JP2017111840A - Polishing liquid composition for magnetic disk substrates - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing liquid composition for magnetic disk substrates that enables short-wavelength waviness to be reduced after polishing without substantially sacrificing the velocity of rough polishing.SOLUTION: A polishing liquid composition for magnetic disk substrates contains non-spherical silica particles A, a non-ionic organic compound B, and water; its pH is not below 0.5 and not above 6.0. The non-ionic organic compound is not above 300 in molecular weight and has in its molecule at least one functional group selected from hydroxyl groups and ether.SELECTED DRAWING: None

Description

  The present disclosure relates to a polishing composition for a magnetic disk substrate, a method for producing a silica slurry, a method for producing a magnetic disk substrate, and a method for polishing a substrate.

  In recent years, magnetic disk drives have been reduced in size and capacity, and high recording density has been demanded. In order to increase the recording density, it is necessary to reduce the unit recording area and improve the detection sensitivity of the weakened magnetic signal. For this reason, technical development for lowering the flying height of the magnetic head has been underway. For magnetic disk substrates, the smoothness and flatness are improved (reduction of surface roughness, waviness, and edge sagging) and surface defects are reduced (residual abrasive, Reduction of scratches, protrusions, pits, etc.) is strictly demanded.

  In response to such demands, from the viewpoint of achieving both improvement in surface quality and productivity that are smoother and less scratched, a multi-stage polishing method having two or more stages of polishing processes in the method of manufacturing a magnetic disk substrate Is often adopted. In general, in the final polishing step of the multi-stage polishing method, that is, the final polishing step, a polishing composition for finishing that contains colloidal silica particles in order to satisfy the requirements of reducing surface roughness and scratches such as scratches, protrusions, and pits. In a polishing step (also referred to as a rough polishing step) prior to the final polishing step, a polishing liquid composition containing alumina particles as abrasive grains is used from the viewpoint of improving productivity. However, when alumina particles are used as abrasive grains, the piercing of alumina particles into the substrate may cause defects in the magnetic disk substrate or a magnetic disk having a magnetic layer applied to the magnetic disk substrate.

  Then, the polishing liquid composition which does not contain alumina particles but contains silica particles as abrasive grains has been proposed (Patent Documents 1 to 3).

JP 2014-1116057 A JP 2012-111869 A JP 2014-29754 A

  In a conventional polishing composition in which silica particles are used in place of alumina particles, alumina residue due to alumina adhesion or sticking can be suppressed, and protrusion defects on the substrate surface after polishing can be reduced. However, when a polishing liquid composition using silica particles as abrasive grains instead of alumina particles is used for rough polishing, in order to reduce short wavelength waviness in rough polishing, it is longer than a polishing liquid composition containing alumina particles. There is a problem that time is required for polishing and productivity is lowered.

  Therefore, the present disclosure provides a polishing liquid composition for a magnetic disk substrate that can reduce short-wave waviness on the surface of the substrate after rough polishing without significantly impairing the polishing rate in rough polishing even when silica particles are used as abrasive grains. provide.

  The present disclosure includes non-spherical silica particles A, a non-ionic organic compound B, and water, and has a pH of 0.5 or more and 6.0 or less, and the non-ionic organic compound B has a molecular weight of 300 or less. And a polishing liquid composition for a magnetic disk substrate (hereinafter also referred to as a polishing liquid composition according to the present disclosure), which is a compound having at least one functional group selected from a hydroxyl group and an ether bond in the molecule.

  The present disclosure includes a step of blending at least non-spherical silica particles A, non-ionic organic compound B, and water, and the non-ionic organic compound B has a molecular weight of 300 or less, and has hydroxyl groups and ether bonds in the molecule. It is related with the manufacturing method of the silica slurry used for manufacture of the polishing liquid composition for magnetic disc substrates which is a compound which has at least 1 functional group chosen from these.

  The present disclosure relates to a method for manufacturing a magnetic disk substrate, which includes a step of polishing a substrate to be polished using the polishing composition according to the present disclosure.

  The present disclosure relates to a method for polishing a substrate, including a step of polishing a substrate to be polished using the polishing composition according to the present disclosure, wherein the substrate to be polished is a substrate used for manufacturing a magnetic disk substrate.

  According to the present disclosure, even when silica particles are used as the abrasive grains, the effect of reducing the short wavelength waviness on the substrate surface after the rough polishing can be achieved without greatly impairing the polishing rate in the rough polishing. As a result, the productivity of the magnetic disk substrate with improved substrate quality can be improved.

FIG. 1 is an example of a transmission electron microscope (hereinafter also referred to as “TEM”) observation photograph of a confetti type colloidal silica abrasive grain. FIG. 2 is an example of a TEM observation photograph of deformed colloidal silica abrasive grains.

  The present disclosure is based on the finding that by using a polishing composition containing non-spherical silica particles and a specific nonionic organic compound for rough polishing, it is possible to reduce short wavelength waviness without greatly impairing the polishing rate. In general, in the manufacture of a magnetic disk substrate, productivity can be improved if short-wave waviness can be reduced.

  Although the details of the mechanism by which the polishing composition of the present disclosure can reduce short wavelength waviness without significantly degrading the polishing rate are not clear, it is presumed as follows. Since the nonionic organic compound has a specific functional group, it acts on the surface of the non-spherical silica particles and efficiently suppresses aggregation of the silica particles. For this reason, it is considered that the cutting action of the silica particles on the substrate becomes uniform during polishing, thereby improving the polishing rate and reducing short wavelength waviness. Furthermore, since the nonionic organic compound has a low molecular weight, it is considered that the influence on the cutting action is minimized and the polishing rate can be maintained or improved. However, the present disclosure need not be construed as being limited to these mechanisms.

  That is, the polishing composition according to the present disclosure includes non-spherical silica particles A, a non-ionic organic compound B, and water, and has a pH of 0.5 or more and 6.0 or less, and the non-ionic organic compound B Relates to a polishing composition for a magnetic disk substrate, which is a compound having a molecular weight of 300 or less and having at least one functional group selected from a hydroxyl group and an ether bond in the molecule.

  In the present disclosure, “undulation” of a substrate refers to irregularities on the surface of the substrate having a wavelength longer than the roughness. In the present disclosure, “short wavelength waviness” refers to waviness observed at a wavelength of 80 to 500 μm. By reducing the short wavelength waviness of the substrate surface after polishing, the flying height of the magnetic head in the magnetic disk drive can be reduced, and the recording density of the magnetic disk can be improved. The short wavelength waviness of the substrate surface can be measured by the method described in Examples.

[Non-spherical silica particles A]
As described above, the polishing liquid composition according to the present disclosure contains non-spherical silica particles A (hereinafter also referred to as “particles A”).

The average sphericity of the particles A is preferably 0.60 or more, more preferably 0.70 or more, and preferably 0.85 or less, more preferably 0.80 or less, and even more preferably 0.75 or less. In the present disclosure, the average sphericity of the particles A is an average value of the sphericity of at least 200 particles A. The sphericity of the particle A can be calculated from the following equation by obtaining the projected area S and the projected perimeter L of the particle A using, for example, TEM observation and image analysis software.
Sphericality = 4π × S / L ²
The sphericity of the individual particles A is preferably 0.60 or more, more preferably 0.70 or more, and preferably 0.85 or less, more preferably 0.80 or less, like the average sphericity. 75 or less is more preferable.

  The average secondary particle diameter of the particles A is preferably 50 nm or more, more preferably 60 nm or more, still more preferably 100 nm or more, and even more preferably 110 nm or more, from the viewpoint of reducing short wavelength waviness without significantly impairing the polishing rate. 140 nm or more is still more preferable, and from the viewpoint of reducing short wavelength waviness, 500 nm or less is preferable, 400 nm or less is more preferable, 300 nm or less is further preferable, 200 nm or less is even more preferable, and 170 nm or less is even more preferable.

  In the present disclosure, the average secondary particle diameter of the particles A refers to an average particle diameter based on a scattering intensity distribution measured by a dynamic light scattering method. In the present disclosure, the “scattering intensity distribution” means a particle size distribution in terms of volume of sub-micron particles or less determined by dynamic light scattering (DLS) or quasielastic light scattering (QLS). I mean. Specifically, the average secondary particle diameter of the particles A in the present disclosure can be obtained by the method described in Examples.

BET specific surface area of the particles A, without impairing the stock removal rate in the rough grinding large, from the viewpoint of reducing the short wavelength undulations of the substrate surface after rough polishing is preferably not more than 200 meters ² / g, more is 100 m ² / g or less Preferably, 80 m ² / g or less is more preferable, and from the same viewpoint, 10 m ² / g or more is preferable, 20 m ² / g or more is more preferable, and 30 m ² / g or more is more preferable. In the present disclosure, the BET specific surface area can be calculated by a nitrogen adsorption method.

  Examples of the particles A include colloidal silica, fumed silica, and surface-modified silica. From the viewpoint of reducing short wavelength waviness without greatly impairing the polishing rate, the particle A is preferably colloidal silica, and more preferably colloidal silica having the following specific shape.

  From the viewpoint of reducing short wavelength waviness without greatly impairing the polishing rate, the shape of the particle A is preferably a plurality of precursors using silica particles having a particle size smaller than the secondary particle size of the particle A as precursor particles. The body particles are aggregated or fused. From the same point of view, the particle A is preferably at least one silica particle selected from a confetti-type silica particle Aa, a deformed-type silica particle Ab, and a deformed and confetti-type silica particle Ac. Silica particles Ab are more preferable.

  In the present disclosure, confetti-type silica particles Aa (hereinafter, also referred to as “particles Aa”) refer to silica particles having unique hook-shaped protrusions on the surface of spherical particles (see FIG. 1). The particle Aa preferably has a shape in which the largest precursor particle a1 and one or more precursor particles a2 having a particle size of 1/5 or less of the precursor particle a1 are aggregated or fused. The particles Aa are preferably in a state in which a plurality of precursor particles a2 having a small particle size are partially embedded in one precursor particle a1 having a large particle size. The particles Aa can be obtained, for example, by the method described in JP 2008-137822 A. The particle diameter of the precursor particles can be obtained as an equivalent circle diameter measured in one precursor particle in an observation image by TEM or the like, that is, the diameter of a circle having the same area as the projected area of the precursor particles. The particle diameters of the precursor particles in the silica particles Ab and the silica particles Ac can be obtained in the same manner.

  In the present disclosure, irregular-shaped silica particles Ab (hereinafter also referred to as “particles Ab”) have a shape in which two or more precursor particles, preferably two or more and ten or less precursor particles are aggregated or fused. This refers to silica particles (see FIG. 2). The particle Ab preferably has a shape in which two or more precursor particles having a particle size of 1.5 times or less are aggregated or fused on the basis of the particle size of the smallest precursor particle. The particles Ab can be obtained, for example, by the method described in JP-A-2015-86102.

  In the present disclosure, irregular and confetti-type silica particles Ac (hereinafter also referred to as “particles Ac”) have the particle Ab as the precursor particle c1, the largest precursor particle c1, and the particle size of the precursor particle c1. It is a shape in which one or more precursor particles c2 which are 1/5 or less are aggregated or fused.

  The particle A preferably contains one or more selected from the particles Aa, Ab and Ac. The total amount of the particles Aa, Ab, and Ac in the particle A is preferably 50% by mass or more, more preferably 70% by mass or more, and still more preferably 80% by mass or more, from the viewpoint of improving the polishing rate and reducing short wavelength waviness. 90% by weight or more is even more preferable, and substantially 100% by weight is even more preferable.

  The particles A may be produced by the flame melting method, the sol-gel method, and the pulverization method from the viewpoint of suppressing the decrease in the polishing rate in the rough polishing, reducing the short wavelength waviness, and reducing the protrusion defects after the rough polishing and the final polishing The silica particles are preferably produced by a particle growth method using an alkali silicate aqueous solution as a starting material (hereinafter also referred to as “water glass method”). The usage form of the particles A is preferably a slurry.

  The method for adjusting the particle size distribution of the particles A includes, for example, a method of giving a desired particle size distribution by adding particles serving as a new nucleus in the process of particle growth in the production stage, and a different particle size distribution. A method in which two or more types of silica particles are mixed to have a desired particle size distribution can be mentioned.

  The content of the particles A in the polishing composition is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, from the viewpoint of reducing short wavelength waviness without greatly impairing the polishing rate. More preferably 2% by weight or more, still more preferably 2% by weight or more, and from the viewpoint of economy, 30% by weight or less is preferred, 25% by weight or less is more preferred, 20% by weight or less is further preferred, 15% by weight The following are even more preferred:

  The polishing liquid composition according to the present disclosure may contain silica particles other than the particles A. The silica particles other than the particles A are preferably spherical silica particles from the viewpoint of reducing protrusion defects. The sphericity of the spherical silica particles is preferably 0.86 or more. The sphericity can be measured by the same method as the sphericity of the particle A. The content of silica particles other than the particles A in the polishing composition is preferably 0% by mass or more, more preferably more than 0% by mass, from the viewpoint of not greatly impairing the reduction in polishing rate and short wavelength waviness. 1 mass% or more is still more preferable, and from the same viewpoint, 2.0 mass% or less is preferable, 1.5 mass% or less is more preferable, and 1.2 mass% or less is more preferable. From the same viewpoint, the mass ratio of the spherical silica particles to the particles A (spherical silica particles / particles A) is preferably 0/100 or more, more preferably more than 0/100, and preferably 30/70 or less. 25/75 or less is more preferable, and 20/80 or less is still more preferable.

[Nonionic organic compound B]
As described above, the polishing composition according to the present disclosure contains a nonionic organic compound B (hereinafter also referred to as “compound B”).

  Compound B is a compound having at least one functional group selected from a hydroxyl group and an ether bond in the molecule. Examples of compound B include compound B1 having one or more hydroxyl groups and no ether bond, compound B2 having one or more ether bonds and no hydroxyl group, and one or more hydroxyl groups and one or more ethers And at least one compound selected from compound B3 having a bond.

  The number of carbon atoms of compound B is 1 or more, preferably 2 or more, and preferably 20 or less from the viewpoint of reducing short-wave waviness on the substrate surface after rough polishing without significantly impairing the polishing rate in rough polishing. Preferably, 10 or less is more preferable. The number of carbon atoms of the compound B1 is 1 or more, preferably 2 or more, preferably 5 or less, more preferably 3 or less from the same viewpoint. From the same viewpoint, the number of carbon atoms of the compound B2 is preferably 4 or more, more preferably 5 or more, and preferably 10 or less, more preferably 6 or less. From the same viewpoint, the number of carbon atoms of the compound B3 is preferably 4 or more, more preferably 6 or more, and preferably 20 or less, more preferably 10 or less.

  Specific examples of compound B1 include at least one selected from methanol, ethanol, ethylene glycol, propylene glycol, propanediol, butanediol, and glycerin. Specific examples of compound B2 include at least one selected from diethyl ether, diethylene glycol monomethyl ether, diethylene glycol dimethyl ether, and diethylene glycol diethyl ether. Specific examples of compound B3 include at least one selected from diethylene glycol, diethylene glycol monoethyl ether, triethylene glycol, tetraethylene glycol, polyethylene glycol, and polyglycerin.

  The molecular weight of Compound B is preferably 30 or more, more preferably 40 or more, preferably 300 or less, more preferably 250 or less, and even more preferably 95 or less, from the viewpoint of reducing short wavelength waviness without greatly impairing the polishing rate. preferable. From the same viewpoint, the molecular weight of Compound B1 is preferably 30 or more, more preferably 40 or more, 95 or less, more preferably 80 or less, and even more preferably 70 or less. From the same viewpoint, the molecular weight of the compound B2 is preferably 70 or more, more preferably 100 or more, and preferably 200 or less, more preferably 150 or less. From the same viewpoint, the molecular weight of Compound B3 is preferably 100 or more, more preferably 120 or more, still more preferably 140 or more, and preferably 300 or less, more preferably 200 or less, and even more preferably 150 or less.

  The molecular weight per carbon atom of Compound B is preferably 15 or more, more preferably 20 or more, and preferably 40 or less, more preferably 30 or less, from the viewpoint of reducing short wavelength waviness without greatly impairing the polishing rate. From the same viewpoint, the molecular weight per carbon atom of the compound B1 is preferably 20 or more, preferably 35 or less, and more preferably 30 or less. From the same viewpoint, the molecular weight per carbon atom of the compound B2 is preferably 15 or more, more preferably 20 or more, and preferably 30 or less, more preferably 25 or less. From the same viewpoint, the molecular weight per carbon atom of the compound B3 is preferably 20 or more, more preferably 25 or more, and preferably 40 or less, more preferably 30 or less. In the present disclosure, “molecular weight per carbon atom” can be calculated by dividing the molecular weight of Compound B by the number of carbons contained in Compound B.

  The molecular weight per hydroxyl group of Compound B is preferably 30 or more, more preferably 35 or more, and more preferably 150 or less, and even more preferably 100 or less, from the viewpoint of reducing short wavelength waviness without greatly impairing the polishing rate. From the same viewpoint, the molecular weight per hydroxyl group of the compound B1 is preferably 30 or more, more preferably 35 or more, and preferably 50 or less. From the same viewpoint, the molecular weight per hydroxyl group of Compound B3 is preferably 50 or more, preferably 150 or less, and more preferably 100 or less. In the present disclosure, the “molecular weight per hydroxyl group” can be calculated by dividing the molecular weight of Compound B by the number of hydroxyl groups contained in Compound B.

  The molecular weight per ether bond of Compound B is preferably 40 or more, more preferably 45 or more, more preferably 110 or less, and more preferably 80 or less, from the viewpoint of reducing short wavelength waviness without greatly impairing the polishing rate. From the same viewpoint, the molecular weight per ether bond of Compound B2 is preferably 40 or more, more preferably 45 or more, and preferably 75 or less, more preferably 60 or less. From the same viewpoint, the molecular weight per ether bond of Compound B3 is preferably 60 or more, preferably 110 or less, and more preferably 80 or less. In the present disclosure, “molecular weight per ether bond” can be calculated by dividing the molecular weight of compound B by the number of ether bonds contained in compound B.

  The content of Compound B in the polishing liquid composition according to the present disclosure is preferably 0.0001% by mass or more, more preferably 0.0005% by mass or more, and 0.001% by mass from the viewpoint of reducing short wavelength waviness. The above is more preferable, 0.005% by mass or more is even more preferable, and from the viewpoint of reducing short wavelength waviness without greatly impairing the polishing rate, 1.0% by mass or less is preferable, and 0.5% by mass or less is preferable. More preferably, 0.1 mass% or less is still more preferable, and 0.05 mass% or less is still more preferable.

  The content of Compound B in the polishing liquid composition according to the present disclosure is preferably 0.001 part by mass or more with respect to 100 parts by mass of the entire silica particles in the polishing liquid composition from the viewpoint of reducing short wavelength waviness. 0.005 parts by mass or more is more preferable, 0.01 parts by mass or more is more preferable, 0.5 parts by mass or more is still more preferable, 1.0 parts by mass or more is still more preferable, and the polishing rate is greatly impaired. From the viewpoint of reducing short-wave waviness, the amount is preferably 20 parts by mass or less, more preferably 10 parts by mass or less, and further preferably 2.0 parts by mass or less, based on 100 parts by mass of the entire silica particles in the polishing composition. preferable. In the present disclosure, when the polishing liquid composition contains other silica particles other than the particles A, the content of the compound B with respect to 100 parts by mass of the entire silica particles in the polishing liquid composition is the particles A and the The content with respect to 100 mass parts of silica particles other than particle A in total is said.

[PH adjuster]
The pH of the polishing composition according to the present disclosure is 0.5 or more and 6.0 or less from the viewpoint of improving the polishing rate and reducing short wavelength waviness. The polishing composition according to the present disclosure preferably contains a pH adjusting agent from the viewpoint of improving the polishing rate, reducing short wavelength waviness, and adjusting the pH. As a pH adjuster, 1 or more types chosen from an acid and a salt are preferable from the same viewpoint.

  Examples of the acid include inorganic acids such as nitric acid, sulfuric acid, sulfurous acid, persulfuric acid, hydrochloric acid, perchloric acid, phosphoric acid, phosphonic acid, phosphinic acid, pyrophosphoric acid, polyphosphoric acid, and amidosulfuric acid; organic phosphoric acid and organic phosphonic acid Organic acids such as, and the like. Among these, at least one selected from phosphoric acid, sulfuric acid, and 1-hydroxyethylidene-1,1-diphosphonic acid is preferable, and at least one selected from sulfuric acid and phosphoric acid is preferable from the viewpoint of improving the polishing rate and reducing short wavelength waviness. More preferred is phosphoric acid.

  As a salt, the salt of said acid and at least 1 sort (s) chosen from a metal, ammonia, and an alkylamine is mentioned, for example. Specific examples of the metal include metals belonging to Groups 1 to 11 of the periodic table. Among these, from the viewpoint of improving the polishing rate and reducing short wavelength waviness, a salt of the above acid with a metal belonging to Group 1 or ammonia is preferable.

  The content of the pH adjusting agent in the polishing liquid composition is preferably 0.001% by mass or more, more preferably 0.01% by mass or more, from the viewpoint of reducing short wavelength waviness without significantly impairing the polishing rate. 0.05% by mass or more is more preferable, 0.1% by mass or more is further more preferable, and from the same viewpoint, 5.0% by mass or less is preferable, 4.0% by mass or less is more preferable, 3.0% The mass% or less is further preferable, and the 2.5 mass% or less is even more preferable.

[Oxidant]
The polishing composition according to the present disclosure may contain an oxidizing agent from the viewpoint of improving the polishing rate and reducing short wavelength waviness. Examples of the oxidizing agent include peroxide, permanganic acid or a salt thereof, chromic acid or a salt thereof, peroxo acid or a salt thereof, oxygen acid or a salt thereof, nitric acid, sulfuric acid, and the like from the same viewpoint. . Among these, at least one selected from hydrogen peroxide, iron nitrate (III), peracetic acid, ammonium peroxodisulfate, iron sulfate (III) and ammonium iron sulfate (III) is preferable. Hydrogen peroxide is more preferred from the viewpoint of preventing metal ions from adhering to the surface and the viewpoint of availability. These oxidizing agents may be used alone or in admixture of two or more.

  The content of the oxidizing agent in the polishing liquid composition is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, further preferably 0.1% by mass or more, from the viewpoint of improving the polishing rate. And 4.0 mass% or less is preferable from a viewpoint of polishing rate improvement and short wavelength waviness reduction, 2.0 mass% or less is more preferable, and 1.5 mass% or less is still more preferable.

[water]
The polishing liquid composition according to the present disclosure contains water as a medium. Examples of water include distilled water, ion exchange water, pure water, and ultrapure water. The content of water in the polishing liquid composition is preferably 61% by mass or more, more preferably 70% by mass or more, still more preferably 80% by mass or more, and 85% by mass from the viewpoint of easy handling of the polishing liquid composition. % Or more is more preferable, and from the same viewpoint, 99 mass% or less is preferable, 98 mass% or less is more preferable, and 97 mass% or less is still more preferable.

[Other ingredients]
The polishing liquid composition according to the present disclosure may contain other components as necessary. Examples of other components include a thickener, a dispersant, a rust inhibitor, a basic substance, a polishing rate improver, a surfactant, and a polymer compound other than Compound B. The other components are preferably contained in the polishing liquid composition within a range not impairing the effects of the present disclosure, and the content of the other components in the polishing liquid composition is preferably 0% by mass or more, More than 0 mass% is more preferable, 0.1 mass% or more is still more preferable, 10 mass% or less is preferable, and 5 mass% or less is more preferable.

[Alumina abrasive]
In the polishing liquid composition according to the present disclosure, the content of alumina abrasive grains is preferably 0.1% by mass or less, more preferably 0.05% by mass or less, from the viewpoint of reducing protrusion defects, and 0.02% by mass. The following is more preferable, and it is further preferable that the alumina abrasive grains are not substantially contained. In the present disclosure, “substantially free of alumina abrasive grains” means that no alumina particles are contained, no alumina particles functioning as abrasive grains, or an amount of alumina particles that affect the polishing result. May not be included. The content of the alumina particles in the polishing liquid composition is preferably 2% by mass or less, more preferably 1% by mass or less, still more preferably 0.5% by mass or less, based on the total amount of abrasive grains in the polishing liquid composition. Even more preferably, it is substantially 0%.

[PH]
The pH of the polishing composition according to the present disclosure is 0.5 or more, preferably 0.7 or more, more preferably 0.9 or more, from the viewpoint of improving the polishing rate and reducing short wavelength waviness, and more preferably 1.0. The above is more preferable, 1.2 or more is still more preferable, 1.4 or more is still more preferable, and from the same viewpoint, it is 6.0 or less, 4.0 or less is preferable, and 3.0 or less is more Preferably, 2.5 or less is further preferable, and 2.0 or less is even more preferable. It is preferable to adjust pH using the above-mentioned pH adjuster. The above pH is the pH of the polishing composition at 25 ° C. and can be measured using a pH meter, and is preferably a value two minutes after the electrode of the pH meter is immersed in the polishing composition.

[Method for producing polishing composition]
The polishing composition according to the present disclosure comprises particles A, compound B, and water, and has a pH of 0.5 or more and 6.0 or less. The polishing composition according to the present disclosure includes, for example, a silica slurry containing the particles A and the compound B and, if desired, a pH adjuster, an oxidizing agent, and other components by a known method, and the pH is adjusted to 0. It can manufacture by setting it as 5 or more and 6.0 or less. Therefore, this indication is related with the manufacturing method of the silica slurry used for manufacture of polishing liquid composition including the process of blending at least particles A, compound B, and water. Furthermore, this indication is related with the manufacturing method of polishing liquid composition including the process of mix | blending at least particle | grains A, the compound B, and water, and including the process of adjusting pH to 0.5 or more and 6.0 or less as needed. . In the present disclosure, “mixing” includes mixing the particles A, the compound B and water, and, if necessary, a pH adjuster, an oxidizing agent and other components simultaneously or in any order. The said mixing | blending can be performed using mixers, such as a homomixer, a homogenizer, an ultrasonic disperser, and a wet ball mill, for example. The preferable compounding amount of each component in the method for producing the silica slurry and the polishing liquid composition is the same as the preferable content of each component in the polishing liquid composition according to the present disclosure described above.

The manufacturing method of the polishing composition of the present disclosure preferably includes the following steps from the viewpoint of dispersibility of silica particles.
Step 1: Water, a pH adjuster, and optionally an oxidizing agent are mixed to prepare a dispersion medium having a pH of 6.0 or less. Step 2: The dispersion medium, and a silica slurry containing particles A and compound B, In the step 1 of mixing, the pH of the resulting dispersion medium is preferably adjusted so that the pH of the polishing composition is a desired value.

  In the present disclosure, the “content of each component in the polishing liquid composition” refers to the content of each component at the time when the polishing liquid composition is used for polishing. Therefore, when the polishing liquid composition according to the present disclosure is prepared as a concentrate, the content of each component can be increased by the concentration.

[Polishing liquid kit]
The present disclosure relates to a polishing liquid kit for producing a polishing liquid composition, which includes a container-containing slurry in which a silica slurry containing the particles A and the compound B is housed in a container. The polishing liquid kit according to the present disclosure may further include a dispersion medium having a pH of 6.0 or less housed in a container different from the container-containing slurry. According to the present disclosure, it is possible to provide a polishing liquid kit capable of obtaining a polishing liquid composition capable of reducing short wavelength waviness without greatly impairing the polishing rate even when silica particles are used as abrasive grains.

  As a polishing liquid kit according to the present disclosure, for example, a silica slurry (first liquid) containing the particles A and the compound B, and other components that can be blended in a polishing liquid composition used for polishing an object to be polished. The solution (2nd liquid) to contain is preserve | saved in the state which is not mutually mixed, The polishing liquid kit (2 liquid type polishing liquid composition) with which these are mixed at the time of use is mentioned. Examples of other components that can be blended in the polishing liquid composition include a pH adjuster and an oxidizing agent. The first liquid and the second liquid may each contain an optional component as necessary. Examples of the optional component include a thickener, a dispersant, a rust inhibitor, a basic substance, a polishing rate improver, a surfactant, and a polymer compound.

[Polished substrate]
The target substrate to be polished by the polishing composition according to the present disclosure is a substrate used for manufacturing a magnetic disk substrate. For example, a Ni—P plated aluminum alloy substrate is preferable. In the present disclosure, the “Ni—P plated aluminum alloy substrate” refers to a surface of an aluminum alloy base material that has been subjected to electroless Ni—P plating after being ground. A magnetic disk substrate can be produced by performing a step of forming a magnetic layer on the surface of the substrate by sputtering or the like after the step of polishing the surface of the substrate to be polished using the polishing composition according to the present disclosure. Examples of the shape of the substrate to be polished include a shape having a flat portion such as a disk shape, a plate shape, a slab shape, and a prism shape, and a shape having a curved surface portion such as a lens. is there. In the case of a disk-shaped polished substrate, the outer diameter is, for example, 10 to 120 mm, and the thickness is, for example, 0.5 to 2 mm.

  In general, a magnetic disk is manufactured through a magnetic layer forming process in which a substrate to be polished that has undergone a grinding process is polished through a rough polishing process and a final polishing process. The polishing composition according to the present disclosure is preferably used for polishing in the rough polishing step.

[Method of manufacturing magnetic disk substrate]
The present disclosure includes a step of polishing a substrate to be polished using the polishing liquid composition of the present disclosure (hereinafter also referred to as “polishing step using the polishing liquid composition according to the present disclosure”). The present invention relates to a method (hereinafter also referred to as “substrate manufacturing method according to the present disclosure”). In the substrate manufacturing method according to the present disclosure, the polishing step using the polishing composition according to the present disclosure is preferably a rough polishing step.

  In the polishing process using the polishing liquid composition according to the present disclosure, for example, the substrate to be polished is sandwiched by a surface plate with a polishing pad attached thereto, the polishing liquid composition according to the present disclosure is supplied to the polishing surface, and pressure is applied. The substrate to be polished can be polished by moving the polishing pad and the substrate to be polished.

  The polishing load in the polishing step using the polishing liquid composition according to the present disclosure is preferably 3 kPa or more, more preferably 5 kPa or more, still more preferably 7 kPa or more, from the viewpoint of improving the polishing rate and reducing short wavelength waviness, and 30 kPa or less is preferable, 25 kPa or less is more preferable, and 20 kPa or less is still more preferable. In the present disclosure, “polishing load” refers to the pressure of the surface plate applied to the surface to be polished of the substrate to be polished during polishing. The polishing load can be adjusted by applying air pressure or weight to the surface plate or the substrate.

In the polishing step using the polishing liquid composition according to the present disclosure, the polishing amount per 1 cm ^{2 of the} substrate to be polished is preferably 0.20 mg or more and 0.30 mg or more from the viewpoint of improving the polishing rate and reducing short wavelength waviness. More preferably, 0.40 mg or more is more preferable, and from the same viewpoint, 2.50 mg or less is preferable, 2.00 mg or less is more preferable, and 1.60 mg or less is more preferable.

In the polishing process using the polishing liquid composition according to the present disclosure, the supply rate of the polishing liquid composition per 1 cm ^{2 of the} substrate to be polished is preferably 2.5 mL / min or less from the viewpoint of economy, and 2.0 mL / Min. Or less is more preferable, 1.5 mL / min or less is more preferable, and from the viewpoint of improving the polishing rate, 0.01 mL / min or more per 1 cm ^{2 of the} substrate to be polished is preferable, and 0.03 mL / min or more is more preferable. 0.05 mL / min or more is more preferable.

  Examples of a method for supplying the polishing liquid composition according to the present disclosure to a polishing machine include a method of continuously supplying using a pump or the like. When supplying the polishing liquid composition to the polishing machine, in addition to the method of supplying it with one liquid containing all the components, considering the storage stability of the polishing liquid composition, etc., it is divided into a plurality of component liquids for blending. Two or more liquids can be supplied. In the latter case, for example, the plurality of compounding component liquids are mixed in the supply pipe or on the substrate to be polished to obtain the polishing liquid composition according to the present disclosure.

  According to the substrate manufacturing method according to the present disclosure, it is possible to reduce the short wavelength waviness of the substrate surface after rough polishing without significantly impairing the polishing speed in rough polishing, and thus efficiently manufacture a magnetic disk substrate with improved substrate quality. The effect that it is possible can be produced.

[Polishing method]
The present disclosure relates to a magnetic disk substrate polishing method (hereinafter, also referred to as a polishing method according to the present disclosure) including a polishing step using the polishing liquid composition according to the present disclosure. In the polishing method according to the present disclosure, the polishing step using the polishing composition according to the present disclosure is preferably a rough polishing step.

  By using the polishing method according to the present disclosure, it is possible to reduce short-wave waviness on the substrate surface after rough polishing without significantly impairing the polishing rate in rough polishing, and thus the productivity of a magnetic disk substrate with improved substrate quality. The effect that it can improve can be show | played. The specific polishing method and conditions can be the same as those of the substrate manufacturing method according to the present disclosure described above.

  Hereinafter, the present disclosure will be described in more detail by way of examples. However, these examples are illustrative, and the present disclosure is not limited to these examples.

1. Preparation of Polishing Liquid Composition Examples 1 to 21 and Comparative Example 1 using the abrasive grains (colloidal silica) in Table 1, the additives in Table 2, an acid (phosphoric acid), an oxidizing agent (hydrogen peroxide), and water. 10 polishing liquid compositions were prepared (Table 3). The content of each component in the polishing composition is: abrasive grain: 6.0 mass%, additive: 0.0017 to 17% (ratio to abrasive grains), phosphoric acid: 2 mass%, hydrogen peroxide: 1 It was set as mass%. The pH of the polishing composition was 1.4. The colloidal silica particle of the silica abrasive grain of Table 1 is manufactured by the water glass method. The pH was measured using a pH meter (manufactured by Toa DKK Co., Ltd.), and the value 2 minutes after the electrode was immersed in the polishing composition was adopted. In Table 2, “molecular weight per carbon atom” is a value obtained by dividing the molecular weight of a compound by the number of carbons contained in the compound and rounding off to the first decimal place. “Molecular weight per hydroxyl group” is a value obtained by dividing the molecular weight of a compound by the number of hydroxyl groups contained in the compound and rounding off to the first decimal place. “Molecular weight per ether bond” is a value obtained by dividing the molecular weight of a compound by the number of ether bonds contained in the compound and further rounding off to the first decimal place.

2. Measurement method of each parameter [Measurement method of average secondary particle diameter of silica particles]
Silica particles were diluted with ion-exchanged water to prepare a dispersion containing 1% by mass of silica particles. And this dispersion liquid was thrown in into the following measuring apparatus, and the volume particle size distribution of the silica particle was obtained. The particle diameter (Z-average value) at which the cumulative volume frequency of the obtained volume particle size distribution was 50% was defined as the average secondary particle diameter.
Measuring equipment: Malvern Zetasizer Nano “Nano S”
Measurement conditions: Sample volume 1.5mL
: Laser He-Ne, 3.0 mW, 633 nm
: Scattered light detection angle 173 °

[Measurement method of BET specific surface area]
The BET specific surface area (m ² / g) was measured by the following [pre-treatment], and weighed about 0.1 g of the measurement sample into the measurement cell to 4 digits after the decimal point (0.1 mg digit). Immediately before the measurement, the sample was dried for 30 minutes in an atmosphere of 110 ° C., and then measured by a BET method using a specific surface area measuring device (Micromeritic automatic specific surface area measuring device, Flowsorb III 2305, manufactured by Shimadzu Corporation).
[Preprocessing]
Slurry particles were placed in a petri dish and dried in a hot air dryer at 150 ° C. for 1 hour. The dried sample was finely pulverized in an agate mortar to obtain a measurement sample.

[Measuring method of average sphericity of silica particles]
A photograph obtained by observing silica particles with a TEM (“JEM-2000FX” manufactured by JEOL Ltd., 80 kV, 1 to 50,000 times) is captured as image data with a scanner on a personal computer, and analysis software (Mitani Corporation “WinROOF (Ver. 3. 6) ”) was used to analyze the projection image data of 500 silica particles. Then, the sphericity of the individual silica particles was calculated from the projected area S and the projected circumference L of the individual silica particles by the following formula, and the average value of the sphericity (average sphericity) was obtained.
Sphericality = 4π × S / L ²

3. Polishing of Substrates Using the prepared polishing liquid compositions of Examples 1 to 21 and Comparative Examples 1 to 10, the substrate to be polished was polished under the following polishing conditions.

[Polishing conditions]
Polishing machine: Double-side polishing machine (9B-type double-side polishing machine, manufactured by Speed Fam Co., Ltd.)
Substrate to be polished: Ni-P plated aluminum alloy substrate, thickness 1.27 mm, diameter 95 mm, 10 sheets polishing liquid: polishing composition polishing pad: suede type (foam layer: polyurethane elastomer), thickness: 1. 0 mm, average pore diameter: 30 μm, compression ratio of surface layer: 2.5% (manufactured by Filwel)
Surface plate rotation speed: 45 rpm
Polishing load: 9.8 kPa (set value)
Polishing liquid supply amount: 100 mL / min
Polishing time: 5 minutes

4). Evaluation method [Evaluation of polishing rate]
The polishing rates of the polishing composition of Examples 1 to 21 and Comparative Examples 1 to 10 were evaluated as follows. First, the weight of each substrate before and after polishing was weighed (measured by Sartorius, “BP-210S”), and the amount of mass reduction was determined from the change in mass of each substrate. A value obtained by dividing the average mass reduction amount of all 10 sheets by the polishing time was used as a polishing rate, and was calculated by introducing it into the following formula. And the relative value which set the comparative example 1 to 100 was computed.
Weight loss (g) = {mass before polishing (g) −mass after polishing (g)}
Polishing rate (g / min) = mass reduction amount (g) / polishing time (min)
(Evaluation criteria)
Polishing speed (relative value): Evaluation 95 or higher: “A: Excellent polishing speed and improvement in productivity can be expected”
90 or more and less than 95: “B: Polishing rate is good and improvement is required for actual production”
Less than 90: “C: Productivity decreases”

[Evaluation of swell (short wavelength swell)]
Two substrates were arbitrarily selected from the 10 substrates after polishing, and both surfaces of each selected substrate were measured at any three points (12 points in total) under the following conditions. The average value of the measured values at the 12 points was calculated as the short wavelength waviness of the substrate.
(Measurement condition)
Equipment: Zygo NewView 5032
Lens: 2.5x Michelson
Zoom ratio: 0.5x Remove: Cylinder
Filter: FFT Fixed Band Pass
Waviness wavelength: 80-500 μm
Area: 4.33mm x 5.77mm
(Evaluation criteria)
Swell (relative value): Less than evaluation 91: “A: Excellent swell reduction effect and improved productivity”
91 to less than 100: “B: Swelling reduction effect is good and actual production is possible”
100 or more: "C: Improvement is required for actual production"

5). Results The results of each evaluation are shown in Table 3.

  As shown in Table 3, Examples 1 to 21 containing particles A and a specific compound B significantly impair the polishing rate compared to Comparative Examples 1 to 5 and 10 not containing the specific compound B. The short wavelength waviness after polishing was reduced. Furthermore, Examples 1-21 improved the grinding | polishing rate compared with Comparative Examples 6-9 which does not contain the particle | grains A. FIG.

  According to the present disclosure, the short-wave waviness after polishing can be reduced while maintaining the polishing rate, so that the productivity of manufacturing the magnetic disk substrate can be improved. The present disclosure can be suitably used for manufacturing a magnetic disk substrate.

Claims (14)

Non-spherical silica particles A, non-ionic organic compound B and water,
pH is 0.5 or more and 6.0 or less,
The nonionic organic compound B is a polishing liquid composition for a magnetic disk substrate, which has a molecular weight of 300 or less and has at least one functional group selected from a hydroxyl group and an ether bond in the molecule.   The nonionic organic compound B includes a compound B1 having one or more hydroxyl groups and no ether bond, a compound B2 having one or more ether bonds and no hydroxyl group, and one or more hydroxyl groups and one or more. The polishing composition for a magnetic disk substrate according to claim 1, which is at least one compound selected from Compound B3 having an ether bond of: Compound B1 has a molecular weight of 95 or less,
The molecular weight of the compound B2 is 200 or less,
The polishing composition for a magnetic disk substrate according to claim 2, wherein the compound B3 has a molecular weight of 300 or less.   The content of the nonionic organic compound B is 0.001 part by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the entire silica particles in the polishing liquid composition. The polishing liquid composition for magnetic disk substrates as described.   5. The polishing composition for a magnetic disk substrate according to claim 1, wherein the nonspherical silica particles A have an average sphericity of 0.85 or less.   6. The polishing composition for a magnetic disk substrate according to claim 1, wherein the non-spherical silica particles A have an average secondary particle diameter of 50 nm or more and 500 nm or less.   7. The polishing composition for a magnetic disk substrate according to claim 1, wherein the content of the alumina abrasive grains is 0.1% by mass or less.   The polishing composition for a magnetic disk substrate according to claim 1, wherein the non-spherical silica particles A are colloidal silica.   The polishing composition for a magnetic disk substrate according to any one of claims 1 to 8, which is used for polishing an Ni-P plated aluminum alloy substrate.   The polishing composition for a magnetic disk substrate according to any one of claims 1 to 9, further comprising a pH adjuster.   The polishing composition for a magnetic disk substrate according to any one of claims 1 to 10, further comprising an oxidizing agent. Having a step of blending at least non-spherical silica particles A, non-ionic organic compound B and water,
The nonionic organic compound B has a molecular weight of 300 or less and is a compound having at least one functional group selected from a hydroxyl group and an ether bond in the molecule, and is used for producing a polishing liquid composition for a magnetic disk substrate. A method for producing a silica slurry.   A method for producing a magnetic disk substrate, comprising a step of polishing a substrate to be polished using the polishing composition for a magnetic disk substrate according to claim 1.   A step of polishing a substrate to be polished using the polishing composition for a magnetic disk substrate according to any one of claims 1 to 11, wherein the substrate to be polished is a substrate used for manufacturing a magnetic disk substrate. A method for polishing a substrate.