Polishing liquid composition

Abstract

To provide a polishing liquid composition that can satisfy both improvement of polishing speed and scratch reduction on a substrate surface after polishing.SOLUTION: Provided, in one aspect, is a polishing liquid composition for magnetic disk substrate which contains silica particles (component A), acid (component B) and aqueous medium, where the component A is silica particles having a kinetic instantaneous corrosion rate in In-situ electrochemical measurement of 170 μA / cm2 or more and less than 330 μA / cm2, and pH of 1 or more and 4 or less. The kinetic instantaneous corrosion rate in In-situ electrochemical measurement is a value of current density obtained by measuring an amount of electrons generated by corrosion reaction of a substrate due to polishing by an electrochemical measurement device.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

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

[0003] In response to such demands, for example, Patent Document 1 discloses a polishing composition containing silica particles, an acid, an oxidizing agent, a water-soluble polymer, a nitrogen-containing organic compound, and water, and having a pH of 4.0 or less. The document describes that in an immersion-washing test in which a magnetic disk substrate plated with Ni-P is immersed in the polishing composition, removed from the polishing composition, washed with water, and then washed with an alkaline aqueous solution, the difference in corrosion potential of the substrate before and after immersion in the polishing composition is within a specified range. Patent Document 2 discloses a polishing liquid for removing excess copper from areas other than the grooves for forming wiring after copper is embedded by electroplating on an insulating film in which grooves have been formed in advance. The polishing liquid contains abrasive grains (e.g., silica), a metal oxidizing agent (e.g., hydrogen peroxide), a compound that dissolves copper and forms a complex with copper (e.g., inorganic acid, organic acid), a pH adjuster, a dissolution rate accelerator (e.g., nitrate) that promotes the dissolution of copper under load, and a dissolution inhibitor (e.g., benzotriazole) that suppresses the dissolution of copper under no load, and has a pH of 3 or less. Patent Document 3 proposes a polishing composition for polishing cobalt-containing materials, the polishing composition comprising an abrasive such as silica, a weak acid removal rate enhancer, an azole-containing corrosion inhibitor, and a pH adjuster, the removal rate enhancer, the corrosion inhibitor, and the pH adjuster each having a pKa between 1 and 18, the pH of the composition being between 7 and 12, and the polishing composition each having less than about 100 parts per million sulfate ions and less than about 100 parts per million halide ions based on the total weight of the composition. Patent Document 4 proposes a polishing composition for polishing a layer containing cobalt, which contains abrasive grains, an acid or a salt thereof having a first acid dissociation constant of 2 or more, an anticorrosive agent, and a dispersant, and has an electrical conductivity of 3 mS / cm or more and a pH of 6.5 or more. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2020-128479 A [Patent Document 2] WO 2006 / 30595 [Patent Document 3] JP 2018-93204 A [Patent Document 4] JP 2018-157164 A Summary of the Invention [Problem to be solved by the invention]

[0005] As the capacity of magnetic disk drives increases, the requirements for the surface quality of substrates become more stringent, and there is a demand for the development of a polishing composition that can further reduce scratches on the substrate surface. Furthermore, in recent years, substrates have become thinner, and the rigidity of the substrate tends to decrease. When the rigidity of the substrate decreases, it becomes difficult to process the substrate, and it becomes necessary to relax the processing conditions. However, when the processing conditions are relaxed (for example, by reducing the processing pressure), conventional silica abrasive grains cannot ensure a sufficient polishing rate. In general, there is a trade-off between the polishing rate and scratches, and there is a problem that improving one will deteriorate the other.

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

[0007] In one embodiment, the present disclosure provides a composition comprising silica particles (component A), an acid (component B), and an aqueous medium, the composition having a dynamic instantaneous corrosion rate of 170 μA / cm in in-situ electrochemical measurement. 2 More than 330μA / cm 2 and a pH of 1 or more and 4 or less. Here, the dynamic instantaneous corrosion rate in the in-situ electrochemical measurement is measured using an electrochemical measurement device that includes a plate electrode evaluation cell in which an evaluation target plate electrode (Ni-P plated aluminum alloy substrate for magnetic disk substrate) is arranged as a working electrode, a reference electrode (silver-silver chloride electrode) and a counter electrode (platinum electrode) are arranged in the cell, a potentiostat connected to each electrode, and a rotation control body having a polishing pad (suede pad) arranged so as to be in contact with the evaluation target plate electrode, and an electrolyte (a polishing liquid composition containing 5 mass% silica particles, 1 mass% phosphoric acid, 0.3 mass% hydrogen peroxide, and water and having a pH of 2.5) is stored in the cell so as to immerse or contact each of the electrodes, and is measured in the following steps. At a liquid temperature of about 26°C, the polishing pad attached to the rotation control body was brought into contact with the working electrode (applied load: 300 g / cm 2 ±100g / cm 2 ), the rotation control body is rotated (rotation speed: 25 rpm). The open circuit voltage measured at this time is taken as the corrosion potential E corr Let us assume that. Corrosion potential E corrWhen the potential is scanned from 0.05 V to 0.5 V anode side using LSV (Linear Sweep Voltammetry) method, the current curve of the anodic reaction is observed, and the current density is measured using the Tafel plot method. This current density is calculated as the dynamic instantaneous corrosion rate.

[0008] In one aspect, the present disclosure relates to a method for producing a magnetic disk substrate, the method comprising the step of polishing a substrate to be polished with the polishing liquid composition of the present disclosure.

[0009] In one aspect, the present disclosure relates to a method for improving a removal rate of a substrate to be polished, the method comprising polishing the substrate to be polished with the polishing liquid composition of the present disclosure. Effect of the Invention

[0010] According to the polishing composition of the present disclosure, in one or a plurality of embodiments, an effect of achieving both an improvement in the removal rate and a reduction in scratches on the substrate surface after polishing can be achieved. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram of an electrochemical measurement apparatus for measuring the dynamic instantaneous corrosion rate of silica particles. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] As mentioned above, in recent years, substrates have become thinner, and the rigidity of the substrate tends to decrease. When the rigidity of the substrate decreases, it becomes difficult to process the substrate, and therefore it is necessary to relax the processing conditions. However, when the processing conditions are relaxed (for example, the processing pressure is reduced), it is not possible to ensure a sufficient polishing rate with conventional silica abrasive grains. The present inventors have discovered that by using silica having a corrosion-accelerating effect on the particle surface, it is possible to improve the polishing rate while reducing scratches. It was also found that the corrosion-accelerating effect of silica particles could be detected by measuring the dynamic instantaneous corrosion rate during polishing using in-situ electrochemical measurements. The present disclosure is based on the discovery that when a polishing liquid composition containing specific silica particles having a corrosion-accelerating effect and an acid and having a pH of 1 to 4 is used for polishing a magnetic disk substrate, the polishing rate can be improved while reducing scratches on the substrate surface after polishing.

[0013] Conventionally, as a method for measuring the corrosion rate of a polishing composition for a substrate to be polished, there is a method (weighing method) in which the substrate to be polished is immersed in the polishing composition and the average corrosion rate for the immersion time is calculated from the change in weight of the substrate before and after immersion. However, the corrosion mechanism of metals in a polishing composition containing an oxidizing agent is that the metal (M) is oxidized by the oxidizing agent (M→MO), and the metal oxide dissolves as metal ions (MO→M n+ ) mechanism is generally used, but this requires that the weight change be observed using a balance or similar device, simultaneously measuring the reaction in which oxygen bonds to increase the substrate weight and the reaction in which metal ions dissolve and decrease the substrate weight. In addition, since the weight change is observed using a balance, the immersion time must be increased until a sufficient weight change occurs (a weight change of several tens of mg is required), which results in a long evaluation time. In contrast, in-situ electrochemical measurement observes the electrons that are generated when the metal dissolves, and this can take as long as 10 -19 The corrosion rate can be accurately measured from a change in substrate weight of about g.

[0014] Another method for estimating the corrosion rate is to immerse the substrate to be polished in the polishing agent composition as described above, and measure the amount of dissolved metal in the liquid by ICP-OES (which can measure in the ppm order). However, if the substrate contains solid abrasive grains, the ICP-OES measurement is likely to lead to equipment failure, and is not practical. In addition, both methods are methods for estimating the static average corrosion rate, and cannot measure the dynamic corrosion rate during polishing. In contrast, in-situ electrochemical measurement is the only method that can observe the dynamic corrosion rate, and the present invention was achieved by observing the dynamic corrosion rate during polishing of silica particles.

[0015] That is, in one embodiment, the present disclosure provides a method for producing a coating composition comprising: a) a silica particle (component A), an acid (component B), and an aqueous medium; and b) a coating composition comprising: a coating material having a dynamic instantaneous corrosion rate of 170 μA / cm in in-situ electrochemical measurement; 2 More than 330μA / cm 2 and a pH of 1 or more and 4 or less (hereinafter also referred to as the "polishing liquid composition of the present disclosure").

[0016] Although the details of the mechanism by which the effects of the present disclosure are manifested are not clear, it is presumed as follows. Conventionally, the corrosion rate of the Ni-P plated substrate was controlled by the acid, oxidizing agent, and protective assistants contained in the polishing agent, but this time, it was newly discovered that the corrosion potential and corrosion rate also change depending on the silica species contained in the polishing agent. This is thought to be because the acid and oxidizing agent contribute to the corrosion reaction near the particle and substrate interface due to the frictional energy and thermal energy generated during polishing at the interface between the silica particle surface and the Ni-P plated substrate. For example, silanol groups react with acid to undergo dehydration condensation and are converted to siloxane groups, and the particle surface is converted to a hydrophobic surface, which increases the frictional force between particles and between particles and substrate, thereby improving the polishing rate. In addition, when the frictional force is increased, heat is easily generated, and the chemical reaction at the particle and substrate interfaces is also improved. As a result, it is thought that the oxidation reaction and corrosion reaction of the substrate by the oxidizing agent are easily promoted, which can achieve a high polishing rate. In other words, by using an abrasive composition containing silica particles having an optimal range of corrosion potential and corrosion rate at which the corrosion (oxidation) reaction proceeds, polishing can be carried out with the best balance of mechanical polishing power and chemical polishing power, and as a result, high-quality substrates that have excellent scratch suppression while having a practically high polishing rate can be produced. However, the present disclosure need not be construed as being limited to these mechanisms.

[0017] In the present disclosure, scratches on the substrate surface can be detected, for example, by an optical defect inspection device and can be quantitatively evaluated as the number of scratches. The number of scratches can be specifically evaluated by the method described in the Examples.

[0018] [Silica particles (component A)] The polishing composition of the present disclosure contains silica particles (hereinafter also referred to as "Component A") as abrasive grains. Component A has a dynamic instantaneous corrosion rate of 170 μA / cm in in-situ electrochemical measurement. 2 More than 330μA / cm 2 The silica particles are those having a particle size of less than 100 nm. Component A may be one type or a combination of two or more types.

[0019] In the present disclosure, the dynamic instantaneous corrosion rate in in-situ electrochemical measurement is a current density value obtained by measuring the amount of electrons generated by the corrosion reaction of the substrate due to polishing using an electrochemical measurement device. Here, the dynamic instantaneous corrosion rate in the in-situ electrochemical measurement is measured using an electrochemical measurement device that includes a plate electrode evaluation cell in which an evaluation target plate electrode (Ni-P plated aluminum alloy substrate for magnetic disk substrate) is arranged as a working electrode, a reference electrode (silver-silver chloride electrode) and a counter electrode (platinum electrode) are arranged in the cell, a potentiostat connected to each electrode, and a rotation control body having a polishing pad (suede pad) arranged so as to be in contact with the evaluation target plate electrode, and an electrolyte (a polishing liquid composition containing 5 mass% silica particles, 1 mass% phosphoric acid, 0.3 mass% hydrogen peroxide, and water and having a pH of 2.5) is stored in the cell so as to immerse or contact each of the electrodes, and is measured in the following steps. At a liquid temperature of about 26°C, the polishing pad attached to the rotation control body was brought into contact with the working electrode (applied load: 300 g / cm 2 ±100g / cm 2 ), the rotation control body is rotated (rotation speed: 25 rpm). The open circuit voltage measured at this time is taken as the corrosion potential E corr Let us assume that. Corrosion potential E corr When the potential is scanned from 0.05 V to 0.5 V anode side using LSV (Linear Sweep Voltammetry) method, the current curve of the anodic reaction is observed, and the current density is measured using the Tafel plot method. This current density is calculated as the dynamic instantaneous corrosion rate. An example of the electrochemical measurement device is an electrochemical measurement device as shown in FIG. In one or more embodiments, the working electrode may be a Ni-P plated aluminum alloy substrate for magnetic disk substrate. The Ni-P plated aluminum alloy substrate for magnetic disk substrate may be a substrate that has been polished and washed. Examples of the polishing method include polishing using a polishing composition containing silica particles. Specifically, examples of the polishing method include polishing (e.g., rough polishing) using a polishing composition containing 5% by mass of colloidal silica with an average primary particle size of 150 nm, 1% by mass of phosphoric acid, 0.8% by mass of hydrogen peroxide, and the balance being water, and polishing (e.g., finish polishing) using a polishing composition containing 5% by mass of colloidal silica with an average primary particle size of 20 nm, 1% by mass of phosphoric acid, 0.4% by mass of hydrogen peroxide, and the balance being water. Examples of the cleaning method include at least one selected from ultrasonic cleaning and brush cleaning. The substrate that has been polished and washed may be a substrate that has been further polished with water-resistant sandpaper, and then rinsed and washed with ethanol and water, and then dried. In one or more embodiments, the polishing pad may be a suede pad. The suede pad may be, for example, a polyurethane soft suede pad. The compression ratio of the polishing pad may be, for example, 20% or less. The polishing pad may be, for example, a polyurethane soft suede pad that has been opened with a diamond dress and then polished with the electrolyte for a predetermined time (for example, 5 hours).

[0020] The dynamic instantaneous corrosion rate is set to 170 μA / cm from the viewpoint of improving the polishing rate and reducing scratches. 2 More than 200 μA / cm 2 More than 240μA / cm is preferable. 2 More preferably, 330 μA / cm 2 Less than 320A / cm 2 Less than 300 μA / cm is preferable. 2 More specifically, the dynamic instantaneous corrosion rate (current density) during polishing is 170 μA / cm2 More than 330μA / cm 2 Less than 200 μA / cm 2 More than 320μA / cm 2 Less than 240 μA / cm is preferable. 2 More than 300μA / cm 2 The following is more preferred:

[0021] The corrosion potential E observed in the in-situ electrochemical measurement corr From the viewpoints of improving the polishing rate and reducing scratches, the corrosion potential E is preferably greater than -0.32 V, more preferably equal to or greater than -0.25 V, and even more preferably equal to or greater than -0.23 V, and from the viewpoint of reducing scratches, the corrosion potential E is preferably equal to or less than -0.19 V, more preferably equal to or less than -0.20 V, even more preferably equal to or less than -0.20 V, and even more preferably equal to or less than -0.21 V. corr The corrosion potential is a potential at which the amount of electrons consumed or generated during the cathodic and anodic reactions in the measurement system are balanced, and no current appears to flow. For example, in the reaction system disclosed in this disclosure, it is a potential at which the amount of electrons generated when nickel oxidizes and dissolves is balanced with the amount of electrons consumed by the electrolysis of water and the reduction reaction of protons and hydrogen peroxide. Generally, a lower corrosion potential value means that the metal species is more likely to be oxidized, but this is merely the ease of oxidation, and the corrosion rate cannot be estimated from the corrosion potential value alone. For example, in Reference 1 "Basics of Electrochemical Measurement of Corrosion - Corrosion Potential" (Materials and Environment, Vol. 67, No. 1, pp2-8 (2018), by Takumi Haruna) and Reference 2 "Electrochemistry and Measurement of Corrosion" (by Toru Mizunare), examples are explained in which the corrosion potential increases and the corrosion rate increases, and examples in which the corrosion potential increases and the corrosion rate decreases. In this way, it is difficult to estimate the corrosion rate from the value of the corrosion potential. The corrosion potential E in this disclosure corr Specifically, it can be measured by the method described in the Examples.

[0022] Component A is produced by a general water glass method. For example, sodium silicate, potassium silicate, or the like is used as the alkali silicate, and Component A can be produced through a process of ripening the alkali silicate, a process of producing a polymerized sol by adding a basic compound, and a growth process. Specific methods will be described in the examples. In one or more embodiments, component A may be made by selecting silica particles having a dynamic instantaneous corrosion rate within a predetermined range from those produced by a water glass method.

[0023] Examples of component A include colloidal silica, fumed silica, pulverized silica, and surface-modified silica thereof, from the viewpoints of improving the polishing rate and reducing scratches. Of these, colloidal silica is preferred.

[0024] The shape of component A may be spherical or non-spherical. The use form of Component A is preferably a slurry-like polishing liquid component.

[0025] From the viewpoint of improving the polishing rate, the average primary 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 15 nm or more, and from the viewpoint of reducing scratches, 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 primary 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 15 nm or more and 25 nm or less. In the present disclosure, the average primary particle diameter of silica particles is determined based on the specific surface area S (m 2 The average primary particle size can be measured by the method described in the Examples.

[0026] The content of component A in the polishing liquid composition of the present disclosure is preferably 0.1 mass% or more, more preferably 1 mass% or more, and even more preferably 3 mass% or more, calculated as SiO2, from the viewpoint of improving the polishing rate, and is preferably 20 mass% or less, more preferably 15 mass% or less, and even more preferably 10 mass% or less, calculated as SiO2, from the viewpoint of reducing scratches. Furthermore, the content of component A in the polishing liquid composition of the present disclosure is preferably 0.1 mass% or more and 20 mass% or less, more preferably 1 mass% or more and 15 mass% or less, and even more preferably 3 mass% or more and 10 mass% or less, calculated as SiO2, from the viewpoint of improving the polishing rate and reducing scratches. When component A is composed of two or more kinds of silica particles, the content of component A refers to the total content thereof.

[0027] [Acid (component B)] The polishing composition of the present disclosure contains an acid (hereinafter also referred to as "component B"). In the present disclosure, the use of an acid includes the use of an acid or a salt thereof. Component B may be one type or a combination of two or more types.

[0028] Examples of component B include inorganic acids such as nitric acid, sulfuric acid, sulfurous acid, persulfuric acid, hydrochloric acid, perchloric acid, phosphoric acid, phosphonic acid, phosphinic acid, pyrophosphoric acid, tripolyphosphoric acid, and amidosulfuric acid; organic acids such as organic phosphoric acid, organic phosphonic acid, and carboxylic acid; and the like. Among these, component B preferably contains an inorganic acid and an organic phosphonic acid, and more preferably contains an inorganic acid, from the viewpoint of improving the polishing rate and reducing scratches. From the same viewpoint, the content of the inorganic acid in component B is preferably 0.5% by mass or more, more preferably 0.7% by mass or more, and even more preferably 0.8% by mass or more. The inorganic acid is preferably at least one selected from nitric acid, sulfuric acid, hydrochloric acid, perchloric acid and phosphoric acid, and more preferably phosphoric acid. The organic phosphonic acid is preferably at least one selected from 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP), aminotri(methylenephosphonic acid), ethylenediaminetetra(methylenephosphonic acid), and diethylenetriaminepenta(methylenephosphonic acid), and HEDP is more preferable. Examples of salts of these acids include salts of the above acids and at least one selected from metals, ammonia, and alkylamines. Examples of the above metals include metals belonging to Groups 1 to 11 of the periodic table.

[0029] The content of component B in the polishing liquid composition of the present disclosure is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and even more preferably 0.5% by mass or more, from the viewpoint of improving the polishing rate and reducing scratches, and from the same viewpoint, it is preferably 5% by mass or less, more preferably 4% by mass or less, even more preferably 3% by mass or less, and even more preferably 2% by mass or less. From the same viewpoint, the content of component B in the polishing liquid composition of the present disclosure is preferably 0.01% by mass or more and 5% by mass or less, more preferably 0.1% by mass or more and 4% by mass or less, even more preferably 0.5% by mass or more and 3% by mass or less, and even more preferably 0.5% by mass or more and 2% by mass or less. When component B is a combination of two or more kinds, the content of component B refers to the total content thereof.

[0030] The mass ratio A / B of component A to component B (content of component A / content of component B) in the polishing liquid composition of the present disclosure is, from the viewpoints of improving the polishing rate and reducing scratches, preferably 0.5 or more, more preferably 1 or more, even more preferably 2 or more, and even more preferably 4 or more, and from the same viewpoint, it is preferably 10 or less, more preferably 8 or less, and even more preferably 6 or less. From the same viewpoint, the mass ratio A / B in the polishing liquid composition of the present disclosure is preferably 0.5 or more and 10 or less, more preferably 1 or more and 8 or less, even more preferably 2 or more and 6 or less, and even more preferably 4 or more and 6 or less.

[0031] [Aqueous medium] The aqueous medium contained in the polishing liquid composition of the present disclosure includes water such as distilled water, ion-exchanged water, pure water, and ultrapure water, or a mixed solvent of water and a solvent. The above-mentioned solvent includes a solvent miscible with water (for example, alcohol such as ethanol). When the aqueous medium is a mixed solvent of water and a solvent, the ratio of water to the entire mixed medium is not particularly limited as long as the effect of the present disclosure is not hindered. From the viewpoint of economic efficiency, for example, 95 mass% or more is preferable, 98 mass% or more is more preferable, and substantially 100 mass% is even more preferable. From the viewpoint of surface cleanliness of the substrate to be polished, ion-exchanged water and ultrapure water are preferable as the aqueous medium. The content of the aqueous medium in the polishing liquid composition of the present disclosure can be the remainder excluding component A, component B, and optional components described below that are blended as necessary.

[0032] [Oxidizing agent (component C)] The polishing composition of the present disclosure may further contain an oxidizing agent (hereinafter also referred to as "component C") from the viewpoint of improving the polishing rate and further reducing scratches. Component C may be one type or a combination of two or more types.

[0033] Examples of component C include, from the viewpoint of improving the polishing rate and further reducing scratches, peroxides, permanganic acid or its salts, chromic acid or its salts, peroxoacid or its salts, oxyacid or its salts, metal salts, nitric acids, sulfuric acids, etc. Among these, at least one selected from hydrogen peroxide, iron(III) nitrate, peracetic acid, ammonium peroxodisulfate, iron(III) sulfate, and ammonium iron(III) sulfate is preferred, and hydrogen peroxide is more preferred from the viewpoint of improving the polishing rate, not attaching metal ions to the surface of the substrate to be polished, and being easily available.

[0034] When the polishing liquid composition of the present disclosure contains component C, the content of component C in the polishing liquid composition of the present disclosure is preferably 0.01 mass% or more, more preferably 0.05 mass% or more, even more preferably 0.1 mass% or more, and preferably 4 mass% or less, more preferably 2 mass% or less, and even more preferably 1 mass% or less, from the viewpoint of further improving the polishing rate and further reducing scratches. From the same viewpoint, the content of component C in the polishing liquid composition of the present disclosure is preferably 0.01 mass% or more and 4 mass% or less, more preferably 0.05 mass% or more and 2 mass% or less, and even more preferably 0.1 mass% or more and 1 mass% or less. When component C is a combination of two or more kinds, the content of component C refers to the total content thereof.

[0035] In one or more embodiments, the polishing liquid composition of the present disclosure may further contain at least one selected from a heterocyclic aromatic compound (hereinafter also referred to as "component D"), an aliphatic amine compound or an alicyclic amine compound (hereinafter also referred to as "component E"), and an anionic water-soluble polymer (hereinafter also referred to as "component F"). Components D to F are described below.

[0036] [Heterocyclic aromatic compounds (component D)] In one or more embodiments, the polishing composition of the present disclosure may further contain a heterocyclic aromatic compound (including a salt thereof) (Component D) from the viewpoint of further reducing scratches. Component D may be one type or a combination of two or more types.

[0037] From the viewpoint of further reducing scratches, component D is preferably a heterocyclic aromatic compound containing two or more nitrogen atoms in the heterocycle, more preferably having three or more nitrogen atoms in the heterocycle, even more preferably having 3 to 9 nitrogen atoms, even more preferably having 3 to 5 nitrogen atoms, and even more preferably 3 or 4 nitrogen atoms.

[0038] In one or more embodiments, component D is preferably at least one selected from 1,2,4-triazole, 3-amino-1,2,4-triazole, 5-amino-1,2,4-triazole, 3-mercapto-1,2,4-triazole, 1H-tetrazole, 5-aminotetrazole, 1H-benzotriazole (BTA), 1H-tolyltriazole, 2-aminobenzotriazole, 3-aminobenzotriazole, and alkyl or amine substituted derivatives thereof. Examples of the alkyl group of the alkyl substituent include lower alkyl groups having 1 to 4 carbon atoms, and in one or more embodiments, methyl and ethyl groups. In one or more embodiments, examples of the amine substituent include 1-[N,N-bis(hydroxyethylene)aminomethyl]benzotriazole, 1-[N,N-bis(hydroxyethylene)aminomethyl]tolyltriazole, and the like. Among these, from the viewpoint of further reducing scratches, component D is more preferably at least one selected from 1H-benzotriazole (BTA), 1H-tolyltriazole, 2-aminobenzotriazole, and 3-aminobenzotriazole, and further preferably 1H-benzotriazole (BTA).

[0039] When the polishing liquid composition of the present disclosure contains component D, the content of component D in the polishing liquid composition of the present disclosure is preferably 0.005% by mass or more, more preferably 0.01% by mass or more, and even more preferably 0.02% by mass or more from the viewpoint of further reducing scratches, and is preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 1% by mass or less, and even more preferably 0.2% by mass or less from the viewpoint of improving the polishing rate. More specifically, the content of component D in the polishing liquid composition of the present disclosure is preferably 0.005% by mass or more and 10% by mass or less, more preferably 0.01% by mass or more and 5% by mass or less, even more preferably 0.02% by mass or more and 1% by mass or less, and even more preferably 0.02% by mass or more and 0.2% by mass or less. When component D is a combination of two or more kinds, the content of component D refers to the total content thereof.

[0040] [Aliphatic amine compound or alicyclic amine compound (ingredient E)] In one or more embodiments, the polishing liquid composition of the present disclosure may further contain an aliphatic amine compound or an alicyclic amine compound (component E) from the viewpoint of further reducing scratches. From the viewpoint of further reducing scratches, the number of nitrogen atoms or the total number of amino groups or imino groups in the molecule of component E is preferably 2 or more and 4 or less. Component E may be one type or a combination of two or more types.

[0041] In one or a plurality of embodiments, the aliphatic amine compound is, from the viewpoint of further reducing scratches, preferably at least one selected from ethylenediamine, N,N,N',N'-tetramethylethylenediamine, 1,2-diaminopropane, 1,3-diaminopropane, 1,4-diaminobutane, hexamethylenediamine, 3-(diethylamino)propylamine, 3-(dibutylamino)propylamine, 3-(methylamino)propylamine, 3-(dimethylamino)propylamine, N-aminoethylethanolamine, N-aminoethylisopropanolamine, and N-aminoethyl-N-methylethanolamine, more preferably at least one selected from N-aminoethylethanolamine, N-aminoethylisopropanolamine, and N-aminoethyl-N-methylethanolamine, and even more preferably N-aminoethylethanolamine (AEA). In one or more embodiments, from the viewpoint of further reducing scratches, the alicyclic amine compound is preferably at least one selected from piperazine, 2-methylpiperazine, 2,5-dimethylpiperazine, 1-amino-4-methylpiperazine, N-methylpiperazine, and hydroxyethylpiperazine (HEP), and more preferably hydroxyethylpiperazine (HEP).

[0042] When the polishing liquid composition of the present disclosure contains component E, the content of component E in the polishing liquid composition of the present disclosure is preferably 0.005% by mass or more, more preferably 0.01% by mass or more, and even more preferably 0.02% by mass or more from the viewpoint of further reducing scratches, and is preferably 1% by mass or less, more preferably 0.5% by mass or less, and even more preferably 0.1% by mass or less from the viewpoint of improving the polishing rate. More specifically, the content of component E in the polishing liquid composition of the present disclosure is preferably 0.005% by mass or more and 1% by mass or less, more preferably 0.01% by mass or more and 0.5% by mass or less, and even more preferably 0.02% by mass or more and 0.1% by mass or less. When component E is a combination of two or more kinds, the content of component E refers to the total content thereof.

[0043] [Anionic water-soluble polymer (component F)] In one or more embodiments, the polishing liquid composition of the present disclosure may further contain an anionic water-soluble polymer (component F) from the viewpoint of further reducing scratches. The anionic water-soluble polymer is a water-soluble polymer having an anionic group in the molecule. In the present disclosure, "water-soluble" means having a solubility of 0.5 g / 100 mL or more in water (20° C.), preferably a solubility of 2 g / 100 mL or more. In one or more embodiments, from the viewpoint of further reducing scratches, component F has a repeating unit and a sulfonic acid group or a salt thereof in the molecule, and preferably has a structure having an aromatic ring in the main chain of the repeating unit. Examples of the aromatic ring include a phenol skeleton and a naphthalene skeleton. Examples of the salt include an alkali metal salt, an ammonium salt, and an organic amine salt. Component F may be one type or a combination of two or more types.

[0044] In one or more embodiments, component F may be a copolymer containing a structural unit derived from an unsaturated carboxylic acid and a structural unit derived from a monomer having a sulfonic acid group in the molecule. Examples of the unsaturated carboxylic acid include at least one selected from acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, and salts thereof. Examples of the monomer having a sulfonic acid group in the molecule include 2-acrylamido-2-methylpropanesulfonic acid. Examples of the copolymer containing a structural unit derived from an unsaturated carboxylic acid and a structural unit derived from a monomer having a sulfonic acid group in the molecule include acrylic acid / 2-acrylamido-2-methylpropanesulfonic acid copolymer (AA / AMPS). In one or more embodiments, Component F may be a condensate or a salt thereof of an aromatic monomer having a sulfonic acid group or a salt thereof, a condensate or a salt thereof containing a structural unit derived from an aromatic monomer having a sulfonic acid group or a salt thereof and a structural unit other than the structural unit, etc. Examples of the salt include an alkali metal salt, an ammonium salt, and an organic amine salt. As the condensate or salt thereof of an aromatic monomer having a sulfonic acid group or a salt thereof, from the viewpoint of further reducing waviness, a condensate or salt thereof having a structure in which at least one hydrogen atom of an aromatic ring constituting a main chain is substituted with a sulfonic acid group is preferable, and at least one selected from phenolsulfonic acid, naphthalenesulfonic acid and salts thereof is more preferable. For example, a formalin condensate of phenolsulfonic acid (PhS) and a formalin condensate of naphthalenesulfonic acid (NaS) can be mentioned. An example of a condensate or a salt thereof containing a constituent unit derived from an aromatic monomer having a sulfonic acid group or a salt thereof and a constituent unit other than the constituent unit is a formalin condensate (BisS / PhS) of bis(4-hydroxyphenyl)sulfone (BisS) and phenolsulfonic acid (PhS).

[0045] From the viewpoint of further reducing waviness, the weight average molecular weight of component F is preferably 500 or more, more preferably 1000 or more, and even more preferably 1500 or more, and is preferably 50000 or less, more preferably 30000 or less, more preferably 20000 or less, more preferably 10000 or less, and even more preferably 5000 or less. More specifically, the weight average molecular weight of component F is preferably 500 or more and 50000 or less, more preferably 1000 or more and 30000 or less, more preferably 1500 or more and 20000 or less, more preferably 1500 or more and 10000 or less, and even more preferably 1500 or more and 5000 or less.

[0046] When the polishing liquid composition of the present disclosure contains component F, the content of component F in the polishing liquid composition of the present disclosure is preferably 0.001 mass% or more, more preferably 0.005 mass% or more, even more preferably 0.01 mass% or more, and preferably 1 mass% or less, more preferably 0.5 mass% or less, and even more preferably 0.1 mass% or less, from the viewpoint of further reducing scratches. More specifically, the content of component F in the polishing liquid composition of the present disclosure is preferably 0.001 mass% or more and 1 mass% or less, more preferably 0.05 mass% or more and 0.5 mass% or less, and even more preferably 0.01 mass% or more and 0.1 mass% or less. When component F is a combination of two or more kinds, the content of component F refers to the total content thereof.

[0047] [Other ingredients] In one or more embodiments, the polishing liquid composition of the present disclosure may further contain other components as necessary. Examples of the other components include abrasive grains other than Component A, polymers other than Component F, thickeners, dispersants, rust inhibitors, basic substances, surfactants, solubilizers, etc.

[0048] [pH of polishing composition] The pH of the polishing liquid composition of the present disclosure is 4 or less, preferably 3.5 or less, more preferably 3 or less, from the viewpoint of improving the polishing rate and reducing scratches, and from the same viewpoint, it is 1 or more, preferably 1.5 or more, more preferably 2 or more. From the same viewpoint, the pH of the polishing liquid composition of the present disclosure is 1 or more and 4 or less, preferably 1.5 or more and 3.5 or less, more preferably 2 or more and 3 or less. The pH can be adjusted using the above-mentioned acid (component B) or a known pH adjuster. In the present disclosure, the above pH is the pH of the polishing liquid composition at 25°C, and can be measured using a pH meter, and can be, for example, the value 2 minutes after immersing the electrode of the pH meter in the polishing liquid composition.

[0049] [Method of manufacturing the polishing composition] The polishing liquid composition of the present disclosure can be produced, for example, by blending component A, component B, and an aqueous medium, and, if desired, optional components (component C, component D, component E, component F, and other components) by a known method. That is, in another aspect, the present disclosure relates to a method for producing a polishing liquid composition, which includes a step of blending at least component A, component B, and an aqueous medium. In the present disclosure, "blending" includes mixing component A, component B, and an aqueous medium, and optional components (component C, component D, component E, component F, and other components) simultaneously or in any order as necessary. Component A may be mixed in the form of a concentrated slurry, or may be mixed after diluting with water or the like. When component A is composed of multiple types of silica particles, the multiple types of silica particles can be blended simultaneously or separately. When component B is composed of multiple types of acids, the multiple types of acids can be blended simultaneously or separately. The blending can be carried out using a mixer such as a homomixer, a homogenizer, an ultrasonic disperser, and a wet ball mill. The preferred amount of each component in the method for producing the polishing liquid composition of the present disclosure can be the same as the preferred content of each component in the polishing liquid composition of the present disclosure described above.

[0050] In the present disclosure, "the content of each component in the polishing liquid composition" refers to the content of each component at the time of use, that is, at the time when the use of the polishing liquid composition for polishing is started. In one or more embodiments, the content of each component in the polishing composition of the present disclosure can be considered as the blending amount of each component.

[0051] The polishing composition of the present disclosure may be stored and supplied in a concentrated state within a range that does not impair its storage stability. In this case, it is preferable in that the manufacturing and transportation costs can be further reduced. The concentrated polishing composition of the present disclosure may be appropriately diluted with the above-mentioned aqueous medium when used as necessary. The dilution ratio is not particularly limited as long as the content (when used) of each of the above-mentioned components can be secured after dilution, and may be, for example, 10 to 100 times.

[0052] [Polishing liquid kit] In one aspect, the present disclosure relates to a kit for producing the polishing liquid composition of the present disclosure (hereinafter also referred to as the "polishing liquid kit of the present disclosure"). The polishing liquid kit of the present disclosure may be, for example, a polishing liquid kit (two-liquid type polishing liquid composition) that contains a silica dispersion containing component A and an aqueous medium and an additive aqueous solution containing component B in a mutually unmixed state, and that is mixed when used and diluted with an aqueous medium as necessary. The aqueous medium contained in the silica dispersion may be the entire amount of the aqueous medium used to prepare the polishing liquid composition, or may be a part of the aqueous medium. The additive aqueous solution may contain a part of the aqueous medium used to prepare the polishing liquid composition. The silica dispersion and the additive aqueous solution may each contain the above-mentioned optional components (component C, component D, component E, component F, and other components) as necessary. According to the polishing liquid kit of the present disclosure, a polishing liquid composition that can reduce scratches on the substrate surface after polishing while improving the polishing rate can be obtained.

[0053] [Substrate to be polished] In one or more embodiments, the substrate to be polished is a substrate used for manufacturing a magnetic disk substrate. In one or more embodiments, the surface of the substrate to be polished is polished with the polishing composition of the present disclosure, and then a magnetic layer is formed on the substrate surface by sputtering or the like, thereby manufacturing a magnetic disk substrate.

[0054] The material of the substrate to be polished preferably used in the present disclosure includes, for example, metals or semimetals such as silicon, aluminum, nickel, tungsten, copper, tantalum, titanium, or alloys thereof, glassy substances such as glass, glassy carbon, amorphous carbon, ceramic materials such as alumina, silicon dioxide, silicon nitride, tantalum nitride, titanium carbide, and resins such as polyimide resin. Among them, the substrate to be polished is preferably a substrate to be polished that contains metals such as aluminum, nickel, tungsten, copper, or alloys mainly composed of these metals. As the substrate to be polished, for example, Ni-P plated aluminum alloy substrates, and glass substrates such as crystallized glass, reinforced glass, aluminosilicate glass, and aluminoborosilicate glass are more suitable, and Ni-P plated aluminum alloy substrates are even more suitable. In the present disclosure, the term "Ni-P plated aluminum alloy substrate" refers to an aluminum alloy substrate that has been subjected to electroless Ni-P plating after the surface of the aluminum alloy substrate is ground.

[0055] The shape of the substrate to be polished may be, for example, a shape having a flat surface such as a disk, plate, slab, or prism, or a shape having a curved surface such as a lens. Among them, a disk-shaped substrate to be polished is suitable. In the case of a disk-shaped substrate to be polished, the outer diameter is, for example, about 2 to 100 mm, and the thickness is, for example, about 0.4 to 2 mm.

[0056] [Method of manufacturing magnetic disk substrate] In general, a magnetic disk is manufactured by polishing a substrate to be polished after a grinding process through a rough polishing process and a finish polishing process, and forming the substrate into a magnetic disk in a recording part forming process. The polishing composition of the present disclosure can be used in a polishing process, preferably a finish polishing process, for polishing a substrate to be polished in a method for manufacturing a magnetic disk substrate. That is, in one aspect, the present disclosure relates to a method for manufacturing a magnetic disk substrate (hereinafter also referred to as a "substrate manufacturing method of the present disclosure") including a process for polishing a substrate to be polished using the polishing composition of the present disclosure (hereinafter also referred to as a "polishing process using the polishing composition of the present disclosure"). The substrate manufacturing method of the present disclosure is particularly suitable for a method for manufacturing a magnetic disk substrate for a perpendicular magnetic recording system.

[0057] In one or more embodiments, the polishing process using the polishing liquid composition of the present disclosure is a process of supplying the polishing liquid composition of the present disclosure to the surface of the substrate to be polished, contacting the polishing pad with the surface to be polished, and moving at least one of the polishing pad and the substrate to be polished to perform polishing.In another or more embodiments, the polishing process using the polishing liquid composition of the present disclosure is a process of sandwiching the substrate to be polished between a platen to which a polishing pad such as a nonwoven organic polymer-based polishing cloth is attached, and moving the platen or the substrate to be polished to polish the substrate to be polished while supplying the polishing liquid composition of the present disclosure to a polishing machine.

[0058] When the polishing process of the substrate to be polished is carried out in multiple stages, the polishing process using the polishing liquid composition of the present disclosure is preferably carried out in the second stage or later, and more preferably in the final polishing process or the finish polishing process. In this case, in order to avoid the mixing of the abrasive or the polishing liquid composition of the previous process, a separate polishing machine may be used for each step, and when a separate polishing machine is used, it is preferable to wash the substrate to be polished after each polishing process. Furthermore, the polishing liquid composition of the present disclosure can be used in the circulating polishing in which the used polishing liquid is reused. The polishing machine is not particularly limited, and a known polishing machine for substrate polishing can be used.

[0059] The polishing pad used in the polishing process using the polishing liquid composition of the present disclosure is not particularly limited, and for example, a suede type, nonwoven fabric type, polyurethane independent foam type, or a two-layer type in which these are laminated can be used, and from the viewpoint of polishing speed, a suede type polishing pad is preferred.

[0060] The polishing load in the polishing step using the polishing composition of the present disclosure is preferably 5.9 kPa or more, more preferably 6.9 kPa or more, and even more preferably 7.5 kPa or more from the viewpoint of improving the polishing rate, and is preferably 20 kPa or less, more preferably 18 kPa or less, and even more preferably 16 kPa or less from the viewpoint of reducing scratches. In the manufacturing method of the present disclosure, the polishing load refers to the pressure of the platen applied to the polishing surface of the substrate to be polished during polishing. The polishing load can be adjusted by applying air pressure or weight to at least one of the platen and the substrate to be polished.

[0061] In the polishing step using the polishing composition of the present disclosure, the supply rate of the polishing composition of the present disclosure is set to 1 cm per 1 cm of the substrate to be polished from the viewpoint of reducing scratches. 2 The flow rate is preferably 0.05 mL / min or more and 15 mL / min or less, more preferably 0.06 mL / min or more and 10 mL / min or less, even more preferably 0.07 mL / min or more and 1 mL / min or less, and even more preferably 0.07 mL / min or more and 0.5 mL / min or less.

[0062] The method of supplying the polishing liquid composition of the present disclosure to the polishing machine can be, for example, a method of continuously supplying the composition using a pump or the like. When supplying the polishing liquid composition to the polishing machine, in addition to a method of supplying the composition as a single liquid containing all components, the composition can be divided into a plurality of blending component liquids and supplied as two or more liquids, taking into consideration the stability of the polishing liquid composition, etc. In the latter case, the above-mentioned plurality of blending component liquids are mixed, for example, in the supply pipe or on the substrate to be polished, to form the polishing liquid composition of the present disclosure.

[0063] According to the substrate manufacturing method of the present disclosure, by using the polishing liquid composition of the present disclosure, it is possible to achieve the effect of producing high-quality magnetic disk substrates with reduced scratches on the substrate surface after polishing, with high yield and good productivity.

[0064] [Methods to improve polishing speed] In one aspect, the present disclosure relates to a method for improving a polishing rate of a substrate to be polished, comprising polishing the substrate to be polished with the polishing composition of the present disclosure (hereinafter, also referred to as the "polishing rate improving method of the present disclosure"). According to the polishing rate improving method of the present disclosure, by using the polishing composition of the present disclosure, both an improvement in the polishing rate and a reduction in scratches on the substrate surface after polishing can be achieved.

[0065] In one or more embodiments, the polishing of the substrate to be polished using the polishing liquid composition of the present disclosure is to supply the polishing liquid composition of the present disclosure to the surface to be polished of the substrate to be polished, bring a polishing pad into contact with the surface to be polished, and move at least one of the polishing pad and the substrate to be polished to perform polishing, or to sandwich the substrate to be polished between a platen to which a polishing pad such as a nonwoven organic polymer-based polishing cloth is attached, and while supplying the polishing liquid composition of the present disclosure to a polishing machine, move the platen or the substrate to be polished to polish the substrate to be polished. The polishing method and conditions in the polishing rate improving method of the present disclosure can be the same method and conditions as those in the substrate manufacturing method of the present disclosure described above.

[0066] [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 composition of the present disclosure, and the substrate to be polished is a substrate used in the manufacture of a magnetic disk substrate. The substrate to be polished in the polishing method of the present disclosure may be the substrate to be polished described above, and among them, a substrate to be used in the manufacture of a magnetic disk substrate for a perpendicular magnetic recording system is preferred. The polishing method of the present disclosure can be used, for example, in a finish polishing process. By using the polishing method of the present disclosure, it is possible to achieve the effect of producing a high-quality magnetic disk substrate with reduced scratches on the substrate surface after polishing, with high yield and good productivity. 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. EXAMPLES

[0067] The present disclosure will be described in more detail below with reference to examples, but these are merely illustrative and the present disclosure is not limited to these examples.

[0068] 1. Silica particles A1 to A7 For the silica particles A1 to A7 shown in Table 1, the following were used. A1 manufacturing example: The No. 3 sodium silicate was diluted with pure water to a concentration of 5%, and ultrafiltered to obtain 5,000g of purified water glass silicate solution. 600g of pure water was added to 400g of the above-mentioned aqueous silicic acid solution, and 1% ammonia was further added to adjust the pH to 4.8, and then the solution was stored at room temperature for 2.5 hours to obtain about 1000g of polymerized silicic acid solution. 23% ammonia was added to the obtained polymerized silicic acid solution 1000g, the pH was adjusted to 10.6, the liquid temperature was raised to 90°C, and a silicic acid sol was obtained after 1 hour. 20% sodium silicate No. 3 was added to the obtained sol 100g, the pH was adjusted to 12.5, the temperature was raised to 85°C, and the state was maintained for 30 minutes. Next, 600g of pure water was added to the remaining 900g of the above-mentioned purified water glass silicate solution, and 1% sulfuric acid was further added to prepare a silicic acid solution for growth, which was added to the sol maintained at the raised temperature for 6 hours. After the addition was completed, the mixture was kept at 85° C. for an additional hour and then cooled to room temperature. The obtained silica sol was concentrated with a rotary evaporator (EYELA), to obtain a silica dispersion (silica particles A1) with a silica concentration of 25%. A2 manufacturing example: The No. 3 sodium silicate was diluted with pure water to a concentration of 5%, and ultrafiltered to obtain 5,000g of purified water glass silicate solution. 600g of pure water was added to 400g of the above-mentioned aqueous silicic acid solution, and 1% ammonia was further added to adjust the pH to 4.8, and then the solution was stored at room temperature for 2.5 hours to obtain about 1000g of polymerized silicic acid solution. 23% ammonia was added to the obtained polymerized silicic acid solution 1000g, the pH was adjusted to 10.6, the liquid temperature was raised to 90°C, and a silicic acid sol was obtained after 1 hour. 20% sodium silicate No. 3 was added to the obtained sol 100g, the pH was adjusted to 11.2, the temperature was raised to 85°C, and the state was maintained for 30 minutes. Next, 600g of pure water was added to the remaining 900g of the above-mentioned purified water glass silicate solution, and 1% sulfuric acid was further added to prepare a silicic acid solution for growth, which was added to the sol maintained at the raised temperature for 6 hours. After the addition was completed, the mixture was kept at 85° C. for another hour and then cooled to room temperature. The obtained silica sol was concentrated with a rotary evaporator (EYELA), to obtain a silica dispersion (silica particles A2) with a silica concentration of 25%. A3 production example: The No. 3 sodium silicate was diluted with pure water to a concentration of 5%, and ultrafiltered to obtain 5,000g of purified water glass silicate solution. 600g of pure water was added to 400g of the above-mentioned aqueous silicic acid solution, and 1% ammonia was further added to adjust the pH to 4.8, and then stored at 35°C for 2.5 hours to obtain about 1000g of polymerized silicic acid solution. 23% ammonia was added to the obtained polymerized silicic acid solution 1000g, the pH was adjusted to 10.6, the liquid temperature was raised to 90°C, and after 1 hour, a silicic acid sol was obtained. 20% sodium silicate No. 3 was added to the obtained sol 100g, the pH was adjusted to 11.2, the temperature was raised to 85°C, and the state was maintained for 30 minutes. Next, 600g of pure water was added to the remaining 900g of the above-mentioned purified water glass silicate solution, and 1% sulfuric acid was further added to prepare a silicic acid solution for growth, which was added to the sol maintained at the raised temperature for 6 hours. After the addition was completed, the mixture was kept at 85° C. for an additional hour and then cooled to room temperature. The obtained silica sol was concentrated with a rotary evaporator (EYELA), to obtain a silica dispersion (silica particles A3) with a silica concentration of 25%. A4 production example: The No. 3 sodium silicate was diluted with pure water to a concentration of 5%, and ultrafiltered to obtain 5,000g of purified water glass silicate solution. 600g of pure water was added to 400g of the above-mentioned aqueous silicic acid solution to adjust the pH to 3.6, and then stored at room temperature for 2.5 hours to obtain about 1000g of polymerized silicic acid solution. 23% ammonia was added to the obtained 1000g of polymerized silicic acid solution to adjust the pH to 10.6, and the liquid temperature was raised to 90°C, and after 1 hour, a silicic acid sol was obtained. 20% sodium silicate No. 3 was added to the obtained sol 100g, the pH was adjusted to 12.5, and the temperature was raised to 85°C, and the state was maintained for 30 minutes. Next, 600g of pure water was added to the remaining 900g of the above-mentioned purified water glass silicate solution, and 1% sulfuric acid was added to make a silicic acid solution for growth, which was added to the sol maintained at the raised temperature for 6 hours. After the addition was completed, the mixture was kept at 85° C. for an additional hour and then cooled to room temperature. The obtained silica sol was concentrated with a rotary evaporator (EYELA), to obtain a silica dispersion (silica particles A4) with a silica concentration of 25%. A5 production example: The No. 3 sodium silicate was diluted with pure water to a concentration of 5%, and ultrafiltered to obtain 5,000g of purified water glass silicate solution. 600g of pure water was added to 400g of the above-mentioned aqueous silicic acid solution, and 1% ammonia was further added to adjust the pH to 4.8, and then stored at 35°C for 2.5 hours to obtain about 1000g of polymerized silicic acid solution. 23% ammonia was added to the obtained polymerized silicic acid solution 1000g, the pH was adjusted to 10.6, the liquid temperature was raised to 90°C, and after 1 hour, a silicic acid sol was obtained. 20% sodium silicate No. 3 was added to the obtained sol 100g, the pH was adjusted to 12.5, the temperature was raised to 85°C, and the state was maintained for 30 minutes. Next, 600g of pure water was added to the remaining 900g of the above-mentioned purified water glass silicate solution, and 1% sulfuric acid was further added to prepare a silicic acid solution for growth, which was added to the sol maintained at the raised temperature for 6 hours. After the addition was completed, the mixture was kept at 85° C. for an additional hour and then cooled to room temperature. The obtained silica sol was concentrated with a rotary evaporator (EYELA), to obtain a silica dispersion having a silica concentration of 25% (silica particles A5). A6: Colloidal silica [PL-2 manufactured by Fuso Chemical Industry Co., Ltd.] A7: Colloidal silica [Cataloid SI-30W manufactured by JGC Catalysts and Chemicals]

[0069] [In situ electrochemical measurements of dynamic instantaneous corrosion rate and corrosion potential E corr Measurement of The dynamic instantaneous corrosion rate and corrosion potential were measured using an electrochemical device using a potentiostat as shown in FIG. 1 as follows. First, 45 mL of electrolyte stored in a thermostatic bath at 30°C for 12 hours is poured into the electrochemical cell, and the reference electrode, counter electrode, and working electrode are brought into contact with the electrolyte. Each electrode is connected to a potentiostat. Then, the polishing pad attached to the rotation control body is brought into contact with the working electrode, the position of the balance is adjusted with a jack so that a specified load is applied, and the rotation control body is rotated. The open circuit voltage measured at this time is taken as the corrosion potential E corr The corrosion potential E corrWhen the potential is scanned from 0.05 V to 0.5 V anode side using LSV (Linear Sweep Voltammetry) method, the current curve of the anodic reaction is observed, and the current density is measured using the Tafel plot method. This current density is calculated as the dynamic instantaneous corrosion rate. Electrochemical cell: VM3, manufactured by EC Frontier Co., Ltd. Potentiostat: BAS electrochemical analyzer, model: 611D Electrolyte: a polishing liquid composition containing 5 mass% silica particles (here, any one of silica particles A1 to A7 shown in Table 1), 1 mass% phosphoric acid, 0.3 mass% hydrogen peroxide, and water (balance), and having a pH of 2.5. The pH of the polishing liquid composition may be appropriately adjusted with potassium hydroxide so that the pH of the polishing liquid composition is 2.5. Open circuit voltage measurement method: The measurement method in the attached software was set to open circuit voltage (OCP) mode, and the measurement time was 200 seconds. The open circuit voltage value 200 seconds after the start of measurement was taken as the corrosion potential E corr In addition, since the corrosion potential value changes depending on the electrolyte temperature, the measurement can be performed at room temperature, which is 25 to 26 degrees. LSV measurement method: Select the LSV method from the measurement method in the included software. The sampling interval is 1mV, and the current value flowing every 1mV is observed. As with open circuit voltage measurement, the current density value varies depending on the electrolyte temperature, so measurements can be taken at room temperature of 25 to 26 degrees. Analysis by Tafel plot method: (Explained below using Comparative Example 1 as an example.) Comparative Example 1 When scanning the potential 0.5 V from the corrosion potential toward the anode side, in the case of Comparative Example 1, in an electrolyte of pH 2.5 containing silica particles A6, phosphoric acid, hydrogen peroxide, water (and potassium hydroxide), the open circuit voltage (corrosion potential) becomes -0.32 V, and at the same time, the voltage at the start of the measurement becomes -0.32 V, which is the same value as the corrosion potential. When the potential is scanned 0.5 V from this point (corrosion potential) toward the anode side in increments of 0.1 mV, the voltage at the end of the measurement becomes 0.18 V. Here, it is assumed that the corrosion reaction occurs at the location where the working electrode surface is in contact with the rotation control body to which the polishing pad is attached, and the reaction area must be divided by the obtained current value. The area of ​​the working electrode of the electrochemical cell (VM3) used in this system is approximately 1.0 cm 2 The diameter of the rotation control body to which the polishing pad is attached is about 8 mm, so the area where the polishing pad and the working electrode can interact is 0.502655 cm 2 By dividing this value (area) by the obtained current value, the current value per unit area (amount of generated electrons) is calculated. In the case of Comparative Example 1, in an electrolyte containing silica particles A6, phosphoric acid, hydrogen peroxide, and water (and potassium hydroxide) and having a pH of 2.5, the open circuit voltage (corrosion potential) was −0.32 V, the obtained current value was 0.00007572 A, and the current value per unit area was 0.00015064 A / cm 2 The logarithm (=Log 10 If we take the logarithm (0.00015064=-3.82205925), we get the value -3.82205925. If the current value per unit area is negative, Log 10 Convert the current value per unit area to a positive value and take the logarithm, such as |Current value per unit area|. Take the logarithm of the current value per unit area obtained every 1 mV from -0.32 V (open circuit voltage) to 0.18 V (voltage at the end of measurement), and plot the vertical axis as Log 10A scatter plot of |current value per unit area| versus horizontal axis: potential (for example, a range including the scanned potential, such as -0.50V to +0.50V) is obtained. According to the Butler-Volmer equation derived from the Nernst equation, when the overpotential is large, the reaction current at the counter electrode can be ignored, and the Butler-Volmer equation can be simplified to the Tafel equation. In other words, in this system, when the overpotential is large, the cathodic reaction is ignored, and the anode reaction current is the amount of electrons generated in the corrosion reaction, that is, the dynamic instantaneous corrosion reaction rate defined in this disclosure. In the Tafel method, generally, when the corrosion potential is 50mV away, the overpotential can be considered large, and the cathodic reaction can be ignored. From the above, the Log 10 |Current value per unit area| is calculated, and a linear approximation is performed on the scatter plot for values ​​in this range. The corrosion potential value is substituted for x in the linear approximation equation to calculate the y value. In the case of Comparative Example 1, for an electrolyte containing silica particles A6, phosphoric acid, hydrogen peroxide, water (and potassium hydroxide) and having a pH of 2.5, the linear approximation equation is y = 3.7214x - 2.5878, and when the corrosion potential is substituted for x, the linear approximation equation is y = -3.77864800 (=Log 10 If you remove the logarithm, the corrosion current density becomes 10 to the power of -3.77864800, which is 166.5 μA / cm 2 can be calculated. In order to avoid fluctuations in the corrosion current density value depending on the range of values ​​used for linear approximation, a value of 50 mV to 100 mV from the corrosion potential to the anode side is used in the present disclosure. For Examples 1 to 8 and Comparative Example 2, the corrosion potential and corrosion current density were determined in the same manner as in Comparative Example 1, and the results are shown in Table 1. Working electrode: The substrate to be polished is subjected to finish polishing and cleaning under the following conditions, polished with water-resistant sandpaper (two-stage polishing with #600 and then #1000), and then the substrate surface is rinsed with ethanol and water and dried. Reference electrode: Silver-silver chloride electrode (BAS, RE-1B) Counter electrode: Platinum electrode (BAS, model number: 012961, coiled / electrode length 23 cm, electrode diameter 0.5 mm) Polishing pad: A polyurethane soft suede pad (compressibility: 20% or less) that has been opened with diamond dressing (#600) and polished with the electrolyte for 5 hours. Electrolyte liquid temperature during measurement: approx. 26°C - Rotation speed of the rotating control unit during measurement: 25 rpm -Applied load during measurement (actual value measured during rotation using an electronic balance): 300g / cm 2 ±100g / cm 2 <Finishing polishing> [Substrate to be polished] The substrate to be polished was a Ni-P plated aluminum alloy substrate for magnetic disk substrates (Western Digital-Sarawak Factory) that had been roughly polished with a polishing composition containing silica abrasive grains. The substrate to be polished had a thickness of 0.635 mm, an outer diameter of 97 mm, an inner diameter of 25 mm, and a center line average roughness Ra of 1 nm measured by AFM (Dimension FastScan AFM, Bruker). [Polishing conditions] Polishing test machine: Speedfam's "Double-sided 9B polishing machine" Polishing pad: Fujibo suede type (foam layer: polyurethane elastomer, thickness: 0.7 mm, average pore size: 10 μm) Polishing composition: A polishing composition containing 5% by mass of colloidal silica having an average primary particle size of 20 nm, 1% by mass of phosphoric acid, 0.4% by mass of hydrogen peroxide, and the remainder being water. Polishing liquid composition supply amount: 100mL / min (substrate to be polished 1cm) 2 Feed rate per unit: 0.145mL / min) Lower surface plate rotation speed: 24rpm Polishing load: 10.0kPa Polishing time: 6 minutes Number of boards: 10 <Cleaning> The substrate after the above polishing was cleaned using a cleaning machine manufactured by Hikari Co., Ltd. according to the following steps. [Washing conditions] (1) Ultrasonic cleaning (5 min, 430 kHz, immersion liquid: ultrapure water) (3) PVA brush cleaning (9 seconds) (4) Rinse with ultrapure water (9 seconds) (5) Spin dry (9 seconds)

[0070] [Relative value of corrosion current density] The corrosion current density of silica particles A6 is set to 100, and the relative values ​​are shown in Table 1.

[0071] [Table 1]

[0072] 2. Preparation of Polishing Composition (Examples 1 to 8, Comparative Examples 1 to 2) (Polishing Compositions of Examples 1 to 5 and Comparative Examples 1 and 2) Polishing liquid compositions of Examples 1 to 5 and Comparative Examples 1 and 2 shown in Table 2 were prepared by mixing and stirring component A or non-component A (silica particles A1 to A7 shown in Tables 1 and 2), component B (phosphoric acid), component C (hydrogen peroxide), and water. The content (effective amount) of each component in each polishing liquid composition is as shown in Table 2. The content of water is the remainder excluding component A or non-component A, component B, and component C. (Polishing Compositions of Examples 6 to 8) The polishing liquid compositions of Examples 6 to 8 shown in Table 2 were prepared by mixing and stirring component A (silica particles A1 shown in Tables 1 and 2), component B (phosphoric acid), component C (hydrogen peroxide), additives (component D: BTA, component E: AEA, component F: AA / AMPS) and water. The content (effective amount) of each component in each polishing liquid composition is as shown in Table 2. The content of water is the remainder excluding component A, component B, component C and additives (components D, E, and F).

[0073] In preparing each polishing composition, the following components B, C and additives (components D, E and F) were used. Phosphoric acid [Wako Pure Chemical Industries, Ltd., special grade] (ingredient B) Hydrogen peroxide [35% concentration, manufactured by ADEKA] (ingredient C) BTA [1,2,3-benzotriazole, manufactured by Tokyo Chemical Industry Co., Ltd.] (Component D) AEA [N-aminoethylethanolamine, manufactured by Nippon Nyukazai Co., Ltd.] (ingredient E) AA / AMPS [acrylic acid / 2-acrylamide-2-methylpropanesulfonic acid copolymer, molar ratio (AA / AMPS): 90 / 10, manufactured by Toa Gosei Co., Ltd., product name: A6016, weight average molecular weight: 2000] (component F)

[0074] 3. Measurement of each parameter [Average primary particle size of silica particles (component A)] The average primary particle diameter (nm) of silica particles (component A) is calculated by the BET (nitrogen adsorption) method. 2 / g) using the following formula: Average primary particle diameter (nm)=2727 / S The specific surface area S of silica particles (component A) was measured by carrying out the following [pretreatment], and then weighing out approximately 0.1 g of a measurement sample into a measurement cell to four decimal places, drying the sample for 30 minutes in an atmosphere at 110°C immediately before measuring the specific surface area, and then measuring the specific surface area by the nitrogen adsorption method (BET method) using a specific surface area measuring device (Micromeritic automatic specific surface area measuring device "Flowsorb III2305", manufactured by Shimadzu Corporation). <Pretreatment> (a) The pH of the slurry of silica particles (component A) is adjusted to 2.5±0.1 with an aqueous nitric acid solution. (b) The slurry of component A, adjusted to pH 2.5±0.1, is placed in a petri dish and dried in a hot air dryer at 150°C for 1 hour. (c) After drying, the obtained sample is finely ground in an agate mortar. (d) The ground sample is suspended in ion-exchanged water at 40°C and filtered through a membrane filter with a pore size of 1 μm. (e) The residue on the filter is washed five times with 20 g of ion-exchanged water (40°C). (f) The filter with the filtrate attached thereto is placed in a petri dish and dried in an atmosphere at 110°C for 4 hours. (g) The dried filtrate (component A) was taken, being careful not to mix in any filter debris, and finely ground in a mortar to obtain a measurement sample.

[0075] [Weight average molecular weight of anionic water-soluble polymer (component F)] The weight average molecular weight of Component F was measured by gel permeation chromatography (GPC) under the following conditions. <Measurement conditions> Column: TSKgel GMPWXL + TSKgel GMPWXL (Tosoh Corporation) Eluent: 0.2M phosphate buffer / CH3CN=7 / 3 (volume ratio) Temperature: 40℃ Flow rate: 1.0mL / min Sample size: 2mg / mL Detector: RI Standard substance: sodium polystyrene sulfonate (weight average molecular weight: 1,100, 3,610, 14,900, 152,000, manufactured by POLMER STANDARDS SERVICE)

[0076] [pH measurement] The pH of the polishing composition was measured at 25° C. using a pH meter (manufactured by DKK-TOA Corporation), and the value measured 2 minutes after the electrode was immersed in the polishing composition was recorded. The results are shown in Table 1.

[0077] 4.Polishing method The following substrates were polished under the polishing conditions shown below using the polishing compositions of Examples 1 to 8 and Comparative Examples 1 and 2 prepared as described above. Then, the polishing rate and the number of scratches were measured.

[0078] [Substrate to be polished] The substrate to be polished was an aluminum alloy substrate plated with Ni-P and roughly polished with a polishing composition containing an alumina abrasive. The substrate to be polished had a thickness of 0.8 mm, an outer diameter of 95 mm, an inner diameter of 25 mm, and a center line average roughness Ra of 1 nm measured by an AFM (Digital Instrument NanoScope IIIa Multi Mode AFM). The ratio of Ni to P in the Ni-P plating was 88:12 by mass.

[0079] [Polishing conditions] Polishing test machine: Speedfam's "Double-sided 9B polishing machine" Polishing pad: Fujibo suede type (foam layer: polyurethane elastomer, thickness 0.9 mm, average pore size 10 μm) Polishing liquid composition supply amount: 100mL / min (substrate to be polished 1cm) 2 Feed rate per unit: 0.076mL / min) Lower surface plate rotation speed: 32.5rpm Polishing load: 13.0kPa Polishing time: 6 minutes Number of boards: 10

[0080] 5. Evaluation [Evaluation of polishing speed] The weight of each substrate was measured before and after polishing using a tool (manufactured by Sartorius, "BP-210S"), and the mass loss was calculated from the change in mass of each substrate. The polishing rate was calculated by dividing the average mass loss of all 10 substrates by the polishing time using the following formula. The polishing rate measurement results are shown in Table 2 as relative values ​​with Comparative Example 2 set to 100. Mass loss (mg) = {mass before polishing (mg) - mass after polishing (mg)} Polishing speed (mg / min) = mass loss (mg) / polishing time (min)

[0081] [Scratch rating] Measuring equipment: KLA-Tencor "Candela OSA7100" Evaluation: Four of the substrates were randomly selected from those placed in the polishing tester, and each substrate was irradiated with a laser at 10,000 rpm to measure the number of scratches. The total number of scratches on both sides of each of the four substrates was divided by 8 to calculate the number of scratches per substrate surface. The evaluation results of the number of scratches are shown in Table 2 as a relative value with Comparative Example 2 taken as 100.

[0082] [Table 2]

[0083] As shown in Table 2 above, the dynamic instantaneous corrosion rate in in-situ electrochemical measurements was 170 μA / cm 2 More than 330μA / cm 2 The polishing compositions of Examples 1 to 8 using silica particles having a dynamic instantaneous corrosion rate of 170 μA / cm 2 Comparative Example 1 using silica particles with a dynamic instantaneous corrosion rate of less than 330 μA / cm 2 It was found that, as described above, compared with Comparative Example 2 in which silica particles were used, both an improvement in the polishing rate and a reduction in scratches could be achieved. In addition, the corrosion potential E corr In Examples 1 to 3 and 6 to 8, the corrosion potential E of the silica particles is −0.23 V to −0.21 V. corr The number of scratches was further reduced as compared to Examples 4 to 5 in which the potential difference was −0.19 V. Examples 6 to 8 in which Component D, Component E, and Component F were added, respectively, had fewer scratches than Example 1. [Industrial Applicability]

[0084] According to the present disclosure, for example, it is possible to provide a magnetic disk substrate suitable for achieving high recording density.

Claims

1. Contains silica particles (component A), an acid (component B), and an aqueous medium, Component A has a dynamic instantaneous corrosion rate of 170 μA / cm in in-situ electrochemical measurements. 2 330μA / cm or more 2 silica particles, A polishing composition for magnetic disk substrates, having a pH of 1 or more and 4 or less. Here, the dynamic instantaneous corrosion rate in in-situ electrochemical measurement is measured using an electrochemical measurement device that includes a plate electrode evaluation cell in which a plate electrode to be evaluated (a Ni—P-plated aluminum alloy substrate for a magnetic disk substrate) is placed as a working electrode, a reference electrode (a silver-silver chloride electrode) and a counter electrode (a platinum electrode) are placed in the cell, a potentiostat connected to each electrode, and a rotation control body having a polishing pad (suede pad) placed so as to be in contact with the plate electrode to be evaluated, and in which an electrolyte (a polishing liquid composition containing 5% by mass of silica particles, 1% by mass of phosphoric acid, 0.3% by mass of hydrogen peroxide, and water and having a pH of 2.5) is stored in the cell so as to immerse or bring the electrodes into contact with each other, and is measured in the following steps. At a liquid temperature of about 26°C of the electrolyte, the polishing pad attached to the rotation control body was brought into contact with the working electrode (applied load: 300 g / cm 2 ±100g / cm 2 ), the rotation control body is rotated (number of revolutions: 25 rpm). The open circuit voltage measured at this time is taken as the corrosion potential E corr Let's say. Corrosion potential E corr The current density of the anodic reaction current curve observed when the potential is scanned from 0.5 V to the anode side using the LSV (Linear Sweep Voltammetry) method is measured using the Tafel plot method, and this current density is calculated as the dynamic instantaneous corrosion rate.

2. Component A has a corrosion potential E corr The polishing composition according to claim 1, wherein the potential difference is greater than −0.32 V.

3. 2. The polishing composition according to claim 1, wherein the average primary particle size of component A is 1 nm or more and 50 nm or less.

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

5. 5. The polishing composition according to claim 4, further comprising at least one selected from the group consisting of a heterocyclic aromatic compound (component D), an aliphatic amine compound or an alicyclic amine compound (component E), and an anionic water-soluble polymer (component F).

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

7. A method for improving a removal rate of a substrate to be polished, comprising polishing the substrate to be polished with the polishing composition according to claim 1 .

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