Magnetic tape, magnetic tape cassette and magnetic recording and reproducing apparatus

Abstract

The present invention provides a magnetic tape having a non-magnetic support and a magnetic layer containing a strong magnetic powder, in a small-angle X-ray scattering spectrum of the non-magnetic support obtained by small-angle X-ray scattering measurement, in a region where q is 0.5 to 1.5 A-1, a ratio of a scattering intensity I at a q value q max at which a maximum of a rate of change of the scattering intensity is present to a scattering intensity I max at which a minimum of the rate of change of the scattering intensity is present is 2.7 or more, q min < 1.5 A-1 min < 0.5 A-1 max < 0.5 A-1 min < 0.5 A-1 min < 0.5 A-1 max and a glass transition temperature Tg of the non-magnetic support is 140°C or more, a magnetic tape cartridge including the magnetic tape, and a magnetic recording and reproducing apparatus.

Description

Technical Field

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

[0002] Magnetic recording media typically include a magnetic layer and a non-magnetic support (e.g., see Patent Document 1).

[0003] Previous technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2-037519 Summary of the Invention

[0006] The technical problem to be solved by the invention

[0007] Magnetic recording media can be disc-shaped or strip-shaped. Patent Document 1 discloses a film used as a non-magnetic support for a disc-shaped magnetic recording medium.

[0008] On the other hand, in recent years, magnetic recording media (i.e., magnetic tape) have been widely used as magnetic recording media for data storage such as archiving.

[0009] Magnetic tapes are typically stored in cassettes. Specifically, the magnetic tape is usually wound onto the cassette reel under tension. This tension can cause deformation of the tape within the cassette. To improve the reliability of magnetic tapes as data storage media, it is desirable to suppress this deformation. The reasons are as follows: Data recording on magnetic tape is typically performed by recording magnetic signals on the data tape. This forms data tracks on the data tape. When reproducing the recorded data, a magnetic head follows the data tracks within a magnetic recording playback device to read the magnetic signals recorded on the data tracks. The higher the accuracy of the magnetic head following the data tracks, the more easily reproduction errors can be suppressed, thereby improving the reliability of the magnetic tape as a data storage medium. However, if the magnetic tape undergoes significant deformation after data recording, the accuracy of the magnetic head following the data tracks during data reproduction will decrease, leading to a higher likelihood of reproduction errors. For this reason, it is desirable to suppress magnetic tape deformation during storage.

[0010] One objective of the present invention is to provide a magnetic tape capable of suppressing deformation during storage.

[0011] means for solving technical problems

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

[0013] In the small-angle X-ray scattering spectrum of the aforementioned non-magnetic support obtained by small-angle X-ray scattering, at a q value... The q-value q at the maximum rate of change of scattering intensity within the region. max Scattering intensity I at point max The q value at the minimum of the rate of change of scattering intensity min Scattering intensity I at point min The ratio of I max / I min For values ​​above 2.7, q min <q max ,and

[0014] The glass transition temperature (Tg) of the aforementioned non-magnetic support is above 140℃.

[0015] In one embodiment, the aforementioned non-magnetic support may be an aromatic polyetherketone support.

[0016] In one embodiment, the aromatic polyetherketone can be a polyetheretherketone.

[0017] In one embodiment, the aromatic polyetherketone can be a polyetherketone.

[0018] In one embodiment, the aforementioned strongly magnetic powder can be hexagonal barium ferrite powder.

[0019] In one embodiment, the aforementioned strongly magnetic powder can be hexagonal strontium ferrite powder.

[0020] In one embodiment, the aforementioned strongly magnetic powder may be ε-iron oxide powder.

[0021] In one embodiment, the magnetic tape may further have a non-magnetic layer containing non-magnetic powder between the non-magnetic support and the magnetic layer.

[0022] In one embodiment, the magnetic tape may further have a back coating containing non-magnetic powder on the surface of the non-magnetic support opposite to the surface having the magnetic layer.

[0023] In one embodiment, the average roughness Ra of the centerline of the surface of the non-magnetic support having the magnetic layer, as measured by an optical interferometer, can be 15.0 nm or less.

[0024] One aspect of the present invention relates to a magnetic tape cassette comprising the aforementioned magnetic tape.

[0025] One aspect of the present invention relates to a magnetic recording and reproducing apparatus comprising the aforementioned magnetic tape.

[0026] Invention Effects

[0027] According to one aspect of the present invention, a magnetic tape capable of suppressing deformation during storage can be provided. Furthermore, according to another aspect of the present invention, a magnetic tape cassette including the magnetic tape and a magnetic recording and playback apparatus can be provided. Detailed Implementation

[0028] [Cassette tape]

[0029] One aspect of the present invention relates to a magnetic tape having a non-magnetic support and a magnetic layer containing strongly magnetic powder. In the small-angle X-ray scattering spectrum of the aforementioned non-magnetic support, obtained by small-angle X-ray scattering measurement, at a q value... The q-value q at the maximum rate of change of scattering intensity within the region. max Scattering intensity I at point max The q value at the minimum of the rate of change of scattering intensity min Scattering intensity I at point min The ratio of I max / I min (Hereinafter referred to as "scattering intensity ratio I") max / I min The value is above 2.7, q min <q max Furthermore, the glass transition temperature (Tg) of the aforementioned non-magnetic support is above 140°C.

[0030] The following is a more detailed explanation of the aforementioned magnetic tape.

[0031] <Non-magnetic support>

[0032] (scattering intensity ratio I) max / I min )

[0033] In the small-angle X-ray scattering spectrum of the non-magnetic support (hereinafter also referred to as the "support") included in the aforementioned magnetic tape, obtained by small-angle X-ray scattering measurement, at a q value The q-value q at the maximum rate of change of scattering intensity within the region. max Scattering intensity I at point max The q value at the minimum of the rate of change of scattering intensity min Scattering intensity I at point min The ratio of I max / I min (scattering intensity ratio I) max / I min ) is above 2.7, q min <q max Regarding the unit, (Å) = 0.1 nm.

[0034] The following section describes the determination of the scattering intensity ratio I. max / I min The method will be explained.

[0035] (1) Preparation of the test sample

[0036] Multiple sample pieces are cut from the non-magnetic support to be tested. Sample pieces can be cut from a support obtained by removing the portion other than the non-magnetic support from the magnetic tape using known methods. The orientation of the sample pieces described below refers to their orientation within the magnetic tape. The length direction refers to the direction along the length of the magnetic tape, and the width direction refers to the direction along the width of the magnetic tape.

[0037] Multiple cut sample pieces are overlapped to a thickness of 200 μm or more (e.g., dozens of pieces). When overlapping, the sample pieces are aligned with each other in both the length and width directions.

[0038] A sample piece with dimensions of several cm in length and several cm in width is cut from the laminate formed by overlapping the above multiple sample pieces, and this sample is used as the test sample.

[0039] (2) Measurement of small-angle X-ray scattering and acquisition of various spectra

[0040] X-rays are incident on any randomly selected surface of the test sample from a direction perpendicular to the sample itself. The scattered X-rays after transmission through the sample are detected by a two-dimensional detector, resulting in small-angle X-ray scattering (SAXS) measurements, which yield SAXS spectra. Small-angle X-ray scattering is also commonly referred to as "SAXS (Small Angle X-ray Scattering)". The energy (wavelength λ) of the X-rays is between 5 and 20 keV. Choose from the range.

[0041] In the obtained two-dimensional SAXS intensity distribution data, the azimuth angle is calculated for both the meridian direction and the equatorial direction. Within the arc of the range, the average scattering intensity I at each scattering angle 2θ is calculated, obtaining a "2θ-I one-dimensional SAXS intensity spectrum" with 2θ as the horizontal axis and I as the vertical axis. The data in the meridian direction are data about the length of the sample, and the data in the equatorial direction are data about the width of the sample. The measurement interval for the scattering intensity (i.e., the interval between adjacent measurement points) is set as... The following is the interval for the following q values. "I" is used as an abbreviation for "Intensity".

[0042] According to the "2θ-1 one-dimensional SAXS intensity spectrum", for a scattering angle of 2θ, in Within a certain range, a "qI one-dimensional SAXS intensity spectrum" is obtained, with the horizontal axis representing the value q and the vertical axis representing I. The value q is the scattering vector, q = 4πsinθ / λ.

[0043] As described above, a SAXS measurement without a background sample was performed using the same cumulative time as the SAXS measurement with the sample present, and a qI one-dimensional SAXS intensity spectrum was obtained in the same manner as described above. This qI one-dimensional SAXS intensity spectrum is then used as the background for the one-dimensional SAXS intensity spectrum obtained in this way.

[0044] Furthermore, the intensity of incident X-rays I0 during the SAXS measurement and the intensity of transmitted X-rays I after transmission through the sample are measured, and the transmittance T of the X-rays used for the SAXS measurement relative to the sample is calculated using "T = I / I0".

[0045] Regarding the sample used for measurement, in the qI one-dimensional SAXS intensity spectrum obtained along the meridian and the qI one-dimensional SAXS intensity spectrum obtained along the equator, the q value at each measurement point is referred to as q, and the scattering intensity at q value = q is referred to as "I(q)". In the qI one-dimensional SAXS intensity spectrum of the background, the q value at each measurement point is referred to as q, and the scattering intensity at q value = q is referred to as "I_Bg(q)". "Bg" is used as an abbreviation for "Background".

[0046] For the q value at each measurement point, the net scattering intensity (hereinafter referred to as "scattering intensity") obtained by subtracting IBg(q) from the value obtained by dividing I(q) by T is plotted as "I(q) / T-I_Bg(q)". The "net one-dimensional SAXS intensity spectrum" is plotted on the vertical axis and the q value on the horizontal axis. Hereinafter, the "net one-dimensional SAXS intensity spectrum" is referred to as "I_saxs(q)".

[0047] Moving average processing is performed on "I_saxs(q)" in order of q values. The moving average calculation is performed on all measurement points, and specifically on the central point and the five points preceding (i.e., the side with smaller q values) and the five points following (i.e., the side with larger q values) of the central point, totaling 11 points. However, the measurement points with the smallest, second smallest, third smallest, fourth smallest, and fifth smallest q values, and the measurement points with the largest, second largest, third largest, fourth largest, and fifth largest q values ​​(a total of 10 points) are excluded from the calculation. The spectrum thus obtained will be referred to as "I_saxs(q) after moving average processing".

[0048] The net one-dimensional SAXS intensity spectrum “I_saxs(q)” is set to satisfy the following two conditions.

[0049] Condition 1: In Within a given range, the arithmetic mean (Ave) of the scattering intensity at all measurement points is divided by the standard deviation (σ), and the value “Ave / σ” is used as the SNR (Signal-to-Noise Ratio), with an SNR value of 3.0 or higher. “Ave” is used as an abbreviation for “Average”.

[0050] Condition 2: In Within the range, when fitted using the least squares method with the exponential decay function (I = a * exp(-b * q)), the correlation coefficient R0 2 For R 2 ≥0.95. In the above formula for the exponential decay function, "q" is the value of q in I_saxs(q), and "I" is an approximate function of I_saxs(q) obtained through fitting. Furthermore, "a" and "b" are coefficients determined in the fitting process.

[0051] If a net one-dimensional SAXS intensity spectrum “I_saxs(q)” that does not meet one or both of the above conditions is obtained, the operation of changing one or more of the following to obtain the net one-dimensional SAXS intensity spectrum “I_saxs(q)” is repeated until a net one-dimensional SAXS intensity spectrum “I_saxs(q)” that meets both of the above conditions is obtained.

[0052] The first-order differential spectrum is obtained by taking the first derivative of the "moving average processed I_saxs(q)" calculated using the net one-dimensional SAXS intensity spectrum "I_saxs(q)" that satisfies the above two conditions with the q value. In the first-order differential spectrum, the vertical axis represents the rate of change of scattering intensity (unitless), and the horizontal axis represents the q value (unit: Furthermore, first-order differential spectra do not necessarily need to be graphical; for example, tabular data representing the rate of change of scattering intensity at each measurement point with respect to the q-value can also be used. This applies to various spectra before first-order differential and before and after moving average processing.

[0053] Moving average processing is performed on the first-order differential spectra obtained above, in order of q values. The moving average calculation is performed on the data consisting of the moving averaged I_saxs(q) obtained from the data before the first-order differential and the pairs of q values. Five adjacent data points are considered: the central one, the two preceding (i.e., the side with the smaller q value), and the two following (i.e., the side with the larger q value). However, the four data points with the smallest, second smallest, largest, and second largest q values ​​are excluded from the calculation. The first-order differential spectra obtained by moving average processing along the meridian and equatorial directions are used to calculate q (described later). min and q max .

[0054] (3) Scattering intensity ratio I max / I min Calculation

[0055] In the first-order differential spectrum obtained after moving average processing as described in (2) above, the value of q will be... Within the region, from q value The first time the rate of change of scattering intensity on the vertical axis changes from "negative or 0" to "positive" is exactly when the rate of change of scattering intensity at the previous measurement point is set as the "minimum value V of the rate of change of scattering intensity". min ", will take the minimum value V min The q value is set to "q min "Therefore, in cases where the q value is greater than q..." min Within the region, in the direction of increasing q value, the scattering intensity change rate on the vertical axis first changes from "positive" to "negative" or "0" at the point exactly the next measurement point. This is set as the "maximum value V of the scattering intensity change rate". max "will take the maximum value V" max The q value is set to "q max Therefore, q min <q max “V” is used as an abbreviation for “Variation”, “min” is used as an abbreviation for “local minimum”, and “max” is used as an abbreviation for “local maximum”.

[0056] For I_saxs(q) after the moving average processing before performing the first-order differential above, calculate q as described above in both the meridian and equatorial directions. max Scattering intensity I at point max With q min Scattering intensity I at point min The ratio (I) max / I minThe ratio (I) will be calculated separately for each of the two directions. max / I min The arithmetic mean of the scattering intensity of the nonmagnetic support to be measured is I. max / I min .

[0057] In the non-magnetic support included in the aforementioned magnetic tape, the scattering intensity ratio I calculated as described above is... max / I min It is above 2.7. The inventors believe that the scattering intensity is greater than I. max / I min This value represents an index of the arrangement of crystalline regions within a non-magnetic support. Crystalline regions can be defined as regions with regularly arranged polymer chains, and can be regions harder than amorphous regions. It is speculated that if such crystalline regions have a certain size and are regularly distributed among each other, the scattering intensity will be higher than I. max / I min The value will increase. It is assumed that the crystalline portion has a scattering intensity greater than I. max / I min Non-magnetic supports with a value of 2.7 or higher exhibit high hardness and excellent resistance to deformation during storage. From the viewpoint of further suppressing magnetic tape deformation during storage, the scattering intensity of the aforementioned non-magnetic supports is higher than that of I. max / I min Preferably, the value is 2.8 or higher, more preferably 2.9 or higher. Furthermore, the scattering intensity ratio of the aforementioned non-magnetic support is higher than that of I. max / I min For example, it can be below 20.0, below 15.0, or below 10.0, or it can be greater than the values ​​exemplified here. Scattering intensity ratio I max / I min For example, this can be controlled based on the manufacturing conditions of the non-magnetic support. This will be discussed later.

[0058] (Glass transition temperature Tg)

[0059] The glass transition temperature (Tg) of the non-magnetic support included in the aforementioned magnetic tape is 140°C or higher. The inventors believe this also helps to suppress deformation of the magnetic tape during storage. It is believed that the polymer chains contained in the non-magnetic support with a glass transition temperature (Tg) of 140°C or higher have stronger inter-chain binding forces, which helps to improve resistance to deformation during storage. From the viewpoint of further suppressing deformation of the magnetic tape during storage, the glass transition temperature (Tg) of the aforementioned non-magnetic support is preferably 142°C or higher, more preferably 145°C or higher, and even more preferably 150°C or higher. Furthermore, the glass transition temperature (Tg) of the aforementioned non-magnetic support can, for example, be 180°C or lower, 175°C or lower, 170°C or lower, or 165°C or lower, or it can be greater than the values ​​exemplified herein. The glass transition temperature of the non-magnetic support can, for example, depend on the type of resin constituting the non-magnetic support. Resins that can constitute the non-magnetic support will be described later.

[0060] The glass transition temperature Tg of the non-magnetic support in this invention and this specification is determined according to JIS K 7121-1987 "Method for determination of transition temperature of plastics", and more specifically, it is the value determined by the following method.

[0061] The sample is cut from the non-magnetic support to be tested. The sample can be cut from the support obtained by removing the portion other than the non-magnetic support from the magnetic tape using known methods.

[0062] The glass transition temperature (Tg) is determined using a differential scanning calorimeter (DSC). For example, a TA Instruments Q100 DSC can be used.

[0063] After placing the above sample pieces in an environment with an ambient temperature of 23±2℃ and a relative humidity of 50±5% for more than 24 hours, they were installed in a DSC and subjected to the following two temperature increases and decreases. The extrapolated glass transition onset temperature (referred to as "Tig" in the above JIS) recorded in item 9.3(2) of JIS K7121-1987 "Method for determination of transition temperature of plastics" was determined using the DSC curve obtained during the second temperature increase, and this was taken as the glass transition temperature Tg.

[0064] (First temperature rise and fall)

[0065] Heat up to 300℃ and hold for 10 minutes.

[0066] Cooling: Cool to 25°C

[0067] Heating rate: 10℃ / min

[0068] Cooling rate: 5℃ / min

[0069] Nitrogen flow rate during measurement: 50 ml / min

[0070] (Second temperature rise and fall)

[0071] Heat up to 300℃ and hold for 10 minutes.

[0072] Cooling: Any

[0073] Heating rate: 10℃ / min

[0074] Cooling rate: arbitrary

[0075] Nitrogen flow rate during measurement: 50 ml / min

[0076] As described above, the inventors believe that the scattering intensity is greater than I. max / I min A glass transition temperature of 2.7 or higher and a glass transition temperature of 140°C or higher can help suppress magnetic tape deformation during storage. Regarding magnetic tapes, in recent years, there has been an increasing demand for tapes that can withstand use in environments where deformation is more likely (e.g., higher temperature and humidity environments). Furthermore, with the increase in capacity, the number of tracks and track density have increased, making reproduction errors more likely if the tape deforms. Under these circumstances, the requirements for suppressing tape deformation are even more stringent. The aforementioned magnetic tape can be designed to withstand these stringent requirements for deformation suppression.

[0077] (Average roughness Ra of the centerline)

[0078] The magnetic layer of the magnetic tape exhibits excellent surface smoothness, which reduces spacing loss and contributes to improved electromagnetic conversion characteristics. From the viewpoint of forming a magnetic layer with excellent surface smoothness, it is preferable that the surface smoothness of the side of the non-magnetic support with the magnetic layer is high. Therefore, the average roughness of the centerline of the surface of the non-magnetic support included in the aforementioned magnetic tape, as measured by an optical interferometer, is preferably 15.0 nm or less, more preferably 12.0 nm or less, and even more preferably 10.0 nm or less. On the other hand, from the viewpoint of ease of handling of the non-magnetic support during magnetic tape manufacturing, the average roughness Ra of the centerline of the surface of the non-magnetic support included in the aforementioned magnetic tape, as measured by an optical interferometer, is preferably 0.1 nm or more, more preferably 0.15 nm or more, even more preferably 0.2 nm or more, and even more preferably 0.3 nm or more.

[0079] The centerline average roughness Ra in this invention and specification is a value measured and determined using an optical interferometer. Specifically, measurements are performed using a 20x objective lens and a 1x zoom lens over a region of 340–360 μm on the long side and 250–270 μm on the short side of the surface being measured. After measurement, filtering is applied to remove wavelength components below 1.65 μm and wavelength components above 50 μm. Cylinder filters are then used to remove distortion, and the Ra value is determined. For example, a Zygo Corporation Newview 6300 optical interferometer can be used, and the filtering process can be performed using Metropro 8.3.5 software for this optical interferometer. Regarding the centerline average roughness Ra of the surface of the non-magnetic support, the layer of the non-magnetic support stacked on the magnetic layer side can be removed from the magnetic tape using known methods, exposing the surface of the non-magnetic support, and the centerline average roughness Ra can be determined for this surface.

[0080] (Types of non-magnetic supports)

[0081] The non-magnetic support included in the aforementioned magnetic tape can be a support comprising a resin film. Preferably, the resin is of a type capable of producing supports with a glass transition temperature (Tg) of 140°C or higher. Based on this, the aforementioned non-magnetic support is preferably an aromatic polyetherketone (APH) support. In this invention and specification, "aromatic polyetherketone" refers to a resin having multiple partial structures, which are formed by ether bonds, phenylene bonds, and ketone bonds linked in the order of "ether bond-phenylene-ketone bond-phenylene". In the above, "-" indicates direct bonding. The bonding position of the aforementioned bonds on each phenylene group is independently any one of para, ortho, or meta positions, for example, para. The multiple phenylene groups contained in the aforementioned partial structure can each be independently unsubstituted or substituted phenylene groups. The above points also apply to various aromatic polyetherketones described later. In this invention and specification, "aromatic polyetherketone" includes aromatic polyetherketones whose repeating units constituting the resin are composed only of the aforementioned partial structures, and aromatic polyetherketones containing the aforementioned partial structures and other partial structures. "Aromatic polyetherketone (PAK) support" refers to a support comprising at least one layer of aromatic polyetherketone (PAK) film. "Aromatic polyetherketone (PAK) film" refers to a film in which aromatic polyetherketone is the most abundant component by mass. In this invention and specification, "aromatic polyetherketone (PAK) support" includes both PAK supports in which all resin films are aromatic polyetherketone (PAK) films and PAK supports in which other resin films are included. Specific examples of PAK film supports include single-layer PAK films, laminated films consisting of two or more layers of PAK films with the same composition, laminated films consisting of two or more layers of PAK films with different compositions, and laminated films comprising one or more PAK films and one or more resin films other than PAK. An adhesive layer may also be arbitrarily included between adjacent layers in a laminated film. Furthermore, the aromatic polyetherketone support may also optionally include a metal film and / or a metal oxide film formed on one or both surfaces by means of vapor deposition.Examples of aromatic polyetherketones include polyetherketones (PEK) with alternating ether and ketone bonds via phenylene groups; polyetheretherketones (PEEK) with ether and ketone bonds via phenylene groups in the order of "ether bond, ether bond, ketone bond"; polyetherketoneketones (PEKK) with ether and ketone bonds via phenylene groups in the order of "ether bond, ketone bond, ketone bond"; polyetheretherketoneketones (PEEKK) with ether and ketone bonds via phenylene groups in the order of "ether bond, ether bond, ketone bond, ketone bond"; and polyetherketoneetherketoneketones (PEKEKK) with ether and ketone bonds via phenylene groups in the order of "ether bond, ketone bond, ether bond, ketone bond, ketone bond"; and polyetherketoneetherketoneketones (PEKEKK) with ether and ketone bonds via phenylene groups in the order of "ether bond, ketone bond, ether bond, ketone bond, ketone bond"; with polyetheretherketones and polyetherketoneketones being preferred. In detail, polyetheretherketone (PEEK) is a resin having multiple partial structures, which are formed by ether bonds, phenylene bonds, and ketone bonds linked in the order of "ether bond-phenylene-ether bond-phenylene-ketone bond-phenylene". In this invention and this specification, "polyetheretherketone" includes polyetheretherketone in which the repeating units constituting the resin are composed only of the above-mentioned partial structures, and polyetheretherketone containing the above-mentioned partial structures and other partial structures. Polyetherketoneketone (PEKK) is a resin having multiple partial structures, which are formed by ether bonds, phenylene bonds, and ketone bonds linked in the order of "ether bond-phenylene-ketone bond-phenylene-ketone bond-phenylene". In this invention and this specification, "polyetherketoneketone" includes polyetherketoneketone in which the repeating units constituting the resin are composed only of the above-mentioned partial structures, and polyetherketoneketone containing the above-mentioned partial structures and other partial structures.

[0082] (Manufacturing method of non-magnetic support)

[0083] The non-magnetic support included in the aforementioned magnetic tape can be manufactured, for example, through a manufacturing process including stretching a commercially available resin film or a resin film produced by known methods. The stretching process, which involves stretching along both the length and width directions, is biaxial stretching. Stretching in the length and width directions can be performed simultaneously or sequentially. The length direction of the non-magnetic support is the MD direction (Machine direction) when manufacturing the roll support, and the width direction is the TD direction (Transverse direction) when manufacturing the roll support. The MD direction is the direction of travel of the roll support during manufacturing, and the TD direction is a direction orthogonal to the MD direction. The stretching ratio is preferably 2.6 times or more in both the length and width directions, more preferably 2.8 times or more. The stretching ratio is the ratio of the dimension after stretching to the dimension before stretching. Furthermore, from the viewpoint of suppressing the decrease in surface smoothness of the support by utilizing crystallization precipitation, the stretching ratio is preferably 6.0 times or less in both the length and width directions, and more preferably 3.3 times or less if considering the suppression of fracture for stable stretching. The stretching temperature can be, for example, 150°C or more, or 155°C or more. From the viewpoint of suppressing the decrease in surface smoothness of the support by utilizing crystallization precipitation, the stretching temperature is preferably 175°C or less, more preferably 170°C or less, and even more preferably 165°C or less. Here, "stretching temperature" refers to the ambient temperature of the environment in which the stretching treatment is performed. The stretching speed during the stretching treatment can be set to, for example, in the range of 10 to 90,000% / min, preferably in the range of 20 to 10,000% / min, and more preferably in the range of 50 to 3,000% / min. The stretching speed is the value obtained by dividing ((dimension after stretching treatment / dimension before stretching treatment) - 1) × 100 (unit: %) by the stretching treatment time (unit: min).

[0084] The stretched resin film can be subjected to any known post-treatment. A specific example of post-treatment is heat treatment. Heat treatment can be performed, for example, by holding the stretched resin film in an atmosphere at a temperature above the stretching temperature. The heat treatment temperature is preferably above the stretching temperature and below 10°C lower than the melting point of the resin film, more preferably above the stretching temperature and below 20°C lower than the melting point of the resin film. Furthermore, the melting point can be determined according to the melting peak temperature determination method described in JIS K7121-1987. Heat treatment helps to fix the orientation state of the polymer chains of the resin oriented by the stretching treatment. The relaxation rate during heat treatment can be 0.80 times or more and less than 1.00 times in both the length and width directions. The relaxation rate is the ratio of the size after heat treatment to the size before heat treatment.

[0085] One or more of the following treatments can be applied to a non-magnetic support before forming a magnetic layer or other layers: corona discharge, plasma treatment, or easy-bonding treatment.

[0086] <Magnetic Layer>

[0087] (Strongly magnetic powder)

[0088] The magnetic layer contains a strongly magnetic powder. The strongly magnetic powder contained in the magnetic layer can be any strongly magnetic powder known for its use in the magnetic layers of various magnetic recording media. From the viewpoint of increasing recording density, it is preferable to use a strongly magnetic powder with a small average particle size. Therefore, the average particle size of the strongly magnetic powder is preferably 50 nm or less, more preferably 45 nm or less, even more preferably 40 nm or less, even more preferably 35 nm or less, even more preferably 30 nm or less, and even more preferably 25 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.

[0089] Hexagonal ferrite powder

[0090] As a preferred specific example of a strongly magnetic powder, hexagonal ferrite powder can be cited. For details regarding hexagonal ferrite powder, see, for example, paragraphs 0012 to 0030 of Japanese Patent Application Publication No. 2011-225417, paragraphs 0134 to 0136 of Japanese Patent Application Publication No. 2011-216149, paragraphs 0013 to 0030 of Japanese Patent Application Publication No. 2012-204726, and paragraphs 0029 to 0084 of Japanese Patent Application Publication No. 2015-127985.

[0091] In this invention and specification, "hexagonal ferrite powder" refers to a strongly magnetic powder whose hexagonal ferrite crystal structure is detected as the main phase by X-ray diffraction analysis. The main phase refers to the structure to which the highest intensity diffraction peak in the X-ray diffraction spectrum obtained by X-ray diffraction analysis belongs. For example, if the highest intensity diffraction peak in the X-ray diffraction spectrum obtained by X-ray diffraction analysis belongs to a hexagonal ferrite crystal structure, then the hexagonal ferrite crystal structure is determined to be the main phase. If only a single structure is detected by X-ray diffraction analysis, that detected structure is considered the main phase. As constituent atoms, the hexagonal ferrite crystal structure contains at least iron atoms, divalent metal atoms, and oxygen atoms. Divalent metal atoms refer to metal atoms that can become divalent cations as ions; examples include strontium atoms, barium atoms, calcium atoms, and lead atoms. In this invention and specification, hexagonal strontium ferrite powder refers to a hexagonal ferrite in which the predominant divalent metal atom is strontium, and hexagonal barium ferrite powder refers to a hexagonal ferrite in which the predominant divalent metal atom is barium. The predominant divalent metal atom refers to the divalent metal atom that constitutes the largest proportion of divalent metal atoms in the powder, based on an atomic percentage. However, rare earth atoms are not included in the aforementioned divalent metal atoms. In this invention and specification, "rare earth atoms" is selected from the group consisting of scandium (Sc), yttrium (Y), and lanthanides. The lanthanide atoms are selected from the group consisting of lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and argonium (Lu).

[0092] The following is a more detailed description of hexagonal strontium ferrite powder as one type of hexagonal ferrite powder.

[0093] The activation volume of hexagonal strontium ferrite powder is preferably in the range of 800–1500 nm. 3 Within the aforementioned range, micronized hexagonal strontium ferrite powder with an activation volume within this range is suitable for manufacturing magnetic tapes that exhibit excellent electromagnetic conversion properties. The preferred activation volume of the hexagonal strontium ferrite powder is 800 nm. 3 The above, for example, could also be 850nm. 3 That's all. Furthermore, from the viewpoint of further improving electromagnetic conversion characteristics, the activation volume of hexagonal strontium ferrite powder is more preferably 1400 nm. 3 The following is a further preferred option: 1300nm 3 The following is a further preferred option: 1200nm 3 Hereinafter, 1100nm is further preferred.3 the following.

[0094] "Activation volume" is a unit of magnetization reversal and is an indicator of the magnetic strength of a particle. The activation volume and anisotropy constant Ku described in this invention and specification were determined using a vibrating sample type fluxmeter at magnetic field scanning speeds of 3 and 30 minutes (measurement temperature: 23℃±1℃) and based on the following relationship between Hc and activation volume V. Furthermore, regarding the unit of the anisotropy constant Ku, lerg / cc = 1.0 × 10⁻⁶. -1 J / m 3 .

[0095] Hc=2Ku / Ms{1-[(kT / KuV)ln(At / 0.693)] 1 / 2}

[0096] 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)

[0097] 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.

[0098] Hexagonal strontium ferrite powder may or may not contain rare earth atoms. When hexagonal strontium ferrite powder contains rare earth atoms, it is preferable that it contains rare earth atoms at a content of 0.5 to 5.0 atomic% (bulk content) relative to 100 atomic% of iron atoms. In one embodiment, the hexagonal strontium ferrite powder containing rare earth atoms may have a rare earth atom surface bias. In this invention and this specification, "rare earth atom surface layer bias" refers to the rare earth atom content (hereinafter referred to as "rare earth atom surface layer content" or simply "surface layer content") in a solution obtained by partially dissolving hexagonal strontium ferrite powder with acid relative to 100 atomic percent of iron atoms, compared to the rare earth atom content (hereinafter referred to as "rare earth atom bulk content" or simply "bulk content") in a solution obtained by completely dissolving hexagonal strontium ferrite powder with acid, satisfying the following ratio:

[0099] The ratio of rare earth atoms in the surface layer to rare earth atoms in the bulk layer is >1.0.

[0100] 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 ratio satisfying "rare earth atom surface portion content / rare earth atom bulk content > 1.0" indicates that rare earth atoms are predominantly present in the surface portion (i.e., in greater quantities than in the interior) of the particles constituting the hexagonal strontium ferrite powder. In this invention and this specification, the surface portion refers to a region extending from the surface of the particles constituting the hexagonal strontium ferrite powder towards the interior.

[0101] When hexagonal strontium ferrite powder contains rare earth atoms, the rare earth atom content (bulk content) relative to 100 atomic% of iron atoms is preferably in the range of 0.5 to 5.0 atomic%. It is believed that containing rare earth atoms at a bulk content within the above range, with the rare earth atoms predominantly located on the surface of the particles constituting the hexagonal strontium ferrite powder, helps to suppress the decrease in reproduction output during repeated reproduction. This is presumably because containing rare earth atoms at a bulk content within the above range, with the rare earth atoms predominantly located on the surface of the particles constituting the hexagonal strontium ferrite powder, can increase the anisotropy constant Ku. A higher value of the anisotropy constant Ku is more effective in suppressing the phenomenon known as thermal fluctuation (in other words, it improves thermal stability). By suppressing thermal fluctuation, the decrease in reproduction output during repeated reproduction can be suppressed. Hypothesis: The rare earth atoms biased towards the surface of hexagonal strontium ferrite powder particles help stabilize the spin of the iron (Fe) positions within the surface lattice, thereby increasing the anisotropy constant Ku.

[0102] Furthermore, it is hypothesized that using hexagonal strontium ferrite powder with rare-earth atom bias on the surface as a strong magnetic powder in the magnetic layer can also help suppress wear of the magnetic layer surface due to slippage with the magnetic head. That is, it is hypothesized that hexagonal strontium ferrite powder with rare-earth atom bias on the surface can also help improve the tape travel durability. This is hypothesized because the rare-earth atom bias on the surface of the particles constituting the hexagonal strontium ferrite powder helps to enhance the interaction between the particle surface and the organic matter (e.g., binders and / or additives) contained in the magnetic layer, thereby increasing the strength of the magnetic layer.

[0103] From the viewpoint of further suppressing the decline in reproduction output during repeated reproduction and / or further improving the durability of the conveyor belt, the rare earth atom content (bulk content) is more preferably in the range of 0.5 to 4.5 atomic%, more preferably in the range of 1.0 to 4.5 atomic%, and even more preferably in the range of 1.5 to 4.5 atomic%.

[0104] The aforementioned 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 aforementioned 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 is based on the sum of the two or more types.

[0105] When the hexagonal strontium ferrite powder contains rare earth atoms, the rare earth atoms contained can be any one or more of the rare earth atoms. From the viewpoint of further suppressing the decrease in reproduction output during repeated reproduction, preferred rare earth atoms include neodymium atoms, samarium atoms, yttrium atoms, and dysprosium atoms, more preferably neodymium atoms, samarium atoms, and yttrium atoms, and even more preferably neodymium atoms.

[0106] In hexagonal strontium ferrite powder exhibiting a surface-partial predominance of rare earth atoms, the rare earth atoms only need to be present in the surface portion of the particles constituting the hexagonal strontium ferrite powder, and the degree of predominance is not limited. For example, regarding hexagonal strontium ferrite powder exhibiting a surface-partial predominance of rare earth atoms, the ratio of the surface portion content of rare earth atoms obtained by partial dissolution under the dissolution conditions described later to the bulk content of rare earth atoms obtained by complete dissolution under the dissolution conditions described later, "surface portion content / bulk content," exceeds 1.0, and can be 1.5 or more. A "surface portion content / bulk content" greater than 1.0 indicates that rare earth atoms are predominantly present in the surface portion (i.e., their quantity is greater than that in the interior) of the particles constituting the hexagonal strontium ferrite powder. Furthermore, the ratio of the surface portion content of rare earth atoms obtained by partial dissolution under the dissolution conditions described later to the bulk content of rare earth atoms obtained by complete dissolution under the dissolution conditions described later, "surface portion content / bulk content", can be, for example, 10.0 or less, 9.0 or less, 8.0 or less, 7.0 or less, 6.0 or less, 5.0 or less, or 4.0 or less. However, in hexagonal strontium ferrite powder with a rare earth atom surface portion bias, the rare earth atoms only need to be biased in the surface portion of the particles constituting the hexagonal strontium ferrite powder, and the above-mentioned "surface portion content / bulk content" is not limited to the upper or lower limit shown.

[0107] The partial and complete dissolution of hexagonal strontium ferrite powder will be described below. For hexagonal strontium ferrite powder existing in powder form, the partially and completely dissolved sample powders are collected from the same batch of powder. On the other hand, for hexagonal strontium ferrite powder contained in the magnetic layer of a magnetic tape, a portion of the hexagonal strontium ferrite powder removed from the magnetic layer is used for partial dissolution, and another portion is used for complete dissolution. When removing the hexagonal strontium ferrite powder from the magnetic layer, the method described, for example, in paragraph 0032 of Japanese Patent Application Publication No. 2015-91747 can be used.

[0108] The aforementioned partial dissolution refers to the point at which dissolution is complete, to the point where the hexagonal strontium ferrite powder residue can be visually identified in the liquid. For example, through partial dissolution, an area where 10-20% by mass (with the total number of particles as 100% by mass) of the particles constituting the hexagonal strontium ferrite powder can be dissolved is possible. On the other hand, the aforementioned complete dissolution refers to the point at which dissolution is complete, to the point where the hexagonal strontium ferrite powder residue cannot be visually identified in the liquid.

[0109] The determination of partial dissolution and surface layer content mentioned above is performed, for example, by the following method. However, the dissolution conditions, such as the amount of sample powder described below, are merely illustrative, and any dissolution conditions capable of partial or complete dissolution can be used.

[0110] A container (e.g., a beaker) containing 12 mg of sample powder and 10 ml of 1 mol / L hydrochloric acid is kept on a hot plate at a set temperature of 70°C for 1 hour. The resulting solution is filtered through a 0.1 μm membrane filter. Elemental analysis of the filtrate is performed using an inductively coupled plasma (ICP) analyzer. This allows the determination of the surface portion content of rare earth atoms relative to 100 atomic percent of iron atoms. In cases where multiple rare earth atoms are detected by elemental analysis, the total content of all rare earth atoms is taken as the surface portion content. This process is also applied to the determination of bulk content.

[0111] On the other hand, the determination of complete dissolution and bulk content is carried out, for example, by the following method.

[0112] A container (e.g., a beaker) containing 12 mg of sample powder and 10 ml of 4 mol / L hydrochloric acid is kept on a hot plate at a set temperature of 80°C for 3 hours. Then, the same steps as the above-described determination of partial dissolution and surface content are performed to determine the bulk content relative to 100 atomic percent of iron atoms.

[0113] From the viewpoint of improving the reproduction output when reproducing data recorded onto magnetic tape, it is preferable that the magnetic tape contains a strongly magnetic powder with a high mass magnetization σs. In this regard, hexagonal strontium ferrite powder containing rare-earth atoms but lacking a rare-earth atom surface bias tends to exhibit a significantly lower σs compared to hexagonal strontium ferrite powder without rare-earth atoms. Therefore, to suppress this significant decrease in σs, hexagonal strontium ferrite powder with a rare-earth atom surface bias is 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 a known measuring device capable of measuring magnetic properties, such as a vibrating sample type fluxmeter. In this invention and this specification, unless otherwise specified, the mass magnetization σs is the value measured with a magnetic field strength of 1194 kA / m (15 kOe).

[0114] 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% (100 atomic% of iron atoms). In one embodiment, the hexagonal strontium ferrite powder may contain only strontium atoms as divalent metal atoms in the powder. Furthermore, in another embodiment, the hexagonal strontium ferrite powder may also contain one or more other divalent metal atoms besides strontium atoms. For example, it may contain barium atoms and / or calcium atoms. In the case of containing divalent metal atoms other than strontium atoms, the barium atom content and calcium atom content in the hexagonal strontium ferrite powder can, for example, be in the range of 0.05 to 5.0 atomic% (100 atomic% of iron atoms), respectively.

[0115] As for the crystal structures of hexagonal ferrites, the known types are magnetoplumbide (also known as "M-type"), W-type, Y-type, and Z-type. Hexagonal strontium ferrite powder can adopt any crystal structure. The crystal structure can be confirmed by X-ray diffraction analysis. Hexagonal strontium ferrite powder can be detected by X-ray diffraction analysis to have a single crystal structure or two or more crystal structures. For example, in one embodiment, hexagonal strontium ferrite powder can be detected by X-ray diffraction analysis to have only an M-type crystal structure. For example, M-type hexagonal ferrite is made from AFe... 12 O 19The composition is represented by the formula. Here, A represents a divalent metal atom. In the case of hexagonal strontium ferrite powder being 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 generally 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 percent of iron atoms may be, for example, 0.5 to 10.0 atomic percent. From the viewpoint of further suppressing the decrease in reproduction output during repeated reproduction, hexagonal strontium ferrite powder preferably contains iron atoms, strontium atoms, oxygen atoms, and rare earth atoms, and the content of atoms other than these atoms is 10.0 atomic% or less relative to 100 atomic% of iron atoms, more preferably in the range of 0 to 5.0 atomic%, and may also be 0 atomic%. That is, in one embodiment, hexagonal strontium ferrite powder may be free of atoms other than iron atoms, strontium atoms, oxygen atoms, and rare earth atoms. The content expressed in atomic% is obtained by converting the content of each atom (unit: mass%) obtained by completely dissolving the hexagonal strontium ferrite powder into a value expressed in atomic% using the atomic weight of each atom. Furthermore, in this invention and this specification, "free of" for a certain atom 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 include cases where the content is less than the detection limit of the ICP analyzer. In one embodiment, the hexagonal strontium ferrite powder may be bismuth-free (Bi).

[0116] Metal powder

[0117] As a preferred specific example of a strongly magnetic powder, strongly magnetic metal powder can be cited. For details regarding strongly magnetic metal powder, see, for example, 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.

[0118] ε-iron oxide powder

[0119] 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 ε-iron oxide-type crystal structure is detected as the main phase by X-ray diffraction analysis. For example, if the highest intensity diffraction peak in the X-ray diffraction spectrum obtained by X-ray diffraction analysis belongs to an ε-iron oxide-type crystal structure, then the ε-iron oxide-type crystal structure is determined to be the main phase. Methods for manufacturing ε-iron oxide powder include methods using goethite, reverse micelle methods, etc. These manufacturing methods are all well known. Furthermore, regarding methods for manufacturing ε-iron oxide powder in which a portion of Fe is replaced by Ga, Co, Ti, Al, Rh, etc., for example, see J. Jpn. Soc. Powder Metallurgy Vol. 61 Supplement, No. S1, pp. S280-S284, J. Mater. Chem. C, 2013, 1, pp. 5200-5206, etc. However, the method for manufacturing ε-iron oxide powder, which can be used as a strong magnetic powder in the magnetic layer of the magnetic tape described above, is not limited to the methods listed herein.

[0120] 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 with an activation volume within this range is suitable for manufacturing magnetic tapes that exhibit excellent electromagnetic conversion properties. The preferred activation volume of the ε-iron oxide powder is 300 nm. 3 The above, for example, could also be 500nm. 3 That's all. Furthermore, from the viewpoint of further improving electromagnetic conversion characteristics, the activation volume of 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 value: 1200 nm. 3 Hereinafter, 1100nm is further preferred. 3 the following.

[0121] An anisotropy constant Ku can be cited as an indicator of reducing thermal fluctuations (in other words, improving thermal stability). ε-iron oxide powder preferably has a Ku value of 3.0 × 10⁻⁶. 4 J / m 3 The above-mentioned Ku, more preferably, can have 8.0 × 10 4 J / m 3 The above refers to the Ku. Furthermore, the Ku of ε-iron oxide powder can, for example, be 3.0 × 10⁻⁶. 5 J / m 3 However, a higher Ku value indicates higher thermal stability and is therefore preferred; it is not limited to the values ​​exemplified above.

[0122] From the viewpoint of improving the reproduction output when reproducing data recorded onto magnetic tape, it is preferable that the magnetic tape contains strongly magnetic powder with a high mass magnetization σs. In this regard, in one embodiment, the σs of the ε-iron oxide powder can be 8 A·m. 2 / kg or above, or 12A·m 2 / kg or more. On the other hand, from the viewpoint of noise reduction, the σs of ε-iron oxide powder is preferably 40 A·m. 2 Below / kg, preferably 35A·m 2 / kg or less.

[0123] 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.

[0124] The powder was photographed at 100,000x magnification using a transmission electron microscope, and then printed at a total magnification of 500,000x on photographic paper or displayed on a monitor to obtain photographs of the particles that make up 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.

[0125] The above measurements were performed on 500 randomly selected particles. The arithmetic mean of the particle sizes of these 500 particles was taken as the average particle size of the powder. For example, a Hitachi, Ltd. H-9000 transmission electron microscope can be used as the transmission electron microscope described above. Furthermore, the particle size measurement can be performed using known image analysis software (e.g., Carl Zeiss AG KS-400 image analysis software). Unless otherwise specified, the average particle size shown in the embodiments described below is the value measured using a Hitachi, Ltd. H-9000 transmission electron microscope as a transmission electron microscope and Carl Zeiss AG KS-400 image analysis software as image analysis software. In this invention and specification, "powder" refers to a collection of multiple particles. For example, "strong magnetic powder" refers to a collection of multiple strongly magnetic particles. Furthermore, the collection of multiple particles is not limited to the particles constituting the collection being in direct contact, but also includes the presence of binders, additives, etc., between the particles, as described later. The term "particle" is sometimes also used to refer to powder.

[0126] 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.

[0127] 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.

[0128] (1) In the case of needle-shaped, spindle-shaped, columnar (where the height is greater than the maximum major diameter of the base), it represents the length of the major axis constituting the particle, i.e., the length of the major axis.

[0129] (2) In the case of a plate or column (where the thickness or height is less than the maximum major diameter of the plate surface or bottom surface), indicate the maximum major diameter of the plate surface or bottom surface.

[0130] (3) When the particle is spherical, polyhedral, or of any unspecified shape, and the major axis of the particle cannot be determined based on its shape, the equivalent diameter of the circle is represented. The equivalent diameter of the circle is determined by the circular projection method.

[0131] Furthermore, in the above measurements, the length of the minor axis of the particles, i.e., the minor axis length, was measured, and the value of (major axis length / minor axis length) for each particle was calculated. The average needle-like ratio of the powder refers to the arithmetic mean of the values ​​obtained for the above 500 particles. Here, unless otherwise specified, regarding the minor axis length, in the above definition of particle size (1), it refers to the length of the minor axis constituting the particle; similarly, in the case of (2), it refers to the thickness or height; and in the case of (3), since it is impossible to distinguish between the major axis and the minor axis, for convenience, (major axis length / minor axis length) is regarded as 1.

[0132] 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).

[0133] The content (filling rate) of the strongly magnetic powder in the magnetic layer is preferably in the range of 50 to 90% by mass, and more preferably in the range of 60 to 90% by mass. From the viewpoint of increasing recording density, a higher filling rate of the strongly magnetic powder in the magnetic layer is preferred.

[0134] (Adhesive)

[0135] The aforementioned magnetic tape can be a coated magnetic tape and may contain an adhesive in the magnetic layer. The adhesive is one or more resins. Various resins commonly used as adhesives in coated magnetic recording media can be used as adhesives. For example, resins selected from polyurethane resins, polyester resins, polyamide resins, vinyl chloride resins, copolystyrene, acrylonitrile, methyl methacrylate, etc., acrylic resins, cellulose resins such as nitrocellulose, epoxy resins, phenoxy resins, polyvinyl acetal, polyvinyl butyral, etc., can be used alone as adhesives, or multiple resins can be used in combination. Polyurethane resins, acrylic resins, cellulose resins, and vinyl chloride resins are preferred. These resins can be homopolymers or copolymers. These resins can also be used as adhesives in the non-magnetic layer and / or back coating layer described later. For more information on the above adhesives, please refer to paragraphs 0028 to 0031 of Japanese Patent Application Publication No. 2010-24113 and paragraphs 0006 to 0021 of Japanese Patent Application Publication No. 2004-5795. The average molecular weight of the resin used as a binder, based on weight-average molecular weight, can be, for example, 10,000 or more and 200,000 or less. The average molecular weight in this invention and specification refers to a value obtained by converting a value measured by gel permeation chromatography (GPC) under the following testing conditions to polystyrene. The average molecular weight of the binder shown in the examples described later is a value obtained by converting a value measured under the following testing conditions to polystyrene. The binder can be used, for example, in an amount of 1.0 to 80.0 parts by weight relative to 100.0 parts by weight of the strongly magnetic powder. Regarding the binder dosage of the non-magnetic layer and the back coating, the strongly magnetic powder can be referred to as non-magnetic powder, and the description related to the binder dosage of the magnetic layer applies.

[0136] GPC Unit: HLC-8120 (manufactured by Tosoh Corporation)

[0137] Column: TSK gel Multipore HXL-M (manufactured by TOSOH CORPORATION, 7.8mmID (InnerDiameter) × 30.0cm)

[0138] Eluent: Tetrahydrofuran (THF)

[0139] A curing agent can also be used in conjunction with a resin that can be used as an adhesive. Regarding the curing agent, in one approach, it can be a thermosetting compound that undergoes a curing reaction (crosslinking reaction) by heating; in another approach, it can be a photocuring compound that undergoes a curing reaction (crosslinking reaction) by light irradiation. The curing agent undergoes a curing reaction during the magnetic layer forming process, and at least a portion of it can be included in the magnetic layer in a state of reaction (crosslinking) with other components such as the adhesive. This also applies to layers formed using the same composition when the composition used to form other layers contains a curing agent. A thermosetting compound is preferred as the curing agent, and polyisocyanate is suitable. For details regarding polyisocyanate, refer to paragraphs 0124-0125 of Japanese Patent Application Publication No. 2011-216149. The content of the curing agent in the magnetic layer forming composition can be, for example, 0 to 80 parts by weight relative to 100.0 parts by weight of the adhesive, and from the viewpoint of improving the strength of the magnetic layer, it can be 50.0 to 80.0 parts by weight. This also applies to compositions for forming non-magnetic layers and compositions for forming a back coating layer.

[0140] (additive)

[0141] The magnetic layer may contain one or more additives as needed. Examples of additives include the curing agent described above. Furthermore, additives contained in the magnetic layer may include non-magnetic powders (e.g., inorganic powders, carbon black, etc.), lubricants, dispersants, dispersing aids, mildew inhibitors, antistatic agents, antioxidants, etc. For example, regarding lubricants, see paragraphs 0030-0033, 0035, and 0036 of Japanese Patent Application Publication No. 2016-126817. The non-magnetic layer described later may contain lubricants. Regarding lubricants that may be contained in the non-magnetic layer, see paragraphs 0030-0031, 0034, 0035, and 0036 of Japanese Patent Application Publication No. 2016-126817. Regarding dispersants, see paragraphs 0061 and 0071 of Japanese Patent Application Publication No. 2012-133837. Furthermore, regarding additives for the magnetic layer, please refer to paragraphs 0035 to 0077 of Japanese Patent Application Publication No. 2016-51493. Dispersants can also be added to the composition for forming a non-magnetic layer. Regarding dispersants that can be added to the composition for forming a non-magnetic layer, please refer to paragraph 0061 of Japanese Patent Application Publication No. 2012-133837. Examples of non-magnetic powders that can be contained in the magnetic layer include non-magnetic powders that function as abrasives and non-magnetic powders that function as protrusion forming agents (e.g., non-magnetic colloidal particles). Additionally, the average particle size of the colloidal silica (silica colloidal particles) shown in the examples described later is a value obtained by a method described in paragraph 0015 of Japanese Patent Application Publication No. 2011-048878 for measuring the average particle size. Additives can be selected from commercially available products or manufactured by known methods according to the desired properties, and used in any amount. As an example of an additive that can be used in a magnetic layer containing abrasives to improve the dispersibility of the abrasives, the dispersant described in paragraphs 0012 to 0022 of Japanese Patent Application Publication No. 2013-131285 can be cited.

[0142] As described above, high surface smoothness of the magnetic layer of the magnetic tape contributes to improved electromagnetic conversion characteristics. From the viewpoint of improving electromagnetic conversion characteristics, the average roughness Ra of the centerline of the magnetic layer surface of the magnetic tape, as measured by an optical interferometer, is preferably 4.0 nm or less, more preferably 3.8 nm or less, and even more preferably 3.7 nm or less. In this invention and this specification, the term "magnetic layer (surface)" in the magnetic tape has the same meaning as the side surface of the magnetic layer of the magnetic tape. Furthermore, from the viewpoint of improving tape transport stability, the average roughness Ra of the centerline of the magnetic layer surface of the magnetic tape, as measured by an optical interferometer, is preferably 0.3 nm or more, more preferably 0.5 nm or more.

[0143] 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.

[0144] <Nonmagnetic layer>

[0145] Next, the non-magnetic layer will be described. The magnetic tape described above can have a magnetic layer directly on the surface of the non-magnetic support, or it can have a magnetic layer on the surface of the non-magnetic support via a non-magnetic layer containing non-magnetic powder. The non-magnetic powder used for the non-magnetic layer can be an inorganic powder or an organic powder. Furthermore, carbon black can also be used. Examples of inorganic powders include powders of metals, metal oxides, metal carbonates, metal sulfates, metal nitrides, metal carbides, and metal sulfides. These non-magnetic powders can be obtained as commercially available products or manufactured using known methods. For details, please refer to paragraphs 0146 to 0150 of Japanese Patent Application Publication No. 2011-216149. For information on 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 the non-magnetic powder in the non-magnetic layer is preferably in the range of 50 to 90% by mass, more preferably in the range of 60 to 90% by mass.

[0146] Other details regarding the adhesives, additives, etc., of the non-magnetic layer can be found in known techniques related to the non-magnetic layer. Furthermore, for example, the type and content of the adhesive, the type and content of the additive, etc., can also be found in known techniques related to the magnetic layer.

[0147] In this invention and specification, the non-magnetic layer also includes a substantially non-magnetic layer that, together with the non-magnetic powder, contains, for example, in the form of 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, a magnetic retention force of 7.96 kA / m (100 Oe) or less, or a layer with a remanent magnetic flux density of 10 mT or less and a magnetic retention force of 7.96 kA / m (100 Oe) or less. Preferably, the non-magnetic layer does not have a remanent magnetic flux density or a magnetic retention force.

[0148] <Back Coating>

[0149] 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 this back coating. Preferably, the back coating contains one or both of carbon black and inorganic powder. As carbon black, for example, carbon black with an average particle size of 17 nm or more and 50 nm or less (hereinafter referred to as "particulate carbon black") may be used, or carbon black with an average particle size of more than 50 nm and 300 nm or less (hereinafter referred to as "coarse carbon black"). Furthermore, both particulate carbon black and coarse carbon black may be used simultaneously.

[0150] Examples of inorganic powders include non-magnetic powders commonly used in non-magnetic layers and non-magnetic powders commonly used as abrasives in magnetic layers, with α-iron oxide and α-alumina being preferred. The average particle size of the inorganic powder in the back coating can, for example, be in the range of 5 to 250 nm. When both carbon black and inorganic powder are used as the non-magnetic powder in the back coating, in one embodiment, it is preferable to contain more than 50 parts by mass of inorganic powder relative to 100.0 parts by mass of the total amount of non-magnetic powder, and more preferably, 70.0 to 90.0 parts by mass of inorganic powder. In one embodiment, the above descriptions related to the non-magnetic powder in the back coating can also be applied to the non-magnetic powder in the non-magnetic layer.

[0151] The back coating may contain an adhesive and, if necessary, additives. Regarding the adhesive and additives for the back coating, prior art related to the back coating itself, as well as prior art related to the formulation of the magnetic and / or non-magnetic layers, may be applied. For example, regarding the back coating, refer to paragraphs 0018 to 0020 of Japanese Patent Application Publication No. 2006-331625 and lines 65-38 of column 4 of U.S. Patent No. 7,029,774.

[0152] Various thicknesses

[0153] From the viewpoint of maximizing the capacity of each magnetic tape cartridge, a thin magnetic tape is preferable. Reducing the thickness of the non-magnetic support contributes to reducing the overall thickness of the magnetic tape, and is therefore preferred. In this regard, the thickness of the non-magnetic support included in the magnetic tape is preferably less than 10.0 μm, more preferably 9.0 μm or less, even more preferably 8.0 μm or less, even more preferably 7.0 μm or less, and even more preferably 6.0 μm or less. Furthermore, the thickness of the non-magnetic support can, for example, be 0.5 μm or more or 1.0 μm or more.

[0154] 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, 0.015 μm to 0.12 μm is preferred, and 0.02 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. When divided into two or more magnetic layers, the thickness of the magnetic layer refers to the total thickness of these layers.

[0155] The thickness of the non-magnetic layer is, for example, 0.1 to 1.5 μm, preferably 0.1 to 1.0 μm.

[0156] The thickness of the back coating is preferably less than 0.9 μm, and more preferably 0.1 to 0.7 μm.

[0157] The thickness of the non-magnetic support and the thickness of each layer in this invention and specification can be determined by known methods. For example, the thickness of the magnetic layer can be determined by the following method: After exposing a cross-section in the thickness direction of the magnetic tape using a known device such as an ion beam or a slicer, a cross-sectional image of the exposed cross-section is acquired using a scanning electron microscope (SEM) or a transmission electron microscope (TEM). Cross-sectional images are acquired at 10 randomly selected locations. For each of the 10 acquired images, the thickness of the magnetic layer is measured at a randomly selected location in each image. The thickness of the magnetic layer can be calculated by the arithmetic mean of the 10 measurements obtained from the 10 images. When the thickness of the magnetic layer is determined, the interface with the portion adjacent to the magnetic layer (e.g., the non-magnetic layer) can be determined by the method described in paragraph 0029 of Japanese Patent Application Publication No. 2017-33617. Other thicknesses can also be determined in the same way.

[0158] <Manufacturing Process>

[0159] (Preparation of the composition for forming each layer)

[0160] The process of preparing a composition for forming a magnetic layer, a non-magnetic layer, or a back coating typically includes at least a mixing process, a dispersion process, and a blending process arranged before or after these processes as needed. Each process can be divided into two or more stages. Components used in the preparation of the composition for forming each layer can be added at the beginning or middle of any process. As a solvent, one or more solvents commonly used in the manufacture of coated magnetic recording media can be used. For example, regarding solvents, see paragraph 0153 of Japanese Patent Application Publication No. 2011-216149. Furthermore, the components can be added in stages during two or more processes. For example, the binder can be added in stages during the mixing process, the dispersion process, and the blending process for adjusting the viscosity after dispersion. To manufacture the aforementioned magnetic tape, known manufacturing techniques can be used in various processes. In the mixing process, kneaders with strong mixing forces, such as open kneaders, continuous kneaders, pressure kneaders, and extruders, are preferred. For details regarding the mixing process, please refer to Japanese Patent Application Publication Nos. 1-106338 and 1-79274. A known disperser can be used. Filtration can be performed at any stage of preparing the composition for each layer formation by a known method. Filtration can be performed, for example, by using a filter. As a filter for filtration, for example, a filter with a pore size of 0.01 to 3 μm (e.g., a glass fiber filter, a polypropylene filter, etc.) can be used.

[0161] (Coating process)

[0162] The magnetic layer can be formed by directly applying the magnetic layer forming composition to the surface of the non-magnetic support, or by sequentially or simultaneously applying multiple layers of the magnetic layer forming composition. The back coating can be formed by applying the back coating forming composition to the surface of the non-magnetic support opposite to the surface having the non-magnetic layer and / or the magnetic layer (or the surface to which the non-magnetic layer and / or the magnetic layer will be applied). For details regarding the coatings used to form each layer, please refer to paragraph 0066 of Japanese Patent Application Publication No. 2010-231843.

[0163] (Other processes)

[0164] For various other processes used in the manufacture of magnetic tape, known technologies can be applied. For example, reference can be made to paragraphs 0067 to 0070 of Japanese Patent Application Publication No. 2010-231843. For instance, the coating layer of the magnetic layer forming composition can be oriented while still wet (not dried). Regarding the orientation process, various known technologies, beginning with paragraph 0052 of Japanese Patent Application Publication No. 2010-24113, can be applied. For example, vertical orientation can be performed using known methods such as the use of opposite-pole magnets. In the orientation zone, the drying speed of the coating layer can be controlled based on the temperature and flow rate of the drying air and / or the conveying speed in the orientation zone. Furthermore, the coating layer can be pre-dried before being conveyed to the orientation zone.

[0165] Through various processes, long, rolled magnetic tapes can be obtained. These rolls are then cut (divided) using a known cutting machine to the width required for mounting in a cassette. This width is determined by standards, for example, 1 / 2 inch. 1 inch = 0.0254 meters.

[0166] To achieve tracking control of the magnetic head and control of the tape feed speed in a magnetic recording and playback device, a servo pattern can be formed on the magnetic tape manufactured as described above using known methods. "Servo pattern formation" can also be referred to as "servo signal recording." The formation of the servo pattern will be explained below.

[0167] Servo patterns are typically formed along the length of the magnetic tape. Examples of control methods that utilize servo signals (servo control) include time-based servo (TBS), amplitude servo, and frequency servo.

[0168] As shown in ECMA (European Computer Manufacturers Association) 319 (June 2001), a time-based servo method is used in LTO (Linear Tape-Open) compliant magnetic tapes (commonly referred to as "LTO tapes"). In this time-based servo method, the servo pattern is constructed by continuously arranging multiple pairs of non-parallel magnetic strips (also referred to as "servo strips") along the length of the tape. A servo system refers to a system that uses servo signals for head tracking. In this invention and specification, "time-based servo pattern" refers to a servo pattern capable of head tracking in a time-based servo system. As described above, the reason for constructing the servo pattern with a pair of non-parallel magnetic strips is to notify the servo signal readout element passing over the servo pattern of its position. Specifically, the pair of magnetic strips is formed such that the interval changes continuously along the width of the tape, and the servo signal readout element can determine the relative position of the servo pattern and the servo signal readout element by reading this interval. This relative position information makes data track tracking possible. Therefore, multiple servo tracks are typically set along the width of the magnetic tape on the servo pattern.

[0169] The servo tape consists of a continuous servo pattern along the length of the magnetic tape. Multiple servo tapes are typically present on the tape. For example, in an LTO tape, there are five. The area between two adjacent servo tapes is the data tape. The data tape consists of multiple data tracks, each corresponding to a servo track.

[0170] Furthermore, in one approach, as shown in Japanese Patent Application Publication No. 2004-318983, each servo tape contains embedded information indicating the servo tape's number (also referred to as "servo tape ID (identification)" or "UDIM (Unique Data Band Identification Method) information"). This servo tape ID is recorded by moving a specific pair of servo magnetic strips from a pair of servo magnetic strips present in the servo tape, causing their positions to shift relative to each other along the length of the magnetic tape. Specifically, the movement of a specific pair of servo magnetic strips from a pair of servo magnetic strips is changed for each servo tape. Therefore, the recorded servo tape ID is unique for each servo tape, and thus, by reading a servo tape using a servo signal reading element, the servo tape can be uniquely identified.

[0171] Another method for uniquely identifying servo tapes is the interleaving method shown in ECMA-319 (June 2001). In this interleaving method, each servo tape is recorded by moving a group of multiple pairs of non-parallel magnetic strips arranged consecutively along the length of the magnetic tape (servo strips). Since this combination of movement patterns between adjacent servo tapes is unique throughout the entire magnetic tape, the servo tape can also be uniquely identified when reading the servo pattern using two servo signal readout elements.

[0172] Furthermore, as shown in ECMA-319 (June 2001), information indicating the position of the magnetic tape along its length (also known as "LPOS (Longitudinal Position) information") is typically embedded in each servo tape. Similar to UDIM information, this LPOS information is recorded by shifting the position of a pair of servo strips along the length of the tape. However, unlike UDIM information, the same signal is recorded in each servo tape in this LPOS information.

[0173] Other information, different from the UDIM and LPOS information mentioned above, can also be embedded into the server tape. In this case, the embedded information can vary depending on the server tape, like the UDIM information, or it can be universal across all server tapes, like the LPOS information.

[0174] Furthermore, other methods besides those mentioned above can also be used as a way to embed information in the servo strip. For example, a specified code can be recorded by pulling a specified pair from the middle of a pair of servo magnetic strips.

[0175] The magnetic head used for servo pattern formation is called a servo write head. A servo write head typically has a pair of gaps corresponding to the aforementioned pair of magnetic strips, and the number of these gaps is the same as the number of servo tapes. Generally, a magnetic core and a coil are connected to each pair of gaps. By supplying current pulses to the coils, the magnetic field generated in the magnetic core produces a leakage magnetic field in the pair of gaps. When forming a servo pattern, by feeding the magnetic tape onto the servo write head while simultaneously inputting current pulses, the magnetic pattern corresponding to the pair of gaps can be transferred onto the magnetic tape, thereby forming a servo pattern. The width of each gap can be appropriately set according to the density of the formed servo pattern. For example, the width of each gap can be set to less than 1 μm, 1–10 μm, or more than 10 μm.

[0176] Before forming servo patterns on the magnetic tape, the tape is typically demagnetized (erased). This erasure process can be performed by applying a uniform magnetic field to the tape using a DC or AC magnet. Erasure processes include DC (Direct Current) erasure and AC (Alternating Current) erasure. AC erasure is performed by gradually reducing the strength of the magnetic field while reversing the direction applied to the tape. On the other hand, DC erasure is performed by applying a unidirectional magnetic field to the tape. DC erasure includes two methods. The first method is horizontal DC erasure, which applies a unidirectional magnetic field along the length of the tape. The second method is vertical DC erasure, which applies a unidirectional magnetic field along the thickness of the tape. Erasure processes can be performed on the entire tape or on each servo section of the tape.

[0177] The orientation of the magnetic field in the formed servo pattern depends on the erasure orientation. For example, when performing horizontal DC erasure on a magnetic tape, the servo pattern is formed with the magnetic field orientation opposite to the erasure orientation. This increases the output of the servo signal obtained by reading the servo pattern. Furthermore, as shown in Japanese Patent Application Publication No. 2012-53940, when a magnetic pattern using the aforementioned gap is transferred to a magnetic tape that has been vertically DC erased, the servo signal obtained by reading the formed servo pattern is a unipolar pulse shape. On the other hand, when a magnetic pattern using the aforementioned gap is transferred to a magnetic tape that has been horizontally DC erased, the servo signal obtained by reading the formed servo pattern is a bipolar pulse shape.

[0178] Magnetic tapes are usually housed in tape cases.

[0179] [Cassette Tape Case]

[0180] One aspect of the present invention relates to a magnetic tape cassette comprising the aforementioned magnetic tape.

[0181] The details of the magnetic tapes included in the aforementioned cassette are as described above.

[0182] 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 magnetic recording and playback device 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 magnetic recording and playback device 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 magnetic recording and playback device side (take-up reel). During this process, for example, the magnetic head contacts and slides against the magnetic layer surface of the magnetic tape, thereby recording and / or reproducing data. In contrast, a double-reel cassette has both a feed reel and a take-up reel inside the cassette. The aforementioned magnetic tape cassette can be either a single-reel or a double-reel type. The aforementioned magnetic tape cassette may include the magnetic tape involved in one aspect of the present invention; other types may utilize known technologies.

[0183] [Magnetic Recording Reproduction Device]

[0184] One aspect of the present invention relates to a magnetic recording and reproducing apparatus comprising the aforementioned magnetic tape.

[0185] In this invention and specification, "magnetic recording and playback apparatus" refers to an apparatus capable of at least one of recording data onto a magnetic tape and reproducing data recorded onto the magnetic tape. This apparatus is commonly referred to as a drive. The aforementioned magnetic recording and playback apparatus can, for example, be a sliding type magnetic recording and playback apparatus. A sliding type magnetic recording and playback apparatus is an apparatus in which the surface of the magnetic layer side contacts and slides against the magnetic head during data recording and / or reproduction of the recorded data on the magnetic tape. For example, the aforementioned magnetic recording and playback apparatus may include the aforementioned magnetic tape cassette in a detachable manner.

[0186] The aforementioned magnetic recording and playback apparatus may include a magnetic head. The magnetic head may be a recording head capable of recording data onto a magnetic tape, or a playback head capable of reproducing data recorded onto a magnetic tape. Furthermore, in one embodiment, the magnetic recording and playback apparatus may include both a recording head and a playback head as a single magnetic head. In another embodiment, the magnetic head included in the aforementioned magnetic recording and playback apparatus may have a structure comprising an element for recording data (recording element) and an element for reproducing data (reproduction element) on a single magnetic head. Hereinafter, the element for recording data and the element for reproducing data will be collectively referred to as "data element". Preferably, the playback head includes a magnetoresistive (MR) element capable of sensitively reading data recorded onto a magnetic tape as the playback element (MR head). As the MR head, various known MR heads such as AMR (Anisotropic Magnetoresistive) heads, GMR (Giant Magnetoresistive) heads, and TMR (Tunnel Magnetoresistive) heads can be used. Furthermore, the head for recording and / or reproducing data may include a servo signal readout element. Alternatively, the aforementioned magnetic recording and reproducing apparatus may include a head equipped with a servo signal readout element (servo head) as a separate head from the head for recording and / or reproducing data. For example, the head for recording and / or reproducing recorded data (hereinafter also referred to as a "recording and reproducing head") may include two servo signal readout elements, each capable of simultaneously reading two adjacent servo tapes. One or more data elements may be configured between the two servo signal readout elements.

[0187] In the aforementioned magnetic recording and playback apparatus, data recording on a magnetic tape and / or playback of data recorded on a magnetic tape can be performed, for example, by contacting and sliding the magnetic layer surface of the magnetic tape against a magnetic head. The aforementioned magnetic recording and playback apparatus may include the magnetic tape described in one aspect of the present invention; other applications may utilize known technologies.

[0188] For example, when recording and / or reproducing recorded data, the first step is to track the data using servo signals. That is, the servo signal readout element follows a predetermined servo track, thereby controlling the data readout element to move along the target data track. Movement of the data track is achieved by changing the servo track read by the servo signal readout element in the width direction of the magnetic tape.

[0189] Furthermore, the recording and playback head can also record and / or reproduce data for other data bands. In this case, simply use the aforementioned UDIM information to move the servo signal readout element to the specified servo band to begin tracking that servo band.

[0190] Example

[0191] The present invention will now be described in more detail through examples. However, the present invention is not limited to the embodiments shown. Unless otherwise specified, “parts” and “%” as used below refer to “parts by mass” and “% by mass”, respectively. “eq” is equivalent, a unit that cannot be converted to SI units. Unless otherwise specified, the following processes and evaluations are performed in an atmosphere at 23°C ± 1°C.

[0192] [Non-magnetic support]

[0193] The supports listed as "PEEK" in the "Resin" column of Table 1 are made by the following method.

[0194] Commercially available PEEK membranes (Victrex Aptiv membrane 1000) were cut into 165mm × 115mm pieces and installed in an intermittent synchronous biaxial stretching device. They were stretched at the stretching temperature, stretching ratio, and stretching speed specified in Table 1.

[0195] Next, it was heat-treated in a furnace with an atmosphere temperature of 300°C and a relaxation rate of 0.95.

[0196] The stretched film thus obtained is cut into 1 / 2-inch widths, and the ends are joined together with a film obtained by cutting a commercially available polyethylene terephthalate film into 1 / 2-inch widths to create a roll support. Using this roll support, a roll of magnetic tape is produced by the method described later. As the magnetic tape to be evaluated in the evaluation described later, a magnetic tape obtained by cutting the portion of the support that is a PEEK film from the produced roll of magnetic tape is used.

[0197] The support structure listed as "PEKK" in the "Resin" column of Table 1 is manufactured using the following method.

[0198] Polyetherketoneketone (glass transition temperature: 162°C, melting point: 331°C), whose constituent resin is composed only of repeating units having the following structural formula, is melted and mixed in an extruder, and then extruded from a T-die at a resin temperature of 390°C and cooled to obtain a film.

[0199] [Chemical Formula 1]

[0200]

[0201] Before extrusion, foreign matter (presumably unmelted resin or over-crosslinked resin) was removed by filtration. The film was cut into 165mm × 115mm pieces and installed in an intermittent synchronous biaxial stretching device, and stretched at the stretching temperature, stretching ratio, and stretching speed listed in Table 1.

[0202] Next, it was heat-treated in a heat treatment furnace with an atmosphere temperature of 300°C and a relaxation rate of 0.95.

[0203] The stretched film thus obtained was cut into 1 / 2-inch widths, and films cut into 1 / 2-inch widths from commercially available biaxially stretched polyethylene terephthalate film were joined at both ends to create a roll support. Using this roll support, a roll of magnetic tape was produced by the method described later. As the magnetic tape to be evaluated in the evaluation described later, a magnetic tape obtained by cutting the portion of the support portion that was a PEKK film from the produced roll of magnetic tape was used.

[0204] As a support body listed as "PEEK" in the "Resin" column and "None" in the "Stretch Ratio" column of Table 1, the film used was cut from a commercially available PEEK film (Aptiv film 1000 manufactured by Victrex) to a width of 1 / 2 inch and the length used in the manufacture of roll magnetic tape without either the above-mentioned stretching treatment or heat treatment.

[0205] The support listed as "PET" in the "Resin" column of Table 1 is made from commercially available biaxially stretched polyethylene terephthalate film cut to 1 / 2-inch width and the length used in the manufacture of roll magnetic tape.

[0206] The support labeled "PEN" in the "Resin" column of Table 1 is made from commercially available biaxially stretched polyethylene naphthalate film cut to 1 / 2-inch width and the length used in the manufacture of rolled magnetic tape.

[0207] The support listed as "aromatic polyamide" in the "Resin" column of Table 1 is the length used in the manufacture of commercially available biaxially stretched aromatic polyamide films cut to 1 / 2-inch widths and rolls of magnetic tape.

[0208] [Example 1]

[0209] (1) Preparation of alumina dispersion

[0210] Compared to an α-oxidation rate of approximately 65% ​​and a BET (Brunauer-Emmett-Teller) specific surface area of ​​20 m², 2100.0 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.

[0211] (2) Formulation of the composition for forming a magnetic layer

[0212] (Magnetic fluid)

[0213] 100.0 parts of strong magnetic powder

[0214] Hexagonal barium ferrite powder with an average particle size (average plate diameter) of 21 nm (“BaFe” in Table 1).

[0215] 14.0 parts of polyurethane resin containing SO3Na groups

[0216] Weight-average molecular weight: 70,000, SO3Na group: 0.2 meq / g

[0217] Cyclohexanone 150.0 parts

[0218] 150.0 parts of methyl ethyl ketone

[0219] (Abrasive solution)

[0220] 6.0 parts of the alumina dispersion prepared in (1) above

[0221] (Silica sol (protrusion forming agent solution))

[0222] Colloidal silica (average particle size 120 nm) 2.0 parts

[0223] 1.4 parts of methyl ethyl ketone

[0224] (Other ingredients)

[0225]

[0226] (Solvent-1)

[0227] Cyclohexanone 200.0 parts

[0228] 200.0 parts of methyl ethyl ketone

[0229] (Solvent-2)

[0230] Cyclohexanone 350.0 parts

[0231] 350.0 parts of methyl ethyl ketone

[0232] (3) Formulation of the composition for forming a non-magnetic layer

[0233] Non-magnetic inorganic powder: 100.0 parts of α-iron oxide

[0234] Average particle size (average major axis length): 0.15 μm

[0235] Average needle ratio: 7

[0236] BET specific surface area: 52m² 2 / g

[0237] 20.0 parts carbon black

[0238] Average particle size: 20nm

[0239] 18.0 parts of polyurethane resin containing SO3Na groups

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

[0241]

[0242] (4) Preparation of the composition for forming each layer

[0243] A composition for forming a magnetic layer was prepared by the following method. The above-mentioned components were dispersed (bead dispersion) for 24 hours using an intermittent vertical sand mill, thereby preparing a magnetic fluid. Zirconia beads with a diameter of 0.5 mm were used as the dispersion beads. The magnetic fluid, the above-mentioned abrasive fluid, silica sol, other components, and solvent-1 were mixed using the sand mill described above, and dispersed as beads for 5 minutes. Then, the mixture was treated with an intermittent ultrasonic device (20 kHz, 300 W) for 0.5 minutes (ultrasonic dispersion). After filtration using a filter with a pore size of 0.5 μm, solvent-2 was added to prepare the composition for forming a magnetic layer.

[0244] A nonmagnetic layer-forming composition was prepared by the following method: The above-mentioned components, excluding the lubricant (stearic acid, stearamide, and butyl stearate), were kneaded and diluted using an open kneader, and then dispersed using a horizontal bead mill disperser. Next, the lubricant (stearic acid, stearamide, and butyl stearate) was added, and the mixture was stirred and mixed using a dissolving mixer to prepare the nonmagnetic layer-forming composition.

[0245] The back coating composition is prepared by further diluting the composition prepared in the same manner as the non-magnetic layer composition described above with the following solvent.

[0246] Cyclohexanone 300.0 parts

[0247] 300.0 parts of methyl ethyl ketone

[0248] (5) Methods for making magnetic tapes

[0249] A non-magnetic layer forming composition was coated onto the surface of the support shown in Table 1 to a thickness of 1.0 μm after drying, and then dried to form a non-magnetic layer.

[0250] Next, a magnetic layer forming composition is coated onto the surface of the non-magnetic layer to a thickness of 0.1 μm after drying, and then dried to form a magnetic layer.

[0251] Then, the back coating composition is applied to the surface of the support opposite to the surface where the non-magnetic layer and the magnetic layer are formed, with a dried thickness of 0.5 μm, and then dried to form the back coating.

[0252] Then, using a calendering roller consisting of two metal rollers, a surface smoothing process (calendering treatment) was performed twice at a speed of 20 m / min, a linear pressure of 320 kN / m (327 kg / cm), and a calendering temperature of 95°C (the surface temperature of the calendering roller). After that, heat treatment was carried out by holding the roller in a heat treatment furnace at an atmosphere temperature of 70°C for 36 hours.

[0253] At the junction of the portion of the support portion being a PEKK film and the portion of the support portion being a polyethylene terephthalate film, the portion of the magnetic tape with the PEKK film support portion is cut from the roll of magnetic tape thus manufactured to obtain a magnetic tape for evaluation described later.

[0254] [Examples 2-5, Comparative Examples 1-7]

[0255] The objects shown in Table 1 were used as supports and / or strongly magnetic powders, and the reel magnetic tape was otherwise manufactured in the same manner as in Example 1.

[0256] Regarding Examples 2-5 and Comparative Examples 1-4, similarly to Example 1, the portion of the support body that is a PEEK film or a PEKK film was cut from the rolled magnetic tape to obtain the magnetic tape for evaluation described later.

[0257] Regarding Comparative Examples 5-7, magnetic tapes obtained by cutting regions of arbitrary length into rolls of magnetic tape were used for the evaluation described later.

[0258] [Method for preparing strongly magnetic powder]

[0259] <Preparation Method of Hexagonal Strontium Ferrite Powder>

[0260] The “SrFe” shown in Table 1 is a hexagonal strontium ferrite powder produced by the following method.

[0261] Weigh out 1707g of SrCO3, 687g of H3BO3, 1120g of Fe2O3, 45g of Al(OH)3, 24g of BaCO3, 13g of CaCO3 and 235g of Nd2O3, and mix them in a mixer to obtain a raw material mixture.

[0262] The obtained raw material mixture was melted in a platinum crucible at a melting temperature of 1390°C. While stirring the melt, the melt outlet located at the bottom of the platinum crucible was heated, and the melt was discharged into a rod shape at a rate of approximately 6 g / s. The discharged melt was then rapidly cooled by rolling using water-cooled twin rollers to produce an amorphous substance.

[0263] 280g of the prepared amorphous material was placed in an electric furnace and heated to 635℃ (crystallization temperature) at a heating rate of 3.5℃ / min. The temperature was then maintained at the same temperature for 5 hours to allow hexagonal strontium ferrite particles to precipitate (crystallize).

[0264] Next, the crystals obtained above, containing hexagonal strontium ferrite particles, were coarsely pulverized in a mortar. Then, 1000g of 1mm zirconium oxide beads and 800mL of 1% acetic acid aqueous solution were added to a glass bottle, and the mixture was dispersed using a paint stirrer for 3 hours. The resulting dispersion was then separated from the beads and placed in a stainless steel beaker. After dissolving the glass components by standing the dispersion at 100°C for 3 hours, it was precipitated using a centrifuge, repeatedly decanted, washed, and dried in a furnace at 110°C for 6 hours to obtain hexagonal strontium ferrite powder.

[0265] The hexagonal strontium ferrite powder obtained above (“SrFe1” in Table 1) has an average particle size of 18 nm and an activation volume of 902 nm. 3 The anisotropy constant Ku is 2.2 × 10⁻⁶. 5 J / m 3 The mass magnetization σs is 49 A·m 2 / kg.

[0266] 12 mg of sample powder was collected from the hexagonal strontium ferrite powder obtained above. The elemental composition of the filtrate obtained by partially dissolving the sample powder under the above-described dissolution conditions was determined by an ICP analyzer.

[0267] In addition, 12 mg of sample powder was collected from the hexagonal strontium ferrite powder obtained above, and the elemental analysis of the filtrate obtained by completely dissolving the sample powder under the above-described dissolution conditions was performed by an ICP analysis device to determine the bulk content of neodymium atoms.

[0268] In the hexagonal strontium ferrite powder obtained above, the content of neodymium atoms relative to 100 atomic% of iron atoms (bulk content) is 2.9 atomic%. Furthermore, the surface portion of neodymium atoms contains 8.0 atomic%. The ratio of surface portion content to bulk content, "surface portion content / bulk content", is 2.8, confirming that neodymium atoms are predominantly located on the surface of the particles.

[0269] The powder obtained above was confirmed to exhibit a hexagonal ferrite crystal structure by scanning CuKa rays under a voltage of 45 kV and an intensity of 40 mA, and by measuring the X-ray diffraction pattern under the following conditions (X-ray diffraction analysis). The powder obtained above exhibits a magnetoplumbleite-type (M-type) hexagonal ferrite crystal structure. Furthermore, the crystal phase detected by X-ray diffraction analysis is a magnetoplumbleite-type single phase.

[0270] PANalytical X'Pert Pro diffractometer, PIXcel detector

[0271] Soller slit for incident and diffracted beams: 0.017 radians

[0272] Fixed angle of the dispersing slit: 1 / 4 degree

[0273] Mask: 10mm

[0274] Slit prevention for scattering: 1 / 4 degree

[0275] Measurement mode: Continuous

[0276] Measurement time for each stage: 3 seconds

[0277] Measurement speed: 0.017 degrees per second

[0278] Measurement step size: 0.05 degrees

[0279] <Preparation method of ε-iron oxide powder>

[0280] The “ε-iron oxide” shown in Table 1 is ε-iron oxide powder produced by the following method.

[0281] A solution containing 8.3 g of ferric(III) nonahydrate, 1.3 g of gallium(III) octahydrate, 190 mg of cobalt(II) hexahydrate, 150 mg of titanium(IV) sulfate, and 1.5 g of polyvinylpyrrolidone (PVP) dissolved in 90 g of pure water was stirred using a magnetic stirrer. Simultaneously, 4.0 g of a 25% ammonia solution was added to the solution under atmospheric conditions and at 25°C. The mixture was stirred for 2 hours while maintaining the atmospheric temperature at 25°C. A citric acid solution containing 1 g of citric acid dissolved in 9 g of pure water was then added to the resulting solution, and the mixture was stirred for 1 hour. The precipitated powder was collected by centrifugation, washed with pure water, and dried in a furnace at 80°C.

[0282] 800g of pure water was added to the dried powder to redisperse it, yielding a dispersion. The dispersion was heated to 50°C, and 40g of a 25% ammonia solution was added dropwise while stirring. After stirring for 1 hour while maintaining the temperature at 50°C, 14mL of tetraethoxysilane (TEOS) was added, and stirring continued for 24 hours. 50g of ammonium sulfate was added to the resulting reaction solution. The precipitated powder was collected by centrifugation, washed with pure water, and dried in an oven at 80°C for 24 hours to obtain a precursor for the strongly magnetic powder.

[0283] The obtained strong magnetic powder precursor was placed in a heating furnace at a temperature of 1000°C under atmospheric conditions and subjected to heating treatment for 4 hours.

[0284] The precursor of the heat-treated strong magnetic powder was added to a 4 mol / L sodium hydroxide (NaOH) aqueous solution, and the solution temperature was maintained at 70°C and stirred for 24 hours, thereby removing the silica compound as an impurity from the precursor of the heat-treated strong magnetic powder.

[0285] Then, the strongly magnetic powder after removing the silica compounds was collected by centrifugation and washed with pure water to obtain the strongly magnetic powder.

[0286] The composition of the strongly magnetic powder, confirmed by high-frequency inductively coupled plasma-optical emission spectrometry (ICP-OES), was Ga, Co, and Ti-substituted ε-iron oxide (ε-Ga). 0.28 Co 0.05 Ti 0.05 Fe 1.62O3). Furthermore, under the same conditions as those described in the method for preparing hexagonal strontium ferrite powder, X-ray diffraction analysis was performed, and the peaks of the X-ray diffraction pattern confirmed that the obtained strongly magnetic powder has an ε-phase single-phase crystal structure (ε-iron oxide type crystal structure) that does not contain α-phase or γ-phase crystal structures.

[0287] The obtained ε-iron oxide powder (“ε-iron oxide” in Table 1) has an average particle size of 12 nm and an activation volume of 746 nm. 3 The anisotropy constant Ku is 1.2 × 10⁻⁶. 5 J / m 3 The mass magnetization σs is 16 A·m 2 / kg.

[0288] [Evaluation Method]

[0289] <Average roughness Ra of the centerline of the magnetic layer surface of the magnetic tape>

[0290] Sample pieces cut from the magnetic tapes of the examples and comparative examples were adhered to a glass slide with the magnetic layer surface facing upwards, making it impossible to visually inspect for wrinkles. The glass slide was placed in a Zygo Corporation Newview 6300 optical interferometer, and the centerline average roughness Ra of the magnetic layer surface was determined using the method described above. Filtering was performed using MetroPro 8.3.5 software for the aforementioned optical interferometer. The calculated values ​​are shown in the "Centerline Average Roughness Ra" column of "Magnetic Tape" in Table 1.

[0291] <Determination of creep changes using TMA (Thermal Mechanical Analysis) on magnetic tape>

[0292] In an evaluation environment with an ambient temperature of 35°C and a relative humidity of 50%, the TMA / SS6100 manufactured by Hitachi High-TechScience Corporation was used as the evaluation device, and the creep change measured by the TMA was determined by the following method.

[0293] Samples with a length of 15.0 mm and a width of 5.0 mm were cut from the magnetic tapes of the Examples and Comparative Examples along their length direction. The samples were fixed to the evaluation device with a clamp spacing of 10.0 mm, and a load was applied along the length direction in two stages. The first stage was maintained at a load of 39.2 mN for 2 hours, and the second stage was maintained at a load of 392 mN for a further 24 hours. The sample length (hereinafter referred to as "sample length 1") was measured 10 hours after the application of the second stage load, and the sample length (hereinafter referred to as "sample length 2") was measured 24 hours after the application of the second stage load. These sample lengths are lengths along the length direction, in μm. The creep change measured by TMA was calculated using the formula: "TMA measured creep change = Sample length 2 - Sample length 1". The calculated values ​​are shown in the "TMA measured creep change" column of Table 1.

[0294] <Thickness of the non-magnetic support>

[0295] Cross-sectional observation specimens were prepared from the magnetic tapes of the Examples and Comparative Examples using the methods described below. As the SEM used for SEM observation, a Hitachi FE-SEM S4800 manufactured by Hitachi, Ltd., was used as an electric field emission scanning electron microscope (FE-SEM).

[0296] (i) A sample of the magnetic tape with dimensions of 10 mm in width and 10 mm in length was cut using a razor.

[0297] A protective film is formed on the surface of the magnetic layer of the cut sample to obtain a sample with a protective film. The formation of the protective film is carried out by the following method.

[0298] A platinum (Pt) film (30 nm thick) was formed on the magnetic layer surface of the above sample by sputtering. The sputtering of the platinum film was carried out under the following conditions.

[0299] (Sputtering conditions for platinum films)

[0300] Target: Pt

[0301] Vacuum level in the sputtering device chamber: below 7 Pa

[0302] Current value: 15mA

[0303] A carbon film with a thickness of 100–150 nm was further formed on the platinum-coated sample prepared above. The carbon film was formed using gallium ions (Ga ions) in a FIB (Focused Ion Beam) apparatus used in (ii) below. +The process is carried out using a CVD (Chemical vapor deposition) apparatus.

[0304] (ii) The sample with a protective film prepared in (i) above is subjected to gallium ion (Ga) treatment using a FIB apparatus. + The FIB (Fiber Optic Injection) process was performed on the magnetic tape to expose its cross-section. The accelerating voltage for the FIB process was set to 30kV, and the probe current was set to 1300pA.

[0305] SEM observation was performed on the specimen for cross-sectional observation, and SEM images of the cross-section were obtained. Ten SEM images were obtained from ten randomly selected locations on the fabricated specimen. Each SEM image was obtained as a secondary electron image captured at an accelerating voltage of 5 kV, a magnification of 20,000x, and a resolution of 960 pixels vertically × 1280 pixels horizontally. The interface between the magnetic layer and the non-magnetic layer was determined using the method described in paragraph 0029 of Japanese Patent Application Publication No. 2017-33617. The interface between the non-magnetic layer and the non-magnetic support, and the interface between the back coating and the non-magnetic support, were determined by visually observing the SEM images. At any location on each SEM image, the thickness-direction interval between the interface between the magnetic layer and the non-magnetic layer and the outermost surface of the magnetic layer side of the magnetic tape was measured, and the arithmetic mean of the values ​​obtained for the ten images was taken as the thickness of the magnetic layer. At any location on each SEM image, the thickness-direction interval between the interface between the non-magnetic layer and the magnetic layer, and between the interface between the non-magnetic layer and the non-magnetic support, was measured, and the arithmetic mean of the values ​​obtained for 10 images was taken as the thickness of the non-magnetic layer. At any location on each SEM image, the thickness-direction interval between the outermost surface of the back coating side of the magnetic tape and the interface between the back coating and the non-magnetic support was measured, and the arithmetic mean of the values ​​obtained for 10 images was taken as the thickness of the back coating. At any location on each SEM image, the thickness-direction interval between the interface between the non-magnetic support and the back coating, and between the interface between the non-magnetic support and the non-magnetic layer, was measured, and the arithmetic mean of the values ​​obtained for 10 images was taken as the thickness of the non-magnetic support. The thickness of the non-magnetic support thus determined is shown in the "Thickness" column of "Non-magnetic Support" in Table 1. In all magnetic tapes of the examples and comparative examples, the thicknesses of the non-magnetic layer, magnetic layer, and back coating were: non-magnetic layer: 1.0 μm, magnetic layer: 0.1 μm, and back coating: 0.5 μm.

[0306] The evaluation described below was performed on the support removed after the non-magnetic layer, magnetic layer, and back coating of each magnetic tape of the Examples and Comparative Examples were removed using a solvent. The removal of the support was carried out in a manner that avoided unnecessary application of large amounts of external energy (stress, heat, etc.) to the support during the removal process.

[0307] <The scattering intensity ratio of the nonmagnetic support is I max / I min >

[0308] Using a Bruker NANOSTAR as the measuring apparatus, small-angle X-ray scattering measurements were performed on supports removed from the magnetic tapes of the Examples and Comparative Examples, as described above. Based on the measurement results, the scattering intensity ratio I was determined using the method described above. max / I min A rotating cathode-type X-ray generator was used as the X-ray source, and the energy (wavelength λ) of the X-rays was set to 8.04 keV (Cu Kα line). Furthermore, the transmittance T was determined using glassy carbon as a standard sample. The calculated values ​​are shown in Table 1, "Scattering Intensity Ratio I of Non-magnetic Supports". max / I min In the column.

[0309] <Glass transition temperature Tg of nonmagnetic supports>

[0310] A 10 mg sample was cut from the support taken from each magnetic tape of the Examples and Comparative Examples. Using this sample, a Q100 DSC from TA Instruments was used to determine the glass transition temperature Tg using the method described above. The determined value is shown in the "Glass Transition Temperature Tg" column of "Non-magnetic Support" in Table 1. Regarding Comparative Example 7, the glass transition temperature Tg was not confirmed below 140°C, therefore it is recorded as "above 140°C" in Table 1.

[0311] <Average roughness Ra of the centerline of the surface of the side of the non-magnetic support with the magnetic layer>

[0312] Sample pieces cut from the supports taken from the magnetic tapes of the examples and comparative examples were adhered to a glass slide with the side having the magnetic layer facing upwards, making it impossible to visually inspect wrinkles. This glass slide was placed on a Zygo Corporation Newview 6300 optical interferometer, and the centerline average roughness Ra of the original magnetic layer side of the non-magnetic support was determined using the method described above. Filtering was performed using Metropro 8.3.5 software for the aforementioned optical interferometer. The calculated values ​​are shown in the "Centerline Average Roughness Ra" column of "Non-magnetic Support" in Table 1.

[0313] The results are shown in Table 1.

[0314]

[0315] Based on the creep values ​​measured by TMA shown in Table 1, the magnetic tapes of Examples 1 to 3 can be evaluated as magnetic tapes that can meet the requirements of suppressing magnetic tape deformation during long-term storage in future magnetic tapes.

[0316] In the 2019 INSIC Technology Roadmap published by the Information Storage Industry Consortium (INSIC), the target for Tape Dimensional Stability (TDS) by 2029 is below 32 ppm (parts per million) after 10 years of storage, regarding the width-direction deformation of the tape when wound onto a reel. From the perspective of suppressing errors during recording and / or playback, the higher the recording density, the lower the permissible TDS value of the product tape tends to be. In this regard, tapes that can achieve a TDS of below 32 ppm after 10 years of storage are suitable for magnetic recording and playback systems with a track density of 50,000 TPI (tracks per inch) (approximately 500 nm / track) or higher, and are also suitable for magnetic recording and playback systems with track densities of 75,000 TPI or higher, 100,000 TPI or higher, and even 200,000 TPI or higher.

[0317] On the other hand, regarding magnetic tape deformation, Figure 9 of the article "Viscoelastic analysis applied to the determination of long-term creep behavior for magnetic tape materials" (by Brian L. Weick, published online in Wiley InterScience) in the *Journal of Applied Polymer Science, Vol. 102, 1106-1128 (2006)* proposes predicting the creep change of magnetic tape after long-term storage based on the creep change obtained through creep testing. Specifically, in Figure 9, if the logarithm of time (log) is plotted on the horizontal axis and the logarithm of the creep change (log) is plotted on the vertical axis, an almost linear curve is obtained. Therefore, considering that there is a proportional relationship between the logarithm of time (log) and the creep change, the following calculations were performed.

[0318] Table 1 shows the creep change measured by TMA, which is the difference between the specimen length 10 hours after the end of the two-stage load application and the specimen length 24 hours later. Therefore, it is the creep change that occurs during a 14-hour period. If we express 14 hours logarithmically, it is approximately 1.15. On the other hand, 10 years = 87,600 hours, and if we express it logarithmically, it is approximately 4.94. As a coefficient used for calculations proportional to time (logarithm), we use "logarithmic representation of 87,600 hours / logarithmic representation of 10 hours = 4.31". Furthermore, in this literature, Poisson's ratio = 0.3 was used to convert deformation in the length direction to deformation in the width direction. If we label the creep change measured by TMA obtained by the above method as "A", and standardize it using a clamp spacing of 10.0 mm as the reference length, we can calculate "standardized A = (A / 10000) × 10". 6 "(Unit: ppm). The standardized A is the amount of deformation in the length direction, which can be converted into the value B in the width direction by using Poisson's ratio = 0.3 and "B = standardized A × 0.3". The predicted value of TDS after 10 years of storage is calculated by multiplying the B obtained here by the above coefficient 4.31 and "B × 4.31". The values ​​calculated in this way are shown in Table 2. As shown in Table 2, in Examples 1 to 5, the predicted TDS value after 10 years of storage is less than 32 ppm. Based on this result, it can be evaluated that the magnetic tapes of Examples 1 to 5 are magnetic tapes that can meet the requirements of future magnetic tapes for suppressing magnetic tape deformation during long-term storage."

[0319]

[0320] Industrial availability

[0321] One aspect of the present invention is useful for data storage applications.

Claims

1. A magnetic tape having a non-magnetic support and a magnetic layer containing a strong magnetic powder, In the small-angle X-ray scattering spectrum of the non-magnetic support obtained by small-angle X-ray scattering, the q values ​​are in the range of 0.01–0.10 Å. -1 The q-value q at the maximum rate of change of scattering intensity within the region. max Scattering intensity I at point max The q value at the minimum of the rate of change of scattering intensity min Scattering intensity I at point min The ratio of I max / I min For values ​​between 2.7 and 20.0, q min <q max ,and the non-magnetic support has a glass transition temperature Tg of 140°C or higher and 180°C or lower.

2. The magnetic tape according to claim 1, wherein the non-magnetic support is an aromatic polyether ketone support.

3. The magnetic tape according to claim 2, wherein the aromatic polyether ketone is a polyether ether ketone.

4. The magnetic tape according to claim 2, wherein the aromatic polyether ketone is a polyether ketone ketone.

5. The magnetic tape according to any one of claims 1 to 3, wherein the strong magnetic powder is a hexagonal barium ferrite powder.

6. The magnetic tape according to any one of claims 1 to 3, wherein the strong magnetic powder is a hexagonal strontium ferrite powder.

7. The magnetic tape according to any one of claims 1 to 3, wherein the strong magnetic powder is an ε-iron oxide powder.

8. The magnetic tape of any one of claims 1 to 3, wherein, a non-magnetic layer containing a non-magnetic powder is further provided between the non-magnetic support and the magnetic layer.

9. The magnetic tape of any one of claims 1 to 3, wherein, a back coating layer containing a non-magnetic powder is further provided on a surface side of the non-magnetic support opposite to a surface side having the magnetic layer.

10. The magnetic tape according to any one of claims 1 to 3, wherein a center line average roughness Ra of a surface of a side of the non-magnetic support having the magnetic layer is 15.0 nm or lower as measured by an optical interference roughness meter.

11. The magnetic tape of any one of claims 1 to 3, wherein, The I max / I min 2.7 or more and 10.0 or less, and the glass transition temperature Tg of the non-magnetic support is 140°C or more and 165°C or less.

12. A magnetic tape cartridge comprising the magnetic tape according to any one of claims 1 to 11.

13. A magnetic recording and reproducing apparatus comprising the magnetic tape according to any one of claims 1 to 11.

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