JP7590122B2 - Silica particles, their production method, and slurry composition - Google Patents

Description

The present invention relates to silica particles, a method for producing the same, and a slurry composition.

In recent years, the miniaturization of electronic devices (including electronic components) has shown no signs of stopping. Materials used in such electronic devices are required to have extremely high performance in accordance with their size. For example, semiconductor devices, which are one type of electronic component, are generally manufactured by encapsulating semiconductor elements with an encapsulant. The encapsulant is required to have a wide range of performance capabilities, such as isolating the semiconductor element from the outside and ensuring heat dissipation, and extremely high performance is required as semiconductor devices become more miniaturized.

Similarly, electronic boards are also required to have high performance due to the finer wiring. Electronic boards are formed by arranging wiring made of conductive material on the surface or inside of an insulating layer, and the insulating layer is composed of a resin composition in which a filler is dispersed in a resin material. Therefore, by reducing the particle size of the filler, the thickness of the insulating layer can be reduced, and the entire electronic board can also be made thinner. In particular, electronic boards include laminated boards formed by stacking multiple insulating layers and conductor layers, and by reducing the particle size of the filler, the thickness of this insulating layer can be reduced, and as a result, the entire laminated board can also be made thinner. Furthermore, by reducing the particle size of the filler, the particle size of the filler exposed on the surface of the board also becomes smaller, making it possible to reduce the roughness of the board surface and improve surface smoothness.

As a sealant, silica is widely dispersed as a filler because it has high physical and chemical stability and reduces volumetric changes caused by thermal fluctuations. Since sealants must be filled into minute gaps, such as between semiconductor elements and substrates, the dispersed filler must also be fine. In addition, the particle size distribution of the filler must be considered to improve gap filling. It has been found that favorable performance can be achieved by removing coarse particles larger than a specified particle size.

JP 2008-247726 A

The present invention was completed in light of the above-mentioned circumstances, and the problem to be solved by the present invention is to provide a filler-containing composition that can be suitably used in sealing materials for semiconductor devices, silica particles suitable for use as a filler in the composition, a method for producing the same, and a slurry composition containing the silica particles.

As a result of intensive research conducted by the present inventors in order to solve the above problems, it became clear that various properties are required for silica particles to be used as fillers in packaging materials such as sealing materials and electronic substrates. Specifically, (a) the content of alkali metals and alkaline earth metals such as sodium is low (high purity), and (b) water absorption is low. Water absorption can be evaluated by the water absorption rate. Reducing water absorption can improve electrical properties. The low water absorption is determined by the amount of silanol, and the lower the amount of silanol, the lower the water absorption. Silica produced by the VMC method is characterized by a low amount of silanol and low water absorption.

The purity and water absorption of silica particles are affected by the manufacturing method. For example, different raw materials are used depending on the type of manufacturing method, and some raw materials are easier to improve the purity of than others. In addition, the crystal structure and the bonding state between atoms vary depending on the manufacturing method, which affects the water absorption. Methods for manufacturing silica particles include the VMC method (Vaporized Metal Combustion Method), the water glass method, and the alkoxide method. The VMC method makes it possible to inexpensively manufacture silica particles that satisfy both (a) and (b) above.

In the water glass method, the raw materials inevitably contain alkali metals, etc., so it is difficult to satisfy requirement (a). Furthermore, while the water absorbency is somewhat lower than that of silica particles produced by the alkoxide method, it is difficult to say that it is sufficiently small. Silica particles produced by the alkoxide method are produced from low molecular weight raw materials, making it easy to purify the raw materials, and in principle do not need to contain alkali metals, etc., so it is possible to provide products that satisfy requirement (a), but the water absorbency of (b) is high.

Although the VMC method can produce silica particles with such excellent properties, it was discovered that the coarse particles, which are larger than the desired particle size, include solid particles and hollow particles (hollow particles). It was also discovered that the inclusion of hollow particles may prevent the desired performance from being fully achieved when used as a filler, etc.

Conventionally, when performing precise classification, centrifugal separation is widely used because of its high classification efficiency. However, since hollow particles have a low specific gravity, it is difficult to sufficiently classify and remove them by centrifugal separation. Since the content of hollow particles is small and even if they remain, their presence has been left unattended, but in recent years, it has been found that it is preferable to have no hollow particles, even if they are small, when applying them to fine applications. For example, when silica particles are used in fine applications as a filler to be contained in a resin composition, the surface of the resin composition may be scraped by polishing or etching, and in that case, if the hollow particles are scraped, the hollow parts are exposed as unevenness, making it difficult to achieve a smooth surface. Based on this knowledge, a method for removing hollow particles was investigated and the present invention was completed.

(1) The method for producing silica particles of the present invention, which solves the above problems, includes a raw silica particle production step in which raw particle material made of metal silicon is dispersed in a carrier and then charged into a flame in an oxidizing atmosphere and combusted to produce raw silica particles; a surface treatment step in which the raw silica particles are surface-treated using a silane compound to produce surface-treated raw silica particles; and a classification step in which the surface-treated raw silica particles are dispersed in a solvent, and the resulting dispersion slurry is centrifuged to remove coarse particles, and hollow particles are removed using a filter to produce silica particles.

Although centrifugation, a precise and highly efficient method, is used as the classification process, what is different from conventional methods is that classification using a filter is performed after centrifugation.

In particular, it is preferable that the (centrifugal field residence time: min)/(classified slurry viscosity: mPa·s) in the centrifugation in the classification step is 0.9 or more, and the (centrifugal acceleration: G)/(classified slurry viscosity: mPa·s) is 700 or more. The centrifugal field residence time is defined as the time (average value on a mass basis) during which the slurry remains in a centrifugal field with a centrifugal acceleration equal to or greater than the above-mentioned centrifugal acceleration.

(2) The silica particles of the present invention that solve the above problems have a D50 of 100 nm to 200 nm as measured by laser diffraction particle size distribution measurement, a specific surface area of 30 ^m2 /g or less, a number of hollow particles of 2 μm or more of 1000 particles/0.1 g or less, a water absorption rate of 1.0% or less based on the total mass, and a total amount of alkali metals and alkaline earth metals of 100 ppm or less. It is particularly preferable that the number of hollow particles of 0.8 μm or more is 1000 particles/0.1 g or less.

By making the specific surface area 30 m ² /g or less, it is possible to reduce the viscosity when the material is contained in a slurry composition or a resin composition. Since the material has low water absorption, it is possible to improve electrical properties.

Furthermore, if necessary, it is preferable that the surface is treated with a silane compound. The surface properties of the silica particles can be appropriately controlled by the type of silane compound.

In this specification, the particle size distribution is obtained by laser diffraction using a SALD-7500 manufactured by Shimadzu Corporation. The number of hollow particles can be measured using an image analyzer (JASCO International Co., Ltd.: IF3200). Whether or not a particle is hollow is determined based on the difference in appearance. Hollow particles are easily identifiable because they look significantly different from solid particles.

(3) The slurry composition of the present invention that solves the above problem comprises the above-mentioned silica particles of the present invention and a dispersion medium that disperses the silica particles.

The silica particles produced by the manufacturing method of the present invention can be used as a filler dispersed in a slurry composition or a resin composition, and can be used as a sealant that has excellent filling properties and stability. The manufacturing method of silica particles of the present invention can easily produce the silica particles of the present invention.

The silica particles, manufacturing method thereof, and slurry composition of the present invention will be described in detail below based on the embodiments.

(Silica particles)
The silica particles of this embodiment have a D50 measured by laser diffraction particle size distribution measurement of 100 nm or more and 200 nm or less, a specific surface area of 30 ^m2 /g or less, a number of hollow particles of 2 μm or more of 1,000 particles/0.1 g or less, a water absorption rate of 1.0% or less based on the total mass, and a total amount of alkali metals and alkaline earth metals of 100 ppm or less.

For D50, examples of lower limit values include 110 nm, 120 nm, and 130 nm, and examples of upper limit values include 190 nm, 180 nm, and 170 nm. These upper and lower limit values can be combined arbitrarily. D50 is a value measured by laser diffraction particle size distribution measurement, and is the particle size that is 50% of the smallest particle size by volume. Incidentally, D100 is the particle size that is 100% of the smallest particle size. Note that the values of D50 and D100 are values calculated as values within the measurement limit range of laser diffraction particle size distribution measurement, and in reality, coarse particles and fine particles that cannot be detected by laser diffraction particle size distribution measurement exist. Therefore, there is no contradiction in the existence of particles with a particle size larger than the value of D100.

The D50 value can be adjusted by controlling the particle size distribution of the silica particles themselves by controlling the manufacturing conditions of the silica particles, and can also be adjusted by classification. A suitable example of classification is centrifugation, which will be explained in the manufacturing method below.

The specific surface area can be 28 m ² /g or less, 26 m ² /g or less, etc. The specific surface area is a value measured by the BET method using nitrogen. The smaller the specific surface area value, the lower the viscosity when used in a slurry composition, etc., and therefore it is preferable. The method for controlling the specific surface area is not particularly limited, but the specific surface area can be reduced by performing a method in which the amount of fine powder is reduced when synthesizing silica, or by controlling the residence time in a classifier to be long when performing classification.

The number of hollow particles of 2 μm or more can be 800 particles/0.1 g or less, 600 particles/0.1 g or less, or 400 particles/0.1 g or less. The number of hollow particles can be reduced by classification. As a classification operation, removal by a filter is desirable, but it is preferable to first reduce the number of solid particles above the classification point by centrifugation and then remove the hollow particles by a filter.

The water absorption value is based on the mass of silica particles when dry. To measure the water absorption, a dry sample is left at 40°C and 80% RH for 1 hour, and the moisture generated by heating at 200°C is measured using a Karl Fischer moisture analyzer, and the water absorption is calculated. To lower the water absorption, the VMC method can be used as a manufacturing method for the silica material, or the manufactured silica material can be heated to lower the water absorption. Heating temperatures of 200°C or higher, 300°C or higher, 400°C or higher, etc. can be used.

The total amount of alkali metals and alkaline earth metals is preferably 80 ppm or less, 50 ppm or less, or 30 ppm or less. This can be achieved by purifying the materials used to manufacture the silica particles. Since alkali metals and alkaline earth metals are oxidized and eluted or precipitated as ions, unexpected effects on the semiconductor device may be expected if they are used as a sealant for semiconductor devices. For example, assuming the electrical conductivity (EC) of the water extract, it is desirable that it is 10 μS/cm or less. In order to lower this value, it is desirable that the content of alkali metals and alkaline earth metals is low, so the above-mentioned content range is set. EC is measured as follows. Metal oxide particles are suspended in ion-exchanged water (electrical conductivity 1 μS/cm or less) to form a 10% slurry, which is then placed in a pressure-resistant container and shaken at room temperature for 30 minutes. The conductivity of the supernatant, which is then centrifuged and sedimented, is measured using a Horiba Ltd. electrical conductivity meter (EC meter) ES-51.

The silica particles of this embodiment are preferably surface-treated with a silane compound. The silane compound is not particularly limited, and a silane compound having an appropriate functional group can be selected as necessary for surface treatment. Surface treatment can also be performed with two or more types of silane compounds.

The silica particles of this embodiment can be surface-treated with a silane compound. The specific structure of the silane compound and the method of introducing it to the surface of the silica particles will be described in detail in the method for producing silica particles described later, and therefore will not be described here. It is also possible to obtain silica particles that are not surface-treated by removing the surface treatment agent after performing the surface treatment with the surface treatment agent.

The silica particles of this embodiment preferably have an α-ray production rate of 0.001 c/cm ² ·h or less. In particular, it is preferable that the uranium and thorium as the α-ray source are 3 ppb or less (even more preferably 1 ppb or less).

(Method for producing silica particles)
The method for producing silica particles of the present embodiment includes a raw silica particle production step, a surface treatment step, a classification step, and other steps that are adopted as necessary. The method for producing silica particles of the present embodiment is a method that can suitably produce the silica particles of the present embodiment described above.

The raw silica particle manufacturing process is a process in which raw silica particles are manufactured by burning raw particle materials. This process is known as the VMC method, and the obtained raw silica particles tend to be highly spherical, dense, and have excellent electrical properties.

The VMC method is a method in which a chemical flame is formed by burning a combustion enhancer (such as hydrocarbon gas) with a burner in an oxygen-containing atmosphere, and raw material particles are added to this chemical flame in an amount sufficient to form a dust cloud, causing a deflagration to occur and obtaining raw silica particles.

The operation of the VMC method can be explained as follows. First, a container is filled with a gas containing oxygen, which is a reactive gas, and a chemical flame is formed in this reactive gas. Next, the raw material particles are poured into this chemical flame to form a dust cloud. The chemical flame then imparts thermal energy to the surface of the raw material particles, raising the surface temperature of the metallic silicon that constitutes the raw material particles, and metallic silicon vapor spreads from the surface of the raw material particles to the surrounding area. This vapor reacts with oxygen gas, igniting and generating a flame. The heat generated by this flame further promotes the vaporization of the raw material particles, and the resulting vapor and oxygen gas are mixed, causing a chain reaction of ignition and propagation. Therefore, the smaller the particle size of the raw material particles, the larger the specific surface area and the improved reactivity, allowing less energy to be input.

As this chain reaction of ignition progresses, the raw material particles themselves are destroyed and scattered, promoting flame propagation. After combustion, the resulting gas cools naturally, forming a cloud of raw silica particles. The resulting raw silica particles are collected using a bag filter or electrostatic precipitator.

The VMC method utilizes the principle of dust explosion. With the VMC method, a large amount of metal oxide particles can be obtained instantly. The metal oxide particles obtained are almost perfectly spherical. By adjusting the particle size, amount of metal particles, flame temperature, etc. of the metal particles added, it is possible to adjust the particle size distribution of the obtained metal oxide particles. In addition to metal particles (metallic silicon) alone, metal oxide particles (e.g., silica) can also be added as raw materials. By using metal oxide particles obtained by this method as the metal oxide particles added at the same time, the purity of the obtained metal oxide particles can be maintained.

The raw particle material can also be surface-treated with a silane compound or the like. There are no particular limitations on the type of silane compound that can be used, and those used in the surface treatment process described below can be used.

The raw particle material is burned by dispersing it in a carrier and feeding it into the flame. There is no particular limit to the speed at which the raw particle material is fed into the flame. The carrier can be a gas such as nitrogen, argon, or air, or a liquid such as water or alcohol. There is no particular limit to how the raw particle material is dispersed, but when dispersing it in a liquid, it is preferable to spray it into the flame as a mist. For example, it is preferable to have the raw particle material contained in an amount of about 10% to 80% by volume of the total.

The flame used is a flame in an oxidizing atmosphere. For example, a flame obtained by burning a flammable gas such as LPG in an atmosphere containing an excess of oxygen can be used. Thermal plasma is also included in the flame category.

The raw material particles, consisting of metallic silicon, are fed into the flame and vaporize by combustion, and are rapidly cooled to become raw silica particles consisting of silica. The resulting raw silica particles are collected using a bag filter or the like. Classification can be performed before or after collection to obtain raw silica particles with the required particle size distribution. Classification can be performed using cyclone classification or the like.

The surface treatment process is a process in which raw silica particles are surface-treated with a silane compound to produce surface-treated raw silica particles. The surface treatment is carried out by contacting the surface with a silane compound directly (either in liquid or gas form) or by contacting the surface with a silane compound dissolved in some kind of solvent. In the surface treatment, the raw silica particles can be heated after contacting the silane compound with them. The surface treatment process can also be carried out in the form of a slurry after preparing the classification slurry used in the classification process described below.

The amount of silane compound used for surface treatment is not particularly limited, and can be selected as 100%, 75%, 50%, 25%, etc. based on the amount of OH groups present on the surface of the raw silica particles. An excess amount exceeding 100% (120%, 150%, etc.) can also be selected.

The silane compound is not particularly limited, but examples include those having a phenyl group, an alkyl group, a vinyl group, a methacryl group, an epoxy group, a phenylamino group, an amino group, a styryl group, etc.

The classification process is a process for removing particles (coarse particles) having a particle size equal to or larger than a certain size from the surface-treated raw silica particles. Coarse particles include solid coarse particles and hollow coarse particles. In the classification process, first, in order to separate the solid coarse particles, a dispersion slurry is prepared by dispersing the surface-treated raw silica particles in a solvent, and then centrifugation is performed. The classified slurry may be prepared after the surface-treated raw silica particles are prepared, or the surface treatment may be performed after the classified slurry is prepared.

The solvent used for the dispersion slurry in this process is preferably low in viscosity. Examples include methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), and toluene. By dispersing the material in MEK at a concentration of about 10% to 30% by mass (particularly 15% to 25% by mass), and then centrifuging the mixture, solid coarse particles can be separated with high accuracy.

Centrifugation is carried out by decantation of the classified slurry in a centrifugal field. The relationship between the physical properties of the classified slurry and the classification conditions can be such that (centrifugal field residence time: min)/(classified slurry viscosity: mPa·s) is 0.9 or more, preferably 1.4 or more, more preferably 1.8 or more, and (centrifugal acceleration: G)/(classified slurry viscosity: mPa·s) is 700 or more, preferably 900 or more, more preferably 1100 or more. The centrifugal field residence time is defined as the time spent in a centrifugal field with a centrifugal acceleration equal to or greater than the above-mentioned centrifugal acceleration.

After separating the coarse particles, the dispersed slurry is classified using a filter with a pore size required to separate the hollow coarse particles, and the hollow coarse particles are removed. Hollow coarse particles cannot be sufficiently separated by centrifugation, but can be sufficiently removed by classification using a filter. Classification using a filter is performed on the dispersed slurry dispersed in a solvent. It is desirable to perform classification using a filter multiple times. When performing classification multiple times, it is preferable to perform classification using a filter while changing from a filter with a large pore size to a filter with a small pore size.

(Slurry Composition)
The slurry composition of the present embodiment is a mixture of the above-mentioned silica particles and a liquid dispersion medium (solvent, resin material precursor, etc.) The mixing ratio of the silica particles to the dispersion medium is not particularly limited.

The silica particles and the method for producing the same of the present invention will be described with reference to examples.
(Test Example 1)
-Production of raw silica particles Test Example 1: Raw silica particles were produced by the VMC method. The specific explanation is as follows. The reaction vessel has a reaction chamber, a combustor that is installed in the upper part of the reaction vessel and opens into the reaction chamber, a collector that is installed in the lower side wall of the reaction vessel and communicates with the reaction chamber, a hopper, and a powder supplying device that supplies the raw particle material in the hopper to the combustor.

The combustor is composed of a raw material particle supply passage that opens into the reaction chamber, a combustible gas supply passage that is arranged coaxially with the raw material particle supply passage and opens into the reaction chamber in a ring shape, and an oxygen supply passage that is arranged coaxially outside the combustible gas supply passage and opens into the reaction chamber in a ring shape.

The collection device consists of an exhaust pipe that opens into the reaction chamber, a bag filter connected to the other end of the exhaust pipe, and a blower. The blower is driven to suck in and exhaust the combustion exhaust gas in the reaction chamber, and collect the raw silica particles that are produced. The inside of the reaction chamber is kept at negative pressure by the suction of the blower.

Using the above-mentioned manufacturing apparatus, spherical silica was manufactured by the manufacturing method shown below. A raw material particle material made of metal silicon was put into a hopper and fed into a reaction chamber together with air as a carrier from a powder feeder. The raw material particle material was fed at a rate of 30 kg/hr, and the amount of conveying air was 30 Nm ³ /hr. In addition, a combustible gas (LPG) serving as a fuel for ignition was fed from a combustible gas feed line at a rate of 10 Nm ³ /hr, and oxygen gas serving as a combustion supporting gas was fed from an oxygen feed line at a rate of 300 Nm ³ /hr.

The mixed powder fed from the powder feeder to the combustor was ignited by the ignition flame formed by the continuous combustion of the combustible gas together with oxygen gas, and burned explosively to generate a flame. This flame extended from the combustor to the reaction chamber, and the generated raw silica particles (volume average particle size 300 nm) were collected by the collector (raw silica particle production process). The specific surface area of the obtained raw silica particles was 17.8 ^m2 /g.

The raw silica particles were surface-treated with N-phenyl-3-aminopropyltrimethoxysilane as a silane compound to prepare surface-treated raw silica particles (surface treatment step). The amount of the silane compound was 2% based on the weight of the raw silica particles.

The obtained surface-treated raw silica particles were dispersed in MEK to obtain a dispersion liquid (dispersed slurry) with a solid content concentration of 20% by mass. The viscosity of the dispersed slurry measured with a vibration viscometer was 2 mPa·s.

Next, the coarse particles were precipitated and removed by decantation in a centrifugal field under conditions of a centrifugal acceleration of 1700 G and a retention time of 2.8 minutes. (Residence time in centrifugal field: minutes)/(Classified slurry viscosity: mPa·s) was 1.4, and (Centrifugal acceleration: G)/(Classified slurry viscosity: mPa·s) was 850. After that, classification was performed once each using filters with pore sizes of 5 μm, 3 μm, and 1 μm, and hollow coarse particles were removed. After classification, the classified slurry was left to dry for 30 minutes in a dryer at 160°C, and the dried silica particles were used as the test sample for this test example.

The obtained silica particles had a D50 of 150 nm, a D100 of 270 nm, a specific surface area of 21.3 ^m2 /g, 104 hollow particles of 2 μm or more per 0.1 g, a water absorption of 0.08%, and a total amount of alkali metals and alkaline earth metals of 30 ppm or less, as measured by laser diffraction particle size distribution measurement.

(Test Example 2)
Silica particles were produced as a test sample in this test example in the same manner as in Test Example 1, except that the silane compound was changed to 3-glycidoxypropyltrimethoxysilane. The viscosity of the classified slurry was 1 mPa·s. Therefore, (residence time in centrifugal field: min)/(classified slurry viscosity: mPa·s) was 2.8, and (centrifugal acceleration: G)/(classified slurry viscosity: mPa·s) was 1700.

The obtained silica particles had a D50 of 200 nm, a D100 of 370 nm, a specific surface area of 20.3 ^m2 /g, 429 hollow particles of 2 μm or more per 0.1 g, a water absorption of 0.08%, and a total amount of alkali metals and alkaline earth metals of 30 ppm or less, as measured by laser diffraction particle size distribution measurement.

(Test Example 3)
Silica particles were produced as a test sample for this test example in the same manner as in Test Example 1, except that the removal of hollow particles using a filter in the classification step was not performed.

The obtained silica particles had a D50 of 200 nm, a D100 of 370 nm, a specific surface area of 21.3 ^m2 /g, 9,400 hollow particles of 2 μm or more per 0.1 g, a water absorption of 0.08%, and a total amount of alkali metals and alkaline earth metals of 30 ppm or less, as measured by laser diffraction particle size distribution measurement.

(Test Example 4)
Silica particles were produced in the same manner as in Test Example 1, except that the MEK used in preparing the classified slurry was changed to cyclohexanone, the centrifugal acceleration was set to 1900 G, the centrifugal field residence time was set to 5.5 minutes, and the hollow particles were not removed by a filter. The viscosity of the classified slurry was 7 mPa·s. Therefore, (centrifugal field residence time: minutes)/(classified slurry viscosity: mPa·s) was 0.786, and (centrifugal acceleration: G)/(classified slurry viscosity: mPa·s) was 271.4. The reason why the hollow particles were not removed by a filter is that under these centrifugal classification conditions, the filter was clogged immediately, and the hollow particles could not be sufficiently removed.

The obtained silica particles had a D50 of 330 nm, a D100 of 590 nm, a specific surface area of 19.1 ^m2 /g, a water absorption of 0.08%, and a total amount of alkali metals and alkaline earth metals of 30 ppm or less, as measured by laser diffraction particle size distribution. The number of hollow particles 2 μm or larger was not measured because it was too large.

(Test Example 5)
Silica particles were produced in the same manner as in Test Example 1, except that the MEK used in preparing the classified slurry was changed to isopropyl alcohol, the centrifugal acceleration was set to 2500 G, the centrifugal field residence time was set to 5.5 minutes, and the hollow particles were not removed by a filter. The viscosity of the classified slurry was 5 mPa·s. Therefore, (centrifugal field residence time: minutes)/(classified slurry viscosity: mPa·s) was 1.1, and (centrifugal acceleration: G)/(classified slurry viscosity: mPa·s) was 500. The reason why the hollow particles were not removed by a filter is that, as in Test Example 4, under these centrifugal classification conditions, the filter was clogged immediately, and the hollow particles could not be sufficiently removed.

The obtained silica particles had a D50 of 160 nm, a D100 of 740 nm, a specific surface area of 19.8 m ² /g, a water absorption of 0.08%, and a total amount of alkali metals and alkaline earth metals of 30 ppm or less, as measured by laser diffraction particle size distribution measurement.

(Test Example 6)
Colloidal silica (D50 100 nm, D100 210 nm: Cataloid SI-80P: manufactured by JGC Catalysts and Chemicals Co., Ltd., dispersed in water with a solid content of 40 mass%, surface-treated) was used as the raw silica particles, and the silica particles obtained by drying at 160° C. for 30 minutes were used as the test sample of this test example.

The obtained silica particles had a D50 of 100 nm, a D100 of 210 nm, a specific surface area of 35.6 ^m2 /g, 0 hollow particles of 2 μm or more per 0.1 g, a water absorption of 1.2%, and a total amount of alkali metals and alkaline earth metals of 3,000 ppm or less, as measured by laser diffraction particle size distribution measurement.

The results of Test Examples 1 and 3 show that hollow particles cannot be sufficiently removed by centrifugal separation alone. In addition, due to differences in the dispersion medium used to prepare the classified slurry, Test Example 4, in which the (centrifugal field residence time: minutes)/(classified slurry viscosity: mPa·s) was 0.4 and less than 0.9, contained large particles that were too large to be classified using a filter.

In addition, in test examples 4 and 5, where the (centrifugal acceleration: G)/(classified slurry viscosity: mPa·s) was less than 900, large particles remained that were too large to be classified using a filter.

Furthermore, in Test Example 6, which used colloidal silica as the raw silica particles, the particle size distribution and amount of coarse particles (including hollow particles) were quite satisfactory, but the water absorption rate was high at 1.2%, and the total amount of alkali metals and alkaline earth metals was high, so the performance was not sufficient for practical use.

Claims (4)

D50 measured by laser diffraction particle size distribution measurement is 100 nm or more and 200 nm or less,
A specific surface area of 30 m ² /g or less;
The number of hollow particles of 0.8 μm or more is 1,000 pieces/0.1 g or less,
Water absorption rate is 1.0% or less based on the total mass.
The total amount of alkali metals and alkaline earth metals is 100 ppm or less.
Silica particles (excluding surface-modified silica particles having D90/D10 of 2 or more and D50 of 250 nm or less when integrating the volumes from the smallest particle size, water absorption of 1.0% or less based on the mass when dried, and a total amount of alkali metals and alkaline earth metals of 100 ppm or less, and having carbon-containing functional groups introduced onto the surface). Silica particles according to claim 1, which have been surface-treated with a silane compound. The silica particles according to claim 1 or 2,
A dispersion medium for dispersing the silica particles;
1. A slurry composition comprising: A method for producing silica particles, comprising the steps of:
The silica particles are
D50 measured by laser diffraction particle size distribution measurement is 100 nm or more and 200 nm or less,
A specific surface area of 30 m ² /g or less;
The number of hollow particles of 2 μm or more is 1,000 pieces/0.1 g or less,
Water absorption rate is 1.0% or less based on the total mass.
The total amount of alkali metals and alkaline earth metals is 100 ppm or less.
Silica particles that have been surface-treated with a silane compound (excluding surface-modified silica particles having a D90/D10 of 2 or more and a D50 of 250 nm or less when integrating the volumes from the smallest particle size, a water absorption of 1.0% or less based on the mass when dried, and a total amount of alkali metals and alkaline earth metals of 100 ppm or less, and having a carbon-containing functional group introduced onto the surface),
a raw silica particle production step in which a raw particle material made of metal silicon is dispersed in a carrier and then charged into a flame in an oxidizing atmosphere to combust the material, thereby producing raw silica particles;
a surface treatment step of surface-treating the raw silica particles with a silane compound to obtain surface-treated raw silica particles;
a classification step in which the dispersion slurry in which the surface-treated raw silica particles are dispersed in a solvent is centrifuged to remove coarse particles, and then a classification operation is carried out multiple times using filters having pore sizes ranging from large to small, thereby removing hollow particles to obtain silica particles;
having
The method for producing silica particles, wherein in the centrifugation in the classification step, (residence time in centrifugal field: min)/(classified slurry viscosity: mPa·s) is 0.9 or more, and (centrifugal acceleration: G)/(classified slurry viscosity: mPa·s) is 700 or more.