JP2021075438A - Hollow silica particle, method for producing the same, resin composite composition using the same, and resin composite - Google Patents

Abstract

To provide hollow silica particles that have excellent dielectric properties in the millimeter-wave band having frequencies of 60 GHz to 80 GHz and have a plurality of closed pores, and to provide a resin composite for high-frequency device applications which comprises a resin mixed with the particles.SOLUTION: Used are hollow silica particles that have a closed porosity of 1.0% or more and 70.0% or less, contain 50% by mass or more of crystalline silica, and have a plurality of closed pores.SELECTED DRAWING: Figure 2

Description

The present invention relates to hollow silica particles having a plurality of closed pores, a method for producing the same, and a resin composite containing the hollow silica particles. The present invention particularly relates to a resin composite of a resin and hollow silica particles having a plurality of closed pores, which can be used for producing an insulating film of a high frequency wiring substrate corresponding to a high frequency signal having a frequency of 60 GHz or more. Is.

Due to the increase in the amount of information accompanying the sophistication of communication technology and the rapid expansion of the use of millimeter-wave bands such as millimeter-wave radar, the frequency is increasing. The circuit board that transmits these high-frequency signals is composed of an electrode and a dielectric board that form a circuit pattern. In order to suppress energy loss during transmission of high-frequency signals, it is necessary that the dielectric loss tangent (tan δ) of the dielectric material is small. For low dielectric loss, the dielectric material must have low polarity and low dipole moments.

As the dielectric material, ceramic particles, resins, and composites obtained by combining them are mainly used. In particular, with the recent expansion of the use of the millimeter wave band, ceramic particles and resins having a lower dielectric loss tangent (tan δ) are required. Resins have a relatively small relative permittivity (εr) and are suitable for high-frequency devices, but have a dielectric loss tangent (tan δ) and a coefficient of thermal expansion larger than those of ceramic particles. For this reason, the composite of the ceramic particles for the millimeter wave band and the resin is (1) made into a low dielectric loss tangent (tan δ) of the ceramic particles themselves, and (2) is highly filled with the ceramic particles and has a large dielectric loss tangent (tan δ). It is suitable to reduce the amount of resin shown.

Silica (SiO ₂ ) particles have been conventionally used as ceramic particles. If the shape of the silica particles is angular, the fluidity, dispersibility, and filling property in the resin are deteriorated, and the manufacturing apparatus is also worn. In order to improve these, spherical silica particles are widely used. It is considered that the closer the spherical silica particles are to a true sphere, the better the filling property, fluidity, and mold abrasion resistance in the resin, and particles having a high roundness have been pursued. Furthermore, further improvement of filling property has been studied by optimizing the particle size distribution of the particles.

The thermal spraying method is known as a method for producing spherical silica particles. In the thermal spraying method, crushed silica powder as a raw material is passed through a flame at 2000 ° C. or higher to melt the silica powder, and the shape is spheroidized by surface tension. The molten spheroidized particles are transported by air flow so as not to fuse with each other and collected, and the particles after thermal spraying are rapidly cooled. Since it is rapidly cooled from the molten state, the obtained silica particles have an amorphous structure.

Since the spherical silica particles produced by the thermal spraying method are amorphous, their coefficient of thermal expansion and thermal conductivity are low. The coefficient of thermal expansion of the amorphous silica particles is 0.5 ppm / K, and the thermal conductivity is 1.4 W / mK. These physical properties are substantially the same as the coefficient of thermal expansion of quartz glass having an amorphous structure without having a crystal structure. Therefore, when it is mixed with a resin having a high thermal expansion and used as a filler for a semiconductor encapsulant, the effect of lowering the thermal expansion of the encapsulant itself can be obtained. By setting the coefficient of thermal expansion of the sealing material to a value close to Si, it is possible to suppress deformation due to the thermal expansion behavior when sealing the IC chip.

As described above, the characteristics required of silica particles for encapsulant materials include filling property, fluidity, and mold abrasion resistance, which can be blended in a large amount with a resin to maintain the performance as a composite. , Excellent dielectric properties of high frequencies in the millimeter wave band. Since the dielectric property is a physical property value of the material, it is difficult to reduce the dielectric loss tangent of the silica particles.

Patent Document 1 is characterized in that a Zn compound is added in an amount of 0.5% by mass or more in terms of ZnO to silica gel having an average particle size of 0.1 to 20 μm, and this mixture is heat-treated at 900 to 1100 ° C. A method for producing a porous powder in which the main crystal phase is quartz is described. There is a description that the obtained porous powder has fine pores and is useful for aggregates for lowering the dielectric constant, but the fine pores here are open pores and closed pores. Is not listed.

Patent Document 2 describes a production method of heating a particle material made of spherical amorphous silica (heating step) to crystallize it. The obtained spherical crystalline silica powder for adding a resin composition is described. Has no pores.

JP-A-2002-20111 JP-A-2018-1450437

The present inventors have been searching for hollow silica particles having a plurality of closed pores having excellent dielectric properties in the millimeter wave band having a frequency of 60 GHz to 80 GHz, and a resin composite for high frequency devices in which they are mixed with a resin. I aimed to make it.

The inventor of the present application has conducted intensive research for the purpose of solving the above problems, and as a result, in order to obtain a resin composite having a low dielectric loss tangent, first, spherical molten (amorphous) silica is heat-treated and crystallized. Found to be valid. That is, it was confirmed for the first time that the dielectric loss tangent in the millimeter wave band (60 GHz to 80 GHz) of crystalline silica is significantly lower than that of amorphous silica which has been widely used in the past. As a result, the spherical crystalline silica particles become silica particles exhibiting excellent dielectric properties for high-frequency device applications.

The inventors of the present application further studied to obtain excellent silica particles for high-frequency device applications. Air is known as a substance with a small dielectric loss tangent. Therefore, it is effective to introduce an air phase into the silica particles. However, it has been impossible to introduce an air phase into the crystalline silica particles produced by the thermal spraying method. The present inventors have stated that hollow spherical crystalline silica particles having a plurality of closed pores can be produced by heat-treating the silica granulated powder to control the sintering behavior and crystallization behavior of the silica granulated powder. Findings have led to the present invention.

Thus, according to the present invention, the following is provided:
(1) Hollow silica particles having a plurality of closed pores having a closed porosity of 1.0% or more and 70.0% or less and containing 50% by mass or more of crystalline silica.
(2) The hollow silica particles according to (1) above, wherein the closed porosity is 2.0% or more and 70.0%.
(3) The hollow silica particles according to (1) or (2) above, which contain 80% by mass or more of crystalline silica.
(4) The hollow silica particles according to any one of (1) to (3) above, wherein the crystalline silica is at least one of cristobalite and quartz.
(5) The hollow silica particles according to any one of (1) to (4) above, wherein the average particle size (D50) of the hollow silica particles is 3 to 100 μm.
(6) The hollow silica particles according to any one of (1) to (5) above, wherein the circularity of the hollow silica particles is 0.8 or more.
(7) The hollow silica particle according to any one of (1) to (6), wherein the dielectric loss tangent of the hollow silica particle at a frequency of 70 GHz is 0.0042 or less.
(8) A step of granulating silica fine powder as raw material particles or granulating a mixed fine powder composed of the silica fine powder and graphite fine powder as raw material particles to obtain a granulated powder, and the granulated powder. A step of heat-treating at 1200 ° C. to 1600 ° C. to obtain hollow silica particles having a closed pore ratio of 1.0% or more and 70.0% or less and having a plurality of closed pores containing 50% by mass or more of crystalline silica. A method for producing hollow silica particles having a plurality of closed pores, which comprises.
(9) The production method according to (8) above, wherein the crystalline silica fine powder is a natural quartz fine powder.
(10) The production method according to (8) above, wherein the silica fine powder is a mixture of natural quartz fine powder and amorphous silica fine powder.
(11) The production method according to (8) to (10) above, wherein the average particle size (D50) of the granulated powder is 3 to 100 μm.
(12) A resin composite composition containing at least the resin and the hollow silica particles according to any one of (1) to (7) above.
(13) A resin composite obtained by curing the resin composite composition according to (12) above.

According to the present invention, the resin complex has a low dielectric loss tangent due to the inclusion of crystalline silica. Further, the hollow spherical silica of the present invention contains pores containing an air phase having a low dielectric loss tangent with a closed porosity of 1% or more, and therefore has excellent dielectric properties as compared with conventional amorphous silica particles and is a semiconductor for high frequency devices. It becomes silica particles suitable for the field.

FIG. 1 is a cross-sectional SEM image of a granulated powder obtained by granulating silica fine powder having an average particle size of less than 3 μm with a spray dryer. FIG. 2 is a cross-sectional SEM image of hollow silica particles having a plurality of closed pores of the present invention obtained by heat-treating the granulated powder shown in FIG. 1 in an air atmosphere at 1500 ° C.

The silica particles of the present invention are hollow silica particles having a plurality of closed pores, characterized by having a closed porosity of 1.0% or more and 70.0% or less and containing 50% by mass or more of crystalline silica. is there.

The crystal structure of silica (SiO ₂ ) includes cristobalite, quartz and the like. Silica having these crystal structures has a higher coefficient of thermal expansion and thermal conductivity than amorphous silica. Therefore, by replacing the molten (amorphous) silica with crystalline silica in an appropriate amount, it is possible to improve the thermal conductivity while suppressing the difference in thermal expansion from the IC chip or the like. Crystalline silica has excellent dielectric properties in the millimeter wave band. Furthermore, by introducing an air phase into crystalline silica, it is suitable as silica particles for high-frequency device applications.

The more the air phase is introduced into the crystalline silica, the better the dielectric properties, but on the other hand, the porosity is 70% or less, more preferably 50% due to the decrease in heat conduction and the decrease in mechanical properties. It is as follows. If the closed porosity is less than 1.0%, the effect of improving the dielectric characteristics by introducing the air phase is small and cannot be expected, so it is 1.0% or more. The closed porosity is preferably 2.0% or more. The pores include open pores that are connected to the outside air and closed pores that are isolated inside the particles. The content of the air phase specified in the present invention is the air contained in the closed pores.

The method for measuring the dielectric loss tangent of the silica particles of the present invention is shown below. Since the dielectric loss tangent cannot be measured directly with respect to the silica particles, in the present invention, a composite with a resin was prepared and the dielectric loss tangent of the resin composite was measured. The dielectric loss tangent of the silica particles can be obtained by varying the content of the silica particles with respect to the resin to determine the relationship between the silica particle content and the dielectric loss tangent, and then extrapolating the dielectric loss tangent of the silica particles having a content of 100%. it can. In the present invention, the resin composite was measured at a frequency of 70 GHz using a network analyzer "N5227A (manufactured by Keysight Technology Co., Ltd.)" based on the blocking cylindrical waveguide method (JIS R1660-1: 2004). From the relationship between the composite with 0 and 80% by mass of silica particles and the dielectric loss tangent with respect to the epoxy resin, the numerical value of 100% of the silica particles was extrapolated, and the obtained numerical value was defined as the dielectric loss tangent of the silica particles.

The dielectric loss tangent of the hollow silica particles having a plurality of closed pores of the present invention at a frequency of 70 GHz is preferably 0.0042 or less having a closed porosity of more than 1.0% and less than 0.0013. The rate is preferably 0.0013 to 0.0042 because the rate may exceed 70% and the mechanical strength may decrease. The dielectric loss tangent is more preferably in the range of 0.0013 to 0.0040, and even more preferably in the range of 0.0013 to 0.0037.

The silica particles of the present invention are hollow silica particles having a plurality of closed pores. When there is a single closed pore in the silica particle, the pores are inevitably unevenly distributed in the particle. As a result, the mechanical strength of the particles becomes non-uniform. It is not preferable that a single closed pore exists because a problem occurs in which the closed pore is crushed starting from the strength lowering portion when the closed pore ratio becomes high. On the other hand, in the case of silica particles having a plurality of closed pores, the mechanical strength is leveled, so that the above-mentioned problems do not occur.

For the silica particles of the present invention to have a plurality of closed pores, the cross-sectional structure of the silica particles may be observed. For observation of the cross-sectional structure, for example, after embedding a plurality of silica particles in an epoxy resin, polishing is performed with a diamond slurry so that the silica cross section is exposed on the observation surface, and the cross section is observed with a scanning electron microscope (SEM). Just do it.

The calculation method of the closed porosity is shown below. The pores existing in the silica particles are closed pores. When the density of silica particles is determined by using the Archimedes method, the obtained density does not consider open pores, but only closed pores, and is called "apparent density". The Archimedes method is a method for determining the density of a sample by using the fact that a solid in a liquid receives the same amount of buoyancy as the mass of the same volume of liquid. The closed porosity can be determined by dividing the apparent density of silica particles by the true density, which is the ideal density for a real material. The porosity of the hollow silica particles having a plurality of closed pores of the present invention was measured by the Archimedes method using water as a liquid.
Porosity = 100 x {1- (apparent density / true density)} (%)

When the particles are composed of amorphous silica and crystalline silica, the true density of the silica particles can be obtained by multiplying the true density of each silica by the abundance ratio. For example, when amorphous silica is 66.2% and crystalline silica is 33.2% (cristobalite 32.0%, quartz 1.8%), the true density of the silica particles is amorphous silica. It can be obtained by true density × 0.662 + cristobalite true density × 0.320 + quartz true density × 0.018. True density of amorphous silica, cristobalite, quartz, 25 ° C., at atmospheric pressure, ^{respectively, 2.196g / cm 3, 2.334g /} cm 3, a 2.648g / cm ^3. The abundance ratio when the silica particles are composed of amorphous and crystalline can be determined by XRD.

The constitution of the present invention is hollow spherical silica particles having a plurality of closed pores containing at least one kind of crystalline silica of cristobalite or quartz. The content of crystalline silica in the spherical silica particles is 50% or more. When it is 50% or more, excellent dielectric properties are exhibited as compared with amorphous silica having no closed pores. More preferably, it contains 80% or more of crystalline silica. The higher the proportion of crystalline silica, the better the dielectric properties.

The proportion of crystal phases was measured by X-ray diffraction (XRD). In the measurement by XRD, the ratio of the crystal phase was obtained by calculating from the sum of the integral strengths of the crystalline peaks (Ic) and the integral strengths of the amorphous halo portion (Ia) by the following formula.
X (crystal phase ratio) = Ic / (Ic + Ia) x 100 (%)
Furthermore, the content of crystal phases such as cristobalite and quartz was determined by quantitative analysis by X-ray diffraction. In the quantitative analysis by X-ray diffraction, an analysis method such as the Rietveld method was used, and the quantitative analysis was performed without using a standard sample. In the present invention, an X-ray diffractometer "D2 PHASER" (manufactured by Bruker) was used. The quantitative analysis of the crystal phase by the lead belt method was performed by the crystal structure analysis software "TOPAS" (manufactured by Bruker).

The average particle size (D50) of the hollow silica particles having a plurality of closed pores of the present invention is preferably 3 to 100 μm. If the average particle size is less than 3 μm, the cohesiveness of the particles becomes large and the fluidity is remarkably lowered, which is not preferable. If the average particle size exceeds 100 μm, voids between the particles tend to remain and it becomes difficult to improve the filling property, which is not preferable. More preferably, the average particle size is in the range of 10 to 80 μm.

For the average particle size (D50), a median size D50 having a cumulative volume of 50% was determined in a volume-based particle size distribution measured by a laser diffraction / scattering particle size distribution measurement method. The laser diffraction / scattering type particle size distribution measurement method is a method in which a dispersion liquid in which silica particles are dispersed is irradiated with laser light, and the particle size distribution is obtained from an intensity distribution pattern of the diffraction / scattering light emitted from the dispersion liquid. In the present invention, a laser diffraction / scattering type particle size distribution measuring device "CILAS920" (manufactured by Cirrus) was used.

The hollow spherical silica particles of the present invention preferably have a circularity of 0.80 or more. If the circularity is less than 0.80, the fluidity, dispersibility, and packing property are not sufficient when used as silica particles or the like of a resin composite composition for a semiconductor encapsulant, and the encapsulant is produced. Equipment wear may be accelerated.

The circularity is obtained by "perimeter of the circle corresponding to the projected area of the photographed particle ÷ perimeter of the photographed particle image", and the closer this value is to 1, the closer to a true sphere. The circularity of the present invention was determined by a flow-type particle image analysis method. In the flow-type particle image analysis method, silica particles are flowed into a liquid and imaged as a still image of the particles, and image analysis is performed based on the obtained particle image to determine the circularity of the silica particles. The average value of these plurality of circularities was defined as the average circularity. If the number of particles when measuring the average circularity by the flow type particle image analysis method is too small, the average value cannot be obtained correctly. At least 100 or more particles are required, preferably 500 or more, and more preferably 1000 or more. In the present invention, about 500 particles were used by using the flow type particle image analyzer "FPIA-3000" (manufactured by Spectris).

For the hollow silica particles having a plurality of closed pores of the present invention, silica fine powder is granulated as raw material particles, or a mixed fine powder composed of the silica fine powder and graphite fine powder is granulated as raw material particles. The step of obtaining the granulated powder and the step of heat-treating the granulated powder at 1200 ° C. to 1600 ° C. are included.

Crystalline silica is usually obtained by heat-treating spherical amorphous silica in an air atmosphere to crystallize it. By changing the heat treatment temperature and time, it is possible to change and control the content of crystalline silica.
The hollow silica particles having a plurality of closed pores of the present invention are characterized in that the closed pore ratio is 1.0% or more and 70.0% or less, and the crystalline silica is contained in an amount of 50% by mass or more. In order to introduce the air phase into the silica particles, silica fine powder or a mixed fine powder composed of silica fine powder and graphite fine powder is granulated as raw material particles.

The introduction of the air phase into crystalline silica is performed by spherically granulating silica fine powder having an average particle size of submicron to several microns as raw material particles, and then filling the container with the granulated powder and heat-treating it. .. The container may be an oxide-based material that is stable at the heat treatment temperature, and for example, alumina can be used. Granulation methods include fluidized bed granulation, stirring granulation, spray drying, extruded granulation and the like. In the production method of the present invention, the granulation method is not particularly limited as long as a granulation powder having a nearly spherical shape can be obtained. FIG. 1 is a cross-sectional SEM image of a granulated powder obtained by granulating silica fine powder having an average particle size of less than 3 μm using a spray dryer.

Granulated powder having an average particle size of 3 μm to 100 μm can be produced separately depending on the size of the raw material particles of silica used and the granulation conditions. As the raw material particles, in addition to the crystalline silica fine powder, an amorphous fine powder or a fine powder of a mixture thereof can also be used. When the granulated powder is prepared from the mixed fine powder of the fine powder of natural quartz and the fine powder of amorphous silica, more closed pores can be introduced as compared with the case of using the raw material particles consisting of only the fine powder of natural quartz.

The reason for this can be considered as follows. For example, when a raw material particle composed of only natural quartz fine powder is undergoing a phase transition to Christovalite by a heat treatment at 1200 ° C. or higher, an air phase is formed while the voids in the granulated powder which is the raw material particle are coalesced. At this time, due to the difference in the true density of the cristobalite phase-transitioned with quartz, the hollow silica particles having a plurality of closed pores obtained are expanded as a whole, and the coalescence of voids and the formation of pores proceed. FIG. 2 is a cross-sectional SEM image of hollow silica particles having a plurality of closed pores of the present invention obtained by heat-treating the granulated powder shown in FIG. 1 in an air atmosphere at 1500 ° C.
On the other hand, when amorphous silica fine powder is present in the raw material particles other than natural quartz fine powder, the phase-transitioned cristobalite and amorphous silica have almost the same true density, so that the amorphous silica portion expands. Crystallization proceeds without doing so. Since the amorphous silica raw material particle portion does not expand while the granulated powder as a whole expands, new voids are generated around the amorphous silica raw material particle portion.

When graphite fine powder having the same average particle size as silica fine powder is added as raw material particles for granulation, when the granulated powder is heat-treated, the graphite fine powder burns and gasifies, so that the graphite fine powder exists. A new space is formed in the place where it was. The amount of voids introduced by the combustion of the graphite fine powder is large, whereby hollow silica particles having a plurality of closed pores having a maximum closed porosity of about 70% can be obtained.

By heat-treating the granulated powder at 1200 ° C. to 1600 ° C., hollow spherical crystalline silica having a closed porosity of 1% or more can be obtained. When silica granulated powder containing graphite fine powder is used, graphite reacts with oxygen at a temperature of 700 ° C. or higher in the heat treatment step and burns to become CO ₂ , which is released and disappears. Therefore, many pores can be introduced into the silica particles. By controlling the sintering behavior as well as the crystallization behavior in the heat treatment step, the holes on the particle surface created by gasification of graphite can be closed during the heat treatment, and closed pores can be generated. If open pores remain in the silica particles during kneading with the resin described later, the resin invades the open pores, which hinders the introduction of air into the silica particles. Further, the interaction between the silica particles and the resin becomes too strong, which reduces the fluidity of the resin composite composition, which is not preferable.

In the present invention, it is possible to produce a finally obtained composite composition of hollow silica particles having a plurality of closed pores and a resin, and further a resin composite obtained by curing the resin composite composition. The composition of the resin composite composition will be described below.

A resin composite composition such as a semiconductor encapsulant (particularly a solid encapsulant) or an interlayer insulating film can be obtained by using a slurry composition containing hollow silica particles having a plurality of closed pores and a resin. Further, by curing these resin complex compositions, a resin complex such as a sealing material (cured body) and a substrate for a semiconductor package can be obtained.
When producing the resin composite composition, for example, in addition to hollow silica particles having a plurality of closed pores and a resin, a curing agent, a curing accelerator, a flame retardant and the like are blended as necessary, and known kneading and the like are performed. Complex by method. Then, it is molded according to the application such as pellet form or film form.
Further, when the resin composite composition is cured to produce a resin composite, for example, the resin composite composition is melted by applying heat to be processed into a shape suitable for the intended use, and heat is higher than that at the time of melting. In addition, it is completely cured. In this case, a known method such as a transfer molding method can be used.

When manufacturing semiconductor-related materials such as packaging substrates and interlayer insulating films, it is preferable to use an epoxy resin as the resin composition used for the resin composite composition. The epoxy resin is not particularly limited, and for example, a bisphenol A type epoxy resin, a bisphenol F type epoxy resin, a biphenyl type epoxy resin, a phenol novolac type epoxy resin, a naphthalene type epoxy resin, a phenoxy type epoxy resin and the like can be used. One of these can be used alone, or two or more having different molecular weights can be used in combination. Among these epoxy resins, bisphenol A type epoxy resin is particularly preferable.

As the curing agent, for example, a phenolic curing agent can be used. As the phenolic curing agent, a phenol novolac resin, an alkylphenol novolak resin, polyvinylphenols and the like can be used alone or in combination of two or more.

The compounding amount of the phenol curing agent is preferably 0.1 or more and less than 1.0 in the equivalent ratio with the epoxy resin (phenolic hydroxyl group equivalent / epoxy group equivalent). As a result, the unreacted phenol curing agent does not remain, and the hygroscopic heat resistance is improved.

The amount of hollow silica particles having a plurality of closed pores of the present invention to be blended in the resin composition is preferably large from the viewpoint of heat resistance and coefficient of thermal expansion. Generally, it is preferably 80% by mass or more and less than 95% by mass with respect to the total mass of the resin composition.

The present invention will be described with reference to the following examples and comparative examples. However, the present invention is not construed as being limited to the following examples.

The porosity, circularity, average particle size and crystalline silica ratio (%) of the hollow silica particles having a plurality of closed pores produced in the following Examples and Comparative Examples were measured according to the above description. Those having a dielectric loss tangent value of 0.0042 or less were regarded as acceptable.

(Making a complex of silica particles and resin)
Using silica particles and an epoxy resin (YX-4000H manufactured by Mitsubishi Chemical Co., Ltd.), 0% by mass (no additives) and 80% by mass of silica particles were kneaded with respect to the epoxy resin at a temperature of 100 ° C. using a two-roll mill. The kneaded sample was crushed with a mortar and pestle. The crushed sample was filled in a mold (50φ) and set in a press. After pressurizing at a molding temperature of 175 ° C. for about 1 minute at 1 MPa, the pressure was maintained at 5 MPa for 9 minutes. Then, the mold was transferred to a water-cooled press, cooled for about 10 minutes, and then the cured silica particle-resin plate was taken out from the mold. The produced silica particle-resin plate was cut with an outer peripheral blade and processed to a size of about 10 mm × 10 mm. In order to change the thickness of the cured silica particles-resin plate, it was ground by high-precision surface grinding (SGM-5000 manufactured by Hidewa Kogyo Co., Ltd.), and the thickness was varied between 0.2 mm and 1.0 mm.

(Examples 1 to 4)
Crushed silica (quartz) fine powder with an average particle size of 2 μm is granulated with a spray dryer (CL-8 manufactured by Ohkawara Kakohki Co., Ltd.), filled in an alumina container, and electric furnace SUPER-BURN (Motoyama Co., Ltd.) The heat treatment temperature was 1400 ° C. (Example 1), 1450 ° C. (Example 2), 1500 ° C. (Example 3), 1550 ° C. (Example 4), and the treatment was performed in an air atmosphere for 6 hours. .. As a result of SEM observation, no adhesion or change in shape of silica particles due to fusion was observed due to heat treatment. The average particle size was 84 μm, respectively. A composite with a resin was prepared using the obtained hollow silica particles having a plurality of closed pores. The proportion of crystalline silica is shown in Table 1.

(Examples 5 to 7)
Crushed silica (quartz) fine powder with an average particle size of 2 μm and spherical amorphous silica fine powder with an average particle size of 2 μm are mixed at a mass ratio of 75:25 and manufactured with a spray dryer (CL-8 manufactured by Ohkawara Kakohki Co., Ltd.). The particles were granulated, filled in an alumina container, and treated using an electric furnace SUPER-BURN (manufactured by Motoyama Co., Ltd.) at 1450 ° C. to 1550 ° C. shown in Table 1 for 6 hours in an air atmosphere. .. As a result of SEM observation, no adhesion or change in shape of silica particles due to fusion was observed due to heat treatment. The average particle size was 78 μm, respectively. A composite with a resin was prepared using the obtained silica containing crystalline material. The proportion of crystalline silica is shown in Table 1.

(Examples 8 to 10)
Crushed silica (quartz) fine powder with an average particle size of 2 μm and spherical amorphous silica fine powder with an average particle size of 2 μm are mixed at a mass ratio of 65:35 and manufactured with a spray dryer (CL-8 manufactured by Ohkawara Kakohki Co., Ltd.). The particles were granulated, filled in an alumina container, and treated using an electric furnace SUPER-BURN (manufactured by Motoyama Co., Ltd.) at 1450 ° C. to 1550 ° C. shown in Table 1 for 6 hours in an air atmosphere. .. As a result of SEM observation, no adhesion or change in shape of silica particles due to fusion was observed due to heat treatment. The obtained silica particles were quantified for the content of crystalline silica using XRD. The average particle size was 75 μm each. A composite with a resin was prepared using the obtained silica containing crystalline material. The proportion of crystalline silica is shown in Table 1.

(Examples 11 to 13)
Crushed silica (quartz) fine powder with an average particle size of 2 μm and spherical amorphous silica fine powder with an average particle size of 2 μm are mixed at a mass ratio of 45:55 and manufactured with a spray dryer (CL-8 manufactured by Ohkawara Kakohki Co., Ltd.). The particles were granulated, filled in an alumina container, and treated using an electric furnace SUPER-BURN (manufactured by Motoyama Co., Ltd.) at 1450 ° C. to 1550 ° C. shown in Table 1 for 6 hours in an air atmosphere. .. As a result of SEM observation, no adhesion or change in shape of silica particles due to fusion was observed due to heat treatment. The obtained silica particles were quantified for the content of crystalline silica using XRD. The average particle size was 76 μm, respectively. A composite with a resin was prepared using the obtained silica containing crystalline material. The proportion of crystalline silica is shown in Table 1.

(Example 14)
Crushed silica (quartz) fine powder with an average particle size of 2 μm and spherical amorphous silica fine powder with an average particle size of 2 μm are mixed at a mass ratio of 25:75 and manufactured with a spray dryer (CL-8 manufactured by Ohkawara Kakohki Co., Ltd.). The particles were granulated, filled in an alumina container, and treated using an electric furnace SUPER-BURN (manufactured by Motoyama Co., Ltd.) at 1450 ° C. shown in Table 1 for 6 hours in an air atmosphere. As a result of SEM observation, no adhesion or change in shape of silica particles due to fusion was observed due to heat treatment. The obtained silica particles were quantified for the content of crystalline silica using XRD. The average particle size was 77 μm. A composite with a resin was prepared using the obtained silica containing crystalline material. The proportion of crystalline silica is shown in Table 1.

(Examples 15 to 18)
Crushed silica (quartz) fine powder with an average particle size of 2 μm, spherical amorphous silica fine powder with an average particle size of 2 μm, and graphite fine powder with an average particle size of 2 μm in a mass ratio of 59:32: 9 (Example 15). , 54: 29: 17 (Example 16), 46:25: 29 (Example 17), 40:22:38 (Example 18), and spray dryer (CL-8 manufactured by Ohkawara Kakohki Co., Ltd.). The mixture was granulated in, filled in an alumina container, and treated in an electric furnace SUPER-BURN (manufactured by Motoyama Co., Ltd.) at a heat treatment temperature of 1500 ° C. for 6 hours in an air atmosphere. As a result of SEM observation, the obtained silica particles had a plurality of closed pores. In addition, no adhesion or change in shape of silica particles due to fusion was observed due to heat treatment. The obtained silica particles were quantified for the content of crystalline silica using XRD. The average particle size was 82 μm, 84 μm, 79 μm, and 80 μm, respectively. A composite with a resin was prepared using the obtained silica containing crystalline material. The proportion of crystalline silica is shown in Table 1.

(Examples 19 to 21)
Crushed silica (quartz) fine powder with an average particle size of 2 μm is granulated with a spray dryer, filled in an alumina container, and the heat treatment temperature is 1500 ° C. using an electric furnace SUPER-BURN (manufactured by Motoyama Co., Ltd.). Examples 19, 20) and 1400 ° C. (Example 21) were treated in an air atmosphere for 6 hours. As a result of SEM observation, each silica particle obtained had a plurality of closed pores. In addition, no adhesion or change in shape of silica particles due to fusion was observed due to heat treatment. The average particle size was 21 μm, 98 μm, and 11 μm, respectively. A composite with a resin was prepared using the obtained hollow silica particles having a plurality of closed pores. The proportion of crystalline silica is shown in Table 1.

(Comparative Examples 1 to 3)
In Comparative Examples 1 to 3, spherical amorphous silica fine powder was placed in an alumina container at 1400 ° C. (Comparative Example 1), 1450 ° C. (Comparative Example 2), and 1100 ° C. (Comparative Example 3) 6 Heat-treated in an atmospheric atmosphere for hours. As a result of SEM observation, each silica particle obtained had a plurality of closed pores. In addition, no adhesion or change in shape of silica particles due to fusion was observed due to heat treatment. The content of crystalline silica in the obtained spherical silica particles was quantified using XRD. The average particle size was 35 μm, respectively. A composite with a resin was prepared using the obtained silica containing crystalline material. The proportion of crystalline silica is shown in Table 1.

(Comparative Example 4)
Crushed silica (quartz) fine powder having an average particle size of 2 μm was granulated with a spray dryer (CL-8 manufactured by Ohkawara Kakohki Co., Ltd.). After that, the container was filled with alumina and treated in an electric furnace SUPER-BURN (manufactured by Motoyama Co., Ltd.) at a heat treatment temperature of 1200 ° C. for 6 hours in an air atmosphere. As a result of SEM observation, each silica particle obtained had a plurality of closed pores. In addition, no adhesion or change in shape of silica particles due to fusion was observed due to heat treatment. In the obtained spherical silica, the content of crystalline silica was quantified by XRD. The average particle size was 84 μm. Moreover, the obtained silica particles were used to prepare a complex with a resin. The proportion of crystalline silica is shown in Table 1.

Table 1 shows the porosity, circularity, and dielectric loss tangent values of the silica particles obtained in Examples and Comparative Examples.

In Comparative Examples 1 and 2, the obtained silica particles contained 50% by mass or more of crystalline silica, but the closed porosity was 0.0%, so that the value of dielectric loss tangent exceeded 0.0042. In Comparative Examples 3 and 4, in addition to the closed porosity being less than 1.0%, the content of crystalline silica was less than 50% by mass, so that the value of dielectric loss tangent exceeded 0.0050. You can see that there is.
On the other hand, in the examples of the present invention, the obtained silica particles had a crystalline silica of 50% by mass or more and a closed porosity of 1.0% or more, so that the dielectric loss tangent value was 0.0042 or less. It can be seen that it has excellent dielectric properties in the wave band.

In Examples 1 to 4 and Examples 19 to 21, which contain 50% by mass or more of crystalline silica and have a closed porosity of 1.0% or more and less than 2.0%, the value of the dielectric loss tangent is 0.0041 to 0. It was 0042.
In particular, Examples 5 to 14 in which a mixture of crystalline silica fine powder and amorphous silica fine powder was granulated as raw material particles, and Examples in which a mixed fine powder composed of the silica fine powder and graphite powder was granulated as raw material particles. In Nos. 17 to 20, by heat-treating these granulated powders at 1200 to 1600 ° C., hollow particles having a plurality of closed pores and having a closed pore ratio of 2.0% or more were obtained, and the dielectric positive contact value was 0. It is 0040 or less, and it can be seen that the dielectric properties are further excellent. Granulation using graphite powder allowed the porosity to exceed 8% and increase to 70%. As a result, the value of the dielectric loss tangent was 0.0037 or less, which was found to be more preferable as the dielectric property.

Claims (13)

Hollow silica particles having a plurality of closed pores having a closed porosity of 1.0% or more and 70.0% or less and containing 50% by mass or more of crystalline silica. The hollow silica particles according to claim 1, wherein the closed porosity is 2.0% or more and 70.0%. The hollow silica particles according to claim 1 or 2, which contain 80% by mass or more of crystalline silica. The hollow silica particles according to any one of claims 1 to 3, wherein the crystalline silica is at least one of cristobalite or quartz. The hollow silica particles according to any one of claims 1 to 4, wherein the average particle size (D50) of the hollow silica particles is 3 to 100 μm. The hollow silica particles according to any one of claims 1 to 5, wherein the circularity of the hollow silica particles is 0.80 or more. The hollow silica particles according to any one of claims 1 to 6, wherein the hollow silica particles have a dielectric loss tangent of 0.0042 or less at a frequency of 70 GHz. A step of granulating silica fine powder as raw material particles or granulating a mixed fine powder composed of the silica fine powder and graphite fine powder as raw material particles to obtain granulated powder.
The granulated powder is heat-treated at 1200 ° C. to 1600 ° C. to provide hollow silica having a plurality of closed pores having a porosity of 1.0% or more and 70.0% or less and containing 50% by mass or more of crystalline silica. The process of obtaining particles and
A method for producing hollow silica particles having a plurality of closed pores, which comprises. The production method according to claim 8, wherein the silica fine powder is a natural quartz fine powder. The production method according to claim 8, wherein the silica fine powder is a mixture of natural quartz fine powder and amorphous silica fine powder. The production method according to any one of claims 8 to 10, wherein the average particle size (D50) of the granulated powder is 3 to 100 μm. A resin composite composition containing at least the resin and the hollow silica particles according to any one of claims 1 to 7. A resin composite obtained by curing the resin composite composition according to claim 12.

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