Polishing liquid composition

Abstract

To provide a polishing liquid composition for a magnetic disk substrate that improves polishing speed and reduces scratches on the substrate surface after polishing.SOLUTION: A polishing liquid composition contains silica particles (component A), a water-soluble polymer (component B), an acid (component C), and an aqueous medium, the component B is a copolymer containing structural units derived from acrylic acid and / or its salts, the ratio of structural units derived from acrylic acid and / or its salts constituting the component B is 50 mol% or more, the weight average molecular weight of the component B is 700 or more and is 10000 or less, the component B has an adsorption rate of 5 mass% or more to nickel oxide particles of the component B when 0.4 mass% of nickel oxide particles, the same concentration of the component C as in the polishing liquid composition, and the same concentration of the component B as in the polishing liquid position are mixed, and the ratio d / d0 of the average particle diameter d of the component A in the polishing liquid composition to the average particle diameter d0 of the component A in a composition obtained by removing the component B from the polishing liquid composition is 1.1 or less, and the pH is 0.1 or more to 4 or less.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present disclosure relates to a polishing composition, and a method for manufacturing and polishing a substrate using the same. [Background technology]

[0002] In recent years, magnetic disk drives have become smaller and have larger capacities, and higher recording densities are being demanded. To achieve higher recording densities, technological developments are being made to reduce the unit recording area and lower the flying height of the magnetic head in order to improve the detection sensitivity of weakened magnetic signals. In order to lower the flying height of the magnetic head and ensure a sufficient recording area, there are increasingly strict requirements for magnetic disk substrates in terms of improving smoothness and flatness, as typified by reducing surface roughness, waviness, and edge sagging (roll-off), and reducing defects, as typified by reducing scratches, protrusions, pits, etc.

[0003] In response to such demands, for example, Patent Document 1 proposes a method for manufacturing a magnetic disk substrate including a rough polishing step and a finish polishing step, in which the rough polishing step includes, in the same polishing machine, a first rough polishing step using a polishing liquid composition A containing alumina particles and water, a rinsing treatment after the first rough polishing, and a second rough polishing step using a polishing liquid composition B containing silica particles and water after the rinsing treatment, in this order. Paragraph 0073 of the same document states that the polishing liquid composition A preferably contains polyacrylic acid or a salt thereof. Patent Document 2 proposes a polishing composition for magnetic disk substrates, which contains silica particles as abrasives and water, and further contains at least one selected from a phosphorous acid ester and a phosphoric acid ester having a molecular weight of 150 or more. Patent Document 3 proposes an abrasive composition for magnetic disk substrates that contains colloidal silica, a phosphorus-containing compound, a water-soluble polymeric compound, and water, in which the water-soluble polymeric compound is a copolymer containing a constituent unit derived from an unsaturated aliphatic carboxylic acid and a constituent unit derived from an unsaturated amide. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2014-29753 A [Patent Document 2] JP 2020-166924 A [Patent Document 3] JP 2017-204313 A Summary of the Invention [Problem to be solved by the invention]

[0005] With the increase in the capacity of magnetic disk drives, the required characteristics for the surface quality of substrates are becoming more severe, and there is a demand for the development of a polishing composition that can further reduce scratches on the substrate surface. In addition, there is generally a trade-off between the polishing rate and scratches, and there is a problem that improving one of them leads to a deterioration of the other.

[0006] Therefore, the present disclosure provides a polishing composition that can achieve both an improvement in the removal rate and a reduction in scratches on the substrate surface after polishing, as well as a method for producing a magnetic disk substrate and a method for polishing a substrate using the same. [Means for solving the problem]

[0007] In one aspect, the present disclosure provides a polishing liquid composition containing silica particles (component A), a water-soluble polymer (component B), an acid (component C), and an aqueous medium, wherein component B is a copolymer containing structural units derived from acrylic acid and / or a salt thereof, and a structural ratio of the structural units derived from acrylic acid and / or a salt thereof to all structural units constituting component B is 50 mol % or more, and component B has a weight average molecular weight of 700 or more and 10,000 or less, and component B is such that, when 0.4 mass % of nickel oxide particles, component C at the same concentration as in the polishing liquid composition, and component B at the same concentration as in the polishing liquid composition are blended, the adsorption rate of component B to nickel oxide particles is 5 mass % or more, and the average particle diameter d of component A in the polishing liquid composition and the average particle diameter d of component A in a composition obtained by excluding component B from the polishing liquid composition are 0 Ratio of d / d 0 The polishing composition for magnetic disk substrates has a viscosity of 1.1 or less and a pH of 0.1 or more and 4 or less.

[0008] In one aspect, the present disclosure relates to a polishing liquid composition for magnetic disk substrates, comprising silica particles (component A), a water-soluble polymer (component B), an acid (component C), and an aqueous medium, wherein component B is a copolymer containing structural units derived from acrylic acid and / or a salt thereof and is a copolymer containing a structure represented by the following formula (I), wherein the structural units derived from acrylic acid and / or a salt thereof account for 50 mol % or more of all structural units constituting component B, the weight average molecular weight of component B is 700 or more and 10,000 or less, and the pH is 0.1 or more and 4 or less. [ka] In formula (I), m and n represent the constituent ratio (molar ratio) of each constituent unit in component B, and satisfy m>0, n>0, and m+n=100. M represents a hydrogen atom, an alkali metal ion, an alkaline earth metal ion, an organic cation, or ammonium (NH 4 + ) R is a hydrocarbon group having 2 to 6 carbon atoms, and the dashed line connecting X and R indicates that a carbon atom constituting R may be bonded to X. X represents an oxygen atom, a nitrogen atom, or an NH group.

[0009] In one aspect, the present disclosure relates to a method for producing a magnetic disk substrate, the method comprising the step of polishing a substrate to be polished with the polishing liquid composition of the present disclosure.

[0010] In one aspect, the present disclosure relates to a method for polishing a substrate, comprising polishing a substrate to be polished with the polishing liquid composition of the present disclosure, wherein the substrate to be polished is a substrate used in the manufacture of magnetic disk substrates. Effect of the Invention

[0011] According to the polishing composition of the present disclosure, in one or a plurality of embodiments, an effect of achieving both an improvement in the removal rate and a reduction in scratches on the substrate surface after polishing can be achieved. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The present disclosure is based on the discovery that when a polishing liquid composition containing silica particles, a specific water-soluble polymer, an acid, and an aqueous medium and having a pH of 0.1 to 4 is used for polishing a magnetic disk substrate, the polishing rate can be improved while reducing scratches on the substrate surface after polishing.

[0013] That is, in one aspect, the present disclosure provides a polishing liquid composition containing silica particles (component A), a water-soluble polymer (component B), an acid (component C), and an aqueous medium, wherein component B is a copolymer containing structural units derived from acrylic acid and / or a salt thereof, and the structural units derived from acrylic acid and / or a salt thereof account for 50 mol % or more of all structural units constituting component B, and the weight average molecular weight of component B is 700 or more and 10,000 or less, and component B is such that, when 0.4 mass % of nickel oxide particles, component C at the same concentration as in the polishing liquid composition, and component B at the same concentration as in the polishing liquid composition are blended, the adsorption rate of component B to nickel oxide particles is 5 mass % or more, and the average particle size d of component A in the polishing liquid composition and the average particle size d of component A in a composition obtained by excluding component B from the polishing liquid composition are 0 Ratio of d / d 0The polishing composition for magnetic disk substrates has a viscosity of 1.1 or less and a pH of 0.1 or more and 4 or less. In another aspect, the present disclosure relates to a polishing liquid composition for magnetic disk substrates, comprising silica particles (component A), a water-soluble polymer (component B), an acid (component C), and an aqueous medium, wherein component B is a copolymer containing structural units derived from acrylic acid and / or a salt thereof and is a copolymer containing a structure represented by formula (I) above, wherein the structural units derived from acrylic acid and / or a salt thereof account for 50 mol % or more of all structural units constituting component B, the weight average molecular weight of component B is 700 or more and 10,000 or less, and the pH is 0.1 or more and 4 or less. Hereinafter, these are collectively referred to as "the polishing composition of the present disclosure."

[0014] Although the details of the mechanism by which the effects of the present disclosure are manifested are not clear, it is presumed as follows. The carbonyl group has the property of coordinating to nickel atoms on the substrate surface. In the present disclosure, since the carbonyl group of component B is located far from the main chain, it is considered that the carbonyl group has a high degree of steric freedom and is easily coordinated to the substrate surface. In addition, it is considered that component B is adsorbed to the substrate by the carbonyl group, and the carboxylic acid group, which is a hydrophilic group, is oriented toward the surface layer side, thereby making the substrate surface hydrophilic. It is considered that this improves the wettability and spread of the polishing liquid, and the polishing liquid is efficiently distributed over the substrate surface, thereby improving the polishing rate and reducing scratches. However, the present disclosure need not be construed as being limited to these mechanisms.

[0015] In the present disclosure, scratches on the substrate surface can be detected, for example, by an optical defect inspection device and can be quantitatively evaluated as the number of scratches. The number of scratches can be specifically evaluated by the method described in the Examples.

[0016] [Silica particles (component A)] Examples of the silica particles (hereinafter also referred to as "Component A") contained in the polishing composition of the present disclosure include colloidal silica, fumed silica, pulverized silica, and surface-modified silica thereof, from the viewpoints of ensuring the polishing rate and reducing scratches, with colloidal silica being preferred. Component A may be one type or a combination of two or more types.

[0017] From the viewpoint of improving the polishing rate, the average secondary particle diameter of component A is preferably 1 nm or more, more preferably 5 nm or more, and even more preferably 10 nm or more, and from the viewpoint of reducing scratches, it is preferably 500 nm or less, more preferably 300 nm or less, more preferably 100 nm or less, even more preferably 70 nm or less, and even more preferably 40 nm or less. More specifically, the average secondary particle diameter of component A is preferably 1 nm or more and 500 nm or less, more preferably 1 nm or more and 300 nm or less, even more preferably 1 nm or more and 100 nm or less, even more preferably 5 nm or more and 70 nm or less, and even more preferably 10 nm or more and 40 nm or less. In the present disclosure, the "average secondary particle diameter of silica particles" is a value measured by a dynamic light scattering method, and for example, the value (D50) at which the cumulative volume ratio of the particle diameter distribution obtained by the dynamic light scattering method is 50% when the detection angle is 173° can be taken as the average particle diameter (average secondary particle diameter). Specifically, the average secondary particle diameter of silica particles can be determined by the method described in the Examples.

[0018] [Average particle size ratio d / d 0 ] In the polishing liquid composition of the present disclosure, the average particle diameter d of the silica particles (component A) in the polishing liquid composition and the average particle diameter d of the silica particles (component A) in a composition obtained by removing component B from the polishing liquid composition 0 Ratio of d / d 0 (Hereinafter referred to as “average particle size ratio d / d 0 From the viewpoint of reducing scratches, the average particle diameter d and the average particle diameter d are preferably 1.5 or less, more preferably 1.3 or less, and even more preferably 1.1 or less, and from the same viewpoint, are preferably 1 or more. 0 are values ​​measured by dynamic light scattering, and specifically, they can be measured by the method described in the Examples.

[0019] The content of Component A in the polishing liquid composition of the present disclosure is, from the viewpoint of improving the polishing rate, SiO 2 In terms of reducing scratches, the content is preferably 0.1% by mass or more, more preferably 1% by mass or more, and even more preferably 3% by mass or more, and from the viewpoint of reducing scratches, SiO 2 In terms of SiO 2 , the content of component A in the polishing composition of the present disclosure is preferably 20 mass % or less, more preferably 15 mass % or less, and even more preferably 10 mass % or less. 2 In terms of conversion, the content is preferably 0.1% by mass or more and 20% by mass or less, more preferably 1% by mass or more and 15% by mass or less, and even more preferably 3% by mass or more and 10% by mass or less. When component A is composed of two or more types of silica particles, the content of component A refers to the total content thereof.

[0020] [Water-soluble polymer (component B)] The water-soluble polymer (hereinafter also referred to as "component B") contained in the polishing liquid composition of the present disclosure is a copolymer containing a structural unit derived from acrylic acid and / or a salt thereof (hereinafter also referred to as "structural unit b1"). Examples of the salt include sodium salt, potassium salt, magnesium salt, ammonium salt, amine salt, and alkylammonium salt. Component B may be one type or a combination of two or more types.

[0021] The constituent ratio of the structural unit b1 in all the structural units constituting the component B is preferably 50 mol% or more, more preferably 60 mol% or more, and even more preferably 70 mol% or more from the viewpoint of suppressing aggregation of silica, and is preferably 98 mol% or less, more preferably 95 mol% or less, and even more preferably 90 mol% or less from the viewpoint of improving the polishing rate and reducing scratches. The constituent ratio of the structural unit b1 is preferably 50 mol% or more and 98 mol% or less, more preferably 60 mol% or more and 95 mol% or less, and even more preferably 70 mol% or more and 90 mol% or less.

[0022] In the present disclosure, as the content (mol %) of a certain structural unit among all structural units constituting component B, depending on the synthesis conditions, the amount (mol %) of the compound for introducing the structural unit charged into the reaction tank among the compounds for introducing all structural units charged into the reaction tank in all steps of the synthesis of component B may be used. In addition, in the present disclosure, when component B contains two or more structural units, the composition ratio (molar ratio) of the two or more structural units may be the amount ratio (molar ratio) of the compounds for introducing the two or more structural units charged into the reaction tank in all steps of the synthesis of component B, depending on the synthesis conditions.

[0023] Component B has a structural unit other than the structural unit b1 (hereinafter, also referred to as "structural unit b2"). As a monomer forming the structural unit b2, a monomer having a carbonyl oxygen atom at a position 2 atoms or more away from the main chain is preferable, and examples thereof include vinyl propionate, vinyl butanoate, vinyl pentanoate, vinyl hexanoate, vinyl heptanoate, vinyl benzoate, vinyl pivalate, vinyl pyrrolidone, ε-caprolactam, and the like, and preferably vinyl pivalate, vinyl pyrrolidone, and the like. The content of the structural unit b2 in all the structural units constituting component B is preferably 50 mol% or less, more preferably 40 mol% or less, and even more preferably 30 mol% or less, from the viewpoint of suppressing silica aggregation, and is preferably 2 mol% or more, more preferably 5 mol% or more, and even more preferably 10 mol% or more, from the viewpoint of improving the polishing rate and reducing scratches. In one or more embodiments, the monomer forming the structural unit b2 preferably does not contain vinyl acetate, from the viewpoint of improving storage stability.

[0024] The arrangement of the structural units constituting component B may be random, block, or graft, and from the viewpoints of improving the polishing rate and reducing scratches, random arrangement is preferred.

[0025] In one or more embodiments, from the viewpoint of improving the polishing rate and reducing scratches, when 0.4% by mass of nickel oxide particles, component C at the same concentration as the polishing composition, and component B at the same concentration as the polishing composition are mixed, the adsorption rate of component B to nickel oxide particles is 5% by mass or more. From the same viewpoint, the adsorption rate is preferably 6% by mass or more, more preferably 7% by mass or more, and even more preferably 10% by mass or more. When component B satisfies these adsorption rates, in one or more embodiments, the substrate surface is hydrophilized and the wettability and spreadability of the polishing composition is improved, and the polishing composition is efficiently distributed over the substrate surface, which contributes to improving the polishing rate and reducing scratches. In the present disclosure, the adsorption rate of component B to nickel oxide particles can be measured using a total organic carbon meter, and specifically, can be measured by the method described in the Examples.

[0026] In one or more embodiments, from the viewpoints of improving the polishing rate and reducing scratches, Component B may be a copolymer having a structure represented by the following formula (I). [ka]

[0027] In formula (I), m and n represent the constituent ratio (molar ratio) of each constituent unit in component B, and satisfy m>0, n>0, and m+n=100. M represents a hydrogen atom, an alkali metal ion, an alkaline earth metal ion, an organic cation, or ammonium (NH 4 + ) R is a hydrocarbon group having 2 to 6 carbon atoms, and the dashed line connecting X and R indicates that a carbon atom constituting R may be bonded to X. X represents an oxygen atom, a nitrogen atom, or an NH group. In formula (I), from the viewpoint of improving the storage stability of Component B in the product, R is preferably a hydrocarbon group having 2 or more carbon atoms, and from the viewpoint of improving the solubility of Component B in the product, R is preferably a hydrocarbon group having 6 or less carbon atoms. In formula (I), from the viewpoint of suppressing aggregation of silica, m is preferably 50 or more, more preferably 60 or more, and even more preferably 70 or more, and from the viewpoint of improving the polishing rate and reducing scratches, m is preferably 98 or less, more preferably 95 or less, and even more preferably 90 or less. In formula (I), from the viewpoints of improving the polishing rate and reducing scratches, n is preferably 2 or more, more preferably 5 or more, and even more preferably 10 or more, and from the viewpoint of suppressing silica aggregation, n is preferably 50 or less, more preferably 40 or less, and even more preferably 30 or less.

[0028] In one or more embodiments, component B includes at least one selected from a copolymer of acrylic acid and / or a salt thereof with vinyl pivalate, and a copolymer of acrylic acid and / or a salt thereof with vinylpyrrolidone.

[0029] Although there are no particular limitations on the method for producing component B, aqueous solution polymerization is preferred. Component B can be produced by mixing and reacting the structural unit b1, the structural unit b2, a polymerization initiator, and a chain transfer agent in a polymerization solvent. Examples of the polymerization solvent for the aqueous solution polymerization include water, alcohols such as ethanol, and ketones such as acetone. These may be used alone or in combination of two or more. In the polymerization reaction, a known polymerization initiator can be used, and a radical polymerization initiator is preferably used. Examples of the radical polymerization initiator include persulfates such as sodium persulfate, potassium persulfate, and ammonium persulfate, hydroperoxides such as t-butyl hydroperoxide, water-soluble peroxides such as hydrogen peroxide, ketone peroxides such as methyl ethyl ketone peroxide and cyclohexanone peroxide, oil-soluble peroxides such as dialkyl peroxides such as di-t-butyl peroxide and t-butyl cumyl peroxide, and azo compounds such as azobisisobutyronitrile and 2,2-azobis(2-methylpropionamidine)dihydrochloride. From the viewpoint of the stability of the product, at least one selected from persulfates and azo compounds is preferred, and azo compounds such as azobisisobutyronitrile and 2,2'-azobis(2,4-dimethylovaleronitrile are more preferred. These may be used alone or in combination of two or more. In order to adjust the molecular weight in the production of component B, a chain transfer agent may be appropriately added to the polymerization system. Examples of the chain transfer agent include sodium phosphite, sodium hypophosphite, potassium hypophosphite, sodium sulfite, sodium hydrogen sulfite, mercaptoacetic acid, mercaptopropionic acid, thioglycolic acid, 2-propanethiol, 2-mercaptoethanol, and thiophenol. The polymerization temperature is not particularly limited, but is preferably 60° C. or higher from the viewpoint of improving reactivity, and is preferably 100° C. or lower from the viewpoint of suppressing coloration. The polymerization time is not particularly limited, but is preferably 2 hours or more from the viewpoint of improving reactivity, and is preferably 20 hours or less from the viewpoint of suppressing coloration. After the polymerization reaction, neutralization can be performed with a basic compound as necessary. Examples of basic compounds used for neutralization include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, alkaline earth metal hydroxides such as calcium hydroxide and magnesium hydroxide, ammonia water, and organic amines such as monoethanolamine, diethanolamine, and triethanolamine. Ammonia water is preferred from the viewpoint of dispersibility of the water-soluble polymer compound produced and avoidance of contamination of the substrate to be polished. The pH value (25°C) after neutralization is preferably 3 to 10, more preferably 4 to 9, from the viewpoint of improving the stability of the product.

[0030] The weight average molecular weight of component B is 700 or more, preferably 1,000 or more, more preferably 1,500 or more, from the viewpoint of improving the polishing rate and reducing scratches, and is 10,000 or less, preferably 8,500 or less, more preferably 7,000 or less, from the viewpoint of suppressing the aggregation of silica. More specifically, the weight average molecular weight of component B is 700 or more and 10,000 or less, preferably 1,000 or more and 8,500 or less, more preferably 1,500 or more and 7,000 or less. In the present disclosure, the weight average molecular weight is a value measured using gel permeation chromatography (GPC) under the conditions described in the examples.

[0031] The content of component B in the polishing liquid composition of the present disclosure is preferably 10 mass ppm or more, more preferably 20 mass ppm or more, and even more preferably 50 mass ppm or more from the viewpoint of improving the polishing rate and reducing scratches, and is preferably 10000 mass ppm or less, more preferably 5000 mass ppm or less, more preferably 3000 mass ppm or less, more preferably 1000 mass ppm or less, and even more preferably 500 mass ppm or less from the viewpoint of suppressing silica aggregation. More specifically, the content of component B in the polishing liquid composition of the present disclosure is preferably 10 mass ppm or more and 10000 mass ppm or less, more preferably 20 mass ppm or more and 5000 mass ppm or less, more preferably 50 mass ppm or more and 3000 mass ppm or less, more preferably 50 mass ppm or more and 1000 mass ppm or less, and even more preferably 50 mass ppm or more and 500 mass ppm or less. When component B is a combination of two or more kinds, the content of component B is the total content thereof. In this disclosure, 1% by mass is equal to 10,000 ppm by mass (the same applies below).

[0032] The mass ratio A / B of the content of component A to the content of component B in the polishing liquid composition of the present disclosure is, from the viewpoints of improving the polishing rate and reducing scratches, preferably 10 or more, more preferably 30 or more, and even more preferably 50 or more, and from the same viewpoint, is preferably 3000 or less, more preferably 2500 or less, and even more preferably 2000 or less. From the same viewpoint, the mass ratio A / B in the polishing liquid composition of the present disclosure is preferably 10 or more and 3000 or less, more preferably 30 or more and 2500 or less, and even more preferably 50 or more and 2000 or less.

[0033] [Acid (component C)] The polishing composition of the present disclosure contains an acid (component C). In the present disclosure, the use of an acid includes the use of an acid or a salt thereof. Component C may be one type or a combination of two or more types.

[0034] Examples of component C include inorganic acids such as nitric acid, sulfuric acid, sulfurous acid, persulfuric acid, hydrochloric acid, perchloric acid, phosphoric acid, phosphonic acid, phosphinic acid, pyrophosphoric acid, tripolyphosphoric acid, and amidosulfuric acid; organic acids such as organic phosphoric acid, organic phosphonic acid, and carboxylic acid; and the like. Among them, from the viewpoint of ensuring the polishing rate and reducing scratches, at least one selected from inorganic acids and organic phosphonic acids is preferable. As the inorganic acid, at least one selected from nitric acid, sulfuric acid, hydrochloric acid, perchloric acid, and phosphoric acid is preferable, at least one selected from sulfuric acid and phosphoric acid is more preferable, and phosphoric acid is even more preferable. As the organic phosphonic acid, at least one selected from 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP), aminotri(methylenephosphonic acid), ethylenediaminetetra(methylenephosphonic acid), and diethylenetriaminepenta(methylenephosphonic acid) is preferable, and HEDP is more preferable. Examples of salts of these acids include salts of the above acids and at least one selected from metals, ammonia, and alkylamines. Examples of the metal include metals belonging to groups 1 to 11 of the periodic table.

[0035] The content of component C in the polishing liquid composition of the present disclosure is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and even more preferably 1% by mass or more, from the viewpoint of ensuring the polishing rate and reducing scratches, and from the same viewpoint, it is preferably 5% by mass or less, more preferably 4% by mass or less, and even more preferably 3% by mass or less. From the same viewpoint, the content of component C in the polishing liquid composition of the present disclosure is preferably 0.01% by mass or more and 5% by mass or less, more preferably 0.1% by mass or more and 4% by mass or less, and even more preferably 1% by mass or more and 3% by mass or less. When component C is a combination of two or more kinds, the content of component C refers to the total content thereof.

[0036] From the viewpoints of improving the polishing rate and reducing scratches, the mass ratio A / C of the content of component A to the content of component C in the polishing liquid composition of the present disclosure is preferably 0.2 or more, more preferably 0.5 or more, and even more preferably 1 or more, and from the same viewpoint, it is preferably 10 or less, more preferably 7 or less, and even more preferably 4 or less. From the same viewpoint, the mass ratio A / C in the polishing liquid composition of the present disclosure is preferably 0.2 or more and 10 or less, more preferably 0.5 or more and 7 or less, and even more preferably 1 or more and 4 or less.

[0037] [Aqueous medium] The aqueous medium contained in the polishing liquid composition of the present disclosure includes water such as distilled water, ion-exchanged water, pure water, and ultrapure water, or a mixed solvent of water and a solvent. The above-mentioned solvent includes a solvent miscible with water (for example, alcohol such as ethanol). When the aqueous medium is a mixed solvent of water and a solvent, the ratio of water to the entire mixed medium is not particularly limited as long as the effect of the present disclosure is not hindered. From the viewpoint of economic efficiency, for example, 95 mass% or more is preferable, 98 mass% or more is more preferable, and substantially 100 mass% is even more preferable. From the viewpoint of surface cleanliness of the substrate to be polished, ion-exchanged water and ultrapure water are preferable as the aqueous medium. The content of the aqueous medium in the polishing liquid composition of the present disclosure can be the remainder excluding component A, component B, component C, and optional components described below that are blended as necessary.

[0038] [Oxidizing agent (component D)] The polishing composition of the present disclosure may further contain an oxidizing agent (hereinafter also referred to as "Component D") from the viewpoint of further improving the polishing rate and further reducing scratches. Component D may be one type or a combination of two or more types.

[0039] Examples of component D, from the viewpoint of further improving the polishing rate and further reducing scratches, include peroxides, permanganic acid or its salts, chromic acid or its salts, peroxoacid or its salts, oxyacid or its salts, metal salts, nitric acids, sulfuric acids, etc. Among these, at least one selected from hydrogen peroxide, iron(III) nitrate, peracetic acid, ammonium peroxodisulfate, iron(III) sulfate, and ammonium iron(III) sulfate is preferred, and hydrogen peroxide is more preferred from the viewpoint of further improving the polishing rate, from the viewpoint of not attaching metal ions to the surface of the substrate to be polished, and from the viewpoint of easy availability.

[0040] When the polishing liquid composition of the present disclosure contains component D, the content of component D in the polishing liquid composition of the present disclosure is preferably 0.01 mass% or more, more preferably 0.05 mass% or more, even more preferably 0.1 mass% or more, and preferably 4 mass% or less, more preferably 2 mass% or less, and even more preferably 1.5 mass% or less, from the viewpoint of further improving the polishing rate and further reducing scratches. More specifically, the content of component D in the polishing liquid composition of the present disclosure is preferably 0.01 mass% or more and 4 mass% or less, more preferably 0.05 mass% or more and 2 mass% or less, and even more preferably 0.1 mass% or more and 1.5 mass% or less. When component D is a combination of two or more kinds, the content of component D refers to the total content thereof.

[0041] In one or more embodiments, the polishing liquid composition of the present disclosure may further contain at least one selected from a heterocyclic aromatic compound (component E) and an aliphatic amine compound or an alicyclic amine compound (component F). Components E and F are described below.

[0042] [Heterocyclic aromatic compounds (component E)] From the viewpoint of further reducing scratches, the polishing composition of the present disclosure may further contain a heterocyclic aromatic compound (including a salt thereof) (hereinafter, also referred to as "Component E"). Component E may be one type or a combination of two or more types.

[0043] From the viewpoint of further reducing scratches, component E is preferably a heterocyclic aromatic compound containing two or more nitrogen atoms in the heterocycle, more preferably having three or more nitrogen atoms in the heterocycle, even more preferably having 3 to 9 nitrogen atoms, even more preferably having 3 to 5 nitrogen atoms, and even more preferably 3 or 4 nitrogen atoms.

[0044] In one or more embodiments, component E is preferably at least one selected from 1,2,4-triazole, 3-amino-1,2,4-triazole, 5-amino-1,2,4-triazole, 3-mercapto-1,2,4-triazole, 1H-tetrazole, 5-aminotetrazole, 1H-benzotriazole (BTA), 1H-tolyltriazole, 2-aminobenzotriazole, 3-aminobenzotriazole, and alkyl or amine substituted derivatives thereof. Examples of the alkyl group of the alkyl substituent include lower alkyl groups having 1 to 4 carbon atoms, and in one or more embodiments, methyl and ethyl groups are included. In one or more embodiments, examples of the amine substituent include 1-[N,N-bis(hydroxyethylene)aminomethyl]benzotriazole and 1-[N,N-bis(hydroxyethylene)aminomethyl]tolyltriazole.

[0045] When the polishing liquid composition of the present disclosure contains component E, the content of component E in the polishing liquid composition of the present disclosure is preferably 0.005% by mass or more, more preferably 0.01% by mass or more, and even more preferably 0.02% by mass or more from the viewpoint of further reducing scratches, and is preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 1% by mass or less, and even more preferably 0.2% by mass or less from the viewpoint of suppressing a decrease in polishing rate. More specifically, the content of component E in the polishing liquid composition of the present disclosure is preferably 0.005% by mass or more and 10% by mass or less, more preferably 0.01% by mass or more and 5% by mass or less, even more preferably 0.02% by mass or more and 1% by mass or less, and even more preferably 0.02% by mass or more and 0.2% by mass or less from the viewpoint of further reducing scratches and suppressing a decrease in polishing rate. When component E is a combination of two or more kinds, the content of component E refers to the total content thereof.

[0046] [Aliphatic amine compound or alicyclic amine compound (component F)] From the viewpoint of further reducing scratches, the polishing liquid composition of the present disclosure may further contain at least one selected from an aliphatic amine compound and an alicyclic amine compound (hereinafter also referred to as "Component F"). From the viewpoint of further reducing scratches, the number of nitrogen atoms or the total number of amino groups or imino groups in the molecule of Component F is preferably 2 to 4. Component F may be one type or a combination of two or more types.

[0047] In one or a plurality of embodiments, the aliphatic amine compound is, from the viewpoint of further reducing scratches, preferably at least one selected from ethylenediamine, N,N,N',N'-tetramethylethylenediamine, 1,2-diaminopropane, 1,3-diaminopropane, 1,4-diaminobutane, hexamethylenediamine, 3-(diethylamino)propylamine, 3-(dibutylamino)propylamine, 3-(methylamino)propylamine, 3-(dimethylamino)propylamine, N-aminoethylethanolamine, N-aminoethylisopropanolamine, and N-aminoethyl-N-methylethanolamine, more preferably at least one selected from N-aminoethylethanolamine, N-aminoethylisopropanolamine, and N-aminoethyl-N-methylethanolamine, and even more preferably N-aminoethylethanolamine (AEA).

[0048] In one or more embodiments, from the viewpoint of further reducing scratches, the alicyclic amine compound is preferably at least one selected from piperazine, 2-methylpiperazine, 2,5-dimethylpiperazine, 1-amino-4-methylpiperazine, N-methylpiperazine, and hydroxyethylpiperazine (HEP), and more preferably hydroxyethylpiperazine (HEP).

[0049] When the polishing liquid composition of the present disclosure contains component F, the content of component F in the polishing liquid composition of the present disclosure is preferably 0.005% by mass or more, more preferably 0.01% by mass or more, and even more preferably 0.02% by mass or more from the viewpoint of further reducing scratches, and is preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 1% by mass or less, and even more preferably 0.1% by mass or less from the viewpoint of suppressing a decrease in polishing rate. More specifically, the content of component F in the polishing liquid composition of the present disclosure is preferably 0.005% by mass or more and 10% by mass or less, more preferably 0.01% by mass or more and 5% by mass or less, even more preferably 0.02% by mass or more and 1% by mass or less, and even more preferably 0.02% by mass or more and 0.1% by mass or less from the viewpoint of further reducing scratches and suppressing a decrease in polishing rate. When component F is a combination of two or more kinds, the content of component F refers to the total content thereof.

[0050] [Anionic surfactant (ingredient G)] In one or more embodiments, the polishing liquid composition of the present disclosure may further contain an anionic surfactant (hereinafter, also referred to as "component G") from the viewpoint of further reducing scratches. Component G has a repeating unit and a sulfonic acid group or a salt thereof in the molecule, and from the viewpoint of further reducing scratches, it is preferable that the repeating unit has a structure having an aromatic ring in the main chain. Examples of the aromatic ring include a phenol skeleton and a naphthalene skeleton. Examples of the salt include an alkali metal salt, an ammonium salt, and an organic amine salt. Component G may be one type or a combination of two or more types. Component G is preferably water-soluble and preferably has a solubility of 0.5 g / 100 mL or more in water (20° C.).

[0051] In one or more embodiments, the component G may be a copolymer containing a structural unit derived from an unsaturated carboxylic acid and a structural unit derived from a monomer having a sulfonic acid group in the molecule. Examples of the unsaturated carboxylic acid include at least one selected from acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, and salts thereof. Examples of the monomer having a sulfonic acid group in the molecule include 2-acrylamido-2-methylpropanesulfonic acid. Examples of the copolymer containing a structural unit derived from an unsaturated carboxylic acid and a structural unit derived from a monomer having a sulfonic acid group in the molecule include acrylic acid / 2-acrylamido-2-methylpropanesulfonic acid copolymer (AA / AMPS). In one or more embodiments, component G may be a condensate or a salt thereof of an aromatic monomer having a sulfonic acid group or a salt thereof, a condensate or a salt thereof containing a structural unit derived from an aromatic monomer having a sulfonic acid group or a salt thereof and a structural unit other than the structural unit, etc. Examples of the salt include an alkali metal salt, an ammonium salt, and an organic amine salt. As the condensate or salt of an aromatic monomer having a sulfonic acid group or a salt thereof, from the viewpoint of further reducing scratches, a condensate or salt thereof having a structure in which at least one hydrogen atom of an aromatic ring constituting a main chain is substituted with a sulfonic acid group is preferable, and at least one selected from phenolsulfonic acid, naphthalenesulfonic acid and their salts is more preferable. For example, a formalin condensate of phenolsulfonic acid (PhS) and a formalin condensate of naphthalenesulfonic acid (NaS) can be mentioned. An example of a condensate or a salt thereof containing a constituent unit derived from an aromatic monomer having a sulfonic acid group or a salt thereof and a constituent unit other than the constituent unit is a formalin condensate (BisS / PhS) of bis(4-hydroxyphenyl)sulfone (BisS) and phenolsulfonic acid (PhS).

[0052] From the viewpoint of further reducing scratches, the weight average molecular weight of component G is preferably 1500 or more, more preferably 2000 or more, and even more preferably 3000 or more, and from the viewpoint of suppressing a decrease in the polishing rate, it is preferably 100000 or less, more preferably 70000 or less, and even more preferably 50000 or less. More specifically, from the viewpoint of further reducing scratches and suppressing a decrease in the polishing rate, the molecular weight of component G is preferably 1500 or more and 100000 or less, more preferably 2000 or more and 70000 or less, and even more preferably 3000 or more and 50000 or less.

[0053] When the polishing liquid composition of the present disclosure contains component G, the content of component G in the polishing liquid composition of the present disclosure is preferably 0.001 mass% or more, more preferably 0.005 mass% or more, even more preferably 0.01 mass% or more, and preferably 10 mass% or less, more preferably 5 mass% or less, and even more preferably 1 mass% or less, from the viewpoint of further reducing scratches. More specifically, the content of component G in the polishing liquid composition of the present disclosure is preferably 0.001 mass% or more and 10 mass% or less, more preferably 0.05 mass% or more and 5 mass% or less, and even more preferably 0.01 mass% or more and 1 mass% or less. When component G is a combination of two or more types, the content of component G refers to the total content thereof.

[0054] [Other ingredients] In one or more embodiments, the polishing liquid composition of the present disclosure may further contain other components as necessary. Examples of the other components include a polymer compound other than Component B, a thickener, a dispersant, a rust inhibitor, a basic substance, a surfactant other than Component G, a solubilizer, etc.

[0055] In one or a plurality of embodiments, the polishing liquid composition of the present disclosure can be substantially free of at least one of a phosphite ester and a phosphate ester having a molecular weight of 150 or more. For example, the content (total amount) of the phosphite ester and the phosphate ester having a molecular weight of 150 or more in the polishing liquid composition of the present disclosure is preferably less than 0.001 mM, and more preferably 0 mM (i.e., no content).

[0056] [pH of polishing composition] The pH of the polishing liquid composition of the present disclosure is 4 or less, preferably 3.5 or less, more preferably 3.2 or less, and even more preferably 3 or less, from the viewpoint of improving the polishing rate and reducing scratches, and from the same viewpoint, it is 0.1 or more, more preferably 0.5 or more, and even more preferably 1 or more. From the same viewpoint, the pH of the polishing liquid composition of the present disclosure is 0.1 or more and 4 or less, and more preferably 1 or more and 3 or less. The pH can be adjusted using the above-mentioned acid (component C) or a known pH adjuster. In the present disclosure, the above pH is the pH of the polishing liquid composition at 25°C, and can be measured using a pH meter, and can be, for example, the value 2 minutes after immersing the electrode of the pH meter in the polishing liquid composition.

[0057] [Method of manufacturing the polishing composition] The polishing liquid composition of the present disclosure can be produced, for example, by blending component A, component B, component C, and an aqueous medium, and, if desired, optional components (component D, component E, component F, component G, and other components) by a known method. That is, in another aspect, the present disclosure relates to a method for producing a polishing liquid composition, which includes a step of blending at least component A, component B, component C, and an aqueous medium. In the present disclosure, "blending" includes mixing component A, component B, component C, and an aqueous medium, and optional components (component D, component E, component F, component G, and other components) simultaneously or in any order as necessary. Component A may be mixed in the form of a concentrated slurry, or may be mixed after diluting with water or the like. When component A is composed of multiple types of silica particles, the multiple types of silica particles can be blended simultaneously or separately. When component B is composed of multiple types of water-soluble polymers, the multiple types of water-soluble polymers can be blended simultaneously or separately. When component C is composed of multiple types of acids, the multiple types of acids can be blended simultaneously or separately. The blending can be carried out using a mixer such as a homomixer, a homogenizer, an ultrasonic disperser, a wet ball mill, etc. The preferred blending amount of each component in the method for producing the polishing liquid composition can be the same as the preferred content of each component in the polishing liquid composition of the present disclosure described above.

[0058] In the present disclosure, "the content of each component in the polishing liquid composition" refers to the content of each component at the time of use, that is, at the time when the use of the polishing liquid composition for polishing is started. The polishing composition of the present disclosure may be stored and supplied in a concentrated state within a range that does not impair its storage stability. In this case, it is preferable in that the manufacturing and transportation costs can be further reduced. The concentrated polishing composition of the present disclosure may be appropriately diluted with the above-mentioned aqueous medium when used as necessary. The dilution ratio is not particularly limited as long as the content (when used) of each of the above-mentioned components can be secured after dilution, and may be, for example, 10 to 100 times.

[0059] [Polishing liquid kit] In another aspect, the present disclosure relates to a kit for producing the polishing liquid composition of the present disclosure (hereinafter, also referred to as the "polishing liquid kit of the present disclosure"). The polishing liquid kit of the present disclosure includes, for example, a polishing liquid kit (two-liquid type polishing liquid composition) that contains a silica dispersion containing component A and an aqueous medium and an additive aqueous solution containing component B and component C in a mutually unmixed state, which are mixed at the time of use and diluted with an aqueous medium as necessary. The aqueous medium contained in the silica dispersion may be the entire amount of water used in preparing the polishing liquid composition, or may be a part of the amount. The additive aqueous solution may contain a part of the aqueous medium used in preparing the polishing liquid composition. The silica dispersion and the additive aqueous solution may each contain the above-mentioned optional components (components D to G and other components) as necessary. According to the polishing liquid kit of the present disclosure, a polishing liquid composition that can simultaneously improve the polishing rate and reduce scratches on the substrate surface after polishing can be obtained.

[0060] [Substrate to be polished] In one or more embodiments, the substrate to be polished is a substrate used for manufacturing a magnetic disk substrate. In one or more embodiments, the surface of the substrate to be polished is polished with the polishing composition of the present disclosure, and then a magnetic layer is formed on the substrate surface by sputtering or the like, thereby manufacturing a magnetic disk substrate.

[0061] The material of the substrate to be polished preferably used in the present disclosure includes, for example, metals or semimetals such as silicon, aluminum, nickel, tungsten, copper, tantalum, titanium, or alloys thereof, glassy materials such as glass, glassy carbon, amorphous carbon, ceramic materials such as alumina, silicon dioxide, silicon nitride, tantalum nitride, titanium carbide, and resins such as polyimide resin. Among them, the substrate to be polished is preferably a substrate to be polished that contains metals such as aluminum, nickel, tungsten, copper, or alloys mainly composed of these metals. As the substrate to be polished, for example, Ni-P plated aluminum alloy substrates, and glass substrates such as crystallized glass, reinforced glass, aluminosilicate glass, and aluminoborosilicate glass are more suitable, and Ni-P plated aluminum alloy substrates are even more suitable. In the present disclosure, the term "Ni-P plated aluminum alloy substrate" refers to an aluminum alloy substrate that has been subjected to electroless Ni-P plating after the surface of the aluminum alloy substrate is ground.

[0062] The shape of the substrate to be polished may be, for example, a shape having a flat surface such as a disk, plate, slab, or prism, or a shape having a curved surface such as a lens. Among them, a disk-shaped substrate to be polished is suitable. In the case of a disk-shaped substrate to be polished, the outer diameter is, for example, about 2 to 95 mm, and the thickness is, for example, about 0.4 to 2 mm.

[0063] [Method of manufacturing magnetic disk substrate] In general, a magnetic disk is manufactured by polishing a substrate to be polished after a grinding process through a rough polishing process and a finish polishing process, and forming the substrate into a magnetic disk in a recording part forming process. The polishing composition of the present disclosure can be used in a polishing process, preferably a finish polishing process, for polishing a substrate to be polished in a method for manufacturing a magnetic disk substrate. That is, in another aspect, the present disclosure relates to a method for manufacturing a magnetic disk substrate (hereinafter also referred to as a "substrate manufacturing method of the present disclosure") including a process for polishing a substrate to be polished using the polishing composition of the present disclosure (hereinafter also referred to as a "polishing process using the polishing composition of the present disclosure"). The substrate manufacturing method of the present disclosure is particularly suitable for a method for manufacturing a magnetic disk substrate for a perpendicular magnetic recording system.

[0064] In one or more embodiments, the polishing process using the polishing liquid composition of the present disclosure is a process of supplying the polishing liquid composition of the present disclosure to the surface of the substrate to be polished, contacting the polishing pad with the surface to be polished, and moving at least one of the polishing pad and the substrate to be polished to perform polishing.In another or more embodiments, the polishing process using the polishing liquid composition of the present disclosure is a process of sandwiching the substrate to be polished between a platen to which a polishing pad such as a nonwoven organic polymer-based polishing cloth is attached, and moving the platen or the substrate to be polished to polish the substrate to be polished while supplying the polishing liquid composition of the present disclosure to a polishing machine.

[0065] When the polishing process of the substrate to be polished is carried out in multiple stages, the polishing process using the polishing liquid composition of the present disclosure is preferably carried out in the second stage or later, and more preferably in the final polishing process or the finish polishing process. In this case, in order to avoid the mixing of the abrasive or the polishing liquid composition of the previous process, a separate polishing machine may be used for each step, and when a separate polishing machine is used, it is preferable to wash the substrate to be polished after each polishing process. Furthermore, the polishing liquid composition of the present disclosure can be used in the circulating polishing in which the used polishing liquid is reused. The polishing machine is not particularly limited, and a known polishing machine for substrate polishing can be used.

[0066] The polishing pad used in the present disclosure is not particularly limited, and for example, a suede type, a nonwoven fabric type, a polyurethane independent foam type, or a two-layer type in which these are laminated can be used, and from the viewpoint of polishing speed, a suede type polishing pad is preferred.

[0067] The polishing load in the polishing step using the polishing composition of the present disclosure is preferably 5.9 kPa or more, more preferably 6.9 kPa or more, even more preferably 7.5 kPa or more from the viewpoint of ensuring the polishing rate, and is preferably 20 kPa or less, more preferably 18 kPa or less, even more preferably 16 kPa or less from the viewpoint of reducing scratches. In the manufacturing method of the present disclosure, the polishing load refers to the pressure of the platen applied to the polishing surface of the substrate to be polished during polishing. The polishing load can be adjusted by applying air pressure or weight to at least one of the platen and the substrate to be polished.

[0068] In the polishing step using the polishing composition of the present disclosure, the supply rate of the polishing composition of the present disclosure is set to 1 cm per 1 cm of the substrate to be polished from the viewpoint of reducing scratches. 2 The flow rate is preferably 0.05 mL / min or more and 15 mL / min or less, more preferably 0.06 mL / min or more and 10 mL / min or less, even more preferably 0.07 mL / min or more and 1 mL / min or less, and even more preferably 0.07 mL / min or more and 0.5 mL / min or less.

[0069] The method of supplying the polishing liquid composition of the present disclosure to the polishing machine can be, for example, a method of continuously supplying the composition using a pump or the like. When supplying the polishing liquid composition to the polishing machine, in addition to a method of supplying the composition as a single liquid containing all components, the composition can be divided into a plurality of blending component liquids and supplied as two or more liquids, taking into consideration the stability of the polishing liquid composition, etc. In the latter case, the above-mentioned plurality of blending component liquids are mixed, for example, in the supply pipe or on the substrate to be polished, to form the polishing liquid composition of the present disclosure.

[0070] According to the substrate manufacturing method of the present disclosure, by using the polishing composition of the present disclosure, which can achieve both an improvement in the polishing rate and a reduction in scratches on the substrate surface after polishing, it is possible to achieve the effect of producing high-quality magnetic disk substrates with high yield and good productivity.

[0071] [Polishing method] In another aspect, the present disclosure relates to a method for polishing a substrate (hereinafter also referred to as the "polishing method of the present disclosure"), which includes polishing a substrate to be polished using the polishing composition of the present disclosure. According to the polishing method of the present disclosure, by using the polishing composition of the present disclosure, which can simultaneously improve the polishing rate and reduce scratches on the substrate surface after polishing, a high-quality magnetic disk substrate can be manufactured with high yield and good productivity. As described above, the substrate to be polished in the polishing method of the present disclosure includes those used in the manufacture of magnetic disk substrates, and among them, substrates used in the manufacture of magnetic disk substrates for perpendicular magnetic recording systems are preferable. The polishing method and conditions in the polishing method of the present disclosure can be the same as those in the substrate manufacturing method of the present disclosure described above.

[0072] In one or more embodiments, polishing a substrate to be polished with the polishing liquid composition of the present disclosure means supplying the polishing liquid composition of the present disclosure to the surface to be polished of the substrate to be polished, bringing a polishing pad into contact with the surface to be polished, and moving at least one of the polishing pad and the substrate to be polished to perform polishing, or means sandwiching the substrate to be polished between a platen to which a polishing pad such as a nonwoven organic polymer-based abrasive cloth is attached, and polishing the substrate to be polished by moving the platen and the substrate to be polished while supplying the polishing liquid composition of the present disclosure to a polishing machine. EXAMPLES

[0073] The present disclosure will be described in more detail below with reference to examples, but these are merely illustrative and the present disclosure is not limited to these examples.

[0074] 1.Water-soluble polymer B1~B10 The following water-soluble polymers B1 to B10 were used. (raw materials) Acrylic acid: Tokyo Chemical Industry Co., Ltd. Vinyl pivalate: manufactured by Tokyo Chemical Industry Co., Ltd. Vinylpyrrolidone: Tokyo Chemical Industry Co., Ltd. Ethanol: Fujifilm Wako Pure Chemical 99.5% ethanol Mercaptopropionic acid: Tokyo Chemical Industry Co., Ltd. 2,2'-Azobis(2,4-dimethylovaleronitrile): Fujifilm Wako Pure Chemical Industries, Ltd. N-tert-butylacrylamide: Tokyo Chemical Industry Co., Ltd. 2-Acrylamide-2-methylpropanesulfonic acid: Tokyo Chemical Industry Co., Ltd. Ammonia water: Kanto Chemical Co., Ltd. 29% ammonia water (for electronics industry) (Component B or non-component B) Synthesis example of B1: A 300 mL three-neck glass flask was prepared, to which a stirring blade, a thermometer, a Dimroth condenser, a nitrogen gas inlet tube, a bubbler tube, and two dropping funnels (dropping funnels 1 and 2) were connected. Mercaptopropionic acid (1.74 g), acrylic acid (20.00 g), vinyl pivalate (6.28 g), and ethanol (17.52 g) were added to dropping funnel 1, and 2,2'-azobis(2,4-dimethylovaleronitrile) (0.49 g) and ethanol (23.84 g) were added to dropping funnel 2. Ethanol (19.95 g) was added to the three-neck glass flask, nitrogen gas was introduced, tap water was introduced to the Dimroth condenser, and the flask was heated to 80°C while rotating with a stirring blade, and the mixture in the dropping funnels 1 and 2 was added dropwise at a uniform rate over 60 minutes. After the dropwise addition, the mixture was stirred at 80° C. for 3 hours and then cooled to 25° C. 500 g of ethanol was added, and aqueous ammonia was added dropwise with vigorous stirring until the pH reached 7.0. The precipitated white solid was filtered under reduced pressure and dried in vacuum to obtain the target compound B1. Synthesis of B2: A 300 mL three-neck glass flask was prepared, to which a stirring blade, a thermometer, a Dimroth condenser, a nitrogen gas inlet tube, a bubbler tube, and two dropping funnels (dropping funnels 1 and 2) were connected. Mercaptopropionic acid (1.89 g), acrylic acid (20.00 g), vinyl pivalate (10.03 g), and ethanol (20.02 g) were added to dropping funnel 1, and 2,2'-azobis(2,4-dimethylovaleronitrile) (0.53 g) and ethanol (25.98 g) were added to dropping funnel 2. Ethanol (24.07 g) was added to the three-neck glass flask, nitrogen gas was introduced, tap water was introduced to the Dimroth condenser, and the flask was heated to 80°C while rotating with a stirring blade, and the mixture in the dropping funnels 1 and 2 was added dropwise at a uniform rate over 60 minutes. After the dropwise addition, the mixture was stirred at 80° C. for 3 hours and then cooled to 25° C. 500 g of ethanol was added, and aqueous ammonia was added dropwise while vigorously stirring until the pH reached 7.0. The precipitated white solid was filtered under reduced pressure and dried in vacuum to obtain the target compound B2. Synthesis example of B3: A 300 mL three-neck glass flask was prepared, to which a stirring blade, a thermometer, a Dimroth condenser, a nitrogen gas inlet tube, a bubbler tube, and two dropping funnels (dropping funnels 1 and 2) were connected. Mercaptopropionic acid (1.73 g), acrylic acid (20.00 g), vinylpyrrolidone (5.44 g), and ethanol (16.96 g) were added to dropping funnel 1, and 2,2'-azobis(2,4-dimethylovaleronitrile) (0.49 g) and ethanol (23.84 g) were added to dropping funnel 2. Ethanol (18.56 g) was added to the three-neck glass flask, nitrogen gas was introduced, tap water was introduced to the Dimroth condenser, and the flask was heated to 80°C while rotating with a stirring blade, and the mixture in the dropping funnels 1 and 2 was added dropwise at a uniform rate over 60 minutes. After the dropwise addition, the mixture was stirred at 80° C. for 3 hours and then cooled to 25° C. 500 g of ethanol was added, and aqueous ammonia was added dropwise while vigorously stirring until the pH reached 7.0. The precipitated white solid was filtered under reduced pressure and dried in vacuum to obtain the target compound B3. Synthesis example of B4: A 300 mL three-neck glass flask was prepared, to which a stirring blade, a thermometer, a Dimroth condenser, a nitrogen gas inlet tube, a bubbler tube, and two dropping funnels (dropping funnels 1 and 2) were connected. Mercaptopropionic acid (0.35 g), acrylic acid (20.00 g), vinylpyrrolidone (5.44 g), and ethanol (16.96 g) were added to dropping funnel 1, and 2,2'-azobis(2,4-dimethylovaleronitrile) (0.08 g) and ethanol (26.95 g) were added to dropping funnel 2. Ethanol (15.45 g) was added to the three-neck glass flask, nitrogen gas was introduced, tap water was introduced to the Dimroth condenser, and the flask was heated to 80°C while rotating with a stirring blade, and the mixture in the dropping funnels 1 and 2 was added dropwise at a uniform rate over 60 minutes. After the dropwise addition, the mixture was stirred at 80° C. for 3 hours and then cooled to 25° C. 500 g of ethanol was added, and ammonia water was added dropwise while vigorously stirring until the pH became 7.0. The precipitated white solid was filtered under reduced pressure and dried in vacuum to obtain the target compound B4. Synthesis example of B5: A 300 mL three-neck glass flask was prepared, to which a stirring blade, a thermometer, a Dimroth condenser, a nitrogen gas inlet tube, a bubbler tube, and two dropping funnels (dropping funnels 1 and 2) were connected. Mercaptopropionic acid (1.89 g), acrylic acid (20.00 g), vinylpyrrolidone (8.70 g), and ethanol (19.13 g) were added to dropping funnel 1, and 2,2'-azobis(2,4-dimethylovaleronitrile) (0.53 g) and ethanol (25.98 g) were added to dropping funnel 2. Ethanol (21.85 g) was added to the three-neck glass flask, nitrogen gas was introduced, tap water was introduced to the Dimroth condenser, and the flask was heated to 80°C while rotating with a stirring blade, and the mixture in the dropping funnels 1 and 2 was added dropwise at a uniform rate over 60 minutes. After the dropwise addition, the mixture was stirred at 80° C. for 3 hours and then cooled to 25° C. 500 g of ethanol was added, and aqueous ammonia was added dropwise while vigorously stirring until the pH reached 7.0. The precipitated white solid was filtered under reduced pressure and dried in vacuum to obtain the target compound B5. Synthesis example of B6: A 300 mL three-neck glass flask was prepared, to which a stirring blade, a thermometer, a Dimroth condenser, a nitrogen gas inlet tube, a bubbler tube, and two dropping funnels (dropping funnels 1 and 2) were connected. Mercaptopropionic acid (0.30 g), acrylic acid (15.00 g), vinylpyrrolidone (7.71 g), and ethanol (15.14 g) were added to dropping funnel 1, and 2,2'-azobis(2,4-dimethylovaleronitrile) (0.07 g) and ethanol (22.91 g) were added to dropping funnel 2. Ethanol (14.94 g) was added to the three-neck glass flask, nitrogen gas was introduced, tap water was introduced to the Dimroth condenser, and the flask was heated to 80°C while rotating with a stirring blade, and the mixture in the dropping funnels 1 and 2 was added dropwise at a uniform rate over 60 minutes. After the dropwise addition, the mixture was stirred at 80° C. for 3 hours and then cooled to 25° C. 500 g of ethanol was added, and ammonia water was added dropwise while vigorously stirring until the pH became 7.0. The precipitated white solid was filtered under reduced pressure and dried in vacuum to obtain the target compound B6. Synthesis example of B7: A 300 mL three-neck glass flask was prepared, to which a stirring blade, a thermometer, a Dimroth condenser, a nitrogen gas inlet tube, a bubbler tube, and two dropping funnels (dropping funnels 1 and 2) were connected. Mercaptopropionic acid (0.34 g), acrylic acid (20.00 g), N-tert-butylacrylamide (5.75 g), and ethanol (17.16 g) were added to dropping funnel 1, and 2,2'-azobis(2,4-dimethylovaleronitrile) (0.08 g) and ethanol (15.95 g) were added to dropping funnel 2. Ethanol (26.96 g) was added to the three-neck glass flask, nitrogen gas was introduced, tap water was introduced to the Dimroth condenser, and the flask was heated to 80°C while rotating with a stirring blade, and the mixture in the dropping funnels 1 and 2 was added dropwise at a uniform rate over 60 minutes. After the dropwise addition, the mixture was stirred at 80° C. for 3 hours and then cooled to 25° C. 500 g of ethanol was added, and aqueous ammonia was added dropwise while vigorously stirring until the pH became 7.0. The precipitated white solid was filtered under reduced pressure and dried in vacuum to obtain the target compound B7. Synthesis example of B8: A 300 mL three-neck glass flask was prepared, to which a stirring blade, a thermometer, a Dimroth condenser, a nitrogen gas inlet tube, a bubbler tube, and two dropping funnels (dropping funnels 1 and 2) were connected. Mercaptopropionic acid (0.33 g), acrylic acid (20.00 g), 2-acrylamido-2-methylpropanesulfonic acid (6.39 g), and ethanol (17.59 g) were added to dropping funnel 1, and 2,2'-azobis(2,4-dimethylovaleronitrile) (0.08 g) and ethanol (15.24 g) were added to dropping funnel 2. Ethanol (28.74 g) was added to the three-neck glass flask, nitrogen gas was introduced, tap water was introduced to the Dimroth condenser, and the flask was heated to 80°C while rotating with a stirring blade, and the mixture in the dropping funnels 1 and 2 was added dropwise at a uniform rate over 60 minutes. After the dropwise addition, the mixture was stirred at 80° C. for 3 hours and then cooled to 25° C. 500 g of ethanol was added, and ammonia water was added dropwise while vigorously stirring until the pH became 7.0. The precipitated white solid was filtered under reduced pressure and dried in vacuum to obtain the target compound B8. B9: Polyacrylic acid [Toagosei Co., Ltd. (A-210), weight average molecular weight: 2,000] Synthesis of B10: A 300 mL three-neck glass flask was prepared, to which a stirring blade, a thermometer, a Dimroth condenser, a nitrogen gas inlet tube, a bubbler tube, and two dropping funnels (dropping funnels 1 and 2) were connected. Mercaptopropionic acid (0.57 g), vinylpyrrolidone (20.00 g), and ethanol (13.33 g) were added to dropping funnel 1, and 2,2'-azobis(2,4-dimethylovaleronitrile) (0.22 g) and ethanol (10.95 g) were added to dropping funnel 2. Ethanol (22.38 g) was added to the three-neck glass flask, nitrogen gas was flowed, tap water was flowed into the Dimroth condenser, and the temperature was raised to 80°C while rotating with a stirring blade, and the mixture in the dropping funnels 1 and 2 was dropped at a uniform rate over 60 minutes. After dropping, the mixture was stirred at 80°C for 3 hours and then cooled to 25°C. The solvent was removed by distillation under reduced pressure, and the residue was dried in vacuum to obtain the target compound B10.

[0075] [Table 1]

[0076] 2. Preparation of Polishing Compositions (Examples 1 to 19, Comparative Examples 1 to 5) (Polishing Compositions of Examples 1 to 14 and Comparative Examples 1 to 5) Polishing liquid compositions of Examples 1 to 14 and Comparative Examples 1 to 5 shown in Table 2 were prepared by mixing and stirring component A (colloidal silica), component B or non-component B (B1 to B10 shown in Table 1), component C (phosphoric acid), component D (hydrogen peroxide), and water. The content (mass % or mass ppm, effective amount) of each component in each polishing liquid composition is as shown in Table 2. The content of water is the remainder excluding component A, component B or non-component B, component C, and component D. (Polishing Compositions of Examples 15 to 19) The polishing liquid compositions of Examples 15 to 19 shown in Table 2 were prepared by mixing and stirring component A (colloidal silica), component B (B3 shown in Table 1), component C (phosphoric acid), component D (hydrogen peroxide), additives (components E, F, and G shown in Table 2), and water. The content (mass % or mass ppm, effective amount) of each component in each polishing liquid composition is as shown in Table 2. The content of water is the remainder excluding components A, B, C, D, and additives (components E, F, and G).

[0077] In preparing each polishing composition, the following were used as component C and additives (component D, component E, component F, and component G). (Component C) Phosphoric acid [Wako Pure Chemical Industries, special grade] (Component D) Hydrogen peroxide [concentration 35% by mass, manufactured by ADEKA] (Component E) BTA [1,2,3-benzotriazole, manufactured by Tokyo Chemical Industry Co., Ltd.] (Component F) HEP [N-hydroxyethylpiperazine, manufactured by Wako Pure Chemical Industries, Ltd.] (Component G) BisS / PhS [bisphenol S / phenolsulfonic acid formalin condensate, manufactured by Konishi Chemical Industries, molar ratio (BisS / PhS): 20 / 80, weight average molecular weight: 5000] NaS [Naphthalenesulfonic acid formaldehyde condensate, Kao Corporation, product name: Demol N, weight average molecular weight: 2800] AA / AMPS [acrylic acid / 2-acrylamide-2-methylpropanesulfonic acid copolymer, molar ratio (AA / AMPS): 80 / 20, manufactured by Toa Gosei Co., Ltd., product name: A6012, weight average molecular weight: 10,000]

[0078] 3. Measurement of each parameter [Average secondary particle size of colloidal silica (component A)] Component A (colloidal silica) used in preparing the polishing composition was added to ion-exchanged water to a concentration of 0.25% by mass, and the resulting aqueous dispersion was placed in a disposable sizing cuvette (polystyrene cell) to a height of 10 mm from the bottom, and measured using a dynamic light scattering method (apparatus name: "Zetasizer Nano ZS", manufactured by Malvern Panalytical). The particle size (D50) at which the cumulative volume ratio of the particle size distribution obtained at 20 integrations and a detection angle of 173° was 50% was determined, and this was taken as the average secondary particle size of the colloidal silica. The results are shown in Table 2.

[0079] [Average particle size d / d 0 ] Average particle size d The average particle size d of component A was measured using a dynamic light scattering method (apparatus name: "Zetasizer Nano ZS", manufactured by Malvern Panalytical) after pouring the polishing liquid composition shown in Table 2 into a disposable sizing cuvette (polystyrene cell) to a height of 10 mm from the bottom. The Z-average value (Z-average size) of the particle size distribution obtained at an accumulation count of 20 times and a detection angle of 173° was determined and used as the average particle size d of the silica particles. Average particle size d 0 Average particle size of component A d 0The average particle diameter d of the silica particles was measured by dynamic light scattering (apparatus name: "Zetasizer Nano ZS", manufactured by Malvern Panalytical Co., Ltd.) after pouring a composition obtained by removing component B from the polishing liquid composition in Table 2 into a disposable sizing cuvette (polystyrene cell) to a height of 10 mm from the bottom. The Z-average value (Z-average size) of the particle size distribution obtained at an accumulation number of 20 times and a detection angle of 173° was calculated. 0 It was decided. Average particle size ratio d / d 0 The obtained average particle size d and average particle size d 0 Using the average particle size ratio d / d 0 The results are shown in Table 2.

[0080] [Weight average molecular weight of water-soluble polymer (component B or non-component B)] The weight average molecular weight of the water-soluble polymer (component B or non-component B) was measured by gel permeation chromatography (GPC) under the following conditions. The results are shown in Table 1. <Measurement conditions> Column: TSKgel GMPWXL + TSKgel GMPWXL (Tosoh Corporation) Eluent: 0.2M phosphate buffer / CH 3 CN=7 / 3 (volume ratio) Temperature: 40℃ Flow rate: 1.0mL / min Sample size: 2mg / mL Detector: RI Standard substance: sodium polystyrene sulfonate (weight average molecular weight: 1,100, 3,610, 14,900, 152,000, manufactured by POLMER STANDARDS SERVICE)

[0081] [Adsorption rate of water-soluble polymer (component B or non-component B) onto nickel oxide particles] A nickel oxide dispersion was prepared containing 0.4% nickel oxide particles (manufactured by Aldrich, average particle size: 50 nm), component C at the same concentration as in the polishing liquid composition described in the Examples, component B (or non-component B) at the same concentration as in the polishing liquid composition described in the Examples, and ion-exchanged water as the remainder. 30 mL of the obtained nickel oxide dispersion was placed in a sedimentation tube, and ultrasonic vibration (Yamato Scientific Co., Ltd., tabletop ultrasonic cleaner W-113, 28 kHz) was applied for 30 minutes at 25° C., and then the tube was left to stand for 3 hours at 25° C. The sedimentation tube was placed in a centrifuge (Beckman Coulter, tabletop centrifuge Allegra 64R) and centrifuged at 25,000 rpm for 30 minutes. The supernatant was separated from the centrifuge tube, and the carbon concentration C1 of the supernatant was measured using the following device under the following conditions. Next, an aqueous solution containing component C at the same concentration as in the polishing composition described in the Examples, component B (or non-component B) at the same concentration as in the polishing composition described in the Examples, and ion-exchanged water as the remainder was prepared, and the carbon concentration C2 in the aqueous solution was measured. The proportion (adsorption rate) of component B (or non-component B) adsorbed to the nickel oxide particles was calculated by calculating (C2-C1) / C2×100. The results are shown in Table 2. <Measurement conditions> Equipment: Shimadzu Corporation, total organic carbon meter TOC-L Sample volume: 10mL Measurement mode: NPOC Measurement temperature: 25℃

[0082] [pH measurement] The pH of the polishing composition was measured at 25° C. using a pH meter (manufactured by DKK-TOA Corporation), and the value measured 2 minutes after the electrode was immersed in the polishing composition was recorded. The results are shown in Table 2.

[0083] 4.Polishing method The polishing compositions of Examples 1 to 19 and Comparative Examples 1 to 5 prepared as described above were used to polish the following substrates under the polishing conditions shown below. The polishing rate and the number of scratches were then measured. The results are shown in Table 2. In addition, since silica aggregated in Comparative Example 5, polishing was not performed using the polishing composition of Comparative Example 5.

[0084] [Substrate to be polished] The substrate to be polished was a Ni-P plated aluminum alloy substrate that had been roughly polished with a polishing composition containing an alumina abrasive. The substrate had a thickness of 0.8 mm, an outer diameter of 95 mm, an inner diameter of 25 mm, and a center line average roughness Ra of 1 nm measured by an AFM (Digital Instrument NanoScope IIIa Multi Mode AFM).

[0085] [Polishing conditions] Polishing test machine: Speedfam's "Double-sided 9B polishing machine" Polishing pad: Fujibo suede type (foam layer: polyurethane elastomer, thickness 0.9 mm, average pore size 10 μm) Polishing liquid composition supply amount: 100mL / min (substrate to be polished 1cm) 2 Feed rate per unit: 0.076mL / min) Lower surface plate rotation speed: 32.5rpm Polishing load: 13.0kPa Polishing time: 6 minutes Number of boards: 10

[0086] 5. Evaluation [Evaluation of polishing speed] The weight of each substrate was measured before and after polishing using a tool (manufactured by Sartorius, "BP-210S"), and the mass loss was calculated from the change in mass of each substrate. The polishing rate was calculated by dividing the average mass loss of all 10 substrates by the polishing time using the following formula. The polishing rate measurement results are shown in Table 2 as relative values ​​with Comparative Example 1 set to 100. Mass loss (mg) = {mass before polishing (mg) - mass after polishing (mg)} Polishing speed (mg / min) = mass loss (mg) / polishing time (min)

[0087] [Scratch rating] Measuring equipment: KLA-Tencor "Candela OSA7100" Evaluation: Four of the substrates were randomly selected from those placed in the polishing tester, and each substrate was irradiated with a laser at 10,000 rpm to measure the number of scratches. The total number of scratches on both sides of each of the four substrates was divided by 8 to calculate the number of scratches per substrate surface. The evaluation results of the number of scratches are shown in Table 2 as a relative value with Comparative Example 1 taken as 100.

[0088] [Table 2]

[0089] As shown in Table 2 above, the polishing compositions of Examples 1 to 19 had improved removal rates and reduced scratches compared to the polishing compositions of Comparative Examples 1 to 5. [Industrial Applicability]

[0090] According to the present disclosure, for example, it is possible to provide a magnetic disk substrate suitable for achieving high recording density.

Claims

1. A polishing composition comprising silica particles (component A), a water-soluble polymer (component B), an acid (component C), and an aqueous medium, Component B is a copolymer containing structural units derived from acrylic acid and / or a salt thereof, the constituent ratio of constituent units derived from acrylic acid and / or a salt thereof to all constituent units constituting component B is 50 mol % or more, The weight average molecular weight of component B is 700 or more and 10,000 or less, Component B is such that, when 0.4 mass% of nickel oxide particles, component C having the same concentration as that of the polishing liquid composition, and component B having the same concentration as that of the polishing liquid composition are blended, the adsorption rate of component B to the nickel oxide particles is 5 mass% or more, The average particle size d of component A in the polishing composition and the average particle size d of component A in a composition obtained by excluding component B from the polishing composition 0 The ratio d / d 0 is 1.1 or less, A polishing composition for magnetic disk substrates, having a pH of 0.1 or more and 4 or less.

2. The composition contains silica particles (component A), a water-soluble polymer (component B), an acid (component C), and an aqueous medium, Component B is a copolymer containing a structural unit derived from acrylic acid and / or a salt thereof, and is a copolymer containing a structure represented by the following formula (I): the constituent ratio of constituent units derived from acrylic acid and / or a salt thereof to all constituent units constituting component B is 50 mol % or more, The weight average molecular weight of component B is 700 or more and 10,000 or less, A polishing composition for magnetic disk substrates, having a pH of 0.1 or more and 4 or less. 【Chemical 1】 In formula (I), m and n represent the constituent ratio (molar ratio) of each constituent unit in component B, and satisfy m>0, n>0, and m+n=100. M represents a hydrogen atom, an alkali metal ion, an alkaline earth metal ion, an organic cation, or ammonium (NH 4 + ) R is a hydrocarbon group having 2 to 6 carbon atoms, and the dashed line connecting X and R indicates that a carbon atom constituting R may be bonded to X. X represents an oxygen atom, a nitrogen atom, or an NH group.

3. 3. The polishing composition according to claim 1, wherein component B is at least one selected from the group consisting of a copolymer of acrylic acid and / or a salt thereof with vinyl pivalate and a copolymer of acrylic acid and / or a salt thereof with vinylpyrrolidone.

4. The polishing composition according to claim 1 or 2, further comprising an oxidizing agent (component D).

5. 3. The polishing composition according to claim 1, further comprising at least one selected from a heterocyclic aromatic compound (component E), and an aliphatic amine compound or an alicyclic amine compound (component F).

6. 3. The polishing composition according to claim 1, further comprising an anionic surfactant (component G) having a repeating unit and a sulfonic acid group or a salt thereof in the molecule.

7. 3. The polishing composition according to claim 1, wherein component G has a structure having an aromatic ring in the main chain of the repeating unit.

8. A method for producing a magnetic disk substrate, comprising a polishing step of polishing a substrate to be polished with the polishing composition according to claim 1 or 2.

9. A method for polishing a substrate, comprising polishing a substrate to be polished with the polishing composition according to claim 1 or 2, wherein the substrate to be polished is a substrate used in the manufacture of magnetic disk substrates.

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