JP5513364B2 - Hollow silica particles - Google Patents

Description

  The present invention relates to hollow silica particles and a method for producing the same.

Fine hollow silica particles have a lower specific gravity than non-hollow silica particles and have a low dielectric constant effect due to the form of hollow particles. Therefore, they are low in multilayer printed circuit boards, wire coating materials, semiconductor sealing materials, etc. It is expected to be used in fields with dielectric constant needs.
Various proposals have been made for fine hollow silica particles. For example, Patent Document 1 discloses a refined spherical silica hollow having an average particle size of 8 μm or less, an average sphericity of 0.85 or more, a 50% breaking pressure of 10 MPa or more, and an average hollowness of 20 to 70% by volume. A powder is disclosed.
However, the average particle diameter of the hollow silica particles of Patent Document 1 is 0.5 to 8 μm in a specific embodiment, and 1.2 to 7.8 μm in the examples.

JP 2005-206436 A

In recent years, in a field where there is a need for a low dielectric constant such as a multilayer printed circuit board, smoothness of an insulating film and further thinning have been desired along with miniaturization of circuits. Therefore, further miniaturization is desired for the particles used as the constituent material.
An object of the present invention is to provide extremely fine hollow silica particles and a method for producing the same.

That is, the present invention provides the following [1] and [2].
[1] The volume average particle diameter measured by the laser diffraction / scattering method is 0.05 to 0.45 μm, the maximum particle diameter is within 5 times the volume average particle diameter, and the porosity is 20 to 70% by volume. Hollow silica particles having a BET specific surface area of less than 30 m ² / g and 98 mass% or more of SiO ₂ [2] The method for producing hollow silica particles according to [1], comprising the following steps (I) to (III):
Step (I): Step of preparing an aqueous solution containing a hydrophobic organic compound (a), a quaternary ammonium salt (b), and a silica source (c) that produces a silanol compound by hydrolysis Step (II): The aqueous solution obtained in step (I) is stirred at a temperature of 10 to 100 ° C., and water of core-shell type silica particles having an outer shell composed of silica and having a hydrophobic organic compound (a) in the nucleus. Step of preparing dispersion Step (III): Step of separating the core-shell type silica particles from the aqueous dispersion obtained in Step (II) and calcining at a temperature of 950 ° C. or higher to obtain hollow silica particles.

  According to the present invention, there are provided hollow silica particles having a volume average particle diameter of 0.45 μm or less measured by a laser diffraction / scattering method and having a sufficiently low dielectric constant and dielectric loss tangent, and an efficient production method thereof. be able to.

[Hollow silica particles]
The hollow silica particles of the present invention have a volume average particle size of 0.05 to 0.45 μm measured by a laser diffraction / scattering method, a maximum particle size within 5 times the volume average particle size, and a porosity of 20 to 70% by volume, BET specific surface area is less than 30 m ² / g, and 98% by mass or more is SiO ₂ .
In the hollow silica particles of the present invention, 98% by mass or more, preferably 99% by mass or more is SiO ₂ . Examples of components other than silica include alumina, zirconia, titania, magnesia, calcia, etc. From the viewpoint of strength, low thermal expansion, and electrical insulation, the purity of the hollow silica particles needs to be 98% by mass or more. It is. The silica purity can be measured using, for example, a plasma emission spectrometer (ICP), an X-ray fluorescence analyzer (XRF), an energy dispersive X-ray fluorescence analyzer (EDX), an atomic absorption photometer (AAS), or the like. it can.
The physical properties of the hollow silica particles are measured by the method described in the examples.

The volume average particle diameter of the hollow silica particles is 0.05 to 0.45 μm, but preferably 0.08 to 0.42 μm, more preferably 0.10 to 0.40 μm from the viewpoint of low dielectric properties and the like. Preferably it is 0.15-0.40 micrometer.
Further, the maximum particle size of the hollow silica particles is within 5 times the volume average particle size, preferably within 4.5 times, more preferably within 4 times, and even more preferably within 3.5 times.
For the measurement of the volume average particle size, a laser diffraction / scattering particle size distribution measuring device “LA-920” manufactured by Horiba, Ltd., a laser diffraction scattering method particle size distribution measuring device “LS 13 320” manufactured by Beckman Coulter, Inc., etc. Can be used.
As the hollow silica particles, a plurality of types of hollow particles having different volume average particle diameters can be mixed in order to improve the filling rate, and the particle diameter distribution can be widened. A plurality of narrow distributions can be used in combination.

The porosity of the hollow silica particles is 20 to 70% by volume. If the porosity is less than 20% by volume, the effects such as lightness, heat insulation, and low dielectric properties that are the characteristics of the hollow silica particles are not sufficiently exhibited. If the porosity exceeds 70% by volume, the shell thickness of the particles becomes thin. The strength is lowered, and there is a possibility that the particles are broken during the handling of the powder or the kneading with the resin. The air Anaritsu is capable of appropriately adjusted in consideration of the use and the like, from the viewpoint of dielectric characteristics improvement, preferably 15 to 65 vol%, more preferably 20 to 60 vol%, more preferably, 25 to 55 % By volume .
When the porosity is the same, higher strength can be expected when the volume average particle size is larger.
When importance is attached to particle strength, 80% by mass or more of the entire hollow silica particles, more preferably 85% by mass or more, still more preferably 90% by mass or more, and particularly preferably 95 % by mass or more is within a volume average particle diameter of ± 30%. It is desirable that it is composed of a group of particles having a very uniform particle size. Furthermore, when importance is attached to strength, fillers other than hollow silica particles may be added.

The average thickness of the outer shell part of the hollow silica particles is preferably thin as long as the hollow silica particles can maintain the strength as a carrier, and the average diameter (average volume) of the hollow part is large from the viewpoint of increasing the porosity. Is preferred. From these viewpoints, the average thickness of the outer shell is usually 0.5 to 150 nm, preferably 2 to 120 nm, more preferably 3 to 100 nm.
The ratio of [average thickness of outer shell / average particle radius of hollow silica particles] is usually 0.13 to 0.47, preferably 0.16 to 0.42, more preferably 0.18 to 0.37. is there.
The volume average particle diameter of the hollow silica particles and the average thickness of the outer shell can be appropriately adjusted depending on the production conditions of the protocore-shell type silica particles described later, the particle diameter of the hollow part forming material, the firing conditions, and the like.

The BET specific surface area of the hollow silica particles is less than 30 m ² / g, and is preferably 25 m ² / g or less, more preferably 20 m ² / g or less, still more preferably 18 m ² / g or less from the viewpoint of low dielectric properties and the like. is there.
The 50% breaking pressure of the hollow silica particles is preferably 100 MPa or more. A 50% breaking pressure of less than 100 MPa is not preferable because the number of particles to be broken increases when used in various applications, for example, when mixed with a resin. Here, the 50% fracture pressure, for example, Nikkiso and made of cold isostatic pressing apparatus Co., the powder was pressurized by Kobe Steel, Ltd. made of cold isostatic pressing device, an average pore It is defined as the pressure at which the rate is halved. More specifically, it is measured by the method described in the examples.
In the powder X-ray diffraction (XRD) measurement, the hollow silica particles do not show a peak at the diffraction angle (2θ) corresponding to the range where the crystal lattice spacing (d) is less than 1 nm from the viewpoint of low dielectric properties and the like. Preferably there is.
Further, it is preferable that the hollow silica particles do not substantially exhibit a pore distribution of 1 nm or more in the pore diameter distribution.

The hollow silica particles of the present invention have a signal area ratio of (Q ² × 2 + Q ³ ) to a signal area of Q ² + Q ³ + Q ⁴ according to solid ²⁹ Si-NMR spectrum [(Q ² × 2 + Q ³ ) / (Q ² + Q ³ + Q ⁴ )] is preferably 0.15 or less.
The signal areas of Q ² , Q ³ , and Q ⁴ are calculated based on the results of solid ²⁹ Si-NMR measurement. Analysis of solid ²⁹ Si-NMR measurement data (determination of peak position) can be performed by a method of dividing and extracting each peak by, for example, waveform separation analysis using a Gaussian function. More specifically, it can be carried out by the method described in the examples.
The chemical shift obtained by peak splitting as described above is assigned as follows.
Q ² : Signal area of a peak expressed at −88 to −94 ppm Q ³ : Signal area of a peak expressed at −94 to −103 ppm Q ⁴ : Signal area of a peak expressed at −103 to −115 ppm Here, Q ² The peak attributed to is derived from the fact that four oxygen atoms are bonded to a silicon atom, two oxygen atoms are siloxane bonds, and two oxygen atoms are silanol groups.
The peak attributed to Q ³ is derived from the fact that four oxygen atoms are bonded to a silicon atom, three oxygen atoms are siloxane bonds, and one oxygen atom is a silanol group.
The peak attributed to Q ⁴ is derived from the fact that four oxygen atoms are bonded to a silicon atom and the four oxygen atoms are siloxane bonds. That is, [(Q ² × 2 + Q ³ ) / (Q ² + Q ³ + Q ⁴ ) ] is considered to mean OH / Si.
The ratio [(Q ² × 2 + Q ³ ) / (Q ² + Q ³ + Q ⁴ ) ] is calculated using the areas of the signals Q ² , Q ³ , and Q ⁴ obtained as described above.
The ratio of [(Q ² × 2 + Q ³ ) / (Q ² + Q ³ + Q ⁴ )] is desirably as small as possible from the viewpoint of low dielectric properties and the like, preferably 0.15 or less, more preferably 0 to 0. 14, more preferably 0 to 0.13.

Since the hollow silica particles of the present invention have the specific structure, the dielectric constant and dielectric loss tangent are reduced.
For example, the dielectric constant of the hollow silica is preferably 2.8 or less, more preferably 2.5 or less, still more preferably 2.3 or less, and particularly preferably 1.2 to 2.0 at a frequency of 5.8 GHz. The dielectric constant can be measured by a conventional method using a cavity resonator perturbation method or the like.
The dielectric loss tangent of the hollow silica is, for example, preferably 0.01 or less, more preferably 0.009 or less, and still more preferably 0.008 or less, under the measurement conditions described in the examples.

[Method for producing hollow silica particles]
Although there is no restriction | limiting in particular in the manufacturing method of the hollow silica particle of this invention, According to the method which has the following process (I)-(III), it can manufacture efficiently.
Step (I): Step of preparing an aqueous solution containing a hydrophobic organic compound (a), a quaternary ammonium salt (b), and a silica source (c) that produces a silanol compound by hydrolysis Step (II): The aqueous solution obtained in step (I) is stirred at a temperature of 10 to 100 ° C., and water of core-shell type silica particles having an outer shell composed of silica and having a hydrophobic organic compound (a) in the nucleus. Step of preparing dispersion Step (III): Step of separating core-shell type silica particles from the aqueous dispersion obtained in Step (II) and calcining at a temperature of 950 ° C. or higher to obtain hollow silica particles. Details of (I) to (III) and components used therein will be described.

<Process (I)>
Step (I) is a step of preparing an aqueous solution containing a hydrophobic organic compound (a), a quaternary ammonium salt (b), and a silica source (c) that produces a silanol compound by hydrolysis.
In the step (I), the hydrophobic organic compound (a) is 0.1 to 100 mmol / L and one or more selected from quaternary ammonium salts represented by the following general formulas (1) and (2) ( Preferably, b) is a step of preparing an aqueous solution containing 0.1 to 100 mmol / L and a silica source (c) that generates a silanol compound by hydrolysis.
[R ¹ (CH ₃ ) ₃ N] ⁺ X ⁻ (1)
[R ¹ R ² (CH ₃ ) ₂ N] ⁺ X ⁻ (2)
(In the formula, R ¹ and R ² each independently represents a linear or branched alkyl group having 4 to 22 carbon atoms, and X represents a monovalent anion.)

(Hydrophobic organic compound (a))
In the present invention, the hydrophobic organic compound (a) means a compound that has low solubility in water and forms a phase separation with water. Preferably, the compound is dispersible in the presence of the quaternary ammonium salt. Examples of such hydrophobic organic compounds include compounds having a LogP value of 1 or more, preferably 2 to 25.
Examples of the hydrophobic organic compound (a) include oil agents such as hydrocarbon compounds having 7 to 22 carbon atoms, ester compounds, fatty acids having 7 to 22 carbon atoms, alcohols having 7 to 22 carbon atoms, and silicone oils, fragrances, Examples include various base materials such as agricultural chemicals and pharmaceuticals.
Examples of the hydrocarbon compound having 7 to 22 carbon atoms include linear or branched saturated aliphatic hydrocarbons such as heptane, octane, nonane, decane, dodecane, tetradecane, hexadecane, octadecane, icosane, docosan, and the basic skeleton thereof. Examples thereof include the same unsaturated aliphatic hydrocarbons, cyclic hydrocarbons such as cyclohexane and cyclooctane, and aromatic hydrocarbons such as benzene and toluene. Among these, a linear or branched saturated aliphatic hydrocarbon having 7 to 16 carbon atoms is preferable, and a linear or branched saturated aliphatic hydrocarbon having 8 to 14 carbon atoms is more preferable.
Since the volume average particle diameter of the hollow silica particles and the size of the hollow part are affected by the size of the droplets of the hydrophobic organic compound (a), the melting point, reaction temperature, and stirring of the hydrophobic organic compound (a) The speed can be adjusted as appropriate depending on the surfactant used.

(Quaternary ammonium salt (b))
The quaternary ammonium salt (b) is used for forming mesopores and dispersing the hydrophobic organic compound (a).
R ¹ and R ² in the general formulas (1) and (2) are linear or branched alkyl groups having 4 to 22 carbon atoms, preferably 6 to 18 carbon atoms, and more preferably 8 to 16 carbon atoms. It is. Examples of the alkyl group having 4 to 22 carbon atoms include various butyl groups, various pentyl groups, various hexyl groups, various heptyl groups, various octyl groups, various nonyl groups, various decyl groups, various dodecyl groups, various tetradecyl groups, and various hexadecyl groups. , Various octadecyl groups, various eicosyl groups, various docosyl groups, and the like.
X in the general formulas (1) and (2) is preferably at least one selected from monovalent anions such as halogen ions, hydroxide ions, and nitrate ions from the viewpoint of obtaining high crystallinity. X is more preferably a halogen ion, still more preferably a chlorine ion or a bromine ion.

Examples of the alkyltrimethylammonium salt represented by the general formula (1) include butyltrimethylammonium chloride, hexyltrimethylammonium chloride, octyltrimethylammonium chloride, decyltrimethylammonium chloride, dodecyltrimethylammonium chloride, tetradecyltrimethylammonium chloride, hexadecyltrimethyl Ammonium chloride, stearyltrimethylammonium chloride, butyltrimethylammonium bromide, hexyltrimethylammonium bromide, octyltrimethylammonium bromide, decyltrimethylammonium bromide, dodecyltrimethylammonium bromide, tetradecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide Bromide, stearyl trimethyl ammonium bromide, and the like.
Examples of the dialkyldimethylammonium salt represented by the general formula (2) include dibutyldimethylammonium chloride, dihexyldimethylammonium chloride, dioctyldimethylammonium chloride, dihexyldimethylammonium bromide, dioctyldimethylammonium bromide, didodecyldimethylammonium bromide, ditetradecyl. Examples thereof include dimethylammonium bromide.
Among these quaternary ammonium salts (b), from the viewpoint of forming regular mesopores, alkyltrimethylammonium salts represented by the general formula (1) are particularly preferred, and alkyltrimethylammonium bromide or alkyltrimethyl Ammonium chloride is more preferred, and dodecyltrimethylammonium bromide or dodecyltrimethylammonium chloride is particularly preferred.

(Silica source (c))
A silica source (c) produces | generates a silanol compound by hydrolysis of alkoxysilane etc., and can mention the compound shown by following General formula (3)-(7).
SiY ₄ (3)
R ³ SiY ₃ (4)
R ³ ₂ SiY ₂ (5)
R ³ ₃ SiY (6)
Y ₃ Si—R ⁴ —SiY ₃ (7)
(In the formula, each R ³ independently represents an organic group in which a carbon atom is directly bonded to a silicon atom, R ⁴ represents a hydrocarbon group or a phenylene group having 1 to 4 carbon atoms, and Y represents A monovalent hydrolyzable group that becomes a hydroxy group by hydrolysis.)
More preferably, in the general formulas (3) to (7), each R ³ is independently a hydrocarbon group having 1 to 22 carbon atoms in which a part of hydrogen atoms may be substituted with fluorine atoms, Specifically, it is an alkyl group, a phenyl group, or a benzyl group having 1 to 22 carbon atoms, preferably 4 to 18 carbon atoms, more preferably 6 to 18 carbon atoms, and particularly preferably 8 to 16 carbon atoms, and R ⁴ Is an alkanediyl group having 1 to 4 carbon atoms (methylene group, ethylene group, trimethylene group, propane-1,2-diyl group, tetramethylene group, etc.) or phenylene group, and Y is more preferably 1 to 22 carbon atoms. Is a C1-C8, particularly preferably C1-C4 alkoxy group or a halogen group excluding fluorine.

Preferable examples of the silica source (c) include the following compounds.
-The silane compound in which Y is a C1-C3 alkoxy group or a halogen group except a fluorine in General formula (3).
In general formula (4) or (5), Y is an alkoxy group having 1 to 3 carbon atoms or a halogen group excluding fluorine, and R ³ is a phenyl group, a benzyl group, or a part of a hydrogen atom Is a trialkoxysilane or dialkoxysilane, which is a hydrocarbon group having 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, more preferably 1 to 5 carbon atoms, substituted with a fluorine atom.
In General Formula (6), Y is an alkoxy group having 1 to 3 carbon atoms or a halogen group excluding fluorine, and R ³ is a phenyl group, a benzyl group, or a hydrogen atom partially substituted with a fluorine atom. Monoalkoxysilane which is a hydrocarbon group having 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, more preferably 1 to 5 carbon atoms.
A compound in which Y is a methoxy group and R ⁴ is a methylene group, an ethylene group or a phenylene group in the general formula (7).
Among these, tetramethoxysilane, tetraethoxysilane, phenyltriethoxysilane, and 1,1,1-trifluoropropyltriethoxysilane are particularly preferable.

The hydrophobic organic compound (a) in the aqueous solution in the step (I) (hereinafter also referred to as “component (a)”), a quaternary ammonium salt (b) (hereinafter also referred to as “component (b)”), and The content of the silica source (c) (hereinafter also referred to as “component (c)”) is as follows.
The content of component (a) is 0.1 to 100 mmol / L, more preferably 1 to 100 mmol / L, and particularly preferably 5 to 80 mmol / L.
The content of component (b) is preferably 0.1 to 100 mmol / L, more preferably 1 to 100 mmol / L, particularly preferably 5 to 80 mmol / L, and the content of component (c) is And preferably 0.1 to 100 mmol / L, more preferably 1 to 100 mmol / L, and particularly preferably 5 to 80 mmol / L.
Although there is no restriction | limiting in particular in the order which contains (a)-(c) component, The method of throwing in order of the suspension of (a) component, (b) component, and (c) component is preferable, stirring aqueous solution.
The aqueous solution containing the components (a) to (c) may contain other components such as an organic compound such as methanol and an inorganic compound as long as the formation of protocore-shell particles is not inhibited. As described above, when it is desired to carry other elements other than silica and organic groups, metal raw materials such as alkoxy salts and halide salts containing these metals can be added during or after production.

  In the method of the present invention, an aqueous solution in the step (I) is prepared using 0.1 to 50 g / L of polymer particles instead of the hydrophobic organic compound (a), and the polymer particles are prepared in the step (II). A hollow silica particle can also be obtained by preparing an aqueous dispersion of core-shell type silica particles having sinter and firing in step (III). The polymer particles used here are preferably water-insoluble cationic polymers. The average particle diameter of the polymer particles can be appropriately selected according to the diameter of the hollow part of the target hollow silica particles.

<Process (II)>
In step (II), the aqueous solution obtained in step (I) is stirred at a temperature of 10 to 100 ° C., has an outer shell composed of silica, and has a hydrophobic organic compound (a) in the nucleus. This is a step of preparing an aqueous dispersion of core-shell type silica particles.
The aqueous solution obtained in the step (I) is stirred for a predetermined time at a temperature of 10 to 100 ° C., preferably 10 to 80 ° C., and then left to stand on the surface of the hydrophobic organic compound (a). An aqueous dispersion in which mesopores are formed by the salt (b) and the silica source (c) and protocore-shell type silica particles containing the hydrophobic organic compound (a) are precipitated can be obtained. The stirring treatment time varies depending on the temperature, but is usually 0.1 to 24 hours at 10 to 80 ° C.
In the step (I) and / or (II), when a cationic surfactant or the like is used, the mesopores of the protocore-shell type silica particles are clogged with the surfactant. The surface-active agent and the like are removed by contact once or a plurality of times, and protocore-shell type silica particles having a mesopore structure on the surface and including the hydrophobic organic compound (a) can be obtained.

<Process (III)>
In step (III), the core-shell type silica particles are separated from the aqueous dispersion obtained in step (II), and if necessary, contacted with an acidic aqueous solution, washed with water and dried, and then calcined at a temperature of 950 ° C. or higher. In this step, hollow silica particles are obtained.
The firing temperature is preferably from the viewpoint of appropriately compacting the pores, making the volume average particle size 0.05 to 0.45 μm, the porosity 20 to 70% by volume, and the BET specific surface area less than 30 m ² / g. Is 960 to 1500 ° C, more preferably 970 to 1300 ° C, still more preferably 980 to 1200 ° C. The firing time varies depending on the firing temperature and the like, but is usually 0.5 to 100 hours, preferably 1 to 80 hours. The hollow silica particles obtained have the same basic structure of the outer shell, but the hydrophobic organic compound (a) inside is removed by calcination.
In the method of the present invention, since the core-shell type silica particles containing the hydrophobic organic compound (a) are baked, by controlling the form of the encapsulated hydrophobic organic compound (a) in a desired state in advance, Hollow silica particles having a desired form can be easily produced.
In the present invention, hollow silica particles having a smaller BET specific surface area can be obtained by once producing hollow silica particles and then further firing.
The hollow silica particles of the present invention can be dispersed in various matrix resins as a raw material for a low dielectric film or a coating agent for a low dielectric film.

Various measurements of the hollow silica particles obtained in Examples and Comparative Examples were performed by the following methods.
(1) Volume average particle diameter and maximum particle diameter of hollow silica particles Using an ethanol dispersion of hollow silica particles as a measurement sample, a laser diffraction / scattering particle size distribution measuring apparatus “LA-920” manufactured by Horiba, Ltd. is used. It was measured by a wet method. For the analysis, HORIBA LA-920 WET (LA-920) Version 3.02 attached to the apparatus was used, and a range of 0.020 μm to 2000 μm was measured. Using ethanol as a dispersion medium, a sample was introduced so that the transmittance was 70 to 95%, the relative refractive index was set to 1.08 corresponding to silica / ethanol, and the particle diameter standard was set as volume. The volume average particle diameter was a median diameter corresponding to 50% by volume , and the maximum particle diameter was 100% by volume .
(2) Porosity of hollow silica particles The porosity (% by volume ) is calculated using the following formula from the density using nitrogen as the measurement gas and the true density of silica 2.2 g / cm ³ using ULTRAPYCNOMETER1000 manufactured by QUANTACHROME. Calculated by
Porosity ( volume %) = [1− (measured density with nitrogen gas / 2.2)] × 100
(3) BET specific surface area of hollow silica particles Using a specific surface area / pore distribution measuring device “ASAP2020” manufactured by Shimadzu Corporation, the BET specific surface area is measured by a multipoint method using liquid nitrogen, and the parameter C is Values were derived in the positive range.
(4) Silica purity A liquid obtained by acid-decomposing hollow silica particles with hydrogen fluoride was used as a measurement sample, and measurement was performed using a plasma emission spectrometer (7700x ICP-MS) manufactured by Agilent.

(5) Powder X-ray diffraction of the hollow silica particles (XRD) measurement Rigaku powder X-ray diffraction apparatus Industry Co., Ltd. using "RINT2500VPC", X-rays source: Cu- K alpha, tube current: 40 mA, tube voltage : 40 kV, sampling width: 0.02 °, divergence slit: 1/2 °, divergence slit length: 1.2 mm, scattering slit: 1/2 °, and light receiving slit: 0.15 mm Went. A continuous scanning method with a scanning range of diffraction angle (2θ) of 1 to 20 ° and a scanning speed of 4.0 ° / min was used. The measurement was performed by packing the pulverized sample in an aluminum plate.

(6) Breaking pressure of hollow silica particles A dispersion obtained by dispersing 5 g of hollow silica particles in 300 g of ion-exchanged water was filled in a 2 L Tedlar bag manufactured by AS ONE Co., Ltd., and the opening was heat sealed and sealed. This container was inserted into a cold isostatic press “CL10-55-40” manufactured by Nikkiso Co., Ltd., and a predetermined water pressure was applied for 10 minutes. After decompression, the container was taken out and the dispersion was filtered to obtain a powder. After drying at 100 ° C. for 12 hours, the porosity measurement of (2) above was performed to confirm the change in porosity before and after the application of water pressure, and the pressure at which the porosity was reduced by half was taken as the breaking pressure.
The hollow silica obtained in the present invention had a porosity decrease of 5% or less even after applying 400 MPa, which is the upper limit pressure of the apparatus.

(7) [(Q ² × 2 + Q ³ ) / (Q ² + Q ³ + Q ⁴ ) ] Ratio of Hollow Silica Particles Using a solid ²⁹ Si-NMR apparatus “NMR AVANCE300” manufactured by Bruker, ²⁹ Si nuclei (59. 6 MHz) was measured. About 100 mg of the measurement sample was closely packed in a zirconia 7.5 mmφ rotor. The NMR measurement method was DDMAS (3 kHz), the number of integrations was 640, the waiting time was 120 seconds, and hexamethylcyclotrisiloxane (-9.66 ppm) was used as the reference substance.
Waveform analysis was performed on the obtained spectrum, and the chemical shift and integrated value of each signal were obtained. Q ² , Q ³ , and Q ⁴ were assigned from this chemical shift, and the area percentage was calculated from the integrated value of each component. Using this value, the [(Q ² × 2 + Q ³ ) / (Q ² + Q ³ + Q ⁴ )] ratio was calculated.

(8) Dielectric constant, dielectric loss tangent (i) The dielectric constant and dielectric loss tangent of the hollow silica particles are measured by measuring the dielectric constant and dielectric loss tangent of the composite composed of the particles and the epoxy resin, and based on the Maxwell-Garnet equation below, Physical property values were calculated.

In the equation, ε _p represents the complex dielectric constant of the hollow silica particles, ε _m represents the complex dielectric constant of the resin, ε _av represents the complex dielectric constant of the composite, and f represents the volume fraction of the particles. The volume fraction of particles can be calculated from the composite composition, resin density, and hollow silica density. The dielectric constant is the real part (ε _r ) of the complex dielectric constant, and the dielectric loss tangent tand is calculated as the ratio of the imaginary part (ε _i ) of the complex dielectric constant and the real part (ε _r ) of the complex dielectric constant using the following formula: it can.

(Ii) The dielectric constant and dielectric loss tangent of the composite were measured according to the following procedure.
0.6 g of hollow silica particles were added to a bisphenol A type epoxy resin (manufactured by Japan Epoxy Resin Co., Ltd., liquid type, grade: 828 (2 to trimer), viscosity: 12 to 15 Pa · s (25 ° C.), epoxy equivalent: 184 To 194), epoxy resin curing agent (Japan Epoxy Resin Co., Ltd., acid anhydride grade: YH306), curing accelerator (Japan Epoxy Resin Co., Ltd., 2-ethyl-4 (5) -methylimidazole, grade: EMI24) ) Was mixed with 1.4 g of a matrix resin mixed at a mass ratio of 5: 6: 0.05 to produce a resin composition. This composition was poured into a mold in which a groove having a width of 2 mm, a depth of 1.5 mm and a length of 120 mm was dug in Teflon (registered trademark) resin, cured by heating, cooled, and then taken out from the mold to obtain a measurement sample. The resin composition was cured by heating in an electric dryer at 80 ° C. for 3 hours and further at 120 ° C. for 6 hours.
Dielectric property evaluation is a device in which a dielectric constant measuring device (resonator, 5.8 GHz) manufactured by Kanto Electronics Co., Ltd. is connected to an Agilent PNA microwave network analyzer “E8361A” (10 MHz to 67 GHz). Used and measured at 5.8 GHz using the cavity resonator perturbation method.

(9) Smoothness on the surface of the thin film 0.6 g of hollow silica particles is bisphenol A type epoxy resin (manufactured by Japan Epoxy Resin Co., Ltd., liquid type, grade: 828 (2 to trimer), viscosity: 12 to 15 Pa · s ( 25 ° C.), epoxy equivalent: 184-194), epoxy resin curing agent (Japan Epoxy Resin Co., Ltd., acid anhydride grade: YH306), curing accelerator (Japan Epoxy Resin Co., Ltd., 2-ethyl-4 (5 ) -Methylimidazole, grade: EMI24) was kneaded with 1.4 g of a matrix resin mixed in a mass ratio of 5: 6: 0.05 to produce a resin composition. This resin composition was diluted with 2-butanone (manufactured by Wako Pure Chemical Industries, Ltd.) so that the solid content concentration was 2% by mass to obtain a composition for forming a thin film.
Spin coating (1000 rpm, 30) using a spin coater (manufactured by Able Co., Ltd.) on a slide glass substrate (trade name: S-1111, refractive index 1.52, manufactured by Matsunami Glass Industrial Co., Ltd.) washed with acetone. Second) and then dried at 120 ° C. for 360 minutes to produce a thin film in which hollow particles are dispersed in an epoxy resin.
The surface of this thin film was observed using an electrolytic emission type high resolution scanning electron microscope (manufactured by Hitachi, Ltd., trade name: FE-SEM S-4000), and smoothness was confirmed.
(Evaluation criteria)
○: Smooth △: Slightly uneven ×: Uneven

Example 1
In a 500 mL flask, 100 g of methanol (manufactured by Wako Pure Chemical Industries, Ltd., special grade), 1.7 g of dodecyltrimethylammonium chloride (manufactured by Tokyo Chemical Industry Co., Ltd.), 1 g of dodecane (hydrophobic organic compound, manufactured by Wako Pure Chemical Industries, Ltd.) The mixture was stirred and liquid A was prepared. Further, 300 g of water and 0.825 g of 25 mass % tetramethylammonium hydroxide aqueous solution (manufactured by Wako Pure Chemical Industries, Ltd.) were added to a 500 mL flask and stirred to prepare a B liquid.
While stirring the obtained liquid A at 25 ° C., liquid B was added, and then 1.7 g (liquid C) of tetramethoxysilane (manufactured by Tokyo Chemical Industry Co., Ltd.) was added and stirred at 25 ° C. for 5 hours. The obtained cloudy aqueous solution was filtered off with 5C filter paper, washed with water, and dried at 100 ° C. with a dryer (manufactured by Advantech, DRM420DA) to obtain a white powder.
The obtained white powder was heated to 600 ° C. at a rate of 1 ° C./min with air flow (3 L / min) using a high-speed heating furnace (trade name: SK-2535E, manufactured by Motoyama Co., Ltd.). And the organic component was removed by baking at 600 degreeC for 2 hours, and the hollow silica particle was obtained. The silica particles were transferred to an alumina crucible and calcined at 1000 ° C. for 72 hours in air using the electric furnace. The results are shown in Table 1.

Example 2
Hollow silica particles were obtained in the same manner as in Example 1 except that dodecane (hydrophobic organic compound) in Example 1 was changed to octane (manufactured by Wako Pure Chemical Industries, Ltd.). The results are shown in Table 1.
Comparative Example 1
Hollow silica particles were obtained in the same manner as in Example 1 except that the dodecane (hydrophobic organic compound) in Example 1 was changed to hexane (Wako Pure Chemical Industries, Ltd.). The results are shown in Table 1.
Comparative Example 2
In Example 1, hollow silica particles were obtained in the same manner as in Example 1 except that the firing was performed at 600 ° C. for 2 hours and the firing was not performed at 1000 ° C.
However, in Comparative Example 2, since baking was not performed at 1000 ° C., the outer shell portion was porous, and the porosity by density measurement could not be measured. Therefore, the porosity is determined by measuring the hollow part diameter and outer shell thickness with a transmission electron microscope to determine the porosity of the hollow part, and the porosity of the porous part of the outer shell from the nitrogen adsorption measurement. did. The obtained porosity was 70% by volume .
In addition, even when the breaking pressure was 50%, water as a dispersion medium entered and exited through the outer shell portion, so that no pressure was applied to the particles, and measurement was impossible. The results are shown in Table 1.

  From Table 1, the low dielectric resin composition containing the epoxy resin of Examples 1 and 2 containing the hollow silica particles of the present invention as a matrix resin has a sufficiently low dielectric constant and dielectric loss tangent, and is smoother than Comparative Examples 1 and 2. It can be seen that a thin film with high properties can be formed.

Claims (4)

Volume average particle diameter measured by laser diffraction / scattering method is 0.05 to 0.45 μm, maximum particle diameter is within 5 times of volume average particle diameter, porosity is 20 to 70% by volume, BET ratio surface area less than 30 m ² / g, Ri least 98 mass% SiO ₂ der, is 50% breakdown pressure is 100MPa or more, and, according to the solid ²⁹ Si-NMR spectrum for the signal area of ^{Q 2 + Q 3 + Q 4} (Q ² × 2 + Q ³ ) hollow silica particles having a signal area ratio [(Q ² × 2 + Q ³ ) / (Q ² + Q ³ + Q ⁴ )] of 0.15 or less .   The hollow silica particles according to claim 1, wherein, in powder X-ray diffraction measurement, the silica lattice spacing (d) does not show a peak at a diffraction angle (2θ) corresponding to a range of less than 1 nm. The hollow silica particles according to claim 1 or 2 , having a dielectric constant of 1.2 to 2.0 and a dielectric loss tangent of 0.01 or less. The manufacturing method of the hollow silica particle in any one of Claims 1-3 which has following process (I)-(III).
Step (I): An aqueous solution containing a hydrophobic organic compound (a) comprising a hydrocarbon having 7 or more carbon atoms, a quaternary ammonium salt (b), and a silica source (c) that produces a silanol compound by hydrolysis. Step (II): The aqueous solution obtained in Step (I) is stirred at a temperature of 10 to 100 ° C., has an outer shell composed of silica, and has a hydrophobic organic compound (a Step of preparing an aqueous dispersion of core-shell type silica particles having a step) (III): The core-shell type silica particles are separated from the aqueous dispersion obtained in step (II), and calcined at a temperature of 950 ° C. or higher. Process for obtaining hollow silica particles