Hollow silica particles

Abstract

The purpose of the present disclosure is to provide hollow silica particles which have small particle diameters, have a small dielectric loss tangent, and are monodisperse, and in which the formation of coarse particles is suppressed. The present disclosure provides hollow silica particles which have an average primary particle diameter d of 1 μm or less, a coefficient of variation of primary particle diameters of 10% or less, a ratio of the cumulative 90% diameter D90 to the cumulative 50% diameter D50, i.e., D90 / D50, as measured by the centrifugal sedimentation method of 2.0 or less, and a dielectric loss tangent of 1.5 × 10-2 or less at 10 GHz.

Description

Hollow Silica Particles

[0001] The present disclosure relates to hollow silica particles.

[0002] In recent years, with the increase in the volume of information communication and the increase in data processing speed in information and communication devices, the radio wave signals handled are becoming higher in frequency. As the radio wave signals become higher in frequency, the signal transmission loss increases. Therefore, materials that can handle higher frequencies, such as semiconductor sealants and resin materials for printed circuit boards that constitute electrical and electronic components, are required to have low relative dielectric constants and dielectric loss tangents.

[0003] Silica is usually added to the resin material to suppress thermal expansion. However, due to the above-mentioned demand for a low dielectric constant and a low dielectric loss tangent, silica is also required to have a low dielectric constant and a low dielectric loss tangent, and the use of hollow silica particles as silica that satisfies these properties has been investigated.

[0004] For example, Patent Document 1 discloses hollow silica particles having an average particle diameter of 0.5 μm to 3.0 μm, which have a relative dielectric constant of 2.5 or less and a dielectric loss tangent of 0.0050 or less at a measurement frequency of 5.8 GHz. Patent Document 2 discloses hollow silica particles having an average particle diameter of 0.5 μm to 3.0 μm, which have an increase in particle density of 8% or less when heat-treated at 1100° C. for 1 hour.

[0005] International Publication No. 2023 / 140378 Japanese Patent Application Laid-Open No. 2023-107038

[0006] The hollow silica particles used by mixing with the resin material must have a low dielectric constant and dielectric loss tangent, and in addition, from the viewpoints of homogenizing the resin composition (cured product) containing the hollow silica particles, reducing the surface roughness, and improving the filling rate of the hollow silica particles in the resin, it is important that the particle size is monodispersed and the amount of coarse particles is suppressed. In order to meet the recent demand for thinner films for the resin material, it is also necessary that the amount of coarse particles in the silica particles is suppressed. It is particularly difficult for hollow silica particles with a small particle size to satisfy all of these properties.

[0007] The hollow silica particles disclosed in the above-mentioned Patent Documents 1 and 2 all have a large coefficient of variation of particle diameter, and no hollow silica particles having a small particle diameter and suppressing the formation of coarse particles are disclosed. Therefore, it has been difficult to apply the techniques of Patent Documents 1 and 2 to resin materials that can accommodate higher frequencies and thinner films.

[0008] Therefore, an object of the present disclosure is to provide hollow silica particles that are useful for resin materials that can accommodate higher frequencies and thinner films.

[0009] The present disclosure achieves the above-mentioned object as follows: [1] An average primary particle diameter d of 0.05 μm or more and 1 μm or less, a coefficient of variation of the primary particle diameter of 10% or less, a ratio of the cumulative 90% diameter D90 to the cumulative 50% diameter D50 measured by centrifugal sedimentation method: D90 / D50 of 2.0 or less, and a dielectric loss tangent at 10 GHz of 1.5×10 －２ [2] Hollow silica particles having a dielectric loss tangent of 2.5 × 10 at 10 GHz or less. －３ [1] The hollow silica particles according to [1], which are as follows: [3] The hollow silica particles according to [1] or [2], which have a void ratio of 10 to 50%. [4] The hollow silica particles according to any one of [1] to [3], which have a Na content of 1 ppm or less. [5] The hollow silica particles according to any one of [1] to [4], which have a ratio D50 / d of the cumulative 50% diameter D50 measured by centrifugal sedimentation to the average primary particle diameter d, which is less than 1.2. [6] The hollow silica particles according to any one of [1] to [5], which have fewer than 5 particles per 500 particles that are less than half the average primary particle diameter d. [7] The hollow silica particles according to any one of [1] to [6], which have not been surface-treated with a surface treatment agent. [8] The hollow silica particles according to any one of [1] to [7], which have a void ratio of 10 to 35%. [9] The hollow silica particles according to any one of [1] to [8], which have an average primary particle diameter d of 0.05 μm or more and 0.7 μm or less.

[10] Hollow silica particles according to any one of [1] to [9], wherein the hollow silica particles have an average sphericity (length in the major axis direction / length in the minor axis direction) of 1 to 1.2.

[0010] According to the present disclosure, it is possible to provide hollow silica particles that have a small particle size, a low dielectric loss tangent, are monodisperse, and are suppressed from becoming coarse particles.

[0011] Fig. 1 is a photograph, substituted for a drawing, showing an image of the hollow silica particles after calcination obtained in Example 1, observed with a scanning electron microscope. Fig. 2 is a photograph, substituted for a drawing, showing an image of the hollow silica particles after calcination obtained in Example 3, observed with a scanning electron microscope.

[0012] <Hollow Silica Particles> The hollow silica particles of the present disclosure have an average primary particle diameter d of 0.05 μm or more and 1 μm or less, a coefficient of variation of the primary particle diameter of 10% or less, a ratio of the cumulative 90% diameter D90 to the cumulative 50% diameter D50 measured by centrifugal sedimentation method: D90 / D50 of 2.0 or less, and a dielectric loss tangent at 10 GHz of 1.5×10 －２ Hollow silica particles with a small particle size tend to have an increased dielectric dissipation factor due to an increased surface area, and calcining them to reduce this tends to produce coarse particles, making it difficult for small hollow silica particles to achieve both a low dielectric dissipation factor and suppress the formation of coarse particles. However, according to the present disclosure, even small hollow silica particles with an average primary particle size of 1 μm or less can satisfy both of these properties.

[0013] The average primary particle diameter d is preferably 1 to 0.05 μm, more preferably 0.9 to 0.1 μm, even more preferably 0.7 to 0.15 μm, still more preferably 0.55 to 0.2 μm, and particularly preferably 0.5 to 0.3 μm. The average primary particle diameter d is the arithmetic mean value when the major axis length of a plurality of hollow silica particles is measured, and can be determined, for example, by observing the particles with a transmission electron microscope at a magnification such that 100 to 300 particles are included in one visual field, measuring the major axis lengths of 100 silica particles selected from each visual field, and observing this for five visual fields to determine the arithmetic mean value for a total of 500 particles.

[0014] The coefficient of variation (CV value) of the primary particle diameter, i.e., the ratio (percentage) of the standard deviation of the primary particle diameter to the average primary particle diameter d, is 10% or less, preferably 10 to 1%, more preferably 9 to 1%, even more preferably 8 to 1%, and particularly preferably 7.5 to 1%. The hollow silica particles of the present disclosure are preferably produced using a sol-gel method as described below, and producing silica particles by the sol-gel method allows the production of hollow silica particles with a small CV value.

[0015] Regarding particle size, by measuring the hollow silica particles of the present disclosure by centrifugal sedimentation, the particle size distribution, including secondary particles, can be determined, and the coarse particle rate can be estimated by the ratio of the cumulative 90% diameter D90 to the cumulative 50% diameter D50: D90 / D50. The value of D90 / D50 is 2.0 or less, preferably 2.0 to 1.05, more preferably 1.8 to 1.1, even more preferably 1.6 to 1.1, and even more preferably 1.5 to 1.1. The particle size D50 measured by centrifugal sedimentation is, for example, 0.1 to 1 μm, or may be 0.2 to 0.5 μm, and the particle size D90 measured by centrifugal sedimentation is, for example, 0.2 to 1.2 μm, or may be 0.3 to 0.7 μm.

[0016] The dielectric loss tangent Df of the hollow silica particles of the present disclosure at 10 GHz is 1.5 × 10 －２ is less than or equal to 1.5 × 10 －２ ~1.0 x 10 －４ is preferable, and 8.0 × 10 －３ ~1.0 x 10 －４ More preferably, 6.0 × 10 －３ ~1.0 x 10 －４ is more preferably 2.5 × 10 －３ ~5.0 x 10 －４ is more preferable.

[0017] The relative dielectric constant Dk at 10 GHz is preferably 2.0 to 4.5, more preferably 2.5 to 4.0, even more preferably 2.8 to 3.8, and particularly preferably 2.8 to 3.5.

[0018] The agglomeration rate can be estimated by the ratio of the cumulative 50% diameter D50 measured by centrifugal sedimentation to the average primary particle diameter d: D50 / d. The value of D50 / d is preferably less than 1.2, more preferably less than 1.2 and 0.7 or more, even more preferably 1.1 to 0.7, and still more preferably 1.0 to 0.8.

[0019] Furthermore, it is preferable that the hollow silica particles of the present disclosure are suppressed in the generation of fine particles, and specifically, it is preferable that the number of particles having a size less than 1 / 2 of the average primary particle diameter d be less than 5 out of 500 particles. The presence of fine particles deteriorates the dielectric properties and tends to aggregate, which can cause problems such as an increase in viscosity of the resin composition when mixed with a resin.

[0020] The hollow silica particles have a void ratio of, for example, 10 to 50%, preferably 10 to 45%, more preferably 12 to 35%, and may even have a void ratio of 16 to 35%. Such a void ratio ensures sufficient strength. The void ratio can be calculated by measuring the specific gravity with nitrogen gas using a dry automatic densimeter, as shown in the examples below.

[0021] The hollow silica particles have an average sphericity (long axis length / short axis length) of, for example, 1 to 1.5, preferably 1 to 1.3, more preferably 1 to 1.2, and even more preferably 1 to 1.1.

[0022] Furthermore, since the present disclosure employs a sol-gel method, the amount of Na in the hollow silica particles can be reduced to 1 ppm or less. The amount of Na can be measured according to ICP atomic emission spectroscopy in accordance with JIS K 0116, as described below.

[0023] The hollow silica particles of the present disclosure are preferably not surface-treated with a surface treatment agent, and the carbon content in 100% by mass of the non-surface-treated hollow silica particles is, for example, 0.1% by mass or less.

[0024] <Method for producing hollow silica particles> The hollow silica particles of the present disclosure can be produced by a production method including: a first step of hydrolyzing and condensing an alkoxysilane in a solvent containing water and alcohol in the presence of a quaternary ammonium compound to obtain a dispersion of silica particles; a second step of subjecting the silica particles to hydrothermal treatment to obtain hollow silica particles; a third step of pulverizing the silica particles produced in the second step; and a fourth step of firing the silica particles pulverized in the third step.

[0025] The above-described production method includes a so-called sol-gel process, in which silica particles are obtained by hydrolysis and condensation of alkoxysilane. When the hydrolysis and condensation of alkoxysilane in the first step is carried out in the presence of a quaternary ammonium compound, the high basicity of the quaternary ammonium compound increases the pH during the initial nucleation stage of the hydrolysis and condensation reaction, resulting in a low degree of condensation. Meanwhile, the pH decreases during the final shell formation stage of the hydrolysis and condensation reaction, resulting in a high degree of condensation. The resulting silica particles are then subjected to hydrothermal treatment in the second step, removing the nuclei with a low degree of condensation and producing hollow silica particles with only the shells with a high degree of condensation remaining. The temperature of the hydrothermal treatment in the second step is, for example, 100 to 250°C, and may be 150 to 250°C. The pressure during the hydrothermal treatment in the second step may be, for example, 0.1 MPa (i.e., atmospheric pressure) to 2 MPa, or 0.5 to 2 MPa.

[0026] For details of the first step and the second step, please refer to the descriptions of the first step and the second step described in JP 2021-195275 A, respectively.

[0027] In obtaining the hollow silica particles of the present disclosure, it is important to perform the third step of pulverizing the silica particles after obtaining the hollow silica particles in the first and second steps and before the calcination in the fourth step. In the present disclosure, the silica particles are calcined in the fourth step in order to sufficiently reduce the dielectric tangent of the hollow silica particles. However, if the calcination treatment is performed without the third step of pulverizing the hollow silica particles, the generation of coarse particles due to aggregation of the hollow silica particles becomes significant, and once such coarse particles are generated, it is difficult to sufficiently disintegrate the coarse particles even if a subsequent pulverization treatment is performed.

[0028] The hollow silica particles subjected to the third step may be a dispersion in which hollow silica particles are dispersed in a solvent, or wet hollow silica particles separated from a solvent dispersion of hollow silica particles by filtration, centrifugation, solvent evaporation, or the like. The silica particles subjected to the third step may be dried while being pulverized, or may be pulverized after drying. When drying is performed in the third step, the drying temperature is, for example, 100 to 250°C. To dry while being pulverized, an airflow drying method can be used in which the silica particles are dispersed by an airflow and collide with the inner wall of the drying apparatus. Airflow drying is preferably performed in a drying apparatus having a tubular structure with straight and bent sections, such as the Crax System 8B (manufactured by Hosokawa Micron Corporation). Furthermore, to pulverize the silica particles after drying, they can be dried in a state in which the powder is fluidized, such as by spray drying, and then pulverized in a jet mill using compressed air (particularly a swirl-flow jet mill in which powder particles are pulverized by collision and friction between each other). The processing air pressure of the jet mill using compressed air is, for example, 0.3 to 1.0 MPa, and the processing speed is, for example, 0.1 to 3 kg / hr.

[0029] Regarding the firing conditions in the fourth step, the firing temperature is, for example, 900 to 1100°C, the firing time is, for example, 30 minutes to 10 hours, preferably 30 minutes to 5 hours, and more preferably 30 minutes to 3 hours, and the average temperature rise rate from room temperature to the firing temperature may be, for example, 200 to 450°C / hour.

[0030] This application claims the benefit of priority based on Japanese Patent Application No. 2024-110374, filed on July 9, 2024. The entire contents of the specification of Japanese Patent Application No. 2024-110374, filed on July 9, 2024, are incorporated herein by reference.

[0031] The present disclosure will be described in more detail below with reference to examples. The present disclosure is not limited to the following examples, and can be implemented with appropriate modifications within the scope of the above and below-described aims, and all such modifications are within the technical scope of the present disclosure.

[0032] The measurement and evaluation methods in each example are as follows.

[0033] <Measurement of Average Primary Particle Diameter d and Sphericity> The average primary particle diameter d was determined by collecting a particle dispersion dispersed in water or a solvent, observing it using a transmission electron microscope (JEM-2100F, manufactured by JEOL Ltd.) at a measurement magnification such that the number of particles in one field of view was 100 to 300, and measuring the major axis (length in the major axis direction) of all particles included in the transmission electron microscope image of five fields of view obtained for 100 particles arbitrarily selected per field of view, and determining the number-based arithmetic mean value of a total of 500 particles as the primary particle diameter d. The minor axis of each particle was also measured, and the sphericity (major axis / minor axis) of each particle was calculated, and the arithmetic mean value of the sphericity for a total of 500 particles was determined.

[0034] <Coefficient of variation (CV value) of average primary particle diameter> The coefficient of variation (CV value) of primary particle diameter was calculated using the average primary particle diameter d and the standard deviation of the primary particle diameter according to the following formula: CV value of primary particle diameter (%) = (standard deviation of primary particle diameter / average primary particle diameter d) × 100

[0035] <Measurement of particle size by centrifugal sedimentation method> 1 g of ion-exchanged water was added to 0.1 g of powdered hollow silica particles, and the particles were dispersed for 5 minutes using an ultrasonic disperser (KS-140B, manufactured by Kyowa Irika). Next, 8.9 g of ion-exchanged water was added, and the particles were similarly dispersed ultrasonically for 5 minutes. The particles were then ultrasonically dispersed for 5 minutes using an ultrasonic disperser (US-300T, manufactured by Nippon Seiki Seisakusho, tip diameter φ12 mm) at 300 μA to prepare a measurement sample. The particle size was measured by a wet method using a disk centrifugal sedimentation light transmission method ("DC24000" manufactured by CPS INSTRUMENTS), and the particle size corresponding to 50% of the total volume was defined as D50, and the particle size corresponding to 90% of the total volume was defined as D90.

[0036] <Agglomerated Particle Ratio> The aggregated particle ratio was calculated based on the following formula using the average primary particle diameter d and the particle diameter (D50) measured by centrifugal sedimentation: Aggregated particle ratio = Particle diameter (D50) measured by centrifugal sedimentation / Average primary particle diameter d

[0037] <Coarse Particle Ratio> The coarse particle ratio was calculated based on the particle diameter measured by centrifugal sedimentation according to the following formula: Coarse particle ratio = particle diameter measured by centrifugal sedimentation (D90) / particle diameter measured by centrifugal sedimentation (D50)

[0038] <Measurement of Hollowness> The specific gravity was measured using a dry automatic density meter (Shimadzu Corporation, Accupyc II 1340) under nitrogen gas, and the hollowness was calculated from the ratio to the true specific gravity (2.20) of silica particles having no hollow portion. Hollowness (%) = 100 × (1 - ((specific gravity under nitrogen gas) / 2.20))

[0039] <Measurement of Na Content> The Na content in the hollow silica particles was calculated by ICP emission spectroscopy according to JIS K 0116. In Examples 1 to 3, Comparative Examples 1 and 2, and Reference Example 1 described below, the Na content was 1 ppm or less in all cases.

[0040] <Measurement of Microparticle Abundance Ratio> The microparticle abundance ratio was measured using a scanning electron microscope (manufactured by JEOL Ltd., JSM-7600F, vapor deposition sputtering) at a measurement magnification such that the number of particles contained in one visual field was 100 to 300. In the obtained scanning electron microscope images of five visual fields, particles less than 1 / 2 of the average particle diameter d (primary particle diameter) were counted for particles of any 100 particles per visual field × 5 visual fields. Evaluation A: Fewer than 5 microparticles, Evaluation B: 5 or more microparticles

[0041] <Measurement of Relative Dielectric Constant and Dielectric Loss Tangent> The relative dielectric constant and dielectric loss tangent of the hollow silica particles were measured at a temperature of 25°C and a frequency of 10 GHz using a network analyzer (manufactured by Anritsu Corporation, product name: MS46122B) connected to a powder cavity resonator (manufactured by AET Corporation) by the cavity resonator perturbation method. A measurement sample was prepared by filling a quartz glass cell (inner diameter 4 mm, outer diameter 6 mm) with hollow silica powder so that the entire powder was within the measurement range (35.845 mm to 56.98 mm from the bottom). The weight of the hollow silica powder was calculated by measuring the weight before and after filling, and the volume of the hollow silica powder filled in the quartz glass cell was determined from the filling weight and specific gravity of the hollow silica powder. The relative dielectric constant and dielectric loss tangent were calculated by the difference between the measurement value of an empty quartz glass cell not filled with hollow silica powder and the measurement value of the quartz glass cell filled with hollow silica powder. (Evaluation of relative permittivity) A: 3.5 or less B: More than 3.5, 3.8 or less C: More than 3.8, 4.5 or less D: More than 4.5 (Evaluation of dielectric tangent) A: 2.5 x 10 －３ Below B: 2.5×10 －３ Super, 6.0×10 －３ Below C: 6.0×10 －３ Super, 1.5×10 －２ Below D: 1.5×10 －２ Super

[0042] Example 1 A reaction vessel equipped with a stirrer, a dropping device, and a thermometer was charged with 536.1 parts of ethanol as an organic solvent, 221.5 parts of methanol, and 119.1 parts of ion-exchanged water, and the liquid temperature was adjusted to 25±0.5°C while stirring. Meanwhile, a solution obtained by dissolving 100 parts of tetraethoxysilane as an alkoxysilane in 137.6 parts of ethanol and 62.4 parts of methanol was charged into the dropping device. Furthermore, 129.2 parts of a 4% aqueous tetramethylammonium hydroxide solution was charged into a different dropping device. Then, each solution was dropped from the dropping device over one hour.

[0043] After the dropwise addition, the mixture was stirred for another 2 hours to carry out hydrolysis and condensation of tetraethoxysilane, thereby obtaining a suspension of silica particles. The solvent in the obtained suspension of silica particles was replaced with ion-exchanged water using an ultrafiltration device to obtain an aqueous dispersion of silica particles. A reflux condenser was then attached to the reaction vessel, and the mixture was subjected to hydrothermal treatment at 100°C for 4 hours to obtain hollow silica particles.

[0044] The obtained hollow silica particles were subjected to solid-liquid separation by centrifugation, dispersed in 261 parts of ion-exchanged water, and then dried using a spray dryer (MiniSprayDryer B-290, manufactured by Buchi Co., Ltd., inlet temperature 180°C) to obtain a hollow silica particle powder.

[0045] After obtaining the powdery silica hollow particles, they were pulverized using a pulverizer (airflow type fine pulverizer "Super Jet Mill", processing air pressure 0.6 MPa, processing rate 1 kg / hr).

[0046] The obtained hollow silica particle powder (I) was placed in a crucible, heated from room temperature to 1000°C over 3 hours in an electric furnace, held at that temperature for 1 hour, and then cooled to obtain calcined hollow silica particles (1). The physical properties of the obtained particles are shown in Table 1. An image of the calcined hollow silica particles (1) observed with an electron microscope is shown in Figure 1, and it can be seen that the CV value of the particle size is small and aggregation is suppressed.

[0047] (Example 2) An aqueous dispersion of silica particles was obtained in the same manner as in Example 1, and then subjected to hydrothermal treatment at 180°C for 4 hours (inside vessel pressure: 1.0 MPa) in a pressure-resistant reaction vessel (TAS-2 model, manufactured by Taiatsu Glass Industries Co., Ltd.) to obtain hollow silica particles. The drying conditions, grinding conditions, and firing temperature were the same as in Example 1 to obtain fired silica particles (2). The physical properties of the obtained particles are shown in Table 1.

[0048] Example 3 A reaction vessel equipped with a stirrer, a dropping device, and a thermometer was charged with 536.0 parts of ethanol as an organic solvent, 243.3 parts of methanol, and 119.1 parts of ion-exchanged water, and the liquid temperature was adjusted to 25±0.5°C while stirring. Meanwhile, a solution obtained by dissolving 100 parts of tetraethoxysilane as an alkoxysilane in 137.6 parts of ethanol and 62.3 parts of methanol was charged into the dropping device. Furthermore, 129.1 parts of a 6% aqueous tetramethylammonium hydroxide solution was charged into a different dropping device. Then, the silicon compound solution was dropped from the dropping device over 1 hour, and the tetramethylammonium hydroxide aqueous solution was dropped over 1.5 hours.

[0049] After the addition of the aqueous tetramethylammonium hydroxide solution was completed, the mixture was stirred for an additional 1.5 hours to carry out hydrolysis and condensation of tetraethoxysilane, thereby obtaining a suspension of silica particles. The solvent of the obtained suspension of silica particles was replaced with ion-exchanged water using an ultrafiltration device, and then the suspension was subjected to hydrothermal treatment at 210°C for 4 hours in a pressure-resistant reaction vessel (inner vessel pressure: 2.0 MPa), thereby obtaining hollow silica particles. The drying conditions, grinding conditions, and calcination temperature were the same as in Example 1, and calcined hollow silica particles (3) were obtained. The physical properties of the obtained particles are as shown in Table 1. Furthermore, an image of the calcined hollow silica particles (3) observed with an electron microscope is shown in Figure 2, which confirms that the CV value of the particle size is small and aggregation is suppressed.

[0050] Comparative Examples 1 and 2 Calcined hollow silica particles (4) and (5) were obtained in the same manner as in Example 3, except that the drying conditions, grinding conditions, and calcination temperature were changed as shown in Table 1.

[0051] Reference Example 1 A 2 L glass reactor equipped with a stirrer, a dropping device, and a thermometer was charged with 675.4 g of methyl alcohol as an organic solvent and 263.3 g of 28 wt % aqueous ammonia (water and catalyst), and the liquid temperature was adjusted to 20±0.5° C. while stirring. Meanwhile, a solution obtained by dissolving 134.5 g of tetramethoxysilane as a silicon compound in 55.9 g of methyl alcohol was charged into the dropping device. The solution was then dropped from the dropping device over 1 hour.

[0052] After the dropwise addition, the mixture was stirred for another hour to carry out hydrolysis and condensation of tetramethoxysilane, thereby obtaining a suspension of silica particles. The suspension was dried using an instantaneous vacuum evaporator to obtain powdery solid silica particles (I).

[0053] The instantaneous vacuum drying device used was a Crux System 8B model (manufactured by Hosokawa Micron Corporation). The drying conditions were a heating tube temperature of 175°C and a reduced pressure of 200 torr.

[0054] The obtained silica particles (I) were placed in a crucible, heated in an electric furnace from room temperature to 1000°C over 3 hours, held at that temperature for 1 hour, and then cooled to obtain calcined solid silica particles (6). The physical properties of the obtained particles are shown in Table 1.

[0055]

[0056] The hollow silica particles of the present disclosure, which have achieved a low dielectric loss tangent, are useful as sealants for semiconductors in high-speed communication devices and peripheral materials for printed circuit boards.

Claims

1. The average primary particle diameter d is 0.05 μm or more and 1 μm or less, the coefficient of variation of the primary particle diameter is 10% or less, the ratio of the cumulative 90% diameter D90 to the cumulative 50% diameter D50 measured by centrifugal sedimentation method: D90 / D50 is 2.0 or less, and the dielectric loss tangent at 10 GHz is 1.5 × 10 －２ Hollow silica particles are:

2. The dielectric loss tangent at 10 GHz is 2.5 x 10 －３ The hollow silica particles according to claim 1, wherein the hollow silica particles are:

3. The hollow silica particles according to claim 1 or 2, which have a void ratio of 10 to 50%.

4. The hollow silica particles according to claim 1 or 2, wherein the amount of Na is 1 ppm or less.

5. Hollow silica particles according to claim 1 or 2, wherein the ratio of the cumulative 50% diameter D50 measured by centrifugal sedimentation to the average primary particle diameter d: D50 / d is less than 1.

2.

6. The hollow silica particles according to claim 1 or 2, wherein the number of particles having a diameter less than 1 / 2 of the average primary particle diameter d is less than 5 per 500 particles.

7. The hollow silica particles according to claim 1 or 2, which have not been surface-treated with a surface treatment agent.

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