Magnetic tape, magnetic tape cassette and magnetic tape apparatus

Abstract

The present invention provides a magnetic tape having a non-magnetic support and a magnetic layer containing a ferromagnetic powder, a magnetic tape cartridge including the magnetic tape, and a magnetic tape device. The amount of fluid lubricant collected by wiping the surface of the magnetic layer with a non-woven cloth is in the range of 5 to 400 ng / m 2 2 of the surface of the magnetic layer per unit area.

Description

TECHNICAL FIELD

[0001] The present application relates to a magnetic tape, a magnetic tape cartridge, and a magnetic tape device. BACKGROUND

[0002] Magnetic recording media are of a tape type and a disk type, and the tape type magnetic recording medium, i.e., a magnetic tape, is mainly used in data storage applications such as data backup and archiving (see, for example, Patent Literature 1).

[0003] PRIOR ART DOCUMENTS

[0004] PATENT LITERATURE

[0005] Patent Literature 1: Japanese Patent Application Laid-Open No. 2002-367142 SUMMARY

[0006] PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] It is required that the magnetic tape be capable of exhibiting excellent electromagnetic conversion characteristics.

[0008] On the other hand, in recent years, magnetic tapes for data storage applications are sometimes used in temperature-managed data centers. On the other hand, in order to reduce costs, data centers are required to save power. In order to save power, it is expected that the temperature management conditions of data centers can be relaxed more than now or that management can not be performed. However, if the temperature management conditions are relaxed or management is not performed, the magnetic tape is expected to be exposed to high temperatures.

[0009] With regard to the above points, according to the present inventor's research, it has been found that if a magnetic tape is repeatedly run in a high temperature environment (e.g., a severe high temperature environment of 60°C or higher) to record data on the magnetic tape and / or reproduce data recorded in the magnetic tape, the electromagnetic conversion characteristics tend to easily deteriorate.

[0010] An object of one embodiment of the present application is to provide a magnetic tape in which deterioration of electromagnetic conversion characteristics is less even if the magnetic tape is repeatedly run in a high temperature environment.

[0011] MEANS FOR SOLVING THE PROBLEMS

[0012] One embodiment of the present application relates to a magnetic tape including a non-magnetic support and a magnetic layer containing a ferromagnetic powder,

[0013] The amount of fluid lubricant collected by wiping the surface of the magnetic layer with a nonwoven fabric is in the range of 5 to 400 ng / m2per unit area of the surface of the magnetic layer. 2

[0014] In one embodiment, the amount of fluid lubricant can be in the range of 30 to 250 ng / m2. 2

[0015] ​​In one embodiment, the fluid lubricant amount can be in the range of 120 to 200 ng / m 2

[0016] In one embodiment, the projection cross-sectional area 0.1 % pitch on the surface of the magnetic layer can be in the range of 1.0 to 20.0 nm.

[0017] In one embodiment, the projection cross-sectional area 0.1 % pitch can be in the range of 1.0 to 10.0 nm.

[0018] In one embodiment, the projection cross-sectional area 0.1 % pitch can be in the range of 1.0 to 7.0 nm.

[0019] In one embodiment, the magnetic tape can further have a non-magnetic layer containing non-magnetic powder between the non-magnetic support and the magnetic layer.

[0020] In one embodiment, the magnetic tape can further have a back coating layer containing non-magnetic powder on the surface side of the non-magnetic support opposite to the surface side having the magnetic layer.

[0021] One embodiment of the present application relates to a magnetic tape cartridge including the above-described magnetic tape.

[0022] One embodiment of the present application relates to a magnetic tape device including the above-described magnetic tape and a magnetic head.

[0023] Effects of Invention

[0024] According to one embodiment of the present application, a magnetic tape in which degradation of electromagnetic conversion characteristics is less even when repeatedly running in a high-temperature environment, and a magnetic tape cartridge and a magnetic tape device including the same can be provided. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 An example of an apparatus for wiping the surface of the magnetic layer of a magnetic tape is shown.

[0026] Figure 2 An example of the arrangement of a data tape and a servo tape is shown.

[0027] Figure 3 An example of the arrangement of a servo pattern of an LTO (Linear Tape-Open) Ultrium format magnetic tape is shown. DETAILED DESCRIPTION

[0028] [Magnetic Tape]

[0029] ​One aspect of the present invention relates to a magnetic tape having a non-magnetic support and a magnetic layer containing strongly magnetic powder. In the aforementioned magnetic tape, the fluid lubricant dosage, collected by wiping the surface of the magnetic layer with a non-woven fabric, is between 5 and 400 ng (nanograms) / m², expressed as a value per unit area of ​​the magnetic layer surface. 2 Within the range.

[0030] In this invention and this specification, the aforementioned fluid lubrication dosage is determined by the following method. Furthermore, in this invention and this specification, the term "surface of the magnetic layer" has the same meaning as the magnetic layer side surface of the magnetic tape.

[0031] Figure 1 An example of an apparatus for wiping the surface of the magnetic layer of a magnetic tape is shown. The wiping is performed in an environment with an ambient temperature of 23°C and a relative humidity of 50%.

[0032] like Figure 1 As shown, a reel tester with two magnetic tape reels is used. As a reel tester, a commercially available product or a reel tester assembled using known methods can be used.

[0033] In a reel tester, a fixing component is typically installed at the part where the magnetic head is mounted. This fixing component uses a curved surface with a radius of curvature R = 43 mm. Alternatively, a hemispherical fixing component can be used, with a diameter of, for example, 40 mm.

[0034] The nonwoven fabric used for wiping is configured to meet the following conditions: As the nonwoven fabric, a virgin, unused nonwoven fabric is used, and it is a nonwoven fabric that does not contain any components that affect the quantitative results of the fluid lubricant in the quantitative analysis described later, or contains components in an amount that does not affect the quantitative results. Examples of such components include the components described later, fatty acids, and fatty acid amides contained in the fluid lubricants of this invention and this specification. The amount that does not affect the quantitative results can be an amount less than the detection limit in the quantitative analysis of the methods described later. No solvent is imparted to the nonwoven fabric. For example, 4000CR manufactured by Japan Vilene Company, Ltd. can be used as the nonwoven fabric.

[0035] Area weight: 40±5g / m² 2

[0036] Thickness: 0.27±0.05μm

[0037] Width: 25mm

[0038] Average fiber diameter: 10±5μm

[0039] Raw materials: A blend of rayon, polyester, and nylon (any mixing ratio)

[0040] The nonwoven fabric does not advance and is fixed at the time of wiping. The tension applied to the nonwoven fabric was set to 225 gf. As for the unit, "gf" is gram force, and 1 N (Newton) is about 102 gf.

[0041] In the capstan tester, the magnetic tape was run and the surface of the magnetic layer was brought into contact with the nonwoven fabric, so that wiping was performed with the nonwoven fabric. The running conditions of the magnetic tape were set to the following conditions. The following values of the tension applied to the longitudinal direction of the magnetic tape are the set values in the capstan tester. The meaning of the "running length" below is the same as the meaning of the length in the longitudinal direction of the portion in contact with the nonwoven fabric at the time of running in the magnetic tape as described above.

[0042] Running speed of the magnetic tape: 2 m / sec

[0043] Tension applied to the longitudinal direction of the magnetic tape: 100 gf

[0044] Running length of the magnetic tape: 200 m

[0045] Running path of the magnetic tape: 1 single pass

[0046] Winding angle θ: 25°

[0047] After the above wiping, a cloth piece of 60 mm in length was cut out from the above nonwoven fabric. The cut-out cloth piece included the portion in contact with the magnetic tape at the time of wiping.

[0048] The cut-out cloth piece was put into a container. As the container, for example, a sample bottle having a volume of 13.5 cm3 3 was used. In the above container, 10 cm3 3 of n-hexane was put. The lid of the container was closed, and after being left overnight in an environment having an atmospheric temperature of 23°C, the components were extracted from the nonwoven fabric.

[0049] Quantitative analysis of the fluid lubricant in the n-hexane (hereinafter, referred to as "extracted liquid") in the above container was performed by the MRM (Multiple Reaction Monitoring) method using a gas chromatograph tandem mass spectrometer (GC / MS / MS). The analysis conditions (for example, injector temperature, detector temperature, column temperature, column type, and the like) for the quantitative analysis can be determined depending on the kind of the fluid lubricant to be quantitatively analyzed, and as an example, the analysis conditions described in the examples to be described later can be cited. In the case where the kind of the fluid lubricant contained in the magnetic tape to be measured is not known, qualitative analysis of the components contained in the magnetic tape to be measured can be performed by a publicly known method, so that the kind of the fluid lubricant contained can be determined.

[0050] By dividing the quantitative value obtained through quantitative analysis by the area of ​​the magnetic layer surface in contact with the nonwoven fabric during wiping, the value is expressed as the area per unit area (1m²) of the magnetic layer surface. 2 The amount of fluid lubricant collected from the surface of the magnetic layer through the above wiping is calculated in the form of the value of ). In the case where multiple components are collected as fluid lubricant, the above calculation is performed for the sum of their quantitative values.

[0051] In this invention and in this specification, "fluid lubricant" refers to a compound selected from the group consisting of fatty acid esters, carbonates, organic amines, and fluorinated compounds. Specific examples of these will be described later.

[0052] In the aforementioned magnetic tapes, the fluid lubrication dosage determined by the above method ranges from 5 to 400 ng / m. 2 Within this range. As a result of in-depth research, the inventors have discovered that, based on this magnetic tape, even when the tape is repeatedly driven at high temperatures, the degradation of its electromagnetic conversion characteristics can be suppressed. This will be further explained below.

[0053] Data recording and reproduction on magnetic tape are typically performed by bringing the magnetic layer surface of the tape into contact with and sliding it against the magnetic head. It is believed that a fluid lubricant helps to suppress stick slip between the magnetic head and the magnetic layer surface during this sliding. However, it is believed that in high-temperature environments, especially harsh environments above 60°C, the fluid lubricant on the magnetic layer surface may be depleted due to sliding relative to the magnetic head and / or exposure to high temperatures, leading to stick slip between the magnetic head and the magnetic layer surface. It is speculated that the pitch variation caused by this stick slip is the reason for the deterioration of electromagnetic conversion characteristics during repeated tape runs at high temperatures. For example, the inventors believe that the difficulty in recording to the depths of the magnetic layer due to pitch variation is the main cause of the aforementioned deterioration of electromagnetic conversion characteristics.

[0054] Regarding lubricants, in the aforementioned Patent Document 1 (Japanese Patent Application Publication No. 2002-367142), the amount of lubricant extracted using n-hexane was measured for magnetic tape. This extraction was carried out by immersing a sample cut from the magnetic tape in n-hexane (paragraph 0203 of Patent Document 1). However, it is believed that simply increasing the extracted lubricant amount would degrade durability due to plasticization of the magnetic layer and / or, in magnetic tapes with a back coating, make the surface shape of the back coating easily transfer to the surface of the magnetic layer, leading to deterioration of electromagnetic conversion characteristics.

[0055] In contrast, the inventors believe that the amount of fluid lubricant collected from the surface of the magnetic layer by wiping with a nonwoven fabric, as described above, corresponds well to the amount of fluid lubricant that can seep from within the layer to the surface of the magnetic layer to exert lubricating properties when sliding relative to the magnetic head under shear and / or pressure. The inventors hypothesize that if the magnetic layer surface of the magnetic tape slides relative to this fluid lubricant amount within the aforementioned range, an appropriate amount of fluid lubricant can be supplied to the magnetic head, thereby suppressing the deterioration of electromagnetic conversion characteristics during repeated tape runs at high temperatures. The reason for using a fluid lubricant as the measurement object is that it is believed that the fluid lubricant can help suppress stick-slip by forming a liquid film on the surface of the magnetic layer.

[0056] However, the foregoing includes the inventors' conjectures. The present invention is not limited to the conjectures described in this specification.

[0057] The following is a more detailed explanation of the aforementioned magnetic tape.

[0058] <Fluorescence Dosage>

[0059] In the aforementioned magnetic tape, the fluid lubricant dosage collected by wiping the surface of the magnetic layer with a non-woven fabric ranges from 5 to 400 ng / m², calculated per unit area of ​​the magnetic layer surface. 2 Within the range. It is assumed that if the fluid lubricant dosage on the magnetic layer surface is 5 ng / m... 2 The above indicates that a suitable amount of fluid lubricant can be present on the surface of the magnetic layer during sliding relative to the magnetic head. It is speculated that this can suppress the deterioration of electromagnetic conversion characteristics during repeated tape runs at high temperatures. Based on the above, the fluid lubricant dosage is 5 ng / m³. 2 The above is preferably 10 ng / m 2 The above, preferably 20 ng / m 2 The above is further preferred to be 30 ng / m 2 The above is further preferred to be 40 ng / m 2 Above, and at 50ng / m 2 Above, 60ng / m 2 Above, 70ng / m 2 Above, 80ng / m 2 Above, 90ng / m 2 Above, 100ng / m 2 Above, 110ng / m 2 Above, 120ng / m 2 The above order can be further optimized.

[0060] On the other hand, it is speculated that in the aforementioned magnetic tape, by setting the fluid lubrication dosage to 400 ng / m 2The following describes a meniscus that, when sliding relative to the magnetic head, can suppress the formation of fluid lubricant between the magnetic head and the surface of the magnetic layer. This is believed to help suppress head adhesion. Based on the above viewpoint, the fluid lubricant dosage is 400 ng / m². 2 The preferred value is 350 ng / m 2 The preferred value is 300 ng / m 2 The following is a further preferred value: 250 ng / m 2 The following is a further preferred value: 200 ng / m 2 the following.

[0061] The method for controlling the above-mentioned fluid lubrication dosage will be described later.

[0062] <Fluoride Lubricant>

[0063] The fluid lubricant used in this invention and this specification is a compound selected from the group consisting of fatty acid esters, carbonates, organic amines and fluorinated compounds.

[0064] Examples of fatty acid esters include mono-, di-, or tri-fatty acid esters composed of monobasic fatty acids (which may contain unsaturated bonds or be branched) with 10 to 24 carbon atoms and mono-, di-, tri-, tetra-, penta-, or hexa-ols (which may contain unsaturated bonds or be branched) with 2 to 24 carbon atoms, as well as fatty acid esters of monoalkyl ethers of epoxide polymers. More preferred mono-fatty acid esters include, for example, butyl stearate, octyl stearate, pentyl stearate, isooctyl stearate, butyl myristate, octyl myristate, butoxyethyl stearate, butoxydiethyl stearate, 2-ethylhexyl stearate, 2-octyl dodecyl palmitate, 2-hexyl dodecyl palmitate, isohexadecanyl stearate, and oleic acid ester.

[0065] Examples of carbonates include those described in Japanese Patent Application Publication No. 2008-239575.

[0066] Examples of organic amines include primary organic amines, secondary organic amines, and tertiary organic amines, with secondary organic amines and tertiary organic amines being preferred, tertiary organic amines being more preferred, and trialkylamines being even more preferred. The alkyl group in a trialkylamine is preferably an alkyl group having 1 to 18 carbon atoms. The three alkyl groups in a trialkylamine may be the same or different.

[0067] Fluorine-containing compounds are compounds containing one or more fluorine atoms (F) within a molecule. Specific examples include fluoroalkyl carboxylic acid esters. More preferably, fluorine-containing compounds are represented by Rf-(L)n-COOR, where Rf represents a fluorinated hydrocarbon group, L represents a divalent linking group, R represents an alkyl or fluorinated hydrocarbon group, and n is 0 or 1.

[0068] The fluorinated hydrocarbon group is a monovalent group in which one or more hydrogen atoms constituting a saturated (or unsaturated) straight-chain (or branched) hydrocarbon group are replaced by fluorine atoms. The fluorinated hydrocarbon group has 1 or more carbon atoms, preferably 2 or more, more preferably 3 or more. Furthermore, the fluorinated hydrocarbon group preferably has 20 or fewer carbon atoms, more preferably 18 or fewer, even more preferably 16 or fewer, even more preferably 14 or fewer, even more preferably 12 or fewer, even more preferably 10 or fewer, even more preferably 8 or fewer. As the fluorinated hydrocarbon group represented by Rf, a fluorinated alkyl group is preferred, where one or more hydrogen atoms constituting the alkyl group are replaced by fluorine atoms; more preferably, a fluorinated alkyl group is preferred, where two or more hydrogen atoms constituting the alkyl group are replaced by fluorine atoms; and even more preferably, a perfluoroalkyl group is preferred, where all hydrogen atoms constituting the alkyl group are replaced by fluorine atoms.

[0069] Examples of divalent linking groups represented by L include those composed of alkylene groups, ester groups (-C(=O)O-), and combinations of alkylene groups and ester groups. The alkylene group contained in the divalent linking group represented by L can be, for example, an alkylene group with 1 to 20 carbon atoms. A divalent linking group composed of a combination of alkylene groups and ester groups can contain one or more alkylene groups and one or more ester groups. When the linking group represented by L contains two or more alkylene groups, the number of carbon atoms in the aforementioned alkylene groups refers to the sum of the number of carbon atoms in the contained alkylene groups. The alkylene group contained in the divalent linking group represented by L can be a substituted (or unsubstituted) alkylene group. Examples of substituents that can be substituted alkylene groups include, for example, hydroxyl groups, carboxyl groups and their salts (e.g., alkali metal salts), sulfonic acid groups and their salts (e.g., alkali metal salts), phosphate groups and their salts (e.g., alkali metal salts), etc. The number of carbon atoms in the substituted alkylene group refers to the number of carbon atoms excluding the carbon atoms in the substituent portion.

[0070] Examples of alkyl groups represented by R include substituted (or unsubstituted) straight-chain (or branched) alkyl groups. Regarding the substituents in substituted alkyl groups, refer to the above description relating to the substituents in substituted alkylene groups. The alkyl group represented by R has 1 or more carbon atoms, and may also have 2 or more. Furthermore, the alkyl group represented by R may have, for example, 10 or less, 8 or less, 6 or less, 4 or less, or 2 or less. The number of carbon atoms in a substituted alkyl group refers to the number of carbon atoms excluding the carbon atoms of the substituent portion.

[0071] For information on fluorinated hydrocarbon groups represented by R, please refer to the above descriptions related to fluorinated hydrocarbon groups represented by Rf.

[0072] The aforementioned magnetic tape may contain one or more fluid lubricants in the magnetic layer side portion on the non-magnetic support. In this invention and specification, the term "magnetic layer side portion on the non-magnetic support" refers to the magnetic layer for magnetic tapes with a magnetic layer directly on the non-magnetic support, and to magnetic tapes with a non-magnetic layer between the non-magnetic support and the magnetic layer (details to be described later) and / or a magnetic layer and a non-magnetic layer. Hereinafter, "magnetic layer side portion on the non-magnetic support" will also be simply referred to as "magnetic layer side portion." The presence of lubricant on the surface of the magnetic layer side of the magnetic tape is also included in the magnetic layer side portion. It is believed that in magnetic tapes with a lubricant dosage within the aforementioned range as determined by the above method, the fluid lubricant contained in the magnetic layer side portion of the magnetic tape can be appropriately exuded from within the magnetic layer side portion to the surface of the magnetic layer due to shear and / or pressure effects when the magnetic head slides relative to the magnetic layer surface. The inventors speculate that this can suppress the deterioration of electromagnetic conversion characteristics during repeated tape runs at high temperatures.

[0073] Magnetic tapes containing a fluid lubricant in the magnetic layer portion can be manufactured, for example, by adding a fluid lubricant as a component of a magnetic layer forming composition. In this case, the content of the fluid lubricant in the magnetic layer forming composition (or magnetic layer; hereinafter the same) is preferably in the range of 0.2 to 7.0 parts by weight relative to 100.0 parts by weight of the strong magnetic powder, more preferably in the range of 1.0 to 4.0 parts by weight. When two or more fluid lubricants are contained, the above content refers to their total content. This also applies to the various contents described in this invention and this specification.

[0074] In magnetic tapes having a non-magnetic layer, a fluid lubricant may also be contained in the non-magnetic layer. Magnetic tapes containing a fluid lubricant in the non-magnetic layer can be manufactured by adding the fluid lubricant as a component of a composition for forming the non-magnetic layer. In this case, the content of the fluid lubricant in the composition for forming the non-magnetic layer (or the non-magnetic layer; hereinafter the same) is preferably in the range of 0.2 to 7.0 parts by weight relative to 100.0 parts by weight of the non-magnetic powder, more preferably in the range of 1.0 to 4.0 parts by weight. The fluid lubricant contained in the non-magnetic layer can, for example, seep to the surface of the magnetic layer when sliding relative to the magnetic head.

[0075] If the amount of fluid lubricant added to the composition for forming magnetic layers and / or the composition for forming non-magnetic layers is increased, the value of the fluid lubricant amount obtained by the above method tends to increase.

[0076] <Fatty acids, fatty acid amides>

[0077] The magnetic tape described above may contain one or more components selected from the group consisting of fatty acids and fatty acid amides in the portion on the magnetic layer side. Fatty acids and fatty acid amides are components that can function as boundary lubricants. Boundary lubricants are considered to be components that can be adsorbed onto the surface of powder to form a lubricating film. The inventors believe that adsorbing fatty acids and / or fatty acid amides onto particles of non-magnetic powders (e.g., abrasives and / or protrusion forming agents described later) contained in the magnetic layer can help increase the value of the fluid lubricant dosage obtained by the above method. Specifically, it is believed that: In the magnetic layer, non-magnetic powders (abrasives and / or protrusion forming agents) may exist in the form of protrusions on the surface of the magnetic layer, and when in contact with the nonwoven fabric, these protrusions may contact the magnetic head (so-called actual contact) on the surface of the magnetic layer. It is believed that if fatty acids and / or fatty acid amides are adsorbed onto particles with such protrusions, the affinity of the particles for the fluid lubricant can be increased, resulting in an increase in the amount of fluid lubricant collected in the layer by the nonwoven fabric via these particles. In this type of magnetic tape, the fluid lubricant easily seeps from within the layer to the surface of the magnetic layer through sliding relative to the magnetic head. It is speculated that this could help suppress the degradation of electromagnetic conversion characteristics during repeated tape runs at high temperatures. The inventors believe that, for example, when preparing a composition for forming a magnetic layer, dispersing the non-magnetic powder with components selected from the group consisting of fatty acids and / or fatty acid amides before mixing it with strongly magnetic powder (so-called separate dispersion) could help adsorb components selected from the group consisting of fatty acids and / or fatty acid amides onto the particles of the non-magnetic powder and / or increase their adsorption amount.

[0078] Examples of fatty acids include lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, behenic acid, erucic acid, and transoleic acid, with stearic acid, myristic acid, and palmitic acid being preferred, and stearic acid being more preferred. Fatty acids may also be contained in the portion on the magnetic layer side in the form of salts such as metal salts.

[0079] Examples of fatty acid amides include the various fatty acid amides mentioned above, such as lauryl amide, myristyl amide, palmitamide, stearyl amide, etc.

[0080] The amount of fatty acids relative to 100.0 parts by weight of the strong magnetic powder is, for example, 0.1 to 5.0 parts by weight, preferably 0.3 to 2.0 parts by weight, based on the content in the composition for forming the magnetic layer.

[0081] When dispersed separately, the amount of fatty acids mixed with the abrasive is, for example, 1.0 to 25.0 parts by weight relative to 100.0 parts by weight of the abrasive, preferably 5.0 to 15.0 parts by weight.

[0082] When dispersed separately, the amount of fatty acids mixed with the protrusion forming agent is, for example, 1.0 to 25.0 parts by weight relative to 100.0 parts by weight of the protrusion forming agent, preferably 5.0 to 15.0 parts by weight.

[0083] The content of fatty acid amide in the composition for forming the magnetic layer is, for example, 0.1 to 1.0 parts by weight, preferably 0.2 to 0.6 parts by weight, relative to 100.0 parts by weight of the strong magnetic powder.

[0084] When dispersed separately, the amount of fatty acid amide mixed with the abrasive is, for example, 1.0 to 10.0 parts by weight relative to 100.0 parts by weight of the abrasive, preferably 3.0 to 6.0 parts by weight.

[0085] When dispersed separately, the amount of fatty acid amide mixed with the protrusion forming agent is, for example, 1.0 to 10.0 parts by weight relative to 100.0 parts by weight of the protrusion forming agent, preferably 3.0 to 6.0 parts by weight.

[0086] Fatty acids and / or fatty acid amides may also be added to compositions for forming nonmagnetic layers.

[0087] The fatty acid content in the composition for forming the nonmagnetic layer is, for example, 1.0 to 10.0 parts by weight relative to 100.0 parts by weight of the nonmagnetic powder, preferably 0.5 to 7.0 parts by weight.

[0088] The content of fatty acid amide in the composition for forming the nonmagnetic layer is, for example, 0.1 to 3.0 parts by weight relative to 100.0 parts by weight of the nonmagnetic powder, preferably 0.1 to 1.0 parts by weight.

[0089] <0.1% of the cross-sectional area of ​​the protrusions on the surface of the magnetic layer>

[0090] In one embodiment, in the magnetic tape described above, the spacing of the protrusions on the surface of the magnetic layer, which is 0.1% of the cross-sectional area, is preferably in the range of 1.0 to 20.0 nm.

[0091] In this invention and this specification, the 0.1% pitch of the protrusion cross-sectional area on the surface of the magnetic layer is a value that can be considered as an index of the surface roughness of the magnetic layer, obtained by the following method.

[0092] Atomic force microscopy (AFM) was used in tapping mode to measure randomly selected areas (40 μm × 40 μm) on the surface of the magnetic layer of the magnetic tape to be measured. Measurements were performed at 10 different locations. For example, the Veeco Nanoscope 4 could be used as the AFM. For example, the BRUKER RTESP-300 could be used as the probe. The resolution was set to 512 pixels × 512 pixels, and the scan speed was set to the speed required to measure one frame (512 pixels × 512 pixels) in 341 seconds. After applying a Flatten: three-stage filter to the measured data, the following processing was performed to calculate the 0.1% pitch of the raised cross-sectional area.

[0093] The data processed by the above filters was converted into a text file. Height data from 512 × 512 = 262,144 reference planes were converted into a text file. A reference plane is a surface where the volume of convex and concave surfaces becomes equal (zero height).

[0094] Read the 262nd (equivalent to 0.1%) largest value from 512 × 512 = 262,144 values. Take this value as the 0.1% spacing of the bulge cross-sectional area.

[0095] The values ​​of 0.1% of the convex cross-sectional area spacing were determined for 10 measurement locations, and their arithmetic mean was taken as the 0.1% convex cross-sectional area spacing on the surface of the magnetic layer of the magnetic tape to be measured.

[0096] Regarding the 0.1% pitch of the protrusion cross-sectional area obtained by the above method, the inventors believe that the larger this value, the coarser the aggregates formed by non-magnetic powders (abrasives and / or protrusion forming agents) in the magnetic layer. The frequency of contact between the protrusions on the surface of the magnetic layer and the nonwoven fabric (so-called actual contact) decreases due to the formation of coarse aggregates. As a result, the amount of fluid lubricant collected by the nonwoven fabric via non-magnetic powder particles within the layer decreases, thus presumably reducing the value of the fluid lubricant dosage obtained by the above method. Conversely, it is believed that suppressing the formation of coarse aggregates to reduce the value of the 0.1% pitch of the protrusion cross-sectional area can increase the value of the fluid lubricant dosage obtained by the above method. In such magnetic tapes, the fluid lubricant easily seeps from within the layer to the surface of the magnetic layer through contact with the magnetic head during sliding, which presumably helps to suppress the degradation of electromagnetic conversion characteristics during repeated tape runs at high temperatures. Based on the above viewpoints, in the aforementioned magnetic tape, the spacing of the protrusions on the surface of the magnetic layer, representing 0.1% of the cross-sectional area, is preferably 20.0 nm or less, more preferably 18.0 nm or less, even more preferably 16.0 nm or less, even more preferably 14.0 nm or less, even more preferably 12.0 nm or less, even more preferably 10.0 nm or less, and even more preferably 7.0 nm or less. Furthermore, in the aforementioned magnetic tape, from the viewpoint of further suppressing the deterioration of electromagnetic conversion characteristics during repeated tape running in a high-temperature environment, the spacing of the protrusions on the surface of the magnetic layer, representing 0.1% of the cross-sectional area, is preferably 1.0 nm or more, more preferably 1.2 nm or more.

[0097] The spacing of the protrusions on the surface of the magnetic layer at 0.1% of their cross-sectional area can be controlled according to the dispersion conditions during the preparation of the composition for forming the magnetic layer. For example, the more the dispersion conditions of the separately dispersed abrasive and / or protrusion-forming agent are strengthened, the more likely it is that the value of the spacing of the protrusions on the surface of the magnetic layer can be reduced. Examples of strengthening the dispersion conditions include using small-diameter beads as dispersion beads, extending the dispersion time, and increasing the number of dispersion cycles.

[0098] The following is a more detailed explanation of the aforementioned magnetic tape.

[0099] <Magnetic Layer>

[0100] (Strongly magnetic powder)

[0101] As the strongly magnetic powder contained in the magnetic layer, one or more strongly magnetic powders known for use in the magnetic layers of various magnetic recording media can be used. From the viewpoint of improving recording density, it is preferable to use a strongly magnetic powder with a small average particle size. Therefore, the average particle size of the strongly magnetic powder is preferably 50 nm or less, more preferably 45 nm or less, even more preferably 40 nm or less, even more preferably 35 nm or less, even more preferably 30 nm or less, even more preferably 25 nm or less, and even more preferably 20 nm or less. On the other hand, from the viewpoint of magnetization stability, the average particle size of the strongly magnetic powder is preferably 5 nm or more, more preferably 8 nm or more, even more preferably 10 nm or more, even more preferably 15 nm or more, and even more preferably 20 nm or more.

[0102] Hexagonal ferrite powder

[0103] As a preferred example of a strongly magnetic powder, hexagonal ferrite powder can be cited. For details regarding hexagonal ferrite powder, please refer to, for example, paragraphs 0012-0030 of Japanese Patent Application Publication No. 2011-225417, paragraphs 0134-0136 of Japanese Patent Application Publication No. 2011-216149, paragraphs 0013-0030 of Japanese Patent Application Publication No. 2012-204726, and paragraphs 0029-0084 of Japanese Patent Application Publication No. 2015-127985.

[0104] In this invention and specification, "hexagonal ferrite powder" refers to a strongly magnetic powder in which the hexagonal ferrite crystal structure is detected as the main phase by X-ray diffraction analysis. The main phase refers to the structure to which the highest intensity diffraction peak in the X-ray diffraction spectrum obtained by X-ray diffraction analysis belongs. For example, if the highest intensity diffraction peak in the X-ray diffraction spectrum obtained by X-ray diffraction analysis belongs to a hexagonal ferrite crystal structure, then the hexagonal ferrite crystal structure is determined to be the main phase. If only a single structure is detected by X-ray diffraction analysis, that detected structure is considered the main phase. As constituent atoms, the hexagonal ferrite crystal structure contains at least iron atoms, divalent metal atoms, and oxygen atoms. Divalent metal atoms refer to metal atoms that can become divalent cations as ions; examples include strontium atoms, barium atoms, calcium atoms, and lead atoms. In this invention and specification, hexagonal strontium ferrite powder refers to a hexagonal ferrite in which the predominant divalent metal atom is strontium, and hexagonal barium ferrite powder refers to a hexagonal ferrite in which the predominant divalent metal atom is barium. The predominant divalent metal atom refers to the divalent metal atom that constitutes the largest proportion of divalent metal atoms in the powder, based on an atomic percentage. However, the aforementioned divalent metal atoms do not include rare earth atoms. In this invention and specification, "rare earth atoms" is selected from the group consisting of scandium (Sc), yttrium (Y), and lanthanides. The lanthanide atoms are selected from the group consisting of lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and argonium (Lu).

[0105] The following is a more detailed description of hexagonal strontium ferrite powder as one type of hexagonal ferrite powder.

[0106] The activation volume of hexagonal strontium ferrite powder is preferably in the range of 800–1600 nm. 3 Within the aforementioned range, micronized hexagonal strontium ferrite powder with an activation volume within this range is suitable for manufacturing magnetic tapes that exhibit excellent electromagnetic conversion properties. The preferred activation volume of the hexagonal strontium ferrite powder is 800 nm. 3 The above, for example, could also be 850nm. 3 That's all. Furthermore, from the viewpoint of further improving electromagnetic conversion characteristics, the activation volume of hexagonal strontium ferrite powder is more preferably 1500 nm. 3 Hereinafter, 1400nm is further preferred. 3 The following is a further preferred option: 1300nm 3 The following is a further preferred option: 1200nm3 Hereinafter, 1100nm is further preferred. 3 The activation volume of this hexagonal barium ferrite powder is also the same.

[0107] "Activation volume" is the unit of magnetization reversal and is an indicator of the magnetic strength of a particle. The activation volume and anisotropy constant Ku described in this invention and specification were determined using a vibrating sample type fluxmeter at a magnetic field scanning speed of 3 minutes and 30 minutes (measurement temperature: 23℃±1℃) using the coercivity Hc measuring unit, and calculated according to the following relationship between Hc and activation volume V. Regarding the unit of the anisotropy constant Ku, lerg / cc = 1.0 × 10⁻⁶. -1 J / m 3 .

[0108] Hc=2Ku / Ms{1-[(kT / KuV)ln(At / 0.693)] 1 / 2}

[0109] In the above formula, Ku: anisotropy constant (unit: J / m) 3 Ms: saturation magnetization (kA / m), k: Boltzmann constant, T: absolute temperature (K), V: activated volume (cm³) 3 A: Spin precession frequency (unit: s) -1 ), t: magnetic field reversal time (unit: s)

[0110] An anisotropy constant Ku can be cited as an indicator of reducing thermal fluctuations (in other words, improving thermal stability). Hexagonal strontium ferrite powder preferably has a Ku value of 1.8 × 10⁻⁶. 5 J / m 3 The above-mentioned Ku, more preferably, can have 2.0 × 10 5 J / m 3 The above refers to the Ku value. Furthermore, the Ku value of hexagonal strontium ferrite powder can, for example, be 2.5 × 10⁻⁶. 5 J / m 3 However, a higher Ku value indicates higher thermal stability and is therefore preferred; it is not limited to the values ​​exemplified above.

[0111] Hexagonal strontium ferrite powder may or may not contain rare earth atoms. When hexagonal strontium ferrite powder contains rare earth atoms, it is preferable that it contains rare earth atoms at a content of 0.5 to 5.0 atomic% (bulk content) relative to 100 atomic% of iron atoms. In one embodiment, the hexagonal strontium ferrite powder containing rare earth atoms may have a rare earth atom surface bias. In this invention and this specification, "rare earth atom surface layer bias" refers to the rare earth atom content (hereinafter referred to as "rare earth atom surface layer content" or simply "surface layer content") in a solution obtained by partially dissolving hexagonal strontium ferrite powder with acid relative to 100 atomic percent of iron atoms, compared to the rare earth atom content (hereinafter referred to as "rare earth atom bulk content" or simply "bulk content") in a solution obtained by completely dissolving hexagonal strontium ferrite powder with acid, satisfying the following ratio:

[0112] The ratio of rare earth atoms in the surface layer to rare earth atoms in the bulk layer is greater than 1.0.

[0113] The meaning of the rare earth atom content of hexagonal strontium ferrite powder, as described later, is the same as the meaning of the rare earth atom bulk content. In contrast, since partial dissolution with acid dissolves only the surface portion of the particles constituting the hexagonal strontium ferrite powder, the rare earth atom content in the solution obtained through partial dissolution refers to the rare earth atom content in the surface portion of the particles constituting the hexagonal strontium ferrite powder. A rare earth atom surface portion content that satisfies the ratio "rare earth atom surface portion content / rare earth atom bulk content > 1.0" indicates that rare earth atoms are predominantly present in the surface portion (i.e., in greater quantities than in the interior) of the particles constituting the hexagonal strontium ferrite powder. In this invention and this specification, the surface portion refers to a region extending from the surface of the particles constituting the hexagonal strontium ferrite powder towards the interior.

[0114] When hexagonal strontium ferrite powder contains rare earth atoms, the rare earth atom content (bulk content) relative to 100 atomic% of iron atoms is preferably in the range of 0.5 to 5.0 atomic%. It is believed that containing rare earth atoms at a bulk content within the above range, with the rare earth atoms predominantly located in the surface layer of the particles constituting the hexagonal strontium ferrite powder, helps to suppress the decrease in reproduction output during repeated reproduction. This is presumably because containing rare earth atoms at a bulk content within the above range, with the rare earth atoms predominantly located in the surface layer of the particles constituting the hexagonal strontium ferrite powder, can increase the anisotropy constant Ku. A higher value of the anisotropy constant Ku is more effective in suppressing the phenomenon known as thermal fluctuations (in other words, it improves thermal stability). By suppressing thermal fluctuations, the decrease in reproduction output during repeated reproduction can be suppressed. It is speculated that the rare earth atoms biased towards the surface of hexagonal strontium ferrite powder particles help stabilize the spin of the iron (Fe) position within the lattice of the surface layer, thereby increasing the anisotropy constant Ku.

[0115] Furthermore, it is speculated that using hexagonal strontium ferrite powder with rare-earth atom surface bias as a strong magnetic powder in the magnetic layer can also help suppress the wear of the magnetic layer surface due to slippage relative to the magnetic head. That is, it is speculated that hexagonal strontium ferrite powder with rare-earth atom surface bias can also help improve the tape travel durability. This is speculated because the rare-earth atom bias on the surface of the particles constituting the hexagonal strontium ferrite powder helps to enhance the interaction between the particle surface and the organic matter (e.g., binders and / or additives) contained in the magnetic layer, thereby increasing the strength of the magnetic layer.

[0116] From the viewpoint of further suppressing the decline in reproduction output during repeated reproduction and / or further improving the durability of the conveyor belt, the rare earth atom content (bulk content) is more preferably in the range of 0.5 to 4.5 atomic%, more preferably in the range of 1.0 to 4.5 atomic%, and even more preferably in the range of 1.5 to 4.5 atomic%.

[0117] The above-mentioned bulk content rate is the content rate obtained by completely dissolving hexagonal strontium ferrite powder. In this invention and this specification, unless otherwise specified, the content rate for atoms refers to the bulk content rate obtained by completely dissolving hexagonal strontium ferrite powder. As rare earth atoms, the hexagonal strontium ferrite powder containing rare earth atoms may contain only one type of rare earth atom or may contain two or more types of rare earth atoms. The above-mentioned bulk content rate when containing two or more rare earth atoms is calculated based on the sum of the two or more rare earth atoms. This also applies to other components in this invention and this specification. That is, unless otherwise specified, a component may use only one type or two or more types. The content or content rate when using two or more types refers to the sum of the two or more types.

[0118] When the hexagonal strontium ferrite powder contains rare earth atoms, the rare earth atoms contained can be any one or more of the rare earth atoms. From the viewpoint of further suppressing the decrease in reproduction output during repeated reproduction, preferred rare earth atoms include neodymium atoms, samarium atoms, yttrium atoms, and dysprosium atoms, more preferably neodymium atoms, samarium atoms, and yttrium atoms, and even more preferably neodymium atoms.

[0119] In hexagonal strontium ferrite powder exhibiting a surface-partial predominance of rare earth atoms, the rare earth atoms only need to be present in the surface portion of the particles constituting the hexagonal strontium ferrite powder, and the degree of predominance is not limited. For example, regarding hexagonal strontium ferrite powder exhibiting a surface-partial predominance of rare earth atoms, the ratio of the surface portion content of rare earth atoms obtained by partial dissolution under the dissolution conditions described later to the bulk content of rare earth atoms obtained by complete dissolution under the dissolution conditions described later, "surface portion content / bulk content," exceeds 1.0, and can be 1.5 or more. A "surface portion content / bulk content" greater than 1.0 indicates that rare earth atoms are predominantly present in the surface portion (i.e., their quantity is greater than that in the interior) of the particles constituting the hexagonal strontium ferrite powder. Furthermore, the ratio of the surface portion content of rare earth atoms obtained by partial dissolution under the dissolution conditions described later to the bulk content of rare earth atoms obtained by complete dissolution under the dissolution conditions described later, "surface portion content / bulk content", can be, for example, 10.0 or less, 9.0 or less, 8.0 or less, 7.0 or less, 6.0 or less, 5.0 or less, or 4.0 or less. However, in hexagonal strontium ferrite powder with a rare earth atom surface portion bias, the rare earth atoms only need to be biased in the surface portion of the particles constituting the hexagonal strontium ferrite powder, and the above-mentioned "surface portion content / bulk content" is not limited to the upper or lower limit shown.

[0120] The partial and complete dissolution of hexagonal strontium ferrite powder will be described below. For hexagonal strontium ferrite powder existing in powder form, the partially and completely dissolved sample powders are collected from the same batch of powder. On the other hand, for hexagonal strontium ferrite powder contained in the magnetic layer of a magnetic tape, a portion of the hexagonal strontium ferrite powder removed from the magnetic layer is used for partial dissolution, and another portion is used for complete dissolution. When removing the hexagonal strontium ferrite powder from the magnetic layer, the method described, for example, in paragraph 0032 of Japanese Patent Application Publication No. 2015-91747 can be used.

[0121] The aforementioned partial dissolution refers to the point at which dissolution is complete, to the point where the hexagonal strontium ferrite powder residue can be visually identified in the liquid. For example, through partial dissolution, 10-20% by mass of the particles constituting the hexagonal strontium ferrite powder can be dissolved (with the total number of particles representing 100% by mass). On the other hand, the aforementioned complete dissolution refers to the point at which dissolution is complete, to the point where the hexagonal strontium ferrite powder residue cannot be visually identified in the liquid.

[0122] The determination of partial dissolution and surface layer content mentioned above is performed, for example, by the following method. However, the dissolution conditions, such as the amount of sample powder described below, are merely illustrative, and any dissolution conditions capable of partial or complete dissolution can be used.

[0123] A container (e.g., a beaker) containing 12 mg of sample powder and 10 mL of 1 mol / L hydrochloric acid is kept on a hot plate at a set temperature of 70 °C for 1 hour. The resulting solution is filtered through a 0.1 μm membrane filter. Elemental analysis of the filtrate is performed using an inductively coupled plasma (ICP) analyzer. This allows the determination of the surface portion content of rare earth atoms relative to 100 atomic percent of iron atoms. In cases where multiple rare earth atoms are detected by elemental analysis, the total content of all rare earth atoms is taken as the surface portion content. This process is also applied to the determination of bulk content.

[0124] On the other hand, the determination of complete dissolution and bulk content is carried out, for example, by the following method.

[0125] A container (e.g., a beaker) containing 12 mg of sample powder and 10 mL of 4 mol / L hydrochloric acid is kept on a hot plate at a set temperature of 80°C for 3 hours. Then, the same steps as those described above for determining partial dissolution and surface content are performed to determine the bulk content relative to 100 atomic percent of iron atoms.

[0126] From the viewpoint of improving the reproduction output when reproducing data recorded on magnetic tape, it is preferable that the magnetic tape contains a strongly magnetic powder with a high mass magnetization σs. In this regard, hexagonal strontium ferrite powder containing rare-earth atoms but lacking a rare-earth atom surface bias tends to exhibit a significantly lower σs compared to hexagonal strontium ferrite powder without rare-earth atoms. Therefore, to suppress this significant decrease in σs, hexagonal strontium ferrite powder with a rare-earth atom surface bias is preferred. In one embodiment, the σs of the hexagonal strontium ferrite powder can be 45 A·m. 2 / kg or above, or 47A·m 2 / kg or more. On the other hand, from the viewpoint of noise reduction, σs is preferably 80 A·m. 2 / kg or less, preferably 60A·m 2 / kg or less. σs can be measured using a known measuring device capable of measuring magnetic properties, such as a vibrating sample type fluxmeter. In this invention and this specification, unless otherwise specified, the mass magnetization σs is the value measured with a magnetic field strength of 15 kOe. 1 [kOe] = 10 6 / 4π[A / m].

[0127] Regarding the atomic content (bulk content) of the hexagonal strontium ferrite powder, the strontium atom content relative to 100 atomic% of iron atoms can, for example, be in the range of 2.0 to 15.0 atomic% (bundle content). In one embodiment, the hexagonal strontium ferrite powder may contain only strontium atoms as divalent metal atoms in the powder. Furthermore, in another embodiment, the hexagonal strontium ferrite powder may also contain one or more other divalent metal atoms besides strontium atoms. For example, it may contain barium atoms and / or calcium atoms. In the case of containing divalent metal atoms other than strontium atoms, the barium atom content and calcium atom content in the hexagonal strontium ferrite powder relative to 100 atomic% of iron atoms can, for example, be in the range of 0.05 to 5.0 atomic% (bundle content), respectively.

[0128] As for the crystal structures of hexagonal ferrites, the known types are magnetoplumbide (also known as "M-type"), W-type, Y-type, and Z-type. Hexagonal strontium ferrite powder can adopt any crystal structure. The crystal structure can be confirmed by X-ray diffraction analysis. Hexagonal strontium ferrite powder can be detected by X-ray diffraction analysis to have a single crystal structure or two or more crystal structures. For example, in one embodiment, hexagonal strontium ferrite powder can be detected by X-ray diffraction analysis to have only an M-type crystal structure. For example, M-type hexagonal ferrite is made from AFe... 12 O 19The composition is represented by the formula. Here, A represents a divalent metal atom. In the case of hexagonal strontium ferrite powder of type M, A is only a strontium atom (Sr), or when A contains multiple divalent metal atoms, as mentioned above, the strontium atom (Sr) accounts for the largest proportion on an atomic percentage basis. The divalent metal atom content of hexagonal strontium ferrite powder is usually determined according to the type of crystal structure of hexagonal ferrite and is not particularly limited. The same applies to the iron atom content and oxygen atom content. Hexagonal strontium ferrite powder contains at least iron atoms, strontium atoms, and oxygen atoms, and may also contain rare earth atoms. Furthermore, hexagonal strontium ferrite powder may contain atoms other than these atoms, or it may not contain atoms other than these atoms. As an example, hexagonal strontium ferrite powder may contain aluminum atoms (Al). The aluminum atom content relative to 100 atomic percent of iron atoms may be, for example, 0.5 to 10.0 atomic percent. From the viewpoint of further suppressing the decrease in reproduction output during repeated reproduction, hexagonal strontium ferrite powder preferably contains iron atoms, strontium atoms, oxygen atoms, and rare earth atoms, and the content of atoms other than these atoms is 10.0 atomic% or less relative to 100 atomic% of iron atoms, more preferably in the range of 0 to 5.0 atomic%, and may also be 0 atomic%. That is, in one embodiment, hexagonal strontium ferrite powder may be free of atoms other than iron atoms, strontium atoms, oxygen atoms, and rare earth atoms. The content expressed in atomic% is obtained by converting the content of each atom (unit: mass%) obtained by completely dissolving the hexagonal strontium ferrite powder using the atomic weight of each atom into a value expressed in atomic% by means of the content of each atom. Furthermore, in this invention and this specification, "free of" for a certain atom means that the content is 0 mass% after complete dissolution and measured by an ICP analyzer. The detection limit of the ICP analyzer is generally 0.01 ppm (parts per million) or less on a mass basis. The term "excluding" is used to include cases where the content is less than the detection limit of the ICP analyzer. In one embodiment, the hexagonal strontium ferrite powder may be bismuth-free (Bi).

[0129] Metal powder

[0130] As a preferred example of a strongly magnetic powder, strongly magnetic metal powder can be cited. For details regarding strongly magnetic metal powder, please refer to paragraphs 0137 to 0141 of Japanese Patent Application Publication No. 2011-216149 and paragraphs 0009 to 0023 of Japanese Patent Application Publication No. 2005-251351.

[0131] ε-iron oxide powder

[0132] As a preferred specific example of a strongly magnetic powder, ε-iron oxide powder can be cited. In this invention and this specification, "ε-iron oxide powder" refers to a strongly magnetic powder in which an ε-iron oxide crystal structure is detected as the main phase by X-ray diffraction analysis. For example, if the highest intensity diffraction peak in the X-ray diffraction spectrum obtained by X-ray diffraction analysis belongs to an ε-iron oxide crystal structure, then the ε-iron oxide crystal structure is determined to be the main phase. Methods for manufacturing ε-iron oxide powder include methods using goethite, reverse micelle methods, etc. These manufacturing methods are all well known. Furthermore, methods for manufacturing ε-iron oxide powder in which a portion of Fe is replaced by Ga, Co, Ti, Al, Rh, etc., can be found, for example, in J. Jpn. Soc. Powder Metallurgy Vol. 61 Supplement, No. S1, pp. S280-S284, J. Mater. Chem. C, 2013, 1, pp. 5200-5206, etc. However, the method for manufacturing ε-iron oxide powder, which can be used as a strong magnetic powder in the magnetic layer of the magnetic tape described above, is not limited to the methods listed herein.

[0133] The activation volume of ε-iron oxide powder is preferably in the range of 300–1500 nm. 3 Within the aforementioned range, micronized ε-iron oxide powder with an activation volume within this range is suitable for manufacturing magnetic tapes that exhibit excellent electromagnetic conversion properties. The preferred activation volume of the ε-iron oxide powder is 300 nm. 3 The above, for example, could also be 500nm. 3 That's all. Furthermore, from the viewpoint of further improving electromagnetic conversion characteristics, the activation volume of the ε-iron oxide powder is more preferably 1400 nm. 3 The following is a further preferred option: 1300nm 3 The following is a further preferred option: 1200nm 3 Hereinafter, 1100nm is further preferred. 3 the following.

[0134] An anisotropy constant Ku can be cited as an indicator of reducing thermal fluctuations (in other words, improving thermal stability). ε-iron oxide powder preferably has a Ku value of 3.0 × 10⁻⁶. 4 J / m 3 The above-mentioned Ku, more preferably, can have 8.0 × 10 4 J / m 3 The above refers to the Ku. Furthermore, the Ku of ε-iron oxide powder can, for example, be 3.0 × 10⁻⁶. 5 J / m 3 However, a higher Ku value indicates higher thermal stability and is therefore preferred; it is not limited to the values ​​exemplified above.

[0135] From the viewpoint of improving reproduction output when reproducing data recorded on magnetic tape, it is preferable that the magnetic tape contains strongly magnetic powder with a high mass magnetization σs. In this regard, in one embodiment, the σs of the ε-iron oxide powder can be 8 A·m. 2 / kg or above, or 12A·m 2 / kg or more. On the other hand, from the viewpoint of noise reduction, the σs of ε-iron oxide powder is preferably 40 A·m. 2 Below / kg, preferably 35A·m 2 / kg or less.

[0136] Unless otherwise specified in this invention and specification, the average particle size of various powders, such as strongly magnetic powders, is the value determined using a transmission electron microscope by the following method.

[0137] The powder was photographed at 100,000x magnification using a transmission electron microscope, and then printed on photographic paper at a total magnification of 500,000x to obtain photographs of the particles constituting the powder. Target particles were selected from the obtained particle photographs, and their outlines were traced using a digitizer to determine the size of the particles (primary particles). Primary particles refer to unaggregated, independent particles.

[0138] The above measurements were performed on 500 randomly selected particles. The arithmetic mean of the particle sizes of these 500 particles was taken as the average particle size of the powder. For example, a Hitachi, Ltd. H-9000 transmission electron microscope can be used as the transmission electron microscope described above. Furthermore, the particle size can be measured using known image analysis software (e.g., Carl Zeiss AG KS-400 image analysis software). Unless otherwise specified, the average particle size shown in the embodiments described below refers to the value measured using a Hitachi, Ltd. H-9000 transmission electron microscope as a transmission electron microscope and Carl Zeiss AG KS-400 image analysis software as image analysis software. In this invention and specification, "powder" refers to a collection of multiple particles. For example, "strong magnetic powder" refers to a collection of multiple strongly magnetic particles. Furthermore, the collection of multiple particles is not limited to the particles constituting the collection being in direct contact, but also includes the presence of binders, additives, etc., between the particles, as described later. The term "particle" is sometimes also used to refer to powder.

[0139] As a method for collecting sample powder from magnetic tape to determine particle size, the method described in paragraph 0015 of Japanese Patent Application Publication No. 2011-048878 can be used, for example.

[0140] Unless otherwise specified in this invention and specification, the size of the particles constituting the powder (particle size) refers to the shape of the particles observed in the aforementioned particle photographs.

[0141] (1) In the case of needle-shaped, spindle-shaped, columnar (where the height is greater than the maximum major diameter of the base), it represents the length of the major axis constituting the particle, i.e., the length of the major axis.

[0142] (2) In the case of a plate or column (where the thickness or height is less than the maximum major diameter of the plate surface or bottom surface), indicate the maximum major diameter of the plate surface or bottom surface.

[0143] (3) When the shape is spherical, polyhedral, irregular, etc., and the major axis of the constituent particles cannot be determined based on the shape, the equivalent diameter of the circle is represented. The equivalent diameter of the circle is determined by the circular projection method.

[0144] Furthermore, in the above measurements, the length of the minor axis of the particles, i.e., the minor axis length, was measured, and the value of (major axis length / minor axis length) for each particle was calculated. The average needle-like ratio of the powder refers to the arithmetic mean of the values ​​obtained for the above 500 particles. Here, unless otherwise specified, regarding the minor axis length, in the above definition of particle size (1), it refers to the length of the minor axis constituting the particle; similarly, in the case of (2), it refers to the thickness or height; and in the case of (3), since it is impossible to distinguish between the major axis and the minor axis, for convenience, (major axis length / minor axis length) is regarded as 1.

[0145] Furthermore, unless otherwise specified, when the particles have a specific shape, for example, in the case of the above definition of particle size (1), the average particle size is the average major axis length; in the case of the above definition of particle size (2), the average particle size is the average plate diameter; and in the case of the above definition of particle size (3), the average particle size is the average diameter (also referred to as the average particle size).

[0146] The content (fill rate) of the strongly magnetic powder in the magnetic layer is preferably in the range of 50 to 90% by mass, and more preferably in the range of 60 to 90% by mass. From the viewpoint of increasing recording density, a higher filling rate of the strongly magnetic powder in the magnetic layer is preferred.

[0147] In one embodiment, the anisotropic magnetic field Hk of the magnetic tape is preferably 10 kOe or more, more preferably 12 kOe or more, and even more preferably 14 kOe or more. From the viewpoint of increasing recording density, it is preferable that the anisotropic magnetic field Hk is higher in the area where data is recorded. On the other hand, it is believed that in areas with a higher anisotropic magnetic field Hk, it becomes more difficult to record to the depths of the magnetic layer due to spacing variations, thus making the electromagnetic conversion characteristics more prone to deterioration during repeated tape runs at high temperatures. In contrast, in the magnetic tape, the fluid lubrication dosage determined by the above method is within the above range, which helps to suppress this deterioration of electromagnetic conversion characteristics. Furthermore, the anisotropic magnetic field Hk of the magnetic tape is preferably 90 kOe or less, more preferably 80 kOe or less, and even more preferably 70 kOe or less.

[0148] In this invention and specification, the "anisotropic magnetic field Hk" of the magnetic tape refers to the magnetic field that saturates the magnetization when a magnetic field is applied in the direction of the non-magnetization axis of the magnetic layer. The anisotropic magnetic field Hk can be measured using a known measuring device capable of measuring magnetic properties, such as a vibrating sample type fluxmeter. A sample piece suitable for insertion into the measuring device is cut from the measurement area of ​​the magnetic tape to be measured, and Hk is measured on the sample piece at a temperature of 23°C. By setting the ambient temperature around the sample piece to 23°C, the temperature of the sample piece can be set to 23°C by establishing temperature equilibrium. For example, in a magnetic layer containing hexagonal ferrite powder and / or ε-iron oxide powder as strongly magnetic powder, the non-magnetization axis direction of the magnetic layer is in-plane. Regarding units, 1 [kOe] = 10 6 / 4π[A / m].

[0149] (Adhesive)

[0150] The magnetic tape described above can be a coated magnetic tape and may contain an adhesive in the magnetic layer. The adhesive is one or more resins. Various resins commonly used as adhesives in coated magnetic recording media can be used as adhesives. For example, resins selected from polyurethane resins, polyester resins, polyamide resins, vinyl chloride resins, styrene, acrylonitrile, acrylic resins made from co-methyl methacrylate, cellulose resins such as nitrocellulose, epoxy resins, phenoxy resins, polyvinyl acetal, polyvinyl butyral, and polyvinyl alkyl resins can be used alone, or multiple resins can be used in combination. Polyurethane resins, acrylic resins, cellulose resins, and vinyl chloride resins are preferred. These resins can be homopolymers or copolymers. These resins can also be used as adhesives in the non-magnetic layer and / or back coating layer described later.

[0151] Regarding the above-mentioned adhesive, please refer to paragraphs 0028 to 0031 of Japanese Patent Application Publication No. 2010-24113. The average molecular weight of the resin used as the adhesive, based on weight-average molecular weight, can be, for example, 10,000 or more and 200,000 or less. The weight-average molecular weight in this invention and specification refers to a value obtained by converting a value measured by gel permeation chromatography (GPC) under the following testing conditions to polystyrene. The weight-average molecular weight of the adhesives shown in the examples described later is a value obtained by converting a value measured under the following testing conditions to polystyrene. The adhesive can be used, for example, in an amount of 1.0 to 30.0 parts by weight relative to 100.0 parts by weight of the strongly magnetic powder.

[0152] GPC Unit: HLC-8120 (manufactured by Tosoh Corporation)

[0153] Column: TSK gel Multipore HXL-M (manufactured by TOSOH CORPORATION, 7.8mmID (InnerDiameter) × 30.0cm)

[0154] Eluent: Tetrahydrofuran (THF)

[0155] (Curing agent)

[0156] The curing agent can also be used in conjunction with a resin that can be used as an adhesive. Regarding the curing agent, in one approach, it can be a thermosetting compound that undergoes a curing reaction (crosslinking reaction) by heating; in another approach, it can be a photocurable compound that undergoes a curing reaction (crosslinking reaction) by light irradiation. The curing agent undergoes a curing reaction during the magnetic layer forming process, and at least a portion of it can be included in the magnetic layer in a state of reaction (crosslinking) with other components such as the adhesive. This also applies to layers formed using the same composition when the composition used to form other layers contains a curing agent. A thermosetting compound is preferred as the curing agent, and polyisocyanate is suitable. For details regarding polyisocyanate, please refer to paragraphs 0124-0125 of Japanese Patent Application Publication No. 2011-216149. In the composition for forming the magnetic layer, the curing agent can be used, for example, in an amount of 0 to 80 parts by weight relative to 100.0 parts by weight of the adhesive; from the viewpoint of improving the strength of the magnetic layer, it is preferable to use an amount of 50.0 to 80.0 parts by weight.

[0157] (additive)

[0158] The magnetic layer may contain one or more additives as needed. Examples of additives include the curing agent described above. Furthermore, examples of additives contained in the magnetic layer include non-magnetic powders (abrasives and / or protrusion forming agents), dispersants, dispersing aids, mildew inhibitors, antistatic agents, antioxidants, etc. Regarding dispersants, please refer to paragraphs 0061 and 0071 of Japanese Patent Application Publication No. 2012-133837. The dispersant may also be added to the composition for forming the non-magnetic layer. Regarding dispersants that can be added to the composition for forming the non-magnetic layer, please refer to paragraph 0061 of Japanese Patent Application Publication No. 2012-133837.

[0159] abrasive

[0160] As an abrasive, a non-magnetic powder with a Mohs hardness greater than 8 is preferred, and a non-magnetic powder with a Mohs hardness of 9 or greater is more preferred. The maximum Mohs hardness is 10. The abrasive can be an inorganic powder or an organic powder. The abrasive can be an inorganic oxide powder, an organic oxide powder, or a carbide powder. Examples of carbides include boron carbide (e.g., B4C) and titanium carbide (e.g., TiC). Diamond can also be used as an abrasive. In one embodiment, an inorganic oxide powder is preferred. Specifically, examples of inorganic oxides include alumina (e.g., Al2O3), titanium oxide (e.g., TiO2), cerium oxide (e.g., CeO2), and zirconium oxide (e.g., ZrO2), with alumina being preferred. Alumina has a Mohs hardness of approximately 9. For information on alumina powder, see paragraph 0021 of Japanese Patent Application Publication No. 2013-229090. Specific surface area can be used as an indicator of the particle size of the abrasive. It can be assumed that the larger the specific surface area, the smaller the particle size of the primary particles constituting the abrasive. As an abrasive, it is preferable to use an abrasive with a specific surface area (hereinafter referred to as "BET specific surface area") measured by the BET (Brunauer-Emmett-Teller) method of 14 m². 2 Abrasives with a surface area of ​​40 m² or more are preferred, based on dispersibility considerations. 2 The abrasive content in the magnetic layer is preferably 1.0 to 20.0 parts by weight, more preferably 1.0 to 18.0 parts by weight, relative to 100.0 parts by weight of the strong magnetic powder. The abrasive is preferably provided separately from the strong magnetic powder in the dispersion process (separate dispersion), and more preferably also separately from the protrusion forming agent in the dispersion process (separate dispersion). In one embodiment, as described above, when separately dispersed, it is preferable to mix fatty acids and / or fatty acid amides.

[0161] Protrusion forming agent

[0162] Carbon black can be cited as an example of a protrusion forming agent. Colloidal particles can be cited as another type of filler. From the viewpoint of availability, inorganic colloidal particles are preferred, inorganic oxide colloidal particles are more preferred, and silica colloidal particles (colloidal silica) are even more preferred. In this invention and specification, "colloidal particles" refers to particles that, when added at least 1 g per 100 mL of at least one organic solvent selected from methyl ethyl ketone, cyclohexanone, toluene, or ethyl acetate, or a mixture containing two or more of the above solvents in any mixing ratio, disperse without precipitation, thereby providing a colloidal dispersion. The average particle size of the protrusion forming agent can be, for example, 30 to 300 nm, preferably 40 to 200 nm. The content of the protrusion forming agent in the magnetic layer is preferably 0.5 to 4.0 parts by mass relative to 100.0 parts by mass of the strongly magnetic powder, more preferably 0.5 to 3.5 parts by mass. The protrusion forming agent is preferably provided separately from the strongly magnetic powder in the dispersion process, and more preferably also separately from the abrasive in the dispersion process. In one approach, as described above, when dispersed separately, it is preferable to mix fatty acids and / or fatty acid amides.

[0163] The magnetic layer described above can be directly applied to the surface of a non-magnetic support, or it can be applied indirectly via a non-magnetic layer.

[0164] <Non-magnetic layer>

[0165] Next, the non-magnetic layer will be described. The magnetic tape described above can have a magnetic layer directly on the surface of the non-magnetic support, or it can have a magnetic layer on the surface of the non-magnetic support via a non-magnetic layer containing non-magnetic powder. The non-magnetic powder used for the non-magnetic layer can be an inorganic powder or an organic powder. Furthermore, carbon black can also be used. Examples of inorganic powders include powders of metals, metal oxides, metal carbonates, metal sulfates, metal nitrides, metal carbides, and metal sulfides. These non-magnetic powders can be obtained as commercially available products or manufactured using known methods. For details, please refer to paragraphs 0146 to 0150 of Japanese Patent Application Publication No. 2011-216149. Regarding the carbon black that can be used in the non-magnetic layer, please also refer to paragraphs 0040 and 0041 of Japanese Patent Application Publication No. 2010-24113. The content (filling rate) of non-magnetic powder in the non-magnetic layer is preferably in the range of 50 to 90% by mass, and more preferably in the range of 60 to 90% by mass.

[0166] The non-magnetic layer may contain adhesives or additives. Further details regarding the adhesives, additives, etc., of the non-magnetic layer can be found in known techniques related to non-magnetic layers. Furthermore, for example, information regarding the type and content of adhesives, and the type and content of additives, can also be found in known techniques related to magnetic layers.

[0167] In this invention and specification, the non-magnetic layer also includes a substantially non-magnetic layer, which, together with the non-magnetic powder, may be present, for example, as an impurity or intentionally containing a small amount of strongly magnetic powder. Here, a substantially non-magnetic layer refers to a layer with a remanent magnetic flux density of 10 mT or less, a coercivity of 7.96 kA / m (100 Oe) or less, or a layer with a remanent magnetic flux density of 10 mT or less and a coercivity of 7.96 kA / m (100 Oe) or less. Preferably, the non-magnetic layer does not have remanent magnetic flux density or coercivity.

[0168] <Non-magnetic support>

[0169] Next, the non-magnetic support will be described. Examples of non-magnetic supports (hereinafter referred to simply as "support") include biaxially stretched polyethylene terephthalate, polyethylene naphthalate, polyamide, polyamide-imide, and aromatic polyamide. Among these, polyethylene terephthalate, polyethylene naphthalate, and polyamide are preferred. These supports can be pre-treated with corona discharge, plasma treatment, easy-bonding treatment, heat treatment, etc.

[0170] <Back Coating>

[0171] The magnetic tape described above may have a back coating containing non-magnetic powder on the surface of the non-magnetic support opposite to the surface with the magnetic layer, or it may not have such a back coating. Preferably, the back coating contains one or both of carbon black and inorganic powder. The back coating may contain a binder or additives. Regarding the binder and additives of the back coating, known techniques related to the back coating, as well as known techniques related to the formulation of the magnetic layer and / or non-magnetic layer, may be applied. For example, regarding the back coating, reference can be made to paragraphs 0018 to 0020 of Japanese Patent Application Publication No. 2006-331625 and lines 65 to 38 of column 4 of the specification of U.S. Patent No. 7,029,774.

[0172] Various thicknesses

[0173] Regarding the thickness (total thickness) of magnetic tape, with the tremendous increase in information volume in recent years, there is a demand for increased recording capacity (high capacity). As a means of increasing capacity, examples include reducing the thickness of the magnetic tape (hereinafter also referred to as "thinning") and increasing the length of the tape contained in each tape reel. From this perspective, the thickness (total thickness) of the aforementioned magnetic tape is preferably 5.6 μm or less, more preferably 5.5 μm or less, more preferably 5.4 μm or less, even more preferably 5.3 μm or less, and even more preferably 5.2 μm or less. Furthermore, from the viewpoint of ease of operation, the thickness of the magnetic tape is preferably 3.0 μm or more, more preferably 3.5 μm or more.

[0174] The thickness (total thickness) of the magnetic tape can be determined by the following methods.

[0175] Ten magnetic tape samples (e.g., 5–10 cm in length) are cut from any portion of the magnetic tape and overlapped to measure the thickness. The thickness of each magnetic tape sample is taken as the thickness of the tape by dividing the measured thickness by 10. The thickness measurement described above can be performed using a known measuring instrument capable of measuring thicknesses in the 0.1 μm range.

[0176] The thickness of the non-magnetic support is preferably 3.0 to 5.0 μm.

[0177] The thickness of the magnetic layer can be optimized based on factors such as the saturation magnetization of the magnetic head, the head gap length, and the frequency band of the recorded signal. It is typically 0.01 μm to 0.15 μm, and from the viewpoint of high-density recording, 0.02 μm to 0.12 μm is preferred, and more preferably 0.03 μm to 0.1 μm. At least one magnetic layer is required, and the magnetic layer can also be divided into two or more magnetic layers with different magnetic properties. Known structures related to multilayer magnetic layers can be applied to them. When divided into two or more magnetic layers, the thickness of the magnetic layer refers to the total thickness of these layers.

[0178] The thickness of the non-magnetic layer is, for example, 0.1 to 1.5 μm, preferably 0.1 to 1.0 μm.

[0179] The thickness of the back coating is preferably less than 0.9 μm, and more preferably 0.1 to 0.7 μm.

[0180] The thickness of the magnetic layer and other thicknesses can be determined using the following methods.

[0181] After exposing a cross-section of the magnetic tape along its thickness using an ion beam, the exposed cross-section is observed using a scanning electron microscope. Various thicknesses can be calculated as the arithmetic mean of the thicknesses obtained at any two locations during the cross-sectional observation. Alternatively, various thicknesses can also be calculated as design thicknesses based on manufacturing conditions, etc.

[0182] <Manufacturing Process>

[0183] (Preparation of the composition for forming each layer)

[0184] The process of preparing the composition for forming a magnetic layer, non-magnetic layer, or back coating typically includes at least a mixing process, a dispersion process, and a blending process arranged before or after these processes as needed. Each process can be divided into two or more stages. The components used to prepare the composition for forming each layer can be added at the beginning or middle of any process. As a solvent, one or more solvents commonly used in the manufacture of coated magnetic recording media can be used. For example, regarding solvents, see paragraph 0153 of Japanese Patent Application Publication No. 2011-216149. Furthermore, the components can be added in stages in two or more processes. For example, the binder can be added in stages in the mixing process, the dispersion process, and the blending process for adjusting the viscosity after dispersion. To manufacture the magnetic tape described above, known manufacturing techniques can be used in various processes. In the mixing process, kneaders with strong mixing forces, such as open kneaders, continuous kneaders, pressure kneaders, and extruders, are preferred. For details regarding the mixing process, please refer to Japanese Patent Application Publication Nos. 1-106338 and 1-79274. A known disperser can be used. Filtration can be performed at any stage of preparing the composition for each layer formation by a known method. Filtration can be performed, for example, by using a filter. As a filter for filtration, for example, a filter with a pore size of 0.01 to 3 μm (e.g., a glass fiber filter, a polypropylene filter, etc.) can be used.

[0185] (Coating process)

[0186] The magnetic layer can be formed by directly coating the magnetic layer forming composition onto the surface of the non-magnetic support, or by sequentially or simultaneously coating it with the non-magnetic layer forming composition in multiple layers. The back coating layer can be formed by coating the back coating forming composition onto the surface of the non-magnetic support opposite to the surface having the non-magnetic layer and / or the magnetic layer (or the surface to which the non-magnetic layer and / or the magnetic layer will be applied). For details regarding the coatings used to form each layer, please refer to paragraph 0066 of Japanese Patent Application Publication No. 2010-231843.

[0187] (Other processes)

[0188] Regarding various other processes used in the manufacture of magnetic tape, known technologies can be applied. For example, reference can be made to paragraphs 0067 to 0070 of Japanese Patent Application Publication No. 2010-231843. For instance, the coating layer of the magnetic layer forming composition can be oriented in an orientation zone while it is in a wet state. Regarding the orientation treatment, various known technologies, beginning with paragraph 0052 of Japanese Patent Application Publication No. 2010-24113, can be applied. For example, vertical orientation treatment can be performed using known methods such as the use of opposite-pole magnets. In the orientation zone, the drying speed of the coating layer can be controlled based on the temperature and flow rate of the drying air and / or the conveying speed in the orientation zone. Furthermore, the coating layer can be pre-dried before being conveyed to the orientation zone.

[0189] Through various processes, a long strip of raw magnetic tape can be obtained. The resulting raw magnetic tape is then cut (divided) using a known cutting machine to the width required for reeling into a tape cassette. This width is determined by standards and is typically 1 / 2 inch. 1 / 2 inch = 12.65 mm.

[0190] Servo patterns are typically formed on the cut magnetic tape. Details of servo patterns will be discussed later.

[0191] (Heat treatment)

[0192] In one embodiment, the magnetic tape may be a magnetic tape manufactured under the following heat treatment. In another embodiment, the magnetic tape may also be a magnetic tape manufactured without the following heat treatment.

[0193] As a heat treatment, heat treatment can be performed by winding a magnetic tape cut and trimmed to a standard width around a core component while it is in the wound state.

[0194] In one embodiment, the heat treatment can be performed while the magnetic tape is wound around a heat treatment core-shaped component (hereinafter referred to as "heat treatment core"), and the heat-treated magnetic tape can be wound onto a reel of a magnetic tape cassette, thereby producing a magnetic tape cassette with the magnetic tape wound on the reel.

[0195] The heat treatment core can be made of metal, resin, paper, etc. From the viewpoint of suppressing winding defects such as spoke defects, the material of the heat treatment core is preferably a material with high rigidity. Therefore, the heat treatment core is preferably made of metal or resin. Furthermore, as an indicator of rigidity, the flexural modulus of the heat treatment core material is preferably 0.2 GPa or more, more preferably 0.3 GPa or more. On the other hand, since materials with high rigidity are generally more expensive, using a heat treatment core with a material having greater rigidity than that that can suppress winding defects would lead to increased costs. Considering this, the flexural modulus of the heat treatment core material is preferably 250 GPa or less. The flexural modulus is a value measured according to ISO (International Organization for Standardization) 178, and thus the flexural modulus of various materials is well known. Furthermore, the heat treatment core can be a solid or hollow core-shaped component. In the case of a hollow core, from the viewpoint of maintaining rigidity, the wall thickness is preferably 2 mm or more. Furthermore, the heat treatment core may or may not have a flange.

[0196] Preferably, a magnetic tape of a length (hereinafter referred to as "final product length") or greater, which is ultimately housed in the magnetic tape cassette, is wound onto a heat treatment core, and the magnetic tape is placed in a heat treatment environment while wound onto the heat treatment core, thereby undergoing heat treatment. The length of the magnetic tape wound onto the heat treatment core is greater than or equal to the final product length, and from the viewpoint of ease of winding the heat treatment core, it is preferably "final product length + α". From the viewpoint of ease of winding, this α is preferably 5m or more. The tension when wound onto the heat treatment core is preferably 0.1N (Newtons) or more. Furthermore, from the viewpoint of suppressing excessive deformation, the tension when wound onto the heat treatment core is preferably 1.5N or less, more preferably 1.0N or less. From the viewpoint of ease of winding and suppressing coiling (curling in the length direction), the outer diameter of the heat treatment core is preferably 20mm or more, more preferably 40mm or more. Furthermore, the outer diameter of the heat treatment core is preferably 100mm or less, more preferably 90mm or less. The width of the heat treatment core only needs to be greater than or equal to the width of the magnetic tape wound on it. Furthermore, when removing the magnetic tape from the heat treatment core after heat treatment, to prevent unintentional tape deformation during the removal operation, it is preferable to remove the magnetic tape from the heat treatment core after it has been sufficiently cooled. The removed magnetic tape is preferably first wound onto another core (called a "temporary winding core"), and then wound from the temporary winding core onto the cassette reel (typically with an outer diameter of about 40-50 mm). This allows the magnetic tape to be wound onto the cassette reel while maintaining the inward and outward relationship of the magnetic tape relative to the heat treatment core during heat treatment. For details regarding the temporary winding core and the tension when winding the magnetic tape onto it, please refer to the above description related to the heat treatment core. In the above-described heat treatment method for a magnetic tape with a length of "final product length + α", a length equivalent to "+α" of the tape can be cut at any stage. For example, in one method, a length of magnetic tape equivalent to the final product length can be wound from a temporary winding core onto a reel of the magnetic tape cassette, and the remaining length of the tape, equivalent to "+α", can be cut off. From the viewpoint of reducing the cut-off and discarded portion, the aforementioned α is preferably 20m or less.

[0197] The following describes the specific method of heat treatment performed while the part is wound around the core component as described above.

[0198] The ambient temperature at which the heat treatment is performed (hereinafter referred to as the "heat treatment temperature") is preferably 40°C or higher, more preferably 50°C or higher. On the other hand, from the viewpoint of suppressing excessive deformation, the heat treatment temperature is preferably 75°C or lower, more preferably 70°C or lower, and even more preferably 65°C or lower.

[0199] The absolute humidity of the atmosphere used for heat treatment is preferably 0.1 g / kg dry air or more, more preferably 1 g / kg dry air or more. Since an atmosphere with an absolute humidity within this range can be prepared without the need for special equipment to reduce moisture, it is preferred. On the other hand, from the viewpoint of suppressing the decrease in operability caused by condensation, the absolute humidity is preferably 70 g / kg dry air or less, more preferably 66 g / kg dry air or less. The heat treatment time is preferably 0.3 hours or more, more preferably 0.5 hours or more. Furthermore, from the viewpoint of production efficiency, the heat treatment time is preferably 48 hours or less.

[0200] (Formation of servo patterns)

[0201] The formation of servo patterns can also be called the recording of servo signals. The formation of servo patterns will be explained below.

[0202] Servo patterns are typically formed along the length of the magnetic tape. Examples of control methods utilizing servo signals (servo control) include timing-based servo (TBS), amplitude servo, and frequency servo.

[0203] As shown in ECMA (European Computer Manufacturers Association) 319 (June 2001), a timing-based servo method is used in LTO (Linear Tape-Open) compliant magnetic tapes (generally referred to as "LTO tapes"). In this timing-based servo method, the servo pattern is constructed by continuously arranging multiple pairs of non-parallel magnetic strips (also referred to as "servo strips") along the length of the tape. In this invention and specification, "timing-based servo pattern" refers to a servo pattern capable of head tracking in a timing-based servo system. As described above, the reason for constructing the servo pattern with a pair of non-parallel magnetic strips is to notify the servo signal readout element passing over the servo pattern of its position. Specifically, the pair of magnetic strips is formed such that the interval changes continuously along the width of the tape. By having the servo signal readout element read this interval, the relative position of the servo pattern and the servo signal readout element can be determined. This relative position information makes data track tracking possible. Therefore, multiple servo tracks are typically arranged along the width of the tape on the servo pattern.

[0204] The servo tape consists of a continuous servo pattern along the length of the magnetic tape. Multiple servo tapes are typically present on the tape. For example, in an LTO tape, there are five. The area between two adjacent servo tapes is the data tape. The data tape consists of multiple data tracks, each corresponding to a servo track.

[0205] Furthermore, in one approach, as shown in Japanese Patent Application Publication No. 2004-318983, each servo tape contains embedded information indicating its servo tape number (also referred to as "servo tape ID (identification)" or "UDIM (Unique Data Band Identification Method) information"). This servo tape ID is recorded by moving a specific pair of servo magnetic strips from among multiple pairs of servo magnetic strips present in the servo tape, causing their positions to shift relative to each other along the length of the magnetic tape. Specifically, the movement of a specific pair of servo magnetic strips from among multiple pairs of servo magnetic strips is changed for each servo tape. Therefore, the recorded servo tape ID is unique for each servo tape, and thus, by reading a single servo tape using a servo signal reading element, the servo tape can be uniquely identified.

[0206] Another method for uniquely identifying servo tapes is the interleaving method shown in ECMA-319 (June 2001). In this interleaving method, each servo tape is recorded by moving a group of multiple pairs of non-parallel magnetic strips arranged consecutively along the length of the magnetic tape (servo strips). Since this combination of movement patterns between adjacent servo tapes is unique throughout the entire magnetic tape, the servo tape can also be uniquely identified when reading the servo pattern using two servo signal readout elements.

[0207] Furthermore, as shown in ECMA-319 (June 2001), information indicating the position of the magnetic tape along its length (also known as "LPOS (Longitudinal Position) information") is typically embedded in each servo tape. Similar to UDIM information, this LPOS information is recorded by shifting the position of a pair of servo strips along the length of the tape. However, unlike UDIM information, the same signal is recorded in each servo tape in this LPOS information.

[0208] Other information, different from the UDIM and LPOS information mentioned above, can also be embedded into the server tape. In this case, the embedded information can vary depending on the server tape, like the UDIM information, or it can be universal across all server tapes, like the LPOS information.

[0209] Furthermore, other methods besides those mentioned above can also be used as a way to embed information in the servo strip. For example, a specified code can be recorded by pulling a specified pair from the middle of a pair of servo magnetic strips.

[0210] The magnetic head used for servo pattern formation is called a servo write head. A servo write head typically has a pair of gaps corresponding to the aforementioned pair of magnetic strips, and the number of these gaps is the same as the number of servo tapes. Generally, a magnetic core and a coil are connected to each pair of gaps. By supplying current pulses to the coils, the magnetic field generated by the magnetic core can produce a leakage magnetic field in the pair of gaps. When forming a servo pattern, by feeding the magnetic tape onto the servo write head while simultaneously inputting current pulses, the magnetic pattern corresponding to the pair of gaps can be transferred onto the magnetic tape, thereby forming a servo pattern. The width of each gap can be appropriately set according to the density of the formed servo pattern. For example, the width of each gap can be set to less than 1 μm, 1–10 μm, or more than 10 μm.

[0211] Before forming servo patterns on the magnetic tape, the tape is typically demagnetized (erased). This erasure process can be performed by applying a uniform magnetic field to the tape using a DC or AC magnet. Erasure processes include DC (Direct Current) erasure and AC (Alternating Current) erasure. AC erasure is performed by gradually reducing the strength of the magnetic field while reversing the direction applied to the tape. On the other hand, DC erasure is performed by applying a unidirectional magnetic field to the tape. DC erasure includes two methods. The first method is horizontal DC erasure, which applies a unidirectional magnetic field along the length of the tape. The second method is vertical DC erasure, which applies a unidirectional magnetic field along the thickness of the tape. Erasure processes can be performed on the entire tape or on each servo section of the tape.

[0212] The orientation of the magnetic field in the formed servo pattern depends on the erasure orientation. For example, when performing horizontal DC erasure on a magnetic tape, the servo pattern is formed with the magnetic field orientation opposite to the erasure orientation. This increases the output of the servo signal obtained by reading the servo pattern. Furthermore, as shown in Japanese Patent Application Publication No. 2012-53940, when a magnetic pattern using the aforementioned gap is transferred to a magnetic tape that has been vertically DC erased, the servo signal obtained by reading the formed servo pattern is a unipolar pulse shape. On the other hand, when a magnetic pattern using the aforementioned gap is transferred to a magnetic tape that has been horizontally DC erased, the servo signal obtained by reading the formed servo pattern is a bipolar pulse shape.

[0213] Furthermore, in one approach, by utilizing servo signals to acquire the dimensional information of the magnetic tape in the width direction during transport, and adjusting and changing the tension applied to the tape in the length direction based on the acquired dimensional information, the dimensional size of the tape in the width direction can be controlled. This tension adjustment can help prevent the magnetic head used for recording or reproducing data from deviating from the target track position due to tape width deformation during recording or reproduction.

[0214] [Cassette Tape Case]

[0215] One aspect of the present invention relates to a magnetic tape cassette comprising the aforementioned magnetic tape.

[0216] The details of the magnetic tapes included in the aforementioned tape cassette are as described above.

[0217] In a magnetic tape cassette, the magnetic tape is typically housed inside the cassette body while being wound onto a reel. The reel is configured to rotate within the cassette body. Widely used magnetic tape cassettes include single-reel cassettes with one reel inside the cassette body and dual-reel cassettes with two reels inside the cassette body. When a single-reel cassette is mounted on a tape drive for recording and / or reproducing data on the magnetic tape, the magnetic tape is pulled out of the cassette and wound onto a reel on the tape drive side. A magnetic head is positioned along the magnetic tape transport path from the cassette to the take-up reel. Magnetic tape feeding and winding occur between the reel on the cassette side (feed reel) and the reel on the tape drive side (take-up reel). During this process, the magnetic head contacts and slides against the magnetic layer surface of the magnetic tape, thereby recording and / or reproducing data. In contrast, a dual-reel cassette has both a feed reel and a take-up reel inside the cassette.

[0218] [Magnetic tape device]

[0219] One aspect of the present invention relates to a magnetic tape apparatus comprising the aforementioned magnetic tape and a magnetic head. In the aforementioned magnetic tape apparatus, data recording on the magnetic tape and / or reproduction of data recorded on the magnetic tape can be performed by contacting and sliding the magnetic head with the surface of the magnetic layer of the magnetic tape.

[0220] In this invention and specification, "magnetic tape apparatus" refers to a device capable of at least one of recording data onto a magnetic tape and reproducing data recorded on the magnetic tape. This device is commonly referred to as a drive. The magnetic head included in the aforementioned magnetic tape apparatus can be a recording head capable of recording data onto a magnetic tape, or a reproduction head capable of reproducing data recorded on the magnetic tape. Furthermore, in one embodiment, the aforementioned magnetic tape apparatus may include both a recording head and a reproduction head as separate magnetic heads. In another embodiment, the magnetic head included in the aforementioned magnetic tape apparatus may also have a structure that includes both a recording element and a reproduction element on a single magnetic head. As a reproduction head, it is preferable to include a magnetic head (MR head) capable of sensitively reading information recorded on the magnetic tape as a reproduction element. Various known MR heads (e.g., GMR (Giant Magnetoresistive) heads, TMR (Tunnel Magnetoresistive) heads, etc.) can be used as MR heads. Furthermore, the magnetic head performing data recording and / or data reproduction may include a servo signal readout element. Alternatively, the aforementioned magnetic tape device may include a magnetic head equipped with servo signal readout elements (servo head) as a separate head from the magnetic head for recording and / or reproducing data. For example, the magnetic head for recording and / or reproducing the recorded data (hereinafter also referred to as the "recording / reproducing head") may include two servo signal readout elements, each capable of simultaneously reading two adjacent servo tapes sandwiching a data tape. One or more data elements may be configured between the two servo signal readout elements. The elements for recording data (recording elements) and the elements for reproducing data (reproducing elements) are collectively referred to as "data elements."

[0221] When recording and / or reproducing recorded data, the first step is to track servo signals. That is, by making the servo signal read element follow a specified servo track, the data element can be controlled to move along the target data track. Movement of the data track is achieved by changing the servo track read by the servo signal read element in the width direction of the magnetic tape.

[0222] Furthermore, the recording and playback head can also record and / or reproduce data for other data bands. In this case, simply use the aforementioned UDIM information to move the servo signal readout element to the specified servo band to begin tracking that servo band.

[0223] Figure 2 The diagram shows an example of the configuration of the data band and the servo band. Figure 2In this design, multiple servo tapes 1 are arranged on the magnetic layer of the magnetic tape MT, sandwiched between guide tapes 3. Multiple regions 2 sandwiched between two servo tapes are data tapes. The servo pattern is a magnetized region, formed by magnetizing specific areas of the magnetic layer using a servo writing head. The region magnetized by the servo writing head (the location where the servo pattern is formed) is determined according to a standard. For example, for LTUltrium format magnetic tape, which is an industry standard, during tape manufacturing, such as... Figure 3 As shown, multiple servo patterns are formed on the servo tape, tilted relative to the tape width direction. More specifically, Figure 3 In the context of servo frame SF on servo band 1, it consists of servo subframe 1 (SSF1) and servo subframe 2 (SSF2). Servo subframe 1 is composed of A bursts (...). Figure 3 Symbols A and B in the middle) sudden ( Figure 3 The A burst consists of servo patterns A1 to A5, and the B burst consists of servo patterns B1 to B5. On the other hand, servo subframe 2 consists of the C burst (… Figure 3 The symbol C) and D burst ( Figure 3 The symbols in the diagram are: (D) The C burst consists of servo patterns C1 to C4, and the D burst consists of servo patterns D1 to D4. These 18 servo patterns are configured in combinations of 5 and 4 on subframes arranged in an array of 5, 5, 4, 4, used to identify servo frames. For illustration, Figure 3 Only one servo frame is shown in the image. However, in reality, in the magnetic layer of a magnetic tape that performs timing-based servo head tracking, multiple servo frames are arranged along the tape travel direction on each servo tape. Figure 3 In the image, the arrow indicates the direction of tape transport. For example, LTO Ultrium format tapes typically have more than 5,000 servo frames per 1m of tape length on each servo tape of the magnetic layer.

[0224] In one embodiment of the aforementioned magnetic tape apparatus, the magnetic tape is considered a removable medium (a so-called replaceable medium), and a tape cassette containing the magnetic tape is inserted into and removed from the magnetic tape apparatus. In another embodiment, the magnetic tape is not considered a replaceable medium, and the magnetic tape is wound onto a reel of the magnetic tape apparatus equipped with magnetic heads, and the magnetic tape is housed within the magnetic tape apparatus.

[0225] Example

[0226] Hereinafter, one aspect of the present invention will be described with reference to an embodiment. However, the present invention is not limited to the aspect shown in the embodiment. Unless otherwise specified, the terms "parts" and "%" in the following description refer to "parts by mass" and "% by mass". "eq" is equivalent, which is a unit that cannot be converted to SI units.

[0227] Furthermore, unless otherwise specified, the following procedures and operations are carried out in an environment with a temperature of 20–25°C and a relative humidity of 40–60%.

[0228] [Example 1]

[0229] (1) Preparation of alumina dispersion

[0230] An alumina dispersion used as an abrasive liquid in the preparation of compositions for forming magnetic layers was prepared by the following method.

[0231] Compared to an α-oxidation rate of approximately 65% ​​and a BET specific surface area of ​​20m², 2 100.0 parts of alumina powder (HIT-80 manufactured by Sumitomo Chemical Company, Limited), 10.0 parts of mixed stearic acid, 5.0 parts of stearamide, 15.7 parts of a 32% solution of polyester polyurethane resin with SO3Na groups as polar groups (UR-4800 manufactured by TOYOBO CO., LTD. (polar group amount: 80 meq / kg)) (solvent is a mixture of methyl ethyl ketone and toluene), and 570.0 parts of a mixed solution of methyl ethyl ketone and cyclohexanone in a 1:1 (mass ratio) as solvent were dispersed using a paint stirrer in the presence of dispersion beads (zirconia beads with the bead diameter shown in Table 1) (dispersion time: refer to Table 1). After dispersion, the dispersion and beads were separated by sieving to obtain an alumina dispersion.

[0232] (2) Preparation of carbon black dispersion

[0233] The carbon black dispersion used as a protrusion forming agent liquid in the preparation of compositions for magnetic layer formation was prepared by the following method.

[0234] Liquefaction was achieved by ultrasonically treating 100.0 parts of carbon black with an average particle size of 80 nm, mixed with 10.0 parts of stearic acid, 5.0 parts of stearamide, and 985.0 parts of cyclohexanone as a solvent, at a stirring speed of 1500 rpm (rotations per minute) for 6 hours using an intermittent ultrasonic dispersion device with a stirrer. The liquefied carbon black dispersion was then dispersed in a horizontal bead mill using zirconia beads (the bead diameters shown in Table 1) at a bead filling rate of 80% by volume and a rotor front circumferential speed of 10 m / s, as shown in Table 1, with a residence time of 2 minutes for each dispersion. After stirring the resulting dispersion for 30 minutes using a dissolving mixer at a circumferential speed of 10 m / s, it was then treated three times using a flow ultrasonic disperser at a flow rate of 3 kg / min to obtain the final carbon black dispersion.

[0235] (3) Formulation of the composition for forming a magnetic layer

[0236] (Magnetic fluid)

[0237] 100.0 parts of strong magnetic powder

[0238] Hexagonal barium ferrite powder with an average particle size (average plate diameter) of 21 nm (“BaFe” in Table 1).

[0239] 14.0 parts of polyurethane resin containing SO3Na groups

[0240] Weight-average molecular weight: 70,000, SO3Na group: 0.2 meq / g

[0241] Cyclohexanone 150.0 parts

[0242] 150.0 parts of methyl ethyl ketone

[0243] (Abrasive solution)

[0244] 40.0 parts of the alumina dispersion prepared in (1) above

[0245] (Protrusion-forming agent solution)

[0246] 10.0 parts of the carbon black dispersion prepared in (2) above

[0247] (Other ingredients)

[0248] Stearic acid 2.0 parts

[0249] 0.2 parts stearamide

[0250] 2.0 parts of butyl stearate

[0251] 2.5 parts of polyisocyanate (TOSOH CORPORATION CORONATE (registered trademark) L)

[0252] (Add solvent at the end)

[0253] Cyclohexanone 200.0 parts

[0254] 200.0 parts of methyl ethyl ketone

[0255] (4) Formulation of the composition for forming a non-magnetic layer

[0256] Non-magnetic inorganic powder: 100.0 parts of α-iron oxide

[0257] Average particle size (average major axis length): 0.15 μm

[0258] Average needle ratio: 7

[0259] BET specific surface area: 52m² 2 / g

[0260] 20.0 parts carbon black

[0261] Average particle size: 20nm

[0262] 18.0 parts of polyurethane resin containing SO3Na groups

[0263] Weight-average molecular weight: 70,000, SO3Na group: 0.2 meq / g

[0264] Stearic acid 2.0 parts

[0265] 0.2 parts stearamide

[0266] Fatty acid esters (butyl stearate) - Reference Table 1

[0267] Cyclohexanone 300.0 parts

[0268] 300.0 parts of methyl ethyl ketone

[0269] (5) Formulation of the composition for forming the back coating

[0270] 100.0 parts carbon black

[0271] DBP (Dibutyl phthalate) oil absorption: 74cm³ 3 / 100g

[0272] 27.0 parts nitrocellulose

[0273] 62.0 parts of polyester polyurethane resin containing sulfonic acid groups and / or their salts.

[0274] 4.0 parts polyester resin

[0275] Alumina powder (BET specific surface area: 17m²) 2 / g) 0.6 parts

[0276] 600.0 parts of methyl ethyl ketone

[0277] Toluene 600.0 parts

[0278] Polyisocyanate (TOSOH CORPORATION CORONATE (registered trademark) L) 15.0 parts

[0279] (6) Preparation of the composition for forming each layer

[0280] A magnetic layer forming composition was prepared by the following method. The components were dispersed (bead dispersion) for 24 hours using an intermittent vertical sand mill to prepare the aforementioned magnetic fluid. Zirconia beads with a diameter of 0.5 mm were used as the dispersion beads. The prepared magnetic fluid, abrasive fluid, protrusion forming agent fluid, and the other components and finishing solvent were mixed using the aforementioned sand mill and dispersed as beads for 5 minutes. Then, the mixture was treated with an intermittent ultrasonic device (20 kHz, 300 W) for 0.5 minutes (ultrasonic dispersion). Finally, the mixture was filtered using a filter with a pore size of 0.5 μm to prepare the magnetic layer forming composition.

[0281] A nonmagnetic layer-forming composition was prepared by the following method: The above-mentioned components, excluding the lubricant (stearic acid, stearamide, and butyl stearate), were kneaded and diluted using an open kneader, and then dispersed using a horizontal bead mill disperser. Next, the lubricant (stearic acid, stearamide, and butyl stearate) was added, and the mixture was stirred and mixed using a dissolving mixer to prepare the nonmagnetic layer-forming composition.

[0282] A composition for forming a back coating was prepared by the following method: The above-mentioned components, excluding polyisocyanate, were introduced into a dissolving mixer and stirred at a circumferential speed of 10 m / s for 30 minutes, followed by dispersion using a horizontal bead mill. Then, polyisocyanate was added, and the mixture was stirred and mixed using the dissolving mixer to prepare the composition for forming a back coating.

[0283] (7) Production of magnetic tapes and cassette cases

[0284] The non-magnetic layer forming composition prepared in (6) was coated onto the surface of a biaxially stretched polyethylene terephthalate support with a thickness of 4.1 μm after drying to a thickness of 0.7 μm, and then dried to form a non-magnetic layer. Next, the magnetic layer forming composition prepared in (6) was coated onto the non-magnetic layer with a thickness of 0.1 μm after drying to form a coating layer. Then, while the coating layer of the magnetic layer forming composition was still wet, a magnetic field with a magnetic field strength of 0.3 T was applied to the surface of the coating layer in the vertical direction for vertical orientation treatment, and then dried to form a magnetic layer. Then, the back coating forming composition prepared in (6) was coated onto the surface of the support opposite to the surface on which the non-magnetic layer and the magnetic layer were formed with a thickness of 0.3 μm after drying, and then dried to form a back coating layer.

[0285] Then, a surface smoothing treatment (calendering process) was performed using a calendering roll made of only metal rolls at a speed of 100 m / min, a linear pressure of 300 kg / cm, and a calendering temperature of 90°C (the surface temperature of the calendering roll).

[0286] Then, the raw magnetic tape, in strips, was heat-treated in a heat treatment furnace at an atmospheric temperature of 70°C (heat treatment time: 36 hours). After heat treatment, it was cut into 1 / 2-inch widths to obtain magnetic tape. Servo signals were recorded on the magnetic layer of the obtained magnetic tape using a commercially available servo writer, resulting in a magnetic tape with a data tape, servo tape, and guide tape configured according to the LTO (Linear Tape-Open) Ultrium format, and a servo pattern (timing-based servo pattern) with an LTO Ultrium format-based configuration and shape on the servo tape. The servo pattern thus formed is based on the servo pattern described in JIS (Japanese Industrial Standards) X6175:2006 and Standard ECMA-319 (June 2001). The total number of servo tapes is 5, and the total number of data tapes is 4.

[0287] The magnetic tape (970m in length) with the aforementioned servo pattern formed was wound onto a heat treatment core and heat-treated while wound on the core. A solid core-shaped component (outer diameter: 50mm) made of resin with a flexural modulus of 0.8 GPa was used as the heat treatment core, and the tension during winding was 0.6 N. The heat treatment was performed at a temperature of 50°C for 5 hours. The absolute humidity of the heat treatment atmosphere was 10 g / kg dry air.

[0288] After the aforementioned heat treatment, once the magnetic tape and heat treatment core have cooled sufficiently, the magnetic tape is removed from the heat treatment core and wound onto a temporary winding core. Then, a length of magnetic tape equivalent to the final product length (960m) is wound from the temporary winding core onto the reel of the cassette (LTO Ultrium 7 data cassette) (reel outer diameter: 44mm). The remaining 10m of magnetic tape is cut off, and a lead-in tape based on Section 3, Item 9 of Standard ECMA (European Computer Manufacturers Association)-319 (June 2001) is attached to the cut end using commercially available splicing tape. The temporary winding core is a solid core-shaped component made of the same material as the heat treatment core and having the same outer diameter, with a winding tension of 0.6N.

[0289] Thus, a single-reel type magnetic tape cassette of Example 1, with a length of 960m, was produced.

[0290] [Examples 2-11, Comparative Examples 1-7]

[0291] As shown in Table 1, various items were changed, but the magnetic tape cassette containing the magnetic tape was manufactured in the same manner as in Example 1.

[0292] Regarding the examples and comparative examples in Table 1 where "whether stearic acid and stearamide are present in the preparation of alumina dispersions and carbon black dispersions" is "yes", alumina dispersions and carbon black dispersions were prepared in the same manner as in Example 1.

[0293] Regarding the comparative examples listed as "none" in the above column, alumina dispersions and carbon black dispersions were prepared without mixing stearic acid and stearamide.

[0294] In Table 1, “SrFe1” in the “Strong Magnetic Powder” column refers to hexagonal strontium ferrite powder prepared as follows.

[0295] Weigh out 1707g of SrCO3, 687g of H3BO3, 1120g of Fe2O3, 45g of Al(OH)3, 24g of BaCO3, 13g of CaCO3 and 235g of Nd2O3, and mix them in a mixer to obtain a raw material mixture.

[0296] The obtained raw material mixture was melted in a platinum crucible at a melting temperature of 1390°C. While stirring the melt, the melt outlet located at the bottom of the platinum crucible was heated, and the melt was discharged into a rod shape at a rate of approximately 6 g / s. The discharged melt was then subjected to calendering and rapid cooling using water-cooled twin rollers to produce an amorphous body.

[0297] 280g of the prepared amorphous material was placed in an electric furnace and heated to 635℃ (crystallization temperature) at a heating rate of 3.5℃ / min. The temperature was then maintained at the same temperature for 5 hours to allow hexagonal strontium ferrite particles to precipitate (crystallize).

[0298] Next, the crystals obtained above, containing hexagonal strontium ferrite particles, were coarsely pulverized in a mortar. Then, 1000g of 1mm zirconium oxide beads and 800mL of 1% acetic acid aqueous solution were added to a glass bottle, and the mixture was dispersed using a paint stirrer for 3 hours. The resulting dispersion was then separated from the beads and placed in a stainless steel beaker. After dissolving the glass components by standing at 100°C for 3 hours, the dispersion was precipitated using a centrifuge and repeatedly washed by decantation. Finally, it was dried in a furnace at 110°C for 6 hours to obtain hexagonal strontium ferrite powder.

[0299] The hexagonal strontium ferrite powder obtained above has an average particle size of 18 nm and an activation volume of 902 nm. 3 The anisotropy constant Ku is 2.2 × 10⁻⁶. 5J / m 3 The mass magnetization σs is 49 A·m 2 / kg.

[0300] 12 mg of sample powder was collected from the hexagonal strontium ferrite powder obtained above. The elemental composition of the filtrate obtained by partially dissolving the sample powder under the above-described dissolution conditions was determined by an ICP analyzer.

[0301] In addition, 12 mg of sample powder was collected from the hexagonal strontium ferrite powder obtained above, and the elemental analysis of the filtrate obtained by completely dissolving the sample powder under the above-described dissolution conditions was performed using an ICP analysis device to determine the bulk content of neodymium atoms.

[0302] In the hexagonal strontium ferrite powder obtained above, the content of neodymium atoms relative to 100 atomic% of iron atoms (bulk content) is 2.9 atomic%. Furthermore, the surface portion of neodymium atoms contains 8.0 atomic%. The ratio of surface portion content to bulk content, "surface portion content / bulk content", is 2.8, confirming that neodymium atoms are predominantly located on the surface of the particles.

[0303] CuKα rays were scanned at a voltage of 45 kV and an intensity of 40 mA, and the X-ray diffraction pattern was measured under the following conditions (X-ray diffraction analysis), thereby confirming that the powder obtained above exhibits a hexagonal ferrite crystal structure. The powder obtained above exhibits a magnetoplumbide (M-type) hexagonal ferrite crystal structure. Furthermore, the crystal phase detected by X-ray diffraction analysis is a magnetoplumbide single phase.

[0304] PANalytical X'Pert Pro diffractometer, PIXcel detector

[0305] Soller slit for incident and diffracted beams: 0.017 radians

[0306] Fixed angle of the dispersing slit: 1 / 4 degree

[0307] Mask: 10mm

[0308] Scattering prevention slit: 1 / 4 degree

[0309] Measurement mode: Continuous

[0310] Measurement time for each stage: 3 seconds

[0311] Measurement speed: 0.017 degrees per second

[0312] Measurement step size: 0.05 degrees

[0313] In Table 1, “SrFe2” in the “Strong Magnetic Powder” column refers to hexagonal strontium ferrite powder prepared as follows.

[0314] Weigh out 1725g of SrCO3, 666g of H3BO3, 1332g of Fe2O3, 52g of Al(OH)3, 34g of CaCO3, and 141g of BaCO3, and mix them in a mixer to obtain a raw material mixture.

[0315] The obtained raw material mixture was melted in a platinum crucible at a melting temperature of 1380°C. While stirring the melt, the melt outlet located at the bottom of the platinum crucible was heated, and the melt was discharged into a rod shape at a rate of approximately 6 g / s. The discharged melt was then rapidly cooled by rolling using a water-cooled double roller to produce an amorphous body.

[0316] 280g of the obtained amorphous body was placed in an electric furnace and heated to 645℃ (crystallization temperature), and kept at the same temperature for 5 hours to allow hexagonal strontium ferrite particles to precipitate (crystallize).

[0317] Next, the crystals obtained above, containing hexagonal strontium ferrite particles, were coarsely pulverized in a mortar. Then, 1000g of 1mm zirconium oxide beads and 800mL of 1% acetic acid aqueous solution were added to a glass bottle, and the mixture was dispersed using a paint stirrer for 3 hours. The resulting dispersion was then separated from the beads and placed in a stainless steel beaker. After dissolving the glass components by standing at 100°C for 3 hours, the dispersion was precipitated using a centrifuge and repeatedly washed by decantation. Finally, it was dried in a furnace at 110°C for 6 hours to obtain hexagonal strontium ferrite powder.

[0318] The obtained hexagonal strontium ferrite powder has an average particle size of 19 nm and an activation volume of 1102 nm. 3 The anisotropy constant Ku is 2.0 × 10⁻⁶. 5 J / m 3 The mass magnetization σs is 50 A·m 2 / kg.

[0319] In Table 1, “ε-iron oxide” in the “Strong magnetic powder” column refers to ε-iron oxide powder prepared as follows.

[0320] A solution containing 8.3 g of ferric(III) nonahydrate, 1.3 g of gallium(III) octahydrate, 190 mg of cobalt(II) hexahydrate, 150 mg of titanium(IV) sulfate, and 1.5 g of polyvinylpyrrolidone (PVP) dissolved in 90 g of pure water was stirred using a magnetic stirrer. Simultaneously, 4.0 g of a 25% ammonia solution was added to the solution under atmospheric conditions and at 25°C. The mixture was stirred for 2 hours while maintaining the atmospheric temperature at 25°C. A citric acid solution containing 1 g of citric acid dissolved in 9 g of pure water was then added to the resulting solution, and the mixture was stirred for 1 hour. The precipitated powder was collected by centrifugation, washed with pure water, and dried in a furnace at 80°C.

[0321] 800g of pure water was added to the dried powder to redisperse it, yielding a dispersion. The dispersion was heated to 50°C, and 40g of a 25% ammonia solution was added dropwise while stirring. After stirring for 1 hour while maintaining the temperature at 50°C, 14mL of tetraethoxysilane (TEOS) was added, and stirring continued for 24 hours. 50g of ammonium sulfate was added to the resulting reaction solution. The precipitated powder was collected by centrifugation, washed with pure water, and dried in an oven at 80°C for 24 hours to obtain a precursor for the strongly magnetic powder.

[0322] The obtained strong magnetic powder precursor was placed in a heating furnace at a temperature of 1000℃ under atmospheric conditions and subjected to heat treatment for 4 hours.

[0323] The heat-treated strong magnetic powder precursor was added to a 4 mol / L sodium hydroxide (NaOH) aqueous solution, and the solution temperature was maintained at 70°C while stirring for 24 hours. This process removed silica compounds, which were impurities, from the heat-treated strong magnetic powder precursor.

[0324] Then, the strongly magnetic powder after removing the silica compounds was collected by centrifugation and washed with pure water to obtain the strongly magnetic powder.

[0325] The composition of the strongly magnetic powder, confirmed by high-frequency inductively coupled plasma-optical emission spectrometry (ICP-OES), was Ga, Co, and Ti-substituted ε-iron oxide (ε-Ga). 0.28 Co 0.05 Ti 0.05 Fe 1.62O3). Furthermore, under the same conditions as those described above for hexagonal strontium ferrite powder SrFe1, X-ray diffraction analysis was performed, and the peaks of the X-ray diffraction pattern confirmed that the obtained strongly magnetic powder has an ε-phase single-phase crystal structure (ε-iron oxide type crystal structure) that does not contain α-phase or γ-phase crystal structures.

[0326] The obtained ε-iron oxide powder has an average particle size of 12 nm and an activation volume of 746 nm. 3 The anisotropy constant Ku is 1.2 × 10⁻⁶. 5 J / m 3 The mass magnetization σs is 16 A·m 2 / kg.

[0327] The activation volume and anisotropy constant Ku of the hexagonal strontium ferrite powder and ε-iron oxide powder mentioned above were obtained by using a vibrating sample type fluxmeter (manufactured by TOEI INDUSTRY CO., LTD.) for each strongly magnetic powder using the above method.

[0328] Furthermore, the mass magnetization σs was measured using a vibrating sample type fluxmeter (manufactured by TOEI INDUSTRY CO., LTD.) at a magnetic field strength of 1194 kA / m (15 kOe).

[0329] For the embodiments and comparative examples, two magnetic tape cassettes were manufactured respectively. One cassette was used for the following physical property evaluation, and the other was used for the following electromagnetic conversion characteristic evaluation.

[0330] [Evaluation of the physical properties of magnetic tape]

[0331] <Fluoride concentration collected by wiping the surface of the magnetic layer with a nonwoven fabric>

[0332] use Figure 1 The reel tester with the structure shown was used as a nonwoven fabric, and a 4000CR manufactured by Japan Vilene Company, Ltd. was used to wipe the surface of the magnetic layer of the magnetic tape of the examples and comparative examples using the nonwoven fabric as described above.

[0333] Using the wiped nonwoven fabric, the components are extracted from the nonwoven fabric into n-hexane using the method described above, resulting in an extract.

[0334] As described above, the magnetic tapes of the examples and comparative examples contained butyl stearate as a fatty acid ester and a fluid lubricant; therefore, the butyl stearate in the obtained extract was quantified. Quantitative analysis was performed using GC / MS / MS via the MRM method. The analytical conditions are as follows.

[0335] (Analysis conditions)

[0336] Column type: HP-5MS UI (manufactured by Agilent Technologies, Inc.)

[0337] Tube length: 30m

[0338] Inner diameter of the tubing: 0.25mm

[0339] Injection volume: 1 μl (splitless)

[0340] Syringe temperature: 300℃

[0341] Detector temperature: 300℃

[0342] Column temperature: 40℃ (0 min.) → 40℃ (0.5 min.) → 280℃ (16.5 min.) → Stop (18 min.)

[0343] <0.1% of the cross-sectional area of ​​the protrusions on the surface of the magnetic layer>

[0344] As an AFM, a Veeco Nanoscope4 was used as the probe, and a BRUKER RTESP-300 was used. The 0.1% pitch of the protrusion cross-sectional area on the surface of the magnetic layer of each magnetic tape in the examples and comparative examples was determined using the method described above. The text file was opened as an Excel file created by Microsoft Corporation, and the 262nd (equivalent to 0.1%) largest value was read from 512 × 512 = 262,144 values ​​in the Excel file.

[0345] <Anisotropic magnetic field Hk>

[0346] For the magnetic tape samples cut from the magnetic tapes of the examples and comparative examples, a TM-VSM5050-SMS type (manufactured by TAMAKAWA CO.,LTD) was used as a vibration sample type fluxmeter, and the anisotropic magnetic field Hk was determined using the method described above. The anisotropic magnetic field Hk was 25 kOe in Example 9, 30 kOe in Example 11, and in the range of 10 to 20 kOe in other examples and comparative examples.

[0347] [Evaluation of electromagnetic conversion characteristics during repeated tape transport in a high-temperature environment]

[0348] The following evaluation was conducted in an environment with an ambient temperature of 60℃±1℃ and a relative humidity of 10%.

[0349] In the embodiments and comparative examples, magnetic tapes removed from the tape cartridges were installed onto a 1 / 2-inch reel tester equipped with a recording and playback head mounted on an IBM LTO8 tape drive. The relative speed between the head and the tape during recording and playback was set to 4 m / s, and data was recorded and reproduced.

[0350] Recording was performed at a line recording density of 300 kfci, and the reproduction output was measured during reproduction. The SNR (Signal-to-Noise Ratio) was then calculated as the signal-to-noise ratio (the ratio of reproduction output to noise). The unit kfci is the unit of line recording density (it cannot be converted to SI units).

[0351] The difference between the SNR recorded during the first pass and the SNR recorded during the 10,000th pass is calculated. Cases where the SNR at the 10,000th pass is more than 5.0 dB lower than the SNR at the first pass are classified as NG.

[0352] In Comparative Examples 6 and 7, the magnetic head would stick to the surface of the magnetic layer during repeated tape feeding, causing the tape feeding to stop. Therefore, the SNR at the 10,000th tape feeding (referred to as "sticking stop" in Table 1) could not be calculated. Therefore, Comparative Examples 6 and 7 were also judged as NG.

[0353] Other cases are judged as OK.

[0354] The results are shown in Table 1 (Table 1-1, Table 1-2).

[0355]

[0356]

[0357] The results shown in Table 1 confirm that the magnetic tape of the embodiment exhibits less degradation in electromagnetic conversion characteristics even after repeated tape runs in harsh high-temperature environments.

[0358] Industrial availability

[0359] One aspect of the present invention is useful in the field of magnetic tape for data storage.

Claims

1. A magnetic tape having a non-magnetic support and a magnetic layer containing strongly magnetic powder, The fluid lubricant dosage, collected by wiping the surface of the magnetic layer with a nonwoven fabric, ranges from 5 to 400 ng / m², calculated per unit area of ​​the magnetic layer surface. 2 Within the range, The fluid lubrication dosage is obtained according to the following method: In an environment with an ambient temperature of 23°C and a relative humidity of 50%, the magnetic tape is fed through a reel tester with two magnetic tape reels, bringing the surface of the magnetic layer into contact with the nonwoven fabric. The nonwoven fabric is then used for wiping. After wiping, the fluid lubricant is extracted from the nonwoven fabric, and the dosage of the fluid lubricant is determined through quantitative analysis. The tape transport conditions are set as follows: Magnetic tape transport speed: 2 m / s Tension applied along the length of the magnetic tape: 100gf Magnetic tape transport length: 200m Tape transport path: 1 single trip Wrap angle θ: 25° The nonwoven fabric meets the following conditions: Area weight: 40±5g / m² 2 Thickness: 0.27±0.05μm Width: 25mm Average fiber diameter: 10±5μm Raw materials: A mixture of rayon, polyester, and nylon.

2. The magnetic tape according to claim 1, wherein, The fluid lubricant dosage is 30–250 ng / m 2 Within the range.

3. The magnetic tape according to claim 1 or 2, wherein, The fluid lubricant dosage is 120–200 ng / m³. 2 Within the range.

4. The magnetic tape according to claim 1 or 2, wherein, The cross-sectional area of ​​the protrusions on the surface of the magnetic layer is 0.1%, and the spacing is in the range of 1.0 to 20.0 nm.

5. The magnetic tape according to claim 4, wherein, The cross-sectional area of ​​the protrusions is 0.1% and the spacing is in the range of 1.0 to 10.0 nm.

6. The magnetic tape according to claim 4, wherein, The cross-sectional area of ​​the protrusions is 0.1% and the spacing is in the range of 1.0 to 7.0 nm.

7. The magnetic tape according to claim 1 or 2, wherein, Between the non-magnetic support and the magnetic layer, there is also a non-magnetic layer containing non-magnetic powder.

8. The magnetic tape according to claim 1 or 2, wherein, The non-magnetic support also has a back coating containing non-magnetic powder on the side opposite to the side with the magnetic layer.

9. A magnetic tape cassette comprising the magnetic tape according to any one of claims 1 to 8.

10. A magnetic tape device comprising a magnetic tape and a magnetic head as described in any one of claims 1 to 8.

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