JPH07176043A - Lubricating layer - Google Patents

Abstract

PURPOSE:To obtain excellent lubricity, wear resistance and durability of a lubricating layer of a small film thickness as about a monomolecular film by applying a mixture of lubricant molecules having basic functional groups at only one end of the molecule and lubricant molecules having acid functional groups at only one end of the molecule on a solid surface to form a lubricating layer. CONSTITUTION:The magnetic recording medium has a magnetic layer 2, protective film 3, and lubricating layer 4 successively on a nonmagnetic substrate. The recording medium contains functional groups of lubricant molecules having basic functional groups at only one end of the molecule and functional groups of lubricant molecules having acid functional groups at only one end of the molecules. These functional groups cause electrostatic interaction with the surface of the protective film 3 as well as forms the lubricating layer 4 by the electrostatic interaction between the lubricant molecules. Thereby, a lubricant oil excellent in lubricity and wear resistance even when a thin film is obtd. and maintains its state for a long time without causing aggregation of lubricant molecules. Moreover, by applying this lubricant oil to a magnetic recording medium, the data recording density can be increased and reliability of the medium can be highly maintained for a long time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a lubricating layer that exhibits a lubricating function with a thin film at a solid contact interface that slides at high speed. Specifically, it relates to a lubricating layer in a high recording density magnetic recording medium used in the information industry and the like.

[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 nitrogen film, a boride film, etc. are 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 meniscus 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 order to avoid these phenomena, it is proposed to introduce a functional group into the perfluoropolyether compound to improve the binding force of the molecule, or to fix the perfluoropolyether compound to the substrate by ultraviolet irradiation, Further, a solid lubricant that does not fundamentally form a meniscus is desired, and higher fatty acids and metal salts thereof have been proposed for some time.

As a method of introducing a functional group into a perfluoropolyether compound to improve the binding force of molecules, for example, a perfluoropolyether compound having amino groups at both ends and a perfluoropolyether having carboxyl groups at both ends are used. There has been proposed a method of forming a hydrogen bond network by mixing with a polyether compound (JP-A-5-205253). According to this method, an apparent molecular weight is increased due to hydrogen bonds between lubricant molecules, and scattering due to rotation of the disk is less likely to occur, but the hydrogen bond network formed in this case is three-dimensional. Therefore, like gels, the molecules are three-dimensionally connected and their free movement is suppressed, and a film thickness of about 100Å is required to obtain sufficient lubrication performance. If a thin film having a thickness of about 50 Å or less is used in response to the demand for lower flying height of the head, it is difficult to obtain sufficient lubricity because free movement of molecules is suppressed.

A method of fixing a perfluoropolyether compound to a substrate by irradiation with ultraviolet rays (eg, H. Ohtani et.
al., Proceedings of Japan International Tribology
Conf., 1689 (1990).) Does not control at which position in the lubricant molecule the bond is formed, and forms a chemical bond everywhere between the lubricant molecule and the substrate or between the lubricant molecules. However, since the fixation of the lubricant molecules has a trade-off relationship with the lubrication performance, if the fixation is prioritized, satisfactory lubricity cannot be obtained.

On the other hand, solid lubricants such as higher fatty acids and metal salts thereof have a stable solid state at room temperature, and therefore, when applied on a disk, a part of the coating film is likely to crystallize and aggregate. was there. Especially when the substrate is smoothed, the tendency of aggregation is remarkable. If the agglomeration occurs, the thickness of the coating becomes uneven, which increases the possibility that the head and the disk come into direct contact with each other, and may cause the head to become dirty or cause the flight of the head to become unstable. 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.As a method for fixing the lubricant layer molecules to the substrate, a long chain alkyl group is used. Method of fixing by siloxane bond (Japanese Patent Application Laid-Open No. 2-10
3721 and JP-A-2-103722) have been proposed. However, the method of fixing the lubricating layer by covalent bonding suppresses the movement of molecules, and the lubricity is insufficient. This is because fixing the lubricant has a trade-off relationship with the lubricating performance.

The fixing system is ideally a reversible fixing method in which the lubricant molecules interact with the substrate with sufficient strength to prevent agglomeration, and the fixing does not have a trade-off relationship with the lubricating performance. Target. The present invention provides a lubricating layer that exhibits excellent lubricity even when it is a thin film and in which lubricant molecules do not aggregate, that is, if fixing the lubricant has a trade-off relationship with the lubricating performance. It was achieved by designing the lubrication system on the molecular / atomic order for the purpose of obtaining a lubricating layer having excellent durability.

[0011]

SUMMARY OF THE INVENTION An object of the present invention is to provide a lubricating layer which exhibits lubricity and wear resistance on a solid surface for a long period of time and has no aggregation of lubricant molecules. Is a lubricant layer in which a lubricant molecule having a basic functional group only at one end and a mixture of two or more lubricant molecules having an acidic functional group at only one end are attached to a solid surface, A functional layer of each of the two or more lubricant molecules forms a bond with the solid surface by electrostatic interaction and is also bonded to each other by electrostatic interaction. To be achieved.

That is, in the lubricating layer of the present invention, the lubricant molecules are bound to the solid surface by electrostatic interaction due to the functional groups at the ends of the molecules, and the lubricant molecules are mutually interacted on the solid surface by electrostatic interaction. By binding, a two-dimensional network due to these electrostatic interactions is formed on the solid surface, so that the lubricant molecules stick to the solid surface with good orientation and the binding mode is reversible. Not only can the lubricant be prevented from agglomerating, but a more durable lubricating layer can be realized.

When the lubricating layer of the present invention is applied to a magnetic recording medium, it is excellent in lubricity and wear resistance and the flying height of the head can be lowered, so that the data recording density of the disk can be increased. In addition to being possible, it is possible to build a highly reliable disk system for a long period of time. Hereinafter, the present invention will be described in detail.

FIG. 1 shows the structure of a magnetic recording medium having a lubricating layer formed on its surface according to the present invention. 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, a lubricant molecule having a basic functional group at only one end and an acidic functional group at only one end. It is shown that the respective functional groups of the lubricant molecule having the above have an electrostatic interaction with the surface of the protective film 3 and form the lubricating layer 4 by the mutual electrostatic interaction.

In forming a lubricating layer on a magnetic recording medium, an aluminum alloy plate or a glass substrate provided with a nickel-phosphorus layer formed by an electroless plating method is usually used as the non-magnetic substrate. A ceramic substrate, a resin substrate or the like can also be used. A thin film magnetic layer of cobalt, cobalt alloy, etc. is formed on a non-magnetic substrate,
It is formed by an electroless plating method, a sputtering method, or the like, directly or through an undercoat layer if necessary. The film thickness of the thin film magnetic layer is determined by the characteristics required for the magnetic recording medium, and is usually 200 to 1500Å. As the protective film, a carbonaceous film is preferable, which is formed by a sputtering method, an ion plating method, a plasma polymerization method or the like, and is usually used in a thickness of 50 to 500 Å, preferably 100 to 300 Å.

The center line average roughness (Ra) of the surface of the protective film on which the lubricating layer is formed can correspond to 20 to 100 Å, and it is also used for those having a smooth surface such as 20 to 70 Å. Therefore, it is also advantageous to realize a low flying height of the head. When a carbonaceous film is used as a protective film, if left in the atmosphere after film formation, the surface condition will change and due to adsorption of organic substances in the air, etc.
The contact angle of water on the surface may rise to about 50 degrees. In this way, for a carbonaceous protective film that has changed to an inactive state or a film in which unbonded carbon atoms are terminated by hydrogen atoms such as hydrogenated carbon, a lubricant having a basic functional group at only one end is used. Even if it is made to act, it is difficult to obtain a sufficiently strong interaction.

It is considered that when the protective film containing carbon as a main component is irradiated with ultraviolet rays, a functional group containing active hydrogen bonded to an oxygen atom is generated, and the contact angle of water on the surface is reduced to 5 degrees or less. When a lubricant molecule having a basic functional group at only one end is applied to the surface of the protective film that has changed to hydrophilic, the basic functional group strongly interacts with the functional group on the surface of the protective film. The ultraviolet irradiation method has a wavelength of 185.
nm, 254 nm, and an output of 50 W or more for 30 seconds to 1 from a distance of 10 mm to 50 mm in an oxygen-containing atmosphere.
Irradiate for 5 minutes, preferably 1 to 5 minutes.

When a functional group containing active hydrogen bonded to an oxygen atom such as a hydroxyl group or a carboxyl group is present on the surface of the protective film to a certain extent or more, a lubricant having a basic functional group at only one end such as an amino group. When the molecule is applied to the surface of the protective film, the basic functional group strongly interacts with the functional group on the surface of the protective film, and at this time, a lubricant molecule having an acidic functional group at only one end such as a carboxyl group is surrounded by the surrounding functional group. If present, the basic functional group also interacts strongly with the acidic functional group to form a network. That is, a lubricant molecule having a basic functional group at only one end and a lubricant molecule having an acidic functional group at only one end are allowed to coexist on the solid surface at an appropriate mixing ratio, thereby allowing The basic functional group of the lubricant molecule forms a two-dimensional network with the acidic functional group of the other lubricant molecule and the functional group on the solid surface by electrostatic interaction such as ionic bond and hydrogen bond. . In addition, since the terminal functional group is coordinated to the substrate side and the alkyl chain portion of the lubricant molecule is oriented upward with respect to the substrate, the contact angle of water on the surface of the lubricating layer is 90 degrees or more, and the orientation of the entire lubricating layer is The property is improved.
Regarding the orientation of the alkyl chain, FT-IR (R
It can be confirmed by analysis by the AS method) and measuring the absorption derived from the CH ₂ group of the alkyl chain and the absorption derived from the CH ₃ group of the tip of the alkyl chain. As a result, a lubricating layer having an ideal structure and having superior lubricating performance and durability can be obtained.

The lubricant molecule having a basic functional group at only one end and the lubricant molecule having an acidic functional group at only one end, which constitute the lubricating layer of the present invention, are both long-chain molecules in the molecule. It is preferable to have a skeleton. Higher aliphatic amines and the like are used as the lubricant molecules having a basic functional group, and higher fatty acids and the like are used as the lubricant molecules having an acidic functional group. The long-chain molecular skeleton may be a branched or straight-chain saturated or unsaturated higher aliphatic hydrocarbon chain, the higher aliphatic hydrocarbon chain containing an aromatic residue or a hetero atom, or the higher aliphatic carbon chain. A long-chain molecular skeleton in which a part or all of the hydrogen chains form a polyether chain can be selected as long as it has a lubricating action regardless of the type of bond. In order to exhibit excellent lubricity, it is preferable that the long-chain molecular skeleton has 8 or more carbon atoms, particularly 12 or more carbon atoms. Also, from the viewpoint of solubility in a solvent,
The number of carbon atoms in a single linear alkyl group (ie, consisting of continuous carbon-carbon bonds such as methylene-methylene bonds) is preferably 24 or less.

In the lubricating layer of the present invention, 2 on the solid surface
In order to form a three-dimensional electrostatic interaction network and enhance the orientation of the lubricant molecule, it is important that the basic functional group or the acidic functional group exists only at one end of the lubricant molecule. When a basic functional group or an acidic functional group exists at both ends or at one end other than one end, such as in the middle of the lubricant molecular chain, the functional group of another molecule at a distance from the solid surface or the molecule itself. Forms a bond due to electrostatic interaction in the molecule, and has a three-dimensional gel-like network structure, which results in no orientation and impaired good lubricity. The advantage of the network due to the two-dimensional electrostatic interaction is that the network is formed on the solid surface by the functional group existing at one end of the lubricant molecule, as shown in FIG. Not only are the lubricant molecules lined up in a good orientation like a comb, but also because each molecule has a large degree of freedom, excellent lubricity is exhibited with a very thin film thickness of about a single molecule.

Further, since the bond fixing the lubricant molecule to the solid surface is a reversible bond mode called electrostatic interaction, it is possible to prevent aggregation, and even when the lubricant film is broken by impact, The lubricating layer of the present invention has a great feature of self-repairing, and not only has excellent lubricity but also excellent durability. A comb model in which lubricant molecules are fixed by a two-dimensional network on a solid surface can be realized by using a covalent bond such as a siloxane bond, but since the bonding mode is irreversible, that part breaks once. It is impossible to restore the bond. That is, the part where the lubricant is once removed loses lubricity thereafter, which is insufficient in terms of durability.

In order to effectively form a two-dimensional electrostatic interaction network on a solid surface, the ratio of lubricant molecules having a basic functional group to lubricant molecules having an acidic functional group is 100. ~ 1/100, preferably 10-1
It is / 10. For example, when the ratio of stearic acid and stearylamine was changed and the orientation of the formed lubricating layer was confirmed, when the system in which stearylamine was 1/1000 with respect to stearic acid, the orientation was comparable to that in stearic acid alone. Although there is almost no change, if it is present at about 1/100, changes in the orientation of the lubricating layer as a whole begin to appear, and at the same time, the effect of suppressing agglomeration can be seen. Was formed, and the above-mentioned effects became remarkable.

When the number of functional groups containing active hydrogen bonded to oxygen atoms such as hydroxyl groups and carboxyl groups existing on the solid surface is small, the bond due to electrostatic interaction between the lubricant molecule and the solid surface becomes insufficient. Therefore, the solid surface on which the lubricant molecules are attached preferably contains 5 atom% or more of oxygen atoms, and particularly preferably carbonaceous material containing 5 atom% or more of oxygen atoms. The sticking force of the lubricant molecules to the solid surface was evaluated by a wash test using stearylamine.As a result, in the case of a carbonaceous film containing a large number of functional groups containing active hydrogen bonded to oxygen atoms, it was fixed even after rinsing with chloroform. Whereas the lubricant layer remains, in the case of hydrogenated carbonaceous film with few functional groups containing active hydrogen bonded to oxygen atoms, almost no adhered lubricant layer remains after rinsing, and the hydrogenated carbonaceous film is irradiated with ultraviolet rays. It can also be confirmed from the fact that when the stearylamine is applied after the above treatment, the fixed lubricating layer remains after the rinse. If the oxygen content of the carbonaceous film is too high, the mechanical properties of the carbonaceous film will be problematic. Therefore, the oxygen content of the carbonaceous film is preferably 30 atomic% or less.

As a method of applying the lubricant to the solid surface,
Usually, it is carried out by immersing a solid in a solution in which two or more kinds of lubricants are dissolved, but a method of forming a coating by applying a load to a tape or the like, which is impregnated with the solution, to form a coating, the solid surface It is possible to use a method in which the pad is attached while rotating the pad, a spray method, an LB film method, or the like. The time from the irradiation of ultraviolet rays to the application of the lubricant is not particularly limited, but it is usually preferably within 1 day. Although the concentration of the solution varies depending on the type of lubricant and the type of solvent, it is usually used at 0.1 to 1.5 g / l as the total concentration in the solution.

[0025]

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 chromium underlayer (2000 Å) was formed on a smooth aluminum alloy substrate having a Ra of 60 to 70 Å by a sputtering method.
A magnetic disk with a diameter of 3.5 inches on which a magnetic thin film of cobalt alloy (400Å) and a carbon protective film (300Å) with an oxygen content of about 15 atom% were formed was used, and stearic acid and stearylamine were added at 0.5 mmol / l each. After immersing in a chloroform solution containing a concentration (total of 0.28 g / l), it was pulled up to form a uniform lubricating film having a thickness of 18Å on the surface of the disk.

Lubricating performance and cohesiveness of the disc 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 the same disc as in Example 1, stearic acid and stearylamine were added at 3 mmol / l and 0.
By immersing in a chloroform solution containing a concentration of 3 mmol / l (total 0.93 g / l), and then pulling up,
A uniform lubricating film having a thickness of 30Å 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 disk similar to that used in Example 1 was used and immersed in a chloroform solution containing stearic acid and stearylamine at concentrations of 0.3 mmol / l and 3 mmol / l (0.89 g / l in total), respectively. After that, by pulling up,
A uniform lubricating film having a thickness of 35Å 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 4 Using the same disk as in Example 1, β- (N, N-diheptadecylaminocarbonyl) propionic acid and stearylamine were added at 1.2 mmol / l and 0.
A uniform lubricating film having a thickness of 23Å was formed on the surface of the disk by immersing in a chloroform solution containing a concentration of 72 mmol / l (total 0.91 g / l) and then pulling it up. 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.
Shown in.

Example 5 A hydrogenated carbon protective film (200 Å) was formed on a disk having a cobalt alloy magnetic thin film formed in the same manner as in Example 1. Wavelength of 185 nm, 25
After irradiating with ultraviolet rays of 4 nm and an output of 90 W from a distance of 15 mm for 5 minutes, it was immersed in a chloroform solution containing stearic acid and stearylamine at a concentration of 0.8 mmol / l within 1 hour and then pulled up to A 32 Å thick uniform lubricating film was formed on the surface.
With respect to the disc on which the lubricating layer was formed, the adhesion test and the cohesion test were carried out in the same manner as in Example 1. The adhesion test was evaluated by the change in the film thickness of the lubricating layer after washing with chloroform. Chloroform was washed by immersing the disk in chloroform for 5 minutes and then pulling it up at a speed of 30 mm / min. The results are shown in Table 1.

Example 6 Using a disk which had been irradiated with ultraviolet rays in the same manner as in Example 5, β- (N, N-diheptadecylaminocarbonyl) was used.
Propionic acid and stearylamine were added to 1 mmo each
After being immersed in a chloroform solution containing a concentration of 1 / l, it was pulled up to form a uniform lubricating film having a thickness of 35Å on the surface of the disk. The disc having the lubricating layer was tested for adhesion and cohesiveness in the same manner as in Example 5.
The results are shown in Table 1.

Example 7 Using a disk having a carbon protective film (300 Å) formed in the same manner as in Example 1, UV irradiation treatment was carried out in the same manner as in Example 5, and then β- (N, N- After dipping in a chloroform solution containing diheptadecylaminocarbonyl) propionic acid and stearylamine each at a concentration of 1 mmol / l, the disk was pulled up to form a uniform lubricating film having a thickness of 29Å on the surface of the disk. The disc having the lubricating layer was tested for adhesion and cohesiveness in the same manner as in Example 5. The results are shown in Table 1.

Example 8 A hydrogenated carbon protective film (200 Å) was formed on a substrate of Ra35Å smooth aluminum alloy in the same manner as in Example 5, and β- (N, N-diheptadecylaminocarbonyl) was formed.
1 mmol each of propionic acid and stearylamine
A uniform lubricating film having a thickness of 30 Å was formed on the surface of the disk by immersing it in a chloroform solution containing a concentration of 1 / l and then pulling it up.

Regarding the disk on which the lubricating layer was formed, CS
An S test was conducted. Peripheral speed of 8.7m / for CSS test
70% thin film head that floats 750Å sec (Material:
Al ₂O₃-TiC, pressing force: 6 gf) using 22 ° C,
The measurement was performed at a position with a radius of 23 mm in an atmosphere with a humidity of 40%.
Turn on the power for 3 seconds and then turn off the power for 7 seconds.
1 second is CSS1 cycle and 20000 cycles
I went to Le. Head every CSS2000 cycle
Let stand on the disc for 60 minutes and spin the disc at 1 rpm.
Rotate at 1 degree to measure the frictional force between the head and
The average friction coefficient was calculated. The results are shown in Fig. 3.

Example 9 A disk obtained by forming a hydrogenated carbon protective film on a disk similar to that in Example 8 and performing ultraviolet irradiation in the same manner as in Example 5 was used, and β- (N, N-diheptadecylaminocarbonyl) was used. ) Propionic acid and stearylamine each 1mm
After soaking in a chloroform solution containing ol / l in concentration, by pulling it up, a uniform lubricating film having a thickness of 31Å was formed on the surface of the disk. The CSS test was performed on the disk on which the lubricating layer was formed in the same manner as in Example 8. The results are shown in Fig. 3.

Comparative Example 1 The same disc as in Example 1 was used, and stearic acid was added to 3 m.
After soaking in a methanol solution containing a mol / l concentration (0.85 g / l) for 5 minutes, the disk was pulled up at a speed of 10 mm / sec to give a thickness of 1 on the surface of the disk.
A 6Å lubricating film 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 2 Using the same disk as in Example 1, stearylamine was dipped in a chloroform solution containing 3 mmol / l (0.81 g / l) and then pulled up to give a thickness on the surface of the disk. A 25Å lubricating film 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 3 Using the same disc as in Example 1, 1 mM of β- (N, N-diheptadecylaminocarbonyl) propionic acid was added.
A uniform lubricating film having a thickness of 28Å was formed on the surface of the disk by immersing it in a chloroform solution containing a concentration of 1 / l (0.593 g / l) and then pulling it up. 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 A disk similar to that of Example 1 was used except that a silica film having a thickness of 100 Å was formed instead of the carbon protective film, and [γ-
(N-Octadecylsuccinylamino) propyl] triethoxysilane is prepared by a known method (K. Ariga et al., J. Am. C.
hem.Soc., 111,5618 (1989)), a uniform lubricating film having a thickness of 24Å in which a long chain alkyl group is bonded by a siloxane bond is formed as an LB film 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 5 As in Example 5, the surface of the disk on which the hydrogenated carbon protective film had been formed was not irradiated with ultraviolet rays, and was added to a chloroform solution containing stearic acid and stearylamine at a concentration of 0.8 mmol / l. After the immersion, by pulling up, a uniform lubricating film having a thickness of 23Å was formed on the surface of the disk. The disc having the lubricating layer was tested for adhesion and cohesiveness in the same manner as in Example 5. The results are shown in Table 1.

Comparative Example 6 In the same manner as in Example 5, β- (N, N-diheptadecylaminocarbonyl) propionic acid and stearylamine were added to the surface of the disk on which the hydrogenated carbon protective film had been formed, without irradiation of ultraviolet rays. After immersing in a chloroform solution containing each at a concentration of 1 mmol / l and then pulling up, a uniform lubricating film having a thickness of 21Å was formed on the surface of the disk. The disc having the lubricating layer was tested for adhesion and cohesiveness in the same manner as in Example 5. The results are shown in Table 1.

COMPARATIVE EXAMPLE 7 A hydrogenated carbon protective film was formed on the same disk as in Example 8, and 2 mmol of β- (N, N-diheptadecylaminocarbonyl) propionic acid was prepared without irradiation of ultraviolet rays.
A uniform lubricating film having a thickness of 30 Å was formed on the surface of the disk by immersing it in a chloroform solution containing a concentration of 1 / l and then pulling it up. The CSS test was performed on the disk on which the lubricating layer was formed in the same manner as in Example 8. The results are shown in Fig. 3.

[0043]

[Table 1]

As is clear from Table 1, in the lubricating layers of the present invention (Examples 1 to 4), the aggregation of the lubricants observed in the case of the lubricants having an acidic functional group alone (Comparative Examples 1 and 3) was It was confirmed that it was suppressed or suppressed, and it was also confirmed that it had better lubricity and durability than the lubricant alone system having a basic functional group (Comparative Example 2). That is, in the lubricating system according to the present invention, it is understood that the fixation of the lubricant and the lubricating performance do not have a trade-off relationship, and excellent lubricating performance is exhibited while suppressing aggregation. Further, the system in which the lubricant molecules are fixed by covalent bonds (Comparative Example 4) does not exhibit sufficient lubricity and durability.

The lubricating layers of Examples 5 to 7 have a larger residual film thickness after washing with chloroform as compared with the lubricating layers of Comparative Examples 5 to 6, the adhesion between the protective film and the lubricating layer is high, and aggregation is suppressed or suppressed. Is confirmed. Comparative Examples 5-6
, Without irradiating the hydrogenated carbon protective film with ultraviolet light,
A lubricant molecule having a basic end group only on one end,
Even if a lubricant molecule having an acidic end group is mixed and applied only to one end, the lubricant layer does not adhere to the protective film, resulting in severe aggregation. That is, according to the present invention, a highly oriented monomolecular film with high reproducibility can be obtained very easily and reproducibly even by an ordinary dipping method without using the LB film method, which is complicated and has difficulty in productivity. .

[0046]

EFFECTS OF THE INVENTION According to the present invention, a thin film (thickness of about a monomolecular film) has excellent lubricity and wear resistance, and moreover, lubricant molecules are maintained for a long time without agglomerating. It is possible to obtain a lubricating layer capable of Further, 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 is a conceptual diagram showing the principle of the constitution of a fixed lubricating layer by the electrostatic interaction network of the present invention, using stearic acid and stearylamine as an example.

FIG. 3 shows CSS test results of a lubricating layer of the present invention and a comparative example.

[Explanation of symbols]

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

Claims (9)

[Claims] 1. A lubricating layer comprising a lubricant molecule having a basic functional group only at one end and a mixture of two or more lubricant molecules having an acidic functional group at only one end attached to a solid surface. It is characterized in that each functional group of the two or more kinds of lubricant molecules forms a bond with the solid surface by electrostatic interaction, and is also bonded to each other by electrostatic interaction. Lubrication layer 2. The lubricating layer according to claim 1, wherein the electrostatic interaction is hydrogen bonding. 3. The electrostatic interaction is an ionic bond.
Lubrication layer described 4. The basic functional group is 10 relative to the acidic functional group.
The lubricating layer according to any one of claims 1 to 3, wherein the lubricating layer is contained in a ratio of 1/10. 5. The solid surface is carbonaceous, and the solid surface is carbonaceous.
Lubrication layer according to any one 6. The lubricating layer according to claim 1, wherein the solid surface is carbonaceous containing 5 to 30 atomic% of oxygen atoms. 7. The lubricating layer according to claim 1, wherein the solid surface is carbonaceous material that has been irradiated with ultraviolet rays. 8. A magnetic recording medium having the lubricating layer according to claim 1 on its surface. 9. The magnetic recording medium according to claim 8, wherein the center line average roughness of the solid surface on which the lubricating layer is formed is 20Å to 100Å.