JP2018174009A - Polishing composition, manufacturing method for magnetic disk substrate, and polishing method for magnetic disk - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing composition capable of effectively reducing the number of scratches existing on a surface after polishing.SOLUTION: A polishing composition provided here includes an abrasive grain containing a silica particle and water. The abrasive grain has an average aspect ratio of 1 to 1.25 of a Dgrain of accumulation 0 to 5% in number based an accumulation grain size distribution from a small-diameter side, and an average aspect ratio of all grains of 1 to 1.30 .SELECTED DRAWING: None

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 is performed on the surface of a material such as a metal, a semimetal, a nonmetal, or an oxide thereof. For example, in the manufacturing process of a polished product that requires a highly accurate surface, generally, polishing with a higher emphasis on polishing efficiency (primary polishing) and final polishing step (final polishing step) performed to finish the surface accuracy of the final product ) And has been done. Patent document 1 is mentioned as a prior art regarding the polishing composition used in the use which grind | polishes the disk board | substrate (Ni-P board | substrate) to which nickel phosphorus plating was given.

JP 2010-167553 A

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

Therefore, an object of the present invention is to provide a polishing composition that can effectively reduce 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 related object is to provide a method of manufacturing a disk substrate having a surface with a reduced number of scratches.

According to this invention, the polishing composition containing the abrasive grain containing a silica particle and water is provided. The abrasive has an average aspect ratio of 1 to 1.25 D _0-5 particles having a cumulative 0 to 5% in a cumulative particle size distribution based on the number from the small diameter side, and an 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 polished surface.

  In a preferred embodiment of the polishing composition disclosed herein, the abrasive grains have a relationship between a cumulative 5% particle diameter D5 and a cumulative 50% particle diameter D50 in the cumulative particle size distribution from the small diameter side according to the following formula: 0.3 ≦ D5 / D50; When the ratio is within the D5 / D50 ratio range of such abrasive grains, the above-described 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 diameter D5 in the cumulative particle size distribution from the small diameter side of 30 nm or less. The effect of reducing the number of scratches described above can be more effectively exhibited when the cumulative particle diameter is within the range of 5%.

  The polishing composition disclosed herein is suitable as a polishing composition for polishing a magnetic disk substrate, for example. In the field of magnetic disk substrates, a surface with less scratches is required for higher capacity and higher reliability. Therefore, the magnetic disk substrate can be a preferable application target of the technology 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, a magnetic disk substrate having a high-quality surface in which scratches are highly suppressed can be manufactured. The polishing composition disclosed herein is particularly suitable for the final polishing step (finish polishing step) of the magnetic disk substrate.

  According to this specification, a method for polishing a magnetic disk substrate is further provided. The polishing method includes supplying any of the polishing compositions disclosed herein to a magnetic disk substrate and polishing the magnetic disk substrate. According to this polishing method, it is possible to realize a high-quality surface in which scratches are highly suppressed.

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

<Abrasive>
The polishing composition disclosed herein contains abrasive grains. This abrasive grain has an average aspect ratio of 0 to 5% of D _0-5 particles in the cumulative particle size distribution from the small diameter side of 1 to 1.25, and an average aspect ratio of all particles of 1 to 1. 30. Here, the D _0-5 particles are particles having a particle size corresponding to a cumulative size from 0 to 5% from the small diameter side in the number-based cumulative particle size distribution (cumulative number distribution from the small diameter side). Say. The cumulative number distribution typically extends from the end of the small diameter side (lower left) to the upper right of the cumulative 0% and particle diameter in a graph in which the horizontal axis is the particle diameter and the vertical axis is the cumulative number (%). , Represented by a curve that reaches 100% of the cumulative and end of the large diameter side (upper right) of the particle diameter. D _0-5 particles are small-diameter particles occupying 5% on the basis of the number from the small-diameter side. Moreover, all the particles of the abrasive grains are D _0-100 particles having a particle diameter corresponding to the accumulation from the small diameter side in the range of 0 to 100% in the cumulative particle size distribution based on the number, 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 diameter of 1 to 1.25, and an average aspect ratio of the entire particles of 1 to 1.30. Thus, 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 is considered as follows, for example. That is, a polishing composition satisfying an average aspect ratio of 1 to 1.30 of the abrasive grains as a whole is easy to roll and move because spherical or nearly spherical abrasive grains are easily processed, and the surface quality after polishing is improved. It is thought to 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 whole particle is reduced, the irregularly shaped particles having a small diameter play a role of wedges with respect to the spherical particles, so that even if the particles are spherical particles, the abrasive grains are not easily rolled locally. Therefore, scratches are likely to occur on the polished surface. In contrast, abrasive grains having an average aspect ratio of D _0-5 particles of 1 to 1.25 have a shape in which small-diameter particles that can serve as the wedges are closer to a sphere. Such small-diameter particles having a high sphericity are unlikely to become wedges during polishing, and therefore, it is difficult for an event that the abrasive grains are locally difficult to roll. This is considered to contribute to the reduction of scratches.

The average aspect ratio of D _0-5 grains of the abrasive grains disclosed herein is usually 1.25 or less, and preferably 1.24 or less, more preferably 1 from the viewpoint of better reducing scratches. .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 is not particularly limited, but may be, for example, 1.05 or more, typically 1.08 or more. The technique disclosed here can be implemented, for example, in an embodiment in which the average aspect ratio of D _0-5 particles of the abrasive grains in the polishing composition is 1.11 or more and 1.21 or less.

  The average aspect ratio of the entire abrasive grains disclosed herein is suitably 1.30 or less. By reducing the average aspect ratio of the entire grains, the abrasive grains are easy to roll and move, so that the processing is stable and scratches can be more preferably reduced. The average aspect ratio of the whole particle is preferably 1.28 or less, more preferably 1.25 or less (for example, 1.2 or less). The average aspect ratio of all the particles is 1 or more in principle, and the lower limit 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 grains of the abrasive grains may be larger than the average aspect ratio A _{all of the} whole grains. 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 D _0-5 particles and all particles of the abrasive grains can be adjusted by selecting abrasive grains to be used or a combination thereof. For example, the particles of the above-mentioned abrasive grains and D can be obtained by mixing smaller spherical particles closer to a spherical shape with larger particles at an appropriate weight ratio, or by removing small-diameter irregular particles from commercially available abrasive grains. The average aspect ratio of _0-5 particles can be adjusted to the appropriate range disclosed herein.

In this specification, the average aspect ratio of D _0-5 particles and all particles is the number average aspect ratio of particles in the corresponding cumulative range. Specifically, the average aspect ratio of the D _0-5 particles and the whole particles is determined by the following method. That is, using a transmission electron microscope (TEM, STEM HD-2700 manufactured by Hitachi High-Technologies Corporation), the abrasive grains to be measured (one kind of abrasive grains may be used, and two or more kinds of abrasive grains may be used). A particle particle mixture.) 1000 or more particles that can be observed with a TEM included in the TEM are photographed at a magnification (for example, 200000 times to 400000 times) in which about 100 particles can be observed in one field of view. Acquire a TEM image. Then, for the smallest rectangle circumscribing each particle image, the value obtained by dividing the long side length (major axis value) by the short side length (minor axis value) is the major axis / minor axis ratio ( (Aspect ratio). Further, the area of each particle is calculated from the image of each particle, and the diameter of an ideal circle (true 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 on the horizontal axis and the cumulative number (%) on the vertical axis for each particle constituting the abrasive grain. . Then, 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 obtained 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. The ratio can be determined. The above aspect ratios can be obtained by using image analysis software MacView manufactured by Mountec. The same applies to the embodiments described later.

  Although the particle diameter of the abrasive grain disclosed here is not particularly limited, it is typically preferable to use an abrasive having an accumulated 50% particle diameter D50 of 5 nm or more in the cumulative particle size distribution from the small diameter side. By increasing the cumulative 50% particle size, higher polishing rates can be achieved. The cumulative 50% particle size is preferably 10 nm or more, more preferably 15 nm or more, from the viewpoint of the 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 here can be preferably implemented, for example, in an embodiment using abrasive grains having a cumulative 50% particle diameter of 15 nm to 35 nm, and further 15 nm to 30 nm.

  The cumulative 5% particle diameter D5 in the cumulative particle size distribution from the small diameter side of the abrasive grains may be, for example, 30 nm or less. When the cumulative particle diameter is within the range of 5%, the above-described effect of reducing the number of scratches can be better exhibited. 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. Moreover, the cumulative 5% particle diameter of the abrasive grains may be, for example, 1 nm or more. From the viewpoint of manufacturability and the like, the cumulative 5% particle diameter of the abrasive grains is, for example, 3 nm or more, preferably 5 nm or more, more preferably 10 nm or more. The technique disclosed here can be preferably implemented, for example, in an embodiment using abrasive grains having a cumulative 5% particle diameter of 8 nm to 30 nm, and further 10 nm to 25 nm.

  From the viewpoint of more effectively exerting the effect of reducing the number of scratches, the relationship between the cumulative 5% particle diameter D5 and the cumulative 50% particle diameter D50 in the cumulative particle size distribution from the small diameter side satisfies 0.3 ≦ D5 / D50. It is preferable. The technique disclosed here can be preferably implemented, for example, in an embodiment where 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 may be various silica particles mainly composed of silica. Here, 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 (eg, sodium silicate method silica, alkoxide method silica, etc.), fumed silica, precipitated silica, and the like. The abrasive grains in the polishing composition disclosed herein may contain one kind of silica particles as described above alone or in combination of two or more kinds. In one aspect of the technology 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, and may be 70% by weight or more. 85% by weight or more, 95% by weight or more, or 99% by weight or more. Even if it is 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 wt% of the entire abrasive grains). Good.

The particle shape of silica is not particularly limited as long as the average aspect ratio of D _0-5 particles and 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 particles other than silica particles, any of inorganic particles, organic particles, and organic-inorganic composite particles can be used. Specific examples of 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 bengara particles; nitrides such as silicon nitride particles and boron nitride particles Product particles; carbide particles such as silicon carbide particles and boron carbide particles; diamond particles; carbonates such as calcium carbonate and barium carbonate; Specific examples of the organic particles include polymethyl methacrylate (PMMA) particles and poly (meth) acrylic acid particles (here, (meth) acrylic acid is a generic term for acrylic acid and methacrylic acid). And polyacrylonitrile particles. These abrasive grains other than silica particles can be used alone or in combination of two or more.

<Polishing composition>
(water)
The polishing composition disclosed herein typically contains water in which the abrasive grains are dispersed in addition to the abrasive grains as described above. As water, ion exchange 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 implemented, for example, in a form in which the solid content is 0.5 wt% to 30 wt%. The form whose said solid content is 1 to 20 weight% is more preferable.

<Polymer>
It is preferable that the polishing composition disclosed here contains a polymer. The polymer here means a compound having the same (homopolymer; homopolymer) or different (copolymer; copolymer) repeating unit, and typically has a weight average molecular weight (Mw) of 500 or more (preferably Can be 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. There is no restriction | limiting in particular as a kind of polymer, Any of anionic polymer, a nonionic polymer, a cationic polymer, and an amphoteric polymer can be used. Among these, it is preferable that an anionic polymer is included. Examples of the anionic polymer include carboxylic acid polymers and sulfonic acid polymers.
Specific examples of the polymer include polyalkylaryl sulfonic acid compounds such as naphthalene sulfonic acid formaldehyde condensate, methyl naphthalene sulfonic acid formaldehyde condensate, anthracene sulfonic acid formaldehyde condensate; melamine formalin resin sulfone such as melamine sulfonic acid formaldehyde condensate Acid-based compounds; Lignin sulfonic acid-based compounds such as lignin sulfonic acid and modified lignin sulfonic acid; Aromatic amino sulfonic acid-based compounds such as aminoaryl sulfonic acid-phenol-formaldehyde condensates; Others such as polyacrylic acid, polyvinyl acetate, Polymaleic acid, polyitaconic acid, polyvinyl alcohol, polyglycerin, polyvinylpyrrolidone, polyvinylpyrrolidone polyacrylic acid copolymer, polyvinylpyrrolidone acetic acid Cycloalkenyl copolymers, diallylamine hydrochloride-sulfur dioxide copolymer, carboxymethyl cellulose, carboxyethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, pullulan and chitosan. A water-soluble polymer can be used singly or in combination of two or more.

  Although there is no restriction | limiting in particular in content of the said polymer (in the aspect containing a some polymer, those total content), For example, it is suitable to set it as 0.0001 weight% or more. The content is preferably 0.001% by weight or more, more preferably 0.01% by weight or more, and still more preferably 0.000% by weight or more from the viewpoint of the surface smoothness of the polished object (eg, magnetic disk substrate) after polishing. 02% by weight or more. Further, from the viewpoint of polishing rate and the like, the content is suitably 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 polymer is used as the polymer. Here, the sulfonic acid polymer refers to a polymer 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 polymer. Refers to coalescence. Monomers 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, methallyl sulfone. An acid etc. are mentioned. The sulfonic acid polymer preferably contains one or more structural units X derived from the sulfonic acid group-containing monomer. Moreover, you may contain the component originating in monomers other than a sulfonic acid group containing monomer.

  Preferable examples of the sulfonic acid polymer disclosed herein include a high molecular weight sulfonic acid polymer A substantially composed of only the structural unit X derived from the sulfonic acid group-containing monomer. In other words, in the sulfonic acid 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, 99.99%). 9 mol% or more, typically 99.9 to 100 mol%). Examples of such a sulfonic acid polymer A include a homopolymer consisting of only one sulfonic acid group-containing monomer disclosed herein and a copolymer consisting of two or more sulfonic acid group-containing monomers. (Copolymer). Examples of homopolymers include polystyrene sulfonic acid, polyisoprene sulfonic acid, polyvinyl sulfonic acid, polyallyl sulfonic acid, polyisoamylene sulfonic acid and the like.

The molecular weight of the sulfonic acid 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. It is. In a preferred embodiment, the molecular weight of the sulfonic acid polymer A may be 40 × 10 ⁴ or more, for example, 45 × 10 ⁴ or more. The molecular weight of the sulfonic acid polymer A is typically 100 × 10 ⁴ or less, and preferably 80 × 10 ⁴ or less, more preferably 60 × 10 ⁴ from the viewpoints of dispersion stability and filterability. It is as follows. The molecular weight of the sulfonic acid polymer A is the weight average molecular weight (Mw) determined by GPC (aqueous, converted to polyethylene glycol, solvent: 0.1 M sodium nitrate aqueous solution, flow rate: 1 ml / min, measuring instrument: Tosoh Corporation (Manufactured by HLC-8320GPC) can be employed.

  Another preferred example of the sulfonic acid-based polymer disclosed herein is 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. Here, “(meth) acrylic acid” is a concept including one or both of acrylic acid and methacrylic acid. Such a (meth) acrylic acid / sulfonic acid copolymer may contain one or more structural units X derived from the above-described sulfonic acid group-containing monomer. Moreover, the component derived from monomers other than a sulfonic acid group containing monomer and a (meth) acrylic acid monomer may be contained. Examples of the (meth) acrylic acid / sulfonic acid copolymer include (meth) acrylic acid / isoprenesulfonic acid copolymer, (meth) acrylic acid-2-acrylamido-2-methylpropanesulfonic acid copolymer, (Meth) acrylic acid / isoprenesulfonic acid / 2-acrylamido-2-methylpropanesulfonic acid copolymer and the like.

  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 50000 or less, and preferably 30000 or less, more preferably 20000 or less, and more preferably 20000 or less, from the viewpoint of dispersion stability, filterability, and the like. Is 15000 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, converted to polyethylene glycol, solvent: 0.1 M sodium nitrate aqueous solution, flow rate: 1 ml / min, measuring device: HLC-8320GPC manufactured by Tosoh Corporation) can be employed.

In a preferred embodiment of the polishing composition disclosed herein, the above-described sulfonic acid polymer A and (meth) acrylic acid / sulfonic acid copolymer are used in combination. 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 polymer content W _B (W _B / W _A ) is usually suitably 1 or more on a weight basis, preferably 3 or more, more preferably 5 or more, still more preferably 8 or more. It is. The upper limit of the ratio (W _B / W _A ) is not particularly limited, but is usually suitably 30 or less, preferably 25 or less, more preferably 20 or less, and even more preferably 15 or less.

  When the sulfonic acid polymer A is used, the content of the sulfonic acid polymer A in the polishing composition is, for example, suitably 0.0001% by weight or more, preferably 0.0002% by weight or more, More preferably, it is 0.001 weight% or more, More preferably, it is 0.002 weight% or more. Further, the content of the sulfonic acid polymer A is suitably 0.02% by weight or less, preferably 0.015% by weight or less, for example 0.01% by weight or less. In the case of using a (meth) acrylic acid / sulfonic acid copolymer, the content of the (meth) acrylic acid / sulfonic acid copolymer in the polishing composition is suitably 0.0001% by weight or more, for example. Preferably, it is 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 suitably 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 implemented in an embodiment containing an acid as a polishing accelerator. Examples of acids that can be suitably used include inorganic acids and organic acids (for example, organic carboxylic acids having 1 to 10 carbon atoms, organic phosphonic acids, organic sulfonic acids, amino acids, etc.). It is not limited. An acid can be used individually by 1 type or in combination of 2 or more types.

  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, iminodiacetic acid, gluconic acid, lactic acid, mandelic acid, tartaric acid, crotonic acid, nicotinic acid, acetic acid , Adipic acid, formic acid, oxalic acid, propionic acid, valeric acid, caproic acid, caprylic acid, capric acid, cyclohexanecarboxylic acid, phenylacetic acid, benzoic acid, crotonic acid, methacrylic acid, glutaric acid, fumaric acid, phthalic acid, isophthalic acid Acid, terephthalic acid, glycolic acid, tartronic acid, glyceric acid, hydroxybutyric acid, hydroxyacetic acid, hydroxybenzoic acid, salicylic acid, isocitric acid, methylene succinic acid, gallic acid, ascorbic acid, nitroacetic acid, oxaloacetic acid, glycine, alanine, glutamic acid , Aspartic acid, valine, leucine, a Leucine, serine, threonine, cysteine, methionine, phenylalanine, tryptophan, tyrosine, proline, cystine, glutamine, asparagine, lysine, arginine, nicotinic acid, picolinic acid, methyl acid phosphate, ethyl acid phosphate, ethyl glycol 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, Tan-1,2-dicarboxy-1,2-diphosphonic acid, methanehydroxyphosphonic acid, 2-phosphonobutane-1,2-dicarboxylic acid, 1-phosphonobutane-2,3,4-tricarboxylic acid, α-methylphosphono Examples include succinic acid, aminopoly (methylenephosphonic acid), methanesulfonic acid, ethanesulfonic acid, aminoethanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, and 2-naphthalenesulfonic acid.

  Preferred acids from the viewpoint of the 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 an acid is contained in the polishing composition, the content is not particularly limited. In general, the acid content is suitably 0.1% by weight or more, preferably 0.5% by weight or more, and more preferably 0.8% by weight or more (eg, 1.2% by weight or more). If the acid content is too small, the polishing rate tends to be insufficient, which may be undesirable in practice. The acid content is usually 15% by weight or less, preferably 10% by weight or less, and more preferably 5% by weight or less (eg, 3% by weight or less). When there is too much content of an acid, the surface precision of a grinding | polishing target object will fall easily, and it may be unpreferable practically.

The acid may be used in the form of a salt of the acid. Examples of the salt 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 inorganic acids and organic acids described above. Quaternary ammonium salts), alkanolamine salts (for example, monoethanolamine salts, diethanolamine salts, triethanolamine salts) and the like.
Specific examples of the salt include tripotassium phosphate, dipotassium hydrogen phosphate, potassium dihydrogen phosphate, trisodium phosphate, disodium hydrogen phosphate, sodium dihydrogen phosphate and the like alkali metal phosphates and alkali metals Hydrogen phosphate salt; alkali metal salt of organic acid exemplified above; other alkali metal salt of glutamic acid diacetic acid, alkali metal salt of diethylenetriaminepentaacetic acid, alkali metal salt of hydroxyethylethylenediaminetriacetic acid, triethylenetetramine hexaacetic acid Alkali metal salts; and the like. The alkali metal in these alkali metal salts can be, for example, lithium, sodium, potassium, and the like.

  As a 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 used. For example, potassium chloride, sodium chloride, ammonium chloride, potassium nitrate, sodium nitrate, ammonium nitrate, potassium phosphate and the like can be preferably used.

  An acid and its salt can be used individually by 1 type or in combination of 2 or more types. 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 as necessary. Examples of oxidizing agents are peroxides, nitric acid or salts thereof, periodic acid or salts thereof, peroxo acids or salts thereof, permanganic acid or salts thereof, chromic acid or salts thereof, oxygen acids or salts thereof, metal salts And sulfuric acids, but are not limited to these. An oxidizing agent can be used individually by 1 type or in combination of 2 or more types. Specific examples of the oxidizing agent include hydrogen peroxide, sodium peroxide, barium peroxide, nitric acid, iron nitrate, aluminum nitrate, ammonium nitrate, peroxomonosulfuric acid, ammonium peroxomonosulfate, peroxomonosulfuric acid metal salt, peroxodisulfuric acid, peroxodioxide. Ammonium sulfate, peroxodisulfate metal salt, peroxophosphoric acid, peroxosulfuric acid, sodium peroxoborate, performic acid, peracetic acid, perbenzoic acid, perphthalic acid, hypobromite, hypoiodous acid, chloric acid, bromic acid, Iodic acid, periodic acid, perchloric acid, hypochlorous acid, sodium hypochlorite, calcium hypochlorite, potassium permanganate, metal chromate, metal dichromate, iron chloride, iron sulfate, Examples thereof include iron citrate and ammonium iron sulfate. Examples of preferable 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, its content is preferably 0.01% by weight or more, more preferably 0.1% by weight or more, and still more preferably 0.3% by weight based on the amount of active ingredients. % By weight. If the content of the oxidizing agent is too small, the rate of oxidizing the object to be polished becomes slow and the polishing rate is lowered, which may be undesirable in practice. Moreover, when an oxidizing agent is included in polishing composition, it is preferable that the content is 5 weight% or less on the basis of the amount of active ingredients, More preferably, it is 1 weight% or less. When there is too much content of an oxidizing agent, the surface precision of a grinding | polishing target object will fall easily, and it may be unpreferable practically.

(Basic compound)
The polishing composition can contain a basic compound as necessary. Here, the basic compound refers to a compound having a function of increasing the pH of the composition when added to the polishing composition. Examples of basic compounds include alkali metal hydroxides, carbonates and hydrogen carbonates, quaternary ammonium or salts thereof, ammonia, amines, phosphates and hydrogen phosphates, organic acid salts and the like. A basic compound can be used individually by 1 type or in combination of 2 or more types.

Specific examples of the alkali metal hydroxide include potassium hydroxide and sodium hydroxide.
Specific examples of the carbonate and bicarbonate include ammonium bicarbonate, ammonium carbonate, potassium bicarbonate, potassium carbonate, sodium bicarbonate, sodium carbonate and the like.
Specific examples of the quaternary ammonium or a salt thereof include quaternary ammonium hydroxides such as tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrabutylammonium hydroxide; alkali metals of such quaternary ammonium hydroxides Salt (for example, sodium salt, potassium salt); and the like.
Specific examples of amines include methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylenediamine, monoethanolamine, N- (β-aminoethyl) ethanolamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, anhydrous piperazine , 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 are mentioned.
Specific examples of the organic acid salt include potassium citrate, potassium oxalate, potassium tartrate, potassium sodium tartrate, ammonium tartrate and the like.

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

The polishing composition can contain a surfactant as required. The surfactant as used herein refers to a compound having at least one hydrophilic site (typically a hydrophilic group) and one or more hydrophobic sites (typically a hydrophobic group) in one molecule. The surfactant is not particularly limited, and any of an anionic surfactant, a nonionic surfactant, a cationic surfactant, and an amphoteric surfactant can be used. By using the surfactant, the dispersion stability of the polishing composition can be improved. Surfactant can be used individually by 1 type or in combination of 2 or more types.
Specific examples of the anionic surfactant include polyoxyethylene alkyl ether acetic acid, polyoxyethylene alkyl sulfate ester, alkyl sulfate ester, polyoxyethylene alkyl sulfate, alkyl sulfate, alkylbenzene sulfonic acid, alkyl phosphate ester, polyoxyethylene Alkyl phosphate ester, polyoxyethylene sulfosuccinic acid, alkyl sulfosuccinic acid, alkyl naphthalene sulfonic acid, alkyl diphenyl ether disulfonic acid, polyacrylic acid, sodium lauryl sulfate, ammonium lauryl sulfate, sodium dodecylbenzene sulfonate, sodium polyoxyethylene alkyl ether sulfate, Polyoxyethylene alkyl phenyl ether ammonium sulfate, polyoxyethylene alkyl phenyl ether sulfate Sodium and the like.
Other specific examples of anionic surfactants include polyalkylaryl sulfonic acid compounds such as naphthalene sulfonic acid formaldehyde condensate, methyl naphthalene sulfonic acid formaldehyde condensate, anthracene sulfonic acid formaldehyde condensate, benzene sulfonic 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 System compounds and the like. 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 amphoteric surfactants include alkyl betaines and alkyl amine oxides.

  In the polishing composition containing the 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 the smoothness of the surface after polishing. Further, from the viewpoint of polishing rate and the like, the content is suitably 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 chelating agents and organic phosphonic acid chelating agents. Examples of aminocarboxylic acid chelating agents include ethylenediaminetetraacetic acid, ethylenediaminetetraacetic acid sodium, nitrilotriacetic acid, nitrilotriacetic acid sodium, nitrilotriacetic acid ammonium, hydroxyethylethylenediaminetriacetic acid, hydroxyethylethylenediamine sodium triacetate, diethylenetriaminepentaacetic acid Diethylenetriamine sodium pentaacetate, triethylenetetramine hexaacetic acid and sodium triethylenetetramine hexaacetate. Examples of organic phosphonic acid chelating agents include 2-aminoethylphosphonic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, aminotri (methylenephosphonic acid), ethylenediaminetetrakis (methylenephosphonic acid), diethylenetriaminepenta (methylenephosphonic). 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 Ethane-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 Nosuccinic acid is included. Of these, organic phosphonic acid-based chelating agents are more preferable, and ethylenediaminetetrakis (methylenephosphonic acid) and diethylenetriaminepenta (methylenephosphonic acid) are particularly preferable. A particularly preferred chelating agent is ethylenediaminetetrakis (methylenephosphonic acid).

  Examples of preservatives and fungicides include isothiazoline preservatives such as 2-methyl-4-isothiazolin-3-one and 5-chloro-2-methyl-4-isothiazolin-3-one, and paraoxybenzoic acid esters And phenoxyethanol.

(Polishing liquid)
The polishing composition disclosed herein is typically supplied to a polishing object (for example, a magnetic disk substrate) in the form of a polishing liquid containing the polishing composition, and used for polishing the polishing object. . The polishing liquid can be prepared, for example, by diluting (typically diluting with water) a polishing composition. Or you may use polishing composition as polishing liquid as it is. That is, the concept of the polishing composition in the technology disclosed herein is used as a polishing liquid diluted with a polishing liquid (working slurry) that is supplied to a polishing object and used for polishing the polishing object. Both concentrates are included. Such a polishing composition in the form of a concentrated solution is advantageous from the viewpoints of convenience, cost reduction, etc. during production, distribution, storage and the like. The concentration factor can be set to about 1.5 to 50 times, for example. From the viewpoint of the storage stability of the concentrate, a concentration factor of about 2 to 20 times (typically 2 to 10 times) is usually appropriate.

  The content of abrasive grains in the polishing liquid (in the case where plural kinds of abrasive grains are included, the total content thereof) is not particularly limited, but is typically 0.1% by weight or more and 0.5% by weight. Preferably, it is preferably 1% by weight or more, and more preferably 1.5% by weight or more. A higher polishing rate tends to be realized 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 suitably 20% by weight or less, preferably 15% by weight or less, more preferably 10% by weight or less, and 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 liquid can be, for example, 12.0 or less (typically 0.5 to 12.0), or 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 is 5.0 or less (typically 1.0 to 5). 0.0), 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). A pH adjusting agent such as an organic acid, an inorganic acid, a basic compound, or the like can be included as necessary so that the above pH is realized in the polishing liquid. The pH can be preferably applied to a polishing liquid for polishing a magnetic disk substrate such as a Ni-P substrate.

(Multi-drug polishing composition)
The polishing composition disclosed herein may be a one-part type or a multi-part type including a two-part type. For example, the liquid A containing a part of the constituent components (typically components other than water) of the polishing composition and the liquid B containing the remaining components are mixed to polish the polishing object. It may be configured to be used. A multi-component polishing composition according to a preferred embodiment includes an A liquid containing abrasive grains (typically an abrasive dispersion liquid that may contain a dispersing agent) and components other than abrasive grains (for example, acid, water-soluble). Liquid B containing a conductive polymer and other additives). Usually, these are stored separately before use, and can be mixed at the time of use (during polishing of the substrate to be polished). During mixing, an oxidizing agent such as hydrogen peroxide can 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 a liquid C constituting the multi-drug polishing composition.

(Use)
The application target of the technique disclosed here is not particularly limited. According to the technology disclosed herein, a polishing composition capable of highly reducing scratches after polishing can be provided. 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 an optical such as a lens and a reflection mirror. It can be preferably used for polishing various polishing objects such as materials that require a highly accurate surface. Especially, it is suitable for the use which grind | polishes a magnetic disc board | substrate. Examples of the magnetic disk substrate herein include a Ni-P substrate (referred to as a magnetic disk substrate having a nickel phosphorus plating layer on the surface of a base disk made of aluminum alloy or the like) and a glass magnetic disk substrate. In such an application for polishing a magnetic disk substrate, it is particularly meaningful to apply the technique disclosed herein. Application to a Ni-P substrate is particularly preferable.

  Since the polishing composition disclosed here 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, there is provided a method for producing a polished article (for example, a method for producing a magnetic disk substrate) comprising a final polishing step using the polishing composition disclosed herein, and a magnetic disk substrate produced by the method. obtain. Note that final polishing refers to the final polishing step in the manufacturing process of the object (that is, a step in which no further polishing is performed after that step).

  The polishing composition disclosed herein may also be used in a polishing step upstream of final polishing. Here, the polishing process upstream of the final polishing refers to a preliminary polishing process between the rough polishing process and the final polishing process. The preliminary polishing step typically includes at least a primary polishing step, and may further include secondary, tertiary, etc. polishing steps. 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), for example, in an embodiment including the following operations. Hereinafter, a preferred embodiment of a method for 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. Preparing the polishing liquid may include preparing a polishing liquid by adding operations such as concentration adjustment (for example, dilution) and pH adjustment to the polishing composition. Or you may use polishing composition as polishing liquid as it is.

  Next, the polishing liquid is supplied to the object to be polished and polished by a conventional method. For example, a polishing object is set in a general polishing apparatus, and a polishing liquid is supplied to the surface (polishing object surface) of the polishing object through a polishing pad of the polishing apparatus. Typically, while supplying the polishing liquid continuously, the polishing pad is pressed against the surface of the object to be polished, and both are relatively moved (for example, rotated). The polishing of the object to be polished is completed through this polishing step.

  The polishing step as described above can be part of a manufacturing process for a substrate (eg, a magnetic disk substrate, typically a Ni-P substrate). Therefore, according to this specification, a substrate manufacturing method and a polishing method including the 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 time required for the entire polishing step and increasing the productivity can be realized. The step (P) may be one polishing step using one type of polishing composition, or may include two or more polishing steps performed using two or more types of polishing compositions in sequence. Good.

  The polishing composition (hereinafter also referred to as “polishing composition (P)”) used in the step (P) is not particularly limited. For example, as the abrasive grains, the abrasive grains exemplified as materials that can be used in the above-described 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 polishing composition described above. The difference between the silica particles contained in the polishing composition (P) and the silica particles contained in the polishing composition described above is, for example, a difference in one or more of particle diameter, particle shape, density and other characteristics. possible.

  Polishing composition (P) typically contains water in addition to abrasive grains. In addition, the polishing composition (P) contains the same components (acid, oxidizing agent, basic compound, polymer, surfactant, various additives, and the like) as those described above as necessary. be able to. Although it does not specifically limit, pH of polishing composition (P) can be 12.0 or less (typically 0.5-12.0), for example, Preferably it is 7.0 or less ( For example, it is 0.5-7.0), More preferably, it is 5.0 or less (typically 1.0-5.0), More preferably, it is 4.0 or less (for example, 1.0-4.0). . In a preferred embodiment, the polishing composition (P) can have a pH of 3.0 or less (typically 1.0 to 3.0).

  Several examples relating to the present invention will be described below, but the present invention is not intended to be limited to those shown in the 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, a polystyrene sulfonic acid copolymer (Mw: 500000) as a polymer, phosphoric acid, 31% hydrogen peroxide solution, and deionized water are mixed. Example containing 6% by weight of abrasive grains, 0.004% by weight of polystyrene sulfonic acid copolymer, 1.5% by weight of phosphoric acid, and 0.4% by weight of 31% hydrogen peroxide solution 1 to 11 polishing compositions 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 properties of the abrasive grains used in each example.

[Disk polishing]
The polishing composition according to each example was directly used as a polishing liquid, and a standard polishing test was performed to polish the object to be polished under the following conditions. As an object to be polished, an aluminum substrate for hard disk having an electroless nickel phosphorus plating layer on the surface was used. Here, pre-polished so that the surface roughness (arithmetic mean roughness (Ra)) measured by a laser scanning surface roughness meter “TMS-3000WRC” manufactured by Schmitt Measurement System is 6 mm is used. did. The polishing object (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-side polishing machine, model “9B-5P” manufactured by Speed Fem Co., Ltd.
Polishing pad: Suede non-buffing type Number of Ni-P substrates: 20 (2 sheets / carrier x 5 carriers) x 2 batch Polishing liquid supply rate: 130 mL / min Polishing load: 120 g / cm ²
Lower platen rotation speed: 25rpm
Polishing time: 5 minutes

[Polishing rate]
The polishing rate when the polishing target substrate 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 calculation formula.
Polishing rate [μm / min] = Reduction in weight of substrate by polishing [g] / (One side area of substrate [cm ² ] × Nickel phosphorus plating density [g / cm ³ ] × Polishing time [min]) × 10 ⁴
(Calculated as substrate one side area: 66 cm ² , Ni—P plating density: 7.9 g / cm ² )
The obtained value is shown in the column of “Polishing rate” in Table 1. Here, “◎” indicates that the polishing rate is 0.12 μm / min or more, “◎” indicates that the polishing rate is 0.06 μm / min or more and less than 0.12 μm / min, and “×” indicates that the polishing rate is less than 0.06 μm / min. evaluated.

[scratch]
Select a total of 6 (3/1 batch) from the polished substrates, and measure the number of scratches on both sides of each substrate under the following measurement conditions. The number of 6 (total 12) scratches Was divided by 12 to calculate the number of scratches per side of the substrate (lines / surface). And the relative value of the number of scratches of each example when the number of scratches of example 6 was set to 100 was evaluated. Here, the case where the relative value of the number of scratches was less than 50 was evaluated as “◎”, the case where it was 50 or more and less than 100 was evaluated as “◯”, and the case where it was 100 or more was evaluated as “×”. The results are shown in the column “Scratch” in Table 1.

[Scratch measurement conditions]
Measuring apparatus: CANDEL OSA6100 manufactured by KLA-Tencor Corporation
Spindle speed: 10000rpm
Measurement range: 17000-47000 μm
Step size: 4 μm
Encoder multiplier: x32
Detection channel: P-Sc channel

As shown in Table 1, abrasive grains having an average aspect ratio of 1 to 1.30 of the whole grains and an average aspect ratio of 1 to 1.25 of D _0-5 grains having a cumulative 0 to 5%. In Examples 1 to 5 used, better results were obtained in terms of the number of scratches than Examples 6 to 11 in which the average aspect ratio of D _0-5 particles exceeded 1.25. This result, polishing an average aspect ratio of the whole grain is 1 to 1.30, and an average aspect ratio of cumulative 0-5% _{D 0-5} particles with abrasive grains is 1.25 According to the composition, it was confirmed that a high-quality polished surface with a small number of scratches could be realized.

  Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.

Claims (6)

A polishing composition comprising abrasive grains containing silica particles and water,
The abrasive has an average aspect ratio of 1 to 1.25 D _0-5 particles having a cumulative 0 to 5% in a cumulative particle size distribution based on the number from the small diameter side, and an average aspect ratio of all particles is 1. Polishing composition which is -1.30.   The abrasive grains according to claim 1, wherein the relationship between the cumulative 5% particle diameter D5 and the cumulative 50% particle diameter D50 in the cumulative particle size distribution from the small diameter side satisfies the following formula: 0.3 ≦ D5 / D50. The polishing composition as described.   The abrasive composition according to claim 1 or 2, wherein the abrasive grains have a cumulative 5% particle diameter D5 of 30 nm or less in the cumulative particle size distribution from the small diameter side.   The polishing composition according to claim 1, which is used for polishing a magnetic disk substrate. Preparing the polishing composition according to any one of claims 1 to 4, and
A method of manufacturing a magnetic disk substrate, comprising supplying the polishing composition to a magnetic disk substrate and polishing the magnetic disk substrate. A method for polishing a magnetic disk substrate, comprising supplying the polishing composition according to claim 1 to the magnetic disk substrate and polishing the magnetic disk substrate.