JPS62279519A - Magnetic disk - Google Patents

Abstract

PURPOSE:To decrease defects such as surface depressions and projections of a cured nonmagnetic layer by using an alloy contg. nickel to form the cured nonmagnetic layer to be provided between a substrate and magnetic medium layer. CONSTITUTION:The cured nonmagnetic layer 21, the magnetic recording medium layer 3 and a lubricating layer 4 are successively laminated on the nonmagnetic substrate 1. The layer 21 is formed of an alloy contg. nickel, more preferably a ternary alloy of nickel, copper and phosphorus. The cracking of the layer 3 by a heat treatment during the formation of said layer is prevented if the content of the nickel in the ternary alloy is specified to <=60wt% and the content of the copper therein to 34+ or -5%. Since the layer 21 having substantial hardness and decreased surface defects is obtd. according to the above-mentioned constitution, the surface defects of the magnetic disk are decreased.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention [Field of Industrial Application] This invention relates to improvement of a magnetic disk used as a storage medium.

[Conventional technology]

The structure of a conventional magnetic disk is shown in FIG. In Fig. 8, 1 is a disk-shaped non-magnetic substrate made of aluminum alloy, and 2 is a 9-12 μm plated on the non-magnetic substrate 1 in a chromic acid bath.
The alumite layer formed to a film thickness of Neutral method (in Ar), reduction method (, A, r
+82).

Sputtering is performed in a sputtering atmosphere such as oxidation method (A, r+02) to form a Fe3O4 film on the substrate, or
After forming an α-Fe203 film on the substrate by sputtering using the oxidation method (Ar +02) using a target of
4 is a lubricating layer covering the magnetic recording medium layer 3;

By the way, in a magnetic disk configured in this way, even if the recording density is increased, in order to obtain the same readout output waveform as in the case of a low density, the film thickness of each layer is made thinner to improve the resolution and one recording bit cell is used. Sputtering 1M in which the magnetic material content of the magnetic recording medium layer is increased to 100% in order to prevent a continuous drop in output voltage due to a decrease in the magnetic material volume per area.
We are trying to adopt a thin film continuous medium formed by a deposition method.

In addition, when the magnetic disk rotates, the magnetic head floats about 0.1 to 0.3 μm above the disk, and when the rotation stops, the magnetic head is in contact with the disk. This is because the so-called contact start-stop (C3S) method is used. Efforts are being made to ensure a stable head flying state at low flying heights and to prevent head-disk collisions (head crashes).

Therefore, the conditions for the nonmagnetic substrate 1 suitable for high-density recording include good mechanical flatness and surface roughness, and a small number of defects.

Furthermore, as the recording medium becomes thinner, the substrate needs to have sufficient hardness. In other words, if the substrate is soft, it will cause deformation such as depression when the magnetic head comes into contact with the magnetic disk, and the magnetic head will not be able to maintain a stable floating state, resulting in continuous output voltage fluctuations and accompanying data errors. ,
This not only causes partial loss of recorded data, which can be said to be fatal for a storage device, but also reduces the contact start/stop (C3S) count, which indicates the reliability of a magnetic recording device, which can lead to a head crash, causing complete loss of recorded data. The problem arises that it leads to

In the above explanation, problems caused by insufficient substrate hardness were discussed, but even if the substrate hardness is sufficient and no depression occurs when the magnetic head and the substrate come into contact, the friction of the lubricant layer 4 If the magnetic head is large, the frictional force generated at that time disturbs the stable floating state of the magnetic head, causing a head crash, resulting in the same problem as the above-mentioned loss of data.

[Problem that the invention seeks to solve]

However, when an alumite layer is formed on a conventionally used aluminum alloy and then polished, the hardness distribution in the cross-sectional direction is as shown in Figure 9. The cross section of the mark is as shown in FIG.

As mentioned above, in the case of conventional substrates in which an alumite layer is formed on an aluminum alloy, surface defects such as surface depressions and protrusions have not been sufficiently improved.

The present invention has been made to solve the above-mentioned problems, and an object thereof is to provide a non-magnetic substrate having sufficient hardness and improving surface defects.

[Means for solving problems]

Therefore, the magnetic disk according to the present invention is characterized in that the nonmagnetic hardened layer 21 is made of an alloy containing at least nickel.

[Effect]

In the present invention, the alloy containing at least nickel formed on the nonmagnetic substrate greatly reduces surface defects such as surface depressions and protrusions of the nonmagnetic hardened layer 21.

〔Example〕

An embodiment of the present invention will be described below based on the drawings.

FIG. 1 is a configuration diagram showing one embodiment of the present invention, and (2).

3.4 is the same component as a conventional magnetic disk, and 21 is a nonmagnetic hardened layer made of an alloy containing at least nickel.

Nickel-phosphorus (Ni-P) as an alloy containing nickel
When using the alumite coating, the hardness was relatively high as shown in FIG. 9, and it was also found that the surface protrusions were greatly improved compared to the conventional alumite coating.

The reason for this is that in the case of conventional alumite coatings, small amounts of Mg, Fe, or their compounds contained in aluminum exist as hard impurities on the soft aluminum alloy substrate, forming protrusions. This is thought to be because the substrate of the P alloy is relatively hard, and even if similar impurities are present, they will be processed into a concave shape as soft particles in the substrate when polished.

Thus, it was found that the Ni-based alloy film is excellent as the nonmagnetic hardened layer 21.

However, in the above-mentioned process for TFe2e co-film magnetic disk, the substrate temperature during sputtering is usually around 240℃, and the atmospheric oxidation process for γ-1; Requires heating.

Therefore, the magnetism generation temperature of the N1-P plating film is usually 2
Since the temperature is around 00° C., the N1-P plating film is magnetized after the above process.

If the hardened layer becomes magnetized, it will be recorded in the magnetic medium layer and the hardened layer below this during magnetic recording, increasing the magnetization transition width, and during reproduction, the magnetization of the magnetic medium layer will be changed by the hardened layer below this. Due to the closing, the magnetic flux generated outside the magnetic recording medium is reduced, resulting in a problem that the head output is reduced.

Therefore, in order to solve this problem, a Ni--Cu--P ternary alloy plating film that exhibits nonmagnetic properties when the Ni content is 60 wt% or less was considered.

As shown in FIG. 2, this ternary alloy plating film was found to be non-magnetic when the Ni content was 60 wt% or less, and as shown in FIG. 9, it was found to have extremely high hardness.

However, in order to use the γ-Fe203 spunter film as a magnetic material, there is an oxidation heat treatment step at 300''C or higher for several hours during production, and it is necessary to withstand this heat treatment and it is necessary that no cracks occur.

However, during this process, many concentric or radial cracks appeared on the entire disk surface or near the inner and outer edges of the disk that was initially produced as a prototype, which revealed the problem of insufficient heat resistance.

It was also found that this clutter is classified into concentric clutter and radial clutter as shown in FIG. 3, and the cross-sectional structure of the clutter is shown in FIG.

As a result, the cause of clutter in the ternary alloy was presumed to be stress cracking, and in order to eliminate this stress cracking, we created samples with various Ni, Cu, and P contents, and investigated the stress state before and after heat treatment. did.

This investigation was conducted by forming a plating film on one side of a rectangular aluminum plate and measuring the amount of warpage of the plate.

As a result of this investigation, a stress-Cu content graph shown in FIG. 5 was obtained.

Furthermore, a plating film of a ternary alloy was formed on both sides of the aluminum foil, and the coefficient of thermal expansion from room temperature to 300°C was measured.

As a result, a graph showing the relationship between copper content and thermal expansion coefficient shown in FIG. 6 was obtained.

According to these figures 5 and 6, the Cu content is 34±
It was found that there was no stress change before and after heat treatment at 5 wt%, and the content at this time was equal to the coefficient of thermal expansion of aluminum.

Therefore, when the copper (Cu) content was set to 34±5 wt%, films containing 15 to 60 wt% were prepared in various disk sizes (outer diameters of 3", 5%", and 8").

8.8", 9", and 10.5"), and the situation of generation of cod vines was investigated.

As a result, the graph shown in FIG. 7 was obtained.

It can be seen from this that the allowable range differs depending on the disc size.

This can be understood in relation to the thermal stress generated by the coefficient of thermal expansion.

The material of the nonmagnetic hardened layer used in magnetic disks is a ternary alloy consisting of nickel (Ni), copper (Cu), and phosphorus (P), and the copper content is 34±
It was concluded that 5% or less is the most effective.

Although the present invention has shown an example in which an aluminum alloy is used as the non-magnetic substrate 1, similar effects can be obtained even if the non-magnetic substrate is made of other metals.

Although the case where TFe20) is used as the magnetic recording medium layer 3 has been described, Co-Ni.

Co-Cu, Co-N1-P, Ba-Fer
rite.

It is clear that there is no problem in applying it to other magnetic materials such as Tb-Fe and Gd-Co.
2. It is clear that there is no problem in application even when a protective crotch made of TiN, SiC, C, etc. is provided, and in any case, the effects of non-magnetism, high hardness, and heat resistance can be obtained.

〔Effect of the invention〕

As described above, in this invention, since the nonmagnetic hardened layer is made of an alloy containing at least nickel, a magnetic disk with few surface defects can be obtained.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the configuration of the magnetic disk of the present invention, Fig. 2 is a diagram showing the relationship between nickel content and magnetism, Fig. 3 is a diagram showing the state of clutter in a ternary alloy of nickel-copper-phosphorus, and Fig. 4 The figure also shows the cross-sectional structure of clutter, Figure 5 shows the relationship between copper content and stress, Figure 6 shows the relationship between copper content and thermal expansion, and Figure 7 shows the relationship between non-magnetic Figure 8 is a diagram showing the structure of a conventional magnetic disk, Figure 9 is a diagram showing the hardness distribution of various materials, and Figure 10 is a diagram showing the relationship between the disk size of the body substrate and the occurrence of clutter. It is a sectional view showing a cross section. DESCRIPTION OF SYMBOLS 1...Nonmagnetic substrate, 2...Nonmagnetic hardened layer, 3...Magnetic recording medium layer, 4...Lubricant layer. Agent: Yoshinori Oone (and 2 others) Taku2fu (phantom cJv″0-fence)
1℃ yen "K cp C) '(
) Y90 Box 10 WIdt, h (μ error procedural amendment (volunteer 23 name of invention magnetic disk 3, person making the amendment representative Moriya Shiki 4, agent 5, scope of patent claims to be amended, invention Column for detailed description, drawings, and brief explanation of drawings. 6. Contents of amendment + 11 Amend the claims as shown in the attached sheet. (2) Change rRwaxJ to rRwaxJ on page 2, line 9 of the specification.
Correct it with RmaxJ. (3) In the fourth line of page 3 of the same book, the words "each layer" are corrected to read "magnetic layer." (4) In the same book, page 6, line 17, the words rMg and FeJ are corrected to rMg, Si, and FeJ. (5) Page 8, line 16, line 17, line 18, line 20 of the same book, page 9, line 20, page 11, line 12, line 13, line 16 Lines to 17th “Clutter”
Correct that to "crank." (6) Ibid., page 3, No. 4 Claims (1) A nonmagnetic substrate is coated with a nonmagnetic hardened layer, the coated nonmagnetic hardened layer is coated with a magnetic recording medium layer, and the magnetic recording medium layer is further coated with a magnetic recording medium layer. A magnetic disk coated with a lubricating layer, characterized in that the nonmagnetic hardened layer is made of an alloy containing at least nickel. (2) The magnetic disk according to claim 1, wherein the nonmagnetic hardened layer is made of a ternary alloy of nickel, copper, and phosphorus. (3) The magnetic disk according to claim 1 or 2, wherein the nickel content is 60 wt% or less. +4) The magnetic disk according to claim 2 or 3, characterized in that the content of W4 is 34±5%. 5th Figure 10wrath (Ptnr

Claims (4)

[Claims] (1) In a magnetic disk constructed by coating a nonmagnetic hardened layer on a nonmagnetic substrate, coating the coated nonmagnetic hardening layer with a magnetic recording medium layer, and further coating the magnetic medium layer with a lubricating layer, A magnetic disk characterized in that the magnetic hardening layer is made of an alloy containing at least nickel. (2) The magnetic disk according to claim 1, wherein the nonmagnetic hardened layer is made of a ternary alloy of nickel, copper, and phosphorus. (3) The magnetic disk according to claim 1 or 2, characterized in that the nickel content is 60% or less. (4) The magnetic disk according to claim 2 or 3, characterized in that the content of copper is 34±5%.