JPH0836742A - Lubricating layer and magnetic recording medium - Google Patents

Abstract

PURPOSE:To provide a lubricating layer which has excellent durability for a long term by combining a cyclic polydentate ligand having a molecular skeleton bearing a lubricating action as a substituent with a chain lubricant molecule having a polar functional group for use. CONSTITUTION:This lubricanting layer is characterized by combining a cyclic polydentate ligand having a molecular skeleton bearing a lubricating action as a substituent with a chain lubricant molecule having a polar functional group for use. The lubricating layer is provided in a magnetic recording medium, thereby providing excellent lubricity and abrasion resistance and preventing stiction phenomena to obtain a magnetic recording medium which has high reliability under the severe conditions of high humidity and the like. Particularly, when it is applied to a magnetic recording medium and a smooth base to deal with the low floating of a head is used, the adsorption of the head which is peculiar to a liquid lubricant is not generated, so that excellent lubricity and sufficient durability my be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lubricating layer that exhibits a lubricating function even at a film thickness of several nm or less at a solid contact interface that 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 order to avoid these phenomena, the suppression of the meniscus of the liquid lubricant has been studied, and a fixing method thereof has been proposed.

Various methods have been proposed so far for introducing a functional group into a perfluoropolyether compound to improve the binding force of a molecule. For example, as a method for immobilizing a lubricant molecule, a fluorine-containing polymer having an acylazide group is used. A perfluoropolyether compound having amino groups at both ends may be used as a method in which a combined lubricant is attached to the surface of the protective film and then heat treated (JP-A-2-27521), or a method in which two kinds of lubricants are combined. And a perfluoropolyether compound having a carboxyl group at both ends are mixed to form a hydrogen bond network (JP-A-5-205253). However, the demands for improving the performance of magnetic recording media are strict, and it cannot be said that the conventional configuration has sufficient characteristics. Especially, the lubricity, the wear resistance, the corrosion resistance, and the adsorption (stiction) characteristics under high humidity are required. Further improvement in long-term durability including the above is desired.

[0008]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it can be used for many years by constructing a lubricating layer having excellent durability even under severe conditions. An object of the present invention is to provide a magnetic recording medium having a high recording density that withstands the above-mentioned problems. That is, the gist of the present invention resides in a lubricating layer characterized by using a cyclic polydentate ligand having a molecular skeleton having a lubricating action as a substituent and a chain lubricant molecule having a polar functional group in combination. By providing the magnetic recording medium with the lubricating layer, the magnetic recording medium has excellent lubricity and wear resistance, prevents stiction phenomenon, and is highly reliable even under more severe conditions such as high humidity. Is obtained.

A chain lubricant molecule having a polar functional group is used as one of the components constituting the lubricating layer of the present invention.
The polar functional group is preferably located at the end of the lubricant molecule from the viewpoint of interaction with the cyclic polydentate ligand. As the chain lubricant molecule, either a liquid lubricant molecule or a solid lubricant molecule can be used. The liquid lubricant molecules, usually, used an alkyl fluoride liquid lubricant such as _{perfluoropolyether, - (CF 2 CF 2 CF} 2 O)
Fomblin lubricant having _m (CF ₂ O) _n -skeleton manufactured by Montedison Co., Ltd .- (CF ₂ CF ₂ CF ₂ O) _p-
Daikin Industries, Ltd. demnum-based lubricant having a skeleton,-
(CF ₂ CF (CF ₃ ) O) _q- Crytox type lubricant having a skeleton manufactured by DuPont and the like can be mentioned. In the above formula, m, n, p, and q are integers of 1 or more, but usually 5
The thing of about 50 is used. Further, the molecular weight is preferably 500 or more, and particularly preferably about 600 to 8000. In addition, the perfluoropolyether-based molecular skeleton exemplified above further includes a branched or straight-chain saturated or unsaturated higher aliphatic hydrocarbon chain, and a higher aliphatic hydrocarbon chain containing an aromatic group or a hetero atom. It is also possible to use a combination of the above. Other lubricant skeletons are polybutene-based, polyalkylene glycol-based, phosphoric acid ester-based, polyolefin-based, polyol ester-based, alkylnaphthalene-based, silicone oil-based, polyarylalkane-based, polyphenyl-based, silicate-based, polyphenyl A liquid lubricant having an ether skeleton can be used. As the solid lubricant molecule, a branched or linear saturated or unsaturated higher aliphatic hydrocarbon chain, the higher aliphatic hydrocarbon chain containing an aromatic residue or a hetero atom,
Alternatively, any one having a lubricating action, such as one having a long chain molecular skeleton in which a part or all of the higher aliphatic hydrocarbon chain forms a polyether chain, can be selected regardless of the type of bond. . The number of carbon atoms in the long chain molecular skeleton is 8 or more, preferably 12 or more.

The polar functional group serving as the binding site for the cyclic polydentate ligand is a polar functional group that interacts with the donor atom of the cyclic polydentate ligand, specifically, a hydroxyl group or a carboxyl group. Oxygen-containing polar functional groups such as, amino groups, nitrogen-containing functional groups such as imino groups, phosphorus-containing functional groups such as phosphoric acid groups and phosphoric acid ester groups, or mercapto groups, sulfonic acid groups, sulfonic acid ester groups and the like. A sulfur functional group or the like is used. A chain lubricant molecule having a typical polar group is exemplified below.

[0011]

Embedded image HOCH ₂ CF ₂ (OCF ₂ CF ₂ ) _p- (OCF ₂ ) _q-
OCF ₂ CH ₂ OH F- (CF ₂ CF ₂ CF ₂ O) _n -CF ₂ CF ₂ COOH HOOCCF ₂ CF ₂ O- (CF ₂ CF ₂ CF ₂ O) _n -CF ₂ C
F ₂ COOH F- (CF ₂ CF ₂ CF ₂ O) _n -CF ₂ CF ₂ CH ₂ CH ₂ CO
OH HOOCCH ₂ CH ₂ CF ₂ CF ₂ O- (CF ₂ CF ₂ CF ₂ O)
_{n -CF 2 CF 2 -CH 2 CH} 2 COOH F- (CF 2 CF 2 CF 2 O) n -CF 2 CF 2 CH 2 OH HOCH 2 CF 2 CF 2 O- (CF 2 CF 2 CF 2 O) n CF ₂ C
F ₂ CH ₂ OH F- (CF ₂ CF ₂ CF ₂ O) _n -CF ₂ CF ₂ NH ₂ H ₂ NCF ₂ CF ₂ O- (CF ₂ CF ₂ CF ₂ O) _n -CF ₂ CF _{2
NH 2 F- (CF 2 CF 2} CF 2 O) n -CF 2 CF 2 OP (= O) (OH)
₂ (HO) ₂ (O =) POCF ₂ CF ₂ O- (CF ₂ CF ₂ CF ₂ O) _{n
-CF 2 CF 2 -OP (= O} ) (OH) 2 RCH 2 OCH 2 CF 2 (OCF 2 CF 2) p - (OCF 2) q -O
_{CF 2 CH 2 OCH 2 -R CF} 3 CH 2 CF 2 (OCF 2 CF 2) p - (OCF 2) q -OCF 2
CH ₂ OCH ₂ —R (in the formula, represents a 1,3-dioxaindan-5-yl group, n, p, and q are 1 or more, preferably an integer of 5 to 50)

The cyclic polydentate ligand, which is another component of the lubricating layer of the present invention, is a polydentate ligand in which donor atoms are arranged in a ring, and the molecular skeleton having a lubricating function is used as a substituent. By having them, it is possible to effectively interact with the above-mentioned chain lubricant molecules to form an excellent lubrication system. In order to impart flexibility as a molecule in the skeleton of a cyclic structure, it is preferable that the atoms constituting the ring, particularly the donor atom, have a lone electron pair composed of sp ³ electron orbit. In general, cyclic ethers collectively called crown ethers, cyclic ether amines generally called cryptands or cryptates, cyclic amines, cyclic polypeptides and their chemically modified products are used. Among them, cryptand and benzo-9 -Crown-3, benzo-12-crown-4, benzo-15-
Crown-5, benzo-18-crown-6, dibenzo-12-crown-4, dibenzo-15-crown-
5, dibenzo-18-crown-6, tribenzo-18
Compounds having a crown ether skeleton such as -crown-6, tribenzo-21-crown-7 and tetrabenzo-24-crown-8 are particularly effective. As the crown ether compound, the following general formula

[0013]

Embedded image

(In the formula, n is an integer of 3 to 10, the structural unit A represents an ethylene group or a phenylene group which may have a substituent, and at least one of A is a long chain carbon skeleton. Having an organic group having as a substituent), at least one of the structural units A in the formula has the formula

[0015]

Embedded image

(Wherein R ₁ represents an organic group having a long-chain carbon skeleton, R ₂ represents an organic group having a long-chain carbon skeleton or hydrogen, and m is an integer of 1 to 4). A crown ether compound having a phenylene group is preferable. As the crown ether compound, particularly preferably used are the following general formulas.

[0017]

[Chemical 4]

(In the formula, R represents an organic group having a long-chain carbon skeleton, m is an integer of 1 to 3, n is an integer of 1 to 9,
In addition, when m = 1, n = 2 to 9, when m = 2, n = 1 to 4, and when m = 3, n = 1 to 2
Is a compound). The organic group having a long-chain carbon skeleton which at least one of the structural units A has as a substituent can be selected regardless of the presence or absence of a branched structure, an unsaturated bond, or a hetero atom. Those having a number of 12 to 24 are preferable. If the number of carbon atoms in the straight chain portion is less than 12, the durability is insufficient, and if the number of carbon atoms exceeds 24, the solubility in the solvent becomes poor and it becomes difficult to coat the disk. The long-chain carbon skeleton is usually composed of hydrocarbons, but may be partially fluorinated or composed of perfluoropolyether.

Specific examples of the long-chain carbon skeleton include C₁₂H_{twenty five}
-, C₁₆H₃₃-, C₁₇H₃₅-, C₁₈H₃₇-, C₁₉H
₃₉-, C₂₀H₄₁-, C_{twenty two}H₄₅-, C_{twenty four}H₄₉-Straight chain
Rukiru group, C₁₄H₂₉O (CH₂)_n-, C_FifteenH₃₁O (C
H₂)_n-, C₁₆H₃₃O (CH₂)_n-, C₁₇H₃₅O
(CH₂)_n-, C₁₈H₃₇O (CH₂)_n-, C₁₉H₃₉
O (CH₂)_n-, C₂₀H₄₁O (CH₂)_n-C such as_m
H_{(2m + 1)}O (CH₂)_nAn alkoxy alk represented by
Group, C₁₁H_{twenty three}COO (CH₂)_n-, C₁₂H_{twenty five}COO
(CH₂)_n-, C₁₃H₂₇COO (CH₂)_n-, C₁₄
H₂₉COO (CH₂) _n-, C_FifteenH₃₁COO (CH₂)
_n-C such as_mH_{(2m + 1)}COO (CH₂)_nIndicated by-
Alkylcarbonyloxyalkyl group, C₁₆H₃₃NHC
O (CH₂)_n-, C₁₇H₃₅NHCO (CH₂)_n-,
C₁₈H₃₇NHCO (CH₂)_n-, C₁₉H₃₉NHCO
(CH₂)_n-C such as_mH_{(2m + 1)}NHCO (CH₂)_n
An alkylcarbamoylalkyl group represented by-, C₁₆H
₃₃NHCONH (CH₂)_n-, C ₁₇H₃₅NHCONH
(CH₂)_n-, C₁₈H₃₇NHCONH (CH₂)
_n-, C ₁₉H₃₉NHCONH (CH₂)_n-C such as_mH
_{(2m + 1)}NHCONH (CH₂)_nAlkyl represented by-
Ureidoalkyl group, C₁₆H₃₃NHCOO (CH₂)_n
-, C₁₇H₃₅NHCOO (CH₂)_n-, C₁₈H₃₇NH
COO (CH₂)_n-, C ₁₉H₃₉NHCOO (CH₂)
_n-C such as_mH_{(2m + 1)}NHCOO (CH₂)_nIndicated by-
Alkylcarbamoyloxyalkyl group (m is 12
Or more, preferably an integer of 12 to 24, n is 1 or more, preferably
Or an integer of 1 to 11), C₁₂H_{twenty five}(C₁₂H_{twenty five})
CH-, C₁₂H_{twenty five}(C₁₂H_{twenty five}) CHCH₂-, C₁₃H₂₇
(C₁₁H_{twenty three}) CHCH₂-, C₁₆H₃₃(C₁₆H₃₃) CH
CH₂-, C₁₈H₃₇(C₁₂H_{twenty five}) CHCH₂-, C₁₈H
₃₇(C₁₈H₃₇) CHCH₂-C such as_xH_{(2x + 1)}(C_yH
_{(2y + 1)}) CH (CH₂)_(z-1)-A branched chain
Rukiru group, C₁₂H_{twenty five}(C₁₂H_{twenty five}) CHO (CH₂)
_z-, C₁₂H_{twenty five}(C₁₂H_{twenty five}) CHCH₂O (CH₂)_z
-, C₁₃H₂₇(C₁₁H_{twenty three}) CHCH₂O (CH₂)
_z-, C₁₆H₃₃(C₁₆H₃₃) CHCH₂O (CH₂)_z
-, C₁₈H₃₇(C₁₂H_{twenty five}) CHCH₂O (CH₂)
_z-, C₁₈H₃₇(C₁₈H₃₇) CHCH₂O (CH₂)_z
-C such as_xH_{(2x + 1)}(C_yH_{(2 y + 1)}) CH (CH₂)_n
O (CH₂)_zA branched-chain alkyloxy group represented by-
Rukiru group, (C₁₆H₃₃OCH₂)₂CHOCH₂CH₂
-, (C₁₈H₃₇OCH₂)₂CHOCH₂CH₂-, (C
₁₈H₃₇OCH₂)₂CHO (CH₂)₆-, (C₁₈H₃₇
OCH₂)₂CHO (CH₂)₁₁-Etc. (C_xH_{(2x + 1)}
OCH₂)₂CHO (CH₂)_zIndicated by- (branched chain
Alkyloxyalkyl) oxyalkyl group, (C₁₆
H₃₃)₂NCO (CH₂)₃-, (C₁₈H₃₇)₂NCO
(CH₂)₃-C such as_xH_{(2x + 1)}(C_yH_{(2y + 1)}) NC
O (CH₂)_zDialkylcarbamoylurea represented by
Rualkyl group (x is an integer of 12 or more, preferably 12 to 24)
Is an integer of 1, y is an integer of 1 or more, z is an integer of 1 or more, preferably
Or an integer of 1 to 11, n is an integer of 0 or more, preferably 0
~ 11 is an integer), (C₁₂H_{twenty five})₃C-, (C ₁₆H
₃₃)₃CCH₂-, (C₁₈H₃₇OCH₂)₃CCH₂−
A branched chain alkyl group having a tertiary carbon such as
(CF₃CH₂OCH₂)₂CHO (CH₂)₁₁-,
(CF₃(CF₂)_FiveCH₂CH₂OCH₂)₂CHO
(CH₂)₁₁-, F (CF (CF₃) CF₂O)_nCF
(CF₃) CF₂CH₂-, F (CF₂CF₂CF
₂O)_nCF₂CF₂CH₂-, F (CF₂CF₂O)
_p(CF₂O)_qCF₂CH₂-(N, p and q are 1
Or more, preferably an integer of 5 to 50)
Included are polyether substituents. Specifically, for example
The following compounds may be mentioned.

[0020]

Embedded image

[0021]

[Chemical 6]

[0022]

[Chemical 7]

The lubricating layer of the present invention can be applied to various solid surfaces, for example, polymers, carbon, oxides, nitrides, borides, metals, etc., to which cyclic polydentate ligands can be attached. If so, it is widely applied regardless of its type.
In particular, 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 lowered, so that the data recording density of the disk can be increased and the reliability can be maintained for a long time. It is possible to build a highly reliable disk system.

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 are sequentially formed on a non-magnetic substrate 1, a cyclic polydentate ligand 4 having a molecular skeleton 5 in which the lubricating layer plays a lubricating action, and a polar functional group are provided. The group 6 is a lubricating layer composed of chain lubricant molecules 7 trapped in the cyclic polydentate ligand 4. 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. The thin film magnetic layer provided on the non-magnetic substrate is not particularly limited, but, for example, after providing an undercoat layer of chromium or the like, for example, a Co-P-based or Co-based
-Ni-P system, Co-Ni-Cr system, Co-Cr-Ta
System, Co-Ni-Pt system, Co-Cr-Pt system, Co-
A Co alloy such as a Cr-Pt-B type alloy or a Co-Cr-Ta-Pt type alloy is formed by an electroless plating method, a sputtering method or the like. The film thickness of the thin film magnetic layer is determined by the characteristics required for the magnetic recording medium, and is usually 20 to 100 n.
m. 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 usually 5 to 5
It is used in a film thickness of 0 nm, preferably 10 to 30 nm. In addition, the substrate on which the lubricating layer is provided reduces the contact area with the head to bring out better tribological performance,
Add texture to measure the average roughness of the surface to 2
It is desirable to set the thickness to 10 nm, preferably 3 to 8 nm.

To form the lubricating layer of the present invention on the surface of a solid substrate, usually, a solution in which a chain lubricant compound is dissolved together with the cyclic polydentate ligand having the above-mentioned lubricating function, or a solid substrate is added to each solution. Other than this, the spin coat method, or a method of forming a coating by contacting a tape impregnated with the solution onto the surface of the solid substrate under a load to form a coating, or a pad on the solid substrate. A method of attaching while rotating, a spray method, an LB film method, or the like can be used. Although the concentration of the coating liquid varies depending on the type of polydentate ligand compound or chain lubricant compound and the type of solvent, it is usually 0.1 to 5 as the concentration in the solution.
Used at g / l. The film thickness of the lubricating layer is preferably up to about 8 nm, but if the film thickness is small, the lubrication performance is inferior, and if the film thickness is large, stains may occur during sliding.
It is preferably within the range of nm.

[0027]

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 (120 nm), a cobalt alloy magnetic thin film (50 nm) and hydrogenated carbon were formed on a smooth aluminum alloy substrate having a center line average roughness (Ra) of 4 nm and a diameter of 3.5 inches and a sputtering method. Protective film (20nm)
Was formed.

A chloroform solution containing 4,4'-di (stearylamino) benzo-18-crown-6 at a concentration of 0.93 mmol / l was used, and the surface of the disk was uniformly distributed to a thickness of 2.2 nm by a dipping method. Formed a film. 0.5 mmol of perfluoropolyether having an average molecular weight of 2000 and OH at both ends (Fomblin Z DOL manufactured by Montedison Co., Ltd.) was added to a disk having a fixed film of 4,4-di (stearylamino) benzo-18-crown-6. /
Fluorine-based solvent PF5080 (Sumitomo 3M
Solution was used to form a uniform film on the surface of the disk by the dipping method, and then the film was baked at 80 ° C. for 45 minutes to form a uniform lubricating film having a total thickness of 3.5 nm.

A CSS test was conducted using the obtained disk. CSS test is 75 nm at a peripheral speed of 8.7 m / sec.
Floating 70% thin film head slider (material: Al ₂ O
_3- TiC, pressing force 6 gf). After the spindle was energized for 3 seconds and the power was turned off for 9 seconds, a total of 12 seconds was set as CSS1 cycle, and the torque at the start of spindle rotation and the torque at sliding were measured for each cycle. The torque during sliding was determined from the maximum value of the force acting on the head between 0.3 seconds and 1 second after the spindle was energized. The CSS cycle was performed 20,000 times, and the torque at the start of rotation and the torque at the time of sliding were selected from the highest 10 points, and the average was obtained.

As a result of the above CSS test, neither the disk nor the head was dirty, and the torque at the start of rotation was 27.8 gf.
cm, and the sliding torque was 10.6 gf · cm. Example 2 4,4'-di (octadecylamino) dibenzo-18-
Using a chloroform solution containing Crown-6 at a concentration of 0.93 mmol / l, a protective layer was formed by a dipping method in the same manner as in Example 1 on the surface of a disk having a thickness of 2.5.
A uniform film having a thickness of nm was formed. 0.5 mmo of perfluoropolyether having an average molecular weight of 4,000 and OH at both ends (Fomblin Z DOL manufactured by Montedison Co.) was added to this disk.
A uniform lubricating film having a total thickness of 4.0 nm was formed on the surface of the disk by a dipping method using a solution of a fluorine-based solvent PF5080 (manufactured by Sumitomo 3M Co., Ltd.) contained at a concentration of 1 / l.

Using the obtained disk, a CSS test was conducted in the same manner as in Example 1 under the conditions of 32 ° C. and 80% relative humidity. As a result, neither the disk nor the head was stained, and the torque at the start of rotation was 20.0 gf.・ Cm, sliding torque is 8.0g
It was f · cm. Example 3 A chromium underlayer (200 nm) and a cobalt alloy magnetic thin film (40 nm) were formed by sputtering on an aluminum alloy substrate.
nm), and stearylamine and 4,4′-di (stearylamino) benzo-18-crown-6 on the surface of a 3.5-inch diameter magnetic disk having a hydrogenated carbon protective film (30 nm) formed thereon. 1.0 mmol / l each
Using a chloroform solution containing the above concentration, a lubricating layer having a thickness of 3.1 nm was formed by the spin coat method. Using the obtained disc, a continuous sliding test with a thin film head (load 9.5 gf, sliding linear velocity 0.32 m / sec (radius 35 m
m, 100 rpm)). As a result, continuous sliding 2
The frictional force after the lapse of time was 3.2 gf, and it was confirmed that good lubricating performance was retained, and no sliding mark was found on the disc after the test.

Comparative Example 1 A perfluoropolyether having an average molecular weight of 2000 and OH at both ends (Fomblin Z DOL manufactured by Montedison Co.) was 1.0.
Fluorine-based solvent PF5080 containing at a concentration of mmol / l
A uniform film having a thickness of 3.0 nm was formed on the surface of the disk on which the protective film was formed by the dipping method using the solution (Sumitomo 3M). Then 80
℃, burned for 45 minutes, the thickness of the disk surface 1.7nm
To form a uniform film. The obtained disc was subjected to a CSS test in the same manner as in Example 1, and
The head was clean, but the torque at the start of rotation was 6
7.4 gf · cm, sliding torque is 19.8 gf · cm
Met.

Comparative Example 2 A perfluoropolyether having an average molecular weight of 4000 and OH at both ends (Fomblin Z DOL manufactured by Montedison Co.) was 1.0.
Fluorine-based solvent PF5080 containing at a concentration of mmol / l
A uniform film having a thickness of 2.2 nm was formed on the surface of the disk on which the protective film was formed by the dipping method using the solution (Sumitomo 3M). Then 80
℃, burned for 45 minutes, the thickness of the disk surface 1.7nm
Of the lubricating layer was formed. The obtained disk was subjected to a CSS test in the same manner as in Example 2. As a result, neither the disk nor the head was contaminated, but the torque at the start of rotation was 93.6.
The gf · cm and the sliding torque were 93.4 gf · cm.

Comparative Example 3 A chloroform solution containing stearylamine at a concentration of 3 mmol / l was used to dip the protective film in the same manner as in Example 1, and the thickness of the disk was 2.5 n.
m uniform lubricating layer was formed. The obtained disc was tested for lubrication performance in the same manner as in Example 1,
After 27 minutes of continuous sliding, the frictional force exceeded 7 gf and sliding marks were observed on the disc after the test.

When a smooth disc was directly coated with perfluoropolyether as a liquid lubricant as in Comparative Examples 1 and 2, the lubricant moved on the surface because the interaction with the surface of the protective film was low. It is considered that the meniscus gathers at the actual contact portion between the head and the disk. In particular,
Under high humidity, meniscus due to water is added to this, and stiction remarkably increases as in Comparative Example 2. On the other hand, when crown ether is used as the liquid lubricant, the liquid lubricant is fixed on the smooth substrate, and
In the case of 2, the torque at the start of rotation is 30g even under high humidity.
It can be seen that the stiction is suppressed because it is reduced to f · cm or less.

[0036]

According to the present invention, a thin film having excellent lubricity
A highly reliable lubricating layer having wear resistance and capable of maintaining excellent durability for a long period of time can be obtained. In particular,
When applied to a magnetic recording medium, when a smooth substrate compatible with low flying height of the head is used, it does not cause adsorption to the head, which is peculiar to liquid lubricants, and has good lubricity and sufficient durability. Have sex. 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 diagram showing the structure of a lubricating layer of the present invention.

[Explanation of symbols]

 1 Non-magnetic Substrate 2 Magnetic Layer 3 Protective Film 4 Cyclic Polydentate 5 Molecular Skeleton for Lubrication 6 Polar Functional Group 7 Chain Lubricants Molecules

Continuation of the front page (72) Fumiaki Yokoyama Inventor, Fumiaki Yokoyama 1000 Kamoshida-cho, Midori-ku, Yokohama-shi, Kanagawa Mitsubishi Kasei Co., Ltd.

Claims (5)

[Claims] 1. A lubricating layer comprising a combination of a cyclic polydentate ligand having a molecular skeleton having a lubricating function as a substituent and a chain lubricant molecule having a polar functional group. 2. The donor atom in the cyclic polydentate ligand is sp.
The lubricating layer according to claim 1, having a lone electron pair consisting of ^three electron orbits. 3. The lubricating layer according to claim 1, wherein the cyclic polydentate ligand has a crown ether skeleton. 4. The lubricating layer of claim 1, wherein the polar functional group is located at the end of the chain lubricant molecule. 5. A magnetic recording medium comprising the lubricating layer according to claim 1.