JPH0448435A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve durability by forming a lubricant layer comprising a mixture of a lubricant which easily nd chemically adsorbs to a carbon protective layer and a lubricant which easily and chemically adsorbs to an oxide material. CONSTITUTION:A mixture of lubricants, the one having polar groups which chemically adsorbs at least to an oxide material which constitutes a magnetic head, and the other lubricant having polar groups which chemically adsorbs to a magnetic recording medium. Thereby, when a head slides on the protective film on CSS (contact-start-stop system) operation, with heat generated by sliding out of the mixed lubricants, the latter lubricant chemically adsorbs to the protective film while the former lubricant chemically adsorbs to the head. This means that the lubricant layers slide mutually. Thereby, stable wear resistance property and antifriction property can be obtained in wide temp. and humidity ranges.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a magnetic recording medium used in a magnetic recording device, etc., and the present invention relates to a magnetic recording medium used in a magnetic recording device etc. This invention relates to a magnetic recording medium with excellent durability.

Conventional technology Magnetic recording devices include magnetic hard disk devices, magnetic tape devices, floppy disk devices, magnetic card devices, etc., but among these, magnetic recording devices require the most wear resistance and friction resistance due to high recording density. It is thought to be a hard disk device. A typical configuration diagram of the magnetic hard disk is shown in Figure 1. A nonmagnetic support N1-P is plated on an aluminum substrate, and a ferromagnetic metal thin film (Co-Ni, etc.), a corrosion-resistant protective film (Cr, etc.), and a carbon protective film are formed on it by sputtering, and finally is coated with a lubricant (perfluoroalkyl polyether, etc.). the current,
In the case of magnetic hard disks, the contact start/stop method (hereinafter referred to as C8S) is the mainstream method for starting and stopping magnetic recording devices using floating magnetic heads. At times, a recording/reproducing magnetic head (hereinafter referred to as a head) comes into contact with the surface of a magnetic recording medium. This may cause the heads and magnetic recording media surfaces to wear out, increase the coefficient of friction between them,
In severe cases, destruction (crash) of the head or the magnetic layer of the magnetic recording medium may occur. Therefore, in order to avoid such problems, a protective film such as graphite-based carbon, silicon dioxide, etc. is formed on the magnetic layer, and a perfluoroalkyl polyether having an ether bond is formed on the protective film. A lubricating layer using such a liquid lubricant is generally used, and the provision of this layer has improved the durability of magnetic recording media by several orders of magnitude. But 1. However, the durability was still not fully satisfactory, so a new lubricant was developed, a partially fluorinated alkyl lubricant (Japanese Patent Application Laid-Open No. 1983-21).
9314), this development has made it possible to obtain sufficient durability under normal environments.

Problems to be Solved by the Invention Now, the use of magnetic recording devices is in use in all parts of the world. Therefore, depending on the region, there are environmental conditions such as high temperature and high humidity, high temperature and low humidity, low temperature and high humidity, and low temperature and low humidity, and it is necessary to exhibit stable durability under all of these environmental conditions.

Among these, perfluoroalkyl polyethers and partially fluorinated alkyl lubricants that have polar groups that chemically adsorb to heads or magnetic recording media have sufficient durability under normal environments or high temperatures (high humidity). However, there is a slight deterioration in durability at low temperatures (low humidity).

Experimental results showing this tendency are shown in FIG. This is considered to be because the lubricant is chemically adsorbed only on the magnetic recording medium or only on the head. That is, at low humidity, the amount of adsorbed water on the surface of the magnetic recording medium or head, on which the lubricant is not chemically adsorbed, decreases, making it more likely to wear out.

For this reason, even if lubricant is chemically adsorbed only on either the head or the magnetic recording medium, wear cannot be sufficiently suppressed and deterioration occurs. Furthermore, if the lubricant that has been chemically adsorbed at low temperatures peels off due to wear between the head and the magnetic recording medium, the low temperature makes it difficult for the lubricant to re-adsorb to the place where it has peeled off, resulting in insufficient durability. There is a point.

Means for Solving the Problems The present invention uses a mixture containing a lubricant having at least a polar group that chemically adsorbs to the oxide material constituting the magnetic head and a polar group that chemically adsorbs to the magnetic recording medium in the lubricating layer. there was.

Effect: With this configuration, the sliding heat generated when the head and protective film slide in the C8S causes the lubricant that chemically adsorbs to the protective film in the mixed lubricant to be absorbed into the protective film, and the lubricant that chemically adsorbs to the head to the head. The lubricating layers will be able to slide against each other.

EXAMPLES Hereinafter, examples of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing the basic configuration of a magnetic recording medium in an embodiment of the present invention. In the figure, 1 is a non-magnetic support, 2 is a ferromagnetic metal thin film, 3 is a corrosion-resistant protective film, 4 is a carbon protective film, and 5 is two types of polar groups that chemically adsorb to the oxide materials that make up the disk and head. It is a mixed lubricant layer containing lubricant. An example of the chemical structure of a perfluoroalkyl polyether having a polar group that chemically adsorbs to the disk and head used in the mixed lubricant layer 5 is A (C2FA-〇)ll-A B (C2F-0). -BCF3 (CFCF20). -A-CF
:1 F3CF3-B (CF2CF2CF2
-○), CF3, and its derivatives.

A is a polar group that chemically adsorbs to the protective film of the disk, and B
is a polar group that chemically adsorbs to the oxide material constituting the head. Polar groups chemically adsorbed onto the carbon protective film 4 include aromatic groups such as benzene, amine groups (-NH2, C
There are nitrides represented by ON H2, -N-). It is more effective if these polar groups are located at the ends of the molecular structure as in this example, but they may be located not only at the ends of the molecular structure but also within the chain of the molecule. When the protective film is made of carbon, when the polar group is aromatic, a π bond is formed to share π electrons with the carbon protective film having a graphite structure, so it exhibits strong bonding strength. In the case of nitrides, the unpaired electrons of nitrogen form a coordination bond with carbon or organic matter chemically adsorbed on the carbon surface. By having these polar groups, the lubricant is chemically bonded to the carbon protective film.

Next, as polar groups that chemically adsorb to the oxide material constituting the head, hydroxyl group (-OH), carboxyl group (-C○○H)
) etc. The hydroxyl group or carboxyl group forms a hydrogen bond with the surface of the oxide used in the head, such as ferrite, calcium titanate, barium titanate, altic, etc. The average molecular weight of these perfluoroalkyl polyethers having polar groups is 1000 to 8000, more preferably 2000 to 600.
0 is appropriate. If the average molecular weight is less than 1000, the vapor pressure will be high and it will easily volatilize at high temperatures, resulting in poor durability. When the average molecular weight is 8,000 or more, the viscosity becomes high and the abrasion resistance is improved, but the frictional force becomes large and stick/slip occurs, and the durability deteriorates, making it unsuitable for magnetic recording media. On the other hand, those used as partially fluorinated alkyl lubricants are represented by the general formulas shown in formulas [1] to [3].

Rr (Z) Yaw X [1] Formula [1]
Co~ [3, Rt and R't are perfluoroalkyl polyether terminal group, fluoroaryl terminal group, fluoroalkyl terminal group having 3 or more carbon atoms, phenylene group having 6 or more carbon atoms or derivatives thereof, or 1 or more carbon atoms CF3 (CF2C
F20).

CF3 (CFCF20)nF3 (where n represents an integer of 5 or more) CnF2n*+-HCF2 (CF2) as the fluoroalkyl terminal group.

CnF2n-+- (However, n represents an integer of 3 or more.) Examples of the fluoroaryl terminal group include.

R consists of an aliphatic alkyl terminal group having 8 or more carbon atoms,
Alternatively, it represents a hydrocarbon chain consisting of a phenylene group or a derivative thereof having 6 or more carbon atoms, and a specific example thereof is C0H2n as an aliphatic alkyl terminal group. , - oH2-- Cl1H2111- (However, n represents an integer of 6 or more.) As a hydrocarbon terminal group consisting of a bond with a phenylene group or its derivative (however, p is 0 to 4, m is 1 or more, n represents an integer of 8 or more).

(Z), and (Z’),’ are -[○-(CH2). ].

-[S (CH2)-]- -[COO(CH2)n]- - [CON (CH2). ].

−〇− S −〇〇〇− CON 5O2N O(CH2).

S-(CH2). --COO-(CH2).

CON-(CH2). -5O2N-(CH2).

ES02N (CH2) n] - (However, m,
m' is 0 or 1, n is O or an integer of 1 or more, R
represents H, CH3 or C2H6. ) represents a bonding chain selected from the following (margins below) RR (where n is an integer of 1 or more, R represents H, CH3° or C2H5) Y is -CH -(CH2).

-N-(CH2).

CON (CH2) n 5O2N (CH2)n (where n represents an integer of 0 or 1 or more), and X represents a bond chain selected from 10H1-3H
, -COOHl-COSHl CON H2, -NH2, -NC○, Represents a terminal polar group selected from the following. Among lubricants expressed by one of these formulas, aromatic lubricants and lubricants containing nitrogen are chemically adsorbed to the carbon protective film, and other polar groups are chemically adsorbed to the oxide material constituting the head. Adsorb. In addition to mixing lubricants each having a polar group that chemically adsorbs to these disks and heads, it is also possible to use mixtures with other generally known lubricants, rust preventives, and the like.

When mixing two types of lubricants with polar groups that chemically adsorb to disks and heads, perfluoroalkyl polyethers may be mixed together, partially fluorinated alkyl lubricants may be mixed together, or perfluoroalkyl polyether and partially fluorinated alkyl lubricants may be mixed together. Combinations of lubricants can be considered, but any combination will be effective. Furthermore, the mixing ratio of the two types of lubricants having polar groups that chemically adsorb to the disk and the head is 20:1 to 2:8, preferably 10:1 to 5: by weight.
When used at a mixing ratio of about 5, no deterioration in lubricating properties is observed under any environmental conditions.

The coating method involves dissolving two types of lubricants with polar groups that chemically adsorb onto the disk and head in a mixing ratio determined within the above range in alcohol or an organic solvent such as Freon 113, and then applying the lubricants to the magnetic recording medium. Apply by spraying, dipping, spin-coding, or other methods. The amount of application is 0.5~
It is desirable that it be 500 mg/m2, but this cannot be said unconditionally because the appropriate film thickness is determined by the surface roughness of the magnetic recording medium. If the coating amount is too small, the abrasive force and wear will increase, making it impossible to obtain stable durability. On the other hand, if the amount of coating is too large, a sticking phenomenon (adsorption) between the recording/reproducing head and the magnetic recording medium may occur, resulting in deterioration of durability.

Furthermore, if the disk surface is pretreated with plasma treatment or ozone treatment before applying the mixed lubricant, more stable durability may be exhibited. Furthermore, if the mixed lubricant is applied to the disk and then heat-treated, the lubricant tends to chemically adsorb onto the disk surface, improving its properties.

A C8S test was conducted on each of the samples thus prepared under environmental conditions A and B using a monolithic head made of ferrite as the head, and the maximum value of the coefficient of dynamic friction after 20,000 cycles of C3S was determined. The environmental conditions A and B tested here are said to be extremely severe environmental conditions within the operating range of magnetic recording and reproducing devices currently in use.

A: 5°C 10% R, H.

B: 65°C, 80% R, H.

The C8S test results for each of the above samples are compared with the contents of the samples and are listed in Tables 1 (a) and (b).

(The following is the margin) Table (The following is the margin) Table (The following is the margin) (b) As is clear from the results of Tables 1 (a) and (b),
Each example of the present invention has low temperature and low humidity (condition A), high temperature and high humidity (condition A),
Each dynamic friction coefficient under B condition) becomes 0 at C8820000 times.
．． It is small, less than 4, and shows extremely stable durability. Further, the characteristics are improved even if heat treatment is performed after applying this mixed lubricant (Example 5) or the carbon surface is treated with ozone before applying the mixed lubricant (Example 6). In addition, from the results of comparative examples, a lubricant alone with a polar group that chemically adsorbs on the head (Comparative Example 1), a lubricant alone with a polar group that chemically adsorbs on carbon (Comparative Example 2), and even a head and a disk. A mixed lubricant (Comparative Example 3) consisting of lubricants that do not have polar groups that chemically adsorb to the surface of the lubricant did not have stable durability under all environmental conditions (Conditions A and B).

It has been confirmed that a magnetic recording medium made by applying the invented mixed lubricant layer to a metal thin film tube similarly exhibits stable methyl properties under the environmental conditions of A and H. In addition, although we used a monolithic magnetic head made entirely of ferrite, we used a composite in which the slider was made of a non-magnetic material such as ceramic, and a core chip made of a magnetic material and having a magnetic gap was inserted into the notch of the slider. You can also get the same effect with molds.

Effects of the Invention According to the present invention, by forming a lubricant layer as a mixture of a lubricant having a polar group that chemically adsorbs to carbon and a lubricant having a polar group chemically adsorbing to the head (oxide), carbon A lubricant with a polar group that chemically adsorbs on the carbon surface chemically adsorbs on the carbon surface, and a lubricant with a polar group that chemically adsorbs on the head (oxide) chemically adsorbs on the head (oxide). Furthermore, each chemical adsorption reaction is promoted by the frictional heat generated between the head and disk during C8S, and C8S is performed by the contact between the lubricants coated on the head and disk, which is better than conventional lubricants. It has become possible to obtain stable wear and friction resistance properties over a wide temperature and humidity range of magnetic recording devices, which could not be obtained with each component alone or as a mixture. In general, when the head and magnetic recording medium come into contact with each other when the magnetic recording device is not operating, lubricant (particularly liquid lubricant perfluoroalkyl polyether) diffuses into the gap between the head and the magnetic recording medium, causing a sticking phenomenon. However, in the case of the present invention, the lubricant is chemically adsorbed on the carbon and the head, so even if the temperature rises, it does not diffuse into the minute gap between the head and the disk, causing a sticking phenomenon (adsorption). It also has the effect of suppressing The invention of this mixed lubricant can be applied not only to magnetic hard disks and magnetic tapes, but also to floppy discs and magnetic cards, making it possible to greatly contribute to the reliability of magnetic recording devices for high recording densities.

[Brief explanation of drawings]

FIG. 1 is an enlarged sectional view of a main part of an embodiment of the magnetic recording medium of the present invention, and FIG. 2 is a graph showing the relationship between C8S and durability of a conventional magnetic recording medium. 1...Nonmagnetic support 2...Ferromagnetic metal thin film 3.
...Corrosion-resistant protective film 4...Carbon protective film 5...-
Name of agent for mixed lubricant layer Patent attorney Shigetaka Awano 1 person Fig. 1: Non-magnetic support 2X ferromagnetic gold hawk thin belly 3: Corrosion-resistant protective film 4: Carbon protective film 5: Mixed lubricant layer Fig. 2 D: 23°C, 40% ■: 5°C110% C5S TIMES +5000

Claims (3)

[Claims] (1) A magnetic recording medium in which a magnetic layer, a carbon protective layer, and a lubricant layer are sequentially formed on a substrate, and at least a lubricant that is easily chemically adsorbed to the carbon protective layer and a lubricant that is easily chemically adsorbed to the oxide material. A magnetic recording medium characterized in that a lubricant layer is composed of a mixture of agents. (2) -OH as a polar group chemisorbed to the oxide material;
2. The magnetic recording medium according to claim 1, further comprising a lubricant having one or more of the following polar groups: -COOH, -SH, -COSH-CHO. (3) The magnetism according to claim 1, characterized in that the lubricant contains a lubricant having one or more types of polar groups selected from aromatic groups and functional groups including amines as polar groups that chemically adsorb onto the carbon protective film. recoding media.