Magnetic tapes, cassettes and tape devices

Abstract

The present invention provides a magnetic tape, a magnetic tape cassette including the magnetic tape, and a magnetic tape device, wherein the magnetic tape includes one or more regions A and B having different centerline average surface roughness Ra measured on the surface of the magnetic layer in a region extending across a portion of the length of the magnetic tape, and when the amount of a component selected from the group consisting of fatty acids, fatty acid esters, and fatty acid amides extracted from the magnetic layer side of the regions A and B per unit area is respectively set to A. Mag 、B Mag When the ratio B Mag / A Mag is 1.20 or more and 10.00 or less, and when the amount of the component selected from the group consisting of fatty acids, fatty acid esters and fatty acid amides extracted from the back coating layer side of region B per unit area is defined as B Back When the ratio B Mag / B Back 2.0 or above.

Description

Technical Field

[0001] The present invention relates to a magnetic tape, a magnetic tape box and a magnetic tape device. Background Art

[0002] Magnetic recording media are available in tape and disk forms. For data storage applications such as data backup and archiving, tape-shaped magnetic recording media, ie, magnetic tapes, are mainly used (for example, see Patent Document 1).

[0003] Previous technical literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2002-367142 Summary of the Invention

[0006] Technical issues to be solved by the invention

[0007] The magnetic tape is required to exhibit excellent electromagnetic conversion characteristics.

[0008] Meanwhile, in recent years, magnetic tapes used for data storage have been used in temperature-controlled data centers. Furthermore, data centers are demanding power conservation to reduce costs. To achieve this, there is a desire to relax or even eliminate current data center temperature control requirements. However, if temperature control requirements are relaxed or eliminated, magnetic tapes are expected to be exposed to high temperatures.

[0009] Regarding the above points, the inventors' research has found that if the magnetic tape is repeatedly run in a high temperature environment (for example, a harsh high temperature environment above 60°C) to record data on the tape and / or reproduce data recorded on the tape, the electromagnetic conversion characteristics tend to deteriorate easily.

[0010] An object of one aspect of the present invention is to provide a magnetic tape that has minimal degradation of electromagnetic conversion characteristics even when the tape is repeatedly run in a high-temperature environment.

[0011] Means for solving technical problems

[0012] One embodiment of the present invention relates to a magnetic tape having a non-magnetic support and a magnetic layer containing ferromagnetic powder.

[0013] The non-magnetic support has a back coating layer containing non-magnetic powder on the surface side opposite to the surface side having the magnetic layer.

[0014] The magnetic tape includes one or more regions A in a region across a portion of the length of the magnetic tape and one or more regions B in a region across another portion of the length of the magnetic tape.

[0015] The region A is a region where the center line average surface roughness Ra measured on the surface of the magnetic layer is less than 2.5 nm.

[0016] The region B is a region where the center line average surface roughness Ra measured on the surface of the magnetic layer is 2.5 nm or more and 10.0 nm or less.

[0017] The amount of the component selected from the group consisting of fatty acids, fatty acid esters, and fatty acid amides extracted from the magnetic layer side of the region A and the region B per unit area is respectively represented by A. Mag 、B Mag When the ratio B Mag / A Mag is 1.20 or more and 10.00 or less, and

[0018] The amount of the component selected from the group consisting of fatty acids, fatty acid esters, and fatty acid amides extracted from the back coating layer side of the region B per unit area is defined as B. Back When the ratio B Mag / B Back 2.0 or above.

[0019] In one embodiment, the ratio B Mag / A Mag It may be 1.80 or more and 5.00 or less.

[0020] In one embodiment, the ratio B Mag / B Back It can be 7.0 or higher.

[0021] In one embodiment, the wear volume of the steel ball measured on the surface of the magnetic layer in the region B can be 1×10 -7 mm 3 Above and 1×10 -4 mm 3 the following.

[0022] In one embodiment, when the area of the region A is set to S A And the area of the above region B is set to S B When S B Relative to S A and S B The ratio of the sum of B / (S A +S B ))×100 may be 0.15% or more and 50.00% or less. Hereinafter, the above ratio is also referred to as “area ratio of region B”.

[0023] In one embodiment, the magnetic tape may include two or more areas B.

[0024] In one embodiment, the magnetic tape may further include a non-magnetic layer containing non-magnetic powder between the non-magnetic support and the magnetic layer.

[0025] In one embodiment, the magnetic tape may have a servo pattern on at least a portion of the magnetic layer.

[0026] In one embodiment, the magnetic tape may include the servo pattern on at least the magnetic layer in the region A.

[0027] In one embodiment, the magnetic tape may further include the servo pattern on the magnetic layer in the region B.

[0028] One aspect of the present invention relates to a magnetic tape cassette including the magnetic tape described above.

[0029] One aspect of the present invention relates to a magnetic tape device including the above-mentioned magnetic tape and a magnetic head.

[0030] In one embodiment, the area where the magnetic head records data may be included in at least the area A.

[0031] In one embodiment, the magnetic tape device may control the tape running conditions in the area B based on a measurement result regarding the recording and reproducing quality of data in the area A.

[0032] Effects of the Invention

[0033] According to one aspect of the present invention, it is possible to provide a magnetic tape having minimal degradation of electromagnetic conversion characteristics even when the tape is repeatedly run in a high-temperature environment, and a tape cassette and a tape device including the magnetic tape. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 An example of the arrangement of data bands and servo bands is shown.

[0035] Figure 2 An example of the servo pattern arrangement of an LTO (Linear Tape-Open) Ultrium format tape is shown.

[0036] Figure 3 An example of the arrangement of area A and area B on a magnetic tape is shown. DETAILED DESCRIPTION

[0037] [Tape]

[0038] One embodiment of the present invention relates to a magnetic tape having a non-magnetic support and a magnetic layer containing ferromagnetic powder, wherein a back coating layer containing non-magnetic powder is provided on the surface side of the non-magnetic support opposite to the surface side having the magnetic layer. The magnetic tape includes one or more regions A in a region spanning a portion in the longitudinal direction of the magnetic tape, and one or more regions B in a region spanning another portion. The region A is a region where the centerline average surface roughness Ra measured on the surface of the magnetic layer is less than 2.5 nm, and the region B is a region where the centerline average surface roughness Ra measured on the surface of the magnetic layer is greater than 2.5 nm and less than 10.0 nm. When the amount of components selected from the group consisting of fatty acids, fatty acid esters and fatty acid amides extracted from the magnetic layer side of the region A and the region B per unit area is respectively set to A Mag 、B Mag When the ratio B Mag / A Mag is 1.20 or more and 10.00 or less, and when the amount of the component selected from the group consisting of fatty acids, fatty acid esters and fatty acid amides extracted from the back coating layer side of the above-mentioned region B per unit area is set as B Back When the ratio B Mag / B Back It is 2.0 or more. In addition, "Mag" is the abbreviation of magnetic layer, and "Back" is the abbreviation of back coating layer.

[0039] In the present invention and this specification, the centerline average surface roughness Ra measured on the surface of the magnetic layer is the value measured using an atomic force microscope (AFM) on a randomly selected area of 40 μm × 40 μm on the surface of the magnetic layer. The centerline average surface roughness Ra measured on the surface of the non-magnetic support, described later, is also the value measured on the surface of the non-magnetic support.

[0040] As an example of the measurement conditions, the following measurement conditions can be given: The center line average surface roughness Ra shown in the examples described below is a value obtained by measurement under the following measurement conditions.

[0041] An AFM (Nanoscope 4 manufactured by Veeco) was used in tapping mode to measure a 40 μm × 40 μm area on the surface of the magnetic layer of the magnetic tape. A BRUKER RTESP-300 probe was used, with a resolution of 512 pixels × 512 pixels and a scanning speed that allowed one frame (512 pixels × 512 pixels) to be measured in 341 seconds.

[0042] Hereinafter, the centerline average surface roughness Ra measured on the magnetic layer surface of region A will also be referred to as "region A magnetic layer surface Ra," and the centerline average surface roughness Ra measured on the magnetic layer surface of region B will also be referred to as "region B magnetic layer surface Ra." When the magnetic tape includes two or more regions A, the magnetic layer surface Ra values of these regions A may be the same in one embodiment and different in another. This also applies to the magnetic layer surface Ra value of region B. In the present invention and this specification, the "magnetic layer surface" of the magnetic tape has the same meaning as the side surface of the magnetic layer of the magnetic tape.

[0043] In the present invention and this specification, the amount A per unit area of the component selected from the group consisting of fatty acids, fatty acid esters, and fatty acid amides extracted from the magnetic layer side of the region A is Mag It is a value obtained by the following method: Hereinafter, a component selected from the group consisting of fatty acids, fatty acid esters, and fatty acid amides is also referred to as a "lubricant," and the amount of the component extracted per unit area is also referred to as a "lubricant extraction amount."

[0044] Cut a 5 cm long tape sample from any position in the longitudinal direction of region A. Remove the back coating by a known method before or after cutting. Immerse the tape sample after removing the back coating in 30 ml of methanol at a liquid temperature of 60°C for 3 hours. After partially or completely evaporating the methanol as needed, perform qualitative and quantitative analysis on the components extracted from the tape sample into the methanol by gas chromatography. Based on the analysis results thus obtained, calculate the amount of components selected from the group consisting of fatty acids, fatty acid esters and fatty acid amides extracted from the tape sample. Calculate the amount of extraction per unit area A by dividing the calculated extraction amount by the area of one side of the tape sample. Mag The area of one side of the tape sample is the value calculated by "the length of the tape sample x the width". The tape width of the tape is specified in the standard of the tape device (usually called a "drive") that uses the tape. For example, the tape width specified in the standard is 1 / 2 inch, and 1 / 2 inch = 0.0127m. As the width of the tape sample, the tape width specified in the standard for the tape used to cut the tape sample can be used.

[0045] Region A is an area where the centerline average surface roughness Ra measured on the surface of the magnetic layer is less than 2.5 nm. If the number of regions A included in the magnetic tape to be measured is one, tape samples are cut from two locations different from the region A. The extraction amount A per unit area calculated by the above method for these two tape samples is calculated as follows: Mag The arithmetic mean of the area A of the tape to be measured is MagWhen the number of areas A included in the tape to be measured is two or more, for each area A, a tape sample is cut from two locations different from the area A, and the extraction amount A per unit area is calculated for these two tape samples using the above method. Mag Therefore, two calculated values can be obtained for one area A. The arithmetic average of the calculated values obtained for all areas A is taken as the A of the area A of the tape to be measured. Mag .

[0046] However, if a magnetic tape from which a tape piece forming the area A is cut (hereinafter referred to as "area A tape") is available, the values obtained using the tape sample cut from the area A tape can be used as the various physical property values (A) of the magnetic tape related to the area A to be measured. Mag , the magnetic layer surface Ra of region A, etc.). Furthermore, when a plurality of tape pieces cut from the same region A tape are used to produce a magnetic tape including a plurality of regions A, as long as the region A tape can be obtained, the values obtained using the tape samples cut from the region A tape can be used as the various physical property values (A values) related to region A of the thus produced magnetic tape. Mag , the magnetic layer surface Ra of region A, the anisotropic magnetic field Hk, etc.), and the values thus obtained can be used as various physical property values for each of the plurality of regions A. In this case, various physical property values can be obtained in the same manner as when the number of regions A included in the magnetic tape is one. That is, for example, Mag Two tape samples can be cut from area A using a tape, and the extraction amount A per unit area obtained by the above method for these two tape samples is calculated. Mag The arithmetic mean of the area A of the tape to be measured is Mag .

[0047] In the present invention and this specification, the amount of the component selected from the group consisting of fatty acids, fatty acid esters and fatty acid amides extracted from the magnetic layer side of the region B per unit area is B. Mag is the value obtained by the following method.

[0048] A 5 cm long tape sample is cut from any position in the longitudinal direction of region B. The tape sample is cut into pieces by the method for determining the extraction amount A. Mag The extraction amount per unit area was calculated by the same method as that of Mag .

[0049] Region B is an area where the centerline average surface roughness Ra measured on the surface of the magnetic layer is greater than or equal to 2.5 nm and less than or equal to 10.0 nm. When the number of regions B included in the magnetic tape to be measured is one, the magnetic tape samples are cut from two locations different from the region B, and the extraction amount B per unit area calculated by the above method for these two magnetic tape samples is calculated. Mag The arithmetic mean of the area B of the tape to be measured is Mag When the number of regions B included in the tape to be measured is two or more, for each region B, a tape sample is cut from two locations different from the region B, and the extraction amount B per unit area is calculated for these two tape samples using the above method. Mag Therefore, two calculated values can be obtained for one area B. The arithmetic average of the calculated values obtained for all areas B is taken as the B of the area B of the magnetic tape to be measured. Mag .

[0050] However, if a magnetic tape for cutting out a tape piece forming area B (hereinafter referred to as "area B tape") is available, the values obtained using the tape sample cut out from the area B tape can be used as the various physical property values (B) of the magnetic tape related to area B to be measured. Mag 、B Back , the magnetic layer surface Ra of region B, the steel ball wear volume measured on the magnetic layer surface of region B, the anisotropic magnetic field Hk, etc.). Furthermore, when a plurality of tape pieces cut from the same region B tape are used to produce a magnetic tape including a plurality of regions B, as long as the region B tape can be obtained, the values obtained using the tape samples cut from the region B tape can be used as the various physical property values related to region B of the thus produced magnetic tape (B Mag 、B Back , the magnetic layer surface Ra of region B, the steel ball wear volume measured on the magnetic layer surface of region B, the anisotropic magnetic field Hk, etc.), and the values thus obtained are used as the various physical property values of each of the plurality of regions A. In this case, the various physical property values can be obtained in the same manner as when the number of regions B included in the magnetic tape is one. That is, for example, Mag Two tape samples can be cut from area B using a tape, and the extraction amount per unit area B obtained by the above method for these two tape samples is calculated. Mag The arithmetic mean of the area B of the tape to be measured is Mag .

[0051] In the present invention and this specification, the amount of the component selected from the group consisting of fatty acids, fatty acid esters and fatty acid amides extracted from the back coating layer side of the region B per unit area is B. back is the value obtained by the following method.

[0052] From any position in the longitudinal direction of region B (however, it is not necessary to cut out the Mag A tape sample of 5 cm in length was cut from a different position of the tape sample. For this tape sample, except that the back coating layer was not removed, the same method as that used to determine the extraction amount A was used. Mag The extraction amount per unit area is determined by measuring and calculating in the same way as in the method of Total .

[0053] When the number of regions B included in the tape to be measured is one, tape samples are cut from two locations different from the region B, and the extraction amount B per unit area obtained by the above method for the two tape samples is calculated. Total The arithmetic mean of the area B of the tape to be measured is Total When the number of regions B included in the tape to be measured is two or more, for each region B, a tape sample is cut from two locations different from the region B, and the extraction amount B per unit area is calculated for these two tape samples using the above method. Total Therefore, two calculated values can be obtained for one area B. The arithmetic average of the calculated values obtained for all areas B is taken as the B of the area B of the magnetic tape to be measured. Total .

[0054] B of the tape to be measured Back is the B obtained based on the tape to be measured. Total and B obtained for the tape to be measured as described above Mag By "B Total -B Mag ” calculated value.

[0055] The magnetic tape includes region A and region B. The inventors believe that this can contribute to suppressing degradation of electromagnetic conversion characteristics even when the magnetic tape is repeatedly run in a high-temperature environment. This point will be further described below.

[0056] Data recording on a magnetic tape and reproduction of the recorded data are usually performed by bringing the surface of the magnetic layer into contact with and sliding the magnetic head. It is believed that during this sliding, the component selected from the group consisting of fatty acids, fatty acid esters, and fatty acid amides functions as a lubricant, thereby helping to suppress stick-slip between the magnetic head and the surface of the magnetic layer. However, it is believed that in a high-temperature environment, especially in a harsh high-temperature environment of 60°C or above, the lubricant on the surface of the magnetic layer will be exhausted due to sliding relative to the magnetic head and / or exposure to a high-temperature environment, resulting in stick-slip between the magnetic head and the surface of the magnetic layer. It is speculated that the spacing variation caused by this stick-slip is the cause of the degradation of the electromagnetic conversion characteristics during repeated tape movement in a high-temperature environment. For example, the inventors believe that the difficulty in recording deep into the magnetic layer due to the spacing variation is the main cause of the above-mentioned degradation of the electromagnetic conversion characteristics.

[0057] However, it is believed that if the amount of lubricant in the magnetic layer is increased over the entire magnetic tape, rather than locally providing an area containing a large amount of lubricant as in the above-mentioned tape, the durability will be deteriorated due to plasticization of the magnetic layer and / or the surface shape of the back coating layer will be easily transferred to the surface of the magnetic layer, resulting in deterioration of the electromagnetic conversion characteristics.

[0058] In contrast, the magnetic tape has, in addition to region A, region B containing a larger amount of lubricant than region A. The inventors speculate that this allows lubricant to be supplied to the magnetic head by sliding against the surface of the magnetic layer in region B, thereby suppressing degradation of electromagnetic conversion characteristics during repeated tape travel in a high-temperature environment.

[0059] However, the above includes speculations by the inventors, and the present invention is not limited to the speculations described in this specification.

[0060] The following is a more detailed description of the above-mentioned magnetic tape.

[0061] <Ratio B Mag / A Mag >

[0062] In the above tape, the ratio B Mag / A Mag It is estimated that in the above magnetic tape, by making the ratio B Mag / A Mag When the ratio B is 1.20 or more, when the surface of the magnetic layer slides relative to the magnetic head, lubricant can be properly supplied to the magnetic head from the area B containing a large amount of lubricant. As a result, the lubricant is not easily exhausted even in a severe high-temperature environment. It is believed that this helps to suppress the degradation of electromagnetic conversion characteristics when the tape is repeatedly moved in a high-temperature environment. Based on the above viewpoint, the ratio B Mag / A Mag It is 1.20 or more, preferably 1.40 or more, more preferably 1.60 or more, and further preferably 1.80 or more.

[0063] On the other hand, it is presumed that in the above-mentioned magnetic tape, by making the ratio B Mag / A Mag When the ratio B is less than 10.00, the formation of a meniscus of lubricant between the lubricant and the magnetic head can be suppressed. This is believed to help suppress the occurrence of stick-slip and / or magnetic head adhesion. Mag / A Mag It is 10.00 or less, preferably 9.00 or less, more preferably 8.00 or less, further preferably 7.00 or less, further preferably 6.00 or less, further preferably 5.00 or less.

[0064] <Ratio B Mag / B Back >

[0065] In the above tape, in region B, the ratio B Mag / B Back It is 2.0 or more, preferably 3.0 or more, more preferably 4.0 or more, further preferably 5.0 or more, further preferably 6.0 or more, further preferably 7.0 or more.

[0066] The present inventors speculate that, as described below, in region B, the ratio B Mag / B Back Being within the above range can help suppress the degradation of electromagnetic conversion characteristics during repeated tape travel in a high-temperature environment.

[0067] When the magnetic tape is wound on the reel, the surface of the magnetic layer contacts the surface of the back coating. The component (lubricant) selected from the group consisting of fatty acids, fatty acid esters, and fatty acid amides is generally a low molecular weight component, so it is possible that the lubricant will move between the magnetic layer and the back coating when the magnetic layer and the back coating are in contact. However, it is speculated that the ratio B Mag / B Back In region B where the ratio is 2.0 or greater, the movement of the lubricant from the magnetic layer side to the back coating side can be suppressed or the amount of movement can be reduced. It is believed that this can make the lubricant on the magnetic layer side of region B more abundant, and as a result, the ability to supply lubricant from the magnetic layer side of region B to the magnetic head can be improved, making it possible to suppress the degradation of electromagnetic conversion characteristics during repeated tape travel in a high-temperature environment.

[0068] Ratio B Mag / B Back For example, it may be 40.0 or less, 35.0 or less, 30.0 or less, or 25.0 or less, or may exceed the values exemplified here. As described above, from the perspective of suppressing the degradation of electromagnetic conversion characteristics when the tape is repeatedly moved under a high temperature environment, the ratio B is preferably Mag / B Back The value of is larger.

[0069] <Area Ratio of Region B>

[0070] In the above tape, when the area of region A is set to S A And let the area of region B be S B When S B Relative to S A With S B The ratio of the sum of (area ratio of region B) is given by “(S B / (S A +S B ))×100”. In the case where the above magnetic tape includes more than two areas A, the area S of area A A The area S of the region B is the sum of the areas of the two or more regions A. B The area ratio of region B is preferably 0.10% or more, more preferably 0.15% or more. Furthermore, the area ratio of region B is preferably 60.00% or less, more preferably 55.00% or less, and even more preferably 50.00% or less. From the perspective of supplying an appropriate amount of lubricant to the magnetic head during sliding, the area ratio of region B is preferably within the above range.

[0071] The following further describes area A and area B.

[0072] <Area A>

[0073] Region A is a region where the center line average surface roughness Ra measured on the surface of the magnetic layer is less than 2.5 nm. In the above magnetic tape, the A calculated for region A by the above method is Mag Satisfy ratio B of 1.20 or more and 10.00 or less Mag / A Mag In the above magnetic tape, region A may be a region where the centerline average surface roughness Ra measured on the magnetic layer surface is smaller than that of region B (i.e., the magnetic layer surface has high smoothness), and where the amount of lubricant extracted from the magnetic layer side is smaller than that of region B.

[0074] The centerline average surface roughness Ra (magnetic layer surface Ra) measured on the magnetic layer surface in region A is less than 2.5 nm. As described later, region A can serve as a data recording area. Therefore, from the perspective of improving electromagnetic conversion characteristics, the magnetic layer surface in region A preferably has a high smoothness. From this perspective, the magnetic layer surface Ra in region A is preferably 2.4 nm or less, more preferably 2.3 nm or less, even more preferably 2.2 nm or less, even more preferably 2.1 nm or less, and even more preferably 2.0 nm or less. The magnetic layer surface Ra in region A can be, for example, 1.2 nm or more, 1.3 nm or more, or 1.4 nm or more, or can be smaller than the values exemplified here.

[0075] The surface Ra of the magnetic layer in region A can be controlled by known methods. For example, the surface Ra of the magnetic layer in region A can be controlled based on the surface shape of the surface of the non-magnetic support on the side where the magnetic layer is provided (for example, the centerline average surface roughness Ra), the particle size of the powder used as a component of the magnetic layer in region A, and the like. This also applies to the surface Ra of the magnetic layer in region B.

[0076] As long as the ratio B Mag / A Mag Within the above range, the A obtained by the above method for the above tape is Mag In one embodiment, the A Mag Can be 20.0mg / m 2 Above or 25.0 mg / m 2 Above, and can be 40.0mg / m 2 Below or 35.0 mg / m 2 Furthermore, when the number of regions A included in the magnetic tape is two or more, in one embodiment, for a portion of the regions A, and in another embodiment, for all the regions A, A is obtained as the arithmetic mean of the values obtained by the above method for two magnetic tape samples cut from each region A. Mag It can be within the above range.

[0077] The magnetic tape may include one or more areas A, or may include two or more areas A. The number of areas A included in the magnetic tape may be, for example, 5 or less, 4 or less, or 3 or less, or the magnetic tape may include a number of areas A exceeding the number exemplified here. The total length of the areas A (the sum of their lengths when multiple areas A are included) may be, for example, in the range of 100 to 10,000 m, or in the range of 100 to 1,800 m. Furthermore, the length of one area A may be, for example, in the range of 10 to 1,500 m. When the magnetic tape includes multiple areas A, the layer structures, the composition of each layer, the thickness, etc. of these multiple areas A may be the same in one embodiment, and different in another embodiment.

[0078] <Area B>

[0079] The center line average surface roughness Ra of region B measured on the surface of the magnetic layer is 2.5 nm or more and 10.0 nm or less. In the above magnetic tape, the center line average surface roughness Ra of region B obtained by the above method for region A is 2.5 nm or more and 10.0 nm or less. Mag Satisfy ratio B of 1.20 or more and 10.00 or less Mag / A Mag In the above magnetic tape, region B may be a region where the centerline average surface roughness Ra measured on the magnetic layer surface is greater than that of region A (i.e., the magnetic layer surface smoothness is low), and where the amount of lubricant extracted from the magnetic layer side is greater than that of region A.

[0080] The centerline average surface roughness Ra (magnetic layer surface Ra) measured on the surface of the magnetic layer in region B is greater than or equal to 2.5 nm and less than or equal to 10.0 nm. The present inventors speculate that the magnetic layer surface Ra of region B within the above range can help supply an appropriate amount of lubricant from region B to the magnetic head. Based on the above viewpoint, the magnetic layer surface Ra of region B is preferably greater than or equal to 2.6 nm, more preferably greater than or equal to 2.8 nm, and even more preferably greater than or equal to 3.0 nm. Furthermore, based on the above viewpoint, the magnetic layer surface Ra of region B is preferably less than or equal to 9.0 nm, more preferably less than or equal to 8.5 nm, even more preferably less than or equal to 8.0 nm, even more preferably less than or equal to 7.5 nm, even more preferably less than or equal to 7.0 nm, even more preferably less than or equal to 6.5 nm, and even more preferably less than or equal to 6.0 nm.

[0081] As long as the ratio B Mag / A Mag Within the above range, the B obtained by the above method for the above tape is Mag In one embodiment, the B Mag Can be 20.0mg / m 2 Above 25.0 mg / m 2 Above or 30.0 mg / m2 Above, and can be 400.0mg / m 2 Below 350.0 mg / m 2 Below or 300.0 mg / m 2 Furthermore, when the number of regions B included in the magnetic tape is two or more, in one embodiment, for a portion of the regions B, and in another embodiment, for all the regions B, the B value obtained as the arithmetic average of the values obtained by the above method for two magnetic tape samples cut from each region B is Mag It can be within the above range.

[0082] As long as the ratio B Mag / B Back Within the above range, the B obtained by the above method for the above tape is Back In one embodiment, the B Back Can be 1.0mg / m 2 Above 2.0 mg / m 2 Above or 3.0 mg / m 2 Above, and can be 50.0mg / m 2 Below 45.0 mg / m 2 Below or 40.0 mg / m 2 Furthermore, when the number of regions B included in the magnetic tape is two or more, in one embodiment, for a part of the regions B, and in another embodiment, for all the regions B, as a function of B Total (calculated as the arithmetic mean of the values obtained by the above method for two tape samples cut out from each area B) and B Mag (Calculated as the arithmetic mean of the values obtained by the above method for two tape samples cut out from each area B) Total -B Mag The calculated value of B Back It can be within the above range.

[0083] The magnetic tape includes one or more regions B. From the perspective of increasing the frequency of supplying lubricant from the regions B to the magnetic head, it is preferable to include two or more regions B. The number of regions B included in the magnetic tape may be, for example, 5 or less, 4 or less, or 3 or less, or the magnetic tape may include a number of regions B exceeding the number exemplified here. The total length of the regions B (the sum of their lengths when multiple regions B are included) may be, for example, in the range of 1 to 5,000 m, or in the range of 1 to 900 m. Furthermore, the length of one region B may be, for example, in the range of 1 to 200 m. When the magnetic tape includes multiple regions B, the layer structures, the composition of each layer, the thickness, etc. of these multiple regions B may be the same in one embodiment and different in another embodiment.

[0084] In one embodiment, in the above magnetic tape, the wear volume of the steel ball measured on the surface of the magnetic layer in region B may be, for example, 1×10 -8 mm 3 Above and 1×10 -3 mm 3 Below, preferably 1×10 -7 mm 3 Above and 1×10 -4 mm 3 The wear volume of the steel ball is estimated to be 1×10 -7 mm 3 The above is preferable in terms of supplying an appropriate amount of lubricant to the magnetic head from the surface of the magnetic layer in region B. It is estimated that the wear volume of the steel ball is 1×10 -4 mm 3 The following is preferable in terms of supplying lubricant to the magnetic head at an appropriate supply speed. Based on the above viewpoint, the wear volume of the steel ball measured on the surface of the magnetic layer in region B is preferably 1×10 -7 mm 3 More than 8×10 -7 mm 3 More than 3×10 -6 mm 3 Furthermore, based on the above viewpoint, the wear volume of the steel ball measured on the surface of the magnetic layer in region B is preferably 1×10 -4 mm 3 Below, more preferably 5×10 -5 mm 3 Below, more preferably 1×10 -5 mm 3 The steel ball wear volume can be controlled by, for example, the type and size of the non-magnetic powder contained in the magnetic layer as an abrasive, the content in the magnetic layer, and the like.

[0085] The above-mentioned steel ball wear volume is a value obtained by the following method.

[0086] A 4 cm long magnetic tape sample was cut from an arbitrary location in area B. Adhesive tape was applied to two opposing sides of the tape sample, and the tape sample was then secured to a glass slide for optical microscopy. Under an ambient temperature of 23°C and a relative humidity of 50%, a 6.25 mm diameter steel ball was slid on the surface of the magnetic layer while applying a load of 10 g. Steel balls conforming to JIS B 1501:2009, "Rolling Bearings - Steel Balls," were used. The following procedure was performed at 20 locations on the magnetic layer surface: after sliding once for a distance of 25 mm at a speed of 20 mm / s, the steel ball was moved to another location on the magnetic layer surface where it had not slid and slid similarly. Each sliding operation was performed with the same location on the steel ball in contact with the magnetic layer surface. The locations where the steel ball slid in contact with the magnetic layer surface were then observed using an optical microscope at 40x magnification. The area of the surface exposed by grinding due to sliding was determined, and the equivalent circular diameter was calculated based on this area. The volume of the ball calculated from the circle-equivalent diameter as the diameter of the ball is defined as the wear volume of the steel ball.

[0087] When the number of regions B included in the magnetic tape to be measured is one, the steel ball wear volume determined by the above method in that region B is used as the steel ball wear volume measured on the magnetic layer surface of region B in the magnetic tape to be measured. When the number of regions B included in the magnetic tape to be measured is two or more, the steel ball wear volume is determined by the above method in each region B, and the arithmetic average of the steel ball wear volumes determined for all regions B is used as the steel ball wear volume measured on the magnetic layer surface of region B in the magnetic tape to be measured. When the number of regions B included in the magnetic tape is two or more, the steel ball wear volume determined by the above method for some regions B in one embodiment and for all regions B in another embodiment can be within the above range.

[0088] Region A and Region B can be continuous regions along the length of the tape. Here, "continuous regions" means that no other regions exist between these regions. For example, if the tape is wound up by a cassette reel and contained in a tape cassette, the side closer to the cassette reel is called the inner side, and the side farther from the cassette reel is called the outer side. Then, from the outer end toward the inner end, the continuous form of "region B / region A / region B / region A / region B," "region B / region A / region B," "region A / region B / region A," "region A / region B," "region B / region A," or "region B / region A" can be used. Preferably, at least one of the two ends of the tape is the end of Region B, and more preferably, both ends are the ends of Region B.

[0089] In one embodiment, the magnetic tape including region A and region B can be manufactured by joining a magnetic tape forming region A and a magnetic tape forming region B. The joining can be performed using a known method such as splicing tape. In another embodiment, a magnetic tape including region A and region B can be manufactured by providing multiple regions on a non-magnetic support by varying the composition and / or manufacturing conditions.

[0090] The magnetic layer of the magnetic tape will be described in more detail below. Unless otherwise specified, the following description applies to both area A and area B.

[0091] <Magnetic Layer>

[0092] (Strong magnetic powder)

[0093] As the ferromagnetic powder contained in the magnetic layer, one or more ferromagnetic powders known as ferromagnetic powders used in the magnetic layers of various magnetic recording media can be used. From the viewpoint of improving the recording density, it is preferred to use a ferromagnetic powder having a smaller average particle size as the ferromagnetic powder. From this point of view, the average particle size of the ferromagnetic powder is preferably 50 nm or less, more preferably 45 nm or less, further preferably 40 nm or less, further preferably 35 nm or less, further preferably 30 nm or less, further preferably 25 nm or less, further preferably 20 nm or less. On the other hand, from the viewpoint of magnetization stability, the average particle size of the ferromagnetic powder is preferably 5 nm or more, more preferably 8 nm or more, further preferably 10 nm or more, further preferably 15 nm or more, further preferably 20 nm or more.

[0094] Hexagonal ferrite powder

[0095] A preferred specific example of ferromagnetic powder is hexagonal ferrite powder. For details of hexagonal ferrite powder, see, for example, paragraphs 0012 to 0030 of Japanese Patent Application Laid-Open No. 2011-225417, paragraphs 0134 to 0136 of Japanese Patent Application Laid-Open No. 2011-216149, paragraphs 0013 to 0030 of Japanese Patent Application Laid-Open No. 2012-204726, and paragraphs 0029 to 0084 of Japanese Patent Application Laid-Open No. 2015-127985.

[0096] In the present invention and this specification, "hexagonal ferrite powder" refers to a ferromagnetic powder in which a hexagonal ferrite type crystal structure is detected as the main phase by X-ray diffraction analysis. The main phase refers to the structure to which the diffraction peak with the highest intensity in the X-ray diffraction spectrum obtained by X-ray diffraction analysis belongs. For example, when the diffraction peak with the highest intensity in the X-ray diffraction spectrum obtained by X-ray diffraction analysis belongs to the hexagonal ferrite type crystal structure, it is determined that the hexagonal ferrite type crystal structure is detected as the main phase. When only a single structure is detected by X-ray diffraction analysis, the detected structure is regarded as the main phase. As constituent atoms, the hexagonal ferrite type 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, and examples include alkaline earth metal atoms such as strontium atoms, barium atoms, and calcium atoms, and lead atoms. In the present invention and this specification, hexagonal strontium ferrite powder refers to hexagonal ferrite in which the primary divalent metal atoms contained in the powder are strontium atoms, and hexagonal barium ferrite powder refers to hexagonal ferrite in which the primary divalent metal atoms contained in the powder are barium atoms. The primary divalent metal atoms refer to the divalent metal atoms that constitute the largest proportion of the divalent metal atoms contained in the powder, based on atomic percentage. However, these divalent metal atoms do not include rare earth atoms. "Rare earth atoms" in the present invention and this specification are selected from the group consisting of scandium atoms (Sc), yttrium atoms (Y), and lanthanide atoms. The lanthanide atom is selected from the group consisting of lanthanum atom (La), cerium atom (Ce), praseodymium atom (Pr), neodymium atom (Nd), promethium atom (Pm), samarium atom (Sm), europium atom (Eu), gadolinium atom (Gd), terbium atom (Tb), dysprosium atom (Dy), holmium atom (Ho), erbium atom (Er), thulium atom (Tm), ytterbium atom (Yb) and lutetium atom (Lu).

[0097] Hereinafter, hexagonal strontium ferrite powder, which is one embodiment of the hexagonal ferrite powder, will be described in more detail.

[0098] The activation volume of hexagonal strontium ferrite powder is preferably between 800 and 1600 nm. 3 The micronized hexagonal strontium ferrite powder having an activation volume within the above range is suitable for the production of magnetic tapes that exhibit excellent electromagnetic conversion characteristics. The activation volume of the hexagonal strontium ferrite powder is preferably 800 nm. 3 Above, for example, it can also be 850nm 3 Furthermore, from the perspective of further improving electromagnetic conversion characteristics, the activation volume of the hexagonal strontium ferrite powder is more preferably 1500 nm. 3 Below, more preferably 1400nm 3 Below, more preferably 1300nm 3 Below, more preferably 1200nm3 Below, more preferably 1100nm 3 The activation volume of the hexagonal barium ferrite powder is also the same.

[0099] "Activation volume" is a unit of magnetization reversal and is an indicator of the magnetic strength of a particle. The activation volume and the anisotropy constant Ku described in the present invention and this specification are values obtained using a vibrating sample fluxmeter at a magnetic field sweep rate of 3 minutes and 30 minutes in the coercive force Hc measurement unit (measurement temperature: 23°C ± 1°C) and are calculated using the following relationship between Hc and activation volume V. The unit of the anisotropy constant Ku is 1 erg / cc = 1.0 × 10 -1 J / m 3 .

[0100] Hc=2Ku / Ms{1-[(kT / KuV)ln(At / 0.693)] 1 / 2}

[0101] [In the above formula, Ku: anisotropy constant (unit: J / m 3 ), Ms: saturation magnetization (unit: kA / m), k: Boltzmann constant, T: absolute temperature (unit: K), V: activation volume (unit: cm 3 ), A: Spin precession frequency (unit: s -1 ), t: magnetic field reversal time (unit: s)]

[0102] As an index for reducing thermal fluctuation (in other words, improving thermal stability), the anisotropy constant Ku can be cited. The hexagonal strontium ferrite powder preferably has a value of 1.8×10 5 J / m 3 More preferably, Ku can be 2.0×10 5 J / m 3 Furthermore, the Ku of the hexagonal strontium ferrite powder can be, for example, 2.5×10 5 J / m 3 However, a higher Ku indicates higher thermal stability, which is more preferable, and therefore it is not limited to the values exemplified above.

[0103] Hexagonal strontium ferrite powder may or may not contain rare earth atoms. When the hexagonal strontium ferrite powder contains rare earth atoms, the rare earth atoms are preferably present at a content (bulk content) of 0.5 to 5.0 atomic percent relative to 100 atomic percent of iron atoms. In one embodiment, the hexagonal strontium ferrite powder containing rare earth atoms may have surface localization of the rare earth atoms. The term "surface localization of rare earth atoms" as used in the present invention and this specification means that the rare earth atom content relative to 100 atomic % of iron atoms in a solution obtained by partially dissolving hexagonal strontium ferrite powder using an acid (hereinafter referred to as the "surface content of rare earth atoms" or simply the "surface content" for rare earth atoms) and the rare earth atom content relative to 100 atomic % of iron atoms in a solution obtained by completely dissolving hexagonal strontium ferrite powder using an acid (hereinafter referred to as the "bulk content of rare earth atoms" or simply the "bulk content" for rare earth atoms) satisfy the following ratio:

[0104] Rare earth atom surface content / rare earth atom bulk content>1.0.

[0105] The rare earth atom content of the hexagonal strontium ferrite powder described later has the same meaning as the rare earth atom bulk content. In contrast, since the partial dissolution using acid dissolves the surface portion of the particles constituting the hexagonal strontium ferrite powder, the rare earth atom content in the solution obtained by partial dissolution refers to the rare earth atom content in the surface portion of the particles constituting the hexagonal strontium ferrite powder. The rare earth atom surface portion content ratio that satisfies "rare earth atom surface portion content / rare earth atom bulk content>1.0" indicates that the rare earth atoms in the particles constituting the hexagonal strontium ferrite powder are concentrated in the surface portion (i.e., the amount present is greater than the interior). The surface portion in the present invention and this specification refers to a portion of the area from the surface of the particles constituting the hexagonal strontium ferrite powder toward the interior.

[0106] In the case where the hexagonal strontium ferrite powder contains rare earth atoms, the rare earth atom content (bulk content) is preferably in the range of 0.5 to 5.0 atomic % relative to 100 atomic % of iron atoms. It is believed that the presence of rare earth atoms in the bulk content within the above range and the presence of rare earth atoms in the surface portion of the particles constituting the hexagonal strontium ferrite powder contributes to suppressing the decrease in the reproduction output during repeated reproduction. It is speculated that this is because the anisotropy constant Ku can be increased by the presence of rare earth atoms in the bulk content within the above range in the hexagonal strontium ferrite powder and the presence of rare earth atoms in the surface portion of the particles constituting the hexagonal strontium ferrite powder. The higher the value of the anisotropy constant Ku, the more it can suppress the occurrence of the so-called thermal fluctuation phenomenon (in other words, the more it can improve thermal stability). By suppressing the occurrence of thermal fluctuation, the decrease in the reproduction output during repeated reproduction can be suppressed. It is speculated that the concentration of rare earth atoms in the surface layer of the hexagonal strontium ferrite powder particles contributes to stabilizing the spin of iron (Fe) sites in the crystal lattice of the surface layer, thereby improving the anisotropy constant Ku.

[0107] Furthermore, it is speculated that using hexagonal strontium ferrite powder with surface localization of rare earth atoms as the ferromagnetic powder for the magnetic layer can also help prevent the surface of the magnetic layer from being worn away by the sliding motion of the magnetic head. In other words, it is speculated that hexagonal strontium ferrite powder with surface localization of rare earth atoms can also help improve the running durability of the magnetic tape. This is presumably because the localization of rare earth atoms on the surface of the particles constituting the hexagonal strontium ferrite powder enhances the interaction between the particle surface and the organic substances (e.g., binder and / or additives) contained in the magnetic layer, thereby improving the strength of the magnetic layer.

[0108] From the perspective of further suppressing the decrease in reproduction output during repeated reproduction and / or further improving the durability of the tape run, the rare earth atom content (bulk content) is more preferably in the range of 0.5 to 4.5 atomic %, further preferably in the range of 1.0 to 4.5 atomic %, and further preferably in the range of 1.5 to 4.5 atomic %.

[0109] The above-mentioned bulk content is the content obtained by completely dissolving the hexagonal strontium ferrite powder. In addition, in the present invention and this specification, unless otherwise specified, the content refers to the bulk content obtained by completely dissolving the hexagonal strontium ferrite powder for atoms. As rare earth atoms, the hexagonal strontium ferrite powder containing rare earth atoms may contain only one rare earth atom or may contain two or more rare earth atoms. The above-mentioned bulk content when containing two or more rare earth atoms is obtained for the sum of the two or more rare earth atoms. This is also the same for other components in the present invention and this specification. That is, unless otherwise specified, a certain component may be used in one kind or in two or more kinds. The content or content when using two or more kinds refers to the sum of the two or more kinds.

[0110] When the hexagonal strontium ferrite powder contains rare earth atoms, the contained rare earth atoms may be any one or more rare earth atoms. Preferred rare earth atoms from the viewpoint of further suppressing a decrease in reproduced output during repeated reproduction include neodymium atoms, samarium atoms, yttrium atoms, and dysprosium atoms. Neodymium atoms, samarium atoms, and yttrium atoms are more preferred, and neodymium atoms are even more preferred.

[0111] In the hexagonal strontium ferrite powder having a surface partiality of rare earth atoms, the rare earth atoms only need to be partial to the surface of the particles constituting the hexagonal strontium ferrite powder, and the degree of partiality is not limited. For example, with respect to the hexagonal strontium ferrite powder having a surface partiality of rare earth atoms, the ratio of the surface 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 content / bulk content", exceeds 1.0 and may be 1.5 or more. "Surface content / bulk content" being greater than 1.0 indicates that the rare earth atoms in the particles constituting the hexagonal strontium ferrite powder are partial to the surface (i.e., the amount present is greater than that in the interior). Furthermore, the ratio of the surface content of rare earth atoms determined by partial dissolution under the dissolution conditions described below to the bulk content of rare earth atoms determined by complete dissolution under the dissolution conditions described below, "surface 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 the hexagonal strontium ferrite powder having surface localization of rare earth atoms, the rare earth atoms only need to be localized in the surface portion of the particles constituting the hexagonal strontium ferrite powder, and the above-mentioned "surface content / bulk content" is not limited to the upper or lower limits exemplified.

[0112] The following describes partial and complete dissolution of hexagonal strontium ferrite powder. For hexagonal strontium ferrite powder in powder form, partially dissolved and completely dissolved samples 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, while another portion is used for complete dissolution. Removing the hexagonal strontium ferrite powder from the magnetic layer can be performed, for example, using the method described in paragraph 0032 of Japanese Patent Application Laid-Open No. 2015-91747.

[0113] Partial dissolution refers to dissolution to the point where the hexagonal strontium ferrite powder remains visible in the liquid at the end of the dissolution. For example, partial dissolution may dissolve 10-20% by mass of the particles comprising the hexagonal strontium ferrite powder (with the total particles comprising 100% by mass). Complete dissolution, on the other hand, refers to dissolution to the point where the hexagonal strontium ferrite powder remains undetectable in the liquid at the end of the dissolution.

[0114] The above-mentioned partial dissolution and surface content are measured, for example, by the following method. However, the dissolution conditions such as the amount of sample powder described below are merely examples, and any dissolution conditions that allow partial dissolution and complete dissolution may be adopted.

[0115] 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 set at 70°C for 1 hour. The obtained solution is filtered using a 0.1 μm membrane filter. The elemental analysis of the filtrate thus obtained is performed using an inductively coupled plasma (ICP; Inductively Coupled Plasma) analyzer. In this way, the surface content of rare earth atoms relative to 100 atomic % of iron atoms can be calculated. When multiple rare earth atoms are detected by elemental analysis, the total content of all rare earth atoms is taken as the surface content. This is also the same in the determination of the bulk content.

[0116] On the other hand, the above-mentioned complete dissolution and bulk content are measured, for example, by the following method.

[0117] Place 12 mg of sample powder and 10 mL of 4 mol / L hydrochloric acid in a container (e.g., a beaker) on a hot plate set at 80°C for 3 hours. Then, perform the same steps as described above for determining the partial dissolution and surface content to determine the bulk content relative to 100 atomic % of iron atoms.

[0118] From the perspective of improving the reproduction output when reproducing data recorded on the magnetic tape, it is preferred that the mass magnetization σs of the ferromagnetic powder contained in the magnetic tape is higher. In this regard, hexagonal strontium ferrite powder containing rare earth atoms but not having surface localization of rare earth atoms tends to have a significantly lower σs than hexagonal strontium ferrite powder not containing rare earth atoms. In contrast, it is believed that in order to suppress this significant decrease in σs, hexagonal strontium ferrite powder having surface localization of rare earth atoms is preferred. In one embodiment, the σs of the hexagonal strontium ferrite powder can be 45A·m 2 / kg or more, or 47A·m 2 / kg or more. On the other hand, from the perspective of noise reduction, σs is preferably 80A·m 2 / kg or less, more 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 the present invention and this specification, unless otherwise specified, the mass magnetization σs is the value measured at a magnetic field strength of 15 kOe. 1 [kOe] = 10 6 / 4π[A / m].

[0119] Regarding the content of constituent atoms of the hexagonal strontium ferrite powder (bulk content), the strontium atom content can be, for example, in the range of 2.0 to 15.0 atomic % relative to 100 atomic % of iron atoms. In one embodiment, the hexagonal strontium ferrite powder can contain only strontium atoms as divalent metal atoms contained in the powder. Furthermore, in another embodiment, the hexagonal strontium ferrite powder can also contain one or more other divalent metal atoms in addition to strontium atoms. For example, barium atoms and / or calcium atoms can be contained. In the case of containing other divalent metal atoms besides strontium atoms, the barium atom content and the calcium atom content in the hexagonal strontium ferrite powder can be, for example, in the range of 0.05 to 5.0 atomic % relative to 100 atomic % of iron atoms, respectively.

[0120] As the crystal structure of hexagonal ferrite, magnetoplumbite type (also called "M type"), W type, Y type and Z type are known. 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 as a single crystal structure or two or more crystal structures by X-ray diffraction analysis. For example, in one embodiment, hexagonal strontium ferrite powder can be detected as only M type crystal structure by X-ray diffraction analysis. For example, M type hexagonal ferrite is made of AFe 12 O 19The composition formula is represented by . Here, A represents a divalent metal atom. When the hexagonal strontium ferrite powder is of M type, A is only strontium atoms (Sr) or when A contains multiple divalent metal atoms, strontium atoms (Sr) account for the largest proportion on an atomic % basis as described above. The divalent metal atom content of the hexagonal strontium ferrite powder is generally determined by the type of crystal structure of the hexagonal ferrite and is not particularly limited. This also applies to the iron atom content and the oxygen atom content. The hexagonal strontium ferrite powder contains at least iron atoms, strontium atoms and oxygen atoms, and may further contain rare earth atoms. Furthermore, the hexagonal strontium ferrite powder may contain atoms other than these atoms, or may not contain atoms other than these atoms. As an example, the hexagonal strontium ferrite powder may contain aluminum atoms (Al). The content of aluminum atoms can be, for example, 0.5 to 10.0 atomic % relative to 100 atomic % of iron atoms. From the perspective of further suppressing the drop in reproduction output during repeated reproduction, the 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 within the range of 0 to 5.0 atomic %, and may also be 0 atomic %. That is, in one embodiment, the hexagonal strontium ferrite powder may not contain atoms other than iron atoms, strontium atoms, oxygen atoms, and rare earth atoms. The content expressed in the above atomic % is obtained by converting the content of each atom (unit: mass %) obtained by completely dissolving the hexagonal strontium ferrite powder into a value expressed in atomic % using the atomic weight of each atom. Furthermore, in the present invention and this specification, "not containing" for a certain atom means that the content is 0 mass % when completely dissolved and measured by an ICP analyzer. The detection limit of an ICP analyzer is generally 0.01 ppm (parts per million) or less based on mass. The term "not containing" is used to include the case where the amount contained is less than the detection limit of the ICP analyzer. In one embodiment, the hexagonal strontium ferrite powder may not contain bismuth atoms (Bi).

[0121] metal powder

[0122] Preferred specific examples of ferromagnetic powder include ferromagnetic metal powder. For details of ferromagnetic metal powder, see, for example, paragraphs 0137 to 0141 of Japanese Patent Application Laid-Open No. 2011-216149 and paragraphs 0009 to 0023 of Japanese Patent Application Laid-Open No. 2005-251351.

[0123] ε-Iron Oxide Powder

[0124] As a preferred specific example of a ferromagnetic powder, ε-iron oxide powder can be cited. In the present invention and this specification, "ε-iron oxide powder" refers to a ferromagnetic powder in which an ε-iron oxide type crystal structure is detected as the main phase by X-ray diffraction analysis. For example, when the diffraction peak with the highest intensity in the X-ray diffraction spectrum obtained by X-ray diffraction analysis belongs to the ε-iron oxide type crystal structure, it is judged that the ε-iron oxide type crystal structure is detected as the main phase. As methods for producing ε-iron oxide powder, methods for producing it from goethite and reverse micelle methods are known. All of the above production methods are well known. In addition, regarding methods for producing ε-iron oxide powder in which a portion of Fe is substituted with substituent atoms such as Ga, Co, Ti, Al, and Rh, for example, reference can be made to 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 producing the ε-iron oxide powder that can be used as the ferromagnetic powder in the magnetic layer of the magnetic tape is not limited to the method listed here.

[0125] The activation volume of ε-iron oxide powder is preferably between 300 and 1500 nm. 3 The micronized ε-iron oxide powder having an activation volume within the above range is suitable for the production of magnetic tapes that exhibit excellent electromagnetic conversion properties. The activation volume of the ε-iron oxide powder is preferably 300 nm. 3 Above, for example, it can also be 500nm 3 Furthermore, from the perspective of further improving electromagnetic conversion characteristics, the activation volume of the ε-iron oxide powder is more preferably 1400 nm. 3 Below, more preferably 1300nm 3 Below, more preferably 1200nm 3 Below, more preferably 1100nm 3 the following.

[0126] As an index for reducing thermal fluctuation (in other words, improving thermal stability), the anisotropy constant Ku can be cited. The ε-iron oxide powder preferably has a value of 3.0×10 4 J / m 3 More preferably, the Ku may be 8.0×10 4 J / m 3 Furthermore, the Ku of the ε-iron oxide powder can be, for example, 3.0×10 5 J / m 3 However, a higher Ku indicates higher thermal stability, which is more preferable, and therefore it is not limited to the values exemplified above.

[0127] From the perspective of improving the reproduction output when reproducing data recorded on the magnetic tape, it is preferable that the mass magnetization σs of the ferromagnetic powder contained in the magnetic tape is high. In this regard, in one embodiment, the σs of the ε-iron oxide powder can be 8 A·m 2 / kg or more, or 12A·m 2 / kg or more. On the other hand, from the viewpoint of noise reduction, the σs of the ε-iron oxide powder is preferably 40 A·m 2 / kg or less, more preferably 35A·m 2 / kg or less.

[0128] In the present invention and this specification, unless otherwise specified, the average particle size of various powders such as ferromagnetic powder is a value measured by the following method using a transmission electron microscope.

[0129] The powder was photographed at 100,000x magnification using a transmission electron microscope and printed on photographic paper at a total magnification of 500,000x to obtain a photograph of the particles that make up the powder. Target particles were selected from the resulting photographs, and their outlines were traced using a digitizer to measure the size of the particles (primary particles). Primary particles are independent, unagglomerated particles.

[0130] The above measurement is performed on 500 particles randomly extracted. The arithmetic mean of the particle size of the 500 particles thus obtained is taken as the average particle size of the powder. As the above-mentioned transmission electron microscope, for example, a transmission electron microscope H-9000 manufactured by Hitachi, Ltd. can be used. In addition, the measurement of the particle size can be performed using a known image analysis software (for example, image analysis software KS-400 manufactured by Carl Zeiss AG). Unless otherwise specified, the average particle size shown in the embodiments described later is a value measured using a transmission electron microscope H-9000 manufactured by Hitachi, Ltd. and an image analysis software KS-400 manufactured by Carl Zeiss AG as an image analysis software. In the present invention and this specification, powder represents a collection of multiple particles. For example, ferromagnetic powder represents a collection of multiple ferromagnetic particles. In addition, the collection of multiple particles is not limited to a method in which the particles constituting the collection are in direct contact, but also includes a method in which a binder, additive, etc. described later are interposed between the particles. The term particle is sometimes also used to represent a powder.

[0131] As a method for collecting a sample powder from a magnetic tape to measure the particle size, for example, the method described in paragraph 0015 of Japanese Patent Application Laid-Open No. 2011-048878 can be used.

[0132] In the present invention and this specification, unless otherwise specified, the size of the particles constituting the powder (particle size) and the shape of the particles observed in the above-mentioned particle photographs are

[0133] (1) In the case of needle-shaped, spindle-shaped, columnar (where the height is greater than the maximum diameter of the base), the length of the major axis constituting the particle, i.e., the major axis length,

[0134] (2) In the case of a plate or column (where the thickness or height is smaller than the maximum major diameter of the plate surface or bottom surface), the maximum major diameter of the plate surface or bottom surface is indicated.

[0135] (3) When the particle is spherical, polyhedral, or irregular in shape and the major axis of the particle cannot be determined from the shape, the equivalent circle diameter is used. The equivalent circle diameter is obtained by the circular projection method.

[0136] Furthermore, in the above measurement, the length of the short axis of the particle, i.e., the short axis length, is measured, and the value of (major axis length / minor axis length) is calculated for each particle. The average needle-shaped ratio of the powder refers to the arithmetic average of the values obtained for the above 500 particles. Here, unless otherwise specified, the short axis length in the above definition of particle size, in the case of (1), refers to the length of the short axis constituting the particle. Similarly, in the case of (2), it refers to the thickness or height. In the case of (3), since the long axis and the short axis cannot be distinguished, (major axis length / minor axis length) is regarded as 1 for convenience.

[0137] Furthermore, unless otherwise specified, when particles have a specific shape, for example, in the case of the above-mentioned definition of particle size (1), the average particle size is the average major axis length, in the case of the above-mentioned definition of particle size (2), the average particle size is the average plate diameter, and in the case of the above-mentioned definition of particle size (3), the average particle size is the average diameter (also referred to as the average particle size).

[0138] The content (filling rate) of the ferromagnetic powder in the magnetic layer is preferably in the range of 50 to 90 mass %, more preferably in the range of 60 to 90 mass %. From the viewpoint of improving recording density, a higher filling rate of the ferromagnetic powder in the magnetic layer is preferred.

[0139] In one embodiment, the anisotropic magnetic field Hk of the magnetic tape is preferably greater than or equal to 10 kOe, more preferably greater than or equal to 12 kOe, and even more preferably greater than or equal to 14 kOe. When the magnetic tape includes two or more regions A, the anisotropic magnetic field Hk determined for each region A is calculated as the arithmetic average of the anisotropic magnetic fields Hk determined for each region A. Furthermore, when the magnetic tape includes two or more regions A, the Hk determined for each region A may be the same value in one embodiment but different values in another embodiment. The above points also apply to regions B when the magnetic tape includes two or more regions B. However, the above description applies to the cases where a magnetic tape for region A and a magnetic tape for region B are available.

[0140] From the perspective of improving recording density, the anisotropic magnetic field Hk in the area where data is recorded is preferably higher. On the other hand, it is believed that in areas with high anisotropic magnetic field Hk, pitch variations occur, making it more difficult to record data deep into the magnetic layer, and thus more likely to degrade electromagnetic conversion characteristics during repeated tape travel in high-temperature environments. In contrast, including region B in addition to region A in the magnetic tape described above can help suppress this degradation of electromagnetic conversion characteristics. Furthermore, regarding the anisotropic magnetic field Hk of the magnetic tape, the anisotropic magnetic field Hk determined for at least region A is preferably 90 kOe or less, more preferably 80 kOe or less, and even more preferably 70 kOe or less.

[0141] When the number of regions A included in the magnetic tape is two or more, the anisotropic magnetic field Hk may be within the above range in some of the regions A in one embodiment and in all of the regions A in another embodiment.

[0142] The anisotropic magnetic field Hk obtained for region B of the magnetic tape may be 5 kOe or greater in one embodiment, and may be within the range described above for region A in another embodiment. When the magnetic tape includes two or more regions B, the anisotropic magnetic field Hk may be 5 kOe or greater in some of the regions B in one embodiment, and may be within the range described above for region A in another embodiment.

[0143] In the present invention and this specification, the above-mentioned "anisotropic magnetic field Hk" refers to the magnetic field of magnetization saturation when a magnetic field is applied in the direction of the hard magnetization axis of the magnetic layer. The anisotropic magnetic field Hk can be measured using a known measuring device that can measure magnetic properties, such as a vibrating sample type fluxmeter. A sample piece that can be introduced into the measuring device is cut out from the measurement object area of the magnetic tape to be measured, and Hk is measured for the sample piece at a temperature of 23°C. By setting the ambient temperature of 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 ferromagnetic powder, the hard magnetization axis direction of the magnetic layer is the in-plane direction. Regarding units, 1[kOe]=10 6 / 4π[A / m].

[0144] (Binder)

[0145] The magnetic tape may be a coated magnetic tape, and may contain a binder in the magnetic layer. The binder is one or more resins. As the binder, various resins commonly used as binders for coated magnetic recording media may be used. For example, as the binder, a resin selected from polyurethane resin, polyester resin, polyamide resin, vinyl chloride resin, styrene, acrylonitrile, acrylic resin obtained by copolymerizing methyl methacrylate, cellulose resins such as nitrocellulose, epoxy resin, phenoxy resin, polyvinyl acetal, polyvinyl butyral, and other polyvinyl alkyl resins may be used alone, or a plurality of resins may be used in combination. Among them, polyurethane resin, acrylic resin, cellulose resin, and vinyl chloride resin are preferred. These resins may be homopolymers or copolymers. These resins may also be used as binders in the non-magnetic layer and / or back coating layer described later.

[0146] Regarding the above binders, reference can be made to paragraphs 0028 to 0031 of Japanese Patent Application Publication No. 2010-24113. In terms of weight average molecular weight, the average molecular weight of the resin used as a binder can be, for example, 10,000 or more and 200,000 or less. The weight average molecular weight in the present invention and this specification refers to the value obtained by converting the value measured under the following measurement conditions by gel permeation chromatography (GPC) into polystyrene. The weight average molecular weight of the binder shown in the examples described below is the value obtained by converting the value measured under the following measurement conditions into polystyrene. The binder can be used in an amount of, for example, 1.0 to 30.0 parts by mass relative to 100.0 parts by mass of the ferromagnetic powder.

[0147] GPC apparatus: HLC-8120 (manufactured by TOSOH CORPORATION)

[0148] Column: TSK gel Multipore HXL-M (manufactured by TOSOH CORPORATION, 7.8mmI D (InnerDiameter) × 30.0cm)

[0149] Eluent: tetrahydrofuran (THF)

[0150] (Curing Agent)

[0151] A curing agent can also be used together with the resin that can be used as a binder. Regarding the curing agent, in one embodiment, it can be a compound that undergoes a curing reaction (cross-linking reaction) by heating, that is, a thermosetting compound, and in another embodiment, it can be a photocuring compound that undergoes a curing reaction (cross-linking reaction) by light irradiation. The curing agent undergoes a curing reaction in the magnetic layer forming process, and at least a part of it can be contained in the magnetic layer in a state of reacting (cross-linking) with other components such as the binder. In the case where the composition for forming other layers contains a curing agent, this also applies to the layer formed using the composition. A preferred curing agent is a thermosetting compound, and polyisocyanate is suitable. For details about polyisocyanate, reference can be made to paragraphs 0124 to 0125 of Japanese Patent Application Laid-Open No. 2011-216149. In the composition for forming the magnetic layer, the curing agent can be used in an amount of, for example, 0 to 80.0 parts by mass relative to 100.0 parts by mass of the binder. From the viewpoint of improving the strength of the magnetic layer, it is preferably used in an amount of 50.0 to 80.0 parts by mass.

[0152] (Lubricant)

[0153] Above-mentioned magnetic tape can contain more than one composition being selected from the group that comprises fatty acid, fatty acid ester and fatty acid amide in magnetic layer and / or nonmagnetic layer.And, also can contain more than one composition being selected from the group that comprises fatty acid, fatty acid ester and fatty acid amide in back coating layer.

[0154] Examples of the fatty acid include lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, behenic acid, erucic acid, and elaidic acid. Stearic acid, myristic acid, and palmitic acid are preferred, and stearic acid is more preferred. The fatty acid may also be included in the magnetic layer in the form of a salt such as a metal salt.

[0155] Examples of fatty acid esters include esters of lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, behenic acid, erucic acid, and elaidic acid. Specific examples include butyl myristate, butyl palmitate, butyl stearate, isocetyl stearate, neopentyl glycol dioleate, sorbitan monostearate, sorbitan distearate, sorbitan tristearate, oleyl oleate, isocetyl stearate, isotridecyl stearate, octyl stearate, isooctyl stearate, amyl stearate, and butoxyethyl stearate.

[0156] Examples of the fatty acid amide include amides of the above-mentioned various fatty acids, for example, lauric acid amide, myristic acid amide, palmitic acid amide, stearic acid amide, and the like.

[0157] Lubricant extraction amount A Mag and B Mag The amount of lubricant can be adjusted by the amount of lubricant contained in the composition for forming the magnetic layer of each region and / or the composition for forming the non-magnetic layer.

[0158] The fatty acid content in the magnetic layer-forming composition used to form region A is, for example, 0.1 to 5.0 parts by mass, preferably 0.2 to 3.0 parts by mass, and more preferably 0.3 to 2.0 parts by mass, relative to 100.0 parts by mass of the ferromagnetic powder. The fatty acid ester content in the magnetic layer-forming composition used to form region A is, for example, 0.5 to 6.0 parts by mass, preferably 1.0 to 4.0 parts by mass, relative to 100.0 parts by mass of the ferromagnetic powder. The fatty acid amide content in the magnetic layer-forming composition used to form region A is, for example, 0.1 to 1.0 parts by mass, preferably 0.2 to 0.7 parts by mass, and more preferably 0.3 to 0.5 parts by mass, relative to 100.0 parts by mass of the ferromagnetic powder.

[0159] The fatty acid content in the magnetic layer-forming composition used to form region B is, for example, 0.3 to 10.0 parts by mass, preferably 0.5 to 6.0 parts by mass, and more preferably 0.7 to 3.0 parts by mass, relative to 100.0 parts by mass of the ferromagnetic powder. The fatty acid ester content in the magnetic layer-forming composition used to form region B is, for example, 0.5 to 15.0 parts by mass, preferably 1.0 to 5.0 parts by mass, relative to 100.0 parts by mass of the ferromagnetic powder. The fatty acid amide content in the magnetic layer-forming composition used to form region B is, for example, 0.1 to 1.0 parts by mass, preferably 0.2 to 0.7 parts by mass, and more preferably 0.3 to 0.5 parts by mass, relative to 100.0 parts by mass of the ferromagnetic powder.

[0160] Furthermore, when the magnetic tape has a non-magnetic layer between the non-magnetic support and the magnetic layer in region A, the fatty acid content in the non-magnetic layer-forming composition used to form region A is, for example, 0.1 to 5.0 parts by mass, preferably 0.3 to 3.0 parts by mass, and more preferably 0.5 to 2.0 parts by mass, relative to 100.0 parts by mass of the non-magnetic powder. The fatty acid ester content in the non-magnetic layer-forming composition used to form region A is, for example, 0.5 to 6.0 parts by mass, preferably 1.5 to 4.0 parts by mass, relative to 100.0 parts by mass of the non-magnetic powder. The fatty acid amide content in the non-magnetic layer-forming composition used to form region A is, for example, 0.1 to 1.0 parts by mass, preferably 0.2 to 0.6 parts by mass, relative to 100.0 parts by mass of the non-magnetic powder.

[0161] When the magnetic tape has a non-magnetic layer between the non-magnetic support and the magnetic layer in region B, the fatty acid content in the non-magnetic layer-forming composition used to form region B is, for example, 0.5 to 10.0 parts by mass, preferably 0.7 to 6.0 parts by mass, and more preferably 1.0 to 3.0 parts by mass, relative to 100.0 parts by mass of the non-magnetic powder. The fatty acid ester content in the non-magnetic layer-forming composition used to form region B is, for example, 0.5 to 15.0 parts by mass, preferably 1.0 to 5.0 parts by mass, relative to 100.0 parts by mass of the non-magnetic powder. The fatty acid amide content in the non-magnetic layer-forming composition used to form region B is, for example, 0.1 to 1.0 parts by mass, preferably 0.2 to 0.6 parts by mass, relative to 100.0 parts by mass of the non-magnetic powder.

[0162] In the present invention and this specification, unless otherwise specified, a component may be used alone or in combination of two or more. When two or more components are used, the content thereof refers to the total content of the two or more components.

[0163] (additive)

[0164] The magnetic layer may contain one or more additives as needed. As specific examples of additives, the above-mentioned curing agent may be cited. In addition, as additives contained in the magnetic layer, non-magnetic powder (such as inorganic powder, carbon black, etc.), dispersants, dispersing aids, mildew inhibitors, antistatic agents, antioxidants, etc. may be cited. Regarding dispersants, reference may be made to paragraphs 0061 and 0071 of Japanese Patent Application Laid-Open No. 2012-133837. Dispersants may also be added to the composition for forming the non-magnetic layer. Regarding dispersants that may be added to the composition for forming the non-magnetic layer, reference may be made to paragraph 0061 of Japanese Patent Application Laid-Open No. 2012-133837. In addition, as non-magnetic powders that may be contained in the magnetic layer, non-magnetic powders that can function as abrasives, non-magnetic powders that can function as protrusion-forming agents that can form appropriately protruding protrusions on the surface of the magnetic layer (for example, non-magnetic colloidal particles, etc.) may be cited. In addition, the average particle size of the colloidal silica (colloidal silica particles) shown in the examples described below is a value obtained by the method described in paragraph 0015 of Japanese Patent Application Laid-Open No. 2011-048878 as a method for measuring the average particle size. Additives can be used in any amount by appropriately selecting commercially available products according to the desired properties, or can be used in any amount by manufacturing them using known methods. As an example of an additive that can be used in a magnetic layer containing an abrasive to improve the dispersibility of the abrasive, the dispersants described in paragraphs 0012 to 0022 of Japanese Patent Application Laid-Open No. 2013-131285 can be cited.

[0165] As the abrasive, non-magnetic powder with a Mohs hardness of more than 8 is preferred, and non-magnetic powder with a Mohs hardness of 9 or more is more preferred. The maximum value of the Mohs hardness is 10. The abrasive can be a powder of an inorganic substance or a powder of an organic substance. The abrasive can be a powder of an inorganic oxide or an organic oxide or a powder of a carbide. Examples of carbides include boron carbide (e.g., B4C) and titanium carbide (e.g., TiC). In addition, diamond can also be used as an abrasive. In one embodiment, the abrasive is preferably a powder of an inorganic oxide. Specifically, examples of inorganic oxides include aluminum oxide (e.g., Al2O3), titanium oxide (e.g., TiO2), cerium oxide (e.g., CeO2), zirconium oxide (e.g., ZrO2), etc., among which aluminum oxide is preferred. The Mohs hardness of aluminum oxide is about 9. Regarding aluminum oxide powder, reference can also be made to paragraph 0021 of Japanese Patent Application Laid-Open No. 2013-229090. Furthermore, the average particle size of the abrasive is preferably in the range of 0.02 to 0.50 μm, more preferably in the range of 0.05 to 0.40 μm, and further preferably in the range of 0.12 to 0.32 μm. Furthermore, as an indicator of the particle size of the abrasive, the specific surface area can be used. As the abrasive, a specific surface area (hereinafter referred to as "BET specific surface area") of 14 m is preferably used as measured by the BET (Brunauer-Emmett-Teller) method. 2 / g or more. In addition, from the viewpoint of dispersibility, it is preferred to use a grinding agent with a BET specific surface area of 40m 2 The content of the abrasive in the magnetic layer is preferably 1.0 to 20.0 parts by mass, more preferably 1.0 to 18.0 parts by mass, relative to 100.0 parts by mass of the ferromagnetic powder.

[0166] The magnetic layer described above may be provided directly on the surface of the non-magnetic support, or may be provided indirectly via a non-magnetic layer.

[0167] <Nonmagnetic Layer>

[0168] Next, the non-magnetic layer will be described. The magnetic tape in region A and / or region B may have a magnetic layer directly on the surface of the non-magnetic support, or it may 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 in the non-magnetic layer may be an inorganic powder or an organic powder. Furthermore, carbon black and the like may 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 may 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. For information on carbon black that can be used in the non-magnetic layer, please refer to paragraphs 0040 and 0041 of Japanese Patent Application Publication No. 2010-24113. The content (filling rate) of the non-magnetic powder in the non-magnetic layer is preferably in the range of 50 to 90 mass %, more preferably in the range of 60 to 90 mass %.

[0169] The non-magnetic layer may contain a binder and may contain additives. For other details regarding the binder and additives in the non-magnetic layer, known techniques related to non-magnetic layers may be applied. Furthermore, for example, regarding the type and content of the binder and the type and content of the additives, known techniques related to magnetic layers may also be applied.

[0170] In the present invention and this specification, the term "non-magnetic layer" also includes a substantially non-magnetic layer that contains a small amount of ferromagnetic powder along with non-magnetic powder, for example, as an impurity or intentionally. Here, a substantially non-magnetic layer means a layer having a residual magnetic flux density of 10 mT or less, a layer having a coercive force of 7.96 kA / m (100 Oe) or less, or a layer having a residual magnetic flux density of 10 mT or less and a coercive force of 7.96 kA / m (100 Oe) or less. The non-magnetic layer preferably has neither residual magnetic flux density nor coercive force.

[0171] <Non-magnetic Support>

[0172] Next, the non-magnetic support is described. As a non-magnetic support (hereinafter, also referred to as "support"), known non-magnetic supports such as polyethylene terephthalate, polyethylene naphthalate, polyamide, polyamide-imide, aromatic polyamide, etc. that have been subjected to biaxial stretching can be cited. Among them, polyethylene terephthalate, polyethylene naphthalate and polyamide are preferred. These supports can be subjected to corona discharge, plasma treatment, easy adhesion treatment, heat treatment, etc. in advance. As described above, the magnetic layer surface Ra of region A and the magnetic layer surface Ra of region B can be controlled according to the surface shape (for example, center line average surface roughness Ra) of the surface of the side with the magnetic layer of the non-magnetic support. In this regard, for example, in region A, the center line average surface roughness Ra of the surface of the side with the magnetic layer of the non-magnetic support can be within the range mentioned above for the magnetic layer surface Ra of region A. In region B, the centerline average surface roughness Ra of the surface of the non-magnetic support on the side having the magnetic layer is preferably 2.6 nm or greater, more preferably 2.8 nm or greater, and even more preferably 3.0 nm or greater. Furthermore, in region B, the centerline average surface roughness Ra of the surface of the non-magnetic support on the side having the magnetic layer is preferably 15.0 nm or less, more preferably 13.0 nm or less, and even more preferably 10.0 nm or less.

[0173] <Back coating>

[0174] The magnetic tape has 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. That is, region A and region B include the back coating layer. Preferably, the back coating layer contains either one or both of carbon black and inorganic powder. The back coating layer may contain a binder or an additive. Regarding the binder and additive of the back coating layer, known techniques related to the back coating layer may be applied, as may known techniques related to the formulation of the magnetic layer and / or non-magnetic layer. For example, regarding the back coating layer, reference may be made to paragraphs 0018 to 0020 of Japanese Patent Application Publication No. 2006-331625 and the description of U.S. Patent No. 7,029,774, column 4, line 65 to column 5, line 38.

[0175] The magnetic tape may contain one or more components selected from the group consisting of fatty acids, fatty acid esters and fatty acid amides in the back coating layer of region B. Mag / B BackThe scheme of controlling the ratio to be 2.0 or above can include providing two layers of back coating and increasing the proportion of the binder in the upper back coating. Here, the "upper back coating" refers to the back coating located on the surface side of the two layers of back coating. In contrast, the back coating located on the non-magnetic support side of the two layers of back coating is referred to as the "lower back coating". By increasing the proportion of the binder in the upper back coating, the gaps in the back coating can be reduced. Therefore, it is believed that when the surface of the magnetic layer is in contact with the surface of the back coating, the lubricant can be suppressed from moving from the magnetic layer side to the back coating, or its movement amount can be reduced.

[0176] Also, the lubricant extraction amount B of the back coating layer in region B is Back For example, the amount of lubricant contained in the composition for forming the back coating layer in the region B can be adjusted.

[0177] The fatty acid content in the back coat layer forming composition for forming region B is, for example, 0.0 to 10.0 parts by mass, preferably 0.0 to 5.0 parts by mass, and more preferably 0.0 to 2.0 parts by mass relative to 100.0 parts by mass of the non-magnetic powder. The fatty acid ester content in the back coat layer forming composition for forming region B is, for example, 0.0 to 10.0 parts by mass, preferably 0.0 to 3.0 parts by mass relative to 100.0 parts by mass of the non-magnetic powder. The fatty acid amide content in the back coat layer forming composition for forming region B is, for example, 0.0 to 1.0 parts by mass, preferably 0.0 to 0.7 parts by mass, and more preferably 0.0 to 0.4 parts by mass relative to 100.0 parts by mass of the non-magnetic powder.

[0178] Furthermore, the magnetic tape may contain one or more components selected from the group consisting of fatty acids, fatty acid esters, and fatty acid amides in the back coating layer of region A.

[0179] The fatty acid content in the back coat forming composition for forming region A is, for example, 0.0 to 10.0 parts by mass, preferably 0.0 to 5.0 parts by mass, and more preferably 0.0 to 2.0 parts by mass relative to 100.0 parts by mass of the non-magnetic powder. The fatty acid ester content in the back coat forming composition for forming region A is, for example, 0.0 to 10.0 parts by mass, preferably 0.0 to 3.0 parts by mass relative to 100.0 parts by mass of the non-magnetic powder. The fatty acid amide content in the back coat forming composition for forming region A is, for example, 0.0 to 1.0 parts by mass, preferably 0.0 to 0.7 parts by mass, and more preferably 0.0 to 0.4 parts by mass relative to 100.0 parts by mass of the non-magnetic powder.

[0180] <Various thicknesses>

[0181] Regarding the thickness (total thickness) of the magnetic tape, with the dramatic increase in the amount of information in recent years, there is a demand for increased recording capacity (higher capacity) of magnetic tape. Options for increasing capacity include reducing the thickness of the magnetic tape (hereinafter referred to as "thinning") and increasing the length of tape contained in each tape cassette. From this perspective, the thickness (total thickness) of at least region A of the 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 perspective of ease of handling, the thickness of the magnetic tape is preferably 3.0 μm or greater, and more preferably 3.5 μm or greater.

[0182] Regarding region B, in one embodiment, the thickness (total thickness) can be within the above range. In another embodiment, the thickness of region B can be a thickness exceeding the above range (e.g., 5.7 μm to 7.0 μm). The thicknesses of region A and region B can be the same in one embodiment, but different in another embodiment.

[0183] When the magnetic tape includes two or more regions A, the thickness (total thickness) of these regions A may be the same in one embodiment, or different in another embodiment. When the magnetic tape includes two or more regions A, the thickness of the magnetic layers in these regions A may be the same in one embodiment, or different in another embodiment. This also applies to the other layers. Furthermore, the above points also apply to the thickness (total thickness) of the regions B and the thicknesses of the various layers when the magnetic tape includes two or more regions B.

[0184] In the region A, the thickness of the non-magnetic support is preferably 3.0 to 5.0 μm.

[0185] The thickness of the magnetic layer can be optimized based on the saturation magnetization of the magnetic head used, the head gap length, the frequency band of the recorded signal, and other factors. In region A, the thickness of the magnetic layer is, for example, 0.01 μm to 0.15 μm. From the perspective of high-density recording, it is preferably 0.02 μm to 0.12 μm, and more preferably 0.03 μm to 0.1 μm. A single magnetic layer is sufficient, and the magnetic layer may be divided into two or more magnetic layers having different magnetic properties, and known structures related to multilayer magnetic layers may be applied to these layers. The thickness of the magnetic layer when divided into two or more magnetic layers refers to the total thickness of these layers.

[0186] In the region A, the thickness of the nonmagnetic layer is, for example, 0.1 to 2.0 μm, preferably 0.1 to 1.5 μm, and more preferably 0.1 to 1.0 μm.

[0187] In region A, the thickness of the back coat layer is preferably 0.9 μm or less, more preferably 0.1 to 0.7 μm.

[0188] The various thicknesses in region B may also fall within the above range. When region B has two or more back coating layers, the thickness of the back coating layer refers to the total thickness of these layers. In one embodiment, the thickness of the non-magnetic layer in region B is preferably thicker than that of the non-magnetic layer in region A. This is because increasing the thickness of the non-magnetic layer is believed to allow the non-magnetic layer to contain more lubricant, thereby increasing the amount of lubricant supplied from region B.

[0189] Various thicknesses such as the thickness of the magnetic layer can be obtained by the following method.

[0190] After exposing a cross section of the tape in its thickness direction using an ion beam, the exposed cross section is observed using a scanning electron microscope. Various thicknesses can be calculated as the arithmetic average of the thicknesses measured at any two locations during the cross-sectional observation. Alternatively, various thicknesses can be calculated as design thicknesses based on manufacturing conditions, etc.

[0191] <Manufacturing process>

[0192] (Preparation of Compositions for Forming Each Layer)

[0193] The process of preparing a composition for forming a magnetic layer, a non-magnetic layer or a back coating layer may generally include at least a kneading process, a dispersion process and a mixing process provided before and after these processes as needed. Each process may be divided into two or more stages. The components used to prepare the composition for forming each layer may be added at the initial stage or in the middle of any process. As a solvent, one or more of the various solvents commonly used in the manufacture of coated magnetic recording media may be used. For example, reference may be made to paragraph 0153 of Japanese Patent Application Laid-Open No. 2011-216149. Furthermore, each component may be added in stages in two or more processes. For example, the binder may be added in stages in the kneading process, the dispersion process and the mixing process for adjusting the viscosity after dispersion. In order to manufacture the above-mentioned magnetic tape, known manufacturing techniques may be used in various processes. In the kneading process, it is preferred to use a kneader with a strong kneading force, such as an open kneader, a continuous kneader, a pressure kneader, or an extruder. For details of the kneading process, reference may be made to Japanese Patent Application Laid-Open No. 1-106338 and Japanese Patent Application Laid-Open No. 1-79274. A known disperser may be used. Filtration may be performed by a known method at any stage in the preparation of the composition for forming each layer. Filtration may be performed, for example, by filtration through a filter. As a filter for filtration, for example, a filter having a pore size of 0.01 to 3 μm (e.g., a glass fiber filter, a polypropylene filter, etc.) may be used.

[0194] (Coating process)

[0195] The magnetic layer can be formed by directly applying the magnetic layer forming composition on the surface of the non-magnetic support or by carrying out multilayer coating with the non-magnetic layer forming composition in sequence or simultaneously. The back coating layer can be formed by applying the back coating layer forming composition on the surface of the non-magnetic support on the side opposite to the surface with the non-magnetic layer and / or magnetic layer (or the non-magnetic layer and / or magnetic layer to be provided). For details on the coating for forming each layer, reference can be made to paragraph 0066 of Japanese Patent Application Laid-Open No. 2010-231843.

[0196] (Other processes)

[0197] Regarding the various other processes used to manufacture magnetic tapes, known techniques can be applied. For example, reference can be made to paragraphs 0067 to 0070 of Japanese Patent Application Laid-Open No. 2010-231843 regarding the various processes. For example, the coating layer of the magnetic layer-forming composition can be oriented in the orientation zone while the coating layer is wet. Regarding the orientation treatment, various known techniques, including those described in paragraph 0052 of Japanese Patent Application Laid-Open No. 2010-24113, can be applied. For example, vertical orientation treatment can be performed using known methods such as the method of using oppositely polarized magnets. In the orientation zone, the drying speed of the coating layer can be controlled by the temperature and air volume 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.

[0198] After going through various steps, a long raw tape is obtained. The raw tape is then cut (or chopped) using a known cutting machine to the width of the tape to be wound into a tape cassette. This width is determined by a standard, usually 1 / 2 inch.

[0199] In the cut magnetic tape, a servo pattern may be formed on at least a portion of the magnetic layer. Details of the servo pattern will be described later.

[0200] (Heat Treatment)

[0201] In one embodiment, the magnetic tape may be manufactured by undergoing the following heat treatment. Alternatively, in another embodiment, the magnetic tape may be manufactured without undergoing the following heat treatment. Furthermore, in one embodiment, at least a portion of either region A or region B may be manufactured by undergoing the following heat treatment, while the remaining portion may not be manufactured by undergoing the following heat treatment.

[0202] As the heat treatment, a magnetic tape cut and trimmed to a width determined according to a standard may be wound around a core member and heat treated in the wound state.

[0203] In one embodiment, the heat treatment can be performed while the magnetic tape is wound around a core member for heat treatment (hereinafter referred to as a "heat treatment core"), and the heat-treated magnetic tape can be wound onto another reel such as a reel of a tape cassette.

[0204] The heat treatment core can be made of metal, resin, paper, etc. From the perspective of suppressing the occurrence of poor winding of the spokes, the material of the heat treatment core is preferably a material with high rigidity. From this point of view, the heat treatment core is preferably made of metal or resin. Moreover, as an indicator of rigidity, the bending modulus of the material of the heat treatment core is preferably 0.2GPa (gigaPascals) or more, more preferably 0.3GPa or more. On the other hand, since materials with high rigidity are generally more expensive, using a heat treatment core with a material with greater rigidity than that which can suppress the occurrence of poor winding will lead to increased costs. Taking this into account, the bending modulus of the material of the heat treatment core is preferably 250GPa or less. The bending modulus is a value measured in accordance with ISO (International Organization for Standardization) 178, and the bending 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 perspective of maintaining rigidity, the wall thickness is preferably 2mm or more. Furthermore, the heat treatment core may or may not have a flange.

[0205] Preferably, a magnetic tape having a length equal to or longer than the final length to be obtained (hereinafter referred to as the "final length") is prepared as the magnetic tape to be wound on the heat treatment core, and the magnetic tape is placed in a heat treatment environment while being wound on the heat treatment core, thereby performing heat treatment. The length of the magnetic tape wound on the heat treatment core is equal to or longer than the final length, and from the perspective of ease of winding of the heat treatment core, etc., is preferably "final length + α". From the perspective of the above-mentioned ease of winding, this α is preferably equal to or longer than 5m. The tension when winding on the heat treatment core is preferably equal to or longer than 0.1N (Newton). Furthermore, from the perspective of suppressing excessive deformation, the tension when winding on the heat treatment core is preferably equal to or shorter than 1.5N, more preferably equal to or shorter than 1.0N. From the perspective of ease of winding and suppression of coiling (curling in the longitudinal direction), the outer diameter of the heat treatment core is preferably equal to or longer than 20mm, more preferably equal to or longer than 40mm. Furthermore, the outer diameter of the heat treatment core is preferably equal to or shorter than 100mm, more preferably equal to or shorter than 90mm. The width of the heat treatment core only needs to be greater than the width of the tape wound around it. Furthermore, when removing the tape from the heat treatment core after heat treatment, it is preferable to fully cool the tape and the heat treatment core before removing the tape. The removed tape is preferably first wound onto another core (referred to as a "temporary winding core"), and then the tape is taken up from the temporary winding core onto another reel (e.g., with an outer diameter of approximately 40-50 mm). This allows the tape to be wound onto the reel of a tape cassette, etc., while maintaining its internal and external relationship with the heat treatment core during heat treatment. For details about the temporary winding core and the tension used when winding the tape onto it, please refer to the above description regarding the heat treatment core. In the method described above where the tape is heat treated to a length of "final length + α," a length of tape equivalent to "+ α" may be cut at any stage. For example, in one embodiment, the tape of the final length can be wound onto another reel from the temporary winding core, and the remaining length of the tape equal to "+α" can be cut. From the perspective of reducing the amount of tape cut and discarded, the above α is preferably 20m or less.

[0206] Hereinafter, a specific embodiment of the heat treatment performed in the state of being wound around the core member as described above will be described.

[0207] The temperature of the atmosphere during the heat treatment (hereinafter referred to as "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.

[0208] The weight absolute humidity of the atmosphere for heat treatment is preferably more than 0.1g / kg Dry air, more preferably more than 1g / kg Dry air. Since the weight absolute humidity is within the above range, it is not necessary to use a special device for reducing moisture to prepare an atmosphere, so it is preferred. On the other hand, from the viewpoint of suppressing the operability decline caused by the generation of condensation, the weight absolute humidity is preferably less than 70g / kg Dry air, more preferably less than 66g / kg Dry air. The heat treatment time is preferably more than 0.3 hours, more preferably more than 0.5 hours. And, from the viewpoint of production efficiency, the heat treatment time is preferably less than 48 hours.

[0209] (Formation of Servo Pattern)

[0210] “Forming a servo pattern” may also be referred to as “recording a servo signal.” Hereinafter, forming a servo pattern will be described.

[0211] The servo pattern is usually formed along the longitudinal direction of the magnetic tape. Examples of control methods using servo signals (servo control) include timing-based servo (TBS), amplitude servo, and frequency servo.

[0212] As described in ECMA (European Computer Manufacturers Association)-319 (June 2001), magnetic tapes conforming to the LTO (Linear Tape-Open) standard (commonly referred to as "LTO tapes") employ a timing-based servo method. In this timing-based servo method, a servo pattern is formed by continuously arranging multiple pairs of non-parallel magnetic stripes (also referred to as "servo stripes") along the length of the tape. In the present invention and this specification, a "timing-based servo pattern" refers to a servo pattern that enables head tracking in a servo system using a timing-based servo method. As described above, the servo pattern is formed by a pair of non-parallel magnetic stripes to notify a servo signal reader element passing over the servo pattern of its passing position. Specifically, the pair of magnetic stripes is formed so that the spacing between them continuously changes along the width of the tape. By having the servo signal reader element read this spacing, the relative position of the servo pattern and the servo signal reader element can be determined. This relative position information enables tracking of the data track. Therefore, multiple servo tracks are typically provided along the width of the tape on the servo pattern.

[0213] A servo band consists of a continuous servo pattern running the length of the tape. Typically, there are multiple servo bands on a tape. For example, LTO tape has five servo bands. The area between two adjacent servo bands is the data band. The data band consists of multiple data tracks, each corresponding to a servo track.

[0214] Furthermore, in one embodiment, as described in Japanese Patent Application Laid-Open No. 2004-318983, each servo band is embedded with information indicating the servo band number (also referred to as "servo band ID (identification)" or "UDIM (Unique Data Band Identification Method) information"). This servo band ID is recorded by shifting a specific pair of servo stripes among the multiple pairs of servo stripes present in the servo band so that their positions are relatively displaced along the length of the magnetic tape. Specifically, the shifting method of the specific pair of servo stripes among the multiple pairs of servo stripes is changed for each servo band. This recorded servo band ID is thus unique for each servo band, allowing the servo band to be uniquely identified simply by reading a servo band using a servo signal reading element.

[0215] Another method for uniquely identifying servo bands is using an interleaved method, as described in ECMA-319 (June 2001). In this interleaved method, each servo band is recorded by shifting a plurality of pairs of non-parallel magnetic stripes (servo stripes) arranged continuously along the length of the tape. Because the combination of these shifting patterns between adjacent servo bands is unique across the entire tape, the servo band can be uniquely identified when the servo pattern is read using two servo signal reading elements.

[0216] Furthermore, as described in ECMA-319 (June 2001), each servo band typically includes information indicating the position of the tape in the longitudinal direction (also referred to as "LPOS (Longitudinal Position) information"). Similar to UDIM information, this LPOS information is recorded by shifting the position of a pair of servo stripes in the longitudinal direction of the tape. However, unlike UDIM information, the same signal is recorded in each servo band in LPOS information.

[0217] Other information other than the UDIM information and LPOS information may also be embedded in the servo band. In this case, the embedded information may be different for each servo band like the UDIM information, or may be common to all servo bands like the LPOS information.

[0218] Furthermore, as a method of embedding information in the servo band, methods other than those described above may be employed. For example, a predetermined code may be recorded by extracting a predetermined pair from a pair of servo magnetic stripes.

[0219] The magnetic head used to form the servo pattern is called a servo write head. The servo write head usually has a pair of gaps corresponding to the above-mentioned pair of magnetic stripes, and the number of the pair of gaps is the same as the number of servo bands. Usually, a magnetic core and a coil are connected to each pair of gaps, and by supplying a current pulse to the coil, the magnetic field generated by the magnetic core can generate a leakage magnetic field in the pair of gaps. When forming a servo pattern, by feeding a current pulse while running the magnetic tape on the servo write head, the magnetic pattern corresponding to the pair of gaps can be transferred to the magnetic tape, thereby forming a servo pattern. The width of each gap can be appropriately set according to the density of the servo pattern to be formed. The width of each gap can be set to, for example, less than 1 μm, 1 to 10 μm, or more than 10 μm.

[0220] Before forming a servo pattern on the magnetic tape, the magnetic tape is usually demagnetized (erased). The erasing process can be performed by applying a uniform magnetic field to the magnetic tape using a DC magnet or an AC magnet. The erasing process includes DC (Direct Current) erasing and AC (Alternating Current) erasing. AC erasing is performed by gradually reducing the intensity of the magnetic field applied to the magnetic tape while reversing the direction of the magnetic field. On the other hand, DC erasing is performed by applying a unidirectional magnetic field to the magnetic tape. DC erasing also includes two methods. The first method is horizontal DC erasing in which a unidirectional magnetic field is applied along the length direction of the magnetic tape. The second method is vertical DC erasing in which a unidirectional magnetic field is applied along the thickness direction of the magnetic tape. The erasing process can be performed on the entire magnetic tape or on each servo band of the magnetic tape.

[0221] The orientation of the magnetic field of the formed servo pattern is determined by the direction of the erasure. For example, when horizontal DC erasure is applied to the magnetic tape, the servo pattern is formed in such a way that the orientation of the magnetic field is opposite to the direction of the erasure. This increases the output of the servo signal obtained by reading the servo pattern. Furthermore, as shown in Japanese Patent Application Laid-Open No. 2012-53940, when a magnetic pattern with the gap described above is transferred to a vertically DC-erased magnetic tape, the servo signal obtained by reading the formed servo pattern has a unipolar pulse shape. On the other hand, when a magnetic pattern with the gap described above is transferred to a horizontally DC-erased magnetic tape, the servo signal obtained by reading the formed servo pattern has a bipolar pulse shape.

[0222] The magnetic tape preferably has a servo pattern on at least the magnetic layer of region A, and more preferably also has a servo pattern on the magnetic layer of region B. Region A can preferably be a data recording region for recording data using a magnetic head. In one embodiment, data can also be recorded in region B using a magnetic head. More preferably, when the magnetic tape is run in order to record data and / or reproduce recorded data on the magnetic tape, the running conditions of region B can be controlled based on the measurement results related to the recording and reproduction quality of the data in region A. The running conditions of region B can be controlled using a servo signal read by a servo pattern reading element. The above-mentioned recording and reproduction quality is used to include the meaning of recording quality and reproduction quality. As an example, the measurement results related to the recording and reproduction quality can include SNR (Signal-to-Noise Ratio) as an indicator of electromagnetic conversion characteristics. The running conditions of region B can include, for example, the number of times the surface of the magnetic layer of region B slides relative to the magnetic head, the distance the magnetic head slides relative to the surface of the magnetic layer of region B, etc. For example, when the SNR decreases in region A during repeated tape movement, more lubricant can be supplied to the head by increasing the number of times the head slides relative to the magnetic layer surface in region B and / or lengthening the distance the head slides relative to the magnetic layer surface in region B, thereby improving the electromagnetic conversion characteristics.

[0223] Furthermore, in one embodiment, the width of the tape can be controlled by using servo signals to obtain information about the width of the tape during tape travel. The tension applied to the tape in the longitudinal direction is adjusted and varied based on the obtained information. This tension adjustment helps 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.

[0224] [Tape Cassette]

[0225] One aspect of the present invention relates to a magnetic tape cassette including the magnetic tape described above.

[0226] The details of the magnetic tape included in the above-mentioned magnetic tape cassette are as described above.

[0227] In a tape cassette, the magnetic tape is typically contained within the cassette body while being wound onto a reel. The reel is configured to rotate within the cassette body. Commonly used tape cassettes include single-reel cassettes with a single reel inside the cassette body and dual-reel cassettes with two reels inside the cassette body. When a single-reel cassette is installed in a tape drive to record and / or reproduce 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 tape transport path from the cassette to the take-up reel. The magnetic tape is fed and wound between the reel (supply reel) on the cassette side and the reel (take-up reel) on the tape drive side. During this process, the magnetic head contacts and slides against the magnetic surface of the tape, thereby recording and / or reproducing data. In contrast, a dual-reel cassette has two reels inside the cassette: a supply reel and a take-up reel.

[0228] [Tape Device]

[0229] One embodiment of the present invention relates to a magnetic tape device including the magnetic tape and a magnetic head. In the magnetic tape device, data recording on the magnetic tape and / or data reproduction recorded on the magnetic tape can be performed by sliding the magnetic head in contact with the magnetic layer surface of the magnetic tape.

[0230] In the present invention and this specification, a "tape device" refers to a device capable of at least one of recording data on a magnetic tape and reproducing data recorded on the magnetic tape. This device is generally referred to as a drive. The magnetic head included in the magnetic tape device may be a recording head capable of recording data on the magnetic tape, or a reproducing head capable of reproducing data recorded on the magnetic tape. Furthermore, in one embodiment, the magnetic tape device may include both a recording head and a reproducing head in the form of separate heads. In another embodiment, the magnetic head included in the magnetic tape device may have a structure in which both a recording element and a reproducing element are included on a single head. The reproducing head preferably includes a magnetoresistive (MR) element as a reproducing element that can sensitively read information recorded on the magnetic tape. Various known MR heads (e.g., GMR (Giant Magnetoresistive) heads, TMR (Tunnel Magnetoresistive) heads, etc.) may be used as the MR head. Furthermore, the magnetic head that records and / or reproduces data may include a servo signal reading element. Alternatively, the magnetic tape device may include a magnetic head (servo head) having a servo signal reading element as a head separate from a magnetic head for recording data and / or reproducing data. For example, a magnetic head for recording data and / or reproducing recorded data (hereinafter also referred to as a "recording and reproducing head") may include two servo signal reading elements, and the two servo signal reading elements may respectively read two adjacent servo bands sandwiching the data band at the same time. One or more data elements may be arranged between the two servo signal reading elements. The elements for recording data (recording elements) and the elements for reproducing data (reproducing elements) are collectively referred to as "data elements."

[0231] As described above, the area where the magnetic head records data is preferably included in at least area A and may also be included in area B.

[0232] When recording and / or reproducing data, tracking using servo signals is first performed. Specifically, by causing the servo signal reading element to follow a predetermined servo track, the data element can be controlled to pass over the target data track. The data track is moved by changing the servo track read by the servo signal reading element across the width of the tape.

[0233] Furthermore, the recording and reproducing head can also record and / or reproduce data in other data bands. In this case, the servo signal reading element can be moved to a predetermined servo band using the UDIM information to start tracking the servo band.

[0234] Figure 1An example of the arrangement of the data band and the servo band is shown in FIG. Figure 1 In the embodiment, a plurality of servo bands 1 are arranged on the magnetic layer of the magnetic tape MT in a manner sandwiched between guide bands 3. The plurality of areas 2 sandwiched between the two servo bands are data bands. The servo pattern is a magnetized area formed by magnetizing a specific area of the magnetic layer using a servo write head. The area magnetized by the servo write head (the location where the servo pattern is formed) is determined according to the standard. For example, for the LTO Ultrium format magnetic tape, which is an industry standard, when manufacturing the tape, as shown in FIG. Figure 2 As shown, a plurality of servo patterns tilted relative to the width direction of the tape are formed on the servo band. Figure 2 In the servo band 1, the servo frame SF is composed of servo subframe 1 (SSF1) and servo subframe 2 (SSF2). The servo subframe 1 is composed of A burst ( Figure 2 Symbol A) and B burst ( Figure 2 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, the servo subframe 2 consists of the C burst ( Figure 2 Symbol C) and D burst ( Figure 2 The C burst is composed of servo patterns C1 to C4, and the D burst is composed of servo patterns D1 to D4. These 18 servo patterns are arranged in a 5, 5, 4, 4 array on the subframes in a combination of 5 and 4 to identify the servo frame. For illustration, Figure 2 However, in reality, in a magnetic layer of a magnetic tape that performs head tracking using a timing-based servo method, a plurality of servo frames are arranged along the tape running direction on each servo band. Figure 2 For example, an LTO Ultrium format tape typically has more than 5000 servo frames per 1 m of tape length on each servo band of the magnetic layer.

[0235] In one embodiment of the above-described magnetic tape device, the magnetic tape is considered a removable medium (so-called replaceable medium), and the magnetic tape is wound onto a reel, and a tape cassette containing the magnetic tape is inserted and removed from the magnetic tape device. In another embodiment, the magnetic tape is not considered a replaceable medium, and the magnetic tape is wound onto a reel of a magnetic tape device equipped with a magnetic head, and the magnetic tape is stored within the magnetic tape device. In either embodiment, the outer diameter of the reel on which the magnetic tape is wound can be, for example, approximately 80.0 to 100.0 mm, and the inner diameter of the reel can be, for example, approximately 22.0 to 50.0 mm.

[0236] Example

[0237] The following describes one embodiment of the present invention based on examples. However, the present invention is not limited to the embodiments shown in the examples. Unless otherwise specified, the expressions "parts" and "%" described below refer to "parts by mass" and "mass %." "eq" stands for equivalent and is a unit that cannot be converted into SI units.

[0238] Furthermore, unless otherwise specified, the following steps and operations are performed at a temperature of 20 to 25° C. and a relative humidity of 40 to 60%.

[0239] [Example 1]

[0240] <Creation of Tape for Area A>

[0241] (1) Preparation of alumina dispersion

[0242] The alpha rate is about 65%, and the BET specific surface area is 20m 2 100.0 parts of alumina powder (HIT-80, manufactured by Sumitomo Chemical Company, Limited) with a concentration of 1 / g was mixed with 3.0 parts of 2,3-dihydroxynaphthalene (manufactured by Tokyo Chemical Industry Co., Ltd.), 31.3 parts of a 32% solution (solvent: a mixed solvent of methyl ethyl ketone and toluene) of a polyester polyurethane resin having SO₃Na groups as polar groups (UR-4800, manufactured by TOYOBO CO., LTD. (polar group content: 80 meq / kg)), and 570.0 parts of a mixed solution of methyl ethyl ketone and cyclohexanone in a 1:1 (mass ratio) solvent. The mixture was then dispersed in the presence of zirconium oxide beads using a paint shaker for 5 hours. After dispersion, the dispersion and beads were separated using a sieve to obtain an alumina dispersion.

[0243] (2) Formulation of the composition for forming the magnetic layer

[0244] (Magnetic fluid)

[0245]

[0246] (Abrasive Liquid)

[0247] 6.0 parts of the alumina dispersion prepared in (1) above

[0248] (Silica sol (projection forming agent liquid))

[0249] Colloidal silicon dioxide (average particle size 120 nm) 2.0 parts

[0250] 1.4 parts of methyl ethyl ketone

[0251] (Other ingredients)

[0252]

[0253]

[0254] (Add solvent at the end)

[0255] 200.0 parts of cyclohexanone

[0256] 200.0 parts of methyl ethyl ketone

[0257] (3) Formulation of the composition for forming the non-magnetic layer

[0258] (4) Formulation of the back coating layer forming composition

[0259] (5) Preparation of compositions for forming each layer

[0260] The composition for forming a magnetic layer was prepared by the following method. The components were dispersed (bead dispersion) for 24 hours using an intermittent vertical sand mill to prepare the above-mentioned magnetic liquid. Zirconia beads with a bead diameter of 0.5 mm were used as dispersed beads. The prepared magnetic liquid was mixed with the above-mentioned abrasive liquid and other components (silica sol, other components and finishing solvent) using the above-mentioned sand mill, and after bead dispersion for 5 minutes, an intermittent ultrasonic device (20 kHz, 300 W) was used for 0.5 minutes (ultrasonic dispersion). Then, a filter with a pore size of 0.5 μm was used for filtration to prepare a composition for forming a magnetic layer.

[0261] A non-magnetic layer-forming composition was prepared by the following method. The above 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. The lubricant (stearic acid, stearamide, and butyl stearate) was then added and stirred and mixed using a dissolver mixer to prepare a non-magnetic layer-forming composition.

[0262] A back coating layer-forming composition was prepared by the following method. The above components, excluding the polyisocyanate, were introduced into a dissolver and stirred at a peripheral speed of 10 m / s for 30 minutes, followed by dispersion using a horizontal bead mill. Subsequently, the polyisocyanate was added, and stirring and mixing were performed using the dissolver and stirrer to prepare a back coating layer-forming composition.

[0263] (6) Production of tapes

[0264] The non-magnetic layer forming composition prepared in (5) above was applied to the surface of a biaxially stretched polyethylene terephthalate support having a centerline average surface roughness Ra ("support surface Ra in region A" in Table 1) of the value shown in Table 1, to a thickness of 0.7 μm after drying, and dried to form a non-magnetic layer. Next, the magnetic layer forming composition prepared in (5) above was applied to the non-magnetic layer to a thickness of 0.1 μm after drying, forming a coating layer. While the coating layer of the magnetic layer forming composition was still undried, a magnetic field with a magnetic field strength of 0.3 T was applied perpendicularly to the surface of the coating layer to perform a vertical orientation treatment, and then dried to form a magnetic layer. Next, the back coating layer forming composition prepared in (5) above was applied to the surface of the support opposite to the surface on which the non-magnetic layer and magnetic layer were formed, to a thickness of 0.3 μm after drying, and dried to form a back coating layer.

[0265] Then, surface smoothing treatment (calendering treatment) was performed using a calendering roll consisting only of a metal roll at a speed of 100 m / min, a linear pressure of 300 kg / cm, and a calendering temperature of 90° C. (surface temperature of the calendering roll).

[0266] The long raw magnetic tape was then stored in a heat treatment furnace at an ambient temperature of 70° C. and heat treated (heat treatment time: 36 hours). After the heat treatment, the raw magnetic tape was cut into 1 / 2 inch widths to obtain magnetic tapes.

[0267] The tape (970 m in length) was then wound onto a heat treatment core and heat treated while wound on it. A solid resin core (50 mm in outer diameter) 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.

[0268] After the heat treatment, the tape and heat treatment core were allowed to cool sufficiently. The tape was then removed from the heat treatment core and wound onto a temporary take-up core. The tape, equivalent to the final length (960 m), was then wound from the temporary take-up core onto another reel (44 mm outer diameter), and the remaining 10 m of tape was cut. A solid core member made of the same material and with the same outer diameter as the heat treatment core was used as the temporary take-up core. The tension during winding was 0.6 N.

[0269] <Preparation of Tape for Area B>

[0270] (1) Formulation of the composition for forming the magnetic layer

[0271] Strong magnetic powder (see Table 1) 100.0 parts

[0272] 10.0 parts of vinyl chloride copolymer (MR110 manufactured by Kaneka Corporation)

[0273] (SO3Na base: 5×10 -6 eq / g, degree of polymerization: 350, epoxy group: 3.5% by mass based on monomer unit)

[0274] 10.0 parts of polyester polyurethane resin

[0275] (neopentyl glycol / caprolactone polyol / 4,4'-diphenylmethane diisocyanate (MDI) = 0.9 / 2.6 / 1 (mass ratio),

[0276] (SO3Na base: 1×10 -4 eq / g)

[0277]

[0278]

[0279] (2) Formulation of the non-magnetic layer forming composition

[0280]

[0281] (3) Formulation of the back coating layer forming composition

[0282]

[0283] (4) Formulation of the lower back coating layer forming composition

[0284]

[0285] (5) Preparation of compositions for forming each layer

[0286] The magnetic layer-forming composition and the non-magnetic layer-forming composition were kneaded using a continuous kneader and then dispersed using a sand mill. To each of the resulting dispersions, 5.0 parts of polyisocyanate (CORONATE L manufactured by TOSOH CORPORATION) was added, followed by 40.0 parts of methyl ethyl ketone. The mixture was then filtered using a filter with a pore size of 1 μm to prepare the magnetic layer-forming composition and the non-magnetic layer-forming composition.

[0287] The composition for forming the upper back coating layer was prepared by introducing the above components except the polyisocyanate into a dissolver and stirring at a peripheral speed of 10 m / s for 30 minutes, followed by dispersion using a horizontal bead mill. Subsequently, the polyisocyanate was added, and stirring and mixing were performed using the dissolver and stirrer to prepare a composition for forming the upper back coating layer.

[0288] The lower back coating layer-forming composition was prepared by kneading the above components using a continuous kneader and then dispersing them using a sand mill. 40.0 parts of polyisocyanate (CORONATE L manufactured by TOSOH CORPO RATION) and 1000.0 parts of methyl ethyl ketone were added to the resulting dispersion, followed by filtration using a filter having a pore size of 1 μm to prepare a lower back coating layer-forming composition.

[0289] (6) Production of tapes

[0290] On the surface of a biaxially stretched polyethylene terephthalate support having a centerline average surface roughness Ra ("support surface Ra of region B" in Table 1) of the value shown in Table 1, a non-magnetic layer forming composition and a magnetic layer forming composition were simultaneously laminated and coated in such a manner that the thickness of the non-magnetic layer after drying became 2.0 μm and the thickness of the magnetic layer after drying became 0.1 μm. Next, while the coating layer of the magnetic layer forming composition was still undried, a magnetic field with a magnetic field intensity of 0.3 T was applied to the surface of the coating layer in a perpendicular direction to perform a vertical orientation treatment, and then dried. In this way, a non-magnetic layer and a magnetic layer were formed. Then, on the surface of the support opposite to the surface on which the non-magnetic layer and the magnetic layer were formed, an upper back coating layer forming composition and a lower back coating layer forming composition were simultaneously laminated and coated in such a manner that the thickness after drying became the thickness described in Table 1, and then dried. In this way, an upper back coating layer and a lower back coating layer were formed.

[0291] <Production of Tapes Including Area A and Area B>

[0292] Figure 3 , an example of the arrangement of area A and area B on a magnetic tape is shown in FIG.

[0293] like Figure 3 As shown, a tape with continuous areas A and B is produced.

[0294] Three tape pieces are cut out from the area B magnetic tape, and these are used as area B1, area B2, and area B3, respectively.

[0295] Two tape pieces of the same length are cut from the magnetic tape in area A, one of which is arranged as area A between area B1 and area B2, and the other is arranged as area A between area B2 and area B3.

[0296] Region A and region B are joined on the back coating side by a splicing tape.

[0297] By recording servo signals on the magnetic layer of the tape thus produced using a commercially available servo writer, a tape is obtained that has data bands, servo bands, and guide bands arranged in accordance with the LTO (Linear Tape-Open) Ultrium format. The servo bands also have servo patterns (timing-based servo patterns) arranged and shaped in accordance with the LTO Ultrium format. The servo patterns thus formed are based on JIS (Japanese Industrial Standards) X6175:2006 and Standard ECMA-319 (June 2001). There are five servo bands and four data bands.

[0298] The magnetic tape after the servo pattern is formed in this manner is wound onto a tape reel (reel inner diameter: 44.0 mm, reel outer diameter: 96.8 mm) removed from a tape cartridge (LTO Ultrium 7 data cartridge) so that the area B3 is located inside and the area B1 is located outside.

[0299] [Examples 2 to 23, Comparative Examples 1 to 10]

[0300] A tape cassette containing a magnetic tape was produced in the same manner as in Example 1 except that various items were changed as shown in the table described later.

[0301] In Table 2, the "Region A Length" column shows the sum of the lengths of the plurality of regions A for a magnetic tape having the plurality of regions A.

[0302] In the examples and comparative examples where "3" is written in the "number of regions B" column in Table 2, the regions A and B are arranged in the same manner as in Example 1.

[0303] In the embodiment where "1" is recorded in the "Number of Areas B" column in Table 2, one area A and one area B are provided, and the magnetic tape is accommodated in the tape cassette with area A located outside and area B located inside.

[0304] In the embodiment where "2" is recorded in the "Number of Areas B" column in Table 2, Figure 3 In the configuration example, "area B1 / area A / area B2" is used, and other areas (area B3 and area A between area B2 and area B3) are not set, and the tape is wound onto the tape reel in such a way that area B2 is located inside and area B1 is located outside.

[0305] In the comparative example in which "0" is written in the "Number of Areas B" column in Table 2, only the magnetic tape for area A is wound onto the tape reel.

[0306] For each tape, the length of area A and area B and the tape width (1 / 2 inch) are determined by "(S B / (S A +S B ))×100” to calculate the area ratio of region B.

[0307] For the tape samples cut from the tape in each area A of the embodiments and comparative examples, and the tape samples cut from the tape in each area B, a TM-VSM5050-SMS model (manufactured by TAMAKAWA CO., LTD.) was used as a vibrating sample type fluxmeter, and the anisotropic magnetic field Hk was calculated by the above method. The results were 25 kOe in Example 21, 30 kOe in Example 23, and within the range of 10 to 20 kOe in the other embodiments and comparative examples.

[0308] In Table 1, "BaFe" in the "ferromagnetic powder" column indicates hexagonal barium ferrite powder having an average particle size (average plate diameter) of 21 nm.

[0309] In Table 1, "SrFe1" in the "Ferromagnetic Powder" column indicates hexagonal strontium ferrite powder produced as follows.

[0310] 1707 g of SrCO3, 687 g of H3BO3, 1120 g of Fe2O3, 45 g of Al(OH)3, 24 g of BaCO3, 13 g of CaCO3 and 235 g of Nd2O3 were weighed and mixed in a blender to obtain a raw material mixture.

[0311] The resulting raw material mixture was melted in a platinum crucible at a melting temperature of 1390°C. The melt was stirred while heating the melt outlet located at the bottom of the crucible. The melt was discharged into a rod shape at a rate of approximately 6 g / second. The discharged melt was then rapidly rolled using water-cooled twin rolls to produce an amorphous body.

[0312] 280 g of the prepared amorphous body was placed in an electric furnace, heated to 635° C. (crystallization temperature) at a heating rate of 3.5° C. / min, and maintained at the same temperature for 5 hours to precipitate (crystallize) hexagonal strontium ferrite particles.

[0313] Next, the crystals obtained above, containing hexagonal strontium ferrite particles, were coarsely pulverized in a mortar. 1000 g of zirconia beads with a particle size of 1 mm and 800 mL of a 1% aqueous acetic acid solution were added to a glass bottle and dispersed for 3 hours using a paint shaker. The resulting dispersion was then separated from the beads and placed in a stainless steel beaker. The dispersion was allowed to stand at 100°C for 3 hours to dissolve the glass component, then precipitated using a centrifugal separator and washed by repeated decantation. The mixture was then dried in a heating furnace at 110°C for 6 hours to obtain hexagonal strontium ferrite powder.

[0314] The average particle size of the hexagonal strontium ferrite powder obtained above is 18nm, and the activation volume is 902nm. 3 , the anisotropy constant Ku is 2.2×10 5 J / m 3 , mass magnetization σs is 49A·m 2 / kg.

[0315] 12 mg of a sample powder was collected from the hexagonal strontium ferrite powder obtained above, and the filtrate obtained by partially dissolving the sample powder under the above-mentioned dissolution conditions was subjected to elemental analysis using an ICP analyzer to determine the surface content of neodymium atoms.

[0316] Furthermore, 12 mg of a sample powder was collected from the hexagonal strontium ferrite powder obtained above, and the filtrate obtained by completely dissolving the sample powder under the above-mentioned exemplary dissolution conditions was subjected to elemental analysis using an ICP analyzer to determine the bulk content of neodymium atoms.

[0317] In the hexagonal strontium ferrite powder obtained above, the content of neodymium atoms relative to 100 atomic % of iron atoms (bulk content) was 2.9 atomic %. Furthermore, the surface content of neodymium atoms was 8.0 atomic %. The ratio of the surface content to the bulk content (surface content / bulk content) was 2.8, confirming that the neodymium atoms were concentrated in the surface layer of the particles.

[0318] CuKα radiation was scanned at a voltage of 45 kV and an intensity of 40 mA, and an X-ray diffraction pattern (X-ray diffraction analysis) was measured under the following conditions, thereby confirming that the powder obtained above exhibited a crystal structure of hexagonal ferrite. The powder obtained above exhibited a crystal structure of magnetoplumbite-type (M-type) hexagonal ferrite. Furthermore, the crystal phase detected by X-ray diffraction analysis was a magnetoplumbite-type single phase.

[0319] PANalytical X'Pert Pro diffractometer, PIXcel detector

[0320] Soller slits for incident and diffracted beams: 0.017 radians

[0321] Fixed angle of dispersion slit: 1 / 4 degree

[0322] Mask: 10mm

[0323] Scattering prevention slit: 1 / 4 degree

[0324] Measurement mode: continuous

[0325] Measurement time for each stage: 3 seconds

[0326] Measuring speed: 0.017 degrees per second

[0327] Measuring step: 0.05 degrees

[0328] In Table 1, "SrFe2" in the "Ferromagnetic Powder" column indicates hexagonal strontium ferrite powder prepared as follows.

[0329] 1725 g of SrCO 3 , 666 g of H 3 BO 3 , 1332 g of Fe 2 O 3 , 52 g of Al(OH) 3 , 34 g of CaCO 3 , and 141 g of BaCO 3 were weighed and mixed in a blender to obtain a raw material mixture.

[0330] The resulting raw material mixture was melted in a platinum crucible at a melting temperature of 1380°C. The melt was stirred while heating the melt outlet located at the bottom of the crucible. The melt was discharged into a rod shape at a rate of approximately 6 g / second. The discharged melt was then rapidly cooled by rolling using water-cooled twin rolls to produce an amorphous body.

[0331] 280 g of the obtained amorphous body was placed in an electric furnace, heated to 645° C. (crystallization temperature), and maintained at the same temperature for 5 hours to precipitate (crystallize) hexagonal strontium ferrite particles.

[0332] Next, the crystals obtained above, containing hexagonal strontium ferrite particles, were coarsely pulverized in a mortar. 1000 g of zirconia beads with a particle size of 1 mm and 800 mL of a 1% aqueous acetic acid solution were added to a glass bottle and dispersed for 3 hours using a paint shaker. The resulting dispersion was then separated from the beads and placed in a stainless steel beaker. The dispersion was allowed to stand at 100°C for 3 hours to dissolve the glass component, then precipitated using a centrifugal separator and washed by repeated decantation. The mixture was then dried in a heating furnace at 110°C for 6 hours to obtain hexagonal strontium ferrite powder.

[0333] The average particle size of the obtained hexagonal strontium ferrite powder is 19nm and the activation volume is 1102nm 3, the anisotropy constant Ku is 2.0×10 5 J / m 3 , mass magnetization σs is 50A·m 2 / kg.

[0334] In Table 1, "ε-iron oxide" in the "ferromagnetic powder" column indicates ε-iron oxide powder prepared as follows.

[0335] A solution obtained by dissolving 8.3 g of iron (III) nitrate nonahydrate, 1.3 g of gallium (III) nitrate octahydrate, 190 mg of cobalt (II) nitrate hexahydrate, 150 mg of titanium (IV) sulfate, and 1.5 g of polyvinyl pyrrolidone (PVP) in 90 g of pure water was stirred using a magnetic stirrer. 4.0 g of a 25% aqueous ammonia solution was added to the solution under the conditions of an atmospheric atmosphere and an atmospheric temperature of 25°C. The mixture was stirred for 2 hours while maintaining the atmospheric temperature at 25°C. A citric acid aqueous solution obtained by dissolving 1 g of citric acid in 9 g of pure water was added to the resulting solution and stirred for 1 hour. The powder precipitated after stirring was collected by centrifugation, washed with pure water, and dried in a heating furnace at a furnace temperature of 80°C.

[0336] 800g of pure water was added to the dried powder, and the powder was redispersed in water to obtain a dispersion. The obtained dispersion was heated to a liquid temperature of 50°C, and while stirring, 40g of a 25% ammonia solution was added dropwise. After stirring for 1 hour while maintaining a temperature of 50°C, 14mL of tetraethoxysilane (TEOS) was added dropwise and stirred for 24 hours. 50g of ammonium sulfate was added to the obtained reaction solution, and the precipitated powder was collected by centrifugation and washed with pure water. It was dried in a heating furnace at a furnace temperature of 80°C for 24 hours to obtain a precursor of a ferromagnetic powder.

[0337] The obtained precursor of the ferromagnetic powder was placed in a heating furnace at a furnace temperature of 1000° C. in an air atmosphere and subjected to a heat treatment for 4 hours.

[0338] The heat-treated ferromagnetic powder precursor was added to a 4 mol / L sodium hydroxide (NaOH) aqueous solution and stirred for 24 hours while maintaining the liquid temperature at 70° C., thereby removing silicic acid compounds as impurities from the heat-treated ferromagnetic powder precursor.

[0339] Then, the ferromagnetic powder after the silicic acid compound is removed is collected by centrifugal separation and washed with pure water to obtain a ferromagnetic powder.

[0340] The composition of the obtained ferromagnetic powder was confirmed by high frequency inductively coupled plasma-optical emission spectrometry (ICP-OES) and the result showed that the ferromagnetic powder contained Ga, Co and Ti substituted ε-iron oxide (ε-Ga 0.28 Co 0.05 Ti 0.05 Fe 1.62 Furthermore, an X-ray diffraction analysis was performed under the same conditions as those described above for the hexagonal strontium ferrite powder SrFe1. Based on the peaks of the X-ray diffraction pattern, it was confirmed that the obtained ferromagnetic powder had an ε-phase single-phase crystal structure (ε-iron oxide type crystal structure) that did not contain α-phase and γ-phase crystal structures.

[0341] The average particle size of the obtained ε-iron oxide powder is 12nm and the activation volume is 746nm 3 , the anisotropy constant Ku is 1.2×10 5 J / m 3 , mass magnetization σs is 16A·m 2 / kg.

[0342] The activation volume and anisotropy constant Ku of the hexagonal strontium ferrite powder and the ε-iron oxide powder are values obtained for each ferromagnetic powder using a vibrating sample type fluxmeter (manufactured by TOEI INDUSTRY CO., LTD.) by the above-mentioned method.

[0343] The mass magnetization σs is a value measured at a magnetic field intensity of 1194 kA / m (15 kOe) using a vibrating sample type fluxmeter (manufactured by TOEI INDUSTRY CO., LTD.).

[0344] [Evaluation of magnetic tape properties]

[0345] In the Examples and Comparative Examples, tape samples cut from the tape for Region A and tape samples cut from the tape for Region B can be used for various measurements. Therefore, based on the above description regarding the availability of tape for Region A and tape for Region B, the following physical property evaluations were conducted using tape samples cut from the tape for Region A and tape for Region B to obtain various physical property values for each of the magnetic tapes in the Examples and Comparative Examples.

[0346] <Magnetic Layer Surface Ra of Region A, Magnetic Layer Surface Ra of Region B>

[0347] A randomly selected 40 μm x 40 μm area on the magnetic layer surface of each magnetic tape sample was measured using an AFM (Nanoscope 4, manufactured by Veeco) in tapping mode to determine the centerline average surface roughness Ra. A BRUKER RTESP-300 probe was used, with a resolution of 512 pixels x 512 pixels and a scanning speed that allows one frame (512 pixels x 512 pixels) to be measured in 341 seconds.

[0348] <Ratio B Mag / A Mag Ratio B Mag / B Back >

[0349] Using each magnetic tape sample, the lubricant extraction amount A was calculated by the above method. Mag 、B Mag and B Back Calculate the ratio B based on the obtained value Mag / A Mag and ratio B Mag / B Back .

[0350] <Steel Ball Wear Volume Measured on the Magnetic Layer Surface in Region B>

[0351] Using a magnetic tape sample cut out from the magnetic tape in region B, the steel ball wear volume on the magnetic layer surface was measured by the above-mentioned method.

[0352] Regarding the various physical property values associated with the magnetic tapes of the Examples and Comparative Examples, when a single magnetic tape includes multiple regions A, the various physical property values of the multiple regions A can be considered to be the same as the values obtained using the aforementioned magnetic tape sample. When a single magnetic tape includes multiple regions B, the various physical property values of the multiple regions B can be considered to be the same as the values obtained using the aforementioned magnetic tape sample.

[0353] [Evaluation of electromagnetic conversion characteristics during repeated tape travel in a high-temperature environment]

[0354] In an environment with an ambient temperature of 60°C ± 1°C and a relative humidity of 10%, the tape reel after winding the tape as described above was installed on a 1 / 2-inch reel tester fixed with a recording and reproducing head mounted on an LTO8 tape drive manufactured by IBM. The relative speed between the head and the tape during recording and reproducing was set to 4 m / s, and data was recorded and reproduced.

[0355] Recording was performed at a linear recording density of 300 kfci, and the reproduction output during reproduction was measured to determine the signal-to-noise ratio (SNR) (ratio of reproduction output to noise). The unit kfci is the unit of linear recording density (not convertible to the SI unit system).

[0356] Calculate the difference between the SNR during recording and playback during the first run and the SNR during the 10,000th run. If the SNR during the 10,000th run is more than 5.0 dB lower than the SNR during the first run, the result is considered NG. SNR measurements are performed in area A.

[0357] In Comparative Examples 7 and 8, the magnetic head stuck to the surface of the magnetic layer during repeated tape travel, causing the tape to stop. Therefore, the SNR at the 10,000th tape run (referred to as "sticking stop" in Table 2) could not be determined. Therefore, Comparative Examples 7 and 8 were also judged as NG.

[0358] In cases other than the above, the judgment is OK.

[0359] The above results are shown in Table 1 (Table 1-1 to Table 1-3) and Table 2 (Table 2-1 to Table 2-3).

[0360]

[0361]

[0362]

[0363]

[0364]

[0365]

[0366] From the results shown in Table 2, it was confirmed that the magnetic tape of the example has little deterioration in electromagnetic conversion characteristics even when repeatedly traveling in a severe high-temperature environment.

[0367] Industrial applicability

[0368] One aspect of the present invention is useful in the technical field of magnetic tapes for data storage.

Claims

1. A magnetic tape comprising a non-magnetic support and a magnetic layer containing ferromagnetic powder, The non-magnetic support has a back coating layer containing non-magnetic powder on the surface side opposite to the surface side having the magnetic layer. The magnetic tape includes one or more regions A in a region across a portion of the length of the magnetic tape, and one or more regions B in a region across another portion of the length of the magnetic tape. The region A is a region where the center line average surface roughness Ra measured on the surface of the magnetic layer is less than 2.5 nm. The region B is a region where the center line average surface roughness Ra measured on the surface of the magnetic layer is 2.5 nm or more and 10.0 nm or less. When the amount of the component selected from the group consisting of fatty acids, fatty acid esters, and fatty acid amides extracted from the magnetic layer side of the region A and the region B per unit area is respectively represented by A Mag 、B Mag When the ratio B Mag / A Mag is 1.20 or more and 10.00 or less, and The amount of the component selected from the group consisting of fatty acids, fatty acid esters, and fatty acid amides extracted from the back coating layer side of the region B per unit area is defined as B. Back When the ratio B Mag / B Back 2.0 or above.

2. The magnetic tape according to claim 1, wherein The ratio B Mag / A Mag It is 1.80 or more and 5.00 or less.

3. The magnetic tape according to claim 1 or 2, wherein The ratio B Mag / B Back is 7.0 or above.

4. The magnetic tape according to claim 1 or 2, wherein The wear volume of the steel ball measured on the surface of the magnetic layer in the region B is 1×10 -7 mm 3 Above and 1×10 -4 mm 3 the following.

5. The magnetic tape according to claim 1 or 2, wherein When the area of the region A is set to S A And the area of the region B is set to S B When S B Relative to S A and S B The ratio of the sum of B / (S A +S B ))×100% is 0.15% or more and 50.00% or less.

6. The magnetic tape according to claim 1 or 2, wherein The magnetic tape includes two or more areas B.

7. The magnetic tape according to claim 1 or 2, wherein A non-magnetic layer containing non-magnetic powder is further provided between the non-magnetic support and the magnetic layer.

8. The magnetic tape according to claim 1 or 2, wherein A servo pattern is provided on at least a portion of the magnetic layer.

9. The magnetic tape according to claim 8, wherein The magnetic tape has the servo pattern on at least the magnetic layer of the region A.

10. The magnetic tape according to claim 9, wherein The magnetic tape also has the servo pattern on the magnetic layer of the region B.

11. A magnetic tape cassette comprising the magnetic tape according to any one of claims 1 to 10.

12. A magnetic tape device comprising a magnetic head and the magnetic tape according to any one of claims 1 to 10.

13. The magnetic tape device according to claim 12, wherein The area where the head records data is included at least in the area A.

14. The magnetic tape device according to claim 13, wherein The tape transport conditions in the area B are controlled based on the measurement results regarding the recording and reproduction quality of the data in the area A.

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