Polishing solution for magnetic disk substrates

Abstract

In one embodiment, a polishing solution for magnetic disk substrates is provided that can reduce waviness on the surface of the magnetic disk substrate. [Solution] In one embodiment, this disclosure relates to a polishing solution for magnetic disk substrates comprising silica particles (component A) and an acid (component B), wherein the maximum ammonia desorption temperature of the silica particles, as measured by an ammonia temperature rise desorption method, is 150°C or higher and 250°C or lower.

Description

[Technical Field]

[0001] This disclosure relates to a polishing solution for magnetic disk substrates and a method for manufacturing magnetic disk substrates using the same. [Background technology]

[0002] In recent years, magnetic disk drives have become smaller and have increased in capacity, which has led to a demand for even higher recording density. To achieve this, technological developments are underway to reduce the unit recording area and lower the levitation height of the magnetic head to improve the detection sensitivity of weakened magnetic signals. To accommodate the reduction in magnetic head levitation height and the securing of recording area, there are increasingly stringent requirements for improved smoothness and flatness of the magnetic disk substrate, such as reducing surface roughness, waviness, and edge roll-off, as well as reducing surface defects such as scratches, protrusions, and pits. Furthermore, increasing capacity requires increasing the number of magnetic disks mounted in a single disk drive, and thus requires improved polishing speed to enable the production of more magnetic disk substrates.

[0003] To address such requirements, for example, Patent Document 1 proposes an abrasive in which inorganic oxide fine particles, having a solid acid or solid base content of 0.01 mmol / g or more and an average particle diameter of 2 μm or less, are dispersed in a dispersion medium, and the pH is 8.0 to 11.5. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2012-200832 [Overview of the project] [Problems that the invention aims to solve]

[0005] As magnetic disk drives increase in capacity, the requirements for substrate surface quality have become even more stringent. There is a need for polishing solutions that can improve polishing speed (productivity) while simultaneously reducing surface waviness (substrate quality). Generally, polishing speed and waviness are in a trade-off relationship; for example, improving polishing speed can worsen the surface waviness of the substrate after polishing.

[0006] This disclosure provides, in one embodiment, a polishing solution for magnetic disk substrates that can reduce waviness on the surface of the magnetic disk substrate. [Means for solving the problem]

[0007] This disclosure relates, in one embodiment, to a polishing solution for magnetic disk substrates comprising silica particles (component A) and an acid (component B), wherein the maximum ammonia desorption temperature of the silica particles, as measured by ammonia temperature-controlled desorption method, is 150°C or higher and 250°C or lower.

[0008] This disclosure relates, in one embodiment, to a polishing solution for magnetic disk substrates comprising silica particles (component A) and an acid (component B), wherein the maximum ammonia desorption temperature of the silica particles, as measured by an ammonia temperature rise desorption method, is 150°C or higher and 250°C or lower.

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

[0010] This disclosure relates, in one embodiment, to a polishing solution for glass substrates comprising silica particles (component A) and an acid (component B), wherein the maximum ammonia desorption temperature of the silica particles, as measured by an ammonia temperature rise desorption method, is 150°C or higher and 250°C or lower.

[0011] The present disclosure relates to a kit for manufacturing a polishing liquid for a magnetic disk substrate of the present disclosure, which contains a silica dispersion containing silica particles (component A) and water, and an additive aqueous solution containing an acid (component B), and the silica dispersion and the additive aqueous solution are included in a state where they are not mixed with each other, and the silica dispersion and the additive aqueous 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, which 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.

[0013] In one aspect, the present disclosure relates to a method for polishing a substrate, which includes a step of supplying the polishing liquid for a magnetic disk substrate of the present disclosure between a substrate to be polished and a polishing pad, and polishing the substrate to be polished, and the substrate to be polished is a substrate used for manufacturing a magnetic disk substrate.

Advantages of the Invention

[0014] According to the present disclosure, in one or more embodiments, it is possible to provide a polishing liquid for a magnetic disk substrate that can reduce the waviness on the surface of the magnetic disk substrate.

Embodiments for Carrying Out the Invention

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

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

[0017] Although the details of the mechanism of the effect manifestation of the present disclosure are not clear, it is presumed as follows. Typical 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, in the polishing operation of magnetic disk substrates using silica particles, high external energy such as high load and high rotation is applied. As a result, the Si-O-Si bond of the silica particles breaks and Si-O - and H + This process generates a structure that can release protons even under strongly acidic conditions. In this disclosure, the ability to release protons when high external energy such as high load and high rotation is applied can be estimated even when high external energy such as high load and high rotation is not applied, by an evaluation method for estimating the acidity of a solid substance called the ammonia temperature rise desorption method. By using silica particles that have excellent proton release ability when high external energy is applied, that is, silica particles whose ammonia desorption maximum temperature is within a predetermined range, in the polishing solution for polishing magnetic disk substrates, it is thought that corrosion of the object to be polished is promoted independently of the contribution of acid, thereby improving the polishing speed. Furthermore, since the silica particles act as solid anions after proton release, contact of the silica particles with the magnetic disk substrate is suppressed, and it is thought that waviness on the surface of the magnetic disk substrate can be reduced during the polishing operation. However, this disclosure does not have to be construed as being limited to these mechanisms.

[0018] In this disclosure, "surface waviness" refers to surface irregularities of the substrate with a period longer than that of "roughness." In this 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 surface waviness (short-wavelength waviness and long-wavelength waviness) of the substrate after polishing, the levitation height of the magnetic head in a magnetic disk drive can be lowered, thereby improving the recording density of the magnetic disk. Surface waviness (short-wavelength waviness and long-wavelength waviness) of the substrate can be measured, for example, by the method described in the examples. In this disclosure, "reduction of waviness" means that at least one of the short-wavelength waviness and the long-wavelength waviness is reduced.

[0019] [Silica particles (component A)] The silica particles contained in the polishing solution of this disclosure (hereinafter also referred to as "component A") are silica particles whose maximum ammonia desorption temperature, as measured by the ammonia temperature rise desorption method, is between 150°C and 250°C. Component A may be a single type or a combination of two or more types.

[0020] In this disclosure, the maximum ammonia desorption temperature of component A, as measured by the ammonia temperature-controlled desorption method, is 150°C or higher, preferably 155°C or higher, more preferably 160°C or higher, and even more preferably 165°C or higher, from the viewpoint of reducing waviness, and from the viewpoint of increasing the polishing speed, 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 maximum ammonia desorption temperature of component A, as measured by the ammonia temperature-controlled 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 is a method that allows for the measurement of the intensity and amount of solid acid and base sites. It involves adsorbing probe molecules (NH3, CO2, etc.) onto a solid sample and measuring the desorbed gas produced by continuously increasing the sample temperature. When measuring the amount and intensity of acid sites using temperature-programmed desorption, NH3, a basic gas, is used, and it is therefore called ammonia temperature-programmed desorption. In this case, NH3 adsorbed on weak acid sites is desorbed at low temperatures, and NH3 adsorbed on strong acid sites is desorbed at high temperatures. That is, the ammonia desorption maximum temperature measured by ammonia temperature-programmed desorption is the temperature (unit: °C) at which the amount of ammonia detected in the spectrum obtained by measurement using ammonia temperature-programmed desorption is maximum. This is also an indicator of the acid intensity of the silica particles, and the higher the ammonia desorption maximum temperature, the more H is present in the ammonia. + This means that the silica particles have a high ability to provide acidity, and that they possess strong acidity. In the present disclosure, the maximum ammonia desorption temperature determined by the ammonia temperature-programmed desorption method of silica particles can be specifically calculated by the method described in the examples.

[0022] In the present disclosure, the ammonia adsorption amount measured by the ammonia temperature-programmed desorption method of component A is an index indicating the amount of acid sites. The larger the ammonia adsorption amount, the more acid sites the silica particles have. In the present disclosure, the ammonia adsorption amount measured by the ammonia temperature-programmed desorption method of component A is preferably 410 mmol / m 2 or more, more preferably 420 mmol / m 2 or more, still more preferably 430 mmol / m 2 or more, even more preferably 440 mmol / m 2 or more, even more preferably 450 mmol / m 2 or more, and from the viewpoint of increasing the polishing rate, preferably 650 mmol / m 2 or less, more preferably 600 mmol / m 2 or less, still more preferably 590 mmol / m 2 or less, even more preferably 580 mmol / m 2 or less, even more preferably 570 mmol / m 2 or less, even more preferably. More specifically, the ammonia adsorption amount measured by the ammonia temperature-programmed desorption method of component A in the present disclosure is preferably 410 mmol / m 2 or more and 650 mmol / m 2 or less, more preferably 420 mmol / m 2 or more and 600 mmol / m 2 or less, still more preferably 430 mmol / m 2 or more and 590 mmol / m 2 or less, even more preferably 440 mmol / m<000002�>or more and 580 mmol / m 2 or less, even more preferably 450 mmol / m 2 or more and 570 mmol / m 2 or less, even more preferably. In this disclosure, the amount of ammonia adsorbed by the ammonia temperature-controlled desorption method of component A is preferably 50,000 mmol / g or more, more preferably 60,000 mmol / g or more, even more preferably 70,000 mmol / g or more, even 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 speed, 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 this disclosure, the amount of ammonia adsorbed by component A as measured by the ammonia temperature-controlled 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, even more preferably 80,000 mmol / g or more and 220,000 mmol / g or less, even more preferably 90,000 mmol / g or more and 210,000 mmol / g or less, and even more preferably 100,000 mmol / g or more and 200,000 mmol / g or less.

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

[0024] Examples of component A include wet silica, dry silica, pulverized silica, and silica obtained by surface modification thereof. Among these, wet silica is preferred from the viewpoint of improving polishing speed and reducing waviness. In this disclosure, colloidal silica is more preferred for component A. Examples of methods for producing colloidal silica include particle growth using an aqueous alkali silicate solution as a raw material (water glass method), condensation of hydrolysates of alkoxysilanes (sol-gel method), and precipitation of silica particles by neutralization reaction between a silicate such as sodium silicate and a mineral acid such as sulfuric acid (precipitation method).

[0025] Component A can be obtained in one or more embodiments as follows. Alkali silicate, the raw material for silica particles, is dissolved in water to a concentration of 2-8% by mass. A strong acid (preferably one or more selected from hydrochloric acid, sulfuric acid, and nitric acid) is added to this aqueous solution to neutralize the alkali silicate and form a silica hydrogel. The pH at this time is preferably around 4-6. The silica hydrogel of alkali silicate neutralized with a strong acid is allowed to stand at a temperature range of 10-40°C for 1-5 hours to allow the silica to mature. After that, it is washed with pure water or alkaline water to remove the salt. After washing, an alkaline solution (preferably one or more selected from sodium hydroxide, potassium hydroxide, and ammonium hydroxide) is added to the dispersion, and the pH of the dispersion is adjusted to a range of 6-12. The temperature at this time is preferably 40-120°C. The adjusted dispersion is stirred for 30 minutes to 3 hours to perform colloidalization of the silica hydrogel. Subsequently, the obtained silica sol is subjected to hydrothermal treatment at a temperature of 100-300°C and a pressure of 0.1-0.3 MPa for 30 minutes to 6 hours to promote the growth and stabilization of silica particles, thereby obtaining the desired silica particles (component A). From the viewpoint of polishing speed, the silicon content in component A, as 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. The silicon content in component A is a value detected by X-ray fluorescence analysis (XRF), which can be measured, for example, with a wavelength-dispersive X-ray fluorescence analyzer PrmusII manufactured by Rigaku Corporation, and specifically, by the method described in the examples.

[0026] From the viewpoint of improving polishing speed, the content of component A in the polishing solution of this 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 reducing waviness, it is preferably 10% by mass or less, more preferably 9% by mass or less, and even more preferably 8% by mass or less. More specifically, the content of component A in the polishing solution of this 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 silica particles are a combination of two or more types, the silica particle content refers to their total content.

[0027] [Acid (component B)] The polishing solution of this disclosure contains an acid (hereinafter also referred to as "component B"). In this disclosure, the acid may be partially in the form of a salt. In this disclosure, the acid content in component B (value as the acid in its acidic state (not in salt form), 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, even more preferably 95% by mass or more, and even more preferably 100% by mass, from the viewpoint of improving polishing speed and reducing waviness. Component B may be a single 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, pyrophosphate, tripolyphosphate, and amidosulfuric acid; and organic acids such as organic phosphoric acid, organic phosphonic acid, and carboxylic acid. In particular, from the viewpoint of improving polishing speed and reducing waviness, it is preferable to include inorganic acids and organic phosphonic acids, and it is more preferable to include inorganic acids or to be inorganic acids. In this disclosure, from the same viewpoint, the content of inorganic acids 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 a similar viewpoint, at least one inorganic acid selected from nitric acid, sulfuric acid, hydrochloric acid, perchloric acid, and phosphoric acid is preferred, at least one selected from sulfuric acid and phosphoric acid is more preferred, and phosphoric acid is even more preferred. From a similar viewpoint, at least one of the following organic phosphonic acids is preferred: 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP), aminotrimethylenephosphonic acid, ethylenediaminetetramethylenephosphonic acid, and diethylenetriaminepentamethylenephosphonic acid, with HEDP being more preferred. Examples of salts of these acids include salts of the above-mentioned acids with at least one selected from metals, ammonia, and alkylamines. Examples of the above-mentioned metals include metals belonging to groups 1 to 11 of the periodic table. Among these, from the viewpoint of improving polishing speed and reducing waviness, salts of the above-mentioned acids with metals belonging to group 1A or ammonia are preferred.

[0029] The content of component B in the polishing solution of this 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 polishing speed and reducing waviness, and similarly, 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 solution of this 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 of those types.

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

[0031] Examples of component C from the viewpoint of improving polishing speed and reducing waviness include peroxides, permanganate or its salts, chromic acid or its salts, peroxoacid or its salts, oxygen acids 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 iron(III) ammonium sulfate is preferred, and hydrogen peroxide is more preferred from the viewpoint of improving polishing speed, 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 solution of this 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 polishing speed, and from the viewpoint of reducing waviness, it is preferably 4% by mass or less, more preferably 3% by mass or less, and even more preferably 2% by mass or less. The content of component C in the polishing solution of this 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 of those types.

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

[0034] [Mass ratio of component C to component A] In the polishing fluid of this disclosure, the mass ratio C / A (content of component C / content of component A) of component C to component A is preferably 0.001 or higher, more preferably 0.01 or higher, even more preferably 0.05 or higher, even more preferably 0.1 or higher, and even more preferably 0.15 or higher, and from the viewpoint of improving polishing speed and reducing waviness, it is preferably 0.4 or lower, more preferably 0.3 or lower, even more preferably 0.25 or lower, and even more preferably 0.2 or lower. The mass ratio C / A is preferably 0.001 or higher and 0.4 or lower, more preferably 0.01 or higher and 0.3 or lower, even more preferably 0.05 or higher and 0.25 or lower, even more preferably 0.1 or higher and 0.2 or lower, and even more preferably 0.15 or higher and 0.2 or lower.

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

[0036] [Other ingredients] In one or more embodiments, the polishing solutions of this disclosure may contain other components as necessary, provided that they do not impair the effects of this disclosure. Examples of other components include corrosion inhibitors, thickeners, dispersants, rust inhibitors, basic substances, surfactants, water-soluble polymers, and the like.

[0037] [pH of polishing solution for magnetic disk substrates] From the viewpoint of reducing waviness, the pH of the polishing solution of this disclosure is preferably 1 or higher, more preferably 1.1 or higher, and even more preferably 1.2 or higher. From the viewpoint of improving the polishing speed, it is preferably 6 or lower, more preferably 4 or lower, and even more preferably 2 or lower. More specifically, the pH of the polishing solution of this disclosure is preferably 1 to 6, more preferably 1.1 to 4, and even more preferably 1.2 to 2. The pH can be adjusted using the acid (component B) mentioned above or a known pH adjusting agent. In this disclosure, the above pH is the pH of the polishing solution at 25°C and can be measured using a pH meter. For example, it can be the value obtained 2 minutes after immersing the electrode of the pH meter in the polishing solution for magnetic disk substrates.

[0038] [Method for manufacturing polishing solution for magnetic disk substrates] The polishing fluid of this disclosure can be prepared, for example, by compounding component A, component B and optionally water, and optionally an optional component (component C, other components) in a known manner. For example, in one or more embodiments, the polishing fluid of this disclosure may consist of at least component A, component B and optionally water. Accordingly, in one embodiment, this disclosure relates to a polishing solution for magnetic disk substrates comprising silica particles (component A) and an acid (component B), wherein the maximum ammonia desorption temperature of the silica particles, as measured by the ammonia temperature rise desorption method, is 150°C or higher and 250°C or lower. In this disclosure, "comprising" means that not only components A and B, but also any additional components may be added as needed. This disclosure relates, in one embodiment, to a method for producing an abrasive solution, comprising the step of compounding at least component A, component B, and optionally water. In this disclosure, "compounding" includes mixing component A, component B, and optionally water, and optionally optional components (component C, other components) simultaneously or in any order. Silica particles (component A) may be mixed in a concentrated slurry state, or they may be mixed after being diluted with water or the like. If component A consists of multiple types of silica particles, the multiple types of silica particles may be compounded simultaneously or separately. If component B consists of multiple types of acids, the multiple types of acids may be compounded simultaneously or separately. If component C consists of multiple types of oxidizing agents, the multiple types of oxidizing agents may be compounded simultaneously or separately. The compounding can be carried out, for example, using a mixer such as a homomixer, homogenizer, ultrasonic disperser, and wet ball mill. The preferred compounding amounts of each component in the method for producing the abrasive solution of this disclosure may be the same as the preferred content of each component in the abrasive solution of this disclosure described above.

[0039] In this disclosure, "content of each component in the polishing solution" means the content of each component at the time of use, that is, at the time when the polishing solution is first used to polish a magnetic disk substrate. The content of each component in the polishing solution of this disclosure can be considered as the amount of each component blended in one or more embodiments.

[0040] The polishing fluids of this disclosure may include forms that are manufactured as concentrates and diluted at the time of use, from the standpoint of storage and transport. That is, this disclosure relates in one or more embodiments to concentrates of the polishing fluids of this disclosure. The concentration ratio of the concentrated polishing solution of this 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 manufacturing and transportation costs, and 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 solution concentrate in this disclosure means [solid content concentration of the polishing solution concentrate / solid content concentration of the polishing solution at the time of use]. Here, "solid content concentration of the polishing solution concentrate" is the ratio of the mass of components other than water in the polishing solution concentrate to the mass of the polishing solution concentrate, and "solid content concentration of the polishing solution at the time of use" is the ratio of the mass of components other than water in the polishing solution at the time of use to the mass of the polishing solution at the time of use. The concentrated polishing solution of this disclosure can be used after diluting it with water so that the content of each component at the time of use is as described above (i.e., the content of each component in the polishing solution at the time of use).

[0042] The pH of the concentrated polishing solution of the disclosed polishing solution is preferably 1 or higher, more preferably 1.1 or higher, and even more preferably 1.2 or higher, from the viewpoint of reducing undulation when preparing the polishing solution of the disclosed polishing solution. From the viewpoint of improving the polishing speed, the pH is preferably 6 or lower, more preferably 4 or lower, and even more preferably 2 or lower. In the disclosed disclosure, the pH of the concentrated polishing solution is the value at 25°C and can be measured using a pH meter. For example, it can be the value obtained 2 minutes after immersing the electrode of the pH meter in the concentrated polishing solution.

[0043] [Polishing solution kit] This disclosure relates, in one embodiment, to a kit for preparing the polishing solution of this disclosure (hereinafter also referred to as the "polishing solution kit of this disclosure"). The polishing solution kit of this disclosure may include a form in which a combination of liquids is obtained by arbitrarily selecting components A and B. One embodiment of the polishing solution kit of this disclosure includes a silica dispersion containing component A and water (first solution) and an additive aqueous solution containing component B (second solution), which are mixed separately. The first solution and the second solution are mixed at the time of use and may be diluted with water as needed. The water contained in the first solution may be all or part of the water used to prepare the polishing solution of this disclosure. The second solution may contain part of the water used to prepare the polishing solution of this disclosure. The first solution and the second solution may each contain the above-mentioned optional components (component C, other components) as needed. The above-mentioned optional components (component C, other components) may be further mixed when mixing the first solution and the second solution. According to this disclosure, a polishing solution kit capable of reducing waviness on the substrate surface after polishing can be obtained.

[0044] [Manufacturing method for magnetic disk substrates] This disclosure relates, in one embodiment, to a method for manufacturing a magnetic disk substrate (hereinafter also referred to as "the substrate manufacturing method of this disclosure") which includes a step of supplying the polishing liquid of this 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, magnetic disks are manufactured by polishing a substrate that has undergone a grinding process, then going through a rough polishing process and a finish polishing process, and finally going through a magnetic layer formation process. The substrate manufacturing method of the present disclosure is preferably one or more selected from the following: a manufacturing method in which the polishing liquid of the present disclosure is supplied between the substrate to be polished and the polishing pad during 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 the polishing pad during 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 the polishing pad during both the rough polishing process and the finish polishing process.

[0045] In one or more embodiments, the polishing step includes supplying the polishing liquid of the Disclosure to the surface of a substrate to be polished, bringing a polishing pad into contact with the surface to be polished, and polishing by moving at least one of the polishing pad and the substrate to be polished. In one or more embodiments, the polishing step includes clamping the substrate to be polished between a platen to which a polishing pad is attached, supplying the polishing liquid of the present disclosure to the polishing surface, and polishing the substrate 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 a magnetic disk substrate, and examples include Ni-P plated aluminum alloy substrates and glass substrates such as crystallized glass, tempered glass, aluminosilicate glass, and aluminoborosilicate glass. In other words, in one or more embodiments, the polishing solution of this disclosure is preferably for polishing Ni-P plated aluminum alloy substrates and glass substrates. Accordingly, in one embodiment, this disclosure relates to a polishing solution for Ni-P plated aluminum alloy substrates comprising silica particles (component A) and an acid (component B), wherein the maximum ammonia desorption temperature of the silica particles, as measured by the ammonia temperature rise desorption method, is 150°C or higher and 250°C or lower. This disclosure relates, in one embodiment, to a polishing solution for glass substrates comprising silica particles (component A) and an acid (component B), wherein the maximum ammonia desorption temperature of the silica particles, as measured by an ammonia temperature rise desorption method, is 150°C or higher and 250°C or lower. In this disclosure, "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 solution of this disclosure, followed by a step of forming a magnetic layer on the substrate surface by sputtering or the like. A glass substrate refers to crystallized glass, tempered glass, aluminosilicate glass, aluminoborosilicate glass, etc., and, similar 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 solution of this disclosure, followed by a step of forming a magnetic layer on the substrate surface by sputtering or the like. The shape of the substrate to be polished can be, for example, a disc-shaped, plate-shaped, slab-shaped, or prism-shaped substrate with a flat surface, or a lens-shaped substrate with a curved surface. Preferably, the substrate to be polished is disc-shaped. In the case of a disc-shaped substrate, its outer diameter is, for example, 10 to 120 mm, and its thickness is, for example, 0.5 to 2 mm.

[0047] There are no particular limitations on the polishing pad used in this disclosure. For example, a polishing pad of the suede type, nonwoven fabric type, polyurethane closed-cell foam type, or a two-layer type made by laminating these can be used. From the viewpoint of improving polishing speed, a suede type polishing pad is preferred.

[0048] The polishing load in the polishing process is preferably 3 kPa or more, more preferably 5 kPa or more, even more preferably 7 kPa or more, preferably 30 kPa or less, more preferably 25 kPa or less, and even more preferably 20 kPa or less, from the viewpoint of maintaining the polishing speed and reducing waviness. In this disclosure, "polishing load" refers to the pressure of the polishing plate applied to the surface of the substrate to be polished during polishing. The polishing load can be adjusted by applying air pressure or weights to the polishing plate or substrate.

[0049] In the polishing process, the substrate to be polished 1 cm 2 From the viewpoint of ensuring polishing speed and reducing waviness, the amount of polishing per unit is preferably 0.2 mg or more, more preferably 0.3 mg or more, even more preferably 0.4 mg or more, and from the same viewpoint, 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 1 cm in the polishing process 2 From an economic standpoint, the supply rate of polishing fluid for magnetic disk substrates per unit 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. From the viewpoint of improving the polishing speed, 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] One method for supplying the polishing solution of this disclosure to a polishing machine is, for example, a method of continuous supply using a pump or the like. When supplying the polishing solution to the polishing machine, in addition to supplying it as a single liquid containing all the components, it is also possible to divide it into multiple compounding component liquids and supply it as two or more liquids, taking into consideration the storage stability of the polishing solution. In the latter case, for example, the multiple compounding component liquids are mixed in the supply piping or on the substrate to be polished to become the polishing solution of this disclosure.

[0052] According to the substrate manufacturing method of this disclosure, by using the polishing solution of this disclosure, it is possible to reduce the waviness of the substrate surface after polishing, thereby achieving the effect of manufacturing high-quality magnetic disk substrates in high yield and with high productivity.

[0053] [Method for polishing circuit boards] This disclosure relates to a method for polishing a substrate (hereinafter also referred to as "the polishing method of this disclosure"), which in one embodiment includes a step of supplying the polishing liquid of this disclosure between a substrate to be polished and a polishing pad to polish the substrate (hereinafter also referred to as "the polishing step"), wherein the substrate to be polished is a substrate used in the manufacture of magnetic disk substrates. According to the polishing method of this disclosure, by using the polishing liquid of this disclosure which can reduce the waviness of the substrate surface after polishing, high-quality magnetic disk substrates can be manufactured in high yield and with high productivity. As described above, the substrate to be polished in the polishing method of this disclosure is a substrate used in the manufacture of a magnetic disk substrate. The polishing method and conditions in the polishing step of the polishing method of this disclosure include the same methods and conditions as those in the polishing step of the substrate manufacturing method of this disclosure described above. [Examples]

[0054] The present disclosure will be further described below with reference to examples, but these are illustrative and the disclosure is not limited to these examples.

[0055] 1. Preparation of silica particles Preparation of silica particles (I) to (V) Alkali silicate salts, the raw material for silica particles, are dissolved in water to a concentration of 2-8% by mass. Strong acids such as hydrochloric acid, sulfuric acid, and nitric acid are added to this aqueous solution to neutralize the silica and form a silica hydrogel. The pH at this time is maintained between 4 and 6. The silica hydrogel, neutralized with a strong acid, is allowed to mature by standing at a temperature range of 10-40°C for 1-5 hours. Afterward, it is washed with pure water or alkaline water to remove the salt. Alkaline solutions such as sodium hydroxide, potassium hydroxide, and ammonium hydroxide are added to the washed dispersion, and the pH of the dispersion is adjusted to a range of 6-12. The temperature at this time is 40-120°C. The adjusted dispersion is stirred for 30 minutes to 3 hours to colloidize the silica hydrogel. Then, the resulting silica sol is subjected to hydrothermal treatment at a temperature of 100-300°C and a pressure of 0.1-0.3 MPa for 3-6 hours to promote the growth and stabilization of silica particles. By adjusting the reaction temperature, pressure, and time, silica particles (I)-(V) (colloidal silica) with the ammonia desorption maximum temperature and ammonia adsorption amount shown in Table 1 are obtained. For Comparative Example 1, Fuso Chemical Co., Ltd.'s PL-3 (colloidal silica) silica particles were used. [Silicon content in silica] The silicon content in silica was measured as follows. • X-ray fluorescence analysis (XRF): Rigaku PrmusII wavelength-dispersive X-ray fluorescence analyzer 50 mg of each silica solid sample, pre-dried at 110°C, was placed on filter paper, covered with a PET film, and pressed for measurement. The analysis angle 2θ varied depending on the element being measured. The target was a rhodium tube, the tube voltage was 50kV, and the tube current was 50mA for the measurement. The spectroscopic crystals used were LiF(200), Ge, PET, and RX25, and SC and PC were used as detectors. The measurement depth for the sample is several micrometers. The silicon content of each component was as follows: silica particle (I) 99.5 mass%, silica particle (II) 99.4 mass%, silica particle (III) 98.8 mass%, silica particle (IV) 98.9 mass%, silica particle (V) 99.4 mass%, and PL-3 100 mass%.

[0056] 2. Measurement methods for various parameters [Method for measuring the maximum temperature of ammonia desorption and the amount of ammonia adsorbed by the ammonia temperature-induced desorption method] The maximum temperature for ammonia desorption and the amount of ammonia adsorbed by the ammonia temperature-controlled desorption method (NH3-TPD) were determined as follows. Measuring device: "BELCAT-B" manufactured by Nippon Bell Co., Ltd. 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. Then, adsorption was carried out for 1 hour at 100°C in a 5 vol% NH3 / He (30 cc / min) atmosphere. Furthermore, the temperature was increased at a heating rate of 10°C / min in a He gas (30 cc / min) atmosphere until the maximum temperature of 800°C was reached, and measurements were performed. A quadrupole mass spectrometer was used as the detector. To avoid confusion with water (H2O = mass number 18), the detection of ammonia (NH3 = mass number 17) was set to detect mass numbers 16 and 17. The temperature at which the amount of detected ammonia was maximum in the obtained spectrum (unit: °C) was defined as the ammonia desorption maximum temperature. The results are shown in Table 1. Also, ammonia adsorption amount (mmol / m³ 2 The amount of ammonia adsorbed per 1 mg of sample (mmol / mg) is calculated from the integral value of the obtained spectrum, and the specific surface area (m²) of each silica is calculated. 2 Using ( / g), the amount of ammonia adsorbed per unit area (mmol / m²) 2 The results are shown in Tables 1 and 2. The ammonia adsorption amount converted to mmol / g is also shown in Tables 1 and 2. Note that the specific surface area of ​​silica (m²) 2 / g) was calculated as follows. Each silica particle was hot-air dried 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 BET specific surface area measurement, and the specific surface area (unit: m²) was measured using the BET method (nitrogen adsorption method) with a Micromeritic automatic specific surface area analyzer "Flowsorb III 2305" (manufactured by Shimadzu Corporation). 2 The measurement ( / g) was taken.

[0057] [Measuring pH] The pH of the polishing solution for magnetic disk substrates was measured at 25°C using a pH meter (manufactured by Toa DKK Co., Ltd.), and the value was taken 2 minutes after immersing the electrode in the polishing solution.

[0058] 3. Preparation of polishing solution for magnetic disk substrates (Examples 1-6, Comparative Example 1) Polishing solutions for Examples 1 to 6 were prepared by mixing 10 parts by mass of the silica particles (I) to (V), acid (component B), oxidizing agent (component C), and water. A polishing solution for Comparative Example 1 was prepared using the same procedure as in Example 1, except that silica particles PL-3 (colloidal silica) manufactured by Fuso Chemical Co., Ltd. were used instead of silica particles (I). The effective amounts of each component in each polishing solution were 6.0% by mass for silica particles, 1.6% or 1.0% by mass for acid (component B), and 1.0% by mass for oxidizing agent (component C). The water content was the residue after removing components A, B, and C from the total amount of polishing solution. The pH of each polishing solution measured at 25°C was 1.6. (Examples 7-8, Comparative Example 2) Polishing solutions for Examples 7 and 8 were prepared by mixing 10 parts by mass of the silica particles (I) to (II), acid (component B), and water. A polishing solution for Comparative Example 2 was prepared using the same procedure as in Example 7, except that silica particles PL-3 (colloidal silica) manufactured by Fuso Chemical Co., Ltd. were used instead of silica particles (I). The effective amounts of each component in each polishing solution were 6.0% by mass for silica particles and 1.6% by mass for acid (component B). The water content was the residue remaining after removing components A and B from the total amount of polishing solution. The pH of each polishing solution measured at 25°C was 1.6.

[0059] The following acid (component B) and oxidizing agent (component C) were used to prepare the polishing solution. (Component B) Phosphoric acid [manufactured by Nippon Chemical Industrial Co., Ltd., 75% phosphoric acid] Sulfuric acid [Purified dilute sulfuric acid, manufactured by Teika Co., Ltd., 62.5%] (Component C) Hydrogen peroxide [Manufactured by ADEKA Corporation, 35% hydrogen peroxide]

[0060] 4-1. Polishing Method (Examples 1-6, Comparative Example 1) The following substrates were polished using the polishing solutions of Examples 1-6 and Comparative Example 1 under the polishing conditions shown below. The polishing speed and waviness were then measured using the measurement method described later, and 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 (Type 9B double-sided polishing machine, manufactured by Speedfam Co., Ltd.) Number of circuit boards: 10 Polishing solution: Polishing solution as described in the Examples and Comparative Examples Polishing pad: Suede type (Foam layer: Polyurethane elastomer, thickness 1.0 mm, average pore size 30 μm, surface layer compression ratio 2.5%, manufactured by Filwel) Plate rotation speed: 40 rpm Grinding load: 9.8 kPa (set value) Polishing liquid supply amount: 100mL / min Substrate to be polished 1cm 2 Supply rate per unit: 0.8 mL / min Substrate to be polished 1cm 2 Abrasive amount per unit: 0.8 mg Polishing time: 5 minutes After polishing, the circuit board is removed from the double-sided polishing machine and the surface is cleaned using an automatic cleaning machine.

[0063] 4-2. Polishing Method (Examples 7-8, Comparative Example 2) The following substrates were polished using the polishing solutions of Examples 7-8 and Comparative Example 2 under the polishing conditions shown below. The polishing speed and waviness were then measured using the measurement method described later, and 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 (Type 9B double-sided polishing machine, manufactured by Speedfam Co., Ltd.) Number of circuit boards: 10 Polishing solution: Polishing solution as described in the Examples and Comparative Examples Polishing pad: Suede type (Foam layer: Polyurethane elastomer, thickness 1.0 mm, average pore size 30 μm, surface layer compression ratio 2.5%, manufactured by Filwel) Plate rotation speed: 40 rpm Grinding load: 9.8 kPa (set value) Polishing liquid supply amount: 100mL / min Substrate to be polished 1cm 2 Supply rate per unit: 0.8 mL / min Substrate to be polished 1cm 2 Abrasive amount per unit: 0.8 mg Polishing time: 12 minutes After polishing, the circuit board is removed from the double-sided polishing machine and the surface is cleaned using an automatic cleaning machine.

[0066] 5. Rating [Evaluation of polishing speed] The polishing speed was determined by measuring the mass of each substrate before and after polishing using an electronic balance (Sartorius BP-210S). The amount of mass loss for each substrate was calculated. The average mass loss for all 10 substrates was divided by the polishing time to determine the polishing speed, which was then used in the following formula. The calculated polishing speeds for Examples 1-6 are shown in Table 1 as relative values ​​with the polishing speed of Comparative Example 1 set to 100. The calculated polishing speeds for Examples 7-8 are shown in Table 2 as relative values ​​with the polishing speed of Comparative Example 2 set to 100. A higher number indicates a faster polishing speed. Mass reduction (g) = {Mass before polishing (g) - Mass after polishing (g)} Polishing speed (g / min) = mass loss (g) / polishing time (min)

[0067] [Evaluation of short-wavelength and long-wavelength swells] Short-wavelength and long-wavelength waviness were measured by selecting two substrates at random from ten polished substrates and measuring three arbitrary points (12 points in total) on both sides of the selected substrates under the following conditions. The average of these 12 measurements was calculated as the short-wavelength and long-wavelength waviness of the substrate. The calculation results for short-wavelength and long-wavelength waviness in Examples 1 to 6 are shown in Table 1 as relative values ​​with the short-wavelength and long-wavelength waviness of Comparative Example 1 set to 100. The calculation results for short-wavelength and long-wavelength waviness in Examples 7 to 8 are shown in Table 2 as relative values ​​with the short-wavelength and long-wavelength waviness of Comparative Example 2 set to 100. For short-wavelength and long-wavelength waviness, a smaller number indicates less 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 solutions of Examples 1 to 6, which used silica particles with an ammonia desorption maximum temperature of 150°C to 250°C as measured by the ammonia temperature rise desorption method, showed improved polishing speed and reduced short-wavelength and long-wavelength undulation compared to the polishing solution of Comparative Example 1, which used silica particles with an ammonia desorption maximum temperature of less than 150°C. As shown in Table 2 above, the polishing solutions of Examples 7 and 8, which used silica particles with an ammonia desorption maximum temperature of 150°C to 250°C as measured by the ammonia temperature rise desorption method, showed improved polishing speed and reduced short-wavelength and long-wavelength undulation compared to the polishing solution of Comparative Example 2, which used silica particles with an ammonia desorption maximum temperature of less than 150°C. [Industrial applicability]

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

Claims

1. It contains silica particles (component A) and acid (component B), A polishing solution for magnetic disk substrates, wherein the maximum ammonia desorption temperature, as measured by the ammonia temperature rise desorption method of the silica particles, is 150°C or higher and 250°C or lower.

2. The ammonia adsorption amount of component A, measured by the ammonia temperature-induced desorption method, was 410 mmol / m³. 2 650 mmol / m or more 2 The polishing solution for magnetic disk substrates according to claim 1, which is as follows:

3. The polishing solution for magnetic disk substrates according to claim 1, wherein the amount of ammonia adsorbed by the ammonia temperature-controlled desorption method of component A is 50,000 mmol / g or more and 250,000 mmol / g or less.

4. The polishing solution for magnetic disk substrates according to claim 1, wherein the pH is 1 or more and 6 or less.

5. The polishing solution for magnetic disk substrates according to claim 1, wherein the silicon element content in component A, as measured by X-ray fluorescence analysis, is 90% by mass or more.

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

7. The polishing solution 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. The polishing solution 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. The polishing solution for magnetic disk substrates according to claim 1, wherein component B is at least one selected from sulfuric acid and phosphoric acid.

10. The polishing solution 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. It is composed of silica particles (component A) and acid (component B), A polishing solution for magnetic disk substrates, wherein the maximum ammonia desorption temperature, as measured by the ammonia temperature rise desorption method of the silica particles, is 150°C or higher and 250°C or lower.

12. It contains silica particles (component A) and acid (component B), A polishing solution for Ni-P plated aluminum alloy substrates, wherein the maximum ammonia desorption temperature, as measured by the ammonia temperature rise desorption method of silica particles, is 150°C or higher and 250°C or lower.

13. It contains silica particles (component A) and acid (component B), A polishing solution for glass substrates, wherein the maximum ammonia desorption temperature, as measured by the ammonia temperature rise desorption method of the silica particles, is 150°C or higher and 250°C or lower.

14. A kit for manufacturing a polishing solution for magnetic disk substrates according to any one of claims 1 to 13, A polishing solution kit comprising a silica dispersion containing silica particles (component A) and water, and an additive aqueous solution containing an acid (component B), which are mixed together before use.

15. A method for manufacturing a magnetic disk substrate, comprising the step of supplying a polishing liquid for magnetic disk substrates according to any one of claims 1 to 11 between a substrate to be polished and a polishing pad, and polishing the substrate to be polished.

16. A method for polishing a substrate, comprising the step of supplying a polishing liquid for magnetic disk substrates according to any one of claims 1 to 11 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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