JP6138677B2 - Polishing liquid composition for magnetic disk substrate - Google Patents

Description

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

  In recent years, magnetic disk drives have been reduced in size and capacity, and high recording density has been demanded. Therefore, it is necessary to improve the detection sensitivity of high recording density magnetic signals, and technical development is underway to reduce the flying height of the magnetic head and reduce the unit recording area. The magnetic disk substrate is designed to improve the smoothness and flatness (reduction of surface roughness, waviness and edge sag) and to reduce surface defects (residual abrasive grains and scratches) in order to reduce the flying height of the magnetic head and ensure the recording area. , Reduction of protrusions, pits, etc.) is strictly demanded.

  From the viewpoint of achieving both improvement in surface quality and productivity, such as smoother and less scratches, such a requirement, the hard disk substrate manufacturing method includes a multi-stage polishing method having two or more polishing steps. 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 the polishing step (also referred to as rough polishing step) prior to the final polishing step, a polishing liquid composition containing alumina particles is used from the viewpoint of improving productivity. However, when alumina particles are used as abrasive grains, media scratches may be caused by texture scratches caused by the piercing of alumina particles to the substrate.

  As long as alumina is used, the piercing of the alumina particles to the substrate is not zero, and recently, the first polishing machine is used to include the pulverized silica abrasive grains without using the alumina abrasive grains in the rough polishing process. Proposing a method for manufacturing a substrate for a magnetic recording medium having a rough polishing step of polishing while supplying a polishing liquid, and a final polishing step of polishing while supplying a polishing liquid containing colloidal silica abrasive grains using a second polishing disk (For example, Patent Document 1).

  However, it is generally known that when silica particles are used, the polishing rate is lower than that of alumina particles. As means for improving the polishing rate of silica particles, control of the shape of silica particles (for example, Patent Documents 2 and 3), mixing of silica particles (for example, Patent Document 4), and the like have been studied. On the other hand, a polishing composition comprising a combination of a plurality of silica particles having different shapes is also disclosed (for example, Patent Documents 5, 6, and 7).

JP 2012-155785 A JP 2012-054281 A JP 2013-121631 A JP 2002-30274 A JP 2006-080406 A JP 2013-171856 A JP 2011-104694 A

  As the capacity of magnetic disk drives is increased, the required characteristics for the surface quality of the substrate are becoming stricter, and it is possible to further reduce the residue of the abrasive grains used in the rough polishing process (for example, alumina adhesion, alumina sticking). There is a need for development of polishing liquid compositions. As means for reducing the piercing of the abrasive grains derived from the rough polishing process, the piercing of the abrasive grains can be greatly reduced by using pulverized silica abrasive grains (for example, Patent Document 1), but achieving zero completely is achieved. It has not been completed and is still insufficient. In addition, it has been found that when a rough polishing process is performed with silica particles instead of alumina particles, a problem that long-period defects cannot be removed newly occurs. In the case of performing the rough polishing process with alumina particles, the problem of long-period defects generally does not occur.

  In response to this problem, if rough polishing is performed using non-spherical silica particles defined by predetermined parameters as abrasive grains, the polishing time for rough polishing can be significantly prolonged even when alumina particles are substantially not included. It was found that long-period defects after rough polishing can be reduced without conversion (Japanese Patent Application Nos. 2012-267314 and 2012-267313). However, silica particles produced without using a pulverization process generally have a lower cutting force than pulverized abrasive grains, so the removal rate of long-period defects tends to be low. Therefore, since the removal rate of long-period defects is highly correlated with the substrate yield, further improvement of the removal rate of long-cycle defects is desired in rough polishing.

  Therefore, in one aspect, the present disclosure can improve the removal rate of long-period defects without impairing productivity (ie, without impairing the polishing rate) in rough polishing using non-spherical silica particles as abrasive grains. A polishing liquid composition is provided.

  In one or a plurality of embodiments, the present disclosure is a polishing liquid composition for a magnetic disk substrate containing silica particles, an acid, an oxidizing agent, and water, wherein the silica particles have a volume average particle diameter determined by a dynamic light scattering method. A non-spherical silica particle A having (D1) of 120.0 nm or more and less than 300.0 nm, and a spherical silica particle B having a volume average particle size (D1) by a dynamic light scattering method of 6.0 nm or more and 40.0 nm or less; The silica particles in the polishing composition are mixed so that the mass ratio (A / B) of the non-spherical silica particles A and the spherical silica particles B in the polishing composition is 80/20 or more and 99/1 or less. The total mass ratio of non-spherical silica particles A and spherical silica particles B with respect to the whole exceeds 98.0% by mass, and the non-spherical silica particles A have a volume average particle diameter (D1) and BET by the dynamic light scattering method. Specific surface area conversion The ratio (D1 / D2) of the particle diameter (D2) is 2.00 or more and 4.00 or less, and the volume particle size distribution overlap of each of the non-spherical silica particles A and the spherical silica particles B by the dynamic light scattering method. The present invention relates to a polishing composition for a magnetic disk substrate having a total frequency of 0% to 40%.

  In one or a plurality of other embodiments, the present disclosure is obtained in (1) a step of polishing a polishing target surface of a substrate to be polished using the polishing composition according to the present disclosure, and (2) a step (1). And (3) a step of polishing the surface to be polished using a polishing liquid composition containing silica particles, the step (1). And (3) are performed by another polishing machine, and the polishing substrate is a substrate for manufacturing a magnetic disk substrate.

  In one or a plurality of other embodiments, the present disclosure is obtained in (1) a step of polishing a polishing target surface of a substrate to be polished using the polishing composition according to the present disclosure, and (2) a step (1). And (3) a step of polishing the surface to be polished using a polishing liquid composition containing silica particles, the step (1). And (3) with a separate polishing machine.

  Since the polishing liquid composition for a magnetic disk substrate according to the present disclosure does not use alumina particles, it can greatly reduce protrusion defects after rough polishing and after final polishing. In addition, according to the polishing composition for a magnetic disk substrate according to the present disclosure, it is possible to achieve an effect that it is possible to improve the removal rate of long-period defects without impairing productivity.

FIG. 1 is an example of an electron microscope (TEM) observation photograph of irregular-shaped silica particles A (abrasive grains a). FIG. 2 is a graph showing the volume particle size distribution of the abrasive grains a, abrasive grains d, and abrasive grains e by the dynamic light scattering method.

  In the polishing process of the magnetic disk substrate, when the rough polishing process is performed with a polishing liquid composition using silica particles produced by the particle growth method as an alternative to alumina in the polishing process, protrusion defects can be significantly reduced, but the removal rate of long-period defects is improved. There is a problem of lowering. This problem can be solved to some extent by performing a rough polishing step using a polishing liquid composition containing non-spherical silica particles, an acid, and an oxidizing agent defined by predetermined parameters. In the present disclosure, by mixing spherical silica having a predetermined size and ratio with the non-spherical silica, the productivity of the long-period defects in the rough polishing can be further improved without impairing the productivity (that is, without impairing the polishing speed). Based on the knowledge that it can be further improved.

  That is, in one aspect, the present disclosure is a polishing composition for a magnetic disk substrate containing silica particles, an acid, an oxidizing agent, and water, wherein the silica particles have a volume average particle diameter (D1) determined by a dynamic light scattering method. Nonspherical silica particles A having a particle size of 120.0 nm or more and less than 300.0 nm, and spherical silica particles B having a volume average particle diameter (D1) by a dynamic light scattering method of 6.0 nm or more and 40.0 nm or less, The non-spherical silica particles A and the spherical silica particles B in the polishing composition are mixed so that the mass ratio (A / B) is 80/20 or more and 99/1 or less. The total mass ratio of the spherical silica particles A and the spherical silica particles B exceeds 98.0% by mass, and the non-spherical silica particles A have a volume average particle diameter (D1) determined by the dynamic light scattering method and a specific surface area determined by the BET method. Equivalent particle size ( 2) The ratio (D1 / D2) is 2.00 or more and 4.00 or less, and the total overlap frequency of volume particle size distributions of the non-spherical silica particles A and the spherical silica particles B by the dynamic light scattering method However, the present invention relates to a polishing liquid composition for a magnetic disk substrate (hereinafter also referred to as “polishing liquid composition according to the present disclosure”) of 0% or more and 40% or less.

  Although the detailed mechanism by which the removal rate of long-period defects in rough polishing can be further improved without impairing productivity by the polishing composition according to the present disclosure is not clear, it is considered as follows. Due to its surface shape, non-spherical silica has more voids in a filled state than spherical silica. By blending particles of a specific size that enter this void, the mixing system increases the filling rate of the abrasive grains, and can impart the effect of reducing the frictional resistance unique to non-spherical silica during polishing. It is estimated that the removal rate can be improved. In addition, it is considered that the polishing rate can be maintained or improved because an increase in the filling rate of the abrasive grains gives an effect of improving the cutting area on the substrate or more easily transmitting the load applied during polishing to the substrate. It is done. The shape of the particles of a specific size that enter the voids of the filled non-spherical silica is not limited. However, since non-spherical silica is generally difficult to control to a particle size of 40 nm or less from its production method, It is considered that the particles entering the voids are preferably spherical silica. At this time, if the mixing ratio of the spherical silica of a specific size entering the void of the non-spherical silica with respect to the non-spherical silica is too high, the frictional resistance during polishing may be adversely affected. There is an optimum range for the mixing ratio of the spherical silica that enters the voids of the non-spherical silica. Therefore, by setting the mixing ratio of non-spherical silica and spherical silica with a predetermined particle size, the frictional resistance during polishing is reduced without impairing productivity, and a good long-period defect removal rate is achieved. It is considered possible. However, the present disclosure need not be construed as being limited to these mechanisms.

  In the present disclosure, the “long-period defect” includes a grind scratch and a PED (polish enhanced defect) that occur in the manufacturing process of the NiP plated aluminum substrate. Grind scratches refer to grinding marks on a grindstone in the process of grinding an aluminum substrate before plating (grinding process). PED refers to a portion of insufficient annealing caused by water or foreign matter adhering to the substrate surface in an annealing step in the step of forming a plating film on an alumina substrate. In one or a plurality of embodiments, the long-period defect and its removal rate can be measured using the measuring device described in the examples.

  In the present disclosure, the “protrusion defect” mainly refers to a defect on the surface of the substrate that is considered to be derived from residual abrasive grains, abrasive grain adhesion, and abrasive grain sticking after the rough polishing process and after final polishing. The protrusion defect on the substrate surface can be evaluated by a surface defect inspection apparatus such as microscopic observation or scanning electron microscope observation of the substrate surface obtained after polishing, and can be specifically evaluated by the method described in the examples. .

[Non-spherical silica particles A]
The polishing liquid composition according to the present disclosure contains non-spherical silica particles A as abrasive grains. In one or a plurality of embodiments, examples of the non-spherical silica particles A include colloidal silica, fumed silica, and surface-modified silica. Colloidal silica is preferable from the viewpoints of suppressing a decrease in polishing rate, improving the long-period defect removal rate, and reducing protrusion defects.

  In the present disclosure, the “non-spherical silica particles” are, in one or a plurality of embodiments, a shape in which two or more particles are aggregated or fused from the viewpoint of suppressing a decrease in polishing rate and improving a long-period defect removal rate. Particles. In one or a plurality of embodiments, the non-spherical silica particles A are selected from the group consisting of confetti-type silica particles A1, deformed-type silica particles A2, and deformed and confetti-type silica particles A3. At least one type of silica particles is preferred.

  In the present disclosure, the confetti-type silica particle A1 refers to a silica particle having unique ridge-like protrusions on the spherical particle surface. In one or a plurality of embodiments, the silica particle A1 has a shape in which two or more particles different in particle size by 5 times or more are aggregated or fused on the basis of the particle size of the smallest silica particle. Preferably, the small particles are partially embedded in the large particles. The particle diameter can be obtained as the equivalent circle diameter measured in one particle in an electron microscope (TEM or the like) observation image, that is, the major axis of an equivalent circle having the same area as the projected area of the particle. The particle diameter in silica particle A2 and silica particle A3 can be similarly determined.

  In the present disclosure, the irregular-shaped silica particle A2 refers to a silica particle having a shape in which two or more particles, preferably 2 to 10 particles are aggregated or fused. In one or a plurality of embodiments, the silica particle A2 has a shape in which two or more 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 silica particle.

  In the present disclosure, odd-shaped and confetti-type silica particles A3 are particles having a shape in which two or more particles are aggregated or fused. In one or a plurality of embodiments, the silica particle A3 is a particle obtained by agglomerating or fusing two or more particles having a particle size of 1.5 times or less. A shape in which small particles having a particle size of 1/5 or less on the basis of the particle size are aggregated or fused.

  In one or more embodiments, the non-spherical silica particle A is any one of the silica particles A1, A2, and A3, any two of the silica particles A1, A2, and A3, or the silica particles A1, A2, and Includes all of A3. The proportion (mass ratio) occupied by the total of silica particles A1, A2 and A3 in silica particle A is preferably 50% by mass or more, more preferably from the viewpoint of suppressing reduction in polishing rate and improving the long-period defect removal rate. It is 70 mass% or more, More preferably, it is 80 mass% or more, More preferably, it is 90 mass% or more.

  When the non-spherical silica particles A include silica particles A1 and A2, the mass ratio of A1 / A2 is preferably in the range of 5/95 to 95/5 in one or more embodiments. From the viewpoint of suppressing the decrease in the polishing rate and improving the long cycle defect removal rate, the mass ratio of A1 / A2 is more preferably 20/80 or more and 80/20 or less, and further preferably 20/80 or more and 60/40 or less. More preferably, it is 20/80 or more and 40/60 or less, and still more preferably 20/80 or more and 30/70 or less.

[ΔCV value of non-spherical silica particle A]
In one or a plurality of embodiments, the non-spherical silica particles A preferably have a ΔCV value of more than 0.0%, more preferably from the viewpoint of suppressing a decrease in polishing rate and improving a long-period defect removal rate. It is 0.2% or more, more preferably 0.3% or more, and still more preferably 0.4% or more. In one or more embodiments, the non-spherical silica particles A preferably have a ΔCV value of less than 10.0%, more preferably 8.0% or less, and even more preferably 7. It is 0% or less, more preferably 4.0% or less. Further, in one or a plurality of embodiments, the non-spherical silica particles A are preferably from 0.0% to less than 10.0%, more preferably from 0.2% to 8.0%, from the same viewpoint. Further preferably, it is 0.3% or more and 7.0% or less, and further preferably 0.4% or more and 4.0% or less.

  In the present disclosure, the ΔCV value of the silica particles is the standard deviation of the particle diameter measured based on the scattering intensity distribution at the detection angle of 30 ° (forward scattering) by the dynamic light scattering method, and the detection angle of 30 ° by the dynamic light scattering. The coefficient of variation (CV30) multiplied by 100 divided by the average particle diameter measured based on the scattering intensity distribution (CV30) and the scattering intensity distribution at a detection angle of 90 ° (side scattering) by the dynamic light scattering method. The coefficient of variation (CV90) obtained by dividing the standard deviation of the particle diameter measured based on the average particle diameter measured based on the scattering intensity distribution at a detection angle of 90 ° by dynamic light scattering and multiplying by 100 (CV90 ) (ΔCV = CV30−CV90) and a value indicating the angular dependence of the scattering intensity distribution measured by the dynamic light scattering method. The ΔCV value can be specifically measured by a method described in a practical example.

  The present inventor, as a method for showing the characteristics of non-spherical silica particles, the average particle size (D1) described above, the average particle size (D1) measured by the dynamic light scattering method and the specific surface area converted particle size by the BET method It was thought that the polishing performance of the silica particles could not be expressed only by the conventional view expressed using the ratio (D1 / D2) to (D2). According to further studies by the present inventors, the ΔCV value is effective as a means for knowing the state of the entire system (bulk) of non-spherical silica particles, and by focusing on these parameters, polishing that has not been known in the past It has been found that the reduction in speed is suppressed, the removal rate of long-period defects is improved, and the range of non-spherical silica that can reduce protrusion defects can be accurately defined. That is, the non-spherical silica particles have different ΔCV values depending on the degree of irregularity, and the ΔCV value can be an index indicating the degree of irregularity of the non-spherical silica particles. For example, when the degree of irregularity of non-spherical silica particles increases, pseudo multiple scattering (self-scattering) is likely to occur, and the angle dependency of the scattering intensity distribution measured by the dynamic light scattering method decreases and the ΔCV value decreases. .

  In this disclosure, “scattering intensity distribution” means three particle size distributions (scattering) of sub-micron or less particles determined by dynamic light scattering (DLS) or quasielastic light scattering (QLS). The particle size distribution of the scattering intensity among the intensity, volume conversion, and number conversion. Normally, particles of submicron or less have a Brownian motion in a solvent, and when irradiated with laser light, the intensity of scattered light changes (fluctuates) with time. The fluctuation of the scattered light intensity is calculated by, for example, calculating the autocorrelation coefficient (D) using the photon correlation method (JIS Z 8826), and further using the Einstein-Stokes equation to calculate the average particle size (d: fluid dynamics). Target diameter) can be obtained. In addition to polydispersity index (Polydispersity Index, PI) by cumulant method, particle size distribution analysis includes histogram method (Marquardt method), Laplace inverse transformation method (CONTIN method), non-negative least square method (NNLS method), etc. There is. In the particle size distribution analysis of the dynamic light scattering method, a polydispersity index (PI) by the cumulant method is generally widely used. However, in the detection method that enables detection of non-spherical particles present in the particle dispersion, the average particle size (d50) is determined from the particle size distribution analysis by the histogram method (Marquardt method) or the Laplace inverse transform method (CONTIN method). D1) and the standard deviation are calculated, a CV value (Coefficient of variation: a numerical value obtained by dividing the standard deviation by the average particle diameter and multiplied by 100) is calculated, and its angular dependence (ΔCV value) is preferably used.

  In this disclosure, “angle dependency of the scattering intensity distribution of the particle dispersion” means the scattering intensity according to the scattering angle when the scattering intensity distribution of the particle dispersion is measured at a different detection angle by the dynamic light scattering method. The size of the distribution fluctuation. For example, if the difference in the scattering intensity distribution between the detection angle of 30 ° and the detection angle of 90 ° is large, it can be said that the angle dependency of the scattering intensity distribution of the particle dispersion is large. Therefore, in the present disclosure, measurement of the angle dependence of the scattered intensity distribution includes determining a difference (ΔCV value) between measured values based on the scattered intensity distribution measured at two different detection angles.

  As a combination of two detection angles used for measuring the angle dependency of the scattering intensity distribution, a combination of forward scattering and side or back scattering is preferable from the viewpoint of improving the accuracy of detection of non-spherical particles. Similarly, the detection angle of the forward scattering is preferably 0 to 80 °, more preferably 0 to 60 °, still more preferably 10 to 50 °, and still more preferably 20 to 40 °. Similarly, the side or backscattering detection angle is preferably 80 to 180 °, more preferably 85 to 175 °. In the present disclosure, 30 ° and 90 ° are used as two detection angles for obtaining the ΔCV value.

[Volume average particle diameter of non-spherical silica particle A by dynamic light scattering method (D1)]
The volume average particle diameter (D1) of the non-spherical silica particles A is 120.0 nm or more and less than 300.0 nm from the viewpoint of suppressing a decrease in the polishing rate and improving the long-period defect removal rate. In one or a plurality of embodiments, the volume average particle diameter (D1) of the non-spherical silica particles A is 120.0 nm or more, preferably 150.0 nm or more, more preferably 160.0 nm or more, from the same viewpoint. More preferably, it is 170.0 nm or more, still more preferably 180.0 nm or more, still more preferably 190.0 nm or more, and even more preferably 200.0 nm or more. In one or more embodiments, the volume average particle diameter (D1) of the non-spherical silica particles A is less than 300.0 nm, preferably less than 260.0 nm, more preferably less than 250.0 nm, from the same viewpoint. Even more preferably less than 220.0 nm, even more preferably less than 210.0 nm. Moreover, the volume average particle diameter (D1) of the non-spherical silica particles A is 150.0 nm or more and less than 260.0 nm, preferably 160.0 nm or more and 260.nm, from the same viewpoint in one or more embodiments. Less than 0 nm, more preferably from 170.0 nm to less than 260.0 nm, even more preferably from 180.0 nm to less than 250.0 nm, even more preferably from 190.0 nm to less than 220.0 nm, even more preferably from 200.0 nm to 210 nm Less than 0.0 nm.

  In the present disclosure, the volume average particle diameter (D1) of silica particles refers to an average particle diameter based on a scattering intensity distribution measured by a dynamic light scattering method, and unless otherwise specified, the average particle diameter of silica particles is The average particle diameter based on the scattering intensity distribution measured at a detection angle of 90 ° in the dynamic light scattering method. The volume average particle diameter (D1) of the silica particles in the present disclosure can be specifically obtained by the method described in the examples.

[Particle size ratio of non-spherical silica particles A (D1 / D2)]
The ratio (D1 / D2) of the volume average particle diameter (D1) of the non-spherical silica particles A by the dynamic light scattering method and the specific surface area equivalent particle diameter (D2) by the BET method is determined by the polishing rate in one or a plurality of embodiments. From the standpoint of suppressing the decrease in the length and improving the long-period defect removal rate, it is preferably 2.00 or more, more preferably 2.50 or more, still more preferably 3.00 or more, and even more preferably 3.50 or more. In one or a plurality of embodiments, the particle size ratio (D1 / D2) is preferably 4.00 or less, more preferably 3.90 or less, and further preferably 3.80 or less from the same viewpoint. Moreover, the ratio (D1 / D2) of the volume average particle diameter (D1) of the non-spherical silica particles A by the dynamic light scattering method and the specific surface area converted particle diameter (D2) by the BET method is, in one or more embodiments, From the same viewpoint, 2.00 or more and 4.00 or less are preferable, more preferably 2.50 or more and 3.90 or less, still more preferably 3.00 or more and 3.90 or less, and even more preferably 3.50 or more and 3.3 or less. 80 or less.

In the present disclosure, the specific surface area equivalent particle diameter (D2) of the silica particles is given by the formula of D2 = 2720 / S [nm] from the specific surface area Sm ² / g measured by the nitrogen adsorption method (BET method).

  The ratio (D1 / D2) of the volume average particle diameter (D1) measured by the dynamic light scattering method and the specific surface area converted particle diameter (D2) by the BET method may mean the degree of deformation of the silica particles A. In general, the volume average particle diameter (D1) measured by the dynamic light scattering method is to detect the light scattering in the long direction in the case of irregularly shaped particles. Considering this, the larger the degree of deformation, the larger the numerical value, and the specific surface area equivalent particle diameter (D2) by the BET method is expressed in terms of a sphere based on the volume of the obtained particle, and is a smaller numerical value than D1. From the viewpoint of the polishing rate, the ratio (D1 / D2) is preferably large in the above range.

[CV90 of non-spherical silica particle A]
In one or a plurality of embodiments, the CV90 of the non-spherical silica particles A is preferably 20.0% or more, more preferably 25.0% or more, from the viewpoint of suppressing a decrease in polishing rate and improving the long-period defect removal rate. More preferably, it is 27.0% or more, and / or, similarly, 40.0% or less is preferable, More preferably, it is 38.0% or less, More preferably, it is 35.0% or less, More preferably, it is 32. 0.0% or less. In one or more embodiments, the CV90 of the non-spherical silica particles A is 20.0% or more and 40.0% or less, preferably 25.0% or more and 38.0% or less from the same viewpoint. More preferably, it is 21.0% or more and 35.0% or less, and further preferably 27.0% or more and 32.0% or less.

  In the present disclosure, CV90 of silica particles is a coefficient of variation obtained by dividing the standard deviation based on the scattering intensity distribution by the average particle diameter and multiplying by 100 in the dynamic light scattering method, and has a detection angle of 90 ° (side scatter). ) Is the CV value measured. Specifically, CV90 of silica particles A can be obtained by the method described in the examples.

[Content of non-spherical silica particles A in the polishing composition]
In one or a plurality of embodiments, the content of the non-spherical silica particles A contained in the polishing composition is preferably 0.1% by mass or more from the viewpoint of suppressing a decrease in polishing rate and improving a long-period defect removal rate. 0.5 mass% or more is more preferable, 1 mass% or more is further more preferable, and 2 mass% or more is further more preferable. The content is preferably 30% by mass or less, more preferably 25% by mass or less, still more preferably 20% by mass or less, and even more preferably 15% by mass or less from the viewpoint of economy. In one or a plurality of embodiments, the content of the non-spherical silica particles A contained in the polishing composition is 0.1 from the viewpoint of suppressing the decrease in polishing rate, improving the long-period defect removal rate, and economically. % By mass to 30% by mass is preferable, 0.5% by mass to 25% by mass is more preferable, 1% by mass to 20% by mass is further preferable, and 2% by mass to 15% by mass is even more preferable.

[Method for producing non-spherical silica particle A]
Silica particles A are manufactured by the flame melting method, the sol-gel method, and the pulverization method from the viewpoint of suppressing the decrease in the polishing rate in the rough polishing, removing the long-period defects, 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 aqueous alkali silicate solution as a starting material. In addition, as a usage form of the non-spherical silica particles A, a slurry form is preferable.

Silica particles are usually 1) a mixture (seed solution) of less than 10% by weight of No. 3 sodium silicate and seed particles (small-size silica) is put in a reaction vessel and heated to 60 ° C. or higher. 2) Spherical particles are grown by dropping an acidic active silicic acid aqueous solution obtained by passing No. 3 silicate through a cation exchange resin and an alkali (alkali metal or quaternary ammonium) to keep the pH constant, and 3) evaporating after aging. It is obtained by concentrating by a method or an ultrafiltration method (Japanese Patent Application Laid-Open No. 47-1964, Japanese Patent Publication No. 1-223412, Japanese Patent Publication No. 4-55125, Japanese Patent Publication No. 4-55127). However, it is often reported that non-spherical silica particles A can be produced if the steps are slightly changed in the same production process. For example, activated silicic acid is very unstable, and when a polyvalent metal ion such as Ca or Mg is intentionally added, an elongated silica sol can be produced. Furthermore, the temperature of the reaction product (evaporates when the boiling point of water is exceeded and the silica is dried at the gas-liquid interface), the pH of the reaction product (silica particles are liable to be linked below 9), and the reaction product SiO ₂ / M ₂ O. (M is an alkali metal or quaternary ammonium), and non-spherical silica can be produced by changing the molar ratio (selectively producing non-spherical silica at 30 to 60) (Japanese Patent Publication No. 8-5657, Patent 2803134, JP-A-2003-133267, JP-A-2006-80406, JP-A-2007-153671, JP-A-2009-137791, JP-A-2009-149493, JP-A-2011-16702). However, the manufacturing method of the silica particle A is limited to these and is not interpreted.

  The method of adjusting the particle size distribution of the non-spherical silica particles A is not particularly limited, but a method of giving a desired particle size distribution by adding particles as new nuclei in the process of particle growth in the production stage. Alternatively, a method of mixing two or more types of silica particles having different particle size distributions to have a desired particle size distribution can be used.

[Spherical silica particles B]
The polishing liquid composition according to the present disclosure further contains spherical silica particles B as abrasive grains. In one or more embodiments, examples of the spherical silica particles B include colloidal silica, fumed silica, and surface-modified silica. Colloidal silica is preferable from the viewpoints of suppressing a decrease in polishing rate, improving the long-period defect removal rate, and reducing protrusion defects.

  In the present disclosure, the “spherical silica particle” may be a spherical particle close to a true sphere in one or a plurality of embodiments from the viewpoint of suppressing a decrease in polishing rate and improving a long-period defect removal rate. If it is 0.9-1.1, it can fully be used. The “spherical silica particles” may correspond to generally commercially available colloidal silica in one or more embodiments.

  In one or a plurality of embodiments, the spherical silica particle B may be one type of spherical silica particle or a combination of two or more types of spherical silica particles. When the spherical silica particles B are a combination of two or more types of spherical silica particles, in one or more embodiments, each spherical silica particle meets the requirements for “spherical silica particles B” described in this disclosure. Fulfill. In one or a plurality of embodiments, the spherical silica particles B are preferably two or more types having different particle diameters from the viewpoint of suppressing a decrease in polishing rate and improving a long-period defect removal rate.

[Volume average particle diameter of spherical silica particle B by dynamic light scattering method (D1)]
The volume average particle diameter (D1) of the spherical silica particles B is 6.0 nm or more and 40.0 nm or less from the viewpoint of suppressing a decrease in the polishing rate and improving the long-period defect removal rate. In one or a plurality of embodiments, the volume average particle diameter (D1) of the non-spherical silica particles A is 6.0 nm or more, preferably 7.0 nm or more, from the same viewpoint. In one or a plurality of embodiments, the volume average particle diameter (D1) of the spherical silica particles B is 40.0 nm or less, preferably 35.0 nm or less, more preferably 30.0 nm or less, from the same viewpoint. is there. Further, the volume average particle diameter (D1) of the spherical silica particles B is 6.0 nm or more and 40.0 nm or less, preferably 60.0 nm or more and 35.0 nm, from the same viewpoint in one or a plurality of embodiments. Hereinafter, it is more preferably 7.0 nm or more and 30.0 nm or less.

[Particle size ratio of spherical silica particles B (D1 / D2)]
The ratio (D1 / D2) of the volume average particle diameter (D1) obtained by the dynamic light scattering method of the spherical silica particles B and the specific surface area converted particle size (D2) obtained by the BET method is the polishing rate in one or more embodiments. From the viewpoint of suppressing the decrease and improving the long-period defect removal rate, it is preferably 1.00 or more, more preferably 1.10 or more, and still more preferably 1.15 or more. In one or more embodiments, the particle diameter ratio (D1 / D2) of the spherical silica particles B is preferably 1.50 or less, more preferably 1.40 or less, and still more preferably 1.30 or less, from the same viewpoint. It is. Moreover, the ratio (D1 / D2) of the volume average particle diameter (D1) of the spherical silica particles B by the dynamic light scattering method and the specific surface area equivalent particle diameter (D2) by the BET method is the same in one or a plurality of embodiments. From this point of view, it is 1.00 or more and 1.50 or less, preferably 1.10 or more and 1.40 or less, more preferably 1.15 or more and 1.30 or less.

[Content of spherical silica particles B in polishing liquid composition]
In one or a plurality of embodiments, the content of the non-spherical silica particles A contained in the polishing composition is preferably 0.1% by mass or more from the viewpoint of suppressing a decrease in polishing rate and improving a long-period defect removal rate. 0.5 mass% or more is more preferable, 1 mass% or more is further more preferable, and 2 mass% or more is further more preferable. The content is preferably 30% by mass or less, more preferably 25% by mass or less, still more preferably 20% by mass or less, and even more preferably 15% by mass or less from the viewpoint of economy.

[Method for producing spherical silica particle B]
Spherical silica particles B are produced by the flame melting method, the sol-gel method, and the pulverization method from the viewpoint of suppressing the decrease in the polishing rate in the rough polishing, removing the long-period defects, and reducing the protrusion defects after the rough polishing and the final polishing. Rather, silica particles produced by a particle growth method using an alkali silicate aqueous solution as a starting material are preferable. In addition, as a usage form of the spherical silica particles B, a slurry form is preferable.

[Frequency of volume particle size distribution of non-spherical silica particles A and spherical silica particles B]
The total overlap frequency of the volume particle size distributions of the non-spherical silica particles A and the spherical silica particles B in the polishing liquid composition according to the present disclosure is the reduction in the polishing rate and the long-period defect removal rate in one or more embodiments. From the viewpoint of improvement, it is preferably 0% to 40%, more preferably 10% to 38%, still more preferably 15% to 36%, and even more preferably 20% to 35%. In addition, the overlapping frequency of the volume particle size distribution of the non-spherical silica particles A and the spherical silica particles B can be specifically obtained by the method described in the examples.

[Mass ratio of non-spherical silica particles A and spherical silica particles B in the polishing composition]
The mass ratio (A / B) of the content of the non-spherical silica particles A and the spherical silica particles B in the polishing liquid composition according to the present disclosure is such that, in one or a plurality of embodiments, the polishing rate is reduced and long-period defects are suppressed. From the viewpoint of improving the removal rate, it is 80/20 or more, preferably 85/15 or more, more preferably 90/10 or more. In one or more embodiments, the mass ratio (A / B) of the content of the non-spherical silica particles A and the spherical silica particles B is 99/1 or less, and preferably 95/5 or less, from the same viewpoint. More preferably, it is 96/4 or less. In addition, when the spherical silica particle B is a combination of two or more types of spherical silica particles, the content of the spherical silica particles B refers to the total content thereof. The same applies to the content of non-spherical silica particles A.

[Content of Other Silica Particles in Polishing Liquid Composition]
In one or more embodiments of the polishing liquid composition according to the present disclosure, when the polishing liquid composition contains silica particles in addition to the non-spherical silica particles A and the spherical silica particles B, the entire silica particles in the polishing liquid composition are used. The total mass ratio of the non-spherical silica particles A and the spherical silica particles B exceeds 98.0% by mass, preferably 98.5% by mass or more, from the viewpoint of suppressing a decrease in the polishing rate and improving the long-period defect removal rate. More preferably, it is 99.0% by mass or more, more preferably 99.5% by mass or more, and still more preferably 99.8% by mass or more.

[acid]
In one or a plurality of embodiments, the polishing liquid composition contains an acid from the viewpoint of suppressing a decrease in polishing rate and improving a long-period defect removal rate. The use of an acid in the polishing liquid composition includes the use of an acid and / or a salt thereof. Examples of acids used include nitric acid, sulfuric acid, sulfurous acid, persulfuric acid, hydrochloric acid, perchloric acid, phosphoric acid, phosphonic acid, phosphinic acid, pyrophosphoric acid, tripolyphosphoric acid, amidosulfuric acid, 2-aminoethylphosphonic acid, and the like. 1-hydroxyethylidene-1,1-diphosphonic acid, aminotri (methylenephosphonic acid), ethylenediaminetetra (methylenephosphonic acid), diethylenetriaminepenta (methylenephosphonic acid), ethane-1,1, -diphosphonic acid, ethane-1, 1,2-triphosphonic acid, ethane-1-hydroxy-1,1-diphosphonic acid, ethane-1-hydroxy-1,1,2-triphosphonic acid, ethane-1,2-dicarboxy-1,2-diphosphonic acid , Methanehydroxyphosphonic acid, 2-phosphonobutane-1,2-dicarboxylic acid, 1-phosphonobutane-2 Organic phosphonic acids such as 3,4-tricarboxylic acid and α-methylphosphonosuccinic acid, aminocarboxylic acids such as glutamic acid, picolinic acid and aspartic acid, citric acid, tartaric acid, oxalic acid, nitroacetic acid, maleic acid, oxaloacetic acid, etc. And carboxylic acid. In one or a plurality of embodiments, phosphoric acid, sulfuric acid, citric acid, tartaric acid, maleic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, from the viewpoint of suppressing a decrease in polishing rate and improving a long-period defect removal rate, More preferred are aminotri (methylenephosphonic acid), ethylenediaminetetra (methylenephosphonic acid), diethylenetriaminepenta (methylenephosphonic acid) and salts thereof, sulfuric acid, 1-hydroxyethylidene-1,1-diphosphonic acid, aminotri (methylenephosphonic acid) And their salts are more preferred, and sulfuric acid is even more preferred.

  These acids and salts thereof may be used alone or as a mixture of two or more thereof. However, in one or a plurality of embodiments, two types are used from the viewpoint of suppressing a decrease in polishing rate and improving a long-period defect removal rate. It is preferable to use a mixture of the above, and two or more acids selected from the group consisting of phosphoric acid, sulfuric acid, citric acid, tartaric acid, 1-hydroxyethylidene-1,1-diphosphonic acid, and aminotri (methylenephosphonic acid) It is more preferable to use a mixture of these.

  When these acid salts are used, there is no particular limitation, and specific examples include metals, ammonium, alkylammonium and the like. Specific examples of the metal include metals belonging to the periodic table (long-period type) 1A, 1B, 2A, 2B, 3A, 3B, 4A, 6A, 7A, or Group 8. In one or a plurality of embodiments, a salt with a metal belonging to Group 1A or ammonium is preferable from the viewpoint of suppressing a decrease in polishing rate and improving a long-period defect removal rate.

  In one or a plurality of embodiments, the content of the acid in the polishing composition is preferably 0.001% by mass or more, more preferably from the viewpoint of suppressing a decrease in polishing rate and improving a long-period defect removal rate. 0.01% by mass or more, more preferably 0.05% by mass or more, still more preferably 0.1% by mass or more, preferably 5.0% by mass or less, more preferably 4.0% by mass or less, Preferably it is 3.0 mass% or less, More preferably, it is 2.0 mass% or less.

[Oxidant]
In one or a plurality of embodiments, the polishing composition contains an oxidizing agent from the viewpoint of suppressing a decrease in polishing rate and improving a long-period defect removal rate. The oxidizing agent used includes at least one selected from the group consisting of hydrogen peroxide, peroxodisulfate, and periodic acid and salts thereof. Further, other peroxides, permanganic acid or a salt thereof, chromic acid or a salt thereof, peroxo acid or a salt thereof, oxygen acid or a salt thereof may be included. Periodic acid may be metaperiodic acid or orthoperiodic acid. These oxidizing agents may be used alone or in admixture of two or more.

  In one or a plurality of embodiments, the content of the oxidizing agent in the polishing composition is preferably 0.01% by mass or more, more preferably from the viewpoint of suppressing a decrease in polishing rate and improving the long-period defect removal rate. 0.05% by mass or more, more preferably 0.1% by mass or more, and in one or a plurality of embodiments, preferably 4% by mass or less from the viewpoint of suppressing a decrease in polishing rate and improving a long-period defect removal rate. More preferably, it is 2 mass% or less, More preferably, it is 1.5 mass% or less.

[water]
The polishing composition contains water as a medium. As water, distilled water, ion-exchanged water, pure water, ultrapure water, or the like can be used. The content of water in the polishing liquid composition is preferably 55% by mass or more and 99.98% by mass or less, more preferably 70% by mass or more and 98% by mass or less, because handling of the polishing liquid composition becomes easy. Preferably they are 80 mass% or more and 97 mass% or less, More preferably, they are 85 mass% or more and 97 mass% or less.

[Other ingredients]
Another component can be mix | blended with polishing liquid composition as needed. Examples of other components include buffers, thickeners, dispersants, rust inhibitors, basic substances, surfactants, and polymer compounds. The content of these other optional components in the polishing composition is preferably blended within a range not impairing the effects of the present disclosure, preferably 0% by mass to 10% by mass, and more preferably 0% by mass to 5% by mass. The following is more preferable.

[PH of polishing composition]
In one or a plurality of embodiments, the pH of the polishing composition is 0.5 or more using the above-described acid or a known pH adjuster from the viewpoint of suppressing a decrease in polishing rate and improving the long-period defect removal rate. It is preferable to adjust to 6.0 or less, more preferably pH 0.7 or more, further preferably pH 0.8 or more, still more preferably pH 0.9 or more, more preferably pH 4.0 or less, still more preferably pH 3 0.0 or less, even more preferably pH 2.0 or less. In addition, said pH is pH of polishing liquid composition in 25 degreeC, can be measured using a pH meter, and is a numerical value 4 minutes after immersing an electrode in polishing liquid composition.

[Method for preparing polishing liquid composition]
The polishing composition according to the present disclosure can be prepared by, for example, mixing non-spherical silica particles A, spherical silica particles B, acid, an oxidizing agent, and water, and, if desired, other components by a known method. . As another embodiment, the polishing composition may be prepared as a concentrate. The mixing is not particularly limited, and can be performed using a homomixer, a homogenizer, an ultrasonic disperser, a stirrer such as a wet ball mill, or the like.

  Therefore, in one aspect, the present disclosure relates to a method for producing a polishing liquid composition for a magnetic disk substrate, which includes mixing non-spherical silica particles A, spherical silica particles B, an acid, an oxidizing agent, and water. The non-spherical silica particles A, the spherical silica particles B, and the mixing ratio thereof are as described above.

[Method of manufacturing magnetic disk substrate]
In general, a magnetic disk is made by polishing a glass substrate that has undergone a fine grinding process or an aluminum alloy substrate that has undergone a Ni-P plating process in a rough polishing process and a final polishing process, and then converted into a magnetic disk in a recording part forming process. Manufactured by. In one aspect, the present disclosure relates to a method for manufacturing a magnetic disk substrate having the following steps (1) to (3).
(1) A step of polishing a surface to be polished of a substrate to be polished using the polishing liquid composition according to the present disclosure,
(2) a step of cleaning the substrate obtained in step (1), and
(3) The substrate obtained in step (2) has a step of polishing the surface to be polished using the polishing liquid composition B containing silica particles,
The steps (1) and (3) are performed with another polishing machine.

In one or a plurality of embodiments, a method for manufacturing a magnetic disk substrate according to the present disclosure is a method for manufacturing a magnetic disk substrate having the following steps (1) to (3).
(1) Supplying the polishing composition according to the present disclosure to a surface to be polished of a substrate to be polished, bringing the polishing pad into contact with the surface to be polished, and moving the polishing pad and / or the substrate to be polished to move the polishing target Polishing the surface.
(2) A step of cleaning the substrate obtained in step (1).
(3) A polishing liquid composition B containing silica particles and water is supplied to the polishing target surface of the substrate obtained in step (2), and the polishing pad is brought into contact with the polishing target surface, and the polishing pad and / or Moving the substrate to be polished to polish the surface to be polished;

[Step (1): Rough polishing step]
In the step (1), the polishing composition according to the present disclosure is supplied to the surface to be polished of the substrate to be polished, the polishing pad is brought into contact with the surface to be polished, and the polishing pad and / or the substrate to be polished is moved. In this step, the surface to be polished is polished. The polishing machine used in the step (1) is not particularly limited, and a known polishing machine for polishing a magnetic disk substrate can be used. As a polishing method using a polishing machine, in one embodiment that is not limited, the substrate to be polished is sandwiched between the surface plates to which the polishing pad is attached, and the surface plate or the substrate to be polished is supplied while supplying the polishing composition to the surface to be polished. A method of moving and polishing the substrate to be polished can be mentioned.

[Step (1): Substrate to be polished]
The substrate to be polished in step (1) is a magnetic disk substrate or a substrate used for a magnetic disk substrate. For example, a Ni-P plated aluminum alloy substrate, silicate glass, aluminosilicate glass, crystallization Examples thereof include glass substrates such as glass and tempered glass. Especially, as a to-be-polished substrate used by this indication, the aluminum alloy substrate by which Ni-P plating was carried out is preferred. There is no restriction | limiting in particular in the shape of the said to-be-polished substrate, For example, what is necessary is just the shape which has planar parts, such as a disk shape, plate shape, slab shape, prism shape, and the shape which has curved surface parts, such as a lens. Of these, a disk-shaped substrate to be polished is suitable. In the case of a disk-shaped substrate to be polished, the outer diameter is, for example, about 2 to 95 mm, and the thickness is, for example, about 0.5 to 2 mm.

[Step (1): Polishing pad]
There is no restriction | limiting in particular as a polishing pad used by the rough | crude grinding | polishing process of a process (1), It is using the polishing pad of a suede type, a nonwoven fabric type, a polyurethane closed-cell foam type, or the two-layer type which laminated | stacked these. However, a suede type polishing pad is preferable from the viewpoint of suppressing a decrease in polishing rate. A suede type polishing pad is composed of a foam layer having a base layer and spindle-shaped pores perpendicular to the base layer. Examples of the material of the base layer include a non-woven fabric made of natural fibers such as cotton and synthetic fibers, and a base layer obtained by filling a rubber-like substance such as styrene butadiene rubber. In one or a plurality of embodiments, polishing is performed. From the viewpoint of suppressing the decrease in speed and improving the long-period defect removal rate, a polyester film is preferable, and a polyethylene terephthalate (PET) film from which a high-hardness resin film can be obtained is more preferable. In addition, examples of the material for the foam layer include polyurethane, polystyrene, polyester, polyvinyl chloride, natural rubber, and synthetic rubber. From the viewpoint of improving the physical properties such as compressibility and improving the abrasion resistance during polishing. Therefore, polyurethane is preferable, and polyurethane elastomer is more preferable.

  Further, the average pore diameter of the polishing pad used in the step (1) is preferably 10 μm or more from the viewpoint of suppressing a decrease in polishing rate and improving a long-period defect removal rate in one or a plurality of embodiments. Is 20 μm or more, more preferably 30 μm or more, even more preferably 35 μm or more, and preferably 100 μm or less, more preferably 80 μm or less, still more preferably 60 μm or less, and even more preferably 55 μm or less.

[Step (1): Polishing load]
In the present disclosure, the polishing load means the pressure of the surface plate applied to the polishing surface of the substrate to be polished during polishing. In one or a plurality of embodiments, the polishing load in the step (1) is preferably 30.0 kPa or less, more preferably 20.0 kPa or less, more preferably 20.0 kPa or less, from the viewpoint of suppressing reduction in polishing rate and improving the long-period defect removal rate. Preferably it is 14.0 kPa or less. In one or a plurality of embodiments, the polishing load is preferably 3.0 kPa or more, more preferably 7.0 kPa or more, and still more preferably, from the viewpoint of suppressing reduction in polishing rate and improving the long-period defect removal rate. It is 9.0 kPa or more. The polishing load can be adjusted by applying air pressure or weight to the surface plate or the substrate.

[Step (1): Polishing amount]
In one or more embodiments, the polishing amount per unit area (1 cm ² ) of the substrate to be polished and the polishing time per minute in the step (1) is a reduction in the polishing rate and an improvement in the long-period defect removal rate. From the viewpoint, 0.05 mg / (cm ² · min) or more is preferable, more preferably 0.10 mg / (cm ² · min) or more, and further preferably 0.12 mg / (cm ² · min) or more. On the other hand, from the viewpoint of avoiding a significant increase in the polishing time of rough polishing, and in one or a plurality of embodiments, from the viewpoint of suppressing a decrease in polishing rate and improving the long-period defect removal rate, 0.50 mg / (cm ² · min) or less, more preferably 0.30 mg / (cm ² · min) or less, and still more preferably 0.25 mg / (cm ² · min) or less.

[Step (2): Cleaning step]
Step (2) is a step of cleaning the substrate obtained in step (1). Step (2) is a step of cleaning the substrate that has been subjected to the rough polishing in step (1) with a cleaning composition in one or more embodiments. Although the cleaning method in the step (2) is not particularly limited, in one or a plurality of embodiments, the method of immersing the substrate obtained in the step (1) in the cleaning composition (cleaning method a), and the cleaning agent The method (cleaning method b) which injects a composition and supplies a cleaning composition on the surface of the board | substrate obtained by process (1) is mentioned.

[Step (2): Cleaning method a]
In the cleaning method a, the conditions for immersing the substrate in the cleaning composition are not particularly limited. For example, the temperature of the cleaning composition is 20 ° C. or more and 100 ° C. or less from the viewpoint of safety and operability. The immersion time is preferably 10 seconds or longer and 30 minutes or shorter from the viewpoint of the cleaning properties and production efficiency of the cleaning composition. Moreover, it is preferable that ultrasonic vibration is given to the cleaning composition from the viewpoint of improving the removability of the residue and the dispersibility of the residue. The frequency of the ultrasonic wave is preferably 20 kHz to 2000 kHz, more preferably 40 kHz to 2000 kHz, and still more preferably 40 kHz to 1500 kHz.

[Step (2): Cleaning method b]
In the cleaning method b, from the viewpoint of promoting the cleaning performance of the residue and the solubility of the oil, the cleaning composition to which ultrasonic vibration is applied is injected to bring the cleaning composition into contact with the surface of the substrate. Or cleaning the surface by supplying the cleaning composition onto the surface of the substrate to be cleaned by injection and rubbing the surface supplied with the cleaning composition with a cleaning brush. preferable. Furthermore, the cleaning composition to which ultrasonic vibration is applied is supplied to the surface to be cleaned by injection, and the surface to which the cleaning composition is supplied is cleaned by rubbing with a cleaning brush. Is preferred.

[Step (2): Cleaning composition]
As a cleaning composition of a process (2), in one or some embodiment, what contains an alkali agent, water, and various additives as needed can be used.

[Step (2): Alkaline agent in cleaning composition]
The alkaline agent used in the cleaning composition may be either an inorganic alkaline agent or an organic alkaline agent. Examples of the inorganic alkaline agent include ammonia, potassium hydroxide, and sodium hydroxide. Examples of the organic alkali agent include one or more selected from the group consisting of hydroxyalkylamine, tetramethylammonium hydroxide, and choline. These alkaline agents may be used alone or in combination of two or more. From the viewpoint of improving the dispersibility of the residue on the substrate of the cleaning composition and improving the storage stability, the alkaline agent includes potassium hydroxide, sodium hydroxide, monoethanolamine, methyldiethanolamine, and aminoethylethanol. At least one selected from the group consisting of amines is preferred, and at least one selected from the group consisting of potassium hydroxide and sodium hydroxide is more preferred.

[Step (3): Final polishing step]
In the step (3), the polishing composition B containing silica particles and water is supplied to the polishing target surface of the substrate obtained in the step (2), the polishing pad is brought into contact with the polishing target surface, and the polishing pad And / or polishing the surface to be polished by moving the substrate to be polished. The polishing machine used in the step (3) is a step (1) from the viewpoint of reducing protrusion defects after finish polishing and using pads having different pore diameters from rough polishing in order to efficiently reduce other surface defects. The polishing machine is different from the polishing machine used in the above. As a polishing method using a polishing machine, in one embodiment that is not limited, the polishing substrate is sandwiched between the surface plates to which the polishing pad is attached, and the polishing liquid composition B is supplied to the surface to be polished while the surface plate or the polishing target substrate is supplied. The method of grind | polishing a to-be-polished substrate by moving is mentioned. The supply rate of the polishing liquid composition B used in the step (3) and the method of supplying the polishing liquid composition B to the polishing machine can be the same as in the case of the polishing liquid composition described above.

  The method of manufacturing a magnetic disk substrate according to the present disclosure includes a rough polishing step in step (1), a cleaning step in step (2), and a final polishing step in step (3), whereby long-period defects after polishing are removed. A substrate with improved removal rate and reduced protrusion defects can be efficiently manufactured.

[Step (3): Polishing liquid composition B]
Polishing liquid composition B used at a process (3) contains a silica particle as an abrasive from a viewpoint of protrusion defect reduction. The silica particles used are preferably colloidal silica from the viewpoint of reducing protrusion defects after finish polishing. Moreover, it is preferable that the polishing liquid composition B does not contain an alumina particle from a viewpoint of reducing the protrusion defect after final polishing.

[Step (3): Volume average particle diameter of silica particles of polishing composition B by dynamic light scattering method (D1)]
The volume average particle diameter (D1) of the silica particles of the polishing composition B is preferably 1.0 nm or more, more preferably 5.0 nm or more, and still more preferably 10.5 nm from the viewpoint of reducing protrusion defects after finish polishing. It is 0 nm or more, 40.0 nm or less is preferable, More preferably, it is 37.0 nm or less, More preferably, it is 35.0 nm or less. Further, the volume average particle diameter (D1) of the silica particles of the polishing composition B is preferably smaller than the volume average particle diameter (D1) of the silica particles A from the viewpoint of reducing protrusion defects after finish polishing. In addition, this average particle diameter can be calculated | required by the method as described in an Example.

[Content of silica particles in polishing liquid composition B]
The content of the silica particles contained in the polishing composition B is preferably 0.5% by mass or more, from the viewpoint of improving the polishing rate in finish polishing, and from the viewpoint of reducing protrusion defects after finish polishing, and 1.0% by mass. % Or more is more preferable, 3.0% by mass or more is more preferable, 4.0% by mass or more is further more preferable, 20% by mass or less is preferable, 15% by mass or less is more preferable, and 10% by mass or less is more preferable. 8 mass% or less is still more preferable.

[Step (3): pH of polishing composition B]
The pH of the polishing composition B is from 0.5 to 3 by using the above-mentioned acid or a known pH adjuster from the viewpoint of improving the polishing rate in finish polishing and reducing the protrusion defects after finish polishing. It is preferably adjusted to 0 or less, more preferably pH 1.0 or more, further preferably pH 2.5 or less, and even more preferably pH 2.0 or less. In addition, said pH is pH of polishing liquid composition in 25 degreeC, can be measured using a pH meter, and is a numerical value 4 minutes after immersing an electrode in polishing liquid composition.

  The polishing composition B preferably contains at least one selected from a heterocyclic aromatic compound, a polyvalent amine compound, and a polymer having an anionic group, from the viewpoint of reducing protrusion defects after finish polishing. It is more preferable to contain 2 or more types, and it is more preferable to contain a heterocyclic aromatic compound, a polyvalent amine compound, and a polymer having an anionic group.

  The polishing composition B preferably contains an acid and an oxidizing agent from the viewpoint of improving the polishing rate. About the preferable usage aspect of an acid, it is the same as that of the case of the above-mentioned polishing liquid composition. Moreover, about the water used for polishing liquid composition B, and the preparation method of polishing liquid composition B, it is the same as that of the case of the above-mentioned polishing liquid composition.

[Step (3): Polishing pad]
As the polishing pad used in the step (3), the same type of polishing pad as that used in the step (1) can be used. The average pore diameter of the polishing pad used in the step (3) is preferably 1 μm or more and 50 μm or less, more preferably 2 μm or more and 40 μm or less, and further preferably 3 μm or more and 30 μm or less, from the viewpoint of reducing protrusion defects after finish polishing. It is.

[Step (3): Polishing load]
The polishing load in the step (3) is preferably 16.0 kPa or less, more preferably 14.0 kPa or less, still more preferably 10.0 kPa or less, and even more preferably 8, from the viewpoint of reducing protrusion defects after finish polishing. 0 kPa or less. From the viewpoint of reducing protrusion defects after finish polishing, 6.0 kPa or more is preferable, more preferably 7.0 kPa or more, and further preferably 7.5 kPa or more.

[Step (3): Polishing amount]
In the step (3), the polishing amount per unit area (1 cm ² ) of the substrate to be polished and the polishing time per minute is 0.02 mg / (cm ² · min) from the viewpoint of reducing protrusion defects after the final polishing. or more, more preferably 0.03mg / (cm ² · min) or more, still more preferably 0.04mg / (cm ² · min) or more. Further, from the viewpoint of improving productivity, preferably 0.15mg / (cm ² · min) or less, more preferably 0.12mg / (cm ² · min) or less, more preferably 0.10mg / (cm ² · Min) or less.

  According to the manufacturing method of the present disclosure, it is possible to provide a magnetic disk substrate with improved long-period defect removal rate and reduced protrusion defects with high productivity.

[Polishing method]
As another aspect, the present disclosure relates to a polishing method having the above-described step (1), step (2), and step (3). That is, the present disclosure includes (1) a step of polishing a surface to be polished of a substrate to be polished using the polishing composition according to the present disclosure, (2) a step of cleaning the substrate obtained in step (1), and (3) The substrate obtained in the step (2) has a step of polishing the surface to be polished using the polishing composition B containing silica particles, and the steps (1) and (3) are different from each other. The present invention relates to a polishing method, which is performed by a polishing machine, and the substrate to be polished is a substrate for manufacturing a magnetic disk substrate. Regarding the substrate to be polished, the polishing pad, the polishing liquid composition B, the polishing method and conditions, the cleaning agent composition, and the cleaning method in the steps (1) to (3), The same can be said.

  Regarding the above-described embodiment, the present disclosure further discloses a composition, a production method, or an application according to one or more of the following embodiments.

  <1> A polishing composition for a magnetic disk substrate containing silica particles, an acid, an oxidizing agent, and water, wherein the silica particles have a volume average particle diameter (D1) determined by a dynamic light scattering method of 120.0 nm or more. A non-spherical silica particle A having a particle diameter of less than 300.0 nm and a spherical silica particle B having a volume average particle diameter (D1) by a dynamic light scattering method of 6.0 nm or more and 40.0 nm or less. The nonspherical silica particles A and the spherical silica particles B are mixed so that the mass ratio (A / B) is 80/20 or more and 99/1 or less, and the nonspherical silica particles A with respect to the entire silica particles in the polishing composition are The total mass ratio of the spherical silica particles B exceeds 98.0% by mass, and the non-spherical silica particles A have a volume average particle diameter (D1) determined by the dynamic light scattering method and a specific surface area converted particle diameter (D2) determined by the BET method. ) Ratio (D1 / D2) Is 2.00 or more and 4.00 or less, and the total overlap frequency of the volume particle size distribution by the dynamic light scattering method of each of the non-spherical silica particles A and the spherical silica particles B is 0% or more and 40% or less. Polishing liquid composition for magnetic disk substrates.

<2> The non-spherical silica particles A preferably have a ΔCV value of more than 0.0%, more preferably 0.2% or more, still more preferably 0.3% or more, and even more preferably 0.00. The polishing composition for a magnetic disk substrate according to <1>, which is 4% or more.
<3> The non-spherical silica particles A preferably have a ΔCV value of less than 10.0%, more preferably 8.0% or less, still more preferably 7.0% or less, and even more preferably 4.0. % Of the polishing composition for a magnetic disk substrate according to <1> or <2>.
<4> The non-spherical silica particles A preferably have a ΔCV value of more than 0.0% and less than 10.0%, more preferably 0.2% to 8.0%, and even more preferably 0.3. % Polishing composition for magnetic disk substrate according to any one of <1> to <3>, wherein the polishing liquid composition is from 0.4% to 7.0%, more preferably from 0.4% to 4.0%.
<5> The volume average particle diameter (D1) of the non-spherical silica particles A is 120.0 nm or more, preferably 150.0 nm or more, more preferably 160.0 nm or more, still more preferably 170.0 nm or more, The magnetic disk substrate polishing liquid according to any one of <1> to <4>, more preferably 180.0 nm or more, still more preferably 190.0 nm or more, and even more preferably 200.0 nm or more. Composition.
<6> The volume average particle diameter (D1) of the non-spherical silica particles A is less than 300.0 nm, preferably less than 260.0 nm, more preferably less than 250.0 nm, and even more preferably less than 220.0 nm. The polishing composition for a magnetic disk substrate according to any one of <1> to <5>, which is even more preferably less than 210.0 nm.
<7> The volume average particle diameter (D1) of the non-spherical silica particles A is preferably 150.0 nm or more and less than 260.0 nm, more preferably 160.0 nm or more and less than 260.0 nm, and further preferably 170.nm. 0 to 260.0 nm, even more preferably 180.0 to 250.0 nm, even more preferably 190.0 to 220.0 nm, even more preferably 200.0 to 210.0 nm, <1 The polishing composition for a magnetic disk substrate according to any one of <6> to <6>.
<8> The ratio (D1 / D2) of the volume average particle diameter (D1) by the dynamic light scattering method of the non-spherical silica particles A to the specific surface area equivalent particle diameter (D2) by the BET method is preferably 2.00 or more. The polishing composition for a magnetic disk substrate according to any one of <1> to <7>, more preferably 2.50 or more, further preferably 3.00 or more, and even more preferably 3.50 or more.
<9> The ratio (D1 / D2) of the volume average particle diameter (D1) by the dynamic light scattering method of the non-spherical silica particles A to the specific surface area equivalent particle diameter (D2) by the BET method is preferably 4.00 or less. The polishing composition for a magnetic disk substrate according to any one of <1> to <8>, more preferably 3.90 or less, and still more preferably 3.80 or less.
<10> The ratio (D1 / D2) of the volume average particle diameter (D1) by the dynamic light scattering method of the non-spherical silica particles A to the specific surface area equivalent particle diameter (D2) by the BET method is preferably 2.50 or more. 3.90 or less, more preferably 3.00 or more and 3.90 or less, and further preferably 3.50 or more and 3.80 or less, the polishing liquid for a magnetic disk substrate according to any one of <1> to <9> Composition.
<11> The CV90 of the non-spherical silica particles A is preferably 20.0% or more, more preferably 25.0% or more, and further preferably 27.0% or more, and any one of <1> to <10> 2. A polishing liquid composition for a magnetic disk substrate according to 1.
<12> The CV90 of the non-spherical silica particles A is preferably 40.0% or less, more preferably 38.0% or less, still more preferably 35.0% or less, and even more preferably 32.0% or less. The polishing composition for a magnetic disk substrate according to any one of <1> to <11>.
<13> The CV90 of the non-spherical silica particles A is preferably 20.0% or more and 40.0% or less, more preferably 25.0% or more and 38.0% or less, and further preferably 21.0% or more and 35.0%. % Or less, and more preferably 27.0% or more and 32.0% or less, the polishing composition for a magnetic disk substrate according to any one of <1> to <12>.
<14> The content of the non-spherical silica particles A contained in the polishing composition is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, further preferably 1% by mass or more, The polishing composition for a magnetic disk substrate according to any one of <1> to <13>, more preferably 2% by mass or more.
<15> The content of non-spherical silica particles A contained in the polishing composition is preferably 30% by mass or less, more preferably 25% by mass or less, still more preferably 20% by mass or less, and even more preferably 15% by mass. The polishing composition for a magnetic disk substrate according to any one of <1> to <14>, wherein:
<16> The content of non-spherical silica particles A contained in the polishing composition is preferably 0.1% by mass to 30% by mass, more preferably 0.5% by mass to 25% by mass, and still more preferably. The polishing composition for a magnetic disk substrate according to any one of <1> to <15>, which is 1% by mass to 20% by mass, and more preferably 2% by mass to 15% by mass.
<17> The magnetic disk according to any one of <1> to <16>, wherein the volume average particle diameter (D1) of the spherical silica particles B is preferably 6.0 nm or more, more preferably 7.0 nm or more. Polishing liquid composition for substrates.
<18> The volume average particle diameter (D1) of the spherical silica particles B is preferably 40.0 nm or less, more preferably 35.0 nm or less, and even more preferably 30.0 nm or less. <1> to <17> A polishing composition for a magnetic disk substrate according to any one of the above.
<19> The volume average particle diameter (D1) of the spherical silica particles B is preferably 6.0 nm or more and 40.0 nm or less, more preferably 60.0 nm or more and 35.0 nm or less, and still more preferably 7.0 nm or more and 30.30. The polishing composition for a magnetic disk substrate according to any one of <1> to <18>, which is 0 nm or less.
<20> The ratio (D1 / D2) of the volume average particle diameter (D1) by the dynamic light scattering method of the spherical silica particles B and the specific surface area equivalent particle diameter (D2) by the BET method is preferably 1.00 or more. The polishing composition for a magnetic disk substrate according to any one of <1> to <19>, more preferably 1.10 or more, and still more preferably 1.15 or more.
<21> The ratio (D1 / D2) of the volume average particle diameter (D1) by the dynamic light scattering method of the spherical silica particles B and the specific surface area converted particle diameter (D2) by the BET method is preferably 1.50 or less, The polishing composition for a magnetic disk substrate according to any one of <1> to <20>, more preferably 1.40 or less, and still more preferably 1.30 or less.
<22> The ratio (D1 / D2) of the volume average particle diameter (D1) by the dynamic light scattering method of the spherical silica particles B to the specific surface area converted particle diameter (D2) by the BET method is preferably 1.00 or more and 1 .50 or less, more preferably 1.10 or more and 1.40 or less, and further preferably 1.15 or more and 1.30 or less, the polishing composition for a magnetic disk substrate according to any one of <1> to <21> object.
<23> The content of the spherical silica particles B contained in the polishing composition is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, still more preferably 1% by mass or more, and even more preferably. Is a polishing composition for a magnetic disk substrate according to any one of <1> to <22>, which is 2% by mass or more.
<24> The content of spherical silica particles B contained in the polishing composition is preferably 30% by mass or less, more preferably 25% by mass or less, still more preferably 20% by mass or less, and even more preferably 15% by mass or less. The polishing composition for a magnetic disk substrate according to any one of <1> to <23>, wherein
<25> The total overlap frequency of the volume particle size distribution of the non-spherical silica particles A and the spherical silica particles B in the polishing composition is preferably 10% to 38%, more preferably 15% to 36%, The polishing composition for a magnetic disk substrate according to any one of <1> to <24>, preferably 20% to 35%.
<26> The magnetic disk according to any one of <1> to <25>, wherein the non-spherical silica particles A and / or the spherical silica particles B are silica particles produced by a particle growth method using water glass as a raw material. Polishing liquid composition for substrates.
<27> The polishing composition for a magnetic disk substrate according to any one of <1> to <26>, wherein the polishing composition contains substantially no alumina abrasive grains.
<28> The polishing composition for a magnetic disk substrate according to any one of <1> to <27>, wherein the pH of the polishing composition is preferably 0.5 or more and 6.0 or less.
<29> The pH of the polishing composition is preferably 0.7 or more, more preferably 0.8 or more, and even more preferably 0.9 or more, <1> to <28> A polishing composition for a magnetic disk substrate.
<30> The magnetic disk according to any one of <1> to <29>, wherein the polishing composition preferably has a pH of 4.0 or less, more preferably pH 3.0 or less, still more preferably pH 2.0 or less. Polishing liquid composition for substrates.
<31> The polishing composition for a magnetic disk substrate according to any one of <1> to <30>, wherein the substrate to be polished is a Ni—P plated aluminum alloy substrate.
<32> (1) A step of polishing a surface to be polished of a substrate to be polished using the polishing composition according to any one of <1> to <31>,
(2) a step of cleaning the substrate obtained in step (1), and
(3) The substrate obtained in step (2) has a step of polishing the surface to be polished using a polishing liquid composition containing silica particles,
The steps (1) and (3) are performed with another polishing machine,
A polishing method, wherein the substrate to be polished is a substrate for manufacturing a magnetic disk substrate.
<33> (1) A step of polishing the surface to be polished of the substrate to be polished using the polishing composition according to any one of <1> to <3>,
(2) a step of cleaning the substrate obtained in step (1), and
(3) The substrate obtained in step (2) has a step of polishing the surface to be polished using a polishing liquid composition containing silica particles,
A method of manufacturing a magnetic disk substrate, wherein the steps (1) and (3) are performed by another polishing machine.
<34> Use of the polishing composition according to any one of <1> to <31> in the polishing method according to <32> or the method for producing a magnetic disk substrate according to <33>.

  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.

  Polishing liquid compositions A and B were prepared as described below, and the substrate to be polished including steps (1) to (3) was polished under the following conditions. A method for preparing the polishing liquid composition, a method for measuring each parameter, a polishing condition (polishing method), and an evaluation method are as follows.

1. Preparation of polishing liquid composition A Polishing liquid composition A was prepared using the abrasive grains (abrasive grains a to k), sulfuric acid, oxidizing agent, and water shown in Table 1-1 (Examples 1 to 8, Reference Example 1). Comparative Examples 1 to 10, Table 2). The content of each component in the polishing liquid composition A was 6% by mass of abrasive grains, 0.5 to 1.0% by mass of sulfuric acid, and 0.7 to 1.0% by mass of hydrogen peroxide. The pH of the polishing composition A was 1.0 to 1.6.

  The “atypical silica particles” of the type of silica abrasive grains in Table 1-1 refers to particles having a shape such that two or more particles aggregate or fuse in one or a plurality of embodiments. “Spherical silica particles” refer to true spheres or spherical particles close to true spheres. Commonly commercially available colloidal silica is applicable. The “pulverized silica” is not a particle growth method, but refers to silica particles obtained by pulverizing raw materials.

  In addition, the silica particles (abrasive grains a to h) in Table 1-1 are silica particles produced by a particle growth method using an alkali silicate aqueous solution as a starting material.

  An example of an electron microscope (TEM) observation photograph of the deformed non-spherical silica of the abrasive grains a in Table 1-1 is shown in FIG.

2. Preparation of Polishing Liquid Composition B Polishing liquid composition B was prepared using colloidal silica abrasive grains (abrasive grains 1) shown in Table 1-2 below, sulfuric acid, hydrogen peroxide, and water. The content of each component in the polishing liquid composition B was colloidal silica particles (abrasive grains 1): 5.0% by mass, sulfuric acid: 0.4% by mass, and hydrogen peroxide: 0.4% by mass. The pH of the polishing composition B was 1.4.

3. Measuring method of each parameter [Volume average particle diameter (D1) of abrasive grains a to h measured by dynamic light scattering method and CV90]
A standard sample was prepared by adding abrasive grains, sulfuric acid, and hydrogen peroxide to ion-exchanged water and mixing them. The contents of abrasive grains A to L, p, sulfuric acid, and hydrogen peroxide in the standard sample are 0.1 to 5.0 mass%, 0.2 to 0.4 mass%, and 0.2 to 0.4, respectively. It was mass%, and it adjusted suitably according to the type of the silica abrasive grain to be used. The area of the scattering intensity distribution obtained by the Marquardt method at a detection angle of 90 ° when this standard sample is integrated 200 times according to the instructions attached by the manufacturer using the dynamic light scattering device DLS-6500 manufactured by Otsuka Electronics Co., Ltd. Was determined as the volume average particle diameter (D1) of the silica particles. Further, the CV value (CV90) of the silica particles at a detection angle of 90 ° was calculated as a value obtained by dividing the standard deviation in the scattering intensity distribution measured according to the above measurement method by the volume average particle diameter and multiplying by 100.

[ΔCV value]
In the same manner as the CV90 measurement method, the CV value (CV30) of the silica particles at a detection angle of 30 ° was measured, and a value obtained by subtracting CV90 from CV30 was obtained to obtain the ΔCV value of silica particles A or B.
(Measurement conditions for DLS-6500)
Detection angle 90 °
Sampling time: 2-10 (μm) as appropriate Correlation Channel: 256-512 (ch) as appropriate Correlation Method: TI
Sampling temperature: 25.0 ° C
Detection angle 30 °
Sampling time: Adjusted appropriately at 4-20 (μm) Correlation Channel: Adjusted appropriately at 512-2048 (ch) Correlation Method: TI
Sampling temperature: 25 ° C

[Measurement of specific surface area converted particle diameter (D2) of abrasive grains a to h by BET method]
The specific surface area of the abrasive grains is subjected to the following [pretreatment], and then approximately 0.1 g of a measurement sample is precisely weighed to 4 digits after the decimal point in a measurement cell, and immediately under the measurement at 110 ° C. for 30 minutes immediately before the measurement of the specific surface area. After drying, the surface area was measured by a nitrogen adsorption method (BET method) using a specific surface area measuring device (micromeritic automatic specific surface area measuring device “Flowsorb III2305” (manufactured by Shimadzu Corporation)).

[Preprocessing]
(A) The slurry-like abrasive grains are adjusted to pH 2.5 ± 0.1 with a nitric acid aqueous solution.
(B) A slurry-like abrasive adjusted to pH 2.5 ± 0.1 is placed in a petri dish and dried in a hot air dryer at 150 ° C. for 1 hour.
(C) After drying, the obtained sample is finely ground in an agate mortar.
(D) The pulverized sample is suspended in ion exchange water at 40 ° C. and filtered through a membrane filter having a pore size of 1 μm.
(E) The filtrate on the filter is washed 5 times with 20 g of ion exchange water (40 ° C.).
(F) The filter with the filtrate attached is taken in a petri dish and dried in an atmosphere of 110 ° C. for 4 hours.
(G) The dried filtrate (abrasive grains) was taken so as not to be mixed with filter waste, and finely pulverized with a mortar to obtain a measurement sample.

[Measurement of average secondary particle diameter of abrasive grains i to k]
A 0.5% “Poise 530” (polycarboxylic acid type polymer activator, manufactured by Kao Corporation) was used as a dispersion medium and placed in the following measuring device, and then the sample was adjusted so that the transmittance was 75 to 95%. After that, after applying ultrasonic waves for 5 minutes, the particle size was measured.
Measuring equipment: Laser diffraction / scattering type particle size distribution measuring instrument LA920 manufactured by HORIBA, Ltd.
Circulation strength: 4
Ultrasonic intensity: 4

[Volume average particle diameter (D50), D10 and D90 of silica particles (abrasive grains)]
Silica particles were diluted with ion-exchanged water to a 1% dispersion, charged into the following measuring apparatus, and volume average particle diameters (D50), D10 and D90, and standard deviations of particle diameters were measured by a laser diffraction / scattering method.
Measuring equipment: Malvern Zetasizer Nano “Nano S”
Measurement conditions: Sample volume 1.5mL
: Laser He-Ne, 3.0 mW, 633 nm
: Scattered light detection angle 173 °
The particle diameter at which the cumulative volume frequency of the obtained volume distribution particle diameter is 50% is defined as the volume average particle diameter (D50) of the silica particles, and the particle diameters at which the cumulative volume frequency is 10% and 90% are D10 and D90, respectively. did.

[Total overlap frequency of volume particle size distribution of silica particles]
Volume average particle diameter (D50), each volume particle size distribution of the silica particle component (abrasive grains a to h) obtained by the same measurement method as D10 and D90 was obtained. In the combination of abrasive grains used in Examples 2 to 8 and Comparative Examples 1 to 7 (Table 2), the sum of the cumulative volume frequencies in the overlapping particle size range is the cumulative volume frequency of all silica particle components (200 for the two-component mixed system). In a three-component mixed system, a value obtained by dividing by 300) and multiplying by 100 was calculated as an overlap frequency [%]. FIG. 2 shows an example of a graph in which the volume particle size distributions of combinations of abrasive grains (abrasive grains a, d, e) in Examples 3 to 6 and Comparative Example 1 are overlapped.

4). Polishing conditions The substrate to be polished including steps (1) to (3) was polished. The conditions for each step are shown below. The step (1) was performed with the same polishing machine, and the step (3) was performed with a polishing machine separate from the polishing machine.
[Polished substrate]
The substrate to be polished was an aluminum alloy substrate plated with Ni-P. The substrate to be polished had a thickness of 1.27 mm and a diameter of 95 mm.

[Step (1): Rough polishing]
Polishing machine: Double-side polishing machine (9B-type double-side polishing machine, manufactured by Speed Fam Co., Ltd.)
Polishing liquid: Polishing liquid composition A
Polishing pad: Suede type (foam layer: polyurethane elastomer), thickness 1.04mm, average pore diameter 43μm (manufactured by FILWEL)
Lower platen rotation speed: 32.5 rpm
Polishing load: 9.8 kPa (set value)
Polishing liquid supply amount: 100 mL / min (0.076 mL / (cm ² · min) per substrate area)
Polishing time: 4.0 to 16.5 minutes (Examples and Comparative Examples in Table 3)
Polishing amount: 0.1 to 0.32 mg / (cm ² · min)
Number of substrates loaded: 10

[Step (2): Cleaning]
The substrate obtained in the step (2) was washed under the following conditions.
1. The substrate obtained in step (2) is immersed for 5 minutes in a bath containing an alkaline detergent composition having a pH of 12 consisting of a 0.1% by mass aqueous KOH solution.
2. The substrate after immersion is rinsed with ion exchange water for 20 seconds.
3. The rinsed substrate is transferred to a scrub cleaning unit in which a cleaning brush is set and cleaned.

[Step (3): Final polishing]
Polishing machine: Double-side polishing machine (9B type double-side polishing machine, manufactured by Speedfam Co., Ltd.), polishing machine separate from the polishing machine used in step (1): Polishing liquid composition B
Polishing pad: Suede type (foam layer: polyurethane elastomer), thickness 1.0mm, average pore diameter 5μm (manufactured by FILWEL)
Lower platen rotation speed: 32.5 rpm
Polishing load: 7.9 kPa (set value)
Polishing liquid supply amount: 100 mL / min (0.076 mL / (cm ² · min))
Polishing time: 2 to 6 minutes Polishing amount: 0.04 to 0.10 mg / (cm ² · min)
Number of loaded substrates: 10 sheets After the step (3), cleaning was performed. The washing conditions were the same as in the above step (2).

5. Evaluation Method [Measuring Method of Polishing Rate in Step (1)]
[Measurement method of polishing rate]
The polishing rate (μm / min) was calculated by dividing the polishing amount obtained as follows by the polishing time (min). The results are shown in Table 2 below as relative values with reference example 1 taken as 100. In addition, the relative values were evaluated in four stages of A, B, C, and D. A = 115 or more, B = 100 to 114, C = 86 to 99, D = 85 or less.
Each substrate before and after polishing was weighed (Sartorius, “BP-210S”) and measured to determine the amount of polishing.
Weight reduction (g) = {weight before polishing (g) −weight after polishing (g)}
Polishing amount (μm) = weight reduction amount (g) / substrate single-sided area (mm ² ) / 2 / Ni—P plating density (g / cm ³ ) × 10 ⁶
(The substrate single-sided area is calculated as 6597 mm ² and Ni-P plating density 8.4 g / cm ³ )

[Method for evaluating long-period defects on substrate surface after step (1)]
Step (1) Three substrates were arbitrarily selected from the ten substrates after post-polishing, and both surfaces (total of 6 points) of each selected substrate were measured under the following conditions. The average value of the long wavelength waviness on the entire surface of the six points was calculated as the relative value of the long-period defect rate of the substrate. The results are shown in Table 2 below as relative values with Reference Example 1 as 75%. The relative value was evaluated in five stages of 5, 4, 3, 2, and 1. 5 = 90% or more, 4 = 80% to 89%, 3 = 70% to 79%, 2 = 50% to 69%, 1 = 49% or less. That is, the larger the value, the fewer long-period defects.
Equipment: OptiFLATIII (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

[Method for evaluating protrusion defect after step (3)]
Measuring instrument: OSA7100 (manufactured by KLA Tencor)
Evaluation: Polishing was performed using the polishing composition B, and then 4 pieces were selected at random, and each substrate was irradiated with a laser at 10000 rpm to measure the number of abrasive sticks. The total number of abrasive stabs (pieces) on both surfaces of each of the four substrates was divided by 8, and the number of abrasive stabs per substrate surface (number of protrusion defects) (relative value) was calculated. Table 2 below shows the relative values with Reference Example 1 as 100. In addition, the relative values were evaluated in four stages of A, B, C, and D. A = 94 or less, B = 95 to 109, C = 110 to 120, D = 121 or more.

As shown in Table 2, in Examples 1 to 8, the polishing rate is maintained or improved and the removal rate of long-period defects equal to or higher than that of Reference Example 1 is shown, and the protrusion defects are greatly deteriorated. I never did. In Examples 1 to 8, a higher polishing rate and a higher long-period defect removal rate were obtained than in Comparative Examples 1 to 7, and a reduction in protrusion defects equivalent to or higher was obtained. Moreover, it was shown that Examples 1-8 can reduce a protrusion defect remarkably, without impairing a polishing rate and a long period defect removal rate large compared with Comparative Examples 8-10.

Claims (9)

A polishing composition for a magnetic disk substrate containing silica particles, an acid, an oxidizing agent and water,
The silica particles have non-spherical silica particles A having a volume average particle size (D1) of 120.0 nm or more and less than 300.0 nm by a dynamic light scattering method, and a volume average particle size (D1) of 6 by a dynamic light scattering method. Including spherical silica particles B having a diameter of from 0.0 nm to 40.0 nm,
The non-spherical silica particles A and the spherical silica particles B in the polishing composition are mixed so that the mass ratio (A / B) is 80/20 or more and 99/1 or less,
The total mass ratio of the non-spherical silica particles A and the spherical silica particles B to the entire silica particles in the polishing composition exceeds 98.0% by mass,
The non-spherical silica particle A has a ratio (D1 / D2) of a volume average particle diameter (D1) determined by a dynamic light scattering method and a specific surface area equivalent particle diameter (D2) determined by a BET method to 2.00 or more and 4.00 or less. And
A polishing liquid composition for a magnetic disk substrate, wherein the total overlap frequency of volume particle size distributions of each of the non-spherical silica particles A and the spherical silica particles B by a dynamic light scattering method is 0% or more and 40% or less.   The polishing composition for a magnetic disk substrate according to claim 1, wherein the nonspherical silica particles A have a ΔCV value of more than 0.0% and less than 10.0%.   3. The polishing composition for a magnetic disk substrate according to claim 1, wherein the nonspherical silica particles A have a CV90 of 20.0% or more and 40.0% 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 and / or the spherical silica particles B are silica particles produced by a particle growth method using water glass as a raw material. object.   The polishing liquid composition for magnetic disk substrates according to any one of claims 1 to 4, wherein the polishing liquid composition is substantially free of alumina abrasive grains.   The polishing composition for a magnetic disk substrate according to any one of claims 1 to 5, wherein the polishing composition has a pH of 0.5 or more and 6.0 or less.   The polishing composition for a magnetic disk substrate according to any one of claims 1 to 6, wherein the substrate to be polished is a Ni-P plated aluminum alloy substrate. (1) A step of polishing a polishing target surface of a substrate to be polished using the polishing composition according to any one of claims 1 to 7,
(2) a step of cleaning the substrate obtained in step (1), and
(3) The substrate obtained in step (2) has a step of polishing the surface to be polished using a polishing liquid composition containing silica particles,
The steps (1) and (3) are performed with another polishing machine,
A polishing method, wherein the substrate to be polished is a substrate for manufacturing a magnetic disk substrate. (1) A step of polishing a polishing target surface of a substrate to be polished using the polishing composition according to any one of claims 1 to 7,
(2) a step of cleaning the substrate obtained in step (1), and
(3) The substrate obtained in step (2) has a step of polishing the surface to be polished using a polishing liquid composition containing silica particles,
A method of manufacturing a magnetic disk substrate, wherein the steps (1) and (3) are performed by another polishing machine.