JP2022079977A - Abrasive grain dispersion liquid - Google Patents

Abstract

To provide an abrasive grain dispersion liquid capable of polishing at high speed and achieving high face accuracy and by which settleability of abrasive grains, redispersibility of the precipitated grains or residue of the grains is improved.SOLUTION: An abrasive grain dispersion liquid comprises dispersing a dispersant comprising polycarboxylate in a silica-based grain dispersion liquid including the silica-based grain group consisting of irregular-shape and non-irregular shape silica-based grains. Besides, the dispersion liquid satisfies the following conditions: the weight average grain size, average grain size in specific surface area conversion and irregular shape degree of the silica-based grain group are in a specific range, respectively: the volume-based grain size distribution of the silica-based grain group becomes multi-peak in waveform separation; the weight average molecular weight of polycarboxylate is in a specific range; the number of carbon atoms directly bonded to carbonyl carbon is in the specific range; and the mass ratio of polycarboxylate to the silica-based grain group is in a specific range.SELECTED DRAWING: None

Description

The present invention relates to a silica-based particle dispersion liquid and the like. Specifically, a silica-based particle group having a preferable particle size, particle size distribution, irregularity, etc. as an abrasive is included, and for example, a NiP-plated substrate to be polished and a silica-based substrate are chemically mechanically polished (for example, in the production of a magnetic disk). The present invention relates to a silica-based particle dispersion liquid suitable as an abrasive grain dispersion liquid for polishing for flattening by chemical mechanical polishing (CMP).

In the manufacturing process of magnetic disks, semiconductors, etc., chemical mechanical polishing (CMP) is applied to flatten substrates such as Si wafers, glass HD, and aluminum HD. In this chemical mechanical polishing, a so-called polishing slurry in which abrasive grains such as silica and ceria are dispersed in water and a chemical component is added to control the polishing performance is used. In particular, it is known that the abrasive grains have a great influence on the polishing performance, and as the performance required for the abrasive grains, a high polishing speed can be obtained and the polished surface has defects such as scratches (streak marks). Defects) do not occur.

As a method of obtaining a high polishing rate, it is common to use abrasive grains having a large particle size. However, if the particle size of the abrasive grains becomes too large, the number of abrasive grains per mass decreases, so that the polishing speed decreases and the scratch tends to increase. Therefore, in order to obtain a high polishing rate without increasing scratches, it is known that it is effective to make the abrasive grains non-spherical, that is, to make the abrasive grains irregularly shaped particles (odd particles).

As a method for preparing a silica particle group containing irregularly shaped silica particles having a particle size suitable for an abrasive material, a method of aggregating silica particles at the time of nucleation using water glass as a raw material, or a method of aggregating silica particles at the time of nucleation, or an irregularly shaped seed particle prepared by this method or the like. A method of adding a silicic acid solution to a large particle size to grow a large particle size (Patent Document 1) has been conventionally known.

Further, it is known that the larger the particle size of the deformed silica sol, the more likely it is that the particles settle when left to stand. For example, it is known that the hardened settling accumulates at the bottom of the storage container of the deformed silica sol. When such particle sedimentation occurs, long-term stirring is required for redispersion, which has been a factor that hinders practical use, especially in a relatively large variant silica sol. The use of various dispersants is known as a means for suppressing particle precipitation, and for example, vinyl alcohol polymers and derivatives thereof, betaine, laurylbetaine, lauryldimethylamine oxide and the like (Patent Document 2) have been conventionally known. There is.

Japanese Patent No. 5,127,452 Japanese Patent No. 5,862,720

For irregularly shaped particles, the degree of irregularity (ratio of weight average particle diameter to specific surface area equivalent particle diameter) also greatly affects the polishing performance. Specifically, particles with a large degree of deformation tend to have a high polishing rate. On the other hand, particles having a small degree of deformation tend to have a low polishing rate because they are spherical or nearly elliptical particles. However, since the irregularly shaped particles are non-spherical in shape, they are usually more prone to scratches than spherical or substantially spherical particles (non-irregular particles), especially when the degree of irregularity is high. The tendency becomes remarkable.

Further, it is generally known that the particle size of the abrasive grains and the particle size distribution greatly affect the polishing performance, and when the abrasive grains having a relatively large particle size are used for polishing, the polishing speed is relatively high. However, the surface accuracy (surface roughness, waviness, scratches, etc.) of the polished substrate after polishing tends to deteriorate. On the other hand, when abrasive grains having a relatively small particle size are used for polishing, the surface of the substrate can be finished smoothly and scratches are unlikely to occur, but the polishing speed is relatively slow. This tends to be seen not only in spherical particles but also in irregular particles.
The particle size distribution of the irregularly shaped particles is diverse, but usually, when particles with a relatively large particle size are used as abrasive grains, the polishing speed is relatively high, so if a higher polishing speed is required, Variant particles with as large an average particle diameter as possible are used. However, in the case of irregularly shaped particles having a relatively large average particle size, the tail of the particle size distribution tends to spread widely toward the large particle size side, and often contains a small amount of particles coarser than the average particle size. Then, due to such coarse particles, scratches are generated on the polished substrate, and the surface roughness and waviness of the substrate tend to be deteriorated. Therefore, as abrasive particles used for polishing applications that require a high polishing speed, coarse particles and excessive large particles (these are collectively referred to as "coarse particles") having a relatively large average particle diameter are extremely large. A small number of irregularly shaped particles are desired.

Further, when particles having a relatively small particle diameter are used as the abrasive grains, the polishing rate tends to be low because the polishing amount of one abrasive grain is small regardless of whether it is spherical particles or irregularly shaped particles. Further, in the case of abrasive grains composed of particles having a relatively small particle size, the abrasive grains tend to remain on the substrate after polishing (this is called "abrasive grain residue"). This abrasive grain residue tends to be difficult to remove even in the cleaning step after polishing. This tendency is also seen in the abrasive grains made of deformed particles having a relatively large average particle size, and the abrasive grains made of deformed particles having a distribution in which the tail of the particle size distribution spreads toward the small particle size It can be said that abrasive grain residue is likely to occur.
Therefore, in order to realize suitable chemical mechanical polishing that achieves both high polishing speed and high surface accuracy, the abrasive grains contain relatively large irregularly shaped particles, and the number of effective abrasive grains per mass is large, and the polishing performance is high. It is desired that the abrasive grains contain as little coarse particles as possible, which may reduce the amount of abrasive grains, and also contain as little as possible relatively small particles that cause residual abrasive grains.

However, in the method for producing deformed silica particles including the step of generating nuclear particles for particle growth by using water glass as a raw material and aggregating the silica particles, the deformed silica particles having an average particle diameter of 100 nm or more in terms of specific surface area are used. Was difficult to obtain. Further, in this production method, in the silica particle aggregation step at the time of nucleation, some nucleus particles may cause a runaway reaction to generate coarse aggregates, and such coarse aggregates may cause scratches. It sometimes became. Further, when irregular silica particles having an average particle diameter of 100 nm or less in terms of specific surface area as obtained by this production method are used as seed particles and a silicic acid solution is added to the seed particles to increase the particle size, the seed particles are grown. Since it grows spherically or substantially spherically, it is difficult to grow irregularly shaped seed particles in a deformed state to obtain relatively large irregularly shaped silica particles.

Furthermore, the present inventors investigated a method for obtaining deformed silica particles by pulverizing wet silica as another method for preparing a group of silica particles containing deformed silica particles, and although the deformed silica particles were obtained. Wet silica with a gel structure contains these deformed silica particles because its particle strength is weak for controlling the particle size and particle size distribution by crushing or crushing, and the obtained deformed silica particles also have weak particle strength. When the silica particle group was used as the abrasive particles, the required polishing rate could not be obtained.

When applied to polishing applications, the present invention is a group of silica-based particles (comparative) capable of achieving practical polishing speed and surface accuracy with respect to, for example, a silica-based substrate or a NiP-plated substrate to be polished. To provide an abrasive grain dispersion liquid containing a specific dispersant and a silica-based particle group containing atypical silica-based particles, which is an abrasive grain containing a large irregularly shaped particle and exhibits a specific particle size distribution. The purpose.
Although the abrasive grain dispersion liquid for polishing of the present invention contains abrasive grains composed of relatively large irregularly shaped silica-based particles having a maximum weight-equivalent particle size of 600 nm, it has an ability to suppress sedimentation of the abrasive grains. Excellent (low sedimentation rate of abrasive grains), low proportion (residual rate) of components that settle and do not easily disperse in the abrasive grain dispersion liquid for polishing, yet the viscosity of the abrasive grain dispersion liquid for polishing is its filterability. In addition, the redispersion rate of the abrasive grains, the polishing speed, and the surface accuracy (for example, suppressing the generation of waviness on the polished substrate) are at a practical level.
Further, since the polishing abrasive grain dispersion liquid of the present invention has a low viscosity, no bubbles are observed during the polishing treatment or filtration, and the ease of handling of the polishing abrasive grain dispersion liquid does not decrease. Good condition is maintained.

In order to solve the above problems, the present inventor has investigated a method for growing seed particles by using particles made of a highly deformed silica-based gel, adding a silicic acid solution, and heating the particles.
The particles made of this highly deformed silica-based gel have a relatively large specific surface area (typically 100 m ² / g or more) and a relatively small primary particle diameter (typically 27 nm or less) as a raw material. Can be obtained by wet crushing it under alkaline conditions.
As described above, the raw material silica-based gel particles have a relatively small primary particle diameter and have a stronger particle strength than silica gel particles having a larger primary particle diameter, and are difficult to crush. However, by preferentially crushing the coarse particles with a bead mill, particles made of a highly deformed silica-based gel containing almost no coarse particles can be obtained.

The particles made of such a highly deformed silica-based gel are crushed to a smaller size and used as seed particles, and the seed particles are heated in the coexistence of a silicic acid solution to grow the seed particles. It is preferentially deposited from the pores between the primary particles (recesses between the primary particles). Here, since the primary particles of the seed particles are small in size, the pores can be completely filled with silicic acid. Therefore, it is presumed that the particles grew while maintaining a high particle strength and a high degree of deformation, and the deformed silica-based particles could be obtained.
By using the silica-based particle group containing the irregularly shaped silica-based particles as abrasive grains, the polishing speed is relatively high and the polished surface has high surface accuracy (for example, a polished surface with small waviness can be obtained). I found that I could do it.

Based on the above findings, the present inventor has a silica-based particle group consisting of deformed silica-based particles and non-deformed silica-based particles having a particle size, particle size distribution, irregularity and particle strength suitable as an abrasive, and a specific dispersant. The present invention, which is an abrasive grain dispersion liquid for polishing containing and, has been completed.

The present invention is the following (1) to (8).
(1) A dispersant made of a polycarboxylate is dispersed in a silica-based particle dispersion liquid containing a silica-based particle group composed of atypical silica-based particles and a non-deformed silica-based particle, and the following [1] to [5] Abrasive particle dispersion for polishing that meets the requirements.
[1] The weight average particle diameter (D ₁ ) of the silica-based particle group is 50 to 600 nm, and the specific surface area-equivalent average particle diameter (D ₂ ) is 15 to 300 nm.
[2] The degree of deformation D (D = D ₁ / D ₂ ) represented by the ratio of the weight average particle diameter (D ₁ ) of the silica-based particle group to the specific surface area equivalent particle diameter (D ₂ ) is 1.1. Must be in the range of ~ 10.
[3] When the volume-based particle size distribution of the silica-based particle group is waveform-separated, a multi-peak distribution in which three or more separation peaks are detected is obtained.
[4] The polycarboxylate has a weight average molecular weight in the range of 20,000 to 400,000, and has m the number of carbon atoms directly bonded to carbonyl carbon and the number of carbon atoms not directly bonded to carbonyl carbon. When n, the value of m / (m + n) × 100 is in the range of 40 to 50%.
[5] The mass ratio of the silica-based particle group to the polycarboxylate is in the range of 100: 0.1 to 100:10.
(2) The abrasive grain dispersion liquid for polishing according to (1) above, wherein the dispersant is made of polyacrylic acid salt.
(3) The abrasive grain dispersion liquid for polishing according to (1) or (2) above, wherein the skewness in the volume-based particle size distribution of the silica-based particle group is in the range of −20 to 20.
(4) Among the separation peaks obtained as a result of waveform-separating the volume-based particle size distribution of the silica-based particle group, the volume ratio of the maximum particle component is 75% or less. The abrasive grain dispersion for polishing according to any one of (3).
(5) The aspect ratio of the small particle side component is in the range of 1.05 to 5.0 in the number-based particle size distribution obtained by SEM image analysis of the silica-based particle group (1). )-(4). The abrasive grain dispersion for polishing.
(6) The abrasive grain for polishing according to any one of (1) to (5) above, wherein the coefficient of variation of the particle size of the volume-based particle size distribution of the silica-based particle group is 30% or more. Dispersion solution.
(7) Smoothness S (S = S) represented by the ratio of the area of a circle (S ₂ ) equivalent to the average outer peripheral length by the image analysis method to the average area (S ₁ ) by the image analysis method in the silica-based particle group. The abrasive grain dispersion for polishing according to any one of (1) to (6) above, wherein ₂ / S ₁ ) is in the range of 1.1 to 5.0.
(8) In the volume-based particle size distribution of the silica-based particle group, the ratio Q (Q = Q ₂ / Q ₁ ) of the volume (Q ₂ ) of particles of 0.7 μm or more to the total volume (Q ₁ ) is 5. The abrasive grain dispersion for polishing according to any one of (1) to (7) above, which is characterized by having a content of 0% or less.

The silica-based particle group composed of the deformed silica-based particles and the non-deformed silica-based particles of the present invention has a particle size, a particle size distribution, a degree of deformation, and a particle strength suitable as an abrasive, and thus has a specific dispersion. When polishing with an abrasive grain dispersion liquid containing an agent, for example, even if the target is a NiP-plated film to be polished and a silica-based substrate, it can be polished at a practical speed, and the abrasive grains can be polished. Achieves practical surface accuracy (less scratches on the substrate to be polished, small surface roughness (Ra) of the substrate to be polished, small waviness (Wa), etc.) without sticking into the base material. Can be done.
Further, the silica-based particle group contained in the abrasive grain dispersion liquid for polishing of the present invention has a non-smooth surface and has minute protrusions, and polishing debris, ionic components, oligomer components, and organic substances generated during polishing. It also has a scavenger effect that adsorbs such things. Therefore, it is possible to prevent the reattachment of these components to the polishing substrate, and it is possible to achieve a polished surface with a small amount of residue.

The polishing abrasive grain dispersion liquid of the present invention is a polishing abrasive grain dispersion liquid exhibiting practical polishing performance as described above, but the abrasive grains are acted on by the action of a specific dispersant contained in the polishing abrasive grain dispersion liquid. Practical problems as a dispersion, that is, 1) high sedimentation property of abrasive grains (high sedimentation rate), 2) ratio of components in the abrasive grain dispersion liquid for polishing that settle and do not easily disperse. It solves all of the problems such as high (residual rate), 3) deterioration of filterability and ease of handling due to high viscosity of the abrasive grain dispersion for polishing.

Explanatory diagram of kurtosis in particle size distribution Explanatory diagram of skewness in particle size distribution

A silica-based particle group composed of modified silica-based particles and non-modified silica-based particles of the present invention, a silica-based particle dispersion liquid containing the same, a dispersant composed of a specific polycarboxylate of the present invention, and the present invention. The abrasive grain dispersion liquid for polishing will be specifically described. In the present invention, the word "particle swarm" means a set of a large number of particles. Further, the abrasive grain dispersion liquid for polishing of the present invention may be referred to as "slurry".

<Weight average particle size (D ₁ )>
The weight average particle diameter (D ₁ ) of the silica-based particle group of the present invention is 50 to 600 nm, preferably 60 to 400 nm, and most preferably 80 to 300 nm. When a silica-based particle group having a weight average particle diameter (D ₁ ) in the range of 50 to 600 nm is used as the abrasive grains, a high polishing rate can be obtained and scratches are less likely to occur. When a silica-based particle group having a weight average particle diameter (D ₁ ) of less than 50 nm is used as the abrasive grains, it is difficult to obtain the required polishing rate, and smaller particles tend to remain on the polished substrate. be. Further, when a silica-based particle group having a weight average particle diameter (D ₁ ) of more than 600 nm is used as an abrasive grain, scratches tend to occur, and even if the weight average particle diameter is made larger than this, the mass tends to occur. Since the number of abrasive particles per hit is reduced, the polishing speed may not be improved.

Here, in the present invention, the weight average particle diameter (D ₁ ) is defined as 2% by mass in terms of solid content concentration by diluting the abrasive grain dispersion for polishing to be measured with a 0.05% by mass sodium dodecyl sulfate aqueous solution. Inject 0.1 ml into a conventionally known disc centrifugal particle size distribution measuring device (for example, manufactured by CPS Instrument) with a syringe, and in an 8% to 24% sucrose density gradient solution at 18,000 rpm. It is an average particle diameter obtained from the weight-based particle diameter distribution obtained by measuring under the conditions. That is, in the present invention, this weight average particle size (D ₁ ) means "weight average particle size of weight conversion particle size distribution".

<Average particle size in terms of specific surface area (D ₂ )>
The specific surface area equivalent average particle diameter (D ₂ ) of the silica-based particle group of the present invention is 15 to 300 nm, preferably 20 to 200 nm, more preferably 22 to 100 nm, and most preferably 25 to 80 nm. .. When a silica-based particle group having a specific surface area conversion average particle diameter (D ₂ ) in the range of 15 to 300 nm is used as the abrasive grains, a high polishing rate can be obtained and scratches are less likely to occur. When a silica-based particle group having a specific surface area-equivalent average particle diameter (D ₂ ) of less than 15 nm is used as the abrasive grains, it is difficult to obtain the required polishing rate, and smaller particles tend to remain on the substrate after polishing. There is a tendency. Further, when a silica-based particle group having a specific surface area equivalent average particle diameter (D ₂ ) of more than 300 nm is used as an abrasive grain, scratches tend to occur and the surface roughness of the substrate after polishing tends to deteriorate. be. Further, even if the average particle diameter (D ₂ ) converted to the specific surface area is made larger than this, the number of abrasive grains per mass decreases, so that the polishing rate tends to decrease.

In the present invention, the specific surface area-equivalent average particle diameter (D ₂ ) means the specific surface area-equivalent average particle diameter, and the specific surface area (SA: m ² / g) measured by the BET method and the density of the particles. (Ρ) Using [in the case of silica ρ = 2.2], it is calculated from the formula D ₂ = 6000 / (SA × ρ).
Here, the BET method is the following method.
First, adjust the pH of 50 ml of silica sol (abrasive grain dispersion for polishing) to be measured to 3.5 with nitric acid, add 40 ml of 1-propanol to it, and dry the sample at 110 ° C for 16 hours in a mortar. After crushing, it is fired at 500 ° C. for 1 hour in a muffle furnace to prepare a sample for measurement. Then, using a known specific surface area measuring device (for example, manufactured by Yuasa Ionics, model number Multisorb 12, etc.), the specific surface area is calculated from the amount of nitrogen adsorbed by the BET 1-point method using the nitrogen adsorption method (BET method). In the specific surface area measuring device, 0.5 g of the sample after firing is taken in a measuring cell, degassed in a mixed gas stream of nitrogen 30 vol% / helium 70 vol% at 300 ° C. for 20 minutes, and then the sample is subjected to the above mixed gas. Keep the liquid nitrogen temperature in the air stream and allow nitrogen to equilibrate and adsorb to the sample. Next, the sample temperature is gradually raised to room temperature while flowing the mixed gas, the amount of nitrogen desorbed during that period is detected, and the specific surface area (SA) of the silica fine particles in the sample is calculated from a calibration curve prepared in advance. ..

Further, when the specific surface area of the silica-based particle group is high, sintering proceeds during firing in the BET method, so when the specific surface area (SA) is 100 m ² / g or more, the specific surface area is determined by the titration method. Find (SA).
Here, the titration method is the following method.
First, a sample corresponding to 1.5 g of SiO ₂ is collected in a beaker, then transferred to a constant temperature reaction tank (25 ° C.), and pure water is added to make the liquid volume 90 ml (the following operation is 25). Perform in a constant temperature reaction tank maintained at ° C). Next, a 0.1 mol / L hydrochloric acid aqueous solution is added here so as to have a pH of 3.6. Further, 30 g of sodium chloride is added, diluted with pure water to 150 ml, and stirred for 10 minutes. Then, the pH electrode is set, and a 0.1 mol / L sodium hydroxide solution is added dropwise with stirring to adjust the pH to 4.0. Further, the sample adjusted to pH 4.0 was titrated with a 0.1 mol / L sodium hydroxide solution, and the drip quantification and the pH value in the range of pH 8.7 to 9.3 were recorded at 4 points or more, and 0. A calibration line is prepared with the titration amount of 1 mol / L sodium hydroxide solution as the X-axis and the pH value at that time as the Y-axis. Then, from the formula of V = (A × f × 100 × 1.5) / (W × C), 0.1 mol / L sodium hydroxide required from pH 4.0 to 9.0 per 1.5 g of SiO ₂ The amount of solution V (ml) is determined, and the specific surface area is determined using the formula of SA = 29.0V-28.
In the above formula, A is a titration amount (ml) of a 0.1 mol / L sodium hydroxide solution required for pH 4.0 to 9.0 per 1.5 g of SiO ₂ , and f is 0.1 mol / L. The titer of the sodium hydroxide solution, C means the SiO ₂ concentration (%) of the sample, and W means the sampling amount (g).

<Degree of irregularity>
The degree of deformation is obtained by dividing the value of the weight average particle diameter (D ₁ ) described above by the value of the specific surface area equivalent particle diameter (D ₂ ).

The silica-based particle group of the present invention has a degree of deformation D (D = D ₁ / D ₂ ) in the range of 1.1 to 10, preferably in the range of 1.5 to 8.0, and preferably in the range of 1.6 to 7. A range of 0 is more preferred. A silica-based particle group having a high degree of deformation indicates that the average aspect ratio of the particle group (the average value of the "major axis / minor axis ratio of the minimum inscribed square") is high, and when this average aspect ratio is high. At the time of polishing, it is preferable because it comes into contact with the substrate mainly on the major axis of the particles, the contact area with the substrate becomes large, and the polishing speed becomes high. The speed does not improve, and scratches and swells tend to occur more easily. Further, when the degree of deformation is less than 1.1, it indicates that the shape of the particles is close to a spherical shape, and polishing is performed using a silica-based particle dispersion liquid containing such a silica-based particle group. If done, the polishing rate tends to decrease.
Here, the aspect ratio means the ratio of the long side to the short side (long side / short side) in the rectangle (including the square) inscribed by the particles and having the smallest area. Further, the average aspect ratio means a simple average value of the aspect ratios of 50 or more particles.

The proportion of the deformed silica-based particles contained in the silica-based particle dispersion liquid containing the silica-based particle group according to the present invention is particularly limited as long as the requirements of [1], [2] and [3] are satisfied. However, the ratio of the number of deformed silica-based particles having an aspect ratio of 1.1 or more to the whole (the silica-based particle group) is preferably 50% or more, more preferably 70% or more, still more preferably 90%. The above is the most recommended.
The method for measuring the number ratio of the deformed silica-based particles having an aspect ratio of 1.1 or more is as shown in Examples described later.

<Kurtosis>
The kurtosis in the volume-based particle size distribution of the silica-based particle group of the present invention is preferably −20 to 20, more preferably −10 to 10, and most preferably −5 to 3. When a silica-based particle group having a kurtosis in this range is used as an abrasive grain, a higher polishing rate can be obtained, and after polishing, the surface is smoother (the surface roughness (Ra) is small and the waviness of the substrate is small). It is possible to obtain a substrate having a surface (Wa) is also small and scratches are small.

Here, the kurtosis is calculated only from the particle size distribution regardless of the shape and size of the particles, and when the kurtosis is close to zero (normal distribution), the particle size distribution is close to the normal distribution. It shows that it is. The particle size distribution in which the kurtosis is larger than zero indicates that the center of the peak is sharper than the normal distribution and the left and right sides of the tail of the distribution are widened (Fig. 1 (a)). The particle size distribution showing a kurtosis smaller than zero indicates that the peak is flat and the left and right sides of the hem of the distribution are not widened (FIG. 1 (b)).

In the present invention, the kurtosis in the volume-based particle size distribution of the silica-based particle group may be a negative value. A negative kurtosis indicates that the peak is flat, the left and right small particles and large particle components are few, and the peak is flat and the particle size distribution is relatively uniform. When such a silica-based particle group having a small amount of small particle components and a small amount of large particle components is used as the abrasive grains, it is preferable because the amount of remaining abrasive grains is small and the polishing speed is high.

<Skewness>
The skewness in the volume-based particle size distribution of the silica-based particle group of the present invention is preferably −20 to 20, more preferably −15 to 15, and most preferably −10 to 10. When a silica-based particle group having a skewness in this range is used as an abrasive grain, a higher polishing rate can be obtained, and after polishing, the surface is smoother (the surface roughness (Ra) is small and the waviness of the substrate is small). It is possible to obtain a substrate having a surface (Wa) is also small and scratches are small.

Here, the skewness is calculated only from the particle size distribution regardless of the shape and size of the particles like the kurtosis, and when the skewness is close to zero, the particle size distribution is close to the normal distribution. It shows that it is. The particle size distribution in which the skewness is larger than zero shows that the distribution has a peak on the left side (smaller particle size side) of the distribution and a long tail on the right side (Fig. 2 (a)). )) On the other hand, the particle size distribution in which the skewness is smaller than zero shows that the distribution has a peak on the right side of the distribution (the side with the larger particle size) and has a long tail on the left side. (Fig. 2 (b)).

Usually, the skewness in the volume-based particle size distribution of the silica-based particle group obtained by the crushing and crushing method often takes a positive value, and the skewness is easy because the particles obtained by the build-up method tend to have a normal distribution. It often takes a value close to zero. When the skewness is positive, the particle size distribution has a peak at a position where the particle size is slightly smaller and a wide tail on the large particle size side. When a silica-based particle group having a particle size distribution having a peak on the small particle size side is used as an abrasive grain, a smooth surface tends to be easily obtained after polishing because many components have a small particle size. On the other hand, the silica-based particle group having a remarkably large skewness has a particle size distribution in which the hem is greatly widened toward the large particle size side, and although it depends on the average particle size, scratches tend to occur easily when used as abrasive grains. ..

In the present invention, the skewness in the volume-based particle size distribution of the silica-based particle group may be a negative value. The silica-based particle group having a negative strain degree has a peak at a position where the particle size is large and has a particle size distribution in which the hem is widened on the small particle side, but the particle size distribution on the large particle side is good. Therefore (that is, because there are few remarkably large particles), scratches are unlikely to occur even when used as abrasive grains. However, in the silica-based particle group having a skewness of less than -20, the hem on the small particle side becomes too wide and the particle size distribution increases, and the small particle component increases. be.

<Measurement of volume-based particle size distribution and calculation method of kurtosis / skewness>
In the present invention, the volume-based particle size distribution of the silica-based particle group is measured by the centrifugal sedimentation method. For example, a silica-based particle dispersion is diluted with a 0.05 mass% sodium dodecyl sulfate aqueous solution to adjust the solid content concentration to 2 mass%, and a known disc centrifugal particle size distribution measuring device (for example, manufactured by CPS Instrument) or the like is used. ) Can be used to measure the volume-based particle size distribution.
The kurtosis and skewness are calculated from the mean value and standard deviation of the volume reference particle size distribution thus obtained by a conventionally known formula. For example, JMP Ver. Manufactured by SAS Institute Japan. The kurtosis and skewness can be calculated using 13.2. In rare cases, the frequency of a predetermined particle size may take a negative value in the volume-based particle size distribution, and in such a case, the frequency is calculated as zero.

<Multi-peak distribution>
The volume-based particle size distribution of the silica-based particle group of the present invention is a multi-peak distribution in which three or more separation peaks are detected when waveforms are separated by the following method. In the case of a particle group with a single peak distribution, polishing speed and swell are generated according to the particle size, when the particle size is large, the polishing speed is high but the swell is large, and when the particle size is small, the swell is improved. However, the polishing speed is low. On the other hand, in the case of a particle group having a multi-peak distribution, polishing proceeds while leaving polishing marks corresponding to the particle diameter of each component, and the sum of these becomes the waviness and the polishing rate. Therefore, at the same time as the large particle component, the distribution in which the small particle component shows a sufficient polishing rate (for example, a trapezoidal distribution containing many small particles and large particles, and a distribution with multiple peaks when the waveform is separated). ), Both polishing speed and waviness can be achieved. However, if the aspect ratio of the small particle side component is not high as in the silica-based particle group of the present invention, that is, if there are many spherical particles, the polishing rate will be slow even with a multi-peak distribution, so depending on the large particles. Since the effect of repairing the deteriorated surface roughness and scratches and smoothing the surface of the substrate is weak, it tends to be difficult to obtain a smooth surface.

Waveform separation is performed by analyzing the volume-based particle size distribution obtained by the above-mentioned disk centrifugal type particle size distribution measuring device using a peak analyzer of the graph creation / data analysis software Origin (manufactured by OriginLab Corporation). conduct. First, the baseline is set to 0, the peak type is set to Gaussian, the maximum point of the particle size distribution is selected as the peak position, peak fitting is performed without weighting, and the calculated peak deviates from the following conditions 1 and 2. If it does not deviate, the peak position is shifted to an arbitrary position within the distribution range until the following conditions 1 and 2 are satisfied, and peak fitting is repeated. After that, if the corrected R-squared value is 0.99 or less, a peak is added at an arbitrary position in the distribution range, and peak fitting is repeated until the corrected R-squared value becomes 0.99 or more. The number of separated peaks at this time is defined as the number of peaks.
Condition 1: Each calculated peak does not take a value larger than the original distribution.
Condition 2: Each calculated peak does not take a negative value.

The silica-based particle group having such a volume-based particle size distribution with multiple peaks has a wide distribution from large particles to small particles (the distribution is broad), and has more suitable polishing performance.
Specifically, it is desirable that the volume ratio of the maximum particle component waveform-separated is 75% or less of the total volume. This is because when the volume ratio of the maximum particle component is 75% or less, the distribution becomes broad, and when the waveform is separated, the separation peak tends to be a multi-peak distribution of 3 or more.
When the volume ratio of this maximum peak exceeds 75%, the distribution is substantially close to a single peak distribution, and even if such a volume reference particle size distribution is waveform-separated, the separation peak tends to be less than 3. be.

Further, in the silica-based particle group of the present invention, the volume ratio of the maximum particle component among the separation peaks detected when the volume reference particle size distribution is waveform-separated is preferably 75% or less, preferably 73%. The following is more preferable. When such a silica-based particle group is used as an abrasive grain, the surface roughness and waviness of the substrate are further improved during polishing due to the small amount of large particle components. Here, the "maximum particle component" in the present invention means a particle component included in the separation peak on the particle side having the largest particle size when the volume-based particle size distribution of the silica-based particle group is waveform-separated. ..

<Aspect ratio of small particle side components>
In the silica-based particle group of the present invention, the aspect ratio of the small particle side component is preferably in the range of 1.05 to 5.0 in the number-based particle size distribution obtained as a result of SEM image analysis, and 1.05. It is more preferably in the range of ~ 3.0, more preferably in the range of 1.05 to 2.0, and even more preferably in the range of 1.05 to 1.5. The aspect ratio of the small particle side component in the number-based particle size distribution obtained by SEM image analysis is measured and calculated by the following method. First, using a known scanning electron microscope (SEM) and a known image analysis system, 15 fields of view were taken with an area of 1.1 × 10 ^-3 mm ² per field of view at a magnification of 3000 times, and the silica-based particle group was photographed. Count the total number of particles. Further, the area of each particle is obtained by determining the diameter of a circle having an area equal to the area, and this is used as the particle diameter. Then, the obtained particle diameters are arranged in order of size, and the particles up to 1/3 of the number of particles counted from the small side are set as the small particle side component, and the aspect ratio (minimum inscribed square) is used for each of the particles of the small particle side component. Major axis / minor axis ratio) is obtained, and the simple average value thereof is defined as the "aspect ratio of the small particle side component".

The aspect ratio of the small particle side component of the silica-based particle group of the present invention is usually smaller than the average aspect ratio of the silica-based particle group. When the aspect ratio of the small particle side component is less than 1.05, such particles are substantially equivalent to spherical particles, so that the polishing rate is low and the polishing rate of the silica-based particle group tends to be low. However, when a silica-based particle group having an aspect ratio of the small particle-side component of 1.05 or more is used as the abrasive grains, the small-particle-side component also exhibits a high polishing rate, so that the polishing rate of the silica-based particle group is further increased. It is possible to prevent defects and the like, and high surface accuracy tends to be obtained. Further, when the aspect ratio of the component on the small particle side is larger than 5.0, the average aspect ratio of the entire silica-based particle group is also higher, so that the polishing speed is higher, but the substrate is more likely to be defective, and the surface of the substrate is further increased. Roughness and waviness of the substrate surface also tend to worsen.

Here, as a method for producing particles having a high aspect ratio in which single particles are bonded, for example, a method of associating particles having a diameter of several tens of nm using ion intensity adjustment or a polymer to increase the aspect ratio, or preparation of particles. Sometimes, there is a method of associating particles by adjusting the ionic strength and the like at the same time as nucleation, and further growing the generated irregular seed particles to obtain particles having a high aspect ratio. However, in the case of these methods, particles having a high aspect ratio are generated, and at the same time, particles that do not associate are likely to remain. Since the polishing speed is low, the polishing speed of the entire particle group tends to be low. On the other hand, the silica-based particle group including the deformed silica-based particles of the present invention is crushed into an irregular shape (non-spherical) by the impact energy received from the beads by the raw material silica-based gel particles in the crushing step. Therefore, since the small particle side component is also a deformed particle, a high polishing rate can be obtained.

<Coefficient of variation (CV value)>
The coefficient of variation of the particle size of the volume-based particle size distribution of the silica-based particle group according to the present invention is preferably 30% or more, and more preferably 50% or more. By setting the coefficient of variation within a predetermined range, the volume-based particle size distribution becomes broad, that is, a silica-based particle group having a wide particle size distribution, and more suitable polishing performance (for example, waviness on a substrate to be polished). Demonstrate the suppression of occurrence, etc.). In the present invention, the "coefficient of variation (CV value)" is the value obtained by dividing the standard deviation by the average value (weight average) as a percentage, and indicates relative variation.
The CV value of the present invention is determined from the volume-based particle size distribution using a disk centrifugal particle size distribution measuring device (manufactured by CPS Instrument).
The coefficient of variation is preferably in the range of 30% to 250%. If the coefficient of variation is 250% or more, the polishing performance may deteriorate.

<Smoothness S>
In the silica-based particle group of the present invention, the smoothness S (S = S ₂ ) represented by the ratio of the area of a circle (S ₂ ) equivalent to the average outer peripheral length by the image analysis method to the average area (S ₁ ) by the image analysis method. _/ S1) is preferably in the range of 1.1 to 5.0, and more preferably in the range of 1.3 to 4.0. When the S value is higher than 1.0, it indicates that the surface of the deformed silica-based particles contained in the silica-based particle group is not smooth and has a shape having minute irregularities. This is because the deformed seed particles are an aggregate of primary particles and are porous, so that the surface of the seed particles also has minute protrusions, and the deformed silica-based particles obtained by growing the seed particles are fine. This is because the shape is such that the protrusions are maintained. Further, when a silica-based particle group containing irregular silica-based particles having appropriate fine protrusions on the surface of the deformed silica-based particles is used as the polishing abrasive grains, the polishing pressure is concentrated on the protrusions, so that a high polishing rate can be obtained. When the protrusions on the surface of the particles are excessive, the surface roughness and waviness of the surface of the substrate after polishing do not deteriorate, but the abrasive grains are easily worn and the polishing speed tends to decrease.

Here, the measurement and calculation of the average area (S ₁ ) by the image analysis method and the area of the circle (S ₂ ) equivalent to the average outer peripheral length by the image analysis method in the silica-based particle group will be described.
These are measured and calculated by the following methods. First, using a known scanning electron microscope (SEM), an arbitrary part of the particle surface is photographed in 15 fields with an area of 1.1 × 10 ^-3 mm ² per field at a magnification of 3000 times. For all the silica fine particles contained in the individual images taken in each of the visual fields, the area and the outer peripheral length of each particle were measured using a known image analysis system, and the measured area and the outer peripheral length data were used. The average area (S ₁ ) (simple average value) and the average outer circumference length (simple average value) are calculated, and from this average outer circumference length, a circle equivalent to the average outer circumference length (a circle having the same circumference as the average outer circumference length). The area of (S ₂ ) is calculated.

<Q ₂ / Q ₁ >
In the volume-based particle size distribution of the silica-based particle group of the present invention, the ratio Q (Q = Q ₂ / Q ₁ ) of the volume (Q ₂ ) of particles of 0.7 μm or more to the total volume (Q ₁ ) is based on the percentage. Display) is preferably 5.0% or less, and more preferably 3.0% or less. In such a silica-based particle group, since the proportion of coarse particles is small, defects such as scratches are less likely to occur during polishing, and the surface roughness of the polished substrate can be further reduced.

The total volume ( _Q1 ) in the volume-based particle size distribution of the silica-based particle group of the present invention, the volume ratio of each component of the separation peak obtained as a result of waveform separation, the volume ratio of the maximum particle component, and 0. The volume (Q ₂ ) of particles of 7 μm or more can also be measured by the method using the above-mentioned disc centrifugal particle size distribution measuring device.

<Dispersant>
The abrasive grain dispersion liquid for polishing of the present invention contains a silica-based particle dispersion liquid containing a silica-based particle group composed of the deformed silica-based particles and non-deformed silica-based particles, and further comprises a dispersant made of a specific polycarboxylate. It includes.
Dispersants made of such specific polycarboxylates have a weight average molecular weight in the range of 20,000 to 400,000.
Further, when the number of carbon atoms directly bonded to the carbonyl carbon in the polycarboxylic acid is m and the number of carbon atoms not directly bonded to the carbonyl carbon is n, the value of m / (m + n) × 100 is 40 to 50. It is in the range of%, preferably in the range of 45 to 49%. Within such a range, the abrasive grain dispersion liquid for polishing of the present invention has a more excellent sedimentation rate and residual rate of the abrasive grains while having a practical viscosity range.
The measurement method of m and n will be described later.

When the weight average molecular weight of the polycarboxylic acid salt is in the range of 20,000 to 400,000, the sedimentation rate of the abrasive grains is lower than that when the dispersant composed of the polycarboxylic acid is not added, and the abrasive grains and the like remain. The rate is kept low.
When the weight average molecular weight of the polycarboxylate is less than 20,000, the properties of the polycarboxylate as a surfactant are exhibited and foaming occurs on the liquid surface of the abrasive grain dispersion for polishing, so that the polishing slurry is formed. Not suitable as. When the weight average molecular weight exceeds 400,000, the viscosity of the slurry increases, the filterability and the ease of handling are lowered, and it becomes difficult to put it into practical use.
The weight average molecular weight is more preferably in the range of 50,000 to 200,000. More preferably, the range of 70,000 to 180,000 is recommended.

In the abrasive grain dispersion liquid for polishing of the present invention, the mass ratio of the silica-based particle group to the polycarboxylic acid salt is preferably in the range of 100: 0.1 to 100:10. If the mass ratio is within this range, it is possible to exhibit a practical level of polishing performance, and further to exhibit excellent performance in the sedimentation rate, residual rate, and the like of the abrasive grains.
If the amount of the polycarboxylic acid salt is less than 0.1 part by mass with respect to 100 parts by mass of the silica-based particle group, the amount of the carboxylate salt is too small. No effect is seen. On the other hand, when the polycarboxylate exceeds 10 parts by mass, the carboxylate becomes excessive and the salt concentration increases, so that the particles tend to aggregate easily, which makes it difficult to put into practical use.
The mass ratio of the silica-based particle group to the polycarboxylate in the abrasive grain dispersion liquid for polishing of the present invention is preferably in the range of 100: 0.5 to 100: 2.

The amount of the dispersant used in the polishing abrasive grain dispersion liquid of the present invention is preferably 0.001 to 10 g, more preferably 0.01 to 5 g in 1 L of the polishing abrasive grain dispersion liquid. It is particularly preferable to use 0.1 to 3 g.
The content of the surfactant and / or the hydrophilic compound is preferably 0.001 g or more in 1 L of the abrasive grain dispersion for polishing, and 10 g or less from the viewpoint of preventing a decrease in the polishing speed in order to obtain a sufficient effect. Is preferable.

Polyacrylate is preferable as the carboxylate used as a dispersant in the abrasive grain dispersion of the present invention, and specifically, sodium polyacrylate, ammonium polyacrylate, and potassium polyacrylate. , Polyacrylic acid lithium salt, and the like.

A dispersant made of a polycarboxylate is dispersed in a silica-based particle dispersion (a silica-based particle dispersion containing the silica-based particle group of the present invention) in which the silica-based particle group of the present invention is dispersed in a dispersion solvent. , Can be preferably used as an abrasive grain dispersion liquid for polishing (hereinafter, also referred to as "abrasive particle dispersion liquid for polishing" of the present invention).
In particular, it can be preferably used for polishing a magnetic disk. Further, it can be suitably used as a polishing abrasive grain dispersion liquid for flattening a semiconductor substrate on which a SiO ₂ insulating film is formed. Further, a chemical component can be added to control the polishing performance, and the polishing slurry can be suitably used.

The polishing abrasive grain dispersion liquid of the present invention has effects such as high polishing speed when polishing a magnetic disk or a semiconductor substrate, less scratches on the polished surface during polishing, and less residual abrasive grains on the substrate. Excellent, and the efficiency of polishing work can be significantly improved.

The abrasive grain dispersion liquid for polishing of the present invention contains water and / or an organic solvent as a dispersion solvent. As the dispersion solvent, it is preferable to use water such as pure water, ultrapure water, and ion-exchanged water. Further, the polishing abrasive grain dispersion liquid of the present invention is selected from the group consisting of a polishing accelerator, a surfactant, a heterocyclic compound, a pH adjuster and a pH buffer as an additive for controlling the polishing performance1. By adding seeds or more, it is more preferably used as a polishing slurry.

<Abrasive accelerator>
Although it depends on the type of the material to be polished, it can be used as a polishing slurry by adding a conventionally known polishing accelerator to the abrasive grain dispersion liquid for polishing of the present invention, if necessary. Examples of such include hydrogen peroxide, peracetic acid, urea peroxide and the like, and mixtures thereof. When such an abrasive composition containing a polishing accelerator such as hydrogen peroxide is used, the polishing rate can be effectively improved when the material to be polished is a metal.

Other examples of polishing accelerators include inorganic acids such as sulfuric acid, nitrate, phosphoric acid, oxalic acid and hydrofluoric acid, organic acids such as acetic acid, or sodium salts, potassium salts, ammonium salts, amine salts and the like of these acids. And the like. In the case of a polishing composition containing these polishing accelerators, when polishing a material to be polished composed of a composite component, by accelerating the polishing rate for a specific component of the material to be polished, finally flat polishing is performed. You can get a face.

When the abrasive grain dispersion liquid for polishing of the present invention contains a polishing accelerator, the content thereof is preferably 0.1 to 10% by mass, more preferably 0.5 to 5% by mass. ..

<Surfactant>
Since the abrasive grain dispersion liquid for polishing of the present invention contains the above-mentioned specific carboxylate, it is not necessary to add a dispersant for the purpose of improving dispersibility, but application of the abrasive grain dispersion liquid for polishing Other known dispersants (cationic, anionic) dispersants (cationic, anionic) as long as the performance of the abrasive abrasive dispersion of the present invention is not deteriorated when other components are added to the application or the abrasive grain dispersion for polishing. , Nonionic, amphoteric surfactants, hydrophilic compounds, etc.) can be added.

<Heterocyclic compound>
The abrasive grain dispersion liquid of the present invention has the purpose of forming a passivation layer or a dissolution suppressing layer on the metal when the base material to be polished contains a metal to suppress erosion of the base material to be polished. Heterocyclic compounds may be contained. Here, the "heterocyclic compound" is a compound having a heterocycle containing one or more heteroatoms. Heteroatom means an atom other than a carbon atom or a hydrogen atom. The heterocycle means a cyclic compound having at least one heteroatom. Heteroatoms refer only to the atoms that form the constituents of the heterocyclic ring system, and may be located outside the ring system, separated from the ring system by at least one unconjugated single bond, or the ring system. It does not mean an atom that is part of a further substituent of. Preferred heteroatoms include, but are not limited to, nitrogen atoms, sulfur atoms, oxygen atoms, selenium atoms, tellurium atoms, phosphorus atoms, silicon atoms, and boron atoms. As an example of the heterocyclic compound, imidazole, benzotriazole, benzothiazole, tetrazole and the like can be used. More specifically, 1,2,3,4-tetrazole, 5-amino-1,2,3,4-tetrazole, 5-methyl-1,2,3,4-tetrazole, 1,2,3- Triazole, 4-amino-1,2,3-triazole, 4,5-diamino-1,2,3-triazole, 1,2,4-triazole, 3-amino1,2,4-triazole, 3,5 -Diamino-1,2,4-triazole and the like can be mentioned, but the present invention is not limited thereto.

The content of the heterocyclic compound in the abrasive grain dispersion for polishing of the present invention is preferably 0.001 to 1.0% by mass, preferably 0.001 to 0.7% by mass. Is more preferable, and 0.002 to 0.4% by mass is further preferable.

<pH adjuster>
The pH of the polishing composition can be adjusted by adding an acid or a base and a salt compound thereof, if necessary, in order to enhance the effect of each of the above additives.

When adjusting the polishing abrasive grain dispersion of the present invention to pH 7 or higher, an alkaline pH adjusting agent is used. Desirably, amines such as sodium hydroxide, aqueous ammonia, ammonium carbonate, ethylamine, methylamine, triethylamine, tetramethylamine and the like are used.

When the polishing abrasive grain dispersion of the present invention is adjusted to a pH of less than 7, an acidic pH adjusting agent is used. For example, mineral acids such as hydrochloric acid and nitric acid such as hydroxy acids such as acetic acid, lactic acid, citric acid, malic acid, tartaric acid and glyceric acid are used.

<pH buffer>
A pH buffer may be used to keep the pH value of the abrasive grain dispersion for polishing of the present invention constant. As the pH buffering agent, for example, phosphates such as ammonium dihydrogen phosphate, diammonium hydrogen phosphate, ammo tetrahydrate tetrahydrate, and borates or organic acid salts can be used.

Further, as the dispersion solvent of the abrasive grain dispersion liquid for polishing of the present invention, for example, alcohols such as methanol, ethanol, isopropanol, n-butanol, methylisocarbinol; acetone, 2-butanone, ethyl amylketone, diacetone alcohol, etc. Ketones such as isophorone and cyclohexanone; amides such as N, N-dimethylformamide and N, N-dimethylacetamide; diethyl ether, isopropyl ether, tetrahydrofuran, 1,4-dioxane, 3,4-dihydro-2H-pyran and the like. Ethers; Glycol ethers such as 2-methoxyethanol, 2-ethoxyethanol, 2-butoxyethanol, ethylene glycol dimethyl ether; Glycol ether acetates such as 2-methoxyethyl acetate, 2-ethoxyethyl acetate, 2-butoxyethyl acetate Kind; Ethers such as methyl acetate, ethyl acetate, isobutyl acetate, amyl acetate, ethyl lactate, ethylene carbonate; Fragrant hydrocarbons such as benzene, toluene, xylene; Fat group hydrocarbons such as hexane, heptane, isooctane, cyclohexane Classes; halogenated hydrocarbons such as methylene chloride, 1,2-dichloroethane, dichloropropane, chlorbenzene; sulfoxides such as dimethylsulfoxide; pyrrolidones such as N-methyl-2-pyrrolidone, N-octyl-2-pyrrolidone. And other organic solvents can be used. These may be mixed with water and used.

The solid content concentration contained in the abrasive grain dispersion liquid for polishing of the present invention is preferably in the range of 0.3 to 55% by mass. If this solid content concentration is too low, the polishing rate may decrease. On the contrary, even if the solid content concentration is too high, the polishing rate is rarely improved further, which may be uneconomical.

<Manufacturing Method of Abrasive Grain Dispersion Liquid for Polishing of the Present Invention>
Next, a method for producing the abrasive grain dispersion liquid for polishing of the present invention will be specifically described.

This includes a step a of wet crushing the silica-based gel under alkaline conditions to obtain a solution containing particles composed of highly deformed silica-based gels, and a silicate solution under alkaline conditions in the solution containing particles composed of the highly deformed silica-based gels. Is added and heated, and the particles are grown with a high degree of deformation while filling the space between the primary particles of the particles made of the highly deformed silica-based gel by the reaction with the silicic acid contained in the silicic acid solution to grow the deformed silica-based particles. A step b for forming a silica-based particle group containing the silica-based particle group, a step c for concentrating and recovering the silica-based particle group containing the grown irregular silica-based particle group, and a silica-based particle group containing the silica-based particle group obtained in the above step. This method includes a step d of dispersing a dispersion liquid made of a specific polycarboxylic acid in the dispersion liquid.

[Step a]
This step uses a silica-based gel as a starting material. The silica-based gel may be a composite gel such as silica-alumina gel, silica-titania gel, or silica-zirconia gel as long as it is a silica-based gel. The gel state may be hydrogel, xerogel, or organogels. Then, such a silica-based gel is wet-crushed under alkaline conditions to obtain a solution containing particles composed of a highly deformed silica-based gel. By pulverizing the silica-based gel and using it as seed particles, the seed particles become silica gel having a high degree of deformation, and the seed particles are hardly spherical and become highly deformed particles.
Then, in the subsequent step b, the silicic acid solution to be added deposits while invading the silica surface and the inside of the particles (seed particles) made of highly deformed silica-based gel, and reacts preferentially with the pores between the primary particles. While the pores are filled, silica is deposited on the outer surface of the particles to promote the growth of the particles (this is referred to as build-up in the following description). By this build-up, the convex part of the outer surface of the particle contributes to the increase of the outer diameter more, and the concave part contributes less to the outer shape, so that the strength of the grown particle is increased and the deformation of the particle is suppressed, which is high. It is possible to produce irregularly shaped silica-based particles having a degree of irregularity.

Further, in the present invention, a silica-based gel having a relatively large specific surface area (typically 100 m ² / g or more) and a relatively small primary diameter (typically 27 nm or less) is used as a manufacturing raw material. The strength is strong. Therefore, the silica-based gel is repeatedly pulverized for the purpose of miniaturization so that the weight average particle size is several hundred nm. At the time of pulverization, fine particles of about several tens of nm are also generated at the same time. Therefore, when a silica-based gel is used as a raw material for production, the particles obtained by the pulverization range from small particles to large particles. Therefore, the silica-based particle group of the present invention has a large weight average particle diameter and also has fine particles at the same time, so that the skewness and the kurtosis are high.

The silica-based gel used as a raw material for production is preferably a gel that is easily crushed. For example, a wet hydrogel obtained by washing a gel of a water glass method, a dry silica gel obtained by drying the hydrogel, or a white gel. Carbon, precipitation method silica, precipitation method gel type silica, gel method silica, gel by alkoxide method and the like are preferable. Since the gel obtained by the alkoxide method has few hydroxyl groups that dehydrate and condense, the dry powder is soft and can be used as a highly productive dry powder. The particle size distribution of the particles composed of the irregular silica gel obtained by crushing the silica gel is preferably controlled within a certain range, and if it is a large gel mass that is difficult to crush, the coarse particles are crushed. It is not preferable because it takes time.

The silica-based gel used in the present invention preferably has a specific surface area in the range of 100 to 600 m ² / g. When the specific surface area is smaller than 100 m ² / g, the pores between the primary particles of the silica-based gel are small. The amount of silicic acid that permeates the pores between the primary particles of the irregularly shaped silica-based gel is small, and the added silicic acid solution is consumed so as to grow the particles in a round shape, which tends to make it difficult to maintain the irregular shape.
If the specific surface area is larger than 600 m ² / g, the particle strength is too strong and difficult to crush, and long-time crushing is required to reduce coarse particles or to adjust the particle size to a predetermined size. In particular, the degree of deformation tends to be low.
The size (particle size) of the silica-based gel is preferably in the range of 1 μm to 10 mm.

The silica-based gel is wet-crushed under alkaline conditions to form particles composed of a highly deformed silica-based gel. In particular, a silica-based gel having a specific surface area of about 100 to 600 m ² / g has a strong share such as a bead mill. By simultaneously deforming and crushing underneath, particles made of atypical silica-based gel can be prepared into particles having a high degree of atypical. For crushing, for example, a sand mill crusher containing a glass medium or a bead mill may be used. Crushing is preferably performed in the shortest possible time.

Normally, when powder is crushed with a bead mill or the like, the particle size of the powder becomes smaller in proportion to the crushing time, but the specific surface area is large (typically 100 m ² / g or more) and the primary diameter is small. When the silica-based gel (typically 27 nm or less) is crushed into particles having a weight average particle diameter of about 40 to 550 nm, the particles made of this highly deformed silica-based gel are primary while maintaining the specific surface area before crushing. It has a coarse structure containing a considerable number of necks between particles. Therefore, even if these particles are used as they are as an abrasive, they tend to collapse due to insufficient strength, and a practical polishing rate cannot be obtained.
Therefore, in the present invention, in the subsequent step b, the silicic acid solution is added to the solution containing the particles made of the highly deformed silica gel, and the pores between the primary particles inside the particles made of the deformed silica gel are filled with the silicic acid solution. The strength of the particles is increased by building up and filling. Here, the silicic acid solution used for build-up may be derived from alkoxide, sodium silicate, or amine silicate. Further, it is not limited to silicic acid as long as it can fill the space between the primary particles, and may be silicic acid salts such as an alkaline salt of silicic acid and an alkaline earth salt.

In step a, the silica-based gel is wet-crushed under alkaline conditions, that is, under alkaline conditions, and the alkalinity is preferably in the range of pH 8.0 to 11.5. As the pH drops below the alkaline region, the negative potential gradually decreases and becomes unstable in the neutral to acidic regions, so that the particles generated by crushing cannot exist stably and tend to aggregate immediately. Further, when the pH is higher than 11.5, the dissolution of silica is promoted, so that the silica tends to aggregate. The pH at the time of wet crushing is preferably in the range of 8.5 to 11.0.
The method of adjusting the pH here is not particularly limited. For example, it can be adjusted by adding sodium hydroxide or the like.

The weight average particle diameter of the particles made of the highly deformed silica-based gel obtained by the wet crushing is preferably in the range of 40 to 550 nm. If the weight average particle size of the particles made of a highly deformed silica-based gel is smaller than 40 nm, it may be difficult to obtain a particle size suitable for the abrasive even if the particles are subsequently added with a silicic acid solution to grow the particles. be. Further, if the weight average particle size of the particles made of the highly deformed silica-based gel is larger than 550 nm, the particle size suitable for the abrasive may be exceeded, which is not so preferable. Coarse particles larger than the particle size suitable for such abrasives can cause scratches. Although coarse particles and large particles tend to be preferentially crushed by crushing, centrifugation may be performed for the purpose of removing the coarse particles remaining in the highly deformed silica-based gel. The weight average particle size of the particles made of the highly deformed silica-based gel is preferably in the range of 60 to 400 nm.

Here, the weight average particle size of the particles made of the highly deformed silica-based gel means a value obtained by measuring by the same method as the weight average particle size (D ₁ ) of the silica-based particle group described above.

This crushing can be performed in multiple stages using media of different materials and sizes. For example, when a silica-based gel is crushed with a large-sized zirconia medium, the first-stage crushing can be performed at high speed and in a short time due to a strong shearing force. Next, when the second stage of crushing is performed with a glass medium having a size smaller than that of the first stage, the crushing proceeds with a moderate shearing force, and the particle size can be adjusted to a desired value. At this time, since the primary particles are destroyed from the weak portion, the shape tends to be deformed at the same time as the miniaturization. In addition, since the wet crushing is performed under alkaline conditions, some of the particles made of highly deformed silica-based gel are dissolved, and the neck portion between the primary particles can be preferentially filled, so that the particles are excessively fine during crushing. The conversion does not progress.

[Step b]
In this step, a silicic acid solution is added to a solution containing particles made of a highly deformed silica gel under alkaline conditions to heat the solution, and the pores between the primary particles of the particles made of the highly deformed silica gel are reacted with silicic acid. It is a build-up process that grows particles while filling them in a deformed shape. The SiO ₂ concentration of the solution containing the particles composed of the highly deformed silica-based gel is preferably in the range of 1 to 10% by mass. If the SiO ₂ concentration of the solution containing the particles composed of the highly deformed silica-based gel is less than 1% by mass, the efficiency of producing the deformed silica-based particles tends to decrease. Further, when the SiO ₂ concentration is more than 10% by mass, fine silica nuclei are generated, and the particle growth of the irregular silica-based particles tends to be non-uniform.
In addition, this step b may be performed by a method of adding a silicic acid solution while hydrothermally treating particles made of a highly deformed silica-based gel. In this method, the added silicic acid solution causes supersaturation, and while some particles are dissolved, silica is deposited and the particles grow. However, the neck portion between the primary particles has a faster deposition rate than the dissolution, so that the primary particles are deposited. The pores between the particles are preferentially filled.

The heating temperature is preferably in the range of 60 ° C to 170 ° C. This is because if the temperature is lower than 60 ° C, the growth of the particles made of the highly deformed silica gel tends to be slow, and if the temperature is higher than 170 ° C, the obtained deformed silica particles tend to be spherical. The heating temperature is more preferably in the range of 60 ° C to 100 ° C.

Further, the pH when the silicic acid solution is added to the solution containing the particles composed of the highly deformed silica-based gel is preferably in the range of 9 to 12.5. When the pH is less than 9, the solubility of silica is low, so that the degree of supersaturation becomes extremely high, and the added silicic acid solution is not consumed for particle growth and tends to be produced as fine particles. Further, since the surface potential of the negatively charged particles also approaches zero, the particles tend to aggregate. Further, since the dissociation of the hydroxyl group is insufficient, the reactivity with the primary particles is lowered, and the reinforcement of the neck portion is not sufficient. Further, if the pH is higher than 12.5, the dissolution of silica may be promoted.

The pH of the solution containing the particles of the highly deformed silica-based gel is adjusted as necessary in order to keep the pH in the above range. The adjusting means is not particularly limited, but it is usually adjusted by adding an alkaline substance. Examples of such alkaline substances include sodium hydroxide, water glass, amines and the like. The pH when the silicic acid solution is added to the solution containing the particles of the highly deformed silica gel is preferably in the range of 9.0 to 12.5.

The amount of the silicic acid solution added is preferably in a range in which the SiO ₂ molar concentration of the silicic acid solution is 0.5 to 20 mol times the SiO ₂ molar concentration of the solution containing the particles of the highly deformed silica-based gel. This is because if the amount of the silicic acid solution added is less than the above range, the strength between the primary particles cannot be sufficiently increased, so that the strength of the particles tends to decrease. Further, when the particles are grown by adding a silicic acid solution or the like, the degree of deformation and the aspect ratio are usually lowered, but when the amount of the silicic acid solution added is larger than the above range, the degree of deformation of the particles is significantly lowered, which is desired. This is because the degree of irregularity tends to be unmaintainable.
Further, it is desirable to add the silicic acid solution continuously or intermittently.

The silicic acid solution permeates the inside of the particles through the pores between the primary particles of the particles made of a highly deformed silica-based gel, and deposits on the neck portion of the particles to reduce the specific surface area, thereby increasing the strength of the particles. The specific surface area of the silica-based particle group including the deformed silica-based particles obtained by this step b is preferably 182 m ² / g or less, more preferably in the range of 9 m ² / g to 182 m ² / g. If the specific surface area of the particles made of the irregular silica gel is larger than 182 m ² / g, the size of the obtained irregular silica particles is too small, and the polishing rate tends to be slow.
The specific surface area of the particles made of the irregular silica gel is measured by the BET method as described in "Measurement of specific surface area" of the examples described later.

The silicic acid solution dropped from the outside uniformly falls from the liquid phase onto the surface of the deformed silica gel and binds to the outer surface of the particles made of the deformed silica gel to grow the outer shape of the particles, so that the deformed shape is maintained. It is possible to obtain irregular silica-based particles having a large particle size. The particle size of the deformed silica-based particles after the particle growth is preferably in the range of a weight average particle size of 50 to 600 nm. Here, the weight average particle diameter of the irregularly shaped silica-based particles means a value obtained by measuring by the same method as the weight average particle diameter (D ₁ ) of the silica-based particle group described above.

[Step c]
This step is a step of concentrating and recovering a group of silica-based particles containing grown irregular silica-based particles. Specifically, for example, a solution containing grown irregular silica-based particles is cooled to about room temperature to 40 ° C., concentrated using an ultrafiltration membrane or the like, and further concentrated using an evaporator or the like to remain silica-based. All you have to do is collect the particles. Centrifugation may be performed to remove even coarser particles. From the viewpoint that coarse agglomerates are unlikely to occur due to drying, concentration by an ultrafiltration membrane is preferable.

[Step d]
The abrasive grain dispersion for polishing of the present invention can be obtained by adding a dispersant composed of the above-mentioned specific carboxylate to the silica-based particle dispersion containing the silica-based particle group obtained in the previous step and stirring the mixture. .. Here, the stirring condition may be about 1 hour using a tabletop stirring device at room temperature.

Hereinafter, examples of the present invention will be shown together with comparative examples. In the examples and comparative examples,
Measurement of abrasive grain sedimentation rate, residual rate, abrasive grain redispersion rate, molecular weight of polycarboxylate, etc. in abrasive grain dispersion liquid for polishing, measurement of specific surface area of silica-based particle group, specific surface area conversion average particle Calculation of diameter (D ₂ ), measurement of weight average particle diameter (D ₁ ), calculation of strain / sharpness in volume-based particle diameter distribution, waveform separation of volume-based particle diameter distribution, volume in volume-based particle diameter distribution Measurement, aspect ratio calculation of small particle side component, calculation of fluctuation coefficient, measurement / calculation of average area (S ₁ ) / area of circle equivalent to average outer circumference length (S ₂ ), measurement of silica gel size, irregular shape The measurement and polishing test of the ratio of the deformed silica-based particles contained in the silica-based particle dispersion liquid containing the silica-based particles group composed of the silica-based particles and the non-deformed silica-based particles were performed as follows.

[Settling rate of abrasive grain dispersion for polishing (definition and measuring method of settling rate)]
The sedimentation property of the abrasive grain dispersion for polishing was evaluated by the sedimentation rate (%). The sedimentation rate is the ratio of the sedimentation rate (g) to the total slurry volume (g).
A 500 ml container containing 500 g of the abrasive grain dispersion obtained in each Example and Comparative Example was allowed to stand for one month, and then the supernatant was removed. Then, the residue was weighed as the sedimentation component (sedimentation component A), and the sedimentation rate was calculated.

[Redispersibility and residual ratio of abrasive grain dispersion for polishing]
The supernatant removed when calculating the sedimentation rate was returned to a 500 ml container, sonicated for 1 hour, and redispersed. Then, the container was allowed to stand upside down for 1 minute, and then the supernatant component was removed again.
Then, the residue was weighed as the sediment that could not be redispersed (precipitation component B), and the redispersion rate was obtained from the following formula.
Further, the sedimentation content (precipitation component B) that could not be redispersed even after the ultrasonic treatment was taken as the residual solid content, and divided by the total amount of the slurry introduced first, and the residual ratio was obtained from the following formula.
-Redispersion rate = (precipitation component A-precipitation component B) / sedimentation component A
・ Residual rate = sedimentation component B / 500g (total amount of slurry)

[Explanation of measurement method for molecular weight, etc. of dispersant composed of polycarboxylate]
The weight average molecular weight of the dispersant composed of the polycarboxylate was determined by GPC measurement. The measurement conditions were as follows.
・ Analytical method: GPC measurement ・ Equipment: Water, 2695 HPLC
・ Column: Water Ultrahydrogen 500 + Water Ultrahydrogen 120 Column temperature 40 ℃
・ Sample injection amount: 20 μml
-Mobile phase: 50 ml aqueous sodium phosphate solution (pH = 7): acetonitrile = 9: 1, flow rate 0.8 mL / min
・ Detector: Water 2410RI
・ Standard substance: Polyethylene glycol

0.4 ml of heavy water was added to 0.2 ml of the sample, and the liquid that had been ultrasonically dispersed for 5 minutes was placed in a 5 mmφ Pylex sample tube, and the liquid probe of an NMR device (ECZ-400R manufactured by JEOL Ltd.) was used for ¹ H. It was measured by the single pulse method. The flip angle of the pulse was 45 °, the pulse repetition time was 5 seconds, and the number of integrations was 16. A 5% deuterated chloroform solution of tetramethylsilane was used as the shift standard, and the peak position was set to 0 ppm. For the obtained spectrum, the integration ratio of each peak was calculated by the software Delta attached to the apparatus. Then, the integral ratio between 1.8 and 3.0 ppm is defined as a carbon source atom directly connected to carbonyl oxygen, the number thereof is defined as m, and the integral ratio between 1.0 and 1.8 ppm is defined as a carbon atom not directly linked to carbonyl carbon. , The number was set to n.
Using m and n thus obtained, m / (m + n) × 100 was calculated.

[Measurement of specific surface area]
For Examples 1 and Comparative Examples 1 to 3, the specific surface areas of the porous silica gel charged in step a and the deformed silica-based particles obtained in step b were measured and calculated by the BET method. Specifically, the pH of 50 ml of the object to be measured was adjusted to 3.5 with nitric acid, 40 ml of 1-propanol was added thereto, and the sample dried at 110 ° C. for 16 hours was crushed in a mortar and then placed in a muffle furnace. It was calcined at 500 ° C. for 1 hour to prepare a sample for measurement. Then, using a specific surface area measuring device (manufactured by Yuasa Ionics, model number Multisorb 12), the specific surface area was calculated from the amount of nitrogen adsorbed by the BET 1-point method using the nitrogen adsorption method (BET method).
In the specific surface area measuring device, 0.5 g of the sample after firing is taken in a measuring cell, degassed in a mixed gas stream of nitrogen 30 v% / helium 70 v% at 300 ° C. for 20 minutes, and then the sample is subjected to the above mixed gas. The temperature was maintained at the liquid nitrogen temperature in the air stream, and nitrogen was equilibrium-adsorbed to the sample. Next, the sample temperature was gradually raised to room temperature while flowing the mixed gas, the amount of nitrogen desorbed during that period was detected, and the specific surface area of the silica fine particles in the sample was calculated from a calibration curve prepared in advance.

[Calculation of average particle size (D ₂ ) converted to specific surface area]
Using the specific surface area (SA) measured by the above BET method and the particle density (ρ = 2.2), the specific surface area conversion average of the silica-based particle group is obtained from the formula D ₂ = 6000 / (SA × ρ). The particle size (D ₂ ) was calculated.

[Measurement of weight average particle size (D ₁ )]
A silica-based particle dispersion diluted with a 0.05 mass% sodium dodecyl sulfate aqueous solution to a solid content concentration of 2 mass% was used in a disk centrifugal particle size distribution measuring device (model number: DC24000UHR, manufactured by CPS instruments). , 0.1 ml was injected with a syringe, and the weight average particle size (D ₁ ) was measured under the condition of 18000 rpm in a density gradient solution of 8 to 24% by mass of sucrose. The crushed product of the porous silica-based gel (particles made of the irregularly shaped porous silica-based gel) was also measured by the same method.

[Calculation of kurtosis / skewness in volume-based particle size distribution]
The volume-based particle size distribution was also measured by the method using the above-mentioned disk centrifugal particle size distribution measuring device. Then, using the obtained volume-based particle size distribution data, JMP Ver. Kurtosis and skewness were calculated using 13.2. In the volume-based particle size distribution, when the frequency of the predetermined particle size was a negative value, the frequency was set to zero.

[Waveform separation of volume-based particle size distribution]
The above-mentioned volume-based particle size distribution measurement data was analyzed using a peak analyzer of the graph creation / data analysis software Origin (manufactured by OriginLab Corporation). First, the baseline is set to 0, the peak type is set to Gaussian, the maximum point of the particle size distribution is selected as the peak position, peak fitting is performed without weighting, and the calculated peak deviates from the following conditions 1 and 2. It was confirmed that there was no deviation, and if it deviated, the peak position was shifted to an arbitrary position within the distribution range until the following conditions 1 and 2 were satisfied, and peak fitting was repeated. After that, when the corrected R-squared value was 0.99 or less, a peak was added at an arbitrary position in the distribution range, and peak fitting was repeated until the corrected R-squared value exceeded 0.99. The number of separated peaks at this time was taken as the number of peaks.
Condition 1: Each calculated peak does not take a value larger than the original distribution.
Condition 2: Each calculated peak does not take a negative value.

[Measurement of volume in volume-based particle size distribution]
The total volume ( _Q1 ) in the volume-based particle size distribution of the silica-based particle group, the volume ratio of each component of the separation peak obtained as a result of waveform separation, the volume ratio of the maximum particle component, and the volume ratio of particles of 0.7 μm or more. The volume (Q ₂ ) was measured using the above-mentioned disk centrifugal particle size distribution measuring device.

[Aspect ratio calculation of small particle side component]
For the aspect ratio of the small particle side component, first, the total number of particles in the silica-based particle group is counted using a scanning electron microscope (SEM) and an image analysis system, and the area of each particle is calculated and the area thereof. The diameter of the circle having the same area as was obtained, and it was used as the particle diameter. Then, the obtained particle diameters are arranged in order of size, and particles up to 1/3 of the number of particles counted from the small side are used as small particle side components, and the aspect ratio (major axis / minor axis ratio of the minimum inscribed square) is averaged. The value was set as "aspect ratio of small particle side component".

[Calculation of coefficient of variation]
For the coefficient of variation of the particle size of the volume-based particle size distribution of the silica-based particle group, each standard deviation and average value are calculated from the above-mentioned volume-based particle size distribution measurement data, and this standard deviation is divided by the average value. Was calculated by showing the percentage.

[Measurement / calculation of the area of a circle (S ₂ ) equivalent to the average area (S ₁ ) / average outer circumference length]
The measurement of the average area (S ₁ ) and the area of the circle equivalent to the average outer peripheral length (S ₂ ) in the silica-based particle group was performed by an image analysis method. Specifically, first, using a scanning electron microscope (SEM), an arbitrary part of the surface of silica-based particles was photographed in 15 fields with an area of 1.1 × 10 ^-3 mm ² per field at a magnification of 3000 times. .. Then, the area and the outer peripheral length of all the silica fine particles contained in the individual images taken in each of the visual fields are measured by an image analysis method using an image analysis system, and the measured areas and the outer peripheral lengths are measured. The average area (S ₁ ) and the average outer circumference length (simple average value) are calculated from the data, and from this average outer circumference length, the area of the circle equivalent to the average outer circumference length (the circle having the same circumference as the average outer circumference length) ( S ₂ ) was calculated.

[Silica gel size measurement method]
The size of the silica-based gel was measured using LA-950 manufactured by HORIBA under the following measurement conditions.
The version of LA-950V2 is 7.02, the algorithm option is standard calculation, the refractive index of solid is 1.450, the refractive index of solvent (pure water) is 1.333, the number of repetitions is 15, and the circulation speed of the sample input bus is 5. The stirring speed was set to 2, and the measurement was performed using a measurement sequence in which these were set in advance. Then, the measurement sample was put into the sample inlet of the apparatus as the undiluted solution using a dropper. Here, it was input so that the numerical value of the transmittance (R) became 90%. Then, after the value of the transmittance (R) became stable, ultrasonic waves were irradiated for 5 minutes to measure the particle size.

[Method for measuring the proportion of deformed silica-based particles contained in a silica-based particle dispersion containing a group of silica-based particles composed of deformed silica-based particles and non-deformed silica-based particles]
Arbitrary 100 pieces in a photographic projection obtained by taking a photograph of a silica-based particle dispersion at a magnification of 250,000 times (or 500,000 times) with an electronic microscope (manufactured by Hitachi, Ltd., model number "S-5500"). For each particle, the aspect ratio (major axis / minor axis ratio of the minimum inscribed square) was determined. Here, the particles having an aspect of 1.1 or more are irregular silica-based particles. Then, the ratio of the deformed silica-based particles was determined from the number of particles having an aspect ratio of 1.1 or more and the number of measured particles (100 particles).

[Polishing test]
Substrate to be polished An aluminum substrate coated with nickel plating for hard disks (nickel-plated substrate manufactured by Toyo Kohan Co., Ltd.) was used as the substrate to be polished. This substrate is a donut-shaped substrate (outer diameter 95 mmφ, inner diameter 25 mmφ, thickness 1.27 mm).
Polishing test For each Example and Comparative Example, 344 g of an abrasive grain dispersion for polishing of 9% by mass was prepared, 5.65 g of 31% by mass hydrogen peroxide solution was added thereto, and then the pH was adjusted to 1 with 10% by mass of nitric acid. The polishing slurry was prepared by adjusting to 5.5.
The substrate to be polished is set in a polishing device (Nanofactor: NF300), and a polishing pad (FILWEL "Veratrix NO178") is used, and the substrate load is 0.05 MPa, the surface plate rotation speed is 50 rpm, and the head rotation speed is increased. At 50 rpm, 1 μm polishing was performed while supplying the polishing slurry at a rate of 40 g / min.
Polishing speed
The polishing speed was calculated from the weight difference of the polishing substrate before and after polishing and the polishing time.
undulation
In a polished donut-shaped aluminum substrate, the amplitude of minute irregularities at an undulating wavelength of several tens to several hundreds of μm was measured at an arbitrary portion that divides the outer circle and the inner circle into two equal parts.
Next, on a straight line connecting the measurement point and the center point of the donut-shaped aluminum substrate, and at the point where the center point is bisected with the measurement point, the swell wavelength is similarly several tens to several tens. The amplitude of the minute unevenness at 100 μm was measured. Then, the average value of these two values was used as the measured value of the swell. The measurement conditions are as follows.
Equipment: ZygoNewView7200
Lens: 2.5x Zoom ratio: 1.0
Filter: 50-500 μm
Measurement area: 3.75 mm x 2.81 mm

[Synthesis Example DS1 (Dispersant)]
Take 228 ml of n-hexane in a 500 ml round-bottom flask equipped with a stirrer, a reflux condenser, a dropping funnel, and a nitrogen gas introduction tube, and then add 1.8 g of sorbitan monosteerate as a surfactant. After dissolving, nitrogen gas was blown in to expel the dissolved oxygen.
Separately, 30 g of acrylic acid was taken in an Erlenmeyer flask, and 26 g of water and 26 g of 48% chemical soda were added while cooling to prepare an aqueous solution of sodium acrylic acid.
After dissolving 0.1 g of sodium persulfate in this aqueous solution, nitrogen gas was blown into the aqueous solution to remove oxygen present in the aqueous solution.
The aqueous sodium acrylic acid salt solution thus obtained was added to n-hexane in which the above-mentioned surfactant was dissolved to disperse it, and while introducing nitrogen gas little by little, the mixture was stirred at 65 ° C. for 6 hours for polymerization. Was done.
The obtained sodium polyacrylic acid salt (DS1) was linear and had a weight average molecular weight of 84,000. The ratio of carbon atoms directly bonded to the carbonyl carbon atom of the carboxyl group (value of m / (m + n) × 100) was 47%.

[Synthesis Example DS2 (Dispersant)]
Take 228 ml of n-hexane in a 500 ml round-bottom flask equipped with a stirrer, a reflux condenser, a dropping funnel, and a nitrogen gas introduction tube, and then add 1.8 g of sorbitan monosteerate as a surfactant. After dissolving, nitrogen gas was blown in to expel the dissolved oxygen.
Separately, 30 g of acrylic acid was taken in an Erlenmeyer flask, and 26 g of water and 26 g of 48% chemical soda were added while cooling to prepare an aqueous solution of sodium acrylic acid.
After dissolving 1.0 g of sodium persulfate in this aqueous solution, nitrogen gas was blown into the aqueous solution to remove oxygen present in the aqueous solution.
The aqueous sodium acrylic acid salt solution thus obtained was added to n-hexane in which the above-mentioned surfactant was dissolved to disperse it, and while introducing nitrogen gas little by little, the mixture was stirred at 65 ° C. for 6 hours for polymerization. Was done.
The obtained sodium polyacrylic acid salt (DS2) was linear and had a weight average molecular weight of 13,000. The ratio of carbon atoms directly bonded to the carbonyl carbon atom of the carboxyl group (value of m / (m + n) × 100) was 47%.

[Synthesis Example DS3 (Dispersant)]
Take 228 ml of n-hexane in a 500 ml round-bottom flask equipped with a stirrer, a reflux condenser, a dropping funnel, and a nitrogen gas introduction tube, and then add 1.8 g of sorbitan monosteerate as a surfactant. After dissolving, nitrogen gas was blown in to expel the dissolved oxygen.
Separately, 30 g of acrylic acid was taken in an Erlenmeyer flask, and 26 g of water and 19 g of a 28% aqueous ammonia solution were added while cooling to prepare an aqueous ammonium acrylate salt solution.
After dissolving 0.05 g of sodium persulfate in this aqueous solution, nitrogen gas was blown into the aqueous solution to remove oxygen present in the aqueous solution.
The aqueous solution of ammonium acrylic acid thus obtained is added to n-hexane in which the above-mentioned surfactant is dissolved to disperse it, and while introducing nitrogen gas little by little, the mixture is stirred at 65 ° C. for 6 hours for polymerization. Was done.
The obtained polyacrylic acid ammonium salt (DS3) was linear and had a weight average molecular weight of 150,000. The ratio of carbon atoms directly bonded to the carbonyl carbon atom of the carboxyl group (value of m / (m + n) × 100) was 48%.

[Synthesis Example DS4 (Dispersant)]
Take 228 ml of n-hexane in a 500 ml round-bottom flask equipped with a stirrer, a reflux condenser, a dropping funnel, and a nitrogen gas introduction tube, and then add 1.8 g of sorbitan monosteerate as a surfactant. After dissolving, nitrogen gas was blown in to expel the dissolved oxygen.
Separately, 30 g of acrylic acid was taken in an Erlenmeyer flask, and 26 g of water and 26 g of 48% caustic soda were added while cooling to prepare an aqueous solution of sodium acrylic acid.
After dissolving 0.01 g of sodium persulfate in this aqueous solution, nitrogen gas was blown into the aqueous solution to remove oxygen present in the aqueous solution.
The aqueous sodium acrylic acid salt solution thus obtained was added to n-hexane in which the above-mentioned surfactant was dissolved to disperse it, and while introducing nitrogen gas little by little, the mixture was stirred at 65 ° C. for 6 hours for polymerization. Was done.
The obtained sodium polyacrylic acid salt (DS4) was linear and had a weight average molecular weight of 500,000. The ratio of carbon atoms directly bonded to the carbonyl carbon atom of the carboxyl group (value of m / (m + n) × 100) was 48%.

<Preparation of silica gel>
Sodium silicate was dissolved in water to prepare a 24 wt% sodium silicate aqueous solution in terms of SiO ₂ . A solution containing silica hydrogel was obtained by adding a 24 wt% sodium silicate aqueous solution to 200.0 g of 25 wt% sulfuric acid so as to have a pH of 4.0. After maintaining this silica hydrogel solution at a temperature of 40 ° C. in a constant temperature bath and allowing it to stand for 2.75 hours for aging, the content of sodium sulfate is higher than that of silicon as SiO ₂ contained in the silica hydrogel. Purified silica hydrogel was obtained by washing with pure water until the content became 0.05% by weight. The concentration of this purified silica hydrogel was 5% by weight in SiO ₂ content (concentration). The specific surface area was 350 m ² / g.
By drying the purified silica hydrogel at 110 ° C, silica gel (composition [SiO ₂ : 88.9% by mass, Na: 0.3% by mass, SO ₄ : 0.4% by mass, H ₂ O: balance], average. A particle size of 14 μm and a specific surface area of 350 m ² / g) were obtained.

<Highly deformed silica-based gel fine particle dispersion (1)>
28 g of silica gel and 472 g of pure water obtained by drying the purified silica hydrogel at 110 ° C. were placed in a 2 L glass beaker, and a 4.8 mass% sodium hydroxide aqueous solution was further added to adjust the pH to 10.0. 2390 g of zirconia medium having a diameter of 1 mm was added thereto, and the gel was crushed by a sand mill crusher until the weight average particle size became 426 nm (first stage crushing), and a highly deformed silica-based gel having a SiO ₂ concentration of 4.0% by mass was obtained. A fine particle dispersion liquid (1) was obtained.

<Highly deformed silica-based gel fine particle dispersion (2)>
Next, 1135 g of 0.5 mmφ glass medium was added to the highly deformed silica-based gel fine particle dispersion (1), and the mixture was crushed by a sandmill crusher until the weight average particle size became 249 nm (second stage crushing), and SiO ₂ was used. A highly deformed silica-based gel fine particle dispersion (2) having a concentration of 3.5% by mass was obtained.

<Highly deformed silica-based gel fine particle dispersion (3)>
Next, 1135 g of 0.25 mmφ glass medium was added to the highly deformed silica-based gel fine particle dispersion (2), and the mixture was crushed with a sandmill crusher until the weight average particle size became 135 nm (third-stage crushing), and SiO ₂ was used. A highly deformed silica-based gel fine particle dispersion (3) having a concentration of 3.0% by mass was obtained.

<Preparation of silica-based particle group consisting of irregularly shaped silica-based particles and non-modified silica-based particles>
Ion-exchanged water was added to the obtained highly deformed silica-based gel fine particle dispersion (3) to obtain 2716 g of a solution having a SiO ₂ concentration of 2.76% by mass. Next, a 4.8% by mass sodium hydroxide aqueous solution and ion-exchanged water were added to prepare a solution having a pH of 10.7 and a SiO ₂ concentration of 2.5% by mass. Then, the temperature was raised to 98 ° C. and kept at 98 ° C. for 30 minutes. Next, 5573.1 g of an acidic silicic acid solution of 4.6% by mass was added over 20 hours while maintaining the temperature at 98 ° C., and stirring was continued for 1 hour while further maintaining the temperature at 98 ° C.
After cooling this preparation to room temperature, it was concentrated to a SiO ₂ concentration of 12% by mass with an ultrafiltration membrane (SIP-1013 manufactured by Asahi Kasei Corporation). Further, the mixture was concentrated to 30% by mass with a rotary evaporator to obtain a silica-based particle dispersion liquid (1) containing a silica-based particle group composed of deformed silica-based particles and non-atypical silica-based particles. The weight average particle diameter of the obtained silica-based particle group was 111 nm.

[Example 1]
Preparation of abrasive grain dispersion for polishing
To 150 g of the silica-based particle dispersion (1) (SiO ₂ concentration: 30% by mass) obtained as described above, 0.45 g of sodium polyacrylate (DS1) (sodium polyacrylate with respect to 100 parts by mass of silica). (Equivalent to 1 part by mass of salt) was added, and the mixture was stirred at room temperature for 60 minutes to prepare an abrasive grain dispersion liquid A1 for polishing.

[Comparative Example 1]
Preparation of abrasive grain dispersion for polishing
150 g of the silica-based particle dispersion liquid (1) (SiO ₂ concentration: 30% by mass) obtained as described above was used as a polishing abrasive grain dispersion liquid B1.

[Comparative Example 2]
Preparation of abrasive grain dispersion for polishing
To 150 g of the silica-based particle dispersion (1) (SiO ₂ concentration: 30% by mass) obtained as described above, 0.45 g of sodium polyacrylate (DS2) (sodium polyacrylate with respect to 100 parts by mass of silica). (Equivalent to 1 part by mass of salt) was added, and the mixture was stirred at room temperature for 60 minutes to prepare an abrasive grain dispersion liquid B2 for polishing.

[Example 2]
Preparation of abrasive grain dispersion for polishing
To 150 g of the silica-based particle dispersion (1) (SiO ₂ concentration: 30% by mass) obtained as described above, 0.45 g of an ammonium polyacrylic acid salt (DS3) (ammonium polyacrylic acid with respect to 100 parts by mass of silica). (Equivalent to 1 part by mass of salt) was added, and the mixture was stirred at room temperature for 60 minutes to prepare an abrasive grain dispersion liquid A2 for polishing.

[Comparative Example 3]
Preparation of Abrasive Grain Dispersion Liquid for Polishing To 150 g of the silica-based particle dispersion liquid (1) (SiO ₂ concentration: 30% by mass) obtained as described above, 0.45 g of sodium polyacrylate (DS4) (100% by mass of silica). (Equivalent to 1 part by mass of sodium polyacrylate) was added to the portion, and the mixture was stirred at room temperature for 60 minutes to prepare an abrasive grain dispersion liquid B3 for polishing.

Table 3 summarizes the above-mentioned measurement and calculation data for the above-mentioned Examples and Comparative Examples. Table 3 also shows the viscosity measurement of the abrasive grain dispersion for polishing in each Example and each Comparative Example, and the observation results of the presence or absence of foaming. Here, the viscosity was measured using a B-type viscometer. In Table 3, "slurry state / viscosity" and "slurry state (presence or absence of foaming)" are expressed.

The abrasive grain dispersion liquid for polishing of the examples obtained by a predetermined production method has a particle size, a particle size distribution and a degree of irregularity suitable as an abrasive, and is a silica-based particle dispersion containing these silica-based particle groups. When the liquid is used as an abrasive grain dispersion liquid for polishing, a practical polishing speed can be obtained, and at the same time, a practical surface accuracy can be achieved. Further, this abrasive grain dispersion liquid for polishing is excellent in suppressing the sedimentation property of the abrasive grains, improving the redispersibility of the settled abrasive grains, or suppressing the residue of the abrasive grains and the like.

Since the silica-based particle group of the present invention has suitable particle size, particle size distribution, degree of deformation, and particle strength, the silica-based particle dispersion liquid containing the silica-based particle group may be, for example, a NiP-plated substrate to be polished. It can be preferably used for surface polishing of silica-based substrates and the like.

Claims (8)

A dispersant made of a polycarboxylate is dispersed in a silica-based particle dispersion liquid containing a silica-based particle group consisting of atypical silica-based particles and a non-atypical silica-based particle, and polishing that satisfies the following [1] to [5]. Abrasive particle dispersion liquid.
[1] The weight average particle diameter (D ₁ ) of the silica-based particle group is 50 to 600 nm, and the specific surface area-equivalent average particle diameter (D ₂ ) is 15 to 300 nm.
[2] The degree of deformation D (D = D ₁ / D ₂ ) represented by the ratio of the weight average particle diameter (D ₁ ) of the silica-based particle group to the specific surface area equivalent particle diameter (D ₂ ) is 1.1. Must be in the range of ~ 10.
[3] When the volume-based particle size distribution of the silica-based particle group is waveform-separated, a multi-peak distribution in which three or more separation peaks are detected is obtained.
[4] The polycarboxylate has a weight average molecular weight in the range of 20,000 to 400,000, and has m the number of carbon atoms directly bonded to carbonyl carbon and the number of carbon atoms not directly bonded to carbonyl carbon. When n, the value of m / (m + n) × 100 is in the range of 40 to 50%.
[5] The mass ratio of the silica-based particle group to the polycarboxylate is in the range of 100: 0.1 to 100:10. The abrasive grain dispersion liquid for polishing according to claim 1, wherein the dispersant is made of polyacrylic acid salt. The abrasive grain dispersion for polishing according to claim 1 or 2, wherein the skewness in the volume-based particle size distribution of the silica-based particle group is in the range of −20 to 20. Any of claims 1 to 3, wherein the volume ratio of the maximum particle component is 75% or less among the separation peaks obtained as a result of waveform-separating the volume-based particle size distribution of the silica-based particle group. The abrasive grain dispersion for polishing according to the above. The aspect ratio of the small particle side component is in the range of 1.05 to 5.0 in the number-based particle size distribution obtained by the SEM image analysis of the silica-based particle group, according to claims 1 to 4. Abrasive particle dispersion for polishing according to any one. The abrasive grain dispersion for polishing according to any one of claims 1 to 5, wherein the coefficient of variation of the particle size of the volume-based particle size distribution of the silica-based particle group is 30% or more. Smoothness S (S = S ₂ / S) expressed by the ratio of the area of a circle (S ₂ ) equivalent to the average outer peripheral length by the image analysis method to the average area (S ₁ ) by the image analysis method in the silica-based particle group. The abrasive grain dispersion for polishing according to any one of claims 1 to 6, wherein ₁ ) is in the range of 1.1 to 5.0. In the volume-based particle size distribution of the silica-based particle group, the ratio Q (Q = Q ₂ / Q ₁ ) of the volume (Q ₂ ) of particles of 0.7 μm or more to the total volume (Q ₁ ) is 5.0% or less. The abrasive grain dispersion for polishing according to any one of claims 1 to 7, wherein the abrasive grain dispersion liquid is characterized by the above.

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