JP2632898B2 - Polishing composition - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a polishing composition (also simply referred to as an abrasive), and more particularly, to forming an excellent polished surface with high polishing efficiency and no defects. The present invention relates to a polishing composition which can be used.

[Prior Art] Conventionally, an aqueous dispersion of alumina powder is known as a polishing composition, and is widely used as an abrasive in various fields. For example, in JP-A-54-89389,
An abrasive for a synthetic resin molded article comprising water and calcined alumina obtained by calcining boehmite (boehmite will be described later) at a high temperature (1100 to 1200 ° C.) is disclosed. The calcined alumina referred to in the invention disclosed in this publication is presumed to be mainly α-alumina in view of the firing conditions.

[Problems to be Solved by the Invention] However, with the conventional abrasives described above, the polishing rate is not sufficient, and if the particle size of alumina is increased for the purpose of increasing the polishing rate, the polishing surface becomes rough. Thus, there was a problem that both the polishing rate and the surface state of the polished surface could not be satisfied.

On the other hand, in the past 10 years, the precision polishing of materials such as silicon and compound semiconductors, various hard disks for magnetic memories, and laser components, for which the production on an industrial scale has increased dramatically, has been particularly demanded for the smoothness of the processed surface and the lack of smoothness. Defects (scratch, orange peel, pit, nodule,
The requirement level for the absence of defects such as cracks) has become much more sophisticated, and on the other hand, a large investment is required for production and inspection equipment, so it is important to improve production speed and cut costs by reducing losses. It has become a challenge.

Therefore, there is a strong demand for polishing agents used in these fields to improve the polishing rate as well as the processing accuracy.

[Means for Solving the Problems] The inventors of the present invention have conducted intensive studies to obtain an excellent polishing composition that satisfies such a demand, and as a result, water and α-alumina were used as main components. In the polishing composition, boehmite and a water-soluble metal salt are present, without reducing the polishing finish effect such as the smoothness of the 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 reached the present invention.

That is, the polishing composition according to the present invention is obtained by adding a fine powder of boehmite and a water-soluble metal salt to a conventional abrasive comprising an aqueous suspension of α-alumina in which fine α-alumina particles are dispersed in water. Are dispersed.

[Operation] Hereinafter, the configuration of the present invention will be described in more detail.

Α used as one component of the polishing composition according to the present invention
-Alumina is high hardness alumina known as a form of aluminum oxide. The raw material of the α-alumina is not particularly limited, but aluminum hydroxide and boehmite such as bayerite, gibbsite, and hydrazite (all ore names), γ-alumina, θ-
Alumina obtained by calcining alumina (aluminum oxide) other than α-alumina such as alumina at a temperature of 1100 ° C. or higher according to a conventional method is used. Since the polishing rate tends to increase as the firing temperature increases,
As described above, α-alumina obtained by firing at 1200 to 1500 ° C. is particularly desirable.

The α-alumina used in consideration of processing accuracy and polishing rate has an average particle size of 0.1 to 10 μm, preferably 0.1 to 3 μm.
And a fine powder having a maximum particle size of 30 μm or less, preferably 20 μm or less. Therefore, α-alumina obtained by calcination is pulverized by a ball mill or a vibrating mill or the like in a usual fine pulverizing apparatus, that is, a wet slurry method, and coarse particles are classified by a device such as gravity sedimentation or centrifugal sedimentation, or dry type. The particles are sized to a desired particle size by, for example, a pulverization 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 decreases. On the other hand, if the amount is too large, uniform dispersion cannot be maintained, and the viscosity of the slurry becomes too large to make handling difficult.

On the other hand, boehmite, which is one of the important substances that characterize the present invention, is a kind of alumina hydrate. Alumina hydrate includes gibbsite, vialite, norstrandite, and boehmite depending on the crystal form. (Also called boehmite), diaspore, etc. (both ore names)
It is an essential requirement that the polishing composition of the present invention contains alumina hydrate having the same crystal form as boehmite (hereinafter referred to as boehmite).

That is, the boehmite referred to in the present invention does not refer to the boehmite itself of the ore, but to 250 ° C.
(A1) organic compound [Al (OR) ₃ ] (provided that R
Is a material widely produced by a method of producing the compound by hydrolysis of an alkyl group). It is widely used as a raw material for alumina sol, ceramic binder, antistatic agent for textiles and carpets, agent for purifying water, cosmetics, thickener for ointments, alumina-based catalyst or catalyst carrier, etc. Material.

Boehmite displayed by the chemical formula Al · OOH or _{Al 2 O 3 · H 2 O} , as the powder product, for example, KAISER (USA), VIST
Commercially available from A Chemical (USA), Condea Chemie (Germany) and the like. For example, 95% below 200μ, 50 below 45μ
% Of the particles is stirred in water or acidic water, a part of which is fibrous, a part of which is granular and has a size of 0.1%.
It has the property of dispersing in the form of ultra-fine particles of 1 μ or less and forming a colloidal sol.

The boehmite sol has an isoelectric point of 9.4, and it has been observed by electrophoresis that the particles themselves are positively charged. This phenomenon and properties are important points of the present invention as described later.

Boehmite dispersed by adding α-alumina to the aqueous dispersion in the present invention can be used in powder or boehmite sol, but in any case, the particle diameter when dispersed in water is 0.1μ or less The one that forms the sol is used.

The boehmite content is 0.1% based on the total amount of the polishing composition.
It is 1 to 20% by weight, preferably 0.5 to 10% by weight. 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. This makes it difficult to take out of the container from the container, for example, and presents a problem in handling.

Further, in the polishing composition according to the present invention, a water-soluble metal salt is added to a dispersion system comprising water, α-alumina and boehmite as described above in order to enhance the dispersibility of the particles or, conversely, the cohesion. It is necessary to.

This water-soluble metal salt has a solubility in water of 1 g
/ 100 g water or more can be used, but preferably 5
g / 100g water or more is desirable.

Such water-soluble metal salts include alkali metals such as lithium, sodium and potassium, alkaline earth metals such as magnesium and calcium, metals such as zinc, aluminum and nickel, and nitric acid, sulfuric acid, hydrochloric acid and phosphoric acid. And salts with an inorganic acid such as, for example, or an organic acid such as formic acid, acetic acid, and citric acid.

Specific examples of these metal salts include lithium nitrate, lithium sulfate, lithium citrate, sodium nitrate, sodium sulfate, sodium thiosulfate, sodium chloride, sodium acetate, potassium sulfate, potassium chloride, magnesium nitrate, magnesium sulfate, and magnesium sulfate. Ammon, magnesium chloride, magnesium acetate, calcium nitrate, calcium chloride, zinc sulfate, zinc chloride, zinc acetate, aluminum nitrate, aluminum sulfate, aluminum phosphate, aluminum phosphate, aluminum chloride, potassium alum, nickel nitrate, nickel sulfate, nickel acetate And the like.

Among these, magnesium nitrate,
Preferred are inorganic acid salts of magnesium, calcium or aluminum, such as calcium nitrate, aluminum nitrate, aluminum sulfate.

The content of the water-soluble metal salt is 0.5 to 2 with respect to the total amount of the composition.
0% by weight, preferably 1 to 10% by weight. If the amount is too small, the effect of the present invention cannot be expected. Conversely, if the amount is too large, the effect of the addition will not be improved, and disadvantages such as precipitation of salt crystals at low temperatures such as in winter and an increase in the burden of wastewater purification treatment will occur.

Although the grounds or supporting details of the fact that the polishing composition of the present invention has a practically excellent polishing effect are not necessarily clear, it seems appropriate to think as follows.

That is, it is considered that the presence of boehmite and the water-soluble metal salt has some influence on the dispersion state of α-alumina in the polishing composition, and such a dispersion state advantageously acts on the polishing process. That is, first, when the α-alumina particles are stirred and dispersed in water or acidic water, the individual particles have a positive charge and adsorb water or anions of the electrolyte to form an electric double layer.

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. However, when boehmite coexists here, the boehmite is positively charged in water, so that the dispersion effect between the particles due to the electric repulsion becomes stronger as a whole of the dispersion system. That is, uniform dispersion of the composition is achieved.

In precision polishing with such a slurry-like abrasive, α-alumina particles, which are free abrasive grains, are held in a polishing pad in a monodispersed or aggregated state, and as the workpiece slides at a certain processing pressure, Abrasive grains (α-alumina particles)
Is performing a polishing action while rolling or sliding. In this case, the greater the number of action points at which the abrasive grains grind the workpiece surface and the more uniform the grinding action force at each action point, the greater the unit sliding amount during processing, the polishing amount per unit time, and It is expected that the machining surface accuracy will increase.

However, on the contact surface between the polishing pad and the surface of the workpiece, there is a slurry state in which abrasive particles (α-alumina particles) and fine particles (shavings) generated by grinding the workpiece are suspended in water. It is presumed that the dispersion or aggregation state of the individual particles strongly affects the polishing amount and the polishing finish. However, as in the present invention, water, α-alumina, boehmite and a water-soluble metal salt are used for polishing. In the composition, it is considered that the boehmite and the water-soluble metal salt affect the dispersion or aggregation state of each particle, thereby improving the polishing performance.

The polishing composition according to the present invention may be prepared by mixing and stirring water, α-alumina, boehmite, and the above-mentioned water-soluble metal salt, and the order of mixing these is not particularly limited.

Further, in preparing the polishing composition of the present invention, various known additives such as those listed below may be added according to the type of the workpiece and the necessary polishing conditions such as the processing conditions. .

(A) Water-soluble alcohols such as ethanol, propanol and ethylene glycol.

(B) Surfactants such as sodium alkylbenzenesulfonate and formalin condensate of naphthalenesulfonic acid.

(C) Acids such as sulfuric acid, hydrochloric acid, and acetic acid.

(D) Organic polyanionic substances such as lignin sulfonate, carboxymethyl cellulose salt, polyacrylate and the like.

(E) Cellulose such as cellulose, carboxymethylcellulose, hydroxyethylcellulose and the like.

(F) Inorganic salts such as ammonium sulfate, ammonium chloride, ammonium acetate and the like.

The pH of the polishing composition of the present invention is 3 to 8, preferably 4 to 7. The pH varies depending on the type of salt and the amount of salt added.In general, when the pH is shifted to the alkaline side with a water-alumina abrasive, the viscosity becomes high, and the polishing pad made of a porous mesh or a mesh structure deteriorates. Therefore, it is customary to adjust the pH of the polishing composition to the acidic side, since scratches on the surface of the workpiece tend to occur, and it is customary to add a small amount of acids for this purpose. May be used to adjust the pH.

The polishing composition of the present invention is used for polishing metals, glass, plastics, etc., and is particularly suitable for polishing metal materials such as memory hard disks or various plastics, since a polishing surface without defects can be obtained. It is.

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

Examples 1 to 24 (Comparative Example 1) A. Preparation of Polishing Composition Aluminum hydroxide was fired at 1300 ° C. for 5 hours and pulverized and sized by a dry method.
0.54 μm and a maximum particle diameter of 5 μm) were dispersed in water by a high-speed mixer to prepare a slurry having an α-alumina concentration of 6% by weight. This slurry was used as Comparative Example 1.

Boehmite and a water-soluble metal salt were added and dispersed at the ratios shown in Tables 1 and 2 to prepare Polishing Composition Examples 1 to 24.

And as the boehmite to be added, Condea / Chem
ie, SCF (trade name) SCF (average particle diameter: about 20 μ) was used.

Examples of the water-soluble metal salt to be added include magnesium sulfate, magnesium chloride, calcium nitrate and potassium alum.

B. Polishing test A 3.5-inch memory hard disk (outer diameter of about 95 mm), which is made by electroless plating of nickel and phosphorus (alloy plating layer of 90 to 92% nickel and 10 to 8% phosphorus) on an aluminum substrate as a workpiece A substrate was used. This disk was loaded into a double-sided polishing machine in which a suede-type polyurethane substrate polishing pad was mounted on each of the upper and lower platens of the polishing machine, and the disc and both polishing pads were relatively slid to perform polishing for 5 minutes. .

The polishing was performed by supplying each abrasive sample between the disk and both polishing pads at a rate of 300 cc per minute and a processing pressure of 100 g / cm ^2.
I went in. 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 presence or absence and degree of defects were evaluated by visual inspection. Further, the thickness of the disk was measured, and the average polishing rate per minute was calculated from the decrease. This test result is
As shown in Tables (Examples 1 to 12) and Table 2 (Examples 13 to 24 and Comparative Example 1).

From the results in Tables 1 and 2, all of the abrasives of Examples 1 to 24 to which boehmite and the water-soluble metal salt were added were polished compared to the conventional comparative example 1 to which boehmite was not added. Both the performance of the speed and the surface defect were excellent, and the effect of having a polishing rate of about twice or more and three times or more of the polishing agent of Comparative Example 1 was obtained.

In particular, it was found that those of Examples 13 to 24 in which the amount of boehmite added was 3.0% by weight were overall more effective than those of Examples 1 to 12.

[Examples 25 to 28 (Comparative Example 2)] C. Preparation of Polishing Composition Aluminum hydroxide was fired at 1200 ° C for 5 hours and pulverized and sized by a dry method.
0.49 μm, maximum particle size 5 μm) was dispersed in water using a high-speed mixer to prepare a slurry having an α-alumina concentration of 8% by weight.

Boehmite and a water-soluble metal salt were added and dispersed in the proportions shown in Table 2 to prepare Examples 25 to 28 in the same manner as in Example 1. Here, as the boehmite, a boehmite sol obtained by hydrothermally treating aluminum hydroxide at 250 ° C. in an autoclave was used.

Comparative Example 2 is a sample without addition of boehmite and a water-soluble metal salt, and is a comparative example sample.

D. Polishing Test A 50 mm-diameter polycarbonate disk was used as a workpiece, and this was loaded into a double-side polishing machine and polished.

In addition, a suede type soft polyurethane substrate polishing pad is loaded on each of the upper and lower platens of the polishing machine,
500c abrasive sample per minute between disc and polishing pad
While supplying at the rate of c, the disc and the polishing pad were relatively slid under the condition of the processing pressure of 80 g / cm ² to perform polishing for 5 minutes. After polishing, the disk was taken out from the polishing machine, the processed surface was cleaned by ultrasonic cleaning, and the presence / absence and degree of surface defects were evaluated by visual inspection.

Next, the weight of the disk was measured, the weight loss before and after polishing was calculated, and the average polishing amount per minute was obtained.

 The test results are as shown in Table 3.

From the results in Table 3, it can be seen that Examples 25 to 28 in which boehmite and a water-soluble metal salt were added all had an average polishing amount as compared with the polishing agent of Comparative Example 2 in which boehmite and a water-soluble metal salt were not added. In addition, both examples of surface defects are excellent, and the example has an excellent effect that the polishing rate is about 2.5 to 3 times or more of that of the comparative example and the scratch is extremely small.

[Effects of the Invention] As described above, according to the present invention, boehmite and a water-soluble metal salt are added and dispersed in a conventional polishing composition composed of an aqueous dispersion of α-alumina. Polishing with this polishing composition expresses a higher polishing rate without generating surface defects on the polished surface, so that the polishing efficiency can be remarkably improved as compared with the conventional polishing composition.

Moreover, since the polishing composition of the present invention has a high polishing rate, the polishing time is shortened, the consumption of the polishing composition is reduced, and the number of replacements of expensive polishing pads is reduced. Contributes and is extremely useful.

Claims (1)

(57) [Claims] 1. A polishing composition comprising water, α-alumina in fine particles, boehmite in fine powder, and a water-soluble metal salt.