JP2725191B2 - Abrasive composition - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an abrasive composition. More specifically, the present invention relates to a polishing composition having good polishing efficiency and capable of forming an excellent polishing surface.

(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, and when the particle size of alumina is increased for the purpose of increasing the polishing rate. , The polishing 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 peels, pits, 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.

[Problems to be solved by the invention]

The present inventors have conducted intensive studies in order to obtain a better abrasive composition that satisfies such demands. As a result, water and α
-When metal nitrite is present in the abrasive composition comprising alumina, it does not decrease the polishing finish effect such as the smoothness of the processed surface of the workpiece or the prevention of surface defects (scratch, orange peel, etc.). In addition, the inventors have found that the polishing rate can be greatly improved, and have completed the present invention.

[Means for solving the problem]

The gist of the present invention resides in an abrasive composition containing water, α-alumina and a metal nitrite.

 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 classified into coarse particles pulverized by a ball mill, a vibration mill or the like in an ordinary fine pulverizing apparatus, that is, a wet slurry method, by means of 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.

Examples of the metal nitrite include salts of various metals, and salts of metals belonging to Groups I to III of the periodic table are preferable. Specific examples include nitrites such as sodium, potassium, calcium, magnesium, barium, zinc, and aluminum.

Among these, calcium nitrite, potassium nitrite, sodium nitrite and the like are preferable in that they have a high dispersing or aggregating effect on the alumina-water slurry system.

The content of metal nitrite is 0.1% with respect to the total amount of the composition.
-20% by weight, preferably 0.1-10% by weight. If the amount is too small, the effect of the present invention cannot be expected.
Conversely, even if it is too large, the addition effect does not improve,
Problems such as precipitation of salt crystals at a low temperature in winter and an increase in the burden of wastewater purification treatment occur.

Although the details of the abrasive composition of the present invention having an excellent polishing effect are unknown, the presence of metal nitrite has any effect on the dispersion state of α-alumina in the abrasive composition, It is thought that such a dispersed state works advantageously for polishing.

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

Boehmite is a type of alumina hydrate, and is obtained by subjecting gypsite or the like to pressurized hydrothermal treatment at about 250 ° C. or an aluminum organic compound [Al (OR) synthesized by the Ziegler method.
₃ ] (where R is an alkyl group), which is generally produced by a method of producing by hydrolysis, and comprises alumina sol, ceramic binder, antistatic treatment of textile carpet, water purification treatment, cosmetics, It is an industrial material widely used as a raw material for 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 sol having a particle diameter 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 contrary, 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 taking out from the container.

The details of the action of further containing boehmite in the polishing composition of the present invention containing water, α-alumina and metal nitrite are unknown, but are presumed as follows.
That is, when the above-mentioned α-alumina particles are stirred and dispersed in water or acidic water, the individual particles retain a positive charge and adsorb water or electrolyte anions to form an electric double layer. I do. In such a dispersion of fine particles, a certain equilibrium state is formed by agglomeration due to van der Waals attractive force and repulsive action force due to electric repulsion, but when boehmite coexists here, boehmite Is positively charged in the water, and as a whole dispersion system, the dispersion effect between particles due to electric repulsion is enhanced. In precision polishing with such a slurry-type abrasive, α-alumina particles, which are free abrasive grains, are held on a polishing pad in a monodispersed or aggregated state, and as the workpiece slides at a certain processing pressure, The abrasive grains (α-alumina particles) exert a rolling or sliding grinding action, and the number of action points at which the abrasive grains grind the surface of the workpiece is large, and grinding at each action point is performed. The more uniform the acting force, the larger the unit sliding amount during processing and the polishing amount per unit time, and the higher the processing surface accuracy. However, at the contact surface between the polishing pad and the surface of the workpiece, the abrasive grains (α-alumina) and the fine particles (shavings) generated by grinding the workpiece are present in a slurry state suspended in water. It is estimated that the state of dispersion or aggregation of the particles will strongly affect the polishing amount and the polishing finish, but as in the present invention, water, α-alumina and metal nitrite, and in some cases, further add boehmite. In the abrasive contained, it is considered that the metal nitrite and boehmite affect the dispersion or aggregation state of each particle, thereby improving the polishing performance.

The abrasive composition of the present invention may be prepared by mixing and stirring the above components, and the mixing order and the like are not particularly limited.

In addition, in preparing the abrasive composition, various known additives as described below 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,
Organic acids such as nitric acid and acetic acid, lignin sulfonate, carboxymethyl cellulose salt, organic polyanionic substances such as polyacrylate, celluloses such as cellulose, carboxymethyl cellulose and hydroxyethyl cellulose, ammonium sulfate, ammonium chloride, ammonium acetate And the like inorganic salts.

The pH of the polishing composition of the present invention is 3 to 8, preferably 4 to 7. The pH varies depending on the sugars and the amount of salt added. Generally, when the pH is shifted to the alkali side with a water-alumina abrasive, the viscosity becomes high and the polishing pad is made of a porous network. Deterioration of clogging and scratches on the surface of the workpiece tend to occur, so it is customary to adjust the pH of the polishing composition to the acidic side, and a small amount of acids may be added for this purpose. is there.

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.

〔Example〕

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 8 and Comparative Example 1 [Preparation of Abrasive Composition] α-Alumina, which was obtained by calcining aluminum hydroxide at 1300 ° C. for 5 hours and pulverizing and sizing with 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 8% by weight.

To this was added and dispersed metal nitrite in the proportions shown in Table 1 to prepare an abrasive composition.

(Polishing test)

3.5 inch memory hard disk (outer diameter about 95m / m) with electroless plating of nickel and phosphorus (alloy plating layer of nickel 90-92%, phosphorus 10-8%) on aluminum substrate did.

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

Polishing was performed at a processing pressure of 100 g / cm ² by supplying the above-mentioned abrasive sample at a rate of 300 c.c./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.

Examples 9 to 38 and Comparative Example 2 Aluminum hydroxide was fired at 1300 ° C. for 5 hours, and α-alumina (average particle diameter) pulverized and sized by a dry method was used.
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.

The metal nitrite and boehmite shown in Table 2 were added and dispersed to prepare an abrasive composition.

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

The results of a polishing test performed in the same manner as in Example 1 are as shown in Table 2 below.

[Effects of the Invention] The polishing composition in which a metal nitrite is added to an α-alumina-water dispersion system according to the present invention expresses a higher polishing rate without generating surface defects on the polished surface, and is polished. Processing 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.

Claims (1)

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