Magnetic recording media and cartridges

Abstract

Provided is a magnetic recording medium with which a decrease in electromagnetic conversion characteristics can be suppressed.　This magnetic recording medium has a tape shape and comprises a base body including a polyester, an underlayer provided on the base body, and a magnetic layer provided on the underlayer and containing a magnetic powder. The magnetic recording medium includes a lubricant. The arithmetic average roughness Ra of the surface of the magnetic layer is 1.3 nm or less. In a case where, when the magnetic recording medium is caused to slide on the glass-made simulated head, the average value of peak half-widths in a space increase region generated on an inlet side of a glass-made simulated head to which the magnetic recording medium is inserted is defined as a space index SRL, and when the magnetic recording medium is caused to slide on the glass-made simulated head, the average value of peak half-widths in a space increase region generated in the vicinity of a widthwise edge of the magnetic recording medium is defined as a space index SRT, the space index SRL is 35 μm or less, and the space index SRT is 68 μm or less.

Description

[Technical Field]

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

[0002] In recent years, with the development of information technology (IT), there has been a demand for higher recording density in tape-type magnetic recording media as data storage media. If the thickness of the magnetic layer is reduced to meet this demand and short-wavelength recording is performed, there is a risk that the electromagnetic conversion characteristics will deteriorate due to a slight deterioration in the spacing between the magnetic layer and the magnetic head.

[0003] For example, Patent Document 1 discloses that the surface roughness Ra of the aromatic polyamide film constituting the non-magnetic support is set to 0.2 to 5 nm on the side on which the magnetic layer is applied. It also discloses that if the surface roughness Ra is greater than 5 nm, the surface roughness of the magnetic recording medium after the magnetic layer is applied increases, resulting in greater spacing loss with the magnetic head. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-181121 Summary of the Invention [Problem to be solved by the invention]

[0005] As mentioned above, conventionally, attempts have been made to suppress the deterioration of electromagnetic conversion characteristics by adjusting the surface roughness of the magnetic layer, but it is difficult to suppress the deterioration of electromagnetic conversion characteristics by simply adjusting the surface roughness of the magnetic layer.

[0006] An object of the present disclosure is to provide a magnetic recording medium capable of suppressing deterioration in electromagnetic conversion characteristics, and a cartridge including the same. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems, the first disclosure provides: A tape-shaped magnetic recording medium, a substrate comprising polyesters; an underlayer provided on a substrate; a magnetic layer containing magnetic powder provided on the underlayer; Equipped with The magnetic recording medium includes a lubricant, The average value of the arithmetic mean roughness Ra of the surface of the magnetic layer is 1.3 nm or less, When the magnetic recording medium is slid over the glass pseudo head, the average value of the half-width of the peak of the spacing increase region that occurs at the entrance side of the glass pseudo head where the magnetic recording medium enters is defined as the spacing index SRL, When a magnetic recording medium is slid over a glass pseudo head, the average value of the half-width of the peak of the spacing increase region that occurs near the edge in the width direction of the magnetic recording medium is defined as the spacing index SRT. The magnetic recording medium has a spacing index SRL of 35 μm or less and a spacing index SRT of 68 μm or less.

[0008] The second disclosure is a cartridge including the magnetic recording medium of the first disclosure. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is an exploded perspective view showing an example of the configuration of a cartridge according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a block diagram showing an example of the configuration of the cartridge memory. [Figure 3] FIG. 3 is a cross-sectional view showing an example of the configuration of a magnetic tape. [Figure 4] FIG. 4 is a schematic diagram showing an example of the layout of the data band and the servo band. [Figure 5] FIG. 5 is an enlarged view showing an example of the configuration of a data band. [Figure 6]FIG. 6 is an enlarged view showing an example of the configuration of a servo band. [Figure 7] FIG. 7 is a perspective view showing an example of the shape of a particle. [Figure 8] FIG. 8 is a diagram showing an example of a TEM photograph of the magnetic layer. [Figure 9] FIG. 9 is a diagram showing an example of a TEM photograph of the magnetic layer. [Figure 10] FIG. 10 is a schematic diagram showing the configuration of the measurement device. [Figure 11] Fig. 11A is an enlarged view showing the relationship between the dummy and the magnetic tape in the measuring device, and Fig. 11B is a cross-sectional view taken along line XIB-XIB in Fig. 11A. [Figure 12] FIG. 12 is a diagram showing an example of a 2D profile acquired by the measurement device. [Figure 13] 13A is a graph showing an example of an average 1D profile PaL(L), and FIG. 13B is a graph showing an example of an average 1D profile PaT(T). [Figure 14] Fig. 14A is a perspective view for explaining a method for calculating cupping, and Fig. 14B is a cross-sectional view taken along line XIVB-XIVB in Fig. 14A. [Figure 15] FIG. 15 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 16] FIG. 16 is a graph showing acceptable ranges for stiffness and cupping. DETAILED DESCRIPTION OF THE INVENTION

[0010] 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

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

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

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

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

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

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

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

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

[0019] The management ledger data includes at least one type of data selected from the group consisting of the capacity, creation date, edit date, and storage location of the data files recorded on the magnetic tape MT. The index information is metadata for searching the contents of the data files. The thumbnail information is a thumbnail of the video or still image stored on the magnetic tape MT.

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

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

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

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

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

[0025] The magnetic tape MT is long and runs longitudinally during recording and playback. The magnetic tape MT is preferably used in a recording and playback device that has a maximum linear recording density of 550 KFCI or more when recording signals. The magnetic tape MT is preferably used in a recording and playback device that has a ring-type head as a recording head. The magnetic tape MT is preferably used in a recording and playback device that is configured to be able to record data with a data track width of 1500 nm or less or 1000 nm or less.

[0026] As shown in FIG. 4, data is recorded on or reproduced from the magnetic tape MT by a magnetic head 56. The magnetic head 56 has a sliding surface on which the magnetic tape MT slides. The sliding surface is long. A recording / reproducing element is provided at the center of the sliding surface in the width direction. The width direction of the sliding surface coincides with the longitudinal direction of the magnetic tape MT, i.e., the running direction of the magnetic tape MT. The longitudinal direction of the sliding surface coincides with the width direction of the magnetic tape MT.

[0027] For recording and reproducing the magnetic tape MT, it is preferable to use a flat head as the magnetic head 56. In a flat head, the air near the running magnetic tape MT is actively scraped off by the edge of the head before it reaches the sliding surface, so that the air pressure between the sliding surface of the magnetic head 56 and the magnetic tape MT can be reduced. Therefore, the spacing between the sliding surface of the magnetic head 56 and the magnetic tape MT can be reduced. This allows the R in FIG. L , RT is expected to be smaller than when the flat head is not used.

[0028] (Base) The substrate 41 is a non-magnetic support that supports the underlayer 42 and the magnetic layer 43. The substrate 41 has a long film shape. The average thickness T s The upper limit of the average thickness T of the substrate 41 is, for example, 4.4 μm or less, preferably 4.2 μm or less, more preferably 4.0 μm or less, even more preferably 3.8 μm or less, particularly preferably 3.6 μm or less, and most preferably 3.4 μm or less. s If the upper limit of the average thickness T 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 a general magnetic tape. s The lower limit of the average thickness T of the substrate 41 is preferably 3 μm or more, and more preferably 3.2 μm or more. s When the lower limit is 3 μm or more, the decrease in strength of the base 41 can be suppressed.

[0029] Average thickness T of the substrate 41 s is determined as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and three samples of 250 mm are cut out from the magnetic tape MT in the longitudinal direction from the joint 21 between the magnetic tape MT and the leader tape LT, in the ranges of 10 m to 20 m, 30 m to 40 m, and 50 m to 60 m, to prepare three samples. In this specification, the "longitudinal direction" when referring to the "longitudinal direction from the joint 21 between the magnetic tape MT and the leader tape LT" means the direction from one end on the leader tape LT side to the other end on the opposite side.

[0030] Next, the layers other than the substrate 41 of each sample (i.e., the underlayer 42, the magnetic layer 43, and the back layer 44) are removed with a solvent such as MEK (methyl ethyl ketone) or dilute hydrochloric acid. Next, the thickness of each sample (substrate 41) is measured at five positions using a Mitutoyo Laser Hologram (LGH-110C) as a measuring device, and the arithmetic average of these measurements (a total of 15 sample thicknesses) is calculated to obtain the average thickness T of the substrate 41. s The five measurement positions are selected randomly from each sample so that they are different positions in the longitudinal direction of the magnetic tape MT.

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

[0032] Of the above polymer resins, the substrate 41 preferably contains polyesters as a main component. By including polyesters in the substrate 41, the average Young's modulus in the longitudinal direction of the substrate 41 can be reduced to preferably 2.5 GPa or more and 7.8 GPa or less, more preferably 3.0 GPa or more and 7.0 GPa or less. Therefore, by adjusting the longitudinal tension of the magnetic tape MT during running using a recording / playback device, it is particularly easy to control the width of the magnetic tape MT to be constant or approximately constant. A method for measuring the average Young's modulus in the longitudinal direction of the substrate 41 will be described later.

[0033] In this specification, the term "main component" means the component that is contained in the highest proportion among the components that constitute the base 41. That the main component of the base 41 is polyester may mean that the content of polyester in the base 41 is, 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 may mean that the base 41 is composed only of polyester.

[0034] The polyesters include, for example, at least one selected from the group consisting of PET (polyethylene terephthalate), PEN (polyethylene naphthalate), PBT (polybutylene terephthalate), PBN (polybutylene naphthalate), PCT (polycyclohexylene dimethylene terephthalate), PEB (polyethylene-p-oxybenzoate), and polyethylene bisphenoxycarboxylate. When the base 41 includes two or more polyesters, the two or more polyesters may be mixed, copolymerized, or laminated. At least one of the terminals and side chains of the polyesters may be modified.

[0035] The inclusion of polyesters in the substrate 41 can be confirmed, for example, as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and a section of the magnetic tape MT is cut out from the joint 21 between the magnetic tape MT and the leader tape LT in the longitudinal direction, ranging from 30 to 40 m, to prepare a sample. After that, the layers of the sample other than the substrate 41 are removed. Next, an IR spectrum of the sample (substrate 41) is obtained by infrared absorption spectrometry (IR). Based on this IR spectrum, it can be confirmed that the substrate 41 contains polyesters.

[0036] The polyolefins include, for example, at least one selected from the group consisting of PE (polyethylene) and PP (polypropylene). The cellulose derivatives include, for example, at least one selected from the group consisting of cellulose diacetate, cellulose triacetate, CAB (cellulose acetate butyrate), and CAP (cellulose acetate propionate). The vinyl resins include, for example, at least one selected from the group consisting of PVC (polyvinyl chloride) and PVDC (polyvinylidene chloride).

[0037] Examples of other polymer resins include at least one selected from the group consisting of PA (polyamide, nylon), aromatic PA (aromatic polyamide, aramid), PI (polyimide), aromatic PI (aromatic polyimide), PAI (polyamideimide), aromatic PAI (aromatic polyamideimide), PBO (polybenzoxazole, such as Zylon (registered trademark)), polyether, PEK (polyetherketone), PEEK (polyetheretherketone), polyetherester, PES (polyethersulfone), PEI (polyetherimide), PSF (polysulfone), PPS (polyphenylene sulfide), PC (polycarbonate), PAR (polyarylate), and PU (polyurethane).

[0038] 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.

[0039] (magnetic layer) The magnetic layer 43 is a recording layer for recording signals using a magnetization pattern. The magnetic layer 43 may be a recording layer for perpendicular recording or a recording layer for longitudinal recording. The magnetic layer 43 contains, for example, magnetic powder and a binder. If necessary, the magnetic layer 43 may further contain at least one additive selected from the group consisting of lubricants, carbon, antistatic agents, abrasives, hardeners, rust inhibitors, and non-magnetic reinforcing particles. The magnetic layer 43 may have an uneven surface.

[0040] 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 magnetic head 56 (specifically, servo read heads 56A and 56B) when recording or reproducing data. A servo pattern (servo signal) for tracking control of the magnetic head 56 is written in advance in the servo bands SB. User data is recorded in the data bands DB.

[0041] The total area S of multiple servo bands SB relative to the area S of the magnetic surface SB The ratio R S (=(S SB From the viewpoint of ensuring a high recording capacity, the upper limit of the average value of (S / S)×100) is preferably 4.0% or less, more preferably 3.0% or less, and even more preferably 2.0% or less. SB The ratio R S The lower limit of the average value is preferably 0.8% or more, from the viewpoint of ensuring 5 or more servo bands SB.

[0042] The total area S of the plurality of servo bands SB relative to the area S of the entire surface of the magnetic layer 43 SB The ratio R S The average value of is found as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and the magnetic tape MT is cut into 250 mm lengths from the longitudinal range of 10 m to 20 m, 30 m to 40 m, and 50 m to 60 m from the joint 21 between the magnetic tape MT and the leader tape LT, to prepare three samples. Next, each sample is developed using a ferricolloid developer (Sigma Marker Q, manufactured by Sigma High Chemical Co., Ltd.), and then each developed sample is observed under an optical microscope to determine the servo bandwidth W SB and the number of servo bands SB. Next, calculate the ratio R of each sample using the following formula: S Ask for. Ratio R S [%]=(((Servo bandwidth W SB ) x (number of servo bands SB)) / (width of magnetic tape MT)) x 100 Next, the proportion of the three samples, R S The arithmetic mean is the ratio R S Calculate the average value of

[0043] 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.

[0044] The number of servo bands SB is determined as follows: First, the magnetic tape MT housed in the cartridge 10 is unwound, and a sample of 250 mm is cut from the magnetic tape MT in a range of 30 m to 40 m in the longitudinal direction from the joint 21 between the magnetic tape MT and the leader tape LT. Next, the ratio R S In the same manner as in the calculation of (1), the sample is developed and the number of servo bands SB is measured.

[0045] Servo Bandwidth W SB From the viewpoint of ensuring a high recording capacity, the upper limit of the average value of is preferably 95 μm or less, more preferably 60 μm or less, and even more preferably 30 μm or less. SB The lower limit of the average value of is preferably 10 μm or more. SB It is difficult to manufacture a magnetic head 56 that can read such servo signals.

[0046] Servo Bandwidth W SB The average value of the above ratio R SThe servo bandwidth W of the three samples is calculated in the same way as SB Next, the servo bandwidth W of the three samples is calculated. SB The servo bandwidth W is calculated by arithmetically averaging SB Calculate the average value of

[0047] 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.

[0048] 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.

[0049] 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. Three 250 mm lengths of the magnetic tape MT are cut from the connection 21 between the magnetic tape MT and the leader tape LT, extending longitudinally from 10 to 20 m, 30 to 40 m, and 50 to 60 m, to create three samples. Next, the data recording pattern in the data band DB portion of the magnetic layer 43 of each sample is observed using a magnetic force microscope (MFM) to obtain an MFM image. A Digital Instruments Dimension3100 and its analysis software are used for the MFM. The measurement area of ​​the MFM image is 10 μm × 10 μm, and this 10 μm × 10 μm measurement area is divided into 512 × 512 (= 262,144) measurement points. For each sample, MFM measurements were performed in a 10 μm × 10 μm measurement area, resulting in three MFM images. Using the analysis software provided with the Dimension3100, the track width was measured at 10 locations and the average (simple average) was calculated from the three MFM images. This average value was the data track width W. The MFM measurement conditions were: sweep speed: 1 Hz, tip used: MFMR-20, lift height: 20 nm, and correction: Flatten order 3.

[0050] The minimum distance L between magnetization reversals is calculated as follows. First, a cartridge 10 is prepared with data recorded on the entire surface of the magnetic tape MT. The magnetic tape MT is unwound from the cartridge 10. Three 250 mm lengths of the magnetic tape MT are cut from the connection 21 between the magnetic tape MT and the leader tape LT, ranging from 10 to 20 m, 30 to 40 m, and 50 to 60 m in the longitudinal direction, to prepare three samples. Next, the data recording pattern in the data band DB portion of the magnetic layer 43 of each sample is observed using a magnetic force microscope (MFM) to obtain an MFM image. A Digital Instruments Dimension3100 and its analysis software are used for the MFM. The measurement area of ​​the MFM image is 2 μm × 2 μm, and this 2 μm × 2 μm measurement area is divided into 512 × 512 (= 262,144) measurement points. For each sample, MFM measurements were performed on a 2 μm x 2 μm measurement area, resulting in three MFM images. Fifty inter-bit distances were measured from a two-dimensional concavo-convex chart of the recording pattern of the obtained MFM image. The inter-bit distance measurements were performed using the analysis software provided with the Dimension3100. The value that is approximately the greatest common denominator of the 50 measured inter-bit distances was taken as the minimum value L of the distance between magnetization reversals. The measurement conditions were: sweep speed: 1 Hz, tip used: MFMR-20, lift height: 20 nm, and correction: Flatten order 3.

[0051] 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).

[0052] 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.

[0053] 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).

[0054] 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.

[0055] 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 regular intervals and inclined at a predetermined angle φ with respect to the width direction of the magnetic tape MT. 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 regular intervals and inclined at a predetermined angle φ with respect to the width direction of the magnetic tape MT. 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.

[0056] 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.

[0057] Reading the servo band SB with the magnetic head 56 provides information for determining the tape speed and the longitudinal position of the magnetic head 56. The tape speed is calculated from the time between four timing signals (A1-C1, A2-C2, A3-C3, A4-C4). The position of the magnetic head 56 is calculated from the time between the aforementioned four timing signals and the time between another four timing signals (A1-B1, A2-B2, A3-B3, A4-B4). The servo pattern may be a shape containing two parallel lines.

[0058] 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.

[0059] The upper limit of the average thickness of magnetic layer 43 is preferably 80 nm or less, more preferably 70 nm or less, even more preferably 60 nm or less, and particularly preferably 50 nm or less. If the upper limit of the average thickness of magnetic layer 43 is 80 nm or less, when a ring-type head is used as the recording head, the influence of the demagnetizing field can be reduced, thereby achieving even better electromagnetic conversion characteristics.

[0060] The lower limit of the average thickness of the magnetic layer 43 is preferably 35 nm or more. If the lower limit of the average thickness of the magnetic layer 43 is 35 nm or more, output can be ensured when an MR head is used as the reproducing head, and therefore even better electromagnetic conversion characteristics can be obtained.

[0061] The average thickness of the magnetic layer 43 is determined as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and three 250 mm lengths of the magnetic tape MT are cut from the connection 21 between the magnetic tape MT and the leader tape LT in the longitudinal direction, from 10 to 20 m, 30 to 40 m, and 50 to 60 m, to prepare three samples. Next, each sample is thinned using a FIB method or other processing. When using the FIB method, a carbon layer and a tungsten layer are formed as protective films as a pretreatment for observing the cross-sectional TEM image described below. The carbon layer is formed by vapor deposition on the surface of the magnetic tape MT facing the magnetic layer 43 and the surface facing the back layer 44, and the tungsten layer is further formed by vapor deposition or sputtering on the surface facing the magnetic layer 43. The thinning is performed along the longitudinal direction of the magnetic tape MT. That is, the thinning results in a cross section parallel to both the longitudinal and thickness directions of the magnetic tape MT.

[0062] 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

[0063] Next, using the TEM image of each thinned sample, the thickness of the magnetic layer 43 is measured at 10 positions on each thinned sample. The 10 measurement positions on each thinned sample are randomly selected from each sample so that they are different positions in the longitudinal direction of the magnetic tape MT. The arithmetic mean of the measured values ​​of each thinned sample (a total of 30 thicknesses of the magnetic layer 43) is taken as the average thickness [nm] of the magnetic layer 43.

[0064] (magnetic powder) The magnetic powder includes a plurality of magnetic particles. The magnetic particles are, for example, particles containing a metal oxide (hereinafter referred to as "metal oxide particles"). The metal oxide particles are, for example, particles containing hexagonal ferrite (hereinafter referred to as "hexagonal ferrite particles"), particles containing epsilon-type iron oxide (ε-iron oxide) (hereinafter referred to as "ε-iron oxide particles"), or particles containing Co-containing spinel ferrite (hereinafter referred to as "cobalt ferrite particles"). It is preferable that the magnetic powder has a crystal orientation preferentially in the perpendicular direction of the magnetic tape MT. In this specification, the perpendicular direction (thickness direction) of the magnetic tape MT means the thickness direction of the magnetic tape MT in a flat state.

[0065] (Hexagonal ferrite particles) The hexagonal ferrite particles have, for example, a plate shape such as a hexagonal plate or a columnar shape such as a hexagonal column (however, the thickness or height is smaller than the major axis of the plate surface or base). In this specification, the term "hexagonal plate" includes a substantially hexagonal plate shape. The hexagonal ferrite preferably contains at least one element selected from the group consisting of Ba, Sr, Pb, and Ca, more preferably at least one element selected from the group consisting of Ba and Sr. Specifically, the hexagonal ferrite may be, for example, barium ferrite or strontium ferrite. The barium ferrite may further contain at least one element selected from the group consisting of Sr, Pb, and Ca in addition to Ba. The strontium ferrite may further contain at least one element selected from the group consisting of Ba, Pb, and Ca in addition to Sr.

[0066] 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 one or more metals selected from the group consisting of Sr, Pb, and Ca. M may also be a combination of Sr and one or more metals selected from the group consisting of Ba, Pb, and Ca. In the above general formula, part of Fe may be substituted with another metal element.

[0067] When the magnetic powder contains hexagonal ferrite particles, the average particle size of the magnetic powder is preferably 13 nm to 22 nm, more preferably 13 nm to 19 nm, even more preferably 13 nm to 18 nm, particularly preferably 14 nm to 17 nm, and most preferably 14 nm to 16 nm. When the average particle size of the magnetic powder is 22 nm or less, even better electromagnetic conversion characteristics (e.g., SNR) can be obtained in high-recording-density magnetic tapes MT. On the other hand, when the average particle size of the magnetic powder is 13 nm or more, the dispersibility of the magnetic powder is further improved, and even better electromagnetic conversion characteristics (e.g., SNR) can be obtained.

[0068] When the magnetic powder contains hexagonal ferrite particles, the average aspect ratio of the magnetic powder is preferably 1.0 or more and 3.0 or less, more preferably 1.5 or more and 2.8 or less, and even more preferably 1.8 or more and 2.7 or less. When the average aspect ratio of the magnetic powder is within the range of 1.0 or more and 3.0 or less, aggregation of the magnetic powder can be suppressed. Furthermore, when the magnetic powder is vertically oriented in the process of forming the magnetic layer 43, the resistance applied to the magnetic powder can be suppressed. Therefore, the vertical orientation of the magnetic powder can be improved.

[0069] When the magnetic powder contains hexagonal ferrite particles, the average particle size and average aspect ratio of the magnetic powder can be determined as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and a section of the magnetic tape MT is cut out from the connection 21 between the magnetic tape MT and the leader tape LT in the longitudinal direction, approximately 30 to 40 meters in length. The cut magnetic tape MT is then processed and thinned using a FIB method or similar. When using the FIB method, a carbon layer and a tungsten layer are formed as protective films as a pretreatment for observing the cross-sectional TEM image described below. The carbon layer is formed by vapor deposition on the surface of the magnetic tape MT facing the magnetic layer 43 and the surface facing the back layer 44, and the tungsten layer is further formed by vapor deposition or sputtering on the surface facing the magnetic layer 43. The thinning is performed along the length (longitudinal direction) of the magnetic tape MT. That is, the thinning results in a cross section parallel to both the longitudinal and thickness directions of the magnetic tape MT.

[0070] The cross section of the obtained thin sample is observed using a transmission electron microscope (H-9500 manufactured by Hitachi High-Technologies Corporation) at an acceleration voltage of 200 kV and a total magnification of 500,000 times, so as to include the entire magnetic layer 43 in the thickness direction of the magnetic layer 43, and a TEM photograph is taken. The number of TEM photographs prepared is such that 50 particles can be extracted that can measure the plate diameter DB and plate thickness DA (see Figure 7) shown below.

[0071] In this specification, when the shape of the particle observed in the above TEM photograph is plate-like or columnar (however, the thickness or height is smaller than the major axis of the plate surface or base), as shown in Figure 7, the major axis of the plate surface or base of the particle is taken as the plate diameter DB value. The thickness or height of the particle observed in the above TEM photograph is taken as the plate thickness DA value. When the plate surface or base of the particle observed in the TEM photograph is hexagonal, the major axis means the longest diagonal distance. When the thickness or height of a particle is not constant within a single particle, the thickness or height of the largest particle is taken as the plate thickness DA.

[0072] Next, 50 particles are selected from the TEM photograph based on the following criteria. Particles with parts outside the field of view of the TEM photograph are not measured, and only particles with a clear outline and that exist independently are measured. If particles overlap, those with a clear boundary between them and whose overall shape can be determined are measured as individual particles, but particles with unclear boundaries and whose overall shape cannot be determined are not measured as their shape cannot be determined.

[0073] Examples of TEM photographs are shown in Figures 8 and 9. In Figures 8 and 9, the particles indicated by arrows a and d are selected because their plate thickness (thickness or height) DA can be clearly confirmed. The plate thickness DA of each of the selected 50 particles is measured. The plate thicknesses DA thus obtained are arithmetically averaged to obtain the average plate thickness DA. ave Average plate thickness DA ave is the average particle plate thickness. Next, the plate diameter DB of each magnetic powder is measured. In order to measure the particle plate diameter DB, 50 particles whose particle plate diameter DB can be clearly confirmed are selected from the TEM photograph. For example, in Figures 8 and 9, the particles indicated by arrows b and c are selected because their plate diameter DB can be clearly confirmed. The plate diameter DB of each of the selected 50 particles is measured. The plate diameters DB thus determined are simply averaged (arithmetic average) to obtain the average plate diameter DB. ave Average plate diameter DB ave is the average grain size. And the average plate thickness DA aveand average plate diameter DB ave The average aspect ratio of the particles (DB ave / DA ave ) is found.

[0074] When the magnetic powder includes hexagonal ferrite particles, the average particle volume of the magnetic powder is preferably 500 nm 3 More than 2500nm 3 Less than 500 nm, more preferably 3 More than 1600nm 3 Less than 500 nm, more preferably 3 More than 1500nm 3 Below 600 nm, particularly preferably 3 More than 1200nm 3 Below 600 nm, most preferably 3 More than 1000nm 3 The average particle volume of the magnetic powder is 2500 nm or less. 3 When the average particle size of the magnetic powder is 22 nm or less, the same effect as when the average particle volume of the magnetic powder is 500 nm or less can be obtained. 3 If the average particle size of the magnetic powder is 13 nm or more, the same effect as that obtained when the average particle size of the magnetic powder is 13 nm or more can be obtained.

[0075] The average particle volume of the magnetic powder can be calculated as follows: First, as described above in relation to the method for calculating the average particle size of the magnetic powder, the average plate thickness DA ave and average plate diameter DB ave Next, calculate the average volume V of the magnetic powder using the following formula:

number

[0076] (ε iron oxide particles) ε-iron oxide particles are hard magnetic particles that can achieve high coercivity even in the form of fine particles. ε-iron oxide particles have a spherical or cubic shape. In this specification, spherical includes nearly spherical. Furthermore, cubic includes nearly cubic. Because ε-iron oxide particles have the above-described shape, when ε-iron oxide particles are used as magnetic particles, the contact area between particles in the thickness direction of the magnetic tape MT can be reduced and particle aggregation can be suppressed compared to when hexagonal plate-shaped barium ferrite particles are used as magnetic particles. This improves the dispersibility of the magnetic powder and allows for even better electromagnetic conversion characteristics (e.g., SNR).

[0077] 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.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] 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 selected from the group consisting of Al, Ga, and In, and even more preferably at least one selected from the group consisting of Al and Ga.

[0085] Specifically, the ε-iron oxide containing additives is ε-Fe2-x M x O3 crystal (wherein M is a metal element other than iron, preferably a trivalent metal element, more preferably at least one selected from the group consisting of Al, Ga, and In, and even more preferably at least one selected from the group consisting of Al and Ga. x is, for example, 0 <x<1である。)である。

[0086] When the magnetic powder contains ε-iron oxide particles, the average particle size of the magnetic powder is preferably 10 nm to 20 nm, more preferably 10 nm to 18 nm, even more preferably 10 nm to 16 nm, particularly preferably 10 nm to 15 nm, and most preferably 10 nm to 14 nm. In magnetic tape MT, the actual magnetization region is a region half the size of the recording wavelength. Therefore, by setting the average particle size of the magnetic powder to less than half the shortest recording wavelength, even better electromagnetic conversion characteristics (e.g., SNR) can be obtained. Therefore, when the average particle size of the magnetic powder is 20 nm or less, even better electromagnetic conversion characteristics (e.g., SNR) can be obtained in high-recording-density magnetic tape MT (e.g., magnetic tape MT configured to record signals at the shortest recording wavelength of 40 nm or less). On the other hand, when the average particle size of the magnetic powder is 10 nm or more, the dispersibility of the magnetic powder is further improved, and even better electromagnetic conversion characteristics (e.g., SNR) can be obtained.

[0087] When the magnetic powder contains ε-iron oxide particles, the average aspect ratio of the magnetic powder 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 powder is within the range of 1.0 to 3.0, aggregation of the magnetic powder can be suppressed. Furthermore, when the magnetic powder is vertically oriented in the process of forming the magnetic layer 43, the resistance applied to the magnetic powder can be suppressed. Therefore, the vertical orientation of the magnetic powder can be improved.

[0088] When the magnetic powder contains ε-iron oxide particles, the average particle size and average aspect ratio of the magnetic powder can be determined as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and a section of the magnetic tape MT is cut out from a range of 30 to 40 meters in the longitudinal direction from the joint 21 between the magnetic tape MT and the leader tape LT. Next, the cut magnetic tape MT is processed and thinned using a method such as FIB (Focused Ion Beam). When using the FIB method, a carbon layer and a tungsten layer are formed as protective layers as a pretreatment for observing the cross-sectional TEM image described below. The carbon layer is formed by vapor deposition on the surface of the magnetic tape MT facing the magnetic layer 43 and the surface facing the back layer 44, and the tungsten layer is further formed by vapor deposition or sputtering on the surface facing the magnetic layer 43. The thinning is performed along the length (longitudinal direction) of the magnetic tape MT. That is, the thinning results in a cross section parallel to both the longitudinal and thickness directions of the magnetic tape MT.

[0089] The cross section of the obtained thin sample was observed using a transmission electron microscope (H-9500, manufactured by Hitachi High-Technologies Corporation) at an acceleration voltage of 200 kV and a total magnification of 500,000 times, so as to include the entire magnetic layer 43 in the thickness direction of the magnetic layer 43, and a TEM photograph was taken. Next, 50 particles whose particle shape could be clearly confirmed were selected from the TEM photograph, and the long axis length DL and short axis length DS of each particle were measured. Here, the long axis length DL refers to the longest distance between two parallel lines drawn from all angles so as to be tangent to the outline of each particle (the so-called maximum Feret diameter). Meanwhile, the short axis length DS refers to the longest length of the particle in the direction perpendicular to the long axis (DL) of the particle. Next, the long axis lengths DL of the measured 50 particles were arithmetically averaged to obtain the average long axis length DL. ave The average major axis length DL ave is the average particle size of the magnetic powder. The minor axis lengths DS of the 50 particles measured are arithmetically averaged to obtain the average minor axis length DS ave Then, calculate the average major axis length DL ave and mean minor axis length DS aveThe average aspect ratio of the particles (DL ave / DS ave ) is found.

[0090] When the magnetic powder contains ε-iron oxide particles, the average particle volume of the magnetic powder is preferably 500 nm 3 More than 4000nm 3 Less than 500 nm, more preferably 3 More than 3000nm 3 less than or equal to 500 nm, and even more preferably 3 More than 2000nm 3 Below 600 nm, particularly preferably 3 More than 1600nm 3 Below 600 nm, most preferably 3 More than 1300nm 3 Generally, the noise of magnetic tape MT is inversely proportional to the square root of the number of particles (i.e., proportional to the square root of the particle volume), so by making the particle volume smaller, it is possible to obtain even better electromagnetic conversion characteristics (for example, SNR). Therefore, when the average particle volume of the magnetic powder is 4000 nm 3 When the average particle size of the magnetic powder is 500 nm or less, it is possible to obtain even better electromagnetic conversion characteristics (for example, SNR), similar to when the average particle size of the magnetic powder is 20 nm or less. 3 If the average particle size of the magnetic powder is 10 nm or more, the same effect as that obtained when the average particle size of the magnetic powder is 10 nm or more can be obtained.

[0091] When the ε-iron oxide particles are spherical, the average particle volume of the magnetic powder can be calculated as follows: First, the average major axis length DL is calculated in the same manner as in the above-mentioned method for calculating the average particle size of the magnetic powder. ave Next, calculate the average volume V of the magnetic powder using the following formula: V=(π / 6)×DL ave 3

[0092] When the ε-iron oxide particles have a cubic shape, the average volume of the magnetic powder is calculated as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and a section of the magnetic tape MT is cut out from a range of 30 to 40 m in the longitudinal direction from the joint 21 between the magnetic tape MT and the leader tape LT. Next, the cut magnetic tape MT is processed and thinned using a method such as FIB (Focused Ion Beam). When using the FIB method, a carbon film and a tungsten thin film are formed as protective films as a pretreatment for observing the cross-sectional TEM image described below. The carbon film is formed by vapor deposition on the surface of the magnetic tape MT facing the magnetic layer 43 and the surface facing the back layer 44, and the tungsten thin film is further formed by vapor deposition or sputtering on the surface facing the magnetic layer 43. The thinning is performed along the length (longitudinal direction) of the magnetic tape MT. In other words, the thinning results in a cross section parallel to both the longitudinal and thickness directions of the magnetic tape MT.

[0093] The obtained thin film sample is observed using a transmission electron microscope (H-9500 manufactured by Hitachi High-Technologies Corporation) at an acceleration voltage of 200 kV and a total magnification of 500,000 times to observe the cross section of the magnetic layer 43 in the thickness direction of the magnetic layer 43 so as to include the entire magnetic layer 43, and a TEM photograph is obtained. Note that the magnification and acceleration voltage may be adjusted appropriately depending on the type of device. Next, 50 particles whose particle shape is clear are selected from the TEM photograph, and the side length DC of each particle is measured. Next, the side lengths DC of the measured 50 particles are arithmetically averaged to obtain the average side length DC. ave Next, calculate the average side length DC ave Using the following formula, the average volume of the magnetic powder V ave (particle volume) is calculated. V ave =DC ave 3

[0094] (cobalt ferrite particles) The cobalt ferrite particles preferably have uniaxial crystal anisotropy. The uniaxial crystal anisotropy of the cobalt ferrite particles allows the magnetic powder to be preferentially crystalline oriented in the direction perpendicular to the magnetic tape MT. The cobalt ferrite particles may have, for example, a cubic shape. In this specification, the term "cubic shape" includes a substantially cubic shape. The Co-containing spinel ferrite may further contain at least one element selected from the group consisting of Ni, Mn, Al, Cu, and Zn in addition to Co.

[0095] 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, for example, 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, with the proviso that 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.)

[0096] When the magnetic powder contains cobalt ferrite particles, the average particle size of the magnetic powder is preferably 8 nm to 16 nm, more preferably 8 nm to 13 nm, and even more preferably 8 nm to 10 nm. When the average particle size of the magnetic powder is 16 nm or less, even better electromagnetic conversion characteristics (e.g., SNR) can be obtained in high-recording-density magnetic tapes MT. On the other hand, when the average particle size of the magnetic powder is 8 nm or more, the dispersibility of the magnetic powder is further improved, and even better electromagnetic conversion characteristics (e.g., SNR) can be obtained. The method for calculating the average particle size of the magnetic powder is the same as the method for calculating the average particle size of the magnetic powder when the magnetic powder contains ε-iron oxide particles.

[0097] When the magnetic powder contains cobalt ferrite particles, the average aspect ratio of the magnetic powder is preferably 1.0 to 2.5, more preferably 1.0 to 2.1, and even more preferably 1.0 to 1.8. When the average aspect ratio of the magnetic powder is within the range of 1.0 to 2.5, aggregation of the magnetic powder can be suppressed. Furthermore, when the magnetic powder is vertically oriented in the process of forming the magnetic layer 43, the resistance applied to the magnetic powder can be suppressed. Therefore, the vertical orientation of the magnetic powder can be improved. The method for calculating the average aspect ratio of the magnetic powder is the same as the method for calculating the average aspect ratio of the magnetic powder when the magnetic powder contains ε-iron oxide particles.

[0098] When the magnetic powder includes cobalt ferrite particles, the average particle volume of the magnetic powder is preferably 500 nm 3 More than 4000nm 3 Less than 600 nm, more preferably 3 More than 2000nm 3 or less, even more preferably 600 nm 3 More than 1000nm 3 The average particle volume of the magnetic powder is 4000 nm or less. 3 If the average particle size of the magnetic powder is 16 nm or less, the same effect as when the average particle volume of the magnetic powder is 500 nm or less can be obtained. 3 This produces the same effect as when the average particle size of the magnetic powder is 8 nm or more. The method for calculating the average particle volume of the magnetic component is the same as the method for calculating the average particle volume when the ε-iron oxide particles have a cubic shape.

[0099] (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.

[0100] 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.

[0101] All of the above binders may contain -SO3M, -OSO3M, -COOM, P=O(OM)2 (where M represents a hydrogen atom or an alkali metal such as lithium, potassium, or sodium), -NR1R2, -NR1R2R3, etc., in order to improve the dispersibility of the magnetic powder. + X - A side chain amine having a terminal group represented by the formula: >NR1R2 + X - (wherein R1, R2, and R3 represent a hydrogen atom or a hydrocarbon group, and X -represents a halogen element ion such as fluorine, chlorine, bromine, or iodine, or an inorganic ion or an organic ion.) Furthermore, polar functional groups such as -OH, -SH, -CN, and epoxy groups may be introduced. The amount of these polar functional groups introduced into the binder is 10 -1 mol / g or more 10 -8 It is preferably 10 mol / g or less. -2 mol / g or more 10 -6 It is more preferably mol / g or less.

[0102] (lubricant) The lubricant contains at least one selected from, for example, a fatty acid and a fatty acid ester, and preferably both a fatty acid and a fatty acid ester. The inclusion of a lubricant in magnetic layer 43, and particularly the inclusion of both a fatty acid and a fatty acid ester in magnetic layer 43, contributes to improving the running stability of magnetic tape MT.

[0103] 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).

[0104] 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).

[0105] 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.

[0106] 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.)

[0107] 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.)

[0108] CH3(CH2) p COO(CH2) q CH3···(3) (However, in general formula (3), p is an integer selected from the range of 14 or more and 22 or less, more preferably 14 or more and 18 or less, and q is an integer selected from the range of 2 or more and 5 or less, more preferably 2 or more and 4 or less.)

[0109] 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.)

[0110] (carbon) The carbon contained in the magnetic layer 43 may function as an antistatic agent, a lubricant, etc. A portion of the carbon contained in the magnetic layer 43 is exposed from the surface of the magnetic layer 43. The unevenness on the surface of the magnetic layer 43 may be formed by carbon, an abrasive, etc.

[0111] The carbon is specifically carbon particles, and the carbon particles include, for example, one or more selected from the group consisting of carbon black, acetylene black, ketjen black, carbon nanotubes, and graphene.

[0112] (antistatic agent) Examples of antistatic agents include natural surfactants, nonionic surfactants, and cationic surfactants.

[0113] (abrasive) Examples of abrasives include acicular α-iron oxide obtained by dehydrating and annealing raw materials such as α-alumina with an α-conversion rate of 90% or more, β-alumina, γ-alumina, silicon carbide, chromium oxide, cerium oxide, α-iron oxide, corundum, silicon nitride, titanium carbide, titanium oxide, silicon dioxide, tin oxide, magnesium oxide, tungsten oxide, zirconium oxide, boron nitride, zinc oxide, calcium carbonate, calcium sulfate, barium sulfate, molybdenum disulfide, and magnetic iron oxide, and, if necessary, surface-treated with aluminum and / or silica.

[0114] (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.

[0115] (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.

[0116] (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).

[0117] (base layer) The underlayer 42 serves to reduce the unevenness of the surface of the substrate 41 and adjust the unevenness of the surface of the magnetic layer 43. The underlayer 42 is a non-magnetic layer containing non-magnetic powder, a binder, and a lubricant. The underlayer 42 supplies the lubricant to the surface of the magnetic layer 43. If necessary, the underlayer 42 may further contain at least one additive selected from the group consisting of an antistatic agent, a hardener, an anti-rust agent, etc.

[0118] The upper limit of the average thickness of the underlayer 42 is preferably 1.20 μm or less, more preferably 0.90 μm or less, even more preferably 0.80 μm or less, particularly preferably 0.70 μm or less, and most preferably 0.60 μm or less. When the upper limit of the average thickness of the underlayer 42 is 1.20 μm or less, the thickness of the magnetic tape MT can be reduced, thereby increasing the recording capacity that can be recorded in one data cartridge compared to general magnetic tape. Furthermore, when the average thickness of the underlayer 42 is 1.20 μm or less, the magnetic tape MT is more elastic due to external forces, making it easier to adjust the width of the magnetic tape MT by adjusting the tension. The lower limit of the average thickness of the underlayer 42 is preferably 0.30 μm or more. When the lower limit of the average thickness of the underlayer 42 is 0.30 μm or more, degradation of the functionality of the underlayer 42 can be suppressed. The average thickness of the underlayer 42 can be determined in the same manner as the average thickness of the magnetic layer 43. However, the magnification of the TEM image is adjusted appropriately depending on the thickness of the underlayer 42.

[0119] (Non-magnetic powder) The non-magnetic powder includes, for example, at least one of inorganic particle powder and organic particle powder. The non-magnetic powder may also include carbon powder such as carbon black. One type of non-magnetic powder may be used alone, or two or more types of non-magnetic powder may be used in combination. The inorganic particles include, for example, metals, metal oxides, metal carbonates, metal sulfates, metal nitrides, metal carbides, or metal sulfides. The shape of the non-magnetic powder may be, for example, acicular, spherical, cubic, plate-like, or other various shapes, but is not limited to these shapes.

[0120] (binder, lubricant) The binder and lubricant are the same as those used in the magnetic layer 43 described above.

[0121] (additives) The antistatic agent, hardener, and anticorrosive agent are the same as those in the magnetic layer 43 described above.

[0122] (Back layer) The back layer 44 contains a binder and a non-magnetic powder. If necessary, the back layer 44 may further contain at least one additive selected from the group consisting of a lubricant, a hardener, an antistatic agent, etc. The binder and non-magnetic powder are the same as those in the underlayer 42 described above. The hardener and antistatic agent are the same as those in the magnetic layer 43 described above.

[0123] The average particle size of the non-magnetic powder is preferably 10 nm or more and 150 nm or less, more preferably 15 nm or more and 110 nm or less. The average particle size of the non-magnetic powder is determined in the same manner as the average particle size of the magnetic powder. The non-magnetic powder may contain non-magnetic powder having two or more particle size distributions.

[0124] The upper limit of the average thickness of the back layer 44 is preferably 0.6 μm or less, more preferably 0.3 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 5.3 μm or less, thereby maintaining running stability of the magnetic tape MT within a recording / reproducing device. The lower limit of the average thickness of the back layer 44 is not particularly limited, but is, for example, 0.2 μm or more.

[0125] The average thickness t of the back layer 44 bis obtained as follows. First, the average thickness Tt of the magnetic tape MT is measured. The method for measuring the average thickness Tt is as described below in "Average Thickness of Magnetic Tape." Next, the magnetic tape MT housed in the cartridge 10 is unwound, and the magnetic tape MT is cut into lengths of 250 mm from the longitudinal range of 10 m to 20 m, 30 m to 40 m, and 50 m to 60 m from the joint 21 between the magnetic tape MT and the leader tape LT, to prepare three samples. Next, the back layer 44 of each sample is removed with a solvent such as MEK (methyl ethyl ketone) or dilute hydrochloric acid. Next, the thickness of each sample is measured at five positions using a Mitutoyo Laser Hologram Gauge (LGH-110C), and the arithmetic average of these measurements (a total of 15 sample thicknesses) is calculated to obtain the average value t B Then, the average thickness t of the back layer 44 is calculated using the following formula: b The five measurement positions are selected randomly from each sample so that they are different positions in the longitudinal direction of the magnetic tape MT. t b [μm]=Tt[μm]-t B [μm]

[0126] (average thickness of magnetic tape) The upper limit of the average thickness (average total thickness) Tt of the magnetic tape MT is preferably 5.3 μm or less, more preferably 5.1 μm or less, even more preferably 4.9 μm or less, particularly preferably 4.6 μm or less, and most preferably 4.4 μm or less. If the average thickness Tt of the magnetic tape MT is 5.3 μm or less, the recording capacity that can be recorded in one data cartridge can be increased compared to general magnetic tapes. The lower limit of the average thickness Tt of the magnetic tape MT is not particularly limited, but is, for example, 3.5 μm or more.

[0127] The average thickness Tt of the magnetic tape MT is calculated as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and three 250 mm samples are cut from the magnetic tape MT at lengths of 10 to 20 m, 30 to 40 m, and 50 to 60 m, respectively, from the joint 21 between the magnetic tape MT and the leader tape LT. Next, the thickness of each sample is measured at five positions using a Mitutoyo Laser Hologram (LGH-110C) as a measuring device, and the arithmetic mean of these measurements (a total of 15 sample thicknesses) is calculated to calculate the average thickness Tt [μm]. The five measurement positions are randomly selected from each sample so that they are different positions in the longitudinal direction of the magnetic tape MT.

[0128] Average thickness T of the substrate 41 s Average thickness T of magnetic tape MT t The ratio (T t / T s ) is preferably 1.2 or more. t / T s When the SR is 1.2 or more, the thickness of the coating layer (magnetic layer 43, underlayer 42, backing layer 44, etc.) relative to the substrate 41 is sufficiently ensured, and this coating layer promotes stabilization of contact with the head and keeps cupping within an appropriate range, resulting in a spacing SR L , S.R. T The electric characteristics herein mean electromagnetic conversion characteristics.

[0129] Average thickness T of the substrate 41 s and the average thickness T of the magnetic tape MT t The calculation method is as described above.

[0130] (Arithmetic mean roughness Ra of the magnetic layer surface) The average value of the arithmetic mean roughness Ra of the surface of the magnetic layer 43 is 1.3 nm or less, preferably 1.2 nm or less, and more preferably 1.1 nm or less. When the average value of the arithmetic mean roughness Ra is 1.3 nm or less, output reduction due to spacing loss can be suppressed, thereby obtaining excellent electromagnetic conversion characteristics. The lower limit of the average value of the arithmetic mean roughness Ra of the surface of the magnetic layer 43 is preferably 1.0 nm or more. When the lower limit of the average value of the arithmetic mean roughness Ra of the surface of the magnetic layer 43 is 1.0 nm or more, deterioration of running performance due to increased friction can be suppressed.

[0131] The average value of the arithmetic mean roughness Ra is calculated as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and three 250 mm lengths of the magnetic tape MT are cut from the connection 21 between the magnetic tape MT and the leader tape LT in the longitudinal direction, from 10 to 20 m, 30 to 40 m, and 50 to 60 m, to prepare three samples. Next, the surface of the magnetic layer 43 of each sample is observed using an AFM (Atomic Force Microscope), and a 40 μm × 40 μm AFM image is obtained. The AFM used is a Digital Instruments Nano Scope IIIa D3100, and the cantilever is made of single crystal silicon (Note 1). Measurements are performed with a tapping frequency tuning of 200 to 400 Hz. Next, each AFM image is divided into 512 x 512 (= 262,144) measurement points, and the height Z(i) (i: measurement point number, i = 1 to 262,144) is measured at each measurement point. The heights Z(i) at each measurement point are arithmetically averaged to determine the average height (average surface) Zave (= (Z(1) + Z(2) + ··· + Z(262,144)) / 262,144). Next, the deviation Z"(i) (= Z(i) - Zave) from the average center line at each measurement point is calculated, and the arithmetic mean roughness Ra [nm] (= (Z"(1) + Z"(2) + ··· + Z"(262,144)) / 262,144) is calculated. In this case, the image is filtered using Flatten order 2 and planefit order 3 XY before being used as data. (Note 1) Nano World SPM probe NCH normal type PointProbe L (cantilever length) = 125 μm Next, the arithmetic mean roughnesses Ra of the three samples are arithmetically averaged to calculate the average value of the arithmetic mean roughnesses Ra.

[0132] (Surface roughness R b ) Surface roughness of the back surface (surface roughness of the back layer 44) R b The average value of R b The surface roughness R of the back surface is preferably ≦6.0 [nm]. b When the average value is within the above range, even better electromagnetic conversion characteristics can be obtained.

[0133] Back surface roughness R b The average value of is calculated as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and the magnetic tape MT is cut into 100 mm lengths from the connection 21 between the magnetic tape MT and the leader tape LT in the longitudinal direction in the ranges of 10 m to 20 m, 30 m to 40 m, and 50 m to 60 m, respectively, to prepare three samples. Next, the sample is placed on a slide glass with the surface to be measured (the surface on the magnetic layer side) facing up, and the 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

[0134] (Average value of coercive force Hc2) The upper limit of the average value of the coercive force Hc2 of the magnetic layer 43 in the longitudinal direction of the magnetic tape MT is preferably 3000 Oe or less, more preferably 2000 Oe or less, even more preferably 1900 Oe or less, and particularly preferably 1800 Oe or less. If the average value of the coercive force Hc2 of the magnetic layer 43 in the longitudinal direction of the magnetic tape MT is 3000 Oe or less, sufficient electromagnetic conversion characteristics can be obtained even at high recording densities.

[0135] The lower limit of the average value of the coercive force Hc2 of the magnetic layer 43 measured in the longitudinal direction of the magnetic tape MT is preferably 1000 Oe or more. When the average value of the coercive force Hc2 of the magnetic layer 43 measured in the longitudinal direction of the magnetic tape MT is 1000 Oe or more, demagnetization due to leakage flux from the recording head can be suppressed.

[0136] The average value of the coercive force Hc2 is calculated as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and 250 mm lengths of magnetic tape MT are cut out from the longitudinal ranges of 10 m to 20 m, 30 m to 40 m, and 50 m to 60 m from the joint 21 between the magnetic tape MT and the leader tape LT. The coercive force Hc2 of each cut magnetic tape MT is measured as follows. Three magnetic tapes 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 using acetone, ethanol, or the like, leaving only the substrate 41. Three of the obtained substrates 41 are then stacked together with double-sided tape and punched out with a φ6.39 mm punch to prepare a sample for background correction (hereinafter simply referred to as the "correction sample"). Thereafter, the MH loop of the correction sample (substrate 41) corresponding to the longitudinal direction of the substrate 41 (the longitudinal direction of the magnetic tape MT) is measured using a VSM.

[0137] 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.

[0138] After obtaining the MH loop of the measurement sample (the entire magnetic tape MT) and the MH loop of the correction sample (substrate 41), background correction is performed by subtracting the MH loop of the correction sample (substrate 41) from the MH loop of the measurement sample (the entire magnetic tape MT), resulting in a background-corrected MH loop. This background correction calculation is performed using the measurement and analysis program included with the VSM-P7-15. The coercive force Hc2 is calculated from the background-corrected MH loop. This calculation is performed using the measurement and analysis program included with the VSM-P7-15. All of the above MH loop measurements are performed in an environment of 25°C ± 2°C and 50% RH ± 5% RH. Furthermore, no "demagnetization field correction" is performed when measuring the MH loop in the longitudinal direction of the magnetic tape MT. Next, the coercive forces Hc2 of the three samples obtained in this manner are arithmetically averaged to calculate the average coercive force Hc2.

[0139] (Average value of squareness ratios S1 and S2) The average squareness ratio S1 of the magnetic layer 43 in the perpendicular direction of the magnetic tape MT is preferably 65% ​​or more, more preferably 70% or more, even more preferably 75% or more, particularly preferably 80% or more, and most preferably 85% or more. When the average squareness ratio S1 is 65% or more, the perpendicular orientation of the magnetic powder is sufficiently high, resulting in even better electromagnetic conversion characteristics.

[0140] The average squareness ratio S1 of the magnetic tape MT in the perpendicular direction is calculated as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and 250 mm lengths of the magnetic tape MT are cut out from the longitudinal ranges of 10 to 20 m, 30 to 40 m, and 50 to 60 m from the joint 21 between the magnetic tape MT and the leader tape LT. The squareness ratio S1 of each cut magnetic tape MT is measured as follows. Three magnetic tapes 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 (thickness direction of the magnetic tape MT) is measured using a vibrating sample magnetometer (VSM). Next, the coatings (underlayer 42, magnetic layer 43, back layer 44, etc.) of the magnetic tape MT cut out above are wiped off using acetone, ethanol, or the like, leaving only the substrate 41. Three of the obtained substrates 41 are then stacked together with double-sided tape and punched out with a φ6.39 mm punch to prepare a sample for background correction (hereinafter simply referred to as the "correction sample"). Thereafter, the MH loop of the correction sample (substrate 41) corresponding to the perpendicular direction of the substrate 41 (the perpendicular direction of the magnetic tape MT) is measured using a VSM.

[0141] 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.

[0142] 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."

[0143] The saturation magnetization Ms (emu) and residual magnetization Mr (emu) of the MH loop after background correction are substituted into the following equation to calculate the squareness ratio S1 (%). Note that all of the above MH loop measurements are performed in an environment of 25°C ± 2°C and 50% RH ± 5% RH. Furthermore, no "demagnetizing field correction" is performed when measuring the MH loop in the perpendicular direction to the magnetic tape MT. Note that this calculation uses the measurement and analysis program included with the "VSM-P7-15 model." Squareness ratio S1(%)=(Mr / Ms)×100 Next, the squareness ratios S1 of the three samples obtained as described above are arithmetically averaged to calculate the average squareness ratio S1.

[0144] The average squareness ratio S2 of the magnetic layer 43 in the longitudinal direction (running direction) of the magnetic tape MT is preferably 35% or less, more preferably 30% or less, even more preferably 25% or less, particularly preferably 20% or less, and most preferably 15% or less. When the average squareness ratio S2 is 35% or less, the magnetic powder has a sufficiently high perpendicular orientation, resulting in even better electromagnetic conversion characteristics.

[0145] The average squareness ratio S2 in the longitudinal direction of the magnetic tape MT is determined in the same manner as the average squareness ratio S1, except that the MH loop is measured in the longitudinal direction (running direction) of the magnetic tape MT and the substrate 41.

[0146] (Average Young's modulus in the longitudinal direction of magnetic tape) The upper limit of the average Young's modulus in the longitudinal direction of the magnetic tape MT is preferably 9.0 GPa or less, more preferably 8.0 GPa or less, even more preferably 7.5 GPa or less, and particularly preferably 7.1 GPa or less. When the average Young's modulus in the longitudinal direction of the magnetic tape MT is 9.0 GPa or less, the magnetic tape MT becomes more elastic due to external forces, making it easier to adjust the width of the magnetic tape MT by adjusting the tension. Therefore, off-track can be more appropriately suppressed, and data recorded on the magnetic tape MT can be more accurately reproduced. The lower limit of the average Young's modulus in the longitudinal direction of the magnetic tape MT is preferably 3.0 GPa or more, more preferably 4.0 GPa or more. When the lower limit of the average Young's modulus in the longitudinal direction of the magnetic tape MT is 3.0 GPa or more, deterioration of running stability can be suppressed.

[0147] The average Young's modulus in the longitudinal direction of the magnetic tape MT is a value that indicates the resistance of the magnetic tape MT to expansion and contraction in the longitudinal direction due to external forces; the larger this value, the more difficult it is for the magnetic tape MT to expand and contract in the longitudinal direction due to external forces, and the smaller this value, the more easily the magnetic tape MT expands and contracts in the longitudinal direction due to external forces.

[0148] The average Young's modulus in the longitudinal direction of the magnetic tape MT is a value related to the longitudinal direction of the magnetic tape MT, but it also correlates with the resistance to expansion and contraction in the width direction of the magnetic tape MT. In other words, the larger this value, the less likely the magnetic tape MT is to expand and contract in the width direction due to external forces, and the smaller this value, the more likely the magnetic tape MT is to expand and contract in the width direction due to external forces. Therefore, from the perspective of tension adjustment, it is advantageous for the average Young's modulus in the longitudinal direction of the magnetic tape MT to be small, as described above, 9.0 GPa or less.

[0149] A tensile tester (AG-100D, manufactured by Shimadzu Corporation) is used to measure Young's modulus. The average Young's modulus in the longitudinal direction of the tape is determined as follows. The magnetic tape MT housed in the cartridge 10 is unwound, and three 180 mm lengths of magnetic tape MT are cut from the junction 21 between the magnetic tape MT and the leader tape LT in the longitudinal direction, from 10 to 20 m, 30 to 40 m, and 50 to 60 m, respectively, to prepare three measurement samples. The following measurements are performed on the three prepared measurement samples. 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 (the length of the tape between the chucks) is 100 mm. After chucking the tape sample, stress is gradually applied in the direction in which the sample is pulled (the longitudinal direction of the sample). The pulling speed is 0.1 mm / min. From the change in stress and the amount of elongation, 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 is the cross-sectional area before the tensile operation, and is calculated by multiplying the width (1 / 2 inch) of the measurement sample by the thickness of the measurement sample. The range of tensile stress during measurement is set to the linear region of tensile stress depending on the thickness of the magnetic tape MT, etc. In this case, the stress range is set to 0.5 N to 1.0 N, and the change in stress (ΔN) and elongation (Δx) at this time are used for calculation. The above Young's modulus measurement is performed at 25°C ± 2°C and 50% RH ± 5% RH. Next, the Young's moduli in the longitudinal direction measured using the three samples are arithmetically averaged to calculate the average Young's modulus in the longitudinal direction of the magnetic tape MT.

[0150] (Average Young's modulus in the longitudinal direction of the substrate) The average Young's modulus in the longitudinal direction of the substrate 41 is preferably 7.8 GPa or less, more preferably 7.0 GPa or less, even more preferably 6.6 GPa or less, and particularly preferably 6.4 GPa or less. When the average Young's modulus in the longitudinal direction of the substrate 41 is 7.8 GPa or less, the magnetic tape MT becomes more elastic due to external forces, making it easier to adjust the width of the magnetic tape MT by adjusting the tension. Therefore, off-track can be more appropriately suppressed, and data recorded on the magnetic tape MT can be more accurately reproduced. The lower limit of the average Young's modulus in the longitudinal direction of the substrate 41 is preferably 2.5 GPa or more, more preferably 3.0 GPa or more. When the lower limit of the average Young's modulus in the longitudinal direction of the substrate 41 is 2.5 GPa or more, deterioration of running stability can be suppressed.

[0151] The average Young's modulus in the longitudinal direction of the substrate 41 is determined as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and the magnetic tape MT is cut into 180 mm lengths from the joint 21 between the magnetic tape MT and the leader tape LT in the longitudinal direction in the ranges of 10 to 20 m, 30 to 40 m, and 50 to 60 m, respectively, to prepare three samples. Next, the underlayer 42, magnetic layer 43, and back layer 44 are removed from each cut sample to obtain the substrate 41. Using 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. Next, the Young's modulus in the longitudinal direction measured using the three substrates 41 is arithmetically averaged to calculate the average Young's modulus in the longitudinal direction of the substrate 41.

[0152] The thickness of the substrate 41 accounts for more than half of the overall thickness of the magnetic tape MT. Therefore, the average Young's modulus in the longitudinal direction of the substrate 41 correlates with the resistance of the magnetic tape MT to expansion and contraction due to external force, and the larger this value, the less the magnetic tape MT is able to expand and contract in the width direction due to external force, and the smaller this value, the more the magnetic tape MT is able to expand and contract in the width direction due to external force.

[0153] The average Young's modulus in the longitudinal direction of the substrate 41 is a value related to the longitudinal direction of the magnetic tape MT, but it also correlates with the resistance to expansion and contraction in the width direction of the magnetic tape MT. In other words, the larger this value, the less likely the magnetic tape MT is to expand and contract in the width direction due to external force, and the smaller this value, the more likely the magnetic tape MT is to expand and contract in the width direction due to external force. Therefore, from the perspective of tension adjustment, it is advantageous for the average Young's modulus in the longitudinal direction of the substrate 41 to be small, as described above, 7.8 GPa or less.

[0154] (Spacing Index SRL) The upper limit of the spacing index SRL when sliding on a glass pseudo head is 35 μm or less, preferably 33 μm or less, and more preferably 31 μm or less. When the spacing index SRL exceeds 35 μm, the increased spacing region R L This causes a decrease in electromagnetic conversion characteristics.

[0155] The spacing index SRL represents the tape floating state at the head entrance side when the magnetic tape MT enters the glass pseudo head. Specifically, the spacing index SRL is the increased spacing region R that occurs at the entrance side of the glass pseudo head where the magnetic tape MT enters when the magnetic tape MT slides over the glass pseudo head. L where R is the average value of the peak half-width. L This refers to the region where the spacing increases at the head entrance side when the magnetic tape MT enters the magnetic head 56 or the glass pseudo head compared to the central part in the width direction of the sliding surface of the magnetic head 56. The spacing refers to the distance between the running magnetic tape MT and the magnetic head 56 or the glass pseudo head.

[0156] The lower limit of the spacing index SRL when sliding on a glass pseudo head is, for example, 0 μm or more.

[0157] 4, the read / write element is provided at the center of the width of the sliding surface of the magnetic head 56, and the width of the sliding surface coincides with the longitudinal direction of the magnetic tape MT, i.e., the running direction of the magnetic tape MT. At the head entrance side when the magnetic tape MT enters the magnetic head 56, there is an increased spacing region R L Spacing increase region R L When becomes wider, the spacing increase region R L reaches the recording / reproducing element, leading to deterioration of electromagnetic conversion characteristics.

[0158] In future recording and reproducing devices, further reduction in friction is required to perform higher density recording and reproducing, and it is considered that the width of the magnetic head 56 in the longitudinal direction of the magnetic tape MT will become even narrower. Therefore, the distance from the edge of the magnetic head 56 to the central recording and reproducing element in the longitudinal direction of the magnetic tape MT will become shorter, and the above-mentioned increased spacing region R L It is desirable to further narrow this.

[0159] Spacing increase region R L Narrowing the spacing index SRL, that is, reducing the spacing index SRL, can be achieved by reducing the stiffness of the magnetic tape MT to within a specified range, for example, by adjusting the thickness configuration of the magnetic tape MT, including the material type and thickness of the substrate 41 and the thickness of the underlayer 42, and by adjusting the calendering conditions. As a result, the magnetic tape MT that has floated from the sliding surface of the magnetic head 56 near the entrance head will not continue to float due to its stiffness, and will return to approach the sliding surface of the magnetic head 56.

[0160] In addition, the spacing increase region R LNarrowing, i.e., reducing the spacing index SRL, can also be achieved by keeping the cupping of the magnetic tape MT within a specified range by adjusting the thickness configuration of the magnetic tape MT, including the material type and thickness of the substrate 41, the thickness of the underlayer 42, and the thickness of the back layer 44. It is believed that by ensuring that the magnetic surface of the magnetic tape MT has a cupping that is not too concave, floating in the vicinity of the head on the entrance side can be suppressed.

[0161] (Spacing Index SRT) The upper limit of the spacing index SRT when sliding on a glass pseudo head is 68 μm or less, preferably 66 μm or less, and more preferably 64 μm or less. When the spacing index SRT exceeds 68 μm, the increased spacing region R T This reduces driving stability.

[0162] The spacing index SRT represents the tape floating state near the edge of the magnetic tape MT in the width direction. Specifically, the spacing index SRT is the increased spacing region R that occurs near the edge of the magnetic tape MT in the width direction when the magnetic tape MT is slid over a glass pseudo head. T where R is the average value of the peak half-width. T This refers to a region in the vicinity of the edge in the width direction of the magnetic tape MT where the spacing is increased compared to the central part in the width direction of the sliding surface of the magnetic head 56.

[0163] The lower limit of the spacing index SRT when sliding on a glass pseudo head is, for example, 0 μm or more.

[0164] Near the edges of the magnetic tape MT in the width direction, there are servo bands SB, which are recording areas for servo signals that control the running of the magnetic tape MT. T When becomes wider, the spacing increase region R TThis causes the magnetic recording medium to approach the servo signal recording area, which reduces the accuracy of reading the servo signal. Future magnetic recording and playback devices will be required to have a higher accuracy in reading servo signals in order to perform higher density recording and playback.

[0165] On the other hand, in order to perform high density recording and reproduction, it is necessary to smooth the surface of the magnetic tape MT and reduce the thickness of the magnetic tape MT, but both of these lead to a deterioration in the accuracy of reading the servo signal. Therefore, in the future, it will be necessary to reduce the influence of the floating state near the edge in the width direction of the magnetic tape MT on the accuracy of reading the servo signal more than at present. To achieve this, it is necessary to create an increased spacing region R T It is desirable to narrow the

[0166] Spacing increase region R T Narrowing the gap, i.e., reducing the spacing index SRT, can be achieved by adjusting the thickness configuration of the magnetic tape MT, including the material type and thickness of the substrate 41 and the thickness of the underlayer 42, as well as by adjusting the calendering conditions, thereby reducing the stiffness of the magnetic tape MT to within a specified range. As a result, it is believed that the magnetic tape MT floating near the edge in the width direction of the magnetic tape MT can easily follow the head even near the edge of the magnetic tape MT due to its low stiffness.

[0167] In addition, the spacing increase region R T Narrowing the spacing index SRT, i.e., reducing the spacing index SRT, can be achieved by adjusting the thickness of the magnetic tape MT, including the type and thickness of the material of the substrate 41, the thickness of the underlayer 42, and the thickness of the backing layer, as well as by adjusting the drying temperature, thereby keeping the cupping of the magnetic tape MT within a specified range. By ensuring that the magnetic surface of the magnetic tape MT has a cupping that is neither too concave nor too convex, it is believed that tracking by the magnetic head 56 becomes easier even near the edges of the magnetic tape MT in the width direction.

[0168] (Calculation method for spacing indices SRL and SRT) The method for calculating the spacing indices SRL and SRT will be described below.

[0169] First, a measuring device 80 for acquiring a 2D profile will be described with reference to Fig. 10. The 2D profile is used in the process of calculating the spacing index SRL and the spacing index SRT, as will be described later.

[0170] The measuring device 80 can measure the distance (spacing) between the sliding surface 70S of the dummy 70 and the running magnetic tape MT as a 2D profile. The measuring device 80 includes a light source 81, a beam splitter 82, an imaging unit 83, an amplifier unit 84, a control device 85, a display unit 86, and an input unit 87. In the following description, a sample cut out from the magnetic tape MT may be referred to as a tape sample MT1 or a test sample MT2.

[0171] The Cartesian coordinate system based on the rectangular parallelepiped dummy 70 is represented by an XYZ coordinate system. In the dummy 70, the length direction (Y-axis direction) corresponds to the width direction of the magnetic tape MT, and the width direction (X-axis direction) corresponds to the longitudinal direction (length direction) and running direction of the magnetic tape MT. In addition, in the dummy 70, the height direction (Z-axis direction) corresponds to the thickness direction of the magnetic tape MT.

[0172] The dummy 70 is a glass pseudo head. Detailed information about the dummy 70 is as follows: Material: BK7 glass Shape: Rectangular (width 1mm x length 20mm x depth 3mm) Processing: Each edge is a sharp edge. The parallelism must be within 10 minutes. The roughness of the sliding surface 70S (tape contact surface) and its opposing surface is Ra≦0.2 nm.

[0173] The long side surface (1 mm wide x 20 mm long) of the dummy 70 is used as the sliding surface 70S. The reason why a glass material is used as the material of the dummy 70 is to evaluate the contact state between the sliding surface 70S and the magnetic tape MT by optical interference fringes.

[0174] The light source 81 is configured to be able to emit monochromatic light in a specific wavelength region (for example, red). The beam splitter 82 transmits the light emitted from the light source 81 and guides the light reflected by the dummy 70 and the magnetic tape MT to the imaging unit 83 side.

[0175] The imaging unit 83 captures an image of the dummy 70 and the magnetic tape MT using reflected light. The amplifier 84 amplifies the signal of the image captured by the imaging unit 83 and outputs it to the control device 85. The control device 85 includes, for example, a control unit, a storage unit, a communication unit, etc. The control unit is composed of, for example, a CPU (Central Processing Unit), etc., and controls each unit of the measuring device 80 in accordance with a program stored in the storage unit.

[0176] The storage unit includes a non-volatile memory for storing various data and programs, and a volatile memory used as a work area for the control unit. The various programs may be read from a portable recording medium such as an optical disk or semiconductor memory, or may be downloaded from a server device on a network. The communication unit is configured to be able to communicate with other devices, such as a server device.

[0177] The display unit 86 is configured with, for example, a liquid crystal display or an EL (Electro-Luminescence) display, and displays the image captured by the imaging unit 83 on the display unit 86 in response to an instruction from the control device 85. The input unit 87 is, for example, a keyboard or a contact sensor, and inputs various instructions from the user and outputs them to the control device 85.

[0178] Here, the movement of light will be explained. First, light emitted from the light source 81 passes through the beam splitter 82 and enters the dummy 70 from the back side of the dummy 70 (the side opposite the sliding surface 70S). A portion of the light that enters the dummy 70 is reflected by the sliding surface 70S. Another portion of the light that enters the dummy 70 passes through the sliding surface 70S and is reflected by the magnetic tape MT. The light reflected by the sliding surface 70S and the magnetic tape MT is guided by the beam splitter 82 to the imaging unit 83, and an image is captured by the imaging unit 83.

[0179] If there is a distance between the sliding surface 70S and the magnetic tape MT, the reflected light from the sliding surface 70S and the reflected light from the magnetic tape MT will strengthen or weaken each other depending on this distance, and will appear as interference fringes in the image captured by the imaging unit 83.

[0180] Fig. 11A is an enlarged view showing the relationship between the dummy 70 and the magnetic tape MT in the measurement device 80. Fig. 11B is a cross-sectional view taken along line XIB-XIB in Fig. 11A. Fig. 12 is a diagram showing an example of a 2D profile acquired by the measurement device 80. The measurement position of the 2D profile shown in Fig. 12 is region R in Fig. 11A.

[0181] 11A and 11B, the measuring device 80 includes a guide 88 for guiding the magnetic tape MT in addition to the components shown in Fig. 10. Although not shown, the measuring device 80 also includes a drive device for running the magnetic tape MT and a dummy moving mechanism for moving the dummy 70 toward the magnetic tape MT.

[0182] The two guides 88 are arranged at a predetermined distance from the dummy 70 in a position where they sandwich the dummy 70 in the width direction of the dummy 70 (X-axis direction: running direction of the magnetic tape MT). When the dummy 70 is installed in the measuring device 80, it is installed so that the line connecting the corresponding positions of the two guides 88 (dotted line in FIG. 11B) is parallel to the surface of the dummy 70 (dotted line in FIG. 11B). The distance D between the dummy 70 and the two guides 88 is set to be the same. In this measurement, the distance D was set to 19.5 mm.

[0183] In this measurement, air guides were used as the two guides 88 used to guide the magnetic tape MT. A certain amount of air, released from holes in the surface of the guides 88, remains between the magnetic tape MT and the guides 88, preventing direct contact between the two. As a result, friction between the two is significantly reduced. The reason for using air guides as the guides 88 in this measurement is to achieve this low friction, which allows for more accurate spacing evaluation. Additionally, the two guides 88 on both sides of the dummy 70 are equipped with air pressure measuring devices, and these measurements can be used to measure the tape tension. The measuring device 80 automatically controls the air pressure to achieve the tension value (0.6 N) used in this measurement (described below). Calibration was performed before measurement to ensure an accurate relationship between the tension value and air pressure.

[0184] The dummy 70 can be moved in the thickness direction (Z-axis direction) of the dummy 70 by a dummy moving mechanism, and can be protruded toward the magnetic tape MT. The distance by which the dummy 70 protrudes toward the magnetic tape MT and penetrates into the magnetic tape MT will hereinafter be referred to as the penetration distance P. The penetration distance P is based on the position of the dummy 70 when the magnetic tape MT is flat and the dummy 70 is in contact with this flat magnetic tape MT (penetration distance P=0).

[0185] Furthermore, the angle formed between the sliding surface 70S of the dummy 70 and the magnetic tape MT when viewed from the length direction of the dummy 70 (Y-axis direction: width direction of the magnetic tape MT) will hereinafter be referred to as the wrap angle θ (not the part of the magnetic tape MT that faces the sliding surface 70S, but the parts on both sides that sandwich the part that faces the sliding surface 70S in the running direction of the magnetic tape MT). In this measurement, the entry distance P was adjusted so that the wrap angle θ was 5°. Also, in this measurement, the speed V at which the magnetic tape MT was run was set to 5 m / s. The reason for setting the wrap angle θ to 5° and the speed V to 5 m / s in this measurement is to reduce variation in the measurement values.

[0186] The spacing indices SRL and SRT are determined using the above-mentioned measuring device 80 as follows. First, the magnetic tape MT contained in the cartridge 10 is unwound, and the magnetic tape MT is cut out longitudinally from the connection 21 between the magnetic tape MT and the leader tape LT in the ranges of 10 m to 210 m, 350 m to 550 m, and 700 m to 900 m, to create three 200 m long tape samples MT1.

[0187] Next, the spacing index srl and the spacing index srt are determined from the three tape samples MT1 as follows: First, the tape sample MT1 is placed in the drive device of the measurement device 80 shown in Fig. 10. As the drive device, a Tape Transport System manufactured by Mountain Engendering is used. The measurement conditions for the measurement device 80 are as follows. Light source: MORITEX red LED (wavelength 620nm). CCD camera: Sony XC-75 Horizontal resolution = L: 640pix x T: 480pix, Vertical resolution 256 (8bit) Objective lens: TV-ZH (4x magnification) A dummy (a glass pseudo head) 70 is pressed into the tape sample MT1 side, and the wrap angle is set to 5°. Measurement environment: 23℃±2℃, 40%RH or more and 60%RH or less The tape sample MT1 is run at a speed of 5 m / s, and the tension of the tape sample MT1 is set to 0.6 N.

[0188] Next, the tape sample MT1 is run by the drive device, and the spacing state of the tape sample MT1 is observed at three positions using the measurement device 80, and 2D profiles P1(L,T) to P3(L,T) are obtained (see FIG. 12). The measurement position is near the upper tape edge (specifically, area R in FIG. 11A). The 2D profiles P1(L,T) to P3(L,T) are obtained after at least three seconds have passed since the start of running, after the running speed has stabilized at 5 m / s, and during one run.

[0189] Position L in the 2D profile P1(L,T) indicates the position of the tape sample MT1 in the longitudinal direction (X-axis direction) and the running direction of the tape sample MT1, and position T in the 2D profile P1(L,T) indicates the position of the tape sample MT1 in the width direction (Y-axis direction).

[0190] Next, the 2D profile Pa(L,T) in the spacing state is determined by arithmetically averaging the 2D profiles P1(L,T) to P3(L,T) at the same L, T position. Next, from the 2D profile Pa(L,T) in the spacing state, the spacing index srl in the longitudinal direction of the tape sample MT1 and the spacing index srt in the width direction of the tape sample MT1 are calculated as follows:

[0191] The profiles of the 2D profile Pa(L,T) within a specified range R1 (see FIG. 12) at the same longitudinal position L (position in the X-axis direction) are averaged to calculate an average 1D profile PaL(L) within the specified range R1. Here, the specified range R1 is a range of 500 μm to 600 μm from one edge of the tape sample MT1 in the width direction toward the inside of the tape sample MT1. The specified range R1 has a long, narrow rectangular shape with a width of 100 μm, and both longitudinal ends of the specified range R1 are set outside the dummy 70.

[0192] 13A is a graph showing an example of the average 1D profile PaL(L). In the average 1D profile PaL(L), the spacing increase region R on the upstream side (left side in FIG. 12) in the running direction of the tape sample MT1 is L Focusing only on this spacing increase region R L The peak half-width of the average 1D profile PaL(L) is calculated and the result is defined as the spacing index srl (μm).

[0193] The profiles of the 2D profiles Pa(L,T) within a specified range R2 (see FIG. 12) at the same widthwise position T (position in the Y-axis direction) are arithmetically averaged to calculate an average 1D profile PaT(T) within the specified range R2. Here, the specified range R2 is a range extending from one end of the sliding surface 70S of the dummy 70 in the widthwise direction (one end upstream in the running direction of the tape sample MT1) to 450 μm or more and 550 μm or less in the running direction of the tape sample MT1. The specified range R2 has a narrow rectangular shape with a width of 100 μm and is centered on the center line of the dummy 70. One end of the specified range R2 in the longitudinal direction is set outside one edge of the tape sample MT1, and the other end is set at a position inside the tape sample MT1 relative to the specified range R1.

[0194] 13B is a graph showing an example of the average 1D profile PaT(T). T Focusing only on this spacing increase region R T The peak half-width of the average 1D profile PaT(T) is calculated and the result is defined as the spacing index srt (μm).

[0195] The three spacing indices srl obtained from the three tape samples MT1 as described above are arithmetically averaged, and the calculation result is designated as the spacing index SRL. Similarly, the three spacing indices srt obtained from the three tape samples MT1 as described above are arithmetically averaged, and the calculation result is designated as the spacing index SRT.

[0196] (average stiffness) The average stiffness (bending rigidity) of the magnetic tape MT is preferably 1.2 mg / μm or less, more preferably 1.0 mg / μm or less. When the average stiffness is 1.2 mg / μm, the increased spacing region R generated on the entrance side of the magnetic head 56 L In addition, the width of the increased spacing region R occurring near the edge of the magnetic tape MT in the width direction can be reduced. T Therefore, the electromagnetic conversion characteristics can be improved. In addition, the running stability can be improved. L Narrowing the width of the increased spacing region R contributes to improving the electromagnetic conversion characteristics. T Narrowing the width of the tire contributes to improving driving stability.

[0197] The stiffness of the magnetic tape MT is determined as follows: First, the magnetic tape MT housed in the cartridge 10 is unwound, and five samples of 8.0 mm are cut out from the magnetic tape MT in the longitudinal direction from the joint 21 between the magnetic tape MT and the leader tape LT in the ranges of 10 m to 20 m, 30 m to 40 m, 50 m to 60 m, 70 m to 80 m, and 90 m to 100 m, to prepare five samples.

[0198] Next, the flexural rigidity S1 to S5 of each of the five samples is measured. The flexural rigidity S1 to S5 is measured in accordance with the ECMA-319 method. The measurement is performed in an environment of 23°C ± 2°C and 40% RH or higher and 60% RH or lower. Next, the arithmetic mean of the flexural rigidity S1 to S5 of the measured five samples is calculated, and this calculation result is defined as the average stiffness S.

[0199] (average cupping) The average cupping C of the magnetic tape MT is preferably −1.5 mm or more and +0.5 mm or less, more preferably −0.5 mm or more and 0 mm or less. When the average cupping C of the magnetic tape MT is −1.5 mm or more and +0.5 mm or less, the spacing increase region R generated on the entrance side of the magnetic head 56 isL Therefore, the electromagnetic conversion characteristics can be improved. T Therefore, the running stability can be improved. Here, cupping means the curvature of the magnetic tape MT in the width direction.

[0200] The average cupping C of the magnetic tape MT is calculated as follows. First, the magnetic tape MT contained in the cartridge 10 is unwound, and five samples are prepared by cutting the magnetic tape MT into 1-meter lengths from the connection 21 between the magnetic tape MT and the leader tape LT in the longitudinal direction in the ranges of 10 m to 20 m, 30 m to 40 m, 50 m to 60 m, 70 m to 80 m, and 90 m to 100 m.

[0201] The cupping C1 of one of the five test samples is determined as follows. First, immediately after one hour has elapsed from the time the magnetic tape MT was unwound, a 300 mm section from the center of the 1 m long sample is cut out and designated as test sample MT2. Next, as shown in Figures 14A and 14B, test sample MT2 is placed on a metal base 91 having a rectangular, smooth mounting surface 91S (size of mounting surface 91S: 100 mm x 200 mm). At this time, test sample MT2 is placed on mounting surface 91S so that the following conditions are satisfied: Visually, the concave surface of the test sample MT2 faces the mounting surface 91S (the convex surface CV faces upward). The long sides of the mounting surface 91S of the metal base 91 and the long sides of the test sample MT2 are parallel to each other, and the test sample MT2 is positioned at the center of the mounting surface 91S of the metal base 91 in the width direction. The test sample MT2 hangs down by its own weight by approximately 50 mm (approximately 5 cm) from each of the short sides of the mounting surface 91S of the metal stand 91. However, both longitudinal ends of the test sample MT2 must not touch the floor or the like.

[0202] Next, the height Hc of the convex surface CV of the test sample MT2 is measured using a laser displacement meter. Before measurement, the test sample MT2 is placed in a slightly adjusted position so that both widthwise edges of the test sample MT2 are in contact with the mounting surface 91S of the metal base 91 at the measurement position. The measurement position is selected from the central 100 mm area of ​​the 200 mm long portion of the test sample MT2 located on the mounting surface 91S. The measurement is performed in an environment of 23°C ± 2°C and 40% to 60% RH.

[0203] The height Hc of the convex surface CV of the test sample MT2 is a relative height with respect to the mounting surface 91S of the metal base 91, and is specifically defined by the following formula. Hc = Ht - 1 / 2 × (Ha + Hb) In the formula, Ha, Hb, and Ht are as follows: Ha: Height of the point where one end of the test sample MT2 in the width direction touches the mounting surface 91S Hb: Height of the point where the other end of the test sample MT2 in the width direction touches the mounting surface 91S Ht: Height of the apex of the convex CV of test sample MT2 The measurement reference positions for Ha, Hb, and Ht are arbitrarily selected from positions lower than the placement surface 91S.

[0204] Next, if the magnetic surface (surface on the magnetic layer 43 side) of the test sample MT2 is convex, a minus sign "-" is added to the calculated height Hc of the convex surface CV to obtain the cupping value C 1-1 That is, C 1-1 =-1×Hc, and the result is C 1-1 On the other hand, when the back surface (surface on the back layer 44 side) of the test sample MT2 is a convex surface CV, the calculated height Hc of the convex surface is used as the cupping value C 1-1 That is, C 1-1 =Hc, and the result is C 1-1 >0.

[0205] The above measurements were taken at five locations, and the cupping value C 1-1 From C 1-5The four measurements are taken at intervals of 25 mm along the longitudinal direction of the test sample MT2. 1-1 From C 1-5 The arithmetic mean of these values ​​is calculated and the result is designated as cupping C1.

[0206] Next, the cuppings C2 to C5 of the remaining four samples are determined using the same procedure as for determining the cupping C1. The arithmetic mean of the cuppings C1 to C5 determined as above is calculated, and this result is designated as the average cupping C.

[0207] [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.

[0208] (Paint preparation process) First, a paint for forming the base layer is prepared by kneading and dispersing a non-magnetic powder, a binder, etc. in a solvent. Next, a paint for forming the magnetic layer is prepared by kneading and dispersing a magnetic powder, a binder, etc. in a solvent. The following solvents, dispersing devices, and kneading devices can be used to prepare the paint for forming the magnetic layer and the paint for forming the base layer.

[0209] 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.

[0210] 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.

[0211] (coating process) Next, a base layer forming paint is applied to one main surface of the substrate 41 and dried to form the base layer 42. Subsequently, a magnetic layer forming paint is applied to the base layer 42 and dried to form the magnetic layer 43 on the base layer 42. During drying, the magnetic powder may be magnetically oriented in the thickness direction of the substrate 41, for example, using a solenoid coil. Furthermore, during drying, the magnetic powder may be magnetically oriented in the running direction (longitudinal direction) of the substrate 41, for example, using a solenoid coil, and then magnetically oriented in the thickness direction of the substrate 41. By performing a process to orient the magnetic powder in the longitudinal direction in this manner, the degree of perpendicular orientation of the magnetic powder (i.e., the squareness ratio S1) can be further improved. After the magnetic layer 43 is formed, a back layer 44 is formed on the other main surface of the substrate 41. This results in a magnetic tape MT.

[0212] The squareness ratios S1 and S2 can be set to desired values ​​by, for example, adjusting the strength of the magnetic field applied to the coating film of the magnetic layer-forming paint, the concentration of solids in the magnetic layer-forming paint, and the drying conditions (drying temperature and drying time) of the coating film of the magnetic layer-forming paint. The strength of the magnetic field applied to the coating film is preferably between two and three times the coercive force of the magnetic powder. To further increase the squareness ratio S1 (i.e., to further reduce the squareness ratio S2), it is preferable to improve the dispersion state of the magnetic powder in the magnetic layer-forming paint. To further increase the squareness ratio S1, it is also effective to magnetize the magnetic powder before the magnetic layer-forming paint enters an orientation device that magnetically orients the magnetic powder. The above methods for adjusting the squareness ratios S1 and S2 may be used alone or in combination.

[0213] (hardening process) After the magnetic tape MT is wound into a roll, the magnetic tape MT is subjected to a heat treatment in this state, thereby hardening the underlayer 42 and the magnetic layer 43.

[0214] (calendering process) Next, the obtained magnetic tape MT is subjected to a calendering process to smooth the surface of the magnetic layer 43.

[0215] (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.

[0216] (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.

[0217] [5. Effects] As described above, in the magnetic tape MT according to one embodiment, the spacing index SRL when the magnetic tape MT is slid over the glass pseudo head is 35 μm or less, and the spacing index SRT when the magnetic tape MT is slid over the glass pseudo head is 68 μm or less. L and spacing increase region R T Therefore, excellent electromagnetic conversion characteristics and running stability can be obtained.

[0218] [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.

[0219] 15 is an exploded perspective view showing an example of the configuration of a two-reel type cartridge 121. The cartridge 121 comprises an upper half 102 made of synthetic resin, a transparent window member 123 fitted into and fixed to a window 102a opened in the top surface of the upper half 102, a reel holder 122 fixed to the inside of the upper half 102 to prevent the reels 106 and 107 from floating up, a lower half 105 corresponding to the upper half 102, the reels 106 and 107 stored in the space formed when the upper half 102 and the lower half 105 are joined together, the magnetic tape MT wound on the reels 106 and 107, a front lid 109 that closes the front opening formed when the upper half 102 and the lower half 105 are joined together, and a back lid 109A that protects the magnetic tape MT exposed in this front opening.

[0220] 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.

[0221] 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 embodiment. [Example]

[0222] The present disclosure will be specifically described below using examples, but the present disclosure is not limited to these examples.

[0223] In the following examples and comparative examples, the average aspect ratio of the magnetic powder, the average particle volume of the magnetic powder, the average thickness of the magnetic layer, the average thickness of the underlayer, the average thickness of the substrate (base film), the average thickness of the back layer, the average thickness of the magnetic tape, the squareness ratio S1 of the magnetic layer in the perpendicular direction of the magnetic tape, the squareness ratio S2 of the magnetic layer in the longitudinal direction of the magnetic tape, and the arithmetic mean roughness Ra of the surface of the magnetic layer are values ​​obtained by the measurement method described in the above embodiment.

[0224] [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.

[0225] (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 Resin solution in which vinyl chloride resin is dispersed in cyclohexanone (resin solution: vinyl chloride resin content 30% by mass, cyclohexanone content 70% by mass): 60 parts by mass (Vinyl chloride resin: degree of polymerization 300, number average molecular weight Mn=10,000, polar groups OSO3K=0.07 mmol / g, secondary OH=0.3 mmol / g) Medium-sized aluminum oxide powder: 5 parts by mass (α-Al2O3, average particle size (D50) 0.09μm)

[0226] (Second composition) Resin solution in which vinyl chloride resin is dispersed in cyclohexanone (resin solution: vinyl chloride resin content 30% by mass, cyclohexanone content 70% by mass): 3.6 parts by mass (Vinyl chloride resin: degree of polymerization 300, number average molecular weight Mn=10,000, polar groups OSO3K=0.07 mmol / g, secondary OH=0.3 mmol / g) Medium-sized aluminum oxide powder: 5 parts by mass (α-Al2O3, average particle size (D50) 0.09μm) n-Butyl stearate: 2 parts by mass Methyl ethyl ketone: 121.3 parts by mass Toluene: 121.3 parts by mass Cyclohexanone: 60.7 parts by mass Carbon black: 2 parts by mass (Manufactured by Tokai Carbon Co., Ltd., product name: Seest TA)

[0227] 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.

[0228] (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.

[0229] (Third composition) Medium particle size acicular iron oxide powder (non-magnetic powder): 100 parts by mass (α-Fe2O3, average major axis length 0.08μm) Vinyl chloride resin: 55.6 parts by mass (Resin solution: 30% resin by mass, 70% cyclohexanone by mass) Carbon black: 10 parts by mass (Average particle size 20nm)

[0230] (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

[0231] 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.

[0232] (Preparation process of paint for forming back layer) The coating material for forming a back layer was prepared as follows: The following raw materials were mixed in a stirring tank equipped with a disperser, and the mixture was filtered to prepare the coating material for forming a back layer. Carbon black powder (average particle size (D50) 20 nm): 100 parts by mass Polyester polyurethane: 100 parts by mass (Nippon Polyurethane Co., Ltd., product name: N-2304) Methyl ethyl ketone: 500 parts by mass Toluene: 400 parts by mass Cyclohexanone: 100 parts by mass

[0233] (coating process) Using the magnetic layer-forming paint and primer layer-forming paint prepared as described above, a primer layer and a magnetic layer were formed on one main surface of a non-magnetic support (substrate) of long PEN film with an average thickness of 4.0 μm as follows.

[0234] First, a coating material for forming a primer layer was applied to one main surface of a PEN film, and then the coating film was dried while being heated and exposed to air, thereby forming a primer layer with an average thickness of 0.82 μm after calendaring.

[0235] Next, a magnetic layer-forming paint was applied to the underlayer, and the paint was dried by heating and blowing air onto the coating, forming a magnetic layer with an average thickness of 80 nm after calendaring. During drying of the magnetic layer-forming paint, a neodymium magnet was used to magnetically orient the magnetic powder in the thickness direction of the PEN film. As a result, 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%.

[0236] Next, a back layer coating was applied to the other main surface of the PEN film, and the coating was dried by heating and blowing air onto the coating, forming a back layer with an average thickness of 0.3 μm after calendaring. This final drying step simultaneously accelerates the drying of not only the back layer coating applied immediately before, but also both the primer layer coating and the magnetic layer coating. The drying temperature was set at 100°C. Hereinafter, the drying temperature of 100°C will be referred to as the standard drying temperature. This resulted in the production of a magnetic tape.

[0237] (hardening process) The magnetic tape was wound into a roll, and then heated in this state at 60° C. for 24 hours to harden the underlayer and magnetic layer.

[0238] (calendering process) A calendering treatment was performed to smooth the surface of the magnetic layer. The calendering temperature was 125°C and the calendering pressure was 255 kg / cm. Hereinafter, the calendering temperature of 125°C will be referred to as the reference calendering temperature, and the calendering pressure of 255 kg / cm will be referred to as the reference calendering pressure.

[0239] (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.

[0240] (Servo pattern writing process) After demagnetizing the magnetic tape, a servo writer was used to write a servo pattern onto the magnetic tape, forming five servo bands. The servo pattern conformed to the LTO-8 standard.

[0241] [Example 2] The average thickness of the PEN film, the average thickness of the underlayer after calendaring, and the average thickness of the magnetic layer after calendaring were set to the values ​​shown in Table 1. Other than the above, the same procedures as in Example 1 were carried out to obtain magnetic tapes with the average thicknesses shown in Table 1.

[0242] [Example 3] A PET film was used as the non-magnetic support. Other than the above, the same procedures as in Example 1 were carried out to obtain magnetic tapes having the average thicknesses shown in Table 1.

[0243] [Examples 4 to 7] In Examples 4 to 7, the average thickness of the PEN film, the average thickness of the underlayer after calendering, and the average thickness of the magnetic layer after calendering were set to the values ​​shown in Table 1. In Examples 4 to 7, the calendering temperature was set to a temperature higher than the standard calendering temperature. In Example 6, the calendering pressure was set to a pressure higher than the standard calendering pressure. Other than the above, magnetic tapes were obtained in the same manner as in Example 1, with the average thicknesses shown in Table 1.

[0244] [Examples 8 and 9] In Examples 8 and 9, a PET film was used as the non-magnetic support. In Examples 8 and 9, the average thickness of the PET film, the average thickness of the underlayer after calendering, and the average thickness of the magnetic layer after calendering were set to the values ​​shown in Table 1. In Examples 8 and 9, the calendering temperature was set to a temperature higher than the standard calendering temperature. In Example 8, the calendering pressure was set to a temperature higher than the standard calendering pressure. In Examples 8 and 9, the final drying temperature was set to a temperature higher than the standard drying temperature. Other than the above, magnetic tapes with the average thicknesses shown in Table 1 were obtained in the same manner as in Example 1.

[0245] [Examples 10 and 11] In Examples 10 and 11, a PET film was used as the non-magnetic support. In Examples 10 and 11, the average thickness of the PET film, the average thickness of the underlayer after calendering, and the average thickness of the magnetic layer after calendering were set to the values ​​shown in Table 1. In Examples 10 and 11, the calendering temperature was set to a temperature higher than the standard calendering temperature. Other than the above, magnetic tapes were obtained in the same manner as in Example 1, with the average thicknesses shown in Table 1.

[0246] [Comparative Example 1] The average thickness of the PEN film, the average thickness of the underlayer after calendaring, and the average thickness of the magnetic layer after calendaring were set to the values ​​shown in Table 1. The calendaring temperature was set to a temperature lower than the standard temperature for calendaring. The final drying temperature was set to a temperature higher than the standard temperature for drying. Other than the above, the same procedures were followed as in Example 1 to obtain magnetic tapes with the average thicknesses shown in Table 1.

[0247] Comparative Example 2 The average thickness of the underlayer after calendering and the average thickness of the magnetic layer after calendering were set to the values ​​shown in Table 1. The calendering temperature was set to a temperature lower than the standard calendering temperature. Other than the above, the same procedures were followed as in Example 1 to obtain magnetic tapes with the average thicknesses shown in Table 1.

[0248] Comparative Example 3 A PET film was used as the non-magnetic support. The average thickness of the PET film, the average thickness of the underlayer after calendering, and the average thickness of the magnetic layer after calendering were set to the values ​​shown in Table 1. The calendering temperature was set to a temperature lower than the standard calendering temperature. Other than the above, the same procedures were followed as in Example 1 to obtain a magnetic tape with the average thickness shown in Table 1.

[0249] Comparative Example 4 A PA film was used as the non-magnetic support. The average thickness of the PA film, the average thickness of the underlayer after calendering, and the average thickness of the magnetic layer after calendering were set to the values ​​shown in Table 1. The calendering temperature was set to a temperature lower than the standard calendering temperature. Other than the above, the same procedures were followed as in Example 1 to obtain a magnetic tape with the average thickness shown in Table 1.

[0250] [Comparative Examples 5 and 6] The average thickness of the PEN film, the average thickness of the underlayer after calendaring, the average thickness of the magnetic layer after calendaring, and the average thickness of the back layer after calendaring were set to the values ​​shown in Table 1. The calendaring temperature was set to a temperature higher than the reference temperature. Other than the above, the same procedures were followed as in Example 1 to obtain magnetic tapes with the average thicknesses shown in Table 1.

[0251] Comparative Example 7 The average thickness of the PEN film, the average thickness of the underlayer after calendering, and the average thickness of the magnetic layer after calendering were set to the values ​​shown in Table 1. The calendering temperature was set to a temperature higher than the reference temperature. Other than the above, the same procedures were followed as in Example 1 to obtain magnetic tapes with the average thicknesses shown in Table 1.

[0252] [evaluation] The magnetic tapes obtained as described above were evaluated as follows.

[0253] (average stiffness) The average stiffness was calculated by the method described in the above embodiment.

[0254] (average cupping) The average cupping was determined by the method described in the above embodiment.

[0255] (Spacing state) The spacing index SRL and the spacing index SRT were calculated by the method described in the above embodiment.

[0256] (Electromagnetic conversion characteristics) First, a loop tester (manufactured by Microphysics) was used to obtain a playback signal from the magnetic tape. The conditions for obtaining the playback signal are as follows: head:GMR Head speed: 1.85 m / s signal: single recording frequency (10MHz) Recording current: Optimum recording current

[0257] Next, the playback signal was captured using a spectrum analyzer with a span of 0 to 20 MHz (resolution bandwidth = 100 kHz, VBW = 30 kHz). Next, the peak of the captured spectrum was taken as the signal amount S, and the floor noise excluding the peak was integrated from 3 MHz to 20 MHz to obtain the noise amount N. The ratio S / N of the signal amount S to the noise amount N was calculated as the SNR (Signal-to-Noise Ratio). Next, the calculated SNR was converted into a relative value (dB) using the SNR of Comparative Example 3 as the reference media as the standard (0 dB).

[0258] (Driving stability) First, the magnetic tape was incorporated into an LTO cartridge. Next, the LTO cartridge was loaded into an LTO drive connected to a PC via serial cable communication, and the magnetic tape was run. Next, of the five servo bands (servo bands 0, 1, 2, 3, and 4) written on the magnetic tape, the servo band closest to one edge of the magnetic tape in the width direction, i.e., servo band 0, was used, and the actuator of the drive head was operated so that the drive head would follow the servo track, and the magnetic tape was run. From the servo signal obtained at this time, a statistical value σ, which indicates the nonlinearity of the servo pattern, was calculated. SW-0 The statistical value σ SW-0 The method described in Japanese Patent No. 6624332 was used as the measurement method.

[0259] Next, the servo band closest to the other edge in the width direction of the magnetic tape, i.e., servo band 4, is used to calculate σ SW-4 was measured.

[0260] The arithmetic mean of the above data is taken, and the obtained value is the σ SW (nm). SW is set to 100%, and the relative value from there is the relative σ SW The values ​​are expressed as (%). SW The smaller the value, the higher the running stability, which is preferable from the viewpoint of running stability.

[0261] Table 1 shows the magnetic tape configuration, process conditions, and evaluation results. Figure 16 is a graph showing the favorable ranges for stiffness and cupping.

[0262] [Table 1]

[0263] Table 1 reveals the following: In a magnetic tape having an average value of the arithmetic mean roughness Ra of the surface of the magnetic layer of 1.3 nm or less, if the spacing index SRL when the magnetic tape is slid across a glass pseudo head is 35 μm or less and the spacing index SRT when the magnetic tape is slid across a glass pseudo head is 68 μm or less, excellent electromagnetic conversion characteristics and running stability can be obtained.

[0264] 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.

[0265] 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.

[0266] The present disclosure may also employ the following configuration. (1) A tape-shaped magnetic recording medium, a substrate comprising polyesters; an underlayer provided on the substrate; a magnetic layer including magnetic powder provided on the underlayer; Equipped with the magnetic recording medium contains a lubricant; the average value of the arithmetic mean roughness Ra of the surface of the magnetic layer is 1.3 nm or less; When the magnetic recording medium is slid over a glass pseudo head, the average value of the half-width of the peak of the spacing increase region occurring at the entrance side of the glass pseudo head where the magnetic recording medium enters is defined as a spacing index SRL, When the magnetic recording medium is slid over the glass pseudo head, the average value of the half-width of the peak of the spacing increase region occurring near the edge in the width direction of the magnetic recording medium is defined as the spacing index SRT. A magnetic recording medium, wherein the spacing index SRL is 35 μm or less, and the spacing index SRT is 68 μm or less. (2) the average thickness Tt of the magnetic recording medium is 5.1 μm or less; The average thickness T of the substrate s the average thickness T of the magnetic recording medium t The ratio (T t / T s ) is 1.2 or more. (3) The magnetic recording medium according to (1) or (2), wherein the average stiffness of the magnetic recording medium is 1.2 mg / μm or less, and the average cupping of the magnetic recording medium is −1.5 mm or more and +0.5 mm or less. (4) The magnetic recording medium according to (3), wherein the average stiffness of the magnetic recording medium is 1.0 mgf / μm or less. (5) The magnetic recording medium according to (3) or (4), wherein the average cupping of the magnetic recording medium is −0.5 mm or more and 0 mm or less. (6) The magnetic recording medium according to any one of (1) to (5), wherein a flat head is used as a magnetic head for recording and reproducing information on the magnetic recording medium. (7) The magnetic recording medium according to any one of (1) to (6), which is used in a recording and reproducing device in which the maximum linear recording density when recording signals is 550 KFCI or more. (8) The magnetic recording medium according to any one of (1) to (7), wherein the magnetic powder contains hexagonal ferrite. (9) The magnetic recording medium according to any one of (1) to (7), wherein the magnetic powder contains ε-iron oxide or Co-containing spinel ferrite. (10) The average particle volume of the magnetic powder is 2500 nm 3 A magnetic recording medium according to any one of (1) to (9) below. (11) The magnetic recording medium according to any one of (1) to (10), wherein the average thickness of the magnetic layer is 80 nm or less. (12) The magnetic recording medium according to any one of (1) to (11), wherein the underlayer has an average thickness of 0.90 μm or less. (13) The magnetic recording medium according to any one of (1) to (12), wherein the substrate has an average thickness of 4.4 μm or less. (14) The magnetic recording medium according to any one of (1) to (13), wherein the substrate contains at least one selected from the group consisting of polyethylene terephthalate and polyethylene naphthalate. (15) Further, a back layer is provided on the opposite side of the underlayer, The magnetic recording medium according to any one of (1) to (14), wherein the back layer has an average thickness of 0.3 μm or less. (16) A cartridge comprising a magnetic recording medium according to any one of (1) to (15). [Explanation of symbols]

[0267] 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 Magnetic Head 56A, 56B servo readhead 110 servo frames 111 Servo subframe 1 111A A Burst 111B B Burst 112 Servo subframe 2 112C C-Burst 112D D Burst 113 Servo Stripe MT magnetic tape SB servo band DB Data Binding

Claims

1. A tape-shaped magnetic recording medium, a substrate comprising polyesters; an underlayer provided on the substrate; a magnetic layer including magnetic powder provided on the underlayer; Equipped with the magnetic recording medium contains a lubricant; the average value of the arithmetic mean roughness Ra of the surface of the magnetic layer is 1.3 nm or less; When the magnetic recording medium is slid over a glass pseudo head, the average value of the half-width of the peak of the spacing increase region occurring at the entrance side of the glass pseudo head where the magnetic recording medium enters is defined as a spacing index SRL, When the magnetic recording medium is slid over the glass pseudo head, the average value of the half-width of the peak of the spacing increase region occurring near the edge in the width direction of the magnetic recording medium is defined as the spacing index SRT. A magnetic recording medium in which the spacing index SRL is 35 μm or less and the spacing index SRT is 68 μm or less.

2. the average thickness Tt of the magnetic recording medium is 5.1 μm or less; The average thickness T of the substrate ｓ the average thickness T of the magnetic recording medium ｔ The ratio (T ｔ / T ｓ 2. The magnetic recording medium according to claim 1, wherein the ratio of the surface roughness to the surface roughness is 1.2 or more.

3. 2. The magnetic recording medium according to claim 1, wherein the average stiffness of the magnetic recording medium is 1.2 mgf / μm or less, and the average cupping of the magnetic recording medium is −1.5 mm or more and +0.5 mm or less.

4. 4. The magnetic recording medium according to claim 3, wherein the average stiffness of the magnetic recording medium is 1.0 mgf / .mu.m or less.

5. 4. The magnetic recording medium according to claim 3, wherein the average cupping of the magnetic recording medium is −0.5 mm or more and 0 mm or less.

6. 2. The magnetic recording medium according to claim 1, wherein a flat head is used as a magnetic head for recording and reproducing information on the magnetic recording medium.

7. 2. The magnetic recording medium according to claim 1, wherein the magnetic recording medium is used in a recording / reproducing device having a maximum linear recording density of 550 KFCI or more when recording signals.

8. 2. The magnetic recording medium according to claim 1, wherein the magnetic powder contains hexagonal ferrite.

9. 2. The magnetic recording medium according to claim 1, wherein the magnetic powder contains ε-iron oxide or Co-containing spinel ferrite.

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

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

12. 2. The magnetic recording medium according to claim 1, wherein the average thickness of the underlayer is 0.90 [mu]m or less.

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

14. 2. The magnetic recording medium according to claim 1, wherein the substrate comprises at least one material selected from the group consisting of polyethylene terephthalate and polyethylene naphthalate.

15. Further, a back layer is provided on the opposite side of the underlayer, 2. The magnetic recording medium according to claim 1, wherein the average thickness of the back layer is 0.3 [mu]m or less.

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

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