JPS61224139A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain the titled high-density and high-reliability recording medium with less aged deterioration by forming a metallic magnetic film layer and then oxidizing the magnetic film layer. CONSTITUTION:A metallic magnetic thin film layer is formed and then the magnetic film layer is oxidized. For example, a nonmagnetic NiP substrate layer is chemically formed on an aluminum or an aluminum-base alloy substrate by using a plating bath using sodium hypophosphite as a reducing agent. Then a CoNi-Pt alloy thin film is formed in a pure gaseous Ar atmosphere on the substrate layer by sputtering, etc., and then a C protective film is immediately formed by sputtering. Subsequently, the magnetic film layer is heated in the atmosphere at 120 deg.C for 1hr and oxidized.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing a magnetic recording medium, and in particular to a magnetic recording medium in which a metal magnetic film layer with a high in-plane orientation of the axis of easy magnetization is formed on a substrate. This is a method for manufacturing recording media.

[Conventional technology]

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, research into manufacturing and methods of magnetic recording media with high recording density for use in external memory devices has been greatly promoted in recent years.

One of them is a method for manufacturing a magnetic thin film in which a cobalt (CCo) and nickel (Xi) alloy is sputtered in an Ar and N2 atmosphere and then heat treated. (Unexamined Japanese Patent Publication No. 5
7-72307) Todoroki r+) 12 It is known that magnetic thin films sputtered in the Middle East have good magnetic properties.

[Problem that the invention seeks to solve]

This has been a practical hindrance in that it is inferior to coated magnetic recording media in which iron oxide powder is coated on a substrate together with a binder in terms of chemical composition.

[Means for solving problems]

In order to solve the above-mentioned problems of the prior art, the gist of the present invention is a method of manufacturing a magnetic recording medium, which is characterized in that a metal magnetic film is processed on the surface of a disk-shaped substrate.

The present invention will be explained in more detail below.

The material of the substrate used in the magnetic recording medium of the present invention is preferably aluminum or aluminum with two or more improved properties. For example, several weight percent of magnesium,
For example, one containing 3 to 4% by weight is used.

Note that since silicon is easily precipitated as silicon dioxide, it is preferable to use a substrate with a low silicon content.In addition, it is also preferable to use ceramics, glass, or resin as the substrate.

The base layer formed on the aluminum or aluminum alloy substrate is an alumite layer or a Cr layer applied by NIP or sputtering.

The base layer for alumite is easily formed by oxidizing the surface of an aluminum or aluminum-based alloy substrate by anodizing in an acid solution, but during this oxidation, metals other than aluminum contained in the substrate are removed. Oxides generated by oxidation are mixed in the base layer, and therefore the type and amount of metal oxides other than aluminum oxide in the base layer are usually influenced by the type and content of metals other than aluminum in the substrate. Ru. Also, unlike the alumite base layer, the NIP base layer does not have any adverse effects due to the presence of metals other than aluminum in the substrate, but 2
Heating over 0.00 to 250°C will magnetize it and cause noise.

Since this method cannot be applied to manufacturing methods that require a heating process to a temperature higher than this, care must be taken regarding the temperature during heating.

Even if a material other than these is used, a hard non-magnetic underlayer with a Vickers hardness H of 300 or more is preferably used for the present invention, as long as it has good adhesion to the substrate and the metal magnetic film layer. It is also effective in the present invention to form a metal magnetic film layer on the underlayer and then oxidize the magnetic film layer or apply a liquid lubricant on the protective/lubricant layer.

In addition, when forming a protective lubricant layer and/or applying a liquid lubricant, the oxidation treatment process may be performed after any process as long as it is after forming the metal magnetic film layer (used in the present invention). As the metal magnetic layer, Go-Ml, Go-Cr, Co-Ni-Cr, Co-
Formed by Pt, GO-Pt-Ni or plating
Examples include Go-Ni-P. This oxidation treatment will be explained below.

The methods used for this oxidation treatment include a wet method in which the metal magnetic recording medium is directly immersed in pure water, followed by cleaning and drying, and a dry method in which heat treatment is performed in an atmospheric gas containing oxygen. It is. In the wet method, oxidation progresses quickly, making it difficult to control the degree of oxidation7, and dust particles tend to adhere to the magnetic recording medium during the cleaning and drying process after processing.On the other hand, in the dry method, It is preferable to the wet method because it is easier to control the speed and there is less dust adhesion.

The dry method includes heating a metal magnetic recording medium to 50°C to 350°C in an oxygen gas atmosphere or an oxygen-containing gas atmosphere, such as the air, or an oxygen gas atmosphere or an oxygen-containing gas atmosphere of 1 atm or more, such as the air. 50
A preferred method is to leave the metal magnetic recording medium in an atmosphere heated above ℃ and humidified to a relative humidity of 70% or above.
In a method for manufacturing a magnetic recording medium in which sputtering is performed in an atmosphere of r and ψ, followed by heat treatment, the heat treatment process is performed in a low vacuum, or oxygen gas or a gas containing oxygen, such as air, is introduced in the cooling process after the heat treatment.

It is effective to carry out oxidation treatment and acceleration of cooling at the same time.In the present invention, oxidation treatment must be performed appropriately.In other words, the oxidation treatment results in poor head output, low head output, and high error rate. What is the preferred degree of oxidation in the present invention?

Compared to before the melting treatment, the saturation magnetization decreased by 1 to 10%, and the coercive force increased by 1 to 10%. The squareness ratio S and the coercive force generally do not change much even if the saturation magnetization and coercive force change by about lθ%.

When forming a protective lubricant layer such as carbon after forming a metal magnetic film layer and/or applying a liquid lubricant, the oxidation treatment process can be performed after any step as long as the metal magnetic film layer is formed. good.

If oxidation treatment is performed immediately after the formation of the metal magnetic film layer and then a protective lubricant film is formed, the oxidation treatment will proceed quickly because the metal magnetic film layer is exposed, but dust particles will accumulate during the oxidation treatment. If it is difficult to remove, or if a protective lubricant film is formed without removing it, it will become semi-permanently fixed as a surface protrusion on the magnetic recording medium. When a magnetic recording medium is rotated at high speed with a small gap of less than 1 inch between the head and the head, as in a recording device, this can cause a head crash. If oxidation treatment is performed after forming a metal magnetic film layer and a protective lubricant film, the progress of the oxidation treatment will be slow, but dust particles will accumulate during the oxidation treatment, which reduces the reliability of the actual recording medium. The magnetic recording medium of the present invention can be manufactured, for example, in the following manner.
That is, a thin metal film is formed on an underlayer using sodium phosphate as a reducing agent on an aluminum or aluminum-based alloy substrate, and immediately thereafter a C protective film is formed by sputtering.

Thereafter, it is oxidized by heat treatment in the atmosphere at 120°C for 1 hour. This magnetic recording medium has good magnetic properties, has no increase in defects, and has little change over time. When performing oxidation treatment in an atmosphere containing oxygen gas, particularly preferred oxidation treatment conditions are
゛ r1゛ 50℃～ 20
Hold at 0℃ for about 0.5 to 12 hours When using an alumite base layer or using a ceramic substrate, 50
It is held at ~1450°C for about 0.1 to 12 hours. When performing oxidation treatment in an oxygen gas atmosphere of 1 atm or more or in the air, particularly preferred oxidation treatment conditions are: pressure: 1 to 3 atm; temperature: BO to 100°C; relative humidity: 7
It is maintained for 0.5 to 10 hours at 0 to 98%. Ar+N2
When performing oxidation treatment in an atmosphere containing nitrogen, heat is maintained at 320°C to 450°C for 1 to 5 hours at a pressure below the preferred oxidation heat of 5X 11' Torr, then heating is stopped, and then oxygen gas or atmospheric air is introduced. In this method, oxidation treatment and cooling are performed at the same time, and by doing so, it is possible to manufacture products with excellent magnetic properties and little change over time at low cost.

[Effect]

The method for manufacturing a magnetic recording medium of the present invention is characterized in that the aging of the magnetic recording medium is reduced by performing the oxidation treatment. Furthermore, this has the effect of increasing the reliability of the magnetic recording device over a long period of time.

In the examples described below, the gold magnetic film layer is formed using a magnetron sputtering apparatus, but it is of course possible to obtain the effects of the present invention by wet plating, vacuum evaporation, ion beam tower sputtering, or the like.

Comparative Example 1 An alumite base layer was formed on the surface of an aluminum alloy substrate, and the seventh surface was polished to form a smooth C-low-Ni (Ni composition: 5 atomic %) alloy thin film.Furthermore, a carbon protective film was formed.

Comparative Example 2 An alumite base layer was formed on the surface of an aluminum alloy substrate, and a Go-Ni (Xi composition 20 atomic %) alloy thin film was provided, and then a carbon protective film was formed.

Comparative Example 3 After forming a thin film in the same manner as Comparative Example 2, LXIQ-'T
Heat treatment was performed at 340° C. for 3 hours at a pressure of 0τr or less to perform denitrification and crystallization of the film or growth of crystal grains.

Comparative Example 4 A nonmagnetic NIP underlayer was purely chemically formed on the surface of an aluminum alloy substrate using a plating bath using sodium hypophosphate as a reducing agent.

And its surface was polished and smoothed.

Next, a Co-Ni-Pt alloy magnetic ill (Go 110at%, N15at%, P
t5at%) was formed, and then a carbon bonding ssi was formed.

Comparative Example 5 A coated magnetic recording medium was prepared in which γ iron oxide powder was fixed onto an aluminum alloy substrate using a binder.

Example 1 Comparative Example A magnetic recording medium prepared in the same manner as in 1 was placed in the atmosphere.
Oxidation treatment was performed in the air at 300°C for 0.2 hours.

Example 2 Processed.

Example 3 Immediately after heat treatment of a magnetic recording medium prepared in the same manner as in Comparative Example 3, when the temperature had dropped to 250°C, air was introduced and oxidation treatment was performed while cooling.Example 4 Prepared in the same manner as in Comparative Example 4 magnetic recording medium at 3 atmospheres 85
The oxidation treatment was carried out by holding at 80% relative humidity for 8 hours.

Comparative Examples 1 to 4 and Examples 1 to 4 have an outer diameter of 130
The results of measuring the magnetic properties and electromagnetic conversion characteristics of a magnetic disk plate on which a magnetic thin film was formed on an aluminum alloy substrate (Ai-4 wt% Mg) with an inner diameter of 25 mm and a thickness of 1.8 mm are shown below. Shown in Table 1.

reactor This electromagnetic conversion characteristic was measured under the following conditions.

Head used: Mn-Zn ferrite Winchester type (track @: 52 ILm gap length: 0.9 J
L4 layer gear size: 451 number of turns 19TX2 flying hide = 0.3? JLI 2F Frequency: 2.5 MHz Disc rotation speed: 3800 γp These magnetic disks were exposed to an atmosphere of 60° C. and 90% relative humidity for 2 weeks and their changes over time were measured. The magnetic properties and electromagnetic conversion properties after the exposure test were measured and shown in the same table.

As is clear from this table, there is no big difference in the magnetic properties and electromagnetic conversion characteristics during thin film creation between those of the present invention and those of the comparative example, but the number of negative missing errors in the electromagnetic conversion characteristics after the exposure test is The number of samples of the comparative example has increased, but the number of samples of the present invention has not increased. Thus, it is recognized that there is little change over time.

From the above, this method of manufacturing a magnetic recording medium improves the performance of a high-density, highly reliable recording medium.

〔effect〕

As described in detail above, according to the manufacturing method of the present invention, an excellent magnetic recording medium with little change over time can be easily manufactured.

Claims (3)

[Claims] (1) A method of manufacturing a magnetic recording medium having a metal magnetic film layer on the surface of a disk-shaped substrate, which comprises performing an oxidation treatment on the magnetic film layer after forming the metal magnetic film layer. Production method. (2) A metal film layer is sputtered on the substrate in a nitrogen gas atmosphere or an inert gas atmosphere containing nitrogen to form a metal film containing nitrogen, and then heat treated to denitrify it to form a metal magnetic film layer. A method for manufacturing a magnetic recording medium according to claim 1, characterized in that: (3) The method for manufacturing a magnetic recording medium according to claim 1 or 2, wherein the metal magnetic film layer is a Co-based alloy magnetic film layer.