JP2007179612A - Polishing liquid composition for magnetic disk substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polishing liquid composition for reducing the waviness of the surface of a substrate, especially the waviness of an outer circumferential part of the surface, and to provide a method of polishing the substrate using the polishing liquid composition. <P>SOLUTION: The polishing liquid composition for a magnetic disk substrate contains silica and a surfactant and has a pH of 0 to 2.5, wherein the surfactant is one or more compounds selected from a group composed of a sulfonic acid compound represented by following general formulae (1) to (3). In the general formula (1) R<SP>1</SP>-(O)n<SP>1</SP>-SO<SB>3</SB>M<SP>1</SP>, R<SP>1</SP>denotes a 3-20C hydrocarbon group, M<SP>1</SP>denotes a hydrogen atom, an inorganic cation or an organic cation and n<SP>1</SP>denotes 0 or 1. In the general formula (2) R<SP>2</SP>OOC-CH<SB>2</SB>-CH(SO<SB>3</SB>M<SP>2</SP>)-COOR<SP>3</SP>, R<SP>2</SP>and R<SP>3</SP>each independently denotes a 3-20C hydrocarbon group and M<SP>2</SP>denotes a hydrogen atom, an inorganic cation or an organic cation. In the general formula (3), R<SP>4</SP>denotes a 3-20C hydrocarbon group and M<SP>3</SP>and M<SP>4</SP>each independently denotes a hydrogen atom, an inorganic cation or an organic cation. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a polishing composition for a magnetic disk substrate and a method for polishing a substrate.

  In recent years, magnetic disk drives tend to be smaller and have larger capacities, and this trend can be accommodated by reducing the unit recording area of the magnetic disk and increasing the capacity per disk. Since the magnetic signal becomes weaker as the unit recording area becomes smaller, it is necessary to increase the detection sensitivity. Therefore, it is necessary to lower the flying height of the magnetic head, and accordingly, it is required to reduce the surface roughness and waviness of the magnetic disk substrate.

Patent Document 1 discloses a polishing liquid composition containing silica and a sulfonic acid-based anionic surfactant, but the swell reduction effect of the composition is not sufficient.
International Publication No. 98/21289 Pamphlet

  Since the magnetic head floats and moves over the entire surface of the magnetic disk substrate, the swell is also required to be reduced over the entire surface of the substrate. However, until now, since a stylus type or optical measuring instrument has been used, only undulations of minute portions (for example, stylus diameter 0.2 μm, cutoff 800 μm) could be evaluated. Therefore, the measurement of the waviness on the entire surface of the substrate is very difficult because it takes a very long time. Therefore, the evaluation of the swell over the entire surface of the substrate has not been made.

  As a result of the swell evaluation over the entire surface of the substrate using the device (model M4224, manufactured by ThoT Co., Ltd.) that allows the inventors to evaluate the entire surface of the magnetic disk substrate for the first time, the size of the swell varies greatly within the substrate surface. It was found. In particular, it has been found that the undulation at the outer peripheral portion (for example, a position having a radius of 46 mm from the center of the substrate) is significantly larger than the inside (for example, a position having a radius of 20 mm from the center of the substrate). Therefore, it is considered that by reducing the waviness of the outer peripheral portion, the waviness over the entire surface of the substrate is reduced, and as a result, the flying height of the magnetic head can be further reduced.

  An object of the present invention is to provide a polishing composition capable of reducing the undulation of the substrate surface, particularly the undulation of the outer peripheral portion, and a method of polishing a substrate using the polishing composition, based on such novel findings. .

That is, the gist of the present invention is as follows.
[1] A polishing composition for a magnetic disk substrate comprising silica and a surfactant and having a pH of 0 to 2.5, wherein the surfactant is represented by the following general formulas (1) to (3) The polishing composition for magnetic disk substrate R ^1- (O) n ¹ -SO ₃ M ¹ (1), which is one or more compounds selected from the group consisting of sulfonic acid compounds represented by
[Wherein, R ¹ represents a hydrocarbon group having 3 to 20 carbon atoms, M ¹ represents a hydrogen atom, an inorganic cation, or an organic cation, and n ¹ represents 0 or 1. ]
_{^{R 2 OOC-CH 2 -CH (}} SO 3 M 2) -COOR 3 (2)
[Wherein, R ² and R ³ each independently represent a hydrocarbon group having 3 to 20 carbon atoms, and M ² represents a hydrogen atom, an inorganic cation, or an organic cation. ]

[Wherein, R ⁴ represents a hydrocarbon group having 3 to 20 carbon atoms, and M ³ and M ⁴ each independently represent a hydrogen atom, an inorganic cation, or an organic cation. And [2] While supplying the polishing composition according to [1] to a polishing machine at a supply rate of 0.05 to 15 mL / min per 1 cm ^{2 of the} substrate to be polished, the polishing pad is used to adjust the polishing composition to 5 to 50 kPa. The present invention relates to a method for polishing a magnetic disk substrate having a step of polishing with a polishing pressure.

  INDUSTRIAL APPLICABILITY According to the present invention, there are provided a polishing liquid composition capable of reducing the undulation of the substrate surface, particularly the undulation of the outer peripheral portion, and a substrate polishing method using the polishing liquid composition. By using the polishing composition or the polishing method of the present invention in, for example, a manufacturing process of a magnetic disk substrate, it is possible to obtain a substrate in which waviness, particularly waviness of the outer peripheral portion is significantly reduced. .

The magnetic disk substrate polishing liquid composition of the present invention comprises a silica and a surfactant, and has a pH of 0 to 2.5 (hereinafter referred to as “polishing liquid composition”). And the surfactant is one or more compounds selected from the group consisting of sulfonic acid compounds represented by the following general formulas (1) to (3). One feature.
R ¹ — (O) n ¹ —SO ₃ M ¹ (1)
[Wherein, R ¹ represents a hydrocarbon group having 3 to 20 carbon atoms, M ¹ represents a hydrogen atom, an inorganic cation, or an organic cation, and n ¹ represents 0 or 1. ]
_{^{R 2 OOC-CH 2 -CH (}} SO 3 M 2) -COOR 3 (2)
[Wherein, R ² and R ³ each independently represent a hydrocarbon group having 3 to 20 carbon atoms, and M ² represents a hydrogen atom, an inorganic cation, or an organic cation. ]

[Wherein, R ⁴ represents a hydrocarbon group having 3 to 20 carbon atoms, and M ³ and M ⁴ each independently represent a hydrogen atom, an inorganic cation, or an organic cation. ]
By having such characteristics, the polishing composition of the present invention can reduce the undulation of the substrate surface, particularly the undulation of the outer peripheral portion. Among the undulations of various wavelengths, it is known that the undulation of the size of the magnetic head (in this application, the undulation having a wavelength of 0.4 to 2 mm) has a great effect on the flying height of the magnetic head. . Therefore, the swell evaluation in this invention is performed about the swell of wavelength: 0.4-2mm.

  Examples of the silica used in the polishing composition of the present invention include colloidal silica, fumed silica, and surface-modified silica. Among these, colloidal silica is preferable from the viewpoint of obtaining a higher level of flatness on the surface of the substrate to be polished. The colloidal silica may be a commercially available one or one obtained by a known production method or the like produced from a silicic acid aqueous solution. The usage form of silica is preferably a slurry from the viewpoint of operability.

  The average particle size of the primary particles of silica is preferably 1 nm or more, more preferably 3 nm or more, and even more preferably 5 nm from the viewpoint of improving the polishing rate regardless of whether silica is used alone or in combination of two or more. From the viewpoint of reducing the surface roughness (centerline average roughness: Ra, Peak to Valley value: Rmax), it is preferably 30 nm or less, more preferably 25 nm or less, still more preferably 20 nm or less, and even more. It is preferably 15 nm or less, and more preferably 13 nm or less. Accordingly, the average particle size of the primary particles is preferably 1-30 nm, more preferably 1-25 nm, even more preferably 1-20 nm, even more preferably 3-20 nm, even more preferably 5-15 nm, even more preferably. Is preferably 5 to 13 nm. When primary particles are aggregated to form secondary particles, the average particle size of the secondary particles is preferably 5 from the viewpoint of improving the polishing rate and reducing the surface roughness of the substrate. It is ˜150 nm, more preferably 5 to 100 nm, still more preferably 5 to 80 nm, still more preferably 5 to 50 nm, and even more preferably 5 to 30 nm.

  Further, the average particle size of the primary particles of the silica is determined by using an image observed with a transmission electron microscope to obtain a particle size (D50) at which the cumulative volume frequency from the small particle size side of the primary particles becomes 50%. The value is the average particle size of the primary particles. The average particle diameter of the secondary particles can be measured as a volume average particle diameter using a laser light scattering method.

  As a particle size distribution of silica, D90 / D50 is preferably 1 to 3, more preferably 1.3 to 3 from the viewpoint of achieving reduction of nanoscratches, reduction of surface roughness, and high polishing rate. Note that D90 is a particle size at which the cumulative volume frequency from the small particle size side of the primary particles becomes 90% using an image observed with a transmission electron microscope.

  From the viewpoint of improving the polishing rate, the content of silica in the polishing composition is preferably 0.5% by weight or more, more preferably 1% by weight or more, still more preferably 3% by weight or more, and even more preferably 5%. From the viewpoint of improving the surface properties, it is preferably 20% by weight or less, more preferably 15% by weight or less, still more preferably 13% by weight or less, and even more preferably 10% by weight or less. That is, the content is preferably 0.5 to 20% by weight, more preferably 1 to 15% by weight, still more preferably 3 to 13% by weight, and even more preferably 5 to 10% by weight.

  The surfactant used in the polishing liquid composition of the present invention is one or more compounds selected from the group consisting of sulfonic acid compounds represented by general formulas (1) to (3).

The sulfonic acid compound represented by the general formula (1) is a sulfonic acid represented by the following general formula (1) or a salt thereof.
R ¹ — (O) n ¹ —SO ₃ M ¹ (1)
[Wherein, R ¹ represents a hydrocarbon group having 3 to 20 carbon atoms, M ¹ represents a hydrogen atom, an inorganic cation, or an organic cation, and n ¹ represents 0 or 1. ]
R ¹ may be a saturated hydrocarbon or an unsaturated hydrocarbon, and may be a linear structure or a branched structure. From the viewpoint of reducing the waviness of the outer peripheral portion, R ¹ is preferably an alkyl group having 6 to 20 carbon atoms, more preferably an alkyl group having 8 to 16 carbon atoms, and further preferably an alkyl group having 8 to 14 carbon atoms. Examples of the inorganic cation of M ¹ include alkali metal ions, alkaline earth metal ions, and ammonium ions. Among these, alkali metal ions and ammonium ions are preferable, and alkali metal ions are more preferable from the viewpoint of reducing the waviness of the outer peripheral portion. Examples of the organic cation of M ¹ include primary to quaternary ammonium ions and various amines. Of these, amine salts are preferable, and triethanolamine is more preferable.

  Specific examples of the surfactant represented by the formula (1) include sodium octyl sulfonate, sodium alkane (C14-16) sulfonate, sodium lauryl sulfate, ammonium lauryl sulfate, triethanolamine lauryl sulfate, higher alcohol. A sodium sulfate etc. are mentioned.

The sulfonic acid compound represented by the general formula (2) is a sulfonic acid represented by the following general formula (2) or a salt thereof.
_{^{R 2 OOC-CH 2 -CH (}} SO 3 M 2) -COOR 3 (2)
[Wherein, R ² and R ³ each independently represent a hydrocarbon group having 3 to 20 carbon atoms, and M ² represents a hydrogen atom, an inorganic cation, or an organic cation. ]
R ² and R ³ may each independently be a saturated hydrocarbon or an unsaturated hydrocarbon, and may have a linear structure or a branched structure. From the viewpoint of reducing the waviness of the outer peripheral portion, preferred examples of R ² and R ³ are the same as those of R ¹ described above. Examples of the inorganic cation and organic cation of M ² are the same as those of M ¹ described above.

  Specific examples of the surfactant represented by the formula (2) include sodium dioctyl sulfosuccinate, sodium ditridecyl sulfosuccinate, sodium dicyclohexyl sulfosuccinate and the like.

  The sulfonic acid compound represented by the general formula (3) is a sulfonic acid represented by the following general formula (3) or a salt thereof.

[Wherein, R ⁴ represents a hydrocarbon group having 3 to 20 carbon atoms, and M ³ and M ⁴ each independently represent a hydrogen atom, an inorganic cation, or an organic cation. ]
R ⁴ may be a saturated hydrocarbon or an unsaturated hydrocarbon, and may be a linear structure or a branched structure. From the viewpoint of reducing the waviness of the outer peripheral portion, preferred R ⁴ is exemplified by those similar to R ¹ described above. Examples of the inorganic cation and organic cation of M ³ and M ⁴ are the same as those of M ¹ described above.

  Specific examples of the surfactant represented by the formula (3) include sodium alkyl (C9-C14) diphenyl ether disulfonate.

The effect of the present invention can be obtained by adjusting the pH of the polishing composition to 0 to 2.5 using the surfactant as described above together with an acid having high solubility in water. For example, by using sodium lauryl sulfate together with sulfuric acid having a solubility in water (25 ° C.) of 80.3 g per 100 g of the saturated aqueous solution, the undulation of the outer peripheral portion can be remarkably reduced.
In addition, the surfactant in the polishing composition may be used alone or as a mixture of two or more.

  The content of the surfactant in the polishing composition is preferably 0.005 to 1% by weight, more preferably 0.01 to 1% by weight, and still more preferably 0.02 to 1% by weight, from the viewpoint of reducing the waviness of the outer peripheral portion. . Furthermore, in consideration of operability such as foaming resistance, the content is preferably 0.02 to 0.5% by weight, more preferably 0.02 to 0.2% by weight.

  The polishing composition of the present invention has a pH of 0 to 2.5. The pH can be adjusted with the sulfonic acid compounds represented by the general formulas (1) to (3), but from the viewpoint of reducing swell, the pH is adjusted with an acid having a solubility in water at 25 ° C. of 1 g or more per 100 g of the saturated aqueous solution. Is preferred. From the viewpoint of reducing waviness and improving the polishing rate, the pH is preferably 2.3 or less, more preferably 2 or less, and even more preferably 1.9 or less. Further, from the viewpoint of suppressing corrosion of the polishing apparatus, the pH is preferably 0.1 or more, more preferably 0.5 or more, and further preferably 0.8 or more. Therefore, from the viewpoint of undulation reduction and workability environment, 0.1 to 2.3 is preferable, 0.5 to 2 is more preferable, and 0.8 to 1.9 is more preferable.

  The acid that can be used in the present invention is preferably an acid having a solubility in water at 25 ° C. of 1 g or more per 100 g of a saturated aqueous solution, more preferably 2 g or more of acid, from the viewpoint of improving the polishing rate and reducing waviness. Preferably 3 g or more, even more preferably 4 g or more, even more preferably 5 g or more, even more preferably 6 g or more of acid is desirable. The acid solubility in the present invention represents the mass (g) of acid contained in 100 g of a saturated aqueous solution of acid at 25 ° C. The acid solubility is described, for example, in the revised 4th edition, Chemical Handbook (Basic) II, pp156-178 (Edited by Chemical Society of Japan).

  Examples of the acid include inorganic acids such as sulfuric acid, sulfurous acid, persulfuric acid, nitric acid, hydrochloric acid, pyrophosphoric acid, phosphonic acid, phosphoric acid, and amidosulfuric acid, 2-aminoethylphosphonic acid, 1-hydroxyethylidene-1,1- Diphosphonic acid (HEDP), aminotri (methylenephosphonic acid), ethylenediaminetetra (methylenephosphonic acid), diethylenetriaminepenta (methylenephosphonic acid), ethane-1,1-diphosphonic acid, ethane-1,1,1-triphosphonic acid, methane Hydroxyphosphonic acid, 2-phosphonobutane-1,2-dicarboxylic acid, 1-phosphonobutane-2,3,4-tricarboxylic acid, organic phosphonic acids such as α-methylphosphonosuccinic acid, aminocarboxylic acids such as glutamic acid and picolinic acid And carboxylic acids such as oxalic acid, nitroacetic acid, maleic acid and oxaloacetic acid. Among these, from the viewpoint of reducing scratches and undulations, inorganic acids and organic phosphonic acids having high water solubility are preferable. Among inorganic acids, sulfuric acid, nitric acid, hydrochloric acid, and perchloric acid are more preferable. Among organic phosphonic acids, HEDP, aminotri (methylenephosphonic acid), and diethylenetriaminepenta (methylenephosphonic acid) are more preferable. These acids may be used alone or in combination of two or more.

  These acids used in the present invention may be in the form of partially neutralized salts. Preferred examples of such salts include sodium citrate, sodium sulfate, sodium nitrate and the like.

  The content of the acid in the polishing composition is preferably 0.1% by weight or more, more preferably 0.2% by weight or more, and further preferably 0.4% by weight or more from the viewpoint of reducing waviness and improving the polishing rate. Further, from the viewpoint of influence on the human body and corrosion of the polishing apparatus, the acid content is preferably 2% by weight or less, more preferably 1.5% by weight or less, and further preferably 1% by weight or less. Therefore, 0.1 to 2% by weight is preferable from the viewpoint of swell reduction and working environment, more preferably 0.2 to 1.5% by weight, and still more preferably 0.4 to 1% by weight.

  In the present invention, among acids, an acid whose standard electrode potential (25 ° C.) of the aqueous solution shows a value of 1 V or more is treated as an oxidizing agent. The standard electrode potential of the aqueous solution system is described in, for example, Revised 4th edition, Chemical Handbook (Basic) II, pp464-468 (Edited by Chemical Society of Japan). Here, the standard electrode potential of acid refers to the acid anion.

As the acid used in the present invention, it is preferable to use one having a pKa of 4 or less from the viewpoint of reducing swell. Among them, from the viewpoint of improving the polishing rate and reducing waviness, an acid having a pKa of 3 or less is preferable, more preferably 2 or less, still more preferably 1.5 or less, and even more preferably 1 or less.
The acid corresponding to the sulfonic acid as the surfactant used in the present invention is not included in the “acid” used in the polishing composition of the present invention.

  The polishing liquid composition of the present invention can further improve the polishing rate without worsening the swell by containing an oxidizing agent. As the oxidizing agent, peroxides, permanganates, chromates, nitrates, peroxo acids or salts thereof, oxygen acids or salts thereof, metal salts, and the like can be used.

  As the peroxide, hydrogen peroxide, sodium peroxide, barium peroxide, etc .; As the permanganate, potassium permanganate, etc .; As the chromate, chromate metal salt, dichromate metal salt, etc .; Examples of nitrates include iron (III) nitrate, ammonium nitrate, and the like. Peracetic acid, perbenzoic acid, perphthalic acid, etc .; oxygen acid or its salts include hypochlorous acid, hypobromite, hypoiodous acid, chloric acid, bromic acid, iodic acid, sodium hypochlorite, Calcium hypochlorite, etc .; Examples of metal salts include iron (III) chloride, iron (III) sulfate, iron (III) citrate, and iron (III) ammonium sulfate. It is. Preferable oxidizing agents include hydrogen peroxide, iron (III) nitrate, peracetic acid, ammonium peroxodisulfate, iron (III) sulfate, and iron (III) ammonium sulfate. These oxidizing agents may be used alone or in combination of two or more. It is preferable to use hydrogen peroxide from the viewpoint that ions derived from the oxidizing agent are difficult to adhere to the surface of the object to be polished.

  The content of the oxidizing agent in the polishing liquid composition is preferably 0.002% by weight or more, more preferably 0.005% by weight or more, further preferably 0.007% by weight or more, and still more preferably 0.01% by weight, from the viewpoint of improving the polishing rate. From the viewpoint of reducing surface roughness and waviness, and reducing surface defects such as pits and scratches to improve surface quality, it is preferably 20% by weight or less, more preferably 15% by weight or less, and still more preferably Is 10% by weight or less, and more preferably 5% by weight or less. Therefore, in order to improve the polishing rate while maintaining the surface quality, the content is preferably 0.002 to 20% by weight, more preferably 0.005 to 15% by weight, still more preferably 0.007 to 10% by weight, and even more preferably. Is 0.01 to 5% by weight.

  Examples of the water used in the polishing composition of the present invention include distilled water, ion exchange water, and ultrapure water. From the viewpoint of the surface cleanliness of the substrate to be polished, ion exchange water and ultrapure water are preferable, and ultrapure water is more preferable. The content of water in the polishing composition is preferably 60 to 99% by weight, more preferably 70 to 98% by weight. Moreover, you may contain organic solvents, such as alcohol, in the range which does not inhibit the effect of this invention.

  The polishing liquid composition of the present invention may contain a radical scavenger, a rust inhibitor, an antifoaming agent, an antibacterial agent, and the like as necessary. The content of these other optional components in the polishing liquid composition is preferably 0 to 10% by weight, more preferably 0 to 5% by weight.

The polishing composition of the present invention can be prepared, for example, as follows. That is, an aqueous surfactant solution is prepared, and an acid having a solubility in water (25 ° C.) of 1 g or more per 100 g of a saturated aqueous solution and further a silica slurry are prepared. If necessary, optional components are further blended and supplied to the polishing machine. The surfactant and optional components may be added and mixed in advance before being supplied to the polishing machine, or may be added and mixed in the process of supplying to the polishing machine (for example, in the supply pipe or on the polishing substrate). .
Silica may be mixed in the state of a concentrated slurry when preparing the polishing composition, or may be mixed after being diluted with water or the like. Furthermore, it may be added and mixed in the process of supplying to the polishing machine as described above.

When preparing the polishing composition of the present invention, it is preferable from the viewpoint of silica stability that an aqueous acid solution is prepared in advance, and then a silica slurry is added thereto and mixed. In addition, it is preferable that other optional components are dissolved in water in advance to form an aqueous solution, and then the silica slurry is mixed. Furthermore, when mixing the silica slurry, it is preferable to mix at a speed at which the silica particles do not dry from the viewpoint of preventing aggregation due to drying of the silica particles.
When mixing the silica slurry, from the viewpoint of dispersibility of silica, it is preferable to add and mix the silica slurry while stirring an aqueous solution of components other than silica.

The present invention also relates to a substrate polishing method and a substrate manufacturing method. By polishing the substrate to be polished using the polishing composition of the present invention obtained as described above, it is possible to produce a substrate in which undulation is suppressed. As a specific example, the substrate is sandwiched by a polishing machine to which a polishing pad such as a non-woven organic polymer polishing cloth is attached, and the polishing composition of the present invention is supplied at 0.05 to 15 mL / min per 1 cm ^{2 of the} substrate to be polished. Examples of the substrate polishing method or substrate manufacturing method include a step of polishing a substrate by moving a polishing platen or a substrate at a polishing pressure of 5 to 50 kPa while supplying the polishing machine at a speed. By having such a structure, the substrate obtained by the substrate polishing method or the substrate manufacturing method of the present invention has effectively reduced waviness.

  In the polishing method and the manufacturing method of the present invention, the polishing pressure refers to the pressure of the surface plate applied to the polishing surface of the substrate to be polished during polishing. If the polishing pressure is 5 kPa or more, it is estimated that the substrate to be polished is pressed by the surface plate, the substrate to be polished is less likely to vibrate, and the load on the outer peripheral edge of the substrate is difficult to be applied. Is done. Considering productivity, it is preferably 7 kPa or more, more preferably 10 kPa or more. On the other hand, from the viewpoint of suppressing the generation of scratches, the polishing pressure is 50 kPa or less, preferably 30 kPa or less, more preferably 20 kPa or less. Therefore, in the polishing method and the production method of the present invention, the polishing pressure is 5 to 50 kPa, preferably 7 to 30 kPa, and more preferably 10 to 20 kPa. The polishing pressure can be adjusted by applying air pressure or weight to the surface plate and / or the substrate.

The supply rate of the polishing composition in the polishing method and the production method of the present invention is 0.05 to 15 mL / min per 1 cm ^{2 of the} substrate to be polished. Since the frictional resistance between the polishing cloth and the substrate to be polished is suppressed at 0.05 mL / min or more, the substrate to be polished is less likely to vibrate, and the load at the outer peripheral edge of the substrate is unlikely to be applied. It is estimated to be. Therefore, the feed rate is preferably 0.06 mL / min or more, more preferably 0.07 mL / min or more, further preferably 0.08 mL / min or more, and even more preferably 0.12 mL / min or more. From the viewpoint of economically reducing waviness, the supply rate is 15 mL / min or less per 1 cm ^{2 of the} substrate to be polished, preferably 10 mL / min or less, more preferably 1 mL / min or less, and even more preferably 0.5. Less than mL / min. Accordingly, the supply rate of the polishing composition is 0.05 to 15 mL / min per 1 cm ^{2 of the} substrate to be polished, preferably 0.06 to 10 mL / min, more preferably 0.07 to 1 mL / min, and still more preferably 0.08 to 0.5 mL / min. Min, even more preferably 0.12 to 0.5 mL / min.

  As a method for supplying the polishing 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. At that time, in addition to the method of supplying the polishing composition in one liquid containing all components, considering the stability of the polishing liquid composition, etc., it is divided into several kits and supplied in two or more liquids. You can also. In the latter case, for example, the several kits are mixed in the supply pipe or on the polishing substrate to form the polishing liquid composition of the present invention.

  There is no restriction | limiting in particular as a polishing pad used by this invention, Polishing pads, such as a suede type, a nonwoven fabric type, a polyurethane independent foam type, and the two-layer type which laminated | stacked these, can be used.

  By reducing the relative speed of the substrate to be polished with respect to the polishing pad in the polishing step, it is possible to further improve the undulation of the outer peripheral portion of the substrate. Here, the relative speed of the substrate to be polished with respect to the polishing pad refers to that represented by the following formula.

  From the viewpoint of reducing the waviness of the outer peripheral portion, the relative speed of the substrate to be polished with respect to the polishing pad in the polishing step is preferably 1 m / second or less, more preferably 0.8 m / second or less, and even more preferably 0.6 m / second or less. From the viewpoint of improving productivity, the relative speed is preferably 0.1 m / second or more, more preferably 0.2 m / second or more, further preferably 0.3 m / second or more, and even more preferably 0.4 m / second or more. is there. That is, the relative speed is preferably 0.1 to 1 m / second, more preferably 0.2 to 0.8 m / second, further preferably 0.3 to 0.6 m / second, and still more preferably 0.4 to 0.6 m / second.

  The polishing method is preferably performed in the second and subsequent steps among the plurality of polishing steps, and more preferably in the final polishing step. At that time, in order to avoid mixing of the polishing material or polishing liquid composition in the previous process, different polishing machines may be used, and when different polishing machines are used, the substrate is removed for each polishing process. It is preferable to wash. The polishing machine is not particularly limited.

  The surface properties of the substrate used in the substrate polishing method and the substrate manufacturing method of the present invention are not particularly limited, but in order to manufacture a substrate for high recording density, for example, the surface roughness (Ra) is about 1 nm. A substrate having surface properties is suitable. Surface roughness is a measure of surface smoothness, and the evaluation method is not limited. For example, the surface roughness is evaluated as roughness measurable at a wavelength of 10 μm or less with an atomic force microscope, and expressed as centerline average roughness Ra. be able to.

  Examples of the material of the substrate to be polished 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, amorphous carbon Glass materials such as alumina; ceramic materials such as alumina, silicon dioxide, silicon nitride, tantalum nitride, and titanium carbide; and resins such as polyimide resins. Among these, an object to be polished containing a metal such as aluminum, nickel, tungsten, or copper and an alloy containing such a metal as a main component is preferable. For example, a Ni—P plated aluminum alloy substrate or a glass substrate such as crystallized glass or tempered glass is more suitable, and a Ni—P plated aluminum alloy substrate is more suitable.

  The shape of the object to be polished is not particularly limited. For example, the shape having a flat portion such as a disk shape, a plate shape, a slab shape, or a prism shape, or the shape having a curved surface portion such as a lens can be used. It becomes the object of polishing using. Among them, it is more suitable for polishing a disk-shaped workpiece.

  The polishing composition of the present invention is suitably used for polishing precision component substrates. For example, it is suitable for polishing a substrate of a disk recording medium such as a magnetic disk, an optical disk, a magneto-optical disk, a photomask substrate, a glass for liquid crystal, an optical lens, an optical mirror, an optical prism, a semiconductor substrate and the like. The polishing composition of the present invention and the polishing method and manufacturing method of the substrate can remarkably reduce the waviness important in increasing the capacity, and thus are more suitable for polishing the magnetic disk substrate and manufacturing the same.

  By using the polishing composition or the polishing method of the present invention, the waviness at the outer peripheral portion is, for example, 1.0 nm or less, preferably 0.9 nm or less, more preferably 0.8 nm or less, and further preferably 0.7 nm. The following substrates can be obtained. The swell of the outer peripheral portion can be measured by a laser-type full surface shape measuring instrument such as “ThoT model M4224” manufactured by ThoT Technology.

Experimental Examples 1 to 21
Polishing was performed using the following polishing liquid composition and the substrate to be polished, and the polishing rate and waviness were evaluated.

[Polished substrate]
An aluminum alloy substrate (thickness: 1.27 mm, outer diameter: 95 mmφ, inner diameter: 25 mmφ, Ra: 1 nm) obtained by roughly polishing a Ni-P plated aluminum substrate with a polishing composition containing an alumina abrasive. ) Was used as the substrate to be polished.

[Preparation of polishing composition]
In the ion-exchanged water, sulfuric acid (special grade manufactured by Wako Pure Chemical Industries), hydrogen peroxide (35% by weight manufactured by Asahi Denka Kogyo Co., Ltd.), surfactant (manufactured by Kao Corporation, or Tokyo) in the compounding amounts shown in Table 1 Kasei Chemical Co., Ltd.) was dissolved and stirred well. Thereafter, an aqueous slurry of colloidal silica (silica average primary particle size (D50): 12 nm, D90: 26 nm, silica concentration 25 wt%, pH = 10) was added and stirred again to prepare a polishing composition. About the obtained polishing liquid composition, pH was measured.

[PH measurement conditions]
The pH of the polishing composition was measured at 25 ° C. using a pH meter (manufactured by Toa Denpa Kogyo Co., Ltd., glass type hydrogen ion concentration index meter “HM-30G”. Table 1 shows the results.

[Polishing conditions]
Polishing tester: Speedfam, double-sided 9B polishing machine Polishing pad: Fujibo's suede type (thickness 0.9 mm, average hole diameter 30 μm)
Polishing time: 5 minutes Number of sheets to be fed: 10 sheets / time (see Table 1 for polishing pressure, polishing liquid composition supply speed, and relative speed of substrate to be polished with respect to polishing pad)

[Measurement method of polishing rate]
The weight change of the substrate before and after polishing was measured for 10 substrates (BP-210S manufactured by Sartrius), and the average value divided by the polishing time was taken as the weight change rate. The polishing rate (μm / min) was calculated from the Ni—P density (8.0 g / cm ³ ) and the substrate single-sided area (66.0 cm ² ) according to the following formula. The results are shown in Table 1.
Weight change rate = {Substrate weight before polishing (g)-Substrate weight after polishing (g)} / Polishing time (min)
Polishing rate (μm / min) = Weight change rate (g / min) / Substrate single side area (mm ² ) / Ni-P plating density (g / cm ³ ) × 10 ⁶

[Measurement method of swell]
Arbitrary two substrates were selected from the 10 substrates after polishing, and the waviness was measured on both sides under the following conditions. The results are shown in Table 1.

[Waviness measurement conditions]
Measuring instrument: ThoT Model 4224 (manufactured by ThoT Technology)
Measurement principle: Laser Doppler vibrometer (iodine stabilized He-Ne laser: 633 nm)
Measurement wavelength: 0.4-2mm
Measurement position: The entire surface with a radius of 20 mm to 46 mm from the center of the substrate Substrate rotation speed: 6000 r / m
Gain: 16
Filter: 10kHz
Laser range: 5mm / s / V
Track pitch: 0.01mm

  As shown in Table 1, it can be seen that the substrate obtained by using the polishing composition of the present invention has a significantly reduced waviness at the outer peripheral portion and a reduced waviness over the entire surface of the substrate. . Furthermore, it can be seen that further waviness reduction can be realized by using the polishing method of the present invention.

  The polishing liquid composition and the substrate polishing method of the present invention are suitably used for polishing a magnetic disk substrate.

Claims (6)

A polishing composition for a magnetic disk substrate comprising silica and a surfactant and having a pH of 0 to 2.5, wherein the surfactant is represented by the following general formulas (1) to (3). A polishing liquid composition for a magnetic disk substrate, which is one or more compounds selected from the group consisting of sulfonic acid compounds.
R ¹ — (O) n ¹ —SO ₃ M ¹ (1)
[Wherein, R ¹ represents a hydrocarbon group having 3 to 20 carbon atoms, M ¹ represents a hydrogen atom, an inorganic cation, or an organic cation, and n ¹ represents 0 or 1. ]
_{^{R 2 OOC-CH 2 -CH (}} SO 3 M 2) -COOR 3 (2)
[Wherein, R ² and R ³ each independently represent a hydrocarbon group having 3 to 20 carbon atoms, and M ² represents a hydrogen atom, an inorganic cation, or an organic cation. ]
[Wherein, R ⁴ represents a hydrocarbon group having 3 to 20 carbon atoms, and M ³ and M ⁴ each independently represent a hydrogen atom, an inorganic cation, or an organic cation. ]   The polishing composition for a magnetic disk substrate according to claim 1, wherein the content of the surfactant in the polishing composition is 0.005 to 1% by weight.   3. The polishing composition for a magnetic disk substrate according to claim 1, wherein the average particle size of the primary particles of silica is 1 to 30 nm.   Furthermore, the polishing liquid composition for magnetic disk substrates in any one of Claims 1-3 containing an oxidizing agent. While supplying the polishing composition according to any one of claims 1 to 4 to a polishing machine at a supply rate of 0.05 to 15 mL / min per 1 cm ^{2 of the} substrate to be polished, a polishing pressure of 5 to 50 kPa is used using a polishing pad. A method for polishing a magnetic disk substrate, comprising a step of polishing. 6. The method for polishing a magnetic disk substrate according to claim 5, wherein the relative speed of the substrate to be polished with respect to the polishing pad in the polishing step is 0.1 to 1 m / sec.