WO2001048114A1

WO2001048114A1 - Composition for polishing magnetic disk substrate and polishing method, and magnetic disk substrate polished thereby

Info

Publication number: WO2001048114A1
Application number: PCT/JP2000/009230
Authority: WO
Inventors: Norihiko Miyata
Original assignee: Showa Denko K.K.
Priority date: 1999-12-27
Filing date: 2000-12-26
Publication date: 2001-07-05
Also published as: JP2004127327A; AU2225201A

Abstract

A composition for polishing a magnetic disk substrate containing water, silicon oxide, a metal coordination compound, and an oxidizing agent. The composition may further contain a pH adjusting agent. A magnetic disk substrate polishing method using such compositions and a magnetic disk substrate polished using such compositions by the polishing method are also disclosed. The surface roughness of the magnetic disk substrate is made small using such compositions or by the method. Therefore high-density recording is possible without producing any projections and polishing flaws. A magnetic disk substrate can be polished at an economical speed.

Description

Description Magnetic disk substrate polishing composition and polishing method, and magnetic disk substrate polished thereby

The present invention relates to a magnetic disk substrate polishing composition and a polishing method, and more particularly to a magnetic disk substrate polishing method capable of obtaining a highly accurate magnetic disk surface suitable for flying a magnetic head with a low flying height. The present invention relates to a composition and a polishing method. The present invention also relates to a magnetic disk substrate obtained using such a composition or method. Background art

Magnetic disks (memory hard disks) are widely used as a means of high-speed access in the external storage devices of computer-type processors. A typical example of this magnetic disk is a substrate obtained by electrolessly plating NiP on the surface of an A1 alloy substrate, and after polishing this substrate surface, a Cr alloy base film, a Co alloy magnetic The film and the carbon protective film were formed sequentially by sputtering.

Generally, if a protrusion with a height greater than the magnetic head flying height remains on the surface of a magnetic disk, the magnetic head flying at a high speed while flying at a predetermined height will collide with the protrusion and be damaged. Cause. Also, if the magnetic disk substrate has protrusions or polishing scratches, when Cr alloy base film or Co alloy magnetic film is formed, protrusions appear on the surface of those films, and defects due to polishing scratches occur. However, since the surface of the magnetic disk does not become a smooth surface with high accuracy, it is necessary to precisely polish the substrate in order to increase the accuracy of the disk surface.

For this reason, in polishing a magnetic disk substrate, many polishing compositions have been proposed as polishing compositions which eliminate projections or reduce the height thereof as much as possible and which hardly cause polishing scratches.

Among them, Japanese Patent Laid-Open No. H10-2012 (using a composition obtained by adding aluminum nitrate to titania) is used to grind titanium oxide particles in the sub-micron mouth. Since they are used as particles, they achieve higher surface accuracy and higher polishing rate than conventional products. However, achieving the recently required level of surface accuracy is difficult because of the hardness of the abrasive material.

Further, Japanese Patent Application Laid-Open No. Hei 9-2012 (using a composition obtained by adding aluminum nitrate and an anti-gelling agent to the colloidal silica force) and The composition described in 2) uses aluminum oxide fine particles with low hardness for the abrasive grains, so that surface accuracy can be easily obtained. It was difficult to achieve a usable polishing rate.

In order to increase the polishing rate, the use of many oxidizing agents has been proposed and put into practical use in the past, and the use of Fe salts has been proposed in two cases. 0 4 4 16). However, these were also insufficient compared with the polishing rates that can be used for actual production at present.

The quality required of an aluminum magnetic disk substrate polishing composition that enables high-density magnetic recording is the achievement of a high-precision disk surface that enables low flying of the head. There is a demand for a magnetic disk substrate polishing composition and a polishing method that enable this, and a magnetic disk substrate obtained using the same. Disclosure of the invention

Accordingly, it is an object of the present invention to provide a magnetic disk substrate capable of achieving high-density recording without causing surface roughness of the magnetic disk substrate, generating protrusions and polishing scratches, and capable of polishing at an economical speed. An object of the present invention is to provide a polishing composition of the present invention.

Another object of the present invention is to provide a magnetic disk substrate method using such a composition.

Still another object of the present invention is to provide a magnetic disk substrate obtained by using such a composition or a polishing method.

The present inventors have conducted intensive studies on an abrasive for achieving a high-accuracy polished surface required for a low-flying-type aluminum magnetic disk. The present inventors have found a polishing composition exhibiting excellent performance for polishing a disk, and have reached the present invention. That is, the present invention basically includes the following inventions.

(1) A composition for polishing a magnetic disk substrate, comprising water, silicon oxide, a metal coordination compound, and an oxidizing agent.

(2) The polishing composition according to the above (1), further comprising a pH adjuster.

(3) The polishing composition according to any one of the above (1) and (2), wherein the metal coordination compound is a metal chelate compound.

(4) The polishing composition according to the above (3), wherein the metal chelate compound is an EDTA iron salt.

(5) The polishing composition according to (4), wherein the EDTA iron salt is at least one selected from a monoammonium salt and a monosodium salt.

(6) The polishing composition according to any one of (1) to (5) above, wherein the oxidizing agent is ammonium peroxodisulfate.

(7) The polishing composition according to any one of the above (1) to (6), wherein the silicon oxide is at least one selected from colloidal silica, fumed silica, and white carbon.

(8) The polishing composition according to any one of the above (1) to (7), wherein the average particle diameter of the secondary particles of silicon oxide is 0.03 to 0.5 μηι.

(9) The polishing composition according to any one of the above (1) to (8), wherein the pH is 1 to 8.

(10) The polishing composition according to any one of the above (2) to (9), wherein the pH adjuster is at least one selected from nitric acid and phosphonic acid compounds.

(11) The polishing according to (10) above, wherein the phosphonic acid compound is at least one selected from phosphoric acid, 1-hydroxyxetane-11,1-diphosphonic acid, and aminotrimethylenephosphonic acid. Composition.

(12) The polishing composition according to any one of the above (1) to (11), which is used for polishing a magnetic disk substrate provided with a Ni i plating.

(13) A magnetic disk substrate polishing method for polishing a magnetic disk substrate using the polishing composition according to any one of the above (1) to (12).

(14) A method for polishing a magnetic disk substrate provided with a Ni-P plating. A method for polishing a magnetic disk substrate, which suppresses conversion of trivalent Fe ions to oxides or hydroxides.

(15) Oxide or water of trivalent Fe ion by adjusting pH The method for polishing a magnetic disk substrate according to the above (14), wherein the change to an oxide is suppressed.

(16) The method of polishing a magnetic disk substrate according to the above (14), wherein the complex retains Fe ions to suppress the change of trivalent Fe ions into oxides or hydroxides.

(17) A magnetic disk substrate obtained by polishing using the polishing composition according to any one of (1) to (12).

(18) The magnetic disk substrate according to the above (17), wherein the magnetic disk substrate is a substrate provided with NIP plating.

(19) The magnetic disk substrate as described in (18) above, wherein the magnetic disk substrate is a substrate subjected to NiP plating by electroless plating.

(20) A magnetic disk substrate obtained by polishing by the magnetic disk substrate polishing method according to any one of (13) to (16). BEST MODE FOR CARRYING OUT THE INVENTION

The silicon oxide contained as an abrasive in the polishing composition of the present invention is not particularly limited, and may be colloidal silica, fumed silica, or white carbon. These may be used alone or in combination of two or more. It is preferred that the average particle size of the secondary particles of oxide Kei element is 0. 0 3~ 0. 5 μ _πι. The average particle diameter of the secondary particles is a value measured by a laser-Doppler frequency analysis type particle size distribution analyzer, Microtrac UPA150 (manufactured by oneywe 11).

When the secondary particle diameter of silicon oxide is large, gelation and aggregation of fine particles are easily suppressed, but the probability of existence of coarse particles is also high, which causes polishing scratches. In addition, when the secondary particle diameter is small, the above-mentioned gelation and aggregation tend to occur, which also causes polishing scratches. Therefore, the average particle diameter of the secondary particles of silicon oxide contained as an abrasive in the polishing composition of the present invention is preferably in the range of 0.3 to 0.5 μππ, more preferably 0.03 to 0.5 μπι. Those having 4 to 0.2 ^ m are more preferable.

The metal coordination compound used in the present invention is a complex salt such as a metal chelate compound in a broad sense. Examples of the metal chelate compound include, but are not limited to, EDTA (ethylenediaminetetraacetic acid) and N-diaminetriacetic acid hydroxy. Examples include metal salts having ligands such as ethylene (NHEDTA) and ammonia triacetic acid (NTA). As a metal of the metal salt, it has a high oxidizing ability with respect to Ni, and it can exist in at least two or more different valence states other than zero valence. A metal having an oxidation number higher than the oxidation number in another valence state is suitable, and iron (F e) is particularly preferable. The possible reasons are as follows. Fe is more stable than trivalent than divalent ions, and the trivalent Fe ions oxidize Ni to become divalent Fe ions. The oxidized Ni becomes a hydrate or an oxide in the presence of water. Polishing proceeds by removing the hydrate or oxide with abrasive grains. The divalent Fe ion is converted to a trivalent ion by the oxidizing agent described below, and is retained as a metal chelate compound, for example, an iron salt of EDTA. It is assumed that these reactions are performed repeatedly.

The metal chelate compound used in the present invention is not particularly limited, but is preferably an iron salt of EDTA, and more preferably a monoammonium salt or a monosodium salt. It is effective to add a large amount of iron nitrate, iron chloride, etc. if only increasing the polishing rate. It can be tricky.

The oxidizing agent used in the present invention is not particularly limited, but may be an ammonium salt, a potassium salt, a sodium salt, an ammonium salt of sodium peroxoborate, a sodium salt, or a sodium salt of peroxodisulfuric acid. Peroxo acid salts such as lithium salts and potassium salts, peroxides such as permanganate, dichromate, nitrate, sulfate, and hydrogen peroxide, and perchlorates, etc. Salts are preferred, and ammonium peroxodisulfate is particularly preferred. These may be used alone or in combination of two or more.

Since the oxidizing agent oxidizes not only Fe which has become divalent by oxidizing Ni but also Ni, the polishing rate is increased by a synergistic effect of these. However, the Fe ions returned from divalent to trivalent by the oxidizing agent also change to hydroxides or oxides in the absence of a complex such as a chelate compound. In this state, the trivalent Fe ions are effectively used. Does not work.

Therefore, if trivalent Fe ions are retained in the complex, hydroxide and oxidation As a result, the Fe ions continue to function effectively without changing the material, so that a higher polishing rate can be obtained. However, if the stability as a complex salt increases, ions cannot be retained and the effect as a complex salt is low, but the trivalent EDTA iron salt has a high complexation constant and is extremely stable. For this reason, it is possible to effectively function as trivalent Fe ions without changing Fe into a hydroxide or an oxide, and thus obtain a high polishing rate.

When the abrasive is colloidal silica, gelation may occur. In this case, by adding EDTA iron salt, the dispersibility becomes better and gelation can be suppressed.

In addition, if EDTA iron salt is used as the Fe source, a high polishing rate can be obtained even when the pH of the polishing composition is set to 1 to 8, so the use of EDTA iron salt is trivalent. It is very useful in terms of iron stability, gelation prevention, and pH.

The concentration of silicon oxide in the polishing composition of the present invention is 3% by mass. /. (Hereinafter, unless otherwise specified,% is expressed by mass./.) If it is less than 10%, the polishing rate is significantly reduced. The polishing rate increases as the concentration increases. However, when the concentration exceeds 30%, not only the polishing rate does not increase but also gelation tends to occur particularly in colloidal silica. Therefore, considering the economic efficiency, the upper limit of the silicon oxide concentration is practically 30%. Therefore, the concentration of silicon oxide in the composition is preferably in the range of 3 to 30%, more preferably 5 to 15%.

The amount of the metal coordination compound used in the polishing composition of the present invention is preferably from 1 to 10%, more preferably from 2 to 6%.

1. The amount of metal coordination compound added. /. If it is less than 3, the effect of accelerating polishing is low, and gelation is liable to occur. Further, even if the addition amount of the metal coordination compound exceeds 10%, the polishing promotion effect does not increase.

The amount of the oxidizing agent used in the polishing composition of the present invention is preferably from 1 to 10%, more preferably from 3 to 7%.

When the amount of the oxidizing agent is less than 1%, the effect of accelerating the polishing is reduced. In addition, even if the added amount of the oxidizing agent exceeds 10%, the effect of promoting the polishing is not increased.

The pH adjuster used in the present invention is not particularly limited, but may be nitric acid, At least one member selected from the group consisting of sulfonic acid compounds is preferred. Specific examples of the phosphonic acid compound include phosphoric acid, 1-hydroxylethane 1,1,1-diphosphonic acid (C ₂ H ₆ 〇 ₇ P ₂₎ Moshiku is § Mi Roh Application Benefits Mechirenhosuho phosphate (C _₂ H ₁ ₂ 〇 ₉ P ₃ N) can be exemplified. These may be used alone or in combination of two or more. These are preferably added within 2%. This allows the pH in the composition to be adjusted preferably to 1-8.

The concentrations of the above-mentioned components are those at the time of polishing the magnetic disk substrate. When a polishing composition is manufactured and transported, it is efficient to use a composition having a concentration higher than the above concentration and dilute it to the above concentration before use. The polishing composition for a magnetic disk substrate of the present invention may contain, in addition to the above components, additives usually used in the polishing composition, such as a surfactant and a preservative. However, careful attention must be paid to the type and amount of addition so as not to cause gelation.

The polishing composition of the present invention is prepared by suspending silicon oxide in water, adding a metal coordination compound such as iron salt of EDTA, an oxidizing agent such as ammonium peroxodisulfate, a pH adjusting agent, and the like. can do. When used, the mixture of all components may be diluted and used.However, two sets of additive components, for example, water, silicon oxide, metal coordination compound and water, oxidizing agent, pH adjustment Prepare the ingredients separately and mix the two sets. The polishing composition of the present invention can be used for a substrate for high recording density (typically, a recording density of 3 Gbit / inch ² or more, typified by a magnetic disk for magnetic head utilizing the magnetoresistance (MR) effect). However, it can also be applied to magnetic disks having a recording density lower than that, from the viewpoint of improving reliability.

The magnetic hard disk substrate to which the polishing composition of the present invention is applied is not particularly limited, but an aluminum (including alloy) substrate, in particular, NiP is plated by, for example, electroless plating. When the composition of the present invention is applied to the prepared aluminum substrate, mild mechanical polishing action by silicon oxide, redox ability of Fe in EDTA iron salt, oxidizing action of ammonium peroxodisulfate, and EDTA iron salt The stability of the Fe ion as a complex of the above functions as described above, and a high-quality polished surface can be industrially advantageously obtained. The polishing method is generally a method in which a polishing pad used for a slurry-like abrasive is rubbed on a magnetic disk substrate, and the pad or the substrate is rotated while supplying slurry between the pad and the substrate.

A magnetic disk made from a substrate polished with the polishing composition of the present invention has a very low frequency of occurrence of minute defects such as micropits and microcracks, and has a low surface roughness (Ra). About 3 A, very excellent in smoothness. Example

Hereinafter, examples of the present invention will be specifically described, but the present invention is not limited to these examples.

Table 1 shows silicon oxide (silica) and titania used in Examples and Comparative Examples.

(Examples 1 to 11)

Water, EDTA iron ammonium, ammonium peroxodisulfate, and a pH adjuster were added to DuPont Co., Ltd. (Saiton HT-500F) manufactured by DuPont in the ratios shown in Table 2 for various aqueous polishing. A composition was prepared and polished with the following polishing apparatus and polishing conditions. The results are shown in Table 2. The particle size was measured with a laser Doppler frequency analysis type particle size distribution analyzer, Microtrac UPA150 (manufactured by Honeywell). Table 1 shows the measured particle size.

(Examples 12 and 13)

White carbon (E-150 J) manufactured by Nippon Silica Kogyo Co., Ltd. and fumed silica (AERO SIL 50) manufactured by Nihon Aerosil Co., Ltd. are pulverized by a medium stirring mill, and coarse particles are formed by sizing. After removal, silicon oxide having an average secondary particle diameter of 0.1 μm was first obtained. Next, water, EDTA iron ammonium, ammonium peroxodisulfate, and a pH adjuster were added at the ratios shown in Table 2 to prepare various aqueous polishing compositions.The polishing apparatus and polishing conditions shown below were used. Was polished. The results are shown in Table 2.

Polishing

Substrate used

3.5 inch aluminum disk with electroless NiP Polishing equipment and polishing conditions used

Polishing tester 4-way double-sided polycinder machine

Polishing pad Suede type (Polytex DG, Dale mouth)

Lower platen rotation speed 60 rpm

Slurry supply speed… · ■ 50 m 1 Z min

Polishing time 5 minutes

Processing pressure 50 g / cm ²

Evaluation of polishing characteristics

Polishing rate ······ Calculated from weight loss before and after polishing of aluminum disk

Uses surface roughness tally step and tally data 20000 (rank tailor made by Hobson)

The depth of the polishing flaws and polishing pits was determined by three-dimensional mode analysis using a stylus-type surface analyzer P-12 (manufactured by TENCOR). Table 2 shows the evaluation results of the polishing characteristics. The polishing flaw A in Table 2 has a polishing flaw depth of 5 nm or less, and the pit A has a pit depth of 5 nm or less. Polishing scratch B has a polishing scratch depth of 5 to 10 nm, and pit B has a pit depth of 5 to 10 nm. Those having a polishing scratch depth of more than 10 nm and those having a pit depth of more than 10 nm did not occur in both Examples and Comparative Examples. (Comparative Examples 1 to 5)

Water, EDTA iron salt, ammonium peroxodisulfate, and iron nitrate were added to a colloidal silicide (Cyton HT-5 OF) manufactured by DuPont at a ratio shown in Table 2 to prepare an aqueous polishing composition. Polishing was performed in the same manner as in Examples. The results are shown in Table 2.

(Comparative Example 6)

Titanium oxide (Super Titania F-12) manufactured by Showa Titanium Co., Ltd. is pulverized by a medium stirring mill and coarse particles are removed by sizing to obtain titanium oxide having an average secondary particle diameter of 1.3 m. Was. Next, water and aluminum nitrate were added at the ratios shown in Table 2 to prepare an aqueous polishing composition, and polished in the same manner as in the examples. The results are shown in Table 2. □ α name ー圣

(urn) (m) Oxidized key (1) Sitton 50— 50F 0. 05 0. 05 Oxidized key (m②) Ε-150 J 0.03 03. 0.1 Titanium oxide (Nya) F-2 0.06 0.3

(Below margin

Lab EOTA- 妷ゥ its λH lab table ffifisa lab 8WI bit

(Ra)

^ Kift (wa) (nm) Wei w 1 Siri 2 4.0 5.o HEDP 0.20 0.20 0.2 A A

2 6 4.0 6.00 JJ 0.2 0.22 0.2 A A

3 15 4. 0 5.O 0-2 0.23 0.2 A A

4 6 I. 0 5.0 0 0.2 0 0.20 0.2 A A

5 »6 10. 0 5. 0» 0.2 0 0.22 0.2 A A

6 6 4. 0 1. 0) 0.2 0. 20 0-2 A A

7 6 4. 0 0. 0 0. 2 0. 23 0.2 A A a 6 4. 0 5.0 0. 20 0.2 A A

9 64.0 5.0 v o.30.20 0.2 AA 10 64.0.O Phosphoric acid 0.2 0.20.20 0.2 AA 1 16.4.05 Oo. l 0.22 0.2 AA

1 2 Siri 4 <2) 6 4.0.0 5.0 HEDP 0.2 0.22 0.2 A A

1 3 Series 6 4. 0 6. O "0.2 0.22 0.2 A A Comparison I 1 Series D 6 4.0 0.12 0.2 B A

2 6 5.0 0.15 0.2 A A

3 6 2.o 0.18 0.2 A A

4 6 m, o. 3 0.09 0.2 A A

5 6 si o. 3 5.0 0.16 0. 2 A A

6 rr-6 Fiber Al B. o 0.21 0.2 0.4 B B

HEDP:-\ L \ '^ XTI-\, \-V

≠ 2 Industrial applications

When a disk is polished using the polishing composition of the present invention, the surface roughness of the disk can be extremely reduced, and the polishing can be performed at a high speed. Magnetic disks using polished disks are useful as low-floating-type hard disks, and enable high-density recording.

In particular, its usefulness as a high-density medium (having a recording density of 3 Gbit / inch ² or more) typified by an MR head medium utilizing the magnetoresistance effect of a magnetic disk using a polished disk. However, it is useful for media of lower quality because it is a highly reliable media.

Claims

The scope of the claims

1. A composition for polishing a magnetic disk substrate, comprising water, silicon oxide, a metal coordination compound, and an oxidizing agent.

2. The polishing composition according to claim 1, further comprising a pH adjuster.

3. The polishing composition according to claim 1, wherein the metal coordination compound is a metal chelate compound.

4. The polishing composition according to claim 3, wherein the metal chelate compound is an EDTA iron salt.

5. The polishing composition according to claim 4, wherein the EDTA iron salt is at least one selected from a monoammonium salt and a monosodium salt.

6. The polishing composition according to any one of claims 1 to 5, wherein the oxidizing agent is ammonium peroxodisulfate.

7. The polishing composition according to any one of claims 1 to 6, wherein the silicon oxide is at least one selected from colloidal silica, fumed silica, and white carbon.

8. The polishing composition according to any one of claims 1 to 7, wherein the average particle diameter of the secondary particles of silicon oxide is 0.03 to 0.5 / zm.

9. The polishing composition according to any one of claims 1 to 8, wherein the pH is 1 to 8.

10. The polishing composition according to any one of claims 2 to 9, wherein the pH adjuster is at least one selected from nitric acid and phosphonic acid compounds.

11. The polishing composition according to claim 10, wherein the phosphonic acid-based compound is at least one selected from the group consisting of phosphoric acid, 1-hydroxyxanthane, 1,1-diphosphonic acid, and aminotrimethylenephosphonic acid. object.

12. The polishing composition according to any one of claims 1 to 11, which is used for polishing a magnetic disk substrate provided with NiP plating.

13. A magnetic disk substrate polishing method for polishing a magnetic disk substrate using the polishing composition according to any one of claims 1 to 12.

1 4. This is a method for polishing a magnetic disk substrate provided with a Ni—P plating. A method for polishing a magnetic disk substrate that suppresses the conversion of trivalent Fe ions to oxides or hydroxides.

1 5. Oxide or water of trivalent Fe ion by adjusting pH 15. The method for polishing a magnetic disk substrate according to claim 14, wherein a change to an oxide is suppressed.

16. The method of polishing a magnetic disk substrate according to claim 14, wherein the Fe ions are held by the complex to suppress the change of trivalent Fe ions into oxides or hydroxides.

17. A magnetic disk substrate obtained by polishing using the polishing composition according to any one of claims 1 to 12.

18. The magnetic disk substrate according to claim 17, wherein the magnetic disk substrate is a substrate provided with a NiP plating.

19. The magnetic disk substrate according to claim 18, wherein the magnetic disk substrate is a substrate subjected to NiP plating by electroless plating.

20. A magnetic disk substrate obtained by polishing by the magnetic disk substrate polishing method according to any one of claims 13 to 16.