JP6677339B1 - Magnetic recording media - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic recording medium capable of suppressing a dimensional change in a width direction by adjusting a tension applied in a longitudinal direction of a tape. It has a layer structure having a magnetic layer and a base layer in this order, the average thickness tT is tT ≦ 5.5 μm, and the dimensional change amount Δw in the width direction with respect to the tension change in the longitudinal direction is 660 ppm / N ≦ Δw. There is also provided a magnetic recording medium in which the nonmagnetic layer has an average thickness tn of tn ≦ 1.0 μm. The average thickness tT may be tT ≦ 5.3 μm. The average thickness tn of the nonmagnetic layer may be tn ≦ 0.9 μm. [Selection diagram] Fig. 1

Description

  The present technology relates to a magnetic recording medium.

  2. Description of the Related Art In recent years, in a magnetic tape (magnetic recording medium) used as a data storage for a computer, a track width and a distance between adjacent tracks are extremely narrow in order to improve a data recording density. As described above, when the track width and the distance between the tracks are reduced, the maximum allowable change in the dimensional change of the tape itself due to environmental factors such as temperature and humidity changes becomes smaller.

Several techniques for reducing the amount of dimensional change have been proposed so far. For example, in the magnetic tape medium disclosed in Patent Document 1, X is 850 kg / mm ² or more, where X is the Young's modulus in the width direction of the nonmagnetic support and Y is the Young's modulus in the width direction of the back layer. Or less than 850 kg / mm ^2, X × Y is 6 × 10 ⁵ or more, and Y / Z is 6.0 or less when the Young's modulus in the width direction of the layer including the magnetic layer is Z. It is characterized by being.

JP 2005-332510 A

  An object of the present technology is to provide a magnetic recording medium that can suppress a dimensional change in a width direction by adjusting a tension applied in a longitudinal direction of a tape.

The present technology has a layer structure having a magnetic layer, a non-magnetic layer, a base layer, and a back layer in this order,
The average thickness t _T of the magnetic recording medium is 3.5 μm ≦ t _T ≦ 5.5 μm,
The dimensional change amount Δw in the width direction of the magnetic recording medium with respect to the tension change in the longitudinal direction of the magnetic recording medium is 700 ppm / N ≦ Δw ≦ 20,000 ppm / N, and
The average thickness _{t n} of the non-magnetic layer is 0.01 [mu] m ≦ _{t n} ≦ 1.0 .mu.m, provides an elongated magnetic recording medium.
The dimensional change Δw may be 750 ppm / N ≦ Δw ≦ 20,000 ppm / N.
The dimensional change Δw may be 800 ppm / N ≦ Δw ≦ 20,000 ppm / N.
The average thickness _{t T} of the magnetic recording medium may be a 3.5μm ≦ _{t T} ≦ 5.3μm.
The average thickness _{t T} of the magnetic recording medium may be a 3.5μm ≦ _{t T} ≦ 5.2μm.
The average thickness _{t T} of the magnetic recording medium may be a 3.5μm ≦ _{t T} ≦ 5.0μm.
The average thickness t _m of the magnetic layer may be 35 nm ≦ t _m ≦ 120 nm.
The average thickness _{t n} of the non-magnetic layer may be a 0.4μm ≦ _{t n} ≦ 1.0μm.
The average thickness _{t n} of the non-magnetic layer may be a 0.01μm ≦ _{t n} ≦ 0.9μm.
The average thickness _{t n} of the non-magnetic layer may be a 0.01μm ≦ _{t n} ≦ 0.7μm.
The average thickness of the base layer may be 2.5 μm or more and 3.8 μm or less.
The average thickness of the base layer may be 2.6 μm or more and 3.6 μm or less.
The average thickness t _b of the back layer may be t _b ≦ 0.6 μm.
The magnetic layer includes a magnetic powder and a binder,
The magnetic powder may include ε iron oxide magnetic powder, barium ferrite magnetic powder, or cobalt ferrite magnetic powder.
The magnetic powder contains ε iron oxide magnetic powder,
A peak ratio X / Y between a main peak height X and a subpeak height Y near zero magnetic field in an SFD (Switching Field Distribution) curve of the magnetic recording medium may be 3.0 or more and 100 or less.
The average particle size of the ε iron oxide magnetic powder may be 8 nm or more and 22 nm or less.
The magnetic powder includes barium ferrite magnetic powder,
The average thickness t _{m of the} magnetic layer is 35 nm ≦ t _m ≦ 100 nm;
The coercive force Hc in the perpendicular direction of the magnetic recording medium may be from 160 kA / m to 280 kA / m.
The average particle size of the barium ferrite magnetic powder may be 12 nm or more and 25 nm or less.
The thermal expansion coefficient α of the magnetic recording medium may be 6 ppm / ° C. ≦ α ≦ 9 ppm / ° C.
The humidity expansion coefficient β of the magnetic recording medium may be β ≦ 5.5 ppm /% RH.
The Poisson's ratio ρ of the magnetic recording medium may be 0.25 ≦ ρ.
The longitudinal elastic limit value σ _MD may be 0.7 [N] ≦ σ _MD .
The elastic limit value σ _MD may not depend on the speed V when performing the elastic limit measurement.
The magnetic layer may be vertically oriented.
The magnetic layer may have 3 to 11 servo bands.
The magnetic layer is configured to be able to form a plurality of recording tracks parallel to the longitudinal direction,
The width of the recording track may be 2 μm or less.
The base layer may include a polyester resin.
Having a magnetic surface and a back surface opposite to the magnetic surface,
An interlayer friction coefficient μ between the magnetic surface and the back surface may be 0.20 ≦ μ ≦ 0.80.
The surface roughness R _{ab of the} back layer may be 3.0 nm ≦ R _ab ≦ 7.5 nm.
The perpendicularity of the magnetic recording medium in the perpendicular direction may be 65% or more.
The squareness ratio in the perpendicular direction of the magnetic recording medium may be 73% or more.
The perpendicular magnetic coercive force Hc of the magnetic recording medium may be 220 kA / m or more and 310 kA / m or less.
Further, the present technology, the magnetic recording medium,
A cartridge case,
And a reel,
The present invention also provides a magnetic recording cartridge in which the magnetic recording medium is housed in the cartridge case while being wound on the reel.

FIG. 1 is a cross-sectional view illustrating a configuration of a magnetic recording medium according to a first embodiment. It is sectional drawing which shows the structure of a magnetic particle. FIG. 2 is a perspective view illustrating a configuration of a measurement device. It is a schematic diagram which shows the detail of a measuring device. It is a graph which shows an example of an SFD curve. FIG. 2 is a schematic diagram illustrating a configuration of a recording / reproducing device. FIG. 11 is a cross-sectional view illustrating a configuration of a magnetic particle according to a modification. FIG. 11 is a cross-sectional view illustrating a configuration of a magnetic recording medium according to a modification. FIG. 6 is a cross-sectional view illustrating a configuration of a magnetic recording medium according to a second embodiment. It is the schematic which shows the structure of a sputtering apparatus. FIG. 14 is a cross-sectional view illustrating a configuration of a magnetic recording medium according to a third embodiment.

  Hereinafter, a preferred embodiment for carrying out the present technology will be described. The embodiments described below show typical embodiments of the present technology, and the scope of the present technology is not limited to only these embodiments.

The present technology will be described in the following order.
1. 1. Description of the present technology First Embodiment (Example of coating type magnetic recording medium)
(1) Configuration of magnetic recording medium (2) Description of each layer (3) Physical properties and structure (4) Manufacturing method of magnetic recording medium (5) Recording / reproducing device (6) Effect (7) Modification 3. 2. Second Embodiment (Example of a vacuum thin film type magnetic recording medium)
(1) Configuration of magnetic recording medium (2) Description of each layer (3) Physical properties and structure (4) Configuration of sputtering apparatus (5) Manufacturing method of magnetic recording medium (6) Effect (7) Modification 4. Third Embodiment (Example of a vacuum thin film type magnetic recording medium)
5. Example

1. Description of the technology

There is a demand for further increasing the recording capacity of a magnetic recording medium (for example, a magnetic recording tape). For example, in order to increase the recording capacity (recording area), it is conceivable to make the magnetic recording medium thinner (reducing the total thickness) and increase the tape length per cartridge product including the magnetic recording medium. .
However, as the magnetic recording medium becomes thinner, dimensional changes in the track width direction may easily occur. The dimensional change is likely to occur particularly when stored for a long time. Dimensional changes in the width direction can cause undesirable phenomena for magnetic recording, such as off-track phenomena. The off-track phenomenon means that the target track does not exist at the track position to be read by the magnetic head, or that the magnetic head reads the wrong track position.

Conventionally, the focus has been on suppressing the dimensional change of the magnetic recording medium. The method for suppressing the dimensional change includes, for example, adding a layer for suppressing the dimensional change of the magnetic recording medium.
However, the addition of such a layer may increase the thickness of the magnetic recording tape and does not increase the tape length per cartridge product.

The present inventors have proposed a magnetic recording medium suitable for use in a recording / reproducing apparatus which can keep the width of the long magnetic recording medium constant or almost constant by adjusting the longitudinal tension of the magnetic recording medium. Considering the medium. The recording / reproducing apparatus detects, for example, a dimension or a change in dimension of the magnetic recording medium in the width direction, and adjusts the tension in the longitudinal direction based on the detection result.
However, in the magnetic recording medium in which the dimensional change is suppressed, the dimensional change amount Δw in the width direction due to the tension change in the longitudinal direction is small. For this reason, it is difficult to keep the width of the magnetic recording medium constant or almost constant even when the tension is adjusted in the longitudinal direction by the recording / reproducing device.

In view of the above situation, the present inventors have studied a magnetic recording medium that is thin and is suitable for use in a recording / reproducing apparatus that adjusts the tension in the longitudinal direction. As a result, the present inventors have found that a magnetic recording medium having a specific configuration satisfies these requirements. That is, the present technology has a layer structure having a magnetic layer, a nonmagnetic layer, and a base layer in this order, the average thickness t _T is t _T ≤ 5.5 μm, and the width in the width direction with respect to the longitudinal tension change. Provided is a magnetic recording medium, wherein a dimensional change amount Δw is 660 ppm / N ≦ Δw, and an average thickness t _{n of the} nonmagnetic layer is t _n ≦ 1.0 μm.

When the dimensional change Δw is 660 ppm / N ≦ Δw and the average thickness t _n is t _n ≦ 1.0 μm, the thin magnetic recording medium is suitable for use in a recording / reproducing apparatus for adjusting the tension in the longitudinal direction. Shall be
The dimensional change amount Δw in the width direction due to a change in the tension in the longitudinal direction of the magnetic recording medium greatly depends on the physical characteristics of the base layer among the layers of the magnetic recording medium, but is arranged between the magnetic layer and the base layer. It depends on the physical properties of the non-magnetic layer to be formed, and particularly on the thickness t _n of the non-magnetic layer. It is t _n ≦ 1.0 .mu.m is considered suitable in order to increase the [Delta] w.

The average thickness _{t T} of the magnetic recording medium according to the present technique is 5.5μm or less, and more preferably not more than 5.3 .mu.m, even more preferably 5.2μm or less, be less 5.0μm or less or 4.6μm sell. Since the magnetic recording medium according to the present technology is so thin, for example, the length of the tape wound around one magnetic recording cartridge can be longer, thereby increasing the recording capacity per magnetic recording cartridge. be able to.

In the magnetic recording medium according to the present technology, the dimensional change amount Δw in the width direction with respect to the tension change in the longitudinal direction is 660 ppm / N or more, preferably 670 ppm / N or more, more preferably 700 ppm / N or more. More preferably, it may be 710 ppm / N or more, 730 ppm / N or more, 750 ppm / N or more, 780 ppm / N or more, or 800 ppm / N or more. The fact that the magnetic recording medium has the dimensional change amount Δw within the above numerical range contributes to making it possible to keep the width of the magnetic recording medium constant by adjusting the longitudinal tension of the magnetic recording medium. I do.
The upper limit of the dimensional change Δw is not particularly limited, but is, for example, 170,000 ppm / N or less, preferably 20,000 ppm / N or less, more preferably 8,000 ppm / N or less, still more preferably 5000 ppm / N or less. It can be 4000 ppm / N or less, 3000 ppm / N or less, or 2000 ppm / N or less. If the dimensional change Δw is too large, it may be difficult to drive the vehicle stably in the manufacturing process. This will be described in (3).

The average thickness t _n of the nonmagnetic layer of the magnetic recording medium according to the present technology is preferably t _n ≦ 1.0 μm, more preferably t _n ≦ 0.9 μm, and still more preferably t _n ≦ 0.7 μm. It is. The average thickness _{t n} of the nonmagnetic layer is, for example, 0.01 [mu] m ≦ _{t n,} preferably 0.02 [mu] m ≦ _{t n.}

The surface roughness R _ab of the back layer of the magnetic recording medium according to the present technology is preferably 3.0 nm ≦ R _ab ≦ 7.5 nm, more preferably 3.0 nm ≦ R _ab ≦ 7.3 nm. When the surface roughness _Rab is within the above numerical range, it contributes to the improvement of the handleability of the magnetic recording medium.
The surface roughness R _ab of the back layer is more preferably 7.2 nm or less, and even more preferably 7.0 nm or less, 6.5 nm or less, 6.3 nm or less, or 6.0 nm or less. Further, the surface roughness _{R ab} is more preferably not less than 3.2 nm, still more preferably may be at least 3.4 nm. When the surface roughness _Rab is within the above numerical range, particularly when the surface roughness is not more than the above upper limit, good electromagnetic conversion characteristics can be achieved in addition to the improvement of handling properties.
The method for measuring the surface roughness R _ab is as follows: This will be described in (3).

  According to the present technology, the magnetic recording medium is preferably a long magnetic recording medium, and may be, for example, a magnetic recording tape (especially a long magnetic recording tape).

  The magnetic recording medium according to the present technology may include other layers in addition to the magnetic layer, the non-magnetic layer, and the base layer. The other layer may be appropriately selected according to the type of the magnetic recording medium. The magnetic recording medium according to the present technology may be, for example, a coating type magnetic recording medium or a vacuum thin film type magnetic recording medium. Regarding the coating type magnetic recording medium, the following 2. Will be described in more detail. The vacuum thin film type magnetic recording medium is described below in 3. And 4. Will be described in more detail. For the layers included in the magnetic recording medium other than the above three layers, refer to these descriptions.

A magnetic recording medium according to the present technology may have, for example, at least one data band and at least two servo bands, and preferably may have a plurality of data bands and a plurality of servo bands. The number of data bands can be, for example, 2-10, in particular 3-6, more particularly 4 or 5. The number of servo bands can be, for example, from 3 to 11, especially from 4 to 7, and more particularly from 5 or 6. These servo bands and data bands may be arranged, for example, so as to extend in the longitudinal direction of a long magnetic recording medium (in particular, a magnetic recording tape), and particularly to be substantially parallel. The data band and the servo band may be provided on the magnetic layer. As a magnetic recording medium having a data band and a servo band, a magnetic recording tape conforming to the LTO (Linear Tape-Open) standard can be given. That is, the magnetic recording medium according to the present technology may be a magnetic recording tape according to the LTO standard. For example, the magnetic recording medium according to the present technology may be a magnetic recording tape according to LTO8 or a later standard (eg, LTO9, LTO10, LTO11, or LTO12).
The width of a long magnetic recording medium (especially a magnetic recording tape) according to the present technology is, for example, 5 mm to 30 mm, particularly 7 mm to 25 mm, more particularly 10 mm to 20 mm, and even more particularly 11 mm to 19 mm. It can be. The length of the long magnetic recording medium (particularly, magnetic recording tape) can be, for example, 500 m to 1500 m. For example, the tape width according to the LTO8 standard is 12.65 mm, and the length is 960 m.

2. First Embodiment (Example of coating type magnetic recording medium)

(1) Configuration of magnetic recording medium

  First, the configuration of the magnetic recording medium 10 according to the first embodiment will be described with reference to FIG. The magnetic recording medium 10 is, for example, a magnetic recording medium that has been subjected to a vertical alignment process. As shown in FIG. 1, a long base layer (also referred to as a base) 11 and one main surface of the base layer 11 A magnetic layer (also referred to as a recording layer) 13 provided on the underlayer 12 and a back layer 14 provided on the other main surface of the base layer 11. Is provided. In the following, of the two main surfaces of the magnetic recording medium 10, the surface on which the magnetic layer 13 is provided is referred to as a magnetic surface, and the surface opposite to the magnetic surface (the surface on which the back layer 14 is provided). ) Is called the back surface.

  The magnetic recording medium 10 has a long shape, and runs in the longitudinal direction during recording and reproduction. Further, the magnetic recording medium 10 may be configured to be capable of recording a signal at a shortest recording wavelength of preferably 100 nm or less, more preferably 75 nm or less, still more preferably 60 nm or less, particularly preferably 50 nm or less. It can be used for a recording / reproducing device having a wavelength within the above range. This recording / reproducing apparatus may include a ring-type head as a recording head. The recording track width is, for example, 2 μm or less.

(2) Description of each layer

(Base layer)

  The base layer 11 can function as a support for the magnetic recording medium 10, and may be, for example, a flexible, long non-magnetic substrate, particularly a non-magnetic film. The thickness of the base layer 11 is, for example, 2 μm or more and 8 μm or less, preferably 2.2 μm or more and 7 μm or less, more preferably 2.5 μm or more and 6 μm or less, and still more preferably 2.6 μm or more and 5 μm or less. sell. The base layer 11 may include, for example, at least one of a polyester resin, a polyolefin resin, a cellulose derivative, a vinyl resin, an aromatic polyetherketone resin, and another polymer resin. When the base layer 11 includes two or more of the above materials, the two or more materials may be mixed, copolymerized, or laminated.

  Examples of the polyester resin include PET (polyethylene terephthalate), PEN (polyethylene naphthalate), PBT (polybutylene terephthalate), PBN (polybutylene naphthalate), PCT (polycyclohexylene dimethylene terephthalate), and PEB (polyethylene- p-oxybenzoate), and one or a mixture of two or more of polyethylene bisphenoxycarboxylate. According to a preferred embodiment of the present technology, the base layer 11 may be formed from PET or PEN.

  The polyolefin-based resin may be, for example, one or a mixture of two or more of PE (polyethylene) and PP (polypropylene).

  The cellulose derivative may be, for example, one or a mixture of two or more of cellulose diacetate, cellulose triacetate, CAB (cellulose acetate butyrate), and CAP (cellulose acetate propionate).

  The vinyl resin may be, for example, one or a mixture of two or more of PVC (polyvinyl chloride) and PVDC (polyvinylidene chloride).

  The aromatic polyetherketone resin is, for example, one or two of PEK (polyetherketone), PEEK (polyetheretherketone), PEKK (polyetherketoneketone), and PEEKK (polyetheretherketoneketone). It may be a mixture of more than one species. According to a preferred embodiment of the present technology, the base layer 11 may be formed from PEEK.

  The other polymer resin includes, for example, PA (polyamide, nylon), aromatic PA (aromatic polyamide, aramid), PI (polyimide), aromatic PI (aromatic polyimide), PAI (polyamideimide), aromatic PAI (aromatic polyamideimide), PBO (polybenzoxazole such as Zylon (registered trademark)), polyether, polyetherester, PES (polyethersulfone), PEI (polyetherimide), PSF (polysulfone), It may be one or a mixture of two or more of PPS (polyphenylene sulfide), PC (polycarbonate), PAR (polyarylate), and PU (polyurethane).

(Magnetic layer)

  The magnetic layer 13 can be, for example, a perpendicular recording layer. The magnetic layer 13 can include magnetic powder. The magnetic layer 13 may further include, for example, a binder and conductive particles in addition to the magnetic powder. The magnetic layer 13 may further include additives such as a lubricant, an abrasive, and a rust preventive, if necessary.

The average thickness _{t m} of the magnetic layer 13 is preferably 35nm ≦ _{t m} ≦ 120nm, more preferably 35nm ≦ _{t m} ≦ 100nm, particularly preferably be a 35nm ≦ _{t m} ≦ 90nm. The average thickness t _m of the magnetic layer 13 is within the above numerical ranges, contributing to the improvement of electromagnetic characteristics.

The average thickness t _m of the magnetic layer 13 is determined as follows. First, a test piece is prepared by processing the magnetic recording medium 10 thinly perpendicularly to the main surface, and a cross section of the test piece is observed under a transmission electron microscope (TEM) under the following conditions. I do.
Equipment: TEM (H9000NAR manufactured by Hitachi, Ltd.)
Accelerating voltage: 300 kV
Magnification: 100,000 × Next, after using the obtained TEM image to measure the thickness of the magnetic layer 13 at at least 10 or more positions in the longitudinal direction of the magnetic recording medium 10, the measured values are simply averaged ( (Arithmetic average) to obtain an average thickness t _m (nm) of the magnetic layer 13.

The magnetic layer 13 is preferably a vertically oriented magnetic layer. In this specification, the perpendicular orientation means that the squareness ratio S1 measured in the longitudinal direction (running direction) of the magnetic recording medium 10 is 35% or less. The method of measuring the squareness ratio S1 will be described separately below.
Note that the magnetic layer 13 may be a magnetic layer that is in-plane orientation (longitudinal orientation). That is, the magnetic recording medium 10 may be a horizontal recording type magnetic recording medium. However, from the viewpoint of increasing the recording density, vertical orientation is more preferable.

(Magnetic powder)

  Examples of the magnetic particles constituting the magnetic powder contained in the magnetic layer 13 include epsilon-type iron oxide (ε iron oxide), gamma hematite, magnetite, chromium dioxide, cobalt-coated iron oxide, hexagonal ferrite, barium ferrite (BaFe), and Co. Ferrite, strontium ferrite, metal (metal), and the like can be given, but are not limited thereto. The magnetic powder may be one of them or a combination of two or more thereof. Particularly preferably, the magnetic powder may include ε iron oxide magnetic powder, barium ferrite magnetic powder, cobalt ferrite magnetic powder, or strontium ferrite magnetic powder. Note that the ε-iron oxide may contain Ga and / or Al. These magnetic particles may be appropriately selected by those skilled in the art based on factors such as the method of manufacturing the magnetic layer 13, the standard of the tape, and the function of the tape.

  The average particle size (average maximum particle size) D of the magnetic powder is preferably 22 nm or less, more preferably 8 nm or more and 22 nm or less, and even more preferably 10 nm or more and 20 nm or less.

The average particle size D of the magnetic powder is determined as follows. First, the magnetic recording medium 10 to be measured is processed by an FIB (Focused Ion Beam) method or the like to produce a thin section, and a cross section of the thin section is observed by a TEM. Next, 500 ε iron oxide particles are randomly selected from the taken TEM photograph, and the maximum particle size d _max of each particle is measured to determine the particle size distribution of the maximum particle size d _max of the magnetic powder. Here, the “maximum particle size d _max ” means a so-called maximum Feret diameter, and specifically, a distance between two parallel lines drawn from all angles so as to be in contact with the contour of the ε iron oxide particles. The largest of these. Thereafter, the median diameter (50% diameter, D50) of the maximum particle size d _max is determined from the obtained particle size distribution of the maximum particle size d _max , and is defined as the average particle size (average maximum particle size) D of the magnetic powder.

  The shape of the magnetic particles depends on the crystal structure of the magnetic particles. For example, BaFe and strontium ferrite can be hexagonal. ε iron oxide can be spherical. Cobalt ferrite can be cubic. The metal can be spindle-shaped. In the manufacturing process of the magnetic recording medium 10, these magnetic particles are oriented.

  According to one preferred embodiment of the present technology, the magnetic powder may include a powder of nanoparticles preferably containing ε-iron oxide (hereinafter referred to as “ε-iron oxide particles”). The ε iron oxide particles can obtain a high coercive force even with fine particles. The ε-iron oxide contained in the ε-iron oxide particles is preferably preferentially crystallographically oriented in the thickness direction (perpendicular direction) of the magnetic recording medium 10.

  The ε-iron oxide particles have a spherical or nearly spherical shape, or have a cubic or nearly cubic shape. Since the ε iron oxide particles have the above-described shape, the thickness of the medium when using ε iron oxide particles as the magnetic particles is smaller than when using hexagonal plate-shaped barium ferrite particles as the magnetic particles. The contact area between particles in the direction can be reduced, and aggregation between particles can be suppressed. Therefore, the dispersibility of the magnetic powder can be enhanced, and a better SNR (Signal-to-Noise Ratio) can be obtained.

  The ε iron oxide particles have a core-shell structure. Specifically, as shown in FIG. 2, the ε iron oxide particles include a core portion 21 and a shell portion 22 having a two-layer structure provided around the core portion 21. The shell part 22 having the two-layer structure includes a first shell part 22a provided on the core part 21 and a second shell part 22b provided on the first shell part 22a.

The core 21 contains ε iron oxide. The ε-iron oxide contained in the core portion 21 preferably has a ε-Fe ₂ O ₃ crystal as a main phase, and more preferably a single-phase ε-Fe ₂ O ₃ .

  The first shell portion 22a covers at least a part of the periphery of the core portion 21. Specifically, the first shell portion 22a may partially cover the periphery of the core portion 21 or may cover the entire periphery of the core portion 21. From the viewpoint of sufficient exchange coupling between the core part 21 and the first shell part 22a and improvement in magnetic characteristics, it is preferable that the entire surface of the core part 21 be covered.

  The first shell portion 22a is a so-called soft magnetic layer, and may include a soft magnetic material such as α-Fe, Ni—Fe alloy, or Fe—Si—Al alloy. α-Fe may be obtained by reducing ε iron oxide contained in the core portion 21.

The second shell part 22b is an oxide film as an antioxidant layer. The second shell portion 22b may include α iron oxide, aluminum oxide, or silicon oxide. The α iron oxide may include, for example, at least one iron oxide of Fe ₃ O ₄ , Fe ₂ O ₃ , and FeO. When the first shell portion 22a includes α-Fe (soft magnetic material), the α-iron oxide may be obtained by oxidizing α-Fe included in the first shell portion 22a.

  Since the ε iron oxide particles have the first shell portion 22a as described above, thermal stability can be ensured, whereby the coercive force Hc of the core portion 21 alone can be maintained at a large value and / or ε The coercive force Hc of the iron oxide particles (core-shell particles) as a whole can be adjusted to a coercive force Hc suitable for recording. Further, since the ε-iron oxide particles have the second shell portion 22b as described above, the ε-iron oxide particles are exposed to the air during the manufacturing process of the magnetic recording medium 10 and before the process, and the ε-iron oxide particles are exposed to the surface of the particles. The occurrence of rust or the like can be prevented from deteriorating the characteristics of the ε iron oxide particles. Therefore, characteristic deterioration of the magnetic recording medium 10 can be suppressed.

  The ε-iron oxide particles may have a single-layered shell 23 as shown in FIG. In this case, the shell part 23 has the same configuration as the first shell part 22a. However, from the viewpoint of suppressing the characteristic deterioration of the ε iron oxide particles, it is more preferable that the ε iron oxide particles have the shell portion 22 having a two-layer structure.

The ε-iron oxide particles may include an additive instead of the core-shell structure, or may have the core-shell structure and include the additive. In these cases, a part of Fe of the ε iron oxide particles is replaced by the additive. Even when the ε-iron oxide particles contain an additive, the coercive force Hc of the ε-iron oxide particles as a whole can be adjusted to a coercive force Hc suitable for recording, so that recording easiness can be improved. The additive is a metal element other than iron, preferably a trivalent metal element, more preferably one or more selected from the group consisting of aluminum (Al), gallium (Ga), and indium (In).
Specifically, epsilon iron oxide containing _{additives, ε-Fe 2-x M} x O 3 crystals (where, M is a metal element other than iron, preferably trivalent metal element, more preferably, Al , Ga, and In. X is, for example, 0 <x <1).

  According to another preferred embodiment of the present technology, the magnetic powder may be barium ferrite (BaFe) magnetic powder. The barium ferrite magnetic powder contains iron oxide magnetic particles having barium ferrite as a main phase (hereinafter referred to as “barium ferrite particles”). Barium ferrite magnetic powder has high data recording reliability, for example, the coercive force does not decrease even in a high temperature and high humidity environment. From such a viewpoint, barium ferrite magnetic powder is preferable as the magnetic powder.

  The average particle size of the barium ferrite magnetic powder is 50 nm or less, more preferably 10 nm or more and 40 nm or less, and even more preferably 12 nm or more and 25 nm or less.

If the magnetic layer 13 include a barium ferrite magnetic powder as a magnetic powder, the average thickness _t m of the magnetic layer 13 [nm] is preferably a 35nm ≦ _{t m} ≦ 100nm. The coercive force Hc measured in the thickness direction (perpendicular direction) of the magnetic recording medium 10 is preferably 160 kA / m or more and 280 kA / m or less, more preferably 165 kA / m or more and 275 kA / m or less, and even more preferably 170 kA / m or less. m or more and 270 kA / m or less.

  According to yet another preferred embodiment of the present technology, the magnetic powder may be a cobalt ferrite magnetic powder. The cobalt ferrite magnetic powder contains iron oxide magnetic particles having cobalt ferrite as a main phase (hereinafter referred to as “cobalt ferrite magnetic particles”). The cobalt ferrite magnetic particles preferably have uniaxial anisotropy. The cobalt ferrite magnetic particles have, for example, a cubic shape or a substantially cubic shape. Cobalt ferrite is cobalt ferrite containing Co. The cobalt ferrite may further include at least one selected from the group consisting of Ni, Mn, Al, Cu, and Zn, in addition to Co.

Cobalt ferrite has, for example, an average composition represented by the following formula (1).
_{Co x M y Fe 2 O z} ··· (1)
(However, in the formula (1), M is, for example, at least one metal selected from the group consisting of Ni, Mn, Al, Cu, and Zn. X is 0.4 ≦ x ≦ 1.0. Y is a value within the range of 0 ≦ y ≦ 0.3, where x and y satisfy the relationship of (x + y) ≦ 1.0, and z is 3 ≦ z ≦ This is a value within the range of 4. Part of Fe may be replaced by another metal element.)

  The average particle size of the cobalt ferrite magnetic powder is preferably 25 nm or less, more preferably 23 nm or less. The coercive force Hc of the cobalt ferrite magnetic powder is preferably 2500 Oe or more, more preferably 2600 Oe or more and 3500 Oe or less.

According to still another preferred embodiment of the present technology, the magnetic powder may include a powder of nanoparticles containing hexagonal ferrite (hereinafter, referred to as “hexagonal ferrite particles”). The hexagonal ferrite particles have, for example, a hexagonal plate shape or a substantially hexagonal plate shape. The hexagonal ferrite may preferably include at least one of Ba, Sr, Pb and Ca, more preferably at least one of Ba and Sr. The hexagonal ferrite may specifically be, for example, barium ferrite or strontium ferrite. Barium ferrite may further include at least one of Sr, Pb, and Ca, in addition to Ba. The strontium ferrite may further include at least one of Ba, Pb, and Ca in addition to Sr.
More specifically, the hexagonal ferrite may have an average composition represented by the general formula MFe ₁₂ O ₁₉ . Here, M is, for example, at least one metal of Ba, Sr, Pb, and Ca, and preferably at least one metal of Ba and Sr. M may be a combination of Ba and one or more metals selected from the group consisting of Sr, Pb, and Ca. Further, M may be a combination of Sr and one or more metals selected from the group consisting of Ba, Pb, and Ca. In the above general formula, a part of Fe may be replaced by another metal element.
When the magnetic powder contains hexagonal ferrite particles, the average particle size of the magnetic powder is preferably 50 nm or less, more preferably 10 nm or more and 40 nm or less, and even more preferably 15 nm or more and 30 nm or less.

(Binder)

  As the binder, a resin having a structure obtained by imparting a crosslinking reaction to a polyurethane resin or a vinyl chloride resin is preferable. However, the binder is not limited to these, and other resins may be appropriately compounded according to the physical properties required for the magnetic recording medium 10 and the like. The resin to be blended is not particularly limited as long as it is a resin generally used in the coating type magnetic recording medium 10.

  Examples of the binder include polyvinyl chloride, polyvinyl acetate, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, acrylate-acrylonitrile copolymer Acrylate-vinyl chloride-vinylidene chloride copolymer, acrylate-vinylidene chloride copolymer, methacrylate-vinylidene chloride copolymer, methacrylate-vinyl chloride copolymer, methacrylate-ethylene copolymer Polymer, polyvinyl fluoride, vinylidene chloride-acrylonitrile copolymer, acrylonitrile-butadiene copolymer, polyamide resin, polyvinyl butyral, cellulose derivatives (cellulose acetate butyrate, cellulose diacetate, cellulose triacetate) Over preparative, cellulose propionate, nitrocellulose), styrene-butadiene copolymer, polyester resin, amino resin, and synthetic rubber.

  Further, as the binder, a thermosetting resin or a reactive resin may be used, and examples thereof include a phenol resin, an epoxy resin, a urea resin, a melamine resin, an alkyd resin, a silicone resin, a polyamine resin, And urea-formaldehyde resin.

Moreover, each binder described above, for the purpose of improving the dispersibility of the magnetic _{powder, -SO 3 M, -OSO 3 M} , -COOM, polar functional groups such as P = O _{(OM) 2} is introduced May be. Here, M in the formula is a hydrogen atom or an alkali metal such as lithium, potassium, and sodium.

Further, as the polar functional group, -NR1R2, -NR1R2R3 ⁺ X ^- as the side chain type having an end group of,> NR1R2 ⁺ X ^- include those of the main chain type. Here, R1, R2, and R3 in the formula are a hydrogen atom or a hydrocarbon group, and X ⁻ is a halogen element ion such as fluorine, chlorine, bromine, or iodine, or an inorganic or organic ion. In addition, examples of the polar functional group include -OH, -SH, -CN, and an epoxy group.

(Additive)

  The magnetic layer 13 includes non-magnetic reinforcing particles of aluminum oxide (α, β, or γ alumina), chromium oxide, silicon oxide, diamond, garnet, emery, boron nitride, titanium carbide, silicon carbide, titanium carbide, titanium oxide. (Rutile-type or anatase-type titanium oxide) and the like.

(Non-magnetic layer)

  The nonmagnetic layer 12 contains nonmagnetic powder and a binder as main components. The non-magnetic layer is also called an underlayer. The description regarding the binder contained in the magnetic layer 13 described above also applies to the binder contained in the nonmagnetic layer 12. The nonmagnetic layer 12 may further include at least one kind of additive such as a conductive particle, a lubricant, a curing agent, and a rust inhibitor, if necessary.

The average thickness _{t n} of the non-magnetic layer 12 is 1.0μm or less, and more preferably not more than 0.9 .mu.m, even more preferably _{t n} ≦ 0.7 [mu] m. The average thickness _{t n} of the non-magnetic layer 12 is, for example, 0.01μm or more, preferably not less than 0.02 [mu] m, more preferably 0.4μm or more, and particularly preferably 0.5μm or more. The average thickness t _n of the non-magnetic layer 12 is determined in the same manner as the average thickness t _m of the magnetic layer 13. However, the magnification of the TEM image is appropriately adjusted according to the thickness of the nonmagnetic layer 12. The average thickness t _n of the non-magnetic layer 12 is within the above numerical ranges, contributing to an increase in the [Delta] w, more and being suitable for use in a recording and reproducing apparatus for adjusting the longitudinal tension of the magnetic recording medium I do.

(Non-magnetic powder)

The non-magnetic powder contained in the non-magnetic layer 12 may include, for example, at least one selected from inorganic particles and organic particles. One type of non-magnetic powder may be used alone, or two or more types of non-magnetic powder may be used in combination. The inorganic particles include, for example, one or a combination of two or more metals, metal oxides, metal carbonates, metal sulfates, metal nitrides, metal carbides, and metal sulfides. More specifically, the inorganic particles may be, for example, one or more selected from iron oxyhydroxide, hematite, titanium oxide, and carbon black. Examples of the shape of the nonmagnetic powder include various shapes such as a needle shape, a spherical shape, a cubic shape, and a plate shape, but are not particularly limited thereto.
The nonmagnetic powder contained in the nonmagnetic layer 12 preferably contains Fe-based nonmagnetic particles, and more preferably contains Fe-based nonmagnetic inorganic particles. Examples of Fe-based non-magnetic particles include, for example, iron oxyhydroxide (especially goethite) and hematite, and one or a combination of two or more of these can be used as the non-magnetic powder. .
Particle volume of the Fe-based non-magnetic particles non-magnetic layer 12 is contained, it is preferably 4.0 × ^{10 -5} μm ³ or less, more preferably 3.0 × ^{10 -5} μm ³ or less, It is still more preferably 2.0 × 10 ⁻⁵ μm ³ or less, and still more preferably 1.0 × 10 ⁻⁵ μm ³ or less. As the non-magnetic layer is thinner, the surface properties of the magnetic layer side of the magnetic recording medium tend to deteriorate, but as the particle volume of the non-magnetic powder contained in the non-magnetic layer decreases, the deterioration of the surface properties is suppressed. And Δw can be further increased.

Hereinafter, an example of a method for measuring the particle volume of Fe-based non-magnetic particles will be described step by step.
1. As a sample pretreatment, thinning by the FIB method (μ-sampling method) is performed along the longitudinal direction of the magnetic recording tape.
2. The cross section of the range including the base layer, the nonmagnetic layer, and the magnetic layer of the obtained thin sample is observed. This observation is performed using a transmission electron microscope (H-9500 manufactured by Hitachi High-Technologies Corporation) under the conditions of an acceleration voltage of 300 kV and a total magnification of 250,000 times.
3. In the obtained cross-sectional TEM image, 50 Fe-based nonmagnetic particles are specified for the particles contained in the nonmagnetic layer by using a microelectron diffraction method. This microelectron diffraction method is performed using a transmission electron microscope (JEM-ARM200F manufactured by JEOL Ltd.) under the conditions of an acceleration voltage of 200 kV, a camera length of 0.8 m, and a beam diameter of about 1 nmΦ.
4. Using the 50 Fe-based non-magnetic particles specified as described above, the average particle volume of the Fe-based non-magnetic particles is determined. The average particle volume V _ave of the Fe-based non-magnetic particles can be calculated by V _ave = (π / 6) × DS _ave ² × DL _ave .
Therefore, first, the major axis length DL and the minor axis length DS of each Fe-based nonmagnetic particle are measured. Here, the long axis length DL means the largest one (so-called maximum Feret diameter) of the distance between two parallel lines drawn from all angles so as to be in contact with the contour of the particle. On the other hand, the short axis length DS means the largest of the particle lengths in a direction orthogonal to the long axis of the particle.
Next, the average major axis length DL _ave is obtained by simply averaging (arithmetic averaging) the major axis lengths DL of the 50 measured Fe-based nonmagnetic particles. The obtained average major axis length DL _ave is also called the average particle size of the Fe-based non-magnetic particles. The average short axis length DS _ave is obtained by simply averaging (arithmetic averaging) the measured short axis lengths DS of the 50 Fe-based nonmagnetic particles.
Finally, the average major axis length _{DL ave} and the average minor axis length _{DS ave} obtained above are substituted into the formula for the _{V ave,} seek _{V ave.}

(Back layer)

  The back layer 14 may include a binder and a non-magnetic powder. The back layer 14 may include various additives such as a lubricant, a curing agent, and an antistatic agent as needed. The above description regarding the binder and the non-magnetic powder contained in the underlayer 12 also applies to the binder and the non-magnetic powder contained in the back layer 14.

  The average particle size of the inorganic particles contained in the back layer 14 is preferably from 10 nm to 150 nm, more preferably from 15 nm to 110 nm. The average particle size of the inorganic particles is determined in the same manner as the above-described average particle size D of the magnetic powder.

The average thickness _{t b} of the back layer 14 is preferably a _{t b} ≦ 0.6 .mu.m. By average thickness t _b of the back layer 14 is in the above range, keeping the average thickness t _T of the magnetic recording medium 10 even when the t _T ≦ 5.5 [mu] m, increasing the thickness of the base layer 12 and base layer 11 As a result, the running stability of the magnetic recording medium 10 in the recording / reproducing apparatus can be maintained.

The average thickness t _b of the back layer 14 is determined as follows. First, a magnetic recording medium 10 having a width of 1/2 inch is prepared, cut out to a length of 250 mm, and a sample is prepared. Next, using a laser holometer manufactured by Mitutoyo as a measuring device, the thickness of the sample at different locations was measured at five or more points, the measured values were simply averaged (arithmetic average), and the average value t _T [μm] Is calculated. Subsequently, after removing the back layer 14 of the sample with a solvent such as MEK (methyl ethyl ketone) or dilute hydrochloric acid, the thickness of the sample at different locations is measured at five or more points again using the above-mentioned laser holometer, and the measured values are measured. Is simply averaged (arithmetic average) to calculate an average value t _B [μm]. After that, the average thickness t _b (μm) of the back layer 14 is obtained from the following equation.
t _b [μm] = t _T [μm] −t _B [μm]

(3) Physical properties and structure

(Average thickness t _T of magnetic recording medium)

The average thickness t _T of the magnetic recording medium 10 is t _T ≤ 5.5 μm. When the average thickness t _T of the magnetic recording medium 10 is t _T ≦ 5.5 μm, the recording capacity that can be recorded in one data cartridge can be increased as compared with the conventional case. The lower limit of the average thickness _{t T} of the magnetic recording medium 10 is not particularly limited, for example, is 3.5 [μm] ≦ _{t T.}

The average thickness t _T of the magnetic recording medium 10 is determined by a measurement method of the average value t _T described in the measurement method of the average thickness t _b of the back layer 14.

(Dimension change amount Δw)

The dimensional change amount Δw [ppm / N] in the width direction of the magnetic recording medium 10 with respect to the tension change in the longitudinal direction of the magnetic recording medium 10 is 660 ppm / N ≦ Δw, preferably 670 ppm / N ≦ Δw, and more preferably. Is 680 ppm / N ≦ Δw, more preferably 700 ppm / N ≦ Δw, even more preferably 750 ppm / N ≦ Δw, and particularly preferably 800 ppm / N ≦ Δw. If the dimensional change amount Δw is Δw <660 ppm / N, it may be difficult to suppress a change in width by adjusting the tension in the longitudinal direction by the recording / reproducing apparatus. The upper limit value of the dimensional change amount Δw is not particularly limited. , Δw ≦ 4000 ppm / N, Δw ≦ 3000 ppm / N, or Δw ≦ 2000 ppm / N.
Those skilled in the art can appropriately set the dimensional change amount Δw. For example, the dimensional change amount Δw can be set to a desired value by selecting the thickness of the base layer 11 and / or the material of the base layer 11. The dimensional change amount Δw may be set to a desired value by adjusting, for example, the stretching strength in the vertical and horizontal directions of the film constituting the base layer. For example, by stretching more in the width direction, Δw decreases, and conversely, by increasing the stretching in the longitudinal direction, Δw increases.

The dimensional change amount Δw is obtained as follows. First, a magnetic recording medium 10 having a width of 1/2 inch is prepared, cut out to a length of 250 mm, and a sample 10S is manufactured. Next, a load is applied in the order of 0.2N, 0.6N, and 1.0N in the longitudinal direction of the sample 10S, and the width of the sample 10S under the loads of 0.2N, 0.6N, and 1.0N is measured. Subsequently, the dimensional change amount Δw is obtained from the following equation. The measurement when a load of 0.6 N was applied was performed in order to confirm that there was no abnormality in the measurement (in particular, to confirm that these three measurement results were linear). The measurement result is not used in the following equation.

(However, in the formula, D (0.2N) and D (1.0N) indicate the width of the sample 10S when a load of 0.2N and 1.0N is applied in the longitudinal direction of the sample 10S, respectively.)

  The width of the sample 10S when each load is applied is measured as follows. First, a measuring device shown in FIG. 3A incorporating a digital dimension measuring device LS-7000 manufactured by Keyence Corporation as a measuring device is prepared, and a sample 10S is set in this measuring device. Specifically, one end of the long sample (magnetic recording medium) 10S is fixed by the fixing unit 231. Next, as shown in FIG. 3A, the sample 10S is placed on five substantially columnar and rod-shaped support members 232. The sample 10S is placed on these support members such that the back surface thereof contacts the five support members 232. Each of the five support members 232 (particularly, their surfaces) is formed of stainless steel SUS304, and has a surface roughness Rz (maximum height) of 0.15 μm to 0.3 μm.

The arrangement of the five bar-shaped support members 232 will be described with reference to FIG. 3B. As shown in FIG. 3B, the sample 10S is placed on five support members 232. Regarding the five support members 232, the “first support member”, the “second support member”, the “third support member” (having the slit 232A), the “fourth support member” Member "and" fifth support member "(closest to the weight 233). The diameter of these five support members is 7 mm. The distance d ₁ (particularly the distance between the centers of these support members) between the first support member and the second support member is 20 mm. The distance _{d 2} between the second supporting member and the third support member is 30 mm. The third support member and the distance _{d 3} between the fourth supporting member is 30 mm. The distance _{d 4} between the fourth support member and the fifth support member is 20 mm. In addition, the three support members of the sample 10S are formed such that a portion riding between the second support member, the third support member, and the fourth support member forms a plane substantially perpendicular to the direction of gravity. Is located. Further, the first support member and the second support member are arranged such that the sample 10S forms an angle of θ ₁ = 30 ° with respect to the substantially vertical plane between the first support member and the second support member. Is located. Further, the fourth support member and the fifth support member are arranged such that the sample 10S forms an angle of θ ₂ = 30 ° with the substantially vertical plane between the fourth support member and the fifth support member. Is located.
Further, among the five support members 232, the third support member is fixed so as not to rotate, but all the other four support members are rotatable.

  The sample 10S is held on the support member 232 so as not to move in the width direction of the sample 10S. A slit 232A is provided in the support member 232 of the support member 232, which is located between the light emitter 234 and the light receiver 235 and substantially at the center between the fixed portion 231 and the portion to which a load is applied. Light L is emitted from the light emitter 234 to the light receiver 235 via the slit 232A. The slit width of the slit 232A is 1 mm, and the light L can pass through the width without being blocked by the frame of the slit 232A.

Subsequently, after the measuring apparatus is housed in a chamber controlled under a constant environment of a temperature of 25 ° C. and a relative humidity of 50%, a weight 233 for applying a load of 0.2 N is attached to the other end of the sample 10S. Place 10S in the above environment for 2 hours. After 2 hours, the width of sample 10S is measured. Next, the weight for applying a load of 0.2N is changed to a weight for applying a load of 0.6N, and the width of the sample 10S is measured 5 minutes after the change. Finally, the weight is changed to apply a load of 1.0 N, and the width of the sample 10S is measured 5 minutes after the change.
As described above, by adjusting the weight of the weight 233, the load applied in the longitudinal direction of the sample 10S can be changed. In a state where each load is applied, the light L is irradiated from the light emitter 234 to the light receiver 235, and the width of the sample 10S to which the load is applied in the longitudinal direction is measured. The measurement of the width is performed in a state where the sample 10S is not curled. The light emitting device 234 and the light receiving device 235 are provided in the digital dimension measuring device LS-7000.

(Temperature expansion coefficient α)

  The coefficient of thermal expansion α [ppm / ° C.] of the magnetic recording medium 10 is preferably 5.5 ppm / ° C. ≦ α ≦ 9 ppm / ° C., and more preferably 5.9 ppm / ° C. ≦ α ≦ 8 ppm / ° C. When the temperature expansion coefficient α is within the above range, the change in the width of the magnetic recording medium 10 can be further suppressed by adjusting the tension in the longitudinal direction of the magnetic recording medium 10 by the recording / reproducing apparatus.

The thermal expansion coefficient α is obtained as follows. First, a sample 10S is prepared in the same manner as in the method of measuring the dimensional change Δw, and the sample 10S is set in a measuring device similar to the measuring method of the dimensional change Δw. Housed in a controlled environment chamber. Next, a load of 0.2 N is applied in the longitudinal direction of the sample 10S, and the sample 10S is placed in the above environment for 2 hours. Then, while maintaining the relative humidity of 24%, the temperature was changed in the order of 45 ° C., 29 ° C., and 10 ° C., and the width of the sample 10S at 45 ° C., 29 ° C., and 10 ° C. was measured. Find the expansion coefficient α. Measurements at these temperatures are taken 2 hours after reaching each temperature. The measurement at a temperature of 29 ° C. is performed in order to confirm that no abnormality has occurred in the measurement (particularly, to confirm that these three measurement results are linear). The measurement result is not used in the following equation.

(However, in the formula, D (45 ° C.) and D (10 ° C.) indicate the width of the sample 10S at 45 ° C. and 10 ° C., respectively).

(Humidity expansion coefficient β)

  The humidity expansion coefficient β [ppm /% RH] of the magnetic recording medium 10 is preferably β ≦ 5.5 ppm /% RH, more preferably β ≦ 5.2 ppm /% RH, and still more preferably β ≦%. It can be 5.0 ppm /% RH. When the humidity expansion coefficient β is within the above range, a change in the width of the magnetic recording medium 10 can be further suppressed by adjusting the longitudinal tension of the magnetic recording medium 10 by the recording / reproducing apparatus.

The humidity expansion coefficient β is obtained as follows. First, a sample 10S is prepared in the same manner as in the method of measuring the dimensional change Δw, and the sample 10S is set in a measuring device similar to the measuring method of the dimensional change Δw. Housed in a controlled environment chamber. Next, a load of 0.2 N is applied in the longitudinal direction of the sample 10S, and the sample 10S is placed in the above environment for 2 hours. Thereafter, while maintaining the temperature of 29 ° C., the relative humidity was changed in the order of 80%, 24%, and 10%, and the width of the sample 10S at 80%, 24%, and 10% was measured. Find the coefficient β. Measurements at these humidities are performed immediately after reaching each humidity. Note that the measurement at a humidity of 24% is performed to confirm whether an abnormality has occurred in the measurement, and the measurement result is not used in the following equation.

(However, in the formula, D (80%) and D (10%) indicate the width of the sample 10S at a relative humidity of 80% and 10%, respectively).

(Poisson's ratio ρ)

  The Poisson's ratio ρ of the magnetic recording medium 10 is preferably 0.25 ≦ ρ, more preferably 0.29 ≦ ρ, and even more preferably 0.3 ≦ ρ. When the Poisson's ratio ρ is within the above range, it becomes easier to change the width of the magnetic recording medium 10 by adjusting the tension in the longitudinal direction of the magnetic recording medium 10 by the recording / reproducing apparatus.

The Poisson's ratio ρ is obtained as follows. First, a magnetic recording medium 10 having a width of 1/2 inch is prepared, cut out to a length of 150 mm to produce a sample, and a mark having a size of 6 mm × 6 mm is provided at the center of the sample. Next, both ends in the longitudinal direction of the sample are chucked so that the distance between the chucks becomes 100 mm, an initial load of 2 N is applied, and the length of the mark in the longitudinal direction of the sample at that time is set as the initial length, and the width of the sample is set. The width of the mark in the direction is the initial width. Subsequently, the sample was pulled at a tensile speed of 0.5 mm / min with an Instron type universal tensile tester, and the length of the mark in the longitudinal direction of the sample and the width of the mark in the width direction of the sample were measured using a Keyence image sensor. Is measured. Then, the Poisson's ratio ρ is determined by the following equation.

(Longitudinal elastic limit value σ _MD )

Longitudinal elastic limit σ _MD [N] of the magnetic recording medium 10, preferably 0.7 N ≦ sigma _MD, more preferably from 0.75N ≦ sigma _MD, even more preferably 0.8N ≦ sigma _Can be _MD . When the elastic limit value σ _MD is within the above range, a change in the width of the magnetic recording medium 10 can be further suppressed by adjusting the tension in the longitudinal direction of the magnetic recording medium 10 by the recording and reproducing device. Further, control on the drive side becomes easier. Although the upper limit of the elastic limit value σ _{MD in} the longitudinal direction of the magnetic recording medium 10 is not particularly limited, for example, σ _MD ≦ 5.0 N
It is. It is preferable that the elastic limit value σ _MD does not depend on the speed V when performing the elastic limit measurement. Since the elastic limit value σ _MD does not depend on the speed V, the magnetic force can be effectively increased without being affected by the running speed of the magnetic recording medium 10 in the recording / reproducing device, the tension adjusting speed of the recording / reproducing device, and its response. This is because a change in the width of the recording medium 10 can be suppressed. The elastic limit value σ _MD is set to a desired value by, for example, selecting the curing conditions of the underlayer 12, the magnetic layer 13, and the back layer 14 and / or selecting the material of the base layer 11. For example, the longer the curing time or the higher the curing temperature of the base layer forming paint, the magnetic layer forming paint, and the back layer forming paint, the more the reaction between the binder and the curing agent contained in each of these paints is promoted. . Thereby, the elastic characteristic is improved, and the elastic limit value σ _MD is improved.

The elastic limit value σ _MD is obtained as follows. First, a magnetic recording medium 10 having a width of 1/2 inch is prepared, cut out to a length of 150 mm, and a sample is prepared. The sample is set in a universal tensile tester so that the distance between chucks λ ₀ is λ ₀ = 100 mm. Is chucked at both ends in the longitudinal direction. Next, the sample is pulled at a pulling speed of 0.5 mm / min, and the load σ (N) with respect to the chuck distance λ (mm) is continuously measured. Subsequently, using the obtained data of λ (mm) and σ (N), the relationship between Δλ (%) and σ (N) is graphed. Here, Δλ (%) is given by the following equation.
Δλ (%) = ((λ−λ ₀ ) / λ ₀ ) × 100
Next, in the above graph, a region where the graph is a straight line is calculated in a region of σ ≧ 0.2N, and the maximum load σ is set as an elastic limit value σ _MD (N).

(Friction coefficient μ between magnetic surface and back surface)

  The coefficient of friction μ between the surface on the magnetic layer side and the surface on the back layer side of the magnetic recording medium 10 (hereinafter also referred to as “interlayer friction coefficient μ”) is preferably 0.20 ≦ μ ≦ 0.80. And more preferably 0.25 ≦ μ ≦ 0.75. When the friction coefficient μ is within the above range, the handling of the magnetic recording medium 10 is improved. For example, when the friction coefficient μ is within the above range, it is possible to suppress occurrence of a winding deviation when the magnetic recording medium 10 is wound around a reel (for example, the reel 10C in FIG. 5). More specifically, when the friction coefficient μ is too small (for example, when μ <0.20), the magnetic surface of the outermost portion of the magnetic recording medium 10 already wound on the cartridge reel is The interlayer friction between the magnetic recording medium 10 and the back surface of the magnetic recording medium 10 to be newly wound is extremely low, and the magnetic recording medium 10 to be newly wound is 10 is likely to be displaced from the magnetic surface of the portion located on the outermost periphery. Therefore, the winding deviation of the magnetic recording medium 10 occurs. On the other hand, if the friction coefficient μ is too large (for example, 0.80 <μ), the magnetic recording medium 10 is located just below the back surface of the magnetic recording medium 10 that is about to be unwound from the outermost periphery of the drive-side reel. The interlayer friction between the magnetic surface of the magnetic recording medium 10 still wound on the drive reel is extremely high, and the back surface and the magnetic surface are stuck. Therefore, the operation of the magnetic recording medium 10 toward the cartridge reel becomes unstable, and the winding of the magnetic recording medium 10 is shifted.

The friction coefficient μ is determined as follows. First, a magnetic recording medium 10 having a width of 1/2 inch is wound around a 1-inch diameter cylinder with its back surface facing up, and the magnetic recording medium 10 is fixed. Next, the magnetic recording medium 10 having a width of 1/2 inch is brought into contact with the cylinder at an angle θ (°) of 180 ° + 1 ° to 180 ° -10 ° so that the magnetic surface is brought into contact with the magnetic recording medium 10. One end of the recording medium 10 is connected to a movable strain gauge, and tension T ₀ = 0.6 (N) is applied to the other end. When the movable strain gauge is reciprocated 8 times at 0.5 mm / s for 8 times, the readings of the strain gauges T ₁ (N) to T ₈ (N) in each forward path are measured, and the average value of T _{4 to} T ₈ is calculated. T _ave (N). Then, the friction coefficient μ is determined from the following equation.

(Surface roughness R _{ab of} back layer)

The surface roughness of the back layer 14 (that is, the surface roughness of the back surface) R _ab [nm] is preferably 3.0 nm ≦ R _ab ≦ 7.3 nm, more preferably 3.0 nm ≦ R _ab ≦ 7. 2.0 nm, more preferably 3.0 nm ≦ R _ab ≦ 6.5 nm, and still more preferably 3.0 nm ≦ R _ab ≦ 6.0 nm. When the surface roughness R _ab of the back layer is within the above range, the handleability of the magnetic recording medium 10 can be improved. Further, when the magnetic recording medium 10 is wound, the influence on the surface of the magnetic layer can be reduced, and the adverse effect on the electromagnetic conversion characteristics can be suppressed. Although the handling properties and the electromagnetic conversion properties are contradictory properties, the surface roughness R _ab within the above numerical range enables these to be compatible.

The surface roughness R _ab of the back surface is determined as follows. First, a 1/2 inch wide magnetic recording medium 10 is prepared and attached to a slide glass with its back surface facing upward (that is, the magnetic surface is attached to the slide glass) to obtain a sample piece. Next, the surface roughness of the back surface of the sample piece is measured by a non-contact roughness meter using the following optical interference.
Apparatus: Non-contact roughness meter using optical interference (Non-contact surface / layer cross-sectional shape measurement system VertScan R5500GL-M100-AC manufactured by Ryoka Systems Inc.)
Objective lens: 20 times (approximately 237 μm × 178 μm field of view)
Resolution: 640 points x 480 points
Measurement mode: phase
Wavelength filter: 520 nm
Surface correction: Correction using a second-order polynomial approximation surface As described above, after measuring surface roughness at at least five or more positions in the longitudinal direction, each automatically calculated from the surface profile obtained at each position. The average value of the arithmetic average roughness Sa (nm) is defined as the surface roughness R _ab (nm) of the back surface.

(Coercive force Hc)

  The coercive force Hc measured in the thickness direction (perpendicular direction) of the magnetic recording medium 10 is preferably 220 kA / m or more and 310 kA / m or less, more preferably 230 kA / m or more and 300 kA / m or less, and still more preferably 240 kA / m or more. 290 kA / m or less. When the coercive force Hc is 220 kA / m or more, the coercive force Hc becomes sufficiently large, so that it is possible to suppress the deterioration of the magnetization signal recorded on the adjacent track due to the leakage magnetic field from the recording head. Therefore, a better SNR can be obtained. On the other hand, when the coercive force Hc is equal to or less than 310 kA / m, saturation recording by the recording head becomes easy, so that a more excellent SNR can be obtained.

  The coercive force Hc is obtained as follows. First, a measurement sample is cut out from the long magnetic recording medium 10, and the entire measurement sample is cut in the thickness direction of the measurement sample (thickness direction of the magnetic recording medium 10) using a vibrating sample magnetometer (VSM). Measure the MH loop. Next, the coating film (base layer 12, magnetic layer 13, etc.) is wiped off using acetone or ethanol, etc., and only the base layer 11 is left for background correction. Using the VSM, the thickness direction of the base layer 11 ( The MH loop of the base layer 11 is measured in the thickness direction of the magnetic recording medium 10). Thereafter, the MH loop of the base layer 11 is subtracted from the MH loop of the entire measurement sample to obtain an MH loop after the background correction. The coercive force Hc is obtained from the obtained MH loop. In addition, it is assumed that all the measurements of the above MH loop are performed at 25 ° C. Further, it is assumed that "demagnetizing field correction" is not performed when measuring the MH loop in the thickness direction (vertical direction) of the magnetic recording medium 10.

(Ratio R of coercive force Hc (50) and coercive force Hc (25))

  The ratio R () of the coercive force Hc (50) measured in the thickness direction (perpendicular direction) of the magnetic recording medium 10 at 50 ° C. and the coercive force Hc (25) measured in the thickness direction of the magnetic recording medium 10 at 25 ° C. = (Hc (50) / Hc (25)) × 100) is preferably 95% or more, more preferably 96% or more, still more preferably 97% or more, and particularly preferably 98% or more. When the ratio R is 95% or more, the temperature dependency of the coercive force Hc becomes small, and the deterioration of the SNR in a high-temperature environment can be suppressed.

  The coercive force Hc (25) is obtained in the same manner as in the method for measuring the coercive force Hc. The coercive force Hc (50) is obtained in the same manner as the above-described method of measuring the coercive force Hc, except that the measurement of the MH loop of the sample and the base layer 11 is performed at 50 ° C. .

(Squareness ratio S1 measured in the longitudinal direction)

The squareness ratio S1 measured in the longitudinal direction (running direction) of the magnetic recording medium 10 is preferably 35% or less, more preferably 27% or less, and even more preferably 20% or less. When the squareness ratio S1 is 35% or less, the vertical orientation of the magnetic powder becomes sufficiently high, so that a more excellent SNR can be obtained. Therefore, more excellent electromagnetic conversion characteristics can be obtained. Further, the shape of the servo signal is improved, and control on the drive side becomes easier.
In the present specification, that the magnetic recording medium is vertically oriented may mean that the squareness ratio S1 of the magnetic recording medium is within the above numerical range (for example, 35% or less). Magnetic recording media according to the present technology are preferably vertically oriented.

The squareness ratio S1 is obtained as follows. First, a measurement sample is cut out from the long magnetic recording medium 10, and the MH loop of the entire measurement sample corresponding to the longitudinal direction (running direction) of the magnetic recording medium 10 is measured using a VSM. Next, the coating film (the underlayer 12, the magnetic layer 13, etc.) is wiped off using acetone or ethanol, etc., and only the base layer 11 is left for background correction. The MH loop of the base layer 11 corresponding to (the running direction of the magnetic recording medium 10) is measured. Thereafter, the MH loop of the base layer 11 is subtracted from the MH loop of the entire measurement sample to obtain an MH loop after the background correction. The square magnetization ratio S1 (%) is calculated by substituting the obtained saturation magnetization Ms (emu) and residual magnetization Mr (emu) of the MH loop into the following equation. In addition, it is assumed that all the measurements of the above MH loop are performed at 25 ° C.
Squareness ratio S1 (%) = (Mr / Ms) × 100

(Squareness ratio S2 measured in the vertical direction)

The squareness ratio S2 measured in the perpendicular direction (thickness direction) of the magnetic recording medium 10 is preferably 65% or more, more preferably 73% or more, and even more preferably 80% or more. When the squareness ratio S2 is 65% or more, the vertical orientation of the magnetic powder becomes sufficiently high, so that a more excellent SNR can be obtained. Therefore, more excellent electromagnetic conversion characteristics can be obtained. Further, the shape of the servo signal is improved, and the control on the drive side becomes easier.
In the specification, that the magnetic recording medium is vertically oriented may mean that the squareness ratio S2 of the magnetic recording medium is within the above numerical range (for example, 65% or more).

  The squareness ratio S2 is obtained in the same manner as the squareness ratio S1 except that the MH loop is measured in the perpendicular direction (thickness direction) of the magnetic recording medium 10 and the base layer 11. In the measurement of the squareness ratio S2, "demagnetizing field correction" when measuring the MH loop in the direction perpendicular to the magnetic recording medium 10 is not performed.

  The squareness ratios S1 and S2 are, for example, the strength of the magnetic field applied to the magnetic layer forming paint, the time of applying the magnetic field to the magnetic layer forming paint, the dispersed state of the magnetic powder in the magnetic layer forming paint, or the magnetic layer forming paint. It is set to a desired value by adjusting the concentration of the solid content in the paint. Specifically, for example, as the strength of the magnetic field increases, the squareness ratio S1 decreases, whereas the squareness ratio S2 increases. Further, as the application time of the magnetic field becomes longer, the squareness ratio S1 becomes smaller, whereas the squareness ratio S2 becomes larger. Further, as the dispersion state of the magnetic powder is improved, the squareness ratio S1 becomes smaller, while the squareness ratio S2 becomes larger. Further, as the concentration of the solid content is lowered, the squareness ratio S1 is reduced, whereas the squareness ratio S2 is increased. The above adjustment methods may be used alone or in combination of two or more.

(SFD)

  In the SFD (Switching Field Distribution) curve of the magnetic recording medium 10, the peak ratio X / Y between the main peak height X and the subpeak height Y near zero magnetic field is preferably 3.0 or more, more preferably 5. It is 0 or more, still more preferably 7.0 or more, particularly preferably 10.0 or more, and most preferably 20.0 or more (see FIG. 4). When the peak ratio X / Y is 3.0 or more, low coercive force components (for example, soft magnetic particles and superparamagnetic particles, etc.) peculiar to ε iron oxide are added to magnetic powder in addition to ε iron oxide particles that contribute to actual recording. It can be suppressed from being contained a lot. Therefore, it is possible to suppress the deterioration of the magnetization signal recorded on the adjacent track due to the leakage magnetic field from the recording head, so that a more excellent SNR can be obtained. The upper limit of the peak ratio X / Y is not particularly limited, but is, for example, 100 or less.

  The peak ratio X / Y is determined as follows. First, the MH loop after the background correction is obtained in the same manner as the above-described method of measuring the coercive force Hc. Next, an SFD curve is calculated from the obtained MH loop. For the calculation of the SFD curve, a program attached to the measuring instrument may be used, or another program may be used. The absolute value of the point at which the calculated SFD curve crosses the Y axis (dM / dH) is “Y”, and the height of the main peak seen near the coercive force Hc in the MH loop is “X”. Calculate the peak ratio X / Y. Note that the measurement of the MH loop is performed at 25 ° C. in the same manner as the above-described method of measuring the coercive force Hc. Further, it is assumed that "demagnetizing field correction" is not performed when measuring the MH loop in the thickness direction (vertical direction) of the magnetic recording medium 10.

(Activation volume _Vact )

Activation volume _{V act} is preferably 8000 nm ³ or less, more preferably 6000 nm ³ or less, still more preferably 5000 nm ³ or less, particularly preferably 4000 nm ³ or less, most preferably 3000 nm ³ or less. When the activation volume V _act is 8000 nm ³ or less, the dispersion state of the magnetic powder becomes good, so that the bit inversion region can be made steep, and the recording is performed on the adjacent track by the leakage magnetic field from the recording head. Deterioration of the magnetization signal can be suppressed. Therefore, a better SNR can be obtained.

The above activation volume V _act is obtained by the following equation derived by Street & Woolley.
V _act (nm ³ ) = k _B × T × Χ _irr / (μ ₀ × Ms × S)
(However, k _B : Boltzmann constant (1.38 × 10 ⁻²³ J / K), T: temperature (K), Χ _irr : irreversible magnetic susceptibility, μ ₀ : magnetic permeability in vacuum, S: magnetic viscosity coefficient, Ms: saturation magnetization (emu / cm ³ ))

The irreversible magnetic susceptibility ｉ _irr , the saturation magnetization Ms, and the magnetic viscosity coefficient S substituted in the above equation can be obtained as follows using VSM. Note that the measurement direction by the VSM is the thickness direction (vertical direction) of the magnetic recording medium 10. The measurement by the VSM is performed at 25 ° C. on a measurement sample cut out from the long magnetic recording medium 10. Further, it is assumed that "demagnetizing field correction" is not performed when measuring the MH loop in the thickness direction (vertical direction) of the magnetic recording medium 10.

(Irreversible susceptibility Χ _irr )

The irreversible magnetic susceptibility Χ _irr is defined as the slope of the residual magnetization curve (DCD curve) near the residual coercive force Hr. First, a magnetic field of -1193 kA / m (15 kOe) is applied to the entire magnetic recording medium 10, and the magnetic field is returned to zero to be in a remanent magnetization state. Thereafter, a magnetic field of about 15.9 kA / m (200 Oe) is applied in the opposite direction to return to zero again, and the residual magnetization is measured. Thereafter, similarly, a measurement is performed by repeatedly applying a magnetic field 15.9 kA / m larger than the applied magnetic field and returning the value to zero, and plotting the residual magnetization amount with respect to the applied magnetic field to create a DCD curve. From the obtained DCD curve, the point where the amount of magnetization is zero is defined as the residual coercive force Hr, and the DCD curve is differentiated to obtain the slope of the DCD curve in each magnetic field. In the slope of the DCD curve, the slope near the residual coercive force Hr is _ｉirr .

(Saturation magnetization Ms)

First, the MH loop of the entire magnetic recording medium 10 (measurement sample) is measured in the thickness direction of the magnetic recording medium 10. Next, the coating film (base layer 12, magnetic layer 13, etc.) is wiped off using acetone, ethanol, or the like, and only the base layer 11 is left, and the MH loop of the base layer 11 is similarly used for background correction. In the thickness direction. Thereafter, the MH loop of the base layer 11 is subtracted from the MH loop of the entire magnetic recording medium 10 to obtain the MH loop after the background correction. Ms (emu / cm ³ ) is calculated from the obtained value of the saturation magnetization Ms (emu) of the MH loop and the volume (cm ³ ) of the magnetic layer 13 in the measurement sample. Note that the volume of the magnetic layer 13 is obtained by multiplying the area of the measurement sample by the average thickness of the magnetic layer 13. A method for calculating the average thickness of the magnetic layer 13 necessary for calculating the volume of the magnetic layer 13 will be described later.

(Magnetic viscosity coefficient S)

First, a magnetic field of -1193 kA / m (15 kOe) is applied to the entire magnetic recording medium 10 (measurement sample), and the magnetic field is returned to zero to be in a remanent magnetization state. Thereafter, a magnetic field equivalent to the value of the residual coercive force Hr obtained from the DCD curve is applied in the opposite direction. The magnetization amount is continuously measured at constant time intervals for 1000 seconds with the magnetic field applied. The relationship between the time t and the magnetization amount M (t) obtained in this manner is compared with the following equation to calculate the magneto-viscous coefficient S.
M (t) = M0 + S × ln (t)
(However, M (t): magnetization amount at time t, M0: initial magnetization amount, S: magnetic viscosity coefficient, ln (t): natural logarithm of time)

(Arithmetic average roughness Ra)

  The arithmetic average roughness Ra of the magnetic surface is preferably 2.5 nm or less, more preferably 2.0 nm or less. When Ra is 2.5 nm or less, more excellent SNR can be obtained.

  The arithmetic average roughness Ra is determined as follows. First, the surface on the side on which the magnetic layer 13 is provided is observed using an AFM (Atomic Force Microscope) (manufactured by Bruker, Dimension Icon) to obtain a cross-sectional profile. Next, an arithmetic average roughness Ra is determined from the obtained cross-sectional profile in accordance with JIS B0601: 2001.

(4) Manufacturing method of magnetic recording medium

  Next, a method of manufacturing the magnetic recording medium 10 having the above configuration will be described. First, a coating material for forming an underlayer is prepared by kneading and / or dispersing a nonmagnetic powder and a binder in a solvent. Next, a magnetic layer-forming paint is prepared by kneading and / or dispersing the magnetic powder and the binder in a solvent. For preparing the coating material for forming the magnetic layer and the coating material for forming the underlayer, for example, the following solvents, dispersing devices, and kneading devices can be used.

  Examples of the solvent used in the above-mentioned paint preparation include ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; alcohol solvents such as methanol, ethanol, and propanol; for example, methyl acetate, ethyl acetate, and butyl acetate. Ester solvents such as acetic acid, propyl acetate, ethyl lactate, and ethylene glycol acetate; ether solvents such as diethylene glycol dimethyl ether, 2-ethoxyethanol, tetrahydrofuran, and dioxane; aromatic hydrocarbon solvents such as benzene, toluene, and xylene; And halogenated hydrocarbon solvents such as methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, and chlorobenzene. One of these may be used, or a mixture of two or more.

  As the kneading device used for the above-mentioned paint preparation, for example, a continuous twin-screw kneader, a continuous twin-screw kneader capable of being diluted in multiple stages, a kneader, a kneading device, a kneading device such as a roll kneader can be used. However, the present invention is not particularly limited to these devices. Examples of the dispersing apparatus used for preparing the above-mentioned paint include, for example, a roll mill, a ball mill, a horizontal sand mill, a vertical sand mill, a spike mill, a pin mill, a tower mill, a pearl mill (for example, “DCP Mill” manufactured by Erich Co., Ltd.), a homogenizer, and a super homogenizer. A dispersing device such as a sonic disperser can be used, but is not particularly limited to these devices.

  Next, the base layer 12 is formed by applying a base layer forming paint to one main surface of the base layer 11 and drying the applied base layer. Subsequently, the magnetic layer 13 is formed on the underlayer 12 by applying a coating material for forming a magnetic layer on the underlayer 12 and drying it. At the time of drying, the magnetic powder is magnetically oriented in the thickness direction of the base layer 11 by, for example, a solenoid coil. Further, at the time of drying, the magnetic powder may be magnetically oriented in the longitudinal direction (running direction) of the base layer 11 by, for example, a solenoid coil, and then magnetically oriented in the thickness direction of the base layer 11. After the formation of the magnetic layer 13, the back layer 14 is formed on the other main surface of the base layer 11. Thereby, the magnetic recording medium 10 is obtained.

  Thereafter, the obtained magnetic recording medium 10 is rewound around a large-diameter core and cured. Finally, the magnetic recording medium 10 is cut into a predetermined width (for example, 1/2 inch width) after performing a calendar process. As described above, the intended elongated magnetic recording medium 10 is obtained.

(5) Recording / reproducing device

[Configuration of recording / reproducing device]

  Next, with reference to FIG. 5, an example of the configuration of the recording / reproducing apparatus 30 that performs recording and reproduction on the magnetic recording medium 10 having the above-described configuration will be described.

  The recording / reproducing device 30 has a configuration capable of adjusting the tension applied to the magnetic recording medium 10 in the longitudinal direction. The recording / reproducing device 30 has a configuration in which the magnetic recording medium cartridge 10A can be loaded. Here, for ease of explanation, a case will be described in which the recording / reproducing device 30 has a configuration in which one magnetic recording medium cartridge 10A can be loaded. It may have a configuration in which the medium cartridge 10A can be loaded.

  The recording / reproducing device 30 is connected to information processing devices such as a server 41 and a personal computer (hereinafter, referred to as a “PC”) 42 via a network 43, and transmits data supplied from these information processing devices to a magnetic recording medium. It is configured to be recordable on the cartridge 10A. The shortest recording wavelength of the recording / reproducing device 30 is preferably 100 nm or less, more preferably 75 nm or less, still more preferably 60 nm or less, and particularly preferably 50 nm or less.

  As shown in FIG. 5, the recording / reproducing apparatus includes a spindle 31, a reel 32 on the recording / reproducing apparatus side, a spindle drive unit 33, a reel drive unit 34, a plurality of guide rollers 35, a head unit 36, and a communication unit. An interface (hereinafter, I / F) 37 and a control device 38 are provided.

The spindle 31 is configured to be able to mount the magnetic recording medium cartridge 10A. The magnetic recording medium cartridge 10A conforms to the LTO (Linear Tape Open) standard, and rotatably accommodates a single reel 10C around which the magnetic recording medium 10 is wound in a cartridge case 10B. On the magnetic recording medium 10, a C-shaped servo pattern is recorded in advance as a servo signal. The reel 32 is configured so that the tip of the magnetic recording medium 10 pulled out from the magnetic recording medium cartridge 10A can be fixed.
The present technology also provides a magnetic recording cartridge including a magnetic recording medium according to the present technology. In the magnetic recording cartridge, the magnetic recording medium may be wound around a reel, for example.

  The spindle driving device 33 is a device that drives the spindle 31 to rotate. The reel drive device 34 is a device that drives the reel 32 to rotate. When recording or reproducing data on or from the magnetic recording medium 10, the spindle driving device 33 and the reel driving device 34 cause the spindle 31 and the reel 32 to rotate, thereby causing the magnetic recording medium 10 to travel. . The guide roller 35 is a roller for guiding the running of the magnetic recording medium 10.

  The head unit 36 includes a plurality of recording heads for recording data signals on the magnetic recording medium 10, a plurality of reproducing heads for reproducing data signals recorded on the magnetic recording medium 10, A plurality of servo heads for reproducing recorded servo signals. As the recording head, for example, a ring type head can be used, but the type of the recording head is not limited to this.

  The communication I / F 37 is for communicating with information processing devices such as the server 41 and the PC 42, and is connected to the network 43.

  The control device 38 controls the entire recording / reproducing device 30. For example, the control device 38 records a data signal supplied from the information processing device on the magnetic recording medium 10 by the head unit 36 in response to a request from the information processing device such as the server 41 and the PC 42. Further, in response to a request from an information processing device such as the server 41 and the PC 42, the control device 38 reproduces a data signal recorded on the magnetic recording medium 10 by the head unit 36 and supplies the data signal to the information processing device.

  The control device 38 detects a change in the width of the magnetic recording medium 10 based on the servo signal supplied from the head unit 36. Specifically, a plurality of C-shaped servo patterns are recorded on the magnetic recording medium 10 as servo signals, and the head unit 36 uses the two servo heads on the head unit 36 to generate two different servo patterns. At the same time, they can be reproduced and their respective servo signals can be obtained. Using the relative position information between the servo pattern and the head unit obtained from the servo signal, the position of the head unit 36 is controlled so as to follow the servo pattern. At the same time, the distance information between the servo patterns can be obtained by comparing the two servo signal waveforms. By comparing the distance information between the servo patterns obtained at each measurement, a change in the distance between the servo patterns at each measurement can be obtained. By taking into account the distance information between the servo patterns at the time of recording the servo patterns, a change in the width of the magnetic recording medium 10 can also be calculated. The control device 38 controls the rotation drive of the spindle drive device 33 and the reel drive device 34 based on the change in the distance between the servo patterns obtained as described above or the calculated change in the width of the magnetic recording medium 10. The tension in the longitudinal direction of the magnetic recording medium 10 is adjusted so that the width of the magnetic recording medium 10 becomes a specified width or almost a specified width. Thereby, a change in the width of the magnetic recording medium 10 can be suppressed.

[Operation of recording / reproducing device]

  Next, the operation of the recording / reproducing device 30 having the above configuration will be described.

  First, the magnetic recording medium cartridge 10A is mounted on the recording / reproducing apparatus 30, and the leading end of the magnetic recording medium 10 is pulled out and transferred to the reel 32 via the plurality of guide rollers 35 and the head unit 36. Is attached to the reel 32.

  Next, when an operation unit (not shown) is operated, the spindle driving device 33 and the reel driving device 34 are driven under the control of the control device 38 so that the magnetic recording medium 10 travels from the reel 10C to the reel 32. The spindle 31 and the reel 32 are rotated in the same direction. Thus, while the magnetic recording medium 10 is wound on the reel 32, the recording of information on the magnetic recording medium 10 or the reproduction of the information recorded on the magnetic recording medium 10 is performed by the head unit 36.

  When rewinding the magnetic recording medium 10 on the reel 10C, the spindle 31 and the reel 32 are driven to rotate in the opposite direction, so that the magnetic recording medium 10 travels from the reel 32 to the reel 10C. . Also at the time of rewinding, the recording of information on the magnetic recording medium 10 or the reproduction of the information recorded on the magnetic recording medium 10 are performed by the head unit 36.

(6) Effect

In the magnetic recording medium 10 according to the first embodiment, the average thickness t _T of the magnetic recording medium 10 is t _T ≤ 5.5 μm, and the width of the magnetic recording medium 10 with respect to a change in tension in the longitudinal direction of the magnetic recording medium 10. The dimensional change Δw in the direction is 660 ppm / N ≦ Δw, and the average thickness t _n of the underlayer 12 is t _n ≦ 1.0 μm. Thus, by adjusting the tension in the longitudinal direction of the magnetic recording medium 10 by the recording / reproducing apparatus, it is possible to suppress a change in the width of the magnetic recording medium 10. For example, even if there is a change in temperature and humidity that can cause a change in the width of the magnetic recording medium 10, the width of the magnetic recording medium 10 can be kept constant or almost constant. Further, the magnetic recording medium 10 has a small thickness of t _T ≤ 5.5 μm, but is excellent in handleability.

(7) Modification

[Modification 1]

The magnetic recording medium 10 may further include a barrier layer 15 provided on at least one surface of the base layer 11, as shown in FIG. The barrier layer 15 is a layer for suppressing a dimensional change of the base layer 11 according to the environment. For example, one of the causes of the dimensional change is the hygroscopicity of the base layer 11, and the barrier layer 15 can reduce the rate of entry of moisture into the base layer 11. The barrier layer 15 contains a metal or a metal oxide. Examples of the metal include Al, Cu, Co, Mg, Si, Ti, V, Cr, Mn, Fe, Ni, Zn, Ga, Ge, Y, Zr, Mo, Ru, Pd, Ag, Ba, Pt, At least one of Au and Ta can be used. As the metal oxide, for example, at least one of Al ₂ O ₃ , CuO, CoO, SiO ₂ , Cr ₂ O ₃ , TiO ₂ , Ta ₂ O ₅ , and ZrO ₂ can be used. Any of metal oxides can be used. Alternatively, diamond-like carbon (DLC), diamond, or the like can be used.

The average thickness of the barrier layer 15 is preferably 20 nm or more and 1000 nm or less, more preferably 50 nm or more and 1000 nm or less. The average thickness of the barrier layer 15 is determined in the same manner as the average thickness t _m of the magnetic layer 13. However, the magnification of the TEM image is appropriately adjusted according to the thickness of the barrier layer 15.

[Modification 2]

  The magnetic recording medium 10 may be incorporated in a library device. That is, the present technology also provides a library device including at least one magnetic recording medium 10. The library device has a configuration capable of adjusting the tension applied in the longitudinal direction of the magnetic recording medium 10, and may include a plurality of the recording / reproducing devices 30 described above.

[Modification 3]

  The magnetic recording medium 10 may be subjected to servo signal writing processing by a servo writer. The servo writer can keep the width of the magnetic recording medium 10 constant or almost constant by adjusting the tension in the longitudinal direction of the magnetic recording medium 10 when recording a servo signal or the like. In this case, the servo writer can include a detection device that detects the width of the magnetic recording medium 10. The servo writer can adjust the tension in the longitudinal direction of the magnetic recording medium 10 based on the detection result of the detection device.

3. 2. Second Embodiment (Example of a vacuum thin film type magnetic recording medium)

(1) Configuration of magnetic recording medium

  The magnetic recording medium 110 according to the second embodiment is a long perpendicular magnetic recording medium, and as shown in FIG. 8, a film-like base layer 111 and a soft magnetic underlayer (hereinafter, referred to as “soft magnetic underlayer”). SUL ”) 112, a first seed layer 113A, a second seed layer 113B, a first underlayer 114A, a second underlayer 114B, and a magnetic layer 115. The SUL 112, the first and second seed layers 113A and 113B, the first and second underlayers 114A and 114B, and the magnetic layer 115 are, for example, layers formed by sputtering (hereinafter, also referred to as "sputter layers"). Vacuum thin film. Hereinafter, the first underlayer 114A and the second underlayer 114B are also collectively referred to as a "nonmagnetic layer 114".

  The SUL 112, the first and second seed layers 113A and 113B, and the first and second underlayers 114A and 114B are each formed of one main surface (hereinafter, referred to as “surface”) of the base layer 111 and the magnetic layer 115. The SUL 112, the first seed layer 113A, the second seed layer 113B, the first underlayer 114A, and the second underlayer 114B are stacked in this order from the base layer 111 toward the magnetic layer 115. Have been.

  The magnetic recording medium 110 may further include a protective layer 116 provided on the magnetic layer 115 and a lubricating layer 117 provided on the protective layer 116, if necessary. Further, the magnetic recording medium 110 may further include a back layer 118 provided on the other main surface (hereinafter, referred to as a “back surface”) of the base layer 111 as necessary.

  Hereinafter, the longitudinal direction of the magnetic recording medium 110 (the longitudinal direction of the base layer 111) is referred to as a machine direction (MD). Here, the machine direction refers to a direction in which the recording and reproducing heads move relative to the magnetic recording medium 110, that is, a direction in which the magnetic recording medium 110 travels during recording and reproduction.

The magnetic recording medium 110 according to the second embodiment is suitable for use as a storage medium for data archiving in which demand is expected to increase further in the future. The magnetic recording medium 110 can realize, for example, a surface recording density of 10 times or more that of the current coated magnetic recording medium for storage, that is, a surface recording density of 50 Gb / in ² or more. When a data cartridge of a general linear recording system is formed using the magnetic recording medium 110 having such a surface recording density, a large capacity recording of 100 TB or more per data cartridge is enabled.

  The magnetic recording medium 110 according to the second embodiment has a recording / reproducing having a ring type recording head and a giant magnetoresistive (GMR) type or tunneling magnetoresistive (TMR) type reproducing head. It is suitable for use in an apparatus (recording / reproducing apparatus for recording / reproducing data). The magnetic recording medium 110 according to the second embodiment preferably uses a ring type recording head as a servo signal writing head. A data signal is vertically recorded on the magnetic layer 115 by, for example, a ring-type recording head. A servo signal is vertically recorded on the magnetic layer 115 by, for example, a ring-type recording head.

(2) Description of each layer

(Base layer)

  Since the description of the base layer 111 in the first embodiment applies to the base layer 111, the description of the base layer 111 is omitted.

(SUL)

  The SUL 112 includes a soft magnetic material in an amorphous state. The soft magnetic material includes, for example, at least one of a Co-based material and an Fe-based material. The Co-based material includes, for example, CoZrNb, CoZrTa, or CoZrTaNb. The Fe-based material includes, for example, FeCoB, FeCoZr, or FeCoTa.

  The SUL 112 is a single-layer SUL, and is provided directly on the base layer 111. The average thickness of the SUL 112 is preferably 10 nm or more and 50 nm or less, more preferably 20 nm or more and 30 nm or less.

  The average thickness of the SUL 112 is obtained by the same method as the method for measuring the average thickness of the magnetic layer 13 in the first embodiment. The average thickness of the layers other than the SUL 112 (that is, the average thickness of the first and second seed layers 113A and 113B, the nonmagnetic layer 114, and the magnetic layer 115), which will be described later, is the same as the magnetic layer in the first embodiment. The average thickness is determined by the same method as the method for measuring the average thickness. However, the magnification of the TEM image is appropriately adjusted according to the thickness of each layer. The same applies to the following third embodiment.

(First and second seed layers)

  The first seed layer 113A contains an alloy containing Ti and Cr, and has an amorphous state. The alloy may further contain O (oxygen). This oxygen may be impurity oxygen contained in the first seed layer 113A in a small amount when the first seed layer 113A is formed by a film formation method such as a sputtering method.

  Here, "alloy" means at least one of a solid solution containing Ti and Cr, a eutectic, an intermetallic compound, and the like. The “amorphous state” means that a halo is observed by X-ray diffraction or electron diffraction, and the crystal structure cannot be specified.

  The atomic ratio of Ti to the total amount of Ti and Cr contained in first seed layer 113A is preferably within a range from 30 at% to less than 100 at%, more preferably from 50 at% to less than 100 at%. If the atomic ratio of Ti is less than 30%, the (100) plane of the body-centered cubic lattice (bcc) structure of Cr will be oriented and formed on the first seed layer 113A. There is a possibility that the orientation of the first and second underlayers 114A and 114B may decrease.

The atomic ratio of Ti is determined as follows. While ion milling the magnetic recording medium 110 from the magnetic layer 115 side, Auger Electron Spectroscopy,
Hereinafter, it is referred to as “AES”. ) Is performed in the depth direction (depth profile measurement) of the first seed layer 113A. Next, the average composition (average atomic ratio) of Ti and Cr in the film thickness direction is determined from the obtained depth profile. Next, the atomic ratio of Ti is determined using the determined average composition of Ti and Cr.

When the first seed layer 113A contains Ti, Cr, and O, the atomic ratio of O to the total amount of Ti, Cr, and O contained in the first seed layer 113A is preferably 15 atomic% or less, more preferably. Is 10 atomic% or less. If the atomic ratio of O exceeds 15 atomic%, TiO ₂ crystals are generated, which affects the formation of crystal nuclei of the first and second underlayers 114A and 114B formed on the first seed layer 113A. And the orientation of the first and second underlayers 114A and 114B may be reduced. The atomic ratio of O is determined using the same analysis method as the atomic ratio of Ti.

  The alloy included in the first seed layer 113A may further include an element other than Ti and Cr as an additional element. The additional element may be, for example, one or more elements selected from the group consisting of Nb, Ni, Mo, Al, and W.

  The average thickness of the first seed layer 113A is preferably 2 nm or more and 15 nm or less, more preferably 3 nm or more and 10 nm or less.

  The second seed layer 113B contains, for example, NiW or Ta and has a crystalline state. The average thickness of the second seed layer 113B is preferably 3 nm or more and 20 nm or less, more preferably 5 nm or more and 15 nm or less.

  The first and second seed layers 113A and 113B have a crystal structure similar to the first and second underlayers 114A and 114B, and are not the seed layers provided for crystal growth but the first and second seed layers 113A and 113B. This is a seed layer for improving the vertical orientation of the first and second underlayers 114A and 114B by the amorphous state of the second seed layers 113A and 113B.

(Non-magnetic layer)

The nonmagnetic layer 114 includes a first underlayer 114A and a second underlayer 114B. The first and second underlayers 114A and 114B preferably have the same crystal structure as the magnetic layer 115. When the magnetic layer 115 includes a Co-based alloy, the first and second underlayers 114A and 114B include a material having a hexagonal close-packed (hcp) structure similar to that of the Co-based alloy. It is preferable that the axis is oriented in a direction perpendicular to the film surface (that is, in the film thickness direction). This is because the orientation of the magnetic layer 115 can be increased, and the lattice constant matching between the second underlayer 114B and the magnetic layer 115 can be relatively improved. As a material having a hexagonal close packing (hcp) structure, a material containing Ru is preferably used, and specifically, Ru alone or a Ru alloy is preferable. Examples of the Ru alloy include Ru alloy oxides such as Ru—SiO ₂ , Ru—TiO ₂ , and Ru—ZrO _2, and the Ru alloy may be any one of these.

  As described above, the same material can be used for the first and second underlayers 114A and 114B. However, the desired effects of the first and second underlayers 114A and 114B are different. Specifically, the second underlayer 114B has a film structure that promotes the granular structure of the magnetic layer 115 as an upper layer, and the first underlayer 114A has a film structure with high crystal orientation. In order to obtain such a film structure, it is preferable that the film formation conditions such as the sputtering conditions of the first and second underlayers 114A and 114B are different.

The average thickness t _n of the nonmagnetic layer 114 (the total thickness of the first underlayer 114A and the second underlayer 114B) is t _n ≦ 1.0 μm, preferably t _n ≦ 0.9 μm, Preferably, t _n ≦ 0.7 μm, and even more preferably, t _n ≦ 0.1 μm. The average thickness _{t n} of the non-magnetic layer 114 is preferably 0.01 [mu] m ≦ _{t n,} more preferably 0.02 [mu] m ≦ _{t n.}

(Magnetic layer)

The magnetic layer (also referred to as a recording layer) 115 can be a perpendicular magnetic recording layer in which a magnetic material is vertically oriented. From the viewpoint of improving the recording density, the magnetic layer 115 is preferably a granular magnetic layer containing a Co-based alloy. This granular magnetic layer is composed of ferromagnetic crystal grains containing a Co-based alloy and non-magnetic grain boundaries (non-magnetic material) surrounding the ferromagnetic crystal grains. More specifically, the granular magnetic layer includes a column (columnar crystal) containing a Co-based alloy and a non-magnetic grain boundary (for example, an oxide such as SiO ₂ ) surrounding the column and magnetically separating each column. ). With this structure, the magnetic layer 115 having a structure in which each column is magnetically separated can be formed.

  The Co-based alloy has a hexagonal close-packed (hcp) structure, and its c-axis is oriented in the direction perpendicular to the film surface (in the film thickness direction). As the Co-based alloy, it is preferable to use a CoCrPt-based alloy containing at least Co, Cr, and Pt. The CoCrPt-based alloy may further contain an additional element. Examples of the additional element include one or more elements selected from the group consisting of Ni and Ta.

The non-magnetic grain boundaries surrounding the ferromagnetic crystal grains contain a non-magnetic metal material. Here, the metal includes a semimetal. As the non-magnetic metal material, for example, at least one of a metal oxide and a metal nitride can be used. From the viewpoint of more stably maintaining a granular structure, it is preferable to use a metal oxide. Examples of the metal oxide include metal oxides containing at least one element selected from the group consisting of Si, Cr, Co, Al, Ti, Ta, Zr, Ce, Y, and Hf. Metal oxides containing oxides (ie, SiO ₂ ) are preferred. Specific examples of the metal oxide include SiO ₂ , Cr ₂ O ₃ , CoO, Al ₂ O ₃ , TiO ₂ , Ta ₂ O ₅ , ZrO ₂ , and HfO ₂ . Examples of the metal nitride include a metal nitride containing at least one element selected from the group consisting of Si, Cr, Co, Al, Ti, Ta, Zr, Ce, Y, Hf, and the like. Specific examples of the metal nitride include SiN, TiN, and AlN.

It is preferable that the CoCrPt-based alloy contained in the ferromagnetic crystal grains and the Si oxide contained in the nonmagnetic grain boundary have an average composition represented by the following formula (1). This is because the amount of saturation magnetization Ms that can suppress the influence of the demagnetizing field and secure a sufficient reproduction output can be realized, thereby further improving the recording and reproduction characteristics.
_{(Co x Pt y Cr 100-} x-y) 100-z - (SiO 2) z ··· (1)
(However, in the formula (1), x, y, and z are values within a range of 69 ≦ x ≦ 75, 10 ≦ y ≦ 16, and 9 ≦ z ≦ 12, respectively.)

  The above composition can be determined as follows. While ion milling the magnetic recording medium 110 from the magnetic layer 115 side, the depth direction analysis of the magnetic layer 115 was performed by AES, and the average composition (average atomic ratio) of Co, Pt, Cr, Si, and O in the film thickness direction. Ask for.

The average thickness _t m of the magnetic layer 115 [nm] is preferably 9nm ≦ _{t m} ≦ 90nm, more preferably 9nm ≦ _{t m} ≦ 20nm, even more preferably 9nm ≦ _{t m} ≦ 15nm. By average thickness t _m of the magnetic layer 115 is within the above range, it is possible to improve the electromagnetic conversion characteristics.

(Protective layer)

The protective layer 116 contains, for example, a carbon material or silicon dioxide (SiO ₂ ), and preferably contains a carbon material from the viewpoint of the film strength of the protective layer 116. Examples of the carbon material include graphite, diamond-like carbon (DLC), and diamond.

(Lubricant layer)

The lubrication layer 117 contains at least one type of lubricant. The lubricating layer 117 may further contain various additives as necessary, for example, a rust preventive. The lubricant has at least two carboxyl groups and one ester bond, and contains at least one carboxylic acid compound represented by the following general formula (1). The lubricant may further include a type of lubricant other than the carboxylic acid compound represented by the following general formula (1). General formula (1):

(In the formula, Rf is an unsubstituted or substituted saturated or unsaturated fluorinated hydrocarbon group or hydrocarbon group, Es is an ester bond, and R may be absent, but is unsubstituted or substituted. It is a saturated or unsaturated hydrocarbon group.)

The carboxylic acid compound is preferably represented by the following general formula (2) or (3).
General formula (2):

(In the formula, Rf is an unsubstituted or substituted saturated or unsaturated fluorine-containing hydrocarbon group or hydrocarbon group.)
General formula (3):

(In the formula, Rf is an unsubstituted or substituted saturated or unsaturated fluorine-containing hydrocarbon group or hydrocarbon group.)

  The lubricant preferably contains one or both of the carboxylic acid compounds represented by the general formulas (2) and (3).

  When a lubricant containing the carboxylic acid compound represented by the general formula (1) is applied to the magnetic layer 115 or the protective layer 116, the lubricant is lubricated by the cohesion between the fluorine-containing hydrocarbon groups or the hydrocarbon groups Rf which are hydrophobic groups. The action is manifested. When the Rf group is a fluorine-containing hydrocarbon group, the total carbon number is preferably 6 to 50, and the total carbon number of the fluorinated hydrocarbon group is preferably 4 to 20. The Rf group may be, for example, a saturated or unsaturated linear, branched, or cyclic hydrocarbon group, but may preferably be a saturated linear hydrocarbon group.

For example, when the Rf group is a hydrocarbon group, it is preferably a group represented by the following general formula (4).
General formula (4):

(However, in the general formula (4), 1 is an integer selected from the range of 8 to 30, more preferably 12 to 20.)

When the Rf group is a fluorine-containing hydrocarbon group, it is preferably a group represented by the following general formula (5).
General formula (5):

(However, in the general formula (5), m and n are integers independently selected from the following ranges, and m = 2 to 20, n = 3 to 18, more preferably, m = 4 to 13, n = 3 to 10.)

Fluorinated hydrocarbon group may have concentrated on one place in the molecule as described above, also may be dispersed as the following general formula (6), -CF ₃ or -CF 2 _- only it may be without -CHF ₂ and -CHF- like.
General formula (6):

(However, in the general formula (6), n1 + n2 = n and m1 + m2 = m.)

  In the general formulas (4), (5), and (6), the number of carbon atoms is limited as described above because the number of carbon atoms (l or the sum of m and n) of an alkyl group or a fluorinated alkyl group is limited. When the above is not less than the above lower limit, the length becomes an appropriate length, the cohesive force between the hydrophobic groups is effectively exerted, a good lubricating action is developed, and the friction and wear durability is improved. . Further, when the number of carbon atoms is equal to or less than the above upper limit, the solubility of the lubricant comprising the carboxylic acid compound in a solvent can be kept good.

  In particular, when the Rf group in the general formulas (1), (2) and (3) contains a fluorine atom, it is effective in reducing the friction coefficient and further improving the running property. However, a hydrocarbon group is provided between the fluorinated hydrocarbon group and the ester bond to separate the fluorinated hydrocarbon group and the ester bond, thereby ensuring the stability of the ester bond and preventing hydrolysis. preferable.

  Further, the Rf group may have a fluoroalkyl ether group or a perfluoropolyether group.

  The R group in the general formula (1) may not be present, but in some cases, is preferably a hydrocarbon chain having a relatively small number of carbon atoms.

  The Rf group or the R group contains one or more elements selected from nitrogen, oxygen, sulfur, phosphorus, and halogen as constituent elements, and includes, in addition to the above-described functional groups, a hydroxyl group, a carboxyl group, and a carbonyl group. , An amino group, an ester bond, and the like.

Specifically, the carboxylic acid compound represented by the general formula (1) is preferably at least one of the following compounds. That is, the lubricant preferably contains at least one compound shown below.
CF ₃ (CF ₂ ) ₇ (CH ₂ ) ₁₀ COOCH (COOH) CH ₂ COOH
CF ₃ (CF ₂ ) ₃ (CH ₂ ) ₁₀ COOCH (COOH) CH ₂ COOH
C ₁₇ H ₃₅ COOCH (COOH) CH ₂ COOH
CF ₃ (CF ₂ ) ₇ (CH ₂ ) ₂ OCOCH ₂ CH (C ₁₈ H ₃₇ ) COOCH (COOH) CH ₂ COOH
CF ₃ (CF ₂ ) ₇ COOCH (COOH) CH ₂ COOH
CHF ₂ (CF ₂ ) ₇ COOCH (COOH) CH ₂ COOH
CF ₃ (CF ₂ ) ₇ (CH ₂ ) ₂ OCOCH ₂ CH (COOH) CH ₂ COOH
CF ₃ (CF ₂ ) ₇ (CH ₂ ) ₆ OCOCH ₂ CH (COOH) CH ₂ COOH
CF ₃ (CF ₂ ) ₇ (CH ₂ ) ₁₁ OCOCH ₂ CH (COOH) CH ₂ COOH
CF ₃ (CF ₂ ) ₃ (CH ₂ ) ₆ OCOCH ₂ CH (COOH) CH ₂ COOH
C ₁₈ H ₃₇ OCOCH ₂ CH (COOH) CH ₂ COOH
CF ₃ (CF ₂ ) ₇ (CH ₂ ) ₄ COOCH (COOH) CH ₂ COOH
CF ₃ (CF ₂ ) ₃ (CH ₂ ) ₄ COOCH (COOH) CH ₂ COOH
CF ₃ (CF ₂ ) ₃ (CH ₂ ) ₇ COOCH (COOH) CH ₂ COOH
CF ₃ (CF ₂ ) ₉ (CH ₂ ) ₁₀ COOCH (COOH) CH ₂ COOH
CF ₃ (CF ₂ ) ₇ (CH ₂ ) ₁₂ COOCH (COOH) CH ₂ COOH
CF ₃ (CF ₂ ) ₅ (CH ₂ ) ₁₀ COOCH (COOH) CH ₂ COOH
CF ₃ (CF ₂ ) ₇ CH (C ₉ H ₁₉ ) CH ₂ CH = CH (CH ₂ ) ₇ COOCH (COOH) CH ₂ COOH
CF ₃ (CF ₂ ) ₇ CH (C ₆ H ₁₃ ) (CH ₂ ) ₇ COOCH (COOH) CH ₂ COOH
CH ₃ (CH ₂ ) ₃ (CH ₂ CH ₂ CH (CH ₂ CH ₂ (CF ₂ ) ₉ CF ₃ )) ₂ (CH ₂ ) ₇ COOCH (COOH) CH ₂ COOH

  The carboxylic acid compound represented by the general formula (1) is soluble in a non-fluorinated solvent having a small environmental load, such as a hydrocarbon solvent, a ketone solvent, an alcohol solvent, and an ester solvent. There is an advantage that operations such as coating, dipping, and spraying can be performed using a general-purpose solvent. Specifically, as the general-purpose solvent, for example, hexane, heptane, octane, decane, dodecane, benzene, toluene, xylene, cyclohexane, methyl ethyl ketone, methyl isobutyl ketone, methanol, ethanol, isopropanol, diethyl ether, tetrahydrofuran, dioxane, and cyclohexanone And the like.

  When the protective layer 116 contains a carbon material, when the carboxylic acid compound is applied as a lubricant on the protective layer 116, two carboxyl groups, which are polar groups of lubricant molecules, and at least one The ester bonding group is adsorbed, and the lubricating layer 117 having particularly good durability can be formed by the cohesive force between the hydrophobic groups.

  The lubricant is not only retained on the surface of the magnetic recording medium 110 as the lubricating layer 117 as described above, but also contained in the layers such as the magnetic layer 115 and the protective layer 116 constituting the magnetic recording medium 110, and retained. It may be.

(Back layer)

  Regarding the back layer 118, the description of the back layer 14 in the first embodiment applies.

(3) Physical properties and structure

The above 2. All of the description regarding the physical properties and structure described in (3) above also applies to the second embodiment. For example, the average thickness t _T of the magnetic recording medium 110, the dimensional change Δw, the temperature expansion coefficient α, the humidity expansion coefficient β, the Poisson's ratio ρ, the elastic limit value σ _{MD in the} longitudinal direction, the friction between the magnetic surface and the back surface The coefficient μ and the surface roughness R _ab of the back layer 118 may be the same as those in the first embodiment. Therefore, description of the physical properties and structure of the magnetic recording medium of the second embodiment will be omitted.

(4) Configuration of sputtering equipment

  Hereinafter, an example of a configuration of a sputtering apparatus 120 used for manufacturing the magnetic recording medium 110 according to the second embodiment will be described with reference to FIG. The sputtering apparatus 120 is a continuous winding type sputtering used for forming the SUL 112, the first seed layer 113A, the second seed layer 113B, the first underlayer 114A, the second underlayer 114B, and the magnetic layer 115. As shown in FIG. 9, the apparatus is a film forming chamber 121, a drum 122 that is a metal can (rotating body), cathodes 123a to 123f, a supply reel 124, a take-up reel 125, and a plurality of guide rolls. 127a to 127c and 128a to 128c. The sputtering apparatus 120 is, for example, a DC (direct current) magnetron sputtering system, but the sputtering system is not limited to this system.

  The film formation chamber 121 is connected to a vacuum pump (not shown) via an exhaust port 126, and the atmosphere in the film formation chamber 121 is set to a predetermined degree of vacuum by the vacuum pump. Inside the film forming chamber 121, a rotatable drum 122, a supply reel 124, and a take-up reel 125 are arranged. A plurality of guide rolls 127 a to 127 c for guiding the transport of the base layer 111 between the supply reel 124 and the drum 122 are provided inside the film forming chamber 121, and the drum 122 and the take-up reel 125 are provided. And a plurality of guide rolls 128a to 128c for guiding the transport of the base layer 111 between the guide rollers 128a to 128c. At the time of sputtering, the base layer 111 unwound from the supply reel 124 is taken up by the take-up reel 125 via the guide rolls 127a to 127c, the drum 122, and the guide rolls 128a to 128c. The drum 122 has a columnar shape, and the long base layer 111 is transported along the cylindrical peripheral surface of the drum 122. The drum 122 is provided with a cooling mechanism (not shown), and is cooled to, for example, about −20 ° C. during sputtering. A plurality of cathodes 123 a to 123 f are arranged inside the film forming chamber 121 so as to face the peripheral surface of the drum 122. A target is set on each of the cathodes 123a to 123f. Specifically, the SUL 112, the first seed layer 113A, the second seed layer 113B, the first underlayer 114A, and the second underlayer 114B are respectively provided on the cathodes 123a, 123b, 123c, 123d, 123e, and 123f. A target for forming the magnetic layer 115 is set. A plurality of types of films, namely, SUL 112, first seed layer 113A, second seed layer 113B, first underlayer 114A, second underlayer 114B, and magnetic layer 115 are simultaneously formed by these cathodes 123a to 123f. A film is formed.

  In the sputtering apparatus 120 having the above configuration, the SUL 112, the first seed layer 113A, the second seed layer 113B, the first underlayer 114A, the second underlayer 114B, and the magnetic layer 115 are continuously formed by the RolltoRoll method. Can be membrane.

(5) Manufacturing method of magnetic recording medium

  The magnetic recording medium 110 according to the second embodiment can be manufactured, for example, as follows.

  First, the SUL 112, the first seed layer 113A, the second seed layer 113B, the first underlayer 114A, the second underlayer 114B, and the magnetic layer 115 are formed using the sputtering apparatus 120 shown in FIG. Films are sequentially formed on the surface of the layer 111. Specifically, the film is formed as follows. First, the film forming chamber 121 is evacuated to a predetermined pressure. Then, the targets set on the cathodes 123a to 123f are sputtered while introducing a process gas such as Ar gas into the film formation chamber 121. Thus, the SUL 112, the first seed layer 113A, the second seed layer 113B, the first underlayer 114A, the second underlayer 114B, and the magnetic layer 115 are sequentially formed on the surface of the traveling base layer 111. Is done.

Atmosphere of the film forming chamber 121 during the sputtering, for example, on the order of ^{1 × 10 -5 Pa~5 × 10 -5} Pa. The thickness and characteristics of the SUL 112, the first seed layer 113A, the second seed layer 113B, the first underlayer 114A, the second underlayer 114B, and the magnetic layer 115 are determined by the tape line speed at which the base layer 111 is wound. It can be controlled by adjusting the pressure of a process gas such as Ar gas introduced during sputtering (sputter gas pressure), the input power, and the like.

  Next, a protective layer 116 is formed on the magnetic layer 115. As a method for forming the protective layer 116, for example, a chemical vapor deposition (CVD) method or a physical vapor deposition (PVD) method can be used.

  Next, a binder, inorganic particles, a lubricant and the like are kneaded and dispersed in a solvent to prepare a coating material for forming a back layer. Next, the back layer 118 is formed on the back surface of the base layer 111 by applying a coating material for forming the back layer on the back surface of the base layer 111 and drying the coating material.

  Next, for example, a lubricant is applied on the protective layer 116 to form a lubricant layer 117. As a method of applying the lubricant, for example, various application methods such as gravure coating and dip coating can be used. Next, if necessary, the magnetic recording medium 110 is cut into a predetermined width. Thus, the magnetic recording medium 110 shown in FIG. 8 is obtained.

(6) Effect

In the magnetic recording medium 110 according to the second embodiment, as in the first embodiment, a change in the width of the magnetic recording medium 110 is adjusted by adjusting the tension in the longitudinal direction of the magnetic recording medium 110 using a recording / reproducing apparatus. Can be suppressed. For example, even if there is a change in temperature and humidity that may cause a change in the width of the magnetic recording medium 110, the width of the magnetic recording medium 110 can be kept constant or almost constant. Further, the thickness of the magnetic recording medium 110 is as thin as t _T ≤ 5.5 μm, but is excellent in handling properties.

(7) Modification

  The magnetic recording medium 110 may further include an underlayer between the base layer 111 and the SUL 112. Since the SUL 112 has an amorphous state, it does not play a role in promoting the epitaxial growth of the layer formed on the SUL 112, but does not disturb the crystal orientation of the first and second underlayers 114A and 114B formed on the SUL 112. Is required. For this purpose, it is preferable that the soft magnetic material has a fine structure that does not form a column. However, when the influence of the release of gas such as moisture from the base layer 111 is large, the soft magnetic material becomes coarse and the SUL 112 There is a possibility that the crystal orientation of the first and second underlayers 114A and 114B formed thereon is disturbed. In order to suppress the influence of the release of gas such as moisture from the base layer 111, as described above, an underlayer containing an alloy containing Ti and Cr and having an amorphous state is provided between the base layer 111 and the SUL 112. Is preferably provided. As a specific configuration of the underlayer, a configuration similar to that of the first seed layer 113A of the second embodiment can be adopted.

  The magnetic recording medium 110 may not include at least one of the second seed layer 113B and the second underlayer 114B. However, from the viewpoint of improving the SNR, it is more preferable to include both the second seed layer 113B and the second underlayer 114B.

  The magnetic recording medium 110 may include an APC-SUL (Antiparallel Coupled SUL) instead of a single-layer SUL.

4. Third Embodiment (Example of a vacuum thin film type magnetic recording medium)

(Structure of magnetic recording medium)

  As shown in FIG. 10, the magnetic recording medium 130 according to the third embodiment includes a base layer 111, an SUL 112, a seed layer 131, a first underlayer 132A, a second underlayer 132B, And a layer 115. In the third embodiment, the same parts as those in the second embodiment are denoted by the same reference numerals, and description thereof will be omitted. Hereinafter, the first underlayer 132A and the second underlayer 132B are collectively referred to as a "nonmagnetic layer 132".

  The SUL 112, the seed layer 131, and the first and second underlayers 132A and 132B are provided between one main surface of the base layer 111 and the magnetic layer 115, and extend from the base layer 111 toward the magnetic layer 115. The SUL 112, the seed layer 131, the first underlayer 132A, and the second underlayer 132B are stacked in this order.

(Seed layer)

  The seed layer 131 contains Cr, Ni, and Fe, has a face-centered cubic lattice (fcc) structure, and is preferentially oriented so that the (111) plane of the face-centered cubic structure is parallel to the surface of the base layer 111. doing. Here, the preferred orientation refers to a state in which the diffraction peak intensity from the (111) plane of the face-centered cubic lattice structure is larger than the diffraction peaks from other crystal planes in the θ-2θ scan of the X-ray diffraction method, or X-ray diffraction. Means a state where only the diffraction peak intensity from the (111) plane of the face-centered cubic lattice structure is observed in the θ-2θ scan of the method.

  The intensity ratio of the X-ray diffraction of the seed layer 131 is preferably 60 cps / nm or more, more preferably 70 cps / nm or more, and still more preferably 80 cps / nm or more from the viewpoint of improving the SNR. Here, the X-ray diffraction intensity ratio of the seed layer 131 is a value (I / D) obtained by dividing the X-ray diffraction intensity I (cps) of the seed layer 131 by the average thickness D (nm) of the seed layer 131. (Cps / nm)).

It is preferable that Cr, Ni, and Fe contained in the seed layer 131 have an average composition represented by the following equation (2).
Cr _X (Ni _Y Fe _100-Y ) _100-X (2)
(However, in the formula (2), X is within a range of 10 ≦ X ≦ 45, and Y is within a range of 60 ≦ Y ≦ 90.) When X is within the above range, the face-centered cubic of Cr, Ni, and Fe is obtained. The (111) orientation of the lattice structure is improved, and a better SNR can be obtained. Similarly, when Y is within the above range, the (111) orientation of the face-centered cubic lattice structure of Cr, Ni, and Fe is improved, and a better SNR can be obtained.

  The average thickness of the seed layer 131 is preferably 5 nm or more and 40 nm or less. By setting the average thickness of the seed layer 131 within this range, the (111) orientation of the face-centered cubic lattice structure of Cr, Ni, and Fe can be improved, and a better SNR can be obtained. Note that the average thickness of the seed layer 131 is determined in the same manner as the magnetic layer 13 in the first embodiment. However, the magnification of the TEM image is appropriately adjusted according to the thickness of the seed layer 131.

(Non-magnetic layer)

  The nonmagnetic layer 132 includes a first underlayer 132A and a second underlayer 132B. The first underlayer 132A contains Co and O having a face-centered cubic lattice structure, and has a column (columnar crystal) structure. The first underlayer 132A containing Co and O has almost the same effect (function) as the second underlayer 132B containing Ru. The concentration ratio of the average atomic concentration of O to the average atomic concentration of Co ((average atomic concentration of O) / (average atomic concentration of Co)) is 1 or more. When the concentration ratio is 1 or more, the effect of providing the first underlayer 132A is improved, and a better SNR can be obtained.

  The column structure is preferably inclined from the viewpoint of improving the SNR. The direction of the inclination is preferably the longitudinal direction of the long magnetic recording medium 130. The reason why the longitudinal direction is preferable is as follows. The magnetic recording medium 130 according to the present embodiment is a so-called magnetic recording medium for linear recording, and the recording tracks are parallel to the longitudinal direction of the magnetic recording medium 130. The magnetic recording medium 130 according to the present embodiment is also a so-called perpendicular magnetic recording medium. From the viewpoint of recording characteristics, it is preferable that the crystal orientation axis of the magnetic layer 115 is in the vertical direction. The crystal orientation axis of the magnetic layer 115 may be tilted due to the tilt of the column structure of 132A. In the magnetic recording medium 130 for linear recording, the crystal orientation axis of the magnetic layer 115 is inclined in the longitudinal direction of the magnetic recording medium 130 due to the head magnetic field at the time of recording. As compared with the configuration in which the crystal orientation axis of the magnetic layer 115 is inclined in the direction, the influence of the inclination of the crystal orientation axis on the recording characteristics can be reduced. In order to incline the crystal orientation axis of the magnetic layer 115 in the longitudinal direction of the magnetic recording medium 130, the inclination direction of the column structure of the first underlayer 132A should be the longitudinal direction of the magnetic recording medium 130 as described above. preferable.

  The inclination angle of the column structure is preferably larger than 0 ° and 60 ° or less. In the range where the inclination angle is larger than 0 ° and equal to or smaller than 60 °, the change in the shape of the tip of the column included in the first underlayer 132A is large and substantially triangular mountain-shaped, so that the effect of the granular structure is enhanced and noise is reduced. The SNR tends to improve. On the other hand, if the inclination angle exceeds 60 °, the change in the tip shape of the column included in the first underlayer 132A is so small that it is difficult to form a substantially triangular mountain shape, and the low noise effect tends to be weakened.

  The average particle size of the column structure is 3 nm or more and 13 nm or less. If the average particle diameter is less than 3 nm, the average particle diameter of the column structure included in the magnetic layer 115 becomes small, and therefore, the current magnetic material may have a reduced ability to hold recording. On the other hand, when the average particle size is 13 nm or less, noise can be suppressed and a better SNR can be obtained.

The average thickness _{t n} of the non-magnetic layer 132 (the sum of the first underlying layer 132A having an average thickness and a second average thickness of the underlayer 132B) is a _{t n} ≦ 1.0 .mu.m, preferably _{t n} ≦ 0. 9 μm, more preferably t _n ≦ 0.7 μm, and still more preferably t _n ≦ 0.1 μm. The average thickness _{t n} of the non-magnetic layer 114 is preferably 0.01 [mu] m ≦ _{t n,} more preferably 0.02 [mu] m ≦ _{t n.}

The second underlayer 132B preferably has the same crystal structure as the magnetic layer 115. When the magnetic layer 115 includes a Co-based alloy, the second underlayer 132B includes a material having a hexagonal close-packed (hcp) structure similar to that of the Co-based alloy, and the c-axis of the structure is in the film surface. On the other hand, it is preferable to be oriented in the vertical direction (that is, the film thickness direction). This is because the orientation of the magnetic layer 115 can be enhanced, and the lattice constant matching between the second underlayer 132B and the magnetic layer 115 can be relatively improved. As a material having a hexagonal close-packed structure, a material containing Ru is preferably used, and specifically, Ru alone or a Ru alloy is preferable. Examples of the Ru alloy include Ru alloy oxides such as Ru—SiO ₂ , Ru—TiO _{2, and} Ru—ZrO ₂ .

  The average thickness of the second underlayer 132B may be smaller than the underlayer (eg, an underlayer containing Ru) in a general magnetic recording medium, and may be, for example, 1 nm or more and 5 nm or less. Since the seed layer 131 and the first underlayer 132A having the above-described configuration are provided under the second underlayer 132B, a good SNR even when the average thickness of the second underlayer 132B is small as described above. Is obtained. Note that the average thickness of the second underlayer 132B is determined in the same manner as the magnetic layer 13 in the first embodiment. However, the magnification of the TEM image is appropriately adjusted according to the thickness of the second underlayer 132B.

(effect)

  In the magnetic recording medium 130 according to the third embodiment, similarly to the first embodiment, the width of the magnetic recording medium 10 can be kept constant or almost constant by adjusting the tension in the longitudinal direction of the magnetic recording medium 10. it can.

  The magnetic recording medium 130 according to the third embodiment includes a seed layer 131 and a first underlayer 132A between the base layer 111 and the second underlayer 132B. The seed layer 131 contains Cr, Ni, and Fe, has a face-centered cubic lattice structure, and is preferentially oriented so that the (111) plane of the face-centered cubic structure is parallel to the surface of the base layer 111. . The first underlayer 132A contains Co and O, has a column structure in which the ratio of the average atomic concentration of O to the average atomic concentration of Co is 1 or more, and the average particle size is 3 nm or more and 13 nm or less. Accordingly, the magnetic layer 115 having a good crystal orientation and a high coercive force can be realized without reducing the thickness of the second underlayer 132B and using an expensive material Ru as much as possible.

  Ru contained in the second underlayer 132B has the same hexagonal close-packed lattice structure as Co, which is the main component of the magnetic layer 115. For this reason, Ru has the effect of improving the crystal orientation of the magnetic layer 115 and promoting the granularity. In order to further improve the crystal orientation of Ru contained in the second underlayer 132B, the first underlayer 132A and the seed layer 131 are provided below the second underlayer 132B. In the magnetic recording medium 130 according to the third embodiment, the same effect (function) as that of the second underlayer 132B containing Ru is obtained by using the first underlayer containing inexpensive CoO having a face-centered cubic lattice structure. 132A. For this reason, the thickness of the second underlayer 132B can be reduced. In addition, a seed layer 131 containing Cr, Ni, and Fe is provided to increase the crystal orientation of the first underlayer 132A.

5. Example

  Hereinafter, the present technology will be described specifically with reference to examples, but the present technology is not limited to only these examples.

In the following Examples and Comparative Examples, the average thickness t _{T of} the magnetic recording tape, the dimensional change amount Δw in the width direction of the magnetic recording tape with respect to the change in the tension in the longitudinal direction of the magnetic recording tape, the temperature expansion coefficient α of the magnetic recording tape, humidity expansion coefficient of the recording tape beta, Poisson's ratio of the magnetic recording tape [rho, the average thickness t _m in the longitudinal direction of the elastic limit sigma _MD, a magnetic layer of the magnetic recording _tape, the squareness ratio S2, the average thickness of the back layer t _b, back The surface roughness R _{ab of the} layer and the coefficient of friction μ between the magnetic surface and the back surface are values obtained by the measurement method described in the first embodiment. However, as described later, in Example 11, the speed V when measuring the elastic limit value σ _MD in the longitudinal direction was set to a value different from the measurement method described in the first embodiment.

[Example 1]
(Preparation process of paint for forming magnetic layer)
A coating material for forming a magnetic layer was prepared as follows. First, the first composition having the following composition was kneaded with an extruder. Next, the kneaded first composition and the second composition having the following composition were added to a stirring tank equipped with a disper, and premixed. Subsequently, the mixture was further mixed with a sand mill and filtered to prepare a coating material for forming a magnetic layer.

(First composition)
Powder of ε iron oxide nanoparticles (ε-Fe ₂ O ₃ crystal particles): 100 parts by mass Vinyl chloride resin (30% by mass of cyclohexanone solution): 10 parts by mass (degree of polymerization 300, Mn = 10000, OSO ₃ as a polar group) K = 0.07 mmol / g, secondary OH = 0.3 mmol / g.)
Aluminum oxide powder: 5 parts by mass (α-Al ₂ O ₃ , average particle size 0.2 μm)
Carbon black: 2 parts by mass (Tokai Carbon Co., Ltd., trade name: Seast TA)

(Second composition)
Vinyl chloride resin: 1.1 parts by mass (resin solution: resin content 30% by mass, cyclohexanone 70% by mass)
n-Butyl stearate: 2 parts by mass Methyl ethyl ketone: 121.3 parts by mass Toluene: 121.3 parts by mass Cyclohexanone: 60.7 parts by mass

  Finally, 4 parts by mass of polyisocyanate (trade name: Coronate L, manufactured by Nippon Polyurethane Co.) and 2 parts by mass of myristic acid are added as curing agents to the magnetic layer forming paint prepared as described above. did.

(Preparation process of paint for forming underlayer)
A coating for forming an underlayer was prepared as follows. First, a third composition having the following composition was kneaded with an extruder. Next, the kneaded third composition and the fourth composition having the following composition were added to a stirring tank equipped with a disper, and premixed. Subsequently, the mixture was further mixed with a sand mill and subjected to a filter treatment to prepare a coating material for forming an underlayer.

(Third composition)
Acicular iron oxide powder: 100 parts by mass (α-Fe ₂ O ₃ , average major axis length 0.15 μm)
Vinyl chloride resin: 55.6 parts by mass (resin solution: resin content 30% by mass, cyclohexanone 70% by mass)
Carbon black: 10 parts by mass (average particle size: 20 nm)

(Fourth composition)
Polyurethane resin UR8200 (manufactured by Toyobo Co., Ltd.): 18.5 parts by mass n-butyl stearate: 2 parts by mass Methyl ethyl ketone: 108.2 parts by mass Toluene: 108.2 parts by mass Cyclohexanone: 18.5 parts by mass

  Finally, as a curing agent, 4 parts by mass of polyisocyanate (trade name: Coronate L, manufactured by Nippon Polyurethane Co., Ltd.) and 2 parts by mass of myristic acid are added to the coating material for forming an underlayer prepared as described above. did.

(Preparation process of paint for forming back layer)
A paint for forming a back layer was prepared as follows. The following raw materials were mixed in a stirring tank equipped with a disper, and a filter treatment was performed to prepare a coating for forming a back layer. Carbon black (manufactured by Asahi Carbon Co., Ltd., trade name: # 80): 100 parts by mass Polyester polyurethane: 100 parts by mass (manufactured by Nippon Polyurethane Co., trade name: N-2304)
Methyl ethyl ketone: 500 parts by mass Toluene: 400 parts by mass Cyclohexanone: 100 parts by mass

(Deposition process)
Using a paint prepared as described above, the base layer having an average thickness of 1.0μm polyethylene naphthalate long film is a non-magnetic support (hereinafter referred to as "PEN film".) On, and the average thickness t _m Was formed as follows. First, an underlayer was formed on a film by applying and drying an underlayer-forming paint on the film. Next, a magnetic layer-forming paint was applied on the underlayer and dried to form a magnetic layer on the underlayer. When the coating material for forming a magnetic layer was dried, the magnetic powder was magnetically oriented in the thickness direction of the film by a solenoid coil. The application time of the magnetic field to the coating material for forming the magnetic layer was adjusted, and the squareness ratio S2 in the thickness direction (vertical direction) of the magnetic recording tape was set to 65%.

Subsequently, with respect to the underlying layer and the magnetic layer formed film, the average thickness t _b was shown applied to dry the backing layer of 0.6 .mu.m. Then, a curing treatment was performed on the film on which the underlayer, the magnetic layer, and the back layer were formed. Subsequently, a calendar process was performed to smooth the surface of the magnetic layer. At this time, as the interlayer friction coefficient of the magnetic surface and the back surface μ is approximately 0.5, after adjusting the conditions of calendering (temperature), the re-hardening process applied, the average thickness t _T is 5.5μm of A magnetic recording tape was obtained.

(Cutting process)
The magnetic recording tape obtained as described above was cut into a 1/2 inch (12.65 mm) width and wound around a core to obtain a pancake.

  The magnetic recording tape obtained as described above had the characteristics shown in Table 1. For example, the dimensional change ΔW of the magnetic recording tape was 705 ppm / N.

[Example 2]
A magnetic recording tape was obtained in the same manner as in Example 1 except that the thickness of the PEN film was smaller than that in Example 1 so that the dimensional change Δw was 750 ppm / N. The average thickness of the magnetic recording tape was 5 μm.

[Example 3]
The magnetic recording tape was manufactured in the same manner as in Example 1 except that the thickness of the PEN film was reduced and the average thickness of the back layer and the underlayer was reduced so that the dimensional change Δw was 800 ppm / N. Obtained. The average thickness of the magnetic recording tape was 4.5 μm. Along with that it has thinner backing layer, the surface roughness R _ab of the back layer is increased.

[Example 4]
The thickness of the PEN film is made thinner than in Example 1 so that the dimensional change Δw is 800 ppm / N, the average thicknesses of the back layer and the underlayer are reduced, and the underlayer, the magnetic layer, and the back layer are formed. A magnetic recording tape was obtained in the same manner as in Example 1 except that the conditions for the curing treatment of the formed film were adjusted.

[Example 5]
A magnetic recording tape was obtained in the same manner as in Example 4, except that the composition of the coating material for forming the underlayer was changed so that the thermal expansion coefficient α was 8 ppm / ° C.

[Example 6]
A magnetic recording tape was prepared in the same manner as in Example 4 except that thin barrier layers were formed on both surfaces of the PEN film so that the humidity expansion coefficient β was 3 ppm /% RH, and the average thickness of the underlayer was increased. Obtained. The average thickness of the magnetic recording tape was 4.6 μm.

[Example 7]
A magnetic recording tape was obtained in the same manner as in Example 4, except that the composition of the coating material for forming the back layer was changed so that the Poisson's ratio ρ was 0.31.

Example 8
A magnetic recording tape was obtained in the same manner as in Example 4, except that the composition of the coating material for forming the back layer was changed so that the Poisson's ratio ρ was 0.35.

[Example 9]
A magnetic recording tape was prepared in the same manner as in Example 7, except that the curing conditions of the film on which the underlayer, the magnetic layer, and the back layer were formed were adjusted such that the elastic limit value σ _{MD in the} longitudinal direction was 0.8 N. Obtained.

[Example 10]
Except that the curing condition and the re-curing condition of the film on which the underlayer, the magnetic layer, and the back layer were formed were adjusted so that the elastic limit value σ _{MD in the} longitudinal direction was 3.5 N, the same method as in Example 7 was used. A magnetic recording tape was obtained.

[Example 11]
A magnetic recording tape was obtained in the same manner as in Example 9. Then, the elastic limit sigma _MD of the resulting magnetic recording tape was measured by changing the velocity V when measuring the longitudinal direction of the elastic limit sigma _MD to 5 mm / min. As a result, the elastic limit value σ _MD in the longitudinal direction was 0.8 without any change from the elastic limit value σ _{MD in} the longitudinal direction at a speed V of 0.5 mm / min (Example 9).

[Example 12]
The average thickness t _m of the magnetic layer except for changing the coating thickness of the magnetic layer-forming coating material so as to 40nm to obtain a magnetic recording tape in the same manner as in Example 7. The average thickness of the magnetic recording tape was 4.4 μm.

Example 13
(SUL film formation process)
First, a CoZrNb layer (SUL) having an average thickness of 10 nm was formed on the surface of a long polymer film as a nonmagnetic support under the following film forming conditions. Note that a PEN film was used as the polymer film.
Film formation method: DC magnetron sputtering method Target: CoZrNb Target gas type: Ar
Gas pressure: 0.1 Pa

(Step of forming first seed layer)
Next, a TiCr layer (first seed layer) having an average thickness of 5 nm was formed on the CoZrNb layer under the following film forming conditions.
Sputtering method: DC magnetron sputtering method Target: TiCr target reaching vacuum degree: 5 × 10 ⁻⁵ Pa
Gas type: Ar
Gas pressure: 0.5Pa

(Step of forming second seed layer)
Next, a NiW layer (second seed layer) having an average thickness of 10 nm was formed on the TiCr layer under the following film forming conditions.
Sputtering method: DC magnetron sputtering method Target: NiW Target vacuum degree: 5 × 10 ⁻⁵ Pa
Gas type: Ar
Gas pressure: 0.5Pa

(Step of forming first underlayer)
Next, a Ru layer (first underlayer) having an average thickness of 10 nm was formed on the NiW layer under the following film forming conditions.
Sputtering method: DC magnetron sputtering method Target: Ru Target gas type: Ar
Gas pressure: 0.5Pa

(Step of forming second underlayer)
Next, a Ru layer (second underlayer) having an average thickness of 20 nm was formed on the Ru layer under the following film forming conditions.
Sputtering method: DC magnetron sputtering method Target: Ru Target gas type: Ar
Gas pressure: 1.5Pa

(Magnetic layer forming process)
Next, a (CoCrPt)-(SiO ₂ ) layer (magnetic layer) having an average thickness of 9 nm was formed on the Ru layer under the following film forming conditions.
Film formation method: DC magnetron sputtering method Target: (CoCrPt)-(SiO ₂ ) Target gas type: Ar
Gas pressure: 1.5Pa

(Protective layer forming process)
Next, a carbon layer (protective layer) having an average thickness of 5 nm was formed on the magnetic layer under the following film forming conditions.
Film forming method: DC magnetron sputtering method Target: Carbon target gas type: Ar
Gas pressure: 1.0 Pa

(Lubrication layer forming process)
Next, a lubricant was applied on the protective layer to form a lubricant layer.

(Step of forming back layer)
Next, a back layer having an average thickness of 0.3 μm was formed on the surface opposite to the magnetic layer by applying a back layer forming paint and drying. As a result, a magnetic recording tape having an average thickness of 4.0 μm was obtained.

(Cutting process)
The magnetic recording tape obtained as described above was cut into 1/2 inch (12.65 mm) width.

  The magnetic recording tape obtained as described above had the characteristics shown in Table 1. For example, the dimensional change ΔW of the magnetic recording tape was 800 ppm / N.

[Example 14]
A magnetic recording tape was obtained in the same manner as in Example 7, except that the average thickness of the back layer and the underlayer was reduced. The average thickness of the magnetic recording tape was 4.4 μm.

[Example 15]
A magnetic recording tape was obtained in the same manner as in Example 7, except that the surface roughness R _ab of the back layer was reduced to 3.2 nm and the friction coefficient μ was increased.

[Example 16]
The average thickness t _m of the magnetic layer except for changing the coating thickness of the magnetic layer-forming coating material so as to 110nm to obtain a magnetic recording tape in the same manner as in Example 7.

[Example 17]
A magnetic recording tape was obtained in the same manner as in Example 7, except that the surface roughness R _ab of the base layer was increased and the friction coefficient μ was decreased.

[Example 18]
A magnetic recording tape was obtained again in the same manner as in Example 7, except that the friction coefficient μ was reduced to 0.18.

[Example 19]
A magnetic recording tape was obtained again in the same manner as in Example 7, except that the friction coefficient μ was increased to 0.82.

[Example 20]
A magnetic recording tape was obtained in the same manner as in Example 7, except that the application time of the magnetic field to the magnetic layer forming paint was adjusted and the squareness ratio S2 in the thickness direction (vertical direction) of the magnetic recording tape was set to 73%.

[Example 21]
A magnetic recording tape was obtained in the same manner as in Example 7, except that the application time of the magnetic field to the magnetic layer forming paint was adjusted and the squareness ratio S2 in the thickness direction (vertical direction) of the magnetic recording tape was set to 80%.

[Example 22]
Except that the curing condition and the re-curing condition of the film on which the underlayer, the magnetic layer, and the back layer were formed were adjusted so that the elastic limit value σ _{MD in the} longitudinal direction was 5.0 N, the same method as in Example 7 was used. A magnetic recording tape was obtained.

[Example 23]
A magnetic recording tape was obtained in the same manner as in Example 7, except that barium ferrite (BaFe ₁₂ O ₁₉ ) nanoparticles were used instead of the ε iron oxide nanoparticles.

[Example 24]
A magnetic recording tape was obtained in the same manner as in Example 1, except that the thickness of the back layer and the thickness of the underlayer were reduced. The average thickness of the magnetic recording tape was 5.0 μm. The dimensional change ΔW of the magnetic recording tape was 800 ppm / N.

[Example 25]
Same as Example 1 except that barium ferrite (BaFe ₁₂ O ₁₉ ) nanoparticles were used instead of ε iron oxide nanoparticles, and the thickness of the PEN film, the thickness of the back layer, and the thickness of the underlayer were reduced. A magnetic recording tape was obtained by the method. The average thickness of the magnetic recording tape was 5.0 μm. The dimensional change ΔW of the magnetic recording tape was 800 ppm / N.

[Comparative Example 1]
A magnetic tape was obtained in the same manner as in Example 1 except that the tensilization of the PEN film was changed so that the dimensional change Δw was 650 [ppm / N].

[Comparative Example 2]
A magnetic recording tape was prepared in the same manner as in Example 25, except that a PEN film having an increased stretching strength in the width direction was used instead of the PEN film used in Example 25, and the thickness of the underlayer was increased. Obtained. By changing the PEN film, the dimensional change Δw was reduced as compared with the magnetic recording tape of Example 25. The dimensional change Δw of the magnetic recording tape of Comparative Example 2 was 630 ppm / N. The average thickness of the magnetic recording tape was 5.7 μm.

[Comparative Example 3]
Magnetic recording was performed in the same manner as in Example 25, except that the PEN film used in Example 25 was replaced with a PEN film having an increased stretching strength in the width direction, and the thickness of the underlayer was slightly increased. I got the tape. Due to the change in the PEN film, the dimensional change Δw was significantly reduced as compared with the magnetic recording tape of Example 25. The dimensional change Δw of the magnetic recording tape of Comparative Example 3 was 500 ppm / N. The average thickness of the magnetic recording tape was 6.5 μm.

(Judgment of change in tape width)
First, a cartridge sample incorporating a 1/2 inch wide magnetic recording tape was prepared. The cartridge sample contained the magnetic recording tape wound around a reel provided in a cartridge case. On the magnetic recording tape, two rows of the C-shaped magnetic patterns are arranged in parallel with each other at a known interval (hereinafter, referred to as “an interval between known magnetic pattern rows when pre-recorded”) in the longitudinal direction. More than rows were pre-recorded. Next, the cartridge sample was reciprocated by the recording / reproducing apparatus. At the time of reciprocating travel, two or more of the above-described C-shaped magnetic pattern rows were simultaneously reproduced, and the intervals between the magnetic pattern rows during traveling were continuously measured from the shape of the reproduced waveform of each row. At the time of running, the rotational drive of the spindle drive device and the reel drive device is controlled based on the measured magnetic pattern row interval information so that the magnetic pattern row interval has a specified width or almost a specified width. Then, the tension in the longitudinal direction of the magnetic recording tape was automatically adjusted. A simple average of all measured values for one round trip of the magnetic pattern row interval is referred to as a “measured magnetic pattern row interval”, and the difference between this and the “pre-recorded known magnetic pattern row interval” Is "change in tape width".

  The reciprocation by the recording / reproducing apparatus was performed in a thermo-hygrostat. The reciprocating speed was 5 m / sec. The temperature and humidity during the reciprocating travel are independent of the above-described reciprocating travel, and are in a temperature range of 10 ° C. to 45 ° C. and a relative humidity range of 10% to 80%. Repeat twice from 29 ° C. 80% → 10 ° C. 10%, changing from 10 ° C. 10% to 29 ° C. 80% in 2 hours and changing from 29 ° C. 80% → 10 ° C. 10% in 2 hours. , Gradually and repeatedly.

This evaluation was repeated until the “preset environmental change program” was completed. After the evaluation is completed, an average value (simple average) is calculated using all the absolute values of the “change in tape width” obtained at each reciprocation, and the value is used as the “effective tape width change amount” of the tape. And A judgment was made for each tape in accordance with the deviation of the "effective tape width change amount" from the ideal (the smaller, the better), and eight levels of judgment values were given. The evaluation “8” indicates the most desirable judgment result, and the evaluation “1” indicates the least desirable judgment result. The following states are observed in the magnetic tape having any one of the eight grades during the tape running.
8: No abnormality occurs.
7: A slight increase in the error rate is observed during running.
6: During running, a severe increase in the error rate is observed.
5: During running, the servo signal could not be read and a slight reload (1-2 times) was applied.
4: During running, the servo signal could not be read and a medium (within 10 times) rereading was applied.
3: Servo signals cannot be read during running, and severe (more than 10 times) rereading is required.
2: The servo cannot be read, and sometimes stops due to a system error.
1: The servo cannot be read, and it stops immediately due to a system error.

(Evaluation of electromagnetic conversion characteristics)
First, a reproduction signal of the magnetic recording tape was obtained using a loop tester (manufactured by Microphysics). Hereinafter, conditions for obtaining a reproduction signal will be described.
head: GMR
headspeed: 2m / s
signal: Single recording frequency (10MHz)
Recording current: optimal recording current

Next, a reproduced signal was captured by a spectrum analyzer with a span (SPAN) of 0 to 20 MHz (resolution band width = 100 kHz, VBW = 30 kHz). Next, the peak of the acquired spectrum is used as the signal amount S, and the floor noise excluding the peak is integrated to obtain the noise amount N, and the ratio S / N between the signal amount S and the noise amount N is represented by SNR (Signal-to-Signal). Noise Ratio). Next, the obtained SNR was converted into a relative value (dB) based on the SNR of Comparative Example 1 as a reference medium. Next, using the SNR (dB) obtained as described above, the quality of the electromagnetic conversion characteristics was determined as follows.
Better: The SNR of the magnetic recording tape is 1 dB or more better than the SNR (= 0 (dB)) of the evaluation reference sample (Comparative Example 1).
Good: The SNR of the magnetic recording tape is equal to or exceeds the SNR (= 0 (dB)) of the evaluation reference sample (Comparative Example 1).
Defective: The SNR of the magnetic recording tape is less than the SNR (= 0 (dB)) of the evaluation reference sample (Comparative Example 1).

(Evaluation of gap deviation)
First, a cartridge sample after the “determination of the tape width change amount” was prepared. Next, the reel around which the tape was wound was taken out of the cartridge sample, and the end face of the wound tape was visually observed. The reel has a flange, and at least one flange is transparent or translucent, so that the tape winding state inside can be observed through the flange.

As a result of the observation, when the end face of the tape was not flat, and there was a step or tape jumping out, it was determined that the tape was misaligned. Further, the more the step and the tape jump-out were observed, the worse the "winding deviation". The above determination was made for each sample. The winding misalignment state of each sample was compared with the winding misalignment state of Comparative Example 1 as a reference medium, and pass / fail was determined as follows.
Good: When the sample is out of alignment with or less than the reference sample (Comparative Example 1), poor: When the sample is out of alignment with the reference sample (Comparative Example 1).

  Table 1 shows the configurations and evaluation results of the magnetic recording tapes of Examples 1 to 25 and Comparative Examples 1 to 3.

In addition, each symbol in Table 1 means the following measured value.
_tbs : thickness of base layer (unit: μm)
t _T : thickness of magnetic recording tape (unit: μm)
Δw: dimensional change in the width direction of the magnetic recording tape with respect to a change in tension in the longitudinal direction of the magnetic recording tape (unit: ppm / N)
α: coefficient of thermal expansion of magnetic recording tape (unit: ppm / ° C)
β: coefficient of humidity expansion of magnetic recording tape (unit: ppm /% RH)
ρ: Poisson's ratio of the magnetic recording tape σ _MD : elastic limit value in the longitudinal direction of the magnetic recording tape (unit: N)
V: Speed at the time of performing elastic limit measurement (unit: mm / min)
t _m : average thickness of the magnetic layer (unit: nm)
S2: Squareness ratio (unit:%) in the thickness direction (vertical direction) of the magnetic recording tape
t _b : average thickness of the back layer (unit: μm)
R _ab : Surface roughness of back layer (unit: nm)
μ: Coefficient of friction between the magnetic surface and the back surface t _n : Thickness of the underlayer (non-magnetic layer) (unit: μm)

  From the results shown in Table 1, the following can be understood.

In all of the magnetic recording tapes of Examples 1 to 25, the determination result of the change amount of the tape width was 4 or more (that is, the deviation of the “effective change amount of the tape width” from the ideal was small). Therefore, it can be seen that the magnetic recording medium according to the present technology is suitable for use in a recording / reproducing device that adjusts the tension in the longitudinal direction.
On the other hand, in Comparative Example 1, even when the average thickness of the non-magnetic layer is the same 1.0 μm, the determination result regarding the change amount of the tape width is bad if Δw is 650 ppm / N. In Comparative Example 2, the average thickness of the nonmagnetic layer was 1.1 μm, Δw was 630 ppm / N, and the result of the determination regarding the tape width variation was poor. In Comparative Example 3, even when the average thickness of the non-magnetic layer is 1.0 or less, if Δw is 500 ppm / N, the determination result regarding the amount of change in the tape width is poor.
From these results, it can be seen that when Δw is 660 ppm / N or more and the average thickness of the nonmagnetic layer is 1.0 or less, the magnetic recording tape can be used in a recording / reproducing apparatus for adjusting the tension in the longitudinal direction (particularly, Adjustment of the tape width by adjusting the tension).

  Further, from the results of the determination of the tape width variation in Examples 1 to 25, the dimensional variation Δw of the magnetic recording tape is preferably 700 ppm / N or more, more preferably 750 ppm / N or more. The magnetic recording tape is more preferably 800 ppm / N or more, so that the magnetic recording tape is more suitable for use in a recording / reproducing apparatus for adjusting the tension in the longitudinal direction (particularly, adjusting the width of the tape by adjusting the tension). It turns out that it becomes.

Comparing Example 25 with Comparative Example 2, it is considered that the average thickness of 5.5 μm or less contributes to making the magnetic recording tape suitable for use in the recording / reproducing apparatus.
Further, in Examples 2 to 25, the average thickness of the magnetic recording tape was 5.3 μm or less, and in Example 1, the average thickness of the magnetic recording tape was 5.5 μm. In Examples 2 to 25, the determination result of the tape width change amount is 5 or more, while in Example 1, the determination result of the tape width change amount is 4. This indicates that a magnetic recording tape having an average thickness of 5.3 μm or less is more suitable for use in the recording / reproducing apparatus.

  Further, from the results of the determination of the tape width variation in Examples 1 to 25, the magnetic recording tape was found to have an average thickness of 5.2 μm or less, more preferably 5.0 μm or less, and It can be seen that the tape is even more suitable for use in the recording and playback device.

  In Examples 3 to 5 and 7 to 25, the average thickness of the nonmagnetic layer was 0.9 μm or less, and in Examples 1 and 2, the average thickness of the nonmagnetic layer was 1.0 μm. In Examples 3 to 5 and 7 to 25, the determination result of the tape width is 6 or more, whereas in Examples 1 and 2, the determination result of the tape width is 5 or less. This indicates that a magnetic recording tape in which the average thickness of the nonmagnetic layer is 0.9 μm or less is more suitable for use in the recording / reproducing apparatus.

Further, comparing Example 3 with Example 24, even when Δw is the same 800 ppm / N, the tape is more tapered when the average thickness of the nonmagnetic layer is 0.61 μm than when it is 0.9 μm. The determination result regarding the width change amount is good.
From this result, it is understood that a magnetic recording tape having an average thickness of the non-magnetic layer of 0.7 μm or less is more suitable for use in the recording / reproducing apparatus.

  When the evaluation results of Examples 3 to 6 are compared with each other, from the viewpoint of suppressing the deviation of the “effective tape width variation” from the ideal, the thermal expansion coefficient α is 6 ppm / ° C. ≦ α ≦ It is understood that the concentration is preferably 8 ppm / ° C.

  When the evaluation results of Examples 3 to 5 and the like are compared with each other, from the viewpoint of suppressing the deviation of the “effective tape width variation” from the ideal, the humidity expansion coefficient β is β ≦ 5 ppm /% RH. It is understood that it is preferable that

When the evaluation results of Examples 7, 9, 10 and the like are compared with each other, from the viewpoint of suppressing the deviation of the “effective tape width variation” from the ideal, the longitudinal elastic limit value σ _MD is , 0.8 [N] ≦ σ _MD .
From a comparison between Example 9 and Example 11, it can be seen that the elastic limit value σ _MD does not depend on the speed V when performing the elastic limit measurement.

  When the evaluation results of Examples 7 and 21 are compared with each other, the squareness ratio S2 of the magnetic recording tape in the perpendicular direction is preferably 75% or more, particularly 80% or more from the viewpoint of improving the electromagnetic conversion characteristics. It turns out to be preferable.

  Comparing the evaluation results of Examples 7 and 23 with each other, it can be seen that the same evaluation result is obtained when barium ferrite nanoparticles are used as the magnetic particles, as when ε iron oxide nanoparticles are used as the magnetic particles. I understand.

  From a comparison between the results of Example 13 and the results of the other examples, it can be seen that the same evaluation results as those of the coating type magnetic recording tape can be obtained even with the vacuum thin film type (sputter type) magnetic recording tape.

  Comparing the evaluation results of Examples 7 and 16 with each other, it is understood that the thickness of the magnetic layer is preferably 100 nm or less, particularly preferably 90 nm or less, from the viewpoint of improving the electromagnetic conversion characteristics.

  Comparing the evaluation results of Examples 7, 15, 17 to 19 with each other, from the viewpoint of improving the winding deviation, the friction coefficient μ is 0.18 <μ <0.82, particularly 0.20 ≦ μ. It is understood that it is preferable that ≦ 0.80.

  Although the embodiments and examples of the present technology have been specifically described above, the present technology is not limited to the above embodiments and examples, and various modifications based on the technical idea of the present technology are possible. It is.

  For example, the configurations, methods, steps, shapes, materials, and numerical values and the like cited in the above-described embodiments and examples are merely examples, and different configurations, methods, steps, shapes, materials, and as needed. A numerical value or the like may be used. Further, the chemical formulas of the compounds and the like are typical ones, and are not limited to the listed valences and the like as long as they are general names of the same compounds.

  The configurations, methods, steps, shapes, materials, numerical values, and the like of the above-described embodiments and examples can be combined with each other without departing from the gist of the present technology.

  Further, in this specification, a numerical range indicated by using “to” indicates a range including numerical values described before and after “to” as a minimum value and a maximum value, respectively. In the numerical ranges described stepwise in this specification, the upper limit or the lower limit of the numerical range in one step may be replaced with the upper limit or the lower limit of the numerical range in another step. The materials exemplified in the present specification can be used alone or in combination of two or more, unless otherwise specified.

Note that the present technology may have the following configurations.
[1] has a layer structure having a magnetic layer, a non-magnetic layer, and a base layer in this order;
The average thickness t _T satisfies t _T ≤ 5.5 μm,
The dimension change amount Δw in the width direction with respect to the tension change in the longitudinal direction is 660 ppm / N ≦ Δw, and
The average thickness _{t n} of the non-magnetic layer is a _{t n} ≦ 1.0 .mu.m,
Is,
Magnetic recording medium.
[2] The magnetic recording medium according to [1], wherein the squareness ratio in the vertical direction is 65% or more.
[3] The non-magnetic layer according to [1] or [2], wherein the non-magnetic layer contains Fe-based non-magnetic particles, and a particle volume of the Fe-based non-magnetic particles is 4.0 × 10 ⁻⁵ μm ³ or less. Magnetic recording medium.
[4] The average thickness _{t T} is a _{t T} ≦ 5.3 .mu.m, a magnetic recording medium according to any one of [1] to [3].
[5] The average thickness _{t T} is a _{t T} ≦ 5.2 .mu.m, a magnetic recording medium according to any one of [1] to [4].
[6] The average thickness _{t T} is a _{t T} ≦ 5.0 .mu.m, a magnetic recording medium according to any one of [1] to [5].
[7] The magnetic recording medium according to any one of [1] to [6], wherein the average thickness t _{n of the} nonmagnetic layer is t _n ≦ 0.9 μm.
[8] The average thickness t _n of the non-magnetic layer is t _n ≦ 0.7 [mu] m, the magnetic recording medium according to any one of [1] to [7].
[9] The magnetic recording medium according to any one of [1] to [8], wherein the dimensional change Δw is 700 ppm / N ≦ Δw.
[10] The magnetic recording medium according to any one of [1] to [9], wherein the dimensional change Δw is 750 ppm / N ≦ Δw.
[11] The magnetic recording medium according to any one of [1] to [10], wherein the dimensional change Δw is 800 ppm / N ≦ Δw.
[12] The layer structure has a back layer on the side of the base layer opposite to the nonmagnetic layer side, and the surface roughness R _{ab of the} back layer is 3.0 nm ≦ R _ab ≦ 7.5 nm. The magnetic recording medium according to any one of [1] to [11].
[13] The layer structure has a back layer on a side of the base layer opposite to the nonmagnetic layer side, and a gap between the surface of the magnetic recording medium on the magnetic layer side and the surface of the back layer side. The magnetic recording medium according to any one of [1] to [12], wherein the friction coefficient μ is 0.20 ≦ μ ≦ 0.80. [14] Any one of [1] to [13], wherein the temperature expansion coefficient α is 6 ppm / ° C. ≦ α ≦ 8 ppm / ° C., and the humidity expansion coefficient β is β ≦ 5 ppm /% RH. 3. The magnetic recording medium according to claim 1.
[15] The magnetic recording medium according to any one of [1] to [14], wherein the Poisson's ratio ρ satisfies 0.3 ≦ ρ.
[16] The magnetic recording medium according to any one of [1] to [15], wherein an elastic limit value σ _{MD in the} longitudinal direction satisfies 0.8N ≦ σ _MD .
[17] The magnetic recording medium according to [16], wherein the elastic limit value σ _MD does not depend on the speed V when performing the elastic limit measurement.
[18] The magnetic recording medium according to any one of [1] to [17], wherein the magnetic layer is vertically oriented.
[19] The layer structure has a back layer on a side of the base layer opposite to the nonmagnetic layer side, and the average thickness t _{b of the} back layer is t _b ≦ 0.6 μm, [1] -The magnetic recording medium according to any one of [18].
[20] The magnetic recording medium according to any one of [1] to [19], wherein the magnetic layer is a sputtered layer.
[21] The average thickness _{t m} of the magnetic layer is a 9nm ≦ _{t m} ≦ 90nm, magnetic recording medium according to [20].
[22] The magnetic recording medium according to any one of [1] to [19], wherein the magnetic layer contains a magnetic powder.
[23] The average thickness _{t m} of the magnetic layer is a 35nm ≦ _{t m} ≦ 90nm, magnetic recording medium according to [22].
[24] The magnetic recording medium according to [22] or [23], wherein the magnetic powder includes ε iron oxide magnetic powder, barium ferrite magnetic powder, cobalt ferrite magnetic powder, or strontium ferrite magnetic powder.
[25] The layer structure has a back layer on a side of the base layer opposite to the nonmagnetic layer side,
The magnetic recording medium according to [2], wherein the surface roughness R _{ab of the} back layer satisfies 3.0 nm ≦ R _ab ≦ 7.5 nm.
[26] The layer structure has a back layer on a side of the base layer opposite to the nonmagnetic layer,
The magnetic recording medium according to [2], wherein a friction coefficient μ between the surface on the magnetic layer side and the surface on the back layer side of the magnetic recording medium is 0.20 ≦ μ ≦ 0.80.
[27] The thermal expansion coefficient α is 6 ppm / ° C. ≦ α ≦ 9 ppm / ° C., and
The humidity expansion coefficient β is β ≦ 5.5 ppm /% RH,
The magnetic recording medium according to [2].
[28] The magnetic recording medium according to [2], wherein the Poisson's ratio ρ is 0.25 ≦ ρ.
[29] The magnetic recording medium according to [2], wherein a longitudinal elastic limit value σ _MD satisfies 0.7N ≦ σ _MD .
[30] The magnetic recording medium according to [29], wherein the elastic limit value σ _MD does not depend on the velocity V when performing the elastic limit measurement.
[31] The average thickness _{t n} of the non-magnetic layer is a tn ≦ 0.9 .mu.m, a magnetic recording medium according to [2].
[32] The average thickness _{t n} of the non-magnetic layer is a tn ≦ 0.7 [mu] m, the magnetic recording medium according to [2].

Reference Signs List 10 magnetic recording medium 11 base layer 12 non-magnetic layer 13 magnetic layer 14 back layer

Claims (33)

A layer structure having a magnetic layer, a non-magnetic layer, a base layer, and a back layer in this order,
The average thickness t _T of the magnetic recording medium is 3.5 μm ≦ t _T ≦ 5.5 μm,
The dimensional change amount Δw in the width direction of the magnetic recording medium with respect to the tension change in the longitudinal direction of the magnetic recording medium is 700 ppm / N ≦ Δw ≦ 20,000 ppm / N, and
The average thickness _{t n} of the non-magnetic layer is a 0.01 [mu] m ≦ _{t n} ≦ 1.0 .mu.m,
A long magnetic recording medium.   The magnetic recording medium according to claim 1, wherein the dimensional change Δw is 750 ppm / N ≦ Δw ≦ 20,000 ppm / N.   The magnetic recording medium according to claim 1, wherein the dimensional change Δw is 800 ppm / N ≦ Δw ≦ 20,000 ppm / N. 4. The magnetic recording medium according to claim 1, wherein the average thickness t _T of the magnetic recording medium is 3.5 μm ≦ t _T ≦ 5.3 μm. 5. The magnetic recording medium according to claim 1, wherein an average thickness t _T of the magnetic recording medium is 3.5 μm ≦ t _T ≦ 5.2 μm. The magnetic recording medium according to claim 1, wherein an average thickness t _T of the magnetic recording medium is 3.5 μm ≦ t _T ≦ 5.0 μm. The magnetic recording medium according to claim 1, wherein an average thickness t _{m of the} magnetic layer is 35 nm ≦ t _m ≦ 120 nm. The magnetic recording medium according to claim 1, wherein the nonmagnetic layer has an average thickness t _n of 0.4 μm ≦ t _n ≦ 1.0 μm. The average thickness _{t n} of the non-magnetic layer is 0.01μm ≦ _{t n} ≦ 0.9μm, magnetic recording medium according to any one of claims 1 to 8. The magnetic recording medium according to claim 1, wherein an average thickness t _{n of the} nonmagnetic layer satisfies 0.01 μm ≦ t _n ≦ 0.7 μm. The magnetic recording medium according to claim 1, wherein the average thickness of the base layer is 2.5 μm or more and 3.8 μm or less. The magnetic recording medium according to claim 1, wherein the average thickness of the base layer is 2.6 μm or more and 3.6 μm or less. The magnetic recording medium according to claim 1, wherein the average thickness t _b of the back layer satisfies t _b ≦ 0.6 μm. The magnetic layer includes a magnetic powder and a binder,
The magnetic powder includes ε iron oxide magnetic powder, barium ferrite magnetic powder, or cobalt ferrite magnetic powder,
The magnetic recording medium according to claim 1. The magnetic powder contains ε iron oxide magnetic powder,
A peak ratio X / Y between a main peak height X and a subpeak height Y near zero magnetic field in an SFD (Switching Field Distribution) curve of the magnetic recording medium is 3.0 or more and 100 or less;
The magnetic recording medium according to claim 14.   16. The magnetic recording medium according to claim 14, wherein the average particle size of the ε iron oxide magnetic powder is 8 nm or more and 22 nm or less. The magnetic powder includes barium ferrite magnetic powder,
The average thickness t _{m of the} magnetic layer is 35 nm ≦ t _m ≦ 100 nm;
A coercive force Hc in the perpendicular direction of the magnetic recording medium is 160 kA / m or more and 280 kA / m or less;
The magnetic recording medium according to claim 14.   18. The magnetic recording medium according to claim 14, wherein the barium ferrite magnetic powder has an average particle size of 12 nm or more and 25 nm or less.   19. The magnetic recording medium according to claim 1, wherein a coefficient of thermal expansion α of the magnetic recording medium is 6 ppm / ° C. ≦ α ≦ 9 ppm / ° C.   20. The magnetic recording medium according to claim 1, wherein a humidity expansion coefficient β of the magnetic recording medium is β ≦ 5.5 ppm /% RH.   21. The magnetic recording medium according to claim 1, wherein the Poisson's ratio ρ of the magnetic recording medium satisfies 0.25 ≦ ρ. The magnetic recording medium according to claim 1, wherein the elastic limit value σ _{MD in the} longitudinal direction satisfies 0.7 [N] ≦ σ _MD . 23. The magnetic recording medium according to claim 22, wherein the elastic limit value [sigma] _MD does not depend on the speed V when performing the elastic limit measurement.   24. The magnetic recording medium according to claim 1, wherein the magnetic layer is vertically oriented.   25. The magnetic recording medium according to claim 1, wherein the magnetic layer has three to eleven servo bands. The magnetic layer is configured to be able to form a plurality of recording tracks parallel to the longitudinal direction,
The width of the recording track is 2 μm or less;
The magnetic recording medium according to any one of claims 1 to 25.   27. The magnetic recording medium according to claim 1, wherein the base layer includes a polyester-based resin. Having a magnetic surface and a back surface opposite to the magnetic surface,
The interlayer friction coefficient μ between the magnetic surface and the back surface is 0.20 ≦ μ ≦ 0.80,
A magnetic recording medium according to any one of claims 1 to 27. 29. The magnetic recording medium according to claim 1, wherein the surface roughness R _{ab of the} back layer satisfies 3.0 nm ≦ R _ab ≦ 7.5 nm.   30. The magnetic recording medium according to claim 1, wherein a squareness ratio in a perpendicular direction of the magnetic recording medium is 65% or more.   31. The magnetic recording medium according to claim 1, wherein a squareness ratio of the magnetic recording medium in a vertical direction is 73% or more.   The magnetic recording medium according to any one of claims 1 to 31, wherein a coercive force Hc in the perpendicular direction of the magnetic recording medium is from 220 kA / m to 310 kA / m. A magnetic recording medium according to any one of claims 1 to 32,
A cartridge case,
And a reel,
A magnetic recording cartridge in which the magnetic recording medium is housed in the cartridge case in a state wound on the reel.