Polishing liquid

Abstract

One embodiment of the present disclosure provides a polishing liquid that enables improved polishing speed without increasing scratches even on a thinned substrate.　One embodiment of the present disclosure relates to a polishing liquid that contains silica particles (component A), a compound (component B) represented by structural formula (I), a water-soluble polymer (component C) containing a constituent unit derived from a monomer having a carboxy group, and an aqueous medium, and that satisfies formula (II), where B (mol) is the number of moles of nitrogen atoms in component B and C (mol) is the number of moles of carboxy groups in component C. (I): R1-N(R2)-(CH2)n-N(R3)-R4-X; (II): B / C < 0.8

Description

polishing liquid

[0001] The present disclosure relates to a polishing liquid, a method for manufacturing a magnetic disk substrate, a method for polishing a substrate, and a method for improving the polishing rate of a substrate.

[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, it is necessary to reduce the unit recording area and improve the detection sensitivity of weakened magnetic signals. To address this demand, technological developments are underway to further reduce the flying height of magnetic heads. To address these demands, magnetic disk substrates are increasingly being required to improve smoothness and flatness (reducing surface roughness, waviness, and edge sagging) and reduce surface defects (reducing residual abrasive grains, scratches, protrusions, pits, etc.).

[0003] In response to such demands, in order to achieve both improved surface quality (smoother and fewer scratches) and improved productivity, a multi-stage polishing method having two or more polishing steps is often adopted in manufacturing methods of magnetic disk substrates. Generally, to satisfy the demand for smoothness, an abrasive containing colloidal silica particles is used, and from the viewpoint of improving productivity, a polishing solution containing alumina particles as abrasive grains is used. However, when alumina particles are used as abrasive grains, the alumina particles may penetrate into the substrate, causing defects in the magnetic disk substrate.

[0004] Therefore, for example, Japanese Patent Laid-Open No. 2019-119782 (Patent Document 1) and Japanese Patent Laid-Open No. 2019-182955 (Patent Document 2) propose polishing compositions that do not contain alumina particles but contain silica particles as abrasive grains.

[0005] In one aspect, the present disclosure relates to a polishing liquid containing silica particles (component A), a compound (component B) represented by the following structural formula (I), a water-soluble polymer (component C) containing a structural unit c1 derived from a monomer having a carboxy group, and an aqueous medium, wherein the polishing liquid satisfies the following formula (II) when the number of moles of nitrogen atoms in component B is B (mol) and the number of moles of carboxy groups in component C is C (mol). 1 -N(R 2 )-(CH2) n-N(R 3 )-R 4 -X...(I) In the above structural formula (I), R 1 , R 2 , and R 3 are each independently a hydrogen atom or a hydrocarbon group, and R 4 is a bond or a hydrocarbon group, and X is selected from a hydrogen atom, a hydroxyl group, and an amino group. 2 and R 3 may be bonded to each other to form a cyclic structure, and n is an integer of 1 or more and 15 or less. B / C<0.8 (II)

[0006] In one aspect, the present disclosure relates to a method for manufacturing a magnetic disk substrate, including a polishing step of polishing a substrate to be polished having a thickness of 1.5 mm or less using the polishing liquid of the present disclosure.

[0007] 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 of the present disclosure, wherein the substrate to be polished is a substrate having a thickness of 1.5 mm or less that is used in the manufacture of magnetic disk substrates.

[0008] In one aspect, the present disclosure relates to a method for improving a polishing rate for a substrate, the method comprising polishing a substrate to be polished with the polishing liquid of the present disclosure, wherein the substrate to be polished is a substrate having a thickness of 1.5 mm or less that is used in the manufacture of magnetic disk substrates.

[0009] In one aspect, the present disclosure relates to a polishing liquid kit for producing the polishing liquid of the present disclosure, which is one selected from the following (i) to (iii): (i) a set of a silica dispersion containing component A and an aqueous medium and an aqueous additive solution containing component B and component C; (ii) a set of a silica dispersion containing component A, component B, and an aqueous medium and an aqueous additive solution containing component C; or (iii) a set of a silica dispersion containing component A, component C, and an aqueous medium and an aqueous additive solution containing component B.

[0010] In one aspect, the present disclosure relates to a polishing liquid comprising silica particles (component A), a compound (component B) represented by the following structural formula (I), a water-soluble polymer (component C) containing a structural unit c1 derived from a monomer having a carboxy group, and an aqueous medium, wherein the polishing liquid satisfies the following formula (II) when the number of moles of nitrogen atoms in component B blended in the polishing liquid is B (mol) and the number of moles of carboxy groups in component C is C (mol). 1 -N(R 2 )-(CH2) n -N(R 3 )-R 4 -X...(I) In the above structural formula (I), R 1 , R 2 , and R 3 are each independently a hydrogen atom or a hydrocarbon group, and R 4 is a bond or a hydrocarbon group, and X is selected from a hydrogen atom, a hydroxyl group, and an amino group. 2 and R 3 may be bonded to each other to form a cyclic structure, and n is an integer of 1 or more and 15 or less. B / C<0.8 (II)

[0011] In recent years, substrates have become thinner, and as the substrate becomes thinner, the amount of polishing solution acting on the substrate decreases, making it difficult to ensure a sufficient polishing rate. In addition, there is generally a trade-off between polishing rate and scratches, and improving one will inevitably worsen the other.

[0012] Therefore, the present disclosure provides a polishing liquid that can improve the polishing rate without increasing scratches even on thinned substrates, and a method for manufacturing a magnetic disk substrate using the same.

[0013] The present disclosure is based on the finding that when a polishing liquid containing silica particles, a compound represented by structural formula (I), and a specific water-soluble polymer is used to polish a magnetic disk substrate, the polishing rate can be improved without increasing scratches, even for thin substrates, for example, those having a thickness of 1.5 mm or less.

[0014] That is, in one aspect, the present disclosure relates to a polishing liquid containing silica particles (component A), a compound (component B) represented by the following structural formula (I), a water-soluble polymer (component C) containing a structural unit c1 derived from a monomer having a carboxy group, and an aqueous medium, wherein the polishing liquid (hereinafter also referred to as the "polishing liquid of the present disclosure") satisfies the following formula (II) when the number of moles of nitrogen atoms in component B contained in the polishing liquid is B (mol) and the number of moles of carboxy groups in component C is C (mol). 1 -N(R 2 )-(CH2) n -N(R 3 )-R 4 -X...(I) In the above structural formula (I), R 1 , R 2 , and R 3 are each independently a hydrogen atom or a hydrocarbon group, and R 4 is a bond or a hydrocarbon group, and X is selected from a hydrogen atom, a hydroxyl group, and an amino group. 2 and R 3 may be bonded to each other to form a cyclic structure. n is an integer of 1 or more and 15 or less. In the present disclosure, a bond is a direct bond in which no atom or atomic group is present. R 4 is a bond, "-R 4 "-X" becomes "-X". B / C<0.8 (II)

[0015] According to one aspect of the present disclosure, it is possible to provide a polishing liquid that can improve the polishing rate without increasing scratches on a thinned substrate.

[0016] The mechanism by which the effects of the present disclosure are manifested is unclear, but is speculated as follows. In the present disclosure, by using a compound represented by structural formula (I) (component B) in combination with a specific water-soluble polymer (component C), component B interacts with component C, forming a composite of component B and component C. This composite has adsorptivity to the polishing pad and silica particles (component A), and it is believed that the silica particles (component A) are retained on the polishing pad via the composite, increasing the amount of polishing solution acting on the substrate and improving the polishing rate. Furthermore, it is believed that increasing the amount of polishing solution reduces the frequency of direct contact between the substrate and the polishing pad, reducing friction and preventing an increase in scratches. On the other hand, when component B is present in excess relative to the carboxyl groups of component C, free component B is generated that is not involved in complex formation. Since free component B adsorbs to the substrate surface and inhibits substrate polishing, it is believed that the effect of improving the polishing rate is specifically manifested when the ratio of components B and C satisfies formula (II). However, the present disclosure need not be interpreted as being limited to these mechanisms.

[0017] In the present disclosure, a "scratch" refers to a minute scratch on the surface of a magnetic disk substrate or a semiconductor device substrate, the depth of which is 1 nm or more but less than 100 nm, the width of which is 5 nm or more but less than 500 nm, and the length of which is 100 μm or more. Scratches on the substrate surface can be detected using an optical defect inspection device and can be quantitatively evaluated as the number of scratches. The number of scratches can be specifically evaluated using the method described in the examples.

[0018] [Silica Particles A (Component A)] The polishing liquid of the present disclosure contains silica particles (hereinafter also referred to as "Component A") as abrasive grains. Component A is preferably used in the form of a slurry in which the silica particles are dispersed in an aqueous medium. Component A may be used alone or in combination of two or more types.

[0019] From the viewpoint of improving the polishing rate, D10 of component A in terms of weight measured by centrifugal sedimentation is preferably 5 nm or more, more preferably 10 nm or more, and even more preferably 11 nm or more, and from the viewpoint of not increasing scratches, D10 of component A in terms of weight measured by centrifugal sedimentation is preferably 35 nm or less, more preferably 25 nm or less, and even more preferably 14 nm or less. More specifically, D10 of component A in terms of weight measured by centrifugal sedimentation is preferably 5 nm or more and 35 nm or less, more preferably 10 nm or more and 25 nm or less, and even more preferably 11 nm or more and 14 nm or less.

[0020] The D50 of component A measured by centrifugal sedimentation in terms of weight is preferably 10 nm or more, more preferably 15 nm or more, and even more preferably 17 nm or more from the viewpoint of improving the polishing rate, and is preferably 40 nm or less, more preferably 30 nm or less, and even more preferably 20 nm or less from the viewpoint of not increasing scratches. More specifically, the D50 of component A measured by centrifugal sedimentation is preferably 10 nm or more and 40 nm or less, more preferably 15 nm or more and 30 nm or less, and even more preferably 17 nm or more and 20 nm or less.

[0021] The D90 of component A, calculated as a weight by centrifugal sedimentation, is preferably 65 nm or less, more preferably 60 nm or less, even more preferably 55 nm or less, and even more preferably 52 nm or less, from the viewpoint of not increasing scratches, and is preferably 30 nm or more, more preferably 35 nm or more, and even more preferably 40 nm or more, from the viewpoint of improving the polishing rate. More specifically, the D90 of component A, calculated as a weight by centrifugal sedimentation, is preferably 30 nm or more and 65 nm or less, more preferably 35 nm or more and 60 nm or less, even more preferably 40 nm or more and 55 nm or less, and even more preferably 40 nm or more and 52 nm or less.

[0022] In this disclosure, the D10, D50, and D90 values ​​calculated by centrifugal sedimentation in terms of weight refer to the particle sizes at which the cumulative frequency from the smallest diameter side is 10%, 50%, and 90%, respectively, in the particle size distribution calculated by centrifugal sedimentation in terms of weight obtained by centrifugal sedimentation. In this disclosure, in one or more embodiments, centrifugal sedimentation is a method of classifying and detecting particles by size based on differences in sedimentation velocity (disk centrifugal sedimentation light transmission method). The particle size distribution calculated by centrifugal sedimentation can be measured using a disc centrifugal particle size distribution analyzer (CPS Disc Centrifuge). In the following description, the particle size distribution calculated by centrifugal sedimentation is sometimes referred to as the "particle size distribution measured by CPS measurement." Specifically, it can be calculated using the measurement method described in the Examples.

[0023] Examples of methods for adjusting the particle size distribution of component A in terms of weight by centrifugal sedimentation include methods for adjusting the time, temperature, and concentration during the growth process of silica particles. Other embodiments of methods for adjusting the particle size distribution of component A in terms of weight by centrifugal sedimentation include methods for providing a desired particle size distribution by adding new core particles during the particle growth process in the production stage, and methods for providing a desired particle size distribution by mixing two or more types of silica particles having different particle size distributions.

[0024] From the viewpoint of improving the polishing rate without increasing scratches, the average secondary particle diameter of component A is preferably 1 nm or more, more preferably 5 nm or more, even more preferably 10 nm or more, and even more preferably 20 nm or more. From the same viewpoint, it is preferably 50 nm or less, more preferably 40 nm or less, even more preferably 30 nm or less, and even more preferably 25 nm or less. More specifically, the average secondary particle diameter of component A is preferably 1 nm or more and 50 nm or less, more preferably 5 nm or more and 40 nm or less, even more preferably 10 nm or more and 30 nm or less, and even more preferably 20 nm or more and 25 nm or less. In the present disclosure, the average secondary particle diameter of component A refers to the particle size (D50) at which the cumulative volume fraction from the small diameter side of the particle size distribution obtained based on the scattering intensity distribution measured by dynamic light scattering (DLS) is 50%. The average secondary particle diameter of component A in the present disclosure can be specifically obtained by the method described in the Examples.

[0025] Suitable shapes of component A include spherical particles and cocoon-shaped particles. In the present disclosure, when component A is a cocoon-shaped particle, it means that the diameter perpendicular to the longitudinal direction of the particle has a minimum value along either longitudinal direction. Furthermore, when component A is a spherical particle, it means that the diameter perpendicular to the longitudinal direction of the particle does not have a minimum value along either longitudinal direction. Among these, from the viewpoint of improving the polishing rate without increasing scratches, it is more preferable that component A is a spherical particle. In the present disclosure, the number ratio of spherical particles in component A is preferably more than 50%, more preferably 75% or more, even more preferably 90% or more, and even more preferably 95% or more. Examples of methods for adjusting the shape of component A include adjusting the dripping rate, reaction temperature, and concentration of the silicic acid solution during the growth process of silica particles. In the present disclosure, the shape of component A can be determined by observing particles in one field of view using an electron microscope.

[0026] The loss on ignition of component A on a dry mass basis (hereinafter also referred to as "loss on ignition WL": unit = mass%) is preferably 0.1 mass% or more, more preferably 0.5 mass% or more, and even more preferably 1 mass% or more or 1.0 mass% or more, from the viewpoint of improving the polishing rate without increasing scratches, and from the same viewpoint, is preferably 5 mass% or less, more preferably 3 mass% or less, and even more preferably 2 mass% or less. More specifically, the loss on ignition WL on a dry mass basis of component A is preferably 0.1 mass% or more and 5 mass% or less, more preferably 0.5 mass% or more and 3 mass% or less, and even more preferably 1 mass% or more and 2 mass% or less or 1.0 mass% or more and 2 mass% or less.

[0027] In one or more embodiments of the present disclosure, the loss on ignition WL on a dry mass basis is a value calculated from the following formula: a sample is prepared by mixing silica particles with water to form a silica slurry, drying the mixture at a constant temperature between 105°C and 180°C, allowing the mixture to stand and return to room temperature, and then drying the sample at a constant temperature between 105°C and 180°C. The loss on drying LOD (units = mass%) is measured; and the loss on ignition LOI (units = mass%) is measured after the sample is heat-treated at 800°C or higher. Specifically, the loss on ignition WL can be calculated using the method described in the Examples. The smaller the loss on ignition WL on a dry mass basis, the smaller the total number of silanol groups contained in 1 g of silica particles (component A). Loss on ignition on a dry mass basis WL=100×{1−(100−LOI) / (100−LOD)} The silanol groups of the silica particles (component A) are considered to be the target sites at which the complex formed of the compound represented by structural formula (I) (component B) and the specific water-soluble polymer (component C) exhibits adsorptivity, and in the present disclosure, when the value of loss on ignition WL of component A is within a certain range, the total number of silanol groups contained in component A can be set to an optimum range for exhibiting adsorptivity with the complex, and it is considered that the removal rate can be improved.

[0028] Examples of methods for adjusting the ignition loss WL of component A include adjusting the dropping rate, reaction temperature, and concentration of the silicic acid solution during the growth process of the silica particles. Other embodiments of the method for adjusting the ignition loss WL of component A include adjusting the desired ignition loss by subjecting existing silica particles to heat treatment, metal modification of surface silanol groups, organic acid modification, or silane coupling treatment, and mixing two or more types of silica particles having different ignition losses to achieve the desired ignition loss.

[0029] Examples of Component A include colloidal silica, precipitated silica, fumed silica, pulverized silica, and surface-modified silica thereof. From the viewpoints of improving the polishing rate and ease of availability, Component A is preferably at least one selected from colloidal silica and precipitated silica. From the viewpoint of improving the polishing rate without increasing scratches, colloidal silica, which is less likely to produce a sharp surface shape or localized high surface hardness, is more preferred. Examples of colloidal silica include those obtained by a method involving particle growth using an aqueous alkali silicate solution as a raw material (hereinafter also referred to as the "water glass method") and a method involving condensation of an alkoxysilane hydrolysate (hereinafter also referred to as the "sol-gel method"). From the viewpoints of ease of production and economic efficiency, those obtained by the water glass method are preferred. The precipitated silica is silica particles obtained by a precipitation method. Examples of methods for producing precipitated silica particles include known methods such as those described in Tosoh Research and Technical Report, Vol. 45 (2001), pp. 65-69. A specific example of a method for producing precipitated silica particles is a precipitation method in which silica particles are precipitated by a neutralization reaction between a silicate such as sodium silicate and a mineral acid such as sulfuric acid. The neutralization reaction is preferably carried out under alkaline conditions at a relatively high temperature, which allows the growth of primary silica particles to proceed rapidly, and the primary particles precipitate as flocs, which are then preferably further pulverized to obtain precipitated silica particles.

[0030] From the viewpoint of improving the polishing rate without increasing scratches, the content of component A in the polishing liquid of the present disclosure is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, even more preferably 1% by mass or more, even more preferably 1.5% by mass or more, even more preferably 3% by mass or more, and from the viewpoint of economy, it is preferably 30% by mass or less, more preferably 20% by mass or less, even more preferably 15% by mass or less, even more preferably 10% by mass or less, even more preferably 7% by mass or less. More specifically, the content of component A in the polishing liquid of the present disclosure is preferably 0.1% by mass or more and 30% by mass or less, more preferably 0.5% by mass or more and 20% by mass or less, even more preferably 1% by mass or more and 15% by mass or less, even more preferably 1.5% by mass or more and 10% by mass or less, even more preferably 3% by mass or more and 7% by 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.

[0031] [Compound Represented by Structural Formula (I) (Component B)] The polishing liquid of the present disclosure contains a compound represented by the following structural formula (I) (hereinafter also referred to as "Component B"). Component B may be one type or a combination of two or more types. Component B may be in the form of a salt of the compound represented by the following structural formula (I). R 1 -N(R 2 )-(CH2) n -N(R 3 )-R 4 -X... (I)

[0032] In the structural formula (I), R 1 , R 2 , and R 3 are each independently a hydrogen atom or a hydrocarbon group, and R 4 is a bond or a hydrocarbon group, and X is selected from a hydrogen atom, a hydroxyl group, and an amino group. 2 and R 3 may be bonded to each other to form a cyclic structure, and n is an integer of 1 or more and 15 or less.

[0033] In the structural formula (I), R 1 , R 2 , and R 3R are each independently preferably a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms, from the viewpoint of improving the polishing rate without increasing scratches. 4 From the same viewpoint, R is preferably a hydrocarbon group having 1 to 4 carbon atoms. 2 and R 3 When they are bonded to each other to form a cyclic structure, R 2 +R 3 is preferably a saturated or unsaturated hydrocarbon group having 2 to 4 carbon atoms, more preferably a saturated or unsaturated hydrocarbon group having 2 to 3 carbon atoms, even more preferably one selected from an ethylene group and a trimethylene group, and even more preferably an ethylene group, from the viewpoint of improving the polishing rate without increasing scratches. X is more preferably one selected from a hydroxyl group and an amino group, even more preferably a hydroxyl group, from the viewpoint of improving the polishing rate without increasing scratches. n is preferably an integer of 1 to 10, more preferably an integer of 2 to 5, even more preferably an integer of 2 to 3, and even more preferably 2, from the viewpoint of improving the polishing rate without increasing scratches. In the present disclosure, component B is preferably a group selected from R in structural formula (I) from the viewpoint of improving the polishing rate without increasing scratches. 2 and R 3 are bonded to each other to form a cyclic structure, and R 2 +R 3 is preferably one selected from an ethylene group and a trimethylene group, and n=2.

[0034] From the viewpoint of improving the polishing rate without increasing scratches, component B is selected from the group consisting of ethylenediamine, N,N,N',N'-tetramethylethylenediamine, 1,2-diaminopropane, trimethylenediamine, 1,4-diaminobutane, hexamethylenediamine, N-methyltrimethylenediamine, N,N-dimethyltrimethylenediamine, N,N-diethyltrimethylenediamine, N,N-dibutyltrimethylenediamine, N,N,N',N'-tetramethyltrimethylenediamine, N,N-dimethylethylenediamine, N,N-diethylethylenediamine, N-ethylethylenediamine, N,N,N',N'-tetramethylethylenediamine, N-(2-hydroxyethyl)ethylenediamine (HEA), N-aminoethylisopropanolamine, N-aminoethyl- At least one selected from N-methylethanolamine, diethylenetriamine, 1,4-diazacyclohexane, 2-methyl-1,4-diazacyclohexane, 2,5-dimethyl-1,4-diazacyclohexane, 1-methyl-1,4-diazacyclohexane (MDC), 1-(2-aminoethyl)-1,4-diazacyclohexane (ADC), and 1-(2-hydroxyethyl)-1,4-diazacyclohexane (HDC) is preferred, and at least one selected from N-(2-hydroxyethyl)ethylenediamine (HEA), 1-methyl-1,4-diazacyclohexane (MDC), 1-(2-aminoethyl)-1,4-diazacyclohexane (ADC), and 1-(2-hydroxyethyl)-1,4-diazacyclohexane (HDC) is more preferred.

[0035] From the viewpoint of improving the polishing rate without increasing scratches, the content of component B in the polishing liquid of the present disclosure is preferably 0.001% by mass or more, more preferably 0.003% by mass or more, and even more preferably 0.005% by mass or more. From the same viewpoint, it is preferably 1% by mass or less, more preferably 0.5% by mass or less, even more preferably 0.1% by mass or less, even more preferably 0.05% by mass or less, and even more preferably 0.02% by mass or less. More specifically, the content of component B in the polishing liquid of the present disclosure is preferably 0.001% by mass or more and 1% by mass or less, more preferably 0.003% by mass or more and 0.5% by mass or less, more preferably 0.005% by mass or more and 0.1% by mass or less, even more preferably 0.005% by mass or more and 0.05% by mass or less, and even more preferably 0.005% by mass or more and 0.02% 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.

[0036] [Water-Soluble Polymer (Component C) Containing Structural Unit c1 Derived from Monomer Having a Carboxy Group] The polishing liquid of the present disclosure contains a water-soluble polymer (hereinafter also referred to as "Component C") containing a structural unit c1 derived from a monomer having a carboxy group (hereinafter also referred to simply as "structural unit c1"). In this disclosure, "monomer" refers to a compound having an ethylenically unsaturated bond. In addition, in this disclosure, "water-soluble" refers to having a solubility in water (20°C) of 0.5 g / 100 mL or more, preferably 2 g / 100 mL or more. Component C may be one type or a combination of two or more types. From the viewpoint of improving the polishing rate without increasing scratches, examples of the structural unit c1 derived from a monomer having a carboxy group include structural units derived from at least one monomer selected from acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, and salts thereof. Among these, structural units derived from at least one monomer selected from acrylic acid and methacrylic acid are preferred. Preferred examples of the salt include alkali metal salts such as lithium, sodium, and potassium; alkaline earth metal salts such as magnesium and calcium; ammonium salts; and alkanolamine salts such as triethanolamine. These can be used alone or in combination of two or more.

[0037] When component C is a polymer containing the structural unit c1 but not containing the structural unit c2 described below, in one or more embodiments, component C may be a copolymer further containing a monomer other than the structural unit c1 and the structural unit c2 as a structural unit. In this case, the ratio (mol %) of the structural unit c1 among all structural units of component C is preferably greater than 50 mol %, more preferably 75 mol % or more, even more preferably 90 mol % or more, even more preferably 95 mol % or more, and even more preferably 100 mol %. When component C is a polymer containing the structural unit c1 but not containing component c2, a suitable example thereof is one selected from polyacrylic acid, polymethacrylic acid, and salts thereof, and more preferably polyacrylic acid.

[0038] In one or more embodiments, component C may further include a structural unit c2 (hereinafter simply referred to as "structural unit c2") derived from a monomer having a sulfonic acid group, from the viewpoint of further improving the polishing rate without increasing scratches. From the same viewpoint, preferred examples of the structural unit c2 derived from a monomer having a sulfonic acid group include structural units derived from at least one monomer selected from isoprene sulfonic acid, styrene sulfonic acid, vinyl sulfonic acid, allyl sulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid (AMPS), 2-methacrylamido-2-methylpropanesulfonic acid, 3-allyloxy-2-hydroxypropanesulfonic acid, and salts thereof. Preferred examples of the salt include alkaline earth metal salts; ammonium salts; and alkanolamine salts such as triethanolamine. These may be used alone or in combination of two or more.

[0039] When component C is a copolymer containing structural units c1 and c2, the molar ratio (c2 / c1) of structural units c2 derived from monomers having sulfonic acid groups to structural units c1 derived from monomers having carboxy groups in all structural units of component C is preferably 20 or less, more preferably 10 or less, even more preferably 6 or less, even more preferably 3 or less, and even more preferably 1 or less, from the viewpoint of improving the polishing rate without increasing scratches, and from the same viewpoint, it is preferably more than 0, more preferably 0.05 or more, even more preferably 0.1 or more, even more preferably 0.2 or more, and even more preferably 0.25 or more. More specifically, the molar ratio (c2 / c1) in all structural units of component C is preferably more than 0 and 20 or less, more preferably 0.05 or more and 10 or less, even more preferably 0.1 or more and 6 or less, even more preferably 0.2 or more and 3 or less, and even more preferably 0.25 or more and 1 or less.

[0040] When component C is a copolymer containing the structural unit c1 and the structural unit c2, in one or more embodiments, component C may be a copolymer that further contains, as a structural unit, a monomer other than the structural unit c1 and the structural unit c2. In this case, from the viewpoint of improving the polishing rate without increasing scratches, the ratio (mol %) of the total content of the structural unit c1 and the structural unit c2 among all the structural units of component C is preferably more than 50 mol %, more preferably 75 mol % or more, even more preferably 90 mol % or more, even more preferably 95 mol % or more, and even more preferably 100 mol %. When component C is a copolymer containing structural units c1 and c2, suitable examples thereof include at least one selected from (meth)acrylic acid / isoprene sulfonic acid copolymer, (meth)acrylic acid / styrene sulfonic acid copolymer, (meth)acrylic acid / 3-allyloxy-2-hydroxypropanesulfonic acid copolymer, (meth)acrylic acid / 2-acrylamido-2-methylpropanesulfonic acid copolymer, and salts thereof, with acrylic acid / 2-acrylamido-2-methylpropanesulfonic acid copolymer being more preferred. In the present disclosure, "(meth)acrylic acid" refers to one or more structures selected from acrylic acid and methacrylic acid. In the present disclosure, the content of each structural unit in all structural units of component C can be considered as the ratio of the amount of each monomer used to the total amount of monomers used in polymerization. When component C contains structural units other than structural unit c1, the arrangement of each structural unit in component C may be random, block, or graft, although random is preferred from the viewpoints of improving the polishing rate and reducing scratches.

[0041] From the viewpoint of improving the polishing rate without increasing scratches, the weight-average molecular weight of Component C is preferably 2,000 or more, more preferably 3,000 or more, even more preferably 4,000 or more, even more preferably 5,000 or more, even more preferably 7,000 or more, and is preferably 500,000 or less, more preferably 300,000 or less, even more preferably 200,000 or less, even more preferably 100,000 or less, and even more preferably 50,000 or less. More specifically, the weight-average molecular weight of Component C is preferably 2,000 or more and 500,000 or less, more preferably 3,000 or more and 300,000 or less, even more preferably 4,000 or more and 200,000 or less, even more preferably 5,000 or more and 100,000 or less, and even more preferably 7,000 or more and 50,000 or less. The weight average molecular weight of Component C can be measured by gel permeation chromatography (GPC), specifically by the method described in the examples.

[0042] The method for producing component C is not particularly limited, but aqueous solution polymerization is preferred. It can be produced by mixing and reacting the various structural units, a polymerization initiator, and a chain transfer agent in a polymerization solvent. Examples of polymerization solvents for 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.

[0043] Known polymerization initiators can be used in the polymerization reaction, with radical polymerization initiators being particularly preferred. Examples of radical polymerization initiators 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-butylcumyl peroxide; and azo compounds such as azobisisobutyronitrile and 2,2-azobis(2-methylpropionamidine) dihydrochloride. From the viewpoint of product stability, at least one selected from persulfates and azo compounds is preferred, with azo compounds such as azobisisobutyronitrile and 2,2'-azobis(2,4-dimethylvaleronitrile) being more preferred. These initiators may be used alone or in combination of two or more.

[0044] In the production of Component C, a chain transfer agent may be appropriately added to the polymerization system to adjust the molecular weight. Examples of chain transfer agents include sodium phosphite, sodium hypophosphite, potassium hypophosphite, sodium sulfite, sodium hydrogen sulfite, mercaptoacetic acid, mercaptopropionic acid, thioglycolic acid, 2-propanethiol, 2-mercaptoethanol, thiophenol, and isopropanol. From the viewpoint of product stability, mercaptopropionic acid and isopropanol are more preferred. These may be used alone or in combination of two or more.

[0045] 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.

[0046] 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.

[0047] After the polymerization reaction, neutralization can be carried out with a basic compound as needed. 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, and organic amines such as aqueous ammonia, monoethanolamine, diethanolamine, and triethanolamine. Ammonia water is preferred from the viewpoint of dispersibility of the produced water-soluble polymer compound and avoiding contamination of the substrate to be polished. The pH value (25°C) after neutralization is preferably 3 or more and 10 or less, more preferably 4 or more and 9 or less, from the viewpoint of improving the stability of the product. Specifically, the product is synthesized by the method described in the examples.

[0048] From the viewpoint of improving the polishing rate without increasing scratches, the content of component C in the polishing liquid of the present disclosure is preferably 0.001% by mass or more, more preferably 0.01% by mass or more, even more preferably 0.03% by mass or more, and even more preferably 0.07% by mass or more. From the same viewpoint, it is preferably 1% by mass or less, more preferably 0.5% by mass or less, even more preferably 0.2% by mass or less, and even more preferably 0.15% by mass or less. More specifically, the content of component C in the polishing liquid of the present disclosure is preferably 0.001% by mass or more and 1% by mass or less, more preferably 0.01% by mass or more and 0.5% by mass or less, even more preferably 0.03% by mass or more and 0.2% by mass or less, and even more preferably 0.07% by mass or more and 0.15% by mass or less. When component C is a combination of two or more types, the content of component C refers to the total content thereof.

[0049] In the polishing liquid of the present disclosure, it is preferable that components B and C form a complex. That is, in the polishing liquid of the present disclosure, it is preferable that components B and C form a complex in an aqueous medium. The formation of the complex of components B and C is preferably based on ionic interaction acting between the nitrogen atom of component B and the carboxy group of component C.

[0050] [B / C Molar Ratio of Nitrogen Atoms of Component B to Carboxy Groups of Component C] From the viewpoint of improving the polishing rate without increasing scratches, the polishing liquid of the present disclosure satisfies the following formula (II), where B (mol) is the number of moles of nitrogen atoms of component B contained in the polishing liquid of the present disclosure, and C (mol) is the number of moles of carboxy groups of component C. The "number of moles B of nitrogen atoms of component B contained in the polishing liquid" can be referred to as the number B (unit = mol) of nitrogen atoms derived from component B in the polishing liquid. The "number of moles C of carboxy groups of component C contained in the polishing liquid" can be referred to as the number C (unit = mol) of carboxy groups derived from component C in the polishing liquid. The "molar ratio B / C" can also be referred to as the ratio of the content of nitrogen atoms derived from component B in the polishing liquid (unit = mol / L) to the content of carboxy groups derived from component C in the polishing liquid (unit = mol / L). B / C<0.8 (II)

[0051] From the viewpoint of improving the polishing rate without increasing scratches, the molar ratio B / C represented by the above formula (II) is less than 0.8, preferably 0.7 or less, more preferably 0.5 or less, even more preferably 0.4 or less, and even more preferably 0.2 or less. From the same viewpoint, it is preferably 0.01 or more, more preferably 0.05 or more, and even more preferably 0.1 or more. More specifically, the molar ratio B / C is preferably 0.01 or more and less than 0.8, more preferably 0.05 or more and 0.7 or less, even more preferably 0.1 or more and 0.5 or less, even more preferably 0.1 or more and 0.4 or less, and even more preferably 0.1 or more and 0.2 or less. The molar ratio B / C represented by the above formula (II) can be calculated by the method described in the Examples.

[0052] [Aqueous Medium] The aqueous medium contained in the polishing liquid of the present disclosure may be distilled water, ion-exchanged water, pure water, ultrapure water, or a mixed solvent of water and a solvent. Examples of such solvents include water-miscible solvents (e.g., alcohols such as ethanol). When the aqueous medium is a mixed solvent of water and a solvent, the proportion of water relative to the total mixed medium is not particularly limited as long as the effects of the present disclosure are not impaired. From an economic standpoint, the proportion of water relative to the total mixed medium is preferably 95% by mass or more, more preferably 98% by mass or more, and even more preferably substantially 100% by mass. In the present disclosure, substantially 100% by mass means that the polishing liquid of the present disclosure is allowed to contain a very small amount of solvent components carried over as impurities from Component A, Component B, Component C, and optional components (Component D, Component E, and other components) that are optionally blended. The content of the aqueous medium in the polishing liquid of the present disclosure may be the remainder excluding Component A, Component B, Component C, and optional components (Component D, Component E, and other components) that are optionally blended. The content of the aqueous medium in the polishing liquid of the present disclosure is preferably 80% by mass or more, more preferably 85% by mass or more, and even more preferably 90% by mass or more, from the viewpoint of improving the polishing rate. From the same viewpoint, it is preferably 99% by mass or less, more preferably 97% by mass or less, and even more preferably 95% by mass or less. The content of water in the polishing liquid of the present disclosure is preferably 80% by mass or more, more preferably 85% by mass or more, and even more preferably 90% by mass or more, from the viewpoint of improving the polishing rate. From the same viewpoint, it is preferably 99% by mass or less, more preferably 97% by mass or less, and even more preferably 95% by mass or less. More specifically, from the same viewpoint, the content of water in the polishing liquid of the present disclosure is preferably 80% by mass or more and 99% by mass or less, more preferably 85% by mass or more and 97% by mass or less, and even more preferably 90% by mass or more and 95% by mass or less.

[0053] In one or more embodiments, the polishing liquid of the present disclosure preferably further contains at least one selected from an acid and an oxidizing agent. In one or more embodiments, the polishing liquid of the present disclosure more preferably contains both an acid and an oxidizing agent. The acid and the oxidizing agent are described below.

[0054] [Acid (Component D)] From the viewpoint of improving the polishing rate without increasing scratches, the polishing liquid of the present disclosure preferably further contains an acid (hereinafter also referred to as "Component D"). In the present disclosure, the acid includes an acid and / or a salt thereof. Component D may be one type or a combination of two or more types. Specific examples of Component D preferably 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, polyphosphoric acid, and amidosulfuric acid; and organic acids such as organic phosphoric acid and organic phosphonic acid. Furthermore, examples of salts of these acids include salts of the above acids with at least one selected from metals, ammonia, and alkylamines, and specific examples of the metals include metals belonging to Groups 1 to 11 of the periodic table. In the present disclosure, from the viewpoint of improving the polishing rate without increasing scratches, Component D is preferably at least one selected from phosphoric acid, sulfuric acid, and 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP), more preferably at least one selected from sulfuric acid and phosphoric acid, and even more preferably phosphoric acid.

[0055] When the polishing liquid of the present disclosure contains component D, the content of component D in the polishing liquid of the present disclosure is preferably 0.001% by mass or more, more preferably 0.01% by mass or more, even more preferably 0.05% by mass or more, and even more preferably 0.1% by mass or more, from the viewpoint of improving the polishing rate without increasing scratches. From the same viewpoint, it is preferably 5% by mass or less, more preferably 4% by mass or less, even more preferably 3% by mass or less, and even more preferably 2.5% by mass or less. More specifically, the content of component D in the polishing liquid of the present disclosure is preferably 0.001% by mass or more and 5% by mass or less, more preferably 0.01% by mass or more and 4% by mass or less, even more preferably 0.05% by mass or more and 3% by mass or less, and even more preferably 0.1% by mass or more and 2.5% by mass or less. When component D is a combination of two or more types, the content of component D refers to the total content thereof.

[0056] [Oxidizing Agent (Component E)] From the viewpoint of improving the polishing rate without increasing scratches, the polishing liquid of the present disclosure preferably further contains an oxidizing agent (hereinafter also referred to as "Component E"). Component E may be one type or a combination of two or more types. Specific examples of Component E preferably include peroxides, permanganic acid or a salt thereof, chromic acid or a salt thereof, peroxoacid or a salt thereof, oxyacid or a salt thereof, nitric acid, and sulfuric acid. In the present disclosure, Component E is preferably at least one selected from hydrogen peroxide, iron(III) nitrate, peracetic acid, ammonium peroxodisulfate, iron(III) sulfate, and ammonium iron(III) sulfate. 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, hydrogen peroxide is more preferred.

[0057] When the polishing liquid of the present disclosure contains component E, the content of component E in the polishing liquid of the present disclosure is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and even more preferably 0.1% by mass or more, from the viewpoint of further improving the polishing rate, and is preferably 4% by mass or less, more preferably 2% by mass or less, and even more preferably 1.5% by mass or less, from the viewpoint of improving the polishing rate without increasing scratches. More specifically, the content of component E in the polishing liquid of the present disclosure is preferably 0.01% by mass or more and 4% by mass or less, more preferably 0.05% by mass or more and 2% by mass or less, and even more preferably 0.1% by mass or more and 1.5% 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.

[0058] [Other Components] The polishing liquid of the present disclosure may contain other components as needed, as long as the effects of the present disclosure are not impaired. Examples of other components include amine compounds other than Component B, water-soluble polymers other than Component C, heterocyclic aromatic compounds, corrosion inhibitors, thickeners, dispersants, rust inhibitors, basic substances, surfactants, and polishing rate enhancers.

[0059] In one or more embodiments, the polishing liquid of the present disclosure may be substantially free of urea derivatives. The content of urea derivatives in the polishing liquid of the present disclosure is preferably less than 0.0001% by mass, more preferably 0.00001% by mass or less, and even more preferably 0% by mass (i.e., no urea derivatives are present). In one or more embodiments, the polishing liquid of the present disclosure may be substantially free of urethane softening agents having a weight-average molecular weight of 5,000 or less. The content of urethane softening agents having a weight-average molecular weight of 5,000 or less in the polishing liquid of the present disclosure is preferably less than 0.001% by mass, more preferably 0.0001% by mass or less, and even more preferably 0% by mass (i.e., no urea derivatives are present).

[0060] [Alumina Abrasive Grains] From the viewpoint of reducing protrusion defects, the polishing liquid of the present disclosure preferably does not substantially contain alumina abrasive grains. In one or more embodiments, "substantially does not contain alumina abrasive grains" in the present disclosure may include not containing alumina particles, not containing alumina particles in an amount that functions as abrasive grains, or not containing alumina particles in an amount that affects the polishing results. Specifically, in one or more embodiments, from the viewpoint of reducing protrusion defects, the content of alumina abrasive grains in the polishing liquid of the present disclosure is preferably 5% by mass or less, more preferably 2% by mass or less, even more preferably 1% by mass or less, even more preferably 0.1% by mass or less, even more preferably 0.05% by mass or less, even more preferably 0.02% by mass or less, and even more preferably substantially 0% by mass (i.e., not contained). Furthermore, in one or more embodiments, the content of alumina particles in the polishing liquid of the present disclosure is preferably 2 mass % or less, more preferably 1 mass % or less, even more preferably 0.5 mass % or less, and even more preferably substantially 0 mass % (i.e., not contained), relative to the total amount of abrasive grains in the polishing liquid.

[0061] [pH] From the viewpoint of improving the polishing rate without increasing scratches, the pH of the polishing liquid of the present disclosure is preferably 0.5 or more, more preferably 0.7 or more, even more preferably 0.9 or more, and even more preferably 1 or more. From the same viewpoint, it is preferably 9 or less, more preferably 6 or less, even more preferably 4 or less, even more preferably 3 or less, even more preferably 2.5 or less, and even more preferably 2 or less. More specifically, the pH of the polishing liquid of the present disclosure is preferably 0.5 or more and 9 or less, more preferably 0.5 or more and 6 or less, even more preferably 0.7 or more and 4 or less, even more preferably 1 or more and 3 or less, even more preferably 1 or more and 2.5 or less, and even more preferably 1 or more and 2 or less. The pH can be adjusted using the aforementioned acids or known pH adjusters. The above pH is the pH of the polishing liquid at 25°C and can be measured using a pH meter, preferably the value measured 2 minutes after immersing the pH meter electrode in the polishing liquid.

[0062] [Method for manufacturing the polishing liquid of the present disclosure] The polishing liquid of the present disclosure can be manufactured by blending component A, component B, component C, an aqueous medium, and, as necessary, optional components (component D, component E, other components) using a known method. Therefore, in one or more embodiments, the polishing liquid of the present disclosure is a mixture of component A, component B, component C, and an aqueous medium. That is, in one or more embodiments, the present disclosure relates to a polishing liquid comprising silica particles (component A), a compound (component B) represented by the following structural formula (I), a water-soluble polymer (component C) containing a structural unit c1 derived from a monomer having a carboxy group, and an aqueous medium, wherein the polishing liquid satisfies the following formula (II) when the number of moles of nitrogen atoms in component B blended in the polishing liquid is B (mol) and the number of moles of carboxy groups in component C is C (mol). R 1 -N(R 2 )-(CH2) n -N(R 3 )-R 4 -X...(I) In the above structural formula (I), R 1 , R 2 , and R 3 are each independently a hydrogen atom or a hydrocarbon group, and R 4is a bond or a hydrocarbon group, and X is selected from a hydrogen atom, a hydroxyl group, and an amino group. 2 and R 3 may bond with each other to form a cyclic structure. n is an integer of 1 or more and 15 or less. B / C<0.8 (II) In one aspect, the present disclosure relates to a method for producing a polishing liquid, comprising 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, the aqueous medium, and, as needed, optional components (component D, component E, other components) simultaneously or in any order. The blending can be carried out using a mixer such as a homomixer, homogenizer, ultrasonic disperser, or wet ball mill. The preferred blending amounts of each component in the methods for producing a silica slurry and a polishing liquid can be the same as the preferred contents of each component in the polishing liquid according to the present disclosure described above.

[0063] In the present disclosure, the "content of each component in the polishing liquid" refers to the content of each component at the time of use, i.e., at the time when the polishing liquid starts to be used for polishing. In one or more embodiments, the content of each component in the polishing liquid in the present disclosure can be considered as the blending amount of each component.

[0064] The polishing liquid of the present disclosure may be produced as a concentrate from the viewpoint of storage and transportation, and may include a form that is diluted before use. That is, in one or more embodiments, the present disclosure relates to a concentrate for obtaining the polishing liquid of the present disclosure. The concentration ratio of the polishing liquid concentrate of the present disclosure is preferably 2 times or more, more preferably 10 times or more, even more preferably 30 times or more, and even more preferably 50 times or more from the viewpoint of production and transportation costs, and is preferably 300 times or less, more preferably 200 times or less, even more preferably 150 times or less, and even more preferably 100 times or less from the viewpoint of storage stability. The concentration ratio of the polishing liquid concentrate of the present disclosure means [solids concentration of the polishing liquid concentrate / solids concentration of the polishing liquid at the time of use]. Here, the "solids concentration of the polishing liquid concentrate" refers to the ratio of the mass of components other than water in the polishing liquid concentrate to the mass of the polishing liquid concentrate, and the "solids concentration of the polishing liquid at the time of use" refers to the ratio of the mass of components other than water in the polishing liquid at the time of use to the mass of the polishing liquid at the time of use. The polishing liquid concentrate of the present disclosure can be used by diluting it with water so that the content of each component at the time of use becomes the above-mentioned content (i.e., the content of each component in the polishing liquid at the time of use).

[0065] [Polishing Liquid Kit] In one aspect, the present disclosure provides a polishing liquid kit for producing the polishing liquid of the present disclosure (hereinafter also referred to as the "polishing liquid kit of the present disclosure"). In one or more embodiments, the polishing liquid kit of the present disclosure includes a polishing liquid kit (two-component polishing liquid) that contains a silica dispersion (slurry) containing component A and an aqueous medium and an additive aqueous solution containing components B and C in a mutually unmixed state, and that is mixed at the time of use and diluted with an aqueous medium as needed to obtain the polishing liquid of the present disclosure. In one or more embodiments, the polishing liquid kit of the present disclosure is preferably one selected from the following: (i) a set of a silica dispersion containing component A and an aqueous medium and an additive aqueous solution containing components B and C; (ii) a set of a silica dispersion containing component A, component B, and an aqueous medium and an additive aqueous solution containing component C; or (iii) a set of a silica dispersion containing component A, component C, and an aqueous medium and an additive aqueous solution containing component B. Preferably, the silica dispersion and the aqueous additive solution are mixed at the time of use and diluted with an aqueous medium as needed to obtain the polishing liquid of the present disclosure. The aqueous medium contained in the silica dispersion of the polishing liquid kit of the present disclosure may be an amount equivalent to the amount of the polishing liquid of the present disclosure, or may be a partial amount. The silica dispersion and the aqueous additive solution may each contain the optional components described above (component D, component E, and other components) as needed. According to one or more embodiments of the present disclosure, a polishing liquid that can improve the polishing rate without increasing scratches can be obtained from the polishing liquid kit of the present disclosure.

[0066] Generally, magnetic disks are manufactured by polishing a substrate that has undergone a grinding process through a rough polishing process and a finish polishing process, followed by a magnetic layer formation process. In one or more embodiments, the polishing liquid of the present disclosure is preferably used for polishing a magnetic disk substrate, and more preferably for finish polishing of a magnetic disk substrate. In the present disclosure, finish polishing refers to polishing in the final polishing process when there are multiple polishing processes for a magnetic disk substrate. Furthermore, in one or more embodiments, the polishing liquid of the present disclosure is preferably used for polishing a substrate that has a thickness of 1.5 mm or less. In the present disclosure, the polishing liquid of the present disclosure is more preferably used for a polished substrate that has a thickness of 1.3 mm or less, even more preferably for a polished substrate that has a thickness of 1.0 mm or less, and even more preferably for a polished substrate that has a thickness of 0.6 mm or less.

[0067] [Method for manufacturing magnetic disk substrate] 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”), which includes a polishing step (hereinafter also referred to as the “polishing step of the present disclosure”) of polishing a substrate to be polished with a thickness of 1.5 mm or less using the polishing liquid of the present disclosure. The polishing step in the substrate manufacturing method of the present disclosure is preferably a finish polishing step.

[0068] [Substrate to be polished] In one or more embodiments, the substrate to be polished in the substrate manufacturing method of the present disclosure is preferably a substrate used for manufacturing a magnetic disk substrate. In one or more embodiments, a magnetic disk substrate can be manufactured by polishing the surface of the substrate to be polished using the polishing liquid of the present disclosure, followed by forming a magnetic layer on the substrate surface by sputtering or the like.

[0069] Examples of materials for the substrate to be polished that are suitable for use in the substrate manufacturing method of the present disclosure include 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 containing these metals as their main components, are particularly suitable. More preferred substrates are 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 preferred. 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.

[0070] The shape of the substrate to be polished that is suitable for use in the substrate manufacturing method of the present disclosure includes shapes having flat portions such as disks, plates, slabs, and prisms, and shapes having curved portions such as lenses, with disk-shaped substrates being more preferred. In the case of disk-shaped substrates to be polished, the outer diameter is preferably 2 to 100 mm, and the thickness is preferably 0.4 to 1.5 mm. In the substrate manufacturing method of the present disclosure, the thickness of the substrate to be polished is preferably 1.5 mm or less, more preferably 1.2 mm or less, even more preferably 1.0 mm or less, even more preferably 0.8 mm or less, and even more preferably 0.6 mm or less, from the viewpoint of achieving the effects of the present disclosure.

[0071] In one or more embodiments of the substrate manufacturing method of the present disclosure, the polishing step is a step of supplying the polishing liquid 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 one or more embodiments, the polishing step is a step of sandwiching the substrate to be polished between platens to which polishing pads such as nonwoven organic polymer-based polishing cloths are attached, and polishing the substrate to be polished by moving the platen and the substrate to be polished while supplying the polishing liquid of the present disclosure to a polishing machine.

[0072] In the substrate manufacturing method of the present disclosure, when the polishing process of the substrate to be polished is performed in multiple stages, the polishing process using the polishing liquid of the present disclosure is preferably performed in the second stage or later, and more preferably in the final polishing process or finish polishing process. In this case, separate polishing machines may be used for each stage to avoid contamination with abrasives or polishing liquids from the previous process, 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 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.

[0073] 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 polishing speed, a suede type polishing pad is preferred.

[0074] The polishing load in the polishing step using the polishing liquid 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 ensuring 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 not increasing scratches. In 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.

[0075] In the polishing step, 2 From the viewpoint of improving the polishing rate, the polishing amount per cm of the substrate to be polished is preferably 0.05 mg or more, more preferably 0.1 mg or more, and even more preferably 0.2 mg or more, and from the same viewpoint, it is preferably 2.5 mg or less, more preferably 2 mg or less, and even more preferably 1.6 mg or less. 2 The amount of polishing per unit area is preferably 0.05 mg or more and 2.5 mg or less, more preferably 0.1 mg or more and 2 mg or less, and even more preferably 0.2 mg or more and 1.6 mg or less.

[0076] In the polishing step using the polishing liquid of the present disclosure, the supply rate of the polishing liquid of the present disclosure is set to 1 / cm of the substrate to be polished from the viewpoint of ensuring the polishing rate. 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.

[0077] The polishing liquid of the present disclosure can be supplied to a polishing machine, for example, by continuously supplying the liquid using a pump or the like. When supplying the polishing liquid to a polishing machine, in addition to a method of supplying a single liquid containing all components, the polishing liquid can also be divided into a plurality of component liquids for blending and supplied as two or more liquids, taking into consideration the storage stability of the polishing liquid, etc. In the latter case, the plurality of component liquids for blending are mixed, for example, in the supply pipe or on the substrate to be polished, to produce the polishing liquid of the present disclosure.

[0078] According to the substrate manufacturing method of the present disclosure, the polishing rate can be improved by using the polishing liquid of the present disclosure.

[0079] [Polishing Method] 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 using the polishing liquid of the present disclosure, wherein the substrate to be polished is a substrate having a thickness of 1.5 mm or less used in the manufacture of magnetic disk substrates. Examples of the substrate to be polished in the polishing method of the present disclosure include the substrates described above. The polishing method of the present disclosure is preferably used in a finish polishing process. In the polishing method of the present disclosure, the thickness of the substrate to be polished is preferably 1.5 mm or less, more preferably 1.2 mm or less, even more preferably 1.0 mm or less, even more preferably 0.8 mm or less, and even more preferably 0.6 mm or less, from the viewpoint of achieving the effects of the present disclosure. According to the polishing method of the present disclosure, by using the polishing liquid of the present disclosure, the polishing rate can be improved without increasing scratches. Therefore, the productivity of substrates (e.g., magnetic disk substrates) with assured substrate quality can be improved. 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.

[0080] [Method for Improving Polishing Rate] In one aspect, the present disclosure relates to a method for improving the polishing rate of a substrate (hereinafter also referred to as the "polishing rate improving method of the present disclosure"), which comprises polishing a substrate to be polished using the polishing liquid of the present disclosure, wherein the substrate to be polished is a substrate having a thickness of 1.5 mm or less used in the manufacture of magnetic disk substrates. Examples of the substrate to be polished in the polishing rate improving method of the present disclosure include the substrates to be polished described above. In the method for improving the polishing rate of the present disclosure, the thickness of the substrate to be polished is preferably 1.5 mm or less, more preferably 1.2 mm or less, even more preferably 1.0 mm or less, still more preferably 0.8 mm or less, and even more preferably 0.6 mm or less, from the viewpoint of achieving the effects of the present disclosure. In one or more embodiments, polishing a substrate to be polished using the polishing liquid of the present disclosure means supplying the polishing liquid of the present disclosure to the surface to be polished of the substrate to be polished, contacting a 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; 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 or the substrate to be polished while supplying the polishing liquid of the present disclosure to a polishing machine. The polishing method and conditions in the method for improving the polishing rate of the present disclosure can be the same as those in the substrate manufacturing method of the present disclosure described above. According to the method for improving the polishing rate of the present disclosure, by using the polishing liquid of the present disclosure, the polishing rate can be improved without increasing scratches.

[0081] The present disclosure will be described in more detail below with reference to examples, but these are merely illustrative examples and the present disclosure is not limited to these examples.

[0082] 1. Preparation of Polishing Liquid (Examples 1 to 18 and Comparative Examples 1 to 4) The polishing liquids of Examples 1 to 18 and Comparative Examples 1 to 4 shown in Table 2 were prepared by blending and stirring component A (A1 to A2 shown in Table 2), component B (B1 to B4 shown in Tables 1 and 2), component C (C1 to C9 shown in Table 2), component D (acid shown in Table 2), component E (hydrogen peroxide), and water. The content (mass %, effective amount) of each component in each polishing liquid is as shown in Table 2. The content of water is the remainder after subtracting component A, component B, component C, component D, and component E from the total amount (100 mass %) of the polishing liquid. The pH of the polishing liquids of Examples 1 to 18 and Comparative Examples 1 to 4 was 1.5.

[0083] The following components A, B, C, D, and E were used to prepare the polishing liquid. (Component A) 7 kg of an acidic silicic acid solution adjusted to a silica concentration of 5% was intermittently added dropwise over 1 to 24 hours to 500 g of a metal silicate aqueous solution adjusted to a pH of 10 to 12 and a silica concentration of 2%, thereby increasing the particle size (build-up). By adjusting the dropping rate of the solution, the silicic acid concentration, reaction temperature, pressure, pH, and other factors, silica particles having silanol groups within the desired range can be obtained. In particular, by controlling particle growth by adjusting the dropping rate, the particle shape and the amount of silanol groups, i.e., the ignition loss, can be adjusted. Silica particles A1 and A2 shown below were prepared using the above method. Component A1: Colloidal Silica I (spherical particles) DLS measurement (volume conversion) average secondary particle diameter D50: 20 nm CPS measurement (weight conversion) particle size D10: 11 nm, D50: 18 nm, D90: 44 nm Loss on ignition: 1.17% by mass Component A2: Colloidal Silica II (spherical particles) DLS measurement (volume conversion) average secondary particle diameter D50: 26 nm CPS measurement (weight conversion) particle size D10: 22 nm, D50: 25 nm, D90: 58 nm Loss on ignition: 2.34% by mass (Component B) Component B1: 1-(2-hydroxyethyl)-1,4-diazacyclohexane [HDC, manufactured by Tokyo Chemical Industry Co., Ltd.] Component B2: 1-methyl-1,4-diazacyclohexane [MDC, manufactured by Tokyo Kasei Kogyo Co., Ltd.] Component B3: N-(2-hydroxyethyl)ethylenediamine [HEA, manufactured by Tokyo Chemical Industry Co., Ltd.] Component B4: 1-(2-aminoethyl)-1,4-diazacyclohexane [ADC, manufactured by Tokyo Chemical Industry Co., Ltd.] (Component C) The abbreviation for acrylic acid was AA, and the abbreviation for 2-acrylamido-2-methylpropanesulfonic acid was AMPS.Component C1: Copolymer of AA / AMPS = 80 / 20 (mol%) [weight average molecular weight: 9,000] (Kao Synthetic Products) Component C2: Copolymer of AA / AMPS = 80 / 20 (mol%) [weight average molecular weight: 30,000] (Kao Synthetic Products) Component C3: Copolymer of AA / AMPS=80 / 20 (mol%) [weight average molecular weight: 100,000] (Kao Synthetic Products) Component C4: Copolymer of AA / AMPS=50 / 50 (mol%) [weight average molecular weight: 10,000] (Kao Synthetic Products) Component C5: AA / AMPS=30 / 70 (mol%) copolymer [weight average molecular weight: 8,000] (Kao Synthetic Products) Component C6: Polyacrylic acid [weight average molecular weight: 5,000] (Kao Synthetic Products) Component C7: AA / AMPS=92 / 8 (mol%) copolymer [weight average molecular weight: 2,000] (Kao Synthetic Product) Component C8: AA / AMPS=15 / 85 (mol%) copolymer [weight average molecular weight: 7,000] (Kao Synthetic Product) Component C9: AA / AMPS=5 / 95 (mol%) copolymer [weight average molecular weight: 8,000] (Kao Synthetic Product) As an example of a production method, the production method of Component C1 is shown below. A 300 mL five-neck glass flask is 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) are connected. Mercaptopropionic acid (0.41 g, manufactured by Tokyo Chemical Industry Co., Ltd.), acrylic acid (25.00 g, manufactured by Tokyo Chemical Industry Co., Ltd.), 2-acrylamido-2-methylpropanesulfonic acid (18 g, manufactured by Tokyo Chemical Industry Co., Ltd.), and ethanol (28.65 g, 99.5% ethanol manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) were placed in dropping funnel 1, and 2,2'-azobis(2,4-dimethylovaleronitrile) (0.11 g, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and ethanol (21.43 g) were placed in dropping funnel 2. Ethanol (50.19 g) was placed in the five-neck glass flask, and nitrogen gas was introduced, tap water was poured into the Dimroth condenser, and the flask was heated to 80°C while rotating with a stirring blade, and the mixture in dropping funnels 1 and 2 was added dropwise at a uniform rate over 60 minutes. After the dropwise addition, the mixture is stirred at 80° C. for 3 hours and cooled to 25° C. 500 g of ethanol is added, and 29% aqueous ammonia (Kanto Chemical Co., Ltd.) is added dropwise with vigorous stirring until the pH reaches 7.0. The precipitated white solid is filtered under reduced pressure and dried in vacuo to obtain C1.In the above examples, polymers (components C2 to C9) having molecular weights within the desired range can be obtained by adjusting the amount of initiator, the amount of chain transfer agent, the reaction temperature, etc. For example, polymers with higher molecular weights can be obtained by reducing the amount of initiator, the amount of chain transfer agent, and the reaction temperature. (Component D) Phosphoric acid [manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., special grade, concentration 85% by mass] Sulfuric acid [manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., special grade, concentration 95% by mass] HEDP (1-hydroxyethane-1,1-diphosphonic acid) [manufactured by Tokyo Chemical Industry Co., Ltd., concentration 60%] (Component E) Hydrogen peroxide [manufactured by ADEKA Corporation, concentration 35% by mass].

[0084]

[0085] 2. Measurement Methods for Each Parameter [Method for Measuring Average Secondary Particle Diameter (D50) at a Cumulative Volume Percentage of 50% as Measured by Dynamic Light Scattering] Component A (colloidal silica) used in preparing the polishing liquid was added to ion-exchanged water to a concentration of 0.25% by mass, and the resulting aqueous dispersion was then placed in a Disposable Sizing Cuvette (polystyrene cell) to a height of 10 mm from the bottom. Measurement was performed using the following apparatus under the following conditions by dynamic light scattering: The particle diameter (D50) at which the cumulative volume percentage from the small diameter end of the particle size distribution reached 50% was determined, and this was taken as the average secondary particle diameter of the colloidal silica. The results are shown in Table 2. <Measurement Conditions> Measurement Instrument: Zetasizer Nano ZS [Malvern Panalytical] Laser: He-Ne, 3.0 mW, 633 nm Scattered Light Detection Angle: 173° Number of Accumulations: 20

[0086] [Method for measuring particle diameters D10, D50, and D90 of silica particles by centrifugal sedimentation (CPS measurement)] Silica particles were diluted with ion-exchanged water to prepare a dispersion containing 0.4 mass% silica particles. The particle size distribution of the prepared sample was measured by centrifugal sedimentation using the following measuring device. The particle sizes at which the cumulative frequency from the small diameter side in the particle size distribution obtained by centrifugal sedimentation in weight terms was 10%, 50%, and 90%, respectively, were defined as D10, D50, and D90. The D90 results are shown in Table 2. <Measurement conditions> Measurement device: CPS DC24000UHR [manufactured by CPS Instruments] Measurement range: 0.0004 to 1 μm Particle extinction coefficient: 0.1 Particle shape factor: 1.0 Rotation speed: 20,000 rpm Calibration standard particle diameter: 0.476 μm Standard particle density: 1.0465 (13%, 34° C.) Density gradient solution: sucrose aqueous solution (8%, 24%) Solvent viscosity: 1.16 cp (13%, 34° C.) Solvent refractive index: 1.3592 (18%, 34° C.) Measurement temperature: 15 to 45° C. Measurement time: 100 to 420 minutes

[0087] [Loss on Ignition] Silica particles were mixed with ion-exchanged water to prepare a 40% by mass silica slurry. The prepared silica slurry was adjusted to pH 3.5 with sulfuric acid and heated at 180°C using a Shimadzu Corporation "MOC63u" infrared moisture meter to remove moisture. The mixture was then left to stand for 10 minutes and returned to room temperature to obtain 2 g of sample. The loss on drying (LOD) (loss of moisture absorbed at room temperature: unit = mass%) was determined for 1 g of the sample using the infrared moisture meter again. The remaining 1 g of sample was placed in a ceramic crucible, fired at 1000°C in a firing furnace for 2 hours, and then radiated in a desiccator for 30 minutes to determine the loss on ignition (LOI) (the sum of the mass lost due to dehydration of silanol groups and the loss of moisture absorbed at room temperature: unit = mass%). Finally, the loss on ignition (unit = mass%) based on the dry mass was calculated using the following formula. The results are shown in Table 2. Loss on ignition on a dry weight basis = 100 x {1 - (100 - LOI) / (100 - LOD)}

[0088] [Weight-average molecular weight of water-soluble polymer (component C)] The weight-average molecular weight of component C was measured by gel permeation chromatography (GPC) under the following conditions. The results are shown in Table 2. <GPC conditions> Column: TSKgel G4000PWXL + TSKgel G2500PWXL (manufactured by Tosoh Corporation) Guard column: TSKguard column PWXL (manufactured by Tosoh Corporation) Eluent: 0.2 M phosphate buffer / CH3CN = 9 / 1 (volume ratio) Temperature: 40°C Flow rate: 1.0 mL / min Sample size: 5 mg / mL Detector: RI Standard substance: Polyacrylic acid Na [Molecular weight (Mp): 115,000, 28,000, 4100, 1250 (manufactured by Sowa Scientific Co., Ltd. and American Polymer Standards Corp.)]

[0089] [Molar ratio B / C of nitrogen atoms of component B to carboxyl acid groups of component C] When the structural unit c1 constituting component C is composed of a monovalent acid such as acrylic acid, the molar ratio B / C of the number of moles of nitrogen atoms of component B (B: unit = mol) to the number of moles of carboxyl groups of component C (C: unit = mol) in the polishing liquid was calculated using the following formula. Here, the unit molecular weight of component C is a value obtained by weighting the molecular weights of each constituent unit constituting component C according to the molar ratio of each constituent unit. For example, for component C1, it is calculated as follows: Composition of C1: AA / AMPS = 80 / 20 (mol%) Molecular weight of AA: 72.06 Molecular weight of AMPS: 207.24 Unit molecular weight of C1: 72.06 x 0.8 + 207.24 x 0.2 = 99.10

[0090] [Measurement of pH] The pH of the polishing solution 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 solution was adopted.

[0091] 3. Substrate Polishing The polishing solutions prepared in Examples 1 to 18 and Comparative Examples 1 to 4 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.

[0092] [Polished Substrate] Ni-P plated aluminum alloy substrates S1 and S2 were used as the polished substrates. The dimensions of S1 and S2 were as follows: S1: thickness 1.27 mm, outer diameter 95 mm, inner diameter 25 mm S2: thickness 0.6 mm, outer diameter 97 mm, inner diameter 25 mm The polished substrates were preliminarily roughly polished with a polishing solution containing an alumina abrasive so that the centerline average roughness Ra measured with an AFM (Digital Instrument NanoScope IIIa Multi Mode AFM) was 1 nm.

[0093] [Polishing conditions] Polishing tester: "Double-sided 9B polisher" manufactured by SpeedFam Co., Ltd. Polishing pad: Suede type manufactured by FILWEL Co., Ltd. (foam layer: polyurethane elastomer, thickness 0.9 mm, average pore size 10 μm) Polishing liquid supply rate: 100 mL / min (1 cm of substrate to be polished) 2 Supply rate per unit: 0.076 mL / min) Upper surface plate rotation speed: -16 rpm Lower surface plate rotation speed: 16 rpm Polishing load: 13.0 kPa Polishing time: 6 minutes Number of substrates: 10

[0094] 4. Evaluation Method [Evaluation of Polishing Rate] The mass of each substrate before and after polishing was measured using a precision balance (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 the polishing rates for the polished substrates S1 and S2 of Comparative Example 1 set at 100. Mass loss (mg) = {mass before polishing (mg) - mass after polishing (mg)} Polishing rate (mg / min) = mass loss (mg) / polishing time (min)

[0095] [Scratch Evaluation] Measuring equipment: "Candela OSA7100" 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 2 as relative values, with Comparative Example 1 set to 100.

[0096] 5. Results The results of each evaluation are shown in Table 2.

[0097]

[0098] As shown in Table 2 above, it was found that the polishing solutions of Examples 1 to 18 were able to improve the polishing rate without increasing scratches compared to the polishing solutions of Comparative Examples 1 to 4. Furthermore, the polishing solutions of Examples 1 to 18 effectively improved the polishing rate not only when a 1.27 mm thick substrate was used, but also when a 0.6 mm thick substrate was used.

[0099] According to one aspect of the present disclosure, it is possible to improve the polishing rate while reducing scratches on the substrate surface after polishing, thereby improving the productivity of substrates with improved substrate quality. The present disclosure can be suitably used in the manufacture of magnetic disk substrates.

Claims

1. A polishing liquid containing silica particles (component A), a compound (component B) represented by the following structural formula (I), a water-soluble polymer (component C) containing a structural unit c1 derived from a monomer having a carboxy group, and an aqueous medium, wherein the polishing liquid satisfies the following formula (II) when the number of moles of nitrogen atoms in component B contained in the polishing liquid is B (mol) and the number of moles of carboxy groups in component C is C (mol). 1 -N(R 2 )-(CH2) n -N(R 3 )-R 4 -X...(I) In the above structural formula (I), R 1 , R 2 , and R 3 are each independently a hydrogen atom or a hydrocarbon group; R 4 R is a bond or a hydrocarbon group, and X is selected from a hydrogen atom, a hydroxyl group, and an amino group. 2 and R 3 may be bonded to each other to form a cyclic structure, and n is an integer of 1 or more and 15 or less. B / C<0.8 (II) 2. The polishing liquid according to claim 1, wherein component A has a particle diameter D90 of 65 nm or less, where D90 is the particle diameter at which the cumulative frequency from the small particle diameter side in the particle size distribution calculated by weight obtained by centrifugal sedimentation is 90%.

3. A polishing liquid as described in claim 1 or 2, wherein component A has an ignition loss of 0.1 mass % or more and 5 mass % or less on a dry mass basis.

4. Component B is ethylenediamine, N,N,N',N'-tetramethylethylenediamine, 1,2-diaminopropane, trimethylenediamine, 1,4-diaminobutane, hexamethylenediamine, N-methyltrimethylenediamine, N,N-dimethyltrimethylenediamine, N,N-diethyltrimethylenediamine, N,N-dibutyltrimethylenediamine, N,N,N',N'-tetramethyltrimethylenediamine, N,N-dimethylethylenediamine, N,N-diethylethylenediamine, N-ethylethylenediamine, N,N,N',N'-tetramethylethylenediamine, N-(2-hydro 4. The polishing liquid according to claim 1, wherein the polishing agent is at least one selected from the group consisting of N-(2-hydroxyethyl)ethylenediamine (HEA), N-aminoethylisopropanolamine, N-aminoethyl-N-methylethanolamine, diethylenetriamine, 1,4-diazacyclohexane, 2-methyl-1,4-diazacyclohexane, 2,5-dimethyl-1,4-diazacyclohexane, 1-methyl-1,4-diazacyclohexane (MDC), 1-(2-aminoethyl)-1,4-diazacyclohexane (ADC), and 1-(2-hydroxyethyl)-1,4-diazacyclohexane (HDC).

5. The polishing liquid according to any one of claims 1 to 4, wherein component C is polyacrylic acid.

6. A polishing liquid according to any one of claims 1 to 4, wherein component C further contains a structural unit c2 derived from a monomer having a sulfonic acid group.

7. The polishing liquid described in claim 6, wherein the molar ratio (c2 / c1) of the structural unit c2 derived from a monomer having a sulfonic acid group to the structural unit c1 derived from a monomer having a carboxy group in all structural units of component C is greater than 0 and less than 20.

8. The polishing liquid according to claim 6 or 7, wherein component C is an acrylic acid / 2-acrylamide-2-methylpropanesulfonic acid copolymer.

9. The polishing liquid according to any one of claims 1 to 8, wherein component B and component C form a complex in the aqueous medium.

10. The polishing liquid according to any one of claims 1 to 9, further comprising at least one selected from the group consisting of an acid and an oxidizing agent.

11. The polishing liquid according to any one of claims 1 to 10, which is used for finish polishing of a magnetic disk substrate.

12. The polishing liquid according to any one of claims 1 to 11, which is used for polishing a substrate having a thickness of 1.5 mm or less.

13. A method for manufacturing a magnetic disk substrate, comprising a polishing step of polishing a substrate having a thickness of 1.5 mm or less with the polishing liquid according to any one of claims 1 to 11.

14. The method for producing a magnetic disk substrate according to claim 13, wherein the polishing step is a finish polishing step.

15. A method for polishing a substrate, comprising polishing the substrate with the polishing liquid according to any one of claims 1 to 11, the substrate being a substrate having a thickness of 1.5 mm or less and used in the manufacture of magnetic disk substrates.

16. A method for improving the polishing rate of a substrate, comprising polishing a substrate to be polished with the polishing liquid according to any one of claims 1 to 11, the substrate to be polished being a substrate having a thickness of 1.5 mm or less that is used in the manufacture of magnetic disk substrates.

17. A polishing liquid kit for producing the polishing liquid according to any one of claims 1 to 12, which is one selected from the following (i) to (iii): (i) a set of a silica dispersion containing component A and an aqueous medium, and an additive aqueous solution containing components B and C; (ii) a set of a silica dispersion containing components A, B, and an aqueous medium, and an additive aqueous solution containing component C; (iii) a set of a silica dispersion containing components A, C, and an aqueous medium, and an additive aqueous solution containing component B.

18. A polishing liquid comprising silica particles (component A), a compound (component B) represented by the following structural formula (I), a water-soluble polymer (component C) containing a structural unit c1 derived from a monomer having a carboxy group, and an aqueous medium, wherein the polishing liquid satisfies the following formula (II) when the number of moles of nitrogen atoms in component B blended in the polishing liquid is B (mol) and the number of moles of carboxy groups in component C is C (mol). R 1 -N(R 2 )-(CH2) n -N(R 3 )-R 4 -X...(I) In the above structural formula (I), R 1 , R 2 , and R 3 are each independently a hydrogen atom or a hydrocarbon group; R 4 R is a bond or a hydrocarbon group, and X is selected from a hydrogen atom, a hydroxyl group, and an amino group. 2 and R 3 may be bonded to each other to form a cyclic structure, and n is an integer of 1 or more and 15 or less. B / C<0.8 (II)

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