Polishing liquid composition for magnetic disk substrates

Abstract

An aspect provides a polishing liquid composition that is able to improve the polishing rate and reduce scratches of the substrate surface after polishing, and that has excellent storage stability. In one aspect, the present disclosure relates to a polishing liquid composition for a magnetic disk substrate, which contains silica particles (component A), an acid (component B), a polymer (component C), and water. The polishing liquid composition has a pH of 1 or more and 5 or less. The component C is a copolymer of a monomer having a phenolic hydroxyl group and a monomer having a phenolic hydroxyl group and a nitrogen atom-containing functional group located at the o (ortho) position or m (meta) position of the phenolic hydroxyl group.

Description

Polishing composition for magnetic disk substrates

[0001] The present disclosure relates to a polishing composition for magnetic disk substrates, and a method for manufacturing and polishing magnetic disk substrates using the same.

[0002] In recent years, magnetic disk drives have become smaller and their capacities have increased, resulting in a demand for higher recording densities. To achieve higher recording densities, technological developments are underway to reduce the unit recording area and lower the flying height of the magnetic head to improve the detection sensitivity of weakened magnetic signals. To accommodate the lower flying height of the magnetic head and ensure a sufficient recording area, magnetic disk substrates are increasingly being required to improve smoothness and flatness, such as reducing surface roughness, waviness, and edge sagging (roll-off), as well as to reduce defects, such as scratches, protrusions, and pits.

[0003] For example, Japanese Patent Laid-Open Publication No. 10-102041 (Patent Document 1) proposes a polishing composition for glass materials, which contains at least a processing aid and water, wherein the processing aid is a water-soluble or water-dispersible organic polymer, which has at least one aromatic group having one or more hydroxyl groups per 500 units of molecular weight, and which contains in its main chain a divalent group derived from a polymerizable vinyl monomer or a group represented by -Ar-CH2- (Ar represents a phenylene group which may be substituted with a functional group). Japanese Patent Laid-Open Publication No. 2020-84186 (Patent Document 2) proposes a polishing composition for magnetic disks, which contains an abrasive, a water-soluble polymer, an acid, and an aqueous medium, and wherein the water-soluble polymer is a cationic polymer having a phenyl ether skeleton in the main chain or side chain.

[0004] In one aspect, the present disclosure relates to a polishing liquid composition for magnetic disk substrates, comprising silica particles (component A), an acid (component B), a polymer (component C), and water, wherein the pH is 1 or more and 5 or less, and component C is a copolymer of a monomer having a phenolic hydroxyl group and a monomer having the phenolic hydroxyl group and a nitrogen atom-containing functional group at the o (ortho) position or the m (meta) position of the phenolic hydroxyl group.

[0005] In one aspect, the present disclosure relates to a method for polishing a substrate, which comprises 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.

[0006] In one aspect, the present disclosure relates to a method for producing a magnetic disk substrate, which includes a step of polishing a substrate to be polished using the polishing liquid composition of the present disclosure.

[0007] With the increase in the capacity of magnetic disk drives, the required characteristics for the surface quality of substrates are becoming more stringent, 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 removal rate and scratches, and there is a problem that improving one will worsen the other. Furthermore, from the viewpoint of improving productivity and reducing waste disposal, the polishing composition is also required to have excellent storage stability.

[0008] Therefore, in one aspect, the present disclosure provides a polishing composition that can improve the removal rate and reduce scratches on the substrate surface after polishing, and that has excellent storage stability.

[0009] In one aspect, the present disclosure can provide a polishing composition that can improve the removal rate and reduce scratches on the substrate surface after polishing, and that has excellent storage stability.

[0010] The present disclosure is based on the finding that when a polishing liquid composition containing silica particles, an acid, a specific polymer, and water is used to polish a magnetic disk substrate, the polishing rate can be improved, scratches on the substrate surface after polishing can be reduced, and the storage stability can be excellent.

[0011] That is, in one aspect, the present disclosure relates to a polishing liquid composition for magnetic disk substrates (hereinafter also referred to as the "polishing liquid composition of the present disclosure") that contains silica particles (component A), an acid (component B), a polymer (component C), and water, wherein the pH of the polishing liquid composition is 1 or more and 5 or less, and component C is a copolymer of a monomer having a phenolic hydroxyl group and a monomer having a phenolic hydroxyl group and a nitrogen atom-containing functional group at the o (ortho) position or the m (meta) position of the phenolic hydroxyl group.

[0012] Although the details of the mechanism by which the effects of the present disclosure are realized are not clear, it is speculated as follows. It is believed that Component C in the polishing compound composition of the present disclosure becomes positively charged at the nitrogen atom site in the acidic polishing solution, enabling electrostatic adsorption to the substrate to be polished, and that this acts as a protective film for the substrate to be polished, thereby reducing scratches. Furthermore, it is believed that the adsorption of Component C to the substrate to be polished positively charges the substrate, thereby attracting the silica particles (Component A), which are slightly negatively charged in the acidic polishing solution, to the substrate, allowing the silica abrasive grains to be highly concentrated on the substrate to be polished. As a result, it is believed that the polishing rate is also enhanced in a concerted manner. The contribution ratios of the scratch reduction effect and the polishing rate improvement effect are thought to change depending on the amount of Component C added, etc. Furthermore, since the nitrogen atom in Component C is not ether-bonded to the phenolic hydroxyl group but is oriented in the o (ortho) or m (meta) position, hydrolysis in the acidic polishing solution is suppressed, which is thought to also have the effect of excellent storage stability. Furthermore, component C is not a homopolymer having a nitrogen atom-containing functional group at the o (ortho) or m (meta) position of a phenolic hydroxyl group, but a copolymer with a monomer having a phenolic hydroxyl group. Therefore, it has a relatively lower nitrogen atom content than the homopolymer, and is thought to have the effect of not agglomerating silica particles even when mixed with silica particles (component A) in an acidic polishing liquid. As a result, polishing proceeds more efficiently than the homopolymer, and since it does not contain aggregated silica particles, it is thought to be able to achieve both a higher level of polishing rate improvement and scratch reduction than the homopolymer. However, the present disclosure does not need to be interpreted as being limited to these mechanisms.

[0013] In the present disclosure, scratches on the substrate surface can be detected, for example, by an optical defect inspection device and quantitatively evaluated as the number of scratches. The number of scratches can be specifically evaluated by the method described in the Examples.

[0014] [Silica Particles (Component A)] From the viewpoint of improving the removal rate and reducing scratches, examples of the silica particles (hereinafter also referred to as "Component A") contained in the polishing liquid composition of the present disclosure include colloidal silica, fumed silica, pulverized silica, and surface-modified silica thereof, with colloidal silica being preferred among these. Component A contained in the polishing liquid composition of the present disclosure may be one type or a combination of two or more types.

[0015] 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. From the viewpoint of reducing scratches, it is preferably 500 nm or less, more preferably 300 nm or less, even more preferably 100 nm or less, even more preferably 70 nm or less, and even more preferably 40 nm or less. From the same viewpoint, 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" refers to a value measured by dynamic light scattering. For example, the average secondary particle diameter can be determined by measuring at a detection angle of 173° using dynamic light scattering, and the value (D50) at which the cumulative volume fraction of the particle size distribution obtained is 50% can be used. The average secondary particle diameter of silica particles (component A) can be specifically determined by the method described in the Examples.

[0016] [Average Particle Size Ratio d / d0] The ratio d / d0 (hereinafter also referred to as "average particle size ratio d / d0") of the average particle size d of the silica particles (component A) in the polishing liquid composition of the present disclosure to the average particle size d0 of the silica particles (component A) in a composition obtained by excluding component C from the polishing liquid composition of the present disclosure is preferably 1.4 or less, more preferably 1.3 or less, and even more preferably 1.2 or less, from the viewpoint of improving the polishing rate and / or improving the polishing rate. From the viewpoint of suppressing a decrease in the polishing rate, it is preferably 0.9 or more, more preferably 0.95 or more, even more preferably 0.99 or more, and even more preferably 1 or more. More specifically, the average particle size ratio d / d0 is preferably 0.9 or more and 1.4 or less, more preferably 0.95 or more and 1.3 or less, even more preferably 0.99 or more and 1 or less. More specifically, the average particle size ratio d / d0 is preferably 0.9 or more and 1.4 or less, more preferably 0.95 or more and 1.3 or less, even more preferably 0.99 or more and 1.2 or less, and even more preferably 1 or more and 1.2 or less. In the present disclosure, the average particle sizes d and d0 are each Z-average values ​​measured by dynamic light scattering, and specifically, can be measured by the method described in the Examples.

[0017] From the viewpoint of improving the polishing rate, the content of component A in the polishing liquid composition of the present disclosure is preferably 0.1 mass% or more, more preferably 1 mass% or more, and even more preferably 3 mass% or more, and from the viewpoint of reducing scratches, it is preferably 20 mass% or less, more preferably 15 mass% or less, and even more preferably 10 mass% or less. From the same viewpoint, the content of component A in the polishing liquid composition of the present disclosure is preferably 0.1 mass% or more and 20 mass% or less, more preferably 1 mass% or more and 15 mass% or less, and even more preferably 3 mass% or more and 10 mass% or less. When component A consists of two or more types of silica particles, the content of component A refers to the total content thereof.

[0018] [Acid (Component B)] The polishing liquid composition of the present disclosure contains an acid (component B). In the present disclosure, the use of an acid includes the use of an acid or a salt thereof. Component B contained in the polishing liquid composition of the present disclosure may be one type or a combination of two or more types.

[0019] Examples of Component B 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; and organic acids such as organic phosphoric acid, organic phosphonic acid, and carboxylic acid. Among these, from the viewpoint of improving the polishing rate and reducing scratches, it is more preferable to contain an inorganic acid and an organic phosphonic acid, and even more preferable to contain an inorganic acid. From the same viewpoint, the inorganic acid is preferably at least one selected from nitric acid, sulfuric acid, hydrochloric acid, perchloric acid, and phosphoric acid, more preferably at least one selected from sulfuric acid and phosphoric acid, and even more preferably phosphoric acid. From the same viewpoint, the organic phosphonic acid is preferably at least one selected from 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP), aminotrimethylenephosphonic acid, ethylenediaminetetramethylenephosphonic acid, and diethylenetriaminepentamethylenephosphonic acid, and HEDP is more preferable. Examples of salts of these acids include salts of the above acids with at least one selected from metals, ammonia, and alkylamines. Examples of the above metals include metals belonging to Groups 1 to 11 of the periodic table. Among these, salts of the above acids with metals belonging to Group 1A or ammonia are preferred from the viewpoints of improving the polishing rate and reducing scratches.

[0020] From the viewpoints of improving the polishing rate and reducing scratches, the content of component B 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 0.5% by mass or more. From the viewpoint of achieving both scratch reduction and storage stability, the content of component B in the polishing liquid composition of the present disclosure is preferably 3% by mass or less, and more preferably 2% by mass or less. From the same viewpoint, the content of component B in the polishing liquid composition of the present disclosure is preferably 0.01% by mass or more and 3% by mass or less, more preferably 0.1% by mass or more and 2% by mass or less, and even more preferably 0.5% by mass or more and 2% by mass or less. When component B is a combination of two or more types, the content of component B refers to the total content thereof.

[0021] [Polymer (Component C)] The polymer (hereinafter also referred to as "Component C") contained in the polishing composition of the present disclosure is, from the viewpoint of improving the polishing rate and / or reducing scratches, a copolymer of a monomer having a phenolic hydroxyl group and a monomer having a phenolic hydroxyl group and a nitrogen atom-containing functional group at the o (ortho)- or m (meta)-position of the phenolic hydroxyl group. As the monomer having a phenolic hydroxyl group, a monomer having a phenolic hydroxyl group and a vinyl group is preferred, with vinylphenol being more preferred, and p (para)-vinylphenol being even more preferred. As the monomer having a phenolic hydroxyl group and a nitrogen atom-containing functional group at the o (ortho)- or m (meta)-position of the phenolic hydroxyl group, a monomer having a phenolic hydroxyl group and a nitrogen atom-containing functional group at the o (ortho)- or m (meta)-position of the phenolic hydroxyl group and further having a vinyl group at the p (para)-position is preferred. The number of nitrogen atom-containing functional groups may be 1 to 4, preferably 1 to 3, and more preferably 1 or 2. When the number of nitrogen-atom-containing functional groups is 1, it is preferable that the nitrogen-atom-containing functional group be located at the o (ortho) position of the phenolic hydroxyl group. When the number of nitrogen-atom-containing functional groups is 2, it may be possible to have nitrogen-atom-containing functional groups at the two o (ortho) positions of the phenolic hydroxyl group, or to have nitrogen-atom-containing functional groups at the two m (meta) positions of the phenolic hydroxyl group, or to have nitrogen-atom-containing functional groups at the o (ortho) and m (meta) positions of the phenolic hydroxyl group. When the number of nitrogen-atom-containing functional groups is 2, it is preferable that the nitrogen-atom-containing functional groups be located at the two o (ortho) positions of the phenolic hydroxyl group. Preferred examples of monomers having a phenolic hydroxyl group and a nitrogen-atom-containing functional group at the o (ortho) or m (meta) position of the phenolic hydroxyl group include 2-((dimethylamino)methyl)-4-vinylphenol and 2,6-bis((dimethylamino)methyl)-4-vinylphenol. In the present disclosure, the component C contained in the polishing composition may be one type or a combination of two or more types.

[0022] As component C, for example, a compound having a structure represented by the following formula (I) is preferred. In formula (I), R 1 and R 2are each independently a hydrogen atom, a hydrocarbon group having 1 to 3 carbon atoms, or a hydroxyalkyl group having 1 to 3 carbon atoms. 1 and R 2 x is 1 or 2, and y is 1 or 2. m and n represent molar ratios, and satisfy the conditions m+n=100, 20≦m≦80, and 20≦n≦80. In formula (I), R 1 and R 2 When R 1 and R 2 may be directly bonded to form a ring structure, or R 1 and R 2 and may be bonded via a carbon atom, an oxygen atom, or a nitrogen atom to form a ring structure containing two or more heteroatoms. 1 and R 2 In one or more embodiments, the heterocyclic structure formed by these groups includes a morpholine ring structure. In formula (I), when y = 1, the nitrogen-atom-containing functional group may be bonded to any one of two o-positions or two m-positions relative to the phenolic hydroxyl group, and among these, a structure in which the nitrogen-atom-containing functional group is bonded to the o-position of the phenolic hydroxyl group is preferred. In formula (I), when y = 2, the nitrogen-atom-containing functional group may be bonded to any two selected from two o- (ortho) positions and two m- (meta) positions of the phenolic hydroxyl group, and among these, a structure in which the nitrogen-atom-containing functional group is bonded to the two o- (ortho) positions of the phenolic hydroxyl group is preferred. In formula (I), the molar ratio m / n is preferably from 20 / 80 to 80 / 20, more preferably from 25 / 75 to 70 / 30, even more preferably from 35 / 65 to 70 / 30, still more preferably from 40 / 60 to 60 / 40, and still more preferably from 45 / 55 to 50 / 50, from the viewpoint of ensuring the polishing rate and reducing scratches.

[0023] When component C is a compound having a structure represented by formula (I), the content of the structure represented by formula (I) in all structural units constituting component C, i.e., the sum of the number of moles m of 4-vinylphenol in formula (I) and the number of moles n of a monomer having a phenolic hydroxyl group and a nitrogen atom-containing functional group at the o (ortho)-position or m (meta)-position of the phenolic hydroxyl group relative to the total number of moles of structural units constituting component C, is, in one or more embodiments, preferably 50 mol% or more, more preferably 80 mol% or more, even more preferably 90 mol% or more, and even more preferably 100 mol% from the viewpoint of improving the polishing rate and reducing scratches. In the present disclosure, the content (mol%) of a certain structural unit in all structural units constituting component C may, depending on the synthesis conditions, also be the amount (mol%) of the compound for introducing the structural unit charged into the reaction vessel relative to all compounds for introducing the structural units charged into the reaction vessel in all steps of the synthesis of component C. Furthermore, in the present disclosure, when component C contains two or more types of structural units, the structural ratio (molar ratio) of the two structural units may be the amount ratio (molar ratio) of the compounds for introducing the two structural units charged into the reaction tank in all steps of the synthesis of component C, depending on the synthesis conditions. Component C may also have other structural units not included in formula (I). From the viewpoint of ensuring the polishing rate and reducing scratches, the content of other structural units in all structural units constituting component C is preferably 10 mol% or less, more preferably 5 mol% or less, even more preferably 3 mol% or less, even more preferably 1 mol% or less, and even more preferably substantially 0 mol%, relative to the total number of moles of structural units constituting component C.

[0024] The arrangement of the structural units constituting component C may be random, block, or graft.

[0025] In one or more embodiments, Component C is a copolymer of polyvinylphenol partially modified with dimethylamino or diethanolamino. When Component C is a compound having a structure represented by formula (I), suitable examples of Component C include a copolymer of 4-vinylphenol and vinyldimethylamino-modified polyvinylphenol, a copolymer of 4-vinylphenol and bis(dimethylamino-modified) polyvinylphenol, and a copolymer of 4-vinylphenol and bis(diethanolamino-modified) polyvinylphenol.

[0026] From the viewpoint of improving the polishing rate and / or reducing scratches, component C is preferably a polymer consisting of component C, water, and an acid (e.g., phosphoric acid) added as needed to achieve a pH of 1.5 at 25°C, wherein the concentration of component C is 0.5% by mass, and the zeta potential in the composition at pH 1.5 at 25°C is +1 mV or more and +40 mV or less. Such a polymer (component C) can also be described as a polymer having a zeta potential of +1 mV or more and +40 mV or less measured using the zeta potential measurement sample described below. Zeta potential measurement sample: A composition consisting of water, component C, and an acid (component B) and having a pH of 1.5, wherein the content of component C in the composition is 0.5% by mass. In the present disclosure, the zeta potential measured using the zeta potential measurement sample (hereinafter also referred to as the "zeta potential measurement sample of the present disclosure") (hereinafter also referred to as the "zeta potential of the present disclosure") refers to the zeta potential of colloidal particles formed by component C in the composition. The zeta potential in the present disclosure is, from the viewpoint of improving the polishing rate and / or reducing scratches, preferably +1 mV or more, more preferably +2 mV or more, even more preferably +6 mV or more, still more preferably +10 mV or more, even more preferably +20 mV or more, and even more preferably +21 mV or more, and from the same viewpoint, preferably +40 mV or less, more preferably +36 mV or less, even more preferably +30 mV or less, and even more preferably +27 mV or less. More specifically, in one or a plurality of embodiments, the zeta potential of the present disclosure is, from the viewpoint of improving the polishing rate and reducing scratches, preferably from +1 mV to +40 mV, more preferably from +2 mV to +36 mV, even more preferably from +6 mV to +36 mV, still more preferably from +10 mV to +36 mV, still more preferably from +20 mV to +36 mV, still more preferably from +20 mV to +30 mV, still more preferably from +20 mV to +27 mV, and still more preferably from +21 mV to +27 mV.The zeta potential measurement sample of the present disclosure is a composition consisting of water, component C, and an acid (component B) and has a pH of 1.5. The pH of the zeta potential measurement sample of the present disclosure is 1.5, meaning that the pH is in the range of 1.4 to 1.6, and the acid (component B) contained in the zeta potential measurement sample of the present disclosure is the same as the acid (component B) contained in the polishing liquid composition of the present disclosure. The pH of the zeta potential measurement sample of the present disclosure is measured at 25°C, and is the value measured 2 minutes after the electrode was immersed. The zeta potential of the zeta potential measurement sample of the present disclosure can be determined specifically by the method described in the Examples.

[0027] From the viewpoint of improving the polishing rate and / or reducing scratches, the weight average molecular weight of Component C is preferably 1,000 or more, more preferably 3,000 or more, and even more preferably 4,000 or more, and from the same viewpoint, it is preferably 50,000 or less, more preferably 20,000 or less, and even more preferably 10,000 or less. More specifically, the weight average molecular weight of Component C is preferably 1,000 or more and 50,000 or less, more preferably 3,000 or more and 20,000 or less, and even more preferably 4,000 or more and 10,000 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.

[0028] From the viewpoint of improving the removal rate and / or reducing scratches, the content of component C in the polishing liquid composition of the present disclosure is preferably 10 ppm by mass or more, more preferably more than 10 ppm by mass, even more preferably 15 ppm by mass or more, and even more preferably 20 ppm by mass or more. From the same viewpoint, it is preferably 100 ppm by mass or less, more preferably less than 100 ppm by mass, even more preferably 60 ppm by mass or less, and even more preferably 50 ppm by mass or less. From the same viewpoint, the content of component C in the polishing liquid composition of the present disclosure is preferably 10 ppm by mass or more and 100 ppm by mass or less, more preferably more than 10 ppm by mass and 100 ppm by mass or less, even more preferably 15 ppm by mass or more and 60 ppm by mass or less, and even more preferably 20 ppm by mass or more and 50 ppm by mass or less. In the present disclosure, when the polishing liquid composition contains a combination of two or more types of component C, the content of component C refers to the total content thereof. In the present disclosure, 1% by mass is 10,000 ppm by mass (the same applies hereinafter).

[0029] 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, from the viewpoint of improving the polishing rate and / or reducing scratches, preferably 300 or more, more preferably 800 or more, and even more preferably 1600 or more, and from the same viewpoint, preferably 5000 or less, more preferably 4500 or less, and even more preferably 4000 or less. From the same viewpoint, the mass ratio A / C in the polishing liquid composition of the present disclosure is preferably 300 or more and 5000 or less, more preferably 800 or more and 4500 or less, and even more preferably 1600 or more and 4000 or less.

[0030] [Water] The polishing composition of the present disclosure contains water as a medium. Examples of water include distilled water, ion-exchanged water, pure water, and ultrapure water. The content of water in the polishing composition of the present disclosure can be the remainder excluding Component A, Component B, Component C, and the optional components described below.

[0031] [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 viewpoints of improving the removal rate and reducing scratches. In one or more embodiments, Component D is an oxidizing agent that does not contain a halogen atom. Component D may be one type, or two or more types may be combined.

[0032] Examples of component D, from the viewpoints of improving the polishing rate and reducing scratches, include peroxides, permanganic acid or its salts, chromic acid or its salts, peroxoacids or their salts, oxyacids or their 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 viewpoints of improving the polishing rate, preventing metal ions from adhering to the surface of the substrate to be polished, and ease of availability.

[0033] 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, and even more preferably 0.1 mass% or more, from the viewpoint of improving the removal rate, and is preferably 4 mass% or less, more preferably 2 mass% or less, even more preferably 1 mass% or less, and even more preferably 0.5 mass% or less, from the viewpoint of reducing scratches. From the same viewpoint, 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, even more preferably 0.1 mass% or more and 1 mass% or less, and even more preferably 0.1 mass% or more and 0.5 mass% or less. In the present disclosure, when the polishing liquid composition contains a combination of two or more types of component D, the content of component D refers to the total content thereof.

[0034] [Compound (Component E)] In one or more embodiments, the polishing composition of the present disclosure may further contain at least one compound selected from an aromatic compound having a sulfonic acid group or a carboxylic acid group in the molecule and an azole compound (hereinafter also referred to as "Component E"). Component E contained in the polishing composition of the present disclosure may be one type or a combination of two or more types.

[0035] Examples of aromatic compounds having a sulfonic acid group in the molecule include alkylbenzenesulfonic acid, alkylbenzenedisulfonic acid, benzenesulfonic acid, dihydroxybenzenedisulfonic acid, and paratoluenesulfonic acid. Examples of aromatic compounds having a carboxylic acid group (carboxy group) in the molecule include compounds represented by the following formula (II): In formula (II), R 3 and R 4 are each independently a hydrogen atom or an aromatic group, k and l are 0 to 20, and satisfy the relationship k+l=1 to 20. 3 and R 4are not simultaneously hydrogen atoms. Note that k and l each represent the average number of moles added. In formula (II), from the viewpoints of improving the polishing rate and reducing scratches, the aromatic group is preferably a benzyl group or an alkylbenzyl group having 1 to 3 carbon atoms, and more preferably an alkylbenzyl group having 1 to 3 carbon atoms. Examples of alkylbenzyl groups having 1 to 3 carbon atoms include a methylbenzyl group (xylene group). In formula (II), k is preferably 20 or less, more preferably 15 or less, and even more preferably 10 or less, from the viewpoints of improving the polishing rate and reducing scratches in the polishing composition. From the same viewpoint, k is preferably 1 or more, and more preferably 2 or more. From the same viewpoint, k is preferably 1 or more and 20 or less, more preferably 2 or more and 15 or less, and even more preferably 2 or more and 10 or less. In formula (II), l is preferably 10 or less, more preferably 5 or less, and even more preferably 3 or less, from the viewpoint of ensuring polishing properties in the polishing composition. In formula (II), the molar ratio k / l is preferably 50 / 50 to 80 / 20, more preferably 80 / 20 to 90 / 10, and even more preferably 93 / 7 to 100 / 0, from the viewpoints of improving the polishing rate and reducing scratches. The arrangement of the structural units constituting the compound represented by formula (II) may be random, block, or graft. The compound represented by formula (II) can be produced, for example, by dissolving maleic acid or maleic anhydride in a solvent such as xylene, adding a polymerization initiator, initiating the reaction, and allowing the reaction to proceed for a predetermined period of time. Any compound having an azole structure can be used as the azole compound. Among these, 1H-1,2,3-benzotriazole is preferred.

[0036] From the viewpoints of improving the polishing rate and reducing scratches, Component E is preferably at least one compound selected from aromatic compounds having a sulfonic acid group or a carboxylic acid group in the molecule and azole compounds, and more preferably at least one compound selected from p-toluenesulfonic acid, polymaleic acid having a methylbenzyl group (xylene group) at at least one terminal, and 1H-1,2,3-benzotriazole.

[0037] From the viewpoint of improving the polishing rate and / or reducing scratches, the molecular weight or weight-average molecular weight of Component E is preferably 70 or more, more preferably 100 or more, and even more preferably 110 or more, and from the same viewpoint, it is preferably 1000 or less, more preferably 900 or less, and even more preferably 800 or less. More specifically, the molecular weight or weight-average molecular weight of Component C is preferably 70 or more and 1000 or less, more preferably 100 or more and 900 or less, and even more preferably 110 or more and 800 or less.

[0038] 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 0.0001% by mass or more, more preferably 0.001% by mass or more, and even more preferably 0.002% by mass or more, from the viewpoints of improving the polishing rate and reducing scratches, and from the same viewpoints, is preferably 5% by mass or less, more preferably 1% by mass or less, and even more preferably 0.1% by mass or less. More specifically, the content of component E in the polishing liquid composition of the present disclosure is preferably 0.0001% by mass or more and 5% by mass or less, more preferably 0.001% by mass or more and 1% by mass or less, and even more preferably 0.002% by mass or more and 0.1% by mass or less. When component E is a combination of two or more types, the content of component E refers to the total content thereof.

[0039] [Other Components] In one or more embodiments, the polishing liquid composition of the present disclosure may contain other components as needed, to the extent that the effects of the present disclosure are not impaired. Examples of other components include heterocyclic aromatic compounds, aliphatic amine compounds, alicyclic amine compounds, thickeners, dispersants, rust inhibitors, basic substances, removal rate enhancers, surfactants, and polymers other than Component C.

[0040] [pH of Polishing Liquid Composition] From the viewpoint of improving the polishing rate and / or reducing scratches, the pH of the polishing liquid composition of the present disclosure is 1 or more, preferably 1.2 or more, and more preferably 1.5 or more. From the same viewpoint, it is 5 or less, preferably 3 or less, and more preferably 2 or less. More specifically, the pH of the polishing liquid composition of the present disclosure is 1 or more and 5 or less, preferably 1.2 or more and 3 or less, and more preferably 1.5 or more and 2 or less. The pH can be adjusted using the above-mentioned acid (component B). A known pH adjuster may also be used in combination. In the present disclosure, the above pH is measured at 25°C using a pH meter, and can be the value measured 2 minutes after immersing the electrode of the pH meter in the polishing liquid composition.

[0041] [Method for Producing Polishing Liquid Composition] The polishing liquid composition of the present disclosure can be produced, for example, by blending component A, component B, component C, and water, and, if desired, optional components (component D, component E, and other components) using a known method. For example, in one or more embodiments, the polishing liquid composition of the present disclosure can be produced by blending at least component A, component B, component C, and water. Therefore, in one aspect, the present disclosure relates to a method for producing a polishing liquid composition, including a step of blending at least component A, component B, component C, and water. In this disclosure, "blending" includes mixing component A, component B, component C, and water, and, if necessary, optional components (component D, component E, and other components), simultaneously or in any order. Silica particles (component A) may be mixed in the form of a concentrated slurry, or may be mixed after dilution with water or the like. When component A consists of multiple types of silica particles, the multiple types of silica particles can be blended simultaneously or separately. When component B consists of multiple types of acids, the multiple types of acids can be blended simultaneously or separately. When component C is composed of multiple types of polymers, the multiple types of polymers can be blended together or separately. The blending can be carried out using a mixer such as a homomixer, a homogenizer, an ultrasonic disperser, or a wet ball mill. The preferred blending amounts of each component in the method for producing the polishing composition can be the same as the preferred contents of each component in the polishing composition of the present disclosure described above.

[0042] An embodiment of the polishing liquid composition of the present disclosure may be a so-called one-component type in which all components are premixed and supplied to the market, or may be a so-called two-component type in which components are mixed at the time of use.

[0043] 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, i.e., at the time when the polishing liquid composition is first used for polishing. In one or more embodiments, the content of each component in the polishing liquid composition of the present disclosure can be considered as the blending amount of each component.

[0044] [Concentrate of Polishing Liquid Composition] The polishing liquid composition of the present disclosure may be stored and supplied in a concentrated state to the extent that its storage stability is not impaired. This is preferable in that it can further reduce production and transportation costs. The concentrate of the polishing liquid composition of the present disclosure may be diluted appropriately with the above-mentioned water as needed before use. The dilution ratio is not particularly limited as long as the contents (at the time of use) of each of the above-mentioned components can be ensured after dilution, and can be, for example, 10 to 100 times.

[0045] [Polishing Liquid Kit] In one aspect, the present disclosure relates to a kit for preparing the polishing liquid composition of the present disclosure, the kit including a first liquid containing component A and a second liquid containing components B and C in a mutually unmixed state (hereinafter also referred to as the "polishing liquid kit of the present disclosure"). The first liquid and the second liquid are mixed at the time of use and may be diluted with water as needed. The water contained in the first liquid may be the entire amount of water used to prepare the polishing liquid composition, or a portion thereof. The second liquid may contain a portion of the water used to prepare the polishing liquid composition. The first liquid and the second liquid may each contain the above-mentioned optional components (component D, component E, other components) as needed. The above-mentioned optional components (component D, component E, other components) may be further mixed when the first liquid and the second liquid are mixed. According to the present disclosure, a polishing liquid composition can be obtained that can achieve both an improved polishing rate and reduced scratches on the substrate surface after polishing, and has excellent storage stability.

[0046] [Substrate to be polished] In one or more embodiments, the substrate to be polished is a substrate used in the manufacture of a magnetic disk substrate. In one or more embodiments, the magnetic disk substrate can be manufactured by polishing the surface of the substrate to be polished with the polishing composition of the present disclosure, followed by forming a magnetic layer on the substrate surface by sputtering or the like.

[0047] Suitable materials for the substrate to be polished in the present disclosure include, for example, metals or semimetals such as silicon, aluminum, nickel, tungsten, copper, tantalum, and titanium, or alloys thereof; glassy materials such as glass, glassy carbon, and amorphous carbon; ceramic materials such as alumina, silicon dioxide, silicon nitride, tantalum nitride, and titanium carbide; and resins such as polyimide resins. Among these, substrates containing metals such as aluminum, nickel, tungsten, and copper, and alloys primarily composed of these metals, are particularly suitable. Examples of suitable substrates include Ni-P-plated aluminum alloy substrates and glass substrates such as crystallized glass, tempered glass, aluminosilicate glass, and aluminoborosilicate glass, with Ni-P-plated aluminum alloy substrates being even more suitable. In the present disclosure, the term "Ni-P-plated aluminum alloy substrate" refers to an aluminum alloy substrate whose surface has been ground and then electrolessly plated with Ni-P.

[0048] 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. Of these, a disk-shaped substrate to be polished is suitable. In the case of a disk-shaped substrate to be polished, its outer diameter is, for example, about 2 to 100 mm, and its thickness is, for example, about 0.4 to 2 mm.

[0049] [Method for polishing a substrate] In one 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 comprises 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 production of magnetic disk substrates. According to the polishing method of the present disclosure, it is possible to achieve both an improvement in the polishing rate and a reduction in scratches on the substrate surface after polishing, and by using the polishing liquid composition of the present disclosure, which has excellent storage stability, high-quality magnetic disk substrates can be produced with high yield and good productivity. As described above, the substrate to be polished in the polishing method of the present disclosure can be one used in the production of magnetic disk substrates, and among these, substrates used in the production of magnetic disk substrates for perpendicular magnetic recording systems are preferred.

[0050] In one or more embodiments, polishing a substrate to be polished with the polishing liquid composition of the present disclosure involves 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; alternatively, sandwiching the substrate to be polished between plates to which a polishing pad such as a nonwoven organic polymer-based polishing 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.

[0051] The polishing pad used in the present disclosure is not particularly limited, and for example, a suede type, a nonwoven fabric type, a polyurethane closed-cell type, or a two-layer type laminated with these can be used, and from the viewpoint of improving the polishing rate, a suede type polishing pad is preferred.

[0052] The polishing load in polishing using the polishing composition of the present disclosure is preferably 5.9 kPa or more, more preferably 6.9 kPa or more, and even more preferably 7.5 kPa or more from the viewpoint of improving the polishing rate, and is preferably 20 kPa or less, more preferably 18 kPa or less, and 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 a weight to at least one of the platen and the substrate to be polished.

[0053] In polishing using the polishing composition of the present disclosure, the supply rate of the polishing composition of the present disclosure is set to 1 / cm of the substrate to be polished from the viewpoint of improving the polishing rate and / or 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.

[0054] The polishing composition of the present disclosure can be supplied to a polishing machine by, for example, continuous supply using a pump or the like. When supplying the polishing composition to a polishing machine, in addition to a method of supplying it as a single liquid containing all components, it can also be divided into a plurality of blending component liquids and supplied as two or more liquids, taking into consideration the stability of the polishing composition, etc. In the latter case, the plurality of blending component liquids are mixed, for example, in the supply pipe or on the substrate to be polished, to produce the polishing composition of the present disclosure.

[0055] [Method for manufacturing magnetic disk substrate] Generally, magnetic disks are manufactured by polishing a substrate to be polished through a grinding step, a rough polishing step, a finish polishing step, and then forming a magnetic disk in a recording section forming step. The polishing composition of the present disclosure can be used in the polishing step of polishing the substrate to be polished, preferably the finish polishing step, in the method for manufacturing a magnetic disk substrate. That is, in one aspect, the present disclosure relates to a method for manufacturing a magnetic disk substrate (hereinafter also referred to as the "substrate manufacturing method of the present disclosure") including a step of polishing a substrate to be polished using the polishing composition of the present disclosure (hereinafter also referred to as the "polishing step using the polishing composition of the present disclosure"). The substrate manufacturing method of the present disclosure is particularly suitable for manufacturing magnetic disk substrates for perpendicular magnetic recording systems. The polishing method and conditions in the polishing step using the polishing composition of the present disclosure can be the same as those used in the polishing method of the present disclosure described above.

[0056] In one or more embodiments, the polishing step using the polishing liquid composition of the present disclosure is a step of supplying the polishing liquid composition of the present disclosure to a surface to be polished of a 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. In another one or more embodiments, the polishing step using the polishing liquid composition of the present disclosure is a step of sandwiching the substrate to be polished between plates to which a polishing pad such as a nonwoven organic polymer-based polishing 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.

[0057] 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 finish polishing process.In this case, in order to avoid contamination of abrasive grains or polishing liquid compositions from the previous process, separate polishing machines may be used for each step, and when separate polishing machines are used, it is preferable to clean the substrate to be polished after each polishing process.Furthermore, the polishing liquid composition of the present disclosure can also be used in circulating polishing in which the used polishing liquid is reused.The polishing machine is not particularly limited, and known polishing machines for substrate polishing can be used.

[0058] According to the substrate manufacturing method of the present disclosure, it is possible to achieve both an improved polishing rate and a reduced number of scratches on the substrate surface after polishing, and by using the polishing liquid composition of the present disclosure, which has excellent storage stability, it is possible to manufacture high-quality magnetic disk substrates with high yield and good productivity.

[0059] Hereinafter, the present disclosure will be described in more detail with reference to examples, but these are merely illustrative examples and the present disclosure is not limited to these examples.

[0060] 1. Polymers C1 to C5 (Component C or Non-Component C) The following were used for polymers C1 to C5 shown in Table 1. C1: Dimethylamino-modified polyvinylphenol [synthetic product] (Component C) C2: Bis(dimethylamino-modified) polyvinylphenol [synthetic product] (Component C) C3: Bis(diethanolamino-modified) polyvinylphenol [synthetic product] (Component C) C4: Poly(bis(dimethylamino)methyl)vinylphenol [synthetic product] (Non-Component C) C5: Poly(vinylphenol / N,N-dimethyl-1-(4-vinylphenoxy)methanamine) copolymer [Maruka Linker MAM3ME, manufactured by Maruzen Petrochemical Co., Ltd.] (Non-Component C) Synthesis examples of polymers C1 to C5 are shown below. [Synthesis of Polymer C1] 50 g of poly(p-vinylphenol) (Nippon Soda, trade name: VP-2500, weight-average molecular weight 4,400) was added to a four-neck flask, and a condenser, a three-way stopcock, and a balloon filled with N2 were attached to the top of the flask. After purging the reaction system with nitrogen, 100 mL of isopropyl alcohol (Fujifilm Wako Pure Chemical Industries, Ltd.) was added using a syringe. The flask was then transferred to a dry ice oven so that the entire system was enclosed, and the entire system was cooled and stirring commenced. 1.3 g of trimethyl chloride (Fujifilm Wako Pure Chemical Industries, Ltd.) was then similarly added using a syringe. The mixture was stirred for 3 hours, and all hydroxyl groups of vinylphenol were protected with trimethylsilyl groups. Next, 0.125 g of dimethylamine (Tokyo Chemical Industry Co., Ltd.) was added and stirred. While the entire system was cooled and stirred, formaldehyde was added dropwise (drop rate: 5 g / hour) to introduce amino groups. After the completion of the dropwise addition of formaldehyde, 3.3 g of a tetrabutylammonium fluoride-tetrahydrofuran solution (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added dropwise with cooling (dropping rate: 5 g / hour) to deprotect the hydroxyl groups of vinylphenol. Finally, isopropyl alcohol and tetrahydrofuran were removed using an evaporator to obtain polymer C1. The weight-average molecular weight was 4,400, similar to that of the starting material poly(p-vinylphenol). The molar ratio m / n in Table 1 indicates the ratio of the monomers charged and 1The physical properties of polymer C3 were determined by the same method as for polymer C1. [Synthesis method of polymer C4] Polymer C4 was obtained by the same method as for polymer C1, except that the amount of dimethylamine added as a substituent was changed to 0.5 g. [Synthesis method of polymer C5] In one embodiment, polymer C5 can be produced, for example, by the Mannich reaction using the above-mentioned dialkylamine and formaldehyde. Diethylamine is added to polyvinylphenol having a weight-average molecular weight of 5,000 so as to obtain a desired amount, and formaldehyde is added dropwise while cooling, and the reaction proceeds to obtain polymer C5.

[0061]

[0062] 2. Preparation of Polishing Compositions (Examples 1 to 11, Reference Example 1, and Comparative Examples 1 to 4) The polishing compositions of Examples 1 to 11, Reference Example 1, and Comparative Examples 1 to 4 shown in Table 3 were prepared by blending and stirring silica particles (component A), phosphoric acid (component B), a polymer shown in Table 1 (component C or non-component C), an oxidizing agent (component D), a compound shown in Table 2 (component E), and ion-exchanged water. The content (mass %, effective amount) of each component in each polishing composition is as shown in Table 3. The content of ion-exchanged water is the remainder excluding component A, component B, component C or non-component C, component D, and component E.

[0063] In preparing each polishing composition, the following were used for Component A, Component B, Component D, and Component E. (Component A) Colloidal silica [average secondary particle size: 18 nm] (Component B) Phosphoric acid [concentration 85%, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.] (Component D) Hydrogen peroxide solution [concentration 35% by mass, manufactured by ADEKA Corporation] (Component E) The following were used for the compounds shown in Table 2 (Components E1 to E3). Component E1: paratoluenesulfonic acid monohydrate [reagent, manufactured by Tokyo Chemical Industry Co., Ltd.] The content of this component in Table 3 is the content as paratoluenesulfonic acid (anhydride). Component E2: Polymaleic acid having a methylbenzyl group (xylene group) at the terminal [Kao Preparations] Component E3: 1H-1,2,3-benzotriazole [reagent, manufactured by Tokyo Chemical Industry Co., Ltd.]

[0064] The procedure for preparing component E2 is as follows. <Procedure for preparing component E2> Maleic anhydride (reagent, manufactured by Tokyo Chemical Industry Co., Ltd., 30 g) and xylene (first-grade reagent, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., 100 g) were added to a 300 mL three-necked glass flask connected to a stirring blade, a thermometer, a Dimroth condenser, a 50 mL dropping funnel, a nitrogen gas inlet tube, and a bubbler tube, and the mixture was heated to 100°C using an oil bath to dissolve the mixture. Next, benzoyl peroxide (manufactured by Tokyo Chemical Industry Co., Ltd., 5 g) was dissolved in xylene (20 g) and added to the dropping funnel. Nitrogen gas was introduced, tap water was poured into the Dimroth condenser, and while rotating the Dimroth condenser with a stirring blade, benzoyl peroxide / xylene was added dropwise from the dropping funnel at a uniform rate over 60 minutes. After the dropwise addition, the mixture was stirred at 100°C for 3 hours and then cooled to 25°C. The polymer obtained as a precipitate is removed, 100 g of ion-exchanged water is added to dissolve it, and the xylene is removed under reduced pressure using an evaporator to obtain Component E2. The molar ratios of k and l in Component E2 are determined by dissolving 20 mg of Component E2 in 10 mL of methanol and analyzing by liquid chromatography-mass spectrometry under the following analytical conditions: the content of repeating units having an average number of added moles k is 98.5 mol %, and the content of repeating units having an average number of added moles l is 1.5 mol %. <Analysis conditions> Apparatus: Thermo Q-Exactive Column: L-column 2 ODS (2.1 x 150 mm) A: 10 mM ammonium acetate aqueous solution B: 10 mM ammonium acetate methanol solution Oven temperature: 40°C Injection volume: 5 μL Flow rate: 0.2 mL / min B% (min): 5 (0) - 5 (3) - 100 (15) - 100 (20) - 5 (20.1) - 5 (30) Detector: MS (ESI) positive, negative Scan range: m / z 500-1000

[0065]

[0066] 3. Measurement of Each Parameter [Average Secondary Particle Diameter of Silica Particles] 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 (a 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 diameter (D50) at which the cumulative volume fraction of the particle size distribution obtained at 20 integration times and a detection angle of 173° reached 50% was determined, and this was taken as the average secondary particle diameter of the colloidal silica. The results are shown in Table 3.

[0067] [Average particle size ratio d / d0 of silica particles (component A)] 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 3 into a Disposable Sizing Cuvette (polystyrene cell) to a height of 10 mm from the bottom. The Z-average size of the particle size distribution obtained at an accumulation count of 20 and a detection angle of 173° was determined and used as the average particle size d of the silica particles. Average particle size d0 The average particle size d0 of component A was measured by pouring an aqueous dispersion obtained by stirring and mixing the silica particles (component A), phosphoric acid (component B), hydrogen peroxide (component D), and ion-exchanged water shown in Table 3, from the polishing composition in Table 3, into a Disposable Sizing Cuvette (a polystyrene cell) to a height of 10 mm from the bottom, and then using dynamic light scattering (apparatus name: "Zetasizer Nano ZS" manufactured by Malvern Panalytical). The Z-average size of the particle size distribution obtained at an accumulation count of 20 and a detection angle of 173° was determined and used as the average particle size d0 of the silica particles. Average particle size ratio d / d0 The average particle size ratio d / d0 was calculated using the obtained average particle size d and average particle size d0. The results are shown in Table 3.

[0068] [Weight-average molecular weight of polymer (component C or non-component C) and component E2] The weight-average molecular weight of polymer (component C or non-component C) and component E2 was measured by gel permeation chromatography (GPC) under the following conditions. The results are shown in Tables 1 and 2. <Measurement conditions> Column: TSKgel GMPWXL + TSKgel GMPWXL (manufactured by Tosoh Corporation) Eluent: 0.2 M phosphate buffer / CH3CN = 7 / 3 (volume ratio) Temperature: 40°C Flow rate: 1.0 mL / min Sample size: 2 mg / mL Detector: RI Standard: sodium polystyrene sulfonate (weight-average molecular weight: 1,100, 3,610, 14,900, 152,000, manufactured by Polmer Standards Service)

[0069] [Zeta Potential of Polymer (Component C or Non-Component C) (Zeta Potential of the Present Disclosure)] The zeta potential of a polymer (Component C or Non-Component C) is the average value of measurements taken twice under the following conditions for a composition (no silica particles) (a zeta potential measurement sample prepared as described below) comprising a water-soluble polymer (Component C or Non-Component C, 0.5% by mass concentration) and water, with phosphoric acid (Component B) added as needed so that the pH at 25°C is 1.5. <Preparation of Zeta Potential Measurement Sample> A zeta potential measurement sample (a zeta potential measurement sample of the present disclosure) was prepared using a polymer (Component C or Non-Component C), phosphoric acid (Component B), and water so that the pH at 25°C was 1.5 (measured 2 minutes after electrode immersion) and the concentration of Component C was 0.5% by mass. <Measurement conditions> Measurement device: Zetasizer Nano ZS, manufactured by Malvern Panalytical Measurement cell: DTS1070, manufactured by Malvern Panalytical Measurement temperature: 25°C Refractive index (RI) of sample: 1.50 Absorption coefficient of sample: 0.00 Solvent: water (viscosity at 25°C: 0.8872 cP, RI = 1.33, dielectric constant: 78.5) Equilibration time: 120 seconds Conversion formula: Huckel method (κα value set to 1.00) *κ: Debye-Huckel parameter, α: particle radius (here, radius of polymer particle) Number of accumulations: 200 The attenuator strength and measurement position were set automatically.

[0070] [Measurement of pH] 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 immersing the electrode in the polishing composition was adopted. The results are shown in Table 3.

[0071] 4. Polishing Method The polishing compositions prepared in Examples 1 to 11, Reference Example 1, and Comparative Examples 1 to 4 were used to polish the following substrates under the polishing conditions shown below. Then, the polishing rate and the number of scratches were measured. The results are shown in Table 3.

[0072] [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 alumina abrasive grains. The substrate had a thickness of 0.6 mm, an outer diameter of 97 mm, an inner diameter of 25 mm, and a centerline average roughness (Ra) of 1 nm as measured by an AFM (Digital Instrument NanoScope IIIa Multimode AFM).

[0073] [Polishing conditions] Polishing tester: "Double-sided 9B polisher" manufactured by SpeedFam Co., Ltd. Polishing pad: Suede type manufactured by Fujibo Co., Ltd. (foam layer: polyurethane elastomer, thickness 0.7 mm, average pore size 10 μm) Supply rate of polishing composition: 100 mL / min (1 cm of substrate to be polished) 2 Supply rate per unit: 0.145 mL / min) Lower platen rotation speed: 24 rpm Polishing load: 10.0 kPa Polishing time: 6 minutes Number of substrates: 10

[0074] 5. Evaluation [Evaluation of Polishing Rate] The weight of each substrate was measured before and after polishing using a 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 3 as relative values, with Comparative Example 1 set to 100. Mass loss (mg) = {mass before polishing (mg) - mass after polishing (mg)} Polishing rate (mg / min) = mass loss (mg) / polishing time (min)

[0075] [Scratch Evaluation] Measuring equipment: "Candela OSA6110" manufactured by KLA-Tencor Corporation Evaluation: Four substrates were randomly selected from the substrates 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 for the number of scratches are shown in Table 3 as relative values, with Comparative Example 1 set to 100.

[0076] [Evaluation of Storage Stability] (Example 1) A solution was prepared by removing components A and D from the polishing liquid composition of Example 1 in Table 3 and concentrating the composition 20 times. That is, a solution containing 20 mass % phosphoric acid and 100 ppm mass % component C1 was stored in a thermostatic bath at 60°C for 7 days. The stored solution was returned to room temperature, and the transmittance was measured under the conditions described below. The transmittance values ​​at 800 nm are shown in Table 3. Note that, since precipitates may solidify at the bottom of the storage container, making sampling and measurement impossible, samples in which no precipitate or the like was visually observed before or after storage in the thermostatic bath were rated "A." Samples in which precipitates were generated were rated "B." (A sample having a transmittance of 99% or more and no visible precipitate was determined to have excellent storage stability.) [Conditions for measuring transmittance] Apparatus: UV-2700 manufactured by Shimadzu Corporation Measurement wavelength: 800 nm Solution used in background measurement: Pure water (Examples 2 to 11, Reference Example 1, and Comparative Examples 1 to 4) The storage stability of Examples 2 to 11, Reference Example 1, and Comparative Examples 1 to 4 was also evaluated in the same manner as in Example 1 above.

[0077]

[0078] As shown in Table 3 above, the polishing compositions of Examples 1 to 11 were able to achieve both an improved removal rate and reduced scratches on the substrate surface after polishing, compared to Comparative Examples 1 to 4 and Reference Example 1, which did not contain Component C. Furthermore, it was found that the polishing compositions of Examples 1 to 11 had excellent storage stability.

[0079] According to the present disclosure, for example, a magnetic disk substrate suitable for high recording density can be provided.

Claims

1. A polishing liquid composition for magnetic disk substrates, comprising silica particles (component A), an acid (component B), a polymer (component C), and water, wherein the pH of the polishing liquid composition is 1 or more and 5 or less, and component C is a copolymer of a monomer having a phenolic hydroxyl group and a monomer having a phenolic hydroxyl group and a nitrogen atom-containing functional group at the o (ortho) position or m (meta) position of the phenolic hydroxyl group.

2. The polishing composition according to claim 1, wherein the ratio d / d0 of the average particle size d of the silica particles (component A) in the polishing composition to the average particle size d0 of the silica particles (component A) in a composition obtained by excluding component C from the polishing composition is 1.4 or less.

3. The polishing composition according to claim 1 or 2, wherein component C is a compound having a structure represented by the following formula (I): In formula (I), R 1 and R 2 are each independently a hydrogen atom, a hydrocarbon group having 1 to 3 carbon atoms, or a hydroxyalkyl group having 1 to 3 carbon atoms. 1 and R 2 may form a ring structure. x is 1 or 2, and y is 1 or 2. m and n each represent a molar ratio, and satisfy m+n=100, 20≦m≦80, and 20≦n≦80.

4. The polishing composition according to any one of claims 1 to 3, wherein component C is a polymer having a zeta potential of +1 mV to +40 mV as measured using the following zeta potential measurement sample: A composition having a pH of 1.5 and consisting of water, component C, and an acid (component B), the content of component C in the composition being 0.5% by mass.

5. A polishing composition according to any one of claims 1 to 4, wherein the content of component C in the polishing composition is 10 ppm by mass or more and 100 ppm by mass or less.

6. A polishing composition according to any one of claims 1 to 5, wherein the mass ratio A / C of the content of component A to the content of component C in the polishing composition is 300 or more and 5,000 or less.

7. The polishing composition according to any one of claims 1 to 6, wherein the weight average molecular weight of component C is 1,000 or more and 50,000 or less.

8. The polishing composition according to any one of claims 1 to 7, further comprising an oxidizing agent (component D).

9. The polishing composition according to any one of claims 1 to 8, further comprising at least one compound (component E) selected from aromatic compounds having a sulfonic acid group or a carboxylic acid group in the molecule, and azole compounds.

10. A method for polishing a substrate, comprising polishing a substrate to be polished with the polishing composition according to any one of claims 1 to 9, wherein the substrate to be polished is a substrate used in the manufacture of magnetic disk substrates.

11. 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 any one of claims 1 to 9.