Polishing compound composition for magnetic disk substrates, and method for polishing magnetic disk substrates.

Abstract

To provide an abrasive composition capable of improving a high polishing rate without using alumina particles and realizing good surface smoothness and a surface state without adhesion of residual abrasive grains and polishing dust.SOLUTION: An abrasive composition for a magnetic disk substrate contains colloidal silica having an average particle size in a range of 10 to 120 nm, wet-type silica having an average particle size in a range of 200 to 600 nm, a water-soluble polymer compound, a quaternary ammonium salt-type organic compound, and water. The water-soluble polymer compound contains a copolymer having at least a monomeric substance having a carboxylic acid group and a monomeric substance having a sulfonic acid group as essential monomeric substances, and, in the quaternary ammonium salt-type organic compound, a hydrocarbon group bonded to a nitrogen atom is a saturated aliphatic hydrocarbon group having 1 to 20 carbon atoms and / or an unsaturated aliphatic hydrocarbon group having 2 to 20 carbon atoms.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to an abrasive composition for a magnetic disk substrate and a method for polishing a magnetic disk substrate, and more particularly to an abrasive composition for a magnetic disk substrate (hereinafter simply referred to as "abrasive composition") that can be used for polishing a magnetic disk substrate constituting an electronic component such as a magnetic recording medium such as a semiconductor or a hard disk, and a method for polishing a magnetic disk substrate.

[0002] In particular, the present invention relates to an abrasive composition that can be used for polishing the surface of a magnetic disk substrate for a magnetic recording medium such as a glass magnetic disk substrate or an aluminum magnetic disk substrate, and a method for polishing a magnetic disk substrate. Furthermore, the present invention relates to an abrasive composition that can be used for polishing an aluminum magnetic disk substrate having an electroless nickel-phosphorus plating film on the surface of a substrate made of an aluminum alloy, and a method for polishing a magnetic disk substrate using the abrasive composition.

Background Art

[0003] Conventionally, as an abrasive composition for polishing the surface of an electroless nickel-phosphorus plating film of an aluminum magnetic disk substrate, an abrasive composition in which alumina particles having a relatively large particle size are dispersed in water and capable of achieving a high polishing rate has been widely used from the viewpoint of productivity such as production efficiency.

[0004] However, alumina particles have a physical property of higher hardness than the electroless nickel-phosphorus plating film formed on the substrate surface, and are held in a state where the alumina particles penetrate the substrate surface during polishing. There is a problem that such alumina particles may affect the final polishing step (finishing polishing step) performed as the next step of the polishing process.

[0005] To solve the above problems, for example, the use of an abrasive composition in which alumina particle components and silica particle components are mixed in a predetermined ratio has been proposed (see Patent Documents 1 to 4). Furthermore, a polishing method has also been proposed using an abrasive composition that does not contain alumina particles but contains only silica particles (see Patent Documents 5 to 11). [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2001-260005 [Patent Document 2] Japanese Patent Publication No. 2009-176397 [Patent Document 3] Japanese Patent Publication No. 2011-204327 [Patent Document 4] Japanese Patent Publication No. 2012-43493 [Patent Document 5] Japanese Patent Publication No. 2010-167553 [Patent Document 6] Special Publication No. 2011-527643 [Patent Document 7] Japanese Patent Publication No. 2014-29754 [Patent Document 8] Japanese Patent Publication No. 2014-29755 [Patent Document 9] Special Publication No. 2003-514950 [Patent Document 10] Japanese Patent Publication No. 2012-155785 [Patent Document 11] Japanese Patent Publication No. 2019-16417 [Overview of the project] [Problems that the invention aims to solve]

[0007] The abrasive compositions or polishing methods using the abrasive compositions described in the above-mentioned Patent Documents 1 to 11 sometimes had the following problems.

[0008] For example, by using abrasive compositions combining alumina particle components and silica particle components as shown in Patent Documents 1 to 4, it was possible to improve to some extent the penetration of alumina particles into the substrate surface of magnetic disk substrates. However, because they contained at least alumina particles, the possibility of these alumina particles penetrating the substrate surface still remained. In addition, because the abrasive composition was composed of both alumina particle and silica particle components, the properties of the individual particle components canceled each other out, resulting in a decrease in the properties of the abrasive composition, such as polishing speed and surface smoothness.

[0009] Therefore, abrasive compositions comprising only silica particles without using alumina particles, and polishing methods using such abrasive compositions have been proposed. For example, a combination of colloidal silica and a polishing accelerator is known (see Patent Documents 5 and 6). Furthermore, polishing methods using colloidal silica, fumed silica, surface-modified silica, and silica produced by the water glass method, and in particular polishing methods using colloidal silica with a special shape have already been proposed (see Patent Documents 7 and 8). However, in the case of the above-proposed polishing methods, the polishing performance, such as insufficient polishing speed, may be inferior to that of conventional abrasive compositions, and further improvements have been requested.

[0010] Furthermore, a polishing method using an abrasive composition combining colloidal silica and fumed silica has been proposed (see Patent Document 9). However, while an improvement in polishing speed is observed when using such an abrasive composition, the low bulk density of fumed silica makes it difficult to slurry the abrasive composition, which may affect workability. Furthermore, a polishing method has been proposed that can achieve a polishing speed close to that of alumina particles by using crushed silica particles (see Patent Document 10). However, this polishing method has the problem of worsened surface smoothness compared to conventional abrasive compositions, and further improvements were needed.

[0011] Furthermore, residual abrasive particles and polishing debris sometimes adhered to the substrate surface after the polishing process. Therefore, if these residual particles and debris could not be removed even after cleaning the substrate surface after the polishing process, the workload in the final polishing step after the polishing process could increase significantly. For this reason, there was a need to use an abrasive composition that would not leave residual abrasive particles or polishing debris on the substrate surface after the polishing process, or one that could be easily removed by relatively simple cleaning.

[0012] Therefore, the present invention has been made in view of the problems of the prior art described above, and provides an abrasive composition that can achieve a high polishing speed without using alumina particles, and can achieve good surface smoothness and a surface state free from the adhesion of residual abrasive particles and polishing debris, and a method for polishing a magnetic disk substrate using the abrasive composition. [Means for solving the problem]

[0013] As a result of diligent research to solve the above problems, the inventors of this application have found that by combining colloidal silica and wet-process silica, and further using an abrasive composition containing a specific water-soluble polymer compound and a specific quaternary ammonium salt type organic compound, it is possible to achieve a high polishing speed, good surface smoothness, and a surface state free from the adhesion of residual abrasive grains and polishing debris. Consequently, they have completed the abrasive composition and method for polishing magnetic disk substrates shown below.

[0014] [1] Colloidal silica having an average particle size in the range of 10-120 nm, wet-process silica having an average particle size in the range of 200-600 nm, a water-soluble polymer compound, a quaternary ammonium salt type organic compound, water and , an acid and / or a salt of the acid, It contains, The pH value (at 25°C) is in the range of 0.1 to 4.0. The abrasive composition for magnetic disk substrates comprises a copolymer in which the water-soluble polymer compound contains at least one monomer having a carboxylic acid group and one monomer having a sulfonic acid group as essential monomers, and the quaternary ammonium salt type organic compound is a saturated aliphatic hydrocarbon group having 1 to 10 carbon atoms and / or an unsaturated aliphatic hydrocarbon group having 2 to 20 carbon atoms, wherein the hydrocarbon group bonded to the nitrogen atom is a saturated aliphatic hydrocarbon group having 1 to 10 carbon atoms and / or an unsaturated aliphatic hydrocarbon group having 2 to 20 carbon atoms.

[0016] 2 The quaternary ammonium salt type organic compound is at least one selected from the group consisting of divinyldimethylammonium chloride, diallyldimethylammonium chloride, diethyldimethylammonium chloride, triethylmethylammonium chloride, tetraethylammonium chloride, dibutyldimethylammonium chloride, tetrabutylammonium chloride, dioctyldimethylammonium chloride, didecyldimethylammonium chloride, octyltrimethylammonium chloride, and decyltrimethylammonium chloride. The 1 abrasive composition for a magnetic disk substrate according to the above.

[0017] [3] Colloidal silica having an average particle diameter in the range of 10 to 120 nm, wet-process silica having an average particle diameter in the range of 200 to 600 nm, a water-soluble polymer compound, a quaternary ammonium salt type organic compound, water, Acids and / or salts of the acid, and containing The pH value (at 25°C) is in the range of 0.1 to 4.0. The water-soluble polymer compound contains a copolymer having at least a monomer having a carboxylic acid group and a monomer having a sulfonic acid group as essential monomers. The quaternary ammonium salt type organic compound is a first quaternary ammonium salt type organic compound in which the hydrocarbon groups bonded to the nitrogen atom are four saturated aliphatic hydrocarbon groups having 1 to 20 carbon atoms, and at least one of the hydrocarbon groups bonded to the nitrogen atom is an unsaturated aliphatic hydrocarbon group having 2 to 20 carbon atoms, and the remaining hydrocarbon groups are saturated aliphatic hydrocarbon groups having 1 to 20 carbon atoms. An abrasive composition for a magnetic disk substrate which is a mixture containing at least one or more of the second quaternary ammonium salt type organic compounds.

[0018] 4 The water-soluble polymer compound further contains a copolymer having at least a monomer having a carboxylic acid group and a monomer having an amide group as essential monomers. The abrasive composition for a magnetic disk substrate according to any one of the above [1] to 3 .

[0020] ​​​5 [1]~[ further containing an oxidizing agent 4 A polishing composition for magnetic disk substrates as described in any of the following:

[0021] [ 6 [1]~[ Used for polishing an electroless nickel-phosphorus plated aluminum magnetic disk substrate. 5 A polishing composition for magnetic disk substrates as described in any of the following:

[0022] [ 7 ] The above [1]~[ 6 A method for polishing a magnetic disk substrate using an abrasive composition for magnetic disk substrates described in any of the [ ], comprising a polishing step and a final polishing step performed after the polishing step, wherein the abrasive composition for magnetic disk substrates is used in the polishing step prior to the final polishing step. [Effects of the Invention]

[0023] The present invention provides a polishing agent composition containing two types of silica particles, a specific water-soluble polymer compound, and a specific quaternary ammonium salt type organic compound for polishing an aluminum substrate for magnetic recording media, which has an electroless nickel-phosphorus plating film formed on the surface of an aluminum alloy substrate. This allows for a high polishing speed and a smooth substrate surface free of residual abrasive particles and polishing debris after polishing. [Modes for carrying out the invention]

[0024] The embodiments of the present invention will be described below. The present invention is not limited to the embodiments described below, and modifications, alterations, and improvements may be made without departing from the spirit of the invention.

[0025] 1. Abrasive composition (Abrasive composition for magnetic disk substrates) The abrasive composition of the present invention comprises colloidal silica, wet-process silica, a specific water-soluble polymer compound, a specific quaternary ammonium salt type organic compound, and water as essential components, and optionally contains an acid and / or its salt and an oxidizing agent.

[0026] 1.1 Colloidal Silica The colloidal silica contained in the abrasive composition of the present invention may have an average particle size in the range of 10 to 120 nm, preferably in the range of 10 to 110 nm, and more preferably in the range of 15 to 100 nm. An average particle size of 10 nm or more for the colloidal silica can suppress a decrease in polishing speed. On the other hand, an average particle size of 120 nm or less for the colloidal silica can maintain good surface smoothness of the substrate after polishing.

[0027] Colloidal silica is known to exist in various shapes, including spherical, chain-like, konpeito-shaped (particulate with protrusions on the surface), and irregular shapes, and is monodispersed in water to form a colloid. In the present invention, spherical or nearly spherical colloidal silica is particularly preferred. Using such spherical or nearly spherical colloidal silica can further improve surface smoothness. Colloidal silica can be obtained by conventionally known methods such as the water glass method using sodium silicate or potassium silicate as a raw material, the alkoxysilane method in which alkoxysilanes such as tetraethoxysilane are hydrolyzed with acid or alkali, or a method in which metallic silicon and water are reacted in the presence of an alkaline catalyst to generate hydrogen and form silica particles.

[0028] 1.2 Wet-process silica The wet-process silica contained in the abrasive composition of the present invention is prepared from silica particles obtained as precipitated silicic acid by adding an aqueous alkali silicate solution and an inorganic acid or an aqueous inorganic acid solution to a reaction vessel. Note that the wet-process silica described herein does not include the colloidal silica mentioned above.

[0029] Examples of alkali silicate aqueous solutions used as raw materials for wet silica include sodium silicate aqueous solution, potassium silicate aqueous solution, and lithium silicate aqueous solution, with sodium silicate aqueous solution generally preferred. On the other hand, examples of inorganic acids added to the reaction vessel along with the sodium silicate aqueous solution include sulfuric acid, hydrochloric acid, and nitric acid, with sulfuric acid generally preferred.

[0030] In the reaction vessel, various components such as an aqueous alkali silicate solution and an inorganic acid, which are the raw materials for wet-process silica, are added. After the reaction is complete, the reaction solution is filtered, washed with water, and then dried in a dryer until the moisture content is 6% or less. The dryer used here is not particularly limited and may be any of the following: a static dryer, a spray dryer, or a fluidized bed dryer. After that, the mixture is pulverized in a pulverizer such as a jet mill and further classified to obtain the pulverized wet-process silica described above.

[0031] The obtained wet-process silica may be subjected to further calcination treatment. For example, calcination treatment can be performed using a general calcination apparatus such as an electric furnace or a rotary kiln. In this case, the calcination temperature for the wet-process silica can be set in the range of 600 to 1000°C. Furthermore, the pulverization treatment described above may be performed after the calcination treatment. Wet-process silica pulverized by such pulverization treatment has a particle shape composed of multiple corners, and is expected to have higher polishing performance compared to general spherical wet-process silica particles that have not undergone pulverization treatment.

[0032] The average particle size of the obtained wet-process silica is in the range of 200 to 600 nm, preferably in the range of 200 to 500 nm. An average particle size of 200 nm or more in the wet-process silica suppresses a decrease in polishing speed. On the other hand, an average particle size of 600 nm or less suppresses deterioration of the surface roughness of the substrate after polishing.

[0033] Here, if the average particle size of colloidal silica is defined as A and the average particle size of wet-process silica is defined as B, the ratio of the average particle size of wet-process silica to the average particle size of colloidal silica (=B / A) is in the range of 2.0 to 30.0, preferably in the range of 2.5 to 25.0, and more preferably in the range of 3.0 to 20.0. When the B / A value is 2.0 or higher, an improvement in polishing speed can be expected. On the other hand, when the B / A value is 30.0 or lower, deterioration of surface roughness can be suppressed.

[0034] The combined concentration of colloidal silica and wet-process silica in the abrasive composition, i.e., the total silica particle concentration, is preferably in the range of 1 to 50% by mass, and more preferably in the range of 2 to 40% by mass. A total silica particle concentration of 1% by mass or more in the abrasive composition can suppress a decrease in polishing speed. On the other hand, a total silica particle concentration of 50% by mass or less allows for maintaining a sufficient polishing speed without using more silica particles than necessary.

[0035] The proportion of colloidal silica in the total mass of colloidal silica and wet-process silica is preferably in the range of 5 to 95% by mass, and more preferably in the range of 10 to 90% by mass. A colloidal silica proportion of 5% by mass or more can reduce surface roughness. A colloidal silica proportion of 95% by mass or less can suppress a decrease in polishing speed.

[0036] The proportion of wet-process silica to the total mass of colloidal silica and wet-process silica is preferably in the range of 5 to 95% by mass, and more preferably in the range of 10 to 90% by mass. A proportion of wet-process silica of 95% by mass or less can suppress deterioration of the surface roughness of the substrate after polishing. On the other hand, a proportion of wet-process silica of 5% by mass or more can suppress a decrease in the polishing speed.

[0037] 1.3 Other Silica Particles Examples of silica particles contained in the abrasive composition of the present invention include colloidal silica and wet-process silica, as well as fumed silica.

[0038] Fumed silica is produced by hydrolyzing a volatile silane compound (generally silicon tetrachloride) in a flame of a mixed gas of oxygen and hydrogen (around 1000°C), resulting in extremely fine and high-purity silica particles. Compared to colloidal silica, where colloidal silica exists as individually dispersed primary particles, fumed silica consists of numerous primary particles that aggregate and connect in a chain-like structure to form secondary particles. This formation of secondary particles increases the retention force on the polishing pad, thereby improving the polishing speed.

[0039] 1.4 Quaternary ammonium salt type organic compounds The quaternary ammonium salt type organic compound contained in the abrasive composition of the present invention is a quaternary ammonium salt type organic compound in which the hydrocarbon group bonded to the nitrogen atom is composed of a saturated aliphatic hydrocarbon group having 1 to 20 carbon atoms and / or an unsaturated aliphatic hydrocarbon group having 2 to 20 carbon atoms.

[0040] Specific examples include vinyltrimethylammonium chloride, allyltrimethylammonium chloride, divinyldimethylammonium chloride, diallyldimethylammonium chloride, diethyldimethylammonium chloride, triethylmethylammonium chloride, tetraethylammonium chloride, dipropyldimethylammonium chloride, dibutyldimethylammonium chloride, tetrabutylammonium chloride, dioctyldimethylammonium chloride, didecyldimethylammonium chloride, octyltrimethylammonium chloride, decyltrimethylammonium chloride, and dodecyltrimethylammonium chloride.

[0041] From the viewpoint of suppressing foaming and reducing the polishing speed, a quaternary ammonium salt type organic compound is preferably used in which the four hydrocarbon groups bonded to the nitrogen atom are composed of saturated aliphatic hydrocarbon groups having 1 to 10 carbon atoms and / or unsaturated aliphatic hydrocarbon groups having 2 to 20 carbon atoms.

[0042] Furthermore, these quaternary ammonium salt type organic compounds can be used individually, or two or more types of quaternary ammonium salt type organic compounds can be used in mixtures. In particular, it is preferable to use a mixture containing at least one of the following: a first quaternary ammonium salt type organic compound in which the hydrocarbon groups bonded to the nitrogen atom consist of four saturated aliphatic hydrocarbon groups having 1 to 20 carbon atoms, and a second quaternary ammonium salt type organic compound in which at least one of the hydrocarbon groups bonded to the nitrogen atom is an unsaturated aliphatic hydrocarbon group having 2 to 20 carbon atoms, and the remaining hydrocarbon groups are saturated aliphatic hydrocarbon groups having 1 to 20 carbon atoms. More specifically, for example, a mixture containing diallyldimethylammonium chloride and dodecyltrimethylammonium chloride can be used.

[0043] The concentration of the quaternary ammonium salt type organic compound in the abrasive composition is usually 0.00001 to 1.0% by mass, preferably 0.00005 to 0.5% by mass, more preferably 0.0001 to 0.3% by mass, and even more preferably 0.0001 to 0.1% by mass.

[0044] 1.5 Water-soluble polymer compounds The water-soluble polymer compound used in the abrasive composition of the present invention includes copolymers in which at least one monomer having a carboxylic acid group and one monomer having a sulfonic acid group are essential monomers. Furthermore, it is also preferable to use copolymers in which at least one monomer having a carboxylic acid group and one monomer having an amide group are essential monomers in combination.

[0045] 1.5.1 Copolymers having at least one monomer having a carboxylic acid group and one monomer having a sulfonic acid group as essential monomers Examples of monomers having a carboxylic acid group include acrylic acid, methacrylic acid, maleic acid, itaconic acid, and their salts.

[0046] Examples of monomers having a sulfonic acid group include isoprene sulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, 2-methacrylamido-2-methylpropanesulfonic acid, styrene sulfonic acid, vinyl sulfonic acid, allyl sulfonic acid, vinylnaphthalene sulfonic acid, and salts thereof.

[0047] Copolymers are formed by polymerizing at least these monomers. Examples of copolymer combinations in which at least one monomer having a carboxylic acid group and one monomer having a sulfonic acid group are essential monomers include acrylic acid and 2-acrylamide-2-methylpropanesulfonic acid, acrylic acid and 2-methacrylamide-2-methylpropanesulfonic acid, methacrylic acid and 2-acrylamide-2-methylpropanesulfonic acid, and methacrylic acid and 2-methacrylamide-2-methylpropanesulfonic acid.

[0048] The copolymer used in the present invention, which has at least one monomer having a carboxylic acid group and one monomer having a sulfonic acid group as essential monomers, may also use monomers other than the two types listed above. For example, a copolymer obtained by copolymerizing three types of monomers—one having a carboxylic acid group, one having an amide group, and one having a sulfonic acid group—can be used.

[0049] In copolymers in which at least one monomer having a carboxylic acid group and one monomer having a sulfonic acid group are essential monomers, the ratio of constituent units derived from the carboxylic acid group to constituent units derived from the sulfonic acid group is preferably in the range of 95:5 to 5:95 in molar ratio, and more preferably in the range of 90:10 to 10:90 in molar ratio.

[0050] 1.5.2 Copolymers having at least one monomer having a carboxylic acid group and one monomer having an amide group as essential monomers Examples of monomers having a carboxylic acid group include acrylic acid, methacrylic acid, maleic acid, itaconic acid, and their salts.

[0051] Examples of monomers having an amide group include acrylamide, methacrylamide, N-alkylacrylamide, and N-alkylmethacrylamide.

[0052] Preferred examples of N-alkylacrylamides and N-alkylmethacrylamides, which are monomers having an amide group, include N-methylacrylamide, N-ethylacrylamide, N-n-propylacrylamide, N-iso-propylacrylamide, N-n-butylacrylamide, N-iso-butylacrylamide, N-sec-butylacrylamide, N-tert-butylacrylamide, N-methylmethacrylamide, N-ethylmethacrylamide, N-n-propylmethacrylamide, N-iso-propylmethacrylamide, Nn-butylmethacrylamide, N-iso-butylmethacrylamide, N-sec-butylmethacrylamide, and N-tert-butylmethacrylamide.

[0053] In the above, it is preferable to use N-n-butylacrylamide, N-iso-butylacrylamide, N-sec-butylacrylamide, N-tert-butylacrylamide, N-n-butylmethacrylamide, N-iso-butylmethacrylamide, N-sec-butylmethacrylamide, and N-tert-butylmethacrylamide.

[0054] Copolymers are formed by polymerizing these monomers in combination. Examples of copolymers in which at least one monomer having a carboxylic acid group and one monomer having an amide group are essential monomers include, for example, combinations of acrylic acid and / or its salt with N-alkylacrylamide, acrylic acid and / or its salt with N-alkylmethacrylamide, methacrylic acid and / or its salt with N-alkylacrylamide, and methacrylic acid and / or its salt with N-alkylmethacrylamide. It is particularly preferable to use N-alkylacrylamide or N-alkylmethacrylamide in which the alkyl group is selected from the group consisting of n-butyl, iso-butyl, sec-butyl, and tert-butyl groups.

[0055] Copolymers preferably used in the present invention, which have at least one monomer having a carboxylic acid group and one monomer having an amide group as essential monomers, may also use monomers other than the two types listed above. For example, copolymers obtained by copolymerizing three types of monomers—one having a carboxylic acid group, one having an amide group, and one having a sulfonic acid group—can be used.

[0056] In copolymers in which at least one monomer having a carboxylic acid group and one monomer having an amide group are essential monomers, the ratio of constituent units derived from the carboxylic acid group to constituent units derived from the amide group is preferably in the range of 95:5 to 5:95 in molar ratio, and more preferably in the range of 90:10 to 10:90 in molar ratio.

[0057] 1.5.3 Method for producing water-soluble polymer compounds The method for producing water-soluble polymer compounds is not particularly limited, but aqueous solution polymerization is preferred. By aqueous solution polymerization, water-soluble polymer compounds can be obtained as a homogeneous solution.

[0058] The polymerization solvent for the aqueous solution polymerization described above is preferably an aqueous solvent, and particularly preferably water. Furthermore, to improve the solubility of the monomer components in the solvent, an organic solvent may be added as appropriate, within a range that does not adversely affect the polymerization of each monomer. Examples of organic solvents include alcohols such as isopropyl alcohol and ketones such as acetone. These can be used individually or in combination of two or more.

[0059] The following describes a method for producing a water-soluble polymer compound using the aqueous solvent described above. In the polymerization reaction, known polymerization initiators can be used, but radical polymerization initiators are particularly preferred.

[0060] Examples of radical polymerization initiators include persulfates such as sodium persulfate, potassium persulfate, and ammonium persulfate; hydroperoxides such as t-butyl hydroperoxide; water-soluble peroxides such as hydrogen peroxide; ketone peroxides such as methyl ethyl ketone peroxide and cyclohexanone peroxide; oil-soluble peroxides such as dialkyl peroxides such as di-t-butyl peroxide and t-butylcumyl peroxide; and azo compounds such as azobisisobutyronitrile and 2,2-azobis(2-methylpropionamidine)dihydrochloride. These peroxide-based radical polymerization initiators may be used individually or in combination of two or more.

[0061] The amount of radical polymerization initiator used is not particularly limited, but it is preferable to use it in a proportion of 0.1 to 15% by mass, particularly 0.5 to 10% by mass, based on the total mass of all monomers of the water-soluble polymer compound. By increasing this proportion to 0.1% by mass or more, the copolymerization rate can be improved, and by decreasing it to 15% by mass or less, the stability of the water-soluble polymer compound can be improved.

[0062] In some cases, water-soluble polymer compounds may also be produced using water-soluble redox polymerization initiators. Examples of redox polymerization initiators include combinations of oxidizing agents (e.g., the peroxides mentioned above) and reducing agents such as sodium bisulfite, ammonium bisulfite, ammonium sulfite, sodium hydrosulfite, or iron alum, potassium alum, etc.

[0063] In the production of water-soluble polymer compounds, chain transfer agents may be added to the polymerization system as appropriate to adjust the molecular weight. Examples of chain transfer agents include sodium phosphite, sodium hypophosphite, potassium hypophosphite, sodium sulfite, sodium bisulfite, mercaptoacetic acid, mercaptopropionic acid, thioglycolic acid, 2-propanethol, 2-mercaptoethanol, and thiophenol.

[0064] While there are no particular restrictions on the polymerization temperature when producing water-soluble polymer compounds, it is preferable to carry out the polymerization at a temperature of 60 to 100°C. A polymerization temperature of 60°C or higher allows the polymerization reaction to proceed smoothly and results in excellent productivity, while a temperature of 100°C or lower can suppress discoloration.

[0065] Furthermore, while polymerization reactions can be carried out under pressure or reduced pressure, it is preferable to carry them out at atmospheric pressure because this would incur additional costs for equipment suitable for pressurized or reduced-pressure reactions. The polymerization time is preferably 2 to 20 hours, and more preferably 3 to 10 hours.

[0066] After the polymerization reaction, neutralization with a basic compound is carried out as needed. Examples of basic compounds used for neutralization include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, alkaline earth metal hydroxides such as calcium hydroxide and magnesium hydroxide, aqueous ammonia, and organic amines such as monoethanolamine, diethanolamine, and triethanolamine.

[0067] The pH value after neutralization (at 25°C) is preferably 2 to 9, and more preferably 3 to 8, for an aqueous solution containing 10% by mass of the water-soluble polymer compound.

[0068] 1.5.4 Weight average molecular weight The weight-average molecular weight of the water-soluble polymer compound is preferably in the range of 2,000 or more and 1,000,000 or less, and more preferably in the range of 4,000 or more and 800,000 or less. The weight-average molecular weight of the water-soluble polymer compound was measured in terms of polyacrylic acid by gel permeation chromatography (GPC).

[0069] 1.5.5 Concentration The concentration of the water-soluble polymer compound in the abrasive composition is preferably in the range of 0.0001% by mass or more and 2.0% by mass or less, more preferably in the range of 0.001% by mass or more and 1.0% by mass or less, and even more preferably in the range of 0.005% by mass or more and 0.5% by mass or less, based on solid content.

[0070] 1.6 Oxidizing agents Examples of oxidizing agents preferably included in the abrasive composition of the present invention include peroxides, permanganate or its salts, chromic acid or its salts, periodic acid or its salts. Specific examples include hydrogen peroxide, sodium peroxide, barium peroxide, potassium permanganate, orthoperiodic acid, and sodium metaperiodate. Among these, hydrogen peroxide is preferred.

[0071] The oxidizing agent content in abrasive compositions is typically in the range of 0.1 to 10.0% by mass. A content of 0.1% by mass or more of the oxidizing agent improves the polishing speed. However, a content of 10.0% by mass or more of the oxidizing agent does not improve the polishing speed and is therefore economically disadvantageous.

[0072] 1.7 Acids and / or Salts The abrasive composition of the present invention may use acids and / or their salts for pH adjustment or as an optional component. Examples of acids and / or their salts that can be used include inorganic acids and / or their salts and organic acids and / or their salts.

[0073] Examples of inorganic acids and / or their salts include nitric acid, sulfuric acid, hydrochloric acid, phosphoric acid, phosphonic acid, pyrophosphate, tripolyphosphate, and other inorganic acids and / or their salts.

[0074] Examples of organic acids and / or their salts include aminocarboxylic acids and / or their salts, such as glutamic acid and aspartic acid; carboxylic acids and / or their salts, such as citric acid, tartaric acid, oxalic acid, nitroacetic acid, maleic acid, malic acid, and succinic acid; and organic phosphonic acids and / or their salts. One or more of these acids and / or their salts can be used.

[0075] Examples of organic phosphonic acids and / or salts thereof include 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, α-methylphosphonosuccinic acid, and salts thereof.

[0076] In addition, it is also preferable to use two or more of the above compounds in combination. Specifically, examples include combinations of sulfuric acid and / or its salt with organic phosphonic acid and / or its salt, and combinations of phosphoric acid and / or its salt with organic phosphonic acid and / or its salt.

[0077] 1.8 Water The water used in this invention is preferably distilled water, ion-exchanged water, or other water from which impurities have been removed. Since water has the function of controlling the fluidity of the abrasive composition, its content can be appropriately determined according to the target polishing characteristics, such as polishing speed. For example, the water content is preferably 50 to 95% by mass. If the water content is less than 50% by mass of the abrasive composition, the viscosity of the abrasive will increase, and the fluidity may be impaired. On the other hand, if the water content exceeds 95% by mass, the abrasive particle concentration will be low, and a sufficient polishing speed may not be obtained.

[0078] 2. Physical properties The pH value (at 25°C) of the abrasive composition of the present invention is preferably 0.1 to 4.0, and more preferably 0.5 to 3.0. A pH value (at 25°C) of 0.1 or higher of the abrasive composition can suppress deterioration of surface smoothness. A pH value (at 25°C) of 4.0 or lower can suppress a decrease in polishing speed. In electroless nickel-phosphorus plating, under conditions where the pH value (at 25°C) is 4.0 or lower, nickel tends to dissolve, making plating difficult. On the other hand, in polishing, for example, under conditions where the pH value (at 25°C) is 4.0 or lower, nickel tends to dissolve, so using the abrasive composition of the present invention makes it possible to increase the polishing speed.

[0079] 3. Method for polishing magnetic disk substrates The abrasive composition of the present invention is suitable for use in polishing magnetic disk substrates such as electroless nickel-phosphorus plated aluminum magnetic disks (hereinafter referred to as "aluminum disks") and glass magnetic disk substrates. It is particularly suitable for use in polishing aluminum disks.

[0080] Polishing methods to which the abrasive composition of the present invention can be applied include, 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 surface of the object to be polished (e.g., an aluminum disc) or to the polishing pad, and the surface to be polished is rubbed with the polishing pad (polishing). For example, when polishing the front and back surfaces of an aluminum disc simultaneously, a method can be used in which a double-sided polishing machine is used, with polishing pads attached to the upper and lower platens, respectively. In this method, the abrasive composition is supplied between the polishing pads attached to the upper and lower platens, and the front and back surfaces of the aluminum disc are polished by rotating the two polishing pads simultaneously. The polishing pad can be of any type, such as urethane type, suede type, nonwoven fabric type, or any other type.

[0081] The present invention provides a method for polishing a magnetic disk substrate, comprising a polishing step and a final polishing step performed after the polishing step. The polishing composition of the present invention is used in the polishing step (rough polishing step) performed before the final polishing step (finish polishing step). More preferably, it is used for polishing an electroless nickel-phosphorus plated aluminum magnetic disk substrate, and more preferably, it is used in a polishing step performed before the final polishing step of the electroless nickel-phosphorus plated aluminum magnetic disk substrate. By using the polishing composition of the present invention in such a polishing step, the effects of the present invention can be fully enjoyed. [Examples]

[0082] The present invention will be described in detail below based on examples, but the present invention is not limited to these examples and can be implemented in various forms as long as they fall within the technical scope of the present invention.

[0083] 3.1 Method for preparing an abrasive composition Example 1~ 8、11~20、23、 twenty four , Reference examples 1-4 The abrasive compositions used in Comparative Examples 1-4 include abrasive grains, acid and / or acidThe abrasive composition is prepared such that the salt, oxidizing agent, water-soluble polymer compound, and quaternary ammonium salt type organic compound are of the types and in the amounts listed in Table 1 below.

[0084] In Table 1, "AA" represents acrylic acid, "TBAA" represents N-tert-butylacrylamide, and "ATBS" represents 2-acrylamido-2-methylpropanesulfonic acid.

[0085] The water-soluble polymer compounds used were copolymers of synthesis numbers 1 and 2, as shown in Table 1. All Examples 1- 8、11~20、23、 twenty four , Reference examples 1-4 In comparative examples 1 to 4, the total silica concentration in the abrasive composition was prepared to be 4.0% by mass.

[0086] [Table 1]

[0087] 3.2 Example 1~ 8、11~20、23、 twenty four , Reference examples 1-4 , and preparation of the abrasive compositions of Comparative Examples 1 to 4 Examples 1 to 2 are shown below. 8、11~20、23、 twenty four , Reference examples 1-4 The specific preparation methods for the abrasive compositions of Comparative Examples 1 to 4 are shown. • Example 1 An abrasive composition was prepared by adding colloidal silica (3.6% by mass), wet-process silica (0.4% by mass), sulfuric acid (0.71% by mass), ammonium sulfate (0.85% by mass), hydrogen peroxide (0.89% by mass), copolymer of synthesis number 1 (0.02% by mass) as a water-soluble polymer compound, and diallyldimethylammonium chloride (0.0013% by mass) as a quaternary ammonium salt type organic compound) to pure water while stirring (see Table 1).

[0088] • Example 2 In preparing the abrasive composition of Example 1, the content of diallyldimethylammonium chloride was changed to 0.0026% by mass to obtain the abrasive composition of Example 2. Otherwise, the preparation was the same as that of the abrasive composition of Example 1.

[0089] • Example 3 In the preparation of the abrasive composition of Example 2, the quaternary ammonium salt type organic compound was changed from diallyldimethylammonium chloride to 0.0026% by mass of tetraethylammonium chloride to obtain the abrasive composition of Example 3. Otherwise, the preparation was the same as that of the abrasive composition of Example 2.

[0090] • Example 4 In the preparation of the abrasive composition of Example 2, the quaternary ammonium salt type organic compound was changed from diallyldimethylammonium chloride to 0.0026% by mass of tetrabutylammonium chloride to obtain the abrasive composition of Example 4. Otherwise, the preparation was the same as that of the abrasive composition of Example 2.

[0091] • Example 5 In the preparation of the abrasive composition of Example 2, the quaternary ammonium salt type organic compound was changed from diallyldimethylammonium chloride to 0.0026% by mass of octyltrimethylammonium chloride to obtain the abrasive composition of Example 5. Otherwise, the preparation was the same as that of the abrasive composition of Example 2.

[0092] • Example 6 In the preparation of the abrasive composition of Example 2, an additional 0.02% by mass of copolymer of synthesis number 2 was added as a water-soluble polymer compound to obtain the abrasive composition of Example 6. Otherwise, the preparation was the same as that of the abrasive composition of Example 2.

[0093] • Example 7 In the preparation of the abrasive composition of Example 2, the quaternary ammonium salt type organic compound was changed from diallyldimethylammonium chloride to 0.0026% by mass of decyltrimethylammonium chloride to obtain the abrasive composition of Example 7. Otherwise, the preparation was the same as that of the abrasive composition of Example 2.

[0094] • Example 8 In the preparation of the abrasive composition of Example 7, an additional 0.02% by mass of copolymer of synthesis number 2 was added as a water-soluble polymer compound to obtain the abrasive composition of Example 8. Otherwise, the preparation was the same as that of the abrasive composition of Example 7.

[0095] · reference example 1 In the preparation of the abrasive composition of Example 2, the quaternary ammonium salt type organic compound was changed from diallyldimethylammonium chloride to 0.0026% by mass of dodecyltrimethylammonium chloride. reference example 1 An abrasive composition was obtained. Otherwise, the preparation was the same as that of the abrasive composition in Example 2. reference example 1 Since foaming was observed during stirring of the abrasive composition, it was allowed to stand for a predetermined time until the foam disappeared before being used in the polishing test described below.

[0096] · reference example 2 reference example 1 In the preparation of the abrasive composition, the content of dodecyltrimethylammonium chloride was changed to 0.00055% by mass. reference The abrasive composition of Example 2 was obtained. reference Although foaming was observed in the abrasive composition of Example 2 during stirring, the foam disappeared immediately after preparation, so it was used in the polishing test as usual.

[0097] • Example 11 In preparing the abrasive composition of Example 2, in addition to diallyldimethylammonium chloride as a quaternary ammonium salt type organic compound, 0.00055% by mass of dodecyltrimethylammonium chloride was further added to obtain the abrasive composition of Example 11. Otherwise, the preparation was the same as that of the abrasive composition of Example 2. Although foaming was observed in the prepared abrasive composition of Example 11 during stirring, the foam disappeared immediately after preparation, so it was used in the polishing test as usual.

[0098] • Example 12 In preparing the abrasive composition of Example 11, in addition to the copolymer of synthesis number 1 as a water-soluble polymer compound, 0.02% by mass of the copolymer of synthesis number 2 was further added to obtain the abrasive composition of Example 12. Otherwise, the preparation was the same as that of the abrasive composition of Example 11.

[0099] • Example 13 In the preparation of the abrasive composition of Example 1, the abrasive grain composition was changed to 2.0% by mass of colloidal silica and 2.0% by mass of wet-process silica to obtain the abrasive composition of Example 13. Otherwise, the preparation was the same as that of the abrasive composition of Example 1.

[0100] • Example 14 In the preparation of the abrasive composition of Example 2, the abrasive grain composition was changed to 2.0% by mass of colloidal silica and 2.0% by mass of wet-process silica to obtain the abrasive composition of Example 14. Otherwise, the preparation was the same as that of the abrasive composition of Example 2.

[0101] • Example 15 In the preparation of the abrasive composition of Example 3, the abrasive grain composition was changed to 2.0% by mass of colloidal silica and 2.0% by mass of wet-process silica to obtain the abrasive composition of Example 15. Otherwise, the preparation was the same as that of the abrasive composition of Example 3.

[0102] • Example 16 In the preparation of the abrasive composition of Example 4, the abrasive grain composition was changed to 2.0% by mass of colloidal silica and 2.0% by mass of wet-process silica to obtain the abrasive composition of Example 16. Otherwise, the preparation was the same as that of the abrasive composition of Example 4.

[0103] • Example 17 In the preparation of the abrasive composition of Example 5, the abrasive grain composition was changed to 2.0% by mass of colloidal silica and 2.0% by mass of wet-process silica to obtain the abrasive composition of Example 17. Otherwise, the preparation was the same as that of the abrasive composition of Example 5.

[0104] • Example 18 In the preparation of the abrasive composition of Example 6, the abrasive grain composition was changed to 2.0% by mass of colloidal silica and 2.0% by mass of wet-process silica to obtain the abrasive composition of Example 18. Otherwise, the preparation was the same as that of the abrasive composition of Example 6.

[0105] • Example 19 In the preparation of the abrasive composition of Example 7, the abrasive grain composition was changed to 2.0% by mass of colloidal silica and 2.0% by mass of wet-process silica to obtain the abrasive composition of Example 19. Otherwise, the preparation was the same as that of the abrasive composition of Example 7.

[0106] Example 20 In preparing the abrasive composition of Example 19, in addition to the copolymer of synthesis number 1 as a water-soluble polymer compound, 0.02% by mass of copolymer of synthesis number 2 was further added to obtain the abrasive composition of Example 20. Otherwise, the preparation was the same as that of the abrasive composition of Example 19.

[0107] · reference example 3 reference example 1 In the preparation of the abrasive composition, the abrasive grain composition was changed to 2.0% by mass of colloidal silica and 2.0% by mass of wet-process silica. reference example 3 An abrasive composition was obtained. Otherwise, reference example 1The preparation is the same as that of the abrasive composition. reference example 3 Since foaming was observed during stirring of the abrasive composition, it was allowed to stand for a predetermined time until the foam disappeared before being used in the polishing test described below.

[0108] · reference example 4 reference example 3 In the preparation of the abrasive composition, the content of dodecyltrimethylammonium chloride was changed to 0.00055% by mass. reference example 4 An abrasive composition was obtained. reference example 4 Although foaming was observed during stirring of the abrasive composition, the foam disappeared immediately after preparation, so it was used in the polishing test as usual.

[0109] • Example 23 In preparing the abrasive composition of Example 14, in addition to diallyldimethylammonium chloride as a quaternary ammonium salt type organic compound, 0.00055% by mass of dodecyltrimethylammonium chloride was further added to obtain the abrasive composition of Example 23. Otherwise, the preparation was the same as that of the abrasive composition of Example 2. Although foaming was observed in the prepared abrasive composition of Example 23 during stirring, the foam disappeared immediately after preparation, so it was used in the abrasive test as usual.

[0110] • Example 24 In preparing the abrasive composition of Example 23, in addition to the copolymer of synthesis number 1 as a water-soluble polymer compound, 0.02% by mass of the copolymer of synthesis number 2 was further added to obtain the abrasive composition of Example 24. Otherwise, the preparation was the same as that of the abrasive composition of Example 23.

[0111] • Comparative Example 1 In the preparation of the abrasive composition of Example 1, the abrasive composition of Comparative Example 1 was obtained without adding diallyldimethylammonium chloride, a quaternary ammonium salt type organic compound. Otherwise, the preparation of the abrasive composition was the same as that of Example 1.

[0112] • Comparative Example 2 In the preparation of the abrasive composition of Example 2, the quaternary ammonium salt type organic compound was changed from diallyldimethylammonium chloride to 0.0026% by mass of lauryldimethylbenzylammonium chloride to obtain the abrasive composition of Comparative Example 2. Otherwise, the preparation was the same as that of the abrasive composition of Example 2.

[0113] • Comparative Example 3 In the preparation of the abrasive composition of Example 13, the abrasive composition of Comparative Example 3 was obtained without adding diallyldimethylammonium chloride, a quaternary ammonium salt type organic compound. Otherwise, the preparation was the same as that of the abrasive composition of Example 13.

[0114] • Comparative Example 4 In the preparation of the abrasive composition of Example 14, the quaternary ammonium salt type organic compound was changed from diallyldimethylammonium chloride to 0.0026% by mass of lauryldimethylbenzylammonium chloride to obtain the abrasive composition of Comparative Example 4. Otherwise, the preparation was the same as that of Example 14.

[0115] Examples 1 to 2, prepared as described above 8、11~20、23、 twenty four , Reference examples 1 to 4, The results of polishing tests conducted using the abrasive compositions of Comparative Examples 1 to 4 are shown in Tables 2 and 3.

[0116] 4. Measurement, conditions, and evaluation of each physical property, etc. 4.1 Weight-average molecular weight of water-soluble polymer compounds The weight-average molecular weight of water-soluble polymer compounds was measured by gel permeation chromatography (GPC) in terms of polyacrylic acid, and the GPC measurement conditions are shown below.

[0117] (GPC measurement conditions) Columns: TSKgel G4000PWXL (Tosoh) + G2500PWXL (Tosoh) + SHODEX OHpak SB-806M-HQ (Showa Denko) Eluent: 0.2M phosphate buffer / acetonitrile = 9 / 1 (volume ratio) Flow rate: 1.0ml / min Temperature: 40℃ Detection: Differential refractive index (RI) Sample: Concentration 0.1 wt% (Injection volume 100 μL) Calibration curve polymers: Polyacrylic acid, molecular weight (Mp) 115,000, 28,000, 4,100, 1,250 (Sowa Kagaku Co., Ltd., American Polymer Standards Corp.)

[0118] 4.2 Method for measuring the particle size and average particle size of colloidal silica The particle size (Heywood diameter) of colloidal silica was measured by taking a photograph of the field of view at a magnification of 100,000x using a transmission electron microscope (TEM) (JEOL Ltd., Transmission Electron Microscope JEM2000FX (200kV)), and then analyzing this photograph using analysis software (Mountec Co., Ltd., Mac-View Ver. 4.0) to determine the Heywood diameter (equivalent diameter of the projection area circle).

[0119] The average particle size of colloidal silica is calculated using the aforementioned analysis software (Mac-View Ver. 4.0, manufactured by Mountec Co., Ltd.) to determine the average particle size (D50) at which the cumulative particle size distribution (based on cumulative volume) from the smallest particle size side reaches 50%.

[0120] 4.3 Method for measuring the average particle size of silica using the wet method The average particle size of wet-process silica was measured using a dynamic light scattering particle size distribution analyzer (Microtrac UPA, manufactured by Nikkiso Co., Ltd.). The average particle size of wet-process silica is defined as the average particle size (D50) at which the cumulative particle size distribution from the smallest particle size side, based on volume, accounts for 50%.

[0121] 4.4 Polishing conditions An aluminum disk substrate with an outer diameter of 95 mm and electroless nickel-phosphorus plating was used as the target for polishing, and polishing was performed under the following polishing conditions. Polishing machine: SPEEDFAM (Co., Ltd.), 9B double-sided polishing machine Polishing pad: P1 pad, manufactured by FILWEL Co., Ltd. Plate rotation speed: Upper plate -7.7rpm Lower surface plate 23.5rpm Abrasive composition supply rate: 90 ml / min Polishing time: Polish until the polishing amount reaches 1.2-1.5 μm per side (240-720 seconds). Processing pressure: 120kPa

[0122] 4.5 Polishing speed ratio The polishing speed was calculated by measuring the mass of the aluminum disc substrate after polishing and using the following formula (1). Polishing speed (μm / min) = Mass loss of aluminum disc substrate (g) / Polishing time (min) / Area of ​​one side of aluminum disc substrate (cm²) 2 ) / Density of electroless nickel-phosphorus plating film (g / cm³) 3 ) / 2×10 4 ...Equation (1) (However, in formula (1) above, the area of ​​one side of the aluminum disk substrate is 65.9 cm². 2 The density of the electroless nickel-phosphorus plating film is 8.0 g / cm³. 3 (Calculated as)

[0123] The polishing speed ratio is a relative value in Table 2, which will be described later, with the polishing speed of Comparative Example 1, calculated using formula (1) above, set to 1 (reference), and is a relative value in Table 3, which will be described later, with the polishing speed of Comparative Example 3, calculated using formula (1) above, set to 1 (reference).

[0124] 4.6 Surface roughness ratio The surface roughness of the aluminum disk substrate was measured using a scanning white light interferometry (SUI) 3D surface structure analysis microscope manufactured by AMETEK. The measurement conditions were as follows: SUITEK New View 8300 (lens: 10.0x, zoom: 1.0x), wavelength 20-100 μm, measurement area 0.8 mm × 0.8 mm, and analysis was performed using SUITEK's analysis software (Mx).

[0125] In Table 2, the surface roughness ratio is a relative value with the surface roughness of Comparative Example 1, measured using the above method, set to 1 (reference), and in Table 3, it is a relative value with the surface roughness of Comparative Example 3, measured using the above method, set to 1 (reference).

[0126] 4.7 Method for evaluating the cleaning performance of abrasives Example 1~ 8、11~20、23、 twenty four , Reference examples 1 to 4, The aluminum discs polished using the abrasive compositions of Comparative Examples 1 to 4 were rinsed with deionized water, buffed with deionized water, rinsed again with deionized water after buffing, and then spin-dried. Each of the resulting aluminum discs was used as a substrate for evaluating cleanability. The above operations were carried out in a cleanroom.

[0127] The obtained substrates for cleaning performance evaluation were observed on both the front and back surfaces of the aluminum discs using a MicroMAX VMX-4100 manufactured by VisionScytec, a device capable of highlighting and inspecting fine residual particles on the substrate surface. Six fields of view were observed on the front surface and six fields of view on the back surface (12 fields of view in total) under the measurement conditions described below, and the number of residual particles observed in each field of view (9 mm × 7 mm) was measured. The number of residual particles observed using the method described above was then ranked based on the total number of residual particles in the 12 fields of view according to the "Cleaning Performance Evaluation Criteria" described below. The ranking results are shown in Tables 2 and 3.

[0128] (MicroMAX VMX-4100 measurement conditions) Slope: -5° Iris: 10 Zoom: 10

[0129] (Cleaning performance evaluation criteria (total number of residual particles in 12 fields of view)) ◎: Number of residual particles: 0-10 ○: Number of residual particles: 11-30 △: Number of residual particles: 31-50 ×: Number of residual particles > 50

[0130] [Table 2]

[0131] [Table 3]

[0132] 5. Discussion 5.1 Results in Table 2 The results in Table 2 above will be discussed below. Examples 1 to 5 show improved cleaning performance compared to Comparative Example 1, which used an abrasive composition that does not contain the quaternary ammonium salt type organic compound of the present invention. Furthermore, the polishing speed and surface roughness are equivalent to or improved.

[0133] Comparative Example 2 uses an abrasive composition containing the same amount of quaternary ammonium salt type organic compound as in Examples 2-5, which is not part of the present invention. Although the cleaning performance is improved compared to Comparative Example 1, the polishing speed is significantly reduced and the surface roughness is also worsened. When Comparative Example 2 is compared to Examples 2-5, which contain the same amount of quaternary ammonium salt type organic compound, it becomes even clearer that the polishing speed is significantly reduced and the surface roughness is worsened.

[0134] Examples 1 and 2 show the results when the amount of quaternary ammonium salt type organic compound added is different, while Examples 2 to 5 show the results when the type of quaternary ammonium salt type organic compound is different. Example 6 shows the results when an abrasive composition was used in which a water-soluble polymer compound of synthesis number 2 was further added to the abrasive composition used in Example 2, and the polishing speed was further improved compared to Example 2.

[0135] Example 7 and Reference example 1The quaternary ammonium salt type organic compound used in Example 8 showed even better cleaning performance than the quaternary ammonium salt type organic compounds used in Examples 2 to 5. Example 8 is the result of using an abrasive composition obtained by further adding the water-soluble polymer compound of synthesis number 2 to the abrasive composition used in Example 7, and the polishing speed was further improved compared to Example 7.

[0136] In addition, reference example 1 During the preparation of the abrasive composition, foaming occurred, which disappeared after a while. On the other hand, the amount of quaternary ammonium salt type organic compound added was reduced. reference example 2 However, although the cleaning effect was reduced, the foaming during preparation disappeared quickly.

[0137] Example 11 is an abrasive composition used in Example 2. reference example 2 As a result of adding a small amount of the quaternary ammonium salt type organic compound used in Example 2, the washing performance was further improved compared to Example 2, and the foaming during preparation disappeared immediately.

[0138] Example 12 shows the results of using an abrasive composition obtained by further adding a water-soluble polymer compound of synthesis number 2 to the abrasive composition used in Example 11, and the polishing speed is even better than in Example 11.

[0139] 5.2 Results in Table 3 The results in Table 3 are discussed below. Examples 13-17 show improved cleaning performance compared to Comparative Example 3, which used an abrasive composition that did not contain the quaternary ammonium salt type organic compound of the present invention. Furthermore, the polishing speed and surface roughness are equivalent to or improved.

[0140] Comparative Example 4 uses an abrasive composition containing the same amount of quaternary ammonium salt type organic compound as in Examples 14-17, which is not part of the present invention. Although the cleaning performance is improved compared to Comparative Example 3, the polishing speed is significantly reduced and the surface roughness is also worsened. When Comparative Example 4 is compared with Examples 14-17, which have the same amount of quaternary ammonium salt type organic compound, it becomes even clearer that the polishing speed is significantly reduced and the surface roughness is worsened.

[0141] Examples 13 and 14 show the results when the amount of quaternary ammonium salt type organic compound added is different, and Examples 14-17 show the results when the type of quaternary ammonium salt type organic compound is different. Example 18 is the result of using an abrasive composition in which a water-soluble polymer compound of synthesis number 2 was further added to the abrasive composition used in Example 14, and the polishing speed was further improved compared to Example 14. Example 19 and Reference example 3 The quaternary ammonium salt type organic compound used in this study showed even better cleaning performance than the quaternary ammonium salt type organic compounds used in Examples 14-17.

[0142] In addition, reference example 3 During the preparation of the abrasive composition, foaming occurred, which disappeared after a while. On the other hand, the amount of quaternary ammonium salt type organic compound added was reduced. reference example 4 In this case, although the cleaning performance improvement effect was reduced, the foaming during preparation disappeared quickly. Example 20 is the result of using an abrasive composition in which a water-soluble polymer compound of synthesis number 2 was further added to the abrasive composition used in Example 19, and the polishing speed was further improved compared to Example 19.

[0143] Example 23 is the result of adding a small amount of the quaternary ammonium salt type organic compound used in Example 21 to the abrasive composition used in Example 14. The cleaning performance was further improved compared to Example 14, and the foaming during preparation disappeared quickly. Example 24 is the result of using an abrasive composition in which a water-soluble polymer compound of synthesis number 2 was further added to the abrasive composition used in Example 23. The polishing speed was further improved compared to Example 23. [Industrial applicability]

[0144] The polishing composition of the present invention can be used for polishing electronic components such as semiconductors and magnetic recording media such as hard disks. In particular, it can be used for surface polishing of substrates for magnetic recording media such as glass magnetic disks and aluminum magnetic disks. Furthermore, it can be used for surface polishing of aluminum substrates for magnetic recording media that have an electroless nickel-phosphorus plating film formed on them. In particular, it can be used in a polishing step prior to the final polishing step of aluminum substrates for magnetic recording media that have an electroless nickel-phosphorus plating film formed on them.

Claims

1. Colloidal silica with an average particle size in the range of 10 to 120 nm, Wet-process silica with an average particle size in the range of 200 to 600 nm, Water-soluble polymer compounds, Quaternary ammonium salt type organic compounds, Water and, It contains an acid and / or a salt of the acid, The pH value (at 25°C) is in the range of 0.1 to 4.

0. The aforementioned water-soluble polymer compound is It contains a copolymer in which at least one monomer having a carboxylic acid group and one monomer having a sulfonic acid group are essential monomers, The quaternary ammonium salt type organic compound is A polishing composition for magnetic disk substrates, wherein the hydrocarbon group bonded to the nitrogen atom is a saturated aliphatic hydrocarbon group having 1 to 10 carbon atoms and / or an unsaturated aliphatic hydrocarbon group having 2 to 20 carbon atoms.

2. The quaternary ammonium salt type organic compound is The abrasive composition for magnetic disk substrates according to claim 1, which is at least one selected from the group consisting of divinyldimethylammonium chloride, diallyldimethylammonium chloride, diethyldimethylammonium chloride, triethylmethylammonium chloride, tetraethylammonium chloride, dibutyldimethylammonium chloride, tetrabutylammonium chloride, dioctyldimethylammonium chloride, didecyldimethylammonium chloride, octyltrimethylammonium chloride, and decyltrimethylammonium chloride.

3. Colloidal silica with an average particle size in the range of 10 to 120 nm, Wet-process silica with an average particle size in the range of 200 to 600 nm, Water-soluble polymer compounds, Quaternary ammonium salt type organic compounds, Water and, It contains an acid and / or a salt of the acid, The pH value (at 25°C) is in the range of 0.1 to 4.

0. The aforementioned water-soluble polymer compound is It contains a copolymer in which at least one monomer having a carboxylic acid group and one monomer having a sulfonic acid group are essential monomers, The quaternary ammonium salt type organic compound is A primary quaternary ammonium salt type organic compound in which the hydrocarbon group bonded to the nitrogen atom is a saturated aliphatic hydrocarbon group having 1 to 20 carbon atoms, A second quaternary ammonium salt type organic compound in which at least one hydrocarbon group bonded to the nitrogen atom is an unsaturated aliphatic hydrocarbon group having 2 to 20 carbon atoms, and the remaining hydrocarbon group is a saturated aliphatic hydrocarbon group having 1 to 20 carbon atoms, A polishing composition for magnetic disk substrates, which is a mixture containing at least one of the following.

4. The polishing composition for magnetic disk substrates according to any one of claims 1 to 3, wherein the water-soluble polymer compound further comprises a copolymer having at least a monomer having a carboxylic acid group and a monomer having an amide group as essential monomers.

5. A polishing composition for magnetic disk substrates according to any one of claims 1 to 4, further comprising an oxidizing agent.

6. The polishing composition for magnetic disk substrates according to any one of claims 1 to 5, used for polishing an electroless nickel-phosphorus plated aluminum magnetic disk substrate.

7. A method for polishing a magnetic disk substrate using the polishing agent composition for magnetic disk substrates described in any one of Claims 1 to 6, The system comprises a polishing step and a final polishing step performed after the polishing step, The aforementioned polishing composition for magnetic disk substrates, A method for polishing a magnetic disk substrate used in the polishing step prior to the final polishing step.

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