JPS6142721A - Vartical magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a vertical magnetic disk which has superior magnetic characteristics, running performance, durability, etc., by forming an anode oxidized film on Al (alloy) to thickness with which necessary mechanical strength is obtained, and charging a non-magnetic material in pores of the coating film to specific thickness from pore bottoms and then charging a ferromagnetic material. CONSTITUTION:The anode oxidized film 1 is formed on an Al or Al alloy substrate 5 to an about 6mum thickness. Then, a dipping treatment is carried out to expand pores 2 formed in the film 2 and then an electrolyte obtained by dissolving the nonmagnetic conductor such as Sn and Cu is used to charge the nonmagnetic conductor 3 in pores to >=4mum from pore bottoms. Then, the ferromagnetic material 4 is formed in pores 2 by an electrolyte bath containing, for example, Fe and the surface is polished to obtain the disk 1 having the smooth magnetic recording film 1. A solid lubricant SiO2 is sputtered thinly over the surface of the film 1 and a liquid lubricant is further applied over it to obtain the vertical magnetic recording disk which has superior wear resistance, running performance, and durability and also has superior recording, reproducing, erasing, and recording characteristics.

Description

Detailed Description of the Invention 3.1 Industrial Application Field This invention is a method for depositing a ferromagnetic material into the bore of an oxide film produced by anodizing aluminum (hereinafter referred to as 8L) or A1 alloy. The present invention relates to a perpendicular magnetic recording medium formed by filling the present invention, and particularly relates to a perpendicular magnetic recording medium used in a hard disk.

3.2 Issues to be Solved When this type of direct magnetic recording medium is used in a magnetic disk, when A1 alloy is used as the substrate, impurities such as interstitial compounds and nonmetallic inclusions contained in the alloy may cause problems. , bore diameter, long axis direction and molecular l during anodizing treatment.
In addition to not being able to obtain a uniform magnetic film in terms of i-rate, etc.
While there are drawbacks such as film defects occurring during polishing after magnetic material precipitation treatment, resulting in recording errors and crashing of the magnetic head during use, pure Aj! When using AJ! This applicant has disclosed in Japanese Patent Application No. 59-36594 that the above-mentioned disadvantages of alloys are eliminated, high density storage is possible, and a smooth surface can be obtained for the magnetic head. It was revealed in

The inventor developed various alumite perpendicular magnetic recording media for the purpose of exploring conditions for this type of perpendicular magnetic recording media to have the required recording and reproducing characteristics, especially override characteristics (repeatability of recording and erasing). We made a prototype and measured its recording and reproducing characteristics.

The override characteristic, which is one of the evaluation items for magnetic recording media, needs to be -30 dB or more, but the first
As shown in the figure, the coercive force)-1c is 4
To satisfy the condition of -30dB at 00 (Oe) or more,
The thickness of the magnetic layer made of ferromagnetic material filled in many bores is approximately 2 μm or less (0.5 to 2 μm) for high-density recording at a wavelength of about 1.5 μm. )
was found to be desirable.

By the way, the hardness of the oxide film itself is HV300 or more, but when the film thickness becomes about 2 μm, the hardness of pure Al used for the substrate is as small as HV80, so the mechanical strength of the recording medium becomes a problem. Become. In other words, when the magnetic head runs on the recording surface of the magnetic recording medium, the oxide film alone cannot withstand the impact force when it entrains dirt and dust, and the pure A1 substrate base or the underlying AJ ! This deforms the alloy, causing recording errors and significantly reducing the durability of the recording medium and magnetic head.

A new alloy for high-density thin-film disks has recently been announced (
A similar problem exists in the case of using A1 base metal, additive components, and intermetallic compounds made fine by controlling the manufacturing conditions) as a substrate.

On the other hand, it is known that the hardness of the A1 oxide film increases as the WA thickness increases. Therefore, the inventor tested the relationship between the thickness and hardness of the oxide film and found that Ill! Aj! Or, as a result of searching for a film thickness that would provide a hardness that does not pose any practical problems with the film alone, without being affected by the hardness of the underlying alloy, as shown in Figure 2, we found that the required durability was achieved when the film thickness was at least 3 μm or more. It was found that in the range of 6 μm or more, the hardness was stable at approximately HV350, which was preferable. Note that the load used in this hardness test was 25 g.

Thus, in order to ensure the required override characteristics on the - plane, the thickness of the magnetic layer needs to be approximately 2 μm or less, but on the other hand, when the magnetic head runs,
Strength against Wi impact force.

In order to have durability, the film needs to have a thickness of 6 μm or more, which is a problem that must be met, which is contradictory.

3.3 Purpose of the Invention In view of the above points, the present invention aims to increase the thickness of the magnetic layer in order to provide the required mechanical strength of the magnetic recording medium while increasing the thickness of the magnetic layer in order to provide the required override characteristic. It is an object of the present invention to provide a perpendicular magnetic recording medium that can be made thinner and has improved both recording and reproducing characteristics and durability.

In order to achieve the above object, this invention, in principle,
As schematically shown in FIG. 3, in order to reduce the thickness of the magnetic layer while keeping the thickness of the anodic oxide film 1 thick, a conductive non-magnetic material was first applied to the bottom of the bore 2 of the film. Fill 3,
After that, a ferromagnetic material 4 is filled thereon.

In Figure 3, 1a is a porous layer, 1b is a barrier calendar,
5 is a substrate.

The purpose of making the oxide film thicker is to increase the mechanical strength against the impact force caused by dirt, dust, etc. that may enter between the magnetic head and the recording surface. From this point of view, it is known that a hard coating obtained by anodizing 81 at low bath temperature and high voltage is particularly excellent in mechanical strength and wear resistance. Therefore, also in this invention, it is particularly effective to use this hard coating.

3.4 Examples of the present invention Example 1 A standard anodic oxide film with a thickness of 6 μm was produced on an A1 alloy substrate by a conventional method, and a dipping treatment was performed on the film to form a hole in the bore formed in the film. After enlarging the diameter, 3N with a thickness of 2 μm was deposited at the bottom of the bore by electrolytic treatment using a Ti electrolytic bath in which 3N, an example of a non-magnetic material, was dissolved. Furthermore, after that, Fe was deposited in the remaining part of the bore using an electrolytic bath containing 1"e, and the surface of the film was polished to give a total thickness of 4 μm. A solid lubricant of 5IOz was applied to the surface at 50OA. Then, as a liquid lubricant, DuPont's product Krytx 143ACJ was diluted to 0.5% by weight with Mitsui Fluorochemical's product Freon TFJ and spin-coded. -Using a tapered flat magnetic head made of Fe alloy, with a load of 10g [C8S
(contact start/stop) test was conducted. As a result, it was confirmed that it had durability of 30,000 times or more.

Example 2 A test was conducted under the same conditions as in Example 1 except that pure Δl was used in place of the A1 alloy in Example 1, and durability over 30,000 cycles was similarly confirmed.

Example 3 Cu was used in place of 3n in Example 1, and the rest was the same as Example 1.
When tested under the same conditions, similar results were obtained.

Example 4 Similar to Example 1, 2 μm at the bottom of the bore of the 6 μm coating.
After precipitating 3n, Fe was precipitated until it overflowed, and then polished until the film thickness became 3 μm, and then a protective lubricant film was generated in the same manner as in Example 1, and the same method was used. When a C8S trial test was conducted using this method, a magnetic head crash occurred after 20,000 cycles.

Example 5 The above is an example in which a standard oxide film is used. In this example, 10 to 15% H2SO4, liquid m-5 to O
"C,lff 40 to 50Vr hard anodization treatment was performed to produce a 6 μm hard coating with countless bores, and thereafter, as in Example 1, bore diameter enlargement treatment, nonmagnetic material precipitation treatment, and ferromagnetic treatment. After the body was subjected to precipitation treatment and lubricant filling treatment, surface polishing was performed and a C8S test was conducted, and it was confirmed that the coating had a durability 5 to 10 times higher than that of the standard coating.

The example in Example is also an example of producing a hard film, and instead of HzSOt in Example 5, a mixed acid of HgSO4 and oxalic acid in a ratio of 5:1 was used, and the liquid was easily -5 to O''. C, voltage 5
Hard positive #fA oxidation treatment was performed at 0V, and the following Example 5
The treatment was carried out under the same conditions as above, and the obtained disk was subjected to a similar C8S test. Similar results to Example 5 were obtained.

Example 7 Using a mixed acid with a ratio of oxalic acid and Hz SOa of 10:1, hard layer i was prepared at a liquid temperature of -5 to 0°C and a voltage of 60V.
A hard film with a thickness of 6 μm was obtained by performing a g treatment, and the following is shown below.
When a C8S test was carried out in the same manner as in Example 5, the same results as in Example 5.6 were confirmed.

3.5 Effects of this invention As mentioned above, this inventor has
As disclosed in No. 6 Meill5, the perpendicular coercive force (-1c) of the magnetic layer needs to be in the range of about 300 to 1000 Qe in order to maintain the easy direction of magnetization perpendicular to the film surface. As a result of various tests taking into account that the override characteristic must be -30 dB or more, it is clear from Figure 1, which shows the correlation between various thicknesses of the magnetic layer, override characteristic, and coercive force. Thus, it has been found that the thickness of the magnetic layer needs to be approximately 2 μm or less.

In addition, in order to provide the disk with a strength that allows the number of C8S to be used practically, the film thickness needs to be at least 3 μm or more, preferably 6 μm or more. Therefore, the thickness of the non-magnetic material filled in the bore needs to account for about 30% or more of the total thickness of the coating.

The magnetic recording medium according to the present invention, as described above, is produced with a thickness sufficient to have the required mechanical strength of the coating, and the non-magnetic material is filled into the bore from the bottom to a predetermined thickness, and then Since it is filled with a ferromagnetic material, it has excellent recording and reproducing characteristics, and when used in a disk, it has excellent durability against running of a magnetic head.

[Brief explanation of the drawing]

Fig. 1 is a graph showing the override characteristics in relation to the magnetic layer and coercive force, Fig. 2 is a graph showing the film thickness-hardness characteristics, and Fig. 3 is an enlarged replica of the main parts of the perpendicular magnetic recording medium according to the present invention. , FIG. 4 is a graph showing the relationship between film thickness and durability. 1...Anodized film 1a...Porous layer 1b...Barrier layer 2...Bore 3...Nonmagnetic material 4...Ferromagnetic material 5...Substrate patent applicant Shun Takahashi Department Ku Nenya-゛ku呵 vagina 4# attack; Ku Q Castle

Claims (4)

[Claims] (1) In a perpendicular magnetic recording medium in which a ferromagnetic material is precipitated and filled into micropores (hereinafter referred to as bores) generated in an anodic oxide film of aluminum or its alloy, (a) the anodic oxide film is required. (b) The bore of the coating is filled with a non-magnetic material from the bottom to a predetermined thickness, and then filled with a ferromagnetic material. Perpendicular magnetic recording medium. (2) The vertical axis according to claim 1, wherein the thickness of the anodic oxide film is about 6 μm or more, and the thickness of the ferromagnetic material filled in the bore is about 2 μm or less. magnetic recording medium. (3) The perpendicular magnetic recording medium according to claim 1, wherein the anodic oxide film is a hard film. (4) The perpendicular magnetic recording medium according to claim 1, wherein the nonmagnetic material is a conductive material such as Sn or Cu, and is a metal or alloy that can be deposited in the bore.