JP7636875B2 - Aqueous composition, polishing slurry, and kit for preparing polishing slurry - Google Patents

Description

The present invention relates to an aqueous composition, an abrasive slurry containing the aqueous composition, and an abrasive slurry preparation kit containing the aqueous composition as a component.

Polishing processing is performed on the surfaces of materials such as metals, semi-metals, non-metals, and oxides thereof using polishing slurries containing abrasive grains. The polishing slurry can be distributed and stored in the form of an abrasive grain dispersion liquid in which abrasive grains are dispersed in water, and an aqueous composition (hereinafter also referred to as the secondary composition) containing water and at least some of the components other than the abrasive grains (hereinafter also referred to as the secondary components). The secondary composition can be used to polish an object to be polished, for example, by mixing the abrasive grain dispersion liquid and water for dilution to prepare a polishing slurry, and supplying the polishing slurry to the object to be polished.

In order to prevent spoilage during distribution and storage, a preservative may be added to the above-mentioned abrasive dispersion. Patent documents 1 to 3 are cited as technical documents related to this type of technology. Patent documents 2 and 3 disclose silica dispersions with a pH of 7 or more that contain an organic preservative with a specific structure ([0030] in Patent Document 2, [0030] in Patent Document 3). The above-mentioned silica dispersions do not contain acid. On the other hand, Patent Documents 4 and 5 propose compounds having an isothiazolone group represented by a specific formula, disulfide compounds, and imidazoline compounds as compounds that can solve the problem of coloration of containers ([0004] and [0013] in Patent Document 4, and [0004] and [0020] in Patent Document 5), which is a problem specific to polishing liquid compositions containing alumina and a preservative.

JP 2019-064852 A JP 2016-124743 A JP 2016-124977 A JP 2006-206698 A JP 2006-176733 A

Aqueous compositions for preparing acidic polishing slurries by mixing with abrasive dispersions contain a relatively high concentration of acid, and so have been recognized as being difficult for bacteria to grow in. However, the present inventors have noticed that certain types of bacteria can survive and grow even in such aqueous compositions. The growth of bacteria in an aqueous composition containing acid can cause problems such as the growth of bacteria clogging the filtration filter and the growth of bacteria adhering to the polishing substrate when the composition is used as a polishing slurry.

The present invention therefore aims to provide an aqueous composition containing an acid, which inhibits bacterial growth and is less likely to become discolored during storage. Another related object is to provide an abrasive slurry and an abrasive slurry preparation kit that contain the aqueous composition.

According to this specification, an aqueous composition is provided for use in polishing an object to be polished. The aqueous composition includes an acid, a preservative, and water. The aqueous composition includes, as the preservative, a compound Q that does not include either a sulfur atom (S) or a nitrogen atom (N). By using such a compound Q as a preservative, it is possible to inhibit the growth of bacteria and to inhibit discoloration due to storage. Furthermore, the compound Q is less likely to cause deterioration in the polishing performance (e.g., polishing rate, silica residue) of a polishing slurry containing the aqueous composition, even when the aqueous composition is used after long-term storage.

In some aspects of the technology disclosed herein (including aqueous compositions, polishing slurries prepared using the aqueous compositions, and polishing slurry preparation kits containing the aqueous compositions, the same applies below), a compound containing a structure in which a hydroxyl group and an etheric oxygen are bonded to the same carbon can be preferably used as compound Q. By having such a structure, compound Q containing neither S nor N can suitably exhibit the effect of inhibiting bacterial growth in an aqueous composition containing an acid. The structure in which a hydroxyl group and an etheric oxygen are bonded to the same carbon can be, for example, a -O-CH ₂ OH group. The -O-CH ₂ OH group may constitute a -CH ₂ -O-CH ₂ OH group.

Compound Q can be used alone or in combination of two or more. For example, an aliphatic chain compound Q1 having two or more hydroxyl groups can be used in combination with compound Q2 having a substituent on an aromatic ring that includes a structure in which the hydroxyl group and an ether oxygen are bonded to the same carbon. Such a combination can provide a higher preservative effect.

In some embodiments, the pH of the aqueous composition is in the range of 0.5 to 4.0. In an aqueous composition having a pH in this range, the preservative effect of compound Q can be preferably exerted.

A suitable example of an object to be polished in the technology disclosed herein is a magnetic disk substrate. Among these, a glass substrate or a magnetic disk substrate having a nickel-phosphorus plating layer on the surface is preferred. Hereinafter, a magnetic disk substrate having a nickel-phosphorus plating layer on the surface is also referred to as a "Ni-P substrate" for short. The aqueous composition disclosed herein can be used as an abrasive slurry supplied to a substrate to be polished or as a raw material for preparing the abrasive slurry in the polishing carried out in the manufacturing process of a magnetic disk substrate, and can be useful for realizing a high-quality substrate surface. For example, even if the aqueous composition is used after being stored for a long period of time, the deterioration of the polishing performance (e.g., polishing rate, silica residue) of the abrasive slurry containing the aqueous composition can be suppressed.

In some embodiments, the aqueous composition further contains abrasive grains in addition to the acid, preservative, and water. The aqueous composition containing abrasive grains can be used as a polishing slurry to be applied to the surface of the object to be polished, either as is or by adding additives (e.g., volatile components such as hydrogen peroxide), water for dilution, a pH adjuster, additional abrasive grains, etc. as necessary.

The aqueous composition disclosed herein can be preferably used to prepare a polishing slurry to be supplied to the object to be polished by mixing with abrasive grains. The abrasive grains mixed with the aqueous composition can be in the form of an abrasive grain dispersion. The aqueous composition is preservative with compound Q, so that bacterial growth is inhibited and coloring due to storage is unlikely to occur. In addition, even when used after long-term storage, deterioration of the polishing performance (e.g., polishing rate, silica residue) of the polishing slurry containing the aqueous composition can be inhibited.

According to this specification, a polishing slurry is provided that is supplied to an object to be polished and used to polish the object, the polishing slurry containing any of the aqueous compositions disclosed herein. When polishing is performed using such a polishing slurry, bacterial growth is suppressed, and furthermore, coloring due to storage is unlikely to occur. Furthermore, even when used after long-term storage, deterioration of polishing performance (e.g., polishing rate, silica residue) can be suppressed.

According to this specification, for example, it is possible to provide a kit for preparing an abrasive slurry, which includes an abrasive dispersion liquid containing abrasive grains and water, and a sub-composition consisting of any of the aqueous compositions disclosed herein. In the kit, the abrasive dispersion liquid and the sub-composition are stored separately from each other. In the abrasive slurry preparation kit configured in this manner, the sub-composition has good antiseptic properties and is less likely to become discolored during distribution and storage of the kit. Furthermore, even if the kit is stored for a long period of time and then used to prepare an abrasive slurry, deterioration of the polishing performance can be prevented.

The following describes preferred embodiments of the present invention. Note that matters other than those specifically mentioned in this specification that are necessary for implementing the present invention can be understood as design matters for a person skilled in the art based on the prior art in the relevant field. The present invention can be implemented based on the contents disclosed in this specification and common technical knowledge in the relevant field.

<Aqueous Composition>
The aqueous composition disclosed herein is a composition used for polishing an object to be polished, and contains at least an acid, water, and a predetermined preservative. The aqueous composition may be in a form containing abrasive grains, or may be in a form not containing abrasive grains. The aqueous composition not containing abrasive grains can typically be used in a form in which the aqueous composition is mixed with abrasive grains to prepare a polishing slurry, and the polishing slurry is supplied to the object to be polished. The abrasive grains mixed into the aqueous composition may be in the form of an abrasive grain dispersion in which the abrasive grains are dispersed in water. The aqueous composition containing abrasive grains may be directly supplied to the object to be polished and used as a polishing slurry, or may be used in a form in which a polishing slurry is prepared by adding water for dilution, additives (e.g., volatile components such as hydrogen peroxide), pH adjusters, additional abrasive grains, etc. as necessary, and the polishing slurry is supplied to the object to be polished. That is, the aqueous composition disclosed herein may be in the form of a polishing slurry that is directly supplied to the object to be polished, may be in the form of a polishing slurry concentrate that is diluted and supplied to the object to be polished, or may be in the form of a sub-composition that is mixed with abrasive grains and other components that may be used as necessary and water for dilution to prepare a polishing slurry. The effect of adopting the configuration of the present invention can be appropriately achieved in one or more of these aqueous compositions. The aqueous composition in the form of the slurry concentrate or the sub-composition can be, for example, concentrated to about 1.5 to 50 times as compared with the polishing slurry when supplied to the object to be polished (POU; Point of Use). In some embodiments, the concentration ratio is appropriately about 2 to 20 times, and may be about 5 to 15 times, taking into consideration convenience in transportation, storage, etc., and storage stability of the aqueous composition. The aqueous composition disclosed herein can be used to prepare a polishing slurry by diluting according to the concentration ratio.

(acid)
The acid used in the aqueous composition disclosed herein may be either an inorganic acid or an organic acid. Examples of the organic acid include organic carboxylic acids, organic sulfonic acids, and amino acids each having about 1 to 18 carbon atoms, typically about 1 to 10 carbon atoms. The acids may be used alone or in combination of two or more.

Specific examples of inorganic acids include phosphoric acid (orthophosphoric acid), nitric acid, sulfuric acid, hydrochloric acid, boric acid, sulfamic acid, phosphinic acid, phosphonic acid, pyrophosphoric acid, tripolyphosphoric acid, tetrapolyphosphoric acid, hexametaphosphoric acid, carbonic acid, hydrofluoric acid, sulfurous acid, thiosulfuric acid, chloric acid, perchloric acid, chlorous acid, hydroiodic acid, periodic acid, iodic acid, hydrobromic acid, perbromic acid, bromic acid, chromic acid, and nitrous acid.

Specific examples of organic acids include citric acid, maleic acid, malic acid, glycolic acid, succinic acid, itaconic acid, malonic acid, iminodiacetic acid, gluconic acid, lactic acid, mandelic acid, tartaric acid, formic acid, acetic acid, propionic acid, butyric acid, adipic acid, oxalic acid, valeric acid, enanthic acid, caproic acid, caprylic acid, pelargonic acid, capric acid, lauric acid, myristic acid, palmitic acid, margaric acid, stearic acid, cyclohexanecarboxylic acid, phenylacetic acid, benzoic acid, crotonic acid, oleic acid, linoleic acid, linolenic acid, ricinoleic acid, and methacrylic acid. , glutaric acid, fumaric acid, phthalic acid, isophthalic acid, terephthalic acid, tartronic acid, glyceric acid, hydroxybutyric acid, hydroxyacetic acid, hydroxybenzoic acid, salicylic acid, isocitric acid, methylenesuccinic acid, gallic acid, ascorbic acid, nitroacetic acid, oxaloacetic acid, chloroacetic acid, dichloroacetic acid, trichloroacetic acid, and other organic carboxylic acids; glycine, alanine, glutamic acid, aspartic acid, valine, leucine, isoleucine, serine, threonine, cysteine, methionine, phenylalanine, tryptophan, tyrosine, proline, Amino acids such as lysine, cystine, glutamine, asparagine, lysine, and arginine; nicotinic acid; picric acid; picolinic acid; phytic acid; 1-hydroxyethylidene-1,1-diphosphonic acid, aminotri(methylenephosphonic acid), ethylenediaminetetra(methylenephosphonic acid), diethylenetriaminepenta(methylenephosphonic acid), ethane-1,1-diphosphonic acid, ethane-1,1,2-triphosphonic acid, ethane-1-hydroxy-1,1-diphosphonic acid, ethanehydroxy-1,1,2-triphosphonic acid, ethane-1 , organic phosphonic acids such as 2-dicarboxy-1,2-diphosphonic acid, methanehydroxyphosphonic acid, 2-phosphonobutane-1,2-dicarboxylic acid, 1-phosphonobutane-2,3,4-tricarboxylic acid, α-methylphosphonosuccinic acid, and aminopoly(methylenephosphonic acid); organic sulfonic acids such as methanesulfonic acid, ethanesulfonic acid, aminoethanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, 2-naphthalenesulfonic acid, sulfosuccinic acid, 10-camphorsulfonic acid, isethionic acid, and taurine.

The acid may be used in the form of a salt of the acid. Examples of the salt include metal salts, ammonium salts, alkanolamine salts, etc. of the inorganic acids and organic acids described above. Examples of the metal salts include alkali metal salts such as lithium salts, sodium salts, and potassium salts. Examples of the ammonium salts include quaternary ammonium salts such as tetramethylammonium salts and tetraethylammonium salts. Examples of the alkanolamine salts include monoethanolamine salts, diethanolamine salts, and triethanolamine salts.
Specific examples of salts include alkali metal phosphates and alkali metal hydrogen phosphates such as tripotassium phosphate, dipotassium hydrogen phosphate, potassium dihydrogen phosphate, trisodium phosphate, disodium hydrogen phosphate, sodium dihydrogen phosphate, etc.; alkali metal salts of the organic acids exemplified above; and, in addition, alkali metal salts of glutamic acid diacetate, alkali metal salts of diethylenetriaminepentaacetic acid, alkali metal salts of hydroxyethylethylenediaminetriacetate, alkali metal salts of triethylenetetraminehexaacetic acid; etc. The alkali metal in these alkali metal salts may be, for example, lithium, sodium, potassium, etc.

The acids and their salts may be used alone or in combination of two or more (e.g., two or three). In some preferred embodiments, an acid may be used in combination with a salt of an acid different from the acid. The acid is preferably an inorganic acid. The salt of the acid is preferably an inorganic acid.

The content of the acid in the aqueous composition (when two or more acids are used, the total amount of the acids; the same applies hereinafter unless otherwise specified) may be, for example, 1 g/L or more, preferably 3 g/L or more, and more preferably 5 g/L or more (e.g., 10 g/L or more) from the viewpoint of favorably exerting the effects of the application of the present invention. The upper limit of the content of the acid in the aqueous composition is not particularly limited, but may be, for example, 700 g/L or less, preferably 500 g/L or less, and more preferably 350 g/L or less (e.g., 250 g/L or less) from the viewpoint of the handleability of the aqueous composition and the solubility of the preservative.
The preferred content of acid in the aqueous composition may vary depending on the purpose and mode of use of the aqueous composition.For example, in the aqueous composition used as a polishing slurry or its constituents after dilution, from the viewpoint of easily increasing the polishing removal rate, the lower limit of the content of acid is advantageously 10g/L or more, preferably 30g/L or more, may be 50g/L or more, 100g/L or more, 125g/L or more, or may be 150g/L or more.In addition, in the aqueous composition used as a polishing slurry or its constituents after being treated as it is or to such an extent that the concentration of acid is not significantly reduced (for example, adding additional components such as oxidizing agent, adjusting pH, etc.), from the viewpoint of easily increasing the surface quality after polishing, the upper limit of the content of acid may be, for example, 100g/L or less, 70g/L or less, 50g/L or less, 35g/L or less, or 15g/L or less.

(Preservatives)
The aqueous composition disclosed herein is characterized by containing, as a preservative, a compound Q that does not contain either a sulfur atom or a nitrogen atom. The compound Q can be used alone or in appropriate combination of two or more kinds.

By adding a preservative containing compound Q to the aqueous composition, the proliferation of bacteria in the aqueous composition can be suppressed. In addition, discoloration of the container during storage can be prevented. By using compound Q, which does not contain either sulfur or nitrogen atoms, as a preservative, it is possible to impart preservative properties to an aqueous composition containing acid while suppressing coloration of the aqueous composition or the container containing the aqueous composition that is caused by the use of a preservative. The fact that compound Q does not contain either sulfur or nitrogen atoms is also preferable from the viewpoint of suppressing the residue of abrasive grains on the surface after polishing with a polishing slurry containing the aqueous composition containing compound Q. The reason why such an effect is obtained is thought to be that compound Q avoids the promotion of the residue of the abrasive grains due to the unshared electron pairs of sulfur and nitrogen atoms. However, the present invention is not limited to this mechanism.

Compound Q is a compound that can exert the desired preservative effect in an aqueous composition containing acid. Compound Q in the aqueous composition disclosed herein can be, for example, a compound that, in a test solution containing 0.50 g/L of the compound to be evaluated and 175 g/L of acid, with the remainder being water, and in a preservative performance evaluation performed using this test solution as described in the Examples below, has a viable cell count of 10 cfu/mL or less for Penicillium chermesinum, Teratosphaeria acidotherma, and Rhinocladiella, determined from a measurement sample two days after adding at least the second (preferably third, more preferably fourth) test bacterial solution.

Compound Q in the technology disclosed herein is preferably an organic compound. Compound Q, which is an organic compound containing neither sulfur nor nitrogen atoms, can preferably achieve both the effect of preserving an aqueous composition containing an acid while suppressing coloration caused by storage of the aqueous composition, the effect of suppressing an increase in the number of residual abrasive grains caused by storage deterioration of the aqueous composition during polishing with a polishing slurry containing the aqueous composition, and the effect of suppressing a decrease in the polishing rate.

In some embodiments, compound Q is a nonionic organic compound. Such compound Q is preferred because it is less likely to cause excessive adsorption to abrasive grains or the object to be polished during polishing with a polishing slurry containing the aqueous composition disclosed herein. This can be advantageous from the standpoint of preventing a decrease in the polishing removal rate and reducing residual abrasive grains.

In some embodiments, compound Q is a compound that does not contain halogen atoms such as chlorine or bromine. Compound Q that does not contain any of sulfur atoms, nitrogen atoms, and halogen atoms is less likely to cause coloring of the aqueous composition, and tends to easily suppress the residual abrasive grains in a polishing slurry that uses an aqueous composition containing compound Q.

In some embodiments, compound Q is preferably a compound that does not have a multiple bond. In the above multiple bond, "multiple" means double or more. Therefore, compounds having an aryl group such as a benzene ring are included in the concept of a compound that does not have a multiple bond, except for those that have a multiple bond in addition to the aryl group. Specific examples of multiple bonds include, but are not limited to, carbon-carbon double bonds, carbon-oxygen double bonds, carbon-nitrogen double bonds, carbon-nitrogen triple bonds, etc. Compound Q that does not have a multiple bond is less likely to cause coloring of the aqueous composition, and tends to easily suppress the residual abrasive grains in a polishing slurry that uses an aqueous composition containing compound Q.

In some embodiments, the molecular weight of compound Q (chemical formula weight based on molecular structure) may be, for example, 2000 or less, and from the viewpoint of easily exerting a good preservative effect with a small amount (by weight) of use, it is preferably 1000 or less, and may be 500 or less, 300 or less, or 200 or less. Furthermore, from the viewpoint of easily exerting an appropriate preservative effect, the molecular weight of compound Q is appropriately 50 or more, and preferably 70 or more, and may be 100 or more, or may be 120 or more.

In some embodiments, compound Q may be a compound represented by the following general formula (1) or general formula (2):

In the above general formula (1), R ₁ , R ₂ , and R ₃ are each independently selected from the group consisting of an aliphatic saturated hydrocarbon group and an aromatic group. The above aliphatic saturated hydrocarbon group may be linear, branched, or cyclic. Two or more of _{R 1} , R ₂ , and R ₃ may be bonded to each other to form a ring structure. In some embodiments, the number of carbon atoms in R ₁ is preferably 1 to 3, more preferably 1 to 2 (e.g., 1). The number of carbon atoms in R ₂ is preferably 1 to 4, more preferably 1 to 3 (e.g., 2). The number of carbon atoms in R ₃ is preferably 1 to 3, more preferably 1 to 2 (e.g., 1). In addition, in the above general formula (1), n is 1 to 3, more preferably 1 to 2 (e.g., 1).
In the above general formula (2), R ₄ and R ₅ are each independently selected from the group consisting of an aliphatic saturated hydrocarbon group and an aromatic group. The aliphatic saturated hydrocarbon group may be linear, branched, or cyclic. R ₄ and R ₅ may be bonded to each other to form a ring structure. In some embodiments, the number of carbon atoms in R ₄ is, for example, 1 to 3, preferably 1 to 2 (e.g., 1). The number of carbon atoms in _{R 5} is, for example, 1 to 3, preferably 1 to 2 (e.g., 1).

In some embodiments, compound Q may be a combination of one or more of the compounds represented by the above general formula (1) (hereinafter also referred to as compound (1)) and one or more of the compounds represented by the above general formula (2) (hereinafter also referred to as compound (2)) in any weight ratio. By using such a combination, a higher preservative effect can be achieved. The reason for this is that compound (2) is thought to have a stronger preservative effect than compound (1), but compound (2) is difficult to hydrate because it has an aromatic ring, and by using compound (1) and compound (2) in combination, compound (1) promotes the hydration of compound (2), which increases the activity of compound (2) in the liquid, which has a high preservative performance, and improves the preservative performance. The above mechanism is based on the considerations of the present inventors, and the technology disclosed herein is not limited to the above mechanism. When the above combination is used, the amount of compound (2) used relative to 100 parts by weight of the total amount of compound (1) and compound (2) used can be, for example, 10 parts by weight or more and 90 parts by weight or less.

In some embodiments, the compound Q may preferably be a compound having a structure in which a hydroxyl group and an etheric oxygen are bonded to the same carbon. By having such a structure, the compound Q containing neither a sulfur atom nor a nitrogen atom can preferably exhibit the effect of suppressing bacterial growth in an aqueous composition containing an acid. The compound Q having a structure in which a hydroxyl group and an etheric oxygen are bonded to the same carbon may be a compound corresponding to the above general formula (1) or (2). Non-limiting examples of the compound Q having a structure in which a hydroxyl group and an etheric oxygen are bonded to the same carbon include a compound in which one or both of R ₁ and R ₃ in the above general formula (1) are CR ₆ R ₇ groups, and a compound in which R ₅ in the above general formula (2) is CR ₆ R ₇ groups. Here, R ₆ and R ₇ are each independently selected from a hydrogen atom and an alkyl group (e.g., a methyl group). Preferably, both R ₆ and R ₇ are hydrogen atoms. Alternatively, compound Q may be a compound having a structure in which a hydroxyl group and an etheric oxygen are bonded to the same carbon, and which does not fall into either of the above general formulas (1) or (2).

A preferred example of a structure in which a hydroxyl group and an ether oxygen are bonded to the same carbon is an -O-CH ₂ OH group. The -O-CH ₂ OH group may constitute a -CH ₂ -O-CH ₂ OH group. Compound Q having one or more (preferably one or two) such groups can be preferably used as a preservative in the aqueous composition disclosed herein.

A suitable example of the compound Q is an aliphatic chain compound Q1 having a structure in which a hydroxyl group and an ether oxygen are bonded to the same carbon, and having two or more hydroxyl groups. At least one of the two or more hydroxyl groups is a hydroxyl group contained in a structure in which a hydroxyl group and an ether oxygen are bonded to the same carbon. The compound Q1 may be a compound having one structure in which a hydroxyl group and an ether oxygen are bonded to the same carbon, or a compound having two or more (e.g., two) of the above structures. A preferred specific example of the compound Q1 is a compound in which R ₁ and R ₃ in the above general formula (1) are both CR ₆ R ₇ groups (e.g., CH ₂ groups).

Another preferred example of compound Q is compound Q2 having one or more (e.g., one or two) substituents on an aromatic ring containing a structure in which the hydroxyl group and the etheric oxygen are bonded to the same carbon. Preferred examples of compound Q2 include compounds of the above general formula (2) in which _R5 is a _{CR6R7 group} (e.g., a _CH2 group).

In some embodiments, compound Q may be a combination of one or more types of compound Q1 and one or more types of compound Q2 in any weight ratio. By using such a combination, a higher preservative effect may be exhibited. The total amount of compound Q2 used relative to the total amount of compound Q1 and compound Q2 used of 100 parts by weight may be, for example, 10 parts by weight or more, and may be, for example, 90 parts by weight or less.

The content of compound Q in the aqueous composition is, for example, appropriate to be 0.001 g/L or more, preferably 0.005 g/L or more, may be 0.010 g/L or more, or may be 0.025 g/L or more, from the viewpoint of preventing coloration and suppressing residual abrasive grains, and the content of compound Q in the aqueous composition is, for example, appropriate to be 10 g/L or less, preferably 5 g/L or less, and more preferably 2 g/L or less (for example, 1 g/L or less), from the viewpoint of preventing coloration and suppressing residual abrasive grains.
The preferred content of compound Q in the aqueous composition may vary depending on the purpose and mode of use of the aqueous composition.In the aqueous composition used as a polishing slurry or its constituents after dilution, from the viewpoint of enhancing antiseptic effect, the lower limit of the content of compound Q can be, for example, 0.01 g/L or more, may be 0.05 g/L or more, or may be 0.10 g/L or more (for example, 0.25 g/L or more).In addition, in the aqueous composition used as a polishing slurry or its constituents as it is or after treatment (for example, addition of additional components such as oxidizing agent, pH adjustment, etc.) to the extent that the concentration of compound Q is not significantly reduced, taking into consideration the influence on polishing removal rate and the number of remaining abrasive grains, the upper limit of the content of compound Q is, for example, 1 g/L or less, preferably 0.5 g/L or less, more preferably 0.2 g/L or less (for example, 0.1 g/L or less).

(water)
The water used in the technology disclosed herein may be ion-exchanged water, pure water, ultrapure water, distilled water, etc. Ion-exchanged water may typically be deionized water.

(pH)
The pH of the aqueous composition disclosed herein is typically less than 7.0, preferably 6.0 or less, and may be 5.0 or less. In some embodiments, the pH of the aqueous composition is suitably 4.5 or less, preferably 4.0 or less, more preferably 3.5 or less, may be 3.0 or less, or may be 2.5 or less. The preservative effect of compound Q can be more preferably exhibited in an aqueous composition having such a pH. The lower limit of the pH of the aqueous composition is not particularly limited, but may be, for example, 0.5 or more, 0.8 or more, or 1.0 or more from the viewpoint of the handling property of the aqueous composition.
The preferred pH of the aqueous composition may vary depending on the purpose and mode of use of the aqueous composition.For example, in the aqueous composition that is diluted and used as a polishing slurry or its constituent, from the viewpoint of the polishing removal efficiency of the polishing slurry, the upper limit of the pH of the aqueous composition is preferably 4.0 or less, may be 3.0 or less, may be 2.5 or less, may be less than 2.0, may be less than 1.7, or may be less than 1.5.The pH of the aqueous composition may be, for example, 0.5 or more or 0.8 or more.In addition, in the aqueous composition that is used as a polishing slurry or its constituent as it is or after being treated to such an extent that the pH does not change significantly, from the viewpoint of easily improving the surface quality after polishing with the polishing slurry, the lower limit of the pH of the aqueous composition is suitably 1.0 or more, may be 1.5 or more, may be 1.7 or more, or may be 2.0 or more. Furthermore, from the viewpoint of the polishing removal efficiency of the polishing slurry, etc., the pH of the aqueous composition is suitably 5.0 or less, preferably 4.0 or less, or may be 3.5 or less, 3.0 or less, or 2.5 or less.

In the technology disclosed herein, the pH of a liquid (which may be an aqueous composition, an abrasive dispersion, an abrasive slurry, etc.) can be determined by performing three-point calibration using a pH meter and then placing a glass electrode in the liquid to be measured. Standard buffer solutions are, for example, phthalate pH buffer: pH 4.01 (25°C), neutral phosphate pH buffer: pH 6.86 (25°C), and carbonate pH buffer: pH 10.01 (25°C).

(Abrasive grain)
The aqueous composition disclosed herein may be in a form containing abrasive grains. The aqueous composition containing abrasive grains can be used as a polishing slurry to be supplied to the surface of the object to be polished, either as is or after dilution, or by adding additives (e.g., volatile components such as hydrogen peroxide), pH adjusters, additional abrasive grains, etc. as necessary.

The type of abrasive that can be contained in the aqueous composition can be selected from the same abrasives contained in the abrasive dispersion liquid described below, so a duplicated description will be omitted.

In the aqueous composition containing abrasive grains, the content of abrasive grains is not particularly limited, but is typically 5 g/L or more, preferably 10 g/L or more, more preferably 20 g/L or more (for example, 35 g/L or more). By increasing the content of abrasive grains, a higher polishing rate tends to be realized. In addition, from the viewpoint of the dispersion stability of abrasive grains, the content is usually appropriate to be 800 g/L or less, and preferably 700 g/L or less (for example, 600 g/L or less).
The preferred content of abrasive grains in the aqueous composition containing abrasive grains may vary depending on the purpose and mode of use of the aqueous composition. In the aqueous composition used as a polishing slurry or a component thereof after dilution, the lower limit of the content of abrasive grains is preferably 20 g/L or more, more preferably 50 g/L or more, and may be 100 g/L or more, or may be 200 g/L or more, from the viewpoint of easily realizing a suitable polishing removal rate in the polishing slurry. In the aqueous composition used as a polishing slurry or a component thereof after being treated to such an extent that the concentration of abrasive grains is not significantly reduced, the upper limit of the content of abrasive grains may be, for example, 300 g/L or less, 200 g/L or less, 100 g/L or less, or 70 g/L or less, from the viewpoint of easily improving the surface quality after polishing.

<Abrasive dispersion liquid>
In some embodiments, the aqueous composition disclosed herein can be used to prepare a polishing slurry or a concentrated solution thereof by mixing with an abrasive dispersion. The abrasive dispersion typically contains abrasive grains and water to disperse the abrasive grains. The water can be the same as that used in the aqueous composition.

The material and properties of the abrasive grains are not particularly limited, and any of inorganic particles, organic particles, and organic-inorganic composite particles can be used. Specific examples of inorganic particles include oxide particles such as silica particles, alumina particles, cerium oxide particles, chromium oxide particles, titanium dioxide particles, zirconium oxide particles, magnesium oxide particles, manganese dioxide particles, zinc oxide particles, and red iron oxide particles; nitride particles such as silicon nitride particles and boron nitride particles; carbide particles such as silicon carbide particles and boron carbide particles; diamond particles; carbonates such as calcium carbonate and barium carbonate; and the like. Examples of the alumina particles include α-alumina, intermediate aluminas other than α-alumina, and composites thereof. Intermediate alumina is a general term for alumina particles other than α-alumina, and specific examples include γ-alumina, δ-alumina, θ-alumina, η-alumina, κ-alumina, and composites thereof. Specific examples of organic particles include polymethylmethacrylate (PMMA) particles, poly(meth)acrylic acid particles, polyacrylonitrile particles, etc. Here, (meth)acrylic acid refers to acrylic acid and methacrylic acid in a comprehensive sense. The abrasive grains can be used alone or in combination of two or more types.

A suitable example of the abrasive grains that can be used in the technology disclosed herein is silica particles. The silica particles can be various silica particles that are mainly composed of silica. Here, silica particles that are mainly composed of silica refer to particles that are 90% by weight or more, for example 95% by weight or more, typically 98% by weight or more of the particles are silica. Examples of silica particles that can be used are not particularly limited, and include colloidal silica, agglomerated silica, precipitated silica (also called precipitated silica), sodium silicate silica, alkoxide silica, fumed silica, dried silica, and detonation silica. Furthermore, silica particles obtained using the above silica particles as raw materials can also be used. Examples of such silica particles include silica particles obtained by applying one or more treatments selected from heat treatments such as heating, drying, and firing, pressure treatments such as autoclaving, mechanical treatments such as crushing and grinding, and surface modification to the above raw silica particles (hereinafter also called "raw silica"). Examples of surface modification include chemical modifications such as introduction of functional groups and metal modification. The silica particles in the technology disclosed herein may contain one type of silica particles as described above alone or two or more types in combination.

A suitable example of silica particles is colloidal silica. In particular, it is preferable to use colloidal silica synthesized through particle growth in an aqueous phase, such as sodium silicate silica or alkoxide silica. With silica abrasives containing this type of colloidal silica, good surface quality can be preferably achieved. When the silica abrasives disclosed herein contain colloidal silica, the colloidal silica contained in the silica abrasives may be one type, or two or more types with different manufacturing conditions and/or physical properties. In addition, the silica abrasives may be composed of one or more types of colloidal silica, or may be composed of a combination of colloidal silica and silica particles other than colloidal silica. In some embodiments, the abrasives contained in the polishing slurry contain colloidal silica alone. By using colloidal silica alone, better surface quality can be achieved.

The particle shape of colloidal silica is not particularly limited, and may be, for example, spherical or non-spherical. Specific examples of non-spherical shapes include a peanut shape, a cocoon shape, a shape with protrusions, a rugby ball shape, etc. A peanut shape may be, for example, the shape of a peanut shell. A shape with protrusions may be, for example, a confetti shape.

The technology disclosed herein can be preferably implemented in a form in which the polishing slurry supplied to the object to be polished is substantially free of alumina particles. Such a polishing slurry prevents quality degradation caused by the use of alumina particles. Examples of quality degradation include the occurrence of scratches and dents, residual alumina, and puncture defects. In this specification, "substantially free of alumina particles" means that the proportion of alumina particles in the total amount of solids contained in the polishing slurry is 1% by weight or less, more preferably 0.5% by weight or less (e.g., 0.1% by weight or less). A polishing slurry with a proportion of alumina particles of 0% by weight, i.e., a polishing slurry containing no alumina particles, is particularly preferred. The polishing slurry disclosed herein can also be preferably implemented in a form in which the polishing slurry is substantially free of α-alumina particles.

The technology disclosed herein can also be preferably implemented in an embodiment in which the polishing slurry supplied to the object to be polished contains silica particles as abrasive grains, but does not substantially contain particles other than silica particles, i.e., non-silica particles. Here, "substantially free of non-silica particles" means that the proportion of non-silica particles in the total amount of solids contained in the polishing slurry is 1% by weight or less, more preferably 0.5% by weight or less, and typically 0.1% by weight or less. In such an embodiment, the application effect of the technology disclosed herein can be preferably exerted.

In some embodiments, the average secondary particle diameter of the abrasive grains (e.g., silica particles) may be, for example, about 10 nm to 500 nm. From the viewpoint of polishing efficiency, etc., in some embodiments, the average secondary particle diameter may be, for example, 25 nm or more, or 40 nm or more. The technology disclosed herein may also be suitably implemented in an embodiment in which the average secondary particle diameter of the abrasive grains is 50 nm or more, 60 nm or more, or 70 nm or more. On the other hand, from the viewpoint of improving the surface quality after polishing, the average secondary particle diameter is suitably, for example, 300 nm or less, and may be 200 nm or less, 150 nm or less, 120 nm or less, or 100 nm or less. The above-mentioned average secondary particle diameter may be preferably applied to abrasive grains used for polishing magnetic disk substrates such as Ni-P substrates and glass substrates.

The average secondary particle size (volume average particle size) of the abrasive grains can be determined by performing particle size measurement based on dynamic light scattering using an abrasive-containing liquid containing abrasive grains as a measurement sample. This particle size measurement can be performed using, for example, a model "UPA-UT151" manufactured by Nikkiso Co., Ltd. The same applies to the examples described below.

The content of abrasive grains in the abrasive grain dispersion is not particularly limited. Since the abrasive grain dispersion can be stored and distributed compactly, the content of abrasive grains may be, for example, 10 g/L or more, preferably 20 g/L or more, more preferably 50 g/L or more, may be 100 g/L or more, may be 200 g/L or more, or may be 300 g/L or more. From the viewpoint of the dispersion stability of the abrasive grains, the above content is usually appropriate to be 800 g/L or less, and preferably 700 g/L or less (for example, 600 g/L or less).

The pH of the abrasive dispersion is not particularly limited and may be selected according to the material of the abrasive and the use of the abrasive dispersion. The pH of the abrasive dispersion may be selected, for example, from the range of 2.0 to 12.5. In an abrasive dispersion containing silica particles as abrasives, the pH of the abrasive dispersion (silica dispersion) may be, for example, 5.0 or more, 7.0 or more, 8.0 or more, or 9.0 or more. When the pH of the silica dispersion is high, the dispersion stability of the silica dispersion tends to improve. In addition, from the viewpoint of preventing dissolution of the silica particles, the pH of the silica dispersion is usually appropriate to be 12.0 or less, preferably 11.0 or less, and may be 10.5 or less, for example, 10.0 or less.

<Polishing slurry>
The polishing slurry containing the aqueous composition disclosed herein may contain, as necessary, one or more of the components exemplified below as components to be newly mixed with the aqueous composition (which may be components contained in the abrasive dispersion mixed with the aqueous composition).

The polishing slurry disclosed herein may contain an oxidizing agent as necessary. Examples of oxidizing agents include, but are not limited to, peroxides, nitric acid or its salts, periodic acid or its salts, peroxoacid or its salts, permanganic acid or its salts, chromic acid or its salts, oxyacids or its salts, metal salts, and sulfuric acids. The oxidizing agents may be used alone or in combination of two or more. Specific examples of the oxidizing agent include hydrogen peroxide, sodium peroxide, barium peroxide, nitric acid, iron nitrate, aluminum nitrate, ammonium nitrate, peroxomonosulfuric acid, ammonium peroxomonosulfate, metal peroxomonosulfate, peroxodisulfate, ammonium peroxodisulfate, metal peroxodisulfate, peroxolinic acid, peroxosulfuric acid, sodium peroxoborate, performic acid, peracetic acid, perbenzoic acid, perphthalic acid, hypobromous acid, hypoiodous acid, chloric acid, bromic acid, iodic acid, periodic acid, perchloric acid, hypochlorous acid, sodium hypochlorite, calcium hypochlorite, potassium permanganate, metal chromate, metal dichromate, iron chloride, iron sulfate, iron citrate, ammonium iron sulfate, etc. Preferred examples of the oxidizing agent include hydrogen peroxide, iron nitrate, periodic acid, peroxomonosulfuric acid, peroxodisulfuric acid, and nitric acid. It preferably contains at least hydrogen peroxide, and more preferably consists of hydrogen peroxide.

When an oxidizing agent is contained in the polishing slurry, the content of the oxidizing agent is not particularly limited and can be set so as to achieve the desired effect of use. In some embodiments, the content of the oxidizing agent is preferably 1 g/L or more, more preferably 3 g/L or more, and even more preferably 4 g/L or more. By increasing the amount of the oxidizing agent, the rate at which the object to be polished (e.g., a magnetic disk substrate such as a Ni-P substrate) is oxidized increases, and the polishing removal rate can be improved. In addition, the content of the oxidizing agent in the polishing slurry can be, for example, 50 g/L or less, preferably 30 g/L or less, and may be 20 g2/L or less, or 15 g/L or less, taking into consideration the surface quality after polishing, etc.

The polishing slurry disclosed herein may further contain, as necessary, known additives that can be used in polishing slurries, such as surfactants, water-soluble polymers, dispersants, chelating agents, and basic compounds, to the extent that the effects of the present invention are not significantly impeded.

The surfactant is not particularly limited, and can be any of anionic surfactant, nonionic surfactant, cationic surfactant, and amphoteric surfactant. The use of surfactant can improve the dispersion stability of the polishing slurry. The surfactant can be used alone or in combination of two or more. The surfactant can typically be a water-soluble organic compound with a molecular weight of less than 1× ¹⁰⁴ .
Specific examples of anionic surfactants include polyoxyethylene alkyl ether acetates, polyoxyethylene alkyl sulfates, alkyl sulfates, polyoxyethylene alkyl sulfates, alkyl sulfates, alkyl benzene sulfonates, alkyl phosphates, polyoxyethylene alkyl phosphates, polyoxyethylene sulfosuccinates, alkyl sulfosuccinates, alkyl naphthalene sulfonates, alkyl diphenyl ether disulfonic acids, polyacrylic acids, sodium lauryl sulfate, ammonium lauryl sulfate, sodium dodecylbenzene sulfonate, polyoxyethylene alkyl ether sodium sulfate, polyoxyethylene alkyl phenyl ether ammonium sulfate, polyoxyethylene alkyl phenyl ether sodium sulfate, and salts thereof.
Other specific examples of the anionic surfactant include polyalkylarylsulfonic acid compounds such as naphthalenesulfonic acid formaldehyde condensates, methylnaphthalenesulfonic acid formaldehyde condensates, anthracenesulfonic acid formaldehyde condensates, and benzenesulfonic acid formaldehyde condensates; melamine formalin resin sulfonic acid compounds such as melaminesulfonic acid formaldehyde condensates; ligninsulfonic acid compounds such as ligninsulfonic acid and modified ligninsulfonic acid; aromatic aminosulfonic acid compounds such as aminoarylsulfonic acid-phenol-formaldehyde condensates; polyisoprene sulfonic acid, polyvinylsulfonic acid, polyallylsulfonic acid, polyisoamylenesulfonic acid, polystyrenesulfonic acid; and salts thereof. As the salt, alkali metal salts such as sodium salts and potassium salts are preferred.
Specific examples of nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyalkylene alkyl ethers, sorbitan fatty acid esters, glycerin fatty acid esters, polyoxyethylene fatty acid esters, polyoxyethylene alkyl amines, and alkyl alkanolamides.
Specific examples of the cationic surfactant include alkyltrimethylammonium salts, alkyldimethylammonium salts, alkylbenzyldimethylammonium salts, and alkylamine salts.
Specific examples of amphoteric surfactants include alkyl betaine type, fatty acid amidopropyl betaine type, alkyl imidazole type, amino acid type, and alkyl amine oxide type.

In the polishing slurry containing a surfactant, the surfactant content may be, for example, 0.005 g/L or more. From the viewpoint of the smoothness of the surface after polishing, the content is preferably 0.01 g/L or more, more preferably 0.1 g/L or more. In addition, taking into consideration the polishing removal rate, the content is preferably 100 g/L or less, and is preferably 50 g/L or less, for example 10 g/L or less. The technology disclosed herein may also be preferably implemented in an embodiment in which a surfactant is not substantially used. Here, "not substantially used" means that a surfactant is not used at least intentionally.

The polishing slurry disclosed herein may contain a water-soluble polymer. By containing a water-soluble polymer, the surface precision after polishing can be improved. Examples of water-soluble polymers include polyalkylarylsulfonic acid compounds such as naphthalenesulfonic acid formaldehyde condensates, methylnaphthalenesulfonic acid formaldehyde condensates, and anthracenesulfonic acid formaldehyde; melamine formalin resin sulfonic acid compounds such as melamine sulfonic acid formaldehyde condensates; ligninsulfonic acid compounds such as ligninsulfonic acid and modified ligninsulfonic acid; aromatic aminosulfonic acid compounds such as aminoarylsulfonic acid-phenol-formaldehyde condensates; and others such as polyisoprene sulfonic acid, polyvinyl sulfonic acid, polyaryl Examples of the water-soluble polymer include sulfonic acid, polyisoamylene sulfonic acid, polystyrene sulfonate, polyacrylate, polyvinyl acetate, polymaleic acid, polyitaconic acid, polyvinyl alcohol, polyglycerin, polyvinylpyrrolidone, copolymer of isoprene sulfonic acid and acrylic acid, polyvinylpyrrolidone-polyacrylic acid copolymer, polyvinylpyrrolidone-vinyl acetate copolymer, diallylamine hydrochloride-sulfur dioxide copolymer, carboxymethylcellulose, salt of carboxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, pullulan, chitosan, chitosan salts, etc. The water-soluble polymer can be used alone or in combination of two or more kinds.

In the polishing slurry of an embodiment containing a water-soluble polymer, it is appropriate that the content of the water-soluble polymer in the polishing slurry is, for example, 0.01 g/L or more. From the viewpoint of surface smoothness after polishing, the content is preferably 0.05 g/L or more, more preferably 0.08 g/L or more, and even more preferably 0.1 g/L or more. From the viewpoint of polishing removal rate, the content is preferably 10 g/L or less, preferably 5 g/L or less, for example 1 g/L or less. The technology disclosed herein can also be preferably implemented in an embodiment in which the water-soluble polymer is not substantially used. Here, "not substantially used" means that the water-soluble polymer is not used at least intentionally.

Examples of dispersants include polycarboxylic acid-based dispersants such as sodium polycarboxylate and ammonium polycarboxylate; naphthalenesulfonic acid-based dispersants such as sodium naphthalenesulfonate and ammonium naphthalenesulfonate; alkylsulfonic acid-based dispersants; polyphosphoric acid-based dispersants; polyalkylene polyamine-based dispersants; quaternary ammonium-based dispersants; alkyl polyamine-based dispersants; alkylene oxide-based dispersants; polyhydric alcohol ester-based dispersants; and the like.

Examples of chelating agents include aminocarboxylic acid chelating agents and organic phosphonic acid chelating agents. Of these, organic phosphonic acid chelating agents are more preferred, and among these, ethylenediaminetetrakis(methylenephosphonic acid) and diethylenetriaminepenta(methylenephosphonic acid) are particularly preferred. A particularly preferred chelating agent is ethylenediaminetetrakis(methylenephosphonic acid).

The polishing slurry may contain one or more basic compounds as necessary for purposes such as pH adjustment. Examples of basic compounds include alkali metal hydroxides such as potassium hydroxide and sodium hydroxide; carbonates and bicarbonates such as ammonium bicarbonate, ammonium carbonate, potassium bicarbonate, potassium carbonate, sodium bicarbonate, and sodium carbonate; quaternary ammonium compounds; ammonia; and the like. The basic compound contained in the polishing slurry may be derived from an aqueous composition or an abrasive dispersion.

The pH of the polishing slurry is not particularly limited and can be appropriately set according to the purpose and mode of use of the polishing slurry. The pH of the polishing slurry can be, for example, 12.0 or less, typically 0.5 to 12.0, and may be 10.0 or less, typically 0.5 to 10.0. From the viewpoint of the polishing removal rate and the surface quality after polishing, the pH of the polishing slurry can be 7.0 or less, for example 0.5 to 7.0, more preferably 5.0 or less, typically 1.0 to 5.0, and even more preferably 4.0 or less, for example 1.0 to 4.0. The pH of the polishing slurry can be, for example, 3.0 or less, typically 1.0 to 3.0, and preferably 1.0 to 2.5 (for example 1.5 to 2.5). The above pH can be preferably applied to a polishing slurry used for polishing a nickel phosphorus substrate, for example. In particular, it can be preferably applied to a polishing slurry for primary polishing of a nickel phosphorus substrate.

The polishing slurry containing the aqueous composition disclosed herein may be a single-component type or a multi-component type, including a two-component type. The multi-component type polishing slurry may be configured, for example, so that the polishing slurry is prepared by mixing the abrasive dispersion and a sub-composition consisting of the aqueous composition, together with water and other components used as necessary.

The aqueous composition disclosed herein can be preferably used as a component of a kit for preparing an abrasive slurry. In particular, it is suitable as a component of a kit for preparing an abrasive slurry by mixing the aqueous composition with an abrasive dispersion. Such a kit can be configured to include at least a first composition comprising the above-mentioned abrasive dispersion, and a second composition comprising any of the aqueous compositions disclosed herein. Here, it is preferable that the first composition and the second composition are stored separately from each other.

The polishing slurry containing the aqueous composition disclosed herein can be preferably used for polishing, for example, nickel phosphorus substrates, glass substrates, carbon substrates, etc. The plating material may also be a disk substrate having a metal layer or metal compound layer other than a nickel phosphorus plating layer on the surface of a substrate disk. In particular, it is suitable as a polishing slurry for nickel phosphorus plated substrates having a nickel phosphorus plating layer on an aluminum alloy substrate disk. In such applications, it is particularly meaningful to apply the technology disclosed herein.

The polishing slurry containing the aqueous composition disclosed herein can be used particularly effectively in applications where it is desired to suppress the number of residual abrasive grains on the surface after polishing. One suitable example of such an application is a preliminary polishing step performed before the above-mentioned final polishing step in the manufacturing process of a magnetic disk substrate, which requires a highly accurate surface after the final polishing step. When there are multiple preliminary polishing steps before the final polishing step, the polishing slurry can be used in any of the preliminary polishing steps, and the same or different polishing slurries can be used in these preliminary polishing steps. The polishing slurry containing the aqueous composition disclosed herein is suitable, for example, as a polishing slurry used in the primary polishing step of a magnetic disk substrate. In particular, it can be preferably used in the first polishing step after nickel phosphorus plating, i.e., the primary polishing step, in the manufacturing process of a nickel phosphorus substrate.

The polishing slurry disclosed herein is suitable for polishing a magnetic disk substrate having a surface roughness of about 20 Å to 300 Å as measured by a laser scanning surface roughness meter "TMS-3000WRC" manufactured by Schmitt Measurement System Inc., and adjusting the surface roughness of the magnetic disk substrate to 10 Å or less. In such applications, it is particularly meaningful to apply the technology disclosed herein. The surface roughness referred to here means the arithmetic mean roughness (Ra).

<Polishing method>
The polishing slurry containing the aqueous composition disclosed herein (which may be a polishing slurry prepared using the aqueous composition disclosed herein) can be suitably used for polishing an object to be polished, for example, in an embodiment including the following operations. A preferred embodiment of the method for polishing an object to be polished using the polishing slurry disclosed herein will be described below. Hereinafter, the object to be polished will also be referred to as a substrate to be polished or simply a substrate.
That is, a polishing slurry (working slurry) containing any of the aqueous compositions disclosed herein is prepared. Then, the polishing slurry is supplied to the object to be polished, and polished by a conventional method. For example, the object to be polished is set in a general polishing device, and the polishing slurry is supplied to the surface of the object to be polished, i.e., the surface of the object to be polished, through the polishing pad of the polishing device. Typically, the polishing slurry is continuously supplied, and the polishing pad is pressed against the surface of the object to be polished, and the two are moved relative to each other. The movement can be, for example, a rotational movement. Through such a polishing process, the polishing of the object to be polished is completed.

The polishing pad that can be used is not particularly limited. For example, polishing pads of hard foam polyurethane type, nonwoven fabric type, suede type, etc. can be used. The suede type may be a buff pad, or a polishing pad in a non-buffed state where the surface is not buffed (so-called non-buff pad). Such suede type polishing pads (typically polyurethane polishing pads) are easy to process and can easily achieve high quality of the substrate surface. The polishing pads used in the technology disclosed herein are typically polishing pads that do not contain abrasive grains.

After polishing (specifically, after the primary polishing of the magnetic disk substrate), it is preferable to wash the substrate (cleaning step). The cleaning step is typically performed using a cleaning machine. In the cleaning step, a cleaning liquid may be used, or only running water may be used for cleaning without using a cleaning liquid. Ultrasonic treatment may be performed by applying ultrasonic waves to the substrate immersed in the cleaning liquid or water. By performing such a cleaning step, the abrasive grains remaining on the substrate after polishing can be efficiently removed.

The polishing machine used in the polishing process may be a double-sided polishing machine that polishes both sides of the object to be polished simultaneously, or a single-sided polishing machine that polishes only one side of the object to be polished. When the above-mentioned polishing process is a preliminary polishing process, in some embodiments, a double-sided polishing machine may be preferably used as the polishing machine that performs the polishing process. When a finish polishing process is performed after the primary polishing process, a single-sided polishing machine may be preferably used as the polishing machine that performs the finish polishing process.

The polishing step as described above can be part of a manufacturing process for a magnetic disk substrate, for example a nickel phosphorus substrate. Therefore, this specification provides a manufacturing method and a polishing method for a magnetic disk substrate that include the above polishing step.

The aqueous composition disclosed herein can be preferably used as an abrasive slurry or a component thereof used in a preliminary polishing step of an object to be polished, for example, a primary polishing step. According to this specification, a manufacturing method and a polishing method for a magnetic disk substrate are provided, which include a step of performing preliminary polishing using an abrasive slurry containing any of the aqueous compositions described above. The above method includes a step (1) of supplying the above abrasive slurry to an object to be polished to polish the object to be polished. The above method may include a finish polishing step after the above preliminary polishing step. The polishing slurry used in the finish polishing step is not particularly limited. Therefore, the matters disclosed by this specification include a manufacturing method and a polishing method for a magnetic disk substrate, which include, in this order, a step (1) of polishing an object to be polished with an abrasive slurry containing the aqueous composition disclosed herein, and a step (2) of polishing an object to be polished with an abrasive slurry (for example, a finish polishing slurry) different from the polishing slurry used in step (1). According to such a manufacturing method, a magnetic disk substrate can be efficiently manufactured.

The abrasive grains used in step (2) are not particularly limited, and for example, colloidal silica is preferably used. By using colloidal silica, a polished product with high surface accuracy can be efficiently manufactured. The particle shape of the colloidal silica is not particularly limited, and may be, for example, spherical or non-spherical. In some embodiments, spherical colloidal silica is preferably used.

The finish polishing slurry that can be used in step (2) contains, for example, water in addition to abrasive grains. In addition, the finish polishing slurry can contain the same components as the polishing slurry described above (acid, oxidizing agent, basic compound, various additives, etc.) as necessary.

Several examples of the present invention are described below, but it is not intended that the present invention be limited to those examples.

Experimental Example 1: Preparation and Evaluation of Abrasive-Free Aqueous Composition
(Examples A1 to A11 and Comparative Examples A2 to A7)
An acid, a preservative, and deionized water were mixed to prepare an aqueous composition having the composition and pH shown in Table 1. In Table 1, the abbreviations a to g indicating the type of preservative each represent the compound shown in Table 2 (the same applies below).

(Examples A12 to A14)
Aqueous compositions having the compositions and pHs shown in Table 1 were prepared in the same manner as in the preparation of the aqueous composition of Example A9, except that the pH was adjusted using potassium hydroxide.

(Comparative Example A1)
Aqueous compositions having the compositions and pH values shown in Table 1 were prepared in the same manner as in the preparation of the aqueous composition of Example A1, except that no preservative was used.

(Evaluation of anti-discoloration properties during storage)
2000 g of the aqueous composition according to each example was placed in a transparent polypropylene container with a capacity of 2000 mL and stored at 70° C. for 168 hours or 336 hours, respectively. After storage, the aqueous composition (contents) was taken out of the container, the inside of the container was washed with water, and the presence or absence of discoloration was judged by visual comparison with an unused container. In addition, the aqueous composition (contents) taken out of the container was visually compared with the aqueous composition immediately after preparation (specifically, 3 hours at room temperature after mixing each material. The same applies below) to judge the presence or absence of discoloration. From the obtained results, the storage discoloration prevention properties of the aqueous composition were evaluated according to the following three levels, and are shown in Table 1. The higher the score, the better the storage discoloration prevention properties.
2 points: No discoloration was observed in either the container or the aqueous composition after storage for 168 hours or 336 hours.
1 point: No discoloration was observed in either the container or the aqueous composition after 168 hours of storage, but discoloration was observed in at least one of the container and the aqueous composition after 336 hours of storage.
0 points: After storage for 168 hours, discoloration was observed in at least one of the container and the aqueous composition.

(Method of evaluating antiseptic performance)
Three types of bacteria (Penicillium chermesinum, Teratosphaeria acidotherma, and Rhinocladiella) were each transferred to potato dextrose agar medium and cultured for 7 days at 25° C.±2° C. Spores were extracted from the cultured bacteria using a sterilized 0.005% aqueous solution of dioctyl sodium sulfosuccinate, and the spore count was adjusted to about 10 ⁵ /mL to prepare a test bacterial solution.
The aqueous composition according to each example was dispensed in 100 g portions into clean containers, and 1 g of the test bacteria liquid was added to each of the samples every two days. The samples were then cultured in an incubator adjusted to 28±2°C to obtain measurement samples. After the culture, the viable bacteria count was measured every two days. The viable bacteria count was measured by diluting the measurement sample 10, ¹⁰² ... times in sequence, dispensing 1 mL portions into petri dishes, adding potato dextrose agar medium, stirring well, and leaving the sample to stand. After the medium solidified, the sample was placed in an incubator adjusted to 28°C±2°C and cultured for 3 to 5 days, and the number of grown colonies was counted to obtain the viable bacteria count.
The addition of the test bacteria liquid every two days was repeated up to eight times to evaluate the preservative performance. In the viable cell count measurement, if the viable cell counts of the three types of bacteria were all 10 cfu/mL or less, the evaluation was "2 points." If the viable cell counts of the three types of bacteria were all 100 cfu/mL or less and the viable cell count of at least one of the three types of bacteria was more than 10 cfu/mL, the evaluation was "1 point." If the viable cell count of at least one of the three types of bacteria was more than 100 cfu/mL, the evaluation was "1 point." The results are shown in Table 1. The higher the score, and the higher the score is maintained until the number of times the test bacteria liquid is added increases, the better the preservative performance.

Experimental Example 2: Preparation and Evaluation of Polishing Slurry
In the following Experimental Example 2, the aqueous composition prepared in Experimental Example 1 was used as a sub-composition for mixing with abrasive grains to prepare a polishing slurry.

(Example C1)
Silica particles (colloidal silica having an average secondary particle diameter of 80 nm) as abrasive grains, (ethylenedioxy)dimethanol (preservative a shown in Table 2) as a preservative, and deionized water were mixed to prepare an abrasive grain dispersion having the composition shown in Table 3.
The above abrasive dispersion and the aqueous composition A1 prepared in Experimental Example 1 were both used immediately after preparation (i.e., after 3 hours at room temperature) to prepare a polishing slurry having the composition shown in Table 3. The polishing slurry was prepared by adding 100 mL of the above abrasive dispersion and 100 mL of the above aqueous composition (secondary composition), and further adding 12 g of an active ingredient of an aqueous hydrogen peroxide solution and deionized water to make a total amount of 1000 mL, and mixing them.

The abrasive dispersion liquid prepared above and the aqueous composition A1 prepared in Experimental Example 1 were each placed in a transparent polypropylene container with a capacity of 2000 mL and stored at 70°C for 168 hours. The amount placed in each container was 2000 g. After the liquid temperature of the abrasive dispersion liquid and the aqueous composition after storage was lowered to 23°C, 100 mL of the abrasive dispersion liquid and 100 mL of the aqueous composition (secondary composition) were added, and 12 g of an active ingredient of an aqueous hydrogen peroxide solution and deionized water were added to make a total amount of 1000 mL, and mixed to prepare a polishing slurry with the composition shown in Table 3.

(Examples C2, C5, C10 to C11 and Comparative Examples C2 to C7)
Silica particles (colloidal silica having an average secondary particle diameter of 80 nm) as abrasive particles, a preservative, and deionized water were mixed to prepare an abrasive particle dispersion having the composition shown in Table 3.
This abrasive dispersion and each of the aqueous compositions shown in Table 3 (each of the aqueous compositions (sub-compositions) prepared in Examples A2, A5, A10-A11, and Comparative Examples A2-A7) were used immediately after preparation or after storage at 70°C for 168 hours, and the rest of the procedure was the same as in Example C1 to prepare a polishing slurry having the composition shown in Table 3.

(Comparative Example C1)
Except for not using preservative, the abrasive dispersion liquid of the composition shown in Table 3 was prepared in the same manner as the preparation of the abrasive dispersion liquid of Example C1. This abrasive dispersion liquid and the aqueous composition prepared in Comparative Example A1 were used immediately after preparation or after storing at 70°C for 168 hours, and the other points were the same as in Example C1, to prepare a polishing slurry of the composition shown in Table 3.

The following polishing test was conducted on the day each polishing slurry was prepared, and the number of residual silica particles and the polishing removal rate were evaluated to investigate the effect of storing the compositions (abrasive dispersion liquid and auxiliary composition) used in preparing the polishing slurry on the number of residual silica particles and the polishing removal rate. The number of residual silica particles and the polishing removal rate were evaluated using the following method. The pH of each polishing slurry at the time of supply to the object to be polished (POU) was 2.2.

(Polishing test)
The polishing slurry according to each example was directly supplied to the object to be polished, and the object was polished under the following conditions. The object to be polished was an aluminum substrate for hard disk (substrate to be polished) with an electroless nickel phosphorus plating layer on its surface. The substrate was a doughnut type with a diameter of 3.5 inches, an outer diameter of about 95 mm, an inner diameter of about 25 mm, a thickness of 1.75 mm, and a surface roughness Ra of 130 Å before polishing.
[Polishing conditions]
Polishing equipment: SpeedFam double-sided polishing machine, model "9.0B-5P"
Polishing pad: Suede pad manufactured by FILWEL, product name "CR200" (a pad having a base layer and a surface layer, the surface layer being made of foamed polyurethane)
Number of substrates to be polished: 10 (2 substrates/carrier x 5 carriers)
Polishing slurry supply rate: 90 mL/min Polishing load: 100 g/ ^cm2
Upper platen rotation speed: 27 rpm
Lower surface plate rotation speed: 36 rpm
Sun gear rotation speed: 8 rpm
Amount polished: total thickness of about 2.0 μm on both sides of each substrate. The amount polished was calculated based on the following formula.
Polishing amount [μm]=weight loss of substrate due to polishing [g]/(substrate area [cm ² ]×density of nickel phosphorus plating [g/cm ³ ])×10 ⁴

(Calculation of polishing removal rate)
For each example, the polishing removal rate on both sides of the substrate to be polished was calculated based on the following formula when the polishing slurry prepared using the abrasive dispersion and the sub-composition immediately after preparation (after 3 hours at room temperature) or after storage at 70° C. for 168 hours was used to polish the substrate under the above polishing conditions.
Polishing removal rate [μm/min]=weight loss of substrate due to polishing [g]/(substrate area [cm ² ]×density of nickel phosphorus plating [g/cm ³ ]×polishing time [min])×10 ⁴

The results obtained are shown in the "Polishing removal rate" column of Table 3, converted into relative values with the polishing removal rate of the polishing slurry using the abrasive dispersion and auxiliary composition immediately after preparation taken as 100. If the decrease in the polishing removal rate caused by preparing the polishing slurry using the material after storage for 168 hours at 70°C is less than 10% (relative value greater than 90), the decrease in storage stability caused by the use of the preservative is judged to be within an acceptable range. If the decrease in the polishing removal rate is 5% or less (relative value 95 or more), it is judged to show good storage stability, and if it is 2% or less (relative value 98 or more), it is judged to show excellent storage stability.

(Measurement of the number of residual silica particles)
The substrate polished under the same conditions as those for measuring the polishing rate was washed using a cleaning machine manufactured by Cresen, and the number of particles remaining on the substrate surface was then measured. Specifically, the substrate was washed in running water without using a brush or cleaning agent, and the water droplets adhering to the substrate were removed using a spin dryer and the substrate was dried. The specific cleaning conditions were as follows:
(Washing conditions)
Cleaning agent application time: 0 seconds Disk substrate rotation speed during cleaning: 40 rpm
First cleaning time (running water only): 15 seconds First cleaning flow rate: 750 mL/min Second cleaning time (running water only): 20 seconds Second cleaning flow rate: 900 mL/min Ultrasonic cleaning time (running water only): 20 seconds Ultrasonic cleaning flow rate: 3000 mL/min Spin dry time: 20 seconds Spin dry rotation speed: 3000 rpm
Next, the surface of the substrate (both sides) after cleaning is observed at 50,000 times magnification with 10 fields of view per side using a scanning electron microscope "SU8000" manufactured by Hitachi High-Technologies Corporation. Then, the number of residual silica particles in each field of view is measured using image analysis software "WinROOF" manufactured by Mitani Shoji Co., Ltd., and the average value of the number of residual silica particles per field of view is calculated. The obtained results are converted into relative values with the polishing removal rate of the polishing slurry using the abrasive dispersion liquid and the sub-composition immediately after preparation being set to 100, and are shown in the "number of residual silica particles" column in Table 3. If the increase in the number of residual silica particles by preparing the polishing slurry using the material after storing at 70°C for 168 hours is less than 10% (relative value is less than 110), the increase in the number of residual silica by using the preservative is judged to be within the acceptable range.

As shown in Table 1, the aqueous compositions of Examples A1 to A14 using a preservative corresponding to compound Q exhibited clearly higher preservative properties and also had excellent storage coloring prevention properties compared to the aqueous composition of Comparative Example A1 that did not contain a preservative. Also, as can be seen from the comparison between Examples A1, A2 and A3, the combination of preservative a and preservative b provided a higher preservative effect than the single use of preservative a or preservative b. And, as shown in Table 3, the aqueous compositions of Examples A1, A2, A5, A10 to A11 had little increase in the number of residual silica particles and little decrease in polishing removal rate even when used to prepare polishing slurry after storage, and had excellent storage stability.
On the other hand, the aqueous compositions of Comparative Examples A1 to A7, which used only a preservative not corresponding to Compound Q, were inferior to the aqueous compositions of the above Examples in one or more of the following: preservative properties, prevention of coloration during storage, inhibition of an increase in the number of residual silica particles due to use after storage, and inhibition of a decrease in the polishing removal rate.

Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and variations of the specific examples given above.

Claims (9)

An aqueous composition used for polishing an object to be polished, comprising:
The aqueous composition comprises an acid, a preservative, and water;
The preservative comprises a compound Q that does not contain any of a sulfur atom and a nitrogen atom,
As the compound Q,
an aliphatic chain compound Q1 having two or more hydroxyl groups;
A compound Q2 having, on an aromatic ring, a substituent containing a structure in which a hydroxyl group and an ether oxygen are bonded to the same carbon;
in combination . An aqueous composition used for polishing an object to be polished, comprising:
The aqueous composition comprises an acid, a preservative, and water;
The preservative comprises a compound Q that does not contain any of a sulfur atom and a nitrogen atom,
An aqueous composition comprising, as the compound Q, a compound Q2 having, on an aromatic ring, a substituent containing a structure in which a hydroxyl group and an etheric oxygen are bonded to the same carbon. 3. The aqueous composition according to claim 1 , wherein the compound Q contains a —O—CH ₂ OH group as a structure in which the hydroxyl group and the etheric oxygen are bonded to the same carbon. The aqueous composition according to any one of claims 1 to 3 , having a pH in the range of 0.5 to 4.0. The aqueous composition according to any one of claims 1 to 4 , wherein the object to be polished is a magnetic disk substrate. The aqueous composition according to any one of claims 1 to 5 , further comprising an abrasive. The aqueous composition according to any one of claims 1 to 5 , which is used to prepare a polishing slurry to be supplied to the object to be polished by mixing with abrasive grains. 8. A polishing slurry which is supplied to an object to be polished and used for polishing the object, comprising the aqueous composition according to claim 1 . an abrasive dispersion liquid containing abrasive grains and water;
A sub-composition comprising the aqueous composition according to any one of claims 1 to 5 ;
Including,
The abrasive grain dispersion liquid and the sub-composition are stored separately from each other in the abrasive slurry preparation kit.