Magnetic recording media and cartridges

Abstract

Provided is a magnetic recording medium with which excellent electromagnetic conversion characteristics can be ensured while suppressing increase of a standard deviation σPES due to multiple-time running.　The magnetic recording medium is sequentially provided with a base body, a ground layer, and a magnetic layer. The magnetic layer includes magnetic particles, conductive first particles, and second particles having a Mohs hardness of not less than 7.0. The magnetic layer has an uneven shape on a magnetic surface thereof. The uneven shape includes first protrusions formed by the first particles and second protrusions formed by the second particles. The ratio H1 / H2 of the average height H1 of the first protrusions to the average height H2 of the second protrusions satisfies H1 / H2≤2.3. A height range ΔH obtained from statistical information of the height of the uneven shape satisfies 3.00 nm≤ΔH≤6.00 nm. A gradient range ΔA obtained from statistical information of a gradient of the uneven shape satisfies 4.00 degrees≤ΔA≤9.00 degrees.

Description

[Technical Field]

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

[0002] Tape-type magnetic recording media are widely used for storing electronic data. In tape-type magnetic recording media, in order to obtain good recording and reproduction characteristics (electromagnetic conversion characteristics), it is desirable to reduce the height of the irregularities on the surface of the magnetic layer (hereinafter referred to as the "magnetic surface") and smooth the magnetic surface (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-65953 Summary of the Invention [Problem to be solved by the invention]

[0004] However, reducing the height of the projections and recesses on the magnetic surface has the drawback of increasing the standard deviation σPES of the PES values ​​of the magnetic recording medium after multiple runs.

[0005] An object of the present disclosure is to provide a magnetic recording medium that can ensure good electromagnetic conversion characteristics while suppressing an increase in the standard deviation σPES due to multiple runs, and a cartridge equipped with 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 magnetic particles, first particles having electrical conductivity, and second particles having a Mohs hardness of 7.0 or more; The magnetic layer has a concave-convex shape on the magnetic surface, the uneven shape includes primary protrusions formed by primary particles and secondary protrusions formed by secondary particles, the ratio H1 / H2 of the average height H1 of the primary projections to the average height H2 of the secondary projections is H1 / H2≦2.3; The height range ΔH calculated from the statistical information of the height of the uneven shape is 3.00 nm≦ΔH≦6.00 nm, The magnetic recording medium has a gradient range ΔA determined from statistical information on the gradient of the uneven shape, which is 4.00 degrees≦ΔA≦9.00 degrees.

[0007] The second disclosure is: A tape-shaped magnetic recording medium, A substrate, an underlayer, and a magnetic layer are sequentially provided, the magnetic layer includes magnetic particles, carbon particles, and an abrasive; The magnetic layer has a concave-convex shape on the magnetic surface, the uneven shape includes primary protrusions formed by carbon particles and secondary protrusions formed by an abrasive; the ratio H1 / H2 of the average height H1 of the primary projections to the average height H2 of the secondary projections is H1 / H2≦2.3; The height range ΔH calculated from the statistical information of the height of the uneven shape is 3.00 nm≦ΔH≦6.00 nm, The magnetic recording medium has a gradient range ΔA determined from statistical information on the gradient of the uneven shape, which is 4.00 degrees≦ΔA≦9.00 degrees. [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. 3A is a cross-sectional view showing an example of the configuration of a magnetic tape, and Fig. 3B is a cross-sectional view showing an example of the configuration of a magnetic surface. [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 a first example of a cross-sectional TEM image of the magnetic layer. [Figure 9] FIG. 9 is a diagram showing a second example of a cross-sectional TEM image of the magnetic layer. [Figure 10] FIG. 10 is a diagram showing an example of an FE-SEM image of the surface of the magnetic layer. [Figure 11] FIG. 11 is a diagram showing an example of a composite image obtained by superimposing an AFM image and an FE-SEM image. [Figure 12] FIG. 12 is an enlarged view showing an example of a composite image obtained by superimposing an AFM image and an FE-SEM image. [Figure 13] FIG. 13 is a diagram showing an example of a cross-sectional profile along Line 1 in FIG. [Figure 14] FIG. 14 is a graph showing a first example of the change in the standard deviation σPES over time. [Figure 15] FIG. 15 is a graph showing a second example of the change in standard deviation σPES over time. [Figure 16] FIG. 16 is a graph showing a third example of the change over time in the standard deviation σPES, and a cross-sectional view schematically showing the change in the state of the secondary protrusions on the surface of the magnetic layer. [Figure 17] FIG. 17 is a diagram schematically showing the relationship between the first and second projections and the head unit. [Figure 18] FIG. 18 is a diagram for explaining a method for measuring PES. [Figure 19] FIG. 19 is a graph for explaining the correction of the movement of the magnetic tape in the width direction. [Figure 20]Fig. 20A is a diagram showing an example of a two-dimensional surface profile image after filtering, and Fig. 20B is a diagram showing an example of a numerical data matrix of height ζ(L, W). [Figure 21] FIG. 21 is a diagram showing an example of a numerical data matrix of the relative height Z(L, W). [Figure 22] FIG. 22 is a diagram for explaining a method for calculating the gradients GL(L,W) and GW(L,W) at each point (L,W). [Figure 23] Fig. 23A is a diagram showing an example of a numeric data matrix of the gradient GL(L,W), and Fig. 23B is a diagram showing an example of a numeric data matrix of the gradient GW(L,W). [Figure 24] Fig. 24A is a diagram showing a method for calculating the gradient GL(L,W), and Fig. 24B is a diagram showing a method for calculating the gradient GW(L,W). [Figure 25] FIG. 25 is a diagram for explaining statistical processing of data on the relative height Z(L, W) and the gradient GL(L, W). [Figure 26] FIG. 26 is a diagram for explaining statistical processing of data on the relative height Z(L, W) and the gradient GW(L, W). [Figure 27] FIG. 27 is a diagram for explaining statistical processing of data on the relative height Z(L,W), gradient GL(L,W), and gradient GW(L,W). [Figure 28] FIG. 28 is a diagram for explaining the procedure for creating a distribution map from a numerical data matrix with the number of data items M(H, A). [Figure 29] FIG. 29 is a diagram for explaining a method for calculating the height range ΔH. [Figure 30] FIG. 30 is a diagram for explaining a method for calculating the height range ΔH. [Figure 31] FIG. 31 is a diagram for explaining a method for calculating the gradient range ΔA. [Figure 32] FIG. 32 is a diagram for explaining a method for calculating the gradient range ΔA. [Figure 33] FIG. 33 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 34] FIG. 34 is a graph showing the relationship between the height range ΔH and the gradient range ΔA. DETAILED DESCRIPTION OF THE INVENTION

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

[0010] In this specification, unless a measurement environment is specifically stated in the description of the measurement method, the measurement is performed in an environment of 25°C ± 2°C and 50% RH ± 5% RH.

[0011] [1 cartridge configuration] 1 is an exploded perspective view showing an example of the configuration of a cartridge 10. The cartridge 10 is a single-reel cartridge, and includes a cartridge case 12 composed of a lower shell 12A and an upper shell 12B, a reel 13 on which a tape-like magnetic recording medium (hereinafter referred to as "magnetic tape") MT is wound, a reel lock 14 and a reel spring 15 for locking the rotation of the reel 13, a spider 16 for unlocking the locked state of the reel 13, a sliding door 17 for opening and closing a tape outlet 12C provided in the cartridge case 12 across the lower shell 12A and the upper shell 12B, a door spring 18 for biasing the sliding door 17 to a closed position of the tape outlet 12C, a write protect 19 for preventing accidental erasure, and a cartridge memory 11. The reel 13 for winding the magnetic tape MT is generally disc-shaped with an opening in the center, and is composed of a reel hub 13A and a flange 13B made of a hard material such as plastic. A leader tape LT is connected to the outer peripheral end of the magnetic tape MT, and a leader pin 20 is provided at the tip of the leader tape LT.

[0012] 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.

[0013] The cartridge memory 11 is provided near one corner of the cartridge 10. When the cartridge 10 is loaded into the recording / playback device, the cartridge memory 11 faces the reader / writer of the recording / playback device. The cartridge memory 11 communicates with the recording / playback device, specifically the reader / writer, using a wireless communication standard that complies with the LTO standard.

[0014] [2 Cartridge Memory Configuration] 2 is a block diagram showing an example of the configuration of the cartridge memory 11. The cartridge memory 11 includes an antenna coil (communication unit) 31 that communicates with a reader / writer using a specified communication standard; a rectification / power circuit 32 that generates power by rectifying and generating electricity from radio waves received by the antenna coil 31 using induced electromotive force; a clock circuit 33 that generates a clock from the radio waves received by the antenna coil 31 using induced electromotive force; a detection / modulation circuit 34 that detects the radio waves received by the antenna coil 31 and modulates the signal to be transmitted by the antenna coil 31; a controller (control unit) 35 that is composed of logic circuits and the like for identifying and processing commands and data from the digital signal extracted from the detection / modulation circuit 34; and a memory (storage unit) 36 that stores information. The cartridge memory 11 also includes a capacitor 37 connected in parallel to the antenna coil 31, and the antenna coil 31 and capacitor 37 form a resonant circuit.

[0015] 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.

[0016] The memory 36 has a first memory area 36A and a second memory area 36B. The first memory area 36A corresponds to the memory area of ​​a cartridge memory of a magnetic tape standard prior to a specified generation (e.g., an LTO standard prior to LTO8), and is an area for storing information conforming to the magnetic tape standard prior to the specified generation. The information conforming to the magnetic tape standard prior to the specified generation includes, for example, manufacturing information (e.g., a unique number of the cartridge 10), usage history (e.g., the number of times the tape has been pulled out (Thread Count)), etc.

[0017] The second memory area 36B corresponds to an extended memory area for the memory area of ​​the cartridge memory for magnetic tape standards prior to the specified generation (e.g., LTO standards prior to LTO8). The second memory area 36B is an area for storing additional information. Here, additional information refers to, for example, information related to the cartridge 10 that is not specified in magnetic tape standards prior to the specified generation (e.g., LTO standards prior to LTO8). The additional information includes, but is not limited to, at least one type of information selected from the group consisting of tension adjustment information, management ledger data, index information, and thumbnail information. 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, drive tension information, and drive temperature and humidity information. This information may be managed in conjunction with information regarding the usage status of the cartridge 10. The tension adjustment information is preferably obtained when or before data is recorded on the magnetic tape MT. The tension information of the drive means information about the tension applied to the magnetic tape MT in the longitudinal direction.

[0018] The management ledger data includes at least one of the following data: the capacity, creation date, editing date, and storage location of the data files recorded on the magnetic tape MT. The index information includes 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] [3 Magnetic Tape Configuration] FIG. 3A 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.

[0023] The magnetic tape MT may conform to the LTO standard, or may conform to a standard other than the LTO standard. The width of the magnetic tape MT may be 1 / 2 inch, or may be wider than 1 / 2 inch. If the magnetic tape MT conforms to the LTO standard, the width of the magnetic tape MT is 1 / 2 inch. The magnetic tape MT may be configured to be able to keep the width of the magnetic tape MT constant or approximately constant by adjusting the tension applied to the magnetic tape MT in the longitudinal direction during running using a recording / playback device (drive).

[0024] 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.

[0025] The magnetic tape MT is preferably reproduced by a reproducing head using a TMR element. The signal reproduced by the reproducing head using TMR may be data recorded in the data band DB (see FIG. 4) or a servo pattern (servo signal) recorded in the servo band SB (see FIG. 4).

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

[0027] The average thickness of the substrate 41 is determined as follows: First, the magnetic tape MT housed in the cartridge 10 is unwound, and a sample is prepared by cutting the magnetic tape MT to a length of 250 mm at a position 30 to 40 m in the longitudinal direction from the joint 21 between the magnetic tape MT and the leader tape LT. In this specification, the "longitudinal direction" in the "longitudinal direction from the joint 21 between the magnetic tape MT and the leader tape LT" refers to the direction from one end on the leader tape LT side to the other end on the opposite side.

[0028] Next, the layers of the sample other than the substrate 41 (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 the sample (substrate 41) is measured at five positions, and these measurements 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.

[0029] The base 41 contains, for example, polyester as a main component. The polyester includes, 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 contains two or more types of polyester, the two or more types of polyester may be mixed, copolymerized, or laminated. At least one of the terminals and side chains of the polyester may be modified. The base 41 may contain, in addition to polyester, a resin other than polyester, which will be described later.

[0030] In this specification, the term "main component" refers to the component that has the highest content among the components that make up the base 41. For example, when the main component of the base 41 is polyester, the content of polyester in the base 41 may be, for example, 50% by mass or more, 60% by mass or more, 70% by mass or more, 80% by mass or more, 90% by mass or more, 95% by mass or more, or 98% by mass or more relative to the mass of the base 41, or the base 41 may be composed only of polyester.

[0031] The inclusion of polyester in the substrate 41 can be confirmed, for example, as follows. First, similar to the method for measuring the average thickness of the substrate 41, a magnetic tape MT is prepared and cut into a length of 250 mm to prepare a sample, and then 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 polyester.

[0032] The substrate 41 preferably contains polyester. By including polyester in the substrate 41, the Young's modulus of the substrate 41 in the longitudinal direction can be reduced preferably to 2.5 GPa or more and 7.8 GPa or less, more preferably to 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 / reproducing device, the width of the magnetic tape MT can be kept constant or approximately constant. A method for measuring the Young's modulus of the substrate 41 in the longitudinal direction will be described later.

[0033] The base 41 may contain a resin other than polyester. In this case, the resin other than polyester may be the main component of the material constituting the base 41. The resin other than polyester includes, for example, at least one selected from the group consisting of polyolefin resins, cellulose derivatives, vinyl resins, and other polymer resins. When the base 41 contains two or more of these resins, the two or more materials may be mixed, copolymerized, or laminated.

[0034] The polyolefin resin includes, for example, at least one selected from the group consisting of PE (polyethylene) and PP (polypropylene). The cellulose derivative includes, 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 resin includes, for example, at least one selected from the group consisting of PVC (polyvinyl chloride) and PVDC (polyvinylidene chloride).

[0035] Examples of other polymer resins include at least one selected from the group consisting of PEEK (polyether ether ketone), 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 (polyether ketone), polyether ester, PES (polyethersulfone), PEI (polyetherimide), PSF (polysulfone), PPS (polyphenylene sulfide), PC (polycarbonate), PAR (polyarylate), and PU (polyurethane).

[0036] 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.

[0037] (magnetic layer) The magnetic layer 43 is configured to be capable of 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 includes magnetic particles, first particles, and second particles. The magnetic layer 43 may further include a binder. If necessary, the magnetic layer 43 may further include at least one additive selected from the group consisting of a lubricant, a hardener, an anti-corrosion agent, and non-magnetic reinforcing particles.

[0038] 3B is a cross-sectional view showing an example of the configuration of the surface (hereinafter referred to as the "magnetic surface") of magnetic layer 43. Magnetic layer 43 has an uneven shape on the magnetic surface (surface). The uneven shape includes primary protrusions 51B formed by primary particles 51A and secondary protrusions 52B formed by secondary particles 52A.

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

[0040] The total area S of the plurality of servo bands SB relative to the area S of the magnetic surface (surface of the magnetic layer 43) SB The ratio R S (=(S SB From the viewpoint of ensuring a high recording capacity, the upper limit of the ratio of the total area S of the plurality of servo bands SB to the area S of the magnetic surface 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 is preferably 0.8% or more from the viewpoint of ensuring 5 or more servo bands SB.

[0041] The total area S of multiple servo bands SB relative to the area S of the entire magnetic surface SB Ratio R S The magnetic tape MT is developed using a ferricolloid developer (Sigma Marker Q, manufactured by Sigma High Chemical Co., Ltd.), and the developed magnetic tape MT is then observed under an optical microscope to determine the servo bandwidth W SB and the number of servo bands SB. Next, calculate the ratio R from 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

[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 the ratio R S It can be calculated in the same way as

[0044] Servo Bandwidth W SB From the viewpoint of ensuring a high recording capacity, the upper limit of the servo bandwidth W 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 servo bandwidth W is preferably 10 μm or more. SB It is difficult to manufacture a magnetic head that can read such servo signals.

[0045] Servo Bandwidth W SB The width of is the ratio R S It can be calculated in the same way as

[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 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 particle size, the lower limit 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 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, and a 250 mm sample 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. Next, the data recording pattern in the data band DB portion of the magnetic layer 43 of the 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. MFM measurements are performed on three different 10 μm × 10 μm measurement areas, resulting in three MFM images. From the three MFM images obtained, the track width was measured at 10 locations using the analysis software attached to the Dimension3100, and the average value (simple average) was calculated. This average value is the data track width W. The MFM measurement conditions were: sweep speed: 1 Hz, tip used: MFMR-20, lift height: 20 nm, 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 a 250 mm sample is cut from the magnetic tape MT at a position 30 m longitudinally from the joint 21 between the magnetic tape MT and the leader tape LT. Next, the data recording pattern in the data band DB portion of the magnetic layer 43 of the 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. MFM measurements are performed on three different 2 μm × 2 μm measurement areas, resulting in three MFM images. Fifty inter-bit distances are measured from the two-dimensional concavo-convex chart of the recording pattern of the obtained MFM image. The inter-bit distances are measured using the analysis software included with the Dimension3100. The value that is approximately the greatest common divisor of the 50 measured inter-bit distances is taken as the minimum value L of the distance between magnetization reversals. The measurement conditions are: sweep speed: 1 Hz, tip used: MFMR-20, lift height: 20 nm, 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 unit 56 provides information for determining the tape speed and the longitudinal position of the head unit 56. The tape speed is calculated from the time between four timing signals (A1-C1, A2-C2, A3-C3, A4-C4). The head position 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 t1 of the magnetic layer 43 is preferably 80 nm or less, more preferably 70 nm or less, and even more preferably 50 nm or less. If the upper limit of the average thickness t1 of the magnetic layer 43 is 80 nm or less, when a ring-type head is used as the recording head, the influence of the demagnetizing field can be reduced, thereby achieving even better electromagnetic conversion characteristics.

[0059] The lower limit of the average thickness t1 of the magnetic layer 43 is preferably 35 nm or more. If the lower limit of the average thickness t1 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 t1 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 images 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 the 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 average) to obtain the average thickness t1 [nm] of the magnetic layer 43.

[0063] (magnetic particles) The magnetic particles are, for example, particles containing hexagonal ferrite (hereinafter referred to as "hexagonal ferrite particles"), particles containing epsilon iron oxide (ε-iron oxide) (hereinafter referred to as "ε-iron oxide particles"), or particles containing Co-containing spinel ferrite (hereinafter referred to as "cobalt ferrite particles"). It is preferable that the magnetic particles have a preferential crystal orientation 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] (Hexagonal ferrite particles) Hexagonal ferrite particles have, for example, a plate shape such as a hexagonal plate or a columnar shape such as a hexagonal column (however, the thickness or height is smaller than the major axis of the plate surface or base). In this specification, hexagonal plate shape includes a substantially hexagonal plate shape. Hexagonal ferrite preferably contains at least one of Ba, Sr, Pb, and Ca, more preferably at least one of Ba and Sr. Specifically, the hexagonal ferrite may be, for example, barium ferrite or strontium ferrite. Barium ferrite may further contain at least one of Sr, Pb, and Ca in addition to Ba. Strontium ferrite may further contain at least one of Ba, Pb, and Ca in addition to Sr.

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

[0067] When the magnetic particles are hexagonal ferrite particles, the average aspect ratio of the magnetic particles is preferably 1.0 to 3.0, more preferably 1.5 to 2.8, and even more preferably 1.8 to 2.7. When the average aspect ratio of the magnetic particles is within the range of 1.0 to 3.0, aggregation of the magnetic particles can be suppressed. Furthermore, when the magnetic particles are vertically oriented in the process of forming the magnetic layer 43, the resistance applied to the magnetic particles can be suppressed. Therefore, the vertical orientation of the magnetic particles can be improved.

[0068] When the magnetic particles are hexagonal ferrite particles, the average particle size and average aspect ratio of the magnetic particles can be determined as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound and cut out at a position 30 to 40 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 image is taken. The number of TEM images 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, the size of a hexagonal ferrite particle (hereinafter referred to as "particle size") is defined as the plate diameter DB, which is the longest diameter of the plate surface or base, when the particle shape observed in the TEM image is plate-like or columnar (however, the thickness or height is smaller than the longest diameter of the plate surface or base), as shown in FIG. 7. The thickness or height of the particle observed in the TEM image is defined as the plate thickness DA. When the plate surface or base of the particle observed in the TEM image is hexagonal, the longest diameter 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 defined as the plate thickness DA.

[0071] Next, 50 particles are selected from the captured TEM image based on the following criteria. Particles with parts outside the field of view of the TEM image are not measured, and only particles with a clear outline and that exist independently are measured. If particles overlap, those with a clear boundary and whose overall shape can be determined are measured as individual particles, but particles with an unclear boundary and whose overall shape cannot be determined are not measured as their shape cannot be determined.

[0072] Figures 8 and 9 show first and second examples of TEM images, respectively. In Figures 8 and 9, for example, 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 particle is measured. To measure the particle plate diameter DB, 50 particles whose particle plate diameter DB can be clearly confirmed are selected from the TEM image taken. 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 averaged) to obtain the average plate diameter DB. ave Average plate diameter DB aveis 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] When the magnetic particles are hexagonal ferrite particles, the average particle volume of the magnetic particles is preferably 500 nm 3 More than 2500nm 3 Less than 500 nm, more preferably 3 More than 1600nm 3 Less than 500 nm, more preferably 3 More than 1500nm 3 Below 600 nm, particularly preferably 3 More than 1200nm 3 Below 600 nm, most preferably 3 More than 1000nm 3 The average particle volume of the magnetic particles is 2500 nm or less. 3 When the average particle size of the magnetic particles is 22 nm or less, the same effect as when the average particle volume of the magnetic particles is 500 nm or less can be obtained. 3 If the average particle size of the magnetic particles is 13 nm or more, the same effect as that obtained when the average particle size of the magnetic particles is 13 nm or more can be obtained.

[0074] The average particle volume of magnetic particles can be calculated as follows: First, as described above in relation to the method for calculating the average particle size of magnetic particles, the average plate thickness DA ave and average plate diameter DB ave Next, calculate the average volume V of the magnetic particles using the following formula:

number

[0075] (ε iron oxide particles) ε-iron oxide particles are hard magnetic particles that can achieve high coercivity even in the form of fine particles. ε-iron oxide particles have a spherical or cubic shape. In this specification, spherical includes nearly spherical. Furthermore, cubic includes nearly cubic. Because ε-iron oxide particles have the above-described shape, when ε-iron oxide particles are used as magnetic particles, the contact area between particles in the thickness direction of the magnetic tape MT can be reduced and particle aggregation can be suppressed compared to when hexagonal plate-shaped barium ferrite particles are used as magnetic particles. This improves the dispersibility of the magnetic particles and allows for even better electromagnetic conversion characteristics (e.g., SNR).

[0076] The ε-iron oxide particles have a core-shell structure. Specifically, the ε-iron oxide particles have a core and a two-layer shell structure surrounding the core. The two-layer shell structure includes a first shell portion provided on the core and a second shell portion provided on the first shell portion.

[0077] The core portion contains ε-iron oxide. The ε-iron oxide contained in the core portion preferably has ε-Fe2O3 crystals as a main phase, and more preferably is composed of a single phase ε-Fe2O3.

[0078] The first shell portion covers at least a portion of the periphery of the core portion. Specifically, the first shell portion may cover a portion of the periphery of the core portion, or may cover the entire periphery of the core portion. From the viewpoint of ensuring sufficient exchange coupling between the core portion and the first shell portion and improving magnetic properties, it is preferable that the first shell portion covers the entire surface of the core portion.

[0079] The first shell portion is a so-called soft magnetic layer and includes a soft magnetic material such as α-Fe, a Ni-Fe alloy, or an Fe-Si-Al alloy. The α-Fe may be obtained by reducing ε-iron oxide contained in the core portion.

[0080] The second shell portion is an oxide coating serving as an anti-oxidation layer. The second shell portion contains α-iron oxide, aluminum oxide, or silicon oxide. The α-iron oxide includes at least one iron oxide selected from the group consisting of Fe3O4, Fe2O3, and FeO. When the first shell portion contains α-Fe (soft magnetic material), the α-iron oxide may be obtained by oxidizing the α-Fe contained in the first shell portion.

[0081] By having the first shell portion as described above, the coercivity Hc of the core portion alone can be maintained at a high value to ensure thermal stability, while the coercivity Hc of the entire ε-iron oxide particle (core-shell particle) can be adjusted to a coercivity Hc suitable for recording. Furthermore, by having the second shell portion as described above, the ε-iron oxide particles can be prevented from deteriorating in their properties due to exposure to air during and before the manufacturing process of the magnetic tape MT, which can lead to rust and other damage to the particle surface. Therefore, deterioration of the properties of the magnetic tape MT can be prevented.

[0082] The ε-iron oxide particles may have a shell part with a single layer structure. In this case, the shell part has the same configuration as the first shell part. However, from the viewpoint of suppressing deterioration of the properties of the ε-iron oxide particles, it is preferable that the ε-iron oxide particles have a shell part with a two-layer structure as described above.

[0083] The ε-iron oxide particles may contain an additive instead of the core-shell structure, or may have a core-shell structure and contain an additive. In this case, part of the Fe in the ε-iron oxide particles is substituted with the additive. By containing the additive in the ε-iron oxide particles, the coercivity Hc of the entire ε-iron oxide particles can be adjusted to a coercivity Hc suitable for recording, thereby improving ease of recording. The additive is a metal element other than iron, preferably a trivalent metal element, more preferably at least one of Al, Ga, and In, and even more preferably at least one of Al and Ga.

[0084] Specifically, the ε-iron oxide containing additives is ε-Fe 2-x Mx O crystal (wherein M is a metal element other than iron, preferably a trivalent metal element, more preferably at least one of Al, Ga, and In, and even more preferably at least one of Al and Ga. x is, for example, 0 <x<1である。)である。

[0085] When the magnetic particles are ε-iron oxide particles, the average particle size of the magnetic particles is preferably 10 nm to 20 nm, more preferably 10 nm to 18 nm, even more preferably 10 nm to 16 nm, particularly preferably 10 nm to 15 nm, and most preferably 10 nm to 14 nm. In magnetic tape MT, the actual magnetization region is a region half the size of the recording wavelength. Therefore, by setting the average particle size of the magnetic particles to half the shortest recording wavelength or less, even better electromagnetic conversion characteristics (e.g., SNR) can be obtained. Therefore, when the average particle size of the magnetic particles is 20 nm or less, even better electromagnetic conversion characteristics (e.g., SNR) can be obtained in high-recording-density magnetic tape MT (e.g., magnetic tape MT configured to record signals at the shortest recording wavelength of 40 nm or less). On the other hand, when the average particle size of the magnetic particles is 10 nm or more, the dispersibility of the magnetic particles is further improved, and even better electromagnetic conversion characteristics (e.g., SNR) can be obtained.

[0086] When the magnetic particles are ε-iron oxide particles, the average aspect ratio of the magnetic particles is preferably 1.0 to 3.0, more preferably 1.0 to 2.5, even more preferably 1.0 to 2.1, and particularly preferably 1.0 to 1.8. When the average aspect ratio of the magnetic particles is within the range of 1.0 to 3.0, aggregation of the magnetic particles can be suppressed. Furthermore, when the magnetic particles are vertically oriented in the process of forming the magnetic layer 43, the resistance applied to the magnetic particles can be suppressed. Therefore, the vertical orientation of the magnetic particles can be improved.

[0087] When the magnetic particles are ε-iron oxide particles, the average particle size and average aspect ratio of the magnetic particles can be determined as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound and cut out at a position 30 to 40 m longitudinally from the joint 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 method such as FIB (Focused Ion Beam). When using the FIB method, a carbon layer and a tungsten layer are formed as protective layers as a pretreatment for observing the cross-sectional TEM image described below. The carbon layer is formed by vapor deposition on the surface of the magnetic tape MT facing the magnetic layer 43 and the surface facing the back layer 44, and the tungsten layer is further formed by vapor deposition or sputtering on the surface facing the magnetic layer 43. The thinning is performed along the length (longitudinal direction) of the magnetic tape MT. That is, the thinning results in a cross section parallel to both the longitudinal and thickness directions of the magnetic tape MT.

[0088] The cross section of the obtained thin sample was observed using a transmission electron microscope (H-9500, manufactured by Hitachi High-Technologies Corporation) at an acceleration voltage of 200 kV and a total magnification of 500,000 times, so as to include the entire magnetic layer 43 in the thickness direction of the magnetic layer 43, and a TEM image was taken. Next, 50 particles whose particle shape could be clearly confirmed were selected from the TEM image, and the long axis length DL and short axis length DS of each particle were measured. Here, the long axis length DL refers to the longest distance between two parallel lines drawn from all angles so as to be tangent to the outline of each particle (the so-called maximum Feret diameter). Meanwhile, the short axis length DS refers to the longest length of the particle in the direction perpendicular to the long axis (DL) of the particle. Next, the long axis lengths DL of the measured 50 particles were simply averaged (arithmetic mean) to obtain the average long axis length DL. ave The average major axis length DL ave is the average particle size of the magnetic particles. The minor axis lengths DS of the 50 particles measured were simply averaged (arithmetic mean) to obtain the average minor axis length DS ave Then, calculate the average major axis length DL ave and mean minor axis length DSave The average aspect ratio of the particles (DL ave / DS ave ) is found.

[0089] When the magnetic particles are ε iron oxide particles, the average particle volume of the magnetic particles is preferably 500 nm 3 More than 4000nm 3 Less than 500 nm, more preferably 3 More than 3000nm 3 less than or equal to 500 nm, and even more preferably 3 More than 2000nm 3 Below 600 nm, particularly preferably 3 More than 1600nm 3 Below 600 nm, most preferably 3 More than 1300nm 3 Generally, the noise of magnetic tape MT is inversely proportional to the square root of the number of particles (i.e., proportional to the square root of the particle volume), so by making the particle volume smaller, it is possible to obtain even better electromagnetic conversion characteristics (for example, SNR). Therefore, when the average particle volume of magnetic particles is 4000 nm 3 When the average particle size of the magnetic particles is 20 nm or less, better electromagnetic conversion characteristics (e.g., SNR) can be obtained, as in the case where the average particle size of the magnetic particles is 20 nm or less. 3 If the average particle size of the magnetic particles is 10 nm or more, the same effect as that obtained when the average particle size of the magnetic particles is 10 nm or more can be obtained.

[0090] When the ε-iron oxide particles are spherical, the average particle volume of the magnetic particles can be calculated as follows: First, the average major axis length DL is calculated in the same manner as in the above-mentioned method for calculating the average particle size of the magnetic particles. ave Next, calculate the average volume V of the magnetic particles using the following formula: V=(π / 6)×DL ave 3

[0091] When the ε iron oxide particles have a cubic shape, the average volume of the magnetic particles is calculated as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and the magnetic tape MT is cut out at a position 30 to 40 m longitudinally from the joint 21 between the magnetic tape MT and the leader tape LT. Next, the cut magnetic tape MT is processed and thinned using a method such as FIB (Focused Ion Beam). When using the FIB method, a carbon film and a tungsten thin film are formed as protective films as a pretreatment for observing the cross-sectional TEM image described below. The carbon film is formed by vapor deposition on the surface of the magnetic tape MT facing the magnetic layer 43 and the surface facing the back layer 44, and the tungsten thin film is further formed by vapor deposition or sputtering on the surface facing the magnetic layer 43. The thinning is performed along the length (longitudinal direction) of the magnetic tape MT. In other words, the thinning results in a cross section parallel to both the longitudinal and thickness directions of the magnetic tape MT.

[0092] The obtained thin section sample is observed using a transmission electron microscope (H-9500 manufactured by Hitachi High-Technologies Corporation) at an acceleration voltage of 200 kV and a total magnification of 500,000 times to observe the cross section of the magnetic layer 43 in the thickness direction of the magnetic layer 43 so as to include the entire magnetic layer 43, and a TEM image is obtained. Note that the magnification and acceleration voltage may be adjusted appropriately depending on the type of device. Next, 50 particles whose particle shape is clear are selected from the TEM image taken, and the side length DC of each particle is measured. Next, the side lengths DC of the measured 50 particles are simply averaged (arithmetic mean) to obtain the average side length DC ave Next, calculate the average side length DC ave Using the following formula, the average volume of the magnetic particles, V ave (particle volume) is calculated. V ave =DC ave 3

[0093] (cobalt ferrite particles) The cobalt ferrite particles preferably have uniaxial crystal anisotropy. The uniaxial crystal anisotropy of the cobalt ferrite particles allows the magnetic particles to be preferentially crystalline oriented in the perpendicular direction of the magnetic tape MT. The cobalt ferrite particles may have, for example, a cubic shape. In this specification, the cubic shape includes a substantially cubic shape. The Co-containing spinel ferrite may further contain at least one of Ni, Mn, Al, Cu, and Zn in addition to Co.

[0094] The Co-containing spinel ferrite has an average composition represented by the following formula, for example. Co x M y FeO Z (In the formula, M is at least one metal selected from the group consisting of Ni, Mn, Al, Cu, and Zn. x is a value within the range of 0.4≦x≦1.0. y is a value within the range of 0≦y≦0.3. However, x and y satisfy the relationship (x+y)≦1.0. z is a value within the range of 3≦z≦4. A portion of Fe may be substituted with another metal element.)

[0095] When the magnetic particles are cobalt ferrite particles, the average particle size of the magnetic particles is preferably 8 nm or more and 16 nm or less, more preferably 8 nm or more and 13 nm or less, and even more preferably 8 nm or more and 10 nm or less. When the average particle size of the magnetic particles is 16 nm or less, even better electromagnetic conversion characteristics (e.g., SNR) can be obtained in high-recording-density magnetic tapes MT. On the other hand, when the average particle size of the magnetic particles is 8 nm or more, the dispersibility of the magnetic particles is further improved, and even better electromagnetic conversion characteristics (e.g., SNR) can be obtained. The method for calculating the average particle size of the magnetic particles is the same as the method for calculating the average particle size of the magnetic particles when the magnetic particles are ε-iron oxide particles.

[0096] When the magnetic particles are cobalt ferrite particles, the average aspect ratio of the magnetic particles is preferably 1.0 or more and 3.0 or less, more preferably 1.0 or more and 2.5 or less, and even more preferably 1.0 or more and 2.0 or less. When the average aspect ratio of the magnetic particles is within the range of 1.0 or more and 3.0 or less, aggregation of the magnetic particles can be suppressed. Furthermore, when the magnetic particles are vertically oriented in the process of forming the magnetic layer 43, the resistance applied to the magnetic particles can be suppressed. Therefore, the vertical orientation of the magnetic particles can be improved. The method for calculating the average aspect ratio of the magnetic particles is the same as the method for calculating the average aspect ratio of the magnetic particles when the magnetic particles are ε-iron oxide particle powder.

[0097] When the magnetic particles are cobalt ferrite particles, the average particle volume of the magnetic particles is preferably 500 nm 3 More than 4000nm 3 Less than 600 nm, more preferably 3 More than 2000nm 3 or less, even more preferably 600 nm 3 More than 1000nm 3 The average particle volume of the magnetic particles is 4000 nm or less. 3 If the average particle size of the magnetic particles is 16 nm or less, the same effect as when the average particle volume of the magnetic particles is 500 nm or less can be obtained. 3 This produces the same effect as when the average particle size of the magnetic particles is 8 nm or more. The method for calculating the average particle volume of the magnetic portion is the same as the method for calculating the average particle volume when the ε-iron oxide particles have a cubic shape.

[0098] (1st particle) 3B, some of the first particles 51A contained in the magnetic layer 43 protrude from the magnetic surface to form first protrusions 51B. When the head unit 56 slides over the magnetic tape MT, the first protrusions 51B come into contact with the head unit 56.

[0099] The first particles 51A are electrically conductive. The first particles 51A are preferably an antistatic agent and a solid lubricant. The first particles 51A are particles containing carbon. As the particles containing carbon, for example, at least one selected from the group consisting of carbon particles and hybrid particles can be used, and it is preferable to use carbon particles.

[0100] The carbon particles may be, for example, one or more selected from the group consisting of carbon black, acetylene black, ketjen black, carbon nanotubes, and graphene, and among these carbon particles, carbon black is preferably used. Examples of carbon black that can be used include Seast TA manufactured by Tokai Carbon Co., Ltd., and Asahi #15 and #15HS manufactured by Asahi Carbon Co., Ltd.

[0101] The hybrid particles contain carbon and a material other than carbon. The material other than carbon is, for example, an organic material or an inorganic material. The hybrid particles may be hybrid particles in which carbon is attached to the surface of inorganic particles. Specifically, for example, the hybrid particles may be hybrid carbon in which carbon is attached to the surface of silica particles.

[0102] (2nd particle) 3B, some of the second particles 52A contained in the magnetic layer 43 protrude from the magnetic surface to form second protrusions 52B. When the head unit 56 slides over the magnetic tape MT, the second protrusions 52B come into contact with the head unit 56.

[0103] The second particles 52A may be an abrasive. The lower limit of the Mohs hardness of the second particles 52A is 7.0 or more, preferably 7.5 or more, more preferably 8.0 or more, and even more preferably 8.5 or more, from the viewpoint of suppressing deformation due to contact with the head unit 56. The upper limit of the Mohs hardness of the second particles 52A is preferably 9.5 or less, from the viewpoint of suppressing wear of the head unit 56.

[0104] The second particles 52A are preferably inorganic particles. Examples of inorganic particles include α-alumina, 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, acicular α-iron oxide obtained by dehydrating and annealing raw materials of magnetic iron oxide, optionally surface-treated with aluminum and / or silica, and diamond powder. Examples of inorganic particles that are preferably used include alumina particles such as α-alumina, β-alumina, and γ-alumina, and silicon carbide. The second particles 52A may be acicular, spherical, or cubic in shape, but those with angular shapes are preferred because they have high abrasiveness.

[0105] (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.

[0106] 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.

[0107] 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, or the like, in order to improve the dispersibility of magnetic particles. + 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 Over 10 -8 It is preferably 10 mol / g or less. -2 Over 10 -6 It is more preferably mol / g or less.

[0108] (lubricant) The lubricant contains at least one selected from, for example, a fatty acid and a fatty acid ester, preferably both a fatty acid and a fatty acid ester. The inclusion of a lubricant in the magnetic layer 43, particularly the inclusion of both a fatty acid and a fatty acid ester in the magnetic layer 43, contributes to improving the running stability of the magnetic tape MT. More particularly, the magnetic layer 43 contains a lubricant and has pores, thereby achieving good running stability. This improvement in running stability is thought to be due to the lubricant adjusting the dynamic friction coefficient of the surface of the magnetic tape MT facing the magnetic layer 43 to a value suitable for running the magnetic tape MT.

[0109] 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).

[0110] 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).

[0111] 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.

[0112] 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.)

[0113] 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.)

[0114] 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.)

[0115] 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.)

[0116] (antistatic agent) The antistatic agent includes carbon particles. The antistatic agent may further include at least one selected from the group consisting of natural surfactants, nonionic surfactants, and cationic surfactants. The carbon particles include at least one selected from the group consisting of carbon black, acetylene black, ketjen black, carbon nanotubes, and graphene, for example.

[0117] (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.

[0118] (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.

[0119] (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).

[0120] (base layer) The underlayer 42 is intended to reduce the surface irregularities of the substrate 41 and adjust the irregularities of the magnetic surface. The underlayer 42 is a non-magnetic layer containing non-magnetic particles, a binder, and a lubricant. The underlayer 42 supplies the lubricant to the magnetic surface. If necessary, the underlayer 42 may further contain at least one additive selected from the group consisting of an antistatic agent, a hardener, and an anti-rust agent.

[0121] The average thickness t2 of the underlayer 42 is preferably 0.3 μm or more and 1.2 μm or less, more preferably 0.3 μm or more and 0.9 μm or less, or 0.3 μm or more and 0.6 μm or less. The average thickness t2 of the underlayer 42 is determined in the same manner as the average thickness t1 of the magnetic layer 43. However, the magnification of the TEM image is adjusted appropriately depending on the thickness of the underlayer 42. When the average thickness t2 of the underlayer 42 is 1.2 μm or less, the elasticity of the magnetic tape MT due to external forces is further increased, making it even easier to adjust the width of the magnetic tape MT by adjusting the tension.

[0122] The underlayer 42 preferably has a plurality of holes. By storing lubricant in these holes, it is possible to further suppress a decrease in the amount of lubricant supplied between the magnetic surface and the head unit 56, even after repeated recording or reproduction (i.e., even after repeated running with the head unit 56 in contact with the surface of the magnetic tape MT). This further suppresses an increase in the dynamic friction coefficient. In other words, even better running stability can be obtained.

[0123] (Non-magnetic particles) The non-magnetic particles include, for example, at least one of inorganic particles and organic particles. The non-magnetic particles may also be carbon particles such as carbon black. One type of non-magnetic particle may be used alone, or two or more types of non-magnetic particles 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 shapes of the non-magnetic particles include, for example, various shapes such as needles, spheres, cubes, and plates, but are not limited to these shapes.

[0124] (binder, lubricant) The binder and lubricant are the same as those used in the magnetic layer 43 described above.

[0125] (additives) The antistatic agent, hardener, and anticorrosive agent are the same as those in the magnetic layer 43 described above.

[0126] (Back layer) The back layer 44 contains a binder and non-magnetic particles. The back layer 44 may further contain at least one additive selected from the group consisting of a lubricant, a hardener, and an antistatic agent, as necessary. The binder and non-magnetic particles 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.

[0127] The average particle size of the non-magnetic particles is preferably 10 nm to 150 nm, more preferably 15 nm to 110 nm. The average particle size of the non-magnetic particles is determined in the same manner as the average particle size of the magnetic particles. The non-magnetic particles may include non-magnetic particles having two or more particle size distributions.

[0128] 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 kept thick even when the average thickness of the magnetic tape MT is 5.6 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.

[0129] 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 a length of 250 mm at a position 30 to 40 m in the longitudinal direction from the joint 21 between the magnetic tape MT and the leader tape LT to prepare a sample. Next, the back layer 44 of the 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 the sample is measured at five positions, and these measurements 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 at random from the 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]

[0130] (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 5.0 μm or less, even more preferably 4.6 μm or less, and particularly preferably 4.4 μm or less. T If the average thickness t of the magnetic tape MT is 5.2 μm or less, the recording capacity that can be recorded in one data cartridge can be increased compared to that of a general magnetic tape. T The lower limit is not particularly limited, but is, for example, 3.5 μm or more.

[0131] Average thickness t of magnetic tape MT Tis obtained as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and a sample is cut out of the magnetic tape MT at a length of 250 mm at a position 30 to 40 m in the longitudinal direction from the joint 21 between the magnetic tape MT and the leader tape LT. Next, the thickness of the sample is measured at five positions using a Mitutoyo Laser Hologram (LGH-110C) as a measuring device, and these measurements are simply averaged (arithmetic mean) to obtain the average thickness t T The five measurement positions are selected randomly from the sample so that they are different positions in the longitudinal direction of the magnetic tape MT.

[0132] (Coercive force Hc2) The upper limit of the coercive force Hc2 of the magnetic layer 43 in the longitudinal direction of the magnetic tape MT is preferably 2000 Oe or less, more preferably 1900 Oe or less, and even more preferably 1800 Oe or less. If the coercive force Hc2 of the magnetic layer 43 in the longitudinal direction of the magnetic tape MT is 2000 Oe or less, sufficient electromagnetic conversion characteristics can be obtained even at high recording densities.

[0133] The lower limit of the coercive force Hc2 of the magnetic layer 43 measured in the longitudinal direction of the magnetic tape MT is preferably 1000 Oe or more. When the coercive force Hc2 of the magnetic layer 43 measured in the longitudinal direction of the magnetic tape MT is 1000 Oe or more, demagnetization due to leakage flux from the recording head can be suppressed.

[0134] The coercive force Hc2 is determined as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and the magnetic tape MT is cut out at a position 30 to 40 m longitudinally 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 the magnetic tape MT is the same, and then punched out with a φ6.39 mm punch to prepare a measurement sample. At this time, markings are made with any nonmagnetic ink so that the longitudinal direction (running direction) of the magnetic tape MT can be identified. Then, the MH loop of the measurement sample (the entire magnetic tape MT) corresponding to the longitudinal direction (running direction) of the magnetic tape MT is measured using a vibrating sample magnetometer (VSM). Next, the coatings (underlayer 42, magnetic layer 43, back layer 44, etc.) of the magnetic tape MT cut out above are wiped off with acetone, ethanol, etc., leaving only the substrate 41. Three of the obtained substrates 41 are stacked together with double-sided tape and then punched out with a φ6.39 mm punch to prepare a sample for background correction (hereinafter simply referred to as a "correction sample"). Thereafter, the MH loop of the correction sample (substrate 41) corresponding to the longitudinal direction of the substrate 41 (the longitudinal direction of the magnetic tape MT) is measured using a VSM.

[0135] 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.

[0136] 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 MH loop after background correction. This background correction calculation is performed using the measurement and analysis program included with the VSM-P7-15. The coercive force Hc2 is calculated from the obtained MH loop after background correction. Note that this calculation is performed using the measurement and analysis program included with the VSM-P7-15. Note that all of the above MH loop measurements are performed at 25°C ± 2°C and 50% RH ± 5% RH. Furthermore, no "demagnetizing field correction" is performed when measuring the MH loop in the longitudinal direction of the magnetic tape MT.

[0137] (Square ratio) The squareness ratio S1 of the magnetic layer 43 in the perpendicular direction of the magnetic tape MT is preferably 65% ​​or more, more preferably 70% or more, even more preferably 75% or more, particularly preferably 80% or more, and most preferably 85% or more. When the squareness ratio S1 is 65% or more, the perpendicular orientation of the magnetic particles is sufficiently high, resulting in even better electromagnetic conversion characteristics.

[0138] The squareness ratio S1 of the magnetic tape MT in the perpendicular direction is determined as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and the magnetic tape MT is cut out at a position 30 to 40 m longitudinally 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 the magnetic tape MT is the same, and then punched out with a φ6.39 mm punch to prepare a measurement sample. 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 with acetone, ethanol, etc., leaving only the substrate 41. Three of the obtained substrates 41 are stacked together with double-sided tape and then punched out with a φ6.39 mm punch to prepare a sample for background correction (hereinafter simply referred to as a "correction sample"). Thereafter, the MH loop of the correction sample (substrate 41) corresponding to the perpendicular direction of the substrate 41 (perpendicular direction of the magnetic tape MT) is measured using a VSM.

[0139] 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.

[0140] 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."

[0141] The saturation magnetization Ms (emu) and residual magnetization Mr (emu) of the MH loop after background correction are substituted into the following equation to calculate the squareness ratio S1 (%). Note that all of the above MH loop measurements are performed at 25°C ± 2°C and 50% RH ± 5% RH. Furthermore, no "demagnetizing field correction" is performed when measuring the MH loop in the perpendicular direction to the magnetic tape MT. Note that this calculation uses the measurement and analysis program included with the "VSM-P7-15 model." Squareness ratio S1(%)=(Mr / Ms)×100

[0142] The squareness ratio S2 of the magnetic layer 43 in the longitudinal direction (running direction) of the magnetic tape MT is preferably 35% or less, more preferably 30% or less, even more preferably 25% or less, particularly preferably 20% or less, and most preferably 15% or less. When the squareness ratio S2 is 35% or less, the perpendicular orientation of the magnetic particles is sufficiently high, resulting in even better electromagnetic conversion characteristics.

[0143] The squareness ratio S2 in the longitudinal direction of the magnetic tape MT is determined in the same manner as the squareness ratio S1, except that the MH loop is measured in the longitudinal direction (running direction) of the magnetic tape MT and the substrate 41.

[0144] (ratio Hc2 / Hc1) The ratio Hc2 / Hc1 of the coercive force Hc1 of the magnetic layer 43 in the perpendicular direction of the magnetic tape MT to the coercive force Hc2 of the magnetic layer 43 in the longitudinal direction of the magnetic tape MT preferably satisfies the relationship Hc2 / Hc1≦0.8, more preferably Hc2 / Hc1≦0.75, even more preferably Hc2 / Hc1≦0.7, particularly preferably Hc2 / Hc1≦0.65, and most preferably Hc2 / Hc1≦0.6. When the coercive forces Hc1 and Hc2 satisfy the relationship Hc2 / Hc1≦0.8, the degree of perpendicular orientation of the magnetic grains can be enhanced. This reduces the magnetization transition width and enables high-output signals to be obtained during signal reproduction, resulting in even better electromagnetic conversion characteristics. As mentioned above, a small Hc2 allows the magnetization to respond more sensitively to the perpendicular magnetic field from the recording head, resulting in the formation of a good recording pattern.

[0145] When the ratio Hc2 / Hc1 satisfies Hc2 / Hc1≦0.8, it is particularly effective that the average thickness t1 of the magnetic layer 43 is 90 nm or less. If the average thickness t1 of the magnetic layer 43 exceeds 90 nm, when a ring-type head is used as the recording head, the lower region of the magnetic layer 43 (the region on the underlayer 42 side) may be magnetized in the longitudinal direction of the magnetic tape MT, and the magnetic layer 43 may not be uniformly magnetized in the thickness direction. Therefore, even if the ratio Hc2 / Hc1 satisfies Hc2 / Hc1≦0.8 (i.e., even if the degree of perpendicular orientation of the magnetic grains is increased), there is a risk that even better electromagnetic conversion characteristics may not be obtained.

[0146] The lower limit of Hc2 / Hc1 is not particularly limited, but is, for example, 0.5≦Hc2 / Hc1. Hc2 / Hc1 represents the degree of perpendicular orientation of the magnetic particles, and the smaller Hc2 / Hc1, the higher the degree of perpendicular orientation of the magnetic particles.

[0147] The method for calculating the coercive force Hc2 of the magnetic layer 43 in the longitudinal direction of the magnetic tape MT is as described above. The coercive force Hc1 of the magnetic layer 43 in the perpendicular direction of the magnetic tape MT is determined in the same manner as the coercive force Hc2 of the magnetic layer 43 in the longitudinal direction of the magnetic tape MT, except that the MH loop is measured in the perpendicular direction (thickness direction) of the magnetic tape MT and the substrate 41.

[0148] (Activation volume V act ) Activation volume V act However, preferably 8000 nm 3 Below 6000 nm, preferably 3 or less, and even more preferably 5000 nm 3 Below 4000 nm, particularly preferably 3 Below 3000 nm, most preferably 3 The activation volume V is act is 8000nm 3 If the pitch is less than this, the magnetic particles are well dispersed, making it possible to make the bit inversion region steeper, and it is possible to prevent the magnetic signal recorded on the adjacent track from being degraded by the leakage magnetic field from the recording head. Therefore, there is a risk that it will not be possible to obtain even better electromagnetic conversion characteristics.

[0149] The activation volume V act is calculated by the following formula derived by Street & Woolley. V act (nm 3 )=k B ×T×X irr / (μ0×Ms×S) (However, k B : Boltzmann constant (1.38×10 -23 J / K), T: Temperature (K), Χ irr : irreversible magnetic susceptibility, μ0: magnetic permeability of vacuum, S: magnetic viscosity coefficient, Ms: saturation magnetization (emu / cm 3 ))

[0150] Irreversible magnetic susceptibility X substituted into the above formula irr The saturation magnetization Ms and magnetic viscosity coefficient S are determined using VSM as follows. The measurement direction using VSM is perpendicular to the magnetic tape MT (thickness direction). Measurement using VSM is performed on a measurement sample cut out from a long magnetic tape MT at 25°C ± 2°C and 50% RH ± 5% RH. When measuring the MH loop perpendicular to the magnetic tape MT (thickness direction), no "demagnetizing field correction" is performed.

[0151] (irreversible magnetic susceptibility Χ irr ) Irreversible magnetic susceptibility Χ irr is defined as the slope of the remanence curve (DCD curve) near the remanence Hr. First, a magnetic field of -1193 kA / m (15 kOe) is applied to the entire magnetic tape MT, then returned to zero, creating a remanence state. A magnetic field of approximately 15.9 kA / m (200 Oe) is then applied in the opposite direction, returned to zero, and the remanence is measured. This is followed by a similar measurement, applying a magnetic field 15.9 kA / m larger than the previous one and returning it to zero. The remanence is plotted against the applied magnetic field, and the DCD curve is measured. The point at which the magnetization is zero is taken as the remanence Hr, and the DCD curve is differentiated to determine the slope of the DCD curve at each magnetic field. The slope of this DCD curve near the remanence Hr is X. irr This becomes:

[0152] (Saturation magnetization Ms) First, a background-corrected MH loop is obtained in the same manner as in the measurement method for the squareness ratio S1 described above. Next, the value of the saturation magnetization Ms (emu) of the obtained MH loop and the volume (cm 3 ) to Ms(emu / cm 3 ) is calculated. The volume of the magnetic layer 43 is found by multiplying the area of ​​the measurement sample by the average thickness t1 of the magnetic layer 43. The method for calculating the average thickness t1 of the magnetic layer 43, which is necessary for calculating the volume of the magnetic layer 43, is as described above.

[0153] (Magnetic viscosity coefficient S) First, a magnetic field of -1193 kA / m (15 kOe) is applied to the entire magnetic tape MT (measurement sample), and then the magnetic field is returned to zero, resulting in a state of remanence. Then, a magnetic field equivalent to the value of the remanence Hr obtained from the DCD curve is applied in the opposite direction. With the magnetic field applied, the magnetization is continuously measured at regular intervals for 1000 seconds. The relationship between time t and magnetization M(t) obtained in this way is used to calculate the magnetic viscosity coefficient S using the following equation: M(t) = M0 + S × ln(t) (where M(t) is the amount of magnetization at time t, M0 is the initial amount of magnetization, S is the magnetic viscosity coefficient, and ln(t) is the natural logarithm of time.)

[0154] (Surface roughness R b ) Surface roughness of the back surface (surface roughness of the back layer 44) R b But R b The surface roughness R of the back surface is preferably ≦6.0 [nm]. b When the content of the magnetic layer is within the above range, even better electromagnetic conversion characteristics can be obtained.

[0155] Back surface roughness R b is calculated as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and a sample is prepared by cutting the magnetic tape MT to a length of 100 mm at a position 30 to 40 m longitudinally from the joint 21 between the magnetic tape MT and the leader tape LT. 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 (20x objective lens) as a 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

[0156] (Young's modulus in the longitudinal direction of magnetic tape) The upper limit of the 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 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 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 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.

[0157] The Young's modulus of the magnetic tape MT in the longitudinal direction 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 less the magnetic tape MT is able to expand and contract in the longitudinal direction due to external forces; the smaller this value, the more easily the magnetic tape MT is able to expand and contract in the longitudinal direction due to external forces.

[0158] The 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 Young's modulus in the longitudinal direction of the magnetic tape MT to be small, as described above, 9.0 GPa or less.

[0159] A tensile tester (AG-100D, manufactured by Shimadzu Corporation) is used to measure Young's modulus. To measure Young's modulus in the longitudinal direction of the tape, unwind the magnetic tape MT housed in the cartridge 10 and cut it into a 180 mm length 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 measurement sample. 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 tape between chucks) is set to 100 mm. After chucking the tape sample, stress is gradually applied in the direction of pulling the sample. The pulling speed is 0.1 mm / min. From the change in stress and the amount of elongation at this time, Young's modulus is calculated using the following formula. E(N / m 2 )=((ΔN / S) / (Δx / L))×10 6 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 10S is the cross-sectional area before the tensile operation, and is calculated by multiplying the width (1 / 2 inch) of the measurement sample 10S by the thickness of the measurement sample 10S. 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. Here, 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.

[0160] (Young's modulus in the longitudinal direction of the substrate) The Young's modulus of the substrate 41 in the longitudinal direction 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 Young's modulus of the substrate 41 in the longitudinal direction 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. This makes it possible to more appropriately suppress off-track and more accurately reproduce data recorded on the magnetic tape MT. The lower limit of the Young's modulus of the substrate 41 in the longitudinal direction is preferably 2.5 GPa or more, more preferably 3.0 GPa or more. When the lower limit of the Young's modulus of the substrate 41 in the longitudinal direction is 2.5 GPa or more, deterioration of running stability can be suppressed.

[0161] The Young's modulus in the longitudinal direction of the substrate 41 is determined as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and the magnetic tape MT is cut into a length of 180 mm at a position 30 to 40 m in the longitudinal direction from the joint 21 between the magnetic tape MT and the leader tape LT. Next, the underlayer 42, the magnetic layer 43, and the back layer 44 are removed from the cut magnetic tape MT to obtain the substrate 41. Using this substrate 41, the Young's modulus in the longitudinal direction of the substrate 41 is determined using the same procedure as for the Young's modulus in the longitudinal direction of the magnetic tape MT.

[0162] The thickness of the substrate 41 accounts for more than half of the total thickness of the magnetic tape MT. Therefore, the 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 forces, and the larger this value, the less the magnetic tape MT is able to expand and contract in the width direction due to external forces, and the smaller this value, the more the magnetic tape MT is able to expand and contract in the width direction due to external forces.

[0163] The Young's modulus of the substrate 41 in the longitudinal direction is a value related to the longitudinal direction of the magnetic tape MT, but it also correlates with the resistance of the magnetic tape MT to expansion and contraction in the width direction. In other words, the larger this value, the less the magnetic tape MT will expand and contract in the width direction due to external force, and the smaller this value, the more the magnetic tape MT will expand and contract in the width direction due to external force. Therefore, from the perspective of tension adjustment, it is advantageous for the Young's modulus of the substrate 41 in the longitudinal direction to be small, as described above, 7.8 GPa or less.

[0164] (Ratio of the average height H1 of the primary protrusions to the average height H2 of the secondary protrusions, H1 / H2) The upper limit of the ratio H1 / H2 of the average height H1 of the first projections 51B to the average height H2 of the second projections 52B (hereinafter referred to as the "average height ratio of projections H1 / H2") is H1 / H2≦2.3, preferably H1 / H2≦2.0, more preferably H1 / H2≦1.7, and even more preferably H1 / H2≦1.5. When the average height ratio of projections H1 / H2 is H1 / H2≦2.3, the contact area between the first projections 51B and the head unit 56 can be adjusted within an appropriate range, and the contact frequency between the second projections 52B and the head unit 56 can be adjusted within an appropriate range, thereby suppressing wear of the first projections 51B as the magnetic tape MT runs. Therefore, It is possible to suppress an increase in friction on the magnetic surface due to multiple runs, and therefore it is possible to suppress an increase in the standard deviation σPES of the PES values ​​due to multiple runs.

[0165] The lower limit of the average protrusion height ratio H1 / H2 is preferably 1.0≦H1 / H2, more preferably 1.1≦H1 / H2, and even more preferably 1.2≦H1 / H2. During calendaring of the magnetic surface, the secondary protrusions 52B are more easily crushed than the primary protrusions 51B, and therefore the average height H2 of the secondary protrusions 52B is lower than the average height H1 of the primary protrusions 51B. Therefore, it is difficult to adjust the average protrusion height ratio H1 / H2 of the magnetic surface after calendaring to H1 / H2<1.0.

[0166] (Average height of first protrusion H1) The upper limit of the average height H1 of the first protrusions 51B is preferably 12.0 nm or less, more preferably 11.5 nm or less, and even more preferably 10.5 nm or less, 9.5 nm or less, or 8.5 nm or less. If the average height H1 of the first protrusions 51B exceeds 12.0 nm, the spacing between the head unit 56 and the magnetic tape MT becomes large, and it may become impossible to obtain the desired electromagnetic conversion characteristics.

[0167] The lower limit of the average height H1 of the primary projections 51B is not particularly limited, but is preferably 5.0 nm or more, more preferably 5.5 nm or more, and even more preferably 6.0 nm or more.

[0168] (Average height of secondary projections H2) The upper limit of the average height H2 of the secondary protrusions 52B is preferably 7.0 nm or less, more preferably 6.5 nm or less, and even more preferably 6.0 nm or less, 5.5 nm or less, or 5.3 nm or less. If the average height H2 of the secondary protrusions 52B exceeds 7.0 nm, the spacing between the head unit 56 and the magnetic tape MT becomes too large, and it may become impossible to obtain the desired electromagnetic conversion characteristics.

[0169] The lower limit of the average height H2 of the secondary projections 52B is not particularly limited, but is preferably 2.0 nm or more, more preferably 2.5 nm or more, and even more preferably 3.0 nm or more.

[0170] (Method for measuring the average height H1 of the primary protrusions, the average height H2 of the secondary protrusions, and the average height ratio H1 / H2 of the protrusions) The average height H1 of the first protrusions 51B, the average height H2 of the second protrusions 52B, and the average height ratio H1 / H2 of the protrusions are determined by obtaining an AFM image using an atomic force microscope (AFM) and an FE-SEM image using a field-emission scanning electron microscope (FE-SEM) at the same location on the measurement sample, as described below, and correlating these AFM images with the FE-SEM images.

[0171] The height of each protrusion can be measured by AFM, and it can be determined by FE-SEM whether each protrusion is formed by first particle 51A or second particle 52A. An image of the same location obtained by AFM and an image obtained by FE-SEM are superimposed to obtain a composite image, and the type of particle forming each protrusion (whether it is first particle 51A or second particle 52A) can be associated with the height of each protrusion from the composite image obtained.

[0172] Below, we will explain in order: (1) how to prepare a measurement sample and obtain an AFM image, (2) how to identify the type of particles that form the protrusions using FE-SEM, (3) how to match the height of the protrusions with the type of particles that form the protrusions, (4) how to measure the height of the protrusions using AFM, and (5) how to calculate the average height H1 of the primary protrusions, the average height H2 of the secondary protrusions, and the average height ratio H1 / H2 of the protrusions.

[0173] (1) Preparation of measurement sample and acquisition of AFM image First, the magnetic tape MT housed in the cartridge 10 is unwound and cut into a size that fits on the AFM observation sample stage and the SEM observation sample stage, 30 to 40 m longitudinally from the connection 21 between the magnetic tape MT and the leader tape LT. This creates a measurement sample. Next, markings are made on the surface of the measurement sample, avoiding the center of the measurement sample. Marking methods include forming linear or dot-shaped depressions on the magnetic tape MT using a manipulator or a nine-denter, or forming protrusions on the magnetic tape MT using silver paste. In AFM, the marking area is scanned with a probe. Depending on the condition of the marking area, the probe tip may become contaminated, preventing accurate AFM images from being obtained. Therefore, it is preferable to make the markings small and shallow to prevent contamination of the probe.

[0174] Next, the shape of the marking portion on the surface of the measurement sample is analyzed by AFM. Since the marked marking portion is recessed or protruding, the surface of the measurement sample is measured at a field angle of 5 μm × 5 μm with the AFM so that the marking portion is at the edge of the field of view as much as possible. Note that the protrusions on the periphery of the marking portion are not measured. Specifically, it is measured at a field angle of 10 μm × 10 μm to determine the marked portion, and in accordance with the marked portion, the surface of the measurement sample is measured at a field angle of 5 μm × 5 μm for the non-marked portion. The measurement conditions for the above shape analysis are as described below.

[0175] <AFM Measurement Conditions> Measuring device: AFM Dimension 3100 microscope (with NanoscopeIV controller) (manufactured by Digital Instruments) Measurement mode: Tapping Tapping frequency during tuning: 200 kHz or more and 400 kHz or less Cantilever: SNL-10 (manufactured by Bruker) Scan size: 5 μm × 5 μm Scan rate: 1 Hz Scan line: 256

[0176] <Method for calculating the reference plane when calculating the protrusion height> The AFM image is divided into 256 × 256 (= 65,536) measurement points, the height Z(i) (i: measurement point number, i = 1 to 65,536) is measured at each measurement point, and the heights Z(i) of the measured measurement points are simply averaged (arithmetic mean) to obtain the average height (reference plane) Zave (= (Z(1) + Z(2) + ··· + Z(65,536)) / 65,536).

[0177] (2) Method for identifying the type of particles forming protrusions using FE-SEM The marked portion of the above measurement sample is imaged using FE-SEM under the FE-SEM measurement conditions described below to obtain a FE-SEM image. Figure A in Fig. 10 is an example of a FE-SEM image. From the obtained FE-SEM image, the type of particles forming the protrusions can be identified by utilizing the luminance difference due to the difference in the secondary electron emission amounts of the first particles 51A and the second particles 52A respectively. The image processing for this identification will be described later. Also, the positions of the protrusions formed by the first particles 51A and the second particles 52A respectively in the FE-SEM image are discriminated.

[0178] <FE-SEM Measurement Conditions> Measuring device: HITACHI S-4800 (manufactured by Hitachi High-Technologies Corporation) Field of view angle: 5.1μm × 3.8μm Acceleration voltage: 5kV Measurement magnification: 25000 times

[0179] The obtained FE-SEM image (Figure A in Fig. 10) is subjected to binarization processing using image processing software Image J under each of the two processing conditions described below. From the image obtained by the binarization processing, information on the number of protrusions can be obtained for the first protrusions 51B and the second protrusions 52B formed by the first particles 51A and the second particles 52A respectively. Note that during the binarization processing, the conditions are changed as follows for the second particles 52A with high luminance (the white portions in Figure A of Fig. 10) and the first particles 51A with low luminance (the black portions in Figure A of Fig. 10).

[0180] <Binarization Processing Conditions for Obtaining Information on the First Particles> Software: Image J Ver 1.44p Binarization threshold: Threshold(0.65) Binarization target size: 0.002μm - infinity

[0181] <Binarization Processing Conditions for Obtaining Information on the Second Particles> Software: Image J Ver 1.44p Binarization threshold: Threshold(220,255) Binarization target size: 0.001μm-infinity

[0182] Figure B in Fig. 10 is an image obtained by binarizing the FE-SEM image in Figure A in Fig. 10 under the binarization conditions for the second particles (alumina particles) 52A, i.e., an image showing the position distribution of the second protrusions 52B formed by the second particles (alumina particles) 52A. The following information about the second particles 52A can be obtained from the obtained image.

[0183] <Information about the second particle obtained> Quantity: 58

[0184] Figure 10C is an image obtained by binarizing the FE-SEM image of Figure 10A under the binarization conditions for first particles (carbon black particles) 51A, i.e., an image showing the positional distribution of primary protrusions 51B formed by first particles (carbon black particles) 51A. The following information about first particles 51A can be obtained from the obtained image.

[0185] <Information about the first particle obtained> Quantity: 55

[0186] (3) Method for correlating the height of protrusions with the type of particles that form the protrusions The obtained AFM image and the FE-SEM image before binarization are superimposed to obtain a composite image, and the composite image is used to identify whether the particle forming each protrusion is a first particle 51A or a second particle 52A.

[0187] For example, Figure C in Figure 11 is a composite image obtained by superimposing an AFM image (Figure B) and an FE-SEM image (Figure A) so that the positions of corresponding protrusions coincide. In the FE-SEM image (Figure A in Figure 11) before image synthesis, different marks ("circle" or "square") are added at each position to enable distinction between the positions of the first protrusions 51B and the second protrusions 52B determined by the binarization process. Similarly, in the AFM image (Figure B in Figure 11) before image synthesis, different marks ("circle" or "square") are added at each position to enable distinction between the positions of the first protrusions 51B and the second protrusions 52B determined by the binarization process. From the composite image (Figure C) obtained by superimposing the AFM image (Figure B) and the FE-SEM image (Figure A) so that the positions of corresponding protrusions coincide, it is possible to determine whether each protrusion is formed by the first particle 51A or the second particle 52A. In addition, in Figure 11B, the marked area was measured with an AFM at a field of view of 10 μm × 10 μm, and then the area without the marking was measured at a field of view of 5 μm × 5 μm, so the marking is not present in the image.

[0188] (4) Method for measuring the height of protrusions using AFM Using AFM analysis software (Software version 5.12 Rev.B for Dimension 3100, manufactured by Veeco), the heights of the 20 primary protrusions 51B and the heights of the 20 secondary protrusions 52B in the composite image are measured.

[0189] For example, Fig. 12 is an enlarged view of a composite image obtained by superimposing an AFM image and an FE-SEM image. Fig. 13 is a diagram showing the results of AFM analysis (protrusion height measurement results) for Line 1 (Line 1) set at an arbitrary position in Fig. 12. As shown in Fig. 13, the heights of the first protrusions 51B and second protrusions 52B formed by the first particles (carbon black particles) 51A and the second particles (alumina particles) 52A present on Line 1, respectively, can be identified. In this way, the heights of the first protrusions 51B and second protrusions 52B can be identified from the composite image and the AFM analysis results.

[0190] For each of the first protrusions 51B and the second protrusions 52B, if 20 or more protrusions can be identified in one AFM field of view from one measurement sample, one field of view is measured using the AFM. If for each of the first protrusions 51B and the second protrusions 52B, fewer than 20 protrusions can be identified in one AFM field of view, multiple fields of view (e.g., 3 to 5) are measured from one measurement sample. This ensures that for each of the first protrusions 51B and the second protrusions 52B, 20 points are identified as the first protrusions 51B and the second protrusions 52B through the above-mentioned binarization process. Note that when measuring multiple fields of view from one measurement sample as described above, the multiple fields of view are selected randomly from one measurement sample.

[0191] (5) Calculation method for the average height H1 of the primary protrusions, the average height H2 of the secondary protrusions, and the average height ratio H1 / H2 of the protrusions The heights of the 20 primary projections 51B obtained as described above are simply averaged (arithmetic average) to obtain an average value, which is designated as the average height H1 of the primary projections. Similarly, the heights of the 20 secondary projections 52B obtained as described above are simply averaged (arithmetic average) to obtain an average value, which is designated as the average height H2 of the secondary projections. The average height H1 of the primary projections 51B and the average height H2 of the secondary projections 52B thus obtained are used to calculate the average height ratio H1 / H2 of the projections.

[0192] (Standard deviation of PES values ​​σPES) The standard deviation σPES of the PES values ​​of the magnetic tape MT is preferably less than 50 nm within 40 FV numbers, more preferably 40 nm or less, even more preferably 30 nm or less, and particularly preferably 25 nm or less.

[0193] The PES (Position Error Signal) indicates the deviation (error) of the read position of a servo pattern in the width direction of the magnetic tape MT when the servo pattern is reproduced (read) by a recording / reproducing device. To accurately adjust the longitudinal tension of the magnetic tape MT, it is preferable that the linearity of the servo band when the servo pattern is read by the recording / reproducing device is as high as possible, i.e., the standard deviation σPES of the PES value indicating the deviation of the read position is as low as possible. When the standard deviation σPES of the PES value of the magnetic tape MT is a low value as described above, the linearity of the servo band is high, and the tension of the magnetic tape MT can be accurately adjusted. Furthermore, the standard deviation σPES is related to the friction of the magnetic surface; as the friction of the magnetic surface increases, the standard deviation σPES tends to increase.

[0194] FIG. 14 is a diagram showing a first example of the change over time in the standard deviation σPES of the PES values ​​as the magnetic tape MT runs. As shown in FIG. 14, when σPES is less than 50 nm within 40 FV numbers, no track misalignment occurs. In addition, an increase in friction on the magnetic surface is suppressed and kept almost constant. FIG. 15 is a diagram showing a second example of the change over time in the standard deviation σPES of the PES values ​​as the magnetic tape MT runs. As shown in FIG. 15, when σPES exceeds 50 nm within 40 FV numbers, track misalignment occurs frequently, causing the magnetic tape MT to stop running. In addition, friction on the magnetic surface increases.

[0195] The upper diagram in FIG. 16 shows a third example of the change over time in the standard deviation σPES as the magnetic tape MT runs. The lower left diagram in FIG. 16 is a cross-sectional view schematically showing the relationship between the first protrusion 51B and the second protrusion 52B and the head unit 56 in region A (stable friction) where the σPES in the upper diagram is a substantially constant value. The dashed line in the diagram is a virtual line indicating the contact position between the first protrusion 51B and the surface of the head unit 56. The lower right diagram in FIG. 16 is a cross-sectional view schematically showing the relationship between the first protrusion 51B and the second protrusion 52B and the head unit 56 in region B (increasing friction) where the σPES in the upper diagram tends to increase. The dashed line in the diagram is a virtual line indicating the contact position between the first protrusion 51B and the surface of the head unit 56.

[0196] As shown in Figure 16, the standard deviation σPES is almost constant in region A, but increases in region B. This is presumably because in region A, the contact area between the first protrusions 51B and the surface of the head unit 56 is small and friction is constant, whereas in region B, as the magnetic tape MT runs, the first particles 51A (carbon particles) are worn down by the magnetic tape MT, the first protrusions 51B gradually break down, the contact area between the first protrusions 51B and the surface of the head unit 56 increases, and friction increases.

[0197] 17 is a cross-sectional view schematically showing the relationship between the first protrusion 51B and the second protrusion 52B on the magnetic surface and the head unit 56. The dashed lines in FIG. 17 are imaginary lines indicating the contact positions between the first protrusion 51B on the magnetic surface and the surface of the head unit 56.

[0198] The upper diagram in Fig. 17 is a diagram schematically showing the relationship between the first protrusion 51B and the second protrusion 52B and the head unit 56 before the magnetic tape MT starts running. As shown in the upper diagram in Fig. 17, before the magnetic tape MT starts running, the height of the first protrusion 51B is greater than the height of the second protrusion 52B, the spacing between the head unit 56 and the magnetic tape MT is large, the contact area between the first protrusion 51B and the head unit 56 is small, and it is presumed that the opportunity for contact between the second protrusion 52B and the head unit 56 is low.

[0199] The middle diagram in Fig. 17 is a diagram schematically showing the relationship between the first protrusions 51B and second protrusions 52B and the head unit 56 after the magnetic tape MT has run. As shown in the middle diagram in Fig. 17, after the magnetic tape MT has run, the first protrusions 51B are gradually worn down by contact with the magnetic tape MT, and the height of the first protrusions 51B becomes higher than or equal to the height of the second protrusions 52B. This reduces the spacing between the head unit 56 and the magnetic tape MT, increases the contact area between the first protrusions 51B and the head unit 56, and increases the chances of contact between the second protrusions 52B and the head unit 56. This state results in high friction, which worsens the standard deviation σPES.

[0200] 17 is a diagram schematically illustrating the relationship between the first protrusions 51B and the second protrusions 52B and the head unit 56 in this embodiment. As shown in the lower diagram of Fig. 17, by configuring the height relationship between the first protrusions 51B and the second protrusions 52B to the shape in this embodiment (an uneven shape with an average height ratio of protrusions H1 / H2≦2.3), the contact area between the first protrusions 51B and the head unit 56 is reduced and the contact opportunity between the second protrusions 52B and the head unit 56 is increased, which is presumably to suppress wear of the first protrusions 51B due to the running of the magnetic tape MT and, as a result, to suppress an increase in the standard deviation σPES.

[0201] A method for measuring the standard deviation σPES will be described below with reference to FIGS. 6 and 18. A PES value is measured to determine the standard deviation σPES. To measure the PES value, a PES measurement head unit 300, such as that shown in FIG. 18, is prepared. An LTO2 head (a head conforming to the LTO2 standard) manufactured by HPE (Hewlett Packard Enterprise) is used as the head unit 300. The head unit 300 has two head sections 300A and 300B arranged side by side along the longitudinal direction of the magnetic tape MT. Each head section includes a plurality of recording heads 340 for recording data signals on the magnetic tape MT, a plurality of reproducing heads 350 for reproducing the data signals recorded on the magnetic tape MT, and a plurality of servo heads 320 for reproducing the servo signals recorded on the magnetic tape MT. When the head unit 300 is used only for measuring the PES value, the recording head 340 and the reproducing head 350 do not necessarily have to be included in the head unit.

[0202] First, the head unit 300 is used to reproduce (read) the servo patterns in a predetermined servo band provided on the magnetic tape MT. At this time, the servo head 320 of the head unit 300A and the servo head 320 of the head unit 300B sequentially face each servo pattern in the predetermined servo band, and these two servo heads 320 sequentially reproduce the servo patterns. At this time, the portion of the servo pattern recorded on the magnetic tape MT facing the servo head 320 is read and output as a servo signal.

[0203] As shown in FIG. 6, the PES value for each head part is calculated for each servo frame using the following formula.

number

[0204] The above difference (B a1 -A a1 ) indicates the time [sec] on the actual path between two corresponding servo patterns, servo pattern B1 and servo pattern A1. Similarly, other difference terms also indicate the time [sec] on the actual path between two corresponding servo patterns. These times are calculated from the time between timing signals obtained from the servo signal waveform and the tape running speed. In this specification, the actual path means the position where the servo signal read head actually runs on the servo signal. φ is the azimuth angle. φ was measured by developing the magnetic tape MT with a ferricolloid developer and using a universal tool microscope (TOPCON TUM-220ES) and a data processing device (TOPCON CA-1B). can be done.

[0205] In this technology, the standard deviation σPES of the PES values ​​is calculated using a servo signal that has been corrected for lateral tape movement. Furthermore, the servo signal is subjected to high-pass filtering to reflect the head tracking performance. In this technology, the standard deviation σPES is calculated using a signal obtained by performing the above-described correction and high-pass filtering on the servo signal, and is known as the "written in PESσ." The method for measuring the standard deviation σPES of the PES values ​​will be described below.

[0206] First, the head unit 300 reads the servo signal from an arbitrary 1-meter range in the data recording area of ​​the magnetic tape MT. The signals acquired by the head units 300A and 300B are subtracted as shown in FIG. 19 to obtain a servo signal corrected for the lateral movement of the magnetic tape MT. Then, high-pass filtering is performed on the corrected servo signal. When the magnetic tape MT is actually run in a drive, the recording / playback head mounted on the drive is moved by an actuator in the width direction of the magnetic tape MT to follow the servo signal. Since the Written in PESσ is a noise value that takes into account the width-direction tracking ability of the head, the high-pass filtering is necessary. Therefore, although the high-pass filtering is not particularly limited, it must be a function that can reproduce the width-direction tracking ability of the drive head. Using the signal obtained by the high-pass filtering, the PES value is calculated for each servo frame according to the above formula. The standard deviation of the PES values ​​calculated over the 1-meter range (Written in PESσ) is the standard deviation σPES of the PES values ​​in this technology.

[0207] (Height range ΔH, gradient range ΔA) The height range ΔH (see FIG. 28) calculated from the statistical information (distribution) of the height of the unevenness on the magnetic surface is 3.00 nm≦ΔH≦6.00 nm, preferably 3.00 nm≦ΔH≦4.00 nm, and more preferably 3.00 nm≦ΔH≦3.50 nm. If the height range ΔH is ΔH<3.00 nm, the head unit 300 sticks to the magnetic tape MT, making it difficult for the magnetic tape MT to run. On the other hand, if the height range ΔH is 6.00 nm<ΔH, spacing loss will cause a decrease in electromagnetic conversion characteristics (e.g., SNR).

[0208] The gradient range ΔA (see FIG. 28) obtained from statistical information (distribution) of the gradient of the uneven shape on the magnetic surface is 4.00 degrees≦ΔA≦9.00 degrees. If the gradient range ΔA is ΔA<4.00 degrees, the gradient of the protrusions (protrusions including first protrusions 51B and second protrusions 52B, etc.) on the magnetic surface becomes too shallow, resulting in increased friction. Therefore, the standard deviation σPES of the PES values ​​increases. On the other hand, if the gradient range ΔA is 9.00 degrees<ΔA, the gradient of the protrusions (protrusions including first protrusions 51B and second protrusions 52B, etc.) on the magnetic surface becomes too steep, resulting in the protrusions being scraped off as the magnetic tape MT runs, causing powder to fall off.

[0209] The method for calculating the height range ΔH and the gradient range ΔA will be described in the following order. (1) Surface profile measurement (AFM) (2) Calculating the relative height at each point (3) Calculating the gradient at each point (4) Statistical processing of height and gradient data (5) Calculation of height range ΔH (6) Calculation of gradient range ΔA

[0210] (1) Surface profile measurement (AFM) By measuring the two-dimensional surface profile of the magnetic surface of the magnetic tape MT, a numerical data matrix of height ζ(L,W) is obtained from the two-dimensional surface profile image after filtering. The measurement conditions are as follows: Measurement equipment: AFM (Digital Instruments Nanoscope Dimension 3100) Measurement range: 10μm x 10μm Number of measurement points: 256 points x 256 points Scan rate: 1Hz Filter condition: [Flatten] order 2 [Plane Fit] Not performed

[0211] FIG. 20A is a diagram showing an example of a two-dimensional surface profile image after filtering. FIG. 20B is a diagram showing an example of a numerical data matrix of height ζ(L,W) at each point (L,W). The coordinate L indicates the coordinate in the longitudinal direction of the magnetic tape MT, and the coordinate W indicates the coordinate in the width direction of the magnetic tape MT. Each cell of the numerical data matrix contains the height ζ(L,W) at each point (L,W). In the example shown in FIG. 20B, for example, the height ζ(1,3) at measurement point (1,3) is "0.50". The total number of numerical data (i.e., heights ζ(L,W)) is 256 × 256 = 65,536.

[0212] (2) Calculating the relative height at each point From the numerical data matrix of height ζ(L,W), the relative height Z(L,W) (hereinafter simply referred to as "height Z(L,W)") at each point (L,W) is calculated to obtain a numerical data matrix of height Z(L,W). Specifically, height Z(L,W) at each point (L,W) is calculated as follows. That is, all heights ζ(L,W) are simply averaged (arithmetic mean) to obtain the average center height ζ ave Then, the height ζ(L,W) at each point (L,W) is calculated as the average center height ζ ave is converted into a relative height based on the reference point, and the height Z(L,W) at each point (L,W) is obtained. The calculation method for height Z(L,W) is expressed by the following formula: Figure 21 is a diagram showing an example of a numeric data matrix of height Z(L,W).

number

number

[0213] (3) Calculating the gradient at each point Figure 22 shows the gradient G at each point (L, W). L (L,W), G W FIG. 1 is a diagram for explaining a method for calculating (L, W). Here, the gradient G L(L, W) indicates the gradient in the longitudinal direction of the magnetic tape MT, and the gradient G W (L, W) indicates the gradient in the width direction of the magnetic tape MT.

[0214] From the numerical data matrix of height ζ(L,W), the gradient G in two directions at each point (L,W) L (L,W), G W By calculating (L,W), the gradient G L (L,W), G W (L, W) Numerical data matrix is ​​obtained. Figure 23A shows the gradient G L FIG. 23B is a diagram showing an example of a numerical data matrix of (L, W). W FIG. 10 is a diagram showing an example of a (L, W) numeric data matrix.

[0215] Gradient G L (L,W) is calculated as follows: Gradient G L (L,W) is calculated using the height ζ(L,W) at a certain point (L,W) and the height ζ(L+1,W) at a point (L+1,W) adjacent to the point (L,W) in the longitudinal direction of the magnetic tape MT. L (2,2) is calculated using the height ζ(2,2)(=0.30) of point (2,2) and the height ζ(3,2)(=0.10) of point (3,2).

[0216] Gradient G W (L,W) is calculated as follows: Gradient G W (L,W) is calculated using the height ζ(L,W) at a certain point (L,W) and the height ζ(L,W+1) at a point (L,W+1) adjacent to the point (L,W) in the width direction of the magnetic tape MT. W (2,2) is calculated using the height ζ(2,2)(=0.30) of point (2,2) and the height ζ(2,3)(=0.10) of point (2,3).

[0217] As mentioned above, G at each point (L,W) LThe "neighboring point" used in calculating (L,W) is the point (L+1,W). The neighboring point in the opposite direction, i.e., the point (L-1,W), should not be used. Similarly, the G W The "neighboring point" used in calculating (L,W) is point (L,W+1). The neighboring point in the opposite direction, i.e. point (L,W-1), must not be used.

[0218] As shown in FIG. 22, at each point (256, W) of the numerical data matrix L=256 (i.e., the rightmost column in FIG. 22), the gradient G L (256,W) cannot be calculated. Therefore, as shown in FIG. 23A, the gradient G L In the numerical data matrix of (L, W), each point (256, W) of L=256 has no value. On the other hand, as shown in FIG. 22, each point (L, 256) of W=256 (i.e., the bottom row in FIG. 22) of the numerical data matrix has a gradient G W Therefore, as shown in FIG. 23B, the gradient G W In a (L,W) numerical data matrix, each point (L,256) where W=256 does not have a value.

[0219] However, as shown in FIG. 22, at the point (L, W) where L=256, W=256 (bottom right column and bottom row) of the numerical data matrix, the gradient G L (256,256) and gradient G W (256,256) Since neither can be calculated, the point (256,256) has the gradient G L (256,256) and gradient G W It will not have any gradient of (256,256).

[0220] Figure 24A shows the gradient G L FIG. 24B shows how to calculate (L, W). W A diagram showing how to calculate (L, W). L (L,W), G W The calculation method for (L, W) is expressed as the following formula:

number

number

[0221] (4) Statistical processing of height and gradient data Figures 25, 26, and 27 show the relationship between the height Z(L,W) and the slope G L (L,W) and gradient G W FIG. 10 is a diagram for explaining statistical processing of (L, W) data. The height Z(L,W) and gradient G obtained above L Organize the numerical data matrix of (L,W) and calculate the height Z(L,W) and gradient G L A table showing the relationship between (L, W) is created (see Figure 25). However, the gradient G L Since (256,W) does not exist, the total number of data in the created table is 255 x 256 = 65,280.

[0222] Also, the height Z(L,W) and the slope G W Organize the numerical data matrix of (L,W) and calculate the height Z(L,W) and gradient G W A table showing the relationship between (L, W) is created (see Figure 26). W Since (L, 256) does not exist, the total number of data in the created table is 256 x 255 = 65,280.

[0223] All data in the two tables created (i.e., 130,560 = 65,280 + 65,280) is tallied and a numeric data matrix with data count M(H, A) is created as shown in Figure 27. Adding up all the values ​​in each cell of the numeric data matrix with data count M(H, A) gives the total data count of 130,560.

[0224] In FIG. 27, the range of height Z(L,W) and its representative value H are listed alongside the columns of the numerical data matrix of data number M(H,A). Also, the range of gradient G(L,W) and its representative value A are listed alongside the rows of the numerical data matrix of data number M(H,A). Note that gradient G L (L,W) and gradient GW If (L,W) is not specifically distinguished, the gradient G L (L,W) and gradient G W (L,W) are collectively called the gradient G(L,W).

[0225] The numerical value of each cell of the numerical data matrix of the number of data M(H,A) (see Figure 27) corresponds to the range of the specified height Z(L,W) and the specified gradient G(L,W) (specifically, the gradient G L (L,W) or gradient G W (L,W)) represents the number of data M(H,A) that fall within the range of Z(L,W) L The data in the first row of the (L,W) table is counted in the (H,A)=(0.0,0.00) cell in M(H,A). Also, Z(L,W) vs. G W The 65278th data in the (L,W) table is counted in the (H,A)=(-0.5,0.00) cell in M(H,A).

[0226] If the numerical data matrix M(H,A) (see FIG. 27) obtained as described above is plotted as a distribution map with the horizontal axis A and the vertical axis H, it will look like FIG.

[0227] (5) Calculation of height range ΔH 29 and 30 are diagrams for explaining a method for calculating the height range ΔH. When calculating the height range ΔH, only components (cells) in the ranges of 0≦H and 0.00≦A≦1.20 are used from the numerical data matrix with the number of data items M(H, A). The reason why only components in the range of 0≦H are used for the height H is to take into account only the convex portions of the magnetic surface. In other words, this is because it is believed that concave portions of the magnetic surface do not affect the electromagnetic conversion characteristics or friction. On the other hand, the reason why only components in the range of 0.00≦A≦1.20 are used for the gradient A is because it is believed that using only this range in the calculation is sufficient to define the general outline of the distribution (see FIG. 28).

[0228] As shown in Figure 29, the average value of each row (height H) of the numerical data matrix with the number of data M(H, A) is M ave (H) and the mean value Mave (0) to the average value M ave (40.0), the calculations are carried out in order. However, the average value M ave In calculating (H), only the components of the column (angle A) in the range of 0.00≦A≦1.20 are used.

[0229] Average value M ave The height H when (H) falls below the threshold value (however, the threshold value is set to "2") for the first time is called the height H high Then, the average value M ave (H) Average M ave (H high ) and then the previous height H is set as height H low Then, the average value M ave (H) Average M ave (H low ) If the threshold is set to "1", reproducibility will be poor. In other words, the element of chance will have a large influence. Therefore, the threshold is set to "2", which is the lowest frequency that will ensure reproducibility.

[0230] In the example in Figure 29, the height H high , mean value M ave (H high ), height H low , mean value M ave (H low ) is as follows: H high =11.5, M ave (H high )=1.9 H low =11.0, M ave (H low )=4.2

[0231] As shown in Figure 30, using the above four values, M ave The height H when (H) = threshold = 2 is calculated and defined as the height range ΔH. Note that when calculating the height H, a two-point linear approximation is used.

[0232] (6) Calculation of gradient range ΔA 31 and 32 are diagrams for explaining a method for calculating the gradient range ΔA. When calculating the gradient range ΔA, only components (cells) in the ranges of 0≦H≦ΔH and 0.00≦A≦16.00 are used from the numerical data matrix with the number of data items M(H, A). The value calculated in "(5) Calculation of height range ΔH" above is used for ΔH. For gradient A, only components in the range of 0.00≦A≦16.00 are used because gradient A is usually 0.00≦A≦16.00, and it is considered sufficient to use only this range for calculations.

[0233] As shown in FIG. 31, the average value of M(H,A) in each column (angle A) of the numerical data matrix with the number of data M(H,A) is calculated as M ave (A) and the mean value M ave (0) to the average value M ave (16.00), the calculations are carried out in order. However, the average value M ave In the calculation of (A), only the components of the row (height H) in the range of 0.00≦H≦ΔH are used.

[0234] If the height range ΔH is not a multiple of 0.5, the average value M ave To calculate (A), the height H used in the calculation of the height range ΔH is used. low For example, as shown in Figure 31, when the height range ΔH is between 11.0 and 11.5, the row (height H) components in the range 0.00≦H≦11.0 are used.

[0235] Average value M ave When (A) falls below the threshold (however, the threshold is set to “2”) for the first time, A is defined as A. high Then, the average value M ave (A) Average M ave (A high ) and then the previous angle A is angle A low Then, the average value M ave (A) Average M ave (A low ) The average value M ave The reason for setting the threshold value of (A) to “2” is that the average value Mave The reason for setting the threshold value of (H) to "2" is the same as above.

[0236] In the example in Figure 31, A high , M ave (A high ), A low , M ave (A low ) is as follows: A high =3.5, M ave (A high )=1.9 A low =3.4, M ave (A low )=2.2

[0237] As shown in Figure 32, using the above four values, M ave The angle A when (A) = threshold = 2 is calculated and defined as the gradient range ΔA. Note that when calculating the angle A, a two-point linear approximation is used.

[0238] [4. Magnetic tape manufacturing method] Next, an example of a method for manufacturing the magnetic tape MT having the above-described configuration will be described.

[0239] (Paint preparation process) First, a base layer forming paint is prepared by kneading and dispersing non-magnetic particles, a binder, etc. in a solvent. Next, a magnetic layer forming paint is prepared by kneading and dispersing magnetic particles, first particles 51A, second particles 52A, a binder, etc. in a solvent. The following solvents, dispersing devices, and kneading devices can be used to prepare the magnetic layer forming paint and the base layer forming paint.

[0240] 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.

[0241] 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.

[0242] (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 particles are magnetically oriented in the thickness direction of the substrate 41, for example, by a solenoid coil. Alternatively, during drying, the magnetic particles may be magnetically oriented in the running direction (longitudinal direction) of the substrate 41, for example, by a solenoid coil, and then magnetically oriented in the thickness direction of the substrate 41. By performing a process to orient the magnetic particles in the longitudinal direction in this manner, the degree of perpendicular orientation of the magnetic particles (i.e., the squareness ratio S1) can be further improved. After the magnetic layer 43 is formed, a back layer 44 is formed on the other main surface of the substrate 41. This results in a magnetic tape MT.

[0243] The squareness ratios S1 and S2 can be set to desired values ​​by, for example, adjusting the strength of the magnetic field applied to the coating film of the magnetic layer-forming paint, the concentration of solids in the magnetic layer-forming paint, and the drying conditions (drying temperature and drying time) of the coating film of the magnetic layer-forming paint. The strength of the magnetic field applied to the coating film is preferably between two and three times the coercive force of the magnetic particles. To further increase the squareness ratio S1 (i.e., to further reduce the squareness ratio S2), it is preferable to improve the dispersion state of the magnetic particles in the magnetic layer-forming paint. To further increase the squareness ratio S1, it is also effective to magnetize the magnetic particles before the magnetic layer-forming paint enters an orientation device that magnetically orients the magnetic particles. The above methods for adjusting the squareness ratios S1 and S2 may be used alone or in combination.

[0244] (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.

[0245] (calendering process) Next, the obtained magnetic tape MT is subjected to a calendering process to smooth the magnetic surface.

[0246] (Surface treatment process) Next, if necessary, the magnetic surface may be scraped using, for example, a rectangular pillar, to adjust the average height H1 of the first protrusions 51B on the magnetic surface, the average height H2 of the second protrusions 52B, the average height ratio H1 / H2 of the protrusions, the height range ΔH, and the gradient range ΔA.

[0247] (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.

[0248] (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.

[0249] (Adjustment of the average height of the first protrusion H1, the average height of the second protrusion H2, the average height ratio of the protrusions H1 / H2, the height range ΔH and the gradient range ΔA) The average height H1 of the first protrusions, the average height H2 of the second protrusions, the average height ratio H1 / H2 of the protrusions, the height range ΔH, and the gradient range ΔA can be adjusted to specified values ​​by adjusting, for example, at least one selected from the group consisting of: (1) the size and amount of the first particles 51A and the second particles 52A blended into the magnetic layer forming paint, (2) the amount of the binder blended into the magnetic layer forming paint, (3) the conditions of the calendar treatment (temperature and pressure), and (4) the above-mentioned surface treatment process.

[0250] [5. Effects] As described above, in the magnetic tape MT according to one embodiment, the magnetic layer 43 has a concave-convex shape on its magnetic surface, and this concave-convex shape includes first protrusions 51B formed by first particles 51A and second protrusions 52B formed by second particles 52A. The ratio H1 / H2 of the average height H1 of the first protrusions 51B to the average height H2 of the second protrusions 52B is H1 / H2≦2.3, the height range ΔH is 3.00 nm≦ΔH≦6.00 nm, and the gradient range ΔA is 4.00 degrees≦ΔA≦9.00 degrees. This makes it possible to ensure good electromagnetic conversion characteristics while suppressing an increase in the standard deviation σPES of the PES values.

[0251] [6 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.

[0252] 33 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 lower half 105 are joined together, 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 lower half 105 are joined together, and a back lid 109A that protects the magnetic tape MT exposed in this front opening.

[0253] 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.

[0254] 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]

[0255] The present disclosure will be specifically described below using examples, but the present disclosure is not limited to these examples.

[0256] In the following examples and comparative examples, the average aspect ratio of the magnetic particles, the average particle volume of the magnetic particles, the average height H1 of the primary protrusions, the average height H2 of the secondary protrusions, the average height ratio H1 / H2 of the protrusions, the height range ΔH, the gradient range ΔA, the average thickness of the magnetic tape, the average thickness of the magnetic layer, the average thickness of the underlayer, the average thickness of the back layer, the squareness ratio S1 of the magnetic layer in the perpendicular direction of the magnetic tape, and the squareness ratio S2 of the magnetic layer in the longitudinal direction of the magnetic tape are values ​​obtained using the measurement method described in the above embodiment.

[0257] In the following examples and comparative examples, the average height H1 of the primary projections, the average height H2 of the secondary projections, the average height ratio H1 / H2 of the projections, the height range ΔH, and the gradient range ΔA each refer to values ​​measured on the final magnetic tape (magnetic tape after undergoing the calendaring process).

[0258] Hereinafter, the average height H1 of the primary projections, the average height H2 of the secondary projections, the average height ratio H1 / H2 of the projections, the height range ΔH, and the gradient range ΔA are referred to as the respective numerical values ​​of the uneven shape.

[0259] [Example 1] (Preparation process of paint for forming magnetic layer) The magnetic layer-forming paint was prepared as follows. First, a first composition having the following formulation was kneaded using an extruder. Next, the kneaded first composition and a second composition having the following formulation were added to a stirring tank equipped with a disperser and premixed. Subsequently, further sand mill mixing was performed and filtering was carried out to prepare the magnetic layer-forming paint.

[0260] (First composition) Barium ferrite (BaFe 12 O 19 ) Magnetic powder (hexagonal plate shape, average aspect ratio 3.2, average particle volume 1600nm 3 ):100 parts by mass Vinyl chloride resin solution in which vinyl chloride resin is dispersed in cyclohexanone (30% by mass of vinyl chloride resin, 70% by mass of cyclohexanone): 65 parts by mass (Vinyl chloride resin: degree of polymerization 300, number average molecular weight Mn=10,000, polar groups OSO3K=0.07 mmol / g, secondary OH=0.3 mmol / g) Aluminum oxide powder (α-Al2O3, average particle size (D50) 80 nm): 5.0 parts by mass

[0261] (Second composition) Vinyl chloride resin solution in which vinyl chloride resin is dispersed in cyclohexanone (30% by mass of vinyl chloride resin, 70% by mass of cyclohexanone): 1.1 parts by mass n-Butyl stearate: 2.0 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 (average particle size (D50) 70 nm, manufactured by Tokai Carbon Co., Ltd., product name: Seast S): 2.0 parts by mass

[0262] 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.

[0263] (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.

[0264] (Third composition) Medium-sized acicular iron oxide powder (non-magnetic powder) (α-Fe2O3, average major axis length 0.08 μm): 100 parts by mass Vinyl chloride resin solution in which vinyl chloride resin is dispersed in cyclohexanone (30% by mass of vinyl chloride resin, 70% by mass of cyclohexanone): 55.6 parts by mass Carbon black (average particle size 20 nm): 10 parts by mass

[0265] (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

[0266] 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.

[0267] (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 (manufactured by Nippon Polyurethane Co., Ltd., product name: N-2304): 100 parts by mass Methyl ethyl ketone: 500 parts by mass Toluene: 400 parts by mass Cyclohexanone: 100 parts by mass

[0268] (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 long polyethylene naphthalate film (hereinafter referred to as "PEN film") with an average thickness of 3.6 μm, which served as a non-magnetic support, as follows. First, the primer layer-forming paint was applied to one main surface of the PEN film and dried to form a primer layer with an average thickness of 1.1 μm after calendaring. Next, the magnetic layer-forming paint was applied to the primer layer and dried to form a magnetic layer with an average thickness of 85 nm after calendaring. During drying of the magnetic layer-forming paint, a solenoid coil was used to magnetically orient the magnetic particles in the thickness direction of the film. The squareness ratio S1 in the perpendicular direction (thickness direction) of the magnetic tape was set to 65%, and the squareness ratio S2 in the longitudinal direction of the magnetic tape was set to 38%. Next, a coating material for forming a back layer was applied to the other main surface of the PEN film and dried to form a back layer having an average thickness of 0.4 μm after calendaring, thereby obtaining a magnetic tape.

[0269] (hardening process) The magnetic tape was wound into a roll, and then subjected to a heat treatment in this state at 70° C. for 48 hours to harden the underlayer and magnetic layer.

[0270] (calendering process) The surface of the magnetic layer was smoothed by calendering, with the calendering temperature set to a reference temperature of 100°C and the calendering pressure set to a reference pressure of 200 kg / cm, and the numerical values ​​of the uneven shape were set to the values ​​shown in Table 1.

[0271] (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 5.2 μm.

[0272] [Example 2] A magnetic tape in which the numerical values ​​of the concave and convex shapes were set to the values ​​shown in Table 1 was obtained in the same manner as in Example 1 except for the following points. In the process of preparing the coating material for forming the magnetic layer, the amount of aluminum oxide powder in the first composition was changed from 5.0 parts by mass to 7.5 parts by mass, and the amount of vinyl chloride resin solution in the first composition was changed from 65 parts by mass to 46 parts by mass. After the cutting process, the magnetic surface was scraped off using a square pillar.

[0273] [Example 3] A magnetic tape in which the numerical values ​​of the concave and convex shapes were set to the values ​​shown in Table 1 was obtained in the same manner as in Example 1 except for the following points. In the preparation process of the magnetic layer coating material, the amount of aluminum oxide powder in the first composition was changed from 5.0 parts by mass to 7.5 parts by mass.

[0274] [Example 4] A magnetic tape in which the numerical values ​​of the concave and convex shapes were set to the values ​​shown in Table 1 was obtained in the same manner as in Example 1 except for the following points. In the process of preparing the coating material for forming the magnetic layer, aluminum oxide powder (α-Al2O3, average particle size (D50) 50 nm) was used instead of the aluminum oxide powder (α-Al2O3, average particle size (D50) 80 nm) of the first composition, and the amount of aluminum oxide powder in the first composition was changed from 5.0 parts by mass to 7.5 parts by mass. In the calendering step, the calendering temperature was changed to a temperature lower than the reference temperature of 100°C in Example 1.

[0275] [Example 5] A magnetic tape in which the numerical values ​​of the concave-convex shape were set to the values ​​shown in Table 1 was obtained in the same manner as in Example 4, except for the following points. In the calendering step, the calendering temperature was changed from a temperature lower than the reference temperature of 100°C to the same reference temperature of 100°C as in Example 1.

[0276] [Example 6] A magnetic tape in which the numerical values ​​of the concave-convex shape were set to the values ​​shown in Table 1 was obtained in the same manner as in Example 4 except for the following points. In the calendering step, the calendering temperature was changed from a temperature lower than the reference temperature of 100°C to a temperature higher than the reference temperature of 100°C.

[0277] [Example 7] A magnetic tape in which the numerical values ​​of the concave-convex shape were set to the values ​​shown in Table 1 was obtained in the same manner as in Example 4 except for the following points. In the process of preparing the magnetic layer coating material, aluminum oxide powder (α-Al2O3, average particle size (D50) 50 nm) of the first composition was replaced with aluminum oxide powder (α-Al2O3, average particle size (D50) 80 nm).

[0278] [Example 8] A magnetic tape in which the numerical values ​​of the concave-convex shape were set to the values ​​shown in Table 1 was obtained in the same manner as in Example 2 except for the following points. In the preparation process of the magnetic layer-forming paint, the blending amount of the vinyl chloride resin solution in the first composition was changed from 46 parts by mass to 65 parts by mass.

[0279] [Comparative Example 1] A magnetic tape in which the numerical values ​​of the concave-convex shape were set to the values ​​shown in Table 1 was obtained in the same manner as in Example 2 except for the following points. In the preparation process of the coating material for forming the magnetic layer, barium ferrite (BaFe 12 O 19 ) Magnetic powder (hexagonal plate shape, average aspect ratio 3.2, average particle volume 1600nm 3 ) instead of barium ferrite (BaFe 12 O 19 ) Magnetic powder (hexagonal plate shape, average aspect ratio 3.2, average particle volume 2500nm 3 ) was used. Furthermore, no treatment of the magnetic surface with a rectangular pillar was carried out between the calendering step and the cutting step.

[0280] Comparative Example 2 A magnetic tape in which the numerical values ​​of the concave and convex shapes were set to the values ​​shown in Table 1 was obtained in the same manner as in Example 1 except for the following points. In the process of preparing the coating material for forming the magnetic layer, aluminum oxide powder (α-Al2O3, average particle size (D50) 80 nm) was added to the second composition instead of the first composition, and the amount of vinyl chloride resin solution in the first composition was changed from 65 parts by mass to 46 parts by mass.

[0281] Comparative Example 3 A magnetic tape in which the numerical values ​​of the concave and convex shapes were set to the values ​​shown in Table 1 was obtained in the same manner as in Comparative Example 1 except for the following points. In the process of preparing the coating material for forming the magnetic layer, 2.0 parts by mass of carbon black (average particle size (D50) 70 nm, manufactured by Tokai Carbon Co., Ltd., product name: Seast S) in the first composition were replaced with 2.0 parts by mass of carbon black (average particle size (D50) 100 nm, manufactured by Tokai Carbon Co., Ltd., product name: Seast SP) and 1.5 parts by mass of carbon black (average particle size (D50) 70 nm, manufactured by Tokai Carbon Co., Ltd., product name: Seast S).

[0282] Comparative Example 4 A magnetic tape in which the numerical values ​​of the concave and convex shapes were set to the values ​​shown in Table 1 was obtained in the same manner as in Example 1 except for the following points. In the preparation process of the coating material for forming the magnetic layer, barium ferrite (BaFe 12 O 19 ) Magnetic powder (hexagonal plate shape, average aspect ratio 3.2, average particle volume 1600nm 3 ) instead of acicular metal magnetic powder (average particle volume 3000nm 3 ) was used.

[0283] Comparative Example 5 A magnetic tape in which the numerical values ​​of the concave and convex shapes were set to the values ​​shown in Table 1 was obtained in the same manner as in Example 1 except for the following points. In the preparation process of the magnetic layer-forming paint, the blending amount of the vinyl chloride resin solution in the first composition was changed from 65 parts by mass to 46 parts by mass.

[0284] Comparative Example 6 A magnetic tape in which the numerical values ​​of the concave-convex shape were set to the values ​​shown in Table 1 was obtained in the same manner as in Example 4 except for the following points. In the calendering step, the calendering pressure was changed to a lower pressure than the standard pressure of 200 kg / cm in Example 1.

[0285] Comparative Example 7 A magnetic tape in which the numerical values ​​of the concave-convex shape were set to the values ​​shown in Table 1 was obtained in the same manner as in Example 6 except for the following points. In the process of preparing the magnetic layer coating material, aluminum oxide powder (α-Al2O3, average particle size (D50) 50 nm) of the first composition was replaced with aluminum oxide powder (α-Al2O3, average particle size (D50) 80 nm).

[0286] [Comparative Example 8] A magnetic tape in which the numerical values ​​of the concave and convex shapes were set to the values ​​shown in Table 1 was obtained in the same manner as in Example 1 except for the following points. In the preparation process of the magnetic layer coating material, aluminum oxide powder (α-Al2O3, average particle size (D50) 50 nm) was used in place of the aluminum oxide powder (α-Al2O3, average particle size (D50) 80 nm) of the first composition.

[0287] [evaluation] (Electromagnetic conversion characteristics) The SNR of the magnetic tape with the servo patterns written on it was evaluated as follows. The SNR (electromagnetic conversion characteristics) of the magnetic tape was measured in a 25°C environment using a 1 / 2-inch tape transport device (MTS Transport, manufactured by Mountain Engineering II) equipped with a recording / playback head and a recording / playback amplifier. A ring head with a gap length of 0.2 μm was used as the recording head, and a GMR head with a shield-to-shield distance of 0.1 μm was used as the playback head. The relative speed was 6 m / s, the recording clock frequency was 160 MHz, and the recording track width was 2.0 μm. The SNR was calculated based on the method described in the following document. The results are shown in Table 1 as relative values, with the SNR of Comparative Example 1 being set to 0 dB. Y. Okazaki: “An Error Rate Emulation System.”, IEEE Trans. Man., 31, pp. 3093-3095 (1995)

[0288] (Standard deviation σPES) The standard deviation σPES of the magnetic tape was measured by the method for measuring the standard deviation σPES described in the above embodiment.

[0289] [Evaluation results] Table 1 shows the configurations and evaluation results of the magnetic tapes of Examples 1 to 8 and Comparative Examples 1 to 8. Fig. 34 shows the relationship between the height range ΔH and gradient range ΔA of the magnetic tapes of Examples 1 to 8 and Comparative Examples 1 to 8. In Fig. 34, symbols A1 to A8 correspond to the evaluation results of Examples 1 to 8, respectively, and symbols B1 to B8 correspond to the evaluation results of Comparative Examples 1 to 8, respectively.

[0290] [Table 1]

[0291] The following can be seen from Table 1 and Figure 34. When the ratio H1 / H2 of the average height H1 of the primary protrusions to the average height H2 of the secondary protrusions is H1 / H2≦2.3, the height range ΔH is 3.00 nm≦ΔH≦6.00 nm, and the gradient range ΔA is 4.00 degrees≦ΔA≦9.00 degrees, good electromagnetic conversion characteristics can be ensured while suppressing an increase in the standard deviation σPES (friction) of the PES values. The ratio H1 / H2 of the average height H1 of the primary protrusions to the average height H2 of the secondary protrusions is 2.3 If the height range ΔH is ΔH<3.00 nm, the head unit 300 sticks to the magnetic tape, making it difficult for the magnetic tape to run. On the other hand, if the height range ΔH is 6.00 nm<ΔH, the electromagnetic conversion characteristics (SNR) will decrease due to spacing loss. If the gradient range ΔA is ΔA<4.00 degrees, the gradient of the protrusions on the surface of the magnetic layer becomes too gentle, and the standard deviation of the PES value σPES (friction) increases. On the other hand, if the gradient range ΔA is 9.00 degrees < ΔA, the gradient of the protrusions on the surface of the magnetic layer becomes too steep, and the protrusions are scraped off as the magnetic tape runs, causing powder fall.

[0292] 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.

[0293] ​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.

[0294] 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 includes magnetic particles, first particles having electrical conductivity, and second particles having a Mohs hardness of 7.0 or more; the magnetic layer has an uneven surface; the uneven shape includes first protrusions formed by the first particles and second protrusions formed by the second particles, a ratio H1 / H2 of an average height H1 of the primary projections to an average height H2 of the secondary projections is H1 / H2≦2.3; a height range ΔH calculated from statistical information on the height of the uneven shape is 3.00 nm≦ΔH≦6.00 nm; A magnetic recording medium in which a gradient range ΔA determined from statistical information on the gradient of the concave-convex shape is 4.00 degrees≦ΔA≦9.00 degrees. (2) 1. The magnetic recording medium according to (1), wherein the ratio H1 / H2 is 1.0≦H1 / H2≦1.7 or less. (3) The magnetic recording medium according to (1) or (2), wherein the height range ΔH is 3.00 nm≦ΔH≦4.00 nm. (4) the average height H1 of the primary projections is 5.0 nm or more and 12.0 nm or less, The magnetic recording medium according to any one of (1) to (3), wherein the average height H2 of the secondary projections is 2.0 nm or more and 7.0 nm or less. (5) The magnetic recording medium according to any one of (1) to (4), wherein the first particles are carbon particles. (6) The magnetic recording medium according to any one of (1) to (5), wherein the second particles are inorganic particles. (7) The magnetic recording medium according to any one of (1) to (5), wherein the second particles are alumina particles. (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 thickness of the magnetic recording medium is 5.3 μm or less. (11) The magnetic recording medium according to any one of (1) to (10), wherein the substrate has an average thickness of 4.4 μm or less. (12) The magnetic particles have an average particle volume of 2500 nm 3 The magnetic recording medium according to any one of (1) to (11) below: (13) The magnetic particles have an average particle volume of 1600 nm 3 The magnetic recording medium according to any one of (1) to (11) below: (14) The magnetic recording medium according to any one of (1) to (13), wherein the magnetic particles contain hexagonal ferrite, ε-iron oxide, or Co-containing spinel ferrite. (15) The magnetic recording medium according to any one of (1) to (14), wherein the substrate contains polyester. (16) A tape-shaped magnetic recording medium, A substrate, an underlayer, and a magnetic layer are sequentially provided, the magnetic layer includes magnetic particles, carbon particles, and an abrasive; the magnetic layer has an uneven surface; the uneven shape includes primary protrusions formed by the carbon particles and secondary protrusions formed by the abrasive, a ratio H1 / H2 of an average height H1 of the primary projections to an average height H2 of the secondary projections is H1 / H2≦2.3; a height range ΔH calculated from statistical information on the height of the uneven shape is 3.00 nm≦ΔH≦6.00 nm; A magnetic recording medium in which a gradient range ΔA determined from statistical information on the gradient of the concave-convex shape is 4.00 degrees≦ΔA≦9.00 degrees. (17) The magnetic recording medium according to (16), wherein the abrasive is alumina particles. (18) A cartridge comprising the magnetic recording medium according to any one of (1) to (17). [Explanation of symbols]

[0295] 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, 300 head unit 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 includes magnetic particles, first particles having electrical conductivity, and second particles having a Mohs hardness of 7.0 or more; the magnetic layer has an uneven surface; the uneven shape includes first protrusions formed by the first particles and second protrusions formed by the second particles, a ratio H1 / H2 of an average height H1 of the primary projections to an average height H2 of the secondary projections is H1 / H2≦2.3; a height range ΔH calculated from statistical information on the height of the uneven shape is 3.00 nm≦ΔH≦6.00 nm; A magnetic recording medium in which a gradient range ΔA obtained from statistical information on the gradient of the concave-convex shape is 4.00 degrees≦ΔA≦9.00 degrees.

2. 2. The magnetic recording medium according to claim 1, wherein the ratio H1 / H2 satisfies 1.0≦H1 / H2≦1.

7.

3. 2. The magnetic recording medium according to claim 1, wherein the height range ΔH is 3.00 nm≦ΔH≦4.00 nm.

4. an average height H1 of the primary projections is 5.0 nm or more and 12.0 nm or less; 2. The magnetic recording medium according to claim 1, wherein the average height H2 of the second protrusions is 2.0 nm or more and 7.0 nm or less.

5. 2. The magnetic recording medium according to claim 1, wherein the first particles are carbon particles.

6. 2. The magnetic recording medium according to claim 1, wherein the second particles are inorganic particles.

7. 2. The magnetic recording medium according to claim 1, wherein the second particles are alumina particles.

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 the average thickness of the magnetic recording medium is 5.3 [mu]m or less.

11. 2. The magnetic recording medium according to claim 1, wherein the average thickness of the substrate is 4.4 [mu]m or less.

12. The average particle volume of the magnetic particles is 2500 nm ３ 2. The magnetic recording medium according to claim 1, wherein:

13. The average particle volume of the magnetic particles is 1600 nm ３ 2. The magnetic recording medium according to claim 1, wherein:

14. 2. The magnetic recording medium according to claim 1, wherein the magnetic particles contain hexagonal ferrite, ε-iron oxide, or Co-containing spinel ferrite.

15. 2. The magnetic recording medium according to claim 1, wherein the substrate comprises polyester.

16. A tape-shaped magnetic recording medium, A substrate, an underlayer, and a magnetic layer are sequentially provided, the magnetic layer includes magnetic particles, carbon particles, and an abrasive; the magnetic layer has an uneven surface; the uneven shape includes first protrusions formed by the carbon particles and second protrusions formed by the abrasive, a ratio H1 / H2 of an average height H1 of the primary projections to an average height H2 of the secondary projections is H1 / H2≦2.3; a height range ΔH calculated from statistical information on the height of the uneven shape is 3.00 nm≦ΔH≦6.00 nm; A magnetic recording medium in which a gradient range ΔA obtained from statistical information on the gradient of the concave-convex shape is 4.00 degrees≦ΔA≦9.00 degrees.

17. 17. The magnetic recording medium according to claim 16, wherein the abrasive is alumina particles.

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

Images