JP6864519B2 - Polishing composition, manufacturing method of magnetic disk substrate, and polishing method of magnetic disk - Google Patents

Description

The present invention relates to a polishing composition, a method for producing a magnetic disk substrate using the polishing composition, and a method for polishing a magnetic disk substrate.

Conventionally, a polishing process using a polishing composition has been performed on a material surface such as a metal, a metalloid, a non-metal, or an oxide thereof. For example, in the manufacturing process of a polished product that requires a highly accurate surface, generally, polishing that emphasizes polishing efficiency (primary polishing) and a final polishing process (finish polishing process) that is performed to finish the final product with surface accuracy. ) And are done. Patent Document 1 is mentioned as a prior art relating to a polishing composition used for polishing a disc substrate (Ni-P substrate) plated with nickel phosphorus.

Japanese Unexamined Patent Publication No. 2010-167553

In recent years, there has been a demand for higher quality surfaces for disk substrates and other substrates such as Ni-P substrates, and various studies have been conducted on polishing compositions that can meet such requirements. For example, Patent Document 1 describes a technique capable of reducing scratches and surface roughness of a substrate after polishing without impairing productivity by devising the components (abrasive grains, polymers, etc.) contained in the polishing composition. Has been done. However, even with such a technique, there are cases where it is not possible to sufficiently meet the recent demand level regarding the surface quality after polishing.

Therefore, an object of the present invention is to provide a polishing composition capable of effectively reducing the number of scratches present on the surface after polishing. Another object of the present invention is to provide a method for polishing a disk substrate using such a polishing composition. Another relevant object is to provide a method of manufacturing a disk substrate with a surface with a reduced number of scratches.

According to the present invention, there is provided a polishing composition containing abrasive grains containing silica particles and water. _{In the abrasive grains, the average aspect ratio of D 0-5} particles having a cumulative total of 0 to 5% in the cumulative particle size distribution based on the number from the small diameter side is 1 to 1.25, and the average aspect ratio of all particles is 1. ~ 1.30. According to such a polishing composition, the number of scratches can be effectively reduced on the surface after polishing.

In a preferred embodiment of the polishing composition disclosed herein, the abrasive grains have a relationship between a cumulative 5% particle size D5 and a cumulative 50% particle size D50 in the cumulative particle size distribution from the small diameter side according to the following equation: 0.3 ≦ D5 / D50; is satisfied. When it is within the range of the D5 / D50 ratio of such abrasive grains, the above-mentioned effect of reducing the number of scratches can be more effectively exhibited.

In a preferred embodiment of the polishing composition disclosed herein, the abrasive grains have a cumulative 5% particle size D5 of 30 nm or less in the cumulative particle size distribution from the small diameter side. When it is within the range of the cumulative 5% particle size of the abrasive grains, the above-mentioned effect of reducing the number of scratches can be more effectively exhibited.

The polishing composition disclosed herein is suitable as, for example, a polishing composition for polishing a magnetic disk substrate. In the field of magnetic disk substrates, a surface with less scratches is required for high capacity and high reliability. Therefore, magnetic disk substrates can be preferred application of the techniques disclosed herein.

According to this specification, a method for manufacturing a magnetic disk substrate is also provided. The manufacturing method includes preparing any of the polishing compositions disclosed herein, and supplying the polishing composition to a magnetic disk substrate to polish the magnetic disk substrate. According to this manufacturing method, it is possible to manufacture a magnetic disk substrate having a high quality surface with highly suppressed scratches. The polishing composition disclosed herein is particularly suitable for a final polishing step (finish polishing step) of a magnetic disk substrate.

Further, according to this specification, a method for polishing a magnetic disk substrate is provided. The polishing method includes supplying any of the polishing compositions disclosed herein to a magnetic disk substrate to polish the magnetic disk substrate. According to this polishing method, it is possible to achieve a high quality surface with highly suppressed scratches.

Hereinafter, preferred embodiments of the present invention will be described. Matters other than those specifically mentioned in the present specification and necessary for carrying out the present invention can be grasped as design matters of those skilled in the art based on the prior art in the art. The present invention can be carried out based on the contents disclosed in the present specification and common general technical knowledge in the art.

<Abrasive grains>
The polishing composition disclosed herein comprises abrasive grains. _{In this abrasive grain, the average aspect ratio of D 0-5} particles having a cumulative total of 0 to 5% in the cumulative particle size distribution from the small diameter side is 1 to 1.25, and the average aspect ratio of all particles is 1 to 1. It is thirty. Here, the D _0-5 particles are particles having a particle size corresponding to the cumulative particle size distribution from the small diameter side in the range of 0 to 5% in the cumulative particle size distribution based on the number (cumulative number distribution from the small diameter side). Say. The cumulative number distribution typically extends from the cumulative 0% and the small diameter end (lower left) of the particle size to the upper right in a graph with the horizontal axis as the particle size and the vertical axis as the cumulative number (%). , Accumulated 100% and represented by a curve reaching the large diameter end (upper right) of the particle size. D _0-5 particles are small-diameter particles that occupy 5% on a number basis from the small-diameter side. _{The total particles of the abrasive grains are D 0-100} particles having a particle size corresponding to the cumulative particle size distribution from the small diameter side in the range of 0 to 100% in the cumulative particle size distribution based on the number of particles, that is, the entire particles. .. _{The abrasive grains disclosed herein have an average aspect ratio of D 0-5} particles having a relatively small particle size of 1 to 1.25, and an average aspect ratio of the entire particles of 1 to 1.30. Thereby, the number of scratches can be effectively reduced on the surface after polishing using the polishing composition containing the particles.

The reason why the above effects can be obtained is not particularly limited, but can be considered as follows, for example. That is, in a polishing composition in which the average aspect ratio of all the abrasive particles is 1-1.30, the abrasive grains having a spherical shape or a nearly spherical shape can easily roll and move, so that the processing is stable and the surface quality after polishing is improved. It is thought that it will improve. However, for example, even general spherical silica may contain irregularly shaped particles whose shape is distorted from a spherical shape on the small diameter side. Therefore, even if the average aspect ratio of the entire particles is reduced, the small-diameter irregular particles act as wedges with respect to the spherical particles, so that the abrasive grains are less likely to roll locally even if they are spherical particles. Therefore, scratches are likely to occur on the surface after polishing. On the other _{hand, the abrasive grains having an average aspect ratio of D 0-5} particles of 1 to 1.25 have a shape in which the small-diameter particles that can be wedges are closer to a sphere. Since such small-diameter particles having a high degree of sphericity do not easily form the wedge during polishing, it is unlikely that the abrasive grains will roll easily locally. This is considered to contribute to the reduction of scratches.

_{The average aspect ratio of the D 0-5} particles of the abrasive grains disclosed herein is usually 1.25 or less, and is preferably 1.24 or less, more preferably 1 from the viewpoint of better reducing scratches and the like. It is .23 or less, more preferably 1.22 or less. The average aspect ratio of the D _0-5 particles is 1 or more in principle, and the lower limit thereof is not particularly limited, but may be, for example, 1.05 or more, typically 1.08 or more. The technique disclosed herein can be carried out, for example, in an embodiment in which the average aspect ratio _{of the D 0-5 particles of the abrasive grains in the polishing composition is 1.11 or more and 1.21 or less.}

It is appropriate that the average aspect ratio of all the abrasive grains disclosed here is 1.30 or less. By reducing the average aspect ratio of the entire particles, the abrasive grains can easily roll and move, so that the processing is stable and scratches can be reduced more preferably. The average aspect ratio of the entire particle is preferably 1.28 or less, more preferably 1.25 or less (for example, 1.2 or less). In principle, the average aspect ratio of all the particles is 1 or more, and the lower limit thereof is not particularly limited, but may be, for example, 1.03 or more, typically 1.08 or more.

The average aspect ratio A _0-5 of the D _0-5 particles of the abrasive grains may be larger than the average aspect ratio A _{all of the entire particles.} That is, A _0-5 > A _all may be satisfied. Alternatively, A _0-5 may be smaller than A _all. That is, A _0-5 <A _all may be satisfied.

The average aspect ratio of the D _0-5 particles and the whole particles of the abrasive grains can be adjusted by selecting the abrasive grain particles to be used and a combination thereof. For example, by mixing small-diameter particles that are closer to a sphere with larger-diameter particles in an appropriate weight ratio, or by removing small-diameter irregularly shaped particles from commercially available abrasive grains, the entire particles of the above-mentioned abrasive grains and D. _{The average aspect ratio of 0-5} particles can be adjusted to the appropriate range disclosed herein.

In this specification, _{the average aspect ratios of the D 0-5} particles and the whole particles are the average aspect ratios of the number of particles in the corresponding cumulative range, respectively. The average aspect ratio of the D _0-5 particles and the entire particles is specifically obtained by the following method. That is, using a transmission electron microscope (TEM, STEM HD-2700 manufactured by Hitachi High-Technologies Co., Ltd.), the abrasive grains to be measured (one type of abrasive grain particles may be used, or two or more types of abrasive particles). A mixture of grain particles may be used), and 1000 or more particles that can be observed by TEM are photographed at a magnification (for example, 200,000 to 400,000 times) that can be observed in about 100 particles in one field of view. Acquire a TEM image. Then, for the smallest rectangle circumscribing each particle image, the value obtained by dividing the length of the long side (value of the major axis) by the length of the short side (value of the minor axis) is the major axis / minor axis ratio of each particle (minor axis value). Calculated as aspect ratio). Further, the area of each particle is calculated from the image of each particle, and the diameter of an ideal circle (perfect circle) having the same area as the calculated area is calculated as the particle diameter of each particle. That is, the cumulative particle size distribution of the abrasive grains to be measured is obtained by plotting the calculated particle diameter of each particle constituting the abrasive grains on the horizontal axis and the cumulative number (%) on the vertical axis. .. Then, by arithmetically averaging the number average aspect ratio of the particles in the predetermined cumulative range in the cumulative particle size distribution from the small diameter side from the aspect ratio of the predetermined number of particles, the average aspect ratio of the D _0-5 particles and all the particles is calculated. The ratio can be calculated. Each of the above aspect ratios can be obtained by using the image analysis software MacView manufactured by Mountech. The same applies to the examples described later.

The particle size of the abrasive grains disclosed herein is not particularly limited, but typically, it is preferable to use abrasive grains having a cumulative 50% particle size D50 of 5 nm or more in the cumulative particle size distribution from the small diameter side. Higher polishing rates can be achieved by increasing the cumulative 50% particle size. The cumulative 50% particle size is preferably 10 nm or more, more preferably 15 nm or more, from the viewpoint of polishing rate and the like. The cumulative 50% particle size of the abrasive grains can be, for example, 100 nm or less. From the viewpoint of obtaining a higher quality surface, the cumulative 50% particle size is, for example, 80 nm or less, preferably 60 nm or less, more preferably 50 nm or less, still more preferably 40 nm or less, and particularly preferably 30 nm or less. The technique disclosed herein can be preferably carried out, for example, by using abrasive grains having a cumulative 50% particle size of 15 nm or more and 35 nm or less, and further 15 nm or more and 30 nm or less.

The cumulative 5% particle size D5 in the cumulative particle size distribution from the small diameter side of the abrasive grains can be, for example, 30 nm or less. When the cumulative particle size is within the range of 5%, the above-mentioned effect of reducing the number of scratches can be better exerted. From the viewpoint of obtaining a higher quality surface, the cumulative 5% particle size of the abrasive grains is preferably 28 nm or less, more preferably 25 nm or less. The cumulative 5% particle size of the abrasive grains can be, for example, 1 nm or more. From the viewpoint of ease of production and the like, the cumulative 5% particle size of the abrasive grains is, for example, 3 nm or more, preferably 5 nm or more, and more preferably 10 nm or more. The technique disclosed herein can be preferably carried out, for example, by using abrasive grains having a cumulative 5% particle size of 8 nm or more and 30 nm or less, and further 10 nm or more and 25 nm or less.

From the viewpoint of more effectively exerting the effect of reducing the number of scratches, the relationship between the cumulative 5% particle size D5 and the cumulative 50% particle size D50 in the cumulative particle size distribution from the small diameter side satisfies 0.3 ≦ D5 / D50. Is preferable. The technique disclosed herein can be preferably carried out, for example, in an embodiment in which the relationship between D5 and D50 of the abrasive grains is 0.4 ≦ D5 / D50, more preferably 0.5 ≦ D5 / D50.

(Silica particles)
The polishing composition disclosed herein contains silica particles as abrasive grains. The silica particles contained in the abrasive grains can be various silica particles containing silica as a main component. Here, the silica particles containing silica as a main component refer to particles in which 90% by weight or more (usually 95% by weight or more, typically 98% by weight or more) of the particles is silica. Examples of silica particles that can be used include, but are not limited to, colloidal silica (for example, sodium silicate silica, alkoxide silica, etc.), fumed silica, precipitated silica, and the like. The abrasive grains in the polishing composition disclosed herein may contain one type of silica particles as described above alone or in combination of two or more types. In one aspect of the technique disclosed herein, the weight of the silica particles in the total weight of the abrasive grains contained in the polishing composition may be, for example, 50% by weight or more, or 70% by weight or more. , 85% by weight or more, 95% by weight or more, or 99% by weight or more. Even a polishing composition having a composition that substantially does not contain abrasive grains other than silica particles (for example, a composition in which the content of abrasive grains other than silica particles is 0 to 0.1% by weight of the entire abrasive grains). Good.

The particle shape of silica _{is not particularly limited as long as the average aspect ratio of the D 0-5} particles and the D _0-100 particles of the abrasive grains satisfies the above range, and may be spherical or non-spherical, for example. Good.

(Particles other than silica particles)
The polishing composition disclosed herein can contain particles other than silica particles. As the particles other than the silica particles, any of inorganic particles, organic particles, and organic-inorganic composite particles can be used. Specific examples of the inorganic particles include oxide particles such as cerium oxide particles, chromium oxide particles, titanium dioxide particles, zirconium oxide particles, manganese dioxide particles, zinc oxide particles, and red iron oxide particles; and nitrided silicon nitride particles and boron nitride particles. Object particles; carbide particles such as silicon carbide particles and boron carbide particles; diamond particles; carbonates such as calcium carbonate and barium carbonate; and the like. Specific examples of the organic particles include polymethylmethacrylate (PMMA) particles and poly (meth) acrylic acid particles (here, (meth) acrylic acid means to comprehensively refer to acrylic acid and methacrylic acid). , Polyacrylonitrile particles and the like. As the abrasive grains other than the silica particles, one type can be used alone or two or more types can be used in combination.

<Polishing composition>
(water)
The polishing composition disclosed herein typically contains, in addition to the abrasive grains as described above, water in which the abrasive grains are dispersed. As the water, ion-exchanged water (deionized water), pure water, ultrapure water, distilled water and the like can be preferably used.

The polishing composition disclosed herein (typically a slurry-like composition) can be preferably carried out in the form of, for example, having a solid content of 0.5% by weight to 30% by weight. A form in which the solid content is 1% by weight to 20% by weight is more preferable.

<Polymer>
The polishing composition disclosed herein preferably contains a polymer. The polymer referred to here refers to a compound having the same (homopolymer) or different (copolymer; copolymer) repeating constituent units, and typically has a weight average molecular weight (Mw) of 500 or more (preferably). Can be a compound of 1000 or more). Such a polymer is preferably a water-soluble polymer. By including the polymer in the polishing composition, the surface accuracy after polishing can be improved. The type of polymer is not particularly limited, and any of anionic polymer, nonionic polymer, cationic polymer, and amphoteric polymer can be used. Among them, it is preferable to contain an anionic polymer. Examples of the anionic polymer include carboxylic acid-based polymers and sulfonic acid-based polymers.
Specific examples of the polymer include polyalkylaryl sulfonic acid compounds such as naphthalene sulfonic acid formaldehyde condensate, methyl naphthalene sulfonic acid formaldehyde condensate, and anthracene sulfonate formaldehyde; and melamine formalin resin sulfone such as melamine sulfonic acid formaldehyde condensate. Acid compounds; Ligno sulfonic acid compounds such as lignin sulfonic acid and modified lignin sulfonic acid; Aromatic amino sulfonic acid compounds such as aminoaryl sulfonic acid-phenol-formaldehyde condensate; Polymaleic acid, polyitaconic acid, polyvinyl alcohol, polyglycerin, polyvinylpyrrolidone, polyvinylpyrrolidone polyacrylic acid copolymer, polyvinylpyrrolidone vinyl acetate copolymer, diallylamine hydrochloride / sulfur dioxide copolymer, carboxymethylcellulose, carboxyethylcellulose, hydroxyethylcellulose , Hydroxypropyl cellulose, purulan, chitosan and the like. The water-soluble polymer may be used alone or in combination of two or more.

The content of the polymer (in the embodiment containing a plurality of polymers, the total content thereof) is not particularly limited, but is appropriately set to, for example, 0.0001% by weight or more. From the viewpoint of surface smoothness of the object to be polished (for example, magnetic disk substrate) after polishing, the content is preferably 0.001% by weight or more, more preferably 0.01% by weight or more, still more preferably 0. 02% by weight or more. From the viewpoint of polishing rate and the like, the content is preferably 0.2% by weight or less, preferably 0.15% by weight or less, for example 0.1% by weight or less.

In a preferred embodiment, a sulfonic acid-based polymer is used as the polymer. Here, the sulfonic acid-based polymer is a weight containing a structural unit X derived from a monomer (monomer) having at least one sulfonic acid group in one molecule as a monomer unit constituting the sulfonic acid-based polymer. It means coalescence. Examples of the monomer having a sulfonic acid group include styrene sulfonic acid, isoprene sulfonic acid, vinyl sulfonic acid, allyl sulfonic acid, isoamylene sulfonic acid, 2- (meth) acrylamide-2-methylpropane sulfonic acid, and metallic sulfonate. Acids and the like can be mentioned. The sulfonic acid-based polymer preferably contains one or more structural units X derived from the sulfonic acid group-containing monomer. Further, it may contain a component derived from a monomer other than the sulfonic acid group-containing monomer.

A preferred example of the sulfonic acid-based polymer disclosed herein is a high-molecular-weight sulfonic acid-based polymer A consisting substantially only of the structural unit X derived from the sulfonic acid group-containing monomer. In other words, in the sulfonic acid-based polymer A, the ratio (molar ratio) of the number of moles of the structural unit X to the number of moles of all the structural units contained in the molecular structure of the polymer is 99 mol% or more (for example, 99 mol% or more). It is preferably 9 mol% or more, typically 99.9 to 100 mol%). As an example of such a sulfonic acid-based polymer A, a homopolymer composed of only one kind of the sulfonic acid group-containing monomer disclosed herein or a copolymer composed of two or more kinds of the sulfonic acid group-containing monomer is disclosed. (Copolymer) can be mentioned. Examples of homopolymers include polystyrene sulfonic acid, polyisoprene sulfonic acid, polyvinyl sulfonic acid, polyallyl sulfonic acid, polyisoprene sulfonic acid and the like.

The molecular weight of the sulfonic acid-based polymer A is typically 10 × 10 ⁴ or more, preferably 20 × 10 ⁴ or more, more preferably 30 × 10 ⁴ or more, from the viewpoint of improving the surface accuracy after polishing. Is. In a preferred embodiment, the molecular weight of the sulfonic acid-based polymer A may also be 40 × 10 ⁴ or more, may be for example 45 × 10 ⁴ or more. The molecular weight of the sulfonic acid-based polymer A is typically a 100 × 10 ⁴ or less, from the viewpoint of dispersion stability and filterability, preferably 80 × 10 ⁴ or less, more preferably 60 × 10 ⁴ It is as follows. The molecular weight of the sulfonic acid-based polymer A is the weight average molecular weight (Mw) determined by GPC (aqueous, polyethylene glycol equivalent, solvent: 0.1 M sodium nitrate aqueous solution, flow velocity: 1 ml / min, measuring device: Tosoh Corporation. HLC-8320GPC) can be adopted.

As another preferred example of the sulfonic acid-based polymer disclosed herein, a low molecular weight (meth) acrylic acid containing a structural unit derived from (meth) acrylic acid and a structural unit X derived from a sulfonic acid group-containing monomer. / Sulfonic acid copolymer can be mentioned. The term "(meth) acrylic acid" as used herein is a concept that includes one or both of acrylic acid and methacrylic acid. Such (meth) acrylic acid / sulfonic acid copolymer may contain one or more structural units X derived from the above-mentioned sulfonic acid group-containing monomer. Further, it may contain a component derived from a monomer other than the sulfonic acid group-containing monomer and the (meth) acrylic acid monomer. Examples of the above (meth) acrylic acid / sulfonic acid copolymer include (meth) acrylic acid / isoprene sulfonic acid copolymer, (meth) acrylic acid / 2-acrylamide-2-methylpropanesulfonic acid copolymer, and the like. Examples thereof include (meth) acrylic acid / isoprene sulfonic acid / 2-acrylamide-2-methylpropanesulfonic acid copolymer.

The molecular weight of the (meth) acrylic acid / sulfonic acid copolymer is typically 500 or more, preferably 800 or more, and more preferably 1000 or more from the viewpoint of improving the surface accuracy after polishing. In a preferred embodiment, the molecular weight of the (meth) acrylic acid / sulfonic acid copolymer may be 1500 or more, for example 2000 or more. The molecular weight of the (meth) acrylic acid / sulfonic acid copolymer is typically 50,000 or less, and is preferably 30,000 or less, more preferably 20,000 or less, still more preferably, from the viewpoint of dispersion stability, filterability, and the like. Is 15,000 or less. The molecular weight of the salt of the (meth) acrylic acid / sulfonic acid copolymer is the weight average molecular weight (Mw) determined by GPC (aqueous, polyethylene glycol equivalent, solvent: 0.1 M sodium nitrate aqueous solution, flow velocity: 1 ml / min, measuring device: HLC-8320GPC manufactured by Tosoh Corporation) can be adopted.

In a preferred embodiment of the polishing composition disclosed herein, the sulfonic acid-based polymer A described above and the (meth) acrylic acid / sulfonic acid copolymer are used in combination as the polymer. When used in combination sulfonic acid polymer A and (meth) acrylic acid / sulfonic acid copolymer, with respect to the content W _A of the sulfonic acid-based polymer A in the polishing composition (meth) acrylic acid / sulfonic acid copolymer the ratio of the content of W _B of the polymer _(W B _/ W _a) is a weight basis, usually it is appropriate to one or more, preferably 3 or more, more preferably 5 or more, more preferably 8 or more Is. The upper limit of the ratio _(W B _/ W _A) is not particularly limited, usually it is appropriate to 30 or less, preferably 25 or less, more preferably 20 or less, more preferably 15 or less.

When the sulfonic acid-based polymer A is used, the content of the sulfonic acid-based polymer A in the polishing composition is preferably, for example, 0.0001% by weight or more, preferably 0.0002% by weight or more. It is more preferably 0.001% by weight or more, still more preferably 0.002% by weight or more. The content of the sulfonic acid-based polymer A is preferably 0.02% by weight or less, preferably 0.015% by weight or less, for example 0.01% by weight or less. When a (meth) acrylic acid / sulfonic acid copolymer is used, the content of the (meth) acrylic acid / sulfonic acid copolymer in the polishing composition is preferably 0.0001% by weight or more, for example. It is preferably 0.001% by weight or more, more preferably 0.01% by weight or more, and further preferably 0.02% by weight or more. The content of the (meth) acrylic acid / sulfonic acid copolymer is preferably 0.2% by weight or less, preferably 0.15% by weight or less, for example, 0.1% by weight or less. ..

(acid)
The polishing composition disclosed herein can be preferably carried out in an embodiment containing an acid as a polishing accelerator. Examples of acids that can be preferably used include inorganic acids and organic acids (for example, organic carboxylic acids having about 1 to 10 carbon atoms, organic phosphonic acids, organic sulfonic acids, amino acids, etc.). Not limited. The acid may be used alone or in combination of two or more.

Specific examples of the inorganic acid include phosphoric acid, nitric acid, sulfuric acid, hydrochloric acid, hypophosphorous acid, phosphonic acid, boric acid, sulfamic acid and the like.

Specific examples of organic acids include citric acid, maleic acid, malic acid, glycolic acid, succinic acid, itaconic acid, malonic acid, iminodic acid, gluconic acid, lactic acid, mandelic acid, tartaric acid, crotonic acid, nicotinic acid and acetic acid. , Adipic acid, formic acid, oxalic acid, propionic acid, valeric acid, caproic acid, capric acid, capric acid, cyclohexanecarboxylic acid, phenylacetic acid, benzoic acid, crotonic acid, methacrylic acid, glutaric acid, fumaric acid, phthalic acid, isophthalic acid Acids, terephthalic acid, glycolic acid, tartronic acid, glyceric acid, hydroxybutyric acid, hydroxyacetic acid, hydroxybenzoic acid, salicylic acid, isocitrate, methylene succinic acid, gallic acid, ascorbic acid, nitroacetic acid, oxaloacetate, glycine, alanine, glutamate , Asparaginic acid, valine, leucine, isoleucine, serine, threonine, cysteine, methionine, phenylalanine, tryptophan, tyrosine, proline, cystine, glutamine, asparagine, lysine, arginine, nicotinic acid, picolinic acid, methyl acid phosphate, ethyl acid phosphate, Ethylglycol acid phosphate, isopropyl acid phosphate, phytic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, aminotri (methylenephosphonic acid), ethylenediaminetetra (methylenephosphonic acid), diethylenetriaminepenta (methylenephosphonic acid), ethane-1 , 1-diphosphonic acid, ethane-1,1,2-triphosphonic acid, ethane-1-hydroxy-1,1-diphosphonic acid, ethanehydroxy-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, aminopoly (methylenephosphonic acid) ), Methan sulfonic acid, ethane sulfonic acid, amino ethane sulfonic acid, benzene sulfonic acid, p-toluene sulfonic acid, 2-naphthalene sulfonic acid and the like.

Examples of preferable acids from the viewpoint of polishing rate include phosphoric acid, nitric acid, sulfuric acid, sulfamic acid, phytic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, methanesulfonic acid and the like. Of these, nitric acid, sulfuric acid, phosphoric acid, sulfamic acid, and methanesulfonic acid are preferable.

When the acid is contained in the polishing composition, its content is not particularly limited. The acid content is usually preferably 0.1% by weight or more, preferably 0.5% by weight or more, and more preferably 0.8% by weight or more (for example, 1.2% by weight or more). If the acid content is too low, the polishing rate tends to be insufficient, which may be unfavorable for practical use. The acid content is usually preferably 15% by weight or less, preferably 10% by weight or less, and more preferably 5% by weight or less (for example, 3% by weight or less). If the acid content is too large, the surface accuracy of the object to be polished tends to decrease, which may be unfavorable for practical use.

The acid may be used in the form of a salt of the acid. Examples of salts include metal salts (for example, alkali metal salts such as lithium salt, sodium salt and potassium salt) and ammonium salts (for example, tetramethylammonium salt and tetraethylammonium salt) of the above-mentioned inorganic and organic acids. Tertiary ammonium salts), alkanolamine salts (eg, monoethanolamine salts, diethanolamine salts, triethanolamine salts) and the like.
Specific examples of the salt include alkali metal phosphates and alkali metals such as tripotassium phosphate, dipotassium hydrogen phosphate, potassium dihydrogen phosphate, trisodium phosphate, disodium hydrogen phosphate, and sodium dihydrogen phosphate. Hydrogen phosphate; Alkali metal salt of organic acid exemplified above; Alkali metal salt of diacetate diacetic acid, Alkali metal salt of diethylenetriamine pentaacetic acid, Alkali metal salt of hydroxyethylethylenediamine triacetic acid, Triethylenetetraminehexacetic acid Alkali metal salts; etc. The alkali metal in these alkali metal salts can be, for example, lithium, sodium, potassium and the like.

As the salt that can be contained in the polishing composition disclosed herein, a salt of an inorganic acid (for example, an alkali metal salt or an ammonium salt) can be preferably adopted. For example, potassium chloride, sodium chloride, ammonium chloride, potassium nitrate, sodium nitrate, ammonium nitrate, potassium phosphate and the like can be preferably used.

The acid and its salt may be used alone or in combination of two or more. In a preferred embodiment of the polishing composition disclosed herein, an acid (preferably an inorganic acid) and a salt of an acid different from the acid (preferably a salt of an inorganic acid) can be used in combination.

(Oxidant)
The polishing composition disclosed herein may contain an oxidizing agent, if necessary. Examples of oxidizing agents are peroxide, nitric acid or its salt, perioic acid or its salt, peroxo acid or its salt, permanganic acid or its salt, chromium acid or its salt, oxygen acid or its salt, metal salts. , Sulfuric acid and the like, but are not limited thereto. The oxidizing agent may be used alone or in combination of two or more. Specific examples of the oxidizing agent include hydrogen peroxide, sodium peroxide, barium peroxide, nitrate, iron nitrate, aluminum nitrate, ammonium nitrate, peroxomonosulfuric acid, ammonium peroxomonosulfuric acid, metal salt peroxo monosulfuric acid, peroxodisulfuric acid, and peroxodisulfuric acid. Ammonium sulfate, peroxodisulfuric acid metal salt, peroxophosphate, peroxosulfuric acid, sodium peroxoborate, peroxymonosulfuric acid, peracetic acid, perbenzoic acid, perphthalic acid, hypobromic acid, hypoiodic acid, chloric acid, bromine acid, Iodine acid, perioic acid, perchloric acid, hypochloric acid, sodium hypochlorite, calcium hypochlorate, potassium permanganate, metal chromate salt, metal bicarbonate salt, iron chloride, iron sulfate, Examples thereof include iron citrate and iron ammonium sulfate. Preferred oxidizing agents include hydrogen peroxide, iron nitrate, periodic acid, peroxomonosulfuric acid, peroxodisulfuric acid and nitric acid. It preferably contains at least hydrogen peroxide, and more preferably consists of hydrogen peroxide.

When the polishing composition contains an oxidizing agent, the content thereof is preferably 0.01% by weight or more, more preferably 0.1% by weight or more, still more preferably 0.3, based on the amount of the active ingredient. By weight%. If the content of the oxidant is too small, the rate of oxidizing the object to be polished slows down and the polishing rate decreases, which may be unfavorable for practical use. When the polishing composition contains an oxidizing agent, the content thereof is preferably 5% by weight or less, more preferably 1% by weight or less, based on the amount of the active ingredient. If the content of the oxidizing agent is too large, the surface accuracy of the object to be polished tends to be lowered, which may be unfavorable for practical use.

(Basic compound)
The polishing composition may contain a basic compound, if necessary. Here, the basic compound refers to a compound having a function of raising the pH of the composition by being added to the polishing composition. Examples of basic compounds include alkali metal hydroxides, carbonates and bicarbonates, quaternary ammonium or salts thereof, ammonia, amines, phosphates and hydrogen phosphates, organic acid salts and the like. The basic compound may be used alone or in combination of two or more.

Specific examples of the alkali metal hydroxide include potassium hydroxide, sodium hydroxide and the like.
Specific examples of carbonates and hydrogen carbonates include ammonium hydrogen carbonate, ammonium carbonate, potassium hydrogen carbonate, potassium carbonate, sodium hydrogen carbonate, sodium carbonate and the like.
Specific examples of the quaternary ammonium or a salt thereof include a quaternary ammonium hydroxide such as tetramethylammonium hydroxide, tetraethylammonium hydroxide, and tetrabutylammonium hydroxide; an alkali metal of such a quaternary ammonium hydroxide. Salts (eg, sodium salts, potassium salts); and the like.
Specific examples of amines include methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylenediamine, monoethanolamine, N- (β-aminoethyl) ethanolamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, and piperazine anhydride. , Piperazine hexahydrate, 1- (2-aminoethyl) piperazine, N-methylpiperazine, guanidine, azoles such as imidazole and triazole, and the like.
Specific examples of phosphates and hydrogen phosphates include alkalis such as tripotassium phosphate, dipotassium hydrogen phosphate, potassium dihydrogen phosphate, trisodium phosphate, disodium hydrogen phosphate, and sodium dihydrogen phosphate. Metal salts can be mentioned.
Specific examples of the organic acid salt include potassium citrate, potassium oxalate, potassium tartrate, sodium potassium tartrate, ammonium tartrate and the like.

(Other ingredients)
The polishing composition disclosed herein is a polishing composition (for example, Ni-P substrate) such as a surfactant, a chelating agent, a preservative, and an antifungal agent, as long as the effect of the present invention is not significantly impaired. A known additive that can be used in a polishing composition for a magnetic disk substrate, such as, etc., may be further contained, if necessary.

The polishing composition may contain a surfactant, if necessary. The term "surfactant" as used herein refers to a compound having at least one or more hydrophilic sites (typically hydrophilic groups) and one or more hydrophobic sites (typically hydrophobic groups) in one molecule. The surfactant is not particularly limited, and any of anionic surfactant, nonionic surfactant, cationic surfactant, and amphoteric surfactant can be used. The use of a surfactant can improve the dispersion stability of the polishing composition. As the surfactant, one type may be used alone or two or more types may be used in combination.
Specific examples of anionic surfactants include polyoxyethylene alkyl ether acetic acid, polyoxyethylene alkyl sulfate ester, alkyl sulfate ester, polyoxyethylene alkyl sulfate, alkyl sulfate, alkylbenzene sulfonic acid, alkyl phosphate ester, and polyoxyethylene. Alkyl phosphate ester, polyoxyethylene sulfosuccinic acid, alkyl sulfosuccinic acid, alkylnaphthalene sulfonic acid, alkyldiphenyl ether disulfonic acid, polyacrylic acid, sodium lauryl sulfate, ammonium lauryl sulfate, sodium dodecylbenzene sulfonate, sodium polyoxyethylene alkyl ether sulfate, Examples thereof include ammonium polyoxyethylene alkyl phenyl ether sulfate and sodium polyoxyethylene alkyl phenyl ether sulfate.
Other specific examples of anionic surfactants include polyalkylarylsulfonic acid-based compounds such as naphthalenesulfonic acid formaldehyde condensate, methylnaphthalenesulfonic acid formaldehyde condensate, anthracene sulfonic acid formaldehyde condensate, and benzenesulfonic acid formaldehyde condensate. Melamine formalin resin sulfonic acid compound such as melamine sulfonic acid formaldehyde condensate; lignin sulfonic acid compound such as lignin sulfonic acid and modified lignin sulfonic acid; aromatic amino sulfonic acid such as aminoaryl sulfonic acid-phenol-formaldehyde condensate Examples include system compounds. As the salt, alkali metal salts such as sodium salt and potassium salt are preferable.
Specific examples of the nonionic surfactant include polyoxyethylene alkyl ether, polyoxyalkylene alkyl ether, sorbitan fatty acid ester, glycerin fatty acid ester, polyoxyethylene fatty acid ester, polyoxyethylene alkylamine, alkyl alkanolamide and the like. ..
Specific examples of the cationic surfactant include alkyltrimethylammonium salt, alkyldimethylammonium salt, alkylbenzyldimethylammonium salt, alkylamine salt and the like.
Specific examples of the amphoteric surfactant include alkyl betaine, alkyl amine oxide and the like.

In the polishing composition of the embodiment containing a surfactant, it is appropriate that the content of the surfactant is, for example, 0.0005% by weight or more. The content is preferably 0.001% by weight or more, more preferably 0.01% by weight or more, from the viewpoint of surface smoothness after polishing. From the viewpoint of polishing rate and the like, the content is preferably 1% by weight or less, preferably 0.5% by weight or less, for example 0.1% by weight or less.

Examples of chelating agents include aminocarboxylic acid-based chelating agents and organic phosphonic acid-based chelating agents. Examples of aminocarboxylic acid-based chelating agents include ethylenediaminetetraacetic acid, sodium ethylenediaminetetraacetic acid, nitrilotriacetic acid, sodium nitrilotriacetate, ammonium nitrilotriacetic acid, hydroxyethylethylenediaminetriacetic acid, sodium hydroxyethylethylenediaminetriacetic acid, and diethylenetriaminepentaacetic acid. , Sodium diethylenetriaminepentaacetate, triethylenetetraminehexacetic acid and sodium triethylenetetraminehexacetate. Examples of organic phosphonic acid-based chelating agents include 2-aminoethylphosphonic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, aminotri (methylenephosphonic acid), ethylenediaminetetrax (methylenephosphonic acid), and diethylenetriaminepenta (methylenephosphone). Acid), ethane-1,1-diphosphonic acid, ethane-1,1,2-triphosphonic acid, ethane-1-hydroxy-1,1-diphosphonic acid, ethane-1-hydroxy-1,1,2-triphosphonic acid , Etan-1,2-dicarboxy-1,2-diphosphonic acid, methanehydroxyphosphonic acid, 2-phosphonobutane-1,2-dicarboxylic acid, 1-phosphonobutane-2,3,4-tricarboxylic acid and α-methylphospho Contains succinic acid. Of these, organic phosphonic acid-based chelating agents are more preferable, and among them, ethylenediamine tetrakis (methylenephosphonic acid) and diethylenetriaminepenta (methylenephosphonic acid) are mentioned. Particularly preferred chelating agents include ethylenediamine tetrakis (methylenephosphonic acid).

Examples of preservatives and fungicides include isothiazolin-based preservatives such as 2-methyl-4-isothiazolin-3-one and 5-chloro-2-methyl-4-isothiazolin-3-one, and paraoxybenzoic acid esters. , Phenoxyethanol and the like.

(Abrasive liquid)
The polishing composition disclosed herein is typically supplied to an object to be polished (for example, a magnetic disk substrate) in the form of a polishing liquid containing the composition for polishing, and is used for polishing the object to be polished. .. The polishing liquid may be prepared, for example, by diluting (typically diluting with water) the polishing composition. Alternatively, the polishing composition may be used as it is as a polishing liquid. That is, the concept of the polishing composition in the technique disclosed herein includes a polishing liquid (working slurry) supplied to the polishing object and used for polishing the polishing object, and diluted and used as the polishing liquid. Both with concentrates are included. Such a polishing composition in the form of a concentrated liquid is advantageous from the viewpoint of convenience and cost reduction in production, distribution, storage and the like. The concentration ratio can be, for example, about 1.5 to 50 times. From the viewpoint of storage stability of the concentrated solution, a concentration ratio of about 2 to 20 times (typically 2 to 10 times) is suitable.

The content of abrasive grains in the polishing liquid (when a plurality of types of abrasive grains are contained, the total content thereof) is not particularly limited, but is typically 0.1% by weight or more and 0.5% by weight. The above is preferable, 1% by weight or more is more preferable, and 1.5% by weight or more is further preferable. Higher polishing rates tend to be achieved by increasing the content of abrasive grains. From the viewpoint of the surface smoothness of the substrate after polishing and the stability of polishing, the content is usually preferably 20% by weight or less, preferably 15% by weight or less, more preferably 10% by weight or less, still more preferably. Is 8% by weight or less.

(PH)
The pH of the polishing liquid disclosed herein is not particularly limited. The pH of the polishing solution can be, for example, 12.0 or less (typically 0.5 to 12.0), even 10.0 or less (typically 0.5 to 10.0). Good. From the viewpoint of polishing rate, surface accuracy, etc., the pH of the polishing liquid can be 7.0 or less (for example, 0.5 to 7.0) and 5.0 or less (typically 1.0 to 5). It is more preferably 4.0) or less (for example, 1.0 to 4.0). The pH of the polishing liquid can be, for example, 3.0 or less (typically 1.0 to 3.0). If necessary, a pH adjusting agent such as an organic acid, an inorganic acid, or a basic compound can be contained in the polishing liquid so that the above pH is realized. The pH can be preferably applied to, for example, a polishing liquid for polishing a magnetic disk substrate such as a Ni-P substrate.

(Composition for multi-dosage form polishing)
The polishing composition disclosed herein may be a one-dosage form or a multi-dosage form including a two-dosage form. For example, a solution A containing a part of the constituent components (typically, a component other than water) of the polishing composition and a solution B containing the remaining components are mixed to polish the object to be polished. It may be configured to be used in. The composition for multi-dosage form polishing according to a preferred embodiment includes a liquid A containing abrasive grains (typically, an abrasive grain dispersion liquid which may contain a dispersant) and components other than the abrasive grains (for example, acid, water-soluble). It is composed of a liquid B containing a sex polymer and other additives). Normally, these are stored separately before use and can be mixed at the time of use (when polishing the substrate to be polished). At the time of mixing, an oxidizing agent such as hydrogen peroxide may be further mixed. For example, when the oxidizing agent (for example, hydrogen peroxide) is supplied in the form of an aqueous solution (for example, hydrogen peroxide solution), the aqueous solution can be the C solution constituting the multi-dosage polishing composition.

(Use)
The application of the technology disclosed herein is not particularly limited. According to the technique disclosed herein, it is possible to provide a polishing composition capable of highly reducing scratches after polishing. The polishing composition disclosed herein includes, for example, a magnetic disk substrate, a semiconductor substrate such as a silicon wafer (for example, a silicon single crystal wafer obtained by slicing a silicon single crystal ingot), and optics such as a lens and a reflection mirror. It can be preferably used for polishing various polishing objects that require a highly accurate surface such as a material. Above all, it is suitable for polishing a magnetic disk substrate. Examples of the magnetic disk substrate referred to here include a Ni-P substrate (meaning a magnetic disk substrate having a nickel phosphorus plating layer on the surface of a substrate disk made of aluminum alloy or the like) and a glass magnetic disk substrate. In such applications of polishing magnetic disk substrates, it is particularly meaningful to apply the techniques disclosed herein. Application to a Ni-P substrate is particularly preferable.

Since the polishing composition disclosed herein can highly reduce scratches on the surface after polishing, it can be particularly preferably used in the final polishing step (final polishing step) of the object to be polished. According to this specification, a method for producing a polished product (for example, a method for producing a magnetic disk substrate) including a final polishing step using the polishing composition disclosed herein, and a magnetic disk substrate produced by the method are provided. obtain. The final policing refers to the final policing step in the manufacturing process of the target product (that is, a step in which no further policing is performed after the step).

The polishing composition disclosed herein may also be used in a polishing step upstream of final polishing. Here, the polishing step upstream of the final polishing refers to a pre-polishing step between the rough polishing step and the final polishing step. The pre-polishing step typically includes at least a primary polishing step and may further include a secondary, tertiary ... Etc. polishing step. The polishing composition can be used in any polishing step, and the same or different polishing composition can be used in these polishing steps. The polishing composition disclosed herein may be used, for example, in a polishing step performed immediately before final polishing.

<Polishing process>
The polishing composition disclosed herein can be suitably used for polishing an object to be polished (for example, a magnetic disk substrate) in a mode including, for example, the following operations. Hereinafter, a preferred embodiment of a method of polishing an object to be polished (typically a substrate to be polished) using the polishing composition disclosed herein will be described.
That is, a polishing liquid (working slurry) containing any of the polishing compositions disclosed herein is prepared. The preparation of the polishing liquid may include preparing the polishing liquid by subjecting the polishing composition to operations such as concentration adjustment (for example, dilution) and pH adjustment. Alternatively, the polishing composition may be used as it is as a polishing liquid.

Next, the polishing liquid is supplied to the object to be polished, and polishing is performed by a conventional method. For example, an object to be polished is set in a general polishing device, and a polishing liquid is supplied to the surface of the object to be polished (the surface to be polished) through the polishing pad of the polishing device. Typically, while continuously supplying the polishing liquid, the polishing pad is pressed against the surface of the object to be polished to move the two relative to each other (for example, rotational movement). Polishing of the object to be polished is completed through such a polishing step.

The polishing process as described above can be part of the manufacturing process of a substrate (eg, a magnetic disk substrate, typically a Ni-P substrate). Therefore, according to this specification, a method for manufacturing a substrate and a method for polishing a substrate including the above-mentioned polishing step are provided.

The magnetic disk substrate manufacturing method disclosed herein may further include an upstream polishing step (hereinafter, also referred to as “step (P)”) performed prior to the polishing step using the polishing composition described above. According to the aspect including the step (P), the effect of shortening the required time of the entire polishing step and increasing the productivity can be realized. The step (P) may be one polishing step using one kind of polishing composition, or may include two or more polishing steps performed by sequentially using two or more kinds of polishing compositions. Good.

The polishing composition used in the step (P) (hereinafter, also referred to as “polishing composition (P)”) is not particularly limited. For example, as the abrasive grains, the abrasive grains exemplified as the material that can be used in the above-mentioned polishing composition can be used. When the polishing composition contains silica particles, the silica particles may be the same as or different from the silica particles contained in the above-mentioned polishing composition. The difference between the silica particles contained in the polishing composition (P) and the silica particles contained in the above-mentioned polishing composition is, for example, a difference in one or two or more of the particle size, particle shape, density and other characteristics. possible.

The polishing composition (P) typically contains water in addition to the abrasive grains. In addition, the polishing composition (P) contains the same components (acid, oxidizing agent, basic compound, polymer, surfactant, various additives, etc.) as the above-mentioned polishing composition, if necessary. be able to. Although not particularly limited, the pH of the polishing composition (P) can be, for example, 12.0 or less (typically 0.5 to 12.0), preferably 7.0 or less (preferably 7.0 or less). For example, 0.5 to 7.0), more preferably 5.0 or less (typically 1.0 to 5.0), still more preferably 4.0 or less (for example, 1.0 to 4.0). .. In a preferred embodiment, the pH of the polishing composition (P) can be 3.0 or less (typically 1.0 to 3.0).

Hereinafter, some examples of the present invention will be described, but the present invention is not intended to be limited to those shown in such examples.

<Examples 1 to 11>
[Preparation of polishing composition]
A plurality of types of silica particles having different aspect ratios were prepared. Abrasive grains containing these silica particles alone or in combination, polystyrene sulfonic acid-based copolymer (Mw: 500000) as a polymer, phosphoric acid, 31% hydrogen peroxide solution, and deionized water are mixed. Then, an example containing 6% by weight of abrasive grains, 0.004% by weight of polystyrene sulfonic acid-based copolymer, 1.5% by weight of phosphoric acid, and 0.4% by weight of 31% hydrogen peroxide solution. The polishing compositions of 1 to 11 were prepared. The pH of the polishing composition according to each example was adjusted to 2.5 with potassium hydroxide (KOH). Table 1 shows the types and physical characteristics of the abrasive grains used in each example.

[Abrasion of disc]
The polishing composition according to each example was used as it was in the polishing liquid, and a standard polishing test was conducted to polish the object to be polished under the following conditions. As the object to be polished, an aluminum substrate for a hard disk having an electroless nickel phosphorus plating layer on the surface was used. Here, a surface roughness (arithmetic mean roughness (Ra)) measured by a laser scan type surface roughness meter "TMS-3000WRC" manufactured by Schmitt Measurement System is pre-polished so as to be 6 Å. did. The object to be polished (hereinafter, also referred to as “Ni-P substrate”) had a diameter of 3.5 inches (a donut shape having an outer diameter of about 95 mm and an inner diameter of about 25 mm) and a thickness of 1.27 mm.

[Polishing conditions]
Polishing device: Double-sided polishing machine manufactured by Speedfam Co., Ltd., model "9B-5P"
Polishing pad: Suede non-buff type Ni-P substrate input number: 20 sheets (2 sheets / carrier x 5 carriers) x 2 batch Polishing solution supply rate: 130 mL / min Polishing load: 120 g / cm ²
Lower platen rotation speed: 25 rpm
Polishing time: 5 minutes

[Polishing rate]
The polishing rate when the substrate to be polished was polished under the above polishing conditions using the polishing composition according to each example was calculated. The polishing rate was determined based on the following formula.
Polishing rate [μm / min] = Weight loss of substrate due to polishing [g] / (one side area of substrate [cm ² ] x density of nickel phosphorus plating [g / cm ³ ] x polishing time [min]) x 10 ⁴
(Calculated as substrate single surface area: 66 cm ² , Ni-P plating density: 7.9 g / cm ²⁾
The obtained values are shown in the "polishing rate" column of Table 1. Here, the polishing rate of 0.12 μm / min or more is referred to as “◎”, the polishing rate of 0.06 μm / min or more and less than 0.12 μm / min is referred to as “◎”, and the polishing rate of less than 0.06 μm / min is referred to as “x”. evaluated.

[scratch]
A total of 6 sheets (3 sheets / batch) were randomly selected from the above-polished substrates, and the number of scratches on both sides of each substrate was measured under the following measurement conditions, and the number of scratches on 6 sheets (12 surfaces in total) was measured. The total number of scratches per surface of the substrate was divided by 12 to calculate the number of scratches (books / surface). Then, the relative value of the number of scratches in each example was evaluated when the number of scratches in Example 6 was 100. Here, those having a relative value of the number of scratches less than 50 were evaluated as "⊚", those having a relative value of 50 or more and less than 100 were evaluated as "◯", and those having a relative value of 100 or more were evaluated as "x". The results are shown in the "Scratch" column of Table 1.

[Scratch measurement conditions]
Measuring device: Candela OSA6100 manufactured by KLA Tencor Co., Ltd.
Spindle speed: 10000 rpm
Measuring range: 17,000-47,000 μm
Step size: 4 μm
Encoder multiplier: × 32
Detection channel: P-Sc channel

As shown in Table 1, abrasive grains having an average aspect ratio of 1 to 1.30 for all particles and an average aspect ratio _{of D 0-5} particles having a cumulative total of 0 to 5% are 1 to 1.25. In Examples 1 to 5 used, better results were obtained in terms of the number of scratches as compared with Examples 6 to 11 in which the average aspect ratio of _{the D 0-5 particles exceeded 1.25.} From this result, for polishing using abrasive grains, the average aspect ratio of the entire particles is 1-1.30, and _{the average aspect ratio of D 0-5 particles with a cumulative total of 0 to 5% is 1 to 1.25.} According to the composition, it was confirmed that a high quality polished surface with a small number of scratches could be realized.

Although specific examples of the present invention have been described in detail above, these are merely examples and do not limit the scope of claims. The techniques described in the claims include various modifications and modifications of the specific examples illustrated above.

Claims (5)

A polishing composition containing abrasive grains containing silica particles and water.
The abrasive grains have an average aspect ratio of 1 to 1.25 _{D 0-5} particles with a cumulative total of 0 to 5% in the cumulative particle size distribution based on the number from the small diameter side, and are cumulative in the cumulative particle size distribution from the small diameter side. A polishing composition having a 5% particle size D5 of 30 nm or less and an average aspect ratio of all particles of 1-1.30. The abrasive grain according to claim 1, wherein the relationship between the cumulative 5% particle size D5 and the cumulative 50% particle size D50 in the cumulative particle size distribution from the small diameter side satisfies the following equation: 0.3 ≦ D5 / D50 ;. The polishing composition according to the above. The polishing composition according to claim 1 or 2 , which is used for polishing a magnetic disk substrate. The polishing composition according to any one of claims 1 to 3 is prepared, and
A method for manufacturing a magnetic disk substrate, which comprises supplying the polishing composition to the magnetic disk substrate and polishing the magnetic disk substrate. A method for polishing a magnetic disk substrate, which comprises supplying the polishing composition according to any one of claims 1 to 3 to the magnetic disk substrate to polish the magnetic disk substrate.