JPS61276122A - Magnetic recording medium and its production - Google Patents

Abstract

PURPOSE:To obtain the title medium having a low friction coefficient by providing a nonmagnetic substrate layer which is deposited to form an uneven surface on the surface of a discoid substrate and furnishing a magnetic film layer of a Co-Ni alloy on the substrate layer. CONSTITUTION:A nonmagnetic substrate layer which is deposited to form an uneven surface is provided on the surface of a discoid substrate an a magnetic layer of a Co-Ni alloy is furnished on the substrate layer to obtain a magnetic recording medium. Or the film of a nonmagnetic substrate layer having an uneven surface is formed on the surface of the discoid substrate and the magnetic film layer of a Co-Ni alloy is formed on the surface of the discoid substrate to produce the medium. Consequently, a magnetic recording medium resistant to impact and having an excellent start-stop property, namely the CSS resistance, can be obtained.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a magnetic recording medium and a method for manufacturing the same, and particularly relates to a magnetic recording medium in which an underlayer and a magnetic film layer are formed on a substrate and a method for manufacturing the same. It is something.

[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 or cobalt-nickel (CoNi) alloy by sputtering (J, ApplPhys, 53 (5).
), 1982, Japanese Unexamined Patent Publication No. 57-7230, etc.), cobalt-platinum type and cobalt-nickel-platinum type are also known.

Therefore, when forming a magnetic thin film as described above on a substrate such as an aluminum-based alloy, generally, an underlayer is first formed on the substrate A, and a magnetic thin film is formed on L of this underlayer. ing. 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 Contact with the disc surface. The state of contact when the rotation of the magnetic disk is stopped is that when the rotation of the magnetic disk is slowed down, the flow of air on the surface gradually slows down. In this way, when the buoyancy of the magnetic head is lost, the magnetic head collides with the surface of the magnetic disk. The recoil causes the 12th to fly up into the magnetic field and fall back onto the disk surface. After repeating this slow movement several times, the magnetic head begins to be dragged over the magnetic disk, and finally stops. The magnetic head and magnetic disk must be able to withstand such #attacks when the startup stops, and their performance is evaluated by C3S resistance ([: contact-9tart-S
top).

In order to withstand such impact and provide a magnetic recording medium with sufficient #css properties, the underlayer is required to have sufficient hardness.

Conventionally, in magnetic disks, an alumite film obtained by anodizing an aluminum alloy substrate or a nickel-phosphorus electroless plating film (Ni-PII) was used as the underlayer.
Q) etc. are used.

[Problems to be Solved by the Invention] Conventionally, the surface of the underlayer used as the underlayer is flat, so there has been a problem that the C5S resistance of the magnetic recording medium is poor.

That is, if the surface of the underlayer is flat, the surface of the magnetic film layer formed above it will also be flat. (Furthermore, even if a protective film is provided on the L, the surface becomes flat.) Then, when the magnetic head slides on the magnetic recording medium, the contact area between the magnetic head and the magnetic recording medium As a result, the frictional force acting between the magnetic head and the magnetic recording medium also increases, resulting in a decrease in the C8S resistance of the magnetic recording medium.

On the other hand, CoNi alloy 11 conventionally used as a magnetic layer
The layer had a low orientation of the axis of easy magnetization in the in-plane direction of the film, and its magnetic properties were correspondingly low.

[Means for Solving the Problems] In order to solve the problems of the prior art described in L, the present invention provides the following: A magnetic recording medium having an underlayer and a magnetic film layer of Co-Ni alloy formed on the underlayer, and a disk-shaped substrate plate, and a non-magnetic underlayer with an uneven surface. The gist of the present invention is a method for manufacturing a magnetic recording medium, which comprises forming a Co--Ni alloy magnetic film layer on the surface of the underlayer.

The present invention will be explained in more detail below.

The magnetic recording medium of the present invention has an underlayer and a magnetic film layer formed on a substrate such as an aluminum-based alloy.

As the material of the substrate, various conventionally used materials can be used as long as they are non-magnetic, including those made of metal or alloy, glass, ceramic, etc. For example, it is preferable to use aluminum or a material whose main component is aluminum and other metal elements are added thereto to improve one or more properties such as strength, rigidity, and corrosion resistance. It will be done. As a specific example, one containing 7% by weight or less of magnesium, for example 3 to 4% by weight, is used.

The underlayer formed on this substrate is attached so that its surface is non-flat.

In this way, by making the underlayer a non-flat surface, the surface of the magnetic film layer formed above it (and if a protective film layer is formed on the hill, this protective film layer) also becomes non-flat. It becomes like this. Therefore, the number of contact points between the magnetic head and the magnetic recording medium is reduced, the coefficient of friction between the magnetic head and the magnetic recording medium is reduced, and the C5S resistance wJ is significantly improved.

As will be described later, FIG. 1 shows an example of the vertical cross-sectional shape of the underlayer. As shown in FIG. 1, in the present invention, the surface of the underlayer is microscopically extremely rough. This roughness (
Specifically, the degree of unevenness (non-flatness) is that unevenness is formed continuously, and the pitch of these unevenness is about 3 on average.
00 to 5000A, preferably between about 500 to 3000A, and the average depth of the unevenness is about 200 to 2000A.
A is preferably between about 400 and 800A.

This r layer is deposited and formed by a formation method that makes the surface uneven. That is, the underlayer of the magnetic recording medium of the present invention is different from that obtained by forming an underlayer on a substrate and roughening the underlayer by subjecting the underlayer to a treatment such as texturing.

Suitable methods for attaching and forming the underlayer include sputtering,
Vapor phase deposition methods such as ion blating can be mentioned, but
Among these, sputtering is the most preferable, in this case,
The material used for the underlayer is non-magnetic and has a hardness above a certain level, but specifically, chromium (Cr) with a purity of 99.9 atomic percent or higher is most preferable;
When the base layer is deposited on a substrate to a thickness of 1000 Å or more, a base layer having surface irregularities within the above-mentioned preferred range can be easily formed without any texturing or the like.

Note that if the thickness of this Cr underlayer is thinner than 1000 Å, continuous unevenness will not be formed.

Furthermore, the resistance against head collision is low, and there is a risk of so-called head crash. On the other hand, if it is larger than 3 gm, the roughness will not increase even if it is made thicker, and if the manufacturing time increases unnecessarily, the internal thermal stress caused by the rise and fall of temperature during manufacturing will become excessive. It may cause cracks.

FIG. 2 is a graph showing the results of measuring the relationship between the thickness of the Cr layer formed by the sputtering method, the surface roughness, and the coefficient of static friction. The sputtering conditions were the same as those for N013 (Table 1) in Example 1, which will be described later.0 Surface roughness was determined by observation using an electron microscope.

From Fig. 2, it can be seen that when the thickness of the Cr layer is less than 1000 Å, the surface roughness decreases and the coefficient of static friction increases, while when it exceeds 3 ILm, the increase in surface roughness reaches a plateau. It will be done. In addition, in the present invention, C
between the r layer and the substrate.

Other hard layers may be provided.8 For example, a layer of alumite, Ni--P, or the like may be provided between the Cr layer and the substrate.

The magnetic film layer formed on the underlayer is made of a Co-Ni alloy.

In the present invention, by substituting a part of Co constituting the magnetic film with Ni, Hc can be changed and Hc can be easily adjusted according to the required characteristics of the medium. Note that when the Ni content is lower than 5 at%, this effect is small; on the other hand, when the Ni content exceeds 40 at%, the saturation magnetic flux density Bs decreases, and the crystal system changes from hcp to fcc
, and the in-plane squareness ratio S of the film decreases.

Therefore, as a Co-Ni alloy, the Ni content is 5 to 4.
Preferably, the content is 0 atomic %.

In addition, in the present invention, the ratio of the X-ray diffraction intensity of the (002) plane to the X-ray diffraction intensity of the (100) plane of the magnetic film, that is, I
(002)/I (100) O≦R
By setting ≦1, the in-plane orientation of the easy axis of magnetization (C axis) can be improved.

That is, the C of various Go, -Ni films formed on the substrate]
When considering the axial direction, there is a very close relationship between the above R value and the orientation of the C axis, and when R=O, C
The axis is completely oriented in the in-plane direction of the film, and when R = 3, the distribution in the C-axis direction is completely random and shows no orientation at all. It was observed that the number of particles in the in-plane direction increases, and in the range of R>3, the number of particles in which the C axis is perpendicular to the film surface increases. By setting O≦R≦1, the in-plane orientation of the axis of easy magnetization can be improved.

Note that the thickness of the Co--Ni alloy layer is preferably about 400 to 900, particularly about 600 to 800, from the viewpoint of practicality.

In the present invention, it has been found that by setting the pitch and depth of the unevenness of the base layer within the above-mentioned range, the R value satisfies 0≦R≦1 in most cases. This is presumed to be due to the following reason. That is, when a Co--Ni alloy is formed on the underlayer by sputtering, the Go--Ni alloy film tends to grow so that its C axis is oriented in a direction perpendicular to the surface of the underlayer. If the surface of the underlayer is uneven, the direction 2 perpendicular to the surface is inclined toward the in-plane direction 3 of the film, as shown in FIG. ) are strongly oriented in the in-plane direction of the film.

Such a magnetic recording medium of the present invention can be manufactured according to the manufacturing method of the present invention, for example, as follows.

That is, a base layer is formed on a substrate by a film forming method such as sputtering, first a Co-Ni alloy thin film is formed on the substrate, and if desired, a protective film is formed on this Co-Ni alloy thin film.
It is something that is formed in

To perform this sputtering, a conventional sputtering device is used, namely, a device casing having a target and a sample device stage, a heater for heating the inside of this casing,
A device configured with a vacuum pump for reducing the pressure inside the casing and a gas cylinder connected to the casing is preferably used. This target preferably has an alloy composition that completely or almost matches the alloy composition of the film to be formed.

When performing sputtering, the substrate may be heated or left at room temperature.
The sputtering time, which is preferably 50° C. or less, especially 220° C. or less, is determined by dividing the film thickness to be formed by the average film formation rate.

As the sputtering apparatus, one that can adjust various conditions such as temperature, atmosphere, and atmospheric pressure as described above is suitable. Well-known sputtering equipment includes:
High frequency magnetron sputtering equipment, circular magnetron sputtering equipment, flat plate magnetron sputtering equipment.

Examples include a coaxial cylindrical electrode type magnetron sputtering device, an ion beam sputtering device, a high frequency sputtering device, a DC two-pole spar, and a talling device.

In the manufacturing method of the present invention, when forming a Cr underlayer, the atmosphere is Ar at about 2 to 20 mTorr, the substrate temperature is from room temperature to about 150°C, and the deposition rate is 50 Å/mi.
It is preferable that the number is n or more. After forming the Cr layer, in order to prevent oxidation of the Cr layer or adsorption of gas or moisture onto the Cr layer, Co-Ni is coated continuously without being exposed to the atmosphere.
Preferably, the alloy film is sputtered.

In addition to the underlayer between the substrate and the magnetic thin film, various intermediate layers that increase the adhesion strength of the magnetic thin film, specifically Cr
, M n , V, etc. may be provided with a thickness of about 50 to 500 A. Also, a protective film of carbon, polysilicate, etc. may be provided on the magnetic thin film, and a lubricant 9 may be added to this protective film.
Specifically, perfluoroalkyl polyether, monostearin, triacontyltrimethoxysilane, etc. may be applied.

[Function] In the magnetic recording medium of the present invention, since the underlayer is non-flat, the surface of the magnetic recording medium is also non-flat. This reduces the coefficient of friction with the magnetic head, allowing the magnetic head to slide smoothly over the magnetic recording medium.
The C8S resistance of the magnetic recording medium is significantly improved. Furthermore, since the in-plane orientation of the axis of easy magnetization of the Co--Ni film is improved, the magnetic properties are improved and high-density recording becomes possible.

The present invention can be applied to magnetic recording media ranging from extremely small disk diameters of 1 inch to 2 inches to large disk diameters of 10 inches or more.

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

Although the embodiment described below uses a magnetron r, f, and sputtering device, 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 An aluminum alloy substrate containing 4% magnesium (size: diameter 130 mm, inner diameter 40 mm, thickness 1.9 mm) was electrolytically treated in an acid bath containing chromic acid, and a thickness of 8 mm was applied to the surface.
A base layer of ~17 pm of alumite was formed, and its surface was polished to about 2 μm to make it flat.

Next, using a flat plate magnetron r, f, sputtering device,
A Cr underlayer was formed under the following conditions, and a Co--Ni thin film was subsequently formed on the underlayer without exposing it to the atmosphere.

Initial exhaust 1~2X10-'Torr Atmospheric pressure (Ar) 5~20mTorr Input power IKw Target composition Go-Nt (0 to match the target thin film composition For example, Co/Ni, = ao/ (When forming a thin film of 20 (atomic % ratio), use a target of 80 atomic % Co and 80 atomic % Ni2O.) Pole spacing 108 mm Thin film formation rate 150 A/m tnThe magnetic properties of this magnetic recording medium are other than those mentioned above. Figure 1 is a graphical representation of a cross section of the base layer of N003 taken with a transmission electron 111 microscope. indicates the base layer, and la indicates its surface.

Comparative Example I A magnetic recording medium was manufactured in the same manner as in Example 1 except that the Cr layer was not formed. The measurement results of the magnetic properties are shown in Table 1. (No. 1) Comparative Example 2 Example 1 except that the thickness of Crffj was 800A
A magnetic recording medium was manufactured in the same manner as described above. The measurement results of its magnetic properties are shown in Table 1. (No.

From Table 1, it is recognized that all of the examples according to the present invention have excellent magnetic properties.

Further, when the CSS characteristics of No. 1-No. 6 were measured, the results were as shown in Table 2.

From Table 2 t52, it is clear that the products according to the present invention are also excellent in C5S properties.

Note that the C3S test was conducted by installing a 5y4"φ disk in a 5h"φ disk drive. The head used was M n
-Zn Winchester type, inner circumference R = 50m
The head flying height at 0.45 m (3600 rpm, m
) and tested at this point. The CSS cycle was as shown in FIG.

IfFlcss lifespan is when the playback output compared to the start is 1
The point was taken as the point when the error decreased by 0% or the point when the error increased by even one.

[Effects] As detailed above, the magnetic recording medium of the present invention has an improved surface shape of the underlayer, has a low coefficient of friction with the magnetic head, and has excellent C5S resistance.

Furthermore, since the in-plane orientation of the easy axis of magnetization is excellent, high-density recording is possible.

Therefore, such a magnetic recording medium of the present invention can be easily manufactured by the method of the present invention.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view showing the surface shape of the base layer, Figure 2 is a Cr
FIG. 3 is a graph showing the measurement results of the relationship between layer thickness, coefficient of static friction, and surface roughness, and is a diagram illustrating the direction of C car growth. In addition, Figure 4 shows the C5S resistance in Examples and Comparative Examples.
This is the rotational characteristics of the drive for sex testing. 1... Cr layer 2... Direction perpendicular to the surface, 3... In-plane direction of the film. Agent Patent Attorney Tsuyoshi ShigenoFigure 3Figure 4

Claims (21)

[Claims] (1) A non-magnetic underlayer is deposited on the plate surface of the disk-shaped substrate to form a non-flat surface, and a Co-Ni alloy magnetic film layer is formed on the underlayer. A magnetic recording medium having (2) The magnetic recording medium according to claim 1, wherein the substrate is an aluminum substrate or an aluminum-based alloy substrate. (3) The magnetic recording medium according to claim 2, wherein the substrate is an aluminum-based alloy substrate containing 7% by weight or less of magnesium. (4) The magnetic recording medium according to any one of claims 1 to 3, wherein the underlayer is deposited and formed by a vapor deposition method. (5) The magnetic recording medium according to claim 4, wherein the underlayer is a Cr layer having a thickness of 1000 Å or more. (6) A layer according to any one of claims 1 to 5, characterized in that a layer for increasing the adhesion strength of the magnetic film is provided between the underlayer and the magnetic film. magnetic recording media. (7) The magnetic recording medium according to claim 5, characterized in that an alumite or Ni-P layer is provided between the Cr layer and the substrate. (8) The magnetic recording medium according to any one of claims 1 to 7, characterized in that a protective film layer is formed above the magnetic film layer. (9) The magnetic recording medium according to claim 8, wherein a lubricant is applied on the protective film. (10) The magnetic film layer is a Co-
10. The magnetic recording medium according to claim 1, wherein the magnetic recording medium is a magnetic film layer made of a Ni alloy. (11) A non-magnetic underlayer with an uneven surface is formed on the plate surface of the disk-shaped substrate, and then Co-
A method for manufacturing a magnetic recording medium, comprising forming a Ni alloy magnetic film layer. (12) Claim 1, characterized in that the substrate is an aluminum alloy containing 7% by weight or less of magnesium.
A method for manufacturing a magnetic recording medium according to item 1. (13) The method for manufacturing a magnetic recording medium according to claim 11 or 12, wherein the underlayer is formed by sputtering. (14) The method for manufacturing a magnetic recording medium according to any one of claims 11 to 13, wherein the underlayer is a Cr underlayer. (15) A Cr underlayer was formed in an Ar atmosphere of 2 to 20 mTorr, at a substrate temperature of room temperature to 150°C, and at a deposition rate of 50 Å/mi.
15. The method for manufacturing a magnetic recording medium according to claim 14, wherein the film is formed by sputtering with n or more. (16) A method for manufacturing a magnetic recording medium according to any one of claims 11 to 15, characterized in that the Co-Ni alloy magnetic film layer is formed by sputtering. (17) Magnetic recording according to any one of claims 11 to 16, characterized in that a layer for increasing the adhesion strength of the magnetic film is provided between the underlayer and the magnetic film. Method of manufacturing media. (18) The method for manufacturing a magnetic recording medium according to any one of claims 11 to 17, characterized in that a protective film is provided on the magnetic film. (19) The method for manufacturing a magnetic recording medium according to claim 18, characterized in that a lubricant is applied on the protective film. (20) The method for manufacturing a magnetic recording medium according to claim 13, wherein the sputtering is performed using a magnetron sputtering device or an ion beam sputtering device. (21) The magnetic recording medium according to claim 16, wherein the sputtering is performed using a magnetron sputtering device or an ion beam sputtering device.