Servo measuring device, servo measuring method, program, method for manufacturing magnetic tape, and magnetic tape

Abstract

The present invention provides a servo measuring device, method, and program that allows users to easily and accurately measure the width of a servo pattern, as well as a magnetic tape and a method for manufacturing the same. [Solution] The servo measuring device comprises a servo read head and a control unit. The servo read head reads the servo pattern written on the servo band of the magnetic tape and reconstructs the waveform servo signal. The control unit calculates the width of the servo pattern based on a first point Po1 and a second point Po2, which are different from the positive and negative peak points in the waveform of the servo signal, respectively.

Description

[Technical Field]

[0001] This technology relates to a servo measuring device and the like that performs measurements related to servo patterns on magnetic tape. [Background technology]

[0002] The magnetic tape has multiple data bands on which data is recorded and multiple servo bands on which servo patterns are recorded. In the magnetic tape, first, the servo write head of the servo recording device records the servo pattern onto the servo bands.

[0003] On the other hand, the data write head of the data recording device recognizes the position of the magnetic tape based on a servo pattern written on the magnetic tape and writes data to any position in the data band (see Patent Document 1 below). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] International Publication No. 2023 / 153024 [Overview of the project] [Problems that the invention aims to solve]

[0005] There is a need for technologies such as servo measuring devices that allow users to easily and accurately measure the width of servo patterns.

[0006] In light of the above circumstances, the objective of this technology is to provide a servo measuring device and other technologies that enable users to easily and accurately measure the width of a servo pattern. [Means for solving the problem]

[0007] The servo measuring device relating to this technology comprises a servo read head and a control unit. The servo read head reads the servo pattern written on the servo band of the magnetic tape and reproduces the waveform servo signal. The control unit calculates the width of the servo pattern based on a first point and a second point, which are different from the positive peak point and the negative peak point in the waveform of the servo signal, respectively.

[0008] This makes it possible to provide a servo measuring device that allows users to easily and accurately measure the width of a servo pattern.

[0009] In the servo measuring device described above, the control unit may set the first point to a point corresponding to any of the rising portions of the positive convex portion in the waveform of the servo signal.

[0010] In the servo measuring device described above, the control unit may set the second point to a point corresponding to any of the rising edges of the negative recess in the waveform of the servo signal.

[0011] In the servo measuring device described above, the control unit may set the first point as the first point, which corresponds to an output value that is a first percentage of the positive peak point in the waveform of the servo signal, when the output value of the positive peak point in the waveform of the servo signal is set to 100%.

[0012] In the servo measuring device described above, the control unit may set the second point as the second point, which corresponds to an output value that is a second percentage of the negative peak point in the waveform of the servo signal, when the output value of the negative peak point in the waveform of the servo signal is set to -100%.

[0013] In the servo measuring device described above, the control unit may set the first percentage to any value within the range of 25% or more and 75% or less.

[0014] In the servo measuring device described above, the control unit may set the second percentage to any value within the range of -25% or more and -75% or less.

[0015] In the servo measuring device described above, the control unit may set the first percentage and the second percentage such that the absolute values ​​of the first percentage and the second percentage are equal.

[0016] In the servo measuring device described above, the magnetic tape may include a vertically oriented magnetic layer on which the servo pattern is written.

[0017] In the servo measuring device described above, the aspect ratio of the magnetic layer in the vertical direction may be 60% or more.

[0018] In the servo measuring device described above, the control unit may be able to change at least one of the first point and the second point.

[0019] In the servo measuring device described above, the control unit may change at least one of the first point and the second point based on the degree of vertical orientation of the magnetic layer on which the servo pattern is written.

[0020] In the servo measuring device described above, the control unit may be able to change at least one of the first percentage and the second percentage.

[0021] In the servo measuring device described above, the control unit may change at least one of the first percentage and the second percentage based on the degree of vertical orientation of the magnetic layer on which the servo pattern is written.

[0022] In the servo measuring device described above, the control unit may measure the width of the servo pattern for each servo track in the servo band.

[0023] In the servo measuring device described above, an older data recording device compatible with older LTO-type magnetic tape may be reused as the servo measuring device.

[0024] The servo measurement method related to this technology reads the servo pattern written on the servo band of the magnetic tape and reconstructs the waveform servo signal. The width of the servo pattern is calculated based on a first point and a second point, which are different from the positive and negative peak points in the waveform of the servo signal.

[0025] The program related to this technology reads the servo pattern written on the servo band of the magnetic tape and reproduces the waveform servo signal. The width of the servo pattern is calculated based on a first point and a second point, which are different from the positive and negative peak points in the waveform of the servo signal. The processing is performed by a servo measuring device.

[0026] The method for manufacturing magnetic tape according to this technology reads the servo pattern written on the servo band of the magnetic tape and reproduces a waveform servo signal, The width of the servo pattern is calculated based on a first point and a second point, which are different from the positive and negative peak points in the waveform of the servo signal, respectively. The quality of the magnetic tape is confirmed based on the width of the servo pattern.

[0027] In this technology, the magnetic tape has a servo pattern written on the servo band of the magnetic tape, which is read to reproduce a waveform servo signal. The width of the servo pattern is calculated based on a first point and a second point, which are different from the positive and negative peak points in the waveform of the servo signal. The quality of the magnetic tape is confirmed based on the width of the servo pattern. [Brief explanation of the drawing]

[0028] [Figure 1] This is a schematic diagram of a magnetic tape viewed from the side. [Figure 2] This is a schematic diagram of a magnetic tape viewed from above (the magnetic layer side). [Figure 3] This diagram shows the servo pattern written to the magnetic tape. [Figure 4] This is a diagram showing the servo recording and playback device according to this embodiment. [Figure 5] This is a magnified view of the servo light head and the servo elements contained within the servo light head. [Figure 6] This diagram shows how a servo pattern is written to magnetic tape by a servo light head. [Figure 7] This is an enlarged view of the right-hand side of Figure 5, showing an example of specific dimensions for the first servo element (" / ") and the second servo element ("\"). [Figure 8] This diagram shows the servo light head with the servo light head's coordinate system as the reference point. [Figure 9] This is an enlarged view of the right-hand side of Figure 8, showing an example of specific dimensions for the first servo element (" / ") and the second servo element ("\"). [Figure 10] This figure shows a servo measuring device according to this embodiment. [Figure 11] This diagram shows the servo read head reading the servo pattern in the servo band. [Figure 12] This is a side view showing the process of writing a servo pattern to the magnetic layer of a magnetic tape by the servo write head of a servo recording and playback device, and it shows the width of the servo pattern. [Figure 13] This diagram illustrates the basic concept of the method for measuring the width of the servo pattern according to this embodiment. [Figure 14] This is another diagram illustrating the basic concept of the method for measuring the width of the servo pattern according to this embodiment. [Figure 15] This figure shows the MFM image of the servo pattern on a Type A magnetic tape and the waveform of the magnetic force obtained by MFM. [Figure 16] This figure shows the waveform of the servo signal when reading the servo pattern on a Type A magnetic tape. [Figure 17] This figure shows the width of the servo pattern for each servo band and each servo track (each servo trace line) in a Type A magnetic tape. [Figure 18] This figure shows the MFM image of the servo pattern on a Type B magnetic tape, and the waveform of the magnetic force obtained by MFM. [Figure 19] This figure shows the waveform of the servo signal when reading the servo pattern on a Type B magnetic tape. [Figure 20] This figure shows the width of the servo pattern for each servo band and each servo track (each servo trace line) in a Type B magnetic tape. [Figure 21] This figure illustrates the degree of agreement between the width of the servo pattern measured by the measurement method according to this embodiment and the width of the servo pattern 7 measured by the measurement method in MFM. [Figure 22] This is a flowchart showing the processing performed by the control unit. [Figure 23] This is a flowchart showing the processing performed by the control unit. [Modes for carrying out the invention]

[0029] The embodiments of this technology will be described below with reference to the drawings.

[0030] ≪First Embodiment≫ In this embodiment, the width SPW (see Figure 11, etc.) of the servo pattern 7 written on the magnetic tape 1 by the servo recording and playback device 101 (see Figure 4, etc.) is measured by the servo measuring device 100 (see Figure 10, etc.).

[0031] In describing this embodiment, the magnetic tape 1, the servo recording and playback device 101, and the servo measuring device 100 will be described in that order.

[0032] <Configuration of magnetic tape 1> Figure 1 is a schematic diagram of the magnetic tape 1 viewed from the side, and Figure 2 is a schematic diagram of the magnetic tape 1 viewed from above (magnetic layer 4 side). Figure 3 shows the servo pattern 7 written on the magnetic tape 1.

[0033] As shown in Figures 1 and 2, the magnetic tape 1 is configured as a tape that is long in the longitudinal direction (X-axis direction), short in the width direction (Y-axis direction), and thin in the thickness direction (Z-axis direction).

[0034] The width of the magnetic tape 1 (in the Y-axis direction) is typically about 1 / 2 inch, but the width of the magnetic tape 1 may be about 1 inch, and its size can be changed as appropriate.

[0035] The magnetic tape 1 includes a tape-shaped base material 2 that is long in the longitudinal direction (X-axis direction), a base layer 3 (non-magnetic layer) provided on one main surface of the base material 2, a magnetic layer 4 provided on the base layer 3, and a back layer 5 provided on the other main surface of the base material 2.

[0036] The back layer 5 may be provided as needed, and may be omitted. The magnetic layer 4 may be a coated film of magnetic material, or a vapor-deposited or sputtered film of magnetic material.

[0037] In this embodiment, the magnetic layer 4 is vertically oriented. In this embodiment, the angular ratio S1 of the magnetic layer 4 in the vertical direction (Z-axis direction: thickness direction) of the magnetic tape 1 is set to 60% or more, 65% or more, 70% or more, 75% or more, 80% or more, etc.

[0038] In this embodiment, the aspect ratio S1 of the magnetic layer 4 in the vertical direction of the magnetic tape 1 is set to 60% or more, so the degree of vertical orientation of the magnetic layer 4 is set to a relatively high value. The technology according to this embodiment is particularly effective as a method for measuring the width SPW of the servo pattern 7 in a magnetic tape 1 that includes a magnetic layer 4 in which the degree of vertical orientation is set to a relatively high value.

[0039] Details of each layer that makes up magnetic tape 1 will be described later.

[0040] As shown in Figure 2, the magnetic layer 4 has multiple data bands d (data bands d0 to d3) on which data is written, and multiple servo bands s (servo bands s0 to s4) on which servo patterns 7 are written. Each of the data bands d and servo bands s has a shape that is long in the longitudinal direction (X-axis direction) and short in the width direction (Y-axis direction). The servo bands s are positioned to sandwich each data band d in the width direction (Y-axis direction).

[0041] The four servo bands s are arranged at predetermined intervals in the width direction (Y-axis direction). In this specification, the width distance between two adjacent servo bands s in the width direction (Y-axis direction) is referred to as the servo band pitch SBP. Typically, the servo band pitch SBP is the distance between the widthwise center position of the servo pattern 7 of one servo band s and the widthwise center position of the servo pattern 7 of the other servo band s.

[0042] The example shown in Figure 2 illustrates a case where there are 4 data bands d and 5 servo bands s. Note that the number of data bands d and servo bands s can be changed as needed.

[0043] The ratio of the servoband area s to the total surface area of ​​the magnetic layer 4 is, for example, 4.0% or less. The width of the servoband s is, for example, 96 μm or less for a 1 / 2 inch tape width. The ratio of the servoband area s to the total surface area of ​​the magnetic layer 4 can be measured, for example, by developing the magnetic tape 1 with a developer such as a ferricolloid developer, and then observing the developed magnetic tape 1 with an optical microscope.

[0044] A data band d contains multiple recording tracks 6 that are long in the longitudinal direction and aligned in the width direction. The number of recording tracks 6 in a single data band d is, for example, around 1000 to 2500. Data is recorded along these recording tracks 6 and within the recording tracks 6. The longitudinal bit length of the data recorded in data band d is, for example, 48 nm or less.

[0045] Furthermore, the width of the recording track 6 (track pitch: Y-axis direction) is set to, for example, 2.0 μm or less. This recording track width can be measured, for example, by developing the magnetic layer 4 of the magnetic tape 1 using a developer such as a ferricolloid developer, and then observing the developed magnetic layer 4 of the magnetic tape 1 with an optical microscope.

[0046] Alternatively, a method using a data write head in a head-tilt type data recording and playback device (not shown) may be used to measure the recording track width. In this case, since fluctuations during magnetic tape travel are ignored, the recording track width can be measured from the output change when the azimuth angle of the data write head is changed while the data write head is in the recording and playback state. (IEEE_Sept1996_Crosstrack Profiles of Thin Film MR Tape Heads Using the Azimuth Displacement Method)

[0047] The servo band s has multiple servo bursts, each containing multiple servo patterns 7 recorded by the servo recording and playback device 101 (see Figure 4), which will be described later. The servo pattern 7 includes a striped first servo pattern 7a ("\") and a striped second servo pattern 7b (" / ").

[0048] In this specification, the symbols " / " and "\" in the first servo pattern 7a and the second servo pattern 7b are used to indicate the inclination direction of the servo pattern 7 when viewed from the direction corresponding to the drawing being described at that time. For example, in Figure 2, the magnetic tape 1 is viewed from the surface side (magnetic layer 4 side: top), so the symbols " / " and "\" in the first servo pattern 7a and the second servo pattern 7b are used to indicate the magnetic tape 1 when viewed from the surface side.

[0049] On the other hand, in the drawings described later (Figures 5 to 9, Figure 11), the magnetic tape 1 is sometimes shown as viewed from the back side (back layer 5 side: bottom), and in this case, the symbols " / " and "\" are used as symbols when the magnetic tape 1 is viewed from the back side. In other words, the symbols " / " and "\" are reversed when the magnetic tape 1 is viewed from the front side compared to when it is viewed from the back side. This is also the case for the first servo element 42a and the second servo element 42b that write the servo pattern 7 to the magnetic tape 1 (see Figure 5, etc.).

[0050] Referring to the left side of Figure 3, the first servo pattern 7a ("\") and the second servo pattern 7b (" / ") are written to the servo band s in such a way that they are asymmetrical with respect to the axis of symmetry (see the dashed line on the left side of Figure 3), with respect to the direction parallel to the width direction (Y-axis direction) of the magnetic tape 1.

[0051] In the case of a typical servo pattern 7, the first servo pattern 7a ("\") and the second servo pattern 7b (" / ") are written to the servo band s such that they are symmetrical (line symmetry) when the direction parallel to the width direction of the magnetic tape 1 is taken as the direction of the axis of symmetry.

[0052] Furthermore, referring to the center of Figure 3, the first servo pattern 7a ("\") and the second servo pattern 7b (" / ") are set such that their axes of symmetry (see the dashed line in the center of Figure 3) are non-parallel to the width direction (Y-axis direction) of the magnetic tape 1.

[0053] Typically, the first servo pattern 7a ("\") and the second servo pattern 7b (" / ") are formed symmetrically with respect to the axis of symmetry. However, the length of the first servo pattern 7a ("\") (length along θs1) and the length of the second servo pattern 7b (" / ") (length along θs2) are different (the lengths in the width direction of the magnetic tape 1 are the same: length of the first servo pattern 7a × Cosθs1 = length of the second servo pattern 7b × Cosθs2).

[0054] The first inclination angle Refθ1, which is the angle at which the axis of symmetry is tilted with respect to the width direction of the magnetic tape 1, is, for example, 10° in this embodiment. Typically, the first inclination angle Refθ1 is 8° or more. This first inclination angle Refθ1 coincides with the second inclination angle Refθ2 at which the servo light head 40 of the servo recording and playback device 101 is tilted with respect to the width direction of the magnetic tape 1 (see Figures 5 and 6 described later).

[0055] Furthermore, this first tilt angle Refθ1 typically coincides with the angle at which the data write head, which records data on the data band d of the magnetic tape 1, is tilted with respect to the width direction of the magnetic tape 1 in a head-tilting type data recording and playback device (not shown). The angle at which the data write head is tilted with respect to the width direction of the magnetic tape 1 varies, for example, within the range of Refθ1 ± x (the value of x is typically 0.7° or less).

[0056] The first servo pattern 7a ("\") is tilted counterclockwise with respect to the axis of symmetry at a servo azimuth angle θa, and the second servo pattern 7b (" / ") is tilted clockwise with respect to the axis of symmetry at a servo azimuth angle θa. Note that the angle θa (servo azimuth angle) at which the first servo pattern 7a ("\") and the second servo pattern 7b (" / ") are tilted with respect to the axis of symmetry is the same.

[0057] Referring to the right side of Figure 3, the first servo pattern 7a ("\") is tilted at a first angle θs1 with respect to the width direction (Y-axis direction) of the magnetic tape 1, and the second servo pattern 7b (" / ") is tilted at a second angle θs2 that is different from the first angle θs1, in the opposite direction to the first angle θs1 with respect to the width direction of the magnetic tape 1.

[0058] The first angle θs1 at which the first servo pattern 7a ("\") is tilted with respect to the width direction of the magnetic tape 1 is the value obtained by adding θa to the first tilt angle Refθ1, and is expressed by the following formula. Also, the angle θs2 at which the second servo pattern 7b (" / ") is tilted with respect to the width direction of the magnetic tape 1 is the value obtained by subtracting θa from the first tilt angle Refθ1, and is expressed by the following formula (counterclockwise is positive when viewed from above). θs1 = Refθ1 + θa θs² = Refθ1 - θa

[0059] If the first tilt angle Refθ1 is set to 10° and the servo azimuth angle θa is set to 12°, then the first angle θs1 will be 22° and the second angle θs2 will be -2°. Note that the values ​​for Refθ1, θa, θs1, and θs2 are not limited to the examples given here and can be changed as appropriate.

[0060] The first servo burst ("\") and the second servo burst (" / ") are arranged alternately in the longitudinal direction of the magnetic tape 1. The number of first servo patterns 7a ("\") included in the first servo burst ("\") is typically four or five, and similarly, the number of second servo patterns 7b (" / ") included in the second servo burst (" / ") is typically four or five.

[0061] In this embodiment, the first servo pattern 7 ("\") and the second servo pattern 7 (" / ") are described as asymmetrical with respect to the width direction of the magnetic tape 1 as the axis of symmetry. However, the first servo pattern 7 and the second servo pattern 7 may be symmetrical with respect to the width direction of the magnetic tape 1 as the axis of symmetry (the direction of the axis of symmetry may be parallel to the width direction of the magnetic tape 1).

[0062] Here, the magnetic tape standard LTO (Linear Tape Open) has seen a dramatic increase in recording capacity with each generation, as the number of recording tracks (track 6) has increased. For example, the original LTO-1 had 384 recording tracks (track 6), while LTO-2 through LTO-9 had 512, 704, 896, 1280, 2176, 3584, 6656, and 8960 recording tracks (track 6), respectively. Similarly, the data recording capacity was 100 GB (gigabytes) for LTO-1, but increased to 200 GB, 400 GB, 800 GB, 1.5 TB (terabytes), 2.5 TB, 6.0 TB, 12 TB, and 18 TB for LTO-2 through LTO-9, respectively. Furthermore, the planned LTO-10, LTO-11, and LTO-12 chips will have data storage capacities of 36TB, 72TB, and 144TB, respectively.

[0063] In this embodiment, the number of recording tracks 6 and the recording capacity are not particularly limited and can be changed as appropriate. However, this technology is advantageous when applied to magnetic tape 1 with a large number of recording tracks 6 and a large recording capacity (e.g., 6656 or more tracks, 12TB or more: LTO8 or later).

[0064] <Servo recording and playback device 101> Next, a servo recording and playback device 101 according to one embodiment of this technology will be described. Figure 4 is a diagram showing the servo recording and playback device 101 according to this embodiment.

[0065] As shown in Figure 4, the servo recording and playback device 101 includes a feed roller 31, a demagnetizing unit 32, a servo light head 40, a servo read head 35, a winding roller 36, and four pairs of capstan rollers 37.

[0066] The feed roller 31 is capable of rotatably supporting the roll-shaped magnetic tape 1. The feed roller 31 rotates in response to a drive such as a motor, and feeds the magnetic tape 1 downstream in accordance with the rotation.

[0067] The winding roller 36 is capable of rotatably supporting the roll-shaped magnetic tape 1. The winding roller 36 rotates in response to a drive such as a motor, and winds up the magnetic tape 1 as it rotates.

[0068] Each of the four pairs of capstan rollers 37 is capable of gripping the magnetic tape 1 from both the top and bottom. The four pairs of capstan rollers 37 rotate in response to a motor or the like, and transport the magnetic tape 1 along the transport path in accordance with the rotation.

[0069] The feed roller 31, the take-up roller 36, and the four pairs of capstan rollers 37 are configured to transport the magnetic tape 1 at a constant speed within the transport path.

[0070] The servo light head 40 is positioned, for example, on the upper side (magnetic layer 4 side) of the magnetic tape 1. The servo light head 40 applies a magnetic field to the servo band s at a predetermined timing in response to a square wave pulse signal and records a servo pattern 7 on the servo band s.

[0071] The servo light head 40 is capable of recording a servo pattern 7 for each of the servo bands s (s0 to s4) as the magnetic tape 1 passes beneath the servo light head 40. Further details regarding the configuration of the servo light head 40 will be described later with reference to Figures 5 to 9.

[0072] The demagnetizing unit 32 is positioned, for example, upstream of the servo light head 40 and below the magnetic tape 1 (on the substrate 2 side). The demagnetizing unit 32 is composed of, for example, two permanent magnets 33 and 34. The permanent magnets 33 and 34 apply a magnetic field to the entire magnetic layer 4 using a DC magnetic field before the servo pattern 7 is recorded by the servo light head 40, thereby demagnetizing the entire magnetic layer 4. The permanent magnets 33 and 34 are also configured to apply a magnetic field to the magnetic layer 4 that is opposite to the magnetic field applied to the servo band s by the servo light head 40. In this way, a regenerated waveform of the servo signal with good symmetry can be obtained.

[0073] The servo read head 35 is positioned downstream of the servo write head 40 and on the upper side (magnetic layer 4 side) of the magnetic tape 1. The servo read head 35 is configured to read the magnetic field generated from the servo pattern 7 recorded on the magnetic tape 1, thereby enabling the reproduction of the information of the servo pattern 7.

[0074] The servo read head 35 is capable of reading the servo pattern 7 from all servo bands s (s0 to s4) as the magnetic tape 1 passes beneath the servo read head 35. The information of the servo pattern 7 read by the servo read head 35 is used to verify whether the servo pattern 7 has been recorded accurately.

[0075] The types of servo lead heads 35 include, for example, inductive type, MR type (Magneto Resistive), GMR type (Giant Magneto Resistive), and TMR type (Tunnel Magneto Resistive).

[0076] [Servo Light Head 40] Next, the configuration of the servo write head 40 will be described in detail. Here, in a head-tilting type data recording and playback device (not shown), the data write head is positioned at an angle with respect to the width direction of the magnetic tape 1 in order to accommodate variations in the width of the magnetic tape 1.

[0077] Therefore, in order for the data write head to accurately read the servo pattern 7, the symmetry axis (see center of Figure 3) of the first servo pattern 7a ("\") and the second servo pattern 7b (" / ") is set to be inclined with respect to the width direction of the magnetic tape 1. The writing of this servo pattern 7 is performed by the servo write head 40 according to this embodiment.

[0078] Figure 5 is an enlarged view of the servo light head 40 and the servo element 42 of the servo light head 40. Figure 6 shows the process of writing the servo pattern 7 to the magnetic tape 1 by the servo light head 40.

[0079] Figures 5 and 6 show the servo light head 40 viewed from below (viewed from the side facing the magnetic tape 1). In Figures 5 and 6, since the servo light head 40 and other components are viewed from below, the signs of " / " and "\" in the first servo pattern 7a and the second servo pattern 7b, as well as the signs of " / " and "\" in the first servo element 42a and the second servo element 42b, are reversed compared to Figures 2 and 3. The same applies to Figures 7 to 9 and 11, which will be discussed later.

[0080] As shown in these figures, the servo light head 40 has a shape that is long in the longitudinal direction (Y" axis direction) and short in the width direction (X" axis direction).

[0081] The servo light head 40 is positioned so that its longitudinal direction (Y'' axis direction) is inclined at a predetermined angle (second inclination angle Refθ2) with respect to the width direction (Y axis direction) of the magnetic tape 1. The second inclination angle Refθ2, which is the inclination of the longitudinal direction (Y'' axis direction) of the servo light head 40 with respect to the width direction (Y axis direction) of the magnetic tape 1, coincides with the first inclination angle Refθ1, which is the inclination of the axes of symmetry of the first servo pattern 7a and the second servo pattern 7b with respect to the width direction of the magnetic tape 1 (for example, 10°) (Refθ2 = Refθ1).

[0082] The servo light head 40 has a facing surface 41 that faces the magnetic tape 1. The facing surface 41 has a shape that is long in the longitudinal direction (Y" axis direction) and short in the width direction (X" axis direction).

[0083] The servo light head 40 has five pairs of servo elements 42 (magnetic gaps) on the opposing surface 41. Each servo element 42 is a magnetic gap provided on the servo light head 40, and the servo elements 42 are capable of writing a servo pattern 7 to the servo band s by leakage magnetic flux from the magnetic gap.

[0084] The five pairs of servo elements 42 are arranged in the width direction (Y-axis direction) of the magnetic tape 1 at predetermined intervals (servo light pitch: SWP1).

[0085] The distance between two adjacent pairs of servo elements 42 in the width direction (Y-axis direction) of the magnetic tape 1 (servo light pitch: SWP1) is, for example, 2815.3 ± 4.6 μm. This value corresponds to the distance between two adjacent servo bands s in the width direction (Y-axis direction) of the magnetic tape 1 (servo band pitch SBP). In other words, the servo light pitch SWP1 is typically equal to the servo band pitch SBP.

[0086] Furthermore, the difference in position between two adjacent pairs of servo elements 42 in the longitudinal direction (X-axis direction) of the magnetic tape 1 is expressed as SWP1 × Tan(Refθ2).

[0087] Let's assume that the value of SWP1 is 2815.37 μm and the second tilt angle Refθ2 is 10°. In this case, the difference in position between two adjacent pairs of servo elements 42 in the longitudinal direction (X-axis direction) of the magnetic tape 1 is 2815.37 μm × Tan 10° = 496.43 μm.

[0088] The pair of servo elements 42 includes a first servo element 42a (" / ") and a second servo element 42b ("\") configured asymmetrically with respect to the axis of symmetry, when the width direction (Y-axis direction) of the magnetic tape 1 is taken as the direction of the axis of symmetry (see the right side of Figure 5 in particular).

[0089] Furthermore, the first servo element 42a (" / ") and the second servo element 42b ("\") are set so that their axes of symmetry are non-parallel to the width direction (Y-axis direction) of the magnetic tape 1. Typically, the first servo element 42a (" / ") and the second servo element 42b ("\") are formed symmetrically with respect to the axis of symmetry.

[0090] The angle at which the axes of symmetry of the first servo element 42a (" / ") and the second servo element 42b ("\") are tilted with respect to the width direction of the magnetic tape 1 is equal to the first inclination angle Refθ1 (and also equal to the second inclination angle Refθ2) at which the axes of symmetry of the first servo pattern 7a (" / ") and the second servo pattern 7b ("\") are tilted with respect to the width direction of the magnetic tape 1.

[0091] The first servo element 42a (" / ") is tilted at a first angle θs1 with respect to the width direction (Y-axis direction) of the magnetic tape 1. The second servo element 42b ("\") is tilted at a second angle θs2 with respect to the width direction (Y-axis direction) of the magnetic tape 1, in the opposite direction to the first angle θs1.

[0092] The first angle θs1 at which the first servo element 42a (" / ") tilts with respect to the width direction of the magnetic tape 1 is the value obtained by adding the servo azimuth angle θa to the second tilt angle Refθ2, and is expressed by the following formula. Also, the angle θs2 at which the second servo pattern 7b ("\") tilts with respect to the width direction of the magnetic tape 1 is the value obtained by subtracting the servo azimuth angle θa from the second tilt angle Refθ2, and is expressed by the following formula (clockwise is positive when viewed from below). θs1 = Refθ2 + θa θs² = Refθ² - θa

[0093] If the second tilt angle Refθ2 is 10° and the servo azimuth angle θa is 12°, then the first angle θs1 will be 22° and the second angle θs2 will be -2°.

[0094] Here, in the first servo element 42a (" / "), the direction along the first angle θs1 (the direction at 22° with respect to the width direction of the magnetic tape 1) is defined as the longitudinal direction of the first servo element 42a (" / "). Also, in the second servo element 42b ("\"), the direction along the second angle θs2 (the direction at -2° with respect to the width direction of the magnetic tape 1) is defined as the longitudinal direction of the second servo element 42b ("\").

[0095] The longitudinal length of the first servo element 42a (" / ") is different from the longitudinal length of the second servo element 42b ("\"). In this example, the longitudinal length of the first servo element 42a (" / ") is longer than the longitudinal length of the second servo element 42b ("\").

[0096] On the other hand, the widthwise component (Y-axis direction) SL1 of the magnetic tape 1 in the longitudinal direction of the first servo element 42a (" / ") is the same as the widthwise component (Y-axis direction) SL1 of the magnetic tape 1 in the longitudinal direction of the second servo element 42b ("\"). The widthwise component SL1 of the length of the servo element 42 is, for example, 96 ± 3 μm.

[0097] Figure 7 is an enlarged view of the right-hand side of Figure 5, showing an example of specific dimensions for the first servo element 42a (" / ") and the second servo element 42b ("\") (based on the XYZ coordinate system).

[0098] As shown in Figure 7, the longitudinal length of the first servo element 42a (" / ") is 103.5393 μm (= 96 μm / Cos 22°). The longitudinal length of the second servo element 42b ("\") is 96.0585 μm (= 96 μm / Cos 2°).

[0099] Furthermore, the distance (in the X-axis direction) between the upper end of the first servo element 42a (" / ") and the upper end of the second servo element 42b ("\") is 16.9306 μm (= 38 μm - 48 μm × Tan 22° - 48 μm × Tan 2° = 38 μm - 19.3932 μm - 1.6762 μm).

[0100] Furthermore, the distance (in the X-axis direction) between the lower end of the first servo element 42a (" / ") and the lower end of the second servo element 42b ("\") is 59.0695 μm (= 96 μm × Tan 22° + 16.9306 μm + 96 μm × Tan 2° = 38.7865 μm + 16.9306 μm + 3.3524 μm).

[0101] Furthermore, in the longitudinal direction (X-axis direction) of the magnetic tape 1, the distance between the first servo element 42a (" / ") and the second servo element 42b ("\") is set to 38 μm at, for example, the position at half the width component SL of the length of the servo element 42.

[0102] Here, the first servo pattern 7a (" / ") written onto the magnetic tape 1 by the first servo element 42a (" / ") has basically the same configuration as the first servo element 42a (" / ") described here. Also, the second servo pattern 7b (" / ") written onto the magnetic tape 1 by the second servo element 42b ("\") has basically the same configuration as the second servo element 42b ("\") described here.

[0103] For example, the longitudinal length of the first servo pattern 7a (" / ") is approximately 103.5393 μm (= 96 μm / Cos 22°) (this may vary slightly depending on the magnetic field). Also, the longitudinal length of the second servo pattern 7b ("\") is approximately 96.0585 μm (= 96 μm / Cos 2°) (this may vary slightly depending on the magnetic field).

[0104] Figure 6 shows the servo patterns 7 written to each of the five servo bands s by five pairs of servo elements 42. Each of the five pairs of servo elements 42 receives pulse signals corresponding to the same phase at the same time, and the servo patterns 7 are written to each of the five servo bands s.

[0105] The phase difference in the width direction of the magnetic tape 1 between two adjacent servo bands s in the width direction (Y-axis direction) of the magnetic tape 1 is expressed as SWP1 × Tan(Refθ2).

[0106] Let's assume that the value of SWP1 is 2815.37 μm and the tilt angle Refθ is 10°. In this case, the phase difference of the servo patterns 7 written to two adjacent servo bands s is considered to be a phase difference corresponding to 2815.37 μm × Tan 10° = 496.43 μm.

[0107] Furthermore, the phase differences of servo pattern 7 for servo bands s1, s2, s3, and s4, relative to servo pattern 7 for servo band s0, are considered to correspond to phase differences of 496.43 μm, 992.85 μm, 1489.28 μm, and 1985.70 μm, respectively.

[0108] Of the servo patterns 7 written to each of the five servo bands s, the one with the most advanced phase in the width direction (Y-axis direction) of the magnetic tape 1 is the servo pattern 7 of servo band s0. The order of phases is then the servo pattern 7 of servo band s1, the servo pattern 7 of servo band s2, the servo pattern 7 of servo band s3, and the servo pattern 7 of servo band s4.

[0109] For example, using the servo pattern 7 of servo band s0 and the servo pattern 7 of servo band s1, in the width direction of the magnetic tape 1, the phase of the servo pattern 7 of servo band s0 is set to be 496.43 μm ahead of the servo pattern 7 of servo band s1 by a phase amount corresponding to 496.43 μm.

[0110] In the magnetic tape 1, in the direction of a second inclination angle Refθ2 (10°) with respect to the width direction (Y-axis direction) of the magnetic tape 1, the phases of the servo patterns 7 written on the five servo bands s are in phase.

[0111] The above description explained the configuration of the servo light head 40 based on the coordinate system (XYZ coordinate system) of the magnetic tape 1. The following section will describe the configuration of the servo light head 40 based on its own coordinate system (X"Y"Z" coordinate system).

[0112] Figure 8 is a diagram showing the servo light head 40 with reference to its own coordinate system, and is a view of the servo light head 40 from below (opposite side).

[0113] As shown in Figure 8, the five pairs of servo elements 42 are arranged at predetermined intervals (servo light pitch: SWP2) in the longitudinal direction (Y'' axis direction) of the servo light head 40. In the longitudinal direction (Y'' axis direction) of the servo light head 40, the distance between two adjacent pairs of servo elements 42 (servo light pitch: SWP2) is SWP1 × Cos -1 It is represented by (Refθ2).

[0114] For example, suppose that in the width direction (Y-axis direction) of the magnetic tape 1, the distance between two adjacent pairs of servo elements 42 (servo light pitch: SWP1) is 2815.37 μm, and the second tilt angle Refθ2 of the servo light head 40 is 10°. In this case, the distance between two adjacent pairs of servo elements 42 (servo light pitch: SWP2) in the longitudinal direction (Y'' axis direction) of the servo light head 40 is 2858.8 μm.

[0115] Here, the axes of symmetry between the first servo element 42a (" / ") and the second servo element 42b ("\") are non-parallel to the width direction (Y-axis direction) of the magnetic tape 1 (in the direction of the inclination angle refθ2 with respect to the width direction), while being parallel to the longitudinal direction (Y'' axis direction) of the servo light head 40.

[0116] The first servo element 42a (" / ") is tilted with respect to the longitudinal direction (Y'' axis direction) of the servo light head 40 at a servo azimuth angle θa. On the other hand, the second servo element 42b ("\") is tilted with respect to the longitudinal direction (Y'' axis direction) of the servo light head 40 in the opposite direction to the first servo element 42a (" / "), but at the same servo azimuth angle θa as the first servo element 42a (" / ").

[0117] Here, for the first servo element 42a (" / "), the direction along the servo azimuth angle θa (10° with respect to the longitudinal direction of the servo light head 40) is defined as the longitudinal direction of the first servo element 42a (" / "). Also, for the second servo element 42b ("\"), the direction along the servo azimuth angle θa (-10° with respect to the longitudinal direction of the servo light head 40) is defined as the longitudinal direction of the second servo element 42b ("\").

[0118] The longitudinal length of the first servo element 42a (" / ") is different from the longitudinal length of the second servo element 42b ("\"). In this example, the longitudinal length of the first servo element 42a (" / ") is longer than the longitudinal length of the second servo element 42b ("\").

[0119] Furthermore, the longitudinal component SL21 (Y" axis direction) of the servo light head 40 in relation to the longitudinal length of the first servo element 42a (" / ") and the longitudinal component SL22 (Y" axis direction) of the servo light head 40 in relation to the longitudinal length of the second servo element 42b (" / ") are also different.

[0120] Figure 9 is an enlarged view of the right-hand side of Figure 8, showing an example of specific dimensions for the first servo element 42a (" / ") and the second servo element 42b ("\") (based on the X"Y"Z" coordinate system).

[0121] Let's assume that the width component SL1 (Y-axis direction) of the magnetic tape 1 in the length of the servo element 42 is 96 μm, the second tilt angle Refθ2 of the servo light head 40 is 10°, and the servo azimuth angle θa is 12°.

[0122] In this case, the longitudinal component SL21 (Y'' axis direction) of the servo light head 40 at the length of the first servo element 42a (" / ") is 101.2767 μm (= 103.5093 μm × Cos12°). Also, the longitudinal component SL22 (Y'' axis direction) of the servo light head 40 at the length of the second servo element 42b ("\") is 93.959 μm (= 96.0585 μm × Cos12°) μm.

[0123] Furthermore, in the width direction (X" axis direction) of the servo light head 40, the distance between the upper end of the first servo element 42a (" / ") and the upper end of the second servo element 42b ("\") is 16.673 μm (= 16.9306 μm × Cos 10°). Also, in the longitudinal direction (Y" axis direction) of the servo light head 40, the difference between the position of the upper end of the first servo element 42a (" / ") and the position of the upper end of the second servo element 42b ("\") is 2.94 μm (= 16.9306 μm × Sin 10°).

[0124] Furthermore, in the width direction (X" axis direction) of the servo light head 40, the distance between the lower end of the first servo element 42a (" / ") and the lower end of the second servo element 42b ("\") is 58.1721 μm (= 59.0695 μm × Cos 10°). Also, in the longitudinal direction (Y" axis direction) of the servo light head 40, the difference between the position of the lower end of the first servo element 42a (" / ") and the position of the lower end of the second servo element 42b ("\") is 10.2573 μm (= 59.0695 μm × Sin 10°).

[0125] Furthermore, in the width direction (X" axis direction) of the servo light head 40, the distance (center) between the first servo element 42a (" / ") and the second servo element 42b ("\") is, for example, 38.8253 μm (38 μm × Cos 10° + (38 μm × Sin 10°) × Tan 12° = 37.4227 μm + 6.5986 μm × Tan 12° = 37.4227 μm + 1.4026 μm).

[0126] <Servo measuring device 100> Next, the servo measuring device 100 according to this embodiment will be described. Figure 10 shows the servo measuring device 100 according to this embodiment. The servo measuring device 100 according to this embodiment is configured to measure the width SPW (see Figures 11, 12, etc.) of the servo pattern 7 recorded on the magnetic tape 1.

[0127] In this embodiment, an older data recording and playback device corresponding to an older LTO type magnetic tape 1 (e.g., LTO-7, LTO-8, LTO-9, etc.) is essentially reused as the servo measuring device 100 (however, it is necessary to add a new program to the control unit). Here, "older type" means that it is an older type at the time this technology is used, and also includes types that will become old in the future.

[0128] By reusing older data recording and playback devices as servo measuring devices 100 in this way, costs can be reduced and environmental considerations can be taken into account. However, it is not always necessary to reuse older data recording and playback devices as servo measuring devices 100; a new, dedicated servo measuring device 100 can also be manufactured.

[0129] Referring to Figure 10, the servo measuring device 100 is configured to be able to load a cartridge 10. The cartridge 10 is configured to be able to rotatably house a wound magnetic tape 1 inside. The servo measuring device 100 may be configured to be able to load one cartridge 10, or it may be configured to be able to load multiple cartridges 10 simultaneously.

[0130] The servo measuring device 100 includes a spindle 11, a winding reel 12, a spindle drive device 13, a reel drive device 14, a servo lead head 20, a control device 15, and a plurality of guide rollers 18.

[0131] The spindle 11 is configured to rotate the magnetic tape 1 housed inside the cartridge 10 by its rotation. The spindle drive device 13 rotates the spindle 11 in response to commands from the control device 15.

[0132] The take-up reel 12 is configured to hold the leading edge of the magnetic tape 1, which has been pulled out from the cartridge 10 via a tape loading mechanism (not shown). The reel drive device 14 rotates the take-up reel 12 in response to a command from the control device 15.

[0133] Multiple guide rollers 18 guide the magnetic tape 1 so that the transport path formed between the cartridge 10 and the take-up reel 12 is in a predetermined relative positional relationship with respect to the servo read head 20.

[0134] The servo read head 20 is configured to read the servo pattern 7 recorded on the magnetic tape 1 and reproduce the servo signal as the magnetic tape 1 passes beneath the servo read head 20. The servo read head 20 is a data write head that was originally installed in a reusable older data recording and playback device.

[0135] The data write head is configured to record data onto the data band d (recording track 6) of the magnetic tape 1, and to reproduce the recorded data; however, this function of the data write head is not used in this embodiment.

[0136] When the servo read head 20 reads the servo pattern 7 of the magnetic tape 1, the spindle drive unit 13 and the reel drive unit 14 rotate the spindle 11 and the take-up reel 12, causing the magnetic tape 1 to travel. The magnetic tape 1 can travel in two directions: forward (winding from the spindle 11 side to the take-up reel 12 side) as shown by arrow A1 in Figure 6, and reverse (winding back from the take-up reel 12 side to the spindle 11 side) as shown by arrow A2.

[0137] The servo read head 20 is capable of reading the servo pattern 7 and reproducing the servo signal in both the forward and reverse directions of the magnetic tape 1.

[0138] In this case, older data recording and playback devices that are being reused may have two data write heads: one for forward data writing and one for reverse data writing.

[0139] In such a case, only one of the two data write heads may be used as the servo read head 20, or both data write heads may be used as the servo read head 20. When both data write heads are used as the servo read head 20, the servo read head 20 used may be switched according to the switching of the forward and reverse running directions of the magnetic tape 1.

[0140] The control device 15 includes, for example, a control unit, a memory unit, and a communication unit. The control unit is composed of, for example, a CPU (Central Processing Unit), and comprehensively controls each part of the servo measuring device 100 according to the program stored in the memory unit.

[0141] The memory unit includes a non-volatile memory on which various data and programs are recorded, and a volatile memory used as a workspace for the control unit. These programs may be read from portable recording media such as optical discs or semiconductor memory, or downloaded from a server device on a network. The communication unit is configured to communicate with other devices such as PCs (Personal Computers) and server devices.

[0142] Figure 11 shows the servo read head 20 reading the servo pattern 7 in the servo band s, and is a view of the servo read head 20 from below (opposite side).

[0143] As shown in Figure 11, the servo read head 20 is positioned such that its longitudinal direction (Y' axis direction) is parallel to the width direction (Y axis direction) of the magnetic tape 1. Furthermore, the servo read head 20 is movable in the width direction (Y axis direction) of the magnetic tape 1 (in the longitudinal direction (Y' axis direction) of the servo read head 20).

[0144] The servo read head 20 may be positioned at a predetermined angle (equal to the first inclination angle Refθ1 and the second inclination angle Refθ: 10°) with respect to the width direction of the magnetic tape 1 (for example, when a head-tilting type data recording and playback device is used as the servo measuring device 100).

[0145] The servo read head 20 has a facing surface 21 that faces the magnetic tape 1. The facing surface 21 is long in the longitudinal direction (Y' axis direction) of the servo read head 20 and short in the width direction (X' axis direction) of the servo read head 20. Two servo read portions 22 are provided on the facing surface 21.

[0146] The servo lead section 22 includes a first servo lead section 22a provided on one end of the servo lead head 20 in the longitudinal direction (Y' axis direction) and a second servo lead section 22b provided on the other end. The first servo lead section 22a and the second servo lead section 22b are arranged at a predetermined interval (servo lead pitch: SRP) in the longitudinal direction (Y' axis direction) (width direction of the magnetic tape 1 (Y axis direction)) of the servo lead head 20.

[0147] This interval (servo lead pitch SRP) is the distance between the longitudinal center of the servo lead head 20 in the first servo lead section 22a and the longitudinal center of the servo lead head 20 in the first servo lead section 22a. This servo lead pitch SRP is, for example, 2858.8 μm ± 1 μm.

[0148] The servo read unit 22 is configured to reproduce the servo signal by reading the magnetic field generated by the servo pattern 7 recorded on the servo band s of the magnetic tape 1 using an MR element (MR: Magneto Resistive effect) or the like.

[0149] Examples of MR elements include anisotropic magnetoresistive (AMR), giant magnetoresistive (GMR), and tunnel magnetoresistive (TMR) elements.

[0150] The data write head of the older data recording and playback device that is reused has a data write section for recording data on the data band d of the magnetic tape 1 and a data read section for reading the data recorded on the data band d on the opposing surface 21, but these are not used in this embodiment and are therefore not shown.

[0151] The first servo lead section 22a is capable of reading the servo pattern 7 in one of two servo bands s that are adjacent to each other in the width direction (Y-axis direction) of the magnetic tape 1. The second servo lead section 22b is capable of reading the servo pattern 7 in the other of two servo bands s that are adjacent to each other in the width direction (Y-axis direction) of the magnetic tape 1.

[0152] Specifically, when the first servo lead section 22a is positioned on servo band s0, s1, s2, or s3 and reading the servo pattern 7, the second servo lead section 22b is positioned on the next lower servo band s1, s2, s3, or s4 and reading the servo pattern 7.

[0153] The width (Y-axis direction) of the servo track 8 for reading the servo pattern 7 in the first servo lead section 22a and the second servo lead section 22b is set to approximately 1 μm or more and 5 μm or less (in the case of a type where the servo lead head 20 is tilted, the width of the servo track 8 is approximately 0.1 μm or more and 1.5 μm or less).

[0154] Based on the servo signal from the first servo lead unit 22a, the control unit measures the width SPW of the servo pattern 7 in one of two servo bands s that are adjacent to each other in the width direction of the magnetic tape 1. The control unit also measures the width SPW of the servo pattern 7 in the other servo band s based on the servo signal from the second servo lead unit 22b.

[0155] As shown in the lower part of Figure 11, the width of the servo band s can be measured for each servo track 8 (each servo trace line). The servo tracks 8 (servo trace lines) are tracks that run along the longitudinal direction (X-axis direction) of the magnetic tape 1 and are set at predetermined intervals in the width direction (Y-axis direction) of the magnetic tape 1. Based on the servo signal from the servo lead unit 22, the control unit adjusts the position of the servo lead head 20 in the width direction (Y-axis direction) of the magnetic tape 1 so that the servo lead unit 22 can accurately trace the position of any servo track 8.

[0156] In the servo pattern 7, the area above the center in the width direction of the magnetic tape 1 is the area read by the servo measuring device 100 when the magnetic tape 1 is running in the reverse direction. On the other hand, in the servo pattern 7, the area below the center in the width direction of the magnetic tape 1 is the area read by the servo measuring device 100 when the magnetic tape 1 is running in the reverse direction.

[0157] <Servo pattern 7 width SPW> Next, the width SPW of the servo pattern 7 will be explained. Figure 12 is a side view showing the state when the servo pattern 7 is being written to the magnetic layer 4 of the magnetic tape 1 by the servo write head 40 of the servo recording and playback device 101, and is a diagram showing the width SPW of the servo pattern 7.

[0158] The servo light head 40 of the servo recording and playback device 101 has a head block 43 that is generally inverted U-shaped when viewed from the side (Y-axis direction), and the head block 43 has a magnetic gap on its lower side. This magnetic gap corresponds to the servo element 42 described above. The width W1 of this magnetic gap is, for example, about 1 μm.

[0159] A coil 44 is wound spirally around the head block 43, and a rectangular pulse signal is input to this coil 44. When this rectangular pulse signal is high, magnetic flux is generated within the head block 43, and leakage flux is generated from the magnetic gap (servo element 42). This leakage flux writes the servo pattern 7 to the magnetic layer 4 of the magnetic tape 1.

[0160] The width SPW of the servo pattern 7 corresponds to the distance in the longitudinal direction (X-axis direction) of the magnetic tape 1 from the portion of the magnetic layer 4 that is magnetized as the servo pattern 7. In this specification, the expression "width direction of the servo pattern 7" may be used, but this width direction of the servo pattern 7 corresponds to the longitudinal direction (X-axis direction) of the magnetic tape 1.

[0161] The width SPW of the servo pattern 7 is approximately equal to the sum of the magnetic gap width W1 (the longitudinal direction (X-axis direction) of the magnetic tape 1) and the recording current distance W2, minus the spacing factor Spf based on spacing Sp. In other words, SPW = W1 + W2 - Spf.

[0162] The recording current distance W2 is the distance (in the X-axis direction) of the portion of the magnetic tape 1 that is magnetized as it moves. When the time of the pulse signal being High is t and the tape speed is v, the recording current distance W2 is expressed as t × v.

[0163] Spacing Sp is the distance in the thickness direction (Z-axis direction) of the magnetic tape 1 between the lower surface of the head block 43 (the recording surface of the servo write head 40) and the upper surface of the magnetic layer 4. The spacing factor Spf is a function of spacing Sp and increases as spacing Sp increases. In other words, as spacing Sp increases (the distance between the lower surface of the head block 43 and the upper surface of the magnetic layer 4 increases), the spacing factor Spf increases, and the width SPW of the servo pattern 7 decreases.

[0164] <Basic Concept of This Technology> Next, we will explain the basic concept of how to measure the width SPW of servo pattern 7.

[0165] The LTO standard specifies in detail the criteria that the magnetic tape 1 must meet, and it also specifies the width SPW of the servo pattern 7. Therefore, the width SPW of the servo pattern 7 must also meet certain standards. Consequently, periodic measurement of the width SPW of the servo pattern 7 on the magnetic tape 1 is required.

[0166] Figure 13 is a diagram illustrating the basic concept of the measurement method for the width SPW of the servo pattern 7 according to this embodiment.

[0167] The upper part of Figure 13 shows the servo signals when a servo pattern 7 recorded on a longitudinally oriented magnetic layer 4 is read (see solid line), when a servo pattern 7 recorded on a non-oriented magnetic layer 4 is read (see dashed line), and when a servo pattern 7 recorded on a vertically oriented magnetic layer 4 is read (see dashed line).

[0168] Furthermore, the lower part of Figure 13 shows, from top to bottom, the servo pattern 7 recorded on the longitudinally oriented magnetic layer 4, the servo pattern 7 recorded on the unoriented magnetic layer 4, and the servo pattern 7 recorded on the vertically oriented magnetic layer 4.

[0169] In the longitudinal orientation type, the magnetization direction of the servo pattern 7 is aligned with the longitudinal direction (X-axis direction) of the magnetic tape 1, and this direction is opposite to that of the unmagnetized portion.

[0170] Furthermore, in the case of the non-oriented type, the magnetization direction of the servo pattern 7 is in a direction that follows the leakage magnetic field of the magnetic gap (servo element 42) (a direction that follows an ellipse), and this direction gradually reverses vertically along the longitudinal direction of the magnetic tape 1.

[0171] Furthermore, in the case of the vertical orientation type, the magnetization direction of the servo pattern 7 is aligned with the thickness direction (Z-axis direction) of the magnetic tape 1, and its orientation is reversed vertically at approximately half the length of the magnetic tape 1.

[0172] In the longitudinal orientation type, the positions of the positive and negative peak points in the output waveform of the servo signal approximately coincide with the positions of both ends of the servo pattern 7 in the width direction. Therefore, the difference in detection time between the detection time of the positive peak point and the detection time of the negative peak point, converted into distance (detection time difference × magnetic tape 1 running speed), is approximately equal to the width SPW of the servo pattern 7. Hereinafter, this method of measuring the width SPW of the servo pattern 7 will be referred to as the peak-to-peak measurement method.

[0173] On the other hand, in the case of non-oriented and vertically oriented types, the positions of the positive and negative peak points in the output waveform of the servo signal do not coincide at all with the positions of the ends of the servo pattern 7 in the width direction. Specifically, the positions of the positive and negative peak points in the output waveform of the servo signal are shifted inward from the positions of the ends of the servo pattern 7 in the width direction. This amount of shift increases as the degree of vertical orientation (vertical aspect ratio S1) of the magnetic layer 4 increases.

[0174] Therefore, in the case of non-oriented and vertically oriented types, the value obtained by converting the detection time difference between the detection time of the positive peak point and the detection time of the negative peak point into distance (detection time difference × magnetic tape 1 running speed) is not equal to the width SPW of the servo pattern 7, but is smaller than the width SPW of the servo pattern 7. Consequently, the actual width SPW of the servo pattern 7 cannot be measured using the peak-to-peak measurement method.

[0175] In the LTO standard, as generations progressed, there was a demand for higher density recording, and in response to this demand, the degree of vertical orientation of the magnetic layer 4 increased. Therefore, an alternative measurement method to the peak-to-peak measurement method described above was needed. One example of such an alternative is the measurement method using a magnetic force microscope (MFM).

[0176] A magnetic force microscope is configured to image the distribution of the magnetic force gradient of the object being observed. However, measuring the width SPW of the servo pattern 7 using a magnetic force microscope presents problems such as requiring skilled personnel, and even with skilled personnel, it takes a long time to complete the measurement.

[0177] Figure 14 is another diagram illustrating the basic concept of the measurement method for the width SPW of the servo pattern 7 according to this embodiment.

[0178] The upper part of Figure 14 shows an image obtained by MFM, the center of Figure 14 shows the waveform of the magnetic force detected by MFM, and the lower part of Figure 14 shows the waveform of the servo signal.

[0179] In measuring the width SPW of the servo pattern 7 using MFM, not only the image shown at the top of Figure 14 but also the magnetic force waveform shown in the center of Figure 14 is referenced. In the magnetic force waveform, the width SPW of the servo pattern 7 is measured not as the distance between peaks in the waveform, but as the distance between the starting point and the ending point of the magnetic force waveform (1.55 μm).

[0180] Referring to the lower part of Figure 14, the value obtained by converting the peak-to-peak detection time difference in the servo signal waveform to a distance (approximately 0.95 μm) is completely different from the actual width SPW of the servo pattern 7. On the other hand, the value obtained by converting the detection time difference between two predetermined points in the servo signal waveform to a distance (1.55 μm) is approximately equal to the actual width SPW of the servo pattern 7.

[0181] Therefore, in this embodiment, the servo measuring device 100 employs a method in which the width SPW of the servo pattern 7 is measured based on a first point Po1 and a second point Po2, which are different from the positive peak point Pe1 and the negative peak point Pe2 in the waveform of the servo signal.

[0182] This method is expected to eliminate problems such as the need for skilled techniques, as is required for measurements using MFM, and the long time required to complete the measurement. In other words, users can easily measure the width SPW of the servo pattern 7 using the servo measuring device 100. The above is the basic concept of this technology.

[0183] <Method for measuring the width SPW of servo pattern 7> Next, the method for measuring the width SPW of the servo pattern 7 will be explained in detail. In this example, two types of magnetic tape 1, type A magnetic tape 1 and type B magnetic tape 1, were prepared, and the width SPW of the servo pattern 7 on each magnetic tape 1 was actually measured.

[0184] The Type A magnetic tape 1 and the Type B magnetic tape 1 have different servo patterns 7 widths SPW because the servo patterns 7 were written to them by different types of servo light heads 40.

[0185] Here, as described above in Figure 12, the width SPW of the servo pattern 7 is approximately equal to the sum of the magnetic gap width W1 (the longitudinal direction (X-axis direction) of the magnetic tape 1) and the recording current distance W2, minus the spacing factor Spf based on spacing Sp. In other words, SPW = W1 + W2 - Spf.

[0186] While the recording current distance W2 and the spacing factor Spf are generally considered to be constant values, the magnetic gap width W1 is not constant due to differences in the type of servo light head 40 and individual variations. Therefore, the servo pattern width SPW may differ depending on the type of servo light head 40 and individual variations.

[0187] [Type A magnetic tape 1] Figure 15 shows the MFM image of the servo pattern 7 on the type A magnetic tape 1, and the waveform of the magnetic force obtained by MFM. Note that the MFM image in Figure 15 shows the type A magnetic tape 1 viewed from above (magnetic layer 4 side) (similarly in Figures 17, 18, and 20 described later).

[0188] Each MFM image shown in Figure 15 illustrates the servo pattern 7 (servo burst) on different servo bands s within a Type A magnetic tape 1. Each MFM image is 35 μm × 35 μm in both length and width dimensions. In the example shown in Figure 15, MFM measurements based on the MFM images and magnetic force waveforms showed that the average width SPW of the servo pattern 7 in servo bands s0 and s4 was 1.6 μm, while the average width SPW of the servo pattern 7 in servo bands s1, s2, and s3 was 1.5 μm.

[0189] Figure 16 shows the waveform of the servo signal when the servo pattern 7 on the Type A magnetic tape 1 is read. The horizontal axis of Figure 16 represents time, and the vertical axis represents the output value.

[0190] The waveform of the servo signal corresponding to one servo pattern 7 is generally sine wave-shaped. The servo signal waveform has a positive convex portion and a negative concave portion. The positive convex portion has a positive rising portion (from the point where the output value is 0 to the positive peak point Pe1) and a positive falling portion (from the positive peak point Pe1 to the point where the output value is 0). On the other hand, the negative convex portion has a negative falling portion (from the point where the output value is 0 to the negative peak point Pe2) and a negative rising portion (from the negative peak point Pe2 to the point where the output value is 0).

[0191] One of the reference points for measuring the width SPW of the servo pattern 7, the first point Po1, is defined as a point corresponding to one of the rising edges of the positive convex portion in the servo signal waveform (excluding the positive peak point Pe1). The other reference point for measuring the width SPW of the servo pattern 7, the second point Po2, is defined as a point corresponding to one of the rising edges of the positive concave portion in the servo signal waveform (excluding the negative peak point Pe2).

[0192] When the output value of the positive peak point Pe1 in the servo signal waveform is set to 100%, the first point Po1 is defined as the point corresponding to the output value that is the first percentage relative to the positive peak point Pe1 (excluding 100%). Similarly, when the output value of the negative peak point Pe2 in the servo signal waveform is set to -100%, the second point Po2 is defined as the point corresponding to the output value that is the second percentage relative to the negative peak point Pe2 (excluding -100%).

[0193] In this embodiment, the first percentage is set to any value within a first range of 25% or more and 75% or less. In addition, in this embodiment, the second percentage is set to any value within a second range of -25% or more and -75% or less.

[0194] Furthermore, in this embodiment, the first percentage and the second percentage are set to have the same absolute value. However, the absolute values ​​of the first percentage and the second percentage can also be made different.

[0195] Here, we will explain the basis for the lower and upper limits of the first and second percentages.

[0196] As described above, in this embodiment, a vertically oriented magnetic layer 4 is used as the magnetic layer 4. Also, as described above in Figure 13, when the magnetic layer 4 is vertically oriented, the positions of the positive peak point Pe1 and the negative peak point Pe2 in the output waveform of the servo signal are shifted inward from the positions of both ends in the width direction of the servo pattern 7. This amount of shift increases as the degree of vertical orientation (vertical aspect ratio S1) of the magnetic layer 4 increases.

[0197] Therefore, if the degree of vertical orientation of the magnetic layer 4 (vertical aspect ratio S1) is relatively high, it is necessary to set the absolute values ​​of the first and second percentages to be lower. On the other hand, if the degree of vertical orientation of the magnetic layer 4 is relatively low, it is necessary to set the absolute values ​​of the first and second percentages to be higher.

[0198] For example, when the vertical orientation degree of the magnetic layer 4 (vertical aspect ratio S1) is set to the lowest value (e.g., no orientation), if the absolute values ​​of the first and second percentages are set to 75% to determine the width SPW of the servo pattern 7, it is considered to be approximately equal to the actual width SPW of the servo pattern 7. Also, when the vertical orientation degree of the magnetic layer 4 (vertical aspect ratio S1) is set to the highest value, if the absolute values ​​of the first and second percentages are set to 25% to determine the width SPW of the servo pattern 7, it is considered to be approximately equal to the actual width SPW of the servo pattern 7. The above is the basis for the lower and upper limits of the first and second percentages.

[0199] In the example shown in Figure 16, the first percentage was set to 50%, and the second percentage was set to -50%. The detection time difference between the detection time of the first point Po1, where the output value is 50% of the positive peak point Pe1 in the rising portion of the positive side, and the detection time difference between the detection time of the second point Po2, where the output value is -50% of the negative peak point Pe2 in the rising portion of the negative side, was converted into distance (detection time difference × magnetic tape transport speed 1), and the width SPW of the servo pattern 7 was determined.

[0200] The width SPW of the servo pattern 7 obtained at this time was approximately 1.55 μm (average value). In other words, the width SPW of the servo pattern 7 measured by this embodiment (approximately 1.55 μm) is about the same as the width SPW of the servo pattern 7 measured based on MFM (1.5 μm or 1.6 μm), and therefore, it can be seen that the actual width SPW of the servo pattern 7 can be accurately determined in this embodiment.

[0201] In this example, the difference in detection time between the detection time of the positive peak point Pe1 and the detection time of the negative peak point Pe2, converted to distance (detection time difference × magnetic tape transport speed 1), was approximately 0.95 μm (average value) (T(Transition)-spacing).

[0202] Figure 17 shows the width SPW of the servo pattern 7 for each servo band s and each servo track 8 (each servo trace line) on a Type A magnetic tape 1. In Figure 17, the vertical axis shows the calculated width SPW of the servo pattern 7, and the horizontal axis shows the position in the width direction (Y-axis direction) of the magnetic tape 1 (i.e., the position of the servo track 8).

[0203] In Figure 17, the upper plots show the width SPW of the servo pattern 7 at each servo track 8 in each servo band s, as determined by the measurement method according to this embodiment. On the other hand, the lower plots in Figure 17 show the width SPW of the servo pattern 7 at each servo track 8 in each servo band s, as determined by the peak-to-peak measurement method (T-spacing).

[0204] As shown in the upper plots of Figure 17, the width SPW of the servo pattern 7 obtained by the measurement method according to this embodiment is approximately 1.55 μm, although there is some variation for each servo band s and each servo track 8. In other words, the width SPW of the servo pattern 7 measured by this embodiment (approximately 1.55 μm) is about the same as the width SPW of the servo pattern 7 measured based on MFM (1.5 μm or 1.6 μm), and therefore, it can be seen that the actual width SPW of the servo pattern 7 can be accurately determined in this embodiment.

[0205] In the example shown in Figure 17, the width SPW of the servo pattern 7 in the region below the center in the width direction of the magnetic tape 1, that is, the region read by the servo measuring device 100 when the magnetic tape 1 is running in the forward direction, is plotted. On the other hand, the width SPW of the servo pattern 7 in the region above the center in the width direction of the magnetic tape 1, that is, the region read by the servo measuring device 100 when the magnetic tape 1 is running in the reverse direction, was also measured. In this case as well, the width SPW of the servo pattern 7 was approximately 1.55 μm.

[0206] Furthermore, the width SPW (T-spacing) of the servo pattern 7, as determined by the peak-to-peak measurement method shown in each of the lower plots in Figure 17, was approximately 0.95 μm.

[0207] [Type B magnetic tape 1] Figure 18 shows the MFM image of the servo pattern 7 on a Type B magnetic tape 1, and the waveform of the magnetic force generated by the MFM.

[0208] Each MFM image shown in Figure 18 displays a servo pattern 7 (servo burst) on a different servo band s within a Type B magnetic tape 1. Each MFM image is 35 μm × 35 μm in both length and width dimensions. In the example shown in Figure 18, based on the MFM images and MFM measurements using magnetic force waveforms, the average width SPW of the servo pattern 7 for servo bands s0, s1, s3, and s4 was 1.9 μm, and the average width SPW of the servo pattern 7 for servo band s2 was 1.8 μm.

[0209] Figure 19 shows the waveform of the servo signal when the servo pattern 7 on the Type B magnetic tape 1 is read. The horizontal axis of Figure 19 represents time, and the vertical axis represents the output value.

[0210] In the example shown in Figure 19, similar to Figure 16, the first percentage was set to 50% and the second percentage to -50%. The detection time difference between the detection time of the first point Po1, where the output value is 50% of the positive peak point Pe1 in the rising portion of the positive side, and the detection time difference between the detection time of the second point Po2, where the output value is -50% of the negative peak point Pe2 in the rising portion of the negative side, was converted into distance (detection time difference × magnetic tape transport speed 1), and the width SPW of the servo pattern 7 was determined.

[0211] The width SPW of the servo pattern 7 determined at this time was approximately 1.9 μm (average value). In other words, the width SPW of the servo pattern 7 measured by this embodiment (approximately 1.9 μm) is about the same as the width SPW of the servo pattern 7 measured based on MFM (1.8 μm or 1.9 μm), and therefore, it can be seen that the actual width SPW of the servo pattern 7 can be accurately determined in this embodiment.

[0212] In this example, the difference in detection time between the detection time of the positive peak point Pe1 and the detection time of the negative peak point Pe2, converted to distance, was approximately 1.1 μm (detection time difference × magnetic tape transport speed 1) (T(Transition)-spacing).

[0213] Figure 20 shows the width SPW of the servo pattern 7 for each servo band s and each servo track 8 (each servo trace line) on a Type B magnetic tape 1. In Figure 20, the vertical axis shows the calculated width SPW of the servo pattern 7, and the horizontal axis shows the position in the width direction (Y-axis direction) of the magnetic tape 1 (i.e., the position of the servo track 8).

[0214] In Figure 20, the upper plots show the width SPW of the servo pattern 7 at each servo track 8 in each servo band s, as determined by the measurement method according to this embodiment. On the other hand, the lower plots in Figure 20 show the width SPW of the servo pattern 7 at each servo track 8 in each servo band s, as determined by the peak-to-peak measurement method (T-spacing).

[0215] As shown in the upper plots of Figure 20, the width SPW of the servo pattern 7 obtained by the measurement method according to this embodiment is approximately 1.9 μm, although there is some variation for each servo band s and each servo track 8. In other words, the width SPW of the servo pattern 7 measured by this embodiment (approximately 1.9 μm) is almost the same as the width SPW of the servo pattern 7 measured based on MFM (1.8 μm or 1.9 μm), and therefore, it can be seen that the actual width SPW of the servo pattern 7 can be accurately determined in this embodiment.

[0216] In the example shown in Figure 20, the width SPW of the servo pattern 7 in the region below the center in the width direction of the magnetic tape 1, that is, the region read by the servo measuring device 100 when the magnetic tape 1 is running in the forward direction, is plotted. On the other hand, the width SPW of the servo pattern 7 in the region above the center in the width direction of the magnetic tape 1, that is, the region read by the servo measuring device 100 when the magnetic tape 1 is running in the reverse direction, was also measured. In this case as well, the width SPW of the servo pattern 7 was approximately 1.9 μm.

[0217] Furthermore, the width SPW (T-spacing) of the servo pattern 7, as determined by the peak-to-peak measurement method shown in each of the lower plots in Figure 20, was approximately 1.1 μm.

[0218] [Degree of agreement between the measurement method according to this embodiment and the measurement method using MFM] Next, the degree of agreement between the width SPW of the servo pattern 7 measured by the measurement method according to this embodiment and the width SPW of the servo pattern 7 measured by the measurement method in MFM will be described.

[0219] Figure 21 is a diagram illustrating the degree of agreement between the width SPW of the servo pattern 7 measured by the measurement method according to this embodiment and the width SPW of the servo pattern 7 measured by the measurement method in MFM. In Figure 21, the horizontal axis shows the width SPW of the servo pattern 7 measured by the measurement method in MFM, and the vertical axis shows the width SPW of the servo pattern 7 measured by the measurement method according to this embodiment.

[0220] The following conditions were set for the measurement method according to this embodiment. First, an older type of data recording and playback device compatible with LTO-8 (data write head: non-rotating type with a tilt of 0°) was reused as the servo measurement device 100. The running speed of the magnetic tape 1 was set to 4 m / s. Data was collected at a sampling rate of 125 MS / s.

[0221] Furthermore, for one servo track 8 within one servo band s, 300 servo signal waveforms (each waveform corresponding to one servo pattern 7) were sampled, and the width SPW of the servo pattern 7 was measured for each of the 300 waveforms. The average of these 300 servo pattern 7 widths SPW was determined as the width SPW of the servo pattern 7 for the corresponding servo track 8 within the corresponding servo band s. In other words, the average value of the servo pattern 7 width SPW was calculated for each servo track 8.

[0222] Furthermore, the first percentage at the first point Po1 was set to 50%, and the second percentage at the second point Po2 was set to -50%.

[0223] For each servo band s, measurements were taken at 300 points on each of the 26 servo tracks 8 (13 used in the forward direction of magnetic tape 1's travel and 13 used in the reverse direction), and the average value of the servo pattern width SPW at these 300 points was calculated.

[0224] In other words, for each of the five servo bands s, the average value of the servo pattern 7 width SPW was calculated at 300 locations for every 26 servo tracks 8. The servo pattern 7 width SPW was measured at a total of 39,000 locations (5 × 26 × 300) on one magnetic tape 1. The average value of the servo pattern 7 width SPW for each servo track 8 (the average of 130 values ​​(5 × 26)) was further averaged, and this averaged value was calculated as the servo pattern 7 width SPW for the corresponding magnetic tape 1.

[0225] Furthermore, 25 different types of magnetic tape 1 were prepared (for example, different servo pattern widths due to different servo light heads 40), and the width SPW of the servo pattern 7 was measured for each of these 25 types of magnetic tape 1 using the measurement method according to this embodiment.

[0226] Further, for these 25 types of magnetic tapes 1, the width SPW of the servo pattern 7 was measured by the measurement method using MFM.

[0227] The 25 plots in FIG. 21 respectively correspond to these 25 types of magnetic tapes 1. In FIG. 21, the regression line for the 25 plots was y=1.0358x-0.068 μm. In addition, the coefficient of determination R 2 was 0.9243. From this, it is understood that with the measurement method according to the present embodiment, the width SPW of the servo pattern 7 can be accurately obtained with the same level of accuracy as the measurement method using MFM, regardless of the type of magnetic tape 1 (difference in the width SPW of the servo pattern 7).

[0228] <Measurement conditions for width SPW of servo pattern 7 by MFM> Next, the measurement conditions and the like for the width SPW of the servo pattern 7 by MFM will be described. For example, in order to obtain an MFM image in the range of 35 μm×35 μm as shown in FIG. 15 and FIG. 18 and the width SPW of the servo pattern 7, SPM Dimension Icon (MFM measurement apparatus) manufactured by BRUKER and its analysis software were used. Further, as the cantilever for MFM measurement, SSS-MFMR (manufactured by NANOSENSORS, probe material: single crystal silicon coated with a magnetic film, cantilever length: 225 μm) was used. More specific measurement conditions are as follows.

[0229] [Measurement Conditions] MFM measurement apparatus: SPM Dimension Icon, manufactured by BRUKER Inc. Measurement mode: MFM Measurement range: 35 μm×35 μm Sample lines: 512 lines Lift scan height: 30 nm Cantilever: SSS-MFMR, manufactured by NANOSENSORS Inc.

[0230] From the MFM image obtained under the above measurement conditions, for example, the width SPW of the servo pattern 7 indicated by the arrow in the upper diagram of Figure 14 was measured for each of the servo bands s0 to s4 using the attached analysis software. In addition, in the present specification and the drawings, when a specific numerical value is shown for the measured value of the width SPW of the servo pattern 7 by MFM, it indicates a value measured under these measurement conditions.

[0231] <Processing of Control Unit> Next, the processing of the control unit in the servo measurement apparatus 100 will be described. Figure 22 and Figure 23 are flowcharts showing the processing of the control unit.

[0232] First, the control unit determines whether it is necessary to change the first percentage at the first point Po1 and the second percentage at the second point Po2 according to the type of the magnetic tape 1 in the cartridge 10 loaded in the servo measurement apparatus 100 (ST101).

[0233] In this case, first, the relationship between the type of the magnetic tape 1 and the first percentage and the second percentage (typically having the same absolute value) is tabulated and stored in the storage unit in advance.

[0234] Here, as described above, appropriate values of the first percentage and the second percentage differ according to the perpendicular orientation degree (perpendicular squareness ratio S1) of the magnetic layer 4, and the (absolute values of the) first percentage and the second percentage decrease as the perpendicular orientation degree of the magnetic layer 4 increases. Accordingly, the table in the storage unit stores appropriate first percentages and second percentages corresponding to the type (perpendicular orientation degree) of the magnetic tape 1.

[0235] In other words, in this embodiment, the control unit can automatically change the first percentage and the second percentage according to the degree of vertical orientation (vertical aspect ratio S1) of the magnetic layer 4 in the magnetic tape 1. In this example, the case in which both the first and second percentages can be changed is described, but it is also acceptable for only one of the first and second percentages to be changeable.

[0236] Here, if the first and second percentages are changed, the positions of the first point Po1 and the second point Po2 are also changed. In other words, in this embodiment, the control unit can automatically change the first point Po1 and the second point Po2 according to the degree of vertical orientation (vertical aspect ratio S1) of the magnetic layer 4 in the magnetic tape 1 (it is also acceptable if only one of the first point Po1 and the second point Po2 is changeable).

[0237] Furthermore, while this example describes a case where the control unit automatically changes the first and second percentages (first point Po1 and second point Po2), it is also possible for the user to manually change the first and second percentages (first point Po1 and second point Po2).

[0238] If it is necessary to change the first and second percentages (YES in ST101) (for example, if a magnetic tape 1 (tape cartridge 10) with a different degree of vertical orientation than the previous magnetic tape 1 is loaded), the control unit refers to the table stored in the memory unit and changes the first and second percentages to the corresponding values ​​(ST102).

[0239] On the other hand, if there is no need to change the first and second percentages (for example, if a magnetic tape 1 (tape cartridge 10) with the same degree of vertical orientation as the previous magnetic tape 1 is loaded), the control unit skips ST102 and proceeds to ST103.

[0240] In ST103, the control unit determines whether the user has entered a measurement start command. If the user has not entered a measurement start command (NO in ST103), the control unit returns to ST101.

[0241] On the other hand, when the user inputs a measurement start command (YES in ST103), the control unit moves the servo read head 20 in the longitudinal direction (Y' axis direction) (width direction of the magnetic tape 1 (Y axis direction)) to a position corresponding to the set of servo bands s to be measured (ST104) (see Figure 11).

[0242] The set of servo bands s to be measured is one of the following four sets: servo bands s0 and s1, servo bands s1 and s2, servo bands s2 and s3, or servo bands s3 and s4.

[0243] Next, the control unit starts the magnetic tape 1 from running (ST105). Then, the control unit acquires a first servo signal from the first servo lead unit 22a (ST105) and a second servo signal from the second servo lead unit 22b (ST106).

[0244] Next, based on the first servo signal and the second servo signal (position error signal), the control unit adjusts the position of the servo lead head 20 by moving it in the longitudinal direction (Y' axis direction) of the servo lead head 20 as necessary so that the first servo lead section 22a and the second servo lead section 22b can accurately trace the target servo track 8 (ST108).

[0245] Next, the control unit determines whether the moving magnetic tape 1 has reached the end of the magnetic tape 1 (ST109). If the moving magnetic tape 1 has not reached the end of the magnetic tape 1 (NO in ST109), the control unit returns to ST106 and executes the processes from ST106 onwards again.

[0246] On the other hand, when the moving magnetic tape 1 reaches the end of the magnetic tape 1 (YES in ST109), the control unit determines whether there are any servo tracks 8 for the corresponding set of servo bands s from which a servo signal has not yet been acquired (ST110). The number of servo tracks 8 from which a servo signal should be acquired for each servo band s is set in advance (for example, 13 tracks in the forward direction and 13 tracks in the reverse direction, for a total of 26 tracks).

[0247] If there are still servo tracks 8 for which servo signals have not yet been acquired for the corresponding set of servo bands s (YES in ST110), the control unit moves the servo read head 20 in the longitudinal direction (Y' axis direction) to the position corresponding to the servo track 8 to be measured (ST112). Then, the control unit reverses the direction of travel of the magnetic tape 1 from before (ST113) and returns to ST106.

[0248] On the other hand, if servo signals have been acquired for all scheduled servo tracks 8 for the corresponding set of servo bands s (NO in ST110), the control unit determines whether there are any remaining sets of servo bands s for which servo signals have not yet been acquired (ST114).

[0249] If there are still sets of servo bands s from which servo signals have not yet been acquired (YES in ST114), the control unit moves the servo read head 20 in the longitudinal direction (Y' axis direction) to the position corresponding to the set of servo bands s to be acquired (ST115) (see Figure 11). Then, the control unit reverses the direction of travel of the magnetic tape 1 (ST113) and returns to ST106.

[0250] In this embodiment, servo signals are acquired for each servo band s and each servo track 8 by the processing shown in ST106 to ST115.

[0251] In ST114, when servo signals have been acquired for all sets of servo bands s (NO in ST114), the control unit stops the running of the magnetic tape 1 (ST116).

[0252] Next, the control unit detects the positions of the positive-side peak point Pe1 and the negative-side peak point Pe2 for the waveform of the servo signal at one predetermined sampling position (one waveform corresponds to one servo pattern 7) (ST117).

[0253] The sampling positions and the number of samplings are set in advance for each servo band s and each servo track 8 (for example, 300 positions per one servo track 8, etc.). The sampling positions and the number of samplings may be the same or different for each servo band s and each servo track 8.

[0254] Next, the control unit sets, as a first point Po1, a point at which the output value is a first percentage (for example, 50%) of the output value of the positive-side peak point Pe1, on the rising portion of the positive-side convex part in the waveform of the servo signal (ST118).

[0255] Next, the control unit sets, as a second point Po2, a point at which the output value is a second percentage (for example, -50%) of the output value of the negative-side peak point Pe2, on the rising portion of the negative-side concave part in the waveform of the servo signal (ST119).

[0256] Next, the control unit converts the detection time difference between the detection time of the first point Po1 and the detection time of the second point Po2 into a distance (detection time difference × running speed of the magnetic tape 1) to calculate the width SPW of the servo pattern 7 (ST120).

[0257] Next, the control unit determines whether the measurement of the width SPW of the servo pattern 7 has been completed for all sampling positions (for example, 23 servo tracks 8 per one servo band s: 300 positions per one servo track 8: a total of 39000 positions for 5 servo bands s (5×26×300)).

[0258] If there are still sampling points remaining to measure the width SPW of the servo pattern 7 (NO in ST121), the control unit reads the waveform of the servo signal corresponding to the next sampling point from the storage unit (ST122) and returns to step 117.

[0259] On the other hand, once the measurement of the servo pattern width SPW has been completed for all sampling points (YES in ST121), the control unit calculates the average value of the servo pattern width SPW for each servo band s for each servo track 8 (ST123).

[0260] Next, the control unit further averages the average value of the servo pattern width SPW for each servo track 8 and calculates this value as the corresponding servo pattern width SPW in the magnetic tape 1 (ST124). Next, the control unit determines whether the servo pattern width SPW in the magnetic tape 1 is within the specified range (ST125).

[0261] The specified range for determining whether the width SPW of the servo pattern 7 is accurate may differ for each type of magnetic tape 1. As mentioned above in Figure 21, the width SPW of the servo pattern 7 may differ for each type of magnetic tape 1, and therefore, in such cases, the criteria for determining whether the width SPW of the servo pattern 7 is accurate must also differ.

[0262] In this case, for example, the width SPW of the servo pattern 7 is measured in advance by MFM for each type of magnetic tape, and the width SPW of the servo pattern 7 measured by MFM is used as a reference for the width SPW of the servo pattern 7 of the magnetic tape 1 for the corresponding type.

[0263] In this case, the relationship between the type of magnetic tape and the width SPW of the servo pattern 7 measured by MFM is compiled into a table and stored in the memory unit. The control unit then determines whether the width SPW of the servo pattern 7 measured by this embodiment meets the criteria (specified range) based on the width SPW of the servo pattern 7 measured by MFM. This criterion (specified range) must at least meet the conditions for the width SPW of the servo pattern 7 according to the LTO standard.

[0264] If the width SPW of the servo pattern 7 is within the specified range (YES in ST125), the control unit determines that the magnetic tape 1 is a good product (ST126) and proceeds to the next ST128.

[0265] On the other hand, if the width SPW of the servo pattern 7 is outside the specified range (YES in ST125), the control unit determines that the magnetic tape 1 is defective (ST126) and proceeds to the next ST128. In the case of a magnetic tape 1 determined to be defective, for example, the servo pattern 7 may be rewritten after demagnetization.

[0266] In ST128, the control unit displays the average value of the servo pattern width SPW for each servo track 8 in each servo band s (see Figures 17 and 20), the servo pattern width SPW on the magnetic tape 1, and the quality of the magnetic tape 1 (good, bad) on the display unit screen.

[0267] In this case, the main reason why the servo band s width falls outside the specified range is thought to be some kind of malfunction in the servo recording and playback device 101. Therefore, for example, if a situation arises where defective products occur frequently, the user should check the information displayed on the display unit in ST128 and perform maintenance on the servo recording and playback device 101.

[0268] The measurement of the servo pattern 7 width SPW may be performed for all magnetic tapes 1 (cartridges 10), or it may be performed for some samples of all magnetic tapes 1 (cartridges 10).

[0269] <Effect, etc.> As described above, in the servo measuring device 100 according to this embodiment, the width SPW of the servo pattern 7 is calculated based on a first point Po1 and a second point Po2, which are different from the positive peak point Pe1 and the negative peak point Pe2 in the waveform of the servo signal.

[0270] This allows the user to easily and accurately measure the width SPW of the servo pattern 7 using the servo measuring device 100. In particular, in this embodiment, when the user loads the cartridge 10 containing the magnetic tape 1 into the servo measuring device 100 and starts measuring the width SPW of the servo pattern 7, the servo measuring device 100 automatically measures the width SPW of the servo pattern 7.

[0271] In this embodiment, the first point Po1 is set to a point corresponding to one of the rising edges of the positive convex portion in the servo signal waveform. The second point Po2 is set to a point corresponding to one of the rising edges of the negative concave portion in the servo signal waveform.

[0272] This allows the first point Po1 and the second point Po2 to be set at appropriate positions in the servo signal waveform.

[0273] Furthermore, in this embodiment, when the output value of the positive peak point Pe1 in the servo signal waveform is set to 100%, a point corresponding to the output value that is a first percentage of the positive peak point Pe1 is set as the first point Po1. The first percentage is set to a value within the range of 25% or more and 75% or less.

[0274] This allows the first point Po1 to be set at an appropriate position according to the vertical orientation (vertical aspect ratio S1) of the magnetic layer 4.

[0275] Furthermore, in this embodiment, when the output value of the negative peak point Pe2 in the servo signal waveform is set to -100%, a point corresponding to the output value that is a second percentage of the negative peak point Pe2 is set as the second point Po2. The second percentage is set to a value within the range of -25% or more and -75% or less.

[0276] This allows a second point Po2 to be set at an appropriate position according to the vertical orientation (vertical aspect ratio S1) of the magnetic layer 4.

[0277] Furthermore, this technology is particularly effective when used to measure the width SPW of a servo pattern 7 recorded on a magnetic tape 1 containing a vertically oriented magnetic layer 4 (for example, with a vertical aspect ratio S1 of 60% or more). This is because, as the degree of vertical orientation increases, the inward shift of the positions of the positive peak point Pe1 and the negative peak point Pe2 increases, making it difficult to measure the width SPW of the servo pattern 7 using peak-to-peak measurement methods.

[0278] <Details of Magnetic Tape 1> Next, we will explain the details of magnetic tape 1.

[0279] The magnetic tape 1 is a long, tape-like material that runs longitudinally during the recording and playback of data and servo patterns 7. The surface of the magnetic layer 4 is the surface on which the servo read head 20 and servo write head 40 run. The magnetic tape 1 is preferably used in a recording and playback device equipped with a ring-type head as the recording head. The magnetic tape 1 is preferably used in a recording and playback device configured to record data with a data track width of 1200 nm or less or 1000 nm or less.

[0280] (Base material 2) As shown in Figure 2, the substrate 2 is a non-magnetic support that supports the underlayer 3 and the magnetic layer 4. The substrate 2 has a long film-like structure. The upper limit of the average thickness of the substrate 2 is preferably 4.4 μm or less, more preferably 4.2 μm or less, even more preferably 4.0 μm or less, and most preferably 3.6 μm or less. When the upper limit of the average thickness of the substrate 2 is 4.4 μm or less, the recording capacity that can be recorded in one data cartridge 10 can be increased compared to a typical magnetic tape 1. The lower limit of the average thickness of the substrate 2 is preferably 3 μm or more, more preferably 3.2 μm or more. When the lower limit of the average thickness of the substrate 2 is 3 μm or more, a decrease in the strength of the substrate 2 can be suppressed.

[0281] The average thickness of substrate 2 is determined as follows. First, a 1 / 2-inch wide magnetic tape 1 is prepared and cut to a length of 250 mm to create a sample. Next, layers other than substrate 2 of the sample (i.e., the underlayer 3, magnetic layer 4, and backing layer 5) are removed with a solvent such as MEK (methyl ethyl ketone) or dilute hydrochloric acid. Then, using a Mitutoyo laser hologage (LGH-110C) as the measuring device, the thickness of the sample (substrate 2) is measured at five or more locations, and these measurements are simply averaged (arithmetic mean) to calculate the average thickness of substrate 2. The measurement locations are to be randomly selected from the sample.

[0282] The base material 2 preferably contains polyester. The Young's modulus in the longitudinal direction of the base material 2 is, for example, 2.5 GPa or more and 14 GPa or less, preferably 2.5 GPa or more and 10 GPa or less, more preferably 2.5 GPa or more and 7.8 GPa or less, and even more preferably 3.0 GPa or more and 7.0 GPa or less.

[0283] Polyesters include, for example, at least one of polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polybutylene terephthalate (PBT), polybutylene naphthalate (PBN), polycyclohexylene dimethylene terephthalate (PCT), polyethylene-p-oxybenzoate (PEB), and polyethylene bisphenoxycarboxylate. If the base material 2 contains two or more polyesters, these two or more polyesters may be mixed, copolymerized, or laminated. At least one of the ends and side chains of the polyesters may be modified.

[0284] The presence of polyester in substrate 2 can be confirmed, for example, as follows: First, a magnetic tape 1 is prepared, similar to the method used to measure the average thickness of substrate 2. This tape is cut to a length of 250 mm to create a sample, and then layers other than substrate 2 are removed from the sample. Next, the IR spectrum of the sample (substrate 2) is obtained by infrared absorption spectroscopy (IR). Based on this IR spectrum, it can be confirmed that substrate 2 contains polyester.

[0285] The base material 2 may be, in addition to polyester, for example, polyamide, polyetheretherketone, polyimide and polyamideimide, polyetheretherketone (PEEK), polyolefins, cellulose derivatives, vinyl resins, and other polymer resins. The polyamide may be an aromatic polyamide (aramid). The polyimide may be an aromatic polyimide. The polyamideimide may be an aromatic polyamideimide.

[0286] The base material 2 may contain at least one of polyamide, polyetheretherketone, polyimide, and polyamideimide, or polyetheretherketone (PEEK), or it may mainly consist of resins such as polyamide, polyimide, polyamideimide, polyolefins, cellulose derivatives, and vinyl resins.

[0287] If base material 2 contains polymer resins other than polyester, it is preferable that base material 2 has polyester as its main component. Here, the main component refers to the component with the highest content (mass ratio) among the polymer resins contained in base material 2. If base material 2 contains polymer resins other than polyester, the polyester and the polymer resins other than polyester may be mixed or copolymerized.

[0288] The base material 2 may be biaxially stretched in the longitudinal and width directions. Preferably, the polymer resin contained in the base material 2 is oriented obliquely to the width direction of the base material 2.

[0289] (Magnetic layer 4) The magnetic layer 4 is a recording layer for recording signals by a magnetization pattern. The magnetic layer 4 may be a vertical recording type recording layer or a longitudinal recording type recording layer. The magnetic layer 4 may include, for example, magnetic powder, a binder, and a lubricant. The magnetic layer 4 may further include, if necessary, at least one additive from among antistatic agents, abrasives, hardeners, rust inhibitors, and non-magnetic reinforcing particles. The magnetic layer 4 is not limited to being a coated film of magnetic material, but may also be a sputtered film or a vapor-deposited film of magnetic material.

[0290] The arithmetic mean roughness Ra of the surface of the magnetic layer 4 is 2.0 nm or less, preferably 1.8 nm or less, and more preferably 1.6 nm or less. When the arithmetic mean roughness Ra is 2.0 nm or less, the decrease in output due to spacing loss can be suppressed, and thus excellent electromagnetic conversion characteristics can be obtained. The lower limit of the arithmetic mean roughness Ra of the surface of the magnetic layer 4 is preferably 1.0 nm or more, and more preferably 1.2 nm or more. When the lower limit of the arithmetic mean roughness Ra of the surface of the magnetic layer 4 is 1.0 nm or more, the decrease in running performance due to increased friction can be suppressed.

[0291] The arithmetic mean roughness Ra is determined as follows. First, the surface of the magnetic layer 4 is observed using an AFM (Atomic Force Microscope) to obtain a 40 μm × 40 μm AFM image. A BRUKER SPM Dimension Icon AFM is used, and a silicon single crystal cantilever is used (Note 1). The measurement is performed with a tapping frequency tuned to 200-400 Hz. Next, the AFM image is divided into 512 × 512 (= 262, 144) measurement points, and the height Z(i) (i: measurement point number, i = 1 to 262, 144) is measured at each measurement point. The heights Z(i) of each measured measurement point are simply averaged (arithmetic mean) to obtain the average height (average plane) Zave (= (Z(1) + Z(2) + ... + Z(262, 144)) / 262, 144). Next, the deviation Z"(i) (=Z(i)-Zave) from the average centerline at each measurement point is calculated, and the arithmetic mean roughness Ra[nm] (=(Z"(1)+Z"(2)+···+Z"(262,144)) / 262,144) is calculated. For this, the data used is filtered using Flattenorder2 and planefit order 3 XY as image processing. (Note 1) Nano World SPM probe NCH normal type PointProbe L (Cantilever length) = 125 μm

[0292] Average thickness t of magnetic layer 4 m The upper limit is 80 nm or less, preferably 70 nm or less, and more preferably 50 nm or less. Average thickness t of the magnetic layer 4 m If the upper limit is 80 nm or less, the effect of the demagnetizing field can be reduced when a ring-type head is used as the recording head, thereby achieving even better electromagnetic conversion characteristics.

[0293] Average thickness t of magnetic layer 4 m The lower limit is preferably 35 nm or more. Average thickness t of the magnetic layer 4 m If the lower limit is 35nm or higher, output can be secured when using an MR-type head as the playback head, thus achieving even better electromagnetic conversion characteristics.

[0294] Average thickness t of magnetic layer 4 m The following procedure is used to obtain the desired result. First, the magnetic tape 1 housed in the cartridge 10 is unwound, and three samples are prepared by cutting the magnetic tape 1 at three locations: 10m, 30m, and 50m from one end of the outermost edge. Next, each sample (the magnetic tape 1 to be measured) is processed and thinned using the FIB method or the like. When using the FIB method, a carbon layer and a tungsten layer are formed as protective films as a pretreatment before observing the TEM image of the cross-section described later. The carbon layer is formed on the surface of the magnetic layer 4 and the back layer 5 of the magnetic tape 1 by vapor deposition, and the tungsten layer is further formed on the surface of the magnetic layer 4 by vapor deposition or sputtering. This thinning is performed along the longitudinal direction (longitudinal direction) of the magnetic tape 1. That is, this thinning creates a cross-section parallel to both the longitudinal and thickness directions of the magnetic tape 1.

[0295] The cross-sections of the obtained thinned samples are observed using a transmission electron microscope (TEM) under the following conditions to obtain TEM images of each thinned sample. The magnification and acceleration voltage may be adjusted as appropriate depending on the type of instrument. Equipment: TEM (Hitachi H9000NAR) Acceleration voltage: 300kV Magnification: 100, 000x

[0296] Next, the thickness of the magnetic layer 4 is measured at 10 or more locations on each thinned sample using TEM images of each thinned sample. Since thinning is performed along the longitudinal direction of the magnetic tape 1 as described above, the 10 measurement locations on each thinned sample are randomly selected from the test piece so that they are all different locations along the longitudinal direction of the magnetic tape 1. The average value obtained by simply averaging (arithmetic mean) the measured values ​​of each thinned sample (a total of 30 points of magnetic layer 4 thickness) is used to determine the average thickness t of the magnetic layer 4. m Let it be [nm].

[0297] (Magnetic powder) The magnetic powder includes a plurality of magnetic particles. The magnetic particles are, for example, particles containing hexagonal ferrite (hereinafter referred to as "hexagonal ferrite particles"), particles containing epsilon-type iron oxide (ε-iron oxide) (hereinafter referred to as "ε-iron oxide particles"), or particles containing Co-containing spinel ferrite (hereinafter referred to as "cobalt ferrite particles"). The magnetic powder preferably has uniaxial anisotropy as magnetocrystalline anisotropy.

[0298] (Hexagonal ferrite particles) The hexagonal ferrite particles have, for example, a plate shape such as a hexagonal plate shape, or a columnar shape such as a hexagonal columnar shape (provided that the thickness or height is smaller than the major axis of the plate surface or bottom surface). In the present specification, the hexagonal plate shape includes a substantially hexagonal plate shape. The hexagonal ferrite preferably contains at least one of Ba, Sr, Pb and Ca, and more preferably contains at least one of Ba and Sr. Specifically, the hexagonal ferrite may be, for example, barium ferrite or strontium ferrite. The barium ferrite may further contain at least one of Sr, Pb and Ca in addition to Ba. The strontium ferrite may further contain at least one of Ba, Pb and Ca in addition to Sr.

[0299] More specifically, the hexagonal ferrite has an average composition represented by the general formula MFe 12 O 19 . Here, M is, for example, at least one metal selected from Ba, Sr, Pb and Ca, preferably at least one metal selected from Ba and Sr. M may be a combination of Ba and one or more metals selected from the group consisting of Sr, Pb and Ca. Further, M may be a combination of Sr and one or more metals selected from the group consisting of Ba, Pb and Ca. In the above general formula, part of Fe may be substituted with a metal element other than Fe.

[0300] When the magnetic powder contains hexagonal ferrite particle powder, the average particle size of the magnetic powder is preferably 13 nm to 22 nm, more preferably 13 nm to 19 nm, even more preferably 13 nm to 18 nm, particularly preferably 14 nm to 17 nm, and most preferably 14 nm to 16 nm. If the average particle size of the magnetic powder is 22 nm or less, even better electromagnetic conversion characteristics (e.g., SNR) can be obtained in a magnetic tape 1 with high recording density. On the other hand, if the average particle size of the magnetic powder is 13 nm or more, the dispersibility of the magnetic powder is further improved, and even better electromagnetic conversion characteristics (e.g., SNR) can be obtained.

[0301] When the magnetic powder contains hexagonal ferrite particle powder, the average aspect ratio of the magnetic powder is preferably 1.0 to 3.0, more preferably 1.5 to 2.8, and even more preferably 1.8 to 2.7. When the average aspect ratio of the magnetic powder is within the range of 1.0 to 3.0, aggregation of the magnetic powder can be suppressed. Furthermore, resistance applied to the magnetic powder when vertically oriented during the formation process of the magnetic layer 4 can be suppressed. Therefore, the vertical orientation of the magnetic powder can be improved.

[0302] When the magnetic powder contains hexagonal ferrite particle powder, the average particle size and average aspect ratio of the magnetic powder are determined as follows. First, the magnetic tape 1 to be measured is processed and thinned using the FIB method or the like. When using the FIB method, a carbon layer and a tungsten layer are formed as protective films as a pretreatment before observing the TEM image of the cross section described later. The carbon layer is formed on the surface of the magnetic layer 4 side and the surface of the back layer 5 side of the magnetic tape 1 by vapor deposition, and the tungsten layer is further formed on the surface of the magnetic layer 4 side by vapor deposition or sputtering. This thinning is performed along the longitudinal direction (longitudinal direction) of the magnetic tape 1. That is, this thinning creates a cross section parallel to both the longitudinal direction and the thickness direction of the magnetic tape 1.

[0303] The cross-section of the obtained thin section sample is observed using a transmission electron microscope (Hitachi High-Technologies Corporation H-9500) with an acceleration voltage of 200kV and a total magnification of 500,000x, ensuring that the entire magnetic layer 4 is included in the thickness direction of the magnetic layer 4, and a TEM image is taken. The TEM images are prepared in a number that allows for the extraction of 50 particles capable of measuring the plate diameter DB and plate thickness DA (see Figure 34) shown below.

[0304] In this specification, the particle size of hexagonal ferrite (hereinafter referred to as "particle size") is determined as follows: If the shape of the particle observed in the above TEM image is plate-like or columnar (provided that the thickness or height is smaller than the major axis of the plate surface or base), the major axis of the plate surface or base is used as the plate diameter DB. The thickness or height of the particle observed in the above TEM image is used as the plate thickness DA. If the thickness or height of a particle is not constant within a single particle, the thickness or height of the largest particle is used as the plate thickness DA.

[0305] Next, 50 particles are selected from the captured TEM images based on the following criteria: Particles whose portion extends outside the field of view of the TEM image are not measured; only particles with clear outlines and existing in isolation are measured. If there is overlap between particles, those with clear boundaries and whose overall shape can be determined are measured as individual particles; however, particles with unclear boundaries and whose overall shape cannot be determined are not measured as their shape cannot be determined.

[0306] The thickness DA of each of the 50 selected particles is measured. The thickness DA obtained in this way is simply averaged (arithmetic mean) to obtain the average thickness DA. ave We will find the average plate thickness DA. ave This is the average particle thickness. Next, the diameter DB of each magnetic powder is measured. To measure the particle diameter DB, 50 particles whose particle diameter DB can be clearly identified are selected from the TEM images taken. The particle diameter DB of each of the 50 selected particles is measured. The average particle diameter DB obtained in this way is calculated by taking a simple average (arithmetic mean) of the particle diameter DBs. ave We will find the average plate diameter DB. aveHowever, this is the average particle size. And the average plate thickness DA ave and average plate diameter DB ave From the average aspect ratio of the particles (DB) ave / DA ave )

[0307] When the magnetic powder contains hexagonal ferrite particle powder, the average particle volume of the magnetic powder is preferably 500 nm. 3 More than 2500nm 3 More preferably 500nm 3 More than 1600nm 3 More preferably 500 nm 3 More than 1500nm 3 The following is particularly preferred: 600 nm 3 More than 1200nm 3 Below, most preferably 600nm 3 More than 1000nm 3 The following applies: The average particle volume of the magnetic powder is 2500 nm. 3 If the average particle size of the magnetic powder is less than 22 nm, the same effect can be obtained. On the other hand, if the average particle volume of the magnetic powder is 500 nm 3 With these settings, the same effect as when the average particle size of the magnetic powder is 13 nm or larger can be obtained.

[0308] The average particle volume of magnetic powder can be determined as follows. First, as described above regarding the method for calculating the average particle size of magnetic powder, the average major axis length DA ave and average plate diameter DB ave Next, we calculate the average volume V of the magnetic powder using the following formula.

number

[0309] (ε-iron oxide particles) ε-iron oxide particles are hard magnetic particles that can obtain high coercivity even in fine particles. ε-iron oxide particles are either spherical or cubic in shape. In this specification, "spherical" includes substantially spherical particles, and "cubic" includes substantially cubic particles. Because ε-iron oxide particles have the shapes described above, when ε-iron oxide particles are used as magnetic particles, the contact area between particles in the thickness direction of the magnetic tape 1 can be reduced and particle aggregation can be suppressed compared to when hexagonal plate-shaped barium ferrite particles are used as magnetic particles. Therefore, the dispersibility of the magnetic powder can be improved, and even better electromagnetic conversion characteristics (e.g., SNR) can be obtained.

[0310] ε-iron oxide particles have composite particle structures such as a core-shell structure, a Janus structure, or a structure where particles are joined at a surface.

[0311] The composite structure includes ε-iron oxide as part of the structure. The ε-iron oxide is preferably composed mainly of ε-Fe2O3 crystals, and more preferably of a single phase of ε-Fe2O3.

[0312] In the other parts of the composite structure, the ε-iron oxide portion and the other parts are exchanged-coupled, resulting in magnetic properties. It is preferable for it to behave like a single particle.

[0313] The other portion is preferably a soft magnetic layer 4, which includes, for example, a soft magnetic material such as α-Fe, a Ni-Fe alloy, or a Fe-Si-Al alloy. α-Fe may be obtained by reducing ε-iron oxide contained in the core. Alternatively, it may be a material that is not soft magnetic but has a higher σs and lower Hc than ε-iron oxide.

[0314] The ε-iron oxide particles may contain an additive in place of the above structure, or they may have the above structure and also contain an additive. In this case, a portion of the Fe in the ε-iron oxide particles is replaced by the additive. By including an additive in the ε-iron oxide particles, the coercivity Hc of the ε-iron oxide particles as a whole can be adjusted to a coercivity Hc suitable for recording, thereby improving ease of recording. The additive is a metal element other than iron, preferably a trivalent metal element, more preferably at least one of Al, Ga, and In, and even more preferably at least one of Al and Ga.

[0315] Specifically, ε-iron oxide containing additives is ε-Fe 2-x M x It is an O3 crystal. The additive contains a metal element other than iron, more preferably Al (aluminum), Ga (gallium), In (indium), Co (cobalt), Mn (manganese), Zr (zirconium), Hf (hafnium), Cs (cesium), and at least one of Ti (titanium), Sm (samarium), Nd (neodymium), Pr (praseodymium), and Tb (terbium).

[0316] When the magnetic powder contains ε-iron oxide particles, the average particle size of the magnetic powder is preferably 10 nm to 20 nm, more preferably 10 nm to 18 nm, even more preferably 10 nm to 16 nm, particularly preferably 10 nm to 15 nm, and most preferably 10 nm to 14 nm. In magnetic tape 1, the actual magnetization region is a region with a size of half the recording wavelength. Therefore, by setting the average particle size of the magnetic powder to half or less of the shortest recording wavelength, even better electromagnetic conversion characteristics (e.g., SNR) can be obtained. Accordingly, if the average particle size of the magnetic powder is 20 nm or less, even better electromagnetic conversion characteristics (e.g., SNR) can be obtained in magnetic tape 1 with high recording density (e.g., magnetic tape 1 configured to record signals at the shortest recording wavelength of 40 nm or less). On the other hand, if the average particle size of the magnetic powder is 10 nm or more, the dispersibility of the magnetic powder is further improved, and even better electromagnetic conversion characteristics (e.g., SNR) can be obtained.

[0317] When the magnetic powder contains ε-iron oxide particles, the average aspect ratio of the magnetic powder is preferably 1.0 to 3.0, more preferably 1.0 to 2.5, even more preferably 1.0 to 2.1, and particularly preferably 1.0 to 1.8. When the average aspect ratio of the magnetic powder is within the range of 1.0 to 3.0, aggregation of the magnetic powder can be suppressed. Furthermore, resistance applied to the magnetic powder when vertically oriented during the formation process of the magnetic layer 4 can be suppressed. Therefore, the vertical orientation of the magnetic powder can be improved.

[0318] When the magnetic powder contains ε-iron oxide particles, the average particle size and average aspect ratio of the magnetic powder are determined as follows. First, the magnetic tape 1 to be measured is processed and thinned using the FIB (Focused Ion Beam) method or the like. When using the FIB method, a carbon layer and a tungsten layer are formed as protective layers as a pretreatment before observing the TEM image of the cross-section described later. The carbon layer is formed on the surface of the magnetic layer 4 and the back layer 5 of the magnetic tape 1 by vapor deposition, and the tungsten layer is further formed on the surface of the magnetic layer 4 by vapor deposition or sputtering. Thinning is performed along the longitudinal direction (longitudinal direction) of the magnetic tape 1. That is, this thinning creates a cross-section parallel to both the longitudinal and thickness directions of the magnetic tape 1.

[0319] The cross-section of the obtained thin section sample is observed using a transmission electron microscope (Hitachi High-Technologies Corporation H-9500) with an acceleration voltage of 200kV and a total magnification of 500,000x, ensuring that the entire magnetic layer 4 is included in the thickness direction of the magnetic layer 4, and a TEM image is taken. Next, 50 particles whose particle shape can be clearly confirmed are selected from the taken TEM image, and the major axis length DL and minor axis length DS of each particle are measured. Here, the major axis length DL refers to the maximum distance between two parallel lines drawn from any angle tangent to the contour of each particle (the so-called maximum Ferret diameter). On the other hand, the minor axis length DS refers to the maximum length of the particle in the direction perpendicular to the major axis (DL) of the particle. Subsequently, the average major axis length DL is calculated by simply averaging (arithmetic mean) the major axis lengths DL of the 50 measured particles. ave We calculate the average major axis length DL obtained in this way. ave This is defined as the average particle size of the magnetic powder. Additionally, the short-axis length DS of the 50 measured particles is simply averaged (arithmetic mean) to obtain the average short-axis length DS. ave We calculate the average major axis length DL. ave and average short axis length DS ave From the average aspect ratio of the particles (DL ave / DS ave )

[0320] When the magnetic powder contains ε-iron oxide particles, the average particle volume of the magnetic powder is preferably 500 nm. 3 More than 4000nm 3 More preferably 500nm 3 More than 3000nm 3 More preferably, 500nm 3 More than 2000nm 3 The following is particularly preferred: 600 nm 3 More than 1600nm 3 Below, most preferably 600nm 3 More than 1300nm 3The following applies: Generally, the noise of magnetic tape 1 is inversely proportional to the square root of the number of particles (i.e., proportional to the square root of the particle volume). Therefore, by reducing the particle volume, even better electromagnetic conversion characteristics (e.g., SNR) can be obtained. Thus, the average particle volume of the magnetic powder is 4000 nm. 3 If the average particle size of the magnetic powder is less than 20 nm, even better electromagnetic conversion characteristics (e.g., SNR) can be obtained. On the other hand, if the average particle volume of the magnetic powder is 500 nm 3 With these settings, the same effect as when the average particle size of the magnetic powder is 10 nm or larger can be obtained.

[0321] If the ε-iron oxide particles are spherical, the average particle volume of the magnetic powder can be determined as follows: First, the average major axis length DL is calculated using the same method as for calculating the average particle size of the magnetic powder described above. ave Next, we calculate the average volume V of the magnetic powder using the following formula. V = (π / 6) × DL ave 3

[0322] When the ε-iron oxide particles are cubic in shape, the average volume of the magnetic powder is determined as follows. The magnetic tape 1 is processed and thinned using the FIB (Focused Ion Beam) method or the like. When using the FIB method, a carbon film and a tungsten film are formed as protective films as a pretreatment before observing the TEM image of the cross-section described later. The carbon film is formed on the surface of the magnetic layer 4 and the back layer 5 of the magnetic tape 1 by vapor deposition, and the tungsten film is further formed on the surface of the magnetic layer 4 by vapor deposition or sputtering. This thinning is performed along the longitudinal direction (longitudinal direction) of the magnetic tape 1. That is, this thinning creates a cross-section parallel to both the longitudinal and thickness directions of the magnetic tape 1.

[0323] The obtained thin section sample is subjected to cross-sectional observation using a transmission electron microscope (Hitachi High-Technologies Corporation H-9500) with an acceleration voltage of 200kV and a total magnification of 500,000x, ensuring that the entire magnetic layer 4 is included in the thickness direction of the magnetic layer 4, and a TEM image is obtained. Note that the magnification and acceleration voltage may be adjusted as appropriate depending on the type of instrument. Next, 50 particles whose particle shape is clear are selected from the captured TEM image, and the side length DC of each particle is measured. Subsequently, the average side length DC of the 50 measured particles is simply averaged (arithmetic mean) to obtain the average side length DC. ave Next, we calculate the average side length DC. ave Using the following formula, the average volume V of the magnetic powder can be calculated from the following equation. ave Calculate the particle volume. V ave =DC ave 3

[0324] (Cobalt ferrite particles) The cobalt ferrite particles preferably have uniaxial crystal anisotropy. Uniaxial crystal anisotropy of the cobalt ferrite particles allows the magnetic powder to be preferentially crystallized in the thickness direction (perpendicular direction) of the magnetic tape 1. The cobalt ferrite particles, for example, have a cubic shape. In this specification, cubic shape includes substantially cubic shapes. The Co-containing spinel ferrite may further contain at least one of Ni, Mn, Al, Cu, and Zn in addition to Co.

[0325] Co-containing spinel ferrite has an average composition represented, for example, by the following formula. Co x M y Fe2O Z (However, in the formula, M is at least one metal from, for example, Ni, Mn, Al, Cu, and Zn. x is a value in the range 0.4 ≤ x ≤ 1.0. y is a value in the range 0 ≤ y ≤ 0.3, where x and y satisfy the relationship (x + y) ≤ 1.0. z is a value in the range 3 ≤ z ≤ 4. Part of Fe may be substituted with other metallic elements.)

[0326] When the magnetic powder contains cobalt ferrite particle powder, the average particle size of the magnetic powder is preferably 8 nm to 16 nm, more preferably 8 nm to 13 nm, and even more preferably 8 nm to 10 nm. If the average particle size of the magnetic powder is 16 nm or less, even better electromagnetic conversion characteristics (e.g., SNR) can be obtained in a magnetic tape 1 with high recording density. On the other hand, if the average particle size of the magnetic powder is 8 nm or more, the dispersibility of the magnetic powder is further improved, and even better electromagnetic conversion characteristics (e.g., SNR) can be obtained. The method for calculating the average particle size of the magnetic powder is the same as the method for calculating the average particle size of the magnetic powder when the magnetic powder contains ε iron oxide particle powder.

[0327] When the magnetic powder contains cobalt ferrite particle powder, the average aspect ratio of the magnetic powder is preferably 1.0 to 3.0, more preferably 1.0 to 2.5, even more preferably 1.0 to 2.1, and particularly preferably 1.0 to 1.8. When the average aspect ratio of the magnetic powder is within the range of 1.0 to 3.0, aggregation of the magnetic powder can be suppressed. Furthermore, when the magnetic powder is vertically oriented in the process of forming the magnetic layer 4, the resistance applied to the magnetic powder can be suppressed. Therefore, the vertical orientation of the magnetic powder can be improved. The method for calculating the average aspect ratio of the magnetic powder is the same as the method for calculating the average aspect ratio of the magnetic powder when the magnetic powder contains ε iron oxide particle powder.

[0328] When the magnetic powder contains cobalt ferrite particle powder, the average particle volume of the magnetic powder is preferably 500 nm. 3 More than 4000nm 3 More preferably 600nm 3 More than 2000nm 3 More preferably, 600nm 3 More than 1000nm 3 The following applies: The average particle volume of the magnetic powder is 4000 nm. 3 If the average particle size of the magnetic powder is less than 16 nm, the same effect can be obtained. On the other hand, if the average particle volume of the magnetic powder is 500 nm 3With the above conditions, the same effect as when the average particle size of the magnetic powder is 8 nm or larger can be obtained. The method for calculating the average particle volume of the magnetic component is the same as the method for calculating the average particle volume when the ε iron oxide particles are cubic in shape.

[0329] (Binding agent) Examples of binders include thermoplastic resins, thermosetting resins, and reactive resins. Examples of thermoplastic resins include vinyl chloride, vinyl acetate, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, acrylic acid ester-acrylonitrile copolymer, acrylic acid ester-vinyl chloride-vinylidene chloride copolymer, acrylic acid ester-acrylonitrile copolymer, acrylic acid ester-vinylidene chloride copolymer, methacrylic acid ester-vinylidene chloride copolymer, methacrylic acid ester-vinyl chloride copolymer, methacrylic acid ester-ethylene copolymer, polyvinyl fluoride, vinylidene chloride-acrylonitrile copolymer, acrylonitrile-butadiene copolymer, polyamide resin, polyvinyl butyral, cellulose derivatives (cellulose acetate butyrate, cellulose diacetate, cellulose triacetate, cellulose propionate, nitrocellulose), styrene butadiene copolymer, polyurethane resin, polyester resin, amino resin, and synthetic rubber.

[0330] Examples of thermosetting resins include phenolic resins, epoxy resins, polyurethane curing resins, urea resins, melamine resins, alkyd resins, silicone resins, polyamine resins, and urea-formaldehyde resins.

[0331] All of the above binders include -SO3M, -OSO3M, -COOM, P=O(OM)2 (where M represents a hydrogen atom or an alkali metal such as lithium, potassium, or sodium), and -NR1R2, -NR1R2R3, in order to improve the dispersibility of magnetic powders. + X - Side-chain amines having terminal groups represented by >NR1R2 + X -Main-chain amines represented by (wherein R1, R2, and R3 represent hydrogen atoms or hydrocarbon groups, X - ) represents halogen element ions such as fluorine, chlorine, bromine, and iodine, as well as inorganic or organic ions. Furthermore, polar functional groups such as -OH, -SH, -CN, and epoxy groups may be introduced. The amount of these polar functional groups introduced into the binder is 10 -1 ~10 -8 It is preferable that it be in moles / g, 10 -2 ~10 -6 It is more preferable to use moles / g.

[0332] (Lubricant) The lubricant comprises at least one selected from, for example, fatty acids and fatty acid esters, preferably both fatty acids and fatty acid esters. The inclusion of a lubricant in the magnetic layer 4, and in particular the inclusion of both fatty acids and fatty acid esters in the magnetic layer 4, contributes to improving the running stability of the magnetic tape 1. In particular, good running stability is achieved by the magnetic layer 4 containing a lubricant and having pores. This improvement in running stability is thought to be because the coefficient of dynamic friction on the magnetic layer 4 side surface of the magnetic tape 1 is adjusted by the lubricant to a value suitable for the running of the magnetic tape 1.

[0333] The fatty acid may preferably be a compound represented by the following general formula (1) or (2). For example, the fatty acid may include one of the compounds represented by the following general formula (1) and the compound represented by the following general formula (2), or both.

[0334] Furthermore, the fatty acid ester may preferably be a compound represented by the following general formula (3) or (4). For example, the fatty acid ester may include either a compound represented by the following general formula (3) or a compound represented by the following general formula (4), or both.

[0335] The lubricant contains one or both of the compound represented by general formula (1) and the compound represented by general formula (2), and one or both of the compound represented by general formula (3) and the compound represented by general formula (4), whereby an increase in the dynamic friction coefficient of the magnetic tape 1 due to repeated recording or reproduction can be suppressed.

[0336] CH3(CH2) k COOH ···(1) (Provided that in general formula (1), k is an integer selected from the range of 14 to 22, more preferably from the range of 14 to 18.)

[0337] CH3(CH2) n CH=CH(CH2) m COOH ···(2) (Provided that in general formula (2), the sum of n and m is an integer selected from the range of 12 to 20, more preferably from the range of 14 to 18.)

[0338] CH3(CH2) p COO(CH2) q CH3···(3) (Provided that in general formula (3), p is an integer selected from the range of 14 to 22, more preferably from the range of 14 to 18, and q is an integer selected from the range of 2 to 5, more preferably from the range of 2 to 4.)

[0339] CH3(CH2) r COO-(CH2) s CH(CH3)2···(4) (Provided that in general formula (4), r is an integer selected from the range of 14 to 22, and s is an integer selected from the range of 1 to 3.)

[0340] CH3(CH2) r COO-CH(CH3)(CH2) s CH(CH3) ···(5) (However, in general formula (5), r is an integer selected from the range of 14 to 22, and s is an integer selected from the range of 1 to 3.)

[0341] (Antistatic agent) Examples of antistatic agents include carbon black, natural surfactants, nonionic surfactants, and cationic surfactants.

[0342] (Abrasive) Examples of abrasives include α-alumina, β-alumina, γ-alumina, silicon carbide, chromium oxide, cerium oxide, α-iron oxide, corundum, silicon nitride, titanium carbide, titanium oxide, silicon dioxide, tin oxide, magnesium oxide, tungsten oxide, zirconium oxide, boron nitride, zinc oxide, calcium carbonate, calcium sulfate, barium sulfate, molybdenum disulfide, and needle-shaped α-iron oxide obtained by dehydrating and annealing the raw materials of magnetic iron oxide, and, if necessary, surface-treated with aluminum and / or silica.

[0343] (Hardening agent) Examples of curing agents include polyisocyanates. Examples of polyisocyanates include aromatic polyisocyanates such as adducts of tolylene diisocyanate (TDI) and active hydrogen compounds, and aliphatic polyisocyanates such as adducts of hexamethylene diisocyanate (HMDI) and active hydrogen compounds. The weight-average molecular weight of these polyisocyanates is preferably in the range of 100 to 3000.

[0344] (Rust inhibitor) Examples of rust inhibitors include phenols, naphthols, quinones, heterocyclic compounds containing nitrogen atoms, heterocyclic compounds containing oxygen atoms, and heterocyclic compounds containing sulfur atoms.

[0345] (Non-magnetic reinforcing particles) Examples of non-magnetic reinforcing particles include aluminum oxide (α, β, or γ alumina), chromium oxide, silicon oxide, diamond, garnet, emery, boron nitride, titanium carbide, silicon carbide, titanium carbide, and titanium oxide (rutile or anatase type titanium oxide).

[0346] (base layer 3) The base layer 3 is for mitigating surface irregularities on the substrate 2 and adjusting surface irregularities on the magnetic layer 4. The base layer 3 is a non-magnetic layer 4 containing non-magnetic powder, a binder, and a lubricant. The base layer 3 supplies lubricant to the surface of the magnetic layer 4. The base layer 3 may further contain at least one additive, such as an antistatic agent, a hardening agent, and a rust inhibitor, as needed.

[0347] The average thickness t2 of the base layer 3 is preferably 0.3 μm or more and 1.2 μm or less, more preferably 0.3 μm or more and 0.9 μm or less, or 0.3 μm or more and 0.6 μm or less. The average thickness t2 of the base layer 3 is determined in the same manner as the average thickness t1 of the magnetic layer 4. However, the magnification of the TEM image is adjusted appropriately according to the thickness of the base layer 3. If the average thickness t2 of the base layer 3 is 1.2 μm or less, the elasticity of the magnetic tape 1 due to external force is further increased, making it easier to adjust the width of the magnetic tape 1 by tension adjustment.

[0348] (Non-magnetic powder) The non-magnetic powder includes, for example, at least one of inorganic particulate powder or organic particulate powder. The non-magnetic powder may also include carbon powder such as carbon black. One type of non-magnetic powder may be used alone, or two or more types of non-magnetic powder may be used in combination. Inorganic particles include, for example, metals, metal oxides, metal carbonates, metal sulfates, metal nitrides, metal carbides, or metal sulfides. The shape of the non-magnetic powder can be, for example, needle-shaped, spherical, cubic, or plate-shaped, but is not limited to these shapes.

[0349] (Binding agent, lubricant) The binder and lubricant are the same as those used in the magnetic layer 4 described above.

[0350] (Additives) The antistatic agent, hardening agent, and rust inhibitor are the same as those described above for the magnetic layer 4.

[0351] (Back layer 5) The back layer 5 contains a binder and non-magnetic powder. The back layer 5 may further contain at least one additive, if necessary, from among lubricants, hardeners, and antistatic agents. The binder and non-magnetic powder are the same as those described above for the underlayer 3.

[0352] The average particle size of the non-magnetic powder is preferably 10 nm to 150 nm, more preferably 15 nm to 110 nm. The average particle size of the non-magnetic powder is determined in the same manner as the average particle size of the magnetic powder described above. The non-magnetic powder may contain non-magnetic powder having a particle size distribution of 2 or more.

[0353] The upper limit of the average thickness of the backing layer 5 is preferably 0.6 μm or less. When the upper limit of the average thickness of the backing layer 5 is 0.6 μm or less, the thickness of the underlayment layer 3 and the base material 2 can be kept thick even when the average thickness of the magnetic tape 1 is 5.6 μm or less, so that the running stability of the magnetic tape 1 in the recording and playback device can be maintained. The lower limit of the average thickness of the backing layer 5 is not particularly limited, but for example, it is 0.2 μm or more.

[0354] Average thickness t of back layer 5 b The following can be calculated: First, the average thickness t of the magnetic tape 1. T Measure the average thickness t. T The measurement method is as described in "Average Thickness of Magnetic Tape 1" below. Next, the back layer 5 of the sample is removed with a solvent such as MEK (methyl ethyl ketone) or dilute hydrochloric acid. Then, the thickness of the sample is measured at five or more locations using a Mitutoyo laser hologage (LGH-110C), and these measurements are simply averaged (arithmetic mean) to obtain the average value t B [μm] is calculated. Then, the average thickness t of the back layer 5 is calculated using the following formula. b[μm] is determined. The measurement positions are randomly selected from the sample. t b [μm]=t T [μm]-t B [μm]

[0355] The back layer 5 has a surface provided with a large number of protrusions. The large number of protrusions are for forming a large number of pores on the surface of the magnetic layer 4 when the magnetic tape 1 is wound into a roll. The large number of pores are composed of, for example, a large number of non-magnetic particles protruding from the surface of the back layer 5.

[0356] (Average thickness of magnetic tape 1) The upper limit of the average thickness (average total thickness) t of the magnetic tape 1 T is 5.4 μm or less, preferably 5.2 μm or less, more preferably 4.9 μm or less, and even more preferably 4.6 μm or less. When the average thickness t of the magnetic tape 1 T is 5.4 μm or less, the recording capacity that can be recorded in one data cartridge 10 can be made higher than that of a general magnetic tape 1. The average thickness t of the magnetic tape 1 T is not particularly limited, but is, for example, 3.5 μm or more.

[0357] The average thickness t of the magnetic tape 1 T is determined as follows. First, a magnetic tape 1 with a 1 / 2 inch width is prepared and cut to a length of 250 mm to produce a sample. Next, using a laser holo gauge (LGH-110C) manufactured by Mitutoyo Corporation as a measuring device, the thickness of the sample is measured at 5 or more positions, and the measured values are simply averaged (arithmetic mean) to obtain the average value t T [μm] is calculated. The measurement positions are randomly selected from the sample.

[0358] (Coercivity Hc) The upper limit of the coercivity Hc2 of the magnetic layer 4 in the longitudinal direction of the magnetic tape 1 is preferably 2400 Oe or less, more preferably 2200 Oe or less, more preferably 2000 Oe or less, more preferably 1800 Oe or less, and even more preferably 1600 Oe or less. When the coercivity Hc2 of the magnetic layer 4 in the longitudinal direction is 2200 Oe or less, sufficient electromagnetic conversion characteristics can be obtained even at high recording densities.

[0359] The lower limit of the coercivity Hc2 of the magnetic layer 4 measured in the longitudinal direction of the magnetic tape 1 is preferably 1000 Oe or more. When the coercivity Hc2 of the magnetic layer 4 measured in the longitudinal direction is 1000 Oe or more, demagnetization due to leakage magnetic flux from the recording head can be suppressed.

[0360] The above coercivity Hc2 is determined as follows. First, the magnetic tape 1 housed in the cartridge 10 is unwound, and a section of the magnetic tape 1 is cut 30 m from one end on the outermost side. Three pieces of the magnetic tape 1 are stacked together with double-sided tape so that their longitudinal orientations are the same, and then punched out with a φ6.39 mm punch to create a measurement sample. At this time, the magnetic tape 1 is marked with an arbitrary non-magnetic ink so that its longitudinal direction (direction of travel) can be recognized. Then, the MH loop of the measurement sample (the entire magnetic tape 1) corresponding to the longitudinal direction (direction of travel) of the magnetic tape 1 is measured using a vibrating sample magnetometer (VSM). Next, the coating film (underlayer 3, magnetic layer 4, and backing layer 5, etc.) of the magnetic tape 1 cut out above is wiped off using acetone or ethanol, leaving only the substrate 2. Then, the obtained substrate 2 is stacked three times using double-sided tape, and punched out with a φ6.39 mm punch to create a sample for background correction (hereinafter simply referred to as the "correction sample"). Subsequently, the MH loop of the correction sample (substrate 2) corresponding to the vertical direction of substrate 2 (the vertical direction of magnetic tape 1) is measured using a VSM.

[0361] For measuring the MH loop of the measurement sample (the entire magnetic tape 1) and the MH loop of the correction sample (substrate 2), a high-sensitivity vibrating sample type magnetometer "VSM-P7-15" manufactured by Toei Kogyo Co., Ltd. is used. The measurement conditions are as follows: measurement mode: full loop, maximum magnetic field: 15 kOe, magnetic field step: 40 bits, time constant of locking amp: 0.3 sec, waiting time: 1 sec, MH average number: 20.

[0362] After obtaining the MH loop of the measurement sample (the entire magnetic tape 1) and the MH loop of the correction sample (substrate 2), background correction is performed by subtracting the MH loop of the correction sample (substrate 2) from the MH loop of the measurement sample (the entire magnetic tape 1), and the background-corrected MH loop is obtained. The measurement and analysis program included with the "VSM-P7-15" is used to calculate this background correction. The coercivity Hc2 is determined from the obtained background-corrected MH loop. The measurement and analysis program included with the "VSM-P7-15" is used for this calculation as well. All of the above MH loop measurements are performed at 25℃±2℃ and 50%RH±5%RH. Furthermore, "demagnetization correction" is not performed when measuring the MH loop in the longitudinal direction of the magnetic tape 1.

[0363] (Gangular ratio) The angularity ratio S1 of the magnetic layer 4 in the vertical direction (thickness direction) of the magnetic tape 1 is preferably 60% or more, more preferably 65% ​​or more, even more preferably 70% or more, particularly preferably 75% or more, and most preferably 80% or more. When the angularity ratio S1 is 60% or more, the vertical orientation of the magnetic powder becomes sufficiently high, so even better electromagnetic conversion characteristics (e.g., SNR) can be obtained.

[0364] The aspect ratio S1 in the vertical direction is determined as follows. First, the magnetic tape 1 housed in the cartridge 10 is unwound, and a section of the magnetic tape 1 is cut 30 m from one end on the outermost side. Three pieces of the magnetic tape 1 are stacked together with double-sided tape so that their longitudinal orientations are the same, and then punched out with a φ6.39 mm punch to create a measurement sample. At this time, the magnetic tape 1 is marked with an arbitrary non-magnetic ink so that its longitudinal direction (direction of travel) can be recognized. Then, the MH loop of the measurement sample (the entire magnetic tape 1) corresponding to the longitudinal direction (direction of travel) of the magnetic tape 1 is measured using a vibrating sample magnetometer (VSM). Next, the coating film (underlayer 3, magnetic layer 4, and backing layer 5, etc.) of the magnetic tape 1 cut out above is wiped off using acetone or ethanol, leaving only the substrate 2. Then, the obtained substrate 2 is stacked three times using double-sided tape, and punched out with a φ6.39 mm punch to create a sample for background correction (hereinafter simply referred to as the "correction sample"). Subsequently, the MH loop of the correction sample (substrate 2) corresponding to the vertical direction of substrate 2 (the vertical direction of magnetic tape 1) is measured using a VSM.

[0365] For measuring the MH loop of the measurement sample (the entire magnetic tape 1) and the MH loop of the correction sample (substrate 2), a high-sensitivity vibrating sample type magnetometer "VSM-P7-15" manufactured by Toei Kogyo Co., Ltd. is used. The measurement conditions are as follows: measurement mode: full loop, maximum magnetic field: 15 kOe, magnetic field step: 40 bits, time constant of locking amp: 0.3 sec, waiting time: 1 sec, MH average number: 20.

[0366] After obtaining the MH loop of the measurement sample (the entire magnetic tape 1) and the MH loop of the correction sample (substrate 2), background correction is performed by subtracting the MH loop of the correction sample (substrate 2) from the MH loop of the measurement sample (the entire magnetic tape 1), and the MH loop after background correction is obtained. The measurement and analysis program included with the "VSM-P7-15" is used to calculate this background correction.

[0367] The obtained background-corrected saturation magnetization Ms(emu) and remanent magnetization Mr(emu) of the MH loop are substituted into the following formula to calculate the square aspect ratio S1(%). Note that all MH loop measurements are performed at 25℃±2℃ and 50%RH±5%RH. Furthermore, "demagnetization correction" is not performed when measuring the MH loop perpendicular to the magnetic tape 1. The measurement and analysis program included with the "VSM-P7-15" is used for this calculation. Squareness ratio S1(%)=(Mr / Ms)×100

[0368] The angularity ratio S2 of the magnetic layer 4 in the longitudinal direction (travel direction) of the magnetic tape 1 is preferably 35% or less, more preferably 30% or less, even more preferably 25% or less, particularly preferably 20% or less, and most preferably 15% or less. When the angularity ratio S2 is 35% or less, the vertical orientation of the magnetic powder becomes sufficiently high, so even better electromagnetic conversion characteristics (e.g., SNR) can be obtained.

[0369] The aspect ratio only needs to satisfy a value in either the vertical or longitudinal direction. In particular, for magnetic tapes 1 with a magnetic layer of 100 nm or less, it is better to give more importance to the aspect ratio in the longitudinal direction than the vertical direction, where the effect of the demagnetizing field is more likely to differ.

[0370] The aspect ratio S2 in the longitudinal direction is determined in the same manner as the aspect ratio S1, except that the MH loop is measured in the longitudinal direction (travel direction) of the magnetic tape 1 and the substrate 2.

[0371] (Surface roughness Rb of the back surface) Surface roughness of the back surface (surface roughness of back layer 5) R b However, R b It is preferable that the surface roughness R of the back surface is ≤6.0 [nm]. b If the above range is maintained, even better electromagnetic conversion characteristics can be obtained.

[0372] <Other> This technology can also take the following configuration: (1) A servo read head that reads a servo pattern written on the servo band of a magnetic tape and reproduces a waveform servo signal, A control unit calculates the width of the servo pattern based on a first point and a second point, which are different from the positive peak point and the negative peak point in the waveform of the servo signal, respectively. A servo measuring device equipped with the following. (2) A servo measuring device as described in (1) above, The control unit sets the first point to a point corresponding to any of the rising portions of the positive convex portion in the waveform of the servo signal. Servo measuring device. (3) A servo measuring device as described in (2) above, The control unit sets the second point to a point corresponding to any of the rising edges in the negative recess of the servo signal waveform. Servo measuring device. (4) A servo measuring device as described in (3) above, The control unit sets the first point as the first point, which corresponds to an output value that is a first percentage of the positive peak point in the waveform of the servo signal, when the output value of the positive peak point in the servo signal waveform is set to 100%. Servo measuring device. (5) A servo measuring device as described in (4) above, The control unit sets the second point as the output value that corresponds to a second percentage of the output value relative to the negative peak point in the waveform of the servo signal, when the output value of the negative peak point in the waveform is set to -100%. Servo measuring device. (6) A servo measuring device as described in (5) above, The control unit sets the first percentage to a value within the range of 25% or more and 75% or less. Servo measuring device. (7) A servo measuring device as described in (6) above, The control unit sets the second percentage to a value within the range of -25% or more and -75% or less. Servo measuring device. (8) A servo measuring device described in any one of (5) to (7) above, The control unit sets the first percentage and the second percentage such that their absolute values ​​are equal. Servo measuring device. (9) A servo measuring device described in any one of (1) to (8) above, The magnetic tape includes a vertically oriented magnetic layer on which the servo pattern is written. Servo measuring device. (10) A servo measuring device as described in (9) above, The aspect ratio in the vertical direction of the magnetic layer is 60% or more. Servo measuring device. (11) A servo measuring device described in any one of (1) to (10) above, The control unit is capable of changing at least one of the first point and the second point. Servo measuring device. (12) A servo measuring device as described in (11) above, The control unit modifies at least one of the first and second points based on the degree of vertical orientation of the magnetic layer on which the servo pattern is written. Servo measuring device. (13) A servo measuring device described in any one of (5) to (11) above, The control unit can change at least one of the first percentage and the second percentage. Servo measuring device. (14) A servo measuring device as described in (13) above, The control unit changes at least one of the first percentage and the second percentage based on the degree of vertical orientation of the magnetic layer on which the servo pattern is written. Servo measuring device. (15) A servo measuring device described in any one of (1) to (14) above, The control unit measures the width of the servo pattern for each servo track in the servo band. Servo measuring device. (16) A servo measuring device described in any one of (1) to (15) above, An older data recording device compatible with older LTO-type magnetic tape is reused as the servo measuring device. Servo measuring device. (17) Read the servo pattern written on the servo band of the magnetic tape and regenerate the waveform servo signal, The width of the servo pattern is calculated based on a first point and a second point, which are different from the positive and negative peak points in the waveform of the servo signal. Servo measurement method. (18) Read the servo pattern written on the servo band of the magnetic tape and regenerate the waveform servo signal, The width of the servo pattern is calculated based on a first point and a second point, which are different from the positive and negative peak points in the waveform of the servo signal. A program that causes a servo measuring device to perform a process. (19) Read the servo pattern written on the servo band of the magnetic tape and regenerate the waveform servo signal, The width of the servo pattern is calculated based on a first point and a second point, which are different from the positive and negative peak points in the waveform of the servo signal, respectively. The quality of the magnetic tape is confirmed based on the width of the servo pattern. A method for manufacturing magnetic tape. (20) The servo pattern written on the servo band of the magnetic tape is read and a waveform servo signal is reproduced. The width of the servo pattern is calculated based on a first point and a second point, which are different from the positive and negative peak points in the waveform of the servo signal. The quality of the magnetic tape was confirmed based on the width of the servo pattern. Magnetic tape. [Explanation of Symbols]

[0373] 1… Magnetic tape 7…Servo Pattern 7a...First servo pattern 7b...Second servo pattern 15…Control device 20…Servo lead head 22... Servo lead section 22a...First third lead section 22b...Second servo lead section 40…Servo Light Head 42…Servo element 100... Servo measuring device 101... Servo recording and playback device

Claims

1. A servo read head reads the servo pattern written on the servo band of the magnetic tape and reproduces the waveform servo signal, A control unit calculates the width of the servo pattern based on a first point and a second point, which are different from the positive peak point and the negative peak point in the waveform of the servo signal, respectively. A servo measuring device equipped with the following.

2. A servo measuring device according to claim 1, The control unit sets the first point to a point corresponding to any of the rising edges of the positive convex portion in the waveform of the servo signal. Servo measuring device.

3. A servo measuring device according to claim 2, The control unit sets the second point to a point corresponding to any of the rising portions of the negative concave portion in the waveform of the servo signal. Servo measuring device.

4. A servo measuring device according to claim 3, The control unit sets the first point as the first point, which corresponds to an output value that is a first percentage of the positive peak point in the waveform of the servo signal, when the output value of the positive peak point in the servo signal waveform is set to 100%. Servo measuring device.

5. A servo measuring device according to claim 4, The control unit sets the second point as the output value that corresponds to a second percentage of the output value relative to the negative peak point in the waveform of the servo signal, when the output value of the negative peak point in the waveform is set to -100%. Servo measuring device.

6. A servo measuring device according to claim 5, The control unit sets the first percentage to a value within the range of 25% or more and 75% or less. Servo measuring device.

7. A servo measuring device according to claim 6, The control unit sets the second percentage to a value within the range of -25% or more and -75% or less. Servo measuring device.

8. A servo measuring device according to claim 5, The control unit sets the first percentage and the second percentage such that their absolute values ​​are equal. Servo measuring device.

9. A servo measuring device according to claim 1, The magnetic tape includes a vertically oriented magnetic layer on which the servo pattern is written. Servo measuring device.

10. A servo measuring device according to claim 9, The aspect ratio in the vertical direction of the magnetic layer is 60% or more. Servo measuring device.

11. A servo measuring device according to claim 1, The control unit is capable of changing at least one of the first point and the second point. Servo measuring device.

12. A servo measuring device according to claim 11, The control unit modifies at least one of the first and second points based on the degree of vertical orientation of the magnetic layer on which the servo pattern is written. Servo measuring device.

13. A servo measuring device according to claim 5, The control unit is capable of changing at least one of the first percentage and the second percentage. Servo measuring device.

14. A servo measuring device according to claim 13, The control unit changes at least one of the first percentage and the second percentage based on the degree of vertical orientation of the magnetic layer on which the servo pattern is written. Servo measuring device.

15. A servo measuring device according to claim 1, The control unit measures the width of the servo pattern for each servo track in the servo band. Servo measuring device.

16. A servo measuring device according to claim 1, An older data recording device compatible with older LTO-type magnetic tape is reused as the servo measuring device. Servo measuring device.

17. The servo pattern written on the servo band of the magnetic tape is read to reconstruct the waveform servo signal. The width of the servo pattern is calculated based on a first point and a second point, which are different from the positive and negative peak points in the waveform of the servo signal. Servo measurement method.

18. The servo pattern written on the servo band of the magnetic tape is read to reconstruct the waveform servo signal. The width of the servo pattern is calculated based on a first point and a second point, which are different from the positive and negative peak points in the waveform of the servo signal. A program that causes a servo measuring device to perform a process.

19. The servo pattern written on the servo band of the magnetic tape is read to reconstruct the waveform servo signal. The width of the servo pattern is calculated based on a first point and a second point, which are different from the positive and negative peak points in the waveform of the servo signal, respectively. The quality of the magnetic tape is confirmed based on the width of the servo pattern. A method for manufacturing magnetic tape.

20. The servo pattern written to the servo band of the magnetic tape is read and a waveform servo signal is reproduced. The width of the servo pattern is calculated based on a first point and a second point, which are different from the positive and negative peak points in the waveform of the servo signal. The quality of the magnetic tape was confirmed based on the width of the servo pattern. Magnetic tape.

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