Silica dispersion and abrasive composition

Abstract

To provide an antibacterial agent-blended silica dispersion having an antibacterial properties, scarce in reduction of a polishing speed even when used as one constituent of a polishing agent composition, and good in surface conditions of a board after polishing.SOLUTION: The silica dispersion contains colloidal silica, and an organic compound having a hemiformal structure. The organic compound having a hemiformal structure may be an aliphatic organic compound, an aromatic organic compound, or further a compound formed by combining an aliphatic organic compound with an aromatic organic compound.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a silica dispersion and an abrasive composition. More specifically, the present invention relates to a silica dispersion used as one component of raw materials for abrasives, paints, etc., and an abrasive composition using the silica dispersion. [Background technology]

[0002] Conventionally, silica dispersions in which silica particles such as colloidal silica are dispersed in liquids such as water have been used as a component of raw materials for abrasives, paints, catalyst carriers, or modifiers for resin products and paper products, etc. During storage, the silica dispersions themselves may become discolored, or the silica particles may aggregate or gel, due to the generation of microorganisms such as bacteria and mold.

[0003] In order to prevent such defects, it is common to add an antibacterial agent to the silica dispersion. However, the addition of the antibacterial agent may reduce the inherent performance of the polishing agent. For example, when the silica dispersion is used as one component of the polishing agent composition that constitutes the polishing agent, the antibacterial agent added to the silica dispersion may affect the polishing performance, such as reducing the polishing speed or increasing scratches on the substrate surface after polishing.

[0004] Therefore, there is a demand for the development of an antibacterial agent that can fully exert the antibacterial effect on silica dispersions without impairing the original functions of abrasives, etc. For example, it has already been proposed to add an isothiazolinone compound as an antibacterial agent to a silica dispersion, thereby exerting the antibacterial effect and maintaining good polishing performance in the abrasive (see Patent Documents 1 to 3).

[0005] According to this, by using the isothiazolinone compound 2-methyl-4-isothiazolin-3-one as an antibacterial agent, it is possible to some extent to adjust the balance between exerting the antibacterial effect and maintaining the polishing performance (see Patent Document 1). In addition, there have been proposals to use an isothiazolinone compound having a specific structure (see Patent Document 2), or to add a preservative such as 5-chloro-2-methyl-4-isothiazolin-3-one to an abrasive composition to reduce scratches on the substrate surface after polishing (see Patent Document 3). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2006-176733 A [Patent Document 2] JP 2016-124977 A [Patent Document 3] JP 2003-313542 A Summary of the Invention [Problem to be solved by the invention]

[0007] As mentioned above, isothiazolinone compound is used as antibacterial agent, and it is expected to have some effect when it is added to silica dispersion. However, antibacterial property and polishing property may still be biased, and it is difficult to adjust the balance between them. Therefore, further development of antibacterial agent to be added to silica dispersion is expected.

[0008] In view of the above-mentioned circumstances, an object of the present invention is to provide a silica dispersion and an abrasive composition containing an antibacterial agent that can exhibit sufficient antibacterial effect, suppress a decrease in the polishing rate without impairing the inherent performance of the abrasive, and maintain the condition of the substrate surface after polishing in a good state. [Means for solving the problem]

[0009] As a result of intensive research conducted in order to solve the above-mentioned problems, the inventors of the present application have found that an organic compound having a formaldehyde-donating hemiformal structure is used as an antibacterial agent, and that a silica dispersion to which such an antibacterial agent has been added exhibits good antibacterial performance, and that even when used as one component of the raw materials of an abrasive composition, it does not affect polishing performance such as the removal rate, and have thus completed the present invention described below.

[0010] [1] Contains colloidal silica and an antibacterial agent composed of an organic compound with a hemiformal structure. It is used as one of the raw materials of an abrasive composition used for polishing magnetic disk substrates. Silica dispersion.

[0011] [2] The antibacterial agent is The silica dispersion according to the above [1], wherein the compound is an aliphatic organic compound having a hemiformal structure represented by the general formula 1 below.

[0012] [ka] (In Chemical Formula 1, R 1 represents a linear, branched, or alicyclic hydrocarbon group, including those in which some of the carbon atoms in the hydrocarbon group are replaced with nitrogen atoms and / or oxygen atoms)

[0013] [3] The silica dispersion according to [1], wherein the antibacterial agent is an aromatic organic compound having a hemiformal structure represented by the following general formula 2:

[0014] [ka] (In Chemical Formula 2, R 2 represents a hydrocarbon group having an aromatic ring, including those in which some of the carbon atoms in the hydrocarbon group are replaced with nitrogen atoms and / or oxygen atoms)

[0015] [4] It contains colloidal silica and an antibacterial agent composed of an organic compound having a hemiformal structure, The antibacterial agent is an aliphatic organic compound having a hemiformal structure represented by the following general formula 3; An aromatic organic compound having a hemiformal structure represented by the general formula 4 below. It is formed by a combination of Rusi Rica dispersion.

[0016] [ka] (In Chemical Formula 3, R 3 represents a linear, branched, or alicyclic hydrocarbon group, including those in which some of the carbon atoms in the hydrocarbon group are replaced with nitrogen atoms and / or oxygen atoms)

[0017] [ka] (In Chemical Formula 4, R 4 represents a hydrocarbon group having an aromatic ring, including those in which some of the carbon atoms in the hydrocarbon group are replaced with nitrogen atoms and / or oxygen atoms)

[0018] [5] Before being used as a component of the raw material of an abrasive composition used for polishing magnetic disk substrates. Note [ 4 ] The silica dispersion as described above.

[0019] [6] The above [1]~[ 3 ] and [5] and water. and is used for polishing magnetic disk substrates. Abrasive composition.

[0020] [7] The polishing composition according to [6], further comprising an acid and an oxidizing agent.

[0021] [8] Used to polish nickel-phosphorus-plated aluminum magnetic disk substrates. The polishing composition according to [6] or [7] above. [9] An abrasive composition comprising the silica dispersion according to [4] above and water.

[10] The polishing composition according to [9] above, further comprising an acid and an oxidizing agent. Effect of the Invention

[0022] The silica dispersion of the present invention exhibits sufficient antibacterial effect and has excellent long-term storage stability by containing an organic compound having a hemiformal structure, which is a formaldehyde donor compound, as an antibacterial agent. Furthermore, the polishing agent composition using the silica dispersion of the present invention can have excellent polishing properties that can obtain a substrate surface with reduced scratches without decreasing the polishing rate. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] The following describes the embodiments of the present invention. The present invention is not limited to the following embodiments, and changes, modifications, and improvements can be made without departing from the scope of the invention.

[0024] 1.Silica dispersion The silica dispersion of this embodiment contains colloidal silica and an antibacterial agent composed of an organic compound having a hemiformal structure. The organic compound having a hemiformal structure is a formaldehyde donor compound. The silica dispersion is used as one of the raw materials of an abrasive composition constituting an abrasive for polishing a magnetic disk substrate, or for various purposes such as paints and various modifiers. The silica dispersion of this embodiment is , Ken The following describes the components that can be used as a component of the polishing composition.

[0025] The antibacterial agent in the silica dispersion of this embodiment is preferably an aliphatic organic compound having a hemiformal structure (hereinafter simply referred to as an "aliphatic organic compound"), or preferably an aromatic organic compound having a hemiformal structure (hereinafter simply referred to as an "aromatic organic compound"), and more preferably a combination of both the aliphatic organic compound and the aromatic organic compound.

[0026] 1.1 Colloidal Silica The colloidal silica contained as one component of the silica dispersion of this embodiment preferably has an average particle diameter (D50) in the range of 1 to 150 nm, more preferably in the range of 3 to 120 nm. If the average particle diameter (D50) of the colloidal silica is less than 1 nm, the silica particles tend to aggregate, and the stability of the dispersion state deteriorates. On the other hand, if the average particle diameter (D50) of the colloidal silica exceeds 150 nm, scratches on the substrate after polishing may deteriorate. Here, the average particle diameter (D50) of the colloidal silica is calculated by analysis based on the observation results by a transmission electron microscope (TEM) (details will be described later).

[0027] Colloidal silica can be used in known shapes such as spherical and confetti-shaped (particulate shape with convex portions on the surface), and the primary particles are monodispersed in water to form a colloid. In particular, it is preferable to use spherical or nearly spherical colloidal silica. By using spherical or nearly spherical colloidal silica, it is expected to reduce scratches on the substrate after polishing.

[0028] The colloidal silica used can be manufactured by a conventionally known manufacturing method, for example, the water glass method, which uses alkali metal silicate such as sodium silicate or potassium silicate as a raw material and grows colloidal silica particles by condensation reaction of the raw material in an aqueous solution, the alkoxysilane method, which uses tetraalkoxysilane such as tetraethoxysilane as a raw material, which is hydrolyzed with an acid or alkali in a solvent containing a water-soluble organic solvent such as alcohol, and further grows colloidal silica particles by condensation reaction, or a method of synthesizing colloidal silica by reacting metal silicon with water in the presence of an alkali catalyst. Note that the water glass method can be used preferably in terms of manufacturing cost. The colloidal silica used as the material of the polishing compound composition of the present embodiment can be manufactured by appropriately using these synthesis methods.

[0029] In the silica dispersion of this embodiment, the content (content rate) of colloidal silica contained in the silica dispersion is preferably in the range of 5 to 60 mass%, more preferably in the range of 10 to 50 mass%. If the concentration of colloidal silica in the silica dispersion is less than 5 mass%, it is often disadvantageous from the viewpoint of compact storage and transportation of silica particles. On the other hand, if the concentration of colloidal silica in the silica dispersion is more than 60 mass%, the colloidal silica may easily gel. Therefore, it is preferable to adjust the content rate of colloidal silica to the above range. In addition, the silica dispersion of this embodiment may contain silica particles other than colloidal silica or solid particles other than silica.

[0030] Here, when preparing an abrasive composition using the silica dispersion of this embodiment, a silica dispersion in which the content of colloidal silica has been previously adjusted to a high concentration is used, and the silica dispersion is diluted with water to reduce the content of colloidal silica to a low concentration. In addition, when preparing the abrasive composition, silica particles other than colloidal silica or solid particles other than silica may be mixed.

[0031] 1.2 Aliphatic organic compounds with hemiformal structure The aliphatic organic compound having a hemiformal structure used in the silica dispersion of this embodiment is a formaldehyde donor compound, specifically, one represented by the general formula 1 below.

[0032] [ka]

[0033] Here, in Chemical Formula 1, R 1 represents a linear, branched, or alicyclic hydrocarbon group, and may include a structure in which some of the carbon atoms in the hydrocarbon group are substituted with nitrogen atoms and / or oxygen atoms.

[0034] The synthesis of the above aliphatic organic compounds is carried out by mixing an aqueous formaldehyde solution with an aliphatic alcohol compound, which causes a nucleophilic addition reaction of the alcohol to the carbonyl group of the formaldehyde. For example, (ethylenedioxy)dimethanol, a type of aliphatic organic compound, can be obtained by reacting ethylene glycol with an aqueous formaldehyde solution.

[0035] Further, other examples of aliphatic organic compounds include n-butanol hemiformal, 2,4-diethyl-1,5-pentanediol hemiformal, 2-ethyl-1,3-hexanediol hemiformal, 1-octanol hemiformal, propylene glycol hemiformal, dipropylene glycol hemiformal, diethylene glycol monobutyl ether hemiformal, and the like.

[0036] Here, the content of the aliphatic organic compound in the silica dispersion can generally be in the range of 1 to 10,000 ppm by mass, and more preferably in the range of 10 to 1,000 ppm by mass.If the content of the aliphatic organic compound is less than 1 ppm by mass, the effect of improving storage stability by adding the aliphatic organic compound to the silica dispersion cannot be fully achieved.On the other hand, if the content of the aliphatic organic compound is more than 10,000 ppm by mass, there is a risk that the polishing speed will decrease when the silica dispersion is used as one component of an abrasive.

[0037] 1.3 Aromatic organic compounds with a hemiformal structure The aromatic organic compound having a hemiformal structure used in the silica dispersion of this embodiment is a formaldehyde donor compound, specifically, one represented by the general formula 2 below.

[0038] [ka]

[0039] Here, in Chemical Formula 2, R 2represents a hydrocarbon group having an aromatic ring, and may include a structure in which some of the carbon atoms in the hydrocarbon group are substituted with nitrogen atoms and / or oxygen atoms.

[0040] The synthesis of the aromatic organic compound is carried out by mixing an aqueous formaldehyde solution with an aromatic alcohol compound, which causes a nucleophilic addition reaction of the alcohol to the carbonyl group of the formaldehyde. For example, (benzyloxy)methanol, which is one of the aromatic organic compounds having a hemiformal structure, can be obtained by reacting benzyl alcohol with an aqueous formaldehyde solution.

[0041] Further, other examples of aromatic organic compounds include benzyl glycol hemiformal, (benzyloxymethoxy)-methanol, (4-methylbenzyloxy)methanol, 2-phenoxyethanol hemiformal, 3-phenoxy-propane-1,2-diol hemiformal, 3-benzyloxy-propane-1,2-diol hemiformal, and the like.

[0042] Here, the content of aromatic organic compound in silica dispersion can be generally in the range of 1-10,000 mass ppm, and more preferably in the range of 10-1,000 mass ppm.If the content of aromatic organic compound is less than 1 mass ppm, the effect of improving storage stability by adding it to silica dispersion cannot be fully exhibited.On the other hand, if the content of aromatic organic compound is more than 10,000 mass ppm, there is a risk of the polishing speed decreasing when silica dispersion is used as one component of polishing agent.

[0043] The above-mentioned aliphatic organic compounds and aromatic organic compounds can be added individually to colloidal silica as antibacterial agents to make the silica dispersion of the present invention.Furthermore, it is also possible to use a combination of both the aliphatic organic compound represented by the general formula of Chemical 1 and the aromatic organic compound represented by the general formula of Chemical 2 as the antibacterial agent to be added to the silica dispersion.Here, Chemical 1 has the same structure as the aliphatic organic compound represented by Chemical 3 in the present invention, and Chemical 2 has the same structure as the aromatic organic compound represented by Chemical 4 in the present invention.In this way, by using a mixture containing both the aliphatic organic compound and the aromatic organic compound as the antibacterial agent, it is possible to further improve the balance between exerting the antibacterial effect and maintaining the polishing performance.

[0044] In addition, when the aliphatic organic compound and the aromatic organic compound are used in combination as an antibacterial agent, the mixing ratio of each is not particularly limited and can be determined arbitrarily. For example, the mass ratio of the aliphatic organic compound and the aromatic organic compound is preferably adjusted to a range of 10:90 to 90:10, and more preferably adjusted to a range of 20:80 to 80:20. By adjusting to this range, a silica dispersion having a good balance between antibacterial properties and polishing properties can be obtained.

[0045] 2. Abrasive composition The polishing compound composition of the present embodiment uses the silica dispersion liquid of the present embodiment described above, and mainly contains colloidal silica, an antibacterial agent composed of an organic compound having a hemiformal structure (an organic aliphatic compound and / or an organic aromatic compound), and water.

[0046] In addition to the above-mentioned constitution, the polishing composition of this embodiment preferably further contains an acid and an oxidizing agent. When the polishing composition of this embodiment is prepared by mixing the silica dispersion containing an antibacterial agent, water, an acid, and an oxidizing agent, it is preferable that the storage period from the completion of preparation is as short as possible, and it is desirable to use it for polishing magnetic disk substrates and the like as soon as possible. If the storage period after preparation as the polishing composition is long, the aggregation of colloidal silica contained in the silica dispersion is likely to progress, which may lead to a decrease in polishing performance.

[0047] 2.1 Acid In the polishing compound of this embodiment, an inorganic acid or an organic acid can be used for the purpose of adjusting the pH value or as an optional component.

[0048] More specifically, examples of inorganic acids include nitric acid, sulfuric acid, hydrochloric acid, phosphoric acid, phosphonic acid, phosphinic acid, pyrophosphoric acid, tripolyphosphoric acid, etc. On the other hand, examples of organic acids include glutamic acid, aspartic acid, citric acid, tartaric acid, oxalic acid, nitroacetic acid, maleic acid, malic acid, succinic acid, phosphorus-containing organic acids, etc.

[0049] As the phosphorus-containing organic acid, which is a type of organic acid, at least one compound selected from 2-aminoethylphosphonic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, aminotri(methylenephosphonic acid), ethylenediaminetetra(methylenephosphonic acid), diethylenetriaminepenta(methylenephosphonic acid), ethane-1,1-diphosphonic acid, ethane-1,1,2-triphosphonic acid, ethane-1-hydroxy-1,1,2-triphosphonic acid, ethane-1,2-dicarboxy-1,2-diphosphonic acid, methanehydroxyphosphonic acid, 2-phosphonobutane-1,2-dicarboxylic acid, 1-phosphonobutane-2,3,4-tricarboxylic acid, and α-methylphosphonosuccinic acid can be used.

[0050] In addition, it is also a preferred embodiment to use two or more of the above-listed acid compounds in combination. For example, it is more preferred to use a combination of an inorganic acid and a phosphorus-containing organic acid. More specifically, a combination of an inorganic acid, sulfuric acid, and a phosphorus-containing organic acid, 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP), or a combination of phosphoric acid and 1-hydroxyethylidene-1,1-diphosphonic acid, is preferred.

[0051] The concentration of the acid in the polishing compound is appropriately changed in order to adjust the pH value.

[0052] 2.2 Oxidizing agents The polishing agent composition of the present embodiment may contain an oxidizing agent as described above. Such an oxidizing agent is known to have the effect of improving the polishing rate. The oxidizing agent used may be a peroxide, permanganic acid or a salt thereof, chromic acid or a salt thereof, peroxoacid or a salt thereof, halogen oxoacid or a salt thereof, oxyacid or a salt thereof, or a mixture of two or more of these.

[0053] More specifically, examples of the agent include hydrogen peroxide, sodium peroxide, barium peroxide, potassium peroxide, potassium permanganate, metal salts of chromate, metal salts of dichromate, persulfuric acid, sodium persulfate, potassium persulfate, ammonium persulfate, peroxolinic acid, sodium perborate, performic acid, peracetic acid, hypochlorous acid, sodium hypochlorite, calcium hypochlorite, etc. In particular, those using hydrogen peroxide, persulfuric acid and its salts, and hypochlorous acid and its salts are preferred, and the use of hydrogen peroxide is even more preferred.

[0054] In the polishing compound of this embodiment, the content (content) of the oxidizing agent contained in the polishing compound is preferably in the range of 0.01 to 10.0 mass%, more preferably 0.1 to 5.0 mass%. If the content of the oxidizing agent is less than 0.01 mass%, the polishing rate may decrease. On the other hand, if the content of the oxidizing agent is more than 10.0 mass%, the surface roughness of the polished substrate surface may deteriorate.

[0055] 1.3 Water The polishing compound of the present embodiment is generally prepared by diluting a silica dispersion prepared at a high concentration with water, and further adding the above-mentioned acid and oxidizing agent as appropriate. As the water used here, for example, pure water, ultrapure water, and distilled water can be suitably used.

[0056] The dilution ratio of the silica dispersion can be appropriately determined based on, for example, the colloidal silica concentration in the polishing agent composition. For example, in the case of a polishing agent composition used for polishing a magnetic disk substrate, dilution is generally performed so that the colloidal silica concentration in the polishing agent composition is in the range of 0.5 to 20 mass%, more preferably in the range of 1 to 10 mass%.

[0057] If the colloidal silica concentration is less than 0.5% by mass, the polishing rate may decrease, whereas if the colloidal silica concentration is more than 20% by mass, the polishing stability may not be maintained.

[0058] 2. Physical properties of the polishing compound The pH value (25°C) of the polishing compound of this embodiment can be in the range of 0.1 to 4.0. More preferably, it is in the range of 0.5 to 3.0. By making the pH value (25°C) of the polishing compound composition 0.1 or more, it is possible to suppress roughness of the substrate surface after polishing. On the other hand, by making the pH value (25°C) of the polishing compound composition 4.0 or less, it is possible to suppress a decrease in the polishing rate.

[0059] The polishing agent composition of the present embodiment can be used for polishing various electronic parts such as magnetic recording media (magnetic disk substrates) such as hard disks. In particular, it can be suitably used for polishing aluminum magnetic disk substrates among magnetic disk substrates. Furthermore, it can be suitably used for polishing electroless nickel-phosphorus plated aluminum magnetic disk substrates.

[0060] The electroless nickel-phosphorus plating treatment for an aluminum magnetic disk substrate is usually carried out under conditions of a pH value (25°C) in the range of 4 to 6. less than Under these conditions, nickel tends to dissolve, making plating difficult. On the other hand, for polishing, for example, under conditions of a pH value (25°C) of 4.0 or less, there is an effect of increasing the polishing rate.

[0061] 3. Method for polishing magnetic disk substrate As described above, the polishing compound of the present embodiment can be suitably used for polishing magnetic disk substrates such as aluminum magnetic disk substrates and glass magnetic disk substrates. In particular, it can be suitably used for polishing electroless nickel-phosphorus plated aluminum magnetic disk substrates (hereinafter simply referred to as "aluminum disks").

[0062] A known polishing method using the abrasive composition of this embodiment is, for example, a method in which a polishing pad is attached to the platen of a polishing machine, the abrasive composition is supplied to the polishing surface of an aluminum disk that is the object to be polished or to the pad surface of the polishing pad, and the polishing pad is rubbed against the polishing surface (polishing).

[0063] More specifically, when the front and back surfaces of an aluminum disk are polished simultaneously, a double-sided polisher is used with polishing pads attached to the upper and lower plates. In this case, the aluminum disk to be polished is sandwiched between a pair of polishing pads attached to the upper and lower plates, and the abrasive composition is supplied between the polishing surface and the polishing pads, while the pair of polishing pads are rotated simultaneously, thereby polishing the front and back surfaces of the aluminum disk. The polishing pads used may be, for example, urethane type, suede type, nonwoven fabric type, or other well-known types. EXAMPLES

[0064] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In addition to the following examples, various modifications and improvements can be made to the present invention based on the knowledge of those skilled in the art, as long as they do not deviate from the gist of the present invention. In the preparation of the polishing compound composition shown below, HEDP stands for 1-hydroxyethylidene-1,1-diphosphonic acid.

[0065] (Method of Preparing Silica Dispersion and Polishing Compound Composition) <Example 1> Preparation of silica dispersion a To a commercially available colloidal silica slurry (average particle size (D50) = 21 nm, silica concentration = 40 mass%, no antibacterial agent), 50 mass ppm of commercially available (ethylenedioxy)dimethanol was added to prepare "silica dispersion a". (Ethylenedioxy)dimethanol is an antibacterial agent equivalent to the aliphatic organic compound having a hemiformal structure in the present invention. Note that the colloidal silica slurry and (ethylenedioxy)dimethanol are both raw materials or compounds that are easily available to those skilled in the art (hereinafter the same).

[0066] Preparation of abrasive composition A Using the prepared silica dispersion a, "polishing compound composition A" was prepared with pure water so that the colloidal silica concentration was 5.6 mass%, and the concentrations of sulfuric acid, HEDP, and hydrogen peroxide were the values ​​shown in Table 1 below. The prepared polishing compound composition A was used in the polishing test of Example 1. Here, sulfuric acid and HEDP correspond to the "acid" in the present invention, and hydrogen peroxide corresponds to the "oxidizing agent" in the present invention (the same applies below). Note that sulfuric acid, HEDP, and hydrogen peroxide are all raw materials or compounds that are easily available to those skilled in the art (the same applies below).

[0067] <Example 2> Preparation of silica dispersion b To the same commercially available colloidal silica slurry as that used for the above-mentioned silica dispersion a, 200 mass ppm of commercially available (ethylenedioxy)dimethanol was added to prepare "silica dispersion b".

[0068] Preparation of abrasive composition B Using the prepared silica dispersion b, "polishing compound composition B" was prepared with pure water so that the colloidal silica concentration was 5.6 mass % and the concentrations of sulfuric acid, HEDP, and hydrogen peroxide were the values ​​shown in Table 1. The prepared polishing compound composition B was used in the polishing test of Example 2.

[0069] <Example 3> Preparation of silica dispersion c To the same commercially available colloidal silica slurry as that used for the above-mentioned silica dispersion liquid a, 50 mass ppm of commercially available (benzyloxy)methanol was added to prepare "silica dispersion liquid c". (benzyloxy)methanol corresponds to the aromatic organic compound having a hemiformal structure in the present invention. Note that (benzyloxy)methanol is a compound that is easily available to those skilled in the art (hereinafter the same).

[0070] Preparation of abrasive composition C Using the prepared silica dispersion c, "polishing compound composition C" was prepared with pure water so that the colloidal silica concentration was 5.6 mass % and the concentrations of sulfuric acid, HEDP, and hydrogen peroxide were the values ​​shown in Table 1. The prepared polishing compound composition C was used in the polishing test of Example 3.

[0071] <Example 4> Preparation of silica dispersion d To the same commercially available colloidal silica slurry as that used for the above-mentioned silica dispersion a, 200 ppm by mass of commercially available (benzyloxy)methanol was added to prepare "silica dispersion d".

[0072] Preparation of abrasive composition D Using the prepared silica dispersion d, "polishing compound composition D" was prepared with pure water so that the colloidal silica concentration was 5.6 mass % and the concentrations of sulfuric acid, HEDP, and hydrogen peroxide were the values ​​shown in Table 1. The prepared polishing compound composition D was used in the polishing test of Example 4.

[0073] <Example 5> Preparation of silica dispersion To the same commercially available colloidal silica slurry as that used for the above-mentioned silica dispersion a, 25 ppm by mass of commercially available (ethylenedioxy)dimethanol and 25 ppm by mass of commercially available (benzyloxy)methanol were added to prepare "silica dispersion e".

[0074] Preparation of abrasive composition E Using the prepared silica dispersion e, "polishing compound composition E" was prepared with pure water so that the colloidal silica concentration was 5.6 mass % and the concentrations of sulfuric acid, HEDP, and hydrogen peroxide were the values ​​shown in Table 1. The prepared polishing compound composition E was used in the polishing test of Example 5.

[0075] <Example 6> Preparation of silica dispersion f To the same commercially available colloidal silica slurry as that used for the above-mentioned silica dispersion a, 100 ppm by mass of commercially available (ethylenedioxy)dimethanol and 100 ppm by mass of commercially available (benzyloxy)methanol were added to prepare "silica dispersion f".

[0076] Preparation of abrasive composition F Using the prepared silica dispersion f, "polishing compound composition F" was prepared with pure water so that the colloidal silica concentration was 5.6 mass % and the concentrations of sulfuric acid, HEDP, and hydrogen peroxide were the values ​​shown in Table 1. The prepared polishing compound composition F was used in the polishing test of Example 6.

[0077] <Example 7> Preparation of silica dispersion g To the same commercially available colloidal silica slurry as that used for the above-mentioned silica dispersion a, 60 ppm by mass of commercially available (ethylenedioxy)dimethanol and 140 ppm by mass of commercially available (benzyloxy)methanol were added to prepare "silica dispersion g".

[0078] Preparation of abrasive composition G Using the prepared silica dispersion g, "polishing compound composition G" was prepared with pure water so that the colloidal silica concentration was 5.6 mass % and the concentrations of sulfuric acid, HEDP, and hydrogen peroxide were the values ​​shown in Table 1. The prepared polishing compound composition G was used in the polishing test of Example 7.

[0079] <Example 8> Preparation of silica dispersion h To the same commercially available colloidal silica slurry as that used for the above-mentioned silica dispersion a, 140 ppm by mass of commercially available (ethylenedioxy)dimethanol and 60 ppm by mass of commercially available (benzyloxy)methanol were added to prepare "silica dispersion h".

[0080] Preparation of abrasive composition H Using the prepared silica dispersion h, "polishing compound composition H" was prepared with pure water so that the colloidal silica concentration was 5.6 mass % and the concentrations of sulfuric acid, HEDP, and hydrogen peroxide were the values ​​shown in Table 1. The prepared polishing compound composition H was used in the polishing test of Example 8.

[0081] <Comparative Example 1> Preparation of silica dispersion i To the same commercially available colloidal silica slurry as that used for the above-mentioned silica dispersion a, 50 ppm by mass of commercially available 2-methyl-4-isothiazolin-3-one was added to prepare "silica dispersion i".

[0082] Preparation of abrasive composition I Using the prepared silica dispersion i, "polishing compound composition I" was prepared with pure water so that the colloidal silica concentration was 5.6 mass % and the concentrations of sulfuric acid, HEDP, and hydrogen peroxide were the values ​​shown in Table 1. The prepared polishing compound composition I was used in the polishing test of Comparative Example 1.

[0083] <Comparative Example 2> Preparation of silica dispersion To the same commercially available colloidal silica slurry as that used for the above-mentioned silica dispersion a, 200 mass ppm of commercially available 2-methyl-4-isothiazolin-3-one was added to prepare "silica dispersion j".

[0084] Preparation of abrasive composition J Using the prepared silica dispersion j, "polishing compound composition J" was prepared with pure water so that the colloidal silica concentration was 5.6 mass % and the concentrations of sulfuric acid, HEDP, and hydrogen peroxide were the values ​​shown in Table 1. The prepared polishing compound composition J was used in the polishing test of Comparative Example 2.

[0085] <Comparative Example 3> Preparation of silica dispersion To the same commercially available colloidal silica slurry as that used for the above-mentioned silica dispersion a, 50 mass ppm of commercially available 5-chloro-2-methyl-4-isothiazolin-3-one was added to prepare "silica dispersion k".

[0086] Preparation of abrasive composition K Using the prepared silica dispersion k, "polishing compound composition K" was prepared with pure water so that the colloidal silica concentration was 5.6 mass % and the concentrations of sulfuric acid, HEDP, and hydrogen peroxide were the values ​​shown in Table 1. The prepared polishing compound composition K was used in the polishing test of Comparative Example 3.

[0087] <Comparative Example 4> Preparation of silica dispersion To the same commercially available colloidal silica slurry as that used for the above-mentioned silica dispersion a, 200 mass ppm of commercially available 5-chloro-2-methyl-4-isothiazolin-3-one was added to prepare "silica dispersion l".

[0088] Preparation of abrasive composition L Using the prepared silica dispersion 1, "polishing compound composition L" was prepared with pure water so that the colloidal silica concentration was 5.6 mass % and the concentrations of sulfuric acid, HEDP, and hydrogen peroxide were the values ​​shown in Table 1. The prepared polishing compound composition L was used in the polishing test of Comparative Example 4.

[0089] [Table 1]

[0090] The silica dispersions a to l used in the polishing tests of Examples 1 to 8 and Comparative Examples 1 to 4 shown above were prepared using the raw materials or compounds shown in Table 2 below to have the contents (addition amounts) shown in Table 2. Furthermore, the polishing compound compositions A to L used in the polishing tests of Examples 1 to 8 and Comparative Examples 1 to 4 were prepared using the silica dispersions prepared by the above-mentioned method using the colloidal silica and antibacterial agent shown in Table 2 below to have the contents (addition amounts) shown in Table 2, and the acids and oxidizing agents shown in Table 1 to have the contents (addition amounts) of colloidal silica, antibacterial agent, acid and oxidizing agent shown in Table 1.

[0091] [Table 2]

[0092] The results of the antibacterial evaluation of the silica dispersions a to l, and the results of the polishing test of Examples 1 to 8 and Comparative Examples 1 to 4 are shown in Table 3 below. As already explained, when the silica dispersion is mixed with an acid, an oxidizing agent, and water in preparing the polishing composition, it is preferable to shorten the storage period as much as possible and to subject the composition to the polishing test as soon as possible. That is, if the storage period after the preparation of the polishing composition is long, colloidal silica may gradually aggregate and the polishing performance may decrease. Therefore, the results shown below are of the polishing test immediately after the preparation of the polishing composition.

[0093] (Colloidal silica particle size) The particle size (Heywood diameter) of colloidal silica was measured as the Heywood diameter (diameter equivalent to a circle with a projected area) by taking a photograph of a field of view at a magnification of 100,000 times using a transmission electron microscope (TEM) (JEOL Ltd., transmission electron microscope JEM2000FX (200 kV)) and analyzing the photograph using analysis software (Mountec Co., Ltd., Mac-View Ver. 4.0). The average particle size of colloidal silica was determined by analyzing the diameters of approximately 2,000 colloidal silica particles using the above-mentioned method, and calculating the particle size at which the cumulative particle size distribution (accumulated volume basis) from the small particle size side is 50% using the above-mentioned analysis software (Mountec Co., Ltd., Mac-View Ver. 4.0), which is the average particle size (D50).

[0094] (Method for evaluating antibacterial properties) 10 ml of each of the prepared silica dispersions a to l was collected as a test sample, and the antibacterial properties against the three types of bacteria and the three types of molds shown below were evaluated. 10 ml of the collected silica dispersion was inoculated with bacteria or mold and left to stand at room temperature. This state was continued for four weeks, and the change in the number of bacteria after four weeks was confirmed to evaluate the antibacterial properties.

[0095] The strains used in the antibacterial evaluation were three types of bacteria, Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa, and three types of mold, Aspergillus niger, Penicillium citrinum, and Cladosporium cladosporoides.

[0096] To measure the change in bacterial count, 0.1 ml of the test sample was taken, spread on an agar medium, and cultured at 30°C for three days. The number of surviving bacteria was calculated from the number of colonies obtained. Antibacterial properties were observed when the number of bacteria was reduced by 50% or more compared to the initial number of bacteria.

[0097] The specific evaluation criteria for antibacterial properties are as follows. The evaluation results of antibacterial properties are shown in Table 3. ◎: Antibacterial properties observed against all six types of bacteria. 〇: Antibacterial properties are observed against five types of bacteria. ×: Antibacterial properties observed against only 4 or fewer types of bacteria.

[0098] (polishing conditions) The prepared polishing compound compositions A to L were passed through a filter with an aperture of 0.45 μm and then introduced into a polishing device, and polishing tests were carried out for Examples 1 to 8 and Comparative Examples 1 to 4. The polishing conditions for the polishing tests were as follows. The results of the polishing tests carried out under the following polishing conditions are shown in Table 3 below. Polishing equipment: Speedfam Co., Ltd. 9B double-sided polishing machine Polishing target: Electroless nickel-phosphorus plated aluminum magnetic disk substrate with an outer diameter of 95 mm, roughly polished Polishing pad: FILWEL P2 pad Rotation speed of upper platen: -8.3min -1 :Lower surface plate 25.0min -1 Abrasive composition supply rate: 100ml / min Polishing time: 300s Processing pressure: 11kPa

[0099] (Evaluation of polished disk surfaces) (polishing speed ratio) The removal rate was calculated based on the following formula by measuring the mass of the aluminum magnetic disk substrate reduced after polishing. Polishing speed (μm / min) = [Mass reduction of aluminum magnetic disk substrate (g)] / [Polishing time (min)] / [Area of ​​one side of aluminum magnetic disk substrate (cm 2 )] / [Electroless nickel-phosphorus plating film density (g / cm 3 )] / 2×10 4

[0100] In the above formula, the area of ​​one side of the aluminum magnetic disk substrate is 65.9 cm 2 The density of the electroless nickel-phosphorus plating film is 8.0g / cm 3 The polishing rate ratio is shown as a relative value when the value of Comparative Example 1 is set to 1 (reference). A larger polishing rate ratio indicates a higher polishing rate and higher productivity.

[0101] (scratch ratio) The number of scratches on the substrate was measured using a MicroMAX VMX-4100 manufactured by Vision Cytec Co., Ltd. under the measurement conditions of a tilt angle of -5° and a magnification of 20x. The scratch ratio is a relative value with the number of scratches in Comparative Example 1 taken as 1 (reference). The smaller the scratch ratio value, the fewer the number of scratches, indicating that the substrate surface is in a good condition.

[0102] [Table 3]

[0103] (Consideration) As shown in Table 3, Example 1, which uses an aliphatic organic compound having a hemiformal structure as an antibacterial agent, has better antibacterial properties than Comparative Examples 1 and 3, which use an isothiazolinone compound, and the polishing test results show that the polishing speed is improved and scratches are reduced. Similar results are also shown in the comparison of Example 2 with Comparative Examples 2 and 4.

[0104] On the other hand, in the case of Example 3, which uses an aromatic organic compound having a hemiformal structure as an antibacterial agent, the antibacterial properties are superior to those of Comparative Examples 1 and 3, which use an isothiazolinone compound, and furthermore, in the polishing test results, it is found that the polishing speed is improved and scratches are reduced. Similar results are also shown in the comparison of Example 4 with Comparative Examples 2 and 4.

[0105] Furthermore, in the case of Example 5, in which an aliphatic organic compound having a hemiformal structure and an aromatic organic compound having a hemiformal structure were used in combination, the balance of the evaluation items of antibacterial properties, polishing speed, and scratches was improved compared to Examples 1 and 3, in which each was used alone. Similar results were also shown in the comparison of Example 6 with Examples 2 and 4.

[0106] In Examples 7 and 8, silica dispersions g and h and abrasive compositions G and H were prepared by varying the ratio (mixture ratio) of the aliphatic organic compound having a hemiformal structure and the aromatic organic compound having a hemiformal structure in Example 6, and antibacterial properties were evaluated and abrasive tests were performed.

[0107] As described above, it has been confirmed that the silica dispersion containing the organic compound having a hemiformal structure of the present invention has better antibacterial properties than silica dispersions using conventional antibacterial agents such as isothiazoline compounds, and that by polishing with a polishing agent composition to which an acid and an oxidizing agent have been added, the balance between polishing rate and scratches is improved compared to that of a polishing agent composition using conventional isothiazoline compounds. [Industrial Applicability]

[0108] The silica dispersion of the present invention and the polishing agent composition using the silica dispersion can be used as a modifier for resin products, a modifier for paper products, a catalyst carrier, paint, and for polishing electronic parts such as semiconductors and magnetic recording media such as hard disks. In particular, it is suitable for polishing aluminum magnetic disk substrates for magnetic recording media, which have an electroless nickel-phosphorus plating film formed on the surface of an aluminum alloy substrate. Agent It can be suitably used for the following:

Claims

1. Colloidal silica, An antibacterial agent composed of an organic compound having a hemiformal structure. Contains A silica dispersion used as one component of the raw materials of an abrasive composition used for polishing magnetic disk substrates.

2. The antibacterial agent is 2. The silica dispersion according to claim 1, wherein the compound is an aliphatic organic compound having a hemiformal structure represented by the following general formula 1. 【Chemistry 1】 (In Chemical Formula 1, R １ represents a linear, branched, or alicyclic hydrocarbon group, including those in which some of the carbon atoms in the hydrocarbon group are substituted with nitrogen atoms and / or oxygen atoms)

3. The antibacterial agent is 2. The silica dispersion according to claim 1, wherein the aromatic organic compound has a hemiformal structure represented by the following general formula (2). 【Chemistry 2】 (In Chemical Formula 2, R ２ represents a hydrocarbon group having an aromatic ring, including a structure in which some of the carbon atoms in the hydrocarbon group are substituted with nitrogen atoms and / or oxygen atoms)

4. Colloidal silica, An antibacterial agent composed of an organic compound having a hemiformal structure. Contains The antibacterial agent is an aliphatic organic compound having a hemiformal structure represented by the following general formula 3; An aromatic organic compound having a hemiformal structure represented by the following general formula 4. A silica dispersion formed by combining 【Chemistry 3】 (In Chemical Formula 3, R ３ represents a linear, branched, or alicyclic hydrocarbon group, including those in which some of the carbon atoms in the hydrocarbon group are substituted with nitrogen atoms and / or oxygen atoms) 【Chemistry 4】 (In Chemical Formula 4, R ４ represents a hydrocarbon group having an aromatic ring, including a structure in which some of the carbon atoms in the hydrocarbon group are substituted with nitrogen atoms and / or oxygen atoms)

5. 5. The silica dispersion according to claim 4, which is used as one component of raw materials of an abrasive composition used for polishing a magnetic disk substrate.

6. A silica dispersion according to any one of claims 1 to 3 and claim 5, Water and The abrasive composition is used for polishing a magnetic disk substrate.

7. Acid, Oxidizing agent and The polishing composition according to claim 6, further comprising:

8. 8. The polishing composition according to claim 6, which is used for polishing a nickel-phosphorus plated aluminum magnetic disk substrate.

9. A silica dispersion according to claim 4, Water and An abrasive composition comprising:

10. An acid, Oxidizing agent and The polishing composition according to claim 9, further comprising:

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