JPH0329110A - Magnetic recording medium and its manufacturing method - Google Patents

Abstract

PURPOSE:To obtain a medium having excellent sliding resistance against a magnetic head by using a chromium nitride (Cr2N) layer having high hardness or a mixture of Cr2N and CrN as a base layer. CONSTITUTION:The base layer 2 on a substrate 1 consists of a Cr2N layer having enough mechanical strength which protects the magnetic recording medium from damage caused by contact or collision of a magnetic head, or the base layer consists of a mixture layer of Cr2N and CrN. A CrN layer is not used because of its inferior bardness. After the base layer 2 is formed, there are formed an intermediated layer 3, magnetic layer 4 and protective layer 5, or further protective layer 6, for example, by physical vapor deposition (PVD) method such as sputtering. Thereby, the obtd. disk has enough surface flatness which can maintain a stable floating state of a head even when the head floats at small height from the disk. Thus, the medium has excellent sliding resistance to the magnetic head.

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 used in a magnetic recording device.

[Conventional technology]

In recent years, the importance of magnetic disks as external storage devices in computer systems has increased, and their storage density has increased significantly year by year. Conventionally, magnetic recording media have acicular γ
-Development has been focused on reducing the thickness of coated media that is burnt out after spin coating a viscous material in which -Fe20avIi particles are dispersed in an organic binder on an aluminum alloy substrate, and is currently widely used. However, in order to achieve higher density, it is necessary to make the media thinner, but current coated media are considered to have technical limitations, and as an alternative high-density magnetic disk, it is easy to make the media thinner. Magnetic disks with thin metal magnetic thin film media are attracting attention. This metal magnetic thin film medium has been developed as a plated magnetic disk formed by plating technology, a metal magnetic film (Co-Cr, Go-Ni, etc.), or a sputter disk using metal oxide (γ-FezOa, etc.). It is expected that this technology will significantly increase recording density. The general structure of a magnetic disk using such a thin film continuous medium is as follows. A high-purity aluminum alloy is used for the substrate, and a base layer is formed on it. A magnetic layer is formed on the underlayer, but an intermediate layer is sometimes formed between these two layers to improve the adhesion between the two layers and the properties of the magnetic layer. A protective layer or a lubricating layer is formed on top of the magnetic layer. This underlayer enables the magnetic layer to be thinned, requires flatness and smoothness to ensure a stable head flying state at a low flying height, and requires a significant reduction in substrate defects. In addition, the base layer has mechanical strength, workability,
In addition to various properties such as polishability. For example, JP-A-59-
As described in Japanese Patent No. 45634, it is required that the underlayer is not magnetized even by heat treatment during the formation process of the magnetic layer, protective layer, or lubricant layer. , a Ni-P film formed by electroless plating is generally used as the underlayer, but there are also other
As described in Japanese Patent Publication No. 7-169930, a method for forming a metal undercoat layer and Japanese Patent Application Laid-Open No. 49-749
11, JP-A-57-50324, JP-A-59-217225, JP-A-60-2
Methods of forming metal oxides, nitrides, etc. are known, as described in Japanese Patent Laid-Open No. 01524 and Japanese Patent Application Laid-open No. 183612/1983.

[Problem to be solved by the invention]

The substrate of a magnetic recording medium is generally . AQ-Mg alloy is used, but in order to prevent the surface of the magnetic recording medium from being damaged by impact when the magnetic head and magnetic recording medium come into contact,
As described in JP-A-60-201524, it has been known for a long time to use chromium nitride as an underlayer. However, as a result of studies by the present inventors, chromium nitride may contain Cr, which has high hardness, depending on the combination or conditions.
It has been found that 2N and CrN, which has low hardness and is not suitable as an underlayer, are formed.

The object of the present invention is to provide a high hardness chromium nitride Cr2N layer;
Alternatively, by using a mixed layer of Cr2N and CrN as an underlayer, it is possible to provide a magnetic recording medium with excellent sliding resistance against a magnetic head.

[Means to solve the problem]

The above purpose is to use 5 as an underlayer on the substrate surface of a magnetic recording medium.
Instead of using CrN, which has low hardness, we use a Cr2N layer, which is a non-magnetic material with excellent mechanical strength, or a Cr2
This can be achieved by providing a mixed layer of N and CrN. Here, the magnetic layer is preferably a metal magnetic layer containing CO as a main component, a metal oxide thin film, or a metal nitride thin film. Moreover, between the underlayer and the magnetic layer, Cr, Mo
, W, Si, Ti, Ge, C.
An intermediate layer containing 0.00 to 5000 may be provided. In addition, from the viewpoint of sliding resistance, the thickness of the base layer mainly composed of Cr2N is 0.05 to 10.0 μm, more preferably 1.0 μm.
It is preferable to set the thickness to 5.0 μm or less.

The substrate for magnetic recording media is generally made of AQ-Mg alloy, and Cr2 is added to this substrate with groups arranged in the circumferential direction for the purpose of preventing adhesion problems of the magnetic head and lowering the coefficient of friction.
After forming the underlayer containing N as a main component, the intermediate layer and the magnetic layer may be formed. Further, after forming an underlayer mainly composed of Cr2N, grooves or convex shapes may be formed on the surface of the underlayer for the purpose of preventing adhesion of the magnetic head and lowering the coefficient of friction.

[Effect]

The magnetic recording medium of the present invention does not use a CrN layer, which has poor hardness, as the underlayer on the substrate, but has sufficient mechanical strength to prevent damage to the magnetic recording medium even when it comes into contact with a magnetic head or collides with it. The material Cr2N layer or C
It is formed using a mixed layer of r2N and CrN.

For this reason, if an intermediate layer, magnetic layer, protective layer, or lubricant layer is formed on the base layer on which the underlayer is formed, for example, by physical vapor deposition (PVD), typically sputtering, The magnetic recording medium has a surface precision that can ensure a stable head flying state even when the magnetic head is flying at a low level, and has excellent sliding resistance against the magnetic head.

〔Example〕

Embodiments of the present invention will be described below in more detail with reference to the drawings.

The substrate material of the magnetic recording medium of the present invention is AQ alloy, glass,
Although ceramics, plastic chips, etc. can be used, the most common and economically superior substrate at present is an AIJ alloy substrate. Physical vapor deposition (PVD), chemical vapor deposition (CVD), vapor deposition, etc. can be used to form the base layer of the present invention. Since it uses a sputtering method, which is a type of P V D), it is preferable to carry out on an industrial scale.

When forming the Cr2N layer of the present invention or a mixed layer of Cr2N and CrN as a base layer, for example. When using the sputtering method, Cr is used as the target. Spatters in a mixed gas of Ar and N2, so-called
An underlayer can be formed on the substrate by reactive sputtering.

The underlayer consisting of a Cr2N layer or a mixed layer of Cr2N and CrN needs to prevent damage to the magnetic layer from shocks caused by contact between the magnetic head and the magnetic recording medium. If a material with low hardness is used, the thickness of the underlayer needs to be at least 1 μm or more. As the thickness of this base layer increases, the sliding resistance improves, but on the other hand, as the film thickness increases, the film stress also increases, and in severe cases, there is a risk of deformation of the substrate, and there are also economical problems. From the viewpoint of producing magnetic recording media in general, it is not preferable to make the film thicker than necessary;
It is desirable that the thickness be less than μm. However, if it is possible to reduce the film stress or to form a film at high speed on an industrial scale, it is of course possible to use a film thicker than this.

Next, a more detailed explanation will be provided using specific examples. Example 1> An example of the present invention will be described with reference to FIG. 1 is a substrate, which is generally made of Afl-Mg alloy, but glass, ceramics, etc. may also be used. 2 is a base layer consisting of a Cr2N layer or a mixed layer of Cr2N and CrN, and 3 is a Cr
, Mo, W, Ti, etc., 4 is CoNi, C
Magnetic layer made of oNiCr, CoNiP, etc., 5 is C, S
A protective layer 6 is made of iO2, SiC, etc., and a lubricating layer 6 is made of an organic substance having perfluoro-alkyl ether chains. below,
This example will be described in more detail.

AQ- with outer diameter 130mmφ, inner diameter 40m, thickness 1.9m
Using the Mg alloy substrate 1, the substrate temperature was 160°C and the RF input power was 600 using the RF magnetron sputtering method.
W. The total gas pressure of Ar and N2 is kept constant at 5m Torr.
NZ gas partial pressure N2/(Ar+Nz) ratio is 0.1,0
．． By changing the conditions of 2, 0.3, 0.4, 0.5, C
A base layer having a thickness of 2.5 μm was formed by spuntering using r as a target.

Next, on the AQ-Mg alloy substrate with this underlayer,
Under the same conditions as above, in an Ar gas atmosphere, the film thickness was 250.
Intermediate layer 3 consisting of 0 Cr, film thickness 600 Cr CoNi
After forming a Cr magnetic layer 4 and a protective layer 5 made of carbon having a film thickness of 500 μm, a liquid lubricant layer 6 containing 5 μm of perfluoroalkyl ether chains was formed to obtain a magnetic disk.

The hardness of this magnetic disk was measured using a micro hardness meter with a Knoop indenter at a measuring load of 10 gf, and the Knoop hardness and N
The relationship between the z/(A r + N2) ratio is shown in FIG. N z / (A r + N 2) when forming the base layer
The lower the ratio, the harder the magnetic disk was obtained.

Therefore, thin film X-ray analysis was performed with only the underlayer formed on each magnetic disk, and the composition of each underlayer was evaluated from the diffraction peak. As a result, the Nz/(Ar+N2) ratio was 0.2.
Below, it was found that most of the film was made of Cr2N, and it was presumed that this Cr2N film contributed to improving the hardness of the magnetic disk. In addition, in all magnetic recording media, a 12 μm thick Ni-P film was formed by the conventionally used electroless plating method to form the base layer 2, and on top of that layer, the same conditions as in the above-mentioned example were applied. The hardness of a magnetic recording medium made with the same structure is approximately 600 kg f.
/ m”. From this, the underlayer is a mixed layer of Cr2N and CrN, preferably Cr
It was found that a magnetic recording medium with high hardness can be obtained by using a 2N layer.

Cr2N layer formed in this example or Cr2N
The strength of the underlayer made of a mixed layer of CrN and CrN varies depending on the film thickness. AQ-Mg alloy is used as the substrate, and a base layer is formed on it with a N2/(A r + N2) ratio of 0.1.
The Knoop hardness of the samples was measured with the film thickness kept constant and the film thickness varied. The results are shown in FIG. To be used as an underlayer of a magnetic recording medium, the thickness of the underlayer containing Cr2N as a main component must preferably be 2.0 μm or more.
Even so, it can become a base layer with a thickness of about 1/6 of that of the Ni--P film and a hardness equivalent to that of the Ni--P film.

<Example 2> Another embodiment of the structure shown in FIG. 1 will now be described.

AQ with outer diameter 130φ, inner diameter 40mφ, thickness 1.9++u
Using a Mg alloy substrate, the substrate temperature was 180°C and the total gas pressure of Ar and N2 was 6 mTorr. DC input power is 600 W, the N2 gas partial pressure Nz/(Ar+N2) ratio, which tends to form a Cr2N film, is constant at 0.1, and the film thickness is 2.0 μm, mainly Cr2N.
A base layer containing as the main component was formed. Next, on the AQ-Mg alloy substrate on which this underlayer was formed, an intermediate layer 3 made of Cr with a thickness of 2000% and a CoN layer 3 with a thickness of 600% were deposited in an Ar gas atmosphere under the same conditions as above. After forming the iCr magnetic layer 4 and the protective layer 5 made of C with a film thickness of 450 mm,
The lubricating layer 6 was formed by 60 people to form a magnetic disk.

The hardness of this magnetic disk was measured using a microhardness meter with a Knoop indenter at a measuring load of 10 gf, and the soup hardness was 980 kgf/m''.

This hardness is determined by forming the base layer 2 by forming a 12 μm Ni-P film using the conventional electroless plating method.
The hardness was comparable to that of a magnetic recording medium produced on this layer under exactly the same conditions and with the same configuration as in the above example.

<Example 3> Another example of the structure shown in Figure 1 will be described below. Outer diameter 13
0mφ, inner diameter 40m+φ-, thickness 1.9aa Afl-
Using the Mg alloy substrate 1, the substrate temperature was 150°C, the total gas pressure of Ar and N2 was 5 mm Torr, and the gas partial pressure of Nz was N2/(Ar+N2
) after forming a base layer 2 mainly composed of Cr2N with a thickness of 3.0 μm at a ratio of 0.1 and a DC input power of 600 W. The film thickness was 200 mm in an Ar gas atmosphere under the same conditions as above.
Intermediate layer 3 made of Cr with a thickness of 0λ, CoNi with a film thickness of 600 μm
After forming the Cr magnetic film 4 and the C protective layer 5 with a film thickness of 500 layers, the lubricant layer 6 was formed with 60 layers to obtain a magnetic disk.

This magnetic disk has a relative speed of 13.5 m/s and a flying height of 0.24 μm.
As a result of evaluating the impact resistance by setting it in a magnetic disk device that records and plays with a thin film magnetic head made of slider material, 17
Impacts of 0G or higher may cause errors during playback,
It exhibited good impact resistance without crashing. Also,
The CSS test revealed that the magnetic recording medium had a lifespan of more than 30,000 cycles and had excellent sliding properties. In the above embodiments, an AQ-based substrate was used as the substrate 1, but organic substrates such as polyimide, glass substrates, AQz
A similar effect is also observed with ceramic substrates such as Oa. However, in the case of a substrate having greater hardness than the AQ-based substrate, the thickness of the underlying layer consisting of the Cr2N layer or a mixed layer of Cr.2N and CrN may be smaller than that on the AQ-based substrate.

〔Effect of the invention〕

According to the present invention, it is possible to form an underlayer that has high hardness and excellent adhesion to the substrate, which has the effect of improving the impact resistance and sliding resistance of the magnetic recording medium, and improves reliability. An extremely high performance magnetic recording medium can be provided.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of an embodiment of the present invention, Figure 2 is a graph showing the relationship between the hardness of the magnetic disk and the partial pressure of N2 gas at the time of forming the underlayer, and Figure 3 is the hardness and film thickness of the underlayer material. It is a graph showing the relationship. DESCRIPTION OF SYMBOLS 1... Substrate, 2... Base layer, 3... Intermediate layer, 4...
...Magnetic layer, Nz/(AI-+Ha2) ratio

Claims (1)

[Claims] 1. In a magnetic recording medium having a nonmagnetic underlayer on a substrate and a magnetic layer on the underlayer, the nonmagnetic underlayer is made of C.
A magnetic recording medium comprising an r_2N layer or a mixed layer of Cr_2N and CrN. 2. In claim 1, an intermediate layer made of at least one element selected from the group consisting of Cr, Mo, W, Ti, C, Ge, and Si is formed between the magnetic layer and the underlayer. A magnetic recording medium characterized by: 3. The magnetic recording medium according to claim 1, wherein the magnetic layer is a metal thin film containing Co as a main component. 4. In claim 1, the thickness of the base layer is 1 to 10
A magnetic recording medium characterized in that it is μm. 5. In claim 2, the thickness of the intermediate layer is 500 to 5.
A magnetic recording medium characterized in that the thickness is 000 Å. 6. The magnetic recording medium according to claim 1, wherein the substrate has controlled grooves or controlled unevenness formed along the circumferential direction. 7. A magnetic recording medium characterized in that the nonmagnetic underlayer according to claim 1 is formed by a physical vapor deposition method using a metal target, and is constructed using the nonmagnetic underlayer. 8. A magnetic recording device incorporating the magnetic recording medium having the structure according to claim 1. 9. In claim 7, the gas partial pressure N_2/(Ar
+N_2) A method for manufacturing a magnetic recording medium, characterized in that the ratio is 0.2 or less.