JPH02158682A - Abrasive composition - Google Patents

Abstract

PURPOSE:To provide an abrasive composition containing water, alpha-alumina and a metal nitrite and effective in remarkably improving the polishing speed without lowering the finished state of the polished object such as smoothness and prevention of the surface defects. CONSTITUTION:The objective composition having a pH of 3-8 (preferably 4-7) contains (A) water, (B) 1-30wt.%, (preferably 2-15wt.%) of fine powder of alpha-alumina preferably calcined at 1200-1500 deg.C and having an average particle diameter of 0.1-3mum and a maximum particle diameter of <=20mum and (C) 0.1-20wt.% (preferably 0.1-10wt.%) of a metal nitrite (preferably calcium nitrite, potassium nitrite, sodium nitrite, etc.).

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an abrasive composition.

Specifically, the present invention relates to an abrasive composition that has good polishing efficiency and can form an excellent polished surface.

[Prior art]

Hitherto, a polishing agent 4 composition consisting of water and alumina has been known (for example, see Japanese Patent Application Laid-Open No. Sho! 4t-g9Jg9).
The polishing rate was not sufficient, and when the alumina particle size was increased in order to increase the polishing rate, the 5iυF polished surface became rough, and it could not be said that both the polishing rate and the surface condition were satisfied.

In the past IO years, industrial-scale production has increased dramatically, especially in precision polishing of materials such as silicon and compound semiconductor substrates, magnetic memory node disks in each building, and laser parts. Requirements for surface smoothness and defect-free properties (no defects such as scratches, bits, nodules, cranks, etc.) have become much more sophisticated than in the past, and on the other hand, Since a large amount of investment is required for production, inspection equipment, etc., cost cutting by improving production speed and reducing losses due to defects is also an important issue.

Therefore, there is an extremely strong demand for improvements in processing accuracy and polishing speed for abrasives used in these fields.

[Problem to be solved by the invention]

The inventors of the present invention have conducted extensive research in order to create a better abrasive composition that satisfies such demands, and have added a metal nitrite to an abrasive composition consisting of water and α-alumina. When present, it is possible to significantly improve the polishing speed without reducing the smoothness of the processed surface of the workpiece or the polishing effect such as preventing surface defects (scratch, orange peel, etc.) from occurring. After learning this, the present invention was completed.

[Means to solve the problem]

The gist of the invention resides in an abrasive composition comprising water, alpha-alumina and a metal nitrite.

The present invention will now be described in more detail.

The α-alumina used in the present invention is not particularly limited, but examples include bayerite, gibbsite, bayeragelite, boehmite, r-alumina, and α-alumina.
- Alumina other than alumina according to the usual method / 100℃
Examples include alumina obtained by firing at a temperature above. Since the polishing rate tends to increase as the firing temperature increases, α-alumina obtained by firing at /200oc or higher and /200 to /r000C is preferred.

Considering processing accuracy and polishing speed, the α-alumina used in the present invention has an average grain size of 0. /~10μ, preferably 0. It is a fine powder with a maximum particle size of 30 μm or less, preferably 20 μm or less. Therefore, the α-alumina obtained by sintering is pulverized using a normal pulverizing device, such as a ball mill or a vibration mill in a wet slurry method, and coarse particles are classified using a device such as gravity sedimentation or centrifugal sedimentation, or a dry method is used to classify the coarse particles. That is, the particles are sized to a desired particle size by pulverization and classification using a jet stream.

The content of α-alumina is 7 to 30% of the total amount of the composition.
% by weight, preferably from 2 to 73% by weight.

Examples of the metal nitrite include salts of various metals, but salts of metals from Groups 1 to IIJ of the periodic table are preferred. Specific examples include nitrites such as sodium pentapotassium, calcium, magnesium, barium, zinc, and aluminum.

Among these, calcium nitrite, potassium nitrite, sodium nitrite, and the like are preferred because they have a high dispersion or coagulation effect on alumina-water slurry systems.

The content of metal nitrite is 0.1 based on the total amount of the composition.
~20% by weight, preferably 0. /-/0% by weight. If this amount is too small, the effects of the present invention cannot be expected. On the other hand, if the amount is too large, the effect of addition will not be improved and problems will occur, such as occasional precipitation of salt crystals during winter and an increase in the burden of wastewater purification treatment.

The details of why the abrasive composition of the present invention has an excellent polishing effect are unknown, but the presence of metal nitrite has some influence on the dispersion state of α-alumina in the abrasive composition. It is thought that such a dispersed state works advantageously for If calendar processing.

Further, when boehmite is present in the abrasive composition of the present invention, even better effects can be obtained.

Boehmite is a type of alumina hydrate, and is an aluminum organic compound [Al (
OR,)3) (However, f(is an alkyl group)
It is generally produced by the hydrolysis method of alumina sol, ceramic binder, antistatic treatment of textile carpet, water purification treatment, cosmetics, ointment thickener, alumina catalyst or catalyst carrier. It is an industrial material that is widely used as a raw material.

Boehmite is A100■ or A12C) s-82
It is a substance expressed by the chemical formula 0, and examples of powder products include KAISER (USA) and VISTA Che.
mical (USA), Condea Chemie
(Commercially available from Germany 9, etc.) For example, when a powder consisting of particles of 95% below -00μ and 30% below Sμ is stirred and dispersed in water or acidic water, some of the particles become fibrous and most of the particles become granular. It has the property of dispersing in the form of ultrafine particles with a size of 0.0 μm or less and forming a colloidal sol.The sol of boehmite has an isoelectric point of
It is observed by electrophoresis that the particles themselves are positively charged.

The boehmite to be dispersed in water in the present invention can be used as a powder or as a boehmite sol, but in either case, one that forms a sol with a particle size of o, oiμ or less when dispersed in water is used. .

The content of boehmite is 0.1 to 20% by weight, preferably o,5-io, based on the total weight of the composition. If the boehmite content is too low, no effect of improving the polishing speed can be expected; on the other hand, if the boehmite content is too high, the apparent viscosity and chicken tropism will increase, impairing the uniform dispersion of α-alumina, and at the same time reducing the polishing composition. It has physical properties that are unsuitable for handling, such as difficulty in removing it from the container.

Although the details of the effect of adding boehmite to the abrasive composition of the present invention, which contains water, α-alumina, and metal nitrite, are unknown, it is presumed as follows.

That is, when the α-alumina particles mentioned above are stirred and dispersed in whole water or acidic water, each particle has a positive charge and adsorbs anions of water or electrolyte to form an electrical double layer. do. In such a dispersion system of fine particles, a kind of equilibrium state is formed between agglomeration due to van der Waals attraction and repulsive force due to electrical repulsion.
When boehmite coexists with the water, the boehmite becomes positively charged in the water, so that the dispersion effect between particles due to electrical repulsion becomes stronger in the entire dispersion system.

In precision polishing using such a slurry abrasive, α-alumina particles, which are free abrasive particles, are held in a polishing band in a monodispersed or aggregated state, and as they slide on the surface of the workpiece under the processing pressure, the abrasive The fact that the particles (α-alumina particles) are rolling or sliding is exerting a grinding action is because there are many points of action where the abrasive grains grind the surface of the workpiece, and at each point of action, the abrasive grains grind the surface of the workpiece. The more uniform the grinding force is, the greater the amount of sliding per unit of processing and the amount of polishing per unit time, and the higher the precision of the processed surface. However, before the polishing pad comes into contact with the surface of the workpiece, there is a slurry state in which abrasive grains (α-alumina) and fine particles (abrasive particles) generated by grinding the workpiece are suspended in water. It is presumed that the dispersion or agglomeration state of individual particles will have a strong influence on the polishing amount and polishing finish, but as in the present invention, water, α-alumina, metal nitrite, and in some cases, In a polishing agent containing boehmite, metal nitrite and boehmite are thought to affect the dispersion or agglomeration state of each particle, resulting in improvement in polishing performance.

The abrasive composition of the present invention can be prepared by mixing and stirring the above-mentioned components, and the order of mixing is not particularly limited.

In addition, when preparing this abrasive composition, depending on the processing requirements such as the type of workpiece and processing conditions, various known additives such as those listed below may be added. For example, 5 ethanol, globanol,
Water-soluble alcohols such as ethylene glycol, sodium alkylbenzenesulfonates, surfactants such as formalin condensates of naphthalenesulfonic acids, acids such as sulfuric acid, hydrochloric acid, nitric acid, and acetic acid, lignin sulfonates, carboxymethylcellulose salts, Examples include organic polyanionic substances such as polyacrylates, celluloses such as cellulose, carboxydimethyl cellulose, and hydroxyethyl cellulose, and inorganic salts such as ammonium sulfate, ammonium chloride, and ammonium acetate.

In addition, p) of the abrasive composition of the present invention (in total, 3 to g,
Preferably it is 7 to 7. The pH varies depending on the type of salt, the amount added, etc., but in general, when a water-alumina abrasive is applied to the pi-1'i alkali side, the viscosity becomes high and the porous network structure is This tends to cause problems such as clogging of the polishing pad, deterioration, and scratches on the surface of the workpiece, so it is customary to adjust the pH of the polishing composition to the acidic side, and for this purpose, small amounts of acids are added. There are cases where

The abrasive composition of the present invention is used for σf polishing of metals, glass, plastics, etc., and is particularly suitable for polishing memory hard disks, etc., since it provides a defect-free σ4M surface. .

〔Example〕

Hereinafter, the present invention will be specifically explained with reference to Examples, but the present invention is not limited to the following Examples as long as the gist of the present invention is not exceeded.

Examples 7 to g and Comparative Examples/ [Preparation of abrasive composition] α-alumina (average particle size 0.57μ , maximum particle diameter gμ) in water using a high-speed mixer to prepare a slurry having an α-alumina concentration in g weight.

A metal nitrite was added and dispersed in the proportions shown in Table 1 to prepare a polishing agent and a composition.

[Polishing test]

As a corrugated product, an aluminum substrate was electrolessly plated with nickel phosphorus and Nokel 90-9λ, phosphorus/0-1% alloy plating layer). I used it as a toilet.

Load this disc into a double-sided polisher and polish. The disc was loaded into a double-sided polishing machine with suede type polyurethane substrate polishing pads attached to the upper and lower surface plates of the polisher, and polishing was performed for S minutes by sliding the disc and tooth polishing band relative to each other. Ta.

For polishing, the above abrasive sample was supplied between the disk and both pads at a rate of 3θθ per minute, and the processing pressure was
y 7CIl.

After polishing, the disk was taken out from the double-sided polisher, the ultrasonic cleaning was repeated several times to clean the processed surface of the disk, and the presence or absence 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 thickness.

The test results are shown in Table 1.

Table 1: Examples 9 to Jg and Comparative Examples Aluminum hydroxide α-alumina (average particle size o, syμ, maximum particle size gμ ) was dispersed in water using a high-speed mixer to prepare a slurry having an α-alumina concentration of 6 parts by weight.

Add to this the metal nitrites and salts shown in Table 1.
A polishing agent composition was prepared by adding and dispersing the components.

In addition, as boehmite, Condea Cherni
Pural made by e company (commercial name) sc r=” (
An average particle size of approximately 20 u) was used.

A polishing test was conducted in the same manner as in Example 1, and the results are shown in Table 2 below.

Table [Effects of the Invention] The abrasive composition according to the present invention in which metal nitrite is added to the α-alumina-water dispersion system exhibits a higher polishing rate without generating any surface defects on the polished surface. , polishing efficiency can be increased. Moreover, since the polishing composition of the present invention has a high polishing speed, it shortens polishing time, reduces consumption of polishing agent, and reduces processing costs by reducing wear and deterioration of expensive polishing pads, making it extremely useful. It is.

Sender: Mitsubishi Kasei Corporation Representative Patent Attorney Hase - Others/Names

Claims (1)

[Claims] (1) An abrasive composition containing water, α-alumina, and a metal nitrite.