Magnetic tape, magnetic tape cassette and magnetic tape apparatus

Abstract

This invention provides a magnetic tape in which the fluorine concentration F, determined by ESCA at a photoelectron emission angle of 10°, is 0 atomic% or more and less than 0.5 atomic% on the surface of the magnetic layer. Before 3000 reciprocating slides relative to an LTO8 magnetic head at a head tilt angle of 15° in an environment of 35°C and 80% relative humidity, the dark area ratio on the surface of the magnetic layer before the reciprocating slide is greater than 0% and less than 0.30%. After the reciprocating slide, the dark area ratio on the surface of the magnetic layer after the reciprocating slide is 80% or more and less than 100%, when the dark area ratio before the reciprocating slide is 100%.

Description

Technical Field

[0001] This invention relates to a magnetic tape, a magnetic tape cassette, and a magnetic tape device. Background Technology

[0002] Magnetic recording media include tape-shaped magnetic recording media and disk-shaped magnetic recording media. Tape-shaped magnetic recording media, i.e. magnetic tape, are mainly used for data storage purposes such as data backup and archiving (see, for example, Patent Documents 1-4). Previous technical documents Patent documents

[0003] Patent Document 1: Japanese Patent Publication No. 2016-524774 Patent Document 2: US2019 / 0164573A1 Patent Document 3: Japanese Patent No. 6590104 Specification Patent Document 4: Japanese Patent Application Publication No. 7-320254 Summary of the Invention The technical problem to be solved by the invention

[0004] Data recording on magnetic tape is typically performed as follows: the magnetic tape travels within the tape drive, and a read / write head follows the data track of the tape to record data. This creates data tracks on the data track. Furthermore, when reproducing the recorded data, the magnetic tape travels within the tape drive, and the read / write head follows the data track to read the data recorded on the data track.

[0005] To improve the accuracy of the magnetic head following the data tape during recording and / or reproduction as described above, systems that utilize servo signals for head tracking (hereinafter referred to as "servo systems") have been put into practical use. Furthermore, the following method was proposed: Servo signals are used to acquire dimensional information (contraction, elongation, etc.) of the magnetic tape in the width direction during tape transport, and the angle at which the axis of the magnetic head module is tilted relative to the width direction of the magnetic tape (hereinafter also referred to as "head tilt angle") is changed based on the acquired dimensional information (see Patent Documents 1 and 2, for example, paragraphs 0059-0067 and 0084 of Patent Document 1). During recording or playback, if the magnetic head used for recording or playback deviates from the target track position due to the width deformation of the magnetic tape, overwriting of recorded data and poor playback can occur. As described above, the inventors believe that changing the head tilt angle is one method to suppress the occurrence of this phenomenon.

[0006] For example, assuming the head tilt angle is changed as described above, when recording and / or reproducing data by tilting the axis of the head module relative to the width direction of the magnetic tape (i.e., tilting the head), high tape travel stability is preferable. This is because high tape travel stability is thought to help, for example, further suppress the occurrence of the aforementioned phenomenon.

[0007] In recent years, magnetic tapes have sometimes been used in data centers where temperature and humidity are managed. On the other hand, in data centers, energy efficiency is required to reduce costs. To achieve energy efficiency, it is preferable to have more relaxed management conditions for the use of magnetic tapes in data centers than currently is, or even to eliminate the need for management altogether. However, if the management conditions of the usage environment are relaxed or not managed at all, it is foreseeable that the magnetic tape will be used in environments with high temperature and high humidity, for example. Therefore, it is preferable to have a magnetic tape with excellent tape transport stability when recording and / or reproducing data with a tilted magnetic head in high temperature and high humidity environments.

[0008] Furthermore, it is expected that magnetic tape will exhibit excellent electromagnetic conversion characteristics.

[0009] One aspect of the present invention aims to provide a magnetic tape that exhibits excellent electromagnetic conversion characteristics and excellent tape transport stability when the magnetic head is tilted for recording and / or reproduction under high temperature and high humidity conditions. means for solving technical problems

[0010] The inventors have conducted in-depth research to improve the electromagnetic conversion characteristics and the aforementioned belt transport stability. For example, Patent Document 4 (Japanese Patent Application Publication No. 7-320254) proposes improving the performance of magnetic tapes by using fluorinated lubricants. However, in recent years, for example in Europe, policies have been proposed to strengthen restrictions on fluorinated compounds such as PFOS (Perfluorooctanesulfonic Acid). Therefore, it is preferable to achieve improved electromagnetic conversion characteristics and the aforementioned tape-running stability of magnetic tapes without relying on fluorinated lubricants. In view of the above, the inventors have conducted further and in-depth research and have discovered that the electromagnetic conversion characteristics and the above-mentioned tape transport stability can be improved by using the following magnetic tape.

[0011] One aspect of the present invention is described below. (1) A magnetic tape having a non-magnetic support and a magnetic layer containing strongly magnetic powder, wherein, On the surface of the aforementioned magnetic layer, the fluorine concentration F, determined by X-ray photoelectron spectroscopy analysis at a photoelectron emission angle of 10°, is greater than 0 atomic% and less than 0.5 atomic%. Under conditions of 35°C and 80% relative humidity, before 3000 reciprocating slides relative to the LTO8 magnetic head at a tilt angle of 15°, the area ratio of the dark region on the surface of the aforementioned magnetic layer before the reciprocating slides is greater than 0% and less than 0.30%. The area ratio of the dark region after the reciprocating sliding, calculated from the surface of the magnetic layer, is between 80% and 100%, with the area ratio of the dark region before the reciprocating sliding being 100%. The aforementioned dark area area ratio is defined as follows: A is the total area of ​​multiple dark areas in the binarized image of the secondary electron image obtained by scanning electron microscopy of the surface of the magnetic layer; B is the area of ​​the entire field of view captured in the image; and B is defined as the area of ​​the dark area area ratio. Dark area area ratio = A / B × 100 To calculate. (2) The magnetic tape according to (1), wherein, The area ratio of the dark region before the above reciprocating sliding exceeds 0% and is less than 0.25%. (3) The magnetic tape according to (1) or (2), wherein, The area ratio of the dark region after the reciprocating sliding, calculated on the surface of the magnetic layer after the reciprocating sliding, is 86% or more and 100% or less when the area ratio of the dark region before the reciprocating sliding is 100%. (4) The magnetic tape according to any one of (1) to (3), wherein, The aforementioned magnetic layer also contains one or more non-magnetic powders. (5) The magnetic tape according to (4), wherein, The non-magnetic powder in the aforementioned magnetic layer contains carbon black. (6) The magnetic tape according to any one of (1) to (5), wherein, Between the aforementioned non-magnetic support and the aforementioned magnetic layer, there is also a non-magnetic layer containing non-magnetic powder. (7) The magnetic tape according to any one of (1) to (6), wherein, The non-magnetic support has a back coating containing non-magnetic powder on the side opposite to the side with the magnetic layer. (8) The magnetic tape according to any one of (1) to (7), wherein, The thickness of the strip is less than 5.3 μm. (9) The magnetic tape according to any one of (1) to (8), wherein, The vertical rectangularity ratio of the aforementioned magnetic tape is 0.65 or higher. (10) The magnetic tape according to (1), wherein, The area ratio of the dark region before the aforementioned reciprocating sliding is greater than 0% and less than 0.25%. The area ratio of the dark region after the reciprocating sliding, calculated from the surface of the magnetic layer, is between 86% and 100%, with the area ratio of the dark region before the reciprocating sliding being 100%. The aforementioned magnetic layer also contains one or more non-magnetic powders. The non-magnetic powder in the aforementioned magnetic layer contains carbon black. Between the aforementioned non-magnetic support and the aforementioned magnetic layer, there is also a non-magnetic layer containing non-magnetic powder. On the surface of the non-magnetic support opposite to the surface with the magnetic layer, there is also a back coating containing non-magnetic powder. The thickness of the band is less than 5.3 μm, and, The vertical rectangularity ratio of the aforementioned magnetic tape is 0.65 or higher. (11) A magnetic tape cassette comprising any one of (1) to (10) a magnetic tape. (12) A magnetic tape device comprising any one of (1) to (10) a magnetic tape. (13) The magnetic tape device according to (12) further includes a magnetic head. The aforementioned magnetic head has a module, the module including an array of elements, the array having multiple head elements between a pair of servo signal readout elements, and, During the tape travel within the tape device, the angle θ formed by the axis of the element array relative to the width direction of the tape is changed. Invention Effects

[0012] According to one aspect of the present invention, a magnetic tape exhibiting excellent electromagnetic conversion characteristics and superior tape transport stability during recording and / or reproduction with the magnetic head tilted in high temperature and high humidity environments can be provided. Furthermore, according to one aspect of the present invention, a magnetic tape cassette and a magnetic tape assembly comprising the aforementioned magnetic tape can be provided. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of an example of a module representing a magnetic head. Figure 2 This is an illustration of the relative positional relationship between the modules and the magnetic tape during its transport within the magnetic tape device. Figure 3 This is an explanatory diagram related to the change of angle θ during magnetic tape transport. Figure 4 This shows a configuration example for the data band and servo band. Figure 5The image shows an example of a servo pattern configuration for an LTO (Linear Tape-Open) Ultrium format tape. Figure 6 This is an explanatory diagram illustrating the method for measuring the angle θ during magnetic tape transport. Figure 7 This is a schematic diagram illustrating an example of a magnetic tape device. Detailed Implementation

[0014] [Cassette tape] One aspect of the present invention relates to a magnetic tape having a non-magnetic support and a magnetic layer containing strongly magnetic powder. The fluorine concentration F (hereinafter also referred to as "fluorine concentration F") determined by X-ray photoelectron spectroscopy analysis performed on the surface of the aforementioned magnetic layer at a photoelectron emission angle of 10° is greater than 0 atomic% and less than 0.5 atomic%. In this invention and specification, the "dark area ratio" is defined as the total area of ​​multiple dark areas in a binarized image of a secondary electron image obtained by scanning electron microscopy (SEM) of the surface of a magnetic layer, which is set as A, and the area of ​​the entire field of view of the above-mentioned image is set as B. It is calculated by the formula: Dark area ratio (unit: %) = A / B × 100. Under the above-mentioned magnetic tape temperature of 35°C and relative humidity of 80%, the dark area ratio (hereinafter also referred to as "dark area ratio before reciprocating sliding") on the surface of the magnetic layer before 3000 reciprocating sliding with the magnetic head tilted at a 15° angle relative to the LTO (Linear Tape-Open) 8 magnetic head is greater than 0% and less than 0.30%. Furthermore, the dark area ratio (hereinafter also simply referred to as "dark area ratio after reciprocating sliding") calculated on the surface of the magnetic layer after the reciprocating sliding of the magnetic tape is 80% or more and 100% or less when the dark area ratio before reciprocating sliding is 100%. Hereinafter, this percentage will also be referred to as "dark area ratio maintenance rate after reciprocating sliding".

[0015] <Head tilt angle> In the following explanation of the head tilt angle, we will first describe the "LTO8 head," which is related to the measurement of the dark area ratio after reciprocating sliding, as will be discussed later. Furthermore, we will explain the reasons why it is believed that tilting the axis of the head module relative to the width direction of the tape during tape transport can suppress the phenomena that occur during recording or playback. In this invention and specification, "LTO8 head" refers to a magnetic head conforming to the LTO8 standard. As an LTO8 head, a head mounted on an LTO8 drive can be removed for use, or a commercially available head for LTO8 drives can be used. Here, LTO8 drive refers to a drive (magnetic tape device) conforming to the LTO8 standard. LTO9 drive refers to a drive conforming to the LTO9 standard, and this applies to other generations of drives as well. Furthermore, when multiple magnetic tapes to be tested are slid back and forth relative to an LTO8 head at a head tilt angle of 15°, it is assumed that a new (i.e., unused) LTO8 head is used for each tape test. Additionally, considering that the LTO8 standard is capable of handling the high-density recording of recent years, and LTO8 is used as the head, the aforementioned magnetic tape is not limited to tapes used in LTO8 drives. The aforementioned magnetic tapes can record and / or reproduce data in LTO8 drives, LTO9 drives or next-generation drives, or even LTO7 drives and drives prior to LTO8.

[0016] The LTO8 head has three modules, each comprising an array of head elements between a pair of servo signal readout elements. These three modules are configured in a “recording module - playback module - recording module” configuration (total number of modules: 3) within the LTO8 head.

[0017] Each module includes an array of 32 magnetic head elements between a pair of servo signal readout elements, i.e., the arrangement of the elements. A module with recording elements as magnetic head elements is a recording module for recording data onto magnetic tape. A module with playback elements as magnetic head elements is a playback module for reproducing data recorded on magnetic tape. In the LTO8 head, the three modules are configured such that the axes of the element arrays of each module are oriented parallel to each other. This "parallelism" does not necessarily mean parallelism in a strict sense, but includes a range of errors generally permissible in the art to which this invention pertains. For example, the range of errors can represent strict parallelism within a range of less than ±10°.

[0018] The head tilt angle used to determine the area ratio of the dark region after 3000 reciprocating slides is set to the head tilt angle in the reproduction module of the LTO8 head.

[0019] In each element array, a pair of servo signal readout elements and multiple magnetic head elements (i.e., recording elements or playback elements) are arranged in a straight line with spacing. Here, "arranged in a straight line" means that each magnetic head element is arranged on a straight line connecting the central portion of one servo signal readout element and the central portion of another servo signal readout element. Furthermore, the "axis of the element array" in this invention and this specification refers to the straight line connecting the central portion of one servo signal readout element and the central portion of another servo signal readout element.

[0020] Next, the structure of the module will be further described with reference to the accompanying drawings. However, the embodiments shown in the drawings are merely examples and do not limit the present invention.

[0021] Figure 1 This is a schematic diagram of an example of a module representing a magnetic head. Figure 1 The module shown has multiple head elements between a pair of servo signal readout elements (servo signal readout elements 1 and 2). These head elements are also referred to as "channels." "Ch" in the diagram is an abbreviation for Channel. Figure 1 The module shown has a total of 32 head elements, from Ch0 to Ch31. The LTO8 head reproduction module has a total of 32 reproduction elements, from Ch0 to Ch31.

[0022] Figure 1 In this context, "L" represents the distance between a pair of servo signal reading elements, that is, the distance between one servo signal reading element and another. Figure 1 In the module shown, "L" represents the distance between servo signal reading element 1 and servo signal reading element 2. More specifically, it is the distance between the central portion of servo signal reading element 1 and the central portion of servo signal reading element 2. This distance can be measured, for example, using an optical microscope.

[0023] Figure 2 This is an illustration of the relative positional relationship between the modules and the magnetic tape during its transport within the magnetic tape device. Figure 2 In the diagram, dashed line A represents the width direction of the magnetic tape. Dashed line B represents the axis of the element array. Angle θ can be described as the tilt angle of the magnetic head during tape transport, and is the angle between dashed lines A and B. When angle θ is 0° during tape transport, the distance in the width direction of the magnetic tape between one servo signal read element and another in the element array (hereinafter also referred to as the "effective distance between servo signal read elements") is "L". Conversely, when angle θ exceeds 0°, the effective distance between servo signal read elements is "Lcosθ", where Lcosθ is less than L. That is, "Lcosθ < L".

[0024] As described above, during recording or playback, if the magnetic head used for recording or playback deviates from the target track position due to the deformation of the magnetic tape width, overwriting of recorded data or poor playback may occur. For example, if the width of the magnetic tape shrinks or stretches, the magnetic head element that should record or reproduce data at the target track position may record or reproduce data at a different track position. Furthermore, if the width of the magnetic tape stretches, the effective distance between the servo signal readout elements will become shorter than the interval between the two adjacent servo tapes sandwiching the data tape (also referred to as "servo tape interval" or "servo tape spacing." More specifically, it is the distance between the two servo tapes in the width direction of the magnetic tape). This may result in data not being recorded or reproduced near the edge of the magnetic tape. In contrast, if the element array is tilted at an angle θ greater than 0°, the effective distance between the servo signal readout elements becomes "Lcosθ", as described above. The larger the value of θ, the smaller the value of Lcosθ; conversely, the smaller the value of θ, the larger the value of Lcosθ. Therefore, by changing the value of θ according to the degree of dimensional change (i.e., shrinkage or elongation) in the width direction of the magnetic tape, the effective distance between the servo signal readout elements can be made close to or consistent with the spacing of the servo tape. This prevents overwriting of recorded data and poor reproduction due to the magnetic head shifting from the target track position due to tape width deformation during recording or reproduction, or reduces the frequency of such occurrences.

[0025] Figure 3 This is an explanatory diagram related to the change of angle θ during magnetic tape transport. θ is the angle θ at the start of the tape movement. initial For example, it can be set to above 0° or greater than 0°. Figure 3 In the middle, the diagram shows the state of the module when the conveyor belt starts moving. Figure 3 In the middle, the right figure shows that the angle θ is set to be greater than θ. initial Angle of angle θ c The module's status at that time. The effective distance Lcosθ between servo signal reading elements. c Become less than Lcosθ when the tape starts to travel. initial The value of this angle is preferred when the width of the magnetic tape contracts during tape transport. on the other hand, Figure 3 In the middle, the left figure shows that the angle θ is set to be less than θ. initial Angle of angle θ e The module's status at that time. The effective distance Lcosθ between servo signal reading elements. eBecome greater than Lcosθ when the tape starts to travel. initial The value of this angle is preferred when the width of the magnetic tape expands during tape travel.

[0026] As explained above, changing the tilt angle of the magnetic head during magnetic tape transport can help prevent data from being overwritten or poorly reproduced due to the magnetic head shifting from the target track position because of the width deformation of the magnetic tape. Alternatively, it can help reduce the frequency of such occurrences. On the other hand, data recording and reproduction of magnetic tape are typically performed by sliding the magnetic head against the magnetic layer surface as the tape is moved. The inventors believe that if the magnetic head is tilted during recording and / or reproduction, the contact state between the magnetic head and the magnetic layer surface becomes unstable, which could be a major cause of decreased tape movement stability. Based on the above speculation, the inventors conducted repeated and in-depth research. As a result, the inventors newly discovered that magnetic tapes with a dark area ratio maintenance rate of 80% or more and 100% or less after the reciprocating sliding described later exhibit excellent tape-running stability when recording and / or reproducing data by tilting the magnetic head in a high-temperature and high-humidity environment. Furthermore, the temperature and humidity of the environment in which the reciprocating sliding described later is used as illustrative values ​​for a high-temperature and high-humidity environment. Therefore, the environment for recording and reproducing data on the aforementioned magnetic tape is not limited to this temperature and humidity. Regarding the magnetic head tilt angle during the reciprocating sliding described later, it is also used as an illustrative value for an angle that can be used when changing the magnetic head tilt angle during tape transport to record and / or reproduce data. Therefore, the magnetic head tilt angle for recording and reproducing data on the aforementioned magnetic tape is not limited to the aforementioned angle. Furthermore, the present invention is not limited to the inventors' speculations described in this specification. In this specification, the tape transport stability during data recording and / or reproduction when the magnetic head is tilted during tape transport in a high-temperature and high-humidity environment is also referred to as "tape transport stability". Furthermore, a high-temperature and high-humidity environment can be, for example, an environment with a temperature of approximately 30°C to 50°C. As for the relative humidity, the humidity of this environment can be, for example, approximately 70% to 100%. In this invention and this specification, the temperature and humidity described regarding the environment refer to the ambient temperature and relative humidity of that environment.

[0027] <Dark area percentage before reciprocating slide, and dark area percentage maintenance rate after reciprocating slide> (Slide back and forth) In this invention and this specification, the magnetic tape of the test object is subjected to 3000 reciprocating slides relative to the LTO8 magnetic head at a magnetic head tilt angle of 15° in an environment of 35° and 80% relative humidity by the following method. Furthermore, the head tilt angle (15°) refers to the angle between the axis of the element array of the LTO8 head's reproduction module and the direction orthogonal to the sliding direction during the first outward stroke of the following 3000 reciprocating slides. This angle is used to... Figure 2 In this context, A is referred to as the direction orthogonal to the sliding direction, and the angle θ between A and B is defined. During 3000 reciprocating slides, the tilt angle of the magnetic head remains constant. The magnetic tape to be measured is placed on two parallel cylindrical guide rollers, each 1 inch in diameter (1 inch = 2.54 cm) spaced apart, with the surface of the tape opposite to the magnetic layer surface—for example, the back-coated surface if a back coating is present, and the non-magnetic support surface if no back coating is present—in contact with the guide rollers. Before measurement, to allow the magnetic tape to acclimatize to the measurement environment (temperature 35°C, relative humidity 80%), it is left to stand for at least 24 hours with the tape placed on the guide rollers as described above. In a randomly selected portion of the magnetic tape used for testing, the head tilt angle was set to 15°, and the magnetic layer surface of the tape was slid relative to the LTO8 head for 3000 reciprocating slides. Regarding the testing conditions, the wrap angle θ was set to 6°, and the sliding speed was set to 4 m / s. The tension applied along the length of the tape during sliding was set to 0.55 N (Newtons). The sliding distances for both the outward and return journeys were set to 20 m. In this invention and this specification, "the surface of the magnetic layer" has the same meaning as the magnetic layer side surface of the magnetic tape.

[0028] (Area ratio of dark areas) In this invention and this specification, the details of “A” and “B” used to calculate the area ratio of the dark area using the formula described above are as follows. In this invention and this specification, the scanning electron microscope used to determine the area of ​​the dark region is a field emission scanning electron microscope (FE-SEM). For example, the FE-SEM S4800 manufactured by Hitachi, Ltd. can be used, and this FE-SEM was used in the measurements of the examples and comparative examples described below. Furthermore, the surface of the magnetic layer was not coated before the SEM image was taken. Select an un-photographed area on the surface of the magnetic layer to perform the photographing. The SEM images captured are secondary electron images. In this invention and this specification, the aforementioned dark areas are determined by the following method. Secondary electron images of the magnetic layer surface of the magnetic tape being measured were captured using a scanning electron microscope (FE-SEM). The imaging conditions were set as follows: accelerating voltage 2 kV, working distance 5 mm, and magnification 9,000x. Contrast was set to -1 and brightness to +4. In the unimaged areas of the magnetic layer surface, AutoBrightness Contrast (ABC) was applied to determine contrast and brightness. During imaging, the unimaged areas of the magnetic layer surface were selected, and focus was adjusted under the above conditions to capture secondary electron images. Parts displaying dimensions (micrometer scales, crosshairs, etc.) were removed from the captured images to obtain a secondary electron image with 960 x 1280 pixels. The above operation was performed 10 times on randomly selected locations on the magnetic layer surface of the magnetic tape being measured. Therefore, 10 secondary electron images were acquired on the magnetic layer surface after 3000 reciprocating slides at the aforementioned sliding speed of 4 m / s and on the magnetic layer surface without such reciprocating slides. The acquired secondary electronic image is then read into image processing software and binarized according to the following steps. Image analysis software, such as the free software ImageJ, can be used. Through binarization, the image is separated into bright areas (white parts) and dark areas (black parts). The threshold used for binarizing the secondary electron images acquired above is set with a lower limit of 0 gray levels and an upper limit of 82 gray levels. Binarization is performed using these two thresholds. After binarization, noise removal is performed using image analysis software. Noise removal can be performed, for example, by using the Despeckle noise removal process in ImageJ image analysis software. For the binarized image thus obtained, the areas of multiple dark regions (i.e., black parts) are summed using image analysis software. This summed area is set as the total area A of the dark regions. In determining the dark regions, dark regions that are only partially contained within the binarized image and whose remaining parts are located outside the binarized image are not included in the dark regions of the total area calculation. For both the magnetic layer surface subjected to 3000 reciprocating slides at the aforementioned sliding speed of 4 m / s and the magnetic layer surface not subjected to such reciprocating slides, the above process was performed on 10 binarized images captured using the above method. For each of the 10 images, the dark area ratio was calculated using the following formula, based on the total area A of the dark areas obtained above and the area B of the entire field of view (i.e., the total area of ​​the image at 9000x magnification). Dark area area ratio (unit: %) = A / B × 100 The arithmetic mean of the dark area ratios of 10 images obtained from a magnetic layer surface subjected to 3000 reciprocating slides at the aforementioned sliding speed of 4 m / s is defined as the "dark area ratio after reciprocating slides". The arithmetic mean of the dark area ratios of 10 images obtained from a magnetic layer surface without such reciprocating slides is defined as the "dark area ratio before reciprocating slides". The "dark area ratio maintenance rate after reciprocating slides" is a value expressed as a percentage of the dark area ratio after reciprocating slides, with the dark area ratio before reciprocating slides set to 100%, and is calculated using the following formula. Maintenance rate of dark area percentage after back-and-forth sliding (unit: %) = Dark area percentage after back-and-forth sliding / Dark area percentage before back-and-forth sliding × 100

[0029] (Area ratio of the dark area before reciprocating sliding) The dark area fraction of the aforementioned magnetic tape before reciprocating sliding is greater than 0% and less than 0.30%. A dark area fraction of less than 0.30% before reciprocating sliding contributes to improved electromagnetic conversion characteristics. The inventors speculate on this as follows. The magnetic layer is typically formed using a magnetic layer forming composition that includes one or more non-magnetic powders in addition to a strongly magnetic powder. Examples of such non-magnetic powders include non-magnetic powders (hereinafter also referred to as "fillers") that are included in the magnetic layer to form appropriate protrusions on the surface of the magnetic layer in order to control frictional characteristics. The inventors believe that the dark region determined by the above method is the region where the filler exists on the surface of the magnetic layer. Therefore, the inventors speculate that the dark region area ratio can be considered as the filler occupancy rate on the surface of the magnetic layer. In the magnetic layer surface without reciprocating sliding, magnetic layers with a dark region area ratio (i.e., dark region area ratio before reciprocating sliding) of 0.30% or less exhibit excellent frictional characteristics, and are therefore considered to be able to exhibit excellent electromagnetic conversion characteristics. From the viewpoint of further improving electromagnetic conversion characteristics, the dark region area ratio before reciprocating sliding is preferably 0.25% or less, more preferably 0.20% or less. The area fraction of the dark region before the reciprocating slide of the aforementioned magnetic tape exceeds 0%, and can be 0.01% or more, 0.05% or more, 0.10% or more, or 0.15% or more. From the viewpoint of improving electromagnetic conversion characteristics, a low area fraction of the dark region before the reciprocating slide is preferred.

[0030] (Maintenance of dark area ratio after repeated sliding) The dark area ratio is maintained at 80% or more and 100% or less after the reciprocating slide of the magnetic tape. It is believed that a higher dark area ratio maintenance rate after reciprocating slide indicates less change in the state of the filler material on the magnetic layer surface during the reciprocating slide. Furthermore, the inventors believe that less change in the state of the filler material on the magnetic layer surface during reciprocating slide helps improve tape transport stability when recording and / or reproducing data using a tilted magnetic head in high-temperature and high-humidity environments. From the viewpoint of improving tape transport stability, the dark area ratio maintenance rate after reciprocating slide is 80% or more, preferably 82% or more, more preferably 84% or more, further preferably 86% or more, even more preferably 88% or more, and still more preferably 90% or more. After the tape slides back and forth, the area ratio of the dark area is maintained at less than 100%, or it can be 100%, or less than 100%, less than 98%, less than 96%, or less than 94%.

[0031] The control methods for the dark area ratio before and after the reciprocating sliding motion will be described later.

[0032] <Fluorine concentration F> The "fluorine concentration F" in this invention and specification is the fluorine concentration determined by X-ray photoelectron spectroscopy analysis performed on the surface of the magnetic layer at a photoelectron emission angle of 10°. X-ray photoelectron spectroscopy (XPS) is an analytical method commonly referred to as ESCA (Electron Spectroscopy for Chemical Analysis) or XPS (X-ray Photoelectron Spectroscopy). Hereinafter, X-ray photoelectron spectroscopy will also be referred to as ESCA. ESCA is an analytical method that utilizes the principle that photoelectrons are released when X-rays are irradiated onto the surface of a sample. It is widely used as an analytical method for the surface layer of a sample. According to ESCA, qualitative and quantitative analysis can be performed using the X-ray photoelectron spectrum obtained by analyzing the surface of the sample. The depth from the sample surface to the analysis position (hereinafter also referred to as "detection depth") and the photoelectron take-off angle are generally related by the following formula: Detection depth ≈ Mean free path of electrons × 3 × sinθ. In this formula, the detection depth is the depth at which 95% of the photoelectrons constituting the X-ray photoelectron spectrum are generated, and θ is the photoelectron take-off angle. As shown in the above formula, the smaller the photoelectron emission angle, the shallower the depth from the sample surface can be analyzed; conversely, the larger the photoelectron emission angle, the deeper the depth can be analyzed. Therefore, in ESCA analysis at a photoelectron emission angle of 10°, the polar surface region, typically extending from the sample surface to a depth of several nm, is usually the analysis location. Thus, based on ESCA analysis performed on the surface of the magnetic layer of the magnetic tape at a photoelectron emission angle of 10°, compositional analysis of the polar surface region extending from the surface of the magnetic layer to a depth of several nm can be performed. The aforementioned fluorine concentration F refers to the proportion of fluorine atoms F relative to 100 atomic% of the total (atomic standard) of all elements detected by qualitative analysis using ESCA. The analysis area was defined as a 300 μm × 700 μm region at any location on the surface of the magnetic layer of the magnetic tape. Qualitative analysis was performed using a wide scan measurement using ESCA (pass energy: 160 eV, scan range: 0–1200 eV, energy resolution: 1 eV / step). Next, narrow-spectrum scan measurements were performed (pass energy: 80 eV, energy resolution: 0.1 eV, scan range: set for each element with the entire measured spectrum). The spectra of all elements detected by qualitative analysis were obtained using narrow-spectrum scan measurements (pass energy: 80 eV, energy resolution: 0.1 eV, scan range: set for each element with the entire measured spectrum). Based on the peak areas of each spectrum obtained in this way, the atomic concentration (unit: atomic %) of each element relative to all elements detected by qualitative analysis was calculated. Here, the fluorine concentration was also calculated based on the peak surface area of ​​the F1s spectrum. The test sample is cut from the magnetic tape of the test object. For the cut test sample, the above operation is performed three times at randomly selected different positions on the surface of the magnetic layer, and the fluorine concentration is calculated for each position. The arithmetic mean of the calculated values ​​is taken as the fluorine concentration F of the magnetic tape of the test object. The specific method of the above operation is shown in the Examples section described later.

[0033] The fluorine concentration F of the aforementioned magnetic tape is 0 atomic% or more and less than 0.5 atomic%. The fluorine concentration F can be 0.4 atomic% or less, 0.3 atomic% or less, 0.2 atomic% or less, or 0.1 atomic% or less, or even 0 atomic%. Magnetic tapes with a fluorine concentration F within the aforementioned range can be obtained by manufacturing the tape without using fluorine-based lubricants or other fluorine-based compounds, or by reducing the amount of fluorine-based compounds used. From the viewpoint of addressing future restrictions on fluorine-based compounds, a lower fluorine concentration F is preferred. The aforementioned magnetic tape has a fluorine concentration F within the aforementioned range, but exhibits excellent electromagnetic conversion characteristics and excellent tape-running stability by maintaining the dark area area ratio before and after reciprocating sliding within the range described above.

[0034] The following is a more detailed explanation of the aforementioned magnetic tape.

[0035] <Magnetic Layer> (Strongly magnetic powder) As the strongly magnetic powder contained in the magnetic layer, one or more strongly magnetic powders known for use in the magnetic layers of various magnetic recording media can be used in combination. From the viewpoint of improving recording density, it is preferable to use a strongly magnetic powder with a small average particle size. Considering this, the average particle size of the strongly magnetic powder is preferably 50 nm or less, more preferably 45 nm or less, even more preferably 40 nm or less, even more preferably 35 nm or less, even more preferably 30 nm or less, even more preferably 25 nm or less, and still even more preferably 20 nm or less. On the other hand, from the viewpoint of magnetization stability, the average particle size of the strongly magnetic powder is preferably 5 nm or more, more preferably 8 nm or more, even more preferably 10 nm or more, even more preferably 15 nm or more, and even more preferably 20 nm or more.

[0036] Hexagonal ferrite powder Hexagonal ferrite powder is a preferred specific example of a strongly magnetic powder. For details regarding hexagonal ferrite powder, see, for example, paragraphs 0012-0030 of Japanese Patent Application Publication No. 2011-225417, paragraphs 0134-0136 of Japanese Patent Application Publication No. 2011-216149, paragraphs 0013-0030 of Japanese Patent Application Publication No. 2012-204726, and paragraphs 0029-0084 of Japanese Patent Application Publication No. 2015-127985.

[0037] In this invention and specification, "hexagonal ferrite powder" refers to a strongly magnetic powder whose crystal structure as a hexagonal ferrite can be detected as the main phase by X-ray diffraction analysis. The main phase refers to the structure to which the highest intensity diffraction peak in the X-ray diffraction spectrum obtained by X-ray diffraction analysis belongs. For example, if the highest intensity diffraction peak in the X-ray diffraction spectrum obtained by X-ray diffraction analysis belongs to the crystal structure of a hexagonal ferrite, then the crystal structure of the hexagonal ferrite is determined to be the main phase. If only a single structure is detected by X-ray diffraction analysis, that detected structure is considered the main phase. The crystal structure of a hexagonal ferrite contains at least iron atoms, divalent metal atoms, and oxygen atoms as constituent atoms. Divalent metal atoms refer to metal atoms that can become divalent cations as ions, such as strontium atoms, barium atoms, calcium atoms, and lead atoms. In this invention and specification, hexagonal strontium ferrite powder refers to powder in which the predominant divalent metal atom is strontium, and hexagonal barium ferrite powder refers to powder in which the predominant divalent metal atom is barium. The predominant divalent metal atom refers to the divalent metal atom that occupies the largest proportion of the divalent metal atoms in the powder, based on an atomic percentage. Rare earth atoms are not included in the aforementioned divalent metal atoms. In this invention and specification, "rare earth atoms" are selected from the group consisting of scandium (Sc), yttrium (Y), and lanthanides. The lanthanide atoms are selected from the group consisting of lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu).

[0038] The following is a more detailed description of hexagonal strontium ferrite powder as one type of hexagonal ferrite powder.

[0039] The preferred activation volume of hexagonal strontium ferrite powder is 2500 nm. 3 The preferred option below is 2300nm. 3 The following is a further preferred option: 2000nm 3 Below. On the other hand, from the viewpoint of magnetization stability, the activation volume of the hexagonal strontium ferrite powder is preferably, for example, 800 nm. 3 The above, preferably 1000nm 3 The above is further optimized to 1200nm. 3 The same applies to the activation volume of hexagonal barium ferrite powder.

[0040] "Activation volume" is a unit of magnetization reversal and an indicator of the magnetic strength of a particle. The activation volume and anisotropy constant Ku described in this invention and specification were determined using a vibrating sample type magnetometer at a magnetic field scanning speed of 3 minutes and 30 minutes (measurement temperature: 23℃±1℃) using the coercivity Hc measuring unit, and calculated according to the following relationship between Hc and activation volume V. Furthermore, regarding the unit of the anisotropy constant Ku, 1 erg / cc = 1.0 × 10⁻⁶. -1 J / m 3 . Hc=2Ku / Ms{1-[(kT / KuV)ln(At / 0.693)] 1 / 2} In the above formula, Ku: anisotropy constant (unit: J / m) 3 Ms: saturation magnetization (kA / m), k: Boltzmann constant, T: absolute temperature (K), V: activation volume (cm³) 3 A: Spin precession frequency (unit: s) -1 ), t: magnetic field reversal time (unit: s)

[0041] An anisotropy constant Ku can be cited as an indicator of reducing thermal fluctuations (in other words, improving thermal stability). Hexagonal strontium ferrite powder preferably has a Ku value of 1.8 × 10⁻⁶. 5 J / m 3 The above-mentioned Ku, more preferably, can have 2.0 × 10 5 J / m 3 The above refers to the Ku value. Furthermore, the Ku value of hexagonal strontium ferrite powder can, for example, be 2.5 × 10⁻⁶. 5 J / m 3 However, a higher Ku value indicates higher thermal stability and is therefore preferred; it is not limited to the values ​​exemplified above.

[0042] Hexagonal strontium ferrite powder may or may not contain rare earth atoms. When hexagonal strontium ferrite powder contains rare earth atoms, it is preferable that the rare earth atoms are contained at a content of 0.5 to 5.0 atomic% (bulk content) relative to 100 atomic% of iron atoms. In one embodiment, the hexagonal strontium ferrite powder containing rare earth atoms may exhibit rare earth atom segregation on the surface layer. In this invention and this specification, "rare earth atom surface layer bias" refers to the ratio of the rare earth atom content relative to 100 atomic percent of iron atoms in the solution obtained by partially dissolving hexagonal strontium ferrite powder with acid (hereinafter, "rare earth atom surface layer content" or rare earth atoms are simply referred to as "surface layer content") to the rare earth atom content relative to 100 atomic percent of iron atoms in the solution obtained by completely dissolving hexagonal strontium ferrite powder with acid (hereinafter, "rare earth atom bulk content" or rare earth atoms are simply referred to as "bulk content"). The ratio of rare earth atom surface layer content / rare earth atom bulk content is greater than 1.0. The meaning of the rare earth atom content of hexagonal strontium ferrite powder, as described later, is the same as the meaning of the rare earth atom bulk content. In contrast, since partial dissolution with acid dissolves only the surface portion of the particles constituting the hexagonal strontium ferrite powder, the rare earth atom content in the solution obtained through partial dissolution refers to the rare earth atom content in the surface portion of the particles constituting the hexagonal strontium ferrite powder. A rare earth atom surface portion content that satisfies the ratio "rare earth atom surface portion content / rare earth atom bulk content > 1.0" indicates that rare earth atoms are concentrated in the surface portion (i.e., present in greater quantities than in the interior) of the particles constituting the hexagonal strontium ferrite powder. In this invention and this specification, the surface portion refers to a region extending from the surface of the particles constituting the hexagonal strontium ferrite powder toward the interior.

[0043] When hexagonal strontium ferrite powder contains rare earth atoms, the rare earth atom content (bulk content) relative to 100 atomic% of iron atoms is preferably in the range of 0.5 to 5.0 atomic%. It is believed that containing rare earth atoms at a bulk content within the above range, with the rare earth atoms clustered in the surface layer of the particles constituting the hexagonal strontium ferrite powder, helps to suppress the decrease in reproduction output during repeated reproduction. This is presumably because including rare earth atoms at a bulk content within the above range and with the rare earth atoms clustered in the surface layer of the particles constituting the hexagonal strontium ferrite powder increases the anisotropy constant Ku. A higher value of the anisotropy constant Ku further suppresses the phenomenon known as thermal fluctuation (in other words, it improves thermal stability). By suppressing thermal fluctuations, the decrease in reproduction output during repeated reproduction can be suppressed. It is speculated that the segregation of rare earth atoms in the surface layer of hexagonal strontium ferrite powder particles helps to stabilize the spin of iron (Fe) sites in the lattice of the surface layer, thereby increasing the anisotropy constant Ku. Furthermore, it is speculated that using hexagonal strontium ferrite powder with rare-earth atom segregation on the surface as a strong magnetic powder in the magnetic layer also helps to suppress wear of the magnetic layer surface due to slippage with the magnetic head. That is, it is speculated that hexagonal strontium ferrite powder with rare-earth atom segregation on the surface can also help improve the tape travel durability. This is speculated because the segregation of rare-earth atoms on the surface of the particles constituting the hexagonal strontium ferrite powder helps to enhance the interaction between the particle surface and the organic matter (e.g., binders and / or additives) contained in the magnetic layer, resulting in increased strength of the magnetic layer. From the viewpoint of further suppressing the reduction in reproduction output during repeated reproduction and / or further improving the durability of the conveyor belt, the rare earth atom content (bulk content) is more preferably in the range of 0.5 to 4.5 atomic%, more preferably in the range of 1.0 to 4.5 atomic%, and even more preferably in the range of 1.5 to 4.5 atomic%.

[0044] The above-mentioned bulk content rate is the content rate obtained by completely dissolving the hexagonal strontium ferrite powder. Furthermore, unless otherwise specified in this invention and specification, the content rate for atoms refers to the bulk content rate obtained by completely dissolving the hexagonal strontium ferrite powder. As rare earth atoms, the hexagonal strontium ferrite powder containing rare earth atoms may contain only one type of rare earth atom or may contain two or more types of rare earth atoms. The above-mentioned bulk content rate when containing two or more rare earth atoms is calculated based on the sum of the two or more rare earth atoms. This also applies to other components in this invention and specification. That is, unless otherwise specified, a component may use only one type or two or more types. The content or content rate when using two or more types refers to the sum of the two or more types.

[0045] When the hexagonal strontium ferrite powder contains rare earth atoms, the rare earth atoms contained can be any one or more of the rare earth atoms. From the viewpoint of further suppressing the reduction of reproduction output during repeated reproduction, preferred rare earth atoms include neodymium atoms, samarium atoms, yttrium atoms, and dysprosium atoms, more preferably neodymium atoms, samarium atoms, and yttrium atoms, and even more preferably neodymium atoms.

[0046] In hexagonal strontium ferrite powder exhibiting rare-earth atom segregation on the surface, the rare-earth atoms only need to be segregated on the surface of the particles constituting the hexagonal strontium ferrite powder, and the degree of segregation is not limited. For example, regarding hexagonal strontium ferrite powder exhibiting rare-earth atom segregation on the surface, 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 can be 1.5 or more. A "surface content / bulk content" greater than 1.0 indicates that rare-earth atoms are segregated on the surface of the particles constituting the hexagonal strontium ferrite powder (i.e., their presence is greater than that in the interior). Furthermore, the ratio of the surface portion content of rare earth atoms obtained by partial dissolution under the dissolution conditions described later to the bulk content of rare earth atoms obtained by complete dissolution under the dissolution conditions described later, "surface portion content / bulk content", can be, for example, 10.0 or less, 9.0 or less, 8.0 or less, 7.0 or less, 6.0 or less, 5.0 or less, or 4.0 or less. However, in hexagonal strontium ferrite powder with rare earth atom surface portion segregation, the rare earth atoms only need to be segregated in the surface portion of the particles constituting the hexagonal strontium ferrite powder, and the above-mentioned "surface portion content / bulk content" is not limited to the upper or lower limit shown.

[0047] The partial and complete dissolution of hexagonal strontium ferrite powder will be described below. For hexagonal strontium ferrite powder existing in powder form, the partially and completely dissolved sample powders are collected from the same batch of powder. On the other hand, for hexagonal strontium ferrite powder contained in the magnetic layer of a magnetic tape, a portion of the hexagonal strontium ferrite powder removed from the magnetic layer is used for partial dissolution, and another portion is used for complete dissolution. The removal of the hexagonal strontium ferrite powder from the magnetic layer can be performed, for example, by the method described in paragraph 0032 of Japanese Patent Application Publication No. 2015-91747. The aforementioned partial dissolution refers to the point at which dissolution is complete, to the point where it is visually identifiable that hexagonal strontium ferrite powder remains in the liquid. For example, partial dissolution can dissolve 10-20% by mass (with the total number of particles as 100% by mass) of the particles constituting the hexagonal strontium ferrite powder. On the other hand, the aforementioned complete dissolution refers to the point at which dissolution is complete, to the point where it is no longer visually identifiable that hexagonal strontium ferrite powder remains in the liquid. The determination of partial dissolution and surface layer content mentioned above is performed, for example, by the following method. However, the dissolution conditions, such as the amount of sample powder described below, are merely examples, and any dissolution conditions capable of partial and complete dissolution can be used. A container (e.g., a beaker) containing 12 mg of sample powder and 10 mL of 1 mol / L hydrochloric acid is kept on a hot plate at a set temperature of 70 °C for 1 hour. The resulting solution is filtered through a 0.1 μm membrane filter. Elemental analysis of the filtrate is performed using an inductively coupled plasma (ICP) analyzer. This allows the determination of the surface portion content of rare earth atoms relative to 100 atomic percent of iron atoms. In cases where multiple rare earth atoms are detected by elemental analysis, the total content of all rare earth atoms is taken as the surface portion content. This is also applied to the determination of bulk content. On the other hand, the determination of complete dissolution and bulk content is carried out, for example, by the following method. A container (e.g., a beaker) containing 12 mg of sample powder and 10 mL of 4 mol / L hydrochloric acid is kept on a hot plate at a set temperature of 80 °C for 3 hours. Then, the determination of partial dissolution and surface content is carried out in the same manner as described above, and the bulk content relative to 100 atomic% of iron atoms can be determined.

[0048] From the viewpoint of improving the reproduction output when reproducing data recorded on magnetic tape, it is preferable to have a higher mass magnetization σs of the strongly magnetic powder contained in the magnetic tape. In this regard, hexagonal strontium ferrite powder containing rare-earth atoms but lacking rare-earth atom surface segregation tends to show a significant decrease in σs compared to hexagonal strontium ferrite powder without rare-earth atoms. Therefore, in terms of suppressing this significant decrease in σs, hexagonal strontium ferrite powder with rare-earth atom surface segregation is also considered preferable. In one embodiment, the σs of the hexagonal strontium ferrite powder can be 45 A·m. 2 / kg or above, or 47A·m 2 / kg or more. On the other hand, from the viewpoint of noise reduction, σs is preferably 80 A·m. 2 / kg or less, preferably 60A·m 2 / kg or less. σs can be measured using known measuring devices capable of measuring magnetic properties, such as vibrating sample type magnetometers. In this invention and this specification, unless otherwise specified, the mass magnetization σs is a value measured with a magnetic field strength of 15 kOe. 1 [kOe] = 10 6 / 4π[A / m].

[0049] Regarding the atomic content (bulk content) of the hexagonal strontium ferrite powder, the strontium atom content relative to 100 atomic% of iron atoms can, for example, be in the range of 2.0 to 15.0 atomic%. In one embodiment, the hexagonal strontium ferrite powder may contain only strontium atoms as divalent metal atoms in the powder. Furthermore, in another embodiment, the hexagonal strontium ferrite powder may also contain one or more other divalent metal atoms besides strontium atoms. For example, it may contain barium atoms and / or calcium atoms. When it contains divalent metal atoms other than strontium atoms, the barium atom content and calcium atom content in the hexagonal strontium ferrite powder can, for example, be in the range of 0.05 to 5.0 atomic% relative to 100 atomic% of iron atoms.

[0050] As for the crystal structures of hexagonal ferrites, the known types include magnetoplumbleite (also known as "M-type"), W-type, Y-type, and Z-type. Hexagonal strontium ferrite powder can adopt any crystal structure. The crystal structure can be confirmed by X-ray diffraction analysis. Hexagonal strontium ferrite powder can be detected by X-ray diffraction analysis to have a single crystal structure or two or more crystal structures. For example, in one embodiment, hexagonal strontium ferrite powder can be detected by X-ray diffraction analysis to have only an M-type crystal structure. For example, M-type hexagonal ferrite is made from AFe... 12 O 19The composition is represented by the formula. Here, A represents a divalent metal atom. In the case of hexagonal strontium ferrite powder of type M, A is only a strontium atom (Sr), or when A contains multiple divalent metal atoms, as mentioned above, the strontium atom (Sr) accounts for the largest proportion on an atomic percentage basis. The divalent metal atom content of hexagonal strontium ferrite powder is usually determined according to the type of crystal structure of hexagonal ferrite and is not particularly limited. The same applies to the iron atom content and oxygen atom content. Hexagonal strontium ferrite powder contains at least iron atoms, strontium atoms, and oxygen atoms, and may also contain rare earth atoms. Moreover, hexagonal strontium ferrite powder may contain atoms other than these atoms, or it may not contain atoms other than these atoms. As an example, hexagonal strontium ferrite powder may contain aluminum atoms (Al). The aluminum atom content relative to 100 atomic% of iron atoms may be, for example, 0.5 to 10.0 atoms. From the viewpoint of further suppressing the decrease in reproduction output during repeated reproduction, hexagonal strontium ferrite powder preferably contains iron atoms, strontium atoms, oxygen atoms, and rare earth atoms, and the content of atoms other than these atoms is 10.0 atomic% or less relative to 100 atomic% of iron atoms, more preferably in the range of 0 to 5.0 atomic%, and may also be 0 atomic%. That is, in one embodiment, hexagonal strontium ferrite powder may not contain atoms other than iron atoms, strontium atoms, oxygen atoms, and rare earth atoms. The content expressed as 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 as atomic% using the atomic weight of each atom. Furthermore, in this invention and this specification, for a certain atom, "not containing" means that the content obtained by complete dissolution and measurement by an ICP analyzer is 0 mass%. The detection limit of the ICP analyzer is generally 0.01 ppm (parts per million) or less on a mass basis. The term "excluding" is used to mean including amounts less than the detection limit of the ICP analyzer. In one embodiment, the hexagonal strontium ferrite powder may be free of bismuth atoms (Bi).

[0051] Metal powder As a preferred specific example of a strongly magnetic powder, strongly magnetic metal powder can also be cited. For details regarding strongly magnetic metal powder, please refer to paragraphs 0137 to 0141 of Japanese Patent Application Publication No. 2011-216149 and paragraphs 0009 to 0023 of Japanese Patent Application Publication No. 2005-251351.

[0052] ε-iron oxide powder As a preferred specific example of a strongly magnetic powder, ε-iron oxide powder can be cited. In this invention and this specification, "ε-iron oxide powder" refers to a strongly magnetic powder whose crystal structure of ε-iron oxide is detected as the main phase by X-ray diffraction analysis. For example, if the highest intensity diffraction peak in the X-ray diffraction spectrum obtained by X-ray diffraction analysis belongs to the crystal structure of ε-iron oxide, it is determined that the crystal structure of ε-iron oxide is detected as the main phase. Methods for manufacturing ε-iron oxide powder include methods using goethite, reverse micelle methods, etc. These manufacturing methods are all well known. Furthermore, regarding methods for manufacturing ε-iron oxide powder in which a portion of Fe is replaced by substituted atoms such as Ga, Co, Ti, Al, Rh, etc., for example, refer to J.Jpn.Soc.Powder Metallurgy Vol.61 Supplement, No S1, pp S280-S284, JMater.Chem.C, 2013, 1, pp.5200-5206, etc. However, the method for manufacturing ε-iron oxide powder, which can be used as a strong magnetic powder in the magnetic layer of the magnetic tape described above, is not limited to the methods listed herein.

[0053] The activation volume of ε-iron oxide powder is preferably in the range of 300–1500 nm. 3 Within the range described above, micronized ε-iron oxide powder exhibiting an activation volume within this range is suitable for manufacturing magnetic tapes that exhibit excellent electromagnetic conversion properties. The preferred activation volume of the ε-iron oxide powder is 300 nm. 3 The above, for example, could also be 500nm. 3 That's all. Furthermore, from the viewpoint of further improving electromagnetic conversion characteristics, the activation volume of ε-iron oxide powder is more preferably 1400 nm. 3 The following is a further preferred option: 1300nm 3 The following is a further preferred option: 1200nm 3 The preferred option is 1100nm. 3 the following.

[0054] An anisotropy constant Ku can be cited as an indicator of reducing thermal fluctuations (in other words, improving thermal stability). ε-iron oxide powder preferably has a Ku value of 3.0 × 10⁻⁶. 4 J / m 3 The above-mentioned Ku, more preferably, has 8.0 × 10 4 J / m 3 The above refers to the Ku. Furthermore, the Ku of ε-iron oxide powder can, for example, be 3.0 × 10⁻⁶. 5 J / m 3 However, a higher Ku value indicates higher thermal stability and is therefore preferred; it is not limited to the values ​​exemplified above.

[0055] From the viewpoint of improving reproduction output when reproducing data recorded on magnetic tape, it is preferable that the magnetic tape contains strongly magnetic powder with a high mass magnetization σs. In this regard, in one embodiment, the σs of ε-iron oxide powder can be 8 A·m. 2 / kg or above, or 12A·m 2 / kg or more. On the other hand, from the viewpoint of noise reduction, the σs of ε-iron oxide powder is preferably 40 A·m. 2 Below / kg, preferably 35A·m 2 / kg or less.

[0056] Unless otherwise specified in this invention and specification, the average particle size of various powders, such as strongly magnetic powders, is the value determined using a transmission electron microscope by the following method. The powder was photographed using a transmission electron microscope at a magnification of 100,000, and then printed on photographic paper or displayed on a monitor at a total magnification of 500,000 to obtain photographs of the particles constituting the powder. Target particles were selected from the obtained particle photographs, and their outlines were traced using a digitizer to determine the size of the particles (primary particles). Primary particles refer to unaggregated, independent particles. The above measurements were performed on 500 randomly selected particles. The arithmetic mean of the particle sizes of these 500 particles was taken as the average particle size of the powder. For example, a Hitachi H-9000 transmission electron microscope can be used as the transmission electron microscope described above. Furthermore, the particle size can be measured using known image analysis software, such as Carl Zeiss KS-400 image analysis software. Unless otherwise specified, the average particle size described in the following embodiments refers to the value measured using a Hitachi H-9000 transmission electron microscope as the transmission electron microscope and Carl Zeiss KS-400 image analysis software as the image analysis software. In this invention and specification, "powder" refers to a collection of multiple particles. For example, strongly magnetic powder refers to a collection of multiple strongly magnetic particles. Furthermore, the collection of multiple particles is not limited to the particles constituting the collection being in direct contact, but also includes the presence of binders, additives, etc., between the particles, as described later. The term "particle" is sometimes also used to refer to powder.

[0057] As a method for collecting sample powder from magnetic tape to determine particle size, the method described in paragraph 0015 of Japanese Patent Application Publication No. 2011-048878 can be used, for example.

[0058] Unless otherwise specified in this invention and specification, the size of the particles constituting the powder (particle size) refers to the shape of the particles observed in the aforementioned particle photographs. (1) In the cases of needle-like, spindle-shaped, and columnar shapes (where the height is greater than the maximum major diameter of the base), the length of the major axis constituting the particle is used, i.e., the length of the major axis. (2) In the case of a plate or column (where the thickness or height is less than the maximum major diameter of the plate surface or bottom surface), the maximum major diameter of the plate surface or bottom surface shall be used. (3) In cases where the shape is spherical, polyhedral, irregular, etc., and the major axis of the constituent particles cannot be determined based on the shape, the equivalent circle diameter shall be used. The equivalent circle diameter is the diameter obtained by the circular projection method.

[0059] Furthermore, the average aspect ratio of the powder refers to the arithmetic mean of the values ​​obtained from the above measurements of the minor axis length of the particles, i.e., the minor axis length, and the (major axis length / minor axis length) of each particle. Here, unless otherwise specified, the so-called minor axis length, in the definition of particle size above (1), refers to the length of the minor axis constituting the particle; similarly, in (2), it refers to the thickness or height; and in (3), since there is no difference between the major axis and the minor axis, for convenience, (major axis length / minor axis length) is regarded as 1. Furthermore, unless otherwise specified, when the particles have a specific shape, for example, in the case of the above definition of particle size (1), the average particle size is the average major axis length; in the case of the above definition of particle size (2), the average particle size is the average plate diameter; and in the case of the above definition of particle size (3), the average particle size is the average diameter (also referred to as the average particle size).

[0060] The content (filling rate) of the strongly magnetic powder in the magnetic layer is preferably in the range of 50 to 90% by mass relative to the total mass of the magnetic layer, and more preferably in the range of 60 to 90% by mass. From the viewpoint of increasing recording density, a high filling rate of the strongly magnetic powder in the magnetic layer is preferred.

[0061] (Adhesive) The aforementioned magnetic tape can be a coated magnetic tape and may contain an adhesive in the magnetic layer. The adhesive refers to one or more resins. Various resins commonly used as adhesives in coated magnetic recording media can be used as adhesives. For example, resins selected from polyurethane resins, polyester resins, polyamide resins, vinyl chloride resins, acrylic resins copolymerized from styrene, acrylonitrile, methyl methacrylate, etc., cellulose resins such as nitrocellulose, epoxy resins, phenoxy resins, polyvinyl acetal, polyvinyl butyral, etc., can be used alone or in mixtures. Among these, polyurethane resins, acrylic resins, cellulose resins, and vinyl chloride resins are preferred. These resins can be homopolymers or copolymers. These resins can also be used as adhesives in the non-magnetic layer and / or back coating layer described later. For more information on the above adhesives, please refer to paragraphs 0028 to 0031 of Japanese Patent Application Publication No. 2010-24113. Furthermore, the adhesive can also be a radiation-curable resin such as an electron beam-curable resin. For information on radiation-curable resins, please refer to paragraphs 0044 to 0045 of Japanese Patent Application Publication No. 2011-048878. The average molecular weight of the resin used as a binder, based on its weight-average molecular weight, can be, for example, 10,000 or more and 200,000 or less. The weight-average molecular weight in this invention and specification refers to a value obtained by converting a value measured by gel permeation chromatography (GPC) under the following test conditions to polystyrene. The weight-average molecular weight described in the following examples is a value obtained by converting a value measured under the following test conditions to polystyrene. The binder can be used in an amount of, for example, 1.0 to 30.0 parts by weight relative to 100.0 parts by weight of the strongly magnetic powder, preferably in an amount of 1.0 to 20.0 parts by weight. GPC Unit: HLC-8120 (Manufactured by TOSOH CORPORATION) Column: TSK gel Multipore HXL-M (manufactured by TOSOH CORPORATION, 7.8mm ID (Inner Diameter) × 30.0cm) Eluent: Tetrahydrofuran (THF)

[0062] (Curing agent) The curing agent can also be used together with a resin that can be used as an adhesive. Regarding the curing agent, in one approach, it can be a compound that undergoes a curing reaction (crosslinking reaction) by heating (i.e., a thermosetting compound); in another approach, it can be a photocurable compound that undergoes a curing reaction (crosslinking reaction) by light irradiation. The curing agent undergoes a curing reaction in the magnetic layer forming process, and at least a portion of it can be contained in the magnetic layer in a state where it has reacted (crosslinked) with other components such as the adhesive. This is also true for layers formed using the composition containing the curing agent when it is used to form other layers. A thermosetting compound is preferred as the curing agent, and polyisocyanate is preferred. For details regarding polyisocyanate, please refer to paragraphs 0124-0125 of Japanese Patent Application Publication No. 2011-216149. In the composition for forming the magnetic layer, from the viewpoint of improving the strength of the magnetic layer, it is preferable to use a curing agent in an amount of 50.0-80.0 parts by weight, for example, 0-80.0 parts by weight relative to 100.0 parts by weight of the adhesive, to use the curing agent.

[0063] (additive) The magnetic layer may contain one or more additives as needed. Commercially available additives may be selected based on the desired properties. Alternatively, compounds synthesized by known methods may be used as additives. Additives may be used in any amount. For example, the aforementioned curing agent can be cited as an example of an additive. Furthermore, additives included in the magnetic layer may include non-magnetic powders (e.g., inorganic powders, carbon black, etc.), lubricants, dispersants, dispersing aids, antifungal agents, antistatic agents, antioxidants, etc. For example, regarding lubricants, paragraphs 0030-0033, 0035, and 0036 of Japanese Patent Application Publication No. 2016-126817 can be referenced. Lubricants may also be included in the non-magnetic layer described later. Regarding lubricants that can be included in the non-magnetic layer, paragraphs 0030-0031, 0034, 0035, and 0036 of Japanese Patent Application Publication No. 2016-126817 can be referenced. Regarding dispersants, please refer to paragraphs 0061 and 0071 of Japanese Patent Application Publication No. 2012-133837. Dispersants can also be added to compositions for forming nonmagnetic layers. Regarding dispersants that can be added to compositions for forming nonmagnetic layers, please refer to paragraph 0061 of Japanese Patent Application Publication No. 2012-133837. Furthermore, examples of nonmagnetic powders that can be included in the magnetic layer include nonmagnetic powders that can function as abrasives, and nonmagnetic powders (fillers) included in the magnetic layer to form appropriate protrusions on the surface of the magnetic layer in order to control frictional properties. For example, regarding abrasives, please refer to paragraphs 0030 to 0032 of Japanese Patent Application Publication No. 2004-273070. As an abrasive, it is preferable to use a specific surface area (hereinafter referred to as "BET specific surface area") of 14 m², measured by the BET (Brunauer-Emmett-Teller) method. 2 Abrasives with a surface area of ​​40 m² or more are preferred from a dispersibility perspective. 2 Abrasives of 0.6g or less. Furthermore, regarding dispersants used to improve the dispersibility of abrasives, please refer to paragraphs 0017 to 0028 of Japanese Patent Application Publication No. 2014-179149.

[0064] It is believed that the dark region described above is the region where the filler exists on the surface of the magnetic layer. Therefore, the area ratio of the dark region before reciprocating sliding can be controlled by the size of the non-magnetic powder added as filler, the amount of filler added, and the dispersion conditions of the filler dispersion (hereinafter also referred to as "filler liquid"). As an indicator of the dispersion state of the filler liquid, the particle size described in the examples section below can be cited. For example, the dispersion conditions of the filler liquid can be determined using this particle size as an indicator. Carbon black can be cited as a filler. The BET specific surface area of ​​carbon black is preferably 10 m². 2 / g or more, preferably 15m2 / g or more. From the viewpoint of easily improving dispersibility, the BET specific surface area of ​​carbon black is preferably 50m². 2 / g or less, preferably 40m 2 / g or less. Furthermore, colloidal particles can be cited as another type of filler. From the viewpoint of ease of acquisition, inorganic colloidal particles are preferred, inorganic oxide colloidal particles are more preferred, and silica colloidal particles (colloidal silica) are even more preferred. In this invention and this specification, "colloidal particles" refers to particles that, when 1g is added per 100mL of at least one organic solvent selected from methyl ethyl ketone, cyclohexanone, toluene, or ethyl acetate, or a mixture containing two or more of the above solvents in any mixing ratio, do not settle but disperse and can provide a colloidal dispersion. The average particle size of the colloidal particles can be, for example, 30 to 300 nm, preferably 40 to 200 nm. The filler content in the magnetic layer is preferably 0.1 to 0.8 parts by mass relative to 100.0 parts by mass of the strongly magnetic powder. The filler is preferably provided separately from the strongly magnetic powder in the dispersion process, and more preferably also separately from the abrasive in the dispersion process.

[0065] The magnetic layer described above can be directly applied to the surface of a non-magnetic support, or it can be applied indirectly via a non-magnetic layer.

[0066] <Non-magnetic layer> Next, the non-magnetic layer will be described. The magnetic tape described above can have a magnetic layer directly on a non-magnetic support, or a non-magnetic layer containing non-magnetic powder can be formed between the non-magnetic support and the magnetic layer. The non-magnetic powder used in the non-magnetic layer can be an inorganic powder or an organic powder. Carbon black can also be used. Examples of inorganic materials include metals, metal oxides, metal carbonates, metal sulfates, metal nitrides, metal carbides, and metal sulfides. These non-magnetic powders can be obtained as commercially available products or manufactured using known methods. For details, please refer to paragraphs 0146 to 0150 of Japanese Patent Application Publication No. 2011-216149. For information on the carbon black that can be used in the non-magnetic layer, please refer to paragraphs 0040 to 0041 of Japanese Patent Application Publication No. 2010-24113. The content (filling rate) of non-magnetic powder in the non-magnetic layer is preferably in the range of 50 to 90% by mass relative to the total mass of the non-magnetic layer, and more preferably in the range of 60 to 90% by mass.

[0067] The non-magnetic layer may contain an adhesive or additives. Further details regarding the adhesives, additives, etc., of the non-magnetic layer can be obtained using known techniques related to non-magnetic layers. Furthermore, for example, known techniques related to magnetic layers can also be applied regarding the type and content of the adhesive, the type and content of the additives, etc.

[0068] The non-magnetic layer of the aforementioned magnetic tape also includes a substantially non-magnetic layer that, along with the non-magnetic powder, contains, for example, as an impurity or intentionally in the form of a small amount of strongly magnetic powder. Here, a substantially non-magnetic layer refers to a layer with a remanent magnetic flux density of 10 mT or less and a coercivity of 7.96 kA / m (100 Oe) or less, or a remanent magnetic flux density of 10 mT or less and a coercivity of 7.96 kA / m (100 Oe) or less. Preferably, the non-magnetic layer does not have remanent magnetic flux density or magnetic retention force.

[0069] <Non-magnetic support> Next, the non-magnetic support will be described. Examples of non-magnetic supports (hereinafter referred to simply as "support") include biaxially stretched polyethylene terephthalate, polyethylene naphthalate, polyamide, polyamide-imide, and aromatic polyamide. Among these, polyethylene terephthalate, polyethylene naphthalate, and polyamide are preferred. These supports can be pre-treated with corona discharge, plasma treatment, easy-bonding treatment, heat treatment, etc.

[0070] <Back Coating> The aforementioned magnetic tape may have a back coating containing non-magnetic powder on the surface of the non-magnetic support opposite to the surface with the magnetic layer, or it may not have such a back coating. Preferably, the back coating contains one or both of carbon black and inorganic powder. The back coating may contain a binder or additives. Details regarding the non-magnetic powder, binder, additives, etc., of the back coating can be obtained using known techniques related to the back coating, as well as known techniques related to the magnetic layer and / or non-magnetic layer. For example, regarding the back coating, reference can be made to paragraphs 0018 to 0020 of Japanese Patent Application Publication No. 2006-331625 and lines 65 to 38 of column 4 of the specification of U.S. Patent No. 7,029,774.

[0071] <Various Thicknesses> Regarding the tape thickness (total thickness) of magnetic tape, with the tremendous increase in information volume in recent years, there is a demand for increased recording capacity (high capacity) of magnetic tape. As a method for increasing capacity, reducing the tape thickness and increasing the tape length contained in each tape reel can be cited. Considering this, the tape thickness (total thickness) of the aforementioned magnetic tape is preferably 5.6 μm or less, more preferably 5.5 μm or less, even more preferably 5.4 μm or less, and even more preferably 5.3 μm or less. Furthermore, from the viewpoint of ease of operation, the tape thickness is preferably 3.0 μm or more, more preferably 3.5 μm or more.

[0072] The thickness (total thickness) of a magnetic tape can be determined using the following methods. Ten test samples (e.g., 5–10 cm in length) are cut from any portion of the magnetic tape, and these test samples are overlapped to measure the thickness. The thickness of the magnetic tape is obtained by dividing the measured thickness by one-tenth (the thickness of each test sample). The above thickness measurement can be performed using a known measuring instrument capable of measuring thickness on the order of 0.1 μm.

[0073] The thickness of the non-magnetic support is preferably 3.0 to 5.0 μm. The thickness of the magnetic layer can be optimized based on factors such as the saturation magnetization of the magnetic head, the head gap length, and the frequency band of the recorded signal. It is typically 0.01 μm to 0.15 μm, and from the viewpoint of high-density recording, 0.02 μm to 0.12 μm is preferred, and 0.03 μm to 0.1 μm is even more preferred. At least one magnetic layer is required; the magnetic layer can be divided into two or more magnetic layers with different magnetic properties, and known structures related to multilayer magnetic layers can be applied. The thickness of the magnetic layer when divided into two or more magnetic layers refers to the total thickness of these layers. By thickening the magnetic layer containing high-density, strongly magnetic powder, the sinking of filler into the magnetic layer during reciprocating sliding can be suppressed. This is preferable from the viewpoint of improving the area fraction retention rate in the dark area after reciprocating sliding. On the other hand, if the filler is small, the filler particles are entirely embedded inside the magnetic layer during the magnetic tape manufacturing process, resulting in a lower filler occupancy rate on the surface of the magnetic layer. That is, the area fraction in the dark area before reciprocating sliding becomes lower. Considering the above points, it is preferable to determine the thickness of the magnetic layer and the size of the filler used. The thickness of the non-magnetic layer is, for example, 0.1 to 1.5 μm, preferably 0.1 to 1.0 μm, and more preferably 0.1 to 0.7 μm. The thickness of the back coating is preferably less than 0.9 μm, and more preferably 0.1 to 0.7 μm. The thickness of the magnetic layer and other thicknesses can be determined using the following methods. After exposing a cross-section of the magnetic tape along its thickness direction using an ion beam, cross-sectional observation is performed on the exposed section using a scanning electron microscope or a transmission electron microscope. Various thicknesses can be calculated as the arithmetic mean of the thicknesses obtained from any two locations in the cross-sectional observation. Alternatively, various thicknesses can also be calculated as design thicknesses based on manufacturing conditions, etc.

[0074] <Manufacturing Method> (Preparation of the composition for forming each layer) Compositions used to form magnetic layers, non-magnetic layers, or back coatings typically contain solvents and the various components described above. Various organic solvents commonly used in the manufacture of coated magnetic recording media can be used as solvents. From the viewpoint of the solubility of binders commonly used in coated magnetic recording media, each layer-forming composition preferably contains one or more ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, cyclohexanone, isophorone, and tetrahydrofuran. The amount of solvent in each layer-forming composition is not particularly limited and can be the same as that in typical coated magnetic recording media layer-forming compositions. Furthermore, the process for preparing each layer-forming composition typically includes at least a mixing process, a dispersion process, and a mixing process provided before and after these processes as needed. Each process can be divided into two or more stages. Components used in the preparation of each layer-forming composition can be added at the initial stage or midway through any process. Alternatively, each component can be added separately in two or more processes. For example, the binder can be added in stages during the mixing, dispersion, and further mixing stages for adjusting viscosity after dispersion. Furthermore, filtration can be performed after dispersion. For information on filters used for filtration, please refer to the following description.

[0075] In the aforementioned magnetic tape manufacturing process, conventionally known manufacturing techniques can be used in some or all of the processes. In the mixing process, kneaders with strong mixing power, such as open-type kneaders, continuous kneaders, pressure kneaders, and extruders, are preferred. Details regarding these mixing processes are described in Japanese Patent Application Publication Nos. 1-106338 and 1-79274. Furthermore, glass beads and / or other beads can be used to disperse the compositions for forming each layer. Zirconia beads, titanium dioxide beads, and steel beads, which have high specific gravity, are preferred as such dispersing beads. These dispersing beads are preferably used with optimized particle size (bead diameter) and filler content. Known dispersing machines can be used. The compositions for forming each layer can be filtered using known methods before being applied to the coating process. Filtration can be performed, for example, by using a filter. For example, filters with a pore size of 0.01 to 3 μm (e.g., glass fiber filters, polypropylene filters, etc.) can be used for filtration.

[0076] (Coating process) The magnetic layer can be formed by directly coating a magnetic layer forming composition onto a non-magnetic support, or by sequentially or simultaneously coating multiple layers with the non-magnetic layer forming composition. In the case of an alignment process, the coating layer in the alignment region is aligned while the coating layer of the magnetic layer forming composition is wet. Various known techniques, including those described in paragraph 0052 of Japanese Patent Application Publication No. 2010-24113, can be applied for the alignment process. For example, vertical alignment can be performed using known methods such as the method using opposite-pole magnets. In the alignment region, the drying speed of the coating layer can be controlled based on the temperature and flow rate of the drying air and / or the conveying speed in the alignment region. Furthermore, the coating layer can be pre-dried before being conveyed to the alignment region. The back coating can be formed by applying a back coating forming composition to the side of a non-magnetic support opposite to the side having a magnetic layer (or with an additional magnetic layer). For details regarding the coating used to form each layer, please refer to paragraph 0066 of Japanese Patent Application Publication No. 2010-231843.

[0077] (Other processes) After the coating process described above, calendering is typically performed to improve the surface smoothness of the magnetic tape. If the calendering conditions are intensified, the area fraction of the dark region before reciprocating sliding tends to decrease. This is believed to be because, with intensified calendering conditions, filler particles are more easily and deeply embedded into the magnetic layer through calendering. Therefore, this is preferably considered when determining the calendering conditions. Specific examples of intensifying the calendering conditions include increasing the calendering pressure, increasing the calendering temperature, and setting the calendering speed to a low speed. Regarding the calendering conditions, the calendering pressure is, for example, 200–500 kN / m, preferably 250–350 kN / m; the calendering temperature is preferably 80–95°C; and the calendering speed is, for example, 50–300 m / min, preferably 80–200 m / min. For details on other processes used in the manufacture of magnetic tapes, please refer to paragraphs 0067 to 0070 of Japanese Patent Application Publication No. 2010-231843. Through various processes, a long, thin magnetic tape roll can be obtained. This roll is then cut (divided) using a known cutting machine to the width required to fit into a tape cassette. This width can be determined according to standards, but is typically 1 / 2 inch. 1 inch = 2.54 cm. Servo patterns are typically formed in the resulting magnetic tape after splitting.

[0078] (Formation of servo patterns) The formation of servo patterns can also be called the recording of servo signals. The formation of servo patterns will be explained below.

[0079] Servo patterns are typically formed along the length of the magnetic tape. Examples of control methods utilizing servo signals (servo control) include time-based servo (TBS), amplitude servo, and frequency servo.

[0080] As shown in ECMA (European Computer Manufacturers Association) 319 (June 2001), time-based servoing is used in LTO (Linear Tape-Open) compliant magnetic tapes (commonly referred to as "LTO tapes"). In this time-based servoing method, the servo pattern is constructed by continuously arranging multiple pairs of non-parallel magnetic stripes (also referred to as "servo stripes") along the length of the tape. In this invention and specification, "time-based servo pattern" refers to the servo pattern of the head tracking in a servo system capable of time-based servoing. As mentioned above, the servo pattern is constructed by a pair of non-parallel magnetic stripes to notify the servo signal readout element passing over the servo pattern of its position. Specifically, the pair of magnetic stripes are formed with their interval continuously varying along the width of the tape. By reading this interval by the servo signal readout element, the relative position of the servo pattern and the servo signal readout element can be determined. This information of the relative position enables data track tracking. Therefore, multiple servo tracks are typically arranged along the width of the tape on the servo pattern.

[0081] The servo tape consists of a continuous servo pattern along the length of the magnetic tape. Multiple servo tapes are typically arranged on the tape. For example, in an LTO tape, there are five servo tapes. The area between two adjacent servo tapes is the data tape. The data tape consists of multiple data tracks, each corresponding to a servo track.

[0082] Furthermore, in one approach, as shown in Japanese Patent Application Publication No. 2004-318983, information indicating the serial number of the servo band is embedded in each servo band (also referred to as "servo band ID (identification)" or "UDIM (Unique Data Band Identification Method) information"). This servo band ID is recorded by offsetting specific servo stripes in a pair of servo stripes that exist multiple times within the servo band, by relative displacement of their positions along the length of the magnetic tape. Specifically, the offsetting method of specific servo stripes in a pair of servo stripes that exist multiple times is changed for each servo band. Therefore, the recorded servo band ID is unique for each servo band, and thus, by reading a single servo band using a servo signal reading element, the servo band can be uniquely identified.

[0083] Another method for uniquely identifying servo strips is the interleaving method shown in ECMA-319 (June 2001). In this interleaving method, multiple pairs of non-parallel magnetic stripes are arranged consecutively along the length of the magnetic tape and recorded in a manner that each servo strip is staggered along the length of the tape. The combination of this staggering method between adjacent servo strips is unique throughout the entire magnetic tape, thus allowing for unique identification of the servo strip when the servo pattern is read using two servo signal readout elements.

[0084] Furthermore, as shown in ECMA-319 (June 2001), information indicating the position along the length of the magnetic tape (also known as "LPOS (Longitudinal Position) information") is typically embedded in each servo tape. Similar to UDIM information, this LPOS information is recorded by offsetting the positions of a pair of servo stripes along the length of the tape. However, unlike UDIM information, the same signal is recorded in each servo tape in this LPOS information.

[0085] Other information, different from the UDIM and LPOS information mentioned above, can also be embedded into the server tape. In this case, the embedded information can vary for each server tape, like the UDIM information, or it can be universal across all server tapes, like the LPOS information. Furthermore, other methods besides those described above can also be used as a way to embed information in the servo stripes. For example, a specified code can be recorded by extracting a specified pair from a pair of servo stripe groups.

[0086] The magnetic head used for servo pattern formation is called a servo write head. A servo write head typically has a pair of gaps corresponding to the aforementioned pair of magnetic strips, and the number of these gaps is the same as the number of servo tapes. A core and a coil are usually connected to each pair of gaps. By supplying current pulses to the coils, the magnetic field generated in the core can produce a leakage magnetic field in the pair of gaps. During servo pattern formation, by feeding the magnetic tape onto the servo write head while simultaneously inputting current pulses, the magnetic pattern corresponding to the pair of gaps can be transferred onto the magnetic tape, thereby forming a servo pattern. The width of each gap can be appropriately set according to the density of the formed servo pattern. For example, the width of each gap can be set to less than 1 μm, 1–10 μm, or more than 10 μm.

[0087] Before forming servo patterns on the magnetic tape, the tape is typically demagnetized (erased). This erasure process can be performed by applying the same magnetic field to the tape using either a DC or AC magnet. There are two types of erasure: DC (Direct Current) erasure and AC (Alternating Current) erasure. AC erasure is performed by gradually reducing the strength of the magnetic field while reversing its direction. DC erasure, on the other hand, is performed by applying a directional magnetic field to the tape. DC erasure has two further methods. The first method is horizontal DC erasure, which applies a directional magnetic field along the length of the tape. The second method is vertical DC erasure, which applies a directional magnetic field along the thickness of the tape. Erasure can be performed on the entire tape or on each servo section of the tape.

[0088] The orientation of the magnetic field of the formed servo pattern depends on the erasure orientation. For example, when a horizontal DC erasure is applied to the magnetic tape, the servo pattern is formed with the magnetic field orientation opposite to the erasure orientation. This increases the output of the servo signal obtained by reading the servo pattern. Furthermore, as shown in Japanese Patent Application Publication No. 2012-53940, when a magnetic pattern is transferred to a magnetic tape that has been vertically DC erased using the aforementioned gap, the servo signal obtained by reading the formed servo pattern is a unipolar pulse shape. On the other hand, when a magnetic pattern is transferred to a magnetic tape that has been horizontally DC erased using the aforementioned gap, the servo signal obtained by reading the formed servo pattern is a bipolar pulse shape.

[0089] <Vertical Rectangular Ratio> In one embodiment, the vertical aspect ratio of the magnetic tape can be, for example, 0.55 or higher, and from the viewpoint of improving electromagnetic conversion characteristics, preferably 0.60 or higher, more preferably 0.65 or higher. In principle, the upper limit of the aspect ratio is 1.00 or lower. The vertical aspect ratio of the magnetic tape can be 1.00 or lower, and can be 0.95 or lower, 0.90 or lower, 0.85 or lower, or 0.80 or lower. From the viewpoint of improving electromagnetic conversion characteristics, a larger value for the vertical aspect ratio of the magnetic tape is preferred. The vertical aspect ratio of the magnetic tape can be controlled by known methods such as implementing vertical orientation processing.

[0090] In this invention and this specification, "vertical rectangularity ratio" refers to the rectangularity ratio measured in the vertical direction of the magnetic tape. The "vertical direction" mentioned in the rectangularity ratio refers to the direction orthogonal to the surface of the magnetic layer, and can also be called the thickness direction. In this invention and this specification, the vertical rectangularity ratio is determined by the following method. A test specimen of the required size is cut from the magnetic tape to be tested and imported into a vibrating sample magnetometer. Using the vibrating sample magnetometer, a magnetic field is applied to the test specimen in the direction perpendicular to the magnetic layer surface (orthogonal to the magnetic layer surface) at a maximum applied magnetic field of 3979 kA / m, a measurement temperature of 296 K, and a magnetic field scanning speed of 8.3 kA / m / s. The magnetization intensity of the test specimen relative to the applied magnetic field is measured. The measured value of the magnetization intensity is obtained as a value corrected for the demagnetizing field, and is obtained by subtracting the magnetization of the sample probe of the vibrating sample magnetometer as background noise. When the magnetization intensity under the maximum applied magnetic field is set as Ms and the magnetization intensity under zero applied magnetic field is set as Mr, the squareness ratio SQ is the value calculated by SQ = Mr / Ms. The measurement temperature refers to the temperature of the test specimen. By setting the ambient temperature around the test specimen as the measurement temperature, the temperature of the test specimen can be made the measurement temperature by achieving temperature equilibrium.

[0091] [Cassette Tape Case] One aspect of the present invention relates to a magnetic tape cassette comprising the aforementioned magnetic tape.

[0092] The details of the magnetic tapes included in the aforementioned cassette are as described above.

[0093] In a magnetic tape cassette, the magnetic tape is typically housed inside the cassette body while being wound onto a reel. The reel is configured to rotate within the cassette body. Single-reel cassettes with one reel inside the cassette body and double-reel cassettes with two reels inside the cassette body are widely used. When a single-reel cassette is installed in a tape drive for recording and / or reproducing data on the magnetic tape, the magnetic tape is pulled out of the cassette and wound onto a reel on the tape drive side. A magnetic head is positioned along the magnetic tape transport path from the cassette to the take-up reel. Magnetic tape feeding and winding occur between the reel on the cassette side (feed reel) and the reel on the tape drive side (take-up reel). During this process, the magnetic head contacts and slides against the magnetic layer surface of the magnetic tape, thereby recording and / or reproducing data. In contrast, in a double-reel cassette, both the feed reel and the take-up reel are located inside the cassette.

[0094] In one embodiment, the aforementioned magnetic tape cassette may include a cartridge memory. The cartridge memory may be, for example, a non-volatile memory that has recorded head tilt angle adjustment information or information for adjusting head tilt angle. The head tilt angle adjustment information is information used to adjust the head tilt angle during tape travel within the magnetic tape device. For example, as head tilt angle adjustment information, the value of the servo tape interval at each longitudinal position of the tape during data recording can be recorded. For example, when reproducing data recorded on the tape, the value of the servo tape interval is measured during reproduction, and the head tilt angle can be changed by the control device of the magnetic tape device so that the absolute value of the difference between the servo tape interval recorded at the same longitudinal position in the cartridge memory and the value of the servo tape interval recorded during recording is close to 0. The head tilt angle may be, for example, the aforementioned angle θ. When the tilted head performs data recording and / or reproduction, the aforementioned angle θ may exceed 0°, and may be less than 45°, less than 40°, or less than 35°.

[0095] The aforementioned magnetic tape and cassette can preferably be used in magnetic tape devices (in other words, magnetic recording and playback systems) that record and / or reproduce data by changing the tilt angle of the magnetic head during tape transport. In this mode of use, since the data recording and / or data reproduction includes the period of head tilt, a magnetic tape with high transport stability during data recording and / or reproduction using a tilted head is preferred. However, the aforementioned magnetic tapes and cassettes are not limited to those used in this magnetic tape apparatus. For example, it is also possible to use them in a manner where the head tilt angle is fixed during each recording or playback, based on changes to the head tilt angle during a particular recording or playback and subsequent recordings or playbacks. In this mode of use, the head tilt is included during data recording and / or data playback; therefore, magnetic tapes with high tape transport stability during data recording and / or playback are preferred when the head is tilted.

[0096] [Magnetic tape device] One aspect of the present invention relates to a magnetic tape apparatus comprising the aforementioned magnetic tape. In the magnetic tape apparatus, data recording to the magnetic tape and / or reproduction of data recorded on the magnetic tape can be performed, for example, by contacting and sliding the magnetic layer surface of the magnetic tape against a magnetic head. The magnetic tape apparatus may detachably include the magnetic tape cassette according to one aspect of the present invention.

[0097] The aforementioned magnetic tape cassette can be mounted onto a magnetic tape device equipped with magnetic heads for data recording and / or playback. In this invention and specification, "magnetic tape device" refers to a means capable of at least one of recording data onto a magnetic tape and reproducing data recorded on the magnetic tape. This means is commonly referred to as a drive.

[0098] <Magnetic head> The aforementioned magnetic tape device may include a magnetic head. Regarding the structure of the magnetic head and its tilt angle (θ), please refer to the above reference. Figures 1-3 The magnetic head included in the aforementioned magnetic tape device can be an LTO8 head in one embodiment, an LTO head of another generation in another embodiment, or a head other than an LTO head in yet another embodiment. When the magnetic head includes a playback element, a magnetoresistive (MR) element capable of sensitively reading information recorded on the magnetic tape is preferred as the playback element. Various known MR elements can be used as the MR element (e.g., GMR (Giant Magnetoresistive) elements, TMR (Tunnel Magnetoresistive) elements, etc.). Hereinafter, the magnetic head that performs data recording and / or playback of the recorded data will also be referred to as a "recording and playback head". The element used for recording data (recording element) and the element used for playback of data (playback element) are collectively referred to as "head element".

[0099] When recording and / or reproducing data, the first step is to track servo signals. That is, by making the servo signal read element follow a specified servo track, the read / write head can be controlled to move along the target data track. Movement of the data track is achieved by changing the servo track read by the servo signal read element along the width of the magnetic tape. Furthermore, the recording and playback head can also record and / or reproduce other data tapes. At this point, the servo signal readout element is moved to the specified servo tape using the aforementioned UDIM information, and tracking of that servo tape begins.

[0100] Figure 4 The diagram shows an example of the configuration of the data band and the servo band. Figure 4In this design, multiple servo tapes 1 are arranged on the magnetic layer of the magnetic tape MT, sandwiched between conductor tapes 3. Multiple regions 2 sandwiched between two servo tapes are data tapes. The servo pattern is a magnetized region, formed by magnetizing specific areas of the magnetic layer using a servo writing head. The region magnetized by the servo writing head (the location forming the servo pattern) is determined according to standards. For example, in the LTO Ultrium format magnetic tape, which is an industry standard specification, during tape manufacturing, such as... Figure 5 As shown, multiple servo patterns tilted relative to the bandwidth direction are formed on the servo strip. Specifically, in Figure 5 In the context of server band 1, the server frame SF consists of server subframe 1 (SSF1) and server subframe 2 (SSF2). Server subframe 1 is composed of A burst ( Figure 5 The symbols A and B are in the middle. Figure 5 The A burst consists of servo patterns A1 to A5, and the B burst consists of servo patterns B1 to B5. On the other hand, servo subframe 2 consists of the C burst (…). Figure 5 The symbol C is in the middle and D bursts ( Figure 5 The symbol D is used to represent the servo pattern. A C burst consists of servo patterns C1 to C4, and a D burst consists of servo patterns D1 to D4. These 18 servo patterns are arranged in groups of 5 and 4 in subframes arranged in a 5, 5, 4, 4 pattern to identify servo frames. Figure 5 For illustrative purposes, only one servo frame is shown. However, in reality, in the magnetic layer of a magnetic tape performing time-based servo head tracking, multiple servo frames are arranged along the tape travel direction in each servo tape. Figure 5 In the diagram, the arrows indicate the direction of tape travel. For example, LTO Ultrium format tapes typically have more than 5,000 servo frames per 1 meter of tape length in each servo tape of the magnetic layer.

[0101] In the aforementioned magnetic tape apparatus, the tilt angle of the magnetic head can be changed during the tape's travel within the apparatus. The tilt angle is, for example, the angle θ formed by the axis of the element array relative to the width direction of the magnetic tape. Regarding the angle θ, as described above, for example, by providing an angle adjustment unit in the recording / reproduction head unit of the magnetic head to adjust the angle of the head module, the angle θ can be variably adjusted during tape travel. This angle adjustment unit may, for example, include a rotation mechanism that rotates the module. Known techniques can be applied to the angle adjustment unit.

[0102] Regarding the tilt angle of the magnetic head during tape transport, when the magnetic head consists of multiple modules, a reference can be used to define the angle for a randomly selected module. Figures 1-3 The angle θ is the angle at the start of tape feeding. initial It can be set to 0° or higher than 0°. θ initialThe larger the value of θ, the greater the change in the effective distance between the servo signal readout elements relative to the change in angle θ. Therefore, it is preferable from the viewpoint of adjusting the effective distance between the servo signal readout elements according to the dimensional change in the width direction of the magnetic tape. From this point of view, θ initial Preferably, the angle is 1° or more, more preferably 5° or more, and even more preferably 10° or more. On the other hand, regarding the angle (generally referred to as the "wrapping angle") formed by the magnetic layer surface and the contact surface of the magnetic head when the magnetic tape travels and contacts the magnetic head, keeping the deviation related to the tape width direction small is effective in improving the uniformity of friction in the tape width direction caused by the contact between the magnetic head and the magnetic tape during tape travel. Furthermore, from the viewpoint of magnetic head position tracking and tape travel stability, it is preferable to improve the uniformity of the aforementioned friction in the tape width direction. From the viewpoint of reducing the deviation of the wrap angle in the tape width direction, θ initial Preferably, the angle is 45° or less, more preferably 40° or less, and even more preferably 35° or less.

[0103] Regarding the change of angle θ during tape transport, the angle θ of the magnetic head changes from θ at the start of tape transport during the tape's journey within the tape drive. initial In cases where changes occur to the data recorded on and / or reproduced on the magnetic tape, the maximum change Δθ in the angle θ during tape transport is calculated according to the following formula: max and Δθ min The larger value in the middle. The maximum value of the angle θ during tape transport is θ. max The minimum value is θ min Additionally, "max" is an abbreviation for maximum, and "min" is an abbreviation for minimum. Δθ max =θ max -θ initial Δθ min =θ initial -θ min

[0104] In one embodiment, Δθ can exceed 0.000°. From the viewpoint of adjusting the effective distance between servo signal readout elements in accordance with dimensional changes in the width direction of the magnetic tape, it is preferably 0.001° or more, more preferably 0.010° ​​or more. Furthermore, from the viewpoint of facilitating the synchronization of recorded and / or reproduced data among multiple magnetic head elements during data recording and / or data reproduction, Δθ is preferably 1.000° or less, more preferably 0.900° or less, further preferably 0.800° or less, more preferably 0.700° or less, and even more preferably 0.600° or less.

[0105] exist Figure 2 and Figure 3 In the example shown, the axis of the element array is inclined toward the direction of magnetic tape transport. However, the invention is not limited to this example. Embodiments in the above-described magnetic tape apparatus where the axis of the element array is inclined in the opposite direction to the direction of magnetic tape transport are also included in the invention.

[0106] θ is the tilt angle of the magnetic head at the start of tape feeding. initial It can be set via the control device of the magnetic tape device, etc. Regarding the tilt angle of the magnetic head during magnetic tape transport. Figure 6 This is an explanatory diagram illustrating the method for measuring the angle θ during magnetic tape travel. The angle θ during magnetic tape travel can be determined, for example, by the following method. When determining the angle θ during magnetic tape travel using this method, it is assumed that the angle θ varies within the range of 0 to 90° during magnetic tape travel. That is, if the axis of the component array is tilted towards the direction of magnetic tape travel when the tape begins to travel, then the magnetic tape travel will not cause the component array to tilt so that its axis is tilted in the opposite direction to the initial direction of magnetic tape travel; conversely, if the axis of the component array is tilted in the opposite direction to the initial direction of magnetic tape travel when the tape begins to travel, then the magnetic tape travel will not cause the component array to tilt so that its axis is tilted towards the initial direction of magnetic tape travel. The phase difference (i.e., time difference) ΔT of the reproduced signals of a pair of servo signal readout elements 1 and 2 is measured. The measurement of ΔT can be performed by a measuring unit provided in the magnetic tape device. The structure of this measuring unit is known. The distance L between the central portion of servo signal readout element 1 and the central portion of servo signal readout element 2 can be measured by an optical microscope or the like. When the magnetic tape travel speed is v, the distance between the central portions of the two servo signal readout elements in the magnetic tape travel direction is Lsinθ, and the relationship Lsinθ = v × ΔT holds. Therefore, the angle θ during magnetic tape travel can be calculated according to the formula "θ = arcsin(vΔT / L)". Furthermore, Figure 6 The right figure shows an example where the axis of the element array is tilted towards the direction of the magnetic tape travel. In this example, the phase difference (i.e., time difference) ΔT between the phase of the reproduced signal of servo signal readout element 2 and the phase of the reproduced signal of servo signal readout element 1 is measured. When the axis of the element array is tilted in the opposite direction to the direction of the magnetic tape travel, ΔT is measured as the phase difference (i.e., time difference) between the phase of the reproduced signal of servo signal readout element 1 and the phase of the reproduced signal of servo signal readout element 2. Otherwise, θ can be obtained using the method described above. Furthermore, the measurement interval of angle θ (i.e., the measurement interval of angle θ related to the length direction of the magnetic tape) can be selected based on the frequency of bandwidth deformation related to the length direction of the magnetic tape. As an example, the measurement interval can be set to 250 μm.

[0107] <Structure of magnetic tape device> Figure 7 The magnetic tape device 10 shown controls the recording and playback head unit 12 according to commands from the control device 11 to record and reproduce data for the magnetic tape MT. The magnetic tape device 10 has a structure capable of detecting and adjusting the tension applied to the magnetic tape in the length direction by the spindle motors 17A, 17B and their drive devices 18A, 18B from the rotating control tape cassette reel and take-up reel. The magnetic tape device 10 has a structure capable of loading magnetic tape cartridges 13. The magnetic tape device 10 has a cartridge memory read / write device 14 capable of reading and writing to the cartridge memory 131 inside the magnetic tape cartridge 13. The magnetic tape MT is pulled out from the end of the tape cassette 13 installed in the magnetic tape device 10 by an automatic loading mechanism or by manual pulling out of the guide pin, with the magnetic layer surface of the tape MT in contact with the recording and playback head surface of the recording and playback head unit 12, so that it passes through the guide rollers 15A, 15B and the recording and playback head, thereby winding the tape MT onto the take-up reel 16. The rotation and torque of spindle motors 17A and 17B are controlled based on signals from control device 11, allowing the magnetic tape MT to travel at any speed and tension. Servo patterns pre-formed on the magnetic tape can be used to control tape speed and head tilt angle. A tension detection mechanism can be installed between the tape cassette 13 and the take-up reel 16 to detect tension. In addition to control via spindle motors 17A and 17B, tension control can also be achieved using guide rollers 15A and 15B. The cartridge memory read / write device 14 is configured to read and write information from the cartridge memory 131 according to commands from the control device 11. The communication method between the cartridge memory read / write device 14 and the cartridge memory 131 can be, for example, ISO (International Organization for Standardization) 14443.

[0108] The control device 11 includes, for example, a control unit, a storage unit, and a communication unit.

[0109] The recording and playback head unit 12 comprises, for example, a recording and playback head, a servo tracking actuator for adjusting the position of the recording and playback head in the track width direction, a recording and playback amplifier 19, and a connector cable for connecting to the control device 11. The recording and playback head comprises, for example, a recording element for recording data on the magnetic tape, a playback element for reproducing data on the magnetic tape, and a servo signal readout element for reading servo signals recorded on the magnetic tape. For example, one or more recording elements, playback elements, and servo signal readout elements may be mounted in a single head. Alternatively, each element may be individually housed in multiple heads corresponding to the magnetic tape's travel direction.

[0110] The recording and playback head unit 12 is configured to record data onto the magnetic tape MT according to commands from the control device 11. Furthermore, it is configured to reproduce the data recorded on the magnetic tape MT according to commands from the control device 11.

[0111] The control device 11 has a mechanism that determines the tape travel position based on servo signals read from servo tapes during tape travel and controls a servo tracking actuator to position the recording element and / or playback element at a target tape travel position (track position). This track position control is performed, for example, through feedback control. The control device 11 also has a mechanism that determines the servo tape interval based on servo signals read from two adjacent servo tapes during tape travel. The control device 11 can store the determined servo tape interval information in its internal storage unit, cartridge memory 131, or external connection devices. Furthermore, the control device 11 can change the head tilt angle based on the width-direction dimensional information of the tape during travel. This allows the effective distance between servo signal reading elements to be close to or consistent with the servo tape interval. This dimensional information can be obtained using a servo pattern pre-formed on the tape. For example, during tape travel within the tape drive, the angle θ between the axis of the element array and the width direction of the tape can be changed based on the width-direction dimensional information of the tape obtained during travel. The tilt angle of the magnetic head can be adjusted, for example, by feedback control. Furthermore, the tilt angle of the magnetic head can also be adjusted by the methods described in Japanese Patent Application Publication No. 2016-524774 (Patent Document 1) or US2019 / 0164573A1 (Patent Document 2). Example

[0112] The present invention will now be described in more detail through examples. However, the present invention is not limited to the embodiments shown in the examples. Unless otherwise specified, "parts" and "%" as used below refer to "parts by mass" and "% by mass". Unless otherwise specified, the following processes and evaluations are performed in atmospheric conditions at room temperature (20-25°C). "eq" as used below refers to equivalent, which is a unit that cannot be converted to SI units.

[0113] [Example 1] <Preparation of Alumina Dispersion (Grinding Agent Solution)> Compared to an α-oxidation rate of approximately 65% ​​and a BET specific surface area of ​​20 m², 2 100.0 parts of alumina powder (HIT-80 manufactured by Sumitomo Chemical Company, Limited), 3.0 parts of a 32% solution of 2,3-dihydroxynaphthalene (manufactured by Tokyo Chemical Industry Co., Ltd.), 31.3 parts of a 32% solution of polyester polyurethane resin with SO3Na groups as polar groups (UR-4800 manufactured by TOYOBO CO., LTD. (polar group content: 80 meq / kg)) (solvent being a mixture of methyl ethyl ketone and toluene), and 570.0 parts of a 1:1 (mass ratio) mixed solution of methyl ethyl ketone and cyclohexanone as solvents were dispersed for 5 hours using a paint stirrer in the presence of zirconia beads. After dispersion, the dispersion and beads were separated using a sieve to obtain an alumina dispersion.

[0114] <Preparation of Carbon Black Dispersion (Filling Liquid)> As a solvent, 19.3 parts of mixed cyclohexanone were used relative to 3.3 parts of filler (carbon black) and dispersed in the presence of zirconia beads (bead diameter: 0.1 mm) using a paint stirrer for the times shown in Table 4 (Table 4, "Bead Dispersion Time"). As a filler, Asahi#50 (BET specific surface area: 23 m²) manufactured by ASAHI CARBON CO.,LTD was used. 2 / g). After dispersion, a carbon black dispersion obtained by separating the dispersion and beads using a mesh was used to prepare the following magnetic layer forming composition.

[0115] <Formulation of the composition for forming a magnetic layer> (Magnetic fluid) Strong magnetic powder (hexagonal barium ferrite powder, activated volume: 1500nm) 3 ): 100.0 copies Vinyl chloride copolymer (MR-104 manufactured by Zeon Corporation): 10.0 parts Polyurethane resin containing SO3Na groups: 4.0 parts Weight-average molecular weight: 70,000, SO3Na group: 0.07 meq / g Cyclohexanone: 150.0 parts Methyl ethyl ketone: 170.0 parts (Grinding agent solution) The alumina dispersion prepared above was used in an amount of 4.5 parts, with the alumina content in the alumina dispersion being 4.5 parts. (filler liquid) Used in a manner that the amount of carbon black in the carbon black dispersion prepared above is the amount recorded in the "Filler" column of Table 4. (Other ingredients) Stearic acid: 1.0 part Butyl stearate: 3.3 parts Polyisocyanate (Takenate D-101E manufactured by Mitsui Chemicals, Inc.): 2.5 parts (Adding solvents during finishing) Cyclohexanone: 300.0 parts Methyl ethyl ketone: 140.0 parts

[0116] <Formulation of the composition for forming a non-magnetic layer> Non-magnetic inorganic powder (α-iron oxide): 100.0 parts Average particle size (average major axis length): 0.15 μm, average needle-like ratio: 7, BET specific surface area: 52 m² 2 / g Carbon black: 30.0 parts Average particle size: 20nm Vinyl chloride copolymer containing SO3Na groups: 20.0 parts Weight-average molecular weight: 70,000, SO3Na group: 0.2 meq / g Polyurethane resin containing SO3Na groups: 100.0 parts Weight-average molecular weight: 70,000, SO3Na group: 0.2 meq / g Trioctylamine: 1.0 part Phenylophosphonic acid: 4.0 parts Stearic acid: 1.0 part Stearamide: 0.3 parts Butyl stearate: 3.0 parts Cyclohexanone: 450.0 parts Methyl ethyl ketone: 450.0 parts

[0117] <Formulation of the composition for forming the back coating> Carbon black: 100.0 parts Average particle size: 40nm, DBP (Dibutyl phthalate) oil absorption: 74cm³ 3 / 100g Copper phthalocyanine: 3.0 parts Nitrocellulose: 25.0 parts Polyester polyurethane resin containing SO3Na groups: 60.0 parts Weight-average molecular weight: 70,000, SO3Na group: 0.2 meq / g Polyester resin (Vylon 500 manufactured by Toyobo Co., Ltd.): 4.0 parts Alumina powder (BET specific surface area 21m²) 2 / g of α-alumina): 1.0 part Polyisocyanate (Takenate D-101E manufactured by Mitsui Chemicals, Inc.): 15.0 parts Methyl ethyl ketone: 600.0 parts Toluene: 600.0 parts

[0118] <Preparation of the composition for forming each layer> The composition for forming magnetic layers was prepared by the following method. The various components of the above magnetic fluid were mixed using a homogenizer, and then the magnetic fluid was prepared by bead dispersion for 10 minutes using zirconia beads with a diameter of 0.05 mm in a continuous horizontal bead mill. Using the aforementioned bead mill, the magnetic fluid was mixed with the aforementioned abrasive fluid, filler fluid, other components, and finishing additive solvent, and then treated with an intermittent ultrasonic device (20 kHz, 300 W) for 0.5 minutes (ultrasonic dispersion). The mixture was then filtered using a filter with a pore size of 0.5 μm to prepare a composition for forming a magnetic layer. The composition for forming a nonmagnetic layer was prepared by the following method. A dispersion was obtained by dispersing all components except stearic acid, stearamide, and butyl stearate for 12 hours using an intermittent vertical sand mill. Zirconia beads with a diameter of 0.1 mm were used as dispersion beads. The remaining components were then added to the obtained dispersion and stirred using a disperser. The resulting dispersion was filtered through a filter with a pore size of 0.5 μm, thereby preparing a composition for non-magnetic layer formation. The composition for forming a back coating was prepared by the following method. The above-mentioned components, excluding polyisocyanate, were introduced into a dissolver mixer and stirred at a circumferential speed of 10 m / s for 30 minutes. Dispersion was then performed using a horizontal bead mill disperser. Polyisocyanate was then added, and the mixture was stirred and mixed using a dissolver mixer to prepare a composition for forming a back coating.

[0119] <The Making of Cassette Tapes> A non-magnetic layer is formed by coating a non-magnetic layer forming composition onto the surface of a polyethylene terephthalate support with a thickness of 4.2 μm, and then drying it. A magnetic layer forming composition is applied to the surface of the formed non-magnetic layer to form a coating layer, with the thickness after drying being as described in Table 4. While the coating layer is still wet, a magnetic field with a strength of 0.4T is applied to the surface of the coating layer in the vertical direction to perform a vertical orientation treatment, and then the coating layer is dried. After the above coating layer is dried, a back coating composition is applied to the surface of the polyethylene terephthalate support opposite to the surface on which the non-magnetic layer and the magnetic layer are formed, with a dried thickness of 0.3 μm, and then dried. Then, a surface smoothing treatment (calendering) was performed using a calendering roll made of only metal rolls at a speed of 100 m / min, a linear pressure of 300 kg / cm (294 kN / m), and a calendering temperature (surface temperature of the calendering roll) as recorded in Table 4. Then, after heat treatment at an ambient temperature of 70°C for 36 hours, the magnetic tape was cut into 1 / 2-inch (1.27 cm) widths to obtain the magnetic tape. The thickness of each of the above layers is the design thickness calculated based on manufacturing conditions.

[0120] [Examples 2-5, Comparative Examples 1-5, Reference Example 1] The items listed in Table 4 were modified as described in Table 4, except that the magnetic tape was produced using the method described in Example 1. In Reference Example 1, in the formulation of the composition for forming a magnetic layer, a fluorinated lubricant (KY-108 manufactured by Shin-Etsu Chemical Co., Ltd.) in the amount shown in Table 4 was added as “other ingredients”.

[0121] [Particle size of carbon black dispersion (filler liquid)] For each of the Examples, Comparative Examples and Reference Examples, a portion of the carbon black dispersion (filler liquid) prepared by the above method was collected and diluted with the organic solvent (cyclohexanone) used in the dispersion to a filler concentration of 0.2 by mass. The average particle size obtained by measuring the diluted solution using a HORIBA, Ltd. LB-500 dynamic light scattering particle size distribution measuring device is taken as the dispersed particle size. The smaller the dispersed particle size, the better the dispersibility of the carbon black.

[0122] [Magnetic tape thickness] Ten test samples (5 cm in length) were cut from each of the magnetic tapes used in Examples 1-5, and the thickness was measured by overlapping these test samples. The thickness was measured using a digital thickness gauge with a Millimar 1240 compact amplifier and a Millimar 1301 inductive probe manufactured by MAHR. The thickness of the magnetic tape was taken as the value obtained by dividing the measured thickness by one-tenth (the thickness of each test sample). The thickness of each magnetic tape in Examples 1-5 was 5.3 μm.

[0123] [Vertical Rectangle Ratio] Test samples were cut from each of the magnetic tapes in Examples 1 to 5. Regarding these test samples, a TM-TRVSM5050-SMSL type magnetometer manufactured by TAMAGAWA Ltd. was used as a vibration test sample type magnetometer, and the vertical rectangularity ratio was determined using the method described above. The vertical rectangularity ratio of each magnetic tape in Examples 1 to 5 was 0.65.

[0124] [Evaluation Method] <Dark area percentage before reciprocating slide, and dark area percentage maintenance rate after reciprocating slide> For each of Examples 1-5, Comparative Examples 1-5, and Reference Example 1, two test samples were cut from the magnetic tapes prepared above. The dark area ratio (dark area ratio before reciprocating sliding) was determined by the method described above for one of the two test samples without reciprocating sliding. Regarding another sample used for measurement, the dark area area ratio (dark area ratio after reciprocating sliding) was calculated using the method described above, after 3000 reciprocating slides relative to the LTO8 magnetic head at a tilt angle of 15°, under an environment of 35°C and 80% relative humidity. A commercially available LTO8 magnetic head (manufactured by IBM) was used as the LTO8 magnetic head. Based on the area ratio of the dark region before and after the reciprocating slide, the maintenance rate of the dark region area ratio after the reciprocating slide was calculated using the formula described above. For the FE-SEM, a Hitachi, Ltd. FE-SEM S4800 was used. ImageJ was used as the image analysis software. Denoising was performed using the following method: In the ImageJ image analysis software, the Despeckle noise removal process was selected to remove noise components.

[0125] <Fluorine concentration F> For each of Examples 1-5, Comparative Examples 1-5, and Reference Example 1, a test sample was cut from the magnetic tape prepared above. X-ray photoelectron spectroscopy analysis was performed on the magnetic layer surface of the test sample (measurement area: 300 μm × 700 μm) using an ESCA apparatus by the following method.

[0126] (Analysis and Calculation Methods) The measurements (i) and (ii) below were performed under the conditions shown in Table 1.

[0127] [Table 1]

[0128] (i) Full spectrum scanning determination The magnetic layer surface of the sample was measured using a full-spectrum scanning device (measurement conditions: refer to Table 2), and the types of elements detected were investigated (qualitative analysis).

[0129] [Table 2]

[0130] (ii) Narrow-spectrum scanning determination Narrow-spectrum scanning measurements were performed on all elements detected in (i) above (measurement conditions: refer to Table 3). Using the data processing software (Vision 2.2.6) provided with the apparatus, the atomic concentration (unit: atomic %) of each detected element was calculated based on the peak area. The fluorine concentration of the sample used for measurement was then calculated.

[0131] [Table 3]

[0132] The above operation was performed three times at randomly selected locations on the surface of the magnetic layer of the sample to be measured. The arithmetic mean of the fluorine concentration values ​​obtained in this way was taken as the fluorine concentration F of the magnetic tape to be measured.

[0133] [Electromagnetic Conversion Characteristics] For each magnetic tape of Examples 1-5, Comparative Examples 1-5, and Reference Example 1, the SNR (Signal-to-Noise Ratio) was measured using a 1 / 2-inch (1.27 cm) reel tester with a fixed magnetic head. The relative speed between the magnetic head and the magnetic tape was set to 5.5 m / s. A MIG (Metal-In-Gap) head (gap length 0.15 μm, track width 1.0 μm) was used for recording, and the recording current was set to the optimal recording current for each magnetic tape. A GMR (Giant Magnetoresistive) head with an element thickness of 15 nm, a shielding gap of 0.1 μm, and a readout width of 0.5 μm was used as the readout head. Signals with a recording line density of 700 kfci were measured using a spectrum analyzer manufactured by ShibaSoku Co., Ltd., and the ratio of the carrier signal output to the integrated noise across the entire frequency band was used as the SNR. The SNR was calculated as a relative value relative to Comparative Example 4 (0.0 dB). The unit kfci is the unit of line recording density (which cannot be converted to SI units). Based on the SNR value thus calculated, the electromagnetic conversion characteristics were evaluated according to the following evaluation criteria. The evaluation result is preferably A or B, and more preferably A. (Evaluation Criteria) A: SNR is above 0.9dB B: SNR is above 0.5dB and below 0.9dB C: SNR is above 0.3dB and below 0.5dB D: SNR less than 0.3dB

[0134] [Belt stability] The stability of the conveyor belt was evaluated using the following methods at an environment of 35℃ and 80% relative humidity. Each magnetic tape cassette used in the embodiments and comparative examples, and used Figure 7 The magnetic tape device shown performs data recording and playback. The modules included in the recording and playback head unit are configured in the order of "recording module - playback module - recording module" (total number of modules: 3). Each module contains 32 head elements (Ch0 to Ch31), which are sandwiched between a pair of servo signal readout elements to form an element array. By setting the head tilt angle to 15°, the following steps were performed to record and reproduce data and evaluate the tape transport stability during the reproduction process. The head tilt angle is defined as the angle θ between the axis of the element array of the reproduction module and the width direction of the magnetic tape at the start of tape transport. Angle θ is set by the tape drive control device at the start of tape transport, and the head tilt angle remains fixed during tape transport. A tape cassette is installed in the tape drive, and a tape is loaded. Then, while performing servo tracking, pseudo-random data with a specific data pattern is recorded on the tape by a recording and playback head unit. The tension along the tape length is set to a constant value at this time. Simultaneously with data recording, the servo tape interval is measured every 1m along the entire tape length and recorded in the cassette memory. Next, while performing servo tracking, the data recorded on the magnetic tape is reproduced through the recording and playback head unit. The tension along the tape length is set to a constant value at this time. The belt transport stability was evaluated using the standard deviation (hereinafter referred to as "σPES") of the read position PES (Position Error Signal) in the width direction of the servo signal obtained by the servo signal readout element during the above reproduction process. PES is obtained using the following method. To determine the PES, the dimensions of the servo pattern are needed. The servo pattern dimensions vary depending on the generation of the LTO. Therefore, firstly, using a magnetic force microscope or similar instrument, the average distance AC between the four corresponding fringes of the A-burst and C-burst, as well as the azimuth angle α of the servo pattern, are measured. The average time between the five stripes corresponding to bursts A and B over a length of 1 LPOS word is defined as 'a'. The average time between the four stripes corresponding to bursts A and C over a length of 1 LPOS word is defined as 'b'. The value defined by AC × (1 / 2 - a / b) / (2 × tan(α)) is the read position PES (Position Error Signal) in the width direction of the servo signal obtained by the servo signal read element over a length of 1 LPOS word. Regarding the magnetic tape, the end on one side of the reel wound onto the tape cassette is called the inner end, and the end on the opposite side is called the outer end. The outer end is set to 0m. For a region covering a length of 30m to 200m along the length of the magnetic tape, the standard deviation (σPES) of the PES obtained by the above method is calculated. Based on the σPES value thus obtained, the tape transport stability is evaluated according to the following evaluation criteria. The evaluation result is preferably A or B, more preferably A. (Evaluation Criteria) A: σPES is below 30nm B: σPES exceeds 40nm but is below 50nm C: σPES exceeds 50nm but is below 70nm D: σPES exceeds 70nm

[0135] The results are shown in Table 4 (Table 4-1, Table 4-2).

[0136] [Table 4-1]

[0137] [Table 4-2]

[0138] Based on the evaluation results shown in Table 4, it can be confirmed that the magnetic tapes of Examples 1 to 5 are magnetic tapes with excellent electromagnetic conversion characteristics and tape transport stability. Furthermore, the evaluation results of Reference Example 1 indicate that in magnetic tapes with a high fluorine concentration F due to the presence of fluorine-based lubricants, the tape travel stability is good even when the dark area area ratio maintenance rate deviates from the range described above after reciprocating sliding. Industrial availability

[0139] One aspect of the present invention is applicable to various data storage technologies.

Claims

1. A magnetic tape having a non-magnetic support and a magnetic layer containing strongly magnetic powder, wherein, On the surface of the magnetic layer, the fluorine concentration F, determined by X-ray photoelectron spectroscopy analysis at a photoelectron emission angle of 10°, is greater than 0 atomic% and less than 0.5 atomic%. In an environment with a temperature of 35°C and a relative humidity of 80%, before 3000 reciprocating slides relative to the LTO8 magnetic head at a tilt angle of 15°, the area ratio of the dark region on the surface of the magnetic layer before the reciprocating slides is greater than 0% and less than 0.30%. When the area ratio of the dark region before the reciprocating sliding is 100%, the area ratio of the dark region on the surface of the magnetic layer after the reciprocating sliding is more than 80% and less than 100%. Let A be the total area of ​​multiple dark regions in the binarized image of the secondary electron image obtained by scanning electron microscopy of the surface of the magnetic layer, and let B be the area of ​​the entire field of view of the image. The dark region area ratio is calculated by the following formula: Dark area area ratio = A / B × 100.

2. The magnetic tape according to claim 1, wherein, The area ratio of the dark region before the reciprocating sliding exceeds 0% and is less than 0.25%.

3. The magnetic tape according to claim 1, wherein, When the area ratio of the dark region before the reciprocating sliding is 100%, the area ratio of the dark region after the reciprocating sliding on the surface of the magnetic layer is 86% or more and 100% or less.

4. The magnetic tape according to claim 1, wherein, The magnetic layer also contains one or more non-magnetic powders.

5. The magnetic tape according to claim 4, wherein, The non-magnetic powder in the magnetic layer contains carbon black.

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

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

8. The magnetic tape according to claim 1, wherein, The thickness of the strip is less than 5.3 μm.

9. The magnetic tape according to claim 1, wherein, The vertical rectangularity ratio of the magnetic tape is 0.65 or higher.

10. The magnetic tape according to claim 1, wherein, The area ratio of the dark region before the reciprocating sliding is greater than 0% and less than 0.25%. When the area ratio of the dark region before the reciprocating sliding is 100%, the area ratio of the dark region after the reciprocating sliding, calculated from the surface of the magnetic layer, is 86% or more and less than 100%. The magnetic layer also contains one or more non-magnetic powders. The non-magnetic powder in the magnetic layer contains carbon black. Between the non-magnetic support and the magnetic layer, there is also a non-magnetic layer containing non-magnetic powder. The non-magnetic support also has a back coating containing non-magnetic powder on the surface opposite to the surface with the magnetic layer. The thickness of the band is less than 5.3 μm, and, The vertical rectangularity ratio of the magnetic tape is 0.65 or higher.

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

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

13. The magnetic tape device according to claim 12, wherein, It also includes the magnetic head. The magnetic head has a module, the module including an array of elements, the array having multiple head elements between a pair of servo signal readout elements, and... The magnetic tape device changes the angle θ between the axis of the element array and the width direction of the magnetic tape during the tape's travel within the device.

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