JP2848103B2 - Magnetic recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium such as a magnetic disk and a magnetic drum.

[0002]

2. Description of the Related Art
When manufacturing a magnetic recording medium such as a magnetic disk, a non-magnetic film is formed on a non-magnetic substrate such as aluminum, and a magnetic film is further formed thereon. Ni-P alloy films having a relatively high phosphorus content are widely used.

[0003] This Ni-P alloy film is formed mainly by using an electroless nickel plating bath using hypophosphite as a reducing agent. This Ni-P film has uniform deposition properties, high corrosion resistance and high hardness. Although it has advantages such as high abrasion resistance, 20
There is a problem that when heat-treated at a temperature of 0 ° C. or more, magnetism is easily obtained. For this reason, although the P content in the Ni-P film has been increased by increasing the concentration of hypophosphite ions in the electroless Ni-P plating bath, the improvement of the non-magnetic property is still required. There is room.

In the manufacture of magnetic recording media, after forming a Ni-P film, the Ni-P film is often exposed to a high temperature (eg, 300 ° C.) for a long time by a sputtering method for forming the magnetic film. In such a case, the Ni-P film is likely to be magnetized even if its phosphorus content is increased, so that the non-magnetic film is hardly magnetized even under a high-temperature and long-time thermal condition. A magnetic recording medium capable of maintaining magnetism has been desired.

[0005]

Means and Action for Solving the Problems The present inventors have
As a result of intensive studies to respond to the above demands, nickel 85.2 to 89.1%, phosphorus 10.7 to 13%, and molybdenum 0.1% obtained from a specific electroless Ni-P-Mo plating bath described later. By forming an amorphous Ni-P-Mo alloy film of 2 to 1.8% (% means% by weight; the same applies hereinafter) as a nonmagnetic film of a magnetic recording medium, this nonmagnetic film becomes, for example, 300%. Even after heat treatment at ℃ for 3 hours, it does not take on magnetism.
Therefore, it has been found that a magnetic recording medium in which the non-magnetic film is hardly magnetized even when subjected to high-temperature and long-term thermal conditions can be obtained.

Various proposals have been made for electroless Ni-P-Mo plating films (JP-B-57-54).
No. 545, Japanese Patent Application Laid-Open No. 62-60878 and Japanese Patent Application Laid-Open
-97835). However, these Ni-PMs
The o film has a high Mo content and is usually used with a Mo content of 10% or more.
Conversely, the phosphorus content in the film decreases, the film changes from amorphous to crystalline, and the stability of the bath deteriorates. The non-magnetic properties of the magnetic recording medium in terms of non-magnetism and corrosion resistance Not suitable as a film.

However, the Mo content is reduced, and the P content is set to 1 so that the Mo content is 0.2 to 1.8% as described above.
When Mo is contained in the Ni-P alloy film of 0.7 to 13%, the characteristics of the Ni-P film, particularly high corrosion resistance, high hardness,
An amorphous Ni-P-Mo film that retains the advantage of high abrasion resistance, is hard to be magnetized even after heat treatment at a high temperature for a long time, and maintains a nonmagnetic property with a saturation magnetic flux density of 2 Gauss or less can be obtained. The inventors have found that the above-mentioned object of the present invention can be effectively achieved by using such a Ni-P-Mo film as a non-magnetic film of a magnetic recording medium, and have accomplished the present invention.

Accordingly, the present invention provides a magnetic recording medium comprising a non-magnetic film formed on a non-magnetic substrate and a magnetic film formed thereon, wherein the non-magnetic film comprises a water-soluble nickel salt, Molybdate, hypophosphorous acid or a salt thereof, oxydicarboxylic acid or a salt thereof as a complexing agent and O
Obtained from an acidic electroless Ni-P-Mo plating bath having a pH of 4 to 5 and containing a dicarboxylic acid or a salt thereof containing no H group as a main component, 85.2 to 89.1% of nickel and 10.7 to 1 of phosphorus
Provided is a magnetic recording medium characterized by being a Ni-P-Mo alloy film having an amorphous saturation magnetic flux density of 2 Gauss or less having a composition of 13% and molybdenum of 0.2 to 1.8%.

Hereinafter, the present invention will be described in more detail. The magnetic recording medium of the present invention has a non-magnetic film and a magnetic film formed sequentially on a non-magnetic substrate.

Here, as the non-magnetic substrate, aluminum, an aluminum alloy or the like is used.

Further, in the present invention, the non-magnetic film is composed of 85.2 to 89.1% of Ni, 10.7 to 13% of P,
It is formed from an amorphous Ni-P-Mo alloy film having a composition of 0.2 to 1.8%. If the Mo content is less than 0.2%, the non-magnetic properties decrease, while if it exceeds 1.8%, the phosphorus content decreases, and again the non-magnetic properties decrease.

Further, when the P content is less than 10.7%, the non-magnetic properties deteriorate, and when the P content exceeds 13%, the appearance of the film deteriorates and the surface roughness deteriorates.

As a method of forming the amorphous Ni-P-Mo alloy film, an electroless plating method using an electroless Ni-P-Mo plating bath is employed.

In this case, the electroless Ni-P-Mo plating bath contains a water-soluble nickel salt, a water-soluble molybdate, hypophosphorous acid or a salt thereof, and a complexing agent.

More specifically, electroless Ni-P
In the Mo plating bath, the water-soluble nickel salt includes:
Nickel sulfate, nickel chloride or the like is used, and the concentration in the plating bath is 2 to 10 g / l as nickel, particularly 4 to 8 g / l.
g / l is preferable.

Examples of the water-soluble molybdate include sodium molybdate, ammonium molybdate, potassium molybdate, calcium molybdate, phosphomolybdic acid, ammonium phosphomolybdate, and the like. 01-5 g / l, especially 0.
It is preferable to set the amount to 0.5 to 1 g / l. When the concentration of molybdate is lower than 0.01 g / l, the molybdenum content in the plating film becomes less than 0.2%, while when it exceeds 5 g / l, the molybdenum content becomes more than 1.8%. .

As the hypophosphorous acid or a salt thereof, sodium hypophosphite, potassium hypophosphite or the like is preferably used, and the concentration in the plating bath is 10 to 50 g / l, particularly 20 to 50 g / l.
It is preferably 40 g / l. If the amount is too small, the phosphorus content in the plating film becomes less than 10.7%, and if it is too large, the phosphorus content in the plating film may become more than 13%.

Examples of complexing agents include monocarboxylic acids such as glycolic acid, lactic acid, gluconic acid and propionic acid, tartaric acid,
Dicarboxylic acids such as malic acid and succinic acid; tricarboxylic acids such as citric acid; and carboxylic acids such as sodium salts, potassium salts and ammonium salts thereof alone or in combination with 2 or more.
In the present invention, complexing is preferred because the nonmagnetic properties of the Ni-P-Mo film are particularly good and the Ni-P-Mo film having the above composition can be surely formed. Oxydicarboxylic acid or a salt thereof with O
It is preferable to use a dicarboxylic acid containing no H group or a salt thereof in combination from the viewpoint of nonmagnetic properties, deposition rate, and bath stability. In this case, the combination ratio of the former and the latter is 10:
The ratio of 1 to 0.5: 1, particularly 8: 1 to 1: 1 is recommended because the combined effect can be more effectively exhibited.

The amount of the complexing agent is appropriately selected.
1 to 7 mol, especially 2 to 6 mol per mol of the water-soluble nickel salt
It is preferred to be molar.

In the electroless Ni-P-Mo plating bath, components such as lead salts and other stabilizers and pH adjusters can be added, and the pH is in the acidic range of pH 4-5. .

When a non-magnetic film (Ni-P-Mo amorphous film having the above composition) is formed on a non-magnetic substrate using this plating bath, the non-magnetic substrate is pre-treated according to a conventional method.
It may be immersed in the plating bath, but the plating temperature is usually 70
Performed at ９５95 ° C. In plating, it is preferable to stir the plating bath appropriately by a method such as stirring with a stirrer, stirring with a pump, or rocking the object to be plated, so that a good heat-resistant non-magnetic plating film is reliably obtained by stirring. be able to.

In the present invention, the thickness of the non-magnetic film is preferably 1 to 30 μm, particularly preferably 5 to 15 μm.

After the formation of the non-magnetic film, the magnetic recording medium of the present invention is subjected to ordinary processing such as surface polishing by an ordinary method,
Next, a magnetic film is formed thereon. The magnetic film may be a known one, and a known method can be employed for forming the magnetic film. Further, an appropriate post-treatment such as forming a protective film on the magnetic film can be adopted.

Here, the non-magnetic film of the present invention has better non-magnetic properties than the conventional Ni-P film, and maintains non-magnetism even when heat-treated at 300 ° C. for 3 hours. Non-magnetic coatings such as adopting a sputtering method for the formation, or forming a thin film which generates magnetism by heating and heating to form a magnetic coating as disclosed in JP-A-56-124118. After formation, 200 ° C
As mentioned above, there is no problem even if a process and a manufacturing method in which the atmosphere is at least 250 ° C. or more, and sometimes 300 ° C. or more are adopted.

Further, since the non-magnetic film of the present invention has a small Mo content of 0.2 to 1.8%, it has substantially the same properties as the Ni—P alloy film, for example, high corrosion resistance, high hardness, and high resistance. It exhibits advantages such as abrasion and uniform precipitation.

[0026]

EXAMPLES The present invention will be described below in detail with reference to examples and comparative examples, but the present invention is not limited to the following examples.

Examples 1-4, Comparative Example An electroless plating bath having the following composition was prepared and plated on a zinc-substituted aluminum plate as a sample to be plated at 90 ° C. for 120 minutes with stirring with a stirrer. ,
A plating film having a thickness of about 15 μm was obtained. Next, this plating film was heat-treated in air using an electric oven under the conditions shown in FIGS. 1 to 3 and the saturation magnetic flux density was measured. The results are shown in FIGS. Table 1 shows the film composition when the amount of sodium molybdate was changed.

Bath composition Nickel sulfate (as nickel) 6 g / l Sodium hypophosphite 30 {Sodium molybdate 0-1} Malic acid 18 {Succinic acid 16} Stabilizer Fine pH 4.5 Magnetic measurement conditions Is as follows. Magnetic measurement conditions : Vibrating sample magnetometer (BHV-50, manufactured by Riken Denshi) Applied magnetic field 2500 O _e Sensitivity 0.005 EMU Sample 1 × 1 cm Number of measurements n = 2

[0029]

[Table 1]

From the results shown in Table 1 and FIGS. 1 to 3, the Ni—P—Mo alloy plating film (nonmagnetic film) according to the present invention
Non-magnetic properties are superior to Ni-P alloy plating films containing no o. Conventional Ni-P films are magnetized by heating at 300 ° C. for 2 hours, while non-magnetic properties are maintained. Is recognized.

The Ni—P—Mo alloy plating film is then polished to a smooth surface, then a magnetic film is formed by an ordinary method, and if necessary, a protective film is formed. It is obtained.

[0032]

According to the magnetic recording medium of the present invention, since the non-magnetic film is an amorphous Ni-P-Mo alloy film having a specific composition, it can be exposed to high-temperature and long-term thermal conditions. Also, the non-magnetic film is hardly magnetized and can maintain the non-magnetism.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the Na ₂ MoO ₄ concentration and the saturation magnetic flux density when a plating film obtained from a plating bath containing Na ₂ MoO ₄ at various concentrations is heat-treated at 300 ° C. for 2 hours.

FIG. 2 is a graph showing a relationship between a heat treatment temperature and a saturation magnetic flux density when heat treatment is performed at various temperatures on plating films obtained from a plating bath containing Na ₂ MoO ₄ at 0 g / l or 0.3 g / l. It is.

FIG. 3 is a graph showing a relationship between a heat treatment time and a saturation magnetic flux density when a plating film obtained from a plating bath containing Na ₂ MoO ₄ at 0 g / l or 0.3 g / l is heat-treated at 300 ° C.

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masahiro Saito 1-5-1, Hirakata Exit, Hirakata City, Osaka Pref. Page 53-Page 62 (58) Field surveyed (Int.Cl. ⁶ , DB name) C23C 18/50 G11B 5/66 G11B 5/84

Claims (1)

(57) [Claims] 1. A magnetic recording medium comprising a nonmagnetic film formed on a nonmagnetic substrate and a magnetic film formed thereon, wherein the nonmagnetic film comprises a water-soluble nickel salt, a water-soluble molybdate. Acid electroless Ni-P-Mo plating bath having a pH of 4 to 5 containing, as main components, hypophosphorous acid or a salt thereof, oxydicarboxylic acid or a salt thereof as a complexing agent, and dicarboxylic acid or a salt thereof containing no OH group. From nickel 85.
An amorphous Ni—P—Mo alloy coating having a composition of 2 to 89.1% by weight, phosphorus of 10.7 to 13% by weight, and molybdenum of 0.2 to 1.8% by weight having a saturation magnetic flux density of 2 Gauss or less. A magnetic recording medium, characterized in that: