JPH02228479A - Electroless plating bath - Google Patents

Abstract

PURPOSE:To obtain a plating bath capable of stably forming a magnetic film having excellent characteristics as a vertical recording medium by incorporating glicolate group as a complexing agent into an aq. soln. contg. the respective ions Of Co, Ni, Re and a reducing agent. CONSTITUTION:An electroless plating bath incorporates at least Co ion, Ni ion and Re ion as a metallic ion, a reducing agent of the metallic ion as an additive and a complexing agent contg. at least glycolate group. As glycolate group of the complexing agent, glycolic acid or the soluble salt thereof is utilized in a range within about 0.001-3mol/l. Thereby the need for utilizing the specific complexing agent such as tartronic acid is eliminated and maintenance of the plating bath is made easy. This plating bath is ordinarily utilized in a range within 3-14.5pH.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a plating bath for producing a magnetic recording body (magnetic film) used for so-called perpendicular recording, in which recording is performed by magnetization in the film thickness direction of a magnetic recording body. It is something.

(Conventional technology) A perpendicular recording method has been proposed in which the demagnetizing field becomes smaller as the wavelength becomes shorter, allowing for higher density recording. A CoCr sputtered film has been proposed. Later, as such perpendicular recording media, in addition to CoCr sputtered films, CoM, which was formed by dry film formation methods such as sputtering and vapor deposition,
Co alloy films such as CoCrM (M is the third element), Fe
An alloy film, an Os-added ferrite film, a Ba ferrite film, etc. have been developed, but when these films are produced by a dry film forming method, there is a problem in mass productivity because the film is formed in a vacuum system.

For this reason, a method has been developed for manufacturing perpendicular recording media using an electroless plating method that improves these manufacturing problems and is excellent in mass production. The plating bath used in this method includes:
Electroless CoMnP plating bath (JP-A-57-140869
Publication No.), electroless CoNiMnP plating bath (JP-A-58
-058267), electroless CoNiMnReP plating bath (JP-A-60-103181), electroless C
An oN1ReP plating bath (Japanese Unexamined Patent Publication No. 61-003316) has been discovered.

In general, the conditions for easy magnetization in the direction perpendicular to the film surface are: the anisotropy energy of the medium is Ku, the perpendicular anisotropy energy specific to the film is above, and the shape anisotropy energy is 2nMs2 (Ms2).
is the saturation magnetization), then Kl > 2nMs2 or Ku = 2. , Ms2>0. (This is similar to the relationship Hk > 4nMs between the perpendicular anisotropy magnetic field Hk of the medium and the maximum value of the demagnetizing field 4□Ms.) This condition is not necessarily satisfied in perpendicular recording media. Although it is not necessary, it can be said that the larger the value of Ku or Hk is, the more preferable it is as a medium characteristic.

On the other hand, in order to obtain a large reproduction output, it is desirable to increase the Ms value. That is, IEEE Transaction on Magnetics (IEEETran).
saction on Magnetics) No.Mag
- According to Volume 18, No. 2, Pages 769-771, Ms.
It is said that under the condition of <(3/4rr)He (He is the coercive force of the medium), the reproduction output value is proportional to Ms.

Further, in the above-mentioned literature, it is said that when Ms≧(3/4rt)He, the reproduction output is proportional to He. In order to increase the reproduction output, it is necessary to increase Hc, but the value of He is limited by the type of magnetic head used or the recording conditions. Therefore, it is desirable to select an appropriate value for Hc depending on the required recording density and output.

(Problem to be solved by the invention) The electroless CoMnP plating bath and electroless CoNiMn
By using a P plating bath, a magnetic film in which the C axis of the hcpco hexagonal crystal is oriented perpendicular to the substrate can be obtained, but the magnetic film obtained in this way has a small decrease in Ms and a large value of 4 nMs, making it possible to perform perpendicular recording. I didn't like it physically.

Therefore, by eutectoiding Re into CoNiMnP, M
The aim is to reduce s. Electroless C to produce a magnetic film with excellent properties as such a perpendicular recording medium
Regarding the oNiMnP plating bath, please refer to JP-A-60-103.
181, Japanese Patent Application Laid-open No. 6O-i49785, etc. However, the medium properties are closely related to the film structure and film composition, and it has been difficult to control these and create a multi-component alloy electroless plating bath that can obtain the medium properties with good reproducibility. In particular, it is difficult to control Mn in the bath, and in order to stabilize the plating bath, the C-axis of the HCPCO hexagonal crystal was oriented perpendicular to the substrate without using Mn in the bath, and it became an excellent perpendicular recording medium. It was desired to obtain the characteristics. In order to simplify the alloy system and obtain a plating bath that is easy to control, additives, especially complexing agents, were investigated, and
Electroless CoN added with tartronic acid as seen in JP-A-00316 and JP-A-61-054028
A 1ReP plating bath has been developed.

However, although tartronic acid has a relatively simple structure of CH(○HXCOOH)2, which is a dicarboxylic acid with C, H, and OH attached, it does not exist naturally and must be synthesized. The synthesis method is currently very difficult, and the low yield and lack of stable supply have been a major problem. Therefore, tartronic acid is extremely expensive.

In addition, since it is difficult to obtain a highly pure product during the manufacturing process, the electroless plating reaction is affected by impurity components, which causes deterioration of the film structure, magnetic properties, etc. of the magnetic film, which is a major problem. Therefore, instead of tartronic acid,
It has been desired to use a complexing agent that is easy to produce and easily obtains with high purity.

An object of the present invention is to provide an electroless plating bath for stably and easily producing a magnetic film having excellent properties as a perpendicular recording medium by improving the conventional problems.

(Means for Solving the Problems) The electroless plating bath according to the present invention contains at least cobalt ions, nickel ions, and rhenium ions as metal ions, and the metal ions are added to an aqueous solution containing at least a reducing agent for the metal ions as an additive. It is characterized by containing a glycolic acid group as an ion complexing agent.

The main components of the electroless plating bath of the present invention include at least cobalt ions, nickel ions, and rhenium ions as metal ions, and an aqueous solution containing at least a reducing agent for the metal ions and a complexing agent for the metal ions as additives. , contains at least a glycolic acid group as a complexing agent for the metal ions, but within a range that does not impair the purpose and effect of the present invention, pH buffering agents, brightening agents, smoothing agents,
Additives such as stimulants, anti-pinhole agents, and surfactants may be used.

Cobalt ions and nickel ions are supplied by dissolving soluble salts of cobalt or nickel, such as sulfates, chlorides, acetates, in the electroless plating bath. The concentration of cobalt ions used is in the range of 0.0005 to 1 mol/1, preferably 0.005 to 0.11 mol/1.
It is in the range of ol/1. The concentration of nickel ions is 0.
The range of 001 to 1 mol/1 is used, preferably 1,
< is in the range of 0.01 to 0.17 mol/l. Rhenium ions are supplied by soluble salts such as potassium perrhenate and ammonium perrhenate, and the concentration is as follows:
A range of 0.0001 to 0.3 mol/1 is used, preferably a range of 0.001 to 0-06 mol/1. The metal ions used in the present invention are mainly composed of cobalt, nickel, and rhenium, but also include small amounts of Be, Mg, AI, Ru, Si, and Fe.
, Sr, Y, Zr, Nb, Cd, In, S
b.

Ta, Ir, Hg, Tl, Nb, Gd, T
b, Ti, V, Or, Cu, Zn, Ga,
Ge.

Mn, W, Mo, Rh, Pd, Ag, Au
, Pt, Sn, Te, Ba, Ce, Sm.

Ions such as Os, Pb, Bi, etc. may be included, and these ions are supplied by their respective soluble salts.

As reducing agents, hypophosphites, hydrogenated boron compounds,
One or more of hydrazine, dimethylamine borane, and their derivatives are present in an amount of 0.004 to 0.9 mol
/1, preferably in the range of 0.05 to 0.3 mol/1.

As the complexing agent, a glycolic acid group such as glycolic acid, sodium glycolate, ethyl glycolate, methyl glycolate, cobalt glycolate, or nickel glycolate is used. The glycolic acid group contains 0.001 to 3 mol of glycolic acid or a soluble salt of glycolic acid.
/l, but 0.1 to 1.75 mol/l
A range of 1 is preferred.

In addition to complexing agents, formic acid, acetic acid, propionic acid,
Butyric acid, isobutyric acid, valeric acid, isovaleric acid, oxalic acid, malic acid, glutaric acid, maleic acid, fumaric acid, citraconic acid, itaconic acid, tricarballylic acid, succinic acid, malonic acid, tartaric acid, thioglycolic acid, lactic acid , p-hydroxypropionic acid, citric acid, isocitric acid, alloisocitric acid, pyruvic acid, oxalacetic acid, diglycolic acid, thiodiglycolic acid, mercaptosuccinic acid, dimercaptosuccinic acid, benzoic acid, mandelic acid, phthalic acid, salicylic acid, ascorbic acid, sulfosalicylic acid, tropolone,
Carboxylic acids such as 3-methyltropolone and tyron, amines such as ethylenediamine, diethylenetriamine, triethylenetetraamine, pyridine and their derivatives, iminodiacetic acid, iminodipropionic acid, nitrilotriacetic acid, nitrilotripropionic acid, ethylenediaminediacetic acid, ethylenediaminetetraacetic acid , aminopolycarboxylic acids such as ethylenediaminetetrapropionic acid and diethylenetriaminepentaacetic acid, amino acids such as alanine, sarcosine, valine, norleucine, tyrosine, cysteine, glutamic acid, glycine, aspartic acid, asparagine, and histidine, gluconic acid, allonic acid, and idonic acid. , hexonic acids such as galactonic acid, gulonic acid, gulonic acid, and mannonic acid, weak acids such as pyrophosphoric acid, or soluble salts thereof, or a combination of two or more thereof may be used. The concentration of these complexing agents is 0.0001 to 3.0
A range of mo1/1 is used, 0.1-1.5 mol/
A range of 1 is preferred.

Ammonium salts, carbonates, organic acid salts, etc. are used as pH buffering agents, and ammonium sulfate, ammonium chloride, boric acid, etc. are preferably used.The concentration range is 0.0.
1-3 mol/1, preferably 0.03-1 mol/l
is used.

As a pH adjuster, ammonia or caustic alkali such as NaOH, LiOH, KOH, RbOH, C
sOH.

FrOH, Be(OH)2. Mg(OH)2. Ca
(OH)2. Sr(OH)2゜Ba(OH)2. R
Metal hydroxides such as a(OH)2 are used alone or in combination of two or more.

Usually, the plating solution before bath preparation without the addition of a pH adjuster is in the approximately neutral to acidic range, and the pH is adjusted to alkaline by adding the above-mentioned hydroxide. If above the required pH, the pH
Acids such as hydrochloric acid, sulfuric acid, nitric acid, and acetic acid are used for descent.

pH range is 3-14.5, preferably 7.0-10.0
used between.

The thickness of the magnetic film obtained by the present invention is 0.003 to 10 pm.
A thickness of 3 pm or less is preferably used, and a thinner thickness is desirable for high-density recording.

The substrate on which the magnetic film is formed is usually aluminum alloy, copper,
Metal substrates such as brass, phosphor bronze, iron, titanium, etc. are used, but with appropriate treatment, non-metal substrates such as glass, resin, ceramic, etc., or substrates made of composite materials of metal and non-metal can also be used. . In addition, nickel-phosphorus, nickel-copper-phosphorus, nickel-molybdenum-phosphorus, nickel, tungsten-phosphorus, copper, tin,
A layer of copper-tin, etc., or a soft magnetic layer of permalloy, cobalt-zircon, nickel-iron-phosphorus, etc. may be formed.

(Function) As a plating bath for producing a perpendicular recording medium, an electroless CoN1ReP plating bath with a simplified bath system is preferable to an electroless CoNiMnReP plating bath. Mn
Conventionally, a special complexing agent called tartronic acid has been used to align the C-axis of the hexagonal hexagonal crystal of HCPCO perpendicularly to the substrate and obtain excellent properties as a perpendicular recording medium without using a hexagonal crystal. It is believed that tartronic acid played an important role in maintaining a favorable complex state for vertical orientation of the C axis of Co. However, since the relationship between the complexing agent and the orientation of the precipitated alloy film is not clear, as a result of extensive experimental studies leading up to the present invention,
We have found that among various complexing agents, glycolic acid groups are applicable for this purpose. At present, the relationship between complexing agents and film structure/magnetic properties is not theoretically clarified.
The effect of the glycolic acid group cannot be fully explained. However, after the inventors discovered a suitable bath and considered the results, it was found that glycolic acid HOCH2COOH is similar to tartronic acid CH, which has the effect of vertically aligning the Co crystals of the magnetic film.
This effect is caused by the structural characteristics of (OH)(COOH)2, in which only one C0OH is changed to H, and the structure is similar, and it is a carboxylic acid that has both an OH group and a C0OH group. It is speculated that this is the case.

The present invention was brought about by obtaining such knowledge.

Next, the present invention will be specifically explained with reference to Examples and Comparative Examples.

(Example 1) A nonmagnetic N1-P layer was plated on an aluminum alloy substrate, and the surface was mirror-polished, and then a 2 μm thick CoNlReP alloy magnetic film was formed thereon using the following plating bath.

Plating bath (1) Bath composition Cobalt sulfate 0.06 mol/1
Nickel sulfate 0.08 mol/1
Ammonium perrhenate 0.003 mov1 Sodium hypophosphite 0.2 mov1 Ammonium sulfate 0.5 mol/1 Sodium malonate 0.75 mol/1 Sodium tartrate 0.2 mol/1 Glycolic acid 0.8 mol/ 1 Plating conditions Bath temperature: 80°C Plating bath pH: 8.7 (ammonia water at room temperature
, pH adjustment) A typical MH loop of the magnetic film thus obtained is shown in FIG. In the figure, it can be seen that the loop of this magnetic film has a shape unique to a perpendicular magnetic anisotropic film in which a vertical loop surrounds an in-plane loop. Further, from FIG. 1, the saturation magnetization Ms value was 426 emu/cc, and the coercive force Hc was 7750e in the in-plane direction and 8040e in the perpendicular direction.

The torque curve obtained from magnetic anisotropy energy measurement is
It exhibited clear uniaxial anisotropy and had a positive anisotropy energy Ku value (5 x 1104er/cc).

Next, the structure of the magnetic film, which is thought to be the cause of exhibiting such characteristics, was investigated using X-ray diffraction and electron beam diffraction. In X-ray diffraction, only a sharp peak due to diffraction from the (002) plane, which indicates that the C axis of hcpco (hexagonal crystal) is oriented perpendicular to the substrate surface, was observed, which corresponds to diffraction from other lattice planes. No peak was observed. In addition, the electron diffraction results also show that hcpco has a C-axis oriented perpendicular to the substrate surface.
It has been revealed that the structure consists of a high degree of crystallinity and orientation.

That is, it was revealed that the magnetic film obtained in this example exhibited perpendicular magnetic anisotropy and had various properties preferable as a perpendicular recording medium.

(Example 2) A magnetic film was produced using the same procedure as in Example 1, but in this example, the concentration of glycolic acid was varied in the range of 0 to 2 mol/1 in the plating bath (1), and CoNlReP
An alloy magnetic film was formed.

Magnetic properties of the magnetic film thus obtained (saturation magnetization Ms (top), anisotropic magnetic field Hk, coercive force He (earth), coercive force When the glycolic acid concentration is Omol/1, Hk is 1.4 kOe
According to the MH loop and torque measurements of the magnetic film, the film was easily magnetized in the plane. 0.05 mol of glycolic acid
When /1'r6 was added, Hk became 4.1 kOe, and the MH loop and torque measurements of the magnetic film also showed a tendency to change to a film that is easily perpendicularly magnetized. As the glycolic acid concentration increases, Hk further increases and progresses to a perpendicularly magnetized film. The maximum Hk is 6.4k when the glycolic acid concentration is 0.8mol/l.
At concentrations above Oe, Hk decreases slightly, but
It maintains a large value of 4.4 kOe up to 1.75 mol/1. At a glycolic acid concentration of 2 mol/1, Hk
decreased to 2.0kOe. Further, as shown in the table, in the plating bath of the present invention, even if the perpendicular magnetic anisotropy increases, Ms does not suddenly decrease and maintains a relatively large value.

Hc (1), Hc (7υ) can be varied between about 5000e and about 8000e in a film with Hk of 4 kOe or more. In the glycolic acid concentration range of 0.5 to 1.25 mol/1, The MH loops of the obtained magnetic films all showed a shape peculiar to perpendicular magnetic anisotropic films in which a vertical loop surrounded an in-plane loop as in Example 1.The torque curves of these magnetic films were all clear. They exhibited strong uniaxial anisotropy and had a positive anisotropy energy Ktx value. In X-ray diffraction of these magnetic films, only a sharp peak due to diffraction from the (002) plane was observed, and other lattice planes No peak corresponding to the diffraction from the substrate was observed. Furthermore, the electron beam diffraction results show that the hcpCo structure is composed of an hcpCo structure in which the C axis is oriented perpendicular to the substrate surface, indicating a high degree of crystallinity and orientation. It became clear that

In other words, the magnetic film obtained in this example exhibits perpendicular magnetic anisotropy due to the addition of glycolic acid, and has various properties preferable as a perpendicular recording medium, and the magnetic properties can be controlled by changing the concentration. It became clear.

(Example 3) A magnetic film was produced using the same procedure as in Example 1, but in this example, a CoNlReP alloy magnetic film was formed using the following plating bath.

Plating bath (2) Bath composition Cobalt sulfate 0.01 moυ1 Nickel sulfate 0.05 mol/1 Ammonium perrhenate 0.003 mol/1 Sodium hypophosphite 0.2 mol/]-Ammonium sulfate 0.5 mol/1 Sodium malonate 0.5 mol/1 Sodium glycolate O~0.5 mol/1 Plating conditions Bath temperature 80°C Plating bath pH 8.7 (pH adjusted with aqueous ammonia at room temperature) The magnetic film thus obtained Magnetic properties (saturation magnetization Ms
(Soil), anisotropic magnetic field Hk, coercive force He (1), coercive force 2. Relationship between the concentration of sodium glycolate and magnetic properties In this example as well, as in Example 2, there was a tendency for the film to become easily perpendicularly magnetized by the addition of sodium glycolate, but at a concentration of 0.05 m1/1 big H from
The k value was changed, and as in Example 1, the film exhibited a shape peculiar to a perpendicular magnetic anisotropic film in which a vertical loop surrounded an in-plane loop. The torque curves of these magnetic films all exhibited clear uniaxial anisotropy and had positive anisotropy energy Ku values. In this example, relatively small Ms (Sat), He (Sat), He (/
υ values are obtained and these values can be varied depending on the sodium glycolate concentration. In addition, X-ray diffraction,
The results of electron beam diffraction also revealed that all the samples were composed of an hcpCo structure in which the C axis was oriented perpendicular to the substrate surface, exhibiting high crystallinity and orientation.

In other words, the magnetic film obtained in this example exhibits perpendicular magnetic anisotropy and has favorable properties as a perpendicular recording medium. It became clear that the small Ms (Sat), He (Sat), and Hc (lυi) were directly connected to each other.

(Example 4) A magnetic film was produced using the same procedure as in Example 1, but in this example, a CoNlReP alloy magnetic film was formed using the following plating bath.

Plating bath (3) Bath composition Cobalt sulfate 0.005-7 mol/
1 Nickel sulfate 0.08 mol/
1 Ammonium perrhenate 0.003 mol/
Sodium hypophosphite 0.2 mol/1
Ammonium sulfate 0.5 mol/1 Sodium malonate 0.75 mol/1 Sodium tartrate 0.2 mol/1 Sodium glycolate 1.0 mol/1 Plating conditions Bath temperature 80°C Plating bath pH 8.7 (at room temperature) (pH adjusted with aqueous ammonia) Magnetic properties of the magnetic film thus obtained (saturation magnetization Ms
(earth), anisotropic magnetic field Hk, coercive force He (earth), coercive force H
Table 3 shows the results of measuring c(//)).

Table 3. Relationship between concentration of cobalt sulfate and magnetic properties In this example as well, as in Example 1, a shape peculiar to a perpendicular magnetic anisotropic film in which the vertical loops of the magnetic film surrounded the in-plane loops was exhibited.

The torque curves of these magnetic films all exhibited clear uniaxial anisotropy and had positive anisotropy energy Ku values. Furthermore, the results of X-ray diffraction and electron beam diffraction revealed that all of the samples were composed of an hcpco structure in which the C-axis was oriented perpendicular to the substrate surface, and exhibited high crystallinity and orientation.

In electroless plating, metal ions are consumed by the plating reaction, but as shown in Table 3, the magnetic properties hardly change even if the cobalt sulfate concentration changes, and the present invention shows that a stable plating bath can be obtained. It became clear.

(Example 5) A magnetic film was produced using the same procedure as in Example 1, but in this example, a CoNlReP alloy magnetic film was formed using the following plating bath.

Plating bath (4) Bath composition Cobalt sulfate Nickel sulfate Ammonium perrhenate Sodium hypophosphite Ammonium sulfate 0.06 mol/1 0.08 mol/1 0.003 mol/1 0.2 mol/1 0.5 mol/ 1 Sodium malonate 0.75-0.9mol
/1 Sodium tartrate 0.2 mol/
1 Sodium glycolate 1.0 mol/1
Plating conditions Bath temperature 80°C Plating bath pH 8.6 (pH adjusted with ammonia water at room temperature) Magnetic properties of the magnetic film thus obtained (saturation magnetization Ms
(Up, anisotropic magnetic field Hk, coercive force He (top), coercive force H
Table 4 shows the results of measuring e(//)).

Table 4. Relationship between the concentration of sodium malonate and magnetic properties In this example as well, as in Example 1, the vertical loops of the magnetic film surrounded the in-plane loops, exhibiting a shape unique to a perpendicular magnetic anisotropic film. The torque curves of these magnetic films all exhibited clear uniaxial anisotropy and had positive anisotropy energy Ku values. Furthermore, the results of X-ray diffraction and electron beam diffraction revealed that all of the samples were composed of an hcpco structure in which the C-axis was oriented perpendicular to the substrate surface, and exhibited high crystallinity and orientation. In addition, by changing the concentration of sodium malonate as shown in Table 4, He(1) can be adjusted to approximately 500 to approximately 10,000 e, and HcC1υ to approximately 150 to approximately 5,000 e.
It was possible to change between.

In addition, the electroless plating baths used in Examples 1 to 5 above were
Compared to conventional electroless plating baths using tartronic acid as a complexing agent, bath management is easier and the stability is significantly better, making it possible to produce magnetic films with excellent properties as perpendicular recording media with good reproducibility. Ta. When producing a large number of media from the same volume of plating bath, the bath life is defined as the plating processing amount from the beginning of plating where an anisotropic magnetic field Hk value of 4 kOe or more is obtained until the Hk value becomes 4 kOe or less. The bath life of the electroless plating bath according to the present invention was increased by more than 10 times compared to the conventional electroless plating bath.

(Effects of the Invention) As described above in the examples, according to the present invention, an electroless plating bath for producing a magnetic film contains at least cobalt ions, nickel ions, and rhenium ions as metal ions, and as additives. By including a glycolic acid group as a complexing agent for the metal ions in the aqueous solution containing at least the reducing agent for the metal ions, there is no need to use a special complexing agent such as tartronic acid, and maintenance and management of the plating bath is simplified. Therefore, a magnetic film having excellent properties as a perpendicular recording medium can be stably and easily produced with good reproducibility.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the MH left curve representing the magnetic properties of the magnetic film obtained from the electroless plating bath of the present invention in Example 1.

Claims (1)

[Claims] An aqueous solution containing at least cobalt ions, nickel ions, and rhenium ions as metal ions and containing at least a reducing agent for the metal ions as an additive, and at least a glycolic acid group as a complexing agent for the metal ions. Electrolytic plating bath.