JPS61220128A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To replenish a lubricant from a recessed part and to prevent the damage to a magnetic thin film by forming many recesses on the surface of a medium layer and depositing the liq. lubricant on the surface of the medium layer to fill the recesses with the lubricant. CONSTITUTION:A medium layer consisting of a substrate layer and a magnetic thin film is formed on an aluminum substrate, many recesses are provided to the substrate layer and hence many recesses 2 are also formed on the surface 1 of the medium layer. A liq. lubricant is deposited on the surface 1 of the medium layer to fill the recesses 2 with the lubricant. Accordingly, the liq. lubricant in the recess 2 acts as the supply source of the lubricant. When the lubricant on the surface is reduced, the lubricant is drawn out from the recess 2 and coated on the surface. Consequently, the medium layer is not exposed and the damage to the magnetic thin film, etc., can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic recording medium in which a medium layer including a magnetic thin film is formed on a nonmagnetic substrate.

More specifically, the present invention relates to a magnetic recording medium in which a liquid lubricant is attached to the surface of the medium layer.

[Prior Art] In recent years, as computers have become smaller and their processing power has increased, there has been a demand for further increases in the storage capacity of external memory devices. In order to satisfy this demand, it is necessary to further increase the recording density of magnetic disks used in external memory devices, and for this purpose, it is necessary to improve the magnetic properties of the magnetic thin film that forms the recording layer and to improve the recording density of the recording layer. We must promote further thinning of the film.

Therefore, it has been proposed to form a thin film layer of cobalt (CO) or cobalt nickel (CoN) alloy by sputtering (J.

Appl, Phys, 53 (5), 198
2. In addition, cobalt-platinum and cobalt-nickel-platinum types are also known.

Therefore, when forming a magnetic thin film as described above on a substrate such as an aluminum-based alloy, generally, a base layer is first formed on the substrate, and then a magnetic thin film is formed on this base layer. There is. This underlayer is required to have sufficient hardness because it is intended to withstand the impact when the head collides with the disk surface and to prevent deformation of the disk surface.

That is, as a magnetic head used for reading and writing information to a magnetic recording disk, a floating type head such as that disclosed in Japanese Patent Application Laid-Open No. 57-569 is widely used.

Such a magnetic head does not come into contact with the magnetic disk because it is suspended by air flow while the magnetic disk is rotating, but when the magnetic disk starts rotating and stops rotating, the magnetic head Collisions and slides on the disk surface.

It can withstand such collisions and sliding, and has sufficient resistance to C55 (Conta
In order to provide a magnetic recording medium with ct-5 tart-stop properties, the underlayer is required to have sufficient hardness.

Conventionally, in magnetic disks, an alumite film obtained by anodizing an aluminum alloy substrate, a nickel-phosphorus electroless plating film (Ni-P film), or the like has been used as an underlayer.

Furthermore, conventionally, in order to improve the sliding characteristics between the magnetic head and the medium layer, a liquid lubricant such as a fluorocarbon-based liquid lubricant is often applied to the surface of the medium layer.

[Problems to be Solved by the Invention] Since the surface of the conventional medium layer is flat, the liquid lubricant easily peels off, and the C5S resistance of the magnetic recording medium is poor.

In other words, the liquid lubricant attached to the surface of the medium layer is gradually stripped off by the magnetic head sliding on the medium layer and is reduced. If so, the liquid lubricant may be partially completely stripped off by the sliding movement of the magnetic head, leaving the medium layer exposed. If such an exposed area without liquid lubricant occurs, the protective film or even the magnetic thin film may be peeled off or damaged in this area, causing a decrease in C8S resistance.

[Means and operations for solving the problems] In order to solve the problems of the above-mentioned prior art, the present invention provides.

In a magnetic recording medium in which a medium layer including a magnetic thin film is formed on the plate surface of a disk-shaped substrate, the surface of this medium layer has many recessed holes, and at least a liquid lubricant is applied to the surface of the medium layer. A magnetic recording medium is attached so as to exist in this recessed hole.

The main points are as follows.

In the present invention, a concave hole is formed on the surface of the medium layer, and the liquid lubricant is attached to the surface of the medium layer so that it exists at least in the concave hole. The liquid lubricant in such a recessed hole acts as a supply portion of liquid lubricant to the surface of the medium layer.

In other words, when the liquid lubricant decreases in the surface area other than the recessed hole,
When the magnetic head slides, the liquid lubricant is drawn out from this recessed hole and spread thinly around it, preventing the liquid lubricant from running out on the surface of the media layer and preventing the media layer from becoming exposed. Control.

The configuration of the present invention will be explained in more detail below.

The magnetic recording medium of the present invention includes a medium layer including a magnetic thin film formed on a nonmagnetic substrate. This medium layer is formed to have recesses on its surface.

In the present invention, the base layer is usually formed on the substrate so as to have a recessed hole, thereby forming a recessed hole that imitates the underlayer recessed hole on the surface of the medium layer.

A preferred method for forming a base layer having recessed holes is as follows.

■ A method in which the substrate is aluminum or an aluminum alloy, and an alumite layer with concave holes is formed on the substrate by electrolytically treating it in an acid solution. ■ A method in which chromium is deposited by vapor phase deposition such as sputtering or ion blasting. An example of this is the method of attachment.

When forming the alumite layer (2), an acid solution containing chromic acid is suitable as the acid solution. By using this chromic acid solution, it is possible to form an alumite coating having countless recesses. In the case of the vapor phase deposition method (2), sputtering is most preferable, and if the chromium is sputtered onto the substrate to a thickness of, for example, 100 OA or more, irregularities will be formed continuously on the surface of 5. , a recessed hole suitable for the present invention is formed.

If the thickness of the chromium underlayer is less than 100 OA, it is difficult to form unevenness, and the resistance against head collision is low, which may lead to so-called head crash. If it is larger than 3ILm, the manufacturing time will increase unnecessarily, and the internal thermal stress caused by the rise and fall of temperature during manufacturing may become excessive and cause cracks. It is preferable that the thickness is as follows.

Therefore, in the present invention, the base layer having the recessed holes is different from the one in which groove-shaped recessed holes are provided by applying mechanical treatment to the once formed base layer, such as texture treatment, and the base layer has independent groove-like recessed holes. It is made up of countless recessed holes.

That is, in a method of forming grooves by rubbing, such as in texturing, the intervals between the grooves inevitably become uneven, and the effect of evenly distributing the liquid lubricant over the surface is reduced. (If a severe texturing process was applied to reduce the groove spacing, the surface of the base layer would become excessively rough.) On the other hand, the present invention provides It has a base layer in which the recesses are evenly distributed and there is no excessive gap between the recesses, which is provided by a method in which the recesses are naturally formed during formation. Therefore, the liquid lubricant that has entered the recesses is evenly spread over the surface of the base layer.

In the present invention, aluminum or an aluminum alloy is used as the material for the substrate when the alumite formation method described in (1) above is used when forming the underlayer, but when the vapor deposition method (2) is employed, aluminum or an aluminum alloy is used. Other materials such as titanium alloys, glass, ceramics, etc. may also be used.

Next, the size and formation of the recessed hole will be explained.

The average diameter of the recessed hole is at most 300 to 2000A.
It is preferable that the average distance between the recessed holes (that is, the average value of the distance between the centers of the recessed holes) is within the range of 500 to 5000A.

As described above, in the present invention, the recesses are usually formed in the underlayer, thereby forming the recesses on the surface of the medium layer. When an alumite film is used as the base layer, the first
Independent holes as shown in the figure are formed in a distributed manner. In addition, when using a chrome base, as shown in Figure 2,
Continuous unevenness is formed. In the case of an alumite coating as shown in Figure 1, the upper limit of the average recessed hole diameter is 500 to 200.
The average distance between the recessed holes (the distance between the centers of the recessed holes) is preferably between 0A and 5000A or less.In the case of a chrome base, the diameter of the recessed holes It is preferable that the upper limit of the average value is 300 to 2000A, and the average value of the interval between the recessed holes is preferably 500 to 2000A.Incidentally, in the case of a surface roughened by conventional texturing, the average value Groove width is 0
．． It is about 1 pm, and the average spacing of the grooves is l ” l
It is about Ogm.

The magnetic thin film formed on the underlayer is made of Co-Ni, Co
-Pt, Co-N [-P, Co-Ni-Pt, Co-P
A thin film based on an alloy such as T is preferable, but an oxide based film such as γ-hetamite may also be used. In addition, when forming a cobalt alloy-based thin film, the thickness should be approximately 400 to
It is preferable to set it to about 100OA.

In the present invention, a protective film layer can be provided on this magnetic thin film if desired.

As this protective film, metals such as osmium, ruthenium, iridium, manganese, and tungsten, oxides such as silicon oxide, titanium oxide, tantalum oxide, and hafnium oxide,
Various nitrides, carbides, boron, carbon, alloys of carbon and boron, etc. can be used. Among these, although carbon has excellent sliding properties, it has poor compatibility with the liquid lubricant deposited thereon.Therefore, in the present invention, when carbon is used as the MH retainer, the effect becomes more pronounced.

In the present invention, a liquid lubricant is applied to the surface of the medium layer, that is, to the surface of the magnetic thin film when there is no protective film, and to the surface of the magnetic layer when a protective film is provided. The liquid lubricant is not particularly limited, but higher fatty acids, esterified products of higher fatty acids, or fluorine compounds or organic silicon compounds thereof may be used.For example, fluorine-based lubricants such as perfluoropolyether are used. Examples of such products include Krytox manufactured by DuPont Co., Ltd. and Fonpurin manufactured by Montecatini. The method for attaching this liquid lubricant is to dissolve the liquid lubricant in a suitable organic solvent and heat-treat the surface of the medium at about 100°C by a method such as spraying, spin coating, or dipping to apply the liquid lubricant to the medium. A method such as spreading it thinly on the surface of the layer is used.

In addition, in the present invention, in addition to the underlayer, various intermediate layers for increasing the adhesion strength of the magnetic thin film may be provided between the substrate and the magnetic thin film.

[Example] Hereinafter, the present invention will be explained in detail using specific examples.

Note that the examples described below are r and f.

Although a magnetron sputtering device was used, it is of course possible to obtain the effects of the present invention by ion beam sputtering, etc., which can be said to be similar in terms of ion technology.

Example 1 Aluminum alloy substrate containing 4% magnesium (size: outer diameter 130 mm, inner diameter 40 mm, thickness 1.9 mm)
) was electrolytically treated in an acid bath containing chromic acid to form an alumite base layer with a thickness of IOpm on its surface.

Next, a Go-15Ni thin film was formed using an r, f, magnetron sputtering device under the following conditions.

Initial exhaust 1~2X10-'Torr Atmospheric pressure (Ar) 15~20mTorr Input power
1kw Target composition Go-Ni (The target composition should match the composition of the target thin film. In Example 1, a thin film with Co/N1 = 85/15 (atomic % ratio) is formed, so Co85 atomic % ,Ni
A 15 atom % target is used. ) Pole spacing: 108 mm Thin film formation rate: 150 A/min Furthermore, carbon was sputtered onto this magnetic alloy thin film to a thickness of 40 OA. The surface of this magnetic recording medium was photographed using a SEM, and the diameter of the recessed holes and the average value of the interval between the recessed holes were determined. The results are shown in Table 1. Figure 1 is a drawing that reproduces this photograph, where l is the surface of the medium layer and 2 is the recessed hole.0 As shown in the figure, when alumite is formed In this case, a countless number of concave holes are formed.

Next, a liquid lubricant (Fonprin, manufactured by Montecatini) was applied to the surface of the carbon film to an average thickness of 10A. The attachment method is as follows. Fonprin was dissolved in Freon to a concentration of 0.03%, this solution was applied to the surface of the medium by a spray method, Freon was evaporated, and heat treatment was performed at 100°C for one hour to dissolve Fonprin. It was attached to the surface of the medium.

Table 1 shows the results of measuring the C5S characteristics of the magnetic recording medium thus formed.

Example 2 The thickness of the alumite was 31 Lm, the composition of the magnetic film was Co-25Ni, and the liquid lubricant was 2OA.
A magnetic recording medium was prepared in the same manner as in Example 1 except that thick Krytox manufactured by DuPont was used. Table 1 shows the measurement results of the interval and diameter of the recesses in the underlayer and the C8S characteristics of the magnetic recording medium.

Example 3 The current density during electrolytic treatment in an acid bath was slightly changed,
A magnetic recording medium was produced in the same manner as in Example 2, except that the thickness of the deposited crystals was 5OA. Table 1 shows the measurement results of the average interval and average hole diameter of the recessed holes in the underlayer, and the C8S characteristics.

Example 4 A magnetic recording medium was produced in the same manner as in Example 2 except that a carbon protective film was not provided. Table 1 shows the measurement results of the average interval of the recessed holes in the base film, the average hole diameter, and the C8S characteristics.

Example 5 500OA was applied to the surface of an aluminum alloy substrate containing 4% magnesium (the size and thickness were the same as those of Example 1).
Chromium was sputtered to a thickness of , and a Co-15Ni magnetic film was formed thereon in the same manner as in Example 1. Furthermore, after sputtering a carbon protective film to a thickness of 30 OA, a liquid lubricant (Fonprin) was deposited to a thickness of 5 OA. The measurement results of CSS characteristics are shown in Table 51. In addition, after forming the chromium underlayer, the medium was taken out from the sputtering device, an electron micrograph of the cross section of the chromium layer was taken, and the average spacing of the recessed holes was measured. , 1500A. Note that Figure 2 is a reproduction of this electron micrograph, and as shown in Figure 1, continuous sawtooth-like irregularities are formed in the base film sputtered with chromium, which forms recessed holes. This was recognized.

Comparative Example 1 On the same aluminum alloy substrate as used in the above example, a nickel phosphorous base film was formed to a thickness of 151 Lm by electroless plating, and then textured to create a scratch-like appearance. A groove was provided. The average groove spacing was 3 pm, and the groove width was 0.05 pm. A Go--Ni--P magnetic film was formed on this nickel phosphorous base film to a thickness of 70 OA by plating. Note that the nickel content of the magnetic film was 20 atomic %. A carbon protective film was sputtered onto the magnetic film to a thickness of 40 OA, and then Krytx was deposited as a liquid lubricant to a thickness of 2 OA.

The measurement results of this C5S resistance characteristic are shown in Table 1.

Comparative example? The conditions during texture processing were slightly changed, and the average interval of the grooves was 91Lm, the average width of the grooves was 0.151Lm, no carbon protective film was provided, and 5OA thickness and 5OA thickness of Fonprin as a liquid lubricant were used. A magnetic recording medium was produced in the same manner as in Comparative Example 1, except that the magnetic recording medium was attached so as to be as follows. The results of measuring the C5S resistance characteristics are shown in Table 1.

From Table 1, it is clear that the products according to the present invention are extremely excellent in C5S resistance.

The C5S test was conducted by loading a 5%"φ disk into a 5"φ disk drive. The head used was an Mn-Zn Winchester type head with a width of 4 mm, and R
= Head flying height at 50mm is 0.2pm (3600r
pm) and tested at this point. The CSS cycle was as shown in Figure 3.

The life of the C5S resistance was defined as the point at which the reproduction output decreased by 10% compared to the starting point or the point at which the number of errors increased by even one.

From Table 1, it is recognized that the products according to the present invention are extremely excellent in C5S resistance.

[Effect 1] As detailed above, the magnetic recording medium of the present invention has concave holes formed on the surface of the magnetic medium layer so that the liquid lubricant is well retained on the surface, which improves the interaction with the magnetic head. It has a low coefficient of friction and excellent C8S resistance.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the cross-sectional shape of the alumite base layer, FIG. 2 is a schematic diagram showing the cross-sectional shape of the chrome base layer, and FIG. 3 is the rotational characteristics of the drive for @CSS characteristic test. l...Medium layer surface, 2...Recessed hole.

Claims (4)

[Claims] (1) In a magnetic recording medium in which a medium layer containing a magnetic thin film is formed on the surface of a disk-shaped substrate, the surface of this medium layer has many concave holes and is lubricated with liquid. A magnetic recording medium in which an agent is attached so that it exists at least in the recessed hole. (2) The medium layer includes a nonmagnetic underlayer formed on the substrate and a magnetic alloy thin film provided above the underlayer, and a recessed hole is formed in the nonmagnetic underlayer. 2. The magnetic recording medium according to claim 1, wherein recessed holes are formed on the surface of the medium layer. (3) The magnetic recording medium according to claim 2, wherein the medium layer includes the underlayer, the magnetic alloy thin film, and a carbon protective film provided on the surface side of the magnetic alloy thin film. (4) Any one of claims 1 to 3, wherein the base layer is a porous alumite layer or a chromium vapor deposited layer.
The magnetic recording medium described in section.