Polishing fluid for magnetic disk substrates

Abstract

In one embodiment, a polishing liquid for magnetic disk substrates is provided that can reduce waviness on the surface of a magnetic disk substrate. [Solution] In one aspect, the present disclosure relates to a polishing liquid for magnetic disk substrates, which contains silica particles (component A) and an acid (component B), and in which the ammonia desorption maximum temperature of the silica particles measured by an ammonia temperature-programmed desorption method is 150°C or higher and 250°C or lower.

Description

[Technical Field]

[0001] The present disclosure relates to a polishing liquid for magnetic disk substrates and a method for manufacturing a magnetic disk substrate using the same. [Background technology]

[0002] In recent years, magnetic disk drives have become smaller and their capacity has increased, resulting in the demand for even higher recording densities. To achieve this, technological developments are underway to reduce the unit recording area and lower the flying height of the magnetic head to improve the detection sensitivity of weakened magnetic signals. To accommodate the reduction in the flying height of the magnetic head and the securing of a recording area, magnetic disk substrates are increasingly required to have improved smoothness and flatness, typified by reduced surface roughness, waviness, and edge sagging (roll-off), as well as reduced surface defects such as scratches, protrusions, and pits. Furthermore, increasing capacity also necessitates an increase in the number of magnetic disks mounted in a single disk drive, which requires improved polishing speeds to enable the production of more magnetic disk substrates.

[0003] In response to such demands, for example, Patent Document 1 proposes an abrasive having a pH of 8.0 to 11.5, in which inorganic oxide microparticles having a solid acid amount or solid base amount of 0.01 mmol / g or more and an average particle size of 2 μm or less are dispersed in a dispersion medium. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-200832 Summary of the Invention [Problem to be solved by the invention]

[0005] As the capacity of magnetic disk drives increases, the requirements for substrate surface quality become more stringent, and there is a demand for polishing solutions that can improve the polishing rate (productivity) and reduce the waviness of the substrate surface (substrate quality). Generally, there is a trade-off between the polishing rate and the waviness, and for example, there is a problem that improving the polishing rate worsens the waviness of the substrate surface after polishing.

[0006] In one aspect, the present disclosure provides a polishing liquid for magnetic disk substrates that can reduce waviness on the surface of a magnetic disk substrate. [Means for solving the problem]

[0007] In one aspect, the present disclosure relates to a polishing liquid for magnetic disk substrates, which contains silica particles (component A) and an acid (component B), and in which the silica particles have an ammonia desorption maximum temperature of 150°C or higher and 250°C or lower, as measured by an ammonia temperature-programmed desorption method.

[0008] In one aspect, the present disclosure relates to a polishing liquid for magnetic disk substrates, which comprises silica particles (component A) and an acid (component B), and the silica particles have an ammonia desorption maximum temperature of 150°C or higher and 250°C or lower, as measured by an ammonia temperature-programmed desorption method.

[0009] In one aspect, the present disclosure relates to a polishing liquid for Ni-P plated aluminum alloy substrates, comprising silica particles (component A) and an acid (component B), wherein the silica particles have an ammonia desorption maximum temperature of 150°C or higher and 250°C or lower, as measured by an ammonia temperature-programmed desorption method.

[0010] In one aspect, the present disclosure relates to a polishing slurry for glass substrates, which contains silica particles (component A) and an acid (component B), and in which the silica particles have an ammonia desorption maximum temperature of 150°C or higher and 250°C or lower, as measured by an ammonia temperature-programmed desorption method.

[0011] The present disclosure relates to a kit for producing the polishing liquid for magnetic disk substrates of the present disclosure, which comprises a silica dispersion containing silica particles (component A) and water, and an aqueous additive solution containing an acid (component B) in a mutually unmixed state, and the silica dispersion and the aqueous additive solution are mixed at the time of use.

[0012] In one aspect, the present disclosure relates to a method for manufacturing a magnetic disk substrate, including a step of supplying the polishing liquid of the present disclosure between a substrate to be polished and a polishing pad, and polishing the substrate to be polished.

[0013] In one aspect, the present disclosure relates to a method for polishing a substrate, the method including a step of supplying the polishing liquid for magnetic disk substrates of the present disclosure between a substrate to be polished and a polishing pad, and polishing the substrate to be polished, wherein the substrate to be polished is a substrate used in the manufacture of magnetic disk substrates. [Effects of the Invention]

[0014] According to one or more embodiments of the present disclosure, a polishing liquid for magnetic disk substrates that can reduce waviness on the surface of a magnetic disk substrate can be provided. DETAILED DESCRIPTION OF THE INVENTION

[0015] The present disclosure is based on the finding that by using a polishing liquid containing an acid and silica particles whose ammonia desorption maximum temperature, as measured by the ammonia temperature-programmed desorption method, is 150°C or higher and 250°C or lower, for polishing a magnetic disk substrate, waviness on the polished substrate surface after polishing can be reduced.

[0016] That is, in one aspect, the present disclosure relates to a polishing liquid for magnetic disk substrates (hereinafter also referred to as the "polishing liquid of the present disclosure") that contains silica particles (component A) and an acid (component B), and in which the ammonia desorption maximum temperature of the silica particles measured by an ammonia temperature-programmed desorption method is 150°C or higher and 250°C or lower.

[0017] Although the details of the mechanism by which the effects of the present disclosure are manifested are not clear, it is presumed as follows. Ordinary silica particles (e.g., colloidal silica) have a stable structure, and it is said that there are no strongly acidic points on the surface of silica particles. However, when polishing magnetic disk substrates using silica particles, high external energy such as high load and high rotation speed is applied. Therefore, the Si-O-Si bond of the silica particles is cleaved, and the Si-O - and H + is generated, resulting in a structure that can release a proton even under strongly acidic conditions. In the present disclosure, the ammonia temperature-programmed desorption method, which is an evaluation method for estimating the acidity of solid substances, can estimate the ability to release protons when high external energy such as high load and high rotation is applied, even when such conditions are not applied.By using silica particles that have excellent proton release ability when high external energy is applied, i.e., silica particles whose ammonia desorption maximum temperature is within a predetermined range, in a polishing solution for magnetic disk substrates, it is thought that corrosion of the object to be polished will be promoted, regardless of the contribution of acid, and the polishing rate will be improved.Furthermore, since the silica particles after releasing protons act as solid anions, it is thought that contact of the silica particles with the magnetic disk substrate will be suppressed, and waviness of the magnetic disk substrate surface can be reduced during the polishing operation. However, the present disclosure need not be construed as being limited to these mechanisms.

[0018] In the present disclosure, the "waviness" of a substrate refers to irregularities on the substrate surface that have a longer period than the "roughness." In the present disclosure, irregularities with a period of 60 to 160 μm are referred to as "short wavelength waviness," and irregularities with a period of 500 to 5000 μm are referred to as "long wavelength waviness." By reducing the waviness (short wavelength waviness, long wavelength waviness) of the substrate surface after polishing, it is possible to lower the flying height of the magnetic head in a magnetic disk drive, thereby enabling improvement in the recording density of the magnetic disk. The waviness (short wavelength waviness, long wavelength waviness) of the substrate surface can be measured, for example, by the method described in the Examples. In the present disclosure, "reduced waviness" refers to a reduction in at least one of the short wavelength waviness and the long wavelength waviness.

[0019] [Silica particles (component A)] The silica particles contained in the polishing liquid of the present disclosure (hereinafter also referred to as "Component A") are silica particles having an ammonia desorption maximum temperature of 150° C. or more and 250° C. or less, as measured by an ammonia temperature-programmed desorption method. Component A may be one type or a combination of two or more types.

[0020] In the present disclosure, the ammonia desorption maximum temperature of Component A measured by an ammonia temperature programmed desorption method is 150° C. or higher, and from the viewpoint of reducing waviness, it is preferably 155° C. or higher, more preferably 160° C. or higher, and even more preferably 165° C. or higher, and from the viewpoint of increasing the polishing rate, it is 250° C. or lower, preferably 220° C. or lower, more preferably 200° C. or lower, even more preferably 180° C. or lower, and even more preferably 178° C. or lower. More specifically, the ammonia desorption maximum temperature of Component A measured by an ammonia temperature programmed desorption method is 150° C. or higher and 250° C. or lower, preferably 155° C. or higher and 220° C. or lower, more preferably 160° C. or higher and 200° C. or lower, even more preferably 165° C. or higher and 180° C. or lower, and even more preferably 165° C. or higher and 178° C. or lower.

[0021] Here, temperature-programmed desorption (TDE) is a method that can measure the strength and quantity of solid acid and basic sites. It involves adsorbing probe molecules (NH3, CO2, etc.) onto a solid sample and measuring the desorbed gases produced by continuously increasing the temperature of the sample. When measuring the quantity and strength of acid sites using TDE, the basic gas NH3 is used, so it is called ammonia TDE. In this case, NH3 adsorbed to weak acid sites desorbs at low temperatures, while NH3 adsorbed to strong acid sites desorbs at high temperatures. In other words, the ammonia desorption maximum temperature measured by TDE is the temperature (unit: °C) at which the amount of ammonia detected is at its maximum in the spectrum obtained by measurement using TDE. This is also an index of the acid strength of the silica particles; the higher the ammonia desorption maximum temperature, the more H is adsorbed to ammonia. + This means that the silica particles have a high ability to provide a high level of acidity, and that the silica particles have a strong acidity. In the present disclosure, the ammonia desorption maximum temperature determined by the ammonia temperature programmed desorption method for silica particles can be calculated specifically by the method described in the Examples.

[0022] In the present disclosure, the ammonia adsorption amount of Component A measured by the ammonia temperature programmed desorption method is an index showing the number of acid sites. A larger ammonia adsorption amount means that the silica particles have more acid sites. In the present disclosure, the amount of ammonia adsorption of component A measured by ammonia temperature programmed desorption method is 410 mmol / m 2 More than 420mmol / m 2 More preferably, 430 mmol / m or more 2 More preferably, 440 mmol / m 2 More preferably, 450 mmol / m 2 The above is even more preferable, and from the viewpoint of increasing the polishing rate, 650 mmol / m 2 Preferably less than 600mmol / m 2 Less than 590mmol / m is more preferable. 2 More preferably, 580 mmol / m 2 Even more preferably, 570 mmol / m 2 More specifically, in the present disclosure, the ammonia adsorption amount of component A measured by the ammonia temperature programmed desorption method is 410 mmol / m 2 More than 650mmol / m 2 Preferably less than 420mmol / m 2 More than 600mmol / m 2 Less than 430mmol / m is more preferable. 2 More than 590mmol / m 2 More preferably, 440 mmol / m 2 More than 580mmol / m 2 Even more preferably, 450 mmol / m 2 More than 570mmol / m 2 Even more preferred are the following: In the present disclosure, the ammonia adsorption amount of Component A measured by an ammonia temperature programmed desorption method is, from the viewpoint of reducing waviness, preferably 50,000 mmol / g or more, more preferably 60,000 mmol / g or more, even more preferably 70,000 mmol / g or more, still more preferably 80,000 mmol / g or more, even more preferably 90,000 mmol / g or more, and even more preferably 100,000 mmol / g or more, and from the viewpoint of increasing the polishing rate, it is preferably 250,000 mmol / g or less, more preferably 240,000 mmol / g or less, even more preferably 230,000 mmol / g or less, even more preferably 220,000 mmol / g or less, even more preferably 210,000 mmol / g or less, and even more preferably 200,000 mmol / g or less. In the present disclosure, the ammonia adsorption amount of Component A measured by an ammonia temperature programmed desorption method is preferably 50,000 mmol / g or more and 250,000 mmol / g or less, more preferably 60,000 mmol / g or more and 240,000 mmol / g or less, even more preferably 70,000 mmol / g or more and 230,000 mmol / g or less, still more preferably 80,000 mmol / g or more and 220,000 mmol / g or less, still more preferably 90,000 mmol / g or more and 210,000 mmol / g or less, and still more preferably 100,000 mmol / g or more and 200,000 mmol / g or less.

[0023] The maximum ammonia desorption temperature and ammonia adsorption amount of Component A can be controlled by adjusting the reaction temperature and reaction pressure, for example, using a particle growth method using an aqueous alkali silicate solution as the raw material.

[0024] Examples of component A include wet silica, dry silica, pulverized silica, and surface-modified silica thereof. Among these, wet silica is preferred from the viewpoints of improving the polishing rate and reducing waviness. In the present disclosure, component A is more preferably colloidal silica. The colloidal silica can be obtained by, for example, a method of particle growth using an aqueous solution of alkali silicate as a raw material (water glass method), a method of condensation of a hydrolyzed product of alkoxysilane (sol-gel method), or a method of precipitating silica particles by a neutralization reaction between a silicate such as sodium silicate and a mineral acid such as sulfuric acid (precipitation method).

[0025] In one or more embodiments, component A can be obtained as follows. An alkali silicate, a raw material for silica particles, is dissolved in water to a concentration of 2 to 8% by mass. A strong acid (preferably one or more selected from hydrochloric acid, sulfuric acid, and nitric acid) is added to the aqueous solution to neutralize the alkali silicate, thereby forming a silica hydrogel. The pH at this stage is preferably about 4 to 6. The alkali silicate hydrogel neutralized with the strong acid is allowed to stand at a temperature range of 10 to 40°C for 1 to 5 hours to mature the silica. The salt is then removed by washing with pure water or alkaline water. An alkaline solution (preferably one or more selected from sodium hydroxide, potassium hydroxide, and ammonium hydroxide) is added to the washed dispersion, and the pH of the dispersion is adjusted to a range of 6 to 12. The temperature at this stage is preferably 40 to 120°C. The prepared dispersion is stirred for about 30 minutes to 3 hours to form a colloidal silica hydrogel. The obtained silica sol is then subjected to hydrothermal treatment at a temperature of 100 to 300°C and a pressure of 0.1 to 0.3 MPa for 30 minutes to 6 hours to grow and stabilize the silica particles, thereby obtaining the desired silica particles (component A). The content of silicon element in Component A measured by X-ray fluorescence analysis is preferably 90% by mass or more, more preferably 92.5% by mass or more, even more preferably 95% by mass or more, even more preferably 98% by mass or more, and preferably 99.9% by mass or less, from the viewpoint of the polishing rate. The content of silicon element in component A is a value detected by X-ray fluorescence analysis (XRF), and can be measured, for example, using a wavelength dispersive X-ray fluorescence spectrometer Prmus II manufactured by Rigaku Corporation. Specifically, it can be measured by the method described in the examples.

[0026] The content of component A in the polishing liquid of the present disclosure is preferably 1.5% by mass or more, more preferably 3% by mass or more, and even more preferably 4.5% by mass or more, from the viewpoint of improving the polishing rate, and is preferably 10% by mass or less, more preferably 9% by mass or less, and even more preferably 8% by mass or less, from the viewpoint of reducing waviness. More specifically, the content of component A in the polishing liquid of the present disclosure is preferably 1.5% by mass or more and 10% by mass or less, more preferably 3% by mass or more and 9% by mass or less, and even more preferably 4.5% by mass or more and 8% by mass or less. When two or more types of silica particles are used in combination, the content of the silica particles refers to the total content of the silica particles.

[0027] [Acid (component B)] The polishing liquid of the present disclosure contains an acid (hereinafter also referred to as "component B"). In the present disclosure, the acid may be partially in the form of a salt. In the present disclosure, the content of the acid in component B (the value in the acid state (in the form not in the form of a salt), the same applies hereinafter) is preferably more than 50% by mass, more preferably 80% by mass or more, even more preferably 90% by mass or more, still more preferably 95% by mass or more, and even more preferably 100% by mass, from the viewpoints of improving the polishing rate and reducing waviness. 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; and organic acids such as organic phosphoric acid, organic phosphonic acid, and carboxylic acid. Among these, from the viewpoints of improving the polishing rate and reducing waviness, it is preferable for Component B to contain an inorganic acid or an organic phosphonic acid, and it is more preferable for Component B to contain an inorganic acid or to be an inorganic acid. In the present disclosure, from the same viewpoint, the content of the inorganic acid in Component B is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, and even more preferably 100% by mass. From the same viewpoint, the inorganic acid is preferably at least one selected from nitric acid, sulfuric acid, hydrochloric acid, perchloric acid and phosphoric acid, more preferably at least one selected from sulfuric acid and phosphoric acid, and even more preferably phosphoric acid. From the same viewpoint, the organic phosphonic acid is preferably at least one selected from 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP), aminotrimethylene phosphonic acid, ethylenediaminetetramethylene phosphonic acid, and diethylenetriaminepentamethylene phosphonic acid, with HEDP being more preferred. Examples of salts of these acids include salts of the above acids with at least one selected from metals, ammonia, and alkylamines. Examples of the above metals include metals belonging to Groups 1 to 11 of the periodic table. Among these, salts of the above acids with metals belonging to Group 1A or ammonia are preferred from the viewpoints of improving the polishing rate and reducing waviness.

[0029] From the viewpoints of improving the removal rate and reducing waviness, the content of component B in the polishing liquid 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 same viewpoints, it is preferably 3% by mass or less, more preferably 2% by mass or less, and even more preferably 1.8% by mass or less. More specifically, the content of component B in the polishing liquid of the present disclosure is preferably 0.01% by mass or more and 3% by mass or less, more preferably 0.1% by mass or more and 2% by mass or less, and even more preferably 0.5% by mass or more and 1.8% 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.

[0030] [Oxidizing agent (component C)] The polishing liquid of the present disclosure may further contain an oxidizing agent (hereinafter also referred to as "component C") from the viewpoint of improving the removal rate and reducing waviness. In one or more embodiments, component C is preferably an oxidizing agent that does not contain a halogen atom. Component C may be one type or a combination of two or more types. Component C is preferably contained in the polishing liquid of the present disclosure when the substrate is an Ni-P plated aluminum alloy substrate.

[0031] From the viewpoints of improving the polishing rate and reducing waviness, examples of component C include peroxides, permanganic acid or its salts, chromic acid or its salts, peroxoacids or their salts, oxyacids or their salts, metal salts, nitric acids, and sulfuric acids. Among these, at least one selected from hydrogen peroxide, iron(III) nitrate, peracetic acid, ammonium peroxodisulfate, iron(III) sulfate, and ammonium iron(III) sulfate is preferred, and hydrogen peroxide is more preferred from the viewpoints of improving the polishing rate, preventing metal ions from adhering to the surface of the substrate to be polished, and ease of availability.

[0032] The content of component C 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 improving the polishing rate, and is preferably 4% by mass or less, more preferably 3% by mass or less, and even more preferably 2% by mass or less, from the viewpoint of reducing waviness. The content of component C 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 3% by mass or less, and even more preferably 0.1% by mass or more and 2% 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.

[0033] [Mass ratio of component B to component A] In the polishing liquid of the present disclosure, the mass ratio B / A of component B to component A (content of component B / content of component A) is preferably 0.05 or more, more preferably 0.07 or more, even more preferably 0.10 or more, and even more preferably 0.15 or more, from the viewpoint of improving the polishing rate and reducing waviness, and from the same viewpoint, it is preferably 0.5 or less, more preferably 0.4 or less, even more preferably 0.35 or less, and even more preferably 0.3 or less. From the same viewpoint, the mass ratio B / A is preferably 0.05 or more and 0.5 or less, more preferably 0.07 or more and 0.4 or less, even more preferably 0.10 or more and 0.35 or less, and even more preferably 0.15 or more and 0.3 or less.

[0034] [Mass ratio of component C to component A] In the polishing liquid of the present disclosure, the mass ratio C / A of component C to component A (content of component C / content of component A) is preferably 0.001 or more, more preferably 0.01 or more, even more preferably 0.05 or more, even more preferably 0.1 or more, and even more preferably 0.15 or more, and from the same viewpoints, is preferably 0.4 or less, more preferably 0.3 or less, even more preferably 0.25 or less, and even more preferably 0.2 or less. The mass ratio C / A is preferably 0.001 or more and 0.4 or less, more preferably 0.01 or more and 0.3 or less, even more preferably 0.05 or more and 0.25 or less, even more preferably 0.1 or more and 0.2 or less, and even more preferably 0.15 or more and 0.2 or less.

[0035] [water] In one or more embodiments, the polishing liquid of the present disclosure contains water as a medium. Examples of water include distilled water, ion-exchanged water, pure water, and ultrapure water. The content of water in the polishing liquid of the present disclosure can be the remainder obtained by subtracting component A, component B, and optional components (component C and other components described below) from the total amount of the polishing liquid (100% by mass).

[0036] [Other ingredients] In one or more embodiments, the polishing liquid of the present disclosure may contain other components as needed, provided that the effects of the present disclosure are not impaired. Examples of other components include corrosion inhibitors, thickeners, dispersants, rust inhibitors, basic substances, surfactants, and water-soluble polymers.

[0037] [pH of polishing solution for magnetic disk substrates] The pH of the polishing liquid of the present disclosure is preferably 1 or more, more preferably 1.1 or more, and even more preferably 1.2 or more, from the viewpoint of reducing waviness, and is preferably 6 or less, more preferably 4 or less, and even more preferably 2 or less, from the viewpoint of improving the polishing rate. More specifically, the pH of the polishing liquid of the present disclosure is preferably 1 or more and 6 or less, more preferably 1.1 or more and 4 or less, and even more preferably 1.2 or more and 2 or less. The pH can be adjusted using the above-mentioned acid (component B) or a known pH adjuster. In the present disclosure, the pH is the pH of the polishing liquid at 25°C, and can be measured using a pH meter. For example, the value can be measured 2 minutes after immersing the electrodes of the pH meter in the polishing liquid for magnetic disk substrates.

[0038] [Method of manufacturing a polishing liquid for magnetic disk substrates] The polishing liquid of the present disclosure can be produced, for example, by blending component A, component B, and water as needed, and, if desired, optional components (component C and other components) using a known method. For example, in one or more embodiments, the polishing liquid of the present disclosure can be prepared by blending at least component A, component B, and water as needed. Therefore, in one aspect, the present disclosure relates to a polishing liquid for magnetic disk substrates, which comprises a blend of silica particles (component A) and an acid (component B), and which has an ammonia desorption maximum temperature of the silica particles measured by an ammonia temperature-programmed desorption method of 150° C. or higher and 250° C. or lower. In the present disclosure, the term "combined" means that not only component A and component B but also optional components can be blended as needed. 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, and, if necessary, water. In this disclosure, "blending" includes simultaneously or in any order mixing component A, component B, and, if necessary, water, as well as optional components (component C, other components). Silica particles (component A) may be mixed in the form of a concentrated slurry, or may be diluted with water or the like before mixing. When component A consists of multiple types of silica particles, the multiple types of silica particles can be blended simultaneously or separately. When component B consists of multiple types of acids, the multiple types of acids can be blended simultaneously or separately. When component C consists of multiple types of oxidizing agents, the multiple types of oxidizing agents can be blended simultaneously or separately. The blending can be performed using a mixer such as a homomixer, homogenizer, ultrasonic disperser, or wet ball mill. The preferred amounts of each component in the polishing liquid production method of the present disclosure may be the same as the preferred contents of each component in the polishing liquid of the present disclosure described above.

[0039] 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, that is, at the time when the polishing liquid begins to be used to polish a magnetic disk substrate. In one or more embodiments, the content of each component in the polishing liquid of the present disclosure can be considered as the blending amount of each component.

[0040] In view of storage and transportation, the polishing liquid of the present disclosure may be produced as a concentrate and may include a form that is diluted upon use. That is, in one or more embodiments, the present disclosure relates to a concentrate of 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.

[0041] The concentration ratio of the polishing liquid concentrate in 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" is the ratio of the mass of the 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" is the ratio of the mass of the 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 diluted with water so that the content of each component at the time of use is the content described above (i.e., the content of each component in the polishing liquid at the time of use).

[0042] From the viewpoint of reducing waviness when preparing the polishing liquid of the present disclosure, the pH of the concentrated polishing liquid of the present disclosure is preferably 1 or more, more preferably 1.1 or more, and even more preferably 1.2 or more, and from the viewpoint of improving the polishing rate, it is preferably 6 or less, more preferably 4 or less, and even more preferably 2 or less. In the present disclosure, the pH of the concentrated polishing liquid is a value at 25°C, and can be measured using a pH meter; for example, the value can be measured 2 minutes after immersing the electrode of the pH meter in the concentrated polishing liquid.

[0043] [Polishing liquid kit] In one aspect, the present disclosure relates to a kit for preparing the polishing liquid 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 include a form in which a liquid combination is formed by arbitrarily selecting component A and component B. One embodiment of the polishing liquid kit of the present disclosure includes a silica dispersion (first liquid) containing component A and water, and an additive aqueous solution (second liquid) containing component B, in a mutually unmixed state. The first liquid and the second liquid are mixed at the time of use and may be diluted with water as needed. The water contained in the first liquid may be all or a portion of the water used to prepare the polishing liquid of the present disclosure. The second liquid may contain a portion of the water used to prepare the polishing liquid of the present disclosure. The first liquid and the second liquid may each contain the above-mentioned optional components (component C, other components) as needed. When the first liquid and the second liquid are mixed, the above-mentioned optional components (component C, other components) may be further mixed. According to the present disclosure, it is possible to obtain a polishing liquid kit that can reduce waviness on the surface of a substrate after polishing.

[0044] [Method of 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") that includes a step of supplying the polishing liquid of the present disclosure between a substrate to be polished and a polishing pad and polishing the substrate to be polished (hereinafter also simply referred to as the "polishing step"). Generally, a magnetic disk is 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. The substrate manufacturing method of the present disclosure is preferably one or more selected from a manufacturing method in which the polishing liquid of the present disclosure is supplied between the substrate to be polished and a polishing pad in the rough polishing process, a manufacturing method in which the polishing liquid of the present disclosure is supplied between the substrate to be polished and a polishing pad in the finish polishing process, and a manufacturing method in which the polishing liquid of the present disclosure is supplied between the substrate to be polished and a polishing pad in both the rough polishing process and the finish polishing process.

[0045] In one or more embodiments, the polishing process includes supplying the polishing liquid of the present disclosure to a surface 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 to perform polishing. In one or more embodiments, the polishing step includes: sandwiching the substrate to be polished between plates to which polishing pads are attached, supplying the polishing liquid of the present disclosure to the polishing surface, and polishing the substrate to be polished by moving the polishing pad and the substrate to be polished while applying pressure.

[0046] [Substrate to be polished] In one or more embodiments, the substrate to be polished is a substrate used in the manufacture of magnetic disk substrates, and examples thereof include Ni-P plated aluminum alloy substrates and glass substrates such as crystallized glass, tempered glass, aluminosilicate glass, aluminoborosilicate glass, etc. That is, in one or more embodiments, the polishing liquid of the present disclosure is preferably used for polishing Ni-P plated aluminum alloy substrates and glass substrates. Therefore, in one aspect, the present disclosure relates to a polishing liquid for Ni-P plated aluminum alloy substrates, which contains silica particles (component A) and an acid (component B), and the silica particles have an ammonia desorption maximum temperature of 150°C or higher and 250°C or lower, as measured by an ammonia temperature-programmed desorption method. In one aspect, the present disclosure relates to a polishing slurry for glass substrates, which contains silica particles (component A) and an acid (component B), and in which the silica particles have an ammonia desorption maximum temperature of 150°C or higher and 250°C or lower, as measured by an ammonia temperature-programmed desorption method. In this disclosure, the term "Ni-P plated aluminum alloy substrate" refers to an aluminum alloy substrate whose surface has been ground and then subjected to electroless Ni-P plating. A magnetic disk substrate can be manufactured by polishing the surface of the substrate to be polished using the polishing liquid of this disclosure, followed by forming a magnetic layer on the substrate surface by sputtering or the like. Glass substrates refer to crystallized glass, tempered glass, aluminosilicate glass, aluminoborosilicate glass, etc., and similarly to the "Ni-P plated aluminum alloy substrate," a magnetic disk substrate can be manufactured by polishing the surface of the substrate to be polished using the polishing liquid of this disclosure, followed by forming a magnetic layer on the substrate surface by sputtering or the like. 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, and a disk-shaped substrate is preferred. In the case of a disk-shaped substrate to be polished, its outer diameter is, for example, 10 to 120 mm, and its thickness is, for example, 0.5 to 2 mm.

[0047] 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 in which these are laminated can be used, and from the viewpoint of improving the polishing rate, a suede type polishing pad is preferred.

[0048] From the viewpoint of maintaining the polishing rate and reducing waviness, the polishing load in the polishing step is preferably 3 kPa or more, more preferably 5 kPa or more, even more preferably 7 kPa or more, and is preferably 30 kPa or less, more preferably 25 kPa or less, and even more preferably 20 kPa or less. In the present disclosure, the "polishing load" refers to the pressure of the platen applied to the polished surface of the substrate during polishing. The polishing load can be adjusted by adjusting the air pressure or weight load on the platen, substrate, etc.

[0049] In the polishing process, 2 From the viewpoint of ensuring the polishing rate and reducing waviness, the polishing amount per unit area is preferably 0.2 mg or more, more preferably 0.3 mg or more, and even more preferably 0.4 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.

[0050] The polished substrate in the polishing process 2 From the viewpoint of economy, the supply rate of the polishing liquid for magnetic disk substrates per unit area is preferably 2.5 mL / min or less, more preferably 2 mL / min or less, and even more preferably 1.5 mL / min or less, and from the viewpoint of improving the polishing rate, it is preferably 0.01 mL / min or more, more preferably 0.03 mL / min or more, and even more preferably 0.05 mL / min or more.

[0051] 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 multiple 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 multiple 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.

[0052] According to the substrate manufacturing method of the present disclosure, by using the polishing liquid of the present disclosure, it is possible to reduce waviness on the substrate surface after polishing, thereby achieving the effect of enabling high-quality magnetic disk substrates to be manufactured with high yield and good productivity.

[0053] [Substrate 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 includes a step of supplying a polishing liquid of the present disclosure between a substrate to be polished and a polishing pad to polish the substrate to be polished (hereinafter also referred to as the "polishing step"), where the substrate to be polished is a substrate used in the manufacture of magnetic disk substrates. According to the polishing method of the present disclosure, by using the polishing liquid of the present disclosure, which can reduce waviness on the substrate surface after polishing, high-quality magnetic disk substrates can be manufactured with high yield and good productivity. As described above, examples of the substrate to be polished in the polishing method of the present disclosure include substrates used in the manufacture of magnetic disk substrates. The polishing method and conditions in the polishing step of the polishing method of the present disclosure may be the same as those in the polishing step of the substrate manufacturing method of the present disclosure described above. [Example]

[0054] Hereinafter, the present disclosure will be described in more detail with reference to examples, but these are merely illustrative examples and the present disclosure is not limited to these examples.

[0055] 1. Preparation of Silica Particles Preparation of silica particles (I)-(V) The raw material for silica particles, alkali silicate, is dissolved in water to a concentration of 2-8% by mass. A strong acid such as hydrochloric acid, sulfuric acid, or nitric acid is added to the solution to neutralize the silicic acid, resulting in a silica hydrogel. The pH is maintained at 4-6. The silica hydrogel, neutralized with a strong acid, is left to stand at a temperature between 10 and 40°C for 1 to 5 hours to mature the silica. The mixture is then washed with pure water or alkaline water to remove the salt. An alkaline solution such as sodium hydroxide, potassium hydroxide, or ammonium hydroxide is added to the washed dispersion, and the pH of the dispersion is adjusted to a range of 6 to 12. The temperature is 40 to 120°C. The prepared dispersion is stirred for 30 minutes to 3 hours to form a colloidal silica hydrogel. The resulting silica sol is then hydrothermally treated at a temperature between 100 and 300°C and a pressure between 0.1 and 0.3 MPa for 3 to 6 hours to grow and stabilize the silica particles. The reaction temperature, pressure, and time are adjusted to obtain silica particles (I) to (V) (colloidal silica) with the ammonia desorption maximum temperature and ammonia adsorption capacity shown in Table 1. As the silica particles in Comparative Example 1, silica particles PL-3 (colloidal silica) manufactured by Fuso Chemical Co., Ltd. were used. [Silicon content in silica] The content of silicon element in silica was measured as follows. X-ray fluorescence analysis (XRF): Rigaku Prmus II wavelength dispersive X-ray fluorescence 50 mg of each silica solid sample, which had been dried at 110°C in advance, was dispensed onto filter paper, covered with PET film, and pressed for measurement. The analytical angle 2θ varies depending on the element being measured. Measurements were performed using a rhodium tube as the target, a tube voltage of 50 kV, and a tube current of 50 mA. The analyzing crystals used were LiF(200), Ge, PET, and RX25, and the detectors were SC and PC. The measurement depth for the sample is several μm. The content of each silicon element was 99.5 mass% for silica particles (I), 99.4 mass% for silica particles (II), 98.8 mass% for silica particles (III), 98.9 mass% for silica particles (IV), 99.4 mass% for silica particles (V), and 100 mass% for PL-3.

[0056] 2.Measuring methods for various parameters [Method for measuring the maximum ammonia desorption temperature and ammonia adsorption amount using the ammonia temperature-programmed desorption method] The maximum ammonia desorption temperature and the amount of ammonia adsorption determined by ammonia temperature programmed desorption (NH3-TPD) were determined as follows. Measuring device: "BELCAT-B" manufactured by Japan BEL Corporation Measurement method: Each silica solid sample (0.01 mg) was pre-dried for 1 hour at 120°C in a He gas (50 cc / min) atmosphere. It was then adsorbed at 100°C for 1 hour in a 5 vol% NH3 / He (30 cc / min) atmosphere. The temperature was then increased at a rate of 10°C / min in a He gas (30 cc / min) atmosphere, up to a maximum temperature of 800°C. A quadrupole mass spectrometer was used as the detector. To detect ammonia (NH3 = mass number 17), the mass numbers were set to 16 and 17 to avoid confusion with water (H2O = mass number 18). The temperature (unit: °C) at which the maximum amount of ammonia was detected in the resulting spectrum was defined as the ammonia desorption maximum temperature. The results are shown in Table 1. In addition, the ammonia adsorption amount (mmol / m 2 ) was calculated from the integral value of the obtained spectrum to determine the amount of ammonia adsorbed per 1 mg of sample (mmol / mg), and the specific surface area (m 2 / g to calculate the ammonia adsorption amount per unit area (mmol / m 2 The results are shown in Tables 1 and 2. The ammonia adsorption amounts converted into mmol / g units are also shown in Tables 1 and 2. The specific surface area of ​​silica (m 2 / g) was calculated as follows. Each silica particle was dried with hot air at 110°C for 12 hours and crushed in an agate mortar as needed to obtain a powdered silica particle sample. The obtained sample was pre-dried at 200°C for 15 minutes immediately before measuring the BET specific surface area, and the specific surface area (unit: m) was measured by the BET method (nitrogen adsorption method) using a Micromeritic automatic specific surface area measuring device "Flowsorb III2305" (Shimadzu Corporation). 2 / g) was measured.

[0057] [pH measurement] The pH of the polishing solution for magnetic disk substrates 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 solution was used.

[0058] 3. Preparation of Polishing Solution for Magnetic Disk Substrates (Examples 1 to 6, Comparative Example 1) The polishing liquids of Examples 1 to 6 were prepared by mixing 10 parts by mass of the silica particles (I) to (V), an acid (component B), an oxidizing agent (component C), and water. The polishing liquid of Comparative Example 1 was prepared in the same manner as in Example 1, except that silica particles PL-3 (colloidal silica) manufactured by Fuso Chemical Co., Ltd. were used instead of the silica particles (I). The content (effective amount) of each component in each polishing liquid was 6.0% by mass for the silica particles, 1.6% or 1.0% by mass for the acid (component B), and 1.0% by mass for the oxidizing agent (component C). The content of water is the remainder after subtracting components A, B, and C from the total amount of the polishing liquid. The pH of each polishing liquid measured at 25°C was 1.6. (Examples 7 to 8, Comparative Example 2) The polishing liquids of Examples 7 and 8 were prepared by mixing 10 parts by mass of the silica particles (I) and (II), an acid (component B), and water. The polishing liquid of Comparative Example 2 was prepared in the same manner as in Example 7, except that silica particles PL-3 (colloidal silica) manufactured by Fuso Chemical Co., Ltd. were used instead of the silica particles (I). The content (effective amount) of each component in each polishing liquid was 6.0% by mass for the silica particles and 1.6% by mass for the acid (component B). The content of water was the remainder after subtracting components A and B from the total amount of the polishing liquid. The pH of each polishing liquid measured at 25°C was 1.6.

[0059] The following acids (component B) and oxidizing agents (component C) were used to prepare the polishing liquid. (Component B) Phosphoric acid [75% phosphoric acid, manufactured by Nippon Chemical Industry Co., Ltd.] Sulfuric acid [refined dilute sulfuric acid, manufactured by Teika Corporation, 62.5%] (Component C) Hydrogen peroxide [ADEKA Corporation, Hydrogen peroxide 35%]

[0060] 4-1. Polishing Method (Examples 1 to 6, Comparative Example 1) The following substrates were polished under the polishing conditions shown below using the polishing solutions of Examples 1 to 6 and Comparative Example 1. Then, the polishing rate and waviness were measured by the measurement methods described below. The results are shown in Table 1.

[0061] [Substrate to be polished] Ni-P plated aluminum alloy substrate (thickness 0.5-0.6 mm, diameter 97-100 mm)

[0062] [Polishing conditions] Polishing machine: Double-sided polishing machine (9B type double-sided polishing machine, manufactured by Speedfam Co., Ltd.) Number of boards: 10 Polishing liquid: Polishing liquid described in Examples and Comparative Examples Polishing pad: Suede type (foam layer: polyurethane elastomer, thickness 1.0 mm, average pore size 30 μm, surface layer compressibility 2.5%, Filwel) Plate rotation speed: 40 rpm Polishing load: 9.8 kPa (set value) Polishing liquid supply amount: 100mL / min Substrate to be polished 1cm 2 Feed rate per unit: 0.8 mL / min Substrate to be polished 1cm 2 Polishing amount per piece: 0.8mg Polishing time: 5 minutes After polishing, the substrate is removed from the double-sided polisher and the surface is cleaned in an automatic cleaning machine.

[0063] 4-2. Polishing Method (Examples 7-8, Comparative Example 2) The following substrates were polished under the polishing conditions shown below using the polishing solutions of Examples 7 and 8 and Comparative Example 2. Then, the polishing rate and waviness were measured by the measurement methods described below. The results are shown in Table 2.

[0064] [Substrate to be polished] Glass substrate (thickness 0.4-0.5 mm, diameter 97-100 mm)

[0065] [Polishing conditions] Polishing machine: Double-sided polishing machine (9B type double-sided polishing machine, manufactured by Speedfam Co., Ltd.) Number of boards: 10 Polishing liquid: Polishing liquid described in Examples and Comparative Examples Polishing pad: Suede type (foam layer: polyurethane elastomer, thickness 1.0 mm, average pore size 30 μm, surface layer compressibility 2.5%, Filwel) Plate rotation speed: 40 rpm Polishing load: 9.8 kPa (set value) Polishing liquid supply amount: 100mL / min Substrate to be polished 1cm 2 Feed rate per unit: 0.8 mL / min Substrate to be polished 1cm 2 Polishing amount per piece: 0.8mg Polishing time: 12 minutes After polishing, the substrate is removed from the double-sided polisher and the surface is cleaned in an automatic cleaning machine.

[0066] 5. Evaluation [Evaluation of polishing speed] The polishing rate was determined by measuring the mass of each substrate before and after polishing using an electronic balance (manufactured by Sartorius, "BP-210S") and calculating the mass loss of each substrate. The polishing rate was calculated by dividing the average mass loss of all 10 substrates by the polishing time, and then using the formula below. The calculated polishing rates for Examples 1 to 6 are shown in Table 1 as relative values, with the polishing rate for Comparative Example 1 set to 100. The calculated polishing rates for Examples 7 and 8 are shown in Table 2 as relative values, with the polishing rate for Comparative Example 2 set to 100. The larger the polishing rate, the faster the polishing rate. Mass loss (g) = {mass before polishing (g) - mass after polishing (g)} Polishing speed (g / min) = mass loss (g) / polishing time (min)

[0067] [Evaluation of short wavelength waviness and long wavelength waviness] The short wavelength waviness and long wavelength waviness were measured by randomly selecting two substrates from the ten polished substrates and randomly selecting three points (12 points in total) on both surfaces of the selected substrates under the following conditions. The average values ​​of the measurements at these 12 points were calculated as the short wavelength waviness and long wavelength waviness of the substrate. The calculation results of the short wavelength waviness and long wavelength waviness for Examples 1 to 6 are shown in Table 1 as relative values ​​with the short wavelength waviness and long wavelength waviness for Comparative Example 1 set to 100. The calculation results of the short wavelength waviness and long wavelength waviness for Examples 7 and 8 are shown in Table 2 as relative values ​​with the short wavelength waviness and long wavelength waviness for Comparative Example 2 set to 100. For the short wavelength waviness and long wavelength waviness, the smaller the number, the smaller the waviness. <Measurement conditions> Measuring device: New View (manufactured by Zygo) Lens: 2.5x Zoom: 0.5x Short wavelength range: 60~160μm Long wavelength range: 500~5000μm Analysis software: Zygo Metro pro (manufactured by Zygo)

[0068] [Table 1]

[0069] [Table 2]

[0070] As shown in Table 1 above, the polishing liquids of Examples 1 to 6, which used silica particles having an ammonia desorption maximum temperature of 150°C or more and 250°C or less as measured by the ammonia temperature programmed desorption method, had improved polishing rates and reduced short-wavelength waviness and long-wavelength waviness compared to the polishing liquid of Comparative Example 1, which used silica particles having an ammonia desorption maximum temperature of less than 150°C. As shown in Table 2 above, the polishing liquids of Examples 7 and 8, which used silica particles having an ammonia desorption maximum temperature of 150°C or more and 250°C or less as measured by the ammonia temperature programmed desorption method, had improved polishing rates and reduced short-wavelength waviness and long-wavelength waviness compared to the polishing liquid of Comparative Example 2, which used silica particles having an ammonia desorption maximum temperature of less than 150°C. [Industrial Applicability]

[0071] According to the present disclosure, for example, a magnetic disk substrate suitable for high recording density can be provided.

Claims

1. Contains silica particles (component A) and an acid (component B), The polishing liquid for magnetic disk substrates has a maximum ammonia desorption temperature of 150° C. or higher and 250° C. or lower, as measured by an ammonia temperature programmed desorption method.

2. The ammonia adsorption amount of component A measured by ammonia temperature programmed desorption method is 410 mmol / m 2 650 mmol / m or more 2 2. The polishing liquid for magnetic disk substrates according to claim 1, wherein the polishing liquid is:

3. 2. The polishing liquid for magnetic disk substrates according to claim 1, wherein the amount of ammonia adsorption of component A measured by ammonia temperature programmed desorption method is 50,000 mmol / g or more and 250,000 mmol / g or less.

4. 2. The polishing liquid for magnetic disk substrates according to claim 1, having a pH of 1 or more and 6 or less.

5. 2. The polishing liquid for magnetic disk substrates according to claim 1, wherein the content of silicon element in Component A measured by fluorescent X-ray analysis is 90 mass % or more.

6. 2. The polishing liquid for magnetic disk substrates according to claim 1, wherein component A is colloidal silica.

7. 2. The polishing liquid for magnetic disk substrates according to claim 1, wherein the content of Component A is 1.5% by mass or more and 10% by mass or less.

8. 2. The polishing liquid for magnetic disk substrates according to claim 1, wherein the content of Component B is 0.01% by mass or more and 3% by mass or less.

9. 2. The polishing liquid for magnetic disk substrates according to claim 1, wherein Component B is at least one selected from sulfuric acid and phosphoric acid.

10. 2. The polishing liquid for magnetic disk substrates according to claim 1, wherein the mass ratio B / A of component B to component A is 0.05 or more and 0.5 or less.

11. A composition comprising silica particles (component A) and an acid (component B), The polishing liquid for magnetic disk substrates has a maximum ammonia desorption temperature of 150° C. or higher and 250° C. or lower, as measured by an ammonia temperature programmed desorption method.

12. Contains silica particles (component A) and an acid (component B), The polishing liquid for Ni-P plated aluminum alloy substrates has a maximum ammonia desorption temperature of 150° C. or higher and 250° C. or lower, as measured by an ammonia temperature programmed desorption method.

13. Contains silica particles (component A) and an acid (component B), The polishing liquid for glass substrates, wherein the silica particles have an ammonia desorption maximum temperature of 150°C or higher and 250°C or lower as measured by an ammonia temperature programmed desorption method.

14. A kit for producing the polishing liquid for magnetic disk substrates according to any one of claims 1 to 13, comprising: A polishing liquid kit comprising a silica dispersion containing silica particles (component A) and water, and an additive aqueous solution containing an acid (component B) in a mutually unmixed state, the silica dispersion and the additive aqueous solution being mixed at the time of use.

15. 12. A method for manufacturing a magnetic disk substrate, comprising the step of supplying the polishing liquid for a magnetic disk substrate according to claim 1 between a substrate to be polished and a polishing pad, and polishing the substrate to be polished.

16. 12. A method for polishing a substrate, comprising the steps of supplying the polishing liquid for magnetic disk substrates according to claim 1 between a substrate to be polished and a polishing pad, and polishing the substrate to be polished, wherein the substrate to be polished is a substrate used in the manufacture of magnetic disk substrates.

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