JPH0762377A - Lubricant and magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the travelling properties and durability of a magnetic recording medium by using a lubricant comprising a specific phosphate compd., a specific phosphite compd., and a specific long-chain amine. CONSTITUTION:A lubricant is obtd. by compounding a phosphate compd. of formula 1 (wherein Rf is a perfluoropolyether group; R<1> is a 10C or higher hydrocarbon group; and n is 1 or 2), a phosphite compd. of formula 2 (wherein Rf, R<1>, and n are each the same as in formula 1), and a long-chain amine of formula 3 (wherein at least one of R<2>, R<3>, and R<4> is a 10C or higher hydrocarbon group). The amt. of the amine compounded is 100-0.01mol based on 1mol of the phosphate compd. and/or the phosphite compd. The lubricant is applied pref. in a thickness of 0.5-100mg/m<2> to form a lubricant layer 3 on a magnetic layer 2 of a magnetic recording medium of a thin metal film type, which is obtd. by forming the magnetic layer 2 on the surface of a nonmagnetic support 1 by vapor deposition, etc.

Description

Detailed Description of the Invention

The present invention relates to a lubricant and a magnetic recording medium (magnetic tape, magnetic disk, etc.).

[0002]

2. Description of the Related Art In a so-called metal thin film type magnetic recording medium in which a ferromagnetic metal material is deposited on a non-magnetic support by a technique such as vapor deposition and used as a magnetic layer, the surface of the magnetic layer is extremely smooth. Since it is good, the substantial contact area with sliding members such as magnetic heads and guide rollers is large, so the friction coefficient is large and the adhesion phenomenon (so-called sticking)
Is likely to occur, and there are many problems such as lack of running performance and durability.

For example, a tape inserted in an 8 mm video deck is wound around a drum through 10 or more guide pins. At that time, the tape tension and the tape running speed were kept constant by the pinch roller and capstan, the tension was about 20g and the running speed was 0.5cm / s.
Is. In this running system, the magnetic layer of the tape is in contact with a fixed guide pin made of stainless steel. Therefore, when the friction on the tape surface increases,
The tape causes stick-slip, which causes the phenomenon of so-called tape squeaking, causing the playback screen to become tight.

Further, the relative speed between the tape and the head is very large, and in particular, in the paused state, high-speed contact occurs at the same place, which causes a problem of wear of the magnetic layer, leading to a reduction in reproduction output. In the case of vapor-deposited tape, this problem is exacerbated because the magnetic layer is very thin.

In a hard disk drive, a magnetic head is in contact with the disk before rotation, which is called CSS (contact start stop). When the magnetic head starts to rotate at high speed, it is levitated by the air flow generated. . Therefore, the medium travels by rubbing the medium at the time of start-stop or start-up, and the increase in friction at that time is a serious problem. In order to maintain product level reliability, it is desired that the coefficient of friction after performing 20,000 CSS operations is particularly 0.5 or less. Further, since it rotates at a high speed, the problem of head crash due to the head and the medium is one of the problems in the thin film medium.

Therefore, in order to improve these problems,
The use of various lubricants has been studied, and it has been attempted to suppress the friction coefficient by top-coating a higher fatty acid or its ester on the magnetic layer of the magnetic recording medium.

By the way, the lubricant used in the magnetic recording medium is required to have very strict characteristics by its nature, and it is the current situation that it is difficult to cope with the conventionally used lubricant.

That is, the lubricant used in the magnetic recording medium is (1) excellent in low temperature characteristics so as to ensure a predetermined lubricating effect when used in cold regions, and (2) in combination with a magnetic head. Spacing is a problem, so it can be applied very thinly, sufficient lubrication characteristics can be exhibited, and (3) long-term or long-term use can maintain the lubrication effect, etc. Is required.

The most important solution to these problems of increasing coefficient of friction or durability is to study the lubricant applied to the surface. Realization of requirements such as good lubrication performance with the head, uniform and strong adhesion to the tape or disk surface, and retention of these performances for a long time (for example, 10 years) at a film thickness of approximately a single molecular level of about several nm In order to do so, consideration of the lubricant is necessary.

It is known that the lubrication characteristics obviously depend on the molecular structure of the lubricant, but those developed especially for magnetic recording media are roughly classified into three types. Silicon type, hydrocarbon type, and fluorinated carbon type.

The silicon-based lubricant is one of the lubricants often used in the coating type medium because of its good thermal stability and low vapor pressure. However, even if a thin film type magnetic recording medium having a very good surface property like the current one is top-coated, it does not have a very good lubricating performance, and the lubricating property in the pin-on-disk accelerated wear test or the CSS test is durable. Not very satisfied with the specifications. That is, a lubrication film oriented on the surface of the thin film magnetic recording medium, which is currently the mainstream, is formed,
Satisfying the required lubrication properties is very limited with silicon-based lubricants.

Hydrocarbon lubricants are still the mainstream lubricants in coating type magnetic recording media. However, in terms of thermal or chemical stability, hydrocarbon-based lubricants are generally inferior to silicon-based or fluorine-based lubricants, and frictional polymers formed by the reaction of molecules by friction, It is easily produced by a system that uses a hydrocarbon-based lubricant. This polymer reduces lubrication properties,
Sometimes it becomes a fatal failure. The high vapor pressure is one of the drawbacks of hydrocarbon lubricants. Since the thin film magnetic recording medium cannot replenish the lubricant, it exhibits excellent friction characteristics, but it is difficult to be used in an actual thin film magnetic recording medium because of its high vapor pressure.

Fluorine-based lubricants are currently the most widely used lubricants in thin film magnetic recording media. Among the fluororesins, perfluoropolyether is widely used because it has better lubricating performance and surface protection action than other fluorolubricants.

For this reason, CF ₂ --O--CF ₂
Since the ether bond is flexible, the viscosity is low when the molecular weight is the same, and the viscosity does not change in a wide temperature range. In addition, it must be chemically inert, have low vapor pressure, have high thermal or chemical stability, have low surface energy, have good boundary lubrication properties, and have good water repellency. Is mentioned.

The properties of perfluoropolyethers are very strongly dependent on their molecular structure. Several types of perfluoropolyethers are commercially available, which differ in molecular weight, backbone repeat units, and end groups.

For example, the Fomblin-Y type is CF (C
F ₃ ) a random polymer of CF ₂ O and CF ₂ O,
The repeating unit of the main chain has a branched structure, whereas the Fomblin-Z type is a polymer of CF ₂ CF ₂ O and CF ₂ O and has a linear structure. Demnum type and K
The rytox types are homopolymers of hexafluoropropylene oxide and hexafluoroisopropylene oxide, respectively.

Since it is chemically inert, perfluoropolyether lacks the adsorption ability on the surface of the magnetic recording medium.
Therefore, in order to improve the adsorptive power, Fomblin-Z-DO is used as a perfluoropolyether having polar groups at both ends.
L (containing hydroxyl group) and Fomblin AM2001 (containing piperonyl group) have been developed. AM2001 has a strong immobilizing action particularly on the metal surface or carbon surface, and the introduction of polar groups at the ends tends to reduce the friction coefficient and increase the useful life of the magnetic disk.

As described above, there are very strict demands on the lubricant for the thin film magnetic recording medium, and although various measures have been taken, there is still no lubricant that sufficiently satisfies the required characteristics. Is the reality.

Further, in a magnetic recording system having a relative velocity exceeding several meters, the frictional heat generated at the contact portion causes the surface temperature to increase abruptly, albeit instantaneously. Although there is no accurate method for measuring the temperature at the contact point between the head and the medium, it is estimated by calculation to exceed several hundred degrees.
Particularly under such boundary lubrication conditions, since a reactive surface appears, the temperature at such a contact point accelerates the decomposition reaction of the lubricant molecules.

Perfluoropolyethers are airborne
It is stable even at temperatures of 350 ° C. or higher, but easily decomposes in the presence of metal alloys such as iron and titanium alloys, or Lewis acids and Lewis bases such as AlCl ₃ , FeF ₃ and Al ₂ O ₃ .

The decomposition of such a lubricant adversely affects the lubrication characteristics and, as a result, it impairs the reliability of the magnetic recording system. Therefore, it is necessary not only to improve the lubrication characteristics, but also to develop a lubricant with less decomposition.

Further, since perfluoropolyethers are soluble only in CFCs, CFCs have to be used as a solvent for the preparation of the coating solution, which is a global environmental problem.

As described above, the properties required of the lubricant are extremely strict, and the reliability of the magnetic recording medium can be completely satisfied even if it has thermal or chemical stability or adsorption to the medium surface. The current situation is that there are none.

[0024]

As described above, in the field of magnetic recording media, due to lack of ability of the lubricant used, practical properties such as running property and durability, or solvent used are I am dissatisfied. Therefore, the present invention, while maintaining excellent lubricity under various conditions of use, has a long-lasting lubrication effect, is excellent in runnability, wear resistance, durability, etc., and is also environmentally friendly. An object of the present invention is to provide an advantageous lubricant and a magnetic recording medium having the lubricant.

[0025]

The present inventor has conducted extensive studies as a means to achieve the above-mentioned object, and as a result, has a characteristic of perfluoropolyether and a lubricant having characteristics of phosphoric acid or phosphorous acid. Was newly synthesized, and it was found that a phosphoric acid or phosphorous acid ester-based lubricant having a perfluoropolyether and a long-chain alkyl group in the ester moiety meets the above-mentioned object, and has completed the present invention. .

That is, the present invention provides at least a lubricant comprising at least one of a phosphoric acid ester compound represented by the following general formula 1 and a phosphorous acid ester compound represented by the following general formula 2, and this lubricant. The present invention relates to a magnetic recording medium held on the surface side of a magnetic layer. Formula _{1: (Rf-CH 2 O} ) n PO (OR 1) 3-n ( where, in this formula, Rf is a perfluoropolyether group, R ¹ is a hydrocarbon group having 10 or more carbon atoms, n represents 1 or 2
Is. ) General formula _{2: (Rf-CH 2 O} ) n P (OR 1) 3-n ( where, in this formula, Rf, R ¹ and n are the same as those described above).

The above lubricant of the present invention is characterized by comprising a perfluoropolyether and a phosphoric acid ester compound and / or a phosphorous acid ester compound having a long chain hydrocarbon group in the ester portion.

By applying this lubricant to the surface of a thin film magnetic recording medium such as a vapor deposition tape, it is possible to obtain good running properties even when used under severe conditions such as high temperature and high humidity or low temperature and low humidity. It has wear resistance and durability, and its characteristics do not deteriorate.

The long-chain alkyl ester of perfluoropolyether is sometimes dissolved in a hydrocarbon solvent and exhibits excellent lubricating performance. In the present invention, in order to further improve the lubricating characteristics, It is a phosphoric acid or phosphite ester that has both a perfluoropolyether group and a long-chain hydrocarbon group, and there is no problem in durability and friction coefficient, and its molecular design is such that it dissolves in hydrocarbon solvents other than CFCs. Therefore, the characteristics of both are maintained well.

In the lubricant according to the present invention, the structure of perfluoropolyether (Rf) having a phosphoric acid group at the terminal is shown below by the structural formula, but the structure is not limited thereto.

Monofunctional perfluoropolyether (R
The main chain of f) includes those represented by the following structural formula 1.

Polyfunctional perfluoropolyether (R
Examples of f) include those represented by the following structural formula 2. (Structural Formula 2) (OC ₂ F ₄ ) _p (OCF ₂ ) _{q and the} like.

Here, r, m, n, k, p, and q in the chemical structural formula of the perfluoropolyether are integers of 1 or more. The molecular weight is not particularly limited, but is preferably about 600 to 5000. When the molecular weight is too high, the effect of the terminal group becomes small, and when it is too small, the effect of the perfluoropolyether group becomes weak.

A long-chain hydrocarbon group (R ¹ ) such as a long-chain alkyl group also has the same molecular weight, number of carbon atoms, branched structure, unsaturated group,
It can be selected regardless of the presence or absence of an aromatic ring, an isomer, or an alicyclic structure. Linear or branched hydrocarbons having 10 or more carbon atoms are preferable from the viewpoint of friction coefficient or solubility. The upper limit of the carbon number of R ¹ is preferably 30.

It is desirable that the long-chain amine represented by the following general formula 3 be further added to the lubricant of the present invention in order to further improve durability. General formula 3: R ² N (R ³ ) R ⁴ (provided that in this general formula, at least one of R ² , R ³ and R ⁴ is a hydrocarbon group having 10 or more carbon atoms and is not this hydrocarbon group). Is a hydrogen atom or a hydrocarbon group.)

In this case, the amount of the long-chain amine added is preferably (100 to 0.01): 1, more preferably (10 to 0.01), with respect to the phosphoric acid ester compound and / or the phosphorous acid ester compound. 0.1): 1, especially (4 to 0.25): 1, optimally (2-1): 1.

The magnetic recording medium according to the present invention comprises the above-mentioned lubricant (that is, a perfluoropolyether and / or a phosphoric acid ester-based lubricant having a long-chain hydrocarbon group in the ester portion, and further The above-mentioned lubricant to which a long-chain amine is added is retained on at least the surface side of the magnetic layer provided on the non-magnetic support. This magnetic recording medium exhibits excellent running properties, wear resistance, and durability under various use conditions due to the above lubricant.

The term "at least the surface side of the magnetic layer" means not only the surface of the magnetic layer but also the presence of a lubricant in this surface region or the entire layer even in the magnetic layer. It also means that you may.

The magnetic recording medium to which the present invention is applied can be applied to a so-called metal thin film type magnetic recording medium in which a magnetic coating film is formed as a magnetic layer on the surface of a non-magnetic support by a method such as vapor deposition. It is possible. Further, this metal thin film type magnetic recording medium can be applied to a magnetic recording medium having a structure in which an underlayer is interposed between a non-magnetic support and a magnetic layer. It can also be applied to a coating type magnetic recording medium.

In this case, the non-magnetic support and the metal magnetic thin film of the applicable metal thin film type magnetic recording medium are not particularly limited, and any conventionally known one can be used.

For example, as the non-magnetic support,
The same as the coating type magnetic recording medium can be used.
In this case, when a rigid substrate such as an Al alloy plate or a glass plate is used as the non-magnetic support, an oxide film such as an alumite treatment or a Ni-P film is formed on the surface of the substrate to harden the surface. You may do it.

The metal magnetic thin film is formed as a continuous film by a PVD method such as plating, sputtering, vacuum deposition, and the like. Metals such as Fe, Co and Ni, Co--Ni alloys and Co.
-Pt alloy, Co-Pt-Ni alloy, Fe-Co alloy, Fe-Ni
Alloys, Fe-Co-Ni alloys, Fe-Ni-B alloys, Fe-Co
Examples are an in-plane magnetization recording metal magnetic film and a Co-Cr alloy thin film made of a -B alloy, a Fe-Co-Ni-B alloy, or the like.

In particular, in the case of in-plane magnetization recording metal magnetic thin film,
Bi, Sb, Pb, Sn, Ga, In, Ge, S on the non-magnetic support in advance.
An underlayer of a low melting point non-magnetic material such as i or Ti is formed in advance,
Metal magnetic material is vapor-deposited or sputtered from the vertical direction,
These low melting point non-magnetic materials are diffused in the metal magnetic thin film to eliminate the orientation and ensure the in-plane isotropic property.
The anti-magnetism may be improved.

When a hard disk is used, a carbon film, a diamond-like or amorphous carbon film, a chromium oxide film, ZrO _{2 is} formed on the surface of the metal magnetic thin film.
A hard protective film such as a film or a SiO ₂ film may be formed.

As a method of allowing the metal thin film type magnetic recording medium to retain the lubricant, there is a method of top-coating a lubricant layer on the surface of the metal magnetic thin film or the surface of the protective film.

In this case, the coating amount of the lubricant is 0.5
It is preferably a 100 mg / m ² from, and more preferably 1 to 20 mg / m ^2.

The above lubricant may be used alone as a lubricant for a magnetic recording medium, or may be used in combination with a conventionally known lubricant.

Further, in order to cope with more severe conditions and to maintain the lubricating effect, an extreme pressure agent may be used in combination with a compounding ratio of about 30:70 to 70:30 by weight. The extreme pressure agent acts to prevent friction and wear by reacting with the metal surface due to frictional heat generated when a metal contact is partially generated in the boundary lubrication region and forming a reaction product film. However, any of a phosphorus-based extreme pressure agent, a sulfur-based extreme pressure agent, a halogen-based extreme pressure agent, an organic metal-based extreme pressure agent, a composite-type extreme pressure agent, and the like can be used.

In addition to the above lubricant and extreme pressure agent, a rust preventive agent may be used in combination, if necessary. As the rust preventive, any rust preventive commonly used as a rust preventive for magnetic recording media of this type can be used, and examples thereof include phenols, naphthols, quinones, nitrogen atom-containing heterocyclic compounds, and oxygen atoms. And a heterocyclic compound containing a sulfur atom.

By the way, in the above-mentioned metal thin film type magnetic recording medium, a back coat layer, an undercoat layer and the like may be formed, if necessary, in addition to the metal magnetic thin film which is the magnetic layer.

For example, the back coat layer is formed by coating with a carbon-based fine powder for imparting conductivity to the resin binder and an inorganic pigment for controlling the surface roughness, like the magnetic coating film. It is something.

In the present invention, the above-mentioned lubricant may be internally added to the back coat layer or may be contained by a top coat. Alternatively, the magnetic coating film, the metal magnetic thin film, and the back coat layer may all be combined in various ways such as internally adding the above-mentioned lubricant and top coating.

As a magnetic recording medium to which the present invention is applied, for example, as shown in FIG. 1, a so-called metal thin film in which a magnetic layer is formed as a magnetic layer 2 on the surface of a non-magnetic support 1 by a method such as vapor deposition. Type magnetic recording medium. In this metal thin film type magnetic recording medium, the above-mentioned lubricant layer 3 is provided on the magnetic layer 2. It can be applied to a magnetic recording medium having a structure in which an underlayer (not shown) is interposed between the non-magnetic support 1 and the magnetic layer 2.

[0054]

The lubricant according to the present invention is a phosphoric acid or phosphite ester type lubricant having a perfluoropolyether and a long-chain hydrocarbon group in the ester moiety as shown in the above-mentioned general formula 1 or general formula 2. Therefore, it exerts a good lubricating action to reduce the friction coefficient. Further, this lubricating action is not impaired even under severe conditions such as low temperature. Therefore, in the magnetic recording medium coated with this lubricant, the running property is improved and the durability is improved by the lubricating effect of the lubricant. Further, since this lubricant is an ester of perfluoropolyether, it dissolves in a hydrocarbon solvent other than CFC, which is advantageous in terms of environmental protection.

[0055]

EXAMPLES Hereinafter, specific examples of the present invention will be described, but it goes without saying that the present invention is not limited to these examples.

Lubricants (composites) shown in Tables 1 to 3 below
Was used to prepare the magnetic recording medium shown below. Here, an example applied to a metal thin film type magnetic recording medium (vapor deposition tape) will be described.

Example 1 A 10 μm thick polyethylene terephthalate film was coated with Co by an oblique evaporation method to form a ferromagnetic metal thin film having a film thickness of 200 nm. Next, a solution of perfluoropolyether compound 1 having a phosphoric acid ester group at the end (molecular weight of about 2000) dissolved in hexane was applied to the surface of the metal magnetic thin film so that the application amount was 5 mg / m ^2. Then, it was cut into a width of 8 mm to prepare a sample tape.

Examples 2 to 28 The same compounds as in Example 1 were used except that the perfluoropolyether compounds 2 to 28 shown in Tables 1 and 2 (each having a molecular weight of about 2000) were used. Each corresponding sample tape was produced by the method.

Comparative Examples 1 to 7 As a comparative example, as shown in Table 3 below, a blank tape (Comparative Example 1) containing no lubricant was prepared, and the ends were modified. When a perfluoropolyether compound which is not used alone is used as a lubricant (Comparative Examples 2, 3, 4, and 5 respectively), further, in Compound 1 or 15, R ¹ is C ₉ H ₁₉ having less than 10 carbon atoms. When a certain lubricant was used (Comparative Examples 6 and 7), each comparative tape was prepared in the same manner as above.

[0060]

[0061]

[0062]

For each tape produced as described above, when the temperature was 25 ° C. and the relative humidity was 60%, the coefficient of friction under the conditions of the temperature of −5 ° C., the temperature of 40 ° C. and the relative humidity of 80%, the still The durability and shuttle durability were measured. For the still durability, the decay time of the output in the pause state up to -3 dB was evaluated. The shuttle durability was evaluated by performing shuttle travel for 2 minutes each time and counting the number of shuttles until the output decreased by 3 dB. The measurement results are also shown in Table 4 below.
It shows in Table 11.

[0064]

[0065]

[0066]

[0067]

[0068]

[0069]

[0070]

[0071]

As is clear from the results shown in Tables 4 to 11, as a lubricant, a perfluoropolyether having a hydroxyl group at the terminal or a phosphoric acid ester group or a phosphorous acid ester group having R ¹ having less than 10 carbon atoms. Compared with the case of using, the friction coefficient can be improved under various conditions by using a perfluoropolyether and a phosphoric acid or phosphite ester lubricant having a long chain alkyl group (R ¹ ) having 10 or more carbon atoms in the ester portion. Very good results were obtained, which did not rise so much and still maintained the durability of the still and shuttle. In addition, the solubility in other than CFC was also good. Regarding the solubility, an ester having 10 or more carbon atoms can be dissolved in n-hexane without any problem, but if it is less than 10, some cloudiness was observed and the solubility was not perfect.

Example 29 A 10 μm thick polyethylene terephthalate film was coated with Co by an oblique evaporation method to form a ferromagnetic metal thin film having a film thickness of 200 nm. Then, on the surface of the metal magnetic thin film, a long-chain alkylamine was added to a perfluoropolyether having a phosphoric acid ester group at a terminal in a molar ratio of 1: 1 as shown in Table 12 below.
The composition 29 (having a molecular weight of about 2000) dissolved in hexane was applied at a coating amount of 5 mg / m ^2, and
A sample tape was produced by cutting into a width of 8 mm.

Examples 30-56 Compositions of perfluoropolyethers shown in Tables 12 and 13
Corresponding sample tapes were produced in the same manner as in Example 29 except that 30 to Composition 56 (each having a molecular weight of about 2000) were used.

Comparative Examples 8 to 9 In addition, as Comparative Examples, the compositions shown in Table 14 below were used.
In 29 or 43, when a lubricant to which an amine in which R ² is C ₉ H ₁₉ having less than 10 carbon atoms is added is used (Comparative Example 8,
Regarding 9), each comparative tape was produced in the same manner as above.

[0076]

[0077]

[0078]

For each of the tapes produced as described above, the friction coefficient, the still durability and the shuttle durability were measured in the same manner as described above. The results are shown in Tables 15 to 21 below.

[0080]

[0081]

[0082]

[0083]

[0084]

[0085]

[0086]

As is clear from the results shown in Tables 15 to 21, perfluoropolyether having a phosphoric acid ester group or a phosphorous acid ester group having R ¹ having less than 10 carbon atoms at the terminal was used as the lubricant. More than in the case, by using the same perfluoropolyether having a long-chain alkyl group (R ¹ ) having 10 or more carbon atoms with an amine compound having R ² having 10 or more carbon atoms, the friction coefficient can be varied. Even under the conditions, it did not rise so much, and still better results were obtained in which the durability of the still and the shuttle were sufficiently maintained.

Examples 57-70 In Examples 29, the lubricant used was replaced with the composition shown in Table 22 below (the molecular weight was about 2000), and the amount of amine added was changed variously. Corresponding sample tapes were produced in the same manner as in.

Examples 71 to 84 In Example 29, the lubricant used was replaced with the composition shown in Table 23 (molecular weight of about 2000), and the amount of amine added was changed variously. Corresponding sample tapes were produced in the same manner as in.

[0090]

[0091]

The friction coefficient of each tape produced as described above was measured in the same manner as described above. The results are shown in Tables 24 to 29 below.

[0093]

[0094]

[0095]

[0096]

[0097]

[0098]

From the results shown in Tables 24 to 29, it was found that the amount of amine added to the lubricant changed the friction coefficient,
The addition amount thereof is preferably (10 to 0.1): 1, and more preferably (4 to 0.25): to phosphoric acid ester or phosphorous acid ester.
1, especially (2-1): 1 is desirable. As described above, it is one of the characteristics revealed by the present invention that the characteristics are further improved when the long-chain alkylamine is added in a specific molar ratio range. It is considered that a synergistic effect is working.

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of a magnetic recording medium of the present invention.

[Explanation of reference numerals] 1 ... Non-magnetic support 2 ... Metal magnetic thin film 3 ... Lubricant layer

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location C10N 30:06 40:18

Claims (5)

[Claims] 1. A lubricant comprising at least one of a phosphoric acid ester compound represented by the following general formula 1 and a phosphorous acid ester compound represented by the following general formula 2. Formula _{1: (Rf-CH 2 O} ) n PO (OR 1) 3-n ( where, in this formula, Rf is a perfluoropolyether group, R ¹ is a hydrocarbon group having 10 or more carbon atoms, n represents 1 or 2
Is. ) General formula _{2: (Rf-CH 2 O} ) n P (OR 1) 3-n ( where, in this formula, Rf, R ¹ and n are the same as those described above). 2. The lubricant according to claim 1, wherein a long-chain amine represented by the following general formula 3 is added. General formula 3: R ² N (R ³ ) R ⁴ (provided that in this general formula, at least one of R ² , R ³ and R ⁴ is a hydrocarbon group having 10 or more carbon atoms and is not this hydrocarbon group). Is a hydrogen atom or a hydrocarbon group.) 3. The lubricant according to claim 2, wherein the added amount of the long-chain amine is (100 to 0.01): 1 with respect to the phosphoric acid ester compound and / or the phosphorous acid ester compound in a molar ratio. 4. A magnetic recording medium in which the lubricant according to claim 1 is retained on at least the surface side of a magnetic layer. 5. The magnetic recording medium according to claim 4, wherein the lubricant is applied to the surface of the magnetic layer in an amount of 0.5 to 100 mg / m ² .