JP2521932B2 - Method of manufacturing magnetic recording medium - Google Patents

Description

TECHNICAL FIELD The present invention relates to a magnetic recording medium such as a floppy disk, a hard disk, a cassette tape, etc., and a method for manufacturing the same.

[Prior Art] In this type of magnetic recording medium, improvement of recording density is one of the most important technical problems today. By the way, the main parameters of this recording density are coercive force Hc and residual magnetic flux.
Regarding Br and the thickness δ of the magnetic recording layer, these parameters and electromagnetic characteristics have the following relationship. That is, if the reproduction output of the magnetic head is E and the waveform width of the reproduction waveform is W, then E∝Br · (Hc / Br) ^β · δ ^1-α W∝ (Br / Hc) ^β · δ ^α where α = 0.85 to 0.50 β = 0.15 to 0.50 Therefore, in order to improve the recording density of the magnetic recording medium, it is necessary to suppress the decrease of the reproduction output E as much as possible and reduce the waveform width W as much as possible. For that purpose, it is clear that the coercive force Hc should be increased from the above relation.

[Problems to be Solved by the Invention] However, the coercive force Hc and the thickness δ of the magnetic recording layer are
Conventionally, the relationship is generally inversely proportional as shown by the solid curve in FIG. Therefore, in order to increase the coercive force Hc, the thickness δ of the magnetic recording layer must be reduced. However, in recent years, there has been a shift to ultra-thin film due to the demand for higher density of magnetic recording, and there is a limit in quality control to further reduce the thickness δ of the magnetic recording medium. Further, reducing the thickness δ of the magnetic recording layer lowers the reproduction output E, and if the residual magnetic flux Br is increased correspondingly to cover it, the waveform width W is increased, On the contrary, there is a problem that the recording density is lowered.

[Object of the Invention] The present invention has been made in view of the above conventional problems, and an object of the present invention is to provide a magnetic recording medium capable of obtaining a high coercive force without reducing the thickness of the magnetic recording layer. , To provide a manufacturing method thereof. This is intended to improve the recording density of the magnetic recording medium.

[Means for Solving the Problems] In order to achieve such an object, the first method for producing a magnetic recording medium according to the present invention is the surface of a magnetic layer as an aggregate of magnetic particles formed on the surface of a base material. , Particles having a noble equilibrium potential are adhered to the magnetic particles in a substantially uniform dispersion state, and this material is then immersed in an electrolyte solution to localize the particles having the noble equilibrium potential and the magnetic layer. The gist is that an electrolytic pit is formed on the surface of the magnetic layer by a cell action, and thereafter, a material having weaker magnetism than the magnetic particles or a non-magnetic or diamagnetic material is embedded in the electrolytic pit. .

A second method of manufacturing a magnetic recording medium is to use a material for forming a magnetic layer as an aggregate of magnetic particles on the surface of a base material.
The magnetic particles are immersed in an electroless plating solution containing atomic ions having a noble equilibrium potential to deposit the atomic ions on the surface of the magnetic layer, and a local cell action of the deposited particles and the magnetic layer. Thus, an electrolytic pit is formed on the surface of the magnetic layer, and then a material having a weaker magnetism than the magnetic particles, a nonmagnetic material, or a diamagnetic material is embedded in the electrolytic pit.

[Operation] In the first aspect of the invention thus configured, particles having a noble equilibrium potential with respect to the magnetic particles are attached to the surface of the magnetic layer as an aggregate of the magnetic particles in a substantially uniform dispersion state, When this is immersed in an electrolyte solution, a local battery is formed between the adhered particles and the magnetic layer, and countless electrolytic corrosion holes are formed on the surface of the magnetic layer. Therefore, it is possible to leave only the magnetic layer in the portion to which the adhered particles are attached. After that, the magnetic particles can be isolated by embedding a material having weaker magnetism than the magnetic particles or a non-magnetic or diamagnetic material into the electrolytic corrosion holes. For this reason, a high coercive force can be obtained without reducing the thickness of the magnetic recording layer, and a magnetic recording medium with a high recording density can be obtained.

Further, in the second invention, when the magnetic layer as an aggregate of magnetic particles is immersed in an electroless plating solution containing atomic ions having a noble equilibrium potential with respect to the magnetic particles, the above-mentioned atoms are formed on the surface of the magnetic layer. Ions are deposited, and by forming a local battery between the deposited atomic ions and the magnetic layer,
Countless electrolytic holes are formed on the surface of the magnetic layer. For this reason,
Only the magnetic layer where the atomic ions are deposited can be left. After that, the magnetic particles can be isolated by embedding a material having weaker magnetism than the magnetic particles or a non-magnetic or diamagnetic material into the electrolytic corrosion holes. Therefore, similar to the first invention, a high coercive force can be obtained without reducing the thickness of the magnetic recording layer, and a magnetic recording medium having a high recording density can be obtained.

[Embodiment] FIG. 1 shows a magnetic recording medium according to an embodiment of the present invention. In this figure, for example, a ferromagnetic Co-P film is formed on the surface of a base material 1 on which a non-magnetic layer, which is an aggregate of non-magnetic Ni-P-based crystal particles, is formed on an aluminum substrate.
A magnetic layer 2, which is an aggregate of system crystal grains, is formed.
The magnetic layer 2 has a thickness of about 500 to 700Å, and the surface thereof has micropores 3 with a diameter and depth of about 100 to 200Å.
3 are located in the gaps between the magnetic particles and are innumerably interposed, and in each of the micropores 3, there is a material 4 which is weaker in magnetism than the Co-P magnetic particles, or nonmagnetic or diamagnetic. Intervened. Incidentally, in this embodiment, silver (Ag), which is a non-magnetic material
Particles are interposed.

Next, a method of manufacturing this magnetic recording medium will be described. As shown in FIG. 2, one of the methods is as follows. First, on the surface of the Co—P-based magnetic layer 2 on the surface of the base material 1, Ag having an equilibrium potential of the vessel with respect to the Co—P magnetic particles is used. The particles 4 are attached in a substantially uniform dispersed state. As this means, a sputtering method, a vapor deposition method, an ion plating method or the like, which has already been a common technique, is applied. Next, the material thus obtained is immersed in an electrolyte solution having a solution composition shown in the following table (liquid temperature of about 80 ° C., immersion time of 30 seconds to 1 minute).

CoSO ₄ 15g / NaH ₂ PO ₂ 20g / (NH ₄ ) ₂ SO ₄ 80g / Potassium sodium tartrate 200g / Ag I 20mg / NaCN 10mg / NaOH (for pH adjustment) pH 10 Then Ag particles 4 -polar A local battery as a positive electrode is formed, and countless electrolytic corrosion holes 3, 3, ... Are formed on the surface of the magnetic layer 2 by the redox reaction action. The material thus obtained was taken out of the electrolyte solution, and then the surface was polished and polished to remove Ag on the surface of the magnetic layer 2.
The particles are embedded in the electrolytic corrosion hole 3. In this case, the equilibrium potential of the Ag particles 4 is noble with respect to the Co-P magnetic particles, and at the same time, it is a non-magnetic material, and therefore such a method can be adopted. The manufacturing process can be facilitated by using the same material that is attached to the surface of the magnetic layer 2 by the ion plating method or the like and the material that is embedded in the electrolytic corrosion hole 3. The magnetic layer 2
The material adhered to the surface of is not necessarily Ag, and in short, it is sufficient to select a material that is a negative electrode in the formation of the local battery in the electrolyte solution. Incidentally, Au, Cu, etc. can be applied as a material other than Ag.

FIG. 3 further shows another manufacturing method of the present invention. In this method, the above-mentioned material in which the magnetic layer 2 of Co—P magnetic particles is formed on the surface of the base material 1 is used as a material containing atomic (Ag) ions having a noble equilibrium potential with respect to the Co—P magnetic particles. Immerse in electrolytic plating solution. In this embodiment, this electroless plating solution has the same composition as that shown in the above table.
Thus, in this case, the Ag particles 4 are deposited on the surface of the magnetic layer 2, the deposited Ag particles 4 are the-pole, and the magnetic layer 2 is +.
A local battery is formed as a pole, and countless electrolytic corrosion holes 3, 3, ... Are formed on the surface of the magnetic layer 2 by its redox electrolysis action. Taking out this material from the electroless plating solution and polishing the surface thereof to embed the Ag particles 4 in the electrolytic corrosion holes 3 is the same as in the case of the previous method. According to the manufacturing method thereafter, the precipitation of Ag particles 4 on the surface of the magnetic layer 2 and the formation of the electrolytic corrosion holes 3 on the surface of the magnetic layer 2 due to the local cell action are performed in one step, so that one step is omitted. To be done.

However, the coercive force of the magnetic recording medium thus constructed is
The relationship between Hc and the thickness δ of the magnetic layer 2 is shown by a broken line in FIG. 4 and compared with the conventional product. As a result, as described above, in the conventional product, the coercive force drastically decreases in inverse proportion to the increase in the thickness of the magnetic layer 2, whereas in the product of the present invention, it is clear from this figure. Even when the thickness of the magnetic layer 2 is increased, the coercive force is hardly reduced and a high value is maintained. Such a result was obtained because each magnetic particle on the surface of the magnetic layer 2 was surrounded by the Ag particles 4 and was isolated, thereby increasing the domain wall motion resistance as a magnetic characteristic. Conceivable.

FIG. 5 shows the relationship between the immersion time (T) after immersion of the material in the electroless plating solution, the coercive force (Hc) and the saturation magnetic flux (Ms) in the subsequent manufacturing method. is there. It can be seen from this figure that the coercive force increases as the immersion time increases, while the saturation magnetic flux decreases only slightly. This saturation magnetic flux is generated by the magnetic layer 2
It means that the coercive force is increased even though the thickness of the magnetic layer 2 is not so thin because it has a correlation with the thickness.

Since Ag used in the above-mentioned examples is a material having a relatively low hardness, the self-lubricity of the surface of the magnetic layer 2 is improved by interposing this material on the surface of the magnetic layer 2.
The slidability of the magnetic head is improved. Further, by interposing a material having a higher equilibrium potential than the magnetic particles of the magnetic layer 2 on the surface of the magnetic layer 2, the corrosion resistance is improved.

[Effects of the Invention] As described in detail above, according to the method for manufacturing a magnetic recording medium of the present invention, an electrolytic pit is formed in a magnetic layer as an aggregate of magnetic particles by a local cell action, and the electrolytic pit is formed. The magnetic particles in the magnetic layer can be isolated by embedding a material having weaker magnetism than the magnetic particles in the magnetic layer, or a non-magnetic or diamagnetic material. For this reason, the domain wall motion resistance as a magnetic property becomes large, and a higher coercive force can be obtained as compared with a magnetic layer having the same thickness. For this reason, it is possible to avoid a reduction in the reproduction output, and it is possible to live without increasing the residual magnetic flux more than necessary, so that the reproduction waveform width can be suppressed. Therefore, the magnetic recording density can be significantly improved, and a thin film high density magnetic recording medium can be provided.

[Brief description of drawings]

FIG. 1 is a sectional view of a magnetic recording medium according to an embodiment of the present invention, FIG. 2 is an explanatory view of a manufacturing process for a first manufacturing method of this magnetic recording medium, and FIG. FIG. 4 is an explanatory view of a manufacturing process of the manufacturing method of FIG. 2, FIG. 4 is a view showing comparative data of magnetic recording characteristics (relationship between magnetic layer thickness and coercive force) between the magnetic recording medium according to the present invention and a conventional product, FIG. 5 is an explanatory view of the relationship between the immersion time of the material in the electroless plating solution and the coercive force and the saturation magnetic flux in the second manufacturing method. 1 ... Substrate, 2 ... Magnetic layer, 3 ... Micropores (electrolytic corrosion holes),
4 ... Non-magnetic material (Ag particles).

Claims (2)

(57) [Claims] 1. Particles having a noble equilibrium potential with respect to the magnetic particles are adhered to the surface of a magnetic layer as an aggregate of magnetic particles formed on the surface of a base material in a substantially uniform dispersion state, and then, This material is immersed in an electrolyte solution to form an electrolytic pit on the surface of the magnetic layer by the local cell action of the particles having the noble equilibrium potential and the magnetic layer, and then the magnetic pit is formed in the electrolytic pit. A method of manufacturing a magnetic recording medium, characterized in that a material having weaker magnetism than particles, or a nonmagnetic or diamagnetic material is embedded. 2. A material for forming a magnetic layer as an aggregate of magnetic particles on the surface of a base material is dipped in an electroless plating solution containing atomic ions having a noble equilibrium potential with respect to the magnetic particles. Atomic ions are deposited on the surface of the magnetic layer, and an electrolytic pit is formed on the surface of the magnetic layer by a local cell action of the deposited particles and the magnetic layer, and then the magnetic particle is placed in the electrolytic pit. A method of manufacturing a magnetic recording medium, characterized in that a material having weaker magnetism, non-magnetism, or diamagnetism is embedded.