Hollow silica particle material, method for producing hollow silica particle material, and inorganic filler, slurry composition, and resin composition

Abstract

Provided are a hollow silica particle material having a silica shell exhibiting excellent dielectric properties, a method for producing the same, and a material containing the hollow silica particle material. The hollow silica particle material has one or more voids isolated from the outside by a shell layer made mainly of silica, contains silica representing 90% or more of the total mass, and contains 10-5000 ppm of one or more inorganic elements (intentionally added elements) having an oxidation number of 2-4 based on the total mass of the hollow silica particle material. The content of alkali metals, etc., inevitably admixed is 10 ppm or less in all cases based on the total mass. The relative dielectric constant when measured at 1 GHz is 2.5 or less, and the dielectric loss tangent when measured at 1 GHz is 0.005 or less.

Description

Hollow silica particle material, method for producing hollow silica particle material, inorganic filler, slurry composition, and resin composition

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

[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 voltage are also 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. While adding silica as a filler to resin compositions can achieve a low thermal expansion coefficient that cannot be achieved with resin alone, improvements in dielectric properties have plateaued.

[0003] Therefore, by using a composite material of air and silica, so-called hollow silica, as a filler, it has been studied to achieve a low dielectric constant and a low dielectric loss tangent while maintaining the thermomechanical properties of silica, and various synthesis methods for producing hollow silica are known. The applicant also proposed a method using a water-soluble silicate ester (Patent Document 1).

[0004] International Publication No. WO2023 / 175994

[0005] Journal of the Ceramic Society of Japan, Vol. 104, Pages 963-968, 1996

[0006] As their name suggests, hollow silica particles have a space (hollow structure) inside them that is isolated from the outside world. Due to their structural characteristics, they are produced using a more complex process than solid silica particles (silica particles without a hollow structure). Their production methods can be broadly divided into "template synthesis," "spray pyrolysis" (Non-Patent Document 1), and "foaming" (Non-Patent Document 2). In terms of particle size, production efficiency, and product purity, "template synthesis" is the preferred method for fillers for electronic materials. While recognizing that there are variations, hollow silica particles are synthesized as core-shell particles in which silica or the like is accumulated on the outside of a core material (template), and the core material is then removed by firing or dissolution.

[0007] Generally, the dielectric constant of hollow silica particles decreases with increasing hollowness, but the dielectric loss tangent is worse than the value calculated (predicted) from the material and hollowness. One factor contributing to this is the silanol groups present on the silica surface. Due to their structure, hollow silica particles have not only the outer surface (the so-called outer surface) but also the interface between the isolated space in the hollow structure and the shell (the inner surface). The outer surface, like the surface of solid silica, can be treated to remove silanols. However, the inner surface is inaccessible after the hollow silica particles are completed, making surface treatment unsuitable. Achieving the required dielectric properties requires the creation of particles with a larger hollowness, which presents a dilemma: mechanical properties are compromised.

[0008] Therefore, the first problem is that it is necessary to improve the dielectric properties of silica itself. In the process of solving the first problem, it was found that silica equivalent to the high purity grade of commercially available solid silica can be synthesized by using a precursor whose main components are polysilsesquioxane (Formula 1) and / or polysiloxane (Formula 2). In other words, the amount of inorganic elements other than Si and O that are inevitably mixed in, and the amount of ionic impurities extracted with water, etc., are extremely small, and the amount of radioactive elements such as uranium and thorium is also low. These properties are suitable for the electronic material applications for which this product is intended to be used, but problems have become apparent, such as difficulty in mixing with resins and low adhesion. This has been identified as the second problem to be solved. (Formula 1) (RSiO １．５ ) ｎ (Formula 2) (R２ SiO) ｎ

[0009] The present invention has been made in view of the above-mentioned problems, and provides a hollow silica particle material to which an inorganic component other than silica is intentionally added within a range that maintains properties suitable for electronic material applications, a method for producing the same, and a material containing the hollow silica particle material.

[0010] The hollow silica particles that are the premise of the embodiment are manufactured by "template synthesis," that is, core-shell particles (precursors) are synthesized by depositing and polymerizing silica or a substance that will become silica in a later process (hereinafter referred to as "substance that will become silica") on the outside of a core material (template) having a morphology similar to the target particle shape, and then the core material is removed and the shell is silicified, leaving a silica shell (shell). Specifically, the first problem was solved by finding that dielectric properties can be easily improved by selecting a core material with a surface potential that is not repulsive to silica and forming a shell layer whose main component is polysilsesquioxane and / or polysiloxane. (Formula 3) R １ ｎ Si(OR ２ ) ４－ｎ In formula 3, n is 0, 1, or 2.

[0011] Polysilsesquioxane and / or polysiloxane are synthesized using an organic silane compound (Formula 3) as a raw material. It is known that using these compounds results in silica with even fewer impurities than commercially available high-purity solid silica. In contrast, the second problem was solved by discovering that the inclusion of inorganic elements with oxidation states of 2, 3, or 4 (hereinafter referred to as "intentionally added elements"), such as Al, B, Ca, Mg, Ti, and Zn, facilitates improvements in surface treatment coverage and compatibility / adhesion with resins. Carefully selecting and optimizing the type and amount of the intentionally added elements allowed the completion of this embodiment.

[0012] That is, a hollow silica particle material according to an embodiment has one or more voids inside the particle that are isolated from the outside by a shell layer composed mainly of silica, and is characterized in that it contains 90% or more silica based on the total mass of the hollow silica particle material, contains 10 ppm to 5,000 ppm of intentionally added elements, the contents of alkali metals, alkaline earth metals, halogens, and oxoacids excluding the intentionally added elements are all 100 ppm or less based on the total mass of the hollow silica particle material, the total volume of voids accounts for 40 vol% to 75 vol% of the volume of the hollow silica particle material, the volume average particle diameter of primary particles of the hollow silica particle material is 100 nm to 2 μm, the relative dielectric constant when measured at 1 GHz is 2.5 or less, and the dielectric loss tangent when measured at 1 GHz is 0.003 or less.

[0013] The method for producing a hollow silica particle material is characterized by comprising a core-shell composite formation step of mixing and stirring a hydrolyzate of a hydrolyzable silane and a compound containing an inorganic element that is intentionally added as needed with a core material dispersion obtained by dispersing a core material in water, and carrying out a condensation polymerization reaction of the hydrolyzate on the surface of the core material to obtain a core-shell composite having a shell that contains the intentionally added element as needed, and a calcination step of calcining the core-shell composite to remove the core material.

[0014] The hollow silica particle material of the present invention is a hollow silica particle having a shell layer made of dense silica and having sufficiently small relative dielectric constant and dielectric loss tangent, which can be easily mixed with resins and solvents when processed into electronic materials, is resistant to penetration of resins and solvents, exhibits an excellent low relative dielectric constant and low dielectric loss tangent even in resin compositions, and can exhibit excellent adhesion in the environment in which the resin composition is used.Furthermore, the hollow silica particle material of the present invention has the same configuration as solid silica particles except that it is a silica particle having a hollow structure, and therefore has the same handleability as solid silica particles.

[0015] 1A and 1B are scanning electron microscope photographs of hollow silica particles prepared in Example 1, where (A) is a photograph emphasizing the internal structure, and (B) is a photograph emphasizing the shape. 1B is a graph of the particle size distribution of hollow silica particles prepared in Example 1. 1C is a graph of the infrared absorption spectrum when the hollow silica particles prepared in Example 1 are surface-treated. 1D is a scanning electron microscope photograph of a cross section of a resin composition using hollow silica prepared in Example 1. 1E is a scanning electron microscope photograph of hollow silica prepared in Examples 4, 5, 6, and 7. 1F is a graph comparing the kneading viscosity of hollow silica prepared in Examples 4 to 7, where (A) is a graph showing the viscosity profile, and (B) is a graph comparing the viscosity at a shear of 10 / sec relatively.

[0016] The hollow silica particles (hollow silica particle material) of the embodiment are suitably used as an inorganic filler to be contained in a resin composition for electronic materials. For example, they 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, the hollow silica particles (hollow silica particle material) of the embodiment may be mixed with other inorganic particle materials to form an inorganic filler. The other inorganic particle materials are mixed in a ratio of 50% to 800% based on the mass of the hollow silica. Examples of the other inorganic particle materials include magnesia, alumina, zirconia, titania, and solid silica. The other inorganic particle materials are preferably spherical.

[0017] (Hollow Silica) The hollow silica particles of the embodiment have a shell layer made of silica and one or more voids partitioned inside the shell layer. The presence or absence of voids inside the shell layer of the hollow silica particles can be confirmed by observing the hollow silica 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). In the case of SEM observation, the hollowness can be confirmed not only by observing the cross section of the resin-embedded silica, but also by an observation method that reflects the internal structure of the particle by increasing the acceleration voltage of the electron beam.

[0018] The void ratio is the ratio of the total volume of voids present inside the hollow silica particle to the volume of the hollow silica particle. Unless otherwise specified, the void ratio is the average value of all particles constituting the hollow silica, and is calculated as the ratio of the sum of the void volumes to the sum of the volumes of the hollow silica particles. In detail, the void ratio is calculated by the method described below.

[0019] In the present embodiment, a hollow structure with a sufficiently thin shell layer can be formed, so no upper limit for the hollow ratio is specified. The higher the hollow ratio, the lower the relative dielectric constant and dielectric loss tangent of the hollow silica particle material. However, if the hollow ratio is extremely high, the thickness of the shell layer becomes thin, resulting in a decrease in mechanical strength. Therefore, a hollow ratio that is equal to or greater than the lower limit of the hollow ratio specified based on the required dielectric properties and that has practically acceptable mechanical strength is selected.

[0020] For applications in which the embodiments are used as products, the dielectric constant required for hollow silica particle materials must be 2.8 or less, and more preferably 2.5 or less. The dielectric constant of silica constituting the inorganic material is 3.6 to 4.2, and combining this with the dielectric constant of 1.0 in a vacuum, the dielectric constant of hollow silica 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 at which the dielectric constants are 2.8 and 2.5 are approximately 35% and 45%, respectively. Considering that the dielectric constant of hollow silica increases due to the influence of silanol groups on the void surfaces, the lower limit of the porosity is at least 40%, preferably 45%, and more preferably 50%.

[0021] Here, the "voids partitioned within the shell layer" in hollow silica particle materials refers to the region inside the particle that is isolated from the outside of the particle by the shell layer, through which molecules of solvents, resins, etc. cannot pass. Although the particles may have so-called micropores that are sufficiently small for the molecules of solvents, resins, etc., they must not have holes (mesopores and macropores) through which molecules of solvents, resins, etc. can pass. Silica particles that do not have voids are called solid silica particle materials.

[0022] The size of the pores can be analyzed by measuring the true specific gravity using two types of probes (helium gas and nitrogen gas) for gases that pass through the micropores and gases that do not. Micropores are those that can only pass helium gas but not nitrogen.

[0023] The density (ρ) of the hollow silica of the embodiment is increased by helium gas. Ｈｅ ) was measured, and the density of the shell layer ρ ｓｈｅｌｌ (=ρ Ｈｅ The density of the shell layer, ρshell, is determined to be 2.1 g / cm ３ Above, 2.5g / cm ３ It is preferable that the density is 2.2 g / cm or less. ３ Above, 2.4g / cm ３ More preferably, it is:

[0024] The density (ρ Ｎ２ ) was measured, and the density of the hollow silica particles containing voids, ρ ｐａｒｔｉｃｌｅ (=ρ Ｎ２ ) is determined. The void ratio is the density of the shell layer ρ ｓｈｅｌｌ and the density of hollow silica ρ ｐａｒｔｉｃｌｅ Specifically, the hollow ratio can be calculated from {1-ρ Ｎ２ / ρ Ｈｅ}×100(%) (Calculation Method 1). The hollow ratio is calculated by determining the particle diameter (D) and the shell layer thickness (t) from a TEM image or an SEM image, and then calculating (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 silica particles that can be identified on the image is used.

[0025] In measuring the hollow fraction, calculation method 1 is used when 1 g or more of hollow silica particles (hollow silica particle material) can be measured independently. Calculation method 2 is used when the hollow fraction value for each hollow silica particle is required. Calculation method 2 is used when the hollow silica to be measured is 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.

[0026] In the hollow silica particles according to the embodiment, the volume average particle diameter of the primary particles is 100 nm or more and 2 μm or less. Examples of lower limits of the volume average particle diameter of the primary particles include 100 nm, 120 nm, and 150 nm, and examples of upper limits include 2 μm, 1.5 μm, and 1 μm. These lower and upper limits can be combined in any manner.

[0027] The shell layer is composed of an inorganic material primarily composed of silica, and contains insoluble inorganic components consisting of intentionally added elements as needed. However, unavoidably mixed organic components and unavoidably mixed inorganic components may also be included. The inorganic components include 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. The intentionally added inorganic components are not particularly limited, and examples include inorganic elements with an oxidation number of 2, 3, or 4, such as Al, B, Ca, Mg, Ti, and Zn, which exist in the form of oxides, nitrides, oxoacids, or composite oxides of these elements with silicon. Two or more intentionally added elements may also be included.

[0028] In the hollow silica particle material of the embodiment, when intentionally added elements are contained, the intentionally added elements are at least 10 ppm or more. If the concentration is less than this, it is difficult to distinguish them from the inorganic materials that are inevitably mixed in, making it impossible to determine their effect. Furthermore, the upper limit is 5000 ppm. Although it is possible to produce a higher concentration, if the concentration is higher than this, the properties of silica are reduced, making it unusable for electronic material applications. Elements other than these intentionally added elements are each 150 ppm or less, preferably 100 ppm or less, more preferably 50 ppm or less, more preferably 20 ppm or less, and even more preferably 10 ppm or less.

[0029] In the embodiment, the hollow silica particle material is extracted with water containing F, Cl, NO ２ ,Br,NO ３ , S.O. ４ , P.O. ４ , Li, Na, NH ４The content of each of the 13 types of cations and anions listed as 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.

[0030] By keeping the amount of inorganic components other than silicon at or below this upper limit, the amount of ionic impurities extracted from the hollow silica particle material of the embodiment is reduced. In particular, by keeping the amount of alkali metal ions and alkaline earth metal ions at or below this upper limit, the insulating properties are improved. By keeping the amount of halogen ions at or below this upper limit, when the hollow inorganic particle material of the embodiment is used as a filler for electronic materials, the occurrence of wiring corrosion due to the infiltration and diffusion of halogens into products is sufficiently suppressed. Furthermore, by keeping the amount of oxo acid ions at or below this upper limit, the amount of oxo acid that exists as free oxo acid and does not form a shell layer as a complex oxide is sufficiently reduced, improving the insulating properties and corrosion resistance.

[0031] In the hollow silica particle material of the embodiment, the uranium (U) and thorium (Th) contents are each 10 ppb or less, preferably 5 ppb or less, further preferably 3 ppb or less, more preferably 2 ppb or less, and further preferably 1.5 ppb or less.

[0032] 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 products when the hollow silica particle material of the embodiment is used as a filler for electronic materials to a level that cannot be distinguished from soft errors caused by alpha rays originating from other components or cosmic radiation.

[0033] Dielectric properties of hollow silica The dielectric constant is as described above, and considering the applications of hollow silica particle materials, the dielectric loss tangent must also be sufficiently low. The dielectric loss tangent is typically evaluated in the composite material to be used, but it is essential that the dielectric loss tangent of the hollow silica particle material alone is 0.01 or less, desirably 0.005 or less, preferably 0.003 or less, more preferably 0.002 or less, and even more preferably 0.001 or less.

[0034] Surface Treatment of Hollow Silica The hollow silica particle material of the embodiment is subjected to a surface treatment, which is expected to improve the dielectric properties and affinity with other materials.

[0035] The first purpose of the surface treatment is to eliminate silanol groups remaining on the surface of the hollow silica particle material by so-called capping. For example, surface treatment agents include compounds having trimethylsilyl groups, more specifically, methoxytrimethylsilane, ethoxytrimethylsilane, hexamethyldisilazane (HMDS), etc. In addition, surface treatment agents used for the second purpose described below can also be expected to have a capping effect.

[0036] A second purpose of surface treatment is to use a surface treatment agent that improves the affinity between the material and the final contact material. For example, a silane compound is used as the surface treatment agent. Examples of silane compounds include compounds having alkyl groups, vinyl groups, phenyl groups, methacryl groups, and epoxy groups as functional groups, as well as alkyl groups having these groups on their side chains. More specifically, without being limited by the examples, examples include 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 aryltrialkoxysilane, 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 (in each case, alkoxy is a functional group derived from an alcohol such as methoxy, ethoxy, isopropoxy, etc.).

[0037] (Method for producing hollow silica particle material) The method for producing hollow silica particles (hollow silica particle material) of the embodiment is a method that can suitably produce the hollow silica particles of the embodiment described above. This method produces a precursor, a core-shell particle having a core material as the core and silica or a substance that becomes silica by calcination or the like as the shell, and produces hollow silica particles by removing the core from the precursor and silicating the shell. The method for producing hollow silica particles of the embodiment includes a core-shell composite formation step, a calcination step, and other necessary steps.

[0038] Core Material Dispersion The core material dispersion is a dispersion medium in which a core material is dispersed. A catalyst (typically, but not limited to, an acid or alkali) that promotes the hydrolysis and polymerization of the organosilicon compound is added to the dispersion medium as needed. The core material may be dispersed before or after the addition of other components to the dispersion medium, or the other components and the core material may be dispersed simultaneously. The catalyst that promotes the polymerization of the hydrolyzed product of the organosilicon compound may be added when preparing the core material dispersion, after preparing the core material dispersion, simultaneously with the addition of the organosilicon compound, or after the addition of the organosilicon compound has been completed. Furthermore, a compound containing an intentionally added element may be added to the core material dispersion as needed. In this case, the compound containing the intentionally added element may be added at any time.

[0039] The dispersion medium may be either 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), or may be a mixture of two or more thereof.

[0040] Core material: By selecting the core material, it is possible to synthesize hollow silica of various sizes. Voids are formed with a size and shape that correlate with the size and shape of the selected core material. The core material is preferably a particulate material that is dispersed in water or can be dispersed in water.

[0041] The core material is preferably made of an organic material that is easily removable, and is particularly preferably made of a resin material. It is preferable to make the core material from a resin material and remove the core material made of the resin material by baking. For example, a resin dispersed in water, such as a resin emulsion, is suitable for the core material. It may be synthesized by a known method, or a commercially available product can be used. The type of resin and the method of obtaining it are not limited here.

[0042] Generally, polymers of silica or hydrolyzed organosilicon compounds (silica source) are weakly negatively charged. Therefore, if a material other than particles that becomes strongly negatively charged under the reaction conditions for producing the silica source is used as the core material, the repulsion between the periphery of the core material and the resulting silica source is reduced, and a shell layer made of the silica source is formed in a suitable form around the core material. Various experiments have shown that the surface potential in a liquid of a resin that is preferably used as a core material is -3 mV or higher, and more preferably 3 mV or higher. When resin particles or resin emulsions that do not meet this condition are used as the core material, the surface potential can be converted to positive by a known method.

[0043] Core-shell complex formation: The core-shell complex formation process involves mixing and stirring a hydrolyzate of a hydrolyzable organosilicon compound with a core material dispersion, and adsorbing the hydrolyzate or polymerized hydrolyzate onto the surface of the core material to form an adsorption complex. The hydrolyzate of the hydrolyzable organosilicon compound to be mixed may be one that has been hydrolyzed in advance, or it may be added as a hydrolyzable organosilicon compound when added, and the hydrolysis reaction and polymerization can proceed in the core material dispersion to form the hydrolyzate.

[0044] Hydrolyzable organosilicon compound The organosilicon compound is a compound represented by the above formula 3, where n is an integer of 0 to 3. １ is an alkane or alkene having a main skeleton of one or more carbon atoms, which may have a substituent containing a hetero element, and when n is 2 or 3, R １ may be the same or different structures. ２The main skeleton is an alkane having 1 to 4 carbon atoms, and may have a hydroxyl group in the side chain.

[0045] Although hollow silica can be synthesized using only orthosilicate esters (n = 0), such as TEOS (tetraethyl silicate), the dielectric properties after calcination are difficult to improve. On the other hand, when precursors were prepared using monoalkyltrialkoxysilanes (n = 1) or dialkyldialkoxysilanes (n = 2) and calcined, the resulting precursors had lower dielectric properties than those prepared using orthosilicate esters alone. Starting with orthosilicate esters alone produces amorphous silica directly from orthosilicic acid in the precursor shell layer. However, microscopically, the four arms of orthosilicic acid form a three-dimensional, four-coordinated structure, i.e., a three-dimensionally continuous cage structure, which is rigid and makes it difficult for dehydration between free silanol groups present at grain boundaries to proceed during calcination. On the other hand, starting with monoalkyltrialkoxysilanes or dialkyldialkoxysilanes results in polysilsesquioxanes and polysiloxanes, respectively, in the precursor shell layer. These have two-dimensional and one-dimensional molecular structures, respectively, which allows for easy intermolecular positional changes during calcination, which is thought to facilitate dehydration between the silanol groups present inside.Furthermore, copolymerization of trialkylmonoalkoxysilanes also allows for the adjustment of the silica microstructure, making it possible to synthesize precursors composed of shells with more flexible molecular structures.

[0046] Specific examples of the monoalkyltrialkoxysilane include, but are not limited to, methyltrialkoxysilane, phenyltrialkoxysilane, n-propyltrialkoxysilane, hexyltrialkoxysilane, octyltrialkoxysilane, decyltrialkoxysilane, vinyltrialkoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrialkoxysilane, 3-glycidoxypropyltrialkoxysilane, p-styryltrialkoxysilane, 3-methacryloxypropyltrialkoxysilane, 3-acryloxypropyltrialkoxysilane, N-2-(aminoethyl)-3-aminopropyltrialkoxysilane, 3-aminopropyltrialkoxysilane, N-phenyl-3-aminopropyltrialkoxysilane, 3-ureidopropyltrialkoxysilane, 3-mercaptopropyltrialkoxysilane, 3-isocyanatopropyltrialkoxysilane, and 3-trialkoxysilylpropylsuccinic anhydride (wherein alkoxy is a functional group derived from an alcohol such as methoxy, ethoxy, or isopropoxy).

[0047] Specific examples of dialkyldialkoxysilanes are not limited to those exemplified above, and commercially available from various companies include dimethyldialkoxysilane, dialkoxydiphenylsilane, 3-glycidoxypropylmethyldialkoxysilane, 3-methacryloxypropylmethyldialkoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldialkoxysilane, and 3-mercaptopropylmethyldialkoxysilane (in each case, alkoxy is a functional group derived from an alcohol, such as methoxy, ethoxy, or isopropoxy).

[0048] Specific examples of orthosilicate esters include, but are not limited to, tetramethoxysilane (TMOS), tetraethoxysilane (TEOS), tetrapropoxysilane, etc. Specific examples of trialkylmonoalkoxysilanes, etc., are also not limited to, but include methoxytrimethylsilane, ethoxytrimethylsilane, etc., as well as silazanes whose hydrolyzates give compounds with the same structure, such as hexamethyldisilazane.

[0049] Monoalkyltrialkoxysilanes, dialkyldialkoxysilanes, orthosilicate esters, and trialkylmonoalkoxysilanes are almost always oil-soluble compounds. To adjust the water solubility of these compounds, they may be converted into compounds with hydroxyl groups introduced into the side chains of the alkoxy groups by transesterification in the presence of a polyhydric alcohol and an acid. Examples of polyhydric alcohols include ethylene glycol, propylene glycol, and glycerol.

[0050] The monoalkyltrialkoxysilane, dialkyldialkoxysilane, orthosilicate ester, and trialkylmonoalkoxysilane may be used either alone or as a mixture in any desired ratio.

[0051] Calcination: The calcination process involves calcining the core-shell composite to decompose and remove the core material (denucleation), and then decomposing and removing the organic components of the shell layer (debinding), converting them to silica. At the same time, the shell layer is densified. All of the steps may be performed in a single heating step, or a separate step, a "debinding step," may be added before densifying the shell layer, in which heating is performed at a lower temperature of approximately 600°C for the purpose of denucleation and debinding. The conditions are not particularly limited as long as the core material is decomposed and removed without destroying the shell layer formed on the surface of the core material, and examples include heating in an oxidizing atmosphere. For example, calcination is performed in air at a temperature and for a time sufficient to decompose and remove the core material.

[0052] 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. While a higher firing temperature is preferable, it should be below the temperature at which the hollow silica particles aggregate or the silica melts. Even if the particles aggregate, they may be allowed to aggregate if they can be separated into primary particles by a crushing operation. Since the core-shell composite is produced while immersed in the mother liquor, a step of separating the particles from the mother liquor can be included before the firing step. For example, steps such as filtration, centrifugation, and drying can be employed. Furthermore, a crushing operation to break down the aggregates may be appropriately incorporated between each of the individual operations.

[0053] Intentionally Added Inorganic Elements Intentionally added inorganic elements (intentionally added elements) are not limited to the examples. Examples include inorganic elements with an oxidation number of 2, 3, or 4, such as Mg, Ca, Ti, Zn, B, and Al. The intentionally added elements may be any elements that remain in the silica layer after the firing process in the form of oxides, nitrides, oxoacids, or composite oxides of these elements with silicon. These inorganic elements are added as compounds (intentionally added element-containing compounds) that change to the above chemical form after the firing process. Such compounds are not limited to the examples, and include industrially available hydroxides, carbonates, nitrates, metal complexes with organic ligands, and other elements that meet the objectives of the embodiments. The intentionally added element-containing compound may be used alone or dissolved in an appropriate solvent. Alternatively, a mixture of multiple intentionally added element-containing compounds may be used.

[0054] Methods for leaving the silica in the silica layer after the firing step include a method in which the silica is incorporated as an insoluble substance into the shell portion of the core-shell particle together with the silica source in the core-shell composite formation step (co-deposition method), and a method in which a compound containing an intentionally added element is brought into contact with the synthesized particles and then insolubilized / fixed (post-addition method).

[0055] In the former synthesis method (eutectoid method), the organosilicon compound and the intentionally added element-containing compound may be mixed in advance and added, or each may be added separately. When added separately, they may be added to the reaction solution at the same time or at different times. When added at different times, the order of the organosilicon compound and the intentionally added element-containing compound does not matter. Furthermore, when multiple intentionally added element-containing compounds are used, each intentionally added element-containing compound may be added by a different method / at a different time.

[0056] In the latter synthesis method (post-addition method), the intentionally added element-containing compound may be contacted immediately after the core-shell particles are obtained, between the debinding step and the densification step, or after the hollow silica particles have been completed. The intentionally added element-containing substance may be insolubilized / fixed by hydrolysis and condensation reaction, or by infiltration by calcination. When the intentionally added element-containing compound is used as a solution, a drying step for removing the solvent may be inserted between the two. When calcination is performed, the drying step may be performed simultaneously (continuously) with a single calcination step, a debinding step, or a densification step.

[0057] Controlling the Shell Layer Thickness and the Size of Hollow Silica Particles To summarize the manufacturing method of hollow silica particles (hollow silica particle material) according to the embodiment, the thickness of the shell layer can be increased by increasing the ratio between the amount of organosilicon compound and the amount of core material or by using a core material with a high surface potential. The size of the hollow silica particles can be controlled by controlling the size of the core material, controlling the thickness of the shell layer, or a combination of these.

[0058] (Slurry Composition) The slurry composition of the embodiment is a composition in which the hollow silica of the above-described embodiment is dispersed in a dispersion medium. The slurry composition of the embodiment is 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.

[0059] The mixing ratio of hollow silica to dispersion medium in the slurry composition is not particularly limited, and it is preferable that the hollow silica content be as high as possible. Note that, since the viscosity tends to increase as the amount of hollow silica mixed increases, hollow silica particles (hollow silica particle material) are mixed until the viscosity reaches the maximum allowable level, taking into account handleability. For example, the hollow silica particles:dispersion medium mass ratio can be about 20:80 to 80:20.

[0060] The dispersion medium is not particularly limited, and 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.

[0061] The hollow silica particles are preferably surface-treated, and the surface treatment preferably involves the introduction of functional groups that can improve the affinity between the dispersion medium used and the mating member with which the hollow silica will come into contact when finally used.

[0062] (Resin Composition) The resin composition of the present embodiment is a cured product comprising the hollow silica particles (hollow silica particle material) and a resin material in which the hollow silica particles are dispersed. The resin material preferably has a moisture content of 1000 ppm or less, more preferably 500 ppm or less.

[0063] The resin composition is preferably used in electronic materials, and as such electronic materials, it is preferably applied to applications using high frequencies such as high frequency substrates. Since the hollow silica particles according to the embodiment have a low Df value (dielectric loss tangent), the occurrence of loss is reduced even when used in applications where high frequencies are passed.

[0064] The mixing ratio of hollow silica particles to resin material in the resin composition is not particularly limited, and the content of hollow silica particles is preferably as high as possible to bring out the properties of the filler. For example, the hollow silica particles:resin material are mixed at a mass ratio of about 10:90 to 90:10.

[0065] The resin material is not particularly limited, and examples thereof include common resin materials such as thermosetting resins (which may be in either a pre-cured or cured state when mixed), thermoplastic resins, and the like, 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 multiple types of resin materials may be mixed (e.g., alloyed) and used. The moisture content of the resin material is preferably 1000 ppm or less, and more preferably 500 ppm or less.

[0066] The hollow silica particles are preferably surface-treated, and the surface treatment preferably involves the introduction of a functional group that can improve affinity with the resin material used.

[0067] (Analysis Method) In the embodiments, each analysis was performed by the following method unless otherwise expressly specified.

[0068] (1) Particle size distribution Optical particle size distribution measurement is the simplest method for analyzing the aggregation state of primary particles. However, because the refractive index of hollow silica particles (hollow silica particle material) differs from that of the inorganic materials that compose them, the average particle size obtained shows a value that deviates from the true average particle size. Therefore, optical particle size distribution measurement was used to analyze the aggregation state of particles, and the average particle size was determined by image analysis.

[0069] (1a) Analysis of Aggregation State The particle size distribution was measured using a laser diffraction particle size distribution analyzer (SALD-7500 nano manufactured by Shimadzu Corporation) under the following conditions: Dispersion medium: isopropyl alcohol Refractive index: 1.45 Calculation mode: volume

[0070] (1b) Average particle size A slurry of hollow silica particles was dropped onto a silicon wafer and dried so that the particles adhered in a single layer. The particles were then observed with a scanning electron microscope (SEM). SEM images were observed at a magnification such that approximately 100 to 1,000 particles were observed in one field of view, and the sizes of a total of approximately 1,000 particles obtained from 1 to 10 fields of view were measured. The volumetric particle size distribution was calculated based on the measurement results, and the particle size at which the cumulative frequency of the volumetric particle size distribution was 50% was taken as the average particle size. For image analysis, "A-zo-kun" (registered trademark) (manufactured by Asahi Kasei Engineering Co., Ltd.) was used as image analysis software.

[0071] (2) Porosity When measuring the void ratio, if 1 g or more of hollow silica particles can be measured independently, (2a) a gas hydrometer is used. When the particles are filled in a resin composition, or if there is only 1 g of sample, or if (2a) a gas hydrometer cannot be used, (2b) image analysis of SEM images is used.

[0072] (2a) Gas-type pycnometer The density was measured using a gas-type pycnometer (Micrometrics AccuPycII 1340) under the following measurement conditions: Sample cell: 10 cm ３ Cell Sample weight: 1 to 3 g Measurement gas: Helium and nitrogen Purge: 10 times, 135 kPa (G) Measurement: 10 times, 135 kPa (G)

[0073] The same sample was measured by switching between helium and nitrogen. Since helium can reach the inner cavity of the hollow silica particles through the micropores, 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 silica. Therefore, the hollowness is calculated as {1-(ρ Ｎ２ / ρ Ｈｅ ) × 100 (%).

[0074] (2b) Image Analysis From TEM (including STEM) images or SEM images taken with the shell layer portion of the hollow silica particles emphasized, the particle diameter (D) of each hollow silica 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 following formula was used, or, when looking at the properties as a powder, the average value calculated for 1,000 or more particles was used. {1-(2t / D)} ３ ×100 (%)

[0075] TEM (including STEM) images are ideal for this analysis. However, it is easier to use a scanning electron microscope (SU8000, manufactured by Hitachi High-Technologies Corporation) and record images that emphasize the shell layer portion even with SEM images measured under the following conditions: Acceleration voltage: 10 kV Probe distance: 15 mm Detector: Lower detector and SE detector

[0076] (3) Specific Surface Area A sample was prepared by drying the hollow silica particles of the embodiment under reduced pressure at 200° C. The specific surface area and pore volume of this sample were measured by a multipoint BET method using nitrogen gas with an automatic specific surface area / pore size distribution analyzer (Trister II manufactured by Micrometrics), or a single-point BET specific surface area measurement was performed.

[0077] (4) Silica Purity A mixture of nitric acid, sulfuric acid, and hydrofluoric acid was added to the hollow silica particles of the embodiment and heated to 120°C for dissolution. This solution was heated to 300°C to distill off the nitric acid and hydrofluoric acid to prepare a sample solution. This was 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 silica 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 Five grams of hollow silica particles according to the embodiment were immersed in 50 grams 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, manufactured by Thermo Scientific). The ion concentrations of F, Cl, NO, and HCl were determined based on the mass of the immersed hollow silica. ２ ,Br,NO ３ , S.O. ４ , P.O. ４ , Li, Na, NH ４ The contents of 13 cations and anions listed as: K, Mg, Ca were calculated.

[0079] (6) Dielectric Properties The dielectric properties of the powder were measured by filling hollow silica particles into a PTFE tube measuring 8 mm diameter x 30 mm length with the particles, and using an empty tube as a 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. From these values, the complex dielectric constant was calculated using a "Perturbation Method Dielectric Constant Calculation Application" (manufactured by Keycom Corporation). In the case of the resin composition, a rectangular column measuring approximately 4 mm x 7 mm x 30 mm was cut out from the resin composition to serve as the measurement sample. The complex dielectric constant 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 cut out from the resin composition was used as a measurement sample. This was heated from -50 ° C to 250 ° C at a heating rate of 5 ° C / min using a thermomechanical analyzer (TA Instruments, TMA Q400), and the linear expansion (coefficient of thermal expansion (CTE)) was recorded. From the plot, the average rate of change in the thermal expansion coefficient from 0 to 50 ° C was designated as CTE1, and the average rate of change in the thermal expansion coefficient from 180 to 220 ° C was designated as CTE2.

[0081] (8) Quantitation of Reactive Silanol Groups The hollow silica particle powder according to the embodiment was mixed with 100 to 500% by mass of hexamethyldisilazane relative to the powder. This mixture was heated at 120°C for 3 hours, and unreacted hexamethyldisilazane was dried and removed. The silanol groups trimethylsilylated by this procedure were defined as reactive silanol groups. Specifically, the amount of introduced trimethylsilyl groups was calculated from the difference in the amount of carbon before and after the treatment. This was then standardized by the specific surface area to obtain the reactive silanol group density.

[0082] The carbon content was measured using the following method. 35 g of methyl ethyl ketone was added to 5 g of sample powder, and the mixture was shaken for 10 minutes using a shaker. The precipitate was then recovered by centrifugation (14,000 G x 30 minutes). This process was repeated twice to remove methyl ethyl ketone-soluble components, and the mixture was then dried to prepare a sample for carbon content measurement. The carbon content of this sample was measured using a LECO CS-444LS carbon / sulfur simultaneous analyzer. JSS061-8 was used as the carbon standard sample.

[0083] (9) Resin kneading viscosity 20 parts by mass of the hollow silica particle powder according to the embodiment and 80 parts by mass of a liquid epoxy resin (a mixture of bis-A type and bis-F type) were mixed using a planetary mixer and homogenized using a triple roll mill. The viscosity of this mixture was measured using a rheometer (TA Instruments, ARES G2) equipped with a 50 mm cone plate, sweeping the shear rate from 0.1 / s to 100 / s.

[0084] (Preparation of Test Samples) (Example 1) <Synthesis of Core-Shell Particles> 67 g of acrylic resin emulsion (average particle size 300 nm, surface potential +52 mV, solid content 40 wt%) was diluted with water to obtain 1000 g of core material dispersion (core material dispersion preparation step). Subsequently, 45 g of methyltrimethoxysilane was added, and the mixture was maintained at 40°C for 12 hours, followed by the addition of 2 g of an aqueous tetraethylammonium hydroxide solution (35 wt%). The mixture was maintained at 40°C for an additional 2 hours to mature the core / shell particles (core-shell composite formation step). The resulting solid was filtered under reduced pressure using filter paper (JIS P 3801 (1995) Standard No. 5A), and the precipitate was collected.

[0085] <Denucleation by calcination> The precipitate was heated to 1000°C at a temperature increase rate of 60°C / hour and held at 1000°C for 6 hours (calcination step). The recovered silica was loosely agglomerated, so it was lightly crushed in a mortar to obtain a hollow silica particle material as a test sample for the example.

[0086] Example 2 A hollow silica particle material as an example test sample was obtained in the same manner as in Example 1, except that 40 g of dimethyldimethoxysilane was used instead of 45 g of methyltrimethoxysilane.

[0087] (Example 3) A hollow silica particle material, which is an example test sample, was obtained in the same manner as in Example 1, except that 67 g of a wax emulsion (average particle size 600 nm, surface potential +65 mV, solid content concentration 40 wt%) was used instead of 67 g of the acrylic resin emulsion in Example 1.

[0088] Example 4 100 g of acrylic resin emulsion (average particle size 300 nm, surface potential +52 mV, solid content 40 wt%) and 0.2 g of phosphoric acid (85 wt%) were diluted with water to obtain 1000 g of core material dispersion (core material dispersion preparation step). Subsequently, 45 g of methyltrimethoxysilane was added, and the mixture was maintained at 40°C for 12 hours. Subsequently, 3 g of an aqueous tetraethylammonium hydroxide solution (35 wt%) was added. The core-shell composite formation step and subsequent steps were carried out in the same manner as in Example 1 to obtain a hollow silica particle material, which was a test sample for this example.

[0089] (Example 5) A hollow silica particle material, which was a test sample of the example, was obtained in the same manner as in Example 4, except that 45 g of methyltrimethoxysilane in Example 4 was replaced with 45 g of methyltrimethoxysilane containing 500 ppm of aluminum isopropoxide.

[0090] (Example 6) A hollow silica particle material, which was a test sample of the example, was obtained in the same manner as in Example 4, except that 45 g of methyltrimethoxysilane in Example 4 was replaced with 45 g of methyltrimethoxysilane containing 1000 ppm of aluminum isopropoxide.

[0091] (Example 7) A hollow silica particle material, which was a test sample of this example, was obtained in the same manner as in Example 4, except that 45 g of methyltrimethoxysilane containing 2000 ppm of aluminum isopropoxide was used instead of 45 g of methyltrimethoxysilane in Example 4.

[0092] (Example 8) A hollow silica particle material, which was a test sample of this example, was obtained in the same manner as in Example 4, except that 45 g of methyltrimethoxysilane in Example 4 was replaced with 45 g of methyltrimethoxysilane containing 1000 ppm of triethyl borate.

[0093] (Example 9) A hollow silica particle material, which was a test sample of this example, was obtained in the same manner as in Example 4, except that the firing step at 1000°C in Example 4 was changed to two steps as follows. <Degreasing step> The core-shell particles were heated to 520°C at a temperature increase rate of 60°C / hour. At this stage, porous silica particles from which most of the organic components had been removed were obtained. <Densification> The porous silica particles from the previous step were heated to 520°C, then heated to 1000°C at a temperature increase rate of 60°C / hour, and held at 1000°C for 6 hours.

[0094] (Example 10) 100 g of the porous silica particles obtained in the degreasing step of Example 9 was suspended in 200 g of ethanol, and 0.2 g of triethyl borate was added. The suspension was heated to 80°C to remove the ethanol, and the densification step and subsequent steps of Example 9 were carried out using the suspension to obtain a hollow silica particle material as a test sample of this example.

[0095] Comparative Example 1 A solid silica particle material (a developed product manufactured by Admatechs Co., Ltd.) synthesized by the VMC (Vaporized Metal Combustion) method was used as is.

[0096] Comparative Example 2 Solid silica (manufactured by Admatechs Co., Ltd., SO-C1) synthesized by the VMC method was used as is.

[0097] Comparative Example 3 A hollow inorganic particle material prepared according to Example 1 of Patent Document 1 (International Publication No. WO2023 / 175994) was used.

[0098] (Evaluation) The appearance of the hollow silica particles obtained in Example 1 is shown in the photographs in Figure 1. The photographs in Figure 1 are scanning electron microscope photographs, with (A) emphasizing the internal structure and (B) emphasizing the shape. Both are at a magnification of 50,000x. It is clear that the particles obtained in Example 1 are hollow silica particle materials with a shell (shell layer) thickness of approximately 20 nm and a particle size of approximately 180 nm, and a shell (shell layer) thickness of approximately 15 nm and a particle size of approximately 120 nm. The reason they are a mixture of two particle sizes is because the core material used in template synthesis consists of two different particle sizes.

[0099] The hollow silica particles were suspended in isopropyl alcohol and subjected to an extrusion process (extrusion pressure 120 MPa) to obtain a homogeneous slurry composition. The particle size distribution obtained by image analysis is shown in Figure 2, and the volume average particle size was 0.14 μm.

[0100] The specific surface area and true specific gravity (ρ Ｎ２ ) were measured, and the results were 41m ２ / g and 1.06 g / cm ３ (See Table 1.) The specific surface area is the theoretical specific surface area (31 m) calculated from the particle size and specific gravity. ２ / g). Generally, silica produced by wet silica particle synthesis has unevenness on the surface due to traces of minute silica particles. For this reason, a specific surface area larger than the ideal specific surface area is observed. Increasing the firing temperature reduces the unevenness. On the other hand, the true specific gravity is determined by the specific gravity of the shell layer (ρ Ｈｅ ) is 2.26 g / cm ３ It was concluded that a substantially pore-free shell layer was formed. The void ratio was calculated to be 53%.

[0101] The hollow silica particles were reacted with 1% by mass of vinyltrimethoxysilane and then dried. Figure 3 shows the infrared absorption spectrum of the powder measured by the diffuse reflectance method. －１ There is a CH stretching vibration peak at 3746 cm, which indicates that the surface was treated with an organic silane compound (here, vinyltrimethoxysilane). －１ There is a peak of OH stretching vibration identified as a silanol group. These hollow silica particles have 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, silanol groups present on the inner surface remain even if a sufficient amount of surface treatment agent is used. These can be identified as unreacted silanol groups. Table 1 shows the average particle size, specific surface area, true specific gravity, and hollowness ratio for the examples and comparative examples.

[0102]

[0103]

[0104]

[0105] The test samples of Example 1, Comparative Example 1, and Comparative Example 3 were subjected to elemental analysis by ICP atomic emission spectrometry (see Table 2) and ion analysis of the extracted water (see Table 3). The results showed that the silica was of high purity and contained almost no elements other than silica, and the extracted water also contained almost no ions that would be problematic in semiconductor applications.

[0106] Comparative Example 1 is a solid silica synthesized by the deflagration method (VMC method), which is commonly used in the field of the present technology. Even in comparison with this, Comparative Example 1 did not contain any particularly problematic elements and had significantly lower levels of impurities than the Comparative Example. Furthermore, the uranium and thorium contents were extremely low, at 1.5 ppb and 1.0 ppb, respectively.

[0107] Comparative Example 3 is a silica particle synthesized by subjecting core-shell particles formed by a method of attaching fine silica units generated from a surfactant and a water-soluble silicate to the same template as in Example 1 to the same calcination process as in Example 1. Although the particle appearance and particle size are nearly identical, the dielectric loss tangent is clearly inferior to that of Example 1. This is thought to be because the conventional method directly obtains a silica layer from the hydrolyzate of an orthosilicate ester, which has a hard three-dimensional network structure, making dehydration between silanols present at internal grain boundaries difficult and leaving silanols more likely to remain. On the other hand, in the case of polysilsesquioxane and dimethylsiloxane, the two-dimensional or one-dimensional structure is flexible, and when Si-C bonds are broken during calcination, nearby Si-O bonds are transferred, resulting in silica formation. This is thought to result in fewer grain boundaries or the silanols on the grain boundary surfaces being easily eliminated.

[0108] An epoxy resin composition was prepared containing 25% by mass of the hollow silica particles obtained in Example 1. This corresponds to a loading of approximately 40% by mass of the solid silica in Comparative Example 1. The photograph in Figure 4 shows the cross section of the cut-out resin piece. Particles embedded inside the resin appeared as white spheres, and particles present in the cross section had a dark depression within a white outline. No resin had infiltrated into the hollow silica particles.

[0109] The hollow silica particle material of Example 1 and the solid silica of Comparative Example 1 were mixed at a mass ratio 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 (see Table 4). The dielectric constant decreased as the proportion of hollow silica particles increased. The thermal expansion coefficient showed nearly constant values ​​for both CTE1 and CTE2. Therefore, the hollow silica particle material of this technology can be said to be suitable for applications in which dielectric properties are improved while maintaining thermomechanical properties.

[0110]

[0111] In Example 2, in which a different hydrolyzable silane compound was used, and in Example 3, in which a different core material was used, hollow silica particles were obtained in the same manner as in Example 1.

[0112] In Examples 1 and 4, the precursor particles were prepared by varying the ratio of the core material to the hydrolyzable organic silane compound that forms the shell. The hollowness of the resulting particles was 53% for the particles of Example 1 and 61% for the particles of Example 4, respectively. The hollowness of the particles of Example 4, which used a large amount of core material, was high. As these results show, hollow particles with an adjusted hollowness can be produced by changing the core / shell ratio of the precursor particles. The reason why the core / shell ratio of the precursor particles and the hollowness of the hollow particles are not in a simple proportional relationship is thought to be because the shrinkage rate when the shell densifies differs from the shrinkage rate of the particles themselves.

[0113] In Examples 4 and 9, the calcination process of the precursor particles was different. In the former, denucleation, debinding, and densification were carried out in a single calcination process, while in the latter, the calcination process was divided into two steps: a debinding process for denucleation and debinding, and a densification process. As shown in Table 1, the particle size, specific surface area, and specific gravity (hollowness) were substantially the same, and no difference in the calcination process was observed. In other words, it was concluded that the processes after obtaining the precursor particles could produce equivalent products using either method.

[0114] Next, the effect of intentional addition will be shown. In Examples 4 to 7, methyltrimethoxysilane (a hydrolyzable organosilane compound) containing 0 ppm, 500 ppm, 1000 ppm, and 2000 ppm of aluminum isopropoxide was used as the intentionally added element-containing substance. As shown in the photographs in Figures 5(A), (B), (C), and (D) (all at 50,000x magnification), no significant differences were observed in the hollow structure or appearance. Furthermore, as shown in Table 1, the particle size and specific surface area were almost the same. However, significant differences were observed in the amount of aluminum (Al). Table 5 summarizes the intentionally added elements, the types and amounts of the intentionally added element-containing substances, the expected values ​​assuming that the entire amount was incorporated into the hollow silica shell, and the elemental analysis results (selected elements).

[0115]

[0116] As shown in Table 5, the amount of aluminum contained in the hollow silica particles increased in proportion to the amount added up to 1000 ppm, and this value was nearly the same as the expected value. In other words, it is believed that the added aluminum was almost quantitatively incorporated into the silica. On the other hand, at 2000 ppm, the amount incorporated was reduced to approximately 90% of the expected value. The solubility of aluminum isopropoxide in methyltrimethoxysilane is low, and when 2000 ppm was added, some of the aluminum isopropoxide precipitated. The dissolved portion decomposed at the same time as the hydrolysis of methyltrimethoxysilane, producing polysilsesquioxane with aluminum co-deposited therein, while the insoluble portion immediately converted to aluminum hydroxide and was thought to have separated during the process of filtering the precursor, etc.

[0117] Example 8 shows an example in which boron (B) was selected as the intentionally added element. Although the boron concentration was higher than in Example 4 (a control example in which the amount of intentionally added element-containing substance was 0 ppm), only approximately 30% of the expected value was incorporated. This is thought to be because the boric acid produced upon hydrolysis of triethylboric acid, used as the intentionally added element-containing compound, is relatively stable in the reaction solution, resulting in low copolymerization efficiency during polymerization of the silica precursor. Therefore, rather than co-depositing the intentionally added element, a method was implemented in which the intentionally added element was contacted with the intentionally added element-containing substance after particle synthesis (Example 10). In this example, the silica precursor was silicaized (after the degreasing process), then contacted with triethylboric acid, and immobilized on the silica in the densification process. This method allowed the added boron to be incorporated into the silica almost quantitatively.

[0118] We concluded that both the co-precipitation and post-addition methods are capable of producing hollow silica particle materials intentionally doped with impurities, although the degree of efficiency varies. The co-precipitation method is suitable when the compound containing the intentionally added element or its hydrolysate is highly soluble, especially when it can be mixed with an organosilicon compound. On the other hand, the post-addition method is suitable when it is difficult to prepare a highly concentrated solution of the compound containing the intentionally added element, or when the compound is too reactive in an aqueous system and remains dissolved in the medium without co-precipitation with the silica precursor, or when precipitation occurs.

[0119] As an example of the effect of intentional addition, the resin kneading viscosity was compared for Examples 4 to 7, which differ in aluminum content (Figure 6). Figure 6 is a graph comparing the kneading viscosity of the hollow silica particles prepared in Examples 4 to 7, where Figure 6(A) is a graph showing the viscosity profile and Figure 6(B) is a graph comparing the relative viscosity at a shear of 10 / sec. For measurement, each hollow silica particle material was surface-treated with 1 mass% vinyltrimethoxysilane and kneaded with epoxy resin to a concentration of 25 vol%. For comparison, Comparative Example 1, which was treated in the same manner, is also shown.

[0120] The addition of aluminum reduced the resin kneading viscosity, and the effect was almost proportional to the amount added up to 1000 ppm (320 ppm content) (Figure 6B). However, the effect plateaued at 2000 ppm (540 ppm content).

[0121] One characteristic correlated with the above results is the reactive silanol group density (see Table 5). In other words, it is thought that adding aluminum makes it possible to increase the amount of surface treatment, thereby improving compatibility with the resin. The reason why the effect decreases when the amount added exceeds a certain level is thought to be because the side chains of the surface treatment agent used to improve compatibility with the resin are bulky, and when the reactive silanol group density exceeds a certain level, the unreacted silanols are masked by the reacted surface treatment agent, preventing further reaction.

[0122] These results demonstrate that intentionally adding inorganic components other than silica can increase compatibility with solvents and resins and increase the amount of surface treatment, which is advantageous for improving adhesion to resins. Furthermore, it can be said that it is possible to reduce the resin mixing viscosity for both untreated and treated powders. This makes it possible to provide hollow silica particle materials that are suitable for electronic materials applications and are easier to mix with resins and have improved adhesion compared to conventional products.

[0123] The hollow silica particle material according to the embodiment is suitable for use as a filler in semiconductor materials due to its purity and dielectric properties. The hollow silica particle material is also expected to improve the performance of slurry compositions or resin compositions containing the hollow silica particle material and inorganic fillers.

Claims

1. A hollow silica particle material having one or more voids inside the particle that are isolated from the outside by a shell layer composed primarily of silica, the hollow silica particle material containing 90% or more silica based on the total mass of the hollow silica particle material, the contents of unavoidably mixed alkali metals, alkaline earth metals, halogens, and oxoacids are all 10 ppm or less based on the total mass of the hollow silica particle material, the total volume of voids in the volume of the hollow silica particle material is 40% by volume or more and 75% by volume or less, the volume average particle diameter of the primary particles of the hollow silica particle material is 100 nm or more and 2 μm or less, the relative dielectric constant when measured at 1 GHz is 2.5 or less, and the dielectric dissipation factor when measured at 1 GHz is 0.005 or less.

2. A hollow silica particle material having one or more voids inside the particle that are isolated from the outside by a shell layer composed primarily of silica, comprising: 90% or more silica based on the total mass of the hollow silica particle material; containing one or more inorganic elements (intentionally added elements) with an oxidation state of 2, 3, or 4, the content of the intentionally added elements being 10 ppm or more and 5,000 ppm or less based on the total mass of the hollow silica particle material; the contents of unavoidably mixed alkali metals, alkaline earth metals, halogens, and oxoacids being each 10 ppm or less based on the total mass of the hollow silica particle material; the total volume of voids in the volume of the hollow silica particle material being 40% by volume or more and 75% by volume or less; the volume average particle diameter of the primary particles of the hollow silica particle material being 100 nm or more and 2 μm or less; the relative dielectric constant when measured at 1 GHz being 2.5 or less, and the dielectric dissipation factor when measured at 1 GHz being 0.005 or less. A hollow silica particle material characterized by:

3. The hollow silica particle material according to claim 2, wherein the intentionally added element is any one of Al, B, Ca, Mg, Ti, and Zn.

4. The hollow silica particle material according to claim 1 or 2, wherein the uranium content is 5 ppb or less and the thorium content is 5 ppb or less.

5. In the following general formulas (1) and (2), R １ represents an alkyl group, a phenyl group, or a substituted alkyl or phenyl group; R ２ is 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, and １ nSi(OR ２ ) （４－ｎ） and an alkoxysilane having a structure of general formula (2): (R １ ３ Si) ２ 3. The hollow silica particle material according to claim 1, which is surface-treated with one or more surface treatment agents selected from the group consisting of silazanes having an NH structure.

6. An inorganic filler comprising the hollow silica particle material according to claim 1 or 2 and another inorganic particle material mixed in a proportion of 50% or more and 800% or less based on the mass of the hollow silica particle material.

7. A slurry composition comprising: a dispersion medium; and a mixture of the hollow silica particle material according to claim 1 or 2 dispersed in the dispersion medium at a ratio of 5% by mass to 60% by mass based on the total mass; or a mixture of the dispersion medium and the inorganic filler according to claim 6.

8. A resin composition comprising: a resin material; and a mixture of the hollow silica particle material according to claim 1 or 2 dispersed in the resin material at a ratio of 5% by mass to 60% by mass based on the total mass; or a mixture of the resin material and the inorganic filler according to claim 6.

9. A method for producing a hollow silica particle material according to claim 1 or 2, comprising: a core-shell composite formation step of mixing and stirring a hydrolysate of a hydrolyzable silane and a compound containing an intentionally added element into a core material dispersion obtained by dispersing a core material in water, and carrying out a condensation polymerization reaction of the hydrolysate on the surface of the core material to obtain a core-shell composite; and a calcination step of calcining the core-shell composite to remove the core material.

10. A method for producing a hollow silica particle material according to claim 1 or 2, comprising: a core-shell composite formation step of mixing a hydrolyzate of a hydrolyzable silane with a core material dispersion obtained by dispersing a core material in water, stirring the mixture, and carrying out a condensation polymerization reaction of the hydrolyzate on the surface of the core material to obtain a core-shell composite; a degreasing step of firing the core-shell composite to remove the core material; an intentionally added element addition step of mixing a compound containing an intentionally added element into the core-shell composite after the degreasing step; and a firing step of firing the core-shell composite after the intentionally added element addition step to densify the silica.

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