JP2850254B2 - Abrasive composition - Google Patents

Description

The present invention relates to an abrasive composition. More specifically, the present invention relates to an abrasive composition containing water, α-alumina, boehmite, and a water-soluble peroxide, and for chemically and mechanically polishing memory hard disks.

[Prior Art] Conventionally, an abrasive composition comprising water and alumina has been known (for example, see Japanese Patent Application Laid-Open No. 54-89389), but the polishing rate is not sufficient. As the diameter increases, the polished surface becomes rough,
It could not be said that both the polishing rate and the surface condition were satisfied.

In the past decade, the precision polishing of materials such as silicon and compound semiconductor substrates, various magnetic memory hard disks, and laser parts, for which the production on an industrial scale has increased dramatically, has been particularly demanded on the smoothness of the processed surface and the lack of smoothness. The required level of defectivity (the absence of defects such as scratches, orange beer, bits, nodules, cracks, etc.) has become much more advanced than the past polishing technology level,
Since a large amount of investment is required for production, inspection equipment, etc., it is also an important issue to improve production speed and cut costs by reducing loss of defective defects.

Accordingly, there is an extremely strong demand for polishing agents used in these fields to improve the processing speed and the polishing rate. In order to satisfy such a demand, the present inventors have found a polishing composition containing water, α-alumina and boehmite, and have applied for a patent (Japanese Patent Application No. 63-9385).

[Problems to be Solved by the Invention] As a result of further intensive studies to obtain a better abrasive composition satisfying the above-mentioned demands,
When boehmite and water-soluble peroxide are present in the abrasive composition composed of water and α-alumina, polishing such as smoothness of the processed surface of the workpiece or prevention of generation of surface defects (scratch, orange beer, etc.). The inventors have found that the polishing rate can be greatly improved without lowering the finishing effect, and the present invention has been completed.

[Means for Solving the Problems] The gist of the present invention resides in an abrasive composition containing water, α-alumina, boehmite, and a water-soluble peroxide.

 Hereinafter, the present invention will be described in more detail.

As the α-alumina used in the present invention, although not particularly limited, alumina other than α-alumina such as bayerite, gypsite, hydrazirite, boehmite, γ-alumina, and θ-alumina, 1100 ° C. or more according to a conventional method Alumina obtained by calcining at a temperature of 0.1 wt. The higher the firing temperature, the higher the polishing rate tends to be.
Α-Alumina obtained by firing at 1200 ° C. or higher and 1200 ° C. to 1500 ° C. is preferable.

Considering processing accuracy and polishing rate, α-alumina used in the present invention has an average particle size of 0.1 to 10 μm, preferably 0.1 to 10 μm.
~ 3μ, and the maximum particle size is 30μ or less, preferably 20μ
It is the following fine powder. Therefore, α-alumina obtained by calcination is pulverized by a conventional fine pulverizer, ie, a ball mill or a vibration mill in a wet slurry method, and coarse particles are classified by a device such as gravity sedimentation, centrifugal sedimentation, or a dry method. That is, the particles are sized to a desired particle size by a pulverizing and classification process using a jet stream.

The content of α-alumina is 1 to 30 with respect to the total amount of the composition.
% By weight, preferably 2 to 15% by weight. If the amount is too small, the polishing rate will decrease. Conversely, if the amount is too large, uniform dispersion cannot be maintained, and the viscosity of the slurry will be excessive, making handling difficult.

On the other hand, boehmite is one type of alumina hydrate.
Alumina hydrate includes gypsite, vialite, norstrandite, boehmite, diaspore, and the like depending on the crystal form, but the abrasive composition of the present invention is required to contain boehmite.

Boehmite is obtained by subjecting gypsite or the like to pressurized hydrothermal treatment at about 250 ° C. or by hydrolysis of an aluminum organic compound [Al (OR) ₃ ] (where R is an alkyl group) synthesized by the Ziegler method. It is commonly produced by a method of manufacturing, alumina sol, ceramic binder,
Textile products, carpet antistatic treatment, water purification treatment,
It is an industrial material widely used as a raw material for cosmetics, ointment thickeners, alumina-based catalysts or catalyst carriers.

Boehmite, a material represented by Formula a AlOOH or _{Al 2 O 3 · H 2 O} , as the powder product, for example, KAISER (USA), VISTA Chemical (USA), available from Condea Chemie (Germany), etc. ing. For example, 95%, 45%
When a powder consisting of particles of 50% or less is stirred and dispersed in water or acidic water, it is dispersed in the form of ultrafine particles, which are partially fibrous, mostly granular, and have a size of 0.01μ or less. ,
It has the property of forming a colloidal sol. The boehmite sol has an isoelectric point of 9.4, and it is observed by electrophoresis that the particles themselves are positively charged.

The boehmite dispersed in water in the present invention may be a powder or a boehmite sol. In any case, a boehmite that forms a sol having a particle size of 0.01 μm or less when dispersed in water is used. The boehmite content is 0.1 to 20% by weight, preferably 0.5 to 10% by weight, based on the total amount of the composition. When the boehmite content is too small, the effect of improving the polishing rate cannot be expected.On the other hand, when the boehmite content is too large, the apparent viscosity, thixotropy increases, and the uniform dispersibility of α-alumina is impaired. Physical properties unsuitable for handling, such as difficulty in removal from the container.

Further, in the present invention, it is necessary to add a water-soluble peroxide to a system comprising water, α-alumina and boehmite.

Examples of the water-soluble peroxide include hydrogen peroxide, sodium peroxide, potassium peroxide, calcium peroxide, barium peroxide, alkali metal or alkaline earth metal peroxides such as magnesium peroxide, sodium peroxocarbonate, Peroxocarbonates such as potassium peroxocarbonate and ammonium peroxocarbonate, peroxosulfates such as sodium peroxosulfate, potassium peroxosulfate and ammonium peroxosulfate, peroxophosphates such as sodium peroxophosphate, potassium peroxophosphate and ammonium peroxophosphate, peroxo Inorganic peroxides such as sodium perborate, potassium peroxoborate and peroxoborate such as ammonium peroxoborate; and organic peroxides such as formic acid, peracetic acid and perpropionic acid.

Of these, hydrogen peroxide, sodium peroxide, peroxides of alkali metals or alkaline earth metals such as potassium peroxide, peroxocarbonates such as sodium peroxocarbonate, since they are relatively inexpensive and readily available,
Sodium peroxosulfate, potassium peroxosulfate,
It is preferable to use inorganic peroxides such as peroxosulfates such as ammonium peroxosulfate, and peroxoborates such as sodium peroxoborate.

The amount of the water-soluble peroxide used is 0.05% based on the total amount of the composition.
-20% by weight, preferably 0.1-5% by weight. If the amount is too small, the effect of the present invention cannot be expected.
On the other hand, if the amount is too large, the polishing rate does not increase temporarily, and the finish of the polished surface may be impaired by the corrosive action of the object to be polished by oxygen generated from the water-soluble peroxide.

Although the details of the abrasive composition of the present invention having an excellent polishing effect are unknown, the presence of boehmite first affects the dispersion and aggregation of α-alumina particles that are abrasive components,
At the same time, atomic oxygen generated from the water-soluble peroxide acts on the surface of the object to be polished, so-called mechanochemical polishing is performed, and it is considered that these two actions act synergistically to exhibit excellent effects.

The polishing composition of the present invention can be adjusted by mixing and stirring the above components, and the mixing order and the like are not particularly limited. However, after the addition of the water-soluble peroxide, as a general property of the peroxide, spontaneous decomposition proceeds and free gaseous oxygen is released. Care must be taken because the internal pressure may increase in a closed container.

Therefore, when using the abrasive composition of the present invention, for example, in the abrasive composition supply tank provided in the vicinity of the polishing machine or in the vicinity of the component mixture of the abrasive composition other than the water-soluble peroxide It is preferable to add a water-soluble peroxide at the time of use, such as a method of adding a water-soluble peroxide, or a method of mixing each component at the time of use.

When adjusting the abrasive composition, various known additives such as the following may be added according to the necessary conditions for polishing, such as the type of the workpiece and the processing conditions.

Examples of the additive include water-soluble alcohols such as ethanol, propanol and ethylene glycol, surfactants such as formalin condensate of sodium alkylbenzene sulfonate and naphthalenesulfonic acid, sulfuric acid, hydrochloric acid,
Examples thereof include acids such as nitric acid and acetic acid, organic polyanionic substances such as lignin sulfonate, carboxymethyl cellulose salt and polyacrylate, and celluloses such as cellulose, carboxymethyl cellulose and hydroxyethyl cellulose.

The pH of the polishing composition of the present invention is 3 to 8, preferably 4 to 7. pH is the type of water-soluble peroxide,
Although it fluctuates depending on the amount added, water-
If the pH is adjusted to the alkaline side with an alumina-based abrasive, the viscosity becomes high, the clogging of the polishing pad made of a porous network deteriorates, and the occurrence of scratches on the surface of the workpiece tends to occur. It is customary to adjust the pH to the acidic side, and a small amount of acids may be added for this purpose.

The polishing composition of the present invention is used for polishing metals, glass, plastics and the like, but is particularly suitable for polishing memory hard disks and the like because a polishing surface free from defects can be obtained.

[Examples] Hereinafter, the present invention will be described specifically with reference to Examples.
The present invention is not limited to the following examples unless it exceeds the gist.

Examples 1 to 12 and Comparative Examples 1 and 2 [Preparation of Abrasive Composition] α-Alumina was fired at 1300 ° C. for 5 hours and pulverized and sized by a dry method (average particle diameter).
0.54 μm and a maximum particle diameter of 8 μm) were dispersed in water using a high-speed mixer to prepare a slurry having an α-alumina concentration of 6% by weight.

Boehmite and a water-soluble peroxide were added and dispersed in the proportions shown in Table 1 to prepare an abrasive composition.

As boehmite, Pural manufactured by Condea Chemie
(Trade name) SCF (average particle diameter of about 20 μ) was used.

[Polishing test] 3.5-inch memory hard disk (external diameter about 95 m / m) with electroless plating of nickel and phosphorus (alloy plating layer of nickel 90-92%, phosphorus 10-8%) on an aluminum substrate as a workpiece Substrate was used.

This disc is loaded into a double-side polishing machine and polished. The disk is loaded into a double-sided polishing machine in which a suede-type polyurethane substrate polishing pad is mounted on the upper and lower platens of the polishing machine, respectively, and the disc and both polishing pads are relatively slid to perform polishing for 5 minutes. Was.

The polishing was performed at a processing pressure of 100 g / cm ² by supplying the above-mentioned abrasive sample at a rate of 300 cc / min between the disk and both polishing pads.

After polishing, the disk was taken out from the double-side polishing machine, and ultrasonic cleaning was repeated to clean the processed surface of the disk, and the degree of surface defects was evaluated by visual inspection.

Next, the thickness of the disk was measured, and the average polishing rate per minute was calculated from the amount of decrease in the thickness.

 The test results are as shown in Table 1.

[Effect of the Invention] The abrasive composition according to the present invention in which boehmite and a water-soluble peroxide are added to an α-alumina-water dispersion system has a surface that is polished by chemically and mechanically polishing memory hard disks. A higher polishing rate can be achieved without generating defects, and the polishing efficiency can be increased. Moreover, since the polishing composition of the present invention has a high polishing rate, the polishing cost is reduced due to a reduction in polishing processing time, a reduction in consumption of the polishing agent, abrasion of expensive polishing pads, a reduction in deterioration, and the like, and is extremely useful. It is.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-188264 (JP, A) JP-B-62-19511 (JP, B2) (58) Fields investigated (Int. Cl. ⁶ , DB name) C09K 3/14 B24B 37/00 G11B 5/858 H01F 41/14 WPI (QUESTEL) CA (STN)

Claims (1)

(57) [Claims] An abrasive composition comprising water, α-alumina, boehmite, and a water-soluble peroxide, wherein the hard disk is chemically and mechanically polished.