JP2017059290A - Magnetic recording medium and magnetic recording/reproducing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic recording medium less likely to be contaminated by an environmental material even if the thickness of lubricant layer is thin, and a magnetic recording/producing apparatus comprising the magnetic recording medium.SOLUTION: There is provided a magnetic recording medium in which an outermost surface of a protective layer 3 on a lubricant layer 4 side contains carbon and nitrogen in the range of 50 atom% to 90 atom%, and the lubricant layer 4 is formed in contact with the outermost surface, contains compounds A-C in the following formulae (1)-(3), and has a film thickness of 0.5-2 nm. R1-CHOCHCH(OH)CHOCH-R2-CHOCHCH(OH)CHOH.. (1), CH(OH)CH(OH)CHOCHCFCF(OCFCFCF)OCFCFCHOCHCH(OH)CHOH.. (2), and HOCHCFCFO(CFCFCFO)sCFCFCHOCHCH(OH)CHOH.. (3).SELECTED DRAWING: Figure 1

Description

  The present invention relates to a magnetic recording medium suitably used for a magnetic recording / reproducing apparatus such as a hard disk drive, and a magnetic recording / reproducing apparatus including the same.

  In order to improve the recording density of a magnetic recording / reproducing apparatus, development of a magnetic recording medium suitable for a high recording density is underway.

  Conventionally, there is a magnetic recording medium in which a recording layer for recording information on a substrate, a protective layer made of carbon or the like, and a lubricant layer are formed in this order. The protective layer protects information recorded on the recording layer and improves the slidability of the magnetic head. However, the durability of the magnetic recording medium cannot be sufficiently obtained only by providing the protective layer on the recording layer.

  Therefore, generally, a lubricant layer is formed by applying a lubricant to the surface of the protective layer. By providing a lubricant layer on the protective layer, it is possible to prevent the magnetic head of the magnetic recording / reproducing apparatus from coming into direct contact with the protective layer and to reduce the frictional force of the magnetic head sliding on the magnetic recording medium. And durability is improved.

As lubricants used for magnetic recording media, perfluoropolyether lubricants, aliphatic hydrocarbon lubricants, and the like have been proposed.
For example, Patent Document _{1, HOCH 2 -CF 2 O- (} C 2 F 4 O) p- (CF 2 O) q-CH 2 OH (p, q are integers.) Perfluoroalkyl poly having a structure of A magnetic recording medium coated with an ether (diol) lubricant is disclosed.

Patent Document _{2, HOCH 2 CH (OH)} -CH 2 OCH 2 CF 2 O- (C 2 F 4 O) p- (CF 2 O) q-CF 2 CH 2 OCH 2 -CH (OH) CH 2 A magnetic recording medium coated with a lubricant made of perfluoroalkyl polyether (tetraol) having a structure of OH (p and q are integers) is disclosed.
Patent Document 3 discloses a lubricant for magnetic recording media having a perfluorooxyalkylene unit selected from —CF ₂ O— or —CF ₂ CF ₂ O— and a phosphazene compound.

Patent Document 4 describes a magnetic recording medium having a lubricant layer in which a phosphazene compound and a compound having a perfluorooxyalkylene unit are mixed in a specific range. Patent Document 4 describes that this lubricant layer has high bonding strength with the protective layer, and a high coverage can be obtained even when the thickness of the protective layer is lowered.
Patent Document 5 discloses a lubricant containing a compound represented by R ¹ —C ₆ H ₄ O—CH ₂ CH (OH) CH ₂ OCH ₂ —R ² —CH ₂ —O—R ³ . .

  Further, as one of ionic contaminants on the magnetic recording medium, there is outgas from siloxane organic Si used as a rubber seal for sealing a magnetic recording / reproducing apparatus. It is known that outgas from siloxane-based organic Si causes damage or contamination of the magnetic head of the magnetic recording / reproducing apparatus (see, for example, Patent Document 6).

JP 62-66417 A JP-A-9-282642 JP 2002-275484 A JP 2010-108583 A JP 2013-163667 A JP 2014-1116060 A

Magnetic recording media are required to improve the recording density by reducing the flying height of the magnetic head. For this reason, it is required to further reduce the thickness of the lubricant layer.
However, when the thickness of the lubricant layer is reduced, a gap is formed in the lubricant layer, and environmental substances enter from the gap of the lubricant layer to generate contaminants, thereby contaminating the magnetic recording medium. When the magnetic recording medium is contaminated, contaminants on the magnetic recording medium are attached (transferred) to the magnetic head.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a magnetic recording medium that is not easily contaminated by environmental substances even when the lubricant layer is thin, and a magnetic recording / reproducing apparatus including the magnetic recording medium. To do.

In order to solve the above-mentioned problems, the present inventor has intensively studied paying attention to the relationship between the surface of the protective layer disposed in contact with the lubricant layer and the material of the lubricant layer.
As a result, the inventors have found that the contamination of the magnetic recording medium due to the entry of environmental substances from the gaps between the lubricant layers can be prevented by using the protective layer and the lubricant layer as shown below. That is, a protective layer having a lubricant layer on the outermost surface containing carbon and nitrogen in the range of 50 atomic% to 90 atomic% is used. The lubricant layer is formed in contact with the outermost surface of the protective layer, and is made of a compound having a specific composition that can obtain a high bonding force with the nitrogen-containing layer without becoming an island shape or a network shape. .
The present invention has been made based on the above findings, and the gist thereof is as follows.

[1] A magnetic recording medium having at least a magnetic layer, a protective layer, and a lubricant layer in this order on a nonmagnetic substrate,
The protective layer includes carbon on the outermost surface on the lubricant layer side and nitrogen in a range of 50 atomic% to 90 atomic%,
The lubricant layer is formed in contact with the outermost surface, has an average film thickness in a range of 0.5 nm to 2 nm, and is represented by the following general formula (1) and the following general formula (2). The ratio of the mass of the compound A (A /) to the sum of the masses of the compounds A, B and C contained in the lubricant layer, including the compound B and the compound C represented by the following general formula (3) (A + B + C)) is in the range of 0.05 to 0.6, the mass ratio (B / (A + B + C)) of the compound B is in the range of 0.05 to 0.5, and A magnetic recording medium having a mass ratio (C / (A + B + C)) in the range of 0.05 to 0.9.

_{R1-C 6 H 4 OCH 2} CH (OH) CH 2 OCH 2 -R2-CH 2 OCH 2 CH (OH) CH 2 OH ‥‥ (1)
(In General Formula (1), R1 is an alkoxy group having 1 to 4 carbon atoms. R2 is —CF ₂ O (CF ₂ CF ₂ O) x (CF ₂ O) yCF ₂ — (x, y The parentheses may be connected in this order, reversely or randomly (x and y are each an integer of 0 to 15).)

CH ₂ (OH) CH (OH) CH ₂ OCH ₂ CF ₂ CF ₂ (OCF ₂ CF ₂ CF ₂ ) _m OCF ₂ CF ₂ CH ₂ OCH ₂ CH (OH) CH ₂ OH (2)
(In general formula (2), m is an integer in the range of 4-50.)

_{HOCH 2 CF 2 CF 2 O (} CF 2 CF 2 CF 2 O) sCF 2 CF 2 CH 2 OCH 2 CH (OH) CH 2 OH ‥‥ (3)
(In general formula (3), s is an integer.)

[2] The magnetic recording medium according to [1], wherein the compound A has an average molecular weight in the range of 1000 to 2500.
[3] The magnetic recording medium according to [1] or [2], wherein the compound B has an average molecular weight in the range of 1000 to 2500.
[4] The magnetic recording medium according to any one of [1] to [3], wherein the average molecular weight of the compound C is in the range of 1000 to 2000.

[5] The magnetic recording medium according to any one of [1] to [4], a medium driving unit that drives the magnetic recording medium in a recording direction, and a magnetic head that records and reproduces information on the magnetic recording medium A magnetic recording / reproducing apparatus comprising: a head moving unit that moves the magnetic head relative to the magnetic recording medium; and a recording / reproducing signal processing unit that processes a recording / reproducing signal from the magnetic head. apparatus.

  The magnetic recording medium of the present invention is formed such that the outermost surface on the lubricant layer side is in contact with the outermost surface of carbon and a protective layer containing carbon and nitrogen in the range of 50 atomic% to 90 atomic%. And a lubricant layer containing the compound B and the compound C in a predetermined ratio. Therefore, in the magnetic recording medium of the present invention, the lubricant layer does not have an island shape or a mesh shape, and the lubricant layer and the protective layer are bonded with a strong bonding force. Therefore, even if the average film thickness of the lubricant layer is reduced within the range of 0.5 nm to 2 nm, contamination of the magnetic recording medium due to the intrusion of environmental substances from the gaps in the lubricant layer can be prevented. Therefore, the magnetic recording medium of the present invention can cope with further improvement in recording density by sufficiently reducing the thickness of the lubricant layer.

  The magnetic recording / reproducing apparatus of the present invention includes the magnetic recording medium of the present invention that is not easily contaminated. For this reason, in the magnetic recording / reproducing apparatus of the present invention, contaminants present on the magnetic recording medium are transferred to the magnetic head of the magnetic recording / reproducing apparatus, and the recording / reproducing characteristics are deteriorated or the flying stability is impaired. Can be prevented. Therefore, the magnetic recording / reproducing apparatus of the present invention has stable magnetic recording / reproducing characteristics.

It is a cross-sectional schematic diagram which shows an example of the magnetic recording medium of this invention. It is a perspective view which shows an example of the magnetic recording / reproducing apparatus of this invention.

Hereinafter, embodiments of the present invention will be described in detail.
FIG. 1 is a schematic cross-sectional view showing an example of a magnetic recording medium according to an embodiment of the present invention.
As shown in FIG. 1, a magnetic recording medium 11 according to an embodiment of the present invention is obtained by laminating a magnetic layer 2, a protective layer 3, and a lubricant layer 4 in this order on a nonmagnetic substrate 1. .

  In the present embodiment, an example in which an adhesion layer, a soft magnetic underlayer, a seed layer, and an orientation control layer are laminated in this order between the nonmagnetic substrate 1 and the magnetic layer 2 is taken as an example. explain. The adhesion layer, the soft magnetic underlayer, the seed layer, and the orientation control layer are provided as necessary, and some or all of them may not be provided.

(Non-magnetic substrate)
As the nonmagnetic substrate 1, a substrate in which a film made of NiP or NiP alloy is formed on a base made of a metal or alloy material such as Al or Al alloy can be used. Further, as the nonmagnetic substrate 1, a substrate made of a nonmetallic material such as glass, ceramics, silicon, silicon carbide, carbon, or resin may be used, and NiP or NiP alloy is formed on a substrate made of the nonmetallic material. You may use what formed the film | membrane.

(Adhesion layer)
The adhesion layer prevents the corrosion of the nonmagnetic substrate 1 when the nonmagnetic substrate 1 and the soft magnetic underlayer provided on the adhesion layer are disposed in contact with each other. As a material for the adhesion layer, for example, Cr, Cr alloy, Ti, Ti alloy and the like can be selected as appropriate. The thickness of the adhesion layer is preferably 2 nm or more so that the effect of providing the adhesion layer is sufficiently obtained.
The adhesion layer can be formed by, for example, a sputtering method.

(Soft magnetic underlayer)
The soft magnetic underlayer preferably has a structure in which a first soft magnetic film, an intermediate layer made of a Ru film, and a second soft magnetic film are sequentially stacked. That is, the soft magnetic underlayer has a structure in which the soft magnetic films above and below the intermediate layer are anti-ferro-coupled (AFC) by sandwiching an intermediate layer made of a Ru film between the two soft magnetic films. It is preferable. Since the soft magnetic underlayer has an AFC structure, resistance to an external magnetic field and resistance to a WAIT (Wide Area Tack Erasure) phenomenon, which is a problem peculiar to perpendicular magnetic recording, are enhanced. be able to.

  The film thickness of the soft magnetic underlayer is preferably in the range of 15 to 80 nm, and more preferably in the range of 20 to 50 nm. If the thickness of the soft magnetic underlayer is less than 15 nm, the magnetic flux from the magnetic head cannot be sufficiently absorbed, writing becomes insufficient, and the recording / reproducing characteristics may be deteriorated. On the other hand, if the thickness of the soft magnetic underlayer exceeds 80 nm, the productivity is remarkably lowered, which is not preferable.

  The first and second soft magnetic films are preferably made of a CoFe alloy. When the first and second soft magnetic films are made of a CoFe alloy, a high saturation magnetic flux density Bs (1.4 (T) or more) can be realized.

  Moreover, it is preferable to add any one of Zr, Ta, and Nb to the CoFe alloy used for the first and second soft magnetic films. This promotes the amorphization of the first and second soft magnetic films, thereby improving the orientation of the seed layer and reducing the flying height of the magnetic head. The soft magnetic underlayer can be formed by a sputtering method.

(Seed layer)
The seed layer is for controlling the orientation and crystal size of the orientation control layer and the magnetic layer 2 provided on the seed layer. The seed layer increases the vertical component of the magnetic flux generated from the magnetic head with respect to the substrate surface, and is magnetic. It is provided in order to more firmly fix the magnetization direction of the layer 2 in the direction perpendicular to the nonmagnetic substrate 1.

  The seed layer is preferably made of a NiW alloy. When the seed layer is made of a NiW alloy, other elements such as B, Mn, Ru, Pt, Mo, and Ta may be added to the NiW alloy as necessary.

The thickness of the seed layer is preferably in the range of 2 to 20 nm. If the film thickness of the seed layer is less than 2 nm, the effect of providing the seed layer may not be sufficiently obtained. On the other hand, when the film thickness of the seed layer exceeds 20 nm, the crystal size increases, which is not preferable.
The seed layer can be formed by a sputtering method.

(Orientation control layer)
The orientation control layer is for controlling the orientation of the magnetic layer 2 to be favorable. The orientation control layer is preferably made of Ru or a Ru alloy.

  The thickness of the orientation control layer is preferably in the range of 5 to 30 nm. By setting the film thickness of the orientation control layer to 30 nm or less, the distance between the magnetic head and the soft magnetic underlayer becomes small, and the magnetic flux from the magnetic head can be made steep. Moreover, the orientation of the magnetic layer 2 can be favorably controlled by setting the thickness of the orientation control layer to 5 nm or more.

The orientation control layer may be composed of one layer or may be composed of a plurality of layers. When the orientation control layer is composed of a plurality of layers, all the orientation control layers may be composed of the same material, or at least part of the orientation control layer may be composed of different materials.
The orientation control layer can be formed by a sputtering method.

(Magnetic layer)
The magnetic layer 2 is made of a magnetic film having an easy magnetization axis oriented in a direction perpendicular to the substrate surface. The magnetic layer 2 contains Co and Pt, and may further contain an oxide, Cr, B, Cu, Ta, Zr, etc. in order to further improve SNR characteristics.
Examples of the oxide contained in the magnetic layer 2 include SiO ₂ , SiO, Cr ₂ O ₃ , CoO, Ta ₂ O ₃ , and TiO ₂ .
The magnetic layer 2 may be composed of one layer, or may be composed of a plurality of layers made of materials having different compositions.

For example, when the magnetic layer 2 is composed of three layers of a first magnetic layer, a second magnetic layer, and a third magnetic layer, the first magnetic layer includes Co, Cr, and Pt, and further includes an oxide. A granular structure is preferred. As the oxide contained in the first magnetic layer, for example, an oxide such as Cr, Si, Ta, Al, Ti, Mg, and Co is preferably used. Among _{them, TiO 2, Cr 2 O 3} , SiO ₂ or the like can be suitably used. The first magnetic layer is preferably made of a composite oxide to which two or more types of oxides are added. Among these, Cr ₂ O ₃ —SiO ₂ , Cr ₂ O ₃ —TiO ₂ , SiO ₂ —TiO _{2 and the} like can be preferably used.

  The first magnetic layer contains at least one element selected from B, Ta, Mo, Cu, Nd, W, Nb, Sm, Tb, Ru, and Re in addition to Co, Cr, Pt, and oxide. Can be included. By including the above elements, it is possible to promote miniaturization of magnetic particles or improve crystallinity and orientation, and to obtain recording / reproducing characteristics and thermal fluctuation characteristics suitable for higher density recording.

  The same material as the first magnetic layer can be used for the second magnetic layer. The second magnetic layer is preferably of a granular structure.

  The third magnetic layer preferably has a non-granular structure made of a material containing Co, Cr, Pt and no oxide. The third magnetic layer contains one or more elements selected from B, Ta, Mo, Cu, Nd, W, Nb, Sm, Tb, Ru, Re, and Mn in addition to Co, Cr, and Pt. be able to. Since the third magnetic layer contains the above elements in addition to Co, Cr, and Pt, it is possible to promote miniaturization of magnetic particles and improve crystallinity and orientation, and recording suitable for higher density recording Reproduction characteristics and thermal fluctuation characteristics can be obtained.

  The thickness of the magnetic layer 2 is preferably 5 to 25 nm. If the thickness of the magnetic layer 2 is less than 5 nm, sufficient reproduction output cannot be obtained, and the thermal fluctuation characteristics are also deteriorated. On the other hand, when the thickness of the magnetic layer 2 exceeds 25 nm, the magnetic particles in the magnetic layer 2 are enlarged and noise during recording / reproduction increases, and a signal / noise ratio (S / N ratio) or This is not preferable because recording / reproduction characteristics represented by recording characteristics (OW) deteriorate.

When the magnetic layer 2 is composed of a plurality of layers, it is preferable to provide a nonmagnetic layer between adjacent magnetic layers. When the magnetic layer 2 is composed of three layers of the first magnetic layer, the second magnetic layer, and the third magnetic layer, between the first magnetic layer and the second magnetic layer, and between the second magnetic layer and the third magnetic layer, It is preferable to provide a nonmagnetic layer therebetween.
By providing a non-magnetic layer with an appropriate thickness between the magnetic layers, the magnetization reversal of the magnetic particles constituting each film (magnetic layer) can be facilitated, and the dispersion of the magnetization reversal of the entire magnetic particles can be reduced. The S / N ratio can be further improved.

  Examples of the material of the nonmagnetic layer provided between the magnetic layers include Ru, Ru alloy, CoCr alloy, and CoCrX1 alloy (X1 is Pt, Ta, Zr, Re, Ru, Cu, Nb, Ni, Mn, Ge , Si, O, N, W, Mo, Ti, V, Zr, or B represents at least one element or two or more elements).

In addition, as a material for the nonmagnetic layer provided between the magnetic layers, it is preferable to use an alloy material containing an oxide, a nitride, or a carbide. Specific examples of the oxide include SiO ₂ , Al ₂ O ₃ , Ta ₂ O ₅ , Cr ₂ O ₃ , MgO, Y ₂ O ₃ , and TiO ₂ . Specific examples of the nitride include AlN, Si ₃ N ₄ , TaN, and CrN. As specific examples of the carbide, TaC, BC, SiC, or the like can be used.

The thickness of the nonmagnetic layer provided between the magnetic layers is preferably 0.1 to 1 nm. By setting the thickness of the nonmagnetic layer within the above range, the S / N ratio can be further improved.
The nonmagnetic layer can be formed by a sputtering method.

  The magnetic layer 2 is preferably a magnetic layer for perpendicular magnetic recording in which the easy axis of magnetization is perpendicular to the substrate surface in order to achieve a higher recording density. May be.

  The magnetic layer 2 may be formed by any conventionally known method such as vapor deposition, ion beam sputtering, or magnetron sputtering, but is usually formed by sputtering.

(Protective layer)
The protective layer 3 protects the magnetic layer 2. As shown in FIG. 1, the protective layer 3 of this embodiment has a protective film layer 3a and a nitrogen-containing layer 3b formed on the lubricant layer 4 side (the upper surface in FIG. 1) of the protective film layer 3a. doing.
The protective film layer 3a contains carbon or hydrogenated carbon, and may be formed of only carbon or hydrogenated carbon, or may contain nitrogen in addition to carbon or hydrogenated carbon. Good. The protective film layer 3a may be composed of a single layer or a plurality of layers.

The nitrogen-containing layer 3b contains nitrogen and carbon. The nitrogen-containing layer 3b may contain other atoms such as hydrogen atoms in addition to nitrogen atoms and carbon atoms.
The nitrogen-containing layer 3b is the outermost surface containing carbon and nitrogen in the range of 50 atomic% to 90 atomic% (the outermost surface on the lubricant layer side of the protective layer, the interface between the nitrogen-containing layer 3b and the lubricant layer 4). Have The nitrogen content in the nitrogen-containing layer 3b may be uniform, or may have, for example, a concentration gradient that is the largest on the outermost surface and decreases with increasing depth.
When the nitrogen content on the outermost surface of the nitrogen-containing layer 3b is within the above range, the nitrogen-containing layer 3b and each of the compounds A to C forming the lubricant layer 4 are bonded with high bonding strength. Is done.

  The nitrogen atom contained in the outermost surface of the nitrogen-containing layer 3b forms a strong bond with the hydroxyl group contained in the compounds A to C described later. When the nitrogen content of the outermost surface of the nitrogen-containing layer 3b is 50 atomic% or more, the number of bonds between the nitrogen atoms contained in the outermost surface of the nitrogen-containing layer 3b and the hydroxyl groups contained in the compounds A to C is sufficiently large. The protective layer 3 and the lubricant layer 4 are bonded with a high bonding force. The nitrogen content of the outermost surface of the nitrogen-containing layer 3b is 60 atomic% or more in order to secure the number of bonds between the nitrogen atoms contained in the nitrogen-containing layer 3b and the hydroxyl groups contained in the compounds A to C. Is preferable, and it is more preferable that it is 70 atomic% or more.

The carbon atom contained in the outermost surface of the nitrogen-containing layer 3b forms a strong bond with the six-membered ring (—C ₆ H ₄ —) contained in the compound A described later. When the nitrogen content on the outermost surface of the nitrogen-containing layer 3b is 90 atomic% or less, the number of carbon atoms contained on the outermost surface of the nitrogen-containing layer 3b is sufficiently secured. Therefore, the number of bonds between the carbon atom contained in the nitrogen-containing layer 3b and the six-membered ring contained in the compound A can be sufficiently secured, and the protective layer 3 and the lubricant layer 4 are bonded with high bonding strength. The nitrogen content on the outermost surface of the nitrogen-containing layer 3b may be 80 atomic% or less in order to secure the number of bonds between the carbon atoms contained in the nitrogen-containing layer 3b and the six-membered ring contained in the compound A. preferable.

  In the present embodiment, the surface of the protective layer on the lubricant layer side "includes carbon and nitrogen in the range of 50 atomic percent to 90 atomic percent" means that the surface of the protective layer on the lubricant layer side is, for example, It means a protective layer measured by X-ray photoelectron spectroscopy (XPS / ESCA) and having a nitrogen content on the outermost surface in the range of 50 atomic% to 90 atomic%.

  The film thickness of the protective layer 3 (total film thickness of the protective film layer 3a and the nitrogen-containing layer 3b) is preferably in the range of 1 nm to 10 nm. When the thickness of the protective layer 3 is 10 nm or less, the magnetic spacing in the magnetic recording / reproducing apparatus provided with the magnetic recording medium 11 of the present embodiment can be sufficiently reduced, and the recording density can be further improved. The magnetic spacing means the distance between the magnetic head and the magnetic layer 4. The narrower the magnetic spacing, the better the electromagnetic conversion characteristics of the magnetic recording / reproducing apparatus. When the thickness of the protective layer 3 is 1 nm or more, the effect of protecting the magnetic layer 2 is enhanced, and durability can be improved.

The protective layer 3 can be formed by the method shown below, for example.
When the protective film layer 3a is made of carbon, for example, it can be formed by a sputtering method using a carbon target material as a raw material.
When the protective film layer 3a is made of hydrogenated carbon, it can be formed by, for example, a CVD (chemical vapor deposition) method using a hydrocarbon raw material such as ethylene or toluene, an IBD (ion beam vapor deposition) method, or the like.
When the protective film layer 3a contains nitrogen in addition to carbon or hydrogenated carbon, for example, when the raw material containing nitrogen is used as the raw material and the protective film layer 3a is made of carbon or made of hydrogenated carbon It can be formed by the same method as that of the case.

Next, the nitrogen-containing layer 3b is formed by nitriding (or dehydrogenating and nitriding) the protective film layer 3a (the surface on the lubricant layer 4 side).
As a method of nitriding (or dehydrogenating and nitriding) the protective film layer 3a, a known method can be used. Specifically, a method of implanting nitrogen ions on the protective film layer 3a, a method of exposing the protective film layer 3a to nitrogen plasma, and the like can be mentioned. The nitrogen-containing layer 3b formed by these methods has the highest nitrogen content on the outermost surface and has a concentration gradient that decreases as the depth increases. Both carbon films containing nitrogen with high lubricant applicability are obtained and preferred.
When using the method of implanting nitrogen ions, for example, the nitrogen content of the outermost surface of the nitrogen-containing layer 3b can be set within a range of 50 atomic% to 90 atomic% by controlling the amount of nitrogen ions implanted. In the case of using the method of exposing to nitrogen plasma, for example, by controlling the time (treatment time) and / or nitrogen plasma density on the protective film layer 3a exposed to the nitrogen plasma, the outermost surface of the nitrogen-containing layer 3b is controlled. The nitrogen content can be in the range of 50 atomic% to 90 atomic%.

In the example shown in FIG. 1, the protective layer 3 includes a protective film layer 3 a and a nitrogen-containing layer 3 b formed by nitriding (or dehydrogenating and nitriding) the protective film layer 3 a as an example. However, the protective layer in the present invention may be any protective layer as long as the outermost surface on the lubricant layer side contains carbon and nitrogen in the range of 50 atomic% to 90 atomic%. .
For example, a layer containing carbon and nitrogen in the range of 50 atomic% to 90 atomic% formed on the magnetic layer 2 by a sputtering method, a CVD method, an IBD method, or the like using a raw material containing carbon and nitrogen. The protective layer which consists only of may be sufficient. In this case, by controlling the nitrogen concentration contained in the raw material, the nitrogen content on the outermost surface of the protective layer can be in the range of 50 atomic% to 90 atomic%.

(Lubricant layer)
The lubricant layer 4 is formed in contact with the outermost surface of the nitrogen-containing layer 3 b of the protective layer 3.
The lubricant layer 4 includes a compound A represented by the general formula (1), a compound B represented by the general formula (2), and a compound C represented by the general formula (3).

_{R1-C 6 H 4 OCH 2} CH (OH) CH 2 OCH 2 -R2-CH 2 OCH 2 CH (OH) CH 2 OH ‥‥ (1)
(In General Formula (1), R1 is an alkoxy group having 1 to 4 carbon atoms. R2 is —CF ₂ O (CF ₂ CF ₂ O) x (CF ₂ O) yCF ₂ — (x, y The parentheses may be connected in this order, reversely or randomly (x and y are each an integer of 0 to 15).)

CH ₂ (OH) CH (OH) CH ₂ OCH ₂ CF ₂ CF ₂ (OCF ₂ CF ₂ CF ₂ ) _m OCF ₂ CF ₂ CH ₂ OCH ₂ CH (OH) CH ₂ OH (2)
(In general formula (2), m is an integer in the range of 4-50.)

_{HOCH 2 CF 2 CF 2 O (} CF 2 CF 2 CF 2 O) sCF 2 CF 2 CH 2 OCH 2 CH (OH) CH 2 OH ‥‥ (3)
(In general formula (3), s is an integer.)

“Compound A”
In the compound A, the six-membered ring (—C ₆ H ₄ —) having a large cyclic skeleton arranged at a position close to the terminal forms a strong bond with the carbon atom contained in the outermost surface of the nitrogen-containing layer 3b. Further, in the compound A, a terminal group composed of —CH (OH) CH ₂ OH having two hydroxyl groups located at the terminal on the opposite side of R1 and an intermediate hydroxyl group are included in the outermost surface of the nitrogen-containing layer 3b. Forms a strong bond with the nitrogen atom. Therefore, in the compound A, it selectively binds to a carbon atom having a relatively small content at the outermost surface of the nitrogen-containing layer 3b at a position close to one end, and at the other end, the outermost surface of the nitrogen-containing layer 3b. To the nitrogen atom of As a result, the compound A is unlikely to form an island shape (island shape) on the outermost surface of the nitrogen-containing layer 3b, and is likely to be spread and arranged in the plane direction.

In the compound A represented by the general formula (1), R1 is an alkoxy group having 1 to 4 carbon atoms. Since R1 is an alkoxy group having 1 to 4 carbon atoms, the six-membered ring (—C ₆ H ₄ —) contained in Compound A is arranged at a position close to the end of Compound A. As the number of carbon atoms of R1 in compound A is smaller, the position of the six-membered ring is closer to the terminal, the position of the six-membered ring is farther from the terminal group consisting of —CH (OH) CH ₂ OH, and compound A is a nitrogen-containing layer. Since it becomes easy to spread in the surface direction on the outermost surface of 3b, it is preferable that the carbon number is 1.

  In the compound A represented by the general formula (1), x and y in R2 are each an integer of 0 to 15. For this reason, the molecular weight of the compound A becomes appropriate. Therefore, when the molecular weight of the compound A is too large, it can be prevented that it becomes difficult to apply the lubricant when the lubricant containing the compound A is applied to form the lubricant layer. Moreover, since the molecular weight of the compound A is too small, the spread of the compound A in the surface direction on the outermost surface of the nitrogen-containing layer 3b is not insufficient.

  The average molecular weight of the compound A represented by the general formula (1) is preferably in the range of 1000 to 2500. When the average molecular weight of Compound A is 2500 or less, when a lubricant containing Compound A to Compound C is applied to form a lubricant layer, a lubricant having low viscosity and easy to apply can be easily obtained. When the average molecular weight of Compound A is 1000 or more, it is easy to obtain the lubricant layer 4 whose thickness is not easily reduced even when used in a high temperature and high humidity environment, and excellent durability is obtained.

  Examples of the compound A include ART-1 (trade name: manufactured by Matsumura Oil Research Institute (MORESCO)). In ART-1 (trade name), R1 in the general formula (1) is an alkoxy group having 1 carbon atom, x and y in R2 are each an integer of 3 to 7, and an average molecular weight is 1000 to 2500. It was adjusted to be within the range.

“Compound B”
Compound B has four hydroxyl groups, and has terminal groups composed of —CH (OH) CH ₂ OH having two hydroxyl groups arranged at both ends. In Compound B, hydroxyl groups and nitrogen atoms having a relatively large content on the outermost surface of the nitrogen-containing layer 3b are bonded at both ends. For this reason, the compound B has a strong binding force with the nitrogen-containing layer 3b.
Compound B does not have a cyclic skeleton, and the number of oxygen atoms relative to the number of carbon atoms in the perfluoropolyether chain (the number of ether bonds (—O—)) is appropriate. Have.

  In the compound B shown in the general formula (2), m is an integer in the range of 4-50. For this reason, the molecular weight of the compound B becomes appropriate. Therefore, when the molecular weight of the compound B is too large, it can be prevented that it becomes difficult to apply the lubricant when the lubricant containing the compound B is applied to form the lubricant layer. Moreover, when the molecular weight of the compound B is too small, the spread of the compound B in the surface direction on the outermost surface of the nitrogen-containing layer 3b is not insufficient.

  The average molecular weight of the compound B represented by the general formula (2) is preferably in the range of 1000 to 2500. When the average molecular weight of Compound B is 2500 or less, when a lubricant containing Compound A to Compound C is applied to form a lubricant layer, a lubricant having low viscosity and easy to apply can be easily obtained. When the average molecular weight of Compound B is 1000 or more, it is easy to obtain the lubricant layer 4 whose thickness is not easily reduced even when used in a high-temperature and high-humidity environment, and excellent durability is obtained.

  Examples of compound B include D4OH (s) (trade name: manufactured by Matsumura Oil Research Institute (MORESCO)). D4OH (s) (trade name) is adjusted so that m in the general formula (2) is an integer in the range of 4 to 50, and the average molecular weight is in the range of 1000 to 2500.

“Compound C”
Compound C has three hydroxyl groups, -CH (OH) CH ₂ OH having two hydroxyl groups at one end is arranged, and -CH ₂ having one hydroxyl group at the other end A terminal group consisting of OH is arranged. In Compound C, hydroxyl groups and nitrogen atoms having a relatively large content on the outermost surface of the nitrogen-containing layer 3b are bonded at both ends. For this reason, the compound C has a strong binding force with the nitrogen-containing layer 3b.
Compound C does not have a cyclic skeleton, and the number of oxygen atoms (the number of ether bonds (-O-)) relative to the number of carbon atoms in the perfluoropolyether chain is appropriate. Have.
Since compound C has three hydroxyl groups, it has intermediate characteristics between a lubricant having four hydroxyl groups (for example, compound B) and a lubricant having two hydroxyl groups (for example, diol). In addition, since Compound C has an asymmetric linear chemical structure, a bonded state different from that of Compound B can be obtained on the surface of the nitrogen-containing layer 3b. Therefore, by mixing the compounds B and C as in the present embodiment, it becomes possible to supplement the uncoated region with both compounds, and it is also possible to supplement the uncoated region of the compound A.

  It is preferable that the average molecular weight of the compound C shown in General formula (3) exists in the range of 1000-2000. When the average molecular weight of Compound C is 2000 or less, when a lubricant containing Compound A to Compound C is applied to form a lubricant layer, a lubricant having a low viscosity and easy to apply can be easily obtained. When the average molecular weight of Compound C is 1000 or more, it is easy to obtain the lubricant layer 4 whose thickness is not easily reduced even when used in a high temperature and high humidity environment, and excellent durability is obtained.

  Examples of compound C include D3OH (s) (trade name: manufactured by Matsumura Oil Research Institute (MORESCO)). D3OH (s) (trade name) is obtained by adjusting the value of s in the general formula (3) so that the average molecular weight is in the range of 1000 to 2000.

In the present embodiment, since the lubricant layer 4 containing the compounds A to C is provided in contact with the outermost surface of the protective layer 3, the thickness of the lubricant layer 4 can be reduced as described below.
As described above, since the compound A is likely to be spread and arranged in the plane direction, it tends to be a network, and a gap is easily formed between the compounds A. Since compound B and compound C do not have a cyclic skeleton and the number of oxygen atoms relative to the number of carbon atoms in the perfluoropolyether chain (the number of ether bonds (—O—)) is appropriate, moderate hardness Have For this reason, in the lubricant layer 4 of this embodiment, the compound B and the compound C enter the gap formed between the compounds A, and the gap between the compounds A is filled. As a result, contamination of the magnetic recording medium 11 due to the intrusion of environmental substances from the gaps in the lubricant layer 4 can be prevented, and the thickness of the lubricant layer 4 can be reduced.

On the other hand, for example, when a film having an average film thickness of 2 nm or less is formed using only the compound A instead of the lubricant layer 4, the compound A has a large cyclic skeleton molecular structure, so that a network-like film is formed. A gap is formed in the lubricant layer 4 and the surface of the protective layer 3 cannot be covered with a sufficiently high coverage.
If there is a gap in the lubricant layer, environmental substances that generate contaminants such as ionic impurities adsorbed on the surface of the magnetic recording medium pass through the gap in the lubricant layer and enter the lower layer of the lubricant layer. To do. The environmental substance that has entered the lower layer of the lubricant layer aggregates minute ionic components present therein to generate ionic contaminants. Then, during magnetic recording / reproduction, this contaminant (aggregation component) adheres (transfers) to the magnetic head, which damages the magnetic head or degrades the magnetic recording / reproduction characteristics of the magnetic recording / reproducing apparatus. Problems caused by the intrusion of environmental substances from the gaps in the lubricant layer appear more markedly than when the magnetic recording medium is held under high temperature conditions.

In addition, when a film having an average film thickness of 2 nm or less is formed using only Compound B instead of the lubricant layer 4, the bond strength (wetting property) between the Compound B and the protective layer 3 is insufficient. Thus, the surface of the protective layer 3 cannot be coated with a sufficiently high coverage.
In addition, when a film having an average film thickness of 2 nm or less is formed using only the compound C instead of the lubricant layer 4, the bond strength (wetting property) between the compound C and the protective layer 3 is insufficient, so Thus, the surface of the protective layer 3 cannot be coated with a sufficiently high coverage.

(Mass ratio (A / (A + B + C)))
The ratio of the mass of compound A to the sum of the masses of compounds A, B and C (A / (A + B + C)) is in the range of 0.05 to 0.6 and in the range of 0.1 to 0.5. It is preferable. By combining the mass ratio (A / (A + B + C)) within the range of 0.05 to 0.6, the bond between the nitrogen atom contained in the outermost surface of the nitrogen-containing layer 3b and the hydroxyl group contained in the compound A to compound C. The number of bonds can be sufficiently secured, and the number of bonds between the carbon atom contained in the outermost surface of the nitrogen-containing layer 3b and the six-membered ring contained in the compound A can be sufficiently secured. Therefore, the protective layer 3 and the lubricant layer 4 are bonded with a high bonding force. In addition, by setting the mass ratio (A / (A + B + C)) to 0.6 or less, preferably 0.5 or less, a gap formed between the compounds A is formed by a sufficient amount of the compound B and the compound C. The magnetic recording medium 11 can be prevented from being contaminated by the intrusion of environmental substances from the gaps in the lubricant layer 4. By setting the mass ratio (A / (A + B + C)) to 0.05 or more, preferably 0.1 or more, excess compound B and compound C are island-shaped on the outermost surface of the nitrogen-containing layer 3b. It is possible to prevent the coverage of the protective layer 3 from being lowered.

  When the mass ratio (A / (A + B + C)) is less than 0.05, the compound A is insufficient and the compound B and the compound C are excessive. The coverage is insufficient. In addition, when the mass ratio (A / (A + B + C)) exceeds 0.6, the compounds B and C are insufficient, and the lubricant layer 4 tends to form a network, and the coverage with respect to the protective layer 3 becomes insufficient. .

(Mass ratio (B / (A + B + C)))
The ratio of the mass of the compound B to the sum of the masses of the compounds A, B and C (B / (A + B + C)) contained in the lubricant layer of the present embodiment is in the range of 0.05 to 0.5, It is preferable to be within the range of 0.1 to 0.4. By setting the mass ratio (B / (A + B + C)) to 0.5 or less, preferably 0.4 or less, the compound B having four hydroxyl groups becomes excessive, and the hydroxyl groups contained in the compounds A to C are excessive. This prevents a hydroxyl group that is not bonded to a nitrogen atom contained on the outermost surface of the nitrogen-containing layer 3b from being generated. Therefore, the binding force due to the bond between the nitrogen atom contained in the outermost surface of the nitrogen-containing layer 3b and the hydroxyl group contained in the compound A compound C, the carbon atom contained in the outermost surface of the nitrogen-containing layer 3b, and the six contained in the compound A. A sufficient binding force with the member ring is obtained. Therefore, the protective layer 3 and the lubricant layer 4 are bonded with a high bonding force. By setting the mass ratio (B / (A + B + C)) to 0.05 or more, preferably 0.1 or more, the shortage of the compound B having four hydroxyl groups is prevented, and it is included in the outermost surface of the nitrogen-containing layer 3b. The number of bonds between the nitrogen atom and the hydroxyl group contained in compound A to compound C can be ensured. Therefore, the protective layer 3 and the lubricant layer 4 are bonded with a high bonding force.

  When the mass ratio (B / (A + B + C)) is less than 0.05 or when the mass ratio (B / (A + B + C)) exceeds 0.5, the mixing balance of the compounds A, B and C is poor. Thus, the uncovered area on the surface of the protective layer 3 by each compound is not complemented, and the coverage of the protective layer 3 becomes insufficient.

(Mass ratio (C / (A + B + C)))
The mass ratio of compound C to the sum of the masses of compounds A, B and C (C / (A + B + C)) is in the range of 0.05 to 0.9 and in the range of 0.1 to 0.8. It is preferable to be within. By setting the mass ratio (C / (A + B + C)) to 0.9 or less, preferably 0.8 or less, the compound C having three hydroxyl groups becomes excessive, and the compound A relatively decreases. It can be prevented that the bonding force between the carbon atom contained in the outermost surface of the nitrogen-containing layer 3b and the six-membered ring contained in the compound A is insufficient. Further, by setting the mass ratio (C / (A + B + C)) to 0.05 or more, preferably 0.1 or more, the compound B having four hydroxyl groups becomes excessive and included in the outermost surface of the nitrogen-containing layer 3b. The generation of a hydroxyl group that is not bonded to the nitrogen atom is prevented, and the compound A is prevented from becoming excessive and the lubricant layer 4 is prevented from becoming a network.

  When the mass ratio (C / (A + B + C)) is less than 0.05 or when the mass ratio (C / (A + B + C)) exceeds 0.9, the mixing balance of the compounds A, B and C is poor. Thus, the uncovered area on the surface of the protective layer 3 by each compound is not complemented, and the coverage with respect to the protective layer 3 becomes insufficient.

(Thickness of lubricant layer)
The average film thickness of the lubricant layer 4 is in the range of 0.5 nm (5Å) to 2 nm (20Å), and preferably in the range of 1 nm to 1.9 nm.
By setting the average film thickness of the lubricant layer 4 to 0.5 nm or more, characteristics due to the lubricant layer 4 containing the compound A, the compound B, and the compound C are sufficiently exhibited. That is, the compound B and the compound C enter the gap formed between the compounds A, the gap between the compounds A is filled, and the nitrogen atoms and the compounds A to C included in the outermost surface of the nitrogen-containing layer 3b. The bonding strength due to the bonding with the contained hydroxyl group and the bonding strength between the carbon atom contained in the outermost surface of the nitrogen-containing layer 3b and the six-membered ring contained in the compound A are sufficiently obtained. Therefore, the lubricant layer 4 having an average film thickness of 0.5 nm or more is bonded to the protective layer 3 with a strong bonding force, does not have an island shape or a mesh shape, and is magnetized by an intrusion of an environmental substance from the gap between the lubricant layers 4. Contamination of the recording medium 11 can be prevented.
Further, by setting the average film thickness of the lubricant layer 4 to 2 nm or less, the flying height of the magnetic head can be sufficiently reduced, and the recording density of the magnetic recording medium 11 can be increased.

(Formation method of lubricant layer)
As the lubricant layer 4, for example, a magnetic recording medium in the middle of production in which the layers up to the protective layer 3 are formed on the nonmagnetic substrate 1 is prepared, and the lubricant layer is formed on the protective layer 3 of the magnetic recording medium in the middle of production. It can be formed by applying a forming solution.

The lubricant layer forming solution is obtained, for example, by mixing the compounds A, B and C so as to be within the above-mentioned mass ratio range and diluting with a solvent to obtain a viscosity and concentration suitable for the coating method. It is done.
Examples of the solvent used in the lubricant layer forming solution include fluorine-based solvents such as Vertrel XF (trade name, manufactured by Mitsui DuPont Fluorochemical Co., Ltd.).
The method for applying the lubricant layer forming solution is not particularly limited, and examples thereof include a spin coating method and a dip method.

  As the dip method, for example, the nonmagnetic substrate 1 on which each layer up to the protective layer 3 is formed is immersed in a lubricant layer forming solution placed in a dip coater of a dip coater, and then from the dip tank. There is a method of pulling up the nonmagnetic substrate 1 at a predetermined speed. By using the dip method, the lubricant layer forming solution can be uniformly applied on the surface of the protective layer 3 of the nonmagnetic substrate 1, and the lubricant layer 4 having a uniform thickness is formed on the protective layer 3. it can.

(Magnetic recording / reproducing device)
Next, an example of a magnetic recording / reproducing apparatus according to an embodiment of the present invention will be described. FIG. 2 is a perspective view showing an example of a magnetic recording / reproducing apparatus according to an embodiment of the present invention.

  A magnetic recording / reproducing apparatus 101 according to an embodiment of the present invention includes a magnetic recording medium 11 according to the embodiment of the present invention shown in FIG. 1, a medium driving unit 123 that drives the magnetic recording medium 11 in the recording direction, a recording unit, and the like. A magnetic head 124 including a reproducing unit, a head moving unit 126 that moves the magnetic head 124 relative to the magnetic recording medium 11, and a recording / reproducing signal processing unit 128 that processes a recording / reproducing signal from the magnetic head 124 are provided. It is a thing.

  By configuring the element part (reproducing part) of the magnetic head 124 with a GMR head or TMR head, a sufficient signal intensity can be obtained even at a high recording density, and a magnetic recording / reproducing apparatus having a high recording density is realized. be able to.

  Since the magnetic recording / reproducing apparatus 101 of the present embodiment includes the magnetic recording medium 11 which is not easily contaminated, the contaminant is transferred to the magnetic head 124, and the recording / reproducing characteristics are deteriorated and the flying stability is impaired. Can be prevented. Therefore, the magnetic recording / reproducing apparatus 101 of this embodiment has stable magnetic recording / reproducing characteristics.

  Hereinafter, the present invention will be specifically described based on examples. In addition, this invention is not limited only to these Examples, In the range which does not change the summary, it can implement on the conditions selected suitably.

Example 1
A cleaned glass substrate (manufactured by HOYA, 2.5 inch outer diameter) is accommodated in a film forming chamber of a DC magnetron sputtering apparatus (C-3040 made by Anelva), and the ultimate vacuum is 1 × 10 ⁻⁵ Pa. The inside of the deposition chamber was evacuated until
Thereafter, an adhesion layer having a layer thickness of 10 nm was formed on the glass substrate using a Cr target by a sputtering method.

  Next, a soft magnetic underlayer was formed on the adhesion layer by sputtering. As the soft magnetic underlayer, a first soft magnetic layer, an intermediate layer, and a second soft magnetic layer were formed in this order. First, using a Co-20Fe-5Zr-5Ta {Fe content 20 atomic%, Zr content 5 atomic%, Ta content 5 atomic%, balance Co} target at a substrate temperature of 100 ° C. or lower, a layer thickness of 25 nm The first soft magnetic layer was formed. Next, an intermediate layer made of Ru having a layer thickness of 0.7 nm was formed. Thereafter, a second soft magnetic layer made of Co-20Fe-5Zr-5Ta having a layer thickness of 25 nm was formed.

Next, a seed layer having a layer thickness of 5 nm was formed on the soft magnetic underlayer by a sputtering method using a Ni-6W {W content 6 atom%, remaining Ni} target.
Thereafter, a Ru layer having a thickness of 10 nm was formed on the seed layer as a first orientation control layer by sputtering, with a sputtering pressure of 0.8 Pa. Next, a Ru layer having a thickness of 10 nm was formed on the first alignment control layer by sputtering as a second alignment control layer with a sputtering pressure of 1.5 Pa.

Subsequently, 91 (Co15Cr16Pt) -6 (SiO ₂ ) -3 (TiO ₂ ) {Cr content of 15 atomic%, Pt content of 16 atomic%, and the remaining Co on the second alignment control layer by sputtering. A first magnetic layer made of the alloy of 91 mol%, SiO ₂ 6 mol%, and TiO ₂ 3 mol% was formed to a layer thickness of 9 nm. The sputtering pressure here was 2 Pa.

Next, by sputtering, the first magnetic layer is made of 88 (Co30Cr) -12 (TiO ₂ ) {Cr content 30 atomic%, balance Co alloy 88 mol%, TiO ₂ 12 mol%}. The magnetic layer was formed to have a layer thickness of 0.3 nm.
Then, 92 (Co11Cr18Pt) -5 (SiO ₂ ) -3 (TiO ₂ ) {Cr content of 11 atomic%, Pt content of 18 atomic%, and the balance Co of 92 mol on the nonmagnetic layer by sputtering. %, SiO ₂ 5 mol%, TiO ₂ 3 mol%} was formed to a layer thickness of 6 nm. The sputtering pressure here was 2 Pa.

Thereafter, a nonmagnetic layer made of Ru was formed with a layer thickness of 0.3 nm on the second magnetic layer by sputtering.
Next, a target composed of Co-20Cr-14Pt-3B {Cr content 20 atomic%, Pt content 14 atomic%, B content 3 atomic%, balance Co} is formed on the nonmagnetic layer by sputtering. Then, the third magnetic layer was formed with a layer thickness of 7 nm at a sputtering pressure of 0.6 Pa.

`` Formation of protective layer ''
A hydrogenated carbon film was formed on the surface of the magnetic layer by ion beam deposition using gasified toluene as a source gas. When forming the hydrogenated carbon film, first, the gas flow rate of the source gas supplied to the film formation chamber was set to 2.9 SCCM, and the reaction pressure was set to 0.2 Pa. Furthermore, the cathode power, which is an excitation source of the source gas, was set to 225 W (AC 22.5 V, 10 A). The voltage between the cathode electrode and the anode electrode covering it is 75 V, the current is 1650 mA, the ion acceleration voltage is 200 V, the current is 180 mA, the film formation time is 1.5 seconds, and the thickness is 3.5 nm. A hydrogenated carbon film was formed. After the hydrogenated carbon film was formed, the supply of the source gas was stopped and the film formation chamber was evacuated for 2 seconds.

  Next, nitrogen gas was supplied into the film formation chamber at a gas flow rate of 2 SCCM and a reaction pressure of 5 Pa. The cathode power is 128W (AC16V, 8A), the voltage between the cathode and anode is 75V, the current is 1000mA, the ion acceleration voltage is 200V, the current is 90mA, the treatment time is 1 second, and it is formed from nitrogen gas. The surface of the hydrogenated carbon film was irradiated with the nitrogen ions thus exposed to nitrogen plasma. Thereby, the surface of the hydrogenated carbon film was dehydrogenated and nitrided.

  After the surface treatment (dehydrogenation and nitridation) of the hydrogenated carbon film, the composition of the outermost surface (outermost surface of the protective layer) was measured by X-ray photoelectron spectroscopy (Electron Spectroscopy for Chemical Analysis (ESCA)). The results are shown in Table 1.

"Formation of lubricant layer"
Next, Table 1 and the compounds shown below were dissolved in Vertrel XF (trade name, manufactured by Mitsui Dupont Fluoro Chemical Co., Ltd.) at a mass ratio shown in Table 1 to obtain a lubricant layer forming solution. The concentration of the compound contained in the lubricant layer forming solution was 0.3% by mass.

Next, a solution for forming a lubricant layer was applied on the protective layer of the nonmagnetic substrate by using a dip method.
That is, the nonmagnetic substrate on which each layer up to the protective layer is formed is immersed in the lubricant layer forming solution placed in the immersion tank of the dip coater, and then the nonmagnetic substrate is removed from the immersion tank at a constant speed. Raised. In this way, the lubricant layer forming solution was applied to the surface of the nonmagnetic substrate on the protective layer so that the layer thickness of the lubricant layer was 1.3 nm.
Thereafter, the surface coated with the lubricant layer forming solution was dried to form a lubricant layer, whereby the magnetic recording medium of Example 1 was obtained.

(Examples 2-9, Comparative Examples 1-16)
By adjusting the treatment time of the surface treatment (dehydrogenation and nitridation) of the hydrogenated carbon film, the composition of the outermost surface of the protective layer was changed, and the type of compound used to form the formation of the lubricant layer The magnetic recording media of Examples 2 to 9 and Comparative Examples 1 to 16 were obtained in the same manner as in Example 1 except that the mass ratio was changed as shown in Table 1. In Comparative Example 11 and Comparative Example 12, the mass ratio was calculated by regarding the mass of other compounds as the mass of Compound A.
Further, at the stage where the surface treatment of the hydrogenated carbon film during the production of the magnetic recording media of Examples 2 to 9 and Comparative Examples 1 to 16 was completed, the outermost surface of the hydrogenated carbon film (the outermost surface of the protective layer) The composition was measured by secondary ion mass spectrometry (SIMS). The results are shown in Table 1.

In the examples and comparative examples, the compounds used for forming the lubricant layer are as follows.
ART-1 (trade name: manufactured by Matsumura Oil Research Institute (MORESCO)) average molecular weight 1700
D4OH (s) (trade name: Made by Matsumura Oil Research Institute (MORESCO)) Average molecular weight 1600
D3OH (s) (trade name: Matsumura Oil Research Institute (MORESCO)) average molecular weight 1700
A2OH; A2OH-2000 (trade name: Made by Matsumura Oil Research Institute (MORESCO))
ADOH; ADOH-2000 (trade name: Made by Matsumura Oil Research Institute (MORESCO))

A2OH-2000 is represented by the following general formula (4), wherein x is 5, R ₁ is CF _3, and R ₂ is —OCH ₂ CF ₂ O (CF ₂ CF ₂ O) _t (CF ₂ O) _u CF ₂ CH ₂ OH (t is 10.5, u is 10.1).
In ADOH-2000, in the following general formula (4), x is 5, R ₁ is CF _3, and R ₂ is —OCH ₂ CF ₂ O (CF ₂ CF ₂ O) _p (CF ₂ O) _q CF ₂ CH ₂ OCH ₂ CH (OH) CH ₂ OH (p is 10.7, q is 10.4).

(Evaluation of environmental resistance of magnetic recording media)
The environmental resistance of the magnetic recording media of Examples 1 to 9 and Comparative Examples 1 to 16 is evaluated using one of the methods for examining the state of contamination of the magnetic recording media by environmental substances that generate pollutants in a high temperature environment. did. In the environmental resistance evaluation shown below, Si ions were used as environmental substances, and the amount of adsorbed Si was measured as the amount of contaminants generated by the environmental substances.

  Specifically, first, the magnetic recording medium to be evaluated was held for 240 hours in the presence of a siloxane-based Si rubber in a high-temperature environment at a temperature of 85 ° C. and a humidity of 0%. Next, the amount of Si adsorbed on the surface of the magnetic recording medium was analyzed and measured using SIMS to evaluate the degree of contamination by Si ions. In addition, evaluation of Si adsorption amount was evaluated using the relative numerical value when the result of the comparative example 1 was set to 1.00. The results are shown in Table 1.

  Table 1 reveals that the magnetic recording media of Examples 1 to 9 have a smaller amount of Si adsorption than the magnetic recording media of Comparative Examples 1 to 16, and are less likely to be contaminated with environmental substances in a high temperature environment. It was. This is because in the magnetic recording media of Examples 1 to 9, the lubricant layer does not have an island shape or a mesh shape, and the lubricant layer and the protective layer are bonded with a strong bonding force. Even if the film thickness is small, it is presumed that the protective layer is covered with the lubricant layer at a high coverage.

  The magnetic recording medium and magnetic recording / reproducing apparatus of the present invention can be used in industries that use and manufacture high-density magnetic recording media and magnetic recording / reproducing apparatuses.

DESCRIPTION OF SYMBOLS 1 ... Nonmagnetic board | substrate, 2 ... Magnetic layer, 3 ... Protective layer, 4 ... Lubricant layer, 11 ... Magnetic recording medium, 101 ... Magnetic recording / reproducing apparatus, 123 ... Medium drive part, 124 ... Magnetic head, 126 ... Head movement 128, a recording / reproducing signal processing unit.

Claims (5)

A magnetic recording medium having at least a magnetic layer, a protective layer, and a lubricant layer in this order on a nonmagnetic substrate,
The protective layer includes carbon on the outermost surface on the lubricant layer side and nitrogen in a range of 50 atomic% to 90 atomic%,
The lubricant layer is formed in contact with the outermost surface, has an average film thickness in a range of 0.5 nm to 2 nm, and is represented by the following general formula (1) and the following general formula (2). The ratio of the mass of the compound A (A /) to the sum of the masses of the compounds A, B and C contained in the lubricant layer, including the compound B and the compound C represented by the following general formula (3) (A + B + C)) is in the range of 0.05 to 0.6, the mass ratio (B / (A + B + C)) of the compound B is in the range of 0.05 to 0.5, and A magnetic recording medium having a mass ratio (C / (A + B + C)) in the range of 0.05 to 0.9.
_{R1-C 6 H 4 OCH 2} CH (OH) CH 2 OCH 2 -R2-CH 2 OCH 2 CH (OH) CH 2 OH ‥‥ (1)
(In General Formula (1), R1 is an alkoxy group having 1 to 4 carbon atoms. R2 is —CF ₂ O (CF ₂ CF ₂ O) x (CF ₂ O) yCF ₂ — (x, y The parentheses may be connected in this order, reversely or randomly (x and y are each an integer of 0 to 15).)
CH ₂ (OH) CH (OH) CH ₂ OCH ₂ CF ₂ CF ₂ (OCF ₂ CF ₂ CF ₂ ) _m OCF ₂ CF ₂ CH ₂ OCH ₂ CH (OH) CH ₂ OH (2)
(In general formula (2), m is an integer in the range of 4-50.)
_{HOCH 2 CF 2 CF 2 O (} CF 2 CF 2 CF 2 O) sCF 2 CF 2 CH 2 OCH 2 CH (OH) CH 2 OH ‥‥ (3)
(In general formula (3), s is an integer.)   2. The magnetic recording medium according to claim 1, wherein the compound A has an average molecular weight in the range of 1000 to 2500.   3. The magnetic recording medium according to claim 1, wherein the compound B has an average molecular weight in a range of 1000 to 2500. 4.   4. The magnetic recording medium according to claim 1, wherein the average molecular weight of the compound C is in the range of 1000 to 2000. 5.   5. The magnetic recording medium according to claim 1, a medium driving unit that drives the magnetic recording medium in a recording direction, a magnetic head that records and reproduces information on the magnetic recording medium, and the magnetic A magnetic recording / reproducing apparatus comprising: a head moving unit that moves a head relative to the magnetic recording medium; and a recording / reproducing signal processing unit that processes a recording / reproducing signal from the magnetic head.

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