Spherical silica powder and method for producing spherical silica powder

Abstract

The present invention provides a new spherical silica powder having a sufficiently small dielectric loss tangent and excellent miscibility with a resin composition. The spherical silica powder of the present invention has a median particle diameter d50 of 0.5 to 20 μm, a specific surface area A (m 2 / g) of 50 to 200 m 2 / g, and a product A x d50 of 2.7 to 5.0 μm m / g.

Description

Technical Field

[0001] This invention relates to spherical silica powder and a method for manufacturing spherical silica powder. Background Technology

[0002] In recent years, there has been a demand for miniaturization of electronic devices, high-speed signals, and high-density wiring. To meet these requirements, it is necessary to reduce the dielectric constant, dielectric loss tangent, and thermal expansion of the resin compositions used in insulating resin sheets such as adhesive films and prepregs, as well as the insulating layers formed on printed circuit boards.

[0003] The dielectric properties of ceramic materials are known, for example, from non-patent literature 1, and are characteristics of sintered substrates. Silica (SiO2) is promising as a filler material with a low dielectric constant (3.9), low thermal expansion coefficient (3–7.9 ppm / ℃), and low dielectric constant and thermal expansion coefficient, and has already been used in many applications. Therefore, its widespread application in high-frequency dielectric devices is expected.

[0004] To meet these requirements, Patent Document 1 studies the reduction of dielectric loss tangent by heat-treating molten spherical silica powder. Patent Document 2, on the other hand, studies the reduction of dielectric constant and dielectric loss tangent by using crystalline silica as a raw material and molding it into a hollow shape.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent No. 6793282

[0008] Patent Document 2: Japanese Patent Application Publication No. 2021-075438

[0009] Non-patent literature:

[0010] [Non-Patent Literature 1: Noboru Ichinose, "Trends in Inorganic Dielectric and Insulating Materials", Theory of Electricity A, 1993, Vol. 113, No. 7, pp. 495-502] Summary of the Invention

[0011] The problem the invention aims to solve

[0012] Conventional spherical silica powders are formed from parent particles and tiny attached particles, with the specific surface area increasing due to the attached particles. Consequently, the region where the dielectric loss tangent originating from surface residues can be reduced is limited.

[0013] In the technology described in Patent Document 1, spherical silica powder is produced using spherical silica raw materials derived from silica. However, micro-powder is generated during the silica pulverization process, which adheres to the silica and is thus contained within it. Therefore, the specific surface area does not decrease, resulting in a limitation on the reduction of the dielectric loss tangent. Furthermore, the technology described in Patent Document 2 requires granulation of crystalline silica and melting it at high temperatures, which presents problems in terms of productivity.

[0014] The present invention was made in view of the above-mentioned problems, and its objective is to provide a new type of spherical silica powder with a sufficiently small dielectric loss tangent and excellent miscibility with resin compositions.

[0015] Solution for solving the problem

[0016] The inventors conducted in-depth research and found that by reducing the specific surface area corresponding to the particle size to produce spherical silica powder in which the product of the specific surface area and the median particle size is within a specific range, the above-mentioned problems can be solved, thus completing the present invention.

[0017] This invention relates to the following (1) to (10).

[0018] (1) A spherical silica powder, wherein the average particle size d50 is 0.5–20 μm and the specific surface area A(m²) is [missing information]. 2 The product A×d50 of the median particle size d50 (μm) and the aforementioned g / g particle size is 2.7–5.0 μm·m. 2 / g.

[0019] (2) The spherical silica powder according to (1) above, wherein the dielectric loss tangent of the spherical silica powder is less than 0.0020 at a frequency of 1 GHz.

[0020] (3) The spherical silica powder according to (1) or (2) above, wherein the viscosity of the compound containing the aforementioned spherical silica powder is less than 5000 mPa·s as determined by the following method.

[0021] (Determination Method)

[0022] The mixture obtained by mixing 6 parts by weight of cooked flaxseed oil and 8 parts by weight of the aforementioned spherical silica powder and kneading at 2000 rpm for 3 minutes was analyzed using a rotational rheometer at a shear rate of 1 s. -1 The viscosity was measured for 30 seconds to determine the viscosity at that time point.

[0023] (4) The spherical silica powder according to any one of (1) to (3) above, wherein the bonded silanol groups originating from the surface of the aforementioned spherical silica powder are located at 3300-3700 cm. -1 The maximum IR peak intensity is below 0.2.

[0024] (5) The spherical silica powder according to any one of (1) to (4) above, wherein the spherical silica powder contains 30 to 1500 ppm of Ti.

[0025] (6) A method for manufacturing spherical silica powder, which is the method for manufacturing spherical silica powder according to any one of (1) to (5) above, the method comprising forming spherical silica precursor by a wet process.

[0026] (7) The method for manufacturing spherical silica powder according to (6) above, wherein, according to JIS K0067:1992, the mass reduction of the silica precursor when 1 g of the silica precursor is heated and dried at 850°C for 0.5 hours is 5.0 to 15.0% by mass.

[0027] (8) The method for manufacturing spherical silica powder according to (6) or (7) above, wherein the pore volume of the aforementioned silica precursor is 0.3 to 2.2 ml / g.

[0028] (9) A resin composition comprising 5 to 90% by mass of the spherical silica powder described in any one of (1) to (5) above.

[0029] (10) A slurry composition comprising 1 to 50% by mass of the spherical silica powder described in any one of (1) to (5) above.

[0030] The effects of the invention

[0031] According to the present invention, spherical silica powder with a small specific surface area and a sufficiently small dielectric loss tangent can be provided. Because of its low dielectric loss tangent, the spherical silica powder of the present invention exhibits excellent low dielectric loss tangent performance in resin compositions. Furthermore, due to its sufficiently small specific surface area relative to particle size, it has excellent dispersibility in resins. Attached Figure Description

[0032] Figure 1 A scanning electron microscope (SEM) image of the spherical silica powder obtained in Example 1 is shown. Detailed Implementation

[0033] The present invention will now be described, but it is not limited to the examples described below. It should be noted that in this specification, the term "~" indicating a numerical range refers to the inclusion of the values ​​preceding and following it as both a lower and upper limit.

[0034] It should be noted that in this instruction manual, "mass" and "weight" have the same meaning.

[0035] The spherical silica powder of this invention is solid silica. The median particle size (d50) at the point where the cumulative volume reaches 50% in the volume-based particle size distribution curve is 0.5–20 μm, and the specific surface area A(m²) is… 2 The product of g / g and median particle size d50 (μm), A×d50, is between 2.7 and 5.0 μm·m. 2 / g(2.7≤A×d50(μm·m 2 The range is / g)≤5.0).

[0036] When the median particle size d50 of the spherical silica powder is 0.5 μm or more, the dielectric loss tangent can be significantly reduced. However, if the median particle size becomes too large, the particle gauge value increases, thus increasing the minimum thickness of the film when the resin composition containing the spherical silica powder is formed into a sheet, for example. Therefore, in this invention, the median particle size d50 of the spherical silica powder is set in the range of 0.5 to 20 μm. The median particle size d50 is preferably 0.5 to 10 μm, and more preferably 1 to 5 μm.

[0037] For the particle size distribution curve of spherical silica powder with a cumulative volume of 10%, i.e., the 10% particle size d10, from the viewpoint of improving the uniform dispersion in the resin composition and improving the interaction between the spherical silica powder and the resin, it is preferably 0.5 μm to 5.0 μm, more preferably 1.0 μm to 3.0 μm.

[0038] For the ratio of median particle size d50 to 10% particle size d10 (d50 / d10), from the viewpoint of improving the uniform dispersibility in the resin composition and improving the interaction between the spherical silica powder and the resin, it is preferable to be greater than 1.0 and less than 5.0, more preferably 1.3 to 4.0, and even more preferably 1.5 to 3.0.

[0039] The particle size distribution of the silica particles contained in the resin composition is preferably unimodal. The unimodal particle size distribution of silica particles can be confirmed by the presence of a single peak in the particle size distribution based on laser diffraction and scattering.

[0040] The maximum particle size (Dmax) of the spherical silica powder is preferably less than 150 times, more preferably less than 100 times, even more preferably less than 50 times, and particularly preferably less than 10 times the median particle size d50. When the maximum particle size (Dmax) is less than 150 times the median particle size d50, it is less likely to become a defect during wafer processing. In addition, the maximum particle size (Dmax) is preferably more than 1.2 times the median particle size d50, more preferably more than 1.5 times, and even more preferably more than 2 times.

[0041] The median particle diameter d50 is the volume-based cumulative 50% diameter obtained using a particle size distribution measuring device based on laser diffraction (for example, "MT3300EXEXII= EXII" manufactured by Microtrac BELCorp.). That is: the particle size distribution is measured by the laser diffraction / scattering method, the total volume of the spherical silica powder is set to 100%, and the cumulative curve is obtained. The particle diameter at the point where the cumulative volume is 50% on this cumulative curve.

[0042] The 10% particle diameter d10 is the volume-based cumulative 10% diameter obtained using a particle size distribution measuring device based on laser diffraction (for example, "MT3300EXII" manufactured by Microtrac BELCorp.). That is: the particle size distribution is measured by the laser diffraction / scattering method, the total volume of the spherical silica powder is set to 100%, and the cumulative curve is obtained. The particle diameter at the point where the cumulative volume is 10% on this cumulative curve.

[0043] The maximum particle diameter is also obtained by the same measurement as the median particle diameter d50 and the 10% particle diameter d10.

[0044] The specific surface area A of the spherical silica powder of the present invention is preferably in the range of 0.2 to 2.0 m 2 / g. When the specific surface area is 0.2 m 2 / g or more, when the resin composition contains spherical silica powder, there are sufficient contacts with the resin, so the compatibility with the resin becomes good. In addition, when it is 2.0 m 2 / g or less, the dielectric loss tangent can be reduced, so excellent low dielectric loss tangent can also be exhibited in the resin composition, and in addition, the dispersibility in the resin composition is improved. The specific surface area A is preferably 0.2 to 2.0 m 2 / g, more preferably 0.5 to 2.0 m 2 / g, further preferably 0.5 to 1.5 m 2 / g, particularly preferably 0.8 to 1.5 m 2 / g. Here, the specific surface area A is preferably 2.0 m 2 / g or less, more preferably 1.5 m 2 / g or less. In addition, it is preferably 0.2 m 2 / g or more, more preferably 0.5 m 2 / g or more, particularly preferably 0.8 m 2 / g or more. It should be noted that it is substantially difficult to obtain those with a specific surface area A less than 0.2 m 2 / g.

[0045] The specific surface area was determined by the BET method based on nitrogen adsorption using a specific surface area and pore distribution measuring device (e.g., Microtrac BELCorp. "BELSORP-miniII", Micromeritics "TriStar II", etc.).

[0046] Moreover, the specific surface area A(m²) of spherical silica powder 2 The product of the median particle size (g) and the median particle size d50 (μm), A×d50, is 2.7–5.0 μm·m. 2 / g, preferably 2.7–4.5 μm·m 2 / g, more preferably 2.7–4.0 μm·m 2 / g. The theoretical value of A×d50 is 2.7 [through specific surface area = 6 / (silicon dioxide true density 2.2 (g / cm³)]. 3 [A×d50 (μm)] is derived from the median particle size d50, but in reality, values ​​below this are unattainable. The larger the value of A×d50, the larger the specific surface area relative to the particle size, and the larger the dielectric loss tangent. Therefore, in order to reduce the dielectric loss tangent to below approximately 0.0020 at a frequency of 1 GHz, A×d50 is set to 5.0 μm·m. 2 / g or less.

[0047] The sphericity of the spherical silica powder is preferably 0.75 to 1.0. If the sphericity is lower, the specific surface area becomes larger, and therefore the dielectric loss tangent becomes easier to increase. Therefore, the sphericity is preferably 0.75 or higher. The sphericity is preferably 0.75 or higher, more preferably 0.90 or higher, even more preferably 0.93 or higher, and the closer to 1.0, the more preferred.

[0048] For sphericity, the maximum diameter (DL) and the minor diameter (DS) orthogonal to it can be determined for any 100 particles in the photographic projection obtained by scanning electron microscopy (SEM). The average value is obtained by calculating the ratio of the minimum diameter (DS) to the maximum diameter (DL) (DS / DL).

[0049] For the spherical silica powder of the present invention, the dielectric loss tangent frequency in the powder state is preferably 0.0020 or less, more preferably 0.0010 or less, and even more preferably 0.0008 or less at 1 GHz. Especially in the determination of the dielectric loss tangent and dielectric constant of the powder, the sample space becomes smaller and the measurement accuracy deteriorates at frequencies above 10 GHz. Therefore, the present invention uses the measurement value at a frequency of 1 GHz. When the dielectric loss tangent of the spherical silica powder at a frequency of 1 GHz is 0.0020 or less, excellent dielectric loss suppression effect can be obtained, thus improving the high-frequency characteristics of the substrate or wafer. The smaller the dielectric loss tangent, the more the transmission loss of the circuit is suppressed; therefore, the lower limit value is not particularly limited.

[0050] From the same point of view, the dielectric constant of the spherical silica powder is preferably 5.0 or less, more preferably 4.5 or less, and even more preferably 4.1 or less at a frequency of 1 GHz.

[0051] The dielectric loss tangent and dielectric constant can be determined using a dedicated device (e.g., the KEYCOM Corporation “Vector Network Analyzer E5063A”) via the perturbation resonator method.

[0052] The spherical silica powder of the present invention preferably has a viscosity of 5000 mPa·s or less, as determined by the following measurement method.

[0053] (Determination Method)

[0054] For the compound obtained by mixing 6 parts by weight of cooked flaxseed oil as specified in JIS K 5421:2000 and 8 parts by weight of spherical silica powder and kneading at 2000 rpm for 3 minutes, a rotational rheometer was used to measure the mixture at a shear rate of 1 s. -1 The viscosity was measured for 30 seconds to determine the viscosity at that time point.

[0055] The compound measured using the above method has a shear rate of 1s. -1 When the viscosity is 5000 mPa·s or less, the amount of solvent added during the molding and film formation of the resin composition containing spherical silica powder can be reduced, the drying speed can be accelerated, and productivity can be improved. Furthermore, if the specific surface area corresponding to the particle size of the silica powder increases, the viscosity tends to rise when added to the resin composition; however, the spherical silica powder of the present invention has a small specific surface area, thus suppressing the increase in viscosity of the resin composition. The viscosity of the compound is more preferably 4000 mPa·s or less, and even more preferably 3500 mPa·s or less.

[0056] The aforementioned compound at a shear rate of 1 second -1The lower the viscosity, the better the coatability of the resin composition and the higher the productivity; therefore, there is no specific limit to the lower limit.

[0057] 3746 cm³ of isolated silanol groups on the surface of the spherical silica powder derived from the present invention -1 The intensity of the nearby IR peak is preferably 0.1 or less, more preferably 0.08 or less, and even more preferably 0.06 or less. Isolated silanol groups refer to silanol (Si-OH) groups that are not bonded to water or other substances adsorbed on the silica particles. The amount of isolated silanol (Si-OH) groups on the surface of the silica particles is obtained by IR measurement. Specifically, the IR spectrum is set to 800 cm⁻¹. -1 Normalization was performed at 3800cm -1 After aligning with the baseline, the value of 3746cm is calculated. -1 The relative values ​​of the Si-OH peak intensities near the particles. If there are many isolated silanol groups on the particle surface, the dielectric loss tends to increase when the component mixed with the resin is used for electronic applications. The 3746 cm⁻¹ value is particularly significant for components originating from isolated silanol groups on the particle surface. -1 If the intensity of the nearby IR peak is below 0.1, the dielectric loss can be reduced.

[0058] Furthermore, the bonded silanol groups on the surface of the spherical silica powder derived from the present invention are located at 3300–3700 cm⁻¹. -1 The maximum IR peak intensity is preferably 0.2 or less, more preferably 0.17 or less, and even more preferably 0.15 or less. Bonded silanol groups refer to silanol (Si-OH) groups bonded to water adsorbed on the silica particles, silanols on the silica surface, etc. The amount of bonded silanol (Si-OH) groups on the silica particle surface is obtained by IR measurement. Specifically, the IR spectrum is set at 800 cm⁻¹. -1 Normalization was performed at 3800cm -1 After aligning with the baseline, based on the position between 3300 and 3700 cm -1 The relative values ​​of the peak intensities of bonded Si-OH groups were determined from the maximum peak values. If there are many bonded silanol groups on the particle surface, the dielectric loss tends to increase when components mixed with the resin are used in electronic applications. This is especially true if the bonded silanol groups originating from the particle surface are located between 3300 and 3700 cm⁻¹. -1 If the maximum IR peak intensity is below 0.2, the dielectric loss can be reduced.

[0059] The spherical silica powder of the present invention is preferably a non-porous particle. When it is a porous particle, there is a tendency for increased oil absorption, increased viscosity in the resin, increased surface area, and increased silanol (Si-OH) groups on the surface of the silica particles, thereby worsening the dielectric loss tangent. Specifically, the oil absorption is preferably 100 ml / 100 g or less, more preferably 70 ml / 100 g or less, and most preferably 50 ml / 100 g or less. The lower limit is not particularly limited, but it is practically difficult to achieve an oil absorption of 20 ml / 100 g or less.

[0060] The oil absorption rate is preferably determined according to JIS K 5101-13-2:2004 using cooked flaxseed oil.

[0061] The spherical silica powder of the present invention preferably contains titanium (Ti) in the range of 30 to 1500 ppm, more preferably 100 to 1000 ppm, and even more preferably 100 to 500 ppm. The concentration of titanium can be determined by adding perchloric acid and hydrofluoric acid to the silica powder and calcining it to remove the silicon component, followed by inductively coupled plasma (ICP) emission spectroscopy.

[0062] Ti is an optional component included in the manufacture of spherical silica powder. During the manufacture of spherical silica powder, if microparticles are generated due to the breakage of silica particles, these microparticles adhere to the surface of the parent particles, increasing the specific surface area of ​​the particles. By including Ti in the manufacture of spherical silica powder, it becomes easier to thermally compact during calcination. This reduces breakage during post-calcination processing, thus suppressing the generation of microparticles and decreasing the number of particles adhering to the surface of the silica parent particles, thereby suppressing the increase in specific surface area. By including 30 ppm or more of Ti, it becomes easier to thermally compact during calcination, suppressing the generation of microparticles caused by breakage. If the Ti content is 1500 ppm or less, the aforementioned effects are achieved, and the increase in silanol group content is suppressed, thus suppressing the deterioration of the dielectric loss tangent.

[0063] The spherical silica powder of the present invention may contain impurity elements other than titanium (Ti) to a extent that does not impair the effects of the present invention. Examples of impurity elements besides Ti include Na, K, Mg, Ca, Al, and Fe.

[0064] The total content of alkali metals and alkaline earth metals in the impurity elements is preferably less than 2000 ppm, more preferably less than 1000 ppm, and even more preferably less than 200 ppm.

[0065] The spherical silica powder of the present invention can be treated with a silane coupling agent.

[0066] By using a silane coupling agent to treat the surface of spherical silica powder, the amount of residual silanol groups on the surface is reduced, the surface is hydrophobic, and water adsorption is inhibited, thereby improving dielectric loss. Furthermore, when the resin composition is made, the affinity with the resin, dispersibility, and strength of the resin film are improved.

[0067] Examples of silane coupling agents include aminosilane coupling agents, epoxysilane coupling agents, mercaptosilane coupling agents, silane coupling agents, and organosilazane compounds. One type of silane coupling agent can be used, or two or more can be used in combination.

[0068] The amount of silane coupling agent attached is preferably 0.01 to 5 parts by mass, more preferably 0.02 to 5 parts by mass, and even more preferably 0.1 to 2 parts by mass, relative to 100 parts by mass of spherical silica powder. Here, the amount of silane coupling agent attached is preferably 0.01 parts by mass or more, more preferably 0.02 parts by mass or more, and even more preferably 0.1 parts by mass or more, and even more preferably 5 parts by mass or less, and even more preferably 2 parts by mass or less, relative to 100 parts by mass of spherical silica powder.

[0069] The surface of the spherical silica powder has been treated with a silane coupling agent by detecting peaks based on the substituents of the silane coupling agent using IR spectroscopy. Furthermore, the amount of silane coupling agent adhering to the surface can be determined by measuring the carbon content.

[0070] (Method for manufacturing spherical silica powder)

[0071] The method for manufacturing spherical silica powder of the present invention includes forming a spherical silica precursor by a wet process. The wet process refers to a method that includes using a liquid substance as a silica source and gelling it to obtain a raw material for spherical silica powder. By using the wet process, spherical silica particles can be formed, thus eliminating the need to adjust the particle shape through crushing or other methods, resulting in particles with a small specific surface area. Furthermore, the wet process is less likely to produce particles with a significantly smaller average particle size, and these particles tend to have a smaller specific surface area after calcination. Additionally, in the wet process, by adjusting the impurities in the silica source, the amount of impurity elements such as titanium can be adjusted, thereby achieving a state in which the aforementioned impurity elements are uniformly dispersed in the particles.

[0072] Examples of wet methods include spraying and emulsion-gelation. For example, in an emulsion-gelation method, a dispersed phase containing a silica precursor and a continuous phase are emulsified, and the resulting emulsion is gelled to obtain spherical silica precursors. A preferred emulsification method is to supply the dispersed phase containing the silica precursor to the continuous phase via micropores or a porous membrane to produce the emulsion. This produces an emulsion with uniform droplet diameter, resulting in spherical silica particles with uniform particle size. Micromixer methods and membrane emulsification methods can be used for such emulsification. For example, a micromixer method is disclosed in International Publication No. 2013 / 062105.

[0073] Ideally, the pore volume of the spherical silica precursor obtained in the wet process is 0.05–2.2 ml / g. When the pore volume of the silica precursor is 0.05 ml / g or higher, the silica particles shrink sufficiently during calcination, reducing the specific surface area. Furthermore, when the pore volume of the silica precursor is 2.2 ml / g or lower, it can prevent the feed volume density from becoming excessively high before calcination, thus improving productivity. The preferred pore volume of the silica precursor is 0.05–2.2 ml / g, more preferably 0.1–2.2 ml / g, even more preferably 0.3–2.2 ml / g, further preferably 0.3–1.8 ml / g, particularly preferably 0.6–1.8 ml / g, and most preferably 0.7–1.5 ml / g. Here, the pore volume of the silica precursor is preferably 0.05 ml / g or more, more preferably 0.1 ml / g or more, even more preferably 0.3 ml / g or more, particularly preferably 0.6 ml / g or more, most preferably 0.7 ml / g or more, and preferably 2.2 ml / g or less, more preferably 1.8 ml / g or less, and most preferably 1.5 ml / g or less.

[0074] The pore volume was determined by the BJH method based on nitrogen adsorption using a specific surface area and pore distribution measuring device (e.g., Microtrac BEL Corp.'s "BELSORP-miniII", Micromeritics' "TriStar II", etc.).

[0075] Ideally, the weight loss on ignition of the silica precursor obtained in the wet process is 5.0–15.0% by mass, more preferably 6.0–13.0% by mass, and even more preferably 7.0–12.0% by mass. The weight loss on ignition is the sum of the mass of water adhering to the silica precursor and the mass of water produced by the condensation of silanol groups contained in the silica precursor. By ensuring the silica precursor has a suitable amount of silanol groups, condensation occurs during calcination, making it easier to reduce the number of silanol groups. If the weight loss on ignition is too high, the yield during calcination decreases, and productivity deteriorates. Therefore, the weight loss on ignition of the silica precursor is preferably 15.0% by mass or less, more preferably 13.0% by mass or less, and most preferably 12.0% by mass or less. If the weight loss on ignition is too low, silanol groups tend to remain during calcination. Therefore, the weight loss on ignition of the silica precursor is preferably 5.0% by mass or more, more preferably 6.0% by mass or more, and most preferably 7.0% by mass or more.

[0076] Here, the loss on ignition is calculated according to JIS K0067:1992 as the mass reduction when 1 g of silica precursor is heated and dried at 850 °C for 0.5 hours.

[0077] The average pore size of the silica precursor is preferably 1.0 to 50.0 nm. When the average pore size is 1.0 nm or more, it can homogenize and eliminate pores within the particles, reducing the dielectric loss tangent without leaving air bubbles inside. When the average pore size is 50.0 nm or less, the silica particles can be densified (reduced specific surface area) without leaving fine pores by calcination, thus reducing the dielectric loss tangent. The average pore size is preferably 1.0 to 50.0 nm, more preferably 2.0 to 40.0 nm, further preferably 3.0 to 30.0 nm, and particularly preferably 4.0 to 20.0 nm. Here, the average pore size is preferably 1.0 nm or more, more preferably 2.0 nm or more, further preferably 3.0 nm or more, and particularly preferably 4.0 nm or more. In addition, it is preferably 50.0 nm or less, more preferably 40.0 nm or less, further preferably 30.0 nm or less, and particularly preferably 20.0 nm or less.

[0078] The average pore size was determined by the BET method based on nitrogen adsorption using a specific surface area and pore size distribution measuring device (e.g., Microtrac BELCorp. "BELSORP-miniII", Micromeritics "TriStar II", etc.).

[0079] Furthermore, the weight reduction rate of the silica precursor after drying at 230°C for 12 hours is preferably 10% or less. When the weight reduction rate is 10% or less, sintering of the particles is less likely to occur when the silica precursor is calcined with its particles in contact with each other, and spherical silica powder is easily obtained.

[0080] The weight reduction rate is more preferably 9% or less, further preferably 8% or less, particularly preferably 6% or less, and ideally there is no weight change even after drying at 230°C for 12 hours, so there is no particular lower limit.

[0081] If the resulting silica precursor has a high water content and the weight reduction rate exceeds 10% after drying at 230°C for 12 hours, it is preferable to dry it to below 10%. Examples of drying methods include spray drying, static drying within a dryer, and ventilation treatment of the drying air.

[0082] Spherical silica powder is obtained by heat-treating the aforementioned spherical silica precursor. Heat treatment compacts the spherical silica powder, densifies it, and reduces the amount of silanol groups on the surface, thereby lowering the dielectric loss tangent. The heat treatment temperature is preferably 700–1600°C, more preferably 800–1500°C, and even more preferably 900–1400°C. Here, the heat treatment temperature is preferably above 700°C, more preferably above 800°C, and most preferably above 900°C. If the temperature becomes too high, the particles tend to aggregate, and the particle size in the resin composition becomes larger. Therefore, the temperature is preferably below 1600°C, more preferably below 1500°C, and most preferably below 1400°C.

[0083] The heat treatment time can be adjusted appropriately according to the equipment used. For example, it is preferred to perform the heat treatment for 0.5 to 50 hours, and more preferably for 1 to 10 hours.

[0084] The atmosphere during heat treatment can be either oxygen-containing or oxygen-free. In the case of wet spheroidization, organic substances such as emulsifiers are often used, resulting in residual organic matter in the silica precursor. When calcining a silica precursor containing a small amount of organic matter, the organic matter will carbonize under low-oxygen conditions, thus contributing to the increase in dielectric loss tangent and coloration. Therefore, when the silica precursor contains organic matter, calcination is preferably performed in an oxygen-containing atmosphere, and more preferably in an atmospheric atmosphere.

[0085] The aforementioned heat treatment methods are not particularly limited, and examples include heat treatment based on static placement, heat treatment based on rotary kiln, and heat treatment based on spray combustion.

[0086] The preferred heat treatment method involves calcining the spherical and porous silica precursor in a state where the particles are in contact with each other. Calcining the silica precursor in this state allows for calcination within a smaller volume, thus reducing temperature and time inconsistencies compared to calcination where the silica precursor is dispersed in a gas. This results in spherical silica powder of consistent quality. Calcining the silica precursor in this state ensures uniform calcination conditions for each particle, guaranteeing consistent quality.

[0087] Spherical silica powder sometimes exhibits weak sintering of particles after calcination, thus requiring crushing. Crushing is preferably performed in a manner that does not impair the effects of the invention, and maintains sphericity and surface area such that the average sphericity of the particles is not less than 0.90. Furthermore, it is preferable that the surface area does not increase due to the crushing process. A significant increase in surface area due to crushing means that some spherical particles are pulverized, resulting in fine surface damage and the formation of micropowder. An increase in surface area leads to increased viscosity during dispersion in the resin and a deterioration of the dielectric loss tangent, which is therefore undesirable.

[0088] Crushing can be carried out using crushing devices such as cyclone mills and jet mills. In addition, crushing can also be achieved using vibrating screens.

[0089] The calcined spherical silica powder can be surface-treated with a silane coupling agent. Through this process, the silanol groups present on the surface of the spherical silica powder react with the silane coupling agent, reducing the number of silanol groups and increasing the dielectric loss tangent. Furthermore, the surface is hydrophobized, improving its affinity for resins and thus enhancing resin dispersibility.

[0090] There are no particular restrictions on the surface treatment conditions; they can be any standard surface treatment conditions, and either wet or dry treatment methods can be used. From the viewpoint of achieving uniform treatment, wet treatment is preferred.

[0091] Examples of silane coupling agents used in surface treatment include aminosilane coupling agents, epoxysilane coupling agents, mercaptosilane coupling agents, silane coupling agents, and organosilazane compounds. One or more of these can be used in combination.

[0092] Specifically, as surface treatment agents, examples include aminosilane-based coupling agents such as aminopropylmethoxysilane, aminopropyltriethoxysilane, ureopropyltriethoxysilane, N-phenylaminopropyltrimethoxysilane, and N-2-(aminoethyl)aminopropyltrimethoxysilane; epoxysilane-based coupling agents such as epoxypropyltrimethoxysilane, epoxypropyltriethoxysilane, epoxypropylmethyldiethoxysilane, glycidylbutyltrimethoxysilane, and (3,4-epoxycyclohexyl)ethyltrimethoxysilane; mercaptosilane-based coupling agents such as mercaptopropyltrimethoxysilane and mercaptopropyltriethoxysilane; methyltrimethoxysilane; vinyltrimethoxysilane; and octadecyltrimethoxysilane. Silane coupling agents such as methoxysilane, phenyltrimethoxysilane, methacryloxypropyltrimethoxysilane, imidazole silane, and triazine silane; CF3(CF2)7CH2CH2Si(OCH3)3, CF3(CF2)7CH2CH2SiCl3, CF3(CF2)7CH2CH2Si(CH3)(OCH3)2, CF3(CF2)7CH2CH2Si(CH3)C12, CF3(CF2)5CH2CH2SiCl3, CF3(CF2)5CH2CH2Si(OCH3)3, CF3CH2CH2SiCl3, CF3CH2CH2Si(OCH3)3, C8F 17 SO2N(C3H7)CH2CH2CH2Si(OCH3)3, C7F 15 CONHCH2CH2CH2Si(OCH3)3、C8F 17 CO2CH2CH2CH2Si(OCH3)3、C8F 17 Fluorosilane coupling agents such as -O-CF(CF3)CF2-O-C3H6SiCl3 and C3F7-O-(CF(CF3)CF2-O)2-CF(CF3)CONH-(CH2)3Si(OCH3)3, as well as organosilane compounds such as hexamethyldisilazane, hexaphenyldisilazane, trisilazane, cyclotrisilazane, and 1,1,3,3,5,5-hexamethylcyclotrisilazane.

[0093] The amount of silane coupling agent used is preferably 0.01 parts by mass or more, more preferably 0.02 parts by mass or more, and even more preferably 0.10 parts by mass or more, relative to 100 parts by mass of spherical silica powder. In addition, it is preferably 5 parts by mass or less, and more preferably 2 parts by mass or less.

[0094] Examples of methods for treating silica with silane coupling agents include, for instance, the dry method of spraying silane coupling agents onto spherical silica powder, and the wet method of dispersing spherical silica powder in a solvent and then adding silane coupling agents for reaction.

[0095] (Resin composition and slurry composition)

[0096] The spherical silica powder of the present invention has a small specific surface area, thus exhibiting good dispersibility in various solvents and excellent mixability in resin compositions.

[0097] The resin composition of this embodiment comprises the spherical silica powder of the present invention and a resin. The content of the spherical silica powder in the resin composition is preferably 5-90% by mass, more preferably 10-85% by mass, further preferably 10-80% by mass, particularly preferably 10-75% by mass, especially further preferably 10-70% by mass, and most preferably 15-70% by mass. When the content of the spherical silica powder is 5% by mass or more, sufficient peel strength can be obtained; when it is 90% by mass or less, the viscosity of the resin composition does not increase excessively, making it easy to handle. Here, the content of the spherical silica powder in the resin composition is preferably 5% by mass or more, more preferably 10% by mass or more, further preferably 15% by mass or more, and preferably 90% by mass or less, more preferably 85% by mass or less, further preferably 80% by mass or less, particularly preferably 75% by mass or less, and most preferably 70% by mass or less.

[0098] As resins, one or more of the following can be used: epoxy resin, silicone resin, phenolic resin, melamine resin, urea resin, unsaturated polyester resin, fluororesin, polyimide resin, polyamide-imide resin, polyetherimide, etc.; polyester resins such as polybutylene terephthalate and polyethylene terephthalate; polyphenylene ether resin, polyphenylene sulfide resin, phenolic resin, o-divinylbenzene resin, aromatic polyester resin, polysulfone, liquid crystal polymer, polyethersulfone, polycarbonate, maleimide modified resin, ABS (acrylonitrile-butadiene-styrene) resin, AAS (acrylonitrile-acrylic rubber-styrene) resin, AES (acrylonitrile-ethylene-propylene-diene rubber-styrene) resin, polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-ethylene copolymer (ETFE), etc. The dielectric loss tangent of a resin composition also depends on the properties of the resin, so these can be taken into account when selecting the resin to use.

[0099] Thermosetting resin is preferred. One type of thermosetting resin or two or more types can be used. Examples of thermosetting resins include epoxy resin, polyphenylene ether resin, polyimide resin, phenolic resin, and o-divinylbenzene resin. From the viewpoints of adhesion and heat resistance, epoxy resin, polyphenylene ether resin, or o-divinylbenzene resin is preferred as the thermosetting resin.

[0100] From the viewpoint of adhesion, dielectric properties, etc., the weight-average molecular weight of thermosetting resins is preferably 1000–7000, more preferably 1000–5000, and even more preferably 1000–3000. The weight-average molecular weight is determined by gel permeation chromatography (GPC) using polystyrene conversion.

[0101] From the viewpoints of suppressing the excessive presence of silica particles, reducing water absorption, lowering the dielectric loss tangent, and improving adhesion, the content of spherical silica powder is preferably 10 to 400 parts by weight, more preferably 50 to 300 parts by weight, and even more preferably 70 to 250 parts by weight, relative to 100 parts by weight of thermosetting resin. Particularly when a high filler content of silica particles is desired, the aforementioned silica particle content is preferably 80 parts by weight or more, more preferably 90 parts by weight or more.

[0102] The spherical silica powder is fully wetted and uniformly dispersed through the above-described mechanism, and it also readily interacts with the thermosetting resin. Therefore, in this composition where the content is within the aforementioned range, i.e., where the spherical silica powder accounts for a larger proportion of the thermosetting resin, both components are easily stabilized, enabling the formation of a molded product with excellent adhesion to the metal substrate layer.

[0103] Furthermore, the spherical silica powder of the present invention can be used as a filler material in slurry compositions. A slurry composition refers to a mud-like composition in which the spherical silica powder of the present invention is dispersed in an aqueous or oil-based medium.

[0104] The slurry composition preferably contains 1 to 50% by mass of spherical silica powder, more preferably 5 to 40% by mass.

[0105] Examples of oil-based media include acetone, methanol, ethanol, butanol, 2-propanol, 1-propanol, isobutyl alcohol, 1-butanol, 2-butanol, 2-methoxyethanol, 2-ethoxyethanol, 1-methoxy-2-propanol, 2-acetoxy-1-methoxypropane, propyl acetate, isobutyl acetate, butyl acetate, toluene, xylene, methyl ethyl ketone, methyl isobutyl ketone, N,N-dimethylformamide, methyl isobutyl ketone, N-methylpyrrolidone, n-hexane, n-heptane, cyclohexane, methylcyclohexane, cyclohexanone, and naphtha mixtures. These can be used individually or in mixtures of two or more.

[0106] In addition to the resin and medium described above, the resin composition and slurry composition may contain any other components. Examples of such components include, for example, dispersing agents, surfactants, and fillers other than silica.

[0107] The dispersion treatment of a mixture containing solvent and spherical silica powder can be performed using dispersion equipment used in pigment dispersion, etc. Examples include dispersers, homogenizers, planetary mixers, homogenizers (e.g., M-Technique Co., Ltd.'s "Clearmix", PRIMIX's "FILMIX", Silverson's "Abramix"), paint conditioners (RED DEVIL), colloid mills (e.g., PUC's "PUC Colloid Mill", IKA's "Colloid Mill MK"), conical mills (e.g., IKA's "Cone Mill MKO"), ball mills, sand mills (e.g., SHINMARU ENTERPRISES CORPORATION's "DYNO-MILL"), grinders, pearl mills (e.g., Eirich's "DCP Mill"), media dispersers such as CoBall-Mill, wet spray mills (e.g., Genas PY, SUGINO MACHINE LIMITED's "Star Burst", NANOMIZER) Media-free dispersers such as the "NANOMIZER" manufactured by Genas Inc., the "CLEAR SS-5" manufactured by M-Technique Co., Ltd., and the "MICROS" manufactured by Nara Machinery Co., Ltd., as well as other roller mills and kneaders, are preferred. Ideally, media should not be used (balls, beads, etc.). This is because the use of media raises concerns about contamination from wear-prone media. Specifically, media-free dispersers such as wet spray mills ("Genas PY" manufactured by Genas Inc., "Star Burst" manufactured by SUGINO MACHINE LIMITED, "NANOMIZER" manufactured by Genas Inc., "CLEAR SS-5" manufactured by M-Technique Co., Ltd., and "MICROS" manufactured by Nara Machinery Co., Ltd.) are ideal.

[0108] Furthermore, the dispersion process is preferably carried out at a temperature between 0 and 100°C. By performing the dispersion process within the aforementioned temperature range, the viscosity of the solvent can be appropriately maintained, productivity can be preserved, and solvent evaporation can be suppressed, thereby easily controlling the solid content. The processing temperature is preferably 0 to 100°C, more preferably 5 to 90°C, and even more preferably 10 to 80°C. Here, the processing temperature is more preferably 5°C or higher, even more preferably 10°C or higher, and even more preferably 90°C or lower, even more preferably 80°C or lower.

[0109] The dispersion time can be appropriately set according to the dispersion device used to prevent particle damage, preferably 0.5 to 60 minutes, more preferably 0.5 to 10 minutes, and even more preferably 0.5 to 5 minutes.

[0110] Subsequently, the aggregates of spherical silica powder that remained even after dispersion treatment were subjected to wet classification. Examples of wet classification include classification based on sieving and centrifugal force. When using a sieve, it is preferable to use a sieve with an opening of 100 μm or less for classification. As a sieve, for example, a metal with a dense lattice structure, such as an electroforming sieve, is preferably used.

[0111] The opening of the sieve is preferably 0.2–100 μm, more preferably 0.5–75 μm, even more preferably 0.5–50 μm, and particularly preferably 1–35 μm. Here, the opening of the sieve is preferably less than 100 μm, more preferably less than 75 μm, even more preferably less than 50 μm, and particularly preferably less than 35 μm. It is also preferably more than 0.2 μm, more preferably more than 0.5 μm, and even more preferably more than 1 μm.

[0112] Subsequently, dilution or concentration can be performed as needed to adjust to an appropriate concentration. Methods of concentration include gasification concentration and solid-liquid separation.

[0113] It should be noted that in the method for manufacturing the slurry composition of the present invention, a silane coupling agent may be added to the mixture of solvent and spherical silica powder. Examples of silane coupling agents include the aforementioned silane coupling agents.

[0114] When a resin film is made using a resin composition containing the spherical silica powder of the present invention, its dielectric loss tangent is preferably 0.012 or less, more preferably 0.010 or less, and even more preferably 0.009 or less at a frequency of 10 GHz. When the dielectric loss tangent of the resin film is 0.012 or less at a frequency of 10 GHz, it exhibits excellent electrical characteristics and is therefore expected to be used in electronic devices, communication devices, and the like. The smaller the dielectric loss tangent, the more the transmission loss of the circuit is suppressed; therefore, the lower limit value is not particularly limited.

[0115] Furthermore, when a resin film is made using a resin composition containing the spherical silica powder of the present invention, its relative permittivity at a frequency of 10 GHz is preferably 2.0 to 3.5, more preferably 2.2 or more, and even more preferably 2.3 or more. Additionally, the upper limit is more preferably 3.2 or less, and even more preferably 3.0 or less. When the relative permittivity of the resin film at a frequency of 10 GHz is within the aforementioned range, its electrical properties are excellent, and therefore its application in electronic devices, communication devices, and the like is expected.

[0116] The relative permittivity can be determined using a dedicated device (e.g., the KEYCOM Corporation “Vector Network Analyzer E5063A”) via the perturbation resonator method.

[0117] The dielectric loss tangent of the resin film can be measured using a split column dielectric resonator (SPDR) (e.g., manufactured by Agilent Technologies).

[0118] Furthermore, the average linear expansion rate of the aforementioned resin film is preferably 10 to 50 ppm / °C. When the average linear expansion rate is within the aforementioned range, it is close to the range of the coefficient of thermal expansion of copper foil, which is widely used as a substrate, and therefore exhibits excellent electrical properties. More preferably, the average linear expansion rate is 12 ppm / °C or higher, even more preferably 15 ppm / °C or higher, and further preferably 40 ppm / °C or lower, even more preferably 30 ppm / °C or lower.

[0119] The average linear expansion rate is calculated by heating the resin film with a load of 5 N and a heating rate of 2 °C / min using a thermomechanical analysis device (e.g., Shimadzu Corporation's "TMA-60"), measuring the dimensional changes of the sample from 30 °C to 150 °C, and then averaging the results.

[0120] Furthermore, the spherical silica powder of the present invention can be used as a variety of filler materials, and is particularly suitable as a filler material for resin compositions used in the fabrication of electronic substrates for electronic devices such as computers, laptops, digital cameras, smartphones, and communication devices such as game consoles. Specifically, in order to reduce dielectric loss tangent, reduce transmission loss, reduce moisture absorption, and improve peel strength, the silica powder of the present invention is also expected to be used in resin compositions, prepregs, metal-clad laminates, printed circuit boards, resin sheets, adhesive layers, adhesive films, solder resists, bump reflow insulation layers, rewiring insulation layers, chip bonding materials, sealing materials, underfill, mold underfill, and laminated inductors.

[0121] Example

[0122] The present invention will now be described in more detail by way of examples, but the invention is not limited thereto. In the following description, the common components are the same substances. Furthermore, unless otherwise specified, “parts” and “%” refer to “parts by mass” and “% by mass”. Examples 1-12 are examples, and Examples 13-14 are comparative examples.

[0123] <Experimental Example 1>

[0124] (Example 1)

[0125] As a precursor for spherical silica, silica powder 1 (manufactured by AGC SI-TECHCO.,LTD.: H-31, d50 = 3.5 μm) manufactured by a wet process was used. The titanium (Ti) content of silica powder 1 was determined to be 300 ppm. 15 g of silica powder 1 was filled into an alumina crucible and heated in an electric furnace at 1300 °C for 1 hour. After heating, it was cooled to room temperature and crushed in an agate mortar to obtain spherical silica powder.

[0126] (Example 2)

[0127] As a precursor for spherical silica, silica powder 2 (manufactured by AGC SI-TECHCO.,LTD.: H-51, d50=5.5μm) manufactured by wet process was used, and otherwise the same treatment as in Example 1 was performed to obtain spherical silica powder.

[0128] It should be noted that the Ti content of silica powder 2 used as a precursor for spherical silica was measured and found to be 300 ppm.

[0129] (Example 3)

[0130] As a precursor for spherical silica, silica powder 3 (manufactured by AGC SI-TECHCO.,LTD.: H-121, d50=13μm) manufactured by wet process was used, and otherwise the same treatment as in Example 1 was performed to obtain spherical silica powder.

[0131] It should be noted that the Ti content of silica powder 3 used as a precursor for spherical silica was measured and found to be 300 ppm.

[0132] (Example 4)

[0133] As a precursor for spherical silica, silica powder 4 (manufactured by AGC SI-TECHCO.,LTD.: H-201, d50=20μm) manufactured by wet process was used, and otherwise the same treatment as in Example 1 was performed to obtain spherical silica powder.

[0134] It should be noted that the Ti content of silica powder 4, used as a precursor for spherical silica, was measured and found to be 300 ppm.

[0135] (Example 5)

[0136] 15g of the same silica powder 1 (manufactured by AGC SI-TECH CO.,LTD.: H-31, d50 = 3.5μm, Ti content = 300ppm) produced by wet method as used in Example 1 was filled into an SUS tray and exposed in a constant temperature and humidity bath at 40°C and 80% relative humidity for 24 hours to obtain spherical silica precursor.

[0137] The obtained spherical silica precursor was completely filled into an alumina crucible and heated in an electric furnace at 1300℃ for 1 hour. After heating, it was cooled to room temperature and crushed in an agate mortar to obtain spherical silica powder.

[0138] (Example 6)

[0139] 15g of the same silica powder 1 (manufactured by AGC SI-TECH CO.,LTD.: H-31, d50 = 3.5μm, Ti content = 300ppm) produced by wet method as used in Example 1 was placed in a 200ml beaker, 100ml of ethanol was added and stirred for 1 hour, and then solid-liquid separation was performed. The obtained solid was vacuum dried at 60°C for 24 hours to obtain spherical silica precursor.

[0140] The obtained spherical silica precursor was completely filled into an alumina crucible and heated in an electric furnace at 1300℃ for 1 hour. After heating, it was cooled to room temperature and crushed in an agate mortar to obtain spherical silica powder.

[0141] (Example 7)

[0142] 15g of the same silica powder 1 (manufactured by AGC SI-TECH CO.,LTD.: H-31, d50 = 3.5μm, Ti content = 300ppm) produced by wet method as used in Example 1 was placed in a 200ml beaker, 100ml of distilled water was added, and the mixture was heated to 80°C in a water bath for 1 hour. The water temperature in the beaker was maintained at 78-82°C while stirring for 4 hours. Then, solid-liquid separation was performed, and the obtained solid was vacuum dried at 100°C for 24 hours to obtain spherical silica precursor.

[0143] The obtained spherical silica precursor was completely filled into an alumina crucible and heated in an electric furnace at 1300℃ for 1 hour. After heating, it was cooled to room temperature and crushed in an agate mortar to obtain spherical silica powder.

[0144] (Example 8)

[0145] As a precursor for spherical silica, silica powder 5 (manufactured by AGC SI-TECHCO.,LTD.: H-33, d50=3.0μm) manufactured by wet process was used, and otherwise the same treatment as in Example 1 was performed to obtain spherical silica powder.

[0146] It should be noted that the Ti content of silica powder 5, used as a precursor for spherical silica, was measured and found to be 300 ppm.

[0147] (Example 9)

[0148] As a precursor for spherical silica, silica powder 6 (manufactured by AGC SI-TECHCO.,LTD.: H-51, d50=5.5μm) manufactured by wet process was used, and otherwise the same treatment as in Example 1 was performed to obtain spherical silica powder.

[0149] It should be noted that the Ti content of silica powder 6, used as a precursor for spherical silica, was measured and found to be 1450 ppm.

[0150] (Example 10)

[0151] As a precursor for spherical silica, silica powder 7 (manufactured by AGC SI-TECHCO.,LTD.: H-51, d50=5.5μm) manufactured by wet process was used, and otherwise the same treatment as in Example 1 was performed to obtain spherical silica powder.

[0152] It should be noted that the Ti content of silica powder 7 used as a precursor for spherical silica was measured and found to be 35 ppm.

[0153] (Example 11)

[0154] 10g of silica powder obtained in Example 1 was mixed with 10mg of 3-(methacryloyloxy)propyltrimethoxysilane and 5g of decane, and the mixture was vacuum dried at 150°C to remove the solvent, resulting in surface-treated spherical silica powder.

[0155] (Example 12)

[0156] As a precursor for spherical silica, silica powder 1 (manufactured by AGC SI-TECHCO.,LTD.: H-31, d50 = 3.5 μm) manufactured by a wet process was used. The titanium (Ti) content of silica powder 1 was determined to be 300 ppm. 15 g of silica powder 1 was filled into an alumina crucible and heated in an electric furnace at 1050 °C for 6 hours. After heating, it was cooled to room temperature and crushed in an agate mortar to obtain spherical silica powder.

[0157] (Example 13)

[0158] Spherical silica powder 8 (manufactured by Denka Co., Ltd.: FB-5D) was used, which was made from raw silica produced by a dry process. The Ti content of the spherical silica powder 8 was determined to be 22 ppm. 15 g of spherical silica powder 8 was filled into an alumina crucible and heated in an electric furnace at 1300°C for 1 hour. After heating, it was cooled to room temperature and crushed in an agate mortar to obtain spherical silica powder.

[0159] (Example 14)

[0160] Spherical silica powder 9 (Admatechs: SC-04) manufactured directly from raw silica produced by the VMC method was used. The Ti content of the spherical silica powder 9 was determined to be 28 ppm.

[0161] The spherical silica powders of Examples 1-14 were evaluated as follows. The results are shown in Table 1.

[0162] In addition, scanning electron microscopy (SEM) images of the spherical silica powder of Example 1 are shown below. Figure 1 .

[0163] "evaluate"

[0164] 1. Median particle size

[0165] The median particle size was determined using a particle size distribution measuring device (Microtrac BEL Corp. MT3300EXII) employing laser diffraction. The spherical silica powder was dispersed by irradiation with ultrasound for 60 seconds, repeated three times, before measurement. The measurement was performed twice, each time for 60 seconds, and the average value was calculated.

[0166] 2. Specific surface area

[0167] Spherical silica powder was dried under reduced pressure at 230°C to completely remove moisture, and this sample was used as the specimen. The specific surface area of ​​this specimen was determined using a Micromeritics TriStar II automated specific surface area and pore size distribution measuring device via the multi-point BET method under nitrogen gas.

[0168] 3. Kong Rong

[0169] The silica powder used as a precursor was completely dried under reduced pressure at 230°C to remove moisture, and this was used as a sample. The pore volume of this sample was determined using the BJH method with nitrogen gas in the TriStarII automated surface area and pore size distribution measuring device manufactured by Micromeritics.

[0170] 4. Weight loss upon burning

[0171] According to JIS K 0067:1992, the mass reduction of 1g of silica powder used as a precursor when heated and dried at 850°C for 0.5 hours is defined as loss on ignition.

[0172] 5. Ti concentration

[0173] After adding perchloric acid and hydrofluoric acid to silica powder used as a precursor and calcining it to remove the main component silicon, the silica powder was measured using inductively coupled plasma (ICP) emission spectroscopy.

[0174] 6. Dielectric loss tangent

[0175] For the dielectric loss tangent, a dedicated apparatus (Vector Network Analyzer E5063A, KEYCOM) was used, employing the perturbation-mode resonator method, with a test frequency of 1 GHz, a test temperature of approximately 24°C, a humidity of approximately 45%, and three measurements. Specifically, spherical silica powder was vacuum-dried at 150°C, and then filled into polytetrafluoroethylene (PTFE) cylinders while being thoroughly tapped. After measuring the dielectric constant of each container, the dielectric loss tangent was calculated using the powder filling rate within the container.

[0176] 7. Silanol group content

[0177] The amount of silanol groups on the particle surface was determined by infrared spectrophotometry.

[0178] For infrared spectrophotometry, an IR Prestige-21 (manufactured by Shimadzu Corporation) was used. Spherical silica powder was dispersed in diamond, and measurements were performed using the diffusion-reflectance method. The measurement range was set to 400–4000 cm⁻¹. -1 The resolution is set to 4cm. -1 The cumulative number of times is set to 128.

[0179] The dilution of diamond powder is defined as [mass dilution rate] = ([sample mass]) / ([diamond mass] + [sample mass]), and is set as [mass dilution rate] = 85 - 2.5 × [BET specific surface area].

[0180] In addition, spherical silica powder is used that is vacuum dried at 180°C for 1 hour.

[0181] IR spectra at 800 cm⁻¹ -1 Normalization was performed at 3800cm -1 After aligning with the baseline, based on 3746cm -1The relative intensities of the nearby Si-OH peaks and those in the 3300–3700 cm⁻¹ range -1 The relative value of the peak intensity of bonded Si-OH is determined by the maximum peak in the matrix.

[0182] 8. Viscosity and particle size

[0183] To investigate the resin dispersibility of spherical silica powder, the following experiment was conducted.

[0184] Six parts of cooked flaxseed oil (manufactured by Yamagata Sangyo Co., Ltd.) and eight parts of spherical silica powder were mixed and kneaded for 3 minutes at 2000 rpm using a rotary mixer (manufactured by THINKY CORPORATION.) to prepare a compound. The resulting compound was then tested using a rotational rheometer at a shear rate of 1 second. -1 A 30-second measurement was performed to determine the viscosity at that 30-second time point. It should be noted that the viscosity obtained using only cooked flaxseed oil was 46 mPa·s.

[0185] In addition, the obtained mixture was measured by the fineness tester method of JIS K 5400:1990.

[0186] 9. Moisture absorption capacity

[0187] To investigate the hygroscopicity of spherical silica powder, the following experiment was conducted.

[0188] After drying spherical silica particles at 200℃, 5g was weighed into an aluminum dish with a diameter of 10cm and spread evenly. The spherical silica particles placed at 40℃ and in an environment with RH of 90% for 24 hours were measured by Karl Fischer titration (electromagnetic titration).

[0189] [Conditions for the Karl Fischer method (coulometric titration)]

[0190] Trace Moisture Analyzer (CA-200 type, manufactured by Mitsubishi Chemical Analytech Co., Ltd.)

[0191] Moisture vaporization unit (VA-200, manufactured by Mitsubishi Chemical Analytech Co., Ltd.)

[0192] Anode solution (HYDRANAL-Coulomat AG-OVEN, manufactured by Hayashi Chun-Yao Co., Ltd.)

[0193] Cathodic solution (HYDRANAL-Coulomat CG, manufactured by Hayashi Chun-Yao Co., Ltd.)

[0194] Heating temperature: 200℃

[0195] Nitrogen flow rate: approximately 250 ml / min

[0196] [Table 1]

[0197] Table 1

[0198]

[0199] According to the results in Table 1, changing the product of the specific surface area and the median particle size of the spherical silica powder resulted in the following: Examples 1-12 showed low dielectric loss tangent, viscosity, particle size, and moisture absorption. Examples 13 and 14 showed that if the product of the specific surface area and the median particle size became too large, the dielectric loss tangent worsened. A large specific surface area relative to the median particle size suggests the presence of small particles and surface roughness, thus increasing the amount of surface residues and raising the dielectric loss tangent. Furthermore, the presence of small particles and surface roughness can lead to increased viscosity and tackiness when forming resin compositions. The median particle size is preferably 0.5–20 μm. This is because a small median particle size increases viscosity, while a large median particle size increases particle size.

[0200] Furthermore, as shown in Examples 1-14, if the silicon dioxide precursor experiences significant weight loss upon ignition, the dielectric loss tangent decreases. This is believed to be because when the weight loss upon ignition of the silicon dioxide precursor is less than 1.0%, silanol groups tend to remain during calcination, thus increasing the dielectric loss tangent. It should be noted that when the weight loss upon ignition of the silicon dioxide precursor exceeds 15.0%, the reduction during calcination becomes larger, predicting a deterioration in yield.

[0201] Furthermore, as shown in Examples 1-14, the pore volume of the silica precursor is also related to the dielectric loss tangent. It is believed that if the pore volume is too small, the silica will not shrink during calcination, and the specific surface area will not easily decrease, thus increasing the dielectric loss tangent.

[0202] <Experimental Example 2>

[0203] Resin films were made using spherical silica powder of grades 11 and 14.

[0204] 25 parts of biphenyl epoxy resin (epoxy equivalent 276, manufactured by Nippon Kayaku Co., Ltd., "NC-3000") were dissolved in 13 parts of methyl ethyl ketone (MEK) while stirring and heating. After cooling to room temperature, 32 parts of an active ester curing agent (a toluene solution with an active group equivalent of 223 and 65% non-volatile components, manufactured by DIC Co., Ltd.) were mixed in and kneaded at 2000 rpm for 5 minutes using a rotary mixer, namely AWATORI RENTARO (manufactured by THINKY CORPORATION). Next, 0.3 parts of 4-dimethylaminopyridine (DMAP) and 1.8 parts of 2-ethyl-4-methylimidazolium (manufactured by Shikoku Kasei Corporation, "2E4MZ") were mixed as curing accelerators and kneaded in AWATORI RENTARO at 2000 rpm for 5 minutes. Mix 65.2 parts of spherical silica powder with AWATORI RENTARO at 2000 rpm for 5 minutes.

[0205] Next, a transparent polyethylene terephthalate (PET) film (LINTEC Corporation "PET5011 550", 50 μm thick) was prepared after demolding. Using an applicator, the obtained varnish was applied to the demolded surface of the PET film to a dried thickness of 40 μm. The film was then dried in a Gear oven at 190°C for 90 minutes to cure. Afterward, the film was cut to produce cured resin films measuring 200 mm x 200 mm x 40 μm (evaluation samples).

[0206] (1) Evaluation of dielectric loss tangent

[0207] The dielectric loss tangent of the obtained evaluation samples was measured using a split-column dielectric resonator (manufactured by Agilent Technologies) (measurement frequency: 10 GHz). Additionally, the dielectric loss tangent of the evaluation samples was also measured after they were stored in a constant temperature and humidity bath at 85°C and 85% RH for 24 hours and allowed to absorb moisture.

[0208] (2) Determination of mean linear expansion rate

[0209] The evaluation sample was cut into 3mm × 25mm pieces. The sample was heated using a thermomechanical analyzer (Shimadzu Corporation, "TMA-60") with a load of 5N and a heating rate of 2℃ / min. The dimensional changes of the sample from 30℃ to 150℃ were then measured, and the average linear expansion rate (ppm / ℃) was calculated by dividing the change in the length of the sample by the temperature.

[0210] The results are shown in Table 2.

[0211] [Table 2]

[0212] Table 2

[0213]

[0214] As shown in Table 2, when using the spherical silica powders of Examples 1, 3, and 11, the dielectric loss tangent is significantly improved even when a resin composition is formed due to the small dielectric loss tangent of the spherical silica powder. Furthermore, it is known that the spherical silica powder of the present invention is not easily hygroscopic, thus suppressing the hygroscopicity of the resin composition and exhibiting good electrical properties even after storage under humidified conditions.

[0215] The present invention has been described in detail with reference to specific embodiments, but various changes and modifications can be made without departing from the spirit and scope of the invention, which will be apparent to those skilled in the art. This application is based on Japanese Patent Application No. 2021-123495, filed July 28, 2021, and Japanese Patent Application No. 2021-194372, filed November 30, 2021, the contents of which are incorporated herein by reference.

Claims

1. A spherical silica powder, wherein the average particle size d50 is 0.5~20 μm, and the specific surface area A (m²) is... 2 The product A×d50 of the median particle size d50 (μm) and the median particle size (g) is 2.7~5.0μm. m 2 / g, The bonded silanol groups originating from the surface of the spherical silica powder are located at 3300~3700 cm. -1 The maximum IR peak intensity is below 0.

2. The method for manufacturing the spherical silica powder includes forming a spherical silica precursor by a wet process. During the manufacturing of the spherical silica powder, the presence of 30 ppm to 1500 ppm Ti facilitates hot compaction during calcination.

2. The spherical silica powder according to claim 1, wherein, The dielectric loss tangent of the spherical silica powder is below 0.0020 at a frequency of 1 GHz.

3. The spherical silica powder according to claim 1 or 2, wherein, The viscosity of the compound containing the spherical silica powder, as determined by the following method, is 5000 mPa. Below s, The determination method is as follows: A mixture obtained by mixing 6 parts by weight of cooked flaxseed oil and 8 parts by weight of the spherical silica powder and kneading at 2000 rpm for 3 minutes is analyzed using a rotational rheometer at a shear rate of 1 second. -1 The viscosity was measured for 30 seconds to determine the viscosity at that time point.

4. A method for manufacturing spherical silica powder, which is the method for manufacturing spherical silica powder according to any one of claims 1 to 3, the method comprising forming a spherical silica precursor by a wet process.

5. The method for manufacturing spherical silica powder according to claim 4, wherein, According to JIS K0067:1992, the mass reduction of the silica precursor when 1g of the silica precursor is heated and dried at 850°C for 0.5 hours is 5.0~15.0% by mass.

6. The method for manufacturing spherical silica powder according to claim 4 or 5, wherein, The pore volume of the silica precursor is 0.3~2.2 ml / g.

7. A resin composition comprising 5-90% by weight of spherical silica powder as described in any one of claims 1-3.

8. A slurry composition comprising 1-50% by mass of spherical silica powder as described in any one of claims 1-3.

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