is unwound, and a sample of 70 mm is cut from the magnetic tape MT at a position 30 to 40 m longitudinally from the joint 21 between the magnetic tape MT and the leader tape LT to prepare a sample.

[0080] Next, sample 60 for X-ray diffraction measurement shown in Figures 10A and 10B is prepared as follows. First, a rectangular glass slide 61 is prepared, and double-sided tapes 63A and 63B are attached to both longitudinal ends of one surface of the glass slide 61. Then, the back layer 44 side of magnetic tape sample 62 is attached to one surface of glass slide 61 with double-sided tapes 63A and 63B so that the longitudinal directions of magnetic tape sample 62 and glass slide 61 are parallel and so that magnetic tape sample 62 does not sag or wrinkle. In this way, sample 60 for X-ray diffraction measurement is prepared.

[0081] Next, the sample 60 for X-ray diffraction measurement is placed at the X-ray irradiation position of the X-ray diffraction device, and the X-ray diffraction pattern is measured. The conditions for measuring X-ray diffraction are as follows. Equipment used: XRD (Smart-lab, manufactured by Rigaku) Measurement mode: Oblique incidence method Radiation source: Cu (CuKα ray, wavelength λ=0.154nm) Voltage: 45kV Current: 200mA Incident X-ray Soller slit angle: 0.5° Incident X-ray limiting slit: 10.0 mm X-ray receiving solar slit angle (PSA): 0.5° X-ray receiving solar slit angle: 5° Incident X-ray angle (ω): 0.4° Detector initial position (2θ): 0.4° Scan axis: 2θ Step width: 0.05° Scan speed: 3° / min Scanning range: 15° to 80° in the normal direction to the sample magnetic layer Analysis software: PDXL2 Next, the crystallite size is calculated from the diffraction peak of the (1,1,0) plane (2θ = 30.3° to 30.6° (e.g., 30.5°)) obtained by grazing incidence X-ray diffraction. The following Scherrer formula is used to calculate the crystallite size. Scherrer's formula: Dx=Kλ / Bcosθ Dx: Crystallite size (nm) λ: wavelength of the measured X-ray (nm) B: Broadening of diffraction lines due to crystallite size (half-width of diffraction peak) θ: angle at which the diffraction peak appears K: Scherrer constant (=0.94)

[0082] (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.

[0083] 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.

[0084] 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.

[0085] (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, 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.

[0086] 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).

[0087] 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).

[0088] 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.

[0089] 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.)

[0090] 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.)

[0091] CH3(CH2) p COO(CH2) q CH3···(3) (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.)

[0092] 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.)

[0093] (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.

[0094] Specifically, the carbon is carbon particles, which include, for example, at least one selected from the group consisting of carbon black, acetylene black, ketjen black, carbon nanotubes, and graphene.

[0095] (dispersant) Dispersants are used to improve the dispersibility of magnetic powder. Examples of dispersants include fatty acids having 12 to 18 carbon atoms (RCOOH, where R is an alkyl or alkenyl group having 11 to 17 carbon atoms), such as caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, oleic acid, elaidic acid, linoleic acid, linolenic acid, and stearic acid. Or compounds represented by X-R-COOH, such as phthalic acid, adipic acid, and salicylic acid. X, in this case, is selected from a carboxylic acid, a ketone group, an aldehyde group, an ester group, a hydroxyl group, and a hydrocarbon chain having 1 to 10 carbon atoms. R is selected from a hydrocarbon chain having 12 to 18 carbon atoms, an aromatic ring, and a naphthalene ring. Metal soaps made from alkali metals or alkaline earth metals of the above acidic compounds; fluorine-containing compounds of the above fatty acid esters; amides of the above fatty acids; polyalkylene oxide alkyl phosphate esters; lecithin; trialkyl polyolefinoxy quaternary ammonium salts (wherein the alkyl has 1 to 5 carbon atoms and the olefin is ethylene, propylene, or the like); phenylphosphenic acid; copper phthalocyanine, etc., can be used. These may be used alone or in combination. The content of the dispersant is preferably 0.2 to 7 parts by mass, more preferably 5 to 7 parts by mass, per 100 parts by mass of the non-magnetic powder.

[0096] (antistatic agent) Examples of antistatic agents include natural surfactants, nonionic surfactants, and cationic surfactants.

[0097] (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.

[0098] (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.

[0099] (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.

[0100] (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).

[0101] (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 and a binder. If necessary, the underlayer 42 may further contain at least one additive selected from the group consisting of a lubricant, carbon, a dispersant, an antistatic agent, a hardener, an anti-rust agent, and the like.

[0102] The upper limit of the average thickness of the underlayer 42 is preferably 1.2 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 1.2 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 1.2 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. However, the magnification of the TEM image is appropriately adjusted depending on the thickness of the underlayer 42.

[0103] (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.

[0104] (binder) The binder is the same as that used in the magnetic layer 43 described above.

[0105] (additives) The lubricant, carbon, dispersant, antistatic agent, hardener and anticorrosive agent are the same as those in the magnetic layer 43 described above.

[0106] (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, an antistatic agent, etc. 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.

[0107] 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.

[0108] 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.

[0109] 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 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 250 mm lengths from positions 10 m to 20 m, 30 m to 40 m, and 50 m to 60 m in the longitudinal direction from the joint 21 between the magnetic tape MT and the leader tape LT, respectively, to prepare three samples. Next, the back layer 44 of each sample is removed with a solvent such as MEK (methyl ethyl ketone) or dilute hydrochloric acid. Next, using a Mitutoyo Laser Hologram (LGH-110C), the thickness of each sample is measured at five positions, and these measurements (15 points in total) are simply averaged (arithmetic mean) 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]

[0110] (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 5.3 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.

[0111] 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 positions 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 in the longitudinal direction, respectively, 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 these measurements (15 points in total) are simply averaged (arithmetic mean) 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.

[0112] (Average value of 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 achieving excellent electromagnetic conversion characteristics.

[0113] In the grazing incidence X-ray diffraction method, the angle of incidence of X-rays is extremely shallow, and if the surface properties of the magnetic layer 43 are poor, information on protruding parts such as abrasives is likely to be picked up, which may result in poor measurement of the diffraction peaks of hexagonal ferrite on the surface of the magnetic layer 43. As described above, if the average value of the arithmetic mean roughness Ra of the surface of the magnetic layer 43 is 1.9 nm or less, good diffraction peaks of hexagonal ferrite on the surface of the magnetic layer 43 can be measured by the grazing incidence X-ray diffraction method.

[0114] The lower limit of the average value of the arithmetic mean roughness Ra of the surface of 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 magnetic layer 43 is 1.0 nm or more, deterioration of running performance due to increased friction can be suppressed.

[0115] The average value of the arithmetic mean roughness Ra 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 positions 10 to 20 m, 30 to 40 m, and 50 to 60 m longitudinally from the joint 21 between the magnetic tape MT and the leader tape LT to prepare three samples. Next, the surface of the magnetic layer 43 of each sample is observed with an AFM (Atomic Force Microscope), and a 40 μm × 40 μm AFM image is obtained. The AFM measurement conditions are as follows. AFM: Digital Instruments, Nano Scope IIIa D3100 Cantilever: Single crystal silicon (Nano World SPM probe NCH normal type PointProbe L (cantilever length) = 125 μm) Measurement mode: Tapping (tapping frequency: 200 to 400 Hz) Scan size: 30 μm Scan rate: 1.00Hz Scan line: 512 The position on the surface of the magnetic layer 43 of each sample where the AFM image is acquired is selected at random from among the positions free of foreign matter, scratches, and the like.

[0116] Next, for each sample, the 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 simply averaged (arithmetic mean) to determine the average height (average surface) Zave (= (Z(1) + Z(2) + ··· + Z(262,144)) / 262,144). Next, the deviation Z"(i) from the average center line at each measurement point (= Z(i) - Zave) 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 use. Next, the arithmetic mean roughnesses Ra of the three samples are arithmetically averaged to calculate the average value of the arithmetic mean roughnesses Ra.

[0117] (Back 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]. b When the average value is within the above range, even better electromagnetic conversion characteristics can be obtained.

[0118] 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 three 100 mm lengths of the magnetic tape MT are cut out from the longitudinal positions 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 sample is placed on a slide glass with the surface to be measured (the surface on the magnetic layer side) facing up, and the ends 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

[0119] (Average value of coercive force Hc) The upper limit of the average value of the coercive force Hc 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 Hc 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.

[0120] The lower limit of the average value of the coercive force Hc 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 Hc of the magnetic layer 43 measured in the longitudinal direction of the magnetic tape MT is 1000 Oe or more, demagnetization due to leakage magnetic flux from the recording head can be suppressed.

[0121] The average value of the coercive force Hc is calculated as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and the magnetic tape MT is cut out from positions 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. Three pieces of the magnetic tape MT are stacked with double-sided tape so that the longitudinal direction of each sample 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 of each sample cut out above are wiped off using acetone, ethanol, etc., 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 samples for background correction (hereinafter simply referred to as "correction samples"). 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.

[0122] 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.

[0123] 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 the 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 Hc 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, when measuring the MH loop in the longitudinal direction of the magnetic tape MT, "demagnetization field correction" is not performed. Next, the coercive forces Hc of the three samples are arithmetically averaged to calculate the average value of the coercive forces Hc.

[0124] (Average value of squareness ratios Rs1 and Rs2) The average squareness ratio Rs1 of the magnetic layer 43 in the perpendicular direction of the magnetic tape MT is preferably 65% ​​or more, more preferably 67% or more or 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 Rs1 is 65% or more, the perpendicular orientation of the magnetic powder is sufficiently high, resulting in even better electromagnetic conversion characteristics.

[0125] The average squareness ratio Rs1 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 the magnetic tape MT is cut out from positions 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 in the longitudinal direction. Three pieces of the magnetic tape MT 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 of the magnetic tape MT (the perpendicular 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 perpendicular direction of the substrate 41 (the perpendicular direction of the magnetic tape MT) is measured using a VSM.

[0126] 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.

[0127] 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."

[0128] 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 Rs1 (%). 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 Rs1(%)=(Mr / Ms)×100 Next, the squareness ratios Rs1 of the three samples are arithmetically averaged to calculate the average squareness ratio Rs1.

[0129] The average squareness ratio Rs2 of the magnetic layer 43 in the longitudinal direction (running direction) of the magnetic tape MT is preferably 35% or less, more preferably 33% or less or 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 Rs2 is 35% or less, the magnetic powder has a sufficiently high perpendicular orientation, resulting in even better electromagnetic conversion characteristics.

[0130] The average squareness ratio Rs2 in the longitudinal direction of the magnetic tape MT is determined in the same manner as the average squareness ratio Rs1, except that the MH loop is measured in the longitudinal direction (running direction) of the magnetic tape MT and the substrate 41.

[0131] (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.

[0132] 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.

[0133] 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.

[0134] 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 positions 10 m to 20 m, 30 m to 40 m, and 50 m to 60 m longitudinally 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.

[0135] 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.

[0136] (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.

[0137] 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 three 180 mm lengths of the magnetic tape MT are cut out from positions 10 to 20 m, 30 to 40 m, and 50 to 60 m longitudinally from the joint 21 between the magnetic tape MT and the leader tape LT to prepare three samples. Next, the underlayer 42, magnetic layer 43, and back layer 44 are removed from each of the cut samples 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.

[0138] 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.

[0139] 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.

[0140] [5. Magnetic tape manufacturing method] Next, an example of a method for manufacturing the magnetic tape MT having the above configuration will be described.

[0141] (Magnetic powder manufacturing process) Barium ferrite magnetic powder is prepared as follows. First, sodium tetraborate, α-iron oxide, barium carbonate, and titanium oxide are weighed and mixed. Next, the mixture is placed in a melting furnace that has been maintained at a predetermined high temperature (e.g., 1350°C to 1400°C). After the mixture is melted for a predetermined time (e.g., 80 to 90 minutes), the melted material is poured into water to obtain a molten glass sample.

[0142] Next, the molten glass sample is collected and roughly dried, and then pulverized. The pulverized material is then carried into a firing furnace, which is heated to a temperature of 500°C or higher (preferably 550°C or higher and 590°C or lower) at a predetermined heating rate (e.g., 5°C / min or higher and 10°C / min or lower), and the furnace is maintained at the temperature of 500°C or higher for a predetermined time (e.g., 8 hours or higher and 9.5 hours or lower).

[0143] If necessary, before the above firing step (firing at 500° C. or higher), the firing furnace may be maintained at a temperature in the range of, for example, 400° C. to 470° C. to promote the formation of nuclei of barium ferrite particles.

[0144] Barium ferrite particle nuclei are formed at firing temperatures between 400°C and 470°C. The more nuclei formed, the smaller the particle size of the barium ferrite particles produced. At firing temperatures above 500°C, a crystallization reaction occurs. At low crystallization temperatures, it is easier to produce small barium ferrite particles, but the crystallinity is poor and the magnetic properties deteriorate. At high crystallization temperatures, the crystallinity is high and the magnetic properties are improved, but the particle volume increases. For example, if nucleation is promoted in advance at 450°C for 12 hours, many barium ferrite particle nuclei are formed, so coarsening of the barium ferrite particles can be suppressed even when crystallized at high temperatures.

[0145] The furnace is then cooled to room temperature, the fired product is removed from the furnace, and the glass is removed by acid washing. This yields barium ferrite magnetic powder. In this process, the size of the magnetic powder can be controlled by adjusting the compounding ratio of α-iron oxide, barium carbonate, and titanium oxide and the firing temperature.

[0146] (Paint preparation process) First, a base layer-forming paint is prepared by kneading and dispersing non-magnetic powder, binder, etc., in a solvent. Next, a magnetic layer-forming paint is prepared by kneading and dispersing magnetic powder, binder, etc., in a solvent. If necessary, at least one additive selected from the group consisting of lubricants, carbon, dispersants, antistatic agents, abrasives, curing agents, rust inhibitors, and non-magnetic reinforcing particles may be added to the magnetic layer-forming paint. When a dispersant is added to the magnetic layer-forming paint, the dispersion time of the magnetic powder may be reduced by adjusting the amount of dispersant added. Reducing the dispersion time of the magnetic powder can suppress deterioration of the magnetic powder. Here, deterioration of the magnetic powder includes damage to the magnetic particles, i.e., a decrease in the crystallinity of the magnetic particles and a reduction in crystallite size.

[0147] The following solvents, dispersing devices, and kneading devices can be used to prepare the coating material for forming the magnetic layer and the coating material for forming the undercoat layer.

[0148] 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.

[0149] 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.

[0150] (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., squareness ratio Rs1) 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.

[0151] The squareness ratios Rs1 and Rs2 can be set to the 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 Rs1 (i.e., to further reduce the squareness ratio Rs2), it is preferable to improve the dispersion state of the magnetic powder in the magnetic layer-forming paint. To further increase the squareness ratio Rs1, 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 Rs1 and Rs2 may be used alone or in combination.

[0152] (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.

[0153] (calendering process) Next, the obtained magnetic tape MT is subjected to a calendering process to smooth the surface of the magnetic layer 43.

[0154] (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.

[0155] (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.

[0156] [6 Action and Effects] As described above, in the magnetic tape MT according to one embodiment, the crystallite size calculated from the peak derived from the (1,1,0) plane of hexagonal ferrite obtained by measuring the magnetic surface (surface of the magnetic layer 43) of the magnetic tape MT using the grazing incidence X-ray diffraction method is 11 nm or more and 15 nm or less, thereby achieving excellent electromagnetic conversion characteristics.

[0157] [7 Variations] In the above embodiment, the magnetic tape cartridge is a one-reel type cartridge 10, but it may also be a two-reel type cartridge.

[0158] 11 is an exploded perspective view showing an example of the configuration of a two-reel type cartridge 121. The cartridge 121 comprises an upper half 102 made of synthetic resin, a transparent window member 123 fitted into and fixed to a window 102a opened in the top surface of the upper half 102, a reel holder 122 fixed to the inside of the upper half 102 to prevent the reels 106 and 107 from floating up, a lower half 105 corresponding to the upper half 102, the reels 106 and 107 stored in the space formed when the upper half 102 and the lower half 105 are joined together, the magnetic tape MT wound on the reels 106 and 107, a front lid 109 that closes the front opening formed when the upper half 102 and the lower half 105 are joined together, and a back lid 109A that protects the magnetic tape MT exposed in this front opening.

[0159] The reels 106 and 107 are used to wind the magnetic tape MT. The reel 106 includes a lower flange 106b having a cylindrical hub portion 106a in the center around which the magnetic tape MT is wound, an upper flange 106c having approximately the same size as the lower flange 106b, and a reel plate 111 sandwiched between the hub portion 106a and the upper flange 106c. The reel 107 has a similar configuration to the reel 106.

[0160] The window member 123 has mounting holes 123a for assembling reel holders 122, which are reel holding means for preventing these reels from floating up, at positions corresponding to the reels 106 and 107. The magnetic tape MT is the same as the magnetic tape MT in the first embodiment. [Example]

[0161] The present disclosure will be specifically described below using examples, but the present disclosure is not limited to these examples.

[0162] In the following examples and comparative examples, the average thickness of the magnetic layer, the average thickness of the underlayer, the average thickness of the substrate (base film), the average thickness of the back layer, the average thickness of the magnetic tape, etc. are values ​​obtained using the measurement method described in the above embodiment.

[0163] [Example 1] (Magnetic powder manufacturing process) Barium ferrite magnetic powder was prepared as follows. First, sodium tetraborate, α-iron oxide, barium carbonate, and titanium oxide were weighed and mixed. Next, the mixture was poured into a melting furnace previously maintained at 1350°C and held there for 80 minutes to melt the mixture. The melted material was then poured into water to obtain a glass melt sample. The glass melt sample was then recovered, roughly dried, and pulverized. The pulverized material was then loaded into a firing furnace, which was heated to 590°C at a rate of 5°C / min and held at 590°C for 8 hours. The furnace was then allowed to cool naturally to room temperature, and the fired material was removed from the furnace and acid-washed to remove the glass. This resulted in the production of barium ferrite magnetic powder.

[0164] (Measurement of crystallite size and crystallite volume of powdered magnetic powder) The crystallite size and crystallite volume of powdered barium ferrite magnetic powder were determined as follows. First, the magnetic powder was placed in a recess (circular, 5 mm diameter) of a non-reflective silicon sample plate for XRD, and a measurement sample was prepared by leveling it with a glass plate. Next, the X-ray diffraction pattern of the measurement sample was measured using the focusing method, and the crystallite size D1 was calculated from the diffraction peak of the (0,0,6) plane (2θ = 26.7°). Furthermore, the crystallite size D2 was calculated from the diffraction peak of the (2,2,0) plane (2θ = 74.9°). The results are shown in Table 1. The above-mentioned Scherrer formula was used to calculate the crystallite size D1 and crystallite size D2.

[0165] The conditions for measuring X-ray diffraction are as follows. Equipment used: XRD (Ultima IV, manufactured by Rigaku) Measurement mode: Concentration method Source: Co (CoKα line, wavelength λ=0.179nm) Voltage: 40kV Current: 40mA Divergence slit: 1 / 2° Divergence vertical limit slit: 2mm Scattering slit: 8 mm Receiving slit: open Step width: 0.02° Scan speed: 1° / min Scanning range: 20° to 80° Analysis software: PDXL2

[0166] Next, the crystallite volume V of the barium ferrite magnetic powder is calculated using the following formula: c The results are shown in Table 1.

number

[0167] (Measurement of the average plate thickness, average plate diameter and average particle volume of powdered magnetic powder) The average plate diameter, average plate thickness, and average particle volume of the magnetic powder were determined in the same manner as described in the embodiment above for determining the average plate diameter, average plate thickness, and average particle volume of the magnetic powder from magnetic tape, except that a scanning transmission electron microscope (STEM, Hitachi High-Technologies Corporation, product name: S-4800) was used to observe the powdered magnetic powder before the paint preparation process, STEM photographs were taken, and 300 particles were extracted from the STEM photographs and their average plate thickness and average plate diameter were calculated. The results are shown in Table 1.

[0168] (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. Next, a dispersion treatment was carried out using a Dynomill for 20 hours, and then a filter treatment was carried out to obtain a mixture. In this way, the magnetic layer-forming paint was prepared.

[0169] The amount of dispersant (stearic acid) was adjusted to 5 parts by mass per 100 parts by mass of magnetic powder (barium ferrite magnetic powder). The mass ratio (M2 / M1) of the amount of magnetic powder (barium ferrite magnetic powder) M2 to the amount of binder (vinyl chloride resin) M1 was adjusted to 5. The amount of binder (vinyl chloride resin) M1 is the sum of the amount of vinyl chloride resin contained in the first composition and the amount of vinyl chloride resin contained in the second composition described below.

[0170] (First composition) The barium ferrite (BaFe 12 O 19):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): 60 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) Medium-sized aluminum oxide powder: 5 parts by mass (α-Al2O3, average particle size (D50) 0.09μm)

[0171] (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): 3.6 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) Medium-sized aluminum oxide powder: 5 parts by mass n-Butyl stearate: 2 parts by mass Methyl ethyl ketone: 121.3 parts by mass Toluene: 121.3 parts by mass Cyclohexanone: 60.7 parts by mass Carbon black: 2 parts by mass (Manufactured by Tokai Carbon Co., Ltd., product name: Seest TA)

[0172] Finally, 4 parts by mass of polyisocyanate (product name: Coronate L, manufactured by Tosoh Corporation) as a curing agent and 2 parts by mass of stearic acid as a lubricant were added to the magnetic layer-forming coating material prepared as described above.

[0173] (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.

[0174] (Third composition) Medium particle size acicular iron oxide powder (non-magnetic powder): 100 parts by mass (α-Fe2O3, average major axis length 0.08μm) 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)

[0175] (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

[0176] 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 stearic acid as a lubricant were added to the paint for forming the undercoat layer prepared as described above.

[0177] (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 powder (average particle size (D50) 20 nm): 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

[0178] (coating process) Using the magnetic layer forming paint and primer layer forming paint prepared as described above, a primer layer and a magnetic layer were formed on one main surface of a non-magnetic support, a long polyethylene naphthalate film (hereinafter referred to as "PEN film") with an average thickness of 3.9 μm, as follows.

[0179] First, a coating material for forming a primer layer was applied to one main surface of a PEN film, and then the coating film was dried while being heated and exposed to air, thereby forming a primer layer with an average thickness of 1.0 μm after calendaring.

[0180] Next, a magnetic layer-forming paint was applied onto the undercoat layer, and the coating was then dried by heating and blowing air onto the coating, thereby forming a magnetic layer with an average thickness of 80 nm after calendaring.

[0181] Next, a coating material for forming a back layer was applied to the other main surface of the PEN film, and the coating was dried by heating and blowing air onto the coating, forming a back layer with an average thickness of 0.58 μm after calendaring, thereby obtaining a magnetic tape.

[0182] (hardening process) After the magnetic tape was wound into a roll, the magnetic tape was subjected to a heat treatment in this state to harden the underlayer and the magnetic layer.

[0183] (calendering process) A calendering process was carried out to smooth the surface of the magnetic layer.

[0184] (Cutting process) The magnetic tape obtained as described above was cut into a width of 1 / 2 inch (12.65 mm), resulting in a magnetic tape with an average thickness of 5.6 μm.

[0185] (Servo pattern writing process) After demagnetizing the magnetic tape, a servo writer was used to write a servo pattern onto the magnetic tape, forming five servo bands. The servo pattern conformed to the LTO-8 standard.

[0186] [Example 2] (Magnetic powder manufacturing process) Barium ferrite magnetic powder was prepared as follows. First, α-iron oxide, barium carbonate, and titanium oxide were weighed and mixed. Next, the mixture was placed in a melting furnace previously maintained at 1350°C and held there for 90 minutes to melt. The melted material was then poured into water to obtain a glass melt sample. The glass melt sample was then recovered, roughly dried, and pulverized. The pulverized material was then loaded into a firing furnace, where it was heated to 450°C at a heating rate of 5°C / min and held at 450°C for 12 hours. The furnace was then heated to 550°C at a heating rate of 10°C / min and held at 550°C for 9.5 hours. The furnace was then allowed to cool naturally to room temperature, and the fired material was removed from the furnace and the glass was removed by acid washing. This resulted in the production of barium ferrite magnetic powder. The crystallite size and crystallite volume of the powdered magnetic powder were then determined in the same manner as in Example 1. The average plate thickness, average plate diameter and average particle volume of the powdered magnetic powder were also determined in the same manner as in Example 1. The results are shown in Table 1.

[0187] (Preparation process of paint for forming magnetic layer) The amount of dispersant (stearic acid) blended was adjusted to 7 parts by mass per 100 parts by mass of magnetic powder (barium ferrite magnetic powder). The dispersion treatment time was set to 12.5 hours. As described above, in Example 2, the amount of dispersant blended was increased compared to Example 1, thereby shortening the dispersion treatment time compared to Example 1. As a result, deterioration of characteristics due to damage to the magnetic particles was suppressed compared to Example 1. A coating material for forming a magnetic layer was prepared in the same manner as in Example 1 except for the above.

[0188] The magnetic tape was obtained in the same manner as in Example 1 except for the above steps.

[0189] [Example 3] (Magnetic powder manufacturing process) Barium ferrite magnetic powder was obtained in the same manner as in Example 2, except that the firing furnace was maintained at 450°C for 12 hours, then the temperature was increased to 580°C at a heating rate of 10°C / min, and the firing furnace was maintained at 580°C for 9.5 hours. Next, the crystallite size and crystallite volume of the powdered magnetic powder were determined in the same manner as in Example 1. The average plate thickness, average plate diameter, and average particle volume of the powdered magnetic powder were also determined in the same manner as in Example 1. The results are shown in Table 1.

[0190] (Preparation process of paint for forming magnetic layer) The amount of dispersant (stearic acid) blended was adjusted to 7 parts by mass per 100 parts by mass of magnetic powder (barium ferrite magnetic powder). The dispersion treatment time was set to 13 hours. As described above, in Example 3, the amount of dispersant blended was increased compared to Example 1, thereby shortening the dispersion treatment time compared to Example 1. As a result, deterioration of characteristics due to damage to the magnetic particles was suppressed compared to Example 1. A coating material for forming a magnetic layer was prepared in the same manner as in Example 1 except for the above.

[0191] The magnetic tape was obtained in the same manner as in Example 1 except for the above steps.

[0192] [Example 4] (Magnetic powder manufacturing process) The pulverized material was carried into a sintering furnace, which was heated to 595°C at a heating rate of 5°C / min and held at 595°C for 8 hours. Barium ferrite magnetic powder was obtained in the same manner as in Example 1, except that the pulverized material was carried into a sintering furnace, which was heated to 595°C at a heating rate of 5°C / min and held at 595°C for 8 hours. The crystallite size and crystallite volume of the powdered magnetic powder were then determined in the same manner as in Example 1. The average plate thickness, average plate diameter, and average particle volume of the powdered magnetic powder were also determined in the same manner as in Example 1. The results are shown in Table 1.

[0193] The magnetic tape was obtained in the same manner as in Example 1 except for the above steps.

[0194] [Example 5] (Magnetic powder manufacturing process) The mixture was placed in a melting furnace that had been previously maintained at 1400°C. The pulverized material was then placed in a sintering furnace, which was heated to 550°C at a heating rate of 5°C / min and maintained at 550°C for 8 hours. Other than the above, barium ferrite magnetic powder was obtained in the same manner as in Example 1. Next, the crystallite size and crystallite volume of the powdered magnetic powder were determined in the same manner as in Example 1. The average plate thickness, average plate diameter, and average particle volume of the powdered magnetic powder were also determined in the same manner as in Example 1. The results are shown in Table 1.

[0195] (Preparation process of paint for forming magnetic layer) A coating material for forming a magnetic layer was prepared in the same manner as in Example 1, except that the mixture was placed in a Dynomill dispersing machine and subjected to dispersion treatment for 15 hours.

[0196] The magnetic tape was obtained in the same manner as in Example 1 except for the above steps.

[0197] [Comparative Example 1] (Magnetic powder manufacturing process) The pulverized material was carried into a sintering furnace, which was heated to 575°C at a heating rate of 5°C / min and held at 575°C for 8 hours. Barium ferrite magnetic powder was obtained in the same manner as in Example 1, except that the pulverized material was carried into a sintering furnace, which was heated to 575°C at a heating rate of 5°C / min and held at 575°C for 8 hours. The crystallite size and crystallite volume of the powdered magnetic powder were then determined in the same manner as in Example 1. The average plate thickness, average plate diameter, and average particle volume of the powdered magnetic powder were also determined in the same manner as in Example 1. The results are shown in Table 1.

[0198] (Preparation process of paint for forming magnetic layer) A coating material for forming a magnetic layer was prepared in the same manner as in Example 1, except that the mixture was placed in a sand mill as a dispersing machine and the dispersion treatment was carried out for 20 hours.

[0199] The magnetic tape was obtained in the same manner as in Example 1 except for the above steps.

[0200] Comparative Example 2 (Magnetic powder manufacturing process) The mixture was placed in a melting furnace that had been previously maintained at 1400°C. The pulverized material was then placed in a sintering furnace, which was heated to 570°C at a heating rate of 5°C / min and maintained at 570°C for 8 hours. Other than the above, barium ferrite magnetic powder was obtained in the same manner as in Example 1. Next, the crystallite size and crystallite volume of the powdered magnetic powder were determined in the same manner as in Example 1. The average plate thickness, average plate diameter, and average particle volume of the powdered magnetic powder were also determined in the same manner as in Example 1. The results are shown in Table 1.

[0201] (Preparation process of paint for forming magnetic layer) The amount of dispersant (stearic acid) blended was adjusted to 10 parts by mass, assuming 100 parts by mass of magnetic powder (barium ferrite magnetic powder). The dispersion treatment time was set to 10.5 hours. As described above, in Comparative Example 2, the amount of dispersant blended was increased compared to Example 1, thereby shortening the dispersion treatment time compared to Example 1. As a result, deterioration of characteristics due to damage to the magnetic particles was suppressed compared to Example 1. A coating material for forming a magnetic layer was prepared in the same manner as in Example 1 except for the above.

[0202] The magnetic tape was obtained in the same manner as in Example 1 except for the above steps.

[0203] [evaluation] The magnetic tapes obtained as described above were evaluated as follows.

[0204] (XRD crystallite size in magnetic tape state) The XRD crystallite size in the magnetic tape state was determined by the method described in the above embodiment. The results are shown in Table 1.

[0205] (Mst, Mrt in the longitudinal direction of the magnetic tape) Mst [mA] and Mrt [mA] (Mr) (where Mst is the product of saturation magnetization Ms and thickness t of the recording layer, and Mrt is the product of remanent magnetization Mr and thickness t of the recording layer) were calculated as follows. First, a background-corrected MH loop was obtained using the same method as for calculating coercive force Hc in the above-described embodiment. Next, the saturation magnetization Ms [emu] and remanent magnetization Mr [emu] were obtained from the obtained background-corrected MH loop. After that, Mst [mA] was calculated by dividing the saturation magnetization Ms [emu] by the area of ​​the measurement sample. Furthermore, Mrt [mA] was calculated by dividing the remanent magnetization Mr [emu] by the area of ​​the measurement sample. The calculation results are shown in Table 1.

[0206] (Coercive force Hc and squareness ratio Rs in the longitudinal direction of the magnetic tape) The coercive force Hc and squareness ratio Rs were calculated using the method described in the embodiment above. The calculation results are shown in Table 1.

[0207] (Average value of arithmetic mean roughness Ra) The average value of the arithmetic mean roughness Ra was calculated using the method described in the embodiment above. The calculation results are shown in Table 1.

[0208] (SNR) The SNR was measured as follows: First, a loop tester (manufactured by Microphysics) was used to obtain a read signal from the magnetic tape. The conditions for obtaining the read signal are shown below. head:GMR Head speed: 1.85 m / s Signal: Single recording frequency 10MHz (2T half Nyquist frequency) Recording current: Optimum recording current

[0209] Next, the playback signal was captured using a spectrum analyzer with a span of 0 to 20 MHz (resolution bandwidth = 100 kHz, VBW = 30 kHz). The peak of the captured spectrum was then taken as the signal amount S, and the floor noise excluding the peak was integrated from 3 MHz to 20 MHz to obtain the noise amount N. The ratio S / N of the signal amount S to the noise amount N was calculated as the SNR (Signal-to-Noise Ratio). The calculated SNR was then converted into a relative value (dB) based on the SNR of Comparative Example 1 used as the reference media. The calculation results are shown in Table 1.

[0210] Table 1 shows the evaluation results. Table 2 shows the manufacturing conditions for the magnetic powder. Table 3 shows the manufacturing conditions for the magnetic tape. Figure 12 shows the relationship between the crystallite size calculated from the diffraction peak of oblique incidence X-ray diffraction and the SNR.

[0211] [Table 1] 1php (per 100 parts): 1g of dispersant for 100g of magnetic powder

[0212] [Table 2]

[0213] [Table 3]

[0214] The following can be seen from Table 1 and Figure 12. When the crystallite size calculated from the peak derived from the (1,1,0) plane of hexagonal ferrite obtained by measuring the magnetic surface (surface of the magnetic layer) of the magnetic tape MT using oblique incidence X-ray diffraction is 11 nm or more and 15 nm or less, the SNR can be made 0.8 dB or more, thereby achieving excellent electromagnetic conversion characteristics.

[0215] Table 1 reveals the following: The crystallite size measured in magnetic tape state differs from the crystallite size measured in magnetic powder state. This is thought to be due to changes in the size of the magnetic particles themselves or damage to the magnetic particles during the magnetic tape manufacturing process (for example, the paint dispersion process). Therefore, in order to obtain excellent electromagnetic conversion characteristics, it is necessary to specify the XRD crystallite size in magnetic tape state. Table 1 reveals the following: The crystallite size measured when the magnetic powder is in its powder state is different from the particle size measured when the magnetic powder is in its powder state. This is because when a media disperser such as a sand mill is used in the paint dispersion process, the magnetic particles are damaged by collisions between the dispersion media and the magnetic particles.

[0216] 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.

[0217] 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.

[0218] The present disclosure may also employ the following configuration. (1) A tape-shaped magnetic recording medium, A substrate, an underlayer, and a magnetic layer are sequentially provided, the magnetic layer contains hexagonal ferrite particles; A magnetic recording medium in which the crystallite size calculated from the peak derived from the (1,1,0) plane of hexagonal ferrite obtained by measuring the magnetic layer using oblique incidence X-ray diffraction is 11.0 nm or more and 15.0 nm or less. (2) 10. The magnetic recording medium according to (1), wherein the average value of the arithmetic mean roughness Ra of the surface of the magnetic layer is 1.6 nm or less. (3) 10. The magnetic recording medium according to (1), wherein the average value of the arithmetic mean roughness Ra of the surface of the magnetic layer is 1.3 nm or less. (4) The magnetic recording medium according to any one of (1) to (3), wherein the crystallite size is 12.0 nm or more and 14.0 nm or less. (5) The magnetic recording medium according to any one of (1) to (4), wherein the hexagonal ferrite particles are barium ferrite particles or strontium ferrite particles. (6) The average particle volume of the hexagonal ferrite particles determined from the state of the magnetic recording medium is 1500 nm 3 A magnetic recording medium according to any one of (1) to (5) below. (7) The magnetic recording medium according to any one of (1) to (6), wherein the average thickness of the magnetic recording medium is 5.3 μm or less. (8) The magnetic recording medium according to any one of (1) to (7), wherein the average thickness of the magnetic layer is 80 nm or less. (9) The magnetic recording medium according to any one of (1) to (8), wherein the underlayer has an average thickness of 0.9 μm or less. (10) The magnetic recording medium according to any one of (1) to (9), wherein the average squareness ratio Rs of the magnetic layer in the perpendicular direction of the magnetic recording medium is 65% or more. (11) The magnetic recording medium according to any one of (1) to (10), wherein the average squareness ratio Rs of the magnetic layer in the longitudinal direction of the magnetic recording medium is 35% or less. (12) The magnetic recording medium according to any one of (1) to (11), wherein the average value of the coercive force Hc of the magnetic layer in the longitudinal direction of the magnetic recording medium is 2000 Oe or less. (13) the magnetic layer is configured to be able to form a plurality of data tracks; The magnetic recording medium according to any one of (1) to (12), wherein the average width of the data tracks is 1500 nm or less. (14) The magnetic recording medium according to any one of (1) to (13), wherein the substrate contains polyesters. (15) A cartridge comprising a magnetic recording medium according to any one of (1) to (14). [Explanation of symbols]

[0219] 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 56A, 56B servo readhead 110 servo frames 111 Servo subframe 1 111A A Burst 111B B Burst 112 Servo subframe 2 112C C-Burst 112D D Burst 113 Servo Stripe MT magnetic tape SB servo band DB Data Binding

Claims

1. A tape-shaped magnetic recording medium, A substrate, an underlayer, and a magnetic layer are sequentially provided, the magnetic layer contains hexagonal ferrite particles; A magnetic recording medium in which the crystallite size calculated from the peak derived from the (1,1,0) plane of hexagonal ferrite obtained by measuring the magnetic layer in the state of the magnetic recording medium using oblique incidence X-ray diffraction is 11.0 nm or more and 15.0 nm or less.

2. 2. The magnetic recording medium according to claim 1, wherein the average value of the arithmetic mean roughness Ra of the surface of the magnetic layer is 1.6 nm or less.

3. 2. The magnetic recording medium according to claim 1, wherein the average value of the arithmetic mean roughness Ra of the surface of the magnetic layer is 1.3 nm or less.

4. 2. The magnetic recording medium according to claim 1, wherein the crystallite size is 12.0 nm or more and 14.0 nm or less.

5. 2. The magnetic recording medium according to claim 1, wherein the hexagonal ferrite particles are barium ferrite particles or strontium ferrite particles.

6. The average particle volume of the hexagonal ferrite particles determined from the state of the magnetic recording medium is 1500 nm ３ 2. The magnetic recording medium according to claim 1, wherein:

7. 2. The magnetic recording medium according to claim 1, wherein the average thickness of the magnetic recording medium is 5.3 [mu]m or less.

8. 2. The magnetic recording medium according to claim 1, wherein the average thickness of the magnetic layer is 80 nm or less.

9. 2. The magnetic recording medium according to claim 1, wherein the average thickness of the underlayer is 0.9 [mu]m or less.

10. 2. The magnetic recording medium according to claim 1, wherein an average squareness ratio Rs of the magnetic layer in the perpendicular direction of the magnetic recording medium is 65% or more.

11. 2. The magnetic recording medium according to claim 1, wherein the average squareness ratio Rs of the magnetic layer in the longitudinal direction of the magnetic recording medium is 35% or less.

12. 2. The magnetic recording medium according to claim 1, wherein the average value of the coercive force Hc of said magnetic layer in the longitudinal direction of said magnetic recording medium is 2000 Oe or less.

13. the magnetic layer is configured to be able to form a plurality of data tracks; 2. The magnetic recording medium according to claim 1, wherein the average width of the data tracks is 1500 nm or less.

14. 2. The magnetic recording medium according to claim 1, wherein the substrate comprises polyesters.

15. A cartridge comprising the magnetic recording medium according to claim 1.

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