Spherical silica particles and a resin composition using the spherical silica particles

Abstract

The present invention provides spherical silica particles that can achieve a lower dielectric loss tangent when filled into a resin, and a resin composition using the spherical silica particles. The present invention relates to spherical silica particles (X) having a surface fractal dimension of 1.0 to 2.3. The present invention relates to a resin composition containing the spherical silica particles (X) and at least one resin selected from a thermoplastic resin and a thermosetting resin. The specific surface area of the above spherical silica particles (X) is preferably 0.1 to 2.0 m<supgt;2< / supgt> / g. The average particle diameter of the above spherical silica particles (X) is preferably 1 to 30 μm.

Description

Technical Field

[0001] The present invention relates to spherical silica particles and a resin composition using the spherical silica particles. Background Art

[0002] In recent years, with the increase in information communication volume in the communication field, the effective use of high-frequency signals in electronic devices, communication devices, etc. has become increasingly widespread. On the other hand, there has also arisen a problem that the transmission loss of circuit signals increases due to the application of high-frequency signals to the above devices. Therefore, for materials used in devices for high-frequency bands, materials having a low dielectric loss tangent are required. The transmission loss is roughly composed of conductor loss due to the skin effect of wiring and dielectric loss due to the characteristics of the dielectric material of insulators constituting electrical and electronic parts such as substrates. Since the dielectric loss is proportional to the first power of the frequency, the square root of the dielectric constant of the insulator, and the first power of the dielectric loss tangent, materials used in devices for high-frequency bands are required to have both a low dielectric constant and a low dielectric loss tangent.

[0003] The dielectric properties of GHz-band ceramic materials are described, for example, in Non-Patent Document 1 and the like, but they are all the properties of sintered substrates. Since silica has a small dielectric constant and a quality factor Qf (a value obtained by multiplying the reciprocal of the dielectric loss tangent by the measurement frequency) of about 120,000, it is expected as a ceramic filler having a low dielectric constant and a low dielectric loss tangent. From the viewpoint of being easily blended into a resin, the closer its shape is to spherical, the more preferable it is. Spherical silica particles can be manufactured, for example, by a flame melting method (Patent Document 1). Regarding spherical silica particles synthesized by such a method, their application to the above devices for high-frequency bands is expected.

[0004] However, there are many polar functional groups such as adsorbed water and silanol groups on the surface of spherical silica particles, and there is a problem that the dielectric loss tangent is liable to deteriorate. As methods for reducing adsorbed water and silanol groups on the surface of spherical silica particles, they are described, for example, in Patent Documents 2 to 4 and the like, but the effect of reducing the dielectric loss tangent of spherical silica particles obtained by these methods is insufficient.

[0005] Patent Document 1: International Publication No. 2016 / 031823

[0006] Patent Document 2: Japanese Patent No. 2926348

[0007] Patent Document 3: Japanese Unexamined Patent Application Publication No. 2020-097498

[0008] Patent Document 4: Japanese Unexamined Patent Application Publication No. 2020-138880

[0009] Non-Patent Document 1: International Materials Reviews vol.60 No.7 Supplementary data (2015) Summary of the Invention

[0010] Accordingly, an object of the present invention is to provide spherical silica particles that can achieve a lower dielectric loss tangent when filled into a resin, and a resin composition using such spherical silica particles.

[0011] The inventors of the present invention focused on the surface state of spherical silica particles and evaluated them. As a result, it was found that spherical silica particles with a surface fractal dimension, which is an index representing the uneven shape of the particle surface, within a certain numerical range can achieve a lower dielectric loss tangent, and thus the present invention was completed.

[0012] That is, the present invention has the following aspects.

[0013] [1] A spherical silica particle (X) having a surface fractal dimension of 1.0 to 2.3.

[0014] [2] The spherical silica particle (X) according to [1], wherein the average circularity of the spherical silica particle (X) is 0.85 or more.

[0015] [3] The spherical silica particle (X) according to [1] or [2], wherein the specific surface area of the spherical silica particle (X) is 0.1 to 2.0 m 2 / g.

[0016] [4] The spherical silica particle (X) according to any one of [1] to [3], wherein the average particle diameter of the spherical silica particle (X) is 1 to 30 μm.

[0017] [5] The spherical silica particle (X) according to any one of [1] to [4], wherein the spherical silica particle (X) is surface-treated with a surface treatment agent.

[0018] [6] The spherical silica particle (X) according to any one of [1] to [5], which is used for resin filling.

[0019] [7] A resin composition containing the spherical silica particle (X) according to any one of [1] to [6], and at least one resin selected from a thermoplastic resin and a thermosetting resin.

[0020] According to the present invention, it is possible to provide spherical silica particles that can achieve a lower dielectric loss tangent when filled into a resin, and a resin composition using such spherical silica particles. Brief Description of the Drawings

[0021] Figure 1 An electron micrograph showing one form of the spherical silica particles (X) of the present invention.

[0022] Figure 2 An electron micrograph of the amorphous spherical silica particles before classification treatment. Detailed Description of the Invention

[0023] The present invention will be described in detail below. However, the present invention is not limited to the following embodiments and can be appropriately modified and implemented within the scope that does not impair the effects of the present invention. When a specific description given for one embodiment is also applicable to other embodiments, the description may be omitted in other embodiments. In addition, the notation "~" in this specification means "above and below". For example, "1.0~2.3" means "1.0 or more and 2.3 or less". In addition, the "spherical silica particles" in this specification means silica particles whose projected image (including a three-dimensional view and a top view) is close to a circular shape when observing the silica particles with a microscope or the like. In addition, "silica particles" means an aggregate of multiple particles.

[0024] [Spherical silica particles (X)]

[0025] The spherical silica particles (X) according to the present invention are characterized in that the surface fractal dimension is 1.0 to 2.3. The "surface fractal dimension" as used herein is an index indicating the concavo-convex shape of the particle surface. The lower the value of the surface fractal dimension, the fewer the concavo-convexities on the particle surface and the smoother the surface. Since the spherical silica particles (X) according to the present invention have a surface fractal dimension of 1.0 to 2.3, a lower dielectric loss tangent can be achieved when incorporated into a resin. In addition, the surface fractal dimension of the spherical silica particles (X) (hereinafter sometimes also referred to as "surface fractal dimension (Ds)") can be measured by the following method.

[0026] [Method for Measuring Surface Fractal Dimension]

[0027] The spherical silica particles are directly placed as they are in a sample cell for transmission measurement of an X-ray diffraction analyzer (for example, manufactured by Rigaku Corporation, product name: SmartLab), and the particles are measured under the following conditions using the ultra-small angle X-ray scattering method (USAXS). Moreover, during analysis, background removal and desmearing processing are performed. The desmearing processing is performed using analysis software (for example, manufactured by Rigaku Corporation, product name: Particle Size - Pore Diameter Analysis Software NANO-Solver).

[0028] X-ray tube target: Cu Kα,

[0029] Tube voltage - tube current: 45 kV - 200 mA,

[0030] Detector: Scintillation counter,

[0031] Scanning range: 0.00 to 0.50 deg,

[0032] Scanning step: 0.0006 deg,

[0033] Scanning speed: 0.03 deg / min,

[0034] Incident - side spectroscopic crystal: Ge(220)×2,

[0035] Receiving - side spectroscopic crystal: Ge(220)×2.

[0036] <Calculation method of surface fractal dimension>

[0037] The surface fractal dimension is calculated according to the following method. First, the scattering angle 2θ is converted into the scattering vector q using the following formula (1). The measured X - ray wavelength λ is 0.154 nm.

[0038] q = 4πsinθ / λ…(1)

[0039] Then, for the USAXS pattern after background removal and de - blurring, a double - logarithmic graph showing the relationship between the scattering vector q and the intensity I(q) is made, and power approximation is performed at q = 0.0124 - 0.0627 nm -1 (2θ = 0.174 - 0.0882°). The exponent α in the approximation formula is substituted into the following formula (2) to calculate the surface fractal dimension (Ds).

[0040] Ds = 6 + α…(2)

[0041] The surface fractal dimension of the spherical silica particles (X) involved in the present invention is 1.0 - 2.3, more preferably 1.0 - 2.1, and further preferably 1.0 - 1.9.

[0042] As described above, polar functional groups such as silanol groups and adsorbed water exist on the surface of silica particles, which are the factors deteriorating the dielectric loss tangent. The inventors of the present application focused on the surface state of spherical silica particles and evaluated them. As a result, it was unexpectedly found that as long as the surface fractal dimension of the spherical silica particles (X) is within the above - mentioned range, a lower dielectric loss tangent than that of conventional spherical silica particles can be achieved. The spherical silica particles (X) with a surface fractal dimension in the range of 1.0 - 2.3 have less unevenness and a very smooth surface. It is speculated that the absolute amounts of polar functional groups and adsorbed water on the particle surface of such spherical silica particles (X) are reduced, and as a result, a lower dielectric loss tangent can be achieved.

[0043] In order for the surface fractal dimension of the spherical silica particles (X) to be within the above range, it is preferable to reduce the foreign matter adhering to the surface of the spherical silica particles (X) and reduce the unevenness on the particle surface.

[0044] Figure 1 An electron micrograph showing one form of the spherical silica particles (X) according to the present invention, that is, the spherical silica particles (X) having a surface fractal dimension of 1.0 to 2.3. As Figure 1 shown, the spherical silica particles (X) according to the present invention have few foreign matters on the particle surface and few surface irregularities. Moreover, its surface is very smooth.

[0045] As a method for reducing the foreign matter on the surface of the spherical silica particles (X), for example, a method of classifying the raw material silica particles under wet conditions can be cited. The manufacturing method of the spherical silica particles (X) according to the present invention will be described later.

[0046] As described above, the spherical silica particles (X) according to the present invention have few foreign matters on the particle surface and small surface irregularities. Therefore, the specific surface area of the spherical silica particles (X) according to the present invention is preferably 0.1 to 2.0 m 2 / g, more preferably 0.3 to 2.0 m 2 / g, and even more preferably 0.5 to 2.0 m 2 / g. In addition, the above specific surface area may also be in the range of 0.7 to 1.8 m 2 / g. In one embodiment, the above specific surface area may also be 0.1 to 0.7 m 2 / g, or may be 0.1 to 0.5 m 2 / g. Since the spherical silica particles (X) according to the present invention have few foreign matters on the particle surface, the specific surface area is also likely to be a smaller value. By having such a small specific surface area, the absolute number of polar functional groups such as adsorbed water and silanol groups on the silica particle surface is likely to be further reduced. As a result, when the spherical silica particles (X) according to the present invention are filled into a resin, it is easy to achieve both a low dielectric constant and a low dielectric loss tangent at the same time. In addition, the specific surface area of the spherical silica particles can be measured by the BET method.

[0047] <Method for measuring specific surface area>

[0048] 1 g of spherical silica particles was filled into a measurement cell, and the specific surface area of the spherical silica particles was measured using a fully automatic specific surface area and particle size analyzer (e.g., manufactured by Mountech Co., Ltd., product name: Macsorb HM model-1201 (BET single point method)). In addition, the degassing conditions before measurement can be set at 200 °C for 10 minutes.

[0049] The average circularity of the spherical silica particles (X) according to the present invention is preferably 0.85 or more, more preferably 0.90 or more, and still more preferably 0.94 or more. When the average circularity of the spherical silica particles (X) is 0.85 or more, the dispersibility in the resin is easily improved, and the dielectric properties are easily stabilized when the spherical silica particles (X) are mixed with the resin. In addition, it is easy to prevent an increase in the viscosity of the resin and a decrease in fluidity, and the processability and fillability are not easily deteriorated. Moreover, it is easy to adjust the specific surface area to a preferred range. In addition, the term "stable dielectric properties" as used in this specification means that when measuring the dielectric constant and the loss tangent of the resin composition containing the spherical silica particles (X), the numerical deviation caused by the difference in the measurement position is small.

[0050] The "average circularity" of the spherical silica particles (X) can be calculated by the following method.

[0051] <Average circularity>

[0052] After fixing the spherical silica particles with a carbon tape, osmium coating was performed. Then, using a scanning electron microscope (e.g., manufactured by JEOL Ltd., product name: JSM-7001F SHL), the particles were photographed at a magnification of 500 to 50,000 times. After calculating the projected area (S) and the projected perimeter (L) of one particle using an image analysis device (manufactured by ROPER Co., Ltd., product name: Image-Pro Premier Ver. 9.3), the circularity was calculated by the following formula (3). The circularity was calculated for any 200 particles, and the average value thereof was used as the average circularity.

[0053] Circularity = 4πS / L 2 …(3)

[0054] The average particle size of the spherical silica particles (X) involved in the present invention is preferably 1 to 30 μm, more preferably 1 to 15 μm, and further preferably 1 to 6 μm. When the average particle size of the spherical silica particles (X) is within the above range, the fillability in the resin is likely to be better, and it is easy to adjust the values of the dielectric constant and the dielectric loss tangent of the resin composition. In addition, the average particle size of the spherical silica particles (X) refers to the particle size (D50) when the cumulative value corresponds to 50% in the volume-based cumulative particle size distribution measured using a laser diffraction particle size distribution measuring device. The cumulative particle size distribution is represented by a distribution curve with the particle size (μm) on the horizontal axis and the cumulative value (%) on the vertical axis.

[0055] The spherical silica particles (X) involved in the present invention can be surface-treated with a surface treatment agent. By surface-treating with a surface treatment agent, the fillability of the spherical silica particles (X) involved in the present invention in the resin is likely to be better. In addition, it is easy to reduce polar functional groups on the particle surface, etc., and it is easy to obtain spherical silica particles that can achieve a lower dielectric loss tangent. Examples of the surface treatment agent include silane coupling agents and aluminate coupling agents. These can be used alone, or two or more of them can be used in combination. Among these, from the viewpoint of easily reducing polar functional groups on the particle surface, etc., treatment with a silane coupling agent is preferred, and silazanes such as hexamethyldisilazane (HMDS) and vinyl group-containing silane coupling agents such as vinyltrimethoxysilane are more preferred. In addition, whether the spherical silica particles (X) are surface-treated can be confirmed by analyzing the spherical silica particles (X) using IR, TG-DTA, mass spectrometry, etc.

[0056] The number of water molecules detached (hereinafter referred to as "detached water molecular weight") when the spherical silica particles (X) involved in the present invention are heated from 50 °C to 1000 °C at a heating rate of 25 °C / minute can be 0.001 to 0.010 mmol / g. When the detached water molecular weight is within the above range, it is easy to achieve a lower dielectric loss tangent. The above detached water molecular weight is more preferably 0.001 to 0.008 mmol / g, further preferably 0.002 to 0.008 mmol / g, and particularly preferably 0.003 to 0.007 mmol / g. The detached water molecular weight can be measured by the following method. In one embodiment, the number of the above detached water molecules can also be 0.001 to 0.004 mmol / g, or 0.001 to 0.003 mmol / g.

[0057] <Method for measuring the amount of detached water>

[0058] Using a gas chromatography mass analyzer (e.g., manufactured by JEOL Ltd., product name: JMS-Q1500GC) and a thermal decomposition apparatus (e.g., manufactured by Frontier Lab Co., Ltd., product name: PY-3030D), 15 μg of spherical silica particles were heated from 50°C to 1000°C at a heating rate of 25°C / minute in a helium atmosphere. The area value of the obtained mass spectrum (m / z = 18) in the range of 50°C to 1000°C was calculated, and the number of detached water molecules was calculated from the calibration curve. In addition, for the calibration curve, the area value of the number of detached water molecules (m / z = 18) of an aluminum hydroxide standard sample (manufactured by Kanto Chemical Co., Inc., product name: aluminum hydroxide (purity: 59.5%)) was used. Specifically, 23 μg, 122 μg, and 270 μg of the aluminum hydroxide standard sample were accurately weighed using a microbalance, heated under the same conditions as above, and the area value of the water molecules detached from the aluminum hydroxide was measured, thereby enabling the production of a calibration curve. In addition, the purity of the aluminum hydroxide here is the value calculated from the mass reduction amount from 200°C to 320°C using a high-sensitivity differential type differential thermal balance.

[0059] In the crystal structure of the spherical silica particles (X) according to the present invention, the amorphous phase is 95% by mass or more of the whole. By making the amorphous phase 95% or more, the effect of suppressing the thermal expansion rate when filled in a resin becomes larger. In addition, within the above range, other crystal phases such as quartz and cristobalite may also be contained.

[0060] The average particle density of the spherical silica particles (X) according to the present invention is preferably 1.8 to 2.4 g / cm 3 , more preferably 1.9 to 2.4 g / cm 3 , still more preferably 2.0 to 2.4 g / cm 3 . If the average particle density is 1.8 g / cm 3 or more, the voids contained in the silica particles will not be excessive, and the kneading in the resin will easily become good. If the average particle density is 2.4 g / cm 3 or less, it is not easy to contain α-quartz, cristobalite, etc. in the crystal structure of the silica particles. Therefore, adverse effects on the physical properties of the silica particles such as an increase in the thermal expansion rate are not likely to occur. In addition, the average particle density of the spherical silica particles (X) can be measured by the following method.

[0061] <Method for measuring average particle density>

[0062] 2.0 g of spherical silica particles were placed in a measurement sample cell, and a dry density meter (e.g., manufactured by Shimadzu Corporation, product name: AccuPyc II 1340) was used to measure the average particle density by the gas (helium) replacement method.

[0063] The spherical silica particles (X) involved in the present invention can achieve a lower dielectric loss tangent when filled into a resin. In one embodiment, the resin sheet containing the spherical silica particles (X) involved in the present invention prepared by the following method preferably has a dielectric constant of 3.0 or less at 35 GHz. In addition, the dielectric loss tangent of the above resin sheet at 35 GHz is preferably less than 4.8×10 -4 , more preferably 4.5×10 -4 Hereinafter, it is further preferably 4.0×10 -4 Hereinafter.

[0064] [Manufacturing method of spherical silica particles (X)]

[0065] Next, an embodiment of the manufacturing method of the spherical silica particles (X) involved in the present invention will be described. In addition, the manufacturing method of the spherical silica particles (X) involved in the present invention is not limited to the following manufacturing method.

[0066] The manufacturing method of the spherical silica particles (X) in this embodiment includes: classifying the amorphous spherical silica particles (hereinafter sometimes also referred to as "spherical silica particles (A)") (step (i)), and then performing heat treatment at a temperature of 800 to 1200 °C (step (ii)). In addition, the manufacturing method of the spherical silica particles (X) in this embodiment may also include: preparing amorphous spherical silica particles (step (i')).

[0067] [Preparation step: step (i')]

[0068] The manufacturing method of the spherical silica particles (X) in this embodiment may also include: step (i'), preparing amorphous spherical silica particles (spherical silica particles (A)).

[0069] The spherical silica particles (A) can be spherical silica particles prepared by a conventionally known method. From the viewpoint of productivity, spherical silica particles prepared by the powder melting method are preferred. In this embodiment, step (i') may also be a step of preparing the spherical silica particles (A) by the powder melting method. In addition, the "amorphous spherical silica particles" referred to in the present invention means spherical silica particles with a silica purity of 98% or more and an amorphous phase of 95% by mass or more of the whole.

[0070] The powder melting method is a method in which pulverized materials such as silica sand and silica stone (hereinafter sometimes referred to as "crude raw materials") are melted and spheroidized under high-temperature conditions above the melting point of the crude raw materials using a flame, plasma, electric furnace, gas furnace, etc. The melting atmosphere is not particularly limited, and from an economic point of view, it is preferably carried out in an air atmosphere. The average particle size (D50) of the crude raw materials is preferably 0.1 to 100 μm, more preferably 0.2 to 50 μm, and further preferably 0.3 to 10 μm. In one embodiment, the average particle size of the crude raw materials can be 10 to 100 μm or 50 to 100 μm.

[0071] The average particle size (D50) of the spherical silica particles (A) (hereinafter referred to as "average particle size (Da50)") is preferably 1 to 30 μm, more preferably 1 to 15 μm. In one embodiment, the average particle size (Da50) can be 1 to 10 μm or 2 to 8 μm. In addition, from the viewpoint of easily adjusting the average circularity of the finally obtained spherical silica particles (X) to 0.85 or more, its average circularity is preferably 0.85 or more, more preferably 0.90 or more. In addition, the specific surface area of the spherical silica particles (A) (hereinafter referred to as "specific surface area (Sa)") is not particularly specified and can be set to, for example, 0.1 to 10 m 2 / g. In addition, the average particle size (Da50), average circularity, and specific surface area (Sa) of the spherical silica particles (A) can be measured by the same measurement methods as those of the above-mentioned spherical silica particles (X).

[0072] After obtaining the spherical silica particles (A) by performing the process (i') as needed, the spherical silica particles (A) are classified as follows.

[0073] <Classification process: Process (i)>

[0074] The method for manufacturing the spherical silica particles (X) in the present embodiment includes: Process (i) of classifying the spherical silica particles (A). Process (i) is a process in which the spherical silica particles (A) are put into a classification device and centrifugally separated at a certain circumferential speed to remove fine particles from the spherical silica particles (A). Hereinafter, the spherical silica particles obtained after Process (i) (after classification) are referred to as "spherical silica particles (B)".

[0075] As the classification device, for example, a gravity field classifier, a centrifugal force field classifier, etc. can be used.

[0076] Step (i) is preferably a step of removing particles of 0.9 μm or less contained in the spherical silica particles (A). In addition, step (i) is preferably a step of removing fine foreign matters adhering to the surface of the spherical silica particles (A). The so-called "foreign matters on the surface of the spherical silica particles (A)" refers to, for example, the particles adhering to the surface of the spherical silica particles (A) as shown in Figure 2 . By classifying the spherical silica particles (A), fine foreign matters on the particle surface are removed, and spherical silica particles (X) with less surface unevenness and a surface fractal dimension of 1.0 to 2.3 can be easily obtained. Step (i) can also be a step of classifying the spherical silica particles (A) to obtain spherical silica particles (B) with a surface fractal dimension of 1.0 to 2.3.

[0077] Step (i) can also be a step of removing foreign matters on the surface of the spherical silica particles (A) to reduce the specific surface area of the spherical silica particles (A). In one aspect, the specific surface area (Sb) of the spherical silica particles (B) obtained after step (i) relative to the specific surface area (Sa) of the spherical silica particles (A), i.e., (Sb) / (Sa), can also be 0.2 or more and 0.6 or less, or can be 0.3 or more and 0.6 or less.

[0078] Step (i) can be a step of removing particles from the spherical silica particles (A) by dry classification, or can be a step of removing particles from the spherical silica particles (A) by wet classification. From the viewpoint of efficiently removing particles of 0.9 μm or less, wet classification is preferred.

[0079] (Wet classification)

[0080] When step (i) is wet classification, a slurry containing the spherical silica particles (A) and a dispersion medium is introduced into a classification device. When step (i) is wet classification, as the classification device, for example, a gravity field classifier, a centrifugal force field classifier, etc. can be used.

[0081] Examples of the dispersion medium include: water (including pure water, ion-exchanged water, etc.); organic solvents such as ethanol and acetone. Among them, from the viewpoints of the ease of dispersion of the spherical silica particles (A) and economy, it is preferred to contain at least water as the dispersion medium.

[0082] The proportion of water in the dispersion medium is more preferably 50 to 100% by mass relative to the total mass of the dispersion medium. In addition, the concentration of the spherical silica particles (A) in the slurry is preferably 1 to 50% by mass, more preferably 20 to 40% by mass, relative to the total mass of the slurry.

[0083] As a method for preparing the slurry, for example, a method may be cited in which spherical silica particles (A) are introduced into a dispersion medium so as to achieve a desired solid content concentration, and then stirred at room temperature for 1 to 24 hours.

[0084] When using the classifier described in the following examples, from the viewpoint of efficiently classifying fine particles, the circumferential speed of the rotor during wet classification is preferably 10 to 30 m / s, more preferably 20 to 30 m / s.

[0085] In addition, the temperature during wet classification is not particularly limited, and from the viewpoint of economy, it is preferably room temperature.

[0086] When step (i) is wet classification, the classified slurry is allowed to stand and the supernatant is removed to obtain spherical silica particles (B). Then, heat treatment is further performed in the following manner to prepare spherical silica particles (X). In addition, the spherical silica particles (B) may be dried at 40 to 200 °C for 1 to 24 hours before step (ii). Alternatively, drying may be performed under vacuum.

[0087] <Heat treatment step: step (ii)>

[0088] The method for manufacturing the spherical silica particles (X) in the present embodiment includes the following steps: After step (i), heat treatment is further performed at a temperature of 800 to 1200 °C. In step (ii), the heating temperature of the spherical silica particles (B) is 800 to 1200 °C, preferably 900 to 1100 °C. As the heating device, for example, an electric furnace, a gas furnace, etc. may be used. Further, from the viewpoint of reducing the moisture content, step (ii) is preferably performed in a nitrogen or argon atmosphere, or in a vacuum atmosphere. The heating time is preferably 1 to 24 hours, more preferably 2 to 8 hours. If the heating time is 1 to 24 hours, the productivity is also likely to be good. In one embodiment, step (ii) may be to heat-treat the spherical silica particles (B) at 800 to 1200 °C for 1 to 24 hours, or may be to heat-treat at 800 to 1200 °C for 2 to 8 hours.

[0089] By the method including the above steps (i) to (ii) (optionally, by the method including step (i'), step (i) and step (ii)), spherical silica particles (X) can be obtained. In addition, after step (ii), if necessary, the spherical silica particles (X) can also be surface-treated with a surface treatment agent. In addition, the spherical silica particles (X) obtained after step (i) or step (ii), or after an optional surface treatment step, sometimes become aggregates. Therefore, after these steps, a pulverization treatment can be carried out if necessary. As the pulverization method, it is preferably carried out under dry conditions without contacting with moisture. For example, an agate mortar, a ball mill, a vibration mill, a jet mill, etc. can be used.

[0090] The spherical silica particles (X) obtained by the manufacturing method in the present embodiment have, for example, a surface structure as shown in Figure 1 . On the other hand, Figure 2 is an electron micrograph showing a form of the amorphous spherical silica particles (spherical silica particles (A)) before the classification treatment. From the comparison of Figure 1 and 2 , a large amount of very fine foreign substances are attached to the surface of the spherical silica particles (A), and the specific surface area (Sa) becomes larger due to the fine foreign substances. According to the manufacturing method according to the present embodiment, the fine foreign substances on the surface of the spherical silica particles (A) can be easily removed by step (i). As a result, it is easy to obtain spherical silica particles (X) with few surface foreign substances and small irregularities as shown in Figure 1 . Since such spherical silica particles (X) have a surface fractal dimension in the range of 1.0 to 2.3, when filled into a resin, it is easy to achieve a lower dielectric loss tangent. That is, the manufacturing method of the present embodiment is more preferably a method that satisfies the following conditions (1) and (2).

[0091] Condition (1): The average particle diameter (Dx50) of the spherical silica particles (X) relative to the average particle diameter (Da50) of the spherical silica particles (A), i.e., (Dx50) / (Da50), is 0.8 or more and 1.2 or less.

[0092] Condition (2): The specific surface area (Sx) of the spherical silica particles (X) relative to the specific surface area (Sa) of the spherical silica particles (A), i.e., (Sx) / (Sa), is 0.2 or more and 0.6 or less.

[0093] By satisfying conditions (1) to (2), it is easy to obtain spherical silica particles (X) that maintain the range of the average particle diameter (Da50) of the spherical silica particles (A) and have a small specific surface area.

[0094] [Use]

[0095] When the spherical silica particles (X) according to the present invention are filled into a resin, a low dielectric constant and a low dielectric loss tangent can be achieved. Therefore, it can be suitably used as a filler for resin materials.

[0096] [Resin composition]

[0097] The resin composition according to the present invention contains the above-mentioned spherical silica particles (X) and at least one resin selected from a thermoplastic resin and a thermosetting resin.

[0098] There is no particular limitation on the content of the spherical silica particles (X) in the resin composition, and it can be appropriately adjusted according to the purpose. For example, when used for a substrate material for high-frequency bands or an insulating material, it can be blended in the range of 1 to 95% by mass based on the total mass of the resin composition, and more preferably in the range of 10 to 80% by mass.

[0099] [Resin]

[0100] The resin composition according to the present invention contains at least one resin selected from a thermoplastic resin and a thermosetting resin. More specifically, for example, polyethylene resin; polypropylene resin; epoxy resin; silicone resin; phenolic resin; melamine resin; urea resin; unsaturated polyester resin; fluororesin; polyamide resins such as polyimide resin, polyamideimide resin, and polyetherimide resin; polyester resins such as polybutylene terephthalate resin and polyethylene terephthalate resin; polyphenylene sulfide resin; wholly aromatic polyester resin; polysulfone resin; liquid crystal polymer resin; polyethersulfone resin; polycarbonate resin; maleimide-modified resin; ABS resin; AAS (acrylonitrile-acrylic rubber-styrene) resin; AES (acrylonitrile-ethylene-propylene-diene rubber-styrene) resin; hydrocarbon-based elastomer resin; polyphenylene ether resin; aromatic polyene resin, etc. These can be used alone or in combination of two or more.

[0101] When the resin composition according to the present invention is used as a substrate material for high-frequency bands or an insulating material, a known low-dielectric resin used in this application can be adopted. Specifically, as the low-dielectric resin, at least one resin selected from a hydrocarbon-based elastomer resin, a polyphenylene ether resin, and an aromatic polyene resin can be used. Among them, a hydrocarbon-based elastomer resin or a polyphenylene ether resin is preferred.

[0102] In the resin composition according to the present invention, within a range that does not hinder the effects of the present invention, a curing agent, a curing accelerator, a release agent, a coupling agent, a coloring agent, a flame retardant, an ion scavenger, etc. can also be blended.

[0103] [Manufacturing method of resin composition]

[0104] The method for manufacturing the resin composition is not particularly limited, and it can be manufactured by stirring, dissolving, mixing, and dispersing predetermined amounts of the respective materials. The apparatuses for mixing, stirring, dispersing, etc. of these mixtures are not particularly limited, and a kneader equipped with stirring and heating apparatuses, a three-roll mill, a ball mill, a planetary mixer, etc. can be used. In addition, these apparatuses can also be used in appropriate combinations.

[0105] As described above, the resin composition containing the spherical silica particles (X) according to the present invention can achieve a low dielectric constant and a lower dielectric loss tangent. In addition, the resin composition containing the spherical silica particles according to the present invention has a low viscosity, so it has good fluidity and excellent moldability.

[0106] [Examples]

[0107] The present invention will be described in detail with reference to the following examples, but the present invention is not limited by the following description.

[0108] As the spherical silica particles (A), the spherical silica particles (A-1) shown in Table 1 (manufactured by Denka Company Limited, trade name: FB-5D, specific surface area 2.3 m 2 / g) and the spherical silica particles (A-2) (manufactured by Denka Company Limited, trade name: FB-3SDC, specific surface area 3.3 m 2 / g) were prepared. In addition, the average circularity, average particle density, average particle diameter, specific surface area, and water desorption molecular weight of the spherical silica particles (A-1) and (A-2), and the dielectric constant and dielectric loss tangent when made into a resin film are values measured according to the methods described later.

[0109] [Table 1]

[0110]

[0111] [Example 1]

[0112] 2 kg of spherical silica particles (A-1) shown in Table 1 was added to 3 kg of pure water, and the mixture was stirred at room temperature for 6 hours to prepare a slurry with a particle concentration of 40% by mass. This slurry was put into a classification device (manufactured by Satake Chemical Machinery Co., Ltd., product name: SATAKE i Classifier (registered trademark) standard machine) for wet classification. The classification conditions were set as follows: rotor circumferential speed: 26 m / s, fine particle discharge speed: 10 L / hr. The supernatant was removed by decanting the slurry after removing the fine particles, and the obtained spherical silica particles (B) were dried at 110 °C for 24 hours. The dried spherical silica particles (B) were pulverized in a mortar, and 50 g was put into an alumina crucible. Using an electric furnace (manufactured by Fuji Denpa Kogyo Co., Ltd., product name: HiMulti (registered trademark) 10000), the particles were heat-treated at an electric furnace internal temperature of 1000 °C for 4 hours in a nitrogen atmosphere. Then, after natural cooling until the inside of the furnace reached room temperature, the spherical silica particles (X) were recovered. The surface fractal dimension, specific surface area, water desorption molecular weight, average particle size, average roundness, and average particle density of the obtained spherical silica particles (X) were measured by the following methods. In addition, the surface state of the spherical silica particles (X) was observed by the following methods to confirm the presence or absence of fine particles on the surface. The results are shown in Table 2.

[0113] <Method for measuring surface fractal dimension>

[0114] The spherical silica particles were directly placed as they were in a sample cell for transmission measurement of an X-ray diffraction analyzer (manufactured by Rigaku Corporation, product name: SmartLab), and the particles were measured under the following conditions using the ultra-small angle X-ray scattering method (USAXS). During analysis, background removal and deblurring processing were performed. The deblurring processing was carried out using analysis software (manufactured by Rigaku Corporation, product name: Particle Size-Pore Diameter Analysis Software NANO-Solver).

[0115] X-ray tube target: Cu Kα,

[0116] Tube voltage - tube current: 45 kV - 200 mA,

[0117] Detector: Scintillation counter,

[0118] Scanning range: 0.00 - 0.50 deg,

[0119] Scanning step: 0.0006 deg,

[0120] Scanning speed: 0.03 deg / min,

[0121] Incident side spectroscopic crystal: Ge(220)×2,

[0122] Receiving side spectroscopic crystal: Ge(220)×2.

[0123] <Calculation method of surface fractal dimension>

[0124] The surface fractal dimension is calculated according to the following method. First, the scattering angle 2θ is converted into a scattering vector q using the following formula (1). In addition, in the following formula (1), λ represents the wavelength (nm) of the incident X-ray, which is 0.154 nm.

[0125] q = 4πsinθ / λ ··· (1)

[0126] Then, for the USAXS pattern after background removal and deblurring, a double-logarithmic graph showing the relationship between the scattering vector q and the intensity I(q) is made, and a power approximation is performed in the range of q = 0.0124 to 0.0627 nm -1 (2θ = 0.174 to 0.0882°). The exponent α in the approximation formula is substituted into the following formula (2) to calculate the surface fractal dimension (Ds).

[0127] Ds = 6 + α ··· (2)

[0128] <Method for measuring specific surface area>

[0129] 1 g of spherical silica particles is filled into a measuring cell, and the specific surface area of the spherical silica particles is measured using a fully automatic specific surface area and diameter measuring device (manufactured by Mountech Co., Ltd., product name: Macsorb HM model-1201 (BET single-point method)). In addition, the degassing conditions before measurement are set to 200 °C and 10 minutes.

[0130] <Method for measuring molecular weight of dehydrated water>

[0131] Using a gas chromatography mass analyzer (manufactured by JEOL Ltd., product name: JMS-Q1500GC) and a thermal decomposition device (manufactured by Frontier Lab Co., Ltd., product name: PY-3030D), 15 μg of spherical silica particles were heated from 50 °C to 1000 °C at a heating rate of 25 °C per minute under a helium atmosphere. The area value of the obtained mass spectrum (m / z = 18) in the range of 50 °C to 1000 °C was calculated, and the number of detached water molecules was calculated from the calibration curve. In addition, for the calibration curve, the area value of the number of detached water molecules (m / z = 18) of an aluminum hydroxide sample (manufactured by Kojundo Chemical Laboratory Co., Ltd., product name: Aluminum Hydroxide) as a standard sample was used. Specifically, 23 μg, 122 μg, and 270 μg of the aluminum hydroxide standard sample were accurately weighed using a microbalance, heated under the same conditions as above, the area value of the water molecules detached from the aluminum hydroxide was measured, and a calibration curve was made. In addition, the moisture content of the aluminum hydroxide sample was calculated by the following method. Using a high-sensitivity differential type differential thermal balance (manufactured by NETZSCH GmbH, product name: STA 2500 Regulus), the mass reduction of aluminum hydroxide particles (manufactured by Kojundo Chemical Laboratory Co., Ltd., product name: Aluminum Hydroxide, ALI06PB) in the range of 200 °C to 320 °C was measured (heating conditions: heated from room temperature (23 °C) to 800 °C at a heating rate of 10 °C / min, carrier gas: air, measurement container: platinum pan, sample amount: 13 mg).

[0132] <Method for Measuring Average Circularity>

[0133] After fixing the spherical silica particles to the sample stage with a carbon tape, osmium coating was performed. Then, an image with a magnification of 500 to 50000 times and a resolution of 1280 × 1024 pixels taken with a scanning electron microscope (manufactured by JEOL Ltd., JSM-7001F SHL) was read into a computer. For this image, after calculating the projected area (S) and projected perimeter (L) of one particle using an image analysis device (manufactured by ROPER Co., Ltd., Japan, product name: Image-Pro Premier Ver. 9.3), the circularity was calculated from the following formula (3). The circularity was calculated for any 200 particles, and the average value was taken as the average circularity.

[0134] Circularity = 4πS / L 2 …(3)

[0135] <Method for Measuring Average Particle Size>

[0136] The average particle size was measured using a laser diffraction particle size distribution analyzer (manufactured by Beckman Coulter, Inc., product name: LS13 320). First, 50 cm was placed in a glass beaker 3Pure water and 0.1 g of spherical silica particles were subjected to a 1-minute dispersion treatment using an ultrasonic homogenizer (manufactured by BRANSON, trade name: SFX250). The dispersion of the spherical silica particles after the dispersion treatment was added drop by drop to a laser diffraction particle size distribution measuring device, and the measurement was carried out 30 seconds after adding a predetermined amount. The particle size distribution was calculated from the data of the light intensity distribution of the diffraction / scattering light of the spherical silica particles detected by the sensor in the laser diffraction particle size distribution measuring device. The average particle size was calculated from the particle size at which the cumulative value corresponded to 50% in the volume-based cumulative particle size distribution of the measured particle sizes.

[0137] <Method for Measuring Average Particle Density>

[0138] 2.0 g of spherical silica particles were placed in a sample cell for measurement, and the average particle density was measured by the gas (helium) replacement method using a dry density meter (manufactured by Shimadzu Corporation, product name: AccuPyc II 1340).

[0139] <Observation of Particle Surface>

[0140] The surface of the spherical silica particles (X) was observed with an electron microscope to evaluate whether there were fine particles on the particle surface.

[0141] (Evaluation Criteria)

[0142] Qualified: Fine particles have been removed from the surface of the spherical silica particles (X), and the surface unevenness has become smaller.

[0143] Unqualified: A large amount of fine particles are attached to the surface of the spherical silica particles (X).

[0144] <Evaluation of Dielectric Properties (Dielectric Constant and Dielectric Loss Tangent)>

[0145] The spherical silica particles (X) and polyethylene resin powder (manufactured by Sumitomo Seika Chemicals Co., Ltd., trade name: FLO-THENE (registered trademark) UF-20S) were weighed so that the filling amount of the spherical silica particles (X) was 40% by volume, and a resin composition was obtained by mixing using a vibratory mixer (manufactured by Resodyn) at an acceleration of 60 G and a processing time of 2 minutes. The obtained resin composition was put into a 3-cm-diameter metal frame in an amount such that the thickness became about 0.3 mm, and sheeted under the conditions of 140 °C, 5 minutes, and 30000 N using a nanoimprint device (manufactured by SCIVAX, trade name: X-300). An evaluation sample was obtained by cutting out a 1.5 cm × 1.5 cm size from the obtained sheet.

[0146] Then, a 36 GHz cavity resonator (manufactured by SAMTECH) was connected to a vector network analyzer (85107, manufactured by Keysight Technologies). The evaluation sample was configured to block the 10 mm diameter hole provided in the cavity resonator, and the resonance frequency (f0) and the unloaded Q value (Qu) were measured. Each time a measurement was made, the evaluation sample was rotated 60 degrees, and the same measurement was repeated 5 times. The average values of the obtained f0 and Qu were used as the measured values, and the dielectric constant was calculated from f0 and the dielectric loss tangent (tanδc) was calculated from Qu using analysis software (software manufactured by SAMTECH Co., Ltd.). In addition, the measurement was carried out under the conditions of a measurement temperature of 20 °C and a humidity of 60% RH. The obtained values of the dielectric constant and the dielectric loss tangent were evaluated according to the following evaluation criteria. The results are shown in Table 2.

[0147] (Evaluation Criteria)

[0148] <Dielectric Constant>

[0149] 3 points: The dielectric constant is 3.0 or less.

[0150] 2 points: The dielectric constant exceeds 3.0 and is 3.2 or less.

[0151] 1 point: The dielectric constant exceeds 3.2 and is 3.4 or less.

[0152] 0 points: The dielectric constant exceeds 3.4.

[0153] <Dielectric Loss Tangent>

[0154] 3 points: The dielectric loss tangent is less than 4.0×10 -4

[0155] 2 points: The dielectric loss tangent is 4.0×10 -4 or more and less than 4.5×10 -4

[0156] 1 point: The dielectric loss tangent is 4.5×10 -4 or more and less than 5.0×10 -4

[0157] 0 points: The dielectric loss tangent is 5.0×10 -4 or more

[0158] <Comprehensive Evaluation>

[0159] The points of the dielectric constant and the dielectric loss tangent were added up, and the dielectric properties were evaluated according to the following criteria.

[0160] Excellent: The points of both the dielectric constant and the dielectric loss tangent are 3 points (total points are 6 points).

[0161] Good: One of the dielectric constant or the tangent of the dielectric loss angle is 3 points, and the other is 2 points (total points are 5 points).

[0162] Acceptable: The points of both the dielectric constant and the tangent of the dielectric loss angle are 2 points (total points are 4 points).

[0163] Not acceptable: The points of one of the dielectric constant or the tangent of the dielectric loss angle are less than 2 points (total points are less than 4 points).

[0164] [Examples 2 to 3 and Comparative Examples 1 to 3]

[0165] Spherical silica particles (X) were prepared under the manufacturing conditions shown in Table 2. In addition, Comparative Examples 1 to 3 are examples of manufacturing spherical silica particles (X) without performing step (i) (classification step). For the spherical silica particles (X) of each example, the surface fractal dimension, specific surface area, water desorption molecular weight, average particle size, average roundness, and average particle density were measured in the same manner as in Example 1. In addition, the surface state and dielectric properties of the particles were evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0166] [Example 4]

[0167] Spherical silica particles (X) were prepared under the manufacturing conditions shown in Table 2. With respect to 100 parts by mass of the obtained spherical silica particles (X), 1 part by mass of hexamethyldisilazane (recorded as "HMDS" in Table 2) (manufactured by Shin-Etsu Chemical Co., Ltd., trade name: SZ-31) was added as a surface treatment agent. Then, using a vibratory mixer (manufactured by Resodyn, product name: LabRAMII), after mixing and treating at an acceleration of 60G for 2 minutes, the mixture was dried using a mixed powder vacuum dryer at 120 °C under an environment of less than -133 Pa for 24 hours to obtain surface-treated spherical silica particles (X). For the obtained spherical silica particles (X), the surface fractal dimension, specific surface area, water desorption molecular weight, average particle size, average roundness, and average particle density were measured in the same manner as in Example 1. In addition, the surface state and dielectric properties of the particles were evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0168] [Example 5]

[0169] Spherical silica particles (X) were prepared under the manufacturing conditions shown in Table 2. With respect to 100 parts by mass of the obtained spherical silica particles (X), 1 part by mass of vinyltriethoxysilane (described as "vinyl" in Table 2) (manufactured by Shin-Etsu Chemical Co., Ltd., trade name: KBE-1003) was added as a surface treatment agent. Then, using a vibratory mixer (manufactured by Resodyn Corporation, product name: LabRAMII), after mixing and treating at an acceleration of 60G for 2 minutes, it was dried for 24 hours using a mixed powder vacuum dryer in an environment of 120 °C and less than -133 Pa to obtain surface-treated spherical silica particles (X). For the obtained spherical silica particles (X), the surface fractal dimension, specific surface area, water desorption molecular weight, average particle size, average circularity, and average particle density were measured in the same manner as in Example 1. In addition, the surface state and dielectric properties of the particles were evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0170] [Table 2]

[0171]

[0172] As shown in Table 1, the spherical silica particles (X) of Examples 1 to 5 that satisfy the constitution of the present invention have a lower dielectric loss tangent than the spherical silica particles of the comparative examples. In addition, as a result of observing the spherical silica particles (X) of Examples 1 to 5 with an electron microscope, fine particles have been removed from the surface of the particles. On the other hand, in Comparative Examples 1 to 3 where the surface fractal dimension exceeds 2.3, the dielectric loss tangents of the resin sheets are all high. Many foreign substances adhere to the particle surfaces of these comparative example spherical silica particles, resulting in particles with large surface irregularities. Therefore, it is considered that the amount of adsorbed water and functional groups on the particle surface is large, deteriorating the dielectric loss tangent. From the above results, it can be confirmed that the spherical silica particles (X) according to the present invention can achieve a lower dielectric loss tangent when filled into a resin.

[0173] [Industrial Applicability]

[0174] The spherical silica particles according to the present invention can achieve a lower dielectric loss tangent when filled into a resin. Such spherical silica particles can be suitably used as a filler for resin materials such as high-frequency band substrate materials and insulating materials.

Claims

1. A spherical silica particle (X) having a surface fractal dimension (Ds) of 1.0 to 1.9 and an average circularity of 0.85 or more.

2. The spherical silica particles (X) according to claim 1, wherein, The specific surface area of the spherical silica particles (X) is 0.1 to 2.0 m 2 / g.

3. The spherical silica particles (X) according to claim 1 or 2, wherein, The spherical silica particle (X) has an average particle diameter of 1 to 30 μm.

4. The spherical silica particles (X) according to any one of claims 1 to 3, wherein, The spherical silica particle (X) is surface-treated with a surface treatment agent.

5. The spherical silica particle (X) according to any one of claims 1 to 4, which is used for resin filling.

6. A resin composition comprising the spherical silica particle (X) according to any one of claims 1 to 5 and at least one resin selected from a thermoplastic resin and a thermosetting resin.

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