WO2017094592A1

WO2017094592A1 - Polishing liquid composition for magnetic disk substrate

Info

Publication number: WO2017094592A1
Application number: PCT/JP2016/084837
Authority: WO
Inventors: 多久島大樹; 山口哲史; 木村陽介
Original assignee: 花王株式会社
Priority date: 2015-11-30
Filing date: 2016-11-24
Publication date: 2017-06-08
Also published as: TW201727626A; MY187480A; JPWO2017094592A1; GB201809369D0; JP6771484B2; TWI723085B; GB2560842A

Abstract

Provided is a polishing liquid composition for a magnetic disk substrate, the polishing liquid composition being capable of reducing post-polishing long wavelength waviness without significantly impairing polishing speed in rough polishing. The present invention pertains to a polishing liquid composition for a magnetic disk substrate, the polishing liquid composition containing non-spherical silica particles A, spherical silica particles B, and water, and having a pH value of 0.5-6.0, wherein the average minor diameter of the non-spherical silica particles A is greater than or equal to 105 mm and greater than the average minor diameter of the spherical silica particles B.

Description

Polishing liquid composition for magnetic disk substrate

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

Therefore, a polishing composition containing no silica particles and containing silica particles as abrasive grains has been proposed (Patent Documents 1 to 7).

JP 2014-1116057 A JP 2012-111869 A JP 2014-29754 A JP2015-203108A Japanese Patent Laying-Open No. 2015-204127 JP 2014-210912 A JP 2010-192904 A

In the conventional polishing liquid composition in which silica particles are used in place of alumina particles, alumina residue due to alumina adhesion or sticking is suppressed, and projection defects on the substrate surface after polishing can be reduced. However, when rough polishing is performed with a polishing composition comprising silica particles instead of alumina particles, long-wave waviness on the substrate surface after polishing becomes a problem. And in order to reduce the long wavelength wave | undulation in rough | crude grinding | polishing, a polishing time longer than the polishing liquid composition containing an alumina particle is required, and there exists a problem that productivity falls.

Therefore, the present disclosure provides a polishing composition for a magnetic disk substrate that can reduce long-wave waviness on a substrate surface after rough polishing without greatly 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, spherical silica particles B, and water, the pH is 0.5 or more and 6.0 or less, and the average minor axis of the non-spherical silica particles A is 105 nm or more, The present invention also relates to a polishing composition for a magnetic disk substrate, which is larger than the average minor axis of the spherical silica particles B.

The present disclosure includes at least non-spherical silica particles A, spherical silica particles B, and water, and has a pH of 0.5 or more and 6.0 or less, and the average minor axis of the non-spherical silica particles A is 105 nm. The present invention relates to a polishing composition for a magnetic disk substrate, which is larger than the average minor axis of the spherical silica particles B.

The present disclosure includes a step of blending at least non-spherical silica particles A, spherical silica particles B, and water, the average minor axis of the non-spherical silica particles A is 105 nm or more, and the spherical silica particles B The present invention relates to a method for producing a silica slurry that is larger than an average minor axis and is used for producing a polishing liquid composition for a magnetic disk substrate.

The present disclosure relates to a method for manufacturing a magnetic disk substrate including 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, it is possible to achieve the effect of reducing the long wavelength waviness of the substrate surface after the rough polishing 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. FIG. 3 is an example of a TEM observation photograph of precipitated silica abrasive grains.

The present disclosure uses a polishing composition containing non-spherical silica particles having an average minor axis larger than spherical silica particles as abrasive grains together with spherical silica particles for rough polishing, without significantly reducing the polishing rate. Based on the knowledge that wavelength waviness can be reduced. In general, in the manufacture of a magnetic disk substrate, productivity can be improved if long-wave waviness can be reduced.

The details of the mechanism that can reduce long wavelength waviness without significantly reducing the polishing rate by using non-spherical silica particles having an average shorter diameter than spherical silica particles as abrasive grains together with spherical silica particles are not clear, but the following It is guessed as follows. By using non-spherical silica particles whose average minor axis is larger than the spherical silica particles during polishing, the spherical silica particles enter the gaps between the non-spherical silica particles, and polishing between the polishing pad being polished and the surface to be polished of the substrate It is thought that the filling rate of grains increases. For this reason, it is considered that the polishing rate can be maintained or improved by increasing the cutting area of the substrate by increasing the contact area of the abrasive grains with the surface to be polished and by making the polishing load applied to the substrate during polishing over a wide range uniform. Furthermore, it is considered that the magnitude of vibration that occurs between the polishing pad and the substrate during polishing can be reduced, and long-wave waviness can be reduced. The above effect is considered to be particularly remarkable when the average minor axis of the spherical silica particles is a predetermined value or more. However, the present disclosure need not be interpreted as being limited to these mechanisms.

That is, the polishing liquid composition according to the present disclosure includes non-spherical silica particles A, spherical silica particles B, and water, and has a pH of 0.5 or more and 6.0 or less. The diameter is 105 nm or more and is larger than the average minor axis of the spherical silica particles B, or a magnetic disk substrate polishing liquid composition, or at least non-spherical silica particles A, spherical silica particles B and water are blended. A magnetic disk substrate having a pH of 0.5 or more and 6.0 or less, an average minor axis of the non-spherical silica particles A of 105 nm or more, and larger than an average minor axis of the spherical silica particles B The present invention relates to a polishing liquid composition.

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, “long wavelength undulation” refers to undulation observed with a wavelength of 500 to 5000 μm. By reducing long-wave waviness on 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 long wavelength waviness of the substrate surface can be measured by the method described in the 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 minor axis of the particles A is larger than the average minor axis of the spherical silica particles B. The average minor axis of the particles A is 105 nm or more, preferably 160 nm or more, more preferably 180 nm or more, further preferably 185 nm or more, and preferably 500 nm or less, from the viewpoint of improving the polishing rate and reducing long wavelength waviness. 450 nm or less is more preferable, and 400 nm or less is still more preferable.

In the present disclosure, the average minor axis of the particles A is an average value of the minor axis of at least 200 particles A. The minor axis of the particle A is the length of the short side of the rectangle when a minimum rectangle circumscribing the projected image of the particle A is drawn using, for example, TEM observation and image analysis software. Similarly, the major axis of the particle A is the length of the long side of the rectangle.

The average aspect ratio of the particles A is preferably 1.10 or more, more preferably 1.15 or more, further preferably 1.20 or more, from the viewpoint of improving the polishing rate and reducing the long wavelength waviness, and from the same viewpoint, 2.00 or less is preferable, 1.70 or less is more preferable, and 1.50 or less is still more preferable.

In the present disclosure, the average aspect ratio of the particles A is an average value of the aspect ratios of at least 200 particles A. The aspect ratio of the particle A is the ratio of the major axis to the minor axis of the particle A (major axis / minor axis).

BET specific surface area of the particles A, from the viewpoint of improving the polishing rate and a long wavelength waviness reduction is preferably 50 m ² / g or less, more preferably 45 m ² / g, still more preferably 40 m ² / g or less, and, 10 m ² / G or more is preferable, 15 m ² / g or more is more preferable, and 20 m ² / g or more is still more preferable. In the present disclosure, the BET specific surface area can be calculated by a nitrogen adsorption method (hereinafter also referred to as “BET method”). Specifically, it can be calculated by the measurement method described in the examples.

The average primary particle diameter D1 _A of the particles _A is preferably 60 nm or more, more preferably 70 nm or more, still more preferably 80 nm or more, from the viewpoint of improving the polishing rate and reducing the long wavelength waviness, and from the viewpoint of reducing the long wavelength waviness, 200 nm or less is preferable, 150 nm or less is more preferable, and 120 nm or less is still more preferable.

In the present disclosure, the average primary particle diameter of the particles A can be calculated from the following formula using the BET specific surface area S (m ² / g). Specifically, it can be calculated by the measurement method described in the examples.
Average primary particle diameter (nm) = 2727 / S

The average secondary particle diameter D2A of the particles _A is preferably 160 nm or more, more preferably 180 nm or more, further preferably 200 nm or more, and 500 nm or less from the same viewpoint from the viewpoint of improving the polishing rate and reducing the long wavelength waviness. Is preferable, 400 nm or less is more preferable, and 350 nm or less is still more preferable.

In the present disclosure, the average secondary particle diameter of the particle A refers to an average particle diameter based on a scattering intensity distribution measured by a dynamic light scattering method. In this disclosure, “scattering intensity distribution” means a particle size distribution in terms of weight of submicron particles or less obtained by dynamic light scattering (DLS) or quasielastic light scattering (QLS: Quasielastic Light Scattering). 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.

The particle diameter ratio (D2 _A / D1 _A ) between the average secondary particle diameter D2 _A and the average primary particle diameter D1 _A of the particles _A is preferably 2.00 or more from the viewpoint of improving the polishing rate and reducing long wavelength waviness, 2.50 or more is more preferable, 2.50 or more is more preferable, and 4.00 or less is preferable, 3.00 or less is more preferable, and 2.80 or less is more preferable from the viewpoint of improving the polishing rate.

In the present disclosure, the particle size ratio (D2 _A / D1 _A ) may mean the degree of deformation of the particles A. The average secondary particle diameter D2 _A commonly measured by dynamic light scattering method, when the silica particles are of irregular particles, in order to perform detection and processing light scattering in the long direction, the long direction and short direction Considering the length, the larger the degree of deformation, the larger the value. The average primary particle size D1 _A converted from the specific surface area value measured by the BET method, because it is represented by the equivalent spherical volume of the obtained particles as a base, the small numbers compared to the average secondary particle diameter D2 _A . From the viewpoint of improving the polishing rate and reducing long wavelength waviness, the particle size ratio (D2 _A / D1 _A ) is preferably large in the above range.

The coefficient of variation (hereinafter also referred to as “CV value”) of the particle diameter of the particles A is preferably 10% or more, more preferably 15% or more, and more preferably 20% or more from the viewpoint of improving the polishing rate and reducing long wavelength waviness. Further, it is preferably 35% or less, preferably 30% or less, and more preferably 28% or less.

In the present disclosure, the CV value of the secondary particle diameter of the particle A is based on the scattering intensity distribution at a detection angle of 90 ° by the dynamic light scattering method, and the standard deviation of the secondary particle diameter measured is the average secondary particle diameter. The value (unit:%) obtained by dividing and multiplying by 100. Specifically, the CV value can be measured by the method described in Examples.

Examples of the particles A include colloidal silica, fumed silica, surface-modified silica, and precipitated silica. From the viewpoint of improving the polishing rate and reducing long wavelength waviness, the particle A is preferably at least one selected from colloidal silica and precipitated silica, more preferably colloidal silica, and further colloidal silica having the following specific shape. preferable.

From the viewpoint of improving the polishing rate and reducing long-wave waviness, the shape of the particle A is preferably a silica particle having a particle size smaller than the secondary particle size of the particle A, and a plurality of precursor particles are aggregated. Or it is a fused shape. From the same point of view, the particle A is at least one kind of silica particle selected from the gold-peeled silica particles Aa, the irregular-shaped silica particles Ab, the irregular-shaped and gold-peeled silica particles Ac, and the precipitated silica particles Ad. More preferably, at least one selected from irregular-shaped silica particles Ab and precipitated silica particles Ad is more preferable, and irregular-shaped silica particles Ab are still more preferable. The particle A may be one type of non-spherical silica particle or a combination of two or more types of non-spherical silica particles.

In the present disclosure, confetti-type silica particles Aa (hereinafter, also referred to as “particles Aa”) refer to silica particles having unique ridge-like projections 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-A-2008-137822. 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.

In the present disclosure, the precipitated silica particles Ad (hereinafter also referred to as “particles Ad”) refer to silica particles produced by the precipitation method (see FIG. 3). The shape of the particles Ad is preferably a shape in which a plurality of primary particles are aggregated from the viewpoint of improving the polishing rate and reducing scratches. Examples of the method for producing the particle Ad include known methods such as those described in Tosoh Research and Technical Report, Vol. 45 (2001), pages 65 to 69. Specific examples of the method for producing the particles Ad include 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 that the neutralization reaction is performed at a relatively high temperature and under alkaline conditions, whereby the primary particle growth of silica proceeds rapidly, and the primary particles aggregate in a floc form and settle, preferably further pulverized. By doing so, the particles Ad can be obtained.

Particle A preferably contains one or more selected from particles Aa, Ab, Ac and Ad. The total amount of the particles Aa, Ab, Ac and Ad in the particles A is preferably 50% by mass or more, more preferably 70% by mass or more, and further preferably 80% by mass or more from the viewpoint of improving the polishing rate and reducing the long wavelength waviness. Preferably, 90% by mass or more is even more preferable, and substantially 100% by mass 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 and reducing the long wavelength waviness in the rough polishing, 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 liquid composition is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and further preferably 1% by mass or more, from the viewpoint of improving the polishing rate and reducing long wavelength waviness. Preferably, 2% by mass or more is still more preferable, and from the viewpoint of economy, 30% by mass or less is preferable, 25% by mass or less is more preferable, 20% by mass or less is further preferable, and 15% by mass or less is even more preferable. .

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

In the present disclosure, the average sphericity of the particles B is preferably 0.86 or more from the viewpoint of suppressing a decrease in polishing rate and reducing long-wave waviness in rough polishing, and reducing protrusion defects after rough polishing and final polishing. 0.88 or more is more preferable, and from the same viewpoint, it is 1.00 or less, and preferably 0.95 or less. The average sphericity of the particle B can be calculated by the same method as that for the particle A. The sphericity of the individual particles B is preferably 0.86 or more, more preferably 0.88 or more, and is preferably 1.00 or less, and preferably 0.95 or less, like the average particle size.

The average sphericity of the particle B is preferably larger than the average sphericity of the particle A from the viewpoint of manifesting the effect of the present disclosure. The difference in average sphericity between the particles A and the particles B is preferably 0.02 or more, more preferably 0.05 or more, still more preferably 0.08 or more, from the viewpoint of expression of the effect of the present disclosure, and the same. From the viewpoint, 0.50 or less is preferable, 0.30 or less is more preferable, and 0.25 or less is more preferable.

The average minor axis of the particle B is smaller than the average minor axis of the particle A from the viewpoint of improving the polishing rate and reducing the long wavelength waviness. From the same viewpoint, the average minor axis of the particle B is preferably 15 nm or more, more preferably 45 nm or more, further preferably 85 nm or more, preferably 200 nm or less, more preferably 150 nm or less, and further preferably 130 nm or less. The average minor axis of the particle B can be calculated by the same method as that for the particle A.

The ratio of the average minor axis of particle A and the average minor axis of particle B (average minor axis of particle A) / (average minor axis of particle B) according to the present disclosure is from the viewpoint of improving the polishing rate and reducing long wavelength waviness. , More than 1.0, preferably 1.5 or more, more preferably 2.0 or more, further preferably 2.5 or more, further preferably 3.0 or more, and from the same viewpoint, 30.0 or less Is preferably 15.0 or less, more preferably 10.0 or less, still more preferably 7.0 or less, and still more preferably 4.0 or less.

The average aspect ratio of the particles B is 1.00 or more, and is preferably 1.15 or less, more preferably 1.10 or less, and further preferably 1.08 or less from the viewpoint of improving the polishing rate and reducing long wavelength waviness. preferable. The average aspect ratio and aspect ratio of the particle B can be calculated by the same method as that for the particle A.

The average primary particle diameter D1 _B of the particles _B is preferably 15 nm or more, more preferably 30 nm or more, further preferably 40 nm or more, and further preferably 150 nm or less from the viewpoint of improving the polishing rate and reducing long wavelength waviness. Preferably, 120 nm or less is more preferable, and 100 nm or less is still more preferable. The average primary particle diameter of the particle B can be calculated by the same method as that for the particle A.

The average secondary particle diameter D2B of the particles _B is preferably 20 nm or more, more preferably 45 nm or more, still more preferably 85 nm or more, and 200 nm or less from the same viewpoint from the viewpoint of improving the polishing rate and reducing the long wavelength waviness. Is preferable, 180 nm or less is more preferable, and 160 nm or less is still more preferable. The average secondary particle diameter of the particle B can be calculated by the same method as that for the particle A.

The particle size ratio (D2 _B / D1 _B ) between the average secondary particle diameter D2 _B and the average primary particle diameter D1 _B of the particles _B is preferably 1.05 or more from the viewpoint of improving the polishing rate and reducing long wavelength waviness, 1.50 or more is more preferable, 2.00 or more is further preferable, and from the same viewpoint, 4.00 or less is preferable, 3.50 or less is more preferable, and 3.00 or less is more preferable.

The CV value of the secondary particle diameter of the particle B is preferably 15% or more, more preferably 18% or more, still more preferably 20% or more, and the same viewpoint from the viewpoint of improving the polishing rate and reducing long wavelength waviness. 45% or less is preferable, 40% or less is more preferable, and 35% or less is still more preferable. The CV value of the secondary particle diameter of the particle B can be calculated by the same method as that for the particle A.

Examples of the particles B include colloidal silica, fumed silica, and surface-modified silica. As the particle B, for example, commercially available colloidal silica may be applicable. Colloidal silica is preferable as the particle B from the viewpoint of suppressing a decrease in polishing rate, reducing long wavelength waviness, and reducing protrusion defects. The particle B may be one type of spherical silica particle or a combination of two or more types of spherical silica particles.

The particles B may be produced by a flame melting method, a sol-gel method, and a pulverization method from the viewpoint of improving the polishing rate, reducing long-wave waviness and reducing protrusion defects, but are silica particles produced by a water glass method. Preferably there is. The usage form of the particles B is preferably a slurry.

The content of the particles B in the polishing liquid composition according to the present disclosure is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, from the viewpoint of improving the polishing rate and reducing long wavelength waviness. 0 mass% or more is still more preferable, and 20.0 mass% or less is preferable from an economical viewpoint, 15.0 mass% or less is more preferable, and 10.0 mass% or less is still more preferable.

The mass ratio A / B between the content of the particles A and the content of the particles B in the polishing composition according to the present disclosure is preferably 5/95 or more from the viewpoint of improving the polishing rate and reducing long wavelength waviness. / 80 or more is more preferable, 40/60 or more is further preferable, 50/50 or more is further preferable, 51/49 or more is further preferable, 60/40 or more is further preferable, and from the same viewpoint, 95/5 or less Is preferable, 90/10 or less is more preferable, 80/20 or less is further preferable, and 75/25 or less is more preferable. When the particle B is a combination of two or more kinds of spherical silica particles, the content of the particle B refers to the total content thereof. The same applies to the content of the particles A.

When the polishing liquid composition according to the present disclosure contains silica particles other than the particles A and the particles B, the total content of the particles A and the particles B with respect to the entire silica particles in the polishing liquid composition increases the polishing rate and From the viewpoint of reducing long wavelength waviness, 98.0% by mass or more is preferable, 98.5% by mass or more is more preferable, 99.0% by mass or more is further preferable, 99.5% by mass or more is further more preferable, and 99. 8% by mass or more is even more preferable, and substantially 100% by mass is even more preferable.

[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 long 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 long 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. Of 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 long-wave waviness. More preferred is sulfuric acid.

Examples of the salt include a salt of the above acid and at least one selected from metals, ammonia, and alkylamines. 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 long 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 long 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 liquid composition according to the present disclosure may contain an oxidizing agent from the viewpoint of improving the polishing rate and reducing long 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 long 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 thickeners, dispersants, rust inhibitors, basic substances, polishing rate improvers, surfactants, and polymer compounds. 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% by weight.

[PH]
The pH of the polishing composition according to the present disclosure is 0.5 or higher, preferably 0.7 or higher, more preferably 0.9 or higher, from the viewpoint of improving the polishing rate and reducing long wavelength waviness, and more preferably 1.0 or higher. 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 at least particles A, particles 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 particles 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, particles 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, particle | grains 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, “compounding” includes mixing the particles A, the particles B and water, and, if necessary, the pH adjusting agent, the 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 quantity of each component in the manufacturing method of polishing liquid composition is the same as the preferable content of each component in polishing liquid composition.

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 particles 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 manufacturing a polishing liquid composition, which includes a slurry in a container in which a silica slurry containing the particles A and the particles B is contained 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, even when silica particles are used as abrasive grains, a polishing composition capable of obtaining a polishing liquid composition capable of reducing long-wave waviness on the substrate surface after rough polishing without greatly impairing the polishing rate in rough polishing. A liquid kit can be provided.

As the polishing liquid kit according to the present disclosure, for example, a silica slurry (first liquid) containing the particles A and the particles 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]
A 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, silicate glass, and aluminosilicate glass are used. Examples thereof include glass substrates such as crystallized glass and tempered glass, and an aluminum alloy substrate plated with Ni—P is preferred from the viewpoint of strength and ease of handling. 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 can be manufactured 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, and preferably a disk-shaped substrate to be polished. It is. In the case of a disk-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.

In general, a magnetic disk is manufactured through a magnetic layer forming step in which a substrate to be polished that has undergone a grinding step is polished through a rough polishing step and a final polishing step. 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 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 is 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 30 kPa or less, more preferably 25 kPa or less, still more preferably 20 kPa or less, and further 3 kPa, from the viewpoints of improving the polishing rate and reducing long wavelength waviness. The above is preferable, 5 kPa or more is more preferable, and 7 kPa or more 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 preferably 0.30 mg or more from the viewpoint of improving the polishing rate and reducing long 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.

The supply rate of the polishing liquid composition per 1 cm ^{2 of the} substrate to be polished in the polishing step using the polishing liquid composition according to the present disclosure is preferably 2.5 mL / min or less from the viewpoint of economy, and is 2.0 mL / min. The following is more preferable, 1.5 mL / min or less is further 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, 0.03 mL / min or more is more preferable, 0.05 mL / min or more is more preferable.

Examples of a method of supplying the polishing composition according to the present disclosure to a polishing machine include a method of supplying continuously 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, long wavelength waviness on the substrate surface after rough polishing can be reduced without significantly impairing the polishing rate in rough polishing, so that a magnetic disk substrate with improved substrate quality can be efficiently manufactured. The effect that it is possible can be produced.

[Polishing method]
The present disclosure relates to a substrate polishing method (hereinafter, also referred to as a polishing method according to the present disclosure) including a polishing step using the polishing composition according to the present disclosure.

By using the polishing method according to the present disclosure, it is possible to reduce long-wave waviness of 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 Implemented using the abrasive grains (non-spherical silica particles A, spherical silica particles B, alumina abrasive grains C), pH adjuster (sulfuric acid), oxidizing agent (hydrogen peroxide), and water shown in Table 1. Polishing liquid compositions of Examples 1 to 15 and Comparative Examples 1 to 7 were prepared (Table 2). The preparation was performed by mixing water, a pH adjuster, and an oxidizing agent in advance to prepare a dispersion medium, and mixing the dispersion medium and a slurry containing abrasive grains. The content of each component in the polishing composition was 6.0% by mass of abrasive grains, 0.5% by mass of sulfuric acid, and 0.5% by mass of hydrogen peroxide. The pH of the polishing composition was 1.4. The particles A1 to 4, 6 and the particles B1 to B6 are colloidal silica particles manufactured by a water glass method. Particle A5 is a fumed silica particle. The particles A6 are precipitated silica particles. The pH was measured using a pH meter (manufactured by Toa DKK Co., Ltd.), and the value after 2 minutes after the electrode was immersed in the polishing composition was adopted (hereinafter the same).

2. Measuring method of each parameter [Measuring method of average minor diameter, average aspect ratio and 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 analyzed software (Mitani Corporation “WinROOF (Ver. 3) .6) ") and the projection image of 500 silica particles was analyzed as follows.
The minor axis and major axis of each silica particle were determined, and the average value of the minor axis (average minor axis) was obtained. Further, an average aspect ratio (average aspect ratio) was obtained from a value obtained by dividing the major axis by the minor axis. Furthermore, from the area S and the perimeter length L of each silica particle, the sphericity of each silica particle was calculated by the following formula, and the average value of sphericity (average sphericity) was obtained.
Sphericality = 4π × S / L ²

[Measurement method of average primary particle diameter of silica particles]
The average primary particle diameter of the silica particles was calculated from the following formula using the BET specific surface area S (m ² / g) calculated by the BET method.
Average primary particle diameter (nm) = 2727 / S

The BET specific surface area S was subjected to the following [pre-treatment], then weighed about 0.1 g of the measurement sample into the measurement cell to 4 digits after the decimal point (0.1 mg digit), and 110 ° C. immediately before the measurement of the specific surface area. After being dried for 30 minutes under the above-mentioned atmosphere, the specific surface area was measured by the BET method using a specific surface area measuring device (Micromeritic automatic specific surface area measuring device, Flowsorb III2305, 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 secondary particle diameter and CV value of silica particles]
Silica particles are diluted with ion-exchanged water, a dispersion containing 0.02% by mass of silica particles is prepared and used as a sample, using a dynamic light scattering apparatus (“DLS-7000” manufactured by Otsuka Electronics Co., Ltd.) It measured on condition of this. The particle size (D50) at which the accumulated particle size distribution in terms of weight obtained was 50% of the total was taken as the average secondary particle size. At the same time, the standard deviation in the obtained weight conversion distribution was divided by the average secondary particle diameter, and a value multiplied by 100 was taken as the CV value (unit:%).
Measurement conditions: Sample volume 30 mL
: Laser He-Ne, 3.0 mW, 633 nm
: Scattered light detection angle 90 °
: Accumulation count 200 times

[Measurement method of average secondary particle diameter of alumina abrasive grains]
An aqueous solution containing 0.5% by mass of Poise 530 (manufactured by Kao Corporation, polycarboxylic acid type polymer surfactant) was introduced as a dispersion medium into the following measuring apparatus, and the transmittance subsequently reached 75 to 95%. In this manner, a sample (alumina particles) was put in, and after applying ultrasonic waves for 5 minutes, the particle size was measured.
Measuring instrument: Laser diffraction / scattering particle size distribution measuring device LA920 manufactured by Horiba, Ltd.
Circulation strength: 4
Ultrasonic intensity: 4

3. Polishing of the Substrate The substrate to be polished was polished under the following polishing conditions using the prepared polishing liquid compositions of Examples 1 to 15 and Comparative Examples 1 to 7.

[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, number of sheets: 10 polishing liquid: polishing liquid composition polishing pad: suede type (foam layer: polyurethane elastomer), thickness: 1 0.0 mm, average pore diameter: 30 μm, compression ratio of surface layer: 2.5% (manufactured by Filwel)
Plate rotation speed: 40 rpm
Polishing load: 9.8 kPa (set value)
Polishing liquid supply amount: 60 mL / min
Polishing time: silica abrasive 5 minutes 30 seconds, alumina abrasive 3 minutes 30 seconds

4). Evaluation method [Evaluation of polishing rate]
The polishing rates of the polishing composition of Examples 1 to 15 and Comparative Examples 1 to 7 were evaluated as follows. First, the weight per one substrate before and after polishing was measured (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 defined as a polishing rate, and was calculated by the following formula.
Weight loss (g) = {mass before polishing (g) −mass after polishing (g)}
Polishing speed (mg / min) = mass reduction amount (mg) / polishing time (min)

[Evaluation of long wavelength swell]
Measurements were made on the following conditions for 10 surfaces after polishing, a total of 20 surfaces. The average value of the measured values on the 20 surfaces was calculated as the long wavelength waviness of the substrate. In this evaluation, the long wavelength waviness is preferably 3.0 mm or less, more preferably 2.7 mm or less, further preferably 2.4 mm or less, and further preferably 2.1 mm or less, from the viewpoint of improving the recording density of the magnetic disk.
Measuring equipment: “OptiFLAT III” manufactured by KLA Tencor
Radius Inside / Out: 14.87mm / 47.83mm
Center X / Y: 55.44mm / 53.38mm
Low Cutoff: 2.5mm
Inner Mask: 18.50mm
Outer Mask: 45.5mm
Long Period: 2.5mm
Wa Correction: 0.9
Rn Correction: 1.0
No Zernike Terms: 8

[Alumina residue evaluation method]
The surface of each substrate after polishing was observed at a magnification of 10,000 with a scanning electron microscope (manufactured by Hitachi, Ltd .: S-4000), and the following three-level evaluation was performed.
○ (A): No alumina residue is observed on the surface Δ (B): A slight alumina residue is observed on the surface × (C): Alumina residue is observed on the surface

5). Results The results of each evaluation are shown in Table 2.

As shown in Table 2, Examples 1 to 15 containing particles A and B as abrasive grains, the average minor axis of the particle A being 105 nm or more and larger than the particle B, have an average minor axis of the particle A. Comparative Examples 1 and 2 smaller than particle B, Comparative Example 3 containing only particle B as abrasive grains, Comparative Example 4 containing only particle A as abrasive grains, Comparative Example 5 containing alumina particles as abrasive grains, Particle A Compared with Comparative Examples 6 to 7 having an average minor axis of less than 105 nm, the long wavelength waviness after polishing was reduced without significantly impairing the polishing rate.

According to the present disclosure, the long wavelength 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

Non-spherical silica particles A, spherical silica particles B and water,
pH is 0.5 or more and 6.0 or less,
The polishing composition for a magnetic disk substrate, wherein the non-spherical silica particles A have an average minor axis of 105 nm or more and are larger than the average minor axis of the spherical silica particles B.
The polishing composition for a magnetic disk substrate according to claim 1, wherein the non-spherical silica particles A have an average minor axis of 160 nm or more.
The polishing composition for a magnetic disk substrate according to claim 1 or 2, wherein the nonspherical silica particles A have an average sphericity of 0.85 or less.
The polishing composition for a magnetic disk substrate according to any one of claims 1 to 3, wherein the non-spherical silica particles A have an average secondary particle size of 160 nm to 500 nm.
The magnetic ratio according to any one of claims 1 to 4, wherein a mass ratio A / B between the content of the non-spherical silica particles A and the content of the spherical silica particles B is 5/95 or more and 95/5 or less. Polishing liquid composition for disk substrates.
The magnetic ratio according to any one of claims 1 to 5, wherein a mass ratio A / B between the content of the non-spherical silica particles A and the content of the spherical silica particles B is 51/49 or more and 95/5 or less. Polishing liquid composition for disk substrates.
The polishing composition for a magnetic disk substrate according to any one of claims 1 to 6, wherein the content of alumina abrasive grains is 0.1 mass% or less.
The polishing composition for a magnetic disk substrate according to any one of claims 1 to 7, 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 a Ni-P plated aluminum alloy substrate.
The polishing composition for a magnetic disk substrate according to claim 1, 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.
At least non-spherical silica particles A, spherical silica particles B and water are blended,
pH is 0.5 or more and 6.0 or less,
The polishing composition for a magnetic disk substrate, wherein the non-spherical silica particles A have an average minor axis of 105 nm or more and are larger than the average minor axis of the spherical silica particles B.
Having a step of blending at least non-spherical silica particles A, spherical silica particles B and water,
A method for producing a silica slurry used for producing a polishing liquid composition for a magnetic disk substrate, wherein the average minor axis of the non-spherical silica particles A is 105 nm or more and is larger than the average minor axis of the spherical silica particles B.
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 any one of claims 1 to 12.
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 12, wherein the substrate to be polished is a substrate used for manufacturing a magnetic disk substrate. A method for polishing a substrate.