JP6257117B2 - Magnetic recording medium and magnetic recording / reproducing apparatus - Google Patents

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.
This application includes Japanese Patent Application No. 2014-257205 filed in Japan on December 19, 2014, Japanese Patent Application No. 2015-119737 filed in Japan on June 12, 2015, and June 12, 2015. Claim priority based on Japanese Patent Application No. 2015-119743 filed in Japan, the contents of which are incorporated herein.

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

  For this reason, in general, a lubricant is applied to the surface of the protective layer to form a lubricant layer, thereby improving the durability of the magnetic recording medium. Providing the lubricant layer can prevent direct contact between the magnetic head of the magnetic recording / reproducing apparatus and the protective layer. Further, by providing the lubricant layer, the frictional force between the magnetic recording medium and the magnetic head sliding on the magnetic recording medium is remarkably reduced. Further, the lubricant layer has a role of preventing the magnetic layer or the like of the magnetic recording medium from being corroded by impurities entering from the surrounding environment.

Conventionally, as a lubricant used for a lubricant layer of a magnetic recording medium, there are a perfluoropolyether lubricant and an aliphatic hydrocarbon lubricant.
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 in which an ether lubricant is coated on a carbon protective film 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) represented by OH (p and q are integers) is disclosed.

  Patent Document 3 describes a magnetic recording medium having a lubricant layer in which a phosphazene compound and a compound having a perfluorooxyalkylene unit are mixed within a specific range. Patent Document 3 discloses that this lubricant layer has a 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 4 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 . .

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

  In a magnetic recording / reproducing apparatus, it is required to further improve the recording density and reduce the flying height of the magnetic head. In order to meet this requirement, it is preferable to further reduce the thickness of the lubricant layer of the magnetic recording medium. However, when the thickness of the lubricant layer is reduced, a gap is easily formed in the lubricant layer. As a result, the coverage of the lubricant layer covering the surface of the protective layer is reduced. When an environmental substance that generates a contaminant enters the lower layer of the lubricant layer from a gap between the lubricant layers having a low coverage, a contaminant that contaminates the magnetic recording medium such as an ionic impurity is generated by the environmental substance.

  The present invention has been made in view of the above circumstances, and includes a magnetic recording medium in which the surface of a protective layer is coated with a sufficiently thin lubricant layer with a high coverage and high bonding properties. It is an object to provide a magnetic recording / reproducing apparatus.

In order to solve the above problems, the present inventor has intensively studied as follows.
That is, it is known that the compound used as the material for the lubricant layer has a higher bondability with a protective layer formed of carbon or the like as the number of OH groups contained in the molecular structure is larger. Therefore, conventionally, the number of OH groups contained in the compound used in the lubricant layer tended to increase to 2, 4, 6, and 8.

  However, as a result of studies by the present inventors, when the number of OH groups in the compound is increased, the surface energy of the magnetic recording medium having the lubricant layer containing this compound is increased by the interaction between the OH groups. It was revealed. Further, increasing the number of OH groups in the compound tends to increase the molecular weight of the compound. For this reason, the viscosity of the lubricant containing the compound is increased, the applicability of the lubricant is lowered, and the lubricant layer formed by applying the lubricant is more likely to have an island shape or a mesh shape.

Therefore, the present inventor has focused on the surface energy of the magnetic recording medium in order to optimize the material of the lubricant layer. That is, conventionally, as a method for evaluating the coverage of the lubricant layer formed on the surface of the magnetic recording medium, a lubricant layer is formed on the magnetic layer to evaluate the corrosion resistance under a high temperature and high humidity environment. There was only an indirect method. This is because the thickness of the lubricant layer of the magnetic recording medium is as thin as about 1 nm, and direct analysis is difficult. This makes it difficult to optimize the material of the lubricant layer. In contrast, the inventor of the present application only needs to calculate the ^total surface energy (hereinafter sometimes referred to as “γ ^total ”) on the surface of the magnetic recording medium by calculation, and form a lubricant layer having a sufficiently low γ ^total . I found out.

The surface energy (γ ^total ) is a total value (γ ^total = γ), where γ ^AB is a parameter representing the bonding property between the lubricant layer and the protective layer, and γ ^LW is a parameter representing the coating property of the lubricant. ^AB + γ ^LW (unit of γ ^total , γ ^AB , γ ^LW is mJ / m ² )). γ ^AB and γ ^LW can be calculated by the method described in, for example, The Measurement of Surface Energy of Polymers by Means of Contact Angles of Liquids on Solid Surfaces (2004, Finn Knut Hansen, University of Oslo). A lower γ ^AB indicates a higher binding property, and a lower γ ^LW indicates a higher covering property.

Therefore, the lower the γ ^AB and γ ^LW (that is, the lower the surface energy (γ ^total )), the less the thickness of the lubricant layer, the less the island-like or network-like shape, and the higher the coverage on the surface of the protective layer. And has binding properties.

This inventor repeated examination about the material from which the lubricant layer with low surface energy ((gamma) ^total ) is obtained. As a result, the surface energy (γ ^total ) is obtained by making the compound A represented by the following general formula (1) and the compound B represented by the following general formula (2) into a predetermined film thickness at a predetermined ratio. It has been found that a sufficiently low lubricant layer can be obtained. And it confirmed that such a lubricant layer had the high coverage with respect to the surface of a protective layer, and bondability, and came to complete this invention shown below.

[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, wherein the protective layer is made of carbon or carbon nitride, and the lubricant layer is It is formed on the protective layer and includes a compound A represented by the following general formula (1) and a compound B represented by the following general formula (2), and the mass ratio of the compound A to the compound B (A / B) is in the range of 0.2 to 3.0, and the average film thickness of the lubricant layer is 0.8 nm to 2 nm.

_{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 in parentheses, in this order, or in reverse, or linked to good (x, y are real numbers respectively 0-15.) randomly.), or _{-CF 2 CF 2 O (CF 2} CF 2 CF 2 O) zCF ₂ CF ₂ — (z is a real number from 1 to 15), or —CF ₂ CF ₂ CF ₂ O (CF ₂ CF ₂ CF ₂ CF ₂ O) nCF ₂ CF ₂ CF ₂ —. (N is a real number from 0 to 4.)

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

[2] The magnetic recording medium according to [1], wherein the total surface energy on the surface of the magnetic recording medium is 25.5 mJ / m ² or less.
[3] The magnetic recording medium according to claim 1, wherein the compound A has an average molecular weight in the range of 1500 to 1800.
[4] The magnetic recording medium according to [1], wherein the compound B has an average molecular weight in the range of 1000 to 1700.

[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.

  In the magnetic recording medium of the present invention, the lubricant layer formed in contact with the protective layer contains a predetermined ratio of the compound A represented by the general formula (1) and the compound B represented by the general formula (2). In a predetermined film thickness. For this reason, a magnetic recording medium is obtained in which the surface of the protective layer is coated with a sufficiently thin lubricant layer with a sufficiently thin thickness and a high bondability.

Therefore, in the magnetic recording medium of the present invention, environmental substances that generate contaminants such as ionic impurities are prevented from entering through the gaps in the lubricant layer, and contamination of the magnetic recording medium due to environmental substances is prevented. . Therefore, the magnetic recording medium of the present invention has excellent environmental resistance and stable magnetic recording / reproducing characteristics.
In addition, since the magnetic recording medium of the present invention has a sufficiently thin lubricant layer, the recording density can be further improved.

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, the magnetic recording medium and magnetic recording / reproducing apparatus of the present invention will be described in detail. In addition, this invention is not limited only to embodiment shown below.
First, the lubricant layer formed in contact with the protective layer made of carbon or carbon nitride in the magnetic recording medium of the present invention will be described.

"Lubricant layer"
As described above, the present inventor examined the optimization of the material of the lubricant layer by paying attention to the surface energy of the magnetic recording medium. Then, a lubricant layer that can reduce the ^total surface energy γ ^total (γ ^total = γ ^AB + γ ^LW ) on the surface of the magnetic recording medium was examined.

γ ^AB is a surface energy that is formed by Lewis acid-base interaction. With γ ^AB , the equilibrium state of electrons existing in the protective layer and the lubricant layer can be estimated. Generally, the protective layer (Lewis base) is an electron donor, and the lubricant layer (Lewis acid) is an electron acceptor. A low value of γ ^AB can be said to be a state in which the interaction between the protective layer and the lubricant layer is sufficiently exhibited. Therefore, it can be considered that the low value of γ ^AB means that the bonding property between the lubricant layer and the protective layer is high.

[gamma] ^LW is a surface energy indicating a London dispersion force or a van der Waals force composed of Dipole-Dipole quantum theory. The dispersibility of the compound forming the lubricant layer can be estimated by γ ^LW . It can be said that the low value of γ ^LW is a state in which the coverage of the lubricant layer is sufficiently exhibited. Therefore, a low value of γ ^LW can be considered to have a high effect of preventing exposure of the protective layer (high coverage).

γ ^AB and γ ^LW were calculated by the following procedure. First, the contact angle on the protective layer of the magnetic recording medium was measured using three types of solvents (solvent A, solvent B, and solvent C).
The contact angle can be measured by a known method. That is, a certain amount of solvent is dropped on the surface of the protective layer of the magnetic recording medium, and the angle formed by the water droplet and the surface of the protective layer after a lapse of a certain time is measured with a contact angle meter.
In the present invention, water was used as the solvent A, methylene iodide as the solvent B, and ethylene glycol as the solvent C. The contact angle when the solvent A was used was θ _A , the contact angle when the solvent B was used was θ _B , and the contact angle when the solvent C was used was θ _C.

Formulas and parameters used for calculating γ ^AB and γ ^LW are as follows.
In the following formula, the number 1 in a symbol such as “γ ₁ ⁺ ” indicates a solvent parameter, and the number 2 in a symbol such as “γ ₂ ⁺ ” indicates a lubricant parameter. In addition, “ ⁺ ” in a symbol such as “γ ₁ ⁺ ” indicates a parameter indicating the contribution of electron acceptability of the Van Oss method, and “ ⁻ ” in a symbol such as “γ ₁ ⁻ ” indicates a Van Oss. It is a parameter indicating the contribution of electron donating properties of the method.
γ ^total , γ ^AB , and γ ^LW were determined by solving the following simultaneous equations using Solvent A to Solvent C in which γ ₁ , γ ₁ ^LW , γ ₁ ⁺ , and γ ₁ ⁻ are known.

_{^{γ AB = 2 (γ 1 +}} γ 2 -) 1/2 +2 (γ 1 - γ 2 +) 1/2
γ ^LW = 2 (γ ₁ ^LW γ ₂ ^LW ) ^1/2
_{γ 1A (1 + COSθ A)} = 2 (γ 1A LW γ 2 LW) 1/2 +2 (γ 1A + γ 2 -) 1/2 +2 (γ 1A - γ 2 +) 1/2
γ _1B (1 + COSθ _B ) = 2 (γ _1B ^LW γ ₂ ^LW ) ^1/2 +2 (γ _1B ⁺ γ ₂ ⁻ ) ^{1 /
_{2 +2 (γ 1B - γ 2}} +) 1/2
_{γ 1C (1 + COSθ C)} = 2 (γ 1C LW γ 2 LW) 1/2 +2 (γ 1C + γ 2 -) 1/2 +2 (γ 1C - γ 2 +) 1/2

Water: γ _1A = 72.8, γ _1A ^LW = 21.8, γ _1A ⁺ = 25.5, γ _1A ⁻ = 25.5
Methylene iodide: γ _1B = 50.8, γ _1B ^LW = 50.8, γ _1B ⁺ = 0, γ _1B ⁻ = 0
Ethylene glycol: γ _1C = 48.0, γ _1C ^LW = 29.0, γ _1C ⁺ = 1.92 and γ _1C ⁻ = 47.0

The lubricant layer of the magnetic recording medium of the present embodiment preferably has a total surface energy (γ ^total ) on the surface of the magnetic recording medium calculated by the above method of 27.25 mJ / m ² or less. Total surface energy (gamma ^total) is preferably at 27.0mJ / ^{m 2} or less, and more preferably 25.5mJ / ^{m 2} or less. When the surface energy (γ ^total ) is 27.25 mJ / m ² or less, a magnetic recording medium is obtained in which the surface of the protective layer is coated with the lubricant layer with a high coverage and high bondability.

The lubricant layer of the magnetic recording medium of the present embodiment contains the compound A represented by the general formula (1) and the compound B represented by the general formula (2). In order to obtain a lubricant layer having a low surface energy (γ ^total ), it is necessary to suppress interaction between OH groups in a compound contained in the lubricant layer. For this reason, in this embodiment, as the compound A and the compound B, those having three OH groups in the molecular structure are used. Further, Compound A and Compound B have three OH groups contained in the molecular structure. For this reason, compared with a compound having 4 or more OH groups, it tends to be a compound having a preferable molecular weight. Therefore, a lubricant layer formed by applying a lubricant containing Compound A and Compound B is preferable because it is unlikely to form an island shape or a network shape. In addition, since the lubricant layer contains the compound A and the compound B, the lubricant layer having a higher binding property to the protective layer than the case where the compound having one or two or more OH groups is used. can get.

The compound A represented by the general formula (1) mainly contributes to the coverage of the lubricant layer on the surface of the protective layer. By including the compound A in the lubricant layer, the value of γ ^LW is lowered, and the surface energy (γ ^total ) is likely to be lowered.
The average molecular weight of the compound A represented by the general formula (1) is preferably in the range of 1500 to 2000, and more preferably in the range of 1500 to 1800. When the average molecular weight of Compound A is within the above range, a lubricant having a sufficiently low viscosity and easy to apply can be obtained when a lubricant containing Compound A and Compound B is applied to form a lubricant layer. When the average molecular weight of Compound A is in the range of 1500 to 1800, a lubricant having a lower viscosity and easier to apply is obtained, which is preferable. Moreover, when the average molecular weight of the compound A is more than 1800 to 2000, a lubricant layer in which the thickness is hardly reduced even when used in a high temperature and high humidity environment is obtained, and excellent durability is obtained.

  The compound A represented by the general formula (1) includes, for example, a linear fluoropolyether having a hydroxyl group at one end and a hydroxyalkyl group at the other end, as disclosed in Patent Document 4, and an epoxy. It is obtained by reacting with a phenoxy compound having a group.

As a commercially available compound A represented by the general formula (1), for example, ART-1 (trade name), DART-1 (trade name) manufactured by MORESCO, etc. can be used.
ART-1 is, R1 in the general formula (1) is an alkoxy group having one carbon atom, R2 is _{-CF 2 O (CF 2 CF 2} O) x (CF 2 O) yCF 2 - a. ART-1 is prepared by adjusting x and y of R2 such that the average molecular weight is 1500-1800.
DART-1 is, R1 in the general formula (1) is an alkoxy group having one carbon atom, R2 is _{-CF 2 CF 2 O (CF 2} CF 2 CF 2 O) zCF 2 CF 2 - is. In DART-1, z of R2 is adjusted so that the average molecular weight is in the range of 1500 to 2000.

The compound B represented by the general formula (2) mainly contributes to the bonding force between the protective layer and the lubricant layer. When the lubricant layer contains the compound B, the value of γ ^AB becomes low, and the surface energy (γ ^total ) tends to become low.
The average molecular weight of the compound B represented by the general formula (2) is preferably in the range of 1000 to 2000, and more preferably in the range of 1000 to 1700. When the average molecular weight of Compound B is within the above range, a lubricant having a sufficiently low viscosity can be obtained when a lubricant containing Compound A and Compound B is applied to form a lubricant layer. preferable. When the average molecular weight of Compound B is in the range of 1000 to 1700, a lubricant having a lower viscosity and easier to apply is obtained, which is preferable. Moreover, when the average molecular weight of the compound B is more than 1700 to 2000, a lubricant layer in which the thickness is hardly reduced even when used in a high temperature and high humidity environment is obtained, and excellent durability is obtained.

  Compound B represented by general formula (2) can be produced, for example, by the following method. That is, an alcohol that is a precursor of a perfluoropolyether containing the basic skeleton of Compound B is synthesized, and this alcohol is modified to synthesize a mixture having a terminal group structure of a diol compound, a triol compound, or a tetraol compound. . Thereafter, only the compound B which is a triol compound is separated and purified from this mixture.

  In the lubricant layer of the magnetic recording medium of the present embodiment, the mass ratio (A / B) of the compound A represented by the general formula (1) to the compound B represented by the general formula (2) is in the range of 0.2 to 3.0. It is preferable that it is in the range of 0.25 to 2.3. By setting the mass ratio (A / B) within the range of 0.2 to 3.0, the surface of the protective layer is coated with a lubricant layer with a high coverage and high bonding properties.

  When the mass ratio (A / B) exceeds 3.0, the compound B is insufficient. For this reason, the lubricant layer tends to have an island shape, and the coverage of the protective layer becomes insufficient. Moreover, when the mass ratio (A / B) is less than 0.2, the compound A is insufficient. For this reason, the lubricant layer is likely to become a network, and the bonding force between the protective layer and the lubricant layer becomes insufficient.

The lubricant layer has an average film thickness in the range of 0.8 nm (8 cm) to 2 nm (20 cm), and preferably in the range of 1 nm to 1.9 nm. By setting the average thickness of the lubricant layer to 0.8 nm or more, the lubricant layer does not have an island shape or a mesh shape, and the lubricant layer allows the surface of the protective layer to have a uniform thickness and high coverage. Can be coated. As the average film thickness of the lubricant layer is thicker, the values of γ ^AB and γ ^LW are lower, so the surface energy (γ ^total ) is lower. Therefore, as the average film thickness of the lubricant layer is thicker, the surface of the protective layer is covered with the lubricant layer with a higher coverage and higher bonding properties. Further, by setting the average thickness of the lubricant layer to 2 nm or less, the flying height of the magnetic head can be made sufficiently small, and the recording density of the magnetic recording medium can be increased.

"Magnetic recording media"
Embodiments of the present invention will be described below in detail with reference to the drawings.
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 this embodiment has a magnetic layer 2, a protective layer 3, and a lubricant layer 4 according to the above-described embodiment laminated on a nonmagnetic substrate 1 in this order. It is.

  In the present embodiment, a case where 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 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.

  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 material such as Al or an alloy material such as an 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.

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 can be sufficiently obtained.
The adhesion layer can be formed by, for example, a sputtering method.

  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 an intermediate layer made of a Ru film is sandwiched between two soft magnetic films so that upper and lower soft magnetic films of the intermediate layer are anti-ferro-coupled (AFC) coupled. It is preferable to have. Since the soft magnetic underlayer has an AFC-coupled structure, it has 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. Can be increased.

  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 one or more 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, improves the orientation of the seed layer formed on the soft magnetic underlayer, and reduces the flying height of the magnetic head. It becomes possible to reduce.
The soft magnetic underlayer can be formed by, for example, a sputtering method.

  The seed layer controls the orientation and crystal size of the orientation control layer and the magnetic layer 2 provided thereon. By providing the seed layer, the component perpendicular to the substrate surface of the magnetic flux generated from the magnetic head is increased, and the magnetization direction of the magnetic layer 2 is more firmly fixed in the direction perpendicular to the nonmagnetic substrate 1. The

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, for example, a sputtering method.

The orientation control layer is controlled so that the orientation of the magnetic layer 2 is good. 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 is reduced, and the magnetic flux from the magnetic head can be sharpened. 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 a single layer or a plurality of layers. When there are a plurality of orientation control layers, all the orientation control layers may be the same material, or at least some of the orientation control layers may be different materials.
The orientation control layer can be formed by a sputtering method.

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 a single layer or a plurality of layers 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 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 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. When the third magnetic layer contains the above elements in addition to Co, Cr, and Pt, it is possible to promote miniaturization of the magnetic particles or improve crystallinity and orientation. As a result, recording / reproduction characteristics and thermal fluctuation characteristics suitable for higher density recording 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 the above, sufficient reproduction output cannot be obtained, and the thermal fluctuation characteristics also deteriorate. On the other hand, when the thickness of the magnetic layer 2 exceeds the above range, the magnetic particles in the magnetic layer 2 are enlarged, and noise during recording / reproduction increases, resulting in a signal / noise ratio (S / N ratio). And recording / reproducing characteristics represented by recording characteristics (OW) are not preferable.

  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 nonmagnetic layer with an appropriate thickness between the magnetic layers, the magnetization reversal of individual films is facilitated. As a result, the dispersion of magnetization reversal of the entire magnetic particles can be reduced, and the S / N ratio can be further improved.

  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, O, N, W, Mo, Ti, V, Zr and B represent at least one element or two or more elements).

As the nonmagnetic layer provided between the magnetic layers, an alloy material containing an oxide, a metal nitride, or a metal carbide is preferably used. Specifically, for example, SiO ₂ , Al ₂ O ₃ , Ta ₂ O ₅ , Cr ₂ O ₃ , MgO, Y ₂ O ₃ , and TiO ₂ can be used as the oxide. As the metal nitride, for example, AlN, Si ₃ N ₄ , TaN, CrN or the like can be used. As the metal carbide, for example, 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.

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

The protective layer 3 protects the magnetic layer 2. The protective layer 3 may be a single layer or a plurality of layers.
The protective layer 3 of the present embodiment is made of carbon or carbon nitride. When the protective layer 3 is made of carbon or carbon nitride, the carbon atoms contained in the protective layer 3, or the carbon atoms and nitrogen atoms contained in the protective layer 3, and the lubricant layer 4 are combined to form the protective layer 3 The lubricant layer 4 is bonded with a high bonding force. As a result, even if the thickness of the lubricant layer 4 is small, the magnetic recording medium 11 is coated with the surface of the protective layer 3 with a high coverage and bonding property by the lubricant layer 4, and the surface of the magnetic recording medium 11 is contaminated. Can be effectively prevented.

The thickness of the protective layer 3 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 this embodiment can be sufficiently reduced. The magnetic spacing means the distance between the magnetic head and the magnetic layer 2. 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 sufficiently obtained, and the durability can be improved.

  As a method for forming the protective layer 3, when the protective layer 3 is made of carbon, a sputtering method using a carbon target material, a CVD (chemical vapor deposition) method using a hydrocarbon raw material such as ethylene or toluene, IBD, etc. (Ion beam evaporation) method or the like can be used. When the protective layer 3 is made of carbon nitride, the protective layer 3 can be formed by adding nitrogen to the raw material used when the protective layer 3 is made of carbon.

The lubricant layer 4 of this embodiment is formed on and in contact with the protective layer 3. As described above, the lubricant layer 4 has a predetermined film thickness containing the compound A represented by the general formula (1) and the compound B represented by the general formula (2) in a predetermined ratio. The lubricant layer 4 has a very high bondability and coverage with respect to the carbon or carbon nitride forming the protective layer 3.
The lubricant layer 4 improves the durability of the magnetic recording medium 11 by preventing contamination of the magnetic recording medium 11 and reducing the frictional force of the magnetic head of the magnetic recording / reproducing apparatus that slides on the magnetic recording medium 11. It is something to be made.

The lubricant layer 4 can be formed by, for example, the following method.
First, 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 produced. Next, a lubricant layer forming solution is applied on the protective layer 3 of the magnetic recording medium being manufactured.

The lubricant layer forming solution is prepared by mixing compound A and compound B so that the mass ratio (A / B) of compound A to compound B is in the range of 0.2 to 3.0. Accordingly, it is obtained by diluting with a solvent to obtain a viscosity and concentration suitable for the coating method.
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.
When using the dip method, for example, the following method can be used. First, the nonmagnetic substrate 1 on which the layers up to the protective layer 3 are formed is immersed in the lubricant layer forming solution placed in the immersion tank of the dip coater. Thereafter, the nonmagnetic substrate 1 is pulled up from the immersion tank at a predetermined speed. As a result, the lubricant layer forming solution is applied to the surface of the nonmagnetic substrate 1 on the protective layer 3. 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.

  The magnetic recording medium 11 of this embodiment has at least a magnetic layer 2, a protective layer 3, and a lubricant layer 4 in this order on a nonmagnetic substrate 1, and the protective layer 3 is made of carbon or carbon nitride and is lubricated. The agent layer 4 is formed on and in contact with the protective layer 3. And lubricant layer 4 contains compound A shown in general formula (1) and compound B shown in general formula (2), and mass ratio (A / B) of compound A to compound B is 0.2- It is in the range of 3.0, and the average film thickness is 0.8 nm to 2 nm. Thus, the magnetic recording medium 11 of the present embodiment does not have an island shape or a mesh shape even when the lubricant layer 4 is thin, and the surface of the protective layer 3 with a high coverage and bonding property by the lubricant layer 4. Is covered.

Therefore, in the magnetic recording medium 11 of the present embodiment, the environmental substance that has entered the lower layer of the lubricant layer 4 through the gaps in the lubricant layer 4 aggregates the ionic components present in the lower layer of the lubricant layer 4, thereby It is possible to prevent the medium 11 from being contaminated.
Further, since the magnetic recording medium 11 of this embodiment has the lubricant layer 4 that can effectively prevent contamination of the surface of the magnetic recording medium 11 even if the thickness is small, the lubricant layer 4 is made sufficiently thin. As a result, the recording density can be further improved.
Further, the magnetic recording medium 11 of this embodiment is hardly contaminated, has excellent environmental resistance, and has stable magnetic recording / reproducing characteristics even when used in a high temperature state where the contamination of the magnetic recording medium 11 becomes more conspicuous. Is obtained.

"Magnetic recording and playback device"
Next, an example of the magnetic recording / reproducing apparatus of this embodiment 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.
The magnetic recording / reproducing apparatus 101 of this embodiment includes the magnetic recording medium 11 shown in FIG. 1, a medium driving unit 123, a magnetic head 124, a head moving unit 126, and a recording / reproducing signal processing unit 128. is there.

  The medium driving unit 123 drives the magnetic recording medium 11 in the recording direction. The magnetic head 124 records and reproduces information on the magnetic recording medium 11. The magnetic head 124 has a recording unit and a reproducing unit. The head moving unit 126 moves the magnetic head 124 relative to the magnetic recording medium 11. The recording / reproducing signal processing unit 128 processes the recording / reproducing signal from the magnetic head 124.

  In the magnetic recording / reproducing apparatus 101 of the present embodiment, the surface of the protective layer 3 is covered with a sufficiently thin lubricant layer 4 with a sufficiently thin coating layer, so that contaminants present on the magnetic recording medium are not present. Fewer magnetic recording media 11 are provided. Therefore, it is possible to prevent contaminants existing on the magnetic recording medium 11 from being transferred to the magnetic head 124 of the magnetic recording / reproducing apparatus 101, thereby deteriorating the recording / reproducing characteristics and impairing the flying stability. It becomes. Therefore, the magnetic recording / reproducing apparatus 101 of the present invention 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.
(Example)
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 thickness of 10 nm was formed on the glass substrate by sputtering using a Cr target.
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. First, using a target of Co-20Fe-5Zr-5Ta {Fe content 20 atomic%, Zr content 5 atomic%, Ta content 5 atomic%, balance Co}, at a substrate temperature of 100 ° C. or less, the layer thickness A 25 nm first soft magnetic layer was deposited. Next, an intermediate layer made of Ru having a thickness of 0.7 nm was formed on the first soft magnetic layer. Thereafter, a second soft magnetic layer made of Co-20Fe-5Zr-5Ta with a layer thickness of 25 nm was formed on the intermediate layer.

Next, a seed layer having a layer 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 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 as a second alignment control layer by sputtering on the first alignment control layer at 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 orientation control layer by sputtering. A first magnetic layer made of 91 mol% alloy, 6 mol% SiO ₂ oxide, and 3 mol% TiO ₂ oxide was formed with a sputtering pressure of 2 Pa and a layer thickness of 9 nm.

Next, on the first magnetic layer, 88 (Co30Cr) -12 (TiO ₂ ) {Cr content of 30 atomic%, the remaining Co alloy is 88 mol%, and the oxide of TiO ₂ is 12 mol% by sputtering method} A nonmagnetic layer made of a film having a thickness of 0.3 nm was formed.
Then, 92 (Co11Cr18Pt) -5 (SiO ₂ ) -3 (TiO ₂ ) {Cr content of 11 atomic%, Pt content of 18 atomic%, and the remaining Co, 92 mol% on the nonmagnetic layer by sputtering. Then, a second magnetic layer made of 5 mol% of an oxide made of SiO ₂ and 3 mol% of an oxide made of TiO ₂ was formed with a sputtering pressure of 2 Pa and a layer thickness of 6 nm.

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. The third magnetic layer was formed with a layer thickness of 7 nm at a sputtering pressure of 0.6 Pa.
Next, a hard carbon film having a layer thickness of 3 nm was formed by an ion beam method. Thereafter, the outermost surface of the hard carbon film was nitrided by nitrogen plasma treatment to form a protective layer. The nitrogen content in the surface layer portion of the protective layer was about 40 atomic%.

  Next, a solution for forming a lubricant layer was prepared by dissolving the following compounds A and B or other compounds in the following solvents. Then, the obtained lubricant layer forming solution was put in a dipping tank of a dip coater, and the nonmagnetic substrate on which each layer up to the protective layer was formed was dipped. Thereafter, the lubricant layer forming solution was applied to the surface of the nonmagnetic substrate on the protective layer by pulling up the nonmagnetic substrate from the immersion tank at a constant speed, thereby forming a lubricant layer. By performing the above steps, magnetic recording media of Examples 1 to 26 and Comparative Examples 1 to 10 were obtained.

"Compound A"
ART-1 (trade name: manufactured by MORESCO)
DART-1 (trade name: manufactured by MORESCO) average molecular weight 1700
“Compound B”
The triol compound of the formula (2) was synthesized by modifying the alcohol that is a precursor of perfluoropolyether. The precursor of perfluoropolyether was adjusted so that the average molecular weight of formula (2) was 1700.
"Other compounds"
D4OH (Product name: MORESCO)
In D4OH, p in the following general formula (3) is in the range of 4 to 30, and the average molecular weight is about 2500.
"solvent"
Vertrel XF (Brand name: Mitsui DuPont Fluoro Chemical Co., Ltd.)

（一般式（３）中、ｐは４〜３０の範囲内である。）

(In general formula (3), p is in the range of 4-30.)

For the magnetic recording media of Examples 1 to 26 and Comparative Examples 1 to 10, the average film thickness of the lubricant layer was measured by Fourier transform infrared spectroscopy (FT-IR). The results are shown in Tables 1 and 2.
Tables 1 and 2 show the mass ratio (A: B) between compound A and compound B contained in the lubricant layer and the mass ratio (A / B) of compound A to compound B.

In addition, with respect to the magnetic recording media of Examples 1 to 26 and Comparative Examples 1 to 10, the γ ^AB (binding property) and γ ^LW (covering property) of the lubricant layer were measured by the method described above, and (γ ^{The total} (γ ^AB + γ ^LW ) was calculated and evaluated, and the contact angle of the surface of the magnetic recording medium (on the protective layer) was measured using three types of solvents: water, methylene iodide, and ethylene glycol. The results are shown in Tables 1 and 2.

As shown in Tables 1 and 2, the magnetic recording media of Examples 1 to 26 are compared with the magnetic recording media of Comparative Examples 1 to 10 in terms of the total surface energy ( γ ^total (γ ^AB + γ ^LW )) was low. For this reason, in the magnetic recording media of Examples 1 to 26, it is presumed that the surface coverage of the protective layer was high and the connectivity was high.

In contrast, since Comparative Example 1 and Comparative Example 7 have too much Compound A, and Comparative Example 2 and Comparative Example 8 have too much Compound B, the surface energy (γ ^total (γ ^AB + γ ^LW )) increases. It is presumed that the coverage rate and the bonding property to the surface of the protective layer by the lubricant layer were insufficient.
In Comparative Example 3 and Comparative Example 9, since the average film thickness of the lubricant layer is too thin, the surface energy (γ ^total (γ ^AB + γ ^LW )) increases, and the coverage of the protective layer with the surface of the protective layer by the lubricant layer And it is estimated that the connectivity was insufficient.

Further, since Comparative Example 4 and Comparative Example 10 do not contain Compound B, and Comparative Example 5 does not contain Compound A, the surface energy (γ ^total (γ ^AB + γ ^LW )) is increased, and the protective layer formed by the lubricant layer It is presumed that the coverage ratio and the binding property to the surface of the film were insufficient.
In Comparative Example 6, since the compound is a lubricant having a structure having four OH groups, the surface energy (γ ^total (γ ^AB + γ ^LW )) is increased, and the coverage ratio of the surface of the protective layer by the lubricant layer and It is estimated that the connectivity was insufficient.

  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 unit 124... Magnetic head 126. Head moving unit 128. Recording / reproduction 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 is made of carbon or carbon nitride;
The lubricant layer is formed on and in contact with the protective layer, and includes the compound A represented by the following general formula (1) and the compound B represented by the following general formula (2), and the compound for the compound B A magnetic recording medium, wherein a mass ratio (A / B) of A is in a range of 0.2 to 3.0, and an average film thickness of the lubricant layer is 0.8 nm to 2 nm.
_{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 in parentheses, in this order, or in reverse, or linked to good (x, y are real numbers respectively 0-15.) randomly.), or _{-CF 2 CF 2 O (CF 2} CF 2 CF 2 O) zCF ₂ CF ₂ — (z is a real number from 1 to 15), or —CF ₂ CF ₂ CF ₂ O (CF ₂ CF ₂ CF ₂ CF ₂ O) nCF ₂ CF ₂ CF ₂ —. (N is a real number from 0 to 4.)
_{HOCH 2 CF 2 CF 2 O (} CF 2 CF 2 CF 2 O) mCF 2 CF 2 CH 2 OCH 2 CH (OH) CH 2 OH ‥‥ (2)
(In general formula (2), m is an integer.) 2. The magnetic recording medium according to claim 1, wherein the total surface energy on the surface of the magnetic recording medium is 25.5 mJ / m < ² > or less.   The magnetic recording medium according to claim 1, wherein the compound A has an average molecular weight in the range of 1500 to 1800.   The magnetic recording medium according to claim 1, wherein the compound B has an average molecular weight in the range of 1000 to 1700. The magnetic recording medium according to any one of claims 1 to 4,
A medium driving unit for driving the magnetic recording medium in a recording direction;
A magnetic head for recording and reproducing information on the magnetic recording medium;
A head moving unit for moving the magnetic head relative to the magnetic recording medium;
A magnetic recording / reproducing apparatus comprising: a recording / reproducing signal processing unit for processing a recording / reproducing signal from the magnetic head.

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