JP2023174608A - polishing liquid composition - Google Patents

Abstract

To provide a polishing liquid composition that can reduce residual silica on the substrate surface after polishing, while maintaining the polishing speed.SOLUTION: According to one embodiment, a polishing liquid composition contains silica particles and an aqueous medium. The silica particles have an ignition loss of 4% or less on a dry weight basis. The silica particles have a D90 of 140 nm and 600 nm, where the D90 is the particle size where the cumulative frequency from the smaller particle size side becomes 90% in a weight-based particle size distribution as determined by centrifugal sedimentation.SELECTED DRAWING: None

Description

The present disclosure relates to a polishing liquid composition, a method for manufacturing a magnetic disk substrate, and a method for polishing a substrate.

In recent years, magnetic disk drives have become smaller and larger in capacity, and higher recording densities are required. 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. Therefore, technological development is underway to further lower the flying height of the magnetic head. In order to lower the flying height of the magnetic head and secure the recording area, magnetic disk substrates have been developed to improve smoothness and flatness (reduce surface roughness, waviness, and edge sagging) and to reduce surface defects (residual abrasive grains, (reduction of scratches, protrusions, pits, etc.) is strictly required.

In response to these demands, from the viewpoint of both improving surface quality such as smoother surfaces with fewer scratches and improving productivity, a multi-stage polishing method that includes two or more polishing steps has been adopted in the manufacturing method of magnetic disk substrates. is often adopted. Generally, in order to satisfy the requirement for smoothness, a polishing agent containing colloidal silica particles is used, and from the viewpoint of improving productivity, a polishing liquid composition containing alumina particles as an abrasive grain is used. However, when alumina particles are used as abrasive grains, the alumina particles stick into the substrate, which may cause defects in the magnetic disk substrate or a magnetic disk in which a magnetic layer is provided on the magnetic disk substrate.

Therefore, for example, Patent Documents 1 and 2 propose polishing liquid compositions that do not contain alumina particles but contain silica particles as abrasive grains.

JP 2017-19978 Publication Japanese Patent Application Publication No. 2021-175774

As the recording density of magnetic disk drives has increased in recent years, reading heads have come to be located several nanometers above a substrate that rotates at high speed. Drive failures are occurring due to the lowering of the reading head.
As a result of studies conducted by the present inventors, it was discovered that silica particles remaining on the surface of the substrate after polishing (hereinafter also referred to as "silica residue") are a cause of drive failure. It has also been found that the amount of residual silica correlates with the size of the silica particles that are abrasive grains.
The remaining silica can be reduced by reducing the particle size of the silica abrasive grains. However, when the particle size of the abrasive grains is reduced, the polishing rate also decreases.

Therefore, in one aspect, the present disclosure provides a polishing liquid composition that can improve the polishing rate without significantly increasing the amount of residual silica. In another aspect, the present disclosure provides a polishing liquid composition that can reduce silica residue on the surface of a substrate after polishing while maintaining the polishing rate.

In one embodiment, the present disclosure includes silica particles and an aqueous medium, the silica particles have an ignition loss of 4% or less on a dry weight basis, and the silica particles have a weight loss obtained by a centrifugal sedimentation method. The present invention relates to a polishing liquid composition having D90 of 140 nm or more and 600 nm or less, where D90 is the particle size at which the cumulative frequency from the small particle size side is 90% in the converted particle size distribution.

In one aspect, the present disclosure relates to a method for manufacturing a magnetic disk substrate, including a polishing step of polishing a substrate to be polished using the polishing liquid composition of the present disclosure.

In one embodiment, the present disclosure relates to a method for polishing a substrate, the substrate being polished is a substrate used for manufacturing a magnetic disk substrate, including polishing a substrate to be polished using the polishing liquid composition of the present disclosure. .

In one aspect, the present disclosure relates to a method for reducing silica residue on a substrate after polishing, which includes polishing a substrate to be polished using the polishing liquid composition of the present disclosure.

In one aspect of the present disclosure, the abrasive grains have an ignition loss of 4% or less on a dry weight basis, and have a cumulative frequency of 90% from the small particle size side in the particle size distribution in terms of weight obtained by centrifugal sedimentation. A step of selecting silica particles whose D90 is 140 nm or more and 600 nm or less when the particle diameter of % is D90, and a step of polishing a substrate to be polished using a polishing liquid composition containing the silica particles and an aqueous medium. The present invention relates to a method of manufacturing a magnetic disk substrate, including:

According to the present disclosure, in one embodiment, it is possible to provide a polishing liquid composition that can improve the polishing rate without significantly increasing the amount of residual silica. In another aspect, the present disclosure can provide a polishing liquid composition that can reduce silica residue on the surface of a substrate after polishing while maintaining the polishing rate.

FIG. 1 is an example of a transmission electron microscope (hereinafter also referred to as "TEM") photograph of confetti-type colloidal silica abrasive grains. FIG. 2 is an example of a TEM observation photograph of irregularly shaped colloidal silica abrasive grains.

Silica particles (silica residue) remaining on the substrate surface after polishing take time and effort to measure, are rarely recognized as a quality evaluation item for the substrate surface after polishing, and are not considered to be the cause of drive failures. It wasn't recognized. It should be noted that ``silica residue'', which has been a problem in conventional technology, is a physical defect such as getting stuck in a scratch or sticking into a wound, and can be detected relatively easily using a model test using simple cleaning or an electron microscope. The problem and effects are different from the "silica residue" in the present disclosure.
In Patent Document 1, since heat-treated silica having a generally high surface hardness is used, there is a problem that the substrate surface tends to have many dent defects and punctures. Further, in Patent Document 2, a high polishing rate and excellent substrate surface quality are both achieved, but further improvement in the polishing rate has been desired from the viewpoint of improving substrate productivity. However, Patent Documents 1 and 2 do not have the problem of reducing residual silica.
The present disclosure is based, in one aspect, on the finding that the amount of silica residue correlates with the ignition loss of silica abrasive grains having a predetermined particle size distribution.

That is, in one embodiment, the present disclosure includes silica particles and an aqueous medium, the silica particles have an ignition loss of 4% or less on a dry weight basis, and the silica particles are obtained by centrifugal sedimentation. A polishing liquid composition (hereinafter referred to as "polishing liquid composition of the present disclosure") having D90 of 140 nm or more and 600 nm or less, where D90 is the particle size at which the cumulative frequency from the small particle size side is 90% in the particle size distribution in terms of weight. (also referred to as "liquid composition").

The mechanism by which the present disclosure exerts its effects is not clear, or it is speculated as follows.
As a result of studies conducted by the present inventors, it is believed that D90, which means the proportion of large-diameter particles, is involved in the silica residue that leads to drive failure. Since large-diameter particles have a large force of transmitting the polishing load to the substrate to be polished, they tend to remain on the substrate. However, simply reducing D90 lowers the polishing rate, resulting in a trade-off relationship. Further, it is considered that another factor behind the residual silica is the hydrogen bond between the silanol groups of the silica particles and the substrate surface. However, the amount of residual silica shows only a weaker correlation with the "silanol group density" of the silica abrasive grains than the ignition loss of the silica abrasive grains. Additional mechanisms may be involved in the correlation between the amount of silica remaining and loss on ignition.
Silanol group density is generally determined by titration, and only the silanol groups on the outermost surface are detected. On the other hand, the ignition loss detects all silanol groups, including those inside the particles. It is also believed that a high load is applied to the particles during polishing, and some of the particles collapse, exposing internal silanol groups. Since this internal silanol group is also considered to be involved in remaining on the substrate, it is considered that there is a high correlation between the loss on ignition and the remaining silica.
However, the present disclosure does not need to be interpreted as being limited to these mechanisms.

[Silica particles A (component A)]
The polishing liquid composition of the present disclosure contains silica particles A (hereinafter also referred to as "component A") as abrasive grains. In one or more embodiments, the silica particles A (component A) have an ignition loss of 4% or less on a dry weight basis, and are from the small particle size side in the particle size distribution in terms of weight obtained by centrifugal sedimentation. These are silica particles whose D90 is 140 nm or more and 600 nm or less, where D90 is the particle diameter at which the cumulative frequency of 90% is 90%. Component A is preferably used as a polishing liquid component in the form of slurry. Component A may be used alone or in combination of two or more.

The particle diameter D10 of component A in terms of weight obtained by the centrifugal sedimentation method is preferably 50 nm or more, more preferably 52 nm or more, even more preferably 53 nm or more, from the viewpoint of maintaining the polishing rate, and 120 nm or more from the viewpoint of substrate surface quality. The thickness is preferably below, more preferably 100 nm or less, and even more preferably 60 nm or less. More specifically, the particle diameter D10 of component A measured by centrifugal sedimentation is 50 nm or more and 120 nm or less, more preferably 52 nm or more and 100 nm or less, and even more preferably 53 nm or more and 60 nm or less.

The particle diameter D50 of component A in terms of weight obtained by the centrifugal sedimentation method is preferably 80 nm or more, more preferably 85 nm or more, even more preferably 90 nm or more, from the viewpoint of maintaining the polishing rate, and 340 nm or more from the viewpoint of substrate surface quality. The thickness is preferably below, more preferably 200 nm or less, and even more preferably 100 nm or less. More specifically, the particle diameter D50 of component A determined by centrifugal sedimentation is 80 nm or more and 340 nm or less, more preferably 85 nm or more and 200 nm or less, and even more preferably 90 nm or more and 100 nm or less.

The particle diameter D90 of component A calculated by centrifugal sedimentation in terms of weight is 140 nm or more, preferably 150 nm or more, more preferably 160 nm or more, even more preferably 170 nm or more, from the viewpoint of maintaining the polishing rate, and the silica residue is From the viewpoint of reduction, it is 600 nm or less, preferably 400 nm or less, more preferably 200 nm or less, and even more preferably 190 nm or less. More specifically, the particle diameter D90 of component A measured by centrifugal sedimentation is 140 nm or more and 600 nm or less, preferably 150 nm or more and 400 nm or less, more preferably 160 nm or more and 200 nm or less, and even more preferably 170 nm or more and 190 nm or less.

In the present disclosure, D10, D50, and D90 refer to particle sizes at which the cumulative frequency from the small diameter side is 10%, 50%, and 90%, respectively, in the weight-based particle size distribution obtained by centrifugal sedimentation. In one or more embodiments of the present disclosure, the centrifugal sedimentation method is a method (disk centrifugal sedimentation light transmission method) in which particles are classified and detected by size based on a difference in sedimentation velocity. Particle size distribution by centrifugal sedimentation can be measured using, for example, a disk centrifugal particle size distribution measuring device (CPS Disc Centrifuge). In the following explanation, the particle size distribution obtained by centrifugal sedimentation may also be referred to as "particle size distribution obtained by CPS measurement." Specifically, it can be calculated by the measuring method described in Examples.

Examples of methods for adjusting the particle size distribution of component A by centrifugal sedimentation include methods for adjusting particle growth time, particle temperature, particle concentration, etc. during the growth process of silica particles. As another embodiment of the method for adjusting the particle size distribution of component A by centrifugal sedimentation, for example, a desired particle size distribution can be achieved by adding new core particles during the particle growth process in the production stage. Examples include a method in which two or more types of silica particles having different particle size distributions are mixed to give a desired particle size distribution.

The average secondary particle diameter of component A is preferably 100 nm or more, more preferably 110 nm or more, even more preferably 130 nm or more, from the viewpoint of maintaining the polishing rate, and preferably 340 nm or less, and 200 nm or less from the viewpoint of substrate surface quality. is more preferable, and even more preferably 140 nm or less. More specifically, the average secondary particle diameter of component A is preferably 100 nm or more and 340 nm or less, more preferably 110 nm or more and 200 nm or less, and even more preferably 130 nm or more and 140 nm or less. In the present disclosure, the average secondary particle size of component A refers to the average particle size based on the scattering intensity distribution measured by a dynamic light scattering method. In this disclosure, "scattering intensity distribution" refers to the volume-based particle size distribution of submicron or smaller particles determined by dynamic light scattering (DLS) or quasielastic light scattering (QLS). It refers to Specifically, the average secondary particle diameter of component A in the present disclosure can be obtained by the method described in Examples.

The loss on ignition of component A on a dry weight basis is 4% or less, preferably 3.6% or less, more preferably 3.4% or less, and 3.3% or less from the viewpoint of reducing silica residue. More preferably, from the viewpoint of storage stability, it is preferably 0% or more, more preferably 1% or more, and even more preferably 2% or more. More specifically, the loss on ignition of component A on a dry weight basis is preferably 0% or more and 3.6% or less, more preferably 1% or more and 3.4% or less, and 2% or more and 3.3% or less. is even more preferable.
In the present disclosure, the ignition loss WL on a dry weight basis refers to the weight change of a sample due to water evaporation when a silica slurry in which silica particles are mixed with water is heated at a temperature between 105° C. and 200° C. in one or more embodiments. Prepare a sample that has been sufficiently dried until it is completely free of water, let it stand, and return it to room temperature (20 to 25 degrees Celsius). In order to measure the amount of moisture adsorbed by the silica particles at room temperature, it is heated again from 105 degrees Celsius to 200 degrees Celsius. The sample was heat-treated at a temperature of 800°C or higher to determine the loss on drying (LOD (wt%)) when sufficiently dried at a temperature between The subsequent ignition loss LOI (weight %) is measured and is a value calculated from the following formula. Specifically, it can be calculated by the method described in Examples. It can be evaluated that the smaller the ignition loss WL on a dry weight basis, the smaller the total number of silanol groups contained in 1 g of abrasive grains.
Ignition loss WL on dry weight basis = 100 x {1-(100-LOI)/(100-LOD)}
The heating temperature for measuring LOD is preferably 105°C or higher, more preferably 120°C or higher, even more preferably 150°C or higher, from the viewpoint of sufficient water evaporation, and from the viewpoint of not evaporating components other than water. , preferably 200°C or lower, more preferably 190°C or lower, and even more preferably 180°C or lower. More specifically, the heating temperature for measuring LOD is preferably 105°C or more and 200°C or less, more preferably 120°C or more and 190°C or less, and even more preferably 150°C or more and 180°C or less.
The heating temperature for measuring LOI is preferably 800°C or higher, more preferably 850°C or higher, even more preferably 900°C or higher, from the viewpoint of sufficient silanol group elimination, and 1200°C or higher from the viewpoint of safety. The temperature is preferably below, more preferably 1150°C or less, and even more preferably 1100°C or less. More specifically, the heating temperature for measuring LOI is preferably 800°C or more and 1200°C or less, more preferably 850°C or more and 1150°C or less, and even more preferably 900°C or more and 1100°C or less.

Examples of methods for adjusting the ignition loss of component A include methods such as adjusting the dropping rate, reaction temperature, and concentration of the silicic acid solution during the growth process of silica particles (for example, as described in Japanese Patent No. 6756422 and Japanese Patent No. 5892882). method described). As another embodiment of the method for adjusting the ignition loss of component A, for example, existing silica particles are subjected to heat treatment, metal modification of surface silanol groups, organic acid modification, or silane coupling treatment to achieve desired ignition loss. Examples include a method of adjusting the loss on ignition, and a method of mixing two or more types of silica particles having different ignition losses to have a desired ignition loss. From the viewpoint of economy and ease of production, the method of adjusting the ignition loss of component A is preferably controlled by the growth conditions of the silica particles, more preferably controlled by the concentration of the silicic acid liquid, and the dropping rate of the silicic acid liquid is controlled. Control by is even more preferred.

As an index showing a stronger correlation than "loss on ignition" with respect to silica residue, "the value expressed by the following formula (I) when WL is the loss on ignition of component A on a dry weight basis" is cited. It will be done. {(WL) ³ ×D90}/100 (I)
By setting the value represented by the above formula (I) to a predetermined value or less, it is possible to achieve both a high silica residue reduction effect and a good polishing rate.
The value represented by the above formula (I), where WL is the loss on ignition of component A on a dry weight basis, is preferably 150 or less, more preferably 100 or less, and 80 or less from the viewpoint of reducing silica residue. More preferably, from the viewpoint of polishing rate maintenance and storage stability, the number is preferably 10 or more, more preferably 20 or more, and even more preferably 40 or more. More specifically, the value represented by the above formula (I) is preferably 10 or more and 150 or less, more preferably 20 or more and 100 or less, and even more preferably 40 or more and 80 or less.

Examples of component A include colloidal silica, wet silica (precipitated silica), fumed silica, ground silica, and surface-modified silica thereof. Component A is preferably at least one selected from colloidal silica and wet silica from the viewpoint of polishing rate maintenance and availability. From the viewpoint of substrate surface quality, component A is preferably at least one selected from colloidal silica and wet silica. Colloidal silica, which is difficult to obtain, is more preferred.
The colloidal silica can be produced, for example, by a method of particle growth using an aqueous alkali silicate solution as a raw material (hereinafter also referred to as "water glass method"), and a method by condensation of a hydrolyzate of alkoxysilane (hereinafter referred to as "sol-gel method"). From the viewpoint of ease of production and economic efficiency, those obtained by the water glass method are preferred. Silica particles obtained by the water glass method and the sol-gel method can be produced by conventionally known methods.
The precipitated silica is silica particles obtained by a precipitation method. Examples of the method for producing precipitated silica particles include known methods such as the method described in Tosoh Research and Technical Report, Vol. 45 (2001), pp. 65-69. A specific example of the precipitation method for producing silica particles includes a precipitation method in which silica particles are precipitated by a neutralization reaction between a silicate such as sodium silicate and a mineral acid such as sulfuric acid. It is preferable to carry out the neutralization reaction under alkaline conditions at a relatively high temperature, whereby the growth of the primary silica particles proceeds rapidly, and the primary particles aggregate into flocs and settle, which is preferably further pulverized. By doing so, precipitated silica particles are obtained.

The shape of component A may be non-spherical or spherical. From the viewpoint of polishing rate maintenance and substrate surface quality, component A preferably contains spherical silica particles and non-spherical silica particles (mixed silica) in one or more embodiments.
In the present disclosure, the average aspect ratio of the spherical silica particles is preferably 1.00 or more, more preferably 1.02 or more from the viewpoint of maintaining polishing rate, and preferably 1.02 or more from the viewpoint of substrate surface quality. It is 20 or less, more preferably 1.1 or less, even more preferably 1.06 or less.
The average aspect ratio of the non-spherical silica particles is preferably 1.00 or more, more preferably 1.02 or more, even more preferably 1.05 or more from the viewpoint of maintaining the polishing rate, and from the viewpoint of substrate surface quality. , preferably 1.30 or less, more preferably 1.15 or less, still more preferably 1.08 or less.
The average aspect ratio is a simple average value of the length/breadth ratio of the minimum inscribed square determined for each particle using a known scanning electron microscope (SEM) and a known image analysis system.
When component A is mixed silica containing spherical silica particles and non-spherical silica particles, preferred numerical values for the average aspect ratio of the mixed silica include the same numerical values as for the above-mentioned non-spherical silica particles. The average aspect ratio of mixed silica can be calculated, for example, by the method described in Examples.

When component A contains non-spherical silica particles, the shape of the non-spherical silica particles is determined by using silica particles as a precursor whose particle size is smaller than the secondary particle size of the non-spherical silica particles from the viewpoint of maintaining polishing rate and substrate surface quality. The particles include a shape in which a plurality of precursor particles are aggregated or fused. Examples of the type of non-spherical silica particles include at least one selected from silica particles Aa of a confectioner's sugar type, silica particles of an irregularly shaped type Ab, and silica particles Ac of an irregular shape and a confetti type.

In the present disclosure, confetti-shaped silica particles Aa (hereinafter also referred to as "particles Aa") refer to silica particles having unique wart-like projections on the spherical particle surface. The particles Aa preferably have 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 together. 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. Particles Aa can be obtained, for example, by the method described in JP-A No. 2008-137822. The particle size of the precursor particle can be determined as the equivalent circle diameter measured within one precursor particle in an image observed by TEM etc., that is, the major axis of a circle having the same area as the projected area of the precursor particle. . The particle diameters of the precursor particles in the irregularly shaped silica particles Ab and the irregularly shaped and confetti-type silica particles Ac can also be determined in the same manner.

In the present disclosure, irregularly 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 together. Refers to silica particles (see Figure 1). Particles Ab preferably have a shape in which two or more precursor particles having a particle size within 1.5 times the particle size of the smallest precursor particle are agglomerated or fused together. Particles Ab can be obtained, for example, by the method described in JP-A-2015-86102.

In the present disclosure, irregularly shaped and confetti-shaped silica particles Ac (hereinafter also referred to as "particles Ac") include the particles Ab as precursor particles c1, the largest precursor particle c1, and the particle size of the precursor particle c1. One or more precursor particles c2 whose size is 1/5 or less are aggregated or fused together.

The content of component A in the polishing liquid composition of the present disclosure is preferably 0.1% by mass or more, more preferably 0.5% by mass or more in terms of SiO ₂ from the viewpoint of maintaining polishing rate and substrate surface quality. , more preferably 1% by mass or more, even more preferably 1.5% by mass or more, and from the viewpoint of economy, preferably 30% by mass or less, more preferably 20% by mass or less, even more preferably 15% by mass or less. , 10% by mass or less is even more preferred. More specifically, the content of component A is preferably 0.1% by mass or more and 30% by mass or less, more preferably 0.5% by mass or more and 20% by mass or less, and even more preferably 1% by mass or more and 15% by mass or less. It is preferably 1.5% by mass or more and 10% by mass or less, even more preferably. When component A consists of two or more types of silica particles, the content of component A refers to their total content.

When component A contained in the polishing liquid composition of the present disclosure includes spherical silica particles and non-spherical silica particles, the proportion of spherical silica particles in component A should be 10% or more from the viewpoint of maintaining polishing rate and substrate surface quality. It is preferably 20% or more, still more preferably 30% or more, and preferably less than 100%, more preferably 80% or less, and even more preferably 70% or less. From the same viewpoint, the proportion of non-spherical silica particles in component A is preferably 90% or less, more preferably 80% or less, even more preferably 70% or less, and preferably more than 0%, more preferably 20% or more. , more preferably 30% or more.

[Aqueous medium]
Examples of the aqueous medium included in the polishing liquid composition of the present disclosure include water such as distilled water, ion exchange water, pure water, and ultrapure water, or a mixed solvent of water and a solvent. Examples of the solvent include solvents that are miscible with water (for example, alcohols such as ethanol). When the aqueous medium is a mixed solvent of water and a solvent, the proportion of water to the entire mixed medium may not be particularly limited as long as the effects of the present disclosure are not hindered, and from an economical point of view, for example, , is preferably 95% by mass or more, more preferably 98% by mass or more, and even more preferably substantially 100% by mass.
The content of the aqueous medium in the polishing liquid composition of the present disclosure can be the remainder after removing component A and optional components (component B, component C, and other components) that will be described later and are added as necessary. .

[Acid (component B)]
The polishing liquid composition of the present disclosure may contain an acid (hereinafter also referred to as "component B") from the viewpoint of further improving the polishing rate and further reducing short wavelength waviness. In this disclosure, the use of acids includes the use of acids and/or salts thereof. Component B may be used alone or in combination of two or more.
Component B includes, for example, 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, amidosulfuric acid; organic phosphoric acid, organic phosphonic acid; organic acids such as acids; and the like. Among them, from the viewpoint of further improving the polishing rate and further reducing short wavelength waviness, as component B, at least one selected from phosphoric acid, sulfuric acid and 1-hydroxyethylidene-1,1-diphosphonic acid is preferable. At least one selected from sulfuric acid and phosphoric acid is more preferred, and phosphoric acid is even more preferred. Examples of the salts of these acids include salts of the above acids and at least one selected from metals, ammonia, and alkyl amines. Specific examples of the above metals include metals belonging to groups 1 to 11 of the periodic table. Among these, salts of the above acids and metals belonging to Group 1 or ammonia are preferred from the viewpoint of further improving the polishing rate and further reducing short wavelength waviness.

When the polishing liquid composition of the present disclosure contains component B, the content of component B in the polishing liquid composition of the present disclosure is set to 0. 0.001% by mass or more is preferred, 0.01% by mass or more is more preferred, 0.05% by mass or more is even more preferred, 0.1% by mass or more is even more preferred, and from the same point of view, 5% by mass or less It is preferably 4% by mass or less, more preferably 3% by mass or less, even more preferably 2.5% by mass or less. More specifically, the content of component B is preferably 0.001% by mass or more and 5% by mass or less, more preferably 0.01% by mass or more and 4% by mass or less, and 0.05% by mass or more and 3% by mass or less. is more preferable, and even more preferably 0.1% by mass or more and 2.5% by mass or less. When component B is a combination of two or more types, the content of component B refers to their total content.

[Oxidizing agent (component C)]
The polishing liquid composition of the present disclosure may contain an oxidizing agent (hereinafter also referred to as "component C") from the viewpoint of further improving the polishing rate and further reducing short wavelength waviness. Component C may be used alone or in combination of two or more.
From the same point of view, component C includes, for example, peroxides, permanganic acid or its salts, chromic acid or its salts, peroxo acids or its salts, oxygen acids or its salts, nitric acids, sulfuric acids, etc. . Among these, as component C, at least one selected from hydrogen peroxide, iron(III) nitrate, peracetic acid, ammonium peroxodisulfate, iron(III) sulfate, and ammonium iron(III) sulfate is preferable, and it is preferable for improving the polishing rate. Hydrogen peroxide is more preferable from the viewpoint of preventing metal ions from adhering to the surface of the substrate to be polished and from the viewpoint of easy availability.

When the polishing liquid composition of the present disclosure contains component C, the content of component C in the polishing liquid composition of the present disclosure is preferably 0.01% by mass or more from the viewpoint of further improving the polishing rate, It is more preferably 0.05% by mass or more, even more preferably 0.1% by mass or more, and from the viewpoint of further improving the polishing rate and further reducing short wavelength waviness, it is preferably 4% by mass or less, and 2% by mass. The following is more preferable, and 1.5% by mass or less is even more preferable. More specifically, the content of component C is preferably 0.01% by mass or more and 4% by mass or less, more preferably 0.05% by mass or more and 2% by mass or less, and 0.1% by mass or more and 1.5% by mass. % or less is more preferable. When component C is a combination of two or more types, the content of component C refers to their total content.

[Other ingredients]
The polishing liquid composition of the present disclosure may contain other components as necessary. Other components include corrosion inhibitors, thickeners, dispersants, rust preventives, basic substances, surfactants, water-soluble polymers, and the like. The other components are preferably contained in the polishing liquid composition within a range that does not impair the effects of the present disclosure. When containing other components, the content of the other components in the polishing liquid composition of the present disclosure is preferably 0% by mass or more, more preferably more than 0% by mass, and further preferably 0.1% by mass or more. The content is preferably 10% by mass or less, and more preferably 5% by mass or less. More specifically, it is preferably from 0% by mass to 10% by mass, more preferably from more than 0% by mass to 10% by mass, even more preferably from 0.1% by mass to 10% by mass, and from 0.1% by mass to 5% by mass. It is more preferably less than % by mass.

[Alumina abrasive]
The polishing liquid composition of the present disclosure preferably does not substantially contain alumina abrasive grains from the viewpoint of reducing protrusion defects. In the present disclosure, "substantially not containing alumina abrasive grains" means, in one or more embodiments, not containing alumina particles, not containing alumina particles in an amount that functions as abrasive grains, or not containing alumina particles in an amount that functions as abrasive grains, or polishing results. and not containing alumina particles in an amount that affects the amount of alumina particles. Specifically, in one or more embodiments, the content of alumina abrasive grains in the polishing liquid composition of the present disclosure is preferably 5% by mass or less, and 2% by mass or less from the viewpoint of reducing protrusion defects. More preferably 1% by mass or less, still more preferably 0.1% by mass or less, even more preferably 0.05% by mass or less, even more preferably 0.02% by mass or less, even more preferably substantially 0% by mass. . Further, in one or more embodiments, the content of alumina particles in the polishing liquid composition of the present disclosure is preferably 2% by mass or less, and 1% by mass or less with respect to the total amount of abrasive grains in the polishing liquid composition. It is more preferably 0.5% by mass or less, even more preferably substantially 0% by mass.

[pH]
From the viewpoint of substrate surface quality, the pH of the polishing liquid composition of the present disclosure is preferably 0.5 or higher, more preferably 0.7 or higher, even more preferably 0.9 or higher, and even more preferably 1 or higher, and From the viewpoint of maintaining the polishing rate, it is preferably 9 or less, more preferably 6 or less, even more preferably 4 or less, even more preferably 3 or less, even more preferably 2.5 or less, and even more preferably 2 or less. More specifically, the pH of the polishing liquid composition of the present disclosure is preferably 0.5 or more and 9 or less, more preferably 0.5 or more and 6 or less, even more preferably 0.7 or more and 4 or less, and 1 or more and 3 or less. is more preferable, more preferably 1 or more and 2.5 or less, even more preferably 1 or more and 2 or less. The pH can be adjusted using the above-mentioned acid (component B) or a known pH adjuster. The above pH is the pH of the polishing liquid composition at 25° C., and can be measured using a pH meter, preferably the value obtained 2 minutes after immersing the electrode of the pH meter in the polishing liquid composition.

[Method for manufacturing polishing liquid composition]
The polishing liquid composition of the present disclosure can be produced, for example, by blending component A, an aqueous medium, and optional components (component B, component C, and other components) by a known method. Therefore, in one embodiment, the present disclosure relates to a method for producing a polishing liquid composition, which includes a step of blending at least component A and an aqueous medium. In the present disclosure, "blending" includes mixing component A, an aqueous medium, and optional components (component B, component C, and other components) simultaneously or in any order. The blending can be performed using a mixer such as a homomixer, a homogenizer, an ultrasonic disperser, and a wet ball mill. The preferred content of each component in the method for producing a silica slurry and polishing liquid composition can be the same as the preferred content of each component in the polishing liquid composition according to the present disclosure described above.

In the present disclosure, "the content of each component in the polishing liquid composition" refers to the content of each of the components at the time of use, that is, at the time when the polishing liquid composition starts to be used for polishing.
The polishing liquid composition of the present disclosure may be stored and supplied in a concentrated state as long as its storage stability is not impaired. This case is preferable in that manufacturing and transportation costs can be further reduced. The concentrate of the polishing liquid composition of the present disclosure may be appropriately diluted with the above-mentioned water as necessary at the time of use.

[Polishing liquid kit]
In one aspect, the present disclosure provides a polishing liquid kit for manufacturing the polishing liquid composition of the present disclosure, the kit comprising a container containing a silica dispersion containing component A and an aqueous medium. , relates to a polishing liquid kit (hereinafter also referred to as "polishing liquid kit of the present disclosure"). The polishing liquid kit according to the present disclosure can further include an additive aqueous solution containing at least one of component B and component C, which is housed in a container separate from the container-packed silica dispersion. According to the present disclosure, in one or more embodiments, it is possible to obtain a polishing liquid composition that can improve the polishing rate without significantly increasing the amount of residual silica. In one or more other embodiments, it is possible to obtain a polishing liquid composition that can reduce silica residue on the substrate surface after polishing while maintaining the polishing rate.
In one or more embodiments, the polishing liquid kit of the present disclosure includes, for example, a silica dispersion (slurry) containing component A and an aqueous medium, and optionally an additive aqueous solution containing component B and component C. Examples include a polishing liquid kit (two-component polishing liquid composition) in which the components are not mixed with each other, are mixed at the time of use, and are diluted with an aqueous medium as necessary. The aqueous medium contained in the silica dispersion may be the entire amount or a portion of the aqueous medium used for preparing the polishing liquid composition. The silica dispersion liquid and the additive aqueous solution may each contain the other components mentioned above as necessary.

[Substrate to be polished]
In one or more embodiments, the substrate to be polished is a substrate used for manufacturing a magnetic disk substrate, and includes, for example, an aluminum alloy substrate plated with Ni--P. In the present disclosure, "Ni--P plated aluminum alloy substrate" refers to an aluminum alloy base material whose surface is ground and then subjected to electroless Ni--P plating. After the step of polishing the surface of the substrate to be polished using the polishing liquid composition of the present disclosure, a magnetic disk substrate can be manufactured by performing a step of forming a magnetic layer on the surface of the substrate by sputtering or the like. The shape of the substrate to be polished includes, for example, a shape having a flat portion such as a disk shape, a plate shape, a slab shape, a prism shape, and a shape having a curved surface portion such as a lens. Preferably, the shape of the substrate to be polished is a disk shape. be. In the case of a disc-shaped substrate to be polished, its outer diameter is, for example, 10 to 120 mm, and its thickness is, for example, 0.5 to 2 mm.

Generally, a magnetic disk is manufactured by subjecting a polished substrate that has undergone a grinding process to a rough polishing process, a final polishing process, and a magnetic layer forming process. In one or more embodiments, the polishing liquid composition of the present disclosure is preferably used for polishing in a rough polishing step. In one or more embodiments, the polishing liquid composition of the present disclosure is a polishing liquid composition for magnetic disk substrates.

[Method for reducing silica residue]
In one aspect, the present disclosure provides a method for reducing silica residue on a substrate after polishing, the method comprising polishing a substrate to be polished using the polishing liquid composition of the present disclosure (hereinafter referred to as (also referred to as "method for reducing silica residue of the present disclosure"). Examples of the substrate to be polished in the method for reducing silica residue of the present disclosure include the substrate to be polished described above.
In one or more embodiments, the method for reducing silica residue of the present disclosure may further include selecting silica particles A (component A) contained in the polishing liquid composition of the present disclosure. In the present disclosure, "selecting silica particles A" refers to a product that has a description in the catalog, product manual, label, etc. of the physical properties of silica particles A (component A) and/or that it can reduce silica residue. including purchasing.
Therefore, in one or more embodiments, the method for reducing silica residue of the present disclosure includes selecting silica particles A (component A), and polishing liquid of the present disclosure containing the selected silica particles A (component A). The present invention relates to a method for reducing silica residue, which includes polishing a substrate to be polished using a composition.
In another aspect of the present disclosure, the abrasive grains have an ignition loss of 4% or less on a dry basis, and a cumulative frequency of 90% from the small particle size side in the particle size distribution in terms of weight obtained by centrifugal sedimentation. Selecting silica particles whose D90 is 140 nm or more and 600 nm or less, and polishing the substrate to be polished using a polishing liquid composition containing the silica particles and an aqueous medium. The present invention relates to a method for reducing silica residue, including: Examples of the silica particles in the method for reducing silica residue of this embodiment include the above-mentioned silica particles A (component A). Examples of the polishing liquid composition in the silica residue reduction method of this embodiment include the polishing liquid composition of the present disclosure described above.
According to the silica residue reduction method of the present disclosure, by using the polishing liquid composition of the present disclosure, the polishing rate can be improved without significantly increasing the silica residue in one or more embodiments. Furthermore, in one or more embodiments, the amount of silica remaining on the surface of the substrate after polishing can be reduced while maintaining the polishing rate. The specific polishing method and conditions can be the same as in the substrate manufacturing method of the present disclosure, which will be described later.

[Polishing method]
In one aspect, the present disclosure includes polishing a substrate to be polished using the polishing liquid composition of the present disclosure, the substrate to be polished being a substrate used for manufacturing a magnetic disk substrate, a method for polishing a substrate. (hereinafter also referred to as "polishing method of the present disclosure"). Examples of the substrate to be polished in the polishing method of the present disclosure include the substrate to be polished described above. The polishing method of the present disclosure can be used, for example, in a rough polishing step.
According to the polishing method of the present disclosure, by using the polishing liquid composition of the present disclosure, in one or more embodiments, the polishing rate can be improved without significantly increasing the amount of residual silica. Further, according to the polishing method of the present disclosure, in one or more embodiments, it is possible to reduce the amount of silica remaining on the substrate surface after polishing while maintaining the polishing rate. Therefore, the productivity of substrates (for example, magnetic disk substrates) with improved substrate quality can be improved. The specific polishing method and conditions can be the same as in the substrate manufacturing method of the present disclosure, which will be described later.

[Method for manufacturing magnetic disk substrate]
In one aspect, the present disclosure provides a method for manufacturing a magnetic disk substrate (hereinafter referred to as "the present invention"), which includes a polishing step (hereinafter also referred to as "polishing step") of polishing a substrate to be polished using the polishing liquid composition of the present disclosure. (Also referred to as "Disclosed Substrate Manufacturing Method"). The polishing step in the substrate manufacturing method of the present disclosure is, for example, a rough polishing step.
In one or more embodiments, the substrate manufacturing method of the present disclosure may further include a step of selecting silica particles A (component A) contained in the polishing liquid composition of the present disclosure. In the present disclosure, "selecting silica particles A" means, as described above, information in catalogs, product manuals, labels, etc. that indicates the physical properties of silica particles A (component A) and/or that silica residue can be reduced. Including purchasing the products listed.
Therefore, in one or more embodiments, the substrate manufacturing method of the present disclosure includes a step of selecting silica particles A (component A), and a polishing liquid composition of the present disclosure containing the selected silica particles A (component A). The present invention relates to a method for manufacturing a magnetic disk substrate, including a step of polishing a substrate to be polished using a material.
In another aspect of the present disclosure, the abrasive grains have an ignition loss of 4% or less on a dry basis, and a cumulative frequency of 90% from the small particle size side in the particle size distribution in terms of weight obtained by centrifugal sedimentation. A step of selecting silica particles whose D90 is 140 nm or more and 600 nm or less when the particle diameter of % is D90, and a step of polishing a substrate to be polished using a polishing liquid composition containing the silica particles and an aqueous medium. The present invention relates to a method of manufacturing a magnetic disk substrate, including: Examples of the silica particles in the method for manufacturing a magnetic disk substrate of this embodiment include the above-mentioned silica particles (component A). Examples of the polishing liquid composition in the method of manufacturing a magnetic disk substrate of this embodiment include the polishing liquid composition of the present disclosure described above.

In the polishing step, for example, the substrate to be polished is sandwiched between surface plates to which a polishing pad is attached, the polishing liquid composition of the present disclosure is supplied to the polishing surface, and the polishing pad and the substrate to be polished are moved while applying pressure. , the substrate to be polished can be polished.

The polishing load in the polishing step is preferably 3 kPa or more, more preferably 5 kPa or more, even more preferably 7 kPa or more, and preferably 30 kPa or less, more preferably 25 kPa or less, from the viewpoint of maintaining the polishing rate and reducing short wavelength waviness. , 20 kPa or less is more preferable. More specifically, the polishing load is preferably 3 kPa or more and 30 kPa or less, more preferably 5 kPa or more and 25 kPa or less, and even more preferably 7 kPa or more and 20 kPa or less. In the present disclosure, "polishing load" refers to the pressure of a 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, substrate, or the like.

In the polishing step, the polishing amount per 1 cm ² of the substrate to be polished is preferably 0.2 mg or more, more preferably 0.3 mg or more, and still more preferably 0.4 mg or more, from the viewpoint of maintaining the polishing rate and reducing short wavelength waviness. Preferably, and from the same viewpoint, the amount is preferably 2.5 mg or less, more preferably 2 mg or less, and even more preferably 1.6 mg or less. More specifically, the amount of polishing per 1 cm ² of the substrate to be polished is preferably 0.2 mg or more and 2.5 mg or less, more preferably 0.3 mg or more and 2 mg or less, and even more preferably 0.4 mg or more and 1.6 mg or less.

The supply rate of the polishing liquid composition per 1 cm ² of the substrate to be polished in the polishing step is preferably 2.5 mL/min or less, more preferably 2 mL/min or less, and 1.5 mL/min or less from an economical point of view. More preferably, from the viewpoint of improving the polishing rate, the rate is preferably 0.01 mL/min or more, more preferably 0.03 mL/min or more, and even more preferably 0.05 mL/min or more. More specifically, the supply rate of the polishing liquid composition per 1 cm ² of the substrate to be polished is preferably 0.01 mL/min or more and 2.5 mL/min or less, more preferably 0.03 mL/min or more and 2 mL/min or less. , more preferably 0.05 mL/min or more and 1.5 mL/min or less.

Examples of a method for supplying the polishing liquid composition of the present disclosure to a polishing machine include a method of continuously supplying the polishing composition using a pump or the like. When supplying the polishing liquid composition to the polishing machine, in addition to supplying it as a single liquid containing all the components, it is also possible to divide it into multiple component liquids in consideration of the storage stability of the polishing liquid composition. , it is also possible to supply two or more liquids. In the latter case, the plurality of compounding component liquids are mixed, for example, in the supply piping or on the substrate to be polished, to form the polishing liquid composition of the present disclosure.

According to the substrate manufacturing method of the present disclosure, by using the polishing liquid composition of the present disclosure, in one or more embodiments, the polishing rate can be improved without significantly increasing the amount of residual silica. Further, according to the substrate manufacturing method of the present disclosure, in one or more embodiments, the amount of silica remaining on the substrate surface after polishing can be reduced while maintaining the polishing rate. Therefore, it is possible to efficiently manufacture a substrate (for example, a magnetic disk substrate) with improved substrate quality.

Hereinafter, the present disclosure will be explained in more detail with reference to Examples, but these are merely illustrative and the present disclosure is not limited to these Examples.

1. Preparation of polishing liquid composition Silica particles (component A or non-component A), acid (component B), oxidizing agent (component C), and water are mixed and Examples 1 to 5 and Comparative Examples 1 to 1 shown in Table 1 are prepared. A polishing liquid composition of No. 2 was prepared. The content (effective content) of each component in the polishing liquid composition is as follows: silica particles (component A): 5.5% by mass, acid (component B): 1.6% by mass, oxidizing agent (component C): 1 It was expressed as mass%. The water content is the remainder after removing component A, component B, and component C. The polishing liquid compositions of Examples 1 to 5 and Comparative Examples 1 to 2 do not contain alumina abrasive grains. The silica particles (component A) used as the abrasive grains were manufactured by the water glass method. The pH of the polishing liquid compositions of Examples 1 to 5 and Comparative Examples 1 to 2 was 1.5. The pH was measured at 25° C. using a pH meter (manufactured by Toa DKK Co., Ltd.), and the value obtained 2 minutes after immersing the electrode in the polishing liquid composition was adopted.

The following components were used as component A, non-component A, component B, and component C used in preparing the polishing liquid composition.
<Silica particles (component A or non-component A)>
(Preparation of silica particles A1 to A5)
Particle size is determined by intermittently dropping 7 kg of an acidic silicate solution adjusted to a silica concentration of 5% to 500 g of a metal silicate aqueous solution adjusted to a pH of 10 to 12 and a silica concentration of 2% over a period of 1 to 24 hours. increase (build up). At this time, by adjusting the dropping rate, silicic acid concentration, reaction temperature, pressure, pH, etc. of the dropping liquid, silica abrasive grains having silanol groups in a desired range can be obtained. In particular, by slowing down the dropping rate and growing the particles slowly, a dense surface and internal structure are formed, and the number of siloxane bonds increases, making it possible to adjust the silanol groups and the loss on ignition.
Silica particles A1 to A5 shown below were prepared by the above manufacturing method.
A1: Non-spherical silica particles [colloidal silica (water glass method), aspect ratio 1.11, average secondary particle diameter 143 nm]
A2: Non-spherical silica particles [colloidal silica (water glass method), aspect ratio 1.19, average secondary particle diameter 221 nm]
A3: Non-spherical silica particles [colloidal silica (water glass method), aspect ratio 1.09, average secondary particle diameter 160 nm]
A4: Non-spherical silica particles [colloidal silica (water glass method), aspect ratio 1.11, average secondary particle diameter 162 nm]
A5: Non-spherical silica particles [colloidal silica (water glass method), aspect ratio 1.12, average secondary particle diameter 142 nm]
In Example 3, non-spherical silica particles A1 (aspect ratio 1.11, average secondary particle diameter 143 nm, loss on ignition 2.02%) and spherical colloidal silica SCS1 (aspect ratio 1.03, average secondary particle diameter 106 nm) were used. , loss on ignition 3.4%) in a weight ratio A1/SCS1 = 70/30 (mixed silica, aspect ratio 1.06, average secondary particle diameter 133 nm, loss on ignition 3.24%) ) was used as the silica abrasive grain.
(Details of silica particles A6)
A6: Non-spherical silica particles [precipitation method silica, Nipsil E-743 manufactured by Tosoh Silica Co., Ltd. was crushed using a wet bead mill to adjust the average secondary particle diameter, aspect ratio 1.34, average secondary particle diameter 349 nm ]
<Acid (component B)>
Phosphoric acid [concentration 75%, manufactured by Nihon Kagaku Kogyo Co., Ltd.]
<Oxidizing agent (component C)>
Hydrogen peroxide [concentration 35% by mass, manufactured by ADEKA]

2. Method for measuring each parameter [Method for measuring particle diameters D10, D50, and D90 of silica particles by centrifugal sedimentation method (CPS measurement)]
Silica particles were diluted with ion-exchanged water to prepare a dispersion containing 0.4% by mass of silica particles, which was used as a sample. In Example 3 (mixed silica), the mass ratio of non-spherical silica particles A1 and spherical silica particles SCS1 was 70/30.
The particle size distribution of the prepared sample was measured by centrifugal sedimentation using the following measuring device. The particle sizes at which the cumulative frequency from the small diameter side is 10%, 50%, and 90% in the weight-based particle size distribution obtained by centrifugal sedimentation were defined as D10, D50, and D90, respectively.
<Measurement conditions>
Measuring device: “CPS DC24000 UHR” manufactured by CPS Instruments
Measurement range: 0.02~3μm
Particle extinction coefficient: 0.1
Particle shape factor: 1.2 or 1.0
Rotation speed: 18,000rpm
Calibration standard particle size: 0.476μm
Standard particle density: 1.0465 (13%, 34°C)
Density gradient solution: sucrose aqueous solution (8%, 24%)
Solvent viscosity: 1.16 cp (13%, 34°C)
Refractive index of solvent: 1.3592 (18%, 34°C)
Measurement temperature: 15-45℃
Measurement time: 3-420 minutes

[Method for measuring particle diameter D50 (average secondary particle diameter) of silica particles by DLS measurement]
Silica particles were mixed with phosphoric acid and ion-exchanged water to prepare a 1% by mass silica particle dispersion. In Example 3 (mixed silica), the mass ratio of non-spherical silica particles A1 and spherical silica particles SCS1 was 70/30. The prepared 1% by mass silica particle dispersion was placed in the following measuring device and measured under the following conditions. In the obtained particle size distribution, the particle size at which the cumulative volume frequency from the small diameter side is 50% was defined as D50. In addition, D50 by DLS was taken as the average secondary particle diameter (volume average particle diameter) of silica particles. The measurement results are shown in Table 1.
<Measurement conditions>
Measuring equipment: Malvern Zetasizer Nano “Nano S”
Sample amount: 1.5mL
Laser: He-Ne, 3.0mW, 633nm
Scattered light detection angle: 173°

[Average aspect ratio of silica particles]
A photograph of silica particles observed with a TEM (JEOL Ltd. "JEM-2000FX", 80 kV, 10,000 to 50,000 times) was imported into a personal computer as image data using a scanner, and an analysis software (Mitani Shoji "WinROOF (Ver. 3) The projected images of 500 silica particles were analyzed using the following method.
The short axis and long axis of each silica particle were determined, and the average value of the aspect ratio (average aspect ratio) was obtained from the value obtained by dividing the long axis by the short axis.
The average aspect ratio in the case of the mixed silica of Example 3 was determined by blending so that the mass ratio of non-spherical silica particles A1 and spherical silica particles SCS1 was 70/30, and then drying and performing TEM observation. It was calculated using the short axis to long axis ratio in the analysis.

[Ignition loss]
Silica particles were mixed with ion-exchanged water to prepare a 40% by mass silica slurry. In Example 3 (mixed silica), the mass ratio of non-spherical silica particles A1 and spherical silica particles SCS1 was 70/30.
The prepared silica slurry was adjusted to pH=3.5 with sulfuric acid and heated at 180° C. using an infrared moisture meter “MOC63u” manufactured by Shimadzu Corporation to remove moisture. Thereafter, the sample was allowed to stand for 10 minutes and returned to room temperature to obtain 2 g of sample. Among them, 1 g of the sample is used again to determine the loss on drying LOD (how much moisture is absorbed at room temperature) using an infrared moisture meter. The remaining 1 g of the sample was placed in a ceramic crucible and fired at 1000° C. for 2 hours in a firing furnace, and after dissipating the heat in a desiccator for 30 minutes, the loss on ignition LOI (weight lost due to dehydration of silanol groups) was determined. Note that since silica particles tend to absorb water, it is preferable to avoid measurements indoors or outdoors where the humidity exceeds 80%, as this will affect accuracy. Similarly, if the standing time after firing exceeds 30 minutes, measurement accuracy will be affected, so it is more preferable to avoid this.
Finally, the ignition loss WL on a dry weight basis was determined using the following formula.
Ignition loss WL on dry weight basis = 100 x {1-(100-LOI)/(100-LOD)}

3. Polishing of Substrate Using the prepared polishing liquid compositions of Examples 1 to 5 and Comparative Examples 1 to 2, a substrate to be polished was polished under the following polishing conditions.

[Polishing conditions]
Polishing machine: Double-sided polishing machine (9B type double-sided polishing machine, manufactured by Speed Fam)
Substrate to be polished: Ni-P plated aluminum alloy substrate, thickness 0.8 mm, diameter 95 mm, number of 10 pieces Polishing liquid: Polishing liquid composition Polishing pad: Suede type (foam layer: polyurethane elastomer, thickness 1.0 mm, Average pore diameter 30 μm, surface layer compressibility 2.5%, manufactured by Filwel)
Surface plate rotation speed: 40 rpm
Polishing load: 9.8kPa (set value)
Polishing liquid supply amount: 100mL/min
Supply rate per 1 cm ² of substrate to be polished 0.8 mL/min Amount of polishing per 1 cm ² of substrate to be polished 0.8 mg
Polishing time: 5 minutes

4. Evaluation method [Evaluation of polishing speed]
The polishing rates of the polishing liquid compositions of Examples 1 to 5 and Comparative Examples 1 to 2 were evaluated as follows. First, the weight of each substrate before and after polishing was measured using a "BP-210S" manufactured by Sartorius, and the amount of mass loss was determined from the change in mass of each substrate. The polishing rate was calculated by dividing the average mass loss of all 10 sheets by the polishing time, and incorporating it into the following formula. Then, the relative value when the polishing rate of Comparative Example 1 was set to 100 was calculated and used as an evaluation item.
Mass reduction amount (g) = {mass before polishing (g) - mass after polishing (g)}
Polishing speed (g/min) = mass reduction amount (g) / polishing time (min)

[Evaluation of remaining silica]
After the substrate after polishing was washed using a cleaning machine manufactured by Hikari Co., Ltd., the intensity of the silica particles remaining on the substrate surface was measured using a fluorescent X-ray "ZSX100e" manufactured by Rigaku Co., Ltd. Details are listed below. Then, the relative value when the remaining silica of Comparative Example 1 was set as 100 was calculated and used as an evaluation item.
[Cleaning conditions]
Ultrapure water immersion time: 3 minutes Ultrasonic cleaning time: 3 minutes Brush cleaning time: 4 seconds Ultrapure water rinsing time: 10 seconds Spin dry drying time: 10 seconds [Fluorescent X-ray measurement conditions]
The substrate after polishing and cleaning was placed in the apparatus without being cut, and the peak intensity of the Si element was detected as an indicator of the remaining silica. The lower the peak intensity of the Si element, the less silica remains.
Measurement time: 300 seconds Opening degree: 30mm
Detection angle: 2θ=47degree
Peak detection angle: 144.610
Voltage: 50kv
Current: 50mA
Detection points: 8 arbitrary points per board As measured above, by feeding the board into the device without cutting it, there is a risk of silica remaining falling off due to the impact when cutting the board, foreign matter contamination, and the risk of contamination per board. The effects of variation can be reduced.

5. Results The results of each evaluation are shown in Table 1.

As shown in Table 1, the polishing liquid compositions of Examples 1 to 5 using predetermined silica particles (component A) were able to maintain the polishing rate and remove silica residue compared to Comparative Examples 1 and 2. It was found that this can be reduced.

According to the present disclosure, in one aspect, the polishing rate can be improved without significantly increasing the amount of silica remaining, and in another aspect, the amount of silica remaining on the substrate surface after polishing can be reduced while maintaining the polishing rate. , the productivity of substrates with improved substrate quality can be improved. The present disclosure can be suitably used for manufacturing a magnetic disk substrate.

Claims (12)

Contains silica particles and an aqueous medium,
The silica particles have an ignition loss of 4% or less on a dry weight basis,
The silica particles are a polishing liquid having D90 of 140 nm or more and 600 nm or less, where D90 is the particle size at which the cumulative frequency from the small particle size side is 90% in the weight-based particle size distribution obtained by centrifugal sedimentation. Composition. The polishing liquid composition according to claim 1, wherein a value represented by the following formula (I) is 150 or less, where WL is the loss on ignition.
{(WL) ³ ×D90}/100 (I) The polishing liquid composition according to claim 1 or 2, wherein the silica particles have a D10 of 50 nm or more and 120 nm or less, where D10 is the particle size at which the cumulative frequency from the small particle size side is 10% in the particle size distribution. thing. The silica particles according to any one of claims 1 to 3, have a D50 of 80 nm or more and 340 nm or less, where D50 is the particle size at which the cumulative frequency from the small particle size side is 50% in the particle size distribution. Polishing liquid composition. The polishing liquid composition according to any one of claims 1 to 4, wherein the silica particles include spherical silica particles and non-spherical silica particles. The polishing liquid composition according to any one of claims 1 to 5, wherein the polishing liquid composition is a polishing liquid composition for magnetic disk substrates. A method for manufacturing a magnetic disk substrate, comprising a polishing step of polishing a substrate to be polished using the polishing liquid composition according to any one of claims 1 to 6. 8. The method for manufacturing a magnetic disk substrate according to claim 7, wherein the substrate to be polished is an aluminum alloy substrate plated with Ni--P. The method for manufacturing a magnetic disk substrate according to claim 7 or 8, wherein the polishing step is a rough polishing step. A method for polishing a substrate, the method comprising polishing a substrate to be polished using the polishing liquid composition according to any one of claims 1 to 6, wherein the substrate to be polished is a substrate used for manufacturing a magnetic disk substrate. . A method for reducing silica residue on a substrate after polishing, the method comprising:
A method for reducing silica residue, comprising polishing a substrate to be polished using the polishing liquid composition according to any one of claims 1 to 6. As an abrasive grain, D90 is a particle size that has an ignition loss of 4% or less on a dry weight basis and has a cumulative frequency of 90% from the small particle size side in the particle size distribution in terms of weight obtained by centrifugal sedimentation. a step of selecting silica particles whose D90 is 140 nm or more and 600 nm or less, and
A method for manufacturing a magnetic disk substrate, comprising the step of polishing a substrate to be polished using a polishing liquid composition containing the silica particles and an aqueous medium.