Magnetic recording medium, magnetic recording tape, and magnetic recording tape cartridge

Abstract

The main purpose of the present technology is to provide technology with which it is possible to suppress reduction in the cleaning power for removing dirt from a magnetic head in a magnetic recording medium.　As a result of intensive studies, the present inventors have found that the components of one or more layers that are provided on one surface of a base material layer of a magnetic recording medium include a compound which has a toluene diisocyanate (TDI) structure in each molecule and dibutylhydroxytoluene (BHT), and it is possible to suppress reduction in the cleaning power for removing dirt from a magnetic head by setting the intensity ratio of the detection peaks of the TDI and the BHT to BHT / TDI ≤ 0.030, the detection peaks being obtained when the one or more layers are measured by GC-MS.

Description

Magnetic recording media, magnetic recording tapes, and magnetic recording tape cartridges

[0001] The present technology relates to a magnetic recording medium, a magnetic recording tape, and a magnetic recording tape cartridge, and more particularly to a technology that can suppress a decrease in cleaning power that removes dirt from a magnetic head.

[0002] Conventionally, a method has been known in which a material for enhancing shape stability is used in a layer provided on one side of a substrate layer of a magnetic recording medium.

[0003] For example, Patent Document 1 listed below discloses an example in which polyisocyanate is used as a curing agent in the magnetic layer, underlayer, and back layer of a magnetic recording medium.

[0004] WO2022 / 209316 publication

[0005] The main object of the present technology is to provide a technology that can suppress a decrease in the cleaning power for removing dirt from a magnetic head in a magnetic recording medium.

[0006] As a result of extensive research, the inventors have discovered that by keeping the content of antioxidant used in one or more layers provided on one side of the substrate layer of a magnetic recording medium below a certain level, it is possible to suppress a decrease in the cleaning power that removes dirt from the magnetic head.

[0007] That is, the present technology provides a magnetic recording medium having a base layer and one or more layers disposed on one surface of the base layer, one of the one or more layers being a magnetic layer containing magnetic powder, the components of the one or more layers including a compound having a toluene diisocyanate (TDI) structure in its molecule and dibutylhydroxytoluene (BHT), and the intensity ratio of the detected peaks of the TDI and the BHT obtained when the one or more layers are measured by GC-MS is BHT / TDI≦0.030. In the magnetic recording medium of the present technology, the intensity ratio of the detected peaks obtained when the one or more layers are measured by GC-MS may be BHT / TDI≦0.025. Furthermore, the intensity ratio of the detected peaks obtained when the magnetic layer of the magnetic recording medium of the present technology is measured by GC-MS may be BHT / TDI≦0.030. In addition, in the magnetic recording medium of the present technology, the outermost layer of the one or more layers may be the magnetic layer. The intensity ratio of the detected peaks obtained when the one or more layers of the magnetic recording medium of the present technology are measured by GC-MS may be 0.010≦BHT / TDI. The one or more layers of the magnetic recording medium of the present technology may include a non-magnetic layer, which may be disposed between the substrate layer and the magnetic layer. In the magnetic recording medium of the present technology, a back layer may be provided on the other side of the substrate layer, the back layer may include non-magnetic powder, and the components of the back layer may include a compound having a toluene diisocyanate (TDI) structure in its molecule and dibutylhydroxytoluene (BHT). Furthermore, the intensity ratio of the detected peaks obtained when the back layer is measured by GC-MS may be BHT / TDI≦0.030, and the intensity ratio of the detected peaks obtained when the back layer is measured by GC-MS may be 0.010≦BHT / TDI. The thickness of the magnetic recording medium of the present technology may be 5.40 μm or less, the thickness of the magnetic layer of the magnetic recording medium of the present technology may be 80 nm or less, and the thickness of the layers other than the substrate layer of the magnetic recording medium of the present technology may be 0.95 μm or less.The magnetic powder contained in the magnetic layer of the magnetic recording medium according to the present technology may be any one of hexagonal ferrite, barium ferrite (BaFe), Co ferrite, strontium ferrite, and epsilon iron oxide (ε iron oxide). The magnetic powder may be any one of barium ferrite (BaFe) and strontium ferrite, or may be epsilon iron oxide (ε iron oxide). The magnetic powder has an average particle volume of 1500 nm. ３ It may be the following:

[0008] Furthermore, the present technology provides a magnetic recording tape using the magnetic recording medium of the present technology, which performs recording or playback via a magnetic head. The magnetic head may be a tilt-type magnetic head. In addition, the present technology provides a magnetic recording tape cartridge configured such that the magnetic recording tape of the present technology is wound around a reel and housed in a case.

[0009] 1 is a cross-sectional view showing an example of the configuration of a magnetic recording medium according to the present technology. FIG. 2 is a diagram showing an example of the shape of magnetic powder particles. FIG. 3 is an example of a TEM photograph of a cross section of a sample. FIG. 4 is another example of a TEM photograph of a cross section of a sample. FIG. 5 is a schematic diagram of a magnetic recording medium according to a first embodiment, viewed from above (the magnetic layer side). FIG. 6 is an enlarged view showing recording tracks in a data band of the magnetic recording medium. FIG. 7 is an enlarged view showing a portion of a servo pattern written in a servo band of the magnetic recording medium. FIG. 7 is a cross-sectional view showing an example of a deformed configuration of a magnetic recording medium according to the present technology. FIG. 8 is a diagram showing an example of the configuration of a magnetic recording tape cartridge that houses a magnetic recording tape using the magnetic recording medium according to the present technology. FIG. 9 is a diagram showing an example of the configuration of a recording and reproducing device that uses the magnetic recording tape cartridge according to the present technology. FIG. 10 is a GC-MS measurement result of one or more layers including the magnetic layer of a magnetic recording medium according to the present technology. FIG. 11 is a schematic diagram showing the configuration of a dedicated jig for measuring abrasiveness. FIG. 12 is a schematic diagram showing an abrasiveness bar. FIG. 13 is a schematic diagram showing the average wear pattern length (amount of wear) of the abrasiveness bar. FIG. 14 is an image of an apparatus for measuring the amount of deformation in the shape of a magnetic recording medium.

[0010] Preferred embodiments of the present technology will be described below. However, the embodiments shown below are examples of typical embodiments of the present technology, and the present technology is not limited to only the preferred embodiments below and can be freely modified within the scope of the present technology.

[0011] [Magnetic Recording Medium] The magnetic recording medium of the present technology has at least a base layer and one or more layers provided on one surface of the base layer, and the components of the one or more layers include a compound having a toluene diisocyanate (TDI) structure in its molecule and dibutylhydroxytoluene (BHT).

[0012] The structure of toluene diisocyanate (TDI) in the compound having a toluene diisocyanate (TDI) structure in the molecule contained in one or more layers provided on one side of the substrate layer of the magnetic recording medium of the present technology is shown below. Note that although the TDI shown below is an example of a 2,6 isomer, it may also be an isomer such as a 2,4 isomer, or may be a mixture with an isomer.

[0013]

[0014] When the one or more layers are formed on one side of the substrate layer of the magnetic recording medium of the present technology by a method such as coating, the compound having a toluene diisocyanate (TDI) structure in the molecule fixes the one or more layers by a reaction using the isocyanate group of TDI (for example, a reaction with a hydroxyl group of a compound contained in the layer).For example, when forming the one or more layers of the magnetic recording medium of the present technology, this is preferably achieved by forming a polymer compound having a TDI structure by a polyaddition reaction between a low molecular weight isocyanate compound having a TDI structure in the molecule and a diol compound.

[0015] When a magnetic recording medium is used as, for example, a magnetic recording tape, in a magnetic recording tape cartridge configured so that the magnetic recording tape is wound on a reel and housed in a case, when the magnetic recording tape is stored wound on the reel for a long period of time, or when the magnetic recording tape is run in a high-temperature environment for a long period of time, suppressing changes in shape that occur due to creep of the magnetic recording tape becomes an issue.

[0016] Therefore, when a layer is fixed to one or the other of the substrate layers of a magnetic recording medium, shape stability is required. Note that in this specification, a high-temperature environment refers to an environment of 35°C or higher and 50°C or lower.

[0017] Furthermore, it is preferable that the surface that comes into contact with the magnetic head that writes to or reads from the magnetic recording medium maintains the function of removing dirt from the magnetic head caused by magnetic powder and the like that is generated by repeated writing and reading. To achieve this, the abrasive power of the surface that comes into contact with the magnetic head that writes to or reads from the magnetic recording medium is required. For example, if the magnetic layer of the magnetic recording medium of the present technology is the outermost layer of the one or more layers, if the abrasive power of the magnetic layer that comes into contact with the magnetic head as the outermost layer is high, the function of removing dirt from the magnetic head can be favorably maintained.

[0018] Shape stability can be achieved by fixing the one or more layers of the magnetic recording medium of the present technology with a compound having a TDI structure in its molecule.

[0019] On the other hand, low-molecular-weight isocyanate compounds having a TDI structure, which are raw materials before film formation, are highly reactive, and therefore, in order to ensure the stability of the compounds, they are often used with the inclusion of an antioxidant. In this case, for example, dibutylhydroxytoluene (BHT) shown below is preferably used as the antioxidant.

[0020]

[0021] The stability of raw materials containing a low-molecular-weight isocyanate compound having a TDI structure in the molecule prior to film formation can be improved by adding the above-mentioned antioxidant. However, it has been newly discovered that if the content of the above-mentioned antioxidant BHT is high on the surface of the magnetic recording medium manufactured by film formation that comes into contact with the magnetic head used for recording or playback, the abrasive power of the surface that comes into contact with the magnetic head decreases, and the ability to remove dirt from the magnetic head decreases.

[0022] That is, the magnetic recording medium of the present technology can suitably improve its polishing power by adjusting the ratio of the antioxidant BHT to a compound having a TDI structure in the molecule of one or more layers provided on one side of the substrate layer to a certain level or less. More specifically, the polishing power of the magnetic recording medium can be suitably improved by adjusting the intensity ratio of the detected peaks of the TDI and the BHT obtained when the one or more layers are measured by GC-MS to BHT / TDI≦0.030. Here, TDI, which is the denominator of BHT / TDI, is the total number of TDI structures contained in the compound having a TDI structure in the molecule. For example, if a compound has three TDI structures in its molecule, the number of TDI structures is three.

[0023] In the magnetic recording medium of the present technology, the intensity ratio BHT / TDI of the detected peaks derived from the above structure obtained when one or more layers are measured by GC-MS is preferably 0.030 or less, more preferably 0.025 or less, and particularly preferably 0.020 or less.

[0024] The lower limit of the BHT / TDI ratio obtained by measuring one or more layers by GC-MS is not particularly limited as long as it is within a range that ensures the stability of the compound having a TDI structure in its molecule before film formation. For example, it can be adjusted within a range of 0.010 or more, 0.012 or more, etc.

[0025] In the magnetic recording medium of the present technology, from the viewpoint of removing dirt from the magnetic head that performs recording or reproduction, the polishing power can be effectively improved by reducing the ratio of BHT to the TDI structure of the layer that forms the surface that contacts the magnetic head. For example, the polishing power can be effectively improved by setting the BHT / TDI ratio obtained when measuring the magnetic layer by GC-MS to the above ratio. In this case, the polishing power can be effectively improved by having the magnetic layer as the outermost layer of the one or more layers of the magnetic recording medium.

[0026] In the magnetic recording medium of the present technology, the low molecular weight compound having a TDI structure in its molecule, which serves as a raw material for the compound having a TDI structure in its molecule contained in one or more layers, is not particularly limited as long as it is a compound having a TDI structure in its molecule.

[0027] The magnetic recording medium of the present technology has one or more layers including a magnetic layer on one surface of a substrate layer. The one or more layers may include a layer other than the magnetic layer. Examples of the layer other than the magnetic layer include a non-magnetic layer. The magnetic recording medium of the present technology may also have a back layer provided on the other surface of the substrate layer (the surface opposite to the surface on which the one or more layers are provided). In addition to these layers, the magnetic recording medium may also include other layers. The other layers may be selected appropriately depending on the type of magnetic recording medium.

[0028] When the magnetic recording medium of the present technology is, for example, a coated magnetic recording medium, the coating material for forming each layer is applied to one or the other surface of the base layer to the desired thickness, and then dried to form each layer, thereby producing the magnetic recording medium of the present technology.

[0029] FIG. 1 is a cross-sectional view showing an example of the configuration of a magnetic recording medium according to the present technology. In the example shown in FIG. 1, the magnetic recording medium 10 includes a substrate layer 11, a nonmagnetic layer 12 provided on one side of the substrate layer 11, and a magnetic layer 13 provided on the nonmagnetic layer 12. In the magnetic recording medium 10 shown in FIG. 1, the nonmagnetic layer 12 and the magnetic layer 13 correspond to one or more layers. In addition, in the magnetic recording medium 10 shown in FIG. 1, a back layer 14 is provided on the other side of the substrate layer 11 (the side opposite to the side on which the one or more layers are provided). While the example shown in FIG. 1 shows a four-layer configuration, other layers can be added as needed in addition to these four layers. The thickness of the magnetic recording medium can be adjusted to, for example, 5.40 μm or less in order to increase recording capacity. In this case, it is preferable that the thickness of layers other than the substrate layer be adjusted to 0.95 μm or less.

[0030] The magnetic recording medium of the present technology can be formed into a long shape and used as a magnetic recording tape for continuous recording or playback via a magnetic head. The magnetic recording tape runs in the longitudinal direction during recording or playback. The thickness of the magnetic layer of the magnetic recording medium used in the magnetic recording tape is preferably 96 nm or less, more preferably 80 nm or less, even more preferably 75 nm or less, even more preferably 60 nm or less, and particularly preferably 50 nm or less, so that signals can be recorded at the shortest recording wavelength.

[0031] The magnetic recording medium of the present technology can be used in any recording and reproducing device depending on its application, such as a recording and reproducing device equipped with a ring-type magnetic head as a magnetic head, or a recording and reproducing device equipped with a perpendicular recording magnetic head.

[0032] As an example, a magnetic recording tape using the magnetic recording medium according to the present technology may have, during recording or playback via a magnetic head, a tape running speed of 4 m / s or more, 5 or more servo tracks, preferably a configuration that satisfies 5+4n (n is a natural number), a width of each servo track of 95 μm or less, a bit length of 48 nm or less, and a track width of 3.0 μm or less.

[0033] As described above, the upper limit of the average thickness (average total thickness) of the magnetic recording tape according to the present technology is preferably 5.40 μm or less, more preferably 5.00 μm or less, and even more preferably 4.40 μm or less. Ｔ If the average thickness of the tape T is 5.40 μm or less, the recording capacity that can be recorded in one data cartridge can be increased compared to that of a typical magnetic recording tape. The lower limit of the average thickness of the tape T is not particularly limited, but is, for example, 3.50 μm or more.

[0034] The average thickness of the magnetic recording tape of the present technology is determined by the procedure described below in the section on determining the average thickness of the back layer 4. The upper limit of the coercive force Hc in the longitudinal direction of the tape T is preferably 2000 Oe or less, more preferably 1900 Oe or less, and even more preferably 1800 Oe or less.

[0035] If the lower limit of the coercive force Hc of the magnetic recording tape according to the present technology measured in the longitudinal direction is preferably 1000 Oe or more, demagnetization due to leakage flux from the recording head can be suppressed. This coercive force Hc can be calculated as follows.

[0036] First, a measurement sample is cut out from the magnetic recording tape, and a vibrating sample magnetometer (VSM) is used to measure the M-H loop of the entire measurement sample in the longitudinal direction of the measurement sample (the running direction of the magnetic recording tape). Next, the coating (non-magnetic layer, magnetic layer, backing layer, etc.) is wiped off using acetone or ethanol, leaving only the substrate layer as a sample for background correction, and the VSM is used to measure the M-H loop of the substrate layer in the longitudinal direction (the running direction of the tape T). Then, the M-H loop of the substrate layer is subtracted from the M-H loop of the entire magnetic recording tape (the entire tape without the coating wiped off) that is the measurement sample, to obtain an M-H loop after background correction. The coercive force Hc is calculated from the obtained M-H loop. Note that all of the above M-H loop measurements are performed at 25°C. Furthermore, "demagnetizing field correction" is not performed when measuring the M-H loop in the longitudinal direction of the magnetic recording tape.

[0037] Regarding squareness ratio, the squareness ratio S1 in the perpendicular direction (thickness direction) of the magnetic recording tape is 65% or more, preferably 70% or more, and more preferably 75% or more. When the squareness ratio S1 is 65% or more, the perpendicular orientation of the magnetic powder, which will be described later, is sufficiently high, thereby enabling a better SNR to be obtained.

[0038] The squareness ratio S1 is determined as follows. First, a measurement sample is cut out from the magnetic recording tape, and the M-H loop of the entire measurement sample, corresponding to the perpendicular direction (thickness direction) of the magnetic recording tape, is measured using a VSM. Next, the coating (non-magnetic layer, magnetic layer, backing layer, etc.) is wiped off using acetone or ethanol, leaving only the substrate layer as a sample for background correction. The M-H loop of the substrate layer, corresponding to the perpendicular direction of the substrate layer (the perpendicular direction of the magnetic recording tape), is measured using a VSM. Then, the M-H loop of the substrate layer is subtracted from the M-H loop of the entire measurement sample to obtain an M-H loop after background correction. The saturation magnetization Ms (emu) and remanent magnetization Mr (emu) of the obtained M-H loop are substituted into the following equation to calculate the squareness ratio S1 (%). Note that all of the above M-H loop measurements are performed at 25°C. Furthermore, "demagnetization correction" is not performed when measuring the M-H loop in the perpendicular direction of the magnetic recording tape. Squareness ratio S1 (%) = (Mr / Ms) x 100

[0039] The squareness ratio S2 in the longitudinal direction (running direction) of the magnetic recording tape is preferably 35% or less, more preferably 30% or less, and even more preferably 25% or less. When the squareness ratio S2 is 35% or less, the perpendicular orientation of the magnetic powder is sufficiently high, and therefore a better SNR can be obtained. The squareness ratio S2 is determined in the same manner as the squareness ratio S1, except that the M-H loop is measured in the longitudinal direction (running direction) of the magnetic recording tape and the base layer.

[0040] Each layer of the magnetic recording medium of the present technology will be described in more detail below.

[0041] <Substrate Layer> The substrate layer 11 can function as a support for the magnetic recording medium 10 and can be, for example, a flexible, long, non-magnetic substrate, particularly a non-magnetic film. The substrate layer 11 can contain, for example, at least one of polyester resins, polyolefin resins, cellulose derivatives, vinyl resins, aromatic polyether ketone resins, and other polymer resins. When the substrate layer 11 contains two or more of the above materials, the two or more materials can be mixed, copolymerized, or laminated.

[0042] The polyester-based resin may be, for example, one or a mixture of two or more of PET (polyethylene terephthalate), PEN (polyethylene naphthalate), PBT (polybutylene terephthalate), PBN (polybutylene naphthalate), PCT (polycyclohexylene dimethylene terephthalate), PEB (polyethylene-p-oxybenzoate), and polyethylene bisphenoxycarboxylate. According to a preferred embodiment of the present technology, the base layer 11 may be formed from PET or PEN.

[0043] The polyolefin resin may be, for example, one or a mixture of two or more of PE (polyethylene) and PP (polypropylene).

[0044] The cellulose derivative may be, for example, one or a mixture of two or more of cellulose diacetate, cellulose triacetate, CAB (cellulose acetate butyrate), and CAP (cellulose acetate propionate).

[0045] The vinyl resin may be, for example, one or a mixture of two or more of PVC (polyvinyl chloride) and PVDC (polyvinylidene chloride).

[0046] The aromatic polyetherketone resin may be, for example, one or a mixture of two or more of PEK (polyetherketone), PEEK (polyetheretherketone), PEKK (polyetherketoneketone), and PEEKK (polyetheretherketoneketone). According to a preferred embodiment of the present technology, the base layer 11 may be formed from PEEK.

[0047] Examples of the other polymer resins include PA (polyamide, nylon), aromatic PA (aromatic polyamide, aramid), PI (polyimide), aromatic PI (aromatic polyimide), PAI (polyamideimide), aromatic PAI (aromatic polyamideimide), PBO (polybenzoxazole, e.g., Zylon (registered trademark), polyether, polyetherester, PES (polyethersulfone), PEI (polyetherimide), PSF (polysulfone), PPS (polyphenylene sulfide), PC (polycarbonate), PAR (polyarylate), and PU (polyurethane), and may be one or a mixture of two or more of these.

[0048] The substrate layer of the magnetic recording medium according to the present technology may be formed from a resin that does not contain chlorine, particularly from a polyester resin that does not contain chlorine, or, depending on the application of the magnetic recording medium, from a resin that contains chlorine.

[0049] The average thickness of the base layer 11 is not particularly limited, but for example, the upper limit is less than 4.5 μm, more preferably 4.2 μm or less, more preferably 3.8 μm or less, and even more preferably 3.4 μm or less. If the upper limit of the average thickness of the base layer 11 is 4.2 μm or less, the recording capacity that can be recorded in one data cartridge can be increased compared to that of general magnetic recording media. The lower limit of the thickness of the base layer 11 is determined from the viewpoint of the limitations in film production and the functionality of the base layer 11.

[0050] The average thickness of the substrate layer 11 can be determined as follows. First, a ½-inch wide magnetic recording medium is prepared and cut into a length of 250 mm to prepare a sample. Next, layers other than the substrate layer 11 of the sample (i.e., the nonmagnetic layer 12, magnetic layer 13, and back layer 14) are removed with a solvent such as MEK (methyl ethyl ketone) or dilute hydrochloric acid. Next, using a Mitutoyo laser hologram as a measuring device, the thickness of the sample (substrate layer 11) is measured at five or more positions, and these measurements are simply averaged (arithmetic mean) to calculate the average thickness of the substrate layer 11. Note that the measurement positions are selected randomly from the sample.

[0051] <Magnetic Layer> In the magnetic recording medium of the present technology, the magnetic layer 13 functions as a signal recording layer. In recent years, increasing the information recording capacity of magnetic recording media has become an important issue. For this reason, for example, when a magnetic recording medium is made thinner and used as a magnetic recording tape, in a magnetic recording tape cartridge configured such that the magnetic recording tape is wound around a reel and housed in a case, it is desired to increase the length of tape per reel in the cartridge to increase the recording area (recording capacity).

[0052] The magnetic layer 13 is a longitudinal recording layer or a perpendicular recording layer and contains magnetic powder. In addition to the magnetic powder, it may also contain, for example, a binder and a lubricant. The magnetic layer 13 may further contain additives such as conductive particles, abrasives, and anti-rust agents, as needed. The magnetic layer 13 may have a number of holes for storing the lubricant. When the magnetic layer 13 has a number of holes, the holes preferably extend perpendicular to the surface of the magnetic layer 13.

[0053] The thickness of the magnetic layer 13 may be adjusted to a range of, for example, 20 nm to 100 nm. By setting the thickness to 20 nm or more, the magnetic layer 13 can be applied uniformly and stably. Furthermore, by setting the thickness to 100 nm or less, the bit length of a high-density tape can be suitably set.

[0054] The magnetic layer 13 preferably has a plurality of servo bands SB and a plurality of data bands DB in advance. The plurality of servo bands SB are arranged at equal intervals in the width direction of the tape T. A data band DB is arranged between adjacent servo bands SB. Servo signals for tracking control of the magnetic head are written in advance in the servo bands SB. User data is recorded in the data bands DB. The number of servo bands SB is preferably 5 or more, and more preferably 5 + 4n (where n is a positive integer) or more. If the number of servo bands SB is 5 or more, the effect of dimensional changes in the width direction of the tape T on the servo signal can be suppressed, ensuring stable recording and reproduction characteristics with little off-track.

[0055] The average thickness of the magnetic layer 13 can be determined as follows. First, the magnetic recording medium 10 is thinned perpendicular to its main surface to prepare a test piece, and the cross section of the test piece is observed using a transmission electron microscope (TEM). The apparatus and observation conditions are shown below. Apparatus: TEM (H9000NAR, manufactured by Hitachi, Ltd.) Acceleration voltage: 300 kV Magnification: 100,000x Next, using the obtained TEM image, the thickness of the magnetic layer 11 is measured at at least 10 positions in the longitudinal direction of the magnetic recording medium, and then these measurements are simply averaged (arithmetic mean) to determine the average thickness of the magnetic layer 11. Note that the measurement positions in this case are selected randomly from the test piece.

[0056] This magnetic layer 13 is formed as a layer containing at least magnetic powder (powder-like magnetic particles). Signals are recorded on this magnetic layer 13 by changing the magnetism of the magnetic layer using a known in-plane magnetic recording method or a known perpendicular magnetic recording method. In the former in-plane magnetic recording method, for example, recording is performed in the longitudinal direction of the tape on the magnetic layer 13 containing a magnetic metal powder that exhibits a magnetizing function. In the latter perpendicular recording method, magnetic recording is performed in the perpendicular direction of the magnetic recording medium on the magnetic layer 13 containing a magnetic powder such as BaFe (barium ferrite) that exhibits a magnetizing function. In either case, signals are recorded by magnetizing the magnetic particles in the magnetic layer 13 when a magnetic field is applied from the magnetic head of the recording / reproducing device.

[0057] The magnetic layer 13 is preferably a magnetic layer that is perpendicularly oriented. Generally, perpendicular orientation tends to increase friction between a tape using a magnetic recording medium and a magnetic head. This is because perpendicular orientation aligns magnetic particles in one direction, smoothing the surface shape at the magnetic particle level. For example, the advantageous effects of the present technology can be obtained even with a tape having a magnetic layer 13 with a perpendicular orientation degree of 65% or more without demagnetizing field correction. Note that, in this specification, perpendicular orientation refers to a squareness ratio S1 measured in the longitudinal direction (running direction) of the magnetic recording medium 10 being 35% or less.

[0058] (Magnetic Powder) Examples of magnetic particles constituting the magnetic powder contained in the magnetic layer 13 include, but are not limited to, hexagonal ferrite, epsilon iron oxide (ε-iron oxide), Co-containing spinel ferrite, gamma hematite, magnetite, chromium dioxide, cobalt-coated iron oxide, and metals. The magnetic powder may be one of these, or a combination of two or more. Preferably, the magnetic powder may contain hexagonal ferrite, ε-iron oxide, or Co-containing spinel ferrite. More preferably, the magnetic powder is hexagonal ferrite. The hexagonal ferrite may particularly preferably contain at least one of Ba and Sr. The ε-iron oxide may particularly preferably contain at least one of Al and Ga. These magnetic particles may be appropriately selected by those skilled in the art based on factors such as the manufacturing method of the magnetic layer 13, the tape specifications, and the tape functions.

[0059] The shape of the magnetic particles may be, for example, hexagonal plate-like for barium ferrite (BaFe) and strontium ferrite, spherical for ε-iron oxide, cubic for cobalt ferrite, or spindle-shaped for metal. These magnetic particles are oriented during the manufacturing process of the magnetic recording medium 10.

[0060] (Embodiment in which the magnetic powder contains hexagonal ferrite) The hexagonal ferrite particles contain Fe and a metal M1 other than Fe. The metal M1 contains an alkaline earth metal. The alkaline earth metal may contain at least one or more of Sr, Ba, and Ca, and among these metals, it is preferable to contain Sr. In addition to the alkaline earth metal, the metal M1 may also contain Pb.

[0061] The hexagonal ferrite particles may further contain a metal M2 in addition to Fe and the metal M1. The metal M2 includes, for example, one selected from the group consisting of rare earth elements, transition metal elements other than Fe, and metal elements of Group 13 of the periodic table, and among these, at least one selected from the group consisting of Ti, Al, and Nd is preferred.

[0062] Specifically, the hexagonal ferrite particles may be, for example, barium ferrite particles or strontium ferrite particles. In the present disclosure, strontium ferrite particles refer to hexagonal ferrite particles in which the atomic ratio of Sr to metal M1 is 50 atomic % or more. Therefore, hexagonal ferrite particles containing Sr and a metal M1 other than Sr are included in strontium ferrite particles when the atomic ratio of Sr to metal M1 is 50 atomic % or more. For example, when metal M1 contains Sr and Ba, hexagonal ferrite particles in which the atomic ratio of Sr to the total amount of Sr and Ba is 50 atomic % or more are called strontium ferrite particles.

[0063] More specifically, the hexagonal ferrite may have an average composition represented by the following general formula (1): Sr(1-x)αxFe(12-y)βyO19 (1) (In formula (1), α represents at least one element selected from the group consisting of Ba, Ca, and Pb. β represents at least one element selected from the group consisting of rare earth elements, transition metal elements other than Fe, and metal elements of Group 13 of the periodic table. x is within the range of 0≦x≦0.9, preferably 0≦x≦0.7, and more preferably 0.3≦x≦0.7. y represents 0≦y≦0.80, preferably 0.22≦y≦0.80, and more preferably 0.26≦y≦0.80.)

[0064] When the magnetic powder contains hexagonal ferrite particles, the average particle size of the magnetic powder may preferably be 20 nm or less, 18 nm or less, 16 nm or less, 14 nm or less, or 12 nm or less. The average particle size may be, for example, 8 nm or more, preferably 9 nm or more, and more preferably 10 nm or more. For example, the average particle size of the magnetic powder may be 8 nm or more to 20 nm or less, 8 nm or more to 18 nm or less, 9 nm or more to 18 nm or less, 9 nm or more to 16 nm or less, or 9 nm or more to 14 nm or less. When the average particle size of the magnetic powder is below the upper limit (for example, 20 nm or less), good electromagnetic conversion characteristics (e.g., SNR) can be obtained in a high-recording-density magnetic recording medium 10. When the average particle size of the magnetic powder is above the lower limit (for example, 8 nm or more, preferably 9 nm or more), the dispersibility of the magnetic powder is further improved, and better electromagnetic conversion characteristics (e.g., SNR) can be obtained.

[0065] When the magnetic powder contains hexagonal ferrite particles, the average aspect ratio of the magnetic powder is preferably 1.0 to 3.0, more preferably 1.0 to 2.8, and even more preferably 1.5 to 2.5. By having the average aspect ratio of the magnetic powder within the above range, aggregation of the magnetic powder can be suppressed, and further, the resistance applied to the magnetic powder when the magnetic powder is vertically oriented in the process of forming the magnetic layer 13 can be suppressed. This can lead to improved vertical orientation of the magnetic powder.

[0066] When the magnetic powder contains hexagonal ferrite particles, the average particle size and average aspect ratio of the magnetic powder can be determined as follows. First, the magnetic recording medium (hereinafter also referred to as "magnetic tape") housed in a magnetic recording tape cartridge is unwound, and a 50 mm section of the magnetic tape to be measured is cut out. For example, in the case of a magnetic recording tape cartridge 10A as shown in FIG. 7, the cut-out position may be 30 m longitudinally from the connection 221 between the magnetic tape T and the leader tape LT. Next, the magnetic tape to be measured is processed by FIB or other methods to thin it. When using the FIB method, a carbon layer and a tungsten layer are formed as protective films as a pretreatment for observing the cross-sectional TEM image described below. The carbon layer is formed by vapor deposition on the surface of the magnetic tape facing the magnetic layer and the surface facing the back layer, and the tungsten layer is further formed by vapor deposition or sputtering on the surface facing the magnetic layer. The thinning is performed along the length (longitudinal direction) of the magnetic tape. That is, the thinning process forms a cross section parallel to both the longitudinal direction and the thickness direction of the magnetic tape.

[0067] The cross section of the obtained thin film sample is observed using a transmission electron microscope (H-9500 manufactured by Hitachi High-Technologies Corporation) at an acceleration voltage of 200 kV and a total magnification of 500,000 times, so that the entire magnetic layer is included in the thickness direction of the magnetic layer, and a TEM photograph is taken. The number of TEM photographs prepared is sufficient to extract 50 particles from which the plate diameter DB and plate thickness DA (see Figure 2A) shown below can be measured.

[0068] In this specification, the size of a hexagonal ferrite particle (hereinafter referred to as "particle size") is defined as the plate diameter DB, which is the longest diameter of the plate surface or base, when the shape of the particle observed in the TEM photograph is plate-like or columnar (however, the thickness or height is smaller than the longest diameter of the plate surface or base), as shown in FIG. 2A. The thickness or height of the particle observed in the TEM photograph is defined as the plate thickness DA. When the plate surface or base of the particle observed in the TEM photograph is hexagonal, the longest diameter means the longest diagonal distance. When the thickness or height of a particle is not constant within a single particle, the thickness or height of the largest particle is defined as the plate thickness DA.

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

[0070] 2B and 2C show examples of TEM photographs. In these figures, for example, particles indicated by arrows a and d are selected because their plate thickness (thickness or height) DA can be clearly confirmed. The plate thickness DA of each of the selected 50 particles is measured. The plate thicknesses DA thus determined are simply averaged (arithmetic mean) to determine the average plate thickness DAave. The average plate thickness DAave is the average particle plate thickness. Next, the plate diameter DB of each magnetic powder is measured. To measure the particle plate diameter DB, 50 particles whose particle plate diameter DB can be clearly confirmed are selected from the TEM photograph. For example, in these figures, particles indicated by arrows b and c are selected because their plate diameter DB can be clearly confirmed. The plate diameter DB of each of the selected 50 particles is measured. The plate diameters DB thus determined are simply averaged (arithmetic mean) to determine the average plate diameter DBave. The average plate diameter DBave is the average particle size.

[0071] When the magnetic powder comprises a powder of hexagonal ferrite particles, the average particle volume of the magnetic powder is preferably 1500 nm 3 or less, more preferably 1400 nm 3 or less, and even more preferably 1200 nm 3 Below, 1000nm 3 or less than 900 nm 3 The average particle volume of the magnetic powder is preferably 500 nm or less. 3 More preferably, 700 nm 3 It could be more than that.

[0072] By setting the average particle volume of the magnetic powder to the above upper limit or less, good electromagnetic conversion characteristics (e.g., SNR) can be obtained in the high recording density magnetic recording medium 10. When the average particle volume of the magnetic powder is set to the above lower limit or more, the dispersibility of the magnetic powder is further improved, and better electromagnetic conversion characteristics (e.g., SNR) can be obtained.

[0073] The average particle volume of the magnetic powder can be calculated as follows: First, as described above in relation to the method for calculating the average particle size of the magnetic powder, the average plate thickness DAave and the average plate diameter DBave are calculated. Next, the average particle volume V of the magnetic powder is calculated using the following formula:

[0074]

[0075] Furthermore, the coercive force Hc1 measured in the thickness direction (perpendicular direction) of the magnetic recording medium 10 is preferably 2010 [Oe] or more and 3520 [Oe] or less, more preferably 2070 [Oe] or more and 3460 [Oe] or less, and even more preferably 2140 [Oe] or more and 3390 [Oe] or less.

[0076] (Embodiment in which magnetic powder contains ε-iron oxide) According to another preferred embodiment of the present technology, the magnetic powder may preferably contain a powder of nanoparticles containing ε-iron oxide (hereinafter referred to as "ε-iron oxide particles"). Even fine particles of ε-iron oxide particles can achieve high coercivity. It is preferable that the ε-iron oxide contained in the ε-iron oxide particles has a preferential crystal orientation in the thickness direction (perpendicular direction) of the magnetic recording medium 10.

[0077] The ε-iron oxide particles may have a composite particle structure, specifically, an ε-iron oxide particle and a soft magnetic portion or a magnetic portion having a higher saturation magnetization σs and a lower coercive force Hc than ε-iron oxide (hereinafter referred to as "soft magnetic portion, etc.").

[0078] The ε-iron oxide portion contains ε-iron oxide. The ε-iron oxide contained in the ε-iron oxide portion preferably has ε-Fe2O3 crystals as a main phase, and more preferably is made of single-phase ε-Fe2O3.

[0079] The soft magnetic portion is in contact with at least a portion of the ε-iron oxide portion. Specifically, the soft magnetic portion may partially cover the ε-iron oxide portion or may completely cover the ε-iron oxide portion.

[0080] The soft magnetic portion (the magnetic portion having a higher saturation magnetization σs and a smaller coercive force Hc than ε-iron oxide) contains a soft magnetic material such as α-Fe, a Ni-Fe alloy, or an Fe-Si-Al alloy. α-Fe may be obtained by reducing ε-iron oxide contained in the ε-iron oxide portion.

[0081] The soft magnetic portion may contain, for example, Fe3O4, γ-Fe2O3, or spinel ferrite.

[0082] By providing the ε-iron oxide particle with a portion having soft magnetic properties as described above, the coercive force Hc of the ε-iron oxide portion alone can be maintained at a high value to ensure thermal stability, while the coercive force Hc of the ε-iron oxide particle (composite particle) as a whole can be adjusted to a coercive force Hc suitable for recording.

[0083] The ε-iron oxide particles may contain an additive instead of the above-mentioned composite particle structure, or may have the above-mentioned composite particle structure and also contain an additive. In this case, a portion of the Fe in the ε-iron oxide particles is substituted with the additive. By containing the additive in the ε-iron oxide particles, the coercivity Hc of the 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 selected from the group consisting of Al, Ga, and In, and even more preferably at least one selected from the group consisting of Al and Ga.

[0084] Specifically, the additive-containing ε-iron oxide is an ε-Fe2-xMxO3 crystal (where M is a metal element other than iron, preferably a trivalent metal element, more preferably one or more selected from the group consisting of Al, Ga, and In; x is, for example, 0≦x<1).

[0085] The average particle size (average maximum particle size) of the magnetic powder is preferably 22 nm or less, more preferably 8 nm to 22 nm, and even more preferably 12 nm to 22 nm. In the magnetic recording medium 10, the actual magnetization region is a region half the size of the recording wavelength. Therefore, by setting the average particle size of the magnetic powder to less than half the shortest recording wavelength, a good SNR can be obtained. Therefore, when the average particle size of the magnetic powder is 22 nm or less, good electromagnetic conversion characteristics (e.g., SNR) can be obtained in a high-recording-density magnetic recording medium 10 (e.g., a magnetic recording medium 10 configured to record signals at the shortest recording wavelength of 44 nm or less). 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 better electromagnetic conversion characteristics (e.g., SNR) can be obtained.

[0086] The average aspect ratio of the magnetic powder is preferably 1.0 or more and 3.0 or less, more preferably 1.0 or more and 2.9 or less, and even more preferably 1.0 or more and 2.5 or less. When the average aspect ratio of the magnetic powder is within the above range, aggregation of the magnetic powder can be suppressed, and the resistance applied to the magnetic powder when the magnetic powder is vertically oriented in the process of forming the magnetic layer 13 can be suppressed. Therefore, the vertical orientation of the magnetic powder can be improved.

[0087] When the magnetic powder contains ε-iron oxide particles, the average particle size and average aspect ratio of the magnetic powder can be determined as follows. First, the magnetic recording medium to be measured is cut out as described above for the case where the magnetic powder contains hexagonal ferrite particles. The magnetic recording medium to be measured is processed into thin sections using a focused ion beam (FIB) method or the like. When using the FIB method, a carbon film and a tungsten thin film are formed as protective films as a pretreatment for observing the cross-sectional TEM image described below. The carbon film is formed on the magnetic layer side surface and back layer side surface of the magnetic recording medium by a vapor deposition method, and the tungsten thin film is further formed on the magnetic layer side surface by a vapor deposition method or a sputtering method. The thinning is performed along the length direction (longitudinal direction) of the magnetic recording medium. In other words, the thinning results in a cross section parallel to both the longitudinal direction and the thickness direction of the magnetic recording medium.

[0088] The cross section of the obtained thin film sample is observed using a transmission electron microscope (H-9500 manufactured by Hitachi High-Technologies Corporation) at an acceleration voltage of 200 kV and a total magnification of 500,000 times, so as to include the entire magnetic layer 13 in the thickness direction of the magnetic layer 13, and a TEM photograph is taken.

[0089] Next, 50 particles whose particle shape can be clearly confirmed are selected from the TEM photograph, 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 so as to be tangent to the contour of each particle (so-called maximum Feret 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.

[0090] Next, the major axis lengths DL of the measured 50 particles are simply averaged (arithmetic mean) to determine the average major axis length DLave. The average major axis length DLave thus determined is the average particle size of the magnetic powder. The minor axis lengths DS of the measured 50 particles are also simply averaged (arithmetic mean) to determine the average minor axis length DSave. The average aspect ratio of the particles (DLave / DSave) is then determined from the average major axis length DLave and the average minor axis length DSave.

[0091] When the magnetic powder contains ε-iron oxide, the average particle volume is preferably 1500 nm, similar to when the magnetic powder contains hexagonal ferrite particles. 3 or less, more preferably 1400 nm 3 or less, and even more preferably 1200 nm 3 Below, 1100nm 3 or less than 1000 nm 3 The average particle volume of the magnetic powder is preferably 500 nm 3 More preferably, 700 nm 3 It could be more than that.

[0092] By setting the average particle volume of the magnetic powder to the above upper limit or less, good electromagnetic conversion characteristics (e.g., SNR) can be obtained in the high recording density magnetic recording medium 10. By setting the average particle volume of the magnetic powder to the above lower limit or more, the dispersibility of the magnetic powder is further improved, and better electromagnetic conversion characteristics (e.g., SNR) can be obtained.

[0093] When the ε-iron oxide particles are spherical or nearly spherical, the average particle volume of the magnetic powder can be calculated as follows. First, the average major axis length DLave is calculated in the same manner as in the above-mentioned method for calculating the average particle size of the magnetic powder. Next, the average particle volume V of the magnetic powder is calculated using the following formula: V = (π / 6) × DLave 3

[0094] When the ε-iron oxide particles have a cubic shape, the average particle volume of the magnetic powder can be determined as follows. The magnetic recording medium 10 is processed and thinned by a method such as FIB (Focused Ion Beam). When the FIB method is used, a carbon film and a tungsten thin film are formed as protective films as a pretreatment for observing the cross-sectional TEM image described below. The carbon film is formed on the magnetic layer side surface and the back layer side surface of the magnetic recording medium 10 by a vapor deposition method, and the tungsten thin film is further formed on the magnetic layer side surface by a vapor deposition method or a sputtering method. The thinning is performed along the length direction (longitudinal direction) of the magnetic recording medium 10. In other words, the thinning forms a cross section parallel to both the longitudinal direction and the thickness direction of the magnetic recording medium 10.

[0095] The obtained thin film sample is observed using a transmission electron microscope (H-9500 manufactured by Hitachi High-Technologies Corporation) at an acceleration voltage of 200 kV and a total magnification of 500,000 times to obtain a cross section of the magnetic layer 13 in the thickness direction, including the entire magnetic layer 13, to obtain a TEM photograph. The magnification and acceleration voltage may be adjusted appropriately depending on the type of apparatus.

[0096] Next, 50 particles whose particle shapes are clear are selected from the TEM photograph, and the side length DC of each particle is measured. The side lengths DC of the 50 measured particles are then simply averaged (arithmetic mean) to determine the average side length DCave. Next, the average particle volume Vave of the magnetic powder is calculated using the average side length DCave from the following formula: Vave = DCave 3

[0097] The coercive force Hc of the ε iron oxide particles is, for example, preferably 2500 Oe or more, more preferably 2800 Oe or more, with the upper limit being, for example, 4200 Oe or less.

[0098] (Embodiment in which magnetic powder includes Co-containing spinel ferrite) According to yet another preferred embodiment of the present technology, the magnetic powder may include a powder of nanoparticles containing Co-containing spinel ferrite (hereinafter also referred to as "cobalt ferrite particles"). That is, the magnetic powder may be cobalt ferrite magnetic powder. The cobalt ferrite particles preferably have uniaxial crystal anisotropy. The cobalt ferrite magnetic particles have, for example, a cubic or approximately cubic shape. The Co-containing spinel ferrite may further include one or more elements selected from the group consisting of Ni, Mn, Al, Cu, and Zn in addition to Co.

[0099] Cobalt ferrite has an average composition represented by the following formula, for example: CoxMyFe2Oz (wherein, in the formula, M is one or more metals selected from the group consisting of, for example, Ni, Mn, Al, Cu, and Zn. x is a value within the range of 0.4≦x≦1.0. y is a value within the range of 0≦y≦0.3. However, x and y satisfy the relationship (x+y)≦1.0. z is a value within the range of 3≦z≦4. A portion of Fe may be substituted with another metal element.)

[0100] The average particle size of the cobalt ferrite magnetic powder is preferably 21 nm or less, more preferably 19 nm or less. The coercive force Hc of the cobalt ferrite magnetic powder is, for example, preferably 2500 Oe or more, more preferably 2600 Oe or more, with the upper limit being, for example, 3500 Oe or less.

[0101] When the magnetic powder contains cobalt ferrite particles, the average particle size of the magnetic powder is preferably 25 nm or less, more preferably 10 nm or more and 19 nm or less. Such a small average particle size of the magnetic powder enables good electromagnetic conversion characteristics (e.g., SNR) to be obtained in a high-recording-density magnetic recording medium 10. On the other hand, when the average particle size of the magnetic powder is 10 nm or more, the dispersibility of the magnetic powder is further improved, enabling better electromagnetic conversion characteristics (e.g., SNR) to be obtained. When the magnetic powder contains cobalt ferrite particles, the average aspect ratio and average particle size of the magnetic powder are determined in the same manner as when the magnetic powder contains ε-iron oxide particles.

[0102] When the magnetic powder contains Co-containing spinel ferrite, the average particle volume is preferably 1500 nm, similar to when the magnetic powder contains the other materials described above. 3 or less, more preferably 1400 nm 3 or less, and even more preferably 1200 nm 3 Below, 1100nm 3 or less than 1000 nm 3 The average particle volume of the magnetic powder is preferably 500 nm 3 More preferably, 700 nm 3 It could be more than that.

[0103] By setting the average particle volume of the magnetic powder to the above upper limit or less, it is possible to obtain good electromagnetic conversion characteristics (e.g., SNR) in the high recording density magnetic recording medium 10. By setting the average particle volume of the magnetic powder to the above lower limit or more, the dispersibility of the magnetic powder is further improved, and it is possible to obtain better electromagnetic conversion characteristics (e.g., SNR).

[0104] 1, the magnetic layer 13, together with the non-magnetic layer 12 described below, constitutes one or more layers provided on one side of the substrate layer. The components of the magnetic layer 13 may include, as one or more layers, a compound having a toluene diisocyanate (TDI) structure in its molecule and dibutylhydroxytoluene (BHI).

[0105] The magnetic layer 13 may also contain non-magnetic additives to increase the strength and durability of the magnetic layer 13. Furthermore, for example, the magnetic layer 13 may also contain binders, lubricants, dispersants, abrasives, and the like, as needed. A compound having a toluene diisocyanate (TDI) structure in its molecule may be used as a binder in the magnetic layer 13, or a binder may be added separately from the compound having a toluene diisocyanate (TDI) structure in its molecule. The magnetic layer 13 may be prepared, for example, as a magnetic paint containing a magnetic powder and these selected additives, and then applied to the underlying layer.

[0106] (Binder) The binder to be blended in the magnetic layer 13 is preferably, for example, a resin having a structure in which a crosslinking reaction has been imparted to a polyurethane resin or a vinyl chloride resin. However, the binder is not limited to these, and other resins may be blended as appropriate depending on the physical properties required of the magnetic recording medium 10. There is no particular limitation on the resin to be blended, so long as it is a resin that is generally used in coating-type magnetic recording media 10.

[0107] Examples of the binder include polyvinyl chloride, polyvinyl acetate, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, acrylic acid ester-acrylonitrile copolymer, acrylic acid ester-vinyl chloride-vinylidene chloride copolymer, acrylic acid ester-vinylidene chloride copolymer, methacrylic acid ester-vinylidene chloride copolymer, methacrylic acid ester-vinyl chloride copolymer, methacrylic acid 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, polyester resin, amino resin, and synthetic rubber.

[0108] Furthermore, a thermosetting resin or a reactive resin may be used as the binder, and examples of these include phenolic resin, epoxy resin, urea resin, melamine resin, alkyd resin, silicone resin, polyamine resin, and urea-formaldehyde resin.

[0109] Furthermore, in order to improve the dispersibility of the magnetic powder, polar functional groups such as -SO3M, -OSO3M, -COOM, and P=O(OM)2 may be introduced into each of the binders described above, where M is a hydrogen atom or an alkali metal such as lithium, potassium, or sodium.

[0110] Furthermore, examples of polar functional groups include side chain types having terminal groups of -NR1R2 and -NR1R2R3+X-, and main chain types of >NR1R2+X-. In this formula, R1, R2, and R3 are hydrogen atoms or hydrocarbon groups, and X- is a halogen element ion such as fluorine, chlorine, bromine, or iodine, or an inorganic or organic ion. Other examples of polar functional groups include -OH, -SH, -CN, and epoxy groups.

[0111] In one embodiment of the present technology, the magnetic layer includes a chlorine-containing binder. The chlorine-containing binder may be a chlorine-containing resin. The chlorine-containing resin is a resin that contains a chlorine atom as at least one of the elements that constitute the resin.

[0112] The chlorine-containing binder is, for example, a vinyl chloride resin. More specific examples of the chlorine-containing binder include polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, acrylate-vinyl chloride-vinylidene chloride copolymer, acrylate-vinylidene chloride copolymer, methacrylate-vinylidene chloride copolymer, methacrylate-vinyl chloride copolymer, vinylidene chloride-acrylonitrile copolymer, and synthetic rubber.

[0113] The content of the chlorine-containing binder in the magnetic layer may be, for example, preferably 30 parts by weight or more, more preferably 35 parts by weight or more, and even more preferably 40 parts by weight or more, per 100 parts by weight of magnetic powder, and may be, for example, preferably 70 parts by weight or less, more preferably 65 parts by weight or less, and even more preferably 60 parts by weight or less, per 100 parts by weight of magnetic powder.

[0114] The magnetic layer may further contain a chlorine-free binder in addition to the chlorine-containing binder. The chlorine-free binder may be a chlorine-free resin. The chlorine-free resin may include, for example, a polyurethane-based resin. The polyurethane-based resin is a polymer having a urethane bond (—NH—C(═O)—) and may be produced, for example, by a polyaddition reaction between an isocyanate compound and a diol compound. The polyurethane-based resin may be, for example, a urethane-modified copolymer polyester. The urethane-modified copolymer polyester may be a urethane-modified copolymer polyester having an aromatic polyester as a basic skeleton and a urethane component in the side chain, or a urethane-modified copolymer polyester containing an ester repeating unit and a urethane repeating unit in the basic skeleton.

[0115] The content of the chlorine-free binder in the magnetic layer may be, for example, preferably 1 part by mass or more, more preferably 2 parts by mass or more, and even more preferably 3 parts by mass or more, per 100 parts by mass of magnetic powder, and may be, for example, preferably 15 parts by mass or less, more preferably 12 parts by mass or less, and even more preferably 10 parts by mass or less, per 100 parts by mass of magnetic powder.

[0116] (Lubricant) The magnetic layer 13 may contain a lubricant. The lubricant may be, for example, one or more selected from fatty acids and / or fatty acid esters, and preferably contains both a fatty acid and a fatty acid ester. The fatty acid may preferably be a compound represented by the following general chemical formula (1) or general chemical formula (2). For example, the fatty acid may contain one or both of the compound represented by the following general chemical formula (1) and the compound represented by the general chemical formula (2). The fatty acid ester may preferably be a compound represented by the following general chemical formula (3), general chemical formula (4), or general chemical formula (5). For example, the fatty acid ester may contain any one of the compounds represented by the following general chemical formula (3), the compounds represented by the general chemical formula (4), and the compounds represented by the general chemical formula (5), or two or more selected from these. The lubricant contains either one or both of the compound represented by general chemical formula (1) and the compound represented by general chemical formula (2), and either one or two or more selected from the compound represented by general chemical formula (3), the compound represented by general chemical formula (4), and the compound represented by general chemical formula (5), thereby making it possible to suppress an increase in the dynamic friction coefficient of the magnetic recording medium due to repeated recording or reproduction.

[0117] CH3(CH2)kCOOH (1) (In general chemical formula (1), k is an integer selected from the range of 14 to 22, more preferably from the range of 14 to 18.)

[0118] CH3(CH2)nCH=CH(CH2)mCOOH (2) (In the general chemical formula (2), the sum of n and m is an integer selected from the range of 12 to 20, more preferably from the range of 14 to 18.)

[0119] CH3(CH2)pCOO(CH2)qCH3 (3) (In general chemical formula (3), p is an integer selected from the range of 14 or more and 22 or less, more preferably 14 or more and 18 or less, and q is an integer selected from the range of 2 or more and 5 or less, more preferably 2 or more and 4 or less.)

[0120] CH3(CH2)rCOO-(CH2)sCH(CH3)2 (4) (In general chemical formula (4), r is an integer selected from the range of 14 to 22, and s is an integer selected from the range of 1 to 3.)

[0121] CH3(CH2)tCOO-(CH)(CH3)CH2(CH3)u (5) (In general formula (5), t is an integer selected from the range of 14 to 22, and u is an integer selected from the range of 1 to 3.)

[0122] Examples of the lubricant include esters of monobasic fatty acids having 10 to 24 carbon atoms with any of monohydric to hexahydric alcohols having 2 to 12 carbon atoms, mixed esters thereof, di-fatty acid esters, tri-fatty acid esters, etc. Specific examples of the lubricant include lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, oleic acid, linoleic acid, linolenic acid, elaidic acid, butyl stearate, pentyl stearate, heptyl stearate, octyl stearate, isooctyl stearate, octyl myristate, etc. The magnetic layer may contain any one or more of these.

[0123] The content of the lubricant may be, for example, preferably 1 part by mass or more, more preferably 2 parts by mass or more, per 100 parts by mass of the magnetic powder, and may be, for example, preferably 10 parts by mass or less, more preferably 8 parts by mass or less, and even more preferably 6 parts by mass or less, per 100 parts by mass of the magnetic powder.

[0124] (Additives) The magnetic layer 13 may further contain non-magnetic reinforcing particles such as aluminum oxide (α-, β-, or γ-alumina), chromium oxide, silicon oxide, diamond, garnet, emery, boron nitride, titanium carbide, silicon carbide, titanium carbide, titanium oxide (rutile or anatase titanium oxide), and the like.

[0125] In one embodiment of the present technology, the magnetic layer may contain first particles having electrical conductivity and second particles having a Mohs hardness of 7 or greater. The first particles and the second particles may form protrusions on the surface of the magnetic layer. For example, the first particles can prevent an increase in frictional force during magnetic recording tape running, and function as, for example, a solid lubricant component. Furthermore, the second particles can exert an abrasive effect (and even an anchor effect) for magnetic head cleaning. It is believed that including these two components in the magnetic layer of a magnetic recording tape can prevent an increase in frictional force and clean the magnetic head, thereby improving running performance.

[0126] The first particles are electrically conductive. The first particles may be fine particles primarily composed of carbon, preferably carbon particles, and examples of such carbon particles include carbon black. Examples of carbon black that may be used include Asahi #15 and #15HS from Asahi Carbon Co., Ltd. and Seast TA from Tokai Carbon Co., Ltd. Hybrid carbon in which carbon is attached to the surface of silica particles may also be used.

[0127] The average particle size (arithmetic mean value of particle diameters measured using an electron microscope) of the first particles (particularly carbon particles, for example, carbon black) may be, for example, preferably 15 nm or more, more preferably 30 nm or more, and even more preferably 50 nm or more. Furthermore, the average particle size may be, for example, preferably 200 nm or less, more preferably 180 nm or less, even more preferably 150 nm or less, 130 nm or less, or 120 nm or less. The numerical range of the average particle size may be appropriately selected from these upper and lower limits, and may be, for example, preferably 50 nm to 200 nm, more preferably 50 nm to 180 nm, even more preferably 50 nm to 150 nm, and even more preferably 50 nm to 130 nm.

[0128] From the viewpoint of suppressing deformation due to contact with a magnetic head, the second particles may have a Mohs hardness of preferably 7 or more, more preferably 7.5 or more, even more preferably 8 or more, and even more preferably 8.5 or more. From the viewpoint of suppressing head wear, the Mohs hardness of the second particles may be, for example, preferably 10 or less, more preferably 9.5 or less. That is, the second particles may be formed from a material having such a Mohs hardness.

[0129] The second particles may preferably be inorganic particles. Examples of the second particles include α-alumina (the α-conversion rate may be, for example, 90% or more), β-alumina, γ-alumina, silicon carbide, chromium oxide, cerium oxide, α-iron oxide, corundum, silicon nitride, titanium carbide, titanium oxide, silicon dioxide, tin oxide, magnesium oxide, tungsten oxide, zirconium oxide, boron nitride, zinc oxide, calcium carbonate, calcium sulfate, barium sulfate, molybdenum disulfide, and acicular α-iron oxide obtained by dehydrating and annealing magnetic iron oxide raw materials, optionally surface-treated with aluminum and / or silica, or diamond powder, or a combination of two or more of these. The second particles are preferably alumina particles such as α-alumina, β-alumina, and γ-alumina, or silicon carbide. These second particles may be acicular, spherical, cubic, or other shapes, but those having corners in their shape are preferred because they have, for example, high abrasiveness.

[0130] The average particle size (e.g., the arithmetic mean value of particle diameters measured using an electron microscope) of the second particles (particularly inorganic particles, such as alumina) may be, for example, preferably 15 nm or more, more preferably 30 nm or more, and even more preferably 50 nm or more. Furthermore, the average particle size may be, for example, preferably 200 nm or less, more preferably 180 nm or less, even more preferably 150 nm or less, 130 nm or less, or 120 nm or less. The numerical range of the average particle size may be appropriately selected from these upper and lower limits, and may be, for example, preferably 50 nm to 180 nm, more preferably 60 nm to 150 nm, and even more preferably 60 nm to 120 nm.

[0131] The second particles (particularly inorganic particles, such as alumina) may not be electrically conductive, i.e., they may not have the same electrical conductivity as the first particles.

[0132] 3, the magnetic layer 13 has a plurality of data bands d (data bands d0 to d3) that are long in the longitudinal direction (X-axis direction) in which data is written, and a plurality of servo bands s (servo bands s0 to s4) that are long in the longitudinal direction in which servo patterns 6 are written. The servo bands s are arranged at positions that sandwich each data band d in the width direction (Y-axis direction). It is preferable that the magnetic layer 13 have five or more servo bands s.

[0133] In this technology, the ratio of the area of ​​the servo bands s to the area of ​​the entire surface of the magnetic layer 13 is typically 4.0% or less. The width of the servo bands s is, for example, 98 μm or less for a ½ inch tape width. The ratio of the area of ​​the servo bands s to the area of ​​the entire surface of the magnetic layer 13 can be measured, for example, by developing the magnetic recording medium using a developer such as a ferricolloid developer, and then observing the developed magnetic recording medium with an optical microscope.

[0134] 3 shows an example in which the number of data bands d is 4 and the number of servo bands s is 5. Note that the number of data bands d and the number of servo bands s can be changed as appropriate.

[0135] The data band d includes a plurality of recording tracks 5 that are long in the longitudinal direction and aligned in the width direction. The number of recording tracks 5 included in one data band d is, for example, about 1,000 to 2,500. Data is recorded along these recording tracks 5 within the recording tracks 5. The length of one bit in the longitudinal direction of the data recorded in the data band d is, for example, 48 nm or less. The servo band s includes a servo pattern 6 of a predetermined shape that is recorded by a servo pattern recording device, which will be described later.

[0136] Here, the number of recording tracks 5 increases with each generation of LTO-standard magnetic recording media, dramatically improving recording capacity. For example, the original LTO-1 had 384 recording tracks 5, but the numbers of recording tracks 5 in LTO-2 to LTO-8 are 512, 704, 896, 1280, 2176, 3584, and 6656, respectively. Similarly, the data recording capacity was 100 GB (gigabytes) in LTO-1, but is 200 GB, 400 GB, 800 GB, 1.5 TB (terabytes), 2.5 TB, 6.0 TB, and 12 TB, respectively, in LTO-2 to LTO-8.

[0137] In this embodiment, the number of recording tracks 5 and the recording capacity are not particularly limited and can be changed as appropriate. However, it is advantageous to apply this to magnetic recording media that have a large number of recording tracks 5 and a large recording capacity (for example, 6,656 tracks or more, 12 TB or more: LTO8 or later) and are susceptible to variations in the width of the magnetic recording medium. For example, a magnetic tape with a Young's modulus of the entire tape (Young's modulus in the longitudinal direction of the tape) of 8 GPa or less is used as the magnetic tape recording medium.

[0138] (Data Band and Servo Band) Figure 4 is an enlarged view showing an example of recording tracks (data tracks) 5 in the data band d of a magnetic recording medium conforming to the LTO standard up to the LT09 standard. As shown in Figure 4, the recording tracks 5 are long in the longitudinal direction, aligned in the width direction, and each track has a predetermined recording track width (data track width) Wd in the width direction. This recording track width Wd is set to 2.0 μm or less in LTO-8. From the viewpoint of improving the recording track recording density and ensuring high recording capacity, the upper limit of the average recording track width (data track width) Wd is preferably 1200 nm or less, more preferably 1000 nm or less, even more preferably 800 nm or less, and particularly preferably 600 nm or less. The lower limit of the average recording track width (data track width) Wd is preferably 20 nm or more, taking into account the magnetic grain size. The recording track width Wd can be measured, for example, by developing the magnetic layer 13 of the magnetic recording medium 10 using a developer such as a ferricolloid developer, and then observing the developed magnetic layer 13 of the magnetic recording medium 10 with an optical microscope. Alternatively, as a measurement method using a drive head, the drive head can be placed in a read-while-write state to ignore fluctuations during tape running, and the recording track width Wd can be measured from the change in output when the azimuth of the drive head is changed. (IEEE_Sept1996_Crosstrack Profiles of Thin Film MR Tape Heads Using the Azimuth Displacement Method)

[0139] FIG. 5 is an enlarged view showing a portion of an example of a servo pattern 6 written in a servo band s of a magnetic recording medium conforming to the LTO standard up to the LT09 standard. As shown in FIG. 5 , the servo pattern 6 includes a plurality of stripes inclined at a predetermined azimuth angle α with respect to the width direction (Y-axis direction), as will be described in detail later. These stripes are classified into a first group of stripes 61 inclined clockwise with respect to the width direction (Y-axis direction) and a second group of stripes 62 inclined counterclockwise with respect to the width direction. The first group of stripes 61 and the second group of stripes 62 typically include four or five stripes. The shape of the servo pattern 6 can be measured, for example, by developing the magnetic layer 13 of the magnetic recording medium 10 using a developer such as a ferricolloid developer and then observing the developed magnetic layer 13 of the magnetic recording medium 10 with an optical microscope. The servo band s may also be a servo band for tilting the recording / reproducing head of a drive.

[0140] 5, the servo trace lines TL, which are lines traced by a servo read head 132 (described later) on the servo pattern 6, are shown by dashed lines. The servo trace lines TL are set along the longitudinal direction (X-axis direction) and are also set at a predetermined interval Ps in the width direction.

[0141] The number of servo trace lines TL per servo band s is, for example, about 30 to 60. The spacing Ps between two adjacent servo trace lines TL is the same as the recording track width Wd, and is, for example, 2.0 μm or less. Here, the spacing Ps between two adjacent servo trace lines TL is a value that determines the recording track width Wd. In other words, when the spacing Ps between the servo trace lines TL is narrowed, the recording track width Wd becomes smaller, and the number of recording tracks 5 included in one data band d increases. As a result, the data recording capacity increases.

[0142] <Nonmagnetic Layer> The magnetic recording medium of the present technology has one or more layers including a magnetic layer on one side of a substrate layer, and the one or more layers may include a nonmagnetic layer. The nonmagnetic layer is a nonmagnetic layer containing a nonmagnetic powder and a binder as its main components. The nonmagnetic layer is also sometimes referred to as an intermediate layer or an underlayer. This nonmagnetic layer is provided for the purpose of retaining the effect of magnetic force on the magnetic layer at the magnetic layer and ensuring the flatness required of the magnetic layer. In addition, this nonmagnetic layer also plays a role in retaining a lubricant added to the magnetic layer or the nonmagnetic layer itself.

[0143] In the magnetic recording medium 10 shown in Figure 1, it can be seen that the nonmagnetic layer 12, together with the magnetic layer 13, constitutes one or more layers provided on one side of the substrate layer. In the magnetic recording medium 10 shown in Figure 1, the nonmagnetic layer 12 is disposed between the substrate layer 11 and the magnetic layer 13. The components of the nonmagnetic layer 12 may include, as one or more layers, a compound having a toluene diisocyanate (TDI) structure in its molecule and dibutylhydroxytoluene (BHI).

[0144] The nonmagnetic layer 12 may further contain at least one additive, such as other particles, a lubricant, a curing agent, or a rust inhibitor, as necessary. The compound having a toluene diisocyanate (TDI) structure in its molecule may be used as a binder in the nonmagnetic layer 12, or a binder may be blended in addition to the compound having a toluene diisocyanate (TDI) structure in its molecule. The nonmagnetic layer 12 may be prepared as a paint and formed by coating, for example.

[0145] (Nonmagnetic Powder) The nonmagnetic powder contained in the nonmagnetic layer 12 includes, for example, at least one type selected from inorganic particles and organic particles, particularly at least one type selected from inorganic particles. One type of nonmagnetic powder may be used alone, or two or more types of nonmagnetic powders may be used in combination. The nonmagnetic inorganic particles may be, for example, one or a combination of two or more types selected from metals, metal oxides, metal carbonates, metal sulfates, metal nitrides, metal carbides, and metal sulfides. More specifically, the inorganic particles may be, for example, one or two or more types selected from iron oxide, aluminum oxide, carbon black, iron oxyhydroxide, hematite, titanium oxide, silicon oxide, titanium carbide, silicon carbide, diamond, and calcium carbonate. The shape of the nonmagnetic powder may be, for example, various shapes such as acicular, spherical, cubic, and plate-like, but is not particularly limited thereto.

[0146] In one embodiment of the present technology, the non-magnetic powder includes at least iron oxide, particularly acicular iron oxide. In this embodiment, the non-magnetic powder may further include carbon black and / or aluminum oxide.

[0147] The average major axis length of the iron oxide (particularly acicular iron oxide) may be, for example, preferably 0.01 μm or more, more preferably 0.02 μm or more, and even more preferably 0.03 μm or more, and may be, for example, preferably 0.25 μm or less, more preferably 0.18 μm or less, and even more preferably 0.12 μm or less.

[0148] The average particle size of the carbon black may be, for example, preferably 10 nm or more, more preferably 12 nm or more, and even more preferably 15 nm or more, and may be, for example, preferably 250 nm or less, more preferably 150 nm or less, and even more preferably 100 nm or less.

[0149] The amount of carbon black may be, for example, preferably 15 parts by mass or more, more preferably 20 parts by mass or more, and even more preferably 25 parts by mass or more, per 100 parts by mass of the iron oxide. The amount of carbon black may be, for example, preferably 45 parts by mass or less, more preferably 40 parts by mass or less, and even more preferably 35 parts by mass or less, per 100 parts by mass of the iron oxide.

[0150] The average particle size of the aluminum oxide may be, for example, preferably 30 nm or more, more preferably 40 nm or more, and even more preferably 60 nm or more, and may be, for example, preferably 180 nm or less, more preferably 150 nm or less, and even more preferably 120 nm or less.

[0151] The content of aluminum oxide may be, for example, preferably 1 part by mass or more, more preferably 2 parts by mass or more, and even more preferably 3 parts by mass or more, relative to 100 parts by mass of the iron oxide. The content of aluminum oxide may be, for example, preferably 10 parts by mass or less, more preferably 9 parts by mass or less, and even more preferably 8 parts by mass or less, relative to 100 parts by mass of the iron oxide.

[0152] (Binder) As mentioned above, the non-magnetic layer may contain a binder. The above description of the binder contained in the magnetic layer 13 also applies to the binder contained in the non-magnetic layer 12.

[0153] (Lubricant) As mentioned above, the non-magnetic layer may contain a lubricant. The above description regarding the lubricant contained in the magnetic layer 13 also applies to the lubricant contained in the non-magnetic layer 12.

[0154] <Back Layer> The magnetic recording medium of the present technology may be configured to have a back layer provided on the other side of the base layer. The back layer plays a role in controlling friction that occurs when a magnetic recording tape using the magnetic recording medium runs at high speed while facing a magnetic head, and in preventing winding irregularities. In other words, the back layer plays a fundamental role in ensuring stable running of the magnetic recording tape at high speed.

[0155] 1, it can be seen that the back layer 14 is provided on the surface of the base layer 11 opposite to the surface on which the nonmagnetic layer 12 and magnetic layer 13 are provided. The components of the back layer 14 may include a compound having a toluene diisocyanate (TDI) structure in its molecule and dibutylhydroxytoluene (BHI).

[0156] The back layer 14 may contain a binder and a non-magnetic powder. The back layer 14 may further contain at least one additive selected from the group consisting of a lubricant, a hardener, and an antistatic agent, as necessary. The binder and non-magnetic powder may be the same as those used for the non-magnetic layer 12. The back layer 14 may be prepared as a paint and formed by coating, for example.

[0157] In the magnetic recording medium of the present technology, similarly to the one or more layers described above, the intensity ratio of the detected peaks of the TDI and the BHT obtained when the back layer is measured by GC-MS may be BHT / TDI≦0.030. Even in this range, the stability of the compound having a TDI structure in its molecule before film formation can be ensured. In the magnetic recording medium of the present technology, the BHT / TDI obtained when the back layer is measured by GC-MS is preferably 0.030 or less, more preferably 0.025 or less, and particularly preferably 0.020 or less.

[0158] Similarly, the lower limit of the BHT / TDI ratio obtained when the backing layer is measured by GC-MS is not particularly limited as long as it is within a range that ensures the stability of the compound having a TDI structure in its molecule before film formation. For example, it can be adjusted within a range of 0.010 or more, 0.012 or more, etc.

[0159] The average particle size of the non-magnetic powder is preferably 10 nm or more and 150 nm or less, more preferably 15 nm or more and 110 nm or less. The average particle size of the non-magnetic powder is determined in the same manner as the average particle size of the magnetic powder. The non-magnetic powder may contain non-magnetic powder having two or more particle size distributions.

[0160] The upper limit of the average thickness of the back layer 14 is preferably 0.6 μm or less. If the upper limit of the average thickness of the back layer 14 is 0.6 μm or less, the thickness of the nonmagnetic layer 12 and the base layer 11 can be maintained large even when the average thickness of the tape T is 5.6 μm. This makes it possible to maintain running stability of the magnetic recording tape in a recording / reproducing device using the magnetic recording medium. The lower limit of the average thickness of the back layer 14 is not particularly limited, but is, for example, 0.2 μm or more.

[0161] The average thickness of the back layer 14 is determined as follows. First, a 1 / 2-inch wide tape T is prepared and cut into a length of 250 mm to prepare a sample. Next, the thickness of the sample is measured at five or more points using a laser hologram made by Mitsutoyo Corporation as a measuring device, and the measured values ​​are simply averaged (arithmetic mean) to obtain the average thickness t of the tape T. Ｔ The measurement position is selected randomly from the sample. Next, the back layer 14 of the sample is removed with a solvent such as MEK (methyl ethyl ketone) or dilute hydrochloric acid. Thereafter, the thickness of the sample is measured again at five or more points using the laser hologram, and the measured values ​​are simply averaged (arithmetic mean) to obtain the average thickness t of the tape T from which the back layer 14 has been removed. Ｂ The measurement position is selected randomly from the sample. Then, the average thickness t of the back layer 14 is calculated using the following formula: ｂ Calculate [μm]. ｂ [μm] = t Ｔ [μm]-t Ｂ [μm]

[0162] The thickness of this back layer 14 is preferably 100 nm or more. If it is less than 100 nm, the electrical resistance will be high, causing problems such as poor compatibility with magnetic heads. The upper limit of the thickness should be the minimum thickness that allows the back layer 14 to perform its functions, particularly a thickness that is necessary and sufficient for high-speed stable running of the magnetic recording tape in a recording and reproducing device. From this perspective, there is no particular need for the thickness to be 1 μm or more.

[0163] The back layer 14 is formed from a composition containing a binder and non-magnetic powder, and may contain a lubricant and a hardener as needed. An antistatic agent may also be added to give the back layer 14 an antistatic function, thereby preventing the adhesion of dirt and dust.

[0164] <Barrier Layer> As shown in FIG. 6 , the magnetic recording medium 10 of the present technology may further include a barrier layer 15 provided on at least one surface of the substrate layer 11. The barrier layer 15 is a layer for suppressing dimensional deformation of the substrate layer 11 depending on the environment. For example, one example of a cause of dimensional deformation is the hygroscopicity of the substrate layer 11, and the barrier layer 15 can reduce the rate at which moisture penetrates into the substrate layer 11. The barrier layer 15 includes a metal or a metal oxide. As the metal, for example, at least one of Al, Cu, Co, Mg, Si, Ti, V, Cr, Mn, Fe, Ni, Zn, Ga, Ge, Y, Zr, Mo, Ru, Pd, Ag, Ba, Pt, Au, and Ta can be used. As the metal oxide, for example, Al ２ O ３ , CuO, CoO, SiO ２ , Cr ２ O ３ , TiO ２ , Ta ２ O ５ , and ZrO ２ At least one of the above metals can be used, or any of the oxides of the above metals can be used. Diamond-like carbon (DLC) or diamond can also be used.

[0165] The average thickness of the barrier layer 15 is preferably 20 nm or more and 1000 nm or less, more preferably 50 nm or more and 1000 nm or less. ｍ However, in this case, the magnification of the TEM image is adjusted appropriately depending on the thickness of the barrier layer 15.

[0166] <Other Layers> The magnetic recording medium of the present technology may include other layers in addition to the above-described configuration, as needed, as long as the desired physical properties are not significantly impaired.

[0167] [Magnetic Recording Tape] The present technology provides a magnetic recording tape in the form of a long magnetic recording medium according to the present technology. This magnetic recording tape can be used for recording or playback via a magnetic head. As described above, the magnetic recording tape according to the present technology can effectively suppress a decrease in the abrasive power of the surface that comes into contact with the magnetic head, thereby effectively maintaining the function of removing dirt from the magnetic head.

[0168] There are no particular limitations on the magnetic head that can be used with the magnetic recording tape of the present technology, and recording or playback can be suitably performed using any magnetic head, such as a ring-type magnetic head or a perpendicular recording magnetic head. Furthermore, there are no particular limitations on the running speed of the magnetic recording tape using the magnetic recording medium of the present technology when recording or playback via the magnetic head, and any running speed can be used. Therefore, for example, even if the tape running speed is 4 m / s or higher, recording or playback can be suitably performed using the magnetic head.

[0169] [Magnetic Recording Tape Cartridge] The present technology also provides a magnetic recording tape cartridge (also referred to as a tape cartridge) including a magnetic recording tape using the magnetic recording medium of the present technology. In the magnetic recording tape cartridge, the magnetic recording medium may be configured, for example, to be wound around a reel and housed in a case (cartridge case). The magnetic recording tape cartridge may include, for example, a communication unit that communicates with a recording / playback device described below, a memory unit, and a control unit that stores information received from the recording / playback device via the communication unit in the memory unit, and reads information from the memory unit and transmits it to the recording / playback device via the communication unit in response to a request from the recording / playback device. The information may include adjustment information for adjusting the tension applied to the magnetic recording medium in the longitudinal direction.

[0170] An example of the configuration of a magnetic recording tape cartridge 10A equipped with a magnetic recording medium T having the above-described configuration will be described with reference to FIG.

[0171] 7 is an exploded perspective view showing an example of the configuration of a magnetic recording tape cartridge 10 A. The magnetic recording tape cartridge 10 A is a magnetic recording tape cartridge that conforms to the LTO (Linear Tape-Open) standard, and includes a cartridge case 10 B made up of a lower shell 212 A and an upper shell 212 B, a reel 10 C around which magnetic tape (a tape-like magnetic recording medium) T is wound, a reel lock 214 and a reel spring 215 for locking the rotation of the reel 10 C, a spider 216 for unlocking the locked state of the reel 10 C, a slide door 217 that straddles the lower shell 212 A and the upper shell 212 B and opens and closes a tape pull-out opening 212 C provided in the cartridge case 10 B, a door spring 218 that biases the slide door 217 to a closed position of the tape pull-out opening 212 C, a write protect 219 for preventing accidental erasure, and a cartridge memory 211. The reel 10C is generally disk-shaped with an opening in the center, and is composed of a reel hub 213A and a flange 213B made of a hard material such as plastic. A leader tape LT is connected to one end of the magnetic tape T. A leader pin 220 is provided at the tip of the leader tape LT.

[0172] The cartridge memory 211 is provided near one corner of the magnetic recording tape cartridge 10A. When the magnetic recording tape cartridge 10A is loaded into the recording / reproducing device 80, the cartridge memory 211 faces a reader / writer (not shown) of the recording / reproducing device 80. The cartridge memory 211 communicates with the recording / reproducing device 30, described below, specifically with the reader / writer (not shown), using a wireless communication standard that complies with the LTO standard.

[0173] In the example of the magnetic recording tape cartridge shown in FIG. 7, an example is shown in which the magnetic recording tape is wound around one reel, but the number of reels may be multiple (for example, two).

[0174] [Recording / Reproducing Device] <Configuration of Recording / Reproducing Device> Fig. 8 is a diagram showing an example of the configuration of a recording / reproducing device using a magnetic recording tape cartridge according to the present technology. With reference to Fig. 8, an example of the configuration of a recording / reproducing device 30 that records and reproduces data on a magnetic recording medium 10 will be described.

[0175] The recording and reproducing device 30 has a configuration that allows adjustment of the tension applied in the longitudinal direction of the magnetic recording medium 10. The recording and reproducing device 30 also has a configuration that allows a magnetic recording tape cartridge 10A to be loaded into it. Here, for ease of explanation, a case will be described in which the recording and reproducing device 30 has a configuration that allows one magnetic recording tape cartridge 10A to be loaded into it, but the recording and reproducing device 30 may also have a configuration that allows multiple magnetic recording tape cartridges 10A to be loaded into it.

[0176] The recording and reproducing device 30 is preferably a timing servo type magnetic recording and reproducing device, and the magnetic recording medium of the present technology is suitable for use in a timing servo type magnetic recording and reproducing device.

[0177] The recording / reproducing device 30 is connected to information processing devices such as a server 41 and a personal computer (hereinafter referred to as "PC") 42 via a network 43, and is configured to be able to record data supplied from these information processing devices onto the magnetic recording tape cartridge 10A. The shortest recording wavelength of the recording / reproducing device 30 is preferably 48 nm or less, more preferably 42 nm or less, even more preferably 39 nm or less, and particularly preferably 36 nm or less.

[0178] As shown in Figure 8, the recording and playback device includes a spindle 31, a reel 32 on the recording and playback device side, a spindle drive device 33, a reel drive device 34, a plurality of guide rollers 35, a head unit 36, a communication interface (hereinafter referred to as I / F) 37, and a control device 38.

[0179] The spindle 31 is configured so that a magnetic recording tape cartridge 10A can be attached thereto. The magnetic recording tape cartridge 10A conforms to the LTO (Linear Tape Open) standard, and rotatably houses a single reel 10C around which a magnetic recording medium 10 is wound in a cartridge case 10B. A V-shaped servo pattern is pre-recorded as a servo signal on the magnetic recording medium 10. The reel 32 is configured so that the tip of the magnetic recording medium 10 pulled out from the magnetic recording tape cartridge 10A can be fixed.

[0180] The present technology also provides a magnetic recording tape cartridge including a magnetic recording medium according to the present technology, in which the magnetic recording medium may be wound on a reel, for example.

[0181] The spindle drive device 33 is a device that rotates the spindle 31. The reel drive device 34 is a device that rotates the reel 32. When recording or reproducing data on the magnetic recording medium 10, the spindle drive device 33 and the reel drive device 34 rotate the spindle 31 and the reel 32, thereby running the magnetic recording medium 10. The guide roller 35 is a roller that guides the running of the magnetic recording medium 10.

[0182] The head unit 36 ​​includes a plurality of recording heads for recording data signals on the magnetic recording medium 10, a plurality of reproducing heads for reproducing the data signals recorded on the magnetic recording medium 10, and a plurality of servo heads for reproducing the servo signals recorded on the magnetic recording medium 10. Any magnetic head can be used as the recording head, such as a ring-type magnetic head or a perpendicular recording magnetic head. These magnetic heads may also be tilt-type magnetic heads that allow the head position to be adjusted.

[0183] The communication I / F 37 is for communicating with information processing devices such as a server 41 and a PC 42 , and is connected to a network 43 .

[0184] The control device 38 controls the entire recording / reproducing device 30. For example, in response to a request from an information processing device such as a server 41 or a PC 42, the control device 38 records a data signal supplied from the information processing device onto the magnetic recording medium 10 using the head unit 36. In addition, in response to a request from the information processing device such as the server 41 or a PC 42, the control device 38 reproduces the data signal recorded on the magnetic recording medium 10 using the head unit 36, and supplies the reproduced data signal to the information processing device.

[0185] The control device 38 also detects changes in the width of the magnetic recording medium 10 based on the servo signals supplied from the head unit 36. Specifically, multiple V-shaped servo patterns are recorded on the magnetic recording medium 10 as servo signals, and the head unit 36 ​​simultaneously reproduces two different servo patterns using two servo heads on the head unit 36, thereby obtaining respective servo signals. Using relative position information between the servo patterns and the head unit obtained from these servo signals, the position of the head unit 36 ​​is controlled to track the servo patterns. At the same time, distance information between the servo patterns can be obtained by comparing the two servo signal waveforms. By comparing this distance information between the servo patterns obtained during each measurement, the change in the distance between the servo patterns at each measurement can be obtained. By taking into account the distance information between the servo patterns when the servo patterns were recorded, the change in the width of the magnetic recording medium 10 can also be calculated. The control device 38 controls the rotational drive of the spindle drive device 33 and the reel drive device 34 based on the change in the distance between the servo patterns obtained as described above or the calculated change in the width of the magnetic recording medium 10, and adjusts the tension in the longitudinal direction of the magnetic recording medium 10 so that the width of the magnetic recording medium 10 becomes a specified width or approximately a specified width. This makes it possible to suppress changes in the width of the magnetic recording medium 10.

[0186] <Operation of Recording / Reproducing Device> Next, we will explain the operation of the recording / reproducing device 30 having the above configuration. First, the magnetic recording tape cartridge 10A is loaded into the recording / reproducing device 30, the leading end of the magnetic recording medium 10 is pulled out and transported to the reel 32 via multiple guide rollers 35 and the head unit 36, and the leading end of the magnetic recording medium 10 is attached to the reel 32.

[0187] Next, when an operating unit (not shown) is operated, the spindle drive device 33 and the reel drive device 34 are driven under the control of the control device 38, and the spindle 31 and the reel 32 are rotated in the same direction so that the magnetic recording medium 10 runs from the reel 10C toward the reel 32. As a result, the magnetic recording medium 10 is wound onto the reel 32, while the head unit 36 ​​records information onto the magnetic recording medium 10 or reproduces information recorded on the magnetic recording medium 10.

[0188] When the magnetic recording medium 10 is rewound onto the reel 10C, the spindle 31 and the reel 32 are rotated in the opposite direction to that described above, causing the magnetic recording medium 10 to run from the reel 32 to the reel 10C. During this rewinding, the head unit 36 ​​also records information onto the magnetic recording medium 10 or reproduces information recorded on the magnetic recording medium 10.

[0189] The present technology can have the following configurations. [1] A magnetic recording medium comprising a base layer and one or more layers provided on one surface of the base layer, one of the one or more layers being a magnetic layer containing magnetic powder, the components of the one or more layers including a compound having a toluene diisocyanate (TDI) structure in its molecule and dibutylhydroxytoluene (BHT), and wherein the intensity ratio of the detected peaks of the TDI and the BHT obtained when the one or more layers are measured by GC-MS is BHT / TDI≦0.030. [2] The magnetic recording medium according to [1], wherein the intensity ratio of the detected peaks obtained when the one or more layers are measured by GC-MS is BHT / TDI≦0.025. [3] The magnetic recording medium according to [1] or [2], wherein the intensity ratio of the detected peaks obtained when the magnetic layer is measured by GC-MS is BHT / TDI≦0.030. [4] The magnetic recording medium according to any one of [1] to [3], wherein the outermost layer of the one or more layers is the magnetic layer. [5] The magnetic recording medium according to any one of [1] to [4], wherein the intensity ratio of the detected peaks obtained when the one or more layers are measured by GC-MS is 0.010≦BHT / TDI. [6] The magnetic recording medium according to any one of [1] to [5], wherein the one or more layers include a non-magnetic layer. [7] The magnetic recording medium according to [6], wherein the non-magnetic layer is disposed between the substrate layer and the magnetic layer. [8] The magnetic recording medium according to any one of [1] to [7], wherein a back layer is provided on the other side of the substrate layer, the back layer contains non-magnetic powder, and the components of the back layer include a compound having a toluene diisocyanate (TDI) structure in its molecule and dibutylhydroxytoluene (BHT). [9] The magnetic recording medium according to [8], wherein the intensity ratio of the detected peaks obtained when the back layer is measured by GC-MS is BHT / TDI≦0.030.

[10] The magnetic recording medium according to [8] or [9], wherein the intensity ratio of the detected peaks obtained when the back layer is measured by GC-MS is 0.010≦BHT / TDI.

[11] The magnetic recording medium according to any one of [1] to

[10] , wherein the thickness of the magnetic recording medium is 5.40 μm or less.

[12] The magnetic recording medium according to any one of [1] to

[11] , wherein the thickness of the magnetic layer is 80 nm or less.

[13] The magnetic recording medium according to any one of [1] to

[11] , wherein the thickness of each layer other than the substrate layer is 0.95 μm or less.

[14] The magnetic recording medium according to any one of [1] to

[13] , wherein the magnetic powder is any one of hexagonal ferrite, barium ferrite (BaFe), Co ferrite, strontium ferrite, and epsilon-type iron oxide (ε-iron oxide).

[15] The magnetic recording medium according to any one of [1] to

[13] , wherein the magnetic powder is any one of barium ferrite (BaFe) and strontium ferrite.

[16] The magnetic recording medium according to any one of [1] to

[13] , wherein the magnetic powder is epsilon-type iron oxide (ε-iron oxide).

[17] The average particle volume of the magnetic powder is 1500 nm. ３

[18] A magnetic recording medium according to any one of [1] to

[16] , which is as follows:

[18] A magnetic recording tape using the magnetic recording medium according to any one of [1] to

[17] , which performs recording or reproduction via a magnetic head;

[19] The magnetic recording tape according to

[18] , wherein the magnetic head is a tilt-type magnetic head;

[20] A magnetic recording tape cartridge configured such that the magnetic recording tape according to

[18] or

[19] is wound around a reel and housed in a case.

[0190] The present technology will be described in more detail below using examples, but the present technology is not limited to the contents of the examples shown below.

[0191] [Example 1] <Preparation of Curing Agent> A curing agent A was prepared by adding polyisocyanate to a curing agent (product name: Coronate L, manufactured by Tosoh Corporation) containing polyisocyanate, which is a compound having a toluene diisocyanate (TDI) structure in the molecule, thereby reducing the BHT content in the curing agent.

[0192] <Preparation process of paint for forming magnetic layer> The paint for forming magnetic layer was prepared as follows. First, a first composition having the following formulation was kneaded using an extruder. Next, the kneaded first composition was premixed in a stirring tank equipped with a disperser. Next, a second composition and a third composition having the following formulation were added, and mixed using a Dyno Mill, followed by filtering to prepare the paint for forming magnetic layer.

[0193] (First composition) Strontium-containing barium ferrite (Ba 0.55 Sr 0.45 Fe １２ O １９ ) Magnetic powder (hexagonal plate shape, average aspect ratio 2.6, average particle volume 1300 nm ３ ): 100 parts by mass Vinyl chloride resin (cyclohexanone solution 30% by mass): 30 parts by mass (degree of polymerization 300, Mn = 10,000, containing polar groups OSOK = 0.07 mmol / g and secondary OH = 0.3 mmol / g) Polyurethane resin (resin solution: polyurethane resin content 30% by mass, cyclohexanone content 70% by mass): 29 parts by mass (polyurethane resin: number average molecular weight Mn = 20,000, Tg 100°C) Phenylphosphonic acid 3 parts by mass n-Butyl stearate: 2 parts by mass Methyl ethyl ketone: 220.0 parts by mass Toluene: 120.0 parts by mass Cyclohexanone: 200.0 parts by mass

[0194] (Second composition) Aluminum oxide powder: 4.0 parts by mass (α-Al ２ O ３ , average particle size 100 nm) Vinyl chloride resin (cyclohexanone solution 30% by mass): 3.0 parts by mass (degree of polymerization 300, Mn = 10,000, contains polar groups OSOK = 0.07 mmol / g and secondary OH = 0.3 mmol / g)

[0195] (Third composition) Carbon black: 2.0 parts by mass (manufactured by Tokai Carbon Co., Ltd., product name: Seast S, arithmetic mean particle size 70 nm) Polyurethane resin (resin solution: polyurethane resin content 30% by mass, cyclohexanone content 70% by mass): 4.0 parts by mass (polyurethane resin: number average molecular weight Mn=20,000, Tg 100°C)

[0196] Finally, 3.0 parts by mass of curing agent A and 2.0 parts by mass of stearic acid were added to the magnetic layer-forming coating material prepared as described above.

[0197] <Preparation process of paint for forming non-magnetic layer> The paint for forming non-magnetic layer was prepared as follows. First, a fourth composition having the following formulation was kneaded using an extruder. Next, the kneaded fourth composition and a fifth composition having the following formulation were added to a stirring tank equipped with a disperser and premixed. Subsequently, further mixing was performed using a Dyno Mill and filtering was performed to prepare the paint for forming non-magnetic layer.

[0198] (Fourth composition) Acicular iron oxide powder: 100 parts by mass (α-Fe ２ O ３ , average major axis length 0.11 μm) Vinyl chloride resin (cyclohexanone solution 30% by mass): 40 parts by mass (degree of polymerization 300, Mn = 10,000, contains polar groups OSOK = 0.07 mmol / g and secondary OH = 0.3 mmol / g) Aluminum oxide powder: 4 parts by mass (α-Al ２ O ３ , average particle size 0.1μm)

[0199] (Fifth composition) Carbon black: 30 parts by mass (manufactured by Asahi Carbon Co., Ltd., product name: #80) Polyurethane resin (resin solution: polyurethane resin content 30% by mass, cyclohexanone content 70% by mass): 45 parts by mass (polyurethane resin: number average molecular weight Mn=25000, Tg 70°C) n-butyl stearate: 2 parts by mass Methyl ethyl ketone: 130.0 parts by mass Toluene: 70.0 parts by mass Cyclohexanone: 80.0 parts by mass

[0200] Finally, 3.0 parts by mass of curing agent A and 2.0 parts by mass of stearic acid were added to the coating material for forming the nonmagnetic layer prepared as described above.

[0201] <Step of preparing paint for forming back layer> The paint for forming back layer was prepared as follows: The following raw materials were mixed in a stirring tank equipped with a disperser, and the mixture was filtered to prepare the paint for forming back layer.

[0202] Carbon black (manufactured by Asahi Carbon Co., Ltd., product name: #80): 100 parts by mass Polyester polyurethane: 35 parts by mass (manufactured by Nippon Polyurethane Co., Ltd., product name: N-2304) Nitrocellulose (H 1 / 2): 15 parts by weight (manufactured by Inabata & Co., Ltd., DHX 40-70) Methyl ethyl ketone: 400 parts by mass Toluene: 250 parts by mass Cyclohexanone: 100 parts by mass Curing agent A: 10 parts by mass

[0203] <Film Forming Step> Using the coating material prepared as described above, a magnetic recording medium was prepared as described below.

[0204] First, a long PEN film (base film) with an average thickness of 4.0 μm was prepared as a support that would serve as the substrate layer (base layer) of the magnetic recording medium. Next, a non-magnetic layer-forming paint was applied to one main surface of the PEN film and dried to form a non-magnetic layer on one main surface of the PEN film, so that the average thickness of the final product would be 0.85 μm. Next, a magnetic layer-forming paint was applied to the non-magnetic layer and dried to form a magnetic layer on the non-magnetic layer, so that the average thickness of the final product would be 0.07 μm. In the magnetic recording medium of this example formed by the above film-forming process, one or more layers are formed by a magnetic layer and a non-magnetic layer.

[0205] Next, a back layer-forming coating material was applied to the other main surface of the PEN film on which the nonmagnetic layer and magnetic layer had been formed, and then dried to form a back layer with an average thickness of 0.35 μm in the final product. The PEN film on which the nonmagnetic layer, magnetic layer, and back layer had been formed was then subjected to a curing treatment at 65° C. for 40 hours. The film was then subjected to a calendering treatment to smooth the surface of the magnetic layer.

[0206] <Cutting Step> The magnetic recording medium obtained as described above was cut into 1 / 2 inch (12.65 mm) widths, thereby obtaining a long magnetic recording tape.

[0207] The 1 / 2-inch wide magnetic recording tape was wound around a reel provided inside a cartridge case to obtain a magnetic recording tape cartridge. A servo signal was recorded on the magnetic recording tape using a servo track writer. The servo signal consisted of a series of V-shaped magnetic patterns, and the magnetic patterns were recorded in advance in two or more rows parallel to each other in the longitudinal direction, with known intervals between each other.

[0208] Example 2 Preparation of Curing Agent By adding polyisocyanate to the curing agent A used in Example 1, a curing agent B was prepared in which the content of BHT in the curing agent was further reduced.

[0209] <Production of magnetic recording medium and magnetic recording tape cartridge> A magnetic recording medium was produced using the same raw materials and under the same conditions as in Example 1, except that curing agent B prepared above was used instead of curing agent A. Thereafter, a magnetic recording tape cartridge was produced using this magnetic recording medium under the same conditions as in Example 1.

[0210] Example 3 Preparation of Curing Agent Curing agent C was prepared by adding a smaller amount of polyisocyanate to the curing agent used as a raw material for curing agent A than in the case of curing agent A.

[0211] <Production of magnetic recording medium and magnetic recording tape cartridge> A magnetic recording medium was produced using the same raw materials and under the same conditions as in Example 1, except that curing agent C prepared above was used instead of curing agent A. Thereafter, a magnetic recording tape cartridge was produced using this magnetic recording medium under the same conditions as in Example 1.

[0212] Comparative Example 1 Production of Magnetic Recording Medium and Magnetic Recording Tape Cartridge A magnetic recording medium was produced using the same raw materials and under the same conditions as in Example 1, except that a curing agent without added polyisocyanate (product name: Coronate L, manufactured by Tosoh Corporation) was used instead of curing agent A. Thereafter, a magnetic recording tape cartridge was produced using this magnetic recording medium under the same conditions as in Example 1.

[0213] Comparative Example 2 Preparation of Curing Agent A Curing agent D was prepared by adding an even smaller amount of polyisocyanate to the curing agent used as a raw material for curing agent A than in the case of curing agent A.

[0214] <Production of magnetic recording medium and magnetic recording tape cartridge> A magnetic recording medium was produced using the same raw materials and under the same conditions as in Example 1, except that curing agent D prepared above was used instead of curing agent A. Thereafter, a magnetic recording tape cartridge was produced using this magnetic recording medium under the same conditions as in Example 1.

[0215] The following evaluations were carried out using the magnetic recording media and magnetic recording tape cartridges of Examples 1 to 3 and Comparative Examples 1 and 2. The evaluation results are shown in Table 1.

[0216] <GC-MS Measurement> Measurement samples were prepared by dissolving and removing the backing layer with MEK (methyl ethyl ketone) from each of the magnetic recording tapes of Examples 1 to 3 and Comparative Examples 1 and 2. Two pieces of the measurement samples of Examples 1 to 3 and Comparative Examples 1 and 2 were punched out to 5 mm diameter, and placed in a sample cup (Ecocup LF manufactured by Frontier Labs) and measured by GC-MS.

[0217] (GC-MS measurement conditions) Pyrolyzer device (Frontier Labs PY-3030) Temperature: 300°C, Interface temperature: 250°C GC-MS device (Agilent 7890B / 6977B) Column: DB-5 Temperature conditions: Hold at 50°C for 2 minutes, then heat to 150°C (heating rate 20°C / min), then heat to 250°C (heating rate 10°C / min), and further heat to 300°C (heating rate 10°C / min).

[0218] From the chromatogram obtained above, the BHT / TDI ratio was calculated by determining the peak areas of the detected peaks of the TDI structure derived from the polyisocyanate component in the curing agent and the BHT, an antioxidant component. Figure 9 shows an example of the GC-MS measurement results for one or more layers of a magnetic recording medium. The positions of the detected peaks of TDI and BHT in the measurement results can be confirmed using the results of measuring TDI and BHT standard substances under the above conditions, as shown in Figure 9. Peak analysis was performed using MassHunter workstation software manufactured by Agilent. The BHT / TDI ratios for the magnetic recording tapes of Examples 1 to 3 and Comparative Examples 1 and 2 are listed in Table 1.

[0219] <Abrasive Force Measurement> The abrasiveness of the magnetic recording tapes of Examples 1 to 3 and Comparative Examples 1 and 2 was measured under the following conditions and used as the abrasive force of each magnetic recording tape.

[0220] (Abrasivity) Abrasivity is measured in accordance with ECMA-319 Annex C. Note that abrasivity is measured by changing the ceramic material of the abrasivity bar to AlTiC. Abrasivity is an index that indicates the degree of wear of a magnetic head caused by the magnetic surface of a magnetic recording tape when the magnetic recording tape comes into contact with the magnetic head and runs. For example, a square-prism bar (abrasivity bar) A made of a ceramic material (AlTiC) shown in FIG. 11 is set in a dedicated jig (a jig described in ECMA-319 Annex C) shown in FIG. 10, and the jig is attached to a magnetic head unit of a tape drive or the like so that the corners of the square prism come into contact with the magnetic recording tape. The magnetic recording tape is run for a predetermined time or a predetermined number of passes, and after the run, the width B of the worn abrasive bar is measured as shown in FIG. 12. The measured average wear pattern length (amount of wear) of the abrasive bar is used as an index of abrasivity. The larger the average wear pattern length (amount of wear), the better the abrasiveness and the greater the abrasive power. For example, abrasivity is measured as follows.

[0221] As described above, a square prism bar (abrasiveness bar) A made of a ceramic material (AlTiC) shown in Figure 11 is set in the dedicated jig shown in Figure 10. Next, this square prism bar is attached to the magnetic head of a tape drive or the like so that the corners of the bar come into contact with the magnetic recording tape. Thereafter, the magnetic recording tape is run under the following conditions: tape speed: 3.0 m / s tension: 1.0 N ± 0.1 N wrap angle: 12°

[0222] The average wear pattern length of the abrasive bar was measured by repeatedly running 600 m of magnetic recording tape 100 times. A preferred average wear pattern length of the abrasive bar is 15 μm or longer, allowing the magnetic recording tape to maintain its cleaning power for removing dirt from the magnetic head. Measurements are performed in an environment with a temperature of 23°C ± 2°C and a humidity of 45% ± 5%. After running the magnetic tape 100 times, the average wear pattern length (amount of scraping) is measured. This measurement value is defined as the abrasiveness after 100 passes. The abrasiveness measurement results after 100 passes for the magnetic recording tapes of Examples 1 to 3 and Comparative Examples 1 and 2 are shown in Table 1 as the abrasive force measurement results.

[0223] <Measurement of Temperature Change Amount> For the magnetic recording tapes of Examples 1 to 3 and Comparative Examples 1 and 2, the ½-inch wide magnetic tape T housed in the magnetic recording tape cartridge was unwound, and the magnetic tape was cut into lengths of 250 mm from each of the ranges of 10 m to 20 m, 30 m to 40 m, and 50 m to 60 m in the longitudinal direction to obtain three samples. The temperature change amount was measured using these samples under the following conditions.

[0224] (Conditions for measuring temperature change) Measuring device: Optical Micrometer (manufactured by Sony) Weight: 0.4 N Width definition: edge to edge Environment: 15 deg. C (at 40% RH) 35 deg. C (at 40% RH)

[0225] First, the sample 10S is set in the optical micrometer shown in FIG. 13. Specifically, one end of the long sample (magnetic tape T) 10S is fixed by the fixing portion 231. Next, as shown in FIG. 13, the sample 10S is placed on five roughly cylindrical, rod-shaped support members 2321-2325. The sample 10S is placed on these support members 2321-2325 so that its back surface is in contact with the five support members 2321-2325. All of the five support members 2321-2325 (particularly their surfaces) are formed from stainless steel SUS304, and their surface roughness Rz (maximum height) is 0.15 μm to 0.3 μm.

[0226] The arrangement of the five rod-shaped support members 2321-2325 will be described with reference to FIG. 13. As shown in FIG. 13, the sample 10S is placed on the five support members 2321-2325. The five support members 2321-2325 will be referred to below, from closest to the fixed portion 231, as the "first support member 2321," the "second support member 2322," the "third support member 2323" (having the slit 232A), the "fourth support member 2324," and the "fifth support member 2325" (closest to the weight 233). The diameter of each of these five first to fifth support members 2321-2325 is 7 mm. The distance d1 between the first support member 2321 and the second support member 2322 (particularly, the distance between the central axes of these support members) is 20 mm. The distance d2 between the second support member 2322 and the third support member 2323 is 30 mm. The distance d3 between the third support member 2323 and the fourth support member 2324 is 30 mm. The distance d4 between the fourth support member 2324 and the fifth support member 2325 is 20 mm.

[0227] The three support members 2322-2324 are arranged so that the portion of the sample 10S resting between the second support member 2322, the third support member 2323, and the fourth support member 2324 forms a plane that is approximately perpendicular to the direction of gravity. The first support member 2321 and the second support member 2322 are arranged so that the sample 10S forms an angle of θ1 = 30° with respect to the approximately perpendicular plane between the first support member 2321 and the second support member 2322. The fourth support member 2324 and the fifth support member 2325 are arranged so that the sample 10S forms an angle of θ2 = 30° with respect to the approximately perpendicular plane between the fourth support member 2324 and the fifth support member 2325. Of the five first to fifth support members 2321 to 2325, the third support member 2323 is fixed so as not to rotate, but the other four, the first, second, fourth, and fifth support members 2321, 2322, 2324, and 2325, are all rotatable. Because the support member 2323 is fixed so as not to rotate as described above, the contact angle between the support 2323 and the sample 10S is made shallow in consideration of reducing friction between the support 2323 and the sample 10S.

[0228] The sample 10S is held on the support members 2321 to 2325 so as not to move in the width direction of the sample 10S. Of the support members 2321 to 2325, a support member 2323 is located between the light emitter 234 and the light receiver 235 and is located approximately in the center between the fixing part 231 and the part where the load is applied, and is provided with a slit 232A. Light L is irradiated from the light emitter 234 to the light receiver 235 through the slit 232A. The slit width of the slit 232A is 1 mm, and the light L can pass through the slit 232A without being blocked by the frame of the slit 232A.

[0229] After placing the measuring device in a chamber at room temperature (temperature 25°C, relative humidity 50% RH), a weight 233 is attached to the other end of the sample 10S to apply a load of 0.4 N per 1 / 2 inch of width of the sample 10S. That is, the load applied to the sample 10S is set to 0.4 N if the width is 1 / 2 inch, and a load proportional to the width is set if the width is not 1 / 2 inch. After attaching the weight 233, the sample 10S is left to stand in the room temperature environment for 30 minutes. After standing for 30 minutes, the temperature inside the chamber is increased, and measurement of the width of the sample 10S begins when the chamber reaches the specified environment (temperature 15°C, relative humidity 40% RH). While maintaining the specified environment inside the chamber (temperature 15°C, relative humidity 40% RH), measurement of the width of the sample 10S continued for more than 40 hours from the start of the measurement. (Measurement result: "Width (15)")

[0230] Next, the width of Sample 10S was measured under the same conditions as above, except that the chamber was kept in the specified environment (temperature 35°C, relative humidity 40% RH). (Measurement result: "Width (35)")

[0231] As described above, the widths of the samples were measured in two temperature environments, and the temperature change amounts were calculated using the following formula (1). The calculated temperature change amounts for the magnetic recording tapes of Examples 1 to 3 and Comparative Examples 1 and 2 are shown in Table 1.

[0232] | (Width (35) - Width (15) / (35 - 15)) - (Thermal expansion of the head) | = Temperature change (relative to the head) (nm) .................................................... (1) *Thermal expansion of the head = (Thermal expansion coefficient of the head: 7 ppm / °C) x (Sample width: 12.65 mm) = 88.55 (nm)

[0233]

[0234] From Table 1, it can be seen that the magnetic recording tapes of Examples 1 to 3 were able to adjust the intensity ratio of the detection peak obtained when one or more layers were measured by GC-MS to BHT / TDI≦0.030 by adding polyisocyanate and using a curing agent with a reduced BHT content.

[0235] Furthermore, it was confirmed that the magnetic recording tapes of Examples 1 to 3, in which the intensity ratio of the detected peak obtained when one or more layers were measured by GC-MS was adjusted to BHT / TDI≦0.030, had improved abrasive power, which is expected to favorably maintain the function of removing dirt from the magnetic head when recording or reproducing via the magnetic head.

[0236] In addition, it was confirmed that temperature changes were also suppressed in the magnetic recording tapes of Examples 1 to 3. This is expected to suppress shape changes that may occur due to creep during long-term storage, etc.

[0237] 10 Magnetic recording medium 11 Base layer 12 Non-magnetic layer 13 Magnetic layer 14 Back layer 10A Magnetic recording tape cartridge 30 Recording / reproducing device T Magnetic recording medium (magnetic recording tape)

Claims

1. A magnetic recording medium having a base layer and one or more layers provided on one side of the base layer, wherein one of the one or more layers is a magnetic layer containing magnetic powder, wherein the components of the one or more layers include a compound having a toluene diisocyanate (TDI) structure in its molecule and dibutylhydroxytoluene (BHT), and wherein the intensity ratio of the detected peaks of the TDI and the BHT obtained when the one or more layers are measured by GC-MS is BHT / TDI≦0.

030.

2. The magnetic recording medium according to claim 1, wherein the intensity ratio of the detected peaks obtained when the one or more layers are measured by GC-MS is BHT / TDI≦0.

025.

3. The magnetic recording medium according to claim 1, wherein the intensity ratio of the detected peaks obtained when the magnetic layer is measured by GC-MS is BHT / TDI≦0.

030.

4. The magnetic recording medium according to claim 1, wherein the outermost layer of said one or more layers is said magnetic layer.

5. The magnetic recording medium according to claim 1, wherein the intensity ratio of the detected peaks obtained when the one or more layers are measured by GC-MS is 0.010≦BHT / TDI.

6. The magnetic recording medium according to claim 1, wherein the one or more layers include a non-magnetic layer.

7. The magnetic recording medium according to claim 6, wherein the non-magnetic layer is disposed between the substrate layer and the magnetic layer.

8. The magnetic recording medium according to claim 1, wherein a back layer is provided on the other surface of the base layer, the back layer contains non-magnetic powder, and the components of the back layer include a compound having a toluene diisocyanate (TDI) structure in its molecule and dibutylhydroxytoluene (BHT).

9. The magnetic recording medium according to claim 8, wherein the intensity ratio of the detected peaks obtained when the back layer is measured by GC-MS is BHT / TDI≦0.

030.

10. The magnetic recording medium according to claim 9, wherein the intensity ratio of the detected peaks obtained when the back layer is measured by GC-MS is 0.010≦BHT / TDI.

11. The magnetic recording medium according to claim 1, wherein the thickness of the magnetic recording medium is 5.40 μm or less.

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

13. The magnetic recording medium according to claim 11, wherein the thickness of the layers other than the substrate layer is 0.95 μm or less.

14. The magnetic recording medium according to claim 1, wherein the magnetic powder is any one of hexagonal ferrite, barium ferrite (BaFe), Co ferrite, strontium ferrite, and epsilon iron oxide (ε iron oxide).

15. The magnetic recording medium according to claim 1, wherein the magnetic powder is either barium ferrite (BaFe) or strontium ferrite.

16. The magnetic recording medium according to claim 1, wherein the magnetic powder is epsilon iron oxide (ε iron oxide).

17. The average particle volume of the magnetic powder is 1500 nm ３ 2. The magnetic recording medium according to claim 1, wherein:

18. A magnetic recording tape using the magnetic recording medium according to claim 1, which performs recording or reproduction via a magnetic head.

19. The magnetic recording tape of claim 18, wherein the magnetic head is a tilt type magnetic head.

20. A magnetic recording tape cartridge in which the magnetic recording tape according to claim 18 is housed in a case while wound around a reel.

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