JPH03132913A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve durable reliability by forming lubricant layers consisting of a partially fluorinated alkyl system via protective layers consisting of a carbon system on ferromagnetic metallic thin films. CONSTITUTION:The lubricant layers consisting of the partially fluorinated alkyl system are formed via the protective layers consisting of the carbon system on the ferromagnetic metallic thin films. For example, the ferromagnetic metallic thin films 2, 2 are provided on both surfaces of a nonmagnetic base 1 and further, the lubricating layers 4, 4 are provided via the protective layers 3, 3 consisting of the carbon system on both surfaces of the ferromagnetic metallic thin films 2, 2. The good durable reliability is obtd. in this way without degrading the performance, such as CSS durability and head attraction, even if the surface flatness is fairly improved by decreasing the projection height of the surface for the purpose of improving the recording density.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a metal thin film type magnetic recording medium suitable for high-density recording in magnetic disk drives used in computer storage devices, magnetic tapes used in VTRs, and the like.

Conventional technology] Polymer films such as polyester films, polyimide films, and aluminum alloy plates are produced using vacuum film forming methods such as vacuum evaporation, sputtering, and ion blasting using balt, nickel, iron, or alloys containing these as main components as magnetic layers. A ferromagnetic metal thin film magnetic recording medium formed on a substrate such as a glass plate (Sumo wrestlers) is capable of dramatically increasing the recording density.To achieve this, the magnetic layer must be made extremely thin and the surface of the medium must be made as thin as possible. It is necessary to flatten the media. However, these work to reduce the durability and reliability of the media. Various countermeasures are being considered for the purpose of improving the durability and reliability. In general, the so-called contact start-stop (C3S) method is adopted in the magnetic disk drive used in the device (Table 1), in which the magnetic head floats above the disk surface when the magnetic disk is in operation, and comes into contact with the disk surface when the disk is stopped. To withstand repeated contact and sliding between the magnetic rad slider and the disk surface during starting or stopping, fine irregularities (protrusions) are formed on the disk surface by texturing.A ferromagnetic metal thin film is formed on the surface. Furthermore, a protective layer and a lubricant layer mainly made of graphite, 5iOa, etc. are provided on the ferromagnetic metal thin film, and it has been proposed to use perfluoropolyether or a material modified at its molecular terminal as the lubricant layer. (Tai U.S. Patent No. 3)
778.308 Special Publication No. 109028/1982)
.

Problems to be Solved by the Invention In order to improve the recording density, it is necessary to reduce the flying distance of the magnetic head.In this case, the height of the protrusions produced by texturing is reduced to improve the surface shape. As a result, C8S durability deteriorates, and when the magnetic disk drive is stopped, the lubricant on the disk surface collects between the magnetic head and the disk, causing a so-called adsorption phenomenon in which the magnetic head is stuck to the disk surface. In order to solve this problem, the lubricant on the disk surface strongly adheres to the surface of the protective layer and the surface of the magnetic head, forming a coating layer of lubricant on those surfaces. It is important that the lubricant molecules be easily sheared between the lubricant molecules on the sliding surface with the head.

As described in the above-mentioned prior literature, perfluoropolyether used as a lubricant has good intermolecular shearing properties because almost all of its molecular surface is covered with fluorine atoms. The adhesion force is weak. In order to strengthen the adhesion to the surface of the magnetic head, it has been proposed that various types of polar groups are introduced at the end of the molecule.Perfluoropolyether itself has a molecular weight of at least 3. Since the OOQ is usually as large as 4,000 or more, the effect of introducing polar groups is not so great, and the effect of improving disk durability is not significant either. On the other hand, if the molecular weight of the perfluoropolyether itself is reduced in order to enhance the effect of the polar group, the interaction between its molecules is small, resulting in spin-out or evaporation of the perfluoropolyether itself due to high-speed rotation of the disk. Therefore, it is virtually difficult to reduce the molecular weight.On the other hand, aliphatic hydrocarbons with polar groups, such as stearic acid, have excellent adhesion strength to various surfaces and molecular orientation. The interaction between molecules is greater than that of hydrogen. When these materials are used in lubricants, it is difficult to obtain the desired durability performance. However, due to the effect of the polar group, magnetic head adsorption properties are significantly improved compared to perfluoropolyether systems. Taking into account the above, various studies have revealed that a fluorinated hydrocarbon chain is formed by bonding a fluoroalkyl end group or a fluoroaryl end group and a hydrocarbon chain in the same molecule to increase intermolecular shearability. Based on the above conclusion, we have come to the conclusion that an organic compound sumo wrestler having a specific polar group is suitable as a lubricant for the carbon protective layer on the disk in order to increase its adhesion to the disk surface and the magnetic head surface. The object of the present invention is to provide a magnetic recording medium having good durability and reliability by improving C8S durability deterioration and head attraction.

Means for Solving the Problems To achieve the above objects, the present invention provides a magnetic recording medium in which a ferromagnetic metal thin film is formed on a non-magnetic support, in which a carbon-based protective layer is provided on the ferromagnetic metal thin film. The lubricant layer is characterized by forming a partially fluorinated alkyl lubricant layer with a fluoroaryl end group or a fluoroalkyl end group having 3 or more carbon atoms and a total of 1 carbon number.
A fluorinated hydrocarbon chain bonded to a hydrocarbon chain consisting of 0 or more alkylene-attached phenylene groups or derivatives thereof or aliphatic alkylene groups having 10 or more carbon atoms, and OH, -
According to a feature of the present invention, the organic compound contained in the lubricant contains at least one organic compound having one polar group selected from SH and -CO3H. has a fluorinated hydrocarbon chain formed by bonding a fluoroalkyl end group or a fluoroaryl end group to a hydrocarbon chain and a specific polar group in its molecule, and as is clear from the examples below. Since the molecular weight is about 100 to 2,000, the effect of the polar group is fully exhibited, and this polar group strongly adheres to the surface of the carbon-based protective layer provided on the ferromagnetic metal thin film. The aryl terminal group is exposed on the surface and contributes to lowering the energy of the surface, forming a low-friction sliding surface.

In addition, the hydrocarbon chains are oriented by moderate interaction with the hydrocarbon chains of other adjacent molecules, and this intermolecular interaction prevents the evaporation of organic compound molecules.
The problems of decreased 8S durability and head adsorption will be solved.

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. The drawings are diagrams showing the basic configuration of a magnetic recording medium in one embodiment of the present invention. Ferromagnetic metal thin films 2, 2 are provided on both sides of the non-magnetic support 1, and lubricant layers 4, 4 are provided on both sides of the ferromagnetic metal thin films 2, 20 via carbon-based protective layers 3, 3. ing. The lubricant layer 4 consists of a fluoroaryl terminal group or a fluoroalkyl terminal group having 3 or more carbon atoms (regardless of linear or branched, saturated or unsaturated) and a phenylene group with alkylene or a derivative thereof having a total of 10 or more carbon atoms or carbon A fluorinated hydrocarbon chain bonded with a hydrocarbon chain consisting of an aliphatic alkylene group (straight chain, branched, saturated, unregarded [U]) of 10 or more L, and OH, -8H, -CO3H. The organic compound used in the present invention may be composed of a thin layer containing at least one organic compound having one polar group selected from
As a fluoroalkyl terminal group, CnF2n+1- HCFa(CF2)Il CIIF2n-+ (Ln represents an integer of 3 or more) As a fluoroaryl terminal group, as an aliphatic alkylene group, C, Ha - Cn Han -a Cn H2n -5 CkH2 -CH-C-Ha- CIla1・1 (However, LA n is 10 or more, k, l, m are 1 or more, k
+l+m represents an integer of 10 or more. ) As a phenylene group with alkylene, (L 1 is 0 to 4, m and n are 1 or more h l x m+
+1113 represents an integer of 10 or more. ) etc., and the fluoroalkyl terminal group or fluoroaryl terminal group and the aliphatic alkylene group or alkylene-attached phenylene group are bonded directly or through various bonding groups as shown in the examples below.

0-, -3-, -Coo-, -CON-, -8O2NR (LR is H, CH3 or C2Ha) Also, the fluorinated hydrocarbon chain and the polar group bonded as described above may be directly connected or It takes the form of bonding via various bonding groups such as.

0--(CH2)n-+-3-(Clh). −、−
Co0(CI!2)1-CON-(CH2). −、−
3O2N-(CIla), RR (where n is an integer of 1 or more, 1 is 11.cllt
or C2H5) As the fluoroalkyl terminal group, a fluoroalkyl group having 3 or more carbon atoms (preferably 5 or more carbon atoms) is suitable, and if the number of carbon atoms is 2 or less, the C8S durability decreases. In addition, as the fluoroaryl terminal group, a fluorophenyl extended fluorobiphenyl group or a derivative thereof is suitable, but as a hydrocarbon chain, an aliphatic alkylene group having a total carbon number of 10 or more (preferably 12 or more), an alkylene-attached phenylene group, or a derivative thereof. The molecular weight of the organic compound used in the present invention is i, t, 3. ,000 or less (preferably 2.000 or less)
000 or less) is appropriate. If the molecular weight is 3.000 or more, the effect of the polar group will not be sufficiently exhibited, and the desired performance will not be obtained. The atomic group weight ratio of the fluoroalkyl group or fluoroaryl group is in the range of 10 to 90% (preferably in the range of 20 to 80%) with respect to the molecular weight of the organic compound molecule.
It is within. Outside this range, a sufficient C8S durability improvement effect cannot be obtained. Or other lubricants?L It is also possible to add a rust preventive agent or the like and make it exist in a thin layer.For that purpose, known wet or dry coating methods can be applied. It is obtained by forming a lubricant layer 4 containing an organic compound on a carbon-based protective layer 3.The carbon-based protective layer 3 may be amorphous, graphite, or amorphous obtained by sputtering, plasma CVD, etc. A carbon thin film in a diamond shape, a mixture thereof, or a laminated state can be applied, and the appropriate thickness is 50 to 500.As the ferromagnetic metal thin film 2, Co-Ni, Co-Ni,
Co-Cr, Co-Ni-Cr5Co-Ni-P, Fe
-Co, Fe-C.

-A thin film obtained by vacuum evaporation, sputtering, ion blasting, etc. of Ni, etc. can be applied, and if necessary, an underlayer of Cr, Ti, etc. can be provided. The appropriate thickness of the ferromagnetic metal thin film 2 including the underlayer is 500 to 5,000.

It is also possible to form a non-magnetic metal thin organic plasma polymerized film such as Cr or Ti between the resistive ferromagnetic metal thin film 2 and the carbon-based protective layer 3 as required.a Non-magnetic support 1, the materials include metals such as Galahin ceramics and A1 plywood Ti alloy, polyesters, and polyimides.
Polyamide-imide polycarbonate melon Mainly made of plastics such as polyacrylates, etc., with Co-P plating, polyimide coating film, etc. formed on the surface as necessary, or microscopic grains of melon produced by texture processing, Yamabushi, etc. Although those with wavy or other protrusions can be used, the shape can be selected depending on the purpose, such as discrete, fill cards, drums, etc., and the surface roughness of these supports is the maximum height La. ...and 1
00 to 600 people is appropriate. Examples will be described in more detail below. Diameter 95mmnt, thickness 1.
25μm thick non-magnetic N1 on the surface of 2mm A1 alloy plate
A non-magnetic substrate is prepared by applying -P alloy plating and forming protrusions with an average roughness of 50 mm and a maximum height of 300 mm by texturing.On top of this, a 1300 mm thick Cr undercoat and a 600 mm thick Cr base layer are sputtered. A thin Co--Ni ferromagnetic metal thin film 2 was formed thereon, and a graphite protective layer 3 having a thickness of 200 mm was further formed thereon by sputtering 1 to form a sample). In the above, instead of the graphite protective layer 3, a diamond-like carbon protective layer 3 with a thickness of 50 densities was formed using the plasma CVD method as sample B. The formed product is designated as Sample C, and the product without the carbon-based protective layer is designated as Sample Sample.

Regarding Experimental Examples 1 to 20 obtained by coating each of the above-mentioned organic compounds separately on each of these samples so that the amount present was lomg per 1 m2 of the surface, immediately after coating and at 90°C, 24
C8S measurement and head suction test after standing for a period of time were carried out, and as a CSS durability test, the number of C8S at the time when the magnetic group coefficient exceeded 1.0 or the C at the time of head crash occurred.
Evaluate by the number of 8S and define these points as C8S life.
In the suction test, the slider is fixed on the disk and left at 60℃ for 24 hours.Then, when the disk is rotated at room temperature, if the force applied to the slider at startup shows an abnormal value, it is considered that suction has occurred. For each sample, Example 6: The results of the C8S test and adsorption test are summarized in Table 1.

congratulations nine Organics used in each example and comparative example CeF+tSON(CHa)13SH The compounds are shown below.

In the table, Experimental example (13) to Example 7: (20) is a comparative example 4 Example 1: CeF 1t(CH2)+70H Example 8: Example 2: C2H% C5F1vsO2N(CHa)130H Example 3: Example 9: Example 4: C1 self F2 (CH2) + 6c OS H Example 1 0: HCF2 (CI”2) 3 (CH2) + vCO5t (Example 1 1: Example 5: HCF 2 ( CF2)-(CH2)1a S H Example 1 Comparative Example 1 Comparative Example 1 3: Comparative Example 2 0: C+-Hsto H Comparative Example 1 4: C2F5(CH2)1eOH Comparative Example 1 5: C=F1v(CHa ) esH (Average molecular weight 3,200> Comparative Example 1 6. (Left below blank) Comparative Example 1 7: Comparative Example 1 8: C+sF 2+ (CH2) + eCOS H Table 1 Table 1 (continued) () indicates Comparative Example No. 1-Table, when there is no fluoroalkyl end group or fluoroaryl end group, or when the number of carbon atoms is 2 or less [Experimental Example H3), (+4) 3, when the total number of carbon atoms in the hydrocarbon chain is 9 or less [ Experimental examples (+5), (16)], cases where the polar group has weak adhesion such as an ester group [Experimental example (+7)), cases where the carbon-based protective layer is very thin or absent [Experimental example (+8) ), (19)], the desired performance may not be obtained (even if the conditions are within the scope of the claims of the present invention), the tcss test results and adsorption test results are all good. Experimental example (2
As is clear from 0), when conventionally known perfluoropolyether is used in the lubricant layer, the desired performance cannot be obtained. L C3S reduces the surface roughness and improves the surface flatness considerably.
It is possible to obtain a magnetic recording medium that has good durability and reliability without deteriorating performance such as durability and head adsorption, and is of high industrial value.

[Brief explanation of the drawing]

The drawing is a basic configuration diagram of a magnetic recording medium in an embodiment of the present invention.

Claims (2)

[Claims] (1) In a magnetic recording medium in which a ferromagnetic metal thin film is formed on a non-magnetic support, a partially fluorinated alkyl lubricant layer is formed on the ferromagnetic metal thin film with a carbon-based protective layer interposed therebetween. A magnetic recording medium characterized by: (2) The partially fluorinated alkyl lubricant layer has a fluoroaryl terminal group or a fluoroalkyl terminal group having 3 or more carbon atoms and a phenylene group with alkylene having 10 or more carbon atoms in total or a derivative thereof or an aliphatic alkylene group having 10 or more carbon atoms. It is characterized by containing at least one organic compound having a fluorinated hydrocarbon chain bonded to a hydrocarbon chain consisting of A magnetic recording medium according to claim 1.