JP2017157254A - Magnetic recording medium and magnetic recording reproducer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic recording medium capable of effectively preventing the contamination of the surface of a magnetic recording medium even when a lubricant layer is thinned.SOLUTION: In a magnetic recording medium 11, a magnetic layer 2, a protective layer 3, and a lubricant layer 4 are sequentially stacked on a non-magnetic substrate 1. The protective layer 3 contains carbon or hydrogenated carbon. The lubricant layer 4 is in contact with the protective layer 3. The protective layer 3 contains N on a boundary surface between it and the lubricant layer 4. The lubricant layer 4 contains a compound A expressed by a general formula (1) and a compound B expressed by a general formula (2). The ratio of the mass of the compound A to the total mass of the compound A and compound B is in a range of 0.05-0.9. The average thickness of the lubricant layer 4 is in a range of 0.5 nm to 2 nm.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a magnetic recording medium and a magnetic recording / reproducing apparatus.

  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 are magnetic recording media in which a recording layer or the like is laminated on a nonmagnetic substrate, a protective layer such as carbon is formed on the recording layer, and a lubricant layer is further formed on the protective layer. 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, the magnetic head of the magnetic recording / reproducing apparatus can be prevented from contacting the protective layer, and the frictional force of the magnetic head sliding on the magnetic recording medium can be significantly reduced. 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 discloses a lubricant of perfluoroalkyl polyether having a structure of HOCH ₂ —CF ₂ O— (C ₂ F ₄ O) _p — (CF ₂ O) _q —CH ₂ OH. Yes.

Patent Document 2 discloses that the chemical formula HO—CH ₂ CH (OH) —CH ₂ OCH ₂ CF ₂ O— (CF ₂ CF ₂ O) _m — (CF ₂ O) _n —CF ₂ CH ₂ OCH ₂ —CH _(OH) CH 2 -OH
[Wherein, m and n are integers, and the number average molecular weight is 500 to 5,000. ]
The lubricant which consists of a fluorine-containing compound represented by these is disclosed.

Further, Patent Document _{3, -CF 2 O -, -} CF 2 CF 2 O- from selected perfluorooxyalkylene units becomes more sequences randomly distributed, further comprising a functional end group A, the formula (1 ) And (5)
_{A-OCH 2 CF 2 O (} CF 2 CF 2 O) p (CF 2 O) qCF 2 CH 2 O-A (1)
A- _{[OCH 2 CF 2 O (CF 2} CF 2 O) p (CF 2 O) qCF 2 CH 2 OH ] _6-z (5)
[In formula, A is a specific group, p and q are real numbers of 1-30, z is an integer of 1-5. ]
The lubricant containing the phosphazene compound represented by these is disclosed.

Patent Document 4 discloses a specific phosphazene compound A and a general formula (2).
_{HOCH 2 -CF 2 O- (C 2} F 4 O) p - (CF 2 O) q -CH 2 OH ··· (2)
[Wherein, p is an integer in the range of 4 to 60, and q is an integer in the range of 4 to 60. ]
Compound B ₁ or general formula (3)
_{HOCH 2 CH (OH) -CH 2} OCH 2 CF 2 O- (C 2 F 4 O) r - (CF 2 O) s -CF 2 CH 2 OCH 2 -CH (OH) CH 2 OH ··· (3 )
[Wherein, r is an integer in the range of 4 to 36, and s is an integer in the range of 4 to 36. ]
Lubricant containing a compound B ₂ shown in, is disclosed. Here, a weight ratio of Compound A to Compound _{B 1} (A / _{B 1)} or the weight ratio of Compound A to Compound _{B 2} (A / _{B 2)} is in the range of 0.05 to 0.3.

Further, Patent Document 5 discloses a formula (1).
^{_{R 1 -C 6 H 4 OCH 2}} CH (OH) CH 2 OCH 2 -R 2 -CH 2 -O-R 3
(In the formula, R ¹ is H, an alkoxy group having 1 to 4 carbon atoms, an amino group, or an amide group. R ² is —CF ₂ O (CF ₂ CF ₂ O) _x (CF ₂ O) _y. CF ₂ —, or —CF ₂ CF ₂ O (CF ₂ CF ₂ CF ₂ O) _z CF ₂ CF ₂ —, or —CF ₂ CF ₂ CF ₂ O (CF ₂ CF ₂ CF ₂ CF ₂ O) _n CF ₂ CF ₂ CF _2- , x and y are each a real number of 0 to 15. z is a real number of 1 to 15. n is a real number of 0 to 4. R ³ is H,- CH ₂ CH (OH) CH ₂ OH, or —CH ₂ CH (OH) CH ₂ OCH ₂ CH (OH) CH ₂ OH, or — (CH ₂ ) _m OH, where m is an integer of 2 to 6. .)
The lubricant containing the compound represented by this is disclosed.

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

  Here, in order to improve the recording density by reducing the flying height of the magnetic head of the magnetic recording / reproducing apparatus, it is required to make the lubricant layer much thinner.

  However, when the lubricant layer is made thin, a gap is formed in the lubricant layer, the coverage of the surface of the magnetic recording medium by the lubricant layer is lowered, and a part of the lower layer of the lubricant layer may be exposed. . And when a gap is formed in the lubricant layer, a siloxane-based silicone used as a rubber seal for sealing a magnetic recording / reproducing device as an environmental substance that generates a contaminant in the lower layer of the lubricant layer from the gap in the lubricant layer Outgas from rubber enters and the surface of the magnetic recording medium is contaminated (see, for example, Patent Document 4).

  One embodiment of the present invention has been made in view of the above circumstances, and provides a magnetic recording medium capable of effectively preventing contamination of the surface of the magnetic recording medium even when the lubricant layer is thinned. For the purpose.

[1] A magnetic layer, a protective layer, and a lubricant layer are sequentially laminated on a nonmagnetic substrate. The protective layer contains carbon or hydrogenated carbon, and the lubricant layer is in contact with the protective layer. and which, the protective layer comprises a N at the interface between the lubricant layer, the lubricant layer has the general formula ^{_{R 1 -C 6 H 4 OCH 2}} CH (OH) CH 2 OCH 2 -R 2 -CH _{2 OCH 2 CH (OH) CH} 2 OC 6 H 4 -R 1 ··· (1)
(Wherein R ¹ is an alkoxy group having 1 to 4 carbon atoms, and R ² is a general formula —CF ₂ O (CF ₂ CF ₂ O) _x (CF ₂ O) _y CF ₂ —
(Wherein x and y are each an integer of 0 to 15)
A group represented by the general formula _{-CF 2 CF 2 O (CF 2} CF 2 CF 2 O) z CF 2 CF 2 -
(In the formula, z is an integer of 1 to 15.)
Or a group represented by the general formula —CF ₂ CF ₂ CF ₂ O (CF ₂ CF ₂ CF ₂ CF ₂ O) _n CF ₂ CF ₂ CF ₂ —
(In the formula, n is an integer of 0 to 4.)
It is group represented by these. )
And a compound represented by the general formula: HOCH ₂ CF ₂ CF ₂ O (CF ₂ CF ₂ CF ₂ O) _m CF ₂ CF ₂ CH ₂ OCH ₂ CH (OH) CH ₂ OH (2)
(In the formula, m is an integer.)
The ratio of the mass of the compound A to the total mass of the compound A and the compound B is in the range of 0.05 to 0.9, and the lubricant layer has an average thickness Is in the range of 0.5 nm to 2 nm.
[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 4000.
[4] The protective layer according to any one of [1] to [3], wherein the content of N at the interface with the lubricant layer is in the range of 50 atomic% to 90 atomic%. 2. A magnetic recording medium according to 1.
[5] A magnetic recording / reproducing apparatus comprising the magnetic recording medium according to any one of [1] to [4] and a magnetic head.

  According to one embodiment of the present invention, it is possible to provide a magnetic recording medium that can effectively prevent contamination of the surface of the magnetic recording medium even when the lubricant layer is thin.

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

  Hereinafter, embodiments of the present invention will be described in detail.

(Magnetic recording medium)
First, a magnetic recording medium according to an embodiment of the present invention will be described.

  FIG. 1 shows an example of the magnetic recording medium of this embodiment.

  As shown in FIG. 1, the magnetic recording medium 11 is a nonmagnetic substrate 1 in which a magnetic layer 2, a protective layer 3, and a lubricant layer 4 are sequentially laminated.

  In the present embodiment, a case where an adhesion layer, a soft magnetic underlayer, a seed layer, and an orientation control layer are sequentially stacked between the nonmagnetic substrate 1 and the magnetic layer 2 will be described as an example. . 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 NiP film or a NiP alloy film is formed on a base made of a metal material such as Al or an Al alloy or an alloy material can be used.

  The nonmagnetic substrate 1 may be a substrate made of a nonmetallic material such as glass, ceramics, silicon, silicon carbide, carbon, or resin, or a NiP film or NiP alloy on a substrate made of this nonmetallic material. A substrate on which a film is formed may be used.

(Adhesion layer)
The adhesion layer prevents the nonmagnetic substrate 1 from proceeding with corrosion when the nonmagnetic substrate 1 and the soft magnetic underlayer are disposed in contact with each other.

  As a material for the adhesion layer, for example, Cr, Cr alloy, Ti, Ti alloy, or 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 can be 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 layer, a Ru film (intermediate layer), and a second soft magnetic layer are sequentially stacked. That is, the soft magnetic underlayer has a structure in which the soft magnetic layers above and below the intermediate layer are anti-ferro-coupled (AFC) by sandwiching the intermediate layer between the two soft magnetic layers. Is preferred. Since the soft magnetic underlayer has an AFC structure, it is possible to increase resistance to an external magnetic field and resistance to a WAIT (Wide Area Tack Erasure) phenomenon, which is a problem specific to perpendicular magnetic recording.

  The 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. By setting the thickness of the soft magnetic underlayer to 15 nm or more, magnetic flux from the magnetic head can be sufficiently absorbed, writing becomes sufficient, and recording / reproduction characteristics can be improved. On the other hand, productivity can be improved by making the thickness of a soft-magnetic underlayer into 80 nm or less.

  The first soft magnetic layer and the second soft magnetic layer are preferably CoFe alloy films. When the first soft magnetic layer and the second soft magnetic layer are CoFe alloy films, 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 soft magnetic layer and the second soft magnetic layer. This promotes the amorphization of the first soft magnetic layer and the second soft magnetic layer, thereby improving the orientation of the seed layer and reducing the flying height of the magnetic head. Become.

  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 the magnetic layer. 2 is provided in order to more firmly fix the magnetization direction of 2 in a direction perpendicular to the nonmagnetic substrate 1.

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

  The thickness of the seed layer is preferably in the range of 2 to 20 nm. By setting the thickness of the seed layer to 2 nm or more, the effect obtained by providing the seed layer can be sufficiently obtained. On the other hand, the crystal size is reduced by setting the thickness of the seed layer to 20 nm or less.

  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 a Ru film or a Ru alloy film.

  The thickness of the orientation control layer is preferably in the range of 5 to 30 nm. By setting the 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 has an easy axis of magnetization 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 has a granular structure containing Co, Cr, and Pt and further containing an oxide. It is preferable. 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, in _{particular, TiO 2, Cr 2 O 3} , SiO ₂ or the like can be suitably used. The first magnetic layer is preferably a composite oxide film to which two or more kinds of oxides are added. Among these, in particular, a Cr ₂ O ₃ —SiO ₂ film, a Cr ₂ O ₃ —TiO ₂ film, a SiO ₂ —TiO ₂ film, or 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 element in the first magnetic layer, 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. Can do.

  The same material as the first magnetic layer can be used for the second magnetic layer.

  The second magnetic layer preferably has a granular structure.

  The third magnetic layer preferably has a non-granular structure containing Co, Cr, and 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 or 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. By setting the thickness of the magnetic layer 2 to 5 nm or more, sufficient reproduction output can be obtained and the thermal fluctuation characteristics can be improved. Further, when the thickness of the magnetic layer 2 is 25 nm or less, enlargement of the magnetic particles in the magnetic layer 2 can be suppressed, noise during recording / reproduction is reduced, and a signal / noise ratio (S / N ratio) is reduced. ) And recording characteristics (OW) can be improved.

  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 each magnetic layer can be facilitated, the dispersion of the magnetization reversal of the entire magnetic particles can be reduced, and the S / N ratio is further improved. be able to.

  The nonmagnetic layer provided between the magnetic layers is, for example, Ru, Ru alloy, CoCr alloy, CoCrX1 alloy (X1 is Pt, Ta, Zr, Re, Ru, Cu, Nb, Ni, Mn, Ge, Si, And at least one element selected from O, N, W, Mo, Ti, V, Zr, and B.) can be preferably used.

In addition, as the nonmagnetic layer provided between the magnetic layers, it is preferable to use an alloy material containing an oxide, a metal nitride, or a metal carbide. Specifically, as the oxide, for example, SiO ₂ , Al ₂ O ₃ , Ta ₂ O ₅ , Cr ₂ O ₃ , MgO, Y ₂ O ₃ , TiO _2, etc. As the metal nitride, for example, AlN, Si For example, TaC, BC, SiC, or the like can be used as the metal carbide such as ₃ N ₄ , TaN, or CrN.

  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.

  In order to achieve a higher recording density, 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. It may be a layer.

  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, lubricant layer)
The protective layer 3 protects the recording layer 2. The protective layer 3 may be composed of a single layer or may be composed of a plurality of layers. The protective layer 3 contains carbon or hydrogenated carbon, and preferably contains carbon.

  In the present embodiment, the lubricant layer 4 is provided in contact with the protective layer 3, and N is contained in the protective layer 3 at the interface with the lubricant layer 4.

  The N content at the interface between the protective layer 3 and the lubricant layer 4 is preferably in the range of 50 atomic% to 90 atomic%. By adopting such a configuration, the protective layer 3 and the lubricant layer 4 are bonded with a high bonding force. As a result, even if the thickness of the lubricant layer 4 is thin, the protective layer 3 has a high coverage rate. The surface of the magnetic recording medium 11 is coated, and contamination of the surface of the magnetic recording medium 11 can be effectively prevented.

  That is, the lubricant layer 4 includes the compound A represented by the general formula (1) and the compound B represented by the general formula (2), but according to the study of the inventors of the present application, the lubricant layer 4 is included in the compound A. It was revealed that the six-membered ring strongly bonded to the carbon atom, and the hydroxyl group contained in Compound B was firmly bonded to N. Therefore, by setting the N content at the interface between the protective layer 3 and the lubricant layer 4 within the above-mentioned specific range, the protective layer 3 and the lubricant layer 4 are particularly bonded with a high bonding force and thus lubricated. Even if the thickness of the agent layer 4 is reduced, the surface of the protective layer 3 can be coated with a high coverage.

  The thickness of the protective layer 3 is preferably in the range of 1 nm to 10 nm. By making the thickness of the protective layer 3 1 nm or more, the effect of protecting the recording layer 2 is sufficient. In addition, by setting the thickness of the protective layer 3 to 10 nm or less, the magnetic spacing in the magnetic recording / reproducing apparatus including the magnetic recording medium 11 can be sufficiently reduced, and the recording density can be further improved. In addition, the durability can be 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.

  As a method for forming the protective layer 3, a sputtering method using a carbon target material, 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 can be used. .

  In the present embodiment, a known method can be used as a method for causing the protective layer 3 to contain N, but a method for containing N in the carbon raw material during film formation, and a method for implanting nitrogen ions into the protective layer 3 Is preferably used. In particular, as a method of nitriding only the interface of the protective layer 3 with the lubricant layer 4, a method in which the protective layer 3 is formed of carbon or hydrogenated carbon and then nitrogen ions are implanted only on the surface thereof, or the protective layer 3 It is preferable to employ a method of nitriding by exposing the surface to nitrogen plasma.

  In the above method, the N concentration at the interface between the protective layer 3 and the lubricant layer 4 is controlled by controlling the concentration of N contained in the carbon raw material, the amount of nitrogen ions implanted, the exposure time to nitrogen plasma, and the nitrogen plasma density. The content of can be controlled.

  As shown in FIG. 1, the lubricant layer 4 is formed on and in contact with the protective layer 3, and is represented by the compound A represented by the general formula (1) and the general formula (2). Compound B.

(Compound A)
In the general formula (1), the general formula of R ² —CF ₂ O (CF ₂ CF ₂ O) _x (CF ₂ O) _y CF ₂ —
The structural units in parentheses x and y of the group represented by the above formula may be bonded in this order, may be bonded in the reverse order, or may be bonded at random.

  The average molecular weight of Compound A is in the range of 1000 to 2500, and preferably in the range of 1300 to 2100. By making the average molecular weight of the compound A 1000 or more, the boiling point can be increased and the stability as the lubricant layer 4 can be increased. Moreover, by making the average molecular weight of the compound A 2500 or less, the viscosity can be lowered and the coating property to the surface of the protective layer 3 can be improved.

As a commercial item of the compound A, ART-2 (s) (made by MORESCO) is mentioned, for example. In ART-2 (s), in general formula (1), R ¹ is a methoxy group, and x and y are in the range of 3 to 7, respectively.

  The average molecular weight can be measured with a mass spectrometer.

(Compound B)
The average molecular weight of Compound B is in the range of 1000 to 4000, and preferably in the range of 1300 to 2500. By setting the average molecular weight of Compound B to 1000 or more, the boiling point can be increased and the stability as the lubricant layer 4 can be increased. Moreover, by making the average molecular weight of the compound B 4000 or less, the viscosity can be lowered and the coating property to the surface of the protective layer 3 can be improved.

  As a commercial item of the compound B, D3OH (s) (made by MORESCO) is mentioned, for example. As for D3OH (s), in General formula (2), m is adjusted so that an average molecular weight may be in the range of 1000-4000.

(Mass ratio (A / (A + B)))
The ratio of the mass of Compound A to the total mass of Compound A and Compound B (hereinafter referred to as mass ratio (A / (A + B))) is in the range of 0.05 to 0.9, 0.1 to 0. It is preferable to be within the range of 8. If the mass ratio (A / (A + B)) is less than 0.05, the compound A is insufficient, the lubricant layer 4 tends to be island-like, the coverage of the protective layer 3 is insufficient, and magnetic recording is performed. Contamination of the surface of the medium 11 cannot be effectively prevented. On the other hand, if the mass ratio (A / (A + B)) exceeds 0.9, the compound B is insufficient, the lubricant layer 4 is likely to become a network, the coverage of the protective layer 3 is insufficient, and the magnetic Contamination of the surface of the recording medium 11 cannot be effectively prevented. In addition, when the mass ratio (A / (A + B)) is in the range of 0.1 to 0.8, the bonding force between the protective layer 3 and the lubricant layer 4 becomes higher, so that a contaminant is generated. It is possible to more effectively prevent the environmental substance to be entered from entering the gaps in the lubricant layer 4.

(Average thickness of lubricant layer)
The average thickness of the lubricant layer 4 is in the range of 0.5 nm (5 Å) to 2 nm (20 Å), and preferably in the range of 1 nm to 1.9 nm. If the average thickness of the lubricant layer 4 is less than 0.5 nm, the lubricant layer 4 becomes an island shape or a mesh shape, and the surface of the protective layer 3 cannot be coated with a high coverage, and the magnetic recording medium 11 The surface contamination cannot be effectively prevented. On the other hand, if the average thickness of the lubricant layer 4 exceeds 2 nm, the flying height of the magnetic head cannot be sufficiently reduced, and the recording density of the magnetic recording medium 11 cannot be increased.

  Note that the lubricant layer having an average thickness of 2 nm or less formed using only the compound A has a network structure because the compound A has a large cyclic skeleton molecular structure, and the surface of the protective layer 3 is sufficiently high. It cannot be coated at a covering rate.

  Further, the lubricant layer formed using only Compound B and having an average thickness of 2 nm or less has an island shape because the bonding strength (wetting property) with the protective layer 3 is insufficient, and the surface of the protective layer 3 is sufficient. It cannot be coated at a high coverage.

  When the surface of the protective layer 3 is not covered with the lubricant layer 4 at a sufficiently high coverage, water containing environmental substances that generate contaminants such as ionic impurities adsorbed on the surface of the magnetic recording medium 11 is lubricated. It passes through the gap of the agent layer 4 and enters the lower layer of the lubricant layer 4. The environmental material that has entered the lower layer of the lubricant layer aggregates minute ionic components present in the lower layer of the lubricant layer 4 to generate ionic contaminants. When recording information on the magnetic recording medium or reproducing information recorded on the magnetic recording medium, ionic contaminants adhere to the magnetic head and damage the magnetic head, The magnetic recording / reproducing characteristics of the recording / reproducing apparatus are deteriorated.

  Problems caused by the intrusion of environmental substances from the gaps in the lubricant layer 4 appear more prominently when the magnetic recording medium 11 is held under high temperature conditions.

(Formation method of lubricant layer)
The lubricant layer 4 is prepared by, for example, preparing a magnetic recording medium in the process of forming each layer up to the protective layer 3 on the nonmagnetic substrate 1 and forming the lubricant layer on the protective layer 3 of the magnetic recording medium in the process of manufacturing. It is formed by applying a coating liquid for use.

  The coating solution for forming the lubricant layer is prepared by mixing compound A and compound B and diluting with a solvent so that the mass ratio (A / (A + B)) is in the range of 0.05 to 0.9. It is obtained by setting the viscosity and concentration suitable for the method.

  Examples of the solvent used in the coating solution for forming the lubricant layer include a fluorine-based solvent such as Vertrel XF (manufactured by Mitsui DuPont Fluorochemical Co., Ltd.).

  The method for applying the lubricant layer forming coating solution is not particularly limited, and examples thereof include a spin coating method and a dip method.

  When using the dip method, for example, the nonmagnetic substrate 1 on which the layers up to the protective layer 3 are formed is immersed in a coating solution for forming a lubricant layer placed in the immersion tank of the dip coater, and then the immersion tank The method of applying the lubricant layer forming coating solution on the surface of the nonmagnetic substrate 1 on the protective layer 3 by pulling up the nonmagnetic substrate 1 at a predetermined speed can be used. By using the dip method, the lubricant layer forming coating solution can be uniformly applied to 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. can do.

(Magnetic recording / reproducing device)
Next, a magnetic recording / reproducing apparatus according to an embodiment of the present invention will be described.

  FIG. 2 shows an example of the magnetic recording / reproducing apparatus of this embodiment.

  The magnetic recording / reproducing apparatus 101 includes a magnetic recording medium 11 shown in FIG. 1, a medium driving unit 123 that drives the magnetic recording medium 11 in the recording direction, a recording unit that records information on the magnetic recording medium 11, and the magnetic recording medium 11. A magnetic head 124 including a reproducing unit for reproducing information recorded on the head, a head moving unit 126 for moving the magnetic head 124 relative to the magnetic recording medium 11, and processing the input information to record a recording signal. And a recording / reproduction signal processing unit 128 that processes the reproduction signal received from the reproduction unit and outputs information.

  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 includes the magnetic recording medium 11 with a small amount of contaminants present on the magnetic recording medium, the contaminants present on the magnetic recording medium 11 are caused by the magnetic head 124 of the magnetic recording / reproducing apparatus 101. Therefore, it is possible to prevent the recording / reproducing characteristics from being deteriorated and the flying stability from being deteriorated. Therefore, the magnetic recording / reproducing apparatus 101 has stable recording / reproducing characteristics.

  Hereinafter, based on an Example, this invention is demonstrated concretely. In addition, this invention is not limited only to these Examples.

(Examples 1-14, Comparative Examples 1-7)
The washed outer diameter of 2.5 inches glass substrate (manufactured by HOYA Corporation), and housed in a deposition chamber of a DC magnetron sputtering device C-3040 (Anerva), ultimate vacuum (1 × 10 ^{- The} inside of the film formation chamber was evacuated until ⁵ Pa).

  Thereafter, an adhesion layer having a thickness of 10 nm was formed on the glass substrate by sputtering using a Cr target.

  Next, by sputtering, as a soft magnetic underlayer on the adhesion layer, Co-20Fe-5Zr-5Ta {Fe content 20 atomic%, Zr content 5 atomic%, Ta content 5 atomic%, balance Co} A first soft magnetic layer having a thickness of 25 nm was formed at a substrate temperature of 100 ° C. or lower using a target. Furthermore, a Ru film (intermediate layer) having a thickness of 0.7 nm and a Co-20Fe-5Zr-5Ta film (second soft magnetic layer) having a thickness of 25 nm were formed thereon.

  Next, a seed layer having a thickness of 5 nm was formed on the soft magnetic underlayer by sputtering using a Ni-6W {W content 6 atom%, remaining Ni} target.

  Thereafter, a Ru layer having a thickness of 10 nm and a sputtering pressure of 0.8 Pa was formed as a first orientation control layer on the seed layer by sputtering. Next, a Ru layer having a thickness of 10 nm and a sputtering pressure of 1.5 Pa was formed as a second alignment control layer by sputtering on the first alignment control layer.

Then, on the second orientation control layer by a sputtering method, 91 (Co-15Cr-16Pt ) -6 (SiO 2) -3 (TiO 2) {(Cr content 15 atomic%, Pt content of 16 (Atom%, balance Co alloy) 91 mol%, SiO ₂ 6 mol%, TiO ₂ 3 mol%} film (first magnetic layer) was deposited to a thickness of 9 nm at a sputtering pressure of 2 Pa.

Next, an 88 (Co-30Cr) -12 (TiO ₂ ) {(Cr content of 30 atomic%, balance Co alloy) 88 mol%, TiO ₂ 12 mol%} film is formed on the first magnetic layer by sputtering. (Nonmagnetic layer) was formed to a thickness of 0.3 nm.

Then, 92 (Co-11Cr-18Pt) -5 (SiO ₂ ) -3 (TiO ₂ ) {(Cr content of 11 atomic%, Pt content of 18 atomic%, and the balance on the nonmagnetic layer by sputtering. (Co alloy) 92 mol%, SiO ₂ 5 mol%, TiO ₂ 3 mol%} film (second magnetic layer) was formed at a sputtering pressure of 2 Pa and a thickness of 6 nm.

  Thereafter, a Ru film (nonmagnetic layer) was formed on the second magnetic layer by sputtering to have a thickness of 0.3 nm.

  Next, a Co-20Cr-14Pt-3B {Cr content 20 atomic%, Pt content 14 atomic%, B content 3 atomic%, balance Co} target is formed on the nonmagnetic layer by sputtering. The third magnetic layer was deposited to a thickness of 7 nm at a sputtering pressure of 0.6 Pa.

  Next, a hydrogenated carbon film was formed on the surface of the magnetic layer by ion beam evaporation. Gasified toluene was used as a source gas for forming a hydrogenated carbon film. As film formation conditions, 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, 180 mA, the film formation time is 1.5 seconds, and the thickness is 3.5 nm. A hydrogenated carbon film was formed.

  After forming the hydrogenated carbon film, 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 was set to 128 W (AC16V, 8A). Further, the voltage between the cathode electrode and the anode electrode is 75 V, the current is 1000 mA, the ion acceleration voltage is 200 V, 90 mA, the treatment time is 1 second, and nitrogen ions formed from nitrogen gas are applied to the surface of the hydrogenated carbon film. Irradiated. Thus, the surface of the hydrogenated carbon film was dehydrogenated and nitrided to form a protective layer.

  When the composition of the outermost surface of the protective layer (interface of the protective layer with the lubricant layer) was measured by secondary ion mass spectrometry (SIMS), N was 80 atomic% and C was 20 atomic% (Example) 1).

  In Examples 2 to 11 and Comparative Examples 1 to 10, the composition of the outermost surface of the protective layer is shown in Table 1 by adjusting the time for dehydrogenating and nitriding the surface of the hydrogenated carbon film. Was changed.

  Next, as shown below, a coating solution for forming a lubricant layer was prepared.

  As compound A, ART-2 (s) (manufactured by MORESCO) having an average molecular weight of 1700 was used, and as compound B, D3OH (s) (manufactured by MORESCO) having an average molecular weight of 1700 was used (Example 1). To 14, Comparative Example 7).

  In addition, as shown in Table 1, A2OH-2000 (manufactured by MORESCO) (abbreviated as “A2OH” in Table 1) or ADOH-2000 (manufactured by MORESCO) (“ADOH” in Table 1) Abbreviated as). Neither A2OH nor ADOH corresponds to Compound A, but in Table 1, it is described as Compound A for convenience.

  A2OH-2000 is a general formula

において、ｘが５であり、Ｒ_１がＣＦ_３であり、Ｒ_２が、化学式
−ＯＣＨ_２ＣＦ_２Ｏ（ＣＦ_２ＣＦ_２Ｏ）_１１（ＣＦ_２Ｏ）_１０ＣＦ_２ＣＨ_２ＯＨ
で表される基である化合物である。

In the above, x is 5, R ₁ is CF ₃ , and R ₂ is represented by the chemical formula —OCH ₂ CF ₂ O (CF ₂ CF ₂ O) ₁₁ (CF ₂ O) ₁₀ CF ₂ CH ₂ OH.
It is a compound which is group represented by these.

In addition, in the general formula (3), in the ADOH-2000, x is 5, R ₁ is CF ₃ , and R ₂ is represented by the chemical formula —OCH ₂ CF ₂ O (CF ₂ CF ₂ O) ₁₁ (CF ₂ ). _{O) 10 CF 2 CH 2 OCH} 2 CH (OH) CH 2 OH
It is a compound which is group represented by these.

  And mass ratio (A / (A + B)) was adjusted as shown in Table 1, and it was set as the coating liquid for lubricant layer formation.

  In addition, as the solvent of the coating liquid for forming the lubricant layer of Examples 1 to 14 and Comparative Examples 1 to 7, Bertrell XF (manufactured by Mitsui DuPont Fluorochemical Co., Ltd.) was used. Moreover, all the density | concentrations of the lubrication agent in the coating liquid for lubricant layer formation of Examples 1-14 and Comparative Examples 1-7 were 0.3 mass%.

  Next, using the dipping method, the lubricant layer forming coating solutions of Examples 1 to 14 and Comparative Examples 1 to 7 were respectively applied on the protective layer of the nonmagnetic substrate by the method shown below.

  That is, the nonmagnetic substrate on which each layer up to the protective layer is formed is immersed in the lubricant layer forming coating solution placed in the immersion tank of the dip coater, and then the nonmagnetic substrate is moved from the immersion tank to a constant speed. The coating solution for forming the lubricant layer was applied to the surface of the nonmagnetic substrate on the protective layer. The average thickness of the lubricant layer was all 1.3 nm.

  Then, the lubricant layer was formed by drying the surface on which the coating liquid for forming the lubricant layer was applied, and magnetic recording media of Examples 1 to 14 and Comparative Examples 1 to 7 were obtained.

(Environmental resistance of magnetic recording media)
The environmental resistance of the magnetic recording media of Examples 1 to 14 and Comparative Examples 1 to 7 was evaluated by the following method. The environmental resistance evaluation method described below is one of the methods for evaluating the contamination of the magnetic recording medium by environmental substances that generate pollutants in a high temperature environment. In the environmental resistance evaluation shown below, Si ions are used as an environmental material that generates pollutants in a high temperature environment, and the amount of adsorbed Si is determined as the amount of pollutants that contaminate magnetic recording media generated by the environmental material. It was measured.

  Specifically, first, the magnetic recording medium to be evaluated was held for 240 hours in the presence of a siloxane-based silicone rubber in a high-temperature environment at a temperature of 85 ° C. and a humidity of 0%.

  Next, the amount of Si adsorption existing on the surface of the magnetic recording medium was analyzed and measured using SIMS, and the degree of contamination by Si ions, which are environmental substances in a high temperature environment, was evaluated as the amount of Si adsorption.

  In addition, evaluation of Si adsorption amount was evaluated using the numerical value when the result of the comparative example 1 was set to 1.00.

  Table 1 shows the evaluation results of the environmental resistance of the magnetic recording medium.

  From Table 1, it became clear that the magnetic recording media of Examples 1 to 14 have a small amount of Si adsorption and can effectively prevent surface contamination under a high temperature environment.

  On the other hand, since the magnetic recording media of Comparative Examples 1 and 2 include a lubricant layer containing A2OH or ADOH instead of compound A and not containing compound B, the amount of Si adsorption increases.

  In the magnetic recording media of Comparative Examples 3 and 4, since the lubricant layer containing only Compound A or Compound B is formed, the amount of Si adsorption increases.

  In the magnetic recording media of Comparative Examples 5 and 6, since the lubricant layer containing A2OH or ADOH is formed instead of the compound A, the amount of Si adsorption increases.

  Since the magnetic recording medium of Comparative Example 7 does not contain N on the surface of the protective layer, the amount of Si adsorption increases.

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 moving part 128 Recording / reproducing signal processing part

Claims (5)

On the nonmagnetic substrate, a magnetic layer, a protective layer, and a lubricant layer are sequentially laminated,
The protective layer comprises carbon or hydrogenated carbon;
The lubricant layer is in contact with the protective layer,
The protective layer includes N at the interface with the lubricant layer,
The lubricant layer has a general formula R ¹ —C ₆ H ₄ OCH ₂ CH (OH) CH ₂ OCH ₂ —R ² —CH ₂ OCH ₂ CH (OH) CH ₂ OC ₆ H ₄ —R ^1. 1)
(Wherein R ¹ is an alkoxy group having 1 to 4 carbon atoms, and R ² is a general formula —CF ₂ O (CF ₂ CF ₂ O) _x (CF ₂ O) _y CF ₂ —
(Wherein x and y are each an integer of 0 to 15)
A group represented by the general formula _{-CF 2 CF 2 O (CF 2} CF 2 CF 2 O) z CF 2 CF 2 -
(In the formula, z is an integer of 1 to 15.)
Or a group represented by the general formula —CF ₂ CF ₂ CF ₂ O (CF ₂ CF ₂ CF ₂ CF ₂ O) _n CF ₂ CF ₂ CF ₂ —
(In the formula, n is an integer of 0 to 4.)
It is group represented by these. )
And a compound represented by the general formula: HOCH ₂ CF ₂ CF ₂ O (CF ₂ CF ₂ CF ₂ O) _m CF ₂ CF ₂ CH ₂ OCH ₂ CH (OH) CH ₂ OH (2)
(In the formula, m is an integer.)
And the ratio of the mass of the compound A to the total mass of the compound A and the compound B is in the range of 0.05 to 0.9,
The magnetic recording medium, wherein the lubricant layer has an average thickness in a range of 0.5 nm to 2 nm.   The magnetic recording medium according to claim 1, wherein the compound A has an average molecular weight in the range of 1000 to 2500.   The magnetic recording medium according to claim 1, wherein the compound B has an average molecular weight in the range of 1000 to 4000.   4. The magnetic recording according to claim 1, wherein the protective layer has an N content in an interface with the lubricant layer in a range of 50 atomic% to 90 atomic%. Medium.   A magnetic recording / reproducing apparatus comprising: the magnetic recording medium according to claim 1; and a magnetic head.

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