JPH0883422A - Lubricative layer - Google Patents

Abstract

PURPOSE: To ensure superior lubricity and durability by forming a complex of each lubricant molecule with a multidentate ligand adhered to a solid substrate by utilizing a host-guest complex forming a specifically stable complex. CONSTITUTION: A magnetic layer 2, a protective film 3 and a lubricative layer 4 are successively formed on a nonmagnetic substrate 1 to obtain a magnetic recording medium. The lubricative layer 4 is made of a host-guest complex and lubricant molecules have been fixed as guest molecules by a host compd. stuck on the disk. The protective film 3 is formed if necessary and the lubricative layer 4 may directly be formed on the surface of the magnetic layer 2. Especially when a smooth substrate for low levitation of a head is used, satisfactory lubricity and durability can be ensured without causing the attraction of a head peculiar to a liq. lubricant.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lubricating layer which exhibits a lubricating function with a film thickness of several tens of liters or less at a solid contact interface which slides at high speed. Specifically, it relates to a lubrication system for a high recording density magnetic recording medium used in the information industry or the like, and can be used, for example, as a lubricating layer for a magnetic recording medium such as a fixed type thin film magnetic recording disk. .

[0002]

2. Description of the Related Art A thin film magnetic recording medium, which is a typical example of a high recording density magnetic recording medium used in the information industry, is
It is usually manufactured by depositing a magnetic metal or its alloy on a non-magnetic substrate by plating, vapor deposition or sputtering. In actual use, the magnetic head and the magnetic recording medium come into contact with each other at high speed and slide, so that the magnetic head may be damaged by wear or the magnetic characteristics may be deteriorated.

As a method for solving such a drawback, it has been proposed to provide a protective film or a lubricating layer on the magnetic layer to reduce static / dynamic friction during contact sliding as much as possible and improve wear resistance. ing. As the protective film, a carbonaceous film,
An oxide film, a nitride film, a boride film or the like is used. A liquid lubricant or a solid lubricant is used as the lubricant, and generally, a perfluoropolyether compound which is a liquid lubricant is applied to the disk surface.

[0004]

When the magnetic recording medium is used, the disk medium is rapidly rotated and accelerated from a stopped state. Along with this, buoyancy is applied to the flying head slider and the head flies. When the power is cut off after use, the motor that rotates the disk medium stops, and the head and medium make contact at high speed and slide.

However, in recent years, in order to increase the areal recording density, it has been required to lower the flying height of the head and increase the speed of disk rotation, and the medium substrate tends to be smoother. It is very effective to provide a liquid lubricant film to reduce the dynamic friction coefficient, but as the liquid lubricant film is made thicker, a micromeniscus is formed between the head and the disk due to the surface tension of the liquid lubricant. It is known that the sticking phenomenon occurs. For this reason, it has been pointed out that the static friction coefficient increases, and the head is often inoperable while being stuck to the disk.

That is, as the substrate is made smoother in order to reduce the flying height of the head, the liquid lubricant has a serious drawback that the above adsorption phenomenon is very likely to occur, and the film is used to prevent the adsorption. When the thickness is reduced, there is a problem that sufficient durability cannot be obtained. In addition, as the rotation speed of the disk increases, the lubricant, which is volatilized and the film thickness decreases, becomes more remarkable, which is called spin-off. In order to avoid these phenomena, a solid lubricant that does not form a meniscus is desired, and higher fatty acids and metal salts thereof have been proposed for some time.

However, since these solid lubricants are in a stable phase in the solid state at room temperature, there is a problem that a part of the coating film tends to crystallize and aggregate when applied on a disk. Especially when the substrate is smoothed, the tendency of aggregation is remarkable. When agglomeration occurs, the coating thickness becomes uneven, increasing the possibility of direct contact between the head and disk, and
This may cause dirt on the head or destabilize the flight of the head. In order to prevent the solid lubricant from agglomerating and suppress the spin-off, it is necessary to effectively bond and bond the lubricant molecules to the substrate, and as a measure to enhance the bonding force of the lubricant layer molecules, for example, alkylsilane is polymerized. Method (JP-A-2-103721, JP-A-2-1-1)
No. 03722) has been proposed. However, the lubrication layer formed by these methods has insufficient lubricity because the movement of molecules is suppressed by being polymerized. This is because fixing the lubricant has a trade-off relationship with the lubricating performance.

In the present invention, obtaining a lubricating layer in which excellent lubricity is exhibited even in a thin film and lubricant molecules are not aggregated, that is, fixing the lubricant is a trade-off with the lubricating performance. It was achieved by designing the lubrication system on the molecular / atomic order for the purpose of obtaining a lubrication layer having excellent durability that is not related.

[0009]

The lubricating layer of the present invention is used as a guest molecule in a thin film magnetic recording medium in which a solid surface that slides at high speed is required to have lubricity and wear resistance for a long period of time. It is characterized by containing a host-guest complex formed from an agent molecule and a polydentate ligand as a host compound forming a complex with the agent molecule.

That is, in the lubricating layer of the present invention, the lubricant molecules, which are guest molecules, are trapped by the host compound adhered on the solid substrate due to electrostatic interaction such as ionic bond, so that the solid substrate has good orientation. Since it is fixed to the top and its binding mode is reversible, it is possible not only to prevent the lubricant from agglomerating but also to realize a more durable lubricating performance.

The lubricating layer of the present invention can be applied to various solid surfaces, such as polymers, carbon, oxides, nitrides, borides, and metals, as long as the host compound can be attached to the surface. It is widely applied regardless of its type. By applying the lubricating layer of the present invention to the surface of the magnetic recording medium, the flying height of the head can be reduced,
It is possible to increase the data recording density of the disc and to construct a reliable disc system for a long period of time.

The case where the present invention is applied to a magnetic recording medium will be described in detail below as an example. FIG. 1 shows the structure when the lubricating layer of the present invention is applied to a magnetic recording medium.
In a magnetic recording medium in which a magnetic layer 2, a protective film 3, and a lubricating layer 4 are sequentially formed on a non-magnetic substrate 1, the lubricating layer 4 is composed of a host-guest complex, and a lubricant compound is formed by guest compounds by a host compound fixed on the disk. It is immobilized as a molecule. In FIG. 1, the protective film 3 may be provided if necessary, and the lubricating layer according to the present invention may be directly formed on the surface of the magnetic layer 2.

In applying the lubricating layer of the present invention to a magnetic recording medium, an aluminum alloy plate or a glass substrate provided with a nickel-phosphorus layer is usually used as the non-magnetic substrate. A substrate, a resin substrate or the like can also be used. As the magnetic layer, after providing an undercoat layer if necessary, for example, Co or CoP-based alloy, CoNiP-based alloy, CoNiCr-based alloy, CoNiPt-based alloy, CoCrPt-based alloy, CoC
A Co alloy such as an rTa-based alloy or a CoCrPtTa-based alloy is formed by an electroless plating method, a sputtering method, or the like. The film thickness of the magnetic layer is determined by the characteristics required for the magnetic recording medium and is usually 200 to 1500 Å.
When the lubricating layer of the present invention is applied, the protective film on the thin film magnetic layer is not always indispensable, and is formed as necessary in consideration of physical properties such as hardness and elastic modulus of the magnetic film.
A carbonaceous film, an oxide film, a nitride film, a boride film, or the like is used as the protective film, and is formed by a sputtering method, an ion plating method, a plasma polymerization method, or the like. A carbonaceous film such as amorphous carbon or hydrogenated carbon is preferably used as the protective film, and is usually used in a film thickness of 50 to 500Å, preferably 100 to 300Å. If necessary, surface treatment of the protective film such as irradiation with ultraviolet rays can be performed.

In the host-guest complex constituting the lubricating layer of the present invention, as the guest molecule, one having a molecular skeleton which plays a lubricating function and a binding site for binding with the host molecule is used. Either a liquid lubricant skeleton or a solid lubricant skeleton can be used as the molecular skeleton responsible for the lubricating action. As the liquid lubricant skeleton, for example, a fluoroalkyl-based liquid lubricant such as perfluoropolyether,
Polybutene-based, polyalkylene glycol-based, phosphate ester-based, polyolefin-based, polyol ester-based,
Alkylnaphthalene-based, silicon oil-based, polyarylalkane-based, polyphenyl-based, silicic acid ester-based, polyphenyl ether-based, and the like can be used. As the perfluoropolyether liquid lubricant, for example, fomblin lubricant:-(CF ₂ CF ₂ O) m (CF ₂ O) n
-Skeleton (made by Montedison), demnum type lubricant :-( C
_{F 2 CF 2 CF 2 O)} p- skeleton (manufactured by Daikin Industries, Ltd.), or Krytox lubricant :-( CF ₂ CF (CF ₃₎
0) q- skeleton (manufactured by DuPont) and the like (m, n,
p and q are integers of 1 or more). Usually, about 5 to 50 are used as m, n, p and q. The molecular weight is preferably 500 or more, and particularly preferably about 600 to 8000. A perfluoropolyether-based molecular skeleton further bound to a branched or straight-chain saturated or unsaturated higher aliphatic hydrocarbon chain, a higher aliphatic hydrocarbon chain containing an aromatic group or a hetero atom, etc. It can also be used.

The solid lubricant skeleton includes branched or linear saturated or unsaturated higher aliphatic hydrocarbon chains, aromatic residues such as benzene, naphthalene and pyrene, and F,
The higher aliphatic hydrocarbon chain containing a hetero atom such as N, O, S, or a long chain molecular skeleton in which a part or all of the higher aliphatic hydrocarbon chain forms a polyether chain,
Any material having a lubricating action can be selected regardless of the type of bond.

The binding site for the guest molecule to bind to the host compound is selected to be trapped in the vacancy of the host molecule. Usually, alkali metals such as Na, K and Rb, alkaline earth metals such as Mg, Ca, Sr and Ba, A
Typical metals such as 1, Sn, Pb, transition metals such as Ag, Cu, Fe, etc. are used, and they are used in combination with the terminal group of the molecular skeleton which plays a lubricating function. Specific examples of the terminal group include a hydroxyl group, a carboxyl group, an oxygen-containing polar functional group such as an ester bond and an amide bond, a nitrogen-containing functional group such as an amino group and an imino group, a phosphorus-containing group such as a phosphoric acid group and a phosphoric acid ester group. It is a functional group or a sulfur-containing functional group such as a mercapto group, a sulfonic acid group or a sulfonic acid ester group. Further, the lubricant having such a terminal functional group or ammonium salt, amine acid salt or the like at the end can also be used alone without being combined with a metal ion. In that case, the terminal functional group of the lubricant molecule is It is trapped in the vacancy of the host molecule. Particularly preferred binding sites include K, Ba, Ag, Cu, amino groups,
Examples thereof include ammonium salts and hydroxyl groups.

As the host molecule, cyclic esters, polyethers, polyamines, cyclic ethers collectively called crown ethers, cyclic ether amines and cyclic amines collectively called cryptands or cryptates,
Polydentate ligands having a function of effectively taking in metal ions or organic ions such as polypeptides and their chemically modified products are used, and among them, cyclic ligands such as crown ethers and cryptands are particularly effective. These polydentate ligands form a strong complex with a metal ion or an organic ion. For example, cyclic ligands such as crown ethers and cryptands direct lone electron pairs of O and N to their inner pores to form metal complexes. Because it has a strong affinity for ions, etc.,
When the equilibrium of the complex formation is in the range of 10 ² to 10 ¹⁰ or more, the complex formation can be inclined to the complex formation side, and the metal ions can be taken in extremely strongly. That is, in these cyclic ligands, O, N, etc. are coordinated as donor atoms mainly by electrostatic interaction with lone electron pairs as a donor atom, and metal cations are effectively taken into the inner pores. Compared to monodentate ligands, these polydentate ligands have donor atoms such as O and N that are connected by a methylene bridge from the beginning, so when coordinating around a cation, new repulsion between donors occurs. There is almost no enthalpy complex formation, and since the ligands are regularly arranged, they are also excellent in entropy. In addition to the cyclic polydentate ligand, linear polydentate ligands are also effective, but it is generally known that cyclic ones have higher stability of the complex than linear ones. While it is far superior to monodentate ligands in the case of linear polydentate ligands when surrounding cations, it is electrostatic and steric between the donor atoms at both ends. It is thought that it may be because of the repulsion of the target or the adverse entropy change. There are several reviews of the above cyclic ligands, for example representative crown ethers, cryptands and their analogs, their synthesis,
Detailed table of structure and incorporated cations is JJ Christen
Sen. et al., Chem. Revs., 74, 351 (1974). From the viewpoint of stability as a substance, many cyclic polydentate ligands are thermally stable, and macrocyclic ligands such as porphyrin are stable even at 500 ° C. or higher. well known. It is also reported that crown ethers are generally thermally stable and, for example, dibenzo-18-crown-6 can be distilled at 380 ° C. (CJPederson et al., Angev.Che.
m., Int'L Ed. 11, 16 (1972).).

It has been found that there is a close relationship between the size of the inner hole of the cyclic ligand and the size of the cation which can be easily incorporated in the complex formation. For example, 18-crown-6 has an inner pore size of 2.6 to 3.2 Å, and forms a very stable complex with K ⁺ of an alkali metal ion having an ionic diameter (2.66 Å) which is almost the same as this. (Complexation equilibrium constant in methanol log K = 6.05) is known.

Utilizing the host-guest complex that forms a specifically stable complex as described above, the polydentate ligand (host compound) adhered to the lubricant molecule (guest molecule) and the solid substrate is used.
By forming a complex with, the lubricant molecules can be fixed on the substrate by electrostatic interaction. Figure 1
FIG. 3 is a conceptual diagram showing a host-guest complex formed by a derivative of 8-crown-6 and potassium stearate, which is fixed to the surface of a solid substrate, in which K ^+, which is a cation in the guest molecule, is trapped in the inner hole of the crown ether, The counter anion of K ⁺ , stearate, will coordinate the terminal carboxyl group as an ion pair to the trapped K ⁺ on the crown ether. On the other hand, the crown ether, which is a host molecule, can be fixed to the disk surface by applying an appropriate chemical modification or the like. Therefore, the electrostatic interaction causes the lubricant moiety (long-chain alkyl group of stearate) to be fixed on the crown ether complex on the substrate surface by its terminal carboxyl group,
Agglomeration of lubricant molecules can be prevented. In addition, the fact that the terminal carboxyl group is coordinated to the side of the crown ether complex on the substrate means that all the alkyl chain parts are oriented upward with respect to the substrate in principle, and The orientation of the entire layer is improved,
Since the structure of the ideal lubricating layer is taken, excellent lubricating ability and durability can be obtained even with a film thickness of almost a monomolecular layer.

The application of the lubricant containing these host-guest complexes to the solid substrate is usually carried out by dissolving the above polydentate ligand and the lubricant compound or immersing the solid substrate in each solution. The method is to form a film by contacting a tape, etc., which has been impregnated with the solution with a load on the surface of a solid substrate to form a film, a method of applying a pad while rotating the pad on the solid substrate, or a spray method or an LB film. The method etc. can be used. The concentration of the coating solution varies depending on the type of polydentate ligand or lubricant compound, and the type of solvent, but is usually 0.1 to 5 g as the concentration of the complex in the solution.
/ L. Many of the features of the host-guest complex are generally soluble in an organic solvent, and a general-purpose organic solvent can be used as a solvent for forming the lubricating layer of the present invention. For example, potassium stearate is hardly dissolved in chloroform, but when 18-crown-6 is added, crown ether takes in potassium ions therein and solubilizes it, so that it becomes well dissolved.

[0021]

EXAMPLES Next, the present invention will be described more specifically by way of examples, but the present invention is not limited to the following examples unless it exceeds the gist. Example 1 A 3.5-inch diameter magnetic disk having a chromium underlayer (2000 Å), a cobalt alloy magnetic thin film (400 Å) and a carbon protective film (300 Å) formed on an aluminum alloy substrate by a sputtering method was prepared using potassium stearate. And 4,4′-diaminodibenzo-18-crown-6 at a concentration of 1 mmol / l (total of 0.7
After being soaked in a chloroform solution containing 13 g / l) for 5 minutes, the disk was pulled up at a speed of 10 mm / sec to form a uniform lubricating film having a thickness of 29Å on the surface of the disk.

4,4'-Diaminodibenzo-18-crown-6 is prepared by the method of E. Shchori et al. (J. Am. Chem. Soc., 9
5,3842 (1973)), 4,4'-dinitrodibenzo-18-crown-6 was reduced with hydrazine to obtain 90% isolated yield. 4,4'-Dinitrodibenzo-18-crown-6 is WMFreigenbaum
Et al. (J. Polym. Sci., Part A-1, 9, 817 (1971).)
, A commercially available dibenzo-18-crown-6 was nitrated to obtain 81% of isolated yield.

Lubricating performance and cohesiveness of the disk having the lubricating layer formed thereon were tested. As a test of lubrication performance, a thin film head was used to conduct a continuous sliding test at a load of 9.5 gf and a sliding linear velocity of 0.32 m / sec (radius 30 mm, 100 rpm). Was measured. As a cohesiveness test, a temperature of 25 ° C and a humidity of 4
The disc was left in a 0% environment for the period described in Table 1 and observed for agglomeration and crystal formation with an optical microscope. The results are shown in Table 1.

Example 2 Using a disk similar to Example 1, potassium β- (N, N-diheptadecylaminocarbonyl) propionate and 4,4'-diaminodibenzo-18-crown-6 were used.
At a concentration of 1 mmol / l (total of 1.02 g / l
10m after soaking in chloroform solution containing 1) for 5 minutes
By pulling up the disc at a speed of m / sec,
A uniform lubricating film having a thickness of 45Å was formed on the surface of the disk. With respect to the disk on which the lubricating layer was formed, the lubrication performance and cohesiveness were tested in the same manner as in Example 1. The results are shown in Table 1.

Example 3 A chromium underlayer (1200 Å), a cobalt alloy magnetic layer (500 Å), and a cobalt alloy magnetic layer (500 Å) were formed on a smooth aluminum alloy substrate having a center line average roughness (Ra) of 35 Å by a sputtering method.
And a wavelength of 185n on the surface of a 3.5-inch diameter magnetic disk on which a hydrogenated carbon protective film (200Å) was formed.
m, 254 nm, and an output of 90 W of ultraviolet rays were irradiated in the air from a distance of 15 mm for 5 minutes, and then 4 mmol of 4,4′-diaminodibenzo-18-crown-6-ether was added.
A uniform film having a thickness of 15 Å was formed on the disk surface by the dipping method using a chloroform solution containing a concentration of 0.71 g / l (0.781 g / l).

Next, the disk was immersed in a chloroform solution for 5 minutes and then pulled up to leave a uniform film having a thickness of 5Å on the surface of the disk. Demnam SH (one end C
OOH-modified product; average molecular weight 1650 / manufactured by Daikin Industries, Ltd.) and potassium hydroxide 0.33 mol / l, respectively
A fluorine-based solvent PF5080 (a solution manufactured by Sumitomo 3M Co., Ltd.) containing at a concentration of 1
A uniform film of 5Å was formed.

A spin-off test and a CSS test were carried out on the disk on which the lubricating layer was formed. Table 2 shows the results. For the spin-off test, the disk was rotated at 7200 rpm for 14 days in an atmosphere of 80 ° C.
The residual ratio of the lubricating film thickness was determined from the change in the absorption intensity of the C—F bond in the IR spectrum. For CSS test 70% of the thin film head slider 75nm floats at a peripheral speed of 8.7 m / sec (Material: Al ₂ 0 ₃ TiC, pressing force 6g
f). The CSS1 cycle was 12 seconds in which the spindle was energized for 3 seconds and then the power was turned off for 9 seconds, and the rotation start torque and the sliding torque of the spindle were measured for each cycle. The sliding torque was obtained from the maximum value of the force acting on the head between 0.3 seconds and 1 second after the spindle was energized. 20,000 CSS cycles,
Ten points were selected from the higher values of the torque at the start of rotation and the torque at the time of sliding, and the average was obtained. As a result of the CSS test, neither the disk nor the head was stained.

Example 4 The same disc as in Example 3 was subjected to ultraviolet irradiation treatment, and then 4,4'-diaminodibenzo-18-crown-6.
-Ether at a concentration of 2 mmol / l (0.781 g /
A uniform film having a thickness of 18Å was formed on the surface of the disk by the dipping method using the chloroform solution containing 1).

Next, the disk was immersed in a chloroform solution for 5 minutes and then pulled up to leave a uniform film having a thickness of 9Å on the disk surface. Demnam SH (average molecular weight 2
400) and potassium hydroxide 0.4 mmol each
A uniform film having a thickness of 26 Å (Example 4-1) and a thickness of 24 Å (Example 4-2) was formed on the surface of the disk by a dipping method using a PF5080 solution contained in a concentration of 1 / l. For the disk on which the lubricating layer was formed, the spin-off test (Example 4-1) and the CSS test (Example 4) were carried out in the same manner as in Example 3.
-2) was performed. Table 2 shows the results. As a result of the CSS test, neither the disk nor the head was stained.

Example 5 A disc similar to that used in Example 3 was subjected to an ultraviolet irradiation treatment, and then 4,4'-diaminodibenzo-18-crown-6.
-Ether at a concentration of 2 mmol / l (0.781 g /
A uniform film having a thickness of 16Å was formed on the surface of the disk by the dipping method using the chloroform solution containing 1).

Then, the disk was immersed in a chloroform solution for 5 minutes and then pulled up to leave a uniform film having a thickness of 8Å on the surface of the disk. 0.6 mmo of demnum SH (average molecular weight 2400) and potassium hydroxide, respectively
A uniform film having a thickness of 44Å was formed on the surface of the disk by a dipping method using a PF5080 solution containing 1 / l concentration. Example 3 for a disk having a lubricating layer formed thereon
A spin-off test was conducted in the same manner as in. Table 2 shows the results.

Example 6 A disc similar to that used in Example 3 was irradiated with ultraviolet rays, and then 4,4'-diaminodibenzo-18-crown-6 was used.
-Ether at a concentration of 2 mmol / l (0.781 g /
A uniform film having a thickness of 15Å was formed on the surface of the disk by the dipping method using the chloroform solution containing 1).

Next, the disk was immersed in a chloroform solution for 5 minutes and then pulled up to leave a uniform film having a thickness of 6Å on the surface of the disk. Perfluoropolyether Fomblin Z DOL (both terminal O
1g of H, average molecular weight 2000 / made by Montedison
A uniform film having a thickness of 18Å was formed on the surface of the disk by the dipping method using the PF5080 solution containing the solution at a concentration of 1 / l. A spin-off test was performed on the disk having the lubricating layer formed in the same manner as in Example 3. Table 2 shows the results. Example 7 Using the same disk as in Example 1, using a chloroform solution containing copper stearate and 1,4,8,11-tetraazacyclotetradecane at a concentration of 1 mmol / l, the surface of the disk was dipped. Thickness of 16Å
A uniform lubricating film was formed. The lubricity test and the cohesiveness test were performed on the disk having the lubricating layer formed in the same manner as in Example 1. The results are shown in Table 1. Example 8 Using a disk similar to Example 1, silver acetate and N,
Using a mixed solution of water and methanol each containing N'-dibenzyl-4,13-diaza-18-crown-6 at a concentration of 1 mmol / l, the surface of the disk was uniformly dipped by a dipping method. A lubricating film was formed. Subsequently, this disk was coated with a chloroform solution containing β- (N, N-diheptadecylaminocarbonyl) propionic acid at a concentration of 2 mmol / l, and a thickness of 1 was applied to the surface of the disk.
A 9Å uniform lubricating film was formed. The lubricity test and the cohesiveness test were performed on the disk having the lubricating layer formed in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 1 Using a disk similar to that of Example 1, it was immersed in a methanol solution containing potassium stearate at a concentration of 1 mmol / l (0.316 g / l) for 5 minutes, and then 10 mm / sec.
By pulling up the disc at the speed of, a 13 Å thick lubricating film was formed on the surface of the disc. With respect to the disk on which the lubricating layer was formed, the lubrication performance and cohesiveness were tested in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 2 The same disc as in Example 1 was used, and stearic acid was added to 3 m.
After dipping in a chloroform solution containing a mol / l concentration (0.852 g / l) for 5 minutes, the disk was pulled up at a speed of 10 mm / sec to form a lubricating film having a thickness of 16Å on the surface of the disk. With respect to the disk on which the lubricating layer was formed, the lubrication performance and cohesiveness were tested in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 3 Using the same disk as in Example 1, β- (N, N-diheptadecylaminocarbonyl) propionic acid was added at 1 mmo.
After being immersed in a chloroform solution containing a concentration of 1 / l (0.593 g / l) for 5 minutes, the disk was pulled up at a speed of 10 mm / sec to give a thickness of 2
A uniform lubrication film of 8Å was formed. With respect to the disk on which the lubricating layer was formed, the lubrication performance and cohesiveness were tested in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 4 After forming a hydrogenated carbon protective film on a disk similar to that of Example 3, a PF5080 solution containing demnum SH (average molecular weight 1650) at a concentration of 0.5 mmol / l was used to carry out the dipping method. A uniform film having a thickness of 20Å was formed on the surface of the disk. A spin-off test was performed on the disk having the lubricating layer formed in the same manner as in Example 3. Table 2 shows the results.

Comparative Example 5 After forming a hydrogenated carbon protective film on the same disk as in Example 3, a PF5080 solution containing Demnum SH (average molecular weight 2400) at a concentration of 0.6 mmol / l was used to carry out the dipping method. The surface of the disc has a thickness of 31Å
A uniform film having a thickness of 27Å (Comparative Example 5-2) and (Comparative Example 5-1) was formed. A spin-off test (Comparative Example 5-1) and a CSS test (Comparative Example 5-2) were performed in the same manner as in Example 3 using the disk on which the lubricating layer was formed as described above. Table 2 shows the results. CSS test results, disc,
The head was clean.

Comparative Example 6 After forming a hydrogenated carbon protective film on a disk similar to that of Example 3, a PF5080 solution containing demnum SH (average molecular weight 2400) at a concentration of 0.6 mmol / l was used to carry out the dipping method. A 41 Å thick uniform film was formed on the surface of the disk. A spin-off test was performed on the disk having the lubricating layer formed in the same manner as in Example 3. Table 2 shows the results.

Comparative Example 7 After forming a hydrogenated carbon protective film on a disk similar to that of Example 3, perfluoropolyether Fombli was used.
Using a PF5080 solution containing n Z DOL (average molecular weight 2000) at a concentration of 1 gl / l, the surface of the disk was subjected to a dipping method to have a thickness of 21Å (Comparative Example 7-1) and a thickness of 16Å (Comparative Example 7-2 ) Formed a uniform film.

For the disk on which the lubricating layer was formed, the spin-off test (Comparative Example 7-1) and CSS were carried out in the same manner as in Example 3.
A test (Comparative Example 7-2) was performed. Table 2 shows the results.
As a result of the CSS test, neither the disk nor the head was stained.

[0042]

[Table 1]

[0043]

[Table 2]

As is clear from the results shown in Table 1, when the lubricating layers of Examples 1 to 2 and 7 to 8 according to the present invention have a larger film thickness than Comparative Examples 1 to 3 (because the host layer exists, the lubricating layer should be slightly thicker). In addition, it is confirmed that the aggregation of the lubricating layer, which is seen in the case of the lubricants of Comparative Examples 1 to 3 alone, is suppressed, and is equal to the system of the lubricants of Comparative Examples 1 to 3 alone. It was confirmed that it had better lubricity and runnability.

Further, when the orientation state of the alkyl chain in the lubricating layer formed in Example 2 was analyzed by the FTIR-RAS method, CH stretching vibration derived from the methyl group at the tip of the alkyl chain was clearly observed as shown in FIG. Since the intensity of CH stretching vibration of the methylene chain is relatively small, it was confirmed that the alkyl chain stands vertically to the substrate and is well oriented.

Considering the film thickness, it is considered that this lubricating layer is a monomolecular film having a structure in which the bonding sites are directed to the substrate side and the alkyl chains are directed upward (see FIG. 1).
It can be said that the structure is almost optimal as a lubricating layer. On the other hand, in the conventional lubricant (β- (N, N-diheptadecylaminocarbonyl) propionic acid) alone system (Comparative Example 3), absorption due to CH stretching vibration of the methyl group at the tip of the alkyl chain was observed. Since the strength is low and the CH stretching vibration strength of the methylene chain is high, it can be seen that the orientation of the alkyl chain on the disk is low, and the alkyl chain is in a state of being oriented in various directions as a whole.

From the results shown in Table 2, the lubricating layer according to the present invention is
It was confirmed that the spin-off of the lubricant molecules was effectively suppressed even when the liquid lubricant was used, and the head adsorption observed in the liquid lubricant was significantly less likely to occur. That is, in the lubricating system of the present invention, spin-off is effectively suppressed by fixing the lubricant compound on the substrate by the host-guest complex type lubricating layer, and there is a trade-off relationship between the fixing and the lubricating performance. It can be seen that a lubricating layer having excellent lubricity and durability that does not easily cause adsorption is constructed.

When a smooth disc was directly coated with perfluoropolyether as a liquid lubricant (Comparative Example 5,
7) It is considered that the lubricant moves on the surface due to its low interaction with the surface of the protective film and collects at the real contact portion between the head and the disk to form a meniscus. On the contrary,
It can be seen that when the liquid lubricant is fixed on the smooth substrate using the host-guest complex (Examples 3 and 4), the torque at the start of rotation is reduced to 35 gf · cm or less.

According to the present invention, when a solid lubricant is used, even if the LB film method, which is complicated and has difficulty in productivity, is not used, it is very easily reproducible and highly oriented by the ordinary dipping method. Can be obtained.

[0050]

According to the present invention, a thin film (substantially a monomolecular film thickness) has excellent lubricity and wear resistance, and in the case of a solid lubricant, the aggregation of lubricant molecules is suppressed. Further, in the case of a liquid lubricant, as a result of suppressing spin-off, a highly reliable lubrication system capable of maintaining excellent durability for a long period of time can be obtained. In particular, when a smooth substrate corresponding to the low flying height of the head is used, the liquid lubricant does not cause the adsorption to the head, which is characteristic of the liquid lubricant, and it has good lubricity and sufficient durability. Further, there is no problem of agglomeration peculiar to the solid lubricant. By applying the lubricating layer according to the present invention to a magnetic recording medium, it is possible to increase the data recording density and to obtain a highly reliable magnetic recording medium for a long period of time.

[Brief description of drawings]

FIG. 1 is a conceptual cross-sectional view of a magnetic recording medium using a lubricating layer of the present invention.

FIG. 2 shows the principle of the construction of the lubricating layer by the host-guest complex of the present invention, potassium stearate and 18-crown-6.
It is the conceptual diagram shown using the derivative as an example.

FIG. 3 is a conceptual diagram showing the concept of the constitution of the lubricating layer by the host-guest complex of the present invention using a liquid lubricant and crown ether.

FIG. 4 is a diagram showing an FTIR spectrum by a RAS method of a lubricating layer in Example 2 and Comparative Example 3.

[Explanation of symbols]

 1 non-magnetic substrate 2 magnetic layer 3 protective film 4 lubrication layer

Claims (7)

[Claims] 1. A lubricating layer containing a host-guest complex. 2. The host-guest complex is a complex containing a polydentate ligand having a function of reversibly trapping a metal ion or an organic ion by electrostatic interaction as a host compound. Lubrication layer described 3. The lubricating layer according to claim 2, wherein the host compound is deposited on the solid surface. 4. The guest compound, wherein a metal ion trapped by the host compound and a lubricant molecule having a terminal functional group forming a counter ion with the metal ion are used in combination. Lubrication layer described 5. The lubricating layer according to claim 2, wherein the guest compound is a compound having a molecular skeleton responsible for a lubricating action and a basic end group. 6. A magnetic recording medium provided with the lubricating layer according to claim 1. 7. A method for producing a magnetic recording medium comprising a magnetic layer, a protective layer and a lubricating layer containing a host-guest complex formed on a non-magnetic substrate in this order, wherein a multidentate ligand as a host compound and a guest compound are used as a guest compound. A method for producing a magnetic recording medium, characterized in that a lubricant layer is laminated by applying a solution in which the lubricant compound of