JP6680652B2 - Abrasive dispersion, polishing composition kit containing the same, and method for producing polishing composition, polishing composition, polishing method, and method for producing magnetic disk substrate using the same - Google Patents

Description

  The present invention relates to an abrasive dispersion, a polishing composition kit containing the same, and a method for producing a polishing composition using the same, a polishing composition, a polishing method, and a method for producing a magnetic disk substrate.

  A polishing composition used for polishing an object to be polished such as a magnetic disk substrate is required to have a small number of scratches generated on the surface of the substrate during polishing and a high polishing rate.

In order to meet such requirements, Patent Document 1 discloses that the pH value is 0.1 or more and 7 or less, and the number of abrasive particles having a pH value of 0.56 μm or more and less than 1 μm is 500,000 or less per 1 cm ^{3 of the} polishing liquid composition, A polishing liquid composition having a content of 1 μm or more of polishing particles in an amount of 0.001% by weight or less based on all polishing particles in the polishing liquid composition, or a polishing liquid composition prepared from a polishing particle preparation liquid satisfying the same. It is disclosed that the number of scratches on the object to be polished after polishing is reduced by polishing with such a polishing composition.

  Further, Patent Document 2 contains a silica particle dispersion liquid and an acid or a salt thereof, and the silica particle dispersion liquid comprises a sulfonic acid group-containing monomer and a (meth) acrylic acid / sulfonic acid (co) polymer. It is disclosed that the silica particle dispersion liquid can be stored for a long period of time by a polishing liquid kit containing water and at least one selected from those salts. It is also disclosed that the number of scratches on the object to be polished after polishing can be reduced by polishing with a polishing composition prepared using such a polishing kit.

JP, 2006-75975, A JP, 2008-179763, A

  However, as the recording density has been improved with the recent increase in capacity and diameter of magnetic disks, the required level for the quality of magnetic disk substrates has been improved. As a result, there is a problem that sufficient performance cannot be obtained.

  Here, the present inventors have found that the surface of the magnetic disk substrate has scratches (hereinafter also referred to as fine scratches) of a size smaller than the scratches that are the object of the improvement of the techniques of Patent Documents 1 and 2. I focused on doing. Then, the inventors of the present invention have studied and established means for quantitatively evaluating the number of fine scratches, which have been difficult to measure in the past, and established that the number of fine scratches has a great influence on the performance of the magnetic disk. Found.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide means for reducing fine scratches on a polishing object after polishing.

  The present inventors have made earnest studies in view of the above problems. As a result, surprisingly, the abrasive grain dispersion liquid for preparing the polishing composition is in the range of a predetermined pH value, and the particles of the abrasive grains are in a predetermined particle size range in the abrasive grain dispersion liquid. The inventors have found that the above problems can be solved by controlling the number, and have completed the present invention.

  That is, the said subject of this invention is solved by the following means.

An abrasive grain dispersion liquid containing an abrasive grain having an average primary particle diameter of 1 nm or more and 50 nm or less measured by a BET method, and a dispersion medium, and having a pH value of 7 or more and 12 or less, and containing an abrasive grain. The amount is the number of abrasive grains having a particle diameter of 0.2 μm or more and less than 0.3 μm, which is measured by a number counting type particle size distribution meter when converted to 30% by mass based on the total mass of the abrasive dispersion. Is 25,000,000 or less per 1 cm ³ , an abrasive grain dispersion liquid.

  According to the present invention, there is provided a means capable of reducing fine scratches on a polishing object after polishing.

  Hereinafter, the present invention will be described. The present invention is not limited to the following embodiments.

  In the present specification, the “fine scratch” can be detected by atomic force microscope (AFM) observation and has a depth of 1 nm or more and less than 10 nm, a width of 5 nm or more and less than 100 nm, and a length of 100 nm or more and 1 μm. Represents less than a microscopic scratch on the substrate surface. The average number of fine scratches existing on one surface of the substrate can be measured using Candela OSA6100 manufactured by KLA Tenchor, and the details of the measuring method will be described in Examples. In addition, in the present specification, “scratch” can be detected by atomic force microscope (AFM) observation, and has a depth of 10 nm or more and less than 100 nm, a width of 5 nm or more and less than 500 nm, and a length of 100 μm or more, Represents a scratch on the surface of a substrate that is larger than a fine scratch. The average number of scratches present on one surface of the substrate can be measured using a MicroMax VMX-2100CSP manufactured by VISION PSYTEC, and the details of the measuring method will be described in Examples.

<Abrasive grain dispersion liquid (A liquid)>
Hereinafter, the abrasive dispersion liquid (also referred to as liquid A in the present specification) according to the first embodiment of the present invention will be described.

The abrasive dispersion according to one aspect of the present invention has the following features. That is,
An abrasive grain dispersion liquid containing an abrasive grain having an average primary particle diameter of 1 nm or more and 50 nm or less measured by a BET method, and a dispersion medium, and having a pH value of 7 or more and 12 or less, and containing an abrasive grain. The amount is the number of abrasive grains having a particle diameter of 0.2 μm or more and less than 0.3 μm, which is measured by a number counting type particle size distribution meter when converted to 30% by mass based on the total mass of the abrasive dispersion. Is 25,000,000 or less per 1 cm ³ , and is an abrasive grain dispersion liquid.

  The abrasive dispersion according to one embodiment of the present invention is not particularly limited, but for producing a polishing composition for use in polishing a semi-finished substrate for magnetic disk to obtain a magnetic disk substrate as a polishing product. It is preferably an abrasive dispersion, and an abrasive dispersion for producing a polishing composition for use in polishing a magnetic disk substrate having a nickel phosphorus plating layer on a base disk made of an aluminum alloy. Is particularly preferable. Further, the abrasive dispersion according to one aspect of the present invention is not particularly limited, an abrasive dispersion for producing a polishing composition for secondary polishing or finish polishing of a polishing object that has undergone primary polishing. Is preferred. Note that the final polishing refers to the last polishing step when there are a plurality of polishing steps. Here, in the application of secondary polishing or finish polishing the polishing object that has undergone primary polishing, the application of the abrasive dispersion according to an aspect of the present invention, from the viewpoint of more effectively utilizing the fine scratch reduction effect, The abrasive grain dispersion is more preferable for producing a polishing composition for use in polishing a substrate to be polished for a magnetic disk having a surface roughness (arithmetic mean roughness (Ra)) of 8 Å or less, and 6 Å The following is more preferable. Further, in the application of secondary polishing or finish polishing of an object to be polished that has been subjected to primary polishing, the application of the abrasive dispersion according to one aspect of the present invention, surface roughness (arithmetic It is preferably an abrasive grain dispersion for producing a polishing composition for polishing a substrate to be polished for a magnetic disk having an average roughness (Ra) of 1 Å or more.

  Conventionally, it has been said that the abrasive grains in the particle size range of less than 0.56 μm in the polishing composition or the abrasive grain dispersion liquid are not uniformly coarse particles and are not components that increase the number of scratches. With the above technique, a sufficient effect of reducing fine scratches could not be obtained. Therefore, the inventors of the present invention have found that when the abrasive grain dispersion liquid is brought to a predetermined pH value range, among the abrasive grains having a particle size range of less than 0.56 μm, the abrasive grains in the predetermined particle size range are fine scratches. I suspected that it would cause. Then, the present inventors have found that in the abrasive dispersion, the number of abrasive particles having a particle diameter of 0.2 μm or more and less than 0.3 μm or the number of abrasive particles having a particle diameter of 0.3 μm or more and less than 0.4 μm, In particular, it was found that the number of abrasive grains having a particle size of 0.2 μm or more and less than 0.3 μm has an extremely large effect on the generation of fine scratches, and the condition of the number of abrasive grain particles that is the allowable number of fine scratches is further determined. By finding out, the present invention was completed.

  The present inventors presume the mechanism by which the present invention solves the above problems as follows.

  The polishing composition generally polishes an object to be polished by a physical action by rubbing the surface of a substrate, a chemical action of a component other than abrasive grains on the surface of the substrate, and a combination thereof. Here, it is known that a general polishing composition preferably contains abrasive grains and is under acidic conditions in order to effectively exhibit these effects. The technique of Patent Document 1 mainly focuses on the filling state of coarse particles in the abrasive grains under acidic conditions in the polishing portion. That is, such a technique has an object to reduce the number of coarse particles having a predetermined particle diameter in the polishing composition, which is present under the conditions when actually polishing. However, under acidic conditions, the agglomerates that have progressed to agglomerate are easily crushed when a force is applied in the abrading part during abrading, so that the influence on the surface state of the abrading object is limited. Further, in recent years, a higher level of quality is required for a magnetic disk substrate, and therefore, as found by the present inventors, it is important to reduce fine scratches that are finer surface defects. In this technique, the particle size of the coarse particles of interest is large, and the reduction of the number of coarse particles of such size hardly contributes to the reduction of fine scratches.

  On the other hand, the present invention focuses on coarse particles in the abrasive dispersion for producing the polishing composition in the abrasive dispersion under non-acidic conditions, especially under alkaline conditions. Since the dispersibility of abrasive grains is good under conditions that are not under acidic conditions, especially under alkaline conditions, coarse particles that exist under such conditions are coarse primary particles of abrasive grains or are not easily broken and are strong. Since they are aggregates, many of them continue to exist in the polishing portion during polishing, and have a great influence on the surface state of the object to be polished. The fine scratches may be significantly reduced by reducing the number of coarse particles under such conditions.

  Further, the present invention, as described above, in the conventional, after establishing a means that can quantitatively evaluate the number of fine scratches that were difficult to measure, the range of the particle size of the coarse particles that has an extremely large effect on the fine scratches. It was made by finding. Therefore, the present invention is not made by simply limiting the definition of coarse particles to a range where the particle size is smaller in order to reduce finer scratches.

  The abrasive grain dispersion liquid according to an aspect of the present invention has an extremely large influence on the generation of fine scratches among the abrasive grains in the particle diameter range of less than 0.56 μm, and has 0.2 μm or more and 0.2 μm or more in the abrasive grain dispersion liquid. Paying attention to the number of particles of the abrasive grains having a size of less than 3 μm, the number of particles is set to a predetermined value or less. The reason why the abrasive grains in the particle diameter range of 0.2 μm or more and less than 0.3 μm have a great influence on the generation of fine scratches is not clear, but it is considered as follows. First, conditions that are not under such acidic conditions, in particular, abrasive grains in an abrasive grain dispersion under alkaline conditions, depending on the size and the number of particles, scratches of a specific size during polishing with a polishing composition at a specific frequency. generate. Further, the polishing composition has an effect of reducing the above-mentioned scratches according to the size and the number of particles of the primary particles and the strong aggregate which are not easily broken down in the polishing composition. Since these phenomena occur simultaneously in the polishing section, the size and frequency of scratches generated on the object to be polished are determined by the balance between the two. Here, when the abrasive particles having a particle diameter in the abrasive particle dispersion liquid of 0.2 μm or more and less than 0.3 μm are within the range of the present invention, the above balance results in a very good effect for reducing fine scratches. Therefore, the present invention has an extremely excellent effect of reducing fine scratches.

  Therefore, the present invention controls the number of particles of abrasive grains having a size of 0.2 μm or more and less than 0.3 μm, which has a particularly large effect on fine scratches, in an abrasive grain dispersion liquid under non-acidic conditions, particularly alkaline conditions. It was made by the finding that the fine scratches can be remarkably improved by this, and an extremely good effect of reducing the fine scratches can be obtained.

Further, an abrasive dispersion according to another aspect of the present invention has the following features. That is,
An abrasive grain dispersion liquid containing an abrasive grain having an average primary particle diameter of 1 nm or more and 50 nm or less measured by a BET method, and a dispersion medium, and having a pH value of 7 or more and 12 or less, and containing an abrasive grain. The amount is the number of abrasive grains having a particle size of 0.3 μm or more and less than 0.4 μm, which is measured by a number counting type particle size distribution meter when converted to 30% by mass based on the total mass of the abrasive dispersion. Is 1,500,000 or less per 1 cm ³ , and is an abrasive grain dispersion liquid. The abrasive dispersion according to this embodiment also relates to one embodiment of the present invention in which the number of abrasive particles having the above-mentioned particle diameter of 0.2 μm or more and less than 0.3 μm is 25,000,000 or less per 1 cm ^3. An extremely good improvement effect can be obtained by a mechanism similar to that of the abrasive grain dispersion liquid.

  The above mechanism is based on speculation, and its correctness does not affect the technical scope of the present invention.

  Hereinafter, each component of the abrasive dispersion liquid will be described. The abrasive grain dispersion liquid contains abrasive grains and a dispersion medium. The method for preparing the abrasive grain dispersion is not particularly limited, and it can be prepared by mixing the respective components. Here, as described below, from the viewpoint of controlling the particle size distribution of the abrasive grains in the abrasive dispersion, it is preferable to perform filtration using one or two or more types of filtration filters after mixing the components.

[Abrasive]
The abrasive grain dispersion liquid contains abrasive grains to be contained in the polishing composition. The abrasive grains in the polishing composition play a role of mechanically polishing the object to be polished, and contribute to the improvement of the polishing rate.

  Abrasive grains may be silica, such as colloidal silica, fumed silica, precipitated silica, or other than silica, such as zirconia, alumina, ceria and titania. The abrasive grains are preferably silica such as colloidal silica, fumed silica, and precipitated silica, and more preferably colloidal silica. When the abrasive grains are silica, more specifically, when it is colloidal silica, when polishing an object to be polished with a polishing composition, surface defects that occur on the surface of the object to be polished, especially fine scratches. It is further reduced.

  The abrasive grains have an average primary particle diameter measured by the BET method of 1 nm or more and 50 nm or less. If the average primary particle diameter of the abrasive grains is less than 1 nm, the polishing rate of the object to be polished is insufficient. Further, the polishing resistance increases and the vibration of the polishing machine increases. From the same viewpoint, the average primary particle diameter measured by the BET method is preferably 15 nm or more, more preferably 20 nm or more. Further, when the average primary particle size of the abrasive grains is more than 50 nm (further, the average primary particle size increases), the surface of the polishing target is polished when the polishing target is polished with the polishing composition. Surface defects that occur, especially fine scratches, increase. It is considered that such a reason is that the number of coarse primary particles that continue to exist in the polishing portion during polishing, which causes fine scratches, increases. Therefore, in order to realize a good surface condition of the object to be polished, abrasive grains having an average primary particle diameter within the above range are preferable. From the same viewpoint, the average primary particle diameter measured by the BET method is preferably 40 nm or less, and more preferably 30 nm or less.

  When the abrasive grains are colloidal silica, the average primary particle diameter measured by the BET method is set to be equal to or less than the above upper limit, so that in addition to the effect of reducing surface defects described above, particularly fine scratches, It is possible to suppress precipitation of colloidal silica. From this, it is particularly preferable that the abrasive grains are colloidal silica having an average primary particle diameter measured by the BET method in the above range.

The average primary particle diameter of the abrasive grains by the BET method can be calculated from the specific surface area S (m ² / g) of the abrasive grains measured by the BET method by the formula of average primary particle diameter (nm) = 2727 / S. . The specific surface area of the abrasive grains can be measured, for example, by using a surface area measuring device manufactured by Micromeritics Japan Co., Ltd. under the trade name “Flow Sorb II 2300”.

  The abrasive grains may be used alone or in combination of two or more kinds.

The abrasive grain dispersion has a particle number of 0.2 μm or more and less than 0.3 μm when the content of the abrasive grains is converted to 30% by mass based on the total mass of the abrasive grain dispersion. It is 25,000,000 or less per 1 cm ³ . When the number of particles of the abrasive having a particle diameter of 0.2 μm or more and less than 0.3 μm is 25,000,000 or less per 1 cm ^{3 of the} abrasive dispersion, the object to be polished was polished with the polishing composition. At times, fine scratches generated on the surface of the object to be polished are reduced. Such a reason is considered that the abrasive grains in the abrasive grain dispersion are dispersed in the state of coarse primary particles or a strong aggregate that is not easily crushed, and among the particle diameters of the abrasive grains, the above particles are particularly preferable. This is because when the number of particles in the diameter range is less than a certain value, it is considered that the generation of fine scratches is reduced. From the same viewpoint, the number of particles of the abrasive having a particle diameter of 0.2 μm or more and less than 0.3 μm is preferably 21,000,000 or less per 1 cm ^{3 of the} abrasive dispersion, and 16,000,000. It is more preferable that the number is less than or equal to 12, more preferably 12,000,000 or less, and further preferably less than 10,450,000.

The abrasive grain dispersion has a particle number of 0.3 μm or more and less than 0.4 μm when the content of the abrasive grains is converted to 30% by mass with respect to the total mass of the abrasive grain dispersion. The number may be 1,500,000 or less per 1 cm ³ . The reason is that fine scratches can be reduced by reducing the number of particles in the above-mentioned particle diameter range. From the same viewpoint, the number of abrasive grains having a particle diameter of 0.3 μm or more and less than 0.4 μm is preferably 1,300,000 or less per 1 cm ^{3 of the} abrasive dispersion, and 1,200,000. The number is more preferably the following, particularly preferably 1,000,000 or less, and most preferably 300,000 or less. Here, the abrasive grain dispersion liquid satisfies the number of particles of the above-mentioned particle diameter of 0.2 μm or more and less than 0.3 μm, and the number of particles of the above-mentioned particle diameter of 0.3 μm or more and less than 0.4 μm. By satisfying the condition, fine scratches can be significantly reduced.

Further, from the viewpoint of reducing scratches having a size larger than that of fine scratches, the abrasive grain dispersion liquid has a particle diameter of 30% by mass when the content of the abrasive grains is converted to 30% by mass with respect to the total mass of the abrasive grain dispersion liquid. It is preferable that the number of particles of abrasive grains having a particle size of 0.4 μm or more is 260,000 or less per 1 cm ³ . Further, from the same viewpoint, the abrasive grain dispersion liquid has a particle diameter of 0.56 μm or more when the content of the abrasive grains is 30% by mass based on the total mass of the abrasive grain dispersion liquid. The number of particles is preferably 110,000 or less per 1 cm ³ .

When the content of the abrasive grains is converted to 30% by mass with respect to the total mass of the abrasive grain dispersion liquid, the number of particles of the abrasive grains in each particle diameter range in the abrasive grain dispersion liquid is the diluted abrasive grain dispersion liquid, Alternatively, the particle size distribution of the abrasive particles in the abrasive particle dispersion liquid containing 15% by mass or less of abrasive particles (the number of particles in each particle size range per unit volume of the abrasive particle dispersion liquid) is measured. Can be obtained by doing. First, the content (% by mass) of the abrasive particles with respect to the total mass of the abrasive particle dispersion liquid is calculated. Next, the abrasive dispersion is diluted with water so that the content of the abrasive is 15% by mass or less. If the content of the abrasive particles is 15% by mass or less based on the total mass of the abrasive particle dispersion liquid, the dilution is not necessary. Thereafter, the diluted abrasive grain dispersion liquid or the abrasive grain dispersion liquid having an abrasive grain content of 15% by mass or less is measured using a number counting type particle size distribution analyzer PSS Inc. AccuSizer FX nano. Then, when the content of the abrasive grains is converted to 30% by mass with respect to the total mass of the abrasive grain dispersion liquid, the number of particles of the abrasive grains in each particle size range in the abrasive grain dispersion liquid is the obtained particles. Calculation is performed using the measured value in the diameter range (Count (pieces) / ml, that is, pieces / cm ³ ). More specifically, the measured value of the number of particles of the abrasive particles in the particle size range of interest is N (pieces / cm ³ ), the diluted abrasive particle dispersion liquid used for the measurement, or the content of the abrasive particles is 15% by mass. Assuming that the concentration of the abrasive grain dispersion liquid below is d (mass%), the abrasive in the particle size range of interest when the content of the abrasive grains is converted to 30 mass% with respect to the total mass of the abrasive grain dispersion liquid. The number of particles N ₃₀ (particles / cm ³ ) is calculated by the following formula.

N ₃₀ (pieces / cm ³ ) = N (pieces / cm ³ ) × 30 (mass%) / d (mass%)
(Equation 1)
Here, the reason for setting the content of the abrasive grains to 15% by mass or less with respect to the total mass of the liquid to be measured is to obtain more accurate measurement results using this device. Here, in the measurement, the content of the abrasive grains with respect to the total mass of the liquid to be measured is not particularly limited, but as an example of preferable measurement conditions, it can be set to 15% by mass, for example. Details of the measuring method and the measuring conditions will be described in Examples.

  The method of controlling the particle size distribution of the abrasive grains in the abrasive grain dispersion liquid is not particularly limited, but it is preferably performed by, for example, selecting a filtration filter in the filtration step when preparing the abrasive grain dispersion liquid. The filtration filters can be used alone or in combination (multistage filtration). As the filtration filter, a known filter can be appropriately used so that a desired particle size distribution can be obtained. As the filtration filter, for example, depth type, pleated type, depth pleated type, membrane type, adsorption type and the like can be used, and the shape of the filter can be bag type, cartridge type or the like, and as the cartridge type, A gasket type, an O-ring type, etc. can be used. Among these, as the filtration method, it is preferable to use a filter having a filter fiber layer including a fiber layer having an average fiber diameter of less than 1 μm, as described in JP-A-2015-71659. The type and combination of filtration filters can be appropriately selected according to the type of abrasive grains, the average primary particle diameter, the type and content of components of the abrasive grain dispersion liquid other than the abrasive grains, and the like.

  From the viewpoint of cost, the content of the abrasive grains in the abrasive grain dispersion liquid is preferably 10% by mass or more and 50% by mass or less with respect to the total mass of the abrasive grain dispersion liquid.

[Dispersion medium]
The abrasive grain dispersion liquid contains a dispersion medium (solvent). The dispersion medium has a function of dispersing or dissolving each component. The dispersion medium preferably contains water, and more preferably water. Further, the dispersion medium may be a mixed solution of water and an organic solvent in order to disperse or dissolve each component. In this case, examples of the organic solvent used include water-miscible organic solvents such as acetone, acetonitrile, ethanol, methanol, isopropanol, glycerin, ethylene glycol, and propylene glycol. Further, these organic solvents may be used without being mixed with water, and each component may be dispersed or dissolved and then mixed with water. These organic solvents may be used alone or in combination of two or more.

  The water is preferably water containing as little impurities as possible from the viewpoint of inhibiting the action of other components. Specifically, pure water, ultrapure water, or distilled water obtained by removing impurity ions with an ion exchange resin and then removing foreign matters through a filter is preferable.

[PH adjuster]
The abrasive dispersion may further contain a pH adjuster, if necessary. The pH adjuster is used to control the pH value of the abrasive dispersion. The pH adjuster is not particularly limited, and a known compound having a pH adjusting effect can be used. For example, the same compounds as the acid or the basic compound that can be optionally contained in the solution B described later can be used. Compounds can be used.

[PH value of abrasive dispersion]
The abrasive grain dispersion has a pH value of 7 or more and 12 or less. When the pH value is less than 7, it becomes difficult to reduce fine scratches when polishing an object to be polished with the polishing composition. The reason for this is that under acidic conditions, it is considered difficult to control the number of coarse primary particles that can cause fine scratches or the number of strong agglomerates that are not easily disintegrated, because the agglomerates of the abrasive grains progress over time. Because it will be done. From the same viewpoint, the pH value is preferably 8 or more, more preferably 9 or more. Further, if the pH value exceeds 12, the abrasive grains may be dissolved, and in this case, it may be difficult for the abrasive grains to exhibit the function as the abrasive grains of the polishing composition. From the same viewpoint, the pH value is more preferably 11 or less.

<Polishing composition kit>
The polishing composition kit according to the second aspect of the present invention contains the liquid A which is the abrasive dispersion according to the first aspect of the present invention, and the liquid B containing a dispersion medium. In addition, in the polishing composition kit, the liquid A and the liquid B are assumed not to be mixed with each other.

[B liquid]
The method for preparing the liquid B is not particularly limited, and it can be prepared by mixing the respective components. It is preferable that the liquid B does not contain abrasive grains.

[acid]
The liquid B preferably contains an acid. This acid may be included in the polishing composition produced from the polishing composition kit according to one aspect of the present invention. The acid in the polishing composition plays a role of chemically polishing the object to be polished, and can contribute to the improvement of the polishing rate of the object to be polished by the polishing composition.

  The acid may be either an inorganic acid or an organic acid, but it is preferable to use an inorganic acid.

  The inorganic acid is not particularly limited, and may be, for example, phosphoric acid such as orthophosphoric acid, pyrophosphoric acid, polyphosphoric acid, hexametaphosphoric acid, or phosphonic acid, phosphinic acid, sulfonic acid or sulfuric acid.

  The acid may be an organic acid and is not particularly limited, but an organic carboxylic acid having 1 to 10 carbon atoms, an organic phosphonic acid, an organic sulfonic acid or an amino acid is preferable. Examples of the organic carboxylic acid having 1 to 10 carbon atoms include citric acid, maleic acid, malic acid, glycolic acid, succinic acid, itaconic acid, malonic acid, iminodiacetic acid, gluconic acid, lactic acid, mandelic acid, tartaric acid, Examples thereof include crotonic acid, nicotinic acid, acetic acid, adipic acid, formic acid and oxalic acid. Examples of the organic phosphonic acid include methyl acid phosphate, ethyl acid phosphate, ethyl glycol acid phosphate, isopropyl acid phosphate, phytic acid, 1-hydroxyethylidene-1,1-diphosphonic acid (abbreviation HEDP) and the like. Examples of the organic sulfonic acid include methanesulfonic acid, benzenesulfonic acid, 2-aminoethanesulfonic acid and the like. Examples of the amino acid include glycine, alanine, phenylalanine, proline, valine, leucine, isoleucine, serine, threonine, tryptophan, tyrosine, aspartic acid, glutamic acid, iminodiacetic acid and threonine.

  Among these, as the acid, orthophosphoric acid, pyrophosphoric acid, polyphosphoric acid, phosphoric acid such as hexametaphosphoric acid or methyl acid phosphate, ethyl acid phosphate, ethyl glycol acid phosphate, isopropyl acid phosphate, phytic acid, 1-hydroxyethylidene-1 Preferably, it is an organic phosphonic acid such as 1-diphosphonic acid. In particular, when a substrate disk having a nickel phosphorus plating layer on the surface thereof is polished as an object to be polished, fine scratches and scratches larger than the fine scratches can be further suppressed. The reason for this is that the liquid B contains phosphoric acid or organic phosphonic acid, and thus the polishing composition contains phosphoric acid or organic phosphonic acid, and the phosphate ion or organic phosphonate ion is present on the surface of the nickel phosphorus plating layer. This is because it is considered that an insoluble film is formed and damage to the object to be polished during polishing is further reduced. Among these phosphoric acids, orthophosphoric acid or polyphosphoric acid is more preferable, and orthophosphoric acid is still more preferable, from the viewpoint that the polishing rate of the object to be polished by the polishing composition is greatly improved.

  The acids can be used alone or in combination of two or more.

[Dispersion medium]
The liquid B contains a dispersion medium (solvent). The dispersion medium contained in the liquid B may be the same as the dispersion medium contained in the liquid A. The dispersion medium contained in the liquid B preferably contains water, more preferably water. Further, it is preferable that the dispersion medium contained in the liquid A and the dispersion medium contained in the liquid B are the same.

[Basic compound]
The solution B may contain a basic compound. Here, the basic compound refers to a compound having a function of increasing the pH value of these by being added to the polishing composition produced from the liquid B or the polishing composition kit.

  The basic compound is not particularly limited, and examples thereof include alkali metal hydroxides, quaternary ammonium or salts thereof, ammonia, amines, phosphates, hydrogen phosphates, and organic acid salts.

  Specific examples of the alkali metal hydroxide include lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, cesium hydroxide and francium hydroxide.

  Specific examples of the quaternary ammonium or its salt include quaternary ammonium hydroxide such as tetramethylammonium hydroxide, tetraethylammonium hydroxide and tetrabutylammonium hydroxide.

  Specific examples of amines include methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylenediamine, monoethanolamine, N- (β-aminoethyl) ethanolamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, anhydrous piperazine. , Piperazine hexahydrate, 1- (2-aminoethyl) piperazine, N-methylpiperazine, guanidine, azoles such as imidazole and triazole, and the like.

  Specific examples of phosphates and hydrogen phosphates include alkali such as tripotassium phosphate, dipotassium hydrogen phosphate, potassium dihydrogen phosphate, trisodium phosphate, disodium hydrogen phosphate, and sodium dihydrogen phosphate. Examples thereof include metal salts, ammonium salts such as ammonium phosphate, diammonium hydrogen phosphate and ammonium dihydrogen phosphate.

  Among these, from the viewpoint that it is possible to further suppress fine scratches and scratches having a size larger than that of fine scratches, hydroxides of alkali metals are preferable, and potassium hydroxide, rubidium hydroxide, and hydroxide More preferably, it is cesium, and even more preferably potassium hydroxide. Fine scratches are, as mentioned above, mainly affected by the number of coarse particles in the abrasive dispersion under non-acidic conditions, particularly alkaline conditions, and particularly in the state of the polishing composition which may contain an acid. The effect of the number of coarse particles is limited. However, if the abrasive grains maintain the characteristics of the particle size distribution in the liquid A better even in the polishing composition, an additional effect is that the effect of reducing fine scratches can be further improved. it can. It is also considered that scratches of a size larger than that of the fine scratches can be further reduced. When the liquid B contains the basic compound, the polishing composition may contain the basic compound. At this time, a cation derived from a basic compound is generated in the polishing composition and may adhere to the surface of the abrasive grain. At this time, depending on the type of the basic compound, it is presumed that the cation derived from the basic compound may enter between the colloidal silica particles to promote the aggregation of the abrasive grains. Here, it is assumed that the cohesiveness of the abrasive grains is related to the ionic radius of cations. From the viewpoint of further suppressing the agglomeration of the abrasive grains and maintaining the characteristics of the particle size distribution in the liquid A in the polishing composition in a better manner, potassium hydroxide having a relatively large ionic radius is used. It is preferable to use. Further, by using an alkali metal hydroxide that generates a monovalent metal ion as the basic compound contained in the liquid B, the charging of the abrasive grains in the polishing composition is suppressed, resulting in the polishing composition. It is considered that the agglomeration of the abrasive grains therein is suppressed, and that the fine scratches and the scratches larger in size than the fine scratches are further suppressed.

  The basic compounds may be used alone or in combination of two or more.

<Method for producing polishing composition>
A third aspect of the present invention relates to a method for producing a polishing composition, which comprises mixing a solution A and a solution B using the polishing composition kit according to the second aspect of the present invention.

  The order of mixing the respective liquids when preparing the polishing composition is not particularly limited, but it is preferable to add the liquid A to the liquid B and mix them with stirring. In mixing, in addition to the liquids A and B, a dispersion medium, a dispersion liquid (hereinafter also referred to as an additive liquid) in which any component contained in the polishing composition is dissolved or dispersed, or polishing. Optional components contained in the composition for use may be further added. According to such an addition method, the polishing composition kit, that is, the manufactured polishing composition can be made to have more preferable characteristics while maintaining the preferable characteristics of each of the liquid A and the liquid B. As a method of mixing the respective liquids when preparing the polishing composition, the liquid B is added to the dispersion medium (for example, water) and mixed by stirring, and then the added liquid (for example, an oxidant solution such as hydrogen peroxide solution). It is more preferable to add (1) and stir and mix, and then add the solution A and stir and mix.

  Further, each component of the polishing composition may be contained by being contained in the liquid A or the liquid B in advance, or may be contained by being added as an additive liquid in the production of the polishing composition, Alternatively, it may be contained by directly adding the additive.

  Here, the temperature at the time of mixing the respective components is not particularly limited, but is preferably 10 ° C. or higher and 40 ° C. or lower, and may be heated to increase the dissolution rate. Also, the mixing time is not particularly limited. Further, the polishing composition may be prepared by diluting the stock solution of the polishing composition obtained as described above with water.

  The method for producing the polishing composition is preferably a method in which the liquid A and the liquid B are mixed so that the pH value is 4 or less, and the pH value is 1.5 or more and 4 or less. The mixing method is more preferable, and the mixing method is more preferable so that the pH value is 1.5 or more and 3 or less. When the pH value is 4 or less, the polishing rate and the surface smoothness are further improved. Further, the pH value of the polishing composition produced is preferably 4 or less, more preferably 1.5 or more and 4 or less, and further preferably 1.5 or more and 3 or less. The above pH value can be preferably applied to, for example, a polishing composition used for polishing an object to be polished for a magnetic disk substrate having a nickel phosphorus plating layer.

  The above-mentioned pH value control is performed by further mixing each component such as a pH adjuster which may be optionally contained in the liquid A, each component such as an acid or a basic compound which may be optionally contained in the liquid B, and the liquids A and B. It can be carried out by appropriately adjusting the amount or kind of the dispersion medium, the additive liquid or the optional components contained in the polishing composition, the mixing ratio of the liquid A and the liquid B, or the like.

<Polishing composition>
A fourth aspect of the present invention relates to a polishing composition produced from the polishing composition kit according to the second aspect. The polishing composition according to the fourth aspect can be produced by the method for producing a polishing composition according to the third aspect.

  The polishing composition according to one aspect of the present invention preferably contains abrasive particles and a dispersion medium derived from the liquid A, and a dispersion medium derived from the liquid B. Further, it may optionally contain other components. The other components may not be derived from A liquid or B liquid. Hereinafter, each component of the polishing composition will be described.

[Abrasive]
The polishing composition contains abrasive grains. Since the details of the abrasive grains are the same as those described in the section of the liquid A, the description is omitted here.

  The content of abrasive grains in the polishing composition is preferably 0.1% by mass or more based on the total mass of the polishing composition. When the content of the abrasive grains is 0.1% by mass or more, the polishing rate of the object to be polished by the polishing composition is further improved. Further, it suppresses an increase in polishing resistance and further reduces vibration of the polishing machine. From the same viewpoint, the content of the abrasive grains in the polishing composition is more preferably 0.5% by mass or more, and further preferably 1% by mass or more, based on the total mass of the polishing composition. . The content of abrasive grains in the polishing composition is preferably 20% by mass or less based on the total mass of the polishing composition. The content of abrasive grains in the polishing composition is more preferably 15% by mass or less and even more preferably 10% by mass or less based on the total mass of the polishing composition.

[acid]
The polishing composition preferably contains an acid. Since the details of the acid are the same as those described in the section of the liquid B, the description is omitted here.

  The content of the acid in the polishing composition is preferably 0.01% by mass or more based on the total mass of the polishing composition. When the content of the acid is 0.01% by mass or more, the polishing rate of the object to be polished by the polishing composition is further improved. From the same viewpoint, the content of the acid in the polishing composition is more preferably 0.1% by mass or more based on the total mass of the polishing composition. Further, the content of the acid in the polishing composition is preferably 40% by mass or less based on the total mass of the polishing composition. When the content of the acid is 40% by mass or less, the corrosive action of the polishing composition is further reduced. As a result, when the object to be polished is polished using the polishing composition, it is possible to further suppress the surface roughness of the object to be polished. From the same viewpoint, the content of the acid in the polishing composition is more preferably 20% by mass or less and even more preferably 10% by mass or less based on the total mass of the polishing composition.

[Dispersion medium]
The polishing composition contains a dispersion medium. Here, in the production of the polishing composition, in addition to the dispersion medium derived from the liquid A, a dispersion medium derived from the liquid B may be contained, and a dispersion medium may be further added separately. As such a dispersion medium, it is possible to use the same dispersion medium as described in the above-mentioned liquid A and liquid B sections.

[Basic compound]
The polishing composition preferably further contains a basic compound. The content of the basic compound is not particularly limited and can be appropriately adjusted so that the polishing composition has a desired pH range. Since the details of the basic compound are the same as those described in the section of the liquid B, the description thereof will be omitted here.

[Oxidant]
The polishing composition preferably further contains an oxidizing agent. The oxidizing agent has a function of oxidizing the surface of the object to be polished. When the surface of the object to be polished is oxidized by the oxidizing agent, mechanical polishing of the object to be polished by the abrasive grains is promoted, and as a result, the polishing rate of the object to be polished by the polishing composition is improved.

  The oxidizing agent is not particularly limited, and examples thereof include peroxide, nitric acid or a salt thereof, peroxo acid or a salt thereof, permanganic acid or a salt thereof, chromic acid or a salt thereof, oxyacid or a salt thereof, metal salts, sulfuric acid. And the like. Specific examples of the oxidizing agent include hydrogen peroxide, sodium peroxide, barium peroxide, nitric acid, iron nitrate, aluminum nitrate, ammonium nitrate, peroxodisulfate, ammonium peroxodisulfate, metal salt of peroxodisulfate, peroxophosphoric acid, peroxosulfate. , Sodium peroxoborate, performic acid, peracetic acid, perbenzoic acid, perphthalic acid, hypobromic acid, hypoiodic acid, chloric acid, bromic acid, iodic acid, periodic acid, perchloric acid, hypochlorous acid Examples thereof include acid, sodium hypochlorite, calcium hypochlorite, potassium permanganate, metal chromate, metal dichromate, iron chloride, iron sulfate, iron citrate, and ammonium iron sulfate. Examples of preferable oxidizing agents include hydrogen peroxide, iron nitrate, peroxodisulfuric acid and nitric acid. These oxidizing agents can be used alone or in combination of two or more kinds.

  Among these, from the viewpoint of improving the polishing rate of the object to be polished by the polishing composition and improving the stability of the polishing composition, it is preferable that at least hydrogen peroxide is contained, and it is more preferable that hydrogen peroxide is contained. .

  The content of the oxidizing agent in the polishing composition is preferably 0.01% by mass or more based on the total mass of the polishing composition. When the content of the oxidizing agent is 0.01% by mass or more, the polishing rate of the object to be polished by the polishing composition is further improved. From the same viewpoint, the content of the oxidizing agent in the polishing composition is more preferably 0.1% by mass or more based on the total mass of the polishing composition. Further, the content of the oxidizing agent in the polishing composition is preferably 5% by mass or less based on the total mass of the polishing composition. When the content of the oxidizing agent is 5% by mass or less, the corrosive action of the polishing composition is further reduced. As a result, when the object to be polished is polished with the polishing composition, the surface roughness of the object to be polished can be further suppressed. From the same viewpoint, it is more preferably 3% by mass or less, further preferably 1% by mass or less.

[Water-soluble polymer]
The polishing composition may further contain a water-soluble polymer. Examples of water-soluble polymers that can be used include polystyrene sulfonates such as sodium polystyrene sulfonate, polyacrylates, polyvinyl acetate, and the like, and particularly preferably used are sodium polystyrene sulfonate and the like. Polystyrene sulfonate. The weight average molecular weight of the water-soluble polymer is preferably 1,000 or more, more preferably 10,000 or more, and further preferably 500,000 or more. Further, the weight average molecular weight of the water-soluble polymer is preferably 5,000,000 or less, more preferably 2,500,000 or less, and further preferably 2,000,000 or less.

[Other additives]
The polishing composition according to one aspect of the present invention further contains an antiseptic agent, an antifungal agent, an anticorrosive agent, an antifoaming agent, a chelating agent, etc., if necessary, within a range that does not impair the effects of the present invention. Good. For example, as preservatives and fungicides, isothiazoline preservatives such as 2-methyl-4-isothiazolin-3-one and 5-chloro-2-methyl-4-isothiazolin-3-one, paraoxybenzoic acid esters , And phenoxyethanol, but not limited thereto. These preservatives, fungicides, anticorrosives, defoamers, chelating agents and the like can be used alone or in combination of two or more kinds.

<Polishing method>
A fifth aspect of the present invention relates to a polishing method including a step of polishing an object to be polished using the polishing composition according to the fourth aspect.

  The polishing method according to one aspect of the present invention will be described below.

  The polishing composition according to the fourth aspect of the present invention can be used, for example, in an apparatus and conditions generally used for polishing a substrate to be polished for a magnetic disk substrate. When using a single-sided polishing device, the object to be polished is held by using a holder called a carrier, and the polishing composition is polished while the platen having the polishing pad is pressed against one side of the object to be polished. One surface of the object to be polished is polished by rotating the surface plate while supplying the object. When using a double-sided polishing machine, hold the object to be polished using a holder called a carrier, and press the upper and lower surface plates with the polishing pads attached to both sides of the object to be polished from above. Both surfaces of the object to be polished are polished by rotating the two platens in opposite directions while supplying the polishing composition to the object. At this time, the physical effect of the abrasive grains in the polishing pad and the polishing composition rubbing against the surface of the object to be polished, and the chemicals that the components other than the abrasive grains in the polishing composition give to the surface of the object to be polished. The surface of the object to be polished is polished by the mechanical action.

The higher the polishing load, that is, the polishing load, the higher the polishing rate. The polishing load when polishing an object to be polished with the polishing composition is not particularly limited, but is preferably 30 g or more and 200 g or less, and 60 g or more and 150 g or less per 1 cm ² of the surface of the object to be polished. More preferable. When the polishing load is within the above range, a practically sufficient polishing rate can be obtained, and at the same time, an object to be polished with few surface defects can be obtained after polishing.

  The linear velocity during polishing, that is, the linear velocity of polishing is generally affected by parameters such as the number of rotations of the polishing pad, the number of rotations of the carrier, the size of the object to be polished, and the area of the polishing pad. As the linear velocity increases, the frictional heat applied to the object to be polished increases, which may enhance the chemical polishing action of the polishing composition. However, if the linear velocity is too high, the slurry on the polishing pad may be discharged from the outer peripheral portion due to the centrifugal force, which may lower the polishing rate and cause the polishing machine to vibrate. The linear velocity when polishing an object to be polished using the polishing composition is not particularly limited, but is preferably 300 mm / sec or more and 1400 mm / sec or less, and more preferably 600 mm / sec or more and 950 mm / sec or less. preferable. When the linear velocity is within the above range, it is easy to obtain a practically sufficient polishing rate.

  The number of rotations of the platen and the number of rotations of the carrier during polishing are preferably 10 rpm or more and 100 rpm or less.

  The supply rate of the polishing composition to the polishing apparatus is appropriately set according to the type of the polishing target such as the polishing target to be polished, the type of the polishing apparatus, and the polishing conditions. However, it is preferable that the rate is sufficient to uniformly supply the polishing composition to the polishing surface of the object to be polished and the entire polishing pad.

  As a polishing pad used when polishing an object to be polished, for example, a general nonwoven fabric, suede, a porous body such as polyurethane or a fluororesin can be used without particular limitation. Further, it may contain abrasive grains or may not contain abrasive grains. The polishing pad may be grooved so that the polishing composition may be accumulated, but when used for secondary polishing or finish polishing, it is preferably not grooved. The hardness and thickness of the polishing pad are not particularly limited. As the polishing pad, for example, a suede non-buff type one can be preferably used.

  The type of object to be polished to which the polishing method is applied is not particularly limited, but for example, it is preferably a substrate to be polished (semi-finished substrate) of a substrate which requires a highly accurate surface, and a target to be polished for a magnetic disk. More preferably, it is a substrate. As a substrate to be polished for a magnetic disk, for example, the base disk is made of an aluminum alloy or glass, and the surface of the base disk is a nickel phosphorus plating layer, or a metal layer or a metal compound layer other than the nickel phosphorus plating layer. And a substrate to be polished for a magnetic disk substrate having the above. Among these, the substrate to be polished for the magnetic disk is particularly preferably a substrate having a nickel phosphorus plating layer on a base disk made of an aluminum alloy.

  Further, the use of the polishing method is not particularly limited, but for example, Schmitt Measurement System Inc. The surface roughness (arithmetic mean roughness (Ra)) measured by a laser scanning surface roughness meter “TMS-3000 WRC” manufactured by the same company is 100 Å to 300 Å and is subjected to primary polishing to 10 Å It is preferably used for adjusting to the following surface roughness (arithmetic mean roughness (Ra)) or for further polishing (secondary polishing or finishing) a substrate to be polished for a magnetic disk that has undergone primary polishing. The use of further polishing (secondary polishing or finish polishing) the substrate to be polished for the magnetic disk is more preferable, and the use of finish polishing is further preferable. Note that the final polishing refers to the last polishing step when there are a plurality of polishing steps. Here, the surface roughness (arithmetic mean roughness (Ra)) of the substrate to be polished for the magnetic disk, which is polished by the polishing method according to the aspect of the present invention, is effective in effectively utilizing the fine scratch reduction effect. , 8 Å or less is more preferable, and 6 Å or less is still more preferable. Further, the surface roughness (arithmetic mean roughness (Ra)) of the substrate to be polished for the magnetic disk after the primary polishing to be polished is preferably 1 Å or more from the viewpoint of necessity of further polishing.

<Method of manufacturing magnetic disk substrate>
As described above, in the polishing method according to the aspect of the present invention, the type of the object to be polished is preferably the substrate to be polished for the magnetic disk. Therefore, a sixth aspect of the present invention relates to a method for manufacturing a magnetic disk substrate using the polishing method according to the fifth aspect. Here, the type and application of the substrate to be polished for the magnetic disk, which is the object to be polished, and the preferred embodiment of the magnetic disk substrate to be manufactured are the same as those in the above-described polishing method. Further, the method for manufacturing a magnetic disk substrate according to one embodiment of the present invention is particularly preferably a method for manufacturing a magnetic disk substrate having a surface roughness (arithmetic mean roughness (Ra)) of less than 1Å.

  The present invention will be described in more detail with reference to the following examples and comparative examples. However, the technical scope of the present invention is not limited to the following examples. In addition, unless otherwise specified, "%" and "part" mean "mass%" and "part by mass", respectively.

[Example 1]
<Preparation of Abrasive Grain Dispersion Liquid (A Liquid)>
After dispersing colloidal silica (average primary particle diameter 25 nm) as abrasive grains in water, a filter having a filter fiber layer containing a fiber layer having an average fiber diameter of less than 1 μm described in JP-A-2015-71659 is used. The solution was filtered to prepare a liquid A having a pH value of 9.5. Colloidal silica was 30 mass% with respect to the total mass of liquid A.

Here, the average primary particle diameter of the colloidal silica was calculated from the specific surface area S (m ² / g) measured by the BET method by the equation of average primary particle diameter (nm) = 2727 / S. The specific surface area of the colloidal silica was measured using a surface area measuring device manufactured by Micromeritics Japan Co., Ltd. under the trade name “Flow Sorb II 2300”.

<Preparation of polishing composition kit>
Separately from the above-mentioned solution A, solution B was prepared as follows to prepare a polishing composition kit containing solution A and solution B. In addition, in the polishing composition kit, the liquid A and the liquid B are not mixed with each other.

(Preparation of solution B)
The orthophosphoric acid, which is an acid, is added to water so that the content thereof is 11% by mass with respect to the total mass of the solution B, and the potassium hydroxide is 1.6% by mass with respect to the total mass of the solution B. Then, solution B was prepared.

[Examples 2 to 5 and Comparative Examples 1 to 3]
In the preparation of solution A in Example 1, each solution A according to Examples 2 to 5 and Comparative Examples 1 to 3 was prepared in the same manner except that the type of known filtration filter, the number of combinations and the size of the openings were changed. Prepared. Here, when preparing the liquid A in Examples 2 to 5, a filter having a filter fiber layer containing a fiber layer having an average fiber diameter of less than 1 μm, as described in JP-A-2015-71659, was used. The pH values of these A liquids were the same as those of the A liquid of Example 1. Further, the solution B was prepared in the same manner as in Example 1.

<Number of Abrasive Grains in Each Particle Diameter Range in Liquid A When the Content of Abrasive Grains is Converted to 30% by Mass Based on the Total Mass of Liquid A>
The number of abrasive grains in each particle diameter range in the A liquid when the content of the abrasive grains is converted to 30% by mass with respect to the total mass of the A liquid is the number of particles of the diluted A liquid in the A liquid. It was determined by measuring the particle size distribution of particles (the number of particles in each particle size range per unit volume of liquid A). Here, the particle size distribution (the number of particles in each particle size range per unit volume of A solution) of the abrasive grains in each prepared A solution was measured with the following apparatus and conditions. First, the liquid A was diluted with water so that the content of the abrasive grains was 15% by mass. Next, the particle size distribution of the abrasive grains in the diluted solution A (the number of particles in each particle size range per unit volume of solution A) was measured using a number counting type particle size distribution analyzer, AccuSizer FX nano manufactured by PSS. The following measurement device and measurement conditions were used for the measurement.

[Measuring equipment and conditions]
Measuring machine: Number counting type particle size distribution analyzer Accsizer FX nano manufactured by PSS
(FY-H condition)
・ Data correction time: 60 sec
・ Automatic Sample Dilution target: <2500 count / sec
・ Sample flow rate: 15 ml / min
・ Stir speed factor: 2700
(FY-L condition)
・ Data correction time: 130 sec
・ Automatic Sample Dilution target: <2500 count / sec
・ Sample flow rate: 15 ml / min
-Stir speed factor: 2700.

  In this measurement, the FY-H conditions described above were used to measure the particles of the abrasive grains having a particle size of 0.2 μm or more and less than 0.3 μm. Further, the number of abrasive grains having a particle diameter of 0.3 μm or more and less than 0.4 μm, the number of abrasive grains having a particle diameter of 0.4 μm or more, and the grain of abrasive particles having a particle diameter of 0.56 μm or more. The FY-L conditions described above were used to measure the number.

The number of particles of the abrasive grains in each particle size range in the A liquid when the content of the abrasive grains is converted to 30% by mass with respect to the total mass of the A liquid is the measurement of each obtained particle size range. The value (pieces / cm ³ ) was used for the calculation. More specifically, the measured value of the number of abrasive grains in the particle size range of interest is N (pieces / cm ³ ), and the concentration of the diluted A liquid used for the measurement is d (mass%). When the amount was converted to 30% by mass with respect to the total mass of the liquid A, the number N ₃₀ (particles / cm ³ ) of the abrasive particles in the particle size range of interest was calculated from the following formula.

N ₃₀ (pieces / cm ³ ) = N (pieces / cm ³ ) × 30 (mass%) / d (mass%)
(Equation 1)
As a result of the particle size distribution of coarse particles in each A liquid, the number of abrasive particles having a particle size of 0.2 μm or more and less than 0.3 μm, the particle size of abrasive particles having a particle size of 0.3 μm or more and less than 0.4 μm Table 1 shows the results of the number, the number of particles having a particle size of 0.4 μm or more, and the number of particles of abrasive grains having a particle size of 0.56 μm or more.

<Preparation of polishing composition>
A polishing composition was prepared using each polishing composition kit comprising each of the above-prepared solutions A and B. First, for each polishing composition kit, 16.6 parts by mass of solution B was added to 57.4 parts by mass of water and mixed, and then 0.6 parts by mass of hydrogen peroxide solution was added to and mixed with the solution. Thereafter, 20 parts by mass of solution A was added to this solution and mixed to prepare each polishing composition. The pH values of all the prepared polishing compositions were 2.0 and the same.

<Polishing process>
A magnetic disk substrate was manufactured by using the above-prepared polishing composition to polish a magnetic disk polishing target substrate under the following polishing conditions.

(Polishing conditions)
Substrate to be polished: An aluminum substrate for a hard disk having a diameter of 3.5 inches (about 95 mm) and a thickness of 1.27 mm, which is provided with an electroless nickel-phosphorus plating layer on the surface, and a laser scan surface roughness meter manufactured by Schmitt Measurement System Co. Pre-polished so that the value of the surface roughness (arithmetic mean roughness (Ra)) measured by "TMS-3000WRC" becomes 6Å. Polishing machine: SPEEDFAM double-side polishing machine 9B-5P
Polishing pad: Suede non-buff type Polishing load: 120g / cm ²
Lower surface plate rotation speed: 60 rpm
Supply rate of polishing composition: 80 mL / min.

<Evaluation of polished substrate>
[Fine scratch]
The fine scratches are fine scratches on the substrate surface having a depth of 1 nm or more and less than 10 nm, a width of 5 nm or more and less than 100 nm, and a length of 100 nm or more and less than 1 μm. By using the following apparatus and conditions, the above-prepared four disk substrates were measured on both sides, a total of 8 surfaces, and the total number of fine scratches was divided by the number of measured board surfaces, so that there was one per board. The average number of fine scratches was measured. Table 1 shows the results.

(Measuring equipment and conditions)
Measuring device: KLA Tenchor Candela OSA6100
Rotation 10000rpm
Measuring range = 20-45mm
step size: 4 mm
Encoder multiplier: × 16
Detection channel: P-Sc channel.

[scratch]
The scratch refers to a scratch on the substrate surface having a depth of 10 nm or more and less than 100 nm, a width of 5 nm or more and less than 500 nm, and a length of 100 μm or more. Scratches existing on one surface of the substrate were measured by measuring the total of eight scratches on both surfaces of the four manufactured disk substrates with the following apparatus and conditions, and dividing the total number of scratches by the number of measured substrate surfaces. Was measured. The results of this measurement are shown in Table 1.

(Measuring equipment and conditions)
Measuring instrument: VISION PSYTEC's MicroMax VMX-2100CSP
Light source: 100% for both 2Sλ (250W) and 3Pλ (250W)
Tilt angle: -6 °
Magnification: Maximum (field of view range: 1/120 of the total area)
Observation area: Whole area (substrate with outer diameter of 95 mmφ and inner diameter of 25 mmφ)
Iris: notch.

As shown in Table 1, the comparison of Examples 1 to 5 and Comparative Examples 1 to 3 includes abrasive particles having an average primary particle diameter measured by the BET method of 1 nm or more and 50 nm or less, and a dispersion medium, and When the pH value is 7 or more and 12 or less and the content of the abrasive grains is 30 mass% with respect to the total mass of the abrasive grain dispersion liquid, the particle diameter measured by a number counting type particle size distribution meter is 0.2 μm. It was confirmed that the generation of fine scratches was suppressed when the abrasive grain dispersion liquid in which the number of abrasive grains having a grain size of less than 0.3 μm was 25,000,000 or less per 1 cm ³ .

In addition, by comparison of Examples 1 to 5 and Comparative Examples 1 to 3, abrasive particles having an average primary particle diameter measured by the BET method of 1 nm or more and 50 nm or less and a dispersion medium are included, and a pH value is 7 or more. When the content of the abrasive grains is 12 or less and the content of the abrasive grains is 30% by mass with respect to the total mass of the abrasive grain dispersion liquid, the particle diameter measured by a number counting type particle size distribution meter is 0.3 μm or more and less than 0.4 μm. It was confirmed that the generation of fine scratches was suppressed when the abrasive grain dispersion liquid in which the number of abrasive grains was 1,500,000 or less per 1 cm ³ .

Furthermore, by comparing Examples 1 to 5, when the content of the abrasive grains was 30% by mass relative to the total mass of the abrasive grain dispersion liquid, the particle size measured by a number counting type particle size distribution meter was The number of particles of abrasive grains having a size of 0.2 μm or more and less than 0.3 μm is 25,000,000 or less per 1 cm ³ , and the number of particles of abrasive grains having a particle size of 0.3 μm or more and less than 0.4 μm is 1 cm. It was confirmed that the generation of fine scratches was further suppressed when the abrasive grain dispersion liquid of not more than 1,500,000 particles per ³ was used.

Claims (10)

An abrasive grain dispersion liquid comprising an abrasive grain having an average primary particle diameter of 1 nm or more and 50 nm or less measured by a BET method, and a dispersion medium, and having a pH value of 7 or more and 12 or less,
The content of the abrasive grains is, when converted to 30% by mass with respect to the total mass of the abrasive grain dispersion liquid, measured by a number counting type particle size distribution meter, and the particle diameter is 0.2 μm or more and less than 0.3 μm. An abrasive grain dispersion liquid in which the number of certain abrasive grains is 25,000,000 or less per 1 cm ³ . The content of the abrasive grains is, when converted to 30% by mass based on the total mass of the abrasive grain dispersion liquid, measured by a number counting type particle size distribution meter, and the particle diameter is 0.3 μm or more and less than 0.4 μm. The abrasive grain dispersion liquid according to claim 1, wherein the number of particles of a certain abrasive grain is 1,500,000 or less per 1 cm ³ . A liquid which is the abrasive grain dispersion liquid according to claim 1 or 2,
And a liquid B containing a dispersion medium,
Polishing composition kit.   The polishing composition kit according to claim 3, wherein the liquid B contains an acid.   The polishing composition kit according to claim 3, wherein the solution B contains a basic compound.   Using the polishing composition kit according to any one of claims 3 to 5, the solution A and the solution B are mixed to have a pH value of 1.5 or more and 4.0 or less. A method for producing a polishing composition.   A polishing composition produced by the production method according to claim 6.   A polishing target substrate for a magnetic disk using the polishing composition manufactured using the polishing composition kit according to claim 3 or the polishing composition according to claim 7. A polishing method including a step of polishing.   The polishing method according to claim 8, wherein the substrate to be polished for the magnetic disk has a surface roughness (arithmetic mean roughness (Ra)) of 8 Å or less.   A method for manufacturing a magnetic disk substrate using the polishing method according to claim 8.