MAGNETIC TAPE, MAGNETIC TAPE CARTRIDGE, AND MAGNETIC TAPE APPARATUS

Abstract

The magnetic tape includes a magnetic layer containing a ferromagnetic powder. The magnetic layer has n (n is an integer of 3 or more) servo bands, and, in a case in which the servo bands are sequentially numbered with a servo band located at one most end of the magnetic layer in a width direction as a servo band 0, a servo band located at the other most end as a servo band n-1, a servo band adjacent to the servo band 0 as a servo band 1, and a servo band adjacent to the servo band 1 as a servo band 2, a wrinkle depth S.sub.A at a position A at which a deviation amount of a servo band interval from an arithmetic average of servo band intervals between the servo band 1 and the servo band 2 is largest is 10 m or less.

Claims

1. A magnetic tape comprising: a non-magnetic support; and a magnetic layer containing a ferromagnetic powder, wherein the magnetic layer has n servo bands, where n is an integer of 3 or more, and, in a case in which the servo bands are sequentially numbered with a servo band located at one most end of the magnetic layer in a width direction as a servo band 0, a servo band located at the other most end as a servo band n-1, a servo band adjacent to the servo band 0 as a servo band 1, and a servo band adjacent to the servo band 1 as a servo band 2, a wrinkle depth S.sub.A at a position A at which a deviation amount of a servo band interval from an arithmetic average of servo band intervals between the servo band 1 and the servo band 2 is largest is 10 m or less.

2. The magnetic tape according to claim 1, wherein an arithmetic average of the deviation amounts is 0.40 m or less.

3. The magnetic tape according to claim 1, further comprising: a non-magnetic layer containing a non-magnetic powder between the non-magnetic support and the magnetic layer.

4. The magnetic tape according to claim 3, wherein a thickness of the non-magnetic layer is 0.7 m or more.

5. The magnetic tape according to claim 3, wherein the non-magnetic powder includes an Fe-based inorganic oxide powder having an average particle volume of 2.010.sup.6 m.sup.3 or less.

6. The magnetic tape according to claim 3, wherein the non-magnetic powder includes carbon black having a pH of 9.0 or less.

7. The magnetic tape according to claim 1, wherein a width direction young's modulus of the magnetic tape is 4.0 GPa or more.

8. The magnetic tape according to claim 1, further comprising: a back coating layer containing a non-magnetic powder on a surface side of the non-magnetic support opposite to a surface side having the magnetic layer.

9. The magnetic tape according to claim 1, wherein a vertical squareness ratio of the magnetic tape is 0.70 or more.

10. The magnetic tape according to claim 1, wherein an arithmetic average of the deviation amounts is 0.40 m or less, the magnetic tape further includes a non-magnetic layer containing a non-magnetic powder between the non-magnetic support and the magnetic layer, a thickness of the non-magnetic layer is 0.7 m or more, the non-magnetic powder includes an Fe-based inorganic oxide powder having an average particle volume of 2.010.sup.6 m.sup.3 or less and carbon black having a pH of 9.0 or less, a width direction young's modulus of the magnetic tape is 4.0 GPa or more, and the magnetic tape further includes a back coating layer containing a non-magnetic powder on a surface side of the non-magnetic support opposite to a surface side having the magnetic layer.

11. The magnetic tape according to claim 10, wherein a vertical squareness ratio of the magnetic tape is 0.70 or more.

12. A magnetic tape cartridge comprising: the magnetic tape according to claim 1.

13. A magnetic tape apparatus comprising: the magnetic tape according to claim 1.

14. The magnetic tape apparatus according to claim 13, further comprising: a magnetic head, wherein the magnetic head has a module including an element array with a plurality of magnetic head elements between a pair of servo signal reading elements, and the magnetic tape apparatus changes an angle formed by an axis of the element array with respect to a width direction of the magnetic tape during running of the magnetic tape in the magnetic tape apparatus.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] FIG. 1 shows an arrangement example of data bands and servo bands.

[0024] FIG. 2 shows an arrangement example of a servo pattern of a linear tape-open (LTO) Ultrium format tape.

[0025] FIG. 3 is a schematic view showing an example of a jig on which a magnetic tape is arranged in measurement of a wrinkle depth S.sub.A.

[0026] FIG. 4 shows an example (schematic step diagram) of a manufacturing step of the magnetic tape.

[0027] FIG. 5 is a schematic view showing an example of a module of a magnetic head.

[0028] FIG. 6 is an explanatory diagram of a relative positional relationship between a module and a magnetic tape during magnetic tape running in a magnetic tape apparatus.

[0029] FIG. 7 is an explanatory diagram relating to a change in an angle during magnetic tape running.

[0030] FIG. 8 is an explanatory diagram of a measuring method of an angle during magnetic tape running.

[0031] FIG. 9 is a schematic view showing an example of the magnetic tape apparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Magnetic Tape

[0032] One aspect of the present invention relates to a magnetic tape including a non-magnetic support and a magnetic layer containing a ferromagnetic powder. The magnetic layer has n servo bands, where n is an integer of 3 or more. In a case in which the servo bands are sequentially numbered with a servo band located at one most end of the magnetic layer in a width direction as a servo band 0, a servo band located at the other most end as a servo band n-1, a servo band adjacent to the servo band 0 as a servo band 1, and a servo band adjacent to the servo band 1 as a servo band 2, a wrinkle depth S.sub.A at a position A at which a deviation amount of a servo band interval from an arithmetic average of servo band intervals between the servo band 1 and the servo band 2 is largest is 10 m or less.

[0033] As a result of extensive studies, the present inventor has newly found that a magnetic tape in which the wrinkle depth S.sub.A is 10 m or less can contribute to improvement of operational stability of a drive. Hereinafter, supposition of the present inventor regarding this point is described. Note that the present invention is not limited to the supposition described in the present specification.

[0034] As described above, the tape width deformation generated by the long-term storage may cause a decrease in operational stability of the magnetic tape in the drive. In this regard, in recent years, it has been proposed to acquire information on dimensions in a width direction of the magnetic tape during running by using a servo signal and to change an angle (hereinafter, also referred to as a head tilt angle) at which an axial direction of a module of a magnetic head is tilted against the width direction of the magnetic tape according to the acquired dimension information (see JP2016-524774A and US2019/0164573A1, for example, paragraphs 0059 to 0067 and 0084 of JP2016-524774A). In addition, the information on the dimensions in the width direction of the magnetic tape during running is acquired using the servo signal, and a tension applied in a longitudinal direction of the magnetic tape is adjusted according to the acquired dimension information, thereby controlling the dimensions in the width direction of the magnetic tape (see, for example, a paragraph 0171 of JP6590102B). For example, a controller for a dynamic track position during running of the magnetic tape as described above can be means for suppressing off-track.

[0035] However, the present inventor has made extensive studies in order to further improve the operational stability of the drive in recording and/or reproduction after long-term storage, and paid attention to the fact that there may be off-track factors for which it is difficult to compensate by the controller for the dynamic track position. Hereinafter, this point will be further described.

[0036] In a case where the dynamic track position is controlled by changing the head tilt angle, a pitch of a magnetic head element (specifically, a recording element and/or a reproducing element) changes evenly according to the head tilt angle regardless of the position in the tape width direction. In a case where the dynamic track position is controlled by adjusting the tension applied in the longitudinal direction of the magnetic tape, the tension in the entire width of the tape is usually adjusted, so that the tape width changes evenly by the tension adjustment regardless of the position in the tape width direction. In a case where a degree of the tape width deformation is homogeneous over the entire magnetic tape, it is possible to completely compensate for the off-track by the controller. Therefore, it is possible to completely registrate the data track and the magnetic head element.

[0037] Meanwhile, the present inventor has made studies and has found that it is difficult to completely compensate for the off-track by the control of the dynamic track position. As a result of further studies, the present inventor has considered that, in a case in which deep wrinkles are present at the longitudinal local position of the magnetic layer, the servo signal interval in the width direction of the magnetic tape is changed in a portion where such wrinkles are present and is narrower than the normal portion, and thus, the inability to sufficiently respond to the speed during the recording operation and/or the reproduction operation may be a cause (that is, the off-track factor for which it is difficult to compensate by the controller for the dynamic track position) of the inability to completely compensate for the off-track by the control of the dynamic track position. Therefore, as a result of further extensive studies in order to further reduce the off-track by reducing the servo signal interval change, the present inventor has newly found that it is possible to suppress a decrease in the operational stability of the drive due to the off-track factor for which it is difficult to compensate by the controller for the dynamic track position, by setting the wrinkle depth S.sub.A obtained by the method described later to 10 m or less.

[0038] The present inventor supposes that the above is the reason why the magnetic tape can contribute to the improvement of the operational stability of the drive in the recording and/or the reproduction after the long-term storage.

Servo Band

[0039] A servo band is formed of a servo pattern continuous in the longitudinal direction of the magnetic layer of the magnetic tape. Examples of control (servo control) systems using a servo signal include a timing-based servo (TBS), an amplitude servo, and a frequency servo.

[0040] As shown in a Standard European computer manufacturers association (ECMA)-319 (June 2001), a magnetic tape conforming to a linear tape-open (LTO) standard (generally called LTO tape) employs a timing-based servo system. In the timing-based servo system, the servo pattern is formed by continuously arranging a plurality of pairs of non-parallel magnetic stripes (also referred to as servo stripes) in the longitudinal direction of the magnetic tape. In the present invention and the present specification, the term timing-based servo pattern refers to a servo pattern that enables head tracking in a timing-based servo system. As described above, the reason why the servo pattern is formed of a pair of non-parallel magnetic stripes is to indicate, to a servo signal reading element passing over the servo pattern, a passing position thereof. Specifically, the pair of magnetic stripes is formed such that an interval thereof continuously changes along a width direction of the magnetic tape, and the servo signal reading element reads the interval to thereby sense a relative position between the servo pattern and the servo signal reading element. Information on this relative position enables tracking on a data track. Accordingly, a plurality of servo tracks are usually set on the servo pattern along the width direction of the magnetic tape.

[0041] A servo band is formed of a servo pattern continuous in the longitudinal direction of the magnetic layer of the magnetic tape. The magnetic layer of the magnetic tape includes n servo bands. n is an integer of 3 or more, and can be, for example, 3, 4, or 5. For example, in an LTO tape, n=5. Regions interposed between two adjacent servo bands are data bands. The data band is formed of a plurality of data tracks and each data track corresponds to each servo track.

[0042] Further, in one aspect, as shown in JP2004-318983A, information indicating a servo band number (referred to as servo band identification (ID) or unique data band identification method (UDIM) information) is embedded in each servo band. This servo band ID is recorded by shifting a specific one of the plurality of pairs of the servo stripes in the servo band so that positions thereof are relatively displaced in the longitudinal direction of the magnetic tape. Specifically, a way of shifting the specific one of the plurality of pairs of servo stripes is changed for each servo band. Accordingly, the recorded servo band ID is unique for each servo band, and thus, the servo band can be uniquely specified only by reading one servo band with a servo signal reading element.

[0043] In a method of uniquely specifying the servo band, a staggered method as shown in Standard ECMA-319 (June 2001) is used. In this staggered method, a group of pairs of non-parallel magnetic stripes (servo stripes) arranged continuously in plural in a longitudinal direction of the magnetic tape is recorded so as to be shifted in a longitudinal direction of the magnetic tape for each servo band. Since this combination of shifting methods between adjacent servo bands is unique throughout the magnetic tape, it is possible to uniquely specify a servo band in a case of reading a servo pattern with two servo signal reading elements.

[0044] As shown in Standard ECMA-319 (June 2001), information indicating a position of the magnetic tape in the longitudinal direction (also referred to as longitudinal position (LPOS) information) is usually embedded in each servo band. This LPOS information is also recorded by shifting the positions of the pair of servo stripes in the longitudinal direction of the magnetic tape, as the UDIM information. Note that, unlike the UDIM information, in this LPOS information, the same signal is recorded in each servo band.

[0045] It is also possible to embed, in the servo band, the other information different from the above UDIM information and LPOS information. In this case, the embedded information may be different for each servo band as the UDIM information or may be common to all servo bands as the LPOS information.

[0046] As a method of embedding information in the servo band, it is possible to employ a method other than the above. For example, a predetermined code may be recorded by thinning out a predetermined pair from the group of pairs of servo stripes.

[0047] A head for forming a servo pattern is called a servo write head. The servo write head usually has a pair of gaps corresponding to the pair of magnetic stripes as many as the number of servo bands. Usually, a core and a coil are connected to each pair of gaps, and by supplying a current pulse to the coil, a magnetic field generated in the core can cause generation of a leakage magnetic field in the pair of gaps. In a case of forming the servo pattern, by inputting a current pulse while running the magnetic tape on the servo write head, the magnetic pattern corresponding to the pair of gaps can be transferred to the magnetic tape to form the servo pattern. A width of each gap can be appropriately set according to a density of the servo pattern to be formed. The width of each gap can be set to, for example, 1 m or less, 1 to 10 m, 10 m or more, and the like.

[0048] Before the servo pattern is formed on the magnetic tape, the magnetic tape is usually subjected to a demagnetization (erasing) treatment. This erasing treatment can be performed by applying a uniform magnetic field to the magnetic tape using a direct current magnet or an alternating current magnet. The erasing treatment includes direct current (DC) erasing and alternating current (AC) erasing. AC erasing is performed by gradually decreasing an intensity of the magnetic field while reversing a direction of the magnetic field applied to the magnetic tape. On the other hand, DC erasing is performed by applying a unidirectional magnetic field to the magnetic tape. As the DC erasing, there are two additional methods. A first method is horizontal DC erasing of applying a unidirectional magnetic field along a longitudinal direction of the magnetic tape. A second method is vertical DC erasing of applying a unidirectional magnetic field along a thickness direction of the magnetic tape. The erasing treatment may be performed on the entire magnetic tape or may be performed for each servo band of the magnetic tape.

[0049] A direction of the magnetic field of the servo pattern to be formed is determined according to a direction of the erasing. For example, in a case where the horizontal DC erasing is performed to the magnetic tape, the servo pattern is formed so that the direction of the magnetic field is opposite to the direction of the erasing. Therefore, an output of a servo signal obtained by reading the servo pattern can be increased. As shown in JP2012-53940A, in a case where the magnetic pattern is transferred to, using the gap, a magnetic tape that has been subjected to the vertical DC erasing, a servo signal obtained by reading the formed servo pattern has a monopolar pulse shape. On the other hand, in a case where a magnetic pattern is transferred to, using the gap, a magnetic tape that has been subjected to horizontal DC erasing, a servo signal obtained by reading the formed servo pattern has a bipolar pulse shape. FIG. 1 shows an arrangement example of data bands and servo bands. In FIG. 1, five servo bands 1 are arranged to be interposed between guide bands 3 in a magnetic layer of a magnetic tape MT. A plurality of regions 2 interposed between two servo bands are data bands.

[0050] The servo pattern is a magnetization region, and is formed by magnetizing a specific region of the magnetic layer by the servo write head. A region magnetized by the servo write head (a position where the servo pattern is formed) is determined by the standard. FIG. 2 shows an arrangement example of a servo pattern of an LTO Ultrium format tape. For example, in an LTO Ultrium format tape which is based on a local standard, a plurality of servo patterns inclined with respect to a tape width direction as shown in FIG. 2 are formed on a servo band, in a case of manufacturing a magnetic tape. Specifically, in FIG. 2, a servo frame SF on the servo band 1 is composed of a servo sub-frame 1 (SSF1) and a servo sub-frame 2 (SSF2). The servo sub-frame 1 is composed of an A burst (in FIG. 2, reference numeral A) and a B burst (in FIG. 2, reference numeral B). The A burst is composed of servo patterns A1 to A5 and the B burst is composed of servo patterns B1 to B5. Meanwhile, the servo sub-frame 2 is composed of a C burst (in FIG. 2, reference numeral C) and a D burst (in FIG. 2, reference numeral D). The C burst is composed of servo patterns C1 to C4 and the D burst is composed of servo patterns D1 to D4. Such 18 servo patterns are arranged in the sub-frames in an array of 5, 5, 4, 4, as the sets of 5 servo patterns and 4 servo patterns, and are used for identifying the servo frames. FIG. 2 shows one servo frame for description. Note that, in practice, a plurality of the servo frames are arranged in the running direction in each servo band in the magnetic layer of the magnetic tape on which the head tracking of the timing-based servo system is performed. In FIG. 2, the arrow indicates the running direction of the magnetic tape. For example, an LTO Ultrium format tape usually has 5000 or more servo frames per 1 m of tape length in each servo band of the magnetic layer.

[0051] Measuring method of wrinkle depth S.sub.A [0052] Hereinafter, a measuring method of the wrinkle depth S.sub.A will be described.

[0053] Measurement of servo band interval [0054] The measurement of the servo band interval is performed in a measurement environment of an atmosphere temperature of 23 C.1 C. and a relative humidity of 50%+5% in order to reduce the environmental effect of the dimensions of the magnetic tape and the servo head.

[0055] The servo band interval is measured using information on the servo signal described in Japanese industrial standards (JIS) X6175: 2006 and Standard ECMA-319 (June 2001). The measurement requires the dimensions of the servo signal. Regarding the dimensions of the servo signal, dimension standards differ depending on the generation. First, for the magnetic tape to be measured, an average distance AC between four stripes corresponding to an A burst and a C burst and an azimuth angle of the servo pattern are measured by using a magnetic force microscope or the like.

[0056] Next, the servo pattern formed on the magnetic layer is read sequentially along the longitudinal direction of the magnetic tape using a reel tester and a servo head comprising two servo signal reading elements (hereinafter, one servo signal reading element is referred to as an upper servo signal reading element, and the other servo signal reading element is referred to as a lower servo signal reading element) fixed at an interval in a direction orthogonal to the longitudinal direction of the magnetic tape. An average time between five stripes corresponding to the A burst and the B burst over a length of one LPOS word is defined as a. An average time between four stripes corresponding to the A burst and the C burst over the length of one LPOS word is defined as b. In this case, a value defined by AC*(1/2-a/b)/(2*tan ()) represents a reading position error signal (PES) in the width direction based on the servo signal obtained by the servo signal reading element over a length of one LPOS word. The servo pattern reading with respect to 1 LPOS word is performed simultaneously by the two servo signal reading elements on the upper side and the lower side. A value of the PES obtained by the upper servo signal reading element is referred to as PES1, and a value of the PES obtained by the lower servo signal reading element is referred to as PES2. The servo band interval for each one LPOS word can be obtained as PES1-PES2 calculated from PES1 and PES2 which are obtained in this way. This is because the upper and lower servo signal reading elements are fixed to the servo head and their intervals do not change.

[0057] In the above, a method of obtaining the servo band interval of the magnetic layer in which the servo pattern is arranged in the servo pattern arrangement of the LTO Ultrium format tape has been described. Even for the magnetic layer in which the servo pattern is arranged in another arrangement, the servo band interval can be obtained by using the PES obtained by reading the servo pattern with the servo signal reading element, in the same manner as described above.

Specification of position A

[0058] For example, in the magnetic layer in which the data band and the servo band are arranged as shown in FIG. 1, the number of servo bands is five (that is, n=5). A servo band located at the top in FIG. 1 is referred to as a servo band (SB) 0, a servo band adjacent to SB0 is referred to as SB1, a servo band adjacent to SB1 is referred to as SB2, a servo band adjacent to SB2 is referred to as SB3, and a servo band adjacent to SB3 (servo band located at the bottom in FIG. 1) is referred to as SB4. The numbering of such servo bands is the numbering according to the LTO standard. In the present invention and the present specification, the numbering of the servo bands is determined according to the standard to which the magnetic tape to be measured conforms.

[0059] The arithmetic average of the servo band intervals obtained for all the LPOS words in the servo band interval between SB1 and SB2 is defined as the target servo band interval. Among all the LPOS words in all the servo band intervals, a position of an LPOS word at which the deviation amount of the servo band interval from the target servo band interval is the largest is specified as a position A. For example, in the magnetic layer in which the data band and the servo band are arranged as shown in FIG. 1, the position A is specified from all the LPOS words in the servo band interval between SB0 and SB1, the servo band interval between SB1 and SB2, the servo band interval between SB2 and SB3, and the servo band interval between SB3 and SB4. The deviation amount is an absolute value of a difference between the target servo band interval and the servo band interval of the LPOS word of the target servo band interval. In the measurement of the servo band interval, for example, after the measurement of the servo band interval (all LPOS words) between SB1 and SB2 is performed, the measurement of the servo band interval (all LPOS words) between SB0 and SB1, the measurement of the servo band interval (all LPOS words) between SB2 and SB3, and the measurement of the servo band interval (all LPOS words) between SB3 and SB4 can be sequentially performed.

Measurement of wrinkle depth S.sub.A

[0060] A magnetic tape of which the wrinkle depth S.sub.A is measured is caused to cross a jig having two support rods such that a surface of the magnetic tape opposite to the magnetic layer side comes into contact with the support rod, and the position is fixed by loading 3 gf (gram-force) at both end parts of the magnetic tape in the longitudinal direction. The unit gf indicates gram-force, and 1 N (Newton) is about 102 gf. FIG. 3 is a schematic view showing an example of a jig on which the magnetic tape is arranged in measurement of the wrinkle depth S.sub.A. In FIG. 3, the magnetic tape MT is caused to cross a jig 20 having support rods B1 and B2, and 3 gf is loaded onto both end parts of MT in the longitudinal direction. The position is fixed by performing the registration such that the position A specified by the above-described method on the magnetic layer surface is located near the central portion between the two support rods of the jig.

[0061] At the position A on the magnetic layer surface, the flatness is measured by a three-dimensional laser microscope under the following conditions, and the wrinkle depth S.sub.A is obtained as a maximum depth of the Valley portion in a case in which the width direction of the magnetic tape is the scanning direction. The measurement is performed in a measurement environment of an atmosphere temperature of 23 C.1 C. and a relative humidity of 50%+5%. Hereinafter, 3D is an abbreviation for three dimensions.

Measurement Conditions

[0062] Measuring device: industrial microscope OLS5100 3D measurement laser microscope, manufactured by Olympus Corporation [0063] Objective lens: MPLFLN5, manufactured by Olympus Corporation [0064] Zoom: 1 [0065] Scanning mode: 3D standard+color [0066] Measurement area: 2570 m2563 m [0067] Laser brightness: 40.9 [0068] Beam diameter stop: Out [0069] Brightness unevenness correction: ON [0070] Optical noise filter: ON [0071] Color brightness: automatic [0072] Auto gain: ON [0073] Wrinkle depth S.sub.A

[0074] From the viewpoint of improving the operational stability of the drive in recording and/or reproduction after long-term storage, the wrinkle depth S.sub.A obtained by the above method on the magnetic layer surface of the magnetic tape is 10 m or less, preferably 9 m or less, and more preferably 8 m or less, 7 m or less, 6 m or less, 5 m or less, and 4 m or less in this order. The wrinkle depth S.sub.A can be, for example, more than 0 m, 1 m or more, or 2 m or more. The controller for the wrinkle depth S.sub.A will be described below.

Arithmetic Average of Deviation Amounts

[0075] As described above, it is preferable that the arithmetic average of the deviation amounts obtained for all the LPOS words in all the servo band intervals is small from the viewpoint of further improving the operational stability of the drive in recording and/or reproduction after long-term storage.

[0076] From the above viewpoint, the arithmetic average of the deviation amounts is preferably 0.40 m or less, and more preferably 0.35 m or less, 0.30 m or less, and 0.25 m or less in this order. The arithmetic average of the deviation amounts can be, for example, more than 0 m, 0.01 m or more, 0.10 m or more, 0.15 m or more, or 0.20 m or more. It is preferable to reduce the value of the wrinkle depth S.sub.A in order to reduce the value of the arithmetic average of the deviation amounts.

[0077] Hereinafter, the magnetic tape will be described in more detail.

Width Direction Young's Modulus of Magnetic Tape

[0078] The width direction young's modulus of the magnetic tape can be, for example, 4.0 GPa or more or 5.0 GPa or more. In addition, the width direction young's modulus of the magnetic tape can be, for example, 15.0 GPa or less, 12.0 GPa or less, or 10.0 GPa or less.

[0079] From the viewpoint of reducing the value of the wrinkle depth S.sub.A, it is preferable that the width direction young's modulus of the magnetic tape is large.

[0080] In the present invention and the present specification, the measurement of the young's modulus is carried out in a measurement environment of an atmosphere temperature of 23 C.1 C. and a relative humidity of 50%5%.

[0081] The width direction young's modulus of the magnetic tape is obtained by the following method.

[0082] A sample piece cut out from the magnetic tape to be measured is pulled in the width direction by a universal tensile test device under the conditions of a distance between chucks of 100 mm, a tensile speed of 10 mm/min, and a chart speed of 500 mm/min. As the universal tensile test device, for example, a commercially available universal tensile test device such as Tensilon manufactured by Toyo Baldwin Co., Ltd. or a universal tensile test device having a known configuration can be used. Young's moduli in a width direction of the sample piece are calculated from a tangent line of a rising portion of a load-elongation curve thus obtained. The young's modulus calculated in this way is defined as the width direction young's modulus of the magnetic tape to be measured.

[0083] The width direction young's modulus of the magnetic tape tends to increase as the value of the width direction young's modulus of the non-magnetic support included in the magnetic tape increases. The young's modulus of the non-magnetic support is obtained by the following method.

[0084] A sample piece cut out from the non-magnetic support to be measured is pulled in the width direction by the universal tensile test device under the conditions of a distance between chucks of 100 mm, a tensile speed of 10 mm/min, and a chart speed of 500 mm/min. As the universal tensile test device, for example, a commercially available universal tensile test device such as Tensilon manufactured by Toyo Baldwin Co., Ltd. or a universal tensile test device having a known configuration can be used. Young's moduli in a width direction of the sample piece are calculated from a tangent line of a rising portion of a load-elongation curve thus obtained. The young's modulus calculated in this way is defined as the width direction young's modulus of the non-magnetic support to be measured. Here, the width direction of the sample piece refers to a width direction in a case in which the sample piece cut out from the non-magnetic support taken out from the magnetic tape by a known method is included in the magnetic tape. In a case in which a part of the non-magnetic support original roll is cut out and used as a non-magnetic support of the magnetic tape (hereinafter, referred to as a support for a magnetic tape), and the other part is cut out and used as a sample piece for measuring a young's modulus, the same direction of the support for a magnetic tape as the width direction in the magnetic tape is set as the width direction of the sample piece of the support for a magnetic tape.

Magnetic Layer

Ferromagnetic Powder

[0085] As a ferromagnetic powder included in the magnetic layer, a well-known ferromagnetic powder as a ferromagnetic powder used in magnetic layers of various magnetic recording media can be used alone or in combination of two or more. From the viewpoint of improving recording density, it is preferable to use a ferromagnetic powder having a small average particle size. From this point, the average particle size of the ferromagnetic powder is preferably 50 nm or less, more preferably 45 nm or less, still more preferably 40 nm or less, still more preferably 35 nm or less, still more preferably 30 nm or less, still more preferably 25 nm or less, and still more preferably 20 nm or less. On the other hand, from the viewpoint of magnetization stability, the average particle size of the ferromagnetic powder is preferably 5 nm or more, more preferably 8 nm or more, still more preferably 10 nm or more, still more preferably 15 nm or more, and still more preferably 20 nm or more.

Hexagonal Ferrite Powder

[0086] Preferred specific examples of the ferromagnetic powder include a hexagonal ferrite powder. For details of the hexagonal ferrite powder, for example, descriptions disclosed in paragraphs 0012 to 0030 of JP2011-225417A, paragraphs 0134 to 0136 of JP2011-216149A, paragraphs 0013 to 0030 of JP2012-204726A, and paragraphs 0029 to 0084 of JP2015-127985A can be referred to.

[0087] In the present invention and the present specification, the term hexagonal ferrite powder refers to a ferromagnetic powder in which a hexagonal ferrite crystal structure is detected as a main phase by X-ray diffraction analysis. The main phase refers to a structure to which the highest intensity diffraction peak in an X-ray diffraction spectrum obtained by X-ray diffraction analysis is attributed. For example, in a case where the highest intensity diffraction peak is attributed to a hexagonal ferrite crystal structure in an X-ray diffraction spectrum obtained by X-ray diffraction analysis, it is determined that the hexagonal ferrite crystal structure is detected as the main phase. In a case where only a single structure is detected by X-ray diffraction analysis, this detected structure is taken as the main phase. The hexagonal ferrite crystal structure includes at least an iron atom, a divalent metal atom, and an oxygen atom, as a constituent atom. The divalent metal atom is a metal atom that can be a divalent cation as an ion, and examples thereof may include an alkaline earth metal atom such as a strontium atom, a barium atom, and a calcium atom, and a lead atom. In the present invention and the present specification, a hexagonal strontium ferrite powder refers to a powder in which a main divalent metal atom is a strontium atom, and a hexagonal barium ferrite powder refers to a powder in which a main divalent metal atom is a barium atom. The main divalent metal atom refers to a divalent metal atom that accounts for the most on an at % basis among the divalent metal atoms included in the powder. Note that a rare earth atom is not included in the above divalent metal atom. The term rare earth atom in the present invention and the present specification is selected from the group consisting of a scandium atom (Sc), an yttrium atom (Y), and a lanthanoid atom. The lanthanoid atom is selected from the group consisting of a lanthanum atom (La), a cerium atom (Ce), a praseodymium atom (Pr), a neodymium atom (Nd), a promethium atom (Pm), a samarium atom (Sm), a europium atom (Eu), a gadolinium atom (Gd), a terbium atom (Tb), a dysprosium atom (Dy), a holmium atom (Ho), an erbium atom (Er), a thulium atom (Tm), an ytterbium atom (Yb), and a lutetium atom (Lu).

[0088] Hereinafter, the hexagonal strontium ferrite powder, which is one aspect of the hexagonal ferrite powder, will be described in more detail.

[0089] An activation volume of the hexagonal strontium ferrite powder is preferably in a range of 800 to 1600 nm.sup.3. The finely granulated hexagonal strontium ferrite powder having an activation volume in the above range is suitable for manufacturing a magnetic tape exhibiting excellent electromagnetic conversion characteristics. The activation volume of the hexagonal strontium ferrite powder is preferably 800 nm.sup.3 or more, and may be, for example, 850 nm.sup.3 or more. Further, from the viewpoint of further improving the electromagnetic conversion characteristics, the activation volume of the hexagonal strontium ferrite powder is more preferably 1500 nm.sup.3 or less, still more preferably 1400 nm.sup.3 or less, still more preferably 1300 nm.sup.3 or less, still more preferably 1200 nm.sup.3 or less, and still more preferably 1100 nm.sup.3 or less. The same applies to an activation volume of the hexagonal barium ferrite powder.

[0090] The term activation volume refers to a unit of magnetization reversal and is an index indicating the magnetic size of a particle. An activation volume described in the present invention and the present specification and an anisotropy constant Ku which will be described below are values obtained from the following relational expression between a coercivity Hc and an activation volume V, by performing measurement in a coercivity Hc measurement portion at a magnetic field sweep rate of 3 minutes and 30 minutes using a vibrating sample magnetometer (measurement temperature: 23 C.1 C.). For a unit of the anisotropy constant Ku, 1 erg/cc=1.010.sup.1 J/m.sup.3.

[00001]$\mathrm{Hc}=2\mathrm{Ku}/\mathrm{Ms}\left\{1-{\left[\left(\mathrm{kT}/\mathrm{KuV}\right)\ln \left(\mathrm{At}/0.693\right)\right]}^{1/2}\right\}$

[0091] [In the above expression, Ku: anisotropy constant (unit: J/m.sup.3), Ms: saturation magnetization (Unit: kA/m), k: Boltzmann constant, T: absolute temperature (unit: K), V: activation volume (unit: cm.sup.3), A: spin precession frequency (unit: s.sup.1), t: magnetic field reversal time (unit: s)]

[0092] An index for reducing thermal fluctuation, in other words, for improving the thermal stability may include the anisotropy constant Ku. The hexagonal strontium ferrite powder preferably has Ku of 1.810.sup.5 J/m.sup.3 or more, and more preferably has Ku of 2.010.sup.5 J/m.sup.3 or more. Ku of the hexagonal strontium ferrite powder may be, for example, 2.510.sup.5 J/m.sup.3 or less. Here, since higher Ku means higher thermal stability, which is preferable, a value thereof is not limited to the values exemplified above.

[0093] The hexagonal strontium ferrite powder may or may not include a rare earth atom. In a case where the hexagonal strontium ferrite powder includes a rare earth atom, it is preferable to include a rare earth atom at a content (bulk content) of 0.5 to 5.0 at % with respect to 100 at % of an iron atom. In one aspect, the hexagonal strontium ferrite powder including a rare earth atom may have a rare earth atom surface layer portion uneven distribution property. In the present invention and the present specification, the rare earth atom surface layer portion uneven distribution property means that a rare earth atom content with respect to 100 at % of an iron atom in a solution obtained by partially dissolving the hexagonal strontium ferrite powder with an acid (hereinafter, referred to as a rare earth atom surface layer portion content or simply a surface layer portion content for a rare earth atom.) and a rare earth atom content with respect to 100 at % of an iron atom in a solution obtained by totally dissolving the hexagonal strontium ferrite powder with an acid (hereinafter, referred to as a rare earth atom bulk content or simply a bulk content for a rare earth atom.) satisfy a ratio of a rare earth atom surface layer portion content/a rare earth atom bulk content >1.0.

[0094] A rare earth atom content in the hexagonal strontium ferrite powder described below is synonymous with the rare earth atom bulk content. On the other hand, partial dissolution using an acid dissolves a surface layer portion of a particle constituting the hexagonal strontium ferrite powder, and thus, a rare earth atom content in a solution obtained by partial dissolution is a rare earth atom content in a surface layer portion of a particle constituting the hexagonal strontium ferrite powder. A rare earth atom surface layer portion content satisfying a ratio of rare earth atom surface layer portion content/rare earth atom bulk content >1.0 means that in a particle constituting the hexagonal strontium ferrite powder, rare earth atoms are unevenly distributed in a surface layer portion (that is, more than an inside). The surface layer portion in the present invention and the present specification means a partial region from a surface of a particle constituting the hexagonal strontium ferrite powder toward an inside.

[0095] In a case where the hexagonal strontium ferrite powder includes the rare earth atom, a rare earth atom content (bulk content) is preferably in a range of 0.5 to 5.0 at % with respect to 100 at % of an iron atom. It is considered that a bulk content in the above range of the included rare earth atom and uneven distribution of the rare earth atoms in a surface layer portion of a particle constituting the hexagonal strontium ferrite powder contribute to suppression of a decrease in reproduction output during repeated reproduction. It is supposed that this is because the hexagonal strontium ferrite powder includes a rare earth atom with a bulk content in the above range, and rare earth atoms are unevenly distributed in a surface layer portion of a particle constituting the hexagonal strontium ferrite powder, and thus it is possible to increase an anisotropy constant Ku. The higher a value of an anisotropy constant Ku is, the more a phenomenon called thermal fluctuation can be suppressed (in other words, thermal stability can be improved). By suppressing occurrence of thermal fluctuation, it is possible to suppress a decrease in reproduction output during repeated reproduction. It is supposed that uneven distribution of rare earth atoms in a particulate surface layer portion of the hexagonal strontium ferrite powder contributes to stabilization of spins of iron (Fe) sites in a crystal lattice of a surface layer portion, and thus, an anisotropy constant Ku may be increased.

[0096] Moreover, it is supposed that the use of the hexagonal strontium ferrite powder having a rare earth atom surface layer portion uneven distribution property as a ferromagnetic powder in the magnetic layer also contributes to inhibition of a magnetic layer surface from being scraped by being slid with respect to the magnetic head. That is, it is supposed that the hexagonal strontium ferrite powder having a rare earth atom surface layer portion uneven distribution property can also contribute to an improvement of running durability of the magnetic tape. It is supposed that this may be because uneven distribution of rare earth atoms on a surface of a particle constituting the hexagonal strontium ferrite powder contributes to an improvement of interaction between the particle surface and an organic substance (for example, a binding agent and/or an additive) included in the magnetic layer, and, as a result, a strength of the magnetic layer is improved.

[0097] From the viewpoint of further suppressing a decrease in reproduction output during repeated reproduction and/or the viewpoint of further improving running durability, the rare earth atom content (bulk content) is more preferably in a range of 0.5 to 4.5 at %, still more preferably in a range of 1.0 to 4.5 at %, and still more preferably in a range of 1.5 to 4.5 at %.

[0098] The bulk content is a content obtained by totally dissolving the hexagonal strontium ferrite powder. In the present invention and the present specification, unless otherwise noted, the content of an atom means a bulk content obtained by totally dissolving the hexagonal strontium ferrite powder. The hexagonal strontium ferrite powder including a rare earth atom may include only one kind of rare earth atom as the rare earth atom, or may include two or more kinds of rare earth atoms. The bulk content in a case of including two or more kinds of rare earth atoms is obtained for the total of two or more kinds of rare earth atoms. This also applies to other components in the present invention and the present specification. That is, unless otherwise noted, a certain component may be used alone or in combination of two or more. A content amount or a content in a case where two or more components are used refers to that for the total of two or more components.

[0099] In a case where the hexagonal strontium ferrite powder includes a rare earth atom, the included rare earth atom need only be any one or more of rare earth atoms. As a rare earth atom that is preferable from the viewpoint of further suppressing a decrease in reproduction output during repeated reproduction, there are a neodymium atom, a samarium atom, a yttrium atom, and a dysprosium atom, here, the neodymium atom, the samarium atom, and the yttrium atom are more preferable, and a neodymium atom is still more preferable.

[0100] In the hexagonal strontium ferrite powder having a rare earth atom surface layer portion uneven distribution property, the rare earth atoms need only be unevenly distributed in the surface layer portion of a particle constituting the hexagonal strontium ferrite powder, and the degree of uneven distribution is not limited. For example, for the hexagonal strontium ferrite powder having a rare earth atom surface layer portion uneven distribution property, a ratio of a surface layer portion content of a rare earth atom obtained by partial dissolution under dissolution conditions which will be described below to a bulk content of a rare earth atom obtained by total dissolution under dissolution conditions which will be described below, that is, surface layer portion content/bulk content exceeds 1.0 and may be 1.5 or more. The fact that surface layer portion content/bulk content is larger than 1.0 means that in a particle constituting the hexagonal strontium ferrite powder, rare earth atoms are unevenly distributed in the surface layer portion (that is, more than an inside). Further, a ratio of a surface layer portion content of a rare earth atom obtained by partial dissolution under dissolution conditions which will be described below to a bulk content of a rare earth atom obtained by total dissolution under the dissolution conditions which will be described below, that is, surface layer portion content/bulk content may be, for example, 10.0 or less, 9.0 or less, 8.0 or less, 7.0 or less, 6.0 or less, 5.0 or less, or 4.0 or less. Note that, in the hexagonal strontium ferrite powder having a rare earth atom surface layer portion uneven distribution property, the rare earth atoms need only be unevenly distributed in the surface layer portion of a particle constituting the hexagonal strontium ferrite powder, and the surface layer portion content/bulk content is not limited to the exemplified upper limit or lower limit.

[0101] The partial dissolution and the total dissolution of the hexagonal strontium ferrite powder will be described below. For the hexagonal strontium ferrite powder that exists as a powder, the partially and totally dissolved sample powder is taken from the same lot of powder. On the other hand, for the hexagonal strontium ferrite powder included in the magnetic layer of the magnetic tape, a part of the hexagonal strontium ferrite powder taken out from the magnetic layer is subjected to partial dissolution, and the other part is subjected to total dissolution. The hexagonal strontium ferrite powder can be taken out from the magnetic layer by a method described in a paragraph 0032 of JP2015-91747A, for example.

[0102] The partial dissolution means that dissolution is performed such that, at the end of dissolution, the residue of the hexagonal strontium ferrite powder can be visually checked in the solution. For example, by partial dissolution, it is possible to dissolve a region of 10 to 20 mass % of the particle constituting the hexagonal strontium ferrite powder with the total particle being 100 mass %. On the other hand, the total dissolution means that dissolution is performed such that, at the end of dissolution, the residue of the hexagonal strontium ferrite powder cannot be visually checked in the solution.

[0103] The partial dissolution and measurement of the surface layer portion content are performed by the following method, for example. Note that the following dissolution conditions such as the amount of sample powder are exemplified, and dissolution conditions for partial dissolution and total dissolution can be employed in any manner.

[0104] A container (for example, a beaker) containing 12 mg of the sample powder and 10 mL of 1 mol/L hydrochloric acid is held on a hot plate at a set temperature of 70 C. for 1 hour. The obtained solution is filtered by a membrane filter of 0.1 m. Elemental analysis of the filtrated solution thus obtained is performed by an inductively coupled plasma (ICP) analyzer. In this way, the surface layer portion content of a rare earth atom with respect to 100 at % of an iron atom can be obtained. In a case where a plurality of kinds of rare earth atoms are detected by elemental analysis, the total content of all rare earth atoms is defined as the surface layer portion content. This also applies to the measurement of the bulk content.

[0105] On the other hand, the total dissolution and measurement of the bulk content are performed by the following method, for example.

[0106] A container (for example, a beaker) containing 12 mg of the sample powder and 10 mL of 4 mol/L hydrochloric acid is held on a hot plate at a set temperature of 80 C. for 3 hours. Thereafter, the same procedure as the partial dissolution and the measurement of the surface layer portion content is carried out, and the bulk content with respect to 100 at % of an iron atom can be obtained.

[0107] From the viewpoint of increasing the reproduction output in a case of reproducing data recorded on the magnetic tape, it is desirable that mass magnetization s of the ferromagnetic powder included in the magnetic tape is high. In this regard, the hexagonal strontium ferrite powder including a rare earth atom but not having the rare earth atom surface layer portion uneven distribution property tends to have a larger decrease in s than that of the hexagonal strontium ferrite powder including no rare earth atom. With respect to this, it is considered that the hexagonal strontium ferrite powder having a rare earth atom surface layer portion uneven distribution property is preferable in suppressing such a large decrease in s. In one aspect, s of the hexagonal strontium ferrite powder may be 45 A.Math.m.sup.2/kg or more, and may be 47 A.Math.m.sup.2/kg or more. On the other hand, from the viewpoint of noise reduction, s is preferably 80 A.Math.m.sup.2/kg or less and more preferably 60 A.Math.m.sup.2/kg or less. s can be measured using a well-known measuring device, such as a vibrating sample magnetometer, capable of measuring magnetic properties. In the present invention and the present specification, unless otherwise noted, the mass magnetization s is a value measured at a magnetic field intensity of 15 kOe. 1 [kOe] is 10.sup.6/4[A/m].

[0108] Regarding the content (bulk content) of a constituent atom of the hexagonal strontium ferrite powder, a strontium atom content may be, for example, in a range of 2.0 to 15.0 at % with respect to 100 at % of an iron atom. In one aspect, the hexagonal strontium ferrite powder may include only a strontium atom as a divalent metal atom. In another aspect, the hexagonal strontium ferrite powder may include one or more other divalent metal atoms in addition to a strontium atom. For example, a barium atom and/or a calcium atom may be included. In a case where the other divalent metal atoms other than the strontium atom are included, a content of the barium atom and a content of the calcium atom in the hexagonal strontium ferrite powder respectively can be, for example, in a range of 0.05 to 5.0 at % with respect to 100 at % of the iron atom.

[0109] As the hexagonal ferrite crystal structure, a magnetoplumbite type (also referred to as an M type), a W type, a Y type, and a Z type are known. The hexagonal strontium ferrite powder may have any crystal structure. The crystal structure can be checked by X-ray diffraction analysis. In the hexagonal strontium ferrite powder, a single crystal structure or two or more crystal structures may be detected by X-ray diffraction analysis. For example, according to one aspect, in the hexagonal strontium ferrite powder, only the M-type crystal structure may be detected by X-ray diffraction analysis. For example, M type hexagonal ferrite is represented by a composition formula of AFe.sub.12O.sub.19. Here, A represents a divalent metal atom, and in a case where the hexagonal strontium ferrite powder is the M type, A is only a strontium atom (Sr), or in a case where, as A, a plurality of divalent metal atoms are included, as described above, a strontium atom (Sr) accounts for the most on an at % basis. The divalent metal atom content of the hexagonal strontium ferrite powder is usually determined by the type of crystal structure of the hexagonal ferrite and is not particularly limited. The same applies to the iron atom content and the oxygen atom content. The hexagonal strontium ferrite powder may include at least an iron atom, a strontium atom, and an oxygen atom, and may further include a rare earth atom. Furthermore, the hexagonal strontium ferrite powder may or may not include atoms other than these atoms. As an example, the hexagonal strontium ferrite powder may include an aluminum atom (Al). A content of an aluminum atom may be, for example, 0.5 to 10.0 at % with respect to 100 at % of an iron atom. From the viewpoint of further suppressing a decrease in reproduction output during repeated reproduction, the hexagonal strontium ferrite powder includes an iron atom, a strontium atom, an oxygen atom, and a rare earth atom, and the content of atoms other than these atoms is preferably 10.0 at % or less, more preferably in a range of 0 to 5.0 at %, and may be 0 at % with respect to 100 at % of an iron atom. That is, in one aspect, the hexagonal strontium ferrite powder may not include atoms other than an iron atom, a strontium atom, an oxygen atom, and a rare earth atom. The content expressed in at % is obtained by converting a content of each atom (unit: mass %) obtained by totally dissolving the hexagonal strontium ferrite powder into a value expressed in at % using an atomic weight of each atom. Further, in the present invention and the present specification, the term not include for a certain atom means that a content measured by an ICP analyzer after total dissolution is 0 mass %. A detection limit of the ICP analyzer is usually 0.01 parts per million (ppm) or less on a mass basis. The term not included is used as a meaning including that an atom is included in an amount less than the detection limit of the ICP analyzer. In one aspect, the hexagonal strontium ferrite powder may not include a bismuth atom (Bi).

Metal Powder

[0110] Preferred specific examples of the ferromagnetic powder include a ferromagnetic metal powder. For details of the ferromagnetic metal powder, descriptions disclosed in paragraphs 0137 to 0141 of JP2011-216149A and paragraphs 0009 to 0023 of JP2005-251351A can be referred to, for example.

-Iron Oxide Powder

[0111] Preferred specific examples of the ferromagnetic powder include an &-iron oxide powder. In the present invention and the present specification, the term -iron oxide powder refers to a ferromagnetic powder in which an s-iron oxide crystal structure is detected as a main phase by X-ray diffraction analysis. For example, in a case where the highest intensity diffraction peak is attributed to an s-iron oxide crystal structure in an X-ray diffraction spectrum obtained by X-ray diffraction analysis, it is determined that the s-iron oxide crystal structure is detected as the main phase. As a method of manufacturing an -iron oxide powder, a manufacturing method from a goethite, a reverse micelle method, and the like are known. All of the manufacturing methods are well known. Regarding a method of manufacturing an -iron oxide powder in which a part of Fe is substituted with substitutional atoms such as Ga, Co, Ti, Al, or Rh, a description disclosed in J. Jpn. Soc. Powder Metallurgy Vol. 61 Supplement, No. S1, pp. S280 to S284, J. Mater. Chem. C, 2013, 1, pp. 5200 to 5206 can be referred to, for example. Note that the method of manufacturing the s-iron oxide powder capable of being used as the ferromagnetic powder in the magnetic layer of the magnetic tape is not limited to the methods described here.

[0112] An activation volume of the s-iron oxide powder is preferably in a range of 300 to 1500 nm.sup.3. The finely granulated s-iron oxide powder having an activation volume in the above range is suitable for manufacturing a magnetic tape exhibiting excellent electromagnetic conversion characteristics. The activation volume of the s-iron oxide powder is preferably 300 nm.sup.3 or more, and may be, for example, 500 nm.sup.3 or more. Further, from the viewpoint of further improving the electromagnetic conversion characteristics, the activation volume of the &-iron oxide powder is more preferably 1400 nm.sup.3 or less, still more preferably 1300 nm.sup.3 or less, still more preferably 1200 nm.sup.3 or less, and still more preferably 1100 nm.sup.3 or less.

[0113] An index for reducing thermal fluctuation, in other words, for improving the thermal stability may include the anisotropy constant Ku. The &-iron oxide powder preferably has Ku of 3.010+J/m.sup.3 or more, and more preferably has Ku of 8.010.sup.4 J/m.sup.3 or more. Ku of the -iron oxide powder may be, for example, 3.010.sup.5 J/m.sup.3 or less. Here, since higher Ku means higher thermal stability, which is preferable, a value thereof is not limited to the values exemplified above.

[0114] From the viewpoint of increasing the reproduction output in a case of reproducing data recorded on the magnetic tape, it is desirable that mass magnetization s of the ferromagnetic powder included in the magnetic tape is high. In this regard, in one aspect, s of the s-iron oxide powder may be 8 A.Math.m.sup.2/kg or more, and may be 12 A.Math.m.sup.2/kg or more. On the other hand, from the viewpoint of noise reduction, s of the s-iron oxide powder is preferably 40 A.Math.m.sup.2/kg or less and more preferably 35 A.Math.m.sup.2/kg or less.

[0115] In the present invention and the present specification, unless otherwise noted, an average particle size of various powders such as ferromagnetic powders is a value measured by the following method using a transmission electron microscope.

[0116] The powder is imaged at an imaging magnification of 100000 with a transmission electron microscope, the image is printed on photographic printing paper or displayed on a display so that the total magnification of 500000 to obtain an image of particles configuring the powder. A target particle is selected from the obtained image of particles, a contour of the particle is traced by a digitizer, and a size of the particle (primary particle) is measured. The primary particles are independent particles without aggregation.

[0117] The measurement described above is performed regarding 500 particles randomly extracted. An arithmetic average of the particle sizes of 500 particles thus obtained is an average particle size of the powder. As the transmission electron microscope, a transmission electron microscope H-9000 manufactured by Hitachi, Ltd. can be used, for example. In addition, the measurement of the particle size can be performed by well-known image analysis software, for example, image analysis software KS-400 manufactured by Carl Zeiss. An average particle size described in the columns of Examples which will be described below is a value measured by using a transmission electron microscope H-9000 manufactured by Hitachi, Ltd. as the transmission electron microscope, and image analysis software KS-400 manufactured by Carl Zeiss as the image analysis software, unless otherwise noted. In the present invention and the present specification, the powder means an aggregate of a plurality of particles. For example, the ferromagnetic powder means an aggregate of a plurality of ferromagnetic particles. Further, the aggregate of the plurality of particles not only includes an aspect in which particles constituting the aggregate directly come into contact with each other, but also includes an aspect in which a binding agent or an additive which will be described below is interposed between the particles. The term particle is used to describe a powder in some cases.

[0118] As a method of taking a sample powder from the magnetic tape in order to measure the particle size, a method disclosed in a paragraph 0015 of JP2011-048878A can be employed, for example.

[0119] In the present invention and the present specification, unless otherwise noted, (1) in a case where the shape of the particle observed in the particle image described above is a needle shape, a fusiform shape, or a columnar shape (here, a height is greater than a maximum major diameter of a bottom surface), the size (particle size) of the particles configuring the powder is shown as a length of a long axis configuring the particle, that is, a long axis length, (2) in a case where the shape of the particle is a plate shape or a columnar shape (here, a thickness or a height is smaller than a maximum major diameter of a plate surface or a bottom surface), the particle size is shown as a maximum major diameter of the plate surface or the bottom surface, and (3) in a case where the shape of the particle is a sphere shape, a polyhedron shape, or an amorphous shape, and the long axis configuring the particles cannot be specified from the shape, the particle size is shown as an equivalent circle diameter. The equivalent circle diameter refers to a value obtained by a circle projection method.

[0120] In addition, regarding an average acicular ratio of the powder, a length of a short axis, that is, a short axis length of the particles is measured in the measurement described above, a value of (long axis length/short axis length) of each particle is obtained, and an arithmetic average of the values obtained regarding 500 particles is calculated. Here, unless otherwise noted, in a case of (1), the short axis length as the definition of the particle size is a length of a short axis configuring the particle, in a case of (2), the short axis length is a thickness or a height, and in a case of (3), the long axis and the short axis are not distinguished, thus, the value of (long axis length/short axis length) is assumed as 1, for convenience.

[0121] In addition, unless otherwise noted, in a case where the shape of the particle is specified, for example, in a case of definition of the particle size (1), the average particle size is an average long axis length, and in a case of the definition (2), the average particle size is an average plate diameter. In a case of the definition (3), the average particle size is an average diameter (also referred to as an average particle diameter).

[0122] The content (filling percentage) of the ferromagnetic powder of the magnetic layer is preferably in a range of 50 to 90 mass % and more preferably in a range of 60 to 90 mass %, with respect to the total mass of the magnetic layer. A high filling percentage of the ferromagnetic powder in the magnetic layer is preferable from the viewpoint of improving the recording density.

Binding Agent

[0123] The magnetic tape can be a coating type magnetic tape, and include a binding agent in the magnetic layer. The binding agent is one or more resins. As the binding agent, various resins usually used as a binding agent of a coating type magnetic recording medium can be used. For example, as the binding agent, a resin selected from a polyurethane resin, a polyester resin, a polyamide resin, a vinyl chloride resin, an acrylic resin obtained by copolymerizing styrene, acrylonitrile, or methyl methacrylate, a cellulose resin such as nitrocellulose, an epoxy resin, a phenoxy resin, and a polyvinylalkylal resin such as polyvinyl acetal or polyvinyl butyral can be used alone or a plurality of resins can be mixed with each other to be used. Among these, a polyurethane resin, an acrylic resin, a cellulose resin, and a vinyl chloride resin are preferable. These resins may be homopolymers or copolymers. These resins can be used as the binding agent even in a non-magnetic layer and/or a back coating layer which will be described below. For the above binding agent, descriptions disclosed in paragraphs 0028 to 0031 of JP2010-24113A can be referred to. In addition, the binding agent may be a radiation curable resin such as an electron beam curable resin. For the radiation curable resin, descriptions disclosed in paragraphs 0044 and 0045 of JP2011-048878A can be referred to.

[0124] An average molecular weight of the resin used as the binding agent can be, for example, 10,000 to 200,000 as a weight-average molecular weight. The weight-average molecular weight of the present invention and the present specification is a value obtained by performing polystyrene conversion of a value measured by gel permeation chromatography (GPC) under the following measurement conditions. The weight-average molecular weight described in the columns of Examples described below is a value obtained by performing polystyrene conversion of a value measured under the following measurement conditions. The binding agent may be used in an amount of, for example, 1.0 to 30.0 parts by mass with respect to 100.0 parts by mass of the ferromagnetic powder. [0125] GPC device: HLC-8120 (manufactured by Tosoh Corporation) [0126] Column: TSK gel Multipore HXL-M (manufactured by Tosoh Corporation, 7.8 mm inner diameter (ID)30.0 cm) [0127] Eluent: tetrahydrofuran (THF)

Curing Agent

[0128] A curing agent can also be used together with the resin which can be used as the binding agent. As the curing agent, in one aspect, a thermosetting compound which is a compound in which curing reaction (crosslinking reaction) proceeds due to heating can be used, and in another aspect, a photocurable compound in which a curing reaction (crosslinking reaction) proceeds due to light irradiation can be used. The curing reaction proceeds in a magnetic layer forming step, whereby at least a part of the curing agent can be included in the magnetic layer in a state of being reacted (crosslinked) with other components such as the binding agent. The same applies to the layer formed using this composition in a case where the composition used to form the other layer includes a curing agent. The preferred curing agent is a thermosetting compound, and polyisocyanate is suitable for this. For details of the polyisocyanate, descriptions disclosed in paragraphs 0124 and 0125 of JP2011-216149A can be referred to. The curing agent can be used in the composition for forming a magnetic layer in an amount of, for example, 0 to 80.0 parts by mass, and preferably 50.0 to 80.0 parts by mass from the viewpoint of improving a strength of the magnetic layer, with respect to 100.0 parts by mass of the binding agent.

Additive

[0129] The magnetic layer may include one or more kinds of additives, as necessary. As the additive, a commercially available product can be appropriately selected and used according to a desired property. Alternatively, a compound synthesized by a well-known method can be used as the additive. The additive can be used in any amount. Examples of the additive include the curing agent described above. In addition, examples of the additive which can be included in the magnetic layer include a non-magnetic powder (for example, an inorganic powder or carbon black), a lubricant, a dispersing agent, a dispersing assistant, an antibacterial agent, an antistatic agent, an antioxidant, and the like. For the dispersing agent, descriptions disclosed in paragraphs 0061 and 0071 of JP2012-133837A can be referred to. The dispersing agent may be added to a composition for forming a non-magnetic layer. For the dispersing agent that can be added to the composition for forming a non-magnetic layer, a description disclosed in a paragraph 0061 of JP2012-133837A can be referred to. As the non-magnetic powder that can be contained in the magnetic layer, a non-magnetic powder which can function as an abrasive, or a non-magnetic powder which can function as a protrusion forming agent which forms protrusions appropriately protruded from the magnetic layer surface (for example, non-magnetic colloidal particles) is used. For example, for the abrasive, descriptions disclosed in paragraphs 0030 to 0032 of JP2004-273070A can be referred to. As the abrasive, it is preferable to use an abrasive having a specific surface area (hereinafter, referred to as a BET specific surface area) measured by a Brunauer-Emmett-Teller (BET) method of 14 m.sup.2/g or more and 40 m.sup.2/g or less. As protrusion forming agent, the colloidal particles are preferable, and, from the viewpoint of availability, inorganic colloidal particles are preferable, inorganic oxide colloidal particles are more preferable, and silica colloidal particles (colloidal silica) are still more preferable. An average particle size of the protrusion forming agent is preferably in a range of 30 to 200 nm, and more preferably in a range of 50 to 100 nm.

[0130] The magnetic layer described above can be provided on a surface of the non-magnetic support directly or indirectly through the non-magnetic layer.

Non-Magnetic Layer

[0131] Next, the non-magnetic layer will be described. The above magnetic tape may have a magnetic layer directly on the non-magnetic support, or may have a non-magnetic layer including a non-magnetic powder between the non-magnetic support and the magnetic layer. The non-magnetic powder used for the non-magnetic layer may be an inorganic substance powder (inorganic powder) or an organic substance powder (organic powder). In addition, the carbon black and the like can be used. Examples of the inorganic substance include metal, metal oxide, metal carbonate, metal sulfate, metal nitride, metal carbide, and metal sulfide. The non-magnetic powder can be purchased as a commercially available product or can be manufactured by a well-known method. For details thereof, descriptions disclosed in paragraphs 0146 to 0150 of JP2011-216149A can be referred to. For carbon black which can be used in the non-magnetic layer, descriptions disclosed in paragraphs 0040 and 0041 of JP201024113A can be referred to. The content (filling percentage) of the non-magnetic powder of the non-magnetic layer is preferably in a range of 50 to 90 mass % and more preferably in a range of 60 to 90 mass %, with respect to the total mass of the non-magnetic layer.

[0132] In one aspect, the non-magnetic layer can contain an Fe-based inorganic oxide powder as the non-magnetic powder. In the present invention and the present specification, the term Fe-based inorganic oxide powder refers to an inorganic oxide powder containing iron as a constituent element. Specific examples of the Fe-based inorganic oxide powder include an -iron oxide powder and a goethite powder. In the present invention and the present specification, the term -iron oxide powder refers to a non-magnetic powder in which an -iron oxide crystal structure is detected as a main phase by X-ray diffraction analysis. The -iron oxide powder is also generally called hematite or the like.

[0133] From the viewpoint of reducing the value of the wrinkle depth S.sub.A, the present inventor supposes that it is preferable that an Fe-based inorganic oxide powder having an average particle volume of 2.010.sup.6 m.sup.3 or less is used as the non-magnetic powder of the non-magnetic layer. Therefore, the average particle volume of the Fe-based inorganic oxide powder included in the non-magnetic layer is preferably 2.010.sup.6 m.sup.3 or less, more preferably 1.510.sup.6 m.sup.3 or less, and still more preferably 1.010.sup.6 m.sup.3 or less. The average particle volume may be, for example, 1.010.sup.9 m.sup.3 or more or 1.010.sup.8 m.sup.3 or more, or may be smaller than the values exemplified here.

[0134] In the present invention and the present specification, the average particle volume is a value obtained by the following method.

[0135] In order to observe the Fe-based inorganic oxide powder included in the non-magnetic layer of the magnetic tape, first, as a sample pretreatment, slicing is performed by a microtome method. The slicing is performed such that a slicing sample capable of observing a cross section in a thickness direction of the magnetic tape along the longitudinal direction of the magnetic tape can be obtained. In Examples and Comparative Examples described below, a Leica EM UC6 manufactured by Leica Biosystems Nussloch GmbH was used as a microtome in order to obtain the average particle volume of the Fe-based inorganic oxide powder.

[0136] A cross section of the obtained slicing sample is observed using a transmission electron microscope (TEM) at an acceleration voltage of 300 kV and a total magnification of 200,000 such that a range from the non-magnetic support to the magnetic layer is included. Thereby, a cross-sectional TEM image is obtained. As the transmission electron microscope, for example, JEM-2100Plus manufactured by JEOL Ltd. can be used. In Examples and Comparative Examples described below, in order to obtain the average particle volume of the Fe-based inorganic oxide powder, JEM-2100Plus manufactured by JEOL Ltd. was used as a transmission electron microscope.

[0137] In the obtained cross-sectional TEM image, 50 particles of the Fe-based inorganic oxide powder are specified with respect to the particles contained in the non-magnetic layer by using a microelectron beam diffraction method. The electron beam diffraction in the microelectron beam diffraction method is performed using a transmission electron microscope at an acceleration voltage of 200 kV and a camera length of 50 cm. In Examples and Comparative Examples described below, in order to perform the electron beam diffraction in the microelectron beam diffraction method, JEM-2100Plus manufactured by JEOL Ltd. was used as a transmission electron microscope.

[0138] After that, using 50 particles of the Fe-based inorganic oxide powder specified as described above, the average particle volume is obtained as follows.

[0139] First, a long axis length (hereinafter, referred to as DL) and a short axis length (hereinafter, referred to as DS) of each particle are measured.

[0140] The long axis length DL means the maximum of distances between two parallel lines drawn from all angles so as to be in contact with the contour of the particle (so-called maximum Feret's diameter).

[0141] In a case where a direction of the long axis length defined as described above is called a long axis direction, the short axis length DS means the maximum of lengths of the particles in a direction orthogonal to the long axis direction of the particles.

[0142] Next, an average long axis length DLave is obtained as an arithmetic average of the long axis lengths DL of the 50 measured particles. ave is an abbreviation for average.

[0143] In addition, an average short axis length DSave is obtained as an arithmetic average of the short axis lengths DS of the 50 measured particles.

[0144] From the average long axis length DLave and the average short axis length DSave, an average particle volume Vave is obtained by the following formula.

Vave=/6DSave.sup.2DLave

[0145] In addition, in one aspect, the non-magnetic layer can contain carbon black as the non-magnetic powder. An average particle size of the carbon black can be, for example, 10 nm or more and 50 nm or less. From the viewpoint of reducing the value of the wrinkle depth S.sub.A, the present inventor supposes that it is preferable that carbon black having a pH of 9.0 or less is used as the non-magnetic powder of the non-magnetic layer. Therefore, the pH of the carbon black contained in the non-magnetic layer is preferably 9.0 or less, more preferably 8.5 or less, still more preferably 8.0 or less, and still more preferably 7.5 or less. The pH may be, for example, 1.0 or more, 2.0 or more, 3.0 or more, 4.0 or more, 5.0 or more, or 6.0 or more, or may be smaller than the values exemplified here.

[0146] In the present invention and the present specification, the pH of the carbon black is a value measured according to a standard test method ASTM D1512.

[0147] The non-magnetic layer preferably contains at least one of an Fe-based inorganic oxide powder having an average particle volume of 2.010.sup.6 m.sup.3 or less or carbon black having a pH of 9.0 or less, and more preferably contains both. A content of an Fe-based inorganic oxide powder having an average particle volume of 2.010.sup.6 m.sup.3 or less with respect to 100.0 parts by mass of the total amount of the non-magnetic powder contained in the non-magnetic layer may be 50.0 parts by mass or more, 60.0 parts by mass or more, or 70.0 parts by mass or more, and for example, 90.0 parts by mass or less. A content of carbon black having a pH of 9.0 or less with respect to 100.0 parts by mass of the total amount of the non-magnetic powder contained in the non-magnetic layer may be 10.0 parts by mass or more or 20.0 parts by mass or more, and for example, 50.0 parts by mass or less, 40.0 parts by mass or less, or 30.0 parts by mass or less.

[0148] The non-magnetic layer can include a binding agent, and can also include an additive. For other details of the binding agent or the additive of the non-magnetic layer, a well-known technology regarding the non-magnetic layer can be applied. In addition, in regards to the type and the content of the binding agent, and the type and the content of the additive, for example, the well-known technology regarding the magnetic layer can be applied.

[0149] The non-magnetic layer of the magnetic tape also includes a substantially non-magnetic layer including a small amount of ferromagnetic powder as impurities, for example, or intentionally, together with the non-magnetic powder. Here, the substantially non-magnetic layer is a layer having a residual magnetic flux density equal to or smaller than 10 mT, a layer having a coercivity equal to or smaller than 7.96 kA/m (100 Oe), or a layer having a residual magnetic flux density equal to or smaller than 10 mT and a coercivity equal to or smaller than 7.96 kA/m (100 Oe). It is preferable that the non-magnetic layer does not have a residual magnetic flux density and coercivity.

Non-Magnetic Support

[0150] Next, the non-magnetic support (hereinafter, also simply referred to as a support) will be described. The width direction young's modulus of the non-magnetic support is as described above. Examples of the non-magnetic support include well-known components such as polyethylene terephthalate, polyethylene naphthalate, polyamide, polyamideimide, and aromatic polyamide subjected to biaxial stretching. Among these, polyethylene terephthalate, polyethylene naphthalate, and polyamide are preferable.

[0151] A corona discharge, a plasma treatment, an easy-bonding treatment, or a heat treatment may be performed on these supports in advance.

Back Coating Layer

[0152] The magnetic tape may or may not have a back coating layer including a non-magnetic powder on a surface side of the non-magnetic support opposite to a surface side having the magnetic layer. The back coating layer preferably contains one or both of carbon black and an inorganic powder. The back coating layer can include a binding agent, and can also include an additive. For details of the non-magnetic powder, the binding agent, and the additive of the back coating layer, a well-known technology regarding the back coating layer can be applied, and a well-known technology regarding the magnetic layer and/or the non-magnetic layer can be applied. For example, for the back coating layer, descriptions disclosed in paragraphs 0018 to 0020 of JP2006-331625A and page 4, line 65, to page 5, line 38, of U.S. Pat. No. 7,029,774B can be referred to.

Various Thicknesses

[0153] Regarding a thickness (total thickness) of the magnetic tape, it has been required to increase the recording capacity (increase the capacity) of the magnetic recording medium with the enormous increase in the amount of information in recent years. As means for increasing the capacity of a tape-shaped magnetic recording medium (that is, a magnetic tape), a thickness of the magnetic tape may be reduced to increase a length of the magnetic tape accommodated in one roll of a magnetic tape cartridge. From this point, the thickness (total thickness) of the magnetic tape is preferably 5.6 m or less, and more preferably 5.5 m or less, 5.4 m or less, 5.3 m or less, 5.2 m or less, 5.1 m or less, 5.0 m or less, 4.9 m or less, and 4.8 m or less in this order. In addition, from the viewpoint of ease of handling, the thickness of the magnetic tape is preferably 3.0 m or more, more preferably 3.5 m or more, and still more preferably 4.0 m or more.

[0154] The thickness (total thickness) of the magnetic tape can be measured by the following method.

[0155] Ten samples (for example, 5 to 10 cm in length) are cut out from any part of the magnetic tape, and these samples are stacked to measure the thickness. A value (thickness per sample) obtained by dividing the measured thickness by 1/10 is set as the total thickness. The thickness measurement can be performed using a well-known measuring instrument capable of measuring a thickness on the order of 0.1 m.

[0156] A thickness of the non-magnetic support is preferably 3.0 to 5.0 m.

[0157] A thickness of the magnetic layer can be optimized according to a saturation magnetization amount of a magnetic head used, a head gap length, a band of a recording signal, and the like, and is generally 0.01 m to 0.15 m, and, from the viewpoint of high-density recording, the thickness is preferably 0.02 m to 0.12 m and more preferably 0.03 m to 0.1 m. The magnetic layer need only be at least a single layer, the magnetic layer may be separated into two or more layers having different magnetic properties, and a configuration of a well-known multilayered magnetic layer can be applied as the magnetic layer. A thickness of the magnetic layer in a case where the magnetic layer is separated into two or more layers is a total thickness of the layers.

[0158] From the viewpoint of reducing the value of the wrinkle depth S.sub.A, it is preferable that the thickness of the non-magnetic layer is large. From such a viewpoint, the thickness of the non-magnetic layer is preferably 0.7 m or more and more preferably 0.8 m or more. The thickness of the non-magnetic layer may be, for example, 1.5 m or less or 1.0 m or less.

[0159] A thickness of the back coating layer is preferably 0.9 m or less and more preferably 0.1 to 0.7 m.

[0160] Various thicknesses such as the thickness of the magnetic layer and the like can be obtained by the following method.

[0161] A cross section of the magnetic tape in a thickness direction is exposed by an ion beam, and then the exposed cross section observation is performed using a scanning electron microscope or a transmission electron microscope. Various thicknesses can be obtained as an arithmetic average of thicknesses obtained at two optional points in the cross section observation. Alternatively, the various thicknesses can be obtained as a designed thickness calculated according to manufacturing conditions.

Manufacturing Step

Preparation of Composition for Forming Each Layer

[0162] A composition for forming the magnetic layer, the non-magnetic layer, and the back coating layer usually contains a solvent together with the various components described above. A solvent content of a composition for forming each layer is not particularly limited. As the solvent, one kind or two or more kinds of various organic solvents generally used for manufacturing a coating type magnetic recording medium can be used. Specifically, a ketone-based solvent such as acetone, methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, cyclohexanone, isophorone, and tetrahydrofuran, an alcohol-based solvent such as methanol, ethanol, propanol, butanol, isobutyl alcohol, isopropyl alcohol, and methyl cyclohexanol, an ester-based solvent such as methyl acetate, butyl acetate, isobutyl acetate, isopropyl acetate, ethyl lactate, and glycol acetate, a glycol ether solvent such as glycol dimethyl ether, glycol monoethyl ether, and dioxane, an aromatic hydrocarbon solvent such as benzene, toluene, xylene, cresol, and chlorobenzene, a chlorinated hydrocarbon solvent such as methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, ethylene chlorohydrin, and dichlorobenzene, N,N-dimethylformamide, hexane, and the like can be used in an arbitrary ratio. Among these, from the viewpoint of solubility of a binding agent usually used for a coating type magnetic recording medium, it is preferable that the composition for forming a magnetic layer contains one or more kinds of ketone-based solvents.

[0163] A step of preparing a composition for forming the magnetic layer, the non-magnetic layer, or the back coating layer can usually include at least a kneading step, a dispersing step, and, as necessary, a mixing step provided before and after these steps. Each step may be divided into two or more stages. Various components used in the preparation of the composition for forming each layer may be added at the beginning or during any step. In addition, each component may be separately added in two or more steps. For example, a binding agent may be added separately in a kneading step, a dispersing step, and a mixing step for adjusting a viscosity after dispersion. In the manufacturing step of the magnetic tape, a well-known manufacturing technology in the related art can be used in a part of the steps. In the kneading step, an open kneader, a continuous kneader, a pressure kneader, or a kneader having a strong kneading force such as an extruder can be used. Details of the kneading step are disclosed in JP1989-106338A (JP-H1-106338A) and JP1989-79274A (JP-H1-79274A). As a disperser, various well-known dispersers using a shearing force, such as a beads mill, a ball mill, a sand mill, or a homomixer, can be used. Dispersion beads can be preferably used for the dispersion. Examples of the dispersion beads include ceramic beads and glass beads, and zirconia beads are preferable. Two or more kinds of beads may be used in combination. A bead diameter (particle size) and a bead filling rate of the dispersion beads are not particularly limited and need only be set depending on a powder to be dispersed. The composition for forming each layer may be filtered by a well-known method before performing the coating step. The filtering can be performed by using a filter, for example. As the filter used in the filtering, a filter having a pore diameter of 0.01 to 3 m (for example, a filter made of glass fiber or a filter made of polypropylene) can be used, for example.

Coating Step, Cooling Step, and Heating and Drying Step

[0164] The magnetic layer can be formed by directly applying the composition for forming a magnetic layer onto the non-magnetic support or performing multilayer applying of the composition for forming a magnetic layer with the composition for forming a non-magnetic layer sequentially or simultaneously. For details of the coating for forming each layer, a description disclosed in a paragraph 0066 of JP2010.sup.231843A can be referred to.

[0165] The magnetic tape including the non-magnetic layer between the non-magnetic support and the magnetic layer can be preferably manufactured by sequential multilayer coating. A manufacturing step of performing the sequential multilayer coating can be performed as follows, for example. The non-magnetic layer is formed through a coating step of applying a composition for forming a non-magnetic layer onto a non-magnetic support to form a coating layer, and a heating and drying step of drying the formed coating layer by a heat treatment. Then, the magnetic layer is formed through a coating step of applying a composition for forming a magnetic layer onto the formed non-magnetic layer to form a coating layer, and a heating and drying step of drying the formed coating layer by a heat treatment.

[0166] In one aspect, it is possible to form a coating layer by performing the coating step using the composition for forming a non-magnetic layer, and to perform the cooling step of cooling the coating layer between the coating step and the heating and drying step in a non-magnetic layer forming step of the manufacturing method in which such sequential multilayer coating is performed.

[0167] Hereinafter, an example of the manufacturing step of the magnetic tape will be described with reference to FIG. 4. Note that the present invention is not limited to the following examples.

[0168] FIG. 4 is a schematic step diagram showing an example of a step of manufacturing a magnetic tape including a non-magnetic layer and a magnetic layer in this order on one surface of a non-magnetic support and a back coating layer on the other surface thereof. In the example shown in FIG. 4, an operation of feeding a non-magnetic support (elongated film) from a feeding part and winding the non-magnetic support around a winding part is continuously performed, and various treatments of coating, drying, and alignment are performed in each part or each zone shown in FIG. 4, and thus, it is possible to form a non-magnetic layer and a magnetic layer on one surface of the running non-magnetic support by sequential multilayer coating and to form a back coating layer on the other surface thereof. The example shown in FIG. 4 can be the same as the manufacturing step normally performed for manufacturing a coating type magnetic recording medium, except for including a cooling zone.

[0169] The composition for forming a non-magnetic layer is applied onto the non-magnetic support fed from the feeding part in a first coating part (coating step of composition for forming a non-magnetic layer).

[0170] After the coating step, a coating layer of the composition for forming a non-magnetic layer formed in the coating step is cooled in a cooling zone (cooling step). For example, the cooling step can be performed by allowing the non-magnetic support on which the coating layer is formed to pass through a cooling atmosphere. An atmosphere temperature of the cooling atmosphere may be preferably in a range of 10 C. to 0 C., and more preferably in a range of 5 C. to 0 C. The time for performing the cooling step (for example, time while any part of the coating layer is delivered to and sent from the cooling zone (hereinafter, also referred to as a staying time)) is not particularly limited. In the cooling step, cooled air may blow to the surface of the coating layer.

[0171] After the cooling zone, in a first heat treatment zone, the coating layer is heated after the cooling step to dry the coating layer (heating and drying step). The heating and drying treatment can be performed by allowing the non-magnetic support including the coating layer after the cooling step to pass through a heating atmosphere. An atmosphere temperature of the heating atmosphere here, and an atmosphere temperature of the heating atmosphere in the heating and drying step in a second heat treatment zone and the heating and drying step in a third heat treatment zone, which will be described below, are also referred to as a drying temperature. The drying temperature in each heat treatment zone can be, for example, 95 C. or higher or 100 C. or higher. In addition, the drying temperature in each heat treatment zone can be, for example, 140 C. or lower or 130 C. or lower. In addition, heated air may optionally blow to the surface of the coating layer.

[0172] Next, in a second coating part, the composition for forming a magnetic layer is applied onto the non-magnetic layer formed by performing the heating and drying step in the first heat treatment zone (coating step of composition for forming a magnetic layer).

[0173] After that, in an aspect of performing an alignment treatment, while the coating layer of the composition for forming a magnetic layer is in a wet state, an alignment treatment of the ferromagnetic powder in the coating layer is performed in an alignment zone. For the alignment treatment, various well-known technologies including a description disclosed in a paragraph 0067 of JP2010.sup.231843A can be used. For example, a vertical alignment treatment can be performed by a well-known method such as a method using a polar opposing magnet. In the alignment zone, a drying speed of the coating layer can be controlled depending on a temperature of dry air and an air volume and/or a transportation speed of the magnetic tape in the alignment zone. Further, the coating layer may be preliminarily dried before the transportation to the alignment zone.

[0174] The coating layer after the alignment treatment is subjected to the heating and drying step in the second heat treatment zone.

[0175] Next, in a third coating part, a composition for forming a back coating layer is applied onto a surface of the non-magnetic support opposite to the surface on which the non-magnetic layer and the magnetic layer are formed, to form a coating layer (coating step of composition for forming a back coating layer). After that, in the third heat treatment zone, the coating layer is heated and dried.

[0176] By the above step, it is possible to obtain the magnetic tape including the non-magnetic layer and the magnetic layer in this order on one surface of the non-magnetic support and the back coating layer on the other surface thereof.

[0177] Other steps

[0178] In the manufacturing step of the magnetic tape, a calendering treatment is usually performed in order to improve the surface smoothness of the magnetic tape. Strengthening the calendering treatment conditions can contribute to reduction of the value of the wrinkle depth S.sub.A. Specific examples of strengthening the calendering treatment conditions include increasing a calender pressure, increasing a calender temperature, and decreasing a calender speed. Regarding the calendering treatment conditions, the calender pressure (linear pressure) is preferably 300 to 500 kN/m, and more preferably 310 to 350 kN/m, the calender temperature (surface temperature of a calender roll) is preferably 95 C. to 120 C., and more preferably 100 C. to 120 C., and the calender speed is preferably 25 to 75 m/min.

[0179] For other various steps for manufacturing the magnetic tape, descriptions disclosed in paragraphs 0067 to 0070 of JP2010.sup.231843A can be referred to.

[0180] Through various steps, a long magnetic tape original roll can be obtained. The obtained magnetic tape original roll is cut (slit) by a well-known cutter, for example, to have a width of the magnetic tape to be accommodated in the magnetic tape cartridge. The width can be determined according to the standard, and is usually inches. 1 inch=2.54 cm.

[0181] A servo pattern is usually formed on the magnetic tape obtained by slitting. The term formation of servo pattern can also be referred to as recording of servo signal. The formation of the servo pattern is as described above.

Vertical Squareness Ratio

[0182] In one aspect, the vertical squareness ratio of the magnetic tape, may be, for example, 0.55 or more, and from the viewpoint of improving the electromagnetic conversion characteristics, the vertical squareness ratio is preferably 0.60 or more, more preferably 0.65 or more, and still more preferably 0.70 or more. In principle, the upper limit of the squareness ratio is 1.00 or less. The vertical squareness ratio of the magnetic tape may be 1.00 or less, 0.95 or less, 0.90 or less, 0.85 or less, or 0.80 or less. From the viewpoint of improving the electromagnetic conversion characteristics, a large value of the vertical squareness ratio of the magnetic tape is preferable. The vertical squareness ratio of the magnetic tape can be controlled by a well-known method such as performing a vertical alignment treatment.

[0183] In the present invention and the present specification, the term vertical squareness ratio refers to a squareness ratio measured in the vertical direction of the magnetic tape. The term vertical direction described regarding the squareness ratio refers to a direction orthogonal to the magnetic layer surface, and can also be referred to as a thickness direction. In the present invention and the present specification, the vertical squareness ratio is obtained by the following method.

[0184] A sample piece having a size capable of being introduced into a vibrating sample magnetometer is cut out from the magnetic tape to be measured. For this sample piece, using a vibrating sample magnetometer, a magnetic field is applied in the vertical direction (direction orthogonal to the magnetic layer surface) of the sample piece at a maximum applied magnetic field of 3979 kA/m, a measurement temperature of 296 K, and a magnetic field sweeping speed of 8.3 kA/m/sec, and the magnetization strength of the sample piece with respect to the applied magnetic field is measured. The measured value of the magnetization strength is obtained as a value after demagnetic field correction and as a value obtained by subtracting the magnetization of a sample probe of the vibrating sample magnetometer as a background noise. Assuming that the magnetization strength at the maximum applied magnetic field is Ms and the magnetization strength at zero applied magnetic field is Mr, a squareness ratio SQ is a value calculated as SQ=Mr/Ms. The measurement temperature refers to a temperature of the sample piece, and, by setting an atmosphere temperature around the sample piece to a measurement temperature, the temperature of the sample piece can be set to a measurement temperature by establishing a temperature equilibrium.

Magnetic Tape Cartridge

[0185] Another aspect of the present invention relates to a magnetic tape cartridge comprising the magnetic tape described above.

[0186] The details of the magnetic tape included in the above magnetic tape cartridge are as described above. The magnetic tape cartridge can be mounted on the magnetic tape apparatus comprising the magnetic head and used for recording and/or reproducing data.

[0187] In the magnetic tape cartridge, generally, the magnetic tape is accommodated inside a cartridge body in a state of being wound around a reel. The reel is rotatably provided inside the cartridge body. As the magnetic tape cartridge, a single reel type magnetic tape cartridge having one reel inside the cartridge body and a dual reel type magnetic tape cartridge having two reels inside the cartridge body are widely used. In a case where the single reel type magnetic tape cartridge is mounted on a magnetic tape apparatus for recording and/or reproducing data on the magnetic tape, the magnetic tape is pulled out of the magnetic tape cartridge to be wound around the reel on the magnetic tape apparatus side. A magnetic head is arranged on a magnetic tape transportation path from the magnetic tape cartridge to a winding reel. Sending and winding of the magnetic tape are performed between a reel (supply reel) on the magnetic tape cartridge side and a reel (winding reel) on the magnetic tape apparatus side. For example, during this time, data is recorded and/or reproduced as the magnetic head and the magnetic layer surface of the magnetic tape come into contact with each other to be slid on each other. With respect to this, in the dual reel type magnetic tape cartridge, both reels of the supply reel and the winding reel are provided in the magnetic tape cartridge.

[0188] In one aspect, the magnetic tape cartridge may include a cartridge memory. The cartridge memory can be, for example, a non-volatile memory, and, in one aspect, head tilt angle adjustment information is already recorded or the head tilt angle adjustment information is recorded. The head tilt angle adjustment information is information for adjusting the head tilt angle during running of the magnetic tape in the magnetic tape apparatus. For example, as the head tilt angle adjustment information, the value of the servo band interval at each position in the longitudinal direction of the magnetic tape during data recording can be recorded. For example, in a case of reproducing the data recorded on the magnetic tape, the value of the servo band interval can be measured during reproduction, and the head tilt angle can be changed by a control device of the magnetic tape apparatus such that the absolute value of the difference from the servo band interval during recording at the same longitudinal position recorded in the cartridge memory approaches zero. The head tilt angle may be, for example, the angle described below.

[0189] The magnetic tape and the magnetic tape cartridge can be suitability used in a magnetic tape apparatus (in other words, a magnetic recording and reproducing system) that records and/or reproduces data at different head tilt angles. In such a magnetic tape apparatus, in one aspect, it is possible to record and/or reproduce the data by changing the head tilt angle during running of the magnetic tape. For example, the head tilt angle can be changed according to the information on the dimensions in the width direction of the magnetic tape acquired during running of the magnetic tape. There is also a use form, for example, in which the head tilt angle in one recording and/or reproduction and the head tilt angle in subsequent recording and/or reproduction are changed, and then the head tilt angle is fixed without change during running of the magnetic tape for each recording and/or reproduction.

Magnetic Tape Apparatus

[0190] Still another aspect of the present invention relates to a magnetic tape apparatus including the magnetic tape described above. In the magnetic tape apparatus, recording of data on the magnetic tape and/or reproduction of data recorded on the magnetic tape can be performed, for example, as the magnetic layer surface of the magnetic tape and the magnetic head come into contact with each other to be slid on each other.

[0191] In one aspect, the magnetic tape is treated as a removable medium (so-called replaceable medium), and a magnetic tape cartridge accommodating the magnetic tape therein is inserted into the magnetic tape apparatus and taken out. In another aspect, the magnetic tape is not treated as a replaceable medium, the magnetic tape is wound around the reel of the magnetic tape apparatus comprising a magnetic head, and the magnetic tape is accommodated in the magnetic tape apparatus.

[0192] In the present invention and the present specification, the term magnetic tape apparatus means an apparatus capable of performing at least one of the recording of data on the magnetic tape or the reproduction of data recorded on the magnetic tape. Such an apparatus is generally called a drive.

Description of Head Tilt Angle

[0193] As described above, one example of the controller for the dynamic track position during running of the magnetic tape is to change the head tilt angle. Regarding this point, a configuration of the magnetic head, the head tilt angle, and the like will be described below. Further, the reason why it is possible to control the dynamic track position during running of the magnetic tape by tilting the axial direction of the module of the magnetic head against the width direction of the magnetic tape during running of the magnetic tape will also be described below.

[0194] The magnetic head may have one or more modules including an element array with a plurality of magnetic head elements between a pair of servo signal reading elements, and may have two or more or three or more modules. The total number of such modules may be, for example, 5 or less, 4 or less, or 3 or less, and the modules as many as the number exceeding the total number illustrated here may be included in the magnetic head. Arrangement examples of a plurality of modules include recording module-reproducing module (total number of modules: 2), and recording module-reproducing module-recording module (total number of modules: 3). Note that the present invention is not limited to the examples shown here.

[0195] Each module can include an element array with a plurality of magnetic head elements between a pair of servo signal reading elements, that is, an arrangement of the elements. A module having a recording element as the magnetic head element is a recording module for recording data on the magnetic tape. A module having a reproducing element as the magnetic head element is a reproducing module for reproducing data recorded on the magnetic tape. In the magnetic head, a plurality of modules are arranged, for example, in a recording and reproducing head unit such that axes of the element arrays of the respective modules are oriented in parallel. Such a term parallel does not necessarily mean only parallel in a strict sense, but includes a range of errors normally allowed in the technical field to which the present invention belongs. The range of errors can mean, for example, a range less than strictly parallel=10.

[0196] In each element array, the pair of servo signal reading elements and the plurality of magnetic head elements (that is, the recording element or the reproducing element) are usually arranged linearly to be spaced from each other. Here, the term arranged linearly means that each magnetic head element is arranged on a straight line connecting a central portion of one servo signal reading element and a central portion of the other servo signal reading element. The term axis of the element array in the present invention and the present specification means a straight line connecting a central portion of one servo signal reading element and a central portion of the other servo signal reading element.

[0197] Next, a configuration of a module and the like will be further described with reference to the drawings. Note that the form shown in the drawings is an example and does not limit the present invention.

[0198] FIG. 5 is a schematic view showing an example of the module of the magnetic head. The module shown in FIG. 5 has a plurality of magnetic head elements between a pair of servo signal reading elements (servo signal reading elements 1 and 2). The magnetic head element is also referred to as a channel. Ch in the figure is an abbreviation for channel. The module shown in FIG. 5 has a total of 32 magnetic head elements from Ch0 to Ch31.

[0199] In FIG. 5, L represents a distance between a pair of servo signal reading elements, that is, a distance between one servo signal reading element and the other servo signal reading element. In the module shown in FIG. 5, L represents a distance between the servo signal reading element 1 and the servo signal reading element 2. Specifically, it is a distance between a central portion of the servo signal reading element 1 and a central portion of the servo signal reading element 2. Such a distance can be measured, for example, by an optical microscope or the like.

[0200] FIG. 6 is an explanatory diagram of a relative positional relationship between the module and the magnetic tape during running of the magnetic tape in the magnetic tape apparatus. In FIG. 6, the dotted line A indicates the width direction of the magnetic tape. The dotted line B indicates the axis of the element array. The angle can be said to be a head tilt angle during running of the magnetic tape, and is an angle formed by the dotted line A and the dotted line B. In a case where the angle is 0 during running of the magnetic tape, a distance in the magnetic tape width direction between one servo signal reading element and the other servo signal reading element in the element array (hereinafter, also referred to as effective distance between servo signal reading elements) is L. On the other hand, in a case where the angle exceeds 0, the effective distance between the servo signal reading elements is Lcos, where Lcos is smaller than L. That is, Lcos<L.

[0201] As described above, during recording or reproduction, in a case where the magnetic head for recording or reproducing data records or reproduces data while being deviated from a target track position due to the width deformation of the magnetic tape, a phenomenon such as overwriting of recorded data or reproduction failure may occur. For example, in a case where the width of the magnetic tape contracts or expands, a phenomenon may occur in which the magnetic head element, which should perform recording or reproduction at a target track position, performs recording or reproduction at a different track position. In addition, in a case where the width of the magnetic tape expands, a phenomenon may occur in which the effective distance between the servo signal reading elements becomes shorter than an interval between two servo bands adjacent to each other with the data band interposed therebetween (also referred to as servo band interval or interval between servo bands, specifically, a distance between the two servo bands in the width direction of the magnetic tape), and data is not recorded or reproduced in a portion near an edge of the magnetic tape.

[0202] On the other hand, in a case where the element array is tilted at an angle exceeding , the effective distance between the servo signal reading elements becomes Lcos as described above. The larger the value of , the smaller the value of Lcos, and the smaller the value of , the larger the value of Lcos. Therefore, by changing the value of according to a degree of the dimension change (that is, contraction or extension) in the width direction of the magnetic tape, it is possible to make the effective distance between the servo signal reading elements approximate to or match with the interval between the servo bands. As a result, it is possible to prevent a phenomenon such as overwriting of recorded data or reproduction failure due to the fact that the magnetic head for recording or reproducing data records or reproduces data while being deviated from a target track position due to the width deformation of the magnetic tape during recording or reproduction, or to reduce a frequency of the occurrence of the phenomenon.

[0203] FIG. 7 is an explanatory diagram relating to a change in the angle during running of the magnetic tape. [0204] .sub.initial, which is an angle at the start of running, can be set to, for example, 0 or more or more than 0.

[0205] In FIG. 7, the central figure shows a state of the module at the start of running.

[0206] In FIG. 7, the right figure shows a state of the module in a case where the angle is set to an angle c, which is an angle larger than .sub.initial. The effective distance between the servo signal reading elements Lcos.sub.c is a value smaller than Lcos.sub.initial at the start of running of the magnetic tape. In a case where the width of the magnetic tape contracts during running of the magnetic tape, it is preferable to perform such angle adjustment.

[0207] On the other hand, in FIG. 7, the left figure shows a state of the module in a case where the angle is set to an angle .sub.c, which is an angle smaller than .sub.initial. The effective distance between the servo signal reading elements Lcos, is a value larger than Lcos.sub.initial at the start of running of the magnetic tape. In a case where the width of the magnetic tape expands during running of the magnetic tape, it is preferable to perform such angle adjustment.

[0208] As described above, changing the head tilt angle during running of the magnetic tape can contribute to prevention of the phenomenon such as overwriting of recorded data or reproduction failure due to the fact that the magnetic head for recording or reproducing data records or reproduces data while being deviated from a target track position due to the width deformation of the magnetic tape during recording or reproduction, or can contribute to reduction of the frequency of the occurrence of the phenomenon.

[0209] Meanwhile, for example, an off-track factor for which it is difficult to compensate by the controller for the dynamic track position as described above may be present. With respect to this, in the magnetic tape, it is supposed that the wrinkle depth S.sub.A being 10 m or less contributes to suppression of the occurrence of the off-track caused by such an off-track factor. It is considered that this makes it possible to improve the operational stability of the drive. Such a magnetic tape is preferable in order to further increase track density.

Magnetic Head

[0210] The magnetic tape apparatus may include a magnetic head. The configuration of the magnetic head and the angle , which is the head tilt angle, are as described above with reference to FIGS. 5 to 7. In a case where the magnetic head includes a reproducing element, a magnetoresistive (MR) element capable of sensitively reading information recorded on the magnetic tape is preferable as the reproducing element. As the MR element, various well-known MR elements (for example, a giant magnetoresistive (GMR) element and a tunnel magnetoresistive (TMR) element) can be used. Hereinafter, a magnetic head that records data and/or reproduces recorded data will also be referred to as a recording and reproducing head. An element for recording data (recording element) and an element for reproducing data (reproducing element) are collectively referred to as a magnetic head element.

[0211] In a case of recording data and/or reproducing recorded data, first, tracking using the servo signal can be performed. That is, by causing the servo signal reading element to follow a predetermined servo track, the magnetic head element can be controlled to pass on the target data track. Displacement of the data track is performed by changing a servo track read by the servo signal reading element in a tape width direction.

[0212] The recording and reproducing head can also perform recording and/or reproduction with respect to other data bands. In this case, the servo signal reading element need only be displaced to a predetermined servo band using the above described UDIM information to start tracking for the servo band.

[0213] In one aspect, in the magnetic tape apparatus, the head tilt angle can be changed during running of the magnetic tape in the magnetic tape apparatus. The head tilt angle is, for example, an angle formed by the axis of the element array with respect to the width direction of the magnetic tape. The angle is as described above. For example, by providing the recording and reproducing head unit of the magnetic head with an angle adjustment unit for adjusting the angle of the module of the magnetic head, the angle can be variably adjusted during running of the magnetic tape. Such an angle adjustment unit can include, for example, a rotation mechanism for rotating the module. A well-known technology can be applied to the angle adjustment unit.

[0214] Regarding the head tilt angle during running of the magnetic tape, in a case where the magnetic head includes a plurality of modules, it is possible to specify the angle described with reference to FIGS. 5 to 7 for randomly selected modules. .sub.initial, which is an angle at the start of running of the magnetic tape, can be set to 0 or more or more than 0. This is preferable in terms of adjustment ability to adjust the effective distance between the servo signal reading elements in response to the dimension change in the width direction of the magnetic tape, because the larger .sub.initial, the larger the amount of change in the effective distance between the servo signal reading elements with respect to the amount of change in the angle . From this point, .sub.initial is preferably 1 or more, more preferably 5 or more, and still more preferably 10 or more. On the other hand, for an angle (generally referred to as wrap angle) formed between the magnetic layer surface and the contact surface of the magnetic head in a case where the magnetic tape runs and comes into contact with the magnetic head, it is effective to keep the deviation with respect to the tape width direction small in order to improve the uniformity in the tape width direction of the friction generated by the contact between the magnetic head and the magnetic tape during running of the magnetic tape. In addition, it is desirable to increase the uniformity of the friction in the tape width direction from the viewpoint of the position followability and the running stability of the magnetic head. From the viewpoint of reducing the deviation of the wrap angle in the tape width direction, .sub.initial is preferably 45 or less, more preferably 40 or less, and still more preferably 35 or less.

[0215] Regarding the change in angle during running of the magnetic tape, in a case where the angle of the magnetic head changes from .sub.initial at the start of running while the magnetic tape runs in the magnetic tape apparatus for the recording of data on the magnetic tape and/or for the reproduction of data recorded on the magnetic tape, the maximum change amount 40 of the angle during the running of the magnetic tape is the larger value between 40max and 40 min calculated by the following equation. The maximum value of the angle during running of the magnetic tape is .sub.max, and the minimum value is .sub.min. Note that max is an abbreviation for maximum, and min is an abbreviation for minimum.

[00002]${}_{\max }={}_{\max }-{}_{\mathrm{initial}}$${}_{\min }={}_{\mathrm{initial}}-{}_{\min }$

[0216] In one aspect, may be more than 0.000, and, from the viewpoint of the adjustment ability to adjust the effective distance between the servo signal reading elements in response to the dimension change in the width direction of the magnetic tape, is preferably 0.001 or more and more preferably 0.010 or more. From the viewpoint of easiness of ensuring synchronization of the recorded data and/or the reproduced data between a plurality of magnetic head elements during the recording and/or reproduction of the data, is preferably 1.000 or less, more preferably 0.900 or less, still more preferably 0.800 or less, still more preferably 0.700 or less, and still more preferably 0.600 or less.

[0217] In the example shown in FIG. 6 and FIG. 7, the axis of the element array is tilted in the running direction of the magnetic tape. Note that the present invention is not limited to such an example. In the above-described magnetic tape apparatus, an embodiment in which the axis of the element array is tilted in a direction opposite to the running direction of the magnetic tape is also included in the present invention.

[0218] .sub.initial, which is the head tilt angle at the start of running of the magnetic tape, can be set by a control device of the magnetic tape apparatus or the like.

[0219] Regarding the head tilt angle during running of the magnetic tape, FIG. 8 is an explanatory diagram of a measuring method of the angle during running of the magnetic tape. The angle during running of the magnetic tape can be obtained, for example, by the following method. In a case where the angle during running of the magnetic tape is obtained by the following method, the angle is changed in a range of 0 to 90 during running of the magnetic tape. That is, in a case where the axis of the element array is tilted in the running direction of the magnetic tape at the start of running of the magnetic tape, the element array is not tilted such that the axis of the element array is tilted in the direction opposite to the running direction of the magnetic tape at the start of running of the magnetic tape, during running of magnetic tape, and in a case where the axis of the element array is tilted in the direction opposite to the running direction of the magnetic tape at the start of running of the magnetic tape, the element array is not tilted such that the axis of the element array is tilted in the running direction of the magnetic tape at the start of running of the magnetic tape, during running of the magnetic tape.

[0220] A phase difference (that is, a time difference) AT between the reproduction signals of the pair of servo signal reading elements 1 and 2 is measured. The measurement of AT can be performed by a measurement unit provided in the magnetic tape apparatus. A configuration of such a measurement unit is well-known. The distance L between the central portion of the servo signal reading element 1 and the central portion of the servo signal reading element 2 can be measured by an optical microscope or the like. In a case where the running speed of the magnetic tape is a speed v, the distance between the central portions of the two servo signal reading elements in the running direction of the magnetic tape is Lsin, and a relationship of Lsin=vT is established. Therefore, the angle during running of the magnetic tape can be calculated by the equation 0=arcsin (vT/L). The right figure of FIG. 8 shows an example in which the axis of the element array is tilted in the running direction of the magnetic tape. In this example, the phase difference (that is, the time difference) AT of the phase of the reproduction signal of the servo signal reading element 2 with respect to the phase of the reproduction signal of the servo signal reading element 1 is measured. In a case where the axis of the element array is tilted in the direction opposite to the running direction of the magnetic tape, can be obtained by the above-described method except for a point where AT is measured as the phase difference (that is, the time difference) of the phase of the reproduction signal of the servo signal reading element 1 with respect to the phase of the reproduction signal of the servo signal reading element 2.

[0221] A pitch suitable for a measurement pitch of the angle , that is, a measurement interval of the angle in the tape longitudinal direction can be selected according to a frequency of the tape width deformation in the tape longitudinal direction. As an example, the measurement pitch can be set to, for example, 250 m.

Configuration of Magnetic Tape Apparatus

[0222] FIG. 9 is a schematic view showing an example of the magnetic tape apparatus.

[0223] A magnetic tape apparatus 10 shown in FIG. 9 controls a recording and reproducing head unit 12 in accordance with an instruction from a control device 11, and records and reproduces data on a magnetic tape MT.

[0224] The magnetic tape apparatus 10 has a configuration capable of detecting and adjusting the tension applied in the longitudinal direction of the magnetic tape from spindle motors 17A and 17B for controlling rotation of a magnetic tape cartridge reel and a winding reel and driving devices 18A and 18B thereof.

[0225] The magnetic tape apparatus 10 has a configuration capable of loading a magnetic tape cartridge 13.

[0226] The magnetic tape apparatus 10 has a cartridge memory reading and writing device 14 capable of reading and writing a cartridge memory 131 in the magnetic tape cartridge 13.

[0227] From the magnetic tape cartridge 13 mounted on the magnetic tape apparatus 10, an end part or a leader pin of the magnetic tape MT is pulled out by an automatic loading mechanism or a manual operation, and the magnetic layer surface of the magnetic tape MT passes on the recording and reproducing head through guide rollers 15A and 15B in a direction contacting with a recording and reproducing head surface of the recording and reproducing head unit 12, and thus the magnetic tape MT is wound around a winding reel 16.

[0228] The rotation and torque of the spindle motor 17A and the spindle motor 17B are controlled by a signal from the control device 11, and the magnetic tape MT is run at any speed and tension. A servo pattern formed in advance on the magnetic tape can be used for a control of the tape speed and a control of the head tilt angle. In order to detect the tension, a tension detecting mechanism may be provided between the magnetic tape cartridge 13 and the winding reel 16. The tension may be controlled by using the guide rollers 15A and 15B in addition to the control by the spindle motors 17A and 17B.

[0229] The cartridge memory reading and writing device 14 is configured to be capable of reading out and writing information in the cartridge memory 131 in response to an instruction from the control device 11. As a communication method between the cartridge memory reading and writing device 14 and the cartridge memory 131, for example, an international organization for standardization (ISO) 14443 method can be employed.

[0230] The control device 11 includes, for example, a controller, a storage unit, a communication unit, and the like.

[0231] The recording and reproducing head unit 12 includes, for example, a recording and reproducing head, a servo tracking actuator that adjusts a position of the recording and reproducing head in the track width direction, a recording and reproducing amplifier 19, a connector cable for connection with the control device 11, and the like. The recording and reproducing head includes, for example, a recording element for recording data on the magnetic tape, a reproducing element for reproducing data on the magnetic tape, and a servo signal reading element for reading a servo signal recorded on the magnetic tape. For example, one or more recording elements, reproducing elements, and servo signal reading elements are mounted in one magnetic head. Alternatively, each element may be separately provided in a plurality of magnetic heads according to the running direction of the magnetic tape.

[0232] The recording and reproducing head unit 12 is configured to be capable of recording data on the magnetic tape MT in response to an instruction from the control device 11. In addition, the recording and reproducing head unit 12 is configured to be capable of reproducing the data recorded on the magnetic tape MT in response to an instruction from the control device 11.

[0233] The control device 11 has a mechanism for obtaining the running position of the magnetic tape from the servo signal read from the servo band in a case where the magnetic tape MT is run, and controlling the servo tracking actuator such that the recording element and/or the reproducing element is located at a target running position (track position). The track position is controlled by feedback control, for example. The control device 11 has a mechanism for obtaining a servo band interval from servo signals read from two adjacent servo bands in a case where the magnetic tape MT is run. The control device 11 can store the obtained information on the servo band interval in the storage unit inside the control device 11, the cartridge memory 131, an external connection device, or the like. In addition, the control device 11 can change the head tilt angle according to the dimension information in the width direction of the magnetic tape during running. Accordingly, the effective distance between the servo signal reading elements can be made to approximate to or match with the interval between the servo bands. The dimension information can be acquired by using a servo pattern formed in advance on the magnetic tape. For example, in this way, during running of the magnetic tape in the magnetic tape apparatus, the angle formed by the axis of the element array with respect to the width direction of the magnetic tape can be changed according to the dimension information in the width direction of the magnetic tape acquired during running. The head tilt angle can be adjusted, for example, by feedback control. For example, the adjustment of the head tilt angle can also be performed by the method disclosed in JP2016-524774A or US2019/0164573A1.

EXAMPLES

[0234] Hereinafter, the present invention will be described based on Examples. Note that the present invention is not limited to the embodiments shown in Examples. Parts and % in the following description mean parts by mass and mass %, respectively. The steps and evaluations in the following description were performed in an environment of a temperature of 23 C.1 C., unless otherwise noted. eq in the following description is an equivalent and is a unit that cannot be converted into an SI unit.

Ferromagnetic Powder

[0235] In Table 1, BaFe is a hexagonal barium ferrite powder (coercivity Hc: 196 kA/m, average particle size (average plate diameter) of 24 nm).

[0236] SrFel shown in Table 1 is a hexagonal strontium ferrite powder manufactured by the following method.

[0237] 1707 g of SrCO.sub.3, 687 g of H.sub.3BO.sub.3, 1120 g of Fe.sub.2O.sub.3, 45 g of Al(OH).sub.3, 24 g of BaCO.sub.3, 13 g of CaCO.sub.3, and 235 g of Nd.sub.2O.sub.3 were weighed and mixed by a mixer to obtain a raw material mixture.

[0238] The obtained raw material mixture was melted in a platinum crucible at a melting temperature of 1390 C., and a hot water outlet provided at a bottom of the platinum crucible was heated while stirring a melt, and the melt was discharged in a rod shape at about 6 g/sec. Hot water was rolled and quenched by a pair of water-cooling rollers to manufacture an amorphous body.

[0239] 280 g of the manufactured amorphous body was charged into an electric furnace, was heated to 635 C. (crystallization temperature) at a temperature rising rate of 3.5 C./min, and was kept at the same temperature for 5 hours to precipitate (crystallize) hexagonal strontium ferrite particles.

[0240] Next, a crystallized product obtained above including hexagonal strontium ferrite particles was coarsely pulverized in a mortar, and 1000 g of zirconia beads having a particle diameter of 1 mm and 800 ml of an acetic acid aqueous solution of 1% concentration were added to a glass bottle containing the product, to be dispersed by a paint shaker for 3 hours. Thereafter, the obtained dispersion liquid was separated from the beads, to be put in a stainless beaker. The dispersion liquid was statically left at a liquid temperature of 100 C. for 3 hours and subjected to a dissolving treatment of a glass component, and then the crystallized product was sedimented by a centrifugal separator to be washed by repeatedly performing decantation and was dried in a heating furnace at an in-furnace temperature of 110 C. for 6 hours to obtain a hexagonal strontium ferrite powder.

[0241] An average particle size of the hexagonal strontium ferrite powder obtained above was 18 nm, an activation volume was 902 nm.sup.3, an anisotropy constant Ku was 2.2 10.sup.5 J/m.sup.3, and a mass magnetization s was 49 A.Math.m.sup.2/kg.

[0242] 12 mg of a sample powder was taken from the hexagonal strontium ferrite powder obtained above, elemental analysis of the filtrated solution obtained by partially dissolving this sample powder under dissolution conditions illustrated above was performed by an ICP analyzer, and a surface layer portion content of a neodymium atom was determined.

[0243] Separately, 12 mg of a sample powder was taken from the hexagonal strontium ferrite powder obtained above, elemental analysis of the filtrated solution obtained by totally dissolving this sample powder under dissolution conditions illustrated above was performed by an ICP analyzer, and a bulk content of a neodymium atom was determined.

[0244] A content (bulk content) of a neodymium atom with respect to 100 at % of an iron atom in the hexagonal strontium ferrite powder obtained above was 2.9 at %. A surface layer portion content of a neodymium atom was 8.0 at %. It was confirmed that a ratio between a surface layer portion content and a bulk content, that is, surface layer portion content/bulk content was 2.8, and a neodymium atom was unevenly distributed in a surface layer of a particle.

[0245] The fact that the powder obtained above shows a crystal structure of hexagonal ferrite was confirmed by performing scanning with CuK rays under conditions of a voltage of 45 kV and an intensity of 40 mA and measuring an X-ray diffraction pattern under the following conditions (X-ray diffraction analysis). The powder obtained above showed a crystal structure of hexagonal ferrite of a magnetoplumbite type (M type). A crystal phase detected by X-ray diffraction analysis was a single phase of a magnetoplumbite type. [0246] PANalytical X'Pert Pro diffractometer, PIXcel detector [0247] Soller slit of incident beam and diffracted beam: 0.017 radians [0248] Fixed angle of dispersion slit: 1/4 degrees [0249] Mask: 10 mm [0250] Anti-scattering slit: 1/4 degrees [0251] Measurement mode: continuous [0252] Measurement time per stage: 3 seconds [0253] Measurement speed: 0.017 degrees per second [0254] Measurement step: 0.05 degrees

[0255] SrFe2 shown in Table 1 is a hexagonal strontium ferrite powder manufactured by the following method.

[0256] 1725 g of SrCO.sub.3, 666 g of H.sub.3BO.sub.3, 1332 g of Fe.sub.2O.sub.3, 52 g of Al(OH).sub.3, 34 g of CaCO.sub.3, and 141 g of BaCO.sub.3 were weighed and mixed by a mixer to obtain a raw material mixture.

[0257] The obtained raw material mixture was melted in a platinum crucible at a melting temperature of 1380 C., and a hot water outlet provided at a bottom of the platinum crucible was heated while stirring a melt, and the melt was discharged in a rod shape at about 6 g/sec. Hot water was rolled and quenched by a pair of water-cooling rollers to manufacture an amorphous body.

[0258] 280 g of the obtained amorphous body was charged into an electric furnace, was heated to 645 C. (crystallization temperature), and was held at the same temperature for 5 hours to precipitate (crystallize) hexagonal strontium ferrite particles.

[0259] Next, a crystallized product obtained above including hexagonal strontium ferrite particles was coarsely pulverized in a mortar, and 1000 g of zirconia beads having a particle diameter of 1 mm and 800 ml of an acetic acid aqueous solution of 1% concentration were added to a glass bottle containing the product, to be dispersed by a paint shaker for 3 hours. Thereafter, the obtained dispersion liquid was separated from the beads, to be put in a stainless beaker. The dispersion liquid was statically left at a liquid temperature of 100 C. for 3 hours and subjected to a dissolving treatment of a glass component, and then the crystallized product was sedimented by a centrifugal separator to be washed by repeatedly performing decantation and was dried in a heating furnace at an in-furnace temperature of 110 C. for 6 hours to obtain a hexagonal strontium ferrite powder.

[0260] An average particle size of the obtained hexagonal strontium ferrite powder was 19 nm, an activation volume was 1102 nm.sup.3, an anisotropy constant Ku was 2.010.sup.5 J/m.sup.3, and a mass magnetization s was 50 A.Math.m.sup.2/kg.

[0261] In Table 1, -iron oxide is an &-iron oxide powder manufactured by the following method.

[0262] 8.3 g of iron (III) nitrate nonahydrate, 1.3 g of gallium (III) nitrate octahydrate, 190 mg of cobalt (II) nitrate hexahydrate, 150 mg of titanium (IV) sulfate, and 1.5 g of polyvinylpyrrolidone (PVP) were dissolved in 90 g of pure water, and while the dissolved product was stirred using a magnetic stirrer, 4.0 g of an aqueous ammonia solution having a concentration of 25% was added to the dissolved product under a condition of an atmosphere temperature of 25 C. in an air atmosphere, and the dissolved product was stirred for 2 hours while maintaining a temperature condition of the atmosphere temperature of 25 C. A citric acid solution obtained by dissolving 1 g of citric acid in 9 g of pure water was added to the obtained solution, and the mixture was stirred for 1 hour. The powder sedimented after stirring was collected by centrifugal separation, was washed with pure water, and was dried in a heating furnace at an in-furnace temperature of 80 C.

[0263] 800 g of pure water was added to the dried powder, and the powder was dispersed again in water to obtain dispersion liquid. The obtained dispersion liquid was heated to a liquid temperature of 50 C., and 40 g of an aqueous ammonia solution having a concentration of 25% was dropwise added with stirring. After stirring for 1 hour while maintaining the temperature at 50 C., 14 mL of tetraethoxysilane (TEOS) was added dropwise and was stirred for 24 hours. A powder sedimented by adding 50 g of ammonium sulfate to the obtained reaction solution was collected by centrifugal separation, was washed with pure water, and was dried in a heating furnace at an in-furnace temperature of 80 C. for 24 hours to obtain a ferromagnetic powder precursor. The obtained ferromagnetic powder precursor was loaded into a heating furnace at an in-furnace temperature of 1000 C. in an air atmosphere and was heat-treated for 4 hours.

[0264] The heat-treated ferromagnetic powder precursor was put into an aqueous solution of 4 mol/L sodium hydroxide (NaOH), and the liquid temperature was maintained at 70 C. and was stirred for 24 hours, whereby a silicic acid compound as an impurity was removed from the heat-treated ferromagnetic powder precursor.

[0265] Thereafter, the ferromagnetic powder from which the silicic acid compound was removed was collected by centrifugal separation, and was washed with pure water to obtain a ferromagnetic powder.

[0266] The composition of the obtained ferromagnetic powder that was checked by high-frequency inductively coupled plasma-optical emission spectrometry (ICP-OES) has Ga, Co, and a Ti substitution type -iron oxide (-Ga.sub.0.28Co.sub.0.5Ti.sub.0.05Fe.sub.1.62O.sub.3). In addition, X-ray diffraction analysis was performed under the same condition as that described above for SrFel, and from a peak of an X-ray diffraction pattern, it was confirmed that the obtained ferromagnetic powder does not include -phase and -phase crystal structures, and has a single-phase and -phase crystal structure (-iron oxide crystal structure).

[0267] The obtained s-iron oxide powder had an average particle size of 12 nm, an activation volume of 746 nm.sup.3, an anisotropy constant Ku of 1.210.sup.5 J/m.sup.3, and a mass magnetization s of 16 A.Math.m.sup.2/kg.

[0268] An activation volume and an anisotropy constant Ku of the above hexagonal strontium ferrite powder and -iron oxide powder are values obtained by the method described above using a vibrating sample magnetometer (manufactured by Toei Industry Co., Ltd.) for each ferromagnetic powder.

[0269] In addition, a mass magnetization s is a value measured at a magnetic field intensity of 15 kOe using a vibrating sample magnetometer (manufactured by Toei Industry Co., Ltd.).

Example 1

1. Preparation of Alumina Dispersion (Abrasive Solution)

[0270] 3.0 parts of 2,3-dihydroxynaphthalene (manufactured by Tokyo Chemical Industry Co., Ltd.), 31.3 parts of a 32% solution (solvent is a mixed solvent of methyl ethyl ketone and toluene) of a polyester polyurethane resin having a SO.sub.3Na group as a polar group (UR-4800 manufactured by Toyobo Co., Ltd. (amount of a polar group: 80 meq/kg)), and 570.0 parts of a mixed solution of methyl ethyl ketone and cyclohexanone at 1:1 (mass ratio) as a solvent were mixed with respect to 100.0 parts of an alumina powder (HIT-80 manufactured by Sumitomo Chemical Co., Ltd.) having a pregelatinization ratio of about 65% and a BET specific surface area of 20 m.sup.2/g, and dispersed in the presence of zirconia beads by a paint shaker for 5 hours. After the dispersion, the dispersion liquid and the beads were separated by a mesh and an alumina dispersion was obtained.

2. Formulation of Composition for Forming Magnetic Layer

[0271] Magnetic Liquid [0272] Ferromagnetic powder (type: see Table 1): 100.0 parts [0273] SO.sub.3Na group-containing vinyl chloride copolymer: 10.0 parts [0274] Weight-average molecular weight: 70,000, SO.sub.3Na group: 0.2 meq/g [0275] SO.sub.3Na group-containing polyurethane resin: 4.0 parts [0276] Weight-average molecular weight: 70,000, SO.sub.3Na group: 0.2 meq/g [0277] Cyclohexanone: 150.0 parts [0278] Methyl ethyl ketone: 170.0 parts [0279] Abrasive solution [0280] Alumina dispersion prepared in the section 1:6.0 parts [0281] Other components [0282] Colloidal silica: 2.0 parts [0283] Average particle size: 100 nm [0284] Stearic acid: 10.0 parts [0285] Butyl stearate: 6.0 parts [0286] Polyisocyanate (CORONATE (registered trademark) manufactured by Tosoh Corporation): 2.5 parts [0287] Finishing additive solvent [0288] Cyclohexanone: 300.0 parts [0289] Methyl ethyl ketone: 140.0 parts

3. Formulation of Composition for Forming Non-Magnetic Layer

[0290] -Iron oxide powder (average particle volume: see Table 1): 100.0 parts [0291] Carbon black (average particle size: 20 nm, pH: see Table 1): 25.0 parts [0292] SO.sub.3 Na group-containing polyurethane resin: 18.0 parts [0293] Weight-average molecular weight: 70,000, SO.sub.3Na group: 0.2 meq/g [0294] Stearic acid: 1.0 part [0295] Cyclohexanone: 300.0 parts [0296] Methyl ethyl ketone: 300.0 parts

4. Formulation of Composition for Forming Back Coating Layer

[0297] -Iron oxide powder: 80.0 parts [0298] Average particle size (average long axis length): 0.15 m, average acicular ratio: 7, BET specific surface area: 52 m.sup.2/g [0299] Carbon black: 20.0 parts [0300] Average particle size: 20 nm [0301] Vinyl chloride copolymer: 13.0 parts [0302] Sulfonic acid base-containing polyurethane resin: 6.0 parts [0303] Phenylphosphonic acid: 3.0 parts [0304] Cyclohexanone: 355.0 parts [0305] Methyl ethyl ketone: 155.0 parts [0306] Stearic acid: 3.0 parts [0307] Butyl stearate: 3.0 parts [0308] Polyisocyanate: 5.0 parts
5. Preparation of composition for forming each layer

[0309] The composition for forming a magnetic layer was prepared by the following method.

[0310] The magnetic liquid was prepared by mixing various components of the magnetic liquid with a homogenizer and then dispersing the beads with zirconia beads having a bead diameter of 0.05 mm by a continuous horizontal beads mill for 10 minutes.

[0311] Using the beads mill, the above magnetic liquid was mixed with the above abrasive solution, the above other components, and the finishing additive solvent, and then treated (ultrasonically dispersed) using a batch type ultrasonic device (20 kHz, 300 W) for 0.5 minutes. Thereafter, filtration was performed using a filter having a pore diameter of 0.5 m to prepare a composition for forming a magnetic layer.

[0312] A composition for forming a non-magnetic layer was prepared by the following method.

[0313] The above components were dispersed for 24 hours using a batch type vertical sand mill. As dispersion beads, zirconia beads having a bead diameter of 0.1 mm were used. The obtained dispersion liquid was filtered using a filter having a pore diameter of 0.5 m to prepare a composition for forming a non-magnetic layer.

[0314] A composition for forming a back coating layer was prepared by the following method.

[0315] Various components excluding stearic acid, butyl stearate, polyisocyanate, and cyclohexanone were kneaded and diluted by an open kneader, and then subjected to a dispersion treatment of 12 passes using a horizontal beads mill and zirconia beads having a bead diameter of 1 mm, by setting a bead filling rate to 80 volume %, a circumferential speed of a rotor tip to 10 m/sec, and a retention time per pass to 2 minutes. Thereafter, the remaining components were added to the obtained dispersion liquid, and the mixture was stirred by a disper. The dispersion liquid thus obtained was filtered using a filter having a pore diameter of 1 m to prepare a composition for forming a back coating layer.

6. Manufacture of Magnetic Tape

[0316] A magnetic tape was manufactured according to the manufacturing step shown in FIG. 4. The details are as follows.

[0317] A polyethylene naphthalate support having a thickness of 3.7 m was fed from the feeding part, and the composition for forming a non-magnetic layer was applied onto one surface thereof so that the thickness after drying is the thickness shown in Table 1 in the first coating part, to form a coating layer. The cooling step was performed by allowing the formed coating layer to pass through the cooling zone in which the atmosphere temperature was adjusted to 0 C. for the staying time of 5 seconds while the coating layer is in a wet state, and then the heating and drying step was performed by allowing the coating layer to pass through the first heat treatment zone with the drying temperature of 105 C. (atmosphere temperature, the same applies hereinafter), to form a non-magnetic layer.

[0318] After that, the composition for forming a magnetic layer prepared as described above was applied onto the non-magnetic layer so that the thickness after drying is 0.1 m in the second coating part, to form a coating layer. The vertical alignment treatment was performed in the alignment zone by applying a magnetic field having a magnetic field intensity of 0.7 T onto the surface of the coating layer of the composition for forming a magnetic layer in the vertical direction while the coating layer is in a wet state, and then the coating layer was dried in the second heat treatment zone with the drying temperature of 105 C.

[0319] After that, in the third coating part, the composition for forming a back coating layer prepared as described above was applied onto the surface of the polyethylene naphthalate non-magnetic support opposite to the surface on which the non-magnetic layer and the magnetic layer are formed, so that the thickness after drying is 0.3 m, to form a coating layer, and the formed coating layer was dried in the third heat treatment zone with the drying temperature of 105 C.

[0320] After that, a calendering treatment (surface smoothing treatment) was performed using a calender roll formed of only metal rolls under calendering treatment conditions of a calender pressure of 320 kN/m, a calender temperature of 100 C., and a calender speed shown in Table 1.

[0321] After that, a heat treatment was performed for 36 hours in an environment of an atmosphere temperature of 70 C. After the heat treatment, the resultant was slit to have inches width to manufacture a magnetic tape.

[0322] A servo signal was recorded on the magnetic layer of the magnetic tape obtained above by a commercially available servo writer in a state where the magnetic layer was demagnetized, to obtain a magnetic tape having a data band, a servo band, and a guide band in an arrangement according to a linear tape-open (LTO) Ultrium format and having a servo pattern (timing-based servo pattern) in an arrangement and a shape according to the LTO Ultrium format on the servo band. The servo pattern thus formed is a servo pattern according to the description in Japanese industrial standards (JIS) X6175: 2006 and Standard ECMA-319 (June 2001). The total number of servo bands is 5, and the total number of data bands is 4. In this way, a magnetic tape (960 m in length) on which the servo signal was recorded was manufactured. In the magnetic layer of the magnetic tape manufactured in this way, the data band and the servo band are arranged as shown in FIG. 1, and the servo pattern is arranged as shown in FIG. 2.

Examples 2 to 18 and Comparative Examples 1 to 7

[0323] A magnetic tape was obtained by the method described for Example 1 except that the items shown in Table 1 were changed as shown in Table 1.

[0324] For each of Examples and Comparative Examples, four magnetic tapes having a length of 960 m were manufactured, and each of which was used for evaluation of (1) to (4) below.

Evaluation Method

(1) Wrinkle Depth S.SUB.A .and Arithmetic Average of Deviation Amounts

[0325] For each of the magnetic tapes of Examples and Comparative Examples, the wrinkle depth S.sub.A and the arithmetic average of the deviation amounts were obtained by the measuring method described above. In the measurement of the servo band interval, after the measurement of the servo band interval (all LPOS words) between SB1 and SB2 was performed, the measurement of the servo band interval (all LPOS words) between SB0 and SB1, the measurement of the servo band interval (all LPOS words) between SB2 and SB3, and the measurement of the servo band interval (all LPOS words) between SB3 and SB4 were sequentially performed. In the measurement of the wrinkle depth S.sub.A, the measurement was performed by causing the magnetic tape to cross the jig as shown in FIG. 3.

(2) Width Direction Young's Modulus of Magnetic Tape

[0326] The width direction young's modulus of each magnetic tape of Examples and Comparative Examples was obtained by the following method in a measurement environment of an atmosphere temperature of 23 C.1 C. and a relative humidity of 50%5%.

[0327] A sample piece is cut out from the magnetic tape. The cut-out sample piece is pulled in the width direction by the universal tensile test device (Tensilon manufactured by Toyo Baldwin Co., Ltd) under the conditions of a distance between chucks of 100 mm, a tensile speed of 10 mm/min, and a chart speed of 500 mm/min. Young's moduli in a width direction of the sample piece are calculated from a tangent line of a rising portion of a load-elongation curve thus obtained.

[0328] The width direction young's modulus of the support shown in Table 1 is a value obtained by the following method in a measurement environment of an atmosphere temperature of 23 C.1 C. and a relative humidity of 50%5%.

[0329] A sample piece is cut out from the support film original roll used for the manufacture of each magnetic tape of Examples and Comparative Examples. The cut-out sample piece is pulled in the width direction by the universal tensile test device (Tensilon manufactured by Toyo Baldwin Co., Ltd) under the conditions of a distance between chucks of 100 mm, a tensile speed of 10 mm/min, and a chart speed of 500 mm/min. Young's moduli in a width direction of the sample piece are calculated from a tangent line of a rising portion of a load-elongation curve thus obtained.

(3) Thickness of Non-Magnetic Layer

[0330] Regarding the thicknesses of the magnetic layer, the non-magnetic layer, and the back coating layer of each of the magnetic tapes of Examples and Comparative Examples, cross-sectional observation was performed as described above, and it was confirmed that the thickness of the non-magnetic layer was the value shown in Table 1 and the respective thicknesses of the magnetic layer and the back coating layer were the thicknesses described above.

(4) Recording and Reproducing Performance

[0331] The recording and reproducing performance of each magnetic tape of Examples and Comparative Examples was evaluated by the following method.

[0332] As the magnetic head, a magnetic head comprising a reproducing module including an element array with 10 channels or more of a reproducing element having a reproducing element width of 0.2 m or less between a pair of servo signal reading elements, and a recording module including an element array with 10 channels or more of a recording element having a recording element width, which is equal to or more than 1.5 times the reproducing element width, between a pair of servo signal reading elements was used. In the element array, an interval between two adjacent elements (that is, two adjacent reproducing elements and two adjacent recording elements) in the head width direction was 40 m or more.

[0333] The environment for recording and reproducing the data was such that a temperature is 20 C. to 25 C. and a relative humidity is 40% to 60%. Under such an environment, a magnetic tape apparatus in which the magnetic tape and the magnetic head were mounted to a tape transport system (reel tester) was placed for 24 hours or longer, and then data was recorded and reproduced. The tape transport system of the magnetic tape apparatus is mounted to a recording and reproducing amplifier capable of driving the magnetic head element (specifically, a recording element and a reproducing element) of the magnetic head. The recording and reproducing amplifier can be controlled from a personal computer (PC) via a controller. The magnetic head is mounted on an actuator (piezo motor or voice coil motor (VCM)) that operates in the tape width direction, and can be servo-followed such that the magnetic head is located at a certain track position during tape running based on a servo signal of the magnetic tape. In addition, the dynamic track position can be controlled by changing the head tilt angle of the magnetic head such that a difference between reading position error signals (PES) (difference between PES1 and PES2) in the width direction based on the servo signals obtained by two upper and lower servo signal reading elements is constant. During the following recording and reproduction, the servo-following described above and the dynamic track position control (head tilt angle change) described above were executed. The recording and reproduction of the data were executed in detail as follows.

[0334] A signal was recorded by the recording element while the magnetic tape was run at a constant speed of 5 m/sec. As a bit sequence to be recorded, a 255-bit pseudo random bit sequence (PRBS) generated according to a generating polynomial x{circumflex over ()}8+x{circumflex over ()}6+x{circumflex over ()}5+x{circumflex over ()}4+1 was used. The symbol {circumflex over ()} represents a power. A linear recording density was set to 600 kbpi. The unit kbpi is a unit of the linear recording density (cannot be converted into an SI unit system). Single (shingled) recording of three or more tracks was performed such that a difference of (PES1+PES2)/2 between adjacent tracks was 1.5 times a reproduction track width.

[0335] A magnetization pattern recorded on the magnetic tape was reproduced by the reproducing element immediately after recording (that is, the reproducing element with the same channel number), and the signal was amplified by the reproducing amplifier. The reproduction signal was decoded into a bit sequence based on phase lock loop (PLL) and auto gain control (AGC) processing, followed by a data dependent noise predictive maximum likelihood (DD-NPML) signal processing. Bit-by-bit comparison was made between the recorded bit sequence and the reproduced and decoded bit sequence, and in a case where the bits were different from each other, one-bit-error was counted. Data comparison was made over 10 Mbit, and a value obtained by dividing the accumulated error bit count by 10 Mbit was defined as a bit error rate. It was confirmed that the reproduction signal immediately after recording had a bit error rate of 1/1000 or less in all channels.

[0336] Next, the magnetic tape was stored for 10 days in an environment of a temperature of 60 C. and a relative humidity of 20% in a state of being wound around a reel of the reel tester. A storage condition of storage for 10 days in an environment of a temperature of 60 C. and a relative humidity of 20% is employed as an example of storage conditions in an accelerated environment corresponding to long-term storage of data called archive.

[0337] After the above-mentioned storage, the magnetic tape was taken out from the storage environment and placed 24 hours or longer in an environment of a temperature of 20 C. to 25 C. and a relative humidity of 40% to 60% while being mounted to the same magnetic tape apparatus as the magnetic tape apparatus used before the storage, and then the data track recorded before the storage was reproduced (no recording was performed) in the same environment. In this case, the reproduction was performed only on the data tracks in which the data tracks were recorded on both sides. The bit error rates of all the channels were calculated, and the recording and reproducing performance was evaluated according to the following evaluation standard, with channels with a bit error rate of 1/100 or higher regarded as defective channels.

Evaluation Standard

[0338] A: A ratio of the number of defective channels to the total number of channels was less than 5%.

[0339] B: A ratio of the number of defective channels to the total number of channels was 5% or more and less than 10%.

[0340] C: A ratio of the number of defective channels to the total number of channels was 10% or more.

[0341] The above results are shown in Table 1 (Tables 1-1 to 1-5).

TABLE-US-00001 TABLE 1-1 Unit Example 1 Example 2 Example 3 Example 4 Example 5 Magnetic layer Ferromagnetic powder Type BaFe BaFe BaFe BaFe BaFe Non-magnetic layer Thickness m 0.7 0.7 0.7 0.8 1.0 -Iron oxide powder Average m.sup.3 2.0 10.sup.6 2.0 10.sup.6 2.0 10.sup.6 2.0 10.sup.6 2.0 10.sup.6 particle volume Carbon black pH 9.0 9.0 9.0 9.0 9.0 Support Width direction young's modulus GPa 4.0 4.0 4.0 4.0 4.0 Magnetic tape Width direction young's modulus GPa 4.0 4.0 4.0 4.0 4.0 Calendering treatment Speed m/min 70 50 30 70 70 condition Wrinkle depth S.sub.A m 10 8 7 8 7 Arithmetic average of m 0.40 0.35 0.30 0.35 0.36 deviation amounts Recording and reproducing B B B B B performance

TABLE-US-00002 TABLE 1-2 Unit Example 6 Example 7 Example 8 Example 9 Example 10 Magnetic layer Ferromagnetic powder Type BaFe BaFe BaFe BaFe BaFe Non-magnetic layer Thickness m 0.7 0.7 0.7 0.7 1.0 -Iron oxide powder m.sup.3 1.0 10.sup.6 2.0 10.sup.6 2.0 10.sup.6 1.0 10.sup.6 1.0 10.sup.6 Average particle volume Carbon black pH 9.0 7.5 9.0 7.5 7.5 Support Width direction young's modulus GPa 4.0 4.0 10.0 10.0 10.0 Magnetic tape Width direction young's modulus GPa 4.0 4.0 10.0 10.0 10.0 Calendering treatment Speed m/min 70 70 70 70 70 condition Wrinkle depth S.sub.A m 8 8 7 5 2 Arithmetic average of m 0.35 0.35 0.30 0.30 0.20 deviation amounts Recording and B B B B A reproducing performance

TABLE-US-00003 TABLE 1-3 Unit Example 11 Example 12 Example 13 Example 14 Example 15 Magnetic layer Ferromagnetic powder Type BaFe BaFe BaFe BaFe BaFe Non-magnetic layer Thickness m 0.8 1.0 0.8 0.8 0.8 -Iron oxide powder m.sup.3 2.0 10.sup.6 1.0 10.sup.6 1.0 10.sup.6 1.0 10.sup.6 1.0 10.sup.6 Average particle volume Carbon black pH 9.0 9.0 7.5 7.5 7.5 Support Width direction young's modulus GPa 8.0 10.0 4.0 4.0 4.0 Magnetic tape Width direction young's modulus GPa 8.0 10.0 4.0 4.0 4.0 Calendering treatment Speed m/min 70 70 70 50 30 condition Wrinkle depth S.sub.A m 7 5 7 4 3 Arithmetic average of m 0.30 0.30 0.30 0.25 0.20 deviation amounts Recording and B B B A A reproducing performance

TABLE-US-00004 TABLE 1-4 Unit Example 16 Example 17 Example 18 Magnetic layer Ferromagnetic powder Type SrFe1 SrFe2 -Iron oxide Non-magnetic layer Thickness m 0.7 0.7 0.7 -Iron oxide powder Average m.sup.3 2.0 10.sup.6 2.0 10.sup.6 2.0 10.sup.6 particle volume Carbon black pH 9.0 9.0 9.0 Support Width direction young's modulus GPa 4.0 4.0 4.0 Magnetic tape Width direction young's modulus GPa 4.0 4.0 4.0 Calendering treatment condition Speed m/min 70 70 70 Wrinkle depth S.sub.A m 10 10 10 Arithmetic average of deviation m 0.40 0.40 0.40 amounts Recording and reproducing B B B performance

TABLE-US-00005 TABLE 1-5 Comparative Comparative Comparative Comparative Comparative Comparative Comparative Unit Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Magnetic layer Ferromagnetic BaFe BaFe BaFe BaFe BaFe BaFe BaFe powder Type Non-magnetic Thickness m 0.7 0.7 0.7 0.6 0.5 0.7 0.6 layer -Iron oxide m.sup.3 2.5 10.sup.6 2.5 10.sup.6 2.5 10.sup.6 2.5 10.sup.6 2.5 10.sup.6 2.0 10.sup.6 2.0 10.sup.6 powder Average particle volume Carbon black pH 11.0 11.0 11.0 11.0 11.0 9.0 9.0 Support Width direction GPa 3.0 3.0 3.0 4.0 4.0 3.0 3.0 young's modulus Magnetic tape Width direction GPa 3.0 3.0 3.0 4.0 4.0 3.0 3.0 young's modulus Calendering Speed m/min 100 80 70 70 70 70 70 treatment condition Wrinkle depth m 15 14 13 14 15 13 15 S.sub.A Arithmetic m 1.00 0.90 0.80 0.90 1.00 0.80 1.00 average of deviation amounts Recording and C C C C C C C reproducing performance

[0342] As shown in Table 1, the magnetic tapes of Examples showed superior recording and reproducing performance after being stored in an accelerated environment equivalent to long-term storage as compared with the magnetic tapes of Comparative Examples. From this result, it can be confirmed that the magnetic tapes of Examples contributed to the improvement of the operational stability of the drive (magnetic tape apparatus).

[0343] A magnetic tape was manufactured by the method described in Example 1, except that the vertical alignment treatment was not performed in a case of manufacturing the magnetic tape.

[0344] A sample piece was cut out from the magnetic tape. For this sample piece, a vertical squareness ratio obtained by the method described above using a TM-TRVSM5050-SMSL type manufactured by Tamakawa Co., Ltd. as a vibrating sample magnetometer was 0.55.

[0345] The vertical squareness ratio similarly obtained for the sample piece cut out from the magnetic tape of Example 1 was 0.70.

[0346] Each of the above two magnetic tapes was mounted to a reel tester of inches, and electromagnetic conversion characteristics (signal-to-noise ratio (SNR)) were evaluated by the following method. As a result, for the magnetic tape of Example 1, a value of SNR higher by 6 dB was obtained as compared with the magnetic tape manufactured without the vertical alignment treatment.

[0347] In an environment of a temperature of 23 C. and a relative humidity of 50%, a tension of 0.7 N (Newton) was applied in the longitudinal direction of the magnetic tape, and recording and reproduction were performed for 10 passes. A relative speed between the magnetic tape and the magnetic head was set to 6 m/sec, and recording was performed by using a metal-in-gap (MIG) head (a gap length of 0.15 m and a track width of 1.0 m) as a recording head and setting a recording current to an optimal recording current of each magnetic tape. Reproduction was performed by using a giant-magnetoresistive (GMR) head (an element thickness of 15 nm, a shield interval of 0.1 m, and a reproducing element width of 0.8 m) as a reproducing head. The head tilt angle was set to 0. A signal having a linear recording density of 300 kfci was recorded, and measurement regarding a reproduction signal was performed with a spectrum analyzer manufactured by Shibasoku Co., Ltd. The unit kfci is a unit of a linear recording density (cannot be converted into an SI unit system). As the signal, a portion where the signal was sufficiently stable after start of the running of the magnetic tape was used.

[0348] One aspect of the present invention is useful in various data storage technical fields.