JP2021072140A - Polishing agent composition for magnetic disk substrate and polishing method for magnetic disk substrate - Google Patents

Abstract

To provide a polishing agent composition capable of reducing long wavelength undulation and halation of a substrate after polish while improving productivity in polishing a magnetic disk substrate many times.SOLUTION: A polishing agent composition contains colloidal silica having an average primary particle diameter of 1 to 100nm and water, and the colloidal silica is constituted while containing at least 3 mass% or more of silica particles having Al content of 100 mg/kg or smaller in a solid. Alternatively, the polishing agent composition contains colloidal silica having an average primary particle diameter of 1 to 100nm and water, and the colloidal silica is constituted while containing at least 3 mass% or more of silica particles synthesized by using metal silicon as a raw material.SELECTED DRAWING: None

Description

The present invention relates to an abrasive composition used for polishing electronic components such as magnetic recording media such as semiconductors and hard disks, and a method for polishing a magnetic disk substrate. In particular, a magnetic recording medium substrate such as a glass magnetic disk substrate or an aluminum magnetic disk substrate, or 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 (hereinafter, simply The present invention relates to a magnetic disk substrate polishing agent composition used for surface polishing of a “magnetic disk substrate”), and a method for polishing a magnetic disk substrate using the magnetic disk substrate polishing agent composition.

Conventionally, an abrasive composition for a magnetic disk substrate (hereinafter, simply referred to as "abrasive composition") for polishing the surface of an electroless nickel-phosphorus plating film of an aluminum magnetic disk substrate has improved the magnetic recording density. For the purpose, improvement of various polishing properties is required. For example, with regard to scratches, the scratch portion may cause an error in writing or reading, or the burr portion generated around the scratch may cause a collision with the head. Further, there is another swell that can cause a collision with the head, and reduction of the swell is required.

From the viewpoint of reducing scratches, colloidal silica has been used for an aluminum magnetic disk substrate as an abrasive grain portion responsible for mechanical polishing of an abrasive composition. At that time, in industrial polishing, the abrasive grain portion responsible for mechanical polishing of the abrasive composition and the chemical portion responsible for chemical polishing are often mixed and used immediately before the actual polishing.

However, it is known that when the colloidal silica as the abrasive grain portion and the chemical portion are mixed, the colloidal silica tends to aggregate. As measures for suppressing the adverse effect of agglomerated particles of colloidal silica, removal of coarse particles, adjustment of corrosiveness of abrasive (see Patent Document 1), adjustment of particle shape (see Patent Document 2), inclusion of agglomerated particles Proposals have been made for adjusting the amount (see Patent Document 3).

On the other hand, it is also known that metal impurities contained in colloidal silica remain on the substrate surface of the magnetic disk substrate after the polishing process and impair the surface smoothness. A production method for producing a small amount of colloidal silica has also been proposed. Further, for this purpose, an alkoxysilane method using tetraethoxysilane or the like as a raw material and a method for producing colloidal silica using metallic silicon, which is a more inexpensive raw material, have also been proposed (see, for example, Patent Documents 4 to 6). ).

Japanese Unexamined Patent Publication No. 2009-12850 Japanese Unexamined Patent Publication No. 2009-172709 JP-A-2010-170650 Special Publication No. 49-4637 JP-A-49-64595 International Publication No. 2008/072637

In recent years, the quality requirements have become more sophisticated due to the improvement in magnetic recording density, and in the case of multiple polishing in industrial production forms, it has been required to reduce scratches and waviness while improving productivity. Here, the swell includes a long wavelength swell (500 μm to 1000 μm), a medium wavelength swell (wavelength: 100 to 500 μm), and a short wavelength swell (wavelength: 20 to 100 μm). Since it may cause collisions, it has been required to reduce it.

Furthermore, from the viewpoint of improving the magnetic recording density, a new reduction in halation is also required. Here, halation can be detected as a minute defect on the substrate surface under specific inspection conditions by a substrate all-surface defect inspection machine (NS2000H manufactured by Hitachi High-Tech Fine Systems Corporation), and can be quantitatively evaluated as a halation count. (Details will be described later).

Halation is thought to be a phenomenon caused by the presence of some fine non-uniformity on the surface of the substrate over a wide area of the substrate, due to the polishing pads, carriers, substrates, and abrasive compositions, respectively. It is considered that the characteristics of the are inconsistent. Recently, the existence of halation has become a new problem as an obstacle to the improvement of magnetic recording density, and reduction of such halation is required.

Further, by performing polishing a large number of times, the polishing speed decreases due to dirt on the polishing pad and the like, which causes a problem that productivity decreases, and it is an object of improvement in this respect as well.

Therefore, the present invention provides an abrasive composition capable of reducing long-wavelength waviness and halation of a magnetic disk substrate after polishing while improving productivity in multiple polishing of a magnetic disk substrate, and the abrasive. An object of the present invention is to provide a method for polishing a magnetic disk substrate using a composition.

As a result of diligent studies to solve the above problems, the inventor of the present application uses the following abrasive composition for a magnetic disk substrate to improve productivity in multiple polishing and reduce long-wavelength swell and halation. We have found that it is possible to make it possible, and have completed the present invention.

[1] Colloidal silica having an average primary particle size of 1 to 100 nm and water are contained, and the colloidal silica contains at least 3% by mass or more of silica particles having an Al content of 100 mg / kg or less in a solid. Abrasive composition for disk substrates.

[2] Abrasive for magnetic disk substrates containing colloidal silica having an average primary particle diameter of 1 to 100 nm and water, and the colloidal silica contains at least 3% by mass of silica particles synthesized from metallic silicon as a raw material. Agent composition.

[3] The abrasive composition for a magnetic disk substrate according to the above [2], wherein the colloidal silica contains at least 10% by mass or more of silica particles synthesized from the metallic silicon as a raw material.

[4] The abrasive composition for a magnetic disk substrate according to any one of the above [1] to [3], which further contains a water-soluble polymer compound.

[5] The water-soluble polymer compound is a copolymer containing a monomer having a carboxylic acid group and a monomer having an amide group as essential monomers, and has a weight average molecular weight of 1,000 to 1, 1. The abrasive composition for a magnetic disk substrate according to the above [4], which is ,000,000.

[6] The water-soluble polymer compound is a copolymer containing a monomer having a carboxylic acid group and a monomer having a sulfonic acid group as essential monomers, and has a weight average molecular weight of 1,000 to 1. The polishing agent composition for a magnetic disk substrate according to the above [4], which is 000,000.

[7] The water-soluble polymer compound is a copolymer containing a monomer having a carboxylic acid group, a monomer having an amide group, and a monomer having a sulfonic acid group as essential monomers. The abrasive composition for a magnetic disk substrate according to the above [4], which has a weight average molecular weight of 1,000 to 1,000,000.

[8] The magnetic field according to any one of [5] to [7] above, wherein the monomer having a carboxylic acid group is a monomer selected from acrylic acid or a salt thereof, or methacrylic acid or a salt thereof. Abrasive composition for disk substrates.

[9] The monomer having an amide group is one or more monomers selected from acrylamide, methacrylamide, N-alkylacrylamide, and N-alkylmethacrylamide. 7] The abrasive composition for a magnetic disk substrate.

[10] The monomer having a sulfonic acid group includes isoprene sulfonic acid, 2-acrylamide-2-methylpropanesulfonic acid, 2-methacrylamide-2-methylpropanesulfonic acid, styrenesulfonic acid, vinylsulfonic acid, and allyl. The polishing composition for a magnetic disk substrate according to the above [6] or [7], which is a monomer selected from sulfonic acid, isoamylene sulfonic acid, vinylnaphthalene sulfonic acid, and salts thereof.

[11] The polishing for a magnetic disk substrate according to any one of the above [1] to [10], which further contains an acid and / or a salt thereof and has a pH value in the range of 0.1 to 4.0 at 25 ° C. Agent composition.

[12] The abrasive composition for a magnetic disk substrate according to any one of the above [1] to [11], which further contains an oxidizing agent.

[13] A method for polishing a magnetic disk substrate using the polishing agent composition for a magnetic disk substrate according to any one of [1] to [12] above, wherein a nickel-phosphorus plating film is applied to the surface of the aluminum alloy substrate. A multi-stage polishing method is adopted in which the magnetic disk substrate on which the above-mentioned structure is formed is targeted for polishing, and the polishing process is repeated a plurality of times on the magnetic disk substrate. A method for polishing a magnetic disk substrate using.

The abrasive composition of the present invention contains silica particles having an Al content of 100 mg / kg or less in a solid, or colloidal silica containing silica particles synthesized from metallic silicon as a raw material, and water, and is an aluminum alloy. When polishing the surface of an aluminum magnetic disk substrate for magnetic recording media in which an electroless nickel-phosphorus plating film is formed on the surface of the substrate, the long-wavelength swell of the polished substrate is improved by polishing multiple times. It has an excellent effect of reducing halation and contributing to productivity and surface quality improvement of the substrate. In addition, the method for polishing a magnetic disk substrate of the present invention enables polishing of a magnetic disk substrate exhibiting the above effects by using such an abrasive composition.

Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the following embodiments, and is described below based on the ordinary knowledge of those skilled in the art without departing from the spirit of the present invention. It should be understood that those in which appropriate changes, improvements, etc. are added to the embodiments of the above are also included in the scope of the present invention.

1. 1. Abrasive composition The abrasive composition of the present invention (abrasive composition for magnetic disk substrate) is silica synthesized from silica particles or metallic silicon having an Al content of 100 mg / kg or less in a solid as an essential component. An abrasive composition containing particles-containing colloidal silica and water, preferably containing a water-soluble polymer compound, and containing an acid and / or a salt thereof and an oxidizing agent as other optional components. Is to be done.

1.1 Colloidal silica The colloidal silica used in the abrasive composition of the present invention contains at least 3% by mass or more of silica particles having an Al content of 100 mg / kg or less in a solid. Alternatively, it contains at least 3% by mass or more of silica particles synthesized from metallic silicon as a raw material.

The silica particles synthesized from metallic silicon as a raw material will be described below. Here, the reaction of producing silica from metallic silicon and water proceeds in the presence of an alkaline catalyst in Patent Document 6, for example, as shown in the following formulas (1) to (3), accompanied by hydrogen gas generation. Is disclosed.

Dissolution _{^{reaction: Si + 2OH - + H 2}} O → SiO 3 2- + 2H 2 ↑ (1)
Polymerization reaction: SiO ₃ ^2- + H ₂ O → SiO ₂ + 2OH ⁻ (2)
Summary reaction formula: Si + 2H ₂ O → SiO ₂ + 2H ₂ ↑ (3)

If the above reaction proceeds completely, colloidal silica is produced from metallic silicon in the presence of an alkaline catalyst, as shown in the formula (3). In this case, 2 mol of water is consumed with respect to 1 mol of metallic silicon, and 1 mol is consumed. Silica and 2 mol of hydrogen will be generated.

In order to allow the synthetic reaction to proceed smoothly, the raw material silicon is usually supplied to the reactor together with pure water as a powder finely divided in advance so that the average particle size is 1 mm or less. In order to allow the synthesis reaction to proceed smoothly, an alkali catalyst such as sodium hydroxide, potassium hydroxide, or lithium hydroxide is usually added, and the synthesis reaction is allowed to proceed at a temperature of 60 to 100 ° C., and fine silica particles having a diameter of 5 to 150 nm are allowed to proceed. Obtains a dispersed slurry.

Impurities such as heavy metals are separated as insoluble matter in the process of dissolving the raw material silicon. As a result, colloidal silica having less metal impurities than colloidal silica obtained by the water glass method using sodium silicate or potassium silicate as a raw material can be obtained. In the abrasive composition of the present invention, the silica particles synthesized from metallic silicon as a raw material have an Al content in a solid of 100 mg / kg or less, preferably 80 mg / kg or less, and more preferably 50 mg / kg or less. Some are used.

As a method for producing colloidal silica having few metal impurities, for example, there is known an alkoxysilane method in which an alkoxysilane such as tetraethoxysilane is hydrolyzed with an acid or an alkali. Colloidal silica made from metallic silicon used in the abrasive composition of the present invention can be produced at a lower cost than the above-mentioned alkoxysilane method, and is advantageous in terms of cost.

Colloidal silica contains at least 3% by mass or more, preferably 10% by mass or more, and more preferably 20% by mass or more of silica particles synthesized from metallic silicon as a raw material. A mixture of silica particles synthesized from metallic silicon as a raw material, colloidal silica produced by the water glass method, colloidal silica produced by the alkoxysilane method, and the like can also be appropriately used, if necessary.

The average primary particle size of colloidal silica used in the abrasive composition of the present invention is 1 to 100 nm, preferably 3 to 80 nm. Here, by setting the average primary particle size to 1 nm or more, it is possible to suppress a decrease in the polishing rate. On the other hand, by setting the average primary particle size to 100 nm or less, deterioration of the surface smoothness of the magnetic disk substrate after polishing can be suppressed.

The shape of colloidal silica is known to be spherical, konpeito-type (particulate with convex parts on the surface), irregular-shaped, etc., and the primary particles are monodispersed in water to form a colloid. As the colloidal silica used in the present invention, spherical or nearly spherical colloidal silica is preferable. Surface smoothness can be further improved by using spherical or near-spherical colloidal silica.

1.2 Water-soluble polymer compound The water-soluble polymer compound used in the present invention is preferably a copolymer containing a monomer having a carboxylic acid group as an essential monomer, and more preferably (a). A copolymer in which a monomer having a carboxylic acid group and a monomer having an amide group are essential monomers, (b) a monomer having a carboxylic acid group and a monomer having a sulfonic acid group are essential singles. Examples include a copolymer as a dimer, (c) a monomer having a carboxylic acid group, a monomer having an amide group, and a copolymer having a monomer having a sulfonic acid group as an essential monomer. Can be done.

12.1 Monomer having a carboxylic acid group As the monomer having a carboxylic acid group, an unsaturated aliphatic carboxylic acid and a salt 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.

The pH value of the water-soluble polymer compound is determined by whether the monomer having a carboxylic acid group is present in the acid state or in the salt state in a large proportion among the water-soluble polymer compounds. Can be evaluated with. The higher the proportion present as an acid, the lower the pH value, and the greater the proportion present as a salt, the higher the pH value. In the present invention, for example, a water-soluble polymer compound having a pH value in the range of 0.1 to 13.0 at 25 ° C. in an aqueous solution of a water-soluble polymer compound having a concentration of 10% by mass can be used.

1.2.2 Monomer having an amide group As a specific example of the monomer having an amide group, acrylamide, methacrylamide, N-alkylacrylamide, N-alkylmethacrylamide and the like can be used. Specific examples of N-alkylacrylamide and N-alkylmethacrylicamide include N-methylacrylamide, N-ethylacrylamide, Nn-propylacrylamide, N-iso-propylacrylamide, Nn-butylacrylamide, and N-iso. -Butylacrylamide, N-sec-Butylacrylamide, N-tert-Butylacrylamide, N-Methylmethacrylate, N-Ethylmethacrylate, N-n-propylmethacrylate, N-iso-propylmethacrylate, N-n- Examples thereof include butylmethacrylate, N-iso-butylmethacrylate, N-sec-butylmethacrylate, N-tert-butylmethacrylate and the like.

1.2.3 Monomer having a sulfonic acid group Specific examples of the monomer having a sulfonic acid group include isoprene sulfonic acid, 2-acrylamide-2-methylpropansulfonic acid, and 2-methacrylamide-2-methyl. Examples thereof include propane sulfonic acid, styrene sulfonic acid, vinyl sulfonic acid, allyl sulfonic acid, isoamylene sulfonic acid, vinyl naphthalene sulfonic acid, and salts thereof. Preferred examples thereof include 2-acrylamide-2-methylpropanesulfonic acid, 2-methacrylamide-2-methylpropanesulfonic acid, and salts thereof.

1.2.4 Copolymer A copolymer having a monomer having a carboxylic acid group preferably contained in the abrasive composition of the present invention as an essential monomer will be described.

Here, when the water-soluble polymer compound is (a) a copolymer in which a monomer having a carboxylic acid group and a monomer having an amide group are essential monomers, a monomer having a carboxylic acid group. The molar ratio of the constituent units derived from is preferably 50 to 95 mol%, more preferably 60 to 93 mol%. The molar ratio of the structural unit derived from the monomer having an amide group is preferably 5 to 50 mol%, more preferably 7 to 40 mol%.

On the other hand, when the water-soluble polymer compound is (b) a copolymer in which a monomer having a carboxylic acid group and a monomer having a sulfonic acid group are essential monomers, a monomer having a carboxylic acid group. The molar ratio of the constituent units derived from is preferably 30 to 95 mol%, more preferably 40 to 90 mol%. The molar ratio of the monomer having a sulfonic acid group is preferably 5 to 70 mol%, more preferably 10 to 60 mol%.

Further, when the water-soluble polymer compound is (c) a copolymer containing a monomer having a carboxylic acid group, a monomer having an amide group, and a monomer having a sulfonic acid group as essential monomers. The molar ratio of the structural unit derived from the monomer having a carboxylic acid group is preferably 50 to 95 mol%, more preferably 60 to 93 mol%, still more preferably 70 to 90 mol%. The molar ratio of the structural unit derived from the monomer having an amide group is preferably 1 to 40 mol%, more preferably 3 to 30 mol%, still more preferably 5 to 20 mol%. The molar ratio of the structural unit derived from the monomer having a sulfonic acid group is preferably 0.01 to 20 mol%, more preferably 0.1 to 10 mol%, still more preferably 0.2 to 5 mol%.

1.2.5 Method for Producing Water-Soluble Polymer Compound The method for producing the water-soluble polymer compound used in the abrasive composition of the present invention is not particularly limited, but for example, a water-soluble polymer is produced by using an aqueous solution polymerization method. It is preferable to produce a compound. According to the aqueous solution polymerization method, a water-soluble polymer compound can be obtained as a uniform solution.

The polymerization solvent in the above aqueous solution polymerization method is preferably an aqueous solvent, and particularly preferably water. Further, in order to improve the solubility of the above-mentioned monomer component in a solvent, an organic solvent may be appropriately added as long as it 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.

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

Here, examples of the radical polymerization initiator include persulfates such as sodium persulfate, potassium persulfate and ammonium persulfate, hydroperoxides such as t-butyl hydroperoxide, and water-soluble peroxides such as hydrogen peroxide. , Ketone peroxides such as methyl ethyl ketone peroxide and cyclohexanone peroxide, oil-soluble peroxides such as dialkyl peroxides such as di-t-butyl peroxide and t-butylcumyl peroxide, azobisisobutyronitrile, Examples thereof include azo compounds such as 2,2-azobis (2-methylpropionamidine) dihydrochloride. Only one kind of these peroxide-based radical polymerization initiators may be used, or two or more kinds thereof may be used in combination.

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 produced can be easily controlled. ..

The amount of the radical polymerization initiator used is not particularly limited, but is a mass ratio of 0.1 to 15% by mass, particularly 0.5 to 10% by mass, based on the total mass of all the monomers of the water-soluble polymer compound. It is preferable to use in. By setting this mass 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.

Further, depending on the production conditions, the water-soluble polymer compound may be produced by using a water-soluble redox-based polymerization initiator. As the redox-based polymerization initiator, a combination of an oxidizing agent (for example, the above-mentioned peroxide), a reducing agent such as sodium bisulfite, ammonium bisulfite, ammonium sulfite, sodium hydrosulfite, iron syrup, and potassium syrup is used. Can be mentioned.

Further, 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 sulfite, sodium hypophosphite, potassium hypophosphite, sodium sulfite, sodium hydrogen sulfite, mercaptoacetic acid, mercaptopropionic acid, thioglycolic acid, 2-propanethiol, 2-. Examples thereof 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 is excellent, and when the polymerization temperature is 100 ° C. or lower, coloring can be suppressed.

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

After the polymerization reaction for a predetermined polymerization time, a treatment of neutralizing with a basic compound is performed if necessary. Examples of the basic compound used for neutralization include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, alkali earth metal hydroxides such as calcium hydroxide and magnesium hydroxide, and aqueous ammonia. , Organic amines such as monoethanolamine, diethanolamine, triethanolamine and the like.

The pH value at 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.

1.2.6 Weight Average Molecular Weight The weight average molecular weight of the water-soluble polymer compound is preferably 1,000 to 1,000,000, more preferably 2,000 to 800,000, and even more preferably 3. It is 000 to 600,000. The weight average molecular weight of the water-soluble polymer compound was 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, the waviness after polishing worsens. If it exceeds 1,000,000, the viscosity of the aqueous solution becomes high and handling becomes difficult.

1.2.7 Concentration The concentration of the water-soluble polymer compound in the abrasive composition is preferably 0.0001 to 3.0% by mass, more preferably 0.0005 to 2.0% by mass in terms of solid content. %, More preferably 0.001 to 1.0% by 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 the addition of the above is leveled off, and more water-soluble polymer compounds are added than necessary, which is not economical.

1.3 Acid and / or salt thereof Acid and / or salt thereof can be used for adjusting the pH value of the abrasive composition or as an optional component. Examples of the acid and / or a salt thereof used include an inorganic acid and / or a salt thereof and an organic acid and / or a salt thereof.

Examples of the inorganic acid and / or a salt thereof include an inorganic acid such as nitric acid, sulfuric acid, hydrochloric acid, phosphoric acid, phosphonic acid, pyrophosphate, and tripoliphosphoric acid and / or a salt thereof.

Organic acids and / or salts thereof 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 a salt thereof, an organic phosphonic acid and / or a salt thereof. As these acids and / or salts thereof, one kind or two or more kinds can be used.

Examples of the organic phosphonic acid and / or a salt thereof include 2-aminoethylphosphonic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, aminotri (methylenephosphonic acid), ethylenediaminetetra (methylenephosphonic acid), and diethylenetriaminepenta (methylenephosphone). Acid), ethane-1,1-diphosphonic acid, ethane-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-methylphosphonosuccinic acid, and at least one selected from salts thereof. The above compounds can be mentioned.

It is also a preferred embodiment to use two or more 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.

1.4 Oxidizing agent The abrasive composition of the present invention may contain an oxidizing agent as a polishing accelerator. As the oxidizing agent, peroxide, permanganic acid or its salt, chromic acid or its salt, peroxo acid or its salt, halogenoxo acid or its salt, oxygen acid or its salt, two or more kinds of these oxidizing agents are mixed. Can be used.

Specifically, hydrogen peroxide, sodium peroxide, barium peroxide, potassium peroxide, potassium permanganate, metal salt of chromium acid, metal salt of dichromic acid, persulfate, sodium persulfate, potassium persulfate, excess Examples thereof include ammonium sulfate, peroxophosphate, sodium peroxoborate, pergic acid, peracetic acid, hypochlorite, sodium hypochlorite, calcium hypochlorite and the like. Of these, hydrogen peroxide, persulfuric acid and salts thereof, hypochlorous acid and salts thereof and the like are preferable, and hydrogen peroxide is more preferable.

The oxidant content in the abrasive composition is preferably 0.01 to 10.0% by mass. More preferably, it is 0.1 to 5.0% by mass. Here, the abrasive composition of the present invention may contain a buffer, an antifungal agent, an antibacterial agent, and the like in addition to the above components.

1.5 Physical Properties The pH value of the abrasive composition of the present invention at 25 ° C. (hereinafter referred to as “pH value (25 ° C.)”) is preferably 0.1 to 4.0, more preferably 0. It is 5 to 3.0. When the pH value (25 ° C.) of the abrasive composition is 0.1 or more, deterioration of surface smoothness can be suppressed. When the pH value (25 ° C.) of the abrasive composition is 4.0 or less, it is possible to suppress a decrease in the polishing rate. In electroless nickel-phosphorus plating, when the pH value (25 ° C.) is 4.0 or less, nickel tends to dissolve, which makes it difficult for the plating to proceed. On the other hand, in polishing, for example, nickel tends to dissolve under a condition where the pH value (25 ° C.) is 4.0 or less, so that the polishing rate can be increased by using the abrasive composition of the present invention. become.

2. Method for Polishing Magnetic Disk Substrate The method for polishing the magnetic disk substrate of the present invention is an aluminum magnetic disk substrate (hereinafter referred to as "aluminum disk") or glass magnetism in which the surface of the aluminum alloy substrate is electroless nickel-phosphorus plated. Suitable for use in polishing magnetic disk substrates such as disk substrates. In particular, the polishing method for the magnetic disk substrate of the present invention employs a multi-stage polishing method in which the polishing process is repeated a plurality of times for the magnetic disk substrate, and the polishing agent composition used in the final polishing step for the magnetic disk substrate is used. Suitable for polishing on magnetic disk substrates such as disks.

As a polishing method to which the polishing agent composition of the present invention can be applied, for example, a polishing pad is attached to a platen of a polishing machine, and the surface to be polished (for example, an aluminum disc) or the polishing pad is polished. There is a method (called polishing) in which the agent composition is supplied and the surface to be polished is rubbed with a polishing pad. For example, when polishing the front surface and the back surface of an aluminum disc at the same time, there is a method of using a double-sided polishing machine in which polishing pads are attached to each of the upper surface plate and the lower surface plate. In this method, the abrasive composition is supplied between the polishing pads attached to the upper surface plate and the lower surface plate, and the front surface and the back surface of the aluminum disc are polished by rotating the two polishing pads at the same time. .. As the polishing pad, urethane type, suede type, non-woven fabric type, or any other type can be used.

Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited to these examples, and it is said that the present invention can be carried out in various embodiments as long as it belongs to the technical scope of the present invention. Not to mention.

In the polishing of each of the following Examples and Comparative Examples, an electroless nickel-phosphorus-plated aluminum alloy substrate (hereinafter, may be simply referred to as “substrate”) that has been roughly polished in advance is prepared, and from the first time. Finish polishing was continuously performed up to the 900th time. Tables 2 to 4 show the evaluation results of the polishing speed, the long wavelength swell and the halation on the surface of the substrate during the 20th and 300th times of the continuous finish polishing and the 900th time of the final polishing. The transitions of polishing speed, long wavelength swell and halation in the finish polishing process in Examples and Comparative Examples were compared. Hereinafter, a specific description will be given.

(Method for preparing abrasive composition)
The abrasive composition used in Examples 1 to 16 and Comparative Examples 1 to 6 is an abrasive composition containing the materials shown in Table 1 at the contents shown in Table 1. Tables 2 to 4 show the polishing performed by the polishing test using these abrasive compositions.

(Weight average molecular weight of water-soluble polymer compound)
The weight average molecular weight of the water-soluble polymer compound was measured by gel permeation chromatography (GPC) in terms of polyacrylic acid, and the GPC measurement conditions are shown below.
GPC condition column: TSKgel G4000PWXL (manufactured by Tosoh) + G2500PWXL (manufactured by Tosoh) + SHODEX OHpak SB-806M-HQ (manufactured by Showa Denko)
Eluent: 0.2M phosphate buffer / acetonitrile = 9/1 (volume ratio)
Flow velocity: 1.0 mL / min
Temperature: 40 ° C
Detection: Differential Refractometer (RI)
Sample: Concentration 0.1 wt% (injection volume 100 μL)
Polymer for calibration curve: Polyacrylic acid Molecular weight (Mp) 115,000, 28,000, 4100,
1250 (Souwa Kagaku Co., Ltd., American Polymer Standards Corp.)

(Method for measuring particle size of silica particles)
For the particle size (Heywood size) of colloidal silica, a photograph with a field of view of 100,000 times was taken using a transmission electron microscope (TEM) (transmission electron microscope JEM2000FX (200 kV) manufactured by JEOL Ltd.). This photograph 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.). For the average primary particle size of colloidal silica, the particle size of about 2000 colloidal silica is analyzed by the above method, and the particle size at which the integrated particle size distribution (cumulative volume basis) from the small particle size side is 50% is described above. It is an average primary particle size (D50) calculated using analysis software (Mac-View Ver. 4.0 manufactured by Mountech Co., Ltd.).

(Method for measuring Al content of colloidal silica)
The Al content of colloidal silica was measured by drying the dispersion containing colloidal silica, dissolving all the solids, and then measuring the Al content in the solids of colloidal silica using an ICP emission spectrophotometer.

(Polishing conditions)
An aluminum magnetic disk substrate (substrate) having an outer diameter of 95 mm on which an electroless nickel-phosphorus plating film was formed was roughly polished and polished many times.
Polishing machine: Speed Fam Co., Ltd., 9B double-sided grinding machine Polishing pad: FILWEL Co., Ltd. P2 pad surface plate Rotation speed: Upper surface plate -8.3min ^-1
Lower platen 25.0min ^-1
Abrasive composition supply amount: 50 ml / min
Polishing time: 300 seconds Processing pressure: 14 kPa

After mixing each component to prepare an abrasive composition, it was introduced into a polishing machine through a filter having a mesh size of 0.45 μm, and a polishing test was carried out. The polishing test was evaluated for the polishing speed, long wavelength swell, and halation at the 20th, 300th, and 900th times of multiple polishing.

<Evaluation of polished disc surface>
(Polishing rate ratio)
The polishing rate was calculated based on the following formula by measuring the mass of the aluminum magnetic disk substrate reduced after polishing.
Polishing rate (mg / min) = Mass reduction of aluminum magnetic disk substrate (mg) / Polishing time (min)

The polishing rate ratio is a relative value when the polishing rate obtained by using the above formula when polishing the substrate for the 20th time in the comparative example is 1 (reference). In Table 2, the value when the 20th substrate was polished in Comparative Example 1 was set to 1, in Table 3, the value when the 20th substrate was polished in Comparative Example 3 was set to 1, and in Table 4, the value was set to 1. The value at the time of polishing the substrate for the 20th time in Comparative Example 5 was set to 1.

(Evaluation method for long wavelength swell on the surface of the substrate after polishing)
The long wavelength swell of the substrate was measured using a three-dimensional optical profiler New View 8300 manufactured by AMETEK, Inc.
The measurement conditions are as follows.
Lens 1.4x ZWF type ZOOM 2.0x Measurement Type Surface
Measure Mode CSI
Scan Length 5 μm
Camera Mode 1024 x 1024
Filter Band Pass
Cut Off Short 500.000 μm
Long 100.000 μm
Measurement point radius 30.00 mm
12 points for every 30 ° angle

The long wavelength swell ratio is a relative value when the value obtained by using the above method when the substrate is polished for the 20th time in the comparative example is set to 1 (reference). In Table 2, the value when the 20th substrate was polished in Comparative Example 1 was set to 1, in Table 3, the value when the 20th substrate was polished in Comparative Example 3 was set to 1, and in Table 4, the value was set to 1. The value at the time of polishing the substrate for the 20th time in Comparative Example 5 was set to 1.

(Method of evaluating halation on the surface of the substrate after polishing)
Halation was measured using NS2000H manufactured by Hitachi High-Tech Fine Systems Corporation, a substrate all-surface defect inspection machine. The measurement conditions are as follows.

<Measurement conditions>
PMT / APD Power Control Voltage
Hi-Light 1 OFF
Hi-Light 2 821V
Scan Pitch 3 μm
Inner / Outer Radius 18.0000-47.0000mm
Positive Level 77mV
H2 White Spot Level 80.0mV

Halation is detected as a fine defect on the surface of the substrate under the above inspection conditions, and can be quantitatively evaluated as a halation count.

(Halation ratio)
The halation ratio is a relative value when the halation count obtained by using the above method when the 20th substrate is polished in the comparative example is set to 1 (reference). In Table 2, the value when the 20th substrate was polished in Comparative Example 1 was set to 1, in Table 3, the value when the 20th substrate was polished in Comparative Example 3 was set to 1, and in Table 4, the value when the 20th substrate was polished was set to 1. The value at the time of polishing the substrate for the 20th time was set to 1.

<Discussion>
From the comparison between Example 1 and Comparative Example 1 in Table 2, colloidal silica containing silica particles having an Al content of 100 mg / kg or less in a solid or silica particles synthesized from metallic silicon as a raw material is used. As a result, it can be seen that the decrease in polishing speed is suppressed, the long wavelength waviness is improved, and the halation is also improved in multiple times of polishing.

Example 2 is an example in which the mass ratio of silica particles having an Al content of 100 mg / kg or less in a solid or silica particles synthesized from metallic silicon as a raw material is larger than that of Example 1. In this case as well, it can be seen that the balance of polishing speed, long wavelength swell, and halation is superior to that of Comparative Example 1. The same can be said for the comparison between Example 3 and Comparative Example 2 in which the D50 of the entire colloidal silica is different.

From the comparison between Example 4 and Comparative Example 3 in Table 3, silica particles or metallic silicon having an Al content of 100 mg / kg or less in the solid even when the abrasive composition contains an acrylic acid homopolymer It can be seen that by using colloidal silica containing silica particles synthesized as a raw material, a decrease in polishing rate is suppressed in multiple polishings, long-wavelength waviness is improved, and halation is also improved.

Example 5 is an experimental example in which the mass ratio of silica particles having an Al content of 100 mg / kg or less in a solid or silica particles synthesized from metallic silicon as a raw material is larger than that of Example 4. In this case as well, it can be seen that the balance of polishing speed, long wavelength swell, and halation is superior to that of Comparative Example 3. The same can be said for the comparison between Example 6 and Comparative Example 4 in which the D50 of the entire colloidal silica is different.

From the comparison between Example 7 and Comparative Example 5 in Table 4, the Al content in the solid is 100 mg / kg or less even when the abrasive composition contains an acrylic acid / N-tert-butylacrylamide copolymer. It can be seen that by using colloidal silica containing silica particles synthesized from silica particles or metallic silicon as a raw material, a decrease in polishing rate is suppressed in multiple times of polishing, and long-wavelength waviness and halation are also improved.

From the comparison between Examples 1 and 4, and further the comparison between Examples 4 and 7, the polishing composition contains an acrylic acid homopolymer, so that an acrylic acid-based copolymer can be further obtained. It can be seen that the content suppresses a decrease in the polishing rate in multiple polishings.

In Examples 8, 9 and 10, the mass ratio of silica particles having an Al content of 100 mg / kg or less in a solid or silica particles synthesized from metallic silicon as a raw material in Example 7 to total colloidal silica is increased. As an example of an experiment, the polishing speed is further improved and the long-wavelength waviness and halation are further improved in multiple times of polishing.

Examples 11 and 12 are experimental examples in which the weight average molecular weight of the water-soluble polymer compound is increased in Example 7, and Examples 13 and 14 are experimental examples in which the weight average molecular weight of the water-soluble polymer compound is increased in Example 10. This is an increased experimental example.

From the comparison between Example 12 and Comparative Example 6, silica particles or metallic silicon having an Al content of 100 mg / kg or less in the solid can be obtained even when the weight average molecular weight of the water-soluble polymer compound in the abrasive composition is large. It can be seen that by using colloidal silica containing silica particles synthesized as a raw material, a decrease in the polishing rate is suppressed in multiple times of polishing, and long-wavelength waviness and halation are improved.

In Example 15, in Example 7, the water-soluble polymer compound in the polishing agent composition was changed from an acrylic acid / N-tert-butylacrylamide copolymer to an acrylic acid / 2-acrylamide-2-methylpropanesulfonic acid copolymer. This is an experimental example changed to.

In Example 16, in Example 7, the water-soluble polymer compound in the polishing agent composition was changed from the acrylic acid / N-tert-butylacrylamide copolymer to acrylic acid / N-tert-butylacrylamide / 2-acrylamide-2-. This is an experimental example in which the copolymer was changed to a methylpropanesulfonic acid copolymer.

From the above, it can be seen that by using the abrasive composition of the present invention, a decrease in polishing rate is suppressed in multiple polishings, and long wavelength swell and halation are improved.

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

Claims (13)

Colloidal silica with an average primary particle size of 1 to 100 nm,
Containing with water,
, The colloidal silica
An abrasive composition for a magnetic disk substrate containing at least 3% by mass or more of silica particles having an Al content of 100 mg / kg or less in a solid. Colloidal silica with an average primary particle size of 1 to 100 nm,
Containing with water,
The colloidal silica is
An abrasive composition for a magnetic disk substrate containing at least 3% by mass or more of silica particles synthesized from metallic silicon as a raw material. The colloidal silica is
The abrasive composition for a magnetic disk substrate according to claim 2, which contains at least 10% by mass or more of silica particles synthesized from the metallic silicon as a raw material. The abrasive composition for a magnetic disk substrate according to any one of claims 1 to 3, further containing a water-soluble polymer compound. The water-soluble polymer compound is
A copolymer containing a monomer having a carboxylic acid group and a monomer having an amide group as essential monomers.
The abrasive composition for a magnetic disk substrate according to claim 4, wherein the weight average molecular weight is 1,000 to 1,000,000. The water-soluble polymer compound is
A copolymer containing a monomer having a carboxylic acid group and a monomer having a sulfonic acid group as essential monomers.
The abrasive composition for a magnetic disk substrate according to claim 4, wherein the weight average molecular weight is 1,000 to 1,000,000. The water-soluble polymer compound is
A copolymer containing a monomer having a carboxylic acid group, a monomer having an amide group, and a monomer having a sulfonic acid group as essential monomers.
The abrasive composition for a magnetic disk substrate according to claim 4, wherein the weight average molecular weight is 1,000 to 1,000,000. The monomer having a carboxylic acid group is
The abrasive composition for a magnetic disk substrate according to any one of claims 5 to 7, which is a monomer selected from acrylic acid or a salt thereof, or methacrylic acid or a salt thereof. The monomer having an amide group is
The abrasive composition for a magnetic disk substrate according to claim 5 or 7, which is one or more monomers selected from acrylamide, methacrylamide, N-alkylacrylamide, and N-alkylmethacrylamide. The monomer having a sulfonic acid group is
Isoprene sulfonic acid, 2-acrylamide-2-methylpropanesulfonic acid, 2-methacrylamide-2-methylpropanesulfonic acid, styrenesulfonic acid, vinylsulfonic acid, allylsulfonic acid, isoamylenesulfonic acid, vinylnaphthalenesulfonic acid, The abrasive composition for a magnetic disk substrate according to claim 6 or 7, which is a monomer selected from these salts. The abrasive composition for a magnetic disk substrate according to any one of claims 1 to 10, further containing an acid and / or a salt thereof, and having a pH value at 25 ° C. in the range of 0.1 to 4.0. The abrasive composition for a magnetic disk substrate according to any one of claims 1 to 11, further containing an oxidizing agent. A method for polishing a magnetic disk substrate using the polishing agent composition for a magnetic disk substrate according to any one of claims 1 to 12, wherein a nickel-phosphorus plating film is formed on the surface of the aluminum alloy substrate. A multi-stage polishing method is adopted in which the disk substrate is targeted for polishing and the polishing process is repeated a plurality of times on the magnetic disk substrate, and the magnetic disk using the polishing agent composition for the magnetic disk substrate in the final polishing step on the magnetic disk substrate. Substrate polishing method.