JPS5945634A - Magnetic disk - Google Patents

Abstract

PURPOSE:To reduce defects in a substrate for a magnetic disk in size and number and to obtain a high quality disk by forming an Ni alloy layer having a specified saturation magnetic flux density or below on the surface of a metal for the substrate by an electroless plating method and by forming a thin oxide film as a magnetic medium on the Ni alloy layer. CONSTITUTION:The surface of an Al alloy disk is made flat and smooth by mechanical working, and an Ni alloy layer having <=50G saturation magnetic flux density is formed on the disk by an electroless plating method. The Ni alloy layer is finished to a specular surface by polishing, and a thin gamma-Fe2O3 film as a magnetic medium is formed on the layer by sputtering a sintered Fe3O4 body as a target in an Ar atmosphere and by carrying out heat treatment in air. Thus, impurities such as Si and Fe in the Al alloy substrate are prevented from appearing to the surface, causing defects and deteriorating the flatness of the substrate, so a high quality disk making no bit error is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic disk for use in magnetic recording groups 1.11, ti-ζ.

In recent years, the importance of external storage devices in combinations and systems has increased, and the demand for higher recording densities is increasing. The read/write device is composed of the key components of a recording + q raw head and a total disk.The magnetic disk rotates at high speed, and the recording/reproducing head floats a minute distance above the magnetic disk. In order to increase the recording density and improve the performance of magnetic disks, it is necessary to make the recording medium thinner, more uniform, improve the h-chip characteristics (increase coercive force and squareness), and improve stability at low levitation forces. In order to ensure a constant head flying condition and prevent collisions between the head and the disk (head clarity), the accuracy of the disk surface must be improved, and in order to reduce bit errors during high-density recording, defects in the substrate and recording medium must be reduced. No.

Conventionally, so-called coating media in which a mixture of iron oxide fine particles and a binder is coated on a substrate have been widely used as magnetic disks. In response to the increase in recording density, coach ink media have been made thinner, and the recording density is currently 15.
The film thickness reaches about 05 μm at 000 bits/inch (1 f+ magnetic flux reversal density on the tissue surface, 000 flux reversal/inch). However, in coach ink media, it is extremely difficult to make the film even thinner and to achieve uniform recording and reproducing characteristics in order to achieve higher densities in the future. Did you want to? A significant increase in recording density cannot be expected for media produced by the coating method.

Therefore, continuous thin film media, which can be easily made thin, are attracting attention as high-density +& magnetic recording media to replace coach ink media.

A plating disk using a C metal plating film as a TFI film medium was developed in 2005 and achieved high recording density, but in recent years, -c oxide magnetic thin magnetic disks have begun to attract attention. Ta. This can also be made into a 411 film similar to the metal plating film (it has excellent feel and corrosion resistance, so it is expected to improve recording accuracy.

The manufacturing of magnetic disks using such oxide magnetic thin film media is roughly divided into a substrate forming process and a medium forming process, and the substrate forming process has the following problems. For this purpose, flatness and smoothness are required in order to enable thinning of the medium and to ensure a stable head flying state at a low flying height, and a significant reduction in substrate defects is required.

The substrate also has mechanical strength, workability, polishability, lightness,
Various properties such as low cost and mass productivity were needed, and it was also necessary to maintain non-magnetic properties even after heat treatment in the media forming process. Until now, materials such as metal and glass have been used as this substrate, but although the glass substrate has a smooth and flat surface, it is weak against impact and has the risk of breakage, so it is considered unsuitable for practical use. On the other hand, aluminum alloys, which are inexpensive and have good workability, are generally widely used as metal substrates, but aluminum alloys alone do not provide sufficient hardness and polishability, so the surface of aluminum alloys is anodized. Polished and processed materials are used. Although this board almost satisfies each of the above-mentioned items, it has a fundamental problem in terms of board defects. In other words, impurity particles such as 81*Fe contained in aluminum alloys form many surface defects during anodizing treatment, and to avoid this, when high-purity aluminum alloys are used, the material becomes soft and the substrate is damaged. Flatness cannot be ensured. In order to solve such open circuits and reduce defects in magnetic disk substrates, a film that can be electroplated is formed on an aluminum alloy substrate, and nickel 80 -90 heavy orders, 10 to 20 phosphorus
A substrate on which a heavy nickel-phosphorous alloy film is formed by electroplating and the surface of this nickel-phosphorus alloy film is polished (hereinafter referred to as electroplated nickel-phosphorus substrate) is used for oxide magnetic thin film media. It is proposed as a board.

However, 1. A 0.5 μm thick surface treatment film was formed on the surface of the aluminum alloy disk by zinc substitution treatment, and then a 4 μm thick electrolytic copper plating film was applied using PI (10 M° copper plating solution). A film was formed, and a 15 μm thick nickel phosphorus film was deposited on top of the film while rotating using a perforated baffle plate and an auxiliary cathode.
In this method, a plated film is formed and the surface is polished to form a substrate.
Although the plating film in phosphorus does not become magnetic, many defects occur on the substrate surface, and the plating thickness is highly uneven in the radial direction of the disk, and local unevenness in the plating thickness within the plane of the disk. In addition to that, electrode placement +1! There are problems such as poor productivity and extremely high cost due to the roughness of the board for It 4pi. In other words, in the method of forming a copper plating film and a nickel phosphorous plating film by electroplating, impurities in the plating solution or impurities eluted from the object to be plated and the anode into the plating solution are removed by electricity and the plating film is formed. When it is formed, it is rolled up and eutectoid, which becomes a nucleus and tends to cause surface defects, making it extremely difficult to reduce defects in magnetic disk substrates. In addition, it is difficult to form a plated film of uniform thickness on a disk by electroplating, so using a perforated baffle plate and a slow-painting cathode as described in Japanese Patent Publication No. 45-94471 is necessary. Even after plating, the nickel-phosphorus plating thickness was uneven by ±7 inches or more in the radial direction of a disk with a diameter of 210 m and a thickness of 2 ga. Furthermore, there are minute irregularities on the surface after zinc substitution treatment, but when copper plating or nickel phosphorus plating is performed on the surface by electroplating, the current density increases at the minute convexities on the surface, causing local damage. As a result, the plating film thickness increases and many protrusions are produced on the surface of the disk.Surface defects not only cause bit errors, but also cause polishing defects along with surface protrusions during machining after plating, reducing surface smoothness. lower.

The purpose of the present invention is to overcome the above-mentioned drawbacks of the prior art, and to provide a surface that is suitable for high-density recording (flatness, smoothness, surface defects), mechanical strength, and new productivity. The object of the present invention is to provide a magnetic disk that uses an excellent substrate and has comparable recording and reproducing characteristics in various materials.

According to the present invention, in a magnetic disk having a metal substrate, a nickel alloy plating layer covering the metal substrate, and an oxide magnetic thin film medium covering the nickel alloy plating layer, the nickel alloy plating layer is Provided is a magnetic disk characterized by an electroless plated layer having a saturation magnetic flux density of 50 or less. The substrate of the magnetic disk of the present invention is formed by polishing a nickel alloy plated layer by electroless plating. Therefore, in addition to improving mechanical strength, workability, polishability, and lightness, it is possible to miniaturize and minimize substrate defects, both microscopically and macroscopically. The plating coverage of the uniform r-nickel alloy plating layer ensures sufficient surface precision, and low prices are achieved because bulk production is possible without the need for a complicated tank structure like the electric knob method. Conventionally, in magnetic disks using oxidized magnetic thin film media, the nickel alloy plating layer becomes magnetized during the heat treatment process during media formation, so electroless plating has been used. Although it was thought that it would be difficult to apply a substrate having a nickel alloy plating layer formed thereon (hereinafter referred to as an electroless nickel alloy plating substrate), the present inventors found that the saturation [1 magnetic flux] of a magnetized nickel alloy plating layer If the density is 50 Gauss or less, the reduction in reproduction output will be within 10 Gauss compared to when using an unmagnetized substrate, and the load on the recording and reproduction circuit system will be small. As a result, it has become possible to increase the recording density and quality of magnetic disks using oxide magnetic thin film media. The features of the magnetic tissue according to the invention will be explained using comparative examples and examples.

Comparison f/11° An aluminum alloy disc (diameter 230 txm, thickness 19 mm) that was made flat and smooth by machining was further improved in flatness by heat straightening, heat treatment, etc. 7; ridge, anode An oxide film (alumite film) with a thickness of 4 μm was formed on an aluminum alloy disk that was not oxidized.

Furthermore, both sides of this were machined to give a linear finish, and a magnetic tissue substrate was obtained.

In this way, the Fj et al. substrate has a diameter of 2μrr+ J
There are many defective forces S in the soil, and in this regard, if there is one topic in the collection, we will create a magnetic disk and record and reproduce +* a O)
It was possible to carry out measurements. F on the obtained substrate
es Using the Oa sintered body as a target, perform sputter linking in an Ar gas atmosphere.1. ＋”Cs
An Oa film was formed and then heat treated in the atmosphere at 300° C. for 1 hour to form an oxide film magnetic film medium made of γ-Fe-Os with a film thickness of 0.17 μm. The magnetic properties of the magnetic disk obtained in this way are coercive force Hc7Js 6
200e1 The magnetic disk obtained in Example C, which had a saturation magnetic flux density Bs of 3000 cous and a squareness ratio Br/Bs (Br is residual magnetic flux) of 0.81, was subjected to recording constraints under the following conditions. Measuring conditions under which the stopping characteristics were measured: Disc rotation speed: 3.00 rpm Track used: Short frame 125.6 fins used Head: Track width: 20 μm 1 Gap length: 1.0 μm Head flying height: 0.2 μm Recording current: 50 mA 30.000 F The playback output at high recording density of PI (Flux Reversal/inch) is 0141m.
7J5, a sufficient output value was obtained.Comparative Example 2゜The surface was made flat and smooth by machining. After further improving the flatness of an aluminum alloy disk (diameter 210mm, numbness 1.9mm) by heat straightening, heat treatment, etc.,
05 by zinc substitution treatment as seen in Publication No. 18029.
A μm thick surface treatment film is formed, a 4 μm thick electrolytic copper plating film is formed on it, and a 15 μm thick nickel plating film is applied on top of it while rotating using a perforated block plate and an auxiliary cathode. The surface was polished to obtain an electroplated nickel-phosphorus substrate. The substrate obtained in this way has
01 Polishing defects caused by localized uneven plating thickness and plating defects may cause head clarity on the surface.
There were many protrusions with a height of 0.2 μm or more. There were 30 to 60 defects with a diameter of 2 μm or more on one surface, about 40 on average.As described above, the magnetic plated nickel phosphorus substrate had a practical problem in terms of surface accuracy.

Next, a one-narrow magnetic thin film medium was formed on this substrate in the same manner as in Comparative Example 1. Magnetic properties of the obtained storage disc (
j, Hc=5900e, Bsx 3000cous, Br
/Bs=0.78, and no magnetization was observed on the air-plated nickel-phosphorus substrate. ．．
The playback output at high recording density of 000FILPI is 0.
．． A practically sufficient tjj force value of 40 mV was obtained.

Example 1 An aluminum alloy disc (diameter 210 m, thickness 1.9 wm) whose surface was finished flat and smooth by machining was further improved in flatness by heat straightening, heat treatment, etc., and then acid-washed and zinc-treated. A pretreatment suitable for performing uniform electroless nickel alloy plating on an aluminum alloy consisting of a substituted aluminum alloy was performed. Next, this is an electroless nickel alloy plating solution consisting of nickel salt as a source of metal ions, hypophosphite as a reducing agent for metal ions, a complexing agent for metal ions, a PH buffer, a thread adding agent, etc. A 20 μm thick nickel-phosphorus plating film is formed by dipping the sample into a 20 μm thick film. In this example, Schumer BO solution manufactured by Nippon Kanzen Co., Ltd. was used as the electroless nickel/phosphorous plating solution, the bath temperature was 90°C, and the pH of the plating solution was adjusted from 39 to 5.5.
Seven types of plating baths were used, varying up to: Further, both surfaces of the substrate were machined to a mirror finish to obtain an electroless nickel alloy plated substrate. All of the substrates thus obtained had no defects with a diameter of 1.0 μm or more and no protrusions with a height of 0.1/jm or more, and fully satisfied the surface precision, including flatness and smoothness, suitable for high-density recording. Next, Comparative Example 1. An oxide film magnetic thin film medium was formed in the same manner as in 0. The magnetic properties of the obtained magnetic disk were as follows: Hc = 6300
e, Bs-3000 Caus, and Br/Bs -0.79.As a result of measuring the recording and reproduction characteristics under the same conditions as the comparative example, the reproduction output and each substrate at a high recording density of 30,000FRPI were A relationship as shown in Table 1 was expected between the electroless nickel alloy matte layer and Bs after heat treatment at 300° C. for 1 hour.

Table 1 Relationship between playback output and Bs after heat treatment As shown in the table, in the case of magnetic disks with sizes 51 to 4 where the Bs of the electroless nickel alloy plating layer after heat treatment is greater than 50 cous, the playback output is as shown in the comparative example. In the case of Comparative Example 1.1, the Bs of the electroless nickel alloy plating layer after heat treatment was 50 Gauss or less, which was significantly lower than that of Comparative Example 1. f) The reduction in raw output compared to the case of
It was within 0%, and recording and reproducing characteristics with no practical problems were obtained.

Example 2 A magnetic disk was produced using the same procedure as in Example 1, but in this example, nickel was coated on the film thickness side in a nickel alloy plating bath using a commercially available solution with a relatively high phosphorus content in the plating group.・A phosphorus plating film was formed.

Electroless nickel alloy plating bath Electroless nickel phosphorus plating solution Nimden 11P (manufactured by Uemura Koshu Co., Ltd.) Plating conditions Plating solution PH: 5.5 Bath temperature: 90°C The obtained magnetic disk was as described in Example 1. Similarly, it satisfies the surface precision suitable for high-density recording, and as a result of measuring the recording and reproducing characteristics under the same conditions as Comparative Example 1, it was found to be 30.0OOF.
A relationship as shown in Table 2 was obtained between the reproduction output in RPI and the Bs after heat treatment of the electroless nickel alloy layer and layer at 300° C. for 1 hour.

Table 2. Relationship between reproduction output and Bs after heat treatment In this example, the BS of the electroless nickel alloy plating layer after heat treatment is 5.
Since it is as small as 3 cows, the reproduction output value S obtained in Comparative Example 1 is the same as in the case of magnetic tape and f disk.Example 3゜ Example 1. I made a magnetic disk using the same procedure as above, but
In this example, a nickel-tin-phosphorous plating film with a film thickness of 20 μm was formed using the following electroless nickel alloy plating bath. Sodium hypophosphite 0.30 mol/1 milk 12
0.9 mol/1 [(11 nistin 0.1 mol/1 plating conditions PH value of plating solution 4.2.4.5.4.8.5.1,
5.5 Bath temperature: 90°C The obtained magnetic disk was as described in Example 1. Similarly, it satisfies the surface precision suitable for high-density recording, and the recording and reproducing characteristics were measured under the same conditions as Comparative Example 1, and the result was 30.0OOF.
Table 3 shows the relationship between the regeneration output in RPI and the Bs of the carp ridge heat-treated at 300°C for 1 hour on the electroless nickel alloy plating layer. As shown in Table 3, the relationship between reproduction output and Bs after heat treatment, the Bs of the electroless nickel alloy plating layer after heat treatment is greater than 50 cous (1 In the case of the corrosive disk, the reproduction output was significantly lower than that of Comparative Example 1.A11 to A13 where the Js of the electroless nickel alloy plating layer after heat treatment was 50 Gauss or less.
In the case of Comparative Example 1. Low I of playback output compared to the case of
J was within 10%, and recording and reproducing characteristics with no practical problems were obtained.0 Example 4゜Example 1. I made a magnetic disk using the same procedure as above, but
In this example, Nickloy 22 manufactured by Sibley Far East Co., Ltd. was used as an electroless nickel alloy plating solution that can eutectoid copper.
A nickel/copper/phosphorus plating film with a film thickness of 20 It m was formed in the following electroless nickel alloy plating bath using electroless nickel/copper/phosphorus plating solution.
Sibley) 7-East Co., Ltd. nail condition plating solution PH catfish 4.6, 4.8, 5.0 + 5
．． 3, 5.6 Bath temperature: 90°C The obtained magnetic disk had a clean surface temperature suitable for high-density recording as in Example 1, and the recording and reproducing characteristics were measured under the same conditions as in Comparative Example 1. The result was 30.0OOF.
Table 4 shows the difference between the playback output in RPI 2 and the Bs (!:
．． A relationship like this was obtained.

Table 4: Relationship between reproduction output and Bs after heat treatment As shown in the table, in the case of magnetic disks with a diameter of 14 to 15 where the Bs of the electroless nickel alloy plating layer after heat treatment is greater than 50 Gauss, the reproduction output is compared. This was significantly lower than that of Example 1°. When the Bs of the electroless nickel alloy plating layer after heat treatment is 50 or less, Comparative Example 1. The weight of the 4'4 raw output was within 10φ compared to the case of 1, and recording and reproducing characteristics with no practical problems were obtained.

As shown above in the comparative examples and examples, according to the present invention, gold h=substrate, nickel alloy coating this gold-substrate, plating layer, oxide ability covering this nickel alloy plating layer, Magnetic disk odor consisting of magnetic media:
z l? iJ u self nickel alloy metsukino fil
By using an electroless plating layer with a flux density force of 550 or less, the oxide image quality to membrane barrier formation process is improved by 4.
．． ：+ Heat treatment is carried out (C=MokaijsAlso, it is possible to obtain a high-temperature buoyancy with good recording and reproducing properties without any problems in practical use.

In this way, the application of the electroless 11 nickel alloy plated substrate, which has excellent characteristics such as surface 16 degree and mass-transferability, which are suitable for oxidized magnetic thin magnetic thin 4-media storm recording, enables C+J performance, and oxidized ! Note: An example of 30 examples of an optical system that enables high recording speed and high quality of magnetic disks using thin film media.4. A nickel alloy plating layer containing nickel, phosphorus, and 2 soot or rust was used, but if the saturation magnetic flux density of the nickel alloy plating layer after heat treatment is 50 or less, tin is used in addition to nickel and phosphorus. ,copper,
The object of the present invention can also be achieved by using a nickel alloy plating layer made of a multi-element alloy containing one or more elements such as sunkusten, mankan, molybdenum, zinc, and palladium.

Claims (1)

[Claims] In a C4 disk having a metal substrate, a nickel alloy plating layer covering the metal substrate, and an oxide magnetic thin IBN body covering the nickel alloy, the nickel alloy plating layer is A mountain disc characterized by having a cape-plated layer with a magnetic flux density of 50 Gauss or less.