Polishing liquid

Abstract

To provide polishing liquid capable of achieving both enhancement in a polishing speed and reduction of scratches on the substrate surface after polishing.SOLUTION: In one embodiment, the present invention relates to polishing liquid comprising: silica particles (component A); at least one compound selected from diamines and triamines (component B); a water-soluble polymer (component C) containing a structural unit c1 derived from a monomer having a carboxy group and an ethylenically unsaturated group, and a structural unit c2 derived from a monomer having an amide group; and an aqueous medium, wherein the monomer having the amide group is N-alkylacrylamide or N-alkylmethacrylamide.SELECTED DRAWING: None

Description

Technical Field

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

Background Art

[0002] In recent years, magnetic disk drives have been miniaturized and increased in capacity, and higher recording density has been demanded. To achieve higher recording density, it is necessary to reduce the unit recording area and improve the detection sensitivity of the weakened magnetic signal. Therefore, technological development for making the flying height of the magnetic head lower is underway. For the magnetic disk substrate, in order to cope with the lower flying height of the magnetic head and the securing of the recording area, improvement in smoothness and flatness (reduction of surface roughness, waviness, and end face sag) and reduction of surface defects (reduction of residual abrasive grains, scratches, protrusions, pits, etc.) are severely required.

[0003] In response to such requirements, from the viewpoint of achieving both improvement in surface quality such as being smoother and having fewer scratches and improvement in productivity in the method for manufacturing a magnetic disk substrate, a multi-stage polishing method having two or more polishing steps is often adopted. Generally, in order to satisfy the requirement of smoothness, an abrasive containing colloidal silica particles is used, and from the viewpoint of improving productivity, a polishing liquid containing alumina particles as abrasive grains is used. However, when alumina particles are used as abrasive grains, defects may be caused in the magnetic disk substrate due to the penetration of the alumina particles into the substrate.

[0004] Therefore, for example, Patent Documents 1 to 4 propose a polishing liquid composition that does not contain alumina particles and contains silica particles as abrasive grains.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0006] With the increase in the storage capacity of magnetic disk drives, the required characteristics for the surface quality of the substrate have become even more stringent, and the development of a polishing liquid that can further reduce scratches on the substrate surface is required. Generally, there is a trade-off relationship between the polishing rate and scratches, and there is a problem that if one improves, the other deteriorates.

[0007] Therefore, the present disclosure provides a polishing liquid capable of achieving both an improvement in the polishing rate and a reduction in scratches on the surface of the substrate after polishing, and a method for manufacturing a magnetic disk substrate using the same.

Means for Solving the Problems

[0008] In one aspect, the present disclosure relates to a polishing liquid containing silica particles (Component A), at least one compound selected from diamines and triamines (Component B), a structural unit c1 derived from a monomer having a carboxy group and an ethylenically unsaturated group, and a structural unit c2 derived from a monomer having an N-alkyl (meth)acrylamide structure (Component C), and an aqueous medium.

[0009] In one aspect, the present disclosure relates to a method for manufacturing a magnetic disk substrate, including a polishing step of polishing a substrate to be polished using the polishing liquid of the present disclosure.

Effects of the Invention

[0010] According to the present disclosure, in one aspect, it is possible to provide a polishing liquid capable of achieving both an improvement in the polishing rate and a reduction in scratches on the surface of the substrate after polishing.

Modes for Carrying Out the Invention

[0011] The present disclosure is based on the finding that when a polishing liquid containing silica particles, at least one compound selected from diamines and triamines, and a specific water-soluble polymer is used for polishing a magnetic disk substrate, the polishing rate can be improved while reducing scratches on the surface of the substrate after polishing.

[0012] That is, in one aspect, the present disclosure relates to a polishing liquid (hereinafter, also referred to as "the polishing liquid of the present disclosure") containing silica particles (component A), at least one compound selected from diamines and triamines (component B), a structural unit c1 derived from a monomer having a carboxy group and an ethylenically unsaturated group, and a structural unit c2 derived from a monomer having an N-alkyl (meth)acrylamide structure, and an aqueous medium.

[0013] The mechanism of the effect expression of the present disclosure is not clear, but is presumed as follows. In the present disclosure, by using in combination at least one compound selected from diamines and triamines (component B), a structural unit c1 derived from a monomer having a carboxy group and an ethylenically unsaturated group, and a water-soluble polymer (component C) containing a structural unit c2 derived from a monomer having an N-alkyl (meth)acrylamide structure, component B and component C interact with each other to form a complex of component B and component C. Since this complex has an adsorptivity to the polishing pad and silica particles (component A), it is considered that silica particles are retained on the polishing pad via the complex, the number of particles acting on the substrate increases, and the polishing rate is improved. Further, it is considered that the frequency of direct contact between the substrate and the polishing pad decreases, thereby reducing friction and suppressing the generation of scratches. However, the present disclosure should not be construed as being limited to these mechanisms.

[0014] In the present disclosure, a "scratch" refers to a fine scratch on the surface of a magnetic disk substrate or a substrate for semiconductor elements, having a depth of 1 nm or more and less than 100 nm, a width of 5 nm or more and less than 500 nm, and a length of 100 μm or more. Scratches on the substrate surface can be detected, for example, by an optical defect inspection device and quantitatively evaluated as the number of scratches. The number of scratches can be specifically evaluated by the method described in the examples.

[0015] [Silica particles A (Component A)] The polishing liquid of the present disclosure contains silica particles (hereinafter also referred to as "Component A") as abrasive grains. As the usage form of Component A, it is preferably a silica slurry in which silica particles are dispersed in an aqueous medium. Component A may be used alone or in combination of two or more.

[0016] From the viewpoint of improving the polishing rate and reducing scratches, the average secondary particle diameter of Component A is preferably 1 nm or more, more preferably 5 nm or more, still more preferably 10 nm or more, still more preferably 13 nm or more, even more preferably 18 nm or more, and from the same viewpoint, preferably 50 nm or less, more preferably 40 nm or less, still more preferably 30 nm or less, even more preferably 25 nm or less. More specifically, the average secondary particle diameter of Component A is preferably 1 nm or more and 50 nm or less, more preferably 5 nm or more and 40 nm or less, still more preferably 10 nm or more and 30 nm or less, still more preferably 13 nm or more and 30 nm or less, even more preferably 18 nm or more and 25 nm or less. In the present disclosure, the average secondary particle diameter of Component A means the particle diameter (D50) at which the cumulative volume ratio from the small diameter side of the particle diameter distribution obtained based on the scattering intensity distribution measured by the dynamic light scattering method (DLS: Dynamic Light Scattering) is 50%. The average secondary particle diameter of Component A in the present disclosure can be specifically obtained by the method described in the examples.

[0017] Examples of Component A include colloidal silica, precipitated silica, fumed silica, crushed silica, and silica with surface modification thereof. From the viewpoints of improving polishing rate and ease of obtaining, at least one selected from colloidal silica and precipitated silica is preferable as Component A. From the viewpoints of improving polishing rate and improving substrate quality such as reducing scratches, colloidal silica, which can reduce the ratio of the presence of sharp surface shapes and local surface high-hardness portions, is more preferable. The colloidal silica is, for example, obtained by a method of particle growth using an aqueous alkali silicate solution as a raw material (hereinafter, also referred to as the "water glass method") and a method of condensation of a hydrolyzate of alkoxysilane (hereinafter, also referred to as the "sol-gel method"). From the viewpoints of ease of production and economy, it is preferably obtained by the water glass method. Silica particles obtained by the water glass method and the sol-gel method can be produced by known methods. The precipitated silica is silica particles obtained by a precipitation method. Examples of the production method of the precipitated silica particles include known methods such as the method described in Toso Research & Technical Report, Vol. 45 (2001), pp. 65 to 69. Specific examples of the production method of the precipitated silica particles include, for example, a precipitation method in which silica particles are precipitated by a neutralization reaction between a silicate such as sodium silicate and a mineral acid such as sulfuric acid. It is preferable to carry out the neutralization reaction under alkaline conditions at a relatively high temperature. Thereby, the growth of the primary particles of silica proceeds rapidly, and the primary particles aggregate and precipitate in a flocculent form. Preferably, the precipitated silica particles are obtained by further pulverizing this.

[0018] Suitable shapes of Component A include spherical particles and spindle-shaped particles. In the present disclosure, when Component A is spindle-shaped particles, it means particles in which the diameter in the direction perpendicular to the longitudinal direction of the particles has a minimum value in any of the longitudinal directions. Also, spherical particles mean particles in which the diameter in the direction perpendicular to the longitudinal direction of the particles does not have a minimum value in any of the longitudinal directions. Among these, from the viewpoints of improving the polishing rate and reducing scratches, Component A is more preferably spherical particles. In the present disclosure, the proportion of the number of spherical particles in Component A is preferably more than 50%, more preferably 75% or more, still more preferably 90% or more, and even more preferably 95% or more. Examples of the method for adjusting the shape of Component A include, for example, a method of adjusting the dropping rate of the silicic acid solution, the reaction temperature, and the concentration during the growth process of the silica particles. In the present disclosure, the shape of Component A can be determined by observing the particles in one field of view with an electron microscope.

[0019] From the viewpoints of improving the polishing rate and reducing scratches, the content of Component A in the polishing liquid of the present disclosure is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, still more preferably 1% by mass or more, and even more preferably 1.5% by mass or more. And from the viewpoint of economy, it is preferably 30% by mass or less, more preferably 20% by mass or less, still more preferably 15% by mass or less, and even more preferably 10% by mass or less. More specifically, the content of Component A in the polishing liquid of the present disclosure is preferably 0.1% by mass or more and 30% by mass or less, more preferably 0.5% by mass or more and 20% by mass or less, still more preferably 1% by mass or more and 15% by mass or less, and even more preferably 1.5% by mass or more and 10% by mass or less. When Component A consists of two or more kinds of silica particles, the content of Component A refers to their total content.

[0020] [At least one compound selected from diamine and triamine (Component B)] The polishing liquid of the present disclosure contains at least one compound selected from diamine and triamine (hereinafter also referred to as "Component B"). Component B may be one kind or a combination of two or more kinds. Component B is preferably a saturated compound from the viewpoints of improving the polishing rate and reducing scratches in one or more embodiments. In the present disclosure, the saturated compound means an organic compound in which the hydrocarbon group of at least one compound selected from diamines and triamines does not contain double bonds or triple bonds between carbon atoms in its molecule, all of which are single bonds, and the valence of carbon is satisfied. In one or more embodiments, component B preferably has a molecular weight of 300 or less, more preferably 200 or less, from the viewpoints of improving the polishing rate and reducing scratches. In one or more embodiments, component B preferably has 4 to 10 carbon atoms in the molecule, more preferably 4 to 8 carbon atoms, and still more preferably 5 or 6 carbon atoms, from the viewpoints of improving the polishing rate and reducing scratches.

[0021] In one or more embodiments, component B is preferably a compound represented by the following structural formula (I) from the viewpoints of improving the polishing rate and reducing scratches. Component B may be in the form of a salt of the compound represented by the following structural formula (I). R 1 -N(R 2 )-(CH 2 ) n -N(R 3 )-R 4 -X···(I) In the structural formula (I), R 1 , R 2 , R 3 and R 4 are each independently a hydrogen atom or a hydrocarbon group, and X is selected from a hydrogen atom, a hydroxyl group, and an amino group. R 2 and R 3 may be bonded to each other to form a cyclic structure. n is an integer of 1 or more and 15 or less.

[0022] In the structural formula (I), R 1 , R 2 , R 3 and R 4Independently of each other, from the viewpoints of improving the polishing rate and reducing scratches, a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms is preferable. R 2 and R 3 are bonded to each other to form a cyclic structure, R 2 +R 3 from the viewpoints of improving the polishing rate and reducing scratches, is preferably a saturated or unsaturated hydrocarbon group having 2 to 4 carbon atoms, more preferably 2 to 3 carbon atoms, and still more preferably is one selected from an ethylene group or a trimethylene group. X is preferably a hydroxyl group or an amino group from the viewpoints of improving the polishing rate and reducing scratches. n is preferably an integer of 1 to 10, more preferably an integer of 1 to 5, still more preferably an integer of 1 to 3, and even more preferably 2, from the viewpoints of improving the polishing rate and reducing scratches. In the present disclosure, component B, from the viewpoints of improving the polishing rate and reducing scratches, in the structural formula (I), R 2 and R 3 are bonded to each other to form a cyclic structure, R 2 +R 3 is selected from an ethylene group or a trimethylene group, and it is preferable that n = 2.

[0023] Component B is preferably at least one selected from ethylenediamine, N,N,N',N'-tetramethylethylenediamine, 1,2-diaminopropane, trimethylenediamine, 1,4-diaminobutane, hexamethylenediamine, N-methyltrimethylenediamine, N,N-dimethyltrimethylenediamine, N,N-diethyltrimethylenediamine, N,N-dibutyltrimethylenediamine, N,N,N',N'-tetramethyltrimethylenediamine, N,N-dimethylethylenediamine, N,N-diethylethylenediamine, N-ethylethylenediamine, N,N,N',N'-tetramethylethylenediamine, N-(2-hydroxyethyl)ethylenediamine (HEA), N-aminoethylisopropanolamine, N-aminoethyl-N-methylethanolamine, diethylenetriamine, 1,4-diazacyclohexane, 2-methyl-1,4-diazacyclohexane, 2,5-dimethyl-1,4-diazacyclohexane, 1-methyl-1,4-diazacyclohexane (MDC), 1-(2-aminoethyl)-1,4-diazacyclohexane (ADC), and 1-(2-hydroxyethyl)-1,4-diazacyclohexane (HDC), and more preferably at least one selected from N-(2-hydroxyethyl)ethylenediamine (HEA), 1-methyl-1,4-diazacyclohexane (MDC), 1-(2-aminoethyl)-1,4-diazacyclohexane (ADC), and 1-(2-hydroxyethyl)-1,4-diazacyclohexane (HDC) from the viewpoints of improving the polishing rate and reducing scratches.

[0024] From the perspective of scratch reduction, the content of component B in the polishing liquid of the present disclosure is preferably 0.001% by mass or more, more preferably 0.005% by mass or more, still more preferably 0.01% by mass or more. From the perspective of improving the polishing rate, it is preferably 1% by mass or less, more preferably 0.5% by mass or less, still more preferably 0.1% by mass or less, even more preferably 0.05% by mass or less, and even more preferably 0.02% by mass or less. More specifically, from the perspective of achieving both scratch reduction and polishing rate improvement, the content of component B in the polishing liquid of the present disclosure is preferably 0.001% by mass or more and 1% by mass or less, more preferably 0.005% by mass or more and 0.5% by mass or less, still more preferably 0.005% by mass or more and 0.1% by mass or less, even more preferably 0.005% by mass or more and 0.05% by mass or less, and even more preferably 0.005% by mass or more and 0.02% by mass or less. When component B is a combination of two or more, the content of component B refers to their total content.

[0025] [Water-soluble polymer (component C)] The polishing liquid of the present disclosure contains a water-soluble polymer (hereinafter, also referred to as "component C") including a structural unit c1 derived from a monomer having a carboxy group and an ethylenically unsaturated group, and a structural unit c2 derived from a monomer having an N-alkyl (meth) acrylamide structure. In the present disclosure, "water-soluble" means having a solubility of 0.5 g / 100 mL or more, preferably 2 g / 100 mL or more, in water (20 °C). Component C may be one kind or a combination of two or more kinds.

[0026] [Structural unit c1 derived from a monomer having a carboxy group and an ethylenically unsaturated group]< Examples of the structural unit c1 (hereinafter also simply referred to as "structural unit c1") derived from a monomer having a carboxy group and an ethylenically unsaturated group contained in Component C include, from the viewpoints of improving polishing rate and reducing scratches, at least one selected from acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, and salts thereof. Among these, one selected from acrylic acid and methacrylic acid is more preferable. Examples of the salts include alkali metals such as lithium, sodium, and potassium; alkaline earth metals such as calcium; ammonium; alkanolamines such as triethanolamine; etc. These can be used alone or in combination of two or more. From the viewpoint of improving the solubility of Component C in the dosage form and achieving an improvement in polishing rate and a reduction in scratches, the content (mol%) of the structural unit c1 in all the structural units of Component C is preferably 50 mol% or more, more preferably 60 mol% or more, still more preferably 70 mol% or more, and from the same viewpoint, preferably 98 mol% or less, more preferably 95 mol% or less, still more preferably 90 mol% or less. From the same viewpoint, the content of the structural unit c1 in all the structural units of Component C is preferably 50 mol% or more and 98 mol% or less, more preferably 60 mol% or more and 95 mol% or less, still more preferably 70 mol% or more and 90 mol% or less.

[0027] <Structural unit c2 derived from a monomer having an N-alkyl (meth)acrylamide structure> In the structural unit c2 (hereinafter also simply referred to as "structural unit c2") derived from a monomer having an N-alkyl (meth)acrylamide structure contained in Component C, the number of carbon atoms of the alkyl group bonded to the nitrogen atom of the (meth)acrylamide structure is preferably 1 or more and 6 or less from the viewpoints of improving polishing rate and reducing scratches. Also, the number of alkyl groups bonded to the nitrogen atom of the (meth)acrylamide structure may be plural. Examples of the structural unit c2 derived from a monomer having an N-alkyl (meth) acrylamide structure include structural units derived from one monomer selected from N-methyl (meth) acrylamide, N,N-dimethyl (meth) acrylamide, N-isopropyl (meth) acrylamide, N,N-diethyl (meth) acrylamide, N-n-butyl (meth) acrylamide, N-sec-butyl (meth) acrylamide, and N-t-butyl (meth) acrylamide. Among these, a structural unit derived from N-t-butyl acrylamide (tBuAAm) is more preferable. In the present disclosure, “(meth)acryl” means one selected from acrylic and methacrylic. From the viewpoint of improving the polishing rate and reducing scratches, the content (mol%) of the structural unit c2 in all the structural units of Component C is preferably 2 mol% or more, more preferably 5 mol% or more, still more preferably 10 mol% or more, and from the same viewpoint, preferably 40 mol% or less, more preferably 30 mol% or less, still more preferably 20 mol% or less. From the same viewpoint, the content of the structural unit c2 in all the structural units of Component C is preferably 2 mol% or more and 40 mol% or less, more preferably 5 mol% or more and 30 mol% or less, still more preferably 10 mol% or more and 20 mol% or less.

[0028] From the viewpoint of improving the polishing rate and reducing scratches, the total content (mol%) of the structural unit c1 and the structural unit c2 in all the structural units of Component C is preferably 80 mol% or more, more preferably 90 mol% or more, still more preferably 95 mol% or more. Further, when Component C does not contain the structural unit c3 derived from a monomer having a sulfonic acid group and an ethylenically unsaturated group described later, the total content (mol%) of the structural unit c1 and the structural unit c2 in all the structural units of Component C is preferably 100 mol% from the viewpoint of improving the polishing rate and reducing scratches.

[0029] <Structural unit c3 derived from a monomer having a sulfonic acid group and an ethylenically unsaturated group> Component C may further contain a structural unit c3 (hereinafter also simply referred to as "structural unit c3") derived from a monomer having a sulfonic acid group and an ethylenically unsaturated group from the viewpoint of improving solubility in a pharmaceutical form and improving the polishing rate and reducing scratches in one or more embodiments. From the same viewpoint, as the structural unit c3, structural units derived from at least one monomer selected from isoprene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid (AMPS), 2-methacrylamido-2-methylpropane sulfonic acid, styrene sulfonic acid, vinyl sulfonic acid, allyl sulfonic acid, isoamylene sulfonic acid, and salts thereof are preferably mentioned. Among these, a structural unit derived from 2-acrylamido-2-methylpropane sulfonic acid (AMPS) is more preferable. Examples of the salt include the same salts as those of the monomers having a carboxy group and an ethylenically unsaturated group described above. When Component C contains the structural unit c3, the content (mol%) of the structural unit c3 in all the structural units is preferably 0.1 mol% or more, more preferably 0.2 mol% or more, still more preferably 0.5 mol% or more, even more preferably 0.6 mol% or more from the viewpoint of improving solubility in a pharmaceutical form and improving the polishing rate and reducing scratches, and preferably 10 mol% or less, more preferably 8 mol% or less, still more preferably 5 mol% or less, even more preferably 2 mol% or less from the same viewpoint. From the same viewpoint, the content of the structural unit c3 in all the structural units of Component C is preferably 0.1 mol% or more and 10 mol% or less, more preferably 0.2 mol% or more and 8 mol% or less, still more preferably 0.5 mol% or more and 5 mol% or less, even more preferably 0.6 mol% or more and 2 mol% or less.

[0030] Component C may further contain other constitutional units other than constitutional unit c1, constitutional unit c2, and constitutional unit c3. From the viewpoint of improving the polishing rate and reducing scratches, the content of other constitutional units other than constitutional unit c1, constitutional unit c2, and constitutional unit c3 in all the constitutional units constituting component C is preferably 10 mol% or less, more preferably 5 mol% or less, still more preferably 3 mol% or less, even more preferably 1 mol% or less, and even more preferably substantially 0 mol%. In the present disclosure, substantially 0 mol% means tolerating the mixing of impurities corresponding to constitutional unit c1, constitutional unit c2, and constitutional unit c3, which may be contained in other constitutional units.

[0031] In the present disclosure, the content of each constitutional unit in all the constitutional units of component C can be regarded as the ratio of the amount of each monomer used to the total amount of monomers used in the polymerization.

[0032] The arrangement of constitutional unit c1, constitutional unit c2, constitutional unit c3, and other constitutional units other than these in component C may be any of random, block, or graft, but random is preferred from the viewpoint of improving the polishing rate and reducing scratches.

[0033] As component C, from the viewpoint of improving the polishing rate and reducing scratches, in one or more embodiments, at least one selected from a copolymer containing constitutional unit c1 and constitutional unit c2, and a copolymer containing constitutional unit c1, constitutional unit c2, and constitutional unit c3 is preferably mentioned. When component C is a copolymer containing constitutional unit c1 and constitutional unit c2, preferable examples of component C include (meth)acrylic acid / t-butylacrylamide copolymer, (meth)acrylic acid / N-methyl(meth)acrylamide copolymer, (meth)acrylic acid / N,N-dimethyl(meth)acrylamide copolymer, (meth)acrylic acid / N-isopropyl(meth)acrylamide copolymer, acrylic acid / N,N-diethyl(meth)acrylamide copolymer, acrylic acid / N-n-butyl(meth)acrylamide copolymer, acrylic acid / N-sec-butyl(meth)acrylamide copolymer. Among these, acrylic acid / t-butylacrylamide copolymer is more preferable. When component C is a copolymer containing constitutional unit c1, constitutional unit c2, and constitutional unit c3, preferable examples of component C include one selected from (meth)acrylic acid / t-butyl(meth)acrylamide / 2-(meth)acrylamido-2-methylpropanesulfonic acid copolymer and salts thereof. One selected from acrylic acid / t-butylacrylamide / 2-acrylamido-2-methylpropanesulfonic acid copolymer and salts thereof is more preferable, and acrylic acid / t-butylacrylamide / 2-acrylamido-2-methylpropanesulfonic acid copolymer is even more preferable.

[0034] The weight-average molecular weight of Component C is preferably 2,000 or more, more preferably 3,000 or more, still more preferably 4,000 or more, still more preferably 5,000 or more, still more preferably 7,000 or more, and preferably 500,000 or less, more preferably 300,000 or less, still more preferably 200,000 or less, still more preferably 100,000 or less, from the viewpoint of scratch reduction. More specifically, the weight-average molecular weight of Component C is preferably 2,000 or more and 500,000 or less, more preferably 3,000 or more and 300,000 or less, still more preferably 4,000 or more and 200,000 or less, still more preferably 5,000 or more and 100,000 or less, still more preferably 7,000 or more and 100,000 or less. The weight-average molecular weight of Component C can be measured by gel permeation chromatography (GPC), specifically, it can be measured by the method described in the examples.

[0035] The production method of Component C is not particularly limited, but an aqueous solution polymerization method is preferred. It can be produced by mixing and reacting each constitutional unit, a polymerization initiator, and a chain transfer agent in a polymerization solvent. Examples of the polymerization solvent for aqueous solution polymerization include water, alcohols such as ethanol, and ketones such as acetone. These may be used alone or in combination of two or more.

[0036] In the polymerization reaction, known polymerization initiators can be used, and radical polymerization initiators are particularly preferably used. Examples of radical polymerization initiators include persulfates such as sodium persulfate, potassium persulfate, and ammonium persulfate; hydroperoxides such as t-butyl hydroperoxide; water-soluble peroxides such as hydrogen peroxide; ketone peroxides such as methyl ethyl ketone peroxide and cyclohexanone peroxide; oil-soluble peroxides such as dialkyl peroxides such as di-t-butyl peroxide and t-butyl cumyl peroxide; and azo compounds such as azobisisobutyronitrile and 2,2-azobis(2-methylpropionamidine) dihydrochloride. From the viewpoint of the stability of the product, at least one selected from persulfates and azo compounds is preferable, and azo compounds such as azobisisobutyronitrile and 2,2'-azobis(2,4-dimethylvaleronitrile) are more preferable. These may be used alone or in combination of two or more.

[0037] In the production of Component C, a chain transfer agent may be appropriately added to the polymerization system in order to adjust the molecular weight. Examples of chain transfer agents include sodium phosphite, sodium hypophosphite, potassium hypophosphite, sodium sulfite, sodium bisulfite, mercaptoacetic acid, mercaptopropionic acid, thioglycolic acid, 2-propanethiol, 2-mercaptoethanol, thiophenol, and isopropanol. From the viewpoint of the stability of the product, mercaptopropionic acid and isopropanol are more preferable. These may be used alone or in combination of two or more.

[0038] The polymerization temperature is not particularly limited, but is preferably 60°C or higher from the viewpoint of improving reactivity, and preferably 100°C or lower from the viewpoint of suppressing coloring.

[0039] The polymerization time is not particularly limited, but is preferably 2 hours or longer from the viewpoint of improving reactivity, and preferably 20 hours or shorter from the viewpoint of suppressing coloring.

[0040] After the polymerization reaction, neutralization can be carried out with a basic compound as necessary. Examples of the basic compound used for neutralization include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, alkaline earth metal hydroxides such as calcium hydroxide and magnesium hydroxide, aqueous ammonia, and organic amines such as monoethanolamine, diethanolamine, and triethanolamine. From the viewpoint of avoiding contamination of the polished substrate and improving the dispersibility of the produced water-soluble polymer compound, aqueous ammonia is preferred. The pH value (25 °C) after neutralization is preferably 3 or more and 10 or less, more preferably 4 or more and 9 or less, from the viewpoint of improving the stability of the product. Specifically, it can be synthesized by the method described in the examples.

[0041] From the viewpoint of improving the polishing rate and reducing scratches, the content of Component C in the polishing liquid of the present disclosure is preferably 0.001% by mass or more, more preferably 0.005% by mass or more, still more preferably 0.01% by mass or more, and from the same viewpoint, preferably 1% by mass or less, more preferably 0.5% by mass or less, still more preferably 0.2% by mass or less. More specifically, the content of Component C in the polishing liquid of the present disclosure is preferably 0.001% by mass or more and 1% by mass or less, more preferably 0.05% by mass or more and 0.5% by mass or less, still more preferably 0.01% by mass or more and 0.2% by mass or less. When Component C is a combination of two or more types, the content of Component C refers to their total content.

[0042] [Molar ratio B / C of the nitrogen atom of Component B to the carboxy group of Component C] From the viewpoint of improving the polishing rate and reducing scratches, the polishing liquid of the present disclosure satisfies the following formula (II) when the number of moles of the nitrogen atom of Component B in the polishing liquid is B (mol) and the number of moles of the carboxy group of Component C in the polishing liquid is C (mol). B / C < 15 ··· (II) When Component B is present in an excessive amount relative to the carboxy group of Component C, free Component B that does not participate in the complex formation is generated. Since the free Component B adsorbs to the substrate surface and inhibits the polishing of the substrate, it is considered that the polishing rate improvement effect is specifically exhibited at the quantitative ratio that satisfies the above formula (II). The molar ratio B / C represented by the above formula (II) is preferably less than 15, more preferably 10 or less, still more preferably 8 or less, from the viewpoint of improving the polishing rate; and from the viewpoint of reducing scratches, it is preferably 0.1 or more, more preferably 0.5 or more, still more preferably 1 or more. And from the viewpoint of achieving both improvement in the polishing rate and reduction in scratches, the molar ratio B / C is preferably 0.1 or more and less than 15, more preferably 0.5 or more and 10 or less, still more preferably 1 or more and 8 or less. The molar ratio B / C represented by the above formula (II) can be calculated, for example, by the method described in the examples.

[0043] [Aqueous medium] Examples of the aqueous medium contained in the polishing liquid 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 solvents miscible with water (for example, alcohols such as ethanol). When the aqueous medium is a mixed solvent of water and a solvent, the proportion of water in the entire mixed medium may not be particularly limited as long as the effects of the present disclosure are not hindered. From the viewpoint of economy, for example, 95% by mass or more is preferable, 98% by mass or more is more preferable, and substantially 100% by mass is still more preferable. In the present disclosure, substantially 100% by mass means that the polishing liquid of the present disclosure is allowed to contain a very small amount of solvent components brought in as impurities from component A, component B, component C, and optional components (component D, component E, component F, other components) described later that are blended as necessary. The content of the aqueous medium in the polishing liquid of the present disclosure can be the remainder excluding component A, component B, component C, and optional components (component D, component E, component F, other components) described later that are blended as necessary.

[0044] In one or more embodiments, the polishing liquid of the present disclosure preferably further contains at least one selected from acids and oxidizing agents. Acids and oxidizing agents will be described below.

[0045] [Acid (Component D)] From the perspective of further improving the polishing rate and further reducing scratches, the polishing liquid of the present disclosure preferably further contains an acid (hereinafter also referred to as "Component D"). In the present disclosure, the acid includes an acid and / or its salt. Component D may be one kind or a combination of two or more kinds. Specific examples of Component D preferably include inorganic acids such as nitric acid, sulfuric acid, sulfurous acid, persulfuric acid, hydrochloric acid, perchloric acid, phosphoric acid, phosphonic acid, phosphinic acid, pyrophosphoric acid, polyphosphoric acid, and amidosulfuric acid; and organic acids such as organic phosphoric acid and organic phosphonic acid. Examples of salts of these acids include salts of the above acids and at least one selected from metals, ammonia, and alkylamines. Specific examples of the above metals include metals belonging to Groups 1 to 11 of the periodic table. In the present disclosure, from the perspective of further improving the polishing rate and further reducing scratches, Component D is preferably at least one selected from phosphoric acid, sulfuric acid, and 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP), more preferably at least one selected from sulfuric acid and phosphoric acid, and even more preferably phosphoric acid.

[0046] When the polishing liquid of the present disclosure contains Component D, the content of Component D in the polishing liquid of the present disclosure is preferably 0.001% by mass or more, more preferably 0.01% by mass or more, even more preferably 0.05% by mass or more, and still more preferably 0.1% by mass or more from the perspective of further improving the polishing rate and further reducing scratches. From the same perspective, it is preferably 5% by mass or less, more preferably 4% by mass or less, even more preferably 3% by mass or less, and still more preferably 2.5% by mass or less. More specifically, the content of Component D in the polishing liquid of the present disclosure is preferably 0.001% by mass or more and 5% by mass or less, more preferably 0.01% by mass or more and 4% by mass or less, even more preferably 0.05% by mass or more and 3% by mass or less, and still more preferably 0.1% by mass or more and 2.5% by mass or less. When Component D is a combination of two or more kinds, the content of Component D refers to their total content.

[0047] [Oxidizing agent (Component E)] From the perspective of further improving the polishing rate and further reducing scratches, the polishing liquid of the present disclosure preferably further contains an oxidizing agent (hereinafter also referred to as "Component E"). Component E may be one type or a combination of two or more types. Specific examples of Component E preferably include peroxides, permanganic acid or its salts, chromic acid or its salts, peroxy acids or their salts, oxyacids or their salts, nitric acid, and sulfuric acid. In the present disclosure, as Component E, at least one selected from hydrogen peroxide, iron(III) nitrate, peracetic acid, ammonium peroxydisulfate, iron(III) sulfate, and ammonium iron(III) sulfate is preferred. From the perspectives of improving the polishing rate, preventing metal ions from adhering to the surface of the substrate to be polished, and ease of availability, hydrogen peroxide is more preferred.

[0048] When the polishing liquid of the present disclosure contains Component E, the content of Component E in the polishing liquid of the present disclosure is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, still more preferably 0.1% by mass or more, from the perspective of further improving the polishing rate. And from the perspectives of further improving the polishing rate and further reducing scratches, it is preferably 4% by mass or less, more preferably 2% by mass or less, still more preferably 1.5% by mass or less. More specifically, the content of Component E in the polishing liquid of the present disclosure is preferably 0.01% by mass or more and 4% by mass or less, more preferably 0.05% by mass or more and 2% by mass or less, still more preferably 0.1% by mass or more and 1.5% by mass or less. When Component E is a combination of two or more types, the content of Component E refers to their total content.

[0049] [Anionic surfactant (Component F)] From the perspective of scratch reduction, the polishing liquid of the present disclosure may further contain an anionic surfactant (hereinafter also referred to as "Component F"). It is preferable that the anionic group of Component F is a sulfonic acid group and / or a sulfonate group. Also, it is preferably a polymer type having an aromatic group in the repeating unit of the main chain. That is, in the present disclosure, the anionic surfactant is more preferably a polymeric anionic surfactant in which the anionic group is a sulfonic acid group and / or a sulfonate group, and which has an aromatic group in the repeating unit of the main chain. In the present disclosure, in one or more embodiments, from the viewpoint of scratch reduction, the aromatic group is preferably a group containing an aromatic ring. Examples of the aromatic ring preferably include a benzene ring and a naphthalene ring. Component F may be of one type or a combination of two or more types.

[0050] Specific examples of component F preferably include at least one selected from naphthalene sulfonic acid compounds, lignin sulfonic acid compounds, aromatic amino sulfonic acid compounds, and salts thereof. As the naphthalene sulfonic acid compound, a naphthalene sulfonic acid formaldehyde condensate and a methylnaphthalene sulfonic acid formaldehyde condensate are preferable. As the lignin sulfonic acid compound, lignin sulfonic acid and modified lignin sulfonic acid are preferable. As the aromatic amino sulfonic acid compound, an aminoaryl sulfonic acid-phenol-formaldehyde condensate is preferable. Examples of these salts include alkali metals such as lithium, sodium, and potassium; alkaline earth metals such as calcium; ammonium; alkanolamines such as triethanolamine; and quaternary ammonium such as tetramethylammonium. These can be used alone or in combination of two or more. In the present disclosure, from the viewpoint of scratch reduction, component F is preferably at least one selected from naphthalene sulfonic acid formaldehyde condensates and salts thereof, and more preferably the sodium salt of a naphthalene sulfonic acid formaldehyde condensate.

[0051] When the polishing liquid of the present disclosure contains component F, the content of component E in the polishing liquid of the present disclosure is preferably 0.001% by mass or more, more preferably 0.005% by mass or more, still more preferably 0.01% by mass or more, from the viewpoint of further reducing scratches, and preferably 10% by mass or less, more preferably 5% by mass or less, still more preferably 1% by mass or less, from the viewpoint of suppressing the decrease in polishing rate. More specifically, the content of component F in the polishing liquid of the present disclosure is preferably 0.001% by mass or more and 10% by mass or less, more preferably 0.005% by mass or more and 5% by mass or less, still more preferably 0.01% by mass or more and 1% by mass or less. When component F is a combination of two or more kinds, the content of component F refers to their total content.

[0052] [Other components] The polishing liquid of the present disclosure may contain other components as necessary, as long as the effects of the present disclosure are not impaired. Examples of other components include amine compounds other than component B, water-soluble polymers other than component C, heterocyclic aromatic compounds, corrosion inhibitors, thickeners, dispersants, rust preventives, basic substances, surfactants other than component F, and the like.

[0053] [Alumina abrasive grains] From the perspective of reducing protrusion defects, the polishing liquid of the present disclosure preferably does not substantially contain alumina abrasive grains. In the present disclosure, "not substantially containing alumina abrasive grains" may include, in one or more embodiments, not containing alumina particles, not containing an amount of alumina particles that function as abrasive grains, or not containing an amount of alumina particles that affect the polishing result. Specifically, in one or more embodiments, from the perspective of reducing protrusion defects, the content of alumina abrasive grains in the polishing liquid of the present disclosure is preferably 5% by mass or less, more preferably 2% by mass or less, still more preferably 1% by mass or less, still more preferably 0.1% by mass or less, still more preferably 0.05% by mass or less, still more preferably 0.02% by mass or less, and still more preferably substantially 0% by mass (that is, not containing). Further, in one or more embodiments, the content of alumina particles in the polishing liquid of the present disclosure is preferably 2% by mass or less, more preferably 1% by mass or less, still more preferably 0.5% by mass or less, and even more preferably substantially 0% by mass (that is, not containing) based on the total amount of abrasive grains in the polishing liquid.

[0054] [pH] From the perspective of improving the polishing rate and reducing scratches, the pH of the polishing liquid of the present disclosure is preferably 0.5 or more, more preferably 0.7 or more, still more preferably 0.9 or more, even more preferably 1 or more. And from the same perspective, it is preferably 9 or less, more preferably 6 or less, still more preferably 4 or less, still more preferably 3 or less, even more preferably 2.5 or less, and even more preferably 2 or less. More specifically, the pH of the polishing liquid of the present disclosure is preferably 0.5 or more and 9 or less, more preferably 0.5 or more and 6 or less, still more preferably 0.7 or more and 4 or less, still more preferably 1 or more and 3 or less, still more preferably 1 or more and 2.5 or less, and still more preferably 1 or more and 2 or less. The pH can be adjusted using the aforementioned acids or known pH adjusters. The above pH is the pH of the polishing liquid at 25°C, which can be measured using a pH meter. Preferably, it is the value after 2 minutes of immersing the electrode of the pH meter in the polishing liquid.

[0055] [Manufacturing method of polishing liquid] The polishing liquid of the present disclosure can be produced, for example, by blending component A, component B, component C, an aqueous medium, and optional components (component D, component E, component F, and other components) as needed by a known method. Therefore, in one aspect, the present disclosure relates to a method for producing a polishing liquid, which includes a step of blending at least component A and the aqueous medium. In the present disclosure, "blending" includes mixing component A, component B, component C, the aqueous medium, and optional components (component D, component E, component F, and other components) as needed simultaneously or in any order. The blending can be performed, for example, using a mixer such as a homomixer, a homogenizer, an ultrasonic disperser, and a wet ball mill. The preferred blending amounts of the respective components in the production methods of the silica slurry and the polishing liquid can be the same as the preferred contents of the respective components in the polishing liquid according to the present disclosure described above.

[0056] In the present disclosure, "the content of each component in the polishing liquid" refers to the content of each of the above components at the time of use, that is, when starting to use the polishing liquid for polishing. In one or more embodiments, the content of each component in the polishing liquid in the present disclosure can be regarded as the blending amount of each component.

[0057] The polishing liquid of the present disclosure may be stored and supplied in a concentrated state as long as its storage stability is not impaired. In this case, it is preferable in that the manufacturing and transportation costs can be further reduced. The concentrate of the polishing liquid of the present disclosure may be appropriately diluted with the aforementioned water as needed during use. The dilution ratio is not particularly limited as long as the content (at the time of use) of each component described above can be ensured after dilution, and can be, for example, 10 to 100 times.

[0058] [Polishing Liquid Kit] In one aspect, the present disclosure is a polishing liquid kit (hereinafter, also referred to as "the polishing liquid kit of the present disclosure") for producing the polishing liquid of the present disclosure. As a polishing liquid kit of the present disclosure, in one or more embodiments, for example, it includes a silica dispersion (slurry) containing component A and an aqueous medium, and an aqueous additive solution containing component B and component C in a state where they are not mixed with each other, and these are mixed during use and diluted with an aqueous medium as necessary to obtain the polishing liquid of the present disclosure (two-component type polishing liquid). The aqueous medium contained in the silica dispersion of the polishing liquid kit of the present disclosure may be an amount corresponding to the same amount as the polishing liquid of the present disclosure, or a part thereof. The above-mentioned optional components (component D, component E, component F, other components) may be contained in the silica dispersion and the aqueous additive solution as necessary. According to the present disclosure, in one or more embodiments, a polishing liquid capable of achieving both an improvement in polishing rate and a reduction in scratches on the surface of the substrate after polishing can be obtained from the polishing liquid kit of the present disclosure.

[0059] Generally, a magnetic disk is manufactured through a process in which a substrate to be polished that has undergone a grinding process is polished through a rough polishing process and a finish polishing process, and then through a magnetic layer forming process. The polishing liquid of the present disclosure is preferably used for polishing a magnetic disk substrate in one or more embodiments, and more preferably used for finish polishing of a magnetic disk substrate. In the present disclosure, finish polishing refers to the polishing in the last polishing process when there are multiple polishing processes for a magnetic disk substrate.

[0060] [Method for manufacturing a magnetic disk substrate] In one aspect, the present disclosure relates to a method for manufacturing a magnetic disk substrate (hereinafter, also referred to as "the substrate manufacturing method of the present disclosure") including a polishing step (hereinafter, also referred to as "the polishing step") of polishing a substrate to be polished using the polishing liquid of the present disclosure. Examples of the substrate to be polished in the substrate manufacturing method of the present disclosure include the above-mentioned substrate to be polished. The polishing step in the substrate manufacturing method of the present disclosure is, for example, a finish polishing step.

[0061] [Substrate to be polished] In the method for manufacturing a substrate according to the present disclosure, in one or more embodiments, the substrate to be polished is preferably a substrate used in the manufacture of a magnetic disk substrate. In one or more embodiments, after the step of polishing the surface of the substrate to be polished using the polishing liquid of the present disclosure, a magnetic disk substrate can be manufactured by performing a step of forming a magnetic layer on the surface of the substrate by sputtering or the like. From the viewpoint of exerting the effects of the present disclosure, the substrate to be polished is preferably a substrate having a thickness of 0.6 mm or less used in the manufacture of a magnetic disk substrate.

[0062] Examples of the material of the substrate to be polished preferably used in the method for manufacturing a substrate according to the present disclosure include metals or semimetals such as silicon, aluminum, nickel, tungsten, copper, tantalum, titanium, etc., or alloys thereof, glassy substances such as glass, glassy carbon, amorphous carbon, etc., ceramic materials such as alumina, silicon dioxide, silicon nitride, tantalum nitride, titanium carbide, etc., and resins such as polyimide resin. Among them, it is suitable for a substrate to be polished containing metals such as aluminum, nickel, tungsten, copper, etc. and alloys mainly composed of these metals. As the substrate to be polished, for example, an aluminum alloy substrate plated with Ni-P, a glass substrate such as crystallized glass, tempered glass, aluminosilicate glass, aluminoborosilicate glass, etc. is more suitable, and an aluminum alloy substrate plated with Ni-P is even more suitable. In the present disclosure, the "aluminum alloy substrate plated with Ni-P" refers to a substrate obtained by subjecting the surface of an aluminum alloy base material to grinding and then performing electroless Ni-P plating treatment.

[0063] Examples of the shape of the substrate to be polished in the method for manufacturing a substrate according to the present disclosure include shapes having a flat surface such as a disk shape, a plate shape, a slab shape, a prism shape, etc., and shapes having a curved surface such as a lens. Preferably, it is a disk-shaped substrate to be polished. In the case of a disk-shaped substrate to be polished, its outer diameter is, for example, 2 to 100 mm, and its thickness is, for example, 0.4 to 2 mm. In the substrate manufacturing method of the present disclosure, from the viewpoint of exerting the effects of the present disclosure, the thickness of the substrate to be polished is preferably 1.2 mm or less, more preferably 1.0 mm or less, still more preferably 0.8 mm or less, and even more preferably 0.6 mm or less.

[0064] In the substrate manufacturing method of the present disclosure, in one or more embodiments, the polishing step is a step of supplying the polishing liquid of the present disclosure to the polishing target surface of the substrate to be polished, bringing a polishing pad into contact with the polishing target surface, and moving at least one of the polishing pad and the substrate to be polished to perform polishing. In the substrate manufacturing method of the present disclosure, in one or more embodiments, the polishing step is a step of sandwiching the substrate to be polished with a surface plate to which a polishing pad such as a non-woven organic polymer polishing cloth is attached, and moving the surface plate or the substrate to be polished while supplying the polishing liquid of the present disclosure to a polishing machine to polish the substrate to be polished.

[0065] When the polishing step of the substrate to be polished in the substrate manufacturing method of the present disclosure is performed in multiple stages, the polishing step using the polishing liquid of the present disclosure is preferably performed after the second stage, and more preferably performed in the final polishing step or the finishing polishing step. At that time, in order to avoid mixing of the abrasive and polishing liquid in the previous step, separate polishing machines may be used, and when separate polishing machines are used, it is preferable to wash the substrate to be polished for each polishing step. Furthermore, the polishing liquid of the present disclosure can also be used in the circulating polishing for reusing the used polishing liquid. The polishing machine is not particularly limited, and a known polishing machine for substrate polishing can be used.

[0066] There is no particular limitation on the polishing pad used in the substrate manufacturing method of the present disclosure. For example, polishing pads such as suede type, non-woven type, polyurethane independent foam type, or a two-layer type in which these are laminated can be used. From the viewpoint of polishing speed, a suede type polishing pad is preferable.

[0067] In the method for manufacturing a substrate according to the present disclosure, from the viewpoint of ensuring the polishing rate, the polishing load in the polishing step is preferably 5.9 kPa or more, more preferably 6.9 kPa or more, still more preferably 7.5 kPa or more, and from the viewpoint of reducing scratches, it is preferably 20 kPa or less, more preferably 18 kPa or less, still more preferably 16 kPa or less. In the present disclosure, "polishing load" refers to the pressure of the surface plate applied to the polished surface of the substrate to be polished during polishing. The adjustment of the polishing load can be performed by applying air pressure or a weight to at least one of the surface plate and the substrate to be polished.

[0068] In the polishing step, the polishing amount per 1 cm of the substrate to be polished 2 is preferably 0.05 mg or more, more preferably 0.1 mg or more, still more preferably 0.2 mg or more from the viewpoints of improving the polishing rate and reducing scratches, and from the same viewpoints, it is preferably 2.5 mg or less, more preferably 2 mg or less, still more preferably 1.6 mg or less. More specifically, the polishing amount per 1 cm of the substrate to be polished 2 is preferably 0.05 mg or more and 2.5 mg or less, more preferably 0.1 mg or more and 2 mg or less, still more preferably 0.2 mg or more and 1.6 mg or less.

[0069] From the viewpoint of reducing scratches, the supply rate of the polishing liquid of the present disclosure in the polishing step is preferably 0.05 mL / min or more and 15 mL / min or less per 1 cm of the substrate to be polished, more preferably 0.06 mL / min or more and 10 mL / min or less, still more preferably 0.07 mL / min or more and 1 mL / min or less, and still more preferably 0.07 mL / min or more and 0.5 mL / min or less. 2 As a method for supplying the polishing liquid of the present disclosure to the polishing machine in the polishing step, for example, a method of continuously supplying using a pump or the like can be mentioned. When supplying the polishing liquid to the polishing machine, in addition to the method of supplying it as a single liquid containing all components, considering the storage stability of the polishing liquid, etc., it can also be divided into a plurality of component liquids for blending and supplied with two or more liquids. In the latter case, for example, in the supply pipe or on the substrate to be polished, the plurality of component liquids for blending are mixed to form the polishing liquid of the present disclosure.

[0070] As a method for supplying the polishing liquid of the present disclosure to the polishing machine in the polishing step, for example, a method of continuously supplying using a pump or the like can be mentioned. When supplying the polishing liquid to the polishing machine, in addition to the method of supplying it as a single liquid containing all components, considering the storage stability of the polishing liquid, etc., it can also be divided into a plurality of component liquids for blending and supplied with two or more liquids. In the latter case, for example, in the supply pipe or on the substrate to be polished, the plurality of component liquids for blending are mixed to form the polishing liquid of the present disclosure.

[0071] According to the substrate manufacturing method of the present disclosure, by using the polishing liquid of the present disclosure, it is possible to improve the polishing rate while reducing scratches on the surface of the substrate after polishing. Therefore, a substrate with improved substrate quality (for example, a magnetic disk substrate) can be efficiently manufactured.

[0072] [Polishing Method] In one aspect, the present disclosure relates to a method for polishing a substrate to be polished using the polishing liquid of the present disclosure, wherein the substrate to be polished is a substrate used in the manufacture of a magnetic disk substrate (hereinafter, also referred to as "the polishing method of the present disclosure"). Examples of the substrate to be polished in the polishing method of the present disclosure include the substrate to be polished described above. The polishing method of the present disclosure can be used, for example, in a finish polishing step. According to the polishing method of the present disclosure, by using the polishing liquid of the present disclosure, it is possible to improve the polishing rate while reducing scratches on the surface of the substrate after polishing. Therefore, the productivity of a substrate with improved substrate quality (for example, a magnetic disk substrate) can be improved. The polishing method and conditions in the polishing method of the present disclosure can be the same as those of the substrate manufacturing method of the present disclosure described above.

Examples

[0073] Hereinafter, the present disclosure will be described in more detail by way of examples, but these are illustrative and the present disclosure is not limited to these examples.

[0074] 1. Preparation of polishing liquid (Examples 1 to 16, Comparative Examples 1 to 3) Component A (silica particles shown in Table 2), Component B (at least one compound B1 to B4 selected from diamines and triamines shown in Tables 1 and 2) or non-Component B (B5), Component C (water-soluble polymers C1 to C6 shown in Table 2), Component D (acids shown in Table 2), Component E (hydrogen peroxide), Component F (anionic polymer surfactant shown in Table 2), and water were blended and stirred to prepare the polishing liquids of Examples 1 to 16 and Comparative Examples 1 to 3 shown in Table 2. The content (mass%, effective amount) of each component in each polishing liquid is as shown in Table 2. The content of water is the remainder excluding Component A, Component B or non-Component B, Component C, Component D, Component E, and Component F. The pH of the polishing liquids of Examples 1 to 16 and Comparative Examples 1 to 3 was 1.5.

[0075] The following were used for Component A, Component B or non-Component B, Component C, Component D, Component E, and Component F used in the preparation of the polishing liquid. (Component A) Colloidal silica [DLS measurement (volume conversion) average secondary particle diameter D50: 20 nm] (Component B or non-Component B) Component B1: 1-(2-Hydroxyethyl)-1,4-diazacyclohexane [HDC, manufactured by Tokyo Chemical Industry Co., Ltd.: reagent] Component B2: 1-Methyl-1,4-diazacyclohexane [MDC, manufactured by Tokyo Chemical Industry Co., Ltd.: reagent] Component B3: N-(2-Hydroxyethyl)ethylenediamine [HEA, manufactured by Tokyo Chemical Industry Co., Ltd.: reagent] Component B4: 1-(2-Aminoethyl)-1,4-diazacyclohexane [ADC, manufactured by Tokyo Chemical Industry Co., Ltd.: reagent] Non-Component B5: Triethylenetetramine [TETA, manufactured by Tokyo Chemical Industry Co., Ltd.: reagent] (Component C) The abbreviation of acrylic acid was AA, the abbreviation of N-tert-butylacrylamide was tBuAAm, and the abbreviation of 2-acrylamido-2-methylpropanesulfonic acid was AMPS. Component C1: Copolymer of AA / tBuAAm = 86 / 14 (mol%) [weight average molecular weight: 8,000] (synthetic product of Kao Corporation) Component C2: Copolymer of AA / tBuAAm = 86 / 14 (mol%) [Weight average molecular weight: 60,000] (manufactured by Kao Corporation) Component C3: Copolymer of AA / tBuAAm = 86 / 14 (mol%) [Weight average molecular weight: 150,000] (manufactured by Kao Corporation) Component C5: Copolymer of AA / tBuAAm / AMPS = 86 / 12 / 2 (mol%) [Weight average molecular weight: 9,000] (manufactured by Kao Corporation) Component C6: Copolymer of AA / tBuAAm / AMPS = 87.5 / 12 / 0.5 (mol%) [Weight average molecular weight: 50,000] (manufactured by Kao Corporation) The manufacturing method of Component C1 is shown below. Prepare a 300 mL five-necked glass flask equipped with a stirring blade, thermometer, Dimroth condenser, nitrogen gas blowing tube, bubbler tube, and two dropping funnels (dropping funnel 1 and 2). Add mercaptopropionic acid (0.21 g, manufactured by Tokyo Chemical Industry Co., Ltd.), acrylic acid (20.00 g, manufactured by Tokyo Chemical Industry Co., Ltd.), N-tert-butylacrylamide (5.75 g, manufactured by Tokyo Chemical Industry Co., Ltd.), and ethanol (17.16 g, 99.5% ethanol manufactured by Fujifilm Wako Pure Chemical Corporation) to dropping funnel 1, and add 2,2'-azobis(2,4-dimethylvaleronitrile) (0.08 g, manufactured by Fujifilm Wako Pure Chemical Corporation) and ethanol (15.95 g) to dropping funnel 2. Put ethanol (26.96 g) into the five-necked glass flask, flow nitrogen gas, flow tap water through the Dimroth condenser, and while rotating with the stirring blade, heat up to 80 °C, and drop the mixtures in dropping funnels 1 and 2 at a uniform speed over 60 minutes. After dropping, stir at 80 °C for 3 hours, and then cool to 25 °C. Add 500 g of ethanol, drop 29% aqueous ammonia (manufactured by Kanto Chemical Co., Inc.) while stirring vigorously until the pH reaches 7.0, filter the precipitated white solid by vacuum filtration, and obtain C1 by vacuum drying. In the above example, by adjusting the amount of initiator, the amount of chain transfer agent, reaction temperature, etc., polymers (Components C2 to C6) having a desired range of molecular weight can be obtained. For example, by reducing the amount of initiator, reducing the amount of chain transfer agent, and lowering the reaction temperature, polymers with a larger molecular weight can be obtained. (Component D) Phosphoric acid [manufactured by FUJIFILM Wako Pure Chemical Corporation, special grade reagent, concentration 85% by mass] Sulfuric acid [manufactured by FUJIFILM Wako Pure Chemical Corporation, special grade reagent, concentration 62.5%] HEDP (1-Hydroxyethane-1,1-diphosphonic acid) [manufactured by Tokyo Chemical Industry Co., Ltd., reagent, concentration in aqueous solution 60%] (Component E) Hydrogen peroxide [manufactured by ADEKA Corporation, concentration 35% by mass] (Anionic surfactant) Sodium naphthalenesulfonate formaldehyde condensate [polymeric anionic surfactant: trade name: Demol T, manufactured by Kao Corporation]

[0076]

Table 1

[0077] 2. Measurement method of each parameter [Measurement method of particle size D50 (average secondary particle size) of silica particles by DLS measurement] Component A (colloidal silica) used in the preparation of the polishing liquid was added to ion-exchanged water so as to have a concentration of 0.25% by mass. After that, the obtained aqueous dispersion was put into a Disposable Sizing Cuvette (polystyrene cell) up to a height of 10 mm from the bottom, and measured under the following conditions by the dynamic light scattering method using the following apparatus. The particle size (D50) at which the cumulative volume ratio from the small-diameter side of the particle size distribution becomes 50% was determined and used as the average secondary particle size of the colloidal silica. The results are shown in Table 2. <Measurement conditions> Measuring instrument: Zetasizer Nano ZS [manufactured by Malvern Panalytical] Laser: He-Ne, 3.0 mW, 633 nm Scattered light detection angle: 173° Integration times: 20 times

[0078] [Weight average molecular weight of water-soluble polymer (Component C)] The weight average molecular weight of Component C was measured under the following conditions by gel permeation chromatography (GPC) method. The results are shown in Table 2. <GPC Conditions> Column: TSKgel G4000PWXL + TSKgel G2500PWXL (manufactured by Tosoh Corporation) Guard Column: TSKguardcolumn PWXL (manufactured by Tosoh Corporation) Eluent: 0.2M Phosphate Buffer / CH3CN = 9 / 1 (volume ratio) Temperature: 40 °C Flow Rate: 1.0 mL / min Sample Size: 5 mg / mL Detector: RI Standard Substance: Sodium Polyacrylate (Molecular Weight (Mp): 115,000, 28,000, 4,100, 1,250 (manufactured by Sowa Kagaku Co., Ltd. and American Polymer Standards Corp.))

[0079] [Molar Ratio B / C of the Nitrogen Atom of Component B and the Carboxy Group of Component C] When the structural unit c1 constituting Component C consists of a monovalent acid such as acrylic acid, the molar ratio B / C of the number of moles of nitrogen atoms of Component B (B) and the number of moles of carboxy groups of Component C (C) in the polishing liquid was calculated by the following formula. [Number] Here, the unit molecular weight of Component C is the value obtained by weight-averaging the molecular weights of each structural unit constituting Component C according to the molar ratio of each structural unit. For example, for Component C1, it is calculated as follows. Composition of C1: AA / tBuAAm = 86 / 14 (mol%) Molecular Weight of AA: 72.06 Molecular Weight of tBuAAm: 127.19 Unit Molecular Weight of C1: 72.06 × 0.86 + 127.19 × 0.14 = 79.78

[0080] [Measurement of pH] The pH of the polishing liquid was measured at 25 °C using a pH meter (manufactured by Toa DKK Corporation), and the value after 2 minutes of immersing the electrode in the polishing liquid was adopted.

[0081] 3. Polishing of Substrate Using the prepared polishing liquids of Examples 1 to 16 and Comparative Examples 1 to 3, the following substrates to be polished were polished under the following polishing conditions. Subsequently, the polishing rate and the number of scratches were measured. The results are shown in Table 2.

[0082] [Substrate to be polished] As the substrate to be polished, an aluminum alloy substrate S plated with Ni-P was used. S: Thickness 0.6 mm, outer diameter 97 mm, inner diameter 25 mm The substrate to be polished was pre-polished with a polishing liquid containing alumina abrasive so that the center line average roughness Ra measured by AFM (Digital Instrument NanoScope IIIa Multi Mode AFM) became 1 nm.

[0083] [Polishing conditions] Polishing tester: "Double-sided 9B Polishing Machine" manufactured by Speedfam Polishing pad: Suede type manufactured by FILWEL (foam layer: polyurethane elastomer, thickness 0.9 mm, average open pore diameter 10 μm) Polishing liquid supply rate: 100 mL / min (supply rate per 1 cm of the substrate to be polished: 0.076 mL / min) 2 Upper platen rotation speed: -16 rpm Lower platen rotation speed: 16 rpm Polishing load: 13.0 kPa Polishing time: 6 minutes Number of substrates: 10

[0084] 4. Evaluation method [Evaluation of polishing rate] The mass of each substrate before and after polishing was measured using an analytical balance (Sartorius, "BP-210S"), and the mass reduction amount was obtained from the mass change of each substrate. The value obtained by dividing the average mass reduction amount of all 10 substrates by the polishing time was defined as the polishing rate and calculated by the following formula. The measurement results of the polishing rate are shown in Table 2 as relative values with Comparative Example 1 set to 100. Mass reduction amount (mg) = {Mass before polishing (mg) - Mass after polishing (mg)} Polishing rate (mg / min) = Mass reduction amount (mg) / Polishing time (min)

[0085] [Evaluation of Scratch] Measuring instrument: "Candela OSA7100" manufactured by KLA - Tencor Corporation Evaluation: Among the substrates put into the polishing tester, 4 pieces were randomly selected, and each substrate was irradiated with a laser at 10,000 rpm to measure the number of scratches. The sum of the number of scratches (pieces) on both sides of each of the 4 substrates was divided by 8 to calculate the number of scratches per substrate surface. The evaluation results of the number of scratches are shown in Table 2 as relative values with Comparative Example 1 taken as 100.

[0086] 5. Results The results of each evaluation are shown in Table 2.

[0087]

Table 2

[0088] As shown in Table 2 above, the polishing liquids of Examples 1 to 16 effectively improved the polishing rate without deteriorating the scratches as compared with the polishing liquids of Comparative Examples 1 to 3.

Industrial Applicability

[0089] According to the present disclosure, in one aspect, since it is possible to achieve both an improvement in the polishing rate and a reduction in scratches on the surface of the substrate after polishing, the productivity of substrates with improved substrate quality can be improved. The present disclosure can be suitably used for the manufacture of magnetic disk substrates.

Claims

1. A polishing liquid containing silica particles (Component A), at least one compound selected from diamines and triamines (Component B), a structural unit c1 derived from a monomer having a carboxy group and an ethylenically unsaturated group, and a structural unit c2 derived from a monomer having an N-alkyl(meth)acrylamide structure, and an aqueous medium.

2. The polishing liquid according to Claim 1, wherein Component B is a compound represented by the following structural formula (I). R 1 -N(R 2 )-(CH 2 ) n -N(R 3 )-R 4 -X...(I) In the structural formula (I), R 1 , R 2 , R 3 and R 4 are each independently a hydrogen atom or a hydrocarbon group, and X is selected from any one of a hydrogen atom, a hydroxyl group, and an amino group. R 2 and R 3 may be bonded to each other to form a cyclic structure. n is an integer of 1 or more and 15 or less.

3. The polishing liquid according to Claim 1 or 2, wherein the structural unit c2 derived from the monomer having an N-alkyl(meth)acrylamide structure is a structural unit derived from N-t-butylacrylamide.

4. The polishing liquid according to any one of Claims 1 or 2, wherein Component C is an acrylic acid / N-t-butylacrylamide copolymer.

5. The polishing liquid according to any one of Claims 1 to 3, wherein Component C further contains a structural unit c3 derived from a monomer having a sulfonic acid group and an ethylenically unsaturated group.

6. The polishing liquid according to Claim 5, wherein the structural unit c3 derived from the monomer having a sulfonic acid group and an ethylenically unsaturated group is a structural unit derived from at least one monomer selected from isoprene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, 2-methacrylamido-2-methylpropane sulfonic acid, styrene sulfonic acid, vinyl sulfonic acid, allyl sulfonic acid, isoamylene sulfonic acid, and salts thereof.

7. The polishing liquid according to any one of Claims 1 to 3, wherein Component C is an acrylic acid / N-t-butylacrylamide / 2-acrylamido-2-methylpropane sulfonic acid copolymer.

8. The polishing liquid according to any one of Claims 1 to 7, wherein the weight average molecular weight of Component C is 2,000 or more and 500,000 or less.

9. The polishing liquid according to any one of Claims 1 to 8, which satisfies the following formula (II) when the number of moles of nitrogen atoms of Component B in the polishing liquid is B (mol) and the number of moles of carboxy groups of Component C in the polishing liquid is C (mol). B / C < 15... (II)

10. Further containing an anionic surfactant, The polishing liquid according to any one of Claims 1 to 9, wherein the anionic surfactant is a polymeric anionic surfactant in which the anionic group is a sulfonic acid group and / or a sulfonate group and which has an aromatic group in the repeating unit of the main chain.

11. The polishing liquid according to claim 10, wherein the polymeric anionic surfactant is at least one selected from naphthalene sulfonic acid compounds, lignin sulfonic acid compounds, aromatic amino sulfonic acid compounds, and salts thereof.

12. The polishing liquid according to claim 10, wherein the polymeric anionic surfactant is at least one selected from naphthalene sulfonic acid formaldehyde condensates and salts thereof.

13. The polishing liquid according to any one of claims 1 to 12, further containing at least one selected from acids and oxidizing agents.

14. The polishing liquid according to any one of claims 1 to 13, which is used for the finish polishing of a magnetic disk substrate.

15. A method for manufacturing a magnetic disk substrate, including a polishing step of polishing a substrate to be polished using the polishing liquid according to any one of claims 1 to 14.

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