JP2001072962A - Hard disc abrasive made of glass - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hard disc abrasive made of glass enabling a high quality abraded face to obtain in a high speed abrading properties, improved productivity and cost reduction to bring by comprising ceric oxide particle as a stable slurry dispersed in water, a ratio of the cerium to the whole rare earth elements being at least a certain value and the ceric oxide particle having a specific average secondary particle diameter. SOLUTION: A hard disc abrasive made of glass comprises a stable slurry of a cerie oxide particle having an average secondary particle diameter of 0.1-0.5 μm dispersed in water and contains 0.2-30 wt.% as a CeO2 concentration. A ratio of the cerium to the whole rare earth elements is preferably at least 95% in terms of weight of the oxide. The ceric oxide particle to be used comprises reacting a cerous salt with an alkali in a mole ratio of (OH)/(Ce3+)=3-30 in an aqueous medium under an inert gas atmosphere to prepare a suspension of cerous hydroxide, and then blowing a gas containing oxygen at a temperature of 10-90 deg.C in the atmosphere to produce the crystalline ceric oxide having the average secondary particle diameter of 0.1-0.5 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a polishing composition suitable for polishing the surface of a glass substrate for an optical disk or a magnetic disk.

[0002]

2. Description of the Related Art After polishing bastnaesite ore or rare earth chloride, the polishing agent for glass substrates for optical disks and magnetic disks is used.
The abrasive grains containing cerium oxide obtained by dry pulverization are dispersed in water. Although these abrasive grains are relatively inexpensive, the content of cerium oxide is at most 50 to 90%, and it is difficult to further control the purity because of using natural minerals as raw materials. In addition, the average secondary particle diameter of the powder is 1 to 3 μm, and it is difficult to reduce the average secondary particle diameter to 1 μm or less when the particles are formed into particles by a breakdown method such as dry pulverization.

In polishing a SiO ₂ oxide film of a semiconductor device, Japanese Patent Laid-Open No. 5-326469 discloses a cerium oxide abrasive having an average particle diameter of 1 μm or less and a cerium oxide purity of 99.5% or more. The average particle diameter is 0.1 μm or less and the purity of cerium oxide is 99.
It is described that a high quality oxide film can be obtained by polishing with a polishing agent of cerium oxide of 5% or more.

However, in the polishing of glass substrates for optical disks and magnetic disks, Japanese Patent Application Laid-Open No. 11-60282 discloses polishing of glass substrates for magnetic disks in which the cerium oxide content in the polishing liquid is 0.5 to 8% by weight. A method is disclosed. Further, International Publication No. WO98 / 21289 discloses that an abrasive composition for a magnetic recording medium substrate containing an abrasive, a polishing aid, and water has an average primary particle size of 0.1.
A method using an abrasive having a size of 002 to 3 μm is described.

[0005]

[Problems to be Solved by the Invention] In recent years, the performance of glass substrates for optical disks and magnetic disks has increased
There is a tendency to increase the speed, and therefore, a high-quality polished surface with small surface roughness and small average waviness is required. However, cerium oxide obtained by calcining bastnaesite ore and rare earth chloride and dry-grinding the cerium oxide has a purity of 50 to 90% and an average secondary particle diameter of 1 to 3 μm. It's getting harder to get.

In order to solve these problems, the cerium oxide particles have an average secondary particle diameter of 1 μm or less, while the cerium oxide content has to be reduced in order to compensate for a decrease in polishing rate caused by reducing the average secondary particle diameter of cerium oxide. By making the ratio 95% or more, a high-quality polished surface can be obtained and a polishing agent for a high-speed polishing optical disk or a glass substrate for a magnetic disk has been found, which has led to the present invention.

[0007]

According to a first aspect of the present invention, there is provided a stable slurry in which ceric oxide particles having an average secondary particle diameter of 0.1 to 0.5 μm are dispersed in water as an abrasive. a and glass hard disk polishing agent characterized in that it contains 0.2 to 30 wt% CeO ₂ concentration.

Further, as a second viewpoint, the ratio of cerium to the total rare earth elements in the abrasive is 9% in terms of oxide weight.
The abrasive for a glass hard disk according to the first aspect, which is at least 5%.

[0009]

DETAILED DESCRIPTION OF THE INVENTION The ceric oxide particles are:
Crystalline ceric oxide particles having an average secondary particle diameter of 0.1 to 0.5 μm, preferably 0.2 to 0.3 μm.

[0010] The average secondary particle diameter is defined as a sol in which particles are dispersed in a state of a single particle or in a state close to the single particle is referred to as a primary sol, and particles in the primary sol are referred to as primary particles. As will be referred to, a secondary sol is a collection of some primary particles in the primary sol, and this aggregate is called a secondary particle. And here, in the integrated particle size distribution of these secondary particles,
The particle diameter whose value corresponds to 50%, that is, what is expressed as a median diameter, is called an average secondary particle diameter. For the measurement, a commercially available centrifugal particle size distribution analyzer, for example, Horiba Seisakusho Co., Ltd.
And CAPA-700 (trade name).

The proportion of cerium in the total amount of rare earth elements in the abrasive in the abrasive is 95% or more in terms of oxide weight. This is in ceric oxide particles (cerium oxide)
/ (Cerium oxide + other rare earth oxides).

As the ceric oxide particles, ceric oxide particles produced by a known method can be used.

Particularly preferred ceric oxide particles are primary cerium oxide particles.
As a method, a cerium (III) salt and an alkaline substance are mixed in an aqueous medium under an inert gas atmosphere with 3 to 30 (OH) /
(Ce ³⁺ ) mole ratio to react with cerium (III) hydroxide
Immediately after producing a suspension of
Crystalline cerium oxide particles having an average secondary particle diameter of 0.1 to 0.5 μm (micrometer) manufactured by blowing oxygen or a gas containing oxygen at a temperature of 0 to 95 ° C. are used. That is.

In the first method of the above-mentioned ceric oxide particles, as a first step, a cerium (III) salt and an alkaline substance are mixed with 3 to 30 (O 2) in an aqueous medium under an inert gas atmosphere.
H) / (Ce ³⁺ ) molar ratio to produce a suspension of cerium (III) hydroxide, ie cerous hydroxide.

The reaction in an inert gas atmosphere is, for example, a reaction between a cerium (III) salt and an alkaline substance in an aqueous medium using a reaction vessel equipped with a gas-replaceable stirrer and a thermometer. . The aqueous medium is usually water, but may contain a small amount of a water-soluble organic solvent. Gas replacement involves submerging a tubular gas inlet in an aqueous medium, blowing an inert gas into the aqueous medium, and allowing the gas to flow out from an outlet attached to the upper portion of the aqueous medium in the reaction vessel, and into the reaction vessel. Fill with inert gas. It is preferable to start the reaction after the replacement of the inert gas is completed. The reaction vessel can be made of a material such as stainless steel or glass lining. At this time, it is desirable that the inside of the reaction vessel is under atmospheric pressure. Therefore, it is preferable that the inflow amount and outflow amount of the gas are substantially the same. The gas inflow and outflow are 0.01 to 1 liter per reactor volume.
It is preferred to be 20 liters / minute.

Examples of the inert gas include a nitrogen gas and an argon gas, and a nitrogen gas is particularly preferable.

In the first production method, examples of the cerium (III) salt include cerous nitrate, cerous chloride, ceric sulfate, cerous carbonate, and cerium (III) ammonium nitrate. The above cerium (II
I) The salts can be used alone or as a mixture.

In the first production method, as the alkaline substance,
Sodium hydroxide, alkali metal hydroxides such as potassium hydroxide or ammonia, amines, organic bases such as quaternary ammonium hydroxides, but particularly ammonia,
Sodium hydroxide and potassium hydroxide are preferred, and these can be used alone or as a mixture.

The above cerium (III) salt and alkaline substance can be added to an aqueous medium and reacted in a reaction vessel. However, a cerium (III) salt aqueous solution and an alkaline substance aqueous solution are prepared, and both aqueous solutions are prepared. It is also possible to react by mixing. Cerium (III) salt is 1-5
Preferably, it is used at a concentration of 0% by weight.

In the first production method, the ratio of the cerium (III) salt to the alkaline substance is 3 to 30, preferably 6 to 12, in terms of (OH) / (Ce ³⁺ ) molar ratio. (OH) / (C
e ³⁺ ) When the molar ratio is less than 3, cerium (III)
It is not preferable because the salt is not completely neutralized by cerium (III) hydroxide and partially remains in the suspension as a cerium (III) salt. This cerium (III) salt has a much lower oxidation reaction rate to cerium (IV) than cerium (III) hydroxide, so that cerium (III) hydroxide and cerium (III)
When a salt coexists, the nucleation rate and the crystal growth rate of crystalline ceric oxide cannot be controlled, so that the particle size distribution is widened and the particle size is not uniform. Also, (O
If the (H) / (Ce ³⁺ ) molar ratio is larger than 30, the crystallinity of the obtained crystalline ceric oxide particles will decrease, and if it is used as an abrasive, the polishing rate will decrease. Further, the particle size distribution of the obtained particles is widened and the particle size is not uniform.

In the above-mentioned first production method, the reaction time in the above-mentioned first step varies depending on the amount of the charged amount, and is generally about 1 minute to 24 hours.

In the first step, cerium (III) is added in a gas containing oxygen such as air instead of an inert gas.
When the salt reacts with the alkaline substance, the produced cerium (III) hydroxide comes into contact with oxygen, and then cerium (IV)
Since the cerium oxide is converted into a salt or ceric oxide, a large number of cerium oxide nuclei are generated in the aqueous medium, and the particle size distribution of the obtained ceric oxide particles is widened and the particle size is not uniform.

In a second step, the suspension formed in the first step is blown with oxygen or a gas containing oxygen at atmospheric pressure at a temperature of 10 to 95 ° C. to form a suspension of 0.1 to 0.5 μm.
To produce crystalline ceric oxide particles having an average secondary particle size of In this step, cerium (III) hydroxide in the suspension obtained in the first step is produced in the presence of oxygen or a gas containing oxygen to produce highly crystalline ceric oxide particles. The oxygen or the gas containing oxygen includes gaseous oxygen, air, or a mixed gas of oxygen and an inert gas. Examples of the inert gas include nitrogen and argon. When a mixed gas is used, the content of oxygen in the mixed gas is preferably 1% by volume or more. In the second step, it is particularly preferable to use air from the viewpoint of easiness in the production method.

The second step is performed in the same reaction vessel following the first step, and following the introduction of the inert gas in the first step, the inert gas is immediately replaced with oxygen or a gas containing oxygen. Gas is introduced continuously. That is,
This is carried out by blowing oxygen or a gas containing oxygen into the suspension obtained in the first step from a gas inlet of a thin tube submerged in the suspension.

Since the second step is carried out under atmospheric pressure, almost the same amount of gas as that introduced into the suspension is exhausted from the outlet mounted on the suspension in the reaction vessel. .

In the second step, the total amount of oxygen or oxygen-containing gas blown into the suspension is cerium hydroxide (II
It is an amount capable of converting I) to ceric oxide, and it is preferable that the molar ratio of (O ₂ ) / (Ce ³⁺ ) is 1 or more. If the above molar ratio is less than 1, cerium (III) hydroxide remains in the suspension, which may come into contact with oxygen in the air during washing after the completion of the second step, thereby generating fine particles. The particle size distribution of the obtained ceric oxide particles is widened and the particle size is not uniform.

In the second step, the inflow and outflow of gas per unit time are 0.0
It is preferable to set it to 1 to 50 liter / min.

Inert gas blowing in the first step and second
If the injection of oxygen or a gas containing oxygen in the step is not temporally continuous, the surface of the suspension obtained in the first step comes into contact with air, and the particle size However, since a layer containing ceric oxide particles of various sizes is generated, the particle diameter of the ceric oxide particles obtained in the subsequent second step is not uniform.

This second step is preferably performed while stirring the suspension with a stirrer such as a disper so that oxygen or a gas containing oxygen is uniformly present in the suspension. If the suspension itself is agitated by gas blowing,
Stirring with a stirrer is not always necessary.

Cerium (III) hydroxide in the first production method
Oxidizing to produce crystalline cerium oxide particles means that nucleation and crystal growth of crystalline cerium oxide particles are performed, and the nucleation rate and crystal growth rate are It can be controlled by the concentration, the concentration of an alkaline substance, the reaction temperature, the concentration and the supply amount of the oxidizing aqueous solution, and the like. In the above method, the concentration of the cerium salt, the concentration of the alkaline substance, the reaction temperature, the concentration of the oxidizing aqueous solution, and the supply amount during nucleation and crystal growth can be freely changed. By adjusting these factors, the particle size can be arbitrarily controlled within the range of the average secondary particle size of 0.1 to 0.5 μm.

The ceric oxide particles obtained in the first production method of the above-mentioned particles were obtained by removing impurities by removing them from the reactor as a slurry and washing them by an ultrafiltration method or a filter press washing method. The particles can be dispersed in an aqueous medium to form a polishing liquid.

A preferred method for producing the ceric oxide particles used in the present invention is the second method, in which the cerium (III) salt and the alkaline substance are mixed in an aqueous medium during opening to the atmosphere in an amount of 3 to 30%.
Reaction at a molar ratio of (OH) / (Ce ³⁺ ) to form a suspension of cerium hydroxide and immediately containing oxygen or oxygen at a temperature of 10 to 95 ° C. under atmospheric pressure. Is to use crystalline ceric oxide particles having an average secondary particle diameter of 0.1 to 0.5 μm (micron meter) produced by a method of blowing gas.

That is, in the second method for producing ceric oxide particles,
In the first step, cerium
(III) 3-30 (OH) /
(Ce^{Three +}) Reaction of cerium hydroxide by reacting in molar ratio
And, as a second step, the suspension generated in the first step
Contains oxygen or oxygen at a temperature of 10 to 95 ° C under atmospheric pressure
0.1 to 0.5 μm by blowing gas
Crystalline ceric oxide particles having an average secondary particle size
It is manufactured.

In the second production method, other conditions and raw materials are the same as in the first production method.

In the second production method, if the cerium (III) salt and the alkaline substance are neutralized in the open to the atmosphere without using an inert gas, the produced cerium (III) hydroxide comes into contact with oxygen and gradually becomes cerium (III). (IV) The cerium oxide nucleus is generated in the aqueous medium due to the change to a salt or ceric oxide. After the temperature is raised to a predetermined temperature in the next step, the cerium (III) salt is reacted with an alkaline substance in an oxygen-containing gas such as air to produce cerium hydroxide (II
Since I) comes into contact with oxygen and changes into cerium (IV) salt and cerium oxide one after another, the particle size distribution of the cerium oxide particles becomes wider and the particle size becomes non-uniform compared to the first production method. Become. However, a high-quality polished surface is obtained as a polishing agent for a glass hard disk, and ceric oxide obtained by the second production method is also useful.

The ceric oxide particles obtained by the above method for producing particles were dried at 110 ° C., and the diffraction pattern was measured with an X-ray diffractometer.
These are cubic crystalline ceric oxide particles having main peaks at 8.6 °, 47.5 °, and 56.4 ° and having high cubic crystallinity described in ASTM Card No. 34-394. The specific surface area of the ceric oxide particles measured by a gas adsorption method (BET method) is from ^{2 to} 200 m ² / g.

The ceric oxide particles obtained by this method are used in an aqueous medium in the presence of an ammonium salt in an amount of 50 to 25%.
Abrasives can be obtained by heat treatment at a temperature of 0 ° C.

As the aqueous medium of the present invention, water is usually used, but a small amount of a water-soluble organic medium can be contained.

As the ammonium salt used in the present invention, an ammonium salt whose anionic component is a non-oxidizing component can be used. The ammonium salt having a non-oxidizing anion component is most preferably ammonium carbonate or ammonium hydrogen carbonate, and these can be used alone or as a mixture.

The above ammonium salt having a non-oxidizing anion component can be obtained by mixing [NH ₄ ⁺ ] / [Ce in an aqueous medium.
O ₂ ] molar ratio is preferably 0.1 to 30, and the concentration of the ammonium salt in the aqueous medium is 1 to 30% by weight.
It is preferable that

When the anionic component is heated in an aqueous medium using an ammonium salt of a non-oxidizing component, it is preferably from 50 to 250.
C., preferably at a temperature of 50 to 180 ° C.,
The surface-modified crystalline ceric oxide particles are obtained. The heating time can be 10 minutes to 48 hours. When the heat treatment temperature is 100 ° C. or lower, the heat treatment is performed using an open reaction vessel. When the heat treatment temperature exceeds 100 ° C., the heat treatment is performed using an autoclave apparatus or a supercritical processing apparatus. The heat-treated ceric oxide particles can be taken out of the treatment tank as a slurry and washed by an ultrafiltration method or a filter press method to remove impurities.

The ceric oxide particles whose surface has been modified by heating in the presence of an ammonium salt having a non-oxidizing anionic component can be easily dispersed in an aqueous medium to form a polishing liquid. This aqueous medium preferably uses water.

The sol containing ceric oxide particles surface-modified by heat treatment in an aqueous medium in the presence of an ammonium salt having a non-oxidizing anionic component is subjected to washing to remove impurities, A quaternary ammonium ion (NR ₄ ⁺ , where R is an organic group) is converted to (NR ₄ ⁺ ) /
It is preferable to contain (CeO ₂ ) in a molar ratio of 0.001 to 1 because the stability of the polishing liquid is improved.
The quaternary ammonium ion is provided by adding a quaternary ammonium silicate, a quaternary ammonium halide, a quaternary ammonium hydroxide, or a mixture thereof, particularly a quaternary ammonium silicate, a quaternary ammonium hydroxide. The addition of quaternary ammonium is preferred. R includes a methyl group, an ethyl group, a propyl group, a hydroxyethyl group, a benzyl group and the like. Examples of the quaternary ammonium compound include tetramethylammonium silicate, tetraethylammonium silicate, tetraethanolammonium silicate, monoethyltriethanolammonium silicate, trimethylbenzylammonium silicate, tetramethylammonium hydroxide, and tetraethylammonium hydroxide.

Further, it may contain a small amount of acid or base. The pH of the polishing liquid is preferably from 2 to 12. The polishing liquid (sol) can be made an acidic polishing liquid (sol) by containing a water-soluble acid in a molar ratio of [H ⁺ ] / [CeO ₂ ] in the range of 0.001 to 1. This acidic sol is
It has a pH of 6. The water-soluble acids include, for example, inorganic acids such as hydrogen chloride and nitric acid, formic acid, acetic acid, oxalic acid, tartaric acid, citric acid,
Examples thereof include organic acids such as lactic acid, acid salts thereof, and mixtures thereof. Further, the water-soluble base is changed to [OH ⁻ ] / [Ce
An alkaline sol can be obtained by including the compound in an O ₂ ] molar ratio of 0.001 to 1. This alkaline polishing liquid (sol) has a pH of 8 to 12. The water-soluble base may be, in addition to the quaternary ammonium silicate and the quaternary ammonium hydroxide described above, monoethanolamine, diethanolamine, triethanolamine, aminoethylethanolamine, N, N-dimethylethanolamine, N Amines such as methylethanolamine, monopropanolamine and morpholine, and ammonia.

The polishing liquid is stable at room temperature for a long period of one year or more.

The ceric oxide particles have a mechanical polishing effect and a chemical polishing effect, and are subjected to heat treatment in an aqueous medium in the presence of an ammonium salt having a non-oxidizing anionic component. As a result, a large amount of hydroxyl groups (≡Ce—OH) is formed on the surface of the ceric oxide particles,
e-OH) groups are hydroxyl groups (≡Si-) on the surface of the silicon oxide film.
It is considered that a chemical action was exerted on OH) to improve the polishing rate. It is considered that the ammonium salt having a non-oxidizing anion component exerts a reducing action on the surface of the ceric oxide particles.

A polishing agent whose polishing rate has been reduced (that is, its polishing ability has been reduced) leads to a reduction in productivity in the polishing process, and such a polishing agent discards the polishing agent itself. . However, in the present invention, the used ceric oxide particles having reduced polishing ability are subjected to a heat treatment at a temperature of 50 to 250 ° C. in an aqueous medium in the presence of an ammonium salt having a non-oxidizing anion component. In addition, the polishing ability can be recovered again and the polishing rate can be improved.

The abrasive of the glass substrate for an optical disk or magnetic disk of the present invention prepared by these methods is not preferable because the average secondary particle diameter of the ceric oxide particles is larger than 0.5 μm because the surface roughness becomes large. . If the average particle diameter of ceric oxide is smaller than 0.1 μm, the polishing rate is undesirably low.

If the proportion of cerium in all the rare earth elements in the polishing agent is less than 95% in terms of the weight of oxide, the polishing rate will be low, and the productivity will be poor.

Further, it is preferable to contain CeO _{2 in a} concentration of 0.2 to 30% by weight, and if it is lower than 0.2% by weight, the polishing rate becomes slow and the productivity is deteriorated. If it exceeds 30% by weight, the viscosity of the slurry becomes high and the polishing resistance becomes very large.

[0051]

EXAMPLE 1 A 100 liter stainless steel reaction tank was charged with NH ₃ / Ce ^3+.
= 20 (molar ratio) 20% aqueous ammonia solution 2
3.8 kg was charged, and nitrogen gas of 1 Nm ³ / hour was blown from a glass nozzle while maintaining the liquid temperature at 30 ° C., and cerous nitrate was expressed by the purity of CeO ₂ in all rare earth oxides. Cerium (III) nitrate with 0%
76.2 kg of aqueous solution (8.0 kg as CeO ₂ equivalent)
Was gradually added to obtain a suspension of cerium (III) hydroxide. Subsequently, the temperature of the suspension was raised to 80 ° C. over 1 hour, and then the blowing from the glass nozzle was switched from nitrogen gas to 2 Nm ³ / hour air, and cerium (II)
The oxidation reaction of converting I) to cerium (IV) was started. The oxidation reaction was completed in 5 hours. The solution after the completion of the reaction is returned to room temperature, and pH = 8.7 having light yellow fine particles, conductivity 83
A reaction solution of mS / cm was obtained.

The reaction solution was washed with a rotary filter press (manufactured by Kotobuki Giken), and had a conductivity of 20 μS / cm and C
A slurry having an eO ₂ concentration of 22% by weight was obtained. After dispersing this slurry in pure water, the pH was adjusted to 5 with 10% nitric acid to prepare a slurry having a CeO ₂ concentration of 5% by weight.

The average secondary particle diameter of the obtained particles was measured by a centrifugal particle size distribution analyzer (CAPA-7 manufactured by Horiba, Ltd.).
00), the average secondary particle size was 0.30 μm.
m. The yield of the particles was almost 100%. The particles were dried and analyzed for impurities. As a result, the ratio of cerium to the total rare earth elements in the abrasive was 99.5% in terms of oxide weight, and the powder was analyzed by X-ray diffraction to find that the diffraction angle was 2θ. = 28.6 ゜, 47.5 ゜ and 56.4 ゜ with major peaks and ASTM card 34-
394, which coincided with the characteristic peak of cubic ceric oxide. The specific surface area determined by the gas adsorption method (BET method) was 25.8 m ² / g.

Example 2 A ceric oxide slurry and an aqueous solution of ammonium carbonate washed with a rotary filter press (manufactured by Kotobuki Giken) were added to a 100-liter stainless steel reaction tank.
The slurry was prepared so that the concentration of ammonium carbonate was 10% by weight and the concentration of CeO ₂ was 15% by weight, and the slurry amount was 100 kg. The temperature of the slurry was raised to 95 ° C., and a heat treatment was performed at this temperature for 8 hours. After cooling, the slurry was washed with a rotary filter press (manufactured by Kotobuki Giken Co., Ltd.), and had a conductivity of 25 μS / cm and a CeO ₂ concentration of 23.
A weight percent slurry was obtained. After dispersing this slurry in pure water, the pH was adjusted to 5 with 10% nitric acid to prepare a slurry having a CeO ₂ concentration of 5% by weight.

The average secondary particle size of the obtained particles was measured by a centrifugal particle size distribution analyzer (CAPA-7 manufactured by Horiba, Ltd.).
00), the average secondary particle size was 0.28 μm.
m. The particles were dried and analyzed for impurities. The content of cerium in the total rare earth elements in the abrasive was 99.6% in terms of oxide weight, and the powder X-ray diffraction was measured. 2θ = 28.6
{, Main peaks at 47.5} and 56.4%, AS
It coincided with the characteristic peak of cubic ceric oxide described in TM Card 34-394. The gas adsorption method (B
The specific surface area value by ET method) was 25.5 m ² / g.

Example 3 A 1-liter glass reactor was charged with 238 g of a 20% aqueous ammonia solution corresponding to NH ₃ / Ce ³⁺ = 6 (molar ratio), and CeO ₂ / rare earth element was maintained while the liquid temperature was maintained at 30 ° C. Oxide = cerium (III) nitrate with 99.0% purity
An aqueous solution (762 g, containing 80 g in terms of CeO ₂ ) was gradually added to obtain a suspension of cerium (III) hydroxide. Subsequently, the temperature of the suspension was raised to 80 ° C. over 1 hour, and then air at 2 L / min was blown from a glass nozzle to start an oxidation reaction of cerium (III) to cerium (IV). The oxidation reaction was completed in 5 hours. The solution after the completion of the reaction is returned to room temperature, and pH having pale yellow fine particles = 5.
5. A reaction solution having a conductivity of 127 mS / cm was obtained.

After the reaction solution was washed by pushing it with a Nutsche,
Re-disperse the wet cake with pure water and conductivities 94μS / c
A slurry having a m and CeO ₂ concentration of 25.5 wt% was obtained. The pH of this slurry was adjusted to 5 with 10% nitric acid,
A slurry having an eO ₂ concentration of 5% by weight was prepared.

Observation of the obtained particles with a transmission electron microscope revealed that, in addition to the particles of 80 to 100 nm, 20 to 30 nm
Many small particles were found, and the particle size distribution was non-uniform. When the average secondary particle size was measured with a centrifugal particle size distribution analyzer (CAPA-700, manufactured by Horiba, Ltd.), the average secondary particle size was 0.45 μm. The yield of the particles was almost 100%. The particles were dried and analyzed for impurities. The particles contained 99.5% of cerium oxide, and the powder was analyzed by X-ray diffraction.
394, which coincided with the characteristic peak of cubic ceric oxide. The specific surface area determined by the gas adsorption method (BET method) was 25.0 m ² / g.

Example 4 A 1-liter glass reactor was charged with 238 g of a 20% aqueous ammonia solution corresponding to NH ₃ / Ce ³⁺ = 6 (molar ratio), and CeO ₂ / rare earth element was maintained while maintaining the liquid temperature at 50 ° C. Oxide = cerium (III) nitrate with 99.0% purity
An aqueous solution (762 g, containing 80 g in terms of CeO ₂ ) was gradually added to obtain a suspension of cerium (III) hydroxide. Subsequently, the temperature of the suspension was raised to 80 ° C. over 30 minutes, and then 2 L / min of air was blown from a glass nozzle to start an oxidation reaction of cerium (III) to cerium (IV). The oxidation reaction was completed in 5 hours. The solution after the completion of the reaction is returned to room temperature, and pH = 6 having pale yellow fine particles.
1. A reaction solution having a conductivity of 127 mS / cm was obtained.

After the reaction solution was washed with water by a Nutsche,
The wet cake is redispersed in pure water, and the conductivity is 42 μS / c.
A slurry having a m and CeO ₂ concentration of 23.4 wt% was obtained. The pH of this slurry was adjusted to 5 with 10% nitric acid,
A slurry having an eO ₂ concentration of 5% by weight was prepared.

Observation of the obtained particles with a transmission electron microscope revealed that, in addition to the particles of 80 to 100 nm, 20 to 30 nm
Many small particle sizes were observed, and the particle size distribution was uneven.
When the average secondary particle diameter was measured by a centrifugal particle size distribution analyzer (CAPA-700, manufactured by Horiba, Ltd.), the average secondary particle diameter was 0.47 μm. The yield of the particles was almost 100%. The particles were dried and analyzed for impurities, which contained 99.5% cerium oxide.
When the powder X-ray diffraction was measured, the ASTM card 3
It coincided with the characteristic peak of cubic ceric oxide described in 4-394. The specific surface area determined by the gas adsorption method (BET method) was 26.1 m ² / g.

Comparative Example 1 Commercially available cerium oxide powder (average secondary particle diameter: 1.4 μm,
Cerium oxide content 57%, gas adsorption method (BET method)
Specific surface area by the, 3.0 m ² / g) was dispersed in pure water to prepare a 5% by weight of the slurry as CeO ₂ concentration. [Polishing test] For glass hard disk, SiO ₂
A 3.5-inch aluminosilicate reinforced glass substrate composed of 7.9% by weight, 17.3% by weight of Al ₂ O _{3 and} 4.8% by weight of ZnO was used. This substrate was subjected to primary polishing, and the average surface roughness was 7.3 Å.

An artificial leather type polyurethane polishing cloth (POLITEX DG (trademark), 38 mmφ, made by Speed Fam) was attached to the board of a lap master LM-15 polishing machine (manufactured by lap master), and this was applied to the polished surface of the substrate. The substrates were polished by applying a load of 11 KPa.

The number of revolutions of the platen is 45 revolutions per minute, and the supply amount of the abrasive slurry is 10 ml / min. After polishing, the workpiece was taken out, washed with pure water, dried, and the polishing rate was determined from the weight loss. The average surface roughness (Ra) of the polished surface is N
The measurement was performed using ew View 100 (manufactured by Zygo).

Table 1 shows the polishing rate and the average surface roughness (Ra).
And the ratio of the polishing rate to the average surface roughness.

[0066]

[Table 1] Table 1 ―――――――――――――――――――――――――――――――― Abrasive Polishing rate Average surface roughness Ratio (Polishing rate (nm / min) (Angstrom) / Average surface roughness / min) ――――――――――――――――――――――――――――――― ――― Example 1 40 2.8 142 Example 2 53 3.0 176 Example 3 32 2.7 119 Example 4 35 2.8 125 Comparative Example 1 77 6.5 118 ――――――― ――――――――――――――――――――――――――― From Table 1, the average secondary particle diameter is 0.3 μm and the content of cerium oxide is 99.5. % Of Examples 1 and 2 has a smaller average surface roughness than Comparative Example 1 having an average secondary particle diameter of 1.4 μm and a cerium oxide content of 57%, and furthermore, polishing for the average surface roughness. It was found that the excellent polishing properties become high proportion of degrees.

In Examples 3 and 4, a large number of small particles of 20 to 30 nm are mixed, and the polishing rate is slightly reduced. However, it has a good average surface roughness and is useful as a precision abrasive for optical disks and magnetic glass hard disks.

The ceric oxide particles obtained by the first and second methods of blowing oxygen or an oxygen-containing gas into cerium hydroxide obtained by reacting a cerium salt with an alkaline substance have a large specific surface area and a unit weight. Since there are many hydroxyl groups per unit, it is suitable for chemical and mechanical polishing. While the abrasive obtained by dispersing cerium oxide powder in water scratches the polished surface, the abrasive obtained by the first production method and the second production method of the present application has a good polished surface with less unevenness due to the chemical and mechanical action. And is particularly suitable for applications requiring precise polishing. Further, the ceric oxide abrasive obtained by this method exhibits a good polishing action on glass, and is suitable for polishing a glass hard disk.

[0069]

According to the present invention, an abrasive for an optical disk or a magnetic disk glass substrate comprising a stable slurry in which ceric oxide particles having an average secondary particle diameter of 0.1 to 0.5 μm are dispersed in water; In the above abrasive, the proportion of cerium in the total rare earth elements in the abrasive is 95% or more in terms of oxide weight, the average surface roughness is small, and the ratio of the polishing rate to the average surface roughness is high. And excellent polishing characteristics.

The abrasive of the present invention can reduce the average secondary particle size of the cerium oxide particles to reduce the average surface roughness and obtain a high quality polished surface. Further, the polishing rate is improved by making the ratio of cerium to 95% or more in terms of the weight of the oxide in the total amount of rare earth elements in the polishing agent directly involved in polishing of the glass hard disk,
Since the ratio of the polishing rate to the average surface roughness is increased, the productivity of the polishing step can be improved and the cost can be reduced.

In particular, the polishing agent of the present invention is useful as a finishing polishing agent since a high-quality polished surface can be obtained when polishing a glass substrate for an optical disk or a magnetic disk. The glass substrate for an optical disk or a magnetic disk is a hard disk made of crystallized glass, a glass hard disk made of aluminosilicate tempered glass or soda lime tempered glass.

In addition, aluminum nitrate,
A polishing composition to which a polishing accelerator such as iron nitrate or basic aluminum sulfamate has been added comprises a Ni-P provided on an aluminum disk which can be supplied as an industrial product.
It is useful for polishing the surface of a plating layer, etc., the surface of an aluminum oxide layer, or the surface of aluminum, its alloy, or alumite.

Claims (2)

[Claims] 1. A stable slurry in which ceric oxide particles having an average secondary particle diameter of 0.1 to 0.5 μm are dispersed in water as an abrasive, and a CeO ₂ concentration of 0.1.
An abrasive for hard disks made of glass, comprising 2 to 30% by weight. 2. The glass hard disk abrasive according to claim 1, wherein the proportion of cerium in the total rare earth elements in the abrasive is 95% or more in terms of oxide weight.