Silicon dioxide for electronic materials and its manufacturing method

Abstract

The purpose of this invention is to provide a silicon dioxide with low dielectric loss tangent, excellent uniform dispersibility in resins, and thus high safety. This invention relates to a filler material for electronic materials containing amorphous silicon dioxide, wherein the peak intensity ratio (A / B) of the peak A from isolated hydroxyl groups to the peak B from hydrogen-bonded hydroxyl groups in FT-IR measurements is 1.0–75.0, and there is substantially no peak from adsorbed water at 3500–3100 cm⁻¹.

Description

Technical Field

[0001] This invention relates to silicon dioxide for electronic materials and its manufacturing method. Prior Technology

[0002] Information and communication technology (ICT) is an indispensable technology in modern society for the exchange of massive amounts of information across all sectors. In recent years, in order to achieve even greater information communication, higher frequency radio waves have been used to replace the current 4G communication. The use of 5G communication, which enables massive information communication, is expanding, and electronic devices used for information communication are also becoming more high-frequency. With the increasing frequency of electronic devices, there is a growing demand for inorganic fillers in resins used to manufacture these devices that have low dielectric loss tangent. Silicon dioxide has become a focus of attention as such a material. As silicon dioxide has been conventionally used in electronic devices, this paper discloses molten spherical silicon dioxide powder after dielectric loss tangent reduction treatment (see Patent Document 1); silicon dioxide particles with specific particle size distribution, specific surface area, and dielectric loss tangent (see Patent Document 2), etc. Furthermore, as a method for manufacturing silicon dioxide for electronic materials, the following method is disclosed: A method for manufacturing filler for electronic materials includes: a step of preparing silicon dioxide particle material using a dry method; a step of performing a first surface treatment on the silicon dioxide particle material using a silane compound having a specified functional group; and a second surface treatment step of performing a surface treatment on the material particles after the first surface treatment using a specified amount of organosilazane (see Patent Document 3); A method for manufacturing hydrophobic silica particles involves reacting silica with a specified content of isolated silanol groups and a specific surface area to theoretical surface area with an organosilylating agent (see Patent Document 4). Previous technical documents Patent documents

[0003] Patent Document 1: Japanese Patent No. 6793282 Patent Document 2: Japanese Patent Application Publication No. 2021-70592 Patent Document 3: Japanese Patent No. 6564517 Patent Document 4: Japanese Patent Application Publication No. 2010-228997 Summary of the Invention

[0004] [The problem that the invention aims to solve]

[0005] In recent years, the demand for high-frequency and miniaturized electronic devices has led to a corresponding demand for miniaturized or thin-film electronic materials (electronic components) used in their manufacture. To miniaturize or thin-film electronic materials using resin compositions containing inorganic fillers, uniform dispersion of the inorganic filler within the resin is required. Therefore, both low dielectric loss tangent and uniform dispersion within the resin are essential requirements for the inorganic filler. However, conventional low dielectric loss tangent silica has the following drawbacks: in the pursuit of reducing isolated hydroxyl groups that cause dielectric loss, surface treatment agents cannot bond well with silica, resulting in insufficient dispersion within the resin. When dispersion within the resin is insufficient, high viscosity or agglomeration during resin kneading makes it difficult to meet the requirements of highly high-frequency and miniaturized thin-film electronic materials. Furthermore, from an operability perspective, high safety is also required for the inorganic filler.

[0006] In view of the above-mentioned situation, the present invention aims to provide a silicon dioxide with low dielectric loss tangent, excellent uniform dispersibility in resin, and high safety. [Technical means to solve the problem]

[0007] The inventors have studied silica, which exhibits low dielectric loss tangent, excellent uniform dispersibility in resins, and consequently high safety. They found that, regarding the bonding between silica and surface treatment agents, it was previously considered preferable to minimize isolated hydroxyl groups on the silica surface, up to a certain amount, without significantly affecting the loss coefficient. Furthermore, they studied silica that possesses both good dielectric properties and good dispersibility in resins, finding that amorphous silica meeting specified requirements in FT-IR measurements is suitable as a raw material for surface-treated silica, which combines good dielectric properties and good dispersibility in resins; surface-treated silica obtained by treating this silica with a surface treatment agent is suitable as an inorganic filler for use in electronic devices utilizing high-frequency charged waves; and unlike carcinogenic crystalline silica, amorphous silica also presents no safety issues. The inventors further discovered a suitable manufacturing method for this surface-treated silicon dioxide, which has good dielectric properties, excellent uniform dispersion in resins, and high safety, thus completing the present invention.

[0008] That is, the present invention is as follows. [1] A filler material for electronic materials, comprising amorphous silicon dioxide, wherein the peak intensity ratio (A / B) of the amorphous silicon dioxide in FT-IR measurement is 1.0 to 75.0 from peak A of isolated hydroxyl groups to peak B of hydroxyl groups with hydrogen bonds, and there are substantially no peaks from adsorbed water at 3500 to 3100 cm⁻¹.

[0009] [2] The filler material for electronic materials as described in [1] is characterized in that: the silicon dioxide has a D50 of less than 10 μm and a D10 / D90 of more than 0.30 in a laser diffraction particle size distribution.

[0010] [3] The filler material for electronic materials as described in [1] or [2] is characterized in that the ratio of tanδ to BET specific surface area (tanδ / BET specific surface area) of the silicon dioxide powder at 1 GHz and 10 GHz is 1.0×10⁻³ or less.

[0011] [4] The filler material for electronic materials described in any one of [1] to [3] is characterized in that the peak intensity ratio (A / B) of the silicon dioxide in FT-IR measurement of peak A from isolated hydroxyl groups and peak B from hydroxyl groups with hydrogen bonds is 1.0 to 10.0.

[0012] [5] An amorphous surface-treated silicon dioxide, which is produced by treating with a surface treatment agent, is characterized in that: the surface-treated silicon dioxide has a tanδ of less than 1.0×10⁻³ and an ε of less than 3.15 in powder at 1 GHz, a tanδ of less than 3.0×10⁻³ and an ε of less than 3.15 in powder at 10 GHz, and a viscosity of less than 75000 mPa·s at 25°C as measured under the following conditions. (condition) Using amorphous surface-treated silica and epoxy resin with a viscosity of 11,000~15,000 mPa·s at 25°C, an affinity evaluation resin mixture was prepared by kneading the amorphous surface-treated silica to epoxy resin mixture at a mass ratio of 4:6 (amorphous surface-treated silica: epoxy resin). The viscosity of the obtained affinity evaluation resin mixture at 25°C was measured using a type B viscometer.

[0013] [6] A surface-treated silicon dioxide, which is an amorphous surface-treated silicon dioxide treated with a surface treatment agent, characterized in that: the tanδ of the surface-treated silicon dioxide powder at 1 GHz is less than 1.0 × 10⁻³ and the ε is less than 3.15, the tanδ of the powder at 10 GHz is less than 3.0 × 10⁻³ and the ε is less than 3.15, and the peak intensity ratio (A / B) of the peak A from isolated hydroxyl groups and the peak B from hydroxyl groups with hydrogen bonds in FT-IR measurement is less than 0.50.

[0014] [7] A resin composition for electronic materials, characterized in that it contains surface-treated silicon dioxide and resin as described in [5] or [6].

[0015] [8] An electronic material, characterized in that it is made using a resin composition for electronic materials as described in [7].

[0016] [9] A method for manufacturing surface-treated silica, characterized in that the manufacturing method includes the following steps: firing amorphous silica obtained by sol-gel method at 600~1200°C; pulverizing the fired silica obtained in the firing step; calcining the pulverized fired silica obtained in the pulverization step at 700~1200°C as needed; and surface-treating the pulverized fired silica obtained in the pulverization step or the calcined silica obtained in the calcination step with a surface treatment agent. [Effects of the Invention]

[0017] The filler material of the present invention is a material with high safety of surface-treated silicon dioxide that can produce low dielectric loss tangent and excellent uniform dispersion in resin. It can be used as a raw material for inorganic fillers used in electronic machines that utilize high-frequency radio waves. Simple Explanation of the Diagram

[0018] [Figure 1] is a graph showing the FT-IR measurement results of the re-fired silicon dioxide 1 prepared in Example 1. [Figure 2] is a graph showing the FT-IR measurement results of the re-fired silicon dioxide 2 prepared in Example 2. [Figure 3] is a graph showing the FT-IR measurement results of the comparative re-fired silicon dioxide 1 prepared in Comparative Example 1. [Figure 4] is a graph showing the FT-IR measurement results of the comparative sintered silicon dioxide 2 prepared in Comparative Example 2. [Figure 5] is an overlay diagram showing the FT-IR measurement results of the re-fired silicon dioxide 1 and 2 prepared in Examples 1 and 2, and the comparative re-fired silicon dioxide 1 and comparative fired silicon dioxide 2 prepared in Comparative Examples 1 and 2. Implementation

[0019] The preferred form of the present invention will be described in detail below, but the present invention is not limited to the following description and may be applied by appropriate modifications without changing the spirit of the present invention.

[0020] 1. Materials used in the manufacture of fillers for electronic materials The filler material of the present invention is characterized by containing amorphous silicon dioxide, which, in FT-IR measurements, has a peak intensity ratio (A / B) of 1.0 to 75.0 between peak A, which appears at 3800-3700 cm⁻¹, and peak B, which appears at 3700-3600 cm⁻¹, which appears at 3500-3100 cm⁻¹, and substantially no peak from adsorbed water is present at 3500-3100 cm⁻¹. The inventors have discovered that water adsorption on silica negatively impacts its dielectric properties; therefore, it is preferable to avoid water adsorption. Furthermore, regarding hydroxyl groups, if the ratio of peak A (at 3800-3700 cm⁻¹) from isolated hydroxyl groups to peak B (at 3700-3600 cm⁻¹) from hydrogen-bonded hydroxyl groups is within a certain range, then even with hydroxyl groups, the resulting silica exhibits low dielectric loss tangent, excellent dielectric properties, and strong bonding with the surface treatment agent. Therefore, by reacting a material containing this type of silica with a surface treatment agent, a surface-treated silica with low dielectric loss tangent and excellent uniform dispersion in resins can be obtained, making it suitable for use as an inorganic filler. Moreover, unlike carcinogenic crystalline silica, amorphous silica, which does not have this problem, can be safely used as a surface-treated silica material. In the FT-IR measurement of silicon dioxide, the peak intensity ratio (A / B) of peak A from isolated hydroxyl groups to peak B from hydroxyl groups with hydrogen bonds is preferably 1.0 to 75.0, and more preferably 1.0 to 60.0. Even more preferably, it is 5.0 to 25.0. In the aforementioned silicon dioxide measurements using FT-IR, there are virtually no peaks originating from adsorbed water in the 3500–3100 cm⁻¹ range. "Substantially non-existent" means that in FT-IR peak analysis, it is undetectable when the detection limit is set to 0.01 and the sensitivity to 5. Further lowering the detection limit and sensitivity will result in noise being detected as peaks. Furthermore, the aforementioned silicon dioxide is amorphous. In this invention, "amorphous silicon dioxide" refers to silicon dioxide in which no peak is detected at 20-30° in the analysis of XRD measurement results. Peak detection is performed automatically using analysis software, with the σ cut value set to 3.0.

[0021] In the FT-IR measurement of the surface-treated silicon dioxide obtained by surface treatment with a surface treatment agent at a mass percentage of 0.1 to 30% relative to the silicon dioxide, a peak intensity ratio (A / B) of 0.50 or less for the peak A from isolated hydroxyl groups and the peak B from hydroxyl groups with hydrogen bonds is one of the suitable embodiments of the present invention. The silica of this invention is used as an inorganic filler after surface treatment by reacting with a surface treatment agent. If most of the isolated hydroxyl groups on the surface of silica are consumed by the surface treatment, surface-treated silica with fewer isolated hydroxyl groups will be obtained. In addition to having a low dielectric loss tangent and excellent uniform dispersibility in resins, this surface-treated silica with fewer isolated hydroxyl groups also has excellent moisture resistance because it has fewer isolated hydroxyl groups that can become water adsorption sites. The peak intensity ratio (A / B) of the surface-treated silicon dioxide obtained by surface treatment with a surface treatment agent at a concentration of 0.1 to 30% by mass relative to the aforementioned silicon dioxide, in FT-IR measurements, is preferably 0.40 or less, and more preferably 0.30 or less.

[0022] In the FT-IR measurement of the aforementioned silicon dioxide, the peak intensity ratio (A / B) of the peak A from isolated hydroxyl groups to the peak B from hydroxyl groups with hydrogen bonds is 1.0 to 10.0, which is one of the suitable embodiments of the present invention. As described above, surface-treated silicon dioxide with fewer isolated hydroxyl groups on its surface has not only low dielectric loss tangent and excellent uniform dispersibility in resins, but also excellent moisture resistance. Silicon dioxide with a peak intensity ratio (A / B) of 1.0 to 10.0 from isolated hydroxyl groups to the peak B from hydroxyl groups with hydrogen bonds in FT-IR measurement has excellent moisture resistance because most of the isolated hydroxyl groups on its surface are consumed by reacting with the surface treatment agent. More preferably, the peak intensity ratio (A / B) of 1.0 to 8.0 from isolated hydroxyl groups to the peak B from hydroxyl groups with hydrogen bonds in FT-IR measurement is 1.0 to 5.0.

[0023] The aforementioned silica preferably has a laser diffraction particle size distribution with a D50 of less than 10 μm and a D10 / D90 ratio of 0.30 or higher. Thus, by using silica with small particle size and narrow particle size distribution as the material, the resulting surface-treated silica, when incorporated into the resin, exhibits superior adaptability to thin-film formation, and the molded articles formed using this composition possess higher surface flatness. The D50 of the aforementioned silicon dioxide is preferably below 5 μm, and more preferably below 2 μm. There is no particular limitation on the lower limit of the D50 of silicon dioxide, which is usually above 0.005 μm. Furthermore, the D10 / D90 ratio of the aforementioned silicon dioxide is preferably 0.40 or higher, more preferably 0.60 or higher, especially preferably 0.70 or higher, and most preferably 0.75 or higher.

[0024] The silicon dioxide used is preferably one with a maximum volume frequency of 15% or more in the laser diffraction particle size distribution. By using such silicon dioxide, the molded articles formed by incorporating the obtained surface-treated silicon dioxide into the resin have higher surface flatness, thus further contributing to the improvement of the performance of the molded articles and electronic materials. The maximum volumetric frequency of the aforementioned silicon dioxide is preferably 20% or more, more preferably 30% or more, especially 40% or more, and most preferably 45% or more.

[0025] The silicon dioxide is preferably such that the ratio of the maximum acceptable diameter dmax to the average diameter d50 (dmax / d50) of each particle is 5.0 or less. The maximum acceptable diameter d of each particle is obtained by analyzing more than 100 particles in total from two or more different fields of view in SEM observation using image analysis software A Image Kun (manufactured by Asahi Kasei Engineering Co., Ltd.). As described above, silicon dioxide with small particle size and narrow particle size distribution is preferred as a surface-treated silicon dioxide material. By observing the silicon dioxide particle size using SEM, aggregated particles can be excluded, and a more accurate average particle size (average primary particle size) d50 of the silicon dioxide particles can be obtained. By using silicon dioxide with a dmax / d50 of 5.0 or less obtained from SEM images, the molded body formed by incorporating the obtained surface-treated silicon dioxide into a resin exhibits higher surface flatness, thereby making the dielectric properties more uniform and contributing to improved performance of electronic materials. The dmax / d50 ratio is preferably below 2.5, and even better below 1.8. There is no particular limit to the lower limit of dmax / d50, which is usually above 1.01. The average particle size d50 is the average size of more than 100 silicon dioxide particles automatically selected from the SEM image by image analysis software. The method for determining the maximum particle size dmax and average particle size d50 of silicon dioxide based on SEM observation is described in the following examples. Furthermore, in this specification, the particle size obtained by laser diffraction particle size distribution is marked with "D", while the particle size obtained by SEM observation is marked with "d".

[0026] The aforementioned silicon dioxide preferably has a BET specific surface area of ​​0.5 m² / g or higher. With this specific surface area, the average particle size is relatively small, making it suitable for thin-film applications. More preferably, the BET specific surface area of ​​the aforementioned silicon dioxide is 1 m² / g or higher, and even more preferably 2 m² / g or higher. There is no particular upper limit to the BET specific surface area of ​​silicon dioxide, and it is typically 300 m² / g or lower.

[0027] The ratio of tanδ to BET specific surface area of ​​silicon dioxide powder at 1 GHz and 10 GHz (tanδ / BET specific surface area) is 1.0×10⁻³ or less, and ε is 3.15 or less. The object of this invention is to provide amorphous surface-treated silica particles with low dielectric loss tangent and excellent uniform dispersibility in resins. To provide such surface-treated silica particles, the peak intensity ratio A / B of the peak A from isolated hydroxyl groups and the peak B from hydrogen-bonded hydroxyl groups on the silica surface must be within a specified range. For materials used to produce surface-treated silica particles with low dielectric loss, not only is an appropriate intensity ratio A / B desirable, but also the low dielectric loss tangent is a characteristic of the silica particles themselves. As mentioned above, the isolated hydroxyl groups on the surface of silicon dioxide affect its dielectric properties. There is a tendency for a larger specific surface area of ​​silicon dioxide to correspond to a greater amount of isolated hydroxyl groups; therefore, silicon dioxide with a larger specific surface area tends to have a larger dielectric loss tangent. To address this, by calculating the tanδ per unit specific surface area, the influence of specific surface area can be eliminated, allowing for the evaluation of the material's inherent dielectric properties. If silicon dioxide with a tanδ / BET specific surface area of ​​less than 1.0 × 10⁻³ and a relative permittivity ε of less than 3.15 is used as the material for both 1 GHz and 10 GHz powders, a surface-treated silicon dioxide with superior dielectric properties and uniform dispersion in resins can be obtained. The tanδ / BET specific surface area value of silicon dioxide at 1 GHz and 10 GHz is preferably 1.0 × 10⁻³ or less. More preferably 9.0 × 10⁻⁴ or less, and even more preferably 5.0 × 10⁻⁴ or less. There is no particular limitation on the lower limit of the tanδ / BET specific surface area value at 1 GHz and 10 GHz, and it is usually 1.0 × 10⁻⁶ or more. The relative permittivity ε of the silicon dioxide powder at 1 GHz and 10 GHz is preferably 2.9 or less, and more preferably 2.8 or less. There is no particular limitation on the lower limit of the relative permittivity ε of the powder at 1 GHz, which is usually 1.0 or more. The tanδ values ​​of silicon dioxide at 1 GHz and 10 GHz, and the relative permittivity ε, can be determined by the methods described in the following examples.

[0028] The filler material for the electronic material of this invention only needs to contain "amorphous silica with a peak intensity ratio (A / B) of 1.0 to 75.0 from the peak A of isolated hydroxyl groups and the peak B of hydrogen-bonded hydroxyl groups in FT-IR measurements, and substantially no peak from adsorbed water at 3500 to 3100 cm⁻¹", and may also contain other components. Examples of other components include: metallic elements such as Ti, Zr, Zn, Ba, Sr, and Ca, or light elements such as B, C, and N, or their compounds. Relative to 100% by mass of the filler material for electronic materials, the proportion of other components contained in the filler material for electronic materials of the present invention is preferably 50% by mass or less. More preferably, it is 20% by mass or less, and even more preferably, it is 10% by mass or less.

[0029] Furthermore, when the silicon dioxide contained in the filler material of the electronic material of the present invention is heated from 25°C to 1000°C at a rate of 30°C / min, the number of water molecules detached at 500°C to 1000°C is preferably more than 0.010 mmol / g. More preferably, it is more than 0.011 mmol / g. This type of silicon dioxide can be obtained by performing the steps up to the surface treatment step in the following method for manufacturing surface-treated silicon dioxide.

[0030] 2. Surface treatment with silicon dioxide The surface-treated silicon dioxide of the present invention is characterized by being an amorphous surface-treated silicon dioxide, wherein the amorphous surface-treated silicon dioxide has a tanδ of 1.0 × 10⁻³ or less and an ε of 3.15 or less in powder at 1 GHz, a tanδ of 3.0 × 10⁻³ or less and an ε of 3.15 or less in powder at 10 GHz, and a viscosity of 75000 mPa·s or less at 25°C as measured under the following conditions (hereinafter also referred to as the first surface-treated silicon dioxide of the present invention). (condition) Using amorphous surface-treated silica and epoxy resin with a viscosity of 11,000~15,000 mPa·s at 25°C, an affinity evaluation resin mixture was prepared by kneading the amorphous surface-treated silica to epoxy resin mixture at a mass ratio of 4:6 (amorphous surface-treated silica: epoxy resin). The viscosity of the obtained affinity evaluation resin mixture at 25°C was measured using a type B viscometer. Surface-treated silica with these properties has excellent dielectric properties, excellent dispersibility in resins, and high safety, making it suitable as an inorganic filler for use in electronic machines that utilize high-frequency radio waves. The surface-treated silicon dioxide of the present invention preferably has a tanδ of 5.0 × 10⁻⁴ or less for powders at 1 GHz, and more preferably 2.0 × 10⁻⁴ or less. There is no particular limitation on the lower limit of the tanδ of the powder at 1 GHz, and it is typically 1.0 × 10⁻⁶ or more. Furthermore, the relative permittivity ε of the surface-treated silicon dioxide powder at 1 GHz is preferably 3.10 or less, and more preferably 3.00 or less. There is no particular limitation on the lower limit of the relative permittivity ε of the powder at 1 GHz, and it is generally 1.0 or more. The surface-treated silicon dioxide of the present invention preferably has a tanδ of 2.0 × 10⁻³ or less for 10 GHz powder, and more preferably 1.5 × 10⁻³ or less. There is no particular limitation on the lower limit of the tanδ of the 10 GHz powder, which is typically 1.0 × 10⁻⁶ or more. Furthermore, the relative permittivity ε of the surface-treated silicon dioxide powder at 10 GHz is preferably 3.10 or less, and more preferably 3.00 or less. There is no particular limitation on the lower limit of the relative permittivity ε of the powder at 10 GHz, which is typically 1.0 or more. The tanδ value and relative permittivity ε of surface-treated silicon dioxide at 1 GHz and 10 GHz can be determined by the method described in the following examples.

[0031] The affinity evaluation resin mixture obtained by kneading the surface-treated silica and epoxy resin of the first invention at a mass ratio of 4:6 should have a viscosity of 75,000 mPa·s or less at 25°C, preferably 70,000 mPa·s or less, and more preferably 60,000 mPa·s or less. There is no particular limitation on the lower limit of the viscosity of the affinity evaluation resin mixture at 25°C, but it is generally 100 mPa·s or more. By using surface-treated silica exhibiting this viscosity range, resin compositions for electronic materials containing the surface-treated silica and resin of the present invention can also obtain resins with better viscosity, and electronic materials made using these resin compositions can also be used as electronic materials. The viscosity of the resin mixture used for affinity evaluation at 25°C can be determined by the method described in the following examples.

[0032] Furthermore, the present invention is also a surface-treated silicon dioxide, which is an amorphous surface-treated silicon dioxide obtained by treating with a surface treatment agent. The surface-treated silicon dioxide has a tanδ of 1.0 × 10⁻³ or less and an ε of 3.15 or less for powder at 1 GHz, and a tanδ of 3.0 × 10⁻³ or less and an ε of 3.15 or less for powder at 10 GHz. In addition, the peak intensity ratio (A / B) of the peak A from isolated hydroxyl groups and the peak B from hydroxyl groups with hydrogen bonds in FT-IR measurement is 0.50 or less (hereinafter also referred to as the second surface-treated silicon dioxide of the present invention). This surface-treated silicon dioxide has excellent dielectric properties and moisture resistance, making it suitable as an inorganic filler for use in electronic machines that utilize high-frequency electromagnetic waves. In FT-IR measurements of surface-treated silicon dioxide, the peak intensity ratio (A / B) of peak A from isolated hydroxyl groups to peak B from hydroxyl groups with hydrogen bonds is preferably 0.40 or less. More preferably, it is 0.30 or less, and even more preferably, it is 0.20 or less. The preferred values ​​of tanδ and ε of the surface-treated silicon dioxide of the second invention for the powder at 1 GHz and the powder at 10 GHz are the same as those of the surface-treated silicon dioxide of the first invention.

[0033] The surface-treated silicon dioxide of the present invention includes the first surface-treated silicon dioxide of the present invention and the second surface-treated silicon dioxide of the present invention, either of which is acceptable, but it is more preferably both.

[0034] The surface treatment agent used for the surface-treated silica in this invention is not particularly limited as long as it can improve the dispersibility of silica in the resin. For example, one or more of organosilazane, alkoxysilane, silane coupling agent, titanium coupling agent, polysiloxane oil, organophosphate, etc. can be used.

[0035] The amount of surface treatment agent in the surface-treated silicon dioxide of the present invention is not particularly limited, but is preferably 0.1 to 30% by mass relative to 100% by mass of the silicon dioxide before surface treatment. More preferably, it is 0.1 to 20% by mass, and even more preferably, it is 0.1 to 10% by mass.

[0036] The preferred ranges of particle size or particle size distribution and BET specific surface area of ​​the surface-treated silicon dioxide of the present invention are the same as those of the preferred ranges of particle size or particle size distribution and BET specific surface area of ​​the silicon dioxide contained in the filler material for the above-mentioned electronic materials.

[0037] 3. Resin compositions for electronic materials, electronic materials Furthermore, the present invention is also a resin composition for electronic materials and an electronic material thereof. The resin composition for electronic materials is characterized in that it contains the surface-treated silicon dioxide and resin of the present invention, and the electronic material thereof is made using the resin composition for electronic materials. The surface-treated silica of this invention exhibits excellent dispersibility in resin, thus effectively suppressing the formation of high viscosity or agglomeration during resin kneading. Therefore, when using the electronic material resin composition of this invention to manufacture films and other molded articles, molded articles with high uniformity or surface smoothness can be obtained. The proportion of the surface-treated silicon dioxide of the present invention contained in the resin composition for electronic materials is not particularly limited, and can be appropriately selected according to the required application or characteristics. It is preferably 0.1 to 90% by mass relative to 100% by mass of the resin composition for electronic materials. More preferably, it is 1 to 80% by mass, and even more preferably, it is 10 to 70% by mass.

[0038] There are no particular restrictions on the resins contained in the resin composition of the above-mentioned electronic materials. Examples include: epoxy resin, polyethylene, polypropylene, polyester, polyamide, polyimide, polysiloxane resin, phenolic resin, polyurethane, modified polyphenylene ether resin, polyphenylene sulfide resin, liquid crystal polymer, fluoropolymer, etc. One or more of these resins may be used.

[0039] The proportion of resin in the above-mentioned resin composition for electronic materials is not particularly limited and can be appropriately selected according to the required application or characteristics. It is preferably 10-99% by mass relative to 100% by mass of the resin composition for electronic materials. More preferably 20-99% by mass, and even more preferably 30-90% by mass.

[0040] The resin composition of the aforementioned electronic materials may contain solvents. There are no particular limitations on the solvents used; examples include: alcohols such as methanol, ethanol, and isopropanol; ketones such as acetone and methyl ethyl ketone; esters such as ethyl acetate; ethers such as dimethyl ether and diethyl ether; aromatic hydrocarbon solvents such as xylene, toluene, cyclohexylbenzene, dihydrobenzofuran, trimethylbenzene, and tetramethylbenzene; and solvents such as pyridine and pyridine. Aromatic heterocyclic compounds such as furan, pyrrole, thiophene, and methylpyrrolidone; aliphatic hydrocarbon solvents such as hexane, pentane, heptane, and cyclohexane; and glycol ethers such as propylene glycol monomethyl ether and propylene glycol monomethyl ether acetate may be used, one or more of these solvents may be used.

[0041] There is no particular limitation on the solvent content in the above-mentioned resin composition for electronic materials, but it is preferably 0 to 50% by mass relative to 100% by mass of the resin composition for electronic materials. More preferably, it is 0 to 40% by mass, and even more preferably, it is 0 to 30% by mass.

[0042] The resin composition for electronic materials described above may also contain other components besides the surface-treated silicon dioxide, resin, and solvent of this invention. Examples of other components include fillers, viscosity modifiers, and defoamers. The resin composition for electronic materials described above may contain one or more of these other components.

[0043] The proportion of the above-mentioned other components relative to 100% by mass of the resin composition for electronic materials is preferably 30% by mass or less. More preferably, it is 20% by mass or less, and even more preferably, it is 10% by mass or less.

[0044] The resin composition for electronic materials of the present invention preferably has a viscosity of 100,000 mPa·s or less at 25°C. With this viscosity range, it is easy to use the resin for electronic materials of the present invention to fabricate thin films. More preferably, the viscosity of the resin composition for electronic materials is 10,000 mPa·s or less, and even more preferably 1,000 mPa·s or less. The viscosity of the resin composition for electronic materials of the present invention can be measured using the same method as the method for measuring the viscosity of resin mixtures for affinity evaluation at 25°C as described in the following examples.

[0045] The electronic material of this invention is made using the resin composition for electronic materials of this invention. In the electronic material of this invention, the resin composition for electronic materials of this invention can be shaped and used in any manner. Since silicon dioxide has excellent uniform dispersion in resin, when making thin films, films with high uniformity or surface smoothness can be obtained. Therefore, containing a thin film formed from the resin composition for electronic materials is one of the suitable embodiments of the electronic material of this invention.

[0046] 4. Method for manufacturing surface-treated silicon dioxide Furthermore, the present invention is also a method for manufacturing surface-treated silica, which is a method for manufacturing surface-treated silica, characterized in that the manufacturing method includes the following steps: firing silica obtained by the sol-gel method at 600~1200°C; pulverizing the fired silica obtained in the firing step; if necessary, firing the pulverized fired silica obtained in the pulverization step again at 700~1200°C; and surface-treating the pulverized fired silica obtained in the pulverization step or the refired silica obtained in the refired step with a surface treatment agent. After calcining the silicon dioxide obtained by the sol-gel method at 600~1200°C, the calcined silicon dioxide is pulverized and then calcined again at 700~1200°C as needed. In this way, the silicon dioxide contained in the filler material of the electronic material of the present invention can be easily obtained. The pulverized calcined silicon dioxide or the calcined silicon dioxide obtained in this way is surface treated with a surface treatment agent to obtain the surface-treated silicon dioxide of the present invention.

[0047] The step of firing the silicon dioxide obtained by the sol-gel method at 600~1200℃ can be carried out at 600~1200℃, preferably at 700~1150℃, and even more preferably at 800~1100℃. Furthermore, there is no particular limitation on the holding time at high temperature during the firing process. However, considering the efficiency of fully firing and manufacturing silicon dioxide, it is preferable to keep the time to 10-1500 minutes. More preferably, it is preferable to keep the time to 10-1000 minutes, and even more preferably, it is preferable to keep the time to 30-500 minutes.

[0048] The step described above, which involves pulverizing the calcined silicon dioxide obtained during the calcination process, is a step that breaks up the agglomeration of primary silicon dioxide particles without actually pulverizing them. In the step of calcining silicon dioxide obtained using the sol-gel method at 600-1200°C, necking easily occurs due to sintering between silicon dioxide particles. By breaking up the agglomeration of primary particles caused by necking, the particle size of the silicon dioxide can be made uniform, resulting in silicon dioxide with a small particle size distribution.

[0049] The calcined silica pulverized in the above-mentioned pulverization step preferably has a D50 of less than 10 μm and a D10 / D90 of more than 0.30 in the laser diffraction particle size distribution. By pulverizing the calcined silica in this range, the composition obtained by incorporating the surface-treated silica obtained by the manufacturing method of the surface-treated silica of the present invention into the resin has better adaptability to thin film formation, and the molded body formed using the composition has higher surface flatness. The D50 of the aforementioned silicon dioxide is preferably below 5 μm, and more preferably below 2 μm. There is no particular limitation on the lower limit of the D50 of silicon dioxide, which is usually above 0.005 μm. Furthermore, the D10 / D90 ratio of the aforementioned silicon dioxide is preferably 0.40 or higher, more preferably 0.60 or higher, especially preferably 0.70 or higher, and most preferably 0.75 or higher.

[0050] The calcined silicon dioxide pulverized in the above-mentioned pulverization step is preferably one with a maximum volume frequency of 30% or more in the laser diffraction particle size distribution. By using such silicon dioxide, the molded articles formed by incorporating the surface-treated silicon dioxide obtained by the manufacturing method of the present invention into a resin have higher surface flatness, thus helping to improve the performance of the molded articles and electronic materials. The maximum volumetric frequency of the aforementioned silicon dioxide is preferably 40% or higher, and more preferably 45% or higher.

[0051] In the above-mentioned pulverization step, the calcined silicon dioxide pulverized is preferably such that the ratio of the maximum particle size dmax to the average particle size d50 (dmax / d50) is 5.0 or less. The maximum particle size d is determined by analyzing more than 100 particles in total from two or more different fields of view in SEM observation using image analysis software A Image Kun (manufactured by Asahi Kasei Engineering Co., Ltd.). By using sintered silica with a dmax / d50 of 5.0 or less, the molded body formed by incorporating the surface-treated silica obtained by the manufacturing method of the surface-treated silica of the present invention into the resin has higher surface flatness, thereby making the dielectric properties more uniform and helping to improve the performance of electronic materials. The aforementioned dmax / d50 is obtained by using the more accurate average particle size (average primary particle size) d50 of sintered silica particles excluding agglomerated particles obtained by SEM observation. The dmax / d50 ratio is preferably below 2.5, and even better below 1.8. There is no particular limit to the lower limit of dmax / d50, which is usually above 1.01. The average particle size d50 is the average size of more than 100 silicon dioxide particles automatically selected from the SEM image by image analysis software. The method for determining the maximum particle size dmax and average particle size d50 of silicon dioxide based on SEM observation is described in the following examples.

[0052] The calcined silicon dioxide pulverized in the above-described pulverization step preferably has a BET specific surface area of ​​0.5 m² / g or more. With this specific surface area, the average particle size is relatively small, making it suitable for thin-film applications. More preferably, the BET specific surface area of ​​the calcined silicon dioxide pulverized in the above-described pulverization step is 1 m² / g or more, and even more preferably 2 m² / g or more. There is no particular upper limit to the BET specific surface area of ​​silicon dioxide, and it is typically 300 m² / g or less.

[0053] In the manufacturing method of surface-treated silicon dioxide of the present invention, a step is performed as needed to re-fire the pulverized and fired silicon dioxide obtained in the pulverization step at 700~1200°C. As described above, by utilizing the pulverization step to break up the primary particle agglomeration caused by the necking during the firing step, the particle size of silicon dioxide can be made uniform, resulting in silicon dioxide with minimal particle size distribution variation. However, on the other hand, pulverization generates new interfaces, which become the main cause of variations in the amount of hydroxyl groups on the silicon dioxide surface. Therefore, in the surface-treated silicon dioxide manufacturing method of the present invention, the pulverized silicon dioxide is re-fired as needed to control the amount of hydroxyl groups on the surface of the pulverized silicon dioxide. By manufacturing silicon dioxide through re-firing, the dielectric properties of the obtained silicon dioxide can be improved. The method of pulverizing the calcined silicon dioxide obtained in the calcination process is not particularly limited as long as it can break the agglomeration of primary particles without pulverizing the primary particles of silicon dioxide. It can be carried out by airflow pulverizers or the like.

[0054] If the pulverized and calcined silicon dioxide described above is re-fired at 700~1200℃, necking as seen in the first firing will hardly occur. Through this series of firing, pulverizing, and re-firing steps, both particle size distribution and the amount of hydroxyl groups on the surface of silicon dioxide can be controlled. The re-firing step can be carried out at 700~1200℃, preferably at 800~1200℃. More preferably at 800~1150℃, and even more preferably at 850~1100℃. Furthermore, there is no particular limitation on the holding time at high temperature during the re-firing step. Considering the efficiency of fully firing and manufacturing silicon dioxide, 10 to 1500 minutes is preferred. More preferably, 10 to 1000 minutes is preferred, and even more preferably, 30 to 500 minutes is preferred.

[0055] When the method for manufacturing surface-treated silicon dioxide of the present invention includes both a firing step and a re-firing step, the firing temperature and the re-firing temperature preferably have a difference of 50°C or more. By setting such a temperature difference, the target silicon dioxide can be obtained without applying excessive heat. The difference between the firing temperature and the re-firing temperature is more preferably 100°C or more, and even more preferably 150°C or more. Furthermore, the difference between the firing temperature and the re-firing temperature is typically 600°C or less.

[0056] Furthermore, when manufacturing silica with few isolated hydroxyl groups on the surface that have been largely consumed by the reaction with the surface treatment agent, it is preferable to perform a firing step or a re-firing step at 1050~1200°C. By firing or re-firing at this temperature, silica with fewer isolated hydroxyl groups on the surface, and with most of the isolated hydroxyl groups consumed by the reaction with the surface treatment agent, can be produced. The firing at 1050~1200°C can be performed during the firing step or during the re-firing step, but the re-firing step is preferred.

[0057] The steps of firing the silicon dioxide obtained by the sol-gel method and the re-firing of the pulverized fired silicon dioxide are preferably carried out in a low-humidity environment. By firing in a low-humidity environment, the surface-treated silicon dioxide obtained has a lower dielectric loss tangent and better dielectric properties. As a low-humidity environment, it is preferable to have a humidity of less than 90% at 30°C before the temperature begins to rise. More preferably, it is preferable to have a humidity of less than 70% at 30°C, and even more preferably, it is preferable to have a humidity of less than 60% at 30°C.

[0058] The environment for carrying out the above-mentioned steps of calcining silicon dioxide obtained by the sol-gel method and calcining the pulverized calcined silicon dioxide is not particularly limited except for being a low humidity environment. In addition to air or oxygen environment, it can also be any environment such as nitrogen, argon or other inactive gas environment.

[0059] Preferably, after the aforementioned pulverization step or the step of re-firing the pulverized calcined silicon dioxide and before the step of surface-treating the pulverized calcined silicon dioxide or re-firing silicon dioxide obtained in the pulverization step with a surface treatment agent, a step of cooling the pulverized calcined silicon dioxide or re-firing silicon dioxide obtained in the pulverization step is performed. By performing the step of surface-treating the pulverized calcined silicon dioxide or re-firing silicon dioxide obtained in the pulverization step with a surface treatment agent after cooling, the pulverized calcined silicon dioxide or re-firing silicon dioxide obtained in the pulverization step can react fully with the surface treatment agent. In the step of cooling the pulverized calcined silicon dioxide or re-calcined silicon dioxide obtained in the pulverization step, it is preferable to cool the pulverized calcined silicon dioxide or re-calcined silicon dioxide obtained in the pulverization step to about room temperature, or preferably to cool the pulverized calcined silicon dioxide or re-calcined silicon dioxide obtained in the pulverization step at room temperature for 5 to 1000 minutes.

[0060] In the method for manufacturing surface-treated silica of the present invention, it is preferable to avoid contact with a high-humidity environment as much as possible until the step of surface-treating the pulverized calcined silica obtained in the above-mentioned pulverization step or the re-calcined silica obtained by the re-calcination step using a surface-treatment agent. If the pulverized calcined silica or re-calcined silica obtained in the pulverization step is exposed to a high-humidity environment, there is a risk that isolated hydroxyl groups will form on the surface of the pulverized calcined silica or re-calcined silica obtained in the pulverization step, resulting in a high dielectric loss tangent for the surface-treated silica obtained by the surface-treatment step. Therefore, in the method for manufacturing surface-treated silica of the present invention, it is preferable that, until the step of surface-treating the pulverized calcined silica obtained in the above-mentioned pulverization step or the re-calcined silica obtained by the re-calcination step with a surface-treatment agent, the calcined silica is maintained at an environment of 30°C and humidity below 90%. More preferably, it is maintained at an environment of 30°C and humidity below 70%, and even more preferably, it is maintained at an environment of 30°C and humidity below 25%. Furthermore, the phrase "surface treatment of the pulverized calcined silicon dioxide obtained in the above-mentioned pulverization step or the re-calcined silicon dioxide obtained in the re-calcination step using a surface treatment agent" means that when the pulverized calcined silicon dioxide obtained in the pulverization step is not re-calcined, the pulverized calcined silicon dioxide obtained in the pulverization step is surface treated with a surface treatment agent; and when re-calcination is performed, the re-calcined silicon dioxide obtained in the re-calcination step is surface treated with a surface treatment agent.

[0061] The proportion of the surface treatment agent used in the above surface treatment steps is not particularly limited, as long as it can effectively treat the silicon dioxide surface. Preferably, it is 0.1 to 30% by mass relative to 100% by mass of the pulverized calcined silicon dioxide obtained in the pulverization step or the re-calcined silicon dioxide obtained in the re-calcination step. By using the surface treatment agent in this proportion, the silicon dioxide surface can be adequately treated, preventing moisture absorption. More preferably, the proportion of the surface treatment agent is 0.1 to 20% by mass relative to 100% by mass of the pulverized calcined silicon dioxide or the re-calcined silicon dioxide obtained in the pulverization step, and even more preferably, it is 0.1 to 10% by mass relative to 100% by mass of the pulverized calcined silicon dioxide or the re-calcined silicon dioxide obtained in the pulverization step. The same surface treatment agent as described above can be used as the surface treatment agent in the above surface treatment steps.

[0062] In the above surface treatment steps, in order to fully surface treat the pulverized calcined silicon dioxide or re-calcined silicon dioxide obtained in the pulverization step using a surface treatment agent, it is preferable to perform the following treatment: mix the pulverized calcined silicon dioxide or re-calcined silicon dioxide obtained in the pulverization step with a surface treatment agent, and then heat the mixture to calcine the surface treatment agent onto the silicon dioxide. The heating temperature during the calcification process can be appropriately set according to the type of surface treatment agent, etc., preferably 30~500℃, more preferably 50~300℃, and even more preferably 80~250℃. Furthermore, the heating time during the calcination process is preferably 10 to 600 minutes. More preferably, it is 30 to 400 minutes, and even more preferably, it is 60 to 300 minutes.

[0063] The method for manufacturing surface-treated silicon dioxide according to the present invention may also include other steps besides those described above. Examples of other steps include: dispersion treatment, sieving, pressurization, and pulverization. [Example]

[0064] To explain the present invention in detail, specific examples are given below, but the present invention is not limited to these examples. Unless otherwise specified, "%" and "wt%" mean "weight % (mass %)". Furthermore, the measurement methods for each physical property are as described below. <FT-IR Measurement> Install the diffuse reflection application software on NICOLET 4700 manufactured by Thermo Fisher Scientific K.K., supply the sample to the measurement jig so that the powder becomes smooth, and perform a measurement with 50 scans within the range of 4000 to 1000 cm-1. The obtained data is used to detect peaks using the analysis software OMNIC. Detection of isolated hydroxyl group A: Using OMNIC, set the analysis range to 3800 to 3500 cm-1, perform automatic baseline correction, and then perform peak detection. In peak detection, in order to separate from noise, set the threshold to 0.01, and detect the peak existing near 3800 to 3700 cm-1. The peak intensity is the highest one among these peaks. Detection of hydrogen-bonded hydroxyl group B: Using OMNIC, set the analysis range to 3800 to 3500 cm-1, perform automatic baseline correction, and then perform peak detection. In peak detection, in order to separate from noise, set the threshold to 0.01, and detect the peak existing near 3700 to 3600 cm-1. The peak intensity is the highest one among these peaks. Detection of adsorbed water: Using OMNIC, set the analysis range to 3500 to 3000 cm-1, perform automatic baseline correction, and then perform peak detection. In peak detection, in order to separate from noise, set the threshold to 0.01, and the peak intensity is the highest one among these peaks. The judgment of whether there is adsorbed water in the example means that no peak is detected under this condition. Furthermore, in any case, if the detection sensitivity is too high, all noise will be detected as peaks, so the sensitivity is adjusted to 5. <00,00283>

[0065] <Measurement of average particle diameter and particle size distribution by laser diffraction particle size distribution measurement> The silica powder before surface treatment is used to measure the particle size distribution by LA-950 manufactured by Horiba, Ltd. Add a small amount of powder to 0.05 wt% sodium hexametaphosphate aqueous solution as a pretreatment, disperse it using an ultrasonic homogenizer, and supply it to the measuring device. Set the refractive index of the silica powder to n = 1.460 and the refractive index of water to n = 1.333 for measurement. <XRD Measurement> Before surface treatment, the silica powder was measured using an X-ray diffraction measurement device RINT-TTRIII manufactured by Rigaku Corporation. The measurement range was 2θ: 20~60°, and the measurement was carried out with a step width of 0.02°, a counting time of 0.5 s, a voltage of 50 V, and a current of 300 mA. The measurement results were analyzed using the analysis software PDXL. When peaks were detected on the software between 20~30°, it was determined to have crystallinity. Peak search was automatically performed according to the analysis template, and the σ cut-off value was set to 3.0. <BET specific surface area> Using a degassing device, after degassing under the conditions of a N2 flow rate of 50 mL / min at 200°C for 20 min, the specific surface area was measured by the BET single-point method using Macsorb HM-1220 manufactured by Mountech Company.

[0066] <Moisture absorption rate> 10.0 g of the surface-treated silica obtained from the examples and comparative examples was added to a glass petri dish previously dried at 105°C for 2 hours, and then placed in a thermostatic and humidistatic chamber at a temperature of 85°C and a humidity of 85%RH. After 264 hours, it was taken out, and the mass change of the surface-treated silica before and after being put in was measured. Moisture absorption rate (%) = {(b - a) / a} × 100 a: Mass (g) of the surface-treated silica before being put into the thermostatic and humidistatic chamber b: Mass (g) of the surface-treated silica 264 hours after being put into the thermostatic and humidistatic chamber <Increase rate of dielectric properties and dielectric loss tangent> Using a dielectric constant measurement device manufactured by AET Co., Ltd. based on the resonance cavity perturbation method, the dielectric constant ε and dielectric loss tangent tanδ of the powder at a specified frequency were measured. Furthermore, the dielectric constant ε and dielectric loss tangent tanδ of the surface-treated silica after measuring the moisture absorption rate at 10 GHz were measured to determine the change in the dielectric loss tangent of the powder before and after moisture absorption. Increase rate of dielectric loss tangent (%) = {(tanδ5 - tanδ4) / tanδ4} × 100 tanδ4: Dielectric loss tangent of the surface-treated silica tanδ5: Dielectric loss tangent of the surface-treated silica 264 hours after being put into the thermostatic and humidistatic chamber <Amount of water removed at 500°C~1000°C> Using a temperature-programmed desorption gas analyzer (EMD-WA1000S / W; TDS manufactured by Electronic Science Manufacturing), at the temperature of the upper thermocouple, in an atmospheric environment, the temperature was raised from 25°C to 1000°C at a rate of 30°C / min. According to the area value within the range of 500°C - 1000°C of the obtained mass chromatogram (m / z = 18), the number of H2O desorbed molecules was calculated. The measurement was carried out in the state where carbon sheets, sample powder (10 mg), and carbon sheets were sequentially placed in a quartz sample dish.

[0067] <SEM Image Observation> Silicon dioxide particles were placed on the sample stage and observed using a scanning electron microscope JSM-7000f manufactured by JEOL Ltd., and SEM images were obtained. <Measurement of the maximum particle diameter dmax and average particle diameter d50 of silicon dioxide based on the images obtained by SEM image observation> For the obtained SEM images, image analysis software A image kun manufactured by Asahi Kasei Engineering Corporation was used for analysis. Randomly analyze the maximum measurable diameter d of each of more than 100 particles, calculate the maximum particle diameter dmax and average particle diameter d50 based on the obtained analysis results, and calculate dmax / d50.

[0068] <Method for preparing a resin mixture for affinity evaluation> 30.00 g of surface-treated silicon dioxide obtained from the examples and comparative examples, and 45.00 g of epoxy resin (EPICLON 850 manufactured by DIC Corporation, viscosity at 25°C is 11000 - 15000 mPa·s) were kneaded to prepare a resin mixture for affinity evaluation. <Viscosity Measurement> For the obtained resin mixture for affinity evaluation, the viscosity of the resin mixture for affinity evaluation at 25°C was measured using the BM type of a B-type viscometer manufactured by Tokyo Keiki Co., Ltd. <Affinity Evaluation with Resin> 2.00 g of the obtained resin mixture for affinity evaluation and a spacer with a thickness of 0.18 mm were clamped together with a 100 mm × 100 mm glass plate in a uniform thickness manner to prepare a test sample. The appearance of the obtained test sample was visually confirmed within 15 minutes. When the number of agglomerates that could be visually counted was 0 - 20, it was marked as "○", when it was 21 - 50, it was marked as "Δ", and when it was 51 or more, it was marked as "×", and the affinity between the surface-treated silicon dioxide and the resin was evaluated.

[0069] Examples In the embodiments, it was used in the form of raw material silicon dioxide synthesized using the sol-gel method. The product of the example is silicon dioxide that the applicant plans to start selling after September 2021 under the trade name Sciqas-LT.

[0070] Example 1 The raw material silicon dioxide, synthesized using the sol-gel method, was filled into a mullite-cordierite sagger and placed in a firing furnace. The furnace was heated at 100°C / h until it reached 1000°C, at which point the heating was stopped. After firing at 1000°C for 5 hours, the furnace was cooled to room temperature at 100°C / h. The fired powder was then collected and dry-pulverized using an air-jet mill. The pulverized calcined silicon dioxide was filled into a mullite-cordierite sagger and placed in a firing furnace. The furnace was heated at 100°C / h until it reached 800°C, at which point the heating was stopped. After firing at 800°C for 5 hours, the furnace was cooled to room temperature at 100°C / h and then refired to obtain refired silicon dioxide 1. FT-IR measurements were performed on the obtained re-fired silicon dioxide 1 to confirm the peak intensity ratio (A / B) of peak A (originating from isolated hydroxyl groups at 3800–3700 cm⁻¹) and peak B (originating from hydrogen-bonded hydroxyl groups at 3700–3600 cm⁻¹), and the presence or absence of a peak originating from adsorbed water at 3500–3100 cm⁻¹. The relative permittivity ε and dielectric loss tangent tanδ were measured at 1 GHz and 10 GHz. XRD and BET surface area measurements were also performed. These results are shown in Table 1. The FT-IR results of the re-fired silicon dioxide 1 are shown in Figure 1.

[0071] 50.00 g of the obtained re-fired silicon dioxide 1 was placed into a polyethylene bag. 0.35 g of a surface treatment agent (hexamethyldisilazane (HMDS): SZ-31 manufactured by Shin-Etsu Chemical Co., Ltd., equivalent to 0.7% by mass of the re-fired silicon dioxide 1) was added to disperse it within the re-fired silicon dioxide 1. The polyethylene bag was sealed, and the contents were thoroughly mixed. The contents of the polyethylene bag were then removed and placed into a stainless steel tray, which was then placed in a dryer and subjected to a calcination treatment at 150°C for 3 hours to obtain surface-treated silicon dioxide 1. The obtained surface-treated silicon dioxide 1 was subjected to the following measurements: D10, D50, D90, maximum volume frequency, and D10 / D90. The peak intensity ratio (A / B) of peak A (originating from isolated hydroxyl groups at 3800–3700 cm⁻¹) and peak B (originating from hydrogen-bonded hydroxyl groups at 3700–3600 cm⁻¹) were measured by FT-IR. The relative permittivity ε and dielectric loss tangent tanδ at 1 GHz and 10 GHz were also measured, as well as measurements were performed by SEM image observation. Furthermore, the amount of moisture removed from the silicon dioxide at 500–1000 °C was measured, as well as the moisture absorption rate. The dielectric loss tangent tanδ at 10 GHz after the moisture absorption rate measurement and its increase rate were also measured. A lower increase rate in the dielectric loss tangent indicates that the change in the dielectric loss tangent over time is suppressed. The value is preferably lower, preferably below 200%, even better than below 150%, and further preferably below 100%. Furthermore, 30.00 g of surface-treated silica 1 and 45.00 g of epoxy resin (manufactured by DIC Corporation, EPICLON 850) were kneaded to prepare a resin mixture for evaluating the affinity between surface-treated silica and the resin. Viscosity was measured and the affinity with the resin was evaluated (dispersibility evaluation of surface-treated silica 1). These results are shown in Table 2.

[0072] Examples 2 and 3 The re-firing temperature in the re-firing step was changed as shown in Table 1. Otherwise, re-fired silicon dioxide 2 and 3 were obtained in the same manner as in Example 1, and surface-treated silicon dioxide 2 and 3 were obtained by surface treatment. The obtained re-fired silicon dioxide 2 and 3, as well as the surface-treated silicon dioxide 2 and 3, were subjected to the same various measurements as in Example 1. The results are shown in Tables 1 and 2. Furthermore, the FT-IR measurement results of the re-fired silicon dioxide 2 are shown in Figure 2.

[0073] Example 4 Using silicon dioxide with an average particle size different from that in Example 1 as raw material, the ratio of HMDS to re-fired silicon dioxide was changed. Otherwise, re-fired silicon dioxide 4 was obtained in the same manner as in Example 1, and surface-treated silicon dioxide 4 was obtained. The obtained re-fired silicon dioxide 4 and surface-treated silicon dioxide 4 were subjected to the same various measurements as in Example 1. The results are shown in Tables 1 and 2.

[0074] Example 5 Using silicon dioxide with an average particle size different from that in Example 1 as raw material, the firing and refiring temperatures were changed, and the ratio of HMDS used to refired silicon dioxide was changed. Otherwise, refired silicon dioxide 5 was obtained in the same manner as in Example 1, and surface-treated silicon dioxide 5 was obtained. The obtained re-fired silicon dioxide 5 and surface-treated silicon dioxide 5 were subjected to the same various measurements as in Example 1. The results are shown in Tables 1 and 2.

[0075] Example 6 Re-fired silicon dioxide 6 was obtained in the same manner as in Example 1. Weigh 50.00 g of the obtained re-fired silica 6 and place it into a dry mixer. While mixing, add 0.50 g of surface treatment agent (phenyltrimethoxysilane (PTMS): KBM-103 manufactured by Shin-Etsu Chemical Co., Ltd.) equivalent to 1.0% by mass of the re-fired silica 6 into the dry mixer. Subsequently, the mixed powder was taken out from the dry mixer and placed in a dryer, where it was subjected to a surface treatment step of calcination treatment with a surface treatment agent at 150°C for 3 hours to obtain surface-treated silicon dioxide 6. The obtained re-fired silicon dioxide 6 and surface-treated silicon dioxide 6 were subjected to the same various measurements as in Example 1. The results are shown in Tables 1 and 2.

[0076] Example 7 Vinyltrimethoxysilane (VTMS: KBM-1003 manufactured by Shin-Etsu Chemical Co., Ltd.) was used instead of phenyltrimethoxysilane as a surface treatment agent. The surface treatment agent was used at a concentration of 0.7% by mass relative to the re-fired silica. The surface treatment was performed at 130°C for 3 hours. Otherwise, the re-fired silica 7 was obtained in the same manner as in Example 6. The surface-treated silica 7 was obtained by performing surface treatment on the silica. The obtained re-fired silicon dioxide 7 and surface-treated silicon dioxide 7 were subjected to the same various measurements as in Example 6. The results are shown in Tables 1 and 2.

[0077] Examples 8 and 9 The re-firing temperature in the re-firing step was changed. Otherwise, re-fired silicon dioxide 8 and 9 were obtained in the same manner as in Example 1, and surface-treated silicon dioxide 8 and 9 were obtained by surface treatment. The obtained re-fired silicon dioxide 8 and 9, as well as the surface-treated silicon dioxide 8 and 9, were subjected to the same various measurements as in Example 1. The results are shown in Tables 1 and 2.

[0078] Example 10 Using silicon dioxide with an average particle size different from that in Example 1 as raw material, the re-firing temperature and the ratio of HMDS to re-firing silicon dioxide were changed. Otherwise, re-firing silicon dioxide 10 was obtained in the same manner as in Example 1, and surface treatment was performed on the silicon dioxide to obtain surface-treated silicon dioxide 10. The obtained re-fired silicon dioxide 10 and surface-treated silicon dioxide 10 were subjected to the same various measurements as in Example 1. The results are shown in Tables 1 and 2.

[0079] Example 11 Using silicon dioxide with an average particle size different from that in Example 1 as raw material, the re-firing temperature and time, and the ratio of HMDS used to re-firing silicon dioxide were changed. Otherwise, re-firing silicon dioxide 11 was obtained in the same manner as in Example 1, and surface treatment was performed on the silicon dioxide to obtain surface-treated silicon dioxide 11. The obtained re-fired silicon dioxide 11 and surface-treated silicon dioxide 11 were subjected to the same various measurements as in Example 1. The results are shown in Tables 1 and 2.

[0080] Example 12 Using silicon dioxide with an average particle size different from that in Example 1 as raw material, the firing temperature was changed, refiring was not performed, and the ratio of HMDS used to raw silicon dioxide was changed. Otherwise, refired silicon dioxide 12 was obtained in the same manner as in Example 1, and surface-treated silicon dioxide 12 was obtained by surface treatment. The obtained re-fired silicon dioxide 12 and surface-treated silicon dioxide 12 were subjected to the same various measurements as in Example 1. The results are shown in Tables 1 and 2.

[0081] Example 13 Using silicon dioxide with an average particle size different from that in Example 1 as raw material, the firing temperature, refiring temperature and time, and the ratio of HMDS used to refiring silicon dioxide were changed. Otherwise, refiring silicon dioxide 13 was obtained in the same manner as in Example 1, and surface treatment was performed on these materials to obtain surface-treated silicon dioxide 13. The obtained re-fired silicon dioxide 13 and surface-treated silicon dioxide 13 were subjected to the same various measurements as in Example 1. The results are shown in Tables 1 and 2.

[0082] Example 14 Using silicon dioxide with an average particle size different from that in Example 1 as raw material, the re-firing temperature and the ratio of HMDS to re-firing silicon dioxide were changed. Otherwise, re-firing silicon dioxide 14 was obtained in the same manner as in Example 1, and surface treatment was performed on the silicon dioxide to obtain surface-treated silicon dioxide 14. The obtained re-fired silicon dioxide 14 and surface-treated silicon dioxide 14 were subjected to the same various measurements as in Example 1. The results are shown in Tables 1 and 2.

[0083] Comparative Examples 1 and 2 The firing temperature in the re-firing step was changed to 1300°C (Comparative Example 1), or the re-firing step was not performed (Comparative Example 2). Otherwise, comparative re-fired silicon dioxide 1 and comparative fired silicon dioxide 2 were obtained in the same manner as in Example 1. Surface treatment was performed on these materials to obtain comparative surface-treated silicon dioxide 1 and 2. For the comparative re-fired silicon dioxide 1, comparative calcined silicon dioxide 2, and comparative surface-treated silicon dioxide 1 and 2, the same measurements as in Example 1 were performed. The results are shown in Tables 1 and 2. Furthermore, the FT-IR measurement results of comparative re-fired silicon dioxide 1 and comparative calcined silicon dioxide 2 are shown in Figures 3 and 4, and the overlapping representations of the FT-IR measurement results of re-fired silicon dioxide 1 and 2 and comparative re-fired silicon dioxide 1 and comparative calcined silicon dioxide 2 are shown in Figure 5.

[0084] Comparative Examples 3 and 4 Using other company's product A (Comparative Example 3) and other company's product B (Comparative Example 4) as equivalent to the calcined and pulverized products of raw silicon dioxide obtained by calcining and pulverizing raw silicon dioxide, the ratio of HMDS to recalcined silicon dioxide used was changed (Comparative Example 3). Otherwise, comparative recalcined silicon dioxide 3 and 4 were obtained in the same manner as in Example 1, and surface-treated to obtain comparative surface-treated silicon dioxide 3 and 4. For the obtained comparative re-fired silicon dioxide 3 and 4 and comparative surface-treated silicon dioxide 3 and 4, the same various measurements as in Example 1 were performed. The results are shown in Tables 1 and 2. Product A from other companies is a crystalline silicon dioxide with an average particle size of 0.5 μm manufactured by a dry process. Product B from other companies is an amorphous silicon dioxide manufactured by the sol-gel method. In FT-IR measurements, the peak A from isolated hydroxyl groups at 3800~3700 cm⁻¹ was not observed.

[0085] Comparative Example 5 Using silicon dioxide with an average particle size different from that in Example 1 as raw material, the firing temperature in the re-firing step was changed to 400°C, and the ratio of HMDS used to re-fired silicon dioxide was changed. Otherwise, comparative re-fired silicon dioxide 5 was obtained in the same manner as in Example 1, and surface treatment was performed on these materials to obtain comparative surface-treated silicon dioxide 5. For the obtained comparative re-fired silicon dioxide 5 and comparative surface-treated silicon dioxide 5, the same various measurements as in Example 1 were performed. The results are shown in Tables 1 and 2.

[0086] Comparative Example 6 Using silicon dioxide with an average particle size different from that in Example 1 as raw material, the firing temperature in the re-firing step was changed to 600°C, and the ratio of HMDS used to re-fired silicon dioxide was changed. Otherwise, comparative re-fired silicon dioxide 6 was obtained in the same manner as in Example 1, and surface treatment was performed on these materials to obtain comparative surface-treated silicon dioxide 6. For the obtained comparative re-fired silicon dioxide 6 and comparative surface-treated silicon dioxide 6, the same various measurements as in Example 1 were performed. The results are shown in Tables 1 and 2.

[0087] [Table 1] Primarch Firing Re-firing FT-IR Dielectric properties XRD BET-SSA [m 2 / g] type Average particle size [μm] Temperature [°C] Keep Time [h] Temperature [°C] Keep Time [h] A / B 3500~3100 cm⁻¹ adsorption water peak 1 GHz 10 GHz ε1 tanδ1 tanδ1 / SSA ε2 tanδ2 tanδ2 / SSA Example 1 Sol-gel synthesis of silicon dioxide 1.0 1000 5 800 5 21.2 ND 2.72 9.6.E-05 3.3.E-05 2.73 1.2.E-03 4.1.E-04 amorphous 2.9 Example 2 Sol-gel synthesis of silicon dioxide 1.0 1000 5 1000 5 13.9 ND 2.87 9.5.E-05 3.3.E-05 2.71 1.4.E-03 4.8.E-04 amorphous 2.9 Example 3 Sol-gel synthesis of silicon dioxide 1.0 1000 5 1200 5 1.4 ND 2.84 2.9.E-04 1.9.E-04 2.72 1.2.E-03 8.3.E-04 amorphous 1.5 Example 4 Sol-gel synthesis of silicon dioxide 0.7 1000 5 800 5 5.9 ND 2.75 1.0.E-04 2.3.E-05 2.73 1.2.E-03 2.7.E-04 amorphous 4.5 Example 5 Sol-gel synthesis of silicon dioxide 0.05 950 5 1000 5 56.4 ND 2.73 1.7.E-03 3.5.E-05 2.65 5.4.E-03 1.1.E-04 amorphous 48.3 Example 6 Sol-gel synthesis of silicon dioxide 1.0 1000 5 800 5 21.2 ND 2.72 9.6.E-05 3.3.E-05 2.73 1.2.E-03 4.1.E-04 amorphous 2.9 Example 7 Sol-gel synthesis of silicon dioxide 1.0 1000 5 800 5 21.2 ND 2.72 9.6.E-05 3.3.E-05 2.73 1.2.E-03 4.1.E-04 amorphous 2.9 Example 8 Sol-gel synthesis of silicon dioxide 1.0 1000 5 1100 5 1.3 ND 2.76 9.6.E-05 3.3.E-05 2.91 1.1.E-03 3.9.E-04 amorphous 2.9 Example 9 Sol-gel synthesis of silicon dioxide 1.0 1000 5 700 5 34.4 ND 2.75 2.2.E-04 7.6.E-05 2.75 1.7.E-03 5.9.E-04 amorphous 2.9 Example 10 Sol-gel synthesis of silicon dioxide 0.7 1000 5 1050 5 7.6 ND 2.70 7.7.E-05 1.8.E-05 2.78 1.5.E-03 3.5.E-04 amorphous 4.2 Example 11 Sol-gel synthesis of silicon dioxide 0.7 1000 5 1150 1 3.2 ND 2.82 1.0.E-04 2.3.E-05 2.85 1.3.E-03 2.9.E-04 amorphous 4.4 Example 12 Sol-gel synthesis of silicon dioxide 0.7 1050 5 none - 1.1 ND 2.80 1.8.E-03 4.4.E-04 2.64 3.0.E-03 7.3.E-04 amorphous 4.1 Example 13 Sol-gel synthesis of silicon dioxide 0.7 1100 5 800 1 2.2 ND 2.87 1.0.E-04 2.0.E-05 2.77 1.6.E-03 3.1.E-04 amorphous 5.1 Example 14 Sol-gel synthesis of silicon dioxide 0.1 1000 5 1100 5 8.8 ND 2.84 1.2.E-04 6.3.E-06 2.63 1.9.E-03 1.0.E-04 amorphous 18.4 Comparative Example 1 Sol-gel synthesis of silicon dioxide 1.0 1000 5 1300 5 0.3 0.033 3.22 5.0.E-04 1.2.E-03 3.12 9.1.E-04 2.3.E-03 Crystallinity 0.4 Comparative Example 2 Sol-gel synthesis of silicon dioxide 1.0 1000 5 none - 3.5 0.032 2.90 4.9.E-03 1.7.E-03 2.99 8.2.E-03 2.8.E-03 amorphous 2.9 Comparative Example 3 Other companies' products A 0.5 unknown unknown 800 5 5.9 0.028 2.69 4.0.E-04 2.4E-05 2.38 2.3.E-03 1.4E-04 Crystallinity 16.5 Comparative Example 4 Other companies' products B 1.0 unknown unknown 800 5 0.0 ND 2.77 8.9.E-05 2.8E-05 2.80 1.1.E-03 3.3E-04 amorphous 3.2 Comparative Example 5 Sol-gel synthesis of silicon dioxide 0.05 950 5 400 5 137.6 0.1 2.8 2.4.E-03 5.8.E-05 2.26 9.4.E-03 2.2.E-04 amorphous 41.7 Comparative Example 6 Sol-gel synthesis of silicon dioxide 0.7 1000 5 600 5 54.1 0.022 2.79 2.8.E-04 6.2.E-05 2.81 2.4.E-03 5.3.E-04 amorphous 4.5

[0088] [Table 2] Surface treatment agent Laser diffraction particle size distribution SEM Image Analysis - Granularity Distribution FT-IR Dielectric properties Evaluation of affinity with resin Water loss at 500~1000℃ [mmol / g] After 264 hours at 85℃ / 85%RH type Processing volume [wt%] D10 [μm] D50 [μm] D90 [μm] Maximum frequency [%] D10 / D90 [-] dmax / d50 [-] A B A / B 1 GHz 10 GHz Evaluation of the viscosity of resin mixtures [mPa·s] Visual evaluation Moisture absorption rate [wt%] 10 GHz ε3 tanδ3 ε4 tanδ4 tanδ5 tanδ increase rate [%) Example 1 HMDS 0.7 wt% 0.96 1.08 1.24 64.3 0.78 1.08 0.56 0.36 1.56 2.93 6.8.E-05 2.76 8.9.E-04 43750 ○ - - - - Example 2 HMDS 0.7 wt% 0.89 0.99 1.13 48.0 0.79 1.11 0.72 0.18 4.08 2.93 9.5.E-05 2.76 9.7.E-04 46500 ○ - - - - Example 3 HMDS 0.7 wt% 1.23 4.37 12.00 6.3 0.10 1.10 0.00 0.10 0.00 2.94 1.1.E-04 2.82 1.0.E-03 68250 ○ - - - - Example 4 HMDS 1.0 wt% 0.59 0.68 0.76 47.6 0.78 1.15 0.85 0.30 2.85 2.83 4.5.E-05 2.82 1.3.E-03 57000 ○ 0.189 0.42 5.5.E-03 335 Example 5 HMDS 3.0 wt% 7.85 9.29 11.01 42.8 0.71 1.19 0.06 0.08 0.76 2.84 5.0.E-04 2.76 2.8.E-03 72000 ○ - - - - Example 6 PTMS 1.0 wt% 0.89 0.99 1.12 53.4 0.80 1.12 0.23 0.12 1.95 2.94 5.1.E-04 2.84 1.5.E-03 34000 ○ - - - - Example 7 VTMS 0.7 wt% 0.97 1.08 1.23 67.2 0.79 1.17 0.24 0.16 1.50 2.99 4.3.E-04 2.90 1.6.E-03 34750 Δ - - - - Example 8 HMDS 0.7 wt% 0.88 0.94 1.05 78.4 0.84 1.05 0.00 0.15 0.00 2.79 6.2.E-05 2.78 1.1.E-03 49750 ○ - - - - Example 9 HMDS 0.7 wt% 0.92 1.03 1.22 66.1 0.75 1.11 0.45 0.28 1.61 2.95 1.5.E-04 2.80 1.2.E-04 45500 ○ - - - - Example 10 HMDS 1.0 wt% 0.47 0.71 0.98 21.1 0.48 - 0.00 0.26 0.00 2.98 9.0.E-05 2.98 1.0.E-03 43800 ○ - - - - Example 11 HMDS 1.0 wt% 0.46 0.69 0.95 21.7 0.48 - 0.00 0.38 0.00 2.79 1.1.E-04 2.66 1.3.E-03 - - - 0.10 1.8.E-03 42 Example 12 HMDS 1.0 wt% 0.56 0.65 0.75 49.7 0.76 1.17 0.00 2.52 0.00 2.95 6.7.E-04 2.97 1.7.E-03 - - - 0.06 2.0.E-03 14 Example 13 HMDS 1.0 wt% 0.47 0.72 1.00 20.7 0.47 - 0.00 0.81 0.00 2.80 7.5.E-05 2.82 1.2.E-03 - - 0.017 0.08 2.0.E-03 63 Example 14 HMDS 2.5 wt% 7.98 9.71 11.44 37.4 0.70 - 0.04 0.21 0.17 2.81 3.3.E-05 2.85 1.8.E-03 - - - 0.09 2.9.E-03 61 Comparative Example 1 HMDS 0.7 wt% 4.23 8.62 26.89 8.4 0.16 5.99 0.00 0.14 0.00 3.19 1.3.E-04 3.18 5.8.E-04 50500 × - - - - Comparative Example 2 HMDS 0.7 wt% 0.86 0.95 1.09 65.2 0.79 1.18 0.47 0.74 0.64 2.83 1.3.E-03 2.85 3.2.E-03 58250 × - - - - Comparative Example 3 HMDS 3.5 wt% 0.23 0.5 1.07 8.4 0.21 2.65 0.00 0.22 0.00 2.67 2.0E-04 2.52 1.8E-03 More than 100,000 ○ - - - - Comparative Example 4 HMDS 0.7 wt% 0.90 1.02 1.14 48.1 0.79 1.14 0.00 0.74 0.00 2.94 6.4E-05 2.83 8.1E-04 77500 × - 0.19 2.8.E-03 245 Comparative Example 5 HMDS 3.0 wt% 7.1 8.39 9.97 42.6 0.71 1.28 0.07 0.15 0.48 2.71 6.2.E-04 2.68 3.5.E-03 More than 100,000 Δ - - - - Comparative Example 6 HMDS 1.0 wt% 0.63 0.75 0.81 54.1 0.78 1.12 0.19 0.21 0.89 2.88 1.2E-04 2.68 1.7.E-03 62500 × - - - -

[0089] Based on the comparison of Examples 1-14 and Comparative Examples 1-6, it was confirmed that by using amorphous silica as a raw material, surface treatment can be performed on amorphous surface-treated silica with excellent dielectric properties, uniform dispersibility in resins, and viscosity suppression by using amorphous silica with low dielectric loss tangent tanδ per unit specific surface area as a raw material. The peak intensity ratio (A / B) of peak A from isolated hydroxyl groups and peak B from hydrogen-bonded hydroxyl groups in FT-IR measurement is 1.0-75, and there are substantially no peaks from adsorbed water at 3500-3100 cm⁻¹. Furthermore, it was confirmed that the surface-treated silicon dioxide of Examples 10-14, which had a peak strength ratio (A / B) of 0.50 or less, had a lower moisture absorption rate and a smaller change in dielectric properties after being placed in a humid environment.

[0090] none

Claims

1. A filler material for electronic materials, comprising amorphous silicon dioxide, wherein the peak intensity ratio (A / B) of the amorphous silicon dioxide in FT-IR measurements is 1.0 to 75.0, and there is substantially no peak from adsorbed water at 3500 to 3100 cm⁻¹, wherein the ratio of tanδ to BET specific surface area (tanδ / BET specific surface area) of the silicon dioxide powder at 1 GHz and 10 GHz is 1.0 × 10⁻³ or less, and the BET specific surface area of ​​the amorphous silicon dioxide is 1 m² / g or more.

2. The filler material used in the electronic material filling process as described in claim 1, wherein, The silicon dioxide exhibits a D50 of less than 10 μm and a D10 / D90 ratio of more than 0.30 in the laser diffraction particle size distribution.

3. Materials used for making fillers for electronic materials as requested in item 1 or 2, wherein, The peak intensity ratio (A / B) of this silicon dioxide in FT-IR measurements, from peak A of isolated hydroxyl groups to peak B of hydroxyl groups with hydrogen bonds, is 1.0 to 10.

0.

4. An amorphous surface-treated silicon dioxide, which is produced by treating with a surface treatment agent, characterized in that: the surface-treated silicon dioxide has a tanδ of 1.0 × 10⁻³ or less and an ε of 3.15 or less in powder form at 1 GHz; the surface-treated silicon dioxide has a BET specific surface area of ​​1 m² / g or more; the surface-treated silicon dioxide has a tanδ of 3.0 × 10⁻³ or less and an ε of 3.15 or less in powder form at 10 GHz; and a viscosity at 25°C of 75000 mPa·s or less, measured under the following conditions: (conditions) using the amorphous surface-treated silicon dioxide and a viscosity at 25°C of 11000–15000 mPa·s. An epoxy resin of mPa·s was kneaded with a mass ratio of amorphous surface-treated silica to epoxy resin (amorphous surface-treated silica: epoxy resin) of 4:6 to prepare an affinity evaluation resin mixture. The viscosity of the obtained affinity evaluation resin mixture was measured at 25°C using a type B viscometer.

5. A surface-treated silicon dioxide, which is an amorphous surface-treated silicon dioxide obtained by treating with a surface treatment agent, characterized in that: the surface-treated silicon dioxide has a tanδ of 1.0×10-3 or less and an ε of 3.15 or less in powder at 1 GHz, the surface-treated silicon dioxide has a BET specific surface area of ​​1 m2 / g or more, the surface-treated silicon dioxide has a tanδ of 3.0×10-3 or less and an ε of 3.15 or less in powder at 10 GHz, and the peak intensity ratio (A / B) of the peak A from isolated hydroxyl groups to the peak B from hydroxyl groups with hydrogen bonds in FT-IR measurement is 0.50 or less.

6. A resin composition for electronic materials, characterized in that it contains surface-treated silicon dioxide and resin as claimed in claim 4 or 5.

7. An electronic material, characterized in that it is made using a resin composition of electronic materials as claimed in claim 6.

8. A method for manufacturing surface-treated silica, characterized in that the manufacturing method comprises the following steps: calcining amorphous silica obtained by the sol-gel method at 600–1200°C; pulverizing the calcined silica obtained in the calcination step; calcining the pulverized calcined silica obtained in the pulverization step again at 700–1200°C; and surface-treating the pulverized calcined silica obtained in the pulverization step or the re-calcined silica obtained in the re-calcination step with a surface treatment agent.

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