Magnetic disk substrate manufacturing method

Abstract

To provide a magnetic disk substrate manufacturing method which achieves both of improvement of a polishing speed and reduction of waviness of a substrate surface after polishing, and which has excellent productivity.SOLUTION: A magnetic disk substrate manufacturing method includes a polishing process for polishing a polished substrate with the use of a polishing liquid composition and a polishing pad, so as to allow a substrate thickness after polishing to be equal to or less than 0.6 mm. The polishing liquid composition contains silica particles (component A), acid (component B), and an aqueous medium. In the polishing liquid composition, an average secondary particle diameter of the component A is equal to or less than 40 nm, and pH is equal to or more than 0.5 and equal to or less than 4.0. In the polishing pad, a contact angle with the polishing liquid composition is equal to or less than 70°. The polishing pad is a suede type with a surface roughness being equal to or less than 3 μm.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a method for manufacturing a magnetic disk substrate and a polishing composition. [Background technology]

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

[0003] In response to such demands, for example, Patent Document 1 discloses a polishing composition for use in polishing a magnetic disk substrate by being supplied between a polishing pad and an object to be polished to polish the object, the polishing composition comprising silica particles as abrasive grains and water, the silica particles being particles S having an aspect ratio of 1.10 or more as determined by SEM image analysis. HAR and particles S with an aspect ratio of less than 1.10 based on SEM image analysis. LAR and the particles S HAR The number of particles NA is LAR The polishing composition has been proposed in which the value obtained by dividing by the number of particles NB is 0.10 or more and 1.40 or less. Patent Document 2 proposes a method for manufacturing a magnetic disk substrate, which includes a polishing process in which a polishing pad and the substrate are slid relative to each other to polish the main surface of the substrate, and an opening process in which the surface of the material without openings is scraped to form openings in the surface before the polishing process, in order to turn a material for a polishing pad without openings into the polishing pad, and the polishing pad material is made of a material whose arithmetic mean roughness Ra of the surface roughness is 0.65 μm or less. Patent Document 3 proposes a method for manufacturing a glass substrate for a magnetic recording medium, which includes a polishing step of polishing the main surface of the glass substrate using a soft polishing pad having a polishing surface having a surface roughness Ra of 0.40 to 1.40 μm at a measurement wavelength of 2.5 to 80 μm and a surface roughness Ra of 0.40 to 2.00 μm at a measurement wavelength of 2.5 to 800 μm. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2020-531008 [Patent Document 2] Japanese Patent Application Publication No. 2018-41526 [Patent Document 3] Japanese Patent Application Laid-Open No. 2014-154187 Summary of the Invention [Problem to be solved by the invention]

[0005] As the capacity of magnetic disk drives increases, the requirements for the surface quality of substrates become more stringent, and there is a need for the development of a polishing composition that can improve the removal rate while further reducing the waviness of the substrate surface. Generally, there is a trade-off between the removal rate and the waviness, and there is a problem that improving one will result in a deterioration of the other. Furthermore, in recent years, substrates have become thinner, but as the weight of the polished substrates decreases, the substrates tend to adhere to the upper surface plate after double-side polishing, which creates a new problem: it takes time to recover the substrates, reducing productivity. Productivity here refers to the number of substrates produced per unit time.

[0006] Therefore, the present disclosure provides a method for manufacturing a magnetic disk substrate and a polishing composition that can achieve both an improved removal rate and a reduced waviness on the substrate surface after polishing, and that are also highly productive. In the present disclosure, a high number of substrates produced per unit time is defined as having good productivity. [Means for solving the problem]

[0007] In one aspect, the present disclosure relates to a method for producing a magnetic disk substrate, comprising a polishing step of polishing a substrate to be polished using a polishing liquid composition and a polishing pad so that the thickness of the substrate after polishing is 0.6 mm or less, the polishing liquid composition containing silica particles (component A), an acid (component B), and an aqueous medium, the average secondary particle diameter of component A being 40 nm or less and the pH being 0.5 to 4.0, and the polishing pad being a suede-type polishing pad having a contact angle with the polishing liquid composition of 70° or less and a surface roughness of 3 μm or less.

[0008] In one aspect, the present disclosure relates to a polishing liquid composition used in a polishing step in which a substrate to be polished is polished using a suede-type polishing pad having a contact angle with the polishing liquid composition of 70° or less and a surface roughness of 3 μm or less, resulting in a substrate thickness of 0.6 mm or less after polishing, the polishing liquid composition comprising silica particles (component A), an acid (component B), and an aqueous medium, in which the average secondary particle diameter of component A is 40 nm or less and the pH is 0.5 or more and 4.0 or less. [Effects of the Invention]

[0009] According to one aspect of the present disclosure, it is possible to provide a method for manufacturing a magnetic disk substrate that can achieve both an improvement in the polishing rate and a reduction in waviness on the substrate surface after polishing, and that is also highly productive. DETAILED DESCRIPTION OF THE INVENTION

[0010] One of the challenges in manufacturing magnetic disk substrates is balancing productivity with surface quality (waviness). Conventionally, shortening the polishing time (for example, increasing the polishing rate) has been proposed as a way to solve the productivity issue. However, in recent years, substrates have become thinner, and new productivity issues have arisen. These new productivity issues are explained below. Double-sided polishers are commonly used to polish magnetic disk substrates. Double-sided polishers are batch-type machines that polish multiple substrates at once. They sandwich the substrates between two rotating plates, polishing both sides of the substrates. A polishing pad is attached to each of the upper and lower plates. When using a double-sided polisher, the substrate is first placed on the lower platen, and then the upper platen is lowered to sandwich the substrate between the upper and lower plates. After polishing is complete, the upper platen is raised and the substrate is removed from the lower platen. However, as the thickness of the polished substrate decreases (e.g., a substrate thickness of 0.6 mm or less), the substrate becomes lighter, making it more likely for the polished substrate to adhere to the upper platen (polishing pad). Substrates that adhere to the upper platen (polishing pad) must be manually removed from the lower platen, which requires a long time for substrate removal and reduces productivity. The present disclosure is based on the finding that, in a polishing process in which the thickness of a substrate after polishing is 0.6 mm or less, by using a polishing composition containing silica particles having an average secondary particle diameter of 40 nm or less in combination with a polishing pad having a specific contact angle and specific surface roughness, it is possible to improve the polishing rate while reducing waviness on the substrate surface after polishing, and further to suppress adhesion of the substrate to the surface plate (polishing pad) after polishing, thereby improving productivity.

[0011] That is, in one aspect, the present disclosure relates to a method for manufacturing a magnetic disk substrate (hereinafter also referred to as the "substrate manufacturing method of the present disclosure"), which includes a polishing step (hereinafter also referred to as the "polishing step of the present disclosure") in which a substrate to be polished is polished using a polishing liquid composition and a polishing pad so that the thickness of the substrate after polishing is 0.6 mm or less, the polishing liquid composition containing silica particles (component A), an acid (component B), and an aqueous medium, the average secondary particle diameter of component A being 40 nm or less, and the pH being 0.5 or more and 4.0 or less, and the polishing pad being a suede-type polishing pad having a contact angle with the polishing liquid composition of 70° or less and a surface roughness of 3 μm or less.

[0012] Although the details of the mechanism by which the effects of the present disclosure are manifested are not clear, it is presumed as follows. Waviness, one of the indicators of substrate surface quality, is in a trade-off relationship with pad roughness. As the pad surface roughness increases, the pad surface roughness is transferred to the substrate surface during polishing, worsening the substrate waviness. Conversely, if the pad surface roughness is too low, the silica abrasive particles cannot penetrate between the pad and the substrate, making polishing difficult. Substrate productivity is influenced by the polishing rate and the time required to collect the substrate after polishing. The polishing rate is closely related to the particle size of the abrasive particles; increasing the particle size of the abrasive particles increases the physical force, resulting in a faster polishing rate. However, above a certain particle size, the abrasive particles cannot penetrate between the pad and the substrate, resulting in a decrease in the polishing rate and an increase in waviness. To improve the productivity of thin substrates, shortening the substrate collection time is essential. To solve this problem, it is important to suppress adhesion of the substrate to the pad surface and to control the contact angle of the polishing liquid on the pad surface. When a pad with a high contact angle is used, small amounts of air that unintentionally get trapped between the substrate and the pad during polishing cannot escape, and this air can cause the pad to act like a suction cup and adhere to the surface plate. As a result, this disclosure makes it possible to achieve both high levels of productivity and substrate quality by appropriately controlling the contact angle and roughness of the pad and the selection of abrasive grains. However, the present disclosure need not be construed as being limited to these mechanisms.

[0013] Generally, magnetic disks are manufactured by polishing a substrate that has undergone a grinding process, then polishing it through a rough polishing process and a finish polishing process, and then forming it into a magnetic disk in a recording portion forming process. A rinsing process and a cleaning process may be included between each of the polishing processes. The polishing process in the substrate manufacturing method of the present disclosure is preferably applied to the finish polishing process from the viewpoint of further improving the final substrate quality. The substrate manufacturing method of the present disclosure is particularly suitable for manufacturing magnetic disk substrates for perpendicular magnetic recording systems.

[0014] In the present disclosure, the "waviness" of a substrate refers to irregularities on the substrate surface having a wavelength longer than the roughness. In the present disclosure, for example, waviness observed at a wavelength of 60 to 160 μm is referred to as "short wavelength waviness," and waviness observed at a wavelength of 500 to 5000 μm is referred to as "long wavelength waviness." By reducing the waviness (short wavelength waviness and 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 and 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 reducing at least one of the short wavelength waviness and the long wavelength waviness.

[0015] [Polishing process] The polishing process of the present disclosure is a polishing process in which a substrate to be polished is polished using a polishing composition and a polishing pad, and the thickness of the substrate after polishing is 0.6 mm or less. The thickness of the substrate after polishing is preferably 0.8 mm or less, more preferably 0.6 mm or less, from the viewpoint of suppressing adhesion of the substrate to the polishing machine surface plate. The thickness of the substrate after polishing can be measured with a vernier caliper, specifically, by the method described in the Examples.

[0016] In one or more embodiments, the polishing process of the present disclosure is a process of supplying a polishing liquid composition 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.

[0017] When the polishing process is performed in multiple stages, the polishing process of the present disclosure is preferably performed in the second stage or later, and more preferably in the final polishing process or finish polishing process. In this case, separate polishing machines may be used for each stage to avoid contamination with the abrasive or polishing composition from the previous stage. When separate polishing machines are used, it is preferable to clean the substrate to be polished after each polishing process. Furthermore, the polishing composition of the present disclosure can also be used in circulating polishing, in which the used polishing liquid is reused. The polishing machine used in the polishing process of the present disclosure is not particularly limited, and any known polishing machine for substrate polishing can be used. Examples of polishing machines include double-sided polishing machines.

[0018] The polishing load in the polishing step of the present disclosure is preferably 5.9 kPa or more, more preferably 6.9 kPa or more, and even more preferably 7.5 kPa or more from the viewpoint of improving the polishing rate, and is preferably 20 kPa or less, more preferably 18 kPa or less, and even more preferably 16 kPa or less from the viewpoint of reducing waviness. In the present disclosure, the polishing load refers to the pressure of the platen applied to the polishing surface of the substrate to be polished during polishing. The polishing load can be adjusted by applying air pressure or a weight to at least one of the platen and the substrate to be polished.

[0019] In the polishing step of the present disclosure, the supply rate of the polishing composition is set to 1 cm / cm of the substrate to be polished from the viewpoint of reducing waviness. 2 The flow rate is preferably 0.05 mL / min or more and 15 mL / min or less, more preferably 0.06 mL / min or more and 10 mL / min or less, even more preferably 0.07 mL / min or more and 1 mL / min or less, and even more preferably 0.07 mL / min or more and 0.5 mL / min or less.

[0020] In the polishing step of the present disclosure, the polishing liquid composition of the present disclosure can be supplied to a polishing machine by, for example, continuously supplying the composition using a pump or the like. When supplying the polishing liquid composition to the polishing machine, in addition to a method of supplying a single liquid containing all components, it can also be divided into a plurality of blending component liquids and supplied as two or more liquids, taking into consideration the stability of the polishing liquid composition, etc. In the latter case, the plurality of blending component liquids are mixed, for example, in the supply pipe or on the substrate to be polished, to produce the polishing liquid composition of the present disclosure.

[0021] [Polishing liquid composition] The polishing liquid composition used in the polishing step of a magnetic disk substrate of the present disclosure (hereinafter also referred to as the "polishing liquid composition of the present disclosure") contains silica particles (component A), an acid (component B), and an aqueous medium, and is a polishing liquid composition in which the average secondary particle diameter of component A is 40 nm or less and the pH is 0.5 to 4.0. That is, in one aspect, the present disclosure relates to a polishing liquid composition used in a polishing step in which a substrate to be polished is polished using a suede-type polishing pad having a contact angle with the polishing liquid composition of 70° or less and a surface roughness of 3 μm or less, so that the thickness of the substrate after polishing is 0.6 mm or less, the polishing liquid composition containing silica particles (component A), an acid (component B), and an aqueous medium, the average secondary particle diameter of component A is 40 nm or less, and the pH is 0.5 to 4.0.

[0022] <Silica particles (ingredient A)> From the viewpoints of improving the removal rate and reducing waviness, examples of silica particles contained in the polishing composition of the present disclosure (hereinafter also referred to as "Component A") include colloidal silica, fumed silica, pulverized silica, and surface-modified silica thereof, with colloidal silica being preferred. Component A may be one type or a combination of two or more types.

[0023] From the viewpoint of improving the polishing rate, the average secondary particle diameter of component A is preferably 5 nm or more, more preferably 10 nm or more, and even more preferably 15 nm or more. From the viewpoint of reducing waviness, the average secondary particle diameter of component A is 40 nm or less, preferably 38 nm or less, and more preferably 35 nm or less. More specifically, the average secondary particle diameter of component A is preferably 5 nm or more and 40 nm or less, more preferably 10 nm or more and 38 nm or less, and even more preferably 15 nm or more and 35 nm or less. In the present disclosure, the "average secondary particle diameter of silica particles" refers to a value measured by dynamic light scattering, and can be, for example, the average secondary particle diameter based on the scattering intensity distribution measured at a detection angle of 90° in dynamic light scattering. Specifically, the average secondary particle diameter of silica particles can be determined by the method described in the Examples.

[0024] The content of component A in the polishing liquid composition of the present disclosure is preferably 0.1 mass% or more, more preferably 1 mass% or more, and even more preferably 3 mass% or more, calculated as SiO2, from the viewpoint of improving the removal rate. From the viewpoint of reducing waviness, the content is preferably 20 mass% or less, more preferably 15 mass% or less, and even more preferably 10 mass% or less, calculated as SiO2. More specifically, the content of component A in the polishing liquid composition of the present disclosure is preferably 0.1 mass% or more and 20 mass% or less, more preferably 1 mass% or more and 15 mass% or less, and even more preferably 3 mass% or more and 10 mass% or less, calculated as SiO2. When component A consists of two or more types of silica particles, the content of component A refers to the total content of these particles.

[0025] <Acid (component B)> The polishing composition of the present disclosure contains an acid (component B). In the present disclosure, the use of an acid includes the use of an acid or a salt thereof. Component B may be one type, or two or more types may be combined.

[0026] 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, at least one selected from inorganic acids and organic phosphonic acids is preferred from the viewpoint of improving the polishing rate and reducing waviness. The inorganic acid is preferably at least one selected from nitric acid, sulfuric acid, hydrochloric acid, perchloric acid, and phosphoric acid, and more preferably at least one selected from sulfuric acid and phosphoric acid. The organic phosphonic acid is preferably at least one selected from 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP), aminotri(methylenephosphonic acid), ethylenediaminetetra(methylenephosphonic acid), and diethylenetriaminepenta(methylenephosphonic acid), and HEDP is more 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 metal include metals belonging to groups 1 to 11 of the periodic table.

[0027] The content of component B in the polishing liquid composition of the present disclosure is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, from the viewpoint of improving the removal rate, and is preferably 8% by mass or less, more preferably 6% by mass or less, and even more preferably 4% by mass or less, from the viewpoint of suppressing deterioration of the pad surface roughness. From the same viewpoint, the content of component B in the polishing liquid composition of the present disclosure is preferably 0.1% by mass or more and 8% by mass or less, more preferably 0.5% by mass or more and 6% by mass or less, and even more preferably 0.5% by mass or more and 4% 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.

[0028] From the viewpoint of suppressing deterioration of pad surface roughness, the mass ratio A / B of the content of component A to the content of component B in the polishing liquid composition of the present disclosure is preferably 0.01 or more, more preferably 0.1 or more, and even more preferably 0.5 or more, and from the viewpoint of improving the removal rate, it is preferably 200 or less, more preferably 30 or less, and even more preferably 10 or less. From the same viewpoint, the mass ratio A / B in the polishing liquid composition of the present disclosure is preferably 0.01 or more and 200 or less, more preferably 0.1 or more and 30 or less, and even more preferably 0.5 or more and 10 or less.

[0029] <Aqueous medium> Examples of the aqueous medium contained in the polishing liquid composition of the present disclosure include water such as distilled water, ion-exchanged water, pure water, and ultrapure water, or a mixed solvent of water and a solvent. Examples of the solvent include a water-miscible solvent (e.g., alcohol such as ethanol). When the aqueous medium is a mixed solvent of water and a solvent, the proportion of water relative to the total mixed medium is not particularly limited as long as the effects of the present disclosure are not impaired. From an economical viewpoint, for example, the proportion of water is preferably 95% by mass or more, more preferably 98% by mass or more, and even more preferably substantially 100% by mass. From the viewpoint of surface cleanliness of the substrate to be polished, ion-exchanged water and ultrapure water are preferred as the aqueous medium. The content of the aqueous medium in the polishing liquid composition of the present disclosure can be the remainder excluding component A, component B, and the optional components described below that are blended as necessary.

[0030] <Oxidizing agent (ingredient C)> The polishing composition of the present disclosure may further contain an oxidizing agent (hereinafter also referred to as "component C") from the viewpoint of further improving the removal rate and further reducing waviness. Component C may be one type or a combination of two or more types.

[0031] From the viewpoint of further improving the polishing rate and further 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, sulfuric acids, etc. Among these, at least one selected from hydrogen peroxide, iron(III) nitrate, peracetic acid, ammonium peroxodisulfate, iron(III) sulfate, and ammonium iron(III) sulfate is preferred, and hydrogen peroxide is more preferred from the viewpoint of further improving the polishing rate, preventing metal ions from adhering to the surface of the substrate to be polished, and being easily available.

[0032] When the polishing liquid composition of the present disclosure contains component C, the content of component C in the polishing liquid composition of the present disclosure is, from the viewpoint of further improving the removal rate and further reducing waviness, preferably 0.01% by mass or more, more preferably 0.05% by mass or more, even more preferably 0.1% by mass or more, and preferably 4% by mass or less, more preferably 2% by mass or less, and even more preferably 1.5% by mass or less. More specifically, the content of component C in the polishing liquid composition of the present disclosure is preferably 0.01% by mass or more and 4% by mass or less, more preferably 0.05% by mass or more and 2% by mass or less, and even more preferably 0.1% by mass or more and 1.5% by mass or less. When component C is a combination of two or more types, the content of component C refers to the total content thereof.

[0033] In one or more embodiments, the polishing liquid composition of the present disclosure may further contain at least one selected from a heterocyclic aromatic compound (component D), an aliphatic amine compound or an alicyclic amine compound (component E), and an anionic water-soluble polymer (component F). Components D to F are described below.

[0034] <Heterocyclic aromatic compounds (component D)> From the viewpoint of further reducing waviness, the polishing composition of the present disclosure may further contain a heterocyclic aromatic compound (including its salt) (hereinafter also referred to as "Component D"). Component D may be one type or a combination of two or more types.

[0035] From the viewpoint of further reducing waviness, Component D is preferably a heterocyclic aromatic compound containing two or more nitrogen atoms in the heterocycle, more preferably three or more nitrogen atoms in the heterocycle, even more preferably three to nine nitrogen atoms, even more preferably three to five nitrogen atoms, and even more preferably three or four nitrogen atoms.

[0036] In one or more embodiments, Component D is preferably at least one selected from 1,2,4-triazole, 3-amino-1,2,4-triazole, 5-amino-1,2,4-triazole, 3-mercapto-1,2,4-triazole, 1H-tetrazole, 5-aminotetrazole, 1H-benzotriazole (BTA), 1H-tolyltriazole, 2-aminobenzotriazole, 3-aminobenzotriazole, and alkyl- or amine-substituted derivatives thereof. Examples of the alkyl group in the alkyl substituent include lower alkyl groups having 1 to 4 carbon atoms, and in one or more embodiments, examples include methyl and ethyl groups. In one or more embodiments, examples of the amine substituent include 1-[N,N-bis(hydroxyethylene)aminomethyl]benzotriazole and 1-[N,N-bis(hydroxyethylene)aminomethyl]tolyltriazole.

[0037] When the polishing liquid composition of the present disclosure contains component D, from the viewpoint of further reducing waviness, the content of component D in the polishing liquid composition of the present disclosure is preferably 0.005% by mass or more, more preferably 0.01% by mass or more, even more preferably 0.02% by mass or more, and preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 1% by mass or less, and even more preferably 0.2% by mass or less. More specifically, the content of component D in the polishing liquid composition of the present disclosure is preferably 0.005% by mass or more and 10% by mass or less, more preferably 0.01% by mass or more and 5% by mass or less, even more preferably 0.02% by mass or more and 1% by mass or less, and even more preferably 0.02% by mass or more and 0.2% by mass or less. When component D is a combination of two or more types, the content of component D refers to the total content thereof.

[0038] <Aliphatic amine compound or alicyclic amine compound (ingredient E)> From the viewpoint of further reducing waviness, the polishing composition of the present disclosure may further contain an aliphatic amine compound or an alicyclic amine compound (hereinafter also referred to as "component E"). From the viewpoint of further reducing waviness, the number of nitrogen atoms or the total number of amino groups or imino groups in the molecule of component E is preferably 2 or more and 4 or less. Component F may be one type, or two or more types may be combined.

[0039] In one or more embodiments, from the viewpoint of further reducing waviness, the aliphatic amine compound is preferably at least one selected from monoethanolamine, ethylenediamine, N,N,N',N'-tetramethylethylenediamine, 1,2-diaminopropane, 1,3-diaminopropane, 1,4-diaminobutane, hexamethylenediamine, 3-(diethylamino)propylamine, 3-(dibutylamino)propylamine, 3-(methylamino)propylamine, 3-(dimethylamino)propylamine, N-aminoethylethanolamine (AEA), N-aminoethylisopropanolamine, and N-aminoethyl-N-methylethanolamine, and more preferably N-aminoethylethanolamine (AEA).

[0040] In one or more embodiments, from the viewpoint of further reducing waviness, the alicyclic amine compound is preferably at least one selected from piperazine, 2-methylpiperazine, 2,5-dimethylpiperazine, 1-amino-4-methylpiperazine, N-methylpiperazine, and hydroxyethylpiperazine (HEP), and more preferably hydroxyethylpiperazine (HEP).

[0041] When the polishing liquid composition of the present disclosure contains component E, from the viewpoint of further reducing waviness, the content of component E in the polishing liquid composition of the present disclosure is preferably 0.005% by mass or more, more preferably 0.01% by mass or more, even more preferably 0.015% by mass or more, and preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 1% by mass or less, and even more preferably 0.1% by mass or less. More specifically, the content of component E in the polishing liquid composition of the present disclosure is preferably 0.005% by mass or more and 10% by mass or less, more preferably 0.01% by mass or more and 5% by mass or less, even more preferably 0.015% by mass or more and 1% by mass or less, and even more preferably 0.015% by mass or more and 0.1% by mass or less. When component E is a combination of two or more types, the content of component E refers to the total content thereof.

[0042] <Anionic water-soluble polymer (ingredient F)> In one or more embodiments, the polishing liquid composition of the present disclosure may further contain an anionic water-soluble polymer (hereinafter also referred to as "component F") from the viewpoint of further reducing waviness. The anionic water-soluble polymer is a water-soluble polymer having an anionic group in the molecule. In the present disclosure, "water-soluble" means having a solubility in water (20°C) of 0.5 g / 100 mL or more, preferably 2 g / 100 mL or more. From the viewpoint of further reducing waviness, component F preferably has a repeating unit and a sulfonic acid group or a salt thereof in the molecule, and has a structure in which the repeating unit has an aromatic ring in the main chain. Examples of the aromatic ring include a phenol skeleton and a naphthalene skeleton. Examples of the salt include alkali metal salts, ammonium salts, and organic amine salts. Component F may be one type or a combination of two or more types.

[0043] In one or more embodiments, component F may be a copolymer containing a structural unit derived from an unsaturated carboxylic acid and a structural unit derived from a monomer having a sulfonic acid group in the molecule. Examples of the unsaturated carboxylic acid include at least one selected from acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, and salts thereof. Examples of the monomer having a sulfonic acid group in the molecule include 2-acrylamido-2-methylpropanesulfonic acid. Examples of the copolymer containing a structural unit derived from an unsaturated carboxylic acid and a structural unit derived from a monomer having a sulfonic acid group in the molecule include acrylic acid / 2-acrylamido-2-methylpropanesulfonic acid copolymer (AA / AMPS). In one or more embodiments, Component F may be a condensate or salt thereof of an aromatic monomer having a sulfonic acid group or a salt thereof, or a condensate or salt thereof containing a structural unit derived from an aromatic monomer having a sulfonic acid group or a salt thereof and a structural unit other than the structural unit. Examples of the salt include alkali metal salts, ammonium salts, and organic amine salts. From the viewpoint of further reducing waviness, the condensate or salt thereof of an aromatic monomer having a sulfonic acid group or a salt thereof is preferably a condensate or salt thereof having a structure in which at least one hydrogen atom of an aromatic ring constituting the main chain is substituted with a sulfonic acid group, and more preferably at least one selected from phenolsulfonic acid, naphthalenesulfonic acid, and salts thereof. Examples include a formalin condensate of phenolsulfonic acid (PhS) and a formalin condensate of naphthalenesulfonic acid (NaS). An example of a condensate or salt thereof containing a structural unit derived from an aromatic monomer having a sulfonic acid group or a salt thereof and a structural unit other than the structural unit is a formalin condensate (BisS / PhS) of bis(4-hydroxyphenyl)sulfone (BisS) and phenolsulfonic acid (PhS).

[0044] From the viewpoint of further reducing waviness, the weight average molecular weight of component F is preferably 500 or more, more preferably 1000 or more, and even more preferably 1500 or more, and is preferably 50000 or less, more preferably 30000 or less, and even more preferably 20000 or less. More specifically, the weight average molecular weight of component F is preferably 500 or more and 50000 or less, more preferably 1000 or more and 30000 or less, and even more preferably 1500 or more and 20000 or less.

[0045] When the polishing liquid composition of the present disclosure contains component F, the content of component F in the polishing liquid composition of the present disclosure is preferably 0.001% by mass or more, and preferably 1% by mass or less, more preferably 0.5% by mass or less, and even more preferably 0.1% by mass or less, from the viewpoint of further reducing waviness. More specifically, the content of component F in the polishing liquid composition of the present disclosure is preferably 0.001% by mass or more and 1% by mass or less, more preferably 0.001% by mass or more and 0.5% by mass or less, and even more preferably 0.001% by mass or more and 0.1% by mass or less. When component F is a combination of two or more types, the content of component F refers to the total content thereof.

[0046] [Other ingredients] In one or more embodiments, the polishing liquid composition of the present disclosure may further contain other components as needed. Examples of other components include polymers other than Component F, thickeners, dispersants, rust inhibitors, basic substances, surfactants, solubilizers, etc.

[0047] <pH of polishing composition> From the viewpoints of improving the removal rate and reducing waviness, the pH of the polishing composition of the present disclosure is 0.5 or more, preferably 0.8 or more, more preferably 1.0 or more, and 4.0 or less, preferably 3.0 or less, more preferably 2.0 or less. More specifically, the pH of the polishing composition of the present disclosure is 0.5 or more and 4.0 or less, preferably 0.8 or more and 3.0 or less, more preferably 1.0 or more and 3.0 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 composition 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 polishing composition.

[0048] <Method of manufacturing the polishing composition> The polishing composition of the present disclosure can be produced, for example, by blending component A, component B, an aqueous medium, and, optionally, optional components (components C, D, E, F, and other components) using a known method. That is, in another aspect, the present disclosure relates to a method for producing a polishing composition, comprising blending at least component A, component B, and an aqueous medium. In this disclosure, "blending" includes simultaneously or in any order mixing component A, component B, an aqueous medium, and, if necessary, optional components (components C, D, E, F, and other components). 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. The blending can be carried out using a mixer such as a homomixer, homogenizer, ultrasonic disperser, or wet ball mill. The preferred amount of each component in the method for producing the polishing composition can be the same as the preferred content of each component in the polishing composition of the present disclosure described above.

[0049] In the present disclosure, the "content of each component in the polishing composition" refers to the content of each component at the time of use, that is, at the time when the polishing composition is first used for polishing. The polishing composition of the present disclosure may be stored and supplied in a concentrated state to the extent that its storage stability is not impaired. This is preferable because it further reduces production and transportation costs. The concentrate of the polishing composition of the present disclosure may be appropriately diluted with the above-mentioned aqueous medium when used, as needed. The dilution ratio is not particularly limited as long as the above-mentioned content (at the time of use) of each component can be ensured after dilution, and may be, for example, 10 to 100 times.

[0050] [Polishing pad] The polishing pad used in the polishing process of the present disclosure (hereinafter also referred to as the "polishing pad of the present disclosure") is a suede-type polishing pad having a contact angle with the polishing liquid composition of the present disclosure of 70° or less and a surface roughness of 3 μm or less.

[0051] In one or more embodiments, the polishing pad of the present disclosure is a suede-type polishing pad having a base layer and a surface layer made of a foamed polyurethane elastomer (hereinafter also referred to as a "foamed layer"). In one or more embodiments, the foam layer (surface layer) of the polishing pad can be either a closed-cell or open-cell type, with the open-cell type being preferred from the standpoint of polishing debris discharge. Examples of open-cell type polishing pads include those described in "CMP Technology Basic Examples Lecture Series, Vol. 2, Fundamentals and Examples of Mechanochemical Polishing (CMP) (Polishing Pad Edition), May 27, 1998, Materials, Edited by Global Net Co., Ltd." or "CMP Science, Edited by Kashiwagi Masahiro, Science Forum Co., Ltd., Chapter 4." Here, the term "suede type" refers, in one or more embodiments, to a structure having a base layer and a foam layer with spindle-shaped pores perpendicular to the base layer, as described in JP-A-11-335979. In one or more embodiments, the suede type polishing pad is manufactured by the following method. A solution of polyurethane elastomer dissolved in a solvent such as dimethylformamide (DMF) is applied to a base layer made of polyethylene terephthalate (PET), and the resulting layer is immersed in water or a mixture of water and the solvent for the polyurethane elastomer solution to wet-solidify the layer. The layer is then washed with water to remove the solvent and dried. This results in a foamed layer with spindle-shaped pores perpendicular to the base layer. The surface of the resulting foamed layer is then polished with sandpaper or the like to obtain a suede-type polishing pad with a foamed layer having pores on its surface and spindle-shaped pores perpendicular to the base layer. In one or more embodiments, the material for the base layer of the polishing pad may include a nonwoven fabric made of natural fibers such as cotton or synthetic fibers, or a base layer obtained by filling with a rubber-like substance such as styrene butadiene rubber, and polyethylene terephthalate (PET) film or polyester film is preferred, with PET film being more preferred. In one or more embodiments, the material of the foam layer (surface layer) of the polishing pad may be polyurethane elastomer, polystyrene, polyester, polyvinyl chloride, natural rubber, synthetic rubber, etc., and polyurethane elastomer is preferred from the viewpoint of achieving both improved polishing speed and reduced waviness.

[0052] <Surface roughness of polishing pad> The surface roughness of the polishing pad of the present disclosure is 3 μm or less, preferably 2.5 μm or less, and more preferably 2 μm or less, from the viewpoint of reducing waviness. From the viewpoint of improving the polishing rate, it is preferably 0.1 μm or more, more preferably 0.5 μm or more, even more preferably 0.6 μm or more, and even more preferably 0.7 μm or more. More specifically, the surface roughness of the polishing pad is preferably 0.1 μm or more and 3 μm or less, more preferably 0.5 μm or more and 2.5 μm or less, even more preferably 0.6 μm or more and 2 μm or less, and even more preferably 0.7 μm or more and 2 μm or less. In the present disclosure, the surface roughness of the polishing pad refers to the surface roughness of the polishing pad when polishing with the polishing liquid composition, and can be measured, for example, by the method described in the Examples. In one or more embodiments, the surface roughness of the polishing pad refers to the surface roughness of the surface layer of the polishing pad, and can be controlled, for example, by the pore size on the surface side of the foam layer or the roughness of the pad dresser used to polish the surface of the foam layer.

[0053] <Contact angle of polishing pad> The contact angle of the polishing pad of the present disclosure with the polishing liquid composition of the present disclosure is 70° or less, preferably 68° or less, more preferably 66° or less, from the viewpoint of suppressing adhesion of the substrate to the polishing machine surface plate, and is preferably 15° or more, more preferably 20° or more, and even more preferably 25° or more, from the viewpoint of suppressing adhesion of the substrate to the polishing machine surface plate. More specifically, the contact angle of the polishing pad of the present disclosure with the polishing liquid composition of the present disclosure is preferably 15° or more and 70° or less, more preferably 20° or more and 68° or less, and even more preferably 25° or more and 66° or less. The contact angle can be measured, for example, by the method described in the Examples.

[0054] <Average pore size of polishing pad> From the viewpoint of achieving both an improvement in the polishing rate and a reduction in waviness, the average open pore diameter of the pores on the surface of the polishing pad of the present disclosure is preferably 10 μm or more and 100 μm or less, more preferably 15 μm or more and 80 μm or less, even more preferably 20 μm or more and 60 μm or less, and even more preferably 25 μm or more and 55 μm or less. The average pore size of the pores on the surface of the polishing pad can be controlled by adding additives to the polyurethane elastomer raw material, such as pigments such as carbon black, hydrophilic surfactants that promote foaming, or hydrophobic surfactants that stabilize the wet coagulation of the polyurethane elastomer. In the present disclosure, the average pore size can be determined by the following method. First, the polishing pad surface is observed with a scanning electron microscope (preferably 100 to 300 magnifications), and the image is imported into a personal computer (PC). The imported image is then analyzed using image analysis software on the PC, and the average pore diameter can be determined as the average diameter of the circle-equivalent diameters of the pores. For example, WinROOF (Mitani Corporation) can be used as the image analysis software.

[0055] <Polishing pad thickness> From the viewpoint of achieving both improved polishing rate and reduced waviness, the thickness of the polishing pad of the present disclosure is preferably 0.7 mm or more and 2.5 mm or less, more preferably 0.8 mm or more and 2.0 mm or less, even more preferably 0.8 mm or more and 1.7 mm or less, and even more preferably 0.9 mm or more and 1.5 mm or less.

[0056] [Substrate to be polished] In one or more embodiments, the substrate to be polished is a substrate used in the manufacture of a magnetic disk substrate. In one or more embodiments, a magnetic disk substrate can be manufactured by polishing the surface of the substrate to be polished with the polishing composition of the present disclosure, followed by forming a magnetic layer on the substrate surface by sputtering or the like.

[0057] Suitable substrate materials for polishing in the present disclosure include metals or semimetals such as silicon, aluminum, nickel, tungsten, copper, tantalum, and titanium, or alloys thereof; glassy materials such as glass, glassy carbon, and amorphous carbon; ceramic materials such as alumina, silicon dioxide, silicon nitride, tantalum nitride, and titanium carbide; and resins such as polyimide resins. Substrates containing metals such as aluminum, nickel, tungsten, and copper, and alloys containing these metals as their main components, are particularly suitable. Examples of suitable substrates include Ni-P-plated aluminum alloy substrates and glass substrates such as crystallized glass, tempered glass, aluminosilicate glass, and aluminoborosilicate glass, with Ni-P-plated aluminum alloy substrates being even more suitable. In the present disclosure, the term "Ni-P-plated aluminum alloy substrate" refers to an aluminum alloy substrate whose surface has been ground and then electrolessly plated with Ni-P.

[0058] The shape of the substrate to be polished may be, for example, a shape having a flat surface such as a disk, plate, slab, or prism, or a shape having a curved surface such as a lens. Of these, a disk-shaped substrate to be polished is suitable. In the case of a disk-shaped substrate to be polished, its outer diameter is, for example, about 2 to 97 mm, and its thickness is, for example, about 0.3 to 2 mm.

[0059] [Polishing liquid kit] In one aspect, the present disclosure relates to a kit for producing the polishing liquid composition of the present disclosure (hereinafter also referred to as the "polishing liquid kit of the present disclosure"). Examples of the polishing liquid kit of the present disclosure include a polishing liquid kit (two-component polishing liquid composition) that contains a silica dispersion containing component A and an aqueous medium and an additive aqueous solution containing component B in a mutually unmixed state, which are mixed at the time of use and diluted with the aqueous medium as needed. The aqueous medium contained in the silica dispersion may be the entire amount of water used to prepare the polishing liquid composition, or a portion thereof. The additive aqueous solution may contain a portion of the aqueous medium used to prepare the polishing liquid composition. The silica dispersion and the additive aqueous solution may each contain the optional components described above (components C to F and other components) as needed. The polishing liquid kit of the present disclosure can achieve both an improved polishing rate and a reduced waviness on the substrate surface after polishing, thereby providing a polishing liquid composition with excellent productivity.

[0060] [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 polishing step in which a substrate to be polished is polished using the polishing composition of the present disclosure and the polishing pad of the present disclosure, resulting in a substrate thickness of 0.6 mm or less after polishing. The polishing method of the present disclosure can achieve both an improved polishing rate and a reduced waviness of the substrate surface after polishing. By using the polishing composition of the present disclosure, which has excellent productivity, high-quality magnetic disk substrates can be produced with high yield and good productivity. As described above, the substrate to be polished in the polishing method of the present disclosure can be one used for manufacturing magnetic disk substrates, and in particular, substrates used for manufacturing magnetic disk substrates for perpendicular magnetic recording systems are preferred. The polishing method and conditions in the polishing method of the present disclosure can be the same as those in the substrate manufacturing method of the present disclosure described above.

[0061] In one or more embodiments, the polishing step in the polishing method of the present disclosure is a step of supplying the polishing liquid composition of the present disclosure to the surface to be polished of a substrate to be polished, bringing a polishing pad into contact with the surface to be polished, and moving at least one of the polishing pad and the substrate to be polished to perform polishing. [Example]

[0062] 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.

[0063] 1. Preparation of Polishing Compositions (Examples 1 to 5, Comparative Examples 1 to 6) Polishing liquid compositions of Examples 1 to 5 and Comparative Examples 1 to 6 shown in Table 1 were prepared by blending and stirring component A (colloidal silica), component B (sulfuric acid), additives (components C, D, E, and F), and ion-exchanged water. The content (mass %, effective amount) of each component in each polishing liquid composition is as shown in Table 1. The content of ion-exchanged water is the remainder excluding component A, component B, and the additives (components C, D, E, and F).

[0064] In preparing each polishing composition, the following components were used as component B and additives (components C to F). (Component B) Sulfuric acid [concentration 62.5% by mass, manufactured by Teika] (Component C) Hydrogen peroxide solution [35% by mass, manufactured by ADEKA] (Component D) BTA [1,2,3-benzotriazole, manufactured by Tokyo Chemical Industry Co., Ltd.] (Component E) Amino alcohol [N-(β-aminoethyl)ethanolamine, manufactured by Nippon Nyukazai Co., Ltd.] (Component F) BisS / PhS [bisphenol S / phenolsulfonic acid formalin condensate, manufactured by Konishi Chemical Co., Ltd., molar ratio (BisS / PhS): 20 / 80, weight-average molecular weight: 5,000]

[0065] 2. Measurement of each parameter [Average secondary particle size of colloidal silica (component A)] A standard sample was prepared by adding component A (colloidal silica) and component B (sulfuric acid) used in preparing the polishing composition to ion-exchanged water and stirring. The contents of components A and B in the standard sample were 6.0% by mass and 1.2% by mass, respectively. This standard sample was analyzed using a dynamic light scattering device (DLS-6500, manufactured by Otsuka Electronics Co., Ltd.) according to the manufacturer's instructions. The particle size at which the area of ​​the scattering intensity distribution obtained by the cumulant method at a detection angle of 90° accounted for 50% of the total area after 200 integrations was determined, and this was taken as the average secondary particle size of the colloidal silica. The results are shown in Table 1.

[0066] [Weight-average molecular weight of anionic water-soluble polymer (component F)] The weight average molecular weight of Component F was measured by gel permeation chromatography (GPC) under the following conditions. The results are shown in Table 1. <Measurement conditions> Column: TSKgel GMPWXL + TSKgel GMPWXL (Tosoh Corporation) Eluent: 0.2M phosphate buffer / CH3CN = 7 / 3 (volume ratio) Temperature: 40℃ Flow rate: 1.0mL / min Sample size: 2mg / mL Detector: RI Standard material: sodium polystyrene sulfonate (weight average molecular weight: 1,100, 3,610, 14,900, 152,000, manufactured by Polmer Standards Service)

[0067] [pH measurement] The pH of the polishing composition was measured at 25° C. using a pH meter (manufactured by DKK-Toa Corporation), and the value measured 2 minutes after immersing the electrode in the polishing composition was adopted. The results are shown in Table 1.

[0068] [Surface roughness of polishing pad] The polishing pads used for measuring surface roughness were adjusted to each roughness using a diamond dressing on a double-sided 9B polisher, and the surface roughness (Ra) of the polishing pads was measured using a tactile surface roughness meter (product name: SURFTEST SJ-210, manufactured by Mitutoyo Corporation). The roughness of the measurement pad was measured at nine points on the double-sided 9B polisher, three points each at 3 cm from the outer periphery, 10 cm from the outer periphery, and 3 cm from the inner periphery, and the average value was used. <Measurement conditions> Roughness standard: ISO1997 Measurement speed: 0.5mm / S Cutoff value 0.8 mm

[0069] [Contact angle] The polishing pads used for contact angle measurements were diamond-dressed on a double-sided 9B polisher, adjusted to the desired roughness, washed with water, and air-dried for 48 hours. A 1 μl droplet of polishing solution was placed on a Teflon® needle (18G) and brought close to the measurement pad, bringing the pad into contact with the water droplet. The contact angle was then measured after 30 seconds using a Kyowa Interface Science Co., Ltd. "Drop Master DMo-501." Nine pad pieces were cut from the double-sided 9B polisher, three from each of the outer periphery (3 cm), 10 cm from the outer periphery, and 3 cm from the inner periphery. The average contact angle was measured. Measurements were performed at 25°C. The results are shown in Table 1.

[0070] 3. Polishing method The polishing compositions and polishing pads of Examples 1 to 5 and Comparative Examples 1 to 6 prepared as described above were used to polish the following substrates under the polishing conditions shown below. The polishing rate and waviness were then measured by the measurement methods described below. The results are shown in Table 1.

[0071] [Substrate to be polished] The substrates used were Ni-P plated aluminum alloy substrates that had been roughly polished with a polishing composition containing an alumina abrasive. The substrates had thicknesses of 0.6 mm or 1.27 mm, outer diameters of 97 mm, and inner diameters of 25 mm. The centerline average roughness (Ra) measured with an AFM (Digital Instrument NanoScope IIIa Multimode AFM) was 1 nm.

[0072] [Polishing pad] The polishing pad used was a suede type manufactured by Fujibo Co., Ltd. (foam layer: polyurethane elastomer, thickness: 0.9 mm, average pore size: 40 μm). The pad was dressed using a diamond dressing (#600) on a double-sided 9B polisher until the specified roughness was achieved. Polishing tester: Speedfam "Double-sided 9B polishing machine" Water supply amount: 2000mL / min Lower surface plate rotation speed: 30rpm Polishing load: 3.0 kPa Number of dress boards: 6

[0073] [Polishing conditions (finish polishing)] Polishing tester: Speedfam "Double-sided 9B polishing machine" Polishing liquid composition supply amount: 100mL / min (substrate to be polished 1cm) 2 Feed rate per: 0.076 mL / min Lower surface plate rotation speed: 30rpm Polishing load: 13.7kPa Polishing time: 5 minutes Number of boards: 10

[0074] [Substrate thickness after polishing] The thickness of each substrate after polishing was measured using a vernier caliper (CD-15, manufactured by Mitutoyo Corporation), and the average value of the 10 substrates was calculated.

[0075] 4. Evaluation [Evaluation of polishing speed] The weight of each substrate was measured before and after polishing using a Sartorius BP-210S, and the mass loss was calculated from the change in mass of each substrate. The polishing rate was calculated by dividing the average mass loss of all 10 substrates by the polishing time using the following formula. The polishing rate measurement results are shown in Table 1 as relative values, with Comparative Example 1 set to 100. Mass loss (mg) = {mass before polishing (mg) - mass after polishing (mg)} Polishing speed (mg / min) = mass loss (mg) / polishing time (min)

[0076] [Waviness evaluation] The polishing time was set so that the weight loss after polishing was 50 mg or more and 80 mg or less (polishing time for Examples 1 to 5 and Comparative Examples 1 to 4 and 6: 5 minutes, polishing time for Comparative Example 5: 30 minutes), and the above substrates (thickness: 0.6 mm) were polished under the same polishing conditions as above, except for the polishing time. The waviness of the 0.6 mm thick substrates after polishing was measured under the following conditions. Waviness was measured at three points per side, a total of six points for two substrates on the front and back surfaces, and an average value was obtained. Table 1 shows the relative values, with Comparative Example 1 set to 100. <Measurement conditions> Measuring machine: New View 7300 (Zygo) Lens: 2.5x Zoom: 0.5x Measurement wavelength range: 60~160μm Measurement position: 28mm radius from the center of the board Analysis software: Zygo Metro Pro (Zygo)

[0077] [Measurement of adhesion to surface plate] After the ten substrates (all the same thickness) were finish-polished under the above polishing conditions, the number of substrates remaining on the upper platen was counted when the platen was lifted up. The results are shown in Table 1.

[0078] [Table 1]

[0079] As shown in Table 1 above, in Examples 1 to 5, which used a polishing liquid composition having a pH of 0.5 to 4.0 containing silica particles with an average secondary particle diameter of 40 nm or less and a predetermined polishing pad, the removal rate was improved and waviness was reduced compared to Comparative Examples 1 and 4, in which the surface roughness of the polishing pad exceeded 3 μm, Comparative Example 2, in which the average secondary particle diameter of the silica particles exceeded 40 nm and the surface roughness of the polishing pad exceeded 3 μm, Comparative Example 3, in which the average secondary particle diameter of the silica particles exceeded 40 nm, Comparative Example 5, in which the pH of the polishing liquid composition exceeded 4.0, and Comparative Example 6, in which the contact angle of the polishing pad with the polishing liquid composition exceeded 70°. Furthermore, in Examples 1 to 5, adhesion of a 0.6 mm thick substrate to the surface plate was suppressed, demonstrating excellent productivity. [Industrial Applicability]

[0080] According to the present disclosure, for example, a magnetic disk substrate suitable for high recording density can be provided.

Claims

1. A polishing process that uses a polishing liquid composition and a polishing pad to polish a substrate to be polished, and the thickness of the substrate after polishing is 0.6 mm or less, The polishing liquid composition contains silica particles (Component A), an acid (Component B), and an aqueous medium. The average secondary particle diameter of Component A is 40 nm or less, and the pH is 0.5 or more and 4.0 or less. It is a polishing liquid composition, The polishing pad is a suede type polishing pad with a contact angle of 70° or less with the polishing liquid composition and a surface roughness of 3 μm or less. A method for manufacturing a magnetic disk substrate.

2. The method for manufacturing a magnetic disk substrate according to Claim 1, wherein the surface roughness of the polishing pad is 0.6 μm or more and 2 μm or less.

3. The method for manufacturing a magnetic disk substrate according to Claim 1 or 2, wherein the substrate to be polished is an aluminum alloy substrate plated with Ni-P.

4. The method for manufacturing a magnetic disk substrate according to Claim 1 or 2, wherein the polishing process is a finishing polishing process.

5. A polishing liquid composition used in a polishing process that uses a suede type polishing pad with a contact angle of 70° or less with the polishing liquid composition and a surface roughness of 3 μm or less to polish a substrate to be polished, and the thickness of the substrate after polishing is 0.6 mm or less. Comprising, Silica particles (Component A), an acid (Component B), and an aqueous medium, The average secondary particle diameter of Component A is 40 nm or less, The pH is 0.5 or more and 4.0 or less. A polishing liquid composition.

6. The polishing liquid composition according to Claim 5, further containing an oxidizing agent (Component C).

7. The polishing liquid composition according to Claim 5 or 6, further containing at least one selected from a heterocyclic aromatic compound (Component D), an aliphatic amine compound or an alicyclic amine compound (Component E), and an anionic water-soluble polymer (Component F).