JP2003193037A - Polishing composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a new polishing composition which can prevent the development of surface defects having the following characteristics: (1) the surface defects are developed on a partial or whole surface of a substrate for a magnetic disk, (2) the surface defects are the assembly of fine scratches having a depth of about 5 nm thick scratches, and (3) the scratches are extended in an approximately specific direction (in many cases, in the diameter direction of a magnetic disk). <P>SOLUTION: This polishing composition is characterized by comprising (A) at least one selected from formic acid, acetic acid, succinic acid, malic acid, maleic acid, malonic acid, butyric acid, oxalic acid, iminodiacetic acid, dl- mandelic acid, and l-glutamic acid acidic salt, (B) silica, and (C) water. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a polishing composition used for polishing a magnetic disk substrate.

[0002]

2. Description of the Related Art Generally, in a process of manufacturing a magnetic disk, a polishing composition is used for polishing to remove undulations and irregularities of a magnetic disk substrate and smooth the surface. As the polishing composition used for polishing the magnetic disk substrate, various compositions have been proposed in which various abrasives are combined with a polishing accelerator and other additives.

[0003]

DISCLOSURE OF THE INVENTION The inventors of the present invention have investigated in detail the surface of a magnetic disk substrate polished by using a conventional polishing composition. With the increase in disk capacity, the surface precision required for magnetic disk substrates has become more severe, and new surface defects that could affect the characteristics of magnetic disks have been discovered. The features of this surface defect are (1) occurrence on a part or the whole surface of the magnetic disk substrate,
(2) A collection of minute scratches with a depth of about 5 nm, (3) The direction of the scratches extends almost along a specific direction (in most cases, the radial direction of the magnetic disk substrate), etc. Is mentioned. However, the cause of this defect is currently unknown.

The object of the present invention is to provide a polishing composition capable of suppressing the generation of surface defects having the above-mentioned characteristics (1) to (3) newly found by the present inventors. Especially.

[0005]

In order to achieve the above object, the invention according to claim 1 is a polishing composition for use in polishing a magnetic disk substrate, comprising: (A) formic acid; At least one selected from acetic acid, succinic acid, malic acid, maleic acid, malonic acid, butyric acid, oxalic acid, iminodiacetic acid, dl-mandelic acid and 1-glutamic acid acid salt, (B) silica, and (C) water The gist is that it contains and does not contain (D) an oxidizing agent.

According to a second aspect of the invention, in the polishing composition according to the first aspect, the compound (A) contains formic acid, acetic acid, succinic acid, malic acid, maleic acid or malonic acid. Is the gist.

A third aspect of the invention is characterized in that the polishing composition according to the first or second aspect contains 0.1 to 3% by weight of the compound (A).

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments embodying the present invention will be described below. The polishing composition in the present embodiment is (A) formic acid, acetic acid, succinic acid, malic acid, maleic acid, malonic acid, butyric acid, oxalic acid, iminodiacetic acid, dl-
It is composed of at least one selected from mandelic acid and 1-glutamic acid acid salt, (B) silica, and (C) water.

First, the compound (A) will be described. Formic acid, acetic acid, succinic acid, malic acid, maleic acid, malonic acid, butyric acid, oxalic acid, iminodiacetic acid, dl-mandelic acid and 1-glutamic acid acid salt are used to accelerate the polishing of the magnetic disk substrate by a chemical action. Play a role as an agent. At the same time, it also plays a role of suppressing the occurrence of surface defects having the above-mentioned features (1) to (3) when the magnetic disk substrate is polished by using the polishing composition of the present embodiment. . These compounds reduce the friction generated between the magnetic disk substrate, the polishing pad and silica during the polishing process, and weaken the force of the polishing pad scratching the surface of the magnetic disk substrate, thereby causing the above surface defects. Is supposed to suppress.

The polishing composition contains formic acid, acetic acid, succinic acid, malic acid, maleic acid, malonic acid, butyric acid, oxalic acid, iminodiacetic acid, dl-mandelic acid and 1-glutamic acid as the compound (A). At least one selected from salt is blended. Among them, formic acid, acetic acid, succinic acid, malic acid, maleic acid or malonic acid are preferable, and formic acid or acetic acid is more preferable. The 1-glutamic acid acid salt is preferably 1-glutamic acid hydrochloride.

The amount of the compound (A) compounded in the polishing composition is preferably 0.05 to 5% by weight, more preferably 0.1 to 3% by weight, most preferably 0.3 to 2% by weight. preferable. Next, the silica (B) will be described.

Silica (silicon dioxide) plays the role of an abrasive for polishing the magnetic disk substrate by a mechanical action. Specific examples of silica include colloidal silica and fumed silica, and among them, colloidal silica is preferable. The particle size of silica is preferably 5 to 200 nm, more preferably 10 to 150 nm, and more preferably 15 to 10 as the average particle size obtained from the surface area measured by the BET method.
0 nm is the most preferable. The amount of silica blended is 0.1 to 4
0 wt% is preferable, 1 to 30 wt% is more preferable,
Most preferred is 3 to 25% by weight.

Next, the water (C) will be described. Water that plays a role as a dispersion medium and a solvent is preferably water containing as little impurities as possible, and specifically, water obtained by filtering ion-exchanged water or distilled water is preferable.

Next, at least the above-mentioned (A) formic acid, acetic acid, succinic acid, malic acid, maleic acid, malonic acid, butyric acid, oxalic acid, iminodiacetic acid, dl-mandelic acid and 1-glutamic acid acid salt are selected. A polishing composition composed of one type, (B) silica, and (C) water will be described.

The polishing composition of the present embodiment comprises (C) water and (A) formic acid, acetic acid, succinic acid, malic acid, maleic acid, malonic acid, butyric acid, oxalic acid, iminodiacetic acid, dl-
It is prepared by mixing and dissolving and dispersing at least one selected from mandelic acid and 1-glutamic acid acid salt, and (B) silica. The dispersion method is arbitrary, and examples thereof include stirring with a blade-type stirrer and ultrasonic dispersion.

The pH of the polishing composition is preferably lower than 7, more preferably lower than 4. The polishing composition of this embodiment is used for polishing a magnetic disk substrate. Among the magnetic disk substrates, it is preferable to use the Ni-P substrate having the surface of the blank material electrolessly plated with a nickel-phosphorus alloy by polishing. However, the use of the polishing composition of the present embodiment is not limited to the polishing process of Ni-P substrate, and Ni-Fe substrate, boron carbide substrate, carbon substrate, etc.
Of course, it may be used for polishing a magnetic disk substrate other than the P substrate.

The polishing composition of this embodiment is preferably used for finish polishing in the polishing process of the magnetic disk substrate. However, of course, it may be used in the polishing process in a stage before the finish polishing process.

The effects obtained by this embodiment will be described below. -The polishing composition of the present embodiment can suppress the occurrence of surface defects having the above-mentioned features (1) to (3) newly found by the present inventors. In addition, if formic acid, acetic acid, succinic acid, malic acid, maleic acid or malonic acid is used as the compound (A), the effect can be further enhanced, and if formic acid or acetic acid is used, the effect can be further enhanced. be able to.

Since the polishing composition of the present embodiment does not contain an oxidizing agent, the effect of suppressing the above-mentioned surface defects is not hindered by the action of the oxidizing agent. If the compound (A) is blended in an amount of 0.05 to 5% by weight,
The effect of suppressing the above surface defects can be exhibited more reliably. Further, if the compounding amount of the compound (A) is 0.1 to 3% by weight, the effect can be further enhanced, and
If the amount is 3 to 2% by weight, the effect can be further enhanced.

The above embodiment may be modified as follows. -Various additives generally used in conventional polishing compositions may be added to the polishing composition of the above embodiment.

The polishing composition may be prepared as a stock solution having a relatively high concentration, and may be diluted with water when used for polishing. According to this structure, it is possible to improve handleability during storage and transportation.

[0022]

EXAMPLES Next, the present invention will be described more specifically with reference to Examples and Comparative Examples. Colloidal silica and each compound shown in Table 1 below were mixed with ion-exchanged water to prepare polishing compositions.

With respect to the polishing compositions of Examples 1 to 8 and Comparative Examples 1 to 8, the pH was measured and the following two items were measured and evaluated. The results are shown in Table 1.

<1. Polishing Efficiency> Using the polishing composition of each example, the magnetic disk substrate (Ni
-P substrate) was subjected to polishing processing, and the value of the polishing efficiency was obtained based on the following calculation formula. However, the value of the polishing efficiency in Table 1 is an average value of 10 sheets in one batch. Polishing efficiency [μm / min] = weight reduction of magnetic disk substrate by polishing [g] ÷ (area of surface to be polished of magnetic disk substrate [cm ² ] × nickel-phosphorus plating density [g / cm ³ ] × Processing time [min]) × 10000 Polishing processing condition Polishing object: Chapman 2000PLUS (Cha
Surface roughness R measured by pman (USA)
φ that was pre-polished so that the value of a was about 10Å
3.5 "(≈95 mm) electroless Ni-P substrate, machine: double-side polishing machine (manufactured by Speedfam Co., Ltd .;
SFDL-9B), polishing pad: BELLATRIX
N0058 (Kanebo Corporation), processing pressure: 100
g / cm ² (≈10 kPa), lower platen rotation speed: 20 rp
m, supply amount of polishing composition: 30 ml / min, processing time:
15 minutes <2. Surface Defect> The surface of the magnetic disk substrate after polishing was observed using a differential interference microscope (MX50; manufactured by Olympus Optical Co., Ltd., objective lens 5 ×, eyepiece 10 ×). 20 surfaces of 10 magnetic disk substrates were observed, and the above (1) to (3) were observed.
When the number of the surfaces having the surface defect having the characteristics of 2 is 2 or less, it is evaluated as ⊚, 3 to 5 is evaluated as ◯, and 6 or more is evaluated as x.

[0025]

[Table 1] As shown in Table 1, each of the polishing compositions of the examples
The evaluation of surface defects was good. In addition, among them, when formic acid or acetic acid was used, the evaluation of surface defects tended to be particularly good. On the other hand, when an oxidizing agent (hydrogen peroxide) was used in combination, the polishing efficiency was improved, but on the other hand, the result was that the evaluation of surface defects was poor.

Next, the technical idea which can be understood from the above embodiment will be described below. The polishing composition according to claim 2, wherein the compound (A) contains formic acid or acetic acid.

[0027]

Since the present invention is constructed as described above, it has the following effects. According to the invention of claim 1, the present inventors newly found the following (1) to
It is possible to suppress the occurrence of surface defects having the feature (3). (1) It occurs on a part or the whole surface of the magnetic disk substrate. (2) A collection of minute scratches with a depth of about 5 nm. (3) The direction of the scratch extends substantially along a specific direction (in many cases, the radial direction of the magnetic disk substrate).

According to the invention of claim 2, claim 1
The effect of the invention described in (1) can be improved. According to the invention of claim 3, the effect of the invention of claim 1 can be exhibited more reliably.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Junichi Hirano             2-chome, 1 territory, Nishibiwajima-cho, Nishikasugai-gun, Aichi prefecture             Address 1 Fujimi Incorporated             In Ted (72) Inventor Noboru Anfuku             2-chome, 1 territory, Nishibiwajima-cho, Nishikasugai-gun, Aichi prefecture             Address 1 Fujimi Incorporated             In Ted (72) Inventor Tomohide Kamiya             2-chome, 1 territory, Nishibiwajima-cho, Nishikasugai-gun, Aichi prefecture             Address 1 Fujimi Incorporated             In Ted (72) Inventor Toshiki Owaki             2-chome, 1 territory, Nishibiwajima-cho, Nishikasugai-gun, Aichi prefecture             Address 1 Fujimi Incorporated             In Ted F term (reference) 3C058 AA07 CB02 DA02 DA17

Claims (3)

[Claims] 1. A polishing composition for use in polishing a magnetic disk substrate, comprising: (A) formic acid, acetic acid, succinic acid, malic acid, maleic acid, malonic acid, butyric acid, oxalic acid, iminodiacetic acid. At least one selected from dl-mandelic acid and 1-glutamic acid acid salt, (B) silica, and (C) water, and (D) no oxidizing agent. 2. The polishing composition according to claim 1, wherein the compound (A) contains formic acid, acetic acid, succinic acid, malic acid, maleic acid or malonic acid. 3. The polishing composition according to claim 1, which contains 0.1 to 3% by weight of the compound (A).