JP2020071890A - Polishing agent composition for magnetic disk substrate - Google Patents

Abstract

To provide polishing agent composition for a magnetic disk substrate capable of reducing deposits such as abrasive grain residues and polishing debris on a substrate surface after a rough polishing step in a multi-stage polishing method while maintaining productivity, and further reducing waviness.SOLUTION: A polishing agent composition is an abrasive composition that is used in a step of performing rough polishing of the subsequent step and contains colloidal silica, a water-soluble polymer compound, and water. In a volume-based particle size distribution of colloidal silica measured by Heywood diameter, a cumulative volume frequency of particle diameter 50 nm is 35% or more and the cumulative volume frequency of particle diameter 15 nm in the particle size distribution is 90% or less. Water-soluble polymer compound is a mixture containing a polymer having a monomeric substance having a carboxylic acid group as an essential monomeric substance and a polymer having a monomeric substance having a sulfonic acid group as an essential monomeric substance, and/or a copolymer containing a monomeric substance having a carboxylic acid group and a monomeric substance having sulfonic acid groups as an essential monomeric substance.SELECTED DRAWING: None

Description

  The present invention relates to an abrasive composition used for polishing electronic parts such as magnetic recording media such as semiconductors and hard disks. In particular, it relates to an abrasive composition used for polishing the surface of a magnetic recording medium substrate such as a glass magnetic disk substrate or an aluminum magnetic disk substrate. Furthermore, when performing polishing of an aluminum magnetic disk substrate for a magnetic recording medium having an electroless nickel-phosphorus plating film formed on the surface of an aluminum alloy substrate in a multi-step polishing method, a rough polishing step before the final polishing step is performed. It relates to the abrasive composition used.

  2. Description of the Related Art In recent years, magnetic disk drives have become smaller and larger in capacity, and higher recording density is required. Therefore, it is necessary to improve the detection sensitivity of a high recording density magnetic signal, and technical development is underway to further reduce the flying height of the magnetic head and reduce the unit recording area. The magnetic disk substrate is designed to improve the flying height of the magnetic head and to secure the recording area. Therefore, the smoothness and flatness are improved (surface roughness and waviness are reduced) and surface defects are reduced (abrasive residue, polishing dust, Reduction of scratches and pits) is strictly required.

  For such requirements, an abrasive composition containing α-alumina and intermediate alumina is used from the viewpoint of achieving both improvement of surface quality and improvement of productivity such as reduction of abrasive grain residue, reduction of polishing dust, and further improvement of waviness. By doing so, it has been proposed that a high polishing rate can be achieved and waviness can be reduced (Patent Document 1). However, the undulation reduction effect is insufficient, and improvement is required. Further, in the method for polishing a magnetic disk substrate, a multi-step polishing method having two or more polishing steps is often adopted (Patent Document 2). Generally, in the final polishing step of the multi-step polishing method, that is, in the final polishing step, an abrasive composition containing silica particles is used from the viewpoint of reducing surface roughness and reducing scratches, deposits, pits and the like. On the other hand, in a polishing step (also referred to as a rough polishing step) before that, an abrasive composition containing alumina particles is often used from the viewpoint of improving productivity.

  However, when polishing an aluminum hard disk substrate, the hardness of alumina particles is considerably higher than that of an aluminum alloy substrate, so that residue of abrasive grains and polishing debris adheres to the surface of the substrate, and further waviness worsens, resulting in a finish. It has been a problem that the polishing is adversely affected.

  As a solution to such a problem, a polishing method has been disclosed in which polishing is performed using an alumina-containing abrasive composition in the same polishing machine in the rough polishing step and polishing is performed using a colloidal silica-containing abrasive composition ( Patent Document 3). Further, a polishing method of supplying a cleaning liquid containing no abrasive grains between the polishing using the alumina-containing polishing composition and the polishing using the colloidal silica-containing polishing composition is also disclosed (Patent Document 4).

JP, 2005-23266, A JP-A-62-208869 JP 2012-25873 A JP, 2012-43493, A

  With the increase in capacity of magnetic disk drives, the required characteristics for the surface quality of substrates have become more stringent, and in the polishing process of magnetic disk substrates, while maintaining productivity, abrasive residue on the substrate surface, polishing debris, etc. It is required to reduce the amount of deposits and further reduce the waviness. It is difficult for the proposals of Patent Documents 1 to 4 to sufficiently meet the required characteristics.

  An object of the present invention is to reduce the adhered substances such as abrasive grain residue and polishing dust on the substrate surface after the rough polishing step in the multi-step polishing method while maintaining the productivity, and to further reduce the waviness. An object is to provide an abrasive composition.

  The present inventor, as a result of diligent study on the above problems, found that the above problems can be solved by using the following abrasive composition in the subsequent polishing of the rough polishing step in the multi-step polishing method, Arrived That is, the present invention is the following abrasive composition.

[1] A polishing agent used in step (3) in the rough polishing of a magnetic disk substrate that has the following steps (1) to (3) and performs each of the steps (1) to (3) with the same polishing machine The composition B, which contains colloidal silica, a water-soluble polymer compound and water, wherein the colloidal silica has a cumulative volume frequency of 35% or more with a particle size of 50 nm in a volume-based particle size distribution measured by a Heywood diameter and the particle size. The cumulative volume frequency of particles having a particle size of 15 nm in the distribution is 90% or less, and the water-soluble polymer compound is a polymer having a monomer having a carboxylic acid group as an essential monomer and a monomer having a sulfonic acid group. Polishing for a magnetic disk substrate, which is a mixture containing a polymer as an essential monomer, and / or a copolymer having a monomer having a carboxylic acid group and a monomer having a sulfonic acid group as an essential monomer Agent composition object.
(1) A polishing agent composition A containing α-alumina, intermediate alumina, and water is supplied to a polishing machine, and the substrate obtained in the step (2) step (1) of performing the rough polishing in the preceding stage is subjected to a rinse treatment. Step (3) A step of supplying a polishing composition B containing colloidal silica, a water-soluble polymer compound and water to a polishing machine to perform a rough polishing in the latter stage.

[2] A copolymer having, as an essential monomer, a monomer having a carboxylic acid group and a monomer having a sulfonic acid group, which are the water-soluble polymer compounds, is a monomer having a carboxylic acid group and a sulfone. The abrasive composition for a magnetic disk substrate according to the above [1], which is a copolymer in which a monomer having an acid group and a monomer having an amide group are essential monomers.

[3] The abrasive composition for a magnetic disk substrate according to [2], wherein the amide group-containing monomer is a monomer selected from acrylamide, methacrylamide, N-alkylacrylamide and N-alkylmethacrylamide. object.

[4] The magnetic disk substrate according to any one of [1] to [3], wherein the monomer having a carboxylic acid group is a monomer selected from acrylic acid or a salt thereof, methacrylic acid or a salt thereof. Abrasive composition.

[5] The monomer having a sulfonic acid group is isoprenesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, 2-methacrylamido-2-methylpropanesulfonic acid, styrenesulfonic acid, vinylsulfonic acid, allyl The magnetic disk substrate according to any one of [1] to [4] above, which is one or more monomers selected from sulfonic acid, isoamylenesulfonic acid, vinylnaphthalenesulfonic acid, and salts thereof. Abrasive composition.

[6] The abrasive composition further contains an organic sulfate ester salt compound, and the organic sulfate ester salt compound is represented by the following general formula (1). An abrasive composition for a magnetic disk substrate.
_{R-O-SO 3 M (} 1)
In the formula, R represents a linear or branched alkyl group having 5 to 21 carbon atoms, an alkenyl group, an aryl group or an alkylaryl group, and M represents an alkali metal salt, an alkaline earth metal salt, an ammonium ion or an organic cation. ..

[7] The abrasive composition further contains an organic sulfate ester salt compound, and the organic sulfate ester salt compound is represented by the following general formula (2). [1] to [5] An abrasive composition for a magnetic disk substrate.
_{R-O- (AO) n -SO} 3 M (2)
In the formula, R represents a linear or branched alkyl group having 5 to 21 carbon atoms, an alkenyl group, an aryl group, or an alkylaryl group, AO represents an oxyalkylene group having 2 or 3 carbon atoms, and n is 1 to 1. It represents a natural number of 30, and M represents an alkali metal, an alkaline earth metal, an ammonium ion or an organic cation.

[8] In any of the above-mentioned [1] to [7], wherein the abrasive composition further contains an acid and / or a salt thereof and has a pH value (25 ° C.) in the range of 0.1 to 4.0. An abrasive composition for a magnetic disk substrate as described above.

[9] The abrasive composition for a magnetic disk substrate according to any one of [1] to [8], wherein the abrasive composition further contains an oxidizing agent.

[10] The abrasive composition for a magnetic disk substrate according to any one of [1] to [9], which is used for rough polishing of an electroless nickel-phosphorus plated aluminum magnetic disk substrate.

  By using the abrasive composition for a magnetic disk substrate of the present invention, after the rough polishing step in the multi-step polishing method, the adhered substances such as the abrasive residue and the polishing dust on the substrate surface were reduced, and the waviness was further reduced. The substrate can be manufactured with high productivity.

  Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the following embodiments, and within the scope not departing from the spirit of the present invention, based on ordinary knowledge of a person skilled in the art, It is to be understood that those obtained by appropriately modifying and improving the embodiments of the present invention also fall within the scope of the present invention.

1. Polishing Agent Composition The polishing agent composition of the present invention (the polishing agent composition of the present invention is the polishing agent composition B described below) contains colloidal silica, a water-soluble polymer compound, and water. The colloidal silica has a cumulative volume frequency of particle diameters of 50 nm in the volume-based particle size distribution measured by Heywood diameter of 35% or more and a cumulative volume frequency of particle diameters of 15 nm in the particle size distribution of 90% or less. The water-soluble polymer compound is a mixture containing a polymer having a monomer having a carboxylic acid group as an essential monomer and a polymer having a monomer having a sulfonic acid group as an essential monomer, and / or a carboxylic acid. It is a copolymer in which a monomer having an acid group and a monomer having a sulfonic acid group are essential monomers. The abrasive composition of the present invention is an abrasive composition containing, as an optional component, an organic sulfate ester salt compound, an acid and / or a salt thereof, an oxidizing agent, and other additives.

The polishing composition of the present invention has the following steps (1) to (3), and in the rough polishing of the magnetic disk substrate in which the steps (1) to (3) are performed by the same polishing machine, the step (3) Which is the abrasive composition B used in.
(1) A polishing agent composition A containing α-alumina, intermediate alumina, and water is supplied to a polishing machine, and the substrate obtained in the step (2) step (1) of performing the rough polishing in the preceding stage is subjected to a rinse treatment. Step (3) A step of supplying a polishing composition B containing colloidal silica, a water-soluble polymer compound and water to a polishing machine to perform a rough polishing in the latter stage.
The details will be described below.

1-1. Colloidal Silica The colloidal silica used in the polishing composition B of the present invention is made of an alkali metal salt of silicate such as sodium silicate or potassium silicate as a raw material, and the raw material is subjected to a condensation reaction in an aqueous solution to grow particles. Obtained by the glass method. Alternatively, it can also be obtained by an alkoxysilane method in which an alkoxysilane such as tetraethoxysilane is used as a raw material, and the raw material is grown in water containing a water-soluble organic solvent such as alcohol to cause a condensation reaction by hydrolysis with an acid or an alkali to grow particles. ..

  The colloidal silica is known to have a spherical shape, a chain shape, a Konpeito sugar shape, an irregular shape, etc., and primary particles are monodispersed in water to form a colloidal shape. The shape of colloidal silica is preferably spherical or nearly spherical.

  The average particle diameter (D50) of colloidal silica is preferably 10 to 100 nm, more preferably 20 to 80 nm. Furthermore, the cumulative volume frequency of the particle size 50 nm in the volume-based particle size distribution measured by the Heywood diameter is 35% or more, and the cumulative volume frequency of the particle size 15 nm in the particle size distribution is 90% or less.

  The cumulative volume frequency (%) used here has the same meaning as that normally used, and the volume is integrated in the order of particle size starting from the particle with the smallest particle size for the target particle group. In the distribution thus obtained, the total volume of particles having a particle diameter of a certain value or less represents the ratio (%) to the total volume of all target particles. For example, when the cumulative volume frequency with a particle diameter of 15 nm is 50%, it means that the total volume of particles with a particle diameter of 15 nm or less occupies 50% of the total volume of all particles. The Heywood diameter is a result obtained by analyzing an image obtained by observing with an electron microscope and determining a diameter of a projected area circle.

  The colloidal silica contained in the polishing composition of the present invention has a relatively small proportion of large particles having a particle diameter of 50 nm or more and small particles having a particle diameter of 15 nm or less. When colloidal silica having such a particle size distribution is supplied to the surface of the object being rubbed by the polishing pad, it is likely to be sufficiently retained by the polishing pad. Further, because of the above particle size distribution, the gap formed between the colloidal silica and the surface of the object tends to be smaller than the size of the residue such as abrasive grains or shavings of the object. Therefore, it becomes difficult for the residue to escape into the gap between the colloidal silica and the surface of the object, the collision frequency of the residue and the colloidal silica increases, and the residue can be efficiently removed from the surface of the object.

  Further, since a considerable number of particles of colloidal silica having a particle diameter of 50 nm or less are secured, another state of colloidal silica having a smaller particle diameter enters a gap between a certain colloidal silica and the surface of the object. Is likely to occur. As a result, residues such as shavings of the object are less likely to escape into the gap between the colloidal silica and the surface of the object, and the residue is easily removed from the surface of the object. Further, since colloidal silica has a spherical shape or a shape close to a spherical shape, it tends to be hard to be attached or pierced on the surface of an object. Therefore, the colloidal silica itself does not easily remain on the surface of the object.

  The concentration of colloidal silica in the abrasive composition is preferably 0.1 to 20% by mass, more preferably 0.2 to 10% by mass.

1-2. Water-soluble polymer compound The water-soluble polymer compound used in the polishing agent composition B of the present invention comprises a polymer having a carboxylic acid group-containing monomer as an essential monomer and a sulfonic acid group-containing monomer. It is a mixture containing a polymer as an essential monomer, and / or a copolymer having a monomer having a carboxylic acid group and a monomer having a sulfonic acid group as essential monomers. Further, monomers other than these can also be used. Examples of the monomer other than the monomer having a carboxylic acid group and the monomer having a sulfonic acid group include a monomer having an amide group.

1-2-1. Monomers Having Carboxylic Acid Group As the monomers having a carboxylic acid group, unsaturated aliphatic carboxylic acids and salts thereof are preferably used. Specific examples thereof include acrylic acid, methacrylic acid, maleic acid, itaconic acid, and salts thereof. Examples of the salt include sodium salt, potassium salt, magnesium salt, ammonium salt, amine salt, alkylammonium salt and the like.

  In the water-soluble polymer, the proportion of the monomer having a carboxylic acid group in the acid state or the salt state is high depending on the pH value of the water-soluble polymer compound. Can be evaluated. The higher the proportion of the acid, the lower the pH value, and the higher the proportion of the salt, the higher the pH value. In the present invention, for example, a water-soluble polymer compound having a pH value (25 ° C.) in a water-soluble polymer compound aqueous solution having a concentration of 10% by mass in the range of 0.1 to 13 can be used.

1-2-2. Monomers Having Sulfonic Acid Group Specific examples of the monomer having a sulfonic acid group include isoprenesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, 2-methacrylamido-2-methylpropanesulfonic acid, styrene. Examples thereof include sulfonic acid, vinyl sulfonic acid, allyl sulfonic acid, isoamylene sulfonic acid, vinyl naphthalene sulfonic acid, and salts thereof. From these, one kind or two or more kinds can be selected and used as a monomer. Preferred are 2-acrylamido-2-methylpropanesulfonic acid, 2-methacrylamido-2-methylpropanesulfonic acid, and salts thereof.

1-2-3. Other Monomers In the water-soluble polymer compound used in the polishing composition B of the present invention, a monomer having a carboxylic acid group and a monomer having a sulfonic acid group are essential monomers, Monomers other than these can also be used. For example, a monomer having an amide group can also be used. Specifically, acrylamide, methacrylamide, N-alkyl acrylamide, N-alkyl methacrylamide and the like can be used.

  Specific examples of N-alkyl acrylamide and N-alkyl methacrylamide include N-methyl acrylamide, N-ethyl acrylamide, Nn-propyl acrylamide, N-iso-propyl acrylamide, Nn-butyl acrylamide and N-iso. -Butylacrylamide, N-sec-butylacrylamide, N-tert-butylacrylamide, N-methylmethacrylamide, N-ethylmethacrylamide, Nn-propylmethacrylamide, N-iso-propylmethacrylamide, Nn- Examples thereof include butyl methacrylamide, N-iso-butyl methacrylamide, N-sec-butyl methacrylamide, and N-tert-butyl methacrylamide.

1-2-4. Polymer Mixture The water-soluble polymer compound used in the polishing agent composition B of the present invention comprises a polymer having a carboxylic acid group-containing monomer as an essential monomer and a sulfonic acid group-containing monomer. It may be a mixture containing a polymer as an essential monomer. In that case, as a polymer constituting the mixture, as a polymer having a monomer having a carboxylic acid group as an essential monomer, a polymer obtained by polymerizing a monomer having a carboxylic acid group, a carboxylic acid Group-containing monomer and sulfonic acid group-containing monomer copolymer, carboxylic acid group-containing monomer and other monomer copolymer, carboxylic acid group-containing monomer and Examples thereof include a copolymer of a monomer having a sulfonic acid group and another monomer.

  Further, as the polymer having a monomer having a sulfonic acid group as an essential monomer, a polymer obtained by polymerizing a monomer having a sulfonic acid group, a monomer having a carboxylic acid group and a sulfonic acid A copolymer with a monomer having a group, a copolymer of a monomer having a sulfonic acid group and another monomer, a monomer having a carboxylic acid group and a monomer having a sulfonic acid group Examples thereof include copolymers with other monomers.

  A mixture of a polymer having a carboxylic acid group-containing monomer as an essential monomer and a polymer having a sulfonic acid group-containing monomer as an essential monomer is a monomer having these carboxylic acid groups. It may be a mixture of at least one polymer selected from the polymers having as an essential monomer and the polymers having a monomer having a sulfonic acid group as an essential monomer. The proportion of the polymer containing the monomer having a carboxylic acid group as an essential monomer in the mixture is preferably 5 to 95% by mass, more preferably 8 to 92% by mass, and further preferably 10 to 90% by mass. The proportion of the polymer containing the monomer having a sulfonic acid group as an essential monomer in the mixture is preferably 5 to 95% by mass, more preferably 8 to 92% by mass, and further preferably 10 to 90% by mass.

1-2-5. Copolymer The water-soluble polymer compound used in the polishing composition B of the present invention is a copolymer containing a monomer having a carboxylic acid group and a monomer having a sulfonic acid group as essential monomers. It may be.

  The proportion of the constituent unit derived from the monomer having a carboxylic acid group in the copolymer is preferably 5 to 95 mol%, more preferably 8 to 92 mol%, and further preferably 10 to 90 mol%. The proportion of the constituent unit derived from the monomer having a sulfonic acid group is preferably 5 to 95 mol%, more preferably 8 to 92 mol%, and further preferably 10 to 90 mol%.

  The water-soluble polymer compound used in the polishing agent composition B of the present invention comprises a monomer having a carboxylic acid group, a monomer having a sulfonic acid group and a monomer having an amide group as essential monomers. It is also preferable that it is a copolymer.

1-2-6. Production Method of Water-Soluble Polymer Compound The production method of the water-soluble polymer compound is not particularly limited, but an aqueous solution polymerization method is preferable. According to the aqueous solution polymerization method, the water-soluble polymer compound can be obtained as a uniform solution.

  The polymerization solvent for the above aqueous solution polymerization is preferably an aqueous solvent, and particularly preferably water. Further, in order to improve the solubility of the above-mentioned monomer components in a solvent, an organic solvent may be added as appropriate within a range that does not adversely affect the polymerization of each monomer. Examples of the organic solvent include alcohols such as isopropyl alcohol and ketones such as acetone. These can be used alone or in combination of two or more.

  The method for producing a water-soluble polymer compound using the above aqueous solvent will be described below. In the polymerization reaction, a known polymerization initiator can be used, but a radical polymerization initiator is particularly preferably used.

  Examples of the radical polymerization initiator include persulfates such as sodium persulfate, potassium persulfate and ammonium persulfate, hydroperoxides such as t-butyl hydroperoxide, water-soluble peroxides such as hydrogen peroxide, and methyl ethyl ketone peroxide. Oxides, ketone peroxides such as cyclohexanone peroxide, oil-soluble peroxides such as di-t-butyl peroxide, dialkyl peroxides such as t-butylcumyl peroxide, azobisisobutyronitrile, 2,2 -Azo compounds such as azobis (2-methylpropionamidine) dihydrochloride. These peroxide-based radical polymerization initiators may be used alone or in combination of two or more. Among the peroxide-based radical polymerization initiators described above, persulfates and azo compounds are preferable, and azobisisobutyronitrile is particularly preferable, because the molecular weight of the water-soluble polymer compound to be generated can be easily controlled. ..

  The amount of the radical polymerization initiator used is not particularly limited, but is 0.1 to 15% by mass, particularly 0.5 to 10% by mass based on the total mass of all monomers of the water-soluble polymer compound. Preference is given to using. By setting this ratio to 0.1% by mass or more, the copolymerization rate can be improved, and by setting it to 15% by mass or less, the stability of the water-soluble polymer compound can be improved.

  In some cases, the water-soluble polymer compound may be produced by using a water-soluble redox polymerization initiator. As the redox-type polymerization initiator, an oxidizing agent (for example, the above-mentioned peroxide) and a reducing agent such as sodium bisulfite, ammonium bisulfite, ammonium sulfite, sodium hydrosulfite, and a combination of iron alum, potassium alum, etc. Can be mentioned.

  In the production of the water-soluble polymer compound, a chain transfer agent may be appropriately added to the polymerization system in order to adjust the molecular weight. Examples of the chain transfer agent include sodium phosphite, sodium hypophosphite, potassium hypophosphite, sodium sulfite, sodium hydrogen sulfite, mercaptoacetic acid, mercaptopropionic acid, thioglycolic acid, 2-propanethiol, 2- Examples include mercaptoethanol and thiophenol.

  The polymerization temperature for producing the water-soluble polymer compound is not particularly limited, but the polymerization temperature is preferably 60 to 100 ° C. When the polymerization temperature is 60 ° C. or higher, the polymerization reaction proceeds smoothly and the productivity becomes excellent, and when the polymerization temperature is 100 ° C. or lower, coloring can be suppressed.

  Further, the polymerization reaction can be carried out under pressure or reduced pressure, but it is preferable to carry out the polymerization reaction under normal pressure because the cost for providing equipment for the pressure or reduced pressure reaction is required. The polymerization time is preferably 2 to 20 hours, particularly 3 to 10 hours.

  After the polymerization reaction, neutralization with a basic compound is carried out if necessary. Examples of the basic compound used for neutralization include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, alkaline earth metal hydroxides such as calcium hydroxide and magnesium hydroxide, ammonia water, and monoethanolamine. And organic amines such as diethanolamine and triethanolamine.

  The pH value (25 ° C.) after neutralization is preferably 2 to 9, and more preferably 3 to 8 in the case of an aqueous solution having a water-soluble polymer compound concentration of 10% by mass.

1-2-7. Weight average molecular weight Polymer having a carboxylic acid group-containing monomer as an essential monomer and a sulfonic acid group-containing monomer constituting the water-soluble polymer compound used in the polishing composition B of the present invention The weight average molecular weights of the polymer having an essential monomer and the copolymer having a carboxylic acid group-containing monomer and a sulfonic acid group-containing monomer as an essential monomer are 1,000 to 1 respectively. It is preferably 1,000,000, more preferably 3,000 to 800,000, and further preferably 5,000 to 600,000. The weight average molecular weight of the water-soluble polymer compound is measured by gel permeation chromatography (GPC) in terms of polyacrylic acid. When the weight average molecular weight of the water-soluble polymer compound is less than 1,000, waviness after polishing is deteriorated. On the other hand, when it exceeds 1,000,000, the viscosity of the aqueous solution becomes high and the handling becomes difficult.

1-2-8. Concentration The concentration of the water-soluble polymer compound in the polishing agent composition B is usually 0.0001 to 3.0% by mass, preferably 0.001 to 2.0% by mass in terms of solid content, and Preferably it is 0.005-1.0 mass%. When the concentration of the water-soluble polymer compound is less than 0.0001% by mass, the effect of adding the water-soluble polymer compound is not sufficiently obtained, and when it is more than 3.0% by mass, the water-soluble polymer compound is added. The effect of addition of (1) reaches a ceiling, and an excessive amount of water-soluble polymer compound is added, which is not economical.

1-3. Organic Sulfate Ester Salt Compound The polishing agent composition B of the present invention may contain an organic sulfate ester salt compound as an optional component. As the organic sulfate salt compound, compounds represented by the following general formulas (1) and (2) can be used.

As the organic sulfate compound, a compound represented by the following general formula (1) can be used.
_{R-O-SO 3 M (} 1)
In the formula, R represents a linear or branched alkyl group having 5 to 21 carbon atoms, an alkenyl group, an aryl group, or an alkylaryl group, and M represents an alkali metal, an alkaline earth metal, an ammonium ion, or an organic cation. ..

  In the general formula (1), the carbon number of R is preferably 8 to 14, and more preferably 10 to 14. Further, R is preferably an alkyl group.

  Specific examples of the alkyl group represented by R include pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group, octadecyl group. Group, nonadecyl group, t-butyl group, isooctyl group, isododecyl group and the like. R is preferably an alkyl group from the viewpoint of oxidation stability and dispersion stability.

  Examples of M in the above general formula (1) include alkali metals such as sodium and potassium, alkaline earth metals such as calcium and magnesium, ammonium ions, quaternary ammonium ions, and organic amines such as triethanolamine.

  Specific examples of the organic sulfate ester compound represented by the general formula (1) include heptyl sulfate, octyl sulfate, lauryl sulfate, higher alcohol (coconut oil) sulfate, stearyl sulfate, and the like. It is preferable to use octyl sulfate, lauryl sulfate and stearyl sulfate. The organic sulfuric acid ester salt compound represented by the general formula (1) may be used alone or in combination of two or more.

  The content of the organic sulfate ester salt compound represented by the general formula (1) in the polishing composition is usually 0.0001 to 2.0% by mass, preferably 0.0005 to 1.0% by mass. is there.

As the organic sulfate compound, a compound represented by the following general formula (2) can be used.
_{R-O- (AO) n -SO} 3 M (2)
In the formula, R represents a linear or branched alkyl group having 5 to 21 carbon atoms, an alkenyl group, an aryl group, or an alkylaryl group, AO represents an oxyalkylene group having 2 or 3 carbon atoms, and n is 1 to 1. It represents a natural number of 30, and M represents an alkali metal, an alkaline earth metal, an ammonium ion, or an organic cation.

  In the general formula (2), n is preferably a natural number of 2-4. Specific examples of M in the above general formula (2) include alkali metals such as sodium and potassium, alkaline earth metals such as calcium and magnesium, ammonium ions, quaternary ammonium ions, and organic amines such as triethanolamine. ..

  Specific examples of the organic sulfate ester salt compound represented by the above general formula (2) include oxyethylene tridecyl ether sulfate (two or three oxyethylene groups per molecule), oxyethylene lauryl ether sulfate ( 2 or 3 oxyethylene groups per molecule), oxyethylene nonyl ether sulfate (3 oxyethylene groups per molecule), oxyethylene octylphenyl ether sulfate (3 oxyethylene groups per molecule) , Oxyethylene nonyl phenyl ether sulfate (3 oxyethylene groups per molecule), and the like, particularly oxyethylene tridecyl ether sulfate (3 oxyethylene groups per molecule), oxyethylene lauryl ether sulfate. Salt (3 oxyethylene groups per molecule), Oxyethene Emissions octylphenyl ether sulfate (1 molecule per oxyethylene group 3), (3 1 molecule per oxyethylene groups) oxyethylene nonylphenyl ether sulfate is preferably used.

  The organic sulfate ester salt compound represented by the general formula (2) can be contained in the polishing composition of the present invention in one kind or in combination of two or more kinds. It can also be used in combination with the organic sulfuric acid ester salt compound represented by the general formula (1).

  The content of the organic sulfuric acid ester salt compound of the general formula (2) in the polishing composition is usually 0.0001 to 2.0% by mass, preferably 0.0005 to 1.0% by mass.

1-4. Acid and / or Salt Thereof In the polishing agent composition B of the present invention, an acid and / or a salt thereof can be used for pH adjustment or as an optional component. Examples of the acid and / or its salt used include inorganic acid and / or its salt and organic acid and / or its salt.

  Examples of the inorganic acid and / or its salt include nitric acid, sulfuric acid, hydrochloric acid, phosphoric acid, phosphonic acid, pyrophosphoric acid, tripolyphosphoric acid and the like and / or salts thereof.

  Examples of the organic acid and / or its salt include aminocarboxylic acids such as glutamic acid and aspartic acid and / or salts thereof, carboxylic acids such as citric acid, tartaric acid, oxalic acid, nitroacetic acid, maleic acid, malic acid and succinic acid, and / or Alternatively, a salt thereof, an organic phosphonic acid and / or a salt thereof can be mentioned. These acids and / or salts thereof may be used alone or in combination of two or more.

  Examples of the organic phosphonic acid and / or its salt include 2-aminoethylphosphonic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, aminotri (methylenephosphonic acid), ethylenediaminetetra (methylenephosphonic acid), diethylenetriaminepenta (methylenephosphone). Acid), ethane-1,1-diphosphonic acid, ethane-1,1,2-triphosphonic acid, ethane-1-hydroxy-1,1,2-triphosphonic acid, ethane-1-hydroxy-1,1,2- Triphosphonic acid, ethane-1,2-dicarboxy-1,2-diphosphonic acid, methanehydroxyphosphonic acid, 2-phosphonobutane-1,2-dicarboxylic acid, 1-phosphonobutane-2,3,4-tricarboxylic acid, α- At least one compound selected from methylphosphonosuccinic acid and salts thereof And the like.

  It is also a preferred embodiment to use two or more kinds of the above compounds in combination, specifically, a combination of sulfuric acid and / or a salt thereof and an organic phosphonic acid and / or a salt thereof, phosphoric acid and / or a salt thereof. Examples thereof include a combination of a salt and an organic phosphonic acid and / or a salt thereof.

1-5. Oxidizing Agent The polishing composition B of the present invention may contain an oxidizing agent as a polishing accelerator. As the oxidizing agent, peroxide, permanganic acid or a salt thereof, chromic acid or a salt thereof, peroxo acid or a salt thereof, halogenoxo acid or a salt thereof, oxygen acid or a salt thereof, and a mixture of two or more of these oxidizing agents. What was done can be used.

  Specifically, hydrogen peroxide, sodium peroxide, barium peroxide, potassium peroxide, potassium permanganate, chromic acid metal salts, dichromic acid metal salts, persulfuric acid, sodium persulfate, potassium persulfate, persulfate. Examples thereof include ammonium sulfate, peroxophosphoric acid, sodium peroxoborate, performic acid, peracetic acid, hypochlorous acid, sodium hypochlorite, calcium hypochlorite, and the like. Among them, hydrogen peroxide, persulfuric acid and salts thereof, hypochlorous acid and salts thereof, etc. are preferable, and hydrogen peroxide is more preferable.

  The content of the oxidizing agent in the abrasive composition is preferably 0.01 to 10.0% by mass. More preferably, it is 0.1 to 5.0 mass%.

2. Physical properties of abrasive composition (pH)
The range of pH value (25 ° C.) of the abrasive composition B of the present invention is preferably 0.1 to 4.0. More preferably, it is 0.5 to 3.0. When the pH value (25 ° C.) of the abrasive composition is 0.1 or more, surface roughness can be suppressed. When the pH value (25 ° C.) of the polishing composition is 4.0 or less, it is possible to prevent the polishing rate from decreasing.

  The abrasive composition of the present invention can be used for polishing various electronic components such as magnetic recording media such as hard disks. Particularly, it is preferably used for polishing an aluminum magnetic disk substrate. More preferably, it can be used for polishing an electroless nickel-phosphorus plated aluminum magnetic disk substrate. The electroless nickel-phosphorus plating is usually plated under the condition that the pH value (25 ° C.) is 4 to 6. Under the condition that the pH value (25 ° C.) is 4 or less, nickel tends to dissolve, which makes plating difficult. On the other hand, in polishing, for example, nickel tends to dissolve under the condition that the pH value (25 ° C.) is 4 or less. Therefore, the polishing rate can be increased by using the abrasive composition of the present invention.

3. Method for Polishing Magnetic Disk Substrate The abrasive composition of the present invention is suitable for use in polishing a magnetic disk substrate such as an aluminum magnetic disk substrate or a glass magnetic disk substrate. In particular, it is suitable for use in polishing an electroless nickel-phosphorus plated aluminum magnetic disk substrate.

  The polishing composition of the present invention is a method for polishing a magnetic disk substrate including a rough polishing step and a finishing step in a multi-step polishing method, and the rough polishing step is performed in the following three steps (1) to (3). It is the abrasive composition B used in the step (3). As a specific polishing method, for example, a method in which a polishing pad is attached to a surface plate of a polishing machine, an abrasive composition is supplied to the surface to be polished of an object to be polished or the polishing pad, and the surface to be polished is rubbed with the polishing pad. There is. For example, when polishing the front surface and the back surface of a magnetic disk substrate at the same time, there is a method of using a double-sided polishing machine in which a polishing pad is attached to each of an upper surface plate and a lower surface plate. In this method, the magnetic disk substrate is sandwiched by the polishing pads attached to the upper surface plate and the lower surface plate, the abrasive composition is supplied between the polishing surface and the polishing pad, and the two polishing pads are simultaneously rotated, The front and back surfaces of the magnetic disk substrate are polished. The polishing pad may be of urethane type, suede type, non-woven fabric type, or any other type.

Step (1): rough polishing in the first stage: a step of supplying a polishing agent composition A containing α-alumina, intermediate alumina, and water to a polishing machine to perform the rough polishing in the first stage. A step of bringing the surface into contact with a polishing pad and moving the polishing pad and / or the substrate to be polished to polish the surface to be polished.

  The polishing agent composition A used in this step is a polishing agent composition containing α-alumina, intermediate alumina and water, and, like the polishing agent composition B as an optional component, a water-soluble polymer compound, An organic sulfate ester salt compound, an acid and / or a salt thereof, an oxidizing agent and the like can be appropriately contained as necessary.

  The abrasive composition A contains α-alumina and intermediate alumina, and examples of the intermediate alumina include γ-alumina, δ-alumina, and θ-alumina. The mixing ratio of α-alumina and intermediate alumina is preferably intermediate alumina / α-alumina (mass ratio) = 0.05 to 2.0, more preferably 0.1 to 1.0, and further preferably 0. .15 to 0.5.

  The average particle diameter of alumina is preferably 0.1 to 2.0 μm, more preferably 0.2 to 1.0 μm. When the average particle diameter of alumina is 0.1 μm or more, a decrease in polishing rate can be suppressed. When the average particle diameter of alumina is 2.0 μm or less, it is possible to suppress the waviness deterioration after polishing.

  The concentration of alumina in the abrasive composition A is preferably 1 to 50% by mass, more preferably 2 to 40% by mass. When the concentration of alumina is 1% by mass or more, a decrease in polishing rate can be suppressed. When the concentration of alumina is 50% by mass or less, polishing can be economically performed without using alumina unnecessarily.

  The content of the oxidizing agent in the abrasive composition A is preferably 0.01 to 10.0% by mass, and more preferably 0.1 to 5.0% by mass.

  The range of the pH value (25 ° C.) of the polishing agent composition A is preferably 0.1 to 4.0, more preferably 0.5 to 3.0.

Step (2): rinse treatment From the viewpoint of reducing the waviness of the substrate surface after the rough polishing step in the multi-step polishing method, after the step (1), the substrate obtained in the step (1) in the same polishing machine. The step (2) of rinsing is performed. The rinse liquid used for the rinse treatment is not particularly limited, but water such as distilled water, ion-exchanged water, pure water, and ultrapure water is used from the economical viewpoint. From the viewpoint of productivity, the step (2) is performed in the same polishing machine without taking out the substrate to be polished from the polishing machine used in the step (1).

Step (3): rough polishing in the latter stage From the viewpoint of reducing deposits and waviness on the substrate surface after the rough polishing step in the multi-step polishing method, an abrasive composition containing colloidal silica, a water-soluble polymer compound and water. A step (3) of supplying B to the surface to be polished of the substrate obtained in the rinsing step (2) and moving the polishing pad and / or the substrate to be polished to the surface to be polished to polish the surface to be polished. Carry out. The steps (1) to (3) are performed by the same polishing machine from the viewpoint of improving productivity and reducing the amount of deposits and undulations on the substrate surface after the rough polishing step. The abrasive composition of the present invention is the abrasive composition B used in the step (3).

  Hereinafter, the present invention will be specifically described based on Examples, but it goes without saying that the present invention is not limited to these Examples and can be carried out in various modes within the technical scope of the present invention. Nor.

[Method for preparing abrasive composition]
The abrasive composition used in each of Examples 1 to 10 and Comparative Examples 1 to 7 is an abrasive composition containing the material shown in Table 1 in the content shown in Table 1. In Table 1, abbreviations of acrylic acid (monomer having carboxylic acid group) are AA, abbreviations of 2-acrylamido-2-methylpropanesulfonic acid (monomer having sulfonic acid group) are ATBS, N-tert. The abbreviation of -butylacrylamide (monomer having an amide group) was TBAA. Table 2 shows the results of the polishing test of each example and each comparative example. Incidentally, sodium polyoxyethylene tridecyl ether sulfate having the abbreviation 330T is an organic sulfate ester compound of the general formula (2), and sodium lauryl sulfate of LS-30 is an organic sulfate ester compound of the general formula (1). ..

[Average particle size]
The average particle size of the alumina was measured using a laser diffraction particle size distribution analyzer (SALD2200 manufactured by Shimadzu Corporation). The average particle size of alumina is the average particle size (D50) at which the cumulative particle size distribution from the small particle size side based on volume is 50%.

  The particle diameter of the colloidal silica (Heywood diameter) was taken by using a transmission electron microscope (TEM) (manufactured by JEOL Ltd., transmission electron microscope JEM2000FX (200 kV), and a field of view of 100,000 times was photographed. It was measured as a Heywood diameter (diameter equivalent to a projected area circle) by analyzing using analysis software (Mac-View Ver. 4.0, manufactured by Mountech Co., Ltd.) The average particle diameter of colloidal silica was 2000 by the method described above. The particle size of about colloidal silica is analyzed, and the particle size at which the cumulative particle size distribution (based on cumulative volume) from the small particle size side is 50% is determined by the above analysis software (manufactured by Mountech Co., Ltd., Mac-View Ver. It is the average particle diameter (D50) calculated using 4.0).

[Weight average molecular weight]
The weight average molecular weight of the water-soluble polymer compound is measured by gel permeation chromatography (GPC) in terms of polyacrylic acid, and the GPC measurement conditions are shown below.

[GPC conditions]
Column: G4000PWXL (manufactured by Tosoh Corporation) + G2500PWXL (manufactured by Tosoh Corporation)
Eluent: 0.2 M phosphate buffer / acetonitrile = 9/1 (volume ratio)
Flow rate: 1.0 ml / min
Temperature: 40 ° C
Detection: 210nm (UV)
Sample: Concentration 5 mg / ml (injection volume 100 μl)
Polymer for calibration curve: polyacrylic acid Molecular weight (peak top molecular weight: Mp) 115,000, 28,000, 4100, 1250 (Sowa Kagaku Co., Ltd., American Polymer Standards Corp)

[Polishing conditions]
Polishing was performed under the following polishing conditions, using an electroless nickel-phosphorus plated aluminum magnetic disk substrate having an outer diameter of 95 mm (hereinafter abbreviated as aluminum disk) as a polishing target.

[Preliminary rough polishing conditions]
Polishing machine: manufactured by Speed Fam Co., Ltd., 9B double-sided polishing machine Polishing pad: manufactured by FILWEL Co., P1 pad Surface plate rotation speed: Upper surface plate -7.5 rpm
Lower surface plate 22.5 rpm
Abrasive composition supply rate: 100 ml / min
Polishing time: 4.5 minutes Processing pressure: 100 g / cm ²
In the preliminary rough polishing, the abrasive composition A was used.

[Rinse condition]
Polishing machine: Same as the first-stage rough polishing Pad: Same as the first-stage rough polishing Plate rotation speed: Same as the first-stage rough polishing Supply amount of rinse liquid: 3 L / min
Rinse time: 20 seconds Processing pressure: 15 g / cm ²
Pure water was used as the rinse liquid.

[Post-stage rough polishing conditions]
Polishing machine: Same as the first-stage rough polishing Pad: Same as the first-stage rough polishing Plate speed: Same as the first-stage rough polishing Supply amount of abrasive composition: 100 ml / min
Polishing time: 80 seconds Processing pressure: 100 g / cm ²
In the latter-stage rough polishing, Abrasive Composition B was used.
Table 2 shows the results of the polishing test under the above polishing conditions.

[Polishing speed ratio]
The polishing rate ratio was calculated based on the following formula by measuring the mass of the aluminum disk that was reduced after polishing.
Polishing speed (μm / min) = aluminum disk mass reduction amount (g) / polishing time (min) / area of one side of aluminum disk (cm ² ) / electroless nickel-phosphorus plating film density (g / cm ³ ) / 2 × 10 ⁴
(However, in the above formula, the area of one side of the aluminum disk is 65.9 cm ² , and the density of the electroless nickel-phosphorus plating film is 8.0 g / cm ³ )
The polishing rate ratio is a relative value when the polishing rate of Comparative Example 3 obtained using the above formula is 1 (reference). The measured value of Comparative Example 3 was 0.335 μm / min.

[Adhesion count ratio]
For the purpose of evaluating the presence or absence of deposits such as abrasive grain residues on the surface of the aluminum disk substrate after polishing, the deposit count was evaluated under the following conditions using a scanning electron microscope observation.
Measuring device: JEOL Ltd., field emission scanning electron microscope "JSM-7100F"
Measurement conditions: Acceleration voltage 15 kV, observation magnification 20,000 times Measurement method: A secondary electron image was formed on the aluminum magnetic disk substrate that had been subjected to post-polishing with the above apparatus and conditions with a contrast in which deposits such as abrasive residue on the substrate appeared white. take in. After performing black-and-white binarization on the captured image using the photo retouching software, the number of pixels in the white portion is calculated and counted as the number of adhered substances.
The adhered matter count ratio is a relative value when the adhered matter count of Comparative Example 3 obtained using the above method is set to 1 (reference). The deposit count of Comparative Example 3 was 1501.

[undulation]
The waviness of the aluminum disc was measured by using a three-dimensional surface structure analysis microscope using a scanning white light interferometry manufactured by Ametech. The measuring conditions are a measuring device manufactured by Ametec (New View 8300 (lens: 1.4 times, zoom: 1.0 times), wavelength of 500 to 1000 μm, a measurement area of 6 mm × 6 mm, analysis by Ametech. The analysis was performed using software (Mx) Note that the values shown in Table 2 are relative values when the swell of Comparative Example 3 is 1 (reference). It was 06Å.

[Discussion]
In Comparative Example 3, although the particle size distribution of colloidal silica is within the range of the present invention, since an abrasive composition that does not contain a specific water-soluble polymer compound is used, polishing rate, deposit count, waviness, etc. In the balance of polishing performance, the results are inferior to those of Examples 1, 2, 5, 6, 8, 9, and 10 containing the water-soluble polymer compound which is a specific copolymer. In other words, the effect of the present invention is exerted by using an abrasive composition containing a specific copolymer as one embodiment in addition to the particle size distribution of colloidal silica being within a specific range. ..

  As another aspect, by using an abrasive composition containing a water-soluble polymer compound obtained by mixing two kinds of homopolymers obtained by homopolymerization of the essential monomers constituting the above copolymer Also, it is shown in Example 7 that the effects of the present invention can be obtained.

  However, the effect of the present invention cannot be obtained when an abrasive composition containing only one type of homopolymer is used. This is demonstrated by Comparative Examples 4 and 5.

  The effects of the present invention can be obtained as shown in Examples 3 and 4 even when an abrasive composition containing an organic sulfate compound is added as an optional component.

  On the other hand, when the particle size distribution of colloidal silica is out of the range of the present invention, as shown in Comparative Examples 1, 2, 6 and 7, inclusion of a specific copolymer does not improve the balance of polishing performance. ..

  From the above, it is clear that by using the polishing composition of the present invention, it is possible to achieve all of the improvement of the polishing rate, the reduction of the deposits on the substrate surface, and the improvement of the waviness. Note that it is not easy to simultaneously achieve all of the improvement of the polishing rate, the reduction of the deposits on the substrate surface, and the improvement of the waviness. According to the present invention, it is possible to manufacture a substrate with reduced adhesion and undulation on the surface of the substrate after the rough polishing step in the multi-step polishing method with high productivity.

  The polishing composition of the present invention can be used for polishing electronic parts such as magnetic recording media such as semiconductors and hard disks. In particular, it can be used for surface polishing of substrates for magnetic recording media such as glass magnetic disk substrates and aluminum magnetic disk substrates. Further, it can be used for surface polishing of an aluminum magnetic disk substrate for a magnetic recording medium having an electroless nickel-phosphorus plating film formed on the surface of an aluminum alloy substrate.

Claims (10)

Abrasive composition B used in step (3) in the rough polishing of a magnetic disk substrate having the following steps (1) to (3) and performing each step (1) to (3) with the same polishing machine And
Contains colloidal silica, water-soluble polymer and water,
The colloidal silica has a cumulative volume frequency of particle size 50 nm in the volume-based particle size distribution measured by Heywood diameter of 35% or more and a cumulative volume frequency of particle size 15 nm in the particle size distribution of 90% or less,
The water-soluble polymer compound, a mixture containing a polymer having a monomer having a carboxylic acid group as an essential monomer and a polymer having a monomer having a sulfonic acid group as an essential monomer, and / or A polishing composition for a magnetic disk substrate, which is a copolymer containing a monomer having a carboxylic acid group and a monomer having a sulfonic acid group as essential monomers.
(1) A polishing agent composition A containing α-alumina, intermediate alumina, and water is supplied to a polishing machine, and the substrate obtained in the step (2) step (1) of performing the rough polishing in the preceding stage is subjected to a rinse treatment. Step (3) A step of supplying a polishing composition B containing colloidal silica, a water-soluble polymer compound and water to a polishing machine to perform a rough polishing in the latter stage.   The copolymer having a monomer having a carboxylic acid group and a monomer having a sulfonic acid group, which are the water-soluble polymer compounds, as essential monomers, has a monomer having a carboxylic acid group and a sulfonic acid group. The abrasive composition for a magnetic disk substrate according to claim 1, wherein the abrasive composition is a copolymer containing an essential monomer and a monomer having an amide group.   The abrasive composition for a magnetic disk substrate according to claim 2, wherein the monomer having an amide group is a monomer selected from acrylamide, methacrylamide, N-alkylacrylamide and N-alkylmethacrylamide.   The abrasive composition for a magnetic disk substrate according to claim 1, wherein the monomer having a carboxylic acid group is a monomer selected from acrylic acid or a salt thereof, methacrylic acid or a salt thereof. object.   The monomer having a sulfonic acid group is isoprenesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, 2-methacrylamido-2-methylpropanesulfonic acid, styrenesulfonic acid, vinylsulfonic acid, allylsulfonic acid, The abrasive composition for magnetic disk substrates according to any one of claims 1 to 4, which is one or more monomers selected from isoamylene sulfonic acid, vinyl naphthalene sulfonic acid, and salts thereof. object. The magnetic disk substrate according to any one of claims 1 to 5, wherein the abrasive composition further contains an organic sulfate ester salt compound, and the organic sulfate ester salt compound is represented by the following general formula (1). Abrasive composition.
_{R-O-SO 3 M (} 1)
In the formula, R represents a linear or branched alkyl group having 5 to 21 carbon atoms, an alkenyl group, an aryl group or an alkylaryl group, and M represents an alkali metal salt, an alkaline earth metal salt, an ammonium ion or an organic cation. .. The magnetic disk substrate according to any one of claims 1 to 5, wherein the abrasive composition further contains an organic sulfate ester salt compound, and the organic sulfate ester salt compound is represented by the following general formula (2). Abrasive composition.
_{R-O- (AO) n -SO} 3 M (2)
In the formula, R represents a linear or branched alkyl group having 5 to 21 carbon atoms, an alkenyl group, an aryl group, or an alkylaryl group, AO represents an oxyalkylene group having 2 or 3 carbon atoms, and n is 1 to 1. It represents a natural number of 30, and M represents an alkali metal, an alkaline earth metal, an ammonium ion or an organic cation.   The magnetic disk according to claim 1, wherein the abrasive composition further contains an acid and / or a salt thereof, and has a pH value (25 ° C.) in the range of 0.1 to 4.0. Substrate abrasive composition.   The abrasive composition for magnetic disk substrates according to claim 1, wherein the abrasive composition further contains an oxidizing agent.   The abrasive composition for a magnetic disk substrate according to claim 1, which is used for rough polishing of an electroless nickel-phosphorus plated aluminum magnetic disk substrate.