TW202138500A - Polishing composition for magnetic disk substrate - Google Patents

Abstract

The present invention provides a polishing composition for a magnetic disk substrate capable of reducing waviness and halation of the substrate after polishing without lowering productivity. The polishing composition for magnetic disk substrate contains colloidal silica, a water-soluble polymer compound, an acid and water. The water-soluble polymer compound is a copolymer using a monomer having a carboxylic acid group, a monomer selected from a N-alkyl acrylamide or a N-alkyl methacrylamide, a monomer selected from an acrylamide or a methacrylamide and a monomer having a sulfonic acid group as essential monomers.

Description

Abrasive composition for magnetic disk substrate

The present invention relates to an abrasive composition for magnetic disk substrates used for polishing electronic parts such as magnetic recording media such as semiconductors and hard disks. In particular, it relates to an abrasive composition used for surface polishing of substrates for magnetic recording media such as glass disk substrates or aluminum disk substrates. Furthermore, it relates to an abrasive composition used to form electroless nickel on the surface of aluminum alloy substrates. -An abrasive composition for a magnetic disk substrate for polishing the surface of an aluminum magnetic disk substrate for a magnetic recording medium of a phosphorus-coated thin film.

In the past, in order to increase the magnetic recording density, it has been desired to improve various polishing characteristics of the abrasive composition for a magnetic disk substrate for polishing the surface of the electroless nickel-phosphorus plating film of the aluminum magnetic disk substrate. For example, due to scratches, the scratched part may be a cause of writing errors and reading errors, or the burrs generated around the scratched part may be a cause of a head collision.

Therefore, for the purpose of reducing scratches, colloidal silica is mainly used in the polishing of aluminum magnetic disk substrates as the abrasive grain portion for mechanical polishing in the abrasive composition for magnetic disk substrates. In this case, in industrial polishing, the abrasive grain portion for mechanical polishing and the chemical component for chemical polishing in the abrasive composition for magnetic disk substrates are mostly mixed and used just before the actual polishing.

However, if colloidal silica, which is part of the abrasive grains, is mixed with chemical components, colloidal silica generally tends to agglomerate. As a countermeasure to this phenomenon, for example, the following proposals have been made: try to remove coarse particles or aggregated particles, or adjust the shape of particles, Or adjust the corrosiveness of the abrasive (Patent Document 1); try to adjust the shape of the particles (Patent Document 2); try to adjust the content of agglomerated particles (Patent Document 3); and try to suppress colloidal silica by adding specific copolymers To improve the surface condition of the substrate after polishing (Patent Document 4).

[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 Application Publication No. 2019-79583

Furthermore, from the viewpoint of increasing the magnetic recording density, in addition to reducing scratches, "reduction of halation" and "reduction of fluctuations" are also required. Here, the so-called halo refers to the fine defects on the substrate surface that can be detected under specific inspection conditions using a substrate full-surface defect inspection machine (Hitachi High-Tech Fine Systems NS2000H), which can be measured as a halation count (halation count). ) Perform quantitative evaluation. In addition, the details of the substrate full-surface defect inspection machine are described below.

It is believed that "halo" is a phenomenon caused by the existence of a small unevenness of the substrate surface in a large area of the substrate. It is generally believed that the cause is the respective characteristics of the polishing pad, carrier, substrate, and polishing agent composition. Caused by inconsistent characteristics. Especially in recent years, the existence of halo has become a major factor hindering the improvement of magnetic recording density and has become a new problem, and it is urgent to seek to reduce this halo.

On the other hand, with regard to "fluctuations", it has conventionally been required to reduce the average value of the fluctuations of the entire substrate surface. Furthermore, from the center of the substrate surface to the outer periphery, there are also average values and The tendency of unevenness to increase, which becomes a major cause hindering the increase in magnetic recording density and causes problems.

In contrast to this, for example, Patent Document 4 proposes to improve the undulation and halo of the substrate surface after polishing by adding a specific copolymer. However, in terms of the balance with the polishing speed, it is required to further improve these properties.

Therefore, the present invention was completed in view of the above-mentioned actual situation, and the problem is to provide an abrasive composition for a magnetic disk substrate, which does not reduce productivity and can reduce both the undulation and halo of the substrate after polishing.

In order to solve the above-mentioned problems, as a result of intensive research conducted by the applicant, by using the abrasive composition for magnetic disk substrates shown below, the productivity is not affected, and the reduction of undulations and halos can be achieved, thus achieving the invention.

[1] An abrasive composition for a magnetic disk substrate, comprising colloidal silica, a water-soluble polymer compound, an acid and water, wherein the water-soluble polymer compound is a monomer having a carboxylic acid group, from an N-alkyl group A copolymer in which a monomer selected from acrylamide or N-alkyl methacrylamide, a monomer selected from acrylamide or methacrylamide, and a monomer having a sulfonic acid group are necessary monomers.

[2] The abrasive composition for a magnetic disk substrate according to the above [1], wherein the acid is a phosphorus-containing inorganic acid and/or a phosphorus-containing organic acid.

[3] The abrasive composition for magnetic disk substrates according to [1] or [2] above, wherein the water-soluble polymer compound has a ratio of structural units derived from monomers having carboxylic acid groups of 50 to 95 mol% The ratio of the constituent units derived from monomers selected from N-alkyl acrylamide or N-alkyl methacrylamide is in the range of 5-40 mol%, derived from acrylamide or methyl The ratio of the constituent units of the monomer selected in the acrylamide is in the range of 0.3 to 10 mol%, and the ratio of the constituent unit derived from the monomer having a sulfonic acid group is in the range of 0.01 to 20 mol%.

[4] The abrasive composition for a magnetic disk substrate according to any one of the above [1] to [3], wherein the single system having a carboxylic acid group is selected from acrylic acid or its salt, and methacrylic acid or its salt The monomer.

[5] The abrasive composition for a magnetic disk substrate according to any one of the above [1] to [4], wherein the single system having a sulfonic acid group is selected from isoprene sulfonic acid and 2-acrylamide -2-methyl propane sulfonic acid, 2-methacrylamide-2-methyl propane sulfonic acid, styrene sulfonic acid, vinyl sulfonic acid, allyl sulfonic acid, isopenten sulfonic acid, naphthalene sulfonic acid and Monomers of these salts.

[6] The abrasive composition for a magnetic disk substrate according to the above [2], wherein the phosphorus-containing inorganic acid is selected from at least the group consisting of phosphoric acid, phosphonic acid, phosphinic acid, pyrophosphoric acid and tripolyphosphoric acid More than one compound.

[7] The abrasive composition for a magnetic disk substrate according to the above [2], wherein the phosphorus-containing organic acid is selected from 2-aminoethylphosphonic acid and 1-hydroxyethylene-1,1-diphosphine Acid, amino tris (methylene phosphonic acid), ethylene diamine 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-triphosphonic acid, ethane-1,2-dicarboxy-1,2-diphosphonic acid, methane hydroxyl Phosphonic acid, 2-phosphonobutane-1,2-dicarboxylic acid, 1-phosphonobutane-2,3,4-tricarboxylic acid and α-methylphosphonosuccinic acid At least one compound of the group.

[8] The abrasive composition for a magnetic disk substrate according to any one of [1] to [7] above, wherein the abrasive composition further contains an oxidizing agent.

[9] The abrasive composition for a magnetic disk substrate according to any one of the above [1] to [8], which is used for polishing an aluminum magnetic disk substrate plated with electroless nickel-phosphorus.

The abrasive composition for magnetic disk substrates of the present invention avoids affecting productivity by increasing the polishing speed, and can reduce the fluctuation and halo after polishing.

Hereinafter, an embodiment of the abrasive composition for a magnetic disk substrate of the present invention will be described. In addition, the abrasive composition for a magnetic disk substrate of the present invention is not limited to the following embodiments, and can be changed, modified, and improved as long as it does not deviate from the scope of the invention.

1. Abrasive composition for magnetic disk substrate

The abrasive composition for magnetic disk substrates (hereinafter referred to as "abrasive composition") according to an embodiment of the present invention includes colloidal silica, a water-soluble polymer compound, acid, and water. Each configuration is described in detail below.

1.1 Colloidal silica

The colloidal silica contained in the abrasive composition of this embodiment preferably has an average particle size (D50) of 1-100 nm, and more preferably 3-80 nm.

The shape of colloidal silica is known as a spherical shape, a kimping sugar type (a granular shape with protrusions on the surface), an irregular shape, and the like, and its primary particles are monodispersed 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 of the substrate after polishing can be further improved.

The manufacturing methods of colloidal silica include the water glass method, the alkoxysilane method, and the method of synthesizing silicon dioxide particles by reacting metallic silicon with water in the presence of an alkali catalyst; the water glass method is based on sodium silicate, Alkali metal silicate such as potassium silicate is used as a raw material, and the raw material undergoes a condensation reaction in an aqueous solution to grow particles; the alkoxysilane method uses tetraalkoxysilane such as tetraethoxysilane as the raw material to make the raw material In water containing a water-soluble organic solvent such as alcohol, a condensation reaction proceeds by hydrolysis under acid or alkali to grow particles.

It is known that colloidal silica has spherical, chain-like, and golden sugar type (grains with convex parts on the surface). Shapes), irregular shapes, etc., the primary particles are monodispersed in water to form a gel. The colloidal silica used in the present invention is preferably spherical or nearly spherical colloidal silica.

The concentration of colloidal silica in the abrasive composition is preferably 1-50% by mass. More preferably, it is 2-40% by mass.

1.2 Water-soluble polymer compounds

The water-soluble polymer compound used in the present invention is a monomer having a carboxylic acid group, a monomer selected from N-alkyl acrylamide or N-alkyl methacrylamide, and a monomer selected from acrylamide or methyl acrylate. The monomer selected from the acrylamide and the monomer having a sulfonic acid group are copolymers of essential monomers.

1.2.1 Monomers with carboxylic acid groups

As the monomer having a carboxylic acid group, an unsaturated aliphatic carboxylic acid and its salt are preferably used. Specifically, acrylic acid, methacrylic acid, maleic acid, itaconic acid, and these salts can be cited. Examples of the salt include sodium salt, potassium salt, magnesium salt, ammonium salt, amine salt, and alkylammonium salt.

1.2.2 A monomer selected from N-alkyl acrylamide or N-alkyl methacrylamide

As specific examples of the monomer selected from N-alkyl acrylamide or N-alkyl methacrylamide, N-methacrylamide, N-ethacrylamide, N-normal Propyl acrylamide, N-isopropyl acrylamide, N-n-butyl acrylamide, N-isobutyl acrylamide, N-second butyl acrylamide, N-tertiary butyl propylene Amide, N-methylmethacrylamide, N-ethylmethacrylamide, N-propylmethacrylamide, N-isopropylmethacrylamide, N-n-butylmethyl Acrylic amide, N-isobutyl methacrylamide, N-secondary butyl methacrylamide, N-tertiary butyl methacrylamide, etc.

1.2.3 Monomers with sulfonic acid groups

Specific examples of the monomer having a sulfonic acid group include: isoprene sulfonic acid, 2-propenamide-2-methylpropanesulfonic acid, 2-methacrylamide-2-methylpropanesulfonate Acid, styrene sulfonic acid, vinyl sulfonate Acid, allyl sulfonic acid, isoamylene sulfonic acid, naphthalene sulfonic acid and their salts, etc. Preferable examples include 2-acrylamide-2-methylpropanesulfonic acid, 2-methacrylamide-2-methylpropanesulfonic acid, and their salts.

1.2.4 Copolymer

The water-soluble polymer compound contained in the abrasive composition of the present invention is based on the above-mentioned monomer having a carboxylic acid group, a monomer selected from N-alkylacrylamide or N-alkylmethacrylamide, A copolymer composed of monomers selected from acrylamide or methacrylamide and monomers having sulfonic acid groups as essential monomers.

The ratio of the constituent unit derived from the monomer having a carboxylic acid group in the copolymer is preferably 50 to 95 mol%, more preferably 60 to 93 mol%, and still more preferably 70 to 90 mol%.

The proportion of constituent units derived from monomers selected from N-alkyl acrylamide or N-alkyl methacrylamide in the copolymer is preferably 5-40 mol%, more preferably 6-35 mol %, more preferably 7~30mol%.

The proportion of constituent units derived from monomers selected from acrylamide or methacrylamide in the copolymer is preferably 0.3-10 mol%, more preferably 0.6-9 mol%, and still more preferably 1.0-8 mol %.

The ratio of the constituent unit derived from the monomer having a sulfonic acid group in the copolymer is preferably 0.01-20 mol%, more preferably 0.1-10 mol%, and still more preferably 0.2-5 mol%.

Among the water-soluble polymer compounds, structural units derived from monomers having carboxylic acid groups and structural units derived from monomers having sulfonic acid groups are present in an acid state or in a salt state. The ratio is large and can be evaluated by the pH value of the water-soluble polymer compound. That is, when there is a large proportion of acid, the pH value becomes low, and when there is a large proportion as salt, the pH value becomes high. In the abrasive composition of the present invention, for example, a water-soluble polymer compound having a pH value (25° C.) in the range of 0.1 to 13.0 in an aqueous solution of a water-soluble polymer compound with a concentration of 10% by mass can be used.

1.2.5 Manufacturing methods of water-soluble polymer compounds

The production method of the water-soluble polymer compound is not particularly limited. For example, it is preferably produced by an aqueous solution polymerization method. According to this aqueous solution polymerization method, a water-soluble polymer compound that forms a uniform solution can be obtained.

As the polymerization solvent in the aforementioned aqueous polymerization method, an aqueous solvent is preferred, and water is particularly preferred. In addition, in order to improve the solubility of the above-mentioned monomer components in solvents, an organic solvent may be appropriately added to the polymerization of each monomer within a range that does not cause adverse effects. As said organic solvent, alcohols, such as isopropanol, and ketones, such as acetone, are mentioned. These can be used individually by 1 type or in combination of 2 or more types.

Hereinafter, the production method of the water-soluble polymer compound using the above-mentioned aqueous solvent will be explained. A conventional polymerization initiator can be used for the polymerization reaction, but it is particularly preferable to use a radical polymerization initiator.

Examples of radical polymerization initiators include persulfates such as sodium persulfate, potassium persulfate, and ammonium persulfate, hydroperoxides such as tertiary butyl hydroperoxide, and water-soluble solutions such as hydrogen peroxide. Peroxides, ketone peroxides such as methyl ethyl ketone peroxide and cyclohexanone peroxide, dialkyl peroxides such as di(tertiary butyl) peroxide and tertiary butyl cumyl peroxide Azo compounds such as oil-soluble peroxides such as azobisisobutyronitrile and 2,2-azobis(2-methylpropionamidine) dihydroxide. These peroxide-based radical polymerization initiators may be used alone or in combination of two or more kinds.

Among the above-mentioned peroxide-based radical polymerization initiators, from the viewpoint of easy control of the molecular weight of the water-soluble polymer compound produced, persulfate or azo compound is preferred, and azobisisobutyl is particularly preferred. Nitrile.

The amount of the radical polymerization initiator used is not particularly limited, and it is preferably used in a ratio of 0.1 to 15% by mass, particularly 0.5 to 10% by mass, based on the total mass of all monomers of the water-soluble polymer compound. By making the ratio 0.1% by mass or more, the copolymerization can be improved By setting the ratio to 15% by mass or less, the stability of the water-soluble polymer compound can be improved.

In addition, depending on the circumstances, the water-soluble polymer compound may also be produced using a water-soluble redox-based polymerization initiator. Examples of the redox polymerization initiator include a combination of an oxidizing agent (for example, the above-mentioned peroxide) and a reducing agent such as sodium bisulfite, ammonium bisulfite, ammonium sulfite, sodium hyposulfite, or iron alum, potassium alum, and the like.

In the production of a water-soluble polymer compound, a chain transfer agent may be appropriately added to the polymerization system to adjust the molecular weight. Examples of chain transfer agents include sodium phosphite, sodium hypophosphite, potassium hypophosphite, sodium sulfite, sodium bisulfite, thioacetic acid, mercaptopropionic acid, thioglycolic acid, 2-propanethiol, 2-mercaptoethanol, and Thiophenol and so on.

The polymerization temperature in the production of the water-soluble polymer compound is not particularly limited, but the polymerization temperature is preferably 60 to 100°C. By setting the polymerization temperature to 60°C or higher, the polymerization reaction progresses smoothly and the productivity is excellent, and by setting it to 100°C or lower, coloring can be suppressed. In addition, the polymerization reaction can also be carried out under pressure or reduced pressure, but the installation of equipment for the pressure or reduced pressure reaction requires cost, so it is preferably carried out under normal pressure. The polymerization time is preferably 2 to 20 hours, especially 3 to 10 hours.

After the polymerization reaction, it is neutralized with a basic compound as required. Examples of the basic compound used for neutralization include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, alkaline earth metal hydroxides such as calcium hydroxide and magnesium hydroxide, ammonia, monoethanolamine, and diethanolamine. Organic amines such as ethanolamine and triethanolamine.

In the case of an aqueous solution with a water-soluble polymer compound concentration of 10% by mass, the neutralized pH value (25° C.) is preferably 2-9, more preferably 3-8.

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. In addition, the weight average molecular weight of water-soluble polymer compounds is measured by gel permeation chromatography (GPC) in terms of polyacrylic acid conversion. quantity. When the weight average molecular weight of the water-soluble polymer compound is less than 1,000, the undulation after polishing becomes worse. Moreover, when it exceeds 1,000,000, the viscosity of the aqueous solution becomes high and it becomes difficult to handle.

1.2.7 Concentration

The concentration of the water-soluble polymer compound in the abrasive composition is preferably 0.0001 to 3.0% by mass in terms of solid content, more preferably 0.0005 to 2.0% by mass, and still more preferably 0.001 to 1.0% by mass. When the concentration of the water-soluble polymer compound is less than 0.0001% by mass, the effect of adding the water-soluble polymer compound cannot be sufficiently obtained. When the concentration of the water-soluble polymer compound is more than 3.0% by mass, the effect of adding the water-soluble polymer compound tends to be flat. It is not economical to add excess water-soluble polymer compounds.

1.3 Acid

The abrasive composition of the present invention contains an acid. Examples of the acid include inorganic acids and organic acids. Among them, phosphorus-containing inorganic acids and/or phosphorus-containing organic acids are preferred.

As an inorganic acid, nitric acid, sulfuric acid, hydrochloric acid, etc. are mentioned. Examples of phosphorus-containing inorganic acids include phosphoric acid, phosphonic acid, phosphinic acid, pyrophosphoric acid, tripolyphosphoric acid, and the like.

Examples of organic acids include glutamic acid, aspartic acid, citric acid, tartaric acid, oxalic acid, nitroacetic acid, maleic acid, malic acid, succinic acid, and the like.

Examples of phosphorus-containing organic acids include those selected from the group consisting of 2-aminoethylphosphonic acid, 1-hydroxyethylene-1,1-diphosphonic acid, aminotri(methylenephosphonic acid), ethylenediamine tetra (Methylene phosphonic acid), ethylene triamine penta (methylene phosphonic acid), ethane-1,1-diphosphonic acid, ethane-1,1,2-triphosphonic acid, ethane-1 -Hydroxy-1,1,2-triphosphonic acid, ethane-1,2-dicarboxy-1,2-diphosphonic acid, methane hydroxyphosphonic acid, 2-phosphonobutane-1,2-dicarboxy At least one compound of acid, 1-phosphinobutane-2,3,4-tricarboxylic acid, and α-methylphosphinosuccinic acid.

Combining two or more of the above compounds is also a preferred embodiment, preferably a combination of a phosphorus-containing inorganic acid and a phosphorus-containing organic acid. Specifically, phosphoric acid and 1-hydroxyl A combination of ethylene-1,1-diphosphonic acid.

The concentration of the acid in the abrasive composition can be appropriately set according to the amount required for pH adjustment of the abrasive composition.

1.4 Oxidizer

The abrasive composition of the present invention may contain an oxidizing agent as a polishing accelerator. As the oxidizing agent, peroxide, permanganic acid or its salt, chromic acid or its salt, peroxy acid or its salt, halogen oxyacid or its salt, oxyacid or its salt, two or more of these oxidizing agents can be used Mixtures, etc.

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, persulfuric acid Potassium, ammonium persulfate, peroxyphosphoric acid, sodium peroxyborate, performic acid, peracetic acid, hypochlorous acid, sodium hypochlorite, calcium hypochlorite, etc. Among them, hydrogen peroxide, persulfuric acid and its salts, hypochlorous acid and its salts, etc. are preferred, and hydrogen peroxide is more preferred.

The content of the oxidizing agent in the abrasive composition is preferably 0.01 to 10.0% by mass. More preferably, it is 0.1 to 5.0% by mass.

In addition to the above-mentioned components, the abrasive composition of the present invention may also contain a buffer, an antifungal agent, an antibacterial agent, and the like.

1.5 Physical properties

The pH value (25°C) of the abrasive 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 agent composition 0.1 or more, the deterioration of the surface smoothness can be suppressed. By making the pH value (25°C) of the polishing agent composition 4.0 or less, it is possible to suppress the decrease in polishing rate. In electroless nickel-phosphorus plating, if the pH value (25° C.) is 4.0 or less, nickel tends to dissolve, making it difficult to perform plating. On the other hand, in polishing, for example, if the pH value (25°C) is 4.0 or less, nickel tends to dissolve. Therefore, the polishing rate can be increased by using the polishing composition of the present invention.

2. Grinding method of magnetic disk substrate

The abrasive composition of the present invention is suitable for polishing magnetic disk substrates such as electroless nickel-phosphorus-plated aluminum disk substrates (hereinafter referred to as "aluminum disks") or glass disk substrates. Especially suitable for grinding aluminum discs.

As a polishing method to which the abrasive composition of the present invention can be applied, there are, for example, attaching a polishing pad to the platen of a polishing machine, and supplying the polishing composition to the polishing surface or polishing pad of an object to be polished (for example, an aluminum disc) , The method of rubbing the surface with a polishing pad (called polishing).

For example, when grinding the front and back of an aluminum disc at the same time, there is a method of using a double-sided grinding machine to attach a polishing pad to the upper and lower plates. In this method, the abrasive composition is supplied between the polishing pads attached to the upper pressing plate and the lower pressing plate, and the two polishing pads are rotated at the same time, thereby grinding the front and back surfaces of the aluminum disc. The polishing pad can also be of urethane type, suede type, non-woven type, and any other types.

[Examples]

Hereinafter, the present invention will be specifically described based on embodiments, but the present invention is not limited to these embodiments. As long as it falls within the technical scope of the present invention, it can be implemented in various ways, and it goes without saying.

2.1 Preparation method of abrasive composition

The abrasive compositions prepared as Examples 1 to 21 and Comparative Examples 1 to 5 respectively contained the materials described in Table 1 in the content or addition amount described in Table 1 shown below. In addition, regarding polymer 7 in the water-soluble polymer compound in Table 1, since an aqueous solution in which the copolymer was uniformly dissolved could not be obtained, the polishing test was not carried out.

【Table 1】

In Table 1 above, the abbreviation for 1-hydroxyethylene-1,1-diphosphonic acid is HEDP, the abbreviation for acrylic acid is AA, the abbreviation for acrylamide is AM, and the abbreviation for N-tertiary butyl acrylamide is It is TBAA, and the abbreviation for 2-propenamide-2-methylpropanesulfonic acid is ATBS. The following tables 2, 3 and research also use this abbreviation.

As described in Table 1, the water-soluble high-molecular compound uses polymers 1-10. In addition, the weight average molecular weight of the water-soluble polymer compound is measured by gel permeation chromatography (GPC) in terms of polyacrylic acid. The GPC measurement conditions are shown below.

2.2 GPC conditions

Column: G4000PWXL (manufactured by Tosoh) + G2500PWXL (manufactured by Tosoh)

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

Flow rate: 1.0ml/min

Temperature: 40℃

Detection: 210nm (UV)

Sample: concentration 5mg/ml (injection volume 100μl)

Polymer for calibration curve: polyacrylic acid molecular weight (peak top molecular weight: Mp) 115,000, 28,000, 4100, 1250 (Chuanghe Chemical Co., Ltd., American Polymer Standards)

2.3 Particle size of colloidal silica

The particle size (Heywood diameter) of colloidal silica is a transmission electron microscope (TEM) (manufactured by JEOL Co., Ltd., transmission electron microscope JEM2000FX (200kV)) with a field of view of 100,000 times magnification. An analysis software (made by Mountech Co., Ltd., Mac-View Ver.4.0) was used to analyze the image to measure Haywood's diameter (equivalent circle diameter of the projected area). The average particle size of colloidal silica is analyzed by the above method to analyze the particle size of about 2000 colloidal silica. It is calculated using the above analysis software (manufactured by Mountech Co., Ltd., Mac-View Ver.4.0) to calculate the small particle size. The cumulative particle size distribution (cumulative volume basis) becomes 50% of the particles The average particle diameter (D50) calculated from the diameter.

2.4 Grinding conditions

A 95mm outer diameter aluminum magnetic disk substrate plated with electroless nickel-phosphorus is subjected to rough grinding as the grinding object.

Grinding machine: 9B double-sided grinding machine manufactured by SpeedFam Co., Ltd.

Grinding pad: P2 gasket made by FILWEL Co., Ltd.

Number of rotations of the pressing plate: Upper pressing plate -8.3min ^-1

Lower plate 25.0min ^-1

Abrasive composition supply amount: 50ml/min

Grinding time: 300 seconds

Processing pressure: 14kPa

After mixing each component to prepare an abrasive composition, it was introduced into a grinder through a filter with a pore size of 0.45 μm, and a grinding test was performed. The grinding test results are shown in Table 2 and Table 3. In addition, in Comparative Example 4 of Table 2, the polymer 7 of Table 1 was used as the water-soluble polymer compound, but a uniform aqueous solution of the copolymer could not be obtained, so the polishing test was not performed.

【Table 2】

【table 3】

2.5 Evaluation of the polished disc surface

2.5.1 Grinding speed ratio

The polishing speed is measured by measuring the mass of the aluminum magnetic disk substrate reduced after polishing, and then calculated according to the following formula.

Grinding speed (mg/min) = reduced mass of aluminum magnetic disk substrate (mg) / grinding time (min)

Regarding the polishing rate ratio, Table 2 is the relative value when the polishing rate obtained using the above formula when polishing the substrate in Comparative Example 1 is set to 1 (reference), and in Table 3 is the relative value when the substrate is polished in Comparative Example 5. When using the above formula, the polishing speed is set to 1 (reference) when the relative value. The larger the value of the polishing speed ratio, the better the polishing characteristics.

2.5.2 Evaluation method of the undulation of the substrate surface after polishing

The undulation of the substrate surface was measured using a three-dimensional optical profiler New View 8300 manufactured by AMETEK.

The measurement conditions of the substrate surface are as follows.

Regarding the undulation ratio, in Table 2, the value obtained by the above method when polishing the substrate in Comparative Example 1 is a relative value when 1 (reference), and in Table 3, it is used when polishing the substrate in Comparative Example 5. The value obtained by the above method is a relative value when 1 (reference). The larger the value of the undulation ratio, the better the polishing characteristics.

2.5.3 Evaluation method of halo on the substrate surface after polishing

The halo system was measured using a substrate full-surface defect inspection machine NS2000H manufactured by Hitachi High-Tech Fine Systems.

The measurement conditions of the halo are as follows.

The halo can be detected as a fine defect on the substrate surface under the above-mentioned inspection conditions, and the halo count can be used for quantitative evaluation.

2.5.4 Halo ratio

Regarding the halo ratio, Table 2 shows the relative value when the halo count obtained by the above method when polishing the substrate in Comparative Example 1 is set to 1 (reference), and Table 3 shows the relative value when polishing the substrate in Comparative Example 5. The relative value when the halo count obtained by the above method is set to 1 (reference) when the substrate is used. The greater the value of the halo ratio, the better the polishing characteristics.

3. Research

The following shows the research conclusions discussed based on the above-mentioned experimental results. Table 2 Series of abrasive combinations Compared with the AA/TBAA/ATBS copolymer, the grinding speed of the AA/TBAA/AM/ATBS copolymer has increased (Example 1 and Comparative Example). Comparison of 1, Comparison of Example 6 and Comparative Examples 2 and 3).

In addition, the aqueous solution of the AA/TBAA/AM copolymer could not become a uniform solution, so the polishing test was not performed (Comparative Example 4).

In Example 2, when the inorganic acid in Example 1 was used in combination with sulfuric acid and phosphoric acid, the polishing speed was increased and the halo was improved. The same situation was also found in the comparison between Example 7 and Example 6.

Example 3 is the result of changing the inorganic acid in Example 1 from sulfuric acid to phosphoric acid. The polishing speed is increased, and the fluctuation and halo are improved. The same situation was also found in the comparison between Example 8 and Example 6.

Example 4 is the result of changing the acid used in Example 1 from sulfuric acid to HEDP. The polishing speed is increased, and the fluctuation and halo are improved. The same situation was also found in the comparison between Example 9 and Example 6.

Example 5 is the result when phosphoric acid and HEDP were used in combination in Example 3, and the undulation and halo were improved. The same situation was also found in the comparison between Example 10 and Example 8.

Example 11 is the result when the weight average molecular weight of the copolymer in Example 5 is changed, and Examples 12 and 13 are the result when the average particle size of the colloidal silica abrasive grains in Example 5 is changed.

Table 3 is the grinding test result when the TBAA content of the copolymer in the abrasive composition is 12 mol%. Compared with the AA/TBAA/ATBS copolymer, the grinding speed of the AA/TBAA/AM/ATBS copolymer is improved. (Comparison of Example 14 and Comparative Example 5)

In Example 15, when the inorganic acid in Example 14 was used in combination with sulfuric acid and phosphoric acid, the polishing speed was increased and the halo was improved.

Example 16 is the result of changing the inorganic acid in Example 14 from sulfuric acid to phosphoric acid. The polishing speed is increased, and the fluctuation and halo are improved.

In Example 17, when the acid used in Example 14 was changed from sulfuric acid to HEDP, the polishing speed was increased, and the fluctuation and halo were improved.

Example 18 is the result when phosphoric acid and HEDP are used in combination in Example 16. The polishing speed is increased, and the fluctuation and halo are improved.

Example 19 is the result when the weight average molecular weight of the copolymer in Example 18 is changed, and Examples 20 and 21 are the result when the average particle size of the colloidal silica abrasive grains in Example 18 is changed.

From the above results, it is obvious that by using a monomer having a carboxylic acid group, a monomer selected from N-alkyl acrylamide or N-alkyl methacrylamide, from acrylamide or methacrylamide A copolymer of monomers selected from amides and monomers with sulfonic acid groups as essential monomers is used as the water-soluble polymer compound in the abrasive composition to obtain a product with a good balance of polishing speed, undulation, and halo. .

[Industrial availability]

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

Claims (9)

An abrasive composition for magnetic disk substrates, comprising colloidal silica, water-soluble polymer compounds, acid and water, Among them, the water-soluble polymer compound is a monomer having a carboxylic acid group, a monomer selected from N-alkyl acrylamide or N-alkyl methacrylamide, and a monomer selected from acrylamide or methacrylamide. A copolymer in which monomers selected from amines and monomers with sulfonic acid groups are essential monomers. The abrasive composition for magnetic disk substrates of claim 1, wherein the acid is an inorganic acid containing phosphorus and/or an organic acid containing phosphorus. According to claim 1 or 2, the abrasive composition for magnetic disk substrates, wherein the water-soluble polymer compound, The ratio of constituent units derived from monomers having carboxylic acid groups is in the range of 50 to 95 mol%, The ratio of constituent units derived from monomers selected from N-alkyl acrylamide or N-alkyl methacrylamide is in the range of 5-40 mol%, The ratio of constituent units derived from monomers selected from acrylamide or methacrylamide is in the range of 0.3-10 mol%, The ratio of the structural unit derived from the monomer having a sulfonic acid group is in the range of 0.01 to 20 mol%. The abrasive composition for a magnetic disk substrate according to any one of claims 1 to 3, wherein the single system having a carboxylic acid group is selected from monomers of acrylic acid or a salt thereof, and methacrylic acid or a salt thereof. The abrasive composition for a magnetic disk substrate according to any one of claims 1 to 4, wherein the single system having a sulfonic acid group is selected from isoprene sulfonic acid, 2-propenamide-2-methylpropane Sulfonic acid, 2-methacrylamide-2-methylpropane sulfonic acid, styrene sulfonic acid, vinyl sulfonic acid, allyl sulfonic acid, isopentene sulfonic acid, naphthalene sulfonic acid and the mono body. The abrasive composition for magnetic disk substrates of claim 2, wherein the phosphorus-containing inorganic acid is at least 1 selected from the group consisting of phosphoric acid, phosphonic acid, phosphinic acid, pyrophosphoric acid and tripolyphosphoric acid More than kind of compounds. The abrasive composition for magnetic disk substrates of claim 2, wherein the phosphorus-containing organic acid is selected from 2-aminoethylphosphonic acid, 1-hydroxyethylene-1,1-diphosphonic acid, and amino Tris (methylene phosphonic acid), ethylene diamine 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-triphosphonic acid, ethane-1,2-dicarboxy-1,2-diphosphonic acid, methane hydroxyphosphonic acid, 2 -Phosphosinobutane-1,2-dicarboxylic acid, 1-phosphosinobutane-2,3,4-tricarboxylic acid and at least 1 of the group consisting of α-methylphosphosuccinic acid More than kind of compounds. The abrasive composition for a magnetic disk substrate according to any one of claims 1 to 7, wherein the abrasive composition further contains an oxidizing agent. The abrasive composition for a magnetic disk substrate according to any one of claims 1 to 8, which is used for polishing an aluminum magnetic disk substrate plated with electroless nickel-phosphorus.