JP2001073166A - Aluminum alloy substrate for magnetic recording medium and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce an aluminum alloy substrate for a magnetic recording medium good in texturing propeties and laser beam workability and simultaneously having impact resistance equal to or above that of a glass substrate using an inexpensive aluminum alloy good in workability and to provide a method for producing it. SOLUTION: This aluminum alloy substrate for a magnetic recording medium has a four layer structure in which a 1st layer composed of an aluminum alloy, a 2nd layer composed of a non-porous anodically oxidized film, a 3rd layer composed of a porous anodicallyl oxidized film and a electro plating precipitated metallic layer in the pores and a 4th layer composed of an electroless plating precipitated nickel-phosphorous alloy are laminated in the above order. After the formation of the porous anodically oxidized film in the 3rd layer on the 1st layer, the 2nd layer is formed on the space between the 1st layer and the 3rd layer by anodic oxidation, next, metal is electrolytically precipitated into the pores of the porous anodically oxidized film to complete the 3rd layer, and finally, the 4th layer composed of a nickel-phosphorous alloy is electroless- precipitated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum alloy substrate for a high-density magnetic recording medium such as a fixed-type thin-film magnetic recording disk (hard disk) used for electronic information processing, and more particularly, to an electroless electroless process on an aluminum alloy substrate The present invention relates to an aluminum alloy substrate for a magnetic recording medium having a plated nickel-phosphorus alloy layer and a method for manufacturing the same.

[0002]

2. Description of the Related Art A fixed magnetic recording device (magnetic disk device) called a "hard disk drive" or "hard disk" is used as an external storage device of an information processing apparatus such as a computer. Generally, an aluminum alloy substrate is used as a substrate of a recording medium (magnetic disk) of the fixed magnetic recording device. This magnetic recording medium is usually smoothed by grinding a non-magnetic aluminum alloy base material, cleaning the surface, performing a zinc substitution treatment, then performing electroless nickel-phosphorus alloy plating, smoothing by polishing, and texturing. After the formation, a non-magnetic metal underlayer, a magnetic layer, a protective layer, and a lubricating layer are sequentially formed to manufacture.

In recent years, in order to cope with a portable fixed magnetic disk device mounted on a portable computer or the like, a shock resistance required for a magnetic disk is required so as not to be damaged by a collision with a magnetic head during operation and movement. Also acceleration 3
It is increasing from 00G to 600G. with this,
The impact resistance of a substrate provided with a nickel-phosphorus alloy plating layer on an aluminum alloy substrate as described above is becoming insufficient. Therefore, glass substrates that are expensive and have poor workability but are excellent in impact resistance have begun to be used instead of aluminum alloy substrates.

Electroless nickel An aluminum alloy substrate provided with an electroless nickel-phosphorus alloy plating layer is often provided with concentric texturing along its circumferential direction by polishing its surface. This is to reduce the friction between the magnetic recording head for recording and reproduction and the magnetic recording medium and increase the coercive force. More recently, with the remarkable reduction in the head flying height during operation, fine projections have been formed in the CSS zone of the substrate by laser beam processing.

However, in the case of a glass substrate, it is difficult to perform texturing because it is hard and has poor workability.
In addition, since it is generally transparent, the laser beam absorption is poor, and the melting temperature is extremely high. Therefore, it is difficult to form a large number of projections of a specific shape uniformly. As a countermeasure, it has been proposed to form a nickel-phosphorus alloy plating layer on glass as a substrate having high impact resistance capable of texturing and capable of uniformly forming fine projections by laser beam processing.

However, it is difficult to form a nickel-phosphorous alloy plating layer having good adhesion on glass, and various countermeasures have been studied so far, but sufficient adhesion has not been obtained. . As described above, conventionally, the aluminum alloy substrate is inexpensive and has good workability but has insufficient impact resistance, and the glass substrate has good impact resistance but is expensive and has poor workability. In addition, there has been a problem that the adhesion of the nickel-phosphorus alloy plating layer for imparting laser beam workability is insufficient.

[0007]

DISCLOSURE OF THE INVENTION The present invention uses an aluminum alloy substrate which is inexpensive and has good workability without using a glass substrate. An object of the present invention is to provide an aluminum alloy substrate for a magnetic recording medium having the same or higher impact resistance.

[0008]

In order to achieve the above object, an aluminum alloy substrate for a magnetic recording medium according to the present invention comprises a first layer made of an aluminum alloy, a non-porous material formed by anodic oxidation of the aluminum alloy. A second layer composed of an oxide layer, a third layer composed of a porous oxide layer formed by anodic oxidation of the aluminum alloy and a metal layer deposited in the pores of the porous oxide layer by electrolytic plating, And a four-layer structure in which a fourth layer made of a nickel-phosphorus alloy deposited by an electroless plating method is laminated in the above order.

The thickness of the second layer is preferably 15 to 90 nm. It is desirable that the thickness of the third layer is 15 to 50 μm. It is desirable that the thickness of the fourth layer be 0.5 to 15 μm. Typically, the metal layer deposited by electrolytic plating in the pores of the porous oxide layer is nickel,
One selected from the group consisting of cobalt, iron, tin and copper
It consists of more than one kind of metal.

Typically, the nickel-phosphorus alloy deposited by the above electroless plating method is an amorphous alloy containing 9% or more of phosphorus. Typically, the second non-porous oxide layer comprises a pH comprising one or more acids selected from the group consisting of boric acid, phosphoric acid, adipic acid, tartaric acid, citric acid and succinic acid.
It is produced by anodic oxidation of the above aluminum alloy in an electrolyte of 4.0 to 9.0.

[0011] Typically, the third porous oxide layer has a pH of 3.0 or less containing one or more acids selected from the group consisting of sulfuric acid, oxalic acid, phosphoric acid, chromic acid and tartaric acid. It is produced by anodic oxidation of the above aluminum alloy in an aqueous solution. The method for producing an aluminum alloy substrate for a magnetic recording medium according to the present invention comprises the steps of: preparing a first layer made of an aluminum alloy; forming a porous oxide layer on the first layer by anodic oxidation; The first
Forming a second layer consisting of a non-porous oxide layer between the layer and the porous oxide layer, forming a metal layer in the pores of the porous oxide layer by electrolytic plating, The steps of forming a third layer composed of the porous oxide layer and the metal layer and forming a fourth layer composed of a nickel-phosphorus alloy on the third layer by electroless plating are performed in the above order. It is characterized by performing.

The present inventor has elucidated the phenomenon returning to the principle regarding the relationship between the occurrence of scratches as impact resistance, the adhesion of the electroless nickel-phosphorus alloy plating layer, and the layer structure of the aluminum alloy substrate for magnetic recording media. Started from. First, the mechanism by which the substrate is damaged when the magnetic head collides with an acceleration of 300 G in a two-layer structure in which an electroless nickel-phosphorus alloy plating layer is provided on an aluminum alloy substrate was analyzed. As a result, the occurrence of scratches is not caused by plastic deformation of only the electroless nickel-phosphorus alloy plating layer (hereinafter abbreviated as "Ni-P plating layer"), but is caused by the base aluminum alloy base material (hereinafter referred to as "Al alloy base layer"). Material ").

From the observation results, the following was considered as a mechanism for generating a flaw when an impact load is applied to the surface of the Ni—P plating layer. That is, the Ni-P plating layer has a high hardness but a small load that can be borne by itself because it is thin.
The underlying Al alloy substrate bears the load and supports the Ni-P plating layer. However, since the Al alloy base material has a large thickness but a low hardness, a portion where an impact load is applied is easily and locally plastically deformed, and the Ni-P
The plating layer loses support and is plastically deformed, resulting in damage.

Therefore, as a method for preventing the occurrence of scratches,
The thickness of the Ni-P plating layer was much increased as compared with the Al alloy, and the load bearing capacity of this layer itself was enhanced. However, as the thickness of the Ni-P plating layer is increased, the above mechanism causes scratches up to a thickness of 15 μm, and the thickness becomes 1 μm.
When the thickness exceeds 5 μm, only the flaw generation mechanism changes to generate flaws due to plastic deformation of only the Ni—P plating layer.

As described above, even if the thickness of the Ni-P plating layer is increased in the conventional structure in which the Ni-P plating layer is provided on the Al alloy base material, even if the thickness of the Ni-P plating layer is increased, the scratches due to the collision of the magnetic head at an acceleration of 300 G Was found to be impossible to prevent.
On the other hand, even when a Ni-P plating layer having a thickness of more than 15 μm is provided on a glass substrate having high hardness and no damage at an acceleration of 300 G, scratches are generated due to plastic deformation of only the Ni-P plating layer. Make sure you do.

As described above, when the thickness of the Ni—P plating layer is 1
When the thickness is less than 5 μm, scratches are caused by plastic deformation of the Ni—P plating layer and the Al alloy base material, and when the thickness exceeds 15 μm, damage is caused by plastic deformation of only the Ni—P plating layer. Therefore, to prevent the occurrence of scratches, N
It is necessary to limit the thickness of the i-P plating layer to 15 μm or less, and at the same time, suppress the plastic deformation of the underlying Al alloy substrate.

However, studies were made on Al alloy base materials having various compositions, but there was no hard aluminum alloy suitable for a magnetic recording medium, which was not damaged by collision of a magnetic head at an acceleration of 300 G. Therefore, attention was paid not to the hardness but to the elastic modulus and the yield stress as factors that determine the occurrence of scratches due to the plastic deformation of the Al alloy substrate due to the collision of the magnetic head at the acceleration of 300 G. Based on this idea, a three-layer structure in which a porous anodic oxide film (alumite film) having a hardness slightly lower than that of the Ni-P plating layer is formed on an Al alloy substrate, and an electroless plating Ni-P plating layer is formed thereon. The structure was studied. However, even if the electroless Ni-P plating is applied to the porous anodic oxide film as it is, Ni-
Since the formation reaction of the P plating layer did not occur, electrolytic plating was performed in the pores of the porous anodic oxide film, and electroless Ni-P plating was performed on the deposited metal. At that time, the metal deposited in the pores by electrolytic plating is only a starting point of the electroless deposition reaction, and the type does not need to be particularly limited, but nickel, cobalt, Copper and tin are preferred.

When the impact resistance of the substrate having the three-layer structure was tested, no damage was found even when a 300 G impact was applied. However, although the collision portion of the magnetic head was not damaged, a peeled portion in which the Ni-P plating layer was lifted was found around the collision portion. This is thought to be due to the adhesion of the Ni-P plating layer to the underlying porous anodic oxide film,
The state of formation of the Ni-P plating layer was investigated. As a result, it was found that the amount of the electrodeposited metal as the starting point of the formation of the electroless Ni-P plating layer was not uniform for each hole. That is, the metal is not uniformly deposited in all the pores of the porous anodic oxide film by electrolytic plating, but the amount of deposition differs greatly depending on the pores, and no metal is precipitated in some of the pores.

The electroless deposition of the Ni-P plating alloy on the deposited metal in the holes proceeds at a constant rate after starting from the deposited metal. Therefore, the amount of Ni-P plating alloy deposited per unit time in each hole depends on the amount of electrolytically deposited metal that is the starting point of the deposition. That is, the larger the amount of the electrodeposited metal as the starting point of the electroless deposition, the larger the amount of the electroless deposited Ni-P plating alloy per unit time. Therefore, the timing of the electrolessly deposited Ni-P plating alloy growing to fill the holes and reaching the surface of the porous anodic oxide film (upper end of the holes) is earlier in the holes having a large amount of the electrolytically deposited metal, and the timing is shorter. It is slow for holes with a small amount of analyzed metal. In a hole having a large amount of the electrodeposited metal, the Ni-P plating alloy reaches the surface quickly, rises from the upper end of the hole, grows on the surface of the porous anodic oxide film, and covers the adjacent hole. In the covered hole, the precipitation of the Ni-P plating alloy in the hole stops, so that the hole is not completely filled and a cavity remains. As a result, the Ni finally formed on the porous anodic oxide film
Since the -P plating layer is not bonded to the underlying porous anodic oxide film at the places where the holes remain as unfilled cavities, the adhesion strength is reduced.

As a result of examining the cause of the difference in the amount of the electrodeposited metal for each hole, it was found that the thickness of the barrier layer existing at the bottom of the hole differs for each hole. The barrier layer is a dense oxide layer having a downwardly convex curved shape, and when its thickness is different, the electric resistance is different. At the time of electrolytic plating, the amount of the electrodeposited metal is increased in the portion where the barrier layer is thin and the electric resistance is small, and the amount of the electrodeposited metal is small in the portion where the barrier layer is thick and the electric resistance is large. As a result, the amount of electrolytically deposited metal differs for each hole, and Ni-P
The amount of plating alloy is different for each hole, and Ni
-The adhesion strength of the P plating layer is reduced.

Therefore, in the four-layer structure of the present invention, a nonporous anodic oxide film is formed between the Al alloy substrate and the porous anodic oxide film in the conventional three-layer structure. The non-porous anodized film has a flat and uniform thickness, which functions as a barrier layer having a uniform electric resistance instead of the conventional barrier layer. As a result, the metal is electrolytically deposited uniformly in all the holes of the porous anodic oxide film, so that the amount of the Ni-P plating alloy that is electrolessly deposited thereon is equalized, and cavities remain in all the holes. Thus, a Ni—P plating layer having high adhesion can be obtained.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A typical procedure for manufacturing an aluminum alloy substrate for a magnetic recording medium having a four-layer structure according to the present invention is as follows. FIG. 1 shows a four-layer structure of the present invention, and FIG. 2 shows a flowchart of a manufacturing procedure. The aluminum alloy substrate (first layer) is anodized in an acidic solution, preferably in a strongly acidic aqueous solution having a pH of 3.0 or less, to form a porous anodic oxide film (main part of the third layer).

Next, in a neutral solution, desirably pH 4.0
~ 9.0 in neutral salt electrolyte by constant current electrolysis
The pressure is increased to V to form a nonporous anodized film (second layer) having a typical thickness of about 70 nm between the aluminum alloy substrate and the porous anodized film. This second layer functions as a barrier layer having a uniform electric resistance instead of the conventional barrier layer.

Next, a metal is deposited in the pores of the porous anodic oxide film (main part of the third layer) by electrolytic plating (remaining part of the third layer). When this is observed with a transmission electron microscope, the metal is deposited in all the holes, and the deposited metal has almost the same height. The form of the electrodeposited metal is (1) filling the hole from the bottom to the middle, (2) filling the hole from the bottom to just the top, and (3) filling the hole from the bottom to the top. Further, it may be in any form that covers a part or all of the surface of the porous anodic oxide film.

Finally, electroless plating is performed to form an electroless nickel-phosphorus alloy plating layer (fourth layer). This fourth
The form of the layer is the form (1), (2),
According to (3), (1) fill the remaining portion of each hole filled with electrolytic deposition metal and grow further to cover the surface of the porous anodic oxide film, (2) up to the top of the hole A form that covers the surface of the electrodeposited metal that has reached and the surface of the porous anodic oxide film,
And (3) a mode in which the surface of the electrolytically deposited metal covering a part or all of the porous anodic oxide film and the surface of the uncovered porous anodic oxide film are covered.

In the aluminum alloy substrate for a magnetic recording medium having a four-layer structure according to the present invention, by setting each of the second to fourth layers to a desired thickness, no scratch is generated in an impact test up to an acceleration of 500G, and the periphery is not affected. No peeling of the electroless nickel-phosphorus alloy plating layer occurred in the portions. Furthermore, acceleration 60
Although slight scratches were observed in the 0G impact test, no peeling occurred.

The hardness of the porous anodic oxide film formed on the aluminum alloy substrate is substantially the same as or lower than that of the electroless nickel-phosphorus alloy plating layer. However, the elastic modulus is extremely high and there is almost no elongation. According to the finite element method analysis, the area where the stress due to the magnetic head collision acts
In the case where the collision acceleration is 300 G to 400 G, the depth is 15 to 50 μm from the surface.

When an electroless nickel-phosphorus alloy plating layer is provided directly on an aluminum alloy substrate as in a conventional two-layer structure, the point of concentration of stress generated by collision is limited to aluminum plating when the plating layer is thin. In the alloy base material, when the plating layer is thick, it is in the plating layer. When the stress concentration point is in the aluminum alloy base material, the aluminum alloy having a small yield stress is easily plastically deformed, and the plating layer is also plastically deformed, resulting in damage. When the stress concentration point is in the plating layer, it generally depends on the yield stress of the plating layer. However, in the electroless nickel-phosphorus alloy plating layer, plastic deformation occurs and scratches occur. This also corresponds to the fact that even if the electroless nickel-phosphorus alloy plating layer formed on the glass substrate is thick, the layer is damaged.

When a porous anodic oxide film is provided at the stress concentration point, the film has a large elastic modulus and is hardly elastically deformed, and since it has a large yield stress, it is difficult for plastic deformation to occur, so that it can withstand a larger load. . Further, since the elastic modulus is large, the stress concentration point becomes shallower than when only the electroless nickel-phosphorus alloy plating layer is used, and becomes 10 to 30 μm when only the porous type anodic oxide film is used. Although the non-porous anodic oxide film of the second layer has a higher yield stress, it has a very small thickness (about several tens of nm), and thus hardly contributes to load bearing. Therefore, when the electroless nickel-phosphorus alloy plating layer in the four-layer structure is 10 μm, the stress concentration point is 15 to
It can be estimated to be 40 μm (the value differs depending on the magnitude of the impact load and the thickness and properties of the electroless nickel-phosphorus alloy plating layer). By providing a porous anodic oxide film having a high elastic modulus in a region including the stress concentration point, the impact resistance of the entire substrate is improved.

Conventionally, when a metal is deposited in the pores of a porous anodic oxide film by electrolytic plating, the amount of deposition differs for each hole because the dense oxidized film immediately below (a hole in) the porous anodic oxide film. This is because the shape and thickness of the barrier layer, which is the material layer, are not uniform. The porous anodic oxide film is formed by anodic oxidation in a strongly acidic electrolytic solution. At this time, the porous anodic oxide film is made porous by the action of dissolving the strong acid. However, the chemical dissolution reaction does not necessarily occur uniformly, and variations in the structure and chemical composition of each minute region in the aluminum alloy also induce nonuniform dissolution. As a result, when a slight difference occurs in the amount of dissolution, a slight difference also occurs in the film thickness remaining at the bottom of the hole.
This slight difference has a great effect on the electrochemical reaction at the time of electrolytic deposition in the next step, and induces non-uniform electrolytic deposition. It is difficult to make such an oxide layer uniform in shape and thickness by controlling the dissolution reaction. Therefore, in the present invention, by providing a non-porous anodic oxide film having a uniform shape and thickness, that is, electrochemically uniform, between the aluminum alloy substrate and the porous anodic oxide film,
Substantially, the barrier layer was made uniform, and the next step of the electrolytic deposition reaction was made uniform.

In a typical method for forming such a nonporous anodic oxide film, the solubility is extremely poor, has a buffering action in a neutral region capable of suppressing a pH change at the time of electrolytic deposition, and has a local dissolution property. Anodization is performed using an aqueous solution of a divalent anion that is unlikely to cause the anodization. Thereby, the metal can be uniformly deposited in the pores of the porous anodic oxide film by electrolytic plating.

[0032]

EXAMPLES Table 1 shows the results of an impact resistance test of aluminum alloy substrates having various film structures, and Table 2 shows magnetic recording of a four-layer structure manufactured by changing the thickness of the second to fourth layers. The results of the impact resistance test of the aluminum alloy substrate for media are shown. The impact test method and the criteria for determining scratches were as follows. Impact test method According to JIS C0041.

Impact tester: Pendulum type impact tester (PST-300 manufactured by Yoshida Seiki Co., Ltd.) The presence or absence of scratches was observed with an optical microscope of 50 times the criteria for determining scratches. (A scratch shallower than 3 nm) is evaluated as “○: no scratch”, and a scratch is observed with a stylus-type roughness meter to measure the scratch depth. The sample was evaluated as “Δ: extremely fine flaw”, and the sample with a flaw depth exceeding 20 nm was evaluated as “×: flawed”.

In the aluminum alloy substrate for a magnetic recording medium according to the present invention, the aluminum alloy base plate as the first layer is #
After grinding using a 4000 grindstone, a degreasing treatment was performed, and the second to fourth layers were formed under the following conditions, and then the surface of the fourth layer was polished to manufacture. The following description is made in comparison with the formation conditions of the second and subsequent layers and the results of the impact resistance test.

On the first layer, a porous anodic oxide film as a main part of the third layer is coated with 5 to 30 wt% sulfuric acid, 0.5 to 7 watts.
It was formed by a direct current anodic oxidation method using each aqueous solution of t% oxalic acid, 3-20 wt% phosphoric acid, 10 wt% chromic acid, and 1-5% tartaric acid. With any of the acids, a porous oxide layer could be formed if the pH was 3.0 or less. The film thickness was controlled by the amount of electrolytic electricity. The type of the acid and the electrolysis conditions did not affect the impact resistance at all, but only the thickness of the film (Examples 2, 4, 5, 6 and Comparative Examples 8, 9).
If the thickness exceeds 50 μm, good results can be obtained, but the time required for film formation is undesirably long.

Next, the non-porous anodic oxide film of the second layer is formed to a pH of 4.0 to 9.0 containing at least one ion of boric acid, phosphoric acid, adipic acid, tartaric acid, citric acid and succinic acid.
0 in an electrolyte solution. pH
Was adjusted by the amount of aqueous ammonia, sodium salt or potassium salt of each acid. No difference was observed in the impact resistance when the pH was adjusted by any method using any anion species. Anodization has a current density of 0.01
The evaluation was performed in the range of 10 to 10 Adm- ² , but no difference appeared in the evaluation results at any current density. The ultimate voltage at this time is 30 ~
In the case of 70V, the thickness of the second layer becomes 40 to 100 nm,
Excellent impact resistance was obtained (Examples 1 to 3). Voltages below and above this range resulted in non-uniform electrolytic plating and reduced impact adhesion (Comparative Examples 6 and 7).

Next, the electrodeposited metal in the pores remaining in the third layer was subjected to DC cathodic electrolysis in an aqueous solution of pH 4.5 containing boric acid and nickel sulfate in the case of nickel or cobalt by 0.5 Adm. ^It was formed by electrolytic plating performed at a constant current of ^-2 for 10 seconds. In the case of copper and tin, they were formed by performing 15 V AC electrolysis for 30 seconds at pH 3.0 or lower in the respective sulfate aqueous solutions. The conditions such as composition and temperature of these baths may be any conditions as long as the metal can be precipitated, and no difference in impact resistance appears. Also, the amount of precipitation did not affect the impact resistance, and no difference was observed in the impact resistance even when the deposition was performed until the pores of the porous anodic oxide film were completely filled.

The fourth electroless nickel-phosphorus alloy plating layer was coated with a commercially available electroless nickel-phosphorus alloy plating solution (manufactured by Uemura Kogyo Co., Ltd.) containing hypophosphorous acid and nickel sulfate as main components.
HDX). 3 to 5 from target film thickness
After forming a film having a thickness of μm, the target film thickness was obtained by polishing. Fifteen
Good evaluation results were obtained at μm or less. Although the impact resistance is considered to be excellent even if it is less than 0.5 μm, it is required to be 0.5 μm or more in order to perform texturing.

[0039]

[Table 1]

[0040]

[Table 2]

[0041]

According to the present invention, a glass substrate is not used,
An aluminum alloy substrate for a magnetic recording medium is provided, which uses an aluminum alloy substrate which is inexpensive and has good workability, has good texturing properties and laser beam workability, and has the same or higher impact resistance as a glass substrate. .

[Brief description of the drawings]

FIG. 1 is a sectional view schematically showing an aluminum alloy substrate for a magnetic recording medium having a four-layer structure according to the present invention.

FIG. 2 is a flowchart showing a procedure for manufacturing an aluminum alloy substrate for a magnetic recording medium having a four-layer structure according to the present invention.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G11B 5/84 G11B 5/84 Z (72) Inventor Hideki Shimada 43-3 Harumi-cho, Tomakomai-shi, Hokkaido Nippon Light Metal Inside the Tomakomai Plant, Inc. No. 34 No. 1 Nippon Light Metal Co., Ltd. Group Technology Center F term (reference) 4K044 AA06 AB08 BA06 BA13 BB04 BB05 BC14 CA15 CA17 CA18 CA59 5D006 CB04 CB07 CB08 DA03 EA02 FA00 5D112 AA02 AA11 AA24 BA05 BA06 EE01 GA29 GA30

Claims (11)

[Claims] 1. A first layer comprising an aluminum alloy, a second layer comprising a non-porous oxide layer formed by anodic oxidation of the aluminum alloy, a porous layer formed by anodic oxidation of the aluminum alloy, and A metal layer deposited by electroplating in the pores of the porous oxide layer.
Layer and nickel deposited by electroless plating
An aluminum alloy substrate for a magnetic recording medium, having a four-layer structure in which a fourth layer made of a phosphorus alloy is laminated in the above order. 2. The substrate according to claim 1, wherein the second
A substrate having a layer thickness of 15 to 90 nm. 3. The substrate according to claim 1, wherein the third
A substrate characterized in that the layer has a thickness of 15 to 50 μm. 4. The substrate according to claim 1, wherein
A substrate characterized in that the layer has a thickness of 0.5 to 15 μm. 5. The substrate according to claim 1, wherein the metal layer deposited by electroplating in the pores of the porous oxide layer is selected from the group consisting of nickel, cobalt, iron, tin and copper. A substrate comprising one or more metals. 6. The substrate according to claim 1, wherein the nickel-phosphorus alloy deposited by the electroless plating method has a phosphorous content of 9%.
% Of an amorphous alloy. 7. The substrate according to claim 1, wherein
The second nonporous oxide layer has a pH of 4.0 to 9.0 containing at least one acid selected from the group consisting of boric acid, phosphoric acid, adipic acid, tartaric acid, citric acid and succinic acid. A substrate produced by anodic oxidation of the aluminum alloy in an electrolytic solution. 8. The substrate according to claim 3, wherein the third
A porous oxide layer formed by anodic oxidation of the aluminum alloy in an aqueous solution containing at least one acid selected from the group consisting of sulfuric acid, oxalic acid, phosphoric acid, chromic acid and tartaric acid at a pH of 3.0 or less. A substrate characterized by being made. 9. A method for producing an aluminum alloy substrate for a magnetic recording medium according to claim 1, wherein a step of preparing a first layer made of an aluminum alloy is performed, and a porous oxide is formed on the first layer by anodization. Forming a second layer comprising a nonporous oxide layer between the first layer and the porous oxide layer by anodizing; forming the porous oxide layer by electrolytic plating Forming a metal layer in the holes, thereby forming a third layer comprising the porous oxide layer and the metal layer, and a nickel-phosphorus alloy formed on the third layer by electroless plating. Forming a fourth layer comprising the steps of: 10. The method according to claim 9, wherein the formation of the porous oxide layer is carried out at a pH of at least one selected from the group consisting of sulfuric acid, oxalic acid, phosphoric acid, chromic acid and tartaric acid. A method characterized by performing by anodic oxidation in an aqueous solution of 0 or less. 11. The method according to claim 9, wherein the formation of the non-porous oxide layer is performed by using boric acid, phosphoric acid, adipic acid,
A method characterized in that the method is carried out by anodizing the aluminum alloy in an electrolyte having a pH of 4.0 to 9.0 and containing one or more acids selected from the group consisting of tartaric acid, citric acid and succinic acid.