JPH06274875A - Ni-P plating method for titanium magnetic disk substrate - Google Patents

Abstract

(57) [Abstract] [Purpose] Made of titanium to which a Ni-P plating film formed on a titanium substrate has excellent adhesion to the titanium substrate and which has a small surface roughness. A method of manufacturing a magnetic disk substrate. [Structure] A magnetic disk substrate made of titanium and a cathode material are prepared, and they are separated from each other and immersed in an electrolytic aqueous solution having a predetermined concentration of at least one of fluorine, chlorine, bromine and iodine having a predetermined concentration, and a predetermined concentration. DC voltage is applied to perform anodization, and then the anodized disk substrate is subjected to Ni.
-Plate P coating.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Ni-P plating method for a titanium magnetic disk substrate used as a magnetic disk for high density recording and reproduction.

[0002]

2. Description of the Related Art In recent years, high density recording has been attempted on magnetic disks, and for this purpose, attempts have been made to reduce the material thickness. Therefore, as a new technology, attention has been paid to heat resistance and rigidity of titanium, and it has been attempted to use titanium as a substitute material for the conventional aluminum magnetic disk substrate.

However, when titanium is used as the magnetic disk substrate, since the titanium metal surface remains polycrystalline, a difference in crystal plane is reflected in the magnetic film provided as the storage medium, which is considered to be the cause. Many signal errors occur. The present inventors have found that it is effective to provide an amorphous anodic oxide film on the substrate surface as a countermeasure against this.

There is a problem only by applying an amorphous anodic oxide film to the magnetic disk substrate and then applying the magnetic film. The reason for this is that the anodized film is subjected to texturing (grooving) in order to prevent the magnetic film from sticking to the magnetic head, but it is clear that the anodized film is not suitable for this texturing. Because it became. Therefore, it is desirable to perform Ni—P plating on a titanium disk substrate to a thickness of about 1 to 10 μm, and then apply a magnetic film.

However, Ni is directly deposited on the titanium disk substrate.
It is known that it is difficult to apply plating such as -P (for example, 87th Lecture Meeting of the Surface Technology Association, 199).
3 years, P179).

[0006]

In general, titanium forms an oxide film on its surface when left in the atmosphere. When the known Ni-P film treatment is performed without removing the oxide film, the film is not uniformly formed and the surface roughness is deteriorated. Therefore, the oxide film is usually removed by chemical etching prior to the Ni-P film treatment. When this method is applied to a titanium magnetic disk substrate and the oxide layer formed during mirror polishing is removed, the surface roughness of the material deteriorates due to the difference in etching rate due to the crystal plane, and the film is then formed. The surface roughness of the Ni-P coating is large.

In a titanium magnetic disk substrate, Ni-P
The adhesion of the coating is important. A magnetic film (storage medium) is formed on a Ni-P film by sputtering to form a magnetic disk. However, with a Ni-P film provided by chemical etching, the film peels off during sputtering and it is difficult to apply the magnetic film. Met. Further, in the magnetic disk substrate, the surface roughness of the Ni-P coating becomes a problem. Normal,
The distance between the magnetic disk substrate and the read head is 0.05μ
Since it is about m, the surface roughness of the magnetic disk substrate must be 0.03 μm or less over the entire surface.

Therefore, the object of the present invention is to provide a Ni-P plating method which has excellent adhesion of a Ni-P coating formed on a titanium magnetic disk substrate to the titanium substrate and has a small surface roughness of the coating. To do. The material of the titanium magnetic disk substrate is pure titanium material, but the present invention can be applied to a titanium alloy magnetic disk substrate.

[0009]

In the present invention, the adhesion to a titanium substrate is improved by subjecting it to an anodization which has been specially developed for the above purpose, and then performing Ni-P plating by a known method. It was possible to develop a method for producing a Ni-P plated film which is excellent and has a small surface roughness of the film. Specifically, the following means are adopted.

(1) The invention of claim 1 is a method of Ni-P plating a titanium magnetic disk substrate, which comprises the following steps. (A) a step of preparing a titanium magnetic disk substrate as a material to be treated and a cathode material; (b) separating the magnetic disk substrate and the cathode material so that fluorine (F) has a predetermined concentration,
Furthermore, a step of immersing in an electrolytic aqueous solution in which at least one or more of chlorine (Cl), bromine (Br) and iodine (I) has a predetermined concentration, and (c) the magnetic disk substrate as an anode and the cathode material as A step of applying a predetermined DC voltage as a cathode and performing anodization, and (d) a step of further plating a Ni-P film on the anodized magnetic disk substrate.

(2) The invention of claim 2 is such that the predetermined concentration of fluorine (F) and at least one or more of chlorine (Cl), bromine (Br) and iodine (I) fall within the following range. The method of claim 1, wherein the titanium magnetic disk substrate is Ni-P plated. F: more than 0.2 wt% and less than 10 wt% Cl + Br + I; more than 0.1 wt% and less than 10 wt%. (3) In the invention of claim 3, the predetermined DC voltage is 0.3V.
It is the Ni-P plating method of the titanium magnetic disk substrate of Claim 1 or Claim 2 which is in the range of 10V.

[0012]

As described above, in the present invention, the method of performing the anodizing treatment especially developed for the present invention and subsequently performing the Ni-P plating by the known method is adopted. Here, the conventionally known Ni-P plating method is a method of forming a Ni-P film electrolessly or electrolytically.

In the present invention, the anodizing treatment performed prior to the formation of the Ni-P coating greatly contributes to the adhesion of the Ni-P coating. In this treatment, the oxide layer formed on the surface of the titanium disk during processing is removed, and the Ni-P following this is removed.
A Ni-P film with excellent adhesion is formed by plating.

[0014] In anodizing present invention, a fluorine electrolytic solution used in anodizing, chlorine (Cl), by contained bromine (Br) and at least one or more from among iodine (I) is a Ni-P film It enables Ni-P plating treatment of titanium material, which has excellent adhesion and does not impair the surface roughness of the material.

In the anodic treatment prior to plating, the natural oxide film and the oxide layer formed during polishing are removed.
When a natural oxide film or an oxide layer formed during polishing is present on the surface of a titanium disk substrate, Ni substitution reaction hardly occurs in electroless Ni-P plating, so Ni-P
No film can be obtained, and a uniform film cannot be obtained even in the case of electrolytic Ni-P plating. In electroless plating, generally, if the substitution reaction rate is high, a dense film cannot be obtained and the adhesion of the film is poor.

Although the effect of the anodizing process according to the present invention has not been fully clarified, this anodizing process removes the natural oxide film and the oxide layer formed during polishing, and
It is considered that a uniform and extremely thin oxide film is formed, and a plating film having good adhesion is formed in the subsequent Ni-P plating treatment. That is, a uniform oxide film is formed with the removal of the oxide layer. It is considered that if the thickness of the oxide film is appropriate, the Ni substitution reaction rate is appropriately adjusted to form a dense and uniform Ni-P film.

Regarding the composition and concentration of the electrolytic solution: Fluorine is essential for removing the natural oxide film and the oxide layer formed during polishing. Further, when anodizing is performed using an electrolytic solution in which one or more kinds of chlorine, bromine, and iodine coexist, the resulting anodic oxide film has excellent adhesion to the titanium substrate. In order to find the optimum composition of the electrolytic solution for performing this anodizing treatment, the titanium substrate is anodized with various electrolytic solutions as shown in Table 2, and then a Ni-P coating is plated to obtain the adhesion of the Ni-P coating. And the surface condition was investigated.

As a result, regarding the fluorine concentration, the adhesion of the formed film is not desirable below the concentration range described in claim 2, and above this concentration range, the substrate is abruptly etched and the surface roughness is significantly deteriorated. At least one of chlorine, bromine and iodine must be present together, and if the total concentration is less than the concentration range of the present invention, there is no effect on adhesion, and if the total concentration is more than the concentration range of the present invention, pitting occurs on the substrate surface, It turned out that the roughness deteriorated.

Regarding voltage: In the above-mentioned anodization, the titanium substrate is used as an anode, and preferably the insoluble electrode is used as a cathode,
DC voltage is applied to perform anodization. As a result of various studies, if the anodizing voltage is set in the range of 0.3 V (volt) to 10 V, a desirable Ni-P film with good adhesion can be obtained. The surface roughness of the coating is almost the same as the surface roughness of the substrate.

Regarding other conditions: The distance between the electrodes can be arbitrarily set up to a maximum of 50 cm, but it is usually preferable to be about 5 to 10 cm because the size of the electrolytic cell is limited.
The energization time is not particularly limited as long as the anodic oxide film is formed on the entire surface of the titanium substrate, but is preferably 5 seconds or more.
The Ni-P film may be plated by a known electroless plating method or electroplating method. The thickness of the coating may be about 1-10 microns.

The cathode material is pure titanium, various titanium alloys,
An insoluble electrode such as stainless steel or an insoluble electrode may be used.
Further, the anodization of the titanium disk and the plating of the Ni-P coating are usually performed on both sides of the substrate.

[0022]

EXAMPLES Examples of the present invention will be described below. Example 1 A titanium magnetic disk substrate (diameter 2.5 inches, plate thickness 0.6 mm) was used as a material. Anodic treatment is 0.4 wt% bromine water + 5 wt% NaF + 1vol as electrolyte
% HF aqueous solution, the sample was immersed in the electrolytic solution for 15 seconds and then electrolyzed for 50 seconds. The sample was used as the anode and the cathode was a pure titanium plate, and the distance between the electrodes was 3 cm. The electrolysis was performed by applying a DC voltage without stirring the electrolytic solution. next,
After sufficiently removing the electrolytic solution by washing with water from the substrate, Ni-P plating was performed by an electroless method. The composition of the plating solution and the plating conditions are as follows. As an evaluation method, a surface roughness test (Rmax of material and Rmax after Ni-P plating treatment)
Difference) and adhesion test (cross-cut cellophane tape peel test,
JIS H8602) was used.

The conditions of electroless Ni-P plating are as follows:
Is: Plating Solution Composition: nickel sulfate _{(NiSO 4 · 6H 2 O)} ; 30g / l sodium hypophosphite _{(NaH 2 PO 2 · H 2} O); 20g / l lactic acid _{(CH 3 CH (OH) COOH} ) 30 g / l propionic acid (CH ₃ CH ₂ COOH); 5 g / l lead; 2 mg / l pH; 4.5 plating condition liquid temperature; 90 ° C. treatment time; 90 minutes

The conditions for electrolytic Ni-P plating are as follows:
There: Plating electrolyte composition: nickel sulfate _{(NiSO 4 · 6H 2 O)} ; 240g / l nickel chloride _{(NiCl 2 · 6H 2 O)} ; 45g / l boric acid _{(H 3 BO 3); 30g} / l phosphite ( H ₃ PO ₃ ); 35 g / l pH; 2 plating conditions cathode; substrate, anode; nickel plate, distance between electrodes; 10 cm current density; direct current 1.5 A / dm ² , electrolysis time; 5 minutes Electrolyte temperature; 55 ° C.

Table 1 shows processing conditions and evaluation results. Adhesion is improved by performing the first step of anodizing as compared with the case without anodizing. At this time, if an electrolytic voltage of 0.3 V (volt) or more and 10.0 V or less is applied, Ni-
The P film does not peel off at all. It was also confirmed that the surface roughness of the substrate was maintained. Almost no difference was observed depending on the Ni-P plating method.

[0026]

[Table 1]

Example 2 A magnetic disk substrate made of titanium (diameter 2.5 inches, plate thickness 0.6 mm) was used as a material. In the first stage anodic treatment, a sample was used as an anode and a pure titanium plate was used as a cathode, and the distance between the electrodes was 3 cm. The electrolysis was performed at room temperature, a DC voltage was applied without stirring the electrolytic solution, and electrolytic solutions having various compositions were used. Each ion concentration is sodium salt (NaF, NaC
1), potassium salt, ammonium salt and hydrogen salt (HF, HCl, etc.) commercially available reagents.
After immersing the sample in the electrolytic solution for 15 seconds, a voltage of 4.0 V was applied and electrolysis was performed for 40 seconds. Next, after sufficiently removing the electrolytic solution by washing with water from the substrate, Ni-P plating was performed by an electrolytic method. The composition of the plating solution and the plating conditions are as follows. As an evaluation method, surface roughness (Rmax) and adhesion (cross-cut cellophane tape peeling test, JIS H8602
) Was used.

The Ni-P plating electrolyte composition: nickel sulfate _{(NiSO 4 · 6H 2 O)} ; 240g / l nickel chloride _{(NiCl 2 · 6H 2 O)} ; 45g / l boric acid _{(H 3 BO 3); 30g} / l Phosphorous acid (H ₃ PO ₃ ); 35 g / l pH; 2 plating conditions : cathode; substrate, anode; nickel plate, distance between electrodes; 10 cm current density; direct current 1.5 A / dm ² , electrolysis time; 5 minutes electrolysis Liquid temperature; 55 ° C

Table 2 shows the processing conditions and the evaluation results. When fluorine and other halogen do not coexist in the anodized electrolyte and when the anodization is not performed, the Ni-P coating adhesion is poor, and when the anodization is performed within the concentration range of the electrolyte described in claim 2, the adhesion is improved. However, when the concentration of fluorine or other halogen is higher than this range, the surface tends to be roughened or pits are formed.

[0030]

[Table 2]

[0031]

According to the present invention, it is possible to manufacture a Ni-P plated titanium magnetic disk substrate which is excellent in the adhesion of the Ni-P coating and does not impair the surface roughness of the substrate.

Front page continuation (72) Inventor Masaki Omura 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Steel Pipe Co., Ltd.

Claims (3)

[Claims] 1. A Ni—P plating method for a titanium magnetic disk substrate, which comprises the following steps. (A) a step of preparing a titanium magnetic disk substrate as a material to be treated and a cathode material; (b) separating the magnetic disk substrate and the cathode material so that fluorine (F) has a predetermined concentration,
Furthermore, a step of immersing in an electrolytic aqueous solution in which at least one or more of chlorine (Cl), bromine (Br) and iodine (I) has a predetermined concentration, and (c) the magnetic disk substrate as an anode and the cathode material as A step of applying a predetermined DC voltage as a cathode and performing anodization, and (d) a step of further plating a Ni-P film on the anodized magnetic disk substrate. 2. The predetermined concentration of fluorine (F) and chlorine (C)
2. The Ni-P plating method for a titanium magnetic disk substrate according to claim 1, wherein the predetermined concentration of at least one of l), bromine (Br) and iodine (I) is in the following range. F: more than 0.2 wt% and less than 10 wt% Cl + Br + I; more than 0.1 wt% and less than 10 wt%. 3. The predetermined DC voltage ranges from 0.3V to 10V.
The Ni-P plating method for a titanium magnetic disk substrate according to claim 1 or 2, which is in a range of V.