JP5376934B2 - Rinse agent composition for magnetic disk substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rinse composition for magnetic disk substrates which is capable of realizing the decrease in the defects of scratches or nanoprojections on a substrate surface which may occur when rinsing. <P>SOLUTION: The rinse composition for the magnetic disk substrates includes at least one of the following copolymer (a) and the following amphoteric surfactant (b), and an oxidizing agent, and has a pH of 1-6; (a): a copolymer having at least one of the constitutional unit with a carboxylic acid group and the constitutional unit derived from a styrene derivative, and having the constitutional unit with a sulfonic acid group, (b): an amphoteric surfactant expressed by formula (1): R-(CH<SB>3</SB>-)<SB>2</SB>N<SP>+</SP>O<SP>-</SP>(wherein R is a 8-16C alkyl group). <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a rinsing agent composition for a magnetic disk substrate and a method for producing a magnetic disk substrate using the same.

  In recent years, magnetic disk drives have been reduced in size and capacity, and high recording density has been demanded. In order to increase the recording density, the unit recording area is reduced, and in order to improve the detection sensitivity of the weakened magnetic signal, technological development for lowering the flying height of the magnetic head has been advanced. Magnetic disk substrates have improved smoothness and flatness (reduced surface roughness, waviness, and edge sagging) and reduced defects (scratches, protrusions, pits) in order to reduce the flying height of the magnetic head and secure a recording area. Etc.) is becoming stricter.

In the manufacturing process of a magnetic disk substrate, a multi-stage polishing method having two or more polishing steps is adopted from the viewpoint of both surface quality improvement and productivity improvement such as smoother and less scratches. In addition, in order to remove abrasive grains and polishing residue used in the polishing process, a rinsing process is performed. As a rinsing liquid used in this process, an activator such as polystyrene sulfonic acid, an inorganic acid, and an organic acid are used. And a rinse composition using salts (see Patent Document 1), a rinse composition using oxoacid salts and chlorides (see Patent Document 2), and a rinse agent composition using hydrogen peroxide (Patent Document 3) Have been proposed).
JP 2000-144193 A JP-A-10-152675 JP 2004-182800 A

  In the final polishing process, ie, the final polishing process, in the manufacturing process of the magnetic disk substrate, an acidic final polishing containing colloidal silica particles is used to meet the requirement of reducing surface roughness and scratches without reducing productivity. Although a liquid composition is used, there has been a problem that if rinsing is performed after polishing with such a polishing liquid composition, scratches are newly generated in the rinsing step. However, the conventional rinse agent composition cannot sufficiently prevent the occurrence of scratches newly generated in the rinse step. Furthermore, in order to realize a further increase in capacity of a magnetic disk drive, it is not sufficient to reduce scratches with a conventional rinse agent composition. In addition to scratches, it is also necessary to reduce minute convex defects called nanoprotrusions. There is a need for an excellent rinse agent composition that can reduce these.

  As the capacity has increased, the recording method for magnetic disks has shifted from the horizontal magnetic recording method to the perpendicular magnetic recording method. In the manufacturing process of a perpendicular magnetic recording type magnetic disk, the texture process required for aligning the magnetization direction in the horizontal magnetic recording method is not required, and a magnetic layer is formed directly on the polished substrate surface. The required characteristics for quality are becoming stricter. The conventional rinse agent composition cannot sufficiently satisfy the small number of defects and scratches required for the surface of a perpendicular magnetic recording substrate.

  Accordingly, an object of the present invention is to provide a rinsing agent composition for a magnetic disk substrate that can reduce scratches and nanoprotrusion defects on the substrate surface that can be newly generated in the rinsing process, and a method of manufacturing a magnetic disk substrate using the same. There is.

［上記式（１）において、Ｒは炭素数８〜１６のアルキル基である。］ The present invention relates to a rinsing agent composition for a magnetic disk substrate, which contains at least one of the copolymer (a) below and the amphoteric surfactant (b) below and an oxidizing agent, and has a pH of 1-6. .
(A) A copolymer having at least one of a structural unit having a carboxylic acid group and a structural unit derived from a styrene derivative, and a structural unit having a sulfonic acid group.
(B) An amphoteric surfactant represented by the following formula (1).

[In the above formula (1), R is an alkyl group having 8 to 16 carbon atoms. ]

  The method for producing a magnetic disk substrate of the present invention also relates to a method for producing a magnetic disk substrate including a step of rinsing the substrate using the rinse agent composition for a magnetic disk substrate of the present invention.

According to the rinsing agent composition for a magnetic disk substrate of the present invention, it is possible to produce a magnetic disk substrate, particularly a perpendicular magnetic recording type magnetic disk substrate, in which scratches and nanoprotrusion defects on the substrate surface that can occur in the rinsing step are reduced. Is played.

[Nanoprotrusion defects]
In the present invention, the “nanoprotrusion defect” is a defect on the surface of the substrate after rinsing in the manufacturing process of the magnetic disk substrate, and means a convex defect having a height of less than about 10 nm that can be detected optically. In order to increase the density and capacity of a magnetic disk, the distance between the magnetic head and the magnetic disk needs to be less than 10 nm. Therefore, the nanoprotrusions may reduce the consumption of the magnetic head and decrease the recording density of the magnetic disk drive. May cause instability. If the nanoprojection defects are reduced in the polished substrate, the flying height of the magnetic head can be reduced, and the recording density of the magnetic disk substrate can be improved.

[scratch]
In the present invention, “scratch” is a fine scratch on the substrate surface having a depth of 1 nm or more, a width of 100 nm or more, and a length of 1000 nm or more. The optical defect detection device Candela 6100 series manufactured by Veeco or Hitachi High It can be detected by NS 1500 series manufactured by Technology, and can be quantitatively evaluated as the number of scratches. Further, the size and shape of the detected scratch can be analyzed with an atomic force microscope (AFM), a scanning electron microscope (SEM), and a transmission electron microscope (TEM).

  The present invention reduces scratches and nanoprotrusion defects that may occur in the rinsing step when an acidic rinse agent composition containing a copolymer having a specific structural unit or a specific amphoteric surfactant and an oxidizing agent is used. Based on the knowledge that can be achieved.

  The details of the mechanism by which the rinsing agent composition of the present invention reduces scratches and nanoprotrusion defects that may occur in the rinsing step are not clear, but under acidic conditions, a specific copolymer or amphoteric surfactant is used in the rinsing step. Prevents aggregation of colloidal silica particles that may occur and acts on the polishing pad or the substrate surface to reduce friction between the polishing pad and the substrate, thereby suppressing the generation of scratches and nanoprotrusions on the substrate surface. It is estimated that However, the present invention is not limited to this mechanism.

［上記式（１）において、Ｒは炭素数８〜１６のアルキル基である。］ That is, the present invention provides a rinsing agent composition for a magnetic disk substrate that contains at least one of the following copolymer (a) and the amphoteric surfactant (b) below and an oxidizing agent, and has a pH of 1-6. Product (hereinafter also referred to as rinse agent composition of the present invention).
(A) A copolymer having at least one of a structural unit having a carboxylic acid group and a structural unit derived from a styrene derivative, and a structural unit having a sulfonic acid group.
(B) An amphoteric surfactant represented by the following formula (1).

[In the above formula (1), R is an alkyl group having 8 to 16 carbon atoms. ]

[Structural Unit Having Carboxylic Acid Group]
In the present invention, the structural unit having a carboxylic acid group is preferably derived from a monomer having a carboxylic acid group. The monomer having a carboxylic acid group refers to a monomer having a polymerizable double bond containing at least one carboxylic acid group (—COOH) and / or a salt thereof, such as itaconic acid, itaconic anhydride, (Meth) acrylic acid, maleic acid, maleic anhydride, fumaric acid, fumaric anhydride, citraconic acid, citraconic anhydride, glutaconic acid, vinyl acetic acid, allyl acetic acid, phosphinocarboxylic acid, α-haloacrylic acid, β-carvone Examples thereof include acids or salts thereof. Among these, (meth) acrylic acid is preferable from the viewpoint of reducing scratches and nanoprotrusion defects. In the present invention, (meth) acrylic acid refers to acrylic acid or methacrylic acid.

[Structural units derived from styrene derivatives]
In the present invention, the structural unit derived from the styrene derivative is preferably derived from the following monomer. Monomers having a styrene structure and having a polymerizable double bond, such as styrene, α-methylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, α, 2-dimethylstyrene, 2,4 -Dimethylstyrene, 2,5-dimethylstyrene, 2,4,6-trimethylstyrene, 2-ethylstyrene, 4-ethylstyrene, 4-isopropylstyrene, 2-methoxystyrene, 3-methoxystyrene, 4-methoxystyrene, Examples include 4-ethoxystyrene, 4-phenoxystyrene, 4-phenylstyrene, 2-hydroxystyrene, 4-hydroxystyrene, and the like. Among these, styrene is preferable from the viewpoint of reactivity, scratches, and nanoprotrusion defect reduction.

[Structural unit having sulfonic acid group]
In the present invention, the structural unit having a sulfonic acid group is preferably derived from a monomer having a carboxylic acid group. The monomer containing a sulfonic acid group refers to a monomer having a polymerizable double bond containing at least one sulfonic acid group (—SO ₃ H) and / or a salt thereof, such as isoprenesulfonic acid, Examples include 2- (meth) acrylamide-2-methylpropanesulfonic acid, styrenesulfonic acid, vinylbenzylsulfonic acid, methallylsulfonic acid, vinylsulfonic acid, allylsulfonic acid, and isoamylenesulfonic acid. Among these, from the viewpoint of reducing scratches, isoprenesulfonic acid, 2- (meth) acrylamide-2-methylpropanesulfonic acid, and styrenesulfonic acid are preferable, and styrenesulfonic acid and 2- (meth) acrylamide-2-methylpropanesulfonic acid are preferable. More preferred. In the present invention, 2- (meth) acrylamide-2-methylpropanesulfonic acid refers to 2-acrylamido-2-methylpropanesulfonic acid or 2-methacrylamide-2-methylpropanesulfonic acid.

  The copolymer of the above (a) is a structural unit derived from a monomer other than a monomer having a carboxylic acid group, a monomer having a sulfonic acid group, and a styrene derivative within the scope of the effects of the present invention. You may contain a component. Examples of monomers that can be used as other constituent unit components include hydroxyethyl acrylate, hydroxyethyl methacrylate, glycidyl acrylate, glycidyl methacrylate, ethylene glycol diacrylate, ethylene glycol dimethacrylate, polyethylene glycol monoacrylate, polyethylene glycol monomethacrylate, and the like. Group or glycidyl group-containing ethylenic monomer; ethylenic amides such as acrylamide, methacrylamide, N-methylol acrylamide, N-methylol methacrylamide, N-diacetone acrylamide; aminoethyl acrylate, aminoethyl methacrylate, N, N- Dimethylaminoethyl acrylate, N, N-dimethylaminoethyl methacrylate, N, N-die Aminoethyl acrylate, N, N- diethylaminoethyl methacrylate, N, N, N- trimethyl aminoethyl acrylate, N, N, ethylene amine, or a salt thereof, such as N- trimethyl aminoethyl methacrylate. Two or more of these monomers may be used. However, the content of other structural units in all the structural units constituting the copolymer of the present invention is preferably 0 to 30 mol% from the viewpoint of reduction of scratches and nanoprotrusion defects during rinsing. 20 mol% is more preferable, 0-10 mol% is further more preferable, and 0-5 mol% is still more preferable.

  The content of the structural unit having a carboxylic acid group in all the structural units constituting the copolymer (a) is 99 to 30 mol% from the viewpoint of reducing scratches and nanoprotrusion defects in the rinsing step. Preferably, 99-50 mol% is more preferable, 99-85 mol% is further more preferable, and 99-95 mol% is still more preferable.

  The molar ratio of the structural unit having a carboxylic acid group to the structural unit having a sulfonic acid group in all the structural units constituting the copolymer of the present invention (mol% of the structural unit having a carboxylic acid group / sulfonic acid) The mol% of the structural unit having a group is preferably from 99/1 to 30/70, more preferably from 99/1 to 50/50, from the viewpoint of reducing scratches and nanoprojection defects in the rinsing step, and from 99/1 to 99/1. 85/15 mol is more preferable, and 99/1 to 95/5 is still more preferable.

  The content of the structural unit derived from the styrene derivative occupying in all the structural units constituting the copolymer (a) is from 5 to 95 mol% from the viewpoint of reducing scratches and nanoprotrusion defects in the rinsing step. Preferably, 5-70 mol% is more preferable, 10-60 mol% is further more preferable, and 15-50 mol% is still more preferable.

  The molar ratio of the structural unit derived from the styrene derivative to the structural unit having a sulfonic acid group in all the structural units constituting the copolymer of the present invention (mol% of the structural unit derived from the styrene derivative / sulfonic acid) The mol% of the structural unit having a group is preferably 5/95 to 95/5, more preferably 5/95 to 70/30, from the viewpoint of reducing scratches and nanoprojection defects in the rinsing step, and 10/90 to 60/40 mol is more preferred, and 15/85 to 50/50 is even more preferred.

  In the present invention, the copolymer (a) is preferably a (meth) acrylic acid / isoprenesulfonic acid copolymer, (meth) acrylic acid / 2- (), from the viewpoint of reducing scratches and nanoprotrusion defects in the rinsing step. (Meth) acrylamido-2-methylpropanesulfonic acid copolymer, styrene / styrenesulfonic acid copolymer, (meth) acrylic acid / isoprenesulfonic acid / 2- (meth) acrylamido-2-methylpropanesulfonic acid copolymer (Meth) acrylic acid / 2- (meth) acrylamide-2-methylpropanesulfonic acid copolymer and styrene / styrenesulfonic acid copolymer are more preferable.

  The copolymer (a) is obtained by, for example, converting a base polymer containing a diene structure or an aromatic structure into a known method, for example, edited by The Chemical Society of Japan, New Experimental Chemistry Course 14 (Synthesis and Reaction of Organic Compounds). III, p. 1773, 1978).

  When the copolymer (a) is a salt, the counter ion is not particularly limited, and specific examples include ions of metals, ammonium, alkylammonium, and the like. Specific examples of the metal include metals belonging to the periodic table (long-period type) 1A, 1B, 2A, 2B, 3A, 3B, 4A, 6A, 7A, or Group 8. Among these metals, metals belonging to Group 1A, 3B, or Group 8 are preferable from the viewpoint of surface roughness and nanoscratch reduction, and sodium and potassium belonging to Group 1A are more preferable. Specific examples of alkylammonium include tetramethylammonium, tetraethylammonium, tetrabutylammonium and the like. Among these salts, ammonium salts, sodium salts, and potassium salts are more preferable.

  The weight average molecular weight of the copolymer (a) is preferably 1,000 to 100,000, more preferably 1,500 to 50,000, still more preferably 1, from the viewpoint of scratch reduction and nanoprotrusion defects. 500 to 20,000, even more preferably 3,000 to 15,000. Specifically, the weight average molecular weight is measured by the measurement method described in Examples.

  The content of the copolymer (a) in the rinse agent composition is preferably 0.001 to 1% by weight or more, more preferably 0.005 to 5%, from the viewpoint of achieving both scratch reduction and productivity. It is 0.5% by weight, more preferably 0.01 to 0.3% by weight, still more preferably 0.01 to 0.1% by weight.

[Amphoteric surfactant: Amine oxide]
The amphoteric surfactant (b) is a compound represented by the following formula (1).

  In the above formula (1), R is an alkyl group having 8 to 16 carbon atoms, but from the viewpoint of enhancing the solubility of nickel oxide and effectively suppressing the corrosion of the Ni—P plating layer. Is preferably 8-14, more preferably 10-12. The alkyl group may have a straight chain structure or a branched chain structure.

  The amphoteric surfactant represented by the above formula (1) is alkyldimethylamine oxide, and specifically includes octyldimethylamine oxide, decyldimethylamine oxide, undecyldimethylamine oxide, lauryldimethylamine oxide, trimethylamine. Examples include decyldimethylamine oxide, tetradecyldimethylamine oxide, pentadecyldimethylamine oxide, hexadecyldimethylamine oxide, and the like. These alkyl dimethylamine oxides may be used individually by 1 type, and may use 2 or more types. Among them, octyl dimethylamine oxide, decyl dimethylamine oxide, lauryl dimethylamine oxide, tetradecyl dimethylamine oxide have high nickel oxide solubility, effectively inhibit corrosion of the Ni-P plating layer, and are industrial. From the viewpoint of good availability, octyldimethylamine oxide, decyldimethylamine oxide, and lauryldimethylamine oxide are more preferable from the same viewpoint.

  In the rinse agent composition, the content of the amphoteric surfactant represented by the above formula (1) is 0.001% by weight or more from the viewpoint of effectively suppressing corrosion of the Ni-P plating layer. Preferably, it is 0.005% by weight or more, more preferably 0.01% by weight or more. From the viewpoint of improving rinsing properties, it is preferably 1% by weight or less, more preferably 0.5% by weight or less, and further preferably 0.1% by weight or less. Therefore, the content is preferably 0.001 to 1% by weight, more preferably 0.005 to 0.5% by weight, and still more preferably 0.01 to 0.1% by weight.

  The rinse agent composition of the present invention preferably contains both the copolymer (a) and the amphoteric surfactant (b) from the viewpoint of reducing scratches and nanoprotrusion defects. The total content thereof is preferably 0.001 to 1% by weight, more preferably 0.005 to 0.5% by weight, and still more preferably 0.01 to 0.2% by weight.

[Oxidant]
The rinse agent composition of the present invention contains an oxidizing agent. As the oxidizing agent used in the rinse agent composition of the present invention, from the viewpoint of reducing scratches and nanoprotrusion defects, peroxide, permanganic acid or a salt thereof, chromic acid or a salt thereof, peroxo acid or a salt thereof, oxygen Examples include acids or salts thereof, metal salts, nitric acids, sulfuric acids, and the like.

  Examples of the peroxide include hydrogen peroxide, sodium peroxide, barium peroxide, etc., examples of the permanganic acid or salt thereof include potassium permanganate, and examples of the chromic acid or salt thereof include chromium. Acid metal salts, metal dichromates, and the like. Peroxo acids or salts thereof include peroxodisulfuric acid, ammonium peroxodisulfate, peroxodisulfate metal salts, peroxophosphoric acid, peroxosulfuric acid, sodium peroxoborate, and performic acid. Peroxyacetic acid, perbenzoic acid, perphthalic acid, etc., and oxygen acids or salts thereof include hypochlorous acid, hypobromite, hypoiodous acid, chloric acid, bromic acid, iodic acid, hypochlorous acid. Examples thereof include sodium chlorate and calcium hypochlorite. Examples of metal salts include iron (III) chloride, iron (III) sulfate, iron (III) nitrate, and iron citrate. III), ammonium iron (III), and the like.

  Preferable oxidizing agents include hydrogen peroxide, iron (III) nitrate, peracetic acid, ammonium peroxodisulfate, iron (III) sulfate, and iron (III) ammonium sulfate. As a more preferable oxidizing agent, hydrogen peroxide is mentioned from the viewpoint that metal ions do not adhere to the surface and are generally used and inexpensive. These oxidizing agents may be used alone or in admixture of two or more.

  The content of the oxidizing agent in the rinse agent composition is preferably 0.01% by weight or more, more preferably 0.05% by weight or more, and still more preferably 0.1% by weight from the viewpoint of reducing scratches and nanoprotrusion defects. From the viewpoint of reducing the surface roughness, waviness and scratches, it is preferably 5% by weight or less, more preferably 3% by weight or less, and further preferably 1% by weight or less. Therefore, in order to improve the cleaning effect while maintaining the surface quality, the content is preferably 0.01 to 5% by weight, more preferably 0.05 to 3% by weight, and further preferably 0.1 to 1%. % By weight.

  Further, in the rinse agent composition, the total weight of the copolymer (a) and the amphoteric surfactant (b) and the weight ratio of the oxidizer (copolymer and amphoteric surfactant The total weight% / weight% of the oxidizing agent is preferably 0.0002 to 100, more preferably 0.005 to 10, still more preferably 0.01 to 1, from the viewpoint of reducing scratches and nanoprotrusion defects. .

[water]
The water in the rinse agent composition of the present invention is used as a medium, and examples thereof include distilled water, ion exchange water, and ultrapure water. From the viewpoint of the surface cleanliness of the substrate to be rinsed, ion-exchanged water and ultrapure water are preferable, and ultrapure water is more preferable. 60-99.4 weight% is preferable and, as for content of the water in a rinse agent composition, 70-98.9 weight% is more preferable. Moreover, you may mix | blend organic solvents, such as alcohol, in the range which does not inhibit the effect of this invention.

[PH of rinse agent composition]
The pH of the rinse agent composition of the present invention is 6 or less, preferably 5 or less, more preferably 4 or less, and even more preferably 3 or less, from the viewpoint of reducing scratches and nanoprotrusion defects. Further, from the viewpoint of preventing corrosion of the substrate to be rinsed and the polishing machine, one or more is preferable, more preferably 1.2 or more, still more preferably 1.3 or more, and still more preferably 1.4 or more. Therefore, the pH of the rinse agent composition is 1 to 6, preferably 1.2 to 5, more preferably 1.3 to 4, and even more preferably 1.4 to 3.

[acid]
The rinse agent composition of the present invention preferably contains an acid. In the present invention, the acid includes an acid and / or a salt thereof. The acid used in the rinse agent composition of the present invention is preferably a compound having a pK1 of 2 or less from the viewpoint of reducing scratches and nanoprotrusion defects, and preferably having a pK1 of 1 from the viewpoint of reducing scratches. 5 or less, more preferably 1 or less, and still more preferably a compound exhibiting strong acidity that cannot be expressed by pK1. Examples thereof include inorganic acids such as nitric acid, sulfuric acid, sulfurous acid, persulfuric acid, hydrochloric acid, perchloric acid, phosphoric acid, phosphonic acid, phosphinic acid, pyrophosphoric acid, tripolyphosphoric acid, amidosulfuric acid, and salts thereof, 2-aminoethylphosphone. 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-diphosphonic 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 Organic phosphonic acids such as 2,3,4-tricarboxylic acid and α-methylphosphonosuccinic acid and salts thereof, aminocarboxylic acids such as glutamic acid, picolinic acid and aspartic acid and salts thereof, oxalic acid, nitroacetic acid, maleic acid, Examples thereof include carboxylic acids such as oxaloacetic acid and salts thereof. Among these, from the viewpoint of reducing scratches, inorganic acids, organic phosphonic acids, and salts thereof are preferable. Among inorganic acids and salts thereof, nitric acid, sulfuric acid, hydrochloric acid, perchloric acid and salts thereof are more preferable, and sulfuric acid is more preferable. Among organic phosphonic acids and salts thereof, 1-hydroxyethylidene-1,1-diphosphonic acid, aminotri (methylenephosphonic acid), ethylenediaminetetra (methylenephosphonic acid), diethylenetriaminepenta (methylenephosphonic acid) and their salts are more preferred. 1-hydroxyethylidene-1,1-diphosphonic acid and aminotri (methylenephosphonic acid) are more preferable. These acids and salts thereof may be used alone or in admixture of two or more. Here, pK1 is a logarithmic value of the reciprocal of the first acid dissociation constant (25 ° C.) of the organic compound or inorganic compound. The pK1 of each compound is described in, for example, the revised 4th edition, Chemical Handbook (Basic Edition) II, pp316-325 (Edited by Chemical Society of Japan).

  There are no particular limitations on the counter ion when these acid salts are used, and specific examples include ions of metals, ammonium, alkylammonium, and the like. Specific examples of the metal include metals belonging to the periodic table (long-period type) 1A, 1B, 2A, 2B, 3A, 3B, 4A, 6A, 7A, or Group 8. Among these, a salt with a metal belonging to Group 1A or ammonium is preferable from the viewpoint of reducing scratches.

  The content of the acid in the rinse agent composition is preferably 0.001 to 5% by weight, more preferably 0.01 to 4% by weight, and still more preferably 0, from the viewpoint of reducing scratches and nanoprotrusion defects. 0.05 to 3% by weight, still more preferably 0.1 to 2.0% by weight.

[Other ingredients]
In the polishing composition of the present invention, other components can be blended as necessary. Examples of other components include thickeners, dispersants, rust inhibitors, and basic substances. 0-10 weight% is preferable and, as for content of these other arbitrary components in polishing liquid composition, 0-5 weight% is more preferable.

[Method of manufacturing magnetic disk substrate]
As another aspect, the present invention relates to a method of manufacturing a magnetic disk substrate (hereinafter also referred to as a manufacturing method of the present invention). In one embodiment, the manufacturing method of the present invention is a method of manufacturing a magnetic disk substrate including a rinsing step of rinsing the substrate to be rinsed with the rinse agent composition of the present invention. Examples of the substrate to be rinsed include a polished substrate obtained after the polishing step, as will be described later. Therefore, in another embodiment, the production method of the present invention uses a polishing liquid composition containing an abrasive such as alumina or colloidal silica to polish a substrate to be polished, and the rinse agent composition of the present invention. And a rinsing step of rinsing the substrate after polishing obtained in the polishing step. According to the manufacturing method of the present invention, it is possible to preferably provide a magnetic disk substrate in which scratches on the substrate surface and nanoprotrusion defects generated in the rinsing step are reduced. The manufacturing method of the present invention is particularly suitable for a method for manufacturing a magnetic disk substrate for perpendicular magnetic recording. Therefore, as another aspect, the production method of the present invention is a method of producing a magnetic disk substrate for perpendicular magnetic recording system, which includes a rinsing process using the rinse agent composition of the present invention.

  As a specific example of the method of rinsing the substrate to be rinsed (the substrate obtained in the polishing step) using the rinse agent composition of the present invention, a polishing pad such as a non-woven organic polymer polishing cloth is attached. A method of rinsing the substrate to be rinsed by moving the surface plate or the substrate to be rinsed while sandwiching the substrate to be rinsed with a plate and supplying the rinse agent composition of the present invention to a polishing machine can be mentioned.

  When the polishing process is performed in multiple stages, the rinsing process using the rinse agent composition of the present invention is preferably performed after the rough polishing process, more preferably performed after the final polishing process, and colloidal silica is used. More preferably, it is performed after the final polishing step using the polishing liquid composition. The average particle size of the colloidal silica used in the final polishing step is preferably 1 to 50 nm, more preferably 5 to 40 nm, from the viewpoint of reducing the surface roughness. The polishing machine is not particularly limited, and a known polishing machine for polishing a magnetic disk substrate can be used.

[Polishing pad]
The polishing pad used in the present invention is not particularly limited, and a polishing pad of a suede type, a nonwoven fabric type, a polyurethane closed-cell foam type, or a two-layer type in which these are laminated can be used. From the viewpoint, a suede type polishing pad is preferable.

  The average pore diameter of the surface member of the polishing pad is preferably 50 μm or less, more preferably 45 μm or less, still more preferably 40 μm or less, and even more preferably 35 μm or less, from the viewpoint of scratch reduction and pad life.

[Rinse load]
The rinsing load used in the rinsing step using the rinsing agent composition of the present invention is preferably 1.0 kPa or more, more preferably 2.0 kPa or more, and still more preferably 3, from the viewpoint of improving productivity and cleaning efficiency. 5 kPa or more. Further, from the viewpoint of reducing scratches and nanoprotrusion defects, 7.0 kPa or less is preferable, more preferably 6.0 kPa or less, and still more preferably 5.0 kPa or less. Accordingly, the rinsing load in the rinsing step is preferably 1.0 to 7.0 kPa, more preferably 2.0 to 6.0 kPa, and even more preferably 3.5 to 5.0 kPa. The rinse load can be adjusted by applying air pressure or weight to at least one of the surface plate and the substrate to be rinsed. In the manufacturing method of the present invention, the rinse load refers to the pressure of the surface plate applied to the rinse surface of the substrate to be rinsed during rinsing.

[Supply of rinse agent composition]
The supply rate of the rinse agent composition of the present invention in the rinsing step is preferably 0.3 to 2.0 mL / min, more preferably 0, per 1 cm ^{2 of the} substrate to be rinsed from the viewpoint of reducing scratches and nanoprotrusion defects. .6 to 1.5 mL / min, and more preferably 0.7 to 1.4 mL / min.

[Rinse time]
In the rinsing step of the production method of the present invention, the time for rinsing with a polishing machine is preferably 10 to 120 seconds, more preferably 15 to 60 seconds, and more preferably 15 to 30 from the viewpoint of reducing scratches and nanoprotrusion defects. Seconds are more preferred.

  As a method of supplying the rinse agent composition of the present invention to a polishing machine, for example, a method of continuously supplying using a pump or the like can be mentioned. When supplying the rinsing agent composition to the polishing machine, in addition to the method of supplying it in one liquid containing all the components, considering the stability of the rinsing agent composition, etc., it is divided into a plurality of compounding component liquids, Two or more liquids can be supplied. In the latter case, for example, the plurality of compounding component liquids are mixed in the supply pipe or on the substrate to be rinsed to obtain the rinse agent composition of the present invention.

[Rinse substrate]
Examples of the material of the substrate to be rinsed that are preferably used in the present invention include metals, metalloids such as silicon, aluminum, nickel, tungsten, copper, tantalum, and titanium, or alloys thereof, glass, glassy carbon, and amorphous. Examples thereof include glassy substances such as carbon, ceramic materials such as alumina, silicon dioxide, silicon nitride, tantalum nitride, and titanium carbide, and resins such as polyimide resin. Among these, a substrate to be rinsed containing a metal such as aluminum, nickel, tungsten, or copper, or an alloy containing these metals as a main component is preferable. It is particularly suitable for Ni-P plated aluminum alloy substrates and glass substrates such as crystallized glass and tempered glass, among which Ni-P plated aluminum alloy substrates are suitable.

  In addition, according to the present invention, a magnetic disk substrate with reduced scratches and nanoprotrusion defects on the surface of the substrate can be provided, which is suitable for rinsing a perpendicular magnetic recording type magnetic disk substrate that requires a high degree of surface smoothness. Can be used.

[Rinse method]
In another aspect, the present invention relates to a method for polishing a substrate to be rinsed, which includes rinsing the substrate to be rinsed while bringing the above-described rinse agent composition into contact with a polishing pad. By using the rinsing method of the present invention, a magnetic disk substrate with reduced scratches and nanoprotrusion defects on the substrate surface, in particular, a perpendicular magnetic recording type magnetic disk substrate is preferably provided. Examples of the substrate to be rinsed in the rinsing method of the present invention include those used for manufacturing a magnetic disk substrate and a magnetic recording medium substrate as described above, and in particular, a magnetic disk substrate for a perpendicular magnetic recording system. A substrate used for production is preferred. The specific polishing method and conditions can be as described above.

  Predetermined amounts of compounds shown in Tables 1 and 2 below (copolymer, amphoteric surfactant, hydrogen peroxide solution, sulfuric acid, HEDP (1-hydroxyethylidene-1,1-diphosphonic acid)) and the balance of ion-exchanged water Were mixed and stirred to obtain a rinse agent composition. The measurement method of the weight average molecular weight of a copolymer, polishing conditions, rinse conditions, and an evaluation method are as follows.

[Method for measuring weight average molecular weight of copolymer]
[GPC conditions of acrylic acid / 2-acrylamido-2-methylpropanesulfonic acid copolymer]
Column: TSKgel G4000PWXL + TSKgel G2500PWXL (manufactured by Tosoh Corporation)
Eluent: 0.2M phosphate buffer / CH3CN = 9/1 volume ratio Temperature: 40 ° C.
Flow rate: 1.0 mL / min
Sample size: 5 mg / mL
Detector: RI
Conversion standard: Polyacrylic acid Na

[GPC conditions of styrene / styrene sulfonic acid copolymer and polystyrene sulfonic acid]
Column: TSKgel α-M + TSKgel α-M (manufactured by Tosoh Corporation)
Guard column: TSK guard column α (Tosoh)
Eluent: 60 mmol / L phosphoric acid, 50 mmol / L LiBr / DMF
Temperature: 40 ° C
Flow rate: 1.0 mL / min
Sample size: 3 mg / mL
Detector: RI
Conversion standard: Polystyrene

  An Ni-P plated aluminum alloy substrate (thickness: 1.27 mm, outer diameter: 95 mm, inner diameter: 25 mm, AFM (Digital Instrument NanoScope IIIa Multi Mode AFM), which has been roughly polished with a polishing composition containing an alumina abrasive in advance. The center line average roughness Ra measured by 1) is 1 nm, the amplitude of long wave waviness (wavelength 0.4 to 2 mm) is 2 nm, and the wave length of short wave waviness (wavelength 5 to 50 μm is 2 nm). Then, the substrate after final polishing was rinsed under the following rinse conditions, and the number of scratches and nanoprotrusion defects on the substrate surface after the rinse was measured under the following conditions. The results are shown in Table 2 below.

[Setting conditions for finish polishing process]
Polishing tester: "Fast double-sided 9B polishing machine" manufactured by Speedfam
Polishing pad: Fujibo's suede type (thickness 0.9mm, average hole diameter 30μm)
Polishing liquid composition supply amount: 100 mL / min (supply rate per 1 cm ^{2 of} polishing substrate: 0.072 mL / min)
Lower platen rotation speed: 32.5 rpm
Polishing load: 7.9 kPa
Polishing time: 4 minutes Polishing liquid composition: 4.5 wt% colloidal silica (manufactured by JGC Catalysts & Chemicals, average particle size 25 nm), 0.4 wt% sulfuric acid (special grade, manufactured by Wako Pure Chemical Industries, Ltd.), 0.1 wt% % HEDP (1-hydroxyethylidene-1,1-diphosphonic acid, manufactured by Sorcia Japan), 0.4% by weight hydrogen peroxide (manufactured by Asahi Denka Co., Ltd .: 35% by weight), and the remaining ion-exchanged water.

[Rinse process setting conditions]
Polishing tester: "Fast double-sided 9B polishing machine" manufactured by Speedfam
Polishing pad: Fujibo's suede type (thickness 0.9mm, average hole diameter 30μm)
Rinse agent composition supply amount: 600 mL / min (supply rate per 1 cm ^{2 of} substrate to be rinsed: 0.91 mL / min)
Lower platen rotation speed: 32.5 rpm
Rinse load: 3.92 kPa
Rinse time: 30 seconds

[Evaluation method of nanoprotrusion defects and scratches]
Measuring instrument: OSA6100, manufactured by Candela Instruments
Evaluation: Four substrates were randomly selected from the substrates put in the polishing tester, and each substrate was irradiated with a laser at 10,000 rpm to measure nanoprotrusion defects and scratches. The total number of scratches (lines) on each of the four substrates was divided by 8 to calculate the number of scratches per substrate surface. Similarly, the total number of nanoprotrusion defects (lines) on both surfaces of each of the four substrates was divided by 8 to calculate the number of nanoprojection defects per substrate surface. The results are shown in Table 1 below.

  As shown in Table 1 above, when the rinse agent compositions of Examples 1 to 8 were used, nanoprojections could be reduced in addition to the scratches on the substrate after polishing as compared with Comparative Examples 1 to 4. Furthermore, when the copolymer and the amphoteric surfactant were used in combination, scratches and nanoprotrusions on the substrate after polishing could be more significantly reduced (Examples 7 and 8). In addition, when the rinse function was evaluated by the effect of “reduction of particles (height of 80 nm or more)”, the rinse agent compositions of Examples 1 to 8 were rinses similar to the rinse agent compositions of the conventional and Comparative Examples 1 to 4. Function was demonstrated (data not shown).

  According to the present invention, for example, a magnetic disk substrate suitable for increasing the recording density can be provided.

Claims (7)

A rinsing agent composition for a magnetic disk substrate, comprising at least one of a copolymer (a) below and an amphoteric surfactant (b) below, and an oxidizing agent, and having a pH of 1-6.
(A) a copolymer having a structural unit having a structural unit and a sulfonic acid group having a carboxylic acid group, the molar ratio of the constituent unit having a structural unit and a sulfonic acid group with carboxylic acid groups, 99 A copolymer that is 1/90/10.
(B) An amphoteric surfactant represented by the following formula (1).

[In the above formula (1), R is an alkyl group having 8 to 16 carbon atoms. ]   The rinse agent composition for a magnetic disk substrate according to claim 1, further comprising an acid.   The rinsing agent composition for a magnetic disk substrate according to claim 1 or 2, wherein the content of the oxidizing agent is 0.01 to 5% by weight in the polishing composition.   The rinsing agent composition for a magnetic disk substrate according to any one of claims 1 to 3, wherein a total content of the copolymer and the surfactant is 0.001 to 1% by weight in the polishing composition.   The rinsing agent composition for a magnetic disk substrate according to any one of claims 1 to 4, comprising the copolymer (a) and the amphoteric surfactant (b). A polishing step of polishing a substrate to be polished using a polishing machine;
A rinsing step of rinsing the substrate after polishing obtained in the step using a polishing machine,
The said rinse process is a manufacturing method of a magnetic disk board | substrate including rinsing the said board | substrate using the rinse agent composition for magnetic disk boards | substrates in any one of Claim 1-5 . The method of manufacturing a magnetic disk substrate according to claim 6 , wherein the polishing step includes polishing the substrate to be polished using a polishing liquid composition containing colloidal silica.