TW202140743A - Polishing composition for magnetic disk substrate - Google Patents

Abstract

The present invention provides a polishing composition for a magnetic disk substrate, which can maintain high productivity while reducing polishing grains residues or polished debris on the surface of the substrate after a rough polishing step in a multi-stage polishing method, and further reducing fluctuations. The polishing composition is used in a subsequent rough polishing step, which includes colloidal silica, an organic sulfate ester salt compound and water, wherein in the volume-based particle size distribution of the colloidal silica measured by Haywood diameter, the volume cumulative frequency of the particle size of 50 nm is 35% or more, and the volume cumulative frequency of the particle size of 15nm is less than 90%, and the organic sulfate ester salt compound is composed of a specific structure.

Description

Abrasive composition for magnetic disk substrate

The present invention relates to an abrasive composition for magnetic disk substrates. In particular, it relates to an abrasive composition used for polishing electronic parts such as magnetic recording media such as semiconductors and hard disks, particularly for surface polishing of substrates for magnetic recording media such as glass magnetic disk substrates or aluminum magnetic disk substrates. In more detail, it relates to the polishing of an aluminum magnetic disk substrate for a magnetic recording medium on which an electroless nickel-phosphorus plating film is formed on the surface of an aluminum alloy substrate by a multi-stage polishing method, before the final polishing step. The abrasive composition for a magnetic disk substrate used in the rough polishing step.

In recent years, magnetic disk drives have been miniaturized and increased in capacity, and higher recording density has been sought. Therefore, it is necessary to improve the detection sensitivity of magnetic signals with high recording density, and technologies to further reduce the flying height of the magnetic head and reduce the unit recording area are being developed. For magnetic disk substrates, in order to cope with the low buoyancy of the magnetic head and ensure the recording area, it is strictly required to improve the smoothness and flatness (reduce surface roughness, reduce undulation) and reduce surface defects (reduce abrasive residues or abrasive debris and other attachments) , Reduce scratches, reduce dents).

In response to this requirement, from the viewpoint of reducing abrasive residues or reducing abrasive swarf and other adhesions, and further reducing the surface quality and productivity such as fluctuations, it has been proposed to use α-alumina and intermediate alumina. The abrasive composition of, can achieve high polishing speed and reduce fluctuations (Patent Document 1). However, the effect of reducing fluctuations is not sufficient, and improvement is being sought. In addition, in the polishing method of magnetic disk substrates, a multi-stage polishing method having two or more polishing steps is often used (Patent Document 2). Generally speaking, in the final polishing step of the multi-stage polishing method, that is, the finishing polishing step, from the viewpoint of reducing surface roughness, reducing scratches, reducing abrasive residues or abrasive debris, and reducing dents, etc. An abrasive composition containing silicon dioxide particles. On the other hand, in the preceding polishing step (also referred to as a rough polishing step), from the viewpoint of improving productivity, a polishing composition containing alumina particles is often used.

However, when polishing aluminum hard disk substrates, compared with aluminum alloy substrates, the hardness of aluminum oxide particles is quite high. Therefore, abrasive residues or grinding debris adhere to the surface of the substrate, and even increase the fluctuations. Cause adverse effects and become a problem.

As a solution to this problem, someone has disclosed a polishing method that uses the same grinder to perform polishing using an abrasive composition containing alumina and polishing using an abrasive composition containing colloidal silica in the rough grinding step. (Patent Document 4). [Prior Technical Literature]

Patent literature Patent Document 1: Japanese Patent Application Publication No. 2005-23266 Patent Document 2: Japanese Patent Application Laid-Open No. 62-208869 Patent Document 3: Japanese Patent Application Publication No. 2012-25873 Patent Document 4: JP 2012-43493 A

[The problem to be solved by the invention]

In recent years, with the increase in the capacity of disk drives, the requirements for the surface quality of the substrate have become more stringent, and it is required to maintain high productivity in the polishing step of the disk substrate while reducing the abrasive particles on the substrate surface. Residues or grinding debris and other attachments, and further reduce fluctuations. However, the inventions proposed in the above-mentioned Patent Documents 1 to 4 are difficult to sufficiently cope with the required performance.

Therefore, the subject of the present invention is to provide an abrasive composition for magnetic disk substrates in view of the above circumstances, which can maintain high productivity while reducing abrasive residues or polishing on the surface of the substrate after the rough polishing step in the multi-stage polishing method. Attachments such as crumbs, and further reduce fluctuations. [Means to solve the problem]

The inventors of the present case have conducted in-depth research on the above-mentioned problems and found that in the subsequent stage polishing of the rough polishing step in the multi-stage polishing method, the above-mentioned problems can be solved by using the following abrasive composition for magnetic disk substrates, thereby achieving the present invention . That is, the present invention is the following abrasive composition for magnetic disk substrates.

[1] An abrasive composition for magnetic disk substrates, which has the following steps (1) to (3) and performs each step (1) to (3) with the same grinder for rough polishing of a magnetic disk substrate, The abrasive composition B used in this step (3) contains: colloidal silica, an organic sulfate compound and water, wherein the colloidal silica is in the particle size distribution on the volume basis measured by Heywood diameter , The cumulative volume frequency of the particle size of 50nm is 35% or more, and in the particle size distribution, the volume cumulative frequency of the particle size of 15nm is less than 90%, the organic sulfate ester salt compound is represented by the following general formula (1): RO-( AO) _n -SO ₃ M ･･･ General formula (1) In the above general formula (1), R represents a linear or branched alkyl, alkenyl, aryl or alkyl aryl group with 5 to 21 carbon atoms AO represents an oxyalkylene group with carbon number 2 or 3, n represents a natural number from 1 to 30, and M represents an alkali metal, alkaline earth metal, ammonium ion or organic cation. Step (1) is the step of supplying the abrasive composition A containing α-alumina, intermediate alumina and water to the grinder, and performing the preliminary rough polishing of the magnetic disk substrate. The step (3) of rinsing the magnetic disk substrate is the step of supplying the abrasive composition B containing colloidal silica, organic sulfate ester salt compound and water to the grinder, and performing the subsequent rough grinding of the magnetic disk substrate

[2] The abrasive composition for a magnetic disk substrate as in [1] above, further containing an aliphatic amine compound.

[3] The abrasive composition for magnetic disk substrates as described in [2] above, wherein the aliphatic amine compound is selected from ethylamine, n-propylamine, isopropylamine, n-butylamine, isobutylamine, secondary butylamine, tri Grade butylamine, cyclohexylamine, piperazine, diethylamine, methylpropylamine, ethylpropylamine, triethylamine, ethylenediamine, 1,2-propanediamine, trimethylenediamine, tetramethylenediamine, Pentamethylene diamine, hexamethylene diamine, N,N-dimethylethylenediamine, N,N'-dimethylethylenediamine, N-ethylethylenediamine, N,N,N', N'-tetramethylethylenediamine, N-methyl-1,3-propanediamine, 1,3-diaminepentane, diethylenetriamine, bis(hexamethylene)triamine, tertiary At least one of the group consisting of ethylenetriamine, ethylenetetramine, tetraethylenepentamine, pentaethylenehexamine and tetramethylhexamethylenediamine.

[4] The abrasive composition for a magnetic disk substrate according to any one of [1] to [3] above, which further contains an acid and/or a salt thereof.

[5] The abrasive composition for a magnetic disk substrate according to any one of [1] to [4] above, which further contains an oxidizing agent.

[6] The abrasive composition for magnetic disk substrates according to any one of [1] to [5] above, which is used for rough polishing of aluminum magnetic disk substrates plated with electroless nickel-phosphorus. [Effects of the invention]

By using the abrasive composition for magnetic disk substrates of the present invention, the following effect can be obtained: after the rough polishing step in the multi-stage polishing method can be manufactured with high productivity, the abrasive residues or abrasive debris on the surface of the substrate can be reduced And the substrate with reduced undulation.

Hereinafter, an embodiment of the present invention will be described. The present invention is not limited to the following embodiments, and changes, corrections, and improvements can be made without departing 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 one embodiment of the present invention contains colloidal silica, an organic sulfate compound, and water. Here, the abrasive composition of this embodiment corresponds to the "abrasive composition B" used in step (3).

Furthermore, in the particle size distribution of colloidal silica on the volume basis measured by the Haywood diameter, the volume accumulation frequency of the particle size 50nm is more than 35%, and in the particle size distribution, the volume accumulation frequency of the particle size 15nm is less than 90%.

On the other hand, the organic sulfate ester salt compound is a compound represented by the following general formula (1). RO-(AO) _n -SO ₃ M ･･･General formula (1)

In the above general formula (1), R represents a linear or branched alkyl, alkenyl, aryl or alkylaryl group having 5 to 21 carbons, and AO represents an oxyalkylene group with 2 or 3 carbons, n represents a natural number from 1 to 30, and M represents an alkali metal, alkaline earth metal, ammonium ion or organic cation.

Furthermore, the abrasive composition of this embodiment may contain an aliphatic amine compound, an acid and/or its salt, an oxidizing agent, and other additives as optional components.

The abrasive composition of this embodiment is used as the step ( 3) The abrasive composition B is used. Step (1) is a step of supplying the abrasive composition A containing α-alumina, intermediate alumina, and water to the grinder, and performing the preliminary rough polishing of the magnetic disk substrate. Step (2) is a step of washing the magnetic disk substrate obtained in the above step (1). Step (3) is a step of supplying the abrasive composition B containing colloidal silica, an organic sulfate ester salt compound, and water to the grinder, and performing the subsequent rough polishing on the magnetic disk substrate. Detailed descriptions are given below.

1-1. Colloidal silica The colloidal silica used in the abrasive composition (= abrasive composition B) of this embodiment can be obtained, for example, by the water glass method: using alkali metal silicates such as sodium silicate and potassium silicate as raw materials, the The raw material undergoes a condensation reaction in an aqueous solution to grow particles.

Alternatively, it can also be obtained by the method obtained by the alkoxysilane method or by the reaction of metal silicon with water. In water such as a water-soluble organic solvent, the condensation reaction proceeds by hydrolysis of acid or alkali to grow particles.

Here, it is known that colloidal silica has a spherical shape, a chain shape, a candy shape, an irregular shape, and the like, and its primary particles are monodispersed in water to form a colloidal shape. In the abrasive composition of this embodiment, the colloidal silica is preferably spherical or nearly spherical in shape.

The average particle size (D50) of the colloidal silica used is preferably 10-100 nm, more preferably 20-80 nm. Furthermore, in the particle size distribution on the volume basis measured by the Haywood diameter, the volume accumulation frequency of the particle size 50nm is 35% or more, and in the particle size distribution, the volume accumulation frequency of the particle size 15nm is 90% or less.

The volume accumulation frequency (%) in this specification is the same as the generally used definition. It means that the volume is accumulated in the order of the particle size from the particle with the smallest particle size in the target particle assembly. The ratio (%) of the total volume of particles having a particle diameter below a certain value relative to the total volume of all the target particles.

For example, when the cumulative frequency of the volume with a particle diameter of 15 nm is 50%, it means that the total volume of particles with a particle diameter of 15 nm or less accounts for 50% of the total volume of all particles. In addition, Haywood's diameter is the result of analyzing the image obtained by observation with an electron microscope and finding the equivalent circle diameter of the projected area, which has been conventionally known in the past.

In the colloidal silica contained in the abrasive composition of the present embodiment, the proportion of large particles with a particle size of 50 nm or more and small particles with a particle size of 15 nm or less relative to the entire particle is suppressed to be small. When colloidal silica having such a particle size distribution is supplied to the surface of an object to be polished by the polishing pad, it is easy to be sufficiently held in the polishing pad.

In addition, due to the above-mentioned particle size distribution, the gap formed between the colloidal silica and the surface of the object tends to be smaller than the remaining abrasive grains or abrasive dust. Therefore, the residual abrasive grains or grinding debris cannot easily escape into the gap between the colloidal silica and the surface of the object, and the collision frequency between the residual abrasive grains or grinding debris and the colloidal silica becomes higher, and the residual abrasive particles can be effectively removed from the surface of the object. Or grinding scraps and so on.

Furthermore, by ensuring a considerable number of colloidal silica particles with a particle size of 50 nm or less, it is easy to form a state in which colloidal silica with a smaller particle size enters in the gap between one colloidal silica and the surface of the object. As a result, the remaining abrasive grains, abrasive dust, etc. are not likely to escape into the gap between the colloidal silica and the surface of the object, and are easily removed from the surface of the object. In addition, colloidal silica has a spherical or nearly spherical shape, so it tends to be difficult to adhere to or penetrate into the surface of an object. Therefore, colloidal silica itself does not easily remain on the surface of the object.

The concentration of colloidal silica in the abrasive composition is preferably 0.1-20% by mass, more preferably 0.2-10% by mass.

1-2. Organic sulfate ester compound The organic sulfate ester salt compound used in the abrasive composition, as shown above, is the compound represented by the above general formula (1).

Here, in the above general formula (1), n is preferably a natural number from 2 to 4. In addition, specific examples of M in the above general formula (1) include alkali metals such as sodium or potassium, alkaline earth metals such as calcium or magnesium, ammonium ions, quaternary ammonium ions, or organic amines such as triethanolamine.

Furthermore, as specific examples of the organic sulfate ester compound represented by the general formula (1) above, oxyethylene tridecyl ether sulfate (2 or 3 oxyethylene groups per molecule), oxygen Ethylene lauryl ether sulfate (2 or 3 oxyethylene groups per molecule), oxyethylene nonyl ether sulfate (3 oxyethylene groups per molecule), oxyethylene octyl phenyl ether sulfate ( 3 oxyethylene groups per molecule), oxyethylene nonylphenyl ether sulfate (3 oxyethylene groups per molecule), etc. It is particularly preferable to use oxyethylene tridecyl ether sulfate (per molecule The number of oxyethylene groups is 3), oxyethylene lauryl ether sulfate (3 oxyethylene groups per molecule), oxyethylene octyl phenyl ether sulfate (3 oxyethylene groups per molecule), Oxyethylene nonylphenyl ether sulfate (3 oxyethylene groups per molecule).

In addition, it does not matter if the organic sulfate ester salt compound is contained in the abrasive composition of this embodiment singly or in combination of two or more kinds.

In addition, the content of the organic sulfate ester salt compound in the abrasive composition is generally 0.0001 to 2.0% by mass, preferably 0.0005 to 1.0% by mass.

1-3. Aliphatic amine compounds The abrasive composition of this embodiment can add an aliphatic amine compound as an optional component. Specific examples of aliphatic amine compounds include ethylamine, n-propylamine, isopropylamine, n-butylamine, isobutylamine, secondary butylamine, tertiary butylamine, cyclohexylamine, piperazine, diethylamine, Methylpropylamine, ethylpropylamine, triethylamine, ethylenediamine, 1,2-propanediamine, trimethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, N,N -Dimethylethylenediamine, N,N'-dimethylethylenediamine, N-ethylethylenediamine, N,N,N',N'-tetramethylethylenediamine, N-methyl- 1,3-propanediamine, 1,3-diaminepentane, ethylenetriamine, bis(hexamethylene)triamine, ethylenetriamine, ethylenetetramine, tetraethylenepentamine , Pentaethylenehexamine, tetramethylhexamethylenediamine, etc.

The aliphatic amine compound may contain one kind selected from the above-mentioned group or a combination of two or more kinds. The content of the aliphatic amine compound in the abrasive composition is generally 0.00001 to 4.0% by mass, preferably 0.0001 to 2.0% by mass.

1-4. Acid and/or its salt Furthermore, the abrasive composition of the present embodiment may also contain acid and/or its salt for adjusting the pH value or as an optional component. Here, as an acid and/or its salt, an inorganic acid and/or its salt, an organic acid and/or its salt, etc. are mentioned.

Specific examples of inorganic acids and/or their salts include nitric acid, sulfuric acid, hydrochloric acid, phosphoric acid, phosphonic acid, pyrophosphoric acid, tripolyphosphoric acid, and the like. One kind or two or more kinds of these acids and/or their salts can be used.

On the other hand, specific examples of organic acids and/or their salts include amino carboxylic acids such as glutamic acid and aspartic acid and/or their salts, citric acid, tartaric acid, oxalic acid, nitroacetic acid, and maleic acid. Carboxylic acids such as acid, malic acid, and succinic acid and/or their salts, organic phosphonic acid and/or their salts. One kind or two or more kinds of these acids and/or their salts can be used.

Furthermore, as specific examples of the organic phosphonic acid and/or its salt, it may be selected from the group consisting of 2-aminoethylphosphonic acid, 1-hydroxyethylene-1,1-diphosphonic acid, aminotri(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-phosphonic acid At least one compound of butane-1,2-dicarboxylic acid, 1-phosphonobutane-2,3,4-tricarboxylic acid, α-methylphosphonosuccinic acid and salts thereof.

Combining two or more of the above-mentioned compounds is also a preferred embodiment. Specifically, examples include: a combination of sulfuric acid and/or its salt and organophosphonic acid and/or its salt, phosphoric acid and/or its salt and organophosphine Combinations of acids and/or their salts, etc.

1-5. Oxidizer The abrasive composition of this embodiment may further contain an oxidizing agent as a polishing accelerator. As specific examples of 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, and such oxidizing agents can be used. A mixture of two or more types, etc.

If further specified, it can be enumerated: hydrogen peroxide, sodium peroxide, barium peroxide, potassium peroxide, potassium permanganate, metal salt of chromic acid, metal salt of dichromic acid, persulfuric acid, sodium persulfate, persulfate Potassium sulfate, ammonium persulfate, peroxyphosphoric acid, sodium peroxyborate, performic acid, peracetic acid, hypochlorous acid, sodium hypochlorite and calcium hypochlorite, etc. Among these, hydrogen peroxide, persulfuric acid and its salts, hypochlorous acid and its salts, etc. are particularly preferred, and hydrogen peroxide is even 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.

2. The physical properties of the abrasive composition (pH value) The pH value (25°C) of the abrasive composition is preferably in the range of 0.1 to 4.0. More preferably, it is 0.5 to 3.0. By making the pH value (25°C) of the polishing agent composition 0.1 or more, surface roughness can be suppressed. By setting the pH value (25°C) of the polishing agent composition to 4.0 or less, it is possible to suppress a decrease in polishing rate.

The abrasive composition of this embodiment can be used to polish various electronic parts such as magnetic recording media such as hard disks. It is especially suitable for grinding aluminum magnetic disk substrates. It is more suitable for grinding aluminum magnetic disk substrates plated with electroless nickel-phosphorus. Electroless nickel-phosphorus plating is generally carried out at a pH value (25°C) of 4-6. If the pH value (25°C) is 4 or less, nickel tends to dissolve, making plating difficult. On the other hand, regarding polishing, for example, if the pH (25°C) is 4 or less, nickel tends to dissolve. Therefore, it can be expected that the polishing rate can be increased by using the polishing composition of this embodiment.

3. Grinding method of disk substrate The abrasive composition of this embodiment is suitable for polishing magnetic disk substrates such as aluminum magnetic disk substrates or glass magnetic disk substrates. It is especially suitable for grinding aluminum magnetic disk substrates coated with electroless nickel-phosphorus.

The abrasive composition is a method for polishing a magnetic disk substrate that includes a rough polishing step and a finishing step in a multi-stage polishing method. When the rough polishing step is performed in the following three stages from step (1) to step (3), The abrasive composition B used in step (3). As a specific polishing method, for example, there is a method of attaching a polishing pad to a platen of a polishing machine, supplying the polishing agent composition to the polishing surface or polishing pad of the object to be polished, and rubbing the polishing surface with the polishing pad. For example, when polishing the front and back sides of a magnetic disk substrate at the same time, there is a method of using a double-sided polishing machine to attach polishing pads to the upper pressing plate and the lower pressing plate, respectively. In this method, the magnetic disk substrate is clamped by polishing pads attached to the upper and lower pressing plates, and the abrasive composition is supplied between the polishing surface and the polishing pad, and the two polishing pads are rotated at the same time, thereby polishing the magnetic The front and back of the disc substrate. The polishing pad can also be of urethane type, suede type, non-woven type, and any other types.

Step (1): rough grinding of the front section This is to supply the abrasive composition A containing α-alumina, intermediate alumina, and water to the polishing machine, and perform the first rough polishing step. The polishing target surface of the substrate to be polished is brought into contact with the polishing pad, and the polishing pad is moved. And/or the step of polishing the surface to be polished by the substrate to be polished.

The abrasive composition A used in this step is an abrasive composition containing α-alumina, intermediate alumina, and water. Furthermore, it is the same as the abrasive composition B (the abrasive composition of this embodiment). It is necessary to appropriately include an organic sulfate ester salt compound, an acid and/or its salt, an oxidizing agent, etc. as optional components.

The abrasive composition A used in the step (1) contains α-alumina and intermediate alumina, and as intermediate alumina, γ-alumina, δ-alumina, θ-alumina, etc. can be mentioned. In addition, the mixing ratio of α-alumina and intermediate alumina is preferably in the range of intermediate alumina/α-alumina (mass ratio)=0.05 to 2.0, more preferably in the range of 0.1 to 1.0, and still more preferably 0.15 to The range of 0.5.

Here, the average particle diameter of alumina is preferably in the range of 0.1 to 2.0 μm, more preferably in the range of 0.2 to 1.0 μm. By setting the average particle diameter of alumina to be 0.1 μm or more, it is possible to suppress a decrease in the polishing rate. On the other hand, by setting the average particle size of alumina to 2.0 μm or less, it is possible to suppress the increase in fluctuations after polishing.

Furthermore, the concentration of alumina in the abrasive composition A is preferably in the range of 1 to 50% by mass, and more preferably in the range of 2 to 40% by mass. By making the concentration of alumina in the polishing agent composition A 1% by mass or more, it is possible to suppress a decrease in the polishing rate. On the other hand, by setting the alumina concentration to 50% by mass or less, unnecessary alumina can be avoided, the cost of the abrasive composition A can be saved, and the polishing can be performed more economically.

Furthermore, the content of the oxidizing agent in the abrasive composition A is preferably in the range of 0.01 to 10.0% by mass, and more preferably in the range of 0.1 to 5.0% by mass.

On the other hand, the pH value (25°C) of the abrasive composition A is preferably in the range of 0.1 to 4.0, and more preferably in the range of 0.5 to 3.0.

Step (2): the step of washing the substrate obtained in step (1) From the viewpoint of reducing the fluctuation of the substrate surface after the rough polishing step in the multi-stage polishing method, after the above step (1), the step (2) of washing the substrate obtained in the step (1) is carried out in the same polishing machine. ). Here, the rinsing liquid used for rinsing the substrate is not particularly limited, but from an economical point of view, water such as distilled water, ion-exchanged water, pure water, and ultrapure water is mainly used. At this time, in step (2), from the viewpoint of productivity, the substrate to be polished is not taken out from the grinder used in step (1), but is performed in the same grinder.

Step (3): After-stage rough grinding From the viewpoint of reducing the adhesion of abrasive residues or abrasive dusts after the rough polishing step in the multi-stage polishing method and reducing undulations, the abrasive composition B (corresponding to this The polishing composition of the embodiment) is supplied to the polishing target surface of the substrate after the rinsing step of the above step (2), and the polishing pad and/or the substrate to be polished are moved on the polishing target surface to perform polishing of the polishing target surface Step (3). At this time, from the viewpoint of improving productivity and reducing the adhesion of abrasive residues or grinding chips after the rough grinding step, and reducing fluctuations, the above steps (1) to (3) are all implemented in the same grinding machine. [Example]

Hereinafter, the present invention will be described in detail 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.

Preparation of abrasive composition The abrasive composition used in Examples 1 to 7 and Comparative Examples 1 to 5 shown below is an abrasive composition composed of the content described in Table 1 below and the material described in Table 1 (= Abrasive composition B). Here, the measurement method of the average particle size, the first-stage grinding conditions in step (1), the rinsing conditions in step (2), and the latter rough grinding conditions in step (3) are as follows.

Table 1 Materials used Content in abrasive composition Use experimental examples α-Alumina (average particle size (D50): 0.43μm) 4.0 mass% Examples 1~7, Comparative Examples 1~5 Intermediate alumina (average particle size (D50): 0.45μm) 1.0 mass% Examples 1~7, Comparative Examples 1~5 Colloidal silica (average particle size (D50): 50nm), within the range of particle size characteristics 4.0 mass% Examples 1~5, Comparative Examples 3~5 Volume accumulation frequency (50nm)=49% Volume accumulation frequency (15nm)=1% Colloidal silica (average particle size (D50): 11nm), within the range of particle size characteristics 4.0 mass% Example 6 Volume accumulation frequency (50nm)=94% Volume accumulation frequency (15nm)=81% Colloidal silica (average particle size (D50): 56nm), within the range of particle size characteristics 4.0 mass% Example 7 Volume accumulation frequency (50nm)=43% Volume accumulation frequency (15nm)=8% Colloidal silica (average particle size (D50): 10nm), outside the range of particle size characteristics 4.0 mass% Comparative example 1 Volume accumulation frequency (50nm)=100% Volume accumulation frequency (15nm)=99% Colloidal silica (average particle size (D50): 105nm), outside the range of particle size characteristics 4.0 mass% Comparative example 2 Volume accumulation frequency (50nm)=30% Volume accumulation frequency (15nm)=24% Polyoxyethylene tridecyl ether sodium sulfate (manufactured by Daiichi Kogyo Pharmaceutical: HITENOL 330T) 0.005 mass% Examples 1, 4~7, Comparative Examples 1, 2 Polyoxyethylene tridecyl ether sodium sulfate (manufactured by Daiichi Kogyo Pharmaceutical: HITENOL 330T) 0.02% by mass Example 2 Polyoxyethylene tridecyl ether sodium sulfate (manufactured by Daiichi Kogyo Pharmaceutical: HITENOL 330T) 0.05 mass% Example 3 Sodium Lauryl Sulfate (Toho Chemicals: Alscope LS-30) 0.005 mass% Comparative example 4 Sodium Lauryl Sulfate (Toho Chemicals: Alscope LS-30) 0.05 mass% Comparative example 5 Pentaethylenehexamine 0.005 mass% Example 4 Pentaethylenehexamine 0.02% by mass Example 5 Sulfuric acid (pre-grinding: abrasive composition A) 1.4% by mass Examples 1~7, Comparative Examples 1~5 Sulfuric acid (post-grinding: abrasive composition B) 0.3% by mass Examples 1~7, Comparative Examples 1~5 Hydrogen peroxide (pre-polishing: abrasive composition A) 1.3% by mass Examples 1~7, Comparative Examples 1~5 Hydrogen peroxide (post-polishing: abrasive composition B) 0.3% by mass Examples 1~7, Comparative Examples 1~5

The average particle size The average particle size of alumina was measured using a laser diffraction particle size distribution measuring device (SALD2200 manufactured by Shimadzu Corporation). The average particle size of alumina is the average particle size (D50) at which the cumulative particle size distribution from the small particle size side is 50% based on the volume.

The particle size (Haywood diameter) of colloidal silica was taken using a transmission electron microscope (TEM) (manufactured by JEOL Co., Ltd., a transmission electron microscope JEM2000FX (200kV)) with a field of view of 100,000 times magnification and used for analysis. The software (made by Mountech Co., Ltd., Mac-View Ver. 4.0) analyzes the image, thereby measuring the Haywood diameter (equivalent circle diameter of the projected area). The average particle size of colloidal silica is analyzed by the above method of about 2000 colloidal silica particles, which is calculated by using the above analysis software (manufactured by Mountech Co., Ltd., Mac-View Ver. 4.0) The cumulative particle size distribution (accumulated volume basis) starting from the side becomes the average particle size (D50) calculated from the particle size of 50%.

The first rough polishing conditions used an electroless nickel-phosphorus-plated aluminum disk substrate with an outer diameter of 95 mm (hereinafter referred to as aluminum disk) as the polishing object, and polished under the following polishing conditions. Grinding machine: manufactured by SpeedFam Company Limited, 9B double-sided grinder Polishing pad: manufactured by FILWEL CO., LTD., P1 gasket platen rotation number: upper plate-7.5 rpm lower plate 22.5 rpm Abrasive composition supply: 100ml/min Grinding time: 4.5 minutes Processing pressure: 100 g/cm ² In addition, the abrasive composition A was used in the first-stage grinding.

Washing conditions: Grinding machine: same as the previous rough grinding. Grinding pad: same as the previous rough grinding. Number of platen rotations: same as the previous rough grinding. Washing fluid supply: 3L/min. Washing time: 20 seconds. Processing pressure: 15g/cm ² In addition, washing Use pure water for the liquid.

Rear rough grinding conditions: Grinding machine: the same as the previous rough grinding. Grinding pad: the same as the previous rough grinding. Number of rotations of the platen: the same as the previous rough grinding. Supply amount of abrasive composition: 100ml/min. Grinding time: 80 seconds. Processing pressure: 100g/cm ² In addition, the abrasive composition B was used in the subsequent polishing.

According to the above conditions, the results of the polishing test with the abrasive compositions of Examples 1 to 7 and Comparative Examples 1 to 5 are shown in Table 2 below, respectively. Here, the evaluation items of the polishing speed ratio, the attached matter count ratio, and the undulation ratio obtained from the results of the polishing test were evaluated according to the following.

Table 2 Examples/Comparative Examples Front grinding (alumina abrasive grains) Post-polishing (silica abrasive grains) Grinding test results Abrasive composition A Abrasive composition B α-alumina Intermediate alumina Colloidal silica Organic Sulfate Compound Aliphatic amine compound Grinding speed ratio Attachment count ratio Fluctuation ratio Average particle size D50 (μm) Concentration mass% Average particle size D50 (μm) Concentration mass% Average particle size D50 (nm) Volume accumulation frequency Volume accumulation frequency type Concentration mass% type Concentration mass% (Comparative example 3=1) (Comparative example 3=1) (Comparative example 3=1) 50nm(%) 15nm(%) Example 1 0.43 4.0 0.45 1.0 50 49 1 330T 0.005 - - 1.00 0.89 0.98 ○ ○ ○ Example 2 0.43 4.0 0.45 1.0 50 49 1 330T 0.02 - - 1.00 0.81 0.98 ○ ○ ○ Example 3 0.43 4.0 0.45 1.0 50 49 1 330T 0.05 - - 0.98 0.70 0.93 ○ ○ ○ Example 4 0.43 4.0 0.45 1.0 50 49 1 330T 0.005 PEHA 0.005 1.01 0.10 0.98 ○ ◎ ○ Example 5 0.43 4.0 0.45 1.0 50 49 1 330T 0.005 PEHA 0.02 0.98 0.08 0.98 ○ ◎ ○ Example 6 0.43 4.0 0.45 1.0 11 94 81 330T 0.005 - - 0.94 0.22 1.00 ∆ ○ ○ Example 7 0.43 4.0 0.45 1.0 56 43 8 330T 0.005 - - 0.96 0.78 0.98 ○ ○ ○ Comparative example 1 0.43 4.0 0.45 1.0 10 100 99 330T 0.005 - - 0.81 2.60 1.10 X X X Comparative example 2 0.43 4.0 0.45 1.0 105 30 twenty four 330T 0.005 - - 0.84 0.62 1.12 X ○ X Comparative example 3 0.43 4.0 0.45 1.0 50 49 1 - - - - 1.00 (0.184μm/min) 1.00 (8755) 1.00 (0.92Å) - - - Comparative example 4 0.43 4.0 0.45 1.0 50 49 1 LS-30 0.005 - - 1.02 1.09 1.00 ○ X ○ Comparative example 5 0.43 4.0 0.45 1.0 50 49 1 LS-30 0.05 - - 0.99 1.52 0.97 ○ X ○ 330T: Polyoxyethylene tridecyl ether sodium sulfate (manufactured by Daiichi Kogyo Pharmaceutical: HITENOL 330T) LS-30: Sodium Lauryl Sulfate (Toho Chemicals: Alscope LS-30) PEHA: Pentaethylenehexamine

Evaluation of polishing rate (polishing rate ratio) The polishing rate is calculated by measuring the mass of the aluminum disc reduced after polishing, and then calculating it according to the following formula. Grinding speed (μm/min) = reduction in mass of aluminum disc (g) / grinding time (min) / area of one side of aluminum disc (cm ² ) / density of electroless nickel-phosphorus coating film (g/cm ³ ) /2×10 ⁴ (In the above formula, the area of one side of the aluminum dish is 65.9cm ² , and the density of the electroless nickel-phosphorus coating film is 8.0g/cm ³ )

The actual measurement value (0.184μm/min) of the polishing speed of Comparative Example 3 obtained from the above formula is set to 1 (reference), and the relative values at this time are used to evaluate Examples 1 to 7 and the comparative example according to the following standards The polishing rate ratio of the abrasive composition from 1 to 5. ○: Compared to Comparative Example 3 (=1), the polishing rate ratio is 0.95 or more ∆: Compared to Comparative Example 3 (=1), the polishing rate ratio is in the range of 0.85 or more and less than 0.95 ×: Compared to Comparative Example 3 (=1), the polishing rate ratio is less than 0.85 The above indicates the following evaluations respectively: "○" means having a polishing speed equal to or higher than that of Comparative Example 3, "Δ" means having a practically no problem polishing speed, and "×" means a poor polishing speed.

Evaluation of attachments (attachment count ratio) In order to evaluate the presence or absence of abrasive residues or abrasive debris on the surface of the aluminum disc substrate after polishing, a scanning electron microscope was used to evaluate the attached matter count according to the following conditions. Measuring device: Field emission scanning electron microscope "JSM-7100" manufactured by JEOL Ltd. Measurement conditions: acceleration voltage 15kV, observation magnification 20,000 times Measurement method: Under the above-mentioned equipment and conditions, the aluminum magnetic disk substrate that has been polished until the later stage is used to read the secondary electron image with the contrast that the abrasive residues or abrasive debris on the substrate appear white. Use photo retouching software to convert the read image into black and white binarization, then count the pixels in the white part and count as the number of attachments.

The attached matter count value (8755) of Comparative Example 3 obtained by the above method is set to 1 (reference), and based on the relative value at this time, the following standards are used to evaluate the values of Examples 1 to 7 and Comparative Examples 1 to 5 Adhesion count ratio obtained from the abrasive composition. ◎: Compared to Comparative Example 3 (=1), the attached matter count ratio is less than 0.2 ○: Relative to Comparative Example 3 (=1), the attached matter count ratio is in the range of 0.2 or more and less than 0.9 ∆: Compared with Comparative Example 3 (=1), the attachment count ratio is in the range of 0.9 or more and less than 1.0 ×: Relative to Comparative Example 3 (=1), the attached matter count ratio is 1.0 or more The above respectively indicate the following evaluations: ◎ means that the count of attachments is significantly less than that of Comparative Example 3, "○" means that the count of attachments is less than that of Comparative Example 3, and "∆" is the same level as that of Comparative Example 3 but practically No problem, "×" means a practical problem.

Evaluation of fluctuation ratio The undulation of the aluminum dish was measured using a three-dimensional surface structure analysis microscope using a scanning white light interferometry manufactured by AMETEK, Inc. The measurement conditions are the measuring device made by AMETEK, Inc. (New View 8300 (lens: 1.4 times, zoom: 1.0 times)), the wavelength is 500~1000μm, the measurement area is 6mm×6mm, and the analysis software made by AMETEK, Inc. is used. (Mx) for analysis.

The actual measured value (0.92Å) of the undulation of Comparative Example 3 obtained using the above method was set to 1 (reference), and the relative values at this time were used to evaluate Examples 1 to 7 and Comparative Example 1 according to the following standards ~5 undulation ratio of the abrasive composition. ○: Relative to Comparative Example 3 (=1), the undulation ratio is less than 1.01 ∆: Compared with Comparative Example 3 (=1), the fluctuation ratio is in the range of 1.01 or more and less than 1.10 ×: Compared to Comparative Example 3 (=1), the fluctuation ratio is 1.10 or more The above respectively indicate the following evaluations: "○" means having undulations equal to or better than that of Comparative Example 3, "∆" means having undulations that are not problematic for practical use, and "×" means undulations are inferior.

Research Regarding Comparative Example 3, the particle size distribution of colloidal silica is within the scope of the present invention, but an abrasive composition that does not contain a specific organic sulfate salt compound is used, so the balance of polishing performance, such as polishing speed, adhesion count, and fluctuations, is used. Above, the results are inferior to Examples 1 to 3 containing organic sulfate ester salt compounds with specific structures. In other words, the effect of the present invention is achieved by using an abrasive composition containing an organic sulfate compound having a specific structure, except that the particle size distribution of colloidal silica is within a specific range. In addition, Examples 6 and 7 are the results of using abrasive compositions with different particle size characteristics of colloidal silica compared to the abrasive composition of Example 1.

However, Comparative Examples 4 and 5 using abrasive compositions that are different from the abrasive composition of the present invention and contain organic sulfate ester salt compounds with no specific structure, compared to Comparative Example 3, particularly show that the adhesion count ratio is not improved result.

On the other hand, even if it is an abrasive composition containing an organic sulfate ester salt compound with a specific structure, the particle size characteristics of colloidal silica do not satisfy the conditions specified in the abrasive composition of the present invention in Comparative Examples 1 and 2, compared to In Example 1, there is also a poor balance between the polishing speed and the fluctuations.

In the case of Examples 4 and 5 in which an aliphatic amine compound was further added as an optional component to the abrasive composition of Example 1, it was confirmed that the adhesion count ratio (0.89) was significantly reduced compared to Example 1. (Example 4=0.10 and Example 5=0.08), it can be seen that adhesions such as abrasive residues or abrasive swarf on the surface of the substrate are greatly reduced. This means that the addition of aliphatic amine compounds helps greatly reduce adhesions.

From the above conclusions, it is obvious that by using the abrasive composition of the present invention, it is possible to achieve a balanced increase in the polishing speed, reduction of abrasive residues or abrasive debris on the surface of the substrate, and improvement of undulation. In addition, it is not easy to simultaneously increase the polishing speed, reduce the abrasive residues or abrasive debris on the substrate surface, and improve the undulation. The abrasive composition of the present invention exerts the following excellent effects: it is possible to produce a substrate with reduced undulations, such as abrasive residues or abrasive dust, on the surface of the substrate after the rough polishing step in the multi-stage polishing method with high productivity. [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 magnetic recording medium substrates such as glass magnetic disk substrates and aluminum magnetic disk substrates. Furthermore, it can be used to polish the surface of an aluminum magnetic disk substrate for a magnetic recording medium on which an electroless nickel-phosphorus plating film is formed on the surface of an aluminum alloy substrate.

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Claims (6)

An abrasive composition for magnetic disk substrates, which is used in the rough grinding of magnetic disk substrates with the following steps (1) to (3) and each step (1) to (3) performed by the same grinder The abrasive composition B of step (3), which contains: colloidal silica, organic sulfate ester salt compound and water, wherein the colloidal silica has a volume of 50 nm in the particle size distribution based on the volume measured by the Haywood diameter The cumulative frequency is more than 35%, and in the particle size distribution, the volume cumulative frequency of 15nm particle size is less than 90%. The organic sulfate ester salt compound is represented by the following general formula (1): RO-(AO) _n -SO ₃ M ･･･ General formula (1) In the above general formula (1), R represents a linear or branched alkyl, alkenyl, aryl or alkylaryl group with 5 to 21 carbon atoms, and AO represents the carbon number 2 or 3 oxyalkylene groups, n represents a natural number from 1 to 30, and M represents an alkali metal, alkaline earth metal, ammonium ion or organic cation; step (1) is to combine α-alumina, intermediate alumina and water The abrasive composition A is supplied to the grinder, and the disk substrate is subjected to the first rough polishing step; step (2) is the step of washing the disk substrate obtained in the above step (1); step (3) is the step of rinsing the disk substrate The abrasive composition B of silicon oxide, an organic sulfate ester salt compound, and water is supplied to a grinder, and the magnetic disk substrate is subjected to a subsequent rough polishing step. The abrasive composition for magnetic disk substrates of claim 1, which further contains an aliphatic amine compound. According to claim 2, the abrasive composition for magnetic disk substrates, wherein the aliphatic amine compound is selected from ethylamine, n-propylamine, isopropylamine, n-butylamine, isobutylamine, secondary butylamine, tertiary butylamine, Cyclohexylamine, piperazine, diethylamine, methylpropylamine, ethylpropylamine, triethylamine, ethylenediamine, 1,2-propanediamine, trimethylenediamine, tetramethylenediamine, pentamethylenediamine Amine, hexamethylenediamine, N,N-dimethylethylenediamine, N,N'-dimethylethylenediamine, N-ethylethylenediamine, N,N,N',N'-tetra Methylethylenediamine, N-methyl-1,3-propanediamine, 1,3-diaminepentane, diethylenetriamine, bis(hexamethylene)triamine, triethylenetriamine, At least one of the group consisting of ethylenetetramine, tetraethylenepentamine, pentaethylenehexamine and tetramethylhexamethylenediamine. The abrasive composition for a magnetic disk substrate according to any one of claims 1 to 3, which further contains an acid and/or a salt thereof. The abrasive composition for a magnetic disk substrate according to any one of claims 1 to 4, which further contains an oxidizing agent. The abrasive composition for a magnetic disk substrate according to any one of claims 1 to 5, which is used for rough polishing of an aluminum magnetic disk substrate plated with electroless nickel-phosphorus.