JPS61267931A - Surface treatment of magnetic disk substrate - Google Patents

Abstract

PURPOSE:To obtain appropriate surface roughness by pretreating an Ni-Cu-P layer with an abrasive at specified pH when the titled disk substrate is obtained by providing the Ni-Cu-P plated layer on an Al alloy substrate and depositing a magnetic plated layer thereon through a magnetic plated layer. CONSTITUTION:An electroless-plated Ni-Cu-P ternary alloy layer 2 is coated in 20mum thickness on an Al-Mg alloy substrate 1 by using a bath composition consisting of 0.085-0.095mol/l Na sulfate, 0.005-0.015mol/l Cu sulfate, 0.2mol/l Na hypophosphite, 0.1mol/l Na malonate, 0.2mol/l Na citrate and 3cc/l nonionic surfactant and whose pH is regulated to 10. Then the surface is mecha nochemically polished by using an abrasive whose pH is regulated to 8-11 or to 3-5 and an Ni-P alloy plated layer 3, a Co-P alloy magnetic plated layer 4, an SiO2 protective layer 5 and a surface lubricating layer 6 consisting of a 0.01% freon soln. are successively coated on the surface. The surface rough ness is thus controlled to 0.008-0.013mum and the deposition of the layer 6 is maintained.

Description

[Detailed description of the invention] [Technical field to which the invention pertains]

The present invention relates to a method for surface treatment of a substrate made of an aluminum alloy used as a nonmagnetic support for a magnetic layer of a magnetic disk for high-density recording and reproduction.

[Prior art and its problems]

In recent years, contact start-stop type head floating systems have become common in magnetic disk drives due to demands for higher recording density and higher reliability. In order to increase the recording density, it is necessary to reduce the flying height of the head, as well as to make the medium layer thinner, to increase the coercive force He, and to significantly reduce surface defects. Among these, when the objective was to reduce the flying height of the head, the pursuit of specularity of the disk substrate was an issue. However, if a substrate with too high specularity is used, the surface of the magnetic disk will become too smooth, and surface tension will cause lubricant or condensed atmospheric moisture to enter the gap between the magnetic head and the disk, causing the magnetic head to fail. It was often attracted to the disk and caused damage when the disk was started, ie, hend crush. In addition, because the specularity is too high, liquid lubricants also have the disadvantage of scattering when the disk rotates. To prevent this, Co-Ni
-P or Co-P plated magnetic disk, AI-? After electroless NILP alloy plating on a 1g alloy substrate, it is polished to a surface roughness of RaO, 005 to 0.01#lI, and then polished to a roughness of IIA" 4000 to 10000 or GC@
4,000 to 10,000 tape burnishing to provide regular machining lines in a concentric circle to achieve Ra of 0.008 to 0.
It has become common to perform a so-called texturing process to obtain a roughness of approximately 0.013 mm. In addition, the substrate for T-Pesos spafter type media has traditionally been anodized A.
The I-Mg alloy substrate is precision polished to a roughness of Ra0.
．． After obtaining OIIrm or less, an intermediate layer is formed on the surface of the magnetic layer to create a reservoir of liquid lubricant, or a polished substrate is plasma etched to obtain a suitable roughness to create a reservoir of lubricant. It was reprocessed (Unexamined Japanese Patent Publication No. 5
9-82625), the provision of an intermediate layer for obtaining a reservoir of lubricant increases space loss and greatly impairs the interest in high-density recording. Above, plating type disk substrate or r-We mushroom 02
The alumite substrate for sputter type disks requires special treatment to maintain the lubricant pool (it has the drawback of requiring an additional process).

[Object of the invention] The present invention eliminates the above-mentioned drawbacks, has minute depressions for liquid lubricant reservoirs on the surface of the magnetic layer formed thereon without special treatment, and has the required features. Ra0.00
An object of the present invention is to provide a surface treatment method for obtaining a magnetic disk substrate having a surface roughness of about 8 to 0.013. [Summary of the Invention] According to the present invention, an aluminum alloy substrate is plated with a Ni-Cu-P alloy by an electroless plating method, and then PH8
By performing mechanochemical polishing using an abrasive whose Pf is adjusted to 11 or 13 to 5, the Cu-containing portion is eroded to form appropriate micro-dents, thereby achieving the above objective.

[Embodiments of the invention]

Hereinafter, examples of the present invention will be described with reference to comparative examples with reference to the drawings. Example 1: A JIS A3086 Al-Mg alloy plate was subjected to pressure annealing, inner and outer diameter machining, and then surface lapping to produce a material with an outer diameter of 130 fi, an inner diameter of 40 fi, and a thickness of 2.0 fi, as shown in Figure 1 with reference numeral 1. 5A
A V disk substrate was obtained, and after degreasing, activation, and zincate treatment, electroless Ni--Cu--P ternary alloy plating was performed under the following conditions to form a plating layer 2 with a thickness of 20 mm. Bath composition: Nickel sulfate 0.085-0.095
tru/It sulfur fk [0,005 to 0.015 i%/
Sodium hypophosphite 0.2 mol/1 Sodium malonate 0.1 u/1 Sodium citrate 0.2 mol/l Nonionic surfactant M 3
cc/IIPH (adjusted with NaOH) 10 Plating temperature 80°C Plating time Corresponding to the film thickness The alloy composition changes by changing the ratio of nickel sulfate and copper sulfate in the plating solution, but Ni is 30 to 75%. Adjust as appropriate so that the Cu is within the range of 15 to 75% and the pH is within the range of 11%. After that, the average particle size is 1
The surface thickness 5- was removed by polishing for 5 to 10 minutes using a slurry of PIIIO (Metalli)-01 (trade name of Fujimi Abrasive Industries). Since the slurry is alkaline, the surface obtained in this way is Ni-Cu-
The Cu-rich portion of the P alloy plating is selectively chemically etched, resulting in minute pits. However, the surface roughness is maintained within Ra of 0.009 to 0.013. Plating layer 3 is 0.
After forming with a thickness of 3 to 0.5 nm, C is coated by electroless plating.
o-P alloy magnetic plating layer 4 of 0.07 to 0.08 #ll
Further, 5 lots of film 5 was formed as a protective layer on the thickness of 0.07 to 0.08 #lI by RF sputtering method as a protective layer, and finally, TALITOX 143AD (
A magnetic disk having a surface lubricating layer 6 was obtained by applying a 0.01% Freon solution (trade name of DuPont Co., Ltd.) by a spin code method. Example 2: Ni-C was deposited on the A1 alloy substrate 1 in the same manner as in Example 1.
After forming the u-P plating layer 2, an abrasive having the following composition was prepared and both sides were polished. Altos (050 particle size 1.0-1.IQ) 1
2.5% by weight nonionic surfactant 2.5
Weight % ion-exchanged water Residual amount The pH of the abrasive was adjusted to 9.5 to 10.5 using either Na0Il or 11OH. The surface roughness obtained by this polishing was similar to that of Example 1. Hereinafter, as in Example 1, the Ni-P plating layer 3. C. -P magnetic plating layer 4. SiO protective film 5. A magnetic disk was prepared by sequentially applying the Krytox lubricating film 6. Example 3: Same as Example 1, except that Polypla 103 (Fujimi Abrasive Industries trade name, PI1) was used as an abrasive for double-sided polishing.
3 to 3.5) to generate minute depressions due to etch pits and obtain a predetermined surface roughness to produce a magnetic disk. Example 4 A magnetic disk was manufactured in the same manner as in Example 1, except that an abrasive having the following composition was prepared and used to obtain similar etch-focused depressions and appropriate surface roughness. Altos (050 particle size 1.0-1.1 n>8
Weight % cellulose saccharide 0.5 weight % ion exchange water Residual amount PR of abrasive
was adjusted to 3.0 to 3.5 with sulfuric acid. Example 5: Bolishing was performed using Ni-Cu-P plating and Metalite 01 (trade name of Fujimi Abrasive Industries) in the same manner as in Example 1, and then 0 was removed by reactive sputtering as shown in Figure 2. Fe, O with a thickness of .16-0.18-. A thin film 7 is formed. Note that the sputtering conditions are as shown below. Target used: 2.5%Co-3%Cu-FeTotal pressure: 2 Xl0-” TorrOxygen/argon gas mixture ratio: 1:1O High frequency power: Soow Substrate rotation: 20 rpm Next, heat treatment was performed at 300°C for 3 hours in the air. act r
A magnetic disk was prepared by spin-coding a 0.01% Freon solution of Krytox 143AD (trade name of Depond Co., Ltd.) as a zero-order lubricant. Example 6 = Same as Example 5, except that Polypla 103 (Fujimi Abrasive Industries trade name, PH360~) was used as the abrasive for double-sided polishing.
3.5) to generate minute depressions with etch pits and obtain a predetermined surface roughness to produce a magnetic disk. Comparative Example 1: Ni-Cu-P alloy as in Example 1. After plating, the surface roughness is RaO using a supernatant liquid (2% funnel oil added) of an aqueous suspension of HA" 800G using a double-sided polisher.
, 008~Q, 01JllI mirror finishing. A Co--P alloy magnetic plating layer having a thickness of 0.07 to 0.08 nm was formed thereon by electroless plating, and a protective layer and a lubricating layer were further coated in the same manner as in Example 1. Comparative Example 2: After forming a chromate alumite film to a thickness of 13u on a 5!4P disk substrate made of a high purity AI4%Mg alloy, a supernatant liquid of an aqueous suspension of -A″8000 was prepared using a double-sided polisher. The surface roughness Ra0.007~0
．． A baked surface of 009 am was obtained. A y-Fe*Os magnetic film was formed on this surface by a direct method to a thickness of 0.16 to 0.18. Furthermore, a sample was prepared by applying a lubricant thereon in the same manner as in Example 1 or Comparative Example 1. The following comparative tests were conducted using the magnetic disk samples prepared in Examples 1 to 6 and Comparative Examples 1.2. (1) A magnetic head made of Mn--Zn ferrite and a magnetic disk are left in contact with each other at room temperature for 24 hours, and then the disk adsorption force is measured. (2) Measurement of disc starting torque after 20,000 C3S (abbreviation for contact start stop) tests;
Investigate the occurrence of scratches during the C8S test. The results of the comparative tests are shown in Table 1, including a comparison of manufacturing costs. As can be seen from the upper table of Table 1, the magnetic disk using the substrate according to the present invention has excellent lubrication properties and the cost of the substrate is significantly reduced.

【Effect of the invention】

In order to reduce the adsorption force between the completed magnetic disk and the magnetic helad, the present invention uses alkaline or acidic polishing to form a desired surface roughness on the surface of the base plating layer of the non-magnetic substrate. By performing mechanochemical polishing using an abrasive, a magnetic disk substrate with microscopic depressions for retaining liquid lubricant is obtained. As a result, the magnetic disk surface manufactured using this substrate The lubricating properties of the substrate are maintained well, and the reliability is improved.Furthermore, the manufacturing cost of the substrate whose surface is treated according to the present invention can be significantly reduced for the following reasons.+11 Surface roughening process for retaining lubricant (2) Conventional r-Fez02 sputter type disk A1
It does not require the use of ultra-high-purity materials suitable for alumite treatment, such as alloys, and can take advantage of the advantage of batch simultaneous processing, which is a feature of plating methods. Further, according to the present invention, there is no need to insert a special intermediate layer as seen in the r-We@02 sputter type disk, and the distance between the head and the magnetic layer can be reduced, resulting in an increase in recording density. It is clear that the same effect can be expected even when the substrate surface-treated according to the present invention is used in a CO-based sputter type disk.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an example of a magnetic disk using a substrate according to the present invention, and FIG. 2 is a sectional view of another example. 2: Ni-Cu-P plating layer, 3: NI-P plating layer, 4: magnetic plating layer, 5: protective layer, 6: lubricant layer, 7: magnetic sputter layer.

Claims (1)

[Claims] 1) Ni is deposited on an aluminum alloy substrate by electroless plating.
- A method for surface treatment of a magnetic disk substrate, which comprises plating with a Cu-P alloy and then performing mechanochemical polishing using an abrasive whose pH is adjusted to 8 to 11 or 3 to 5.