JPH0476812A - magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a relatively low coercive force improved in coercive force squareness by incorporating tellurium of specific amount of cobalt into a magnetic film. CONSTITUTION:The Te of 0.01 to 5wt.% of the cobalt is incorporated into the magnetic film of the magnetic recording medium formed with the magnetic film consisting of the cobalt system by an electroless plating method on a nonmagnetic substrate. The sufficient effect of improving the coercive force squareness is not obtainable when the content of the Te is below 0.01wt.% and over 5wt.%. The content of the Te is preferably 0.1 to 3wt.%, more particu larly preferably 0.1 to 1wt.% of the Co. The coercive force squareness (S*) is improved in such a manner and the effect of lowering the coercive force (Hc) is obtd. Then, the desired coercive force is easily obtd. by improving the coercive force squareness.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a magnetic recording medium, and in particular to a magnetic recording medium used in a magnetic recording device such as a magnetic disk, floppy disk, or magnetic tape. The present invention relates to an improved magnetic recording medium.

[Prior Art] In recent years, from the viewpoint of increasing recording density, magnetic recording media used in magnetic recording devices such as magnetic disks, floppy disks, and magnetic tapes have changed from metal thin film type magnetic recording media to coated type magnetic recording media using a binder. It is beginning to be used in place of magnetic recording media.

This metal thin film type magnetic recording medium is easily produced by methods such as electroless plating, electroplating, sputtering, and vapor deposition.

Among these, the electroless plating method is being widely put into practical use due to its high productivity and technical improvements resulting from technology accumulation over many years.

Conventionally, magnetic recording media manufactured by electroless plating have mainly had magnetic thin films made of Co (cobal)-P (phosphorus) or Co-Ni (nickel)-P, and some of them have already been produced. It has been commercialized.

[Problems to be Solved by the Invention] However, when producing a magnetic film using an electroless plating bath using a conventional electroless plating method, even if the electroless plating bath is prepared with the same bath composition, the chemicals used are different. Plating bath composition errors due to slight purity differences that are practically unmanageable;
Alternatively, due to changes in the composition of the plating bath as the number of days of plating passes, that is, due to the degree of depletion of the plating bath or the number of times the temperature of the plating bath is raised and lowered, the obtained magnetic film becomes resistant to electromagnetic conversion characteristics. A phenomenon in which the influencing coercive force changes significantly is observed. For this reason, in the past, there was a drawback that only a limited number of magnetic films having a coercive force within an acceptable range could be obtained from a specific electroless plating bath.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems and to provide a magnetic recording medium having a relatively low coercive force and improved coercive force squareness as desired.

[Means for Solving the Problems] The present invention provides a magnetic recording medium in which a cobalt-based magnetic film is formed on a non-magnetic substrate by electroless plating, in which the magnetic film has a cobalt content of 0.01 to 5. A magnetic recording medium characterized in that it contains % by weight of tellurium.

The present invention will be explained in detail below.

The magnetic recording medium of the present invention is a magnetic recording medium in which a cobalt-based magnetic film is formed on a non-magnetic substrate by electroless plating, in which the magnetic film has a cobalt content of 0.01 to 5.
It is characterized by containing wt% of Te.

Even if the amount of Te is less than 0.01% by weight or more than 5% by weight relative to Co, a sufficient effect of improving coercive force squareness cannot be obtained. The content of Te is especially 0.1 with respect to CO.
~3% by weight, especially 0.1-1% by weight is preferred.

The magnetic recording medium of the present invention has a magnetic film formed on a nonmagnetic substrate by electroless plating. As mentioned above, the electroless plating method is extremely advantageous in that it has high productivity and has many years of accumulated technology.

A reducing agent is used in the electroless plating bath as described below. Examples of the reducing agent include hypophosphites, borohydride compounds, hydrazine, dimethylamine borane, etc., and hypophosphites are preferably used.

The magnetic film becomes a Co-Te-P based magnetic film or a Co-Te-B photomagnetic film, etc., depending on the reducing agent. The content of P or B is 1 to 10% by weight based on Co in the magnetic film.
, particularly preferably 2 to 7% by weight.

In the magnetic recording medium of the present invention, C in the magnetic film.

The amount is preferably 50 to 98% by weight, particularly 70 to 98% by weight based on the total weight of the magnetic film. The magnetic film further contains 0.1 to 60% by weight, especially 1 to 40% by weight of Co.
It is desirable to contain % by weight of Ni.

The cobalt ions and nickel ions in the electroless plating bath are prepared using water-soluble compounds, for example, water-soluble cobalt compounds or water-soluble nickel compounds such as sulfates, chlorides, nitrates, acetates, etc. . Usually, sulfates and chlorides are preferably used. As the reducing agent, hypophosphites, borohydride compounds, hydrazine, dimethylamine borane, etc. are used, preferably hypophosphites.

The complexing agent is one selected from organic acids such as dicarboxylic acids, oxycarboxylic acids, and amino acids, and their soluble salts.
One species or two or more species may be used as appropriate. In addition, the cobalt ion concentration in the electroless plating bath is 0, O1 to 0.5 mol/I
It is preferable that the nickel ion concentration is 0.00
It is preferable that it is 1-0.1 mol/1.

The electroless plating bath for forming the magnetic film of the magnetic recording medium of the present invention may be, for example, a conventional C plating bath prepared from the above raw materials.
The electroless plating bath composition used for producing the o-P based magnetic film contains 0.005 to 15% of the total amount of cobalt compounds.
It can be prepared by adding mol % of a tellurium compound.

Here, examples of the tellurium compound include chlorides, oxides, tellurate salts, etc. Among them, it is preferable to use a tellurate salt.

To form a magnetic film by electroless plating, the pH of the electroless plating bath thus prepared is adjusted to 8 to 11 with caustic soda or an ammonia compound, and the bath temperature is adjusted to 6.
After adjusting the temperature to 0 to 90°C, the nonmagnetic substrate is immersed. The immersion time of the nonmagnetic substrate is appropriately determined depending on the desired thickness of the magnetic film.

Note that as the non-magnetic substrate on which the magnetic film is formed, metal, plastic, ceramic, glass, etc. substrates are used.
Usually, these are subjected to surface treatments such as N1-P electroless plating and Pd catalytic treatment according to known methods, and then used to form a magnetic film.

[Function] The magnetic recording medium of the present invention has the function of improving its coercive force squareness (S*) and lowering its coercive force (He).

Therefore, according to the magnetic recording medium of the present invention, the coercive force squareness can be improved and a desired coercive force can be easily obtained.

[Examples] The present invention will be described in more detail with reference to Examples and Comparative Examples below, but the present invention is not limited to the following Examples unless it exceeds the gist thereof.

Example 1 Cobalt sulfate 0.05 mol, nickel sulfate 0.0
1 mol/1, potassium tellurate 0.003 mol
C, Sodium hypophosphite 0.20 mol C, Boric acid 0.50 mol C, Potassium sodium tartrate 0.5
Electroless plating bath (25°C) having a composition of 0 mol
A caustic soda solution was added to adjust the pH to 9.0. This bath was heated to 80° C., and a Ni--P electroless plating coated aluminum substrate, which had been pretreated with degreasing and activation treatment, was immersed in the bath for 90 to 120 seconds to form a magnetic film. The composition of this magnetic film is Co: 90% by weight, Ni: 6
% by weight, Te: 0.3% by weight, P: 3% by weight,
Te was contained in an amount of 0.33% by weight based on Co.

Coercive force (He) and squareness (S) of the obtained magnetic recording medium
, coercive force squareness (Sa) were measured, and the results are shown in Table 1.

Example 2 In Example 1, 0.001 m of sodium tellurate
A magnetic film was formed in exactly the same manner except that ol/I was used. The composition of this magnetic film is Co: 90% by weight, N
inea weight%, Te: 0.20 weight%, P: 3 weight%
The content of Te was 0.22% by weight relative to Co.

Coercive force (He) and squareness (S) of the obtained magnetic recording medium
The coercive force squareness (S wheel) was measured and the results are shown in Table 1.

Comparative Example 1 A magnetic film was formed in exactly the same manner as in Example 1 except that potassium tellurate was not used, and the coercive force (He), squareness (S), and coercive force squareness ( 8) were measured and the results are shown in Table 1.

Table 1 It is clear from Table 1 that the magnetic recording medium according to the present invention can improve the squareness ratio and coercive force squareness, and reduce the coercive force.

[Effects of the Invention] As detailed above, according to the magnetic recording medium according to the present invention, the squareness ratio and coercive force squareness can be improved, and the coercive force can be reduced. Therefore, a magnetic recording medium is provided that can easily maintain the coercive force within the allowable range even when the coercive force exceeds the upper limit of the allowable range due to variations in manufacturing conditions or the like.

Claims (1)

[Claims] (1) A magnetic recording medium in which a cobalt-based magnetic film is formed on a nonmagnetic substrate by electroless plating, characterized in that the magnetic film contains tellurium in an amount of 0.01 to 5% by weight based on cobalt. magnetic recording media.