JP6721099B1 - Magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thin magnetic recording medium having excellent running stability. A tape-shaped magnetic recording medium includes a magnetic layer, an underlayer, a base layer, and a back layer. The surface side on the magnetic layer 13 has a kurtosis of 3.0 or more, the surface on the back layer 14 side has a kurtosis of 2.0 or more, and the surface on the magnetic layer 13 side has an arithmetic mean roughness Ra of 2.5 nm or less. is there. The base layer 11 contains polyester as a main component, and the average thickness tT of the magnetic recording medium is 5.6 μm or less. The magnetic recording medium contains a lubricant, the lubricant contains a fatty acid and a fatty acid ester, the mass ratio of the fatty acid extracted with hexane and the fatty acid ester is fatty acid/fatty acid ester≦0.6, and The recording medium has pores 13A, and the average diameter of the pores 13A is 6 nm or more and 11 nm or less when measured in a dry state after removing the lubricant from the magnetic recording medium. [Selection diagram] Figure 1

Description

The present technology relates to a magnetic recording medium.

With the development of, for example, IoT, big data, and artificial intelligence, the amount of data collected and stored has increased significantly. A magnetic recording medium is often used as a medium for recording a large amount of data.

Various techniques have been proposed so far for magnetic recording media. For example, Patent Document 1 below discloses a technique relating to a magnetic recording medium having a magnetic layer containing at least a binder and magnetic powder on at least one main surface of a non-magnetic support. In the magnetic recording medium, the thickness of the magnetic layer is 0.12 μm or less, the root mean square surface roughness (Rq) of the surface of the magnetic layer forming surface is 4.0 nm or less, and the magnetic layer is formed. The skewness (Sk: Skewness) in the surface profile of the surface is -1 or more and +1 or less.

JP, 2006-69553, A

The magnetic recording medium is housed in, for example, a magnetic recording cartridge. In order to further increase the recording capacity per magnetic recording cartridge, the magnetic recording medium (eg, magnetic recording tape) housed in the magnetic recording cartridge is made thinner (the total thickness is reduced), and one magnetic recording cartridge is used. It is possible to increase the tape length per hit. However, a magnetic recording medium having a small total thickness may be inferior in running stability. In particular, when recording and/or reproducing repeatedly, the magnetic recording medium having a small total thickness may change its surface condition, particularly the surface condition relating to friction, and may deteriorate the running stability. Therefore, the main purpose of the present technology is to provide a thin magnetic recording medium having a total thickness that is excellent in running stability even after repeated recording or reproduction.

The present technology includes a magnetic layer, an underlayer, a base layer, and a back layer,
The surface side of the magnetic layer has a kurtosis of 3.0 or more,
The back layer side surface has a kurtosis of 2.0 or more,
Arithmetic mean roughness _{R a} of the magnetic layer side of the surface is at 2.5nm or less,
The base layer contains polyester as a main component,
The average thickness t _T of the magnetic recording medium is 5.6 μm or less,
The magnetic recording medium contains a lubricant, the lubricant contains a fatty acid and a fatty acid ester, the mass ratio of the fatty acid and the fatty acid ester extracted by hexane is fatty acid / fatty acid ester ≤ 0.6, and,
The magnetic recording medium has pores, and the average diameter of the pores is 6 nm or more and 11 nm or less when measured in a dry state after removing the lubricant from the magnetic recording medium.
Provided is a tape-shaped magnetic recording medium.
The squareness ratio of the magnetic recording medium in the vertical direction may be 65% or more.
The average thickness _{t m} of the magnetic layer may be at 80nm or less.
The magnetic layer may include magnetic powder, and the magnetic powder may include hexagonal ferrite, ε iron oxide, or Co-containing spinel ferrite.
The hexagonal ferrite may include at least one of Ba and Sr, and the ε iron oxide may include at least one of Al and Ga.
According to one embodiment of the present technology, the coefficient of dynamic friction μ _{C (at} the fifth reciprocation when the magnetic recording medium in a state where a tension of 0.6 N is applied in the longitudinal direction is slid on the magnetic head for 5 reciprocations _{) 5)} and the friction coefficient ratio (μ _C(1000) /μ _C(5) ) between the dynamic friction coefficient μ _{C(1000) at} the 1000th reciprocation when the magnetic head is reciprocated 1000 times, 1.0 to 1 It can be.
The fatty acid may include a compound represented by the following general formula (1) or (2), and the fatty acid ester may include a compound represented by the following general formula (3) or (4).
CH ₃ (CH ₂ ) _k COOH (1)
(However, in the general formula (1), k is an integer selected from the range of 14 or more and 22 or less.)
_{CH 3 (CH 2) n CH} = CH (CH 2) m COOH ··· (2)
(However, in the general formula (2), the sum of n and m is an integer selected from the range of 12 or more and 20 or less.)
_{CH 3 (CH 2) p COO} (CH 2) q CH 3 ··· (3)
(However, in the general formula (3), p is an integer selected from the range of 14 to 22 and q is an integer selected from the range of 2 to 5).
_{CH 3 (CH 2) r COO-} (CH 2) s CH (CH 3) 2 ··· (4)
(However, in the general formula (4), r is an integer selected from the range of 14 to 22 and s is an integer selected from the range of 1 to 3).
The magnetic recording medium may have a coercive force H _c in the longitudinal direction of 2000 Oe or less.
The magnetic layer may have 5 or more servo bands.
The ratio of the total area of the servo band to the area of the magnetic layer side surface of the magnetic recording medium may be 4.0% or less.
The width of the servo band may be 95 μm or less.
The magnetic layer is configured to be able to form a plurality of data tracks, and the width of the data tracks may be 2.0 μm or less.
The magnetic layer may be capable of recording data such that the minimum value of the magnetization reversal distance L is 48 nm or less.
The average thickness of the base layer may be 4.2 μm or less.
The magnetic layer may include magnetic powder, and the magnetic powder may have an average aspect ratio of 1.0 or more and 3.5 or less.
The magnetic layer may include magnetic powder, and the average particle size of the magnetic powder may be 50 nm or less.
The average diameter of the pores may be 6 nm or more and 10 nm or less.
The average diameter of the pores may be 7 nm or more and 9 nm or less.
The kurtosis of the surface on the magnetic layer side may be 3.5 or more.
The surface side of the back layer may have a kurtosis of 2.3 or more.
In addition, the present technology includes the tape-shaped magnetic recording medium,
A communication unit that communicates with the recording/reproducing device,
Storage part,
A control unit that stores information received from the recording/reproducing device via the communication unit in the storage unit, reads the information from the storage unit according to a request from the recording/reproducing device, and transmits the information to the recording/reproducing device via the communication unit. And,
The information also provides a tape cartridge including adjustment information for adjusting the tension applied in the longitudinal direction of the magnetic recording medium.

FIG. 3 is a schematic cross-sectional view of an example of a magnetic recording medium according to the present technology. It is a figure which shows the example of the data band and servo band which are provided in a magnetic recording medium. It is a figure which shows the example of the servo pattern in a servo band. It is a figure which shows the example of the servo pattern in a servo band. It is a sectional view showing composition of a magnetic particle. It is sectional drawing which shows the structure of the magnetic particle in a modification. It is a figure for demonstrating the measuring method of the friction coefficient between a magnetic surface and a magnetic head. It is a schematic diagram showing the composition of a recording and reproducing device. It is a schematic diagram of a cross section of a magnetic recording medium of a modified example. It is an example of the TEM photograph of a magnetic layer. FIG. 3 is an exploded perspective view showing an example of the configuration of a cartridge. It is a block diagram showing an example of composition of a cartridge memory.

Hereinafter, a suitable mode for carrying out the present technology will be described. Note that the embodiments described below are representative 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. Description of the present technology 2. Embodiment of the present technology (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) Cartridge (7) Effect (8) Modification 3. Example

1. Description of the technology

The present inventors have investigated various thin magnetic recording media having a total thickness. As a result, the inventors have found that a magnetic recording medium having a specific structure can suppress an increase in the dynamic friction coefficient due to repeated recording or reproduction. That is, the magnetic recording medium according to the present technology includes a magnetic layer, an underlayer, a base layer, and a back layer, and the surface of the magnetic layer has a kurtosis of 3.0 or more, and the surface of the back layer has a kurtosis of 3.0 or more. is 2.0 or more, the arithmetic mean roughness R _a of the magnetic layer side of the surface is at 2.5nm or less, the base layer comprises a polyester as a main component, the average thickness t _T of the magnetic recording medium 5 .6 μm or less, the magnetic recording medium contains a lubricant, the lubricant contains a fatty acid and a fatty acid ester, and the mass ratio of the fatty acid and the fatty acid ester extracted by hexane is fatty acid/fatty acid ester≦ 0.6, and the magnetic recording medium has pores, and the average diameter of the pores is 6 nm or more and 11 nm or more when measured in a dry state after removing the lubricant from the magnetic recording medium. It is below.

The mass ratio of the fatty acid and the fatty acid ester of the lubricant is within the numerical range, the average diameter of the pores is within the numerical range, and the kurtosis of the surface on the magnetic layer side is within the numerical range. The fact that the back layer side surface kurtosis is within the above numerical range contributes to the suppression of the increase in the dynamic friction coefficient of the magnetic layer side surface due to repeated recording or reproduction, and the total thickness of the magnetic recording layer is thin. This results in maintaining good running stability of the medium. In addition, it is considered that the above-mentioned configuration can provide smoothness suitable for providing running stability when the total thickness of the magnetic recording medium is reduced.

The magnetic recording medium according to the present technology contains a lubricant, and the lubricant contains a fatty acid and a fatty acid ester. The lubricant may be included in the magnetic layer and/or the underlayer, for example. The mass ratio of the fatty acid and the fatty acid ester extracted with hexane is fatty acid/fatty acid ester≦0.6, and preferably fatty acid/fatty acid ester≦0.55. When the mass ratio is within this numerical range, an increase in the dynamic friction coefficient due to repeated recording or reproduction can be suppressed.
The mass ratio of the fatty acid extracted with hexane and the fatty acid ester in the lubricant of the magnetic recording medium according to the present technology may be, for example, fatty acid/fatty acid ester≧0.3. If the mass ratio is too small, sticking may occur when the running direction of the magnetic recording medium is switched.

The magnetic recording medium according to the present technology has pores, and the average diameter of the pores is 6 nm or more and 11 nm or less when measured in a dry state after removing the lubricant from the magnetic recording medium. The average diameter is preferably 10 nm or less, more preferably 9 nm or less. The average diameter is preferably 6.5 nm or more, more preferably 7 nm or more, even more preferably 7.5 nm or more, and particularly preferably 8 nm or more. The average diameter is more preferably 6 nm or more and 10 nm or less, more preferably 6.5 nm or more and 10 nm or less, and still more preferably 7 nm or more and 9 nm or less. When the average pore diameter is within the above numerical range, it is possible to suppress an increase in the dynamic friction coefficient after repeatedly recording or reproducing. When the average pore diameter is outside the above numerical range, the friction between the magnetic recording medium and the head gradually increases as the magnetic recording medium runs, and running stability may deteriorate. It is considered that an appropriate amount of lubricant appears on the magnetic layer side surface due to the average diameter within the above numerical range, and this contributes to improvement of running stability of the magnetic recording medium having a small total thickness. The pores may be formed, for example, on the surface of the magnetic recording medium, and more particularly may be formed on the surface on the magnetic layer side. The pores may be present in the magnetic layer, for example. The pores present in the magnetic layer may be formed only in the magnetic layer, or the pores formed in the magnetic layer may extend to other layers, for example, the underlayer. May be.

The Kurtosis Sku of the magnetic layer side surface of the magnetic recording medium according to the present technology is 3.0 or more, preferably 3.1 or more, and more preferably 3.5 or more. When the Kurtosis of the surface on the magnetic layer side is within this numerical range, it is possible to suppress an increase in the dynamic friction coefficient due to repeated recording or reproduction.
Further, the kurtosis Sku of the surface of the magnetic recording medium according to the present technology on the side of the magnetic layer may be 4.0 or less, for example. When the kurtosis of the surface on the magnetic layer side is too large, the magnetic powder contained in the magnetic layer may easily fall off.

The surface layer on the back layer side of the magnetic recording medium according to the present technology has a kurtosis Sku of 2.0 or more, preferably 2.2 or more, and more preferably 2.3 or more. When the back surface side surface kurtosis is within this numerical range, it is possible to suppress an increase in the dynamic friction coefficient due to repeated recording or reproduction. This is considered to be because the shape of the surface on the back layer side is suitable for forming a surface shape that provides good running stability of the magnetic recording medium having a small total thickness on the surface on the magnetic layer side by transfer.
Further, the Kurtosis Sku of the surface of the magnetic recording medium according to the present technology on the back layer side may be 3.5 or less, for example. When the kurtosis on the surface on the back layer side is too large, the shape transferred to the surface on the magnetic layer side may deteriorate the electromagnetic conversion characteristics.

The average thickness t _T of the magnetic recording medium according to the present technology is 5.6 μm or less, more preferably 5.3 μm or less, and even more preferably 5.2 μm or less, 5.0 μm or less or 4.6 μm or less. sell. Since the magnetic recording medium according to the present technology is thus thin, the length of the tape wound in one magnetic recording cartridge can be made longer, thereby increasing the recording capacity per magnetic recording cartridge. be able to.
The width of the magnetic recording medium according to the present technology can be, for example, 5 mm to 30 mm, in particular 7 mm to 25 mm, more particularly 10 mm to 20 mm, even more particularly 11 mm to 19 mm. The length of the tape-shaped magnetic recording medium according to the present technology may 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.

The magnetic recording medium according to the present technology has a tape shape, and may be, for example, a long magnetic recording tape. The tape-shaped magnetic recording medium according to the present technology may be housed in, for example, a magnetic recording cartridge. More specifically, the magnetic recording cartridge may be accommodated in the cartridge while being wound around a reel in the cartridge.

A magnetic recording medium according to the present technology includes a magnetic layer, an underlayer, a base layer, and a back layer. These four layers may be laminated in this order. The magnetic recording medium according to the present technology may include other layers in addition to these layers. The other layer may be appropriately selected depending on the type of magnetic recording medium. The magnetic recording medium according to the present technology may be, for example, a coating type magnetic recording medium. Regarding the coating type magnetic recording medium, the following 2. Will be described in more detail in.

2. Embodiment of the present technology (example of coating type magnetic recording medium)

(1) Structure 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 vertical alignment treatment, and as shown in FIG. 1, a long base layer (also referred to as a base body) 11 and one main surface of the base layer 11. An underlayer (non-magnetic layer) 12 provided on the underlayer 12, 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. Equipped with. In the present specification, of both main surfaces of the magnetic recording medium 10, the surface on the side where the magnetic layer 13 is provided is also referred to as a magnetic surface or the surface on the magnetic layer side, and the surface opposite to the magnetic surface (back layer). The surface on which 14 is provided) is also referred to as the back surface.

The magnetic recording medium 10 is in the form of a tape and is run 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 the shortest recording wavelength of preferably 100 nm or less, more preferably 75 nm or less, even more preferably 60 nm or less, and particularly preferably 50 nm or less. It can be used for a recording/reproducing apparatus having a wavelength within the above range. The recording/reproducing apparatus may include a ring type head as a recording head. The recording track width can be, for example, 2 μm or less.

(2) Explanation of each layer

(Base layer)

The base layer 11 can function as a support for the magnetic recording medium 10, and can be, for example, a flexible, long non-magnetic substrate, and particularly a non-magnetic film. The thickness of the base layer 11 is, for example, 8 μm or less, preferably 7 μm or less, more preferably 6 μm or less, still more preferably 5 μm or less, and particularly preferably 4.2 μm or less. The thickness of the base layer 11 can be, for example, 2 μm or more, preferably 2.2 μm or more, more preferably 2.5 μm or more, even more preferably 2.6 μm or more.

The average thickness of the base layer 11 is obtained as follows. First, a magnetic recording medium 10 having a width of 1/2 inch is prepared and cut into a length of 250 mm to prepare a sample. Subsequently, the layers other than the base layer 11 (that is, the underlayer 12, the magnetic layer 13, and the back layer 14) of the sample are removed with a solvent such as MEK (methyl ethyl ketone) or dilute hydrochloric acid. Next, using a Mitutoyo laser hog gauge (LGH-110C) as a measuring device, the thickness of the sample (base layer 11) is measured at five or more positions, and the measured values are simply averaged (arithmetic mean). Then, the average thickness of the base layer 11 is calculated. The measurement position shall be randomly selected from the sample.

The base layer 11 contains, for example, polyester as a main component. Examples of the polyester include PET (polyethylene terephthalate), PEN (polyethylene naphthalate), PBT (polybutylene terephthalate), PBN (polybutylene naphthalate), PCT (polycyclohexylene dimethylene terephthalate), PEB (polyethylene-p-). Oxybenzoate) and polyethylene bisphenoxycarboxylate, or a mixture of two or more thereof. In the present specification, the “main component” means the component having the highest content ratio among the components constituting the base layer. For example, that the main component of the base layer 11 is polyester means that the content ratio of the polyester in the base layer 11 is, for example, 50 mass% or more, 60 mass% or more, 70 mass% or more, 80 mass% with respect to the mass of the base layer 11. % Or more, 90% by mass or more, 95% by mass or more, or 98% by mass or more, or it may mean that the base layer 11 is composed only of polyester.
In this embodiment, the base layer 11 may include a resin other than the polyester described below in addition to the polyester.
According to a preferred embodiment of the present technology, the base layer 11 may be formed of PET or PEN.

In another embodiment of the present technology, the base layer 11 may be formed of a resin other than polyester. The resin forming the base layer 11 may include at least one of a polyolefin resin, a cellulose derivative, a vinyl resin, and another polymer resin, for example. When the base layer 11 contains two or more kinds of these resins, these two or more kinds of materials may be mixed, may be copolymerized, or may be laminated.

The polyolefin resin contains, for example, at least one of PE (polyethylene) and PP (polypropylene). The cellulose derivative includes at least one of cellulose diacetate, cellulose triacetate, CAB (cellulose acetate butyrate), and CAP (cellulose acetate propionate). The vinyl-based resin contains, for example, at least one of PVC (polyvinyl chloride) and PVDC (polyvinylidene chloride).

Other polymer resins include, for example, PEEK (polyether ether ketone), PA (polyamide, nylon), aromatic PA (aromatic polyamide, aramid), PI (polyimide), aromatic PI (aromatic polyimide), PAI. (Polyamideimide), aromatic PAI (aromatic polyamideimide), PBO (polybenzoxazole, for example, Zylon (registered trademark)), polyether, PEK (polyether ketone), polyether ester, PES (polyether sulfone). , PEI (polyetherimide), PSF (polysulfone), 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 may include magnetic powder and a lubricant. The magnetic layer 13 may include, for example, a binder, in particular, a binder and conductive particles, in addition to the magnetic powder and the lubricant. The magnetic layer 13 may further include additives such as an abrasive and a rust preventive, if necessary.

The magnetic layer 13 has pores. That is, the magnetic layer 13 has a surface provided with a large number of pores. Preferably, the magnetic layer 13 is provided with pores in a region that comes into contact with the magnetic head during recording and/or reproduction of the magnetic recording medium 10, and particularly preferably, pores are provided over the entire region. You may
The pores may be opened perpendicularly to the surface of the magnetic layer 13. The pores can be formed, for example, by pressing a large number of projections provided on the back layer side surface of the magnetic recording medium 10. In this case, the pore may correspond to the protrusion.
Although the pores are indicated by reference numeral 13A in FIG. 1, FIG. 1 is a schematic diagram for better understanding of the present technology, and the shape of the pores 13A shown in FIG. It does not indicate the shape of.

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.
Particularly preferably, the average thickness _{t m} of the magnetic layer is 80nm or less. Having an average thickness within this numerical range contributes to improving the recording/reproducing characteristics of the magnetic recording medium 10.

The average thickness t _m of the magnetic layer 13, for example, obtained as follows.
The magnetic recording medium 10 is processed by FIB (Focused Ion Beam) method or the like to be thinned. When the FIB method is used, a carbon film and a tungsten thin film are formed as protective films as a pretreatment for observing a TEM image of a cross section described later. The carbon film is formed on the magnetic layer side surface and the back layer side surface of the magnetic recording medium 10 by a vapor deposition method, and the tungsten thin film is further formed on the magnetic layer side surface by a vapor deposition method or a sputtering method. The thinning is performed along the length direction (longitudinal direction) of the magnetic recording medium 10. That is, by the thinning, a cross section parallel to both the longitudinal direction and the thickness direction of the magnetic recording medium 10 is formed.
The cross section of the obtained sliced sample is observed under a transmission electron microscope (TEM) under the following conditions to obtain a TEM image. Note that the magnification and the acceleration voltage may be appropriately adjusted according to the type of device.
Device: TEM (H9000 NAR manufactured by Hitachi Ltd.)
Accelerating voltage: 300kV
Magnification: 100,000 times Next, using the obtained TEM image, the thickness of the magnetic layer 13 is measured at at least 10 points in the longitudinal direction of the magnetic recording medium 10. Obtained the measurement values are simply averaged mean values obtained (arithmetic mean) to the average thickness t _m of the magnetic layer 13 _[nm]. The position where the measurement is performed is randomly selected from the test piece.

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

(Servo pattern)

A servo pattern is recorded on the magnetic layer 13. For example, as shown in FIG. 2A, the magnetic layer may have a plurality of servo bands SB and a plurality of data bands DB. The plurality of servo bands SB are provided at equal intervals in the width direction of the magnetic recording medium 10. A data band DB is provided between the adjacent servo bands SB. Servo signals for controlling tracking of the magnetic head may be written in advance in the servo band SB. User data may be recorded in the data band DB.

The magnetic layer 13 can have, for example, at least one data band and at least two 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, 3 to 11, in particular 4 to 7, and more particularly 5 or 6. These servo bands and data bands may be arranged, for example, so as to extend in the longitudinal direction of a tape-shaped magnetic recording medium (particularly a long magnetic recording tape), and particularly to be substantially parallel to each other. As a magnetic recording medium having a data band and a servo band in this way, a magnetic recording tape conforming to the LTO (Linear Tape-Open) standard can be cited. 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 the LTO8 standard or later.

The ratio R _S of the total area S _SB servo bands SB to the total area S the surface of the magnetic layer _{13 (= (S SB / S} ) × 100) , from the viewpoint of ensuring high recording capacity, preferably 4.0% Or less, more preferably 3.0% or less, still more preferably 2.0% or less.
The servo band width WSB of the servo band _SB is preferably 95 μm or less, more preferably 60 μm or less, still more preferably 30 μm or less, from the viewpoint of ensuring a high recording capacity. The servo bandwidth W _SB is preferably 10 μm or more from the viewpoint of manufacturing the recording head.
The magnetic layer 13 can have, for example, 5 or more servo bands. In order to secure 5 or more servo tracks, the ratio R _S of the total area S _SB of the servo band SB to the surface area S of the magnetic layer 13 may be preferably 0.8% or more.

The ratio R _S of the total area S _SB of the servo band SB to the area S of the entire surface of the magnetic layer 13 is obtained as follows. For example, the magnetic recording medium 10 is developed using a ferri colloid developer (Sigma Marker Q, manufactured by Sigma High Chemical Co., Ltd.), and then the developed magnetic recording medium 10 is observed with an optical microscope to determine the servo bandwidth _WSB. And the number of servo bands SB is measured. Next, the ratio R _S is calculated from the following formula.
Ratio R _S [%]=(((servo band width W _SB )×(number of servo bands))/(width of magnetic recording medium 10 ))×100

As shown in FIG. 2B, the magnetic layer 13 is configured to be able to form a plurality of data tracks Tk in the data band DB. In this case, the data track width W _Tk is preferably 2.0 μm or less, more preferably 1.5 μm or less, still more preferably 1.0 μm or less, from the viewpoint of ensuring a high recording capacity. The data track width W _Tk is preferably 0.02 μm or more from the viewpoint of magnetic particle size. The data track width W _Tk is obtained as follows. For example, an MFM image is obtained by observing a data recording pattern in a data band portion of the magnetic layer 13 on which data is recorded on the entire surface, using a magnetic force microscope (MFM). As the MFM, Dimension3100 manufactured by Digital Instruments and its analysis software are used. The measurement area of the MFM image is 10 μm×10 μm, and the measurement area of 10 μm×10 μm is divided into 512×512 (=262,144) measurement points. MFM measurement is performed on three 10 μm×10 μm measurement regions at different locations, that is, three MFM images are obtained. From the three obtained MFM images, the track width is measured at 10 points using the analysis software attached to Dimension3100, and the average value (simple average) is taken. The average value is the data track width W _Tk . The measurement conditions of the MFM are: sweep rate: 1 Hz, used chip: MFMR-20, lift height: 20 nm, and correction: Flatten order 3.

From the viewpoint of ensuring a high recording capacity, the magnetic layer 13 can record data such that the minimum value of the distance L between magnetization reversals is preferably 48 nm or less, more preferably 44 nm or less, and even more preferably 40 nm or less. It is configured. The minimum value of the distance L between magnetization reversals is taken into consideration by the magnetic particle size. The minimum value of the distance L between magnetization reversals is calculated as follows. For example, an MFM image is obtained by observing a data recording pattern in a data band portion of the magnetic layer 13 on which data is recorded on the entire surface, using a magnetic force microscope (MFM). As the MFM, Dimension3100 manufactured by Digital Instruments and its analysis software are used. The measurement area of the MFM image is 2 μm×2 μm, and the measurement area of 2 μm×2 μm is divided into 512×512 (=262,144) measurement points. MFM measurement is performed on three 2 μm×2 μm measurement regions at different locations, that is, three MFM images are obtained. Fifty bit distances are measured from the obtained two-dimensional unevenness chart of the recording pattern of the MFM image. The measurement of the bit distance is performed using the analysis software attached to Dimension3100. The value that is the greatest common divisor of the measured 50 bit distances is the minimum value of the magnetization reversal distance L. The measurement conditions are sweep rate: 1 Hz, used chip: MFMR-20, lift height: 20 nm, and correction: Flatten order 3.

A more specific example of the servo pattern recorded on the magnetic layer 13 of the magnetic recording medium of the present technology will be described below with reference to FIGS. 3 and 4. FIG. 3 is a schematic diagram of data bands and servo bands formed in the magnetic layer 13 of the magnetic recording medium 10. FIG. 4 is a diagram showing a servo pattern included in each servo band.
As shown in FIG. 3, the magnetic layer 13 has four data bands d0 to d3. The magnetic layer 13 has a total of five servo bands S0 to S4 such that each data band is sandwiched by two servo bands.
As shown in FIG. 4, each servo band includes five linear servo patterns (for example, servo patterns A1 to A5) that are inclined at a predetermined angle φ, and linear servo patterns that are inclined at the same angle in the opposite direction to this signal. Five servo patterns (for example, servo patterns B1 to B5), four linear servo patterns (for example, servo patterns C1 to C4) that incline at a predetermined angle φ, and incline at the same angle in the direction opposite to this signal. It repeatedly has a frame unit (1 servo frame) composed of four linear servo patterns (for example, servo patterns D1 to D4). The predetermined angle φ may be, for example, 5° to 25°, and particularly 11° to 25°.
The servo bandwidth L1 (see FIG. 3) of each of the servo bands S0 to S4 may be, for example, 100 μm or less, particularly 60 μm or less, more particularly 50 μm or less, and further 40 μm or less. The servo bandwidth L1 may be, for example, 15 μm or more, and particularly 25 μm or more.

(Magnetic powder)

As magnetic particles forming the magnetic powder contained in the magnetic layer 13, for example, hexagonal ferrite, epsilon type iron oxide (ε iron oxide), Co-containing spinel ferrite, gamma hematite, magnetite, chromium dioxide, cobalt-coated iron oxide, and metal. (Metal) and the like, but not limited thereto. The magnetic powder may be one of these or a combination of two or more. Preferably, the magnetic powder may include hexagonal ferrite, ε iron oxide, or Co-containing spinel ferrite. Particularly preferably, the magnetic powder is hexagonal ferrite. The hexagonal ferrite may particularly preferably contain at least one of Ba and Sr. The ε-iron oxide may particularly preferably contain at least one of Al and Ga. Those magnetic particles may be appropriately selected by those skilled in the art based on factors such as the manufacturing method of the magnetic layer 13, the standard of the tape, and the function of the tape.

The shape of the magnetic particles depends on the crystal structure of the magnetic particles. For example, barium ferrite (BaFe) and strontium ferrite may have a hexagonal plate shape. The 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.
The average particle size of the magnetic powder can be preferably 50 nm or less, more preferably 40 nm or less, even more preferably 30 nm or less, 25 nm or less, 22 nm or less, 21 nm or less, or 20 nm or less. The average particle size may be, for example, 10 nm or more, preferably 12 nm or more.
The average aspect ratio of the magnetic powder is preferably 1.0 or more and 3.5 or less, more preferably 1.0 or more and 3.1 or less, still more preferably 1.0 or more and 2.8 or less, and particularly preferably 1.1. It may be not less than 2.5 and not more than 2.5.

(Embodiment in which the magnetic powder contains hexagonal ferrite)

According to a preferred embodiment of the present technology, the magnetic powder may include hexagonal ferrite, and more particularly 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 contain at least one of Ba, Sr, Pb and Ca, more preferably at least one of Ba and Sr. The hexagonal ferrite may be, for example, barium ferrite or strontium ferrite. The barium ferrite may further contain at least one of Sr, Pb, and Ca in addition to Ba. The strontium ferrite may further contain at least one of Ba, Pb, and Ca in addition to Sr.

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, 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, part of Fe may be replaced with another metal element.

When the magnetic powder includes hexagonal ferrite particles, the average particle size of the magnetic powder is preferably 50 nm or less, more preferably 40 nm or less, even more preferably 30 nm or less, 25 nm or less, 22 nm or less, 21 nm or less, or 20 nm. It can be: The average particle size may be, for example, 10 nm or more, preferably 12 nm or more, more preferably 15 nm or more. For example, the average particle size of the magnetic powder may be 10 nm or more and 50 nm or less, 10 nm or more and 40 nm or less, 12 nm or more and 30 nm or less, 12 nm or more and 25 nm or less, or 15 nm or more and 22 nm or less. When the average particle size of the magnetic powder is less than or equal to the upper limit value (for example, 50 nm or less, particularly 30 nm or less), good electromagnetic conversion characteristics (for example, SNR) can be obtained in the magnetic recording medium 10 with high recording density. You can When the average particle size of the magnetic powder is not less than the above lower limit (for example, 10 nm or more, preferably 12 nm or more), the dispersibility of the magnetic powder is further improved and more excellent electromagnetic conversion characteristics (eg, SNR) are obtained. be able to.

When the magnetic powder contains hexagonal ferrite particles, the average aspect ratio of the magnetic powder is preferably 1 or more and 3.5 or less, more preferably 1 or more and 3.1 or less, or 2 or more and 3.1 or less, and even more It may be preferably 2 or more and 3 or less. When the average aspect ratio of the magnetic powder is within the above numerical range, the aggregation of the magnetic powder can be suppressed, and the resistance added to the magnetic powder when the magnetic powder is vertically oriented in the process of forming the magnetic layer 13. Can be suppressed. This can improve the vertical orientation of the magnetic powder.

When the magnetic powder contains hexagonal ferrite particles, the average particle size and average aspect ratio of the magnetic powder are determined as follows.
First, the magnetic recording medium 10 to be measured is processed into thin pieces by processing by the FIB (Focused Ion Beam) method or the like. When the FIB method is used, a carbon film and a tungsten thin film are formed as protective films as a pretreatment for observing a TEM image of a cross section described later. The carbon film is formed on the magnetic layer side surface and the back layer side surface of the magnetic recording medium 10 by a vapor deposition method, and the tungsten thin film is further formed on the magnetic layer side surface by a vapor deposition method or a sputtering method. The thinning is performed along the length direction (longitudinal direction) of the magnetic recording medium 10. That is, by the thinning, a cross section parallel to both the longitudinal direction and the thickness direction of the magnetic recording medium 10 is formed.
Using a transmission electron microscope (H-9500 manufactured by Hitachi High-Technologies Corporation), the cross section of the obtained thin sample was subjected to an acceleration voltage of 200 kV and an overall magnification of 500,000 times with respect to the thickness direction of the magnetic layer 13 as a whole. Cross-section observation is performed so as to include and a TEM photograph is taken.
Next, from the photographed TEM photograph, 50 particles whose side faces are directed toward the observation surface and whose thickness can be clearly confirmed are selected. For example, an example of a TEM photograph is shown in FIG. In FIG. 10, for example, the particles indicated by a and d are selected because the thickness can be clearly confirmed. The maximum plate thickness DA of each of the selected 50 particles is measured. The maximum plate thickness DA thus obtained is simply averaged (arithmetic average) to obtain the average maximum plate thickness DA _ave .
Then, the plate diameter DB of each magnetic powder is measured. In order to measure the plate diameter DB of the particles, 50 particles whose plate diameters can be clearly confirmed are selected from the taken TEM photographs. For example, in FIG. 10, the particles indicated by b and c are selected because their plate diameters can be clearly confirmed. The plate diameter DB of each of the selected 50 particles is measured. The plate diameter DB thus obtained is simply averaged (arithmetic average) to obtain an average plate diameter DB _ave . The average plate diameter DB _ave is the average particle size.
Then, the average aspect ratio (DB _ave /DA _ave ) of the particles is obtained from the average maximum plate thickness DA _ave and the average plate diameter DB _ave .

If the magnetic powder contains a powder of hexagonal ferrite particles, average particle volume of the magnetic powder is preferably 5900Nm ³ or less, more preferably 500 nm ³ or more 3400 nm ³ or less, still more preferably 1000 nm ³ or more 2500 nm ³ or less.
When the average particle volume of the magnetic powder is not more than the upper limit value (for example, 5900 nm ³ or less), good electromagnetic conversion characteristics (for example, SNR) can be obtained in the magnetic recording medium 10 having a high recording density. When the average particle volume of the magnetic powder is at least the above lower limit value (for example, 500 nm ³ or more), the dispersibility of the magnetic powder is further improved, and more excellent electromagnetic conversion characteristics (for example, SNR) can be obtained.

The average particle volume of the magnetic powder is obtained as follows. First, the average maximum plate thickness DA _ave and average plate diameter DB _ave are obtained as described above regarding the method of calculating the average particle size of the magnetic powder. Next, the average volume V of the magnetic powder is calculated by the following formula.

According to a particularly preferred embodiment of the present technology, the magnetic powder may be barium ferrite magnetic powder or strontium ferrite magnetic powder, more preferably barium ferrite magnetic powder. The barium ferrite magnetic powder contains magnetic particles of iron oxide having barium ferrite as a main phase (hereinafter referred to as “barium ferrite particles”). The barium ferrite magnetic powder has high reliability in data recording, for example, the coercive force does not drop 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.

When the magnetic layer 13 contains barium ferrite magnetic powder as the magnetic powder, the average thickness t _m [nm] of the magnetic layer 13 is preferably 35 nm≦t _m ≦100 nm, and particularly preferably 80 nm or less.
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. m or more and 270 kA/m or less.

(Embodiment in which the magnetic powder contains ε iron oxide)

According to another preferred embodiment of the present technology, the magnetic powder may preferably include a powder of nanoparticles containing ε iron oxide (hereinafter referred to as “ε iron oxide particles”). Even if the ε iron oxide particles are fine particles, a high coercive force can be obtained. It is preferable that the ε iron oxide contained in the ε iron oxide particles is preferentially crystallized in the thickness direction (vertical direction) of the magnetic recording medium 10.

The ε iron oxide particles have a spherical shape or a substantially spherical shape, or a cubic shape or a substantially cubic shape. Since the ε iron oxide particles have the shape as described above, when the ε iron oxide particles are used as the magnetic particles, the thickness of the medium is larger than that when the hexagonal plate-shaped barium ferrite particles are used as the magnetic particles. The contact area between particles in the direction can be reduced, and the aggregation of particles can be suppressed. Therefore, it is possible to enhance the dispersibility of the magnetic powder and obtain a better SNR (Signal-to-Noise Ratio).

The ε iron oxide particles have a core-shell structure. Specifically, as shown in FIG. 5, the ε iron oxide particle includes 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 a 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 portion 21 contains ε iron oxide. Epsilon iron oxide contained in the core portion 21 is preferably one that the main phase of _ε-Fe 2 _{O 3} crystal, it is more preferably made of _ε-Fe 2 _{O 3} single phase.

The first shell portion 22 a 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 making sufficient exchange coupling between the core portion 21 and the first shell portion 22a and improving the magnetic characteristics, it is preferable to cover the entire surface of the core portion 21.

The first shell portion 22a is a so-called soft magnetic layer, and may include, for example, 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 portion 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 contains α-Fe (soft magnetic material), the α-iron oxide may be obtained by oxidizing α-Fe contained 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, and thus 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 in 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. It is possible to prevent the characteristics of the ε iron oxide particles from being deteriorated due to the generation of rust and the like. Therefore, the characteristic deterioration of the magnetic recording medium 10 can be suppressed.

The ε iron oxide particles may have a shell portion 23 having a single layer structure as shown in FIG. 6. In this case, the shell portion 23 has the same configuration as the first shell portion 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 an additive together with the core-shell structure. In these cases, a part of Fe of the ε iron oxide particles is replaced with the additive. Even if the ε iron oxide particles contain the 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 the ease of recording can be improved. The additive is at least one selected from the group consisting of metal elements other than iron, preferably trivalent metal elements, more preferably aluminum (Al), gallium (Ga), and indium (In).
Specifically, ε-iron oxide containing an additive is an ε-Fe ₂ -xM _x O ₃ crystal (where M is a metal element other than iron, preferably a trivalent metal element, more preferably Al). , Ga, and In selected from the group consisting of In, and x is, for example, 0<x<1.

The average particle size (average maximum particle size) 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 12 nm or more and 22 nm or less. In the magnetic recording medium 10, an area having a size half the recording wavelength is an actual magnetized area. Therefore, a good SNR can be obtained by setting the average particle size of the magnetic powder to be half or less of the shortest recording wavelength. Therefore, when the average particle size of the magnetic powder is 22 nm or less, a good electromagnetic field is obtained in the high recording density magnetic recording medium 10 (for example, the magnetic recording medium 10 configured to be able to record a signal at the shortest recording wavelength of 44 nm or less). The conversion characteristic (for example, SNR) can be obtained. On the other hand, when the average particle size of the magnetic powder is 8 nm or more, the dispersibility of the magnetic powder is further improved, and more excellent electromagnetic conversion characteristics (for example, SNR) can be obtained.

The average aspect ratio of the magnetic powder is preferably 1.0 or more and 3.5 or less, more preferably 1.0 or more and 3.1 or less, and even more preferably 1.0 or more and 2.5 or less. When the average aspect ratio of the magnetic powder is in the range of 1.0 or more and 3.5 or less, aggregation of the magnetic powder can be suppressed, and when the magnetic powder is vertically aligned in the process of forming the magnetic layer 13, The resistance applied to the magnetic powder can be suppressed. Therefore, the vertical orientation of the magnetic powder can be improved.

When the magnetic powder contains ε iron oxide particles, the average particle size and the average aspect ratio of the magnetic powder are determined as follows.
First, the magnetic recording medium 10 to be measured is processed into thin pieces by processing by the FIB (Focused Ion Beam) method or the like. When the FIB method is used, a carbon film and a tungsten thin film are formed as protective films as a pretreatment for observing a TEM image of a cross section described later. The carbon film is formed on the magnetic layer side surface and the back layer side surface of the magnetic recording medium 10 by a vapor deposition method, and the tungsten thin film is further formed on the magnetic layer side surface by a vapor deposition method or a sputtering method. The thinning is performed along the length direction (longitudinal direction) of the magnetic recording medium 10. That is, by the thinning, a cross section parallel to both the longitudinal direction and the thickness direction of the magnetic recording medium 10 is formed.
Using a transmission electron microscope (H-9500, manufactured by Hitachi High-Technologies Corporation), the cross section of the obtained thin sample was subjected to an acceleration voltage of 200 kV and an overall magnification of 500,000 times with respect to the thickness direction of the magnetic layer 13 as a whole. Cross-section observation is performed so as to include, and a TEM photograph is taken.
Next, from the photographed TEM photograph, 50 particles whose shape can be clearly confirmed are selected, and the major axis length DL and the minor axis length DS of each particle are measured. Here, the major axis length DL means the maximum distance (so-called maximum Feret diameter) of the distance between two parallel lines drawn from any angle so as to contact the contour of each particle. On the other hand, the minor axis length DS means the maximum length of the particles in the direction orthogonal to the major axis (DL) of the particles.
Subsequently, the measured major axis lengths DL of 50 particles are simply averaged (arithmetic average) to obtain an average major axis length DL _ave . The average major axis length DL _ave determined in this way is the average particle size of the magnetic powder. In addition, the measured minor axis length DS of 50 particles is simply averaged (arithmetic average) to obtain the average minor axis length DS _ave . Then, the average aspect ratio (DL _ave /DS _ave ) of the particles is obtained from the average major axis length DL _ave and the average minor axis length DS _ave .

The average particle volume of the magnetic powder is preferably 5500Nm ³ or less, more preferably 270 nm ³ or more 5500Nm ³ or less, still more preferably 900 nm ³ or more 5500Nm ³ or less. When the average particle volume of the magnetic powder is 5500 nm ³ or less, the same effect as when the average particle size of the magnetic powder is 22 nm or less is obtained. On the other hand, when the average particle volume of the magnetic powder is 270 nm ³ or more, the same effect as when the average particle size of the magnetic powder is 8 nm or more is obtained.

When the ε iron oxide particles have a spherical shape or a substantially spherical shape, the average particle volume of the magnetic powder is determined as follows. First, the average major axis length DL _ave is obtained in the same manner as the above-described method for calculating the average particle size of magnetic powder. Next, the average volume V of the magnetic powder is calculated by the following formula.
V=(π/6)×DL _ave ³

When the ε iron oxide particles have a cubic shape, the average volume of the magnetic powder is calculated as follows.
The magnetic recording medium 10 is processed by FIB (Focused Ion Beam) method or the like to be thinned. When the FIB method is used, a carbon film and a tungsten thin film are formed as protective films as a pretreatment for observing a TEM image of a cross section described later. The carbon film is formed on the magnetic layer side surface and the back layer side surface of the magnetic recording medium 10 by a vapor deposition method, and the tungsten thin film is further formed on the magnetic layer side surface by a vapor deposition method or a sputtering method. The thinning is performed along the length direction (longitudinal direction) of the magnetic recording medium 10. That is, by the thinning, a cross section parallel to both the longitudinal direction and the thickness direction of the magnetic recording medium 10 is formed.
Using a transmission electron microscope (H-9500 manufactured by Hitachi High-Technologies Corporation), the obtained thin piece sample was made to include the entire magnetic layer 13 in the thickness direction of the magnetic layer 13 at an acceleration voltage of 200 kV and a total magnification of 500,000 times. The cross section is observed to obtain a TEM photograph. Note that the magnification and the acceleration voltage may be appropriately adjusted according to the type of device.
Next, 50 particles whose particle shapes are clear are selected from the photographed TEM photograph, and the side length DC of each particle is measured. Then, the measured side lengths DC of 50 particles are simply averaged (arithmetic average) to obtain an average side length DC _ave . Next, using the average side length DC _ave , the average volume V _ave (particle volume) of the magnetic powder is calculated from the following formula.
V _ave =DC _ave ³

(Embodiment in which the magnetic powder contains Co-containing spinel ferrite)

According to still another preferred embodiment of the present technology, the magnetic powder may include a powder of nanoparticles containing Co-containing spinel ferrite (hereinafter also referred to as “cobalt ferrite particles”). That is, the magnetic powder may be cobalt ferrite magnetic powder. The cobalt ferrite particles preferably have uniaxial crystal anisotropy. The cobalt ferrite magnetic particles have, for example, a cubic shape or a substantially cubic shape. The Co-containing spinel ferrite may further contain one or more 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, one or more metals selected from the group consisting of Ni, Mn, Al, Cu, and Zn. x is 0.4≦x≦1.0. Y is a value in the range of 0≦y≦0.3, where x and y satisfy the relationship of (x+y)≦1.0, and z is 3≦z≦. It is a value within the range of 4. A part of Fe may be replaced with 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.

When the magnetic powder includes powder of cobalt ferrite particles, the average particle size of the magnetic powder is preferably 25 nm or less, more preferably 10 nm or more and 23 nm or less. When the average particle size of the magnetic powder is 25 nm or less, good electromagnetic conversion characteristics (for example, SNR) can be obtained in the magnetic recording medium 10 having a high recording density. On the other hand, when the average particle size of the magnetic powder is 10 nm or more, the dispersibility of the magnetic powder is further improved, and more excellent electromagnetic conversion characteristics (for example, SNR) can be obtained. When the magnetic powder contains cobalt ferrite particles, the average aspect ratio and average particle size of the magnetic powder are obtained by the same method as when the magnetic powder contains ε iron oxide particles.

The average particle volume of the magnetic powder is preferably 15000 nm ³ or less, more preferably 1000 nm ³ or more 12000 nm ³ or less. When the average particle volume of the magnetic powder is 15000 nm ³ or less, the same effect as when the average particle size of the magnetic powder is 25 nm or less is obtained. On the other hand, when the average particle volume of the magnetic powder is 1000 nm ³ or more, the same effect as when the average particle size of the magnetic powder is 10 nm or more is obtained. The average particle volume of the magnetic powder is the same as the method of calculating the average particle volume when the ε iron oxide particles have a cubic shape.

(lubricant)

The magnetic layer contains a lubricant. The lubricant contains a fatty acid and a fatty acid ester. The mass ratio of the fatty acid and the fatty acid ester extracted from the magnetic recording medium 10 with hexane is fatty acid/fatty acid ester≦0.6, and preferably fatty acid/fatty acid ester≦0.55. When the mass ratio is within this numerical range, an increase in the dynamic friction coefficient after repeated recording or reproduction can be suppressed.
The mass ratio of the fatty acid and the fatty acid ester in the lubricant may be, for example, fatty acid/fatty acid ester≧0.3. If the mass ratio is too small, sticking may occur when the magnetic recording medium is folded back.

The mass ratio is measured as follows.
First, preparation of a calibration curve of the same fatty acid and fatty acid ester as the lubricant used in the magnetic recording medium to be measured and preparation of a calibration curve sample will be described. About 1 mg, 2 mg, and 3 mg of fatty acid is taken, and the actual amount of each of these three fatty acid samples is measured by a balance. Each of the three fatty acid samples is dissolved in 100 mL of a solvent of acetonitrile/water=100/3 (mass ratio) to prepare three types of calibration curve samples. Similarly, about 5 mg, 10 mg, and 15 mg of fatty acid ester are taken, and the substantial amount of each of these three fatty acid ester samples is measured by a balance. The three fatty acid ester samples are respectively dissolved in 100 mL of a solvent of acetonitrile/water=100/3 (mass ratio) to prepare three types of calibration curve samples. The peak height of the fatty acid or fatty acid ester of each calibration curve sample is obtained using chromatography, and a calibration curve is created based on the substantial amount of the fatty acid or fatty acid ester of each calibration curve sample and the peak height.
Next, 10 m of a 12.65 mm wide magnetic recording medium to be measured is prepared, immersed in 120 mL of hexane solution, stirred for 5 minutes to extract the lubricant, and the hexane solution in which the lubricant is extracted with a measuring cylinder. Is measured by 100 mL, and then hexane is evaporated by an evaporator (may be volatilized in a fume hood). Next, the extracted lubricant is dissolved in 5 mL of a solvent of acetonitrile/water=100/3 (mass ratio), and the peak heights of fatty acids and fatty acid esters are obtained by using chromatography. From the peak height and the previously prepared calibration curve, the mass of fatty acid and fatty acid ester is calculated, and the mass ratio of fatty acid and fatty acid ester is calculated.
The measurement conditions of chromatography are shown below.
Chromatography type: Reversed phase chromatography Detector: Shodex RI-101 (Shodex RI detector)
Column used: Intersil ODS-2(GL Science) ODS 2.5 μm 4.6×150 mm(W)
Analysis software: SIC-480 II XP (chromatographic data analysis software manufactured by System Instruments)
Carrier: acetonitrile/water = 100/3 (mass ratio)

The fatty acid may be a compound represented by the following general formula (1) or (2). For example, one or both of the compound represented by the following general formula (1) and the compound represented by the following general formula (2) may be contained as the fatty acid.
Further, the fatty acid ester may be preferably a compound represented by the following general formula (3) or (4). For example, one or both of the compound represented by the following general formula (3) and the compound represented by the following general formula (4) may be contained as the fatty acid ester.
The lubricant is one or both of the compound represented by the general formula (1) and the compound represented by the general formula (2), and the compound represented by the general formula (3) and the general formula (4). By including one or both of the compounds, it is possible to suppress an increase in the dynamic friction coefficient due to repeated recording or reproduction of the magnetic recording medium.
CH ₃ (CH ₂ ) _k COOH (1)
(However, in the general formula (1), k is an integer selected from the range of 14 or more and 22 or less, more preferably the range of 14 or more and 18 or less.)
_{CH 3 (CH 2) n CH} = CH (CH 2) m COOH ··· (2)
(However, in the general formula (2), the sum of n and m is an integer selected from the range of 12 or more and 20 or less, more preferably the range of 14 or more and 18 or less.) CH ₃ (CH ₂ ) _p COO (CH ₂ ) _q CH ₃ ...(3)
(However, in the general formula (3), p is an integer selected from the range of 14 or more and 22 or less, more preferably 14 or more and 18 or less, and q is the range of 2 or more and 5 or less, more preferably 2 or more. It is an integer selected from the range of 4 or less.)
_{CH 3 (CH 2) r COO-} (CH 2) s CH (CH 3) 2 ··· (4)
(However, in the general formula (4), r is an integer selected from the range of 14 to 22 and s is an integer selected from the range of 1 to 3).

(Binder)

As the binder, a resin having a structure in which a crosslinking reaction is performed on a polyurethane resin or a vinyl chloride resin is preferable. However, the binder is not limited to these, and other resins may be appropriately mixed depending on the physical properties required for the magnetic recording medium 10. The resin to be mixed 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, acrylic ester-acrylonitrile copolymer. , Acrylic acid ester-vinyl chloride-vinylidene chloride copolymer, acrylic acid ester-vinylidene chloride copolymer, methacrylic acid ester-vinylidene chloride copolymer, methacrylic acid ester-vinyl chloride copolymer, methacrylic acid ester-ethylene copolymer Polymer, polyvinyl fluoride, vinylidene chloride-acrylonitrile copolymer, acrylonitrile-butadiene copolymer, polyamide resin, polyvinyl butyral, cellulose derivative (cellulose acetate butyrate, cellulose diacetate, cellulose triacetate, cellulose propionate, nitro Cellulose), styrene-butadiene copolymer, polyester resin, amino resin, and a combination of two or more selected from synthetic rubber may be used.

In addition, a thermosetting resin or a reactive resin may be used as the binder. Examples of thermosetting resins or reactive resins include phenol resins, epoxy resins, urea resins, melamine resins, alkyd resins, silicone resins, polyamine resins, and urea formaldehyde resins.

In addition, polar functional groups such as —SO ₃ M, —OSO ₃ M, —COOM, and P═O(OM) ₂ are introduced into each of the above-mentioned binders in order to improve the dispersibility of the magnetic powder. 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, and,> NR1R2 ⁺ X ^- include those of the main chain type. Here, R1, R2, and R3 in the formula are each independently 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. Is. Moreover, as a polar functional group, -OH, -SH, -CN, an epoxy group, etc. are also mentioned.

(Additive)

The magnetic layer 13 is, as non-magnetic reinforcing particles, 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 may be further contained.

(Underlayer)

The underlayer 12 is a nonmagnetic layer containing nonmagnetic powder and a binder as main components. The base layer 12 further contains a lubricant. The above description regarding the binder and lubricant contained in the magnetic layer 13 also applies to the binder and lubricant contained in the underlayer 12. The underlayer 12 may further include at least one additive of conductive particles, a curing agent, a rust preventive agent, and the like, if necessary.

The average thickness of the underlayer 12 is preferably 0.6 μm or more and 2.0 μm or less, more preferably 0.8 μm or more and 1.4 μm or less. The average thickness of the underlying 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 underlayer 12.

The underlayer 12 may have pores, that is, the underlayer 12 may be provided with a large number of pores. The pores of the underlayer 12 may be formed, for example, by forming pores in the magnetic layer 13. In particular, a large number of protrusions provided on the back layer side surface of the magnetic recording medium 10 may be formed on the magnetic layer side. It can be formed by pressing against a surface. That is, by forming a recess corresponding to the shape of the protrusion on the surface of the magnetic layer side, pores can be formed in the magnetic layer 13 and the underlayer 12.
Further, the pores may be formed as the solvent volatilizes in the step of drying the magnetic layer-forming coating material. In addition, when the magnetic layer-forming coating material is applied to the surface of the underlayer 12 to form the magnetic layer 13, the solvent in the magnetic layer-forming coating material forms the underlayer formed when the lower layer is applied and dried. It can pass through the pores and penetrate into the underlayer 12. After that, when the solvent that has penetrated into the underlayer 12 volatilizes in the step of drying the magnetic layer 13, the solvent that has penetrated into the underlayer 12 moves from the underlayer 12 to the surface of the magnetic layer 13 to form pores. May be formed. The pores formed in this way can be those that connect the magnetic layer 13 and the underlayer 12, for example. The average diameter of the pores can be adjusted by changing the solid content of the magnetic layer-forming coating material or the type of solvent and/or the drying condition of the magnetic layer-forming coating material.
Since the pores are formed in both the magnetic layer 13 and the underlayer 12, a particularly suitable amount of lubricant appears on the surface of the magnetic layer for good running stability, and dynamic friction due to repeated recording or reproduction occurs. It is possible to further suppress the increase in the coefficient.

(Non-magnetic powder)

The non-magnetic powder contained in the underlayer 12 may contain at least one selected from inorganic particles and organic particles, for example. One kind of non-magnetic powder may be used alone, or two or more kinds of non-magnetic powder may be used in combination. The inorganic particles include, for example, one kind or a combination of two or more kinds selected from 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 non-magnetic 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.

(Back layer)

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

The average thickness t _b of the back layer 14 is preferably t _b ≦0.6 μm. Since the average thickness t _b of the back layer 14 is within the above range, the thicknesses of the underlayer 12 and the base layer 11 are kept thick even when the average thickness t _T of the magnetic recording medium 10 is t _T ≦5.6 μm. Therefore, 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 obtained as follows. First, the average thickness t _T of the magnetic recording medium 10 is measured. The measuring method of the average thickness t _T is as described in “(3) Physical properties and structure” below. Subsequently, the back layer 14 of the sample is removed with a solvent such as MEK (methyl ethyl ketone) or dilute hydrochloric acid. Next, the thickness of the sample is measured at 5 or more positions using a laser hologage (LGH-110C) manufactured by Mitutoyo, and these measured values are simply averaged (arithmetic average) to obtain an average value t _B. Calculate [μm]. Then, the average thickness t _b [μm] of the back layer 14 is calculated by the following formula. The measurement position shall be randomly selected from the sample.
t _b [μm]=t _T [μm]−t _B [μm]

Of the two surfaces of the back layer 14, the surface forming the back layer side surface of the magnetic recording medium 10 is preferably provided with a large number of protrusions. By winding the magnetic recording medium 10 in a roll, a large number of pores can be formed in the magnetic layer 13 by the large number of protrusions.

The protrusions can be formed, for example, by including particles in the back layer-forming coating material. The particles may be inorganic particles such as carbon black. The particle size of the particles can be appropriately selected according to the size of the pores to be formed in the magnetic layer 13.

The average particle size of particles (particularly inorganic particles) contained in the back layer 14 is preferably 10 nm or more and 300 nm or less, more preferably 20 nm or more and 270 nm or less. The average particle size of the non-magnetic powder is determined in the same manner as the average particle size of the above magnetic powder. Further, the non-magnetic powder may have a particle size distribution of 2 or more.

(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 ≦5.6 μm, more preferably 5.3 μm or less, and even more preferably 5.2 μm or less, 5.0 μm or less, or 4.6 μm or less. It is possible. When the average thickness t _T of the magnetic recording medium 10 is within the above numerical range (for example, t _T ≦5.6 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, but is 3.5 μm≦t _T , for example.

The average thickness t _T of the magnetic recording medium 10 is obtained as follows. First, a 1/2 inch wide magnetic recording medium 10 is prepared and cut into a length of 250 mm to prepare a sample. Next, the thickness of the sample is measured at 5 or more positions using a Mitutoyo laser hog gauge (LGH-110C) as a measuring device, and the measured values are simply averaged (arithmetic average) to obtain the average. Calculate the value t _T [μm]. The measurement position shall be randomly selected from the sample.

(Pore distribution of magnetic recording medium (pore volume and average pore diameter))

The average diameter of the pores of the magnetic recording medium 10 is 6 nm or more and 11 nm or less, preferably 6 nm or more and 10 nm or less, more preferably 6 when measured in a dry state after removing the lubricant from the magnetic recording medium 10. It is not less than 0.5 nm and not more than 10 nm, more preferably not less than 7 nm and not more than 9 nm. When the average pore diameter is within the above numerical range, the effect of suppressing an increase in the dynamic friction coefficient after repeated recording or reproduction can be further improved.
Further, the pore volume of the magnetic recording medium 10 is preferably 0.016 cm ³ / g or more, more preferably 0.02 cm ³ / g or more. When the pore volume is within the above numerical range, the effect of suppressing an increase in the dynamic friction coefficient after repeatedly recording or reproducing can be further improved. The pore volume of the magnetic recording medium 10 may be, for example, 0.05 cm ³ /g or less, preferably 0.04 cm ³ /g or less, and more preferably 0.03 cm ³ /g or less.

The pore distribution (pore volume and average pore diameter (which is the maximum pore volume at the time of desorption) of the magnetic recording medium 10 is measured in the dry state after removing the lubricant from the magnetic recording medium. To be done. Specifically, the measurement is performed as follows.
First, the magnetic recording medium 10 having a size about 10% larger than the area of 0.1265 m ² is soaked in hexane (a sufficient amount of the tape, for example, 150 mL) for 24 hours, and then naturally dried to have an area of 0.1265 m ^2. (For example, 50 cm at both ends of the dried tape is cut off to prepare a tape width of 10 m.), and a measurement sample is prepared. The lubricant is removed from the magnetic recording medium 10 by the immersion in hexane for 24 hours, and the magnetic recording medium 10 is dried by the natural drying.
Next, the pore size distribution (pore volume and average pore diameter) is measured by the BJH method using a specific surface area/pore distribution measuring device. The measuring device and the measuring conditions are shown below. In this way, the pore volume and the average diameter of the pores are measured.
Measuring environment: Room temperature measuring device: 3FLEX manufactured by Micromeritics
Measured adsorbate: N ₂ gas Measured pressure range (P/P ⁰ ): ^{0 to} 0.995
For the measured pressure range, the pressure is varied according to the table below. The pressure values in the table below are relative pressures P/P ⁰ . In the following table, for example, in step 1, the pressure is changed from the starting pressure of 0.000 to the ultimate pressure of 0.010 by 0.001 per 10 seconds. When the pressure reaches the ultimate pressure, the pressure change in the next step is performed. The same applies to steps 2 to 10. However, if the pressure does not reach equilibrium at each step, the apparatus waits for the pressure to equilibrate before proceeding to the next step.

(Kurtosis Sku on the magnetic layer side surface)

The Kurtosis Sku of the magnetic layer side surface of the magnetic recording medium 10 is 3.0 or more, preferably 3.1 or more, and more preferably 3.5 or more. When the Kurtosis on the surface on the magnetic layer side is within this numerical range, it is possible to suppress an increase in the dynamic friction coefficient after repeated recording or reproduction.
Further, the kurtosis Sku of the surface of the magnetic recording medium according to the present technology on the side of the magnetic layer may be 4.0 or less, for example. When the kurtosis on the surface on the magnetic layer side is too large, the falling of the magnetic powder contained in the magnetic layer may be deteriorated. The kurtosis of the surface on the magnetic layer side can be adjusted by, for example, the average particle size and shape of the magnetic powder.

The surface kurtosis on the magnetic layer side is measured as follows. First, a magnetic recording medium 10 having a width of 12.65 mm is prepared and cut into a length of 100 mm to prepare a sample. Then, the sample is placed on a slide glass so that the surface to be measured (the surface on the magnetic layer side) faces upward, and the end of the sample is fixed with a mending tape. The surface shape is measured using a VertScan (50 times objective lens) as a measuring device, and the Kurtosis Sku is obtained from the following formula based on the standard of ISO 25178.
Device: Non-contact roughness meter using optical interference (Ryoka System Co., Ltd. non-contact surface/layer cross-section shape measurement system VertScan R5500GL-M100-AC)
Objective lens: 50x
CCD: 1/3 lens Measurement area: 640×480 pixels (field of view: approximately 95 μm×71 μm)
Measurement mode: phase
Wavelength filter: 520nm
Noise removal filter Smoothing 3x3
Surface correction: Corrected by the second-order polynomial approximation surface Measurement software: VS-Measure Version5.5.2
Analysis software: VS-viewer Version5.5.5

Here, the meaning of each symbol in the formulas is as follows.

A: number of samples x: horizontal direction of sample y: vertical direction of sample z: height

As described above, the surface shape of the sample on the magnetic layer side was measured at the positions of at least 5 points in the longitudinal direction, and the average value of the respective kurtosis calculated automatically from the surface profile obtained at each position was used as the magnetic value. Let Kurtosis Sku on the layer side surface.

(Kurtosis Sku on the back layer side)

The Kurtosis Sku of the surface of the magnetic recording medium 10 on the back layer side is 2.0 or more, preferably 2.2 or more, more preferably 2.3 or more, and further preferably 3.0 or more. It is possible. When the kurtosis of the surface on the back layer side is within this numerical range, it is possible to suppress an increase in the dynamic friction coefficient after repeated recording or reproduction.
Further, the Kurtosis Sku of the surface of the magnetic recording medium according to the present technology on the back layer side may be 3.5 or less, for example. If the kurtosis on the surface of the back layer side is too large, the electromagnetic conversion characteristics may be deteriorated due to transfer. The kurtosis of the surface on the back layer side can be adjusted, for example, by adjusting the pressure and temperature of the calendering treatment after forming the back layer 14. For example, by increasing the pressure and temperature of the calendering treatment, the kurtosis on the surface of the back layer side can be reduced.

The back layer side surface kurtosis is determined in the same manner as the magnetic layer side surface kurtosis method, except that the sample surface (back layer side surface) is fixed so that it is facing up. You can

(Friction coefficient ratio (μ _C(1000) /μ _C(5) ))

The magnetic recording medium 10 is preferably a dynamic friction coefficient μ _{C (} in the fifth reciprocation when the magnetic recording medium in a state where a tension of 0.6 N is applied in the longitudinal direction is slid on the magnetic head 5 times _{). 5)} and the friction coefficient ratio (μ _C(1000) /μ _C(5) ) between the dynamic friction coefficient μ _{C(1000) at} the 1000th reciprocation when the magnetic head is reciprocated 1000 times, 1.0 or more 1 It is 0.8 or less, more preferably 1.0 or more and 1.5 or less, and even more preferably 1.0 or more and 1.3 or less. When the friction coefficient ratio (μ _C(1000) /μ _C(5) ) is within the above numerical range, it is possible to reduce the change in the dynamic friction coefficient due to a large number of runs, so that the running of the magnetic recording medium 10 is stabilized. Can be made

The dynamic friction coefficient μ _C(5) and the dynamic friction coefficient μ _C(1000) for calculating the friction coefficient ratio (μ _C(1000) /μ _C(5) ) are obtained as follows.
First, as shown in FIG. 7A, two guide rolls 73-1 and 73-1 having a diameter of 1 inch and a cylindrical shape having a diameter of 1 inch, which are spaced apart from each other and arranged in parallel, are formed. Place it so that the magnetic surface contacts -2. The two guide rolls 73-1 and 73-2 are fixed to the hard plate-like member 76, and their positional relationship is fixed.
Next, with respect to the head block (for recording/reproducing) 74 mounted on the LTO5 drive, the magnetic surface of the magnetic recording medium 10 is brought into contact with and the holding angle θ ₁ (°)=5.6°. Contact. The head block 74 is movably attached to the plate member 76 so that the holding angle θ ₁ can be changed. However, when the holding angle θ ₁ (°) reaches 5.6°, the position of the holding position is changed. It is fixed to the plate-like member 76, and thus the positional relationship between the guide rolls 73-1 and 73-2 and the head block 74 is also fixed.
One end of the magnetic recording medium 10 is connected to the movable strain gauge 71 via a jig 72. The magnetic recording medium 10 is fixed to the jig 72 as shown in FIG.
A weight 75 is connected to the other end of the magnetic recording medium 10. The weight 75 applies a tension of 0.6 N (T ₀ [N]) in the longitudinal direction of the magnetic recording medium 10.
The movable strain gauge 71 is fixed on a base 77. The positional relationship between the base 77 and the plate-shaped member 76 is also fixed, whereby the positional relationship among the guide rolls 73-1 and 73-2, the head block 74, and the movable strain gauge 71 is fixed.
By the movable strain gauge 71, the magnetic recording medium 10 is slid by 60 mm on the head block 74 (outward path) so that the magnetic recording medium 10 moves toward the movable strain gauge 71 at 10 mm/s. Slide 60 mm away (return path). This reciprocating operation is repeated 1000 times. Out of the 1000 times of reciprocating motion, the output value (voltage) of the strain gauge was acquired 13 times from the start of sliding of the 60 mm sliding of the 5th forward path to the stop of sliding, and the output value and the load were Is converted to T[N] based on the linear relationship (described later). T _ave [N] is calculated by simply averaging 11 pieces except the first and last two times. The dynamic friction coefficient μ _{C (5)} is calculated by the following formula.

In order to obtain the linear relationship, the output value (voltage) of the movable strain gauge 71 is obtained for each of the case where a load of 0.4 N is applied to the movable strain gauge 71 and the case where a load of 1.5 N is applied. .. A linear relationship between the output value and the load is obtained from the obtained two output values and the two loads. As described above, the output value (voltage) by the movable strain gauge 71 during sliding is converted into T[N] using the linear relationship.
Further, the dynamic friction coefficient μ _{c (1000)} is obtained in the same manner as the above dynamic friction coefficient μ _{c (5)} except that the 1000th forward trip is measured.
A friction coefficient ratio μ _C(1000) /μ _C(5) is calculated from the dynamic friction coefficient μ _C(5) and the dynamic friction coefficient μ _C(1000) measured as described above.

(Squareness ratio S2 measured in the vertical direction)

The squareness ratio S2 measured in the vertical direction (thickness direction) of the magnetic recording medium 10 is preferably 65% or more, more preferably 70% or more, even more preferably 73% or more, still 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 it becomes easier to control the drive side.
In the present specification, the perpendicular orientation of the magnetic recording medium 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 in the vertical direction is obtained as follows. First, three magnetic recording media 10 are overlaid with a double-sided tape and then punched with a φ6.39 mm punch to prepare a measurement sample. At this time, marking is performed with an arbitrary ink having no magnetism so that the longitudinal direction (traveling direction) of the magnetic recording medium 10 can be recognized. Then, the M-H loop of the measurement sample (entire magnetic recording medium 10) corresponding to the vertical direction (thickness direction) of the magnetic recording medium 10 is measured using VSM. Next, the coating film (the underlayer 12, the magnetic layer 13, the back layer 14 and the like) is wiped using acetone or ethanol or the like, and only the base layer 11 is left. Then, the three obtained base layers 11 are overlapped with a double-sided tape and then punched with a punch having a diameter of 6.39 mm to obtain a sample for background correction (hereinafter, simply referred to as “correction sample”). After that, the MH loop of the correction sample (base layer 11) corresponding to the vertical direction of the base layer 11 (the vertical direction of the magnetic recording medium 10) is measured using VSM.
In the measurement of the MH loop of the measurement sample (entire magnetic recording medium 10) and the MH loop of the correction sample (base layer 11), a high-sensitivity vibration sample magnetometer "VSM-" manufactured by Toei Industry Co., Ltd. P7-15 type" is used. The measurement conditions are as follows: measurement mode: full loop, maximum magnetic field: 15 kOe, magnetic field step: 40 bit, Time constant of Locking amp: 0.3 sec, Waiting time: 1 sec, MH average number: 20.
After the MH loop of the measurement sample (entire magnetic recording medium 10) and the MH loop of the correction sample (base layer 11) are obtained, the MH loop of the measurement sample (entire magnetic recording medium 10) By subtracting the MH loop of the correction sample (base layer 11) from, background correction is performed, and the MH loop after background correction is obtained. A measurement/analysis program attached to "VSM-P7-15 type" is used for the calculation of the background correction.
The saturation magnetization Ms(emu) and the residual magnetization Mr(emu) of the obtained MH loop after background correction are substituted into the following equation to calculate the squareness ratio S2(%). In addition, the measurement of the above-mentioned MH loop shall be performed at 25 degreeC. In addition, "diamagnetic field correction" when measuring the MH loop in the vertical direction of the magnetic recording medium 10 is not performed. A measurement/analysis program attached to the "VSM-P7-15 type" is used for this calculation.
Squareness S2(%)=(Mr/Ms)×100

(Squareness ratio S1 measured in the longitudinal direction)

The squareness ratio S1 measured in the longitudinal direction (traveling direction) of the magnetic recording medium 10 is preferably 35% or less, more preferably 30% or less, 27% or less, or 25% or less, still 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 to perform.
In the present specification, the vertical orientation of the magnetic recording medium 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 in the longitudinal direction is obtained in the same manner as the squareness ratio S2 except that the MH loop is measured in the longitudinal direction (traveling direction) of the magnetic recording medium 10 and the base layer 11.

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

(Arithmetic mean roughness _Ra )

Arithmetic mean roughness _{R a} of the magnetic layer-side surface of the magnetic recording medium 10 (hereinafter referred to as "magnetic surface") is preferably 2.5nm or less, and more preferably not more than 2.0 nm. When R _a is 2.5 nm or less, a more excellent SNR can be obtained.

The arithmetic average roughness _Ra is obtained as follows. First, the surface of the magnetic layer 13 is observed by AFM to obtain an AFM image of 40 μm×40 μm. As the AFM, Dimension3100 manufactured by Digital Instruments and its analysis software are used, as the cantilever, one made of silicon single crystal is used (Note 1), and the tapping frequency is tuned at 200-400 Hz. Next, the AFM image is divided into 512×512 (=262,144) measurement points, and the height Z(i) (i: measurement point number, i=1 to 262,144) is measured at each measurement point and measured. The average height (average surface) Z _ave (=(Z(1)+Z(2)+...+Z(262,144)) is calculated by simply averaging (arithmetic average) the heights Z(i) of the respective measured points. /262,144). Subsequently, the deviation Z″(i) (=|Z(i)−Z _ave |) from the average center line at each measurement point is calculated, and the arithmetic average roughness _Ra [nm](=(Z″(1 )+Z"(2)+...+Z"(262,144))/262,144) is calculated. At this time, as the image processing, data subjected to filtering processing by Flatten order 2 and planefit order 3 XY is used as data.
(Note 1) Nano World SPM probe NCH normal type PointProbe L (cantilever length) = 125 μm

(Coercive force Hc)
The coercive force Hc in the longitudinal direction of the magnetic recording medium 10 is preferably 2000 Oe or less, more preferably 1900 Oe or less, and even more preferably 1800 Oe or less. When the coercive force Hc in the longitudinal direction is 2000 Oe or less, the magnetization reacts with high sensitivity due to the perpendicular magnetic field from the recording head, so that a good recording pattern can be formed.

The coercive force Hc measured in the longitudinal direction of the magnetic recording medium 10 is preferably 1000 Oe or more. When the coercive force Hc in the longitudinal direction is 1000 Oe or more, demagnetization due to leakage magnetic flux from the recording head can be suppressed.

The above coercive force Hc is obtained as follows. First, three magnetic recording media 10 are overlaid with a double-sided tape and then punched with a φ6.39 mm punch to prepare a measurement sample. At this time, marking is performed with an arbitrary ink having no magnetism so that the longitudinal direction (traveling direction) of the magnetic recording medium 10 can be recognized. Then, an MH loop of the measurement sample (entire magnetic recording medium 10) corresponding to the longitudinal direction (traveling direction) of the magnetic recording medium 10 is measured using a vibrating sample magnetometer (VSM). Next, the coating film (the underlayer 12, the magnetic layer 13, the back layer 14 and the like) is wiped using acetone or ethanol or the like, and only the base layer 11 is left. Then, three obtained base layers 11 are overlapped with a double-sided tape, and then punched with a φ6.39 mm punch to prepare a sample for background correction (hereinafter, simply “correction sample”). After that, the MH loop of the correction sample (base layer 11) corresponding to the vertical direction of the base layer 11 (the vertical direction of the magnetic recording medium 10) is measured using VSM.
In the measurement of the MH loop of the measurement sample (entire magnetic recording medium 10) and the MH loop of the correction sample (base layer 11), a high-sensitivity vibration sample magnetometer "VSM-" manufactured by Toei Industry Co., Ltd. P7-15 type" is used. The measurement conditions are as follows: measurement mode: full loop, maximum magnetic field: 15 kOe, magnetic field step: 40 bit, Time constant of Locking amp: 0.3 sec, Waiting time: 1 sec, MH average number: 20.
After the MH loop of the measurement sample (entire magnetic recording medium 10) and the MH loop of the correction sample (base layer 11) are obtained, the MH loop of the measurement sample (entire magnetic recording medium 10) By subtracting the MH loop of the correction sample (base layer 11) from, background correction is performed, and the MH loop after background correction is obtained. A measurement/analysis program attached to "VSM-P7-15 type" is used for the calculation of the background correction.
The coercive force Hc is obtained from the obtained MH loop after background correction. A measurement/analysis program attached to the "VSM-P7-15 type" is used for this calculation. In addition, the measurement of the above-mentioned MH loop shall be performed at 25 degreeC. In addition, "diamagnetic field correction" when measuring the MH loop in the longitudinal direction of the magnetic recording medium 10 is not performed.

(4) Method of manufacturing magnetic recording medium

Next, a method of manufacturing the magnetic recording medium 10 having the above structure will be described. First, a non-magnetic powder, a binder and the like are kneaded and/or dispersed in a solvent to prepare a base layer forming coating material. Next, a magnetic layer-forming coating material is prepared by kneading and/or dispersing magnetic powder, a binder and the like in a solvent. Next, the binder and the non-magnetic powder are kneaded and/or dispersed in a solvent to prepare a back layer-forming coating material. For the preparation of the magnetic layer forming coating material, the underlayer forming coating material, and the back layer forming coating material, for example, the following solvent, dispersing device, and kneading device can be used.

Examples of the solvent used for preparing the above-mentioned paint 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, butyl acetate. , Ester solvents such as 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; In addition, halogenated hydrocarbon solvents such as methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, and chlorobenzene, etc. may be mentioned. One of these may be used, or a mixture of two or more may be used.

As the kneading device used for the above-mentioned paint preparation, for example, a continuous biaxial kneader, a continuous biaxial kneader capable of diluting in multiple stages, a kneader, a pressure kneader, a roll kneader, or the like can be used. However, it is not particularly limited to these devices. Examples of the dispersing device used for preparing the above-mentioned coating material include roll mills, ball mills, horizontal sand mills, vertical sand mills, spike mills, pin mills, tower mills, pearl mills (for example, "DCP mills" manufactured by Erich Co., Ltd.), homogenizers, and super-machines. A dispersing device such as a sonic disperser can be used, but the device is not particularly limited to these.

Next, the base layer 12 is formed by applying the base layer forming coating material on one main surface of the base layer 11 and drying it. 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. During the drying, the magnetic powder is magnetically oriented in the thickness direction of the base layer 11 by, for example, a solenoid coil. In addition, during drying, the magnetic powder may be magnetically oriented in the longitudinal direction (traveling direction) of the base layer 11 and then magnetically oriented in the thickness direction of the base layer 11 by, for example, a solenoid coil. By such a magnetic field orientation treatment, the degree of vertical orientation of magnetic powder (that is, the squareness ratio S1) can be improved. After the magnetic layer 13 is formed, the back layer 14 is formed by applying a back layer forming coating material to the other main surface of the base layer 11 and drying it. Thereby, the magnetic recording medium 10 is obtained.

The squareness ratios S1 and S2 are, for example, adjustment of the strength of the magnetic field applied to the coating film of the magnetic layer forming coating material, adjustment of the concentration of solids in the magnetic layer forming coating material, or coating film of the magnetic layer forming coating material. The desired value can be set by adjusting the drying conditions (for example, the drying temperature and the drying time). The strength of the magnetic field applied to the coating film is preferably 2 times or more and 3 times or less the coercive force of the magnetic powder. In order to further increase the squareness ratio S1 (that is, to further reduce the squareness ratio S2), it is preferable to improve the dispersion state of the magnetic powder in the magnetic layer-forming coating material. In order to further increase the squareness S1, it is effective to magnetize the magnetic powder before the magnetic layer-forming coating material enters the orienting device for orienting the magnetic powder in the magnetic field. The methods for adjusting the squareness ratios S1 and S2 described above may be used alone or in combination of two or more.

After that, the obtained magnetic recording medium 10 is subjected to calendar treatment to smooth the surface of the magnetic layer 13. Next, the calendered magnetic recording medium 10 is wound into a roll, and then the magnetic recording medium 10 is heat-treated in this state, so that a large number of the protrusions 14A on the surface of the back layer 14 are magnetized. Transfer to the surface of layer 13. As a result, pores (a large number of pores 13A) are formed on the surface of the magnetic layer 13.

The temperature of the heat treatment is preferably 55° C. or higher and 75° C. or lower. By adopting a temperature within this numerical range as the temperature of the heat treatment, the shape of the protrusion is satisfactorily transferred to the magnetic layer 13. If the temperature of the heat treatment is too low (for example, less than 55° C.), the shape of the protrusion may not be sufficiently transferred. If the temperature of the heat treatment is too high (for example, higher than 75° C.), the amount of pores may be too large, and the lubricant on the surface of the magnetic layer 13 may be excessive. Here, the temperature of the heat treatment is the temperature of the atmosphere holding the magnetic recording medium 10.

The heat treatment time is preferably 15 hours or more and 40 hours or less. By setting the time of the heat treatment within this numerical range, the shape of the protrusion is satisfactorily transferred to the magnetic layer 13. If the heat treatment time is too short (for example, less than 15 hours), the shape of the protrusion may not be sufficiently transferred. In order to suppress a decrease in productivity, it is desirable that the heat treatment time be 40 hours or less, for example.

Finally, the magnetic recording medium 10 is cut into a predetermined width (for example, 1/2 inch width). From the above, the target magnetic recording medium 10 is obtained. A servo pattern is recorded on the magnetic recording medium 10. Recording of the servo pattern may be performed by, for example, a servo writer known in the art.

In the above-described manufacturing method, the large number of protrusions 14A provided on the surface of the back layer 14 are transferred to the surface of the magnetic layer 13 to form pores on the surface of the magnetic layer 13. The forming method is not limited to this. For example, pores may be formed on the surface of the magnetic layer 13 by adjusting the type of solvent contained in the magnetic layer-forming coating material and/or adjusting the drying conditions of the magnetic layer-forming coating material. Further, for example, in the process of drying the solvent of the magnetic layer-forming coating material, pores may be formed due to uneven distribution of the solid matter and the solvent contained in the magnetic layer-forming coating material. Further, in the process of applying the magnetic layer-forming coating material, the solvent contained in the magnetic layer-forming coating material is absorbed into the underlying layer 12 through the pores of the underlying layer 12 formed when the lower layer is applied and dried. Can be done. By the solvent moving from the underlayer 12 through the magnetic layer 13 in the drying step after the coating, pores that connect the magnetic layer 13 and the underlayer 12 can be formed.

(5) Recording/reproducing device

[Structure of recording/reproducing apparatus]

Next, with reference to FIG. 8, an example of the configuration of the recording/reproducing apparatus 30 for recording and reproducing 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 in the longitudinal direction of the magnetic recording medium 10. Further, the recording/reproducing apparatus 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 apparatus 30 has a configuration in which one magnetic recording medium cartridge 10A can be loaded. However, the recording/reproducing apparatus 30 has a plurality of magnetic recording media. The medium cartridge 10A may be loaded.

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

As shown in FIG. 8, the recording/reproducing device 30 includes a spindle 31, a reel 32 on the recording/reproducing device side, a spindle driving device 33, a reel driving device 34, a plurality of guide rollers 35, a head unit 36, and a head unit 36. A communication interface (hereinafter, I/F) 37 and a control device 38 are provided.

The spindle 31 is configured so that the magnetic recording medium cartridge 10A can be mounted therein. The magnetic recording medium cartridge 10A complies with the LTO (Linear Tape Open) standard, and rotatably houses a single reel 10C in which the magnetic recording medium 10 is wound around a cartridge case 10B. On the magnetic recording medium 10, a V-shaped servo pattern is previously recorded as a servo signal. The reel 32 is configured such that the tip of the magnetic recording medium 10 pulled out from the magnetic recording medium cartridge 10A can be fixed.

The spindle drive 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 drive the magnetic recording medium 10 by rotating the spindle 31 and the reel 32. .. The guide roller 35 is a roller for guiding the traveling of the magnetic recording medium 10.

The head unit 36 includes a plurality of recording heads for recording a data signal on the magnetic recording medium 10, a plurality of reproducing heads for reproducing a data signal recorded on the magnetic recording medium 10, and a magnetic recording medium 10. And 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 an information processing device 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 the 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, the control device 38 reproduces the data signal recorded in 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, and supplies the data signal to the information processing device.

[Operation of recording/reproducing apparatus]

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

First, the magnetic recording medium cartridge 10A is attached to the recording/reproducing apparatus 30, the leading end of the magnetic recording medium 10 is pulled out, and the leading end of the magnetic recording medium 10 is 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 drive device 33 and the reel drive device 34 are driven by 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. As a result, while the magnetic recording medium 10 is wound on the reel 32, the head unit 36 records the information on the magnetic recording medium 10 or reproduces the information recorded on the magnetic recording medium 10.

When the magnetic recording medium 10 is rewound on the reel 10C, the magnetic recording medium 10 is run from the reel 32 to the reel 10C by rotationally driving the spindle 31 and the reel 32 in the opposite direction. .. Also during this rewinding, recording of information on the magnetic recording medium 10 or reproduction of information recorded on the magnetic recording medium 10 is performed by the head unit 36.

(6) Cartridge

[Cartridge configuration]

The present technology also provides a magnetic recording cartridge (also referred to as a tape 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 magnetic recording cartridge stores, for example, a communication unit that communicates with the recording/reproducing apparatus, a storage unit, and the information received from the recording/reproducing apparatus via the communication unit in the storage unit, and A control unit that reads information from the storage unit in response to a request and transmits the information to the recording/reproducing device via the communication unit may be provided. The information may include adjustment information for adjusting the tension applied in the longitudinal direction of the magnetic recording medium.

An example of the configuration of the cartridge 10A including the magnetic recording medium 10 having the above configuration will be described with reference to FIG.

FIG. 11 is an exploded perspective view showing an example of the configuration of the cartridge 10A. The cartridge 10A is a magnetic recording medium cartridge conforming to the LTO (Linear Tape-Open) standard, and a magnetic tape (tape-shaped magnetic recording medium) is provided inside a cartridge case 10B composed of a lower shell 212A and an upper shell 212B. ) The reel 10C on which 10 is wound, the reel lock 214 and the reel spring 215 for locking the rotation of the reel 10C, the spider 216 for releasing the locked state of the reel 10C, the lower shell 212A and the upper shell 212B. A slide door 217 that opens and closes a tape outlet 212C provided in the cartridge case 10B across the door, a door spring 218 that urges the slide door 217 to the closed position of the tape outlet 212C, and a write protect to prevent erroneous erasure. 219 and the cartridge memory 211. The reel 10C has a substantially disc shape having an opening at the center, and is composed of a reel hub 213A made of a hard material such as plastic and a flange 213B. A leader pin 220 is provided at one end of the magnetic tape 10.

The cartridge memory 211 is provided near one corner of the cartridge 10A. When the cartridge 10A is loaded in the recording/reproducing apparatus 30, the cartridge memory 211 faces the reader/writer (not shown) of the recording/reproducing apparatus 30. The cartridge memory 211 communicates with the recording/reproducing device 30, specifically, a reader/writer (not shown) according to a wireless communication standard that complies with the LTO standard.

[Cartridge memory configuration]

An example of the configuration of the cartridge memory 211 will be described with reference to FIG.

FIG. 12 is a block diagram showing an example of the configuration of the cartridge memory 211. The cartridge memory 211 uses an induced electromotive force to generate and rectify an antenna coil (communication unit) 331 that communicates with a reader/writer (not shown) according to a specified communication standard, and radio waves received by the antenna coil 331. A rectification/power supply circuit 332 that generates a power supply, a clock circuit 333 that similarly generates a clock from an electric wave received by the antenna coil 331 by using induced electromotive force, and detection of the electric wave received by the antenna coil 331 and the antenna coil 331. A controller (control unit) including a detection/modulation circuit 334 that modulates a signal to be transmitted, and a logic circuit or the like for determining a command and data from a digital signal extracted from the detection/modulation circuit 334 and processing the command and data. Unit) 335 and a memory (storage unit) 336 for storing information. Further, the cartridge memory 211 includes a capacitor 337 connected in parallel to the antenna coil 331, and the antenna coil 331 and the capacitor 337 form a resonance circuit.

The memory 336 stores information related to the cartridge 10A and the like. The memory 336 is a non-volatile memory (Non Volatile Memory: NVM). The storage capacity of the memory 336 is preferably about 32 KB or more. For example, when the cartridge 10A complies with the LTO format standard of the next generation or later, the memory 336 has a storage capacity of about 32 KB.

The memory 336 has a first storage area 336A and a second storage area 336B. The first storage area 336A corresponds to the storage area of the cartridge memory of the LTO standard before LTO8 (hereinafter referred to as "conventional cartridge memory"), and stores the information compliant with the LTO standard before LTO8. Area. The information based on the LTO standard prior to LTO8 is, for example, manufacturing information (for example, a unique number of the cartridge 10A), usage history (for example, a tape pull-out count (Thread Count), etc.).

The second storage area 336B corresponds to an extended storage area with respect to the storage area of the conventional cartridge memory. The second storage area 336B is an area for storing additional information. Here, the additional information means information related to the cartridge 10A, which is not defined by the LTO standard prior to LTO8. Examples of the additional information include tension adjustment information, management ledger data, Index information, thumbnail information of moving images stored on the magnetic tape 10, and the like, but are not limited to these data. The tension adjustment information includes a distance between adjacent servo bands (a distance between servo patterns recorded in adjacent servo bands) when recording data on the magnetic tape 10. The distance between adjacent servo bands is an example of width-related information related to the width of the magnetic tape 10. Details of the distance between the servo bands will be described later. In the following description, the information stored in the first storage area 336A may be referred to as "first information", and the information stored in the second storage area 336B may be referred to as "second information".

The memory 336 may have a plurality of banks. In this case, some of the plurality of banks may form the first storage area 336A, and the remaining banks may form the second storage area 336B. Specifically, for example, when the cartridge 10A complies with the LTO format standard of the next generation or later, the memory 336 has two banks having a storage capacity of about 16 KB and has one of the two banks. One bank may configure the first storage area 336A, and another bank may configure the second storage area 336B.

The antenna coil 331 induces an induced voltage by electromagnetic induction. The controller 335 communicates with the recording/reproducing device 30 via the antenna coil 331 according to a prescribed communication standard. Specifically, for example, mutual authentication, command transmission/reception, data exchange, etc. are performed.

The controller 335 stores the information received from the recording/reproducing device 30 via the antenna coil 331 in the memory 336. The controller 335 reads information from the memory 336 in response to a request from the recording/reproducing apparatus 30 and transmits the information to the recording/reproducing apparatus 30 via the antenna coil 331.

(7) Effect

A magnetic recording medium 10 according to the present technology includes a magnetic layer 13, an underlayer 12, a base layer 11, and a back layer 14, and has a surface layer on the magnetic layer side having a kurtosis of 3.0 or more and a surface layer on the back layer side. is a but 2.0 or higher, an arithmetic mean roughness R _a of the surface of the magnetic layer side is not more 2.5nm or less, the base layer 11 includes a polyester as a main component, the average thickness t _T of the magnetic recording medium 10 5.6 μm or less, the magnetic recording medium 10 contains a lubricant, the lubricant contains a fatty acid and a fatty acid ester, and the mass ratio of the fatty acid and the fatty acid ester extracted by hexane is fatty acid/fatty acid ester. ≦0.6, and the magnetic recording medium 10 has pores, and the average diameter of the pores is 6 nm or more when measured in a dry state after removing the lubricant from the magnetic recording medium. It is 11 nm or less. As a result, the magnetic recording medium 10 can suppress an increase in the dynamic friction coefficient of the magnetic layer side surface even when recording or reproducing is repeatedly performed, and can maintain good running stability. For example, the magnetic recording medium 10 has good running stability even when running at high speed (for example, 8 m/s or more). Furthermore, the magnetic recording medium 10 also has excellent electromagnetic conversion characteristics. It is considered that the suppression of the increase in the dynamic friction coefficient of the magnetic recording medium 10 is brought about by the combination of the specific lubricant, the specific pores, and the magnetic layer and the back layer having the specific kurtosis.

(8) Modification

[Modification 1]

As shown in FIG. 9, the magnetic recording medium 10 may further include a barrier layer 15 provided on at least one surface of the base layer 11. The barrier layer 15 is a layer for suppressing the dimensional change of the base layer 11 depending on the environment. For example, the hygroscopicity of the base layer 11 can be cited as an example of the cause of the dimensional change, and the barrier layer 15 can reduce the intrusion rate 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 selected from Al ₂ O ₃ , CuO, CoO, SiO ₂ , Cr ₂ O ₃ , TiO ₂ , Ta ₂ O ₅ , and ZrO ₂ can be used, and Any of the metal oxides can be used. Also, diamond-like carbon (DLC) or diamond 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.

3. Example

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

In the following Examples and Comparative Examples, the vertical squareness ratio S2, longitudinal squareness ratio S1, the average thickness t _m of the magnetic _layer, the average thickness of the underlying layer, the mass ratio of the fatty acids and fatty acid esters to be extracted by hexane, The average diameter of the pores, the friction coefficient ratio (μ _C(1000) /μ _C(5) ) and the SNR were measured as described in “2. Embodiment of the present technology (example of coating type magnetic recording medium)”. It is the value obtained by the method.

(1) Production of Magnetic Tape As described below, magnetic tapes of Examples 1 to 12 and Comparative Examples 1 to 6 were produced. The manufacturing conditions are shown in Table 1 below. Further, the following Table 2, these magnetic tapes vertical squareness ratio S2, longitudinal squareness ratio S1, the average thickness t _m, the average thickness of the underlayer of the magnetic layer, the type of magnetic powder, a fatty acid lubricant and fatty acid The mass ratio of the ester and the average diameter of the pores are shown.

[Example 1]

(Preparation process of paint for forming magnetic layer)
A magnetic layer-forming coating material 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, sand mill mixing was further performed and filter treatment was performed to prepare a magnetic layer-forming coating material.

(First composition)
Powder of barium ferrite (BaFe ₁₂ O ₁₉ ) particles (hexagonal plate shape, average aspect ratio 2.8, average particle volume 1950 nm ³ ): 100 parts by mass 42 parts by mass of vinyl chloride resin cyclohexanone solution (the composition of the solution is Resin content 30% by mass and cyclohexanone 70% by mass The details of the vinyl chloride resin were as follows: degree of polymerization 300, Mn=10000, OSO ₃ K=0.07 mmol/g as a polar group, secondary It contains OH=0.3 mmol/g.)
Aluminum oxide powder: 5 parts by mass (α-Al ₂ O ₃ , average particle size 0.1 μm)
Carbon black: 2 parts by mass (manufactured by Tokai Carbon Co., Ltd., product name: Seast TA)

(Second composition)
Cyclohexanone solution of vinyl chloride resin: 3 parts by mass (the composition of the solution is 30% by mass of resin and 70% by mass of cyclohexanone.)
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 In addition, the above n-butyl stearate was added as a lubricant.

Finally, in the magnetic layer-forming coating material prepared as described above, 4 parts by mass of polyisocyanate (trade name: Coronate L, manufactured by Tosoh Corporation) as a curing agent, and 2 parts by mass of stearic acid as a lubricant. Was added.

(Preparation process of base layer paint)
A base layer-forming coating material was prepared as follows. First, the 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, sand mill mixing was further performed and filter treatment was performed to prepare a coating material for forming an underlayer.

(Third composition)
Needle-shaped iron oxide powder: 100 parts by mass (α-Fe ₂ O ₃ , average major axis length 0.15 μm)
Cyclohexanone solution of vinyl chloride resin: 44.4 parts by mass (the composition of the solution is 30% by mass of resin content and 70% by mass of cyclohexanone).
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 In addition, the above n- Butyl stearate was added as a lubricant.

Finally, in the underlayer-forming coating material prepared as described above, 4 parts by mass of polyisocyanate (trade name: Coronate L, manufactured by Tosoh Corporation) as a curing agent and 2 parts by mass of stearic acid as a lubricant are added. Was added.

(Preparation process of back layer paint)
The back layer forming coating material was prepared as follows. The following raw materials were mixed in a stirring tank equipped with a disper and filtered to prepare a back layer-forming coating material. Small particle size carbon black powder (average particle size (D50) 20 nm): 90 parts by mass Large particle size carbon black powder (average particle size (D50) 270 nm): 10 parts by mass Polyester polyurethane: 100 parts by mass (Tosoh Corporation (Product name: N-2304, manufactured by corporation)
Methyl ethyl ketone: 500 parts by mass Toluene: 400 parts by mass Cyclohexanone: 100 parts by mass

(Coating process)
Using the magnetic layer-forming coating material and the underlayer-forming coating material prepared as described above, a long polyethylene naphthalate film (hereinafter referred to as "PEN film"), which is a non-magnetic support and has an average thickness of 4.12 μm. ) On one main surface, a base layer is formed as follows so that the average thickness after drying and calendering is 0.8 μm, and the magnetic layer is formed so that the average thickness after drying and calendering is 80 nm. The layers were formed as follows. First, a base layer-forming coating material was applied onto one main surface of a PEN film and dried to form a base layer. Next, a magnetic layer-forming coating material was applied onto the underlayer and dried to form a magnetic layer. When the paint for forming the magnetic layer was dried, the magnetic powder was magnetically oriented in the thickness direction of the film by a solenoid coil. Further, the drying conditions (drying temperature and drying time) of the magnetic layer-forming coating material were adjusted, and the squareness ratio S2 in the thickness direction (vertical direction) and the squareness ratio S1 in the longitudinal direction of the magnetic tape were set to the values shown in Table 2. .. Subsequently, a back layer-forming coating material was applied onto the other main surface of the PEN film and dried to form a back layer having an average thickness of 0.4 μm. Thereby, a magnetic tape was obtained.

(Calendar process, transfer process)
Then, calendering was performed to smooth the surface of the magnetic layer. Next, the obtained magnetic tape was wound into a roll, and in this state, the magnetic tape was subjected to heat treatment at 60° C. for 10 hours. Then, the magnetic tape was rewound in a roll shape so that the end portion located on the inner peripheral side was located opposite to the outer peripheral side, and then the magnetic tape was heated again at 60° C. for 10 hours in this state. went. As a result, many protrusions on the surface of the back layer were transferred to the surface of the magnetic layer, and many holes were formed on the surface of the magnetic layer.

(Cutting process)
The magnetic tape obtained as described above was cut into ½ inch (12.65 mm) widths. As a result, the intended long magnetic tape (average thickness 5.4 μm) was obtained.

[Example 2]
By adjusting the drying conditions (drying temperature and drying time) of the magnetic layer-forming coating material, the squareness ratio S2 in the thickness direction (vertical direction) of the magnetic tape is set to 66%, and the squareness ratio S1 in the longitudinal direction is set to 30%. A magnetic tape was manufactured by the same method as in Example 1 except that the setting was made.

[Example 3]
By adjusting the drying conditions (drying temperature and drying time) of the magnetic layer-forming coating material, the squareness ratio S2 in the thickness direction (vertical direction) of the magnetic tape is set to 71%, and the squareness ratio S1 in the longitudinal direction is set to 29%. A magnetic tape was manufactured in the same manner as in Example 1 except that the setting was made.

[Example 4]
By adjusting the drying conditions (drying temperature and drying time) of the magnetic layer-forming coating material, the squareness ratio S2 in the thickness direction (vertical direction) of the magnetic tape is set to 70%, and the squareness ratio S1 in the longitudinal direction is set to 25%. A magnetic tape was manufactured in the same manner as in Example 1 except that the setting was made.

[Example 5]
A magnetic tape was produced in the same manner as in Example 2 except that the heating temperature in the heat treatment after the calendar treatment was increased to change the average diameter of the pores to 6 nm.

[Example 6]
A magnetic tape was manufactured in the same manner as in Example 2 except that the average thickness of the underlayer was changed to 0.6 μm and the heating temperature in the transfer step was increased. The average thickness t _T of the magnetic tape was 5.2 μm.

[Example 7]
A magnetic tape was manufactured in the same manner as in Example 2 except that the magnetic powder contained in the magnetic layer was changed from barium ferrite particle powder to strontium ferrite particle powder.

[Example 8]
A magnetic tape was manufactured in the same manner as in Example 2 except that the magnetic powder contained in the magnetic layer was changed from barium ferrite particle powder to ε iron oxide nanoparticle powder.

[Example 9]
A magnetic tape was manufactured in the same manner as in Example 1 except that the magnetic powder contained in the magnetic layer was changed from barium ferrite particle powder to cobalt iron oxide nanoparticle powder. The average thickness t _T of the magnetic tape was 5.2 μm.

[Example 10]
The average thickness of the underlayer was changed to 1 μm, and the content of the small particle size carbon black powder (average particle size (D50) 20 nm) contained in the back layer coating material was set to 80 parts by mass, and the large particle size carbon was A magnetic tape was obtained in the same manner as in Example 2 except that the content of the black powder (average particle size (D50) 270 nm) was 20 parts by mass. By changing the average thickness of the underlayer as described above, the pore volume of the magnetic tape was 0.023 cm ³ /g. The average thickness t _T of the magnetic tape was 5.6 μm.

[Example 11]
A magnetic tape was obtained by the same method as in Example 6 except that the pressure in the heat treatment after the calendar treatment was lowered and the average diameter of the pores of the magnetic layer was changed to 10 nm. The average thickness t _T of the magnetic tape was 5.2 μm.

[Example 12]
The pressure in the heat treatment after the calendering treatment was reduced, and the content of the small particle diameter carbon black powder (average particle diameter (D50) 20 nm) contained in the back layer-forming coating material was set to 80 parts by mass to obtain the large particle diameter carbon. A magnetic tape was obtained in the same manner as in Example 2 except that the content of black powder (average particle diameter (D50) 270 nm) was 20 parts by mass.

[Comparative Example 1]
The content of the small particle diameter carbon black powder (average particle diameter (D50) 50 nm) contained in the back layer forming coating is 70 parts by mass, and the large particle diameter carbon black powder (average particle diameter (D50) 270 nm) ) Content is 30 parts by mass, the heating temperature in the transfer step is increased, the drying time of the magnetic layer-forming coating material is increased, the pressure in the heat treatment after calendering is decreased, and the squareness ratio S1 in the longitudinal direction is set to 31. %, and a magnetic tape was obtained by the same method as in Example 2 except that the average diameter of the pores was changed to 12 nm.

[Comparative example 2]
The content of the small particle diameter carbon black powder (average particle diameter (D50) 20 nm) contained in the back layer forming coating material is 100 parts by mass, the drying temperature of the magnetic layer forming coating material is lowered, and after the calender treatment, A magnetic tape was obtained in the same manner as in Example 2 except that the heating time in the heat treatment was lengthened so that the squareness ratio S1 in the longitudinal direction was 31% and the average diameter of the pores was changed to 5 nm. By changing the composition of the back layer-forming coating material and the conditions in the calendering treatment as described above, the pore volume of the magnetic tape was 0.015 cm ³ /g.

[Comparative Example 3]
A magnetic tape was obtained by the same method as in Example 1 except that the drying temperature of the magnetic layer-forming coating material was set lower than that of Comparative Example 2 and the drying time was lengthened.

[Comparative Example 4]
A magnetic tape was manufactured in the same manner as in Example 1 except that the heating temperature in the transfer step was lowered, the drying time of the coating material for forming the magnetic layer was lengthened, and the heating temperature in the heat treatment after the calender treatment was made higher than that in Comparative Example 2. Got

[Comparative Example 5]
A magnetic tape was obtained in the same manner as in Comparative Example 3 except that the heating temperature in the heat treatment after the calendering was made higher than that in Comparative Example 2 and the pressure in the heat treatment was made higher.

[Comparative Example 6]
A magnetic tape was obtained in the same manner as in Example 1 except that the content of fatty acid ester in the lubricant was reduced.

(2) Evaluation The friction coefficient ratio (μ _C(1000) /μ _C(5) ) of the magnetic tapes of Examples 1 to 12 and Comparative Examples 1 to 6 produced in (1) above was measured. The friction coefficient ratio (μ _C(1000) /μ _C(5) ) was measured by the measuring method described in “2. Embodiment of the present technology (example of coating type magnetic recording medium)”. The measurement results are shown in Table 2 below.

Further, the SNRs of the magnetic tapes of Examples 1-12 and Comparative Examples 1-6 were evaluated. The evaluation results are shown in Table 2 below. The evaluation method of SNR was as follows.
First, the SNR (electromagnetic conversion characteristics) of a magnetic tape in a 25°C environment is measured using a 1/2 inch tape running device (Mounting Engineering II, MTS Transport) equipped with a recording/reproducing head and a recording/reproducing amplifier. did. A ring head having a gap length of 0.2 μm was used as a recording head, and a GMR head having a shield distance of 0.1 μm was used as a reproducing head. The relative speed was 6 m/s, the recording clock frequency was 160 MHz, and the recording track width was 2.0 μm. The SNR was calculated based on the method described in the following document. With respect to the SNR, a relative evaluation was made based on the value of Example 1 as to whether the SNR was higher or lower than that.
Y. Okazaki: “An Error Rate Emulation System.”, IEEE Trans. Man., 31, pp.3093-3095 (1995)

The results shown in Table 2 show the following.

It can be seen that the magnetic tapes of Examples 1 to 12 have a low friction coefficient ratio and can suppress an increase in the dynamic friction coefficient due to repeated recording or reproduction. Further, it can be seen that these magnetic tapes have good SNR and excellent recording/reproducing characteristics.

Further, by comparing the results of Examples 2, 5 and 11 with the results of Comparative Examples 1 and 2, it can be seen that the increase in the dynamic friction coefficient can be suppressed because the average diameter of the pores is 6 nm or more and 11 nm or less.

When the results of Examples 1 to 12 are compared with the results of Comparative Examples 3 to 5, the surface side of the magnetic layer has a kurtosis of 3.0 or more, and the back side of the surface has a kurtosis of 2.0 or more. Therefore, it can be seen that the increase of the dynamic friction coefficient can be suppressed.

Further, comparing the results of Examples 1 to 12 with the results of Comparative Example 6, the mass ratio of the fatty acid and the fatty acid ester extracted by hexane is fatty acid/fatty acid ester≦0.6, and thus the increase of the dynamic friction coefficient is increased. You can see that it can be suppressed.

Further, the magnetic tapes of Examples 8 and 9 have the same friction coefficient ratio and recording/reproducing characteristics as those of Example 1, although the types of magnetic powder are different from those of Example 1. Therefore, it is understood that the effect of the present technology can be achieved even if the type of magnetic powder is changed.

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

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

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

Note that the present technology may also have the following configurations.
[1]
Including a magnetic layer, an underlayer, a base layer, and a back layer,
The surface side of the magnetic layer has a kurtosis of 3.0 or more,
The back layer side surface has a kurtosis of 2.0 or more,
Arithmetic mean roughness _{R a} of the magnetic layer side of the surface is at 2.5nm or less,
The base layer contains polyester as a main component,
The average thickness t _T of the magnetic recording medium is 5.6 μm or less,
The magnetic recording medium contains a lubricant, the lubricant contains a fatty acid and a fatty acid ester, the mass ratio of the fatty acid and the fatty acid ester extracted by hexane is fatty acid / fatty acid ester ≤ 0.6, and,
The magnetic recording medium has pores, and the average diameter of the pores is 6 nm or more and 11 nm or less when measured in a dry state after removing the lubricant from the magnetic recording medium.
Tape-shaped magnetic recording medium.
[2]
The magnetic recording medium according to [1], which has a squareness ratio of 65% or more in the vertical direction.
[3]
The average thickness t _m of the magnetic layer is 80nm or less, the magnetic recording medium according to [1] or [2].
[4]
The magnetic recording medium according to any one of [1] to [3], wherein the magnetic layer contains magnetic powder, and the magnetic powder contains hexagonal ferrite, ε iron oxide, or Co-containing spinel ferrite.
[5]
The magnetic recording medium according to [4], wherein the hexagonal ferrite contains at least one of Ba and Sr, and the ε iron oxide contains at least one of Al and Ga.
[6]
The dynamic friction coefficient μ _{C (5) at} the fifth reciprocation when the magnetic recording medium in a state of being applied with a tension of 0.6 N in the longitudinal direction was slid on the magnetic head for 5 reciprocations, and 1000 friction coefficient ratio of the dynamic friction coefficient _{mu C (1000)} at 1000 reciprocal second when was reciprocated _{(μ C (1000) / μ} C (5)) is 1.0 to 1.8, [1] to The magnetic recording medium according to any one of [5].
[7]
[1] to [6], wherein the fatty acid contains a compound represented by the following general formula (1) or (2), and the fatty acid ester contains a compound represented by the following general formula (3) or (4) 2. The magnetic recording medium according to any one of 1.
CH ₃ (CH ₂ ) _k COOH (1)
(However, in the general formula (1), k is an integer selected from the range of 14 or more and 22 or less.)
_{CH 3 (CH 2) n CH} = CH (CH 2) m COOH ··· (2)
(However, in the general formula (2), the sum of n and m is an integer selected from the range of 12 or more and 20 or less.)
_{CH 3 (CH 2) p COO} (CH 2) q CH 3 ··· (3)
(However, in the general formula (3), p is an integer selected from the range of 14 to 22 and q is an integer selected from the range of 2 to 5).
_{CH 3 (CH 2) r COO-} (CH 2) s CH (CH 3) 2 ··· (4)
(However, in the general formula (4), r is an integer selected from the range of 14 to 22 and s is an integer selected from the range of 1 to 3).
[8]
The magnetic recording medium according to any one of [1] to [7], which has a coercive force H _c in the longitudinal direction of 2000 Oe or less.
[9]
The magnetic recording medium according to any one of [1] to [8], wherein the magnetic layer has 5 or more servo bands.
[10]
The magnetic recording medium according to [9], wherein the ratio of the total area of the servo band to the area of the magnetic layer side surface of the magnetic recording medium is 4.0% or less.
[11]
The magnetic recording medium according to [9] or [10], wherein the width of the servo band is 95 μm or less.
[12]
The magnetic recording medium according to any one of [1] to [11], wherein the magnetic layer is configured to be able to form a plurality of data tracks, and the width of the data tracks is 2.0 μm or less.
[13]
The magnetic recording medium according to any one of [1] to [12], wherein the magnetic layer is capable of recording data such that the minimum value of the magnetization reversal distance L is 48 nm or less.
[14]
The magnetic recording medium according to any one of [1] to [13], wherein the base layer has an average thickness of 4.2 μm or less.
[15]
The magnetic recording medium according to any one of [1] to [14], wherein the magnetic layer contains magnetic powder, and the average aspect ratio of the magnetic powder is 1.0 or more and 3.5 or less.
[16]
The magnetic recording medium according to any one of [1] to [15], wherein the magnetic layer contains magnetic powder, and the average particle size of the magnetic powder is 50 nm or less.
[17]
The magnetic recording medium according to any one of [1] to [16], wherein the average diameter of the pores is 6 nm or more and 10 nm or less.
[18]
The magnetic recording medium according to any one of [1] to [17], wherein the average diameter of the pores is 7 nm or more and 9 nm or less.
[19]
The magnetic recording medium according to any one of [1] to [18], wherein the surface on the magnetic layer side has a kurtosis of 3.5 or more.
[20]
The magnetic recording medium according to any one of [1] to [19], wherein the back layer side surface has a kurtosis of 2.3 or more.
[21]
A tape-shaped magnetic recording medium according to any one of [1] to [20],
A communication unit that communicates with the recording/reproducing device,
Storage part,
A control unit that stores information received from the recording/reproducing device via the communication unit in the storage unit, reads the information from the storage unit according to a request from the recording/reproducing device, and transmits the information to the recording/reproducing device via the communication unit. And,
The tape cartridge contains the adjustment information for adjusting the tension applied in the longitudinal direction of the magnetic recording medium.

10 magnetic recording medium 11 base layer 12 underlayer 13 magnetic layer 14 back layer

Claims (35)

A tape-shaped magnetic recording medium,
Including a magnetic layer, an underlayer, a base layer, and a back layer,
The Kurtosis on the magnetic layer side surface of the magnetic recording medium is 3.0 or more,
The back layer side surface of the magnetic recording medium has a kurtosis of 2.0 or more;
Arithmetic mean roughness R _a of the magnetic layer side of the surface of the magnetic recording medium is not more 2.5nm or less,
The base layer contains polyester as a main component,
The average thickness _{t T} of the magnetic recording medium is not more than 5.3 .mu.m,
The magnetic recording medium contains a lubricant, the lubricant contains a fatty acid and a fatty acid ester, the mass ratio of the fatty acid and the fatty acid ester extracted by hexane is fatty acid / fatty acid ester ≤ 0.6, and,
The magnetic recording medium has pores, and the average diameter of the pores is 6 nm or more and 11 nm or less when measured in a dry state after removing the lubricant from the magnetic recording medium.
The magnetic recording medium. The magnetic recording medium according to claim 1, wherein the squareness ratio in the vertical direction of the magnetic recording medium is 65% or more. The average thickness t _m of the magnetic layer is 80nm or less, the magnetic recording medium according to claim 1 or 2. The magnetic layer comprises a magnetic powder, the magnetic powder of hexagonal ferrite, containing ε iron oxide, or Co-containing spinel ferrite, magnetic recording medium according to any one of claims 1-3. The magnetic recording medium according to claim 4, wherein the hexagonal ferrite contains at least one of Ba and Sr, and the ε iron oxide contains at least one of Al and Ga. The dynamic friction coefficient μ _{C (5) at} the fifth reciprocation when the magnetic recording medium in a state where a tension of 0.6 N is applied in the longitudinal direction is slid on the magnetic head for 5 reciprocations and The friction coefficient ratio (μC ₍₁₀₀₀₎ /μC ₍₅₎ ) to the dynamic friction coefficient μC _{(1000) at} the 1000th reciprocation after 1000 reciprocations is 1.0 or more and 1.8 or less. 6. The magnetic recording medium according to any one of items 5 to 5 . Any of claims 1 to 6 , wherein the fatty acid contains a compound represented by the following general formula (1) or (2), and the fatty acid ester contains a compound represented by the following general formula (3) or (4). The magnetic recording medium as described in 1 above.
CH ₃ (CH ₂ ) _k COOH...(1)
(However, in the general formula (1), k is an integer selected from the range of 14 or more and 22 or less.)
_{CH 3 (CH 2) n CH} = CH (CH 2) m COOH ··· (2)
(However, in the general formula (2), the sum of n and m is an integer selected from the range of 12 or more and 20 or less.)
_{CH 3 (CH 2) p COO} (CH 2) q CH 3 ··· (3)
(However, in the general formula (3), p is an integer selected from the range of 14 to 22 and q is an integer selected from the range of 2 to 5).
_{CH 3 (CH 2) r COO-} (CH 2) s CH (CH 3) 2 ··· (4)
(However, in the general formula (4), r is an integer selected from the range of 14 to 22 and s is an integer selected from the range of 1 to 3). The magnetic coercive force Hc in the longitudinal direction of the recording medium is not more than 2000 Oe, a magnetic recording medium according to any one of claims 1-7. The magnetic recording medium according to claim 1, wherein the magnetic layer has 5 or more servo bands. The magnetic recording medium according to claim 9, wherein the ratio of the total area of the servo band to the area of the magnetic layer side surface of the magnetic recording medium is 4.0% or less. The width of the servo bands is less than 95 .mu.m, a magnetic recording medium according to claim 9 or 10. The magnetic layer is formed can configure the plurality of data tracks, the width of the data track is 2.0μm or less, the magnetic recording medium according to any one of claims 1 to 11. The magnetic recording medium according to any one of claims 1 to 12, wherein the magnetic layer is configured to be able to record data such that the minimum value of the magnetization reversal distance L is 48 nm or less. The average thickness of the base layer is less than 4.2 .mu.m, the magnetic recording medium according to any one of claims 1 to 13. The magnetic layer comprises a magnetic powder, an average aspect ratio of the magnetic powder is 1.0 to 3.5, the magnetic recording medium according to any one of claims 1 to 14. The magnetic recording medium according to claim 1, wherein the magnetic layer contains magnetic powder, and the average particle size of the magnetic powder is 50 nm or less. The average diameter of the pores is 6nm or more 10nm or less, the magnetic recording medium according to any one of claims 1 to 16. The average diameter is 7nm more 9nm or less pores, the magnetic recording medium according to any one of claims 1 to 17. The magnetic recording medium according to claim 1, wherein the surface on the magnetic layer side has a kurtosis of 3.5 or more. The magnetic recording medium according to any one of claims 1 to 19, wherein the back layer side surface has a kurtosis of 2.3 or more. The magnetic recording medium according to claim 1, wherein the average diameter of the pores is 6.5 nm or more and 10 nm or less. Average thickness t of the magnetic recording medium _T The magnetic recording medium according to any one of claims 1 to 21, having a thickness of 5.2 µm or less. Average thickness t of the magnetic recording medium _T Is 5.0 μm or less, the magnetic recording medium according to any one of claims 1 to 22. Average thickness t of the magnetic recording medium _T The magnetic recording medium according to any one of claims 1 to 23, having a value of 4.6 µm or less. The magnetic recording medium according to any one of claims 1 to 24, wherein the magnetic layer contains magnetic powder, and the average particle size of the magnetic powder is 30 nm or less. The magnetic recording medium according to claim 1, wherein the magnetic layer contains magnetic powder, and the average particle size of the magnetic powder is 25 nm or less. 27. The magnetic recording medium according to claim 1, wherein the magnetic layer contains magnetic powder, and the average particle size of the magnetic powder is 20 nm or less. The magnetic recording medium according to any one of claims 1 to 27, wherein the magnetic layer contains magnetic powder, and the average aspect ratio of the magnetic powder is 1.0 or more and 3.1 or less. 29. The magnetic recording medium according to claim 1, wherein the magnetic layer contains magnetic powder, and the average aspect ratio of the magnetic powder is 1.0 or more and 2.8 or less. The magnetic recording medium according to claim 1, wherein the magnetic layer contains magnetic powder, and the average aspect ratio of the magnetic powder is 1.1 or more and 2.5 or less. The magnetic layer contains magnetic powder, and the average particle volume of the magnetic powder is 5900 nm. ^Three The magnetic recording medium according to any one of claims 1 to 30, which is as follows. The magnetic layer contains magnetic powder, and the average particle volume of the magnetic powder is 500 nm. ^Three Above 3400 nm ^Three The following is the magnetic recording medium according to any one of claims 1 to 31. The magnetic layer contains magnetic powder, and the average particle volume of the magnetic powder is 1000 nm. ^Three 2500 nm or more ^Three The magnetic recording medium according to claim 1, wherein the magnetic recording medium is: The pore volume of the magnetic recording medium is 0.016 cm ^Three The magnetic recording medium according to any one of claims 1 to 33, wherein the magnetic recording medium has a magnetic recording medium of not less than /g. The pore volume of the magnetic recording medium is 0.02 cm. ^Three The magnetic recording medium according to any one of claims 1 to 34, wherein the magnetic recording medium has a magnetic recording medium density of at least 1/g.