TW202120638A - Polishing composition for magnetic disk substrate, and method for polishing magnetic disk substrate - Google Patents

Abstract

This invention aims to provide a polishing liquid composition capable of reducing long-wavelength waviness and halation of a substrate after polishing while improving productivity in multiple polishing processes of a magnetic disk substrate. The solution is a polishing liquid composition containing colloidal silica having an average primary particle size of 1 to 100 nm and water, and the colloidal silica contains at least 3% by weight of silica particles having an Al content of 100 mg/kg or less in a solid. Alternatively, the polishing liquid composition contains colloidal silica having an average primary particle size of 1 to 100 nm and water, and the colloidal silica contains at least 3% by weight of silica particles synthesized from metallic silicon as a raw material.

Description

Polishing liquid composition for magnetic disk substrate and method for polishing magnetic disk substrate

The invention relates to a polishing liquid composition for polishing electronic parts such as magnetic recording media (such as semiconductors, hard disks) and a polishing method for magnetic disk substrates. In particular, it relates to a magnetic recording medium substrate such as a glass disk substrate, an aluminum alloy disk substrate, or an aluminum alloy disk substrate for a magnetic recording medium on which an electroless nickel-phosphorus coating is formed on the surface of an aluminum alloy substrate. (Hereinafter, only collectively referred to as " A polishing liquid composition for a magnetic disk substrate used for surface polishing of a magnetic disk substrate".) and a method for polishing a magnetic disk substrate using the polishing liquid composition for a magnetic disk substrate.

In the past, in order to increase the magnetic recording density, various improvements were required to the polishing liquid composition for magnetic disk substrates (hereinafter, simply referred to as "polishing liquid composition"), which is used to polish aluminum alloy magnetic disks. Electroless nickel-phosphorus coating surface of the substrate. For example, scratches. The scratched part is one of the reasons for reading and writing errors, and the burr around the scratched part is the cause of conflict with the magnetic head. Furthermore, it is also necessary to reduce other possible causes of conflict with the magnetic head, such as ripples as one of the reasons.

From the point of view of reducing scratches, colloidal silica is used on aluminum alloy magnetic disk substrates as the abrasive part that serves as a polishing fluid composition for mechanical polishing. At this time, in industrial polishing, most of the abrasive particles used for mechanical polishing of the polishing liquid composition and the chemical polishing agent used for chemical polishing are mixed and used immediately before the actual polishing.

However, once the colloidal silica, which is known as the abrasive part, and the chemical part are mixed When combined, colloidal silica has a tendency to condense. In order to prevent the adverse effects caused by the condensed particles of the related colloidal silica, for example, removal of coarse particles, adjustment of the corrosiveness of the polishing liquid (refer to Patent Document 1), adjustment of the particle shape (refer to Patent Document 2), or adjustment of the condensed particles (Refer to Patent Document 3) and other technologies have been proposed.

On the other hand, it is known that the metal impurities contained in colloidal silica will remain on the surface of the magnetic disk substrate after the polishing process, which will impair the smoothness of the surface. In order to solve this problem, some people have proposed to produce metal impurities The manufacturing method of colloidal silica with rare content. In addition, for the above-mentioned purpose, an alkoxysilane method using tetraethoxysilane or the like as a raw material or a method for producing colloidal silica using a cheaper raw material metal silicon have also been proposed (for example, refer to Patent Documents 4 to 6 .

[Prior Technical Literature]

[Patent Literature]

[Patent Document 1] JP 2009-120850 A

[Patent Document 2] JP 2009-172709 A

[Patent Document 3] JP 2010-170650 A

[Patent Document 4] Japanese Patent Publication No. 49-4637

[Patent Document 5] Japanese Patent Laid-Open No. 49-64595

[Patent Document 6] International Publication No. 2008/072637

In recent years, due to the high quality requirements that have been accompanied by the increase in magnetic recording density and the multiple polishing of industrial production types, it is required that while increasing the production capacity, it is also necessary to reduce scratches and ripples. Here, in the ripples Including long-wavelength ripple (wavelength: 500~1000μm), medium-wavelength ripple (wavelength: 100~500μm) and short-wavelength ripple (wavelength: 20-100μm), especially long-wavelength ripple is the main cause of conflict with the magnetic head, so Need to reduce long-wavelength ripples.

In addition, from the viewpoint of increasing the magnetic recording density, there is a new need for halo reduction. The so-called halo here refers to the entire substrate surface defect inspection machine (NS2000H manufactured by Hitachi High-Tech Co., Ltd.). Under specific inspection conditions, the subtle defects on the substrate surface are detected and quantitatively evaluated as halo count (detailed in Introduced later).

Halo is generally considered to be caused by the existence of some subtle unevenness on the substrate surface on a large area of the substrate. The reason may be due to the inconsistent characteristics of the polishing pad, carrier, substrate and polishing liquid composition. caused. Recently, the existence of halos has become a new problem that hinders the increase in magnetic recording density, so it is necessary to reduce the related halos.

In addition, under the condition of multiple polishing, the polishing speed is reduced due to the contamination of the polishing pad, which in turn causes the problem of low productivity. The improvement to this problem is also the purpose of this case.

In view of the above, the problem to be solved by the present invention is to provide a polishing liquid composition and a polishing method for a magnetic disk substrate using the polishing liquid composition, which can increase the productivity and improve the productivity when the magnetic disk substrate is polished multiple times. It can reduce the long-wavelength ripple and halo of the disk substrate after polishing.

The inventor of the present case has conducted in-depth research on how to solve the above-mentioned problems and found that by using the following polishing liquid composition for magnetic disk substrates, the productivity can be increased and the long-wavelength ripples and halos can be reduced during multiple polishing. The present invention.

[1] A polishing liquid composition for magnetic disk substrates, comprising colloidal silica with an average primary particle size of 1-100 nm and water, wherein the colloidal silica contains at least 3% by weight or more of solid Silica particles with an Al content of 100mg/kg or less in the body.

[2] A polishing liquid composition for magnetic disk substrates contains colloidal silica having an average primary particle size of 1-100 nm and water, and the colloidal silica contains at least 3% by weight and is synthesized using metallic silicon as a raw material.

[3] The polishing liquid composition for a magnetic disk substrate as described in [2], wherein the colloidal silica contains at least 10% by weight of silica particles synthesized using the metallic silicon as a raw material.

[4] The polishing liquid composition for a magnetic disk substrate as described in any one of [1] to [3], and further contains a water-soluble polymer compound.

[5] The polishing liquid composition for a magnetic disk substrate as described in [4], wherein the water-soluble polymer compound is a monomer having a carboxylic acid group and a monomer having an amino group as essential monomers A copolymer with a weight average molecular weight of 1,000 to 1,000,000.

[6] The polishing liquid composition for a magnetic disk substrate as described in [4], wherein the water-soluble polymer compound is based on a monomer having a carboxylic acid group and a monomer having a sulfonic acid group. The weight average molecular weight is 1,000 to 1,000,000.

[7] The polishing liquid composition for a magnetic disk substrate as described in [4], wherein the water-soluble polymer compound is a monomer having a carboxylic acid group, a monomer having an amino group, and a sulfonic acid group. The monomer of the group is a copolymer of necessary monomers, and the weight average molecular weight is 1,000 to 1,000,000.

[8] The polishing liquid composition for a magnetic disk substrate according to any one of [5] to [7], wherein the monomer having a carboxylic acid group is selected from acrylic acid and its salt or methacrylic acid Monomers of esters and their salts.

[9] The polishing liquid combination for magnetic disk substrates as described in any one of [5] or [7] Wherein, the monomer having an amino group is one or more monomers selected from the group consisting of acrylamide, methacrylamide, N-alkyl acrylamide, and N-alkyl methacrylate .

[10] The polishing liquid composition for a magnetic disk substrate according to any one of [6] or [7], wherein the monomer having a sulfonic acid group is selected from isoprenesulfonic acid, 2 -Acrylamide-2-methylpropanesulfonic acid, 2-methylamide-2-methylpropanesulfonic acid, styrenesulfonic acid, vinylsulfonic acid, allylsulfonic acid, isopentansulfonic acid, ethylene Mononaphthalenesulfonic acid and its salts.

[11] The polishing liquid composition for a magnetic disk substrate as described in any one of [1] to [10], which further contains an acid and/or and/or its salt, and has a pH of 25°C 0.1~4.0.

[12] The polishing liquid composition for a magnetic disk substrate as described in any one of [1] to [10], which further contains an oxidizing agent.

[13] A method for polishing a magnetic disk substrate using the polishing liquid composition for a magnetic disk substrate as described in any one of [1] to [12], wherein nickel is formed on the surface of the aluminum alloy substrate. The phosphor-coated magnetic disk substrate is the object of polishing, and a multi-stage polishing method of repeatedly performing polishing procedures on the magnetic disk substrate is adopted, and the magnetic disk substrate is used in the final polishing process with the magnetic disk substrate polishing liquid combination Things.

The polishing liquid composition of the present invention contains: colloidal silica containing silica particles with an Al content of 100 mg/kg or less in solids or silica particles synthesized with metallic silicon as a raw material; and water. When polishing the surface of a magnetic recording medium aluminum alloy disk substrate on which an electroless nickel-phosphorus coating is formed on the surface of an aluminum alloy substrate, the polishing speed can be increased during multiple polishing, while reducing the long-wavelength ripple and the substrate after polishing. Halo, and can play an excellent effect of improving the yield and the quality of the polished surface of the substrate. In addition, the method for polishing a magnetic disk substrate of the present invention uses a related polishing liquid composition to polish a magnetic disk substrate that can achieve the above-mentioned effects.

Hereinafter, the embodiments of the present invention will be described. However, it should be understood that the present invention is not limited to the following embodiments. Without departing from the scope of the present invention, based on the general knowledge of those with ordinary knowledge in the technical field, the following Appropriate changes or improvements are also included in the scope of the present invention.

1. Polishing liquid composition

The polishing liquid composition of the present invention (the polishing liquid composition for magnetic disk substrates) contains: silicon dioxide particles with an Al content of 100 mg/kg or less in solids or silicon dioxide particles synthesized from metallic silicon as a raw material The essential components include colloidal silica; and water, preferably further including water-soluble polymer compounds, and may include other optional components, such as acids and/or their salts or oxidizing agents.

1.1 Colloidal silica

The colloidal silica used in the polishing liquid composition of the present invention contains at least 3% by weight of solid silica particles with an Al content of 100 mg/kg or less, or at least 3% by weight or more and is synthesized with metallic silicon as a raw material Silica particles.

The silica particles synthesized from metallic silicon are described below. Here, for example, the cited document 6 discloses that the reaction to produce silicon dioxide from metallic silicon and water is carried out in the presence of a basic catalyst according to the following reaction formulas (1) to (3), and is accompanied by the generation of hydrogen.

The dissolution _{^{reaction: Si + 2OH - + H 2}} O → SiO 3 2- + 2H 2 ↑ (1)

Polymerization reaction: SiO ₃ ^2- +H2O→SiO ₂ +2OH- (2)

The total reaction formula: Si+2H ₂ O→SiO ₂ +2H ₂ ↑ (3)

If the above reaction formula is completely reacted, as shown in Figure (3), in the presence of a basic catalyst, colloidal silica is generated from metallic silicon. At this time, relative to 1mol of metallic silicon consumes 2mol of water to generate Into 1mol of silicon dioxide and 2mol of hydrogen.

In order to make the synthesis reaction smoother, metal silicon as a raw material is usually formed into a fine powder with an average particle size of 1 mm or less in advance and supplied to the reactor together with pure water. Usually, alkaline catalysts such as sodium hydroxide, potassium hydroxide, lithium hydroxide are added, and the synthesis reaction is carried out at a temperature of 60~100℃ to make the reaction proceed smoothly, so as to obtain fine silicon dioxide dispersed with 5~150nm A slurry of particles.

In the process of dissolving metallic silicon as a raw material, insoluble impurities such as heavy metals are separated. As a result, colloidal silica with less metal impurities can be obtained compared to the colloidal silica obtained by the water glass manufacturing method using sodium silicate or potassium silicate as a raw material. The silica particles synthesized from metallic silicon used in the polishing liquid composition of the present invention have an Al content of 100 mg/kg or less in the solid, preferably 80 mg/kg or less, more preferably 50 mg/kg or less Of silica particles.

As a method for producing colloidal silica with a low metal impurity content, for example, an alkoxysilane method in which alkoxysilanes such as tetraethoxysilane are hydrolyzed with acid or alkali is known. The colloidal silica using metallic silicon as a raw material used in the polishing liquid composition of the present invention can be manufactured at a lower cost than the above-mentioned alkoxysilane method, which has advantages in manufacturing cost.

The colloidal silica contains at least 3% by weight or more of silica particles synthesized using metallic silicon as a raw material, preferably 10% by weight or more, and more preferably 20% by weight or more. In actual use, a mixture of silicon dioxide particles synthesized with metallic silicon as a raw material, colloidal silica manufactured by the water glass method, and colloidal silica manufactured by the alkoxysilane method can be used according to needs.

The colloidal silica used in the polishing liquid composition of the present invention has an average primary particle size of 1-100 nm, preferably 3 to 80 nm. Here, by making the average primary particle size 1nm or more, it is possible to prevent Stop the polishing speed from decreasing. On the other hand, by setting the average primary particle size to 100 nm or less, it is possible to prevent the deterioration of the surface smoothness of the polished magnetic disk substrate.

The shape of colloidal silica is known to be spherical confection shape (particle shape with convex portions on the surface), irregular shape, etc., and primary particles are mono-dispersed in water to form a colloidal shape. The colloidal silica used in the present invention is preferably spherical or nearly spherical colloidal silica. By using spherical or nearly spherical colloidal silica, the surface smoothness can be further improved.

1.2 Water-soluble polymer compounds

The water-soluble polymer compound used in the present invention is preferably a copolymer containing a monomer having a carboxylic acid group as an essential monomer, and more preferably, for example: (a) a monomer having a carboxylic acid group and a monomer having an amino group A copolymer in which the monomer is an essential monomer; (b) a copolymer in which a monomer having a carboxylic acid group and a monomer having a sulfonic acid group are the essential monomer; (c) a copolymer in which a monomer having a carboxylic acid group is A copolymer or the like in which a monomer having an amino group and a monomer having a sulfonic acid group are essential monomers.

1.2.1 Monomers with carboxylic acid groups

It is preferable to use unsaturated aliphatic carboxylic acids and their salts as monomers having carboxylic acid groups. Specifically, acrylic acid, methacrylate, maleic acid, itaconic acid, and salts thereof can be cited. Salts can be listed as sodium salt, potassium salt, magnesium salt, ammonium salt, amine salt, alkyl ammonium salt and the like.

Among the water-soluble polymer compounds, the pH value of the water-soluble polymer compound can be evaluated based on whether the monomer having a carboxylic acid group is present in an acid state or in a salt state. The higher the ratio in the acid state, the lower the pH value, and the higher the ratio in the salt state, the higher the pH value. The water-soluble polymer compound used in the present invention is, for example, a water-soluble polymer compound aqueous solution with a concentration of 10% by weight, which has a pH of 0.1 to 13.0 at 25°C.

1.2.2 Monomers with amino groups

As specific examples of the monomer having an amino group, acrylamide, methacrylamide, N-alkyl acrylamide, N-alkyl methacrylate, etc. can be used. Specific examples of N-alkylacrylamide and N-methacrylic acid alkyl ester include N-methacrylamide, N-ethacrylamide, N-propylacrylamide, N-isopropyl Acrylamide, n-butyl acrylamide, N-isobutyl acrylamide, N-sec-butyl acrylamide, N-tert-butyl acrylamide, N-methylmethacrylamide, N -Ethyl methacrylamide, N-propyl methacrylamide, N-isopropyl methacrylamide, n-butyl methacrylamide, N-isobutyl methacrylamide, N-sec-butyl methacrylamide Acrylamide, N-tert-butyl methacrylamide, etc.

1.2.3 Monomers with sulfonic acid groups

Specific examples of monomers having sulfonic acid groups include isoprene sulfonic acid, 2-propenamide-2-methylpropanesulfonic acid, 2-methylamide-2-methylpropanesulfonic acid, benzene Ethylene sulfonic acid, vinyl sulfonic acid, allyl sulfonic acid, isopentane sulfonic acid, vinyl naphthalene sulfonic acid and their salts, etc. Preferably, they are 2-propenamide-2-methylpropanesulfonic acid, 2-methacrylamide-2-methylpropanesulfonic acid, and salts thereof.

1.2.4 Copolymer

A description will be given of a copolymer containing a monomer having a carboxylic acid group as an essential monomer preferably contained in the polishing liquid composition of the present invention.

Here, when the water-soluble polymer compound is (a) a copolymer containing a monomer having a carboxylic acid group and a monomer having an amino group as essential monomers, it is derived from the constituent unit of the monomer having a carboxylic acid group The molar ratio is preferably 50 to 95 mol%, more preferably 60 to 93 mol%. The molar ratio of the constituent unit derived from the monomer having an amino group is preferably 5 to 50 mol%, and more preferably 7 to 40 mol%.

On the other hand, when the water-soluble polymer compound is (b) a copolymer containing a monomer having a carboxylic acid group and a monomer having a sulfonic acid group as essential monomers, it is derived from a monomer having a carboxylic acid group The molar ratio of the constituent units is preferably 30 to 95 mol%, and more preferably 40 to 90 mol%. The molar ratio of the monomer having a sulfonic acid group is preferably 5 to 70 mol%, and more preferably 10 to 60 mol%.

Furthermore, when the water-soluble polymer compound is (c) a copolymer containing a monomer having a carboxylic acid group, a monomer having an amide group, and a monomer having a sulfonic acid group as essential monomers, it is derived from a copolymer having a carboxylic acid group. The molar ratio of the constituent units of the monomers is preferably 50 to 95 mol%, more preferably 60 to 93 mol%, and particularly preferably 70 to 90 mol%. The molar ratio of the constituent unit derived from the monomer having an amino group is preferably 1 to 40 mol%, more preferably 3 to 30 mol%, and particularly preferably 5 to 20 mol%. The molar ratio of the constituent unit of the monomer derived from the sulfonic acid group is preferably 0.01 to 20 mol%, more preferably 0.1 to 10 mol%, and particularly preferably 0.2 to 5 mol%.

1.2.5 Manufacturing methods of water-soluble polymer compounds

Although the production method of the water-soluble polymer compound used in the polishing liquid composition of the present invention is not particularly limited, for example, it is preferable to use an aqueous polymerization method to produce the water-soluble polymer compound. The water-soluble polymer compound can be obtained as a uniform solution by the aqueous polymerization method.

As the polymerization solvent in the above-mentioned aqueous polymerization method, an aqueous solvent is preferably used, and water is particularly preferably used. In addition, in order to improve the solubility of the monomer components in the solvent, an organic solvent may be appropriately added within a range that does not adversely affect the polymerization of each monomer. Examples of the organic solvent include alcohols such as isopropanol and ketones such as acetone. One type can be used alone or two or more types can be used in combination.

The production method of the water-soluble polymer compound using the above-mentioned aqueous solvent will be described below. A known polymerization initiator can be used for the polymerization reaction, and a radical polymerization initiator is particularly preferably used.

Here, the radical polymerization initiator includes, for example, persulfates such as sodium persulfate, potassium persulfate, and ammonium persulfate, hydroperoxides such as tert-butyl hydroperoxide, and hydrogen peroxide. Water-soluble peroxides, ketone peroxides such as methyl ethyl ketone peroxide and cyclohexanone peroxide, dialkyl peroxides such as di-tert-butyl peroxide and tert-butyl cumyl peroxide, etc. Peroxide, azobisisobutyronitrile and 2,2-azobis(2-methylpropionamidine) dihydrochloride and other azo compounds are peroxide-based free radical polymerization initiators, which can Only one type may be used, or two or more types may be used in combination.

Among the above-mentioned oxide-based radical polymerization initiators, persulfates and azo compounds are preferred, and azobisisobutyronitrile is particularly preferred, which makes it easier to control the molecular weight of the water-soluble polymer compound.

The amount of the above radical polymerization initiator is not particularly limited, but based on the total weight of all monomers of the water-soluble polymer compound, it is preferably 0.1-15% by weight, particularly preferably 0.5-10% by weight. To use. By setting the weight ratio to 0.1% by weight or more, the copolymerization rate can be increased, and by setting the weight ratio to 15% by weight or less, the stability of the water-soluble polymer compound can be improved.

Furthermore, depending on the production conditions, a water-soluble redox polymerization initiator may be used to produce a water-soluble polymer compound. Examples of the redox polymerization initiator include oxidizing agents (for example, the above-mentioned peroxides), reducing agents such as sodium bisulfite, ammonium bisulfite, ammonium sulfite, and sodium bisulfite, or combinations of iron alum, potassium alum, and the like.

Furthermore, when producing a water-soluble polymer compound, a chain transfer agent can be appropriately added to the polymerization system to adjust the molecular weight. Chain transfer agents include, for example, sodium phosphite, sodium hypophosphite, potassium hypophosphite, sodium sulfite, sodium bisulfite, thioglycolic acid, mercaptopropionic acid, thioglycolic acid, 2-propanethiol, 2-mercaptoethanol, and thiophenol Wait.

In addition, the polymerization temperature in the production of water-soluble polymer compounds is not particularly limited. However, it is preferably carried out at a polymerization temperature of 60 to 100°C. By setting the polymerization temperature to 60°C or higher, the polymerization reaction can proceed more smoothly, and the yield can be optimized, and coloring can be prevented by setting the polymerization temperature to 100°C or lower.

Furthermore, the polymerization reaction can be carried out under pressure or reduced pressure, but it is preferable to carry out under normal pressure because of the need to increase the cost of the equipment for the pressure or reduced pressure reaction. The polymerization time is 2 to 20 hours, particularly preferably 3 to 10 hours.

After the polymerization reaction is carried out for a predetermined polymerization time, it is neutralized with a basic compound according to actual needs. The basic compounds used for neutralization include, for example, alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, alkaline earth metal hydroxides such as calcium hydroxide and magnesium hydroxide, or ammonia, monoethanolamine, and two Organic amines such as ethanolamine and triethanolamine.

The pH value at 25° C. after neutralization is preferably 2 to 9 and more preferably 3 to 8 in the case of an aqueous solution in which the concentration of the water-soluble polymer compound is 10% by weight.

1.2.6 Weight average molecular weight

The weight average molecular weight of the water-soluble polymer compound is preferably 1,000 to 1,000,000, more preferably 2,000 to 800,000, and still more preferably 3,000 to 600,000. The weight average molecular weight of water-soluble polymer compounds is measured by gel chromatography (GPC) through polyacrylic acid conversion. When the weight average molecular weight of the water-soluble polymer compound is less than 1,000, the waviness after polishing may be deteriorated. Moreover, when the weight average molecular weight of the water-soluble polymer compound is greater than 1,000,000, the viscosity of the aqueous solution is too high and it is difficult to use.

1.2.7 Concentration

The concentration of the water-soluble polymer compound in the polishing liquid composition is preferably 0.0001 to 3.0% by weight in terms of solid content, more preferably 0.0005 to 2.0% by weight, and still more preferably 0.001 to 1.0% by weight. When the concentration of the water-soluble polymer compound is less than 0.0001% by weight, the water-soluble high score cannot be obtained sufficiently The effect of the addition of the sub-compounds, when the concentration of the water-soluble polymer compound is greater than 3.0% by weight, the effect of the water-soluble polymer compound is saturated, and the water-soluble polymer compound is added in more than necessary amount, which is very uneconomical.

1.3 Acid and/or its salt

The acid and/or its salt can be used to adjust the pH of the polishing liquid composition or as an optional component. Examples of the acid and/or its salts used include inorganic acids and/or their salts, and organic acids and/or their salts.

Examples of inorganic acids and/or salts thereof include inorganic acids and/or salts thereof such as nitric acid, sulfuric acid, hydrochloric acid, phosphoric acid, phosphonic acid, pyrophosphoric acid, and tripolyphosphoric acid.

Examples of organic acids and/or their salts include aminocarboxylic acids such as glutamic acid and aspartic acid and/or their salts, citric acid, tartaric acid, oxalic acid, nitroacetic acid, maleic acid, malic acid, succinic acid and other carbonic acids And/or its salt, organic phosphonic acid and/or its salt. One kind or two or more kinds of these acids and/or their salts can be used.

The organic phosphonic acid and/or its salt may be selected from 2-aminoethylphosphonic acid, 1-hydroxyethylene-1,1-diphosphonic acid, aminotri(methylenephosphonic acid), ethylenediamine tetra (Methylene phosphonic acid), diethylene triamine penta (methylene phosphonic acid), ethane-1,1-diphosphonic acid, ethane-1,1,2-triphosphonic acid, ethane- 1-hydroxy-1,1,2-triphosphoric acid, 1,2-dicarboxy-1,2-diphosphonic acid ethane, methane hydroxyphosphonic acid, 2-phosphonobutane-1,2-dicarboxylic acid, One or more compounds of 1-phosphinopentane-2,3,4-tricarboxylic acid, α-methylphosphonic acid succinic acid and its salts.

Combining two or more of the above-mentioned compounds to use is also a preferred embodiment of the present invention. Specifically, the combination of sulfuric acid and/or its salt, organic phosphonic acid and/or its salt, and phosphoric acid and/or The combination of its salt and organic phosphonic acid and/or its salt.

1.4 Oxidizer

The polishing liquid composition of the present invention may also contain an oxidizing agent as a polishing accelerator. Oxidizer can be listed Examples include peroxides, permanganic acid and its salts, chromic acid and its salts, peroxyacids and their salts, halogen oxyacids and their salts, oxyacids and their salts, or two or more of these oxidants may be mixed.

Specifically, examples include hydrogen peroxide, sodium peroxide, barium peroxide, potassium peroxide, potassium permanganate, metal salts of chromic acid, metal salts of dichromic acid, persulfuric acid, sodium persulfate, and persulfuric acid. Potassium, ammonium persulfate, calcium superphosphate, sodium perborate, ferric acid, peracetic acid, hypochlorous acid, sodium hypochlorite, calcium hypochlorite, etc. Among them, hydrogen peroxide, persulfuric acid and its salts, hypochlorous acid and its salts are preferred, and hydrogen peroxide is more preferred.

The content of the oxidizing agent in the polishing liquid composition is preferably 0.01 to 10.0% by weight, and more preferably 0.1 to 5.0% by weight. Here, the polishing liquid composition of the present invention may also contain a buffer, an anti-mold agent, an antibacterial agent, etc. in addition to the above-mentioned components.

1.5 Physical properties

The pH value at 25°C (hereinafter referred to as "pH value (25°C)") of the polishing liquid composition of the present invention is preferably 0.1 to 4.0, more preferably 0.5 to 3.0. By making the pH value (25°C) of the polishing liquid composition 0.1 or more, the deterioration of the surface smoothness can be prevented. By making the pH value (25°C) of the polishing liquid composition 4.0 or less, it is possible to prevent the polishing speed from decreasing. In electroless nickel-phosphorus electroplating, nickel tends to dissolve under the condition of a pH (25°C) of 4.0 or less, so electroplating is difficult. On the other hand, in polishing, nickel tends to dissolve under conditions such as a pH (25°C) of 4.0 or less. Therefore, the polishing speed can be increased by using the polishing liquid composition of the present invention.

2. Polishing method of disk substrate

The polishing method of the magnetic disk substrate of the present invention is suitable for the aluminum alloy magnetic disk substrate (hereinafter referred to as "aluminum disk") or the glass magnetic disk substrate on which the surface of the aluminum alloy substrate is electroless nickel-phosphorus plating. polishing. In particular, the polishing method of the magnetic disk substrate of the present invention adopts the repeated repetition of the magnetic disk substrate. The multi-stage polishing method of the secondary polishing process is suitable for the polishing of magnetic disk substrates such as aluminum disks that use the relevant polishing liquid composition in the final polishing process of the magnetic disk substrate.

The polishing method in which the polishing liquid composition of the present invention can be applied includes, for example, attaching a polishing pad to a fixed disk of a polishing machine, and supplying the polishing liquid composition to the surface of an object to be polished (such as an aluminum disk) or polishing On the pad, a method of rubbing the surface to be polished with a polishing pad (called sanding). For example, when polishing the front and back surfaces of the aluminum disc at the same time, a double-sided polishing machine can be used to connect a polishing pad to the upper fixed disc and the lower fixed disc. In this method, the polishing liquid composition is supplied between the polishing pads connected to the upper fixed disk and the lower fixed disk, and the two polishing pads rotate at the same time to polish the front and rear surfaces of the aluminum disk. The polishing pad may be polyurethane type, suede type, non-woven fabric type or any other type.

[Example]

Hereinafter, the present invention will be specifically described based on embodiments, but the present invention is not limited to these embodiments, and can be implemented in various ways within the technical field of the present invention.

In the polishing of the following examples and comparative examples, an electroless nickel-phosphorus electroplated aluminum alloy substrate (hereinafter referred to as "substrate") that has been rough-polished in advance is prepared, and the first to 900th final polishing is applied continuously (final polishing). Tables 2 to 4 show the evaluation results of the polishing speed, long-wavelength waviness and halo on the surface of the substrate for the 20th, 300th, and final 900th substrates of the continuous final polishing. , And compared the transition of polishing speed, long-wavelength ripple and halo in the final polishing process in each embodiment and comparative example. The following is a specific description.

(Preparation method of polishing liquid composition)

The polishing liquid compositions used in Examples 1 to 16 and Comparative Examples 1 to 6 are polishing liquid compositions containing the materials shown in Table 1 in the contents described in Table 1. Tables 2 to 4 show the polishing after polishing test using these polishing liquid compositions.

Table 1

In all the examples and comparative examples, the total silica concentration in the polishing composition is 4.0% by weight.

HEDP: Hydroxyethylene diphosphine

Copolymerization type of water-soluble polymer compound:

A: A copolymer containing monomers with carboxylic acid groups and monomers with amino groups as essential monomers

B: A copolymer containing monomers with carboxylic acid groups and monomers with sulfonic acid groups as essential monomers

C: A copolymer containing monomers with carboxylic acid groups, monomers with amino groups, and monomers with sulfonic acid groups as essential monomers

AA: Acrylic

TBAA: N-tert-butyl acrylamide

ATBS: 2-propenamide-2-methyl propane sulfonic acid

(Weight average molecular weight of water-soluble polymer compound)

The weight average molecular weight of the water-soluble polymer compound is measured by the conversion of polyacrylic acid by gel chromatography (GPC). The following are the measurement conditions for GPC.

GPC conditions

Column: TSKgel G4000PWXL(Tosoh)+G2500PWXL(Tosoh)+SHODEX OHpak SB-806M-HQ (Showa Denko)

Eluent: 0.2M phosphate buffer/acetonitrile = 9/1 (volume ratio).

Flow rate: 1.0mL/min

Temperature: 40℃

Detection: refractive index difference (RI)

Sample: 0.1wt% concentration (injection volume 100 μ L).

Polymer for calibration curve: polyacrylic acid molecular weight (Mp) 115,000, 28,000, 4,100, 4,100.

1250 (Sowa Kagaku Corporation, American Polymer Standards Corporation)

(Method for measuring the particle size of silicon dioxide particles)

In order to measure the particle size (Heywood diameter) of colloidal silica, a transmission electron microscope (TEM) (manufactured by JEOL Co., Ltd., transmission electron microscope JEM2000FX (200kV)) was used to take a picture with a magnification of 100,000 times and use it Analysis software (manufactured by Mountech, Mac-View Ver.4.0) analyzes the data to measure the diameter of the Heywood (equivalent to the diameter of the projected area circle). The average primary particle size of colloidal silica is the average primary particle size of about 2000 colloidal silicas analyzed using the above method, and measured from the small particle size using the above analysis software (manufactured by Mountech Corporation, Mac-View Ver.4.0) Cumulative particle size distribution (cumulative volume standard) is the average primary particle size (D50) calculated from 50% of the particle size.

(Method for measuring the Al content of colloidal silica)

The Al content of colloidal silica is to completely dissolve the solid content after drying the dispersion containing colloidal silica, and use the ICP emission spectrum analyzer to measure the Al content of the solid content of colloidal silica.

(Polishing conditions)

A 95mm outer diameter aluminum alloy magnetic disk substrate (substrate) that has been roughly polished and formed with an electroless nickel-phosphorus electroplating film is used as a polished object to be polished multiple times.

Polishing machine: 9B double-sided polishing machine produced by SpeedFam Co., Ltd.

Polishing pad: P-2 polishing pad produced by FILWEL Co., Ltd.

Fixing plate rotation speed: upper fixing plate -8.3 per minute

25.0 per minute

Supply amount of polishing liquid composition: 50 ml/min

Polishing time: 300 seconds

Processing pressure: 14kPa

After mixing the components to prepare a polishing liquid composition, it was put into a polishing machine through a filter with a mesh of 0.45 μm to perform a polishing test. Among them, the polishing test was performed for the polishing speed, long-wavelength waviness, and halo of the 20th, 300th, and 900th polishing.

<Evaluation of polishing disc surface>

(Polishing speed ratio)

The polishing speed is a measurement of the reduced mass of the aluminum alloy magnetic disk substrate after polishing, and the calculation is based on the following formula.

Polishing speed (mg/min) = reduced mass of aluminum alloy disk substrate (mg)/polishing time (min).

The polishing rate ratio is a relative value when the polishing rate calculated by the above formula after the 20th polishing of the substrate in the comparative example is set to 1 (reference). In Table 2, the value when the substrate of Comparative Example 1 was polished for the 20th time was 1; in Table 3, the value was 1 when the substrate of Comparative Example 3 was polished for the 20th time; and in Table 4, the value was 1 when the substrate of Comparative Example 5 was polished for the 20th time. The value at the time of the second polishing is 1.

(Evaluation method of long-wavelength ripple on the surface of the substrate after polishing)

A 3D optical profiler New View 8300 manufactured by AMETEK Co., Ltd. was used to measure the long-wavelength waviness of the substrate.

The measurement conditions are as follows:

Lens 1.4 times ZWF type

ZOOM 2.0 times

Measurement type surface

Measurement mode CSI

Scan length 5 μ m

Camera mode 1024×1024

Filter band pass short wave 500.000 μ m

Long wave 1000.000 μ m

Measuring point

Radius 30.00 mm

Angle 12 points every 30°

The long-wavelength waviness ratio is a relative value when the polishing rate obtained by the above formula after the 20th polishing of the substrate in the comparative example is set to 1 (reference). In Table 2, the value when the substrate of Comparative Example 1 was polished for the 20th time was 1; in Table 3, the value was 1 when the substrate of Comparative Example 3 was polished for the 20th time; and in Table 4, the value was 1 when the substrate of Comparative Example 5 was polished for the 20th time. The value at the time of the second polishing is 1.

(Evaluation method of halo on substrate surface after polishing)

The halo was measured using a full-surface defect inspection machine NS2000H manufactured by Hitachi High-Tech Fine Systems Co., Ltd., and the measurement conditions are as follows:

<Measurement conditions>

PMT/APD power supply control voltage

Hi-Light 1 OFF

Hi-Light 2 821V

Scanning pitch 3 μ m

The inner/outer radius is 18.0000-47.0000mm.

Positive potential 77mV

H2 white point level 80.0mV

The halo is quantitatively evaluated by detecting the micro-defects on the surface of the substrate as halo counts under the above-mentioned inspection conditions.

(Halo ratio)

The polishing speed ratio is a relative value when the halo count calculated by the above formula after the 20th polishing of the substrate in the comparative example is set to 1 (reference). In Table 2, the value when the substrate of Comparative Example 1 was polished for the 20th time was 1; in Table 3, the value was 1 when the substrate of Comparative Example 3 was polished for the 20th time; and in Table 4, the value was 1 when the substrate of Comparative Example 5 was polished for the 20th time. The value at the time of the second polishing is 1.

Table 2

In all the examples and comparative examples, the total silica concentration in the polishing composition is 4.0% by weight

AA: Acrylic

TBAA: N-tert-butyl acrylamide

ATBS: 2-propenamide-2-methyl propane sulfonic acid

table 3

In all the examples and comparative examples, the total silica concentration of the polishing composition is 4.0% by weight

AA: Acrylic

TBAA: N-tert-butyl acrylamide

ATBS: 2-propenamide-2-methyl propane sulfonic acid

Table 4

In all the examples and comparative examples, the total silica concentration in the polishing composition is 4.0% by weight

AA: Acrylic

TBAA: N-tert-butyl acrylamide

ATBS: 2-propenamide-2-methyl propane sulfonic acid

<Result review>

From the comparison of Example 1 and Comparative Example 1 in Table 2, it can be seen that by using a colloid containing silica particles with an Al content of 100 mg/kg or less in solids or silica particles synthesized from metallic silicon Silicon dioxide can prevent the polishing speed from decreasing under repeated polishing, and improve long-wavelength ripples and halos.

Example 2 is an example in which the mass ratio of silicon dioxide particles with an Al content of 100 mg/kg or less in the solid or silicon dioxide particles synthesized from metallic silicon as a raw material is greater than that of Example 1, but the comparative example at this time 2 Compared with Comparative Example 1, a better balance of polishing speed, long-wavelength ripple and halo can be obtained. Similarly, the comparison between Example 3 and Comparative Example 2 in which the D50 of the entire colloidal silica is different is also the same.

From the comparison of Example 4 and Comparative Example 3 in Table 3, even if the polishing liquid composition has an acrylic homopolymer, it uses silicon dioxide particles with a solid Al content of 100 mg/kg or less or uses metallic silicon as a raw material. The colloidal silica of the synthesized silica particles can still prevent the reduction of the polishing speed during multiple polishing, and can improve the long-wavelength ripple and halo.

Example 5 is an experimental example that contains more silicon dioxide particles with an Al content of 100 mg/kg or less in solids and silicon dioxide particles synthesized from metallic silicon as compared to Example 4. From this experimental example, it can be seen that compared to the comparison Example 3 has an excellent balance of polishing speed, long-wavelength moire and halo. Similarly, the comparison between Example 6 and Comparative Example 4 in which the D50 of the entire colloidal silica is different also shows similar results.

In the comparison between Example 7 of Table 4 and Comparative Example 5, even if the polishing liquid composition contains acrylic acid/N-tert-butyl acrylamide copolymer, the use of silica particles with an Al content of 100 mg/kg or less in the solid is used. Or colloidal dioxide of silica particles synthesized from metallic silicon Silicon can still prevent the polishing speed from slowing down during multiple polishing, and can improve long-wavelength waviness and halo.

The comparison between Example 1 and Example 4, as well as the comparison between Example 4 and Example 7, can be seen that making the polishing liquid composition contain acrylic homopolymer, or further make it contain acrylic copolymer, can prevent The polishing speed decreases during multiple polishing processes.

Examples 8, 9, and 10 increase the weight ratio of silica particles with an Al content of less than 100 mg/kg in the solid in Example 7 or silica particles synthesized from metallic silicon as a raw material to the total colloidal silica. However, in these experimental examples, the polishing speed during multiple polishing processes can be increased, and long-wavelength ripples and halos can be further improved.

Examples 11 and 12 are experimental examples for increasing the weight average molecular weight of the water-soluble polymer compound in Example 7, and Examples 13 and 14 are experimental examples for increasing the weight average molecular weight of the water-soluble polymer compound in Example 10.

The comparison between Example 12 and Comparative Example 6 shows that even if the weight average molecular weight of the water-soluble polymer compound in the polishing liquid composition is increased, the use of silicon dioxide particles having an Al content of 100 mg/kg or less in the solid is used. The colloidal silicon dioxide of silicon dioxide particles synthesized from metallic silicon can prevent the polishing speed from slowing during multiple polishing processes, and can improve long-wavelength ripples and halos.

Example 15 is to replace the water-soluble polymer compound in the polishing liquid composition in Example 7 from acrylic acid/N-tert-butyl acrylamide copolymer to acrylic acid/2-acrylamide-2-methylpropanesulfonic acid Experimental example of copolymer.

Example 16 is to replace the water-soluble polymer compound in the polishing liquid composition in Example 7 from acrylic acid/N-tert-butyl acrylamide copolymer to acrylic acid/N-tert-butyl acrylamide/2-acrylamide Experimental example of amine-2-methylpropane sulfonic acid copolymer.

In summary, by using the polishing liquid composition of the present invention, the polishing speed can be prevented from being reduced during multiple polishing processes, and long-wavelength ripples and halos can be improved.

[Industrial Utilization]

The polishing liquid composition of the present invention can be used to polish electronic products such as magnetic recording media such as semiconductors and hard disks. In particular, it can be used to polish the surface of magnetic recording media substrates such as glass disks and aluminum disks. Furthermore, it can be used for the surface polishing of the aluminum alloy substrate surface for the magnetic recording medium on which the electroless nickel-phosphorus plating film is formed on the aluminum alloy substrate surface.

Claims (13)

A polishing liquid composition for magnetic disk substrates, comprising: Colloidal silica with an average primary particle size of 1~100nm; and water; The colloidal silica includes at least 3% by weight or more of silica particles with an Al content of 100 mg/kg or less in solids. A polishing liquid composition for magnetic disk substrates, comprising: Colloidal silica with an average primary particle size of 1~100nm; and water; Wherein, the colloidal silica contains at least 3% by weight or more of silica particles synthesized using metallic silicon as a raw material. The polishing liquid composition for a magnetic disk substrate according to claim 2, wherein the colloidal silica contains at least 10% by weight or more of silica particles synthesized using the metallic silicon as a raw material. For example, the polishing liquid composition for a magnetic disk substrate of any one of claims 1 to 3 further contains a water-soluble polymer compound. The polishing liquid composition for a magnetic disk substrate according to claim 4, wherein the water-soluble polymer compound is a copolymer of a monomer having a carboxylic acid group and a monomer having an amino group as essential monomers, and a weight average molecular weight It is 1,000~1,000,000. The polishing liquid composition for a magnetic disk substrate according to claim 4, wherein the water-soluble polymer compound is a copolymer of a monomer having a carboxylic acid group and a monomer having a sulfonic acid group as essential monomers, and the weight is average The molecular weight is 1,000 to 1,000,000. The polishing liquid composition for a magnetic disk substrate according to claim 4, wherein the water-soluble high score The sub-compounds are copolymers with monomers having carboxylic acid groups, monomers having amide groups, and monomers having sulfonic acid groups as essential monomers, and have a weight average molecular weight of 1,000 to 1,000,000. The polishing liquid composition for a magnetic disk substrate according to any one of claims 5 to 7, wherein the single system having a carboxylic acid group is selected from monomers of acrylic acid and its salts or methacrylate and its salts. According to claim 5-7, the polishing liquid composition for magnetic disk substrates, wherein the single system having an amino group is selected from the group consisting of acrylamide, methacrylamide, N-alkyl acrylamide and N-methyl One or two or more monomers of alkyl acrylate. The polishing liquid composition for a magnetic disk substrate according to any one of claim 6 or 7, wherein the single system having a sulfonic acid group is selected from isoprene sulfonic acid, 2-propenylamine-2-methyl Propanesulfonic acid, 2-methylamide-2-methylpropanesulfonic acid, styrenesulfonic acid, vinylsulfonic acid, allylsulfonic acid, isopentansulfonic acid, vinyl naphthalenesulfonic acid and their salts Class monomer. According to any one of claims 1 to 10, the polishing liquid composition for a magnetic disk substrate further contains acid and/or its salt, and has a pH in the range of 0.1 to 4.0 at 25°C. According to any one of claims 1 to 11, the polishing liquid composition for a magnetic disk substrate further contains an oxidizing agent. A method for polishing a magnetic disk substrate using the polishing liquid composition for a magnetic disk substrate as in any one of Claims 1 to 12, and a magnetic disk substrate with a nickel-phosphorus coating formed on the surface of the aluminum alloy substrate as the polishing object , And adopts a multi-stage polishing method that repeats the polishing process for the magnetic disk substrate multiple times, and uses the polishing liquid composition for the magnetic disk substrate in the final polishing process of the magnetic disk substrate.