JP2022022601A - Manufacturing method of heteromorphic silica particle dispersion, and heteromorphic silica particle dispersion thereof - Google Patents

Abstract

To provide a manufacturing method of a heteromorphic silica particle dispersion.SOLUTION: There is provided a manufacturing method of a heteromorphic silica particle dispersion that comprises the following steps 1 to 3, satisfying the following condition 1. The step 1 is a step of mixing a first acidic silicate solution and an aqueous alkaline solution including an alkaline compound in which Na or K is contained, followed by heat-aging to obtain a precursor dispersion with SiO2 concentration and SiO2/A2O (molar ratio) in specific ranges. The step 2 is a step of adding a second acidic silicate solution into the precursor dispersion obtained in the step 1, in a specific range of a second addition speed ratio, followed by the heat-aging to obtain a seed particle dispersion. The step 3 is a step of adding a third acidic silicate solution into a seed particle dispersion obtained in the step 2, in a specific range of a third addition speed ratio, followed by the heat-aging to obtain the heteromorphic silica particle dispersion. The condition 1 is that the third addition speed ratio/the second addition speed ratio is within a specific range.SELECTED DRAWING: None

Description

The present invention relates to a method for producing a modified silica particle dispersion and a modified silica particle dispersion.

Conventionally, silica sol, fumed silica, fumed alumina, and the like have been used as the polishing particles. In the manufacture of a substrate with an integrated circuit of a semiconductor, an aluminum wiring is formed on a silicon wafer, and an oxide film such as silica is provided as an insulating film on the aluminum wiring. In this case, unevenness occurs due to wiring, so this oxide film is polished and flattened. In such polishing of a substrate, the surface after polishing is required to be flat without steps or irregularities, to be smooth without microscopic scratches, and to have a high polishing speed.

Abrasives used in chemical mechanical polishing (CMP) are usually composed of polishing particles, oxidants, additives such as organic acids and solvents such as pure water. The polishing particles are spherical with an average particle diameter of about 200 nm, which is made of a metal oxide such as silica and alumina. Oxidizing agents accelerate the polishing speed of metal for wiring and circuits.
When there is a step (unevenness) due to the groove pattern for wiring on the surface of the material to be polished, it is required to polish the convex part to the same surface while polishing and removing it to make a flat polished surface. There is. However, with conventional spherical polishing particles, when the part above the coplanarity is polished, the circuit metal in the wiring groove at the bottom of the recess is polished to below the coplanarity (called dishing). There was.). When such dishing (over-polishing) occurs, the thickness of the wiring is reduced and the wiring resistance is increased, and the flatness of the insulating film formed on the wiring is lowered. Therefore, it is required to suppress dishing.
In recent years, non-spherical particles have been proposed as polishing particles instead of the conventional spherical particles.

As a method for producing a silica sol containing irregularly shaped particles, in Patent Document 1, a silicic acid solution is added to an alkali metal silicate aqueous solution of 0.05 to 5.0% by weight as SiO ₂ , and the mixed solution is SiO ₂ / M ₂ O. After setting (molar ratio, M is alkali metal or quaternary ammonium) to 30 to 60, it consists of a group consisting of Ca, Mg, Al, In, Ti, Zr, Sn, Si, Sb, Fe, Cu and rare earth metals. A compound of one or more selected metals is added (the time of addition may be before or during the addition of the silicic acid solution), and the mixed solution is maintained at an arbitrary temperature of 60 ° C. or higher for a certain period of time. Further disclosed is a method for producing a sol in which substantially irregularly shaped silica particles having a SiO ₂ / M ₂ O (molar ratio) of 60 to 100 in the reaction solution are dispersed by adding a silicic acid solution.

In Patent Document 2, an aqueous solution of a water-soluble calcium salt, magnesium salt or a mixture thereof is added to a colloidal aqueous solution of active silicic acid, an alkaline substance is added to the obtained aqueous solution, and a part of the obtained mixture is 60. The feed liquid is added to the heel liquid by heating to a temperature of ° C. or higher to obtain a heel liquid, and the balance is used as a feed liquid. During the addition, water is evaporated to concentrate the SiO ₂ concentration to 6 to 30% by weight. Disclosed is a method for producing a silica sol having an elongated shape.

Patent Document 3 describes a water-soluble II-valent or III-valent metal salt alone in a colloidal aqueous solution of active silicic acid containing 0.5 to 10% by weight of SiO ₂ and having a pH of 2 to 6. Alternatively, the aqueous solution contained as a mixture is designated as MO for a metal oxide (MO in the case of a salt of a II-valent metal, and M ₂ O in the case of a salt of a III-valent metal) with respect to SiO ₂ of a colloidal aqueous solution of the same active silicic acid. However, M represents a metal atom having a valence of II or _III , and O represents an oxygen atom.) An amount of 1 to 10% by weight was added and mixed to obtain a mixed solution (1). In addition, an acidic spherical silica sol having an average particle diameter of 10 to 120 nm and a pH of 2 to 6 is a ratio A / B of the silica content (A) derived from the acidic spherical silica sol and the silica content (B) derived from the mixed solution (1). The (weight ratio) is 5 to 100, and the total silica content (A + B) of the mixed solution (2) obtained by mixing the acidic spherical silica sol and the mixed solution (1) is the SiO ₂ concentration in the mixed solution (2). Add and mix so as to be 5 to 40% by weight, add alkali metal hydroxide or the like to the mixed solution (2) so as to have a pH of 7 to 11, and mix, and the obtained mixed solution (3) is 100. A method for producing a beaded silica sol heated at about 200 ° C. for 0.5 to 50 hours is described.

Patent Document 4 describes alkyl silicates having a composition in the range of SiO ₂ concentration of 1 to 8 mol / liter, acid concentration of 0.0018 to 0.18 mol / liter and water concentration of 2 to 30 mol / liter, without using a solvent. Is hydrolyzed with an acid catalyst, diluted with water so that the SiO ₂ concentration is in the range of 0.2 to 1.5 mol / liter, and then an alkaline catalyst is added and heated so that the pH is 7 or more. By advancing the polymerization of silicic acid, amorphous silica particles having an elongated shape having an average diameter of 5 to 100 nm in the thickness direction and 1.5 to 50 times the length as observed by an electron microscope are liquid-dispersed. A method for producing a silica sol dispersed throughout the body is described.

Patent Document 5 describes an alkaline earth metal, for example, an alkaline earth metal, for example, in an acidic aqueous solution of active silicic acid having a SiO ₂ concentration of about 2 to 6% by mass, which is obtained by decationizing an aqueous solution of an alkali metal silicate such as water glass. Salts such as Ca, Mg, and Ba are added in a weight ratio of 100 to 1500 ppm with respect to SiO ₂ of the active silicic acid in terms of oxide thereof, and further, SiO ₂ / M ₂ O (M is an alkali metal atom, Represents NH ₄ or a quaternary ammonium group.) The liquid obtained by adding the same alkaline substance in an amount having a molar ratio of 20 to 150 is initially used as a heel liquid, and 2 to 6% by mass obtained in the same manner. An active silicic acid aqueous solution having a SiO ₂ concentration and a SiO ₂ / M ₂ O (M is the same as above) molar ratio of 20 to 150 is used as a charging liquid, and the charging liquid is added to the initial heel liquid at 60 to 150 ° C. Distortion caused by adding water from the liquid with or without evaporation at a rate of 0.05 to 1.0 as the weight ratio of charge liquid SiO ₂ / initial heel liquid SiO ₂ per hour. A method for producing a silica sol having a shape is described.

Patent Document 6 describes (1) a method of neutralizing an aqueous solution of alkaline silicate with mineral acid, adding an alkaline substance and aging by heating, and (2) an alkaline substance in active silicic acid obtained by cation exchange treatment of the aqueous solution of alkaline silicate. (3) A method of heating and aging active silicic acid obtained by hydrolyzing an alkoxysilane such as ethyl silicate, or (4) A method of directly dispersing silica fine powder in an aqueous medium. The colloidal silica aqueous solution produced by the method or the like is usually composed of colloidal silica particles having a particle size of 4 to 1,000 nm (nanometers), preferably 7 to 500 nm dispersed in an aqueous medium, and is used as SiO ₂ . It has a concentration of 0.5 to 50% by mass, preferably 0.5 to 30% by mass. It is described that the particle shape of the silica particles includes a spherical shape, a distorted shape, a flat shape, a plate shape, an elongated shape, a fibrous shape, and the like.

Patent Document 7 describes a polishing agent containing separated silica particles, which are spherical and not connected to each other by a bond, in which A) the silica particles having a size of 5-50 nm are 5-95% by mass, and b) the size is 50-200 nm. It is reported that a polishing agent containing 95-5% by mass of silica particles, but having a bimodal particle size distribution as a whole, gives a high polishing rate.

Further, in Patent Document 8, the degree of deformation is in the range of 1.55 to 4, and the particle size distribution is in the particle size range of 30 to 70 nm and the particle size range of 71 to 150 nm in the particle size distribution by the dynamic light scattering method. It is disclosed that an excellent polishing rate is achieved by using a polishing silica sol having a peak in the range of 50 to 100 nm in particle size difference between the two peaks.

Further, in Patent Document 9, a polishing composition containing spherical particles having a sphericity of 0.9 or more and non-spherical particles not corresponding to the spherical particles in a predetermined weight ratio has an uneven surface to be polished. However, it is disclosed that the surface after polishing is excellent in flatness, and deterioration of polishing performance can be suppressed even after long-term polishing.

Further, in Patent Document 10, as colloidal silica useful for polishing agents for electronic materials and the like, an alkaline aqueous solution of silicic acid is brought into contact with a cation exchange resin to prepare active silicic acid, which is used as a compound as a source of potassium ions. After adding alkali metal hydroxide or quaternary ammonium hydroxide as an alkaline agent to make it alkaline, it is heated to form silica particles, and then under heating, the active silicic acid aqueous solution and alkali are maintained while maintaining alkalinity. A group of deformed silica particles containing potassium ions having a major axis / minor axis ratio of 1.2 to 10 by observing a transmission electron micrograph by adding an agent and a compound that is a source of potassium ions to grow silica particles is disclosed. ing.

In Patent Document 11, at least four or more silica primary particles having an average primary particle diameter (D1) in the range of 20 to 100 nm are clustered, an average particle diameter (DCL) is in the range of 40 to 300 nm, and an aspect ratio (aspect ratio). As a method for producing silica particles characterized in that DL) / (DS) is in the range of 1.5 to 5, an acidic silicic acid solution and an alkali halide are added to an alkaline silicate aqueous solution so as to have a predetermined molar ratio range. To obtain a seed particle precursor dispersion of silica particles, which is subsequently heated and aged, and then stirred in the range of the Reynolds number (Re) represented by the following formula (1) in the range of 2000 to 1,000,000. However, it discloses a production method in which an acidic silicic acid solution is added.
Re = nd ² ρ / μ ... (1)
(However, n is the rotation speed of the stirring blade [S-1], d is the diameter of the stirring blade [m], ρ is the density of the dispersion liquid [kg / m ³ ], and μ is the viscosity of the dispersion liquid [Pa · s]. be)

Generally, the following production method is known as a method for producing irregularly shaped silica particles having a relatively large particle diameter.
1) A method of adding a component that becomes a silica source to irregularly shaped seed particles and growing the particles to obtain irregularly shaped silica particles. 2) Bonding spherical particles to form particle-connected silica-based particles or similar irregularly shaped silica particles. Method of obtaining 3) Method of crushing silica particles to obtain deformed silica particles Here, in the manufacturing method of 1), although particles having a high degree of deformity can be prepared, only particles having a small specific surface area equivalent particle diameter can be obtained. When applied to polishing applications, there is a problem that the polishing speed is low. When a silica source such as silicic acid is added to particles having a small specific surface area equivalent particle diameter and grown to a large size, the degree of deformation decreases as the particles grow and the particles approach a spherical shape, so that deformed silica particles having a desired degree of deformation can be obtained. It wasn't easy. Further, when such particles having a low degree of deformation are used for polishing, there is a problem that the polishing speed is low.
The production method of 2) requires components other than silica-based components for linking the particles (for example, calcium oxide and magnesium oxide in Patent Document 2, alkaline catalyst in Patent Document 4, and alkaline earth in Patent Document 5). Metals, potassium chloride, etc. in Patent Document 11), and when deformed silica particles containing these components are applied to polishing for semiconductor applications, there is a concern that they may cause contamination. In addition, these components other than silica cause deformation by functioning as an agglutination promoter for silica particles, but on the other hand, when trying to prepare silica particles having a large size and a high degree of agglutination, a large amount of agglutination promoter is used. Since it is necessary, the agglutination reaction proceeds too much, and coarse agglomerates are partially formed. When such a silica sol is applied to a polishing application, scratches are likely to occur due to a large number of coarse particles, and the polishing performance tends to be unstable due to sedimentation.
In the production method of 3), it was not easy to obtain irregularly shaped silica particles having uniform particle size and particle shape.

Japanese Unexamined Patent Publication No. 4-187512 Japanese Unexamined Patent Publication No. 7-118008 Japanese Unexamined Patent Publication No. 2001-11433 Japanese Unexamined Patent Publication No. 2001-48520 Japanese Unexamined Patent Publication No. 2001-150334 Japanese Unexamined Patent Publication No. 8-279480 Japanese Patent Publication No. 2003-528662 JP-A-2007-137972 Japanese Unexamined Patent Publication No. 2006-80406 Japanese Unexamined Patent Publication No. 2011-98859 Japanese Unexamined Patent Publication No. 2015-86102

INDUSTRIAL APPLICABILITY The present invention uses these elements in addition to alkaline earth metals and halogens derived from raw materials such as sodium silicate in the production of a deformed silica particle dispersion containing deformed silica particles having a relatively large particle size and having excellent polishing properties. An object of the present invention is to provide a method for manufacturing without using the particles. Another object of the present invention is to provide a modified silica particle dispersion liquid containing irregular silica particles having a relatively large particle size and having excellent polishing properties.

According to one aspect of the present invention, there is provided a method for producing a modified silica particle dispersion liquid, which comprises the following steps 1 to 3 and satisfies the following condition 1.
Step 1: The first acidic silicic acid solution is mixed with an alkaline aqueous solution containing an alkaline compound having at least Na or K.
Further, by heating and aging in a temperature range of 50 ° C. or higher and lower than 100 ° C., a precursor dispersion liquid having a SiO ₂ concentration of 3% by mass or more and 20% by mass or less and satisfying the conditions shown by the following formula (F1-1) can be obtained. Obtaining step 2 ≦ SiO ₂ / A ₂ O ≦ 15 ... (F1-1)
(Here, SiO ₂ represents the number of moles of silica in the precursor dispersion, and A ₂ O represents the total number of moles of Na ₂ O and K ₂ O in the precursor dispersion.)
Step 2: The second acidic silicic acid solution is added to the precursor dispersion obtained in the step 1, and the second addition rate ratio represented by the following formula (F2-1) is 0.1 [kg / hr · kg]. Step 2 Addition rate ratio [2 kg / hr · kg] = (silica content in secondary acidic silicic acid solution [kg]) / (addition time of secondary acidic silicic acid solution [hr]) / (silica content in precursor dispersion [kg] ) ... (F2-1)
Step 3: The third acidic silicic acid solution is added to the seed particle dispersion obtained in the above step 2, and the third addition rate ratio shown by the following formula (F3-1) is 1.1 [kg / hr · kg] or more. Step to obtain a modified silica particle dispersion liquid by adding so as to be in the range of 10 [kg / hr · kg] or less and further heating and aging in the range of temperature 50 ° C. or higher and lower than 100 ° C. Third addition rate ratio [kg / kg / hr · kg] = (silica content in the tertiary acidic silicic acid solution [kg]) / (addition time of the tertiary acidic silicic acid solution [hr]) / (silica content in the precursor dispersion liquid [kg]).・ ・ (F3-1)
Condition 1: The condition shown by the following formula (F0-1) is satisfied.
1.9 ≤ [The third addition rate ratio] / [The second addition rate ratio] ≤ 40 ... (F0-1)

In the method for producing a modified silica particle dispersion liquid according to one aspect of the present invention, it is preferable to include the following step 4 following the step 3.
Step 4: A step of concentrating the irregularly shaped silica particle dispersion obtained in the above step 3.

In the method for producing a modified silica particle dispersion liquid according to one aspect of the present invention, it is preferable to further satisfy the following condition 2.
Condition 2: In the precursor dispersion, the number of moles (molar / molar ratio) of the halogen element converted to 1 mol of silica is 0.5% or less, and the alkaline earth metal converted to 1 mol of silica. The number of moles (molar / molar ratio) is 1000 ppm or less.

In the method for producing a modified silica particle dispersion liquid according to one aspect of the present invention, it is preferable to further satisfy the following condition 3.
Condition 3: The silica content ratio represented by the following mathematical formula (F0-2) is in the range of 10 or more and 100 or less.
Silica content ratio = {(silica content in secondary acidic silicic acid solution [kg]) + (silica content in tertiary acidic silicic acid solution [kg])} / (silica content in precursor dispersion liquid [kg] kg]) ・ ・ ・ (F0-2)

In the method for producing a modified silica particle dispersion liquid according to one aspect of the present invention, it is preferable to further satisfy the following condition 4.
Condition 4: The SiO ₂ / A ₂ O molar ratio in the variant silica particle dispersion is in the range of 60 or more and 140 or less.
(Here, SiO ₂ represents the number of moles of silica in the variant silica particle dispersion, and A ₂ O represents the total number of moles of Na ₂ O and K ₂ O in the variant silica particle dispersion.)

In the method for producing a modified silica particle dispersion according to one aspect of the present invention, it is preferable that the alkaline aqueous solution in step 1 is a potassium silicate aqueous solution.

In the method for producing a modified silica particle dispersion according to one aspect of the present invention, it is preferable that the alkaline compound in the step 1 is potassium hydroxide.

In the method for producing a deformed silica particle dispersion liquid according to one aspect of the present invention, the obtained deformed silica particles have a specific surface area equivalent particle diameter (D1) in the range of 10 nm or more and 200 nm or less, and were measured by a dynamic light scattering method. It is preferable that the average particle size (D2) is in the range of 20 nm or more and 300 nm or less, and the value of (D2) / (D1) is in the range of 1.2 or more and 20 or less.

According to one aspect of the present invention, the specific surface area equivalent particle diameter (D1) is in the range of 10 nm or more and 200 nm or less, and the average particle diameter (D2) measured by the dynamic light scattering method is in the range of 20 nm or more and 300 nm or less. And, a variant silica particle dispersion liquid containing the variant silica particles characterized in that the value of (D2) / (D1) is in the range of 1.2 or more and 20 or less is provided.

The variant silica particle dispersion according to one aspect of the present invention preferably contains a potassium compound.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a method for producing a deformed silica particle dispersion liquid containing a deformed silica particle having a relatively large particle size having excellent polishing properties, and further, an alkaline earth derived from a raw material such as sodium silicate. It is possible to provide a method for producing without using these elements other than metal and halogen. Further, according to the present invention, it is possible to provide a deformed silica particle dispersion having a relatively large particle size and having excellent polishing properties.

[Manufacturing method of irregularly shaped silica particle dispersion]
Hereinafter, a method for producing a modified silica particle dispersion liquid according to the present invention will be described.
The method for producing a modified silica particle dispersion liquid according to the present invention is characterized by comprising the following steps 1 to 3 and satisfying the following condition 1.

<Step 1>
In step 1, the primary acidic silicic acid solution is added to the alkaline aqueous solution so as to satisfy the conditions described below, and mixed to obtain a precursor dispersion liquid satisfying the conditions described below.
In preparing this precursor dispersion, for example, it is preferable to produce it as follows.
That is, after adding an alkaline aqueous solution to ultrapure water and stirring until uniform, the primary acidic silicic acid solution is added and mixed sufficiently. The mixture of the alkaline solution and the primary acidic silicic acid solution is heated to a temperature range of 50 ° C. or higher and lower than 100 ° C. and held in the temperature range for 15 minutes or longer and 2 hours or shorter to produce a precursor dispersion liquid. When adding the primary acidic silicic acid solution, it is preferable to continuously add the primary acidic silicic acid solution in order to prevent excessive aggregation.

-Alkaline aqueous solution The alkaline aqueous solution contains an alkaline compound having at least Na or K. Examples of the alkaline compound having at least Na or K include sodium silicate, potassium silicate, potassium hydroxide, sodium hydroxide and the like. As the alkaline silicate compound, sodium silicate, potassium silicate and the like commercially available under the names of No. 1 water glass, No. 2 water glass, No. 3 water glass and the like are preferable. Further, an alkaline silicate aqueous solution obtained by hydrolyzing a hydrolyzable organic compound such as tetraethyl orthosilicate (TEOS) or tetramethyl orthosilicate (TMS) with excess NaOH or KOH is also suitable.
Examples of the alkaline compound arbitrarily contained in the alkaline aqueous solution include lithium silicate and quaternary ammonium silicate, ammonia, amines and salts thereof.
As the alkaline aqueous solution, a potassium silicate aqueous solution or a potassium hydroxide aqueous solution is preferable. Generally, in electronic material applications, sodium ions having a small ionic radius tend to diffuse to a substrate or the like, which may cause defects. Therefore, potassium ions having a relatively large ionic radius are desirable.
The concentration of the alkaline compound component in the alkaline aqueous solution is not particularly limited. The concentration of the alkaline compound component is preferably 1% by mass or more and 50% by mass or less, and more preferably 5% by mass or more and 25% by mass or less.
The alkaline aqueous solution preferably does not contain a halide ion (chloride ion or the like) or an alkaline earth metal (calcium, magnesium or the like). The halogen ion contained in the alkaline aqueous solution is preferably 1000 ppm or less, and the alkaline earth metal (magnesium or the like) is preferably 100 ppm or less.

-Acid silicic acid solution As the acidic silicic acid solution, it is preferable to use an acidic silicic acid solution obtained by dealkalizing an aqueous solution of alkali silicate (alkali metal silicate, ammonium silicate, etc.) with a cation exchange resin. The SiO ₂ concentration of the acidic silicic acid solution is preferably about 0.1% by mass or more and 10% by mass or less, and more preferably 1% by mass or more and 7% by mass or less. Those having a pH of approximately 1 or more and 5 or less are preferably used.

Step 1 is a step of preparing a precursor dispersion of desired irregularly shaped seed particles. In step 1, an aqueous alkaline silicate solution is added to ultrapure water, and the mixture is stirred until uniform, and then the primary acidic silicate solution is continuously or intermittently added and mixed. After mixing, the temperature is raised to 50 ° C. or higher and lower than 100 ° C., the temperature is maintained for 15 minutes or longer and 2 hours or lower, and the mixture is heated and aged to obtain a precursor particle dispersion. If the temperature at the time of mixing is within the above range, the modified silica particle dispersion liquid of the present invention having excellent polishing performance can be obtained after step 2, step 3 and, if necessary, step 4.

The SiO ₂ concentration of the obtained precursor dispersion liquid is a parameter that controls the degree of deformation of the deformed seed particles, and is 3% by mass or more and 20% by mass or less as SiO ₂ and 3% by mass or more and 15% by mass or less. Is more preferable. When the SiO ₂ concentration of the precursor dispersion is less than 3% by mass, it tends to be difficult to obtain deformed seed particles having a high degree of deformity. When the SiO ₂ concentration of the precursor dispersion is more than 20% by mass, aggregation and precipitation are likely to occur, and even if aggregation and precipitation do not occur, a large amount of silica is deposited inside the reaction vessel, and a deformed seed of a desired size is formed. No particles can be obtained. If the SiO ₂ concentration of the precursor dispersion is within the above range, the modified silica particles of the present invention having excellent polishing performance and the dispersion thereof can be obtained after step 2, step 3 and, if necessary, step 4. ..

The obtained precursor dispersion liquid satisfies the conditions shown by the following mathematical formula (F1-1).
2 ≦ SiO ₂ / A ₂ O ≦ 15 ... (F1-1)
Here, SiO ₂ represents the number of moles of silica in the precursor dispersion, and A ₂ O represents the total number of moles of Na ₂ O and K ₂ O in the precursor dispersion.
The SiO ₂ / A ₂ O (molar ratio) in the precursor dispersion is preferably 2 or more and 5 or less. When SiO ₂ / A ₂ O (molar ratio) is in this range, it is suitable for producing dispersed seed particles in which aggregation and precipitation do not occur in step 2.
K ₂ O and Na ₂ O in A ₂ O mean that the amounts of K and Na present in the precursor dispersion are converted into oxides, respectively.
Since the amount of alkali in the precursor dispersion is excessive in the precursor dispersion having a SiO ₂ / A ₂ O (molar ratio) of less than 2, in order to generate the seed particle dispersion in step 2, the dispersion is required. The solubility of silica in it becomes excessive, which is not suitable. On the other hand, when a precursor dispersion having a SiO ₂ / A ₂ O (molar ratio) of more than 15 is applied to step 2, seed particles are excessively generated, so that desired particle growth tends to be difficult to occur.

The pH of the precursor dispersion is preferably in the range of 9 or more and 12.5 or less, more preferably 10 or more and 12 or less.
If the pH of the precursor dispersion is less than 9, the pH is too low and atypical seed particles may not be produced in step 2. Alternatively, even if seed particles are generated, stability may not be maintained and they may aggregate, or the acidic silicic acid solution added in step 2 may not dissolve or deposit, and aggregation or gelation may occur.
On the other hand, when the pH of the precursor dispersion liquid exceeds 12.5, the solubility of silica in the dispersion liquid is remarkably increased, and the ionic strength is also remarkably increased. Therefore, the seed particles produced in step 2 may aggregate, and precipitation may occur due to the aggregation.

<Step 2>
The method for producing a modified silica particle dispersion liquid of the present invention is characterized in that the modified silica particle dispersion liquid is prepared by dividing it into two steps (step 2 and step 3) in which the addition rate of the acidic silicic acid liquid is different.
Step 2 is a step of preparing deformed seed particles having a desired size and degree of deformation from the precursor prepared in step 1. In step 2, a secondary acidic silicic acid solution is added to the precursor dispersion obtained in step 1 so as to satisfy the conditions described below, and further heat-aged to obtain a seed particle dispersion.
Here, the precursor dispersion liquid has a SiO ₂ concentration of 3% by mass or more and 20% by mass or less, and a SiO ₂ / A ₂ O (molar ratio) of 2 or more and 15 or less (SiO ₂ is contained in the precursor dispersion liquid. Represents the number of moles of silica, where A ₂ O represents the total number of moles of K ₂ O and Na ₂ O in the precursor dispersion).

As the second acidic silicic acid solution, it is preferable to use an acidic silicic acid solution obtained by dealkalizing an alkaline silicate aqueous solution with a cation exchange resin, similarly to the first acidic silicic acid solution used in step 1. The acid silicic acid solution preferably has a SiO ₂ concentration of approximately 0.1% by mass or more and 10% by mass or less, and more preferably 1% by mass or more and 7% by mass or less. The pH of the acidic silicic acid solution is preferably 1 or more and 5 or less.

In step 2, the acid silicic acid solution is continuously or intermittently added to the precursor dispersion, and the second addition rate ratio shown by the following formula (F2-1) is 0.1 [kg / hr · kg] or more. Add and mix so as to be in the range of 6 or less [kg / hr · kg]. Then, a seed particle dispersion is prepared by heating and aging at a temperature of 50 ° C. or higher and lower than 100 ° C.
Second addition rate ratio [kg / hr · kg] = (silica content in secondary acidic silicic acid solution [kg]) / (addition time of secondary acidic silicic acid solution [hr]) / (in precursor dispersion) Silica content [kg]) ... (F2-1)

The second addition rate ratio means the addition rate of silica in the secondary acidic silicic acid solution with respect to the silica content in the precursor dispersion, and is a parameter for controlling the size and the degree of deformation of the deformed seed particles. When the second addition rate ratio is in the range of 0.1 or more and 0.6 or less, the generated nuclear particles are appropriately aggregated or associated to obtain irregular seed particles having a large average particle diameter. Further, since the core particles become large, the specific surface area equivalent diameter of the seed particles becomes large, which is preferable. When the second addition rate ratio is less than 0.1, the size of the nuclei produced becomes larger, but the agglutination or association of the nuclei particles progresses too much, coarse agglomerates are formed, and precipitates tend to be generated. Further, when the second addition rate ratio exceeds 0.6, it is difficult to promote aggregation or association of the produced nuclear particles, and it is difficult to obtain irregularly shaped seed particles. Even if the irregularly shaped seed particles are obtained, the particles have a low degree of irregularity. The second addition rate ratio is preferably 0.1 or more and 0.5 or less.

As described above, after adding the secondary acidic silicic acid solution to the precursor dispersion liquid, the mixture is further heated and aged in a temperature range of 50 ° C. or higher and lower than 100 ° C. By aging in this temperature range, the unreacted acidic silicic acid solution and the like remaining in the reaction solution can be dissolved and deposited on the particle surface to complete the reaction. As a result, it is possible to obtain irregularly shaped seed particles that have grown to an appropriate size and dispersed.
The temperature of the heat aging is more preferably 50 ° C. or higher and 99 ° C. or lower, and further preferably 60 ° C. or higher and 98 ° C. or lower.
If the temperature is less than 50 ° C., the unreacted acidic silicic acid solution remaining in the reaction solution may not be sufficiently dissolved and may remain in the reaction solution, causing agglomeration of particles in a subsequent step.
When the temperature at the time of heat aging is 100 ° C. or higher, the boiling point of the reaction solution is such that the solvent easily evaporates and the concentration increases, making it difficult to control the reaction. It goes too far and tends to settle.
The heat aging varies depending on the holding temperature, the SiO ₂ concentration of the acidic silicic acid solution, and the like, but is preferably within 24 hours.

<Process 3>
Step 3 is a step of growing the deformed seed particles obtained in Step 2 to a desired size. In step 3, the third acidic silicic acid solution is added to the seed particle dispersion obtained in step 2, and the third addition rate ratio shown by the following formula (F3-1) is 1.1 [kg / hr · kg] or more. A variant silica particle dispersion is obtained by adding the mixture in a range of 10 [kg / hr · kg] or less and further heating and aging at a temperature of 50 ° C. or higher and lower than 100 ° C.
Third addition rate ratio [kg / hr · kg] = (silica content in tertiary acidic silicic acid solution [kg]) / (addition time of tertiary acidic silicic acid solution [hr]) / (in precursor dispersion) Silica content [kg]) ... (F3-1)
Here, the third addition rate ratio means the addition rate of silica in the tertiary acidic silicic acid solution with respect to the silica content in the precursor dispersion. When the third addition rate ratio is in the range of 1.1 [kg / hr · kg] or more and 10 [kg / hr · kg] or less, an appropriate reaction rate can be obtained. Therefore, the added acidic silicic acid solution is dissolved and the dissolved silica is deposited on the deformed seed particles, and the deformed seed particles obtained in step 2 can be grown to a desired size, which is preferable. When the third addition rate ratio is less than 1.1 [kg / hr · kg], the addition rate of acidic silicic acid becomes significantly slow. Therefore, although it is possible to grow the irregularly shaped seed particles, the production efficiency is poor and the economy is poor. When the third addition rate ratio exceeds 10 [kg / hr · kg], the addition rate of the acidic silicic acid solution is extremely high, so that self-nucleation of the acidic silicic acid solution is likely to occur. The third addition rate ratio is preferably 2 or more and 6 or less.

In step 3, as described above, the seed particle dispersion is heated to 50 ° C. or higher and lower than 100 ° C., a tertiary acidic silicic acid solution is added, and the mixture is kept at that temperature for 15 minutes or more and 24 hours or less for heat aging. do. By performing such heat aging, unreacted silicic acid remaining in the reaction solution is deposited on the particle surface, and the reaction can be completed.
The heat aging temperature is preferably in the range of 60 ° C. or higher and 98 ° C. or lower.
When the heat aging temperature is less than 50 ° C., the added acidic silicic acid solution is not sufficiently dissolved, so that self-nucleation by silicic acid is likely to occur.
The holding time varies depending on the holding temperature, the SiO ₂ concentration of the acidic silicic acid solution, and the like, but is preferably within 24 hours.
As the tertiary acidic silicic acid solution, the same acidic silicic acid solution as the above-mentioned primary acidic silicic acid solution is used.

<Condition 1>
In the method for producing the modified silica particle dispersion liquid of the present invention, it is necessary to further satisfy the following condition 1.
Condition 1 is to satisfy the condition shown by the following mathematical formula (F0-1).
1.9 ≤ [Third addition rate ratio] / [Second addition rate ratio] ≤ 40 ... (F0-1)
The value of [third addition rate ratio] / [second addition rate ratio] is an index for efficiently obtaining silica particles having a deformed shape and a large particle size. When the value is in the range of 1.9 or more and 40 or less, large-sized irregular silica particles can be obtained without using elements that are pollutants such as halogens and alkaline earth metals.
When the value of [third addition rate ratio] / [second addition rate ratio] is less than 1.9, it is difficult to obtain irregularly shaped silica particles, and it is difficult to obtain large-sized particles.
When the value of [Third addition rate ratio] / [Second addition rate ratio] exceeds 40, it is easy to obtain irregularly shaped silica particles, but silicic acid tends to easily self-nucleate, and the desired particle size distribution and size. Silica particles tend to be difficult to obtain.
The value of [third addition rate ratio] / [second addition rate ratio] is more preferably 5 or more and 20 or less.

<Step 4>
The method for producing a modified silica particle dispersion liquid of the present invention may further include the following step 4.
Step 4 is a step of concentrating the irregularly shaped silica particle dispersion obtained in Step 3.
In step 4, the deformed silica particle dispersion obtained in step 3 can be used as it is for polishing or as a raw material for a slurry for polishing. If desired, the variant silica particle dispersion obtained in step 3 may be concentrated and then applied to various uses.
Specifically, for example, the irregularly shaped silica particle dispersion obtained in step 3 is cooled to about room temperature or higher and 40 ° C. or lower. Then, it may be concentrated using an ultrafiltration membrane or the like, further concentrated using an evaporator or the like, and the remaining irregularly shaped silica particles may be recovered. Centrifugation may be used to remove even coarser particles.

In the method for producing silica particles of the present invention, it can be obtained as a modified silica particle dispersion liquid through step 3 or step 4, and can be used as it is as an abrasive or the like. Further, if necessary, it can be dried by a conventional method and used, and further, if necessary, it can be fired by a conventional method and used.

<Condition 2>
It is preferable that the method for producing the modified silica particle dispersion liquid of the present invention further satisfies the following condition 2.
Condition 2 is an alkaline earth metal in which the number of moles (molar / molar ratio) of halogen elements converted per mole of silica is 0.5% or less in the precursor dispersion and the number of moles of halogen element is converted per mole of silica. The number of moles (molar / molar ratio) is 1000 ppm or less.
Halogen elements and alkaline earth metals are contained in trace amounts in silica sand, which is a natural raw material, and are further contained in trace amounts in raw materials for producing cullet and sodium silicate. Therefore, when a silica sol is produced from sodium silicate as a raw material, the content of these elements derived from the raw material contains 0.5% or less as a halogen element converted to 1 mol of silica, and an alkali converted to 1 mol of silica. It contains 1000 ppm or less as an earth metal. However, since the content of these elements derived from the raw material is very small, the influence on the generation of nuclear particles, particle growth, or the shape of the particles is small. Therefore, in the conventional method for producing deformed particles, these elements are added at the time of particle synthesis, and for example, the silica particles of the seed component and the silica particles are bonded via an alkaline earth metal (for example, MgO, CaO, etc.). A method of deforming the seed particles (a method of adding an alkaline earth metal to the seed particle dispersion and bonding the silica particles of the seed component and the silica particles via the alkaline earth metal) or an alkali halide in the seed particle dispersion. A method of deforming seed particles by adding (KCl or the like) to adjust the ionic strength is performed. However, these dissimilar substances such as alkaline earth metals and halogenated alkalis do not exist originally because when the deformed silica particle dispersion is applied to polishing applications, it may have an adverse effect such as contamination on the substrate depending on the application. Is preferable.
The method for producing a modified silica particle dispersion of the present invention is a method for producing a modified silica particle dispersion without using a dissimilar substance such as a halogen element or an alkaline earth metal during particle synthesis, specifically, a seed. It is a production method characterized in that particle growth performed by adding an acidic silicic acid solution to particles is performed in two steps in which the addition rate of the acidic silicic acid solution is different. Therefore, it does not require the different substances required for the conventional transformation method.

<Condition 3>
It is preferable that the method for producing the modified silica particle dispersion liquid of the present invention further satisfies the following condition 3.
Condition 3 is that the silica content ratio represented by the following mathematical formula (F0-2) is in the range of 10 or more and 100 or less.
Silica content ratio = {(silica content in secondary acidic silicic acid solution [kg]) + (silica content in tertiary acidic silicic acid solution [kg])} / (silica content in precursor dispersion liquid [kg] kg]) ・ ・ ・ (F0-2)
The silica content ratio represented by the formula (F0-2) is a weight ratio of silicic acid for particle growth to a precursor to be a seed, and is an index for efficiently growing seed particles to a desired particle size. When the value is in the range of 10 or more and 100 or less, particles can be efficiently grown to a desired size.
When the silica content ratio shown in the formula (F0-2) is less than 10, the amount of silicic acid for growing the produced seed particles is insufficient, and it is not possible to obtain deformed silica particles having a large size.
When the silica content ratio shown in the formula (F0-2) exceeds 100, the amount of silicic acid that grows the nucleated irregular silica seed becomes excessive. Therefore, the shape of the particles approaches a spherical shape, and it is not possible to obtain irregular silica particles having a desired degree of irregularity. In addition, excess silicic acid may cause self-nucleation.
The silica content ratio shown in the formula (F0-2) is more preferably 20 or more and 80 or less.

<Condition 4>
It is preferable that the method for producing the modified silica particle dispersion liquid of the present invention further satisfies the following condition 4.
Condition 4 is that the SiO ₂ / A ₂ O molar ratio in the deformed silica particle dispersion at the end of step 3 is in the range of 60 or more and 140 or less. (Here, SiO ₂ represents the number of moles of silica in the modified silica particle dispersion at the end of step 3, and A ₂ O is Na ₂ O and K ₂ O in the modified silica particle dispersion at the end of step 3. Represents the total number of particles.)
Here, K ₂ O and Na ₂ O in A ₂ O mean that the amounts of K and Na present in the variant silica particle dispersion liquid are converted into oxides, respectively.
The SiO ₂ / A ₂ O molar ratio in the variant silica particle dispersion at the end of step 3 is an index of pH at the time of particle growth. Although it varies depending on the target size, within this range, the silicic acid used for particle growth is sufficiently dissolved and can be deposited on the surface of the irregularly shaped seed particles, and can be grown to a desired particle size.
When the SiO ₂ / A ₂ O molar ratio in the variant silica particle dispersion is less than 60, the pH during the reaction is high, and the particles may aggregate during the reaction. Even if the particles are grown without agglomeration, the ionic strength of the dispersion after the reaction is high, so that agglomeration is likely to occur when concentrating in a subsequent step. It is necessary to reduce the ionic strength in order to prevent aggregation and maintain the stability of the particles, and means such as ion exchange and cleaning can be applied as a method for reducing the ionic strength, but the economic efficiency is reduced.
When the SiO ₂ / A ₂ Omolar ratio in the modified silica particle dispersion exceeds 140, the pH during the reaction is low, so the silicic acid added for particle growth is not sufficiently dissolved and self-nucleation is generated. There is a tendency.
The SiO ₂ / A ₂ O molar ratio in the variant silica particle dispersion is more preferably 80 or more and 120 or less.

[Atypical silica particles]
In the method for producing a deformed silica particle dispersion liquid of the present invention, the obtained deformed silica particles have a specific surface area equivalent particle diameter (D1) in the range of 10 nm or more and 200 nm or less, and are averages measured by a dynamic light scattering method. It is preferable that the particle size (D2) is in the range of 20 nm or more and 300 nm or less, and the value of (D2) / (D1) is in the range of 1.2 or more and 20 or less. Such irregularly shaped silica particles have relatively large particle diameters with excellent polishing characteristics.

[Atypical silica particle dispersion]
The modified silica particle dispersion obtained by the production method of the present invention has a specific surface area equivalent particle diameter (D1) in the range of 10 nm or more and 200 nm or less, and has an average particle diameter (D2) measured by a dynamic light scattering method. It is preferable that the deformed silica particles in the range of 20 nm or more and 300 nm or less and the value of the degree of deformation [(D2) / (D1)] in the range of 1.2 or more and 20 or less are dispersed in water.
When the degree of deformation [(D2) / (D1)] is in the range of 1.2 or more and 20 or less, a polished surface showing a high polishing rate, less defect, and low surface roughness when used as an abrasive grain for polishing. Can be obtained. When the degree of deformation [(D2) / (D1)] is less than 1.2, it becomes close to spherical particles, and when such a deformed silica particle dispersion is applied to a polishing application, the polishing rate tends to decrease. When the degree of deformation [(D2) / (D1)] exceeds 20, if such a deformed silica particle dispersion is applied to a polishing application, defects such as scratches are likely to occur on the substrate to be polished, and the surface of the polishing substrate is easily scratched. Roughness also tends to worsen.
When the average particle size (D2) measured by the dynamic light scattering method is in the range of 20 nm or more and 300 nm or less, a high polishing rate can be obtained, which is preferable. When a deformed silica particle dispersion having an average particle diameter (D2) of less than 20 nm is applied to a polishing application, the practical polishing rate is not sufficient. Further, when a deformed silica particle dispersion having an average particle diameter (D2) of more than 300 nm is applied to a polishing application, the polishing rate tends to decrease, and scratches tend to occur easily on the substrate to be polished.

The specific surface area equivalent particle diameter (D1) is preferably in the range of 10 nm or more and 200 nm or less.
When the specific surface area equivalent particle diameter (D1) is less than 10 nm, the number of particles increases due to the small size, but the polishing rate of each particle is low, so that the polishing rate becomes significantly low when used for polishing purposes. When the specific surface area equivalent particle diameter (D1) exceeds 200 nm, the size is too large and the number of particles is significantly reduced. Therefore, when applied to polishing applications, the polishing speed tends to decrease. In addition, the size may be too large, silica particles may precipitate in the dispersion liquid, and it may take time and effort to redisperse the particles when used, or the silica particles may not be sufficiently dispersed and the polishing performance may not be stable.
The specific surface area equivalent particle diameter (D1) is more preferably 20 or more and 150 or less.

The value of the degree of deformation [(D2) / (D1)] is more preferably 1.5 or more and 15 or less, and particularly preferably 1.5 or more and 5 or less.
The value of the average particle size (D2) measured by the dynamic light scattering method is more preferably 30 nm or more and 250 nm or less.

The SiO ₂ concentration of the modified silica particle dispersion is preferably 10% by mass or more and 50% by mass or less, and more preferably 20% by mass or more and 50% by mass or less.
As the dispersion solvent of the modified silica particle dispersion liquid, water or a mixed solvent of water and a hydrophilic organic solvent can be used.

The modified silica particle dispersion of the present invention preferably contains a potassium compound. By containing the potassium compound, the dispersion can be kept alkaline, the surface silanol groups of the deformed silica particles are dissociated, and the deformed silica particles can be kept stable without agglomeration.
Examples of the potassium compound include potassium hydroxide, a salt of potassium hydroxide, potassium silicate, and the like. The potassium compound may be used alone or in combination of two or more.
The concentration of the potassium compound in the variant silica particle dispersion is preferably 50 or more and 400 or less, and more preferably 60 or more and 300 or less, as a SiO ₂ / K ₂ O molar ratio.

In the present invention, particles having a particle size of 0.51 μm or more contained in the modified silica particle dispersion are referred to as coarse particles. The ratio of the coarse particles is preferably 500,000 particles / cc or less, more preferably 120 thousand particles / cc or less, when the number of coarse particles in the silica particle dispersion liquid having a SiO ₂ concentration of 1% by mass is taken as the number.
When the number of coarse particles exceeds 500,000 / cc, polishing scratches tend to occur during polishing.

[1] Method for quantifying SiO ₂ The content of SiO ₂ in the silica fine particle dispersion is determined by burning the silica fine particle dispersion at 1000 ° C. to determine the mass of the solid content, and then the Na and K contents described later. In the same manner as in the case of measuring, the mass% of Na and K is calculated by the calibration curve method using an atomic absorption spectroscopic analyzer (manufactured by Hitachi, Ltd., Z-2310), and Na and K are Na ₂ O and K. Converted to ₂ O, the solid content component other than Na ₂ O and K ₂ O was assumed to be SiO ₂ , and the content of SiO ₂ was determined.

[2] Method for quantifying Na and K 1. Preparation of measurement sample (1) Approximately 1 g of the irregular silica particle dispersion is precisely weighed in a platinum dish.
(2) To the above (1), add 3 mL of phosphoric acid, 5 mL of nitric acid and 10 mL of hydrofluoric acid, and heat the mixture on a sand bath.
(3) After drying, add a small amount of water and 50 mL of nitric acid to dissolve, put in a 100 mL volumetric flask, add water to make 100 mL, and make a measurement sample.
2. 2. Method for measuring the content ratio of Na and K The above 1. The measurement sample obtained in 1 was measured by an atomic absorption spectrophotometer (manufactured by Hitachi, Ltd., Z-2310) and calculated by the calibration curve method.

[3] Alkaline earth metal quantification method (1) Repeat the operation of collecting 10 mL of the measurement sample prepared by the above [2] Na and K quantification method in a 20 mL volumetric flask 5 times to obtain 5 separate liquids of 10 mL. ..
(2) Using this, measurement is performed by a standard addition method with an ICP plasma emission spectrometer (manufactured by SII, product number SPS5520).
(3) Measure the blank by the same method, subtract the blank amount and adjust, and use it as the measured value for each element.

[4] Halogen quantification method 1. Preparation of sample (1) Dilute 5 g of the sample consisting of the irregular silica particle dispersion with water to make the total volume 100 ml.
(2) Centrifuge at 4000 rpm for 20 minutes with a centrifuge (HIMAC CT06E manufactured by Hitachi) to remove the sedimentation component, and use the obtained liquid as a measurement sample.
2. 2. Method for measuring halogen content ratio 1. The aqueous solution obtained in 1) was measured using an ion chromatograph and calculated by the calibration curve method.
System: DIONEX ICS-1100

[5] Measurement method of average particle size D2 by dynamic light scattering method Atypical silica particle dispersion is diluted with 0.58% aqueous ammonia to adjust the silica concentration to 1% by mass, and measured using a laser particle analyzer. do.
[Laser Particle Analyzer]
Model number "Zeta potential / particle size measurement system ELSZ-1000S" manufactured by Otsuka Electronics Co., Ltd. (Measurement principle: dynamic light scattering method, light source wavelength: 665.70 nm, cell: 10 mm square plastic cell)

[6] Measuring method of specific surface area equivalent particle size D1 50 mL of irregular silica particle dispersion was adjusted to pH 3.5 with HNO ₃ , 40 mL of 1-propanol was added, and the sample dried at 110 ° C. for 16 hours was pulverized in a dairy pot. , Bake at 500 ° C. for 1 hour in a muffle furnace to prepare a sample for measurement. Then, 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) using a specific surface area measuring device (manufactured by Yuasa Ionics, model number Multisorb 12).
Specifically, 0.5 g of a sample is taken in a measurement cell, degassed at 300 ° C. for 20 minutes in a mixed gas stream of 30 v% nitrogen and 70 v% helium, and then the sample is placed in the mixed gas stream. Keep the temperature at the liquid nitrogen level 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 of the deformed silica particles is calculated from a calibration curve prepared in advance. Further, the obtained specific surface area (SA) is substituted into the following formula to obtain the specific surface area conversion particle diameter D1.
Specific surface area conversion particle diameter D1 (nm) = 6000 / (ρ × SA)
(Here, ρ represents the density of silica particles 2.2 [g / cm ³ ].)

[7] Measurement method for coarse particles 1. Preparation of measurement sample The silica particle dispersion was diluted with water to 1% by mass to prepare a measurement sample.
2. 2.
5 mL of the measurement sample is injected into a measuring device (Accusizer 780APS (Accusizer 780APS) manufactured by Particle sizing system Inc.) for measurement. The number of coarse particles of 0.51 μm or more is defined as the number of coarse particles of the measurement sample. The measurement conditions are as follows.
<System Setup>
・ Stir Speed Control / Low Speed Factor 1600 / High Speed Factor 2500
<System Menu>
・ Data Collection Time 120 sec.
・ Syringe Volume 2.5mL
-Sample Line Number: Sum Mode
・ Initial 2nd-Stage Dilution Factor 30
・ Vessel Fast Flush Time 60 sec.
・ System Flush Time / Before Measurement 100 sec. / After Measurement 100 sec.
・ Sample Equilibration Time 25 sec./Sample Flow Time 10 sec.

[Example 1]
-Production of potassium silicate solution 2.766 kg of potassium hydroxide aqueous solution (KOH concentration 48.7% by mass) was added to 3.699 kg of ultrapure water, and the mixture was stirred until uniform. 2.82 kg of silica powder (water content 20% by mass) was added to this potassium hydroxide aqueous solution and mixed. The temperature of this mixed solution was raised to 95 ° C. and kept for 4 hours to obtain a potassium silicate solution.
In the obtained potassium silicate solution, the SiO ₂ concentration was 24.5% by mass, the K ₂ O concentration was 12.4% by mass, and the SiO ₂ / K ₂ O (molar ratio) was 3.10. The Cl ion concentration was 8 ppm (hereinafter, this potassium silicate solution or an equivalent potassium silicate solution is referred to as "potassium silicate solution (1)").

-Production of acidic silicic acid solution 15 kg of an aqueous potassium silicate solution having a SiO ₂ concentration of 5% by mass is passed through 6 L of a strongly acidic cation exchange resin (SK1BH (manufactured by Mitsubishi Chemical Co., Ltd.)) at an air velocity of 2.75 (1 / hr). To obtain 15 kg of an acidic silicic acid solution. In the obtained acidic silicic acid solution, the SiO ₂ concentration was 4.6% by mass (hereinafter, this acidic silicic acid solution or an acidic silicic acid solution equivalent thereto is referred to as "acidic silicic acid solution").

<Preparation of precursor dispersion>
To 2.344 kg of ultrapure water, 0.88 kg of potassium silicate solution (1) was added and stirred until uniform to obtain an alkaline aqueous solution. To this alkaline aqueous solution, 0.15 kg of an acidic silicic acid solution was added and mixed.
The temperature of this mixed solution was raised to 98.5 ° C. and held for 1.3 hours to obtain a precursor dispersion.
The precursor dispersion had a SiO ₂ concentration of 6.6% by mass and a SiO ₂ / A _2O (molar ratio) of 3.2.

<Preparation of seed particle dispersion>
6.97 kg of an acidic silicic acid solution was added to the total amount of the precursor particle dispersion liquid at 98.5 ° C. over 4.9 hours (second addition rate ratio = 0.29). After the addition was completed, the mixture was left at 98.5 ° C. for 0.5 hours to obtain a seed particle dispersion.
The SiO ₂ concentration of this seed particle dispersion was 5.2% by mass, and the _K2O concentration was 1.1% by mass. The average particle size of the seed particles measured by the dynamic light scattering particle size measuring device was 105 nm.

<Manufacturing of irregularly shaped silica particle dispersion>
To 0.113 kg of ultrapure water was added 0.006 kg of potassium silicate solution (1). 10.34 kg of seed particle dispersion was added thereto and mixed. Then, the temperature was raised to 97.5 ° C. and held for 0.5 hours.
Then, at 97.5 ° C., 142.94 kg of an acidic silicic acid solution was added over 12 hours (third addition rate ratio = 2.5). After the addition was completed, the mixture was allowed to stand at 97.5 ° C. for 1 hour and then cooled to room temperature to obtain an irregular silica particle dispersion.
In the obtained variant silica particle dispersion, the SiO ₂ concentration was 4.6% by mass and the _K2O concentration was 0.07% by mass. The average particle size D2 of the irregularly shaped silica particles measured by the dynamic light scattering particle size measuring device was 131 nm. Moreover, when the reaction vessel after the reaction was confirmed, no precipitation was confirmed at the bottom of the vessel.

Subsequently, the silica particles were concentrated using an extraordinary module to prepare a silica particle dispersion having a SiO ₂ concentration of 11.7% by mass.
The specific surface area equivalent particle diameter D1 of the obtained silica particles was 41 nm. Moreover, when the shape of the obtained silica particles was observed with an electron microscope, the shape of the particles was a particle containing irregularly shaped particles as if a plurality of particles were bonded.

[Example 2]
-Potassium silicate solution In this example, a potassium silicate solution prepared in the same manner as in Example 1 was used.
-Acid silicic acid solution In this example, an acidic silicic acid solution prepared in the same manner as in Example 1 was used.

<Preparation of precursor dispersion>
A potassium silicate solution (1) of 0.88 kg was added to 1.989 kg of ultrapure water and stirred until uniform to obtain an alkaline aqueous solution. 0.137 kg of an acidic silicic acid solution was added to this alkaline aqueous solution and mixed.
The temperature of this mixed solution was raised to 87.0 ° C. and held for 1.3 hours to obtain a precursor dispersion.
In the precursor dispersion, the SiO ₂ concentration was 7.4% by mass, and the SiO ₂ / A ₂ O (molar ratio) was 3.2.

<Manufacturing of seed particle dispersion>
To this precursor dispersion, 6.993 kg of an acidic silicic acid solution was added at 87.0 ° C. over 4.9 hours (second addition rate ratio = 0.30). After the addition was completed, the mixture was left at 87.0 ° C. for 0.5 hours to obtain a seed particle dispersion.
The SiO ₂ concentration of this seed particle dispersion was 5.4% by mass, and the _K2O concentration was 1.1% by mass. The average particle size of the seed particles measured by the dynamic light scattering particle size measuring device was 64 nm.

<Manufacturing of irregularly shaped silica particle dispersion>
To 0.461 kg of ultrapure water was added 0.003 kg of potassium silicate solution (1). To this, 10.00 kg of a seed particle dispersion was added and mixed. Then, the temperature was raised to 87.0 ° C. and held for 0.5 hours.
Then, at 87.0 ° C., 142.29 kg of an acidic silicic acid solution was added over 12 hours (third addition rate ratio = 2.5). After the addition was completed, the mixture was allowed to stand at 87.0 ° C. for 1 hour and then cooled to room temperature to obtain an irregular silica particle dispersion.
In the obtained variant silica particle dispersion, the SiO ₂ concentration was 4.6% by mass and the _K2O concentration was 0.07% by mass. The average particle size D2 of the silica particles measured by the dynamic light scattering particle size measuring device was 91 nm. Moreover, when the reaction vessel after the reaction was confirmed, no precipitation was confirmed at the bottom of the vessel.

Subsequently, it was concentrated using an extraordinary module to prepare a modified silica particle dispersion having a SiO ₂ concentration of 11.8% by mass.
The specific surface area-equivalent particle diameter D1 of the obtained irregularly shaped silica particles was 41 nm. Moreover, when the shape of the obtained silica particles was observed with an electron microscope, the shape of the particles was a particle containing irregularly shaped particles as if a plurality of particles were bonded.

[Example 3]
-Potassium silicate solution In this example, a potassium silicate solution prepared in the same manner as in Example 1 was used.
-Acid silicic acid solution In this example, an acidic silicic acid solution prepared in the same manner as in Example 1 was used.

<Manufacturing of precursor dispersion>
A potassium silicate solution (1) of 0.88 kg was added to 1.609 kg of ultrapure water and stirred until uniform to obtain an alkaline aqueous solution. 0.137 kg of an acidic silicic acid solution was added to this alkaline aqueous solution and mixed.
The temperature of this mixed solution was raised to 87.0 ° C. and held for 1.3 hours to obtain a precursor dispersion.
In the precursor dispersion, the SiO ₂ concentration was 8.5 mass and the SiO ₂ / A ₂ O (molar ratio) was 3.2.

<Manufacturing of seed particle dispersion>
To this precursor dispersion, 7.041 kg of an acidic silicic acid solution was added at 87.0 ° C. over 4.9 hours (second addition rate ratio = 0.30). After the addition was completed, the mixture was left at 87.0 ° C. for 0.5 hours to obtain a seed particle dispersion.
In this seed particle dispersion, the SiO ₂ concentration was 5.7% by mass and the _K2O concentration was 1.1% by mass. The average particle size of the seed particles measured by the dynamic light scattering particle size measuring device was 73 nm.

<Manufacturing of irregularly shaped silica particle dispersion>
To 0.870 kg of ultrapure water was added 0.008 kg of a potassium silicate solution (1). 9.67 kg of seed particle dispersion was added thereto and mixed. Then, the temperature was raised to 87.0 ° C. and held for 0.5 hours.
Then, at 87.0 ° C., 143.07 kg of an acidic silicic acid solution was added over 12 hours (third addition rate ratio = 2.5). After the addition was completed, the mixture was left at 87.0 ° C. for 1 hour. Subsequently, the mixture was cooled to room temperature to obtain a modified silica particle dispersion.
In the obtained silica particle dispersion, the SiO ₂ concentration was 4.6% by mass and the _K2O concentration was 0.07% by mass. The average particle size D2 of the irregularly shaped silica particles measured by the dynamic light scattering particle size measuring device was 98 nm. Moreover, when the reaction vessel after the reaction was confirmed, no precipitation was confirmed at the bottom of the vessel.

Subsequently, it was concentrated using an extraordinary module to prepare a modified silica particle dispersion having a SiO ₂ concentration of 11.6% by mass.
The specific surface area-equivalent particle diameter D1 of the obtained irregularly shaped silica particles was 41 nm. Moreover, when the shape of the obtained silica particles was observed with an electron microscope, the shape of the particles was a particle containing irregularly shaped particles as if a plurality of particles were bonded.

[Example 4]
-Potassium silicate solution In this example, a potassium silicate solution prepared in the same manner as in Example 1 was used.
-Acid silicic acid solution In this example, an acidic silicic acid solution prepared in the same manner as in Example 1 was used.

A seed particle dispersion was obtained in the same manner as in Example 3 (SiO ₂ concentration was 5.7% by mass, _K2O concentration was 1.1% by mass, and the average particle size of the seed particles was 73 nm. .).

<Manufacturing of irregularly shaped silica particle dispersion>
9.67 kg of seed particle dispersion was added to 0.335 kg of ultrapure water and mixed. Then, the temperature was raised to 97.5 ° C. and held for 0.5 hours.
Then, at 97.5 ° C., 147.57 kg of an acidic silicic acid solution was added over 12 hours (third addition rate ratio = 2.4). After the addition was completed, the mixture was allowed to stand at 97.5 ° C. for 1 hour and then cooled to room temperature to obtain an irregular silica particle dispersion.
In the obtained variant silica particle dispersion, the SiO ₂ concentration was 4.7% by mass and the _K2O concentration was 0.07% by mass. The average particle size D2 of the irregularly shaped silica particles measured by the dynamic light scattering particle size measuring device was 104 nm. Moreover, when the reaction vessel after the reaction was confirmed, no precipitation was confirmed at the bottom of the vessel.

Subsequently, the mixture was concentrated using an extraordinary module to prepare a modified silica particle dispersion having a SiO ₂ concentration of 11.9% by mass.
The specific surface area-equivalent particle diameter D1 of the obtained irregularly shaped silica particles was 47 nm. Moreover, when the shape of the obtained silica particles was observed with an electron microscope, the shape of the particles was a particle containing irregularly shaped particles as if a plurality of particles were bonded.

[Example 5]
-Production of potassium silicate solution 3.556 kg of potassium hydroxide aqueous solution (KOH concentration 48.7% by mass) was added to 4.757 kg of ultrapure water and stirred until uniform. 3.62 kg of silica powder (water content 20.0%) was added to this potassium hydroxide aqueous solution and mixed.
The temperature of this mixed solution was raised to 95 ° C. and kept for 4 hours to obtain a potassium silicate solution.
In the obtained potassium silicate solution, the SiO ₂ concentration was 24.5% by mass, the K ₂ O concentration was 12.3% by mass, and the SiO ₂ / K ₂ O (molar ratio) was 3.12. The Cl ion concentration was 4 ppm (hereinafter, this potassium silicate solution or an equivalent potassium silicate solution is referred to as "potassium silicate solution (2)").
-Acid silicic acid solution In this example, an acidic silicic acid solution prepared in the same manner as in Example 1 was used.

<Manufacturing of precursor dispersion>
A potassium silicate solution (2) of 0.99 kg was added to 0.672 kg of ultrapure water and stirred until uniform to obtain an alkaline aqueous solution. To this alkaline aqueous solution, 0.132 kg of an acidic silicic acid solution was added and mixed.
The temperature of this mixed solution was raised to 80.0 ° C. and held for 1.3 hours to obtain a precursor dispersion.
In the precursor dispersion, the SiO ₂ concentration was 13.8% by mass, and the SiO ₂ / A ₂ O (molar ratio) was 3.2.

<Manufacturing of seed particle dispersion>
To this precursor dispersion, 7.840 kg of an acidic silicic acid solution was added at 80.0 ° C. over 4.9 hours (second addition rate ratio = 0.30). After the addition was completed, the mixture was left at 80.0 ° C. for 0.5 hours. A seed particle dispersion was obtained.
In the obtained seed particle dispersion, the SiO ₂ concentration was 6.3% by mass, and the _K2O concentration was 1.3% by mass. The average particle size of the seed particles measured by the dynamic light scattering particle size measuring device was 71 nm.

<Manufacturing of irregularly shaped silica particle dispersion>
To 1.970 kg of ultrapure water, 0.001 kg of potassium silicate solution (2) was added. 9.63 kg of seed particle dispersion was added thereto and mixed. Then, the temperature was raised to 97.5 ° C. and held for 0.5 hours.
Then, 160.06 kg of an acidic silicic acid solution was added over 12 hours (third addition rate ratio = 2.5). After the addition was completed, the mixture was left at 97.5 ° C. for 1 hour. Subsequently, the mixture was cooled to room temperature to obtain a modified silica particle dispersion.
In the obtained silica particle dispersion, the SiO ₂ concentration was 4.6% by mass and the _K2O concentration was 0.07% by mass. The average particle size D2 of the irregularly shaped silica particles measured by the dynamic light scattering particle size measuring device was 102 nm. Moreover, when the reaction vessel after the reaction was confirmed, no precipitation was confirmed at the bottom of the vessel.

Subsequently, the mixture was concentrated using an extraordinary module to prepare a modified silica particle dispersion having a SiO ₂ concentration of 11.7% by mass.
The specific surface area-equivalent particle diameter D1 of the obtained irregularly shaped silica particles was 45 nm. Moreover, when the shape of the obtained silica particles was observed with an electron microscope, the shape of the particles was a particle containing irregularly shaped particles as if a plurality of particles were bonded.

[Comparative Example 1]
To 67.2 g of sodium silicate (SiO ₂ concentration 24.28% by mass, Na _2O concentration 8.0% by mass), 839.5 g of pure water was added, and an aqueous sodium silicate solution having a silica concentration of 1.8% by mass was added to 906. 7 g was prepared. 264.1 g (SiO ₂ concentration 4.7% by mass) of the acidic silicic acid solution obtained in the same manner as in Example 1 was added to this sodium silicate aqueous solution, and after stirring, the temperature was raised to 79 ° C. and at 79 ° C. , And held for 30 minutes to prepare a precursor dispersion.
Next, 6,122.2 g of an acidic silicic acid solution was continuously added over 9 hours. Subsequently, 2,040.6 g of an acidic silicic acid solution was continuously added over 2 hours. After the addition was completed, the mixture was kept at 79 ° C. for 1 hour and then cooled to room temperature. The dynamic light scattering method particle diameter D2 was 15 nm. Moreover, when the reaction vessel after the reaction was confirmed, no precipitation was confirmed at the bottom of the vessel.
The obtained silica sol was concentrated using an ultrafiltration membrane (trade name: SIP-1013, manufactured by Asahi Kasei Corporation) until the silica concentration reached 12% by mass. Then, it was concentrated to 20% by mass with a rotary evaporator.
The specific surface area equivalent particle diameter D1 in the obtained silica sol was 11 nm. When the shape of the particles was observed with an electron microscope, the shape of the particles was almost spherical and it was not possible to obtain irregularly shaped particles.

[Comparative Example 2]
To 87.84 g of potassium silicate (SiO ₂ concentration 20.5% by mass, K2O concentration 9.37% by mass), _1,126.6 g of pure water was added, and an aqueous potassium hydroxide solution (KOH concentration 3% by mass) 31. After adding 42 g and stirring, the temperature was raised to 83 ° C. and kept at 83 ° C. for 30 minutes to prepare a precursor dispersion.
Next, 1,493.8 g of the acidic silicic acid solution was continuously added over 3 hours. Subsequently, 8,962.8 g of an acidic silicic acid solution was continuously added over 12 hours. After the addition was completed, the mixture was kept at 83 ° C. for 1 hour and then cooled to room temperature. The dynamic light scattering particle diameter D2 was 35 nm. Moreover, when the reaction vessel after the reaction was confirmed, no precipitation was confirmed at the bottom of the vessel.
The obtained silica sol was concentrated using an ultrafiltration membrane (trade name: SIP-1013, manufactured by Asahi Kasei Corporation) until the silica concentration reached 12% by mass. Then, it was concentrated to 20% by mass with a rotary evaporator.
The specific surface area equivalent particle diameter D1 in the obtained silica sol was 25 nm. When the shape of the particles was observed with an electron microscope, the shape of the particles was almost spherical and it was not possible to obtain irregularly shaped particles.

[Comparative Example 3]
An acidic silicate solution (SiO ₂ concentration) obtained in the same manner as in Example 1 by adding 9,483 g of pure water to 3,294 g of sodium silicate (SiO ₂ concentration 24.3% by mass, Na _2O concentration 8% by mass). 4.6 mass%) 347 g was added, 254 g of an aqueous potassium chloride solution (KCl concentration 20 mass%) was added, and after stirring, the temperature was raised to 97 ° C. and held at 97 ° C. for 30 minutes to disperse the precursor. It was made into a liquid.
Next, 281.8 kg of acidic silicic acid solution was continuously added over 15 hours. After the addition was completed, the mixture was kept at 97 ° C. for 1 hour and then cooled to room temperature. The dynamic light scattering particle diameter D2 was 155 nm. When the reaction vessel was confirmed, precipitation due to coarse silica aggregates was confirmed in a part of the reaction vessel.
The obtained silica sol was concentrated using an ultrafiltration membrane (trade name: SIP-1013, manufactured by Asahi Kasei Corporation) until the silica concentration reached 12% by mass. Then, it was concentrated to 20% by mass with a rotary evaporator.
The specific surface area equivalent particle diameter D1 in the obtained silica sol was 65 nm. When the shape of the particles was observed with an electron microscope, they were irregular particles. However, as shown in Table 2 below, the number of coarse particles was large, and coarse aggregates and precipitates were partially confirmed.

[Comparative Example 4]
1,196 g of pure water was added to 3,804 g (4.6% by mass) of an acidic silicic acid solution, 42.34 g of a potassium fluoride aqueous solution (KF concentration 10% by mass) was added, and a sodium hydroxide aqueous solution (NaOH concentration 3) was added. The pH was adjusted to 8.0 using (0.0% by mass) and kept at 98 ° C. for 1 h to obtain a precursor dispersion.
Next, 7,609 g of an acidic silicic acid solution was added over 2 hours, the pH was maintained at 9 to 10 with NaOH during the addition, and after the addition was completed, aging was carried out at 98 ° C. for 1 hour. The specific surface area-equivalent particle diameter D1 of the obtained silica sol was 9 nm, and the dynamic light scattering particle diameter D2 was 54 nm. Moreover, when the reaction vessel after the reaction was confirmed, no precipitation was confirmed at the bottom of the vessel. When the shape of the particles was observed with an electron microscope, they were irregular particles, but only irregular particles with small primary and secondary diameters could be obtained.

[Comparative Example 5]
Pure water is added to 782.6 g of the acidic silicic acid solution, diluted to a SiO ₂ concentration of 3.6% by mass, 5.8 g of a 10% by mass calcium nitrate aqueous solution is added while stirring, and then 10% by mass of hydroxylation is continued. 6.0 g of sodium was added, and 188.2 g of pure water was further added to prepare a precursor dispersion. The obtained precursor dispersion was put into an autoclave and heated at 120 ° C. for 6 hours with stirring. After heating, it was cooled to room temperature and the silica sol was taken out. Moreover, when the reaction vessel after the reaction was confirmed, no precipitation was confirmed at the bottom of the vessel.
The obtained silica sol was concentrated to 12% by mass using an ultrafiltration membrane. The specific surface area-equivalent particle diameter D1 of the obtained silica sol was 9 nm, and the dynamic light scattering particle diameter D2 was 30 nm. When the shape of the particles was observed with an electron microscope, they were irregular particles, but only irregular particles with small primary and secondary diameters could be obtained.

Table 1 shows each value in the method for producing a modified silica particle dispersion. Table 2 shows the average particle size and the like of the deformed silica particles contained in the obtained deformed silica particle dispersion.

According to the production method of the present invention, a component other than the silica-based component, for example, an alkaline earth metal-based raw material (for example, CaO and MgO) or a raw material containing a halogen element (for example, KCl and KF) is added. It is possible to obtain irregularly shaped silica particles.
Therefore, the deformed silica particle dispersion obtained by the production method of the present invention does not have a possibility of contaminating the substrate to be polished in the SiO ₂ oxide film of the semiconductor device or the silicon semiconductor wafer application.
Therefore, it is possible to efficiently produce a modified silica particle dispersion liquid that does not contain components other than silica-based components and is suitable for semiconductor-related polishing applications.
Further, according to the production method of the present invention, it is possible to obtain a modified silica particle dispersion liquid in which silica particles having a desired degree of irregularity are dispersed in a solvent. Therefore, it is possible to produce a dispersion liquid containing silica particles exhibiting excellent polishing properties for glass hard disk, quartz glass, crystal, aluminum hard disk, SiO ₂ oxide film of semiconductor device, silicon semiconductor wafer, compound semiconductor wafer and the like. ..

Claims (10)

A method for producing a modified silica particle dispersion liquid, which comprises the following steps 1 to 3 and satisfies the following condition 1.
Step 1: The first acidic silicic acid solution is mixed with an alkaline aqueous solution containing an alkaline compound having at least Na or K.
Further, by heating and aging in a temperature range of 50 ° C. or higher and lower than 100 ° C., a precursor dispersion liquid having a SiO ₂ concentration of 3% by mass or more and 20% by mass or less and satisfying the conditions shown by the following formula (F1-1) can be obtained. Obtaining step 2 ≦ SiO ₂ / A ₂ O ≦ 15 ... (F1-1)
(Here, SiO ₂ represents the number of moles of silica in the precursor dispersion, and A ₂ O represents the total number of moles of Na ₂ O and K ₂ O in the precursor dispersion.)
Step 2: The second acidic silicic acid solution is added to the precursor dispersion obtained in the step 1, and the second addition rate ratio represented by the following formula (F2-1) is 0.1 [kg / hr · kg]. Step 2 Addition rate ratio [2 kg / hr · kg] = (silica content in secondary acidic silicic acid solution [kg]) / (addition time of secondary acidic silicic acid solution [hr]) / (silica content in precursor dispersion [kg] ) ... (F2-1)
Step 3: The third acidic silicic acid solution is added to the seed particle dispersion obtained in the above step 2, and the third addition rate ratio shown by the following formula (F3-1) is 1.1 [kg / hr · kg] or more. Step to obtain a modified silica particle dispersion liquid by adding so as to be in the range of 10 [kg / hr · kg] or less and further heating and aging in the range of temperature 50 ° C. or higher and lower than 100 ° C. Third addition rate ratio [kg / kg / hr · kg] = (silica content in the tertiary acidic silicic acid solution [kg]) / (addition time of the tertiary acidic silicic acid solution [hr]) / (silica content in the precursor dispersion [kg]).・ ・ (F3-1)
Condition 1: The condition shown by the following formula (F0-1) is satisfied.
1.9 ≤ [The third addition rate ratio] / [The second addition rate ratio] ≤ 40 ... (F0-1) The method for producing a modified silica particle dispersion liquid according to claim 1, wherein the step 3 is followed by the following step 4.
Step 4: A step of concentrating the irregularly shaped silica particle dispersion obtained in the above step 3. The method for producing a modified silica particle dispersion according to claim 1 or 2, further satisfying the following condition 2.
Condition 2: In the precursor dispersion, the number of moles (molar / molar ratio) of the halogen element converted to 1 mol of silica is 0.5% or less, and the alkaline earth metal converted to 1 mol of silica. The number of moles (molar / molar ratio) is 1000 ppm or less. The method for producing a modified silica particle dispersion liquid according to any one of claims 1 to 3, further satisfying the following condition 3.
Condition 3: The silica content ratio represented by the following mathematical formula (F0-2) is in the range of 10 or more and 100 or less.
Silica content ratio = {(silica content in secondary acidic silicic acid solution [kg]) + (silica content in tertiary acidic silicic acid solution [kg])} / (silica content in precursor dispersion liquid [kg] kg]) ・ ・ ・ (F0-2) The method for producing a modified silica particle dispersion liquid according to any one of claims 1 to 4, further satisfying the following condition 4.
Condition 4: The SiO ₂ / A ₂ O molar ratio in the variant silica particle dispersion is in the range of 60 or more and 140 or less. (Here, SiO ₂ represents the number of moles of silica in the variant silica particle dispersion, and A ₂ O represents the total number of moles of Na ₂ O and K ₂ O in the variant silica particle dispersion.) The method for producing a modified silica particle dispersion liquid according to any one of claims 1 to 5, wherein the alkaline aqueous solution in the step 1 is a potassium silicate aqueous solution. The method for producing a modified silica dispersion according to any one of claims 1 to 5, wherein the alkaline compound in the step 1 is potassium hydroxide. The obtained deformed silica particles have a specific surface area equivalent particle diameter (D1) in the range of 10 nm or more and 200 nm or less, and an average particle diameter (D2) measured by a dynamic light scattering method in the range of 20 nm or more and 300 nm or less. The method for producing a modified silica particle dispersion according to any one of claims 1 to 7, wherein the value of (D2) / (D1) is in the range of 1.2 or more and 20 or less. Specific surface area equivalent particle size (D1) is in the range of 10 nm or more and 200 nm or less.
The average particle size (D2) measured by the dynamic light scattering method is in the range of 20 nm or more and 300 nm or less.
A variant silica particle dispersion liquid containing variant silica particles, wherein the value of (D2) / (D1) is in the range of 1.2 or more and 20 or less. The variant silica particle dispersion according to claim 9, which comprises a potassium compound.