JPH0362794B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a plating bath for producing a magnetic recording medium (magnetic film) used for so-called perpendicular recording, in which recording is performed by magnetizing the magnetic recording medium in the film thickness direction. Conventionally, in magnetic recording devices such as general magnetic disk devices and magnetic tape devices, recording is performed by horizontally magnetizing a magnetic recording medium formed on a substrate with a ring-shaped magnetic head. However, in recording using horizontal magnetization, as the wavelength of the recording signal becomes shorter, that is, as the recording density increases, the demagnetizing field within the medium increases, causing attenuation and rotation of the residual magnetization, resulting in a significant decrease in the reproduction output. There is a drawback. Therefore, in order to solve this problem, a perpendicular recording method was proposed in which the demagnetizing field is not small as the wavelength becomes shorter.A magnetic recording medium suitable for this perpendicular recording has an axis of easy magnetization in the direction perpendicular to the film thickness. A sputtered Co-Cr film has been proposed. It has been reported that this perpendicular magnetization recording method is superior to the conventional recording method using horizontal magnetization in high-density recording (see Japanese Patent Laid-Open No. 134706/1983). By the way, when a Co--Cr film is produced by sputtering, there is a problem in mass production because it is carried out in a vacuum system. For this reason, an electroless plating bath has been developed that solves these manufacturing problems and produces magnetic recording media with an axis of easy magnetization perpendicular to the film surface using an electroless plating method that is superior in mass production. It has been discovered (Special application 1982)
−025833, “Electroless plating bath”). However, in the electroless plating bath, as the manganese concentration increases, the C axis (axis of easy magnetization) of the α-Co hexagonal crystal changes from the in-plane direction to the perpendicular direction with respect to the substrate, but the saturation of the magnetic film increases. The drawback was that the decrease in magnetization Ms was small and the energy of the demagnetizing field expressed in 2πM ² _s was not sufficiently reduced, which could be an obstacle to perpendicular magnetization recording. The purpose of the present invention is to improve this problem and achieve saturation magnetization.
The object of the present invention is to provide an electroless plating bath capable of producing a magnetic recording medium in which Ms is reduced and the axis of easy magnetization is perpendicular to the film surface. The electroless plating bath according to the present invention contains malonic acid groups and malic acid groups or malonic acid groups and gluconic acid groups as cobalt ions, cobalt ion reducing agents, PH buffers, PH regulators, and cobalt ion complexing agents. It is characterized by the addition of nickel ions to an aqueous solution containing 0.02 to 0.2 mol/manganese ions as an additive, which increases the saturation magnetization of a magnetic recording medium in which the axis of easy magnetization is oriented perpendicular to the film surface. can be lowered. Cobalt ions, manganese ions, and nickel ions used as metal ions in the present invention can be obtained by dissolving soluble salts of cobalt, manganese, or nickel such as sulfates, chlorides, and acetates in an electroless plating bath. supplied. The concentration of cobalt ion is 0.002 to 1 mol/
is used, preferably 0.01 to
It is in the range of 0.15 mol/. The concentration of manganese ions used is in the range of 0.003 to 2 mol/, preferably in the range of 0.02 to 0.2 mol/. The concentration of nickel ions used is in the range of 0 to 0.5 mol/, preferably 0.002 to 0.5 mol/
It is in the range of 0.08 mol/. Hypophosphites are commonly used as reducing agents, but hydrazinic acids, borohydrides, and the like can also be used. PH buffers include ammonium salts, carbonates,
Organic acid salts and the like are used at concentrations ranging from 0.01 to 2 mol/. As a PH regulator, ammonia is used to increase the PH.
The alkali of sodium hydroxide is used and the PH
Acids such as sulfuric acid and hydrochloric acid are used for the precipitation. As the complexing agent, malonic acid or a soluble salt of malonic acid, gluconic acid or a soluble salt of gluconic acid, malic acid or a soluble salt of malic acid, etc. are used. Hereinafter, the features of the electroless plating bath according to the present invention will be explained using comparative examples and examples. Comparative example A steel substrate that had been degreased with ethanol and washed with water was subjected to activation treatment under the following conditions, and then a Co-Mn-P film (film thickness 1 μm) was applied thereon using the plating bath composition and plating conditions below. was formed. Activation treatment conditions HS101B (manufactured by Hitachi Chemical) 60c.c./, hydrochloric acid 320c.c./
Immerse for 3 minutes in an active solution containing 620 c.c. of pure water. Acceleration treatment conditions ADP201 (manufactured by Hitachi Chemical) 200 c.c./, pure 800
cc/ for 3 minutes. Plating bath composition Cobalt sulfate 0.025mol / Sodium hypophosphite 0.20mol / Ammonium sulfate 0.50mol / Sodium malonate 0.50mol / Gluconic acid 0.50mol / Manganese sulfate 0 to 0.07mol / Plating conditions Plating bath PH9.0 ( (pH adjusted with NH ₄ OH at room temperature) Plating bath temperature 85℃ To clarify changes in the crystal structure of Co-Mn-P films obtained by changing the concentration of manganese sulfate from 0 to 0.07 mol/min. The results of X-ray diffraction are shown in the table below. The numbers in the table indicate relative intensities with the intensity of the maximum intensity diffraction line in the same sample taken as 100.

[Table] C axis (easy axis of magnetization) of α-Co hexagonal crystal as manganese sulfate concentration increases to 0.02 mol/or more
It can be seen that the angle changes from the in-plane direction to the perpendicular direction with respect to the substrate. Figure 1 shows the changes in the saturation magnetization Ms of the magnetic film when the manganese sulfate concentration was changed from 0 to 0.07 mol/. Ms at 0mol/manganese sulfate is
It is about 132emu/g, but manganese sulfate is 0.01~
Increases by 0.03mol/. manganese sulfate
At 0.04 mol/or more, it shows a slight decreasing tendency, but even at 0.07 mol/g of manganese sulfate, Ms decreased only to about 120 emu/g. Example 1 A Co--Ni--Mn--P film (film thickness: 1 μm) was plated in the same manner as in the comparative example, but the following composition was used as the plating bath. Plating bath composition Cobalt sulfate 0.025mol/ Sodium hypophosphite 0.20mol/ Ammonium sulfate 0.50mol/ Sodium malonate 0.50mol/ Gluconic acid 0.50mol/ Manganese sulfate 0.05mol/ Nickel sulfate 0 to 0.015mol/ Concentration of nickel sulfate to 0 The following table shows the X-ray diffraction results of the Co-Ni-Mn-P film obtained by varying the concentration up to 0.015 mol/.

[Table] Even if the concentration of nickel sulfate is increased from 0 to 0.015 mol/, the relative intensities of (100) and (101) become 0, and the C axis of the α-Co hexagonal crystal is fully oriented perpendicular to the substrate. was held. Figure 2 shows the changes in saturation magnetization Ms when the nickel sulfate concentration was varied from 0 to 0.015 mol/.
Ms at 0 mol/g of nickel sulfate is about 124 emu/g, but decreases as the concentration of nickel sulfate increases, and at 0.015 mol/g of nickel sulfate, Ms is 99 emu/g.
It decreased to about 1.5 g. Example 2 A Co-Ni-Mn-P film (thickness: 1 μm) was plated in the same manner as in the comparative example, but the following plating bath was used. Plating bath composition Cobalt sulfate 0.025mol / Sodium hypophosphite 0.20mol / Ammonium sulfate 0.50mol / Sodium malonate 0.50mol / Gluconic acid 0.50mol / Manganese sulfate 0.04mol / Nickel sulfate 0 to 0.020mol / Plating conditions Plating bath PH9.6 (PH adjusted with NH ₄ OH at room temperature) Plating bath temperature 85℃ X-ray of Co-Ni-Mn-P film obtained by varying the concentration of nickel sulfate from 0 to 0.020 mol/ The diffraction results are shown in the table below.

[Table] Even if nickel sulfate is increased from 0 to 0.020 mol/, the relative intensities of (100) and (101) become 0 and α
The C-axis of the -Co hexagonal crystal remained fully oriented in the direction perpendicular to the substrate. Figure 3 shows the change in saturation magnetization Ms when the nickel sulfate concentration was changed from 0 to 0.020 mol/.
Ms of nickel sulfate up to 0mol/ is 126emu/g
However, as the concentration of nickel sulfate increases, it decreases, and at 0.020 mol of nickel sulfate/Ms
It decreased to about 84emu/g. As described above, in Examples 1 and 2, the magnetic films obtained from the soaking bath with increased nickel sulfate concentration had a decrease in saturation magnetization due to the eutectoid of nickel, and the C-axis was oriented perpendicular to the substrate. Therefore, it can be used in magnetic recording media for perpendicular magnetization recording. In addition, although the case of a metal substrate was described in the example, when using an organic resin substrate such as a polyimide plate, instead of degreasing with ethanol, it may be immersed in a conditioner (manufactured by Shipley Far East Co., Ltd.) for 3 to 5 minutes before the activation treatment. By degreasing and plating in the same manner as in the example, a Co--Ni--Mn--P film in which the C-axis of the α-Co hexagonal crystal was vertically oriented was obtained, and the saturation magnetization was reduced. When using other organic resin substrates such as polyester or ABS resin, the same effect can be achieved by performing appropriate degreasing treatment.
A Co-Ni-Mn-P film is obtained and the objective is achieved. As shown in the examples above, according to the present invention,
Cobalt ions, cobalt ion reducing agents, PH buffers,
Contains malonic acid groups and malic acid groups or malonic acid groups and glyconic acid groups as a PH regulator and complexing agent for cobalt ions, and as an additive 0.02 to 0.2 mol/
By adding nickel ions to an aqueous solution containing manganese ions, it is possible to reduce the saturation magnetization of a magnetic recording medium whose axis of easy magnetization is oriented in a direction perpendicular to the film surface.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the relationship between manganese sulfate concentration and Ms in a plating bath of a comparative example. Figure 2 shows the concentration of nickel sulfate in the plating bath of Example 1.
FIG. 3 is a diagram showing a similar relationship in the plating bath of Example 2.

Claims (1)

[Claims] 1 cobalt ion, cobalt ion reducing agent,
Contains malonic acid and malic acid groups or malonic acid and glyconic acid groups as a PH buffer, PH regulator, complexing agent for cobalt ions, and 0.02 as an additive.
In an aqueous solution containing ~0.2 mol/manganese ion,
An electroless plating bath for producing magnetic recording media (magnetic films) used for perpendicular recording, characterized by the addition of nickel ions.