cartridge

Abstract

Provided is a cartridge with which electric charging of magnetic tape can be minimized even when a drive gear is configured from an insulating resin.　This cartridge comprises an electroconductive reel including a bottom wall, magnetic tape wound around the reel, and an electroconductive member in contact with the reel, the electroconductive member having a reel gear on the lower surface of the bottom wall.

Description

[Technical Field]

[0001] This disclosure relates to cartridges. [Background technology]

[0002] In coated magnetic tapes, the magnetic powder is fixed with a non-conductive binder (organic material), making the surface of the magnetic layer (hereinafter referred to as the "magnetic surface") prone to static charge. When the magnetic surface becomes charged, sudden discharges can occur, potentially damaging the magnetic head. Among magnetic heads, tunnel magnetoresistance effect (TMR) elements are particularly susceptible to damage from sudden discharges because they are vulnerable to excessive current. Therefore, technologies to suppress static charge on magnetic tapes are desired.

[0003] Patent Document 1 discloses that by forming the reel hub from a conductive material, the reel hub is electrically connected to the reel drive shaft during tape loading, thereby preventing the magnetic tape from becoming charged. It also discloses that the above configuration is based on the premise that at least the surface of the reel drive shaft (spindle) is made of a conductive material such as metal, and that the electrical resistance [Ω] from the reel hub, which serves as a grounding terminal, to the earth is on the order of 10 to the power of 7 or less. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2003-223774 [Overview of the project] [Problems that the invention aims to solve]

[0005] In magnetic tape drives, the reel gear of the cartridge reel and the drive gear of the drive come into contact during tape loading. However, in typical drives, the drive gear is made of insulating resin, so even if the reel hub is made of a conductive material as in Patent Document 1, it is difficult to suppress the charging of the magnetic tape.

[0006] The object of this disclosure is to provide a cartridge that can suppress the charging of magnetic tape even when the drive gear is made of an insulating resin. [Means for solving the problem]

[0008] To solve the above problems, This disclosure is, A reel that has conductivity, Magnetic tape wound on a reel, A conductive elastic member and Equipped with, The reel has a reel gear that meshes with the drive gear, The elastic member is a cartridge configured to bias a conductive part provided on the drive spindle when the reel gear is engaged with the drive gear. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is an exploded perspective view showing an example of the configuration of a magnetic tape cartridge according to one embodiment of the present disclosure. [Figure 1A] Figure 1A is an exploded cross-sectional view showing an example of the configuration of a magnetic tape cartridge according to one embodiment of the present disclosure. [Figure 2] Figure 2 is a plan view showing an example of the configuration of the lower side of a magnetic tape cartridge according to one embodiment of the present disclosure. [Figure 3] Figure 3A is a plan view showing an example of a spindle configuration. Figure 3B is an exploded cross-sectional view showing an example of a spindle configuration. [Figure 4] Figure 4 is a cross-sectional view showing an example of the reel configuration. [Figure 5] Figure 5 is a plan view showing an enlarged portion of Figure 2. [Figure 6] Figure 6 is a cross-sectional view showing an enlarged portion of Figure 4. [Figure 7] Figure 7A is a plan view showing an example of the configuration of a leaf spring. Figure 7B is a cross-sectional view along the line VIIB-VIIB in Figure 7A. [Figure 8] Figure 8 is a block diagram showing an example of the cartridge memory configuration. [Figure 9] Figure 9 is a cross-sectional view showing an example of the configuration of a magnetic tape. [Figure 10] Figure 10 is a schematic diagram showing an example of the layout of the data band and servo band. [Figure 11] Figure 11 is an enlarged view showing an example of a data band configuration. [Figure 12] Figure 12 is an enlarged view showing an example of a servoband configuration. [Figure 13] Figure 13 is a perspective view showing an example of a particle shape. [Figure 14] Figure 14 shows an example of a TEM image of a magnetic layer. [Figure 15] Figure 15 shows an example of a TEM image of a magnetic layer. [Figure 16] Figure 16 shows an example of an AFM image of the magnetic surface of a magnetic tape. [Figure 17] Figure 17 shows the results of the AFM analysis of the protrusions. [Figure 18] Figure 18 shows the height distribution of the protrusions as measured by AFM. [Figure 19] Figure 19 shows an example of a FE-SEM image of the magnetic surface of a magnetic tape. [Figure 20] Figure 20 shows an example of a binarized image of the magnetic surface of a magnetic tape. [Figure 21] Figure 21 shows a composite image of the AFM image and the FE-SEM image. [Figure 22] Figure 22 shows the cumulative frequency distribution of the height of the protrusions. [Figure 23] Figure 23 shows the acquisition position (Line 1) of the cross-sectional profile in the composite image. [Figure 24] Figure 24 shows the cross-sectional profile obtained at Line 1 as shown in Figure 23. [Modes for carrying out the invention]

[0010] The embodiments of this disclosure will be described in the following order. 1. Configuration of a magnetic tape cartridge 2. Spindle configuration 3 Reel Configuration 4. Cartridge Memory Configuration 5. The structure of magnetic tape 6. Method for manufacturing magnetic tape 7. Effects 8 Variations

[0011] [1. Cartridge Configuration] Figure 1 is an exploded perspective view showing an example of the configuration of a magnetic tape cartridge 10 (hereinafter simply referred to as "cartridge 10") according to one embodiment of the present disclosure. Figure 1A is an exploded side cross-sectional view of the cartridge 10 according to one embodiment of the present disclosure. Figure 2 is a plan view showing an example of the configuration of the bottom side of the cartridge 10 according to one embodiment of the present disclosure. The cartridge 10 is a single-reel type cartridge and comprises a reel 13 on which a magnetic tape MT as a tape-shaped magnetic recording medium is wound inside a cartridge case 12, a reel lock 14 and a reel spring 15 for locking the rotation of the reel 13, a spider 16 for releasing 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, a door spring 18 for biasing the sliding door 17 to the closed position of the tape outlet 12C, a write protect 19 for preventing accidental erasure, a cartridge memory 11, a metal plate 22, and a leaf spring 23.

[0012] The cartridge case 12 consists of a lower shell 12A and an upper shell 12B. An opening 12D is provided in the center of the lower shell 12A. The tape exit 12C is provided spanning the lower shell 12A and the upper shell 12B. A leader tape LT is connected to the outer edge of the magnetic tape MT. A leader pin 20 is provided at the tip of the leader tape LT.

[0013] The cartridge 10 has a first main surface, a second main surface opposite to the first surface, and a side surface located between the edges of the first and second surfaces. The first and second main surfaces are approximately square in shape. The first main surface is the surface on which an opening 12D is provided for chucking the reel 13 by the spindle of the drive (recording and playback device). In the following description of the cartridge 10, the side of the cartridge 10 with the first main surface will be referred to as the bottom, and the side of the cartridge 10 with the second main surface will be referred to as the top.

[0014] The reel hub 13A is provided with a reel lock mechanism to prevent the tape reel from rotating when the tape cartridge 1 is not in use. As shown in Figure 1A, the reel lock mechanism includes a plurality of gear-forming walls 134 erected on the upper surface of the bottom wall 133 of the reel hub 13A, a reel lock 14 having engaging teeth (not shown) that mesh with the gear portion 134A formed on the upper surface of the gear-forming walls 134, a spider 16 for releasing the engagement between the gear-forming walls 134 and the reel lock 14, and a reel spring 15 provided between the inner surface of the upper shell 12B and the upper surface of the reel lock 14. The reel spring 15 is a coil spring and biases the reel 13 toward the lower shell 12A via the reel lock 14.

[0015] The gear-forming wall 134 has an arc shape and is formed at three equally spaced locations on the same circumference around the axis of the reel hub 13A on the upper surface of the bottom wall 133 of the reel hub 13A. The engaging teeth 14A of the reel lock 14 that face the gear portion 134A of the gear-forming wall 134 are formed in an annular shape on the lower surface of the reel lock 14 and are constantly biased in the direction of engaging with the gear portion 134A by the reel spring 15. A fitting projection 14C is formed on the upper surface of the reel lock 14, and a fitting recess 12E that fits into this fitting projection 14C is formed in the approximate center of the inner surface of the upper shell 2.

[0016] The spider 16 has a roughly triangular shape and is positioned between the bottom wall 133 of the reel hub 13A and the reel lock 14. Three legs 16A protrude downward from near the vertices of each of the roughly triangular points on the underside of the spider 16. When the cartridge is not in use, these legs are positioned between the gears of the chucking gear through through holes formed in the bottom wall 133 of the reel hub 13A.

[0017] Each leg 16A of the spider 16 is pressed upward by the reel rotation drive shaft of the tape drive device, which engages with the reel gear (reel gear 133A described later), when the cartridge is in use, thereby moving the reel lock 14 to the unlocked position against the biasing force of the reel spring 15. The spider is configured to rotate together with the tape reel 5 with respect to the reel lock 14. A support surface 16B is provided on the upper surface of the spider 16 approximately in the center, which supports the arc-shaped sliding contact portion 14B that is formed to protrude from the lower surface of the reel lock 14 approximately in the center.

[0018] Cartridge 10 may be a magnetic tape cartridge conforming to the LTO (Linear Tape-Open) standard, or it may be a magnetic tape cartridge conforming to a standard other than the LTO standard.

[0019] [2 Spindle Configuration] Figure 3A is a plan view showing an example of the configuration of the spindle 101. Figure 3B is an exploded cross-sectional view showing an example of the configuration of the spindle 101. The spindle 101 is a typical drive component. The spindle 101 is configured to chucking a cartridge 10 having the above configuration. The spindle 101 comprises a disc portion 102, a shaft 103, a magnet 104, a magnet fixing jig 105, and a screw 106. The shaft 103 is supported by a bearing 107.

[0020] The disc portion 102 has a drive gear 102A. The drive gear 102A is provided on the upper surface of the disc portion 102. In a plan view from a direction perpendicular to the upper surface of the disc portion 102, the drive gear 102A has an annular shape centered on the rotation axis of the disc portion 102.

[0021] The shaft 103 rotates the disc portion 102. The disc portion 102 is fixed to the upper end of the shaft 103. The shaft 103 is electrically conductive. The shaft 103 is made of, for example, metal. The shaft 103 is grounded. The shaft 103 may also be grounded via a bearing.

[0022] The magnet 104 is located inside the drive gear 102A in a plan view from a direction perpendicular to the upper surface of the disc portion 102. The magnet 104 has a disc shape with a through hole in the center.

[0023] The magnet fixing jig 105 is for fixing the magnet 104 to a specified position on the upper surface of the disc portion 102. The magnet fixing jig 105 has a hole portion 105A. The magnet fixing jig 105 may be made of metal or synthetic resin.

[0024] The screw 106 is for fixing the magnet fixing jig 105 to the upper surface of the disc portion 102. The screw 106 is fitted into a screw hole (not shown) provided at the upper end of the shaft 103 via the hole 105A of the magnet fixing jig. The screw 106 is conductive, and there is electrical contact between the screw 106 and the shaft 103. The screw 106 is made of, for example, metal. The screw 106 is an example of a fixing member (conductive part) provided on the spindle 101. In a plan view from a direction perpendicular to the upper surface of the disc portion 102, the screw 106 is provided on the axis of rotation of the disc portion 102.

[0025] [3 Reel Configuration] Figure 4 is a cross-sectional view showing an example of the configuration of reel 13. Figure 5 is a plan view showing an enlarged portion of Figure 2. Reel 13 is for winding magnetic tape MT. Reel 13 comprises a reel hub 13A and a flange 132. Reel 13 is conductive. Specifically, only the reel hub 13A may be conductive, or both the reel hub 13A and flange 13B may be conductive.

[0026] The upper limit of the surface resistivity of reel 13 is preferably 1 × 10⁻⁶. 6 It is less than or equal to Ω / sq. The lower limit of the surface resistivity of reel 13 is preferably 1 × 10⁻⁶. 4 The surface resistivity is Ω / sq. or greater. In this embodiment, the surface resistivity of the reel 13 refers to the surface resistance of the reel hub 13A. The upper limit of the surface resistivity of the reel 13 is 1 × 10⁻⁶. 6 If the surface resistivity is Ω / sq. or less, a conductive bus can be formed from the magnetic tape MT to the leaf spring 23 during operation. Therefore, charging of the magnetic tape MT during operation can be suppressed. If the surface resistivity of the reel 13 is too low, when a discharge occurs on the magnetic surface side within the drive, an excessive current may flow from the magnetic surface to the elements of the recording / playback head, which may lead to element destruction. Therefore, it is preferable to set a lower limit, which should be 1 × 10⁻⁶. 4 It is preferable that the density is Ω / sq. or greater.

[0027] The surface resistivity of the reel 13 is measured as follows: The surface resistivity of the surface of the flange 132 facing the flange 13B is measured in accordance with ASTM D257, and this measurement result is taken as the surface resistivity of the reel 13.

[0028] Reel 13 comprises a synthetic resin and a conductive material. Reel 13 may further contain known additives such as antioxidants and flame retardants. The synthetic resin includes, for example, acrylonitrile-butadiene-styrene copolymer resin (ABS resin) or polyacetal (POM) resin.

[0029] The conductive material includes, for example, at least one of a conductive filler and a conductive polymer. The conductive material is preferably dispersed in a synthetic resin. Examples of conductive filler shapes include, but are not limited to, spherical, ellipsoidal, needle-shaped, plate-shaped, flake-shaped, tubular, wire-shaped, rod-shaped, fibrous, and irregular shapes. Only one type of conductive filler shape may be used, or two or more types of conductive fillers may be used in combination.

[0030] The conductive filler includes, for example, at least one of the following: carbon-based fillers, metal-based fillers, metal oxide-based fillers, and metal-coated fillers. Here, metal is defined as including metalloids.

[0031] Carbon-based fillers include, for example, at least one of the following: carbon black (e.g., Ketjenblack, acetylene black, etc.), porous carbon, carbon fibers (e.g., PAN-based, pitch-based, etc.), carbon nanofibers, fullerenes, graphene, vapor-grown carbon fibers (VGCF), carbon nanotubes (e.g., SWCNTs, MWCNTs, etc.), carbon microcoils, and carbon nanohorns.

[0032] Metallic fillers include, for example, at least one of the following: copper, silver, gold, platinum, palladium, nickel, tin, cobalt, rhodium, iridium, iron, ruthenium, osmium, manganese, molybdenum, tungsten, niobium, tantalum, titanium, bismuth, antimony, and lead.

[0033] Metal oxide fillers include, for example, indium tin oxide (ITO), zinc oxide, indium oxide, antimony-added tin oxide, fluorine-added tin oxide, aluminum-added zinc oxide, gallium-added zinc oxide, silicon-added zinc oxide, zinc oxide-tin oxide, indium oxide-tin oxide, or zinc oxide-indium oxide-magnesium oxide.

[0034] Metal-coated fillers are those in which a base filler is coated with a metal. Examples of base fillers include mica, glass beads, glass fibers, carbon fibers, calcium carbonate, zinc oxide, or titanium oxide. The metal coating the base filler includes, for example, at least one of Ni and Al.

[0035] The conductive polymer includes, for example, at least one of polyethylenedioxythiophene / polystyrene sulfonic acid (PEDOT / PSS), polyaniline, polyacetylene, and polypyrrole.

[0036] (Reel hub) The reel hub 13A comprises a hub 131, a flange 132, and a bottom wall 133. The hub 131 is for winding the magnetic tape MT. One end of the magnetic tape MT is fixed to the hub 131. The hub 131 has a cylindrical shape with one end closed. The hub 131 and the flange 132 may have a one-piece structure integrally molded by injection molding or the like.

[0037] A bottom wall 133 is provided at the lower end of the hub 131. The bottom wall 133 closes the lower end of the hub 131. The bottom wall 133 has a reel gear 133A. The reel gear 133A meshes with the drive gear 102A on the drive side when the cartridge 10 is chucking by the spindle 101. The reel gear 133A is provided along the outer circumference of the lower surface of the bottom wall 133. The reel gear 133A has an annular shape centered on the rotation axis of the reel hub 13A. The reel gear 133A is positioned to face the opening 12D on the bottom surface of the cartridge case 12.

[0038] (Flange) Flanges 13B and 132 cover both ends of the magnetic tape MT wound around the hub 131 in the width direction. Flanges 13B and 132 are supported on the hub 131 such that their main surfaces face each other, separated by a specified distance. Flange 13B protrudes radially from the upper end of the outer circumferential surface of the hub 131. Flange 132 protrudes radially from the lower end of the outer circumferential surface of the hub 131. Flanges 13B and 132 have a disc shape. Flange 13B is fixed to the upper end of the outer circumferential surface of the hub 131 by adhesive or welding (e.g., ultrasonic welding). Flange 132 is integrally molded with the hub 131 as described above.

[0039] (metal plate) The metal plate 22 is attracted to the magnet 104 by magnetic force when the cartridge 10 is chucking the spindle 101. The metal plate 22 has an annular shape. In a plan view from a direction perpendicular to the lower surface of the bottom wall 133, the metal plate 22 is located on the inner circumference side of the reel gear 2E. The metal plate 22 is positioned together with the reel gear 2E so as to face the opening 12D on the bottom surface of the cartridge case 12. The metal plate 22 has a plurality of holes 22A. A plurality of protrusions 133B are provided on the lower surface of the bottom wall 133. Each of the multiple protrusions 133B is provided at a position corresponding to each hole 22A. The multiple protrusions 133B are integrally molded to the bottom wall 133, for example by injection molding. Each of the multiple protrusions 133B is inserted into each of the multiple holes 22A. In this way, the metal plate 22 is fixed to the lower surface of the bottom wall 133. The reel hub 13A and the metal plate 22 may be integrally molded by insert molding.

[0040] (Leaf spring) Figure 6 is a cross-sectional view along the line VI-VI in Figure 5. Figure 7A is a plan view showing an example of the configuration of the leaf spring 23. Figure 7B is a cross-sectional view along the line VIIB-VIIB in Figure 7A. The leaf spring 23 is configured to bias a screw 106 provided on the spindle 101 when the reel gear 133A is meshed with the drive gear 102A. The leaf spring 23 is an example of an elastic member having conductivity. The leaf spring 23 is provided in an opening in the metal plate 22 in a plan view from a direction perpendicular to the lower surface of the bottom wall 133. The leaf spring 23 is provided on the rotation axis of the reel 13, that is, on the rotation axis of the reel gear 133A.

[0041] The leaf spring 23 comprises a ring portion 23A and a protruding portion 23B. The ring portion 23A is fixed to the lower surface of the bottom wall 133. The ring portion 23A has a plurality of holes 23C. The lower surface of the bottom wall 133 is provided with a plurality of protrusions 133C. Each of the multiple protrusions 133C is provided at a position corresponding to each hole 23C. The multiple protrusions 133C are integrally molded to the bottom wall 133, for example, by injection molding. Each of the multiple protrusions 133C is inserted into each of the multiple holes 23C. In this way, the leaf spring 23 is fixed to the lower surface of the bottom wall 133. The top of each protrusion 133C may be crimped.

[0042] The protruding portion 23B is biased by the screw 106 provided on the spindle 101 and deflects when the reel gear 133A engages with the drive gear 102A. The protruding portion 23B extends downward from a part of the inner circumference of the ring portion 23A, that is, away from the lower surface of the bottom wall 133. In other words, when the leaf spring 23 is provided on the lower surface of the bottom wall 133, the protruding portion 23B protrudes relative to the lower surface of the bottom wall 133. In a plan view from a direction perpendicular to the lower surface of the bottom wall 133, the leaf spring 23 is located inside the inner circumference of the ring portion 23A.

[0043] [4. Cartridge Memory Configuration] The cartridge memory 11 is located near one corner of the cartridge 10. When the cartridge 10 is loaded into the drive, the cartridge memory 11 faces the drive's reader / writer. The cartridge memory 11 communicates with the drive, specifically the reader / writer, using a wireless communication standard compliant with the LTO standard.

[0044] Figure 8 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 the reader / writer according to a specified communication standard, a rectifier / power supply circuit 32 that generates power by generating and rectifying electricity using induced electromotive force from radio waves received by the antenna coil 31, a clock circuit 33 that generates a clock using induced electromotive force from radio waves received by the antenna coil 31, a detection / modulation circuit 34 that detects the radio waves received by the antenna coil 31 and modulates the signal transmitted by the antenna coil 31, a controller (control unit) 35 composed of logic circuits, etc., that distinguishes commands and data from the digital signals extracted from the detection / modulation circuit 34 and processes them, and a memory (storage unit) 36 that stores information. The cartridge memory 11 also includes a capacitor 37 connected in parallel with the antenna coil 31, and the antenna coil 31 and the capacitor 37 constitute a resonant circuit.

[0045] Memory 36 stores information related to the cartridge 10. Memory 36 is non-volatile memory (NVM). The storage capacity of memory 36 is preferably about 32KB or more.

[0046] The memory 36 has a first storage area 36A and a second storage area 36B. The first storage area 36A corresponds to the storage area of ​​a cartridge memory of a magnetic tape standard prior to a specified generation (e.g., an LTO standard prior to LTO8), and is an area for storing information compliant with a magnetic tape standard prior to a specified generation (e.g., an LTO standard prior to LTO8). The information compliant with a magnetic tape standard prior to a specified generation (e.g., an LTO standard prior to LTO8) includes at least one of the following: manufacturing information of the cartridge 10 (e.g., a unique number of the cartridge 10, etc.) and the usage history of the cartridge 10 (e.g., the number of times the magnetic tape MT has been pulled out (Thread Count), etc.).

[0047] The second storage area 36B corresponds to an extended storage area for the cartridge memory of a magnetic tape standard prior to the specified generation (e.g., LTO standards prior to LTO8). The second storage area 36B is an area for storing additional information. Here, additional information means, for example, information related to the cartridge 10 that is not specified in the magnetic tape standard prior to the specified generation (e.g., LTO standards prior to LTO8). The additional information includes, for example, at least one selected from the group consisting of tension adjustment information, management ledger data, index information, and thumbnail information.

[0048] Tension adjustment information is information for adjusting the tension applied to the magnetic tape MT in the longitudinal direction. This information includes, for example, at least one type of information selected from the group consisting of information obtained by intermittently measuring the width between servo bands in the longitudinal direction of the magnetic tape MT, drive tension information, and drive temperature and humidity information. This information may also be managed in conjunction with information regarding the usage status of the cartridge 10. It is preferable that the tension adjustment information is acquired during or before data recording on the magnetic tape MT. Drive tension information refers to information regarding the tension applied to the magnetic tape MT in the longitudinal direction.

[0049] Management ledger data includes data containing at least one of the following: capacity, creation date, editing date, and storage location of data files recorded on magnetic tape MT. Index information is metadata used to search the contents of data files. Thumbnail information is a thumbnail of a video or still image stored on magnetic tape MT.

[0050] The memory 36 may have multiple banks. In this case, a first storage area 36A may be formed by some of the multiple banks, and a second storage area 36B may be formed by the remaining banks.

[0051] The antenna coil 31 induces an induced voltage through electromagnetic induction. The controller 35 communicates with the drive via the antenna coil 31 using a specified communication standard. Specifically, it performs tasks such as mutual authentication, sending and receiving commands, or exchanging data.

[0052] The controller 35 stores information received from the drive via the antenna coil 31 in the memory 36. For example, it stores tension adjustment information received from the drive via the antenna coil 31 in the second storage area 36B of the memory 36. The controller 35 reads information from the memory 36 in response to a request from the drive and transmits it to the drive via the antenna coil 31. For example, in response to a request from the drive, it reads tension adjustment information from the second storage area 36B of the memory 36 and transmits it to the drive via the antenna coil 31.

[0053] [3. Magnetic Tape Configuration] Figure 9 is a cross-sectional view showing an example of the configuration of a magnetic tape MT. The magnetic tape MT comprises a long base body 41, a base layer 42 provided on one main surface (first main surface) of the base body 41, a magnetic layer 43 provided on the base layer 42, and a back layer 44 provided on the other main surface (second main surface) of the base body 41. The base layer 42 and the back layer 44 are provided as needed and may be omitted. The magnetic tape MT may be a vertical recording type magnetic recording medium or a longitudinal recording type magnetic recording medium. From the viewpoint of improving runability, it is preferable that the magnetic tape MT contains a lubricant. The lubricant may be contained in at least one of the base layer 42 and the magnetic layer 43.

[0054] The magnetic tape MT may conform to the LTO standard or to a standard other than the LTO standard. The width of the magnetic tape MT may be 1 / 2 inch or 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 have a configuration that allows the width of the magnetic tape MT to be kept constant or nearly constant by adjusting the tension applied in the longitudinal direction of the magnetic tape MT during running using a drive. A TMR element is preferably used for playback of the magnetic tape MT.

[0055] Magnetic tape MT has a long length and is traveled in the longitudinal direction during recording and playback. Magnetic tape MT is preferably used in a drive equipped with a ring-type head as the recording head. Magnetic tape MT is preferably used in a drive configured to record data with a data track width of 1500 nm or less or 1000 nm or less.

[0056] (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-like structure. The upper limit of the average thickness of the substrate 41 is, for example, 4.4 μm or less, preferably 4.2 μm or less, more preferably 4.0 μm or less, even more preferably 3.8 μm or less, particularly preferably 3.6 μm or less, and most preferably 3.4 μm or less. When the upper limit of the average thickness of the substrate 41 is 4.4 μm or less, the recording capacity that can be recorded in one data cartridge can be increased compared to general magnetic tape. The lower limit of the average thickness of the substrate 41 is preferably 3 μm or more, more preferably 3.2 μm or more. When the lower limit of the average thickness of the substrate 41 is 3 μm or more, a decrease in the strength of the substrate 41 can be suppressed.

[0057] The average thickness of the substrate 41 is determined as follows. First, a magnetic tape MT is prepared and cut to a length of 250 mm to create a sample. Next, layers other than the substrate 41 of the sample (i.e., the base layer 42, magnetic layer 43, and back layer 44) are removed with a solvent such as MEK (methyl ethyl ketone) or dilute hydrochloric acid. Then, using a Mitutoyo laser hologage (LGH-110C) as the measuring device, the thickness of the sample (substrate 41) is measured at five points, and these measurements are simply averaged (arithmetic mean) to calculate the average thickness of the substrate 41. The measurement positions are to be randomly selected from the sample.

[0058] The substrate 41 includes, for example, at least one of polyesters, polyolefins, cellulose derivatives, vinyl resins, and other polymer resins. If the substrate 41 includes two or more of the above materials, those two or more materials may be mixed, copolymerized, or laminated.

[0059] The base material 41 preferably contains polyesters among the polymer resins mentioned above. By including polyesters in the base material 41, the Young's modulus in the longitudinal direction of the base material 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 drive, it is particularly easy to control the width of the magnetic tape MT to be constant or nearly constant. The method for measuring the Young's modulus in the longitudinal direction of the base material 41 will be described later.

[0060] Polyesters include, for example, at least one of PET (polyethylene terephthalate), PEN (polyethylene naphthalate), PBT (polybutylene terephthalate), PBN (polybutylene naphthalate), PCT (polycyclohexylene dimethylene terephthalate), PEB (polyethylene-p-oxybenzoate), and polyethylene bisphenoxycarboxylate. If the base material 41 contains two or more polyesters, these two or more polyesters may be mixed, copolymerized, or laminated. At least one of the ends and side chains of the polyesters may be modified.

[0061] The presence of polyesters in the substrate 41 can be confirmed, for example, as follows: First, a magnetic tape MT is prepared, similar to the method for measuring the average thickness of the substrate 41. This tape is cut to a length of 250 mm to create a sample, and then layers other than the substrate 41 are removed from the sample. Next, the IR spectrum of the sample (substrate 41) is obtained by infrared absorption spectroscopy (IR). Based on this IR spectrum, it can be confirmed that the substrate 41 contains polyesters.

[0062] Polyolefins include, for example, at least one of PE (polyethylene) and PP (polypropylene). Cellulose derivatives include, for example, at least one of cellulose diacetate, cellulose triacetate, CAB (cellulose acetate butyrate), and CAP (cellulose acetate propionate). Vinyl resins include, for example, at least one of PVC (polyvinyl chloride) and PVDC (polyvinylidene chloride).

[0063] Other polymer resins include, for example, at least one of PA (polyamide, nylon), aromatic PA (aromatic polyamide, aramid), PI (polyimide), aromatic PI (aromatic polyimide), PAI (polyamide-imide), aromatic PAI (aromatic polyamide-imide), PBO (polybenzoxazole, e.g., Zylon®), polyether, PEK (polyether ketone), PEEK (polyether ether ketone), polyether ester, PES (polyethersulfone), PEI (polyetherimide), PSF (polysulfone), PPS (polyphenylene sulfide), PC (polycarbonate), PAR (polyarylate), and PU (polyurethane).

[0064] The substrate 41 may be biaxially stretched in the longitudinal and width directions. Preferably, the polymer resin contained in the substrate 41 is oriented obliquely to the width direction of the substrate 41.

[0065] (magnetic layer) The magnetic layer 43 is a recording layer for recording signals by a magnetization pattern. The magnetic layer 43 may be a vertical recording layer or a longitudinal recording layer. The magnetic layer 43 may include, for example, magnetic powder, a binder, and carbon. The magnetic layer 43 may further include, if necessary, at least one additive from among lubricants, antistatic agents, abrasives, hardeners, rust inhibitors, and non-magnetic reinforcing particles.

[0066] As shown in Figure 9, the magnetic layer 43 has numerous protrusions 43A made of carbon that protrude from the magnetic surface on its magnetic surface. The magnetic layer 43 may also have numerous protrusions 43A made of an abrasive (e.g., alumina) that protrude from the magnetic surface on its magnetic surface. Hereinafter, protrusions 43A made of carbon that protrude from the magnetic surface will be referred to as "carbon protrusions 43A", and protrusions 43A made of alumina that protrude from the magnetic surface will be referred to as "alumina protrusions 43A".

[0067] As shown in FIG. 10, 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 band SB is for guiding the head 56 (specifically, servo read heads 56A and 56B) during data recording or reproduction. A servo pattern (servo signal) for tracking control of the head 56 is written in advance in the servo band SB. User data is recorded in the data band DB.

[0068] The total area S of the plurality of servo bands SB with respect to the area S of the magnetic surface SB Ratio R S (=(S SB / S) × 100) The upper limit value is preferably 4.0% or less, more preferably 3.0% or less, and even more preferably 2.0% or less from the viewpoint of ensuring a high recording capacity. On the other hand, the total area S of the plurality of servo bands SB with respect to the area S of the surface of the magnetic layer 43 SB Ratio R S The lower limit value of is preferably 0.8% or more from the viewpoint of ensuring 5 or more servo bands SB.

[0069] The total area S of the plurality of servo bands SB with respect to the entire surface area S of the magnetic layer 43 SB Ratio R S Is obtained as follows. The magnetic tape MT is developed using a ferricolloid developer (manufactured by Sigma Chemical Co., Ltd., Sigma marker Q), and then the developed magnetic tape MT is observed with an optical microscope to measure the servo band width W SB And the number of servo bands SB. Next, the ratio R S Is obtained from the following formula. Ratio R S [%]=(((Servo band width W SB ) × (Number of servo bands SB)) / (Width of magnetic tape MT)) × 100

[0070] The number of servo bands SB is, for example, 5 + 4n (where n is a non-negative integer) or more. Preferably, the number of servo bands SB is 5 or more, more preferably 9 or more. When the number of servo bands SB is 5 or more, the influence of changes in the width direction of the magnetic tape MT on the servo signal is suppressed, and more stable recording and playback characteristics with fewer off-tracks can be ensured. There is no particular upper limit to the number of servo bands SB, but for example, it is 33 or less.

[0071] The number of servo bands SB is the ratio R mentioned above. S It can be calculated in the same way as the calculation method for [another calculation].

[0072] Servo bandwidth W SB The upper limit of the servo bandwidth W is preferably 95 μm or less, more preferably 60 μm or less, and even more preferably 30 μm or less, from the viewpoint of ensuring high recording capacity. SB The lower limit is preferably 10 μm or more. Servo bandwidth W less than 10 μm SB Head 56, which is capable of reading the servo signals, is difficult to manufacture.

[0073] Servo bandwidth W SB The width is the ratio R mentioned above. S It can be calculated in the same way as the calculation method for [another calculation].

[0074] As shown in Figure 11, the magnetic layer 43 is configured to form multiple data tracks Tk in the data band DB. 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, from the viewpoint of improving track recording density and ensuring high recording capacity. The lower limit of the data track width W is preferably 20 nm or more, considering the size of the magnetic particles.

[0075] The magnetic layer 43 is configured to record data such that, from the viewpoint of ensuring high recording capacity, the minimum value L of the magnetization reversal distance is preferably 40 nm or less, more preferably 36 nm or less, and even more preferably 32 nm or less. The lower limit of the minimum value L of the magnetization reversal distance is preferably 20 nm or more, considering the size of the magnetic particles.

[0076] The data track width W is determined as follows: A magnetic tape MT with data recorded across its entire surface is prepared, and the data recording pattern of the data band DB portion of the magnetic layer 43 is observed using a magnetic force microscope (MFM) to obtain an MFM image. A Digital Instruments Dimension3100 and its analysis software are used as the MFM. The measurement area of ​​the MFM image is set to 10 μm × 10 μm, and this 10 μm × 10 μm measurement area is divided into 512 × 512 (= 262,144) measurement points. Measurements are performed using MFM on three different 10 μm × 10 μm measurement areas, thus obtaining three MFM images. From the three obtained MFM images, the track width is measured at 10 locations using the analysis software included with the Dimension3100, and the average value (simple average) is taken. This average value is the data track width W. The measurement conditions for the above MFM were: sweep speed: 1 Hz, chip used: MFMR-20, lift height: 20 nm, and correction: Flatten order 3.

[0077] The minimum value L of the magnetization reversal distance is determined as follows: A magnetic tape MT with data recorded across its entire surface is prepared, and the data recording pattern of the data band DB portion of the magnetic layer 43 is observed using a magnetic force microscope (MFM) to obtain an MFM image. A Digital Instruments Dimension3100 and its analysis software are used as the MFM. The measurement area of ​​the MFM image is set to 2 μm × 2 μm, and this 2 μm × 2 μm measurement area is divided into 512 × 512 (= 262,144) measurement points. Measurements are performed using MFM on three different 2 μm × 2 μm measurement areas, i.e., three MFM images are obtained. Fifty inter-bit distances are measured from the two-dimensional relief chart of the recording pattern of the obtained MFM image. These inter-bit distance measurements are performed using the analysis software included with the Dimension3100. The value that is approximately the greatest common divisor of the 50 measured inter-bit distances is taken as the minimum value L of the magnetization reversal distance. The measurement conditions were: sweep speed: 1 Hz, chip used: MFMR-20, lift height: 20 nm, correction: Flatten order 3.

[0078] The servo pattern is a magnetized region formed by magnetizing a specific region of the magnetic layer 43 in a specific direction using a servo light head during magnetic tape manufacturing. The region of the servo band SB in which the servo pattern is not formed (hereinafter referred to as the "non-pattern region") may be a magnetized region in which the magnetic layer 43 is magnetized, or it may be a non-magnetized region in which the magnetic layer 43 is not magnetized. If the non-pattern region is a magnetized region, the servo pattern formation region and the non-pattern region are magnetized in different directions (for example, opposite directions).

[0079] In the LTO standard, the servo band SB has a servo pattern formed on it consisting of multiple servo stripes (linear magnetized regions) 113 that are inclined with respect to the width direction of the magnetic tape MT, as shown in Figure 12.

[0080] The servo band SB includes multiple servo frames 110. Each servo frame 110 consists of 18 servo stripes 113. Specifically, each servo frame 110 consists of a servo subframe 1 (111) and a servo subframe 2 (112).

[0081] The servo subframe 1(111) consists of an A-burst 111A and a B-burst 111B. The B-burst 111B is positioned adjacent to the A-burst 111A. The A-burst 111A has five servo stripes 113 that are inclined at a predetermined angle φ with respect to the width direction of the magnetic tape MT and are formed at predetermined intervals. In Figure 12, these five servo stripes 113 are labeled A1, A2, A3, A4, and A5, indicating their direction from the EOT (End Of Tape) to the BOT (Beginning Of Tape) of the magnetic tape MT. The B-burst 111B, similar to the A-burst 111A, has five servo pulses 63 that are inclined at a predetermined angle φ with respect to the width direction of the magnetic tape MT and are formed at predetermined intervals. In Figure 12, these five servo stripes 113 are labeled B1, B2, B3, B4, and B5, indicating their direction from the EOT to the BOT of the magnetic tape MT. The servo stripe 113 of the B-burst 111B is tilted in the opposite direction to the servo stripe 113 of the A-burst 111A. In other words, the servo stripe 113 of the A-burst 111A and the servo stripe 113 of the B-burst 111B are arranged in a V-shape.

[0082] The servo subframe 2 (112) consists of a C-burst 112C and a D-burst 112D. The D-burst 112D is positioned adjacent to the C-burst 112C. The C-burst 112C has four servo stripes 113 that are inclined at a predetermined angle φ with respect to the tape width direction and are formed at predetermined intervals. In Figure 12, these four servo stripes 113 are labeled C1, C2, C3, and C4 from the EOT to the BOT of the magnetic tape MT. The D-burst 112D, like the C-burst 112C, has four servo pulses 63 that are inclined at a predetermined angle φ with respect to the tape width direction and are formed at predetermined intervals. In Figure 12, these four servo stripes 113 are labeled D1, D2, D3, and D4 from the EOT to the BOT of the magnetic tape MT. The servo stripe 113 of the D-burst 112D is tilted in the opposite direction to the servo stripe 113 of the C-burst 112C. In other words, the servo stripe 113 of the C-burst 112C and the servo stripe 113 of the D-burst 112D are arranged in a V-shape.

[0083] The predetermined angle φ of the servo stripe 113 in bursts A 111A, B 111B, C 112C, and D 112D can be, for example, 11° to 40°, preferably 11° to 36°, more preferably 11° to 25°, and even more preferably 17° to 25°.

[0084] By reading the servo band SB with head 56, information for obtaining the tape speed and the longitudinal position of head 56 can be obtained. The tape speed is calculated from the time intervals between four timing signals (A1-C1, A2-C2, A3-C3, A4-C4). The position of head 56 is calculated from the time intervals between the aforementioned four timing signals and another four timing signals (A1-B1, A2-B2, A3-B3, A4-B4). The servo pattern may also be a shape containing two parallel lines.

[0085] As shown in Figure 12, it is preferable that the servo pattern (i.e., the multiple servo stripes 113) is arranged linearly in the longitudinal direction of the magnetic tape MT. In other words, it is preferable that the servo band SB is linear in the longitudinal direction of the magnetic tape MT.

[0086] The upper limit of the average thickness of the 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. When the upper limit of the average thickness of the magnetic layer 43 is 80 nm or less, the effect of the demagnetizing field can be reduced when a ring-type head is used as the recording head, thereby obtaining even better electromagnetic conversion characteristics.

[0087] The lower limit of the average thickness of the magnetic layer 43 is preferably 35 nm or more. When the lower limit of the average thickness of the magnetic layer 43 is 35 nm or more, output can be secured when an MR type head is used as the playback head, and thus even better electromagnetic conversion characteristics can be obtained.

[0088] 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 samples are prepared by cutting the magnetic tape MT at three locations at 10m, 30m, and 50m in the longitudinal direction (specifically, from one end on the leader tape LT side to the other end on the opposite side) from the connection portion 21 between the magnetic tape MT and the leader tape LT. Next, each sample is processed by FIB or the like to create thin sections. When using the FIB method, a carbon layer and a tungsten layer are formed as protective films as a pretreatment before observing the TEM image of the cross-section described later. The carbon layer is formed on the surface of the magnetic layer 43 side and the surface of the back layer 44 side of the magnetic tape MT by vapor deposition, and the tungsten layer is further formed on the surface of the magnetic layer 43 side by vapor deposition or sputtering. This thinning is performed along the length direction (longitudinal direction) of the magnetic tape MT. That is, this thinning creates a cross-section parallel to both the longitudinal and thickness directions of the magnetic tape MT.

[0089] The cross-sections of each thinned sample obtained are observed using a transmission electron microscope (TEM) under the following conditions to obtain TEM images of each thinned sample. The magnification and acceleration voltage may be adjusted as appropriate depending on the type of instrument. Equipment: TEM (Hitachi H9000NAR) Acceleration voltage: 300kV Magnification: 100,000x

[0090] Next, the TEM images of each thinned sample are used to measure the thickness of the magnetic layer 43 at 10 points on each thinned sample. As mentioned above, thinning is performed along the longitudinal direction of the magnetic tape MT, so the 10 measurement points on each thinned sample are aligned along the longitudinal direction of the magnetic tape MT. The average value obtained by simply averaging (arithmetic mean) the measured values ​​of each thinned sample (a total of 30 points of magnetic layer 43 thickness) is defined as the average thickness [nm] of the magnetic layer 43. The positions where the above measurements are performed are randomly selected from the test specimen.

[0091] (magnetic powder) The magnetic powder contains a plurality of magnetic particles. The magnetic particles are, for example, particles containing metal oxides (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 is preferentially crystallinely oriented in the direction perpendicular to the magnetic tape MT. In this specification, the direction perpendicular to the magnetic tape MT (thickness direction) means the thickness direction of the magnetic tape MT in a planar state.

[0092] (Hexagonal ferrite particles) Hexagonal ferrite particles have a plate-like shape, such as a hexagonal plate, or a columnar shape, such as a hexagonal prism (provided that the thickness or height is smaller than the major axis of the plate surface or base surface). In this specification, hexagonal plate-like shape includes substantially hexagonal plate-like shape. Hexagonal ferrite preferably contains at least one of Ba, Sr, Pb, and Ca, more preferably at least one of Ba and Sr. Specifically, hexagonal ferrite may be, for example, barium ferrite or strontium ferrite. Barium ferrite may further contain at least one of Sr, Pb, and Ca in addition to Ba. Strontium ferrite may further contain at least one of Ba, Pb, and Ca in addition to Sr.

[0093] More specifically, hexagonal ferrite has the general formula MFe 12 O 19 It has an average composition represented by the formula above. However, M is, for example, at least one metal from among Ba, Sr, Pb, and Ca, preferably at least one metal from among 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. Alternatively, M may be a combination of Sr and one or more metals selected from the group consisting of Ba, Pb, and Ca. In the above general formula, a portion of Fe may be substituted with other metallic elements.

[0094] When the magnetic powder contains hexagonal ferrite particle powder, 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 magnetic tapes (MT) with high recording density. 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.

[0095] When the magnetic powder contains hexagonal ferrite particle powder, the average aspect ratio of the magnetic powder is preferably 1.0 to 3.0, more preferably 1.5 to 2.8, and even more preferably 1.8 to 2.7. When the average aspect ratio of the magnetic 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.

[0096] When the magnetic powder contains hexagonal ferrite particle powder, the average particle size and average aspect ratio of the magnetic powder are determined as follows. First, the magnetic tape MT to be measured is processed and thinned using the FIB method or the like. When using the FIB method, a carbon layer and a tungsten layer are formed as protective films as a pretreatment before observing the TEM image of the cross section described later. The carbon layer is formed on the surface of the magnetic layer 43 side and the surface of the back layer 44 side of the magnetic tape MT by vapor deposition, and the tungsten layer is further formed on the surface of the magnetic layer 43 side by vapor deposition or sputtering. This thinning is performed along the length direction (longitudinal direction) of the magnetic tape MT. That is, this thinning creates a cross section parallel to both the longitudinal and thickness directions of the magnetic tape MT.

[0097] The cross-section of the obtained thin section sample is observed using a transmission electron microscope (Hitachi High-Technologies Corporation H-9500) with an acceleration voltage of 200kV and a total magnification of 500,000x, ensuring that the entire magnetic layer 43 is included in the thickness direction of the magnetic layer 43, and a TEM image is taken. The TEM images are prepared in a number that allows for the extraction of 50 particles capable of measuring the plate diameter DB and plate thickness DA (see Figure 13) shown below.

[0098] In this specification, if the shape of the particles observed in the above TEM image is plate-like or columnar (however, the thickness or height is smaller than the major axis of the plate or base) as shown in Figure 13, the major axis of the plate or base of the particle shall be taken as the plate diameter DB. The thickness or height of the particles observed in the above TEM image shall be taken as the plate thickness DA. If the plate or base of the particles observed in the TEM image is hexagonal, the major axis refers to the longest diagonal distance. If the thickness or height of particles is not constant within a single particle, the thickness or height of the largest particle shall be taken as the plate thickness DA.

[0099] Next, 50 particles are selected from the captured TEM images based on the following criteria: Particles whose portion extends outside the field of view of the TEM image are not measured; only particles with clear outlines and existing in isolation are measured. If there is overlap between particles, those with clear boundaries and whose overall shape can be determined are measured as individual particles; however, particles with unclear boundaries and whose overall shape cannot be determined are not measured as their shape cannot be determined.

[0100] Figures 14 and 15 show examples of TEM images. In Figures 14 and 15, for example, the particles indicated by arrows a and d are selected because their particle thickness (thickness or height) DA can be clearly confirmed. The particle thickness DA of each of the 50 selected particles is measured. The average particle thickness DA obtained by simply averaging (arithmetic mean) these obtained particles is then calculated. ave We will find the average plate thickness DA. ave This is the average particle thickness. Next, the diameter DB of each magnetic powder is measured. To measure the particle diameter DB, 50 particles whose diameter DB can be clearly identified are selected from the TEM images taken. For example, in Figures 14 and 15, the particles indicated by arrows b and c are selected because their diameter DB can be clearly identified. The diameter DB of each of the 50 selected particles is measured. The average diameter DB obtained in this way is calculated by taking a simple average (arithmetic mean) of the resulting diameter DBs. ave We will find the average plate diameter DB. ave However, this is the average particle size. And the average plate thickness DAave and average plate diameter DB ave From the average aspect ratio of the particles (DB) ave / DA ave )

[0101] When the magnetic powder contains hexagonal ferrite particle powder, the average particle volume of the magnetic powder is preferably 500 nm. 3 More than 2500nm 3 More preferably 500nm 3 More than 1600nm 3 More preferably 500 nm 3 More than 1500nm 3 The following is particularly preferred: 600 nm 3 More than 1200nm 3 Below, most preferably 600nm 3 More than 1000nm 3 The following applies: The average particle volume of the magnetic powder is 2500 nm. 3 If the average particle size of the magnetic powder is less than 22 nm, the same effect can be obtained. On the other hand, if the average particle volume of the magnetic powder is 500 nm 3 With these settings, the same effect as when the average particle size of the magnetic powder is 13 nm or larger can be obtained.

[0102] The average particle volume of magnetic powder can be determined as follows. First, as described above regarding the method for calculating the average particle size of magnetic powder, the average plate thickness DA ave and average plate diameter DB ave Next, we calculate the average volume V of the magnetic powder using the following formula.

number

[0103] (ε-iron oxide particles) ε-iron oxide particles are hard magnetic particles that can obtain high coercivity even in fine particles. ε-iron oxide particles are either spherical or cubic in shape. In this specification, "spherical" includes substantially spherical particles, and "cubic" includes substantially cubic particles. Because ε-iron oxide particles have the shapes described above, 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. Therefore, the dispersibility of the magnetic powder can be improved, and even better electromagnetic conversion characteristics (e.g., SNR) can be obtained.

[0104] ε-iron oxide particles have a core-shell structure. Specifically, the ε-iron oxide particles comprise a core portion and a two-layer shell portion surrounding the core portion. The two-layer shell portion comprises a first shell portion provided on the core portion and a second shell portion provided on the first shell portion.

[0105] The core contains ε-iron oxide. The ε-iron oxide contained in the core is preferably composed mainly of ε-Fe2O3 crystals, and more preferably of single-phase ε-Fe2O3.

[0106] The first shell portion covers at least a part of the periphery of the core portion. Specifically, the first shell portion may partially cover the periphery of the core portion or 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.

[0107] The first shell portion is a so-called soft magnetic layer, and includes, for example, a soft magnetic material such as α-Fe, a Ni-Fe alloy, or a Fe-Si-Al alloy. α-Fe may be obtained by reducing ε-iron oxide contained in the core portion.

[0108] The second shell portion is an oxide film serving as an anti-oxidation layer. The second shell portion contains α-iron oxide, aluminum oxide, or silicon oxide. The α-iron oxide includes, for example, at least one of Fe3O4, Fe2O3, and FeO. If the first shell portion contains α-Fe (a soft magnetic material), the α-iron oxide may be obtained by oxidizing the α-Fe contained in the first shell portion.

[0109] Because the ε-iron oxide particles have a first shell portion as described above, the coercivity Hc of the core portion alone can be kept at a high value to ensure thermal stability, while the coercivity Hc of the ε-iron oxide particles (core-shell particles) as a whole can be adjusted to a coercivity Hc suitable for recording. Furthermore, because the ε-iron oxide particles have a second shell portion as described above, exposure of the ε-iron oxide particles to air during and before the manufacturing process of magnetic tape MT can suppress the deterioration of the properties of the ε-iron oxide particles due to rust etc. occurring on the particle surface. Therefore, the deterioration of the properties of magnetic tape MT can be suppressed.

[0110] The ε-iron oxide particles may have a single-layer shell. In this case, the shell has the same structure as the first shell. However, from the viewpoint of suppressing the deterioration of the properties of the ε-iron oxide particles, it is preferable that the ε-iron oxide particles have a two-layer shell, as described above.

[0111] The ε-iron oxide particles may contain additives instead of the core-shell structure described above, or they may have a core-shell structure and contain additives. In this case, a portion of the Fe in the ε-iron oxide particles is replaced by the additive. By including additives in the ε-iron oxide particles, the coercivity Hc of the ε-iron oxide particles as a whole can be adjusted to a coercivity Hc suitable for recording, thereby improving ease of recording. The additive is a metal element other than iron, preferably a trivalent metal element, more preferably at least one of Al, Ga, and In, and even more preferably at least one of Al and Ga.

[0112] Specifically, ε-iron oxide containing additives is ε-Fe 2-x Mx O3 crystal (where M is a metal element other than iron, preferably a trivalent metal element, more preferably at least one of Al, Ga, and In, and even more preferably at least one of Al and Ga. x is, for example, 0 <x<1である。)である。

[0113] 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 with a size of half the recording wavelength. Therefore, by setting the average particle size of the magnetic powder to half or less of the shortest recording wavelength, even better electromagnetic conversion characteristics (e.g., SNR) can be obtained. Accordingly, if 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 magnetic tape MT with high recording density (e.g., magnetic tape MT configured to record signals at the shortest recording wavelength of 40 nm or less). On the other hand, if 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.

[0114] 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, resistance applied to the magnetic powder when vertically oriented during the formation process of the magnetic layer 43 can be suppressed. Therefore, the vertical orientation of the magnetic powder can be improved.

[0115] When the magnetic powder contains ε-iron oxide particles, the average particle size and average aspect ratio of the magnetic powder are determined as follows. First, the magnetic tape MT to be measured is processed and thinned using the FIB (Focused Ion Beam) method or the like. When using the FIB method, a carbon layer and a tungsten layer are formed as protective layers as a pretreatment before observing the TEM image of the cross-section described later. The carbon layer is formed on the surface of the magnetic layer 43 and the back layer 44 of the magnetic tape MT by vapor deposition, and the tungsten layer is further formed on the surface of the magnetic layer 43 by vapor deposition or sputtering. Thinning is performed along the length direction (longitudinal direction) of the magnetic tape MT. That is, this thinning creates a cross-section parallel to both the longitudinal and thickness directions of the magnetic tape MT.

[0116] The cross-section of the obtained thin section sample is observed using a transmission electron microscope (Hitachi High-Technologies Corporation H-9500) with an acceleration voltage of 200kV and a total magnification of 500,000x, ensuring that the entire magnetic layer 43 is included in the thickness direction of the magnetic layer 43, and a TEM image is taken. Next, 50 particles whose particle shape can be clearly confirmed are selected from the taken TEM image, and the major axis length DL and minor axis length DS of each particle are measured. Here, the major axis length DL refers to the maximum distance between two parallel lines drawn from any angle tangent to the contour of each particle (the so-called maximum Ferret diameter). On the other hand, the minor axis length DS refers to the maximum length of the particle in the direction perpendicular to the major axis (DL) of the particle. Subsequently, the major axis length DL of the 50 measured particles is simply averaged (arithmetic mean) to obtain the average major axis length DL. ave We calculate the average major axis length DL obtained in this way. ave This is defined as the average particle size of the magnetic powder. Additionally, the short-axis length DS of the 50 measured particles is simply averaged (arithmetic mean) to obtain the average short-axis length DS. ave We calculate the average major axis length DL. ave and average short axis length DS ave From the average aspect ratio of the particles (DL ave / DS ave )

[0117] 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 More preferably 500nm 3 More than 3000nm 3 More preferably, 500nm 3 More than 2000nm 3 The following is particularly preferred: 500 nm 3 More than 1600nm 3 Below, most preferably 500nm 3 More than 1300nm 3 The following applies: 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). Therefore, by reducing the particle volume, even better electromagnetic conversion characteristics (e.g., SNR) can be obtained. Thus, the average particle volume of the magnetic powder is 4000 nm. 3 If the average particle size of the magnetic powder is less than 20 nm, even better electromagnetic conversion characteristics (e.g., SNR) can be obtained. On the other hand, if the average particle volume of the magnetic powder is 500 nm 3 With these settings, the same effect as when the average particle size of the magnetic powder is 10 nm or larger can be obtained.

[0118] If the ε-iron oxide particles are spherical, the average particle volume of the magnetic powder can be determined as follows: First, the average major axis length DL is calculated using the same method as for calculating the average particle size of the magnetic powder described above. ave Next, we calculate the average volume V of the magnetic powder using the following formula. V = (π / 6) × DL ave 3

[0119] When the ε-iron oxide particles are cubic in shape, the average volume of the magnetic powder is determined as follows. The magnetic tape MT is processed and thinned using the FIB (Focused Ion Beam) method or the like. When using the FIB method, a carbon film and a tungsten film are formed as protective films as a pretreatment before observing the TEM image of the cross-section described later. The carbon film is formed on the surface of the magnetic layer 43 and the back layer 44 of the magnetic tape MT by vapor deposition, and the tungsten film is further formed on the surface of the magnetic layer 43 by vapor deposition or sputtering. This thinning is performed along the length direction (longitudinal direction) of the magnetic tape MT. That is, this thinning creates a cross-section parallel to both the longitudinal and thickness directions of the magnetic tape MT.

[0120] The obtained thin section sample is observed in cross-section using a transmission electron microscope (Hitachi High-Technologies Corporation H-9500) with an acceleration voltage of 200kV and a total magnification of 500,000x, ensuring that the entire magnetic layer 43 is included in the thickness direction of the magnetic layer 43, and a TEM image is obtained. Note that the magnification and acceleration voltage may be adjusted as appropriate depending on the type of instrument. Next, 50 particles whose particle shape is clear are selected from the captured TEM image, and the side length DC of each particle is measured. Subsequently, the average side length DC of the 50 measured particles is simply averaged (arithmetic mean) to obtain the average side length DC. ave Next, we calculate the average side length DC. ave Using the following formula, the average volume V of the magnetic powder can be calculated from the following equation. ave Calculate the particle volume. V ave =DC ave 3

[0121] (Cobalt ferrite particles) The cobalt ferrite particles preferably have uniaxial crystal anisotropy. Uniaxial crystal anisotropy of the cobalt ferrite particles allows the magnetic powder to be preferentially crystallized in the direction perpendicular to the magnetic tape MT. The cobalt ferrite particles, for example, have a cubic shape. In this specification, cubic shape includes substantially cubic shapes. The Co-containing spinel ferrite may further contain at least one of Ni, Mn, Al, Cu, and Zn in addition to Co.

[0122] Co-containing spinel ferrite has an average composition represented, for example, by the following formula. Co x M y Fe2O Z (However, in the formula, M is at least one metal from, for example, Ni, Mn, Al, Cu, and Zn. x is a value in the range 0.4 ≤ x ≤ 1.0. y is a value in the range 0 ≤ y ≤ 0.3, where x and y satisfy the relationship (x + y) ≤ 1.0. z is a value in the range 3 ≤ z ≤ 4. Part of Fe may be substituted with other metallic elements.)

[0123] When the magnetic powder contains cobalt ferrite particle powder, 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 magnetic tapes (MT) with high recording density. 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 particle powder.

[0124] When the magnetic powder contains cobalt ferrite particle powder, 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 particle powder.

[0125] When the magnetic powder contains cobalt ferrite particle powder, the average particle volume of the magnetic powder is preferably 500 nm. 3 More than 4000nm 3 More preferably 500nm 3 More than 2000nm 3 More preferably, 500nm 3 More than 1000nm 3 The following applies: The average particle volume of the magnetic powder is 4000 nm. 3 If the average particle size of the magnetic powder is less than 16 nm, the same effect can be obtained. On the other hand, if the average particle volume of the magnetic powder is 500 nm 3 With the above conditions, the same effect as when the average particle size of the magnetic powder is 8 nm or larger can be obtained. The method for calculating the average particle volume of the magnetic component is the same as the method for calculating the average particle volume when the ε iron oxide particles are cubic in shape.

[0126] (Binding agent) Examples of the binder include thermoplastic resins, thermosetting resins, reactive resins, etc. Examples of the thermoplastic resin include vinyl chloride, vinyl acetate, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, acrylate ester-acrylonitrile copolymer, acrylate ester-vinyl chloride-vinylidene chloride copolymer, acrylate ester-acrylonitrile copolymer, acrylate ester-vinylidene chloride copolymer, methacrylate ester-vinylidene chloride copolymer, methacrylate ester-vinyl chloride copolymer, methacrylate ester-ethylene copolymer, polyvinyl fluoride, vinylidene chloride-acrylonitrile copolymer, acrylonitrile-butadiene copolymer, polyamide resin, polyvinyl butyral, cellulose derivatives (cellulose acetate butyrate, cellulose diacetate, cellulose triacetate, cellulose propionate, nitrocellulose), styrene butadiene copolymer, polyurethane resin, polyester resin, amino resin, synthetic rubber, etc.

[0127] Examples of the thermosetting resin include phenol resin, epoxy resin, polyurethane curing type resin, urea resin, melamine resin, alkyd resin, silicone resin, polyamine resin, urea formaldehyde resin, etc.

[0128] For all of the above binders, for the purpose of improving the dispersibility of magnetic powder, -SO3M, -OSO3M, -COOM, P=O(OM)2 (wherein M represents a hydrogen atom or an alkali metal such as lithium, potassium, sodium, etc.), and side-chain type amines having end groups represented by -NR1R2, -NR1R2R3 + X - main-chain type amines represented by >NR1R2 + X - (wherein R1, R2, and R3 represent a hydrogen atom or a hydrocarbon group, and X -) represents halogen element ions such as fluorine, chlorine, bromine, and iodine, as well as inorganic or organic ions. 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 10 moles / g or more -8 It is preferable that the amount is 10 moles / g or less. -2 10 moles / g or more -6 It is more preferable that the concentration is 1 / mole / g or less.

[0129] (Lubricant) The lubricant comprises at least one selected from, for example, fatty acids and fatty acid esters, preferably both fatty acids and fatty acid esters. The inclusion of a lubricant in the magnetic layer 43, and in particular the inclusion of both fatty acids and fatty acid esters in the magnetic layer 43, contributes to improving the running stability of the magnetic tape MT.

[0130] The fatty acid may preferably be a compound represented by the following general formula (1) or (2). For example, the fatty acid may include one of the compounds represented by the following general formula (1) and the compound represented by the following general formula (2), or both.

[0131] Furthermore, 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 include either a compound represented by the following general formula (3) or a compound represented by the following general formula (4), or both.

[0132] By including either or both of the compounds shown in general formula (1) and general formula (2), and either or both of the compounds shown in general formula (3) and general formula (4), the increase in the coefficient of dynamic friction due to repeated recording or playback of magnetic tape MT can be suppressed.

[0133] 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.)

[0134] 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 or more and 20 or less, more preferably from the range of 14 or more and 18 or less.)

[0135] 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 from the range of 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 from the range of 2 or more and 4 or less.)

[0136] CH3(CH2) r COO-(CH2) s CH(CH3)2···(4) (However, in General Formula (4), r is an integer selected from the range of 14 or more and 22 or less, and s is an integer selected from the range of 1 or more and 3 or less.)

[0137] (Carbon) The carbon contained in the magnetic layer 43 functions as an antistatic agent. The carbon contained in the magnetic layer 43 may function as a lubricant or the like. Specifically, the carbon is carbon particles. 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.)

[0138] (Antistatic agent) Examples of the antistatic agent include natural surfactants, nonionic surfactants, cationic surfactants, and the like.)

[0139] (Abrasive) Examples of abrasives include α-alumina, β-alumina, γ-alumina, silicon carbide, chromium oxide, cerium oxide, α-iron oxide, corundum, silicon nitride, titanium carbide, titanium oxide, silicon dioxide, tin oxide, magnesium oxide, tungsten oxide, zirconium oxide, boron nitride, zinc oxide, calcium carbonate, calcium sulfate, barium sulfate, molybdenum disulfide, and needle-shaped α-iron oxide obtained by dehydrating and annealing the raw materials of magnetic iron oxide, and, if necessary, surface-treated with aluminum and / or silica.

[0140] (Hardening agent) Examples of curing agents include polyisocyanates. Examples of polyisocyanates include aromatic polyisocyanates such as adducts of tolylene diisocyanate (TDI) and active hydrogen compounds, and aliphatic polyisocyanates such as adducts of hexamethylene diisocyanate (HMDI) and active hydrogen compounds. The weight-average molecular weight of these polyisocyanates is preferably in the range of 100 to 3000.

[0141] (Rust inhibitor) Examples of rust inhibitors include phenols, naphthols, quinones, heterocyclic compounds containing nitrogen atoms, heterocyclic compounds containing oxygen atoms, and heterocyclic compounds containing sulfur atoms.

[0142] (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 type titanium oxide).

[0143] (base layer) The base layer 42 is intended to alleviate surface irregularities of the substrate 41 and adjust surface irregularities of the magnetic layer 43. The base layer 42 is a non-magnetic layer containing non-magnetic powder, a binder, and a lubricant. The base layer 42 supplies lubricant to the surface of the magnetic layer 43. The base layer 42 may further contain at least one additive, such as an antistatic agent, a hardening agent, and a rust inhibitor, as needed.

[0144] The upper limit of the average thickness of the base layer 42 is preferably 1.2 μm or less, more preferably 0.9 μm or less, even more preferably 0.8 μm or less, particularly more preferably 0.7 μm or less, and most preferably 0.6 μm or less. When the upper limit of the average thickness of the base layer 42 is 1.2 μm or less, the thickness of the magnetic tape MT can be reduced, so the recording capacity that can be recorded in one data cartridge can be increased compared to general magnetic tapes. Also, when the average thickness of the base layer 42 is 1.2 μm or less, the elasticity of the magnetic tape MT due to external force is further increased, making it easier to adjust the width of the magnetic tape MT by tension adjustment. The lower limit of the average thickness of the base layer 42 is preferably 0.3 μm or more. When the lower limit of the average thickness of the base layer 42 is 0.3 μm or more, a deterioration in the function of the base layer 42 can be suppressed. The average thickness of the base layer 42 is determined in the same way as the average thickness of the magnetic layer 43. However, the magnification of the TEM image is adjusted appropriately according to the thickness of the base layer 42.

[0145] (Non-magnetic powder) The non-magnetic powder includes, for example, at least one of inorganic particulate powder or organic particulate 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. 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 can be, for example, needle-shaped, spherical, cubic, or plate-shaped, but is not limited to these shapes.

[0146] (Binding agent, lubricant) The binder and lubricant are the same as those used in the magnetic layer 43 described above.

[0147] (Additives) The antistatic agent, hardening agent, and rust inhibitor are the same as those described above for the magnetic layer 43.

[0148] (Back layer) The back layer 44 contains a binder and non-magnetic powder. The back layer 44 may further contain at least one additive, such as a lubricant, a hardener, and an antistatic agent, as needed. The binder and non-magnetic powder are the same as those in the base layer 42 described above. The hardener and antistatic agent are the same as those in the magnetic layer 43 described above.

[0149] The average particle size of the non-magnetic powder is preferably 10 nm to 150 nm, more preferably 15 nm to 110 nm. The average particle size of the non-magnetic powder is determined in the same manner as the average particle size of the magnetic powder described above. The non-magnetic powder may contain non-magnetic powder having a particle size distribution of 2 or more.

[0150] The upper limit of the average thickness of the backing layer 44 is preferably 0.6 μm or less. When the upper limit of the average thickness of the backing layer 44 is 0.6 μm or less, the thickness of the underlayment layer 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, thus maintaining the running stability of the magnetic tape MT within the drive. The lower limit of the average thickness of the backing layer 44 is not particularly limited, but for example, it is 0.2 μm or more.

[0151] Average thickness t of back layer 44 b The average thickness t of the magnetic tape MT can be calculated as follows. First, the average thickness t of the magnetic tape MT can be calculated as follows. T Measure the average thickness t. TThe measurement method is as described in "Average Thickness of Magnetic Tape" below. Next, the back layer 44 of the sample is removed with a solvent such as MEK (methyl ethyl ketone) or dilute hydrochloric acid. Then, the thickness of the sample is measured at 5 points using a Mitutoyo laser hologage (LGH-110C), and these measurements are simply averaged (arithmetic mean) to obtain the average value t B [μm] is calculated. Then, the average thickness t of the back layer 44 is calculated using the following formula. b Determine the [μm]. The measurement location will be randomly selected from the sample. t b [μm]=t T [μm]-t B [μm]

[0152] (Average height of carbon protrusions) The upper limit of the average height of the carbon protrusions 43A is preferably 12 nm or less. When the upper limit of the average height is 12 nm or less, the output reduction due to spacing loss can be suppressed, thus suppressing the deterioration of electromagnetic conversion characteristics. The lower limit of the average height of the carbon protrusions 43A is preferably 5 nm or more. When the upper limit of the average height is 5 nm or more, good contact can be made between the head 56 and the carbon when the head 56 and the magnetic tape MT come into contact, thus improving conductivity between the head 56 and the magnetic tape MT. Therefore, charging of the magnetic tape MT can be suppressed.

[0153] (Number of carbon protrusions) The lower limit of the number of carbon protrusions 43A per unit area of ​​the magnetic surface is preferably 1.2 / μm 2 That concludes the explanation. The lower limit of the number is 1.2 / μm. 2 As a result, when the head 56 and the magnetic tape MT come into contact, the number of carbon particles in contact with the head 56 increases, thus improving conductivity between the head 56 and the magnetic tape MT. Therefore, static charge on the magnetic tape MT can be suppressed. The upper limit of the number of carbon protrusions 43A per unit area of ​​the magnetic surface is preferably 2.5 / μm. 2 The following applies: The upper limit of the number is 2.5 / μm.2 If it is as follows, the decrease in the number of magnetic particles on the magnetic surface can be suppressed, so that the deterioration of electromagnetic conversion characteristics can be suppressed.

[0154] (Average area of carbon protrusions) The average area of the carbon protrusion 43A is preferably 8000 nm 2 or more and 15000 nm 2 or less. When the average area of the protrusion 43A is 8000 nm 2 or more, when the head 56 contacts the magnetic tape MT, the contact area between the head 56 and the carbon becomes large, so that the conduction between the head 56 and the magnetic tape MT can be improved. Therefore, the charging of the magnetic tape MT can be suppressed. On the other hand, when the average area of the protrusion 43A is 15000 nm 2 or less, the decrease in the area of the magnetic particles on the magnetic surface can be suppressed, so that the deterioration of electromagnetic conversion characteristics can be suppressed.

[0155] (Method for calculating the average area of carbon protrusions) The average area of the carbon protrusion 43A was calculated as follows. <FE-SEM measurement conditions> Apparatus: HITACHI S-4800 (manufactured by Hitachi High-Technologies Corporation) Field of view angle: 5.1 μm × 3.8 μm Acceleration voltage: 5 kV Measurement magnification: 25000 times The obtained FE-SEM image (Fig. 19) is subjected to binarization processing under each of the two processing conditions described below using the image processing software Image J. From the image obtained by the binarization processing, information on the number of protrusions formed by each of the first particles and the second particles, the average area per protrusion, the total area of the protrusions, and the diameter (Feret diameter) of the protrusions can be obtained. In the binarization process, the conditions are changed as follows for the second particles with high luminance (white portions in Fig. 19) and the first particles with low luminance (black portions in Fig. 19). <Binarization processing conditions for obtaining information on the first particles> Software: Image J Ver 1.44p Binarization threshold: Threshold(0.65) Binarization target size: 0.002 μm-infinity <Binarization processing conditions for obtaining information about the second particle> Software: Image J Ver 1.44p Binarization threshold: Threshold(220,255) Size of data to be binarized: 0.001 μm-infinity

[0156] (Method for calculating the average height of carbon protrusions and the number of carbon protrusions per unit area of ​​the magnetic surface) The average height of the carbon protrusions 43A and the number of carbon protrusions 43A per unit area of ​​the magnetic surface are determined according to the following steps 1-4. Here, we will describe the case where the abrasive is alumina. Step 1: Marking the sample surface with a manipulator Step 2: Acquire AFM image of the marked area Step 3: Acquisition of FE-SEM image of the marked area and binarization of the acquired FE-SEM image. Step 4: Extraction of carbon protrusion 43A Step 5: Measure the height of projection 43A using AFM analysis software.

[0157] The details of steps 1 through 4 will be explained below. (Step 1: Marking the sample surface with a manipulator) First, the magnetic tape MT housed in the cartridge 10 is unwound, and a sample is prepared by cutting the magnetic tape MT at a position 30m in the longitudinal direction (specifically, from one end of the leader tape LT to the other end) from the connection point 21 between the magnetic tape MT and the leader tape LT. Next, the manipulator is used to mark the magnetic surface of the sample. This marking is done to ensure that the AFM image in step S2 and the FE-SEM image in step S3 are acquired at the same location.

[0158] (Step 2: Acquire AFM image of the marked area) The marked portion of the magnetic surface of the sample is observed using AFM to obtain an AFM image (see Figure 16). The AFM observation conditions are shown below. Device name: Nanoscope IV, manufactured by Digital Instruments. Measurement mode: Tapping Cantilever: SNL-10 Scan size: 5×5μm Scan rate: 1Hz Scan line: 256

[0159] AFM can obtain information such as the number and height of the protrusions 43A. Figure 17 shows the analysis results of the protrusions 43A by AFM. Figure 18 shows the calculation results of the height distribution of the protrusions 43A by AFM.

[0160] (Step 3: Acquisition of FE-SEM image of the marked area and binarization of the acquired FE-SEM image) First, the marked portion of the magnetic surface of the sample was observed using FE-SEM, and a Tif file (1260 x 960 pixels) of the FE-SEM image (grayscale image) of the observed surface was obtained (see Figure 19). In the SEM image, the black areas correspond to the areas where carbon is present, and the white areas correspond to the areas where alumina is present. The observation conditions for FE-SEM are shown below. Device name: Hitachi High-Technologies Corporation, S-4800 Acceleration voltage: 5kV Observation magnification: 25,000x (size 5.1 μm x 3.8 μm) (The observation magnification of 25,000x corresponds to the measurement magnification of the AFM scan size (5 × 5 μm) mentioned above.)

[0161] Next, using the difference in brightness due to the difference in secondary electron emission, carbon (black areas) is extracted from the SEM image as follows: Using image analysis software, the SEM image (grayscale image) is converted to 256 levels of grayscale, and then binarized. This yields a binarized image (see Figure 20) showing the carbon-based protrusion 43A. The conditions for the binarization process are as follows: Image analysis software: Image J Ver 1.44p Binarization threshold: Threshold(0.65) Size of image to be binarized: 0.002 μm - infinity Furthermore, the same software used for the 256-level conversion process is employed for the binarization process.

[0162] Using image analysis software (Image J Ver 1.44p), the number of carbon atoms, the average area per carbon atom, the total area of ​​the carbon atoms, and the diameter of the carbon atoms (ferret diameter) can be calculated from the binarized image shown above. The information calculated from the binarized image shown in Figure 20 is as follows: Quantity: 55 pieces Average area: 0.005μm 2 Total area: 0.262 μm² 2 Feret diameter: 0.013 μm

[0163] (Step 4: Extraction of carbon protrusions 43A) First, a composite image is obtained by superimposing the above AFM image and FE-SEM image (see Figure 21). Next, from the obtained composite image, it is determined whether each protrusion 43A is made of carbon or alumina. Then, the number of carbon protrusions 43A is measured using AFM software. In addition, the average height of the carbon protrusions 43A (average height of 20 samples) is calculated using AFM software. Figure 22 shows an example of the cumulative frequency distribution obtained from the above measurement (cumulative frequency distribution of the height of carbon protrusions 43A). In this measurement example, 20 protrusions 43A made of carbon are measured.

[0164] Figure 23 shows the acquisition position (Line 1) for the cross-sectional profile in the composite image. Figure 24 shows the cross-sectional profile acquired at Line 1 shown in Figure 23. Carbon protrusions 43A and alumina protrusions 43A can be seen in the cross-sectional profile at Line 1.

[0165] (Surface resistivity of the magnetic surface of magnetic tape) The upper limit of the surface resistivity of the magnetic surface of the magnetic tape MT is preferably 1 × 10⁻⁶. 6 It is less than or equal to Ω / sq. The upper limit of surface resistivity is 1 × 10⁻⁶. 6 If the surface resistivity is Ω / sq. or less, a conductive path can be formed from the magnetic surface of the magnetic tape MT to the reel 13 during operation, thereby suppressing the charging of the magnetic tape MT during operation. Preferably, the lower limit of the surface resistivity of the magnetic surface of the magnetic tape MT is 1 × 10⁻⁶. 4 The resistance is Ω / sq. or greater. If the surface resistivity of the magnetic surface of the magnetic tape MT is too low, when a discharge occurs on the magnetic surface side within the drive, an excessive current may flow from the magnetic surface to the elements of the recording / playback head, which may lead to element damage. Therefore, it is preferable to set a lower limit, and this lower limit should be 1 × 10⁻⁶. 4 It is preferable that the density is Ω / sq. or greater.

[0166] The surface resistivity of the magnetic surface of the magnetic tape MT is measured as follows. First, the magnetic tape MT housed in the cartridge 10 is unwound, and a sample is prepared by cutting the magnetic tape MT at a position 30 m in the longitudinal direction (specifically, from one end on the leader tape LT side to the other end on the opposite side) from the connection point 21 between the magnetic tape MT and the leader tape LT. Next, the surface resistivity of the magnetic surface of the sample is measured by the method based on the following standard. ECMA-0319 9.18 Electrical resistance of coated surfaces 9.18.1 Requirements 9.18.2 Procedure

[0167] (Average thickness of magnetic tape) Average thickness (average total thickness) of magnetic tape MT T The upper limit of 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. Average thickness t of magnetic tape MT T If the thickness is 5.3 μm or less, the recording capacity that can be recorded in one data cartridge can be increased compared to general magnetic tape. T The lower limit is not particularly restricted, but for example, it is 3.5 μm or larger.

[0168] Average thickness t of magnetic tape MT T The following method is used to determine the value t. First, prepare a magnetic tape MT, cut it to a length of 250 mm, and create a sample. Next, use a Mitutoyo laser hologage (LGH-110C) as the measuring device to measure the thickness of the sample at five points, and simply average these measurements (arithmetic mean) to obtain the average value t. T Calculate the [μm] measurement. The measurement location will be randomly selected from the sample.

[0169] (Surface roughness R of the back surface) b ) Surface roughness of the back surface (surface roughness of back layer 44) R b However, R b It is preferable that the surface roughness R of the back surface is ≤6.0 [nm]. b If the above range is maintained, even better electromagnetic conversion characteristics can be obtained.

[0170] Back surface roughness R b The following method is used to determine the surface roughness R of the back surface. First, prepare a 12.65 mm wide magnetic tape MT, cut it to a length of 100 mm, and prepare a sample. Next, place the sample on a microscope slide with the surface to be measured (the magnetic layer side) facing upwards, and secure the edges of the sample with mending tape. Use a VertScan (50x objective lens) as the measuring device to measure the surface shape, and calculate the surface roughness R of the back surface from the following formula based on the ISO 25178 standard.b Find it. Device: Non-contact roughness meter using optical interference (Non-contact surface and layer cross-sectional shape measurement system VertScan R5500GL-M100-AC, manufactured by Hishikawa System Co., Ltd.) Objective lens: 20x Measurement area: 640 × 480 pixels (Field of view: approximately 237 μm × 178 μm field of view) Measurement mode: phase Wavelength filter: 520 nm CCD: 1 / 3 lens Noise reduction filter: Smoothing 3 × 3 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

[0171] (Coercive force Hc) The upper limit 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 under 1800 Oe. When 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.

[0172] The lower limit of the coercivity Hc2 of the magnetic layer 43, measured in the longitudinal direction of the magnetic tape MT, is preferably 1000Oe or more. When the coercivity Hc2 of the magnetic layer 43, measured in the longitudinal direction of the magnetic tape MT, is 1000Oe or more, demagnetization due to leakage magnetic flux from the recording head can be suppressed.

[0173] The above coercivity Hc2 is determined as follows. First, three magnetic tapes MT are stacked together with double-sided tape, and then punched out with a φ6.39 mm punch to create a measurement sample. At this time, the magnetic tapes MT are marked with an arbitrary non-magnetic ink so that the longitudinal direction (direction of travel) of the magnetic tapes MT can be recognized. Then, the MH loop of the measurement sample (the entire magnetic tape MT) corresponding to the longitudinal direction (direction of travel) of the magnetic tapes MT is measured using a vibrating sample magnetometer (VSM). Next, the coating (underlayer 42, magnetic layer 43, and back layer 44, etc.) is wiped off using acetone or ethanol, leaving only the substrate 41. Then, three of the obtained substrates 41 are stacked together with double-sided tape, and then punched out with a φ6.39 mm punch to create a sample for background correction (hereinafter simply referred to as the "correction sample"). Subsequently, 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.

[0174] For measuring the MH loop of the measurement sample (the entire magnetic tape MT) and the MH loop of the correction sample (substrate 41), a high-sensitivity vibrating sample type magnetometer "VSM-P7-15" manufactured by Toei Kogyo Co., Ltd. is used. 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, MH average number: 20.

[0175] 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 background-corrected MH loop is obtained. The measurement and analysis program included with the "VSM-P7-15" is used to calculate this background correction. The coercivity Hc2 is determined from the obtained background-corrected MH loop. The measurement and analysis program included with the "VSM-P7-15" is used for this calculation as well. All of the above MH loop measurements are performed in an environment of 25℃±2℃ and 50%RH±5%RH. Furthermore, "demagnetization correction" is not performed when measuring the MH loop in the longitudinal direction of the magnetic tape MT.

[0176] (Gangular ratio) The angularity ratio S1 of the magnetic layer 43 in the vertical 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 angularity ratio S1 is 65% or more, the vertical orientation of the magnetic powder becomes sufficiently high, and even better electromagnetic conversion characteristics can be obtained.

[0177] The aspect ratio S1 of the magnetic tape MT in the vertical direction is determined as follows. First, three magnetic tapes MT are stacked together with double-sided tape, and then punched out with a φ6.39 mm punch to create a measurement sample. At this time, the magnetic tape MT is marked with an arbitrary non-magnetic ink so that the longitudinal direction (travel direction) of the magnetic tape MT can be recognized. Then, the MH loop of the measurement sample (the entire magnetic tape MT) corresponding to the vertical direction (thickness direction) of the magnetic tape MT is measured using a VSM. Next, the coating (underlayer 42, magnetic layer 43, and back layer 44, etc.) is wiped off using acetone or ethanol, leaving only the substrate 41. Then, three of the obtained substrate 41 are stacked together with double-sided tape, and then punched out with a φ6.39 mm punch to become a sample for background correction (hereinafter simply referred to as the "correction sample"). After that, the MH loop of the correction sample (substrate 41) corresponding to the vertical direction of the substrate 41 (the vertical direction of the magnetic tape MT) is measured using a VSM.

[0178] For measuring the MH loop of the measurement sample (the entire magnetic tape MT) and the MH loop of the correction sample (substrate 41), a high-sensitivity vibrating sample type magnetometer "VSM-P7-15" manufactured by Toei Kogyo Co., Ltd. is used. 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, MH average number: 20.

[0179] 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. The measurement and analysis program included with the "VSM-P7-15" is used to calculate this background correction.

[0180] The obtained background-corrected saturation magnetization Ms(emu) and remanent magnetization Mr(emu) of the MH loop are substituted into the following formula to calculate the square aspect ratio S1(%). Note that all MH loop measurements described above are performed in an environment of 25℃±2℃ and 50%RH±5%RH. Furthermore, "demagnetization correction" is not performed when measuring the MH loop perpendicular to the magnetic tape MT. The measurement and analysis program included with the "VSM-P7-15" is used for this calculation. Squareness ratio S1(%)=(Mr / Ms)×100

[0181] The angularity ratio S2 of the magnetic layer 43 in the longitudinal direction (travel 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 angularity ratio S2 is 35% or less, the vertical orientation of the magnetic powder becomes sufficiently high, so even better electromagnetic conversion characteristics can be obtained.

[0182] The angular ratio S2 of the magnetic tape MT in the longitudinal direction is determined in the same manner as the angular ratio S1, except that the MH loop is measured in the longitudinal direction (travel direction) of the magnetic tape MT and the base 41.

[0183] (Hc2 / Hc1) The ratio Hc2 / Hc1 of the coercivity Hc1 of the magnetic layer 43 in the vertical direction of the magnetic tape MT to the coercivity Hc2 of the magnetic layer 43 in the longitudinal direction of the magnetic tape MT preferably satisfies the relationship Hc2 / Hc1 ≤ 0.80, more preferably Hc2 / Hc1 ≤ 0.75, even more preferably Hc2 / Hc1 ≤ 0.70, particularly preferably Hc2 / Hc1 ≤ 0.65, and most preferably Hc2 / Hc1 ≤ 0.60. By satisfying the relationship Hc2 / Hc1 ≤ 0.80 for coercivity Hc1 and Hc2, the degree of vertical orientation of the magnetic powder can be increased. Therefore, the magnetization transition width can be reduced and a high-output signal can be obtained during signal reproduction, thus achieving even better electromagnetic conversion characteristics. Furthermore, as described above, when Hc2 is small, the magnetization responds sensitively to the magnetic field in the vertical direction from the recording head, so a good recording pattern can be formed.

[0184] When the ratio Hc2 / Hc1 is Hc2 / Hc1 ≤ 0.80, it is particularly effective for the average thickness of the magnetic layer 43 to be 90 nm or less. If the average thickness of the magnetic layer 43 exceeds 90 nm, when a ring-type head is used as the recording head, the lower region of the magnetic layer 43 (the region on the base layer 42 side) may be magnetized in the longitudinal direction of the magnetic tape MT, and there is a risk that the magnetic layer 43 will not be able to be uniformly magnetized in the thickness direction. Therefore, even if the ratio Hc2 / Hc1 is set to Hc2 / Hc1 ≤ 0.80 (i.e., even if the degree of vertical orientation of the magnetic powder is increased), there is a risk that even better electromagnetic conversion characteristics cannot be obtained.

[0185] There is no particular lower limit to Hc2 / Hc1, but for example, it is 0.5 ≤ Hc2 / Hc1. Note that Hc2 / Hc1 represents the degree of vertical orientation of the magnetic powder, and the smaller Hc2 / Hc1, the higher the degree of vertical orientation of the magnetic powder.

[0186] The method for calculating the coercivity Hc2 of the magnetic layer 43 in the longitudinal direction of the magnetic tape MT is as described above. The coercivity Hc1 of the magnetic layer 43 in the perpendicular direction of the magnetic tape MT can be determined in the same manner as the coercivity Hc2 of the magnetic layer 43 in the longitudinal direction of the magnetic tape MT, except that the MH loop is measured perpendicular to the magnetic tape MT and the substrate 41 (thickness direction).

[0187] (Activated Focal V act ) Activated Fluid V act However, preferably 8000 nm 3 More preferably, 6000nm 3 More preferably, 5000nm 3 The following is particularly preferred: 4000nm 3 Below, most preferably 3000nm 3 The following is the activation volume V. act 8000nm 3 If the following conditions are met, the dispersion state of the magnetic powder will be improved, allowing the bit inversion region to be made steeper, and the degradation of the magnetization signal recorded on adjacent tracks due to leakage magnetic fields from the recording head can be suppressed. Therefore, there is a risk that even better electromagnetic conversion characteristics may not be obtained.

[0188] The above activation volume V act This can be obtained by the following formula derived by Street & Woolley. V act (nm 3 )=k B ×T×X irr / (μ0×Ms×S) (However, k B : Boltzmann constant (1.38 × 10⁻⁶) -23 J / K), T: Temperature (K), Χ irr : irreversible magnetic susceptibility, μ0: permeability of vacuum, S: magnetoviscosity, Ms: saturation magnetization (emu / cm²) 3 ))

[0189] The irreversible magnetic susceptibility X is substituted into the above formula. irr The saturation magnetization Ms and magnetoviscosity S are determined using a VSM as follows. The measurement direction using the VSM is perpendicular to the magnetic tape MT (thickness direction). The VSM measurement is performed on a measurement sample cut from a long magnetic tape MT in an environment of 25°C ± 2°C and 50% RH ± 5% RH. Furthermore, no "demagnetization correction" is performed when measuring the MH loop perpendicular to the magnetic tape MT (thickness direction).

[0190] (Irreversible magnetic susceptibility Χ irr ) Irreversible magnetic susceptibility Χ irr is defined as the slope near the remanent coercive force Hr at the slope of the remanent magnetization curve (DCD curve). First, apply a magnetic field of -1193 kA / m (15 kOe) to the entire magnetic tape MT, return the magnetic field to zero, and set it to the remanent magnetization state. Then, apply a magnetic field of about 15.9 kA / m (200 Oe) in the opposite direction, return it to zero again, and measure the remanent magnetization amount. After that, similarly, repeatedly apply a magnetic field 15.9 kA / m larger than the previous applied magnetic field, return it to zero, plot the remanent magnetization amount against the applied magnetic field, and measure the DCD curve. From the obtained DCD curve, the point where the magnetization amount becomes zero is taken as the remanent coercive force Hr, and further, the DCD curve is differentiated to obtain the slope of the DCD curve at each magnetic field. At the slope of this DCD curve, the slope near the remanent coercive force Hr is Χ irr and becomes.

[0191] (Saturation magnetization Ms) First, obtain the M-H loop after background correction in the same manner as the measurement method of the above squareness ratio S1. Next, from the value of the saturation magnetization Ms (emu) of the obtained M-H loop and the volume (cm 3 ) of the magnetic layer 43 in the measurement sample, calculate Ms (emu / cm 3 ). The volume of the magnetic layer 43 is obtained by multiplying the area of the measurement sample by the average thickness of the magnetic layer 43. The calculation method of the average thickness t1 of the magnetic layer 43 required for calculating the volume of the magnetic layer 43 is as described above.

[0192] (Magnetic viscosity coefficient S) First, apply a magnetic field of -1193 kA / m (15 kOe) to the entire magnetic tape MT (measurement sample), return the magnetic field to zero, and set it to the remanent magnetization state. Then, apply a magnetic field equivalent to the value of the remanent coercive force Hr obtained from the DCD curve in the opposite direction. While the magnetic field is applied, continuously measure the magnetization amount at regular time intervals for 1000 seconds. Calculate the magnetic viscosity coefficient S by comparing the relationship between the time t and the magnetization amount M(t) obtained in this way with the following formula. M(t) = M0 + S × ln(t) (where M(t): magnetization at time t, M0: initial magnetization, S: magnetoviscosity, ln(t): natural logarithm of time)

[0193] (Young's modulus in the longitudinal direction of magnetic tape) The upper limit of the Young's modulus in the longitudinal direction of the magnetic tape MT is preferably 9.0 GPa or less, more preferably 8.0 GPa or less, even more preferably 7.5 GPa or less, and particularly preferably 7.1 GPa or less. When the Young's modulus in the longitudinal direction of the magnetic tape MT is 9.0 GPa or less, the elasticity of the magnetic tape MT due to external forces is further increased, making it easier to adjust the width of the magnetic tape MT by tension adjustment. Therefore, off-tracking can be suppressed more effectively, and the data recorded on the magnetic tape MT can be reproduced more accurately. The lower limit of the Young's modulus in the longitudinal direction of the magnetic tape MT is preferably 3.0 GPa or more, more preferably 4.0 GPa or more. When the lower limit of the Young's modulus in the longitudinal direction of the magnetic tape MT is 3.0 GPa or more, a decrease in running stability can be suppressed.

[0194] The Young's modulus in the longitudinal direction of a magnetic tape MT is a value that indicates how difficult it is for the magnetic tape MT to expand or contract in the longitudinal direction due to external forces. The larger this value, the more difficult it is for the magnetic tape MT to expand or contract in the longitudinal direction due to external forces, and the smaller this value, the more easily the magnetic tape MT expands or contracts in the longitudinal direction due to external forces.

[0195] The Young's modulus in the longitudinal direction of a magnetic tape (MT) is a value related to the longitudinal direction of the magnetic tape (MT), but it also correlates with the resistance of the magnetic tape (MT) to stretching or contracting in the width direction. In other words, the larger this value, the less the magnetic tape (MT) is susceptible to stretching or contracting in the width direction due to external forces, and the smaller this value, the more easily the magnetic tape (MT) is stretched or contracted in the width direction due to external forces. Therefore, from the standpoint of tension adjustment, it is advantageous for the Young's modulus in the longitudinal direction of the magnetic tape (MT) to be small, as described above, and 9.0 GPa or less.

[0196] A tensile testing machine (Shimadzu Corporation, AG-100D) is used to measure Young's modulus. To measure Young's modulus in the longitudinal direction of the tape, prepare a sample by cutting the tape to a length of 180 mm. Attach a jig that can fix the width of the tape (1 / 2 inch) to the tensile testing machine and fix the top and bottom of the tape width. The distance (length of the tape between chucks) should be 100 mm. After chucking the tape sample, gradually apply stress in the direction of tensile strength. The tensile speed should be 0.1 mm / min. From the change in stress and elongation at this time, calculate Young's modulus 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 specimen (mm²) 2 ) Δx: Elongation (mm) L: Distance between gripping fixtures (mm) The stress range will be 0.5N to 1.0N, and the stress change (ΔN) and elongation (Δx) at this range will be used in the calculation. The Young's modulus will be measured at 25℃±2℃ and 50%RH±5%RH.

[0197] (Young's modulus in the longitudinal direction of the substrate) The Young's modulus in the longitudinal direction of the base body 41 is preferably 7.8 GPa or less, more preferably 7.0 GPa or less, even more preferably 6.6 GPa or less, and particularly preferably 6.4 GPa or less. When the Young's modulus in the longitudinal direction of the base body 41 is 7.8 GPa or less, the elasticity of the magnetic tape MT due to external forces is further increased, making it easier to adjust the width of the magnetic tape MT by tension adjustment. Therefore, off-tracking can be suppressed more effectively, and the data recorded on the magnetic tape MT can be reproduced more accurately. The lower limit of the Young's modulus in the longitudinal direction of the base body 41 is preferably 2.5 GPa or more, more preferably 3.0 GPa or more. When the lower limit of the Young's modulus in the longitudinal direction of the base body 41 is 2.5 GPa or more, a decrease in running stability can be suppressed.

[0198] The longitudinal Young's modulus of the substrate 41 described above can be determined as follows. First, the base layer 42, magnetic layer 43, and back layer 44 are removed from the magnetic tape MT to obtain the substrate 41. Using this substrate 41, the longitudinal Young's modulus of the substrate 41 is determined using the same procedure as for the longitudinal Young's modulus of the magnetic tape MT described above.

[0199] The thickness of the substrate 41 accounts for more than half of the total thickness of the magnetic tape MT. Therefore, the Young's modulus in the longitudinal direction of the substrate 41 is correlated with the resistance of the magnetic tape MT to expansion and contraction due to external forces. The larger this value, the less the magnetic tape MT is likely 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.

[0200] The Young's modulus of the substrate 41 in the longitudinal direction is a value related to the longitudinal direction of the magnetic tape MT, but it also correlates with the resistance of the magnetic tape MT to expansion and contraction in the width direction. In other words, the larger this value, the less the magnetic tape MT is susceptible to expansion and contraction in the width direction due to external forces, and the smaller this value, the more easily the magnetic tape MT is expanded and contracted in the width direction due to external forces. Therefore, from the viewpoint of tension adjustment, it is advantageous for the Young's modulus of the substrate 41 in the longitudinal direction to be small, as described above, and 7.8 GPa or less.

[0201] [4 Method for manufacturing magnetic tape] Next, an example of a method for manufacturing a magnetic tape MT having the above configuration will be described.

[0202] (Paint preparation process) First, a primer-forming coating is prepared by mixing and dispersing non-magnetic powder and binders in a solvent. Next, a magnetic layer-forming coating is prepared by mixing and dispersing magnetic powder, binders, lubricants, and carbon in a solvent. For the preparation of the magnetic layer-forming coating and the primer-forming coating, for example, the following solvents, dispersion equipment, and mixing equipment can be used.

[0203] Examples of solvents used in the preparation of the above-mentioned paints 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 individually or in appropriate mixtures.

[0204] For the preparation of the paint described above, mixing equipment such as a continuous twin-screw mixer, a continuous twin-screw mixer capable of multi-stage dilution, a kneader, a pressure kneader, and a roll kneader may be used, but the equipment is not limited to these. Furthermore, for the preparation of the paint described above, dispersion equipment such as a roll mill, a ball mill, a horizontal sand mill, a vertical sand mill, a spike mill, a pin mill, a tower mill, a pearl mill (for example, Eich's "DCP mill"), a homogenizer, and an ultrasonic disperser may be used, but the equipment is not limited to these.

[0205] (coating process) Next, a base layer 42 is formed by applying a base layer forming paint to one main surface of the substrate 41 and drying it. Subsequently, a magnetic layer forming paint is applied to the base layer 42 and dried it to form a 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 using, for example, a solenoid coil. Alternatively, during drying, the magnetic powder may be magnetically oriented in the longitudinal direction of the substrate 41 using, for example, a solenoid coil, and then magnetically oriented in the thickness direction of the substrate 41. By performing this process of first oriented the magnetic powder in the longitudinal direction, the degree of vertical orientation of the magnetic powder (i.e., the square ratio S1) can be further improved. After the formation of the magnetic layer 43, a back layer 44 is formed on the other main surface of the substrate 41. This yields a magnetic tape MT.

[0206] The square ratios S1 and S2 are set to desired values ​​by adjusting, for example, 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 2 to 3 times the coercivity of the magnetic powder. To further increase the square ratio S1 (i.e., to further decrease the square ratio S2), it is preferable to improve the dispersion state of the magnetic powder in the magnetic layer forming paint. In addition, to further increase the square ratio S1, it is also effective to magnetize the magnetic powder before the magnetic layer forming paint enters the orientation device for magnetic field orientation of the magnetic powder. The above methods for adjusting the square ratios S1 and S2 may be used individually or in combination of two or more.

[0207] (hardening process) After winding the magnetic tape into a roll, the underlying layer and magnetic layer are hardened by applying a heat treatment to the magnetic tape in this state.

[0208] (Calendar process) Next, the obtained magnetic tape MT is subjected to calendering to smooth the surface of the magnetic layer 43.

[0209] (Cutting process) Next, the magnetic tape MT is cut to a predetermined width (for example, 1 / 2 inch width). This completes the process of obtaining the magnetic tape MT.

[0210] (Servo pattern writing process) Next, after demagnetizing the magnetic tape, a servo pattern is written to the magnetic tape using a servo writer to form multiple servo bands SB.

[0211] (Assembly process) Next, the magnetic tape on which the servo pattern is written is assembled into the cartridge case 12. This results in the cartridge 10 shown in Figure 1.

[0212] [5 Effects] When a cartridge 10 according to one embodiment is mounted on a drive (not shown), a leaf spring 23 provided on the bottom wall 133 of the reel 13 biases a screw 106 provided at the center of the upper surface of the disc portion 102, and the magnetic surface of the magnetic tape MT and the shaft 103 become electrically connected via the reel 13, leaf spring 23, and screw 106. As a result, even if the drive gear 102A of the drive is made of insulating resin, static charge on the magnetic tape MT can be suppressed. Therefore, even when recording and playing back multiple cartridges 10 continuously, damage to magnetic heads such as TMR elements can be suppressed.

[0213] When the cartridge 10 is chucked into the drive gear 102A, the protruding portion 23B of the leaf spring 23 flexes, so that the contact between the leaf spring 23 and the screw 106 does not affect the meshing of the gears of the reel gear 133A and the drive gear 102A, or the effect is kept to a minimum.

[0214] The average height of the carbon protrusions 43A is set to 12 nm or less, and the lower limit of the number of carbon protrusions 43A is preferably 1.2 / μm. 2 In this manner, the charging of the magnetic tape MT can be particularly suppressed, and the electromagnetic conversion characteristics can also be improved.

[0215] [6 Variations] (Variation 1) In the above embodiment, an example was described in which the conductive elastic member is a leaf spring 23, but the conductive elastic member is not limited to this example and may be, for example, a conductive compression coil spring or a conductive elastomer. The conductive elastomer may be formed in a convex shape relative to the lower surface of the bottom wall 133. It may also be a structure other than a spring that makes contact with the screw. In this case, it is preferable to have a configuration that allows for smooth engagement with the drive side. As a configuration of a hard material other than a spring, an example is a member having a ring shape with an open center that stops in contact with the periphery of the screw.

[0216] (Modification 2) In the above embodiment, an example was described in which the reel 13 includes a synthetic resin and a conductive material, but the reel 13 may also include a resin layer and a conductive layer. The resin layer constitutes the body of the reel 13. The resin layer is an insulating layer containing a synthetic resin. The conductive layer is provided on the surface of the resin layer. The conductive layer may be a plated layer or a thin film. The thin film is a film formed by vacuum deposition technology, for example, a sputtered layer or a vapor-deposited layer. The thin film forms a conductive path connecting the magnetic tape MT and the leaf spring 23. For example, the thin film may be provided on the entire surface of the reel 13 or on a part of the surface of the reel 13, or on the entire surface of the reel hub 13A or on a part of the surface of the reel hub 13A.

[0217] If the reel 13 has the above configuration, the surface resistivity of the reel 13 refers to the surface resistivity of the conductive layer.

[0218] (Variation 3) In the above embodiment, an example was described in which the entire reel 13, i.e., both the reel hub 13A and the flange 13B, contain a conductive material and are conductive. However, the configuration of the reel 13 is not limited to this. For example, of the reel hub 13A and flange 13B, only the reel hub 13A may contain a conductive material and be conductive. In this case, the surface resistivity of the reel 13 refers to the surface resistivity of the reel hub 13A.

[0219] In the above embodiment, an example was described in which the reel hub 13A has a one-piece structure in which the hub 131 and the flange 132 are integrally molded. However, the reel hub 13A may also have a two-piece structure in which the hub 131 and the flange 132 are molded separately. In this case, both the hub 131 and the flange 132 may contain a conductive material and be conductive, or only the hub 131 of the hub 131 and flange 132 may contain a conductive material and be conductive.

[0220] When both the hub 131 and the flange 132 are conductive, the surface resistivity of the reel 13 refers to the surface resistivity of the hub 131. When only the hub 131 contains conductive material, the surface resistivity of the reel 13 refers to the surface resistivity of the hub 131.

[0221] (Modification 4) In the above embodiment, the case where the cartridge is a single-reel type cartridge 10 was described, but it may also be a two-reel type cartridge. [Examples]

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

[0223] In the following examples and comparative examples, the surface resistivity of the reel, the surface resistivity of the magnetic surface of the magnetic tape, the average height of the carbon protrusions, the number of carbon protrusions, and the average area of ​​the carbon protrusions are values ​​obtained by the measurement method described in the above embodiment. In addition, 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 backing layer, the average thickness of the magnetic tape, the angular ratio S1 of the magnetic layer in the vertical direction of the magnetic tape, and the angular ratio S2 of the magnetic layer in the longitudinal direction of the magnetic tape are also values ​​obtained by the measurement method described in the above embodiment.

[0224] [Example 1] (Preparation process for coatings for forming magnetic layers) A coating for forming a magnetic layer was prepared as follows. First, a first composition with the following formulation was kneaded in an extruder. Next, the kneaded first composition and a second composition with the following formulation were added to a stirring tank equipped with a disperser and pre-mixed. Subsequently, sand mill mixing was performed, followed by filtration to prepare the coating for forming a magnetic layer.

[0225] (First composition) Barium ferrite (BaFe 12 O 19 Magnetic powder (hexagonal plate shape, average aspect ratio 3.2, average particle volume 2500 nm) 3 ):100 parts by mass Resin solution in which vinyl chloride resin is dispersed in cyclohexanone (resin solution: 30% by mass of vinyl chloride resin, 70% by mass of cyclohexanone): 60 parts by mass (Vinyl chloride resin: degree of polymerization 300, number average molecular weight Mn = 10000, contains OSO3K = 0.07 mmol / g and secondary OH = 0.3 mmol / g as polar groups.) Medium-particle 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: 30% by mass of vinyl chloride resin, 70% by mass of cyclohexanone): 3.6 parts by mass (Vinyl chloride resin: degree of polymerization 300, number average molecular weight Mn = 10000, contains OSO3K = 0.07 mmol / g and secondary OH = 0.3 mmol / g as polar groups.) Medium-particle aluminum oxide powder: 5 parts by mass n-butyl stearate: 2 parts by mass Methyl ethyl ketone: 121.3 parts by mass Toluene: 121.3 parts by mass Cyclohexanone: 60.7 parts by mass Carbon black: 2.0 parts by mass, particle size (average arithmetic particle diameter) 70.0 nm (Manufactured by Tokai Carbon Co., Ltd., product name: Seast S)

[0227] Finally, to the magnetic layer-forming coating prepared as described above, 4 parts by mass of polyisocyanate (product name: Coronate L, manufactured by Tosoh Corporation) was added as a curing agent, and 2 parts by mass of stearic acid was added as a lubricant.

[0228] (Preparation process for paint used to form the base layer) The primer-forming coating was prepared as follows. First, the third composition with the following formulation was kneaded in an extruder. Next, the kneaded third composition and the fourth composition with the following formulation were added to a stirring tank equipped with a disperser and pre-mixed. Subsequently, sand mill mixing was performed, followed by filtration to prepare the primer-forming coating.

[0229] (Third composition) Medium-particle needle-shaped 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% by mass of resin, 70% by mass of cyclohexanone) Carbon Black: 10 parts by mass (Average particle size 20nm)

[0230] (4th composition) Polyurethane resin UR8200 (manufactured by Toyobo): 18.5 parts by mass n-butyl stearate: 2 parts by mass Methyl ethyl ketone: 108.2 parts by mass Toluene: 108.2 parts by mass Cyclohexanone: 18.5 parts by mass

[0231] Finally, to the primer-forming paint prepared as described above, 4 parts by mass of polyisocyanate (product name: Coronate L, manufactured by Tosoh Corporation) was added as a curing agent, and 2 parts by mass of stearic acid was added as a lubricant.

[0232] (Preparation process for paint used to form the back layer) The coating for forming the back layer was prepared as follows: The following raw materials were mixed in a stirring tank equipped with a disperser, and then filtered to prepare the coating for forming the back layer. Carbon black powder (average particle size (D50) 20 nm): 100 parts by mass Polyester polyurethane: 100 parts by mass (Manufactured by 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 coating and the underlayer-forming coating prepared as described above, an underlayer and a magnetic layer were formed on one main surface of a long polyethylene naphthalate film (hereinafter referred to as "PEN film"), which is a non-magnetic support, with an average thickness of 4.00 μm, as follows.

[0234] First, a primer-forming coating was applied to one main surface of the PEN film. Then, the coating was dried by heating and blowing air onto it, thereby forming a primer layer with an average thickness of 1.05 μm after calendering.

[0235] Next, a magnetic layer-forming coating was applied to the substrate, and the coating was dried by heating and blowing air onto it, thereby forming a magnetic layer with an average thickness of 0.08 μm after calendering. During the drying of the magnetic layer-forming coating, a solenoid coil oriented the magnetic powder in the thickness direction of the film. As a result, the angular ratio S1 in the vertical direction (thickness direction) of the magnetic tape was set to 65%, and the angular ratio S2 in the longitudinal direction of the magnetic tape was set to 38%.

[0236] Next, a back layer forming coating was applied to the other main surface of the PEN film. The coating was then dried by heating and blowing air onto it, thereby forming a back layer with an average thickness of 0.50 μm after calendering. This resulted in the production of a magnetic tape.

[0237] (hardening process) After winding the magnetic tape into a roll, the underlying layer and magnetic layer were hardened by applying a heat treatment to the magnetic tape in this state.

[0238] (Calendar process) The magnetic layer surface was smoothed by calendering. The calendering temperature was set to 100°C and the calendering pressure to 200 kg / cm².

[0239] (Cutting process) The magnetic tape obtained as described above was cut into strips with a width of 1 / 2 inch (12.65 mm). This resulted in magnetic tape with an average thickness of 5.63 μm.

[0240] (Servo pattern writing process) After demagnetizing the magnetic tape, five servo bands were formed by writing a servo pattern onto the magnetic tape using a servo writer. The servo pattern conformed to the LTO-8 standard.

[0241] (Assembly process) A magnetic tape on which the servo pattern was written was incorporated into an LTO cartridge. The LTO cartridge used had the configuration shown in Figure 1, namely, a conductive reel and a leaf spring. This conductive reel consisted of a reel hub and flange (see Figure 1) made of carbon-added synthetic resin. The surface resistivity of the conductive reel was 5 × 10⁻⁶ 5 The value was set to Ω / sq. By going through the above process, the average height of the carbon protrusions, the number of carbon protrusions, and the average area of ​​the carbon protrusions were adjusted.

[0242] [Example 2] In the preparation process for coatings for forming magnetic layers, barium ferrite (BaFe) is used as the magnetic powder. 12 O 19 ) Magnetic powder (hexagonal plate shape, average aspect ratio 3.2, average particle volume 1600 nm) 3 By using this method, the height of the carbon protrusions, the number of carbon protrusions, and the average area of ​​the carbon protrusions were adjusted. By setting the average thickness of the PEN film to 3.98 μm, the average thickness of the underlayer after calendering to 1.07 μm, and the average thickness of the back layer after calendering to 0.49 μm, a magnetic tape with a thickness of 5.62 μm was obtained. A cartridge was obtained in the same manner as in Example 1, except for the details mentioned above.

[0243] [Example 3] In the preparation process for coatings for forming magnetic layers, barium ferrite (BaFe) is used as the magnetic powder. 12 O 19 ) Magnetic powder (hexagonal plate shape, average aspect ratio 3.2, average particle volume 1600 nm) 3 The following was used: The height of the carbon protrusions, the number of carbon protrusions, and the average area of ​​the carbon protrusions were adjusted by surface treatment of the tape magnetic layer with wrapping tape. By setting the average thickness of the underlayer after calendering to 1.02 μm and the average thickness of the back layer after calendering to 0.47 μm, a magnetic tape with an average thickness of 5.57 μm was obtained. A cartridge was obtained in the same manner as in Example 1, except for the details mentioned above.

[0244] [Comparative Example 1] In the preparation process for coatings for forming magnetic layers, barium ferrite (BaFe) is used as the magnetic powder. 12 O 19 ) Magnetic powder (hexagonal plate shape, average aspect ratio 3.2, average particle volume 1600 nm) 3 ) was used. In addition, carbon black with a particle size (average arithmetic particle diameter) of 35.0 nm (manufactured by Tokai Carbon Co., Ltd., product name: Seest 116) was used to adjust the carbon protrusion height, the number of carbon protrusions, and the average area of ​​the carbon protrusions. By setting the average thickness of the PEN film to 4.60 μm, the average thickness of the magnetic layer after calendering to 0.06 μm, the average thickness of the underlayer after calendering to 0.70 μm, and the average thickness of the back layer after calendering to 0.35 μm, a magnetic tape with an average thickness of 5.71 μm was obtained. The LTO cartridge used was the same as in Example 1, except that it had an insulating reel instead of a conductive reel. The surface resistivity of the insulating reel was 6 × 10⁻⁶. 12 It was set to Ω / sq. A cartridge was obtained in the same manner as in Example 1, except for the details mentioned above.

[0245] [Comparative Example 2] In the preparation process for the magnetic layer-forming coating, needle-shaped metal magnetic powder was used as the magnetic powder to adjust the height of the carbon protrusions, the number of carbon protrusions, and the average area of ​​the carbon protrusions. By setting the average thickness of the PEN film to 4.80 μm, the average thickness of the magnetic layer after calendering to 0.09 μm, the average thickness of the underlayer after calendering to 1.08 μm, and the average thickness of the back layer after calendering to 0.45 μm, a magnetic tape with an average thickness of 6.42 μm was obtained. The LTO cartridge used was the same as in Example 1, except that it did not have a leaf spring. A cartridge was obtained in the same manner as in Example 1, except for the details mentioned above.

[0246] [Comparative Example 3] In the preparation process for coatings for forming magnetic layers, barium ferrite (BaFe) is used as the magnetic powder. 12 O 19 ) Magnetic powder (hexagonal plate shape, average aspect ratio 3.2, average particle volume 1600 nm) 3 The following was used: The amount of vinyl chloride resin in the first composition was set to 65 parts by mass to adjust the height of the carbon protrusions, the number of carbon protrusions, and the average area of ​​the carbon protrusions. By setting the average thickness of the PEN film to 4.02 μm, the average thickness of the underlayer after calendering to 1.10 μm, and the average thickness of the back layer after calendering to 0.48 μm, a magnetic tape with an average thickness of 5.68 μm was obtained. The same LTO cartridge used in Comparative Example 2 was employed. A cartridge was obtained in the same manner as in Example 1, except for the details mentioned above.

[0247] [Comparative Example 4] In the preparation process for coatings for forming magnetic layers, barium ferrite (BaFe) is used as the magnetic powder. 12 O 19 ) Magnetic powder (hexagonal plate shape, average aspect ratio 3.2, average particle volume 1600 nm) 3 The following was used: First, the first composition was kneaded in an extruder. Next, the kneaded first composition was placed in a stirring tank equipped with a disperser and sand-milled, then the second composition was added and sand-milled again, followed by filtering to prepare a coating for forming a magnetic layer, thereby adjusting the height of the carbon protrusions, the number of carbon protrusions, and the average area of ​​the carbon protrusions. By setting the average thickness of the PEN film to 4.04 μm, the average thickness of the underlayer after calendering to 1.08 μm, and the average thickness of the back layer after calendering to 0.49 μm, a magnetic tape with an average thickness of 5.69 μm was obtained. The LTO cartridge used was the same as in Example 1, except that it had an insulating reel instead of a conductive reel and did not have a leaf spring. A cartridge was obtained in the same manner as in Example 1, except for the details mentioned above.

[0248] [Comparative Example 5] In the preparation process for the coating for forming a magnetic layer, a second composition with the following formulation was used. (Second composition) Resin solution in which vinyl chloride resin is dispersed in cyclohexanone (resin solution: 30% by mass of vinyl chloride resin, 70% by mass of cyclohexanone): 3.6 parts by mass (Vinyl chloride resin: degree of polymerization 300, number average molecular weight Mn = 10000, contains OSO3K = 0.07 mmol / g and secondary OH = 0.3 mmol / g as polar groups.) Medium-particle aluminum oxide powder: 5 parts by mass n-butyl stearate: 2 parts by mass Methyl ethyl ketone: 121.3 parts by mass Toluene: 121.3 parts by mass Cyclohexanone: 60.7 parts by mass First carbon black: 2.0 parts by mass, particle size (average arithmetic particle diameter) 120.0 nm (Manufactured by Tokai Carbon Co., Ltd., product name: Seast TA) Second carbon black: 1.5 parts by mass, particle size (average arithmetic particle diameter) 70.0 nm (Manufactured by Tokai Carbon Co., Ltd., product name: Seast S) Furthermore, the LTO cartridge used was the same as in Example 1, except that it had an insulating reel instead of a conductive reel. A cartridge was obtained in the same manner as in Example 1, except for the details mentioned above.

[0249] [evaluation] The cartridges obtained as described above were evaluated as follows:

[0250] (Evaluation of surface resistivity of magnetic tape) The surface resistivity of the magnetic tape was measured using the method described in the above embodiment. The results are shown in Table 1.

[0251] (Evaluation of electromagnetic conversion characteristics) First, a loop tester (manufactured by Microphysics) was used to acquire the playback signal from the magnetic tape. The conditions for acquiring the playback signal are described below. For the loop tester, approximately 1 meter of tape was unwound from the cartridge and attached to the tester for measurement. Head: GMR, Head Speed: 2m / s Signal: Single recording frequency (20MHz) Recording current: Optimal recording current

[0252] Next, the regenerated signal was captured using a spectrum analyzer with a span of 0 to 20 MHz (resolution bandwidth = 100 kHz, VBW = 30 kHz). The peaks of the captured spectrum were defined as the signal intensity S, and the floor noise (excluding the peaks) was integrated to determine the noise intensity N. The signal-to-noise ratio (SNR) was then calculated as the ratio S / N of the signal intensity S to the noise intensity N. Next, the calculated SNR was converted to a relative value (dB) based on the SNR of Comparative Example 1, which served as a reference medium. Finally, the quality of the electromagnetic conversion characteristics was determined using the SNR (dB) obtained as described above. The results are shown in Table 1. Better: The SNR of the magnetic tape is 1 dB or more better than the SNR (= 0 (dB)) of the evaluation standard sample (Comparative Example 1). Good: The SNR of the magnetic tape is equivalent to or exceeds the SNR (=0(dB)) of the evaluation standard sample (Comparative Example 1). Defect: The SNR of the magnetic tape is less than the SNR (=0 (dB)) of the reference sample (Comparative Example 1) across all areas.

[0253] (Evaluation of running stability during continuous operation of 100 volumes) First, an LTO cartridge was loaded into an LTO drive connected to a PC via SCSI. Then, a so-called full-volume test was performed by operating the LTO drive from the PC to record and play data across the entire magnetic tape. This full-volume test was performed on 100 cartridges. It should be noted that if the magnetic tape is charged, discharge may occur on the TMR element of the head, and repeated small discharges may lead to damage to the TMR element. It is empirically known that, under the same environment, replacing the cartridge with a new one is less advantageous in terms of charging / discharging than repeatedly running the same tape many times, and this method was used for that reason. Next, the running stability during continuous operation of 100 reels was evaluated according to the following criteria. The results are shown in Table 1. Excellent playback stability: When recording and playing back the entire length of 100 volumes, the total recording capacity of all cartridges exceeds 12TB in LTO8 format. Poor playback stability: When recording and playing back the full length of 100 reels, some cartridges have a recording capacity of less than 12TB for LTO8.

[0254] [Table 1]

[0255] The following can be seen from Table 1. The cartridge is equipped with a conductive reel and a leaf spring on the bottom wall of the reel, which suppresses the charging of the magnetic tape and thus prevents the magnetic tape from sticking to the head. Therefore, good running stability is achieved. Furthermore, if the average height of the carbon black protrusions is 12 nm or less, the output reduction due to spacing loss can be suppressed, thereby suppressing the deterioration of electromagnetic conversion characteristics.

[0256] While embodiments and modifications of the present disclosure have been described in detail above, the present disclosure is not limited to the embodiments and modifications described above, and various modifications are possible based on the technical idea of ​​the present disclosure. For example, the configurations, methods, processes, shapes, materials, and numerical values ​​given in the above embodiments and modifications are merely examples, and different configurations, methods, processes, shapes, materials, and numerical values ​​may be used as needed. The configurations, methods, processes, 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.

[0257] The chemical formulas of the compounds exemplified in the above embodiments and modifications are representative examples, and are not limited to the valencies, etc., described, as long as they are the same compound's common name. In the numerical ranges described stepwise in the above embodiments and modifications, the upper or lower limit of one step in the numerical range may be replaced with the upper or lower limit of another step in the numerical range. Unless otherwise specified, the materials exemplified in the above embodiments and modifications can be used individually or in combination of two or more.

[0258] Furthermore, this disclosure may also adopt the following configuration. (1) A reel that is conductive and includes a bottom wall, The magnetic tape wound on the aforementioned reel, The conductive member in contact with the reel and Equipped with, The conductive member has a reel gear on the lower surface of the bottom wall. cartridge. (2) The cartridge according to (1), wherein the conductive member is provided on the lower surface and center of the bottom wall. (3) The cartridge according to (1) or (2), wherein the reel gear having a convex shape is provided on the outer circumference of the conductive member. (4) The conductive member is a spring that can expand and contract in the convex direction of the reel gear, as described in any of (1) to (3). (5) A reel that has conductivity, The magnetic tape wound on the aforementioned reel, A conductive elastic member and Equipped with, The reel has a reel gear that meshes with a drive gear, The elastic member is a cartridge configured to bias a conductive part provided on the drive spindle when the reel gear is meshed with the drive gear. (6) The cartridge described in (5) is a leaf spring, wherein the elastic member is a leaf spring. (7) The cartridge according to (5) or (6), wherein the elastic member is provided on the rotation axis of the reel. (8) The surface resistivity of the reel is 1 × 10 6 A cartridge listed in any of (5) to (7) below Ω / sq. (9) The reel is a cartridge according to any one of (5) to (8) that contains conductive particles. (10) The aforementioned reel is a cartridge containing carbon, as described in any of (5) to (9). (11) The conductive part is the cartridge described in (9), which is a fixing member. (12) The fixing member is a screw, as described in (11) of the cartridge. (13) The surface resistivity of the magnetic surface of the magnetic tape is 1 × 10 6 A cartridge listed in any of (5) through (12) below Ω / sq. (14) A cartridge according to any of (5) to (13) is used for playback of the aforementioned magnetic tape, wherein a tunnel magnetoresistance element is used. (15) The cartridge described in any of (5) to (14) has an average thickness of 5.3 μm or less of the magnetic tape. (16) The magnetic tape comprises, in order, a substrate, an underlayer, and a magnetic layer. The magnetic layer comprises magnetic powder and carbon. The magnetic layer has protrusions made of carbon on its surface, A cartridge according to any of (5) to (15), wherein the average height of the aforementioned protrusions is 12 nm or less. (17) The number of protrusions per unit area on the surface of the magnetic layer is 1.2 / μm 2 The cartridge described above (16). (18) The average area of ​​the aforementioned protrusions is 8000 nm. 2 More than 15000nm 2 The cartridges described in (16) or (17) below. [Explanation of Symbols]

[0259] 10 cartridges 12 Cartridge Cases 12A Lower Shell 12B Upper Shell 13 reels 13A Reel Hub 13B flange 11 Cartridge Memory 22 Metal plate 23 Leaf spring 31 Antenna coil 32 Rectification / power supply circuit 33 Clock Circuit 34 Detection and Modulation Circuits 35 Controllers 36 memory 36A First memory area 36B Second memory area 41 Base 42 Base layer 43 Magnetic layer 43A protrusion 44 back layer 56 heads 56A, 56B Servo Lead Head 101 Spindle 102 Disc section 102A Drive Gear 103 Shaft 104 Magnets 105 Magnet Fixing Jig 106 screws 110 Servo Frame 111 Servo Subframe 1 111A A-Burst 111B B Burst 112 Servo Subframe 2 112C C-Burst 112D D-Burst 113 Servo Stripe 131 Hub 131 132 Flange 133 Bottom wall 133A Reel Gear MT magnetic tape SB Servo Band DB Data Binding

Claims

1. A reel that has conductivity, The magnetic tape wound on the aforementioned reel, A conductive elastic member and Equipped with, The reel has a reel gear that meshes with a drive gear, The elastic member is a cartridge configured to bias a conductive part provided on the drive spindle when the reel gear is meshed with the drive gear.

2. The cartridge according to claim 1, wherein the elastic member is a leaf spring.

3. The cartridge according to claim 1, wherein the elastic member is provided on the rotation axis of the reel.

4. The surface resistivity of the reel is 1 × 10 ６ The cartridge according to claim 1, wherein the Ω / sq. is less than or equal to Ω.

5. The cartridge according to claim 1, wherein the reel contains conductive particles.

6. The reel is a cartridge according to claim 1, comprising carbon.

7. The cartridge according to claim 1, wherein the conductive part is a fixing member.

8. The cartridge according to claim 7, wherein the fixing member is a screw.

9. The surface resistivity of the magnetic surface of the magnetic tape is 1 × 10 ６ The cartridge according to claim 1, wherein the Ω / sq. is less than or equal to Ω.

10. The cartridge according to claim 1, wherein a tunnel magnetoresistance element is used for playback of the magnetic tape.

11. The cartridge according to claim 1, wherein the average thickness of the magnetic tape is 5.3 μm or less.

12. The magnetic tape comprises, in order, a substrate, an underlayer, and a magnetic layer. The magnetic layer comprises magnetic powder and carbon. The magnetic layer has protrusions made of carbon on its surface, The cartridge according to claim 1, wherein the average height of the protrusions is 12 nm or less.

13. The number of protrusions per unit area on the surface of the magnetic layer is 1.2 / μm ２ The cartridge according to claim 12, wherein the above is true.

14. The average area of ​​the aforementioned protrusions is 8000 nm ２ 15000nm or more ２ The cartridge according to claim 12, which is as follows:

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