Hollow inorganic particle materials and their manufacturing methods, inorganic fillers, slurry compositions and resin compositions

Abstract

The problem to be solved is to provide a method for manufacturing hollow inorganic particle materials with sufficiently small relative permittivity and dielectric loss tangent, and few ionic impurities. It comprises: a core material dispersion preparation step, in which the core material is dispersed in a mother liquor consisting of a mixture of a nonionic surfactant and a dispersion medium, wherein the dispersion medium includes water and may also include an aqueous solvent; a composite formation step, in which hydrolyzed silane is mixed with the aforementioned core material dispersion and stirred to form an adsorbed composite on the surface of the aforementioned core material with the aforementioned hydrolysate adsorbed; a core-shell composite formation step, in which the aforementioned hydrolysate of the adsorbed composite undergoes a polymerization reaction in the aforementioned mother liquor to obtain a core-shell composite; and a calcination step, in which the aforementioned core-shell composite is calcined to remove the aforementioned core material.

Description

Technical Field

[0001] The present invention relates to hollow inorganic particle materials and a manufacturing method thereof, inorganic fillers, slurry compositions and resin compositions. Prior Art

[0002] As information technology becomes increasingly compact, dense, and high-speed, semiconductor components require low-loss, low-latency signal transmission. Furthermore, low power consumption and low-voltage operation are becoming increasingly important. To meet these demands, electronic materials, particularly resin compositions used in redistribution layers and circuit boards, must simultaneously exhibit low relative permittivity, low dielectric loss tangent, and low thermal expansion. While adding silica as a filler to resin compositions can achieve a low thermal expansion coefficient that cannot be achieved with resin alone, this has reached its limits in terms of dielectric properties.

[0003] Consequently, the following research has been conducted, resulting in various proposals (see, for example, Patent Documents 1-3): Using a composite of air and silica, so-called hollow silica, as a filler, aims to achieve a low relative permittivity and dielectric loss tangent while maintaining silica's thermomechanical properties. Furthermore, various proposals have been made for hollow silica materials used in this process, including hollow silica materials with excellent dielectric properties, with consideration for use in electronic materials (see, for example, Patent Documents 4-8).

[0004] Patent Documents Patent Document 1: Japanese Patent Publication No. 2007-056158 Patent Document 2: Japanese Patent No. 5199569 Patent Document 3: Japanese Patent No. 5864299 Patent Document 4: Japanese Patent No. 4112540 Patent Document 5: Japanese Patent No. 5513364 Patent Document 6: International Patent Publication No. 2021 / 172294 Patent Document 7: Japanese Patent Publication No. 2021-143089 Patent Document 8: Japanese Patent No. 6595898 Patent Document 9: Japanese Patent No. 6004435 Patent Document 10: Japanese Patent Publication No. 2008-063209 Patent Document 11: Japanese Patent Publication No. H1-55201

[0005] Non-patent literature 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: "Application of Microparticles in Nanostructure Control and Functional Materials," Journal of Smart Processing 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

[0006] However, even if conventional hollow inorganic particle materials exhibited sufficient relative permittivity and dielectric loss tangent, they often lacked the necessary properties for use as fillers in electronic materials, effectively rendering them unusable. For example, the use of inorganic salts as raw materials or catalysts inevitably resulted in high concentrations of ionic impurities, making them incapable of guaranteeing adequate insulation.

[0007] Furthermore, using salts containing halogens (especially chlorine) as raw materials inevitably results in high halogen content and poor long-term corrosion resistance. These impurities also affect the manufacturing conditions of the resin composition, making simple replacement of conventional solid-core silica fillers for electronic materials impractical.

[0008] Furthermore, to reduce the relative dielectric constant and dielectric loss tangent to the necessary levels, some use hollow inorganic particles to increase the porosity. These generally have poor mechanical properties and can break during mixing during resin composition production. Consequently, some resin compositions fail to maintain the desired hollow structure.

[0009] Furthermore, conventional production methods have many challenges: while hollow silica offers excellent performance, the reaction requires the use of toxic compounds as essential raw materials, making production difficult to manage; specialized equipment is required, making industrial-scale production difficult; and scaling up is fundamentally difficult. Therefore, from an industrial perspective, there is a desire for methods that can achieve mass production using simpler processes.

[0010] The present invention is made in view of the above-mentioned problems. The problem to be solved is to provide a new hollow inorganic particle material with sufficiently small relative dielectric constant and dielectric loss tangent, and ionic impurities as low as those of silica fillers for electronic materials with solid structures.

[0011] Hollow inorganic particle materials are generally produced using "template synthesis (casting synthesis)." Specifically, silicon dioxide is deposited and polymerized on the outside or inside of a template (casting mold) with a shape close to the desired particle shape, and then the template is removed. Various template methods are well known. Broadly speaking, they include forming a silicon dioxide layer on the outer contour of a core material corresponding to the size of the voids to form a precursor for core-shell particles, growing silicon dioxide within the W phase of O / W / O micelles, and forming a silicon dioxide layer inside a removable film formed on the surface of a droplet. Among these methods, the most widely used method is to use core-shell particles as a precursor. The hollow inorganic particle materials of the present invention can also be said to be synthesized using templates used as precursors for core-shell particles.

[0012] The most commonly used method for forming a shell layer is the Stober method, which involves hydrolyzing orthosilicates such as tetraethoxysilane (TEOS) or tetramethoxysilane (TMOS) with an alkaline catalyst. Particle growth using the Stober method requires maintaining the orthosilicate concentration at a low level to allow for a slow reaction. This is because a high reaction rate tends to favor the formation of silica cores, easily producing silica gel. For example, in Non-Patent Document 1, a shell thickness of 24 nm was achieved by adding TMOS at a concentration of 80 mmol / L over approximately 6 hours.

[0013] Increasing the shell thickness using conventional methods requires the addition of alkali metals, etc. Therefore, while high porosity makes fabrication easier, it also has the disadvantage of increasing the amount of residual metal ionic impurities.

[0014] In contrast, the shell of the hollow particles in the present invention differs from the aforementioned method and is derived from a silica structure with a three-dimensional regular structure. This silica structure has a structure in which silica is arranged in a structure corresponding to the microphase separation structure of the surfactant described in the embodiment section. Specifically, it is a three-dimensional layered structure such as an L3 phase (or sponge phase) or a bicontinuous cubic phase (or gyroic tetrahedral phase). This structure is achieved 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 separation structure. We have discovered that by using this structure in the shell portion of core-shell particles formed by template synthesis, it is possible to increase the shell thickness without adding unnecessary catalysts and to form a shell of a certain thickness, thereby completing the following invention.

[0015] That is, the method for producing hollow inorganic particle materials of the present invention, which solves the above-mentioned problems, comprises: a core material dispersion preparation step, wherein the core material is dispersed in a mother liquid which is a mixture of a nonionic surfactant and a dispersion medium to prepare the core material dispersion, wherein the dispersion medium comprises water and may also comprise an aqueous solvent; The composite forming step comprises mixing the hydrolyzate of hydrolyzable silane with the core material dispersion and stirring to form an adsorption composite having the hydrolyzate adsorbed on the surface of the core material. a core-shell complex forming step, wherein the polycondensation reaction of the hydrolyzate of the adsorption complex is carried out in the mother liquor to obtain a core-shell complex; and The firing step is to fire the core-shell complex to remove the core material.

[0016] The hollow inorganic particle material of the present invention that solves the above-mentioned problems is a material that can be manufactured by the manufacturing method of the hollow inorganic particle material of the present invention, has a hollow ratio of more than 20 volume% and less than 75 volume%, has a shell layer composed of an inorganic material, and its shell layer has a structure derived from a microphase separation structure.

[0017] The shell layer having a structure derived from a microphase separation structure means that the shell layer's morphology is reflected in a structure derived from a microphase separation structure that is a three-dimensional layered structure such as an L3 phase (or sponge phase) or a bicontinuous cubic phase (or helical icosahedral phase). In this specification, the microphase separation structure refers to a structure in which, when viewed locally, rod-shaped micelles with diameters ranging from 1 nm to 8 nm are three-dimensionally connected, forming a three-dimensional network structure, with multiple networks interlaced.

[0018] To determine whether a specific upper shell layer possesses a structure derived from microphase separation, one can observe the shell's surface, fractured surface, or cut edge using a transmission electron microscope (TEM), scanning transmission electron microscope (STEM), or scanning electron microscope (SEM). Specifically, slight changes in silica density will reveal patterns derived from microphase separation. It is preferred that at least 50% of the shell layer's volume possess a structure derived from microphase separation. The microphase separation structure preferably has a sponge-like structure.

[0019] 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 composed of an inorganic material, wherein The inorganic material mentioned above contains more than 90% silicon dioxide based on the mass of the entire particle material. Based on the mass of the entire particle material, the contents of alkali metals, alkaline earth metals, halogens, and oxygen-containing acids are all below 10 ppm. The volume average particle size of the primary particles is 100 nm or more and 5 μm or less.

[0020] (Ionic impurity analysis method)

[0021] The determination of whether the alkali metal, alkaline earth metal, halogen, and oxygen-containing acid contents are all below 10 ppm based on the total mass of the particle material is based on the following procedure: 5 g of the sample to be extracted is immersed in 50 g of pure water and heated at 121°C in a sealed container for 20 hours. The precipitate is removed by filtration to prepare the extracted water. The ion concentration in the extracted water is quantitatively analyzed by ion chromatography.

[0022] The present invention provides a hollow inorganic particle material having a shell layer composed of dense silica, a sufficiently low relative dielectric constant and dielectric loss tangent, and ionic impurities comparable to those of solid silica fillers for electronic materials. Furthermore, the present invention provides a hollow inorganic particle material that is difficult to penetrate by resins or solvents during electronic material processing and exhibits excellent low relative dielectric constant and low dielectric loss tangent even in resin compositions.

[0023] Furthermore, in addition to being inorganic particles with internal voids, since they can have the same structure as conventional inorganic particle materials without internal voids (solid particle materials), they do not experience an extreme increase in viscosity when processed as varnishes or resin masterbatches compared to solid particle materials. Even when made into a resin composition in which the hollow particle material is directly dispersed in a resin material, it can be made to have the same handleability as solid particle materials or resin compositions using solid particle materials. Simple diagram description

[0024] 〈 FIG1 〉 is a scanning electron microscope (SEM) photograph of the hollow inorganic particle material obtained in Example 1.

[0025] 〈Figure 2〉 is the particle size distribution of the hollow inorganic particle material obtained in Example 1.

[0026] FIG3 is an infrared absorption spectrum of the hollow inorganic particle material obtained in Example 1 after surface treatment.

[0027] 4 is a scanning electron microscope (SEM) photograph of a cross section of a resin composition using the hollow inorganic particle material obtained in Example 1.

[0028] FIG5 shows the relative dielectric constant and thermal expansion coefficient of a resin composition obtained by mixing the hollow inorganic particle material obtained in Example 1 with that in Comparative Example 1.

[0029] 6 is a scanning electron microscope (SEM) photograph of the inorganic particle material obtained in Comparative Example 2.

[0030] 7 is a scanning electron microscope (SEM) photograph of the inorganic particle material obtained in Comparative Example 3.

[0031] Figure 8 shows scanning electron microscopy (SEM) images of inorganic particle materials obtained by varying the surfactant concentration. The numerical values ​​in the figure represent the surfactant concentration during the synthesis reaction.

[0032] FIG9 is a scanning electron microscope (SEM) image showing a microstructure derived from a microphase separation structure that can be seen in the shell layer of the hollow inorganic particle material obtained in Example 7. Implementation Method

[0033] The hollow inorganic particle material and its manufacturing method of the present invention are described in detail according to the following embodiments. The hollow inorganic particle material of this embodiment can be suitably used as an inorganic filler 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 a sealing material, a varnish, or a resin masterbatch. Furthermore, it can also be mixed with other inorganic particle materials and used as an inorganic filler. Other inorganic particle materials can be mixed in a ratio of more than 50% and less than 800% based on the mass of the hollow inorganic particle material. Examples of other inorganic particle materials include: aluminum oxide, zirconium oxide, titanium dioxide, solid silicon dioxide, etc. As other inorganic particle materials, spherical ones are preferred.

[0034] (Hollow Inorganic Particle Material)

[0035] The hollow inorganic particle material of this embodiment comprises a shell layer made of an inorganic material, which defines voids within the shell layer. The presence of voids within the shell layer of the hollow inorganic particle material can be confirmed by observation using a transmission electron microscope (TEM), a scanning transmission electron microscope (STEM), or a scanning electron microscope (SEM) while the hollow inorganic particle material is being properly separated or divided.

[0036] In the case of SEM observation, in addition to observing the cross-section in the resin-embedded state, hollowness can also be confirmed by increasing the acceleration voltage of the electron beam to reflect the internal structure of the particle.

[0037] The hollowness ratio is the ratio of the volume of the voids within the hollow inorganic particle material to the total volume of the hollow inorganic particle material. Unless otherwise specified, the hollowness ratio is the average value of the particles comprising the hollow inorganic particle material, calculated as the ratio of the total volume of the voids to the total volume of the hollow inorganic particle material. Details are calculated using the method described below.

[0038] The required relative dielectric constant 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 relative dielectric constant of silicon dioxide, which constitutes the inorganic material, is 3.6 to 4.2. When the relative dielectric constant of hollow inorganic particle materials is calculated using the Maxwell-Garnett equation (used for predicting the dielectric constant of composite materials) based on the relative dielectric constant of a vacuum of 1.0, the dielectric constant decreases with increasing hollowness. For relative dielectric constants of 3.4, 3.0, 2.8, and 2.5, the hollowness ratios are approximately 20%, 30%, 35%, and 45%, respectively. Therefore, the lower limit of the void fraction is at least 20%, preferably 30%, more preferably 35%, and even more preferably 45%.

[0039] A high hollowness ratio results in a hollow inorganic particle material with a low relative dielectric constant and low dielectric loss tangent. However, increasing the hollowness ratio reduces the shell thickness and reduces mechanical strength. To achieve sufficient mechanical strength, the upper limit of the hollowness ratio is set at 75%, preferably 70%, and even more preferably 65%. By keeping the hollowness ratio below this upper limit, sufficient mechanical strength is achieved, effectively preventing breakage of the hollow inorganic particle material during handling or when mixed with a resin material to form a resin composition. By making the hollow inorganic particle material break-resistant, sufficient voids are ensured, achieving the necessary electrical properties. These lower and upper limits can be arbitrarily combined. Specifically, examples of lower limits for good shell thickness include 10 nm, 20 nm, 50 nm, and 100 nm, and examples of upper limits include 300 nm, 200 nm, 150 nm, and 100 nm. These lower and upper limits can be arbitrarily combined.

[0040] Here, "having voids within the shell" refers to a region within the particle that is isolated from the outside of the particle by a shell that prevents molecules such as solvents or resins from passing through. The shell defining the voids may contain micropores sufficiently small relative to the particle size, but should not contain pores (mesopores or macropores) through which molecules such as solvents or resins can pass. Particles without voids are referred to as solid silica particle materials. The hollow inorganic particle material of this embodiment has one or more voids per particle.

[0041] The size of the voids was analyzed by measuring the true specific gravity using two probes (helium and nitrogen), one that passes through the micropores and one that does not. Pores that only allow helium to pass, but not nitrogen, were defined as micropores.

[0042] By measuring the density (ρHe) of the hollow inorganic particle material of this embodiment using helium gas, the shell density ρshell (=ρHe) of the portion of the hollow inorganic particle material excluding the voids can be determined. The shell density ρshell is preferably 2.1 g / cm3 or higher and 2.5 g / cm3 or lower, and more preferably 2.2 g / cm3 or higher and 2.4 g / cm3 or lower.

[0043] By measuring the density (ρ N2) of the hollow inorganic particle material of this embodiment through nitrogen gas, the density ρ particle (=ρ N2) of the hollow inorganic particle material containing voids can be determined. The hollow ratio can be calculated from the shell density ρ shell and the density of the hollow inorganic particle material ρ particle. Specifically, the hollow ratio can be calculated as [1-ρ N2 / ρ He] × 100 (%) (Calculation Method 1). Furthermore, the hollow ratio can be calculated by (1-2t / D) 3 × 100 (%) based on the particle size (D) and shell thickness (t) obtained from a TEM or SEM image (Calculation Method 2). In Calculation Method 2, excluding situations where the hollow ratio needs to be calculated for individual particles, the average value of the measured values ​​for 1,000 or more hollow inorganic particle materials is used for particles that can be identified in the image.

[0044] When hollow inorganic particles weighing 1 g or more can be independently measured, use Calculation Method 1. When the hollow ratio value of each particle of the hollow inorganic particle is required, use Calculation Method 2. When the hollow inorganic particle being measured is filled in a resin composition, when there is only a sample less than 1 g, or when Calculation Method 1 is not applicable, use Calculation Method 2.

[0045] The hollow inorganic particle material of this embodiment has a primary particle volume average particle size of 100 nm or greater and 5 μm or less. Examples of lower limits for the primary particle volume average particle size include 100 nm, 120 nm, and 150 nm, while examples of upper limits include 5 μm, 3 μm, 2 μm, and 1 μm. These lower and upper limits may be arbitrarily combined.

[0046] The shell layer is composed of an inorganic material, but may also contain unavoidable organic materials. The inorganic material comprises 90% by mass or greater of silicon dioxide. The proportion of silicon dioxide in the inorganic material is preferably 95% by mass or greater, more preferably 98% by mass or greater, and even more preferably 99% by mass or greater. Inorganic materials other than silicon dioxide that may be included are not particularly limited, but examples include metal oxides such as alumina, zirconia, and titanium dioxide, metal nitrides, and oxygen-containing acids such as boric acid.

[0047] In the hollow inorganic particle material of this embodiment, the content 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 is respectively less than 100 ppm, preferably less than 50 ppm, more preferably less than 20 ppm, and even more preferably less than 10 ppm.

[0048] In the extraction water of the hollow inorganic particle material of this embodiment, the contents of 13 cations and anions, namely, F, Cl, NO2, Br, NO3, SO4, PO4, Li, Na, NH4, K, Mg, and Ca, are each below 10 ppm, preferably below 5 ppm, more preferably below 2 ppm, and even more preferably below 1 ppm.

[0049] By keeping the amount of inorganic components other than silicon below this upper limit, it is possible to reduce the amount of ionic impurities extracted from the hollow inorganic particle material of this embodiment. In particular, by keeping the amount of alkali metal ions and alkaline earth metal ions below this upper limit, insulation properties can be improved. By keeping the amount of halogen ions below this upper limit, when the hollow inorganic particle material of this embodiment is used as a filler for electronic materials, corrosion of wiring caused by halogen wetting and diffusion in the product can be fully suppressed. By keeping the amount of oxyacid ions below this upper limit, the amount of oxyacids that exist as free oxyacids and do not form a shell layer as a composite oxide can be sufficiently reduced, thereby improving insulation properties and corrosion resistance.

[0050] Furthermore, in the hollow inorganic particle material of this embodiment, the contents of uranium (U) and thorium (Th) are each less than 5 ppb, preferably less than 3 ppb, more preferably less than 2 ppb, and even more preferably less than 1.5 ppb.

[0051] By keeping the amount of these radioactive elements below this upper limit, it becomes possible to reduce malfunctions (soft errors) of semiconductor devices caused by alpha rays generated within the product when the hollow inorganic particle material of this embodiment is used as a filler for electronic materials to a level that is indistinguishable from soft errors caused by alpha rays or cosmic radiation originating from other components.

[0052] .Surface area and dielectric properties of hollow inorganic particle materials

[0053] While the relative dielectric constant has been discussed above, considering the applications of the hollow inorganic particles of the present invention, the dielectric loss tangent must also be sufficiently low. While the dielectric loss tangent is typically evaluated within the context of the composite material being used, for hollow inorganic particles alone, it is desirable to have a value of 0.01 or less, preferably 0.005 or less, more preferably 0.003 or less, and even more preferably 0.002 or less.

[0054] Silanols typically exist at the grain boundaries and on the surface of silicon dioxide, degrading its dielectric properties. This has a particularly significant impact on the dielectric loss tangent, which can fluctuate significantly from approximately 10-4 to 10-1. Therefore, considering that normalizing the dielectric loss tangent using specific surface area would serve as an indicator for evaluating the quality of silicon dioxide's surface condition, we decided to use the value calculated using the indicator F = tanδ / SSA (g / m²) (tanδ: dielectric loss tangent (dimensionless), SSA: specific surface area (m² / g)).

[0055] Considering the properties of components using the hollow inorganic particle material of this embodiment, the dielectric loss tangent of the filler is desirably set to 0.01 or less. Achieving this value with a maximum particle diameter (which provides a minimum specific surface area) of 2 μm is set as the upper limit of indicator F. Specifically, in solid silica, the theoretical specific surface area at this point is approximately 1.5 m² / g, so a value of 7×10⁻³ g / m² is set as the upper limit of indicator F as a good value.

[0056] .Surface treatment of hollow inorganic particle materials

[0057] The hollow inorganic particle material of this embodiment can be surface treated. This surface treatment can improve dielectric properties or enhance compatibility with other materials.

[0058] The first goal is to eliminate the silanol groups remaining on the surface of the hollow inorganic particle material through a process called capping. For example, surface treatment agents containing trimethylsilyl groups can be used, more specifically methoxytrimethylsilane or hexamethyldisilazane (HMDS).

[0059] As a secondary goal, a surface treatment agent can be used to enhance affinity with the material with which it will ultimately come into contact. For example, a silane compound can be used as a surface treatment agent. Examples of silane compounds include those having functional groups such as alkyl, vinyl, phenyl, methacryl, epoxy, and alkyl groups having these groups as side chains. More specifically, although not limited to the examples, methyltrialkoxysilane, dimethyldialkoxysilane, phenyltrialkoxysilane, dialkoxydiphenylsilane, n-propyltrialkoxysilane, hexyltrialkoxysilane, octyltrialkoxysilane, decyltrialkoxysilane, 3,3,3-trifluoropropyltrialkoxysilane, vinyltrialkoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrialkoxysilane, 3-glycidoxypropylmethyldialkoxysilane, 3-glycidoxypropyltrialkoxysilane, p-phenylyltrialkoxysilane, 3-methacryloyloxypropylmethyldialkoxysilane, 3 -Methacryloxypropyl trialkoxysilane, 3-acryloxypropyl trialkoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldialkoxysilane, N-(2-aminoethyl)-3-aminopropyltrialkoxysilane, 3-aminopropyltrialkoxysilane, N-phenyl-3-aminopropyltrialkoxysilane, 3-ureidopropyltrialkoxysilane, 3-mercaptopropylmethyldialkoxysilane, 3-mercaptopropyltrialkoxysilane, 3-isocyanatepropyltrialkoxysilane, 3-trialkoxysilylpropylsuccinic anhydride, etc. (the alkoxy group is a functional group derived from alcohol such as methoxy, ethoxy, or isopropoxy).

[0060] (Method for producing hollow inorganic particle material)

[0061] The manufacturing method of the hollow inorganic particle material of this embodiment can be suitably manufactured in the manufacturing method of the hollow inorganic particle material of this embodiment described above, which is as follows: core-shell particles with a core material as the core and silicon dioxide as the shell are made into a precursor, and the core of the precursor is removed and the shell is taken out to manufacture the hollow inorganic particle material.

[0062] The method for producing the hollow inorganic particle material of this embodiment includes a core material dispersion preparation step, a complex formation step, a core-shell complex formation step, a firing step, and other necessary steps.

[0063] Core material dispersion preparation process

[0064] The core material dispersion preparation step involves dispersing the core material in a mother liquor to prepare the core material dispersion. The mother liquor is a mixture of a surfactant and a dispersion medium, and a catalyst (typically, but not limited to, an acid or base) to promote the polymerization of silica may be added as needed. The core material can be dispersed after or during the mother liquor preparation process. In short, the order of mixing the surfactant, core material, and dispersion medium is not particularly limited. Furthermore, if a catalyst to promote the polymerization of silica is added, it can be added during or after the mother liquor preparation, simultaneously with or after the addition of the hydrolyzable silane compound.

[0065] In the core material dispersion, the surfactant is adsorbed on the surface of the core material while forming a three-dimensional layered structure (hereinafter referred to as a "microphase separation structure") such as an L3 phase (or sponge phase) or a bicontinuous cubic phase (or helical icosahedral phase).

[0066] 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 forms a microphase separation structure within an appropriate temperature and concentration range when dissolved in water. Furthermore, such nonionic surfactants may be used alone or in combination of two or more. Details of nonionic surfactants will be described later.

[0067] The dispersion medium can be water or any of the water-based aqueous solvents described below. Aqueous solvents are water-miscible solvents selected from monohydric alcohols (methanol, ethanol, 1-propanol, 2-propanol), dihydric alcohols (ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol), and trihydric alcohols (glycerol) with 1 to 3 carbon atoms. A mixture of two or more of these can also be used.

[0068] The surfactant concentration determines the formation of a microphase-separated structure. The structure created by the surfactant in water is a function of temperature and concentration, varying from surfactant to surfactant. Therefore, the optimal temperature and concentration must be determined experimentally for each surfactant. For example, the optimal conditions for the pluronic surfactant L-64 (POE-POP block copolymer) are 1% to 20% by mass at 40°C.

[0069] Core materials

[0070] The core material, depending on the core material, allows for the synthesis of hollow inorganic particles of various sizes. Voids are formed with sizes and shapes corresponding to those of the selected core material. Particulate components that are dispersible or capable of dispersing in water are preferred as the core material. While micelles or vesicles, which utilize a surfactant and, if necessary, a hydrophobic liquid, are suitable in terms of size and shape, they are difficult to maintain during the reaction that forms silica around the core material. Therefore, a core material composed of particulate components is preferred.

[0071] The core material is preferably made of an easily removable organic material, particularly a resin material. A core material made of a resin material that is removed by firing is also preferred. For example, a resin dispersed in water, such as a resin emulsion, is a suitable core material.

[0072] Furthermore, as described in Non-Patent Document 3, to produce core-shell particles with the desired structure, the size and charge of the core material must be carefully selected. The core material should be larger than the silica core (the smallest unit of silica). This is because larger particles tend to aggregate more readily at the center due to differences in convection velocity. In the reaction of this embodiment, the smallest unit of the microphase separation structure containing silicic acid oligomers between the layers (the silica core in this embodiment) is approximately 10 nm or smaller, and a core material with a size larger than this is used. For example, particles from conventional resin emulsions are preferably larger than 50 nm.

[0073] Generally, silica cores have a weak negative charge. Therefore, if a material other than strongly negatively charged particles is used as the core material under the reaction conditions that generate silica cores, the repulsion between the core material and the generated silica cores is reduced, allowing a silica shell to form around the core material in a suitable configuration. Based on various experiments, it is ideal for the resin used as the core material to have a surface potential in the mother liquor of -3 mV or higher, with 3 mV or higher being more suitable. Resin emulsions with these properties can also be synthesized using well-known methods, and commercially available products can be used. The type of resin and the method of obtaining it are not limited.

[0074] .Surfactants

[0075] The surfactant used in the method for producing hollow inorganic particles in this embodiment is described below. The surfactant in this embodiment is a nonionic surfactant (nonionic surfactant) and, when dissolved in water, forms a microphase-separated structure within an appropriate temperature and concentration range. Compounds with this characteristic possess polar blocks (A) and nonpolar blocks (B), and are classified based on their block structure into AB-type (having 2 blocks), ABA-type (having 3 blocks), or BAB-type (having 3 blocks) (there are also various other types). The block structure is not related to the formation of the microphase-separated structure.

[0076] To achieve a microphase-separated structure, the size (formula weight) of the polar block (MA) and the size (formula weight) of the nonpolar block (MB) must be equal. This is because when MA > MB, spherical or cylindrical micelles are more likely to form, while the opposite situation favors the formation of so-called inverse micelles.

[0077] In industry, A is mostly polyoxyethylene (also known as POE or polyethylene oxide, polyethylene glycol, etc.), and B is mostly polyoxypropylene (also known as POP or polypropylene oxide, polypropylene glycol, etc.) or long-chain alkyl or long-chain carboxylic acid.

[0078] Examples of surfactants with this structure are not limited to those listed in the examples, but include POE-monoalkyl ethers or POE-monoesters (the above are examples of a 2-block type), POE-POP block copolymers, or POE-diesters (the above are examples of a 3-block type). POE-POP block copolymers are generally referred to as pluronic surfactants, and many products with varying 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 defined as 20 × MA ÷ (MA + MB). The HLB values ​​shown below are based on this definition. Here, MA refers to the formula weight of the A site (hydrophilic portion) of the copolymer, and MB refers to the formula weight of the B site (hydrophobic portion) of the copolymer. (MA + MB) represents the molecular weight of the copolymer as a whole.

[0079] Silica grows in the A portion of the block copolymer. When the ratio of A to the overall molecule is small, the shell density is low, leaving a large number of mesopores. On the other hand, if the ratio of A is large, only the silica layer is stabilized, making it difficult for core-shell particles to grow. The optimal HLB range for Pluronic surfactants has been systematically determined to be 6 or higher and 14 or lower. However, not all surfactants meeting these conditions can be used in this embodiment. Specifically, it is necessary to verify and optimize the conditions to determine whether the desired microphase separation structure can be achieved, whether a composite can be formed, and whether a dense shell can be formed by denuclearization during firing.

[0080] Pluronic surfactants are not limited to these examples, but include 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.

[0081] Surfactants other than Pluronic type are not limited to the examples, but include: POE-fatty acid sorbitan esters (for example, POE-sorbitan monooleate, POE-sorbitan monostearate, POE-sorbitan tetraoleate, etc.), POE-fatty acid sorbitol esters (for example, POE-sorbitan monolaurate, POE-sorbitan monooleate, POE-sorbitan pentaoleate, POE-sorbitan monostearate, etc.), POE-fatty acid glycerol esters (for example, POE-glycerol monostearate, POE-glycerol monoisostearate, POE-glycerol triisostearate, POE-glycerol monooleate, etc.), POE-fatty acid esters (for example: POE-distearate, POE-mono- or dioleate, ethylene glycol distearate, etc.), POE-alkyl ethers (for example: POE-lauryl ether, POE-oleyl ether, POE-stearyl ether, POE-royl ether, POE-2-octyldodecyl ether, POE-cholesterol ether, etc.), etc.

[0082] 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 approaches share the same principle of utilizing silica's ease of growth at the A site of the block copolymer, their fundamental objectives differ. In prior art, the purpose of using nonionic surfactants is to form swollen micelles, or oil-in-water emulsions, by allowing the B sites of surfactant molecules with silica adsorbed at the A sites to become compatible with oil droplets, which accumulate on the surface. Consequently, a silica shell forms on the micelle surface. In other words, the goal is not to utilize a three-dimensional, layered microphase separation structure, a technique different from that described in this embodiment.

[0083] 〈Compound Formation Process〉

[0084] The composite forming step involves mixing a hydrolyzed silane with a core material dispersion and stirring to form an adsorption composite with the hydrolyzed silane adsorbed on the surface of the core material. The hydrolyzed silane can be added as a hydrolyzed silane, allowing the hydrolysis reaction to proceed within the core material dispersion to form the hydrolyzed silane.

[0085] The resulting hydrolyzate adsorbs onto the polar block A of the surfactant attached to the core material's surface, polymerizing between the layers to form silicic acid oligomers. This results in an adsorption complex, where a silica-surfactant complex, forming a microphase-separated structure, accumulates on the core material's surface.

[0086] .Hydrolyzed silane

[0087] Examples of hydrolyzable silanes include orthosilicates. Hydrolyzable silanes are hydrolyzed to form hydrolyzates. TEOS and TMOS are commonly used orthosilicates. TEOS and TMOS are oil-soluble, and their use as is would disrupt the surfactant's microphase separation structure. Furthermore, while their contact area with water is small, the areas that do hydrolyze rapidly, resulting in amorphous silica. Consequently, the yield of hollow particles is extremely low.

[0088] The Stober method uses a mixture of TEOS or TMOS with an alcohol, making it compatible with water while also slowing the reaction rate. However, the reaction is not well controlled. For example, when using compounds with diol or triol groups in their side chains, as described later, as orthosilicates, the yield of silica having the target structure is insufficient even with the simple method of adding the necessary amount all at once.

[0089] Therefore, as disclosed in Patent Document 10 and Non-Patent Document 5, orthosilicates with diol or triol groups in their side chains are used. These compounds improve compatibility with water and significantly reduce the reaction rate with water. Consequently, the yield of silica having the target structure derived from microphase separation can be increased.

[0090] Examples of orthosilicates using diol or triol groups in their side chains include compounds represented by Si(OR) 4. The four Rs can be independently determined, with at least one being a polyol residue, and the others being alkyl groups. A polyol residue is represented by eliminating one hydroxyl group from the polyol. These orthosilicates can be prepared by a substitution reaction between tetraalkoxysilane and a polyol. The polyol residue of R varies depending on the type of polyol used, but for example, when ethylene glycol is used as the polyol, R is -CH 2 CH 2 OH. Furthermore, at least one of Rs may be a substituted polyol residue; the others may be unsubstituted alkyl groups.

[0091] Examples of the polyol residue represented by R include an ethylene glycol residue, a diethylene glycol residue, a triethylene glycol residue, a tetraethylene glycol residue, a polyethylene glycol residue, a propylene glycol residue, a dipropylene glycol residue, a polypropylene glycol residue, a butanediol residue, a hexylene glycol residue, a glycerol residue, a diglycerol residue, a polyglycerol residue, a neopentyl glycol residue, a trimethylolpropane residue, a neopentyletrol residue, and a maltitol residue. Among these, R is preferably any of an ethylene glycol residue, a propylene glycol residue, a butanediol residue, and a glycerol residue.

[0092] The synthesis method for this type of orthosilicate is not limited, but for example, it can be synthesized as a raw material by using an acid-catalyzed transesterification reaction, such as disclosed in Patent Document 10 (proton-type cation exchange resin) or Non-Patent Document 5 (hydrochloric acid), by combining orthosilicates such as TEOS or TMOS with the aforementioned polyols. To easily obtain a high-purity compound and avoid introducing halogens into the product, suitable catalytic acids include oxyacids such as boric acid, phosphoric acid, nitric acid, and sulfuric acid, or carboxylic acids such as acetic acid.

[0093] Core-shell complex formation process

[0094] The core-shell complex formation step involves subjecting the hydrolyzate present on the surface of the adsorption complex to a polycondensation reaction in a mother liquor to obtain a core-shell complex. A core-shell complex is a system in which a shell (shell layer) composed of a condensate of a hydrolyzed silane hydrolyzate is formed on the surface of the core material. The condensation of the hydrolyzate can be efficiently promoted by heating the hydrolyzed silane after hydrolysis. Furthermore, the reaction can be accelerated by adding an acid or base as a catalyst, if desired.

[0095] Firing process

[0096] The firing step involves firing the core-shell composite to decompose and remove the surfactant contained in the core material and shell layer. Simultaneously, the shell layer is densified. Conditions are not particularly limited, as long as they allow the core material to be decomposed and removed without damaging the shell layer formed on the core material's surface. Examples include heating in an oxidizing atmosphere. For example, firing can be performed in air at a temperature and for a time sufficient to decompose and remove the core material. Examples of firing temperatures include 700°C or higher, 800°C or higher, 900°C or higher, 1000°C or higher, and 1100°C or higher. A higher firing temperature is preferred, but should not reach a temperature that causes the silicon dioxide, the material of the hollow inorganic particles, to aggregate or melt. Even in the event of aggregation, it is acceptable to allow the composite to aggregate as long as it can be separated into primary particles through a disintegration process. Furthermore, since the core-shell composite is manufactured while immersed in a mother liquor, a separation step from the mother liquor can be performed before the firing step. For example, processes such as filtration, centrifugation, and drying may be employed.

[0097] Controlling the Shell Thickness and Size of Hollow Inorganic Particles

[0098] To summarize the above-mentioned method for producing the hollow inorganic particle material of this embodiment, increasing the shell thickness can be achieved by increasing the ratio of hydrolyzable silane to core material, using a core material with a high surface potential, or 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, controlling the shell thickness, or a combination of these methods.

[0099] (Slurry composition)

[0100] The slurry composition of this embodiment is formed by dispersing the hollow inorganic particle material of this embodiment described above in a dispersion medium. The slurry composition of this embodiment can be used in electronic materials such as semiconductor substrate materials, and is particularly preferred for high-frequency substrate materials. The dispersion medium is substantially free of water, preferably having a water content of 1000 ppm or less, and more preferably 500 ppm or less.

[0101] The mixing ratio of the hollow inorganic particle material to the dispersion medium in the slurry composition is not particularly limited, but it is preferable to maximize the content of the hollow inorganic particle material. Furthermore, as the amount of hollow inorganic particle material increases, the viscosity tends to increase. Therefore, the hollow inorganic particle material should be mixed to a viscosity that is acceptable for workability. For example, the mass ratio of (hollow inorganic particle material): (dispersion medium) can be approximately 20:80 to 80:20.

[0102] 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.

[0103] The hollow inorganic particle material is preferably surface-treated. The surface treatment preferably introduces functional groups that enhance affinity with the dispersion medium or the target object with which the hollow inorganic particle material contacts during final use.

[0104] (Resin composition)

[0105] The resin composition of this embodiment is a cured product made from the aforementioned 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.

[0106] The resin composition is preferably used in electronic materials, and as such electronic materials, it is preferably used in high-frequency applications such as high-frequency substrates. The hollow inorganic particle material of this embodiment has a low Df value, so even when used in applications such as high-frequency circulation, it can reduce losses.

[0107] 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:resin material ratio by mass can be approximately 10:90 to 90:10.

[0108] Resin materials are not particularly limited, but include common resin materials such as thermosetting resins (which may be in either a pre-cured or post-cured state during mixing) and thermoplastic resins, including epoxy resins, melamine resins, acrylic resins, polycarbonate resins, polyesters, silicone resins, liquid crystal polymers (LCPs), polyimides, cycloolefin polymers (COPs), and polyphenylene ether (PPOs). Resin materials may be used singly or as a composite of multiple resin materials. The moisture content of the resin material is preferably 1000 ppm or less, more preferably 500 ppm or less.

[0109] The hollow inorganic particle material is preferably surface-treated. In the surface treatment, it is preferable to introduce functional groups that can enhance the affinity between the hollow inorganic particle and the resin material used.

[0110] 『Example』

[0111] The hollow inorganic particle material and the method for producing the same are described in detail with reference to the following examples.

[0112] (Analysis Method)

[0113] In this specification, unless otherwise specified, each analysis was performed using the following methods.

[0114] (1) Particle size distribution

[0115] Optical measurement of particle size distribution is the simplest method for analyzing the aggregation state of primary particles. On the other hand, since the refractive index of the hollow inorganic particles of the present invention is different from that of the inorganic matter constituting them, the obtained average particle diameter will show a value that does not conform to the true average particle diameter. Accordingly, for the analysis of the aggregation state of particles, optical measurement of particle size distribution is carried out, and the average particle diameter is obtained through image analysis.

[0116] (1a) Analysis of aggregation state

[0117] The particle size distribution was measured using a laser diffraction particle size distribution measuring device (SALD-7500nano manufactured by Shimadzu Corporation) under the following conditions. . Dispersion medium: Isopropyl alcohol . Refractive index: 1.45 . Calculation mode: Volume

[0118] (1b) Average particle diameter

[0119] The slurry of the hollow inorganic particle material was dropped onto a silicon wafer and dried. At this time, the particles were attached as a single layer. Observation was carried out with a scanning electron microscope (SEM). The SEM image was observed at a magnification at which about 100 to 1000 particles could be observed in one field of view, and the sizes of about 1000 particles obtained from 1 to 10 fields of view were measured. Based on this, the volume particle size distribution was compiled, and the particle diameter at which the cumulative frequency of the volume particle size distribution became 50% was defined as the average particle diameter.

[0120] In addition, image analysis software such as "A Image-kun" (Asahi Kasei) can be used. Here, no specific method is particularly specified. <000039​​​​​​​​​​​​​​​ . Sample slot: 10 cm 3 slots . Sample weight: 1 to 3 g .Measured gas: helium and nitrogen .Purge: 10 times, 135 kPa(G) .Measurement: 10 times, 135 kPa(G)

[0125] The same sample was measured alternately using helium and nitrogen. Since helium can penetrate the micropores and reach the inner cavity of the hollow inorganic particle, the density (ρHe) when using helium as the measurement gas represents the density of the shell. On the other hand, the density (ρN2) when using nitrogen represents the density of the hollow inorganic particle material. Based on this, the hollow fraction is calculated as [1-ρN2 / ρHe] × 100 (%).

[0126] (2b) Image Analysis

[0127] Take a TEM (including STEM) or SEM image of the shell of the reinforced particle and calculate the particle size (D) for each particle using the same method as described for the average particle size. Also, record the shell thickness (t). Use the value calculated using the following formula for each particle, or, when considering powder properties, use the average value calculated for 1,000 or more particles. (1-2t / D) 3×100(%)

[0128] TEM (including STEM) images are most suitable for this analysis, but for greater convenience, using a scanning electron microscope (SU8000, manufactured by Hitachi) under the following conditions allows for SEM images to be recorded that emphasize the shell layer. .Accelerating voltage: 10 kV .Probe distance: 15 mm .Detector: Lower detector and SE detector

[0129] (3) Specific surface area

[0130] The hollow inorganic particle material of this embodiment was dried under reduced pressure at 200°C and used as a sample. This sample was subjected to multi-point BET surface area and pore volume measurement or single-point BET surface area measurement using nitrogen using an automated surface area / pore distribution measurement device (Tristar II, manufactured by Micrometrics).

[0131] (4)Silicon dioxide purity

[0132] The hollow inorganic particle material of this embodiment was added to a mixture of nitric acid, sulfuric acid, and hydrofluoric acid and heated at 120°C to dissolve. This solution was then heated at 300°C to distill off the nitric acid and hydrofluoric acid, creating a sample solution. This solution was appropriately diluted and quantitatively analyzed using ICP optical emission spectrometry (5110 ICP-OES, manufactured by Agilent Technologies). The contents of 19 elements, including 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. Furthermore, the same sample was used for quantitative analysis of U and Th using ICP-MS (7800 ICP-MS, manufactured by Agilent Technologies).

[0133] (5) Ionic impurities

[0134] 5 g of the hollow inorganic particles of this embodiment were 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 produce extraction water. The ion concentration of the extraction water was quantitatively analyzed by ion chromatography (Dionex, manufactured by Thermo Scientific). The contents of 13 cations and anions, including F, Cl, NO₂, Br, NO₃, SO₄, PO₄, Li, Na, NH₄, K, Mg, and Ca, were calculated based on the mass of the immersed hollow inorganic particles.

[0135] (6) Dielectric properties

[0136] The dielectric properties of the powder were measured using PTFE tubes with a diameter of 8 mm x 30 mm filled with hollow inorganic particles as the sample, and an empty tube as the control. Each tube was placed in a cavity resonator connected to a network analyzer, and the resonant frequency and Q value in the 1 GHz band were determined. These values ​​were used to calculate the complex dielectric constant using the "Perturbation Method Dielectric Constant Calculation Application" (KEYCOM). For the resin composition, a square column approximately 4 mm x 7 mm x 30 mm cut from the resin composition was used as the sample for measurement, and a sample not placed in the cavity resonator was used as the control for calculating the complex dielectric constant.

[0137] (7) Thermal expansion coefficient

[0138] A rectangular parallelepiped with a side of approximately 4 mm was cut from the resin composition to serve as the measurement sample. Using a thermomechanical analyzer (TA Instruments TMA Q400), the sample was heated from -50°C to 250°C at 5°C / min, and the linear expansion was recorded. The average rates of change from 0 to 50°C and from 180 to 220°C were plotted as CTE1 and CTE2, respectively.

[0139] (Preparation of test specimens)

[0140] (Example 1)

[0141] Synthesis of Hydrolyzable Silanes

[0142] 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. Ethanol was distilled off, and 65 g of propylene glycol-modified orthosilicate (PGMS) with propylene glycol as a side chain was recovered. Although this PGMS contained a small amount of ethanol, it was used in the synthesis of core-shell particles.

[0143] Synthesis of core-shell particles

[0144] 10% by mass of an ABA-type block copolymer (HLB 7.9, average molecular weight 2900) and the remainder were mixed with 6 g of an acrylic resin (average particle size 300 nm, surface potential +52 mV) in 1000 g of a mother liquor made from water (core material dispersion preparation step). Next, 50 g of PGMS was stirred and mixed (complex formation step).

[0145] The reaction mixture was maintained at 40° C. for 36 hours to mature the core / shell particles (core-shell complex formation step). The generated solid was filtered under reduced pressure using filter paper (JIS 5A) to recover the precipitate.

[0146] 〈Pith removal due to firing〉

[0147] The precipitate was heated to 1,000°C at a rate of 50°C / h and held at 1,000°C for 12 hours (the firing step). The recovered silica, being loosely aggregated, was gently crushed in a mortar to obtain the hollow inorganic particle material used as the test sample for this example.

[0148] (Example 2)

[0149] The same operation as in Example 1 was performed except that the concentration of the ABA block copolymer in the mother solution was changed to 5% by mass to obtain the hollow inorganic particle material serving as the test sample of this example.

[0150] (Example 3)

[0151] The same operation as in Example 1 was performed except that the concentration of the POE-POP block copolymer in the mother solution was set to 2% by mass to obtain the hollow inorganic particle material serving as the test sample of this example.

[0152] (Example 4)

[0153] The same operation as in Example 1 was performed except that another ABA block copolymer (HLB 8.8, average molecular weight 1700) was used to prepare the mother solution instead of the ABA block copolymer used in Example 1 to obtain the hollow inorganic particle material which is the test sample of this example.

[0154] (Example 5)

[0155] The same operation as in Example 1 was performed except that a BAB type block copolymer (HLB 8.0, average molecular weight 2700) was used to prepare the mother solution instead of the ABA type block copolymer used in Example 1 to obtain the hollow inorganic particle material which is the test sample of this example.

[0156] (Example 6)

[0157] The same operation as in Example 1 was performed except that an AB-type surfactant (HLB 12.4, average molecular weight 500) was used to prepare the mother solution instead of the ABA-type block copolymer used in Example 1 to obtain the hollow inorganic particle material serving as the test sample of this example.

[0158] (Example 7)

[0159] The same operation as in Example 4 was performed except that 6 g of wax (average particle size 600 nm, surface potential +65 mV, solid content concentration 60%) was used instead of the acrylic resin used in Example 4 to obtain a hollow inorganic particle material which is the test sample of this example.

[0160] (Example 8)

[0161] The same operation as in Example 7 was performed 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 to obtain a hollow inorganic particle material which is the test sample of this example.

[0162] (Comparative Example 1)

[0163] A commercially available silica particle material (SO-C2 manufactured by Admatechs) was used as is.

[0164] (Comparative Example 2)

[0165] Synthesis of core-shell particles

[0166] 10% by mass of an ABA-type block copolymer (HLB 7.9, average molecular weight 2900), 30% by mass of ethanol, and the remainder were mixed with 6 g of acrylic resin (average particle size 300 nm, surface potential +52 mV) in 1000 g of a mother liquid made from water (core material dispersion preparation step). Next, 30 g of tetraethyl orthosilicate was stirred and mixed (composite formation step).

[0167] The same operation as in Example 1 was then carried out to obtain calcined silica. The recovered silica was densely agglomerated and was gently broken apart and crushed in a mortar to obtain comparative silica 2, which served as the test sample for this comparative example.

[0168] (Comparative Example 3)

[0169] The same procedures as in Example 1 were followed, 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 to obtain calcined silica. The recovered silica, which was densely aggregated, was then crushed in a mortar to obtain Comparative Silica 3, which served as the test sample for this Comparative Example.

[0170] (Comparative Example 4)

[0171] The same operation as in Example 1 was performed except that the firing condition of 600° C. was used instead of the firing temperature of 1000° C. in Example 1 to obtain comparative silicon dioxide 4, which is the test sample of this comparative example.

[0172] (Comparative Example 5)

[0173] The same operation as in Example 1 was carried out except that the concentration of the ABA block copolymer in the mother solution was changed to 1% by mass to obtain comparative silica 5, which was the test sample of this comparative example.

[0174] (Comparative Example 6)

[0175] The same procedures as in Example 1 were followed, except that 1000 g of water was used as the mother liquor, to obtain calcined silica. The recovered silica, which was densely agglomerated, was then crushed in a mortar to obtain comparative silica 6, which served as the test sample for this comparative example.

[0176] (Comparative Example 7)

[0177] The same procedures as in Example 1 were followed, except that another ABA block copolymer (HLB 9.3, average molecular weight 4200) was used to prepare the mother solution instead of the ABA block copolymer used in Example 1, to obtain comparative silica 7, which was the test sample of this comparative example.

[0178] (Comparative Example 8)

[0179] The same procedures as in Example 1 were followed, except that another ABA block copolymer (HLB 2.5, average molecular weight 2000) was used to prepare the mother solution instead of the ABA block copolymer used in Example 1, to obtain comparative silica 8, which was the test sample of this comparative example.

[0180] (Comparative Example 9)

[0181] The same procedures as in Example 1 were followed, except that another ABA block copolymer (HLB 15.7, average molecular weight 8350) was used to prepare the mother solution instead of the ABA block copolymer used in Example 1, to obtain comparative silica 9, which served as the test sample of this comparative example.

[0182] (evaluate)

[0183] Figure 1 shows the appearance of the silica obtained in Example 1. 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, as is clear from the preceding text. The reason for this mixture of two particle sizes is that the core material used in the template synthesis consists of two different particle sizes.

[0184] By suspending this hollow inorganic particle material in isopropyl alcohol and subjecting it to a French press treatment (extrusion pressure 120 MPa), a homogeneous slurry composition was obtained. Figure 2(a) shows the particle size distribution obtained using a laser diffraction particle size distribution measurement device. The cumulative frequency shows a peak of approximately 95% at around 0.15 μm. The particle size distribution obtained from the same sample using image analysis is shown in Figure 2(b), with a volume average particle size of 0.18 μm. This clearly demonstrates that the hollow inorganic particle material of this example is dispersed in the slurry almost entirely as primary particles.

[0185] The specific surface area and true specific gravity (ρ N2) of the dried slurry and re-powdered powder were measured to be 95 m2 / g and 1.51 g / cm3, respectively (Table 1). This specific surface area is larger than the theoretical specific surface area (22 m2 / g) calculated from particle size and specific gravity. This is presumably due to the presence of irregularities on the particle surface, originating from a microphase separation structure. Meanwhile, the true specific gravity is smaller than the shell specific gravity (ρ He) of 2.39 g / cm3, indicating that a virtually non-porous shell has been formed. The calculated hollow fraction is 37%.

[0186] After reacting a slurry containing this hollow particle material with 5% by mass of N-phenyl-3-aminopropyltrimethoxysilane (phenylaminosilane) relative to the solid content, the solvent was distilled off and the powder was dried. Figure 3 shows the infrared absorption spectrum of this powder using diffuse reflectance. The presence of a C—H stretching vibration peak at wavenumbers 2800 to 3050 cm⁻¹ indicates surface treatment with an organosilane compound (here, phenylaminosilane). Furthermore, a peak at 3745 cm⁻¹ for the OH stretching vibration, identified as a silanol group, was observed. This hollow inorganic particle material possesses a region within the particle that is isolated from the particle exterior by a shell impermeable to molecules such as solvents and resins. Because the particle interior is untreated, even with the application of a sufficient amount of surface treatment agent, the silanol groups present on the surface will remain. These can be identified as unreacted silanol groups.

[0187] Table 1 Table 1 Average particle size, specific surface area, true specific gravity, and hollow ratio of the examples and comparative examples Sample Type of generated product Analysis Project Shell formation Mesopore Hollow structure Average particle size Specific surface area True specific gravity Hollowness (µm) (m 2 / g) (g / cm 3) (%) Reality Shi example 1 good none good 0.18 95 1.51 37 2 good none good 0.18 99 1.57 35 3 good none good 0.18 92 1.58 34 4 good none good 0.22 49 1.21 50 5 good none good 0.17 102 1.19 51 6 good none good 0.19 120 1.35 44 7 good none good 0.50 18 1.49 38 8 good none good 1.26 4 1.30 46 Compare Comparison example 1 Commercially available solid silica none - 0.50 5 2.26 0 2 Agglomerates - - - - - - 3 Pumice-like fired body - - - - - - 4 good have Difference 0.21 800 2.41 0 5 Mixed with amorphous silica have Difference - - - - 6 Pumice-like fired body - - - - - - 7 good have Difference 0.24 198 2.40 0 8 Mixed with rupture have Difference - - - - 9 Mixed with amorphous silica have Difference - - - - - Indicates items that do not conform or for which analysis was not performed

[0188] Elemental analysis (Table 2) and ion analysis (Table 3) of the extracted water were performed on the test samples of Example 1 and Comparative Example 1 using ICP emission spectrometry. The results showed high-purity silica containing virtually no elements other than silicon dioxide, and the extracted water also contained virtually no ions that could pose a problem for semiconductor applications. Comparative Example 1 synthesized solid silica using the deflagration method (Patent Document 11), a method commonly used in the field targeted by this technology. Compared to this solid silica, it also contained no particularly problematic elements, and in some cases, exhibited significantly lower impurity levels than the comparative example. Furthermore, the uranium and thorium contents were low at 1.3 ppb and 1.0 ppb, respectively. Furthermore, Table 4 lists the relative dielectric constant and dielectric loss tangent values ​​for the test samples of Example 1. These properties demonstrate that the silicon dioxide produced by this technology is fully suitable for semiconductor applications.

[0189] Table 2 Table 2 Elemental analysis (ICP) of inorganic particles other than Si Sample Element content (ppm) Na Mg Al P K Ca Ti Cr Mn Fe Co Ni Cu Zn As Mo Sb B V Implementation Example 1 2 3 1 <1 <1 1 <1 <1 <1 2 <1 <1 <1 <1 <1 1 <1 4 <1 Compare Example 1 3 2 380 9 <1 46 5 <1 1 110 <1 <1 <1 <1 <1 <1 <1 9 <1 The mark < indicates that the detection limit of each element is below

[0190] Table 3 Table 3 Ionic impurities in extracted water (ion chromatography) Sample Ion content (ppm) F Cl NO 2 Br NO 3 SO 4 PO 4 Li Na NH4 K Mg Ca Example 1 <1 <0.1 <1 <1 <1 <1 <1 <1 <0.1 <1 <0.2 <1 <1 Comparative Example 1 <1 0.1 <1 <1 <1 <1 14 <1 <0.1 <1 <0.2 <1 <1 The mark < indicates that the detection limit of each element is below

[0191] An epoxy resin composition containing 25% by mass of the material obtained in Example 1 was prepared. This corresponds to a filling level of approximately 40% by mass for the solid silica in Comparative Example 1. A cross-section of a cut resin sheet is shown in Figure 4. The embedded particles appear as white spheres, while dark depressions are observed within the white outline in the cross-section. The hollow inorganic particles are not impregnated with resin.

[0192] The hollow inorganic particle material from Example 1 and the solid silica from Comparative Example 1 were mixed at a mass ratio of 1:2 (under conditions of nearly identical volume) and 1:1. This mixed powder was used to prepare a resin composition, and the relative dielectric constant and thermal expansion coefficient of the resin sheet were determined (Figure 5). The relative dielectric constant decreased with increasing the proportion of hollow inorganic particles. Meanwhile, the thermal expansion coefficient remained nearly constant at both CTE1 and CTE2. Therefore, hollow inorganic particles are suitable for applications where dielectric properties need to be improved while maintaining thermomechanical properties.

[0193] In Examples 2 to 8, hollow inorganic particles were obtained in the same manner as in Example 1. On the other hand, in Comparative Examples 2 to 9, the particles formed pumice-like aggregates rather than independent particles, failed to form a sufficiently strong shell, or were insufficiently densified, resulting in the presence of mesopores extending into the inner cavity, making them difficult to characterize as hollow inorganic particles. Table 1 shows the analysis results of the average particle size, specific surface area, true specific gravity, and hollowness ratio for the types of particles obtained in these Examples and Comparative Examples. Furthermore, Table 4 lists the relative dielectric constant and dielectric loss tangent values ​​for the test samples of Example 1 surface-treated with HMDS and phenylaminosilane, and for the test samples of Examples 4 and 7 surface-treated with HMDS.

[0194] Table 4 Table 4 Dielectric properties of the examples Sample Surface treatment Dielectric properties Relative dielectric constant (D k) Dielectric loss tangent (D f) D k / specific surface area (g / m 2) Reality Shi example 1 none 3.09 0.0098 1×10-4 HMDS 2.78 0.0052 6×10-5 Phenylaminosilane 2.81 0.0065 7×10-5 4 HMDS 2.30 0.0023 5×10-5 7 HMDS 2.46 0.0027 2×10-4 Comparative Example 1 HMDS 4.21 0.0018 3×10-4

[0195] Comparative Example 2 utilizes the Stober method, and its appearance is shown in Figure 6. A shell appears to have formed, but it is a strongly bonded aggregate of primary particles, unable to break apart. This type of sintering was not observed in Example 1. The key to this technology is the attachment of a sufficiently thick shell during core / shell particle formation, achieved by utilizing a microphase separation structure induced by a surfactant. In contrast, using the Stober method, the hydrolyzed silane cannot adhere uniformly to the hydrophilic portions of the rarely formed L3 phase layers, resulting in localized accumulation. In other words, hydrolysis is thought to have occurred before the reaction solution became homogeneous.

[0196] 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 shown, the product is a sintered body with a checkered pancake shape. Non-Patent Document 3 describes the control of the nanostructure of microparticles in spray pyrolysis, explaining the formation of porous silica from a core material and a silica core with the same surface potential (in this case, negative). While this technique does not involve a spraying step, it is clear that a precursor imparting a porous structure can also be generated in a uniform system. Therefore, 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, resulting in hollow inorganic particles. In this case, the surface potential of the core material, which determines whether the target hollow inorganic particles can be obtained, is estimated to be around -3 mV, which is midway between Comparative Example 3 and Example 8.

[0197] Comparative Example 4 was used to determine firing conditions. The true specific gravity became the same as that of silicon dioxide. These particles appear similar to the hollow inorganic particles of Example 1, but the shell densification is incomplete, and mesopores are likely to remain.

[0198] The effects of surfactant addition concentration were compared in Examples 1-3 and Comparative Examples 5-6. The surfactant concentrations in the mother liquors were adjusted to 10%, 5%, 2%, 1%, and 0% by mass, respectively. Figure 8 shows a comparison of the appearance of the silica produced under these conditions. At a surfactant concentration of approximately 1% by mass, a large amount of amorphous silica was present. In other words, under dilute conditions, the remaining hydrolyzed products, which were not adsorbed to the hydrophilic portion of the surfactant, aggregated and polymerized. On the other hand, the 0% by mass sample was mostly pumice-like sintered, with some hollowing out and then mixing in a fractured state. The core material coating was found to be only approximately 5 nm thick, presumably unable to withstand disintegration. The 1% surfactant concentration sample achieved nearly the desired structure for the hollowed sample, demonstrating the ability to attach a sufficiently thick shell during core / shell particle formation by utilizing the microphase separation structure created by the surfactant. Furthermore, it is conceivable that surfactants also have the effect of inhibiting sintering of particles during denucleation caused by firing. Furthermore, while it is known that concentrations higher than 10% by mass can produce an L3 phase layered structure, for economic reasons, experiments were conducted only up to 10% by mass.

[0199] Example 4 and Comparative Examples 7 to 9 are used to demonstrate the effects of changing the molecular weight or the size of the hydrophobic block of the Pluronic surfactant.

[0200] Example 4 and Comparative Example 7 used materials with an HLB nearly identical to that of Example 1 and examined the effect of molecular weight. The specific surface area of ​​the hollow inorganic particles in Example 4 was even smaller than that of the example. In contrast, Comparative Example 7 exhibited a significantly larger specific surface area. This can be explained as follows. The silica core of this embodiment is a microphase-separated structure containing silicic acid oligomers between layers of a layered structure formed by the adsorption of hydrolyzable silane hydrolysates onto the polar blocks of the surfactant, locally forming mesoporous silica. The surfactant is removed by firing, leaving the mesopores. Next, firing at high temperatures densifies the shell. With surfactants of low molecular weight, the initially generated mesopores are small, making densification easier during firing. While using surfactants of high molecular weight yields larger mesopores, these cannot be sufficiently broken down under the firing conditions used in this study, resulting in the formation of through-pores in Comparative Example 7.

[0201] Comparative Examples 8 and 9, with the same hydrophilic block size, were compared to determine the effect of HLB. This indicates that the desired hollow structure was not achieved regardless of the HLB. This is likely due to the instability of the lamellar structure, resulting in the micelle structure (in the case of a large hydrophilic block) or the inverse micelle structure (in the case of a large hydrophobic block) becoming the primary component.

[0202] Example 5 uses a BAB-type block copolymer, while Example 6 uses an AB-type block copolymer. Regardless of the surfactant used, hollow inorganic particles similar to those in Example 1 were obtained. Thus, the block structure of the surfactant is not a concern; by appropriately selecting the HLB of the surfactant, the desired hollow structure can be achieved.

[0203] Examples 7 and 8 compare the effects of varying the size or material of the core material. This demonstrates that, in this technology, the diameter of the hollow inorganic particles can be altered by varying the size of the core material. Furthermore, although not illustrated as an example, varying the ratio of hydrolyzable silane to core material allows for differentiation of hollow inorganic particles with varying hollow ratios.

[0204] Figure 9 shows the microstructure of the shell layer of the hollow inorganic particles of Example 7. (a) and (b) show observations of the surface and inner contour of the hollow inorganic particles, respectively. Both images reveal the presence of a spongy, random structure originating from the L3 phase. (c) shows a cross-section of the particle using a resin sheet containing the hollow inorganic particles. On the end surface (upper left), traces of the spongy, random structure originating from the L3 phase appear as streaks.

[0205] The silicon dioxide produced by this technology can be suitably used as a filler added to semiconductor materials due to its purity and dielectric properties.

[0206] none

Claims

1. A hollow inorganic particle material, wherein the hollowness is 20% by volume or more and 75% by volume or less and has a shell made of inorganic material, wherein the shell has a structure derived from microphase separation structure, the inorganic material contains more than 90% silicon dioxide based on the total mass of the particle material, and the content of alkali metal, alkaline earth metal, halogen and oxyacid is less than 10 ppm based on the total mass of the particle material, and the volume average particle size of the primary particles is more than 100 nm and less than 5 μm.

2. A hollow inorganic particle material, wherein the hollowness is 20% by volume or more and 75% by volume or less and has a shell composed of inorganic material, wherein the aforementioned inorganic material contains more than 90% silicon dioxide based on the total mass of the particle material, the aforementioned shell has a structure derived from microphase separation structure, and the content of alkali metal and alkaline earth metal is less than 10 ppm based on the total mass of the particle material.

3. The hollow inorganic particle material as described in claim 2, wherein the content of halogens and oxyacids is less than 10 ppm based on the total mass of the particle material.

4. The hollow inorganic particle material as described in any one of claims 1 to 3, wherein the uranium content is less than 5 ppb and the thorium content is less than 5 ppb.

5. The hollow inorganic particle material described in any one of claims 1 to 3 is formed by surface treatment with one or more surface treatment agents selected from the group consisting of alkoxysilanes having the structure of general formula (1): R1nSi(OR2)(4-n): and silazanes having the structure of general formula (2): (R13Si)2NH (in the general formula, R1 is an alkyl, phenyl and alkyl or phenyl with substituents, and R2 is an alkyl having 1 to 5 carbons or a group of which is substituted with heteroatoms).

6. The hollow inorganic particle material as described in any one of claims 1 to 3, wherein the relative permittivity is 3.4 or less and the dielectric loss tangent is 0.01 or less, as measured at 1 GHz.

7. The hollow inorganic particle material as described in claim 6, wherein the relative permittivity is 3.0 or less, the dielectric loss tangent is 0.006 or less, and the dielectric loss tangent per unit specific surface area is 4 × 10⁻³ g / m² or less, as measured at 1 GHz.

8. An inorganic filler comprising an inorganic particle mixture having: a hollow inorganic particle material as described in any one of claims 1 to 7, and other inorganic particle materials mixed in a proportion of 50% to 800% based on the mass of the aforementioned hollow inorganic particle material.

9. A method for manufacturing a hollow inorganic particle material, comprising: a core material dispersion preparation step, wherein a core material is dispersed in a mother liquor comprising a mixture of a nonionic surfactant and a dispersion medium, wherein the dispersion medium comprises water and may also comprise an aqueous solvent; a composite formation step, wherein hydrolysate of a hydrolyzable silane is mixed in the aforementioned core material dispersion and stirred to form an adsorbed composite on the surface of the aforementioned core material having the aforementioned hydrolysate adsorbed thereon; a core-shell composite formation step, wherein a polycondensation reaction of the aforementioned hydrolysate prior to the adsorbed composite is carried out in the aforementioned mother liquor to obtain a core-shell composite; and a firing step, wherein the aforementioned core-shell composite is fired to remove the aforementioned core material.

10. A slurry composition comprising: a dispersion medium, and a hollow inorganic particle material as described in any one of claims 1 to 7 or an inorganic filler as described in claim 8, dispersed in the dispersion medium at a ratio of 5% to 60% by mass based on the total mass.

11. A resin composition comprising: a resin material, and a hollow inorganic particle material as described in any one of claims 1 to 7 or an inorganic filler as described in claim 8, dispersed in the resin material at a ratio of 5% to 60% by mass based on the total mass.

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