Hollow inorganic particle material and method for producing the same, inorganic filler, slurry composition, and resin composition

Abstract

The present invention addresses the problem of providing a method for producing a hollow inorganic particle material which has a sufficiently low relative dielectric constant and a sufficiently low dielectric loss tangent, and contains a small amount of ionic impurities. A method for producing a hollow inorganic particle material according to the present invention comprises: a core material dispersion liquid preparation step in which a core material dispersion liquid is prepared by dispersing a core material into a base liquid that is a mixture of a nonionic surfactant and a dispersion medium that contains water and optionally contains an aqueous solvent; a composite body formation step in which a hydrolysis product of a hydrolyzable silane is mixed and stirred in the core material dispersion liquid, thereby forming an adsorption composite body wherein the hydrolysis product is adsorbed on the surface of the core material; a core-shell composite body formation step in which a core-shell composite body is obtained by performing a condensation polymerization reaction of the hydrolysis product of the adsorption composite body in the base liquid; and a firing step in which the core material is removed by firing the core-shell composite body.

Description

[Technical Field]

[0001] The present invention relates to a hollow inorganic particle material and a method for producing the same, an inorganic filler, a slurry composition, and a resin composition. [Background technology]

[0002] As information devices become smaller, denser, and faster, semiconductor components are required to transmit signals with low loss and delay. Low power consumption and low drive voltages are also becoming increasingly important. To meet these requirements, electronic materials, particularly resin compositions used in rewiring layers and circuit boards, must simultaneously satisfy low dielectric constants, low dielectric dissipation factors, and low thermal expansion coefficients. Adding silica as a filler to resin compositions can impart a low thermal expansion coefficient that cannot be achieved with resin alone, but improvements in dielectric properties have plateaued.

[0003] Therefore, studies have been conducted to achieve a low dielectric constant and a low dielectric loss tangent while maintaining the thermomechanical properties of silica by using a composite material of air and silica, so-called hollow silica, as a filler, and various proposals have been made (see, for example, Patent Documents 1 to 3). Various proposals have also been made regarding the hollow silica used here, and hollow silica materials with good dielectric properties have been proposed with use in electronic materials in mind (see, for example, Patent Documents 4 to 8). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-056158 [Patent Document 2] Patent No. 5199569 [Patent Document 3] Patent No. 5864299 [Patent Document 4] Patent No. 4112540 [Patent Document 5] Patent No. 5513364 [Patent Document 6] International Publication No. 2021 / 172294 [Patent Document 7] Japanese Patent Publication No. 2021-143089 [Patent Document 8] Patent No. 6595898 [Patent Document 9] Patent No. 6004435 [Patent Document 10] Japanese Patent Application Laid-Open No. 2008-063209 [Patent Document 11] Special Publication No. 1-55201 [Non-patent literature]

[0005] [Non-Patent Document 1] "Hollow Silica as an Optically Transparent and Thermally Insulating Polymer Additive" Langmuir 216, 32, 338-345 [Non-patent document 2] "Ultrastable Mesostructured Silica Vesicles" Science 1998, 282, 1302-1305 [Non-patent document 3] "Nanostructure Control of Fine Particles and Their Application to Functional Materials" Journal of Smart Processing Society 2016, 5, 342-349 [Non-patent document 4] "The Formation of Well-Defined Hollow Silica Spheres with Multilamellar Shell Structure" Advanced Materials 2003, 15, 1097-1100 [Non-Patent Document 5] "Glycol-Modified Silanes in the Synthesis of Mesoscopically Organized Silica Monoliths with Hierarchical Porosity" Chemistry of Materials 2005, 17, 4262-4271 Summary of the Invention [Problem to be solved by the invention]

[0006] However, even though conventional hollow inorganic particle materials exhibit sufficient values ​​for the dielectric constant and dielectric loss tangent, they lack the necessary properties for use as fillers in electronic materials, making them unusable in practice. For example, those manufactured using inorganic salts as raw materials or catalysts inevitably have high concentrations of ionic impurities, making it impossible to ensure sufficient insulation.

[0007] Furthermore, materials that use salts containing halogens (especially chlorine) as raw materials inevitably have a high halogen content and poor long-term corrosion resistance. These impurities also affect the manufacturing conditions of the resin composition, making them a problem that cannot be used as a simple replacement for conventional silica fillers for electronic materials with a solid structure.

[0008] In addition, some hollow inorganic particle materials have a high porosity in order to reduce the relative dielectric constant and dielectric loss tangent to the required level, but these generally have poor mechanical properties and tend to break during kneading during the production of the resin composition, and as a result, some do not maintain the expected hollow structure in the resin composition.

[0009] Furthermore, while conventional manufacturing methods provide excellent hollow silica performance, they require the use of compounds that are toxic to the reaction as essential materials, making manufacturing control difficult, and many of them require special equipment, making industrial-scale manufacturing generally difficult, and in principle, making it difficult to scale up. Thus, from an industrial perspective, it is desirable to provide a method that allows mass production using simpler steps.

[0010] The present invention has been made in view of the above problems, and provides a material having a sufficiently small relative dielectric constant and a sufficiently small dielectric loss tangent, Composed of alkali metals and alkaline earth metals The problem to be solved is to provide a new hollow inorganic particle material having a low level of ionic impurities comparable to that of silica fillers for electronic materials having a solid structure. [Means for solving the problem]

[0011] Hollow inorganic particle materials are almost always produced by "template synthesis." That is, silica is deposited and polymerized on the outside or inside of a template (mold) with a morphology similar to the desired particle shape, and then the template is removed. Various template methods are known, broadly classified into those in which a silica layer is formed on the outer periphery of a core material according to the size of the voids, using core-shell particles as a precursor; those in which silica is grown within the W phase of O / W / O type micelles; and those in which a silica layer is formed inside a removable coating formed on the surface of droplets. Of these, the most commonly used method is the one in which core-shell particles are used as precursors. The hollow inorganic particle material of the present invention can also be said to be produced by template synthesis using core-shell particles as precursors.

[0012] Known techniques for forming shell layers often use the Stober method, which involves hydrolyzing orthosilicate esters such as tetraethoxysilane (TEOS) or tetramethoxysilane (TMOS) with a base catalyst. To grow particles using the Stober method, the orthosilicate ester concentration must be kept low and the reaction must proceed slowly. This is because a high reaction rate biases the reaction toward silica nucleation, making it more likely to produce colloidal silica. For example, in Non-Patent Document 1, a shell layer thickness of 24 nm was achieved by adding TMOS at a concentration of 80 mmol / L over approximately six hours.

[0013] Increasing the thickness of the shell layer using conventional methods requires the addition of alkali metals, etc. This makes it easy to create a material with a high porosity, but it also has the disadvantage of leaving a large amount of metal ionic impurities.

[0014] In contrast, the shell layer of the hollow particles in the present invention is derived from a silica structure with a three-dimensional regular structure, unlike the above-mentioned method. This silica structure has a structure in which silica is arranged in a structure corresponding to the microphase-separated structure of the surfactant described in the embodiment section. Specifically, it is a three-dimensional lamellar structure known as an L3 phase (or sponge phase) or a bicontinuous cubic phase (or gyroid phase). This structure is formed by the self-organization of the surfactant, and the resulting structure is determined by the concentration (initial concentration) and temperature. Patent Documents 9 and 10 and Non-Patent Document 2 disclose techniques for synthesizing silica particles with mesopores from this phase-separated structure. The inventors discovered that using this for the shell layer portion of core-shell particles formed by template synthesis allows the thickness of the shell layer to be increased without the need for adding unnecessary catalysts, and also enables the formation of a shell layer of a consistent thickness, leading to the completion of the following invention.

[0015] That is, the method for producing a hollow inorganic particle material of the present invention that solves the above-mentioned problems includes a core material dispersion preparation step of preparing a core material dispersion by dispersing a core material in a mother liquor that is a mixture of a nonionic surfactant and a dispersion medium that contains water and may contain an aqueous solvent;

[0016] a complex formation step of mixing a hydrolyzate of a hydrolyzable silane with the core material dispersion and stirring the mixture to form an adsorption complex in which the hydrolyzate is adsorbed on the surface of the core material;

[0017] a core-shell composite formation step in which a condensation polymerization reaction of the hydrolysate of the adsorption composite is carried out in the mother liquor to obtain a core-shell composite; a firing step of firing the core-shell composite to remove the core material; It has.

[0018] The hollow inorganic particle material of the present invention, which solves the above-mentioned problems, is a material that can be produced by the method for producing a hollow inorganic particle material of the present invention, has a hollow ratio of 20 volume % or more and 75 volume % or less, has a shell layer composed of an inorganic material, and the shell layer has a structure derived from a microphase separation structure.

[0019] The shell layer having a structure derived from a microphase-separated structure means that the shell layer morphology reflects a structure derived from a microphase-separated structure, which is a three-dimensional lamellar structure such as an L3 phase (or sponge phase) or a bicontinuous cubic phase (or gyroid phase). In this specification, the microphase-separated structure refers to a structure in which rod-like micelles with diameters ranging from 1 nm to 8 nm are connected three-dimensionally, forming a three-dimensional network structure, and multiple networks interpenetrate each other when viewed locally.

[0020] Specifically, whether the shell layer has a structure derived from a microphase separation structure can be determined by observing the surface, fracture surface, or cut edge of the shell layer with a transmission electron microscope (TEM), scanning transmission electron microscope (STEM), or scanning electron microscope (SEM). Specifically, minute changes in silica density appear as patterns derived from a microphase separation structure. In particular, it is preferable that 50% or more of the volume of the shell layer has a structure derived from a microphase separation structure. The microphase separation structure is preferably a sponge structure.

[0021] Another hollow inorganic particle material of the present invention that solves the above-mentioned problems is a hollow inorganic particle material having a hollowness of 20% by volume or more and 75% by volume or less and having a shell layer made of an inorganic material, The inorganic material contains 90% or more silica based on the mass of the total particulate material, The content of alkali metals, alkaline earth metals, halogens, and oxoacids is 10 ppm or less based on the mass of the entire particulate material, The volume average particle size of the primary particles is 100 nm or more and 5 μm or less. (Ionic impurity analysis method)

[0022] To determine whether the content of alkali metals, alkaline earth metals, halogens, and oxoacids is 10 ppm or less based on the total mass of the particulate material, 5 g of the sample to be extracted is immersed in 50 g of pure water and heated at 121°C for 20 hours in a sealed container. The precipitate is removed by filtration to prepare extracted water. The ion concentration in the extracted water is determined by the results of ion chromatography of the extracted water. [Effects of the Invention]

[0023] According to the present invention, there is provided a hollow inorganic particle material having a shell layer made of dense silica, which has a sufficiently small relative dielectric constant and dielectric dissipation factor, and which has a low content of ionic impurities comparable to that of a silica filler for electronic materials having a solid structure. Furthermore, according to the present invention, there is provided a hollow inorganic particle material which is resistant to penetration by resins and solvents when processed into electronic materials, and which can exhibit an excellent low relative dielectric constant and low dielectric dissipation factor even in a resin composition.

[0024] Furthermore, other than being inorganic particles with internal voids, they can have the same structure as ordinary inorganic particle materials (solid particle materials) that do not have internal voids. Therefore, compared to solid particle materials, there is no extreme increase in viscosity when processed into a varnish or resin masterbatch. It is also possible to make the hollow particle material, whether as it is or as a resin composition dispersed in a resin material, have the same handleability as solid particle materials or resin compositions using solid particle materials. [Brief explanation of the drawings]

[0025] [Figure 1] 1 is a scanning electron microscope (SEM) photograph of the hollow inorganic particle material obtained in Example 1. [Figure 2] 1 shows the particle size distribution of the hollow inorganic particle material obtained in Example 1. [Figure 3] 1 shows an infrared absorption spectrum of the surface-treated hollow inorganic particle material obtained in Example 1. [Figure 4]1 is a scanning electron microscope (SEM) photograph of a cross section of a resin composition using hollow inorganic particle material obtained in Example 1. [Figure 5] 1 shows the relative dielectric constant and the thermal expansion coefficient of a resin composition using a mixture of the hollow inorganic particle material obtained in Example 1 and Comparative Example 1. [Figure 6] 1 is a scanning electron microscope (SEM) photograph of the inorganic particulate material obtained in Comparative Example 2. [Figure 7] 1 is a scanning electron microscope (SEM) photograph of the inorganic particulate material obtained in Comparative Example 3. [Figure 8] 1 shows scanning electron microscope (SEM) images of inorganic particle materials obtained by varying the surfactant concentration, where the values ​​indicated in the figure represent the surfactant concentration during the synthesis reaction. [Figure 9] 1 is a scanning electron microscope (SEM) photograph showing a fine structure derived from a microphase separation structure observed in the shell layer of the hollow inorganic particle material obtained in Example 7. DETAILED DESCRIPTION OF THE INVENTION

[0026] The hollow inorganic particle material and its manufacturing method of the present invention will be described in detail below based on the following embodiments. The hollow inorganic particle material of this embodiment can be suitably used as an inorganic filler to be contained in a resin composition for electronic materials. For example, it can be contained in a resin composition used for a substrate material, a resin composition used for an encapsulant, a varnish, or a resin masterbatch. It may also be mixed with other inorganic particle materials to be used as an inorganic filler. The other inorganic particle materials can be mixed in a ratio of 50% to 800% based on the mass of the hollow inorganic particle material. Examples of other inorganic particle materials include alumina, zirconia, titania, and solid silica. It is preferable to use spherical inorganic particle materials as the other inorganic particle materials. (Hollow inorganic particle material) The hollow inorganic particle material of this embodiment has a shell layer made of an inorganic material, and the shell layer defines voids therein. The presence or absence of voids within the shell layer of the hollow inorganic particle material can be confirmed by observing the hollow inorganic particle material as is or in a cut state using a transmission electron microscope (TEM), a scanning transmission electron microscope (STEM), or a scanning electron microscope (SEM).

[0027] In the case of SEM observation, hollowness can be confirmed by observing the cross section of the resin-embedded particle, or by using an observation method that reflects the internal structure of the particle by increasing the accelerating voltage of the electron beam.

[0028] The hollow ratio is the ratio of the volume of voids present inside the hollow inorganic particle material to the total volume of the hollow inorganic particle material. Unless otherwise specified, the hollow ratio is the average value of all particles constituting the hollow inorganic particle material, and is calculated as the ratio of the sum of the void volumes to the sum of the volumes of the hollow inorganic particle material. Details of the calculation are described below. The dielectric constant required for hollow inorganic particle materials must be 3.4 or less, preferably 3.0 or less, more preferably 2.8 or less, and even more preferably 2.5 or less. The dielectric constant of silica, which constitutes the inorganic material, is 3.6 to 4.2. When this is combined with the dielectric constant of a vacuum (1.0), and the dielectric constant of hollow inorganic particle materials is calculated using the Maxwell-Garnett equation, which is used to predict the dielectric constant of composite materials, the higher the hollow fraction, the smaller the dielectric constant. The hollow fractions corresponding to dielectric constants of 3.4, 3.0, 2.8, and 2.5 are approximately 20%, 30%, 35%, and 45%, respectively. Therefore, the lower limit of the porosity is at least 20%, preferably 30%, more preferably 35%, and even more preferably 45%.

[0029] A higher hollow ratio results in a hollow inorganic particle material with a lower dielectric constant and dielectric loss tangent, but increasing the hollow ratio results in a thinner shell layer and reduced mechanical strength. To achieve sufficient mechanical strength, the upper limit of the hollow ratio is set to 75%, preferably 70%, and more preferably 65%. By setting the hollow ratio below this upper limit, sufficient mechanical strength can be maintained, effectively preventing breakage during handling of the hollow inorganic particle material or when mixing it with a resin material to form a resin composition. Since the hollow inorganic particle material is not broken, sufficient voids can be secured, allowing the required electrical properties to be achieved. These lower and upper limits can be arbitrarily combined. Specific examples of preferred lower limits for the shell layer thickness include 10 nm, 20 nm, 50 nm, and 100 nm, and examples of preferred upper limits include 300 nm, 200 nm, 150 nm, and 100 nm. These lower and upper limits can be arbitrarily combined.

[0030] Here, "having voids inside the shell layer" means that the particle has an area inside that is isolated from the outside by a shell layer through which molecules such as solvents and resins cannot pass. The shell layer that defines the voids may have so-called micropores that are sufficiently small compared to the particle size, but it must not have holes (mesopores and macropores) through which molecules such as solvents and resins can pass. Particles that do not have voids are called solid silica particle materials. The hollow inorganic particle material of this embodiment has one or more voids per particle.

[0031] The size of the pores is analyzed by measuring the true specific gravity using two types of probes (helium gas and nitrogen gas), one that passes through the micropores and one that does not. Micropores are pores that only helium gas can pass through, but nitrogen cannot.

[0032] The density (ρ He ) to determine the density ρ of the shell layer excluding the voids from the hollow inorganic particle material. shell (=ρ He ) can be determined. The density of the shell layer ρ shell is 2.1g / cm 3 More than 2.5g / cm3 Preferably, it is 2.2 g / cm or less. 3 More than 2.4g / cm 3 More preferably, it is:

[0033] The density (ρ N2 ) to determine the density ρ of the hollow inorganic particle material containing voids. particle (=ρ N2 ) can be determined. The void ratio is the density of the shell layer ρ shell and the density ρ of the hollow inorganic particle material particle Specifically, the hollowness can be calculated from {1-ρ N2 / ρ He}×100(%) (Calculation Method 1). The hollowness can be calculated by determining the particle size (D) and shell layer thickness (t) from a TEM or SEM image, and then calculating the hollowness ratio as (1-2t / D) 3 × 100 (%) (Calculation Method 2). In Calculation Method 2, except when it is necessary to calculate the hollowness ratio for individual particles, the average value of the measured values ​​of 1,000 or more hollow inorganic particle materials for particles that can be identified on the image is used.

[0034] For measuring the hollow ratio, calculation method 1 is used when 1 g or more of hollow inorganic particulate material can be measured independently. Calculation method 2 is used when the hollow ratio value for each particle of hollow inorganic particulate material is required. Calculation method 2 is used when the hollow inorganic particulate material to be measured is in a state filled in a resin composition, when there is only less than 1 g of sample, or when calculation method 1 cannot be used for other reasons.

[0035] The hollow inorganic particle material of this embodiment has a volume average particle size of 100 nm to 5 μm. The lower limit of the volume average particle size of the primary particles can be 100 nm, 120 nm, or 150 nm, and the upper limit can be 5 μm, 3 μm, 2 μm, or 1 μm. These lower and upper limits can be combined in any way.

[0036] The shell layer is composed of inorganic materials, but may contain unavoidably mixed organic materials. The inorganic material contains 90% by mass or more of silica. The proportion of silica in the inorganic material is preferably 95% by mass or more, more preferably 98% by mass or more, and even more preferably 99% by mass or more. Inorganic materials that can be contained other than silica are not particularly limited, but include metal oxides such as alumina, zirconia, and titania, metal nitrides, and oxo acids such as boric acid.

[0037] In the hollow inorganic particle material of this embodiment, the content of each of the 19 elements listed as Na, Mg, Al, P, K, Ca, Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Mo, Sb, B, and V is 100 ppm or less, preferably 50 ppm or less, more preferably 20 ppm or less, and even more preferably 10 ppm or less.

[0038] In the extracted water of the hollow inorganic particle material of this embodiment, the content of 13 types of cations and anions listed as F, Cl, NO2, Br, NO3, SO4, PO4, Li, Na, NH4, K, Mg, and Ca is 10 ppm or less, preferably 5 ppm or less, more preferably 2 ppm or less, and even more preferably 1 ppm or less.

[0039] By setting the amount of inorganic components other than silicon to this upper limit or less, it is possible to reduce the amount of ionic impurities extracted from the hollow inorganic particle material of this embodiment. In particular, by setting the amount of alkali metal ions and alkaline earth metal ions to this upper limit or less, it is possible to improve insulating properties. By setting the amount of halogen ions to this upper limit or less, it is possible to sufficiently suppress the occurrence of wiring corrosion due to the infiltration / diffusion of halogens into products when the hollow inorganic particle material of this embodiment is used as a filler for electronic materials. By setting the amount of oxo acid ions to this upper limit or less, it is possible to sufficiently reduce the amount of oxo acid that exists as free oxo acid and does not form a shell layer as a complex oxide, thereby improving insulating properties and corrosion resistance.

[0040] In the hollow inorganic particle material of this embodiment, the uranium (U) and thorium (Th) contents are each 5 ppb or less, preferably 3 ppb or less, more preferably 2 ppb or less, and even more preferably 1.5 ppb or less.

[0041] By keeping the amount of these radioactive elements below this upper limit, when the hollow inorganic particle material of this embodiment is used as a filler for electronic materials, it is possible to reduce malfunctions (soft errors) of semiconductor devices caused by alpha rays generated within the product to a level that cannot be distinguished from soft errors caused by alpha rays originating from other components or cosmic radiation. Surface area and dielectric properties of hollow inorganic particle materials The dielectric constant has been described above, but considering the applications of the hollow inorganic particles of the present invention, the dielectric loss tangent must also be sufficiently low. The dielectric loss tangent is evaluated in the composite material to be used, but it is desirable that the dielectric loss tangent of the hollow inorganic particle material alone is 0.01 or less, preferably 0.005 or less, more preferably 0.003 or less, and even more preferably 0.002 or less.

[0042] Generally, silanols exist on the grain boundaries and surfaces of silicon dioxide, which cause deterioration of the dielectric properties. In particular, the influence on the dielectric loss tangent is large, and 10 -4 About 10 -1 Therefore, normalizing the dielectric tangent using the specific surface area is thought to provide an index for determining the quality of the surface condition of silicon dioxide, and the index F = tanδ / SSA (g / m 2 ) (tanδ: dielectric tangent (dimensionless), SSA: specific surface area (m 2 / g)).

[0043] Considering the characteristics of the components in which the hollow inorganic particle material of this embodiment is used, it is desirable that the dielectric loss tangent for the filler be 0.01 or less. The condition for achieving this value at the maximum particle diameter of 2 μm (which gives the smallest specific surface area) was set as the upper limit of the index F. Specifically, for solid silica, the theoretical specific surface area at this time is approximately 1.5 m. 2 / g, so the upper limit of index F is 7 × 10-3 g / m 2 was set as the preferred value. Surface treatment of hollow inorganic particle materials The hollow inorganic particle material of this embodiment can be subjected to a surface treatment, which is expected to improve the dielectric properties and affinity with other materials.

[0044] The first purpose is to eliminate silanol groups remaining on the surface of hollow inorganic particles by so-called capping. For example, surface treatment agents containing trimethylsilyl groups, more specifically methoxytrimethylsilane and hexamethyldisilazane (HMDS), can be used.

[0045] As a second objective, a surface treatment agent that can improve the affinity between the material and the final contacting material can be used. For example, a silane compound can be used as the surface treatment agent. Examples of silane compounds include those having functional groups such as alkyl groups, vinyl groups, phenyl groups, methacryl groups, and epoxy groups, as well as alkyl groups having these groups on the side chain. More specifically, examples include, but are not limited to, methyltrialkoxysilane, dimethyldialkoxysilane, phenyltrialkoxysilane, dialkoxydiphenylsilane, n-propyltrialkoxysilane, hexyltrialkoxysilane, octyltrialkoxysilane, decyltrialkoxysilane, 3,3,3-trifluoropropyltrialkoxysilane, vinyltrialkoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrialkoxysilane, 3-glycidoxypropylmethyldialkoxysilane, 3-glycidoxypropyltrialkoxysilane, p-styryltrialkoxysilane, 3-methacryloxypropylmethyldialkoxysilane, 3-methacryloxypropyl Various companies sell propyltrialkoxysilane, 3-acryloxypropyltrialkoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldialkoxysilane, N-2-(aminoethyl)-3-aminopropyltrialkoxysilane, 3-aminopropyltrialkoxysilane, N-phenyl-3-aminopropyltrialkoxysilane, 3-ureidopropyltrialkoxysilane, 3-mercaptopropylmethyldialkoxysilane, 3-mercaptopropyltrialkoxysilane, 3-isocyanatopropyltrialkoxysilane, 3-trialkoxysilylpropylsuccinic anhydride, and the like (alkoxy is a functional group derived from an alcohol such as methoxy, ethoxy, or isopropoxy). (Method for producing hollow inorganic particle material) The method for producing a hollow inorganic particle material of this embodiment is a method that can suitably produce the hollow inorganic particle material of this embodiment described above, and is a method for producing a hollow inorganic particle material by using a core-shell particle as a precursor, the core of which is a core material and the shell of which is silica, removing the core from the precursor and extracting the shell.

[0046] The method for producing hollow inorganic particle material of this embodiment includes a core material dispersion preparation step, a composite formation step, a core-shell composite formation step, a firing step, and other necessary steps. <Core material dispersion preparation process> The core material dispersion preparation step is a step of dispersing a core material in a mother liquor to prepare a core material dispersion. The mother liquor is a mixture of a surfactant and a dispersion medium, to which a catalyst (typically, but not limited to, an acid or alkali) that promotes silica polymerization is added as needed. The core material may be dispersed after the mother liquor is prepared, or the core material may be dispersed during the preparation of the mother liquor. In other words, the order in which the surfactant, core material, and dispersion medium are mixed is not particularly limited. The catalyst that promotes silica polymerization may be added when preparing the mother liquor, after preparing the mother liquor, simultaneously with the addition of the hydrolyzable silane compound, or after the addition of the hydrolyzable silane compound has been completed.

[0047] In the core material dispersion, the surfactant forms a three-dimensional lamellar structure (hereinafter abbreviated as "microphase-separated structure") called an L3 phase (or sponge phase) or a bicontinuous cubic phase (or gyroid phase), and becomes adsorbed onto the surface of the core material.

[0048] The surfactant used in the production method of the present invention is not particularly limited, as long as it is a nonionic surfactant (nonionic surfactant) that can form a microphase-separated structure when dissolved in water within an appropriate temperature and concentration range. Such nonionic surfactants may be used alone or in combination of two or more. Details of nonionic surfactants will be described later.

[0049] The dispersion medium may be water or an aqueous solvent containing water as a main component, as described below. The aqueous solvent is a solvent miscible with water and is selected from monoalcohols having 1 to 3 carbon atoms (methanol, ethanol, 1-propanol, 2-propanol), dialcohols (ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol), and trialcohols (glycerol), and may be a mixture of two or more of these.

[0050] The surfactant concentration is the concentration at which a microphase-separated structure is formed. The structure that a surfactant can adopt in water is a function of temperature and concentration, and varies depending on the surfactant. Therefore, the optimal temperature and concentration must be determined experimentally for each surfactant. For example, the optimal conditions for Pluronic surfactant (POE-POP block copolymer) L-64 were 1% to 20% by mass at 40°C. Core material By selecting the core material, it is possible to synthesize hollow inorganic particle materials of various sizes. Voids having a size and shape correlated with the size and shape of the selected core material are formed. Particulate materials that are dispersed in water or that can be dispersed in water are preferred as core materials. On the other hand, micelles or vesicles using surfactants and, if necessary, hydrophobic liquids are suitable in terms of size and shape, but it is difficult to maintain the shape of the core material when the reaction to form silica around the core material is allowed to proceed, so it is preferable to use core materials made of particulate materials.

[0051] The core material is preferably made of an organic material that is easy to remove, and is particularly preferably made of a resin material. It is preferable that the core material be made of a resin material and that the core material made of the resin material be removed by baking. For example, a resin dispersed in water, such as a resin emulsion, is suitable as the core material.

[0052] Furthermore, as noted in Non-Patent Document 3, in order to create core-shell particles with the desired structure, the size and charge of the core material must be carefully selected. The size of the core material must be larger than the silica nucleus (the smallest unit of silica). This is because, due to differences in convection velocity, larger particles tend to gather more at the center. The smallest unit of the microphase-separated structure containing silicic acid oligomers between lamellar layers used in the reaction of this embodiment (the silica nucleus of this embodiment) is generally 10 nm or less, and a core material with a larger size is used. For example, particles of general resin emulsions are larger than 50 nm, which is preferable.

[0053] Generally, silica nuclei are weakly negatively charged. Therefore, if a material other than particles that is strongly negatively charged under the reaction conditions for producing silica nuclei is used as the core material, the repulsion between the periphery of the core material and the resulting silica nuclei is reduced, resulting in the formation of a suitable silica shell layer around the core material. Various experiments have shown that the surface potential in the mother liquor of a resin that is preferably used as the core material is -3 mV or higher, and more preferably 3 mV or higher. Resin emulsions with such properties may be synthesized by known methods, or commercially available products may be used. The type and method of obtaining the resin are not limited here. Surfactants The surfactant used in the method for producing hollow inorganic particle material of this embodiment will be described. The surfactant of this embodiment is a nonionic surfactant (nonionic surfactant) that forms a microphase-separated structure when dissolved in water within an appropriate temperature and concentration range. Compounds with such properties have a polar block (A) and a nonpolar block (B), and are classified according to the block structure into AB type having two blocks, ABA type having three blocks, or BAB type (there are many other types as well). There is no relationship between the block structure and the formation of a microphase-separated structure.

[0054] In order to form a microphase-separated structure, the size (formula weight) of the polar block (M A ) and "size (formula weight) of nonpolar block" (M B) must be comparable. This means that M A >M B This is because in the case of β-glucan, spherical or cylindrical micelles are likely to be formed, and in the case of β-glucan, so-called reverse micelles are likely to be formed.

[0055] In industry, A is often polyoxyethylene (POE, also known as polyethylene oxide or polyethylene glycol), and B is often polyoxypropylene (POP, also known as polypropylene oxide or polypropylene glycol), a long-chain alkyl group, or a long-chain carboxylic acid.

[0056] Examples of surfactants with such a structure include, but are not limited to, POE-monoalkyl ether and POE-monoester (both of which are examples of two-block type), POE-POP block copolymer and POE-diester (both of which are examples of three-block type). POE-POP block copolymers in particular are collectively known as Pluronic surfactants, and many products with different molecular weights and HLBs are commercially available under trademarks such as Pluronic, Poloxamer, and Pronon. HLB stands for Hydrophilic Lipophilic Balance, and in the Griffin method, it is 20×M A ÷(M A +M B ) is an index defined by the following. The HLB values ​​shown below are based on this definition. Here, M A is the formula weight of the A part (hydrophilic part) of the copolymer, M B means the formula weight of the B part (hydrophobic part) of the copolymer, and (M A +M B ) is the molecular weight of the entire copolymer.

[0057] Silica grows at the A site of the block copolymer. If the ratio of A to the entire molecule is small, the density of the shell layer is low, leaving many mesopores. On the other hand, if the ratio of A is large, the silica layer alone stabilizes the particles, making it difficult for core-shell particles to grow. The optimal HLB range systematically determined for Pluronic surfactants was 6 or more and 14 or less. However, not all surfactants that meet these conditions can necessarily be used in this embodiment. In other words, verification and optimization of conditions are required regarding whether the desired microphase separation structure is obtained, whether a composite can be formed, and whether a dense shell layer can be formed by denucleation by calcination.

[0058] Examples of Pluronic surfactants include, but are not limited to, Pluronic L-122, P-123, P-103, P-104, P-105, L-92, P-94, P-84, P-85, L-72, L-75, L-62, L-64, P-65, L-42, L-43, L-44, L-33, L-34, L-35, L-23, 25R-2, 17R-2, 17R-3, and 17R-4. Equivalent and similar products are also sold by various companies.

[0059] Examples of surfactants other than Pluronic type include, but are not limited to, POE-sorbitan fatty acid esters (e.g., POE-sorbitan monooleate, POE-sorbitan monostearate, POE-sorbitan monooleate, POE-sorbitan tetraoleate, etc.), POE-sorbit fatty acid esters (e.g., POE-sorbit monolaurate, POE-sorbit monooleate, POE-sorbit pentaoleate, POE-sorbit monostearate, etc.), Examples of the POE-glycerin fatty acid esters include POE-monooleates such as POE-glycerin monostearate, POE-glycerin monoisostearate, and POE-glycerin triisostearate, etc., POE-fatty acid esters (e.g., POE-distearate, POE-monodioleate, and ethylene glycol distearate), and POE-alkyl ethers (e.g., POE-lauryl ether, POE-oleyl ether, POE-stearyl ether, POE-behenyl ether, POE-2-octyldodecyl ether, and POE-cholestanol ether).

[0060] Examples of the use of nonionic surfactants in hollow particle synthesis can be found in Patent Document 6 and Non-Patent Document 4. While both techniques utilize the tendency of silica to grow at the A-site of a block copolymer, their fundamental objectives are different. In the prior art, surfactants are used to generate swollen micelles, i.e., oil-in-water emulsions, or to accumulate on the surface of oil droplets by dissolving the B-site of surfactant molecules with silica adsorbed at the A-site into the oil droplets, resulting in the formation of a shell layer made of silica on the micelle surface. In other words, these techniques do not aim to utilize a microphase-separated structure, which is a three-dimensional lamellar structure, and are therefore different from the technology described in this embodiment. <Complex formation process> The complex formation step is a step in which a hydrolyzate of a hydrolyzable silane is mixed with a core material dispersion and stirred to form an adsorption complex in which the hydrolyzate is adsorbed onto the surface of the core material. When the hydrolyzate of a hydrolyzable silane is added, it is added as a hydrolyzable silane, and the hydrolysis reaction can proceed in the core material dispersion to form the hydrolyzate.

[0061] The resulting hydrolyzate is adsorbed onto the polar block A of the surfactant attached to the surface of the core material, and polymerizes between the lamellae to form silicate oligomers. As a result, the silica-surfactant complex, templated by the microphase-separated structure, forms an adsorption complex that accumulates on the surface of the core material. Hydrolyzed products of hydrolyzable silanes An example of a hydrolyzable silane is orthosilicate ester. Hydrolyzable silanes become hydrolyzates through hydrolysis. Commonly used orthosilicate esters include TEOS and TMOS. TEOS and TMOS are oil-soluble, and if used as is, they will destroy the microphase separation structure of the surfactant. In addition, while their contact area with water is small, the parts that come into contact with water hydrolyze extremely quickly, resulting in the production of amorphous silica. As a result, the yield of particles with a hollow structure was extremely low.

[0062] In the Stober method, a mixture of TEOS, TMOS, or other compounds with an alcohol is used to make the compound compatible with water and reduce the reaction rate. However, the reaction cannot be controlled sufficiently, and the yield of silica with the desired structure is still insufficient when the amount required for the reaction is added all at once, as in the case of using compounds with a dialcohol or trialcohol group in the side chain as an orthosilicate ester (discussed below).

[0063] Therefore, as disclosed in Patent Document 10 and Non-Patent Document 5, an orthosilicate ester having a group having a dialcohol or trialcohol in the side chain was used. Such a compound has improved compatibility with water and can significantly reduce the reaction rate with water. As a result, the yield of silica having the desired structure derived from a microphase-separated structure can be increased.

[0064] Examples of orthosilicate esters that employ a group having a dialcohol or trialcohol in the side chain include compounds represented by Si(OR). Each of the four Rs can be determined independently, with at least one being a polyhydric alcohol residue and the others being alkyl groups. The polyhydric alcohol residue is represented by a polyhydric alcohol in which one hydroxyl group has been removed. Such orthosilicate esters can be prepared by a substitution reaction between a tetraalkoxysilane and a polyhydric alcohol. The polyhydric alcohol residue represented by R varies depending on the type of polyhydric alcohol used. For example, when ethylene glycol is used as the polyhydric alcohol, R is -CHCHOH. It is sufficient that at least one of the Rs be a substituted polyhydric alcohol residue, and the others may be unsubstituted alkyl groups.

[0065] Examples of the polyhydric alcohol residue for R include ethylene glycol residue, diethylene glycol residue, triethylene glycol residue, tetraethylene glycol residue, polyethylene glycol residue, propylene glycol residue, dipropylene glycol residue, polypropylene glycol residue, butylene glycol residue, hexylene glycol residue, glycerin residue, diglycerin residue, polyglycerin residue, neopentyl glycol residue, trimethylolpropane residue, pentaerythritol residue, maltitol residue, etc. Among these, R1 is preferably any one of an ethylene glycol residue, propylene glycol residue, butylene glycol residue, and glycerin residue.

[0066] There are no particular limitations on the method for synthesizing such orthosilicate esters, but they can be synthesized from an orthosilicate ester such as TEOS or TMOS and the above-mentioned polyhydric alcohol as raw materials by a transesterification reaction using an acid catalyst, as disclosed in, for example, Patent Document 10 (proton-type cation exchange resin) and Non-Patent Document 5 (hydrochloric acid). To facilitate the availability of high-purity compounds and to avoid introducing halogens into the product, the acid used as the catalyst is preferably an oxoacid such as boric acid, phosphoric acid, nitric acid, or sulfuric acid, or a carboxylic acid such as acetic acid. <Core-shell composite formation process> The core-shell composite formation process involves carrying out a condensation polymerization reaction of the hydrolyzate present on the surface of the adsorption composite in a mother liquor to obtain a core-shell composite. A core-shell composite is a core material in which a shell (shell layer) consisting of a condensate of a hydrolyzate of a hydrolyzable silane is formed on the surface of the core material. The condensation of the hydrolyzate can be effectively promoted by heating the mixture after hydrolyzing the hydrolyzable silane. If necessary, the reaction can be accelerated by adding an acid or base as a catalyst. <Firing process> The calcination process involves calcining the core-shell composite to decompose and remove the core material and surfactant encapsulated in the shell layer. This process also simultaneously densifies the shell layer. The conditions are not particularly limited as long as they decompose and remove the core material without destroying the shell layer formed on the surface of the core material, and examples include heating in an oxidizing atmosphere. For example, calcination can be performed in air at a temperature and for a time sufficient to decompose and remove the core material. Examples of calcination temperatures include 700°C or higher, 800°C or higher, 900°C or higher, 1000°C or higher, and 1100°C or higher. While a higher calcination temperature is preferable, it should be below the temperature at which the silica constituting the hollow inorganic particle material aggregates or melts. Even if aggregation occurs, aggregation is acceptable if it can be separated into primary particles by a crushing operation. Since the core-shell composite is produced while immersed in the mother liquor, a separation process from the mother liquor can be performed before the calcination process. For example, processes such as filtration, centrifugation, and drying can be used. <Control of shell thickness and size of hollow inorganic particle material> To summarize the method for producing hollow inorganic particle materials according to this embodiment, the thickness of the shell layer can be increased by increasing the ratio of the amount of hydrolyzable silane to the amount of core material, by using a core material with a high surface potential, or by using a surfactant with a high HLB and / or molecular weight. The size of the hollow inorganic particle material can be controlled by controlling the size of the core material, by controlling the thickness of the shell layer, or by a combination of these. (Slurry Composition)

[0067] The slurry composition of this embodiment is a composition in which the hollow inorganic particle material of this embodiment described above is dispersed in a dispersion medium. The slurry composition of this embodiment can be used for electronic materials such as semiconductor substrate materials, and is particularly preferably used for high-frequency substrate materials. The dispersion medium is substantially free of moisture, and in particular, the moisture content is preferably 1000 ppm or less, and more preferably 500 ppm or less.

[0068] The mixing ratio of hollow inorganic particle material to dispersion medium in the slurry composition is not particularly limited, but the content of hollow inorganic particle material is preferably as high as possible. Note that the viscosity tends to increase as the amount of hollow inorganic particle material mixed increases, so the hollow inorganic particle material can be mixed until the viscosity is as high as possible, taking into consideration handleability. For example, the hollow inorganic particle material:dispersion medium mass ratio can be about 20:80 to 80:20.

[0069] The dispersion medium is not particularly limited, but examples thereof include organic solvents such as silicone oil, methyl ethyl ketone, alcohol, and hexane, and resin precursors such as epoxy resin precursors, polyester precursors, and silicone resin precursors.

[0070] The hollow inorganic particle material is preferably surface-treated, and the surface treatment preferably introduces a functional group that can improve the affinity between the hollow inorganic particle material and the dispersion medium used and the mating member with which the hollow inorganic particle material will come into contact when finally used. (Resin composition) The resin composition of the present embodiment is a cured product comprising the hollow inorganic particle material and a resin material in which the hollow inorganic particle material is dispersed. The resin material preferably has a water content of 1000 ppm or less, more preferably 500 ppm or less.

[0071] The resin composition is preferably used for electronic materials, and as such electronic materials, it is preferably applied to those used for high frequency applications such as high frequency substrates. Since the hollow inorganic particle material of this embodiment has a low Df value, it is suitable for applications where high frequency is applied. Even if it is used, the occurrence of loss can be reduced.

[0072] The mixing ratio of the hollow inorganic particle material to the resin material in the resin composition is not particularly limited, but the content of the hollow inorganic particle material is preferably as high as possible. For example, the hollow inorganic particle material and the resin material can be mixed at a mass ratio of about 10:90 to 90:10. The resin material is not particularly limited, but examples include common resin materials such as thermosetting resins (which may be mixed in either an uncured or cured state) and thermoplastic resins, such as epoxy resins, melamine resins, acrylic resins, polycarbonate resins, polyesters, silicone resins, liquid crystal polymers (LCPs), polyimides, cyclic olefin polymers (COPs), and polyphenylene oxides (PPOs). The resin material may be used alone or in combination with a plurality of resin materials (such as alloys). The resin material preferably has a moisture content of 1000 ppm or less, and more preferably 500 ppm or less.

[0073] The hollow inorganic particle material is preferably surface-treated, and the surface treatment preferably involves introducing a functional group that can improve affinity with the resin material used. [Example]

[0074] The hollow inorganic particle material and the method for producing the same of the present invention will be described in detail below with reference to examples. (Analysis method) Unless otherwise expressly specified in this specification, each analysis is carried out by the following method. (1) Particle size distribution Optical particle size distribution measurement is the simplest method for analyzing the aggregation state of primary particles. However, since the refractive index of the hollow inorganic particles of the present invention differs from that of the inorganic substance that constitutes them, the obtained average particle size exhibits a value that deviates from the true average particle size. Therefore, optical particle size distribution measurement is performed to analyze the aggregation state of particles, and the average particle size is determined by image analysis. (1a) Analysis of aggregation state The particle size distribution was measured under the following conditions using a laser diffraction particle size distribution analyzer (Shimadzu SALD-7500nano). Dispersion medium: Isopropyl alcohol Refractive index: 1.45 Calculation mode: Volume (1b) Average particle size A slurry of hollow inorganic material is dropped onto a silicon wafer and dried, ensuring that the particles adhere in a single layer. This is then observed with a scanning electron microscope (SEM). SEM images are observed at a magnification that allows for approximately 100 to 1000 particles to be observed in one field of view, and the sizes of a total of approximately 1000 particles obtained from one to ten fields of view are measured. Based on this, the volumetric particle size distribution is determined, and the particle size at which the cumulative frequency of the volumetric particle size distribution is 50% is taken as the average particle size.

[0075] This can be done using image layer analysis software such as "Azokun" (Asahi Kasei). No specific method is specified here. (2) Porosity To measure the hollowness, (2a) a gas hydrometer is used when 1 g or more of hollow inorganic particle material can be measured independently. When the material is filled into a resin composition, when there is less than 1 g of sample, or when calculation method 1 cannot be used, (2b) image analysis of SEM images is used. (2a) Gas hydrometer The density was measured using a gas type hydrometer (Micrometrics AccuPycII 1340) under the following measurement conditions. Sample cell: 10cm 3 cell Sample weight: 1 to 3g Measurement gas: Helium and nitrogen Purge: 10 times, 135kPa(G) Measurement: 10 times, 135kPa(G) The same sample is measured by switching between helium and nitrogen. Helium can reach the inner cavity of hollow inorganic particles through micropores, so the density (ρ He ) represents the density of the shell layer. On the other hand, the density when nitrogen is used (ρ N2 ) represents the density of hollow inorganic materials. Therefore, the hollowness is {1 - ρ N2 / ρ He}×100(%). (2b) Image analysis From TEM (including STEM) or SEM images taken with the shell layer of the particle emphasized, the particle diameter (D) of each particle was determined using the same method as described for the average particle diameter, and the shell layer thickness (t) was also recorded. The value calculated for each particle using the formula below, or the average value calculated for 1,000 or more particles when looking at powder properties, is used. (1-2t / D) 3 ×100(%) TEM (including STEM) images are ideal for this analysis, but a simpler method is to use a scanning electron microscope (Hitachi SU8000) under the following conditions, which will allow SEM images to be recorded that highlight the shell layer. Acceleration voltage: 10kV Probe distance: 15mm Detectors: Lower detector and SE detector

[0076] (3) Specific surface area The hollow inorganic particle material of this embodiment was dried under reduced pressure at 200° C. to prepare a sample. This sample was subjected to multipoint BET specific surface area and pore volume measurement, or single-point BET specific surface area measurement, using nitrogen gas with an automatic specific surface area / pore distribution measurement device (Tristar II manufactured by Micrometrics).

[0077] (4) Silica purity A mixture of nitric acid, sulfuric acid, and hydrofluoric acid was added to the hollow inorganic particle material of this embodiment and heated to 120°C for dissolution. This solution was heated to 300°C to remove the nitric acid and hydrofluoric acid, creating a sample solution. This was then appropriately diluted and quantitatively analyzed by ICP atomic emission spectroscopy (Agilent Technologies 5110 ICP-OES). The contents of 19 elements, listed as Na, Mg, Al, P, K, Ca, Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Mo, Sb, B, and V, were calculated based on the mass of the hollow inorganic particle material used for dissolution. The amounts of U and Th were also quantified using the same sample by ICP-MS (Agilent Technologies 7800 ICP-MS).

[0078] (5) Ionic impurities 5 g of hollow inorganic particle material according to this embodiment was immersed in 50 g of pure water and heated in a sealed container at 121°C for 20 hours. The precipitate was removed by filtration to prepare an extract. The ion concentration of the extract was quantified using ion chromatography (Dionex, Thermo Scientific). The content of 13 types of cations and anions, listed as F, Cl, NO, Br, NO, SO, PO, Li, Na, NH, K, Mg, and Ca, was calculated based on the mass of the immersed hollow inorganic particle material.

[0079] (6) Dielectric properties The dielectric properties of the powder were measured using an 8mm diameter x 30mm PTFE tube filled with hollow inorganic particle material, and an empty tube was used as a control sample. Each was placed in a cavity resonator connected to a network analyzer, and the resonant frequency and Q value in the 1GHz band were determined. From these values, the complex permittivity was calculated using a "Perturbation Method Permittivity Calculation Application" (Keycom Co., Ltd.). In the case of the resin composition, a rectangular pillar approximately 4mm x 7mm x 30mm in size was cut out from the resin composition and used as the measurement sample. The complex permittivity was calculated using a state where the sample was not placed in the cavity resonator as a control.

[0080] (7) Thermal expansion coefficient A rectangular parallelepiped with a side length of approximately 4 mm was cut out from the resin composition and used as a measurement sample. This was heated from -50°C to 250°C at a rate of 5°C / min using a thermomechanical analyzer (TA Instruments TMA Q400), and the linear expansion was recorded. From the plot, the average rate of change from 0 to 50°C and from 180 to 220°C was determined as CTE1 and CTE2, respectively.

[0081] (Preparation of test samples) Example 1 Synthesis of Hydrolyzable Silanes 41 g of TEOS (JIS Grade 1), 60 g of propylene glycol (JIS Grade 1), and 5 mg of boric acid (JIS Grade 1) were placed in a flask and stirred at 80°C for 24 hours. The ethanol was distilled off, and 65 g of orthosilicate ester with propylene glycol side chains (PGMS; Propylene-Glycol Modified Silane) was recovered. Although a small amount of ethanol remained in this PGMS, it was used as is for the synthesis of core-shell particles. <Synthesis of core-shell particles> 1000 g of a mother liquor consisting of 10% by mass of an ABA block copolymer (HLB 7.9, average molecular weight 2900) and the remainder water was mixed with 6 g of acrylic resin (average particle size 300 nm, surface potential +52 mV) (core material dispersion preparation step). Subsequently, 50 g of PGMS was mixed and stirred (complex formation step). The reaction mixture was kept at 40°C for 36 hours to mature the core / shell particles (core-shell composite formation step). The resulting solid was filtered under reduced pressure using filter paper (JIS 5A), and the precipitate was collected. <Removal of cores by firing> The precipitate was heated to 1,000°C at a heating rate of 50°C / h and held at 1,000°C for 12 hours (calcination step). The recovered silica was loosely agglomerated, so it was lightly crushed in a mortar to obtain a hollow inorganic particle material, which was the test sample for this example. Example 2 A hollow inorganic particle material, which was a test sample for this example, was obtained by the same procedure as in Example 1, except that the concentration of the ABA block copolymer in the mother liquor was set to 5% by mass. Example 3 A hollow inorganic particle material, which was a test sample for this example, was obtained in the same manner as in Example 1, except that the concentration of the POE-POP block copolymer in the mother liquor was set to 2% by mass. Example 4 A hollow inorganic particle material, which was a test sample for this example, was obtained by the same procedure as in Example 1, except that a different ABA block copolymer (HLB 8.8, average molecular weight 1700) was used to prepare a mother liquor instead of the ABA block copolymer used in Example 1. Example 5 The hollow inorganic particle material used as the test sample for this example was obtained by the same procedure as in Example 1, except that a BAB block copolymer (HLB 8.0, average molecular weight 2700) was used to prepare the mother liquor instead of the ABA block copolymer used in Example 1. Example 6 The hollow inorganic particle material used as the test sample for this example was obtained by the same procedure as in Example 1, except that the mother liquor was prepared using an AB-type surfactant (HLB 12.4, average molecular weight 500) instead of the ABA-type block copolymer used in Example 1. Example 7 The hollow inorganic particle material, which was the test sample for this example, was obtained by the same procedure as in Example 4, except that 6 g of wax (average particle size 600 nm, surface potential +65 mV, solid content 60%) was used instead of the acrylic resin used in Example 4. Example 8 The hollow inorganic particle material, which is the test sample for this example, was obtained by the same procedure as in Example 7, except that 6 g of another wax (average particle size 1.7 μm, surface potential 4 mV) was used instead of the wax used in Example 7.

[0082] (Comparative Example 1) Commercially available silica particle material (manufactured by Admatechs Co., Ltd.; SO-C2) was used as is. (Comparative Example 2) <Synthesis of core-shell particles> 1000 g of a mother liquor consisting of 10% by mass of an ABA block copolymer (HLB 7.9, average molecular weight 2900), 30% by mass of ethanol, and the remainder water was mixed with 6 g of acrylic resin (average particle size 300 nm, surface potential +52 mV) (core material dispersion preparation step). Subsequently, 30 g of tetraethyl orthosilicate was added and mixed with stirring (complex formation step). Thereafter, calcined silica was obtained by carrying out the same operation as in Example 1. The recovered silica was a hard agglomerate, and was lightly crushed in a mortar to obtain Comparative Silica 2, which was the test sample of this comparative example. (Comparative Example 3) Calcined silica was obtained in the same manner as in Example 1, except that 6 g of wax (average particle size 300 nm, surface potential -7 mV) was used instead of the acrylic resin used in Example 1. The recovered silica was a hard agglomerate and was crushed in a mortar to obtain Comparative Silica 3, the test sample of this comparative example. Comparative Example 4 Comparative Silica 4, a test sample of this comparative example, was obtained by the same procedure as in Example 1, except that the calcination temperature was 600°C instead of 1000°C in Example 1. (Comparative Example 5) Comparative Silica 5, which was a test sample of this comparative example, was obtained by the same procedure as in Example 1, except that the concentration of the ABA block copolymer in the mother liquor was 1% by mass. (Comparative Example 6) Calcined silica was obtained by the same procedure as in Example 1, except that 1000 g of water was used as the mother liquid. The recovered silica was a hard agglomerate and was crushed in a mortar to obtain Comparative Silica 6, the test sample of this comparative example. (Comparative Example 7) Comparative Silica 7, the test sample of this comparative example, was obtained by the same procedure as in Example 1, except that a different ABA block copolymer (HLB 9.3, average molecular weight 4200) was used to prepare a mother liquor instead of the ABA block copolymer used in Example 1. (Comparative Example 8) Comparative Silica 8, the test sample of this comparative example, was obtained by the same procedure as in Example 1, except that a different ABA block copolymer (HLB 2.5, average molecular weight 2000) was used to prepare a mother liquor instead of the ABA block copolymer used in Example 1. (Comparative Example 9) Comparative Silica 9, the test sample of this comparative example, was obtained by the same procedure as in Example 1, except that a different ABA block copolymer (HLB 15.7, average molecular weight 8350) was used to prepare a mother liquor instead of the ABA block copolymer used in Example 1.

[0083] (evaluation) The appearance of the silica obtained in Example 1 is shown in Figure 1. It is clear that the silica obtained in Example 1 is a hollow inorganic particle material with a shell thickness of approximately 20 nm and particle sizes of approximately 220 nm and 110 nm. The reason it is a mixture of two particle sizes is because the core material used in template synthesis consists of two different particle sizes. This hollow inorganic particle material was suspended in isopropyl alcohol and subjected to French press processing (extrusion pressure 120 MPa), resulting in a homogeneous slurry composition. Figure 2(a) shows the particle size distribution obtained using a laser diffraction particle size distribution analyzer. A peak of approximately 95% cumulative frequency was observed near 0.15 μm. Figure 2(b) shows the particle size distribution obtained from the same sample by image analysis, with a volume average particle size of 0.18 μm. As such, it is clear that the hollow inorganic particle material of this example is dispersed in the slurry in the form of almost primary particles. This slurry was dried and re-pulverized, and the specific surface area and true specific gravity (ρ N2 ) were measured, and the results were 95 m 2 / g and 1.51 g / cm 3 The specific surface area was calculated from the theoretical specific surface area (22 m) calculated from the particle size and specific gravity (Table 1). 2 / g), which is presumably due to the presence of irregularities on the particle surface resulting from the microphase separation structure. He ) is 2.39 g / cm 3It was concluded that a substantially pore-free shell layer was formed. The void ratio was calculated to be 37%.

[0084] The slurry containing this hollow particle material was reacted with 5% by mass of N-phenyl-3-aminopropyltrimethoxysilane (phenylaminosilane) based on the solid content, and the solvent was then distilled off and the powder was dried. Figure 3 shows the infrared absorption spectrum of this powder measured by the diffuse reflectance method. Wavenumbers from 2800 to 3050 cm -1 There is a CH stretching vibration peak at 3745cm, which indicates that the surface has been treated with an organic silane compound (phenylaminosilane in this case). -1 has an OH stretching vibration peak identified as a silanol group. This hollow inorganic particle material has an area inside the particle that is isolated from the outside by a shell layer that molecules such as solvents and resins cannot pass through. Since the inside of the particle is not surface treated, the silanol groups present on the inner surface remain as they are, even if a sufficient amount of surface treatment agent is used. These can be identified as unreacted silanol groups. [Table 1]

[0085] The test samples of Example 1 and Comparative Example 1 were subjected to elemental analysis by ICP atomic emission spectrometry (Table 2) and ion analysis of the extracted water (Table 3). The results showed that the silica was highly pure and contained almost no elements other than silica, and the extracted water contained almost no ions that would be problematic for semiconductor applications. Comparative Example 1 was a solid silica synthesized by the deflagration method (Patent Document 11), which is commonly used in the field targeted by this technology. In comparison, Comparative Example 1 contained no particularly problematic elements and had significantly lower levels of impurities than the Comparative Example. The uranium and thorium contents were also low, at 1.3 ppb and 1.0 ppb, respectively. Furthermore, Table 4 lists the relative permittivity and dielectric loss tangent of the test sample of Example 1. Based on these properties, it can be said that the silica produced by this technology is fully suitable for semiconductor applications. [Table 2] [Table 3]

[0086] An epoxy resin composition was prepared containing 25% by mass of the material obtained in Example 1. This corresponds to a loading of approximately 40% by mass for the solid silica in Comparative Example 1. Figure 4 shows the cross section of a cut-out resin piece. Particles embedded inside the resin appear as white spheres, and particles present in the cross section have a dark depression within a white outline. No resin has infiltrated the interior of the hollow inorganic particles.

[0087] The hollow inorganic particle material of Example 1 and the solid silica of Comparative Example 1 were mixed in mass ratios of 1:2 (under conditions of approximately the same volume) and 1:1. A resin composition was prepared using this mixed powder, and the dielectric constant and thermal expansion coefficient of the resin pieces were determined (Figure 5). The dielectric constant decreased as the proportion of hollow inorganic particles increased. On the other hand, the thermal expansion coefficient showed almost constant values ​​for both CTE1 and CTE2. Therefore, hollow inorganic particles are suitable for applications that improve dielectric properties while maintaining thermomechanical properties.

[0088] In Examples 2 to 8, hollow inorganic particles were obtained, as in Example 1. On the other hand, in Comparative Examples 2 to 9, the particles obtained were not considered to be hollow inorganic particles, as they formed pumice-like aggregates and were not independent particles, did not form a sufficiently strong shell layer, or the shell layer was not sufficiently densified, resulting in the presence of mesopores penetrating to the lumen. Table 1 lists the classification of the particles obtained for these Examples and Comparative Examples, as well as the analysis results of the average particle size, specific surface area, true specific gravity, and hollowness for the particles obtained. Table 4 also lists the relative permittivity and dielectric loss tangent for the test sample of Example 1 surface-treated with HMDS and phenylaminosilane, and the test samples of Examples 4 and 7 surface-treated with HMDS. [Table 4]

[0089] Comparative Example 2 is an example where the Stober method was applied, and its appearance is shown in Figure 6. Although a shell layer appears to have formed, the primary particles were strongly bonded to each other and formed agglomerates that could not be disintegrated. Such sintering was not observed in Example 1. The key point of this technology is to adhere a sufficiently thick shell layer when forming core / shell particles by using a microphase-separated structure created by a surfactant. In contrast, when the Stober method was applied, the hydrolyzed product of the hydrolyzable silane was unable to adhere uniformly to the hydrophilic portions of the L3 phase lamellae that had been created, resulting in localized accumulation. In other words, it is believed that hydrolysis proceeded before the reaction solution became uniform.

[0090] Comparative Example 3 is a synthesis example using a core material with a surface potential of -7 mV, and its appearance is shown in Figure 7. As can be seen from this, the product is a waffle-shaped sintered body. Non-Patent Document 3 describes nanostructure control of fine particles during spray pyrolysis, explaining that porous silica is produced from a core material and silica nuclei with the same surface potential (negative in this case). Although this technology does not involve a spraying process, it is clear that a precursor that imparts a porous structure is produced in a homogeneous system as well. Therefore, it can be said that the surface potential of the core material must be sufficiently different from that of silica, preferably positively charged. On the other hand, Example 8 is a synthesis example using a core material with a surface potential of +4 mV, and inorganic hollow particles were obtained. From this, it can be inferred that the surface potential of the core material, which determines whether the desired inorganic hollow particles can be obtained, is around -3 mV, which is the midpoint between Comparative Example 3 and Example 8.

[0091] Comparative Example 4 was used to determine the firing conditions, and the true specific gravity was the same as that of silica. Although these particles appear to be the same as the inorganic hollow particles of Example 1, it is believed that the densification of the shell layer was incomplete and mesopores remained.

[0092] The effect of surfactant concentration can be compared in Examples 1-3 and Comparative Examples 5-6. The surfactant concentrations in these mother liquors were 10 mass%, 5 mass%, 2 mass%, 1 mass%, and 0 mass%, respectively. Figure 8 shows a comparison of the appearance of the silica produced under each condition. When the surfactant concentration was approximately 1 mass%, a large amount of amorphous silica was mixed in. In other words, under dilute conditions, the remaining hydrolyzate that could not be adsorbed by the hydrophilic portion of the surfactant accumulated and polymerized on its own. On the other hand, in the 0 mass% case, most of the silica was pumice-like sintered, with some hollowing out and then cracking. The thickness of the portion that appears to have covered the core material was approximately 5 nm, which is thought to have been too thin to withstand crushing. In the case of the 1% surfactant concentration, the hollow particles almost always had the desired structure, suggesting that the microphase-separated structure induced by the surfactant can form a sufficiently thick shell layer during core / shell particle formation. At the same time, the surfactant is also thought to have had the effect of suppressing sintering of particles during de-nucleation by calcination. It is known from public information that the L3 phase lamellar structure is formed at concentrations higher than 10 mass % on the high concentration side, but from an economical point of view, only tests were conducted up to 10 mass %.

[0093] Example 4 and Comparative Examples 7 to 9 are examples showing the effects when the molecular weight of the Pluronic surfactant and the size of the hydrophobic block are changed.

[0094] In Example 4 and Comparative Example 7, the effect of molecular weight was investigated using inorganic hollow particles with an HLB value similar to that of Example 1. The specific surface area of ​​the inorganic hollow particles in Example 4 was smaller than that of the other examples. In contrast, Comparative Example 7 had a significantly larger specific surface area. This can be explained as follows: The silica core of this embodiment has a microphase-separated structure containing silicic acid oligomers between lamellar layers formed when the hydrolyzed product of the hydrolyzable silane is adsorbed onto the polar blocks of the surfactant, and can be locally considered to be mesoporous silica. The surfactant is removed by calcination, leaving mesopores. Further calcination at high temperatures promotes densification of the shell layer. With surfactants with low molecular weights, the initially formed mesopores are small and easily densified by calcination. On the other hand, when a surfactant with a high molecular weight is used, large mesopores are produced, but the calcination conditions used in this study did not sufficiently collapse the mesopores, resulting in the remaining through-holes in Comparative Example 7. In Comparative Examples 8 and 9, the size of the hydrophilic block was the same, and the effect of HLB was compared. As is clear from these results, the desired hollow structure was not achieved regardless of whether the HLB was large or small. This is thought to be because the lamellar structure was unstable, and a micellar structure (when the hydrophilic block was large) or a reverse micellar structure (when the hydrophobic block was large) became the main constituent.

[0095] Example 5 uses a BAB-type block copolymer, and Example 6 uses an AB-type block copolymer. With both surfactants, hollow inorganic particles similar to those in Example 1 were obtained. As shown above, the block structure of the surfactant is not an issue, and the desired hollow structure can be obtained by appropriately selecting the HLB of the surfactant.

[0096] Examples 7 and 8 compare the effects of changing the size and material of the core material. As is clear from these examples, this technology makes it possible to change the particle size of inorganic hollow particles by changing the size of the core material. Furthermore, although not illustrated as an example, it is possible to produce inorganic hollow particles with different hollow ratios by changing the ratio of the amount of hydrolyzable silane to the core material.

[0097] The microstructure of the shell layer of the hollow inorganic particles of Example 7 is shown in Figure 9. (a) and (b) are images of the surface and inner surface of the hollow inorganic particles, respectively, and in both images, the spongy random structure derived from the L3 phase remains. (c) is an image of the cross section of a particle observed using a thin piece of resin containing hollow inorganic particles, and traces of the spongy random structure derived from the L3 phase are visible as a striped pattern on the edge (upper left). [Industrial Applicability]

[0098] The silica produced by the present technology can be suitably used as a filler to be added to semiconductor materials in terms of purity and dielectric properties.

Claims

1. A hollow inorganic particle material having a hollowness of 20% by volume or more and 75% by volume or less and a shell layer made of an inorganic material, the shell layer has a structure derived from a microphase separation structure, The inorganic material contains 90% or more silica based on the mass of the total particulate material, The content of alkali metals, alkaline earth metals, halogens, and oxoacids is 10 ppm or less based on the mass of the entire particulate material; The volume average particle size of the primary particles is 100 nm or more and 5 μm or less. Hollow inorganic particle material.

2. A hollow inorganic particle material having a hollowness of 20% by volume or more and 75% by volume or less and a shell layer made of an inorganic material, The inorganic material contains 90% or more silica based on the mass of the total particulate material, The shell layer has a structure derived from a microphase separation structure. The content of alkali metals and alkaline earth metals is 10 ppm or less, based on the mass of the entire particulate material. Hollow inorganic particle material.

3. A hollow inorganic particle material as described in claim 2, in which the content of halogens and oxoacids is 10 ppm or less, based on the mass of the entire particle material.

4. 4. The hollow inorganic particle material according to claim 1, wherein the uranium content is 5 ppb or less and the thorium content is 5 ppb or less.

5. General formula (1): R １ nSi(OR ２ ) （４－ｎ） and an alkoxysilane having the structure of general formula (2): (R １ ３ Si) ２ The hollow inorganic particle material according to any one of claims 1 to 4, which has been surface-treated with one or more surface treatment agents selected from the group consisting of silazanes having an NH structure (in the general formula, R 1 represents an alkyl group, a phenyl group, or a substituted alkyl or phenyl group; R 2 represents an alkyl group having 1 to 5 carbon atoms, or a group in which a part of the alkyl group is substituted with a hetero atom).

6. 6. The hollow inorganic particle material according to claim 1, which has a relative dielectric constant of 3.4 or less and a dielectric loss tangent of 0.01 or less as measured at 1 GHz.

7. Measurements at 1 GHz showed that the relative permittivity was 3.0 or less, the dielectric loss tangent was 0.006 or less, and the dielectric loss tangent per specific surface area was 4 x 10 -3 g / m 2 The hollow inorganic particle material according to claim 6, wherein:

8. The hollow inorganic particle material according to any one of claims 1 to 7, Other inorganic particle materials mixed in a ratio of 50% or more and 800% or less based on the mass of the hollow inorganic particle material; An inorganic filler comprising a mixture of inorganic particles having the above structure.

9. A method for producing the hollow inorganic particle material according to claim 1, comprising: a core material dispersion preparation step of preparing a core material dispersion by dispersing a core material in a mother liquor that is a mixture of a nonionic surfactant and a dispersion medium that contains water and may contain an aqueous solvent; a complex formation step of mixing a hydrolyzate of a hydrolyzable silane with the core material dispersion and stirring the mixture to form an adsorption complex in which the hydrolyzate is adsorbed on the surface of the core material; a core-shell composite formation step in which a condensation polymerization reaction of the hydrolysate of the adsorption composite is carried out in the mother liquor to obtain a core-shell composite; a firing step of firing the core-shell composite to remove the core material; A method for producing a hollow inorganic particulate material having the following structure:

10. A dispersion medium; The hollow inorganic particle material according to any one of claims 1 to 7 or the inorganic filler according to claim 8, which is dispersed in the dispersion medium in an amount of 5 mass % to 60 mass % based on the total mass; 1. A slurry composition comprising:

11. A resin material; The hollow inorganic particle material according to any one of claims 1 to 7 or the inorganic filler according to claim 8, which is dispersed in the resin material in an amount of 5 mass % to 60 mass % based on the total mass; A resin composition comprising:

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